JPH07146409A - Optical compensation sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an optical compensation sheet which can be used for a liquid crystal display element for improving visual characteristics of display contrast and display color. CONSTITUTION:An optical compensation sheet has a mono-domain film containing discotheque liquid crystal compound capable of forming a discotheque nematic phase or a uniaxial polar phase, or a thin film of the discotheque nematic phase or uniaxial polar phase formed of the discotheque liquid crystal compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical compensatory sheet capable of improving the viewing angle characteristics of display contrast and display color when used in a liquid crystal display device, and a method for producing the same.
In particular, the present invention relates to an optical compensation sheet having excellent production suitability and durability, and a method for producing the same.

[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,
It has been converted to a liquid crystal display device having the great advantages of thinness, light weight, and low power consumption. Most of the liquid crystal display elements (hereinafter, referred to as LCDs) that are currently popular use twisted nematic liquid crystals. The display method using such a liquid crystal can be roughly classified into a birefringence mode and an optical rotation mode.

An LCD using the birefringence mode has a twisted angle of 90 ° or more in the alignment of liquid crystal molecules and has steep electro-optical characteristics, so that it has a simple matrix without active elements (thin film transistors or diodes). A large-capacity display can be obtained by the time-divisional behavior with the electrode structure in the shape of a circle. But,
The response speed is slow (hundreds of milliseconds), and gradation display is difficult, and a liquid crystal display element (TFT-
It does not exceed the display performance of LCD and MIM-LCD.

For the TFT-LCD and MIM-LCD, a display system (TN type liquid crystal display element) of optical rotation mode in which the alignment state of liquid crystal molecules is twisted by 90 ° is used. This display method is the most effective method compared with other LCDs because it has a high response speed (several tens of milliseconds), can easily obtain a monochrome display, and has a high display contrast. However, since the twisted nematic liquid crystal is used, there is a problem in the viewing angle characteristics that the display color and the display contrast are changed depending on the viewing direction, due to the principle of the display system.
The display performance of will not be exceeded.

Japanese Unexamined Patent Publication Nos. 4-229828 and 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 publication has a retardation of almost zero in the direction perpendicular to the liquid crystal cell, does not exert any optical action from the front, and when tilted. The phase difference is generated in the liquid crystal cell and the phase difference generated in the liquid crystal cell is compensated. However, even with these methods, the viewing angle of LCD is still insufficient, and further improvement is desired. Especially for car and CR
When considered as an alternative to T, it is the current situation that the current viewing angle is not sufficient at all. In addition, Japanese Patent Laid-Open No. 4-366
No. 808 and JP-A-4-366809, a liquid crystal cell containing a chiral nematic liquid crystal having an inclined optical axis is used as a retardation film to improve the viewing angle.
It is a layered 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 optical axis inclined with respect to a liquid crystal cell. A uniaxial polycarbonate is sliced obliquely and used. 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 describes a method of using a photoisomerizable substance and a retardation film having an inclined optical axis. According to this method, a liquid crystal display device having a wide viewing angle characteristic, a light weight, and a low cost can be realized. However, the drawback of this method is that the retardation film is not sufficiently stable against heat and light.

[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, and thirdly, to provide a method for producing an optical compensation sheet, which can inexpensively and easily produce a large-area homogeneous thin film.

[0010]

The above-mentioned problems are characterized by (1) having at least one monodomain thin film containing a discotic liquid crystalline compound capable of forming at least a discotic nematic phase or a uniaxial columnar phase. And an optical compensation sheet. (2) An optical compensation sheet having at least one thin film of a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystalline compound or a mixture thereof. (3) An optical compensation sheet comprising at least one monodomain thin film having a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystal compound or a mixture thereof.
(4) The optical compensation sheet as described in any of (1) to (3) above, wherein the discotic liquid crystalline compound has a triphenylene carbon skeleton in a partial structure.

(5) The optical compensatory sheet according to any one of (1) to (3) above, wherein the discotic liquid crystalline compound is represented by the following general formula (I).

[0012]

[Chemical 2]

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 A substituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group and a substituted carbamoyl group, a substituted sulfamoyl group, and R
May be the same as or different from each other. (6) The substituents R in the general formula (I) representing the liquid crystal compound described in the above (5) may be the same or different from each other, and further, the substituents in the following general formulas (II) to (IX) Group Z ₂
The optical compensation sheet according to (5), characterized by being represented by any one of to Z ₉

General 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, a substituted or unsubstituted Represents an alkyl group, R ²³ 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, a substituted or unsubstituted It represents an unsubstituted aryloxy group, and the n substituents may be the same or different from each other.
n represents an integer of 0 or 1 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, R ³² is a hydrogen atom, a halogen atom Represents 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 It represents an unsubstituted aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group, and the n substituents may be the same or different from each other. m represents an integer of 1 to 4, p represents 0 or 1, and n represents 0 or an integer of 1 to 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 , R ⁴⁵ represents a hydrogen atom, a halogen atom, 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 aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, The n substituents may be the same or different. m represents an integer of 1 to 5, p represents 0, 1 or 2, and n represents 0 or an integer of 1 to 5.

General formula (V) Z ⁵ =-(CR ⁵¹ R ⁵² ) _m —CO—C ₆ H _5-n —R ⁵³ _n where R ⁵¹ and R ⁵² are hydrogen atom, halogen atom, substituted or unsubstituted R ⁵³ 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,
Represents a substituted or unsubstituted aryloxy group, the n of which
The individual substituents may be the same or different from each other. m represents an integer of 1 to 4, n represents 0 or an integer of 1 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 A substituted cycloalkyl group, a substituted or unsubstituted aryl group,
It represents a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and the n substituents thereof may be the same or different from each other. n is 0 or 1 to 1
Represents an integer of 1.

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 It represents an alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group, and the n substituents may be the same or different from each other. n represents 0 or an integer of 1 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, 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. (7) Maintaining the liquid crystal phase, characterized in that at least one interface is heat-treated with the liquid crystalline compound according to any one of claims 1 to 3 in a state of being in contact with a gas phase to form a discotic nematic phase and then cooled. The method for producing an optical compensation sheet according to any one of (2) to (3) above. Achieved by

The present invention will be described in detail below. The discotic liquid crystal phase is a general term for liquid crystal phases formed by discotic molecules, and the details are described in a research report by C. Destrade et al. [Mol.
Cryst.Liq.Cryst. 71, 111 (1981)], the columnar phase in which the central cores of discotic molecules are piled up in a column by intermolecular force.
It is known that it 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 discotic nematic phases used in the present invention are rarely found.

The fact that the triphenylene discotic liquid crystal of the present invention has a negative birefringence is reported by B. Mourey et al. [Mol. Cryst. Liq. Cryst., Vol. 84, p. 193 (19).
1982)], in order to apply this property as an optical compensation sheet, it is necessary to statistically arrange all the molecules constituting the thin film 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 the discotic nematic liquid crystal phase or the liquid crystal forming a uniaxial columnar phase, especially the triphenylene system represented by the following general formula (I) It has been found that a thin film of a compound having a carbon skeleton structure has favorable properties 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 preferentially formed was likely to be in a monodomain state, and high light transmittance and high contrast were easily obtained. Although it is sufficiently possible to use it as an optical compensation 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. Came to complete.

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 above general formula (I).

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

Also used in the present invention are 2, 3, 6, 7,
The 10,11-substituted triphenylene compound is available from Macromo
l. Chem. Rapid Communication., Vol. 4, p. 812 (1
983) and is obtained as a 6-methoxy substitution product by an oxidative trimerization reaction of 1,2-dimethoxybenzene. Also, the synthesis method described in Advanced Materials. Volume 2, page 40 (1990) can be used.

Specific examples of the triphenylene compound and its side chain used in the present invention are shown below, but the present invention is not limited to these compounds.

[0029]

[Chemical 3]

[0030]

[Chemical 4]

[0031]

[Chemical 5]

[0032]

[Chemical 6]

[0033]

[Chemical 7]

[0034]

[Chemical 8]

[0035]

[Chemical 9]

[0036]

[Chemical 10]

[0037]

[Chemical 11]

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 provided on the support. At least one developed liquid crystal layer is provided, and a protective 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 crystal 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 support material should have a good light transmittance and, in addition, be nearly optically isotropic. Therefore,
A support formed of a material having a small intrinsic birefringence value sold under the trade name of glass, ZEONEX (Nippon Zeon), ARTON (Nippon 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. Is also preferably used.

Examples of the material for the protective film include polymethylmethacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene.
Vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc. Polymeric substances; and organic substances such as silane coupling agents may be mentioned. In addition, Langmuir-Blodgett method (LB-method such as ω-tricosanoic acid, dioctadecyldimethylammonium chloride and methyl stearate)
A cumulative film formed by the method) can also be used.

It is a well-known fact in the case of rod-shaped liquid crystals that when a protective film is previously provided on a support, the protective film often has a great influence on the molecular orientation when the liquid crystal layer is formed. 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. .

The liquid crystal layer constituting the optical compensatory sheet of the present invention is most commonly used in the manufacturing process of a liquid crystal display in a liquid crystal formation temperature range, in which a capillary phenomenon is generated in a gap between two supports. Although a method of introducing liquid crystal by utilizing the above can be applied, one of the features of the present invention is that a general coating method can be applied. That is, vapor deposition method, spray coating, spin coating, dip coating, curtain coating,
By a coating method such as extrusion coating, a liquid crystal thin film can be formed on the support through a drying step. 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, isopropanol and perfluoropropanol. Alcohols are preferably used. Particularly, in the liquid crystal of the present invention, at the stage of coating,
It was often observed that the optical axes tended to align in the direction of application.

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 column layer forming temperature range. An optical compensation sheet having desired optical characteristics can be obtained by heat-treating at a temperature for a certain period of time while forming a discotic nematic phase or a uniaxial columnar phase, and then cooling.

The operation of the optical compensation sheet of the present invention will be described below with reference to the drawings using a TN type liquid crystal display device 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 transmittance characteristic of light particularly when a voltage is applied greatly contributes to the viewing angle characteristic of contrast,
Description will be made by taking a voltage application as an example. 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 vertically incident on the polarizing plate A having the polarization axis PA, the light transmitted through the polarizing plate PA becomes the linearly polarized light L1.

When a sufficient voltage is applied to the TN type liquid crystal cell, the alignment state of the liquid crystal molecules is schematically shown as a model with one liquid crystal molecule, which is represented by 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 obliquely enters the liquid crystal cell. Natural light of incident light L
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 is intended to prevent such a decrease in contrast due to oblique incidence and improve viewing angle characteristics. FIG. 3 shows an example of the configuration according to the present invention. An optical anisotropic element RF having an optical axis inclined from the normal direction of the liquid crystal cell is arranged between the polarizing plate B and the liquid crystal cell.
The optically anisotropic element RF is a birefringent body that polarizes 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 that is obliquely incident on the liquid crystal display element having such a structure and is transmitted through the liquid crystal cell is also elliptically polarized light due to the phase delay action when transmitting the optically anisotropic element RF. It was possible to realize a good liquid crystal display device which is modulated into a linearly polarized light and has the same transmittance even at various oblique incidences and has no viewing angle dependence.

It is presumed as follows that the viewing angle of the liquid crystal display device was significantly 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 tilted from the direction of the normal line to the surface of the liquid crystal cell, it is expected that the optical anisotropic body having the optical axis in the normal direction will be insufficiently compensated. 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 these reasons, it is presumed that the negative uniaxial optical anisotropic body in which the optical axis is tilted from the normal direction in the present invention significantly improves the viewing angle characteristics.

Negative uniaxiality in the present invention means a relationship of nα <nβ = nγ, where nα, nβ, and nγ are the refractive indices of the sheet having optical anisotropy in the triaxial directions in ascending order. I 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. In addition, TFT, T
As a condition for significantly improving the viewing angle characteristics of the N-type liquid crystal cell, the optical axis is preferably inclined by 5 to 50 degrees from the normal line direction of the sheet surface, more preferably 10 to 40 degrees, and more preferably 10 degrees. Most preferred is -30 degrees. Further, 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 2-liter three-neck flask cooled with ice, Ice water 135m
l, stir vigorously with a mechanical stirrer,
490 ml of concentrated sulfuric acid was gradually added. Next, at room temperature, 1
Add 50 g of ferric chloride and after 1 hour, add 1,2 more
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 1
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. After 2 hours, it 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 vigorously stirred for 6 hours with a mechanical stirrer while heating under reflux 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,
Redissolve in 200 ml of ethanol and gradually add 40 ml of an aqueous solution containing 15.0 g of potassium hydroxide,
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.
This was stirred in 300 ml of dilute 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. In a heated state, 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 and isolated by silica gel column chromatography. Yield 3.05g (75%)

NMR (measurement solvent CDCl ₃ ) δ0.92 (18H, t) δ1.35 (48H, m) δ1.78 (12H, m) δ3.90 (12H, t) δ6.65 (12H, d) δ7.90 (12H, d) δ8.37 (6H, s) Phase transition temperature measurement by DSC and polarization microscope observation Crystal 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) 4-hydroxycinnamic acid 15.5 g, heptyl bromide 30.
0 g and 50.0 g of potassium carbonate were suspended in 50 ml of dimethyl sulfoxide, and the mixture was heated on a 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 to this, and after extraction, the organic layer was concentrated under reduced pressure. To this, 100 ml of ethanol was added, and 20 ml of an aqueous solution containing 10 g of potassium hydroxide was added.
Stir for hours. After cooling, the precipitated crystals were filtered under reduced pressure, and the residue was washed with 100 ml of ethanol. This 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-1) 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. In a heated state, 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, the excess pyridine was distilled off under reduced pressure, the target product was purified by silica gel column chromatography, and recrystallized with a mixed solvent of acetonitrile and acetone. Yield 3.55g (90%)

NMR (solvent CDCl ₃ ) δ0.92 (18H, t) δ1.35 (48H, m) δ1.78 (12H, m) δ3.90 (12H, t) δ6.50 (6H, d) δ6.65 (12H, d) δ7.25 (12H, d) δ7.83 (6H, d) δ8.20 (6H, s) Phase transition temperature measurement by DSC and polarization 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 an inclination angle of 45 ° and a film thickness of about 400 Å formed on a glass substrate. In this state, the film was cloudy, but 22
After heating at 0 ° C. for 10 minutes and then cooling to room temperature, a colorless transparent film was formed. When observed with a polarizing microscope,
No disclination line, which indicates disorder of molecular orientation in the film, was observed, and it was found that the film formed an optically homogeneous domain.

(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 direction of the construction phrase were calculated from the values. Sought by. The product of the difference in refractive index between extraordinary light and ordinary light of liquid crystal and the gap size of the liquid crystal cell is 480 nm, and the optical compensation sheet prepared in Example 2 is attached to the TN type liquid crystal cell having a twist angle of 90 degrees. On the other hand, 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. The position of contrast 10 was defined as the viewing angle, and the viewing angles in the vertical and horizontal directions were obtained. In addition, this LCD
After standing at 500 ° C. for 50 hours, the vertical viewing angle characteristics were measured. The results are shown in the table below. The polarization axis of the polarizing plate of the TN liquid crystal cell, the rubbing axis of the liquid crystal cell, and the vertical direction 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) Top-Bottom Right-Left Top-Bottom Yes 46-48 52-55 43-47 None 23-27 33-36 23-27

As is clear from the above figure, in the LCD provided with the optical compensation sheet of the present invention, the viewing angle characteristics are remarkably improved. Moreover, the long-term storage stability is also very excellent.

[0064]

According to the present invention, the viewing angle characteristics of the TN type liquid crystal display device are improved, and a high-quality display device having excellent visibility can be provided, and a high-quality image is stably provided for a long period of time. You can also do it. In addition, the present invention can be applied to TFT and 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 drawings]

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

FIG. 2 is a diagram illustrating a configuration of a conventional TN type liquid crystal display element and a light transmission state when light obliquely enters a display surface.

FIG. 3 is a diagram illustrating an example of a configuration of a 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 plates PA, PB: Polarizing axes LCS: TN type liquid crystal cell RF: Optical anisotropic element LO: Incident light L1: Linearly polarized light passing through the polarizing plate A L2: Polarized light passing through the TN type liquid crystal cell ( Mainly elliptically polarized light) LC: Model representation of liquid crystal in TN liquid crystal cell θ: Incident angle of linearly polarized light

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // C08J 5/18 CEZ 9267-4F

Claims (7)

[Claims] 1. An optical compensation sheet comprising at least one monodomain thin film containing a discotic liquid crystalline compound capable of forming at least a discotic nematic phase or a uniaxial columnar phase. 2. An optical compensation sheet comprising at least one thin film of a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystal compound or a mixture thereof. 3. An optical compensation sheet comprising at least one monodomain thin film having a discotic nematic phase or a uniaxial columnar phase formed of a discotic liquid crystal compound or a mixture thereof. 4. The optical compensation sheet according to claim 1, wherein the discotic liquid crystalline compound has a triphenylene carbon skeleton in its partial structure. 5. The optical compensation sheet according to claim 1, wherein the discotic liquid crystal compound is represented by the following general formula (I). [Chemical 1] 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,
A substituted or unsubstituted aryloyl group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group and a substituted carbamoyl group, a substituted sulfamoyl group, and each R may be the same or different. Good. 6. The substituents R in the general formula (I), which represent the liquid crystal compound described in claim 5, may be the same or different from each other, and further have the following general formulas (II) to (IX). The optical compensation sheet according to claim 5, which is represented by any one of the substituents Z ^{2 to} Z ^9. General formula (II) Z ² = -CO-CR ²¹ = CR ²² -C ₆ H _{5- n} —R ²³ _n where R ²¹ and R ²² each represent a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group, and R ²³ represents a halogen atom, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted It represents an 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 substituents may be the same or different from each other.
n represents 0 or an integer of 1 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, R ³² is a hydrogen atom, a halogen atom, a substituted or 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 It represents an aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group, and the n substituents thereof may be the same or different from each other. m represents an integer of 1 to 4, p represents 0 or 1, and n represents 0 or an integer of 1 to 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, R 45 is Represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, and R ⁵³ 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, a substituted or unsubstituted aryloxy group, The n substituents may be the same or different. m represents an integer of 1 to 5, p represents 0, 1 or 2, and n represents 0 or an integer of 1 to 5. Formula ^{(V) Z 5 = - (} CR 51 R 52) m -CO-C 6 H 5-n -R 53 n However, R ^51, R ⁵² is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group the stands, 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,
Represents a substituted or unsubstituted aryloxy group, the n of which
The individual substituents may be the same or different from each other. m represents an integer of 1 to 4, n represents 0 or an integer of 1 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 An alkyl group, a substituted or unsubstituted aryl group,
It represents a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryloxy group, and the n substituents thereof may be the same or different from each other. n is 0 or 1 to 1
Represents an integer of 1. 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, It represents a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group, and the n substituents may be the same or different from each other. n represents 0 or an integer of 1 to 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, 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, a substituted or unsubstituted alkynyl group. 7. The liquid crystalline compound according to claim 1, wherein at least one surface is in contact with a gas phase, the liquid crystalline compound according to claim 1 is heat-treated to form a discotic nematic phase or a uniaxial columnar phase, and then cooled. The method for producing an optical compensation sheet according to claim 2, wherein the liquid crystal phase is maintained.