Liquid crystal display device

Abstract

To provide a liquid crystal display device in which occurrence of light leakage in black display is suppressed.SOLUTION: The liquid crystal display device comprises, in order, a backlight, a first polarizing plate, a first substrate that exhibits birefringence in a direction parallel to the direction of stress, a liquid crystal layer, a second substrate that exhibits birefringence in a direction parallel to the direction of stress, and a second polarizing plate. The first substrate and the second substrate each comprise, on at least one side relative to the first polarizing plate and the second polarizing plate, respectively, a laminate comprising an adhesive layer having a storage modulus of 0.10 MPa or more at 25°C and a film exhibiting birefringence perpendicular to the direction of stress.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The following disclosure relates to a liquid crystal display device. [Background technology]

[0002] It is known that when transparent plastic or glass is distorted by applying an external force, it will exhibit birefringence in response to this distortion, a phenomenon known as "photoelasticity." In the fields of display devices and optical films, materials are sometimes selected with photoelasticity in mind.

[0003] Patent Document 1 describes that in order to provide a liquid crystal display device that can cancel out the phase difference (retardation) that occurs in the glass substrate and display a display screen with inconspicuous light leakage even when stress is applied to the display screen, the positive photoelasticity of the glass substrate is compensated for by the negative photoelasticity of the compensation film, thereby canceling out the retardation that occurs when stress is applied to the glass substrate.

[0004] Patent Document 2 describes an optical film made of a resin composition comprising a thermoplastic resin (A) having a negative photoelastic coefficient and a low molecular weight compound (B) that has a tendency to increase the photoelastic coefficient more than the photoelastic coefficient of the thermoplastic resin (A), in order to provide an optical film that exhibits high birefringence and has small birefringence change due to external force, i.e., has a small absolute value of the photoelastic coefficient.

[0005] Patent Document 3 describes a photoelastic coefficient of 2×10 -11 Pa -1 The following invention of a retardation film is described. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5414960 specification [Patent Document 2] Patent No. 4338759 specification [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-42673 Summary of the Invention [Problem to be solved by the invention]

[0007] In flat-type liquid crystal display devices, attaching a polarizing plate to a liquid crystal panel causes the panel to warp. Forcibly returning the warped panel to a flat state by attaching a cover glass or incorporating it into a bezel (housing) places stress on a portion of the glass substrate that constitutes the liquid crystal panel, resulting in a problem of light leakage (black unevenness) during black display. Figure 1 illustrates the principle behind light leakage during black display in flat-type liquid crystal display devices. As shown in the figure, no warping occurs in liquid crystal panel 310 before the polarizing plate is attached, but warping may occur in liquid crystal panel 320 after the polarizing plate is attached. While warping can be forcibly eliminated by attaching cover glass 350 to liquid crystal panel 320 after the polarizing plate is attached, liquid crystal panel 380, which is a laminate of forcibly flattened liquid crystal panel 330 and cover glass 350, exhibits light leakage during black display after the cover glass is attached. FIG. 2 is a photograph showing a comparison between the black display of liquid crystal panel 310 (top) before the polarizing plate is attached and the black display of liquid crystal panel 380 (bottom) after the cover glass is attached.

[0008] Furthermore, in liquid crystal display devices that are deformed into a curved shape, regardless of the above-mentioned process, the glass substrate is forcibly warped to form the desired curved shape, which causes stress to be applied to part of the glass substrate, resulting in the problem of light leakage (unevenness) in black display.

[0009] The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a liquid crystal display device in which light leakage during black display is suppressed. [Means for solving the problem]

[0010] (1) One embodiment of the present invention is a liquid crystal display device comprising, in order, a backlight, a first polarizing plate, a first substrate that exhibits birefringence in a direction parallel to the stress direction, a liquid crystal layer, a second substrate that exhibits birefringence in a direction parallel to the stress direction, and a second polarizing plate, and further comprising, on at least one of the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate, a pressure-sensitive adhesive layer having a storage modulus at 25°C of 0.10 MPa or more and a laminate of a film that exhibits birefringence in a direction perpendicular to the stress direction.

[0011] (2) Furthermore, in addition to the configuration of (1), one embodiment of the present invention is a liquid crystal display device that includes a plurality of the laminates on at least one of the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate.

[0012] (3) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1) or (2) above, the laminate is provided on both the first polarizing plate side of the first substrate and the second polarizing plate side of the second substrate.

[0013] (4) Furthermore, one embodiment of the present invention is a liquid crystal display device, in addition to the configuration of (1) or (2) above, in which the laminate is provided only on the first polarizing plate side of the first substrate.

[0014] (5) Furthermore, one embodiment of the present invention is a liquid crystal display device, in addition to the configuration of (1) or (2) above, in which the laminate is provided only on the second polarizing plate side of the second substrate.

[0015] (6) Furthermore, one embodiment of the present invention is a liquid crystal display device, in addition to the configuration of (1), (2), (3), (4), or (5) above, wherein the sum of the absolute values ​​of the product of the photoelastic constant and the thickness of the films included in the laminate is substantially equal to the absolute value of the product of the photoelastic constant and the thickness of the substrate arranged adjacent to the first substrate or the second substrate.

[0016] (7) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), or (5), the film comprises a polymethyl methacrylate resin. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a liquid crystal display device in which light leakage during black display is suppressed. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are diagrams illustrating the principle of light leakage during black display in a flat liquid crystal display device. [Figure 2] The photographs show a comparison between the black display of liquid crystal panel 310 (top) before the polarizing plate is attached and the black display of liquid crystal panel 380 (bottom) after the cover glass is attached. [Figure 3] FIG. 10 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a conventional liquid crystal display device. [Figure 4] 4 is a diagram showing birefringence that occurs when stress is applied to the liquid crystal panel with polarizing plates shown in FIG. 3. FIG. [Figure 5] 1 is a cross-sectional view schematically illustrating a configuration of a liquid crystal panel with a polarizing plate included in a liquid crystal display device according to an embodiment. [Figure 6] 6 is a diagram showing birefringence that occurs when stress is applied to the liquid crystal panel with polarizing plates shown in FIG. 5. FIG. [Figure 7] FIG. 2 is a perspective view schematically illustrating a method for measuring the photoelastic coefficient. [Figure 8] 10 is a graph showing the relationship between stress and the phase difference that appears. [Figure 9] 1 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 1. FIG. [Figure 10] 10 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 2. FIG. [Figure 11]10 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 3. FIG. [Figure 12] 10 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 4. FIG. [Figure 13] 10 is a cross-sectional view schematically illustrating the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 5. FIG. [Figure 14] 13 is a cross-sectional view schematically showing the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Example 6. FIG. [Figure 15] 1 is a cross-sectional view schematically showing the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Comparative Example 1. FIG. [Figure 16] 10 is a cross-sectional view schematically showing the configuration of a liquid crystal panel with polarizing plates included in a liquid crystal display device of Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and appropriate design changes can be made within the scope of the configuration of the present invention. In the following description, the same reference numerals will be used in different drawings as appropriate for the same parts or parts having similar functions, and repeated explanations will be omitted as appropriate. Each aspect of the present invention may be combined as appropriate within the scope of the gist of the present invention.

[0020] The liquid crystal display device of this embodiment includes, in order, a backlight, a first polarizing plate, a first substrate that exhibits birefringence in a direction parallel to the stress direction, a liquid crystal layer, a second substrate that exhibits birefringence in a direction parallel to the stress direction, and a second polarizing plate, and includes, on at least one of the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate, a pressure-sensitive adhesive layer having a storage modulus at 25°C of 0.10 MPa or more and a laminate of a film that exhibits birefringence in a direction perpendicular to the stress direction.

[0021] In this specification, "exhibiting birefringence in a direction parallel to the stress direction" also refers to "having a positive photoelasticity (coefficient)," and "exhibiting birefringence in a direction perpendicular to the stress direction" also refers to "having a negative photoelasticity (coefficient)." The stress may be applied temporarily to the liquid crystal display device, or may be applied constantly to the liquid crystal display device. An example of the stress applied temporarily to the liquid crystal display device is the stress applied when operating a touch panel. An example of the stress applied constantly to the liquid crystal display device is the stress applied when the liquid crystal panel is deformed into a predetermined shape (which may be flat) by, for example, bonding a cover glass to the viewer side of the liquid crystal panel or incorporating it into a bezel (housing).

[0022] The material of the first substrate and the second substrate is not particularly limited as long as it exhibits birefringence in a direction parallel to the stress direction (has positive photoelasticity), and examples thereof include glass, cycloolefin polymer, polycarbonate, etc. Glass is a substance that exhibits birefringence in a direction parallel to the stress direction (positive photoelasticity).

[0023] The material of the pressure-sensitive adhesive layer is not particularly limited as long as it has a storage modulus of 0.10 MPa or more at 25°C, and for example, an acrylic pressure-sensitive adhesive or the like can be used. In this specification, the "pressure-sensitive adhesive layer" may be a pressure-sensitive adhesive layer or an adhesive layer formed by curing a liquid adhesive. The storage modulus can be adjusted, for example, by adjusting the composition, such as the type and amount of resin added to the pressure-sensitive adhesive, or by adjusting the curing temperature and curing time when producing the pressure-sensitive adhesive.

[0024] The material of the film is not particularly limited as long as it exhibits birefringence in the direction perpendicular to the stress direction (has negative photoelasticity), and examples thereof include acrylic resins, etc. As the acrylic resin, polymethyl methacrylate resin is preferably used.

[0025] FIG. 3 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in a conventional liquid crystal display device, and FIG. 4 is a diagram illustrating birefringence that occurs when stress is applied to the polarizing plate-equipped liquid crystal panel shown in FIG. 3. As shown in FIG. 3, a polarizing plate-equipped liquid crystal panel 400 included in the conventional liquid crystal display device includes, in order from the backlight (not shown) side, a first polarizing plate 150, a liquid crystal panel 110, and a second polarizing plate 160. The liquid crystal panel 110 is composed of a TFT substrate, a liquid crystal layer, and a color filter substrate, and both the TFT substrate and the color filter substrate include glass substrates. Therefore, as shown in FIG. 4, when stress α is applied to the polarizing plate-equipped liquid crystal panel 400, birefringence occurs in a direction parallel to the direction of the stress α. As a result, a glass photoelastic retardation Rg is generated, which is expressed by the following formula: Rg=β g ×α×d g β g : Photoelastic coefficient of glass α: magnitude of stress d g : Glass thickness

[0026] A polarizing liquid crystal panel has a configuration in which a liquid crystal panel is sandwiched between two polarizing plates (crossed Nicol polarizing plates) whose absorption axes are orthogonal to each other, so when stress is applied to the liquid crystal panel 110, birefringence (phase difference) occurs in the glass substrates within the liquid crystal panel 110. This phase difference causes light leakage from the crossed Nicol polarizing plates, which is observed as uneven black display.

[0027] FIG. 5 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in a liquid crystal display device according to an embodiment, and FIG. 6 is a diagram illustrating birefringence that occurs when stress is applied to the polarizing plate-equipped liquid crystal panel shown in FIG. 5. As shown in FIG. 5, a polarizing plate-equipped liquid crystal panel 100 included in the liquid crystal display device according to an embodiment includes, in order from the backlight 80 side toward the viewer side, a first polarizing plate 150, a negative photoelastic film 120, a high-elasticity adhesive layer 130, a liquid crystal panel 110, and a second polarizing plate 160. The liquid crystal panel 110 is composed of a TFT substrate 116, a liquid crystal layer 114, and a color filter substrate 112. The TFT substrate 116 is the substrate on the backlight 80 side and includes a first glass substrate 117 as the first substrate. The color filter substrate 112 is the substrate on the viewer side and includes a second glass substrate 113 as the second substrate. The first glass substrate 117 and the second glass substrate 113 have the property of exhibiting birefringence in a direction parallel to the direction of stress. Therefore, as shown in FIG. 6, when stress α is applied to the polarizing plate-equipped liquid crystal panel 100, birefringence occurs in the liquid crystal panel 110 in a direction parallel to the direction of the stress α, and glass photoelastic phase difference Rg is generated.

[0028] The negative photoelastic film 120 is a film that exhibits birefringence in a direction perpendicular to the direction of stress, and as shown in Fig. 6, when stress α is applied to the polarizing plate-equipped liquid crystal panel 100, the negative photoelastic film 120 exhibits birefringence in a direction perpendicular to the direction of the stress α. As a result, a film photoelastic phase difference Rf expressed by the following formula is generated. Rf=β f ×α×d f β f : Photoelastic coefficient of film α: magnitude of stress d f : Film thickness

[0029] The high elastic modulus adhesive layer 130 is an adhesive layer having a storage modulus of 0.10 MPa or more at 25°C. By bonding the negative photoelastic film 120 to the liquid crystal panel 110 with the high elastic modulus adhesive layer 130, it becomes possible to cancel out the birefringence that occurs when a stress having a certain direction and magnitude is applied between the glass substrate (first glass substrate 117) and the negative photoelastic film 120, as shown in Fig. 6. As a result, light leakage (unevenness) in black display is improved. When the negative photoelastic film 120 is bonded with a pressure-sensitive adhesive layer having a storage modulus of less than 0.10 MPa, stress relaxation occurs in the pressure-sensitive adhesive layer, and the stress applied to the glass substrate (first glass substrate 117) and the stress applied to the negative photoelastic film 120 cannot be made equal, and the glass photoelastic phase difference Rg and the film photoelastic phase difference Rf cannot be offset. For this reason, in this embodiment, a pressure-sensitive adhesive layer having a storage modulus at 25°C of 0.10 MPa or more is used. The storage modulus can be measured using a rotational rheometer or the like in accordance with JIS K 7244-10 (Plastics - Test methods for dynamic mechanical properties - Part 10: Complex shear viscosity using a parallel plate oscillatory rheometer).

[0030] The photoelastic coefficient can be measured by the following method: Fig. 7 is a perspective view schematically showing a method for measuring the photoelastic coefficient, and Fig. 8 is a graph showing the relationship between stress and the phase difference that appears. As shown in Figure 7, a force gauge 11 is attached to one side of the measurement sample 10. An example of the force gauge 11 is the "FGC-2B" digital force gauge manufactured by SHIMPO Corporation. The end of the measurement sample 10 opposite the end where the force gauge 11 is attached is pulled using a jig or by hand. The stress σ applied to the measurement sample 10 at this time is calculated as σ = (the force magnitude F displayed on the force gauge 11) ÷ (the width w of the measurement sample 10 in the direction perpendicular to the pulling direction) ÷ (the thickness t of the measurement sample 10) [Pa]. The in-plane retardation [nm] exhibited in the measurement sample 10 is measured using a birefringence measurement device. An example of a birefringence measurement device is the "Axoscan" manufactured by Axometrics. Light is irradiated from the light-emitting unit 12A toward the measurement sample 10, and the light transmitted through the measurement sample 10 is received by the light-receiving unit 12B, and the in-plane retardation [nm] exhibited in the measurement sample 10 is measured. By changing the magnitude of the force pulling the measurement sample 10 and measuring the phase difference occurring in the measurement sample 10 at multiple points, a graph like that shown in Figure 8 can be obtained. Phase difference δ [nm] = photoelastic coefficient β [10 -12 Since the relationship is [Pa] × stress σ [Pa] × thickness t [cm], the photoelastic coefficient can be calculated from the slope of the graph. The unit of the photoelastic coefficient is 1 Pa = 1 dyn / cm 2 Using the relationship of "cm 2 / dyn" can also be used.

[0031] An example of the actual measured value of the photoelastic coefficient measured by the above-mentioned measuring method is shown below. Glass plate: +3.60E-13 (cm 2 / dyn) Acrylic film: -2.70E-13 (cm 2 / dyn) In this specification, "Ex (x represents any number)" means "E×10 -x " represents.

[0032] 5 shows an embodiment in which a laminate consisting of one negative photoelastic film 120 and one high elastic modulus pressure-sensitive adhesive layer 130 is disposed on the backlight side of the liquid crystal panel 110 (closer to the first polarizing plate 150 than the first glass substrate 117), but in this embodiment, the laminate may be disposed on at least one of the first polarizing plate 150 side of the first glass substrate 117 and the second polarizing plate 160 side of the second glass substrate 113. That is, the arrangement of the laminate may be any of the following forms (1) to (3). (1) A mode in which the laminate is disposed on both the first polarizing plate 150 side of the first glass substrate 117 and the second polarizing plate 160 side of the second glass substrate 113. (2) The laminate is disposed only on the first polarizing plate 150 side of the first glass substrate 117, and is not disposed on the second polarizing plate 160 side of the second glass substrate 113. (3) A configuration in which the laminate is not disposed on the first polarizing plate 150 side of the first glass substrate 117, but is disposed only on the second polarizing plate 160 side of the second glass substrate 113. From the viewpoint of preventing the polarization disturbance from being accentuated by passing through the liquid crystal layer, the above modes (1) and (2) are preferred.

[0033] The number of layers in the laminate is not particularly limited, and a plurality of the laminates may be provided on at least one of the side closer to the first polarizing plate 150 than the first glass substrate 117 and the side closer to the second polarizing plate 160 than the second glass substrate 113. In this embodiment, it is preferable that the sum of the absolute values ​​of the product of the photoelastic constant and the thickness of the negative photoelastic film 120 included in the laminate is substantially equal to the absolute value of the product of the photoelastic constant and the thickness of the substrate arranged adjacent to the first glass substrate 117 or the second glass substrate 113. For example, it is preferable that the sum of the absolute values ​​of the product of the photoelastic constant and the thickness of the negative photoelastic film 120 included in the laminate is 0.9 to 1.1 times the absolute value of the product of the photoelastic constant and the thickness of the substrate arranged adjacent to the first glass substrate 117 or the second glass substrate 113. When the laminate contains N negative photoelastic films 120 (N is any integer), the absolute value of the product of the photoelastic constant and the thickness of each of the N negative photoelastic films 120 is calculated, and the sum of these values ​​is the total sum of the absolute values ​​of the product of the photoelastic constant and the thickness of each of the negative photoelastic films 120 contained in the laminate.

[0034] The laminate on the first polarizing plate 150 side of the first glass substrate 117 preferably satisfies the following formula (1): The following formula (1) represents the case where the negative photoelastic film 120 arranged on the first polarizing plate 150 side of the first glass substrate 117 has the same photoelastic coefficient and thickness. |β g1 ×d g1 |=|β f1 ×d f1 |×N f1 (1) β g1 : Photoelastic coefficient of the first glass substrate 117 d g1 : Thickness of the first glass substrate 117 β f1 : Photoelastic coefficient of the negative photoelastic film 120 on the first polarizing plate 150 side of the first glass substrate 117 d f1 : The thickness of the negative photoelastic film 120 on the first polarizing plate 150 side of the first glass substrate 117 N f1: The number of negative photoelastic films 120 on the first polarizing plate 150 side of the first glass substrate 117

[0035] The laminate on the second polarizing plate 160 side of the second glass substrate 113 preferably satisfies the following formula (2): The following formula (2) represents the case where the negative photoelastic film 120 arranged on the second polarizing plate 160 side of the second glass substrate 113 has the same photoelastic coefficient and thickness. |β g2 ×d g2 |=|β f2 ×d f2 |×N f2 (2) β g2 : Photoelastic coefficient of the second glass substrate 113 d g2 : thickness of the second glass substrate 113 β f2 : Photoelastic coefficient of the negative photoelastic film 120 on the second polarizing plate 160 side of the second glass substrate 113 d f2 : The thickness of the negative photoelastic film 120 on the second polarizing plate 160 side of the second glass substrate 113 N f2 : The number of negative photoelastic films 120 on the second polarizing plate 160 side of the second glass substrate 113

[0036] <<Examples and Comparative Examples>> The effects of the present invention will be explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0037] <Comparative Example 1> 15 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-attached liquid crystal panel included in a liquid crystal display device of Comparative Example 1. As illustrated, the liquid crystal display device of Comparative Example 1 includes, in order from the backlight (not shown), a first polarizing plate 150, an adhesive layer 231, a liquid crystal panel 110, an adhesive layer 236, and a second polarizing plate 160. The first polarizing plate 150, the adhesive layer 231, the liquid crystal panel 110, the adhesive layer 236, and the second polarizing plate 160 are laminated and integrated. In this specification, a laminate in which the adhesive layers 231 and 236, the liquid crystal panel 110, etc. are arranged between the first polarizing plate 150 and the second polarizing plate 160 is referred to as a "polarizing plate-attached liquid crystal panel."

[0038] The liquid crystal panel 110 of Comparative Example 1 had a screen size of 11.4 inches (259 mm × 151 mm) and a display mode of FFS (Fringe Field Switching). The liquid crystal panel 110 had the configuration shown in FIG. 5 and was composed of a TFT substrate, a liquid crystal layer, and a color filter substrate, and the liquid crystal layer contained positive liquid crystal. The TFT substrate was the substrate on the backlight side and included a first glass substrate as the first substrate. The color filter substrate was the substrate on the viewer side and included a second glass substrate as the second substrate. Hereinafter, when referring to matters common to the first glass substrate and the second glass substrate, they will also be simply referred to as "glass substrates." The first polarizing plate (backlight-side polarizing plate) 150 was a laminate of, from the backlight side, a protective layer (triacetyl cellulose (TAC)), a polarizing layer (polyvinyl alcohol (PVA)), and a protective layer (triacetyl cellulose (TAC)), with a total thickness of 65 μm. The second polarizing plate (observer-side polarizing plate) 160 was a laminate of, from the liquid crystal panel side, a viewing angle compensation layer (cycloolefin polymer (COP)), a polarizing layer (polyvinyl alcohol (PVA)), and a protective layer (triacetyl cellulose (TAC)), with a total thickness of 80 μm. The adhesive layers 231 and 236 were made of an acrylic adhesive, had a thickness of 20 μm, and had a storage modulus of 0.04 MPa at 25°C.

[0039] Photoelastic coefficient β of glass substrate g, thickness d g , and the photoelastic coefficient β g and thickness d g The product of was as follows: The following values ​​represent the values ​​for the glass substrate included in the color filter substrate and the glass substrate included in the TFT substrate. Photoelastic coefficient β g :+3.60E-13(cm 2 / dyn) Thickness d g :150μm(=0.15mm) β g ×d g :+5.40E-15(cm 3 / dyn)

[0040] (Method for evaluating unevenness in black display) The polarizing plate-equipped liquid crystal panel was attached to a flat cover glass with a thickness of 1.7 mm. In this specification, the laminate in which the polarizing plate-equipped liquid crystal panel and the cover glass are attached is referred to as a "liquid crystal panel with cover glass." Note that the polarizing plate-equipped liquid crystal panel of Comparative Example 1, in the state shown in Figure 15, had slight warping due to shrinkage of the polarizing plate. However, by attaching this slightly warped liquid crystal panel with polarizing plate to the cover glass, the warping was forcibly eliminated. The resulting liquid crystal panel with cover glass was placed on a backlight, and the luminance distribution within the panel surface in the black display state was measured using a two-dimensional color luminance meter (CA-2000 manufactured by Konica Minolta, Inc.) From the measurement results, the minimum luminance within the panel surface was divided by the maximum luminance, as shown in the following formula, to obtain an index value for black display unevenness. (Black display unevenness index value) = (minimum luminance on panel surface in black display state) ÷ (maximum luminance on panel surface in black display state) × 100 [%] The smaller the brightness variation within the panel surface in the black display state, i.e., the less unevenness there is, the closer the maximum and minimum brightness values ​​within the panel surface will be, and the closer the index value will be to 100%. In other words, the larger the index value, the less unevenness there will be in a polarizing plate-equipped liquid crystal panel. According to the results of subjective evaluations in which the black display unevenness of polarizing plate-equipped liquid crystal panels having various black display unevenness index values ​​was visually evaluated, it was found that unevenness becomes difficult to see when the index value exceeds 30%.

[0041] (Evaluation results for black display unevenness) The brightness distribution within the panel surface in the black display state of the liquid crystal panel with cover glass of Comparative Example 1 was measured, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 23%, and unevenness was clearly visible. Maximum brightness on panel: 2.730 (cd / m 2 ) Minimum brightness on panel: 0.630 (cd / m 2 ) Black display unevenness index value: 23%

[0042] <Comparative Example 2> 16 is a cross-sectional view schematically showing the configuration of a polarizing plate-equipped liquid crystal panel included in a liquid crystal display device of Comparative Example 2. As shown in the figure, the liquid crystal display device of Comparative Example 2 includes, in order from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 124, an adhesive layer 234, an acrylic film 123, an adhesive layer 233, an acrylic film 122, an adhesive layer 232, an acrylic film 121, an adhesive layer 231, a liquid crystal panel 110, an adhesive layer 236, an acrylic film 126, an adhesive layer 237, an acrylic film 127, an adhesive layer 238, an acrylic film 128, an adhesive layer 239, an acrylic film 129, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0043] In Comparative Example 2, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 were the same as those described in Comparative Example 1, and four acrylic films were attached to both the viewer side and the backlight side of the liquid crystal panel 110 via adhesive layers. The acrylic films 121 to 124 and 126 to 129 were films made of polymethyl methacrylate resin (PMMA). The adhesive layers 231 to 234 and 236 to 239 were made of an acrylic adhesive and had a storage modulus of 0.04 MPa at 25°C.

[0044] The acrylic films 121 to 124 and 126 to 129 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the viewer side and the backlight side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of was as follows. Note that the following β f ×d f ×N f The value of represents the total value on the viewer side of the liquid crystal panel 110 and the total value on the backlight side of the liquid crystal panel 110. Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f : 4 sheets β f ×d f ×N f :-5.40E-15(cm 3 / dyn)

[0045] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state of the liquid crystal panel with cover glass of Comparative Example 2 was measured, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 28%, which was a slight improvement over Comparative Example 1, but did not reach the target improvement of 30%, and unevenness was still clearly visible. Maximum brightness on panel: 2.170 (cd / m 2 ) Minimum brightness on panel: 0.601 (cd / m 2 ) Black display unevenness index value: 28%

[0046] In Comparative Example 2, the number of laminated acrylic films was f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g The number of sheets was set to four so that the difference was equal to the difference in the optical elasticity of the glass substrate. In principle, this configuration should allow the phase difference resulting from the photoelasticity of the glass substrate when stress is applied to be offset by the same magnitude of perpendicular phase difference generated in the acrylic film, which has a negative photoelastic coefficient. However, the results show that this is not actually the case. In the configuration of Comparative Example 2, the stress on the polarizing plate-equipped liquid crystal panel generated by attachment to the cover glass was not transmitted by the adhesive layer, which has a small storage modulus. As a result, the acrylic film was not subjected to the same magnitude of stress as the liquid crystal panel (glass substrate), which is thought to be why black display unevenness was not improved.

[0047] Example 1 9 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in the liquid crystal display device of Example 1. As illustrated, the liquid crystal display device of Example 1 includes, in order from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 124, a high elastic modulus adhesive layer 134, an acrylic film 123, a high elastic modulus adhesive layer 133, an acrylic film 122, a high elastic modulus adhesive layer 132, an acrylic film 121, a high elastic modulus adhesive layer 131, a liquid crystal panel 110, a high elastic modulus adhesive layer 136, an acrylic film 126, a high elastic modulus adhesive layer 137, an acrylic film 127, a high elastic modulus adhesive layer 138, an acrylic film 128, a high elastic modulus adhesive layer 139, an acrylic film 129, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0048] In Example 1, the first polarizing plate 150, the liquid crystal panel 110, and the second polarizing plate 160 used were the same as those described in Comparative Example 1. The liquid crystal panel 110 was composed of a TFT substrate, a liquid crystal layer, and a color filter substrate, the TFT substrate including a glass substrate corresponding to the first substrate that exhibits birefringence in a direction parallel to the direction of stress, the liquid crystal layer containing positive liquid crystals, and the color filter substrate including a glass substrate corresponding to the second substrate that exhibits birefringence in a direction parallel to the direction of stress.

[0049] Four acrylic films were attached to both the viewer side (the second polarizer 160 side of the second substrate) and the backlight side (the first polarizer 150 side of the first substrate) of the liquid crystal panel 110 via high-elasticity adhesive layers. That is, the liquid crystal display device of Example 1 had laminates including four high-elasticity adhesive layers and four acrylic films on each of the viewer side (the second polarizer 160 side of the second substrate) and the backlight side (the first polarizer 150 side of the first substrate) of the liquid crystal panel 110. The acrylic films 121 to 124 and 126 to 129 were films made of polymethyl methacrylate resin (PMMA). The high-elasticity adhesive layers 131 to 134 and 136 to 139 were made of an acrylic pressure-sensitive adhesive and had a storage modulus of 0.11 MPa at 25°C.

[0050] The acrylic films 121 to 124 and 126 to 129 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the viewer side and the backlight side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of was as follows. Note that the following β f ×d f ×N f The value of represents the total value on the viewer side of the liquid crystal panel 110 and the total value on the backlight side of the liquid crystal panel 110. Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f : 4 sheets β f ×d f ×N f :-5.40E-15(cm 3 / dyn)

[0051] In Example 1, four acrylic films were laminated on both the viewer side and the backlight side of the liquid crystal panel 110, and the photoelastic coefficient β f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g was adjusted to be equal to

[0052] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state of the liquid crystal panel with cover glass of Example 1 was measured, and the maximum brightness and minimum brightness were extracted, as shown below. The black display unevenness index value was 60%, which was an improvement over Comparative Example 2 and greatly exceeded the target improvement of 30%, and no unevenness was visible. Maximum brightness on panel: 1.075 (cd / m 2 ) Minimum brightness on panel: 0.645 (cd / m 2 ) Black display unevenness index value: 60%

[0053] In Example 1, it is considered that a high elastic modulus pressure-sensitive adhesive layer having a large storage modulus was used to attach the acrylic film, and therefore stress of the same magnitude as that applied to the liquid crystal panel (glass substrate) was also applied to the acrylic film. Therefore, a photoelastic retardation of the same magnitude as that generated in the glass substrate was generated in the acrylic film, with the retardation axis perpendicular to the retardation axis of the glass substrate. As a result, the retardation generated in the glass substrate and the retardation generated in the acrylic film were offset, and black display unevenness was significantly improved.

[0054] <Example 2> 10 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in a liquid crystal display device of Example 2. As illustrated, the liquid crystal display device of Example 2 includes, in order from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 122, a high elastic modulus tacky adhesive layer 132, an acrylic film 121, a high elastic modulus tacky adhesive layer 131, a liquid crystal panel 110, a high elastic modulus tacky adhesive layer 136, an acrylic film 126, a high elastic modulus tacky adhesive layer 137, an acrylic film 127, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0055] In Example 2, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 were the same as those described in Comparative Example 1, and two acrylic films were attached to each of the viewer side and backlight side of the liquid crystal panel 110 via high-elasticity adhesive layers. The acrylic films 121, 122, 126, and 127 were films made of polymethyl methacrylate resin (PMMA). The high-elasticity adhesive layers 131, 132, 136, and 137 were made of an acrylic adhesive and had a storage modulus of 0.11 MPa at 25°C.

[0056] The acrylic films 121, 122, 126, and 127 have a negative photoelastic coefficient, and their photoelastic coefficient β f , thickness d f , the number of films on the viewer side and the backlight side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of was as follows. Note that the following β f ×d f ×N f The value of represents the total value on the viewer side of the liquid crystal panel 110 and the total value on the backlight side of the liquid crystal panel 110. Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f: 2 sheets β f ×d f ×N f :-2.70E-15(cm 3 / dyn)

[0057] In Example 2, two acrylic films were laminated on both the viewer side and the backlight side of the liquid crystal panel 110, and the photoelastic coefficient β of the film was f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g was adjusted to be half of

[0058] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state was measured for the liquid crystal panel with cover glass of Example 2, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 43%, which was less effective than Example 1 in which four acrylic films were laminated on each side of the liquid crystal panel 110, but the result far exceeded the improvement target of 30%, and unevenness was almost unnoticeable. Maximum brightness on panel: 1.431 (cd / m 2 ) Minimum brightness on panel: 0.617 (cd / m 2 ) Black display unevenness index value: 43%

[0059] Example 3 11 is a cross-sectional view schematically showing the configuration of a liquid crystal panel with a polarizing plate included in a liquid crystal display device of Example 3. As shown in the figure, the liquid crystal display device of Example 3 includes, in order from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 121, a high elastic modulus adhesive layer 131, a liquid crystal panel 110, a high elastic modulus adhesive layer 136, an acrylic film 126, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0060] In Example 3, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 used were the same as those described in Comparative Example 1, and one acrylic film was attached to each of the viewer side and backlight side of the liquid crystal panel 110 via a high elastic modulus adhesive layer. The acrylic films 121 and 126 were films made of polymethyl methacrylate resin (PMMA). The high elastic modulus adhesive layers 131 and 136 were made of an acrylic adhesive and had a storage modulus of 0.11 MPa at 25°C.

[0061] The acrylic films 121 and 126 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the viewer side and the backlight side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of was as follows. Note that the following β f ×d f ×N f The values ​​represent the values ​​on the viewer side of the liquid crystal panel 110 and the backlight side of the liquid crystal panel 110, respectively. Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f : 1 sheet β f ×d f ×N f :-1.35E-15(cm3 / dyn)

[0062] In Example 3, one acrylic film was laminated on each of the viewer side and the backlight side of the liquid crystal panel 110, and the photoelastic coefficient β of the film was f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g It was adjusted to be 1 / 4 of the original value.

[0063] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state was measured for the liquid crystal panel with cover glass of Example 3, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 34%, which was even less effective than Example 2, in which two acrylic films were laminated on each side of the liquid crystal panel 110, but it exceeded the improvement target of 30%, and unevenness was almost invisible. Maximum brightness on panel: 1.830 (cd / m 2 ) Minimum brightness on panel: 0.625 (cd / m 2 ) Black display unevenness index value: 34%

[0064] Example 4 12 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in a liquid crystal display device of Example 4. As illustrated, the liquid crystal display device of Example 4 includes, in order from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 124, a high elastic modulus tacky adhesive layer 134, an acrylic film 123, a high elastic modulus tacky adhesive layer 133, an acrylic film 122, a high elastic modulus tacky adhesive layer 132, an acrylic film 121, a high elastic modulus tacky adhesive layer 131, a liquid crystal panel 110, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0065] In Example 4, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 used were the same as those described in Comparative Example 1, and four acrylic films were attached only to the backlight side of the liquid crystal panel 110 via high elastic modulus adhesive layers. The acrylic films 121 to 124 were films made of polymethyl methacrylate resin (PMMA). The high elastic modulus adhesive layers 131 to 134 were made of an acrylic adhesive and had a storage modulus of 0.11 MPa at 25°C.

[0066] The acrylic films 121 to 124 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the backlight side of the liquid crystal panel 110 N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of these was as follows: Note that the value of βf×df×Nf below represents the total value on the backlight side of the liquid crystal panel 110. Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f : 4 sheets β f ×d f ×N f :-5.40E-15(cm 3 / dyn)

[0067] In Example 4, four acrylic films were laminated only on the backlight side of the liquid crystal panel 110, and the photoelastic coefficient β f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g×d g was adjusted to be equal to

[0068] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state was measured for the liquid crystal panel with cover glass of Example 4, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 51%, which was a higher value than Example 2 in which a total of four acrylic films were used, and exceeded the improvement target of 30%, and no unevenness was visible. Maximum brightness on panel: 1.194 (cd / m 2 ) Minimum brightness on panel: 0.609 (cd / m 2 ) Black display unevenness index value: 51%

[0069] The reasons for the above results are thought to be as follows: First, the general principle behind the occurrence of black display unevenness when stress is applied to a liquid crystal panel is as follows (1) to (6). (1) Stress is applied to the LCD panel (2) A phase difference due to photoelasticity occurs on both the glass substrate placed on the backlight side and the glass substrate placed on the observer side due to the application of stress. (3) The light that has become ideally linearly polarized after passing through the polarizing plate on the backlight side becomes slightly elliptically polarized due to the phase difference caused by photoelasticity that occurs in the glass substrate on the backlight side. (4) The elliptically polarized light is incident on the liquid crystal layer, and as it passes through the liquid crystal layer, it is converted into elliptically polarized light with a greater ellipticity (the polarization disturbance is accentuated by passing through the liquid crystal layer). (5) The light that passes through the liquid crystal layer becomes elliptically polarized light with a greater ellipticity due to the phase difference caused by photoelasticity that occurs on the glass substrate on the observer side (however, this is not as great as the change in polarization that occurs when the light passes through the liquid crystal layer). (6) A portion of the light that has become highly elliptically polarized is ultimately not absorbed by the polarizer placed on the observer side, resulting in light leakage in the black display, which is perceived as unevenness. In the principle of how the black display unevenness described above occurs, the above steps (3) and (4) are the dominant factors for the black display unevenness. Therefore, if the phase difference caused by photoelasticity that occurs in the glass substrate arranged on the backlight side can be reduced, the emphasis on polarization disturbance caused by light passing through the liquid crystal layer in an elliptically polarized state will no longer occur, and the black display unevenness can be effectively improved.

[0070] <Example 5> 13 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in the liquid crystal display device of Example 5. As illustrated, the liquid crystal display device of Example 5 includes, in order from the backlight (not shown) side, a first polarizing plate 150, a liquid crystal panel 110, a high elastic modulus adhesive layer 136, an acrylic film 126, a high elastic modulus adhesive layer 137, an acrylic film 127, a high elastic modulus adhesive layer 138, an acrylic film 128, a high elastic modulus adhesive layer 139, an acrylic film 129, and a second polarizing plate 160. These layers and films are laminated and integrated.

[0071] In Example 5, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 used were the same as those described in Comparative Example 1, and four acrylic films were attached only to the viewer side of the liquid crystal panel 110 via high elastic modulus adhesive layers. The acrylic films 126 to 129 were films made of polymethyl methacrylate resin (PMMA). The high elastic modulus adhesive layers 136 to 139 were made of an acrylic adhesive and had a storage modulus of 0.11 MPa at 25°C.

[0072] The acrylic films 126 to 129 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the viewer side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product of these was as follows: Note that the value of βf×df×Nf below represents the total value on the viewer side of the liquid crystal panel 110. Photoelastic coefficient βf :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films N f : 4 sheets β f ×d f ×N f :-5.40E-15(cm 3 / dyn)

[0073] In Example 5, four acrylic films were laminated only on the viewer side of the liquid crystal panel 110, and the photoelastic coefficient β of the film was f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g was adjusted to be equal to

[0074] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state was measured for the liquid crystal panel with cover glass of Example 5, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 37%, which was smaller than Example 2 in which two acrylic films were laminated on each side of the liquid crystal panel 110, and Example 4 in which four acrylic films were laminated on the backlight side, but it exceeded the improvement target of 30%, and unevenness was almost not visible. Maximum brightness on panel: 1.732 (cd / m 2 ) Minimum brightness on panel: 0.641 (cd / m 2 ) Black display unevenness index value: 37%

[0075] Example 6 14 is a cross-sectional view schematically illustrating the configuration of a polarizing plate-equipped liquid crystal panel included in a liquid crystal display device of Example 6. As illustrated, the liquid crystal display device of Example 6 includes, from the backlight (not shown) side, a first polarizing plate 150, an acrylic film 124, a high elastic modulus adhesive layer 134A, an acrylic film 123, a high elastic modulus adhesive layer 133A, an acrylic film 122, a high elastic modulus adhesive layer 132A, an acrylic film 121, a high elastic modulus adhesive layer 131A, a liquid crystal panel 110, a high elastic modulus adhesive layer 136A, an acrylic film 126, a high elastic modulus adhesive layer 137A, an acrylic film 127, a high elastic modulus adhesive layer 138A, an acrylic film 128, a high elastic modulus adhesive layer 139A, an acrylic film 129, and a second polarizing plate 160, in this order. These layers and films are laminated and integrated.

[0076] In Example 6, the first polarizing plate 150, liquid crystal panel 110, and second polarizing plate 160 were the same as those described in Comparative Example 1, and four acrylic films were attached to both the viewer side and the backlight side of the liquid crystal panel 110 via high-elasticity adhesive layers. The acrylic films 121 to 124 and 126 to 129 were films made of polymethyl methacrylate resin (PMMA). The high-elasticity adhesive layers 131A to 134A and 136A to 139A were made of an acrylic adhesive and had a storage modulus of 0.13 MPa at 25°C.

[0077] The acrylic films 121 to 124 and 126 to 129 have a negative photoelastic coefficient, and the photoelastic coefficient β f , thickness d f , the number of films on the viewer side and the backlight side of the liquid crystal panel 110, N f , and the photoelastic coefficient β f and thickness d f and the number of films N f The product was as follows: Photoelastic coefficient β f :-2.70E-13(cm 2 / dyn) Thickness d f :50μm Number of films Nf : 4 sheets β f ×d f ×N f :-5.40E-15(cm 3 / dyn)

[0078] In Example 6, four acrylic films were laminated on both the viewer side and the backlight side of the liquid crystal panel 110, and the photoelastic coefficient β f and film thickness d f and the number of films N f The product β f ×d f ×N f is the photoelastic coefficient β of the glass substrate. g and the thickness of the glass substrate, d g The product β g ×d g was adjusted to be equal to

[0079] (Evaluation results for black display unevenness) Using the same evaluation method as in Comparative Example 1, the brightness distribution within the panel surface in the black display state was measured for the liquid crystal panel with cover glass of Example 6, and the maximum and minimum brightness values ​​were extracted, as shown below. The black display unevenness index value was 66%, which was far above the improvement target of 30%, and no unevenness was visible. Maximum brightness on panel: 0.973 (cd / m 2 ) Minimum brightness on panel: 0.638 (cd / m 2 ) Black display unevenness index value: 66%

[0080] In Example 6, it is considered that a high elastic modulus pressure-sensitive adhesive layer having a large storage modulus was used to attach the acrylic film, and therefore, stress of the same magnitude as that applied to the liquid crystal panel (glass substrate) was also applied to the acrylic film. Therefore, a retardation due to photoelasticity of the same magnitude as that generated in the glass substrate was generated in the acrylic film, with the retardation axis perpendicular to the retardation axis of the glass substrate. As a result, the retardation generated in the glass substrate and the retardation generated in the acrylic film were offset, and black display unevenness was significantly improved. [Explanation of symbols]

[0081] 10: Measurement sample 11: Force gauge 12A: Light emitting part 12B: Light receiving part 80: Backlight 100: LCD panel with polarizer 110: LCD panel 112: Color filter substrate 113: Second glass substrate 114: Liquid crystal layer 116: TFT substrate 117: First glass substrate 120: Negative photoelastic film 121, 122, 123, 124, 126, 127, 128, 129: Acrylic film 130, 131, 131A, 132, 132A, 133, 133A, 134, 134A, 136, 136A, 137, 137A, 138, 138A, 139, 139A: High elastic modulus adhesive layer 150: First polarizing plate 160: Second polarizing plate 231, 232, 233, 234, 236, 237, 238, 239: Adhesive layer 310: LCD panel before polarizing plate attachment 320: LCD panel after polarizing plate is attached 330: Forced flattened LCD panel 350: Cover glass 380: LCD panel after cover glass is attached 400: LCD panel with polarizer

Claims

1. Backlight and a first polarizer; a first substrate that exhibits birefringence in a direction parallel to the direction of stress; A liquid crystal layer; a second substrate that exhibits birefringence in a direction parallel to the direction of the stress; a second polarizing plate, At least one of the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate is provided with a pressure-sensitive adhesive layer having a storage modulus of 0.10 MPa or more at 25°C and a laminate of a film that exhibits birefringence in a direction perpendicular to the stress direction. LCD display device.

2. The liquid crystal display device according to claim 1 , wherein a plurality of the laminates are provided on at least one of the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate.

3. The liquid crystal display device according to claim 1 , wherein the laminate is provided on both the first substrate closer to the first polarizing plate and the second substrate closer to the second polarizing plate.

4. 2. The liquid crystal display device according to claim 1, wherein the laminate is provided only on the first polarizing plate side of the first substrate.

5. 2. The liquid crystal display device according to claim 1, wherein the laminate is provided only on the second polarizing plate side of the second substrate.

6. A liquid crystal display device according to any one of claims 1 to 5, wherein the sum of the absolute values ​​of the product of the photoelastic constant and the thickness of the films included in the laminate is substantially equal to the absolute value of the product of the photoelastic constant and the thickness of the substrate arranged adjacent to the first substrate and the second substrate.

7. 6. The liquid crystal display device according to claim 1, wherein the film contains a polymethyl methacrylate resin.

Images