JPH0821999A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain excellent characteristics of the angle of visibility by using a specified compensating phase difference layer. CONSTITUTION:A perpendicularly oriented film is obtd. by forming a polymer liquid crystal film showing a nematic phase or smectic phase or forming a polymerizable liquid crystal oligomer and subjecting the film to heat treatment at a temp. higher than the crystal phase-liquid crystal phase transition temp. and lower than the liquid crystal phase-isotropic phase transfer temp. to perpendicularly orient the film. One or two of these perpendicularly oriented films are combined with a uniaxially oriented phase difference film comprising a thermoplastic resin having positive refractive index anisotropy to obtain a compensating phase difference layer having optical characteristics expressed by 1.06>=R40/R0>=1.00. R0 is the retardation measured by making the measuring beams incident in the perpendicular direction or the film, and R40 is the retardation measured by the measuring beams incident on the film in such a manner that the beam and the tilting axis in the direction of the max. refractive index of the plane make 40 deg. angle. By inserting the compensating phase difference layer between the liquid crystal cell and a linearly polarizing film on one side of the cell, a FTN liquid crystal display device having excellent characteristics of the angle of viewfield can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FTN type liquid crystal display device (FTN type LCD).

[0002]

2. Description of the Related Art A liquid crystal display device has a twist angle of the major axis of liquid crystal molecules of 180 to 2 degrees.
70 degree STN type liquid crystal display device (STN type LCD)
Has enabled a large liquid crystal display device of about 10 inches by a simple matrix drive system, and has come to be used for laptop type word processors, personal computers and the like which require a large display capacity. However, this STN type LC
Since D utilizes the birefringence of liquid crystal, it has drawbacks such as poor viewing angle characteristics, colored display, and low contrast.

In order to solve these problems, an FTN type LCD using a uniaxially oriented retardation film made of a thermoplastic resin as a compensating retardation layer for compensating the birefringence of liquid crystal has been developed, and a black and white display is provided. It has become possible to improve the contrast. However, the viewing angle characteristics such that the contrast is lowered or the hue is changed depending on the viewing angle have not yet been satisfied, and improvement of the viewing angle characteristics is desired.

[0004]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that such problems can be solved by using a specific compensating retardation layer.

That is, according to the present invention, nematic liquid crystal molecules having a positive dielectric anisotropy are arranged between a pair of transparent substrates having electrodes inside, and the long axes of the molecules are parallel to the substrates when no voltage is applied. And the long axis of the molecule is 180
Liquid crystal cell configured to have a twisted structure of 1 to 270 degrees, a pair of linear polarizing films disposed outside a pair of transparent substrates, and a compensation disposed between the liquid crystal cell and one linear polarizing film. FTN-type liquid crystal display device comprising a retardation layer for compensation, wherein the compensation retardation layer is one or two vertical alignment films selected from the following: Polymer liquid crystal showing a nematic phase or a smectic phase is formed. A vertical alignment film obtained by performing a vertical alignment by performing heat treatment at a temperature higher than or equal to the crystalline phase (or glass phase) / liquid crystal phase transition temperature (Tg) and lower than the liquid crystal phase / isotropic phase transition temperature (Ti), or a nematic phase. Alternatively, a vertical alignment film obtained by forming a film of a polymerizable liquid crystal oligomer exhibiting a smectic phase and then performing a heat treatment at a temperature of Tg or higher and lower than Ti to perform vertical alignment and polymerizing while maintaining the alignment and a positive refractive index difference 1.06 ≧ R40 / R0 ≧ 1.0, which consists of a combination of one uniaxially oriented retardation film made of a thermoplastic thermoplastic resin.
A liquid crystal display device characterized by being a retardation layer for compensation having an optical property of 0 (where R0 represents a retardation value measured by incidence of measurement light in a direction perpendicular to the plane,
Reference numeral 40 denotes a retardation value measured by injecting measurement light at an inclination of 40 ° with the in-plane maximum refractive index direction as the inclination axis. ) Is related to.

As the polymer liquid crystal, either a main chain polymer liquid crystal or a side chain polymer liquid crystal can be used as long as it is a polymer liquid crystal having a nematic phase or a smectic phase in a liquid crystal state. The transition temperature (Ti) of the liquid crystal phase / isotropic phase of the polymer liquid crystal is, for example, about 200 ° C. or lower, preferably 150 ° C. or lower.

Examples of the main chain type polymer liquid crystal include a wholly aromatic polyester type polymer liquid crystal in which a group imparting liquid crystallinity (mesogen group) is linked by an ester bond, a mesogen group and polymethylene, polyethylene oxide, polysiloxane and the like. A semi-rigid polyester-based polymer liquid crystal composed of a main chain in which bent chains are alternately bonded to each other to impart flexibility is exemplified.

The side chain type polymer liquid crystal is, for example, a mesogen via a spacer consisting of a linear or cyclic skeleton chain composed of methacrylic acid, acrylic acid, polymethylene, polyethylene oxide, polysiloxane, etc. and a bent chain. Those having a side chain to which a group is bound are included. A polysiloxane type is preferable, and a cyclic type is preferable.

The polymerizable liquid crystal oligomer exhibiting a nematic phase or a smectic phase is not particularly limited, but a polymerizable side chain type liquid crystal oligomer is preferable.

The polymerizable side-chain type liquid crystal oligomer is, for example, a linear or cyclic oligomer having the following repeating units (I) and (II) as main constituent units, and the repeating unit ( When the numbers of I) and (II) are n and n ′, respectively, n and n ′ are each independently an integer from 1 to 20, and 4 ≦ n +
A liquid crystal oligomer in which n ′ ≦ 21 is mentioned.

[0011] [Wherein A is a group represented by the following formula (III) or (IV), and in formula (III), -Si-O- is represented by formula (I).
Or the main chain of (II), and in the formula (IV), -C
—CH ₂ — is the backbone of formula (I) or (II),
R ₁ or R ₂ is located on the opposite side of the OO group. Formula (I)
When A is the formula (III) and when A is the formula (III) in the formula (II), R ₁ and R ₂ are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms or a phenyl group. In formula (I), when A is formula (IV), and in formula (II), A is formula (IV),
R ₁ and R ₂ are independently hydrogen or an alkyl group having 1 to 6 carbon atoms. k and k'independently represent an integer of 2 to 10, m and m'independently represent 0 or 1, and Ar ₁ , Ar ₂ , A
r ₃ and Ar ₄ are independently a 1,4-phenylene group, 1,
4-cyclohexane group, pyridine-2,5-diyl group,
Pyrimidine-2,5-diyl group, L and L '-CH ₂ -O- _{independently, -O-CH 2 -, -COO} -, - OCO-, -CH 2 -CH 2 -,
-CH = N-, -N = CH- or Is a divalent group represented by, p and p ′ are independently 0 or 1, R is a halogen, a cyano group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, R'is hydrogen or an alkyl group having 1 to 5 carbon atoms. ]

The skeleton chain is preferably a cyclic structure, and A
For this, SiO is preferable. The ratio of n to n'is preferably in the range of 1: 3 to 3: 1. As k and k ′, an integer of 2 to 6 is preferable, and m and m ′ are preferably 1. Ar ₁ , Ar
1,2-phenylene group is preferable as ₂ , Ar ₃ and Ar ₄ , and -CH ₂ -CH _2- , -COO-, -OCO- group is preferable as L and L ', and -COO- group is particularly preferable. preferable. As R, a cyano group is preferable.

In the case of the polymerizable side chain type liquid crystal oligomer, the liquid crystal phase / isotropic phase transition temperature (Ti) is, for example, 200 ° C. or lower, preferably 170 ° C. or lower, more preferably 150 ° C. or lower. The crystal phase (or glass phase) / liquid crystal phase transition temperature (Tg) is preferably 25 ° C. or lower.

As a substrate for forming a polymer liquid crystal or a polymerizable liquid crystal oligomer, an optically transparent and isotropic resin substrate, a linear polarizing film, and a thermoplastic resin having a positive refractive index anisotropy. And a uniaxially oriented retardation film made of When a polymer liquid crystal or polymerizable liquid crystal oligomer is formed on the surface of a linearly polarizing film (PL) or a uniaxially oriented retardation film (PC) made of a thermoplastic resin having positive refractive index anisotropy, heat treatment is performed. Etc. to form a vertical alignment film (PLC), then use this as it is for PL / PLC, PLC
It can be used as / PC or PC / PLC.

When the vertical alignment film is formed on an optically transparent and isotropic resin substrate, the vertical alignment film is directly attached to a uniaxially oriented retardation film made of a thermoplastic resin without peeling the vertical alignment film from the substrate. PLC / PC or PC / PLC
Can be used as

Optically isotropic means that nX is the maximum in-plane refractive index, nY is the minimum in-plane refractive index, nZ is the refractive index in the film thickness direction, and d is the film thickness. , (NX −nY) × d is 20 nm or less and ((nX +
nY) / 2-nZ) xd is 200 nm or less. Preferably, (nX-nY) * d is 10 nm or less and ((nX + nY) / 2-nZ) * d is 100 nm or less. The optically transparent and isotropic resin substrate is not particularly limited, but preferably has a glass transition temperature of 100 ° C. or higher, and more preferably 110 ° C. or higher. Examples of the resin include polycarbonate, polysulfone, polyarylate, polyether sulfone,
Examples thereof include cellulose diacetate, cellulose triacetate, polyethylene terephthalate, polyethylene naphthalate, polyvinyl alcohol, polystyrene, and polymethyl methacrylate. Among them, polycarbonate, polysulfone, polyarylate, cellulose triacetate, and polyethylene terephthalate are preferable.

A method of forming a vertical alignment film of polymer liquid crystal or the like will be described below using a case of an optically transparent and isotropic resin substrate. In other cases, for example, a linear polarizing film or a uniaxial film. The same can be applied to the formation on the surface of the oriented retardation film.

The surface of the transparent resin substrate is preferably hydrophilic or hydrophobic. As a hydrophilic resin substrate,
Hydrophilic polymer film such as polyvinyl alcohol, 3
Examples thereof include those obtained by saponifying the surface of a cellulose acetate or cellulose diacetate film, those obtained by hydrophilizing the surface of a polymer film, and the like. The hydrophilization treatment is not particularly limited, but treatment with oxygen plasma, a method of applying a hydrophilic polymer on the surface, a method of applying a surfactant, and the like can be used.

As the hydrophilic resin substrate, a film obtained by forming a film of a cellulose resin such as cellulose triacetate or cellulose diacetate by a solvent casting method and saponifying the surface is preferable.

As the hydrophobic treatment, a method of applying a fluoropolymer, a method of applying a surfactant such as lecithin,
A method of reacting a silane coupling agent, a titanium coupling agent or the like can be used.

The method for forming the polymer liquid crystal or the polymerizable liquid crystal oligomer is not particularly limited. For example, a liquid obtained by dissolving a polymer liquid crystal or a polymerizable liquid crystal oligomer in a solvent capable of dissolving a polymer liquid crystal or a polymerizable liquid crystal oligomer and having little dissolution or swelling of a substrate material is subjected to a roll coating method, a gravure coating method, a bar coating method. , Spin coating method, spray coating method, printing method, dipping method, etc., or heating a high molecular liquid crystal or a polymerizable liquid crystal oligomer to a crystal phase (or glass phase) / liquid crystal phase transition temperature (Tg) or higher. There is a method of applying the above by the same method as the above-mentioned method.

Among these, the roll coating method, gravure coating method, bar coating method, spin coating method and dipping method using a polymer liquid crystal solution or a polymerizable liquid crystal oligomer solution are preferable, and R40 / R0 and the like depending on the film thickness and the like. The optical characteristics of can be adjusted.

The heat treatment temperature (Tt) for orienting the polymer liquid crystal or the polymerizable liquid crystal oligomer after film formation in the direction perpendicular to the film surface is set to the crystal phase (or glass phase) of the polymer liquid crystal or the polymerizable liquid crystal oligomer / It is higher than or equal to the liquid crystal phase transition temperature (Tg) and lower than the liquid crystal phase / isotropic phase transition temperature (hereinafter referred to as Ti). It is preferably below the glass transition temperature of the substrate. In the case of a polymerizable liquid crystal oligomer, (Tg + 3
0 ° C.) ≦ Tt <Ti is preferable, and (Tg + 4
0 ° C.) ≦ Tt <Ti is more preferable.

The heat treatment time is not particularly limited, but is, for example, 1 minute or longer, preferably 2 minutes or longer.

In the case of the polymerizable liquid crystal oligomer, the liquid crystal oligomer is polymerized after being heat-treated while maintaining the vertical alignment. The polymerization method is not particularly limited, and photopolymerization, radiation polymerization of γ rays or the like, thermal polymerization and the like can be used, but photopolymerization is preferable. In the case of photopolymerization or thermal polymerization, a known polymerization initiator can be used.

As the uniaxially oriented retardation film, not only a perfect uniaxially oriented film but also a biaxially oriented film has a refractive index anisotropy in the film plane and is seen from a direction perpendicular to the film plane. If it exhibits a retardation similar to that of the uniaxially oriented film, it can be used.

The thermoplastic resin used for the uniaxially oriented retardation film made of a thermoplastic resin having a positive refractive index anisotropy includes polycarbonate, polysulfone, polyarylate, polyether sulfone, polyethylene terephthalate, polyvinyl alcohol, and acetic acid. Examples thereof include cellulose, and polycarbonate and polysulfone are preferable.

The manufacturing method of the uniaxially oriented retardation film made of a thermoplastic resin having a positive refractive index anisotropy is not limited at all. For example, as a method for producing a raw film, a solvent casting method, an extrusion molding method, a molding method such as a pressing method can be used, and when a raw film is stretched into a uniaxially oriented retardation film, a tenter is used. The transverse stretching method, the inter-roll stretching method, the inter-roll compression stretching method and the like can be used. Preferred is a method of transversely stretching a raw film formed by a solvent casting method with a tenter.

By combining one or two such vertical alignment films (PLC) and one uniaxially oriented retardation film (PC) made of a thermoplastic resin having a positive refractive index anisotropy, 1. An FTN type liquid crystal display having excellent viewing angle characteristics by providing a compensating retardation layer having optical characteristics of 06 ≧ R40 / R0 ≧ 1.00 and mounting it between a liquid crystal cell and a linear polarizing film on one side. The device can be obtained. As a configuration of a liquid crystal display device using such a retardation layer for compensation, for example, PL / (PLC / PC) / liquid crystal cell / PL PL / (PC / PLC) / liquid crystal cell / PL PL / (PLC / PC / PLC) / liquid crystal cell / PL, etc. Among them, PL / (PLC / PC) / liquid crystal cell / PL PL / (PC / PLC) / liquid crystal cell / PL is preferable, and PL / (PLC / PC) / liquid crystal cell / PL is more preferable.

The slow axis of the uniaxially oriented retardation film (PC) and the absorption axis of the linearly polarizing film (PL) are adjusted so that the contrast and the like are optimal when incorporated in a liquid crystal display device. When two vertical alignment films (PLC) are used, the two vertical alignment films may have the same optical characteristics or different optical characteristics.

[0031]

The FTN LCD of the present invention has excellent viewing angle characteristics.

[0032]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition, the measurement of the isocontrast curve is performed by LCD-Otsuka Electronics Co., Ltd.
It was carried out by a transmission method using 7000. The voltage applied to the liquid crystal display device was set to a state where the contrast was the best when the liquid crystal display device in the actual driving state was visually observed from the front. In-plane retardation value of uniaxially oriented retardation film (R
0) was determined from the maximum wavelength of the interference spectrum using a spectroscope (MCPD-1000 manufactured by Otsuka Electronics Co., Ltd.) in which two polarizing prisms are arranged in parallel in the optical system. R40 / R0 of the compensating retardation layer was calculated by measuring R40 and R0 using a polarizing microscope (manufactured by Nippon Kogaku) equipped with a Senarmont type compensator and calculating from the values.

Example 1 The following were used as the vertical alignment film (PLC) and the uniaxially oriented retardation film (PC).・ Vertical alignment film (PLC) As a polymerizable liquid crystal oligomer, 4- (allyl-oxy)-
Benzoic acid-4'-cyanophenyl ester and 4- (allyloxy) -benzoic acid- (4'-methacryloyloxy-phenyl)
Cyclic pentasiloxane having a non-polymerizable mesogen group and a polymerizable mesogen group in the side chain, which is obtained by reacting an ester with pentamethylcyclopentasiloxane at a mixing ratio of 1: 1 by the method described in JP-B-63-41400. A liquid crystal oligomer was used (Tg 18.7 ° C., Ti 117.5 ° C.). When the thickness is 80 μm, (nX −nY) × d is 6 nm, ((nX + n
Y) / 2-nz) × d is 50 nm, and a cellulose acetate film (Fujitac SH-80, manufactured by Fuji Photo Film Co., Ltd.) on the surface of which is surface-saponified is treated with a 30% toluene solution of a polymerizable liquid crystal oligomer. Was dried by a gravure coating method so that the film thickness after drying was 2.1 μm, and heat-treated at 80 ° C. for 2 minutes for vertical alignment, and then irradiated with ultraviolet rays while maintaining the alignment (total light amount 50
0 mJ / cm ² ) to form a vertical alignment film (PLC) on the cellulose triacetate film. Uniaxially oriented retardation film (PC) Uniaxially oriented retardation film obtained by uniaxially stretching a solvent cast film of polycarbonate (trade name Sumikalite SEF-400570 manufactured by Sumitomo Chemical Co., Ltd.,
In-plane retardation 570 nm).

PC was laminated on a vertical alignment film (PLC) formed on a cellulose acetate film by using an adhesive to obtain a compensating retardation layer (PLC / PC) (R40 / R0 = 1. 022
9). A commercially available FTN liquid crystal panel (trade name: KL-6440ASTC, manufactured by Kyocera Corp.) was used for the compensation retardation layer.
It was attached with adhesive between the linear polarizing film (PL) on the upper side of the and the liquid crystal cell (PL / (PLC / PC) / liquid crystal cell / P
L). This FTN LCD has a small change in contrast depending on the viewing angle, and exhibits a bilaterally symmetrical viewing angle characteristic. The isocontrast curve is shown in FIG.

Example 2 A compensating retardation layer (R40) was prepared in the same manner as in Example 1 except that the film thickness of the polymerizable liquid crystal oligomer after drying was 1.2 μm.
/ R0 = 1.0580) was obtained. This compensating retardation layer was mounted on the FTN liquid crystal panel in the same manner as in Example 1 (PL / (PLC / PC) / liquid crystal cell / PL). This FTN type L
The CD has a small change in contrast depending on the viewing angle and exhibits a symmetrical viewing angle characteristic. Figure 2 shows the isocontrast curve
Shown in

Example 3 A retardation layer for compensation (PC / PLC) was obtained in the same manner as in Example 1 except that the stacking order of the vertical alignment film (PLC) and the uniaxially oriented retardation film was changed. R40 / R0 = 1.022
9). This compensating retardation layer was made to be F in the same manner as in Example 1.
Attached to TN liquid crystal panel (PL / (PC / PLC) / liquid crystal cell / PL). This FTN LCD has a small change in contrast depending on the viewing angle, and exhibits a bilaterally symmetrical viewing angle characteristic.
The isocontrast curve is shown in FIG.

Example 4 A compensating retardation layer (R40) was prepared in the same manner as in Example 3 except that the film thickness of the polymerizable liquid crystal oligomer after drying was 1.2 μm.
/ R0 = 1.0580) was obtained. This compensating retardation layer was mounted on the FTN liquid crystal panel in the same manner as in Example 1 (PL / (PC / PLC) / liquid crystal cell / PL). This FTN type L
The CD has a small change in contrast depending on the viewing angle and exhibits a symmetrical viewing angle characteristic. Figure 4 shows the isocontrast curve
Shown in

Example 5 Two vertical alignment films (PLC) were obtained in the same manner as in Example 1 except that the film thickness of the polymerizable liquid crystal oligomer after drying was 1.0 μm. One PLC and one PC used in Example 1 were pasted in the order of PLC / PC / PLC,
A retardation layer for compensation was obtained (R40 / R0 = 1.0263).
This compensating retardation layer was mounted on the FTN liquid crystal panel in the same manner as in Example 1 (PL / (PLC / PC / PLC) / liquid crystal cell / PL). This FTN LCD has a small change in contrast depending on the viewing angle, and exhibits a substantially symmetric viewing angle characteristic. The isocontrast curve is shown in FIG.

Comparative Example One of the same PCs used in Example 1 was laminated on the FTN liquid crystal panel in the same manner as in Example 1 (PL / PC / liquid crystal cell /
PL). This FTN type LCD is an FTN type L according to the present invention.
Compared with the CD, the viewing angle characteristics were not symmetrical, and the viewing angle characteristics in the oblique upper right and oblique lower left directions were inferior. The isocontrast curve is shown in FIG.

Reference Example A compensating retardation layer was obtained in the same manner as in Example 1 except that the thickness of the polymerizable liquid crystal oligomer after drying was 3.0 μm (R40 / R0 = 0.9989). This compensating retardation layer was mounted on the FTN liquid crystal panel in the same manner as in Example 1 (PL
/ (PLC / PC) / Liquid crystal cell / PL). This FTN LCD
Has improved viewing angle characteristics as compared with the comparative example, but compared with the FTN LCD according to the present invention, the viewing angle characteristics have poor left-right symmetry, and particularly the downward viewing angle characteristics are inferior. . The isocontrast curve is shown in FIG.

[Brief description of drawings]

FIG. 1 is a diagram showing isocontrast curves in Example 1.

FIG. 2 is a diagram showing isocontrast curves in Example 2.

FIG. 3 is a diagram showing isocontrast curves in Example 3.

FIG. 4 is a diagram showing isocontrast curves in Example 4.

FIG. 5 is a diagram showing isocontrast curves in Example 5.

FIG. 6 is a diagram showing isocontrast curves in a comparative example.

FIG. 7 is a diagram showing isocontrast curves in a reference example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kiminobu No. 6, Kitahara, Tsukuba, Ibaraki Prefecture, Sumitomo Chemical Co., Ltd. (72) Inventor, Masato Kuwahara, No. 6, Kitahara, Tsukuba, Ibaraki, Sumitomo Chemical Co., Ltd.

Claims (3)

[Claims] 1. A pair of transparent substrates having electrodes inside,
Nematic liquid crystal molecules having a positive dielectric anisotropy have a structure in which the long axis of the molecule is twisted parallel to the substrate and the long axis of the molecule is twisted by 180 to 270 degrees in the direction perpendicular to the transparent substrate when no voltage is applied. FTN type liquid crystal display comprising a liquid crystal cell configured as described above, a pair of linear polarizing films arranged outside a pair of transparent substrates, and a compensating retardation layer arranged between the liquid crystal cell and one linear polarizing film. The device is one or two vertical alignment films selected from the following, in which the compensating retardation layer is a crystalline phase (or glass phase) after forming a polymer liquid crystal showing a nematic phase or a smectic phase: Vertical alignment film obtained by vertically aligning by performing heat treatment at a temperature of liquid crystal phase transition temperature (Tg) or higher and lower than liquid crystal phase / isotropic phase transition temperature (Ti) or-Polymerizability exhibiting nematic phase or smectic phase It is composed of a vertical alignment film obtained by forming a crystalline oligomer into a film and then subjecting it to heat treatment at a temperature of Tg or more and less than Ti for vertical alignment, and polymerizing while maintaining the alignment, and a thermoplastic resin having a positive refractive index anisotropy. Composed of one uniaxially oriented retardation film, 1.06 ≧ R40 / R0 ≧ 1.0
A liquid crystal display device comprising a retardation layer for compensation having an optical property of 0. (However, R0 represents the retardation value measured by injecting the measurement light in the direction perpendicular to the plane,
R40 is 40 ° with the direction of maximum refractive index in the plane as the tilt axis
The retardation value measured by injecting the measurement light at an inclination is shown. ) 2. A vertical alignment film is produced by forming a side chain type polymer liquid crystal having a polysiloxane skeletal chain showing a nematic phase or a smectic phase, and then subjecting it to a heat treatment at a temperature of Tg or more and less than Ti to perform vertical alignment. The liquid crystal display device according to claim 1, which is a vertical alignment film obtained by the above process. 3. A vertical alignment film is produced by forming a polymerizable side chain type liquid crystal oligomer having a skeleton chain composed of --SiO-- showing a nematic phase or a smectic phase, and then heat-treating at a temperature of Tg or more and less than Ti. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a vertical alignment film obtained by vertically aligning and vertically polymerizing it while maintaining the alignment.