WO2025192206A1 - Liquid crystal display device - Google Patents

Abstract

The present invention addresses the problem of providing a lateral electric field type liquid crystal display device in which light leakage of black display is reduced when viewed laterally. A liquid crystal display device according to the present invention comprises at least a first polarizer, a first optical compensation layer, a liquid crystal cell, a second polarizer, and a backlight in the stated order. The first optical compensation layer satisfies a prescribed relational expression. An in-plane retardation Re_total (550) and a total Rth_total (550) of retardations in the film thickness direction existing between the second polarizer and the liquid crystal layer in the liquid crystal cell satisfy a prescribed relational expression. The slow axis of the first optical compensation layer and the absorption axis of the first polarizer are parallel to each other.

Description

liquid crystal display device

The present invention relates to a liquid crystal display device.

IPS (In-Plane Switching) and FFS (Fringe Field Switching) liquid crystal display devices are not driven by applying an electric field between upper and lower substrates and causing liquid crystal molecules to rise, as in TN (Twisted Nematic) and VA (Vertical Alignment) types, but are of a type (mode) known as a transverse electric field type, in which liquid crystal molecules are made to respond in an in-plane direction of the substrate by an electric field that includes a component that is nearly parallel to the substrate surface.
In addition, IPS and FFS types are known as driving methods that have characteristics such as a wide viewing angle and little chromaticity shift or color tone change, because their structures in principle have few limitations on the viewing angle. In recent years, they have become widespread in a wide range of applications, from display devices for mobile terminals to high-definition and high-image-quality commercial use, in addition to television applications.

In these in-plane switching type liquid crystal display devices, a configuration is also known in which the protective films of the polarizing plates sandwiching the cell are made isotropic films, thereby utilizing the advantages of the above-mentioned liquid crystal cell without impairing them (for example, Patent Document 1).
However, this configuration does not take into account compensation due to the polarizer, and therefore, when viewed from an oblique direction, contrast decreases due to light leakage, and optical compensation is required for color shift. For this reason, in-plane switching liquid crystal display devices have been proposed in which an optically anisotropic layer is disposed in the display device, thereby taking into account compensation for the entire display device (e.g., Patent Documents 2 and 3).
Furthermore, in recent years, the applications of liquid crystal display devices have become more diverse, and there is a demand for a wider viewing angle in the lateral direction (left-right and horizontal directions) for applications such as in-vehicle displays (see, for example, Patent Document 4). However, with conventional technologies, visibility in the lateral direction is insufficient, and a decrease in contrast due to light leakage in the lateral direction in particular has been an issue.

JP 2010-107953 A Japanese Patent Application Laid-Open No. 2005-309382 Japanese Patent Application Laid-Open No. 2007-279411 Japanese Patent Application Laid-Open No. 2023-054645

To reduce light leakage in oblique viewing angles, an optically anisotropic layer that functions as a λ/2 plate is often used, and the principle behind this is said to be compensation through a mechanism similar to that described in JP 2009-122151 A. There are no particular restrictions on the optically anisotropic layer as long as it is configured to achieve this function, and various configurations have been proposed to date. However, after investigating various configurations, the inventors found that retardation present on the surface opposite the optically anisotropic layer, across the cell substrate, has a significant impact on light leakage in the horizontal direction during black display.

The objective of the present invention is to provide a lateral electric field type liquid crystal display device that reduces light leakage during black display when viewed from the side.

As a result of extensive research into the above-mentioned issues, the inventors have discovered that the above-mentioned issues can be resolved by the following configuration.

[1] A liquid crystal display device having at least a first polarizer, a first optical compensation layer, a liquid crystal cell, a second polarizer, and a backlight in this order,
The liquid crystal cell has a pair of substrates arranged opposite to each other, at least one of which has an electrode, and an alignment-controlled liquid crystal layer arranged between the pair of substrates, and by applying a voltage to the electrodes, an electric field having a component parallel to the substrate having the electrode is formed;
an absorption axis of the first polarizer is parallel to a slow axis of the first optical compensation layer,
a slow axis of the alignment-controlled liquid crystal layer in black display and an absorption axis of the first polarizer are perpendicular to each other;
an absorption axis of the first polarizer and an absorption axis of the second polarizer are perpendicular to each other,
an in-plane retardation Re1(550) of the first optical compensation layer at a wavelength of 550 nm satisfies the following formula (1),
Formula (1): 80nm≦Re1(550)≦320nm
at least one layer having retardation in a film thickness direction is present between the liquid crystal layer and the second polarizer,
A liquid crystal display device characterized in that the total in-plane retardation Re_total(550) and the total retardation in the film thickness direction Rth_total(550) of the layers between the liquid crystal layer and the second polarizer satisfy the following formulas (2) and (3):
Formula (2): 0nm≦Re_total(550)≦10nm
Formula (3): Rth_total (550)≦-10nm
[2] The liquid crystal display device according to [1], wherein a total of in-plane retardations Re_total(450) and a total of retardations in a film thickness direction Rth_total(450) of layers between the liquid crystal layer and the second polarizer satisfy the following formulas (4) and (5):
Formula (4): 0nm≦Re_total(450)≦20nm
Formula (5): Rth_total (450)≦-20nm
[3] The liquid crystal display device according to [1] or [2], wherein the sums of Rth_total(550) and Rth_total(450) of the retardations in the film thickness direction of the layers between the liquid crystal layer and the second polarizer satisfy the following formula (23):
Formula (23): Rth_total(450)−Rth_total(550)≦0nm
[4] The liquid crystal display device according to any one of [1] to [3], wherein the substrate of the pair of substrates disposed between the liquid crystal layer and the second polarizer is an electrode substrate having retardation in the film thickness direction.
[5] The liquid crystal display device according to [4], wherein the in-plane retardation Re3(550) and the retardation Rth3(550) in the film thickness direction at a wavelength of 550 nm of the electrode substrate satisfy the following formulas (6) and (7):
Formula (6): 0nm≦Re3(550)≦10nm
Formula (7): -100nm≦Rth3(550)≦-10nm
[6] The liquid crystal display device according to any one of [1] to [5], further comprising at least a second optical compensation layer between the liquid crystal layer and the second polarizer.
[7] The liquid crystal display device according to any one of [1] to [6], comprising, between the liquid crystal layer and the second polarizer, an electrode substrate having retardation in a film thickness direction and a second optical compensation layer, in this order from the liquid crystal layer side.
[8] The liquid crystal display device according to [6] or [7], wherein the in-plane retardation Re2(550) and the retardation Rth2(550) in the film thickness direction at a wavelength of 550 nm of the second optical compensation layer satisfy the following formulas (8) and (9):
Formula (8): 0nm≦Re2(550)≦10nm
Formula (9): -100nm≦Rth2(550)≦-10nm
[9] The liquid crystal display device according to any one of [6] to [8], wherein the second optical compensation layer is a film in which a liquid crystalline compound is fixed in an aligned state.
[10] The liquid crystal display device according to any one of [6] to [9], wherein the second optical compensation layer is a film in which a rod-like liquid crystalline compound is fixed in a state of being aligned in a direction perpendicular to the substrate surface.
[11] The liquid crystal display device according to any one of [6] to [10], wherein the second optical compensation layer is a cellulose acylate film.
[12] The liquid crystal display device according to any one of [1] to [11], wherein a ratio of an in-plane retardation Re1(450) at a wavelength of 450 nm to an in-plane retardation Re1(550) at a wavelength of 550 nm of the first optical compensation layer satisfies the following formula (10):
Formula (10): 0.70≦Re1(450)/Re1(550)≦1.30
[13] The liquid crystal display device according to any one of [1] to [12], wherein the first optical compensation layer consists of one layer, and an in-plane retardation Re1(550) at a wavelength of 550 nm and a retardation Rth1(550) in a film thickness direction satisfy the following formulas (11) and (12):
Formula (11): 150nm≦Re1(550)≦320nm
Formula (12): -50nm≦Rth1(550)≦50nm
[14] The first optical compensation layer consists of two layers,
The liquid crystal display device according to any one of [1] to [12], wherein a first optical compensation layer a and a first optical compensation layer b are laminated in this order from the liquid crystal cell side.
[15] The in-plane retardation Re1a(550) and the retardation Rth1a(550) in the film thickness direction at a wavelength of 550 nm of the first optical compensation layer a satisfy the following formulas (13) and (14):
Formula (13): 80nm≦Re1a(550)≦200nm
Formula (14): 20nm≦Rth1a(550)≦150nm
The liquid crystal display device according to [14], wherein the in-plane retardation Re1b(550) and the retardation Rth1b(550) in the film thickness direction at a wavelength of 550 nm of the first optical compensation layer b satisfy the following formulas (15) and (16):
Formula (15): 0nm≦Re1b(550)≦40nm
Formula (16): -180nm≦Rth1b(550)≦-50nm
[16] The in-plane retardation Re1a(550) and the retardation Rth1a(550) in the film thickness direction at a wavelength of 550 nm of the first optical compensation layer a satisfy the following formulas (17) and (18):
Formula (17): 0nm≦Re1a(550)≦40nm
Formula (18): 50nm≦Rth1a(550)≦180nm
The liquid crystal display device according to [14], wherein the in-plane retardation Re1b(550) and the retardation Rth1b(550) in the film thickness direction at a wavelength of 550 nm of the first optical compensation layer b satisfy the following formulas (19) and (20):
Formula (19): 80nm≦Re1b(550)≦200nm
Formula (20): -200nm≦Rth1b(550)≦-20nm
[17] The liquid crystal display device according to any one of [1] to [16], which has a color filter between the liquid crystal layer and the first optical compensation layer.
[18] The liquid crystal display device according to any one of [1] to [17], wherein the total Rth_total(550) of retardations in the film thickness direction of layers between the liquid crystal layer and the second polarizer satisfies the following formula (24):
Formula (24): -50nm≦Rth_total(550)≦-15nm
[19] The liquid crystal display device according to any one of [1] to [18], wherein the sums of Rth_total(550) and Rth_total(450) of retardations in the film thickness direction of layers between the liquid crystal layer and the second polarizer satisfy the following formula (25):
Formula (25): Rth_total(450)-Rth_total(550)≦-15nm

The present invention makes it possible to provide an in-plane switching liquid crystal display device that reduces light leakage during black display when viewed from the side.

FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention.

The present invention will be described in detail below.
The following description of the components may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as the lower and upper limits.

In addition, in this specification, a polarizing plate refers to a polarizer with a protective layer or functional layer disposed on at least one surface, and the terms polarizer and polarizing plate are used interchangeably.

Furthermore, in this specification, parallel and perpendicular do not mean parallel and perpendicular in the strict sense, but rather mean a range of ±5° from parallel or perpendicular, respectively.

Furthermore, in this specification, "(meth)acrylate" refers to either acrylate or methacrylate, "(meth)acrylic" refers to either acrylic or methacrylic, and "(meth)acryloyl" refers to either acryloyl or methacryloyl.

In addition, in this specification, the terms liquid crystal composition and liquid crystalline compound also conceptually include those that no longer exhibit liquid crystallinity due to curing or the like.

Retardation
In the present invention, Re(λ) and Rth(λ) respectively represent the in-plane retardation and the retardation in the thickness direction (film thickness direction) at a wavelength λ, which is 550 nm unless otherwise specified.
In the present invention, Re(λ) and Rth(λ) are values measured at a wavelength λ using an AxoScan OPMF-1 (manufactured by Optoscience). By inputting the average refractive index ((Nx+Ny+Nz)/3) and film thickness (d (μm)) into AxoScan,
Slow axis direction (°)
Re(λ)=R0(λ)
Rth(λ)=((Nx+Ny)/2−Nz)×d is calculated.

Refractive Index
In the present invention, the refractive indices Nx, Ny and Nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) and a sodium lamp (λ=589 nm) as a light source.
When measuring wavelength dependency, it can be measured using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter.
Alternatively, values in the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Examples of average refractive index values of major optical films are as follows: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

Embodiments of the present invention will be described below with reference to the drawings. The liquid crystal display device shown in FIG. 1 includes a liquid crystal cell (7-9), first polarizers 16 (1-6) and second polarizers 17 (10-13) sandwiching the liquid crystal cell, and a backlight unit 14 disposed outside the second polarizer 17. The liquid crystal cell (7-9) includes an upper liquid crystal cell substrate 7, a lower liquid crystal cell substrate 9, and a liquid crystal layer 8 sandwiched between them. The lower liquid crystal cell substrate 9 has an electrode layer (not shown in FIG. 1 ) configured to apply an electric field parallel to the surface of the lower liquid crystal cell substrate 9 to the liquid crystal layer. The electrode layer is typically made of transparent indium tin oxide (ITO). Alignment layers (not shown in FIG. 1 ) that control the alignment of the liquid crystal molecules 8 are formed on the electrode layer of the lower liquid crystal cell substrate 9 and on the surface of the upper liquid crystal cell substrate 7 facing the liquid crystal layer 8, thereby controlling the alignment direction of the liquid crystal molecules 8. The alignment layer is preferably a UV (ultraviolet) alignment layer in order to maintain the symmetry of the display. Although the detailed structure is not shown in Fig. 1, a color filter may be disposed on the upper substrate 7 of the liquid crystal cell (between the liquid crystal layer 8 and the first optical compensation layer 15).
In this application, the terms "upper side" and "lower side" do not refer to the vertical direction, but rather to the positional relationship of each layer stacked on the irradiation surface of the backlight unit 14, with the backlight unit 14 side being referred to as the lower side and the side away from the backlight unit 14 being referred to as the upper side.
In addition, in the example shown in Figure 1, for the purpose of explanation, only one row of liquid crystal molecules 8 in the liquid crystal layer of the liquid crystal cell is shown aligned in the vertical direction (film thickness direction), but the liquid crystal layer contains a large number of liquid crystal molecules in the in-plane direction and film thickness direction, and these liquid crystal molecules are aligned in a predetermined orientation state.

In the example shown in FIG. 1, the first polarizing plate 16 has, from the top, a protective film 1, a first polarizer 2, and a first optical compensation layer 15 having a first optical compensation layer b4 and a first optical compensation layer a5, in this order. The second polarizing plate 17 has, from the top, a second optical compensation layer 10, a second polarizer 11, and a protective film 13, in this order. That is, the liquid crystal display device shown in FIG. 1 has, in this order, a protective film 1, a first polarizer 2, a first optical compensation layer 15 having a first optical compensation layer b4 and a first optical compensation layer a5, a liquid crystal cell upper substrate 7, a liquid crystal layer 8, a liquid crystal cell lower substrate 9, a second optical compensation layer 10, a second polarizer 11, a protective film 13, and a backlight unit 14.

Generally, liquid crystal display devices are arranged so that the absorption axis 3 of the polarizer on the viewing side (first polarizer 2) is horizontal, in order to be suitable for polarized sunglasses. Therefore, in this application, the horizontal direction corresponds to the direction of the absorption axis 3 of the first polarizer 2.

In the present invention, at least one layer having retardation in the film thickness direction is present between the liquid crystal layer 8 and the second polarizer 11. In the present invention, the layer having retardation in the film thickness direction means a layer having an absolute value of Rth of 2 nm or more at any one of wavelengths of 450 nm, 550 nm, and 650 nm.
Furthermore, the total in-plane retardation Re_total(550) and the total retardation in the film thickness direction Rth_total(550) of the layers between the liquid crystal layer 8 and the second polarizer 11 satisfy the following formulas (2) and (3).
Formula (2): 0nm≦Re_total(550)≦10nm
Formula (3): Rth_total (550)≦-10nm
As long as the retardation in the film thickness direction satisfies the above formulas (2) and (3), any of the liquid crystal cell lower substrate 9 of the liquid crystal cell, the second optical compensation layer 10 described below, and other members or protective films, or all of them may be present between the liquid crystal layer 8 and the second polarizer 11. Furthermore, when the liquid crystal cell lower substrate 9 alone satisfies the above formulas (2) and (3), the second optical compensation layer 10 may not be used. That is, the layer having retardation in the film thickness direction and present between the liquid crystal layer 8 and the second polarizer 11 may include the liquid crystal cell lower substrate 9, the second optical compensation layer 10, and other members or protective films, or may include the liquid crystal cell lower substrate 9 without the second optical compensation layer 10.
The upper limit of Re_total(550) is preferably 5 nm or less, and more preferably 3 nm or less.
The lower limit of Rth_total(550) is preferably −80 nm or more, more preferably −50 nm or more, and the upper limit is preferably −15 nm or less. That is, it is more preferable that Rth_total(550) satisfies the following formula (24).
Formula (24): -50nm≦Rth_total(550)≦-15nm
It is preferable that the sum of the in-plane retardations Re_total(450) and the sum of the retardations in the film thickness direction Rth_total(450) at a wavelength of 450 nm of the layers between the liquid crystal layer 8 and the second polarizer 11 satisfy the following formulas (4) and (5).
Formula (4): 0nm≦Re_total(450)≦20nm
Formula (5): Rth_total (450)≦-20nm
This enables optical compensation over a wider wavelength range in the visible light region, and light leakage in black display when viewed from the side can be further reduced.
The upper limit of Re_total(450) is preferably 15 nm or less, and more preferably 10 nm or less. The lower limit of Rth_total(450) is preferably −100 nm or more, and more preferably −70 nm or more, and the upper limit is preferably −25 nm or less, and more preferably −30 nm or less.
Furthermore, it is preferable that Rth_total(550) and Rth_total(450) satisfy the following formula (23).
Formula (23): Rth_total(450)-Rth_total(550)≦0nm
This enables optical compensation over a wider wavelength range in the visible light region, and light leakage in black display when viewed from the side can be further reduced.
The upper limit of Rth_total(450)-Rth_total(550) is preferably -5 nm or less, and more preferably -10 nm or less. The lower limit of Rth_total(450)-Rth_total(550) is preferably -80 nm or more, and more preferably -50 nm or more. That is, it is preferable that Rth_total(550) and Rth_total(450) satisfy the following formula (25).
Formula (25): Rth_total(450)-Rth_total(550)≦-15nm
This enables optical compensation over a wider wavelength range in the visible light region, and light leakage in black display when viewed from the side can be further reduced.

1 , first polarizing plate 16 has protective film 1, first polarizer 2, and first optical compensation layer 15 (4 to 6) in this order. Second polarizing plate 17 has second polarizer 11, protective film 13 arranged on the lower surface thereof, and second optical compensation layer 10 arranged on the upper surface of second polarizer 11.
The liquid crystal cell is disposed between the second polarizer 16 and the first polarizer 17 .
The absorption axis 3 of the first polarizer 2 in the first polarizing plate 16 and the absorption axis 12 of the second polarizer 11 in the second polarizing plate 17 are arranged so as to be perpendicular to each other.
The absorption axis 3 of the first polarizer 2 in the first polarizing plate 16 is arranged so as to be perpendicular to the slow axis direction of the liquid crystal molecules 8 in the liquid crystal cell when no voltage is applied (OFF state). In other words, the slow axis of the alignment-controlled liquid crystal layer during black display and the absorption axis 3 of the first polarizer 2 are perpendicular to each other.

In FIG. 1, the in-plane retardation Re1(550) of the first optical compensation layer 15 at a wavelength of 550 nm satisfies the following formula (1).
Formula (1): 80nm≦Re1(550)≦320nm
The first optical compensation layer 15 has the same effect as a known compensation layer used in a lateral electric field type liquid crystal display device, and is preferably a layer having a phase difference of about a λ/2 plate.
1 , the first optical compensation layer 15 is composed of two layers, a first optical compensation layer a5 and a first optical compensation layer b4. In the illustrated example, the first optical compensation layer a5 is a layer having in-plane retardation, and the first optical compensation layer b4 is a layer having retardation in the film thickness direction. In this case, the slow axis 6 of the first optical compensation layer a5 and the absorption axis 3 of the first polarizer 2 are arranged in directions parallel to each other.
Furthermore, it is preferable that the ratio of the in-plane retardation Re1(450) at a wavelength of 450 nm to the in-plane retardation Re1(550) at a wavelength of 550 nm of the first optical compensation layer 15 satisfies the following formula (10).
Formula (10): 0.70≦Re1(450)/Re1(550)≦1.30
This enables optical compensation over a wider wavelength range in the visible light region, and reduces light leakage in black display when viewed from the side.
The lower limit of Re1(450)/Re1(550) is preferably 0.85 or more, more preferably 0.95 or more, and the upper limit is preferably 1.20 or less, more preferably 1.10 or less.

As described above, in FIG. 1 , the first optical compensation layer 15 is composed of two layers, the first optical compensation layer a5 and the first optical compensation layer b6. It is preferable that the in-plane retardation Re1a(550) and the retardation in the film thickness direction Rth1a(550) of the first optical compensation layer a5 at a wavelength of 550 nm satisfy the following formulas (13) and (14), and it is preferable that the in-plane retardation Re1b(550) and the retardation in the film thickness direction Rth1b(550) of the first optical compensation layer b4 at a wavelength of 550 nm satisfy the following formulas (15) and (16).
Formula (13): 80nm≦Re1a(550)≦200nm
Formula (14): 20nm≦Rth1a(550)≦150nm
Formula (15): 0nm≦Re1b(550)≦40nm
Formula (16): -180nm≦Rth1b(550)≦-50nm
This makes it possible to more suitably reduce light leakage in black display when viewed from the side.
As will be described later, the first optical compensation layer 15 may have a different configuration or may be composed of one layer. Details of the first optical compensation layer 15 will be described later.

It is preferable that the second optical compensation layer 10 has retardation in the film thickness direction, and it is more preferable that the in-plane retardation Re2(550) and the retardation Rth2(550) in the film thickness direction of the second optical compensation layer 10 at a wavelength of 550 nm satisfy the following formulas (8) and (9):
Formula (8): 0nm≦Re2(550)≦10nm
Formula (9): -100nm≦Rth2(550)≦-10nm
This makes it possible to more suitably reduce light leakage in black display when viewed from the side.
The second optical compensation layer 10 will be described in detail later.

In FIG. 1 , consider the case where light is incident from a backlight unit 14 disposed outside the second polarizing plate 17 (the side opposite the liquid crystal cell side of the second polarizer 11). In a non-driven state (OFF state) in which no driving voltage is applied to the electrodes (not shown in FIG. 1 ), the liquid crystal molecules 8 in the liquid crystal layer are aligned substantially parallel to the surfaces of the upper substrate 7 and the lower substrate 9 of the liquid crystal cell, with their long axes parallel to the absorption axis 12 of the second polarizer 11. In this state, light polarized to a predetermined state by the second polarizer 11 is not subject to the birefringence effect of the liquid crystal molecules 8, and as a result, is absorbed by the absorption axis 3 of the first polarizer 2. This results in a black display. In contrast, in a driven state (ON state) in which a driving voltage is applied to the electrodes (not shown in FIG. 1 ), an electric field containing a component parallel to the substrates is formed, and the liquid crystal molecules 8 are aligned with their long axes aligned with the direction of the electric field. As a result, the light that has been polarized in a predetermined state by the second polarizer 11 has its polarization state changed by the birefringence effect of the liquid crystal molecules 8, and as a result, passes through the first polarizer 2. At this time, white is displayed.
In the present invention, the retardation in the film thickness direction and the in-plane retardation of the layer between the liquid crystal layer 8 and the second polarizer 11 are controlled within the above-mentioned ranges, and the phase difference of the first optical compensation layer is set within a predetermined range, thereby reducing light leakage in the lateral field of view that occurs during black display.
Specifically, by setting the total thickness-direction retardation Rth_total(550) of the layers between the liquid crystal layer 8 and the second polarizer 11 to a negative value, light leakage during black display when viewed from the lateral direction can be suitably reduced. Generally, an isotropic layer without phase difference is preferred between the liquid crystal layer 8 and the second polarizer 11. This is because an isotropic layer between these layers can suppress changes in the polarization state due to the phase difference of the liquid crystal layer 8. By suppressing the influence of the phase difference of the liquid crystal layer 8, a liquid crystal display device can be designed that reduces light leakage in all viewing directions. On the other hand, even when there is no influence of the phase difference of the liquid crystal layer 8 (when an isotropic layer is present between the liquid crystal layer 8 and the second polarizer 11), the actual first optical compensation layer is not an ideal compensation layer across the entire visible light range, and as a result, light leakage cannot be sufficiently suppressed. In the present invention, by intentionally providing a phase difference in the thickness direction between the liquid crystal layer 8, which is normally an isotropic layer, and the second polarizer 11, the phase difference of the liquid crystal layer 8 is effectively utilized, thereby selectively reducing light leakage in the lateral viewing direction. By utilizing the retardation of the liquid crystal layer 8, compensation for the entire visible light range, which is insufficient with only the first optical compensation layer, can be performed specifically in the horizontal field of view.

The following provides a detailed description of each component that can be used in the liquid crystal display device of the present invention.

[Liquid crystal materials]
The liquid crystal material constituting the liquid crystal layer used in the liquid crystal display device of the present invention is not particularly limited. For example, a nematic liquid crystal with a positive dielectric anisotropy Δε may be used as the liquid crystal material in the liquid crystal display device configured as shown in FIG. 1 . The thickness (gap) of the liquid crystal layer is preferably greater than 2.8 μm and less than 4.5 μm. Setting the retardation (Δn·d) of the liquid crystal layer to greater than 0.25 μm and less than 0.40 μm more easily achieves transmittance characteristics with almost no wavelength dependency within the visible light range. The maximum transmittance can be achieved when the liquid crystal molecules are rotated 45 degrees horizontally from their original alignment direction. The thickness (gap) of the liquid crystal layer can be controlled using polymer beads. Of course, a similar gap can also be achieved using glass beads, fibers, and resin columnar spacers. Furthermore, the liquid crystal material is not particularly limited as long as it is a nematic liquid crystal. The larger the value of the dielectric anisotropy Δε, the lower the driving voltage can be, and the smaller the refractive index anisotropy Δn, the thicker the liquid crystal layer (gap), which shortens the liquid crystal filling time and reduces gap variation.

[Liquid crystal cell]
The liquid crystal cell used in the liquid crystal display device of the present invention comprises a pair of opposing substrates, at least one of which has an electrode, and a liquid crystal layer disposed between the substrates and having an alignment control. It is preferable to form an alignment film for aligning liquid crystal molecules on both inner, facing surfaces of the liquid crystal cell substrates. An electrode layer is formed on the facing surface of one of the pair of substrates, and in this invention, the substrate on which the electrode layer is formed is defined as the electrode substrate. It is also preferable to form a color filter on the facing surface of one of the pair of substrates. The substrates on which the electrode layer and the color filter are formed may be the same or different. Furthermore, a polarizer may be disposed inside the liquid crystal cell, or an optically anisotropic layer that contributes to optical compensation for the retardation of the liquid crystal layer may be disposed. It is also common to dispose columnar or spherical spacers to maintain the distance (cell gap) between the two substrates. Other components that may be disposed within the cell include a reflector, a condenser lens, a brightness enhancement film, a light-emitting layer, a fluorescent layer, a phosphorescent layer, an anti-reflection film, an anti-fouling film, and a hard coat film.

Transparent glass substrates are generally used as substrates for liquid crystal cells, but silicon glass substrates, which are harder and can withstand high temperatures, can also be used. Plastic substrates with excellent heat resistance and substrates made from polymeric materials can also be used. Flexibility can be achieved by using substrates made from deformable materials.

The electrode layer preferably comprises at least a plurality of pixel electrodes and further comprises a common electrode and an insulating layer disposed therebetween. The common electrode may be an unpatterned electrode or a linear electrode. The electrode layer is preferably made of a transparent material, such as an ITO electrode. The pixel electrode is preferably linear, but may be any shape, such as a mesh, spiral, or dotted, as long as it allows the electric field from the common electrode to pass through. A floating electrode with a neutral potential may also be added. The insulating layer may be made of an inorganic material, such as an oxide such as _SiO2 or a nitride such as SiN, or an organic material, such as an acrylic or epoxy material.
The liquid crystal display device of the present invention preferably includes at least an electrode substrate having retardation in the film thickness direction between the liquid crystal layer and the second polarizer. That is, of the pair of substrates, the substrate on the second polarizer side is an electrode substrate, and this electrode substrate preferably has retardation in the film thickness direction. The electrode substrate having retardation in the film thickness direction refers to an electrode substrate having an absolute value of Rth of 2 nm or more at any one of wavelengths of 450 nm, 550 nm, and 650 nm.
The electrode substrate preferably has an in-plane retardation Re3(550) at a wavelength of 550 nm and a retardation Rth3(550) in the film thickness direction that satisfy the following formulas (6) and (7).
Formula (6): 0nm≦Re3(550)≦10nm
Formula (7): -100nm≦Rth3(550)≦-10nm
When the electrode substrate satisfies the formulas (6) and (7), the liquid crystal display device does not need to have a second optical compensation layer.
Here, the in-plane retardation Re and the retardation Rth in the film thickness direction of the electrode substrate are measured values for the entire substrate including the electrodes, and are obtained by separating the two substrates of the liquid crystal cell, washing away the liquid crystal layer with a solvent, and then measuring the phase difference of the entire substrate including the electrodes.
As a method for controlling the Rth of the electrode substrate, for example, it is possible to change the Rth of the electrode layer by selecting a material for the insulating layer. Another method is to develop structural birefringence by laminating electrodes and/or insulating layers. Furthermore, the Rth of the electrode substrate can also be controlled by providing a separate retardation layer on the electrode substrate.
In formula (6), the upper limit of Re3(550) is preferably 5 nm or less, and more preferably 3 nm or less. In formula (7), the lower limit of Rth3(550) is preferably −80 nm or more, and more preferably −50 nm or more, and the upper limit is preferably −15 nm or less, and more preferably −20 nm or less.
The upper limit of the in-plane retardation Re3(450) of the electrode substrate at a wavelength of 450 nm is preferably 15 nm or less, more preferably 10 nm or less. The lower limit of the retardation Rth3(450) in the film thickness direction at a wavelength of 450 nm of the electrode substrate is preferably −100 nm or more, more preferably −70 nm or more, and the upper limit is preferably −10 nm or less, more preferably −20 nm or less.

In a liquid crystal display device that displays color using color filters, a pixel is usually formed by a set of subpixels (pixel regions) of the three primary colors of light, red, green, and blue. A pixel may also be formed by subpixels of three or more colors. One embodiment of the present invention is a multi-gap embodiment in which the subpixels of each color that make up a pixel each have a different cell gap.
Furthermore, a structure called a multi-domain in which one pixel is divided into a plurality of regions may be used to adjust color balance and average viewing angle characteristics.

[First optical compensation layer]
The first optical compensation layer in the present invention can be one having a compensation function used for compensation in a known in-plane switching mode.
The first optical compensation layer may be composed of one layer or two or more layers. The first optical compensation layer satisfies the following formula (1). In addition, the slow axis of the first optical compensation layer is preferably arranged so as to be parallel to the absorption axis of the polarizer arranged on the same side of the liquid crystal cell.
Formula (1): 80nm≦Re1(550)≦320nm
Furthermore, the first optical compensation layer preferably satisfies the formula (10).
Formula (10): 0.70≦Re1(450)/Re1(550)≦1.30
The preferred range of Re1(450)/Re1(550) is as described above.

The first optical compensation layer may be made of any material as long as it has the above-mentioned retardation, but from the viewpoint of ease of production, a polymer film and a layer formed using a liquid crystal composition are preferred.
The polymer film is preferably selected from a cellulose acylate film, a cyclic olefin polymer film, and an acrylic polymer film, and the acrylic polymer film preferably contains an acrylic polymer containing at least one unit selected from a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit.
The liquid crystal compound in the liquid crystal composition may be a known compound such as a discotic liquid crystal compound or a rod-shaped liquid crystal compound, and preferably has a polymerizable group to fix the alignment state, i.e., the liquid crystal composition is preferably a polymerizable liquid crystal composition.
The first optical compensation layer may be a laminate obtained by laminating the above-mentioned polymer film and a layer formed using a liquid crystal composition. Alternatively, the first optical compensation layer may be a laminate obtained by laminating a plurality of polymer films. Alternatively, the first optical compensation layer may be a single layer obtained by peeling off a layer formed from a composition containing a liquid crystal compound having a polymerizable group.
The thickness of the polymer film is preferably as thin as possible for the purpose of reducing the thickness of the device or the like, as long as the optical properties, mechanical properties, and manufacturability are not impaired. The thickness is preferably 1 to 150 μm, more preferably 1 to 70 μm, and particularly preferably 1 to 30 μm.
Hereinafter, examples of a structure in which the first optical compensation layer is made up of one layer and a structure in which the first optical compensation layer is made up of two layers will be described.

<Configuration in which the first optical compensation layer is composed of one layer>
When the first optical compensation layer is composed of one layer, the first optical compensation layer alone preferably has a phase difference of about a λ/2 plate. Specifically, it is preferable that the in-plane retardation Re1(550) at a wavelength of 550 nm and the retardation in the film thickness direction Rth1(550) satisfy the following formulas (11) and (12):
Formula (11): 150nm≦Re1(550)≦320nm
Formula (12): -50nm≦Rth1(550)≦50nm
In formula (11), the lower limit of Re1(550) is preferably 180 nm or more, more preferably 200 nm or more, and the upper limit is preferably 300 nm or less, more preferably 280 nm or less.
In formula (12), the lower limit of Rth1(550) is preferably −40 nm or more, more preferably −30 nm or more, and the upper limit is preferably 40 nm or less, more preferably 30 nm or less.

The first optical compensation layer can be obtained by greatly stretching a film of a polymer having the characteristic that nz>nx.
As a production method, for example, in the case of a film using cellulose acetate benzoate, which is a cellulose acylate substituted with an aromatic acyl group, a dope prepared by dissolving cellulose acetate benzoate in a solvent is cast onto a metal support for film formation, the solvent is dried to obtain a film, and this film is stretched at a large stretching ratio of 1.3 to 1.9 times to orient the cellulose molecular chains.
The first optical compensation layer can also be produced by laminating a shrinkable film to one or both sides of a polymer film and stretching the film under heat, as described in, for example, JP-A Nos. 5-157911 and 2006-72309.

The thickness of the first optical compensation layer is preferably 1 to 150 μm, more preferably 1 to 70 μm, and particularly preferably 1 to 30 μm.

<Configuration of First Optical Compensation Layer Composed of Two Layers (First Embodiment)>
In the case of a two-layer structure, it is preferable that the first optical compensation layer a is composed of a first optical compensation layer a and a first optical compensation layer b, where the first optical compensation layer a is a biaxial film (B-plate or positive A-plate) where nx > ny ≥ nz, and the first optical compensation layer b is a [quasi] uniaxial film (positive [quasi] C-plate) where nx ≈ ny < nz. Specifically, it is preferable that the in-plane retardation Re1a(550) and the thickness direction retardation Rth1a(550) at a wavelength of 550 nm of the first optical compensation layer a satisfy the following formulas (13) and (14), and the in-plane retardation Re1b(550) and the thickness direction retardation Rth1b(550) at a wavelength of 550 nm of the first optical compensation layer b satisfy the following formulas (15) and (16).
Formula (13): 80nm≦Re1a(550)≦200nm
Formula (14): 20nm≦Rth1a(550)≦150nm
Formula (15): 0nm≦Re1b(550)≦40nm
Formula (16): -180nm≦Rth1b(550)≦-50nm
In this embodiment, it is preferable that the first optical compensation layer a is disposed on the cell substrate side, and the first optical compensation layer b is disposed on the polarizer side.

(First optical compensation layer a)
In the first optical compensation layer a, in formula (13), the lower limit of Re1a(550) is preferably 100 nm or more, more preferably 110 nm or more, and the upper limit is preferably 150 nm or less, more preferably 140 nm or less. In formula (14), the lower limit of Rth1a(550) is preferably 50 nm or more, more preferably 60 nm or more, and the upper limit is preferably 120 nm or less, more preferably 110 nm or less.
The preferred range of Re1a(450)/Re1a(550) is the same as that of the above formula (10), and the preferred range is also the same.

The first optical compensation layer a can be obtained by stretching a cellulose acylate film, a cyclic polyolefin film, or a polycarbonate film produced by an appropriate method such as a melt film-forming method or a solution film-forming method, for example, by a longitudinal stretching method using roll peripheral speed control, a transverse stretching method using a tenter, or a biaxial stretching method. Specifically, the description in JP-A-2005-338767 can be referred to. Alternatively, a polymer formed from a composition containing a liquid crystal compound having a polymerizable group that exhibits biaxiality upon orientation can also be used.
The thickness of the first optical compensation layer a is preferably from 1 to 80 μm, more preferably from 1 to 40 μm, and particularly preferably from 1 to 25 μm.

(First optical compensation layer b)
In the first optical compensation layer b, in formula (15), the upper limit of Re1b(550) is preferably 20 nm or less, and more preferably 10 nm or less. In formula (16), the lower limit of Rth1b(550) is preferably −140 nm or more, and more preferably −130 nm or more, and the upper limit is preferably −60 nm or less, and more preferably −70 nm or less.

The retardation in the film thickness direction of the first optical compensation layer b is not particularly limited; however, in terms of more excellent effects of the present invention, it is preferable that the ratio of the film thickness direction retardation Rth1b(450) at a wavelength of 450 nm to the film thickness direction retardation Rth1b(550) at a wavelength of 550 nm of the second optical compensation layer satisfies the following formula (21):
Formula (21): Rth1b(450)/Rth1b(550)≦1.20
This enables optical compensation over a wider wavelength range in the visible light region, and light leakage in black display when viewed from the side can be further reduced.
The lower limit of Rth1b(450)/Rth1b(550) is not particularly limited, and is often 0.80 or more, more often 0.85 or more. The upper limit of Rth1b(450)/Rth1b(550) is preferably 1.10 or less, more preferably 1.00 or less.

The first optical compensation layer b can be obtained by forming a film such as a cellulose acylate film, a cyclic polyolefin film, or a polycarbonate film so as not to exhibit in-plane retardation, and stretching the film in the thickness (nz) direction using a heat-shrinkable film or the like. It is also possible to form a layer having a desired retardation by fixing the alignment state of the liquid crystal material, for example, by vertically aligning the rod-shaped liquid crystal compound. That is, the first optical compensation layer b may be a film in which the liquid crystal compound is fixed in an aligned state. In particular, the first optical compensation layer b may be a film in which the rod-shaped liquid crystal compound is fixed in a state in which it is aligned perpendicular to the substrate surface.
The thickness of the first optical compensation layer b is preferably from 0.5 to 80 μm, more preferably from 1 to 40 μm, and particularly preferably from 1 to 25 μm.

The first optical compensation layer b may be formed directly on the surface of the first optical compensation layer a, or may be laminated thereon via a pressure-sensitive adhesive or adhesive.
The first optical compensation layer preferably has a two-layer structure consisting of a polymer film containing a cycloolefin-based polymer and a liquid crystal composition layer provided adjacent to the polymer film.

<Configuration of First Optical Compensation Layer Composed of Two Layers (Second Embodiment)>
The first optical compensation layer is also preferably a two-layer structure in which the first optical compensation layer a is a [quasi] uniaxial film (negative [quasi] C-plate) where nx≒ny>nz, and the first optical compensation layer b is a biaxial film (B-plate or negative A-plate) where nz≧nx>ny. Specifically, it is preferred that the in-plane retardation Re1a(550) and the thickness direction retardation Rth1a(550) at a wavelength of 550 nm of the first optical compensation layer a satisfy the following formulas (17) and (18), and the in-plane retardation Re1b(550) and the thickness direction retardation Rth1b(550) at a wavelength of 550 nm of the first optical compensation layer b satisfy the following formulas (19) and (20).
Formula (17): 0nm≦Re1a(550)≦40nm
Formula (18): 50nm≦Rth1a(550)≦180nm
Formula (19): 80nm≦Re1b(550)≦200nm
Formula (20): -200nm≦Rth1b(550)≦-20nm
In this embodiment, it is preferable that the first optical compensation layer a is disposed on the liquid crystal cell substrate side, and the first optical compensation layer b is disposed on the first polarizer side.

(First optical compensation layer a)
In the formula (17), the upper limit of Re1a(550) is preferably 20 nm or less, and more preferably 10 nm or less.
In the formula (18), the lower limit of Rth1a(550) is preferably 60 nm or more, more preferably 70 nm or more, and the upper limit is preferably 170 nm or less, more preferably 160 nm or less.
The first optical compensation layer a can be obtained by forming a film having a retardation of nz<nx, such as a cellulose acylate film, a cyclic polyolefin, or a polycarbonate, so as not to exhibit in-plane retardation, or by offsetting the exhibited in-plane retardation so that nx≒ny is satisfied. It is also possible to form a layer having a phase difference of nz<nx by fixing the alignment state of the liquid crystal material.
The thickness of the first optical compensation layer a is preferably from 1 to 80 μm, more preferably from 1 to 60 μm, and particularly preferably from 1 to 40 μm.

(First optical compensation layer b)
In formula (19), the lower limit of Re1b(550) is preferably 90 nm or more, more preferably 100 nm or more, and the upper limit is preferably 180 nm or less, more preferably 160 nm or less.
In the formula (20), the lower limit of Rth1b(550) is preferably −180 nm or more, more preferably −160 nm or more, and the upper limit is preferably −50 nm or less, more preferably −60 nm or less.
The first optical compensation layer b can be obtained by stretching a polymer film produced by an appropriate method such as an extrusion molding method or a casting film forming method, for example, by a longitudinal stretching method using a roll, a transverse stretching method using a tenter, a biaxial stretching method, etc. Specifically, the description in JP-A-2005-338767 can be referred to.
The thickness of the first optical compensation layer b is preferably from 1 to 80 μm, more preferably from 1 to 60 μm, and particularly preferably from 1 to 40 μm.

The first optical compensation layer a and the first optical compensation layer b may be formed directly on one surface of the other, or may be laminated via a pressure-sensitive adhesive or adhesive.

[Second optical compensation layer]
In order to adjust the total retardation of the layers between the liquid crystal layer and the second polarizer to an appropriate range, it is preferable to have a second optical compensation layer in the present invention. As the second optical compensation layer, a known film having any phase difference can be used, but it is preferable that it has retardation in the film thickness direction, and it is more preferable that it is a [quasi] uniaxial film (positive [quasi] C-plate) where nx ≒ ny < nz. Having retardation in the film thickness direction means that the absolute value of Rth at any wavelength of 450 nm, 550 nm, or 650 nm is 2 nm or more. The retardation of the second optical compensation layer is not particularly limited as long as the total retardation of the layers between the liquid crystal layer and the second polarizer is within a predetermined range, but it is preferable that the in-plane retardation Re2(550) at a wavelength of 550 nm and the retardation in the film thickness direction Rth2(550) satisfy the following formulas (8) and (9).
Formula (8): 0nm≦Re2(550)≦10nm
Formula (9): -100nm≦Rth2(550)≦-10nm
In the second optical compensation layer, in formula (8), the upper limit of Re2(550) is preferably 5 nm or less, and more preferably 3 nm or less. In formula (9), the lower limit of Rth2(550) is preferably −80 nm or more, and more preferably −50 nm or more, and the upper limit is preferably −15 nm or less, and more preferably −20 nm or less.
The upper limit of the in-plane retardation Re2(450) at a wavelength of 450 nm is preferably 15 nm or less, more preferably 10 nm or less. The lower limit of the retardation Rth2(450) in the film thickness direction at a wavelength of 450 nm is preferably −100 nm or more, more preferably −70 nm or more, and the upper limit is preferably −10 nm or less, more preferably −20 nm or less.

The retardation in the film thickness direction of the second optical compensation layer is not particularly limited; however, in terms of more excellent effects of the present invention, it is preferable that the ratio of the retardation in the film thickness direction Rth2(450) at a wavelength of 450 nm to the retardation in the film thickness direction Rth2(550) at a wavelength of 550 nm of the second optical compensation layer satisfies the following formula (22):
Formula (22): Rth2(450)/Rth2(550)≧1.00
This enables optical compensation over a wider wavelength range in the visible light region, and light leakage in black display when viewed from the side can be further reduced.
The upper limit of Rth2(450)/Rth2(550) is not particularly limited, and is often 4.00 or less, more often 3.00 or less.

The second optical compensation layer can be obtained by forming a film such as cellulose acylate film, cyclic polyolefin film and polycarbonate film so as not to exhibit the in-plane retardation, and stretching it in the thickness (nz) direction using a heat shrinkable film or the like.In addition, the film such as the above-mentioned cellulose acylate film can be laminated with an adhesive or a pressure sensitive adhesive to adjust the desired in-plane retardation and thickness direction retardation.Preferably, the second optical compensation layer is a triacetyl cellulose film.
In addition, the second optical compensation layer can be formed as a layer having a desired retardation by fixing the alignment state of the liquid crystal material, for example, by vertically aligning the rod-shaped liquid crystal compound. That is, the second optical compensation layer may be a film (liquid crystal composition layer) in which the liquid crystal compound is fixed in an aligned state. In particular, the second optical compensation layer may be a film in which the rod-shaped liquid crystal compound is fixed in a state in which it is aligned vertically to the substrate surface.
When a liquid crystal material is used, a liquid crystal composition layer may be formed directly on a polarizer, or the formed liquid crystal composition layer may be attached to the polarizer with an adhesive or pressure-sensitive adhesive. Alternatively, a two-layer structure including a support and a liquid crystal composition layer may be used, or a structure in which the liquid crystal composition layer is attached to a protective film of the polarizer with an adhesive or pressure-sensitive adhesive. After the liquid crystal composition layer is attached, the support may be peeled off to form a single liquid crystal composition layer.
The thickness of the second optical compensation layer is preferably 0.1 μm or less, more preferably 0.2 μm, and more preferably 200 μm or less, more preferably 185 μm.
The present invention preferably includes, between the liquid crystal layer and the second polarizer, at least an electrode substrate having a retardation in the film thickness direction and a second optical compensation layer, in this order from the liquid crystal layer side. It is more preferable that the second optical compensation layer satisfies the above formulas (8) and (9). In this case, the retardation in the film thickness direction of the electrode substrate is not limited to −10 nm or less, and may have a positive Rth. Because the electrode substrate has other necessary requirements, such as a configuration as an electrode, it may have a retardation in the film thickness direction, and this value may be positive. On the other hand, since the retardation in the film thickness direction of the second optical compensation layer is easier to control than that of the electrode substrate, by combining the second optical compensation layer, a configuration can be achieved in which the total in-plane retardation Re_total(550) and the total retardation in the film thickness direction Rth_total(550) of the layers between the liquid crystal layer and the second polarizer satisfy formulas (2) and (3).

[Polarizing plate]
The polarizing plates (first polarizing plate and second polarizing plate) have at least a polarizer, and, if necessary, an optical compensation layer and/or a protective film is laminated thereon. For example, in FIG. 1 , in the case of a polarizing plate (first polarizing plate) including a first optical compensation layer, the polarizer and the first optical compensation layer are laminated so that the absorption axis of the polarizer and the slow axis of the first optical compensation layer are parallel to each other. A protective film may be provided on the surface of the polarizer opposite the optical compensation layer, or a cured resin layer may be disposed thereon, or the polarizer may be directly attached to another component of the liquid crystal display device. Furthermore, a protective film may be disposed between the optical compensation layer and the polarizer, or on the surface of the optical compensation layer opposite the polarizer, via a pressure-sensitive adhesive or adhesive.

An adhesive can be used to laminate the polarizer and optical films such as optical compensation layers and protective films. The thickness of the adhesive layer between the polarizer and optical film is preferably approximately 0.01 to 30 μm, more preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm. If the thickness of the adhesive layer is within this range, no lifting or peeling occurs between the laminated optical film and polarizer, and adhesive strength that is sufficient for practical use can be obtained.

One of the preferred adhesives is a water-based adhesive, that is, an adhesive in which the adhesive components are dissolved or dispersed in water, and an adhesive made of an aqueous solution of a polyvinyl alcohol-based resin is preferably used.
In adhesives made from aqueous solutions of polyvinyl alcohol-based resins, the polyvinyl alcohol-based resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, vinyl alcohol-based copolymers obtained by saponifying copolymers of vinyl acetate and other monomers copolymerizable therewith, and modified polyvinyl alcohol-based polymers in which the hydroxyl groups of these copolymers are partially modified.
The adhesive may contain crosslinking agents such as polyaldehydes, water-soluble epoxy compounds, melamine compounds, zirconia compounds, zinc compounds, glyoxylates, etc. When a water-based adhesive is used, the thickness of the adhesive layer obtained is usually 1 μm or less.

Other preferred adhesives include curable adhesive compositions containing a cationically polymerizable compound that cures upon irradiation with active energy rays or heating, and curable adhesive compositions containing a radically polymerizable compound. Examples of the cationically polymerizable compound include compounds having an epoxy group or an oxetanyl group. The epoxy compound is not particularly limited as long as it has at least two epoxy groups in the molecule, and for example, compounds described in detail in JP-A-2004-245925 can be used.
The radical polymerizable compound is not particularly limited as long as it is a radical polymerizable compound having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and examples thereof include monofunctional radical polymerizable compounds, polyfunctional radical polymerizable compounds having two or more polymerizable groups in the molecule, (meth)acrylates having a hydroxyl group, acrylamides, and acryloylmorpholines. These compounds may be used alone or in combination. For example, compounds described in detail in JP 2015-11094 A may be used. Furthermore, a radical polymerizable compound and a cationically polymerizable compound may also be used in combination.

When a curable adhesive is used, the optical film is laminated using a laminating roll, dried as necessary, and then irradiated with active energy rays or heated to cure the curable adhesive. There are no particular restrictions on the light source of the active energy rays, but active energy rays with an emission distribution of wavelengths of 400 nm or less are preferred. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, or metal halide lamps are more preferred.

Furthermore, when bonding the optical film and polarizer with an adhesive, the surface of the optical film facing the polarizer may be subjected to a surface treatment (e.g., glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment) or an easy-adhesion layer may be formed, in order to improve the adhesive strength and the wettability of the adhesive to the optical film surface. Materials and methods for forming easy-adhesion layers described in JP 2007-127893 A and JP 2007-127893 A, etc., can be used.

[Polarizer]
The polarizers (first polarizer and second polarizer) of the polarizing plate are not particularly limited, and may be so-called linear polarizers that have the function of converting natural light into specific linearly polarized light. The polarizers are not particularly limited, but an absorption polarizer can be used. For example, an iodine-based polarizer, a dye-based polarizer using a dichroic dye, or a polyene-based polarizer can be used.

In the present invention, the thickness of the polarizer is not particularly limited, but is preferably 3 μm to 60 μm, more preferably 5 μm to 30 μm, and particularly preferably 5 μm to 15 μm.

[Protective film]
The material for the protective film is not particularly limited, and examples thereof include cellulose acylate (e.g., cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate), polyacrylic resins such as polymethyl methacrylate, polyolefins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone films, polyurethane resins, polycarbonate, polysulfone, polyether, polymethylpentene, polyether ketone, (meth)acrylonitrile, and polymers having an alicyclic structure (norbornene resins (Arton: product name, manufactured by JSR Corporation, amorphous polyolefins (Zeonex: product name, manufactured by Zeon Corporation)).

The optical properties of the protective film preferably satisfy the following formula.
0 nm≦Re(550)≦10 nm
−40 nm≦Rth(550)≦40 nm
Furthermore, when a protective film is disposed between the polarizer and the liquid crystal cell, it is more preferable that the following formula be satisfied.
0 nm≦Re(550)≦5 nm
−10 nm≦Rth(550)≦10 nm

[Backlight unit]
The backlight unit of a liquid crystal display device can be any known backlight unit used in various liquid crystal display devices. For example, the backlight unit may be a planar light source in which point light sources such as LEDs (light-emitting diodes), organic light-emitting diodes (OLEDs), and lasers, or linear light sources such as fluorescent lamps (CCFLs), are arranged two-dimensionally, or may be a planar light source using a plate-like light guide plate that receives light emitted from point light sources or linear light sources from the side and emits planar light from the surface. Alternatively, the backlight unit is not limited to a planar light source, and may be a point light source or a linear light source.
The backlight unit may also include optical members for controlling the emitted light, such as a louver member, a prism sheet, and a collimator lens array.

The present invention will be specifically explained below based on the following examples. The materials, reagents, amounts and proportions of substances, and procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples.

[Example 1]
<Fabrication of IPS-mode liquid crystal display device>
A common electrode (ITO) was formed on a glass substrate, and an acrylic organic insulating film (or an inorganic film such as SIN) was formed on top of it. The insulating film was then etched using photolithography (this may be performed simultaneously with the active element manufacturing process such as TFTs) to form domains. Slit pixel electrodes (line width 5 μm, electrode gap 5 μm) were then formed on top of this. A photo-alignment film was then formed on top of this and subjected to photo-alignment treatment. A photo-alignment film was also formed on the surface of a separately prepared glass substrate bearing a color filter and subjected to photo-alignment treatment. Two glass substrates were laminated together with the alignment films facing each other, with a gap (d) of 3.8 μm between the substrates and the alignment treatment directions of the two glass substrates parallel to each other. A nematic liquid crystal composition with a refractive index anisotropy (Δn) of 0.098 and a positive dielectric anisotropy (Δε) of 4.5 was then sealed in to prepare liquid crystal cell 1. The Δn·d value of the liquid crystal layer was 375 nm.
Liquid crystal cell 2 was prepared by applying, aligning, and curing a liquid crystal layer formed on a glass substrate with composition 1 for forming a liquid crystal layer, which will be described later, and then forming an electrode layer on top of this in the same manner as for liquid crystal cell 1. A photo-alignment film was further provided on the electrode layer, and after photo-alignment film treatment was performed, nematic liquid crystal was sealed between the electrode layer and the color filter substrate in the same manner as for liquid crystal cell 1, to prepare liquid crystal cell 2. That is, liquid crystal cell 2 has a configuration in which the layers are laminated in the following order: glass substrate/color filter layer/alignment film/liquid crystal layer/alignment film/electrode layer/cured liquid crystal layer/glass substrate.
The retardation (Re, Rth) of each of the electrode substrate and color filter substrate before the liquid crystal composition was sealed, and the Δn·d of the prepared liquid crystal cell were measured, and the results are shown in Table 1. The above electrode substrate corresponds to an electrode substrate having retardation in the film thickness direction.

<Preparation of First Optical Compensation Layer 1>
As the first optical compensation layer a, an unstretched cycloolefin polymer film (manufactured by JSR Corporation, trade name: Arton Film) was uniaxially stretched to prepare a cycloolefin polymer having Re1a(550)=120 nm, Rth1a(550)=60 nm and a film thickness of 24 μm.
One side of this polymer film was subjected to a corona treatment at a discharge rate of 150 W·min/ ^m2 , and a liquid crystal layer-forming composition 1 prepared with the following formulation was applied to the corona-treated surface using a #3.0 wire bar. Next, the composition was heated with warm air at 70°C for 90 seconds to dry the solvent and ripen the liquid crystal compound. The resulting coating was irradiated with ultraviolet light (300 mJ/ ^cm2 ) at 40°C under a nitrogen purge and an oxygen concentration of 100 ppm to fix the alignment of the liquid crystal compound, forming a 1 μm-thick liquid crystal composition layer (corresponding to first optical compensation layer b), thereby producing first optical compensation layer 1. In the liquid crystal composition layer, the liquid crystal compound was fixed in a state where it was aligned perpendicular to the surface of the cycloolefin polymer film.

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Composition 1 for forming liquid crystal layer
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Liquid crystal compound R1 100.0 parts by mass Alignment aid A1 2.0 parts by mass Compound B1 4.5 parts by mass Monomer K1 8.0 parts by mass Polymerization initiator P1 5.0 parts by mass Polymerization initiator P2 2.0 parts by mass Surfactant S1 0.4 parts by mass Surfactant S2 0.5 parts by mass Acetone 426.0 parts by mass Propylene glycol monomethyl ether acetate 49.0 parts by mass Methanol 14.7 parts by mass

・Liquid crystal compound R1
A mixture of the following liquid crystal compounds (RA), (RB), and (RC) in a ratio of 83:15:2 (by mass)

Orientation aid A1

・Compound B1

Monomer K1: A-TMMT (Shin-Nakamura Chemical Co., Ltd.)

Polymerization initiator P1

Polymerization initiator P2

Surfactant S1 (weight average molecular weight 15,000, the numerical values for each repeating unit in the structural formula represent mass %)

・Surfactant S2 (weight average molecular weight: 11,200)
The numerical values for each repeating unit in the structural formula represent mass %.

The Re(550) and Rth(550) of the prepared first optical compensation layer a and first optical compensation layer b were measured according to the method described above. The results are shown in Table 3 below.

<Preparation of Protective Film 1>
[Preparation of Core Layer Cellulose Acylate Dope 1]
The following components were charged into a mixing tank and stirred to dissolve each component, thereby preparing a core layer cellulose acylate dope 1.
------------------------------------------------------------------
Core layer cellulose acylate dope 1
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Cellulose acetate having an acetyl substitution degree of 2.88: 100 parts by weight Ester oligomer A (described below): 10 parts by weight Polarizer durability improver (described below): 4 parts by weight UV absorber (described below): 2 parts by weight Methylene chloride (first solvent): 430 parts by weight Methanol (second solvent): 64 parts by weight

Ester Oligomer A (weight average molecular weight: 750)

・Polarizer durability improver

・UV absorber

[Preparation of Outer Layer Cellulose Acylate Dope 1]
To 90 parts by weight of the above-mentioned cellulose acylate dope 1 for the core layer, 10 parts by weight of the following matting agent solution was added to prepare cellulose acylate dope 1 for the outer layer.
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Outer layer cellulose acylate dope 1
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Silica particles having an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass Core layer Cellulose acylate dope 1 1 part by mass

[Preparation of Cellulose Acylate Film 1]
The core layer cellulose acylate dope 1 and outer layer cellulose acylate dope 1 on both sides were simultaneously cast onto a drum at 20°C from a casting nozzle. When the solvent content of the film on the drum was approximately 20% by mass, the film was peeled off from the drum. Both ends of the resulting film in the width direction were fixed with tenter clips, and the film was stretched 1.1 times in the transverse direction while drying while the residual solvent content in the film was 3 to 15%. The resulting film was then transported between the rolls of a heat treatment device for further drying, producing a 40 μm-thick cellulose acylate film 1, which was used as protective film 1. The retardation of protective film 1 was measured, revealing Re(550) = 2 nm and Rth(550) = 7 nm.

<Preparation of Protective Film 2>
[Preparation of Core Layer Cellulose Acylate Dope 2]
The following components were charged into a mixing tank and stirred to dissolve each component, thereby preparing a core layer cellulose acylate dope 2.
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Core layer cellulose acylate dope 2
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Cellulose acetate having an acetyl substitution degree of 2.88: 100 parts by weight Polyester below: 12 parts by weight The polarizer durability improver above: 4 parts by weight Methylene chloride (first solvent): 430 parts by weight Methanol (second solvent): 64 parts by weight

Polyester (number average molecular weight 800)

[Preparation of Outer Layer Cellulose Acylate Dope 2]
To 90 parts by weight of the above-mentioned cellulose acylate dope 2 for the core layer, 10 parts by weight of the following matting agent solution was added to prepare cellulose acylate dope 2 for the outer layer.
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Matting agent solution------------------------------------------------
Silica particles having an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass Core layer: Cellulose acylate dope 1 part by mass

[Preparation of Cellulose Acylate Film 2]
The core layer cellulose acylate dope 2 and the outer layer cellulose acylate dope 2 were filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm, and then the core layer cellulose acylate dope 2 and the outer layer cellulose acylate dope 2 on both sides thereof were simultaneously cast onto a drum at 20°C from a casting nozzle (band casting machine).
Next, when the solvent content of the film on the drum was approximately 20% by mass, the film was peeled off from the drum, both ends of the film in the width direction were fixed with tenter clips, and the film was stretched in the transverse direction at a stretch ratio of 1.1 times while being dried.
Thereafter, the obtained film was further dried by conveying it between the rolls of a heat treatment device to prepare a cellulose acylate film 2 having a thickness of 40 μm, which was used as protective film 2. The retardation of protective film 2 was measured to find that Re(550)=1.0 nm, Rth(550)=−5 nm, Re(450)=1.6 nm, and Rth(450)=−13 nm.

<Saponification treatment of protective film>
The protective films 1 and 2 prepared above were immersed in a 2.3 mol/L aqueous sodium hydroxide solution at 55° C. for 3 minutes. The immersed protective films 1 and 2 were then removed, washed in a water bath at room temperature, and neutralized with 0.05 mol/L sulfuric acid at 30° C. The obtained protective films 1 and 2 were washed again in a water bath at room temperature and further dried with hot air at 100° C., and the surfaces of the immersed protective films 1 and 2 were saponified.

<Preparation of Polarizing Plate>
The saponified protective film 1, polyvinyl alcohol-based polarizer, and first optical compensation layer 1 prepared above were bonded together using an adhesive so that the absorption axis of the polarizer and the slow axis of the first optical compensation layer were parallel to each other and the liquid crystal composition layer side of the first optical compensation layer was on the polarizer side, thereby producing a first polarizing plate of Example 1. As the adhesive, a 3% aqueous solution of PVA (PVA-117H, manufactured by Kuraray Co., Ltd.) was used. In this case, the polarizer and first optical compensation layer 1 had sufficient adhesion for practical use.
A second polarizing plate was also produced by similarly laminating a saponified protective film 1, a polyvinyl alcohol-based polarizer, and a saponified protective film 2. Two more protective films 2 were further laminated to the protective film 2 side using SK2057 manufactured by Soken Chemical & Engineering Co., Ltd., to produce the second polarizing plate of Example 1. The three protective films 2 laminated together correspond to the second optical compensation layer. The Re and Rth values of the second optical compensation layer are shown in Table 2 below.

<Fabrication of Liquid Crystal Display Device>
A first polarizing plate and a second polarizing plate were attached to the above-prepared liquid crystal cell 1 using SK2057 manufactured by Soken Chemical Co., Ltd., so that the first optical compensation layer and protective film 2 were respectively on the liquid crystal cell side, thereby producing a liquid crystal display device of Example 1. The first polarizing plate and the second polarizing plate were attached so that the slow axis of the liquid crystal layer in the liquid crystal cell and the absorption axis of the first polarizing plate were perpendicular to each other and parallel to each other. Furthermore, the first polarizing plate was attached to the color filter substrate side of the liquid crystal cell, and the second polarizing plate was attached to the electrode substrate side.

[Optical Performance of Liquid Crystal Display Device]
The prepared liquid crystal display device was placed on a diffuse light source (backlight unit) with the first polarizer facing up (in other words, the diffuse light source was placed on the second polarizer side), and light leakage in the horizontal viewing direction in black display was measured by the following method. The evaluation results are shown in Table 3 below.
The angle of the slow axis shown in Table 3 indicates the orientation of the slow axis of the first optical compensation layer when the direction of the absorption axis of the first polarizer is taken as 0°. That is, when the angle of the slow axis is 0°, the absorption axis of the first polarizer and the slow axis of the first optical compensation layer are parallel, and when the angle of the slow axis is 90°, the absorption axis of the first polarizer and the slow axis of the first optical compensation layer are perpendicular to each other.

<<Light leakage measurement of horizontal field of view with black display>>
The prepared liquid crystal display device was placed on a diffused light source, and light leakage in the horizontal field of view during black display was measured using a measuring device "EZ-Contrast XL88" (manufactured by ELDIM), and evaluated according to the following criteria. Specifically, the horizontal field of view was measured in four directions tilted 40° left and right and 20° up and down with respect to the direction perpendicular to the display surface of the liquid crystal display device (four directions with azimuth angles of 23.4°, 156.6°, 203.4°, and 336.6° at a polar angle of 42.4°). The direction with the worst light leakage among the four directions was used as the evaluation for each Example and Comparative Example.

A: Very little light leakage, particularly excellent B: Little light leakage, excellent C: Somewhat much light leakage, but no practical problem D: Much light leakage, unacceptable

[Example 2]
A liquid crystal display device of Example 2 was produced and evaluated in the same manner as in Example 1, except that the second polarizing plate was changed. The results are shown in Table 3 above.
<Preparation of Protective Film 3>
Protective film 3 was produced in the same manner as protective film 2 except that the film thickness was 60 μm. The retardation of protective film 3 was measured to find that Re(550) was 1.3 nm, Rth(550) was −9 nm, and Re(450) was 2.9 nm, Rth(450) was −19 nm.

<Preparation of Polarizing Plate>
Using protective film 3 instead of protective film 2 in Example 1, a polarizing plate was produced by laminating protective film 1, a polarizer, and protective film 3. Furthermore, another protective film 3 was laminated on the protective film 3 side using SK2057 manufactured by Soken Chemical & Engineering Co., Ltd., to produce a second polarizing plate of Example 2. The laminate of two protective films 3 corresponds to the second optical compensation layer.

[Example 3]
A liquid crystal display device of Example 3 was produced and evaluated in the same manner as in Example 2, except that the film thickness of the first optical compensation layer b was changed to change Rth(550) as shown in Table 3 above, and the number of protective films 3 stacked was changed as shown in Table 2 above. The configuration in which three protective films 3 were stacked corresponds to the second optical compensation layer. The results are shown in Table 3 above.

[Example 4]
<Preparation of Optical Film from Which Liquid Crystal Layer Can Be Peeled Off>
Liquid crystal layer-forming composition 2 prepared as shown in the table below was applied to TAC (cellulose-based polymer film; TG40 manufactured by Fujifilm Corporation) using a #1.2 wire bar. The composition was heated with warm air at 40°C for 60 seconds to dry the solvent and ripen the liquid crystal compound. The resulting coating was then irradiated with ultraviolet light (300 mJ/ ^cm2 ) at 40°C under a nitrogen purge and an oxygen concentration of 100 ppm to fix the alignment of the liquid crystal compound, thereby producing an optical film in which the liquid crystal composition layer (corresponding to the second optical compensation layer) can be peeled off from the TAC support. The liquid crystal composition layer was fixed in a state in which the liquid crystal compound was aligned perpendicular to the TAC surface.

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Composition 2 for forming liquid crystal layer
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Liquid crystal compound R1 100 parts by mass Alignment aid A1 2 parts by mass Monomer K2 8 parts by mass Polymerization initiator P1 2 parts by mass Polymerization initiator P2 4 parts by mass Surfactant S1 0.4 parts by mass Surfactant S3 0.3 parts by mass Polymer compound C1 5 parts by mass Toluene 621 parts by mass Methyl ethyl ketone 69 parts by mass

Monomer K2: Viscoat #360 (Osaka Organic Chemical Industry Ltd.)

Surfactant S3

・High molecular compound C1

The liquid crystal surface of the peelable optical film thus prepared was bonded to a glass plate using SK2057 manufactured by Soken Chemical Co., Ltd., and the TAC support was peeled off to leave a film of the liquid crystal composition layer alone, which was designated Liquid Crystal Composition Layer 1 (thickness: 0.2 μm). The retardation of Liquid Crystal Composition Layer 1 was measured to find Re(550) = 0.1 nm, Rth(550) = -20 nm, Re(450) = 0.2 nm, Rth(450) = -22 nm.

The surface of the peelable optical film prepared on the liquid crystal composition layer side was directly attached to a polarizer using SK2057 manufactured by Soken Chemical Co., Ltd., and then the TAC support was peeled off to prepare a second polarizing plate having protective film 1, polarizer, and liquid crystal composition layer 1 laminated in that order.
A liquid crystal display device of Example 4 was produced using the second polarizing plate and evaluated as described above in the same manner as in Example 1, except that the Rth(550) of the first optical compensation layer b was changed as shown in Table 2. The results are shown in Table 3.

[Example 5]
A liquid crystal display device of Example 5 was produced and evaluated in the same manner as in Example 4, except that Rth was changed to the value shown in Table 2 above by changing the thickness of the liquid crystal composition layer of the peelable optical film (referred to as liquid crystal composition layer 2), and Rth(550) of the first optical compensation layer b was changed to the value shown in Table 3 above. The results are shown in Table 3 above.

[Example 6]
The liquid crystal display device of Example 6 was produced in the same manner as in Example 3, except that the following negative C plate was used as the first optical compensation layer a, the following biaxial film was used as the first optical compensation layer b, and the polarizer, first optical compensation layer b, and first optical compensation layer a were laminated in this order. The results are shown in Table 3 above. At this time, the layers were attached so that the absorption axis of the polarizer and the slow axis of the first optical compensation layer b were parallel to each other.
<Preparation of negative C-plate>
An unstretched cycloolefin polymer film (trade name: Arton Film, manufactured by JSR Corporation) was stretched so as not to exhibit in-plane retardation, to prepare a cycloolefin polymer having Re=0 nm, Rth=100 nm and a film thickness of 40 μm.
<Preparation of biaxial film>
A biaxial film was produced by the method described in JP-A-2014-518294. The produced biaxial film had Re = 130 nm, Rth = -110 nm, and a film thickness of 60 μm.

[Example 7]
A liquid crystal display device of Example 7 was produced in the same manner as in Example 3, except that a first optical compensation layer was produced by the method described in JP 2006-72309 A and the first optical compensation layer was attached so that the slow axis was parallel to the absorption axis of the polarizer. The results are shown in Table 3 above. In Example 7, the first optical compensation layer consisted of one layer.

[Comparative Example 1]
A liquid crystal display device of Comparative Example 1 was produced and evaluated in the same manner as in Example 1, except that a polarizing plate without the 2 × 3 protective films on the liquid crystal cell substrate side, i.e., without the second optical compensation layer, was used as the second polarizing plate. The results are shown in Table 3 above.

[Example 8]
A liquid crystal display device of Example 8 was fabricated and evaluated in the same manner as in Comparative Example 1, except that liquid crystal cell 2 was used instead of liquid crystal cell 1 and Rth(550) of the first optical compensation layer b was changed to the value shown in Table 3. The results are shown in Table 3.

[Comparative Example 2]
A liquid crystal display device of Comparative Example 2 was produced and evaluated in the same manner as in Example 7, except that the stretching conditions for the first optical compensation layer were changed and the film was attached so that the slow axis was perpendicular to the absorption axis of the polarizer. The results are shown in Table 3 above.

[Example 9]
A liquid crystal display device of Example 9 was produced and evaluated in the same manner as in Example 4, except that Rth was changed to the value shown in Table 2 above by changing the thickness of the liquid crystal composition layer of the peelable optical film (referred to as liquid crystal composition layer 3), and Rth(550) of the first optical compensation layer b was changed to the value shown in Table 3 above. The results are shown in Table 3 above.

[Example 10]
A liquid crystal display device of Example 10 was produced and evaluated in the same manner as in Example 2, except that Rth was changed by adjusting the film thickness of the first optical compensation layer b. The results are shown in Table 3 above.

[Example 11]
A liquid crystal display device of Example 11 was produced and evaluated in the same manner as in Example 3, except that Re and Rth were changed by adjusting the stretching ratio of the first optical compensation layer a. The results are shown in Table 3 above.

[Example 12]
A liquid crystal display device of Example 12 was produced and evaluated in the same manner as in Example 7, except that the stretching conditions for the first optical compensation layer were changed to change Re and Rth. The results are shown in Table 3 above.

As a result of the evaluation, it is found that the examples of the present invention can reduce light leakage in black display when viewed from the side compared to the comparative examples.
Comparing Example 1 with Examples 2 and 3, it is clear that Rth_total(550) is preferably −15 nm or less.
Comparing Example 2 with Example 4, it is clear that Rth_total(450) is preferably −20 nm or less.
Comparing Example 3 with Example 5, it is clear that Rth_total(450)-Rth_total(550) is preferably 0 nm or less.
From Example 8, it is clear that when the Rth(550) of the electrode substrate is −10 nm or less, the second optical compensation layer does not need to be provided.
Comparing Examples 4 and 5 with Example 9, it is clear that Rth_total(550) is preferably −50 nm or more.
The above results clearly demonstrate the effectiveness of the present invention.

1: Outer protective film of first polarizer 2: First polarizer 3: Absorption axis of first polarizer 4: First optical compensation layer b
5 First optical compensation layer a
6: Slow axis of first optical compensation layer a 7: Upper substrate of liquid crystal cell 8: Liquid crystal molecules (liquid crystal layer)
9 Lower substrate of liquid crystal cell 10 Second optical compensation layer 11 Second polarizer 12 Absorption axis of second polarizer 13 Outer protective film of second polarizer 14 Backlight unit 15 First optical compensation layer 16 First polarizing plate 17 Second polarizing plate

Claims (19)

A liquid crystal display device having at least a first polarizer, a first optical compensation layer, a liquid crystal cell, a second polarizer, and a backlight in this order,
The liquid crystal cell has a pair of substrates arranged opposite to each other, at least one of which has an electrode, and an alignment-controlled liquid crystal layer arranged between the pair of substrates, and by applying a voltage to the electrodes, an electric field having a component parallel to the substrates having the electrodes is formed,
an absorption axis of the first polarizer is parallel to a slow axis of the first optical compensation layer;
a slow axis of the alignment-controlled liquid crystal layer in black display mode and an absorption axis of the first polarizer are perpendicular to each other;
an absorption axis of the first polarizer and an absorption axis of the second polarizer are perpendicular to each other,
an in-plane retardation Re1(550) of the first optical compensation layer at a wavelength of 550 nm satisfies the following formula (1),
Formula (1): 80nm≦Re1(550)≦320nm
at least one layer having retardation in a film thickness direction is present between the liquid crystal layer and the second polarizer,
A liquid crystal display device characterized in that the sum of the in-plane retardations Re_total(550) and the sum of the retardations in the film thickness direction Rth_total(550) of the layers between the liquid crystal layer and the second polarizer satisfy the following formulas (2) and (3):
Formula (2): 0nm≦Re_total(550)≦10nm
Formula (3): Rth_total (550)≦-10nm The liquid crystal display device according to claim 1, wherein the sum of the in-plane retardations Re_total(450) and the sum of the retardations in the film thickness direction Rth_total(450) of the layers between the liquid crystal layer and the second polarizer satisfy the following formulas (4) and (5):
Formula (4): 0nm≦Re_total(450)≦20nm
Formula (5): Rth_total (450)≦-20nm 3. The liquid crystal display device according to claim 1, wherein the sums of Rth_total(550) and Rth_total(450) of retardations in the film thickness direction of layers between the liquid crystal layer and the second polarizer satisfy the following formula (23):
Formula (23): Rth_total(450)−Rth_total(550)≦0nm The liquid crystal display device according to claim 1 or 2, wherein the substrate of the pair of substrates disposed between the liquid crystal layer and the second polarizer is an electrode substrate having retardation in the film thickness direction. 5. The liquid crystal display device according to claim 4, wherein the in-plane retardation Re3(550) and the retardation Rth3(550) in the film thickness direction of the electrode substrate at a wavelength of 550 nm satisfy the following formulas (6) and (7):
Formula (6): 0nm≦Re3(550)≦10nm
Formula (7): -100nm≦Rth3(550)≦-10nm The liquid crystal display device of claim 1 or 2, comprising at least a second optical compensation layer between the liquid crystal layer and the second polarizer. The liquid crystal display device of claim 1 or 2, comprising, between the liquid crystal layer and the second polarizer, in this order from the liquid crystal layer side, at least an electrode substrate having retardation in the film thickness direction and a second optical compensation layer. 7. The liquid crystal display device according to claim 6, wherein the in-plane retardation Re2(550) and the retardation Rth2(550) in the film thickness direction at a wavelength of 550 nm of the second optical compensation layer satisfy the following formulas (8) and (9):
Formula (8): 0nm≦Re2(550)≦10nm
Formula (9): -100nm≦Rth2(550)≦-10nm The liquid crystal display device according to claim 6, wherein the second optical compensation layer is a film in which a liquid crystalline compound is fixed in an aligned state. The liquid crystal display device according to claim 6, wherein the second optical compensation layer is a film in which a rod-shaped liquid crystal compound is fixed in a state where it is aligned perpendicular to the substrate surface. The liquid crystal display device of claim 6, wherein the second optical compensation layer is a cellulose acylate film. 3. The liquid crystal display device according to claim 1, wherein a ratio of an in-plane retardation Re1(450) at a wavelength of 450 nm to an in-plane retardation Re1(550) at a wavelength of 550 nm of the first optical compensation layer satisfies the following formula (10):
Formula (10): 0.70≦Re1(450)/Re1(550)≦1.30 3. The liquid crystal display device according to claim 1, wherein the first optical compensation layer is composed of one layer, and an in-plane retardation Re1(550) at a wavelength of 550 nm and a retardation Rth1(550) in a film thickness direction satisfy the following formulas (11) and (12):
Formula (11): 150nm≦Re1(550)≦320nm
Formula (12): -50nm≦Rth1(550)≦50nm the first optical compensation layer is composed of two layers,
3. The liquid crystal display device according to claim 1, wherein a first optical compensation layer a and a first optical compensation layer b are laminated in this order from the liquid crystal cell side. the in-plane retardation Re1a(550) and the retardation Rth1a(550) in the film thickness direction of the first optical compensation layer a at a wavelength of 550 nm satisfy the following formulas (13) and (14):
Formula (13): 80nm≦Re1a(550)≦200nm
Formula (14): 20nm≦Rth1a(550)≦150nm
15. The liquid crystal display device according to claim 14, wherein an in-plane retardation Re1b(550) and a retardation Rth1b(550) in a thickness direction of the first optical compensation layer b at a wavelength of 550 nm satisfy the following formulas (15) and (16):
Formula (15): 0nm≦Re1b(550)≦40nm
Formula (16): -180nm≦Rth1b(550)≦-50nm the in-plane retardation Re1a(550) and the retardation Rth1a(550) in the film thickness direction of the first optical compensation layer a at a wavelength of 550 nm satisfy the following formulas (17) and (18):
Formula (17): 0nm≦Re1a(550)≦40nm
Formula (18): 50nm≦Rth1a(550)≦180nm
15. The liquid crystal display device according to claim 14, wherein an in-plane retardation Re1b(550) and a retardation Rth1b(550) in a thickness direction of the first optical compensation layer b at a wavelength of 550 nm satisfy the following formulas (19) and (20):
Formula (19): 80nm≦Re1b(550)≦200nm
Formula (20): -200nm≦Rth1b(550)≦-20nm The liquid crystal display device of claim 1, further comprising a color filter between the liquid crystal layer and the first optical compensation layer. 2. The liquid crystal display device according to claim 1, wherein a total Rth_total(550) of retardations in the film thickness direction of the layers between the liquid crystal layer and the second polarizer satisfies the following formula (24):
Formula (24): -50nm≦Rth_total(550)≦-15nm 3. The liquid crystal display device according to claim 1, wherein the sum of retardations in the film thickness direction of the layers between the liquid crystal layer and the second polarizer, Rth_total(550) and Rth_total(450), satisfies the following formula (25):
Formula (25): Rth_total(450)-Rth_total(550)≦-15nm