WO2019009144A1

WO2019009144A1 - Liquid crystal display device

Info

Publication number: WO2019009144A1
Application number: PCT/JP2018/024262
Authority: WO
Inventors: 健治藤田; 全亮齊藤; 隆行夏目
Original assignee: シャープ株式会社
Priority date: 2017-07-04
Filing date: 2018-06-27
Publication date: 2019-01-10

Abstract

The present invention provides a liquid crystal display device capable of suppressing the occurrence of black irregularities even after being left at high temperatures. The present invention is a liquid crystal display device (1) comprising a liquid crystal panel (2) which is a rectangular shape in plan view, wherein: the liquid crystal panel (2) includes, in this order, a first polarizer (10), two or more optical compensation layers (11), a liquid crystal cell, one or more optical compensating layers (21) and a second polarizer; the total number of optical compensating layers situated between the first polarizer (10) and the liquid crystal cell is larger than the total number of optical compensating layers situated between the second polarizer and the liquid crystal cell; and the angle (α) formed by the absorption axis (10a) of the first polarizer (10) and the long edges (2a) of the liquid crystal panel (2) is 45°-135° inclusive.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device suitable for a liquid crystal display device in a vertical alignment mode provided with a pair of circularly polarizing plates.

Liquid crystal display devices are used in a wide range of fields, taking advantage of features such as thinness, lightness, and low power consumption. A liquid crystal display device generally includes a pair of polarizers and a liquid crystal cell provided between the pair of polarizers, and various display modes such as vertical alignment (VA) mode and horizontal alignment mode are developed. There is.

For example, in Patent Document 1, as a liquid crystal display device capable of obtaining uniform high contrast even when viewed from various directions, a pair of polarizers consisting of polarizer A and polarizer B and a pair of polarizers are disclosed. The liquid crystal display device is provided with a liquid crystal cell of the vertical alignment type disposed in the above, and Nz represented by the following formula (1) between the liquid crystal cell and the polarizer A and between the liquid crystal cell and the polarizer B: Retarders each having a value of more than 2.0, and the in-plane slow axis of the quarter-wave retarder has a positional relationship of approximately 45 ° with the transmission axis of the adjacent polarizer, At least one of A and the adjacent 1⁄4 λ retardation plate and / or between the polarizer B and the adjacent 1⁄4 λ retardation plate comprises a material layer having a negative intrinsic birefringence value, And the in-plane slow axis is in a positional relationship substantially parallel or nearly orthogonal to the absorption axis of the adjacent polarizer A liquid crystal display device comprising an optical anisotropic body is disclosed.
Nz = (nx-nz) / (nx-ny) (1)

Further, according to Patent Document 2, as a liquid crystal display device capable of suppressing deterioration of display quality, a first substrate having a pair of first short sides and a pair of first long sides is opposed to the first substrate. A liquid crystal display panel comprising a second substrate disposed, a liquid crystal layer held between the first substrate and the second substrate, and displaying an image in an active area, and an outer surface side of the first substrate , And the angle a1 formed by the pair of second short sides longer than the first short side, the pair of second long sides, and the second short side is an angle b1 formed by the second long side A liquid crystal display comprising a first polarizing plate having a small first absorption axis and a second polarizing plate disposed on the outer surface side of the second substrate and having a second absorption axis is disclosed. .

Further, in Patent Document 3, a substrate made of glass or resin and a front-side laminate provided on the viewing side of the substrate are provided as an image display device in which the panel is prevented from warping and the decrease in display performance is suppressed. It is an image display apparatus provided with the rectangular panel which has the back side laminated body provided in the back side of the said board | substrate, Comprising: The said front side laminated body has a polarizer, The absorption axis of the said polarizer is the short of the said panel An image display device parallel to the side direction is disclosed.

In addition, according to Patent Document 4, the liquid crystal panel has a small warp even after being placed in a moist heat environment, and as a liquid crystal display device with little display unevenness, the front side with the first adhesive layer on the viewer side of the liquid crystal cell It is a liquid crystal display in which a polarizing plate is laminated, a back side polarizing plate is laminated on the opposite side via a second adhesive layer, and a backlight unit is disposed outside the back side polarizing plate. Layer structure of the first transparent protective film / polarizing film / second transparent protective film / third adhesive layer / retardation film from the light unit side, and the retardation film being a core layer made of a styrenic resin It is considered as the 3 layer structure which formed the skin layer which consists of a rubber particle content acrylic resin composition on both sides, and the first pressure sensitive adhesive layer, the second pressure sensitive adhesive layer and the third pressure sensitive adhesive layer are all stored at 50 ° C. Elastic modulus is 0.01MPa or less A liquid crystal display device is disclosed which consists of the 0.1MPa or less.

Further, in Patent Document 5, in order to prevent a phenomenon in which the liquid crystal display panel is bent by the shrinkage of the polarizing plate in the uniaxial stretching direction when the temperature of the polarizing plate attached to the liquid crystal display panel rises, There is disclosed a liquid crystal display panel in which a TFT substrate and an opposite substrate are formed thin, which is a flexible display, and the opposite substrate and a polarizing plate are fixed at one point by an adhesive.

Further, in Patent Document 6, as a liquid crystal display device for improving peeling of a polarizing plate, a liquid crystal cell having a quadrilateral display surface in which a liquid crystal layer is enclosed in a glass substrate and an adhesive layer on both sides of the display cell In the liquid crystal display device including the above-mentioned polarizing plate, the polarizing plate having a polarizer having a large maximum dimension in the absorption axis direction on the display surface is more glass than the polarizing plate having a polarizer having a smaller maximum dimension in the absorption axis direction. A liquid crystal display device is disclosed which is adhered by an adhesive layer having high adhesion to a substrate.

JP, 2009-37049, A JP, 2014-89398, A JP 2007-133350 A JP 2011-248178 A JP, 2011-107391, A JP, 2013-109250, A

In recent years, high-temperature durability is required for liquid crystal display devices, particularly for vehicles, but as in the liquid crystal display device described in Patent Document 1, as a circularly polarizing plate, in addition to a λ / 4 retardation plate When another optical compensation layer (optical compensation film) is used, whitening (black unevenness) of black display may be confirmed in a partial region of the display region where an image is displayed.

FIG. 13 is a schematic view of a liquid crystal display device according to Comparative Embodiment 1 studied by the present inventors, (a) is a plan view, and (b) is a cross-sectional view.
According to the study of the present inventors, the cause of the black unevenness is a change in characteristics of a component between a pair of polarizers, for example, an optical compensation film, an optical compensation layer such as λ / 4 retardation plate, a glass substrate of a liquid crystal cell It turned out that it was. It is known that solid materials such as glass and plastic exhibit birefringence when a stress is applied (= photoelasticity). In addition, it is known that a stretched film thermally shrinks in the stretching direction in a high temperature state, but a polarizer in which a dichroic substance (dichroic dye) such as a dichroic dye or iodine is oriented is Generally, a method of producing a hydrophilic polymer film such as a polyvinyl alcohol-based film by stretching it in the absorption axis direction is generally used, and hence the polarizer shrinks in the absorption axis direction at high temperature. On the other hand, since the glass does not shrink, stress is generated in the film between the polarizer and the glass substrate, and birefringence different from the optical design is developed. This characteristic change (change in optical parameters) is, as shown in FIG. 13, the both sides of the display area in the absorption axis direction of the front polarizer on the side on which many optical compensation layers such as λ / 4 retardation plates and optical compensation films are arranged. It turned out that it becomes especially remarkable. However, since there is a direction in birefringence due to photoelasticity, whitening of the black display does not necessarily occur where birefringence is large, and the position is determined by the optical design of the panel or polarizing plate (including the optical compensation layer). It is different. However, due to the large difference in characteristics across the panel, whitening occurs on a part of the panel, resulting in black unevenness.

That is, the mechanism of the occurrence of the black unevenness (black screen luminance distribution) is as follows.
1. Due to factors such as high heat, the polarizer shrinks in the absorption axis direction.
2. On the other hand, since the glass of the liquid crystal cell does not shrink, stress is generated between the polarizer and the glass to be shrunk (with all the materials between them).
3. The material to which stress is applied changes its optical parameter (numerical value of optical anisotropy) by photoelasticity.
4. Since the stress is not constant in the plane, the difference in optical parameters becomes large in the panel plane.
5. When a black solid screen is used, the transmittance of each place differs depending on the difference in optical parameters. That is, whitening of the black display (increase in transmittance) occurs in a partial area and is observed as unevenness.

Patent Document 2 focuses on the fact that the polarizing plate shrinks in the absorption axis direction due to a high temperature environment, and proposes an axial direction and a size for reducing light leakage due to the polarizing plate end coming too close to the display region. doing. According to this, although it is possible to prevent light leakage at the end portion due to the reduction of the polarizing plate, the contraction itself of the polarizing plate occurs, so it is considered that the black unevenness due to the above photoelastic effect can not be prevented.

Further, Patent Documents 3 to 6 neither disclose nor suggest the problem of the above-described black unevenness and the means for solving the same.

The present invention has been made in view of the above-mentioned present situation, and it is an object of the present invention to provide a liquid crystal display device capable of suppressing the occurrence of black unevenness even after being placed under high temperature.

The inventors of the present invention variously examined a liquid crystal display device capable of suppressing the occurrence of black unevenness even after being placed under high temperature, and focused attention on heat shrinkage of a polarizer. And although it is difficult to avoid the heat contraction itself of the polarizer manufactured by drawing, since the contraction occurs in the absorption axis direction, the absorption axis of the polarizer is parallel to the long side of the polarizer The closer to the point, the larger the contraction distance, the larger the stress generated in the optical compensation layer and the larger the change in retardation due to the photoelastic effect. It was found that the unevenness became remarkable because the difference of the parameter became large and the part where the whitening became large occurred. When the liquid crystal panel has a rectangular shape, the absorption axis of the polarizer can be made perpendicular to each long side of the liquid crystal panel, thereby suppressing the occurrence of a part where the contraction distance is large, and the panel surface It has been found that unevenness can be reduced by reducing the change in retardation of the optical compensation layer due to the photoelastic effect. However, on the other hand, in the normally black mode generally used as a liquid crystal display device, basically, the absorption axes of the polarizers on the viewing surface side and the back surface side of the liquid crystal cell are often orthogonal to each other. It is difficult to arrange the absorption axes of the respective polarizers on the viewing surface side and the rear surface side perpendicularly to the long side direction of the liquid crystal panel because the contrast is accompanied by a drop in the contrast. Therefore, as a result of further investigation, in the case of a liquid crystal display using a plurality of optical compensation layers, the number of optical compensation layers is asymmetrical between the viewing surface side and the back side of the liquid crystal cell, and then there are many optical compensation layers. More specifically, by making the absorption axis of the side polarizer perpendicular to each long side of the liquid crystal panel, more specifically, the angle formed by the absorption axis of the polarizer and each long side of the liquid crystal panel is 45 By making the temperature more than 135 °, it is found that black unevenness due to high temperature addition to the liquid crystal display device can be reduced, and it is thought that the above problem can be solved remarkably, and the present invention is achieved.

One embodiment of the present invention is a liquid crystal display device including a liquid crystal panel having a rectangular shape in plan view, wherein the liquid crystal panel includes a first polarizer, two or more optical compensation layers, a liquid crystal cell, and one or more optical compensation layers And a second polarizer in this order, and the total number of optical compensation layers provided between the first polarizer and the liquid crystal cell is an optical compensation provided between the second polarizer and the liquid crystal cell The angle between the absorption axis of the first polarizer and each long side of the liquid crystal panel may be 45 ° or more and 135 ° or less, which is larger than the total number of layers.

The angle may be 60 degrees or more and 120 degrees or less.

The optical compensation layer provided between the first polarizer and the liquid crystal cell includes a λ / 4 retardation plate, and the optical compensation layer provided between the second polarizer and the liquid crystal cell is , Λ / 4 retardation plates may be included.

The optical compensation layer provided between the first polarizer and the liquid crystal cell may include an optical compensation layer having a refractive index relationship of nx> nz> ny.

The optical compensation layer provided between the first polarizer and the liquid crystal cell may further include an optical compensation layer having a refractive index relationship of nx = ny> nz.

The display mode of the liquid crystal display may be a vertical alignment mode.

Each aspect of the present invention shown above may be combined suitably in the range which does not deviate from the gist of the present invention.

According to the present invention, it is possible to realize a liquid crystal display device capable of suppressing the occurrence of black unevenness even after being placed under high temperature.

FIG. 1 is a schematic plan view of a liquid crystal display device according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1. FIG. 5 is a schematic cross-sectional view of a liquid crystal display device according to a modification of Embodiment 1. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to another modification of Embodiment 1. FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to Example 1. FIG. 5 is a schematic cross-sectional view of a liquid crystal display device according to Comparative Example 1; It is another schematic diagram of the liquid crystal display device which concerns on Example 1, (a) is a top view which shows the relationship between the absorption axis of a polarizer, and the long side of a liquid crystal panel, (b) is an optical compensation layer. It is sectional drawing for demonstrating arrangement | positioning of and the shrinkage condition of a polarizer. It is another schematic diagram of the liquid crystal display device which concerns on the comparative example 1, (a) is a top view which shows the relationship between the absorption axis of a polarizer and the long side of a liquid crystal panel, (b) is an optical compensation layer. It is sectional drawing for demonstrating arrangement | positioning of and the shrinkage condition of a polarizer. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Example 2. It is another schematic diagram of the liquid crystal display device which concerns on Example 2, (a) is a top view which shows the relationship between the absorption axis of a polarizer, and the long side of a liquid crystal panel, (b) is an optical compensation layer. It is sectional drawing for demonstrating arrangement | positioning of and the shrinkage condition of a polarizer. FIG. 7 is a schematic cross-sectional view of a liquid crystal display device according to Example 3. It is another schematic diagram of the liquid crystal display device which concerns on Example 3, (a) is a top view which shows the relationship between the absorption axis of a polarizer, and the long side of a liquid crystal panel, (b) is an optical compensation layer. It is sectional drawing for demonstrating arrangement | positioning of and the shrinkage condition of a polarizer. It is a schematic diagram of the liquid crystal display device which concerns on the comparison form 1 which the present inventors examined, (a) is a top view, (b) is sectional drawing.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the contents described in the following embodiments, and design changes can be made as appropriate as long as the configuration of the present invention is satisfied.

<Definition of terms and symbols>
The definitions of terms and symbols in the present specification are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), and “ny” is the refractive index in the in-plane direction orthogonal to the slow axis "Nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
The in-plane retardation (Re) refers to the in-plane retardation value of a layer (film) at a wavelength of 550 nm at 23 ° C., unless otherwise specified. Re is obtained by Re = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
The thickness direction retardation (Rth) refers to the thickness direction retardation value of a layer (film) at a wavelength of 550 nm unless otherwise specified. Rth is determined by Rth = {(nx + ny) / 2−nz} × d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is obtained by Nz = (nx−nz) / (nx−ny).
(5) Optical compensation layer The optical compensation layer has an in-plane retardation Re of 15 nm or more and a retardation Rth in the thickness direction of +55 nm or more or -15 nm or less for light of wavelength 550 nm unless otherwise specified. And the function and optical performance thereof are not particularly limited. That is, the optical compensation layer is a layer satisfying 15 nm ≦ Re and Rth ≦ −15 nm or +55 nm ≦ Rth. On the other hand, a layer satisfying Re <15 nm and −15 nm <Rth <+55 nm is also referred to as a layer having no optical anisotropy.
(6) The viewing surface side and the rear surface viewing surface side mean the side closer to the screen (display surface) of the liquid crystal display device, and the rear surface side is more about the screen (display surface) of the liquid crystal display device It means the far side.

First Embodiment
FIG. 1 is a schematic plan view of the liquid crystal display device according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the liquid crystal display device according to the first embodiment.
As shown in FIG. 1, the liquid crystal display device 1 according to the present embodiment includes a liquid crystal panel 2 having a rectangular shape in plan view including a pair of long sides 2a and a pair of short sides 2b. The liquid crystal panel 2 has a rectangular display area 2c corresponding to the shape. A plurality of pixels (not shown) are arranged in a matrix in the display area 2c, and an image is displayed in the display area 2c.

The liquid crystal display device 1 is a transmissive or semi-transmissive (reflective / transmissive) liquid crystal display device, and as shown in FIG. 2, a liquid crystal panel 2 and a back light disposed on the back side of the liquid crystal panel 2 The liquid crystal panel 2 includes a first polarizer 10, an optical compensation layer 11 having two or more layers, a liquid crystal cell 30, an optical compensation layer 21 having one or more layers, and a second polarization. The child 20 is provided in this order from the observation surface side. However, the number (the number of layers) of all the optical compensation layers 11 provided between the first polarizer 10 and the liquid crystal cell 30 is the same as all the optical components provided between the second polarizer 20 and the liquid crystal cell 30. The number is larger than the number of compensation layers 21 (the number of layers). As shown in FIG. 1, all these members are also rectangular in plan view, and the first polarizer 10, the optical compensation layer 11, the optical compensation layer 21 and the second polarizer 20 at least have the display area 2c. It is arranged to cover.

The liquid crystal display device 1 is a normally black mode liquid crystal display device which performs black display when no voltage is applied. From the viewpoint of contrast, the

polarizers

10 and 20 are arranged in crossed nicols, and the first polarizer The ten absorption axes 10a and the absorption axes 20a of the second polarizer 20 are substantially orthogonal to each other. More specifically, the angle (absolute value) between the two axes is in the range of 90 ± 2 °, preferably in the range of 90 ± 0.6 °, and particularly preferably 90 ° (completely orthogonal ). Further, each of the

polarizers

10 and 20 generally includes a uniaxially stretched film which is a uniaxially stretched film, and has

absorption axes

10a and 20a in the stretching direction, respectively. Therefore, when the liquid crystal display device 1 including the

polarizers

10 and 20 is placed at high temperature, stress is applied to the optical compensation layers 11 and 21 due to the contraction in the absorption axis direction of the

polarizers

10 and 20 as described above. It is apprehended that black spots may occur due to characteristic changes.

However, in the present embodiment, the angle (absolute value) between the absorption axis 10 a of the first polarizer 10, that is, the polarizer adjacent to more optical compensation layers 11 and each long side 2 a of the liquid crystal panel 2. α is set to 45 ° or more and 135 ° or less. As a result, the thermal contraction amount of the first polarizer 10 at high temperature can be reduced, and the stress generated in many optical compensation layers 11 can be reduced, so that the deviation of the optical parameters of the optical compensation layer 11 from the design value is reduced be able to. On the other hand, the absorption axis 20 a of the second polarizer 20, that is, the polarizer adjacent to the less optical compensation layer 21 is in a direction close to parallel to each long side 2 a of the liquid crystal panel 2. Of the optical compensation layer 21 adjacent to the second polarizer 20 is smaller than the optical compensation layer 11 of the first polarizer 10, the optical parameters of the optical compensation layer 21 are increased. The influence of deviation from the design value of is relatively small. As described above, the liquid crystal display device 1 can suppress the occurrence of the black unevenness even after being placed under high temperature (of course also under high temperature).

FIG. 3 is a schematic cross-sectional view of a liquid crystal display device according to a modification of Embodiment 1.
If the number of optical compensation layers is asymmetrical on the viewing surface side and the back surface side of the liquid crystal cell 30, it is possible to exhibit the above-described black unevenness suppressing effect. Therefore, as shown in FIG. 3, the liquid crystal panel 2 includes the first polarizer 10, the optical compensation layer 11, the liquid crystal cell 30, the optical compensation layer 21, and the second polarizer 20 from the back side. It may be provided in this order. Also in this case, as in the case shown in FIG. 1, the absorption axis 10 a of the first polarizer 10, that is, the polarizer adjacent to more optical compensation layers 11 and each long side 2 a of the liquid crystal panel 2 Is set to 45 degrees or more and 135 degrees or less, the above-described black unevenness suppressing effect can be exhibited.

If the angle (absolute value) α is 45 ° or more and 135 ° or less, the above effect can be achieved, but preferably 60 ° or more and 120 ° or less, and particularly preferably 90 ° (completely Orthogonal).

FIG. 4 is a schematic cross-sectional view of a liquid crystal display device according to another modification of the first embodiment.
FIGS. 2 and 3 illustrate the case where one optical compensation layer and two optical compensation layers are provided on both sides of the liquid crystal cell 30, but the optical compensation layers disposed on both sides of the liquid crystal cell 30 are illustrated. The number of is not particularly limited as long as the number of optical compensation layers on the viewing surface side and the number of optical compensation layers on the back surface are different, for example, as shown in FIG. One optical compensation layer 21 and three optical compensation layers 11 may be provided, or two optical compensation layers and three optical compensation layers may be provided. In these cases, more optical compensation layers 11 may be disposed on either the viewing surface side or the back surface side of the liquid crystal cell 30. The total number of the larger number of optical compensation layers 11 is preferably 2 to 5 (more preferably 2 to 3) in terms of reliability and cost, but can be set according to the required performance. The total number of the optical compensation layers 21 is preferably 1 to 4 (more preferably 1 to 2) from the viewpoint of reliability and cost, but can be set according to the required performance. The difference between the total number of more optical compensation layers 11 and the smaller number of optical compensation layers 21 is also not particularly limited, but is preferably 1 to 3, and more preferably 1 to 2. Each configuration will be further described below.

<Polarizer>
Any appropriate polarizer may be adopted as the first polarizer 10 and the second polarizer 20 depending on the purpose. For example, a hydrophilic polymer film such as a polyvinyl alcohol-based film (hereinafter, also referred to as a PVA film), a partially formalized polyvinyl alcohol-based film, or an ethylene / vinyl acetate copolymer-based partially saponified film A film obtained by adsorbing a dichromatic substance (dichroic dye) of the above and uniaxially stretched, a dehydrated product of polyvinyl alcohol, a dehydrochlorinated product of polyvinyl chloride, and the like, and a polyene-based oriented film and the like. Among these, a polarizer obtained by adsorbing a dichroic substance (dichroic dye) such as iodine to a polyvinyl alcohol-based film and uniaxially stretching it is particularly preferable because the polarization dichroic ratio is high. The thickness of these polarizers is not particularly limited, but in general, it is about 5 to 30 μm.

A polarizer obtained by adsorbing iodine to a polyvinyl alcohol-based film and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. . If necessary, it may contain boric acid, zinc sulfate, zinc chloride or the like, or it may be immersed in an aqueous solution such as potassium iodide. Furthermore, if necessary, the polyvinyl alcohol-based film may be dipped in water and rinsed before dyeing. Stretching may be carried out after dyeing with iodine, may be stretched while dyeing, or may be dyed with iodine after being stretched. It can also be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

The first polarizer 10 and the second polarizer 20 may each be provided with a protective layer on the viewing surface side and the back surface side. The protective layer is formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material that is the main component of the film include, for example, cellulose resins such as triacetyl cellulose (TAC), and transparent resins such as cycloolefin resins. The cycloolefin resin will be described in detail later. Hereinafter, a film having triacetyl cellulose as a main component is also referred to as a TAC film, and a film having a cycloolefin resin, in particular, a cycloolefin polymer (COP) as a main component is also referred to as a COP film.

When a protective layer is provided on the liquid crystal cell 30 side of the first polarizer 10 and / or the second polarizer 20, the protective layer (inner protective layer) preferably has optical isotropy. Specifically, the retardation Rth in the thickness direction of the inner protective layer is preferably more than -15 nm and less than +15 nm, more preferably -10 nm or more and +10 nm or less, still more preferably -6 nm or more and +6 nm or less, particularly preferably -3 nm or more and +3 nm or less. The in-plane retardation Re of the inner protective layer is preferably 0 nm or more and less than 15 nm, more preferably 0 nm or more and 10 nm or less, still more preferably 0 nm or more and 6 nm or less, and particularly preferably 0 nm or more and 3 nm or less.

Further, instead of separately providing the inner protective layer, the optical compensation layers 11 and 21 on the liquid crystal cell 30 side of the first polarizer 10 and the second polarizer 20 may be used as the protective layer.

<Optical compensation layer>
Any appropriate retardation plate may be employed as each of the optical compensation layers 11 and 21 in accordance with the purpose and the display mode of the liquid crystal display device 1. The material and optical performance of each of the optical compensation layers 11 and 21 are not particularly limited, and, for example, a polymer film processed by stretching or the like, a liquid crystal material having fixed orientation, a thin plate made of an inorganic material, etc. Among them, those obtained by processing a polymer film such as stretching are preferable.

The method of forming each of the optical compensation layers 11 and 21 is not particularly limited, and in the case of a polymer film, for example, a solvent cast method, a melt extrusion method, or the like can be used. It may be a method of simultaneously forming a plurality of birefringent layers by a co-extrusion method. As long as the desired retardation is developed, it may be non-stretching or may be stretched. The stretching method is also not particularly limited, and it is a special stretching in which stretching is performed under the action of the shrinking force of the heat shrinkable film, in addition to the inter-roll tensile stretching method, inter-roll compression stretching method, tenter transverse uniaxial stretching method, longitudinal and transverse biaxial stretching method. A law etc. can be used. Moreover, in the case of a liquid crystalline material, for example, a method of applying a liquid crystalline material on a substrate film subjected to alignment treatment, and orienting and fixing can be used. Even if there is a method in which the substrate film is not subjected to special orientation processing as long as the desired phase difference is expressed, or a method in which the film is peeled off from the substrate film and transferred to another film after orientation fixation. Good. Furthermore, a method in which the orientation of the liquid crystal material is not fixed may be used. Also in the case of a non-liquid crystal material, the same formation method as the liquid crystal material may be used.

As a specific example of the material which becomes a main component of the polymer film for the optical compensation layers 11 and 21, transparent resin, such as cycloolefin type-resin, is mentioned, for example.

The cycloolefin resin used for the protective layer and the optical compensation layers 11 and 21 is not particularly limited as long as it is a resin having a monomer unit composed of cyclic olefin (cycloolefin), and cycloolefin polymer (COP) or cycloolefin resin (COP) It may be any of the olefin copolymers (COC). The cycloolefin copolymer refers to a non-crystalline cyclic olefin resin which is a copolymer of a cyclic olefin and an olefin such as ethylene.

As said cyclic olefin, polycyclic cyclic olefin and monocyclic cyclic olefin are mentioned. Examples of polycyclic cyclic olefins include norbornenes such as norbornene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene and butyl norbornene, dicyclopentadiene, dihydrodicyclopentadiene, methyldicyclopentadiene, dimethyldicyclopentadiene and the like Examples include tetracyclododecenes such as dicyclopentadienes, tetracyclododecene, methyltetracyclododecene and dimethyltetracyclododecene, and polymers of cyclopentadienes such as tricyclopentadiene and tetracyclopentadiene. Furthermore, examples of monocyclic cyclic olefins include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene and cyclododecatriene. Among them, norbornenes are preferable in terms of transparency, moisture resistance, and retardation control.

As shown in FIGS. 2 to 4, the optical compensation layer 11 provided between the first polarizer 10 and the liquid crystal cell 30 includes the λ / 4 retardation plate 11 a, and the second polarizer 20 and the liquid crystal cell The optical compensation layer 21 provided between 30 may include the λ / 4 retardation plate 21a. This form is suitable when the display mode of the liquid crystal display device 1 is set to a VA mode using a circularly polarizing plate. Here, the λ / 4 retardation plate is an electron optical birefringence plate that serves to rotate the polarization plane of the light beam, and has an optical path of 1⁄4 wavelength between linearly polarized light vibrating in directions perpendicular to each other. We say what has function to make difference. That is, it means that the phase between the ordinary ray component and the extraordinary ray component acts so as to be shifted by a quarter cycle, and circularly polarized light is converted to linearly polarized light (or linearly polarized light to circularly polarized light). Therefore, the first polarizer 10 and the λ / 4 retardation plate 11 a, and the second polarizer 20 and the λ / 4 retardation plate 21 a function as left and right circularly polarizing plates orthogonal to each other.

Generally, when the polarizer shrinks, stress is generated not only on the adjacent optical compensation film but also on the glass substrate constituting the liquid crystal cell, and birefringence (phase difference) is also generated on the glass substrate. The influence of the retardation of the glass substrate on the display characteristics tends to be larger when light incident on the glass substrate is circularly polarized than when linearly polarized. Therefore, in the case of using a circularly polarizing plate (usually, a combination of a polarizer and a λ / 4 retardation plate), the black unevenness caused by the contraction of the polarizer becomes strong. Therefore, in the above-described embodiment in which the optical compensation layer 11 includes the λ / 4 retardation plate 11a and the optical compensation layer 21 includes the λ / 4 retardation plate 21a, the black unevenness may be strong. Even according to the present embodiment, the occurrence of the black unevenness can be effectively suppressed.

The λ / 4 retardation plate 11a has an in-plane retardation Re of approximately 137.5 nm, but may be 110 to 165 nm, preferably 130 to 145 nm, and an Nz coefficient of 0.9 to The thing of 2.4 can be used. The slow axis (in-plane slow axis) of the λ / 4 retardation plate 11 a forms an angle of substantially 45 ° with the absorption axis 10 a of the first polarizer 10. More specifically, the angle (absolute value) between the two axes is in the range of 45 ± 5 °, preferably in the range of 45 ± 2 °, more preferably in the range of 45 ± 0.6 °. And particularly preferably 45 ° (completely 45 °).

The λ / 4 retardation plate 21a has an in-plane retardation Re of approximately 137.5 nm, but may be 110 to 165 nm, preferably 130 to 145 nm, and an Nz coefficient of 0.9 to The thing of 2.4 can be used. The slow axis (in-plane slow axis) of the λ / 4 retardation plate 21 a forms an angle of substantially 45 ° with the absorption axis 20 a of the second polarizer 20. More specifically, the angle (absolute value) between the two axes is in the range of 45 ± 5 °, preferably in the range of 45 ± 2 °, more preferably in the range of 45 ± 0.6 °. And particularly preferably 45 ° (completely 45 °).

Further, the slow axis (in-plane slow axis) of the λ / 4 phase difference plate 11a is substantially at an angle of 90 ° with respect to the slow axis (in-plane slow axis) of the λ / 4 phase difference plate 21a. I More specifically, the angle (absolute value) between the two axes is in the range of 90 ± 2 °, preferably in the range of 90 ± 0.6 °, and particularly preferably 90 ° (completely orthogonal ).

Further, as shown in FIGS. 2 to 4, the optical compensation layer 11 provided between the first polarizer 10 and the liquid crystal cell 30 has an optical compensation layer having a relationship of refractive index of nx> nz> ny (so-called Positive B plate) 11 b may be included. Thereby, the viewing angle characteristics of the liquid crystal display device 1 can be improved, that is, whitening in the oblique direction at the time of black display can be suppressed. On the other hand, the fact that the entire whiteness is small when viewed from an oblique direction means that the black unevenness is noticeable, but even in this case, according to the present embodiment, the occurrence of the black unevenness is effective. Can be suppressed.

The optical compensation layer 11 b has an in-plane retardation Re of 135 to 300 nm (preferably 150 to 275 nm, more preferably 170 to 240 nm), and an Nz coefficient of 0 to 0.99 (preferably 0.1 to 0. 6, more preferably 0.25 to 0.4) can be used. The slow axis (in-plane slow axis) of the optical compensation layer 11 b is substantially parallel to the absorption axis 10 a of the first polarizer 10. More specifically, the angle formed by the two axes is in the range of 0 ± 3 °, preferably in the range of 0 ± 1 °, and more preferably in the range of 0 ± 0.5 °. Particularly preferred is 0 ° (perfectly parallel).

In these cases, as shown in FIGS. 2 to 4, the first polarizer 10, the optical compensation layer (positive B plate) 11b, the λ / 4 retardation plate 11a, the liquid crystal cell 30, the λ / 4 retardation plate 21a The second polarizer 20 is laminated in this order from the viewing side or the back side.

Furthermore, as shown in FIG. 4, the optical compensation layer 11 provided between the first polarizer 10 and the liquid crystal cell 30 is an optical compensation layer having a refractive index relationship of nx = ny> nz (so-called negative C Plate) 11 c may be included. Thereby, the viewing angle characteristics of the liquid crystal display device 1 can be further improved, that is, whitening in the oblique direction at the time of black display can be further suppressed. On the other hand, the fact that the entire whitening is smaller when viewed from an oblique direction means that the black unevenness is more noticeable, but even in this case, according to the present embodiment, the occurrence of the black unevenness is It can be effectively suppressed. In this case, as shown in FIG. 4, the first polarizer 10, the optical compensation layer (positive B plate) 11b, the λ / 4 retardation plate 11a, the optical compensation layer (negative C plate) 11c, the liquid crystal cell 30, The λ / 4 retardation plate 21 a and the second polarizer 20 are stacked in this order from the viewing surface side or the back surface side.

The optical compensation layer 11 c has an in-plane retardation Re of 0 to 150 nm (preferably 0 to 40 nm, more preferably 0 nm) and a thickness direction retardation Rth of 20 to 350 nm (preferably 50 to 130 nm). It can be used. When the in-plane retardation is 0 nm, the arrangement direction of the optical compensation layer 11c in the plane is not particularly limited because the optical compensation layer 11c is substantially optically isotropic in the plane. When the in-plane retardation Re of the optical compensation layer 11c is larger than 0 nm, the slow axis (in-plane slow axis) of the optical compensation layer 11c is orthogonal to or parallel to the absorption axis 10a of the first polarizer 10. is there.

<Liquid crystal cell>
The liquid crystal cell 30 has a pair of substrates, and a liquid crystal layer as a display medium sandwiched between the substrates. A color filter and a black matrix are provided on one of the substrates (color filter substrate). On the other substrate (active matrix substrate), a switching element (typically, a TFT) for controlling the electro-optical characteristics of liquid crystal, a scanning line for providing a gate signal to the switching element and a signal line for providing a source signal, and a pixel An electrode is provided. A common electrode is further provided on either of the pair of substrates. The color filter may have a thickness direction retardation Rth of about 10 to 50 nm. In addition, the color filter may be provided on the active matrix substrate side. The distance between the pair of substrates (cell gap) is controlled by a spacer. On the side of the pair of substrates in contact with the liquid crystal layer, for example, an alignment film made of polyimide is provided.

The retardation (panel retardation) Δn · d of the liquid crystal layer represented by the product of the refractive index anisotropy of the liquid crystal material Δn and the cell thickness (cell gap, ie, the thickness of the liquid crystal layer) d is not particularly limited. , 200 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm.

<Liquid crystal display device>
The display mode of the liquid crystal display device 1 is not particularly limited, and examples thereof include horizontal alignment mode such as fringe field switching (FFS) mode and in-plane switching (IPS) mode, and vertical alignment (VA) mode. Among them, the vertical alignment mode is preferable.

In the VA mode, the common electrode is provided on a substrate other than the substrate provided with the pixel electrode among the pair of substrates. When no voltage is applied, the liquid crystal molecules are aligned substantially perpendicular (normal direction) to the surface of each substrate. Here, "substantially perpendicular" also includes the case where the alignment vector of the liquid crystal molecules is inclined with respect to the normal direction of each substrate, that is, the case where the liquid crystal molecules have a tilt angle. The tilt angle (angle from the normal) is at least 0 ° and preferably at all positions of the displayable portion of the liquid crystal panel 2 (the modulatable portion of the light except the light shielding portion in the display area 2c). It is 10 ° or less, more preferably 5 ° or less, and still more preferably 1 ° or less. Such alignment can be realized, for example, by arranging a nematic liquid crystal having negative dielectric anisotropy between substrates on which a vertical alignment film is formed as an alignment film. When light is irradiated to the substrate on the back side by the backlight in such a state, linearly polarized light that has passed through the

polarizer

10 or 20 on the back side and is incident on the liquid crystal layer has substantially vertical alignment of liquid crystal molecules. Proceed along the direction of the long axis. Since birefringence does not occur substantially in the long axis direction of the liquid crystal molecules, incident light travels without changing the polarization direction, and on the viewing surface side having an absorption axis substantially orthogonal to the

rear surface polarizer

10 or 20. It is absorbed by the

polarizer

20 or 10. As a result, a dark state display (black display) can be obtained when no voltage is applied (normally black mode). When a voltage is applied between the pixel electrode and the common electrode, the major axes of the liquid crystal molecules are aligned parallel to the surface of each substrate. The liquid crystal molecules in this state exhibit birefringence with respect to linearly polarized light incident on the liquid crystal layer through the

back polarizer

10 or 20, and the polarization state of the incident light depends on the inclination of the liquid crystal molecules. Change. At the time of application of a predetermined maximum voltage, light passing through the liquid crystal layer becomes, for example, linearly polarized light whose polarization direction is rotated by 90 °, and hence light is transmitted through the

polarizer

20 or 10 on the viewing surface side to display a bright state ( White display is obtained. When the voltage is not applied again, the display can be returned to the dark state by the alignment control force. Further, by changing the applied voltage to control the inclination of the liquid crystal molecules and changing the intensity of the transmitted light from the

polarizer

20 or 10 on the viewing surface side, it is possible to perform gradation display.

In such a VA mode, if the tilt direction of the liquid crystal molecules in the voltage application is one direction, asymmetry will be generated in the viewing angle characteristics. For example, the device of the pixel electrode structure or a protrusion in the pixel An alignment division type VA mode in which the tilt direction of liquid crystal molecules is divided into plural, so-called MVA mode (multi-domain type VA mode), is widely used by providing an alignment control means. From the viewpoint of maximizing the transmittance in the white display state, usually, the polarizer axis orientation and the tilt orientation of liquid crystal molecules at the time of voltage application are set to form an angle of 45 °. The transmittance when a birefringent medium is sandwiched between crossed Nicol polarizers is sin ² (2β), where the angle between the axis of the polarizer and the slow axis of the birefringent medium is β (unit: rad) To be proportional to In a typical MVA mode, the tilt orientation of liquid crystal molecules can be divided into four domains of 45 °, 135 °, 225 °, and 315 °. Even in the MVA mode divided into such four domains, Schlieren orientation or orientation in an unintended direction is often observed in the vicinity of domain boundaries or orientation control means, which causes transmittance loss. There is.

On the other hand, according to the VA mode using the circularly polarizing plate, the transmissivity when the birefringent medium is sandwiched between the left and right circularly polarizing plates orthogonal to each other is the axis of each

polarizer

10, 20 and that of the birefringent medium Since it does not depend on the angle with the slow axis, even if the tilt orientation of the liquid crystal molecules is other than 45 °, 135 °, 225 °, and 315 °, the desired transmittance can be secured as long as the tilt of the liquid crystal molecules can be controlled. Therefore, for example, a circular protrusion may be disposed at the center of the pixel, and liquid crystal molecules may be inclined in all directions, or may be inclined in random directions without controlling the inclination direction at all. May be

Although the embodiments of the present invention have been described above, all the individual matters described can be applied to the whole of the present invention.

EXAMPLES The present invention will be described in more detail by way of the following Examples and Comparative Examples, but the present invention is not limited to these Examples. In each of the following Examples and Comparative Examples, each axial direction is represented by an angle when the right direction of the display area of the liquid crystal panel is 0 ° and the counterclockwise direction is positive when viewed from the viewing surface side. .

Example 1
FIG. 5 is a schematic cross-sectional view of the liquid crystal display device according to the first embodiment.
As shown in FIG. 5, a front polarizer, a first optical compensation layer as a λ / 4 retardation plate, a liquid crystal cell, a second optical compensation layer as a λ / 4 retardation plate, a first B plate as a positive B plate A liquid crystal display device of Example 1 comprising the optical compensation layer of No. 3 and a liquid crystal panel in which the back polarizer is disposed in this order from the viewing surface side, and a backlight (not shown) on the back surface of the liquid crystal panel. Made. The optical parameters of the respective members and the axial directions of the respective polarizers and the respective optical compensation layers are as shown in FIG. In the present embodiment, the front polarizer corresponds to the second polarizer, and the back polarizer corresponds to the first polarizer.

As the liquid crystal cell, a VA mode liquid crystal cell was used. The dielectric anisotropy Δn of the liquid crystal material is 0.113, and the cell thickness (cell gap) d is 3.2 μm. That is, the retardation Δn · d of the liquid crystal layer was 360 nm.

As a liquid crystal panel, a rectangular liquid crystal panel with an aspect ratio of 5: 2 was used. That is, the shape of the display area is also rectangular with an aspect ratio of 5: 2.

As the first and second optical compensation layers, films obtained by obtaining predetermined optical parameters shown in FIG. 5 by biaxially stretching a COP film were used. As the third optical compensation layer, a film having the predetermined optical parameters shown in FIG. 5 obtained by relaxing after stretching the COP film was used. The thicknesses of the first, second and third optical compensation layers were 30 μm, 30 μm and 140 μm, respectively. In each of the examples and the comparative examples, the COP film used did not contain cycloolefin copolymer (COC).

As a front polarizer, a PVA film (30 μm in thickness) was used, and the PVA film was adhered to the first optical compensation layer with an adhesive and laminated on the first optical compensation layer. A TAC film (40 μm thick) was laminated via an adhesive on the surface of the PVA film of the front polarizer opposite to the first optical compensation layer. As a back polarizer, what laminated | stacked the TAC film (40 micrometers in thickness), the PVA film (30 micrometers in thickness), and the COP film (30 micrometers in thickness) in this order via the adhesive agent was used. The COP film of the back polarizer was produced so as not to have optical anisotropy. The back polarizer was placed so that the COP film was on the liquid crystal cell side and the TAC film was on the opposite side of the liquid crystal cell. As a PVA film of a front polarizer and a back polarizer, what has a polarization performance by adding iodine after extending | stretching was used. This film has an absorption axis in the stretching direction.

In addition, a TAC film is widely used as a support body of a PVA film, adhere | attaches with a PVA film, and maintains the intensity | strength as a film. In addition, a COP film is widely used as a broad-band retardation film or as a support of a PVA film, and has birefringence by stretching.

Further, although omitted in FIG. 5, between the first optical compensation layer and the liquid crystal cell, between the liquid crystal cell and the second optical compensation layer, and between the second optical compensation layer and the third optical compensation layer The space between the third optical compensation layer and the back polarizer was filled with a pressure sensitive adhesive (adhesive) having no large optical anisotropy. Such materials that do not have large optical anisotropy, such as adhesive materials, are also omitted from the process of adding them as needed in the manufacturing process as long as the layer formed from the material is a layer without optical anisotropy. It can also be done.

Comparative Example 1
FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Comparative Example 1.
As shown in FIG. 6, a front polarizer, a third optical compensation layer as a positive B plate, a second optical compensation layer as a λ / 4 retardation plate, a liquid crystal cell, and a λ / 4 retardation plate A liquid crystal display device of Comparative Example 1 comprising a liquid crystal panel in which the first optical compensation layer and the back polarizer are arranged in this order from the viewing surface side, and a backlight (not shown) on the back surface of the liquid crystal panel. Made. The optical parameters of the respective members and the axial directions of the respective polarizers and the respective optical compensation layers are as shown in FIG.

As the first and second optical compensation layers, films obtained by obtaining predetermined optical parameters shown in FIG. 6 by biaxially stretching a COP film were used. As the third optical compensation layer, a film having the predetermined optical parameters shown in FIG. 6 obtained by relaxation after stretching of the COP film was used. The thicknesses of the first, second and third optical compensation layers were 30 μm, 30 μm and 140 μm, respectively.

As a front polarizer, what laminated | stacked the TAC film (40 micrometers in thickness), the PVA film (30 micrometers in thickness), and the COP film (30 micrometers in thickness) in this order via the adhesive agent was used. The COP film of the back polarizer was produced so as not to have optical anisotropy. The front polarizer was disposed so that the COP film was on the liquid crystal cell side and the TAC film was on the opposite side to the liquid crystal cell. As a back polarizer, a PVA film (30 μm in thickness) was used, and the PVA film was adhered to the first optical compensation layer with an adhesive and laminated on the first optical compensation layer. A TAC film (40 μm thick) was laminated via an adhesive on the surface of the PVA film of the back polarizer opposite to the first optical compensation layer. As a PVA film of a front polarizer and a back polarizer, what has a polarization performance by adding iodine after extending | stretching was used. This film has an absorption axis in the stretching direction.

Although omitted in FIG. 6, between the front polarizer and the third optical compensation layer, between the third optical compensation layer and the second optical compensation layer, and between the second optical compensation layer and the liquid crystal cell. The liquid crystal cell and the first optical compensation layer were each filled with a pressure sensitive adhesive (adhesive material) having no large optical anisotropy. Such materials that do not have large optical anisotropy, such as adhesive materials, are also omitted from the process of adding them as needed in the manufacturing process as long as the layer formed from the material is a layer without optical anisotropy. It can also be done.

Comparison of Example 1 and Comparative Example 1
FIG. 7 is another schematic view of the liquid crystal display device according to Example 1. FIG. 7 (a) is a plan view showing the relationship between the absorption axis of the polarizer and the long side of the liquid crystal panel. It is sectional drawing for demonstrating arrangement | positioning of an optical compensation layer, and shrinkage | contraction condition of a polarizer. FIG. 8 is another schematic view of the liquid crystal display device according to Comparative Example 1. FIG. 8A is a plan view showing the relationship between the absorption axis of the polarizer and the long side of the liquid crystal panel, and FIG. It is sectional drawing for demonstrating arrangement | positioning of an optical compensation layer, and shrinkage | contraction condition of a polarizer.
In Example 1 and Comparative Example 1, the absorption axis directions of the front polarizer and the back polarizer are the same, but the position of the optical compensation layer is changed, and as shown in FIG. In Comparative Example 1, the absorption axis of the front polarizer having many optical compensation layers is parallel to each long side of the liquid crystal panel, as shown in FIG. It is. The white spots (black unevenness) of the partial black display in the durability test at high temperature etc. are also caused by other factors such as the axial fluctuation of the polarizer and the stress generated in the glass used for the liquid crystal cell. As described above, the change in retardation of the optical compensation layer due to photoelasticity is the main cause. As shown in FIG. 7, in Example 1, the shrinkage amount of the back polarizer with a large number of laminated optical compensation layers is small, and thus the stress on the second and third optical compensation layers is small. It is set. As shown in FIG. 8, in Comparative Example 1, the shrinkage amount of the back polarizer with the large number of laminated optical compensation layers is large, and therefore, the stress on the second and third optical compensation layers is large. It is set.

<Evaluation Results of Example 1 and Comparative Example 1>
The dark room contrast of the liquid crystal display of Example 1 and Comparative Example 1 was measured. The dark room contrast is obtained by measuring the luminance of white display and black display without external light, and dividing the white display luminance by the black display luminance. The higher the display device, the better. Furthermore, from the viewpoint of durability, it is preferable that the change in this numerical value be as small as possible when exposed to a severe environment such as high temperature.

Table 1 below shows dark room contrast at the center of the screen before and after aging for 12 hours at 85 ° C. for Example 1 and Comparative Example 1. Although there is not much difference with the value before the aging, the value in Comparative Example 1 is greatly reduced by the aging.

The black display uniformity of the liquid crystal display devices of Example 1 and Comparative Example 1 was measured. The black display uniformity is an index indicating the intensity of so-called unevenness of black display, which is obtained by dividing the minimum luminance by the maximum luminance by scanning the luminance of the display area when a black solid screen is displayed. As this value is closer to 100%, there is no luminance distribution, that is, the unevenness is weak, which is preferable as a display device. The lower the value, the stronger the unevenness and the lower the quality as a display device.

Table 2 below shows black display uniformity before and after aging for 12 hours at 85 ° C. for Example 1 and Comparative Example 1. Although there is not much difference with the value before the aging, the value in Comparative Example 1 is greatly reduced by the aging. On the other hand, in Example 1, the change was small and it was shown that the unevenness was improved.

Example 2
FIG. 9 is a schematic cross-sectional view of the liquid crystal display device according to the second embodiment.
As shown in FIG. 9, a front polarizer, a third optical compensation layer as a positive B plate, a second optical compensation layer as a λ / 4 retardation plate, a liquid crystal cell, and a λ / 4 retardation plate A liquid crystal display device of Example 2 was prepared, which comprises a liquid crystal panel in which the first optical compensation layer, the back polarizer are disposed in this order from the viewing surface side, and the backlight on the back surface side of the liquid crystal panel. The optical parameters of the respective members and the axial directions of the respective polarizers and the respective optical compensation layers are as shown in FIG. That is, the liquid crystal display device of Example 2 was produced in the same manner as Comparative Example 1 except that the axes of all the polarizers and the optical compensation layer were rotated by 90 °. In the present embodiment, the back polarizer corresponds to the second polarizer, and the front polarizer corresponds to the first polarizer.

Although omitted in FIG. 9, between the front polarizer and the third optical compensation layer, between the third optical compensation layer and the second optical compensation layer, and between the second optical compensation layer and the liquid crystal cell. The liquid crystal cell and the first optical compensation layer were each filled with a pressure sensitive adhesive (adhesive material) having no large optical anisotropy. Such materials that do not have large optical anisotropy, such as adhesive materials, are also omitted from the process of adding them as needed in the manufacturing process as long as the layer formed from the material is a layer without optical anisotropy. It can also be done.

Comparison of Example 2 and Comparative Example 1
FIG. 10 is another schematic view of the liquid crystal display device according to Example 2. FIG. 10 (a) is a plan view showing the relationship between the absorption axis of the polarizer and the long side of the liquid crystal panel, and FIG. It is sectional drawing for demonstrating arrangement | positioning of an optical compensation layer, and shrinkage | contraction condition of a polarizer.
In Example 2 and Comparative Example 1, the position of the optical compensation layer is the same, but the axes of all the polarizers and the optical compensation layer are rotated by 90 °, and as shown in FIG. The absorption axis of the front polarizer having many optical compensation layers is orthogonal to each long side of the liquid crystal panel, and as shown in FIG. 8, in Comparative Example 1, the absorption axis of the front polarizer having many optical compensation layers corresponds to each liquid crystal panel It is parallel to the long side.

<Evaluation Results of Example 2 and Comparative Example 1>
Table 3 below shows dark room contrast at the center of the screen before and after aging for 12 hours at 85 ° C. for Example 2 and Comparative Example 1.

Table 4 below shows black display uniformity before and after aging for 12 hours at 85 ° C. for Example 2 and Comparative Example 1.

As a result, it was found that the same effect as in Example 1 can be obtained also in Example 2. As to how to arrange the panels, there are requirements such as relationship with polarized sunglasses, and since the preferable angle of the front polarizer differs depending on the display device, any arrangement can be selected depending on the situation.

Example 3
FIG. 11 is a schematic cross-sectional view of the liquid crystal display device according to the third embodiment.
As shown in FIG. 11, a front polarizer, a first optical compensation layer as a λ / 4 retardation plate, a liquid crystal cell, a fourth optical compensation layer as a negative C plate, and a fourth λ / 4 retardation plate 2 an optical compensation layer, a third optical compensation layer as a positive B plate, and a liquid crystal panel in which a back polarizer is disposed in this order from the observation surface side, and a backlight on the back side of the liquid crystal panel The liquid crystal display of Example 3 was produced. The optical parameters of the respective members and the axial directions of the respective polarizers and the respective optical compensation layers are as shown in FIG. Thus, in the present embodiment, the fourth optical compensation layer is further added to the back side of the first embodiment.

As the first and second optical compensation layers, films obtained by obtaining predetermined optical parameters shown in FIG. 11 by biaxially stretching a COP film were used. As the third optical compensation layer, a film having a predetermined optical parameter shown in FIG. 11 by stretching and relaxing the COP film was used. As the fourth optical compensation layer, a film having predetermined optical parameters shown in FIG. 11 obtained by biaxially stretching a TAC film was used. The thicknesses of the first, second, third and fourth optical compensation layers were respectively 30 μm, 30 μm, 140 μm and 80 μm.

As a front polarizer, a PVA film (30 μm in thickness) was used, and the PVA film was adhered to the first optical compensation layer with an adhesive and laminated on the first optical compensation layer. In addition, on the surface on the opposite side to the first optical compensation layer of the PVA film of the front polarizer, a TAC (triacetylene cellulose) film (40 μm in thickness) was laminated via an adhesive. As a back polarizer, what laminated | stacked the TAC film (40 micrometers in thickness), the PVA film (30 micrometers in thickness), and the COP film (30 micrometers in thickness) in this order via the adhesive agent was used. The COP film of the back polarizer was produced so as not to have optical anisotropy. The back polarizer was placed so that the COP film was on the liquid crystal cell side and the TAC film was on the opposite side of the liquid crystal cell. As a PVA film of a front polarizer and a back polarizer, what has a polarization performance by adding iodine after extending | stretching was used. This film has an absorption axis in the stretching direction.

Although not shown in FIG. 11, between the first optical compensation layer and the liquid crystal cell, between the liquid crystal cell and the fourth optical compensation layer, and between the fourth optical compensation layer and the second optical compensation layer. , Pressure-sensitive adhesive (adhesive material) having no large optical anisotropy between the second optical compensation layer and the third optical compensation layer, and between the third optical compensation layer and the back polarizer, respectively Filled with). Such materials that do not have large optical anisotropy, such as adhesive materials, are also omitted from the process of adding them as needed in the manufacturing process as long as the layer formed from the material is a layer without optical anisotropy. It can also be done.

Comparison of Example 3 and Comparative Example 1
FIG. 12 is another schematic view of the liquid crystal display device according to Example 3. FIG. 12A is a plan view showing the relationship between the absorption axis of the polarizer and the long side of the liquid crystal panel, and FIG. It is sectional drawing for demonstrating arrangement | positioning of an optical compensation layer, and shrinkage | contraction condition of a polarizer.
As shown in FIGS. 8 and 12, the points are the same as in the case of Example 1 and Comparative Example 1, and thus the description thereof is omitted. However, the number of laminated layers of the optical compensation layer is 1 front / 3 back in the third embodiment as opposed to 1 front / 2 back in the first embodiment.

<Evaluation Results of Example 3 and Comparative Example 1>
Table 5 below shows dark room contrast at the center of the screen before and after aging for 12 hours at 85 ° C. for Example 3 and Comparative Example 1.

Table 6 below shows black display uniformity before and after aging at 85 ° C. for 12 hours for Example 3 and Comparative Example 1.

As shown in Tables 5 and 6 above, since the number of laminated optical compensation layers was increased, the change in contrast is large in Example 3 compared to Examples 1 and 2, and the unevenness after aging is strong. Also from this, it is suggested that the black unevenness is due to the characteristic change of the optical compensation layer. However, since the unevenness is improved more than the comparative example 1 in Example 3, the effect of adjustment of the absorption axis is shown.

[Supplementary note]
One embodiment of the present invention is a liquid crystal display device (1) including a liquid crystal panel (2) having a rectangular shape in plan view, wherein the liquid crystal panel (2) comprises a first polarizer (10) and two or more optical elements. A compensation layer (11), a liquid crystal cell (30), one or more optical compensation layers (21) and a second polarizer (20) in this order, and the first polarizer (10) and the liquid crystal cell (30) The total number of optical compensation layers (11) provided between the two) is greater than the total number of optical compensation layers (21) provided between the second polarizer (20) and the liquid crystal cell (30), The angle (α) between the absorption axis (10a) of the first polarizer (10) and each long side (2a) of the liquid crystal panel (2) may be 45 ° or more and 135 ° or less . Thereby, even after the liquid crystal display device (1) is placed under high temperature, the occurrence of the black unevenness can be suppressed.

The angle (α) may be 60 ° or more and 120 ° or less.

The optical compensation layer (11) provided between the first polarizer (10) and the liquid crystal cell (30) includes a λ / 4 retardation plate (11a), and the second polarizer (20) And the optical compensation layer (21) provided between the liquid crystal cell (30) may include a λ / 4 retardation plate (21a). In this case, there is a possibility that the black unevenness becomes strong, but even in this case, according to the above aspect, the occurrence of the black unevenness can be suppressed. That is, the black unevenness suppressing effect according to the above aspect can be exhibited more effectively.

The optical compensation layer (11) provided between the first polarizer (10) and the liquid crystal cell (30) includes an optical compensation layer (11b) having a refractive index relationship of nx> nz> ny. May be. In this case, the black unevenness may be noticeable, but even in this case, according to the above aspect, the occurrence of the black unevenness can be suppressed. That is, the black unevenness suppressing effect according to the above aspect can be exhibited more effectively. Further, in this case, as described later, it is particularly suitable when the display mode of the liquid crystal display device (1) is the vertical alignment mode.

The optical compensation layer (11) provided between the first polarizer (10) and the liquid crystal cell (30) further includes an optical compensation layer (11c) having a refractive index relationship of nx = ny> nz. May be included. In this case, the black unevenness may be more noticeable, but even in this case, according to the above aspect, the occurrence of the black unevenness can be suppressed. That is, the black unevenness suppressing effect according to the above aspect can be exhibited more effectively. Further, in this case, as described later, it is particularly suitable when the display mode of the liquid crystal display device (1) is the vertical alignment mode.

The display mode of the liquid crystal display device (1) may be a vertical alignment mode.

1: Liquid crystal display device 2: Liquid crystal panel 2a: long side 2b: short side 2c: display area 10: first polarizer 10a: absorption axis 11: optical compensation layer 11a: λ / 4 retardation plate 11b: optical compensation layer (Positive B plate)
11c: Optical compensation layer (negative C plate)
20: second polarizer 20a: absorption axis 21: optical compensation layer 21a: λ / 4 retardation plate 30: liquid crystal cell

Claims

A liquid crystal display device comprising a liquid crystal panel having a rectangular shape in plan view, comprising:
The liquid crystal panel includes a first polarizer, two or more optical compensation layers, a liquid crystal cell, one or more optical compensation layers, and a second polarizer in this order,
The total number of optical compensation layers provided between the first polarizer and the liquid crystal cell is larger than the total number of optical compensation layers provided between the second polarizer and the liquid crystal cell,
The liquid crystal display device, wherein an angle between an absorption axis of the first polarizer and each long side of the liquid crystal panel is 45 ° or more and 135 ° or less.
The liquid crystal display device according to claim 1, wherein the angle is 60 ° or more and 120 ° or less.
The optical compensation layer provided between the first polarizer and the liquid crystal cell includes a λ / 4 retardation plate.
The liquid crystal display according to claim 1, wherein the optical compensation layer provided between the second polarizer and the liquid crystal cell includes a λ / 4 retardation plate.
4. The liquid crystal display device according to claim 3, wherein the optical compensation layer provided between the first polarizer and the liquid crystal cell includes an optical compensation layer having a refractive index relationship of nx> nz> ny.
5. The liquid crystal display device according to claim 4, wherein the optical compensation layer provided between the first polarizer and the liquid crystal cell further includes an optical compensation layer having a refractive index relationship of nx = ny> nz.
The liquid crystal display device according to any one of claims 1 to 5, wherein a display mode of the liquid crystal display device is a vertical alignment mode.