JP2006349748A - Liquid crystal display device and optical film used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IPS (In-Plane Switching) mode liquid crystal display device which is excellent in display quality. <P>SOLUTION: In the IPS mode liquid crystal display device of a normally black mode wherein a first polarizing plate, a liquid crystal cell, a negative and nearly monoaxial optical film having an optical axis in its plane, a positive and nearly monoaxial optical film having an optical axis in its thickness direction, a second polarizing plate are laminated in this order, an absorption axis of the first polarizing plate and a delay phase axis in the plane of the liquid crystal cell in a black state form an angle of nearly 90°, the delay phase axis in the plane of the liquid crystal cell and a delay phase axis of the negative and nearly monoaxial optical film form an angle of nearly 90° and the delay phase axis of the negative and nearly monoaxial optical film and an absorption axis of the second polarizing plate form an angle of nearly 90°. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device excellent in viewing angle characteristics, and an optical film suitable for the liquid crystal display device.

  In recent years, the performance of liquid crystal display devices has improved, and in particular, the vertical alignment mode and in-plane switching (hereinafter referred to as IPS) mode are superior in performance. Therefore, liquid crystal televisions using these have the potential to replace conventional CRT televisions. Hidden. A retardation film, which is an optical film having optical anisotropy, plays an important role in improving the performance of these liquid crystal display devices, particularly in widening the viewing angle. Although the IPS mode has conventionally been characterized by a wide viewing angle without using a retardation film for widening the viewing angle, it is widely used in recent years based on optical design technology using a retardation film. With the advance of viewing angle technology, it is difficult to differentiate from other modes. In such a background, there is an increasing need for development of an optical design technique using a retardation film aiming at further expansion of the viewing angle even in the IPS mode. For example, Non-Patent Document 1 describes a method of performing optical compensation using a biaxial retardation film.

  In addition, the polarizing plate viewing angle expansion technique described in Non-Patent Document 2 described below by combining a positive uniaxial A plate and a positive uniaxial C plate may be used to expand the viewing angle of IPS. Are known.

Yukita Saitoh, Shinichi Kimura, Kaoru Kusafuka, Hidehisa Shimizu, Japanese Journal of Applied Physics 37 1998 4822-4828 J. Chen, K. -H. Kim, J.-J. Jyu, J. H. Souk, J. R. Kelly, P. J. Bos, Society for Information Display '98 Digest, 1998 p. 315

  As a result of examining the techniques of Non-Patent Documents 1 and 2, it was found that when these methods are used to expand the viewing angle of an IPS mode liquid crystal display device, the color shift of black display is one problem. The color shift of black display here means that the color tone of black changes depending on the azimuth angle when the liquid crystal display device during black display is observed from an oblique direction rather than a normal direction. In the present invention, this problem is referred to as an azimuth angle dependency problem of color shift at oblique incidence. In other words, when the liquid crystal display device is observed from an oblique direction, the state changes from a strong reddish black color to a bluish black color depending on the viewing direction. In general, what causes the above color shift in black display also causes a color shift problem in halftone display. Here, the azimuth angle is an angle set in the surface of the liquid crystal display device. On the other hand, the polar angle is an angle set with the normal of the surface of the liquid crystal display device as 0 °, and therefore the incident angle is defined by the polar angle and the azimuth angle.

  The phase difference value of the liquid crystal cell in the in-plane switching mode of the normally black mode is designed considering not only the viewing angle but also the transmittance and response speed, so the optimum phase difference value is not necessarily a half wavelength. It will not be. Here, the phase difference value of the liquid crystal cell is a phase difference value of the liquid crystal cell including the liquid crystal. Therefore, the viewing angle of the liquid crystal display device in the normally black mode in-plane switching mode is mainly determined by the optical anisotropy between the retardation film and the liquid crystal cell. In the said nonpatent literature 1, although a biaxial optical film is used, the relationship between the phase difference value of a liquid crystal cell and the phase difference value of a biaxial optical film is not disclosed. Similarly, Non-Patent Document 2 does not disclose the relationship between the liquid crystal cell and the retardation film.

  Further, the biaxial optical film used in Non-Patent Document 1 has a problem that it is difficult to obtain optical axis accuracy and phase difference accuracy in a large area because the manufacturing method is complicated. As a result, when these are used in a liquid crystal display device, defects such as display unevenness are likely to occur, and it is difficult to improve display quality.

An object of the present invention is to provide an IPS mode liquid crystal display device having excellent display quality.
It is a further object of the present invention to provide a liquid crystal display device having a wide viewing angle and excellent display quality that solves the above-mentioned color shift problem even if the retardation value of the IPS liquid crystal cell changes.

  The negative substantially uniaxial optical film having an optical axis in the plane can be obtained, for example, by forming a polymer material having negative molecular polarizability anisotropy into a film and performing a normal uniaxial stretching process. Therefore, such a film has a very simple manufacturing process and is excellent in the uniformity of optical anisotropy required for a liquid crystal television or the like. Further, a positive substantially uniaxial optical film having an optical axis in the thickness direction is obtained by, for example, forming a polymer material having negative molecular polarizability anisotropy, which is a raw material, by a normal biaxial stretching process or the like. Can be obtained by a simple manufacturing process.

  The present inventors conducted optical design using these optical films and intensively studied the method of expanding the viewing angle of the IPS mode liquid crystal display device. Even if the retardation value of the liquid crystal cell changes due to the design convenience. It was found that an IPS mode liquid crystal display device with a wide viewing angle and suppressed azimuth angle dependency of color shift at oblique incidence can be realized.

That is, the present invention is as follows.
[1] First polarizing plate, liquid crystal cell, negative substantially uniaxial optical film having an optical axis in the plane, positive substantially uniaxial optical film having an optical axis in the thickness direction, second polarizing plate In this order, the normally black mode in-plane switching mode liquid crystal display device is formed by the absorption axis of the first polarizing plate and the in-plane slow axis of the liquid crystal cell in the black state. The angle between the in-plane slow axis of the liquid crystal cell and the slow axis of the negative approximately uniaxial optical film is approximately 90 °, and the slow axis of the negative approximately uniaxial optical film is A liquid crystal display device in which an angle formed by the absorption axis of the polarizing plate 2 is approximately 90 °.

[2] The in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, in the thickness direction of the positive substantially uniaxial optical film. When there is a polarizing layer protective film on the liquid crystal cell side of the first and second polarizing plates, the retardation value is Rth _POC , and the retardation value in the thickness direction of the polarizing layer protective film is , Rth ₁ (λ) and Rth ₂ (λ), the above-mentioned liquid crystal display device satisfying the relations of the following formulas (1) and (2).
90 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <200 nm (1)
−180 <Rth _POC (λ) + Rth ₂ (λ) <− 40 nm (2)
(However, λ = 550 nm)

[3] The in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, in the thickness direction of the positive substantially uniaxial optical film. The liquid crystal display device according to the above, wherein when the phase difference value is Rth _POC , the relationship of the following formulas (3) and / or (4) is satisfied.
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (3)
| Rth _POC (λ ₁ ) | <| Rth _POC (λ ₂ ) | (4)
(However, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.)

[4] A negative substantially uniaxial optical film having an optical axis in a plane used for the liquid crystal display device described above.

[5] A positive substantially uniaxial optical film having an optical axis in the thickness direction used for the liquid crystal display device described above.

[6] The optical film as described above, comprising a polycarbonate having a fluorene skeleton.

[7] A laminated polarizing plate in which the optical film and the polarizing plate described above are integrated, a negative substantially uniaxial optical film having an optical axis in the plane, and a positive substantially having an optical axis in the thickness direction. These are laminated in the order of the uniaxial optical film and the polarizing plate, and the angle formed by the slow axis of the negative substantially uniaxial optical film having the optical axis in the plane and the absorption axis of the polarizing plate is approximately. A laminated polarizing plate characterized by being 90 °.

In the present invention, an optically anisotropic film having refractive index anisotropy is referred to as an optical film or a retardation film. A uniaxial optical film and a biaxial optical film are classified according to their three-dimensional refractive index, and these are also categories of retardation films. The retardation film is expressed by a refractive index ellipsoid, and only the case where the orientations of the three main refractive indexes are parallel or perpendicular to the film plane is considered here. Here consider the orthogonal coordinate system axes are parallel or perpendicular to the surface of the film as shown in FIG. 3, it defines three refractive index corresponding to the orientation of the coordinate n _x, n _y, and n _z. When the slow axis direction in the plane is set as the x axis, the y axis is set in the plane and the z axis is set in the thickness direction. Accordingly, the negative substantially uniaxial optical film having an optical axis in plane of the present invention, with three refractive _{index, n z ≒ n x> n} y , and the late phase n _x is the film plane It becomes an axis. All three biaxial optical films are defined as having different refractive indexes. Further, the positive substantially uniaxial optical film having an optical axis in the thickness direction is defined as _{n z> n x ≒ n y} . The positive uniaxial A plate described above refers to a positive uniaxial medium (uniaxial optical film in the case of a film) having an optical axis in the plane, and in this definition, n _x > _ny = _Nz . On the other hand, the positive uniaxial C plate is a positive uniaxial medium (uniaxial optical film in the case of a film) having an optical axis in the thickness direction. In this definition, n _z > n the _x = _{n y.}

The in-plane retardation value Γ in the present invention is defined by the following formula (5) or (6).
When the optical film of the n _z ≧ _{n x} is
_{Γ (λ) = (n y} -n x) × d (5)
When the optical film of the n _{z <n x} is
_{Γ (λ) = (n x} -n y) × d (6)
Here, d is the thickness (nm) of the film.

Strictly speaking, it is preferable that the negative substantially uniaxial optical film having an in-plane optical axis in the present invention satisfies the relationship of n _z = n _x > _ny , but n _z ≈n _x > _ny . If you can, you can use it without any problems. In addition, since an actual retardation film also has a variation in refractive index, the range of the term of substantially negative uniaxiality is defined using the following formula (7) using these three refractive indexes.
_{Nz = (n x -n z)} / (n x -n y) (7)

What is a negative substantially uniaxial optical film having an optical axis in a plane in the present invention?
−0.4 <Nz <0.1 (8)
Is preferably defined as
−0.35 <Nz <0.05 (9)
And more preferably
−0.20 <Nz <0.03 (10)
More preferably,
−0.10 <Nz <0.02 (11)
It is. Rth is defined as follows.
Rth (λ) = {(n _x + _ny ) / 2−n _z } × d (12)
In the above formula (12), d (nm) is the thickness of the optical film. In the present invention, the phase difference value Γ (λ), Rth (λ), and Nz value are measured at a wavelength of 550 nm unless otherwise specified.

  Further, the in-plane retardation value of the positive substantially uniaxial optical film having an optical axis in the thickness direction in the present invention is preferably 0, but it is necessary to be 20 nm or less, preferably 10 nm or less. More preferably, it is 5 nm or less, More preferably, it is 3 nm or less. The angle formed by the absorption axis of the second polarizing plate and the slow axis of the positive substantially uniaxial optical film is preferably 0 ° or 90 °, more preferably 0 °. When the in-plane retardation value of the positive substantially uniaxial optical film having an optical axis in the thickness direction is 5 nm or less, the absorption axis of the second polarizing plate and the slow phase of the positive substantially uniaxial optical film There is no limitation on the angle of the shaft.

  The black state and the black display in the present invention are the darkest states in the gradation display, and specifically, the state where the transmittance measured by entering light from the normal direction of the surface of the liquid crystal display device is the lowest. Is defined.

  The optical axis alignment angle between the optically anisotropic elements needs to be the above-mentioned angle, but the allowable range is within ± 3 °, preferably within ± 2 °, centered on the set angle. Preferably it is within ± 1 °, more preferably within ± 0.5 °. That is, the expression of approximately 90 ° is defined as 90 ° ± 3 °.

  In the present invention, particularly when two retardation films are used on one side of the liquid crystal cell and the in-plane retardation value thereof and the in-plane retardation value of the liquid crystal cell in the black state are taken into consideration, a wide field of view is particularly excellent. The reason why keratinization can be realized is described below. Here, the wide viewing angle of the liquid crystal display device means that the phenomenon that the contrast changes depending on the viewing angle is improved, and the angular region having a high contrast is widened. In general, widening the viewing angle of a liquid crystal display device is aimed at making the transmittance during black display as close to 0 as possible regardless of the incident angle to the liquid crystal display device. It will be described below that the present invention can reduce the transmittance with respect to light having various incident angles.

  An example of the configuration of the liquid crystal display device according to the present invention is shown in FIG. The principle of wide viewing angle according to the present invention will be described with reference to FIG. In FIG. 1, the second polarizing plate is on the light source side, but the light source may be disposed on either side of the first or second polarizing plate.

  The configuration of FIG. 1 can be regarded as optically almost equivalent to FIG. 2 under certain conditions. First, since the liquid crystal display device in the present invention is in the IPS mode, the liquid crystal cell can be regarded as a positive uniaxial medium having an optical axis in the plane during black display. The negative uniaxial optical film having an optical axis in the plane and the slow axis of the liquid crystal cell are orthogonal to each other, and the absolute value of the in-plane retardation value of the liquid crystal cell is substantially negative uniaxial. Under the condition that it is larger than the absolute value of the retardation value of the diffractive optical film, the combination of the two elements can be regarded as optically substantially equivalent to the positive substantially uniaxial optical film [11] shown in FIG. . Therefore, the wide viewing angle in the liquid crystal display device of the present invention is examined by first considering widening the viewing angle in the configuration of FIG. 2, and based on the result, the optimum position of the optical anisotropic medium used in the present invention is determined. What is necessary is just to obtain | require a phase difference value and its relationship.

Realizing a wide viewing angle in FIG. 2 is to make the transmittance as close to 0 as possible for incident light having any incident angle. Therefore, the in-plane retardation value of the positive substantially uniaxial optical film [11] having the optical axis in the plane in FIG. 2 is Γ ₃ (λ), and the positive substantially uniaxial property having the optical axis in the thickness direction. When the retardation value in the thickness direction of the optical film [12] is Rth ₄ (λ) and the optimum retardation value is examined, it is preferable that the following expressions (15) and (16) are satisfied. all right. By satisfying the following formulas (15) and (16), the transmittance is small and the viewing angle is good in a range where the incident angle of incident light is a polar angle of 0 to 80 ° and an azimuth angle of 0 to 360 °. Can achieve a black display.
90 <Γ ₃ (λ) <200 nm (15)
−180 <Rth ₄ (λ) <− 40 nm (16)

A preferable range of the phase difference value is to satisfy the following formulas (17) and (18). In this case, the incident angle of incident light is a range where the polar angle is 0 to 80 ° and the azimuth angle is 0 to 360 °. The maximum transmittance (λ = 550 nm) at 550 nm, which is the wavelength with the highest visual sensitivity of the human eye, can be reduced to about 0.3% or less.
110 <Γ ₃ (λ) <180 nm (17)
−160 <Rth ₄ (λ) <− 60 nm (18)

A more preferable range of the phase difference value is to satisfy the following formulas (19) and (20). In this case, the incident angle of incident light is a polar angle of 0 to 80 ° and an azimuth angle of 0 to 360 °. In the range, the maximum transmittance (λ = 550 nm) at 550 nm, which is the wavelength with the highest visual sensitivity of the human eye, can be reduced to about 0.1% or less.
120 <Γ ₃ (λ) <165 nm (19)
−140 <Rth ₄ (λ) <− 80 nm (20)
Although the optimum value varies depending on the refractive index of the optical film, it is preferable that the above relationship is satisfied.

As described above, from the comparison of the configurations of FIG. 1 and FIG. 2, it is newly found that the following equations (21) and (22) may be satisfied in order for both to be equivalent.
Γ ₃ (λ) = Γ _LC (λ) + Γ ₁ (λ) (21)
Rth4 (λ) = RthPOC (λ) (22)

  As described above, the reason why the above formula (21) is established is that both the liquid crystal cell and the first negative substantially uniaxial optical film having an optical axis in the plane are optically substantially uniaxial, In addition, since the slow axes are orthogonal to each other, both of them can be optically regarded as one uniaxial medium. Here, when the refractive indexes of all anisotropic media are equal, the structures of FIGS. 1 and 2 are optically equivalent when the above expressions (21) and (22) are satisfied. Actually, the refractive index of all anisotropic media is rarely the same, but in general, the material used as an optically anisotropic medium in a liquid crystal display device is an organic material, and the refractive index is large even if the material is different. Therefore, if the above equations (21) and (22) are satisfied, the configurations of FIGS. 1 and 2 can be regarded as optically equivalent.

On the other hand, the polarizing plate in this invention contains the form by which the protective film for polarizing layers was installed in order to protect a polarizing layer only on a polarizing layer or the single side | surface or both surfaces of a polarizing layer. When the polarizing layer protective film is disposed on at least one surface of the polarizing layer and the polarizing layer protective film is present on the liquid crystal cell side, the polarizing layer protective film generally has an in-plane anisotropy. Although negligibly small, a retardation Rth (λ) in the thickness direction, which will be described later, cannot be ignored in the design of a liquid crystal display device. Then, the influence of this protective film for polarizing layers was examined. As a result, in order for FIG. 1 and FIG. 2 to be optically substantially equal, it has been found that the relationship between the above formulas (21) and (22) is approximately as follows.
Γ ₃ (λ) ≈Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) (23)
Rth ₄ (λ) ≈Rth _POC (λ) + Rth ₂ (λ) (24)

Here, Rth ₁ (λ) and Rth ₂ (λ) are the retardation value in the thickness direction of the polarizing layer protective film on the liquid crystal cell side in the first polarizing plate in FIG. 1, and the optical film in the second polarizing plate, respectively. Represents the retardation value in the thickness direction of the polarizing film protective film on the side. From the definition of the optical anisotropy of the present invention, the value of Rth (λ) of a commonly used polarizing layer protective film is positive. On the other hand, the retardation value of a negative substantially uniaxial optical film having an optical axis in the plane of the present invention is negative. Therefore, they cancel each other out of anisotropy. The above equation shows that the value of Γ ₁ (λ) needs to be increased in absolute value by Rth (λ) as compared with the case where there is no polarizing layer protective film under the condition that Γ _LC (λ) is constant. The relationship between (21) and the above equation (23) is shown. On the other hand, the relationship between the above formula (22) and the above formula (24) indicates that the value of Rth _POC (λ) needs to be increased in absolute value by Rth ₂ (λ). Therefore, from the relations of the above formulas (15), (16) and the above formulas (23), (24), in order to realize a wide viewing angle in the liquid crystal display device of the present invention, the above formulas (1), ( It is derived that it is preferable to satisfy 2).

  In general, in the normally black mode in-plane switching mode liquid crystal display device, the phase difference of the liquid crystal cell is usually about one-half wavelength or more, which takes into account the brightness and response speed. It is determined. In the liquid crystal display device of the present invention, a negative substantially uniaxial optical film having an optical axis in a plane and a liquid crystal cell which is a positive uniaxial medium are combined into one positive one as described above. Since it can be regarded as an axial medium, the prospect of optical design can be easily established, and even if the phase difference value of the liquid crystal cell changes due to the convenience of design, the above formulas (1) and (2) are satisfied. The fact that it is possible to obtain a liquid crystal display device with a wide viewing angle is also an excellent point not found in other methods.

Further, in order to improve performance such as suppression of color shift, it is preferable to take into consideration the wavelength dependence of the retardation value of the optical element. That is, realizing a wider viewing angle and a wider band aiming at further performance improvement in FIG. 2 is to make the transmittance as close to 0 as possible with respect to incident light in the visible light band having all incident angles. . First, as a result of investigation, the two retardation films in FIG. 2 are not mutually compensated for the wavelength dispersion of the respective retardations, so that the wavelength dispersion of the retardation values of these retardation films is at least It has been found that one of them preferably has a wider bandwidth. Unless otherwise specified, the phase difference value is defined in nanometers as a unit of length. The broadening of the phase difference value referred to here is defined as approaching a state where the phase difference value becomes constant without depending on the wavelength when the phase difference value is displayed in an angle. When the phase difference value is converted into a unit of length, it is necessary at least that the absolute value of the phase difference value Γ (λ) be monotonously increased with respect to the wavelength. In other words, it can be said to approach the state of Expression (25).
Γ (λ) / λ = C (25)
Where Γ (λ) is a phase difference value (nm) at the measurement wavelength λ, λ is in the range of 400 to 700 nm, and C is a constant.

Therefore, the retardation value of the positive substantially uniaxial retardation film having the optical axis in the plane in FIG. 2 and the retardation of the positive substantially uniaxial optical film having the optical axis in the thickness direction in the thickness direction. When the values are Γ ₃ (λ) and Rth ₄ (λ), respectively, it is preferable that the following expressions (26) and / or (27) are satisfied.
| Γ ₃ (λ ₁ ) | <| Γ ₃ (λ ₂ ) | (26)
| Rth ₄ (λ ₁ ) | <| Rth ₄ (λ ₂ ) | (27)
Here, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.

More preferably, the above expressions (26) and (27) are satisfied at the same time.
Therefore, the following formulas (3) and (4) are derived from the relationship between the above formulas (26) and (27) and the above formulas (21) and (22). The liquid crystal display device of the present invention preferably satisfies the following formulas (3) and / or (4), and more preferably satisfies both.
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (3)
| Rth _POC (λ ₁ ) | <| Rth _POC (λ ₂ ) | (4)
Here, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.

  A liquid crystal display device optically designed using a negative substantially uniaxial optical film having an optical axis in the plane of the present invention and a positive substantially uniaxial optical film having an optical axis in the thickness direction is in a black state. Even if the phase difference value of the liquid crystal cell changes to various values in combination with other characteristics, it is easy to design a wide viewing angle according to the change, and the color shift at a wide viewing angle and oblique incidence It has excellent performance such that the azimuth angle dependency is small.

In order to obtain the effect of the invention, the first polarizing plate, the liquid crystal cell, the negative substantially uniaxial optical film having an in-plane optical axis, and the positive substantially uniaxial optical having an optical axis in the thickness direction A normally black mode in-plane switching mode liquid crystal display device in which a film and a second polarizing plate are laminated in this order, the absorption axis of the first polarizing plate and the surface of the liquid crystal cell in the black state The angle formed by the inner slow axis is 90 °, the angle formed by the in-plane slow axis of the liquid crystal cell and the slow axis of the negative substantially uniaxial optical film is approximately 90 °, and the negative substantially uniaxial optical film. The angle formed by the slow axis of the second polarizing plate and the absorption axis of the second polarizing plate is approximately 90 °,
And,
The in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, and the positive substantially uniaxial optical film has a thickness direction retardation value. Rth _POC , and when there is a polarizing layer protective film on the liquid crystal cell side of each of the first and second polarizing plates, the retardation value in the thickness direction of the polarizing layer protective film is set to Rth ₁ When (λ) and Rth ₂ (λ), it is preferable that the liquid crystal display device satisfy the relationship of the following formulas (1) and (2).
90 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <200 nm (1)
−180 <Rth _POC (λ) + Rth ₂ (λ) <− 40 nm (2)
(However, λ = 550 nm)

The above range is more preferably
110 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <180 nm (28)
−160 <Rth _POC (λ) + Rth ₂ (λ) <− 60 nm (29)
Even more preferably,
120 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <165 nm (30)
−140 <Rth _POC (λ) + Rth ₂ (λ) <− 80 nm (31)
It is.

More preferably, the in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, and the thickness direction of the positive substantially uniaxial optical film. Rth _POC is used, and when a protective film for polarizing layer is present on the liquid crystal cell side of the first and second polarizing plates, the retardation value in the thickness direction of the protective film for polarizing layer Are respectively Rth ₁ (λ) and Rth ₂ (λ), the relationship of the following formulas (3) and / or (4) is satisfied. In the following formulas (3) and (4), the influence of Rth (λ) is negligible because of the wavelength dependence.
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (3)
| Rth _POC (λ ₁ ) | <| Rth _POC (λ ₂ ) | (4)
However, λ represents a measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.
Preferably, the relationship of the above formulas (3) and (4) is satisfied at the same time.

The wavelength dispersion of the retardation value in the thickness direction of the positive substantially uniaxial optical film having an optical axis in the thickness direction is to satisfy the following formulas (32) and (33):
0.4 <Rth _POC (450) / Rth _POC (550) <0.98 (32)
1.01 <Rth _POC (650) / Rth _POC (550) <1.50 (33)
More preferably, the following expressions (34) and (35) are satisfied.
0.6 <Rth _POC (450) / Rth _POC (550) <0.95 (34)
1.03 <Rth _POC (650) / Rth _POC (550) <1.40 (35)
In the above formulas (32) to (35), the number in () after Γ represents the measurement wavelength (nm).

The above formula (3) preferably satisfies the following formulas (36) and (37):
0.4 <(Γ _LC (450) + Γ ₁ (450)) / (Γ _LC (550) + Γ ₁ (550))
<0.98 (36)
1.01 <(Γ _LC (650) + Γ ₁ (650)) / (Γ _LC (550) + Γ ₁ (550))
<1.50 (37)
More preferably, the following expressions (38) and (39) are satisfied.
0.6 <(Γ _LC (450) + Γ ₁ (450)) / (Γ _LC (550) + Γ ₁ (550))
<0.95 (38)
1.03 <(Γ _LC (650) + Γ ₁ (650)) / (Γ _LC (550) + Γ ₁ (550))
<1.40 (39)
In the above formulas (36) to (39), the number in () after Γ represents the measurement wavelength (nm).

In general, the phase difference value of the liquid crystal cell in the black state of the IPS mode decreases as the wavelength increases due to the liquid crystal material, and has a positive phase difference value. Therefore, in order to satisfy the above formulas (3) and (36) to (39), the absolute value of the retardation of the first negative substantially uniaxial optical film having an optical axis in the plane increases with increasing wavelength. It is preferable to decrease. More specifically, in order to satisfy the relationship of the above formula (3), it is preferable to satisfy the following formulas (40) and (41).
Γ _LC (450) / Γ _LC (550) <Γ ₁ (450) / Γ ₁ (550) (40)
Γ _LC (650) / Γ _LC (550)> Γ ₁ (650) / Γ ₁ (550) (41)

  Each of the negative substantially uniaxial optical film having an optical axis in the plane and the positive substantially uniaxial optical film having an optical axis in the thickness direction, each having a necessary characteristic, is a single sheet. Alternatively, it may be configured by laminating two or more films. However, the thickness of the entire liquid crystal display device can be made thinner if it is composed of one film each, and the process of laminating the films is unnecessary, so that productivity is improved. Is also preferable.

  IPS is a mode in which a liquid crystal director changes in a plane by a lateral electric field. A normally black mode in which black is displayed when a voltage is substantially not applied and a normally white mode in which black is displayed in an applied state are conceivable. In the IPS mode, liquid crystal alignment disorder during voltage application is controlled. In order to obtain high contrast, it is necessary to be in the normally black mode.

  As a phase difference of a liquid crystal cell, it is preferable that it is 200-450 nm, More preferably, it is 250-400 nm, More preferably, it is 270-390 nm. The phase difference value of the liquid crystal cell is a value (in-plane value) at the front incidence in a non-voltage applied state. The phase difference value of the liquid crystal cell varies depending on the cell structure, driving conditions, setting of desired transmittance, and the like, but it is preferable to satisfy these values. As the material used for the liquid crystal, known nematic liquid crystal and smectic liquid crystal having positive dielectric anisotropy and positive refractive index anisotropy are used, and nematic liquid crystal is preferable. Further, in order to drive the liquid crystal in the IPS mode, it is necessary to generate a lateral electric field in the plane, but a known comb electrode arrangement, an electrode forming method, or the like can be used.

  The negative substantially uniaxial optical film having an optical axis in the plane used in the present invention and the positive substantially uniaxial optical film having an optical axis in the thickness direction are preferably made of the same material. Productivity can be improved by mass production.

  Examples of materials for a negative uniaxial optical film having an optical axis in the plane and a positive substantially uniaxial optical film having an optical axis in the thickness direction include polycarbonate, polystyrene, syndiotactic polystyrene, amorphous polyolefin, and norbornene. Examples thereof include polymers having a skeleton, organic acid-substituted cellulose, polyethersulfone, polyarylate, polyester, olefin maleimide, copolymerized olefin maleimide having a phenyl group, and liquid crystalline polymer. Further, among those obtained by aligning a polymerizable liquid crystal and cured, those having a negative molecular polarizability anisotropy are also included. These materials can be made into a negative uniaxial optical film having an optical axis in a plane by, for example, uniaxial stretching after film formation. Moreover, it is possible to produce a positive substantially uniaxial optical film having an optical axis in the thickness direction by forming a film using these materials and biaxially stretching.

  Preferred as the material is a polycarbonate having a fluorene skeleton. Since the fluorene skeleton is oriented perpendicular to the polymer main chain by a stretching operation or the like, it can have a large negative molecular polarizability anisotropy.

ここで、Ｒ^１〜Ｒ^８は、互いに独立に、水素原子、ハロゲン原子、炭素数１〜６の炭化水素基および炭素数１〜６の炭化水素−Ｏ−基よりなる群から選ばれる基であり、そしてＸは下記式（１）−１

で表わされる基であり、Ｒ^３０およびＲ^３１は、互いに独立に、ハロゲン原子または炭素数１〜３のアルキル基であり、そしてｎおよびｍは互いに独立に、０〜４の整数である。 A preferable chemical structure of the polycarbonate having a fluorene skeleton is composed of a polymer or a polymer mixture containing a repeating unit represented by the following formula (I).

Here, R ^{1 to} R ⁸ are each independently a group selected from the group consisting of a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 6 carbon atoms, and a hydrocarbon group having 1 to 6 carbon atoms. And X is the following formula (1) -1

R ³⁰ and R ³¹ are each independently a halogen atom or an alkyl group having 1 to 3 carbon atoms, and n and m are each independently an integer of 0 to 4.

Here, the polymer and the polymer mixture preferably contain 50 to 95 mol%, more preferably 60 to 95 mol% of the repeating units represented by the above formula (I), respectively, based on the total repeating units of the polymer or polymer mixture. More preferably, it is 70-90 mol%. A copolymer is preferred as the polycar.
These polycarbonates having a fluorene skeleton have excellent physical properties as an optical film in the present invention in terms of high glass transition temperature, handling, stretch moldability, and the like.

で示される繰返し単位からなり、かつ上記式（Ｉ）および（ＩＩ）の合計に基づき上記式（Ｉ）で表される繰返し単位は５０〜９５モル％含有するものが好ましく、より好ましくは６０〜９５モル％、さらに好ましくは７０〜９０モル％である。 More preferred polycarbonates include the repeating unit represented by the above formula (I) and the following formula (II):

And the repeating unit represented by the formula (I) based on the sum of the formulas (I) and (II) is preferably contained in an amount of 50 to 95 mol%, more preferably 60 to It is 95 mol%, More preferably, it is 70-90 mol%.

よりなる群から選ばれる少なくとも一種の基である。ここで、Ｙ中のＲ^１７〜Ｒ^１９、Ｒ^２１およびＲ^２２は、それぞれ独立に、水素原子、ハロゲン原子、またはアルキル基、アリール基の如き炭素数１〜２２の炭化水素基であり、Ｒ^２０およびＲ^２３はアルキル基、アリール基の如き炭素数１〜２０の炭化水素基であり、また、Ａｒ^１〜Ａｒ^３は、それぞれ独立に、フェニル基の如き炭素数６〜１０のアリール基である。 In the above formula (II), R ^{9 to} R ¹⁶ are each independently at least one group selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 22 carbon atoms, and Y represents the following formula: Groups represented by each of the groups:

And at least one group selected from the group consisting of: Here, R ^{17 to} R ¹⁹ , R ²¹ and R ²² in Y are each independently a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 22 carbon atoms such as an alkyl group or an aryl group, and R ²⁰ and R ²³ are each a hydrocarbon group having 1 to 20 carbon atoms such as an alkyl group or an aryl group, and Ar ^{1 to} Ar ³ are each independently an aryl group having 6 to 10 carbon atoms such as a phenyl group. is there.

ここでＲ^４０、Ｒ^４１は炭素数１〜３のアルキル基またはアルコキシ基、またはニトロ基またはハロゲン原子を表し、そしてｌおよびｋは互いに独立に、０〜３の整数である。 In addition, as a positive substantially uniaxial optical film having an optical axis in the thickness direction and whose phase difference absolute value increases as the wavelength increases, a repeating unit represented by the following formula (III) is used. A polymer or polymer mixture is preferably contained. Here, the polymer and the polymer mixture preferably contain 50 to 95 mol%, more preferably 60 to 95 mol% of the repeating units represented by the above formula (III), respectively, based on the total repeating units of the polymer or polymer mixture. More preferably, it is 70-90 mol%. More preferably, the repeating unit is composed of repeating units represented by the following formula (III) and the above formula (II), and the repeating unit represented by the following formula (III) based on the sum of the above formulas (III) and (II) is 50 to What contains 95 mol% is preferable, More preferably, it is 60-95 mol%, More preferably, it is 70-90 mol%.

Here, R ⁴⁰ and R ⁴¹ each represents an alkyl group or alkoxy group having 1 to 3 carbon atoms, or a nitro group or a halogen atom, and l and k are each independently an integer of 0 to 3.

  The above-mentioned polycarbonate is suitably produced by a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, a solid phase polymerization method or the like. In the case of a blend, a compatible blend is preferable, but even if it is not completely compatible, light scattering between components can be suppressed and transparency can be improved by adjusting the refractive index between components.

  Furthermore, another preferred material for the positive substantially uniaxial optical film having an optical axis in the thickness direction is to use a blend of polyphenylene oxide and polystyrene. The stereoregularity of polystyrene may be any of atactic, syndiotactic and isotactic. A blend of polyphenylene oxide and polystyrene is a positive substantially uniaxial optical film having an optical axis in the thickness direction, and the absolute value of the phase difference monotonously increases with respect to the wavelength, depending on the blend ratio. Is possible.

  In the present invention, a negative substantially uniaxial optical film having an in-plane optical axis, and a positive substantially uniaxial optical film having an optical axis in the thickness direction (hereinafter sometimes referred to simply as a uniaxial optical film). ) May further contain an ultraviolet absorber such as phenyl salicylic acid, 2-hydroxybenzophenone, and triphenyl phosphate, a bluing agent for changing the color, an antioxidant, and the like.

  The thickness of the uniaxial optical film is preferably 1 μm to 400 μm. In addition, the optical film in this invention is used by the meaning containing both what is called a "sheet" and a "board". Considering the handling of the film, the thickness is preferably 20 to 130 μm, more preferably 30 to 100 μm, still more preferably 40 to 90 μm.

  In general, the polarizing plate preferably has a structure in which a polarizing layer is sandwiched between a pair of films made of cellulose acetate or the like as a film for protecting the polarizing layer (hereinafter sometimes referred to as a protective film for a polarizing layer). It is used for. As the polarizing layer of the polarizing plate, an appropriate layer capable of obtaining light in a predetermined polarization state can be used. In particular, those capable of obtaining transmitted light in a linearly polarized state are preferable. Examples of polarizing layers include iodine and / or dichroic dye adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And a polarizing layer composed of a polyene-oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride.

  When a protective film for a polarizing layer is present on the polarizing plate, the optical anisotropy is preferably as small as possible. Specifically, the in-plane retardation is 10 nm or less, more preferably 7 nm or less, and most preferably 5 nm or less. Rth (λ) is preferably 70 nm or less, more preferably 50 nm or less, and most preferably 40 nm or less. Furthermore, it is preferable that the slow axis in the film plane of the protective film for polarizing layers is orthogonal or parallel to the absorption axis of a polarizing plate, and it is more preferable when performing parallel production of a polarizing plate that it is parallel. Examples of the protective film for the polarizing layer include polycarbonate, polystyrene, syndiotactic polystyrene, amorphous polyolefin, polymer having norbornene skeleton, organic acid substituted cellulose, polyethersulfone, polyarylate, polyester, olefin maleimide And a copolymerized olefin maleimide-based organic acid-substituted cellulose having a phenyl group are used, and cellulose acetate is preferred.

  In the present invention, the negative substantially uniaxial optical film having the optical axis in the plane, the positive substantially uniaxial optical film having the optical axis in the thickness direction, and the polarizing plate are integrated in this order. Also provided is a laminated polarizing plate laminated such that the in-plane slow axis of a negative substantially uniaxial film having an optical axis in the plane and the absorption axis of the polarizing plate are about 90 °.

In the laminated polarizing plate of the present invention, the protective film for the polarizing layer on the side in contact with the positive substantially uniaxial optical film having the optical axis in the thickness direction is omitted, and the positive substantially uniaxial optical film is used for the polarizing layer. It may also serve as a protective film. This also has the advantage that the optical design becomes easier. In this case, Rth ₂ (λ) may be considered as 0 in the above formula (2). Similarly, when there is no polarizing layer protective film in the first polarizing plate, Rth ₁ (λ) may be considered to be 0 in the above formula (1).

  The laminated polarizing plate of the present invention can be formed by an appropriate method such as a method of sequentially laminating a retardation film and a polarizing plate in the course of manufacturing a liquid crystal display device, or a method of using it as a laminate in advance. The latter pre-lamination method has advantages such as excellent quality stability and laminating workability, and can improve the manufacturing efficiency of the liquid crystal display device.

  As a method for producing a negative uniaxial optical film having an optical axis in the plane, it is preferable to produce a material having negative molecular polarizability anisotropy by uniaxial stretching. The azimuth of the slow axis can be controlled depending on whether the longitudinal uniaxial stretching or the transverse uniaxial stretching is performed. In general, a polarizing plate is continuously produced by longitudinal uniaxial stretching, and an absorption axis exists in a direction perpendicular to the film width direction in the film plane. Therefore, the laminated polarizing plate forming the liquid crystal display device of the present invention can be easily formed by controlling the slow axis direction of a negative substantially uniaxial optical film having an optical axis in the plane and laminating with a roll-to-roll. Can be formed. Further, as a material having a negative molecular polarizability anisotropy, for example, a polymer liquid crystal, which has been subjected to an alignment treatment, or a polymerized liquid crystal which has been aligned and then cured can be used as the optical film of the present invention. Also good.

  When laminating the polarizing plate and the optical film, they can be fixed via an adhesive or the like as necessary. From the standpoint of preventing axial misalignment, it is preferable to bond and fix. For the adhesion, for example, a transparent adhesive such as polyvinyl alcohol, modified polyvinyl alcohol, organic silanol, acrylic or silicone, polyester or polyurethane, polyether or rubber can be used. There is no particular limitation on. From the standpoint of preventing changes in optical properties, those that do not require high-temperature processes during curing and drying are preferred, and those that do not require long-time curing or drying treatments are desirable. Moreover, what does not produce peeling | exfoliation etc. on heating or humidification conditions is preferable.

  When triacetyl cellulose (TAC) is used as the protective film for the polarizing layer, TAC and retardation film adhesives include butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate and ( An acrylic pressure-sensitive adhesive composed of an acrylic polymer having a weight average molecular weight of 100,000 or more and a glass transition temperature of 0 ° C. or less, which contains a monomer such as (meth) acrylic acid, can be particularly preferably used. An acrylic pressure-sensitive adhesive is also preferable from the viewpoint of excellent transparency, weather resistance, heat resistance, and the like.

  Adhesives may be appropriately selected from fillers and pigments made of natural or synthetic resins, glass fibers and glass beads, metal powders and other inorganic powders, colorants, antioxidants, and the like as required. Additives can also be blended. In addition, each layer such as the above polarizer, retardation film, polarizing plate protective film, adhesive layer is, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc. An ultraviolet absorbing function can be provided by a method of treating with an ultraviolet absorber.

  The method for producing the liquid crystal display device of the present invention may be a normal method. That is, the liquid crystal display device is formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate, an optical film, and an illumination system as necessary, and incorporating a drive circuit.

  The forming parts of the liquid crystal display device may be laminated and integrated, or may be in a separated state. In forming the liquid crystal display device, for example, appropriate optical elements such as a diffusion plate, an antiglare layer, an antireflection film, a protective layer, a protective plate, and a color filter can be appropriately disposed.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
(Evaluation method)
The material characteristic values and the like described in the present specification are obtained by the following evaluation methods.
(1) Measurement of retardation value Γ (λ) (nm), Rth (λ) value (nm), Nz Phase difference Γ (λ) value, Rth (λ), which is the product of birefringence Δn and film thickness d ) And Nz were measured by a trade name “M150” manufactured by JASCO Corporation, which is a spectroscopic ellipsometer. The Γ value was measured with the incident light beam and the film surface orthogonal. In addition, the Nz and Rth values are obtained by measuring the phase difference value at each angle by changing the angle between the incident light beam and the film surface, and by curve fitting with a known refractive index ellipsoidal expression, It calculated _| required by calculating _| requiring a certain _nx , _ny , _nz and substituting into following formula (7), (12).
_{Nz = (n x -n z)} / (n x -n y) (7)
Rth (λ) = {(n _x + _ny ) / 2−n _z } × d (12)

(2) Preparation method 1 of a substantially uniaxial optical film
A copolymer polycarbonate having a fluorene skeleton was used as the resin material for the optical film. The polymerization of the polycarbonate was performed by an interfacial polycondensation method using a known phosgene. A reaction vessel equipped with a stirrer, a thermometer and a reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and the monomers [A] and [B] having the following structures were dissolved in a molar ratio of 86:14 in this, A small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown in at about 20 ° C. over about 60 minutes. Further, p-tert-butylphenol was added to emulsify, and then triethylamine was added and stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was collected, and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost the same as the charged amount ratio.
This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid concentration of 18% by weight. A cast film was produced from this dope solution to obtain an unstretched film. The residual solvent amount of this unstretched film was 0.9% by weight. A negative substantially uniaxial optical film having an in-plane optical axis is obtained by setting this film to a stretching temperature of 225 ° C. and setting the stretching ratio so that the retardation value shown in Table 1 can be obtained and uniaxially stretching. Obtained. Similarly, a stretching ratio was set so that the retardation values shown in Table 1 were obtained, and biaxial stretching was performed to obtain a positive substantially uniaxial optical film having an optical axis in the thickness direction.

(3) Method 2 for producing a positive substantially uniaxial optical film having an optical axis in the thickness direction
Polystyrene and polyphenylene oxide were adjusted to a weight ratio of 74.5 to 25.5, respectively, and dissolved in a chloroform solvent to prepare a dope solution having a concentration of 23% by weight. A cast film was produced from this dope solution to obtain an unstretched film. The residual solvent amount of this unstretched film was 1.4% by weight. The film was stretched at a stretching temperature of 130 ° C. and biaxially stretched to produce a positive substantially uniaxial optical film having an optical axis in the thickness direction used in Example 2.

[Examples 1-2]
In the liquid crystal display device having the structure shown in FIG. 4, the in-plane retardation values of the negative substantially uniaxial optical film having the optical axis in the plane and the liquid crystal cell in the black state are respectively represented by Γ ₁ (λ), Γ _LC (λ), the thickness direction retardation value of a positive substantially uniaxial optical film having an optical axis in the thickness direction as Rth _POC, and changing each value as shown in Table 1, normally black mode The incident angle dependence of the transmittance (degree of light leakage) at wavelengths of 450, 550, and 650 nm in the black state of the IPS liquid crystal cell was calculated and compared with an actual liquid crystal display device. The positive substantially uniaxial optical films having optical axes in the thickness direction of Examples 1 and 2 were produced by the production methods 1 and 2, respectively. The in-plane retardation value of these positive substantially uniaxial optical films having an optical axis in the thickness direction is 2 nm. Moreover, the negative substantially uniaxial optical film which has an optical axis in a surface was produced by the said preparation method 1 in both Examples 1 and 2, and Nz value is 0.

  Here, the purpose is to enlarge the viewing angle and suppress the color shift, and in order to show the effect, the result of calculating the wavelength dependence of the transmittance when the azimuth is changed at a polar angle of 60 ° will be shown. . The calculation conditions of Examples 1-2 are shown in Table 1, and the results correspond to FIGS. In Table 1, Rth (λ) of 0 means that the protective film for polarizing layer is not used. In this calculation, the measurement data of the optical film produced by the above production methods 1 and 2 were used for the retardation wavelength dispersion and retardation value of this optical film.

  Regarding the retardation wavelength dependence of the liquid crystal cell, the retardation wavelength dispersion of the liquid crystal cell of the product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available normally black mode and IPS mode liquid crystal television, was measured. They were used for the calculation. The polarization degree of the polarizing plate was 100%, and the transmittance of each polarizing plate was 50%. The definition of the azimuth is shown in FIG.

  From the above calculation results, the transmittance at 550 nm, which has the highest human eye visibility, is low, less than 0.2%, and the transmittance at all three wavelengths is less than 1%. It can be seen that the system has been realized. In addition, it can be seen that the wavelength 450 nm, which is the wavelength representative of the three primary colors of light, is always large with respect to the change in azimuth, and the color change such as blue and red does not occur depending on the azimuth. This result indicates that the color tone hardly changes depending on the azimuth angle, and indicates that the color shift is greatly suppressed.

  Actually, the calculation described in Table 1 was performed using a liquid crystal cell having a product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television having substantially the same retardation value as the liquid crystal cells of Examples 1 and 2. A liquid crystal display device having the same configuration and each phase difference value was produced, and the viewing angle and color shift in the black state were confirmed by visual observation. It was confirmed that the color shift was extremely small. It was also found that these liquid crystal display devices have little color shift even in halftone and white display.

[Example 3]
As in Examples 1-2, in the liquid crystal display device having the structure shown in FIG. 7, a negative substantially uniaxial optical film having an in-plane optical axis, a liquid crystal cell in a black state, and an optical axis in the thickness direction The parameters relating to the retardation value of the positive substantially uniaxial optical film having polarizing plate and the protective film for polarizing layer are set as shown in Table 1, and the wavelengths in the black state of the normally black mode IPS liquid crystal cell are 450, 550, and 650 nm. The incident angle dependence of the transmittance (the degree of light leakage) was calculated and compared with an actual liquid crystal display device. In this calculation, the measurement data of the optical film made of the polycarbonate copolymer polymerized by the production method 1 was used for the retardation wavelength dispersion and retardation value of these optical films. Moreover, the phase difference wavelength dispersion of the liquid crystal cell of the product name "W32-L7000" by Hitachi, Ltd. which is a commercially available liquid crystal television was measured, and they were used for calculation. Further, the Nz value of a negative substantially uniaxial optical film having an optical axis in the plane is 0, and the in-plane retardation value of a positive substantially uniaxial optical film having an optical axis in the thickness direction is 3 nm. The protective film for a polarizing layer is produced by a solution casting method using methylene chloride as a solvent, and the in-plane retardation value is 3 nm.

  The results are shown in FIG. The transmittance of 550 nm, which has the highest visual sensitivity of the human eye, is as low as less than 0.1%, and the transmittance at all three wavelengths is less than 1%, and a wide viewing angle can be realized. Recognize. In addition, it can be seen that the wavelength 450 nm, which is the wavelength representative of the three primary colors of light, is always large with respect to the change in azimuth, and the color change such as blue and red does not occur depending on the azimuth. Further, it can be seen that the difference in the azimuth angle dependency of the incident angle depending on the wavelength is remarkably small as compared with a comparative example described later. This result indicates that the color tone hardly changes depending on the azimuth angle, and indicates that the color shift is greatly suppressed.

  Next, using a liquid crystal cell having a product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available normally black mode and IPS mode liquid crystal television having substantially the same retardation value as the calculated liquid crystal cell, Table 1 A liquid crystal display device having the same configurations and phase difference values as those described above was actually manufactured, and the viewing angle and the color shift in the black state were confirmed by visual inspection. It was confirmed that the color shift was remarkably small with a wide viewing angle. It was also found that this liquid crystal display device has little color shift even in halftone and white display.

[Example 4]
Using the product name “W28-L5000” manufactured by Hitachi, Ltd., which is a commercially available normally black mode and IPS mode liquid crystal television as the liquid crystal cell used for the calculation and the liquid crystal cell used for the actual measurement, the configuration of FIG. Evaluation was performed in the same manner as in Example 1 except that the measured value of the optical film produced by the production method 1 was used as the substantially uniaxial optical film. The negative substantially uniaxial optical film having an optical axis in the plane has an Nz value of 0, and the positive substantially uniaxial optical film having an optical axis in the thickness direction has an in-plane retardation value of 2 nm.
The calculation results are shown in FIG. It can be seen that the transmittance is remarkably reduced at all three wavelengths as compared to a comparative example described later.

  Next, using a liquid crystal cell having a product name “W28-L5000” manufactured by Hitachi, Ltd., which is a commercially available normally black mode and IPS mode liquid crystal television having substantially the same retardation value as that of the calculated liquid crystal cell. A liquid crystal display device having the same configurations and phase difference values as those shown in Table 1 was prepared in the same manner as 1 and the viewing angle and color shift in the black state were visually confirmed. As with the results, it was confirmed that the viewing angle was wide and the color shift was remarkably small. It was also found that this liquid crystal display device has little color shift even in halftone and white display.

[Comparative example]
Using the liquid crystal cell used in the product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television, the wavelength dependence of the transmittance obtained by calculation in the same manner as in the example in the configuration of FIG. The results are shown in FIG. The physical property values used for the calculation are shown in Table 1. The definition of the azimuth angle is shown in FIG.

  From FIG. 12, it can be seen that the transmittance is large and the azimuth angle dependency is large regardless of the wavelength. The liquid crystal display device was visually checked for black viewing angle and color shift. When viewed from an oblique direction, depending on the azimuth angle, black changed to blue or red, and it was found that the color shift was very large compared to the example.

  The liquid crystal display device of the present invention is excellent in display quality, particularly viewing angle performance, and is useful for, for example, a liquid crystal television, a liquid crystal monitor, a display for mobile terminals, a display for mobile phones, a display for car navigation, and the like.

It is an example of the schematic of the liquid crystal display device of the normally black mode in-plane switching system of this invention. It is an example of a structure optically substantially equivalent to the normally black mode in-plane switching type liquid crystal display device of the present invention. It is a figure explaining the orthogonal coordinate for the definition of the three-dimensional refractive index of the phase difference film in this invention. FIG. 3 is a layout diagram of optical elements of liquid crystal display devices in Examples 1 and 2. It is the figure which showed the azimuth and wavelength dependence of the transmittance | permeability of the incident light of the polar angle of 60 degrees in Example 1. FIG. It is the figure which showed the azimuth and wavelength dependence of the transmittance | permeability of the incident light of the polar angle of 60 degrees in Example 2. FIG. FIG. 6 is a layout diagram of optical elements of a liquid crystal display device in Example 3. It is the figure which showed the azimuth and wavelength dependence of the transmittance | permeability of the incident light of the polar angle of 60 degrees in Example 3. FIG. 10 is a layout diagram of optical elements of a liquid crystal display device in Example 4. It is the figure which showed the azimuth and wavelength dependence of the transmittance | permeability of the incident light of the polar angle of 60 degrees in Example 4. It is an arrangement view of optical elements of a liquid crystal display device in a comparative example. It is the figure which showed the azimuth and wavelength dependence of the transmittance | permeability of the incident light of the polar angle of 60 degrees in a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st polarizing plate 2 IPS mode liquid crystal cell 3 Negative substantially uniaxial optical film 4 which has an optical axis in the surface 4 Positive substantially uniaxial optical film 5 which has an optical axis in thickness direction 2nd polarization Plate 6 Absorption axis 7 of polarizing plate Slow axis 8 in plane of retardation film Slow axis 9 in plane of IPS mode liquid crystal cell in black state Light 10 emitted from light source and incident on liquid crystal display 1 polarizing plate 11 positive substantially uniaxial optical film 12 having an optical axis in a plane that can be regarded as equivalent to a combination of a negative substantially uniaxial optical film having an optical axis in the plane and an IPS mode liquid crystal cell. Positive substantially uniaxial optical film 13 having an optical axis in the length direction Second polarizing plate 14 Absorption axis 15 of polarizing plate Slow axis 30 in phase of retardation film Retardation film (optical film)
31 Surface 41 of retardation film Second polarizing plate 42 Positive substantially uniaxial optical film 43 having an optical axis in the thickness direction Negative substantially uniaxial optical film 44 having an optical axis in the plane IPS liquid crystal cell 45 First polarizing plate 46 Absorption axis 47 of polarizing plate Slow axis 48 in plane of retardation film Slow axis 49 in plane of IPS liquid crystal cell in black state Light emitted from light source and incident on liquid crystal display device 55 Polarity 60 ° in the black state of the liquid crystal display device of Example 1 and transmittance at a wavelength of 450 nm 56 Polarity in the black state of the liquid crystal display device of Example 1 at 60 ° and transmittance at a wavelength of 550 nm 57 Liquid crystal of Example 1 Polarity 60 ° in the black state of the display device and transmittance 61 at a wavelength of 650 nm 61 in the black state of the liquid crystal display device of Example 2 Transmittance 62 at a wavelength of 450 nm Polarity 60 in the black state of the liquid crystal display device of Example 2 and transmittance 63 at a wavelength of 550 nm Polarity 60 in the black state of the liquid crystal display device of Example 2 and transmittance 71 at a wavelength of 650 nm 71 Second polarizing plate 72 Polarization Layer protective film 73 Positive substantially uniaxial optical film 74 having an optical axis in the thickness direction Negative substantially uniaxial optical film 75 having an optical axis in the plane IPS mode liquid crystal cell 76 Polarizing layer protective film 77 First polarizing plate 78 Light emitted from the light source and incident on the liquid crystal display device Absorption axis 80 of the polarizing plate Slow axis 81 in the plane of the protective film for the polarizing layer Slow axis 82 in the plane of the retardation film In-plane slow axis 85 of liquid crystal cell of IPS mode in black state Transmittance 86 at polar angle 60 °, wavelength 450 nm in black state of liquid crystal display device of Example 3 Liquid crystal display device of Example 3 Transmittance 87 at a polar angle of 60 ° and a wavelength of 550 nm in the black state of the device. Transmittance 91 at a polar angle of 60 ° and a wavelength of 650 nm in the black state of the liquid crystal display device of Example 3 First polarizing plate 92 Liquid crystal cell 93 in IPS mode Negative substantially uniaxial optical film 94 having an optical axis in the plane Positive substantially uniaxial optical film 95 having an optical axis in the thickness direction Second polarizing plate 96 Absorption axis 97 of polarizing plate Surface of retardation film Slow axis 98 in the IPS mode liquid crystal cell in the black state In the plane of the slow axis 99 Light 101 emitted from the light source and incident on the liquid crystal display device Polar angle 60 in the black state of the liquid crystal display device of Example 4 °, transmittance at a wavelength of 450 nm 102 polar angle in the black state of the liquid crystal display device of Example 4 60 °, transmittance at a wavelength of 550 nm 103 black state of the liquid crystal display device of Example 4 Transmittance at polar angle of 60 ° and wavelength of 650 nm 111 Polarizing plate 112 IPS liquid crystal cell 113 Polarizing plate 114 Light emitted from light source in comparative example and incident on liquid crystal display device 115 Absorption axis 116 of polarizing plate IPS liquid crystal in black state The slow axis 121 in the plane of the cell The transmittance of the liquid crystal display device of the comparative example at a polar angle of 60 ° in the black state and a wavelength of 450 nm 122 The transmittance of the liquid crystal display device of the comparative example at a polar angle of 60 ° and a wavelength of 550 nm 123 Transmittance at a polar angle of 60 ° and a wavelength of 650 nm in the black state of the liquid crystal display device of the comparative example

Claims (7)

  The order of the first polarizing plate, the liquid crystal cell, the negative substantially uniaxial optical film having the optical axis in the plane, the positive substantially uniaxial optical film having the optical axis in the thickness direction, and the second polarizing plate. In the normally black mode in-plane switching mode liquid crystal display device in which these are laminated, the angle formed between the absorption axis of the first polarizing plate and the in-plane slow axis of the liquid crystal cell in the black state is approximately 90 °, the angle formed by the in-plane slow axis of the liquid crystal cell and the slow axis of the negative approximately uniaxial optical film is approximately 90 °, the slow axis of the negative approximately uniaxial optical film and the second polarization A liquid crystal display device having an angle of about 90 ° with the absorption axis of the plate. The in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, and the positive substantially uniaxial optical film has a thickness direction retardation value. Rth _POC , and when the first and second polarizing plates each have a polarizing layer protective film on the liquid crystal cell side, the retardation value in the thickness direction of the polarizing layer protective film is set to Rth ₁ ( _2. The liquid crystal display device according to claim 1, wherein the relationship of the following formulas (1) and (2) is satisfied when λ) and Rth ₂ (λ):
90 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <200 nm (1)
−180 <Rth _POC (λ) + Rth ₂ (λ) <− 40 nm (2)
(However, λ = 550 nm) The in-plane retardation values of the negative substantially uniaxial optical film and the liquid crystal cell in the black state are Γ ₁ (λ) and Γ _LC (λ), respectively, and the retardation value in the thickness direction of the positive substantially uniaxial optical film. 3. The liquid crystal display device according to claim 1, wherein when Rth _POC is satisfied, a relationship of the following formulas (3) and / or (4) is satisfied.
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (3)
| Rth _POC (λ ₁ ) | <| Rth _POC (λ ₂ ) | (4)
(However, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.)   The negative substantially uniaxial optical film which has an optical axis in the surface used for the liquid crystal display device in any one of Claims 1-3.   A positive substantially uniaxial optical film having an optical axis in the thickness direction used for the liquid crystal display device according to claim 1.   6. The optical film according to claim 4 or 5, comprising a polycarbonate having a fluorene skeleton.   A laminated polarizing plate in which the optical film according to claim 4 or 5 and a polarizing plate are integrated, a negative substantially uniaxial optical film having an optical axis in a plane, a positive having an optical axis in the thickness direction. These are laminated in the order of a substantially uniaxial optical film and a polarizing plate, and the angle formed by the slow axis of the negative substantially uniaxial optical film having an in-plane optical axis and the absorption axis of the polarizing plate. Is a laminated polarizing plate characterized by being approximately 90 °.

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