本發明係關於一種包含聚合物膜之相位差膜。進而，本發明係關於一種相位差膜與偏光元件積層而成之偏光板及具備該橢圓偏光板之圖像顯示裝置。The present invention relates to a phase difference film including a polymer film, and further relates to a polarizing plate formed by laminating the phase difference film and a polarizing element, and an image display device having the elliptical polarizing plate.
作為行動電話、智慧型手機、平板終端等行動設備，汽車導航裝置等車載裝置，電腦用顯示器、電視等各種圖像顯示裝置，使用有液晶顯示裝置、有機EL(Electroluminescence，電致發光)顯示裝置。Liquid crystal display devices and organic EL (Electroluminescence) display devices are used as various image display devices such as mobile phones, smartphones, and tablet terminals, in-vehicle devices such as car navigation devices, and computer monitors and televisions.
液晶顯示裝置基於其顯示原理，於液晶單元之兩面配置有偏光元件。於液晶單元與偏光元件之間，出於進行對比度提高或視角擴大等光學補償之目的，存在配置相位差膜之情形。例如，橫向電場效應(In Plane Switching，IPS)方式之液晶顯示裝置中，在相對於偏光元件之吸收軸呈45°度之角度(方位角45°、135°、225°、315°)斜方向進行視認之情形時，黑顯示之漏光較大，易產生對比度之下降、色移，因此於液晶單元與偏光元件之間配置相位差膜，進行光學補償。作為用於此種用途之相位差膜，可例舉正面延遲為波長之一半且Nz＝(nx－nz)/(nx－ny)所定義之Nz係數為0.5者。Liquid crystal display devices are based on their display principles, and polarizing elements are arranged on both sides of the liquid crystal unit. Between the liquid crystal unit and the polarizing element, there is a case where a phase difference film is arranged for the purpose of optical compensation such as improving contrast or expanding viewing angle. For example, in a liquid crystal display device of the transverse electric field effect (In Plane Switching, IPS) method, when viewing at an angle of 45° (azimuth angle 45°, 135°, 225°, 315°) relative to the absorption axis of the polarizing element, the light leakage of the black display is large, which is easy to produce a decrease in contrast and color shift. Therefore, a phase difference film is arranged between the liquid crystal unit and the polarizing element for optical compensation. As a retardation film used for such a purpose, one having a front retardation of half the wavelength and an Nz coefficient defined as Nz=(nx-nz)/(nx-ny) of 0.5 can be cited.
有機EL顯示裝置中，為抑制外界光於金屬電極(陰極)反射而被視認成如鏡面，存在於單元之視認側表面配置圓偏光板(偏光板與具有1/4波長之延遲之相位差膜之積層體)之情形。In an organic EL display device, in order to suppress the external light from being reflected by the metal electrode (cathode) and being seen as a mirror, there is a case where a circular polarizer (a laminate of a polarizer and a phase difference film with a retardation of 1/4 wavelength) is arranged on the viewing side surface of the cell.
作為相位差膜，廣泛使用有非液晶性聚合物之延伸膜。用於IPS方式之液晶顯示裝置之光學補償、有機EL顯示裝置之反射光之遮斷之相位差膜理想的是越為長波長，具有越大之延遲，且遍及可見光之全波長區域，波長與延遲之比為固定。As a retardation film, a stretched film of a non-liquid crystal polymer is widely used. The retardation film used for optical compensation of IPS liquid crystal display devices and shielding of reflected light of organic EL display devices is ideally one that has a greater delay as the wavelength becomes longer, and that covers the entire wavelength range of visible light, with a constant ratio of wavelength to delay.
然而，越為長波長則具有越大之延遲(所謂之「反波長色散」)之材料有限，大部分之聚合物膜係越為長波長則呈現越小之延遲(正色散)，或不論波長如何均呈現大致固定之延遲。提出有如下方法：藉由將積層複數之相位差膜而成之積層相位差板與偏光元件組合，而實現與將反波長色散之相位差膜與偏光元件組合之情形同樣之光學補償。However, there are only a limited number of materials that have a greater delay at longer wavelengths (so-called "reverse wavelength dispersion"). Most polymer films show a smaller delay at longer wavelengths (positive dispersion), or show a roughly constant delay regardless of the wavelength. The following method has been proposed: by combining a multilayer phase difference plate formed by laminating multiple phase difference films with a polarizing element, the same optical compensation as the case of combining a phase difference film with reverse wavelength dispersion with a polarizing element is achieved.
例如，專利文獻1中揭示有藉由將1/2波長板、1/4波長板及偏光元件以各自之光學軸既不平行亦不正交之角度積層，而獲得寬頻帶圓偏光板。專利文獻2中揭示有藉由將Nz係數不同之2片相位差膜以遲相軸方向成為平行之方式積層而實現寬頻帶化，且可降低IPS液晶顯示裝置之色移。[先前技術文獻][專利文獻]For example, Patent Document 1 discloses that a wideband circular polarizer is obtained by laminating a 1/2 wavelength plate, a 1/4 wavelength plate, and a polarizing element at an angle where their respective optical axes are neither parallel nor orthogonal. Patent Document 2 discloses that a wideband is achieved by laminating two phase difference films with different Nz coefficients in a manner where the phase retardation axes are parallel, and that the color shift of an IPS liquid crystal display device can be reduced.[Prior Technical Documents][Patent Documents]
[專利文獻1]日本專利特開平10-63816號公報[專利文獻2]日本專利特開2005-99476號公報[Patent document 1] Japanese Patent Publication No. 10-63816[Patent document 2] Japanese Patent Publication No. 2005-99476
[發明所欲解決之問題][The problem the invention is trying to solve]
藉由將複數之相位差膜積層，可實現與反波長色散之相位差膜同樣之光學補償，但由於需要將複數之膜貼合，故而與以1片膜進行光學補償之情形相比，製造步驟繁雜。因此，需要一種可利用更少片數之膜遍及可見光之寬頻帶實現高精度之光學補償之相位差膜。[解決問題之技術手段]By laminating multiple phase difference films, the same optical compensation as the phase difference film for anti-wavelength dispersion can be achieved, but since multiple films need to be bonded together, the manufacturing steps are more complicated than the case of optical compensation with a single film. Therefore, a phase difference film that can achieve high-precision optical compensation over a wide band of visible light with fewer films is needed.[Technical means to solve the problem]
本發明者等發現，藉由將在厚度方向分子之配向狀態不同之聚合物膜與偏光元件積層，可實現與將不同之波長色散之相位差膜與偏光元件積層之情形同樣之偏光狀態。The inventors of the present invention have found that by laminating a polymer film having different molecular orientations in the thickness direction with a polarizing element, the same polarization state as that achieved by laminating a phase difference film having different wavelength dispersions with a polarizing element can be achieved.
本發明之相位差膜包含具有第一主面與第二主面之1片聚合物膜，且於第一主面積層偏光元件之情形時與於第二主面積層偏光元件之情形時，光自斜方向入射時之偏光之橢圓率不同。The phase difference film of the present invention comprises a polymer film having a first main surface and a second main surface, and the ellipticity of polarized light when light is incident from an oblique direction is different when the first main surface is layered with a polarizing element and when the second main surface is layered with a polarizing element.
光自斜方向入射時之橢圓率係於相位差膜積層偏光元件並使光以與法線方向呈45°之角度入射而進行測定。於波長450～700 nm之範圍每隔10 nm測定於相位差膜之第一主面積層偏光元件之情形時之對於波長λ之光之橢圓率E1(λ)、及於相位差膜之第二主面積層偏光元件之情形時之對於波長λ之光之橢圓率E2(λ)，將各波長下之橢圓率差之絕對值｜E1(λ)－E2(λ)｜之合計設為表裏之橢圓率差ΔE。相位差膜之表裏之橢圓率差例如為0.3以上。The ellipticity when light is incident from an oblique direction is measured by making the light incident at an angle of 45° to the normal direction on the phase difference film multilayer polarizer. The ellipticity E1 (λ) for light of wavelength λ in the case of the first main surface layer polarizer of the phase difference film and the ellipticity E 2 (λ) for light of wavelength λ in the case of the second main surface layer polarizer of the phase difference film are measured every 10 nm in the wavelength range of 450 to 700 nm, and the total of the absolute value of the ellipticity difference |E1 (λ)-E2 (λ)| at each wavelength is set as the frontand back ellipticity difference ΔE. The front and back ellipticity difference of the phase difference film is, for example, 0.3 or more.
相位差膜可為面內之遲相軸方向之折射率nx、面內之進相軸方向之折射率ny及厚度方向之折射率nz滿足nx＞nz＞ny者。相位差膜之波長550 nm下之正面延遲例如為250～600 nm。The retardation film may have a refractive index nx in the in-plane slow axis direction, a refractive index ny in the in-plane fast axis direction, and a refractive index nz in the thickness direction satisfying nx>nz>ny. The front retardation of the retardation film at a wavelength of 550 nm is, for example, 250 to 600 nm.
藉由將相位差膜與偏光元件積層，而獲得偏光板。偏光板可為於相位差膜之第一主面側積層偏光元件而成者，亦可為於相位差膜之第二主面側積層相位差膜而成者。相位差膜之遲相軸方向與偏光元件之吸收軸方向可處於平行或正交關係。The polarizing plate is obtained by laminating a phase difference film and a polarizing element. The polarizing plate can be formed by laminating the polarizing element on the first main surface of the phase difference film, or by laminating the phase difference film on the second main surface of the phase difference film. The retardation axis direction of the phase difference film and the absorption axis direction of the polarizing element can be in a parallel or orthogonal relationship.
進而，本發明係關於一種具備上述偏光板之圖像顯示裝置。作為圖像顯示裝置，可例舉液晶顯示裝置及有機EL顯示裝置。[發明之效果]Furthermore, the present invention relates to an image display device having the above-mentioned polarizing plate. Examples of image display devices include liquid crystal display devices and organic EL display devices.[Effects of the invention]
本發明之相位差膜可利用1片膜實現與積層2片以上之相位差膜之情形同樣之寬頻帶之光學補償。The retardation film of the present invention can realize the same wide-band optical compensation as the case of stacking two or more retardation films by using one film.
圖1係相位差膜10之剖視圖。相位差膜10包含1片聚合物膜。圖2A係以與相位差膜10之第一主面11相對向之方式積層有偏光元件20之偏光板51之剖視圖，圖2B係以與相位差膜10之第二主面12相對向之方式積層有偏光元件20之偏光板52之剖視圖。FIG. 1 is a cross-sectional view of a phase difference film 10. The phase difference film 10 includes a polymer film. FIG. 2A is a cross-sectional view of a polarizing plate 51 on which a polarizing element 20 is stacked in a manner opposite to a first main surface 11 of the phase difference film 10, and FIG. 2B is a cross-sectional view of a polarizing plate 52 on which a polarizing element 20 is stacked in a manner opposite to a second main surface 12 of the phase difference film 10.
圖3係表示相位差膜10與偏光元件20之配置關係之模式圖。圖2A、B所示之偏光板51、52中，如圖3所示，以相位差膜10之遲相軸方向15與偏光元件20之吸收軸方向25正交之方式配置。Fig. 3 is a schematic diagram showing the arrangement relationship between the phase difference film 10 and the polarizing element 20. The polarizing plates 51 and 52 shown in Figs. 2A and 2B are arranged so that the retardation axis direction 15 of the phase difference film 10 and the absorption axis direction 25 of the polarizing element 20 are orthogonal to each other as shown in Fig. 3 .
對於在相位差膜10之第一主面11配置有偏光元件20之偏光板51與在相位差膜10之第二主面12配置有偏光元件20之偏光板52，使光從自法線方向傾斜之方向入射而測定出之橢圓率不同。The polarizing plate 51 having the polarizing element 20 disposed on the first main surface 11 of the retardation film 10 and the polarizing plate 52 having the polarizing element 20 disposed on the second main surface 12 of the retardation film 10 have different ellipticities when light is incident from a direction oblique to the normal direction.
圖4係表示測定從自偏光板之法線方向傾斜45°之方向入射之光之橢圓率之情況之模式圖。以與吸收軸方向25及遲相軸方向15所成之角為45°之旋轉軸R(參照圖3)為中心使偏光板51、52旋轉45°，自與偏光板及法線所成之角為45°之方向對偏光元件20入射自然光N，測定自相位差膜10之出射光P之偏光狀態(橢圓率)。Fig. 4 is a schematic diagram showing the measurement of the ellipticity of light incident from a direction inclined 45° from the normal direction of the polarizing plate. The polarizing plates 51 and 52 are rotated 45° around the rotation axis R (see Fig. 3) which forms an angle of 45° with the absorption axis direction 25 and the retardation axis direction 15, and natural light N is incident on the polarizing element 20 from a direction which forms an angle of 45° with the polarizing plate and the normal direction, and the polarization state (ellipticity) of the light P emitted from the phase difference film 10 is measured.
圖5係表示可見光波長區域內之橢圓率之測定結果之一例，橫軸為波長，縱軸為橢圓率。包含聚合物之延伸膜之通常之相位差板中，於相位差膜之任一主面配置偏光元件之情形時，橢圓率均不會產生差異。本發明之相位差膜如圖5所示，於第一主面11積層有偏光元件20之偏光板51之橢圓率E1與於第二主面12積層有偏光元件20之偏光板52之橢圓率E2不同。FIG5 shows an example of the measurement result of the ellipticity in the visible light wavelength region, with the horizontal axis being the wavelength and the vertical axis being the ellipticity. In a conventional phase difference plate including a stretched film of a polymer, when a polarizing element is arranged on any main surface of the phase difference film, there is no difference in the ellipticity. As shown in FIG5 , the phase difference film of the present invention has a polarizing plate 51 with a polarizing element 20 laminated on the first main surface 11 and a polarizing plate 52 with a polarizing element 20 laminated on the second main surface 12. The ellipticityE1 is different from the ellipticityE2 .
相位差膜之延遲根據波長而不同，因此橢圓率E1、E2根據波長λ而發生變化。橢圓率差可利用偏光板51之波長λ下之橢圓率E1(λ)與偏光板52之波長λ下之橢圓率E2(λ)之差之絕對值｜E1(λ)－E2(λ)｜進行評價。於波長450 nm～700 nm之範圍每隔10 nm計算｜E1(λ)－E2(λ)｜，將其合計值設為相位差膜之表裏之橢圓率差ΔE。表裏之橢圓率差由下述式所示，等於圖5中之26條線段之長度之和。The retardation of the phase difference film varies according to the wavelength, so the ellipticitiesE1 andE2 change according to the wavelength λ. The ellipticity difference can be evaluated by the absolute value of the difference between the ellipticityE1 (λ) of the polarizing plate 51 at wavelength λ and the ellipticityE2 (λ) of the polarizing plate 52 at wavelength λ, |E1 (λ)-E2 (λ)|. |E1 (λ)-E2 (λ)| is calculated every 10 nm in the wavelength range of450 nm to 700 nm, and the total value is set as the ellipticity difference ΔE between the front and back of the phase difference film. The ellipticity difference between the front and back is expressed by the following formula, which is equal to the sum of the lengths of the 26 line segments in Figure 5.
[數1]其中，λk＝450＋10k(nm)[Number 1] Where, λk = 450 + 10k (nm)
[基於使用有積層相位差膜之模型之說明]作為相位差膜產生表裏之橢圓率差之原因，可舉出於表裏分子之配向狀態不同。以下，使用將分子配向不同之2片相位差膜積層而成之光學模型，對表裏之橢圓率差進行說明。[Explanation based on a model using a layered phase difference film]The reason why the phase difference film has a difference in ellipticity between the front and back is that the molecular orientations of the front and back molecules are different. Below, the difference in ellipticity between the front and back is explained using an optical model in which two phase difference films with different molecular orientations are layered.
相位差膜之分子配向狀態可利用Nz係數進行評價。將相位差膜之面內之遲相軸方向之折射率設為nx、進相軸方向之折射率設為ny、厚度方向之折射率設為nz，Nz係數由Nz＝(nx－nz)/(nx－ny)所定義。具有正折射率各向異性之聚合物之延伸膜中，於Nz＝1之情形時(nx＞ny＝nz；正A板)，分子沿膜面內之遲相軸方向單軸配向，於Nz＞1之情形時(nx＞ny＞nz)，分子於膜面內雙軸配向。另一方面，若使分子沿厚度方向配向，則獲得具有nx＞nz＞ny之折射率各向異性且0＜Nz＜1之相位差膜。即，呈現出Nz係數越大，膜面內之分子配向性越高，Nz係數越小，向厚度方向之分子配向性越高。The molecular orientation of the phase difference film can be evaluated using the Nz coefficient. The refractive index in the direction of the slow axis in the plane of the phase difference film is set as nx, the refractive index in the direction of the advanced axis is set as ny, and the refractive index in the thickness direction is set as nz. The Nz coefficient is defined by Nz = (nx-nz)/(nx-ny). In the stretched film of the polymer with positive refractive index anisotropy, when Nz = 1 (nx>ny=nz; positive A plate), the molecules are uniaxially aligned along the slow axis in the film plane, and when Nz>1 (nx>ny>nz), the molecules are biaxially aligned in the film plane. On the other hand, if the molecules are aligned along the thickness direction, a phase difference film with a refractive index anisotropy of nx>nz>ny and 0<Nz<1 is obtained. That is, it is shown that the larger the Nz coefficient is, the higher the molecular orientation is within the film surface, and the smaller the Nz coefficient is, the higher the molecular orientation is in the thickness direction.
圖6A1係表示光自斜方向入射至將Nz係數為0.5、波長550 nm下之正面延遲Re(550)為275 nm之相位差膜31與偏光元件20積層而成之偏光板61之情況。圖6A2係以龐加萊球(S2-S3面投影圖)表示透過偏光元件20之直線偏光之偏光狀態由相位差膜31轉換之情況。FIG6A1 shows the situation where light is incident from an oblique direction on a polarizing plate 61 formed by laminating a phase difference film 31 having an Nz coefficient of 0.5 and a front retardation Re(550) of 275 nm at a wavelength of 550 nm and a polarizing element 20. FIG6A2 shows the situation where the polarization state of linear polarization light passing through the polarizing element 20 is converted by the phase difference film 31 using a Pomchartrain sphere (S2-S3 plane projection diagram).
自法線方向入射並透過偏光元件20之直線偏光由龐加萊球之點P0所示。於光在相對於偏光元件之吸收軸方向呈方位角45°之斜方向入射之情形時(自斜方向視認之情形時)，偏光元件之表觀上之軸方向發生變化。因此，透過偏光元件20之光成為振動方向與光自法線方向入射之情形不同之直線偏光，由龐加萊球之點P1所示。與偏光元件20呈正交偏光地配置之偏光元件會吸收處於隔著點P0而與點P1對象之位置之點P2所示之直線偏光。因此，只要使用相位差膜將點P1之直線偏光轉換為點P2之直線偏光，便可抑制漏光。The linear polarized light incident from the normal direction and passing through the polarizing element 20 is indicated by pointP0 of the Pomcaré sphere. When the light is incident from an oblique direction at an azimuth angle of 45° relative to the absorption axis direction of the polarizing element (when viewed from an oblique direction), the apparent axial direction of the polarizing element changes. Therefore, the light passing through the polarizing element 20 becomes linear polarized light having a vibration direction different from that when the light is incident from the normal direction, as indicated by pointP1 of the Pomcaré sphere. The polarizing element arranged in an orthogonal polarization with respect to the polarizing element 20 absorbs the linear polarized light indicated by pointP2 located opposite point P0 to pointP1 . Therefore, light leakage can be suppressed by using a phase difference film to convertthe linear polarized light at pointP1 into the linear polarized light at pointP2 .
此處，使用有對於波長550 nm之光之正面延遲為275 nm，且波長450～650 nm之範圍內之正面延遲大致固定之相位差膜。於波長550 nm(綠光)時，正面延遲275 nm為波長λ之一半，相當於相位差π。對於波長450 nm(藍光)之正面延遲Re(450)大於λ/2，對於波長650 nm(紅光)之正面延遲Re(650)小於λ/2。Here, a retardation film is used, which has a front retardation of 275 nm for light with a wavelength of 550 nm and a substantially constant front retardation within the wavelength range of 450 to 650 nm. At a wavelength of 550 nm (green light), the front retardation of 275 nm is half of the wavelength λ, which is equivalent to a phase difference of π. The front retardation Re(450) for a wavelength of 450 nm (blue light) is greater than λ/2, and the front retardation Re(650) for a wavelength of 650 nm (red light) is less than λ/2.
對於波長550 nm之綠光，由於相位差膜31之相位差為π，故而若於龐加萊球上表現利用相位差膜31之偏光狀態之轉換，則自點P0移動至處於以點P1為中心旋轉180°之位置之點P2。即，自相位差膜31之出射光P於波長550 nm時位於龐加萊球之點P2(點G)，會被與偏光元件20呈正交偏光地配置之偏光元件吸收，因此不會產生漏光。點G位於龐加萊球之赤道上，因此橢圓率為0(直線偏光)。For green light with a wavelength of 550 nm, since the phase difference of the phase difference film 31 is π, if the conversion of the polarization state using the phase difference film 31 is expressed on the Pomcaré sphere, it moves from pointP0 to pointP2 which is 180° rotated around pointP1 . That is, the outgoing light P from the phase difference film 31 is located at pointP2 (point G) of the Pomcaré sphere at a wavelength of 550 nm, and is absorbed by the polarizing element 20 which is arranged in an orthogonal polarization, so no light leakage occurs. Point G is located on the equator of the Pomcaré sphere, so the ellipticity is 0 (linear polarization).
另一方面，於波長450 nm時，延遲大於λ/2(相位差大於π)，因此於龐加萊球上，以點P1為中心以大於180°之角度旋轉。即，自相位差膜31之出射光P於波長450 nm時超出龐加萊球之赤道，位於南半球之點B，成為橢圓率為負之橢圓偏光(左旋橢圓偏光)。於波長650 nm時，延遲小於λ/2(相位差小於π)，因此自相位差膜31之出射光未到達龐加萊球之赤道而位於北半球之點R，成為橢圓率為正之橢圓偏光(右旋橢圓偏光)。On the other hand, at a wavelength of 450 nm, the delay is greater than λ/2 (the phase difference is greater than π), so the light rotates at an angle greater than 180° around pointP1 on the Pomcharais sphere. That is, the light P emitted from the phase difference film 31 exceeds the equator of the Pomcharais sphere at a wavelength of 450 nm and is located at point B in the southern hemisphere, becoming elliptical polarization with a negative ellipticity (left-handed elliptical polarization). At a wavelength of 650 nm, the delay is less than λ/2 (the phase difference is less than π), so the light emitted from the phase difference film 31 does not reach the equator of the Pomcharais sphere but is located at point R in the northern hemisphere, becoming elliptical polarization with a positive ellipticity (right-handed elliptical polarization).
於利用1片通常之相位差膜進行光學補償之情形時，若以不產生波長550 nm時之漏光之方式設定延遲之值，則於其他波長區域，延遲自最佳值偏離。因此，自相位差膜31之出射光P如圖6A2所示，綠光之橢圓率為0，相對於此，藍光之橢圓率為負，紅光之橢圓率為正，根據波長而橢圓率不同。When optical compensation is performed using a conventional phase difference film, if the delay value is set in a manner that does not cause light leakage at a wavelength of 550 nm, the delay deviates from the optimal value in other wavelength regions. Therefore, the ellipticity of the emitted light P from the phase difference film 31 is 0 as shown in FIG. 6A2. In contrast, the ellipticity of the blue light is negative, and the ellipticity of the red light is positive. The ellipticity varies depending on the wavelength.
於圖6B1所示之偏光板62中，自偏光元件20側積層有Nz係數為0.25、Re(550)＝275 nm之相位差膜32與Nz係數為0.75、Re(550)＝275 nm之相位差膜33。圖6B2係以龐加萊球表示透過偏光元件20之直線偏光之偏光狀態由2片相位差膜32、33依序轉換之情況。In the polarizing plate 62 shown in FIG6B1, a phase difference film 32 with an Nz coefficient of 0.25 and Re(550)=275 nm and a phase difference film 33 with an Nz coefficient of 0.75 and Re(550)=275 nm are laminated from the side of the polarizing element 20. FIG6B2 shows the state of the polarization of the linear polarization light passing through the polarizing element 20 being sequentially converted by the two phase difference films 32 and 33 using a Pomfret sphere.
波長550 nm之光藉由相位差膜32自龐加萊球之點P1移動至赤道上之點G1(點P0)之後，藉由相位差膜33移動至龐加萊球之赤道上之點G2。於波長450 nm時，相位差膜32之延遲大於λ/2，因此波長450 nm之光藉由相位差膜32自龐加萊球之點P1移動至南半球之點B1。相位差膜33之延遲亦大於λ/2，因此波長450 nm之光藉由相位差膜33移動至龐加萊球之赤道上之點B2。相位差膜32、33之延遲小於λ/2之波長650 nm之光藉由相位差膜32移動至龐加萊球之北半球之點R1之後，藉由相位差膜33移動至龐加萊球之赤道上之點R2。The light with a wavelength of 550 nm moves from pointP1 of the Pomkalei sphere to pointG1 (pointP0 ) on the equator through the phase difference film 32, and then moves to pointG2 on the equator of the Pomkalei sphere through the phase difference film 33. At a wavelength of 450 nm, the delay of the phase difference film 32 is greater than λ/2, so the light with a wavelength of 450 nm moves from pointP1 of the Pomkalei sphere to pointB1 in the southern hemisphere through the phase difference film 32. The delay of the phase difference film 33 is also greater than λ/2, so the light with a wavelength of 450 nm moves to pointB2 on the equator of the Pomkalei sphere through the phase difference film 33. The light of wavelength 650 nm delayed by less than λ/2 by the phase difference films 32 and 33 moves to point R1 in the northern hemisphere of the Pomkarano sphere through the phase difference film 32 , and then moves to point R2 on the equator of the Pomkarano sphere through the phase difference film 33 .
如圖6B1所示，藉由積層Nz係數不同之2片相位差膜32、33，較波長550 nm為短波長之光及長波長之光之橢圓率均大致成為0(直線偏光)，從而橢圓率之波長依存變小。因此，可進行精度較使用1片相位差膜31之情形高之光學補償。As shown in FIG6B1, by laminating two phase difference films 32 and 33 with different Nz coefficients, the ellipticity of light with a wavelength shorter than 550 nm and light with a wavelength longer than 550 nm is approximately 0 (linear polarization), thereby reducing the wavelength dependence of the ellipticity. Therefore, optical compensation with higher accuracy can be performed than when using a single phase difference film 31.
圖6C1所示之偏光板63係將上述偏光板62中之相位差膜32與相位差膜33之積層順序更替而成者。於將相位差膜32與相位差膜33之積層視為一體之積層相位差膜39之情形時，偏光板63相當於將圖6B1所示之偏光板62中之積層相位差膜39之表裏更替而成者。The polarizing plate 63 shown in FIG6C1 is formed by sequentially replacing the phase difference film 32 and the phase difference film 33 in the polarizing plate 62. When the phase difference film 32 and the phase difference film 33 are considered as a laminated phase difference film 39 as a whole, the polarizing plate 63 is equivalent to replacing the front and back of the laminated phase difference film 39 in the polarizing plate 62 shown in FIG6B1.
圖6C2係以龐加萊球表示透過偏光元件20之直線偏光之偏光狀態由2片相位差膜33、32依序轉換之情況。B1、G1及R1表示藉由Nz係數為0.75之相位差膜33轉換偏光狀態後之波長450 nm、550 nm及650 nm光之偏光狀態。B2、G2及R2表示藉由Nz係數為0.25之相位差膜32轉換偏光狀態後之波長450 nm、550 nm及650 nm光之偏光狀態。FIG6C2 uses a Pomfret sphere to show the polarization state of the linear polarized light passing through the polarizing element 20 being sequentially converted by the two phase difference films 33 and 32.B1 ,G1 , andR1 show the polarization states of the wavelengths of 450 nm, 550 nm, and 650 nm after the phase difference film 33 with an Nz coefficient of 0.75 has converted the polarization state.B2 ,G2 , andR2 show the polarization states of the wavelengths of 450 nm, 550 nm, and 650 nm after the phase difference film 32 with an Nz coefficient of 0.25 has converted the polarization state.
如根據圖6B2與圖6C2之對比可理解，若將Nz係數不同之2片相位差膜32、33積層而成之積層相位差膜之表裏更替，則於積層相位差膜出射之光P之偏光狀態大有不同。圖6B2中，與使用1片相位差膜之情形相比，基於波長之橢圓率之差異(橢圓率之波長依存)較小，可實現更寬頻帶之光學補償，相對於此，圖6C2中成為如下結果：相較於使用1片相位差膜之情形，因相位差膜之波長色散所引起之橢圓率之波長依存被強調。As can be understood from the comparison between FIG. 6B2 and FIG. 6C2, if the front and back of the multilayer phase difference film formed by stacking two phase difference films 32 and 33 with different Nz coefficients are replaced, the polarization state of the light P emitted from the multilayer phase difference film is greatly different. In FIG. 6B2, compared with the case of using a single phase difference film, the difference in ellipticity based on wavelength (wavelength dependence of ellipticity) is smaller, and a wider bandwidth optical compensation can be achieved. In contrast, FIG. 6C2 has the following result: Compared with the case of using a single phase difference film, the wavelength dependence of the ellipticity caused by the wavelength dispersion of the phase difference film is emphasized.
圖7係表示藉由光學模擬計算自偏光板61之出射光(參照圖6A1)、自偏光板62之出射光(參照圖6B1)及自偏光板63之出射光(參照圖6C1)之可見光波長區域內之橢圓率所得之結果之曲線圖。關於偏光板62，於波長450～650 nm之區域內橢圓率大致為0，橢圓率之波長色散較偏光板61小。另一方面，將積層相位差膜39之表裏更替而成之偏光板63之橢圓率之波長色散較偏光板61大。即，可知將Nz係數不同之2片相位差膜積層而成之相位差膜39於在一面積層偏光元件20之情形時與在另一面積層偏光元件20之情形時，橢圓率產生差異。FIG7 is a graph showing the results of calculating the ellipticity of the light emitted from the polarizer 61 (see FIG6A1), the light emitted from the polarizer 62 (see FIG6B1), and the light emitted from the polarizer 63 (see FIG6C1) in the visible light wavelength region by optical simulation. Regarding the polarizer 62, the ellipticity is approximately 0 in the wavelength region of 450 to 650 nm, and the wavelength dispersion of the ellipticity is smaller than that of the polarizer 61. On the other hand, the wavelength dispersion of the ellipticity of the polarizer 63 formed by alternating the front and back of the multilayer phase difference film 39 is larger than that of the polarizer 61. That is, it is known that the retardation film 39 formed by laminating two retardation films having different Nz coefficients has a different ellipticity when the polarizing element 20 is laminated on one area and when the polarizing element 20 is laminated on the other area.
基於以上之內容，可知於1片相位差膜產生表裏之橢圓率差(參照圖5)係與積層Nz係數不同之2片相位差膜之情形(參照圖7)同樣之現象。因此，認為根據要積層偏光元件之面而橢圓率不同之相位差膜(具有表裏之橢圓率差之相位差膜)中，分子之配向狀態於厚度方向發生變化。Based on the above, it can be seen that the difference in ellipticity between the front and back of a phase difference film (see Figure 5) is the same phenomenon as the case of laminating two phase difference films with different Nz coefficients (see Figure 7). Therefore, it is believed that the molecular orientation state in the phase difference film with different ellipticity (phase difference film with ellipticity difference between the front and back) changes in the thickness direction depending on the surface of the polarizing element to be laminated.
[相位差膜之最佳光學特性之研究]為對使用具有表裏之橢圓率差之相位差膜之光學補償的光學設計進行研究，實施利用在呈正交偏光地配置之2片偏光元件之間配置有Nz係數不同之2片相位差膜之光學模型之模擬。圖8係表示用於模擬之光學模型之構成之剖視圖。[Study on the optimal optical properties of phase difference film]In order to study the optical design of optical compensation using a phase difference film with an elliptical coefficient difference between the front and back, a simulation of an optical model was performed using two phase difference films with different Nz coefficients arranged between two polarizers arranged in orthogonal polarization. Figure 8 is a cross-sectional view showing the structure of the optical model used for simulation.
該光學模型中，偏光元件21之吸收軸方向與相位差膜37之遲相軸方向正交，相位差膜37之遲相軸方向、相位差膜38之遲相軸方向及偏光元件23之吸收軸方向平行。偏光元件21側之相位差膜37之Nz係數設為0.5以下，偏光元件23側之相位差膜38之Nz係數設為0.5以上，將2片相位差膜之Nz係數之合計Nz1＋Nz2設為1.0。2片相位差膜37、38之正面延遲設為相同。In this optical model, the absorption axis direction of the polarizing element 21 is orthogonal to the retarded axis direction of the phase difference film 37, and the retarded axis direction of the phase difference film 37, the retarded axis direction of the phase difference film 38, and the absorption axis direction of the polarizing element 23 are parallel. The Nz coefficient of the phase difference film 37 on the polarizing element 21 side is set to be 0.5 or less, and the Nz coefficient of the phase difference film 38 on the polarizing element 23 side is set to be 0.5 or more, and the total Nz coefficient of the two phase difference films Nz1 +Nz2 is set to 1.0. The front retardation of the two phase difference films 37 and 38 is set to be the same.
以與偏光元件之吸收軸方向所成之角及與相位差膜之遲相軸方向所成之角為45°之旋轉軸為中心使光學模型旋轉45°，並讓自然光N自與法線所成之角為45°之方向入射至偏光元件21，利用光學模擬計算此時之自偏光元件23之出射光之亮度。將光學模擬之結果示於圖9。The optical model is rotated 45° around a rotation axis whose angle with the absorption axis of the polarizing element and the retardation axis of the phase difference film is 45°, and natural light N is incident on the polarizing element 21 from a direction with an angle of 45° with the normal line. The brightness of the light emitted from the polarizing element 23 at this time is calculated using optical simulation. The result of the optical simulation is shown in FIG9 .
圖9中，橫軸為相位差膜之正面延遲Re，縱軸為亮度之計算結果。相位差膜之正面延遲為每1片之值，2片積層相位差膜之正面延遲為圖9所示之數值之2倍。圖10係將於各(Nz1、Nz2)時亮度成為最小之正面延遲(最佳延遲)及此時之亮度之值繪製出者。In Figure 9, the horizontal axis is the front retardation Re of the phase difference film, and the vertical axis is the calculation result of the brightness. The front retardation of the phase difference film is the value of each sheet, and the front retardation of the two-sheet laminated phase difference film is twice the value shown in Figure 9. Figure 10 plots the front retardation (optimal retardation) at which the brightness is the minimum at each (Nz1 , Nz2 ) and the brightness value at that time.
於(Nz1、Nz2)＝(0.5、0.5)之情形時，亮度成為最小之正面延遲為137 nm(2片相位差膜之合計為274 nm)，與上述圖6A1之例一致。若對2片相位差膜之Nz係數設置差異，則可見亮度成為最小之正面延遲之值變大，亮度之最小值變小之傾向。於(Nz1、Nz2)＝(0.25、0.75)之情形時，亮度成為最小之正面延遲為274 nm(2片相位差膜之合計為548 nm)，與上述圖6A2之例一致。於(Nz1、Nz2)＝(0.2、0.8)，正面延遲為271 nm時，亮度成為最小。In the case of (Nz1 , Nz2 ) = (0.5, 0.5), the front retardation at which the brightness is minimized is 137 nm (the total of the two phase difference films is 274 nm), which is consistent with the example of Figure 6A1 above. If the Nz coefficient of the two phase difference films is set to be different, it can be seen that the value of the front retardation at which the brightness is minimized becomes larger and the minimum value of the brightness becomes smaller. In the case of (Nz1 , Nz2 ) = (0.25, 0.75), the front retardation at which the brightness is minimized is 274 nm (the total of the two phase difference films is 548 nm), which is consistent with the example of Figure 6A2 above. In the case of (Nz1 , Nz2 ) = (0.2, 0.8), the brightness is minimized when the front retardation is 271 nm.
利用光學模擬計算使用有於各(Nz1、Nz2)時為最佳延遲之積層相位差膜之偏光板之橢圓率。模擬中，如圖11A所示，使用於偏光元件21上積層Nz1≦0.5之相位差膜37與Nz2≧0.5之相位差膜38，且自偏光元件21側入射自然光之光學模型。又，如圖11B所示，對相位差膜37與相位差膜38之配置更替而成之光學模型亦同樣地計算橢圓率，並根據所得之結果計算表裏之橢圓率差。The ellipticity of the polarizing plate using the layered phase difference film with the optimal retardation at each (Nz1 , Nz2 ) is calculated by optical simulation. In the simulation, as shown in FIG11A , a phase difference film 37 with Nz1 ≦ 0.5 and a phase difference film 38 with Nz2 ≧ 0.5 are layered on the polarizing element 21, and the optical model in which natural light is incident from the side of the polarizing element 21 is used. In addition, as shown in FIG11B , the ellipticity is calculated in the same manner for the optical model in which the arrangement of the phase difference film 37 and the phase difference film 38 are replaced, and the ellipticity difference in the table is calculated based on the obtained results.
圖12中表示橢圓率之計算結果。圖12中，可知於Nz1＝0.2，Nz2＝0.8之情形時，遍及可見光之寬波長頻帶，橢圓率接近於0。又，可見圖10中之亮度越小，圖12中橢圓率接近於0之橢圓率之波長色散越小之傾向。根據該等結果可知，藉由評價可見光波長區域之橢圓率，可評價亮度之大小。FIG12 shows the calculation results of the ellipticity. FIG12 shows that when Nz1 = 0.2 and Nz2 = 0.8, the ellipticity is close to 0 over the wide wavelength band of visible light. Also, it can be seen that the smaller the brightness in FIG10, the smaller the wavelength dispersion of the ellipticity in FIG12 where the ellipticity is close to 0. These results show that the brightness can be evaluated by evaluating the ellipticity in the visible light wavelength region.
圖13係將圖10之亮度之曲線圖之橫軸替換成表裏之橢圓率差ΔE之曲線圖。於橢圓率差ΔE為2.7以下之區域，可見表裏之橢圓率差越大，則亮度越小，漏光得到抑制之傾向。又，可知若表裏之橢圓率差為2.9以下，則亮度較橢圓率差為0之情形(表裏之分子配向均一之情形)小而可降低漏光。FIG13 is a graph in which the horizontal axis of the brightness curve of FIG10 is replaced by the curve of the ellipticity difference ΔE between the front and back surfaces. In the region where the ellipticity difference ΔE is less than 2.7, it can be seen that the greater the ellipticity difference between the front and back surfaces, the smaller the brightness, and the tendency of light leakage being suppressed. In addition, it can be seen that if the ellipticity difference between the front and back surfaces is less than 2.9, the brightness is smaller than the case where the ellipticity difference is 0 (the case where the molecular orientation between the front and back surfaces is uniform), and light leakage can be reduced.
如上所述，1片相位差膜之表裏之橢圓率差可將Nz係數不同之2片相位差膜作為模型進行說明。因此，認為與積層有Nz係數不同之2片相位差膜之光學模型同樣地，於使用具有表裏之橢圓率差之1片相位差膜進行光學補償之情形時，亦只要表裏之橢圓率差為2.9以下之範圍內，便可於可見光之寬頻帶抑制漏光，可實現對比度較高之黑顯示。As mentioned above, the ellipticity difference between the front and back of a retardation film can be explained by using two retardation films with different Nz coefficients as a model. Therefore, it is believed that similar to the optical model of stacking two retardation films with different Nz coefficients, when using a retardation film with an ellipticity difference between the front and back for optical compensation, as long as the ellipticity difference between the front and back is within the range of 2.9 or less, light leakage can be suppressed in a wide band of visible light, and a black display with a higher contrast can be achieved.
[相位差膜之光學特性]如上述光學模擬所示，藉由將相位差膜之表裏之橢圓率差設為特定範圍，利用1片相位差膜便可進行與積層複數之相位差膜之情形同樣之光學補償。為發揮基於設置表裏之橢圓率差之效果，表裏之橢圓率差較佳為0.3以上，更佳為0.5以上。表裏之橢圓率差亦可為0.7以上、1.0以上、1.3以上或1.5以上。如上述光學模擬般出於抑制在相對於偏光元件之吸收軸方向呈45°方向之漏光之目的而使用相位差膜之情形時，表裏之橢圓率差較佳為2.9以下，更佳為2.8以下。[Optical properties of phase difference film]As shown in the above optical simulation, by setting the ellipticity difference between the front and back of the phase difference film to a specific range, optical compensation can be performed with a single phase difference film in the same manner as when multiple phase difference films are layered. In order to exert the effect based on setting the ellipticity difference between the front and back, the ellipticity difference between the front and back is preferably 0.3 or more, and more preferably 0.5 or more. The ellipticity difference between the front and back can also be 0.7 or more, 1.0 or more, 1.3 or more, or 1.5 or more. When a phase difference film is used for the purpose of suppressing light leakage in a direction of 45° relative to the absorption axis direction of the polarizing element as in the above optical simulation, the ellipticity difference between the front and back is preferably 2.9 or less, and more preferably 2.8 or less.
相位差膜之正面延遲及Nz係數只要根據相位差膜之用途(光學補償之對象等)而選擇即可。例如，如IPS方式之液晶顯示裝置之光學補償般補償自斜方向視認時之呈正交偏光地配置之2片偏光元件之表觀上之軸偏移而降低黑顯示下之漏光(黑亮度)之情形時，較佳地使用具有nx＞nz＞ny之折射率各向異性且Nz係數大於0且小於1之相位差膜。相位差膜之Nz係數較佳為0.2～0.8，更佳為0.3～0.7，進而較佳為0.4～0.6。The front retardation and Nz coefficient of the phase difference film can be selected according to the purpose of the phase difference film (the object of optical compensation, etc.). For example, when compensating for the apparent axis deviation of two polarizing elements arranged in orthogonal polarization when viewed from an oblique direction, such as the optical compensation of an IPS-type liquid crystal display device, and reducing the light leakage (black brightness) under black display, it is preferred to use a phase difference film with a refractive index anisotropy of nx>nz>ny and an Nz coefficient greater than 0 and less than 1. The Nz coefficient of the phase difference film is preferably 0.2 to 0.8, more preferably 0.3 to 0.7, and further preferably 0.4 to 0.6.
如利用上述模擬所示，延遲之最佳值根據表裏之橢圓率差而不同。例如，於表裏之橢圓率差為2.5～2.9之範圍內之情形時，相位差膜之波長550 nm下之正面延遲Re(550)之最佳值為約540 nm(相當於圖10中之最佳延遲(1片相位差膜之延遲)之2倍)。於表裏之橢圓率差為1.0左右之情形時，相位差膜之Re(550)之最佳值為約340 nm。於表裏之橢圓率差為0.5左右之情形時，相位差膜之Re(550)之最佳值為約280 nm。基於圖9之模擬結果，Re(550)較佳為250～600 nm左右之範圍內。Re(550)亦可為300 nm以上、350 nm以上、400 nm以上、450 nm以上或500 nm以上。As shown by the above simulation, the optimal value of the retardation varies depending on the ellipticity difference between the front and back. For example, when the ellipticity difference between the front and back is in the range of 2.5 to 2.9, the optimal value of the front retardation Re(550) of the retardation film at a wavelength of 550 nm is about 540 nm (equivalent to twice the optimal retardation (retardation of one retardation film) in Figure 10). When the ellipticity difference between the front and back is about 1.0, the optimal value of Re(550) of the retardation film is about 340 nm. When the ellipticity difference between the front and back is about 0.5, the optimal value of Re(550) of the retardation film is about 280 nm. Based on the simulation results of Figure 9, Re(550) is preferably in the range of about 250 to 600 nm. Re(550) may also be 300 nm or more, 350 nm or more, 400 nm or more, 450 nm or more, or 500 nm or more.
再者，於表裏具有橢圓率差之相位差膜若與偏光元件積層而測定橢圓率，則會產生表裏之差異，於針對相位差膜單獨體測定延遲、Nz係數之情形時，使光自任一面入射，Nz係數及延遲之測定值均不會產生差異。Furthermore, if a retardation film having an elliptical ratio difference between the front and back is laminated with a polarizing element and the elliptical ratio is measured, a difference between the front and back will occur. However, when the retardation and Nz coefficient are measured for the retardation film alone, the measured values of the Nz coefficient and retardation will not differ whether the light is incident from any side.
具有表裏之橢圓率差之相位差膜亦可用於上述以外之用途。例如關於IPS方式以外之液晶顯示裝置之光學補償、圓偏光板用之1/4波長板，亦可使用具有表裏之橢圓率差之相位差膜。該等用途中之相位差膜之Nz係數、延遲只要適當設定即可。例如，相位差膜之Re(550)可於0～1000 nm左右之範圍適當設定。相位差膜可為正A板(nx＞ny＝nz：Nz＝1)、負B板(nx＞ny＞nz：Nz＞1)、負C板(nx＝ny＞nz：Nz＝∞)、負A板(nz＝nx＞ny：Nz＝0)、正B板(nz＞nx＞ny：Nz＜0)、或正C板(nz＞nx＝ny；Nz＝-∞)。The phase difference film with the ellipticity difference between the front and back can also be used for purposes other than the above. For example, the optical compensation of liquid crystal display devices other than the IPS method and the 1/4 wavelength plate for circular polarizing plates can also use the phase difference film with the ellipticity difference between the front and back. The Nz coefficient and retardation of the phase difference film in these uses can be appropriately set. For example, the Re (550) of the phase difference film can be appropriately set in the range of about 0 to 1000 nm. The phase difference film can be a positive A plate (nx>ny=nz:Nz=1), a negative B plate (nx>ny>nz:Nz>1), a negative C plate (nx=ny>nz:Nz=∞), a negative A plate (nz=nx>ny:Nz=0), a positive B plate (nz>nx>ny:Nz<0), or a positive C plate (nz>nx=ny;Nz=-∞).
[相位差膜之製作]作為相位差膜之材料，使用各種聚合物材料。作為聚合物材料，可例舉：聚碳酸酯系樹脂；聚對苯二甲酸乙二酯、聚萘二甲酸乙二酯等聚酯系樹脂；聚芳酯系樹脂；聚碸、聚醚碸等碸系樹脂；聚苯硫醚等硫醚系樹脂；聚醯亞胺系樹脂；環狀聚烯烴系(聚降𦯉烯系)樹脂；聚醯胺樹脂；聚乙烯、聚丙烯等聚烯烴系樹脂；纖維素酯類；丙烯酸系樹脂；苯乙烯系樹脂；順丁烯二醯亞胺系樹脂；反丁烯二酸酯系樹脂等。[Production of phase difference film]As materials for phase difference film, various polymer materials are used. Examples of polymer materials include: polycarbonate resins; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyarylate resins; sulfide resins such as polysulfone and polyethersulfone; sulfide resins such as polyphenylene sulfide; polyimide resins; cyclic polyolefin resins (polynorthene resins); polyamide resins; polyolefin resins such as polyethylene and polypropylene; cellulose esters; acrylic resins; styrene resins; butadiene imide resins; fumarate resins, etc.
藉由將該等樹脂材料於支持體形成為層狀而進行成膜。成膜方法可為溶液法及熔融法之任一種。溶液法係於基材上塗佈樹脂溶液之後，利用加熱去除溶劑。藉由將成膜後之膜沿特定方向延伸，使聚合物之分子配向，而獲得相位差膜。相位差膜之厚度例如為5～200 μm左右。The film is formed by forming the resin materials into a layer on the support. The film forming method can be any of the solution method and the melt method. The solution method is to apply the resin solution on the substrate and then remove the solvent by heating. The film after film formation is extended in a specific direction to align the polymer molecules, thereby obtaining a phase difference film. The thickness of the phase difference film is, for example, about 5 to 200 μm.
作為延伸方法，可例舉：縱單軸延伸法、橫單軸延伸法、縱橫逐次雙軸延伸法、縱橫同時雙軸延伸法等。作為延伸機構，可使用輥延伸機、拉幅延伸機、縮放儀式或線性馬達式之雙軸延伸機等任意之恰當延伸機。於藉由溶液法在膜支持體上形成膜之情形時，亦可與支持體一體地進行延伸。如日本專利特開平5-157911號公報、日本專利特開2011-227430等所揭示，亦可藉由在延伸時利用熱收縮膜之收縮力，控制折射率各向異性，而製作具有nx＞nz＞ny之折射率各向異性之相位差膜。As stretching methods, there can be cited: longitudinal uniaxial stretching method, transverse uniaxial stretching method, longitudinal and transverse sequential biaxial stretching method, longitudinal and transverse simultaneous biaxial stretching method, etc. As a stretching mechanism, any appropriate stretching machine such as a roller stretching machine, a tentering stretching machine, a zoom instrument type or a linear motor type biaxial stretching machine can be used. In the case of forming a film on a film support by a solution method, it can also be stretched integrally with the support. As disclosed in Japanese Patent Laid-Open No. 5-157911 and Japanese Patent Laid-Open No. 2011-227430, a retardation film having a refractive index anisotropy of nx>nz>ny can also be produced by controlling the refractive index anisotropy by utilizing the shrinkage force of the heat shrinkable film during stretching.
分子之配向狀態於厚度方向不同之膜可藉由在成膜時及/或延伸時對表裏施加不同之應變而製作。例如，溶液成膜中，若於支持體上塗佈樹脂溶液之後，利用高溫將溶劑乾燥去除，則於表層側(B面)溶劑被急遽地去除，因此存在產生較支持體側(A面)大之應變，分子之面內配向性變高之傾向。該表裏之應變差於延伸後亦會殘存，因此獲得A面側之Nz係數較大、B面側之Nz係數較小之相位差膜。Films with different molecular orientations in the thickness direction can be made by applying different strains to the front and back during film formation and/or stretching. For example, in solution film formation, if a resin solution is applied to a support and the solvent is removed by drying at high temperature, the solvent is removed rapidly on the surface side (B surface), so there is a tendency to produce a larger strain than on the support side (A surface), and the in-plane orientation of the molecules becomes higher. The strain difference between the front and back will also remain after stretching, so a phase difference film with a larger Nz coefficient on the A surface side and a smaller Nz coefficient on the B surface side is obtained.
亦可利用乾燥條件之調整以外之方法，對表裏施加不同之應變。例如，藉由使用多層模嘴於B面(支持體側)與A面(表層側)使樹脂之吐出壓力、吐出量發生變化，而產生表裏之應變差。又，於延伸時，藉由在表裏貼合熱收縮率不同之膜，而產生表裏之應變差。Different strains can also be applied to the front and back by other methods other than adjusting the drying conditions. For example, by using a multi-layer die, the pressure and amount of resin extrusion can be changed on the B side (support side) and the A side (surface side), thereby generating a difference in strain between the front and back. Also, during stretching, by laminating films with different heat shrinkage rates on the front and back, a difference in strain between the front and back can be generated.
[偏光板]如圖2A及圖2B所示，藉由將相位差膜10與偏光元件20積層而形成偏光板。[Polarizing plate]As shown in FIG. 2A and FIG. 2B , a polarizing plate is formed by laminating a phase difference film 10 and a polarizing element 20 .
＜偏光元件＞作為偏光元件，可例舉：使聚乙烯醇系膜、局部縮甲醛化聚乙烯醇系膜、乙烯-乙酸乙烯酯共聚物系局部皂化膜等親水性高分子膜吸附碘、二色性染料等二色性物質並經過單軸延伸而成者；聚乙烯醇之脫水處理物、聚氯乙烯之脫氯化氫處理物等多烯系配向膜等。<Polarizing element>As polarizing elements, there can be cited: hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified films of ethylene-vinyl acetate copolymers adsorbed with dichroic substances such as iodine and dichroic dyes and then uniaxially stretched; polyene alignment films such as dehydrated products of polyvinyl alcohol and dehydrochlorinated products of polyvinyl chloride, etc.
其中，就具有較高之偏光度之方面而言，較佳為使聚乙烯醇或局部縮甲醛化聚乙烯醇等聚乙烯醇系膜吸附碘或二色性染料等二色性物質並沿特定方向配向過之聚乙烯醇(PVA)系偏光元件。例如，藉由對聚乙烯醇系膜實施碘染色及延伸而獲得PVA系偏光元件。Among them, in terms of having a higher polarization degree, a polyvinyl alcohol (PVA) polarizing element in which a polyvinyl alcohol film such as polyvinyl alcohol or partially formalized polyvinyl alcohol is adsorbed with a dichroic substance such as iodine or a dichroic dye and aligned in a specific direction is preferred. For example, a PVA polarizing element is obtained by dyeing a polyvinyl alcohol film with iodine and stretching it.
作為PVA系偏光元件，亦可使用厚度為10 μm以下之薄型之偏光元件。作為薄型之偏光元件，例如可例舉日本專利特開昭51-069644號公報、日本專利特開2000-338329號公報、WO2010/100917號說明書、日本專利第4691205號說明書、日本專利第4751481號說明書等中所記載之薄型偏光膜。此種薄型偏光元件例如藉由將PVA系樹脂層與延伸用樹脂基材以積層體之狀態延伸並進行碘染色而獲得。As the PVA-based polarizing element, a thin polarizing element with a thickness of 10 μm or less may be used. As the thin polarizing element, for example, the thin polarizing film described in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, WO2010/100917, Japanese Patent No. 4691205, Japanese Patent No. 4751481, etc. may be cited. Such a thin polarizing element is obtained, for example, by stretching a PVA-based resin layer and a stretching resin substrate in a laminated state and performing iodine dyeing.
＜偏光元件與相位差膜之配置關係＞相位差膜10與偏光元件20可為任一面貼合。可如圖2A所示，將相位差膜10之第一主面11與偏光元件20相對向地配置，亦可如圖2B所示，將相位差膜10之第二主面12與偏光元件20相對向地配置。<Arrangement relationship between polarizing element and phase difference film>The phase difference film 10 and the polarizing element 20 can be bonded to each other on either side. As shown in FIG2A , the first main surface 11 of the phase difference film 10 and the polarizing element 20 can be arranged opposite to each other, or as shown in FIG2B , the second main surface 12 of the phase difference film 10 and the polarizing element 20 can be arranged opposite to each other.
為定義相位差膜10之表裏，以下將與偏光元件20相對向地貼合時之橢圓率E(λ)之波長依存變小之側之主面設為第1主面。例如，圖5中，E1之波長依存較E2小，因此將上述主面以與偏光元件相對向之方式配置時橢圓率成為E1之側之主面定義為「第一主面」，將上述主面以與偏光元件相對向之方式配置時橢圓率成為E2之側之主面定義為「第二主面」。In order to define the front and back of the phase difference film 10, the principal surface on the side where the wavelength dependence of the ellipticity E(λ) becomes smaller when the phase difference film 10 is bonded to the polarizing element 20 is defined as the first principal surface. For example, in FIG5 , the wavelength dependence ofE1 is smaller than that ofE2 , so the principal surface on the side where the ellipticity becomesE1 when the principal surface is arranged to face the polarizing element is defined as the "first principal surface", and the principal surface on the side where the ellipticity becomesE2 when the principal surface is arranged to face the polarizing element is defined as the "second principal surface".
E(λ)之波長依存性之大小可基於在波長450～700 nm之範圍每隔10 nm測定出之橢圓率E(λ)之標準偏差σ進行判斷。The wavelength dependence of E(λ) can be determined based on the standard deviation σ of the ellipticity E(λ) measured at 10 nm intervals in the wavelength range of 450-700 nm.
[數2]其中，λk＝450＋10k(nm)，Eave為E(λ0)～E(λ25)之算術平均。[Number 2] Wherein, λk =450+10k(nm), Eave is the arithmetic mean of E(λ0 ) to E(λ25 ).
標準偏差σ越小，橢圓率E(λ)之波長依存越小。因此，將以與偏光元件相對向之方式配置時之橢圓率E(λ)之標準偏差σ變小之側之主面設為第一主面。The smaller the standard deviation σ is, the smaller the wavelength dependence of the ellipticity E(λ) is. Therefore, the principal surface on the side where the standard deviation σ of the ellipticity E(λ) becomes smaller when arranged opposite to the polarizing element is set as the first principal surface.
偏光元件20與相位差膜10之配置角度並無特別限定。例如，出於抑制自斜方向視認液晶顯示裝置時之漏光之光學補償之目的而使用相位差膜之情形時，較佳為以偏光元件20之吸收軸方向與相位差膜10之遲相軸方向平行或正交之方式配置兩者。將偏光元件與相位差膜積層而形成圓偏光板之情形時，較佳為以偏光元件之吸收軸方向與相位差膜之遲相軸方向所成之角度成為45°之方式配置兩者。再者，配置角度無需嚴格為上述範圍，亦可包含±2°左右之誤差。The configuration angle of the polarizing element 20 and the phase difference film 10 is not particularly limited. For example, when a phase difference film is used for the purpose of optical compensation for suppressing light leakage when viewing a liquid crystal display device from an oblique direction, it is preferred to configure the two in a manner such that the absorption axis direction of the polarizing element 20 and the retardation axis direction of the phase difference film 10 are parallel or orthogonal. When the polarizing element and the phase difference film are laminated to form a circular polarizing plate, it is preferred to configure the two in a manner such that the angle formed by the absorption axis direction of the polarizing element and the retardation axis direction of the phase difference film is 45°. Furthermore, the configuration angle does not need to be strictly within the above range, and may also include an error of about ±2°.
如圖3所示，相位差膜10之遲相軸方向15與偏光元件20之吸收軸方向25正交之情形時，較佳為以相位差膜10之第一主面11與偏光元件20相對向之方式配置。另一方面，於相位差膜10之遲相軸方向與偏光元件20之吸收軸方向正交之情形時，較佳為以相位差膜10之第二主面12與偏光元件20相對向之方式配置。如上所述，藉由選擇要與偏光元件積層之面，依序透過偏光元件20及相位差膜10之光之橢圓率之波長依存較小，可進行寬頻帶之光學補償。As shown in FIG3 , when the retardation axis direction 15 of the phase difference film 10 is orthogonal to the absorption axis direction 25 of the polarizing element 20, it is preferred to arrange the phase difference film 10 such that the first principal surface 11 faces the polarizing element 20. On the other hand, when the retardation axis direction of the phase difference film 10 is orthogonal to the absorption axis direction of the polarizing element 20, it is preferred to arrange the phase difference film 10 such that the second principal surface 12 faces the polarizing element 20. As described above, by selecting the surface to be laminated with the polarizing element, the wavelength dependence of the ellipticity of the light passing through the polarizing element 20 and the phase difference film 10 in sequence is small, and wideband optical compensation can be performed.
＜偏光元件保護膜＞如圖14所示，偏光板係於偏光元件20之一面具備相位差膜10，於另一面可具備作為偏光元件保護膜之透明膜40。透明膜40之厚度例如為5～200 μm左右。作為構成上述透明膜之樹脂材料，較佳為透明性、機械強度、熱穩定性優異之聚合物，作為其具體例，可例舉以上作為相位差膜之構成材料所例示之聚合物。<Polarizing element protective film>As shown in FIG. 14, the polarizing plate is provided with a phase difference film 10 on one side of the polarizing element 20, and a transparent film 40 as a polarizing element protective film can be provided on the other side. The thickness of the transparent film 40 is, for example, about 5 to 200 μm. As the resin material constituting the above-mentioned transparent film, it is preferably a polymer with excellent transparency, mechanical strength, and thermal stability. As a specific example, the polymers exemplified above as the constituent materials of the phase difference film can be cited.
於偏光元件之一面，亦可設置2片以上之膜。例如，亦可於偏光元件20與相位差膜10之間設置光學各向同性之透明保護膜。又，亦可於偏光元件20與相位差膜10之間設置具有光學各向異性之膜。亦可於相位差膜10之表面(偏光元件20之相反側之面)設置其他膜。Two or more films may be disposed on one surface of the polarizing element. For example, an optically isotropic transparent protective film may be disposed between the polarizing element 20 and the phase difference film 10. In addition, an optically anisotropic film may be disposed between the polarizing element 20 and the phase difference film 10. Other films may also be disposed on the surface of the phase difference film 10 (the surface opposite to the polarizing element 20).
＜黏著、接著劑＞偏光元件20與相位差膜10可經由接著劑或黏著劑(未圖示)而貼合。偏光元件20與透明保護膜40可經由適當之接著劑或黏著劑而貼合。作為接著劑或黏著劑，可適當選擇使用將丙烯酸系聚合物、矽酮系聚合物、聚酯、聚胺基甲酸酯、聚醯胺、聚乙烯醚、乙酸乙烯酯/氯乙烯共聚物、改性聚烯烴、環氧系聚合物、氟系聚合物、橡膠系聚合物等作為基礎聚合物者。<Adhesive, Adhesive>The polarizing element 20 and the phase difference film 10 can be bonded together via an adhesive or adhesive (not shown). The polarizing element 20 and the transparent protective film 40 can be bonded together via an appropriate adhesive or adhesive. As the adhesive or adhesive, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate/vinyl chloride copolymer, modified polyolefin, epoxy polymer, fluorine polymer, rubber polymer, etc. can be appropriately selected and used.
[圖像顯示裝置]上述相位差膜及偏光板係用於液晶顯示裝置、有機EL顯示裝置等圖像顯示裝置之形成。圖像顯示裝置係於液晶單元、有機EL單元等圖像顯示單元之表面具備上述偏光板。[Image display device]The above-mentioned phase difference film and polarizing plate are used to form image display devices such as liquid crystal display devices and organic EL display devices. The image display device is a device that has the above-mentioned polarizing plate on the surface of an image display unit such as a liquid crystal unit and an organic EL unit.
以下，作為圖像顯示裝置之一例，對IPS方式之液晶顯示裝置之構成進行說明。圖15係一實施形態之液晶顯示裝置之結構剖視圖。液晶顯示裝置201包含液晶面板101與光源105。液晶面板101係於液晶單元70之視認側表面具備第一偏光板57，於液晶單元70之光源105側具備第二偏光板56。As an example of an image display device, the structure of an IPS-type liquid crystal display device is described below. FIG. 15 is a cross-sectional view of a structure of a liquid crystal display device in an embodiment. The liquid crystal display device 201 includes a liquid crystal panel 101 and a light source 105. The liquid crystal panel 101 has a first polarizing plate 57 on the viewing side surface of the liquid crystal unit 70 and a second polarizing plate 56 on the light source 105 side of the liquid crystal unit 70.
液晶單元70係於2片基板73、75之間具備液晶層71。基板73、75為玻璃基板或塑膠基板，通常之構成中，於一基板設有彩色濾光片及黑矩陣，於另一基板設有控制液晶之光電特性之開關元件等。The liquid crystal cell 70 has a liquid crystal layer 71 between two substrates 73 and 75. The substrates 73 and 75 are glass substrates or plastic substrates. In a typical structure, a color filter and a black matrix are provided on one substrate, and a switch element for controlling the photoelectric characteristics of the liquid crystal is provided on the other substrate.
液晶層71包含於無電解狀態下沿特定方向配向之液晶分子，若施加電壓，則液晶分子之配向方向(指向矢)發生變化。例如，橫向電場效應(IPS)方式之液晶單元中，液晶層71之液晶分子於無電場狀態下相對於基板平面而平行且均一地配向(水平配向)，若施加電壓，則指向矢於基板面內旋轉。IPS方式之液晶單元之無電解狀態下之液晶分子之配向方向亦可相對於基板平面而稍微傾斜。IPS方式之液晶單元中，無電解狀態下之基板平面與液晶分子之配向方向所成之角(預傾角)通常為10°以下。The liquid crystal layer 71 includes liquid crystal molecules aligned in a specific direction in an electroless state. If a voltage is applied, the alignment direction (director) of the liquid crystal molecules changes. For example, in a liquid crystal unit of the transverse electric field effect (IPS) method, the liquid crystal molecules of the liquid crystal layer 71 are aligned parallel and uniformly (horizontally aligned) relative to the substrate plane in an electric field-free state. If a voltage is applied, the director rotates within the substrate plane. The alignment direction of the liquid crystal molecules in the electroless state of the liquid crystal unit of the IPS method can also be slightly tilted relative to the substrate plane. In the liquid crystal unit of the IPS method, the angle (pre-tilt angle) formed by the substrate plane in the electroless state and the alignment direction of the liquid crystal molecules is usually less than 10°.
於液晶單元之70光源側基板75，經由黏著劑層66而貼合有第一偏光板56，於液晶單元70之視認側基板73，經由黏著劑層68而貼合有第二偏光板57。第一偏光板56之偏光元件20與第二偏光板57之偏光元件29以兩者之吸收軸方向彼此正交之方式配置。A first polarizing plate 56 is bonded to the light source side substrate 75 of the liquid crystal unit 70 via an adhesive layer 66, and a second polarizing plate 57 is bonded to the viewing side substrate 73 of the liquid crystal unit 70 via an adhesive layer 68. The polarizing element 20 of the first polarizing plate 56 and the polarizing element 29 of the second polarizing plate 57 are arranged in such a way that the absorption axes thereof are orthogonal to each other.
第一偏光板56係於偏光元件20之液晶單元70側之面具備表裏之橢圓率差不同之相位差膜10，於偏光元件20之另一面具備透明膜40。第二偏光板57係於偏光元件之兩面具備透明膜41、42。再者，液晶顯示裝置中，不具有作為相位差膜之功能之透明膜40、41、42亦可省略。The first polarizing plate 56 is provided with a phase difference film 10 having different elliptical ratios on the surface of the polarizing element 20 on the liquid crystal unit 70 side, and a transparent film 40 is provided on the other surface of the polarizing element 20. The second polarizing plate 57 is provided with transparent films 41 and 42 on both surfaces of the polarizing element. Furthermore, in the liquid crystal display device, the transparent films 40, 41, and 42 that do not function as phase difference films may also be omitted.
作為構成黏著劑層39、59之黏著劑，可適當選擇使用將丙烯酸系聚合物、矽酮系聚合物、聚酯、聚胺基甲酸酯、聚醯胺、聚乙烯醚、乙酸乙烯酯/氯乙烯共聚物、改性聚烯烴、環氧系、氟系、天然橡膠、合成橡膠等橡膠系等作為基礎聚合物者。黏著劑層66、68之厚度為5～50 μm左右。As the adhesive constituting the adhesive layers 39 and 59, an adhesive having a base polymer such as acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate/vinyl chloride copolymer, modified polyolefin, epoxy, fluorine, natural rubber, synthetic rubber, etc. can be appropriately selected and used. The thickness of the adhesive layers 66 and 68 is about 5 to 50 μm.
液晶顯示裝置亦可包含上述以外之光學層、其他構件。例如，於液晶面板101與光源105之間亦可設置增亮膜(未圖示)。增亮膜亦可與光源側之偏光板56積層。The liquid crystal display device may also include optical layers and other components other than those mentioned above. For example, a brightness enhancement film (not shown) may be disposed between the liquid crystal panel 101 and the light source 105. The brightness enhancement film may also be laminated with the polarizing plate 56 on the light source side.
於視認側之透明膜42，以賦予耐擦傷性等為目的而可設置硬塗層。又，於透明膜42可設置抗反射層。於視認側之偏光板57之更靠視認側，可配置觸控面板感測器、覆蓋窗等。A hard coating layer may be provided on the transparent film 42 on the viewing side for the purpose of imparting scratch resistance, etc. In addition, an anti-reflection layer may be provided on the transparent film 42. A touch panel sensor, a cover window, etc. may be arranged on the viewing side of the polarizing plate 57 closer to the viewing side.
第一偏光板56中，偏光元件20之吸收軸方向與相位差膜10之遲相軸方向正交，相位差膜10之第一主面11與偏光元件20相對向，相位差膜10之第二主面12與液晶單元70相對向。In the first polarizing plate 56 , the absorption axis direction of the polarizing element 20 is orthogonal to the retardation axis direction of the retardation film 10 , the first principal surface 11 of the retardation film 10 faces the polarizing element 20 , and the second principal surface 12 of the retardation film 10 faces the liquid crystal unit 70 .
於自斜方向來看該液晶顯示裝置201之情形時，來自光源105之光透過偏光元件20之後，由相位差膜10轉換偏光狀態。由於以偏光元件20之吸收軸方向與相位差膜10之遲相軸方向正交，相位差膜10之第一主面與偏光元件20相對向之方式配置，故而自相位差膜10之出射光之橢圓率之波長依存較小，可實現寬頻帶之光學補償。When the liquid crystal display device 201 is viewed from an oblique direction, the light from the light source 105 passes through the polarizing element 20 and then is converted into a polarized state by the phase difference film 10. Since the absorption axis direction of the polarizing element 20 is orthogonal to the retardation axis direction of the phase difference film 10, and the first principal surface of the phase difference film 10 is arranged opposite to the polarizing element 20, the wavelength dependence of the ellipticity of the light emitted from the phase difference film 10 is small, and wide-band optical compensation can be achieved.
圖16所示之液晶顯示裝置202具有與上述液晶顯示裝置202類似之構成，但配置於光源105側之第一偏光板58中之相位差膜10與偏光元件20之配置關係不同。於偏光板58中，偏光元件20之吸收軸方向與相位差膜10之遲相軸方向平行，相位差膜10之第二主面12與偏光元件20相對向，相位差膜10之第一主面11與液晶單元70相對向。The liquid crystal display device 202 shown in FIG16 has a similar structure to the above-mentioned liquid crystal display device 202, but the arrangement relationship between the phase difference film 10 and the polarizing element 20 in the first polarizing plate 58 disposed on the light source 105 side is different. In the polarizing plate 58, the absorption axis direction of the polarizing element 20 is parallel to the retardation axis direction of the phase difference film 10, the second main surface 12 of the phase difference film 10 is opposite to the polarizing element 20, and the first main surface 11 of the phase difference film 10 is opposite to the liquid crystal unit 70.
此構成中，於將相位差膜10與視認側之第一偏光板57之偏光元件29視為一組之情形時，以偏光元件29之吸收軸方向與相位差膜10之遲相軸方向正交，相位差膜10之第一主面11與偏光元件29相對向之方式配置。因此，基於與上述液晶顯示裝置201之構成同樣之原理，可實現寬頻帶之光學補償。In this configuration, when the phase difference film 10 and the polarizing element 29 of the first polarizing plate 57 on the viewing side are considered as a set, the absorption axis direction of the polarizing element 29 is orthogonal to the retardation axis direction of the phase difference film 10, and the first main surface 11 of the phase difference film 10 and the polarizing element 29 are arranged to face each other. Therefore, based on the same principle as the configuration of the above-mentioned liquid crystal display device 201, wide-band optical compensation can be achieved.
圖15及圖16中示出於液晶單元70之光源側配置相位差膜10之形態，但亦可如圖17之液晶顯示裝置203及圖18之液晶顯示裝置204般於液晶單元70之視認側之偏光板配置相位差膜10。圖17之液晶顯示裝置203相當於將圖15之液晶顯示裝置201中之液晶面板101之上下更替而成者。圖18之液晶顯示裝置204相當於將圖16之液晶顯示裝置202中之液晶面板102之上下更替而成者。因此，該等液晶顯示裝置中，亦基於與液晶顯示裝置201、202之構成同樣之原理，可實現寬頻帶之光學補償。FIG. 15 and FIG. 16 show a configuration in which a phase difference film 10 is arranged on the light source side of the liquid crystal unit 70, but the phase difference film 10 may also be arranged on the polarizing plate on the viewing side of the liquid crystal unit 70 as in the liquid crystal display device 203 of FIG. 17 and the liquid crystal display device 204 of FIG. 18. The liquid crystal display device 203 of FIG. 17 is equivalent to the liquid crystal panel 101 of the liquid crystal display device 201 of FIG. 15 replaced with the top and bottom. The liquid crystal display device 204 of FIG. 18 is equivalent to the liquid crystal panel 102 of the liquid crystal display device 202 of FIG. 16 replaced with the top and bottom. Therefore, in these liquid crystal display devices, based on the same principle as the liquid crystal display devices 201 and 202, wideband optical compensation can be achieved.
以IPS方式之液晶顯示裝置中之光學補償為中心對相位差膜之用途進行了說明，但如上所述，具有表裏之橢圓率差之相位差膜之用途可應用於IPS方式以外之液晶顯示裝置、有機EL顯示裝置等各種圖像顯示裝置。[實施例]The use of phase difference film is described with the focus on optical compensation in IPS liquid crystal display devices. However, as described above, the use of phase difference film having an elliptical ratio difference between the front and back can be applied to various image display devices other than IPS liquid crystal display devices, organic EL display devices, etc. [Example]
以下，例舉實施例對本發明更詳細地進行說明，但本發明並不限定於下述例。Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.
[相位差膜之製作]＜樹脂溶液之製備＞於具備攪拌裝置之反應容器中，使2,2-雙(4-羥基苯基)-4-甲基戊烷540重量份、苄基三乙基氯化銨12重量份溶解於1 M氧化鈉溶液。向該溶液中，一面攪拌一面一次加入使對苯二甲醯氯304重量份與間苯二甲醯氯102重量份溶解於氯仿而成之溶液，於室溫攪拌90分鐘。之後，將聚合溶液靜置分離而分離含有聚合物之氯仿溶液，繼而利用乙酸水溶液進行洗淨，且利用離子更替水進行洗淨之後，投入至甲醇中使聚合物析出。將析出之聚合物利用蒸餾水洗淨2次及利用甲醇洗淨2次之後，進行減壓乾燥。將所得之聚芳酯系樹脂溶解於甲苯，而製備固形物成分濃度20%之樹脂溶液。[Preparation of phase difference film]<Preparation of resin solution>In a reaction container equipped with a stirring device, 540 parts by weight of 2,2-bis(4-hydroxyphenyl)-4-methylpentane and 12 parts by weight of benzyltriethylammonium chloride were dissolved in a 1 M sodium oxide solution. A solution prepared by dissolving 304 parts by weight of terephthaloyl chloride and 102 parts by weight of isophthaloyl chloride in chloroform was added to the solution at once while stirring, and stirred at room temperature for 90 minutes. Thereafter, the polymer solution was allowed to stand for separation to separate the chloroform solution containing the polymer, and then washed with an acetic acid aqueous solution and ion-exchanging water, and then put into methanol to precipitate the polymer. The precipitated polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure. The obtained polyarylate resin was dissolved in toluene to prepare a resin solution having a solid content concentration of 20%.
＜比較例1＞將PET膜作為支持體，於支持體上，使用棒式塗佈機以乾燥後之厚度成為20 μm之方式塗佈上述樹脂溶液，於溫度80℃乾燥3分鐘而獲得聚合物膜。將該聚合物膜自支持體剝離，於聚合物膜之兩面貼合附設有黏著劑層之熱收縮膜(雙軸延伸聚丙烯膜)，於溫度150℃進行自由端單軸延伸之後，剝離熱收縮膜。相位差膜之Nz係數為0.5，波長550 nm下之正面延遲Re(550)為270 nm。<Comparative Example 1>The above resin solution was applied to a PET film as a support using a rod coater to a thickness of 20 μm after drying, and dried at 80°C for 3 minutes to obtain a polymer film. The polymer film was peeled off from the support, and a heat shrinkable film (biaxially stretched polypropylene film) with an adhesive layer was attached to both sides of the polymer film. After free-end uniaxial stretching at 150°C, the heat shrinkable film was peeled off. The Nz coefficient of the phase difference film was 0.5, and the front retardation Re(550) at a wavelength of 550 nm was 270 nm.
＜實施例1～6＞將支持體上之樹脂溶液之乾燥溫度及乾燥時間如表1所示進行變更，除此以外，以與比較例1同樣之方式製作聚合物膜，且以成為表1所示之Re(550)之方式進行延伸，而獲得Nz係數為0.5之相位差膜。<Examples 1 to 6>The drying temperature and drying time of the resin solution on the support were changed as shown in Table 1. In addition, a polymer film was prepared in the same manner as in Comparative Example 1 and stretched to a Re (550) as shown in Table 1 to obtain a phase difference film with an Nz coefficient of 0.5.
[偏光板之製作]於厚度18 μm之聚乙烯醇系偏光元件之一面貼合厚度40 μm之雙軸延伸丙烯酸膜，於另一面經由紫外線硬化型之接著劑而貼合上述相位差膜，從而製作偏光板。貼合時，使用滾筒貼合機並照射紫外線而使接著劑硬化。[Production of polarizing plate]A 40 μm thick biaxially stretched acrylic film is laminated to one side of a 18 μm thick polyvinyl alcohol-based polarizing element, and the above-mentioned phase difference film is laminated to the other side via a UV-curable adhesive to produce a polarizing plate. During lamination, a roller laminating machine is used and UV rays are irradiated to cure the adhesive.
相位差膜與偏光元件係以相位差膜之遲相軸方向與偏光元件之吸收軸方向正交之方式配置，將相位差膜之B面(成膜時之支持體側之面)與偏光元件貼合。又，為評價相位差膜之表裏之橢圓率差ΔE，亦製作將相位差膜之A面(成膜時之表層側之面)與偏光元件貼合之試樣。The phase difference film and the polarizing element are arranged in such a way that the phase axis direction of the phase difference film is orthogonal to the absorption axis direction of the polarizing element, and the B surface of the phase difference film (the surface on the support side when the film is formed) is bonded to the polarizing element. In addition, in order to evaluate the elliptical ratio difference ΔE between the front and back of the phase difference film, a sample is also prepared in which the A surface of the phase difference film (the surface side when the film is formed) is bonded to the polarizing element.
[評價]＜相位差膜之光學特性＞相位差膜之正面延遲及Nz係數係利用偏光・相位差測定系統(Axometrics製造之「AxoScan」)進行測定。相位差膜之正面延遲及Nz係數係對於相位差膜單獨體進行測定。[Evaluation]＜Optical properties of retardation film＞The front retardation and Nz coefficient of the retardation film are measured using a polarization/retardation measurement system ("AxoScan" manufactured by Axometrics). The front retardation and Nz coefficient of the retardation film are measured for the retardation film alone.
＜橢圓率及橢圓率差＞橢圓率之測定時，使用偏光・相位差測定系統(Axometrics製造之「AxoScan」)。於以相對於偏光元件之吸收軸方向呈方位角45°之方向為旋轉軸使偏光板傾斜45°之狀態下，使光自丙烯酸膜側入射，測定自相位差膜側出射之光之橢圓率。針對將相位差膜之A面與偏光元件貼合之試樣亦進行橢圓率之測定，根據各個試樣之波長450 nm～700 nm之範圍內之每隔10 nm之橢圓率之值，計算表裏之橢圓率差ΔE。<Ellipticity and ellipticity difference>The ellipticity was measured using a polarization/phase difference measurement system ("AxoScan" manufactured by Axometrics). The polarizer was tilted 45° with the rotation axis at an azimuth angle of 45° relative to the absorption axis of the polarizer, and light was incident from the acrylic film side, and the ellipticity of the light emitted from the phase difference film side was measured. The ellipticity of the sample in which the A surface of the phase difference film was bonded to the polarizer was also measured, and the ellipticity difference ΔE in the table was calculated based on the ellipticity value of each sample at every 10 nm within the wavelength range of 450 nm to 700 nm.
＜液晶顯示裝置之黑亮度及對比度＞自具備IPS方式之液晶面板之市售之液晶電視取出液晶面板，且自液晶單元剝下視認側之偏光板，經由丙烯酸系黏著劑而貼合上述偏光板。將視認側偏光板被替換為上述實施例及比較例之偏光板之液晶面板與背光組合，而製作評價用液晶顯示裝置。<Black brightness and contrast ratio of liquid crystal display device>A liquid crystal panel was taken out from a commercially available liquid crystal television equipped with an IPS liquid crystal panel, and the polarizing plate on the viewing side was peeled off from the liquid crystal unit, and the polarizing plate was attached via an acrylic adhesive. The liquid crystal panel with the polarizing plate on the viewing side replaced with the polarizing plate of the above-mentioned embodiment and comparative example was combined with a backlight to produce a liquid crystal display device for evaluation.
將液晶顯示裝置設為黑顯示，測定於方位角45°、極角45°方向之亮度(黑亮度)。又，將液晶顯示裝置設為白顯示，測定於方位角45°、極角45°方向之亮度(白亮度)，並計算對比度(白亮度/黑亮度)。The LCD device was set to black display, and the brightness at an azimuth angle of 45° and an extreme angle of 45° (black brightness) was measured. Also, the LCD device was set to white display, and the brightness at an azimuth angle of 45° and an extreme angle of 45° (white brightness) was measured, and the contrast (white brightness/black brightness) was calculated.
＜評價結果＞將實施例及比較例之相位差膜之製作條件(乾燥溫度及時間)、波長550 nm下之正面延遲Re(550)、表裏之橢圓率差ΔE、液晶顯示裝置之黑亮度及對比度示於表1。再者，黑亮度及對比度係以將比較例1設為100之相對值表示。<Evaluation Results>Table 1 shows the manufacturing conditions (drying temperature and time) of the phase difference films of the embodiment and comparative example, the front retardation Re(550) at a wavelength of 550 nm, the ellipticity difference ΔE between the front and back, and the black brightness and contrast of the liquid crystal display device. In addition, the black brightness and contrast are expressed as relative values with Comparative Example 1 set to 100.
將比較例1、實施例1、實施例3、實施例5及實施例6之橢圓率之測定結果示於圖19。又，將以各實施例及比較例之相位差膜之表裏之橢圓率差ΔE為橫軸、液晶顯示裝置之黑亮度為縱軸所繪製出之曲線圖示於圖20。The measurement results of the ellipticity of Comparative Example 1, Example 1, Example 3, Example 5 and Example 6 are shown in Fig. 19. In addition, a curve is plotted with the ellipticity difference ΔE between the front and back of the retardation film of each Example and Comparative Example as the horizontal axis and the black brightness of the liquid crystal display device as the vertical axis in Fig. 20.
[表1]
如表1所示，可知藉由在支持體上進行高溫、長時間之加熱乾燥，可形成表裏之橢圓率差ΔE較大之相位差膜。As shown in Table 1, it can be seen that by performing heat drying at a high temperature for a long time on a support, a retardation film having a large ellipticity difference ΔE between the front and back can be formed.
與使用無表裏之橢圓率差之相位差膜之比較例1相比，使用表裏之橢圓率不同之相位差膜之實施例1～6中，液晶顯示裝置之黑亮度較小，對比度上升。相對於表裏之橢圓率差ΔE繪製黑亮度所得之圖20呈現出與圖13之模擬結果較高之匹配。Compared with Comparative Example 1 using a retardation film without a front and back ellipticity difference, Examples 1 to 6 using retardation films with different front and back ellipticities have lower black brightness and improved contrast of the liquid crystal display device. FIG. 20 , which plots black brightness against the front and back ellipticity difference ΔE, shows a high match with the simulation result of FIG. 13 .
根據以上之結果，可知藉由使用於厚度方向分子之配向狀態不同而具有表裏之橢圓率差之相位差膜，可實現與積層複數之相位差膜之情形同樣之光學補償，形成漏光較少而對比度較高之圖像顯示裝置。Based on the above results, it can be seen that by using a phase difference film with different elliptical ratios between the front and back due to different molecular orientations in the thickness direction, the same optical compensation as the case of stacking multiple phase difference films can be achieved, forming an image display device with less light leakage and higher contrast.
10:相位差膜11:第一主面12:第二主面15:遲相軸方向20,21,23,29:偏光元件25:吸收軸方向31,32,33,37,38:相位差膜39:積層相位差膜40,41,42:透明膜51,52,56,57,58:偏光板61,62,63:偏光板66,68:黏著劑層70:液晶單元71:液晶層73,75:基板101~104:液晶面板105:光源201~204:液晶顯示裝置E1,E2:橢圓率N:自然光P:出射光R:旋轉軸10: Retardation film 11: First main surface 12: Second main surface 15: Retardation axis direction 20, 21, 23, 29: Polarizer 25: Absorption axis direction 31, 32, 33, 37, 38: Retardation film 39: Laminated retardation film 40, 41, 42: Transparent film 51, 52, 56, 57, 58: Polarizer 61, 62, 63: Polarizer 66, 68: Adhesive layer 70: Liquid crystal unit 71: Liquid crystal layer 73, 75: Substrate 101~104: Liquid crystal panel 105: Light source 201~204: Liquid crystal display deviceE1 ,E2 : Elliptical ratio N: Natural light P: Outgoing light R: Rotation axis
圖1係相位差膜之剖視圖。圖2A、B係將相位差膜與偏光元件積層而成之偏光板之剖視圖。圖3係表示用於橢圓率之測定之偏光板中之相位差膜與偏光元件之配置關係之圖。圖4係表示用於橢圓率之測定之光學系統之圖。圖5係用於對表裏之橢圓率差及其計算方法進行說明之圖。圖6A1、A2、B1、B2、C1、C2係關於光入射至偏光元件與相位差膜之積層體時之利用相位差膜之偏光狀態之轉換之說明圖。圖7係圖6之偏光板之橢圓率之光學模擬結果。圖8係用於亮度之光學模擬之光學模型之結構剖視圖。圖9係使用圖8之光學模型之亮度之模擬結果。圖10係將模擬中亮度成為最小之延遲及此時之亮度之值繪製出之曲線圖。圖11A、B係用於橢圓率之光學模擬之光學模型之結構剖視圖。圖12係橢圓率之光學模擬結果。圖13係將積層相位差板之表裏之橢圓率差與亮度之關係繪製出之曲線圖。圖14係偏光板之剖視圖。圖15係液晶顯示裝置之剖視圖。圖16係液晶顯示裝置之剖視圖。圖17係液晶顯示裝置之剖視圖。圖18係液晶顯示裝置之剖視圖。圖19係表示實施例及比較例之相位差膜之橢圓率之測定結果之曲線圖。圖20係將實施例及比較例之相位差膜之表裏之橢圓率差與液晶顯示裝置之黑亮度之關係繪製出之曲線圖。FIG. 1 is a cross-sectional view of a phase difference film.FIG. 2A and FIG. 2B are cross-sectional views of a polarizing plate formed by laminating a phase difference film and a polarizing element.FIG. 3 is a view showing the arrangement relationship between the phase difference film and the polarizing element in the polarizing plate used for measuring the ellipticity.FIG. 4 is a view showing an optical system used for measuring the ellipticity.FIG. 5 is a view for explaining the ellipticity difference between the surface and the inside and the calculation method thereof.FIG. 6A1, A2, B1, B2, C1, and C2 are explanatory views of the conversion of the polarization state of the phase difference film when light is incident on a laminate of a polarizing element and a phase difference film.FIG. 7 is an optical simulation result of the ellipticity of the polarizing plate of FIG. 6.FIG. 8 is a structural cross-sectional view of an optical model used for optical simulation of brightness.FIG9 is a simulation result of brightness using the optical model of FIG8.FIG10 is a graph plotting the delay at which the brightness is minimum in the simulation and the brightness value at that time.FIG11A and FIG11B are cross-sectional views of the structure of the optical model used for optical simulation of ellipticity.FIG12 is a result of optical simulation of ellipticity.FIG13 is a graph plotting the relationship between the ellipticity difference between the front and back of the multilayer phase difference plate and the brightness.FIG14 is a cross-sectional view of a polarizing plate.FIG15 is a cross-sectional view of a liquid crystal display device.FIG16 is a cross-sectional view of a liquid crystal display device.FIG17 is a cross-sectional view of a liquid crystal display device.FIG18 is a cross-sectional view of a liquid crystal display device.FIG. 19 is a graph showing the measurement results of the ellipticity of the phase difference film of the embodiment and the comparative example. FIG. 20 is a graph showing the relationship between the ellipticity difference between the front and back of the phase difference film of the embodiment and the comparative example and the black brightness of the liquid crystal display device.
10:相位差膜10: Phase difference film
11:第一主面11: First main surface
12:第二主面12: Second main surface
20:偏光元件20: Polarizing element
51:偏光板51: Polarizing plate
52:偏光板52: Polarizing plate
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| JP2019070780AJP7317549B2 (en) | 2019-04-02 | 2019-04-02 | Polarizing plate and image display device |
| JP2019-070780 | 2019-04-02 |
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| TW202043885A TW202043885A (en) | 2020-12-01 |
| TWI841713Btrue TWI841713B (en) | 2024-05-11 |
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| TW109109997ATWI841713B (en) | 2019-04-02 | 2020-03-25 | Phase difference film, polarizing plate and image display device |
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| JP (1) | JP7317549B2 (en) |
| KR (1) | KR20210145783A (en) |
| CN (1) | CN113661419B (en) |
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