TW201348823A - Liquid crystal display - Google Patents

Abstract

An in-plane switching mode liquid crystal display having enhanced black display property and reduced tone change is provided. The liquid crystal display includes in sequence: a first polarizer; a first optical compensation region; a liquid crystal cell including a first substrate, liquid crystal layer and a second substrate; a second optical compensation region; and a second polarizer. When displaying black, the liquid crystal molecule included in the liquid crystal layer is oriented in parallel with respected to surfaces of the pair of substrates. The sum of retardation Rthsub (550) of the first substrate and the second substrate in thickness direction at a wavelength of 550 nm is 3 nm ≤ |Rthsub(550)| ≤ 60 nm. The sum of retardation Rth1(550) of the first substrate, the second substrate and the first optical compensation region in thickness direction at a wavelength of 550 nm is -135 to 25 nm.

Description

Liquid crystal display device

The present invention relates to a horizontal electric field type liquid crystal display device such as an In-Plane Switching (IPS) mode or a Fringe Field Switching (FFS) mode.

The liquid crystal display devices of the IPS type and the FFS type are not driven by an electric field between the upper and lower substrates, such as a twisted nematic (TN) type or a vertical alignment type (VA), and are driven by rising liquid crystal molecules. The mode is a mode (mode) called a transverse electric field method in which liquid crystal molecules are caused to respond in the in-plane direction of the substrate by an electric field including a component substantially parallel to the substrate surface.

In addition, since the IPS type and the FFS type have a principle that the viewing angle is limited in principle according to the configuration, it is known as a driving method having characteristics such as wide viewing angle, small chromaticity shift, and small change in color tone. In recent years, in addition to television use, it has been widely used in display devices from mobile terminals to high-definition and high-definition applications for professional use.

In the liquid crystal display device of the horizontal electric field type, a configuration is also known in which the protective film of the polarizing plate that sandwiches the liquid crystal cell is an isotropic film, and the advantages of the liquid crystal cell are not hindered. use. (eg Japanese Patent Special Open Bulletin 2010-107953)

However, in this configuration, compensation due to the polarizing element has not been studied, and in particular, it is necessary to optically compensate for a contrast reduction or a color shift caused by light leakage at the time of viewing from the oblique direction. Therefore, a horizontal electric field type liquid crystal display device in which the display device as a whole is studied by arranging the optically anisotropic layer is proposed. (Japanese Patent Laid-Open Publication No. 2005-309382, Japanese Patent Laid-Open No. Hei. No. 2007-279411)

As the optically anisotropic layer, optical anisotropy which functions as a λ/2 plate is often used, and the principle is considered to be compensated by a mechanism as described in Japanese Laid-Open Patent Publication No. 2009-122151. . The optically anisotropic layer is not particularly limited as long as it can exhibit its function, and various configurations have been proposed so far. However, the inventors have investigated the various configurations, and as a result, it has been found that the optical compensation ability such as improvement in black display performance and reduction in color tone change is insufficient if only the anisotropic layer functioning as a λ/2 plate is disposed. .

The present invention has been made in an effort to solve the above problems, and in particular, to provide a liquid crystal display device which improves black display performance and reduces color tone change.

As a result of intensive studies on the above-mentioned problems, the inventors have found that there are delays in constituent members such as a color filter or a thin film transistor (TFT) disposed on a liquid crystal cell substrate ( Retardation), the presence of this delay can impede ideal optical compensation.

Based on this finding, it was found that the liquid crystal display device of the prior art is configured to use the optically anisotropic layer to be studied and the optical compensation layer for compensating for the retardation of the constituent members on the substrate. The liquid crystal cell is used to compensate for the retardation of the liquid crystal cell substrate which has not been previously studied, thereby completing the present invention.

Specifically, the method for solving the above problems is the method of the following [1], and the methods of the following [2] to [15] are preferable.

[1] A liquid crystal display device comprising: a first polarizing element; a first optical compensation region; and a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate; a second optical compensation region; In the case of black display, the liquid crystal molecules included in the liquid crystal layer are aligned in parallel with respect to the surface of the pair of substrates, and the retardation in the thickness direction of the first substrate and the second substrate at a wavelength of 550 nm The total value Rth _sub (550) is 3 nm ≦ | Rth _sub (550) | ≦ 60 nm, and the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm The total value of Rth ₁ (550) is -135 to 25 nm.

[2] The liquid crystal display device according to [1], wherein the second optical compensation region has an in-plane retardation Re ₂ (550) of a wavelength of 550 nm of 100 to 250 nm and a retardation Rth _{2 of a} wavelength direction of 550 nm. (550) is -150~10 nm.

[3] The liquid crystal display device according to [1], wherein the second optical compensation region is composed of one layer, and the first substrate, the second substrate, and the first optical compensation region have a wavelength of 550 nm. The total value of the retardation Rth ₁ (550) in the thickness direction is -135 to 5 nm.

[4] The liquid crystal display device according to [1] or [2] wherein the second optical The compensation area includes at least two layers.

[5] The liquid crystal display device according to [4], wherein a retardation Rth _2C (550) in a thickness direction of a layer of the second optical compensation region of 550 nm is 50 to 200 nm, and a wavelength of another layer is 550 nm. The in-plane retardation Re _2B (550) is 70 to 150 nm, and the retardation Rth _2B (550) in the thickness direction of 550 nm is -150 to -70 nm.

[6] The liquid crystal display device according to the above [5], wherein the total value Rth ₁ (550) of the retardation in the thickness direction of the wavelength of 550 nm of the first substrate, the second substrate, and the first optical compensation region is - 45~25 nm.

[7] The liquid crystal display device according to [4], wherein a retardation Rth _2C (550) in a thickness direction of a wavelength of 550 nm of the layer of the second optical compensation region is -200 to -50 nm, and the other layer is The in-plane retardation Re _2B (550) at a wavelength of 550 nm is 50 to 200 nm, and the retardation Rth _2B (550) at a wavelength of 550 nm is 50 to 200 nm.

[8] The liquid crystal display device according to [7], wherein the total value Rth ₁ (550) of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm is - 75~25 nm.

[9] The liquid crystal display device according to any one of [1] to [8] wherein at least one of the first and second optical compensation regions includes a polymer film.

[10] The liquid crystal display device according to [9], wherein the polymer film is selected from the group consisting of a deuterated cellulose film, a cyclic olefin polymer film, or an acrylic polymer film.

[11] The liquid crystal display device according to [9], wherein the polymer film has a thickness of 1 to 90 μm.

[12] The liquid crystal display device of [10] or [11], wherein the acrylic acid The polymer film includes an acrylic polymer containing at least one selected from the group consisting of a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit.

[13] The liquid crystal display device according to any one of [1] to [12] wherein at least one of the first polarizing element or the second polarizing element is sandwiched by an optical compensation region and a polarizing plate protective film Holding a polarizing plate.

[14] The liquid crystal display device according to [13], wherein the protective film has a thickness of 10 to 80 μm.

[15] The liquid crystal display device according to any one of [1], wherein the first polarizing element or the second polarizing element has a thickness of 50 μm or less.

According to the present invention, it is possible to provide a horizontal electric field type liquid crystal display device which improves black display performance and reduces color tone change.

2, 3‧‧‧ electrodes

4‧‧‧The direction of rubbing of the alignment film

5a, 5b, 6a, 6b‧‧‧ alignment direction of liquid crystal molecules

10‧‧‧Liquid cell

11‧‧‧1st substrate

12‧‧‧Liquid layer

12a‧‧‧The direction of the slow phase of the liquid crystal molecules in the liquid crystal layer (black display [no power applied] Field time]

13‧‧‧Color filters

14‧‧‧ pixel electrodes

15‧‧‧2nd substrate

20‧‧‧1st polarizing element

20a‧‧‧Absorption axis of the first polarizing element

22‧‧‧2nd polarizing element

22a‧‧‧Absorption axis of the second polarizing element

24‧‧‧1st phase difference zone

26‧‧‧2nd phase difference zone

28‧‧‧Protective film

30‧‧‧Backlight unit

1 is a schematic cross-sectional view showing an example of an IPS liquid crystal display device of the present invention.

Fig. 2 is a schematic view showing an example of a pixel region usable in the present invention.

Fig. 3 is a schematic cross-sectional view showing another example of the IPS liquid crystal display device of the present invention.

4 is a schematic cross-sectional view showing an example of an FFS liquid crystal display device of the present invention.

Fig. 5 is a schematic cross-sectional view showing another example of the FFS liquid crystal display device of the present invention.

Hereinafter, an embodiment of the liquid crystal display device of the present invention and a configuration thereof The components are described in order. In addition, in this specification, the numerical range represented by "~" means the range of the numerical value contained in the front-back and the upper-limit value containing the "~".

In the present specification, the relationship of the optical axis is tolerable in the technical field to which the present invention pertains. Specifically, the term "parallel" or "orthogonal" means that the precise angle ± is less than 10°, preferably ± less than 5°, more preferably ± less than 3°. In addition, the term "vertical alignment" means a more precise vertical angle ± less than 20°, preferably ± less than 15°, more preferably ± less than 10°. In addition, the "late phase axis" means the direction in which the refractive index becomes maximum. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

In the present specification, the "polarizing plate" is a polarizing plate including a long strip and cutting as long as it is not particularly described (in the present specification, "cutting" is also included as "punching" and "cutting out". It is used in the meaning of both polarizing plates of a size which can be incorporated in a liquid crystal device. In the present specification, the "polarizing element" and the "polarizing plate" are used differently, and the "polarizing plate" is defined as a transparent protective film that protects the polarizing element on at least one side of the "polarizing element". Laminated body.

Further, in the present specification, Re(λ) and Rth(λ) respectively indicate a retardation in the plane of the wavelength λ and a retardation in the thickness direction. In the present specification, the wavelength λ is set to 550 nm unless otherwise specified. Re (λ) is measured by causing light having a wavelength of λ nm to enter the film normal direction in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.). When the measurement wavelength λ nm is selected, the wavelength selection filter can be manually replaced or the measurement value can be changed by a program or the like.

In the case where the film to be measured is a film represented by a uniaxial or biaxial refractive index ellipsoid, Rth(λ) is calculated by the following method.

Rth(λ) is an in-plane slow axis (determined by KOBRA 21ADH or WR) as a tilt axis (rotation axis) (in the case of no slow phase axis, any direction in the film plane is used as the rotation axis), With respect to the normal direction of the film, light having a wavelength of λ nm is incident from each of the oblique directions at a step of 10 degrees from the normal direction to 50 degrees on one side, and all of the above-mentioned Re(λ) are measured, based on the measurement. The assumed value of the retardation value and the average refractive index and the input film thickness value are calculated by KOBRA 21ADH or WR.

In the above, in the case where the film having the retardation value at a certain inclination angle has a zero direction from the normal direction in the normal direction, the retardation value at the inclination angle larger than the inclination angle is After changing the sign to negative, it is calculated by KOBRA 21ADH or WR.

Further, the retardation axis may be an inclined axis (rotation axis) (in the case where the slow phase axis does not exist, any direction in the film plane is the rotation axis), and the delay value is measured from two directions of arbitrary inclination, based on The value and the assumed value of the average refractive index and the input film thickness value are calculated by the following formulas (1) and (2).

Equation (2) Rth={(nx+ny)/2-nz}×d

In the above formula, Re(θ) represents a retardation value in the direction of the inclination angle θ from the normal direction, nx represents the refractive index in the direction of the slow axis in the plane, and ny represents the refractive index in the direction orthogonal to nx in the plane. , nz represents the refractive index in the direction orthogonal to nx and ny. d is the film thickness.

When the film to be measured is a film which cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, and a film having no optic axis, Rth(λ) is calculated by the following method.

Rth(λ) is an in-plane slow phase axis (determined by KOBRA 21ADH or WR) as a tilt axis (rotation axis), which is separated by 10 degrees from -50 degrees to +50 degrees with respect to the film normal direction. The light having a wavelength of λ nm was incident in the oblique direction, and the above-mentioned Re (λ) was measured at 11 points, and the assumed value of the measured retardation value and the average refractive index and the input film thickness value were calculated from KOBRA 21ADH or WR.

In the above measurement, the assumed value of the average refractive index may be a catalogue value of various optical films in a Polymer Handbook (JOHN WILEY & SONS, INC.) A film having an unknown value of the average refractive index may be used. The measurement was carried out using an Abbe refractometer. The values of the average refractive index of the main optical film are exemplified as follows: deuterated cellulose (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate Ester (1.49) and polystyrene (1.59). nx, ny, and nz were calculated from KOBRA 21ADH or WR by inputting the assumed values of the average refractive index and the film thickness. The calculated nx, ny, and nz were further calculated. Nz = (nx - nz) / (nx - ny).

In addition, in this specification, unless otherwise indicated, the measurement wavelength is 550 nm.

A liquid crystal display device according to the present invention includes a first polarizing element, a first optical compensation region, and a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate, a second optical compensation region, and a second polarizing element. In the black display, the liquid crystal molecules included in the liquid crystal layer are aligned in parallel with respect to the surface of the pair of substrates, and the total value of the retardation in the thickness direction of the wavelength of 550 nm of the first substrate and the second substrate is Rth. _Sub (550) is 3 nm ≦ | Rth _sub (550) | ≦ 60 nm, and the total value Rth ₁ of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm (550) is -135~25 nm. Hereinafter, each part of the embodiment or the configuration of the liquid crystal display device will be described in detail below using the drawings.

[Configuration of Liquid Crystal Display Device]

1 is a schematic cross-sectional view showing an example of an IPS liquid crystal display device as an embodiment of a horizontal electric field type liquid crystal display device of the present invention.

The liquid crystal display device shown in FIG. 1 includes at least a pair of first polarizing element 20 and second polarizing element 22, a first optical compensation region 24 that is in contact with the first polarizing element 20, and a second contact with the second polarizing element 22. 2 optical compensation region 26, and IPS or FFS type liquid crystal cell 10.

The outer surface of the first polarizing element 20 and the second polarizing element 22 is usually provided with a polarizing plate protective film 28 for protecting the polarizing element, and the backlight unit 30 is disposed outside the first polarizing element 20. The backlight unit 30 includes, in addition to the light source, a reflector, a brightness enhancement film, or a diffusion plate, a prism sheet, or a lens array for making the point source or the line source a uniform surface light source, for improving the utilization efficiency of light. (Lens Array) and other components.

In addition to the above-described configuration, an optically isotropic functional layer disposed between the first polarizing element 20 and the second polarizing element 22, such as an adhesive or an adhesive, does not affect the effects of the present invention, and thus can be suitably used. .

In the liquid crystal display device of FIG. 1, the liquid crystal cell 10 includes a first substrate 11, a liquid crystal layer 12 including a nematic liquid crystal material, and a second substrate 15. The liquid crystal layer 12 is liquid crystal molecules of the nematic liquid crystal material with respect to the pair of substrates 11 and 15 at the time of black display The surface is aligned parallel to the aligned liquid crystal cells. The product of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn Δn. d In the penetration mode, in the IPS type without a twisted structure, the range of 0.2 to 0.4 μm is considered to be the optimum value. In addition, in the FFS type, the range of 0.3 to 0.5 μm is considered to be the optimum value. Since the white display brightness is high and the black display brightness is small within this range, a bright and high contrast display device can be obtained. An alignment film (not shown) is formed on the surface of the substrates 11 and 15 that is in contact with the liquid crystal layer 12, so that liquid crystal molecules are aligned substantially in parallel with respect to the surface of the substrate, and are controlled by a rubbing treatment direction or the like applied to the alignment film. The alignment direction of the liquid crystal molecules in the voltage state or the low application state is not applied. Further, on the inner surface of the substrate 11 or 15, a (pixel) electrode 14 which can apply a voltage to liquid crystal molecules, and a color filter 13 are formed.

In the liquid crystal layer 12, the liquid crystal molecules are not twisted in a state where no voltage is applied, and are controlled by, for example, the direction of rubbing treatment of the alignment films formed on the inner surfaces of the substrates 11 and 15, and are fixed at a fixed level parallel to the substrate. Orientation in the direction. When a voltage is applied, the liquid crystal molecules are horizontally rotated by a specific angle by an electric field formed in the in-plane direction to be aligned in a specific direction. There are various proposals regarding the shape and arrangement of the electrodes, and any of them can be utilized. FIG. 2 is a view schematically showing an example of alignment of liquid crystal molecules in a pixel region of the liquid crystal layer 12. 2 is a rubbing direction 4 of alignment of liquid crystal molecules in a region of an extremely small area corresponding to one pixel of the liquid crystal layer 12, and an alignment film formed on the inner surfaces of the substrates 11 and 15, and formed on the substrate 11. An example of a schematic diagram of the electrodes 2 and 3 which can apply a voltage to liquid crystal molecules on the inner surface of the 15 and 15 is shown. When the nematic liquid crystal having positive dielectric anisotropy is actively driven as the field effect type liquid crystal, the alignment direction of the liquid crystal molecules in the unapplied voltage state or the low application state is 5a and 5b, and a black display can be obtained. . If When a voltage is applied between the electrodes 2 and 3, the liquid crystal molecules change their alignment directions in the directions of 6a and 6b in accordance with the voltage. Usually, white display is performed in this state.

Further, in FIG. 1, the absorption axis 20a of the first polarizing element 20 and the absorption axis 22a of the second polarizing element 22 are arranged orthogonally. When no voltage is applied, the liquid crystal molecules of the liquid crystal layer 12 are horizontally aligned such that the slow axis 12a of the liquid crystal layer 12 and the absorption axis 22a of the second polarizing element 22 are orthogonal to each other. Therefore, the light incident from the backlight unit 30 is substantially maintained in a polarized state and passes through the liquid crystal layer 12, and is blocked by the absorption axis 20a of the first polarizing element 20 to be black. However, with respect to the obliquely incident light from the light incident from the backlight unit 30, the absorption axes 20a and 22a of the polarizing films 16 and 18 deviate from the orthogonal relationship, thereby causing light leakage, that is, reducing the viewing angle contrast. The same phenomenon occurs in the case of observation from an oblique direction. The second optical compensation region 26 disposed between the second polarizing element 22 and the liquid crystal cell 10 has a function of reducing the light leakage and improving the viewing angle contrast. As described above, the improvement effect is to compensate for the orthogonal relationship of the deviation by the function of the λ/2 plate. The optically anisotropic layer having the function is not particularly limited, and the second optical compensation region 26 is preferable. The in-plane retardation Re ₂ (550) is preferably from 100 to 250 nm, more preferably from 140 to 230 nm, and particularly preferably from 190 to 210 nm.

Further, the retardation Rth ₂ (550) in the thickness direction of the second optical compensation region 26 is preferably -150 to 10 nm, more preferably -100 to -10 nm, and particularly preferably -50 to -30 nm. If it is within this range, it is preferable to reduce the light leakage and the change in color tone during black display to improve the viewing angle characteristics. Details of the second optical compensation region 26 will be described below.

The first optical compensation region 24 is disposed between the first polarizing element 20 and the first substrate 11 .

In the optical compensation of the previous transverse electrolysis mode, as described above, Since the polarization element compensation by the second optical compensation region 26 is performed, it is assumed that an isotropic film having no phase difference or an optical having a low retardation value is disposed at a position of the first optical compensation region so as not to affect the light. The anisotropic film is used as a polarizing plate protective film or has no configuration.

However, when the second optical compensation region 26 is used to eliminate the phase difference caused by the polarizing element, the expected compensation effect cannot be sufficiently obtained, and the inventors have conducted intensive studies, and as a result, it has been found that the substrate 11 and 15 are on the liquid crystal cell. The color filter 13 or the electrode 14 of the member to be formed has birefringence, and the light which is given the phase difference by these is a cause of light leakage or color shift.

Therefore, in the present invention, the first optical compensation region (optical anisotropic layer) having the phase difference (delay value) for eliminating the phase difference is disposed. However, since the first optical compensation region is disposed in order to eliminate the birefringence of the member on the substrate, the required retardation value cannot be easily specified, but is affected by the birefringence of these members.

The inventors of the present invention investigated liquid crystal cell substrates of a plurality of liquid crystal display devices, and as a result, found that there is almost no member having anisotropy in the in-plane direction of these substrates, and the retardation in the thickness direction is dominant, so that only the thickness is considered. The delay in direction can be.

According to the analysis, the total value of the retardation of the two substrates in the thickness direction of the wavelength of 550 nm, Rth _sub (550), falls within the range of 3 nm ≦|Rth _sub (550)|≦60 nm. In this case, it is understood that the total value Rth ₁ (550) of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region in the thickness direction of the wavelength of 550 nm is adjusted to -135 to 25 nm. Optical compensation is then possible.

Further, if the Rth _sub (550) of the liquid crystal display device is 5 ≦|Rth _sub (550)|≦40, the effect of the present invention can be further obtained, so that it is preferable, and particularly preferably 10 ≦|Rth _sub (550)|≦ 20.

The total value Rth ₁ (550) of the retardation in the thickness direction of the first optical compensation region 24 and the substrates 11 and 15 in the thickness direction of 550 nm is -135 to 25 nm, preferably -45 to 25 nm, more preferably -25. ~15 nm.

The reason for eliminating the birefringence caused by the substrate by the total value of the first substrate, the second substrate, and the first optical compensation region is that it is insufficient to consider only the retardation value of each member. For example, by the configuration of the color filter on Array (COA) members constituting the color filter on the electrode (TFT) 14 as shown in FIG. 3, the delay value is further changed, so it is necessary to The substrate was studied together with the retardation value of the first optical compensation region.

The first optical compensation region 20 is preferably made of a polymer film, and it is preferable because it has a function as a polarizing plate protective film and has good manufacturing suitability. As the polymer film used in the first optical compensation region 20, it is preferable to use deuterated cellulose, a cyclic olefin, or an acrylic resin (preferably comprising a selected from a lactone ring unit, a maleic anhydride unit, and A material used for a polarizing plate protective film such as an acrylic polymer of at least one unit in the glutaric anhydride unit. In this case, the thickness of the polymer film is not particularly limited as long as the desired retardation is obtained, and is, for example, preferably 1 to 90 μm, and more preferably 5 to 70 μm from the viewpoint of thinning the device. It is particularly preferably 10 to 50 μm. Details of the first optical compensation region 20 will be described below.

1 and 3, the configuration of the liquid crystal display device in the case where the liquid crystal cell 10 is in the IPS mode is shown. When the liquid crystal cell 10 is in the FFS mode, the slow phase axis direction in the black display of the liquid crystal layer 12 is Since the direction orthogonal to the IPS mode is adopted, the configuration of FIGS. 4 and 5 is adopted as a general configuration. Replace part of the configuration The liquid crystal display device does not change the effects obtained by the present invention, and therefore will not be described in detail in the following description.

In the present invention, the compensation portion that is insufficient by the polarization element of the second optical compensation region 26 is compensated by the first optical compensation region 24, but the second optical compensation region 26 is viewed according to the configuration of the second optical compensation region 26. Since the state of the light passing between the polarizing elements is different depending on the birefringence, the thickness, and the like, the delay required for the first optical compensation region 24, that is, the delay of the total value of the first optical compensation region 24 and the substrates 11 and 15 is slightly delayed. different.

Hereinafter, preferred optical characteristics of various members of the liquid crystal display device of the present invention, materials used for the members, methods for producing the same, and the like will be described in detail.

1. The first optical compensation area

In the liquid crystal display device of the present invention, the first optical compensation region is provided between the first polarizing element and the first substrate, and the first optical compensation region is characterized by having a specific phase difference.

The material and form of the first optical compensation region are not particularly limited as long as they have the above optical characteristics. For example, a retardation film containing a birefringent polymer film, a film obtained by heating a polymer compound on a transparent support, and a low molecular or polymer liquid crystal by coating or transferring a transparent support Any of a retardation film having a retardation layer formed of a compound can be used. In addition, it is also possible to use a laminate in which each layer is laminated.

2. The second optical compensation area

In order to reduce light leakage and improve viewing angle contrast, the liquid crystal display device of the present invention has a second optical compensation region between the second substrate and the second polarizing element. The second optical compensation region includes one embodiment and two or more embodiments. Re ₂ (550) is preferably 100 to 250 nm, and Rth ₂ (550) is preferably -150 to 10 nm.

Hereinafter, specific examples of the second optical compensation region in the liquid crystal display device of the present invention will be described. In the following description, the isotropic layer having no phase difference is omitted from the description of the configuration, but it may be arranged as needed.

In addition, the material or the production method to be specifically exemplified is not limited to the description, and a material having the same property or a method of obtaining an equivalent layer may be selected, or a function of the present invention may be enhanced, or a function other than the present invention may be added. Apply undocumented additives or steps.

[First Embodiment]

In the first embodiment, the second optical compensation region is composed of a single-layer optically anisotropic layer. In this embodiment, the slow axis direction of the second optical compensation region is arranged in parallel with the absorption axis direction of the second polarizing element.

Preferably, the in-plane retardation Re ₂ (550) at a wavelength of 550 nm in the second optical compensation region of the first embodiment is 100 to 250 nm, and the retardation Rth ₂ (550) in the thickness direction at a wavelength of 550 nm is -150~ 10 nm. More preferably, the in-plane retardation Re ₂ (550) of the second optical compensation region is 150 to 230 nm, and the retardation Rth ₂ (550) in the thickness direction is -100 to -10 nm, and particularly preferably the in-plane retardation Re ₂ ( 550) is 190~210 nm, and the retardation Rth ₂ (550) in the thickness direction is -50~-30 nm.

In the first embodiment, since the second optical compensation region is composed of a single layer, it is preferable in terms of thinning of the panel or reduction in the number of components to be produced.

In the first embodiment, the Nz value of the second optical compensation region is preferably -1.0 to 1.0, more preferably -0.5 to 0.7, still more preferably -0.3 to 0.5.

If it is within this range, light leakage and color tone change at the time of black display can be reduced, and the viewing angle characteristics can be improved. In addition, the Nz value is defined by "Rth ₂ (550) / Re ₂ (550) + 0.5".

One of the causes of the color shift in the oblique direction is that the wavelength dispersion of the retardation layer used for optical compensation is not suitable. In general, the wavelength dispersibility of Re of the retardation layer is determined by the properties of the liquid crystal compound used. In order to reduce the color shift, it is understood that in the first embodiment, Re ₂ (450)/Re ₂ (550) is 0.8 to 1.2, and Re ₂ (650)/Re ₂ (550) is 0.9 to 1.1. The color shift is reduced to the extent that there is no sense of discomfort even when observed by the human eye.

The second optical compensation region can be obtained by substantially extending a film of a polymer having a characteristic of nz>nx.

As such a polymer film, a polymer film containing a material having negative intrinsic birefringence such as deuterated cellulose substituted with an aromatic fluorenyl group, polycarbonate, or polystyrene can be preferably used.

As a manufacturing method, for example, in the case of using a film of cellulose acetate benzoate which is an aromatic thiol-substituted deuterated cellulose, it can be obtained by dissolving cellulose acetate benzoate in a solvent. The dope is cast on the metal support for film formation, and the solvent is dried to obtain a film, and the film formed by the solution is stretched at a stretching ratio of 1.3 to 1.9 times or the like to align the cellulose molecular chains.

In the case where the second optical compensation region is the first embodiment, the total value Rth ₁ (550) of the retardation in the thickness direction of the first optical compensation region and the first and second substrates is -135 to 5 nm, preferably -55~-5 nm, more preferably -25~-15 nm.

The thickness in the case where the second optical compensation region is one layer is preferably 1 to 90 μm, more preferably 5 to 70 μm, particularly preferably 10 to 50 μm.

[Second Embodiment]

In the second embodiment, the second optical compensation region includes a biaxial film (B plate) of nx>nz>ny and a [quasi]uniaxial film (negative C plate) of nx≒ny>nz .

In the present embodiment, the order of lamination of the two layers included in the second optical compensation region is not particularly limited. In the case where the uniaxial film is disposed on the liquid crystal cell substrate side and the biaxial film is disposed on the second polarizing element side, the slow axis direction of the biaxial film is parallel to the absorption axis direction of the second polarizing element. Configure it. When the biaxial film is disposed on the liquid crystal cell substrate side and the uniaxial film is disposed on the polarizing element side, the slow axis of the biaxial film is arranged to be orthogonal to the absorption axis direction of the second polarizing element.

In the second embodiment, since the second optical compensation region includes two layers, it is preferable to expand the function of the optical anisotropy design or the selectivity of the production conditions by separating the functions.

(biaxial film)

In the second optical compensation region used in the second embodiment, the in-plane retardation Re _2B (550) of the biaxial film display wavelength of 550 nm is 70 to 150 nm, and the retardation Rth _2B (550) in the thickness direction is -150~. Optical anisotropy at -70 nm.

Preferably, the in-plane retardation Re _2B (550) at a wavelength of 550 nm is 80 to 130 nm, the retardation in the thickness direction Rth _2B (550) is -140 to -80 nm, and more preferably the in-plane retardation Re _2B (550) is From 100 to 110 nm, the retardation Rth _2B (550) in the thickness direction is -130 to -100 nm.

The Nz value of the biaxial film in the second embodiment is preferably -2.0 to 0.5, more Preferably, it is -1.5 to 0, and particularly preferably -1.0 to -0.5. If it is within this range, light leakage and color tone change at the time of black display can be reduced, and the viewing angle characteristics can be improved.

When the Re _2B (450)/Re _2B (550) of the biaxial film according to the second embodiment is 0.8 to 1.2, and Re _2B (650)/Re _2B (550) is 0.9 to 1.1, the color shift can be performed. It is reduced to the extent that there is no sense of discomfort even when observed by the human eye.

The biaxial film can be produced by a suitable method such as extrusion molding or cast film formation by a longitudinal stretching method using a roll, a lateral stretching method using a tenter, or a biaxial stretching method. The film was obtained by stretching treatment. Specifically, the description of Japanese Laid-Open Patent Publication No. 2005-338767 can be referred to.

(uniaxial film)

In the uniaxial film used in the second embodiment, the uniaxial film shows an optical anisotropy in which the retardation Rth _2C (550) in the thickness direction is 50 to 200 nm.

The retardation Rth _2C (550) in the thickness direction of the wavelength of 550 nm is preferably 80 to 170 nm, more preferably 100 to 130 nm.

It is particularly preferable to have no in-plane retardation Re _2C (550) in optical design, but there is a case where in-plane retardation occurs during the manufacturing process, and these can also be used as optical anisotropy suitable for the second embodiment. A film of a layer of uniaxial film. In the present invention, the absolute value of the in-plane retardation is preferably 10 nm or less, more preferably 5 nm or less.

The Nz value of the uniaxial film in the second embodiment is preferably 10 or more, more preferably 20 or more, and particularly preferably 100 or more. If it is within this range, light leakage and color tone change at the time of black display can be reduced, and the viewing angle characteristics can be improved.

When the Re _2C (450)/Re _2C (550) of the uniaxial film according to the second embodiment is 0.8 to 1.2, and Re _2C (650)/Re _2C (550) is 0.9 to 1.1, the color shift can be performed. It is reduced to the extent that there is no sense of discomfort even when observed by the human eye.

The uniaxial film can be obtained by forming a film in such a manner as not to exhibit an in-plane retardation of a film having a retardation of nz < nx such as a deuterated cellulose film, a cyclic polyolefin or a polycarbonate, or the like. The step of canceling the in-plane delay of the performance is set to nx≒ny. Further, the alignment state of the liquid crystal material may be fixed to form a layer having a phase difference of nz < nx.

In the second embodiment, the retardation Rth ₁ (550) of the total value of the first optical compensation region and the first and second substrates is preferably -45 to 25 nm, more preferably -30 to 25 nm, and particularly Good for -15~25 nm.

The thickness of the second optical compensation region in the second embodiment is preferably 1 to 180 μm, more preferably 5 to 140 μm, still more preferably 10 to 100 μm.

[Third embodiment]

In the third embodiment, the second optical compensation region includes a biaxial film (B plate) of nx>ny>nz and a [quasi]uniaxial film (positive C plate) of nx≒ny<nz.

In the present embodiment, the order of lamination of the two layers included in the second optical compensation region is not particularly limited. In the case where the uniaxial film is disposed on the liquid crystal cell substrate side and the biaxial film is disposed on the second polarizing element side, the slow axis direction of the biaxial film is orthogonal to the absorption axis direction of the second polarizing element. The way to configure. When the biaxial film is disposed on the liquid crystal cell substrate side and the uniaxial film is disposed on the polarizing element side, the slow axis of the biaxial film is arranged in parallel with the absorption axis direction of the second polarizing element.

In the third embodiment, since the second optical compensation region includes two layers, in the same manner as in the third embodiment, the design of the optical anisotropy or the selectivity of the manufacturing conditions is expanded by separating the functions. Better words.

(biaxial film)

In the second optical compensation region used in the third embodiment, the biaxial film preferably has an in-plane retardation Re _2B (550) at a wavelength of 550 nm of 50 to 200 nm and a retardation Rth _{2B in} a thickness direction of a wavelength of 550 nm ( 550) is an optical anisotropy of 50 to 200 nm.

The biaxial film preferably has an in-plane retardation Re _2B (550) of 70 to 150 nm, a thickness direction retardation Rth _2B (550) of 60 to 150 nm, and more preferably an in-plane retardation Re _2B (550) of 90 to 130. The retardation Rth _2B (550) in the thickness direction of nm is 80 to 120 nm.

The Nz value of the biaxial film in the third embodiment is preferably from 1.0 to 5.0, more preferably from 1.2 to 2.5, still more preferably from 1.5 to 2.0. If it is within this range, light leakage and color tone change at the time of black display can be reduced, and the viewing angle characteristics can be improved.

When the Re _2B (450)/Re _2B (550) of the biaxial film according to the third embodiment is 0.8 to 1.2, and Re _2B (650)/Re _2B (550) is 0.9 to 1.1, the color shift can be performed. It is reduced to the extent that there is no sense of discomfort even when observed by the human eye.

The biaxial film can be obtained by forming a film so as not to exhibit an in-plane retardation of a film having a retardation of nz < nx such as a deuterated cellulose film, a cyclic polyolefin or a polycarbonate.

As a manufacturing method, for example, in the case of using a film of cellulose acetate, a coating material in which cellulose acetate is dissolved in a solvent is cast on a metal support for film formation, and the solvent is dried to obtain a film. The film formed by the solution is stretched at a stretching ratio of 1.3 to 1.9 times or the like to align the cellulose molecular chains.

(uniaxial film)

In the second optical compensation region used in the third embodiment, the uniaxial film preferably has an optical anisotropy in which the retardation Rth _2C (550) in the thickness direction of 550 nm is -200 to -50 nm. The retardation Rth _2C (550) in the thickness direction is preferably -190 to -100 nm, more preferably -180 to -140 nm.

It is preferable to have no in-plane retardation Re _2C in optical design, but there is a case where an in-plane retardation occurs in the manufacturing process, and these can also be used as a single axis suitable for the second optical compensation region of the third embodiment. Membrane of the membrane. In the present invention, the absolute value of the in-plane retardation is preferably 10 nm or less, more preferably 5 nm or less.

The Nz value of the uniaxial film in the third embodiment is preferably -10 or less, more preferably -20 or less, and particularly preferably -100 or less. If it is within this range, light leakage and color tone change at the time of black display can be reduced, and the viewing angle characteristics can be improved.

When the Re _2C (450)/Re _2C (550) of the uniaxial film according to the third embodiment is 0.8 to 1.2, and Re _2C (650)/Re _2C (550) is 0.9 to 1.1, the color shift can be performed. It is reduced to the extent that there is no sense of discomfort even when observed by the human eye.

The uniaxial film can be obtained by fixing an alignment state of the liquid crystal material to form a layer having a phase difference of nz>nx, or not expressing styrene or a derivative thereof, polycarbonate, acrylic resin, or anti-butyl A film such as a polyester such as enedic acid diester having a negative intrinsic birefringence and exhibiting an in-plane retardation of a film having a retardation of nz>nx is formed, or a step of canceling the in-plane retardation of the expression is used. Nx≒ny.

In the third embodiment, the total value Rth ₁ (550) of the retardation between the first optical compensation region and the first and second substrates is preferably -75 to 25 nm, more preferably -60 to 25 nm, particularly Good for -45~25 nm.

The thickness of the second optical compensation region in the third embodiment is preferably 1 to 180 μm, more preferably 5 to 140 μm, and particularly preferably 10 to 100 μm.

[Other embodiments]

Examples of the configuration of the other second optical compensation region include a biaxial film of nx>nz>ny and a biaxial film of nx>ny>nz, or an A plate and a negative C plate, an A plate, a positive C plate, and an A plate. And a variety of components. Further, from the viewpoint of the optical design, if the number of layers is large, the interface is increased, and there is a concern that the utilization efficiency of light due to reflection or scattering on the interface is lowered. Therefore, the number of layers is preferably as small as possible.

Further, in a liquid crystal display device having a relatively small area, an optical compensation region may be formed by structural birefringence such as oblique vapor deposition instead of the above polymer film.

3. First and second polarizing elements

The polarizing element used in the present invention is not particularly limited. As the polarizing element, any of known polarizing elements such as an iodine-based polarizing element, a dye-based polarizing element using a dichroic dye, a polyene-based polarizing element, and a wire grid polarizing element can be used. The iodine-based polarizing element and the dye-based polarizing element are generally produced by using a polyvinyl alcohol-based film. The absorption axis of the polarizing element corresponds to the direction in which the film extends. Therefore, the polarizing element extending in the longitudinal direction (transport direction) has an absorption axis parallel to the longitudinal direction, and the polarizing element extending in the lateral direction (perpendicular to the transport direction) has an absorption axis perpendicular to the longitudinal direction.

It is preferable that the thickness of the first polarizing element or the second polarizing element is 50 μm or less to contribute to thinning of the device.

The polarizing element generally includes a protective film, and preferably has a protective film on a surface opposite to the surface on which the first optical compensation region is disposed and on a surface opposite to the surface on which the second optical compensation region is disposed. Specifically, at least one of the first polarizing element and the second polarizing element is a polarizing plate sandwiched between the optical compensation regions and the polarizing plate protective film. In the present invention, each of the optical compensation regions described above may function as a protective film of the polarizing element. About the protection of the outside of the polarizing element The film is not particularly limited, and a cellulose fluorite film, a cyclic olefin polymer film, a polypropylene film, a polycarbonate film, an acrylic film, or polyethylene terephthalate (PET) can be used. Mesangial and the like. Among them, a cellulose ionized film is preferably used.

The thickness of the protective film is preferably from 10 to 80 μm, more preferably from 15 to 60 μm.

A preferred method of manufacturing the polarizing plate includes the step of continuously laminating the two protective films and the polarizing element in a strip state. The long polarizing plate is cut according to the size of the screen of the image display device to be used. Further, the optical compensation film is bonded to the surface of the first polarizing element on one surface. The polarizing plate produced in this manner is disposed such that the optical compensation film is the liquid crystal cell side. In addition, although any of the first and second retardation regions constituting the optical compensation film may be disposed on the side of the polarizing element, it is preferable to dispose the polymer film from the viewpoint of adhesion to the polarizing element and the like. In the embodiment in which the first retardation region is bonded to the polarizing element, it is preferable that a polymer film is disposed on the retardation layer formed by the discotic liquid crystal compound, and the polymer film is attached to the polarizing element. . The polymer film is preferably low Re and low Rth, and examples of the polymer film that can be used are the same as those of the polymer film which is preferably used as a protective film (easily layer side protective film) of the second polarizing element.

4. Liquid crystal cell

The liquid crystal display device of the present invention includes liquid crystal cells of the IPS and FFS type. The liquid crystal cell of the horizontal electric field type is described in various documents, and any of the configurations can be employed in the present invention. Available in any display device. For the IPS type liquid crystal display device, for example, Japanese Patent Laid-Open No. 2003-15160, Japanese Patent Laid-Open No. 2003-75850, Japanese Patent Laid-Open No. 2003-295171, Japanese Patent Laid-Open No. 2004-12730, and Japanese Patent Laid-Open No. 2004- No. 12731, Japanese Patent Special 2005-106967, Japanese Patent Laid-Open No. 2005-134914, Japanese Patent Laid-Open No. 2005-241923, Japanese Patent Laid-Open No. Hei No. 2005-284304, Japanese Patent Laid-Open No. Hei No. 2006-189758, Japanese Patent Laid-Open No. 2006-194918, Japanese Patent Laid-Open No. 2006-220680, Japanese Patent Laid-Open No. 2007-140353, Japanese Patent Laid-Open No. 2007-178904, Japanese Patent Laid-Open No. 2007-293290, Japanese Patent Laid-Open No. 2007-328350, Japanese Patent Laid-Open No. 2008 -3251, Japanese Patent Laid-Open No. 2008-39806, Japanese Patent Laid-Open No. 2008-40291, Japanese Patent Laid-Open No. 2008-65196, Japanese Patent Laid-Open No. 2008-76849, and Japanese Patent Laid-Open No. 2008-96815 The IPS type liquid crystal display device described in the publication.

The FFS type (hereinafter also referred to as FFS mode) liquid crystal cell includes a counter electrode (Counter Electrode) and a pixel electrode. These electrodes are formed of a transparent material such as indium tin oxide (ITO), and are spaced apart from each other by an interval such as an interval between the upper and lower substrates, and are capable of driving all liquid crystal molecules disposed on the upper portion of the electrode. The width is formed. According to this configuration, in the FFS mode, an aperture ratio higher than that of the IPS mode can be obtained, and further, since the electrode portion is translucent, a transmittance higher than that of the IPS mode can be obtained. For the FFS mode liquid crystal cell, for example, Japanese Patent Laid-Open No. 2001-100183, Japanese Patent Laid-Open No. 2002-14374, Japanese Patent Laid-Open No. 2002-182230, Japanese Patent Laid-Open No. 2003-131248, Japanese Patent Laid-Open No. 2003-2330830, etc. The description of each bulletin.

Instance

Hereinafter, examples of the invention will be described, but the invention is not limited by these examples. In addition, the "%" and "parts" as the content rate in the examples are based on the quality standard. In the present example, the "parts" indicating the amount of blending means "parts by mass" unless otherwise specified.

<Manufacture of LCD mode cell 1 in IPS mode>

As shown in FIG. 1, the electrode was placed on a single glass substrate so that the distance between the adjacent electrodes was 20 μm, and a polyimide film was placed thereon as an alignment film, and rubbing treatment was performed. The rubbing treatment is performed in the direction 4 shown in FIG. A polyimide film was provided on one surface of a separately prepared glass substrate and subjected to a rubbing treatment to prepare an alignment film. The alignment films were opposed to each other, and the interval (Gap; d) of the substrates was set to 3.9 μm, and the two glass substrates were stacked so that the rubbing directions of the two glass substrates were parallel, and then the refractive index anisotropy (Δn) was sealed. 0.0769 and a dielectric anisotropy (Δε) of a nematic liquid crystal composition of 4.5. d. of the liquid crystal layer The value of Δn is 300 nm.

<Production of LCD cell 1 in FFS mode>

A common electrode ITO is formed on a glass substrate having a color filter, and an acrylic organic insulating film (or an inorganic film such as SIN) is formed thereon. The domain can be formed by etching the insulating film using photolithography (which can also be performed simultaneously with an active device manufacturing step such as TFT). A pixel electrode (line width 5 μm, electrode gap 5 μm) provided with a slit was formed thereon. Further, a polyimide film was provided thereon as an alignment film and subjected to a rubbing treatment. A polyimide film was provided on one surface of a separately prepared glass substrate and subjected to a rubbing treatment to prepare an alignment film. The alignment films are opposed to each other, and the interval (Gap; d) of the substrates is set to 3.8 μm, and the two glass substrates are stacked so as to be parallel to each other in the rubbing direction of the glass substrates, and then the refractive index anisotropy is sealed ( Δn) is a nematic liquid crystal composition having a dielectric anisotropy (Δε) of 0.0 and a positive conductivity of 4.5. d. of the liquid crystal layer The value of Δn is 360 nm.

<Production of the first optical compensation area>

The following composition was placed in a mixing tank, and while stirring, the components were dissolved while heating to prepare a cellulose acetate solution A.

<cellulose acetate solution A composition>

The following composition was placed in another mixing tank, and while stirring, the components were dissolved while heating to prepare an additive solution B.

<Additive Solution B Composition>

60 parts by mass of the additive solution B was added to 477 parts by mass of the cellulose acetate solution A and thoroughly stirred to prepare a coating. The coating was cast from the casting opening onto a drum cooled to 0 °C. Stripping was carried out outside the field in which the solvent content was 70% by mass, and both ends in the width direction of the film were subjected to a pin comber (Pin Tenter) (the needle comb shown in Fig. 3 of Japanese Patent Laid-Open No. 4-1009) In the state where the solvent content is 3 to 5% by mass, the elongation is maintained at a distance of 3% while maintaining the lateral direction (direction perpendicular to the machine direction). Thereafter, by The film was conveyed between the rolls of the heat treatment apparatus and further dried to prepare a first optical compensation region of Example 1 having a thickness of 80 μm.

Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the optical incident angle dependence of Re was measured, and optical characteristics were calculated. As a result, it was confirmed that Re was 1 nm and Rth was -25 nm.

The first optical compensation region having characteristics of Examples 2 to 17 and Comparative Examples 1 to 4 was produced by the same procedure except that the mixing ratio of the cellulose acetate solution A and the additive solution B was changed.

<Production of the second optical compensation area of one layer>

(1) Coating preparation

. Deuterated cellulose solution C

The following composition was placed in a mixing tank and stirred to dissolve each component, and further heated at 90 ° C for about 10 minutes, and then filtered using a filter paper having an average pore diameter of 34 μm and a sintered metal filter having an average pore diameter of 10 μm.

Deuterated cellulose solution C

(2) Cast film formation

After the coating was cast and dried using a metal band casting machine, the film was peeled off from the belt by a stripping drum. Unstretched films were separately produced in the above manner.

(3) Extension

For each unstretched film produced in the above, at (glass transfer point Tg-extension) Extension temperature) = -5 ° C The film direction (Machine Direction, MD) extends 10% in the tenter area by the uniaxial extension of the fixed end. Secondly, at the same temperature, in the width direction (TD), the fixed end uniaxially extends over the tenter region by 65%. A biaxial stretching treatment was carried out in the above manner to produce a deuterated cellulose film. Further, the cast film thickness was adjusted so that the film thickness after stretching and drying became 60 μm.

The optical characteristics were measured to confirm that Re was 220 nm and Rth was -10 nm.

The second optical compensation regions of Examples 2 to 6 and Comparative Example 1 were produced by the same procedure except that the film thickness and the stretching ratio were changed.

<Production of the second optical compensation region of two layers>

(1) Production of a second optical compensation region including a B plate and a positive C plate

. B board production

The following composition was placed in a mixing tank and stirred to dissolve each component, thereby preparing a cellulose-deposited solution D.

Deuterated cellulose solution D

*1: Compound A represents a terephthalic acid/succinic acid/propylene glycol/ethylene glycol copolymer (copolymerization ratio [mol%] = 27.5/22.5/25/25).

Deuterated cellulose solution E for skin layer

The following composition was placed in a mixing tank and stirred to dissolve each component, thereby preparing a deuterated cellulose solution E.

Deuterated cellulose solution E

*1: Compound A represents a terephthalic acid/succinic acid/propylene glycol/ethylene glycol copolymer (copolymerization ratio [mol%] = 27.5/22.5/25/25).

The above-described deuterated cellulose solution D was cast into a core layer having a film thickness of 90 μm to form the surface layer A having a thickness of 2 μm and the surface layer B having a thickness of 2 μm. The solution E is cast.

The web (film) obtained by peeling off is taken and dried, and then taken up. At this time, the amount of residual solvent is 0 to 0.5% with respect to the mass of the film as a whole. Then, the film was sent out and subjected to 75% TD stretching at 190 ° C by a tenter, whereby the first phase difference region of Example 7 was produced. The optical characteristics were measured, and it was confirmed that Re was 110 nm and Rth was 115 nm.

Examples 8 to 14 and Comparative Examples 2 to 3 were produced in the same manner except that the film thickness and the stretching ratio were changed.

. Production of positive C board

The saponification treatment of the surface of the B plate produced above was carried out, and a commercially available vertical alignment film (JALS-204R, manufactured by Japan Synthetic Rubber Co., Ltd.) was diluted to 1:1 with methyl ethyl ketone. It was coated on the film at 2.4 mL/m ² using a wire bar coater (Wire Bar Coater). Immediately dry at 120 ° C for 120 seconds.

Next, 3.8 g of the following rod-like liquid crystal compound, photopolymerization initiator (Irgacure 907, manufactured by Ciba-Geigy Co., Ltd.), 0.06 g, sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) was prepared. Manufactured was a solution of 0.02 g of the following air interface side vertical alignment agent 0.002 g dissolved in 9.2 g of methyl ethyl ketone. This solution was applied to the alignment film side of the film forming the above alignment film by a wire bar of #3.4. This was attached to a metal frame and heated in a thermostat at 100 ° C for 2 minutes to align the rod-like liquid crystal compound. Next, the rod-like liquid crystal compound was crosslinked by irradiation with a 120 W/cm high-pressure mercury lamp at 80 ° C for 20 seconds (Ultraviolet, UV), and then left to cool to room temperature to prepare a retardation layer.

Rod-like liquid crystal compound

Air interface side vertical alignment agent: exemplified compound (II-4) described in Japanese Patent Application No. 2003-119959

The B plate and the negative C plate were bonded together using a polyvinyl alcohol-based adhesive to prepare a second optical compensation region.

Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependency of Re of the produced film was measured, and the amount of participation of the support measured in advance was subtracted, thereby calculating only the transparent region. As a result of the optical characteristics, it was confirmed that Re in the transparent region was 0 nm and Rth was -160 nm, and the rod-like liquid crystals were aligned substantially vertically, and the second phase difference region of Example 7 was obtained.

Regarding the second optical compensation regions of Examples 8 to 14 and Comparative Examples 2 and 3, In addition to changing the number of the bar, it is also produced in the same procedure.

(2) Production of a second optical compensation region including a B plate and a negative C plate

. B board production

After peeling off the polarizing plate from a 42Z1 liquid crystal television (Television, TV) manufactured by Toshiba, the film was peeled off from the polarizing plate and used. The incident angle dependence of Re was measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), and it was confirmed that Re was 100 nm and Rth was -100 nm.

. Production of negative C plate

The following composition was placed in a mixing tank and stirred to dissolve each component, and further heated at 90 ° C for about 10 minutes, and then filtered using a filter paper having an average pore diameter of 34 μm and a sintered metal filter having an average pore diameter of 10 μm.

Cellulose acetate solution F

Polycondensation ester PB-35:

Compound 1:

The flow rate of the polymer coating of the die projection was adjusted so that the film thickness of the completed polymer film became 58 μm, and the tape was cast on a stainless steel belt at a coating temperature of 36 °C. After drying and stripping, the in-plane retardation Re was determined using an automatic birefringence meter KOBRA-WR (Oji Scientific Co., Ltd.) at a wavelength of 550 nm to determine the in-plane retardation Re, Re is 0 nm, and Rth is 110 nm. .

The B plate and the negative C plate were bonded together using a polyvinyl alcohol-based adhesive to prepare a second optical compensation region.

<Production of the second optical compensation region including three layers>

A commercially available triacetonitrile cellulose film "Fujitac TD80UF" (manufactured by Fujifilm Co., Ltd.) was used as the first and third retardation layers of Example 17. Further, the second optical compensation region of one layer of Example 1 was used as the second retardation layer.

The first, second, and third retardation layers were bonded together using a polyvinyl alcohol-based adhesive to prepare a second optical compensation region.

<Production of first and second polarizing elements>

The iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizing element, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fujifilm Co., Ltd. (Re=0 nm, Rth=40 nm) was subjected to saponification treatment, and polycondensation was used. Vinyl alcohol based adhesive bonding The first and second polarizing elements are fabricated on one surface of the polarizing element.

<Production of Liquid Crystal Display Device (Example 1)>

The produced first optical compensation region was attached to the produced first polarizing element using a polyvinyl alcohol-based adhesive. In addition, the second optical compensation region is attached to the produced second polarizing element such that the absorption axis of the second polarizing element and the slow axis of the second optical compensation region are parallel with each other using the polyvinyl alcohol-based adhesive.

On one surface of the IPS mode liquid crystal cell 1 produced as described above, the surface of the first optical compensation region to which the first optical compensation region is attached is formed such that the absorption axis of the first polarizing element and the slow axis of the liquid crystal layer are parallel. The LCD cell is attached.

Then, on the other surface of the IPS mode liquid crystal cell 1, the absorption axis of the second polarizing element is perpendicular to the slow axis of the liquid crystal layer, and the polarization is orthogonal to the first polarizing element (Cross Nicol). In the manner of attaching the surface to which the second optical compensation region is attached, to the liquid crystal cell, the liquid crystal display device of Example 1 was produced.

(Examples 2 to 17, Comparative Examples 1 to 5)

Using the produced first and second optical compensation regions, a polarizing plate was produced by the same procedure and attached to the liquid crystal cell to fabricate a liquid crystal display device.

<evaluation>

The display performance was measured using a commercially available liquid crystal viewing angle and chromaticity characteristic measuring device Ezcom (manufactured by ELDIM), and a commercially available liquid crystal display device 42LE5500 (manufactured by LG) was used as the backlight.

Hereinafter, the Lab tone index, the brightness index, and the overall evaluation were evaluated, and the results are shown in the following table. In the case where the second optical compensation region is one layer, the first to third retardation layers in the table indicate a second optical compensation region (first retardation layer) of one layer. In the case where the second optical compensation region is two layers, the first phase difference The layer represents a film on the liquid crystal cell side, and the second retardation layer represents a film on the second polarizing element side. When the second optical compensation region has three layers, the first retardation layer indicates a film on the liquid crystal cell side, the third retardation layer indicates a film on the second polarizing element side, and the second retardation layer indicates the first retardation layer. A film between the second retardation layer and the second retardation layer.

Lab tone indicator:

Plot the origin from the +a* axis reference (0°) in the range of -15~240° when plotting the black tone change (every 5°) at a polar angle of 60° on the a*b* plane The distance is accumulated. This is an index indicating the intensity of the red and yellow tones which are expected to deteriorate the impression of the black display. The smaller the numerical value, the more excellent the color tone, and the evaluation is performed based on the following criteria.

A: Not up to 0.5

B: 0.5~ not up to 1.0

C: 1.0~ not up to 1.5

D: 1.5 or more

Brightness indicator:

The maximum value of the black luminance (Cd/m ² ) in the upward direction (azimuth angle 0 to 180°, every 5°) and the downward direction (azimuth angle 180 to 360°, every 5°) is averaged. The smaller the value, the smaller the light leakage of the black display, and the evaluation is performed using the following criteria.

A: Not up to 1.3

B: 1.3~ not up to 1.5

C: 1.5~ not up to 1.7

D: 1.7 or more

Overview:

The evaluation was performed using the following criteria.

A: The evaluation results of the Lab tone index and the brightness index are all A.

B: Any one of the evaluation results of the Lab tone index and the brightness index is A, and the other is B.

C: The evaluation results of the Lab tone index and the brightness index are both B, or either one is C.

D: The evaluation results of the Lab tone index and the brightness index are both C, or either one is D.

According to the table, Rth _sub (550) is 3 nm ≦|Rth(550)|≦60 nm, and Rth ₁ (550) is -135~25 nm. Examples 1 to 17 have excellent Lab tone index and brightness index. On the other hand, the comparison of the necessary conditions for Rth _sub (550) to 3 nm ≦|Rth(550)|≦60 nm and Rth ₁ (550) to -135~25 nm is compared with the example. Both indicators and brightness indicators are poor.

<Example of using a film polymer film>

The coating material P10 and the coating material T30 each having the composition shown below were prepared separately.

Composition of coating P10:

Composition of coating T30:

The additive AA1 is a compound represented by the following formula. In the following structural formula, R represents a benzamidine group, and a compound having an average degree of substitution of 5 to 7 is used.

Additive AA1:

The additive AA2 is a compound represented by the following formula. The structural formula and degree of substitution of each of R ⁹ are shown below.

The additive UU1 is a compound represented by the following formula.

Additive UU1:

A laminated film was produced by a solution casting method using the coating material P10 and the coating material T30. Specifically, the above two types of coating materials were cast on a metal support by a cast casting machine (Casting Giesser) which can perform three-layer co-casting. At this time, casting is performed in this order from the side of the metal support body side (T30), the intermediate layer (P10), and the upper layer (T30). The viscosity of each layer is adjusted so that the solid content concentration can be appropriately adjusted according to the combination of the respective coating materials so that co-casting can be performed, and the uniform casting can be performed. During the formation of the metal support, the coating was dried by drying air at 40 ° C to form a film, and then peeled off and the ends of the film were fixed by a needle, and the distance was maintained at the same interval while drying with a dry air at 105 ° C. 5 minutes. After the needle was taken out, it was further dried at 130 ° C for 20 minutes, and wound up in a state of a laminated film.

Thereafter, the three-layer laminated film was peeled off. The film thickness of the lower layer film is 20 Mm. The polymer film of the film can be stably produced in the above manner.

This film was placed in place of the TD80UF for polarizing plate fabrication, and a liquid crystal display device of the same configuration was separately fabricated. These liquid crystal display devices were evaluated in the same manner as described above, and as a result, good evaluation results were obtained in the same manner as in the above examples.

<Example of using a film polarizing film>

According to the method described in Japanese Patent No. 4804588, a polarizing film of a film is produced in the following manner. An isophthalic acid copolymerized polyethylene terephthalate in which 6 mol% of isophthalic acid was copolymerized was prepared as an amorphous ester-based thermoplastic resin substrate. A polyvinyl alcohol (PVA)-based resin layer is formed on the resin substrate by coating. The resin substrate and the PVA-based resin layer are integrally stretched by a two-stage stretching step including air-assisted stretching and boric acid water extension, and the PVA-based resin layer is subjected to a dyeing treatment using a dichroic dye to thereby produce a thickness of 3 Mm polarizing film. Using the polarizing film, evaluation was carried out in the same manner as above, and as a result, good evaluation results were obtained in the same manner as in the above examples.

10‧‧‧Liquid cell

11‧‧‧1st substrate

12‧‧‧Liquid layer

12a‧‧‧The direction of the slow phase axis of the liquid crystal molecules in the liquid crystal layer (black display [when no electric field is applied])

13‧‧‧Color filters

14‧‧‧ pixel electrodes

15‧‧‧2nd substrate

20‧‧‧1st polarizing element

20a‧‧‧Absorption axis of the first polarizing element

22‧‧‧2nd polarizing element

22a‧‧‧Absorption axis of the second polarizing element

24‧‧‧1st phase difference zone

26‧‧‧2nd phase difference zone

28‧‧‧Protective film

30‧‧‧Backlight unit

Claims (18)

A liquid crystal display device comprising: a first polarizing element; a first optical compensation region; a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate; a second optical compensation region; and a second polarized light In the black display, the liquid crystal molecules included in the liquid crystal layer are aligned in parallel with respect to the surfaces of the pair of substrates, and the total retardation in the thickness direction of the first substrate and the second substrate at a wavelength of 550 nm The value Rth _sub (550) is 3 nm ≦ | Rth _sub (550) | ≦ 60 nm, and the total retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm The value Rth ₁ (550) is -135 to 25 nm. The liquid crystal display device according to claim 1, wherein the second optical compensation region has an in-plane retardation Re ₂ (550) of a wavelength of 550 nm of 100 to 250 nm and a retardation Rth _{2 of a} wavelength of 550 nm in the thickness direction. (550) is -150~10 nm. The liquid crystal display device according to claim 1 or 2, wherein the second optical compensation region is composed of one layer, and the first substrate, the second substrate, and the first optical compensation region have a wavelength of 550 nm. The total value of the retardation Rth ₁ (550) in the thickness direction is -135 to 5 nm. The liquid crystal display device according to claim 1 or 2, wherein the second optical compensation region comprises at least two layers. The liquid crystal display device according to claim 4, wherein a retardation Rth _2C (550) in a thickness direction of a layer of the second optical compensation region of 550 nm is 50 to 200 nm, and a wavelength of another layer is 550 nm. The in-plane retardation Re _2B (550) is 70 to 150 nm, and the retardation Rth _2B (550) in the thickness direction of 550 nm is -150 to -70 nm. The liquid crystal display device according to claim 5, wherein the total value Rth ₁ (550) of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm is - 45~25 nm. The liquid crystal display device according to claim 4, wherein the retardation Rth _2C (550) in the thickness direction of the layer 550 nm of the layer of the second optical compensation region is -200 to -50 nm, and the other layer is The in-plane retardation Re _2B (550) at a wavelength of 550 nm is 50 to 200 nm, and the retardation Rth _2B (550) at a wavelength of 550 nm is 50 to 200 nm. The liquid crystal display device according to claim 7, wherein the total value Rth ₁ (550) of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region at a wavelength of 550 nm is - 75~25 nm. The liquid crystal display device according to claim 1 or 2, wherein at least one of the first optical compensation region and the second optical compensation region includes a polymer film. The liquid crystal display device according to claim 9, wherein the polymer film is selected from the group consisting of a deuterated cellulose film, a cyclic olefin polymer film, or an acrylic polymer film. The liquid crystal display device according to claim 9, wherein the polymer film has a thickness of 1 to 90 μm. The liquid crystal display device of claim 10, wherein the above The acrylic polymer film includes an acrylic polymer containing at least one selected from the group consisting of a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit. The liquid crystal display device according to claim 1 or 2, wherein at least one of the first polarizing element or the second polarizing element is a polarizing plate sandwiched between an optical compensation region and a polarizing plate protective film . The liquid crystal display device according to claim 13, wherein the protective film has a thickness of 10 to 80 μm. The liquid crystal display device according to the first or second aspect of the invention, wherein the first polarizing element or the second polarizing element has a thickness of 50 μm or less. The liquid crystal display device according to claim 1 or 2, wherein at least one of the first optical compensation region and the second optical compensation region includes a polymer film, and the second optical compensation region is composed of one layer The total value Rth ₁ (550) of the retardation in the thickness direction of the first substrate, the second substrate, and the first optical compensation region in the thickness direction of 550 nm is -135 to 5 nm. The liquid crystal display device according to claim 4, wherein at least one of the first optical compensation region and the second optical compensation region includes a polymer film, and a layer of the second optical compensation region has a wavelength of 550 nm. The retardation Rth _2C (550) in the thickness direction is 50 to 200 nm, the in-plane retardation Re _2B (550) of the other layer at a wavelength of 550 nm is 70 to 150 nm, and the retardation Rth _2B (550) in the thickness direction at a wavelength of 550 nm is -150~-70 nm. The liquid crystal display device according to claim 4, wherein at least one of the first optical compensation region and the second optical compensation region includes a polymer film, and a layer of the second optical compensation region has a wavelength of 550 nm. The retardation in the thickness direction Rth _2C (550) is -200 to -50 nm, and the in-plane retardation Re _2B (550) of another layer having a wavelength of 550 nm is 50 to 200 nm, and the retardation in the thickness direction of the wavelength of 550 nm is Rth _2B (550 ) is 50~200 nm.