JPH08152519A - Optical anisotropic film, its production and liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a liquid crystal display element having excellent white-black level and high contrast in a wide temp. range by compounding a liquid crystal compsn. which shows a cholesteric phase and contains polymerizable liquid crystal oligomers having a specified structure, and then polymerizing the compsn. CONSTITUTION: The helical axis in a twisted nematic orientation is almost parallel to the normal line direction of the film and the twisted angel ranges from 70 deg. to 300 deg.. The liquid crystal compsn. shows a cholesteric phase with the helical pitch between 0.2μm and 50μm and contains one or more kinds of liquid crystal oligomers selected from among straight-chain or cyclic liquid crystal oligomers having repeating units expressed by formula I and formula II as the main structural units. Further, when the numbers of the repeating units of the formulas I and II in one molecule of the liquid crystal oligomer are defined as n and n' respectively, n and n are integers of 1 to 20, 4<=n+n'<=21 and n:n'=(20:1) to (1:20). The terminal groups of the repeating unit of the formula II are polymerized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an optically anisotropic film containing a liquid crystal composition, a method for producing the same, and an optically anisotropic film which are useful as a member of a retardation film used in a liquid crystal display device or the like. The present invention relates to a retardation film and a liquid crystal display device using them.

[0002]

2. Description of the Related Art Liquid crystal displays have features such as low voltage driving and light weight. Among them, the simple matrix drive type super twist nematic (hereinafter sometimes abbreviated as STN) type liquid crystal display is widely used for personal computers and word processors because it can display a large screen and is inexpensive. Has been. However, the STN system has a drawback in that it displays yellow and blue colors due to the birefringence effect, which makes black and white display impossible. In order to realize black and white display in the STN method, a compensating liquid crystal cell having the same cell gap and an opposite twist direction is stacked on the STN cell to perform color compensation, or a stretched film such as polycarbonate ( A method of compensating for the phase difference by superimposing a phase difference film) has been partially put into practical use. However,
The two-layer cell system has a drawback that the cost is high and the panel is heavy and thick. In addition, the retardation film compensation method is a uniaxially stretched film that does not have a twist structure, so the optical rotation dispersion due to the twist of the STN cell cannot be fully compensated, so perfect black and white display is not possible and the contrast is also a two-layer cell method. In comparison, not good.

Also in the active matrix type liquid crystal display using thin film transistors, when the cell gap is made thinner in order to improve the response speed and viewing angle characteristics, coloring occurs and at the same time, the contrast decreases due to optical rotation dispersion. There is. In order to solve these problems caused by the twist of the liquid crystal cell, the use of a polymer film having a twisted nematic orientation as a compensation film has been studied. As a method for producing a polymer film having a twisted nematic orientation, a method in which a monomer having a cholesteric phase is oriented and then polymerized (Japanese Patent Laid-Open No. 01-222220 and Japanese Patent Laid-Open No. 03-222220).
-140921) or a method of aligning a polymer compound having a cholesteric phase and then rapidly cooling it below the glass transition point to fix the orientation (Japanese Patent Laid-Open No. 03-877720).

[0004]

However, in the method of polymerizing a monomer, since the temperature dependence of the orientation state of the monomer is larger than that of the polymer compound, it is necessary to perform the polymerization immediately at the orientation treatment temperature. There is a problem that the conditions are limited. Further, in the method using the polymer compound having a cholesteric phase, since the twisted nematic structure is fixed by quenching below the glass transition point,
Since it is necessary to use one having a glass transition temperature sufficiently higher than room temperature, there is a problem that the alignment treatment requires a considerably high temperature, which is not preferable in manufacturing. Furthermore, when a polymer compound is used, since the temperature dependence of the refractive index anisotropy is smaller than that of a liquid crystal cell, when the temperature at which the panel is used changes, the refractive index anisotropy of the compensating film, There is a problem that the refractive index anisotropy of the liquid crystal cell is shifted, and the effect of improving the contrast and the viewing angle is reduced.

An object of the present invention is to provide an optically anisotropic film having a fixed twisted nematic orientation, which is effective for compensating for optical rotation dispersion resulting from the twisted structure of a liquid crystal cell and improving contrast in a wide temperature range. Another object of the present invention is to provide an industrially producing method thereof, a retardation plate containing the optically anisotropic film or the optically anisotropic film, and a high contrast liquid crystal display device using the retardation plate.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have aligned a liquid crystal composition showing a cholesteric phase containing a polymerizable liquid crystal oligomer having a specific structure. After that, it was found that a film having a twisted nematic structure fixed by polymerization is effective for improving the contrast of a liquid crystal cell. By the method of the present invention, it is possible to obtain an optically anisotropic film containing a liquid crystal oligomer polymer, which has a twisted nematic orientation on a substrate subjected to a horizontal orientation treatment, is excellent in a black and white level in a wide temperature range, and has a high contrast. The inventors have found that a liquid crystal display device with high efficiency can be obtained, and completed the present invention.

That is, the present invention comprises the following inventions. [1] An optically anisotropic film containing a twisted nematically oriented liquid crystal composition, wherein the helical axis of the twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is in the range of 70 ° to 300 °. The liquid crystal composition exhibits a cholesteric phase with a helical pitch of 0.2 μm or more and 50 μm or less and is selected from linear or cyclic liquid crystal oligomers (A) having the following repeating units (I) and (II) as main constituent units. When the number of repeating units (I) and (II) in one molecule of the liquid crystal oligomer (A) is n and n ′, respectively, n and n ′ are from 1 to 20. Is an integer up to
And 4 ≦ n + n ′ ≦ 21, and the ratio of n: n ′ is 20:
1 to 1:20, wherein the terminal group of the repeating unit (II) is polymerized, which is an optically anisotropic film.

[Chemical 12]

[Chemical 13]

[Wherein A is the following formula (III) or (I
V) is a group represented by the formula (III)
-O- is the main chain of formula (I) or (II),
In V), -C-CH ₂ -has the formula (I) or (II)
And the COO group is located on the side chain that is not R ₁ or R ₂ of the side chain. In formula (I), A is the formula (III)
And when A is the formula (III) in the formula (II), R ₁ and R ₂ are independently hydrogen and a carbon number of 1
~ 6 alkyl group or phenyl group. When A is formula (IV) in formula (I) and A is formula (IV) in formula (II), R ₁ and R ₂ are independently hydrogen or an alkyl group having 1 to 6 carbon atoms.

Embedded image

[Chemical 15]

K and k ′ independently represent an integer of 2 to 10, m and m ′ independently represent 0 or 1, and Ar ₁ ,
Ar ₂ and Ar ₃ are independently a 1,4-phenylene group,
1,4-cyclohexylene group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, and L'is-
_{CH 2 -O -, - O-} CH 2 -, - COO -, - OCO
_{-, - CH 2 -CH 2 -} , - CH = N -, - N = CH-
Or

Embedded image Is a divalent group represented by, p ′ is 0 or 1,
R represents an optically active group, and R ′ is hydrogen or an alkyl group having 1 to 5 carbon atoms. ]

[2] An optically anisotropic film containing a twisted nematically oriented liquid crystal composition, wherein the helical axis of the twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. Is in the range of
The liquid crystal composition shows a cholesteric phase having a helical pitch of 0.2 μm or more and 50 μm or less, and contains one or more kinds of liquid crystal oligomers (A) selected from [1] and a low molecular weight compound having a polymerizable group. An optically anisotropic film, characterized in that one or more kinds of low molecular weight compounds having a terminal group and / or a polymerizable group of the repeating unit (II) of the liquid crystal oligomer (A) are polymerized.

[3] An optically anisotropic film containing a twisted nematically oriented liquid crystal composition, wherein the helical axis of the twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. Is in the range of
The liquid crystal composition exhibits a cholesteric phase having a helical pitch of 0.2 μm or more and 50 μm or less, and one or more liquid crystal oligomers selected from the liquid crystal oligomers (A) according to claim 1 and liquid crystal oligomers (B) other than (A). And a liquid crystal oligomer (B) selected from linear or cyclic liquid crystal oligomers having the following repeating units (V) and (VI) as main constituent units. When the number of repeating units (V) and (VI) in one molecule of the oligomer (B) is n ″ and n ′ ″, respectively, n ″ and n ″ ′ are independently 0 to 2
It is an integer up to 0, and 4 ≦ n ″ + n ′ ″ ≦ 21, the terminal group of the repeating unit (II) of the liquid crystal oligomer (A) and / or the repeating unit (V) of the liquid crystal oligomer (B).
An optically anisotropic film, characterized in that the terminal group of I) is polymerized.

[0012]

[Chemical 17]

Embedded image

(Wherein A, R ₁ , R ₂ , k ', m',
p ′, L ′, Ar ₂ , Ar ₃ and R ′ have the same meanings as described above. k ″ represents an integer of 2 to 10, m ″ is 0 or 1, and Ar ₄ and Ar ₅ are 1,4-phenylene group, 1,4-cyclohexylene group, pyridine-
2,5-diyl group, pyrimidine-2,5-diyl group, L ″ is —CH ₂ —O—, —O—CH ₂ —, —COO.
-, - OCO -, - CH 2 -CH 2 -, - CH = N-,
-N = CH- or

[Chemical 19] Is a divalent group represented by, p ″ is 0 or 1,
R '' is a halogen, a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms or 1 to 10 carbon atoms. 10 shows a benzoyloxy group having 10 alkoxy groups. )

[4] An optically anisotropic film containing a twisted nematically aligned liquid crystal composition, wherein the helical axis of the twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. Is in the range of
The liquid crystal composition exhibits a cholesteric phase having a helical pitch of 0.2 μm or more and 50 μm or less, and one or more liquid crystal oligomers selected from the liquid crystal oligomers (A) according to claim 1 and liquid crystal oligomers (B) other than (A). And one or more liquid crystal oligomers selected from the group (1) and one or more low molecular weight compounds having a polymerizable group, and the end groups of the repeating unit (II) of the liquid crystal oligomer (A) and / or the repeating liquid crystal oligomer (B). End groups of units (VI) and /
Alternatively, an optically anisotropic film characterized in that a low molecular weight compound having a polymerizable group is polymerized.

[5] The optically anisotropic film according to the above [1], [2], [3] or [4], wherein R contains a liquid crystal oligomer represented by the following formula (VII) or (VIII). An optical anisotropic film characterized in that

Embedded image

[Chemical 21]

[Wherein R ₃ represents -H or the following formula (IX),

[Chemical formula 22] R ₄ represents -H or a methyl group, R ₅ represents -H or R
₆ is shown, and R ₆ is a linear or branched carbon number 1 to
It represents an alkyl group of 20 or a linear or branched alkanoyl group having 1 to 20 carbon atoms, and when branched, it may have an asymmetric carbon. ]

[6] The above [1], [2], [3],
After the liquid crystal composition according to [4] or [5] is formed on a film, heat treatment is performed to make the helical axis of the twisted nematic alignment substantially parallel to the normal direction of the film, and then the polymerizable group is polymerized. And a method for producing an optically anisotropic film. [7] The optically anisotropic film according to the above [1], [2], [3], [4] or [5] and a transparent or semitransparent substrate having an alignment film on the surface are laminated. A laminate of an optically anisotropic film and a substrate.

[8] The laminate of the optically anisotropic film and the substrate according to [7], wherein the substrate is a glass plate or a polymer film.

[9] A liquid crystal cell sandwiched between substrates having electrodes, which has a positive dielectric anisotropy, and which is composed of a liquid crystal layer which is substantially horizontal when no voltage is applied and has a helical axis twisted and aligned in a direction perpendicular to the substrate, Between the polarizing film placed on the outside,
From the optically anisotropic film of [1], [2], [3], [4] or [5], or the laminate of the optically anisotropic film of [7] or [8] and a substrate. A liquid crystal display device comprising at least one selected.

Next, the present invention will be described in detail. The liquid crystal oligomer (A) used in the present invention is composed of repeating units (I) and (I
It is a side chain type liquid crystal oligomer composed of I). Examples of the skeletal chain of the side chain type liquid crystal oligomer include poly-1-alkylacrylic acid ester and polysiloxane, and linear or cyclic ones can be used, but from the viewpoint of chemical stability of the liquid crystal oligomer, the cyclic one is cyclic. The structure is preferred. Of the poly-1-alkyl acrylic acid esters, polymethacrylic acid esters or polyacrylic acid esters are preferable, and polymethacrylic acid esters are more preferable. Among these, polysiloxane side chain type liquid crystal oligomers are preferable. As the group that imparts liquid crystallinity (hereinafter sometimes referred to as mesogen group), a group bonded to the main chain via a bent chain (hereinafter sometimes referred to as spacer) can be generally used.

The side-chain type liquid crystal oligomer (A) is not particularly limited in the upper limit temperature at which it exhibits a liquid crystal state, but it is changed from a liquid crystal phase to an isotropic phase due to drying and alignment treatment during lamination with a substrate. The transition temperature (hereinafter sometimes referred to as liquid crystal phase / isotropic phase transition temperature) is 200 ° C. or lower, preferably 170 ° C. or lower, and more preferably 150 ° C.
It is preferable to select the length of the spacer, the kind of the mesogenic group, and the degree of polymerization as follows. The transition temperature between the liquid crystal phase and the crystal phase or glass phase of these liquid crystal oligomers is not particularly limited, and the transition temperature below room temperature can be used.

The side chain type liquid crystal oligomer used in the present invention is
It is necessary to orient to have anisotropy in refractive index, but the number of repeating units is important as a factor that determines the ease of operation. When the number of repeating units is large, the viscosity is high, and the liquid crystal transition temperature is high, so that high temperature and long time are required for the alignment, and when the number of repeating units is small, the alignment is relaxed at room temperature, which is not preferable. The numbers of repeating units, n and n ', are each independently an integer from 1 to 20 and are selected such that the sum of n and n'is 4 to 21. From the viewpoint of alignment of the liquid crystal oligomer and fixing of alignment after polymerization, the ratio of n and n ′ is in the range of 20: 1 to 1:20, and more preferably 5: 1 to 1:10. Control of the ratio of n and n'can be performed when these liquid crystal oligomers are synthesized as described later.

The liquid crystal phase transition temperature and the orientation of the side chain type liquid crystal oligomer are also influenced by the spacer connecting the main chain and the mesogenic group. A short spacer does not have good orientation of the mesogen group, and a long spacer tends to cause relaxation after orientation of the mesogen group. Therefore, an alkylene group having 2 to 10 carbon atoms or an alkyleneoxy group is preferable as the spacer. Particularly, from the viewpoint of high orientation, an alkylene group having 2 to 6 carbon atoms or an alkyleneoxy group is preferable. In addition, an alkyleneoxy group is more preferable because of ease of synthesis. Specifically, as a preferable group,
_{(CH 2) 2 -, -} (CH 2) 3 -, - (CH 2)
_{4 -, - (CH 2)} 5 -, - (CH 2) 6 -, - (CH
_{2) 3 -O -, - (} CH 2) 4 -O -, - (CH 2) 5
_{-O -, - (CH 2)} 6 -O- is exemplified.

In the optically anisotropic film of the present invention, it is industrially advantageous that the refractive index anisotropy is large. For this purpose, the mesogen group is preferably a group having a large refractive index anisotropy.
Examples of the structure that provides such a mesogenic group include Ar ₁ , Ar ₂ , and Ar in the repeating unit (I) or (II).
₃ are each independently a 1,4-phenylene group, 1,4-
Examples thereof include a cyclohexylene group, a pyridine-2,5-diyl group and a pyrimidine-2,5-diyl group.
More preferably, Ar ₁ , Ar ₂ and Ar ₃ are each independently a 1,4-phenylene group, a pyridine-2,5-diyl group or a pyrimidine-2,5-diyl group, and further preferably 1,4- It is a phenylene group. Since the R group in the repeating unit (I) contributes to the development of the cholesteric phase of the liquid crystal oligomer, it is essential that it be an optically active group, and from the viewpoint of stabilizing the cholesteric phase, a group having the following structure is preferable.

[0024]

[Chemical formula 23] Or

[Chemical formula 24] (Here, R ₃ represents -H or the following formula,

[Chemical 25] R ₄ represents -H or a methyl group, R ₅ represents -H or R
₆ is represented by R ₆ , and R ₆ is a linear or branched carbon number of 1 to 2
0 alkyl group or straight or branched carbon number 1
It represents an alkoxycarbonyl group of up to 20 and may have an asymmetric carbon when branched. )

Mesogenic groups used in the linear or cyclic liquid crystal oligomer having the repeating unit (I) are shown in Tables 1 and 2. Here, for example, the number 1 in the spacer column in Table 1 is --Ar ₁ in the repeating unit (I).
-R is

[Chemical formula 26] And the R ₃ group is

[Chemical 27] , And the spacer _{- (CH 2) k - (} O) m - is -
It represents a repeating unit (when k = 3 and m = 0) which is (CH ₂ ) ₃ —. The following numbers have the same meaning, and the same applies to Table 2 and below.

[0026]

[Table 1]

[0027]

[Table 2]

Of these, more preferred structures include Nos. 1-6 and 31-36. Repeating unit (I
The divalent group L ′ for connecting Ar ₂ and Ar ₃ in I) is —CH ₂ —O—, —O—CH ₂ —, —COO.
-, - OCO -, - CH 2 -CH 2 -, - CH = N-,
-N = CH- or

[Chemical 28] Or a group in which Ar ₂ and Ar ₃ are directly bonded. Further, the bonding group L ′ is —CH ₂ —CH ₂ —, —
A COO- group and a -OCO- group are preferable, and a -COO- group is more preferable.

The terminal group in the repeating unit (II) is a group that fixes the orientation of the liquid crystal oligomer by polymerization. The polymerization group is -OCO-C (R ') = CH 2 (R' represents hydrogen or an alkyl group having 1 to 5 carbon atoms), acrylate group, is a methacrylate group are exemplified. The method of polymerizing these groups is not particularly limited, but photopolymerization or thermal polymerization with a radical initiator is exemplified, and photopolymerization is preferable from the viewpoint of ease of operation and efficiency of fixing orientation. Known photopolymerization initiators can be used.

Polymerizable mesogenic groups used in the linear or cyclic liquid crystal oligomer having the repeating unit (II) are shown in Tables 3 and 4.

[Table 3]

[0031]

[Table 4]

Among these polymerizable mesogen groups, numbers 67 to 72, 79 to 84, 9 having a methacrylate group are included.
The groups of 1 to 96, 139 to 144, 151 to 156 are preferable, and the groups of numbers 79 to 84 are more preferable. It is preferable that these mesogen groups are bonded to a linear or cyclic polysiloxane-based main chain because they exhibit good characteristics, and it is more preferable that they are bonded to a cyclic polysiloxane.

In the optically anisotropic film of the present invention,
In order to achieve the desired optical properties, the twist angle of the twisted nematic orientation of the film needs to be in the range of 70 ° or more and 300 ° or less. In order to obtain a film having such a twist angle, the cholesteric phase spiral pitch length of the liquid crystal composition used is preferably adjusted to 0.2 μm or more and 50 μm or less, more preferably 1 μm or more and 35 μm or less, and particularly preferably 2 μm or more and 20 μm or less. It is desirable to do. When the cholesteric phase spiral pitch length is small, in order to adjust the twist angle of the twisted nematic orientation of the obtained film within the range of 70 ° or more and 300 ° or less, it is necessary to reduce the film thickness and obtain sufficient retardation. Difficult to do. Further, when the pitch length is large, the film thickness must be increased in order to realize the required twist angle, which is a problem in terms of economy. The helical pitch length of the cholesteric phase of the liquid crystal composition depends on the structure of the anti-complex unit (I) depending on the structure of the mesogen of the liquid crystal oligomer (A).
It can also be controlled by changing the ratio of (II) and (II).

As a method for synthesizing the liquid crystal oligomer (A), JP-B-63-41400 and JP-B-63-47 are available.
The methods described in Japanese Patent No. 759 and Japanese Patent Laid-Open No. 2-149544 can be adopted. Examples thereof include a method of adding a mesogenic group of the side chain to a polysiloxane chain and a method of polymerizing an acrylate ester or a methacrylate ester having a flexible spacer group on the mesogen group. When a mesogenic group is added to the polysiloxane chain, the repeating unit (I)
Or (II) has the same structure as the side chain mesogenic group,
It can be obtained by reacting a reaction raw material having a ω-alkenyloxy group having an unsaturated double bond at the terminal which forms an alkyleneoxy group as a spacer with a polysiloxane under a platinum catalyst. During this reaction, the bond ratio of the two kinds of mesogen groups can be controlled by the reaction raw material charging ratio corresponding to the non-polymerizable mesogen group and the polymerizable mesogen group. Similarly, in the case where the main chain is an acrylic ester type or an α-alkyl-acrylic acid type, when the two kinds of monomers having the corresponding mesogenic groups are copolymerized, the charging ratio of the monomers is controlled so that a polymerizable mesogenic group is formed. The proportion of non-polymerizable mesogenic groups can be controlled. The liquid crystal oligomer thus obtained preferably has a cholesteric phase.

Another method for controlling the helical pitch length of the liquid crystal composition is a method of mixing the liquid crystal oligomer (A) with another liquid crystal oligomer or a low molecular weight compound. When another liquid crystal oligomer is mixed with the oligomer (A), the liquid crystal oligomer to be mixed is the liquid crystal oligomer (A).
In addition to the liquid crystal oligomer selected from, the liquid crystal oligomer (B) containing the repeating unit (V) and / or (VI) as a main component can be mentioned.

The side chain type liquid crystal oligomer used in the present invention is
It is necessary to orient the liquid crystal so as to have anisotropy in the refractive index, but the number of repeating units of the liquid crystal oligomer (B) is important as a factor that determines the ease of the operation. When the number of repeating units is large, the viscosity is high, and the liquid crystal transition temperature is high, so that high temperature and long time are required for the alignment, and when the number of repeating units is small, the alignment is relaxed at room temperature, which is not preferable. The number of repeating units n ″ and n ′ ″ are each independently an integer from 0 to 20, and the sum of n ″ and n ′ ″ is 4 to 2
It is chosen to be an integer up to 1. The ratio of n ″ and n ′ ″ can be arbitrarily selected, and the ratio of n ″ and n ′ ″ can be controlled when these liquid crystal oligomers are synthesized.

The liquid crystal phase transition temperature and the orientation of the side chain type liquid crystal oligomer are also influenced by the spacer connecting the main chain and the mesogenic group. A short spacer does not have good orientation of the mesogen group, and a long spacer tends to cause relaxation after orientation of the mesogen group. Therefore, an alkylene group having 2 to 10 carbon atoms or an alkyleneoxy group is preferable as the spacer. Particularly, an alkylene group having 2 to 6 carbon atoms or an alkyleneoxy group is preferable from the viewpoint of high orientation. In addition, an alkyleneoxy group is more preferable because of ease of synthesis. Specifically, as preferred groups _{- (CH 2) 2 -,} - (CH 2) 3 -, - (CH 2) 4
_{-, - (CH 2) 5} -, - (CH 2) 6 -, - (C
_{H 2) 3 -O -, -} (CH 2) 4 -O -, - (CH 2)
_{5 -O -, - (CH 2} ) 6 -O- is exemplified.

In order to increase the refractive index anisotropy of the obtained optically anisotropic film, the mesogen group in the liquid crystal oligomer (B) is also preferably a group having large refractive index anisotropy.
As a structure giving such a mesogenic group, Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ in the repeating units (V) and (VI) are each independently a 1,4-phenylene group,
Examples thereof include 1,4-cyclohexylene group, pyridine-2,5-diyl group and pyrimidine-2,5-diyl group. More preferably, Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ are each independently a 1,4-phenylene group, a pyridine-2,5-diyl group, a pyrimidine-2,5-diyl group, and further preferably It is a 1,4-phenylene group.

Repeating units (V) and (VI) Ar in formula
₂And Ar₃, Ar_FourAnd Ar _FiveDivalent to combine
As the groups L ′ and L ″, —CH₂-O-, -O-CH₂
-, -COO-, -OCO-, -CH₂-CH₂-,-
CH = N-, -N = CH- or

[Chemical 29] A group that is or Ar ₂ and Ar ₃ or Ar ₄ and Ar ₅
The group directly bonded to is mentioned. Further, the linking groups L ′ and L ″ are each independently —CH ₂ —CH ₂ —, —COO.
-Or -OCO- group is preferable, and more preferably-
It is a COO-group.

The R "group in the repeating unit (V) affects the dielectric anisotropy and orientation of the mesogenic group, so that from the viewpoint of obtaining a liquid crystal oligomer film having a high refractive index anisotropy, halogen, cyano group, Benzoyloxy group having a C1-10 alkyl group, a C1-10 alkoxy group, a C6-10 aryl group, or a C1-10 alkyl group or a C1-10 alkoxy group. A cyano group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms,
More preferably, it is a cyano group. Mesogenic groups used in the linear or cyclic liquid crystal oligomer having the repeating unit represented by the repeating unit (V) are shown in Table 5, Table 6, Table 7 and Table 8.

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

[Table 8]

Among these mesogen groups, numbers 157 to 162, 187 to 192, and 217 to cyano groups having a cyano group are included.
The groups 222, 337 to 342 and 367 to 372 are preferable, and the numbers 187 to 192 are more preferable. It is preferable that these mesogen groups are bonded to a polysiloxane-based main chain because they exhibit high orientation, and more preferably those bonded to a cyclic siloxane.

The terminal group in the repeating unit (VI) is a group that fixes the orientation of the liquid crystal oligomer by polymerization. The polymerization group is -OCO-C (R ') = CH 2 (R' represents hydrogen or an alkyl group having 1 to 5 carbon atoms), acrylate groups, methacrylate groups. The method of polymerizing these groups is not particularly limited, but photopolymerization or thermal polymerization with a radical initiator is exemplified, and photopolymerization is preferable from the viewpoint of ease of operation and efficiency of fixing orientation. Known photopolymerization initiators can be used.

Examples of the polymerizable mesogen group used in the linear or cyclic liquid crystal oligomer having a repeating unit (VI) are the same as those shown in Tables 3 and 4. Among the polymerizable mesogen groups shown in Table 3 and Table 4, numbers 67 to 72, 79 to 84, 91 to 9 each having a methacrylate group.
6, 139-144, 151-156 groups are preferred,
More preferably, it is a group of numbers 79 to 84. It is preferable that these mesogen groups are bonded to a linear or cyclic polysiloxane-based main chain because they exhibit good characteristics, and it is more preferable that they are bonded to a cyclic polysiloxane. As a method for synthesizing the liquid crystal oligomer (B), the same method as that for the liquid crystal oligomer (A) can be adopted.

The liquid crystal oligomer (B) thus obtained preferably exhibits a nematic phase. When a low molecular weight compound is mixed with the liquid crystal oligomer (A) or a mixture of the liquid crystal oligomers (A) and (B) to control the cholesteric phase spiral pitch length, the liquid crystal composition is aligned in the production of the optically anisotropic film. Since post-polymerization is performed, compatibility after polymerization is important. Therefore, the low molecular weight compound used preferably has a polymerizable group. The structure of the polymerizable low-molecular weight compound added to the liquid crystal oligomer is preferably one showing a liquid crystal phase for uniform mixing. Examples of the polymerizable low molecular weight compound include the following compounds, but these do not limit the low molecular weight compound that can be used in the present invention.

Embedded image (In the above specific example, a represents an integer of 1 to 10, and b
Represents an integer of 0 to 10, and R represents a linear or branched alkyl group or alkoxy group having 1 to 10 carbon atoms. When R is branched, it may be optically active. ) Further, the addition amount of the low molecular weight compound is 0 to 50 w of the liquid crystal composition
t% is preferable, and 0 to 40% is more preferable. If the addition amount of the low molecular weight compound exceeds 50%, the film formability and the stability of orientation may be impaired.

The method for producing the optically anisotropic film of the present invention is as follows:
This is a method in which after the liquid crystal composition is formed into a film, heat treatment is performed to make the helical axis of the twisted nematic alignment substantially parallel to the film normal direction, and then the polymerizable group is polymerized. The method for forming a film of the liquid crystal composition is not particularly limited, but is generally formed on a smooth base material. The optically anisotropic film formed on the substrate can be peeled off from the substrate and used, or can be used together with the substrate. When used together with the base material used for film formation, the base material used is preferably a transparent or semitransparent base material, and specific examples thereof include an inorganic substrate such as glass and a polymer film. As the inorganic substrate, a transparent or translucent glass plate, or the outside of the glass plate used for the liquid crystal cell, Si, Al,
Examples include oxides such as Mg and Zr, inorganic compounds such as fluorides, and ceramics. Examples of the polymer film include polycarbonate, polysulfone, polyarylate, polyether sulfone, cellulose diacetate, cellulose triacetate, polystyrene, ethylene vinyl alcohol copolymer, polyethylene terephthalate, polyethylene naphthalate, and the like, more preferably polycarbonate and polysulfone. Examples include cellulose triacetate, polyethylene terephthalate, and polystyrene. The thickness of the polymer film used is not particularly limited, but 1 μm or more 50
It is preferably 0 μm or less, more preferably 10 μm or more 3
00 μm or less, more preferably 40 μm or more and 200 μm
m or less. As a method for producing these polymer films, a molding method such as a solvent casting method, an extrusion molding method or a press molding method may be used.

When the base material is a polymer film, the glass transition temperature of the base material to be used in the heat treatment of the liquid crystal oligomer as described later, or the flow of the base material in the base material to which the additive is added. It is preferable to select a substrate according to the heat treatment temperature in order to avoid problems in the manufacturing method such as deformation of the substrate at temperatures above the temperature.

In the optically anisotropic film of the present invention,
The liquid crystal composition is oriented so that the spiral axis of the twisted nematic alignment is parallel to the film normal direction.To realize such twisted nematic alignment, it is common to perform horizontal alignment treatment on the substrate surface. is there. As the horizontal alignment treatment method, a known method such as a rubbing method or an oblique vapor deposition method can be used, but the rubbing method is more preferable from the viewpoint of industrialization. When the rubbing method is used, the base material before forming the liquid crystal oligomer is directly rubbed, or the alignment film is formed on the base material and then rubbed, but after the alignment film is formed from the viewpoint of alignment stability. A method of performing rubbing treatment is preferable.
As the alignment film, known films can be used as long as the liquid crystal molecules are horizontally aligned. For example, polyimide, polyamide, polyvinyl alcohol, etc. are exemplified. Examples of the coating method of the alignment film include a roll coating method, a gravure coating method, a bar coating method, a spin coating method, a spray coating method, a printing method, and a dipping method.

The thickness of the alignment film is generally 0.0
If it is 1 μm or more, the alignment performance is exhibited, but if the alignment film is too thick, the workability deteriorates.
μm is preferable, and more preferably 0.02 to 3.0 μm
m. Then, after performing post-treatments such as drying and curing depending on the type of the applied alignment film, the alignment film is rubbed. The rubbing method is not particularly limited, and a known method can be used. For example, when using a rubbing roller, there is no particular limitation on the material of the rubbing roller, the amount of pushing into the alignment film of the rubbing roller, the moving speed of the roller with respect to the substrate, the number of times of rubbing, etc., the type of the alignment film and the liquid crystal oligomer. The optimum condition may be selected according to the type.

An example of the oblique vapor deposition method is a method using an oblique vapor deposition film of an inorganic material. As the inorganic material, columnar growth is preferable at the time of vapor deposition, and SiO, SiO ₂ , SiO _x (where 1 <x <2). , MgO, MgO _y (where 0 <y <
1), MgF ₂ , Pt, ZnO, MoO ₃ , WO ₃ , T
a ₂ O ₅ , SnO ₂ , CeO ₂ , LiNbO ₃ , LiT
aO ₃ , ZrO ₂ , Bi ₂ O ₃ , TiZrO ₄ , HfO
₂ are exemplified, and among these, SiO, SiO ₂ , Si
O _x (here 1 <x <2), MgO, MgOy (here 0 <y <1), MgF ₂ , Pt and ZnO are preferably used, and more preferably SiO, SiO ₂ and SiO _x (here 1 <X <2) is used. As the oblique vapor deposition method, a vapor deposition method by resistance heating, a vapor deposition method by electron beam heating and a sputtering method are exemplified, and a vapor deposition method by electron beam heating and a sputtering method are preferable for vapor-depositing a high melting point inorganic substance. The degree of vacuum during vapor deposition is not particularly limited, but the upper limit of pressure is determined from the viewpoint of uniformity of the deposited film, and the lower limit of pressure is determined from the viewpoint of productivity. Specifically, 1 × 10 ^-3 to 1
^X10-7 Torr is illustrated, Preferably it is 5 * ^10-4 .
It is 5 × 10 ⁻⁶ Torr. Regarding the vapor deposition rate of the inorganic substance, if the vapor deposition rate is low, the productivity is poor, and if the vapor deposition rate is high, the uniformity of the vapor deposition film is poor. Therefore, the vapor deposition rate is preferably 0.01 to 10 nm / sec, and more preferably 0.1 to 5 nm / sec. The film thickness of the deposited inorganic material is, for example, 0.01 μm to 1000 μm, since the orientation becomes poor when the film thickness is thin and the productivity becomes poor when the film thickness is thick, preferably 0.05 to 100 μm, and further preferably Is 0.1 to 5 μm.

Next, a liquid crystal composition is formed into a film on the substrate which has been subjected to the horizontal alignment treatment. As a method for forming a film of the liquid crystal composition,
The method of applying the liquid crystal composition in a solution state and the method of applying it in an isotropic phase are exemplified, and the method of applying from a solution state is preferable. Examples of the coating method include an ordinary roll coating method, gravure coating method, bar coating method, spin coating method, spray coating method, printing method, and depping method. The thickness of the obtained film is 0.1 to 20 μm.
Is more preferable, 0.5 to 10 μm is more preferable, and 1 to 7 μm is particularly preferable. When the thickness is less than 0.1 μm, the expression of optical properties becomes small, and when it exceeds 20 μm, it is economically unfavorable.

Next, the liquid crystal composition is heat-treated. The heat treatment temperature is written as T _t (° C.), the transition temperature of the liquid crystal composition from the crystal phase or the glass phase to T _g (° C.), and the temperature at which the substrate or the alignment film is deformed is written as T _k (° C.). If that, the heat treatment temperature is preferably _{(T g +30) ≦ T t} ≦ (T k -30), it is more preferable to heat treatment in the range of _{(T g +40) ≦ T t} ≦ (T k -40), Considering the ease of production, it is preferable to carry out the treatment in the range of 60 to 200 ° C. If the heat treatment time is too short, the twisted nematic orientation cannot be realized, and if it is too long, it is industrially unfavorable. Therefore, it is preferably 0.2 minutes or more and 20 hours or less, more preferably 1 minute or more and 1 hour or less. By the above heat treatment, the liquid crystal composition comes to have a twisted nematic orientation having a spiral axis parallel to the film normal direction. The heating rate and cooling rate in the heat treatment are not particularly limited. The liquid crystal composition is then polymerized to fix the twisted nematic alignment.
As the polymerization method, it is necessary to carry out polymerization while maintaining the orientation, and thus photopolymerization, radiation polymerization such as γ-ray, and thermal polymerization are exemplified. A known polymerization initiator can be used in photopolymerization or thermal polymerization. Among these polymerization methods, photopolymerization and thermal polymerization are preferable because of the ease of the steps, and further, photopolymerization is more preferable because the retention of orientation is good.

The irradiation light intensity for photopolymerization may be selected as an optimum value depending on the thickness of the film and the type of liquid crystal composition used, but is preferably 0.01 to 5.0 J / cm.
The range is ² and more preferably 0.1 to 3.0 J / c.
m ² . When the irradiation light amount is less than 0.01 J / cm ² , the reaction of the polymerized group may be insufficient, and
When it is more than 0 J / cm ² , there is a problem in manufacturing cost.

The liquid crystal display device of the present invention has a positive dielectric anisotropy sandwiched between substrates having electrodes, and is twisted and oriented substantially horizontally when no voltage is applied and the spiral axis is perpendicular to the substrate. At least one selected from the optically anisotropic film of the present invention, or a laminate of the optically anisotropic film and the substrate, between the liquid crystal cell comprising the liquid crystal layer and the polarizing film arranged on the outside thereof. Is included. Specific examples of the liquid crystal cell composed of a liquid crystal layer which is twisted and aligned substantially horizontally when a voltage is not applied and whose spiral axis is perpendicular to the substrate are a TN type liquid crystal cell having a twist angle of about 90 degrees and a twist angle of 180 to 300 degrees. STN type liquid crystal cell. In the liquid crystal display device of the present invention, the method of arranging the polarizing plate and the optically anisotropic film of the present invention is not particularly limited, and an appropriate arrangement can be selected according to the required characteristics. In the liquid crystal display device, the optically anisotropic film may be disposed on only one side of the liquid crystal cell or on both sides as long as it is between the polarizing plate and the liquid crystal cell.

[0058]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The phase transition temperature of the liquid crystal oligomer was determined by texture observation with a scanning differential calorimeter (DSC) and a polarizing microscope.
The twist angle of the obtained optically anisotropic film is determined by measuring the vibration direction of the linearly polarized light that is incident on and emitted from the optically anisotropic film (MCPD-1000, manufactured by Otsuka Electronics Co., Ltd.). I asked for. The phase difference of the optically anisotropic film [Δn · d (Δn is the apparent refractive index anisotropy of the film, d is the film thickness]] is a cell gap measuring device (TF
M-120AFT, manufactured by Oak Manufacturing Co., Ltd.) was used to analyze and obtain the transmitted light spectrum.

Example 1 A polyvinyl alcohol alignment film was formed on a washed glass substrate by spin coating, and heat-treated at 100 ° C. for 1 hour. The thickness of the obtained alignment film was about 0.05 μm.
Then, the alignment film was rubbed using a rubbing machine. In the same manner as the method described in JP-B-63-41400, the following vinyl monomers (1) and (2) are reacted with pentamethylcyclopentasiloxane at a mixing ratio of 7: 3 to form a cyclic pentasiloxane liquid crystal oligomer (A). Got

[0060]

[Chemical 31]

The glass transition temperature of this liquid crystal oligomer is 1
4 ° C., transition temperature to isotropic phase is 114 ° C., 14 ° C.
It showed a cholesteric phase at 114 ° C. Further, as a result of extrapolation from the measured value of the selective reflection wavelength of the composition of the liquid crystal oligomer and the nematic liquid crystal, the selective reflection wavelength of the liquid crystal oligomer alone was 280 nm. The cholesteric phase spiral pitch of this liquid crystal oligomer is 0.2 μm from this wavelength.
Is calculated. Then, the vinyl monomer (3) was reacted with pentamethylcyclopentasiloxane in the same manner as described above to obtain a cyclic pentasiloxane liquid crystal oligomer (B).

Embedded image

The glass transition temperature of this liquid crystal oligomer is 2
0 ° C., transition temperature to isotropic phase is 97 ° C., 20 ° C. to 9 ° C.
It showed a nematic phase at 7 ° C. The obtained liquid crystal oligomers (A) and (B) were mixed at a ratio of 3:97 (weight ratio), dissolved in toluene so that the solid content was 30 wt%, and further used as a photopolymerization initiator, Irgacure-907 (Ciba Geigy). Was mixed with the liquid crystal oligomer so as to be 2.0 wt%. This solution was spin-coated on a glass substrate with a polyvinyl alcohol alignment film.

As a result of observing the obtained liquid crystal oligomer film with a polarization microscope, it was confirmed that it exhibited a cholesteric phase. Further, this liquid crystal oligomer was clouded, and when observed by a polarizing microscope, it was not aligned at all. Next, this liquid crystal oligomer film was heated to a temperature at which it became an isotropic phase, and then gradually cooled to be oriented. Then, using a high pressure mercury lamp,
Ultraviolet rays were radiated so as to be J / cm ² . The obtained liquid crystal oligomer polymer film was an optically anisotropic film, its thickness was 3.0 μm, and its twist angle was 243.
Δn · d at room temperature was 0.748 μm.
In addition, Δ of the obtained optically anisotropic film at 55 ° C.
When n · d was measured, it was 0.646 μm, which was 86% of Δn · d at room temperature.

Example 2 Example 1 was repeated except that the liquid crystal oligomers (A) and (B) in Example 1 were mixed in a ratio of 4:96 (weight ratio).
A liquid crystal oligomer film was prepared in the same manner as in. The obtained liquid crystal oligomer polymer film is an optically anisotropic film, its thickness is 3.4 μm, and its twist angle is 2
Δn · d at 20 ° and room temperature was 0.980 μm. Further, the Δn · d of the obtained optically anisotropic film at 55 ° C. was measured and found to be 0.906 μm,
It was 92% of Δn · d at room temperature.

Comparative Example 1 A retardation film made of polycarbonate as a uniaxially oriented retardation film made of a thermoplastic polymer having an optical axis in the plane of the film and having positive refractive index anisotropy (trade name: Sumika Light (SEF-400426) manufactured by Sumitomo Chemical Co., Ltd., Δn · d = 380 nm, viewing angle 39 °] was measured for temperature dependence of Δn · d, room temperature and 55 ° C.
There was almost no change.

Example 3 Example 1 was repeated except that the liquid crystal oligomers (A) and (B) in Example 1 were mixed in a ratio of 5:95 (weight ratio).
A liquid crystal oligomer film was prepared in the same manner as in. The thickness of the obtained liquid crystal oligomer polymer film is 2.8 μm.
The twist angle was 213 °, and Δn · d at room temperature was 0.925 μm. The obtained liquid crystal oligomer polymer film is an optically anisotropic film,
When inserted between the liquid crystal cell and the polarizing plate, an STN liquid crystal panel having excellent viewing angle characteristics and contrast can be obtained. Also,
The optically anisotropic film has a temperature dependence of Δn · d of ST
Since it is close to the N liquid crystal cell, the viewing angle characteristics and the contrast at high temperature can be improved.

[0067]

By using the optically anisotropic film having twisted nematic orientation of the present invention, a retardation plate having a wide viewing angle can be obtained. In addition, these are TN type and STN
By applying the liquid crystal display device to a liquid crystal display device, the display characteristics of the liquid crystal display device, especially the viewing angle characteristics can be remarkably improved. Furthermore, since the optical anisotropic film of the present invention has a temperature dependence of refractive index anisotropy close to that of a liquid crystal panel, the viewing angle characteristics of a liquid crystal cell can be improved in a wide temperature range.

Claims (9)

[Claims] 1. An optically anisotropic film containing a twisted nematically aligned liquid crystal composition, wherein the helical axis of the twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. The liquid crystal composition exhibits a cholesteric phase with a helical pitch of 0.2 μm or more and 50 μm or less, and has the following repeating units (I) and (I
I) one or more kinds of liquid crystal oligomers selected from linear or cyclic liquid crystal oligomers (A) having a main constituent unit as a main constitutional unit, and repeating units (I) and (II) in one molecule of the liquid crystal oligomer (A) Where n and n ′ are the integers from 1 to 20, respectively.
And 4 ≦ n + n ′ ≦ 21, and the ratio of n: n ′ is 20:
1 to 1:20, wherein the terminal group of the repeating unit (II) is polymerized, which is an optically anisotropic film. Embedded image Embedded image [In the formula, A is a group represented by the following formula (III) or (IV), and in formula (III), -Si-O- is the main chain of formula (I) or (II), -C-CH ₂ in IV) - is the main chain of the formula (I) or (II), COO group is positioned in the side chain is not a R ₁ or R ₂ side chains. When A is formula (III) in formula (I) and A is formula (III) in formula (II), R ₁
And R ₂ are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms or a phenyl group. When A is formula (IV) in formula (I) and A is formula (IV) in formula (II), R ₁ and R ₂ are independently hydrogen or an alkyl group having 1 to 6 carbon atoms. Embedded image [Chemical 4] k and k ′ independently represent an integer of 2 to 10, m and m ′ independently represent 0 or 1, and Ar ₁ , Ar ₂ and Ar ₃ independently represent a 1,4-phenylene group, 1, 4-cyclohexylene group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, and L ′ is —CH ₂ —O.
_{-, - O-CH 2 -} , - COO -, - OCO -, - CH
_{2 -CH 2 -, - CH =} N -, - N = CH- or embedded image Is a divalent group represented by, p ′ is 0 or 1,
R represents an optically active group, and R ′ is hydrogen or an alkyl group having 1 to 5 carbon atoms. ] 2. An optically anisotropic film containing a twisted nematically aligned liquid crystal composition, wherein the helical axis of twisted nematic orientation is substantially parallel to the normal direction of the film, and the twist angle is 70 ° or more and 300 ° or less. The liquid crystal composition exhibits a cholesteric phase with a helical pitch of 0.2 μm or more and 50 μm or less, and contains one or more liquid crystal oligomers and a polymerizable group selected from the liquid crystal oligomers (A) according to claim 1. An optical anisotropic body characterized in that the low molecular weight compound containing at least one kind of the low molecular weight compound having and having a terminal group and / or a polymerizable group of the repeating unit (II) of the liquid crystal oligomer (A) is polymerized. the film. 3. An optically anisotropic film containing a twisted nematically aligned liquid crystal composition, wherein the helical axis of twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. The liquid crystal composition has a helical pitch of 0.2 μm or more and 50 μm or less, and one or more kinds of liquid crystal oligomers selected from the liquid crystal oligomers (A) according to claim 1 and (A) 1 selected from the liquid crystal oligomer (B)
The liquid crystal oligomer (B) contains at least one kind of liquid crystal oligomer, and the liquid crystal oligomer (B) is selected from linear or cyclic liquid crystal oligomers having the following repeating units (V) and (VI) as main constituent units. The number of repeating units (V) and (VI) in one molecule is n ″ and n ′ ″, respectively.
Where n ″ and n ′ ″ are independently integers from 0 to 20 and 4 ≦ n ″ + n ′ ″ ≦ 21, and the repeating unit (II) of the liquid crystal oligomer (A) is And / or an end group of the repeating unit (VI) of the liquid crystal oligomer (B) is polymerized. [Chemical 6] [Chemical 7] (In the formula, A, R ₁ , R ₂ , k ′, m ′, p ′, L ′, A
r ₂ , Ar ₃ and R ′ have the same meanings as described above. k ''
Represents an integer of 2 to 10, m ″ is 0 or 1, and Ar ₄ and Ar ₅ are 1,4-phenylene groups, 1,
4-cyclohexylene group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, L ″ is —C
_{H 2 -O -, - O-} CH 2 -, - COO -, - OCO
_{-, - CH 2 -CH 2 -} , - CH = N -, - N = CH-
Or Is a divalent group represented by, p ″ is 0 or 1,
R '' is a halogen, a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms or 1 to 10 carbon atoms. 10 shows a benzoyloxy group having 10 alkoxy groups. ) 4. An optical anisotropic film containing a twisted nematically aligned liquid crystal composition, wherein the helical axis of twisted nematic orientation is substantially parallel to the film normal direction, and the twist angle is 70 ° or more and 300 ° or less. The liquid crystal composition has a helical pitch of 0.2 μm or more and 50 μm or less, and one or more kinds of liquid crystal oligomers selected from the liquid crystal oligomers (A) according to claim 1 and (A) 1 selected from the liquid crystal oligomer (B)
One or more kinds of low molecular weight compounds having at least one kind of liquid crystal oligomer and a polymerizable group, and containing a terminal unit of the repeating unit (II) of the liquid crystal oligomer (A) and / or a repeating unit (VI) of the liquid crystal oligomer (B). An optically anisotropic film, characterized in that a low molecular weight compound having a terminal group and / or a polymerizable group is polymerized. 5. The optically anisotropic film according to claim 1, wherein R is the following formula (VII) or (VI):
An optically anisotropic film comprising a liquid crystal oligomer represented by II). [Chemical 9] [Chemical 10] [Wherein R ₃ represents —H or the following formula (IX), and R ₄ represents -H or a methyl group, R ₅ represents -H or R
₆ is shown, and R ₆ is a linear or branched carbon number 1 to
20 represents an alkyl group or a linear or branched alkoxycarbonyl group having 1 to 20 carbon atoms, and when branched, may have an asymmetric carbon. ] 6. A liquid crystal composition according to claim 1, 2, 3, 4 or 5 is formed on a film and then heat-treated to make the helical axis of the twisted nematic alignment substantially parallel to the normal line direction of the film, A method for producing an optically anisotropic film, which comprises polymerizing a polymerizable group. 7. An optical anisotropic film obtained by laminating the optically anisotropic film according to claim 1, 2, 3, 4 or 5 and a transparent or semitransparent substrate having an alignment film on the surface thereof. And a base material laminated body. 8. The laminated body of the optically anisotropic film and the substrate according to claim 7, wherein the substrate is a glass plate or a polymer film. 9. A liquid crystal cell comprising a liquid crystal layer sandwiched between substrates having electrodes, which has a positive dielectric anisotropy, and which is twisted and aligned substantially horizontally when a voltage is not applied and with a helical axis perpendicular to the substrate. And between the polarizing film arranged on the outside,
An optical anisotropic film according to claim 1, 2, 3, 4 or 5, or at least one selected from the laminate of the optical anisotropic film according to claim 7 and a substrate. Characteristic liquid crystal display device.