JPH11194371A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twisted nematic liquid crystal display device which has its display contrast, gradation characteristics, and field angle characteristics of display colors improved. SOLUTION: This device consists of a driving twisted nematic liquid crystal cell consisting of at least one compensation film which is formed of optically positive uniaxial liquid crystal macromolecules and has the nematic hybrid orientation that the liquid crystal macromolecules form in a liquid crystal state fixed, a couple of transparent substrates equipped with electrodes, and a nematic liquid crystal sandwiched between the substrates and two polarizing plates which are arranged above and below the liquid crystal cell. Here, the product (Δnd) of the refractive index anisotropy (Δn) of the nematic liquid crystal constituting the liquid crystal cell and the thickness (d) of the liquid crystal layer of the liquid crystal cell is 200 to 500 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a twisted nematic liquid crystal display device having improved display contrast, gradation characteristics and display color viewing angle characteristics.

[0002]

2. Description of the Related Art An active driving twisted nematic liquid crystal display device (hereinafter abbreviated as a TN-LCD) using a TFT element or an MIM element or the like has a thin, lightweight and low power consumption in addition to the inherent features of an LCD. , To have image quality comparable to a CRT when viewed from the front,
It is widely used as a display device for notebook computers, portable televisions, portable information terminals, and the like. However, in the conventional TN-LCD, the problem of the viewing angle that the display color changes or the display contrast decreases when viewed obliquely due to the refractive index anisotropy of the liquid crystal molecules is essentially unavoidable. There is a strong demand for improvement, and various attempts have been made for improvement.

A method in which one pixel is divided and the applied voltage to each pixel is changed at a fixed ratio (halftone gray scale method). One pixel is divided and the rising direction of the liquid crystal molecules in each pixel is changed. Method (domain division method), a method of applying a horizontal electric field to the liquid crystal (IPS method), a method of driving a vertically aligned liquid crystal (VA liquid crystal method), or a method of combining a bend alignment cell and an optical compensator (O
The CB method has been proposed and is being developed and prototyped.

[0004] However, although these methods have a certain effect, it is necessary to change the alignment film, the electrodes, the liquid crystal alignment, and the like. Therefore, it is necessary to establish a manufacturing technique and to newly install a manufacturing equipment. Inviting higher costs.

On the other hand, there is a method of increasing the viewing angle by incorporating an optical compensation film into a conventional TN-LCD without changing the structure of the TN-LCD at all. This method uses TN-LC
The D production equipment does not require improvement or expansion, and is excellent in cost, and has the advantage of being easily used.

[0006] TN in normally white (NW) mode
The cause of the viewing angle problem in the LCD is the alignment state of the liquid crystal in the cell at the time of black display with applied voltage. In this case, the liquid crystal is substantially vertically aligned and optically positive uniaxial. Therefore, as an optical compensation film for widening the viewing angle, a proposal has been made to use a film having optically negative uniaxiality in order to compensate for positive uniaxiality during black display of a liquid crystal cell. Focusing on the fact that the liquid crystal in the cell has an orientation parallel or inclined to the cell interface near the interface of the alignment film even during black display, compensation is performed using a negative uniaxial film with an inclined optical axis. By,
Further, a method for enhancing the viewing angle expanding effect has been proposed.

For example, JP-A-4-349424, 6-25
No. 0166 discloses an optical compensation film using a cholesteric film having a helical axis inclined and an L-compensation film using the same.
A CD has been proposed. However, it is difficult to produce a cholesteric film with a helical axis inclined,
In fact, none of these patents describes a method for tilting the helical axis. Further, Japanese Patent Application Laid-Open No. H5-2495
47, 6-331979 proposes an LCD using a negative uniaxial compensator whose optical axis is inclined. As a specific embodiment, a multilayer thin film compensator is used. Further, Japanese Patent Application Laid-Open Nos. 7-146409 and 8-5837 have proposed an optical compensation film in which discotic liquid crystals are inclined and oriented, and an LCD using the same as a negative uniaxial compensation film with an inclined optical axis. However, the discotic liquid crystal has a complicated chemical structure and is complicated to synthesize. Also, when forming a film because it is a low molecular liquid crystal,
A complicated process such as photocrosslinking is required, which makes industrial production difficult and results in high cost.

As another form of the compensating film, an alignment film using a liquid crystal polymer having a positive uniaxial property has been proposed. For example, Japanese Patent Application Laid-Open No. Hei 7-140326 proposes an LCD compensator comprising a liquid crystal polymer film having a twisted tilt orientation, which is used for expanding the viewing angle of the LCD. However, it is not industrially easy to simultaneously introduce a twist orientation in addition to the tilt orientation. Japanese Patent Application Laid-Open Nos. 7-198942 and 7-181324 disclose, as a similar technique, a viewing angle compensator made of a film in which a nematic liquid crystalline polymer is oriented so that an optical axis intersects a plate surface, and an LCD using the same. Proposed.
However, also in this case, since the compensating plate in which the optical axis is simply inclined is used, the viewing angle expanding effect cannot be said to be sufficient.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a combination of a specific twisted nematic liquid crystal cell for driving and a nematic hybrid alignment compensation film provides an unprecedented high contrast and wide area. An object of the present invention is to provide a twisted nematic liquid crystal display device having a wide viewing angle.

[0010]

That is, the present invention is to fix a nematic hybrid alignment formed substantially from a liquid crystalline polymer having optically positive uniaxiality and formed in a liquid crystal state by the liquid crystalline polymer. At least one compensating film, a twisted nematic liquid crystal cell for driving composed of a pair of transparent substrates provided with electrodes and a nematic liquid crystal sandwiched between the substrates, and disposed above and below the liquid crystal cell The product (Δnd) of the refractive index anisotropy (Δn) of the nematic liquid crystal constituting the liquid crystal cell and the thickness (d) of the liquid crystal layer in the liquid crystal cell is at least 200 nm. A twisted nematic liquid crystal display device having a thickness of 500 nm or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. When a driving twisted nematic liquid crystal cell (hereinafter abbreviated as a TN liquid crystal cell) used in the present invention is classified according to a driving method, a TFT (Thin Film Tra) using a simple matrix method and an active element as an electrode is used.
Sistor) electrode, MIM (Metal Insul)
ator Metal, and TFD; Thin Fi
(Im Diode) The active matrix method using electrodes can be subdivided. In the present invention, a remarkable effect can be exerted on any of the TN liquid crystal cells of the driving method.

The TN liquid crystal cell used in the present invention usually has a Δnd value represented by the product of the refractive index anisotropy (Δn) of the liquid crystal cell and the thickness (d) of the liquid crystal layer of the liquid crystal cell of 20.
0 nm to 500 nm or less, preferably 250 nm to 47 nm
0 nm or less, particularly preferably 300 nm to 450 nm, most preferably 300 nm to 400 nm. If it is larger than 500 nm, the effect of improving the viewing angle when combined with a compensation film to be described later may be poor, and the response speed may be slow. If it is smaller than 200 nm, when combined with the compensating film, there is a possibility that the brightness and contrast of the front may be reduced although the viewing angle is improved.

In the TN liquid crystal cell, it is preferable to give a pretilt angle to the liquid crystal molecules in advance in order to reduce alignment defects of the liquid crystal molecules of the nematic liquid crystal. The pretilt angle is usually 5 ° or less.

Generally, in a TN liquid crystal cell, the long axis of the nematic liquid crystal in the liquid crystal cell is about 90 degrees between the upper and lower substrates.
° twisted. In the state where no voltage is applied to the liquid crystal cell, the linearly polarized light that has entered is twisted by 90 ° and emitted due to its optical activity. When a voltage is applied to the liquid crystal cell, the major axis of the liquid crystal molecules is oriented in the direction of the electric field, and the optical rotatory power disappears. Therefore, in order to sufficiently obtain the effect of the optical rotation, the twist angle of the TN liquid crystal cell used in the present invention is usually 70 ° to 110 °, preferably 85 ° to 95 °. Note that the twist direction of the liquid crystal molecules in the liquid crystal cell may be either the left or right direction.

Next, the compensation film used in the present invention will be described. The film contains a liquid crystalline polymer having an optically positive uniaxial property, specifically, a liquid crystalline polymer compound having an optically positive uniaxial property, or at least one kind of the liquid crystalline polymer compound. A liquid crystalline polymer composition that exhibits optically positive uniaxiality, and is formed by fixing the nematic hybrid alignment formed by the liquid crystalline polymer compound or the liquid crystalline polymer composition in a liquid crystal state. .

Since the compensating film is a film in which the nematic hybrid orientation is fixed, directors of the liquid crystalline polymer are oriented at different angles everywhere in the film thickness direction. Therefore, the compensation film, when viewed as a structure called a film,
There is no longer an optical axis.

Such a compensation film in which the nematic hybrid orientation is fixed is not optically equivalent between the upper surface and the lower surface of the film. Therefore, when the liquid crystal cell is arranged in the TN liquid crystal cell described above, the viewing angle expanding effect is slightly different depending on which surface is arranged on the liquid crystal cell side. According to the present invention, a sufficient viewing angle enlarging effect can be obtained by arranging either of the planes. Among them, the angle formed by the director of the liquid crystalline polymer and the plane of the film among the upper and lower surfaces of the compensation film. Is desirably arranged such that the smaller surface is closest to the liquid crystal cell. Here, various parameters of the compensation film used in the present invention will be described.

First, the thickness of the compensation film is usually 0.1 to
The range is 20 μm, preferably 0.2 to 10 μm, particularly preferably 0.3 to 5 μm. When the film thickness is less than 0.1 μm, there is a possibility that a sufficient compensation effect cannot be obtained. If the thickness exceeds 20 μm, the display may be unnecessarily colored.

Next, the in-plane apparent retardation value when viewed from the normal direction of the compensation film will be described. In a film having a nematic hybrid orientation, a refractive index in a direction parallel to the director (hereinafter referred to as ne) and a refractive index in a direction perpendicular to the director (hereinafter referred to as no) are different. When a value obtained by subtracting no from ne is an apparent birefringence, the apparent retardation value is given by the product of the apparent birefringence and the absolute film thickness. This apparent retardation value can be easily obtained by polarization optical measurement such as ellipsometry. The apparent retardation value of the compensation film is usually 5 to 500 nm, preferably 10 to 3 with respect to monochromatic light of 550 nm.
00 nm, particularly preferably in the range of 15 to 150 nm. When the apparent retardation value is less than 5 nm,
There is a possibility that a sufficient viewing angle expanding effect cannot be obtained. Also,
If it is larger than 500 nm, the display may be colored unnecessarily when viewed obliquely.

Next, the angle of the director at the upper and lower interfaces of the compensation film will be described. The angle of the director is usually 60 degrees or more and 90 degrees or less, preferably 80 degrees or more and 90 degrees or less as an absolute value in one of the vicinity of the upper surface or the lower surface interface of the film. The absolute value is usually from 0 to 50 degrees, preferably from 0 to 30 degrees.

Next, the average tilt angle of the compensation film will be described. In the present invention, the average angle between the director of the liquid crystalline polymer and the plane of the substrate in the film thickness direction is defined as the average tilt angle. The average tilt angle can be obtained by applying a crystal rotation method.
The average tilt angle of the compensation film used in the present invention is usually 1
The range is 0 to 60 degrees, preferably 20 to 50 degrees. If the average tilt angle is out of the above range, a sufficient viewing angle expanding effect may not be obtained.

The compensation film used in the present invention is not particularly limited as long as the above-mentioned liquid crystalline polymer is substantially formed, has a nematic hybrid orientation of the liquid crystalline polymer, and has the above-mentioned parameters. Not done.

The compensation film used in the liquid crystal display of the present invention will be described in more detail. The liquid crystalline polymer forming the compensation film is, specifically, a homeotropically oriented liquid crystalline polymer, more specifically, a homeotropically oriented liquid crystalline polymer compound or at least one type of homeotropically oriented liquid crystalline polymer. It is a liquid crystal polymer composition containing a liquid crystal polymer compound.

Here, the homeotropic alignment means a state in which the director of the liquid crystal is aligned substantially perpendicular to the plane of the substrate. This homeotropic liquid crystalline polymer is
It is an essential component for realizing the nematic hybrid orientation formed by the compensation film used in the present invention.

The determination as to whether or not the liquid crystalline polymer has homeotropic alignment is made by forming a liquid crystalline polymer layer on a substrate and determining the alignment state. The substrate that can be used for this determination is not particularly limited. For example, a glass substrate, more specifically, an optical glass such as soda glass, potash glass, borosilicate glass, crown glass, and flint glass, or a liquid crystalline polymer A plastic film or sheet having heat resistance at the liquid crystal temperature of, more specifically, polyethylene terephthalate, polyethylene naphthalate, polyphenylene oxide, polyimide, polyamide imide, polyether imide, polyamide, polyether ketone, polyether ether ketone, polyketone sulfide And polyethersulfone can be used as the substrate. The substrate exemplified above is used after its surface is cleaned with an acid, an alcohol, a detergent, or the like, but is used without performing a surface treatment such as a silicon treatment.

The homeotropically-aligned liquid crystalline polymer used in the present invention is obtained by forming a film of a liquid crystalline polymer on the substrate exemplified above, and at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state. The one that forms homeotropic alignment on any one of the substrates is defined as a homeotropic alignment liquid crystalline polymer. However, depending on the type and composition of the liquid crystalline polymer, there is a liquid crystal polymer that is specifically homeotropically aligned at a temperature near the liquid crystal-isotropic phase transition point. Therefore, it is usually desirable to carry out the reaction at a temperature of 15 ° C. or lower, preferably 20 ° C. or lower from the liquid crystal-isotropic phase transition point.

The homeotropically aligning liquid crystalline polymer includes, for example, an aromatic group having a bulky substituent and an aromatic group having a long-chain alkyl group in a structural unit constituting a main chain of the liquid crystalline polymer. A liquid crystalline polymer having an aromatic group having a fluorine atom, etc .;
A monofunctional structural unit derived from a compound having one long-chain alkyl group or a long-chain fluoroalkyl group having 2 to 20 carbon atoms and having one functional site such as a monoalcohol or a monocarboxylic acid. Having a liquid crystalline polymer.

The monofunctional structural unit used in the liquid crystalline polymer is a functional unit corresponding to a functional group of a bifunctional monomer used for forming a condensation polymer which is a liquid crystalline polymer. A structure in which a monomer having one group is incorporated into the polymer molecule by coexisting during the production of the polymer (during or after the polymerization reaction), and usually refers to a fragment of the polymer molecule. It is incorporated at one or both termini. Therefore, the number of the monofunctional structural units present in the polymer molecule is usually 1 to 2 per molecule. The monofunctional structural unit is represented by the following general formula.

[0029]

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[0030]

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In the above formula, R ₁ and R ₂ may be the same or different. R ₁ and R ₂ represent a long-chain alkyl group having 3 to 20 carbon atoms or a long-chain fluoroalkyl group having 2 to 20 carbon atoms. In particular,

[0032]

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And the like can be exemplified as preferable ones. X is a halogen such as hydrogen, fluorine and chlorine. I is 0 or 1. And j is
It is 0 or 1. K is 0 or 1. A is 0 or 1, and b is 0 or 1. However, a +
b ≠ 0. As a monofunctional structural unit formed from the above monoalcohol, monocarboxylic acid and their functional derivatives,

[0034]

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[0035]

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[0036]

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And the like can be exemplified as preferred units. One end or both ends of the polymer chain are constituted by one or two kinds selected from the monofunctional structural units exemplified above. When the structural units are present at both ends, the units at both ends need not be the same.

Specific examples of the liquid crystal polymer include a main chain type liquid crystal polymer such as polyester, polyimide, polyamide, polycarbonate, and polyesterimide which satisfies and / or conditions. Among these, liquid crystalline polyesters are particularly preferred from the viewpoints of ease of synthesis, ease of forming a film, and stability of physical properties of the obtained film. Generally, the main chain of the liquid crystalline polyester is
It is formed from a difunctional structural unit such as a dicarboxylic acid unit, a diol unit and an oxycarboxylic acid unit, or a polyfunctional structural unit other than the unit. As the liquid crystalline polyester forming the compensation film used in the present invention, those having an ortho-substituted aromatic unit in the main chain are more preferable.
Specific examples include the following catechol units, salicylic acid units, phthalic acid units, 2,3-naphthalenediol units, 2,3-naphthalenedicarboxylic acid units, and those having a substituent on the benzene ring. Can be.

[0039]

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(Y represents a halogen such as Cl or Br, a methyl group, an ethyl group, a methoxy group, an ethoxy group or a phenyl group, and k is from 0 to 2.) The specific structural example of the liquid crystalline polyester of orientation is shown.
That satisfy the conditions of

[0041]

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L = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 n / m = 100/0 to 20/80, preferably 98/2
３０30/70 k, l, m and n each indicate a molar composition ratio.

[0043]

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1 = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / n = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0045]

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1 = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 n / m = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0047]

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M = n, (k + 1) / m = 20 / 10-2
/ 10, preferably 15/10 to 5/10 k / l = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0049]

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K = m + n, 1 / m = 100/0 to 1/9
9, preferably 90/10 to 2/98 k, l and m each represent a molar composition ratio.

[0051]

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L = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / n = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0053]

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L = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0055]

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K = 1 + m, 1 / m = 100/0 to 0/1
00, preferably 95/5 to 5/95 k, l, m and n each represent a molar composition ratio.

[0057]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 n / m = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0059]

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M = n, (k + 1) / m = 20 / 10-2
/ 10, preferably 5/10 to 5/10 k, l, m and n each represent a molar composition ratio.

[0061]

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L = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 n / m = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0063]

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N = m + 1, k / n = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / l = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0065]

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L = m, k / l = 20/10 to 0/10,
Preferably, 15/10 to 0/10 k, l, and m each represent a molar composition ratio.

[0067]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio. j is 2
Indicates an integer of 12.

[0069]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio. j is 2
Indicates an integer of 12.

[0071]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 m / n = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0073]

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K + 1 = m + n, k / l = 100 / 0-1
/ 99, preferably 90/10 to 2/98 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0075]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 m / n = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio.

[0077]

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1 = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0079]

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L = m + n, k / l = 20/10 to 0/1
0, preferably 15/10 to 0/10 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio. j is 2
Indicates an integer of 12.

[0081]

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K + 1 = m + n, k / l = 100 / 0-0
/ 100, preferably 95/5 to 5/95 m / n = 100/0 to 1/99, preferably 90/10
２/98 k, l, m, n each indicate a molar composition ratio. And the like. In addition, those that satisfy the conditions

[0083]

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M + n = k / 2 + l k / l = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0085]

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1 = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0087]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0089]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0091]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0093]

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N + o = k / 2 + m k / m = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 1 / (n + o) = 20/10 to 0/10, preferably 1
5/10 to 5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0095]

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M + n = k / 2 + l k / l = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0097]

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M = k / 2 + n k / n = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 l / m = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m and n each indicate a molar composition ratio.

[0099]

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1 = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0101]

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L + m = k / 2 + n k / n = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0103]

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N + o = k / 2 + m k / m = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 1 / (n + o) = 20/10 to 0/10, preferably 1
5/10 to 5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0105]

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M + n = k / 2 + ok k / o = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / (m + n) = 20/10 to 0/10, preferably 1
5/10 to 5/10 i represents an integer of 2 to 12. k, l, m, n, and o each represent a molar composition ratio.

[0107]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0109]

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M + n = k / 2 + ok k / o = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / (m + n) = 20/10 to 0/10, preferably 1
5/10 to 5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0111]

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L + m = k / 2 + n + ok k / (n + o) = 80/60 to 2/99, preferably 4
0/80 to 10/95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m, n and o each indicate a molar composition ratio.

[0113]

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N + o = k / 2 + m k / m = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 l / m = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0115]

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1 + m = k / 2 + ok k / o = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0117]

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N + o = k / 2 + l + m k / (l + m) = 80/60 to 2/99, preferably 4
0/80 to 10/95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m, n and o each indicate a molar composition ratio.

[0119]

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M = k / 2 + n + ok k / (n + o) = 80/60 to 2/99, preferably 4
0/80 to 10/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 l / m = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0121]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / m = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0123]

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N + o = k / 2 + l + m k / (l + m) = 80/60 to 2/99, preferably 4
0/80 to 10/95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m, n and o each indicate a molar composition ratio.

[0125]

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O = k / 2 + m + nk / (m + n) = 80/60 to 2/99, preferably 4
0/80 to 10/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0127]

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L + m = k / 2 + n + ok k / (n + o) = 80/60 to 2/99, preferably 4
0/80 to 10/95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 i represents an integer of 2 to 12. k, l, m, n, and o each represent a molar composition ratio.

[0129]

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O = k / 2 + n k / n = 80/60 to 2/99, preferably 40/80
〜１０10 / 95 l / m = 100/0 to 0/100, preferably 95/5
５5/95 (l + m) / o = 20/10 to 1/10, preferably 1
5/10 to 5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0131]

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O = k / 2 + 1/2 + m + n (k + 1) / (m + n) = 80/60 to 2/99, preferably 40/80 to 10/95 k / l = 100/0 to 0/100, preferably 90 / 1
0/10/90 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m, n and o each indicate a molar composition ratio.

[0133]

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O + p = k / 2 + 1/2 + n (k + 1) / n = 80/60 to 2/99, preferably 4
0/80 to 10/95 k / l = 100/0 to 0/100, preferably 90/1
0/10/90 o / p = 100 / 0-0 / 100, preferably 95/5
５5/95 m / n = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, o, and p each represent a molar composition ratio.

And the like. In addition, as the homeotropic alignment liquid crystalline polymer, a unit having a substituent such as an aromatic group having a bulky substituent, an aromatic group having a long-chain alkyl group, or an aromatic group having a fluorine atom has a side chain. And a side-chain type liquid crystal polymer such as polyacrylate, polymethacrylate, polysiloxane, and polymalonate. A specific structure example is shown below.

[0136]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0138]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0140]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0142]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0144]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0146]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0148]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0150]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0152]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0154]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0156]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0158]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0160]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0162]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

[0164]

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N / m = 80/20 to 20/80, preferably 75/25 to 25/75

In the above-described homeotropically-alignable liquid crystalline polymer, an aromatic group having a bulky substituent, an aromatic group having a long-chain alkyl group, an aromatic group having a long-chain alkyl group, In the case of a main chain type liquid crystalline polymer having an aromatic group having an atom, the molecular weight is determined in various solvents.
For example, phenol / tetrachloroethane (60/40
(Weight ratio)) The logarithmic viscosity measured at 30 ° C. in the mixed solvent is usually 0.05 to 2.0, preferably 0.07 to 1.0. If the logarithmic viscosity is less than 0.05, the mechanical strength of the compensation film may be weak. Also,
When it is larger than 2.0, homeotropic orientation may be lost. On the other hand, if it is larger than 2.0, the viscosity may be too high in the liquid crystal state, and even if it is homeotropically aligned, the time required for alignment may be long. Moreover, the nematic hybrid orientation may not be obtained during the production of the compensation film described below.

At the terminal or both terminals of the polymer chain,
Long chain alkyl group having 3 to 20 carbon atoms or 2 to 20 carbon atoms
In the case of a liquid crystalline polymer having a monofunctional unit derived from a compound having a single functional site such as a monoalcohol or a monocarboxylic acid having a long-chain fluoroalkyl group or the like, the molecular weight may vary depending on various solvents. Logarithmic viscosity measured at 30 ° C. in a phenol / tetrachloroethane (60/40 (weight ratio)) mixed solvent is usually 0.04 to 1.
5, preferably in the range of 0.06 to 1.0. When the logarithmic viscosity is smaller than 0.04, the mechanical strength of the compensation film becomes weak. If it is larger than 1.5, homeotropic orientation may be lost. In addition, the viscosity may be too high in the liquid crystal state, and even if homeotropic alignment is performed, the time required for alignment may be long. Moreover, the nematic hybrid orientation may not be obtained during the production of the compensation film described below.

Further, in the case of the side chain type liquid crystalline polymer, the molecular weight is usually from 1,000 to 1 in terms of polystyrene equivalent weight average molecular weight.
It is preferably in the range of 10,000, preferably 3000 to 50,000. If the molecular weight is less than 1000, the mechanical strength of the compensation film may be weak, which is not desirable. If it is larger than 100,000, homeotropic orientation may be lost. On the other hand, if it is larger than 100,000, the solubility of the liquid crystalline polymer in the solvent may be reduced. This is not desirable because it may cause a problem that a film cannot be obtained.

The method for synthesizing the above liquid crystalline polymer is not particularly limited. The liquid crystalline polymer can be synthesized by a polymerization method known in the art. For example, taking the synthesis of a liquid crystalline polyester as an example, it can be synthesized by a melt polymerization method or an acid chloride method using a corresponding acid chloride of dicarboxylic acid.

In synthesizing the liquid crystalline polymer,
The monofunctional structural unit is the monoalcohol described above,
It is subjected to a polymerization reaction as a monocarboxylic acid compound and a functional derivative thereof, specifically, an acetylated product, a halide, or the like. The content of the monofunctional structural unit in the liquid crystalline polymer, specifically in the liquid crystalline polyester, is 2/201 to 80 in terms of mole fraction in the amount of the remaining constituent components excluding the hydroxycarboxylic acid structural unit. / 240 range. More preferably, it is in the range of 10/205 to 20/220. When the content of the monofunctional structural unit is 2/210
If the molar fraction is smaller, the liquid crystalline polyester may not show homeotropic orientation. When the content of the monofunctional structural unit is larger than 80/240 (molar fraction), the molecular weight of the liquid crystalline polyester may not be increased to a desired value. Further, when a compensation film is produced, the mechanical strength of the film becomes weak, which is not preferable. The content of the monofunctional structural unit is
It depends on the charged amount of the monomer component.

As described above, the liquid crystal polymer having a positive uniaxial property is, in addition to the liquid crystal polymer having homeotropic alignment, a liquid crystal polymer having another alignment or a liquid crystal polymer having any other orientation. May be used as a composition by appropriately mixing a non-liquid crystalline polymer or the like which does not show the above. By using the composition, there is an advantage that the average tilt angle of the nematic hybrid alignment can be freely controlled by adjusting the composition ratio, and the nematic hybrid alignment can be stabilized. However, the compensating film used in the present invention unless the liquid crystalline polymer that is mixed into the composition exhibits optically positive uniaxiality and does not form a nematic hybrid alignment in the liquid crystal state of the liquid crystalline polymer. Cannot be obtained. When used as a composition, it is desirable to contain the homeotropically-aligned liquid crystalline polymer described above in an amount of 5% by weight or more. If the amount is less than 5% by weight, nematic hybrid alignment may not be obtained.

As the polymer that can be mixed, a liquid crystalline polymer exhibiting an orientation other than homeotropic orientation is usually appropriately mixed from the viewpoint of compatibility with a homeotropically oriented liquid crystalline polymer. . Examples of the type of liquid crystalline polymer used include a main chain type liquid crystalline polymer; for example, polyester, polyimide, polyamide, polyester,
Side-chain type liquid crystalline polymers such as polycarbonate and polyesterimide; and polyacrylates, polymethacrylates, polysiloxanes, and polymalonates. It is not particularly limited as long as it has compatibility with homeotropically-oriented liquid crystalline polymer, but among others, homogeneously oriented liquid crystalline polymer, more specifically, homogeneously oriented polyester, polyacrylate,
And polymethacrylate are preferred. Among them, the liquid crystalline polyester having an ortho-substituted aromatic unit ([Chemical Formula 4]) in the main chain is most preferable. Hereinafter, specific structural examples of the liquid crystalline polymer exhibiting homogeneous alignment will be described.

[0173]

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K = l + ml / m = 80/20 to 20/80, preferably 75/2
5 to 25/75 k, l, and m each represent a molar composition ratio.

[0175]

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O = m + n (k + 1) / o = 20/10 to 0/10, preferably 1
5/10 to 0/10 m / n = 100/0 to 0/100, preferably 98/2
２/98 k, l, m, n and o each indicate a molar composition ratio.

[0177]

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N = 1 + m k / m = 20/10 to 0/10, preferably 15/10
０0/10 k, l, m, n each indicate a molar composition ratio.

[0179]

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K + 1 = m + n k / l = 100/0 to 0/100, preferably 95/5
５5/95 m / l = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0181]

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K + 1 = m + n k / l = 100/0 to 0/100, preferably 95/5
５5/95 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0183]

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L = m + nk / l = 15/10 to 0/10, preferably 10/10
０0/10 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0185]

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M + n = k / 2 + l k / l = 40/80 to 0/100, preferably 20/9
0/0/100 m / n = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0187]

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O = k / 2 + m + nk / (m + n) = 40/80 to 0/100, preferably 20/90 to 0/100 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0189]

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O = k / 2 + m + nk / (m + n) = 40/80 to 0/100, preferably 20/90 to 0/100 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0191]

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1 = k / 2 + m + nk / (m + n) = 40/80 to 0/100, preferably 20/90 to 0/100 n / m = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m and n each indicate a molar composition ratio.

[0193]

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M = k / 2 + n + ok k / (n + o) = 40/80 to 0/100, preferably 20/90 to 0/100 n / o = 100/0 to 0/100, preferably 95/5
５5/95 l / m = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0195]

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O = k / 2 + m + nk / (m + n) = 40/80 to 0/100, preferably 20/90 to 0/100 m / n = 100/0 to 0/100, preferably 95/5
５5/95 l / o = 20/10 to 0/10, preferably 15/10
５5/10 k, l, m, n, and o each indicate a molar composition ratio.

[0197]

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N + o = k / 2 + l + m k / (l + m) = 40/80 to 0/100, preferably 20/90 to 0/100 l / m = 100/0 to 0/100, preferably 95/5
５5/95 n / o = 100/0 to 0/100, preferably 95/5
５5/95 k, l, m, n and o each indicate a molar composition ratio.

In the case of the main-chain type liquid crystalline polymer, these molecular weights can be measured in various solvents, for example, in a mixed solvent of phenol / tetrachloroethane (60/40 (weight ratio)).
The logarithmic viscosity measured at ° C is usually preferably from 0.05 to 3.0, more preferably from 0.07 to 2.0.
If the logarithmic viscosity is less than 0.05, the mechanical strength of the compensation film may be weak. On the other hand, if it is larger than 3.0, the homeotropic alignment may be impaired, or the viscosity at the time of forming the liquid crystal may become too high, and the time required for the alignment may become longer, which is not desirable.

In the case of a side chain type polymer liquid crystal, the molecular weight is usually 5,000 to 20 in terms of polystyrene equivalent weight average molecular weight.
It is preferably in the range of 10,000, preferably 10,000 to 150,000. When the molecular weight is smaller than 5000, the mechanical strength of the compensation film may be weak. If it is larger than 200,000,
This is undesirable because it may cause problems in film formation, such as a decrease in solubility of the polymer in the solvent and an excessive increase in the solution viscosity of the coating solution, making it impossible to obtain a uniform coating film.

The determination of the homogeneous orientation is performed using the substrate which has not been subjected to a surface treatment such as a silicon treatment, a rubbing treatment and a uniaxial stretching treatment, like the determination of the homeotropic orientation. A liquid crystalline polymer layer is formed on the substrate, and it is determined whether or not the alignment state indicates homogeneous alignment.

The method for synthesizing the above liquid crystalline polymer is not particularly limited. The liquid crystalline polymer can be synthesized by a polymerization method known in the art. For example, taking polyester synthesis as an example, the polyester can be synthesized by a melt polymerization method or an acid chloride method using a corresponding acid chloride of dicarboxylic acid.

In order to obtain a compensation film in which the nematic hybrid orientation is fixed uniformly using the liquid crystal polymer having a positive uniaxial property as described above, the following steps are required for the orientation substrate and each step. Desirable in the invention.

First, the alignment substrate will be described. In order to obtain a nematic hybrid alignment using a positive uniaxial liquid crystalline polymer, it is preferable that the upper and lower sides of the liquid crystalline polymer layer be sandwiched between different interfaces. When the upper and lower sides are sandwiched by the same interface, the alignment at the upper and lower interfaces of the liquid crystalline polymer layer becomes the same, and it becomes difficult to obtain a nematic hybrid alignment.

As a specific mode, one alignment substrate and an air interface are used. Specifically, the lower interface of the liquid crystalline polymer layer is in contact with the alignment substrate, and the upper interface of the liquid crystalline polymer layer is in contact with air. Although it is possible to use an alignment substrate having different upper and lower interfaces, it is preferable to use one alignment substrate and an air interface from the viewpoint of the manufacturing process.

The alignment substrate that can be used in the present invention is:
It is desirable to have anisotropy so that the direction in which the liquid crystal tilts (projection of the director onto the alignment substrate) can be defined. If the tilt direction of the liquid crystal cannot be specified, only an orientation tilted in a random direction can be obtained (a vector obtained by projecting the director onto the substrate becomes disordered).

As the alignment substrate, specifically, a substrate having in-plane anisotropy is desirable. Polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyetherketone, polyketonesulfide, Polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulosic plastics, epoxy resin, phenolic resin, etc. Plastic film substrate and uniaxially stretched plastic film substrate, aluminum, iron, copper, etc. with slit-shaped grooves on the surface A metal substrate, an alkali glass etched surface in a slit form, borosilicate glass, a glass substrate such as flint glass, and the like.

In the present invention, a rubbing plastic film substrate obtained by subjecting the above-mentioned plastic film substrate to rubbing treatment, a plastic thin film subjected to rubbing treatment, such as the above-mentioned various substrates having a rubbing polyimide film, a rubbing polyvinyl alcohol film or the like; The various substrates described above having an obliquely deposited film or the like can also be used.

Among the above various alignment substrates, various substrates having a rubbing polyimide film, a rubbing polyimide substrate, a rubbing polyetheretherketone substrate, a rubbing polyetheretherketone substrate, a rubbing polyetherketone substrate, and a rubbing polyimide substrate are preferable. A polyether sulfone substrate, a rubbing polyphenylene sulfide substrate, a rubbing polyethylene terephthalate substrate, a rubbing polyethylene naphthalate substrate, a rubbing polyarylate substrate, and a cellulose-based plastic substrate can be given. The rubbing direction applied to these substrates usually corresponds to the tilt direction of the compensation film described above.

In the compensation film used in the liquid crystal display device of the present invention, as described above, the angle between the director of the liquid crystalline polymer and the plane of the film is different between the upper surface and the lower surface of the film. The angle in the vicinity of the interface of the film surface in contact with the alignment substrate is adjusted to any angle range of 0 to 50 degrees or 60 to 90 degrees depending on the method of the alignment treatment and the type of liquid crystalline polymer. You. Generally, it is desirable in the manufacturing process to adjust the angle between the director of the liquid crystalline polymer and the film plane in the vicinity of the interface of the film surface in contact with the alignment substrate to an angle range of 0 to 50 degrees.

The compensating film is obtained by coating a liquid crystalline polymer having optically positive uniaxial uniformity on the alignment substrate as described above and then performing a uniform alignment process and a process of fixing the alignment form. The application of the liquid crystalline polymer to the alignment substrate can be usually performed in a solution state in which the liquid crystalline polymer is dissolved in various solvents or in a molten state in which the liquid crystalline polymer is melted.
Solution application is desirable in the manufacturing process.

In the solution application, a liquid crystal polymer is dissolved in an appropriate solvent to prepare a solution having a predetermined concentration. As the solvent, although it cannot be said unconditionally depending on the type (composition ratio, etc.) of the positive uniaxial liquid crystalline polymer, usually, chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, Halogenated hydrocarbons such as orthodichlorobenzene, phenols such as phenol and parachlorophenol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene and 1,2-dimethoxybenzene, acetone, ethyl acetate, tert
-Butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, ethylcellosolve, butylcellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, Dimethylacetamide, dimethylsulfoxide, acetonitrile, butyronitrile, carbon disulfide and the like, and a mixed solvent thereof, for example, a mixed solvent of a halogenated hydrocarbon and a phenol are used.

The concentration of the solution depends on the solubility of the positive uniaxial liquid crystalline polymer to be used and the final thickness of the target compensating film. And preferably in the range of 7 to 30% by weight.

A positive uniaxial liquid crystalline polymer solution adjusted to a desired concentration using the above-described solvent is then applied onto the above-described alignment substrate. As a coating method, a spin coating method, a roll coating method, a printing method, an immersion pulling method, a curtain coating method, or the like can be adopted.

After the application, the solvent is removed, and a liquid crystal polymer layer having a uniform thickness is formed on the alignment substrate. The conditions for removing the solvent are not particularly limited as long as the solvent can be substantially removed and the liquid crystalline polymer layer does not flow or even falls off. Usually, the solvent is removed by drying at room temperature, drying in a drying furnace, or blowing hot or hot air.

The purpose of this coating and drying step is to first form a layer of a liquid crystalline polymer uniformly on the substrate, and the liquid crystalline polymer has not yet formed a nematic hybrid alignment. In the next heat treatment step, a monodomain nematic hybrid alignment is completed.

In forming the nematic hybrid alignment by the heat treatment, the viscosity of the positive uniaxial liquid crystalline polymer is preferably low in order to assist the alignment by the interface effect. Therefore, a higher heat treatment temperature is desirable. Also, depending on the liquid crystalline polymer, the average tilt angle obtained may vary depending on the heat treatment temperature. In that case, it is necessary to set the heat treatment temperature in order to obtain an average tilt angle according to the purpose. For example, when it is necessary to perform heat treatment at a relatively low temperature in order to obtain an alignment having a certain tilt angle, the viscosity of the liquid crystalline polymer is high at a low temperature, and the time required for the alignment becomes long. In such a case, a method is effective in which a heat treatment is once performed at a high temperature to obtain a monodomain orientation, and then the temperature of the heat treatment is gradually or gradually reduced to a target temperature. In any case, it is desirable to perform the heat treatment at a temperature equal to or higher than the glass transition point according to the characteristics of the optically positive uniaxial liquid crystalline polymer to be used. Heat treatment temperature is usually 5
A range of 0 ° C to 300 ° C, particularly a range of 100 ° C to 260 ° C, is suitable.

The heat treatment time required for the liquid crystalline polymer to be sufficiently aligned on the alignment substrate depends on the kind (for example, composition ratio) of the liquid crystalline polymer to be used and the heat treatment temperature. I can't say, but usually 10 seconds ~
The range is preferably 120 minutes, particularly 30 seconds to 60 minutes. If the time is shorter than 10 seconds, the orientation may be insufficient. If the time is longer than 120 minutes, productivity may decrease, which is not desirable.

In this way, a uniform nematic hybrid alignment can be obtained over the entire surface of the alignment substrate in a liquid crystal state.

In the above-mentioned heat treatment step, a magnetic field or an electric field may be used in order to align the liquid crystalline polymer in the nematic hybrid orientation. However, when a magnetic field or an electric field is applied while performing heat treatment, a uniform field force acts on the liquid crystalline polymer during the application, so that the director of the liquid crystal tends to turn in a certain direction. That is, it is difficult to obtain a nematic hybrid orientation in which the director forms different angles depending on the film thickness direction as in the present invention. Once a non-nematic hybrid orientation, such as homeotropic, homogeneous or other orientation, is formed, a thermally stable nematic hybrid orientation can be obtained by removing the force of the field, but there is no particular advantage in the process. .

The nematic hybrid alignment thus formed in a liquid crystal state is fixed to a temperature lower than the liquid crystal transition point of the liquid crystalline polymer, and thereby can be fixed without impairing the uniformity of the alignment.

The cooling temperature is not particularly limited as long as it is lower than the liquid crystal transition point. For example, 10 ° C from the liquid crystal transition point
By cooling at a low temperature, uniform nematic hybrid orientation can be fixed. There is no particular limitation on the cooling means, and the cooling is carried out by simply taking out from the heating atmosphere in the heat treatment step to an atmosphere below the liquid crystal transition point, for example, at room temperature. In order to increase production efficiency, forced cooling such as air cooling or water cooling or cooling may be performed.
However, the average tilt angle obtained depending on the cooling rate may be slightly different depending on the positive uniaxial liquid crystalline polymer. When it becomes necessary to use such a liquid crystalline polymer and strictly control the average tilt angle, it is preferable to perform the cooling operation in consideration of cooling conditions as appropriate.

Next, the angle control of the nematic hybrid orientation in the film thickness direction will be described. The angle between the director of the liquid crystalline polymer and the plane of the film should be controlled to the desired angles by appropriately selecting the type of liquid crystalline polymer to be used, the composition ratio, the alignment substrate, the heat treatment conditions, and the like. Can be. Even after the nematic hybrid orientation is fixed, the angle can be controlled to a desired angle by using a method such as uniformly shaving the film surface or immersing the film surface in a solvent to uniformly dissolve the film surface. The solvent used at this time must be appropriately selected depending on the type of the liquid crystalline polymer and the type of the alignment substrate.

The compensating film obtained by the above steps is obtained by uniformly orientating and fixing an orientation form called a nematic hybrid orientation, and since the orientation is formed, the upper and lower sides of the film are not equivalent. Also, there is anisotropy in the in-plane direction.

As described above, when the compensation film is disposed between the TN liquid crystal cell and the upper and / or lower polarizing plate, the orientation substrate is peeled off from the film, and the compensation film is used alone. And a method in which a compensation film is used as it is formed on an alignment substrate, and a compensation film is laminated on another substrate different from the alignment substrate. In addition, when used in the state described above, the alignment substrate is necessary for obtaining a nematic hybrid alignment, but when using the substrate which may have an unfavorable effect as a TN-LCD, the alignment substrate is used as a nematic hybrid alignment. It can be removed after the orientation is fixed. In the compensation film after fixation of orientation used in the present invention, orientation disorder or the like does not occur even if the orientation substrate is removed. As described above, in the liquid crystal display device of the present invention,
A compensation film having any form may be used.

The compensatory film may be provided with a protective layer such as a transparent plastic film for the purpose of protecting the surface, increasing the strength, and improving environmental reliability. In addition, a substrate which is preferable in terms of optical properties as a protective layer, for example, polymethacrylate, polycarbonate, polyvinyl alcohol,
A plastic substrate such as polyethersulfone, polysulfone, polyarylate, polyimide, amorphous polyolefin, or triacetylcellulose can also be used by being bonded via an optical-grade adhesive or pressure-sensitive adhesive.

Next, the arrangement when the compensation film of the present invention is combined with the TN liquid crystal cell described above will be specifically described. The position of the compensating film is
One or more compensation films can be arranged as long as the distance is between the N liquid crystal cells. In the present invention, it is practically preferable to perform viewing angle compensation using one or two compensation films. Even if three or more compensation films are used, the viewing angle can be compensated, but this is not so preferable because it leads to an increase in cost. An example of a specific arrangement position is as follows. However, these are merely typical arrangement positions, and the present invention is not limited to these.

First, the tilt direction of the compensating film in the present invention is defined as the tilt direction of the liquid crystal polymer on the surface where the angle between the director of the liquid crystal polymer and the plane of the film is smaller among the upper and lower surfaces of the film. Is defined as the projection direction of the director. Specifically, for example, it is assumed that two upper and lower surfaces of the compensation film in FIG. 1 are a b surface and a c surface. The angle formed between the director of the liquid crystalline polymer and the plane of the film on the b-plane side and the c-plane side of the compensating film has a relationship of angle on the b-plane> angle on the c-plane side. Next, when the c-plane is viewed in the film thickness direction from the b-plane of the compensation film, b
The direction formed by the director on the surface side and the director on the c surface side becomes an acute angle, and the director on the b surface side and c
In the present invention, the direction in which the projected component of the director on the surface side is parallel to the film plane is defined as the tilt direction of the compensation film.

Next, the pretilt direction of the TN liquid crystal cell is defined as follows. Usually, the nematic liquid crystal in the TN liquid crystal cell is not parallel to the cell substrate interface as shown in FIG. 2, but is inclined at a certain angle (when the twist angle of the nematic liquid crystal is 0 degree). In this state, the direction in which the angle between the director of the liquid crystal and the plane of the liquid crystal cell substrate is an acute angle and the direction in which the projection component of the director is parallel is defined as a pretilt direction in the present invention. Therefore, the pretilt direction is defined for each of the upper and lower liquid crystal cell substrates in the TN liquid crystal cell, as shown in FIG.

First, the case where one compensation film is disposed will be described. The compensation film is disposed between the polarizing plate and the TN liquid crystal cell, and may be on the upper surface side or the lower surface side of the liquid crystal cell. In this arrangement, the tilt direction of the compensation film,
The angle between the compensation film and the pretilt direction of the cell substrate on the opposite side of the liquid crystal cell substrate closest to the liquid crystal cell substrate is usually in the range of 165 to 195 degrees, preferably 170 to 190 degrees, particularly preferably 175 to 185 degrees. . That is, when the compensation film is disposed on the upper surface of the TN liquid crystal cell, the angle formed with the pretilt direction in the lower liquid crystal cell substrate, and when the compensation film is disposed on the lower surface of the TN liquid crystal cell, The upper liquid crystal cell substrate is arranged so that the angle formed with the pretilt direction satisfies the above angle range. If the above angle range is not satisfied,
A sufficient viewing angle compensation effect cannot be obtained.

Next, the case where two compensating films are arranged will be described. When placing two compensation films,
Two sheets may be arranged on the same side, for example, between the TN liquid crystal cell and the upper polarizing plate or between the liquid crystal cell and the lower polarizing plate. One sheet may be arranged between the upper and lower polarizing plates and the TN liquid crystal cell. As the two compensation films, films having the same optical parameters may be used, or films having different optical parameters may be used.

A case will be described in which one sheet is disposed between each of the upper and lower polarizing plates and the TN liquid crystal cell.
In this arrangement, each compensating film is connected to the above-described one.
The arrangement is the same as when arranging sheets. That is, the angle between the tilt direction of each compensation film and the pretilt direction on the cell substrate opposite to the substrate of the TN liquid crystal cell where the compensation film is close is usually 165 to 195 degrees, preferably 170 to 190 degrees, particularly preferably. 175-1
It is arranged in a range of 85 degrees.

Next, a case where two compensating films are arranged on one of the TN liquid crystal cell and the upper or lower polarizing plate will be described. It is assumed that the compensation film arranged at the position closest to the TN liquid crystal cell is film 1, and the compensation film arranged between the film 1 and the upper or lower polarizing plate is film 2. TN in the arrangement
The film 1 closest to the liquid crystal cell is arranged in the same manner as the condition for arranging one compensation film described above.
That is, the angle between the tilt direction of the film 1 and the pretilt direction of the cell substrate on the side opposite to the TN liquid crystal cell substrate closest to the film 1 is usually 165 to 195.
Degrees, preferably 170 to 190 degrees, particularly preferably 17 degrees
Arrange in the range of 5 to 185 degrees. Next, the arrangement conditions of the film 2 disposed between the film 1 and the upper or lower polarizing plate will be described. The film 2 has an angle of 165 with respect to the pretilt direction of the cell substrate of the TN liquid crystal cell to which the film 1 is closest, that is, the angle formed by the pretilt direction of the cell substrate opposite to the cell substrate with reference to the arrangement condition of the film 1. To 195 degrees, preferably 170 to 19
It is arranged at 0 degrees, particularly preferably in the range of 175 to 185 degrees.

Next, the arrangement of the polarizing plate will be described. Usually, in a TN-LCD, the transmission axes of the upper and lower polarizers may be arranged orthogonally or parallel to each other. When the transmission axes of the upper and lower polarizers are arranged so as to be orthogonal to each other, the transmission axis of the polarizer and the rubbing direction applied to the TN liquid crystal cell substrate on the side closer to the polarizer are orthogonal, parallel or 45 degrees. In some cases. In the liquid crystal display device of the present invention, when a polarizing plate is mounted on the compensation film,
The arrangement is not particularly limited, and may be any of the above arrangements. Among them, in the liquid crystal display device of the present invention, the transmission axes of the upper and lower polarizers are orthogonal to each other, and the transmission axis of the polarizer and the rubbing direction applied to the TN liquid crystal cell substrate on the side closer to the polarizer are orthogonal or parallel. It is desirable to arrange.

As described above, the present invention provides a twisted nematic liquid crystal display device using a TFT element or an MIM element by disposing a compensation film in which a nematic hybrid alignment is fixed in a TN liquid crystal cell having specific optical parameters. The liquid crystal display device with high contrast and wide viewing angle can be obtained.

[0236]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. In addition, each analysis method used in the Example is as follows. (1) Determination of Composition of Liquid Crystalline Polymer The polymer was dissolved in deuterated chloroform or deuterated trifluoroacetic acid, and measured and determined by 400 MHz 1H-NMR (JNM-GX400 manufactured by JEOL Ltd.). (2) Measurement of logarithmic viscosity The viscosity was measured at 30 ° C. in a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent using an Ubbelohde viscometer. (3) Determination of liquid crystal phase series Determined by DSC (Perkin Elmer DSC-7) measurement and observation with an optical microscope (BH2 polarizing microscope manufactured by Olympus Optical Co., Ltd.). (4) Measurement of Refractive Index The refractive index was measured with an Abbe refractometer (Type-4 manufactured by Atago Co., Ltd.). (5) Polarization analysis Ellipsometer DVA-36V manufactured by Mizojiri Optical Co., Ltd.
Performed using WLD. (6) Film thickness measurement Kosaka Laboratory Co., Ltd. high-precision thin film step measuring device ET-1
0 was used. In addition, a method of determining the film thickness from the data of the refractive index and the interference wave measurement (UV-visible / near-infrared spectrophotometer V-570 manufactured by JASCO Corporation) was also used.

Reference Example <Synthesis of Liquid Crystalline Polyester> 100 mmol of 6-hydroxy-2-naphthoic acid, 100 mm of terephthalic acid
ol, chlorohydroquinone 50 mmol, tert-
Butyl catechol 50 mmol, and acetic anhydride 6
The acetylation reaction was performed at 140 ° C. for 2 hours in a nitrogen atmosphere using 00 mmol. Subsequently, polymerization was performed at 270 ° C. for 2 hours, 280 ° C. for 2 hours, and 300 ° C. for 2 hours. Next, the obtained reaction product was dissolved in tetrachloroethane, and then purified by reprecipitation with methanol to obtain 40.0 g of a liquid crystalline polyester (formula (1)). The liquid crystalline polyester has a logarithmic viscosity of 0.35, a nematic phase as a liquid crystal phase, and an isotropic phase-liquid crystal phase transition temperature of 300.
The glass transition point was 135 ° C. or higher.

<Orientation test of liquid crystalline polyester> A 10 wt% phenol / tetrachloroethane mixed solvent (6/4 weight ratio) solution was prepared using this liquid crystalline polyester. This solution was applied on a soda glass plate by a screen printing method, dried, heat-treated at 230 ° C. for 30 minutes, and then cooled and fixed at room temperature. A uniformly oriented film 1 having a thickness of 20 μm was obtained. Conoscopic observation revealed that the liquid crystalline polyester exhibited optically positive uniaxiality. It was also found that the polyester had homeotropic orientation.

<Operation for Confirming Orientation Structure> An 8 wt% tetrachloroethane solution of the liquid crystalline polyester of the formula (1) is prepared, applied on a glass having a rubbing polyimide film by a spin coating method, dried, and dried at 250 ° C. for 30 minutes. After a heat treatment for 5 minutes, the film was air-cooled and fixed, and as a result, a film 2 was obtained. The obtained film 2 on the substrate was transparent, had no alignment defects, was uniform, and had a thickness of 2.0 μm.

Using the optical measurement system shown in FIGS. 3 and 4,
The film 2 was tilted in the rubbing direction of the alignment substrate, and the retardation value was measured. As a result, a result as shown in FIG. 5 was obtained in which there was no left-right asymmetric and no angle at which the retardation value was 0. From this result, it was found that the director of the liquid crystalline polyester was inclined with respect to the substrate and was not in a uniform tilt orientation (the angle between the director and the substrate surface was not constant in the film thickness direction).

[0241]

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<Operation for Confirming Orientation Structure> Next, the film 2 on the substrate was cut into five pieces, each of which was immersed in a methanol solution containing 5 wt% of chloroform for a certain period of time, and eluted from the upper surface of the liquid crystal layer. Immersion time is 15 seconds, 30 seconds, 1
, 2 minutes, and 5 minutes, the thickness of the liquid crystal layer remaining without being eluted is 1.5 μm, 1.2 μm, and 1.0 μm, respectively.
m, 0.8 μm and 0.5 μm. The retardation value (front retardation value) at θ = 0 degrees was measured using the optical systems of FIGS. 3 and 4, and the relationship between the film thickness and the retardation value was obtained (FIG. 6). As can be seen from FIG. 6, the film thickness and the retardation value do not have a linear relationship, and this also indicates that the film is not in a uniform tilt orientation. The dotted line in the figure is a straight line observed in a film having a uniform tilt orientation.

<Operation for Confirming Orientation Structure> Next, the following equation (1) is used.
The liquid crystalline polyester was oriented and fixed on a high-refractive-index glass substrate having a rubbing polyimide film (having a refractive index of 1.84) by using the same method as described above, thereby producing a film 3. Using the obtained film 3, the refractive index was measured. When the film 3 is arranged so that the glass substrate is in contact with the prism surface of the refractometer, the refractive index in the film surface has anisotropy, and the refractive index in the surface perpendicular to the rubbing direction is 1.
56, the refractive index in the parallel plane was 1.73, and the refractive index in the film thickness direction was constant at 1.56 regardless of the direction of the film 3. From this, it was found that the rod-shaped liquid crystal molecules constituting the liquid crystalline polyester were planarly aligned on the glass substrate side in parallel with the substrate. Next, when the film 3 is arranged so that the air interface side of the film 3 is in contact with the prism surface of the refractometer, the in-plane refractive index has no anisotropy and the refractive index is 1.
The refractive index in the film thickness direction was constant at 1.73 regardless of the direction of the film 3. From this, it was found that on the air interface side, rod-shaped liquid crystal molecules constituting the liquid crystalline polyester were oriented perpendicular to the substrate plane.

From the operations described above, the film formed from the liquid crystalline polyester of the formula (1) forms a nematic hybrid alignment, and the rubbing force at the substrate interface and the air force at the air interface as shown in FIG. It was presumed that they were oriented as described above.

<Analysis of tilt direction and estimation of angle formed between director and substrate plane at interface between alignment substrates> Another film of rubbing polyimide was placed on film 3 formed on a high refractive glass substrate having a rubbing polyimide film. A glass substrate having a film was covered and adhered. That is, the film 3 was sandwiched between two rubbing polyimide films. Note that the rubbing directions of the upper and lower rubbing films are 1
It was arranged so as to be 80 degrees. In this state,
Heat treated for 0 minutes. Refractive index measurement and ellipsometry were performed on the obtained sample film. As a result of the refractive index measurement, the same value is obtained for the top and bottom of the sample film,
The refractive index in the plane of the film was 1.56 in a plane perpendicular to the rubbing direction, 1.73 in a plane parallel to the rubbing direction, and 1.56 in the thickness direction of the film. From this, it was found that the director was substantially parallel to the substrate plane both above and below the sample film near the interface of the substrate. Further, as a result of polarization analysis, the refractive index structure was almost positive uniaxial, and as a result of performing detailed analysis based on the crystal rotation method, the director was slightly inclined near the substrate interface. The angle between the substrate plane and the director is about 3
Degree. Further, the direction in which the director was inclined coincided with the rubbing direction (the tilt direction of the film coincided with the rubbing direction).

From the above, it is considered that the director at the substrate interface is substantially determined by the interaction between the liquid crystalline polyester and the alignment substrate interface. The angle formed between the director and the film plane is estimated to be 3 degrees.

Example 1 A 5 wt% tetrachloroethane solution of the liquid crystalline polyester (formula (1)) used in Reference Example 1 was prepared. The solution was applied to a glass substrate having a rubbing polyimide film by a spin coating method, and the solvent was removed. Then 250 ° C
For 30 minutes. After that, the polyester was cooled to fix the orientation of the polyester. The film 4 thus obtained on the glass substrate has a nematic hybrid alignment structure, is transparent, has no alignment defects, and has a uniform film thickness (0.8
5 μm). The average tilt angle was 44 degrees, and the tilt direction coincided with the rubbing direction.

The two films 4 formed on the glass substrate having the rubbing polyimide film were used and arranged above and below the TN cell so as to have the axial arrangement shown in FIG. The films 1 above and below the cell were both arranged such that the glass substrate side of the film was close to the cell substrate. The TN cell used was ZLI-4792 (Δn = 0.0) as a liquid crystal material.
94), and the cell parameter is cell gap 4.2μ.
m, Δnd 395 nm, twist angle 90 degrees (left twist),
The pretilt angle was 3 degrees. The pretilt direction coincided with the rubbing direction of the liquid crystal cell substrate. A voltage was applied to the TN cell with a rectangular wave of 300 Hz. Using the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio, measurement of the contrast ratio from all directions was performed using an FFP optical system DVS manufactured by Hamamatsu Photonics KK
Using -3000, an isocontrast curve was drawn. The result is shown in FIG.

Example 2 A liquid crystalline polyester represented by the formulas (2) and (3) was synthesized.
The logarithmic viscosity of the liquid crystalline polyester of the formula (2) is 0.10,
It had a nematic phase as a liquid crystal phase, and its isotropic phase-liquid crystal phase transition temperature was 180 ° C. As a result of conducting the same orientation test as in Example 1, it was found that the liquid crystalline polyester of the formula (2) exhibited homeotropic orientation and exhibited optically positive uniaxiality.

The logarithmic viscosity of the liquid crystalline polyester of the formula (3) was 0.18, the liquid crystal phase had a nematic phase, and the isotropic phase-liquid crystal phase transition temperature was 300 ° C. or higher. As a result of the same orientation test as in Example 1, it was found that the liquid crystalline polyester of the formula (3) exhibited homogeneous orientation.

An 8 wt% N-methyl-2-pyrrolidone solution containing the liquid crystalline polyesters of the formulas (2) and (3) at a ratio of 50:50 (weight ratio) was prepared.

The solution was applied on a rubbed polyetheretherketone film having a width of 40 cm by a die coating method over a length of 10 m, dried with hot air at 120 ° C., and then heat-treated at 220 ° C. for 10 minutes. Thereafter, the mixture is cooled, and the polyester composition (formula (9), (1)
The composition (0) (composition containing the polyester in a ratio of 50:50 (weight ratio)) was fixed.

Triacetyl cellulose was adhered to the surface of the obtained film 5 via an adhesive, then the polyetheretherketone film used as the alignment substrate was peeled off and removed, and the film 5 was transferred onto the triacetyl cellulose film. did. The thickness of the film 5 is 0.60μ
m, the average tilt angle in the film thickness direction was 35 degrees. Two films 5 transferred to the triacetyl cellulose film were used, and the films were arranged one by one above and below the TN cell so as to have the arrangement shown in FIG. The same TN cell as that used in Example 1 was used. FIG. 10 shows the result of measuring the contrast ratio in all directions by the same method as in Example 1.

[0254]

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Comparative Example 1 An isocontrast curve was drawn in the same manner as in Example 1 except that the film 4 was not used. The result is shown in FIG.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a tilt direction in the present invention.

FIG. 2 is a conceptual diagram of a pretilt direction in the present invention.

FIG. 3 is a layout diagram of an optical measurement system used for measuring a tilt angle of a compensation film.

FIG. 4 shows the relationship between the sample and the polarizing plate in the optical measurement system used for measuring the tilt angle of the compensation film.

FIG. 5 shows a relationship between an apparent retardation value and a sample inclination angle in a reference example.

FIG. 6 shows the relationship between the thickness of the compensation film after immersion and the apparent retardation value in the front in the reference example.

FIG. 7 is a conceptual diagram of an orientation structure of a compensation film.

FIG. 8 shows the axial arrangement of each optical element in Examples 1 and 2.

FIG. 9 is an isocontrast curve of Example 1.

FIG. 10 is an isocontrast curve of Example 2.

FIG. 11 is an isocontrast curve of Comparative Example 1.

Claims (1)

[Claims] 1. At least one compensation film substantially formed from a liquid crystalline polymer having optically positive uniaxiality, wherein said liquid crystalline polymer fixes a nematic hybrid orientation formed in a liquid crystal state, A driving twisted nematic liquid crystal cell comprising a pair of transparent substrates having electrodes and a nematic liquid crystal sandwiched between the substrates, and at least two polarizing plates disposed above and below the liquid crystal cell. And the product (Δnd) of the refractive index anisotropy (Δn) of the nematic liquid crystal constituting the liquid crystal cell and the thickness (d) of the liquid crystal layer in the liquid crystal cell is 200.
a twisted nematic liquid crystal display device having a thickness of from 500 nm to 500 nm.