Light output device
FIELD OF THE INVENTION
The present invention relates to a light output device comprising at least one light source and a conductive structure electrically connected to said light source , said light source and conductive structure being sandwiched between substrates. The present invention also relates to a method for manufacturing a light output device.
BACKGROUND OF THE INVENTION
Light emitting diodes (LEDs) have been used for illumination panels for some time, where a large number of low power LEDs are embedded in a laminated glass structure. The LEDs in such a structure are connected to each other using a structured conductive layer, for instance a FTO layer. Such a laminated glass structure is typically manufactured by permanently bonding two or more glass plates with an interlayer, for instance polyvinylbutyral (PVB), under heat and pressure, to create a single structure. The conductive layer can be connected to an external power supply using copper foils, which are also embedded in the glass structure. In an existing method the glass plates are broken in order to connect an external power supply to the copper foils. However, this method has the drawback that a strip of glass over the full length of the breaking zone is generated, i.e. an inaccurate amount of glass material is removed from the glass structure. A further drawback with this method is that optical properties may be affected in an uncontrollable manner.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the above described drawbacks, and to provide an improved light output device.
This and other objects that will be apparent from the following summary and description are achieved by a light output device, and a method for manufacturing a light output device, according to the appended claims.
According to an aspect of the present invention, there is provided a light output device comprising at least one light source and a conductive structure electrically connected to said light source, said light source and conductive structure being sandwiched between substrates. At least one of said substrates is provided with a through hole exposing at least part of said conductive structure, thereby enabling electrical interconnection between said conductive structure and an external power supply.
Thus, easy and robust power supply of light sources that are sandwiched between substrates is enabled. The conductive structure can be exposed at certain selected positions. Thus, the size of the exposure can be adapted to the size of a power supply connection in order to minimize the loss of substrate material. As the light sources are electrically connected with each other using a conductive structure, a large number of light sources embedded between substrates can be powered via a through hole. A through hole may be realized by using a prefabricated substrate having a through hole. Alternatively, a through hole may be provided after laminating the substrates.
The light sources may be any kind of light sources suitable for use in an illumination panel, such as, for example, semiconductor-based light sources, including light- emitting diodes (LEDs) and semiconductor lasers, organic light emitting diodes (OLEDs), or fluorescent light sources.
In an embodiment, the conductive structure comprises at least two conductive wires, to which the light sources are arranged. Each light source is electrically coupled to at least two adjacent wires. Since one of the substrates is provided with one or several through holes the wires are exposed to the outside world enabling easy connection with a power supply in order to power the light sources. For instance, light emitting diodes (LEDs) are suitable to be arranged on such conductive wires.
In another embodiment, an inner surface of said through hole is coated with a conductive layer, such as a metal layer, which can be electrically connected to the conductive structure. The conductive layer is connectable to an external power supply. The conductive layer provides for a robust connection between the conductive structure and an external power supply. Thus, each individual wire will stick out and establish contact with the coated surface of the hole. Alternatively, the wire may be permanently connected to the metallization by a soldering process, in which a solder wets both the through hole metal and the wire. Thus a robust and high quality connection is achieved. Furthermore, the use of wires result in a cost-effective light output device.
The conductive structure may comprise a structured thin film layer, such as a transparent FTO or ITO layer, in order to enable power supply of the light sources. In this case, the light output device e.g. comprises an enforcement element electrically connected to the thin film layer. Such an enforcement element provides for a robust connection between an external power supply and the thin film layer. In case a through hole exposing the conductive structure is provided after laminating the substrates, the enforcement element forms a resistance protecting the thin film layer from being damaged by the action of the through hole generation. The enforcement element may be formed by a metal strip. Alternatively, the enforcement element may be formed by a sheet of conductive eleastomer.
The light source device may comprise a plurality of light sources, wherein the conductive structure is arranged to electrically connect said light sources with each other.
In a currently preferred embodiment, the light source(s) is light emitting diode(s) (LED). LEDs are durable structures with a long lifetime, which reduces the maintenance needed. Furthermore, they have low power consumption. By using LEDs, a cost-effective solution is thus achieved.
It is noted that the invention relates to all possible combinations of features recited in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention.
Fig. 1 shows a perspective view of a part of a light output device according to a first embodiment of the present invention.
Fig. 2 shows a perspective view of a part of a second embodiment according to the present invention.
Fig. 3 shows a sectional view of a part of the embodiment shown in Fig. 2. Fig. 4 shows steps of a method for the manufacturing of a light source device according to an embodiment of the present invention.
Fig. 5 shows steps of an alternative method for the manufacturing of a light source device according to an embodiment of the present invention.
DETAILED DESCRIPTION Fig. 1 is a schematic, perspective view of a part of a light output device 1 according to a first embodiment of the present invention. The light output device 1 comprises a plurality of light sources, in this case light emitting diodes 2 (LEDs) arranged in a LED array grid 3. The LED array grid 3 further comprises a conductive structure 4, which in this embodiment is formed by a number of electrically conducting wires 5. Each LED 2 is electrically coupled to at least two adjacent wires 5. The LED array grid 3 is sandwiched between two substrates, in this case glass plates 6 and 7. The space between the glass plates 6 and 7 is filled with polyvinylbutyral (PVB) 10. The PVB provides a strong sandwich structure by bonding the glass plates and also reduces reflections due to the optical properties ofPVB.
At least one through hole 8 is provided in one of the substrates in order to expose the conductive structure 4 and thereby enable interconnection between the conductive structure 4 and an external power supply (not shown). A number of through holes 8 are provided in the upper glass plate 7 exposing wires 5 of the conductive structure 4, see enlarged part of Fig. 1. In this embodiment, an inner surface of each through hole 8 is coated with a conductive layer, such as metal 9. The wires 5 of the LED array grid 3 are aligned with through holes 8 in such a way that individual wires 5 will stick out and establish contact with the metal 9 of a through hole 8. Alternatively, wires 5 may be permanently connected to the metal 9 by means of a soldering process, in which a solder wets both the metal 9 and the wire 5. It is however also possible to directly connect a power source to the exposed wires, for instance using soldering. In this case, the through holes are not coated with a conductive layer as in the embodiment shown in Fig. 1. For instance, an external power supply may be connected to the wires by means of soldering.
Fig. 2 shows a perspective view of a part of a light source device 1 according to a second embodiment. Essentially all features disclosed in the first embodiment are also present in the second embodiment with reference numerals identifying similar or identical features. Having mentioned this the description will focus on explaining the differing features. Instead of electrically connecting the LEDs using wires, the LEDs are in the second embodiment electrically connected by means of a conductive structured thin film layer 15, such as ITO or FTO layer. Conductive enforcement elements 16, in this case formed by metal strips, that are electrically connected to the conductive structured thin film layer 15, are provided between the laminated glass plates 6, 7. The enforcement elements 16 are electrically connected to different layers of the thin film layer 15 to enable a power supply to the LEDs (not shown). Through holes 8 are provided in the upper substrate 7 to expose the enforcement element 16 for enabling interconnection of the conductive structure 4 with an external power supply (not shown). For instance, an external power supply may be connected to the enforcement element(s) by means of soldering. The space between the glass plates 6 and 7 is filled with glue, such as PVB 10, see Fig. 3, which shows a sectional view of a through hole area of the embodiment disclosed in Fig. 2. Fig. 4 shows selected steps of a method for the manufacturing of a light source device according to an embodiment of the present invention.
In a first step Sl, a glass plate is provided with through holes. The through holes may be provided using powder blasting. A blasting mask, exposing the glass plate where it is desired to remove material, is then provided on the glass plate to be processed. Through holes are then generated by directing a jet of abrasive powder onto the surface of the mask, which is present on the glass plate to be processed. It is also possible to carry out the powder blasting without using a mask. In this case, small nozzles may be used in order to direct the jet of abrasive powder to selected areas for providing through holes. The through holes are currently preferably generated at the periphery of the glass plate. The number and location of through holes are adapted to the present need of connections for the actual LED array grid. The through holes are holes through at least one of the two glass plates. After the blasting process, the blast-resistant material is removed in case of using a mask.
An inner surface of each trough hole is then optionally coated with a conductive layer, such as a metal layer, in step S2.
In step S3, there is provided a LED array grid, in this case a LEDs-on-wire grid, on top of the glass plate with through holes. A method for manufacturing such a LED array grid per se is disclosed in non-prepublished European patent application No. 06125674.9, herein incorporated by reference. In step S4, the wires of the LED array grid are aligned with the holes, so as to enable access of the wires through the holes.
Alternatively, in step S3, a structured thin film conducting layer, such as an ITO or FTO layer, is first applied on the glass plate, for instance using laser. Then, a LED array grid comprising a number of LEDs is provided on the assembly and connected to the conducting layer. In this case, step S4 includes providing enforcement elements in alignment with the holes, and are electrically connected to the structured thin film layer.
After aligning the wires and/or enforcement elements with the holes, a bonding layer, such as polyvinylbutyral (PVB), is applied on top of the LEDs and/or wires, in step S5.
A second substrate is then provided on top of the LED array grid 3 and the PVB in order to sandwich the LED array grid between the first and the second glass plates, in step S6.
In step S7, the glass plates are then laminated by permanently bonding the glass plates with the bonding interlayer, under heat and pressure, to create a single structure. The polyvinylbutyral (PVB) provides for a strong sandwich structure bonding the glass plates.
In case carrying out the optional step S2, each individual wire will stick out and establish contact with the conductive layer provided on an inner surface of a through hole. Alternatively, the wire may be permanently connected to the conductive layer by a soldering process, in which a solder wets both the conductive layer provided on an inner surface of a through hole and the wire.
Power supply to the wires of the LED array grid via the conductive layer, which is provided on a inner surface of each through hole, and/or via a solder is thus enabled. Alternatively, an external power supply may be directly connected, for instance by means of soldering, to the wires and/or enforcement elements. In this case, the optional step S2 is not needed.
Fig 5 shows selected steps of an alternative method for the manufacturing of a light source device according to an embodiment of the present invention. In the first step SlO, there is provided a LED array grid, such as a LEDs-on- wire or a grid comprising a number of LEDs, as described above, on top of the glass plate. Alternatively, and as described above, a structured thin film layer, such as an ITO or FTO layer, a LED array grid comprising a number of LEDs and enforcement elements are provided on the assembly. In the next step S 11 , a bonding layer, such as polyvinylbutyral (PVB), is applied on top of the LEDs and/or wires and/or enforcement elements.
Then, a second glass plate is provided on top of the assembly, in step S 12.
After that, the glass plates are laminated, as described above, in step S 13.
In the next step S 14, the laminated sandwich structure is provided with through holes, for instance using powder blasting in the same manner as described above. In case a LEDs-on-wire grid is used, the trough holes are provided at selected areas in order to expose wires of the LEDs on wire grid. In case an FTO or ITO layer is used, the holes are provided to expose the enforcement elements, which are electrically connected to the conductive layer. Providing through holes after laminating, as described here, is possible since the wires respective the enforcement elements will resist the action of the abrasive powder.
The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. It will be appreciated that the described embodiment of the invention can be modified and varied by a person skilled in the art without departing from the inventive concept defined in the claims. It is realized by a person skilled in the art that features from various embodiments disclosed herein may be combined with one another in order to provide further alternative embodiments. In the disclosed embodiments, two substrates form part of the sandwich structure. Alternatively, additional substrates may form part of the sandwich structure. Also, each substrate may be formed by several parts.
In the disclosed embodiments, the substrates embedding the LED array grid are formed by transparent glass plates. Alternatively, transparent organic films like PET may be used. In this case, through holes are e.g. generated using punching.
The coated through holes are easy-to-contact more macroscopic parts for further connections to the outside world. Direct soldering of external wires, flexible substrates and even attachment of active circuitry (e.g. packaged ICs) onto the coated through hole or its footprint around is becomes possible. Furthermore, a LED connection method based on FTO conductive patterns may be combined with electrically conductive wires. This might require the use of a conductive adhesive process to electrically bond the wire to the metal layer on the through hole.
In the first embodiment the LED array grid is bonded to the glass plates by means of lamination using glue between the plates. The LED array grid can also be bonded to the glass plate by means of self-bonding wires. Such wires are coated with a first strong isolating layer - this layer has a high melting point (>300°C) - and a second isolation layer with a lower melting point (<200°C). This second layer is in case of making coils used for bonding the wires within a coil to make it rigid. The heat can be applied by a current through the wires or by placing the coil in an oven, it is also possible to use a solvent to obtain adhesion. In cases where the LEDs are thinner than the wires the same bonding principle can be used by applying temperature and pressure on the glass-LED sandwich structure.
An alternative option of laminating the sandwich structure is filling the space between the glass plates with a liquid material that solidifies by curing.