JPH02216119A - Liquid crystal electrooptical element - Google Patents

Abstract

PURPOSE:To obtain an anisotropic film which has a large difference in refractive index, is thin and inexpensive and allows easy production by uniaxially stretching a high-polymer film essentially consisting of the polymers of specific acrylate derivatives. CONSTITUTION:The optically anisotropic film is formed by uniaxially stretching the film essentially consisting of at least one kind of the polymers of the acrylate derivatives expressed by the general formula CH2=CX-COOR (where X is -Cl, -Br, -CN, -SCN group and R is 1 to 4C alkyl group or dervi. of a benzene ring). This high-polymer film is attached with a halogen and alkyl group to increase the refractive index in the substituent (alpha position of acrylate and an ester group) attached to the main chain of the polymers. The main chains, therefore, line up in the stretching direction and the alpha position, etc., of the acrylate are perpendicular to the main chains. The optically anisotropic film having the large refractive index is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a viewing angle compensator that widens the viewing angle of a liquid crystal electro-optic element that utilizes the birefringence effect.

[Prior art j] In order to widen the viewing angle range of a liquid crystal electro-optic element in which a homogeneously aligned liquid crystal is sandwiched between two electrode substrates, a viewing angle compensating plate, which is an optically anisotropic film, is attached to the liquid crystal electro-optic element. There is a method to adapt to the element. Regarding this, please refer to the patent application No. 63-1
98506. That is, the optically anisotropic film has its three main refractive indices NI0, Nxo, N
Among sm, N3° is the other two refractive indexes N+o and Ni. , and N10 and N2o are the same value, and N3. The axis corresponding to is located in one direction within the plane of the optically anisotropic film. This optically anisotropic film is applied to its N1.
By aligning the axis with the molecular axis of the liquid crystal, the change in Δn of the liquid crystal that occurs in response to the change in the viewing angle is canceled out, thereby producing the effect of widening the viewing angle.

By the way, there are two types of optically anisotropic films: a polymer film type and a discotic liquid crystal type, but the polymer film type is considered to be better in terms of cost, cost, and ease of production. Polymer film types, such as polymethyl methacrylate (PMMA) and polymethyl fluoroacrylate (PMFA), increase the refractive index in the direction perpendicular to the 5M stretching direction by stretching, resulting in negative optical anisotropy. It is necessary that the polymer exhibits the following.

[Problem to be Solved by the Invention 1] However, the polymer film type optically anisotropic film in the above-mentioned prior art is mainly made of PMMA or PMFA;
These have a problem in that the 80 value generated by stretching is small, and it is necessary to make the film as thick as 1 to 2 + nm, resulting in high cost and difficulty in manufacturing.

The present invention is intended to solve these problems, and its purpose is to increase △n generated by stretching and reduce the required thickness of the film, thereby creating an optical film that is inexpensive and easy to manufacture. The purpose is to provide an anisotropic film.

[Means for Solving the Problems] The liquid crystal electro-optical device of the present invention includes a liquid crystal cell in which a homogeneously aligned liquid crystal is sandwiched between two opposing electrode substrates, and an optical device that widens the regulation characteristics of the device. In a liquid crystal electro-optical element that is equipped with an anisotropic film and a pair of polarization handlers placed on both sides of the film, the optical axis is in one direction within the plane of the optically anisotropic film, and the optical axis is optically negative. 6 CH, = C C00R (here, t'X is a -CR1-Dr, -CN, -5CN group, and R is an argyl group having 1 to 4 carbon atoms or one J-shudo of a benzene ring) [Function] By stretching the molecular film, the refractive index in the direction perpendicular to the stretching direction becomes larger than the refractive index in the stretching direction, forming an optically negative refractive index anisotropic body. This principle will be explained here.

First, the case of a polymer film that forms a refractive index anisotropic body exhibiting positive birefringence through normal stretching will be described. This type of polymer film has 2. There are Botethylene and polycarbonate films.

These polymers have molecules extending in the direction of the main chain, and groups that increase the refractive index, such as benzene rings, are also present in the main chain, so if the main chains are aligned in the stretching direction by stretching, the main chain The refractive index in the chain direction is greater than the refractive index in the direction perpendicular to it. Therefore, in this case, it becomes an optical n-paralleloid film exhibiting positive birefringence.

On the other hand, the polymer film of the present invention is a polymer of acrylate derivatives, and the substituents (a-position and ester group of acrylate) attached to the main chain of the polymer include herogel, which is a group that increases the refractive index. It has a derivative group containing an alkyl group, a benzene ring, or an alkyl group. Therefore, when this polymer film is stretched, if the main chain is in the stretching direction, the a-position of the acrylate or the ester group will be one in the direction perpendicular to the main chain. Therefore, in this case, the refractive index in the direction perpendicular to the stretching direction is greater than that in the stretching direction, resulting in an optically anisotropic film exhibiting negative birefringence.

As mentioned above, the a-position of the acrylate and the substituents of the esters J and () must be groups that increase the refractive index, but what kind of groups increase the refractive index will be explained.

Generally, the refractive index is related to the ease with which electrons move within a molecule, and the electrons of large atoms and molecules with π orbitals move very easily, which increases the refractive index. Metal atoms are good as large atoms, but when these atoms enter the polymer, they become opaque, so they cannot be used for the purpose of the present invention. What can be done?

-F, -CJ2, -Br, -■ halogen atoms.

Furthermore, since these are electron-withdrawing, flllll
It has the effect of further increasing the refractive index because it collects electrons to the crystal 111+1. On the other hand, examples of substituents having π electrons include phenyl, biphenyl, terphenyl, naphculene, anthracene, azobenzene, stilbene, and derivatives thereof.

By combining these substituents, an optically anisotropic material suitable for the liquid crystal display element of the present invention can be obtained.

[Example] This will be explained in more detail in Examples below.

Example 1゜Liquid crystal 5S-4008 manufactured by Chisso Corporation (Δn
=0.15) for homogeneous orientation. The cell thickness is 6.0 μm, and the retardation Δnd is 0.9
It was set to be 0 um. On the other hand, phenyl a-chloroacrylate (CH, = ccg-coo-(9) was synthesized and polymerized. This film was heated at 110°C to 3 mm /
Stretched at a speed of s e c to a thickness of l 00 rim
A uniaxially stretched film was obtained. The refractive index difference between the stretching direction and the direction perpendicular to the stretching direction of this film is 0. ．． 009, △nd
was 0.9 um.

A stretched film of σ-phenyl chloroacrylate was placed on the liquid crystal cell, and polarizing plates were placed above and below it in a crossed nicol configuration. Comparing those with and without stretched film, the viewing angle range was wider.

Example 2 a-Biphenyl bromoacrylate, biphenyl methacrylate, biphenyl cyanoacrylate, and biphenyl thiocyanoacrylate were synthesized and polymerized, respectively.

Each polymer was made into 1 piece and 5 mm at 120°C.
The film was stretched at a speed of /sec to obtain a sheet with a film thickness of 1100u. This results in a -axially stretched film,
Δnd of both films was 0.5 μm. When this film was attached to the homogeneously aligned liquid crystal cell described in Example 1, the viewing angle was widened as in Example 1.

Example 3 Nafculene methacrylate, naphthalene a-chloroacrylate, naphculene a-cyanoacrylate, and naphculene a-thiocyanacrylate were synthesized and polymerized, respectively. Each polymer was made into a thin film at 100°C with a thickness of 5 mm/
The sheet was stretched at a speed of 1,100 μm in thickness. These were -axially stretched films, and the Δnd of each film was 0.9 μm. When this film was attached to the homogeneously aligned liquid crystal cell described in Example 1, the viewing range was expanded as in Example 1.

Example 5 4-(phenoxycarbonylphenyl) methacrylate, 4-(phenoxycarbonylphenyl), α-cyanoacrylate were synthesized and polymerized. Each polymer was made into a thin film and stretched at 100° C. at a speed of 5 mm/sec to obtain a sheet with a thickness of 50 μm. These are -axially stretched films, and △nd is 0 for both films.
．． It was 9um. When these films were attached to the homogeneously aligned liquid crystal cell described in Example 1, the viewing range was expanded as in Example 1.

[Effects of the Invention] As described above, according to the present invention, by substituting the 6-position of the acrylic acid ester and the substituent of the ester group with a group having the effect of increasing the refractive index, the polymer can be stretched. In some cases, the refractive index in the direction perpendicular to the stretching direction is higher than that in the stretching direction, resulting in an optically anisotropic film exhibiting negative birefringence. The anisotropic film obtained in this manner has the effect of widening the viewing angle of the liquid crystal optical element.

that's all Applicant: Seiko Epson Corporation

Claims (1)

[Claims] A liquid crystal cell comprising a homogeneously oriented liquid crystal sandwiched between two opposing electrode substrates, an optically anisotropic film that widens the viewing angle characteristics of the device, and an optical anisotropic film on both sides sandwiching them. A liquid crystal electro-optical element comprising a pair of arranged polarizing plates,
An optically anisotropic material having an optically negative uniaxiality in which the optical axis lies in one direction within the plane of the optically anisotropic material film, whose main component is at least one kind of polymer of an acrylate derivative having the general formula below. 1. A liquid crystal electro-optical device, characterized in that it is a uniaxially stretched body of a film. CH_2=CX-COOR (where X is -Cl, -Br, -CN, -SCN group, R is an alkyl group having 1 to 4 carbon atoms or a benzene ring derivative)