JP3142405B2 - Liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device using a polymer film for a substrate.

[0002]

2. Description of the Related Art In a liquid crystal display device comprising a polymer film as a substrate, it is easy to make the thickness of the substrate as thin as 0.2 mm or less. Therefore, the liquid crystal display device is made extremely thin and lightweight. can do. Further, since the substrate is thin, the display does not become a double image, and a display element with a wide viewing angle can be obtained.

In a polymer film, molecules are orientated in a certain direction by a force applied in a manufacturing process thereof, and anisotropy in refractive index is easily generated. For this reason, particularly when displaying is performed using birefringence, when a polymer film is used as a substrate, the birefringence of the substrate has various effects on display.

[0004] If there is a refractive index anisotropy in a direction parallel to the substrate surface, the display color may change and the contrast may be reduced as compared with the case where there is no anisotropy. A film is manufactured so that anisotropy does not occur. However, compared to the refractive index in the direction parallel to the substrate surface, the refractive index in the thickness direction is smaller or larger, even when there is no refractive index anisotropy when viewed from the front, when viewed obliquely, Produces refractive index anisotropy. Therefore, the light incident obliquely changes its polarization state depending on the film substrate.

[0005]

For this reason, the liquid crystal display device using a polymer film as a substrate often has poorer viewing angle characteristics than the liquid crystal display device using a glass substrate. SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device having an excellent display quality by solving the above-mentioned disadvantages found in a conventional liquid crystal display device.

[0006]

In order to achieve the above object, the present invention provides a liquid crystal display device comprising a pair of polymer films as a film substrate, wherein one of the film substrates is formed in a direction parallel to the substrate surface. It is characterized by using a material whose refractive index is larger than the refractive index in the thickness direction of the substrate, and using a material whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the substrate as the other film substrate. It is assumed that.

The present invention is also directed to a liquid crystal display device comprising a pair of polymer films as a film substrate and a polarizing plate disposed outside the film substrate, wherein the pair of film substrates are refracted in a direction parallel to the substrate surfaces. Using a material whose refractive index is larger than the refractive index in the thickness direction of the substrate, a polymer film whose refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film between the film substrate and the polarizing plate. It is characterized by being provided.

According to the present invention, in a liquid crystal display device in which a pair of polymer films is used as a film substrate and a polarizing plate is disposed outside the film substrate, the pair of film substrates have a refractive index in a direction parallel to the substrate surfaces. Using a material smaller than the refractive index in the thickness direction of the substrate, providing a polymer film between the film substrate and the polarizing plate, the refractive index in the direction parallel to the film surface being larger than the refractive index in the thickness direction of the film. It is characterized by the following.

According to the present invention, when the film substrate has a refractive index anisotropy in a direction parallel to the substrate surface, the maximum refractive index direction is set to the x direction, and the maximum refractive index direction is defined as the direction parallel to the film surface in the polymer film. The refractive index also has anisotropy. The maximum refractive index direction is defined as the X direction,
The direction is orthogonal to the direction, the retardation of the film substrate and the retardation of the polymer film are matched, further, the polymer film is a protective film of the polarizing plate. It is characterized by being shared.

Further, according to the present invention, in a liquid crystal display device in which a pair of polymer films is used as a film substrate and a polarizing plate is disposed outside the film substrate, the pair of film substrates are refracted in a direction parallel to the substrate surfaces. A material having a refractive index larger than the refractive index in the thickness direction of the substrate, and a polymer liquid crystal layer oriented in a direction perpendicular to the film substrate is provided between the film substrate and the polarizing plate. is there.

According to the present invention, there is provided a two-layer liquid crystal display device in which two layers of liquid crystal cells each having a pair of polymer films as a film substrate are superposed, wherein one of the liquid crystal cells has a film substrate in a direction parallel to the substrate surface. Use a material whose refractive index is larger than the refractive index in the thickness direction of the substrate, and use a material whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the substrate as the film substrate of the other liquid crystal cell. It is characterized by the following.

According to the present invention, there is provided a two-layer liquid crystal display device comprising two layers of liquid crystal cells each having a pair of polymer films as a film substrate, wherein the film substrate of the liquid crystal cell is refracted in a direction parallel to the substrate surface. Using a material whose refractive index is greater than the refractive index in the thickness direction of the substrate, a polymer film having a refractive index in the direction parallel to the film surface smaller than the refractive index in the thickness direction of the film is provided between the two liquid crystal cells. It is characterized by the following.

According to the present invention, there is provided a two-layer liquid crystal display device comprising two liquid crystal cells each having a pair of polymer films as a film substrate, wherein the liquid crystal cell has a refraction in a direction parallel to the substrate surface. Using a material whose refractive index is smaller than the refractive index in the thickness direction of the substrate, a polymer film having a refractive index in the direction parallel to the film surface larger than the refractive index in the thickness direction of the film is provided between the two liquid crystal cells. It is characterized by the following.

According to the present invention, there is provided a two-layer liquid crystal display device comprising two liquid crystal cells each having a pair of polymer films as a film substrate, wherein the liquid crystal cell has a refraction in a direction parallel to the substrate surface. A material having a higher refractive index in the thickness direction of the substrate, and a polymer liquid crystal layer oriented in a direction perpendicular to the film substrate is provided between the two liquid crystal cells. .

[0015]

When a polymer film is used as a film substrate of a liquid crystal cell, the retardation of the film substrate changes depending on the viewing angle, which causes a reduction in viewing angle characteristics. However, according to the structure of the present invention, the arrangement of a viewing angle compensation film and the like is provided. This has the effect of eliminating deterioration in display characteristics and providing excellent viewing angle characteristics.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a liquid crystal display device (LC) according to the present invention.
The embodiment of D) is shown in cross section. In this drawing, alignment films 3 and 13 and transparent electrodes 4 and 14 each having been subjected to an alignment process are formed on the opposing surfaces of the film substrates 1 and 11, respectively. And during the time that the sealant 5 shuts off the outside air,
Liquid crystal 6 is enclosed. This liquid crystal cell is sandwiched between the first polarizing plate 2 and the second polarizing plate 12, and constitutes a liquid crystal display element.

The liquid crystal layer may have a homogeneous alignment (ECB type LCD), a homeotropic alignment (DAP type LCD), or a twist alignment (TN type) between the upper and lower film substrates 1 and 11. Or STN type LCD). Although not shown in FIG. 1, a phase difference plate may be provided between the liquid crystal cell and the polarizing plate (FSTN type LCD).

As the upper and lower film substrates 1 and 11, one of the film substrates 1 has a refractive index in a direction parallel to the substrate surface larger than a refractive index in a thickness direction of the film substrate. Contrary to the substrate 1, a material whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the film substrate is used.

As a film substrate whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the film substrate, polyvinyl alcohol (PVA), polycarbonate (PC), polyethylene (PE), polypropylene (PP), Films such as ethylene terephthalate (PET) and polyether sulfone (PES) can be used.

In producing a film, the polymer molecules are oriented in a certain direction by a force (particularly, a stretching force) applied in a process such as film formation or film winding.
Since the above-mentioned polymer has a large refractive index in the main chain direction, when stretched, the main chain is oriented in the stretching direction, so that the refractive index in the stretching direction becomes large. Usually, during film production, the film is stretched in a direction parallel to the film surface, so that the refractive index in the thickness direction becomes small.

A polystyrene (PS) or substituted polystyrene film can be used as a film substrate whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the film substrate. Since these polymers have a large refractive index in the direction perpendicular to the main chain direction, when stretched,
The main chain is oriented in the stretching direction, and the refractive index in the direction perpendicular to the stretching direction increases. Therefore, when the film is stretched in the direction parallel to the film surface, the refractive index in the direction parallel to the film surface is small, and the refractive index in the thickness direction is large.

The orientation treatment of each of the film substrates 1 and 11 in the present invention is performed by known oblique deposition or by rubbing with a cotton cloth or the like after forming an inorganic or organic film. As the alignment films 3 and 13 used in the present invention, a film obtained by rubbing a polymer film such as polyamide or polyimide, or a film obliquely deposited by using SiO, MgO, MgF ₂ or the like is used.

By the way, ECB type LCD, DAP type LC
In display modes utilizing birefringence, such as D, STN LCD, FSTN LCD, and DSTN (double-layer STN) LCD, display characteristics such as display color, brightness, and contrast pass through the liquid crystal layer. It depends on the polarization state of the reflected light and the direction of the polarizing plate. The polarization state depends on the retardation (the product of the refractive index anisotropy in the light traveling direction and the optical path length),
Since the retardation differs depending on the viewing angle direction, the display characteristics change depending on the viewing angle.

When a polymer film is used as a film substrate, the retardation of the film substrate also changes depending on the viewing angle, so that the viewing angle characteristics are often lower than when an isotropic substrate such as a glass substrate is used. Therefore, the present invention intends to improve the viewing angle characteristics of an LCD using a polymer film as a film substrate by compensating for a change in retardation of the film substrate due to the viewing angle.

FIG. 6 shows the film substrates 1 and 11
It is the drawing which defined each refractive index. One parallel to the film surface
Of the directions (x direction) where the refractive index is the maximum
To n _x, A direction parallel to the film surface and perpendicular to the x direction (y direction
N) to n_y, In the film thickness direction (z direction)
Refractive index is n_zAnd FIG. 7 shows that the present invention
The definition of the viewing angle direction will be described. That is, z direction
The angle between the viewing direction and the viewing angle direction is θ, and the viewing angle direction is projected on the film surface.
The angle between the shaded direction and the x direction is defined as φ.

When the refractive index in the direction parallel to the film surface is larger than the refractive index in the thickness direction of the film, and there is almost no refractive index anisotropy in the direction parallel to the film surface (n _x ≒ _ny >).
_nz ), the refractive index ellipsoid is as shown in FIG.
The refractive index anisotropy when viewed from is the difference between the major axis and the minor axis of the ellipse formed when the index ellipsoid is cut on a plane perpendicular to the viewing angle direction θ through the center of the index ellipsoid. Become. The major axis of the ellipse is a slow axis having a large refractive index and a slow phase velocity, and the short axis is a fast axis having a small refractive index and a fast phase velocity.

On the other hand, when the refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film, and there is almost no refractive index anisotropy in the direction parallel to the film surface (n
_x ≒ _ny < _nz ), and the refractive index ellipsoid is as shown in FIG.
As is clear from this figure, the directions of the slow axis and the fast axis in this case are orthogonal to the respective directions in FIG.

Therefore, the combination of these two types of film substrates cancels each other's phase change.
The change in retardation due to the viewing angle can be reduced. In the embodiment of the present invention, a liquid crystal display device is constituted by combining two types of films as upper and lower film substrates.

FIG. 2 shows another embodiment of the liquid crystal display device of the present invention. The difference from FIG. 1 is that polymer films 7 and 17 are provided between the film substrates 1 and 11 and the polarizing plates 2 and 12 of the liquid crystal cell. In this case, as the film substrate 1 and 11, with a large film _{(n x ≒ n y> n} z) than the refractive index in the thickness direction of the film parallel to the direction of the refractive index on the film substrate surface, and the film substrate 1 and 11 The polymer films 7 and 17 as viewing angle compensation films provided between the polarizing plates 2 and 12 have films (n _x ≒ n) whose refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film. _y <n
_{Since z} ) is used to cancel each other's phase change, the change in retardation due to the viewing angle can be reduced.

[0030] In the liquid crystal display device of the present invention in FIG. 2, as the film substrate 1 and 11, smaller film than the refractive index in the thickness direction of the refractive index in the direction parallel to the film surface film _{(n x ≒ n y <n} z ), The polymer films 7 and 17 as viewing angle compensating films provided between the film substrates 1 and 11 and the polarizing plates 2 and 12 have a refractive index in a direction parallel to the film surface to the thickness of the film. also by using a large film from the direction of the refractive index _{(n x ≒ n y> n} z), it is possible to achieve a similar effect.

In the liquid crystal display device shown in FIG. 2, if there is a refractive index anisotropy in a direction parallel to the film substrate surface of the film substrate, the birefringence of the film substrate causes not only oblique viewing but also oblique viewing. A phenomenon occurs in which the display characteristics also change. For this reason, when the film substrates 1 and 11 have anisotropy in the refractive index in the direction parallel to the film substrate surface,
As the polymer films 7 and 17 as viewing angle compensation films, those having anisotropy in the refractive index in the direction parallel to the film surface are used. The maximum refractive index directions of the film substrates 1 and 11 in the direction parallel to the film substrate surface are x1 direction in the film substrate 1 and the x11 direction in the film substrate 11, respectively, and the maximum refractive index direction in the direction parallel to the film surfaces of the polymer films 7 and 17 is set. In each of the refractive index directions, X is
7 directions and X17 direction in the polymer film 17, X7 direction with respect to x1 direction and X7 direction with respect to x11 direction.
The film substrates 1, 11 are arranged such that the 17 directions are orthogonal to each other.
The polymer films 7, 17 are disposed on the other hand.

That is, the film substrate is placed on the surface of the film substrate.
Has a refractive index anisotropy in a direction parallel to (n)_x> N_y
> N_zOr n_z> N_x> N_y) Is parallel to the film surface
Viewing angle compensation films with different directions of refractive index anisotropy
Of the film substrates _x> N_y> N_zFilm
For the substrate, n_z> N_x> N_yViewing angle compensation film
To n_z> N_x> N_yN for the film substrate of_x
> N_y> N_zIs used. As a result,
The X direction of the film substrate and the X direction of the viewing angle compensation film
Cancel each other's phase change by making them orthogonal to each other,
The deterioration of the display characteristics due to the birefringence of the plate is suppressed.

As described above, in the case where the film substrate has a refractive index anisotropy in a direction parallel to the film substrate surface, in a liquid crystal display device provided with a polymer film as a viewing angle compensation film for canceling a phase change, The retardation of the viewing angle compensating film when viewed from above is matched with the retardation of the film substrate, so that the mutual phase change can be completely canceled, and the deterioration of the display characteristics can be eliminated.

FIG. 3 shows another embodiment of the liquid crystal display device of the present invention. In the embodiment of FIG. 2, a polymer film as a viewing angle compensating film is disposed between the film substrate and the polarizing plate. In this embodiment, instead of the polymer film, the protective films of the polarizing plates 2 and 12 are provided. 8 and 18 are used as viewing angle compensation films. That is, in a polarizer generally utilizing the dichroism of iodine or a dye, a stretched film is provided with a polarizing ability by adsorbing iodine or a dye, and furthermore, for the protection thereof, the stretched film is formed by two films. Is sandwiched. The protective films 8 and 18 are used as viewing angle compensation films similar to those described above.

In this embodiment, the viewing angle compensating film also serves as a protective film for the polarizing plate, so that the liquid crystal display element is thinner by two films than when a separate polymer film is used. Can be omitted between the film substrate and the polarizing plate.

As another embodiment of the liquid crystal display element of the present invention, in the structure shown in FIG. 2, the film substrates 1 and 2 whose refractive index in the direction parallel to the film substrate surface is larger than the refractive index in the thickness direction of the film substrate. No. 11 is used. Instead of a polymer film as a viewing angle compensation film for preventing the deterioration of display characteristics, a polymer liquid crystal layer oriented in a direction perpendicular to the film substrates 1 and 11 can be provided.

By using a polymer liquid crystal layer oriented in the direction perpendicular to the film substrate in place of the viewing angle compensation film made of a polymer film, the polymer liquid crystal easily aligns like the low molecular liquid crystal. There are advantages in that the direction can be easily controlled and a film can be easily formed by applying the film to a film substrate or the like.

FIG. 4 shows a cross section of another embodiment of the liquid crystal display device of the present invention. This embodiment relates to a liquid crystal display device having a configuration in which a liquid crystal cell A and a liquid crystal cell B are overlapped, and the two layers of liquid crystal cells A and B are sandwiched between two polarizing plates 2 and 12. The film substrates 1a and 11a of the liquid crystal cell A have a larger refractive index in the direction parallel to the substrate surface than the thickness direction of the substrate, and the film substrates 1b and 11b of the liquid crystal cell B have a refractive index in the direction parallel to the substrate surface. Is smaller than the refractive index in the thickness direction of the substrate. Conversely, as the film substrates 1a and 11a of the liquid crystal cell A, films whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the substrate are used, and the film substrates 1b and 11b of the liquid crystal cell B are used. Is
A film whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the substrate may be used.

FIG. 5 shows a cross section of another embodiment of the liquid crystal display device of the present invention. The difference between this embodiment and the embodiment of FIG. 4 is that a polymer film 9 is provided between the liquid crystal cell A and the liquid crystal cell B. The film substrates 1a and 11a of the liquid crystal cell A and the film substrates 1b and 11b of the liquid crystal cell B have a refractive index in the direction parallel to the substrate surface larger than the refractive index in the thickness direction of the substrate.
Use a film whose refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film.

In the liquid crystal display device shown in FIG. 5, the film substrates 1a and 11a and the film substrates 1b and 11b
The polymer film 9 has a refractive index in the direction parallel to the substrate surface smaller than that in the thickness direction of the substrate, and the polymer film 9 has a refractive index in the direction parallel to the film surface larger than the refractive index in the thickness direction of the film. You can also.

Further, in the liquid crystal display device of FIG. 5, the film substrates 1a and 11a and the film substrates 1b and 11b
Uses a film whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the substrate.
Alternatively, a polymer liquid crystal layer oriented in a direction perpendicular to the film substrate can be provided.

The liquid crystal cell shown in FIG. 4 and FIG.
In the layer type liquid crystal display device, each of the above-described embodiments is useful for improving the viewing angle characteristics. In the embodiment shown in FIG. 4, the upper and lower film substrates 1a and 11a of one liquid crystal cell A are provided.
With n _x ≒ n _y> film of n _z, upper and lower film substrates 1b of the other liquid crystal cell B, and 11b, n _x ≒
obtained by using the film of the n _y <n _z, it constitutes a combination of two of the film substrate.

[0043] In the embodiment of FIG. 5, the upper and lower film substrates 1a of the liquid crystal cell A, 11a and the upper and lower film substrates 1b of the liquid crystal cell B, and 11b, and a film of _{n x ≒ n y> n z} , a liquid crystal cell A Between the liquid crystal cell B and _nx ≒ _ny <
A polymer film 9 is provided as a _nz viewing angle compensation film.

[0044] As another embodiment of FIG. 5, the upper and lower film substrates 1a of the liquid crystal cell A, 11a and the upper and lower film substrates 1b of the liquid crystal cell B, and 11b, by using the film of the n _x ≒ n _y <n _z A polymer film 9 is provided between the liquid crystal cell A and the liquid crystal cell B as a viewing angle compensation film _satisfying nx ≒ _ny > _nz .

According to the present invention, the viewing angle is compensated by a combination of two kinds of films, and the viewing angle characteristics of a liquid crystal display device using a polymer film as a film substrate are improved.
In each of the embodiments, a polarizing plate is arranged so as to sandwich the liquid crystal cell. However, one of the polarizing plates disposed outside the liquid crystal cell is provided with a reflecting plate to provide a reflective liquid crystal display. Naturally, the present invention can be applied to a device.

Next, a specific example to which the present invention is applied will be described. (Specific Example 1) Liquid crystal molecules are twisted 240 ° clockwise from lower substrate 11 toward upper substrate 1 between upper and lower polymer film substrates 1 and 11 having transparent electrodes 4 and 14.
A first liquid crystal cell as an STN cell having a retardation of a liquid crystal layer of 880 nm was produced. The liquid crystal used was a liquid crystal obtained by adding a chiral nematic liquid crystal S811 (manufactured by Merck) to a nematic liquid crystal ZLI2293 (manufactured by Merck) having a positive dielectric anisotropy. The alignment treatment was performed by rubbing the polyimide film.

In the first liquid crystal cell shown in FIG. 1, the lower substrate 11 has a film thickness of 106 μm and n _x =
_{1.58115, n y = 1.58112, n} z = 1.5
Using a PC film having a value of 8023, the upper substrate 1, the film thickness 102μm, n _x = 1.59344,
n _y = 1.59342, with PS film having a value of n _z = 1.59445.

At the lower part of the liquid crystal cell, a neutral gray polarizing plate 12 with a reflection plate is arranged so that the transmission axis thereof forms an angle of 50 ° with the liquid crystal molecule alignment direction on the lower substrate 11. On the upper part, a neutral gray polarizing plate 2 is disposed such that its transmission axis forms an angle of 40 ° with respect to the liquid crystal molecule alignment direction on the upper substrate 1, and a STN type liquid crystal display device of yellow mode (the present invention) The liquid crystal display element of the specific example 1) was produced.

Further, a PC film was used as the upper and lower substrates 1 and 11, a second liquid crystal cell having the same cell parameters as the first liquid crystal cell was manufactured, and the arrangement direction of the polarizing plate was made the same as the liquid crystal cell. A liquid crystal display device was manufactured. As a result of comparing the viewing angle characteristics by driving the above two liquid crystal display elements in a time-division manner, the liquid crystal display element using the first liquid crystal cell which is the specific example 1 of the present invention shows a change in the display characteristics due to the viewing angle. The result was small.

(Specific Example 2) The PS used for the substrate of the first liquid crystal cell of Specific Example 1 was provided on both sides of the second liquid crystal cell of Specific Example 1.
A liquid crystal display element in which a film is bonded and a polarizing plate is disposed on both sides in the same manner as in Example 1 (Example 2 of the present invention)
Liquid crystal display device). A viewing angle characteristic was compared between a liquid crystal display element in which a PS film was bonded to both sides of a second liquid crystal cell and a liquid crystal display element in which only a polarizing plate was arranged on both sides of the second liquid crystal cell by time-division driving. As a result, in the liquid crystal display device having the structure in which the PS films were bonded to both sides of the second liquid crystal cell which is the specific example 2 of the present invention, the change in the display characteristics due to the viewing angle was smaller.

(Specific Example 3) A third liquid crystal cell having the same cell parameters as the first liquid crystal cell was prepared by using the PS film used in Specific Example 1 on the upper and lower substrates, and the arrangement direction of the polarizing plate was determined. Was manufactured in the same manner as in Example 1.

A liquid crystal display device in which the PC film used as the substrate in Example 1 was bonded to both sides of the third liquid crystal cell, and polarizing plates were arranged on both sides in the same manner as in Example 1 (Example of the present invention) 3 liquid crystal display element).
A liquid crystal display element having a structure in which a PC film is bonded on both sides of the third liquid crystal cell, and a PC film on both sides of the third liquid crystal cell.
As a result of comparing the viewing angle characteristics with the liquid crystal display element having the structure in which the film is not bonded by dividing and driving the liquid crystal display element, the liquid crystal having the structure in which the PC film is bonded to both sides of the third liquid crystal cell which is the third embodiment of the present invention. In the display element, the change in display characteristics due to the viewing angle was smaller.

(Specific Example 4) Both upper and lower substrates 1 and 11 have
Film thickness 110 μm, n _x = 1.58153, n _y
P having a value of = 1.5817, _nz = 1.5801
Using a C film, a fourth liquid crystal cell having the same cell parameters as the first liquid crystal cell was produced. On both sides of the fourth liquid crystal cell, the film thickness of 105 .mu.m, n _x = 1.593
A PS film having a value of 72, n _y = 1.5934, and _nz = 1.59471 was attached so that the x direction of the substrate of the PC film was orthogonal to the x direction of the PS film.

Further, a retardation film having a retardation of 6 on the PS film stuck on the upper substrate.
A 00 nm stretched PC film was stuck. in this case,
The stretched PC film is attached so that the maximum refractive index direction of the fourth liquid crystal cell forms an angle of 95 ° with the liquid crystal molecule orientation direction on the upper substrate of the fourth liquid crystal cell.

At the lower part of the fourth liquid crystal cell, a neutral gray polarizing plate with a reflecting plate was arranged such that its transmission axis was at an angle of 50 ° to the liquid crystal molecule orientation direction on the lower substrate. In addition, a neutral gray polarizing plate is provided on the upper part of the retardation film, and its transmission axis is at 45 ° with respect to the direction of the maximum refractive index of the retardation plate, which is opposite to the direction of the twist of the liquid crystal molecules.
And a normal white mode FSTN type liquid crystal display device (the liquid crystal display device of Example 4 of the present invention) was produced.

An FSTN type liquid crystal display element manufactured without attaching a PS film to both sides of the fourth liquid crystal cell is a PC
Due to the birefringence of the film substrate, the color compensation was incomplete and a phenomenon of coloring occurred. On the other hand, the PS film of Example 4 of the present invention was attached to
In the case of an N-type liquid crystal display element, since the retardation of the substrate made of the PC film is reduced by the birefringence of the PS film, the display is maintained in black and white without coloring, and
The viewing angle characteristics were also excellent as compared with the case where the film was not attached.

(Specific Example 5) In the specific example 4, the film to be attached to both sides of the substrate made of the PC film is as follows.
The following PS film was used. Film thickness: 110
[mu] m, refractive _{index: n x = 1.59373, n y} = 1.59
338, _nz = 1.5947. In this case, the retardation of the substrate composed of the PC film and the PS film is substantially the same. Therefore, the retardation of the substrate composed of the PC film is almost canceled by the birefringence of the PS film. A display element was obtained.

(Example 6) The PS film used in Example 1 was used for the upper and lower substrates, and the liquid crystal molecules were moved between the lower and upper substrates in a counterclockwise direction from the lower substrate toward the upper substrate.
40 ° twist, liquid crystal layer retardation is 880nm
(Fifth liquid crystal cell) was produced. The liquid crystal is a nematic liquid crystal ZLI2 having a positive dielectric anisotropy.
293 (Merck) with chiral nematic liquid crystal R8
11 (Merck) was used.

On the second liquid crystal cell used in the first embodiment,
A fifth liquid crystal cell is installed. In this case, the liquid crystal molecules were arranged such that the liquid crystal molecule alignment direction of the upper substrate of the second liquid crystal cell was orthogonal to the liquid crystal molecule alignment direction of the lower substrate of the fifth liquid crystal cell. Further, a neutral gray polarizing plate was disposed below the second liquid crystal cell such that the transmission axis thereof was at an angle of 45 ° with respect to the liquid crystal molecule alignment direction on the lower substrate of the second liquid crystal cell. Further, a neutral gray polarizer is disposed above the fifth liquid crystal cell such that the transmission axis thereof is orthogonal to the transmission axis of the lower polarizer, and a DSTN type liquid crystal display element (the liquid crystal of the sixth embodiment of the present invention) is formed. Display element).

A sixth liquid crystal cell having the same cell parameters as the fifth liquid crystal cell was produced using the PC film used in Example 1 as a substrate. On the second liquid crystal cell,
The sixth liquid crystal cell was installed in the same manner as described above, and the polarizing plate was also installed in the same manner as described above, to produce a DSTN liquid crystal display device.

When the two DSTN-type liquid crystal display elements are time-divisionally driven and the viewing angle characteristics are compared, a specific example 6 of the present invention is obtained.
The liquid crystal display element in which the second liquid crystal cell and the fifth liquid crystal cell are combined is displayed at a higher viewing angle than the liquid crystal display element in which the second liquid crystal cell and the sixth liquid crystal cell are combined. The change in characteristics was small.

(Embodiment 7) The second liquid crystal cell and the fifth liquid crystal cell are overlapped as in Embodiment 6, and the PS film used in Embodiment 1 is placed between them. A DSTN liquid crystal display device (a liquid crystal display device of Example 7 of the present invention) was prepared by installing a polarizing plate. This liquid crystal display element was superior in viewing angle characteristics to a DSTN type liquid crystal display element in which only the second liquid crystal cell and the fifth liquid crystal cell were overlapped.

[0063]

According to the constitution of the present invention, the viewing angle characteristics of a liquid crystal display device using a polymer film as a substrate can be improved, and an effect of providing excellent display quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view for explaining a configuration of a liquid crystal display device of the present invention.

FIG. 2 is a side view for explaining another configuration of the liquid crystal display element of the present invention.

FIG. 3 is a side view for explaining another different configuration of the liquid crystal display device of the present invention.

FIG. 4 is a side view for explaining another different configuration of the liquid crystal display element of the present invention.

FIG. 5 is a side view for explaining another different configuration of the liquid crystal display device of the present invention.

FIG. 6 is an explanatory diagram for defining each refractive index of a film.

FIG. 7 is an explanatory diagram for defining a viewing angle direction.

FIG. 8 is an explanatory diagram showing a refractive index ellipsoid when the refractive index in the direction parallel to the film surface is larger than the refractive index in the thickness direction of the film, and there is almost no refractive index anisotropy in the direction parallel to the film surface. is there.

FIG. 9 is an explanatory view showing a refractive index ellipsoid when the refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film, and there is almost no refractive index anisotropy in the direction parallel to the film surface. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,11 Film substrate 2,12 Polarizer 3,13 Orientation film 4,14 Transparent electrode 5 Sealant 6 Liquid crystal 7,17 Polymer film 8,18 Protective film 9 Polymer film

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-238436 (JP, A) JP-A-2-242225 (JP, A) JP-A-2-306217 (JP, A) JP-A-2- 191914 (JP, A) JP-A-63-279229 (JP, A) JP-A-4-258923 (JP, A) JP-A-3-85519 (JP, A) JP-A-3-175417 (JP, A) JP-A-3-233502 (JP, A) JP-A-5-53104 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1333 500 G02F 1/13363

Claims (11)

(57) [Claims] 1. A liquid crystal display device comprising a pair of polymer films as a film substrate, wherein one of the film substrates is made of a material whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the substrate. A liquid crystal display element characterized in that a material having a refractive index in a direction parallel to the substrate surface is smaller than a refractive index in a thickness direction of the substrate as the other film substrate. 2. A liquid crystal display device comprising a pair of polymer films as a film substrate and a polarizing plate disposed outside the film substrate, wherein the pair of film substrates have a refractive index in a direction parallel to the substrate surface. It is characterized in that a polymer film whose refractive index in the direction parallel to the film surface is smaller than the refractive index in the thickness direction of the film is provided between the film substrate and the polarizing plate using a material having a higher refractive index in the thickness direction. Liquid crystal display element. 3. A liquid crystal display device comprising a pair of polymer films as a film substrate and a polarizing plate disposed outside the film substrate, wherein the pair of film substrates have a refractive index in a direction parallel to the substrate surface. It is characterized in that a polymer film having a refractive index in the direction parallel to the film surface is larger than the refractive index in the thickness direction of the film between the film substrate and the polarizing plate using a material having a refractive index smaller than the thickness direction. Liquid crystal display element. 4. The polymer film has an anisotropic refractive index in a direction parallel to the substrate surface, and has a maximum refractive index direction in the x direction, and a refractive index in a direction parallel to the film surface in the polymer film. 4. The liquid crystal display device according to claim 2, wherein the liquid crystal display element also has anisotropy, and its maximum refractive index direction is defined as an X direction, and the x direction is orthogonal to the X direction. 5. The liquid crystal display device according to claim 4, wherein the retardation of said film substrate is matched with the retardation of said polymer film. 6. The liquid crystal display device according to claim 2, wherein said polymer film doubles as a protective film for a polarizing plate. 7. A liquid crystal display device comprising a pair of polymer films as a film substrate and a polarizing plate disposed outside the film substrate, wherein the pair of film substrates has a refractive index in a direction parallel to the substrate surface. A liquid crystal display device comprising a material having a refractive index larger than a thickness direction and a polymer liquid crystal layer oriented in a direction perpendicular to the film substrate between the film substrate and the polarizing plate. 8. A two-layer liquid crystal display device in which two liquid crystal cells each having a pair of polymer films as a film substrate are laminated, wherein one of the liquid crystal cells has a film substrate as a film substrate.
Using a material whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the substrate, as the film substrate of the other liquid crystal cell, the refractive index in the direction parallel to the substrate surface is in the thickness direction of the substrate. A liquid crystal display element characterized by using a material having a lower refractive index. 9. A two-layer liquid crystal display device comprising a liquid crystal cell having a pair of polymer films as a film substrate and two liquid crystal cells stacked on each other, wherein the film substrate of the liquid crystal cell has a refractive index in a direction parallel to the substrate surface. Using a material larger than the refractive index in the thickness direction of the substrate, between the two liquid crystal cells,
A liquid crystal display device comprising a polymer film having a refractive index in a direction parallel to the film surface smaller than a refractive index in a thickness direction of the film. 10. A two-layer liquid crystal display device in which two layers of liquid crystal cells each having a pair of polymer films as a film substrate are laminated, wherein the film substrate of the liquid crystal cell is:
Using a material whose refractive index in the direction parallel to the substrate surface is smaller than the refractive index in the thickness direction of the substrate, between the two liquid crystal cells, the refractive index in the direction parallel to the film surface is in the thickness direction of the film. A liquid crystal display device comprising a polymer film having a refractive index larger than the refractive index. 11. A two-layer liquid crystal display device in which two liquid crystal cells each having a pair of polymer films as a film substrate are laminated, wherein the film substrate of the liquid crystal cell is:
Using a material whose refractive index in the direction parallel to the substrate surface is larger than the refractive index in the thickness direction of the substrate, a polymer liquid crystal layer oriented in a direction perpendicular to the film substrate is provided between the two liquid crystal cells. A liquid crystal display element, which is provided.