JPH09146085A - Elliptic polarizing plate and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elliptic polarizing plate constituted so that the restriction of a material constituting a supporting body is reduced and an almost perfect black- and-white picture can be displayed by arranging the optical principal axis of the supporting body of a phase difference plate by the angle of a specified range with respect to the polarized axis of a polarizing plate and laminating them so that the supporting body side of the phase difference plate is brought into contact with the polarizing plate. SOLUTION: The elliptic polarizing plate is constituted of the polarizing plate 1 and the phase difference plate 6 obtained by laminating a twisted and nematic- oriented liquid crystal polymer layer 3 on the transparent supporting body 4. Then, the optical principal axis of the supporting body 4 of the plate 6 is arranged so as to be set within the range of ±2 deg. with respect to the polarized axis of the plate 1. The double refraction effect of the supporting body 4 is effectively suppressed. Therefore, even when the supporting body constituted of the material having residual phase difference is used as the supporting body 4, the high-quality elliptic polarizing plate is obtained by arranging the plate 6 and the plate 1 to be laminated so that the supporting body 4 side of the plate 6 is brought into contact with the plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elliptically polarizing plate used for improving display quality in an STN (super twisted nematic) liquid crystal display device and the like, and more particularly to a liquid crystal display device equipped with the elliptically polarizing plate. The present invention relates to an elliptical polarizing plate and a liquid crystal display device having a retardation plate excellent in retardation compensation performance.

[0002]

2. Description of the Related Art Conventionally, STN liquid crystal display devices have a problem that a display image is colored due to a phase difference generated in liquid crystal. Therefore, it has been attempted to solve the above coloring problem by bonding a retardation plate made of a transparent resin film to the surface of the liquid crystal display cell to compensate for the retardation.

As the transparent resin film constituting the retardation plate, conventionally, a transparent plastic film such as polycarbonate, polyvinyl alcohol, polysulfone, polyarylate, etc., which is uniaxially stretched, has been used.

However, in order to realize a uniform in-plane retardation, it was necessary to control the thickness unevenness during film formation and the temperature distribution during stretching with extremely high precision. Moreover, it was not possible to completely compensate for the difference in the phase difference due to the wavelength of the light after passing through the liquid crystal.

Therefore, a retardation plate using a twisted nematically aligned liquid crystal polymer (hereinafter referred to as a twisted alignment retardation plate) has been proposed, and the phase difference generated in an STN liquid crystal display cell is converted into the twisted alignment position. It is possible to make almost compensation by using a phase difference plate.

However, in the twist-oriented retardation plate,
The twisted nematically oriented liquid crystal polymer layer itself is several μm
Since it is difficult to handle with only the liquid crystal polymer layer, it is laminated with glass or a synthetic resin film having optical isotropy (Japanese Patent Laid-Open No. 4-55813), a liquid crystal display cell. And a method of directly laminating a liquid crystal polymer layer constituting a twisted alignment retardation plate on a polarizing plate (JP-A-1-
No. 282519) is adopted.

[0007]

However, when glass is used as the support for forming the twist-oriented retardation plate, it becomes heavier than a conventional retardation plate made of synthetic resin, and There is a drawback that impact resistance is also reduced. On the other hand, when an isotropic synthetic resin film is used as a support, it is required that the residual retardation is small. There are many restrictions such as selection and high precision solution coating, and it is difficult to obtain a synthetic resin film suitable as a material that can withstand the alignment treatment temperature of the liquid crystal polymer layer.

Further, when the twist-aligned liquid crystal polymer layer for phase difference compensation is directly laminated on the liquid crystal display cell or the polarizing plate, for example, the retardation plate made of the liquid crystal polymer layer is directly laminated on the polarizing plate. In this case, if the alignment treatment is performed after the liquid crystal polymer layer is laminated, the polarizing plate itself cannot withstand the temperature during the alignment treatment. Further, when the liquid crystal polymer layer for compensating the phase difference is directly laminated on the liquid crystal display cell, the productivity must be deteriorated because it must be laminated in a batch system. Moreover, if a defect of the twist alignment phase difference plate is found in the inspection after stacking, the liquid crystal display cell becomes a defective product. Therefore, the production cost is very high.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to use a twisted nematic alignment liquid crystal polymer as a retardation plate for compensating the retardation in a display element such as a liquid crystal display cell. Even when a synthetic resin film having a twisted nematic alignment retardation plate and a polarizing plate and having a residual retardation is used as a support for the liquid crystal polymer layer, the display quality is improved. Another object of the present invention is to provide an elliptically polarizing plate which is excellent in productivity and which does not decrease the liquid crystal display device, and a liquid crystal display device equipped with the elliptically polarizing plate.

[0010]

Means for Solving the Problems The inventors of the present application have made earnest studies to achieve the above-mentioned object, and as a result, a retardation formed by laminating a polarizing plate and a twisted nematically aligned liquid crystal polymer layer on a transparent support. A plate is laminated to form an elliptically polarizing plate, and in the elliptically polarizing plate, the optical axis of the support of the retardation plate is arranged within a predetermined angle with respect to the polarization axis of the polarizing plate, and the phase difference is It was found that if the support side of the plate is laminated so that the support side is in contact with the polarizing plate, it is difficult to affect the display quality as a display even when a synthetic resin substrate having a residual retardation is used as the support, and the present invention is achieved. Came to.

That is, the invention described in claim 1 is an elliptically polarizing plate obtained by laminating a polarizing plate and a retardation plate obtained by laminating a liquid crystal polymer layer having twisted nematic alignment on a transparent support. Then, the retardation plate and the polarizing plate are arranged such that the optical principal axis of the support of the retardation plate is within ± 2 ° with respect to the polarization axis of the polarizing plate, and the support side of the retardation plate is polarized. It is an elliptically polarizing plate which is laminated so as to be in contact with a plate.

Further, preferably, as described in claim 2, the support of the retardation plate is formed of a uniaxially stretched synthetic resin film. The invention described in claim 3 is a liquid crystal display device equipped with the elliptically polarizing plate according to the invention described in claim 1 or 2.

Hereinafter, the present invention will be described in detail. The elliptically polarizing plate according to the invention of claim 1 or 2,
It has a configuration in which the above-mentioned twist orientation retardation plate is laminated.

The polarizing plate is made of a known material conventionally used as a polarizing plate of a liquid crystal display device,
For example, a type in which iodine is mixed in polyvinyl alcohol and stretched, or a type in which dichroic dye is mixed and stretched can be used.

The retardation plate used in the invention of claim 1 has a structure in which a liquid crystal polymer layer having a twisted nematic orientation is laminated on a transparent support. The twisted nematic oriented liquid crystal polymer layer,
Japanese Patent Laid-Open Nos. 1-282519 and 4-55813
A known twisted nematically aligned liquid crystal polymer layer as disclosed in Japanese Patent Laid-Open Publication No. 2003-242242 can be used. Examples of such a liquid crystal polymer layer include a side chain type liquid crystal polymer represented by the following formula (1) and a side chain type liquid crystal polymer introduced with a chiral substituent represented by the following formula (2). It can be illustrated.

[0016]

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[0017]

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The above-mentioned twisted nematically aligned liquid crystal polymer layer generally has 2 in order to achieve a desired retardation compensation function.
The thickness is about 8 μm. In the invention of claims 1 and 2, since the twisted nematically aligned liquid crystal polymer layer is thin as described above, the twisted nematically aligned liquid crystal polymer layer is laminated on a transparent support. There is.

The material forming the above-mentioned support may be any material as long as it is transparent and has high smoothness, and is not particularly limited. Examples of the material forming the support include various synthetic resin films and inorganic materials. However, in order to reduce the weight of the material and increase the impact resistance, a synthetic resin is preferable, and it is necessary that it can withstand the temperature during the alignment treatment of the liquid crystal polymer. Highly synthetic resin such as polycarbonate,
Polysulfone, polyether sulfone, polyetherimide and the like are more preferable.

When the support made of the synthetic resin as described above is used, the residual retardation of the support is not particularly limited, but in order to prevent the display quality from deteriorating, it may be in-plane. It is desirable that the optical axes are aligned.

Further, in the invention according to claim 2, the support is composed of a uniaxially stretched resin film. As such a uniaxially stretched resin film,
Any resin can be used as long as it is transparent, has high smoothness, and can be stretched. However, as described above, a resin having high heat resistance, polycarbonate, polysulfone, polyethersulfone, polyetherimide, and the like are preferable because it is necessary to withstand the processing temperature in the alignment treatment of the liquid crystal polymer.

The method for stretching the resin film according to the second aspect of the invention is not particularly limited as long as it is uniaxially stretched, and it is longitudinally uniaxially stretched in the transport direction of the film and orthogonal to the transport direction. Any of lateral uniaxial stretching in which the stretching is performed may be used. Further, depending on the heating method at the time of stretching, it is classified into various stretching methods. In the invention of claim 2, the method of uniaxially stretching the resin film may be any method such as roll stretching, zone stretching and a combination thereof. It can be carried out.

The stretching ratio of the uniaxially stretched resin film is not particularly limited. However, with respect to the uniformity of the optical axis of the stretched resin film, the standard deviation of the optical axis in the film plane is preferably within 2 °, more preferably within 1 °. If the deviation of the optical axis exceeds 2 ° in standard deviation, the birefringence effect when light rays pass through the support cannot be ignored even if the optical main axis is aligned with the polarization axis of the polarizing plate, and it is mounted on the liquid crystal display device. In that case, a sufficient contrast ratio cannot be obtained and the display quality deteriorates.

Further, in the invention described in claim 2, the retardation value of the resin film is not particularly limited, but in order not to deteriorate the display quality of the entire screen, the retardation value is not limited. It is desirable that the higher is, the more aligned the optical axes are in the plane.

Regarding the method of laminating the liquid crystal polymer layer on the support in the inventions described in claims 1 and 2, any known method can be adopted. For example, a method in which an alignment film made of a polyimide resin or the like is formed on one surface of a support by coating, and the alignment film is rubbed or obliquely vapor-deposited, and then the liquid crystal polymer layer is laminated, or the support surface itself. And a liquid crystal polymer layer is laminated thereon. In this way, after the liquid crystal polymer layer is laminated on the support, the liquid crystal polymer layer containing the liquid crystal polymer is heated to the phase transition temperature of liquid crystal or higher,
A twisted nematic alignment process is performed.

Any known method can be used for laminating the retardation plate and the polarizing plate, but generally, the light transmittance and the optical retardation are not affected. A method of laminating a retardation plate and a polarizing plate via a transparent adhesive is used.

When laminating the retardation plate and the polarizing plate, the retardation plate is laminated on the polarizing plate from the support side of the retardation plate as described above. In this case, the smaller the arrangement angle between the optical principal axis of the support of the retardation plate and the polarization axis of the polarizing plate, the better, and in the invention according to claims 1 and 2, the deviation of the arrangement angle is ± 2. Must be within °. When the deviation of the arrangement angle between the optical axis of the support and the polarization axis of the polarizing plate exceeds ± 2 °, the birefringence effect of the support becomes prominent, and when viewed as the entire screen, the portion that should be displayed in black. Will appear white and cause a decrease in contrast.

The invention described in claim 3 is based on the above-mentioned claim 1,
The liquid crystal display device is provided with the elliptically polarizing plate according to the invention described in item 2, but the mounting position of the elliptically polarizing plate is not particularly limited. For example, an elliptically polarizing plate may be arranged on the backlight side of the liquid crystal display cell as shown in FIG. 1, or an elliptically polarizing plate may be arranged on the exit surface side of the liquid crystal display cell as shown in FIG. Good.

That is, in the structure shown in FIG. 1, the polarizing plate 1 is laminated on the emission surface side of the liquid crystal display cell 2, and on the other hand,
A retardation plate 6 including a liquid crystal polymer layer 3 and a support 4 and a polarizing plate 1 are laminated on the backlight 5 side. The laminated body of the retardation plate 6 and the polarizing plate 1 constitutes an elliptically polarizing plate according to the present invention, and the elliptically polarizing plate is arranged on the surface of the liquid crystal display cell 2 on the backlight 5 side.

On the other hand, in the structure shown in FIG. 2, the retardation plate 6 composed of the liquid crystal polymer layer 3 and the support 4 and the polarizing plate 1 are laminated on the emission surface side of the liquid crystal display cell 2. The elliptically polarizing plate according to the present invention is constituted by these. The polarizing plate 1 is laminated on the backlight 5 side of the liquid crystal display cell 2.

In the inventions described in claims 1 and 2, the order of laminating the support of the twisted phase difference plate, the liquid crystal polymer layer and the polarizing plate is as shown in FIG. First, it is necessary that the support 4 of the retardation plate is laminated so as to be in contact with the polarizing plate 1. When the support 4 and the polarizing plate 1 are not sequentially laminated in contact with each other, the linearly polarized light after passing through the polarizing plate is due to the birefringence of the polymer liquid crystal while passing through the polymer liquid crystal layer. Since it becomes elliptically polarized light and enters the support 4, the effect of suppressing the deviation of the optical axes of the support 4 and the polarizing plate 1 is lost. Therefore, desired elliptically polarized light can be obtained. In addition, when the elliptically polarizing plate is mounted on a liquid crystal display device, sufficient phase difference compensation performance cannot be obtained, the contrast is lowered, and perfect black and white display cannot be obtained.

[0032] In the invention described in the action claim 1, and a polarizing plate are constituted is the elliptically polarizing plate by the retardation plate formed by laminating a liquid crystal polymer layer which is twisted nematic orientation in the transparent support ,
Since the optical axis of the support of the retardation plate is arranged within ± 2 ° with respect to the polarization axis of the polarizing plate, the birefringence effect of the support is effectively suppressed. Therefore, even when the support made of a material having a residual retardation is used, the retardation plate is arranged so as to be laminated with the polarizing plate so that the support side of the retardation plate is in contact with the polarizing plate. As a result, a high quality elliptically polarizing plate can be provided.

That is, in the invention described in claim 1, the problem which cannot be solved only by the twisted alignment retardation plate is grasped as the whole elliptically polarizing plate formed by laminating the polarizing plate and the twisted alignment retardation plate, As described above, by arranging the optical axis of the support of the twist-oriented retardation plate and the polarization axis of the polarizing plate so as to be within a predetermined angle, there is a constraint on the optical isotropy of the support constituent material. Is relaxed, thereby expanding the selection range of the material constituting the support, facilitating the alignment treatment of the liquid crystal polymer, and making it possible to provide a high-quality elliptically polarizing plate at a low cost.

According to the second aspect of the present invention, the material forming the support is composed of a uniaxially stretched resin film. Therefore, the support is relatively lightweight and has high impact resistance. Since the resin film is further uniaxially stretched, the elliptically polarizing plate can be provided using an inexpensive support.

Further, in the invention described in claim 3, since it is a liquid crystal display device equipped with the elliptically polarizing plate described in claims 1 and 2, the phase difference on the liquid crystal display cell side is suppressed by the elliptically polarizing plate. The shift can be sufficiently compensated, so that the contrast ratio is sufficient, and perfect black and white display can be made possible.

[0036]

EXAMPLES The present invention will be clarified below by giving Examples and Comparative Examples of the present invention.

Example 1 A polycarbonate support (thickness: 75 μm) whose surface has been previously rubbed and whose residual retardation is 23 nm.
m, Tg = 150 ° C.), and the side chain liquid crystal polymer represented by the above formula (1) and the side chain liquid crystal polymer introduced by the chiral substituent represented by the formula (2). A liquid crystal polymer for twisted nematic alignment was laminated by a solution casting method by spin coating and subjected to an alignment treatment to prepare a twisted alignment retardation plate. The thickness of the liquid crystal polymer layer in the twist alignment retardation plate was 4 μm.

The twist-oriented retardation plate is provided with 28 μm on one side.
An elliptically polarizing plate was prepared by laminating it on a polarizing plate made of polyvinyl alcohol mixed with and stretched with iodine having a thickness of 185 μm and provided with a transparent acrylic pressure-sensitive adhesive layer having a thickness of m. In this elliptically polarizing plate, the polarization axis of the polarizing plate,
The deviation from the optical axis of the support was 1.2 °.

The elliptically polarizing plate was mounted on the liquid crystal display device having the structure shown in FIG. That is, in the configuration shown in FIG. 1, a STN liquid crystal cell driven at 1/200 duty was used as the liquid crystal display cell 2, and the elliptical polarizing plate was arranged on the backlight side of the STN liquid crystal cell to form a liquid crystal display device. . When an image signal was input to the liquid crystal display device and driven, the display screen became almost completely black and white display, and the contrast ratio was 62: 1.

Example 2 In Example 1, instead of the polycarbonate film, the residual retardation was 86 nm, the thickness was 93 μm, and Tg = 1.
A polyimide-based low temperature baking type alignment film was applied on a 93 ° C. polyarylate film so that the thickness after drying was 80 nm, and subjected to rubbing treatment to prepare a support. A liquid crystal polymer layer was laminated on this support in the same manner as in Example 1 to obtain a twisted alignment retardation plate, and Example 1
In the same manner as in (1), a polarizing plate was laminated to obtain an elliptically polarizing plate. In the obtained elliptically polarizing plate, the deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 0.1 °.

Using the elliptically polarizing plate obtained as described above, a liquid crystal display device having the configuration shown in FIG. 2 was constructed. As the liquid crystal display cell 2, a 1/200 duty driven STN liquid crystal cell was used, and the elliptically polarizing plate was mounted on the exit surface side of the liquid crystal display cell 2 as shown in FIG. When an image signal was input to and driven by the liquid crystal display device obtained as described above, the display screen was a substantially good black and white display, and the contrast ratio was 42: 1.

Example 3 As the support, a support made of a polycarbonate film (Tg = 150 ° C.) having a residual retardation of 108 nm by transverse uniaxial tenter stretching and an optical axis variation of 0.6 ° in standard deviation was used. A twist-oriented retardation plate was produced in the same manner as in Example 1 except for. This twist-oriented retardation plate was laminated with a polarizing plate in the same manner as in Example 1 to obtain an elliptically polarizing plate. In the obtained elliptically polarizing plate, the deviation between the polarizing axis of the polarizing plate and the optical principal axis of the support was 0 °.

Using the elliptically polarizing plate obtained as described above, a liquid crystal display device was constructed and driven in the same manner as in Example 1. When it was driven, the display screen became almost completely black and white display and the contrast ratio was 58 :. It was 1.

Example 4 In Example 3, as a support, a polyarylate having a phase difference of 84 nm, a variation of the optical axis of 1.4 ° in standard deviation, a thickness of 92 μm and a Tg of 193 ° C. was obtained by longitudinal uniaxial zone stretching. A twisted alignment retardation plate was prepared in the same manner as in Example 3 except that a polyimide low temperature baking type alignment film was applied on the film and subjected to rubbing treatment, and the twisted alignment was prepared. A retardation plate and a polarizing plate were laminated in the same manner as in Example 3 to obtain an elliptically polarizing plate. In the obtained elliptically polarizing plate, the deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 0.1 °.

Using the elliptically polarizing plate obtained as described above, a liquid crystal display device was constructed in the same manner as in Example 2, and when it was driven, the displayed image became almost completely black and white display and the contrast ratio was 54: 1. Met.

Example 5 As the support, a support made of a polycarbonate film (Tg = 150 ° C.) having a residual phase difference of 104 nm by transverse uniaxial tenter stretching and an optical axis variation of 2.5 ° in standard deviation was used. A twist-oriented retardation plate was produced in the same manner as in Example 1 except for. This twist-oriented retardation plate was laminated with a polarizing plate in the same manner as in Example 1 to obtain an elliptically polarizing plate. In the obtained elliptically polarizing plate, the deviation between the polarizing axis of the polarizing plate and the optical principal axis of the support was 0 °.

Using the elliptically polarizing plate obtained as described above, a liquid crystal display device was constructed and driven in the same manner as in Example 1. When it was driven, the display screen became a substantially good black and white display, and the contrast ratio was 43 :. It was 1.

Example 6 As the support, a support made of a polycarbonate film (Tg = 150 ° C.) having a residual retardation of 80 nm by transverse uniaxial tenter stretching and a standard deviation of 3.1 ° in optical axis variation was used. A twist-oriented retardation plate was produced in the same manner as in Example 1 except for. This twist-oriented retardation plate was laminated with a polarizing plate in the same manner as in Example 1 to obtain an elliptically polarizing plate. In the obtained elliptically polarizing plate, the deviation between the polarization axis of the polarizing plate and the optical principal axis of the support was 0.1 °.

Using the elliptically polarizing plate obtained as described above, a liquid crystal display device was constructed and driven in the same manner as in Example 2. When it was driven, the display screen became a substantially good black and white display, and the contrast ratio was 44 :. It was 1.

Comparative Example 1 The deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 2.5 °.
An elliptically polarizing plate having the same configuration as that of Example 1 was produced except that the above was described, and a liquid crystal display device was configured and driven in the same manner as in Example 1. As a result, on the display screen of the liquid crystal display device, the black display became a black and white display, and the contrast ratio was 22: 1.

Comparative Example 2 The deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 2.2 °.
An elliptically polarizing plate having the same structure as in Example 2 was prepared except that the above was described, and a liquid crystal display device was formed and driven in the same manner as in Example 1. As a result, on the display screen of the liquid crystal display device, the black display became a black and white display, and the contrast ratio was 12: 1.

Comparative Example 3 A liquid crystal display device was constructed by combining the elliptically polarizing plate obtained in Example 1 with a 1/200 duty driven STN liquid crystal display cell and a polarizing plate in the arrangement shown in FIG. In FIG. 4, the polarizing plate 1 is laminated on the emission surface side of the STN liquid crystal display cell 2, and the twist alignment retardation plate 6 and the polarizing plate 1 are laminated on the backlight 5 side. However, the support 4 of the twist alignment phase difference plate 6 is arranged on the liquid crystal display cell 2 side, and is arranged on the opposite side of the polarizing plate 1.

When the liquid crystal display device configured as described above was driven in the same manner as in Example 1, the display screen showed a black and white display in which the black display was slightly white, and the contrast ratio was 18: 1.

Comparative Example 4 The liquid crystal display device shown in FIG. 5 was constructed using the elliptically polarizing plate obtained in Example 2. Here, as the liquid crystal display cell 2, a 1/200 duty driven STN liquid crystal cell was used. Further, the twist alignment phase difference plate 6 and the polarizing plate 1 are laminated on the exit surface side of the liquid crystal display cell 2, but the support 4 of the twist alignment phase difference plate 6 is not on the polarization plate 1 side but on the liquid crystal display cell. It is laminated on the 2 side. When the above liquid crystal display device was driven in the same manner as in Example 1, the display screen showed a black and white display in which the black display was slightly white, and the contrast ratio was 9: 1.

Comparative Example 5 The deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 2.5 °.
An elliptically polarizing plate having the same configuration as that of Example 3 was prepared except that the above was described, and a liquid crystal display device was configured and driven in the same manner as in Example 1. As a result, on the display screen of the liquid crystal display device, the black display became a black and white display, and the contrast ratio was 9: 1.

Comparative Example 6 The deviation between the polarization axis of the polarizing plate and the optical main axis of the support was 2.2 °.
An elliptically polarizing plate having the same structure as in Example 4 except that the above was produced, and a liquid crystal display device was formed and driven in the same manner as in Example 1. As a result, on the display screen of the liquid crystal display device, the black display became a black and white display, and the contrast ratio was 14: 1.

Comparative Example 7 The elliptically polarizing plate obtained in Example 3 was placed in the arrangement shown in FIG.
A liquid crystal display device was constructed by combining a / 200 duty driven STN liquid crystal display cell and a polarizing plate. FIG.
In FIG. 1, the polarizing plate 1 is laminated on the emission surface side of the STN liquid crystal display cell 2, and the twist alignment retardation plate 6 and the polarizing plate 1 are laminated on the backlight 5 side. However,
The support 4 of the twist alignment retardation plate 6 is arranged on the liquid crystal display cell 2 side and on the opposite side of the polarizing plate 1.

When the liquid crystal display device configured as described above was driven in the same manner as in Example 1, the display screen showed black and white, which was slightly white, and the contrast ratio was 3: 1.

Comparative Example 8 The liquid crystal display device shown in FIG. 5 was constructed using the elliptically polarizing plate obtained in Example 4. Here, as the liquid crystal display cell 2, a 1/200 duty driven STN liquid crystal cell was used. Further, the twist alignment phase difference plate 6 and the polarizing plate 1 are laminated on the exit surface side of the liquid crystal display cell 2, but the support 4 of the twist alignment phase difference plate 6 is not on the polarization plate 1 side but on the liquid crystal display cell. It is laminated on the 2 side. When the above liquid crystal display device was driven in the same manner as in Example 1, the display screen showed a black and white display in which the black display was slightly white, and the contrast ratio was 10: 1.

Comparative Example 9 The support has a residual retardation of 108 nm, a variation in optical axis of 4.4 ° in standard deviation, a thickness of 78 μm, and an unstretched glass transition point Tg = 150 ° C. An elliptically polarizing plate was produced in the same manner as in Example 3 except that the polycarbonate film was used. In this elliptically polarizing plate, the deviation between the polarizing axis of the polarizing plate and the optical main axis of the support was 2.3 °.

A liquid crystal display device was constructed and driven in the same manner as in Example 3 using the elliptically polarizing plate, and when it was driven, the display screen changed to black and white, and the contrast ratio was 6: 1. It was

Comparative Example 10 Except that the dispersion of the optical axis of the support produced by longitudinal uniaxial proximity roll stretching is 2.6 ° in standard deviation.
An elliptically polarizing plate having the same structure as in Example 4 was produced. In this elliptically polarizing plate, the deviation between the polarizing axis of the polarizing plate and the optical main axis of the support was 2.8 °.

When a liquid crystal display device was constructed and driven in the same manner as in Example 4 using the above elliptically polarizing plate, the display screen was a black and white display in which black display was slightly white, and the contrast ratio was 12: 1.

The results of Examples 1 to 4 and Comparative Examples 1 to 10 are summarized in Table 1 below. The black and white display evaluation symbols in Table 1 have the following meanings. Good ... Almost complete black and white display Possible ... Almost good black and white display Impossible ... Black display is slightly white and black display

[0065]

[Table 1]

As is clear from Table 1, Comparative Examples 1, 2,
In Nos. 5, 6, 9 and 10, the black and white display was impossible because the deviation between the polarization axis of the polarizing plate and the optical main axis of the support was more than 2 °, and the contrast ratio was low. In Examples 1 to 6, since the deviation between the polarization axis of the polarizing plate and the optical main axis of the support was within 1.2 °, almost perfect or good black and white display was possible, and the contrast ratio was also high. it was high.

Further, in Comparative Examples 3, 4, 7 and 8, since the support of the twist alignment phase difference plate is laminated not on the polarizing plate but on the liquid crystal display cell side, linearly polarized light after passing through the polarizing plate 1 is obtained. While passing through the polymer liquid crystal layer, due to the birefringence of the polymer liquid crystal layer, it becomes elliptically polarized light and is incident on the support, so that the deviation of the optical axis between the support and the polarizing plate is suppressed. The effect and the effect of reducing the variation of the optical axis of the support were reduced, and as a result, perfect black and white display was not possible and the contrast ratio was also lowered.

Also, in Comparative Examples 9 and 10, the liquid crystal display devices were arranged in the same manner as in Examples 3 and 4, probably because the dispersion of the optical axis of the support was as large as 2.6 ° in standard deviation. , Good black and white display could not be performed, and the contrast ratio was low.

On the other hand, in Examples 1 to 4, perfect black and white display was possible and the contrast ratio was high.

[0070]

According to the invention described in claim 1, a polarizing plate,
In the structure of the elliptically polarizing plate formed by laminating the twist-oriented retardation plate, the deviation between the optical axis of the support of the retardation plate and the polarization axis of the polarizing plate is within ± 2 °.
The influence of the residual phase difference of the support can be reduced. Therefore, in order to relax the constraint of the material constituting the support,
The support can be made of a synthetic resin film that is lightweight and has excellent impact resistance, and even in that case, the retardation of the liquid crystal display cell is surely compensated by the entire elliptical polarizing plate. be able to. Therefore, by using the elliptically polarizing plate according to the invention of claim 1, the STN
In a liquid crystal display device or the like, almost perfect black and white display can be realized and the contrast ratio can be increased.

Further, since the restrictions on the material constituting the support are alleviated, it becomes possible to provide a liquid crystal display device having excellent display quality at low cost and with high productivity. In the invention according to claim 2, the support is composed of a uniaxially stretched resin film. Therefore, the productivity of the elliptically polarizing plate can be further enhanced, and the elliptically polarizing plate is less expensive,
Consequently, it becomes possible to provide the liquid crystal display element according to the invention described in claim 3.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the configurations of liquid crystal display devices in Examples 1 and 3 and Comparative Examples 1 and 3.

FIG. 2 is a schematic cross-sectional view showing the configurations of liquid crystal display devices in Examples 2 and 4 and Comparative Examples 2 and 4.

FIG. 3 is a schematic cross-sectional view for explaining a laminated structure in an elliptically polarizing plate according to the present invention.

FIG. 4 is a schematic cross-sectional view for explaining the structure of a liquid crystal display device configured in Comparative Example 5.

FIG. 5 is a schematic cross-sectional view for explaining the structure of the liquid crystal display device configured in Comparative example 6.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polarizing plate 2 ... Liquid crystal display cell 3 ... Liquid crystal polymer layer 4 ... Support 5 ... Backlight 6 ... Twist orientation phase difference plate

Claims (3)

[Claims] 1. An elliptically polarizing plate obtained by laminating a polarizing plate and a retardation plate obtained by laminating a liquid crystal polymer layer having a twisted nematic orientation on a transparent support, which is a support for the retardation plate. The retardation plate and the polarizing plate are arranged such that the optical main axis of the retardation plate is within ± 2 ° with respect to the polarizing axis of the polarizing plate, and the support side of the retardation plate is laminated so as to be in contact with the polarizing plate. Elliptical polarizing plate characterized by. 2. The elliptically polarizing plate according to claim 1, wherein the support for the retardation plate is made of a uniaxially stretched resin film. 3. A liquid crystal display device comprising the elliptically polarizing plate according to claim 1 or 2.