JPH09117983A - Optical compensation sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical compensation sheet improved in narrow visual field angle characteristics generated when the polarization state of light propagating through a liquid crystal cell is different according to an incident direction for the first time and having the excellent durability against light for the second time. SOLUTION: An optical compensation sheet has at least one monodomain membrane of a discotic nematic phase formed from discotic liquid crystal liquid crystal compds. or a mixture of them or a uniaxial columnar phase and one surface of the monodomain membrane is in contact with an air phase and the optical axis of the sheet is inclined by 5-50 deg. from the normal line direction of the sheet surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensation sheet which, when used in a liquid crystal display device, can improve the viewing angle characteristics of its display contrast and display color.

[0002]

2. Description of the Related Art CRTs, which are the mainstream display devices for OA equipment such as Japanese word processors and desktop personal computers,
The liquid crystal display device has been converted to a liquid crystal display device 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 display performance of.

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.

[0006] The retardation film proposed in the above-mentioned patent publication has almost zero retardation in the direction perpendicular to the liquid crystal cell, does not exert any optical action from directly in front of the liquid crystal cell, and is tilted when tilted. Then, a phase difference is developed, 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. Especially for in-vehicle and CR
When considered as an alternative to T, it is impossible at present to cope with the current viewing angle. Also, Japanese Patent Application Laid-Open No. Hei 4-366
808 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 whose optical axis is inclined with respect to a liquid crystal cell. Therefore, there is a problem that it is difficult to obtain a large-area retardation film at low cost.

Further, Japanese Patent Application No. 5-5823 discloses a method using a retardation film whose optical axis is inclined using a photoisomerizable substance. According to this method, a lightweight, low-cost liquid crystal display device having a wide viewing angle characteristic can be realized. However, a disadvantage of this method is that the stability of the retardation film against heat and light is not sufficient.

[0009]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to improve the narrow viewing angle characteristic caused by the fact that the polarization state of light propagating in a liquid crystal cell varies depending on the incident direction. Another object of the present invention is to provide an optical compensation sheet having excellent durability against light.

[0010]

The present invention is a sheet having at least one monodomain thin film of a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystalline compound or a mixture thereof, and An optical compensation sheet, wherein at least one surface of at least one layer of the monodomain thin film is in contact with a gas phase, and the optical axis of the sheet is tilted by 5 to 50 degrees from the normal line direction of the sheet surface. is there. The monodomain thin film is preferably formed on the alignment film provided on the support. The discotic liquid crystal compound preferably has a triphenylene carbon skeleton in its partial structure.

The discotic liquid crystalline compound is preferably a compound represented by the following general formula (I).

[0012]

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Wherein R is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkanoyl group, a substituted alkenoyl group, a substituted alkinoyl group, a substituted or unsubstituted aryloyl group, a substituted or unsubstituted aryloyl group, Represents a substituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted carbamoyl group or a substituted sulfamoyl group, and each R may be the same or different. Further, R in the general formula (I) is Z ^{2 in} the following general formula (II),
Z ³ in general formula (IV), Z ⁴ in general formula (V), Z ⁵ in general formula (V), general formula (VI)
Z ⁶ of formula (VII), Z ⁷ of formula (VII), Z ^{8 of} formula (VIII), or Z ⁹ of formula (IX) is preferable.

General formula (II) Z ² = -CO-CR ²¹ = CR ²² -C ₆ H _5-n -R ²³ _n where R ²¹ and R ²² are each a hydrogen atom, a halogen atom or a substituted or unsubstituted represents an alkyl group, R ²³ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted The n groups represented by R ²³ represent a substituted aryloxy group and may be the same or different from each other, and n represents an integer of 0 to 5.

[0015] Formula ^{(III) Z 3 = -CO- (} CR 31 R 32) m - (Y) p -C 6 H 5-n -R 33 n However, R ³¹ and R ³² each represent a hydrogen atom, a halogen Represents an atom or a substituted or unsubstituted alkyl group, Y represents an oxygen atom or a sulfur atom, R ³³ represents a halogen atom,
A cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, R ³³
The n groups represented by may be the same or different from each other, m represents an integer of 1 to 4, and p represents 0 or 1
And n represents an integer of 0-5.

General formula (IV) Z ⁴ =-(CR ⁴¹ R ⁴² ) _m- (CR ⁴⁴ = CR ⁴⁵ ) _p -C ₆ H _5-n -R ⁴³ _n where R ⁴¹ , R ⁴² , R ⁴⁴ and R ⁴⁵ represents a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl group, and R ⁴³ represents a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkyl group. Represents an aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and the n groups represented by R ⁴³ may be the same or different, and m is an integer of 1 to 5 , P is 0, 1 or 2, and n is 0
Represents an integer of up to 5.

[0017] Formula ^{(V) Z 5 = - (} CR 51 R 52) m -CO-C 6 H 5-n -R 53 n However, R ⁵¹ and R ⁵² each represent a hydrogen atom, a halogen atom or a substituted or unsubstituted Represents a substituted alkyl group, R ⁵³ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted Alternatively, it represents an unsubstituted aryloxy group, and the n groups represented by R ⁵³ may be the same as or different from each other, m represents an integer of 1 to 4, and n represents an integer of 0 to 5.

General formula (VI) Z ⁶ = -CO-C ₆ H _11-n -R ⁶³ _n wherein R ⁶³ is a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted Is a cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and is represented by R ^63.
The groups may be the same or different from each other, and n
Represents an integer of 0 to 11.

General formula (VII) Z ⁷ = -CO-C ₆ H _5-n -R ⁷ _{n wherein} R ⁷ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl Group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and the n groups represented by R ⁷ may be the same or different from each other, and n Represents an integer of 0 to 5.

General formula (VIII) Z ⁸ = -CO-R ^{8 wherein} R ⁸ is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group or a substituted or unsubstituted Represents a heterocyclic residue of.

General formula (IX) Z ⁹ = -R ^{9 wherein} R ⁹ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group or a substituted or unsubstituted alkynyl group.

Hereinafter, the present invention will be described in detail. The discotic liquid crystal phase is a general term for the liquid crystal phase formed by the discotic molecules, and details thereof are described in a research report by C. Destrade et al. (Mol.
Cryst. Liq. Cryst. Vol. 71, p. 111 (1981)], a columnar phase in which the central cores of disk-shaped molecules are stacked in a columnar manner by intermolecular force.
It is known that discotic molecules can be roughly classified into a discotic nematic phase in which discotic molecules are randomly aggregated, and a chiral discotic nematic phase. But WHde j
eu's Physical properties of liquid crystalline ma
terials (1980 by Gordon and Breach, Science Pu
As described in blishers), columnar phases are often found, but the discotic nematic phases used in the present invention are rarely found.

The fact that the triphenylene discotic liquid crystal of the present invention has negative birefringence was reported by B. Mourey et al. [Mol. Cryst. Liq. Cryst., 84, 193 (19).
1982)], but in order to apply this property as an optical compensation sheet, it is necessary to arrange all the molecules constituting the thin film statistically in one direction at room temperature. Moreover, the discotic liquid crystal is composed of an alignment region (domain) having a specific directionality microscopically, and does not show optical anisotropy macroscopically, like the liquid crystal composed of conventional rod-shaped molecules. Due to the property of forming a so-called multi-domain, the thin film often does not exhibit favorable optical properties that can be used for an optical compensation sheet.

In this regard, we have studied in detail various discotic liquid crystals, and have found that a discotic nematic liquid crystal phase or a liquid crystal forming a uniaxial columnar phase, especially a triphenylene-based liquid crystal represented by the following general formula (I), It has been found that a thin film of a compound having a carbon skeleton structure has preferable characteristics as an optical compensation sheet.
Furthermore, it was found that a thin film in which a discotic nematic liquid crystal phase or a uniaxial columnar phase was formed preferentially tends to be in a monodomain state, and high light transmittance and high contrast are easily obtained. Although it is possible to use it as an optical compensatory sheet without realizing a complete monodomain state, it was found that a more complete monodomain thin film is preferable in terms of optical characteristics, productivity, etc. Was completed.

Furthermore, it is preferable that the compound having a triphenylene-based carbon skeleton structure has a structure substituted at a substitution position as represented by the general formula (I).

The substituents R in the general formula (I) may be the same or different from each other.
Compounds having a structure represented by any one of the substituents Z ^{2 to} Z ⁹ of I) to (IX) are preferred.

Further, 2,3,6,7,
The 10,11-substituted triphenylene compound is available from Macromo
l. Chem. Rapid Communication., vol. 4, p. 812 (1
983) to give a 6-methoxy-substituted product by oxidative trimerization of 1,2-dimethoxybenzene. The synthesis method described in Advanced Materials. Vol. 2, p. 40 (1990) can also be used.

Hereinafter, specific examples of the triphenylene compound and its side chain used in the present invention will be described, but the present invention is not limited by these compounds.

[0029]

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[0030]

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[0031]

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[0032]

[Chemical 6]

[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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The optical compensatory sheet formed by using the discotic liquid crystal of the present invention may be formed only by the discotic liquid crystal, but generally, a desired optical anisotropy is exhibited on the support. At least one liquid crystal layer is provided, and a protective film (alignment film) or a support may be present above and below the liquid crystal layer or between the liquid crystal layers depending on the application.

The discotic liquid crystals constituting the optical compensation sheet of the present invention may be used alone or in combination. Particularly, by appropriately mixing the liquid crystals, the phase transition temperature is often controlled, the optical structure of the liquid crystal phase is controlled, and the film-forming property is effectively improved.

It is desirable that the material for the support has good optical transmittance and, in addition, has optical isotropy. Therefore, glass, ZEONEX (Japan Zeon), ARTON
A support made of a material having a small intrinsic birefringence value sold under the trade name of (Japan Synthetic Rubber), Fujitac (Fuji Film) or the like is preferable. However, even if the material has a large intrinsic birefringence value such as polycarbonate, polyacrylate, and polysulfone, it is also possible to form an optically isotropic support by controlling the molecular orientation during film formation, They are also preferably used.

Examples of the material for the protective film include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, 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.

It is well known in the case of rod-shaped liquid crystals that the protective film often has a great influence on the molecular orientation when the liquid crystal layer is formed when a protective film (orientation film) is previously provided on the support. In fact, inorganic or organic alignment films are almost always used. This is one of the techniques preferably used in the present invention, and a typical example is an oblique metallized SiO film, and an organic oriented film is a rubbed fluorinated polyimide film. .

A general coating method can be applied to the formation of the liquid crystal layer constituting the optical compensation sheet of the present invention. That is, a liquid crystal thin film can be formed on a support through a drying step by a coating method such as spray coating, spin coating, dip coating, curtain coating, and extrusion coating. Since the liquid crystal of the present invention has properties remarkably different depending on the structure of the side chain, the solvent and concentration to be used cannot be particularly limited, but in view of the uniformity of the thin film, it is preferable to use a solvent having a high solubility, such as methylene chloride. , Halogen compounds such as chloroform, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, amides such as dimethylacetamide, dimethylformamide, N-methyl-pyrrolidone and isopropanol,
Alcohols such as perfluoropropanol are preferably used. In particular, in the liquid crystal of the present invention, it was often observed that the optical axes tended to be aligned in the application direction at this coating stage.

Therefore, in the present invention, the liquid crystal thin film is formed on a suitable support in a state where at least one interface is in contact with the gas phase, that is, by a general coating method, and after drying, the temperature is within the liquid crystal phase forming temperature range. Heat treatment at a temperature for a certain period of time while forming a discotic nematic phase or a uniaxial columnar phase,
Then, by cooling, it is possible to obtain an optical compensation sheet in which the optical axis is tilted by 5 to 50 degrees from the direction normal to the sheet surface. The resulting liquid crystal thin film is a monodomain thin film, one surface of which is in contact with the support, while the other surface is in contact with the gas phase (atmosphere).

Hereinafter, the operation of the optical compensation sheet of the present invention will be described with reference to the drawings, taking a TN type liquid crystal display element as an example. 1 and 2 show polarization states of light propagating in a liquid crystal cell when a sufficient voltage equal to or higher than a threshold voltage is applied to the liquid crystal cell. Since the light transmittance characteristics at the time of applying a voltage greatly contribute to the viewing angle characteristics of the contrast,
A description will be given of an example in which a voltage is applied. FIG. 1 is a diagram showing a polarization state when light is vertically incident on a liquid crystal cell. When the natural light L0 is perpendicularly incident on the polarizing plate A having the polarizing axis PA, the light transmitted through the polarizing plate PA becomes linearly polarized light L1.

When the arrangement state of liquid crystal molecules when a sufficient voltage is applied to the TN type liquid crystal cell is schematically shown by one liquid crystal molecule as a model, it becomes LC in the schematic diagram. 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 the plane perpendicular to the light path), and therefore the light propagates in 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 it is even if it passes through the liquid crystal cell. When the polarization axis PB of the polarizing plate B is set to be perpendicular to the polarization axis PA of the polarizing plate A, the liquid crystal cell and 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
Is almost linearly polarized (in the actual case, it becomes elliptically polarized due to the characteristics of the polarizing plate). In this case, the refractive index anisotropy of the liquid crystal causes a difference in the refractive index on the incident surface of the liquid crystal cell, and the light L2 transmitted through the liquid crystal cell is elliptically polarized light and is not completely blocked by the polarizing plate B. As described above, in the case of oblique incidence, blocking of light in a dark state becomes insufficient, resulting in a large 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 element 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 element RF is a birefringent body that polarizes 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 to the liquid crystal display element having such a configuration and transmitted through the liquid crystal cell as in the case of FIG. Thus, a favorable liquid crystal display element having no viewing angle dependence and having the same transmittance even at various oblique incidences can be realized.

It is presumed as follows that the viewing angle of the liquid crystal display device can be greatly improved by the present invention. Most TN-LCDs adopt a normally white mode. In this mode, the transmittance of light from the black display portion remarkably increases as the viewing angle increases, resulting in a sharp decrease in contrast. 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 direction normal to the surface of the cell. Further, in the case of intermediate gradation, it is considered that the optical axis thereof is further inclined from the normal line 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, compensation is expected to be insufficient with an optically anisotropic body whose optical axis is in the direction of the normal. If the liquid crystal cell can be regarded as a positive uniaxial optical anisotropic body, a negative uniaxial optical anisotropic body is preferable for compensating 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 a relation 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 a characteristic that the refractive index in the optical axis direction is the smallest. However, it is not necessary that the values of nβ and nγ be exactly equal, and it is sufficient if they are almost 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.

Synthesis Example 1 Synthesis of Liquid Crystal Compound TP-1 1-a) Synthesis of 2,3,6,7,10,11-hexamethoxytriphenylene (a) In a two-liter ice-cooled three-necked flask, 135m ice water
l, and with vigorous stirring with a mechanical stirrer,
490 ml of concentrated sulfuric acid was gradually added. Next, at room temperature,
50 g of ferric chloride were added and after 1 hour, a further 1,2
30 g of dimethoxybenzene were added. After 3 hours, the mixture was cooled with ice, 1 liter of ice water was gradually added, and after 1 hour, the reaction mixture was filtered through a glass filter to obtain crude crystals 1 of the desired product.
3 g (43%) were obtained.

1-b) 2,3,6,7,10,11-
Synthesis of hexahydroxytriphenylene (b) 10.3 g of a was suspended in 50 ml of dichloromethane, and 15.5 ml of boron tribromide was gradually added. Two hours later, the mixture was poured into 500 ml of ice water, extracted with 2.5 liters of ethyl acetate, dried over anhydrous sodium sulfate, and filtered through celite. After the solvent was concentrated under reduced pressure, the residue was recrystallized from a mixed solvent of acetonitrile and dichloromethane to obtain 7.50 g (92%) of the desired product.

1-c) Synthesis of 4-heptyloxybenzoic acid (c) In a 1-liter three-necked flask, 35.0 g of ethyl 4-hydroxybenzoate, 54.6 g of heptyl bromide, 150 g of potassium carbonate and 100 ml of acetonitrile It was placed,
The mixture was stirred vigorously with a mechanical stirrer for 6 hours while heating and refluxing on a hot water bath. After cooling, the reaction mixture was filtered through celite, and the residue was washed with 300 ml of ethyl acetate. After concentration under reduced pressure,
It was redissolved in 200 ml of ethanol, and 40 ml of an aqueous solution in which 15.0 g of potassium hydroxide was dissolved was gradually added dropwise.
The mixture was heated and stirred at 80 ° C. for 1 hour. After cooling, the precipitated crystals were filtered under reduced pressure, and the residue was washed with 100 ml of ethanol.
The mixture was stirred in 300 ml of diluted hydrochloric acid at 40 ° C. for 1 hour, filtered under reduced pressure and dried to obtain 40.0 g (80%) of the desired product.

1-d) 2,3,6,7,10,11-
Synthesis of hexa (4-heptyloxybenzoyloxy) triphenylene (TP-1) 8.34 g of c and 10 ml of thionyl chloride were placed in a 200 ml flask, and heated under reflux for 2 hours. While heating, excess thionyl chloride was distilled off under reduced pressure. After cooling,
0.70 g of b and 20 ml of pyridine were added, and the mixture was stirred with heating under reflux for 20 hours. After cooling, excess pyridine was distilled off under reduced pressure, and the desired product was purified and isolated by silica gel column chromatography. Yield 3.05 g (75%)

NMR (measurement solvent CDCl ₃ ) δ 0.92 (18H, t) δ 1.35 (48H, m) δ 1.78 (12H, m) δ 3.90 (12H, t) δ 6.65 (12H, d) δ 7.90 (12H, d) δ 8.37 (6H, s) Phase transition temperature measurement by DSC and polarizing microscope observation Crystalline phase-169 ° C-Discotic nematic phase-
257 ° C-isotropic liquid phase

Synthesis Example 2: Synthesis of liquid crystal compound TP-2 1-e) Synthesis of 4-heptyloxycinnamic acid (e) 15.5 g of 4-hydroxycinnamic acid, heptyl bromide 30.
0 g and 50.0 g of potassium carbonate were suspended in 50 ml of dimethyl sulfoxide, and heated on a hot water bath for 10 hours while vigorously stirring with a mechanical stirrer. After cooling, the mixture was filtered through celite, and the residue was washed with 300 ml of ethyl acetate. 500 ml of water was added thereto, and after extraction, the organic layer was concentrated under reduced pressure. 100 ml of ethanol was added thereto, and 20 ml of an aqueous solution containing 10 g of potassium hydroxide was added.
Stirred for hours. After cooling, the precipitated crystals were filtered under reduced pressure, and the residue was washed with 100 ml of ethanol. The mixture was stirred in 300 ml of dilute hydrochloric acid at 40 ° C. for 1 hour, filtered under reduced pressure and dried to obtain 19.1 g (78%) of the desired product.

1-f) 2,3,6,7,10,11-
Synthesis of hexa (4-heptyloxycinnamoyloxy) triphenylene (TP-2) 10.4 g of e and 10 ml of thionyl chloride were placed in a 200 ml flask and heated under reflux for 2 hours. While heating, excess thionyl chloride was distilled off under reduced pressure. After cooling,
0.70 g of b and 20 ml of pyridine were added, and the mixture was stirred with heating under reflux for 20 hours. After cooling, excess pyridine was distilled off under reduced pressure, and the target product was purified by silica gel column chromatography, and then recrystallized with a mixed solvent of acetonitrile and acetone. Yield 3.55 g (90%)

NMR (measurement solvent CDCl ₃ ) δ 0.92 (18H, t) δ 1.35 (48H, m) δ 1.78 (12H, m) δ 3.90 (12H, t) δ 6.50 (6H, d) δ 6.65 (12H, d) δ 7.25 (12H, d) δ 7.83 (6H, d) δ 8.20 (6H, s) Phase transition temperature measurement by DSC and polarizing microscope observation Crystal phase -155 ° C-discotic Nematic phase-
252 ° C-isotropic liquid phase

[0060]

【Example】

(Preparation of Optical Compensation Sheet) A 10% dichloromethane solution of TP-2 was applied and dried on a SiO oblique deposition film having a tilt angle of 45 ° and a film thickness of about 400 Å formed on a glass substrate. In this state, the film was cloudy.
After heating at 0 ° C. for 10 minutes and cooling to room temperature, a colorless and transparent film was formed. When observed with a polarizing microscope,
No disclination line indicating the disorder of the molecular orientation in the film was observed, indicating that an optically monodomain homogeneous film was formed.

(Performance evaluation) For the measurement, the Shimadzu ellipsometer (AEP-100) was used in the transmission mode to obtain the angle dependence of the retardation, and the optimum triaxial refractive index and the optical axis direction were calculated from the values. Sought by. The product of the difference in refractive index between extraordinary light and ordinary light of the crystal and the gap size of the liquid crystal cell is 480 nm, and the optical compensation sheet prepared above is attached to the TN type liquid crystal cell with a twist angle of 90 degrees, The angle dependence of the contrast in a 0 to 5 V 30 Hz rectangular wave was measured by LCD-5000 manufactured by Otsuka Electronics Co., Ltd. The position of contrast 10 was defined as the viewing angle, and the viewing angles in the vertical and horizontal directions were obtained. Et al is, the LCD
After being left for 500 hours at 50 ° C., vertical viewing angle characteristics were measured. The results are shown in the table below. The directions of the polarization axis of the polarizing plate of the TN liquid crystal cell, the rubbing axis of the liquid crystal cell, and the optical axis of the optical compensation sheet in this measurement are shown in FIG.

Optical Compensation Sheet Viewing Angle Characteristics (0 hr) Viewing Angle Characteristics (500 hr) Up-Down Right-Left Up-Down Yes 46-48 52-55 43-47 No 23-27 33-36 23-27

As is apparent from the above figure, in the LCD provided with the optical compensation sheet of the present invention, a remarkable improvement in the viewing angle characteristics has been achieved. In addition, the long-term storage stability is very excellent.

[0064]

According to the present invention, the viewing angle characteristic of the TN type liquid crystal display device is improved, and a high quality display device having excellent visibility can be provided, and a high quality image can be stably provided for a long period of time. You can do it. Further, the present invention relates to a TFT or MIN.
It goes without saying that excellent effects can be obtained even when applied to an active matrix liquid crystal display device using three terminals and two terminals.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a conventional TN-type liquid crystal display device and a diagram illustrating a light transmission state when light is vertically incident on a display surface.

FIG. 2 is a diagram illustrating a configuration of a conventional TN-type liquid crystal display device and a diagram illustrating a light transmission state when light is obliquely incident on a display surface.

FIG. 3 is a diagram for explaining an embodiment of the configuration of the liquid crystal display element of the present invention.

FIG. 4 is a diagram showing an optical axis direction of a liquid crystal display element used in this example.

[Explanation of symbols]

A, B: Polarizing plate PA, PB: Polarizing axis LCS: TN type liquid crystal cell RF: Optically anisotropic element LO: Incident light L1: Linearly polarized light passing through polarizing plate A L2: Polarized light passing through TN type liquid crystal cell ( LC: Model representation of liquid crystal in TN liquid crystal cell θ: Incident angle of linearly polarized light

Claims (5)

[Claims] 1. A sheet having at least one monodomain thin film of a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystalline compound or a mixture thereof, and at least one of the monodomain thin films. An optical compensation sheet, wherein one surface of the sheet is in contact with the gas phase, and the optical axis of the sheet is tilted by 5 to 50 degrees from the direction normal to the sheet surface. 2. The optical compensation sheet according to claim 1, wherein the monodomain thin film is formed on the surface of an alignment film provided on a support. 3. The optical compensation sheet according to claim 1, wherein the discotic liquid crystalline compound has a triphenylene carbon skeleton in its partial structure. 4. The optical compensation sheet according to claim 1, wherein the discotic liquid crystalline compound is represented by the following general formula (I). Embedded image However, R is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkanoyl group, a substituted alkenoyl group, a substituted alkinoyl group,
Represents a substituted or unsubstituted aryloyl group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted carbamoyl group or a substituted sulfamoyl group, and each R may be the same or different. Good. 5. R in the general formula (I) is represented by the following general formula (I
Z ² of I), Z ³ of formula (III), general formula Z ⁴ of (IV), Z ⁶ of Z ^5, of the general formula (V) (VI), Z 7 of the general formula (VII) The optical compensation sheet according to claim 4, which is represented by Z ^{8 in} formula (VIII) or Z ⁹ in formula (IX). Formula ^{(II) Z 2 = -CO-} CR 21 = CR 22 -C 6 H 5-n -R 23 n However, R ²¹ and R ²² are each a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl group R ²³ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryl. The n groups represented by R ²³ , which represent an oxy group, may be the same or different from each other, and n represents an integer of 0 to 5. Formula ^{(III) Z 3 = -CO- (} CR 31 R 32) m - (Y) p -C 6 H 5-n -R 33 n However, R ³¹ and R ³² each represent a hydrogen atom, a halogen atom or a substituted Alternatively, it represents an unsubstituted alkyl group, Y represents an oxygen atom or a sulfur atom, R ³³ represents a halogen atom,
A cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, R ³³
The n groups represented by may be the same or different from each other, m represents an integer of 1 to 4, and p represents 0 or 1
And n represents an integer of 0-5. Formula ^{(IV) Z 4 = - (} CR 41 R 42) m - (CR 44 = CR 45) p -C 6 H 5-n -R 43 n ^{However, R 41, R 42, R} 44 and R ⁴⁵ are Each represents a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl group, R ⁴³ represents a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group , A substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, the n groups represented by R ⁴³ may be the same or different, and m represents an integer of 1 to 5, p Represents 0, 1 or 2, and n is 0
Represents an integer of up to 5. Formula ^{(V) Z 5 = - (} CR 51 R 52) m -CO-C 6 H 5-n -R 53 n However, R ⁵¹ and R ⁵² each represent a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl It represents a group, R ⁵³ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted And n groups represented by R ⁵³ may be the same as or different from each other, m represents an integer of 1 to 4, and n represents an integer of 0 to 5. Formula ^{(VI) Z 6 = -CO-} C 6 H 11-n -R 63 n However, R ⁶³ is a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl A group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and n represented by R ⁶³
The groups may be the same or different from each other, and n
Represents an integer of 0 to 11. Formula ^{(VII) Z 7 = -CO-} C 6 H 5-n -R 7 n where, R ⁷ is a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted Alternatively, it represents an unsubstituted aryl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, the n groups represented by R ⁷ may be the same or different, and n is 0 to 0. Represents an integer of 5. Formula ^{(VIII) Z 8 = -CO-} R 8 where, R ⁸ is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group or a substituted or unsubstituted heterocyclic Represents a residue. Formula (IX) Z ⁹ = -R ⁹ where, R ⁹ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group.