JP3179283B2 - Method for producing optically anisotropic sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically anisotropic sheet formed from a discotic compound which is particularly useful as an optical compensation sheet for a liquid crystal display device, and a liquid crystal display device provided with the optically anisotropic sheet.

[0002]

2. Description of the Related Art A CRT which is a mainstream display device of OA equipment such as a Japanese word processor and a desktop personal computer.
Has been converted to a liquid crystal display element having great advantages such as thin and light weight and low power consumption. Many of the liquid crystal display elements (hereinafter referred to as LCDs) that are currently widely used use twisted nematic liquid crystals. Display methods using such a liquid crystal can be roughly classified into two modes, a birefringence mode and an optical rotation mode.

An LCD using a birefringence mode has a liquid crystal molecule arrangement in which the twist angle is twisted by 90 ° or more and has a steep electro-optical characteristic. Therefore, a simple matrix without an active element (thin film transistor or diode) is used. A large-capacity display can be obtained by the time-sharing behavior in the shape of the electrode. But,
It has the disadvantage that the response speed is slow (several hundred milliseconds) and that gradation display is difficult.
LCD or MIM-LCD).

In the TFT-LCD and the MIM-LCD, an optical rotation mode display mode (TN type liquid crystal display element) in which the alignment state of liquid crystal molecules is twisted by 90 ° is used. This display method is the most influential method as compared with other types of LCDs, since it has a fast response speed (several tens of milliseconds), easily obtains a black-and-white display, and shows a high display contrast. However, since the twisted nematic liquid crystal is used, there is a problem in viewing angle characteristics that a display color and a display contrast change depending on a viewing direction due to a principle of a display method.
It does not reach the point where the display performance of T is exceeded.

JP-A-4-229828, JP-A-4-4-2
As disclosed in Japanese Patent No. 58923, a method has been proposed in which a viewing angle is increased by disposing a retardation film between a pair of polarizing plates and a TN type liquid crystal cell. The retardation film proposed in the above patent gazette has a phase difference of almost zero in a direction perpendicular to the liquid crystal cell, and has no optical effect from directly in front of the liquid crystal cell.
A phase difference is developed when tilted, and the phase difference developed in the liquid crystal cell is to be compensated. However, even with these methods, the viewing angle of the LCD is still insufficient, and further improvement is desired. In particular, the current viewing angle cannot be used at all at present when considered as an in-vehicle use or as a substitute for a CRT.

In JP-A-4-366808 and JP-A-4-366809, a viewing angle is improved by using a liquid crystal cell containing a chiral nematic liquid crystal having an inclined optical axis as a retardation film. It is a layer liquid crystal system, which is expensive and very heavy. Further, Japanese Patent Application Laid-Open No. 5-80323 proposes a method of using a retardation film having an inclined optical axis with respect to a liquid crystal cell. However, since uniaxial polycarbonate is obliquely sliced and used. However, there is a problem that it is difficult to obtain a large-area retardation film at low cost.

Japanese Patent Application Laid-Open No. 5-215921 proposes a method of optically compensating an LCD by using a birefringent plate in which a pair of alignment-treated substrates is sandwiched with a rod-like compound exhibiting liquid crystallinity when cured. However, in this case, there is no difference from the so-called double-cell type compensator which has been conventionally proposed, so that the cost is greatly increased and it is not suitable for mass production. Further, as long as a rod-shaped compound is used, the birefringent plate has a T
It is impossible to improve the viewing angle in all directions of the N-type LCD.

In Japanese Patent Application Laid-Open Nos. Hei 3-9326 and Hei 3-291601, a polymer liquid crystal is applied to a film-like substrate on which an alignment film is provided.
Although there is a description of an optical compensator for a CD, it is impossible to obliquely orient molecules in this method, so that it is impossible to improve the TN-type LCD in all directions.

In the specification of Japanese Patent Application No. 5-236538, when the triphenylene compound is oriented by an orientation film, the optical axis of the thin film is obliquely inclined, and is useful as an optically anisotropic sheet. It was shown.

[0010] There have been reports from various angles on polymer liquid crystals containing the triphenylene compound in the main chain or side chain. Willi Kreuder et
al, Makromol. Chem. Rapid C
ommun. 4, 807 (1983). 6 volumes,
367 (1985). 7:97 (1986)
Year). Gerhard Wenz, Makromol.
Chem. RapidCommun. 6, 577 (1985). Bernhard Huser, Ma
cromol. Chem. 191, 1597 (19
90 years). Bernhard Huser, Advan
ced Materials. Vol. 2, p. 36 (1990
Year). Hans Wolfgang Spiess, M
akromol. Chem. Rapid Commu
n. 14, 329 (1993). However, no behavior has been reported when they are applied on an alignment film.
In addition, studies on the magnetic field orientation of the above-mentioned polymerization composition of the triphenylene compound include the following reports. Bernh
ard Huser, Makromol. Chem. R
rapid Commun. 9, 337 (1988)
Year). Bernhard Huser, Makromo
recules. 22, 1960 (1989). W
olfgang Kranig, Makromolec
ules. 23, p. 4061 (1990). But,
From the viewpoint of production, a method of tilting the molecule more easily is preferable.

Most of the reported discotic compounds are also triphenylene compounds, and others include inositol reported examples: Bernd Kohne, Liq.
uid Crystals, 4, 165 (1989)
Year). Moreover, the linking mode is such that the hydroxyl group and carboxyl group of the triphenylene ring are ester-bonded or the side-chain terminal vinyl group linked to the triphenylene ring by an ester bond is bonded to the siloxane polymer and S
It is only i-carbon bonded and its structure is very limited for the number of reports.

Further, as for the polymer composition of the discotic compound obtained by cross-linking polymerization, there is only an example of photopolymerization in a cyclohexane solution of a cinnamoyl group used as a side chain of azacrown. C. Mertesdorf, L
liquid Crystals, vol. 9, p. 337 (19
91).

[0013] Even if an optically anisotropic sheet can be obtained from the polymer composition containing the discotic compound, its optical performance is as follows:
It largely depends on the electronic state of the discotic compound and the side chain group, and whether or not the alignment can be performed more efficiently in the alignment step, and whether or not a smooth thin film can be easily formed. Therefore, development of a polymerizable thin film of a discotic compound having various side chains and connecting portions has been required. Further, there has been a demand for the development of a technique for uniformly tilting molecules using such a polymer composition.

[0014]

Accordingly, an object of the present invention is to provide a liquid crystal display device which is particularly useful as an optical compensation sheet.
An object of the present invention is to provide an optically anisotropic sheet using a polymer formed from a discotic compound and a liquid crystal display using the optically anisotropic sheet.

[0015]

According to the present invention, there is provided a method comprising:
Forming a layer containing at least one of the discotic compounds of the following general formula (1) having a radial side chain having a reactive functional group P at the terminal, and then polymerizing the discotic compound on the substrate to obtain a uniaxial direction Optically anisotropic layer consisting of a polymer
A method for producing an optically anisotropic sheet having an optically anisotropic layer, characterized by being produced .

## STR1 general formula _{(1) R nk -D- (L} -P) k [ wherein, D is a triphenylene ring, truxene ring, inositol ring, aza crown ring, hexamethylene phenylethynyl benzene ring or phenylacetylene macrocycles, Which forms the central nucleus of the discotic compound and has a total of n substituents represented by (P-L) or R, provided that when D is a triphenylene ring,
The total number of the substituents is 6, 2, 3, 6, 7, 1
P is in the 0,11-position; P is isocyanate group, thiocyanate group, amino group, alkylamino group, arylamino group, mercapto group, formyl group, acyl group, hydroxyl group, carboxyl group, sulfo group, phosphoryl group, Halocarbonyl group, halosulfonyl group, halophosphoryl group,
A represents an acryloyl group, a vinyloxy group, an epoxy group, or a propargyl group. When D is a triphenylene ring, P represents an isocyanate group, a thiocyanate group, an amino group, an alkylamino group, an arylamino group, a mercapto group, or a formyl group. , An acyl group, a hydroxyl group, a carboxyl group, a sulfo group, a phosphoryl group, a halocarbonyl group, a halosulfonyl group, a halophosphoryl group, or a propargyl group; L represents a group linking P and D or a chemical bond; Represents a functional group not involved in the formation of the polymer; n represents an integer ranging from 3 to 8;
Represents an integer ranging from to n].

D in the above formula (1) is preferably a triphenylene ring. Further, it is preferable that the polymer sheet is a polymer sheet in which the polymer is uniaxially oriented and exhibits optical anisotropy. This orientation can be realized by a method such as application of an electric or magnetic field, stretching, stretching at different peripheral speeds, or coating on an alignment film.

The present invention also provides a liquid crystal display device comprising a polymer sheet exhibiting the above optical anisotropy.

The discotic compound used in the present invention is a compound in which a specific cyclic nucleus such as triphenylmethane is arranged at the center of a molecule, and a linear alkyl group, an alkoxy group, or a substituted benzoyloxy group is used. Is a compound radially attached as a side chain thereof and exhibits properties as a discotic liquid crystal. According to the study of the present inventors, a polymer formed from the above discotic compound (hereinafter, sometimes referred to as a polymer composition) is deformed in response to an external force (eg, it moves upon heating, or molecules are easily oriented). It has been found.

Typical examples of the discotic liquid crystal compound include, for example, C.I. Research reports by Destrade et al.
Mol. Cryst. Liq. Cryst. 71 volumes, 1
Benzene derivative, triphenylene derivative, truxene derivative, phthalocyanine derivative, and B.I. Research report by Kohne et al., An
gew. Chem. Vol. 96, p. 70 (1984) and cyclohexane derivatives described in J. Am. M. J. Lehn et al. Chem. Soc. Chem. Com
mun. , P. 1794 (1985); Zhang
Et al. Am. Chem. Soc. 116
Azacrown-based and phenylacetylene-based macrocycles described in Vol. 2, pp. 2655 (1994).

Hereinafter, with respect to the general formula (1) of the present invention,
This will be described in detail. The polyfunctional group D having a disc-like structure is selected from a triphenylene ring, a truxene ring, an inositol ring, an azacrown ring, a hexaphenylethynylbenzene ring, or a phenylacetylene macrocycle. Particularly preferred are a triphenylene ring and a truxene ring.

The k Ps are each independently an isocyanate group, a thiocyanate group, an amino group, an alkylamino group,
An arylamino group, a mercapto group, a formyl group, an acyl group, a hydroxyl group, a carboxyl group, a sulfo group, a phosphoryl group, a halocarbonyl group, a halosulfonyl group, a halophosphoryl group, an acryloyl group, a vinyloxy group, an epoxy group, and a propargyl group. Preferably, a mercapto group,
A formyl group, a hydroxyl group, a halocarbonyl group, an acryloyl group, a vinyloxy group, and an epoxy group. More preferred are a hydroxyl group and an acryloyl group.

Each of the (nk) Rs independently represents a functional group which does not contribute to the formation of the polymer composition, and whether or not it contributes depends on the functional group of the condensing partner. But,
Generally, an alkyl group, an alkoxy group, an oligooxyethylene group, an acyl group, an acyloxy group, a benzoyloxy group, and a benzoyl group are preferably used. But,
Adjacent Rs may be connected to each other to form a ring, and one or two side chains may be radially substituted.

L independently represents a group or a chemical bond connecting P and D. For example, an alkylene group (for example,
Ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, an alkyleneoxy group (eg, ethyleneoxy, propyleneoxy, butyleneoxy, pentyleneoxy, hexyleneoxy, heptyleneoxy, octyleneoxy, nonyleneoxy), phenylene And a group having a carbonyl group on one of the group and the alkylene group (for example, 1-oxononylene). Preferably, it is an alkyleneoxy group, and more preferably, an ethyleneoxy group or a hexyleneoxy group. However, a structure in which adjacent Ls are connected to each other to form a ring, one or two side chains are substituted radially, and P is substituted at the terminal thereof may be used. n represents an integer of 3 to 8, and k represents an integer of 1 to n.

Hereinafter, specific examples of the compound of the present invention represented by the general formula (1) are shown, but the present invention is not limited thereto.

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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The polymer composition comprising at least one discotic compound of the general formula (1) refers to a composition containing two or more residues of the discotic liquid crystal compound as the same or different residues. Examples of a state containing a plurality of the oligomers include so-called oligomers and so-called polymers of dimers, trimers and quantities. In order to form these states, for example, a method of reacting and linking polymerizable disc-like compounds, a method of reacting and linking a polymerizable disc-like compound with another polymerizable compound, a polymer chain Is formed and then reacted with a discotic compound, for example, a halogen atom, a polymer having a substituent active in a nucleophilic reaction such as an arylsulfonate, for example, a hydroxy group, an amino group, a mercapto group, or the like. Reaction of a discotic compound having a substituent capable of undergoing a nucleophilic reaction can be mentioned. Examples of the formed state include a state in which the disk-shaped molecule is crosslinked around the center, a state in which the disk-shaped molecule itself forms a part of the main chain of the polymer, and a state in which the disk-shaped molecule is pendant to the polymer chain. In a state of being joined together. Hereinafter, specific examples of the polymerization composition will be described.

[0031]

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[0032]

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[0033]

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The fact that the triphenylene-based discotic liquid crystal has negative birefringence is described in B. Mourey et al. [Mol. Cryst. Liq. Cryst. , 8
4, p. 193 (1982)], but in order to apply this property as an optically anisotropic material, all the molecules constituting the thin film are statistically unidirectional at room temperature. It is necessary to line up. In addition, the discotic liquid crystal is microscopically composed of an alignment region (domain) having a specific direction, and does not macroscopically exhibit optical anisotropy, similarly to a conventional liquid crystal composed of rod-like molecules. Due to the nature of forming a so-called multi-domain, in many cases the thin film does not exhibit favorable optical properties that can be used for an optical compensatory sheet.

The above-mentioned polymerization composition often shows liquid crystallinity thermally, but is often optically suspended in white, and has almost no anisotropic properties even when it is transparent. . However, these polymer compositions are dissolved in a suitable solvent and disclosed in JP-A-3-9326 and JP-A-3-291601.
As described in Japanese Patent Application Laid-Open No. 5-142510, a liquid crystal is coated on a polyimide film as an alignment film for liquid crystal.
It became clear that orientation can be easily achieved by heating. As the solvent, for example, chloroform,
Halogenated hydrocarbons such as dichloroethane, tetrachloroethane, trichloroethylene and orthodichlorobenzene; mixed solvents thereof with phenolic solvents such as phenol, o-chlorophenol and cresol; dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone An aprotic polar solvent, tetrahydrofuran, dioxane is used. The coating concentration varies depending on the coating method, the viscosity of the polymer composition, etc., but is used in the range of 5 to 50% by weight, preferably 1 to 50% by weight.
It is in the range of 0 to 30 wt%. As a coating method, a spin coating method, a roll coating method, a gravure coating method, a dipping method, or the like can be adopted.

The solvent is removed by drying, and a heat treatment is performed at a predetermined temperature for a predetermined time to complete a monodomain liquid crystal alignment, followed by cooling to a temperature below the glass transition point. The heat treatment temperature at this time is selected from temperatures higher than the glass transition point of the polymer composition. The viscosity of the polymer composition is preferably low in order to assist the alignment by the interface effect of the alignment film. Therefore, it is preferable that the heat treatment temperature is high. However, if the temperature is too high, the production cost increases and the workability deteriorates, which is not preferable. In general, a liquid crystalline polymer has an isotropic phase at a higher temperature portion than a nematic phase, but even when heat-treated in this temperature range, uniform alignment cannot be obtained in many cases. As described above, the heat treatment temperature needs to be equal to or higher than the glass transition point of the polymer composition of the present invention, and is desirably equal to or lower than the transition point to an isotropic phase. Generally 50-30
A range of 0 ° C is preferable, and a range of 100 to 250 ° C is particularly preferable. The time required to obtain a sufficient alignment in the liquid crystal state on the alignment film depends on the composition and molecular weight of the polymer composition and cannot be specified unconditionally, but is preferably in the range of 10 seconds to 60 minutes, and particularly preferably in the range of 20 seconds to 3 minutes. A range of minutes is preferred.
Further, the same alignment state can be obtained by applying the polymer composition of the present invention on a substrate that has been subjected to an alignment treatment in a molten state, and then performing a heat treatment. Furthermore, surprisingly, only the operations of coating on the alignment film, heating alignment, and cooling resulted in an anisotropic film having not only a monodomain property but also a thin film whose optical axis was often inclined.

As the alignment film, an inorganic or organic alignment film is used. As a metal oblique deposition film, a SiO oblique deposition film is typical, and as an organic alignment film, a rubbed polyimide film is a typical example. Other glass substrates treated with a rubbed modified poval or a rubbed silylating agent. Alternatively, a rubbed gelatin film or the like is used. However, instead of rubbing, a method of stretching a polyvinyl alcohol thin film by a factor of 4 to 5 or directly rubbing a glass substrate without providing the above protective film can also be used.

Without using an alignment film, the polymer composition in the form of a thin film obtained by coating or melting can be used in Helmut.
Ringsdolf, Macromol. Chem. ,
Rapid Commun. 7, 97 (1986)
Year). As described in (1), an optically uniaxial anisotropic sheet can also be obtained by performing a stretching operation at a temperature near the glass transition point. The stretching ratio varies depending on the polymer composition, but ranges from 1.1 times to 50 times, more preferably from 3 times to 8 times.

Further, the polymerization composition of the present invention is disclosed in
No. 120512, Polymer, Vol. 26, 85
3 (1985), Applied Physics
As described in Letter, Vol. 24, page 15, (1974), orientation can be achieved by placing the film in a high electromagnetic field in a heated state at a temperature equal to or higher than its glass transition point. At this time, the optical axis can be inclined by placing the optical axis obliquely in a high electromagnetic field.

As another method of inclining the optical axis, the polymer composition sheet of the present invention obtained by coating and stretching on an alignment film is heated to a temperature higher than its glass transition point and has a difference in peripheral speed or reverse. This is possible by pinching and drawing the sheet between two rollers that rotate to advance the film in the direction. The speed ratio is generally larger than 1 times,
It is preferably 1.1 times or less, more preferably from 1.001 times to 1.01 times.

When a support is used, it is desirable that the material be close to optically isotropic in addition to having good light transmittance. Therefore, a support formed of a material having a small intrinsic birefringence value sold under the trade name of glass, Zeonex (Zeon Japan), ARTON (Japan Synthetic Rubber), Fujitack (Fuji Film), or the like is preferable. But,
Polycarbonate, polyacrylate, polysulfone,
Even for a material having a large intrinsic birefringence value such as polyether sulfone, it is possible to form an optically isotropic support by controlling the molecular orientation at the time of film formation. Is done.

Examples of the material for the protective film include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene
Vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc. And organic substances such as a silane coupling agent. In addition, a Langmuir-Blodgett method (LB) such as ω-tricosanoic acid, dioctadecyldimethylammonium chloride and methyl stearate is used.
) Can also be used.

Hereinafter, the operation of the optically anisotropic material of the present invention, that is, the phase difference film for a liquid crystal display device will be described with reference to the drawings, taking a TN type liquid crystal display device as an example. 1 and 2 show the polarization state of light propagating through the liquid crystal cell when a sufficient voltage equal to or higher than the threshold voltage is applied to the liquid crystal cell. Since the transmittance characteristic of light when a voltage is applied particularly greatly contributes to the viewing angle characteristics of the contrast, the description will be made by taking a voltage application as an example. FIG. 1 is a diagram illustrating a polarization state when light is vertically incident on a liquid crystal cell. Natural light L0 is polarization axis PA
When the light is perpendicularly incident on the polarizing plate A having the following formula, the light transmitted through the polarizing plate PA becomes linearly polarized light L1.

When an arrangement state of liquid crystal molecules when a sufficient voltage is applied to the TN type liquid crystal cell is schematically represented by one liquid crystal molecule as a model, LC is schematically shown in the figure. When the molecular long axis of the liquid crystal molecules LC in the liquid crystal cell LCS is parallel to the light path, there is no difference in the refractive index on the incident surface (in a plane perpendicular to the light path), so that the light propagates through the liquid crystal cell. There is no phase difference between the ordinary light and the extraordinary light, and the linearly polarized light that has passed through the LC cell propagates as a linearly polarized light even though it passes through the liquid crystal cell. When the polarization axis PB of the polarizing plate B is set perpendicular to the polarization axis PA of the polarizing plate A, the light passes through the liquid crystal cell and the other linearly polarized light L2 cannot pass through the polarizing plate B, resulting in a dark state.

FIG. 2 is a diagram showing the polarization state of light when the light is obliquely incident on the liquid crystal cell. Natural light L of incident light
When 0 is obliquely incident, the polarized light L1 transmitted through the polarizing plate A
Becomes almost linearly polarized light (in practice, it becomes elliptically polarized light due to the characteristics of the polarizing plate). In this case, a difference in the refractive index occurs on the incident surface of the liquid crystal cell due to the refractive index anisotropy of the liquid crystal, and the light L2 transmitted through the liquid crystal cell is elliptically polarized and is not completely blocked by the polarizing plate B. As described above, in oblique incidence, light is not sufficiently blocked in a dark state, which causes a significant decrease in contrast, which is not preferable.

The present invention aims to prevent such a decrease in contrast at oblique incidence and improve the viewing angle characteristics. FIG. 3 shows an example of the configuration according to the present invention. An optically anisotropic material RF having an optical axis inclined from the normal direction of the liquid crystal cell is disposed between the polarizing plate B and the liquid crystal cell. The optically anisotropic material RF is a birefringent material that is polarized more as the angle of incidence of light with respect to the optical axis increases. As in the case of FIG. 2, the elliptically polarized light L2 transmitted obliquely into the liquid crystal display element having such a configuration as in the case of FIG. A good liquid crystal display element which is modulated into the original linearly polarized light and has the same transmittance even at various oblique incident angles and has no viewing angle dependence can be realized.

It is presumed as follows that the viewing angle of the liquid crystal display element can be greatly improved by the present invention. Many TN-LCDs employ a normally white mode. In this mode, as the viewing angle is increased, the transmittance of light from the black display section is significantly increased, resulting in a sharp decrease in contrast. The black display is the state when voltage is applied,
At this time, the TN type liquid crystal cell can be regarded as a positive uniaxial optically anisotropic body whose optical axis is slightly inclined from the normal direction to the surface of the cell. In the case of the intermediate gradation, it is considered that the optical axis is further inclined from the normal direction of the LC cell.

When the optical axis of the liquid crystal cell is inclined from the direction normal to the surface of the liquid crystal cell, it is expected that an optically anisotropic body whose optical axis is in the direction of the normal will have insufficient compensation. If the liquid crystal cell can be regarded as a positive uniaxial optically anisotropic body, a negative uniaxial optically anisotropic body is preferable in order to compensate for it. For such a reason, it is presumed that the viewing angle characteristics have been greatly improved by the negative uniaxial optical anisotropic material whose optical axis is inclined from the normal direction in the present invention.

The term “negative uniaxiality” in the present invention refers to the relationship of nα <nβ = nγ, where nα, nβ, and nγ are three-dimensional refractive indexes of a sheet having optical anisotropy in ascending order. Have Therefore, it has the characteristic that the refractive index in the optical axis direction is the smallest. However, the values of nβ and nγ do not need to be exactly equal, but it is sufficient if they are approximately equal. Specifically, nβ-nγ / nβ-nα
If <0.2, there is no practical problem. TFT, T
As a condition for greatly improving the viewing angle characteristics of the N-type liquid crystal cell, the optical axis is preferably inclined at 5 to 50 degrees from the normal direction of the sheet surface, more preferably 10 to 40 degrees, and more preferably 10 degrees. ~ 30 degrees is most preferred. Furthermore, when the thickness of the sheet is D, 100 <(nβ−nα) × D <400
It is desirable to satisfy the condition of nm.

[0050]

The present invention will be described in more detail with reference to Examples 2 and 3 below. Example 2 (Preparation of optically anisotropic sheet using polymer of discotic compound) Example 2A1 A 10 wt% solution of polyamic acid in N-methylpyrrolidone (SE-72 manufactured by Nissan Chemical Industries, Ltd.) was placed on a glass substrate.
10) was applied by spin coating, dried at 70 ° C., and then heated at 1800 ° C. for 2 hours to form a polyimide film having a thickness of about 1 μm. The surface of this polyimide film was rubbed with a flocking cloth to form an alignment film. A triphenylene compound polymer (DP-1: supra) prepared as a 10 wt% dichloromethane solution was applied on the alignment film by a spin coating method, heated at 130 ° C. for 10 minutes, and allowed to cool. Observing the orientation state of the obtained triphenylene compound polymer film with a polarizing microscope using crossed Nicols,
When the rubbing direction is parallel to the polarizing plate transmission axis, a completely dark field is obtained, and when rotated by 45 degrees, an almost colorless bright field is observed, confirming that the optically anisotropic sheet has a uniaxial orientation. Was. Examples 2A2 to 2A5 As a triphenylene compound polymer, the above-mentioned DP-3,
Using DP-4, DP-9, and DP-12, the solution was applied on the alignment film under the same conditions as in Example 2A1. Then, it was heated at the temperature shown in Table 1 and allowed to cool to obtain a triphenylene compound polymer film. Next, the orientation state of these triphenylene compound polymer films was similarly examined. Table 1 shows the results. Comparative Example 2A1 A triphenylene compound polymer film was obtained in the same manner as in Example 2A1, except that the rubbing treatment of the polyimide alignment film was not performed. Next, the orientation state of these triphenylene compound polymer films was similarly examined.
Table 1 shows the results.

[0051]

[Table 1]

Example 2B1 DP-14 as a 20 wt% dichloromethane solution was cast on a steel drum, continuously peeled off, and dried to obtain a film having a thickness of 10 μm. This at 130 ° C for 1
After heating for 0 minutes, the mixture was left to cool, and the alignment state was observed with a polarizing microscope in a crossed Nicol state. As a result, it was confirmed that the light was almost completely dark-field in all directions and was in a non-alignment state. Next, this thin film was stretched about 4 times at 80 ° C., and gradually cooled while its both ends were fixed. X of this film
From the line analysis, it was inferred that this film was optically uniaxial and perpendicular, and the molecules on the disk were almost parallel oriented.
Therefore, the film was guided to two rolls heated at 130 ° C. and having different peripheral speeds, and pulled out from opposite directions. The peripheral speed of the roll at this time was 3.500 cm / min and 3.510
cm / min. From X-ray analysis, this film was optically uniaxial, but was tilted at about 20 °, suggesting that the molecules themselves were also tilted. Example 2C A 10% dichloromethane solution of DP-13 was applied and dried on an SiO oblique deposition film having a tilt angle of 45 ° and a film thickness of about 800 Å formed on a glass substrate. In this state, the film was cloudy, but after heating at 130 ° C. for 10 minutes and cooling to room temperature, a colorless and transparent film was formed. Observation with a polarizing microscope revealed that no disclination line indicating disorder of molecular orientation in the film was observed, indicating that an optically uniform monodomain film was formed. From X-ray analysis, this film was optically uniaxial and tilted at about 13 °, suggesting that the molecules themselves were tilted and oriented. Example 3 (Evaluation of Optical Characteristics of Optically Anisotropic Material) A TN type liquid crystal cell having a product of the difference between the refractive index of the extraordinary light and the ordinary light of the liquid crystal and the gap size of the liquid crystal cell having a twist angle of 90 degrees was 480 nm. The film-shaped product of Example 2C1 was mounted, and the angle dependence of the contrast at a 30 Hz rectangular wave of 0 to 5 V with respect to the liquid crystal cell was measured by Otsuka Electronics LCD-5000. The position of the contrast 10 was defined as the viewing angle, and the up, down, left, and right viewing angles were determined. Also, the contrast ratio when viewed from the front was measured. Here, the measured values of only the TN liquid crystal without the film attached are also shown. The results are shown in Table 2 below. In FIG. 4, arrows indicate the rubbing direction in the retardation film and the rubbing direction in the liquid crystal cell.

[0053]

[Table 2]

As is clear from the above table, in the LCD provided with the optical compensation sheet of the present invention, a remarkable improvement in the viewing angle characteristics has been achieved.

[0055]

According to the present invention, a novel polymer composition comprising various discotic compounds having various side chains and connecting portions useful as an optically anisotropic material according to the present invention, in particular, a negatively tilted uniaxial polymer containing a triphenylene residue. It has been found that a thin film exhibiting birefringence and a method for producing the same can be provided, and furthermore, an optically anisotropic sheet comprising them can significantly improve the viewing angle of a liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a polarization state of light when the light is vertically incident on a liquid crystal cell.

FIG. 2 is a diagram showing a polarization state of light when light is obliquely incident on a liquid crystal cell.

FIG. 3 is a diagram showing an example of using an optically anisotropic material for a retardation film for a liquid crystal display element.

FIG. 4 is a diagram showing a relationship between a polarization axis of a polarizing plate, a rubbing direction of a liquid crystal cell, and a rubbing direction of an optically anisotropic sheet alignment film when viewing angle characteristics are measured in Examples.

[Explanation of symbols]

TNC: TN type liquid crystal cell A, B: polarizing plate PA, PB: polarization axis L0: natural light L1, L5: linearly polarized light L2: modulated light after passing through the liquid crystal cell L3, L4: elliptically polarized light LC: TN type liquid crystal cell State of liquid crystal molecules when voltage is sufficiently applied to the electrodes RF1, RF2: retardation film for liquid crystal display element BL: backlight

Continuation of the front page (56) References JP-A-4-31405 (JP, A) JP-A-2-92524 (JP, A) JP-A-2-75634 (JP, A) JP-A-2-75633 (JP) JP-A-63-273648 (JP, A) JP-A-61-254624 (JP, A) JP-A-57-165480 (JP, A) JP-A-56-79173 (JP, A) 6-207022 (JP, A) Patent 2641086 (JP, B2) Patent 2802719 (JP, B2) Patent table 4-500284 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/30

Claims (3)

(57) [Claims] 1. A layer containing at least one discotic compound of the following general formula (1) having a radial side chain having a reactive functional group P at a terminal is formed on a substrate, and then a layer is formed on the substrate. and to polymerize the discotic compound, light, characterized in that to produce the optically anisotropic layer comprising a polymer obtained by uniaxially oriented
A method for producing an optically anisotropic sheet having a chemically anisotropic layer : embedded image General formula (1): R _nk -D- (LP) _k [wherein D is a triphenylene ring, truxene ring, inositol ring , An azacrown ring, a hexaphenylethynylbenzene ring, or a phenylacetylene macrocycle, which forms a central nucleus of a discotic compound, and has a total of n substituents represented by (PL) or R around it. With the proviso that when D is a triphenylene ring,
The total number of the substituents is 6, 2, 3, 6, 7, 1
P is in the 0,11-position; P is isocyanate group, thiocyanate group, amino group, alkylamino group, arylamino group, mercapto group, formyl group, acyl group, hydroxyl group, carboxyl group, sulfo group, phosphoryl group, Halocarbonyl group, halosulfonyl group, halophosphoryl group,
A represents an acryloyl group, a vinyloxy group, an epoxy group, or a propargyl group. When D is a triphenylene ring, P represents an isocyanate group, a thiocyanate group, an amino group, an alkylamino group, an arylamino group, a mercapto group, or a formyl group. , An acyl group, a hydroxyl group, a carboxyl group, a sulfo group, a phosphoryl group, a halocarbonyl group, a halosulfonyl group, a halophosphoryl group, or a propargyl group; L represents a group linking P and D or a chemical bond; Represents a functional group not involved in the formation of the polymer; n represents an integer ranging from 3 to 8;
Represents an integer ranging from to n]. 2. The method for producing an optically anisotropic sheet according to claim 1, wherein D in the general formula (1) is a triphenylene ring. 3. The method for producing an optically anisotropic sheet according to claim 1, wherein the produced optically anisotropic layer is in a monodomain state.