JP4778718B2 - Liquid crystal display device and negative substantially uniaxial optical film used therefor - Google Patents

Description

  The present invention relates to a liquid crystal display device excellent in viewing angle characteristics and an optical film used therefor.

  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 had a wide viewing angle without using a retardation film for widening the viewing angle, it has a wide range based on the 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 described in Non-Patent Documents 1 and 2, when these methods are used to expand the viewing angle of an IPS mode liquid crystal display device, the color shift of transmitted light at the time of oblique incidence of black display is one. It turns out to be a problem. The color shift of the transmitted light at the time of black incident here means that, when the liquid crystal display device at the time of black display is observed from an oblique direction rather than a normal direction, the transmittance has wavelength dependency, As a result, it means that the color of black changes depending on the viewing angle. In general, what causes a color shift when the black display is obliquely incident causes a color shift problem even in a halftone display. 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. Non-Patent Document 1 describes a biaxial optical film, but does not disclose the relationship between the retardation value of the liquid crystal cell and the retardation value of the biaxial optical film. Similarly, in Non-Patent Document 2, the relationship between the liquid crystal cell and the retardation film is not disclosed.

  Further, since the biaxial optical film and the positive uniaxial C plate described in Non-Patent Documents 1 and 2 are complicated in manufacturing method, the optical axis accuracy and phase difference accuracy can be obtained in a large area. Has the problem of being difficult. 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 a novel liquid crystal display device of IPS mode having a wide viewing angle and wide bandwidth.

  Another object of the present invention is to design an IPS mode liquid crystal display device by using a specific negative substantially uniaxial optical film having an optical axis in a plane in which optical axis accuracy and phase difference accuracy are obtained, An object of the present invention is to provide a liquid crystal display device having a wide viewing angle and a wide band.

  A negative substantially uniaxial optical film having an optical axis in the plane can be obtained, for example, by forming a polymer material having a negative molecular polarizability anisotropy into a film and performing a normal uniaxial stretching process. The manufacturing process is very simple, and the optical anisotropy uniformity required for liquid crystal televisions is excellent.

  Optical design using this optical film and intensive study on the method of widening the viewing angle of the IPS mode liquid crystal display device. Even if the phase difference value of the liquid crystal cell changes due to the design convenience, it has a wide viewing angle and wide bandwidth. It has been found that a certain IPS mode liquid crystal display device can be realized.

Specifically, the first polarizing plate, the first negative substantially uniaxial optical film having an optical axis in the plane, the liquid crystal cell, and the second negative substantially uniaxial optical having an optical axis in the plane. The first negative substantially uniaxial optical film in which the absolute value of the in-plane retardation value of the liquid crystal cell has an optical axis in the plane is formed by laminating the film and the second polarizing plate in this order. A normally black mode in-plane switching mode liquid crystal display device having an absolute value greater than the absolute value of the retardation value of the first polarizing plate, wherein the absorption axis of the first polarizing plate and the first negative substantially uniaxial optical film are in- plane The angle formed by the slow axis in the liquid crystal cell is approximately 0 °, and the angle formed by the slow axis in the plane of the first negative substantially uniaxial optical film and the in- plane slow axis of the liquid crystal cell in the black state is approximately 90 degrees. °, and the slow axis in the plane of the negative substantially uniaxial optical film in-plane slow axis and a second liquid crystal cell in a black state The angle formed between the slow axis in the plane of the second negative substantially uniaxial optical film and the absorption axis of the second polarizing plate is approximately 0 °; The in-plane retardation values of the negative 1 uniaxial optical film, the liquid crystal cell in the black state, and the second negative uniaxial optical film are Γ ₁ (λ), Γ _LC (λ), Γ, respectively. ₂ (λ) (nm) is achieved by a liquid crystal display device characterized by satisfying the relationship of the following formulas (1) and / or (2).
| Γ ₂ (λ ₁₎ | <| Γ ₂ (λ ₂ ) | (1)
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (2)
(However, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.)
Preferably, the relationship of the above formulas (1) and (2) is satisfied at the same time.

In the present invention, an optically anisotropic film having refractive index anisotropy is referred to as 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 we consider the orthogonal coordinate system axes are parallel or perpendicular to the surface of the film as shown in FIG. 3, defines three refractive index corresponding to the orientation of the coordinate n _x, n _y, and n _z. In addition, when the optical axis is in the plane, the x-axis is set, and when the optical axis is in the film thickness direction, the negative substantially uniaxial optical film having the optical axis in the plane is using refractive index, next _{n z ≒ n y> n x} , n y is the slow axis in the film plane. All three biaxial optical films are defined as having different refractive indexes. 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, and in this definition, n _x = n _y < _nz .

Further, the retardation value Γ of the negative substantially uniaxial optical film and the positive substantially uniaxial optical film having an in-plane optical axis in the present invention is defined by the following formula (17). .
_{Γ = (n x -n y)} × d (17)
Here, d is the thickness (nm) of the film.

Negative substantially uniaxial optical film having an in-plane optical axis in the present invention are accurate to preferably those satisfying the relation of _{n z = n y> n x} , with n _z ≒ n _y> n _x 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 negative substantially uniaxial is defined using the following formula (18) using these three refractive indexes.
_{Nz = (n x -n z)} / (n x -n y) (18)

What is a negative substantially uniaxial optical film having an optical axis in a plane in the present invention?
0.90 <Nz <1.40 (19)
Is preferably defined as
0.95 <Nz <1.35 (20)
And more preferably
0.97 <Nz <1.20 (21)
And more preferably
0.98 <Nz <1.10 (22)
It is.

  Since the optical axis is a negative substantially uniaxial optical film, the in-plane fast axis coincides with the optical axis.

Rth is defined by the following formula (23).
_{Rth = {(n x + n} y) / 2-n z} × d (23)
In the above formula (23), d is the thickness (nm) of the optical film. In the present invention, the phase difference value Γ, Rth, and Nz values are measured at a wavelength of 550 nm unless otherwise specified.

  Further, it is necessary that the optical axis alignment angle between the optical anisotropic elements is the above-mentioned angle, but the allowable range is within ± 3 °, preferably within ± 2 °, centered on the set angle. More preferably, it is within ± 1 °, and further preferably within ± 0.5 °. That is, the expression of approximately 90 ° is defined as 90 ° ± 3 °.

  The black state in the present invention is the darkest state in gradation display, and specifically, the state in which the transmittance measured when light is incident from the normal direction of the surface of the liquid crystal display device is the black state. It is defined as

  The wide viewing angle of the liquid crystal display device according to the present invention means that the phenomenon that the contrast changes depending on the viewing angle is improved, and the angular region with 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. Further, broadening means that the transmittance is as close to 0 as possible regardless of the incident angle even if the wavelength is changed, thereby suppressing the color shift described above.

The reason why a wide viewing angle and a wide band can be realized by the present invention will be described below.
A preferred configuration example of the liquid crystal display device of the present invention is shown in FIG. With reference to FIG. 1, the principle of wide viewing angle and wide band according to the present invention will be described. 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 of the present invention is in the IPS mode, the liquid crystal cell can be regarded as a positive uniaxial medium having an in-plane optical axis during black display. The first negative substantially uniaxial optical film having an optical axis in the plane and the optical axis orientation of the liquid crystal cell coincide with each other, and the absolute value of the in-plane retardation value of the liquid crystal cell is more in-plane. The combination of the two elements has an optical axis in the plane shown in FIG. 2 under the condition that it is larger than the absolute value of the retardation value of the first negative substantially uniaxial optical film having the optical axis at It can be regarded as optically substantially equivalent to the positive substantially uniaxial optical film (11).

  Therefore, the wide viewing angle in the liquid crystal display device according to the present invention is first examined with a wide viewing angle and a wide band in the configuration of FIG. 2, and based on the result, the optical anisotropic medium used in the present invention is optimized. Thus, it is only necessary to obtain a correct phase difference value and its relationship.

Realizing a wide viewing angle and a wide band 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. Surprisingly, as a result of investigation, the two substantially uniaxial optical films in FIG. 2 are not compensated for each other in wavelength dispersion of the respective retardations. It has been found that the chromatic dispersion of the phase difference value needs to be at least one, preferably both have a broad band. 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 phase difference value Γ (λ) be monotonously increased with respect to the wavelength. Preferably, the following formula (5 In other words, it can be said to be close to the state of).
Γ (λ) / λ = C (5)
Here, Γ (λ) is the phase difference value (nm) at the measurement wavelength λ, λ is in the range of 400 to 700 nm, and C is a constant.

Accordingly, the phase difference values of the negative substantially uniaxial optical film having the optical axis in the plane and the positive substantially uniaxial optical film having the optical axis in the plane in FIG. 2 are respectively represented by Γ ₃ (λ), Γ _{In the case of 4} (λ), it is necessary to satisfy the following formula (6) and / or (7).

| Γ ₃ (λ ₁ ) | <| Γ ₃ (λ ₂ ) | (6)
| Γ ₄ (λ ₁ ) | <| Γ ₄ (λ ₂ ) | (7)
Here, λ represents a measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.
Preferably, the following formulas (6) and (7) are satisfied at the same time.

Next, when the optimum retardation value was examined, it was found that it was preferable that the following expressions (8) and (9) were satisfied at the same time. By satisfying the following formulas (8) and (9), the transmittance can be less than 1% when the incident angle of incident light is in the range of polar angle 0 to 80 ° and azimuth angle 0 to 360 °. . In the case of a pair of orthogonal polarizing plates, the transmittance obtained under the same condition is about 3% at the maximum, and the IPS liquid crystal cell is absorbed between the optical axis and the polarizing plate between the pair of orthogonal polarizing plates. In the configuration in which the axes coincide with each other, the maximum transmittance is about 2%.
−155 <Γ ₃ (λ) <− 45 nm (8)
45 <Γ ₄ (λ) <155 nm (9)
Here, λ = 550 nm.

More preferably, the following expressions (10) and (11) are satisfied at the same time. In this case, the incident light is transmitted in the range of the polar angle of 0 to 80 ° and the azimuth angle of 0 to 360 °. The rate can be less than about 1.5%.
−130 <Γ ₃ (λ) <− 60 nm (10)
60 <Γ ₄ (λ) <130 nm (11)
However, λ = 550 nm.

More preferably, the following expressions (12) and (13) are satisfied at the same time. In this case, the incident light is transmitted within the range of the polar angle of 0 to 80 ° and the azimuth angle of 0 to 360 °. The rate can be less than about 0.5%.
−120 <Γ ₃ (λ) <− 70 nm (12)
70 <Γ ₄ (λ) <120 nm (13)
However, λ = 550 nm.

Even more preferably, the following expressions (14) and (15) are satisfied at the same time. In this case, the incident angle of incident light is within a range of polar angles 0 to 80 ° and azimuth angles 0 to 360 °. The transmittance can be less than about 0.2%.
−110 <Γ ₃ (λ) <− 80 nm (14)
80 <Γ ₄ (λ) <110 nm (15)
However, λ = 550 nm.

Most preferably, the following expressions (16) and (17) are satisfied at the same time. In this case, the incident light is transmitted in the range of the polar angle of 0 to 80 ° and the azimuth angle of 0 to 360 °. The rate can be less than about 0.1%.
−105 <Γ ₃ (λ) <− 85 nm (16)
85 <Γ ₄ (λ) <105 nm (17)
However, λ = 550 nm.

  Although the optimum value varies somewhat depending on the refractive index of the optical film to be used, it is preferable that the above relationship is satisfied.

As described above, it is newly found from the comparison of the configurations of FIGS. 1 and 2 that the following expressions (18) and (19) only need to be satisfied in order for both to be equivalent.
Γ ₃ (λ) = Γ ₂ (λ) (18)
Γ ₄ (λ) = Γ _LC (λ) + Γ ₁ (λ) (19)

  As described above, the reason why the above formula (19) 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 optical axes are arranged in parallel to each other, both can be optically regarded as one uniaxial medium. Here, when the refractive indexes of all anisotropic media are equal, the above formulas (18) and (19) are completely equal, but in general, the material used as an optically anisotropic medium in a liquid crystal display device is Even if it is an organic substance and the refractive index does not differ greatly even if the materials are different, there are few problems in practical use even if they are regarded as being almost equal. If the above expressions (18) and (19) are satisfied at the same time, the configurations of FIGS. Can be considered optically equivalent.

On the other hand, the polarizing plate in the present invention includes a polarizing layer alone or a form in which a protective film for the polarizing layer is provided in contact with one or both sides of the polarizing layer to protect the 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 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 become optically substantially equal, it turned out that the relationship of said Formula (18), (19) substantially satisfy | fills following Formula (20) and (21).
Γ ₃ (λ) ≈Γ ₂ (λ) + Rth ₂ (λ) (20)
Γ ₄ (λ) ≈Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) (21)

Here, Rth ₁ (λ) and Rth ₂ (λ) are the retardation value in the thickness direction of the protective film (for the polarizing layer) in the first polarizing plate in FIG. Represents the retardation value in the thickness direction of the protective film (for the layer). According to the definition of the optical anisotropy of the present invention described later, the value of Rth (λ) of the protective film is positive. On the other hand, the anisotropy of a negative substantially uniaxial optical film having an in-plane optical axis is negative. Therefore, since both cancel out anisotropy, the values of Γ ₁ (λ) and Γ ₂ (λ) are as compared with the case where Γ _LC (λ) is constant and this protective film is not provided. The relationship between the above formula (18) and the above formula (20) and the relationship between the above formula (19) and the above formula (21) indicate that it is necessary to increase the absolute value by Rth (λ). . Note that Rth ₁ (λ) and Rth ₂ (λ) are considered to be 0 when the polarizing plate has no protective film for the polarizing layer.

Therefore, from the relationship between the above formulas (8) and (9) and the above formulas (20) and (21), in order to realize a wide viewing angle in the liquid crystal display device of the present invention, the following formulas (3) and (3) It is derived that it is preferable to satisfy 4) at the same time.
−155 <Γ ₂ (λ) + Rth ₂ (λ) <− 45 nm (3)
45 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <155 nm (4)
(However, λ = 550 nm)

  In general, the phase difference of the liquid crystal cell in the normally black mode in-plane switching mode liquid crystal display device is usually about one-half wavelength or more, which is determined in consideration of the luminance and response speed. The Since the liquid crystal display device of the present invention can be regarded as being all made of a uniaxial medium having an optical axis in the plane, even if the phase difference of the liquid crystal cell changes due to the convenience of design, the above formulas (3), ( If 4) is satisfied, it is possible to obtain a liquid crystal display device with a wide viewing angle and a wide band, which is an excellent point not found in other methods.

  According to the present invention, in a normally black mode in-plane switching mode (IPS) liquid crystal display device, (1) the phase difference value of one negative uniaxial optical film having an optical axis in the plane and IPS Satisfying the relationship that the total phase difference absolute value with the in-plane retardation value in the black state of the liquid crystal cell increases as the wavelength increases, and (2) negative approximately 1 having an in-plane optical axis. Since one of the axial optical films satisfies at least one of the characteristics that the in-plane retardation absolute value increases as the wavelength increases, a liquid crystal display device having a wide viewing angle and a wide bandwidth is provided. Can be provided. Therefore, the liquid crystal display device of the present invention optically designed using a negative substantially uniaxial optical film having an in-plane optical axis without using a biaxial optical film has excellent image quality and high quality. Express performance.

In order to obtain the effect of the invention, the first polarizing plate, the first negative substantially uniaxial optical film having an optical axis in the plane, the liquid crystal cell, and the second negative having an optical axis in the plane. In a normally black mode in-plane switching mode liquid crystal display device in which a substantially uniaxial optical film and a second polarizing plate are laminated in this order, the optical axis is in-plane with the absorption axis of the first polarizing plate. The angle between the first negative substantially uniaxial optical film having the slow axis and the slow axis of the first negative substantially uniaxial optical film having the in-plane optical axis is black. A second negative substantially uniaxial optical film having an angle between an in-plane slow axis of the liquid crystal cell in a state of approximately 90 ° and an in-plane slow axis of the liquid crystal cell in the black state and an in-plane optical axis; Of the second negative polarizing plate and the second negative uniaxial optical film having an optical axis in the plane and an angle formed by the second polarizing plate An angle formed substantially 0 ° with, and,
The in-plane retardation value of the first negative substantially uniaxial optical film having an optical axis in the plane, the liquid crystal cell in the black state, and the second negative substantially uniaxial optical film having the optical axis in the plane is obtained. When Γ ₁ (λ), Γ _LC (λ), and Γ ₂ (λ) (nm) are satisfied, it is necessary to satisfy the relationship of the following formulas (1) and / or (2).
| Γ ₂ (λ ₁ ) | <| Γ ₂ (λ ₂ ) | (1)
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (2)
Here, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.
Preferably, the relationship of the above formulas (1) and (2) is satisfied at the same time.

The wavelength dispersion of the retardation absolute value of the second negative substantially uniaxial optical film having an optical axis in the plane preferably satisfies the following formulas (29) and (30) for the above formula (1). .
0.4 <Γ ₂ (450) / Γ ₂ (550) <0.98 (29)
1.01 <Γ ₂ (650) / Γ ₂ (550) <1.50 (30)

More preferably, the following expressions (31) and (32) are satisfied.
0.6 <Γ ₂ (450) / Γ ₂ (550) <0.95 (31)
1.03 <Γ ₂ (650) / Γ ₂ (550) <1.40 (32)

  In the above formulas (29) to (32), the number in () after Γ represents the measurement wavelength (nm).

The above formula (2) preferably satisfies the following formulas (33) and (34).
0.4 <(Γ _LC (450) + Γ ₁ (450)) / (Γ _LC (550) + Γ ₁ (550)) <0.98 (33)
1.01 <(Γ _LC (650) + Γ ₁ (650)) / (Γ _LC (550) + Γ ₁ (550)) <1.50 (34)

More preferably, the following expressions (35) and (36) are satisfied.
0.6 <(Γ _LC (450) + Γ ₁ (450)) / (Γ _LC (550) + Γ ₁ (550)) <0.95 (35)
1.03 <(Γ _LC (650) + Γ ₁ (650)) / (Γ _LC (550) + Γ ₁ (550)) <1.40 (36)

  In the above formulas (33) to (36), the number in () after Γ represents the measurement wavelength (nm) of the phase difference value.

In general, the retardation value of the liquid crystal cell decreases as the wavelength increases, and has a positive retardation value. Therefore, in order to satisfy the above formulas (2) and (33) to (36), 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 (2), it is preferable to satisfy the following formulas (37) and (38).
Γ _LC (450) / Γ _LC (550) <Γ ₁ (450) / Γ ₁ (550) (37)
Γ _LC (650) / Γ _LC (550)> Γ ₁ (650) / Γ ₁ (550) (38)

The phase difference value preferably satisfies the following expressions (3) and (4).
−155 <Γ ₂ (λ) + Rth ₂ (λ) <− 45 nm (3)
45 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <155 nm (4)
(However, λ = 550 nm)

More preferably, the following formulas (39) and (40) are satisfied.
130 <Γ ₂ (λ) + Rth ₂ (λ) <− 60 nm (39)
60 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <130 nm (40)
(However, λ = 550 nm)

More preferably, the following formulas (41) and (42) are satisfied.
−120 <Γ ₂ (λ) + Rth ₂ (λ) <− 70 nm (41)
70 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <120 nm (42)
(However, λ = 550 nm)

Even more preferably, the following expressions (43) and (44) are satisfied.
−110 <Γ ₂ (λ) + Rth ₂ (λ) <− 80 nm (43)
80 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <110 nm (44)
(However, λ = 550 nm)

Most preferably, the following expressions (45) and (46) are satisfied.
−105 <Γ ₂ (λ) + Rth ₂ (λ) <− 85 nm (45)
85 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <105 nm (46)
(However, λ = 550 nm)

  Each of the first and second negative substantially uniaxial optical films may be configured by laminating one sheet alone or two or more films as long as it has necessary characteristics. Each of them is preferable from the viewpoint of productivity because the thickness of the entire liquid crystal display device can be reduced, and a laminating process between films is unnecessary.

  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 no voltage is applied and a normally white mode in which black is displayed when applied are conceivable. However, in the IPS mode, it is difficult to control the disorder of liquid crystal alignment during voltage application. Therefore, in order to obtain high contrast, it is necessary to be in the normally black mode.

  The retardation value of the liquid crystal cell in the present invention is preferably 200 to 450 nm, more preferably 250 to 400 nm, still more preferably 270 to 390 nm. The phase difference value of the liquid crystal cell is a value (in-plane value) at the time of front incidence in a black 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.

  Examples of the material for the negative uniaxial optical film having an in-plane optical axis in the present invention include polycarbonate, polystyrene, syndiotactic polystyrene, amorphous polyolefin, polymer having norbornene skeleton, organic acid-substituted cellulose, and polyethersulfone. , Polyarylate, polyester, olefin maleimide, copolymerized olefin maleimide having a phenyl group, thermoplastic or curable polymer such as liquid crystalline polymer, or curable polymer that is cured after aligning the polymerizable liquid crystal, etc. A polymer having a negative molecular polarizability anisotropy is preferably used. These polymer materials are formed into a film and then uniaxially stretched to obtain a negative uniaxial optical film having an in-plane optical axis. A preferred material is 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.

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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、
で表わされる基である、）
で表わされる繰返し単位を含有するポリマーまたはポリマー混合物からなり、ここで該ポリマーおよびポリマー混合物は上記式（Ｉ）で表される繰返し単位をそれぞれポリマーまたはポリマー混合物の全繰返し単位の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。 As a preferred chemical structure of the polycarbonate having a fluorene skeleton, (A) 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-O— 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,
Is a group represented by
Wherein the polymer and the polymer mixture comprise 50 to 95 mol% of the repeating unit represented by the above formula (I), respectively, based on the total repeating unit of the polymer or polymer mixture. What is contained is preferable, More preferably, it is 60-95 mol%, More preferably, it is 70-90 mol%.

  These polycarbonate materials having a fluorene skeleton have excellent physical properties as a negative uniaxial optical film in terms of high glass transition temperature, handling and stretch moldability.

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 preferable polycarbonate materials 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%.

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:

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。

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. 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.

  In addition, an optically negative uniaxial compound whose absolute value of phase difference increases with increasing wavelength is a polymer or polymer mixture containing a repeating unit represented by the following formula (III). You can also list things. 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%. 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%.

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、

Here, R ₄₀ and R ₄₁ each represent 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 polymers and polymer mixtures can be produced by known methods. Polycarbonate is suitably produced by a polycondensation method of a dihydroxy compound and phosgene, a melt polycondensation method, a solid phase polymerization method or the like. In the case of blends, compatible blends are preferred, but even if they are not completely compatible, it is possible to suppress light scattering between components and improve transparency by matching the refractive index between components.

  As a preferable material for the second negative uniaxial optical film having an optical axis in the plane, a blend of polyphenylene oxide and polystyrene can be used in addition to the above materials. The stereoregularity of polystyrene may be any of atactic, syndiotactic and isotactic. Depending on the blend ratio, a blend of polyphenylene oxide and polystyrene can be produced that is optically negative uniaxial and whose phase difference absolute value monotonously increases with respect to the wavelength.

  In the negative substantially uniaxial optical film having an optical axis in the plane, an ultraviolet absorber such as phenyl salicylic acid, 2-hydroxybenzophenone, triphenyl phosphate, a bluing agent for changing the color, an oxidation An inhibitor or the like may be contained.

  The thickness of the negative substantially uniaxial optical film having an optical axis in the plane is preferably 1 μm to 400 μm. In addition, the optical film and retardation film in the present invention are used in the meaning including any of “sheet” and “plate”. 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.

  The polarizing plate is generally provided with a film used in contact with the polarizing layer to protect the polarizing layer as described above (hereinafter sometimes referred to as a protective film for a polarizing layer or simply a protective film). For example, a film having a polarizing layer sandwiched between a pair of films made of cellulose acetate or the like is preferably used. As a polarizing layer which comprises a polarizing plate, the appropriate thing which can obtain the light of 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 the protective film for the polarizing layer is present, 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. is there. Rth 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. Protective films for the polarizing layer include polycarbonates, polystyrenes, syndiotactic polystyrene, amorphous polyolefins, polymers having a norbornene skeleton, organic acid-substituted celluloses, polyethersulfones, polyarylates, polyesters, olefin maleimide And copolymerized olefin maleimide organic acid-substituted celluloses having a phenyl group, cellulose acetate is preferred.

  In the present invention, the negative substantially uniaxial optical film having the optical axis in the plane is integrated with the polarizing plate, and the in-plane slow phase of the negative substantially uniaxial film having the optical axis in the plane is included. A laminated polarizing plate is provided that is laminated so that the axis and the absorption axis of the polarizing plate are parallel to each other.

  In such a laminated polarizing plate, the polarizing layer protective film on the side in contact with the negative uniaxial optical film may be omitted, and the negative uniaxial optical film may also serve as the polarizing layer protective film. This also has the advantage that the optical design becomes easier. In this case, Rth may be set to 0 in the above formulas (3) and (4). In addition, the Rth of the protective film for the polarizing layer should be considered in the above formulas (1) and (2) as well, but since the Rth value is small, the influence of dispersion of the retardation value of this film is too large. Not considering for not.

  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 uniaxially stretching in the longitudinal or transverse direction. More preferably, an unstretched polymer film is preferably produced by transverse uniaxial stretching. By continuously producing an optical film made of a material having negative molecular polarizability anisotropy in the transverse uniaxial direction, the optical axis in the in-plane parallel direction with respect to the film width direction is delayed in the direction perpendicular thereto. There will be an axis. 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, in the laminated polarizing plate forming the liquid crystal display device of the present invention, the polarizing plate manufactured by the above manufacturing method and the negative substantially uniaxial optical film having an optical axis in the plane are bonded together by roll-to-roll. A laminated polarizing plate in which the absorption axis of the polarizing plate and the slow axis of the negative uniaxial optical film, which are preferable axial arrangements, are bonded in parallel can be easily formed. Also, negative uniaxial optics of the present invention include materials in which the molecular polarizability anisotropy is made of, for example, polymer liquid crystal and subjected to alignment treatment, or polymerized liquid crystal is aligned and then cured. It may be used as a film.

  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 alcohols, modified polyvinyl alcohols, organic silanols, acrylics and silicones, polyesters and polyurethanes, polyethers and rubbers 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, the adhesive between TAC and the optical film includes butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate and (meth ) 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 acrylic acid as a component, 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 polarizer, the optical film, the protective film for the polarizing layer, and the adhesive layer includes, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, and the like. 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, a liquid crystal display device is generally 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 phase difference value (Γ = Δn · d (nm)), Rth, Nz value The phase difference Γ value, Rth value, and Nz value, which is the product of birefringence Δn and film thickness d, is a spectroscopic ellipsometer. It was measured by a trade name “M150” manufactured by JASCO Corporation. The Γ value was measured with the incident light beam and the film surface orthogonal. The Nz and Rth values (nm) are three-dimensional by measuring the phase difference value at each angle by changing the angle between the incident light beam and the film surface, and curve fitting with a known refractive index ellipsoid equation. the refractive indices _{n x,} n y, seek _{n z,} the following equation (18), was determined by substituting (23).
_{Nz = (n x -n z)} / (n x -n y) (18)
_{Rth = {(n x + n} y) / 2-n z} × d (23)

(2) Method 1 for producing a negative substantially uniaxial optical film having an in-plane optical axis
A polycarbonate copolymer having a fluorene skeleton was used as the resin material of the first negative substantially uniaxial optical film having an optical axis in the plane. 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 above structure were dissolved in this at a molar ratio of 86:14, 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. The film was stretched at a stretching temperature of 225 ° C., and the stretching ratio was set so that the retardation values shown in Table 1 were obtained, and the film was uniaxially stretched to obtain a first negative substantially uniaxial property having an in-plane optical axis. An optical film was obtained.

(3) Method 2 for producing a negative substantially uniaxial optical film having an in-plane optical axis
Polystyrene and polyphenylene oxide were adjusted to a weight ratio of 25.5 to 74.5, 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 uniaxially at a stretching temperature of 130 ° C. and a stretch ratio of 2.1 times to obtain a second negative substantially uniaxial optical film having an optical axis in the plane.

[Example 1]
In the liquid crystal display device having the structure shown in FIG. 4, the first negative substantially uniaxial optical film having the optical axis in the plane produced by the production method 1, the liquid crystal cell in the black state, and the production method 2 The in-plane retardation values of the second negative substantially uniaxial optical film having the optical axis in the produced plane are respectively Γ ₁ , Γ _LC , Γ ₂ , and liquid crystals of the first and second polarizing plates. When a polarizing layer protective film is present on the cell side, the retardation values in the film thickness direction of these polarizing layer protective films are respectively Rth ₁ and Rth ₂ , and the respective values are as shown in Table 1. 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 in the mari black mode was calculated and compared with an actual liquid crystal display device. Nz of the negative substantially uniaxial optical film was 1 in all cases. Here, the purpose is to obtain a wide viewing angle and broadband liquid crystal display device, and in order to show the effect, the wavelength dependence of the transmittance in black display when the azimuth is changed at a polar angle of 60 °. FIG. 5 shows the result of calculation by the Jones matrix method corresponding to obliquely incident light. 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.

  In Table 1, those having Rth of 0 are cases where the polarizing layer protective film is not used (Examples 1 and 2). In this calculation, the retardation data of the optical film used the measurement data of the optical film produced above. 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. In 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 results of the examples, the transmittance at 550 nm, which has the highest human eye visibility, is as low as less than 0.1%, and the transmittance at all three wavelengths is less than 0.2%. It can be seen that a wide viewing angle and a wide bandwidth can be realized. Using a liquid crystal cell of the product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television, a liquid crystal display device having each configuration and each phase difference value shown in Table 1 was prepared and visually in a black state. The viewing angle and the color shift were confirmed, but it was confirmed that the viewing angle and the color shift were wide as well as having a wide viewing angle and little coloration, as compared with the comparative example described later. Further, it has been found that these liquid crystal display devices have very little dependency on the incident angle of the color shift even in halftone and white display.

[Example 2]
As in Example 1, except that the second negative substantially uniaxial optical film having an optical axis in the plane was used which was prepared by the above-described production method 1, optical calculation and actual measurement based on Table 1 were performed. A liquid crystal display device was produced and the viewing angle was confirmed. The calculation results are shown in FIG. Although it is inferior to Example 1 from FIG. 6, it turns out that a viewing angle is wide compared with the below-mentioned comparative example, and it is excellent also in broadband property. In addition, using a liquid crystal cell having a product name “W32-L7000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television, a liquid crystal display device having each configuration and each phase difference value shown in Table 1 was manufactured and visually observed. The viewing angle and color shift in the black state were confirmed, but it was confirmed that the viewing angle and the color shift were wide as well as having a wide viewing angle and little coloring compared to the comparative example described later. Further, it was found that these liquid crystal display devices have little dependency on the incident angle of the color shift even in halftone and white display.

[Example 3]
As the liquid crystal cell, a commercial liquid crystal television, “W28-L5000” manufactured by Hitachi, Ltd., and a film having an in-plane retardation of 3 nm made of triacetyl cellulose was used as a protective film for the polarizing layer. Except for the above, optical calculation and an actual liquid crystal display device were produced based on Table 1 and the viewing angle was confirmed in the same manner as in Example 1. FIG. 9 shows a layout of the optical elements of the liquid crystal display device. The calculation results are shown in FIG. Although it is inferior to Example 1 from FIG. 9, it turns out that a viewing angle is wide compared with the below-mentioned comparative example, and it is excellent also in broadband property. In addition, using a liquid crystal cell having a product name “W28-L5000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television, a liquid crystal display device having each configuration and each phase difference value shown in Table 1 was prepared and visually observed. The viewing angle and color shift in the black state were confirmed, but it was confirmed that the viewing angle and the color shift were wide as well as having a wide viewing angle and little coloring compared to the comparative example described later. Further, it was found that these liquid crystal display devices have little dependency on the incident angle of the color shift even in halftone and white display.

[Comparative example]
The liquid crystal cell and retardation film used in the product name “W28-L5000” manufactured by Hitachi, Ltd., which is a commercially available liquid crystal television having the configuration of FIG. Similarly, the result of wavelength dependence of transmittance obtained by calculation is shown in FIG. The definition of the azimuth is shown in FIG. In the calculation, a biaxial optical film having Nz of 0.3 and an in-plane retardation value of 135 nm was used as the retardation film in the same manner as the retardation film used in the product. It can be seen that the azimuth angle dependence of the maximum transmittance varies greatly depending on the wavelength, and the color tone varies depending on the azimuth angle. The commercially available product was visually checked for black viewing angle and color shift. When viewed from an oblique direction, depending on the azimuth angle, black changed to bluish black or reddish black, and the color shift was found to be extremely large compared to Examples 1-3. .

  The liquid crystal display device of the present invention is excellent in display quality, 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 a liquid crystal display device 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. 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. 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st polarizing plate 2 The 1st negative substantially uniaxial optical film 3 which has an optical axis in a surface 3 IPS mode liquid crystal cell 4 The 2nd negative substantially uniaxial optical film which has an optical axis in a surface 5 Second polarizing plate 6 Absorption axis 7 of polarizing plate Slow axis 8 in the plane of the negative substantially uniaxial optical film Slow axis 9 in the plane of the IPS mode liquid crystal cell in the black state emitted from the light source Light incident on a liquid crystal display device 10 First polarizing plate 11 Optical in a plane that can be regarded as equivalent to a combination of a first negative substantially uniaxial optical film having an optical axis in the plane and an IPS mode liquid crystal cell. Positive substantially uniaxial optical film 12 having an axis Negative substantially uniaxial optical film 13 having an optical axis in the plane Second polarizing plate 14 Absorption axis 15 of the polarizing plate Slow in the plane of the substantially uniaxial optical film Phase axis 16 Light 30 emitted from the light source and incident on the structure Optical film 31 Optical film surface 41 Second polarizing plate 43 in the embodiment Second negative substantially uniaxial optical film 44 having an optical axis in the plane in the embodiment IPS liquid crystal cell 45 in the embodiment Surface in the embodiment First negative substantially uniaxial optical film 47 having an optical axis therein First polarizing plate 48 in the embodiment Light 49 emitted from the light source in the embodiment and incident on the liquid crystal display device 49 Absorption axis 51 of the polarizing plate Slow axis 52 in the plane of the negative substantially uniaxial optical film Slow axis 55 in the plane of the IPS liquid crystal cell in the black state Transmission at a polar angle of 60 ° and a wavelength of 450 nm in the black state of the liquid crystal display device of Example 1 Ratio 56 Polar angle 60 ° in the black state of the liquid crystal display device of Example 1 and transmittance 57 at the wavelength of 550 nm Polar angle 60 ° in the black state of the liquid crystal display device of Example 1 and wavelength Transmittance 65 at 50 nm Polarity 60 ° in the black state of the liquid crystal display device of Example 2 and transmittance 66 at the wavelength 450 nm Polarity 60 ° in the black state of the liquid crystal display device of Example 2 Transmittance 67 at the wavelength 550 nm 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 2 First polarizing plate 92 in Example 3 First negative substantially uniaxial having an optical axis in the plane in Example 3 Protective film 93 for the polarizing layer on the side of the conductive optical film First negative substantially uniaxial optical film 94 having an optical axis in the plane in Example 3 IPS liquid crystal cell 95 in Example 3 In-plane optical in Example 3 Second negative substantially uniaxial optical film 96 having an axis A polarizing layer protective film 97 on the second negative substantially uniaxial optical film side having an optical axis in the plane in Example 3 Second polarizing plate 98 in Example 3 Light emitted from the light source in Example 3 and incident on the liquid crystal display device 99 Absorption axis 100 of polarizing plate Slow axis 101 in the plane of the protective film for polarizing layer Negative abbreviation Slow axis 102 in the plane of the uniaxial optical film Slow axis 111 in the plane of the IPS liquid crystal cell in the black state Transmittance 112 at a polar angle of 60 ° and a wavelength of 450 nm in the black state of the liquid crystal display device of Example 3 Transmittance 113 at a polar angle of 60 ° in the black state and a wavelength of 550 nm of the liquid crystal display device of Example 3 Transmittance 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 polarization in the comparative example Plate 142 Protective Film 143 for Polarizing Layer on Liquid Crystal Cell Side in Comparative Example Biaxial Optical Film 144 in Comparative Example IPS Liquid Crystal Cell 145 in Comparative Example Polarizing layer protective film 146 on the liquid crystal cell side Second polarizing plate 147 in the comparative example Light 148 emitted from the light source in the comparative example and incident on the liquid crystal display device Absorption axis 149 of the polarizing plate Surface of the polarizing layer protective film Slow axis 150 in the plane of the biaxial optical film Slow axis 151 in the plane of the IPS liquid crystal cell in the black state In the plane of the IPS liquid crystal cell 161 In the black state of the liquid crystal display device of the comparative example 60 °, wavelength 450 nm Transmittance 162 at a polar angle of 60 ° in the black state of the liquid crystal display device of the comparative example and transmittance 163 at a wavelength of 550 nm Transmittance of the liquid crystal display device of the comparative example at a polar angle of 60 ° and wavelength of 650 nm

Claims (3)

A first polarizing plate, a first negative substantially uniaxial optical film having an optical axis in the plane, a liquid crystal cell, a second negative substantially uniaxial optical film having an optical axis in the plane, a second These are laminated in the order of the polarizing plate,
In-plane of normally black mode in which absolute value of in-plane retardation value of liquid crystal cell is larger than absolute value of retardation value of first negative substantially uniaxial optical film having optical axis in plane A switching mode liquid crystal display device,
The angle formed by the absorption axis of the first polarizing plate and the slow axis in the plane of the first negative substantially uniaxial optical film is approximately 0 °,
Angle is approximately 90 ° in-plane slow axis of the liquid crystal cell in the slow axis and the black state in the plane of the first negative substantially uniaxial optical film,
Angle is substantially 0 ° and the slow axis in the plane of the negative substantially uniaxial optical film in-plane slow axis and a second liquid crystal cell in a black state, and,
The angle formed by the slow axis in the plane of the second negative substantially uniaxial optical film and the absorption axis of the second polarizing plate is approximately 0 °, and
The in-plane retardation values of the first negative substantially uniaxial optical film, the liquid crystal cell in the black state, and the second negative substantially uniaxial optical film are respectively Γ ₁ (λ), Γ _LC (λ), When Γ ₂ (λ) (nm), a liquid crystal display device satisfying the relationship of the following formulas (1) and / or (2).
| Γ ₂ (λ ₁ ) | <| Γ ₂ (λ ₂ ) | (1)
| Γ _LC (λ ₁ ) + Γ ₁ (λ ₁ ) | <| Γ _LC (λ ₂ ) + Γ ₁ (λ ₂ ) | (2)
(However, λ represents the measurement wavelength, and 400 nm ≦ λ ₁ <λ ₂ ≦ 700 nm.) When the first and second polarizing plates comprise a polarizing layer or a polarizing layer and a protective film in contact with the polarizing layer, and having a protective film, the retardation value in the thickness direction of the protective film on the liquid crystal cell side is set. _2. The liquid crystal display device according to claim 1, wherein when Rth ₁ (λ) and Rth ₂ (λ) are respectively satisfied, the following expressions (3) and (4) are satisfied.
−155 <Γ ₂ (λ) + Rth ₂ (λ) <− 45 nm (3)
45 <Γ _LC (λ) + Γ ₁ (λ) + Rth ₁ (λ) <155 nm (4)
(However, λ = 550 nm) 3. The liquid crystal display device according to claim 1, wherein the negative substantially uniaxial optical film having an optical axis in a plane is made of polycarbonate having a fluorene skeleton.

Images