JPH03233406A - Optical device - Google Patents

Abstract

PURPOSE:To reduce the dependency of an optical path difference on an incident angle by forming the device with a plate having an optical phase difference function with the maximum main refractive index axis in its facial direction and a film or sheet having a negative intrinsic double refraction value. CONSTITUTION:This device is formed with a plate A having an optical phase difference function with the maximum main refractive index axis in its facial direction and a film B having a negative intrinsic double refraction value. The plate A having an optical phase difference function exhibits birefringence to the incident light vertical to its face, and an anisotropically oriented film obtained by uniaxial orientation or unbalanced biaxial orientation or a liq. crystal cell is exemplified. A transparent homopolymer or copolymer of an unsaturated aromatic compd. such as a polymerizable ester resin and polystyrene or the blend or a polymer alloy consisting essentaially of the resins can be used as the material for the film B having a negative intrinsic double refraction value. Consequently, the dependency of the optical path difference on an incident angle is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical element having an optical phase difference function, and particularly to an optical element in which the optical path difference has a small dependence on the angle of incidence.

[Conventional technology]

Conventionally, transparent resin anisotropic films or sheets (hereinafter "films or sheets" are abbreviated as "film") have been used as materials with an optical retardation function (hereinafter abbreviated as optical retardants) or liquid crystals for special purposes. cells have been used. Optical retardation materials have become increasingly important with the recent development of optical technology.For example, in black and white liquid crystal display panels, optical retardation materials are used to compensate for the inherent birefringence of liquid crystals, which causes coloration. Film etc. are used. However, these conventional optical retardation materials have the disadvantage that the optical path difference changes greatly depending on the incident angle of light, and when used in a black and white liquid crystal display panel, compensation in the oblique direction is not performed properly and coloring occurs. There is a problem with the viewing angle becoming narrower.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the problems of the above-mentioned prior art, that is, to develop an optical element in which the dependence of the optical path difference on the angle of incidence is small.

[Means to solve the problem]

The object of the present invention is to provide a film comprising: (A) a plate-like material having an optical retardation function in which the maximum principal refractive index axis is in the direction of its surface; and (B) a film having a negative intrinsic birefringence value. or (A) a plate-like object having an optical retardation function whose largest principal axis of refraction is in the thickness direction, and (B) a film having a positive intrinsic birefringence value. An optical element characterized by comprising:

A plate-like material having an optical retardation function is one that exhibits birefringence with respect to incident light perpendicular to its surface, such as an anisotropically oriented film or liquid crystal obtained by -axial stretching or unbalanced biaxial stretching. Examples include cells. In particular, an anisotropically oriented film is preferred because it can easily provide a large area film with a suitable optical path difference.

Materials with a positive intrinsic birefringence value for the film include polycarbonate resin, cellulose diacetate resin, polyvinyl alcohol resin, polyphenylene oxide resin, polyester resin such as polyethylene terephthalate, etc.
In addition, as negative materials, poly(meth)acrylic acid ester resins, resins of unsaturated aromatic compounds such as polystyrene, transparent homopolymers, copolymers, blends containing these as main components, polymer alloys, etc. can be used. .

Particularly preferred are polycarbonate resins with excellent transparency, cellulose diacetate resins, polyvinyl alcohol resins, acrylic resins containing methacrylic acid ester as a main component, and styrene resins containing styrene as a main component.

Furthermore, acrylic resin has excellent needle point (climate) properties, moisture resistance, and hardness, and has the advantage that it can also be used as a protective film.

Additives such as a lubricant and an ultraviolet absorber may be added to the resin for the film as necessary.

A liquid crystal cell having an optical retardation function can be a cell in which liquid crystal is aligned by rubbing, for example, homogeneous alignment or twisted alignment.

A balanced orientation stretched product is one that does not substantially exhibit birefringence with respect to incident light perpendicular to the plane, and can be produced, for example, by balanced biaxial stretching of a transparent resin. As the transparent resin, the resins mentioned above can be used.

For a plate-like object having an optical retardation function in which the maximum principal refractive index axis is in the plane direction, the film needs to have a negative intrinsic birefringence value. Further, for a plate-like object whose maximum principal refractive index axis is in the thickness direction, the intrinsic birefringence value needs to be positive. If this does not apply, for example, if a film with a positive intrinsic birefringence value is used for a plate-like object whose maximum principal refractive index axis is in the in-plane direction, the dependence on the angle of incidence will be rather large, and the effect of the present invention will be reduced. cannot be realized.

When the plate-like material having an optical retardation function is a -axially stretched product or an unbalanced biaxially stretched product, the direction of the maximum principal refractive index axis is the in-plane direction for a resin with a positive intrinsic n-refraction value, For negative resins, it is the thickness direction. That is, the anisotropically oriented film and the balanced oriented film need to be made of resins whose intrinsic birefringence values have opposite signs.

Moreover, in a liquid crystal cell with homogeneous alignment or twisted alignment, it is the in-plane direction.

In the laminate (B) of the present invention (hereinafter abbreviated as laminate), a pair of anisotropically oriented films having substantially the same optical path difference and the incident angle dependence of the optical path difference are arranged in a direction in which both degrees of orientation are large. It is preferable that they are superimposed so as to intersect with each other within an angular range of 90°±35°. This structure makes the laminate substantially non-birefringent with respect to perpendicularly incident light.

The anisotropically oriented film constituting the laminate is produced from the same raw material resin and in the same manner as the film mentioned above as the plate-like material having an optical retardation function, but the maximum principal refractive index axis is in the plane direction. For a plate-like object having an optical retardation function, it is necessary to use a resin film with a negative intrinsic birefringence value.

Further, for a plate-like object whose maximum principal refractive index axis is in the thickness direction, the intrinsic birefringence value needs to be positive. If this does not apply, for example, if an anisotropic oriented film with a positive intrinsic birefringence value is used in a laminate for a plate-like object whose maximum principal refractive index axis is in the in-plane direction, the incident angle dependence will be This becomes large, and the effects of the present invention cannot be realized.

The difference in the optical path difference and the incident angle dependence of the optical path difference between the pair of anisotropically oriented films constituting the laminate must be 15%, and preferably within 5%.

It is desirable that these anisotropically oriented films are stacked so that their directions with a high degree of orientation intersect with each other within an angular range of 90°±35°. When the angle is greater than 35° from the right angle, the laminate becomes birefringent with respect to perpendicularly incident light. The birefringence of the laminate must be within 30 nm for optical path difference for boat fishing, especially for 1On
Those within Il1 are preferred. If there is birefringence, the optical properties, that is, the optical path difference and incidence angle dependence of the optical retardation element produced therefrom will differ depending on the direction in which it is superimposed with (A), and the optical properties will not be constant. Further, the reduction of the dependence on the incident angle becomes insufficient.

As an anisotropically oriented film, the ratio of vertical and horizontal stretching ratio is 0.
．． When an unbalanced biaxially stretched product of 5 to 2 is used, a good laminate with little birefringence can be easily obtained, and the optical retardation element obtained therefrom has excellent incident angle dependent characteristics, which is preferable.

The optical element of the present invention can be realized in various forms.

Preferred embodiments will be explained below with reference to FIGS. 1 to 10. Here, (A) is a plate-like material having an optical retardation function, and (B) is a balanced orientation film or a laminate thereof. When composed of multiple (A) or (B), these are (A1), (A2)..., (Bl), (
B2)... is shown.

Fig. 1 shows the simplest form consisting of a pair of (A) and (B), and Fig. 2 shows one in which a protective film or film (C) having a hard coat film or the like is arranged on both sides.

Figure 3 shows a configuration in which (B2) is arranged in addition to (B1). For example, (B1) is a film made of a resin with a large absolute value of the intrinsic birefringence value or a laminate thereof, and the incident angle dependence is rough. This is a form in which (B2) is further finely adjusted, which is a film made of a resin with a small absolute value or a laminate thereof.

Figure 4 shows a configuration in which (B1) and (B2) are placed on both sides of (A). For example, if (A) is a polyvinyl alcohol resin film, (B1) and (B2) are light resistant. By using an acrylic resin film or a laminate thereof, which has good properties and moisture resistance, it is possible to avoid deformation due to moisture absorption.

In Figures 5 and 6, (AI) and (A2) are arranged so that their long axes are parallel, and the optical path difference of the optical element is the sum of the two. By preparing plate-shaped objects having optical phase difference functions with different optical path differences, optical elements with various optical path differences can be obtained by combining these. The angle dependence has been improved, and Figure 6 shows (AI) and (A2).
The incident angle dependence of is improved by (Bl) and (B2), respectively. (At).

The arrangement order may be changed, such as placing (A2), (Bl), and (B2) at both ends.

Figures 7 and 8 show that it is known that the contrast ratio can be improved in monochrome liquid crystal display panels (A
This is a combination of the configuration in which the long axes of I) and (A2) are arranged at an angle of 30°, for example, and (B), and the seventh
The figure shows the overall incident angle dependence improved with one sheet (B), and Figure 8 shows the incident angle dependence of (AI) and (A2) improved with (Bl) and (B2), respectively. It is something. In this case as well, (Al), (A2) or (Bl), (B
The arrangement order may be changed, such as placing 2) at both ends.

In FIG. 9, a protective film for a polarizing plate is used as (B), which has the advantage of reducing the total amount of constituent materials. A polarizing plate whose protective film is a balanced oriented film made of acrylic resin has excellent durability and moisture resistance.

In the optical element of the present invention, (A) and (B) are arranged so that their surfaces are parallel, and they may be separated, simply overlapped, or attached to each other, Further, a plate-like object may be interposed which does not impede the effects of the present invention. 1st
In addition to the preferred examples shown in Figures 9 to 9, the number of (A) and (B) may be set to 3 or more, or the protective film (C
) can be placed at both ends or at one end.

In addition, in the optical element of the present invention, when the anisotropic film that is a component of the laminate is a two-wheel stretched film with similar stretching ratios in the vertical and horizontal directions, a configuration in which the components are separated as shown in FIG. You can also take it.

In the optical element of the present invention, (A) and (B) with various characteristics can be used, but in the form of each pair, the optical path difference at an incident angle of 45'' of (B) is A combination having a value close to the difference between the optical path difference perpendicular to the plane and the optical path difference when tilted by 45 degrees in the major axis direction is preferable because the dependence on the incident angle is small.

The anisotropically oriented film used in the present invention can be produced by, for example, extruding a raw material resin into a bottom shape into a film shape, and then stretching it in one wheel at a temperature 10 to 40°C higher than the glass transition temperature of the resin, or by anisotropic It is obtained by two-wheel stretching under conditions such that .

Balanced oriented film is similar to anisotropic oriented film,
However, it can be obtained by biaxial stretching at the same stretching ratio in the longitudinal and lateral directions. A balanced orientation film is one that has virtually no birefringence for incident light perpendicular to its surface.
- For boat fishing, the optical path difference is within 30 na+, preferably 100 o+. If the balance is poor, the optical characteristics of the optical element, that is, the optical path difference and incidence angle dependence, will differ depending on the direction of superimposition with (A), and it will not be possible to obtain constant optical characteristics.

It should be noted that a layer of 254 μm or more was classified as a sheet, and a layer of 254 μm or more was classified as a film.

Below, methods for measuring physical property values used in the description of the invention will be shown.

・Optical path difference measurement method: Polarizing microscope (manufactured by Nippon Kogaku Kogyo ■, LA
BOPHOT-POL) according to a conventional method. The incident angle dependence was measured by tilting the sample at a predetermined angle and fixing it on a sample stand.

・Evaluation method for incident angle dependence: Calculate the absolute amount of change in optical path difference as a percentage when the incident light ray is tilted in the long axis and short axis directions, based on the case where the light ray is incident at right angles to the optical element. , evaluated by the average value of both. The angle of incidence indicates the angle of inclination.

〔Example〕

The present invention will be specifically explained with reference to Examples.

Example 1 An unstretched sheet of polycarbonate resin (manufactured by Idemitsu Petrochemical Co., Ltd., A-2500) with a positive intrinsic birefringence value was stretched to 180"
The film was uniaxially stretched to a constant width at a stretching temperature of C and a stretching ratio of 2.5 times to obtain an anisotropically oriented film having a thickness of 122 μm and having the maximum principal refractive index axis in the in-plane direction. In addition, an unstretched sheet of acrylic resin (Parapella SH manufactured by Kuraray Co., Ltd.) with a negative intrinsic birefringence value was simultaneously biaxially stretched at a stretching temperature of 140°C and a stretching ratio of 2.2 times in length and width to a thickness of 132μ. A balanced oriented film was obtained in which no optical path difference was observed from the direction perpendicular to the film surface. An optical element was produced by stacking the two layers and sandwiching them between unoriented optically isotropic acrylic resin sheets (Paraglass, manufactured by Kuraray). As shown in Table 1, the optical path difference of this optical element was 304n+w, and the dependence on the incident angle was as small as 3% at an incident angle of 45°. Incidentally, the optical path difference of only the anisotropically oriented polycarbonate resin film was only 308, and the dependence of the optical path difference on the incident angle was large, at 24%.

Example 2 An unstretched sheet of MS resin (Estyrene MS-300, manufactured by Nippon Steel Chemical Co., Ltd.) with a negative intrinsic birefringence value was heated at 130°C.
Uniaxially stretched to a constant width at a stretching temperature of 2.5 times and a stretching ratio of 2.5 times,
An anisotropically oriented film having a thickness of 75 μm with the largest principal refractive index axis in the thickness direction was obtained.

185°C from the polycarbonate resin used in Example 1
A balanced oriented film with a thickness of 107 μm and no optical path difference observed in the direction perpendicular to the film surface was obtained by simultaneous biaxial stretching at a stretching temperature of 2 times in the vertical and horizontal directions. An optical element was produced in the same manner as in Example 1 by overlapping the two. As shown in Table 1, the optical path difference of this optical element was -149 rv, and the dependence on the incident angle was as small as 6% at an incident angle of 45°. Incidentally, the optical path difference of the anisotropically oriented film of MS resin was -147 nm, and the dependence of the optical path difference on the incident angle was large, 27%.

Comparative Example 1 An optical element was produced in the same manner as in Example 1 from the anisotropically oriented film of polycarbonate resin used in Example 1 and the balanced oriented film of polycarbonate resin used in Example 2. The incident angle dependence of the optical element was greater than that of the anisotropic oriented film alone, and was poor at 34% at an incident angle of 45°.

Comparative Example 2 An optical element was produced in the same manner as in Example 1 from the anisotropically oriented film of MS resin used in Example 2 and the balanced oriented film of acrylic resin used in Example 1. The incident angle dependence of the optical element was greater than that of the anisotropic oriented film alone, and was poor at 69% at an incident angle of 45°.

Example 3 1. From the acrylic resin used in Example 1. An anisotropic oriented sheet with the maximum principal refractive index axis in the thickness direction obtained at a magnification of IX2.2 and a balanced oriented film of polycarbonate resin used in Example 1 were pasted together to form an optical element. Created. As shown in Table 1, the optical path difference of this optical element is -144 nm, and the incident angle dependence is 6 at an incident angle of 45°.
It was a small percentage. Incidentally, the optical path difference of the anisotropically oriented sheet of acrylic resin was -150 ni+, and the dependence of the optical path difference on the incident angle was large, at 32%.

Example 4 In addition to the combination of an anisotropically oriented film of cellulose diacetate resin with an optical path difference of 153 nm and an incident angle dependence of 56% at an incident angle of 45° and the balanced oriented film used in Example 1, the optical path For fine adjustment of the incident angle dependence of the difference, a balanced orientation film obtained from an acrylic resin (Barapera EH, manufactured by Kuraray Co., Ltd.) under the conditions shown in Table 1 was adhered to produce an optical element. As shown in Table 1, the optical path difference of this optical element was 154 nn+, and the incident angle dependence was as small as 1% at an incident angle of 45''. The incident angle dependence of the optical element prepared from the balanced orientation film used in Example 1 was 13% at an incident angle of 45''.

Example 5 An anisotropically oriented film of 29% polyvinyl alcohol resin with an optical path difference of 403 nW and an incident angle dependence of 45° was coated with an acrylic resin (■ Kuraray Co., Ltd., Bala) prepared under the conditions shown in Table 1. An optical element was produced by pasting PET EH) balanced orientation sheets on both sides. The incidence angle dependence of these optical elements is 4% at an incidence angle of 45° as shown in Table 1.
It was small. In addition, the dimensional stability upon moisture absorption was superior to that of an anisotropically oriented film made of polyvinyl alcohol (molecular weight) alone.

Example 6 An acrylic resin with the characteristics shown in the construction table (Kuraray, Parapet S
An optical element was produced by pasting the balanced orientation film of H). As shown in Table 1, the optical path difference of this optical element is 29
At 2 nm, the dependence on the incident angle was as small as 3% at an incident angle of 45°. Incidentally, the optical path difference of the liquid crystal cell was 297 n■, and the dependence of the optical path difference on the incident angle was 12%.

Example 7 An anisotropically oriented film of polycarbonate resin with the characteristics shown in Table 1 and polystyrene resin (manufactured by Mitsubishi Monsanto ■,
Dialex ■F-77) balanced oriented film, polystyrene resin balanced oriented film, polycarbonate resin anisotropic oriented film with an optical path difference of 308 nm, polycarbonate resin anisotropic oriented film with an optical path difference of 98 ns, in this order. Then, an optical element was produced by attaching an anisotropically oriented polycarbonate resin film such that both long sleeve directions were parallel to each other. The optical path difference of the optical element is 3
At 91 nm, the dependence on the incident angle was as small as 5% at an incident angle of 45@.

Example Day An anisotropically oriented film of polycarbonate resin and cellulose diacetate resin with the characteristics shown in Table 1, a balanced oriented film of acrylic resin, a balanced oriented film of acrylic resin, and an anisotropically oriented film of polycarbonate resin with an optical path difference of 308 nm. an anisotropically oriented film of cellulose diacetate resin with an optical path difference of 308 nm, a balanced oriented film of acrylic resin, and an anisotropically oriented film of polycarbonate resin and an anisotropically oriented film of cellulose diacetate resin. were adhered so that both major axes were parallel to each other, to produce an optical element. The optical path difference of the optical element was 447 na, and the dependence on the incident angle was as small as 6% at an incident angle of 45°.

Example 9 An anisotropically oriented film of polycarbonate resin and a balanced oriented film of acrylic resin having the characteristics shown in Table 1 were
2.2 Biaxially stretched acrylic resin film, polycarbonate resin film with optical path difference of 225 nm, 2
．． 2. A biaxially stretched acrylic resin film and a polycarbonate resin film with an optical path difference of 158 nm were attached in this order so that the long axis directions of the polycarbonate resin films were at 26° to each other, and the optical element was assembled. Created.

Bending plate, optical path difference is 800 ns+, liquid crystal cell with twist angle of 240' when twisted opposite to the optical element, optical path difference is 158
An optical element was placed by placing a ns+ polycarbonate resin film facing the liquid crystal cell, and finally an analyzer plate was assembled with crossed nicols to create a liquid crystal display element, and the visibility of the liquid crystal display element was evaluated by the darkness in the off state. did. In a liquid crystal display element prepared in the same manner except for using an optical element without the balanced orientation film of acrylic resin, a change in darkness was observed at a viewing angle of 20°, but in a liquid crystal display element using the optical element of the present invention, a change in darkness was observed at a viewing angle of 30°. Viewing angle characteristics were improved with no change in darkness observed up to 30°.

Example 10 An unstretched sheet of acrylic resin (parapet SH, manufactured by Kuraray) with a negative intrinsic birefringence value was sequentially drawn into two wheels at a stretching temperature of 140°C and a stretching ratio of 1.8 times in length and 2.2 times in width. Two films produced by stretching were stacked so that the directions with a high degree of orientation were perpendicular to each other to produce a laminate in which no optical path difference was observed from the perpendicular direction.

An optical element was produced by superimposing the laminate and the anisotropically oriented polycarbonate resin film in Example 1 between sheets of optically isotropic acrylic resin without orientation (Paraglass, manufactured by Kuraray). As shown in Table 2, the optical path difference of this optical element was 305 nm, and the dependence on the incident angle was as small as 2% at an incident angle of 45°. Incidentally, the optical path difference of only the anisotropically oriented polycarbonate resin film is 308 nm, and the dependence of the optical path difference on the incident angle is large.
It was 24%.

Example 11 A film was produced from the polycarbonate resin used in Example 1 by sequential two-wheel stretching at a stretching temperature of 185°C and a stretching ratio of 1.8 times in length and 2.2 times in width. A laminate was produced by stacking two layers in such a manner that no optical path difference was observed from the vertical direction.

The laminate and the anisotropically oriented film of the MS resin in Example 2 were laminated together to produce an optical element in the same manner as in Example 1O. As shown in Table 2, the optical path difference of this optical element was -145 nm, and the dependence on the incident angle was as small as 7% at an incident angle of 45°. Incidentally, the optical path difference of the anisotropically oriented film of MS resin was 147 nm, and the dependence of the optical path difference on the incident angle was large, 27%.

Comparative Example 3 An optical element was produced in the same manner as in Example 10 from a laminate of the anisotropically oriented polycarbonate resin film used in Example 1 and the polycarbonate resin used in Example 11. The incident angle dependence of the optical element is greater than that of the anisotropic oriented film alone, and is 33% at an incident angle of 45°.
It was inferior.

Comparative Example 4 From the laminate of the anisotropically oriented film of MS resin used in Example 2 and the acrylic resin used in Example 10, Example 1 was prepared.
An optical element was produced in the same manner as in Example 1. The incident angle dependence of the optical element was greater than that of the anisotropic oriented film alone, and was poor at 78% at an incident angle of 45°.

Example 12 Anisotropically oriented sheet with the maximum principal refractive index axis in the thickness direction obtained from the acrylic resin used in Example 10 at a magnification of 1.1 x 2.2 and the polycarbonate used in Example 1 An optical element was produced from a laminate with a resin by pasting the two together. As shown in Table 2, the optical path difference of this optical element is -15
At 2 nm, the dependence on the incident angle was as small as 6% at an incident angle of 45°. Incidentally, the optical path difference of the anisotropically oriented sheet of acrylic resin was -150 nm, and the dependence of the optical path difference on the incident angle was large, 32%.

Example 13 In addition to the combination of an anisotropically oriented film of cellulose diacetate resin with an optical path difference of 153 nm and an incident angle dependence of 56% at an incident angle of 45° and the laminate used in Example IO, an optical path difference was added. Acrylic resin (f
An optical element was prepared by pasting a laminate prepared in the same manner as in Example 10 from a film obtained from Parapet EH (manufactured by Kuraray Co., Ltd.) under the conditions shown in Table 2. As shown in Table 2, the optical path difference of this optical retardation element was 149 nm, and the dependence on the incident angle was as small as 1% at an incident angle of 45°. Incidentally, the incident angle dependence of the optical element produced from the anisotropically oriented film of cellulose diacetate resin and the laminate used in Example 10 was 12% at an incident angle of 45°.

Example 14 A laminate was prepared in the same manner as in Example 10 from a sheet of acrylic resin (Kuraray, Parapet EH) prepared under the conditions shown in Table 2 on the anisotropically oriented film of polyvinyl alcohol resin in Example 5. An optical element was fabricated by attaching the body to both sides. The incident angle dependence of these optical elements is the second
As shown in the table, it was as small as 6% at an incident angle of 45''.

Furthermore, it had superior moisture resistance and dimensional stability compared to a single anisotropic oriented film made of polyvinyl alcohol resin.

Example 15 A laminate of an acrylic resin (Parapet SH, manufactured by Kuraray Co., Ltd.) having the characteristics shown in Table 2 was adhered to the outer surface of the liquid crystal cell in Example 6 to produce an optical element.

As shown in Table 2, the optical path difference of this optical element is 294n
m, the incident angle dependence was as small as 2% at an incident angle of 45°. By the way, the optical path difference of the liquid crystal cell is 297 years old.
The dependence of the optical path difference on the incident angle was 12%.

Example 16 An optical element was produced in the same manner as in Example 7, except that a laminate of polystyrene resin (Dialex HF 77, manufactured by Mitsubishi Monsanto ■) was used instead of the anisotropically oriented film of polystyrene resin. did. The optical path difference of the optical element was 397 nm, and the dependence on the incident angle was as small as 3% at an incident angle of 45°.

Example 17 An optical element was produced in the same manner as in Example 8 except that an acrylic resin laminate was used instead of the acrylic resin balanced orientation film. The optical path difference of the optical element was 447 nm, and the dependence on the incident angle was as small as 5% at an incident angle of 45°.

Example 18 An acrylic resin laminate consisting of a laminate of an anisotropically oriented polycarbonate resin film with the characteristics shown in Table 2 and an acrylic resin stretched 1.8 times in length and 2.2 times in width, an optical path Polycarbonate resin film with a difference of 225 nm, length 1
．． An acrylic resin laminate consisting of a stretched product of 7 times and 2 times the width, a polycarbonate resin film with an optical path difference of 158 nm, and a polycarbonate resin film in this order, and the major axis direction of the polycarbonate resin film is They were attached at an angle of 26° to each other to produce an optical element.

Polarizing plate, optical path difference is 800 nm, liquid crystal cell with twist angle of 240 degrees when twisted opposite to the optical element, optical path difference is 158 nm
A polycarbonate resin film is placed facing the liquid crystal cell to form an optical element, and finally an analyzer plate is assembled in a crossed nicol configuration to produce a liquid crystal display element, and the visibility of the liquid crystal display element is evaluated by the darkness in the off state. did. In a liquid crystal display element manufactured in the same manner except for using an optical element without the acrylic resin laminate alignment film, a change in darkness was observed at a viewing angle of 20°, but a liquid crystal display using the optical retardation element of the present invention Changes in darkness were observed up to 30" in the element. [Effects of the Invention] The optical element of the present invention has made it possible to create an optical element with birefringence characteristics in which the dependence of the optical path difference on the angle of incidence is small, which was previously impossible. The product of the present invention is suitably used, for example, as an optical element for compensating a phase difference in a black-and-white liquid crystal display.

[Brief explanation of drawings]

1 to 10 show preferred embodiments of the optical element of the present invention.

Claims (9)

[Claims] (1) Consisting of (A) a plate-like material having an optical retardation function whose largest principal refractive index axis is in the direction of its surface, and (B) a film or sheet with a negative intrinsic birefringence value. An optical element characterized by: (2) Consisting of (A) a plate-like material with a chemical retardation function whose largest principal refractive index axis is in the thickness direction, and (B) a film or sheet with a positive intrinsic birefringence value. An optical element characterized by: (3) The optical element according to any one of claims 1 to 2, wherein the plate-like material of (A) is an anisotropically oriented film or sheet that is a uniaxially stretched product or an unbalanced biaxially stretched product. (4) The optical element according to any one of claims 1 to 3, wherein the film or sheet (B) is a balanced orientation stretched product. (5) Claims 1, 3, and 4, wherein (B) is a laminate of anisotropically oriented films or sheets having a negative intrinsic birefringence value.
The optical element described in . (6) The optical element according to claim 2, wherein (B) is an anisotropic oriented film or sheet laminate having a positive intrinsic birefringence value. (7) The laminate consists of a pair of films or sheets in which the optical path difference and the dependence of the optical path difference on the incident angle are substantially equal, and the directions of the greater degree of orientation intersect with each other within an angular range of 90° ± 35°. 7. The optical element according to claim 5, wherein the optical element is superimposed as shown in FIG. (8) The optical element according to any one of claims 5 to 7, wherein the anisotropically oriented film or sheet is an unbalanced biaxially stretched product. (9) The optical element according to claim 1 or 2, wherein the plate-like object (A) is a liquid crystal cell having nematic liquid crystals aligned in its plane.