HK1174936A - Thermally and dimensionally stable polyimide films and methods relating thereto - Google Patents

Description

Thermally and dimensionally stable polyimide films and methods relating thereto

FIELD OF THE DISCLOSURE

The present disclosure relates generally to filled polyimide films particularly useful in electrical or electronic device type applications. More specifically, the polyimide film of the present disclosure comprises a submicron filler and a polyimide having a hybrid backbone structure.

Background

Broadly, polyimide films for electronic device type applications are known. In such applications, the polyimide film is typically used to at least partially support metal layers, metal patterns, integrated circuit devices, and/or other components related to electronic circuitry. With the development of the electronics industry, there is an increasing demand for lower cost, high performance polyimide films. As the industry demands increase, polyimide films can be problematic if they lack toughness, have poor thermal or dimensional stability, and/or are too expensive. U.S. patent application publication 2008/0044682 to Chan et al relates to filled polyimide-based articles.

Summary of The Invention

The present disclosure relates to film compositions comprising a polyimide and a sub-micron filler. The polyimide is derived from:

a) at least one aromatic dianhydride component selected from the group consisting of rigid rod dianhydride, non-rigid rod dianhydride and combinations thereof, and

b) at least one aromatic diamine component selected from the group consisting of rigid rod diamines, non-rigid rod diamines, and combinations thereof,

a mole ratio of dianhydride to diamine of 48-52:52-48, and a ratio of X: Y of 20-80:80-20, based on the total dianhydride component and the total diamine component of the polyimide, wherein X is a mole percentage of rigid rod dianhydride and rigid rod diamine, and Y is a mole percentage of non-rigid rod dianhydride and non-rigid rod diamine.

The sub-micron filler is less than (number average) 550 nanometers in at least one dimension, has an aspect ratio greater than 3:1, is less than the film thickness in all dimensions, and is present in an amount from 10% to 45% by volume of the film. The film has a thickness of 5 to 150 microns.

Description of The Preferred Embodiment

Definition of

"film" is intended to mean a free-standing film or a coating (self-supporting or non-self-supporting). The term "film" is used interchangeably with the term "layer" and is meant to cover the desired area.

As used herein, "dianhydride" is intended to include "dianhydride" precursors or derivatives, which may not be technically a dianhydride, but would be functionally equivalent to a dianhydride due to the ability to react with a diamine to form a polyamic acid, which in turn can be converted to a polyimide.

As used herein, "diamine" is intended to include diamine precursors or derivatives, which may not be technically a diamine, but would be functionally equivalent to a diamine due to the ability to react with a dianhydride to form a polyamic acid, which in turn can be converted to a polyimide.

As used herein, "polyamic acid" is intended to include any polyimide precursor material derived from a combination of dianhydride and diamine monomers or functional equivalents thereof and capable of being converted to polyimide.

"submicron-sized" is intended to describe compositions having at least one dimension less than (number average) microns.

As used herein, "chemical conversion" or "chemically converted" means the conversion of a polyamic acid to a polyimide using a catalyst (accelerator) or a dehydrating agent (or both) and is intended to include a partially chemically converted polyimide which is then dried at elevated temperatures to a solids content of greater than 98%.

"aspect ratio" is intended to mean the ratio of one dimension to another, such as the ratio of length to width.

In describing certain polymers, it should be understood that sometimes applicants refer to polymers using the monomers from which they are made or the amounts of the monomers from which they are made. Although such descriptions may not include the specific nomenclature used to describe the final polymer or may not contain terms that define the product by way of a method, any such reference to monomers and amounts should be construed to mean that the polymer is made from those monomers, unless the context indicates or implies otherwise.

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, the condition a or B is satisfied in any of the following cases: a is true (or present) and B is spurious (or absent), a is spurious (or absent) and B is true (or present), and both a and B are true (or present).

In addition, the articles "a" and "an" are used to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. Such description should be understood to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

SUMMARY

The films of the present disclosure comprise a polyimide and a sub-micron filler. The polyimide has a hybrid backbone structure comprising rigid rod portions and non-rigid rod portions. The sub-micron filler can generally be incorporated into the film at relatively high loadings without causing undue brittleness of the film while maintaining or reducing the coefficient of thermal expansion and increasing the storage modulus.

Polyimide, polyimide resin composition and polyimide resin composition

The polyimides of the present disclosure are derived from the polymerization of certain aromatic dianhydrides with certain aromatic diamines to provide a polymer backbone structure that includes both rigid rod portions and non-rigid rod portions. The rigid rod portions are incorporated into the polyimide by polymerization of aromatic rigid rod monomers, while the non-rigid rod portions are incorporated into the polyimide by polymerization of non-rigid rod aromatic monomers. Aromatic rigid rod monomers provide a co-linear (about 180 °) configuration to the polymer backbone and therefore have little relative motion capability when polymerized into polyimides.

Examples of aromatic rigid rod diamine monomers are:

1, 4-diaminobenzene (PPD),

4,4' -diaminobiphenyl,

2,2 '-bis (trifluoromethyl) 4,4' -diaminobiphenyl (TFMB),

1, 4-naphthalenediamine,

1, 5-naphthalenediamine,

4,4' -diaminoterphenyl,

4,4' -diaminobenzanilide,

4,4' -diaminophenyl benzoate,

3,3 '-dimethyl-4, 4' -diaminobiphenyl,

2, 5-diaminotoluene, and the like.

Examples of aromatic rigid rod dianhydride monomers are:

pyromellitic dianhydride (PMDA),

2,3,6, 7-naphthalenetetracarboxylic dianhydride, and

3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA).

Monomers having a degree of freedom of rotational movement or bending (once polymerized into the polyimide) substantially equal to or less than the above examples (rigid rod diamines and rigid rod dianhydrides) are intended to be considered rigid rod monomers for the purposes of this disclosure.

Non-rigid rod monomers for the purposes of this disclosure are intended to mean aromatic monomers capable of polymerization into the polyimide backbone structure that have significantly greater freedom of movement than the rigid rod monomers described and illustrated above. The non-rigid rod monomers, when polymerized into the polyimide, provide a backbone structure having bends, or in other words the polyimide backbone formed along them is non-collinear (e.g., not about 180 °). Examples of non-rigid rod monomers according to the present disclosure include any diamine and any dianhydride capable of providing a rotational or flexural bridging group along the polyimide backbone. Examples of rotating or bending bridging groups include-O-, -S-, -SO₂-、-C(O)-、-C(CH₃)₂-、-C(CF₃)₂-and-C (R, R ') -wherein R and R' are the same or different and are any capable of bonding to carbonAn organic group.

Examples of non-rigid rod diamines include: 4,4' -diaminodiphenyl ether ("ODA"), 2-bis (4-aminophenyl) propane, 1, 3-diaminobenzene (MPD), 4' -diaminobenzophenone, 4' -diaminodiphenylmethane, 4' -diaminodiphenyl sulfide, 4' -diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, bis (4- (4-aminophenoxy) phenylsulfone (BAPS), 4' -bis (aminophenoxy) biphenyl (BAPB), 3,4' -diaminodiphenyl ether, 4' -diaminobenzophenone, 4' -isopropylidenedianiline, 2' -bis (3-aminophenyl) propane, N-bis (4-aminophenyl) N-butylamine, n, N-bis (4-aminophenyl) methylamine, m-aminobenzoyl-p-aminobenzamide, 4-aminophenyl-3-aminobenzoate, N-bis (4-aminophenyl) aniline, 2, 4-diaminotoluene, 2, 6-diaminotoluene, 2, 4-diamine-5-chlorotoluene, 2, 4-diamino-6-chlorotoluene, 2, 4-bis (β -aminot-butyl) toluene, bis (p- β -aminot-butylphenyl) ether, p-bis-2- (2-methyl-4-aminopentyl) benzene, m-xylylenediamine, p-xylylenediamine. 1, 2-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 1, 2-bis (3-aminophenoxy) benzene, 1, 3-bis (3-aminophenoxy) benzene, 1- (4-aminophenoxy) -3- (3-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 1, 4-bis (3-aminophenoxy) benzene, 1- (4-aminophenoxy) -4- (3-aminophenoxy) benzene, 2-bis (4- [ 4-aminophenoxy ] phenyl) propane (BAPP), 2 '-bis (4-aminophenyl) hexafluoropropane (6F diamine), 2' -bis (4-phenoxyaniline) isopropylidene, 4,4' -diamino-2, 2' -trifluoromethyldiphenyl ether, 3' -diamino-5, 5' -trifluoromethyldiphenyl ether, 4' -trifluoromethyl-2, 2' -diaminobiphenyl, 2,4, 6-trimethyl-1, 3-diaminobenzene, 4' -oxo-bis [ 2-trifluoromethyl) aniline ] (1, 2, 4-OBABTF), 4' -oxo-bis [ 3-trifluoromethyl) aniline ], 4' -thio-bis [ (2-trifluoromethyl) aniline ], 4' -thio-bis [ (3-trifluoromethyl) aniline ], 4' -sulfoxy-bis [ (2-trifluoromethyl) aniline, 4,4 '-sulfoxy-bis [ (3-trifluoromethyl) aniline ] and 4,4' -keto-bis [ (2-trifluoromethyl) aniline ].

Examples of non-rigid-rod aromatic dianhydrides include 2,2',3,3' -benzophenonetetracarboxylic dianhydride, 2,3,3',4' -benzophenonetetracarboxylic dianhydride, 3,3',4,4' -benzophenonetetracarboxylic dianhydride (BTDA), 2',3,3' -biphenyltetracarboxylic dianhydride, 2,3,3',4' -biphenyltetracarboxylic dianhydride, 4,4 '-thiophthalic anhydride, bis (3, 4-Dicarboxyphenyl) Sulfone Dianhydride (DSDA), bis (3, 4-dicarboxyphenyl) sulfoxide dianhydride, 4,4' -oxydiphthalic anhydride (ODPA), bis (3, 4-dicarboxyphenyl) thioether dianhydride, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride (BPADA), 2-bis- (3, 4-dicarboxyphenyl) 1,1,1,3,3,3, -hexafluoropropane dianhydride (6 FDA), 5- [2,2,2] -trifluoro-1- (trifluoromethyl) ethylene, bis-1, 3-isobenzofurandione, bis (3, 4-dicarboxyphenyl) methane dianhydride, cyclopentadienyl tetracarboxylic dianhydride, vinyl tetracarboxylic dianhydride, 2, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride.

In some embodiments, the molar ratio of dianhydride to diamine is from 48 to 52:52 to 48, and the ratio of X: Y is from 20 to 80:80 to 20, based on the total dianhydride component and diamine component of the polyimide, where X is the mole percentage of rigid rod dianhydride and rigid rod diamine, and Y is the mole percentage of non-rigid rod dianhydride and non-rigid rod diamine. And in an alternative embodiment can be any subrange within that wide ratio (e.g., 20 to 80 includes any range therebetween and optionally includes 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 to 20 includes any range therebetween and optionally includes 80, 75, 70, 65, 60, 55, 45, 40, 35, 30, and 25).

In one embodiment, the polyimide of the present disclosure is derived from substantially equal molar amounts of 4,4 '-diaminodiphenyl ether (4, 4' -ODA) non-rigid rod monomers, and pyromellitic dianhydride (PMDA) rigid rod monomers. In another embodiment, at least 70 mole percent of the aromatic dianhydride component is pyromellitic dianhydride; and at least 70 mole% of the aromatic diamine component is 4,4' -diaminodiphenyl ether. In some embodiments, at least 70 mole%, 75 mole%, 80 mole%, 85 mole%, 90 mole%, or 95 mole% of the aromatic dianhydride component is pyromellitic dianhydride (based on the total dianhydride content of the polyimide); and at least 70, 75, 80, 85, 90 or 95 mole percent of the aromatic diamine component is 4,4' -diaminodiphenyl ether (based on the total diamine content of the polyimide). It has been found that such PMDA//4, 4' ODA polyimides are particularly well suited for combination with the sub-micron filler of the present disclosure for improving properties at relatively low cost. In another embodiment, the polyimide is derived from 100 mole% pyromellitic dianhydride and 100 mole% 4,4' -diaminodiphenyl ether. In another embodiment, the polyimide is a random copolymer derived from 4,4' -diaminodiphenyl ether and 1,4 diaminobenzene with pyromellitic dianhydride and 3,3',4,4' -biphenyltetracarboxylic dianhydride. In another embodiment, the polyimide is a random copolymer derived from 4,4' -diaminodiphenyl ether and 1,4 diaminobenzene with pyromellitic dianhydride.

In another embodiment, at least 75 mole percent of the aromatic dianhydride component is pyromellitic dianhydride and 70 mole percent 4,4' -diaminodiphenyl ether and 30 mole percent 1,4 diaminobenzene are the aromatic diamine component.

In another embodiment, the polyimide is a block copolymer. Block copolymers are polymers in which there is essentially one dianhydride/diamine combination sequence along the polymer backbone, as opposed to a completely random distribution of monomer sequences. Typically this is achieved by successive additions of different monomers during the preparation of the polyamic acid.

In another embodiment, the polyimide is a block copolymer derived from 4,4' -diaminodiphenyl ether and 1, 4-diaminobenzene with pyromellitic dianhydride. In another embodiment, the polyimide is a block copolymer derived from 4,4 '-diaminodiphenyl ether (4, 4' -ODA) and 1, 4-diaminobenzene (PPD) with pyromellitic dianhydride (PMDA) and 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA). In another embodiment, the block copolymer is derived from a block of 10 to 40 mole percent pyromellitic dianhydride and 1, 4-diaminobenzene and a block of 90 to 60 mole percent pyromellitic dianhydride and 4,4' -diaminodiphenyl ether.

Submicron filler

According to the present disclosure, the filler is a submicron (in at least one dimension) filler or a mixture of submicron fillers.

In one embodiment, the polyimide film of the present disclosure comprises a submicron filler:

1. less than 550 nanometers in at least one dimension (and in some embodiments, less than 475 nanometers, 450 nanometers, 425 nanometers, 400 nanometers, 375 nanometers, 350 nanometers, 325 nanometers, 300 nanometers, 275 nanometers, 250 nanometers, 225 nanometers, or 200 nanometers, as fillers can have a variety of shapes in any dimension and as filler shapes can vary along any dimension);

2. having an average aspect ratio of greater than 3,4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, or 15 to 1;

3. less than 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, or 10% of the film thickness in all dimensions; and is

4. Present in an amount between them and optionally including any two of the following percentages: 10%, 15%, 20%, 25%, 30%, 35%, 40% and 45% by volume of the polyimide film.

Suitable sub-micron fillers are generally stable at temperatures above 300 ℃, 350 ℃, 400 ℃, 425 ℃, or 450 ℃, and in some embodiments do not significantly degrade the electrical insulation properties of the film. In some embodiments, the sub-micron filler is selected from the group consisting of needle-like fillers (needles), fibrous fillers, platelet fillers, and mixtures thereof. In one embodiment, the sub-micron filler is substantially non-aggregated. The sub-micron filler may be hollow, porous, or solid.

In one embodiment, the submicron sized filler of the present disclosure exhibits an aspect ratio of at least 3,4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, or 15 to 1. In one embodiment, the submicron filler has an aspect ratio of 5:1 or greater. In another embodiment, the submicron filler has an aspect ratio of 10:1 or greater; in another embodiment, the aspect ratio is 12:1 or greater. In some embodiments, the sub-micron filler is selected from an oxide (e.g., an oxide comprising silicon, magnesium, and/or aluminum), a nitride (e.g., a nitride comprising boron and/or silicon), or a carbide (e.g., a carbide comprising tungsten and/or silicon), and combinations thereof. In some embodiments, the sub-micron filler is acicular titanium dioxide, talc, SiC fiber, platy Al₂O₃Or mixtures thereof. In some embodiments, the sub-micron filler is less than (number average) 50 microns, 25 microns, 20 microns, 15 microns, 12 microns, 10 microns, 8 microns, 6 microns, 5 microns, 4 microns, or 2 microns in all dimensions.

In another embodiment, carbon fibers and graphite can be used in combination with other sub-micron fillers to increase mechanical properties. In one embodiment, however, the loading of graphite, carbon fibers, and/or conductive fillers may need to be below the percolation threshold (possibly less than 10 volume percent) because graphite and carbon fiber fillers may reduce electrical insulation properties and in some embodiments, impaired electrical insulation properties are undesirable.

In some embodiments, the sub-micron filler is coated with a coupling agent. In some embodiments, the sub-micron filler is coated with an aminosilane coupling agent. In some embodiments, the sub-micron filler is coated with a dispersant. In some embodiments, the sub-micron filler is coated with a combination of a coupling agent and a dispersant. In some embodiments, the sub-micron filler is coated with a coupling agent, a dispersant, or a combination thereof. Alternatively, the coupling agent and/or dispersant can be incorporated directly into the film without being coated onto the sub-micron filler. In some embodiments, the sub-micron filler comprises acicular titanium dioxide, at least a portion of which is coated with alumina.

In some embodiments, the sub-micron filler is selected such that it does not itself degrade or generate off-gases at the desired processing temperature. Similarly, in some embodiments, the sub-micron filler is selected such that it does not contribute to the degradation of the polymer.

In one embodiment, a filler composite (e.g., a single or multi-core/shell structure) may be used in which one oxide encapsulates another oxide in one particle.

Film(s)

It has been found that relatively inexpensive polyimides can be filled with sub-micron fillers of the present disclosure, and thus behave more like more expensive polyimides in at least some respects, but at much lower cost. More expensive monomers, such as BPDA or fluorinated monomers, can be at least partially (or fully) replaced with less expensive monomers. In addition to expensive monomers, some polyimides are difficult to process commercially, such as BPDA// PPD, because they can foam. Lower production rates push up the cost of the film. Further, polyimides derived from all rigid rod monomers can have low CTE and high modulus, but low elongation when filled. It has been found that submicron fillers having an aspect ratio of 3:1 or greater can be incorporated (10 to 45 volume percent) into relatively inexpensive, easily processable polyimides at relatively high loading levels. The sub-micron filler of the present disclosure tends to increase the storage modulus and decrease or approximately maintain the CTE of the film of the present disclosure without causing the polyimide film to become unduly brittle.

Surprisingly, the sub-micron filler of the present disclosure does not behave in the same manner in all polyimides. Surprisingly, in rigid rod polyimide (BPDA// PPD), the CTE can be greater than that of the unfilled rigid rod polyimide.

When incorporated into the polyimides of the present disclosure, the sub-micron fillers of the present disclosure yield films with better properties (or balance of properties) than their conventional non-high aspect ratio (less than 3:1 aspect ratio) counterparts.

In some embodiments, the polyimide film comprises a polyimide film derived from 100 mole% pyromellitic dianhydride as the aromatic dianhydride component; and 100 mol% of a polyimide having 4,4' -diaminodiphenyl ether as an aromatic diamine component, and the sub-micron filler is acicular titanium dioxide, talc, or a mixture thereof. In some embodiments, the polyimide is a homopolymer of pyromellitic dianhydride and 4,4' -diaminodiphenyl ether.

In another embodiment, the film composition comprises a polyimide, wherein the polyimide is derived from: 10 to 40 mole% pyromellitic dianhydride and a 1,4 diaminobenzene block; 90 to 60 mole% of a block copolymer of pyromellitic dianhydride and a 4,4' -diaminodiphenyl ether block, and the sub-micron filler is acicular titanium dioxide, talc or a mixture thereof.

Thermal and dimensional stability

While it is generally known that adding filler will lower CTE and increase storage modulus, surprisingly, for the sub-micron filler of the present disclosure, a significant increase in storage modulus and/or a threshold above the CTE reduction is observed. In one embodiment, the sub-micron filler will substantially maintain (within 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 5%, 4%, 3%, 2%, or 1%, plus or minus) the Coefficient of Thermal Expansion (CTE) while improving the mechanical and thermal properties.

In one embodiment, the films of the present disclosure have an in-plane coefficient of thermal expansion in a range between (and optionally including) any two of: 1 ppm/deg.C, 5 ppm/deg.C, 10 ppm/deg.C, 15 ppm/deg.C, 20 ppm/deg.C, 25 ppm/deg.C, 30 ppm/deg.C, and 35 ppm/deg.C, wherein the in-plane Coefficient of Thermal Expansion (CTE) is measured between 60 deg.C (or 50 deg.C) and 350 deg.C.

Some unfilled block or random copolymers of the present disclosure can have relatively low CTE. Thus, in some embodiments, the sub-micron filler of the present disclosure has little effect on the CTE of the block copolymer. In some embodiments, the sub-micron filler of the present disclosure can increase the CTE of block or random copolymers having a low CTE, but the CTE remains within a desired range.

The thickness of the film also affects the coefficient of thermal expansion, with thinner films tending to give lower coefficients of thermal expansion (and thicker films the higher the coefficient of thermal expansion), and thus can be used to fine tune the film coefficient of thermal expansion, depending on any particular application selected. The films of the present disclosure have a thickness in a range between (and optionally including) any two of the following thicknesses (in microns): 5 microns, 6 microns, 8 microns, 10 microns, 12 microns, 15 microns, 20 microns, 25 microns, 50 microns, 75 microns, 100 microns, 125 microns, and 150 microns. Monomers and submicron fillers within the scope of the present disclosure can also be selected or optimized to fine tune the coefficient of thermal expansion within the above ranges. Depending on the particular application, ordinary skill and experimentation may be necessary in fine tuning any particular coefficient of thermal expansion of the films of the present disclosure. In some embodiments, the in-plane CTE of the film can be obtained by thermo-mechanical analysis using a TA instrument TMA-2940, which is run at 10 ℃/min up to 400 ℃, followed by cooling and reheating to 400 ℃, where the CTE is obtained during a reheat scan between 50 ℃ and 350 ℃, in ppm/° c. In another embodiment, the in-plane CTE of the film can be evaluated by Thermal Mechanical Analysis (TA instruments, TMA-2940, heating at 10 deg.C/min up to 460 deg.C, then cooling and reheating to 500 deg.C), reheating between 50 and 350 deg.C. In another embodiment, the in-plane CTE of the film can be evaluated by Thermal Mechanical Analysis (TA instruments, TMA-2940, heating at 10 deg.C/min up to 380 deg.C, then cooling and reheating to 380 deg.C), and reheating between 50 and 350 deg.C.

In some embodiments, the sub-micron filler increases the storage modulus above the glass transition temperature (Tg) of the polyimide. In some embodiments, the submicron fillers of the present disclosure increase storage modulus at 25 ℃ by at least 20%, 22%, 24%, 26%, 28%, or 30% compared to submicron fillers having an aspect ratio of less than 3: 1. In some embodiments, the submicron fillers of the present disclosure increase the storage modulus by at least 40%, 42%, 44%, or 46% at 480 ℃ to 500 ℃ compared to submicron fillers having an aspect ratio of less than 3: 1. In some embodiments, the sub-micron filler of the present disclosure increases the storage modulus by at least 38%, 40%, 42%, 44%, or 46% compared to the unfilled polyimide at 25 ℃. In some embodiments, the sub-micron filler of the present disclosure increases the storage modulus by at least 52%, 53%, 54%, or 55% compared to the unfilled polyimide at 480 ℃ to 500 ℃.

Generally, as the amount of filler in the film increases, the film tends to become more brittle and difficult to process. Generally, when the tensile elongation is less than 20%, the film is difficult to process and thus has limited commercial value. Surprisingly, the tensile elongation remains acceptable when the sub-micron filler of the present disclosure is added to a polyimide having a dianhydride to diamine molar ratio of 48-52:52-48 and a ratio of X: Y of 20-80:80-20, where X is the mole percent of rigid rod dianhydride and rigid rod diamine and Y is the mole percent of non-rigid rod dianhydride and non-rigid rod diamine, based on the total dianhydride component and diamine component of the polyimide. In some embodiments, the tensile elongation remains acceptable when greater than 10 volume percent of submicron fillers are used. In some embodiments, the tensile elongation remains acceptable when greater than 30 volume percent of submicron fillers are used. In another embodiment, the tensile elongation remains acceptable when greater than 40 volume percent of submicron fillers are used.

Generally, when forming polyimides, chemical conversion processes (as opposed to thermal conversion processes) will provide polyimide films with lower coefficients of thermal expansion. Thus, while understanding the polyimide advantages of the present disclosure with respect to both chemical and thermal transformations, the advantages of incorporating the sub-micron filler of the present disclosure are most useful with respect to chemically transformed polyimides of the present disclosure.

Thin film formation

The films of the present disclosure can be prepared by methods well known in the art. In some embodiments, the film may be produced by mixing the above monomers together with a solvent to form a polyamic acid (also referred to as a polyamic acid solution). The dianhydride and diamine components are typically mixed in a molar ratio of aromatic dianhydride component to aromatic diamine component of from 0.90 to 1.10. The molecular weight can be adjusted by adjusting the molar ratio of the dianhydride and diamine components.

Chemical or thermal transformations may be used in the practice of the present disclosure. In examples where chemical transformation is used, the polyamic acid casting solution is derived from the polyamic acid solution. In one embodiment, the polyamic acid casting solution comprises a mixture of polyamic acid solution and conversion chemicals, such as: (i) one or more dehydrating agents such as aliphatic anhydrides (acetic anhydride, etc.), and aromatic anhydrides; and (ii) one or more catalysts such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, etc.) and heterocyclic tertiary amines (pyridine, picoline, isoquinoline, etc.). The anhydride dehydrating agent is generally used in a molar excess over the amic acid groups in the copolyamic acid. Acetic anhydride is generally used in an amount of about 2.0 to 3.0 moles per equivalent of amine acid. Generally, a substantial amount of tertiary amine catalyst is used.

In one embodiment, the polyamic acid is dissolved in an organic solvent at a concentration of from about 5 wt% to up to 40 wt% and including 40 wt%. In one embodiment, the polyamic acid is dissolved in the organic solvent at a concentration of about 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%. Examples of suitable solvents include: formamide solvents (N, N-dimethylformamide, N-diethylformamide, etc.), acetamide solvents (N, N-dimethylacetamide, N-diethylacetamide, etc.), pyrrolidone solvents (N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, etc.), phenol solvents (phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, etc.), hexamethylphosphoramide, and γ -butyrolactone. It is desirable to use one of these solvents or a mixture thereof. Combinations of these solvents with aromatic hydrocarbons such as xylene and toluene, or ether-containing solvents such as diglyme, propylene glycol methyl ether, propylene glycol, methyl ether acetate, tetrahydrofuran, and the like, may also be used.

In one embodiment, the prepolymer can be prepared and mixed with submicron fillers (dispersions or colloids thereof) using a number of variations to form the films described in this disclosure. "prepolymer" is intended to mean a lower molecular weight polymer typically made with a small stoichiometric excess (about 2% to 4%) of diamine monomer (or excess dianhydride monomer). Increasing the molecular weight (and solution viscosity) of the prepolymer can be accomplished by adding an increased amount of additional dianhydride (or additional diamine, in cases where the dianhydride monomer is initially in excess in the prepolymer) so as to approach a 1:1 dianhydride to diamine stoichiometric ratio.

A useful method for producing films according to the present disclosure can be found in U.S.5,166,308 to Kreuz et al. Many variations are possible, such as: (a) a method in which the diamine component and the dianhydride component are preliminarily mixed together, and then the mixture is added to the solvent in portions while stirring, (b) a method in which the solvent is added to the stirred mixture of the diamine and the dianhydride component (contrary to (a) above), (c) a method in which the diamine is solely dissolved in the solvent, and then the dianhydride is added to the solvent in such a ratio as to allow control of the reaction rate, (d) a method in which the dianhydride component is solely dissolved in the solvent, and then the amine component is added to the solvent in such a ratio as to allow control of the reaction rate, (e) a method in which the diamine component and the dianhydride component are separately dissolved in the solvent, and then these solutions are mixed in a reactor, (f) the polyamic acid is preliminarily formed with an excess amount of the amine component and other polyamic acid with an excess amount of the dianhydride component, and then reacting with each other in a reactor, particularly with respect to such processes for forming non-random or block copolymers, (g) a process wherein specific portions of the amine component and the dianhydride component are first reacted followed by reaction of residual diamine component, or vice versa, (h) a process wherein a conversion chemical is mixed with the polyamic acid to form a polyamic acid casting solution, followed by casting to form a gel film, (i) a process wherein the components are added in any order, in part or all, to part or all of the solvent, and wherein part or all of any of the components can be added as a solution in part or all of the solvent, (j) first reacting one of the dianhydride components with one of the diamine components to provide a first polyamic acid, followed by reacting the other dianhydride component with the other amine component to provide a second polyamic acid, then prior to film formation, mixing amic acid in any of a number of ways, and (k) forming a block copolymer by sequentially adding, for example, a first diamine and a first diacid anhydride to form a polyamic acid having an excess of dianhydride (or excess of diamine) to form a first block, and then adding a second diamine and a second diacid anhydride to the polyamic acid in the presence of the first block to form a second block; alternatively, the blocks may be based on different dianhydrides (and the same diamine) or on a process of preparation of different dianhydrides and different diamines (at each block), depending on the particular application or characteristics desired.

The sub-micron fillers (their dispersions or colloids) can be added at multiple points in the film preparation. In one embodiment, the colloid or dispersion is incorporated into the prepolymer to produce a Brookfield solution viscosity in the range of about 50 to 100 poise at 25 ℃. In an alternative embodiment, the colloid or dispersion may be mixed directly with the monomer, and in this case, polymerization occurs during the presence of the filler in the reaction. During this "in situ" polymerization, the monomers may have an excess of either monomer (diamine or dianhydride). The monomers may also be added in a ratio of 1: 1. In such cases where the monomer is added in excess of either the amine (case i) or the dianhydride (case ii), increasing the molecular weight (and solution viscosity) can be achieved, if necessary, by adding an increased amount of additional dianhydride (case i) or diamine (case ii) to approach a dianhydride to amine 1:1 stoichiometric ratio.

The polyamic acid casting solution can then be cast or applied onto a support, such as an endless belt or drum. The polyamic acid includes a conversion chemical reactant. The solvent-containing film may then be converted into a self-supporting film by baking (thermal curing) at an appropriate temperature to remove the solvent or baking (chemical curing) with the chemical conversion reactant. The film can then be separated from the support, oriented such as by tentering, and subsequently heat cured to provide a film.

Generally, film smoothness is desirable because of surface roughness: i. can interfere with the function of one or more filled films of the present disclosure deposited thereon, ii. In one embodiment, the submicron filler (and any other discontinuous regions) are sufficiently dispersed during film formation such that the submicron filler (and any other discontinuous regions) are sufficiently between the film surfaces as the film is formed to provide a final film having an average surface roughness (Ra) of less than 1000 nanometers, 750 nanometers, 500 nanometers, or 400 nanometers. Surface roughness as provided herein can be determined by optical surface topography to provide Ra values, for example, as measured on a Veeco Wyco NT 1000 series apparatus in VSI mode at 25.4x or 51.2x using Wyco Vision 32 software.

The polyamic acid (and casting solution) can further comprise any of a number of additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardant additives, antistatic agents, heat stabilizers, ultraviolet light absorbers, fillers, or various reinforcing agents.

The alkoxysilane coupling agent (or any conventional, unconventional, presently known, or future discovered coupling agent) may be added during processing by pre-treating the sub-micron filler prior to formulation. Alkoxysilane coupling agents may also be added during the "in situ" polymerization by mixing the filler and monomer with the alkoxysilane, generally as long as the coupling agent does not interfere with the polymerization reaction.

In some cases, the dianhydride can be contacted with the sub-micron filler. While not being bound by any particular theory or hypothesis, it is believed that such contact between the dianhydride and the sub-micron filler may functionalize the sub-micron filler with the dianhydride prior to further reaction with the monomer or prepolymer. Finally, the filled polyamic acid composition is typically cast into a film, which is subjected to drying and curing (chemical and/or thermal curing) to form a filled polyimide film. Any conventional or unconventional method of making filled polyimide films can be used in accordance with the present disclosure. Generally, the manufacture of filled polyimide films is well known and need not be described further herein. In one embodiment, the polyimide for the thin film of the present disclosure has a high glass transition temperature of greater than 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, 360 ℃, 370 ℃, 380 ℃, 390 ℃, or 400 ℃. A high glass transition temperature generally helps to maintain mechanical properties, such as storage modulus, at high temperatures.

In some embodiments, electrically insulating fillers may be added to improve the electrical properties of the film. In some embodiments, it is important that the film be free of pinholes or other defects (foreign particles, gels, filler agglomerates, or other contaminants) that adversely affect the electrical integrity and dielectric strength of the film, which can generally be addressed by filtration. Such filtration can be performed at any stage of the film fabrication, for example, filtering the solvated filler before or after it is added to the monomer or monomers and/or filtering the polyamic acid, particularly when the polyamic acid is of low viscosity, or in other words, in any step of the fabrication process that allows filtration. In one embodiment, such filtration is performed at the smallest suitable filter pore size, or to the extent of just exceeding the maximum size of the selected packing material. In some embodiments, the sub-micron filler is subjected to intense dispersion energy, such as stirring and/or high shear mixing or media milling or other dispersion techniques, including the use of dispersants, when incorporated into the film (or into the polyimide precursor) to inhibit unwanted agglomeration beyond the desired maximum filler size, or to break up aggregates that may be originally present in the sub-micron filler. As the aspect ratio of the submicron filler increases, the tendency of the major axis of the submicron filler to align or otherwise align itself parallel to the outer surface of the film also increases.

A single layer film can be made thicker in an attempt to reduce the effect of defects caused by deleterious (or excessive) discontinuous phase material in the film. Alternatively, multiple layers of polyimide can be used to reduce the damage of any particular defect (a detrimental discontinuous phase material of a size that can harm the desired performance) in any particular layer, and in general, such multiple layers will have fewer defects in performance than a single layer of polyimide of the same thickness. The use of multiple polyimide films can reduce or eliminate the occurrence of defects that can span the total thickness of the film, since the likelihood of having defects that overlap in each of the individual layers tends to be minimal. Thus, defects in any of the layers are less likely to cause electrical or other types of failures through the entire thickness of the film. In some embodiments, the film comprises two or more polyimide layers. In some embodiments, the polyimide layers are the same. In some embodiments, the polyimide layers are different. In some embodiments, the film is heated with an inherently heat stable inorganic fabric, paper, sheet, scrim, or combination thereof. Optionally, the 0-55% by weight film may also include other ingredients to improve properties desired or needed for any particular application.

Examples

The invention will be further described in the following examples, which are not intended to limit the scope of the invention as set forth in the claims.

In all examples, densities of 4.2g/cc for acicular titanium dioxide, 2.75g/cc for talc, 3.22g/cc for SiC, and 1.42g/cc for polyimide were used for calculating the conversion composition weight% to equivalent volume%.

Examples 1-4 demonstrate that 10% or more by volume of the sub-micron filler of the present disclosure significantly increases the storage modulus and decreases the CTE when compared to unfilled comparative example 1, while maintaining a suitable elongation at break.

Example 1

15% by volume (34.3% by weight) of acicular TiO in PMDA// ODA₂。

25.0 g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) was mixed with 141.11 grams of anhydrous DMAC. The slurry was mixed under high shear for about 10 to 15 minutes (with a blade speed of about 4000 rpm) using a Silverson Model L4RT high shear mixer (Silverson Machines, LTD, chesham baucks, England) equipped with a square-hole, high shear screen.

In a round bottom flask, 74.1 grams of a solution containing acicular TiO was added₂The slurry was mixed with 116.94 grams of PMDA// ODA prepolymer (20 wt% solution in anhydrous DMAC) and the resulting mixture was stirred for approximately 24 hours. During this operation, a gentle nitrogen purge was used in the round bottom flask.

After stirring for about 24 hours, the material was filtered through 45 micron filtration media (Millipore, 45 micron polypropylene mesh, PP 4504700).

In a different vessel, a 6% by weight solution of pyromellitic anhydride (PMDA) was prepared by combining 9.00g of PMDA (Aldrich 412287, Allentown, Pa.) with 15mL of DMAC.

The PMDA solution was slowly added to the prepolymer slurry to achieve a final viscosity of 1090 poise. The formulation was stored overnight at 0 ℃ to allow degassing.

The formulation was cast onto the surface of a glass plate using a 25mil doctor blade to form a 3 "x 4" film. The cast film and glass plate were then dipped into a solution containing 110ml of 3-methylpyridine (. beta.methylpyridine, Aldrich, 242845) and 110ml of acetic anhydride (Aldrich, 98%, P42053).

The film was then lifted off the glass surface and mounted on a 3 "x 4" pin plate rack. The mounted film was placed in an oven (Thermolyne, F6000 box oven). The furnace was purged with nitrogen and heated according to the following temperature schedule:

40 ℃ to 125 ℃ (slope of 4 ℃/min)

125 ℃ to 125 ℃ (soaking for 30 min)

125 ℃ to 250 ℃ (slope of 4 ℃/min)

250 deg.C (soaking for 30 min)

250 ℃ to 400 ℃ (slope 5 ℃/min)

400 deg.C (20 min soaking)

The coefficient of thermal expansion was measured by thermomechanical analysis (TMA). TA Instrument model 2940 was used for the tension mode. N for the apparatus₂Purge at a rate of 30 to 50 ml/min. Mechanical coolers are also used which cool the temperature of the instrument rapidly between heating cycles. The film was cut to a width of 2.0mm and a length (in the machine or casting direction) of 6 to 9 mm. The film is longitudinally clamped to a length of 7.5-9.0 mm. The preload tension was set to a force of 5 grams. The film was then brought to 10 ℃/minIs subjected to heating from 0 ℃ to 400 ℃, held at 400 ℃ for 3 minutes, and cooled back to 0 ℃. A second heating cycle 400 c was performed in the same manner. The calculation of the coefficient of thermal expansion in μm/m- ° c (or pp/° c) for the casting direction (longitudinal direction) at 60 ℃ to 400 ℃ for the second heating cycle is reported.

The storage modulus (E') measured by a Dynamic Mechanical Analysis (DMA) instrument is used to characterize the mechanical properties of the film. The dynamic mechanical analysis operation is based on the viscoelastic response (TA instruments, New Castle, DE, USA, DMA 2980) of polymers subjected to small oscillatory strains (e.g. 10 μm) as a function of temperature and time. Placing the film under tension in a multi-frequency strain mode. A rectangular specimen of defined dimensions is clamped between a fixed clamp and a movable clamp. The film is 6 to 6.4mm wide, 0.03 to 0.05mm thick and 10mm long. The machine direction was used and the film was fastened with a force of 3in-lb torque. The static force in the length direction was 0.05N, with an automatic tension of 125%. The film was heated from 0 ℃ to 500 ℃ at a rate of 3 ℃/min at a frequency of 1 Hz. The storage modulus at 25 ℃ was determined to be 5757 MPa.

The tensile properties of the films, including elongation at break, were measured on an Instron model 3345 instrument. The collet gap (sample test length) was 1 inch (2.54 cm) and the width was 0.5 inch (1.27 cm). The chuck speed was 1 inch (2.54 cm)/min.

The results are shown in Table 1.

Example 2

10% by volume (24.70% by weight) of acicular TiO in PMDA// ODA₂（FTL-110）。

The same procedure as described in example 1 was followed except for the following differences. 54.24 g of a solution containing acicular TiO₂With 136.15 grams of PMDA// ODA prepolymer (20 wt.% in DMAC) in a slurry of FTL-110, 15 wt.% in DMAC) And (4) mixing.

The material was finished with PMDA solution to 899 poise viscosity.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Example 3

20% by volume (42.5% by weight) of acicular TiO in PMDA// ODA₂（FTL-110）。

The same procedure as described in example 1 was followed except for the following differences. 57.7 g of a solution containing acicular TiO₂(FTL-110, 15 wt% in DMAC, high shear mixing) the slurry was mixed with 63.3 grams of PMDA// ODA prepolymer (20.6 wt% in DMAC).

The material was finished with PMDA solution to 1380 poise viscosity.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Example 4

10% by volume SiC fibers in PMDA// ODA (20.1% by weight)

The same procedure as described in example 1 was followed except for the following differences. 24.75 grams of SiC fibers (b)Silicon Carbide whiskers, type β, Advanced composites, greenr, SC, USA) was mixed with 140.25 grams of anhydrous DMAC. The slurry was mixed under high shear conditions as described in example 1.

45.62 grams of this slurry was mixed with 144.44 grams of PMDA// ODA prepolymer (20.6 wt% in DMAC).

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 1

Unfilled PMDA// ODA

The same procedure as described in example 1 was followed except for the following differences. The slurry containing the inorganic particles was not added to the PDMA// ODA prepolymer (20 wt% prepolymer in DMAC).

The material was finished with PMDA solution to 890 poise viscosity.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative examples 2 to 5 demonstrate that the presence of less than 10% by volume of the sub-micron filler of the present disclosure does not produce a significant increase in storage modulus (especially storage modulus at 500 ℃) or a decrease in CTE (relatively minor improvement in storage modulus and CTE).

Comparative example 2

2.5 vol% (7 wt%) of acicular TiO in PMDA// ODA₂

A method similar to that described in example 1 was used, except for the following differences. 24.08 g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) was mixed with 135.92 grams of anhydrous DMAC and the slurry was mixed under high shear.

10.1 grams of the slurry containing acicular TiO2 was mixed with 109.9 grams of PMDA// ODA prepolymer.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 3

5% by volume (13.5% by weight) of acicular TiO2 in PMDA// ODA。

A method similar to that described in example 1 was used, except for the following differences. 24.08 grams of acicular TiO2 (FTL-110, Ishihara Corporation, USA) was mixed with 135.92 grams of anhydrous DMAC and the slurry was mixed under high shear.

19.1 g of a solution containing acicular TiO₂The slurry was mixed with 100.9 grams of PMDA// ODA prepolymer.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 4

6.5 vol% (17.1 wt%) of acicular TiO in PMDA// ODA₂。

A method similar to that described in example 1 was used, except for the following differences. 24.08 g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) was mixed with 135.92 grams of anhydrous DMAC and the slurry was mixed under high shear.

23.96 g of a solution containing acicular TiO₂The slurry was mixed with 96.1 grams of PMDA// ODA prepolymer.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 5

8.5 vol% (21.6 wt%) of acicular TiO in PMDA// ODA₂。

A method similar to that described in example 1 was used, except for the following differences.

24.08 g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) was mixed with 135.92 grams of anhydrous DMAC and the slurry was mixed under high shear.

30.0 g of a solution containing acicular TiO₂The slurry was mixed with 90.0 grams of PMDA// ODA prepolymer.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 6

15 volume percent (34.3 weight percent) TiO with aspect ratio less than 3:1 in PMDA// ODA₂

Comparative example 6 demonstrates that fillers with aspect ratios less than 3:1 result in films with lower storage modulus and higher CTE than example 1 with submicron fillers having aspect ratios of at least 3:1 at 15 volume%. The film is brittle at the edges and is not feasible in commercial manufacturing processes.

The same procedure as described in example 1 was followed except for the following differences. 33.84 grams of a slurry containing DuPont Light Stabilized titanium, 210 (DuPont, Wilmington, Delaware, 25 wt% in DMAC, high shear mixing) was mixed with 86.2 grams of PMDA// ODA prepolymer (20.6 wt% in DMAC).

The material was finished to a viscosity of 1100 poise with PMDA solution.

DuPont titanium 210 is a fine white powder with particle distribution centered in the 130-140nm range on a weight basis. The particles are substantially spherical.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 7

Unfilled BPDA// PPD

The same procedure as described in comparative example 8 was followed, except that the acicular TiO was₂Was not added to the formulation.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative examples 8 to 9 demonstrate that the sub-micron filler of the present disclosure performs unpredictably in all polyimides. In the case of the BPDA// PPD system, the CTE increases significantly (by a factor of more than 2) with the introduction of approximately 15% by volume of acicular TiO 2.

Comparative example 8

14.64 vol% (33.7 wt%) of acicular TiO2 (FTL-110）。

CTE follows needle TiO₂Is increased.

BPDA// PPD prepolymer (69.3 g of a 17.5% by weight solution in anhydrous DMAC) was mixed with 5.62g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) and the resulting slurry was stirred for 24 hours. In a separate vessel, a 6% by weight solution of pyromellitic anhydride (PMDA) was prepared by combining 0.9g of PMDA (Aldrich 412287, Allentown, Pa.) with 15mL of DMAC.

The PMDA solution was slowly added to the prepolymer slurry to achieve a final viscosity of 653 poise. The formulation was stored overnight at 0 ℃ to allow degassing.

The formulation was cast onto the surface of a glass plate using a 25mil doctor blade to form a 3 "x 4" film. The glass is pretreated with a release agent to facilitate removal of the film from the surface of the glass. The film was dried on a hot plate at 80 ℃ for 20 minutes. The film was then lifted off the surface and mounted on a 3 "x 4" pin plate rack.

After further drying at room temperature under vacuum for 12 hours, the fixed film was placed in an oven (Thermolyne, F6000 box oven). The furnace was purged with nitrogen and heated according to the following temperature schedule:

the CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 9

14.64 vol% acicular TiO in BPDA// PPD₂（FTL-110）。

The elongation at break is very low. The film is too brittle to be manufactured.

The same procedure as described in example 1 was used, except for the following differences. 33.99 g of acicular TiO₂(FTL-110, Ishihara Corporation, USA) was mixed with 191.9 grams of anhydrous DMAC. The slurry was mixed under high shear for about 10 to 15 minutes (with a blade speed of about 4000 rpm) using a Silverson Model L4RT high shear mixer (Silverson Machines, LTD, Chesham Baucks, England) equipped with a square-hole, high shear screen.

129.25g of BPDA// PPD were preponderedThe polymer (in a 17.5 wt.% solution of anhydrous DMAC) was mixed with 69.335 grams of a mixture containing acicular TiO₂The slurry of (a) is mixed. The resulting slurry was stirred for 24 hours. In a separate vessel, a 6% by weight solution of pyromellitic anhydride (PMDA) was prepared by combining 0.9g of PMDA (Aldrich 412287, Allentown, PA) with 15ml of dmac.

The PMDA solution was slowly added to the prepolymer slurry to achieve a final viscosity of 998 poise.

After chemical imidization, the film was lifted off the glass surface and mounted on a 3 "x 4" pin bed. The mounted film was placed in an oven (Thermolyne, F6000 box oven). The furnace was purged with nitrogen and heated according to the following temperature schedule:

the CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 10

Unfilled PMDA// ODA

Three 180g portions of PMDA and ODA prepolymer (prepared at about 20.6% in DMAC, a viscosity of about 50 poise) were diluted to 18% polymer solids by the addition of 26g of DMAC to provide three 206g portions of diluted polymer. One of these three diluted prepolymer samples was reacted ("finished") to a viscosity of about 2100 poise (Brookfield DV-II + viscometer with spindle # LV 5) by stepwise dropwise addition of a 6 wt.% PMDA solution in DMAC with thorough stirring to increase the molecular weight (hereinafter referred to as "finished polymer"). After filter pressing the solution through a polypropylene mesh filter disc (45 microns), the solution was degassed under vacuum to remove air bubbles and then cast onto a letter-sized piece of clear polyester film (approximately 3 mils thick). The polyamic acid coated on the polyester sheet was then immersed in a mixture comprising 1/1v/v acetic anhydride and a bath of 3-methylpyridine. After about 2 minutes, once the partially imidized coating began to separate from the polyester sheet, it was removed from the bath and pinned to a pin bed at about 8 "x 8" and allowed to reach room temperature on a laboratory hood for about 10-20 minutes. Next, the film on the pin plate holder was placed in a nitrogen purged oven and purged at about 40 ℃ for 30 minutes, and after the oven was ramped up to 320 ℃ over 70 minutes, held in the oven for 30 minutes, then ramped up to 450 ℃ over about 16 minutes and held there for 4 minutes to cure the polyimide. After cooling, the resulting 2.4 mil (61 micron) film was removed from the oven and pin frame.

The storage modulus (E') via a Dynamic Mechanical Analysis (TA Instruments, DMA-2980, 5 ℃/min) was measured by heating from room temperature to 500 ℃ at 5 ℃/min.

Reheat evaluation between 50 and 350 ℃ Coefficient of Thermal Expansion (CTE) via Thermal Mechanical Analysis (TA instruments, TMA-2940, heating at 10 ℃/min up to 460 ℃ and then cooling and reheating to 500 ℃).

% tensile elongation (Instron model 3345 tensile tester) -0.5 sample width, 1 inch (2.54 cm) gauge length, 1 inch (2.54 cm)/min collet speed.

The results are shown in Table 1.

Comparative example 11

5.4 vol% (10 wt%) talc in PMDA// ODA。

Comparative example 11 demonstrates that performance of talc below about 5.5 vol% is unpredictable.

A portion of the prepolymer of PMDA and ODA (prepared at approximately 20.6% DMAC, approximately 50 poise viscosity) was diluted to 18% polymer solids by the addition of DMAC in a manner similar to comparative example 10. The prepolymer was then mixed with SF310 talc in a Thinky ARE-250 centrifugal mixer for several minutes to create a dispersion of filler in the PAA solution to achieve a loading of about 10 wt% in the PI film. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1 mil (25 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 5 to 9 demonstrate that talc exceeding about 5.5 vol% significantly increases the storage modulus and lowers the CTE while maintaining a suitable elongation at break.

Example 5

14.0 vol% (24 wt%) talc in PMDA// ODA。

The same procedure as described in example 1 was followed except for the following differences. 25 grams of talc (FlextTalc 610, Kish Company, Inc., Mentor, OH) was mixed under high shear with 141 grams of anhydrous DMAC.

55.9 grams of this slurry was mixed with 134.7 grams of PMDA// ODA prepolymer.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Example 6

18% by volume (30% by weight) of talc in PMDA// ODA。

The second part 206g of the diluted prepolymer from comparative example 10 was mixed with 14.77g of FlextTalc 610 (Lot M1085, Kish Co., Mentor, OH) in a similar manner to comparative example 11. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 3.2 mil (81 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 7

18.1% by volume (30% by weight) of talc in PMDA// ODA。

A third portion 206g of the diluted prepolymer from comparative example 10 was mixed with 14.77g of SF310 talc (Kish co., Mentor, OH) in a similar manner to comparative example 11. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 3.2 mil (81 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 8

34% by volume (50% by weight) of talc in PMDA// ODA。

The PMDA// ODA prepolymer was mixed with SF310 talc in a similar manner to comparative example 11 to obtain a loading of about 50 wt% in the PI film. The finishing, filtration, casting and curing were similar to those described in comparative example 10, with a filler loading of approximately 50 wt% in the polyimide film. A 1.8 mil (46 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 9

43.6 volumes in PMDA// ODA% by weight of talc (60% by weight)。

The PMDA// ODA prepolymer was mixed with SF310 talc in a similar manner to comparative example 11 to obtain a loading of about 60 wt% in the PI film. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1.3 mil (33 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 10 to 11 demonstrate that more than 10 volume percent of the presently disclosed submicron filler in polyimide copolymer significantly increases the storage modulus and lowers the CTE when compared to the unfilled copolymer of comparative example 13.

Example 10

18.1% by volume (30% by weight) of the random copolymer PMDA// ODA/PPD 100//70/30%) Talc。

A portion of 186.87g of the prepolymer from comparative example 13 was mixed with 13.13g of FlextTalc 610 (Lot M6734, Kish Co., Mentor, OH) in a manner similar to comparative example 11. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 2.2 mil (56 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 11

12.6% by volume (30% by weight) of the PMDA// ODA/PPD 100//70/30 random copolymer%) acicular TiO₂。

A portion 173g of the prepolymer from comparative example 13 was admixed with 27g of milled/dispersed 45% by weight of acicular TiO in a similar manner to comparative example 11₂(FTL-110 powder from Ishihara Corp. (USA)) in DMAC. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 1.1 mil (28 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Comparative example 12

Unfilled PMDA// ODA/PPD 100//70/30 random copolymer。

In a 1.5 liter beaker in a nitrogen purged glove box, 15.118g of PPD (0.1398 moles) and 65.318g (0.3262 moles) of ODA were added to 779.2g of DMAC, with thorough stirring with a mechanical stirrer. After brief mixing at room temperature, 99.612g (0.4567 moles) of PMDA was slowly added, maintaining the temperature below 40 deg.C, followed by the addition of 41.0g of DMAC and allowing the reaction to proceed for about 2 hours. The resulting prepolymer solution (dianhydride to diamine 98% overall stoichiometry, 18% polymer solids) was decanted into bottles and stored in a refrigerator until use. A portion of the prepolymer was finished as in example a, filtered and the film was then cast and cured similarly to comparative example 10. A 1.4 mil (36 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 12 and 13 demonstrate that the sub-micron filler mixture of the present disclosure significantly increases the storage modulus and decreases the CTE when compared to the unfilled polyimide in comparative example 10.

Example 12

10% by weight of talc, 20% by weight of acicular TiO in the PMDA// ODA polymer₂。

A portion of 168.21g of PMDA and ODA prepolymer (prepared at about 20.6% in DMAC, viscosity of about 50 poise) was combined with 4.60g of SF310 talc and 20.46g of FTL-110 TiO₂(45% slurry as described in example 11) were mixed together to obtain a 10 wt% and 20 wt% loading (30 wt% total) of submicron filler in the PI film, respectively. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1.0 mil (25 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 13

10% by weight of talc, 20% by weight of acicular TiO in the PMDA// ODA polymer₂。

In a similar manner to example 12, a portion of 173.13 PMDA// ODA prepolymer was combined with 9.45g of SF310 talc and 10.50g of FTL-110 TiO₂(45% slurry as described in example 11) were mixed together to obtain a 20 wt% and 10 wt% loading (30 wt total) of submicron filler in the PI film, respectively. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 2.2 mil (56 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 14 and 15 demonstrate TiO of the present disclosure₂The sub-micron filler has no CTE in all polyimidesThe same way is performed.

Example 14

11.7% by volume of acicular TiO in the MDA// ODA/PPD 100//80/20 block copolymer₂(28.23 wt%)。

TiO with high aspect ratio in the Block copolymer of example 14₂The storage modulus was significantly increased compared to the unfilled block copolymer of comparative example 13 while maintaining the CTE to a large extent.

A similar procedure as described in example 1 was used, except for the following differences. To prepare the prepolymer, 1.36 grams of PPD was mixed with 110.0 grams of anhydrous DMAC and stirred and gently heated at 40 ℃ for approximately 20 minutes. 2.71 grams of PMDA was then added to the mixture to form the first block, which was stirred under mild heating (35 to 40 ℃ C.) for about 2.5 hours. The mixture was allowed to cool to room temperature.

To this formulation, 10.10 grams of ODA was added and allowed to dissolve into the formulation for about 5 minutes. An ice water bath was then used to control the temperature during the subsequent PMDA addition. 10.9g of PMDA was slowly added to the mixture. An additional 15 grams of DMAC was added to the formulation and the reaction was allowed to stir for 90 minutes with gentle heating (30 to 35 ℃). The mixture was allowed to stir at room temperature for about 18 hours.

In a different vessel, 20.88 grams of acicular TiO was added₂(FTL-11) was mixed with 25.52g of anhydrous DMAC and 0.426g of Solplus D540 (Lubrizol) and milled in a jar mill for 24 hours using 8mm spherical milling media.

14.2 g of a solution containing TiO₂The slurry of (a) was mixed with 105.8 grams of the prepolymer formulation described above.

The modified heating method was used as follows:

the CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Example 15

17.5 vol% acicular TiO in the PMDA// ODA/PPD 100//80/20 Block copolymer₂(38.5 wt%)。

In the block copolymer 15, TiO having a high aspect ratio₂The storage modulus was significantly increased compared to the unfilled block copolymer in comparative example 13, while the CTE was slightly lowered in the transverse direction.

A similar procedure as described in example 1 was used, except for the following differences. To prepare the prepolymer, 1.36 grams of PPD was mixed with 113.0 grams of anhydrous DMAC and stirred and gently heated at 40 ℃ for approximately 20 minutes. 2.71 grams of PMDA was then added to the mixture to form the first block, which was stirred under mild heating (35 to 40 ℃ C.) for about 2.5 hours. The mixture was allowed to cool to room temperature.

To this formulation, 10.10 grams of ODA was added and allowed to dissolve into the formulation for about 5 minutes. An ice water bath was then used to control the temperature during the subsequent PMDA addition. 10.9g of PMDA was slowly added to the mixture. An additional 12 grams of DMAC was added to the formulation and the reaction was allowed to stir for 90 minutes with gentle heating (30 to 35 degrees). The mixture was allowed to stir at room temperature for about 18 hours.

In a different vessel, 20.88 grams of acicular TiO was added₂(FTL-11) was mixed with 25.52g of anhydrous DMAC and 0.426g of Solplus D540 (Lubrizol) and used in a 4 "(inside diameter) nylon jar grinder with 8mm sphereThe milling media was milled for 24 hours, rotating at 80 rpm.

15.34 g of a solution containing TiO₂The slurry was mixed with 72.0 grams of the prepolymer formulation described above.

The modified heating method was used as follows:

the CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Comparative example 13

Unfilled PMDA// ODA/PPD 100//80/20 Block copolymer。

The same procedure as described in example 15 was used, except that the acicular TiO was₂The slurry was not added to the formulation. The final viscosity of the formulation is 1000 to 1200 poise.

The CTE, E' and elongation at break were measured as in example 1.

The results are shown in Table 1.

Example 16

12.6 vol% of acicular TiO₂(30% by weight) of a filled PMDA// ODA/PPD100//70/30 block copolymer。

Example 16 demonstrates acicular TiO according to the present disclosure₂Submicron fillers do not behave in the same way for CTE in all polyimides. Compared with in

The unfilled block copolymer of comparative example 14 had an increased CTE, but remained within the desired range.

A portion 173g of the prepolymer from comparative example 14 was admixed with 27g of milled/dispersed 45% by weight of acicular TiO in a similar manner to comparative example 11₂(FTL-110 powder from Ishihara Corp. (USA)) in DMAC. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 3.0 mil (76 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Comparative example 14

Unfilled PMDA// ODA/PPD 100//70/30 Block copolymer。

In a 1.5 liter beaker in a nitrogen purged glove box, 15.115g of PPD was added to 396.7g of DMAC with thorough stirring with a mechanical stirrer. After brief mixing at room temperature (some but not all of the PPD had dissolved), 28.962g of PMDA was slowly added to maintain the temperature below 40C. The dissolved and reacted monomers and the polyamic acid (PAA) solution were stirred for 1 hour. Subsequently, the solution was diluted with 382.3g of DMAC and then 65.304g of ODA were added. The solution was stirred for 30min and the ODA was dissolved in the PAA solution. Subsequently, 70.627g of PMDA followed by 41.0g of DMAC were slowly added and the reaction was allowed to proceed for about 2 hours. The resulting prepolymer solution (dianhydride to diamine 98% overall stoichiometry, 18% polymer solids) was decanted into bottles and stored in a refrigerator until use. A portion of 180g of this prepolymer was trimmed to about 2200 poise as in comparative example 10, filtered, and the film was then cast and cured similarly to comparative example 10. The properties of the resulting 2.2 mil (56 micron) film.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 17-20 demonstrate that block copolymers with talc in excess of about 5.5 vol% significantly increase storage modulus and maintain adequate elongation at break while maintaining CTE.

Example 17

18.1% by volume of talc (30% by weight) filled PMDA// ODA/PPD 100//70/30 blocksSegmented copolymers。

A portion of 186.87g of the prepolymer prepared in comparative example 14 was mixed with 13.13g of SF-310 talc (Lot M685, Kish Co., Mentor, OH) in a manner similar to comparative example 11. The filler comprising PAA solution was finished as similar to comparative example 10 to give a viscosity of approximately 2000 poise. The solution was pressure filtered through a 45 micron polypropylene screen and degassed under vacuum to remove air bubbles. The films were cast and cured similarly to comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 2.6 mil (66 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 18

18.1% by volume of talc (30% by weight) filled PMDA// ODA/PPD 100//70/30 blocksSegmented copolymers。

A portion of 186.87g of the prepolymer from comparative example 14 was mixed with 13.13g of FlextTalc 610 (Lot M1085, Kish Co., Mentor, OH) in a manner similar to comparative example 11. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 2.9 mil (74 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 19

25.6 volume percent talc (40 wt.%) filled PMDA// ODA/PPD 100//70/30 blocksSegmented copolymers。

The PMDA// ODA/PPD 100//70/30 blocked prepolymer was mixed with SF310 talc in a similar manner to comparative example 15 to achieve a loading of about 40 weight percent in the PI film. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1.8 mil (46 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 20

34% by volume of talc (50% by weight) filled PMDA// ODA/PPD 100//70/30 blocksSegmented copolymers。

A blocked prepolymer was prepared in a similar manner to comparative example 14 using the ratio of ODA to PPD 70/30. A portion of 171.75g of this prepolymer was then mixed with 28.255g of SF310 talc in a manner similar to comparative example 11 to obtain about 50 weight percent loading in the PI film. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1.5 mil (38 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Comparative example 15

5.4 bodiesVolume% talc (10% by weight) filled PMDA// ODA/PPD 100//70/30 blocksSegmented copolymers。

Comparative example 15 demonstrates that talc below about 5.5 volume percent does not significantly increase storage modulus.

A blocked prepolymer was prepared in a similar manner to comparative example 14 using the ratio of ODA to PPD 70/30. A portion of 187.16g of this prepolymer was then mixed with 3.48g of SF310 talc in a manner similar to comparative example 11 to obtain about 10 weight percent loading in the PI film. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 1.7 mil (43 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Examples 21-24 illustrate the ability to include additional co-monomers in the compositions of the present invention and still obtain the desired properties.

Example 21

18.1% by volume of talc (30% by weight) of a filled PMDA/BPDA// ODA/PPD95/5//70/30 Block copolymer

In a manner similar to that in comparative example 14, a prepolymer was produced from 14.988g of PPD and 28.720g of PMDA in 393.4g of DMAC, followed by dilution with 386.8g of DMAC, followed by the addition of 64.758g of ODA, followed by 6.796g of BPDA (which was allowed to dissolve/react), followed by 64.998g of PMDA, followed by 41.0g of DMAC. A portion of 186.8g of this prepolymer was mixed with 13.17g of SF310 talc (Lot M685, Kish co., Mentor, OH) analogously to comparative example 11, worked up as in comparative example 10, and the film was then cast and cured analogously to comparative example 10. A 2.0 mil (51 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 22

12.6 vol% (30 wt%) of acicular TiO₂Filled withPMDA/BPDA// ODA/PPD95/5//70/30 Block copolymer。

In a manner analogous to example 21, a portion of 172.7g of the prepolymer from example 21 was admixed with a portion of 27.3g of TiO as described in example 16₂And (4) mixing the slurry. Finishing, filtration, casting and curing were similar to those described in comparative example 10. The filler loading in the polyimide film was about 30 wt%. A 2.2 mil (56 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 23

18.1% by volume of talc (30% by weight) of a filled PMDA/BPDA// ODA/PPD75/25//70/30 Block copolymer

In a manner similar to that in comparative example 14, a prepolymer was produced from 14.407g of PPD and 27.607g of PMDA in 378.1g of DMAC, followed by dilution with 401g of DMAC, followed by the addition of 62.249g of ODA, followed by 32.666g of BPDA (to dissolve/react it), followed by 43.106g of PMDA, followed by 41.0g of DMAC. A portion of 186.8g of this prepolymer was mixed with 13.17g of SF310 talc (Lot M685, Kish co., Mentor, OH) analogously to comparative example 11, finished, cast and cured to a film analogously to comparative example 10. A 1.7 mil (43 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

Example 24

12.6 vol% (30 wt%) of acicular TiO₂Filled PMDA/BPDA// ODA/PPD75/25//70/30 Block copolymer。

In a manner analogous to example 23, a portion of 172.7g of the prepolymer from example 23 was admixed with a portion of 27.3g of TiO as described in example 16₂And (4) mixing the slurry. Finishing, filtration, casting and curing were similar to those described in comparative example 10. A 2.3 mil (58 micron) film was produced.

The CTE, E' and elongation at break were measured as in comparative example 10.

The results are shown in Table 1.

The following examples demonstrate the effect of the characteristics of particles (aspect ratio less than 3: 1) on the characteristics of polyimide films for high aspect ratio platelet fillers (aspect ratio greater than 3: 1). The platelet filler results in advantageously higher modulus and lower CTE at equivalent weight loading. (notably, while the average particle sizes of the two fillers appear to be significantly different by particle size analysis (Horiba LA-930 particle size analyzer) (significantly larger for platelets), it is believed that the effect on the properties is primarily due to the filler shape, rather than any difference in average particle size).

Comparative example 16

In PMDA// ODA (40 wt%) Al with aspect ratio less than 3:1₂O₃(particle)。

A portion of the polyamic acid prepolymer of PMDA and ODA (prepared at about 20.6% in DMAC, approximately 50 poise viscosity) was mixed with a particulate alumina filler (Martoxid MZS-1, Albermarle corporation) under a Silverson (model L4 RT-A) high shear mixer. The amount of alumina was chosen so as to ultimately produce a polyimide film with a final 40 wt% alumina loading in polyimide. The polyamic acid was then further reacted ("worked-up") to a viscosity of about 537 poise (Brookfield DV-II + viscometer with a # LV5 spindle) by stepwise addition of a 6 wt% solution of PMDA in DMAC, thorough mixing with a high torque mechanical mixer/stirring blade. The polymer was then cast on a glass plate and heated to about 80 ℃ until a tack free film was obtained. The film was carefully peeled off the glass and placed on a pin-board rack and placed in a circulating air oven and the temperature was slowly ramped up to 320 ℃ and held there for 30 minutes. The film was then removed from the 320 ℃ oven and placed in a 400 ℃ hot air oven for 5 minutes. The polyimide film on the pin frame was then removed from the oven and allowed to cool to room temperature. The film is then separated from the needle board frame.

E' was measured as in comparative example 10. CTE was measured on the same instrument and at the same rate as in comparative example 10, except that the sample was heated to 380 ℃, then cooled, and reheated to 380 ℃, and evaluated for reheating between 50 and 350 ℃.

The results are shown in Table 1.

Example 25

Al with aspect ratio greater than 3:1 in PMDA// ODA (40 wt.%)₂O₃(plate shape)。

In a manner similar to comparative example 16, a portion of the PMDA// ODA prepolymer was mixed with the same loading level of platelet-shaped alumina (a "Platyl" from Advanced Nanotechnology Limited, Australia) as the particular alumina from comparative example 16 and finished to a Brookfield viscosity of 502 poise. The filled polymer solution was cast and thermally cured as in comparative example 16.

E' was measured as in comparative example 10. CTE was measured on the same instrument and at the same rate as in comparative example 16.

The results are shown in Table 1.

It is noted that not all of the acts described above in the general description or the examples are required, that a portion of a particular act may not be required, and that additional acts other than those described may also be performed. Further, the order in which each of the acts is listed need not be the order in which they are performed. After reading this specification, skilled artisans will be able to determine which behaviors can be used for their specific needs or desires.

In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims.

When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper and lower values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

Claims (15)

1. A film composition comprising:

A) a polyimide derived from:

a) at least one aromatic dianhydride component selected from the group consisting of rigid rod dianhydride, non-rigid rod dianhydride and combinations thereof, and

b) at least one aromatic diamine component selected from the group consisting of rigid rod diamines, non-rigid rod diamines, and combinations thereof;

wherein the mole ratio of dianhydride to diamine is 48-52:52-48 and the ratio of X: Y is 20-80:80-20, based on the total dianhydride component and the total diamine component of the polyimide, wherein X is the mole percentage of rigid rod dianhydride and rigid rod diamine and Y is the mole percentage of non-rigid rod dianhydride and non-rigid rod diamine; and

B) submicron filler:

a) less than (number average) 550 nanometers in at least one dimension;

b) having an aspect ratio greater than 3: 1;

c) less than the film thickness in all dimensions;

d) present in an amount of 10% to 45% by volume of the film; and is

Wherein the film has a thickness of 5 to 150 microns.

2. A film composition according to claim 1, wherein said sub-micron filler is less than 400 nanometers in at least one dimension.

3. A film composition according to claim 1, wherein said sub-micron filler is less than 200 nanometers in at least one dimension.

4. A thin film composition according to claim 1, wherein said sub-micron filler is selected from the group consisting of oxides, nitrides, carbides, and combinations thereof.

5. The film composition according to claim 1, wherein the sub-micron filler is acicular titanium dioxide, talc, SiC fiber, platy Al₂O₃Or mixtures thereof.

6. The film composition according to claim 1, wherein:

a) at least 70 mole percent of the aromatic dianhydride component is pyromellitic dianhydride; and is

b) At least 70 mole% of the aromatic diamine component is 4,4' -diaminodiphenyl ether.

7. The film composition according to claim 6, wherein the sub-micron filler is acicular titanium dioxide, talc, SiC fibers, platy Al₂O₃Or mixtures thereof.

8. The film composition according to claim 1, wherein:

a) at least 75 mole percent of the aromatic dianhydride component is pyromellitic dianhydride; and is

b)70 mol% of 4,4' -diaminodiphenyl ether and 30 mol% of 1,4 diaminobenzene are used as the aromatic diamine component.

9. The film composition of claim 1, wherein the polyimide is a block copolymer.

10. The film composition according to claim 9, wherein the block copolymer is derived from 4,4' -diaminodiphenyl ether and 1,4 diaminobenzene with pyromellitic dianhydride and 3,3',4,4' -biphenyltetracarboxylic dianhydride.

11. The film composition according to claim 9, wherein the block copolymer is derived from:

a)10 to 40 mole% pyromellitic dianhydride and 1,4 diaminobenzene blocks;

b)90 to 60 mole% pyromellitic dianhydride and 4,4' -diaminodiphenyl ether blocks.

12. The film composition according to claim 11, wherein the sub-micron filler is acicular titanium dioxide, talc, SiC fiber, platy Al₂O₃Or mixtures thereof.

13. A thin film composition in accordance with claim 1, wherein said sub-micron filler is coated with a coupling agent, a dispersant, or a combination thereof.

14. The film composition of claim 1 wherein the polyimide is a random copolymer derived from 4,4' -diaminodiphenyl ether and 1,4 diaminobenzene with pyromellitic dianhydride and 3,3',4,4' -biphenyltetracarboxylic dianhydride.

15. The film composition of claim 1 wherein the polyimide is a random copolymer derived from 4,4' -diaminodiphenyl ether and 1,4 diaminobenzene with pyromellitic dianhydride.