JPH10186356A - Optical compensation film for liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to sufficiently obtain an effect of expanding a visual field angle with simple production stages, by adopting the constitution to immobilize the nematic hybrid orientation formed in the liquid crystal state of a liquid crystalline polymer. SOLUTION: This film is substantially formed of the liquid crystalline polymer, which exhibits optical positive uniaxiality and the nematic hybrid orientation formed in the liquid crystal state of the liquid crystalline polymer is immobilized. In such a case, the usable liquid crystalline polymer, which exhibits optically the positive uniaxiality is indispensably required to form the nematic hybrid orientation as a liquid crystal phase and to allow the immobilization thereof in the glassy state without impairing the orientation state. The usable liquid crystalline polymer may be synthesized by a polymn. method known in this field. If an example of polyester synthesis is taken, the liquid crystalline polymer can be synthesized by a melt polymn. method or an acid chloride method using the acid chloride of the corresponding dicarboxylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compensation film for a liquid crystal display device in which the orientation of an optically positive uniaxial liquid crystalline polymer is fixed, and a twisted nematic liquid crystal display device incorporating the film. .

[0002]

2. Description of the Related Art An active drive twisted nematic liquid crystal display device (hereinafter abbreviated as a TN-LCD) using a TET element or an MIM element or the like has a thin, lightweight and low power consumption inherent to LCDs. Since it has an image quality comparable to that of a CRT when viewed from the front, it is widely used as a display device for notebook computers, portable televisions, portable information terminals, and the like. However, in the conventional TN-LCD, the problem of the viewing angle that the display color changes or the display contrast decreases when viewed obliquely due to the refractive index anisotropy of the liquid crystal molecules is essentially unavoidable. There is a strong demand for improvement, and various attempts have been made for improvement. A method of dividing one pixel and changing the applied voltage to each pixel at a fixed ratio (halftone gray scale method), and a method of dividing one pixel and changing the rising direction of liquid crystal molecules in each pixel ( Domain splitting method), a method of applying a horizontal electric field to the liquid crystal (IPS method), a method of driving a vertically aligned liquid crystal (VA liquid crystal method), or a method of combining a bend alignment cell and an optical compensator (OCB method). It has been developed and prototyped. However, although these methods have a certain effect, it is necessary to change the alignment film, electrodes, liquid crystal alignment, etc., and it is necessary to establish a manufacturing technology and to newly install manufacturing equipment. Inviting.

On the other hand, there is a method of expanding the viewing angle by incorporating an optical compensation film into a conventional TN-LCD without changing the structure of the TN-LCD at all. This method uses TN-LC
The D production equipment does not require improvement or expansion, and is excellent in cost, and has the advantage of being easily used. The cause of the problem of the viewing angle in the normally white (NW) mode TN-LCD is the alignment state of the liquid crystal in the cell at the time of displaying black when a voltage is applied. In this case, the liquid crystal is substantially vertically aligned and optically positive uniaxial. Therefore, as an optical compensation film for widening the viewing angle, a proposal has been made to use a film having optically negative uniaxiality in order to compensate for positive uniaxiality during black display of a liquid crystal cell. Focusing on the fact that the liquid crystal in the cell has an orientation parallel or inclined to the cell interface near the interface of the alignment film even during black display, compensation is performed using a negative uniaxial film with an inclined optical axis. By doing so, a method of further enhancing the viewing angle expanding effect has been proposed.

[0004] For example, JP-A-4-349424, 6-25
No. 0166 discloses an optical compensation film using a cholesteric film having a helical axis inclined and an L-compensation film using the same.
A CD has been proposed. However, it is difficult to produce a cholesteric film with a helical axis inclined,
In fact, none of these patents describes a method for tilting the helical axis. Further, Japanese Patent Application Laid-Open No. H5-2495
47, 6-331979 proposes an LCD using a negative uniaxial compensator whose optical axis is inclined. As a specific embodiment, a multilayer thin film compensator is used. Further, Japanese Patent Application Laid-Open Nos. 7-146409 and 8-5837 have proposed an optical compensation film in which discotic liquid crystals are inclined and oriented, and an LCD using the same as a negative uniaxial compensation film with an inclined optical axis. However, the discotic liquid crystal has a complicated chemical structure and is complicated to synthesize. In addition, when a film is formed from a low-molecular liquid crystal, a complicated process such as photocrosslinking is required, and industrial production is difficult, resulting in an increase in cost.

As another form of the compensation film, an alignment film using a liquid crystal polymer having positive uniaxiality has been proposed. For example, Japanese Patent Application Laid-Open No. Hei 7-140326 proposes an LCD compensator comprising a liquid crystal polymer film having a twisted tilt orientation, which is used for expanding the viewing angle of the LCD. However, it is not industrially easy to simultaneously introduce a twist orientation in addition to the tilt orientation. Japanese Patent Application Laid-Open Nos. 7-198942 and 7-181324 describe, as a similar technique, a viewing angle compensator made of a film in which a nematic liquid crystalline polymer is oriented so that an optical axis intersects a plate surface, and an LCD using the same. Has been proposed. However, also in this case, since the compensating plate in which the optical axis is simply inclined is used, the viewing angle expanding effect cannot be said to be sufficient.

[0006]

In view of the problems of each of the above-mentioned technologies, the present inventors have focused on a positive uniaxial polymer liquid crystal in which the production of a liquid crystal compound as a raw material of a film and the production of the film itself are simple. did. Furthermore, the present invention has been completed as a result of resolving the disadvantages of the conventional optical compensation film composed of a polymer liquid crystal exhibiting positive uniaxiality and aiming for further improvement of the optical compensation performance.

[0007]

That is, the first aspect of the present invention is as follows.
Is formed substantially from a liquid crystal polymer having optically positive uniaxiality, and the liquid crystal polymer fixes a nematic hybrid alignment formed in a liquid crystal state, for a liquid crystal display element. It relates to an optical compensation film.
A second aspect of the present invention is a driving liquid crystal cell including a pair of transparent substrates having electrodes and a nematic liquid crystal, and a twisted nematic having at least an upper polarizing plate and a lower polarizing plate disposed above and below the substrate. Type liquid crystal display device, wherein the optical compensation for the liquid crystal display element according to the first aspect of the present invention is provided between the substrate and one of the upper and lower polarizers or between the substrate and the upper and lower polarizers. The present invention relates to a twisted nematic liquid crystal display device incorporating at least one film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The compensation film of the present invention greatly improves the viewing angle dependence of a TN-LCD. First, a TN-LCD to be compensated will be described. TN-L
When the CD is classified by the driving method, a simple matrix method and a TFT (Thin Film) using an active element as an electrode are used.
Transistor) electrode, MIM (Metal I)
nsulator Metal or TFD; Th
It can be subdivided as in an active matrix method using an (in Film Diode) electrode. The compensation film of the present invention is effective for any driving method.
The halftone gray scale method (pixel division method) and the domain division method, which are well-known techniques, were conceived in an attempt to expand the viewing angle of the LCD from the liquid crystal cell side. L in which such a viewing angle is improved to some extent
The compensating film of the present invention also works effectively on CDs, and can further enhance the viewing angle. TN- as described above
The compensating film of the present invention, which can provide an excellent viewing angle enlarging effect to an LCD, is a liquid crystal polymer having an optically positive uniaxial property, specifically, a liquid crystal polymer having an optically positive uniaxial property. A liquid crystal polymer composition having an optically positive uniaxial property containing a molecular compound or at least one liquid crystal polymer compound, wherein the liquid crystal polymer compound or the liquid crystal polymer composition is a liquid crystal polymer. It is formed by fixing the nematic hybrid alignment form formed in the state.

Here, the nematic hybrid orientation referred to in the present invention means that the liquid crystalline polymer is in a nematic orientation,
In this case, the angle between the director of the liquid crystalline polymer and the film plane is different between the upper surface and the lower surface of the film. Therefore, since the angle formed by the director and the film plane is different between the upper surface and the lower surface, it can be said that the angle continuously changes between the upper surface and the lower surface of the film. Since the compensation film of the present invention is a film in which the nematic hybrid alignment state of the positive uniaxial liquid crystalline polymer is fixed, the director of the liquid crystalline polymer is different in all places in the film thickness direction. Facing an angle. Therefore, when viewed as a film structure, the compensation film of the present invention no longer has an optical axis.

The optically positive uniaxial liquid crystalline polymer which can be used in the present invention has a nematic phase as a liquid crystal phase. Furthermore, at a temperature exceeding the liquid crystal transition point, it is essential that a nematic hybrid alignment can be formed on the alignment substrate and fixed in a glass state without impairing the alignment form. As the liquid crystalline polymer having the properties as described above, a homeotropic liquid crystal polymer, specifically, a homeotropic liquid crystal polymer compound or at least one type of homeotropic liquid crystal polymer A homeotropically-aligned liquid crystalline polymer composition containing a compound, at least one kind of homeotropically-aligned liquid crystalline polymer, and at least one kind of homogeneously-oriented liquid crystalline polymer. And a molecular composition. Hereinafter, description will be made in order.

First, the liquid crystal polymer having homeotropic alignment will be described. The homeotropic alignment refers to an alignment state in which the director is substantially perpendicular to the substrate plane. This homeotropic alignment liquid crystalline polymer is an essential component for realizing the nematic hybrid alignment of the present invention. The determination as to whether the liquid crystalline polymer has homeotropic alignment is performed by forming a liquid crystalline polymer layer on a substrate and determining the alignment state. The substrate that can be used for this determination is not particularly limited, but examples thereof include a glass substrate (specifically, an optical glass such as soda glass, potash glass, borosilicate glass, crown glass, and flint glass), A plastic film or sheet that has heat resistance at the liquid crystal temperature of the molecule,
For example, polyethylene terephthalate, polyethylene naphthalate, polyphenylene oxide, polyimide, polyamide imide, polyether imide, polyamide, polyether ketone, polyether ether ketone, polyketone sulfide, polyether sulfone and the like can be mentioned. The substrate exemplified above is used after cleaning the surface with an acid, alcohol, detergent, or the like, but is used without performing a surface treatment such as a silicon treatment.

The homeotropically-aligned liquid crystalline polymer used in the present invention means that a liquid crystalline polymer film is formed on a suitable substrate and is subjected to a heat treatment at a temperature at which the liquid crystalline polymer exhibits a liquid crystal state. In the present invention, a homeotropically-aligned liquid crystalline polymer which is homeotropically aligned on at least any one of these exemplified substrates is defined as the present invention. However, since some liquid crystalline polymers are specifically homeotropically aligned at a temperature near the liquid crystal-isotropic phase transition point, the above heat treatment is usually performed at 15 ° C. from the liquid crystal-isotropic phase transition point. Below, it is desirable to carry out at a temperature of preferably 20 ° C. or less. The liquid crystalline polymer exhibiting homeotropic alignment will be specifically described. The liquid crystalline polymer that can be used in the present invention is not particularly limited as long as it has the above properties. Generally, in order for a liquid crystalline polymer to exhibit homeotropic alignment, it is important that the liquid crystal polymer has an appropriate group in the molecular structure and that the molecular weight is appropriate. Examples of the group capable of imparting homeotropic alignment to the liquid crystalline polymer include an aromatic group having a bulky substituent, an aromatic group having a long-chain alkyl group, and an aromatic group having a fluorine atom. Specific examples of the liquid crystalline polymer include a main chain type liquid crystalline polymer having these substituents in the main chain, such as polyester, polyimide, polyamide, polycarbonate, and polyesterimide. Among these, liquid crystalline polyesters are particularly preferred from the viewpoints of ease of synthesis, ease of forming a film, and stability of physical properties of the obtained film. A specific structure example is shown below.

Main chain type homeotropic alignment liquid crystalline polymer

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[0014]

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[0015]

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[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[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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[0030]

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[0031]

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[0032]

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[0033]

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Among the above, (1), (3),
(4), (6), (7), (10), (11), (1
The liquid crystalline polyesters of 7) and (20) are preferred.

As the homeotropically-aligned liquid crystalline polymer, a side-chain type liquid crystalline polymer having the above-mentioned structural unit having a substituent as a side chain, for example, polyacrylate,
Side chain type liquid crystalline polymers such as polymethacrylate, polysiloxane, and polymalonate are also included. A specific structure example is shown below.

Liquid crystalline polymer having side-chain type homeotropic alignment

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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Of the above, (22), (23),
The side chain type liquid crystalline polymers of (25), (28), (29), (32), (34) and (35) are preferred.

The homeotropically-aligned liquid crystalline polymer described above is used in the present invention as a single type or as a composition containing at least one type of the liquid crystalline polymer. When the composition is used in the present invention, the composition may contain at least two types of liquid crystalline polymers exhibiting homeotropic alignment.

In order to exhibit good homeotropic alignment, the molecular weight of the liquid crystalline polymer is also important. In the case of the main chain type liquid crystalline polymer, the molecular weight is usually from 0.05 to 2. logarithmic viscosity measured at 30 ° C. in various solvents, for example, phenol / tetrachloroethane (60/40 (weight ratio)) mixed solvent. 0 is preferred, and more preferably in the range of 0.07 to 1.0. If the logarithmic viscosity is less than 0.05, the mechanical strength of the compensation film becomes weak, which is not preferable. If it is larger than 2.0, homeotropic orientation may be lost. In addition, the viscosity may be too high in the liquid crystal state, and even if homeotropic alignment is performed, the time required for alignment may be long.
In the case of the side chain type liquid crystalline polymer liquid crystal, the molecular weight is usually from 1,000 to 100,000, preferably from 3,000 to 50,000 in terms of polystyrene equivalent weight average molecular weight. Molecular weight 10
If it is smaller than 00, the mechanical strength of the compensation film may be weak, which is not desirable. On the other hand, when it is larger than 100,000, there is a possibility that a problem in film formation such as a decrease in solubility of the polymer in the solvent and an excessive increase in the solution viscosity of the coating solution and a failure to obtain a uniform coating film may occur. .

In the present invention, another liquid crystal polymer compound (or composition) or a polymer compound having no liquid crystal property (or composition) is added to the above-described homeotropic alignment liquid crystal polymer. A liquid crystalline polymer composition can also be used. The use of the composition has the advantages that the average tilt angle of the nematic hybrid orientation can be freely controlled by adjusting the composition ratio, and the nematic hybrid orientation can be stabilized. As the polymer compound (or composition) to be added to the homeotropic liquid crystal polymer,
As described above, various polymer compounds (or compositions) that do not exhibit liquid crystallinity can be used, but from the viewpoint of compatibility with homeotropic alignment liquid crystal polymers,
It is preferable to use a polymer compound (or composition) which also has liquid crystallinity. The liquid crystalline polymer compound (or composition) here is not limited to homeotropic alignment. As the kind of the liquid crystal polymer used, there are main chain type liquid crystal polymers; for example, polyester,
Side chain type liquid crystalline polymers such as polyimide, polyamide, polyester, polycarbonate, and polyesterimide; and polyacrylates, polymethacrylates, polysiloxanes, and polymalonates. It is not particularly limited as long as it has compatibility with the homeotropic alignment liquid crystal polymer. Among them, a homogeneous alignment liquid crystal polymer compound (or composition), more specifically, a homogeneous alignment polyester, Polyacrylate and polymethacrylate are preferred. An example of the structure is shown below.

Main chain type homogeneously oriented liquid crystalline polymer

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[0056]

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[0057]

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[0058]

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[0059]

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[0060]

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[0061]

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[0062]

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[0063]

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[0064]

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Liquid crystalline polymer having side chain type homogeneous alignment

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[0066]

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[0067]

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[0068]

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[0069]

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For the molecular weight of the main chain type liquid crystalline polymer, the molecular weight is determined based on the logarithmic viscosity measured at 30 ° C. in various solvents, for example, in a phenol / tetrachloroethane (60/40 (weight ratio)) mixed solvent. Is usually 0.05 to 3.
0 is preferred, and more preferably in the range of 0.07 to 2.0. If the logarithmic viscosity is less than 0.05, the mechanical strength of the compensation film may be weak. Also,
If it is larger than 3.0, the homeotropic alignment may be impaired, or the viscosity at the time of forming the liquid crystal may be too high, and the time required for the alignment may be long. In the case of a side-chain type polymer liquid crystal, the molecular weight is generally in the range of 5,000 to 200,000, preferably 10,000 to 150,000 in terms of polystyrene equivalent weight average molecular weight. Molecular weight 50
If it is smaller than 00, the mechanical strength of the compensation film may be weak. On the other hand, when it is larger than 200,000, there is a possibility that problems such as a decrease in solubility of the polymer in the solvent and an excessively high solution viscosity of the coating solution and a uniform coating film cannot be obtained. .

The method for synthesizing various liquid polymers described above is as follows.
There is no particular limitation. The liquid crystalline polymer that can be used in the present invention can be synthesized by a polymerization method known in the art. For example, taking polyester synthesis as an example, the polyester can be synthesized by a melt polymerization method or an acid chloride method using a corresponding acid chloride of dicarboxylic acid. Using a liquid crystalline polymer having a positive uniaxial property as described above, in order to obtain a compensation film in which the nematic hybrid orientation is fixed uniformly, it is preferable in the present invention to take the orientation substrate and each step described below. .

First, the alignment substrate will be described. As in the present invention, in order to obtain a nematic hybrid alignment using a positive uniaxial liquid crystalline polymer, it is desirable to sandwich the upper and lower sides of the liquid crystalline polymer layer at different interfaces, and to sandwich the upper and lower sides at the same interface. In such a case, the alignment at the upper and lower interfaces of the liquid crystalline polymer layer becomes the same, and it becomes difficult to obtain the nematic hybrid alignment of the present invention. As a specific mode, one alignment substrate and the air interface are used, and the lower interface of the positive uniaxial liquid crystal polymer layer is used as the alignment substrate, and the upper interface of the liquid crystal polymer layer is used as the air interface. Contact with Although it is possible to use an alignment substrate having different upper and lower interfaces, it is preferable to use one alignment substrate and an air interface from the viewpoint of the manufacturing process. The alignment substrate that can be used in the present invention desirably has anisotropy so that the tilt direction of the liquid crystal molecules (projection of the director onto the alignment substrate) can be defined. If the alignment substrate cannot define the direction in which the liquid crystal is tilted at all, only an alignment mode tilted in a random direction can be obtained (the vector projected from the director onto the substrate becomes disordered).

As the oriented substrate that can be used in the present invention, specifically, one having in-plane anisotropy is desirable, and polyimide, polyamide imide, polyamide, polyether imide, polyether ether ketone, polyether Ether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol,
Plastic film substrates such as polypropylene, cellulosic plastics, epoxy resin, and phenolic resin, and uniaxially stretched plastic film substrates; metal substrates such as aluminum, iron, and copper with slit-shaped grooves on the surface;
Glass substrates such as alkali glass, borosilicate glass, and flint glass, the surfaces of which are etched in a slit shape, and the like.

In the present invention, a rubbing plastic film substrate obtained by subjecting the above plastic film substrate to a rubbing treatment, or a plastic thin film subjected to a rubbing treatment, such as the above various substrates having a rubbing polyimide film, a rubbing polyvinyl alcohol film, etc .; The various substrates described above having an obliquely deposited film or the like can also be used. In the above various alignment substrates, suitable substrates for forming a positive uniaxial liquid crystalline polymer as in the present invention in a nematic hybrid alignment include various substrates having a rubbing polyimide film, a rubbing polyimide substrate, and a rubbing polyether. Examples include an ether ketone substrate, a rubbing polyether ketone substrate, a rubbing polyether sulfone substrate, a rubbing polyphenylene sulfide substrate, a rubbing polyethylene terephthalate substrate, a rubbing polyethylene naphthalate substrate, a rubbing polyarylate substrate, and a cellulose-based plastic substrate.

In the compensation film of the present invention, the angle formed by the director of the positive uniaxial liquid crystalline polymer and the plane of the film is different between the upper surface and the lower surface of the film. The film surface on the substrate side may be at least 0 degree but not more than 50 degrees or 60 degrees depending on the method of the alignment treatment and the type of the positive uniaxial liquid crystalline polymer.
The angle can be adjusted to any angle range from 90 degrees to 90 degrees.
Normally, the angle between the director of the liquid crystalline polymer near the interface of the film in contact with the alignment substrate and the film plane is set to 0.
It is desirable in the manufacturing process to adjust the angle to an angle range of not less than 50 degrees and not more than 50 degrees. The compensation film of the present invention can be obtained by applying a positive uniaxial liquid crystalline polymer on the alignment substrate as described above, and then performing a uniform alignment process and an alignment mode fixing process.
The application of the liquid crystalline polymer to the alignment substrate can be usually performed in a solution state in which a positive uniaxial liquid crystalline polymer is dissolved in various solvents or in a molten state in which the liquid crystalline polymer is melted.
From the viewpoint of the production process, it is preferable to apply a solution by applying the solution obtained by dissolving a positive uniaxial liquid crystalline polymer in a solvent.

The solution application will be described. A positive uniaxial liquid crystalline polymer is dissolved in a solvent to prepare a solution having a predetermined concentration. Since the thickness of the compensation film of the present invention (the thickness of the layer formed of a positive uniaxial liquid crystalline polymer) is determined at the stage of applying the liquid crystalline polymer to the substrate, the concentration and the coating film are precisely determined. It is necessary to control the film thickness and the like. As the solvent, although it cannot be said unconditionally depending on the type (composition ratio, etc.) of the positive uniaxial liquid crystalline polymer, usually, chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, Halogenated hydrocarbons such as orthodichlorobenzene, phenols such as phenol and parachlorophenol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene and 1,2-dimethoxybenzene, acetone, ethyl acetate, ter
t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, ethylcellosolve, butylcellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide , Dimethylacetamide, dimethylsulfoxide, acetonitrile, butyronitrile, carbon disulfide and the like, and a mixed solvent thereof, for example, a mixed solvent of a halogenated hydrocarbon and a phenol is used.

The concentration of the solution cannot be determined unconditionally because it depends on the solubility of the positive uniaxial liquid crystalline polymer to be used and the final thickness of the target compensating film, but is usually 3 to 50% by weight. And preferably in the range of 7 to 30% by weight. A positive uniaxial liquid crystalline polymer solution adjusted to a desired concentration using the above-mentioned solvent is then applied onto the above-described alignment substrate. As a coating method, a spin coating method, a roll coating method, a printing method, an immersion pulling method, a curtain coating method, or the like can be adopted. After the application, the solvent is removed, and a layer of a liquid crystalline polymer having a uniform thickness is formed on the alignment substrate. The solvent removal conditions are not particularly limited, and it is sufficient that the solvent can be removed substantially and the layer of the positive uniaxial liquid crystalline polymer does not flow or fall off. Normal,
The solvent is removed by drying at room temperature, drying in a drying oven, or blowing hot or hot air. The purpose of this coating / drying step is to first form a liquid crystal polymer layer uniformly on the substrate, and the liquid crystal polymer has not yet formed a nematic hybrid orientation. In the next heat treatment step, a monodomain nematic hybrid alignment is completed.

In forming the nematic hybrid alignment by heat treatment, the viscosity of the positive uniaxial liquid crystalline polymer is preferably low in order to assist the alignment by the interface effect, and therefore, it is desirable that the heat treatment temperature be high. Also, depending on the liquid crystalline polymer, the average tilt angle obtained may vary depending on the heat treatment temperature. In that case, it is necessary to set the heat treatment temperature in order to obtain an average tilt angle according to the purpose. For example, when it is necessary to perform heat treatment at a relatively low temperature in order to obtain an alignment having a certain tilt angle, the viscosity of the liquid crystalline polymer is high at a low temperature, and the time required for the alignment becomes long. In such a case, a method is effective in which a heat treatment is once performed at a high temperature to obtain a monodomain orientation, and then the temperature of the heat treatment is gradually or gradually reduced to a target temperature. In any case, it is preferable to perform the heat treatment at a temperature equal to or higher than the glass transition point according to the characteristics of the positive uniaxial liquid crystalline polymer to be used. The heat treatment temperature is usually from 50 ° C to 3
A range of 00 ° C. is preferred, and a range of 100 ° C. to 260 ° C. is particularly preferred. In addition, the heat treatment time required for the positive uniaxial liquid crystal polymer to be sufficiently aligned on the alignment substrate varies depending on the type (for example, composition ratio) of the liquid crystal polymer to be used and the heat treatment temperature. Although it cannot be said, usually the range of 10 seconds to 120 minutes is preferable,
A range from 0 seconds to 60 minutes is preferred. If the time is shorter than 10 seconds, the orientation may be insufficient. If the time is longer than 120 minutes, productivity may decrease, which is not desirable.
In this way, a uniform nematic hybrid alignment can be obtained in the liquid crystal state over the entire surface of the alignment substrate.

In the present invention, in the heat treatment step, a magnetic field or an electric field may be used in order to align the positive uniaxial liquid crystalline polymer in a nematic hybrid orientation. However, when a magnetic field or an electric field is applied while performing heat treatment, a uniform field force acts on the liquid crystalline polymer during the application, so that the director of the liquid crystal tends to turn in a certain direction. That is, it is difficult to obtain a nematic hybrid orientation in which the director forms different angles depending on the film thickness direction as in the present invention. Once the nematic hybrid orientation, such as homeotropic, homogeneous, tilt orientation or other orientation is formed, a thermally stable nematic hybrid orientation can be obtained by removing the field force. There is no merit.

The nematic hybrid alignment formed in the liquid crystal state of the positive uniaxial liquid crystalline polymer is
Next, by cooling the liquid crystalline polymer to a temperature equal to or lower than the liquid crystal dislocation point, the liquid crystal polymer can be fixed without impairing the uniformity of the alignment. In general, when a liquid crystalline polymer having a smectic phase or a crystalline phase in a lower temperature portion than a nematic phase is used, nematic alignment in a liquid crystal state may be broken by cooling. In the present invention, it has no smectic phase or crystalline phase at a temperature lower than the temperature range showing the nematic phase, and even if it has a potential crystalline phase or smectic phase, no smectic phase or crystalline phase appears upon cooling. Since a liquid crystalline polymer is used, which has properties such that it has no fluidity in the operating temperature range of the compensating film and does not change its alignment form even when an external field or external force is applied, the phase changes to a smectic phase or a crystalline phase. The orientation morphology is not destroyed by the dislocation, and a completely monodomain nematic hybrid orientation can be fixed.

The cooling temperature is not particularly limited as long as it is lower than the liquid crystal transition point. For example, 10 ° C from the liquid crystal transition point
By cooling at a low temperature, uniform nematic hybrid orientation can be fixed. There is no particular limitation on the cooling means, and the cooling is carried out by simply taking out from the heating atmosphere in the heat treatment step to an atmosphere below the liquid crystal transition point, for example, room temperature. In order to increase the efficiency of antacid, forced cooling such as air cooling or water cooling or slow cooling may be performed.
However, the average tilt angle obtained depending on the cooling rate may be slightly different depending on the positive uniaxial liquid crystalline polymer. When it is necessary to use such a liquid crystalline polymer and strictly control the angle, it is preferable to perform a cooling operation in consideration of cooling conditions as appropriate.

Next, the angle control in the film thickness direction of the nematic hybrid orientation in the present invention will be described. In the present compensation film, the absolute value of the angle formed by the director of the positive uniaxial liquid crystalline polymer and the film plane in the vicinity of the film interface is 0 ° or more and 50 ° or less on one of the upper surface and the lower surface of the film. Within the range, and on the surface opposite to the surface, the range is 60 degrees or more and 90 degrees or less. The desired angle can be controlled by appropriately selecting the type (composition, etc.) of the positive uniaxial liquid crystalline polymer to be used, the alignment substrate, the heat treatment conditions, and the like.
Even after the nematic hybrid orientation is fixed, the angle can be controlled to a desired angle by using a method such as uniformly shaving the film surface or immersing the film surface in a solvent to uniformly dissolve the film surface. The solvent used at this time is appropriately selected depending on the type (composition or the like) of the positive uniaxial liquid crystalline polymer and the type of the alignment substrate.

The compensating film of the present invention obtained by the above-mentioned steps is obtained by uniformly orienting and fixing an orientation form called a nematic hybrid orientation, and since the orientation is formed, the upper and lower sides of the film are It is not equivalent and has anisotropy in the in-plane direction, and when it is arranged on the LCD, various characteristics can be derived depending on the arrangement. When the compensation film of the present invention is actually arranged in a twisted nematic liquid crystal cell, as a usage mode of the film, the above-described alignment substrate is peeled off from the film, and the compensation film is used alone. It is possible to use a state in which the compensation film is laminated on another substrate different from the alignment substrate.

When used as a film alone, a method of mechanically peeling the oriented substrate at the interface with the compensation film using a roll or the like, a method of mechanically peeling after dipping in a poor solvent for all structural materials, A method of peeling by applying ultrasonic waves in a poor solvent, a method of peeling by giving a temperature change using a difference in thermal expansion coefficient between the oriented substrate and the film, the oriented substrate itself, or the oriented film on the oriented substrate. A film alone is obtained by a method of dissolving and removing. The releasability depends on the type of positive uniaxial liquid crystalline polymer used (composition, etc.)
Therefore, the method most suitable for the system should be adopted. When the compensation film alone is used, it may not have self-supporting property depending on the film thickness, but in that case, a substrate preferable in optical properties, for example, polymethacrylate, polycarbonate, polyvinyl alcohol, polyether sulfone, polysulfone,
It is preferable to use a plastic substrate made of polyarylate, polyimide, amorphous polyolefin, triacetyl cellulose, or the like with an adhesive or a pressure-sensitive adhesive fixed thereto for the strength and reliability of the compensation film.

Next, a case where a compensation film is used in a state formed on an alignment substrate will be described. The alignment substrate is transparent and optically isotropic, or the alignment substrate is TN-L
If the member is necessary for the CD, it can be incorporated into the TN-LCD as a target compensating element as it is. Further, the compensatory film of the present invention obtained by aligning and fixing the positive uniaxial liquid crystalline polymer on the alignment substrate is peeled off from the substrate, and laminated on another substrate more suitable for optical use. That is, a laminate composed of at least the film and another substrate different from the alignment substrate can be incorporated in the TN-LCD as a compensation element. For example, if the alignment substrate to be used is necessary for obtaining a nematic hybrid alignment, but such a substrate has an unfavorable effect on the TN-LCD, compensation after fixing the alignment of the substrate is used. It can be used after being removed from the film. Specifically, the following method can be adopted. A substrate suitable for a liquid crystal display element to be incorporated in a target TN-LCD (hereinafter, referred to as a second substrate) and a compensation film on an alignment substrate are attached using, for example, an adhesive or an adhesive. Next, the alignment substrate is peeled off at the interface with the compensation film of the present invention, and the compensation film can be transferred to a second substrate side suitable for a liquid crystal display element to obtain a compensation element.

The second substrate used for the transfer is not particularly limited as long as it has an appropriate flatness.
A glass substrate or a transparent plastic film having optical isotropy is preferably used. Examples of such a plastic film include polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyarylate, amorphous polyolefin, triacetyl cellulose, and epoxy resin. Among them, polymethyl methacrylate, polycarbonate, polyarylate, polyether sulfone, triacetyl cellulose and the like are preferably used. Even if it is optically anisotropic, an optically anisotropic film can be used if it is a necessary member for a TN-LCD. Examples of such a film include a retardation film and a polarizing film obtained by stretching a plastic film such as polycarbonate or polystyrene.

The liquid crystal cell itself can be mentioned as an example of the second substrate used. The liquid crystal cell uses a glass or plastic substrate with two upper and lower electrodes, and if the compensation film of the present invention is transferred to one of the upper and lower or both surfaces of the glass or plastic substrate, the incorporation of the compensation film has already been completed. It has been achieved. Of course, it is also possible to manufacture the present compensation film using the glass or plastic substrate itself forming the liquid crystal cell as an alignment substrate. The second explained above
Does not need to have substantially the ability to control the alignment of the positive uniaxial liquid crystalline polymer. Further, an alignment film or the like is not required between the second substrate and the film.

The adhesive or pressure-sensitive adhesive for adhering the second substrate used for the transfer and the compensation film of the present invention is not particularly limited as long as it is of an optical grade. Vinyl acetate copolymers, rubbers, urethanes, and mixtures thereof can be used. As the adhesive, any adhesive such as a thermosetting type, a photocuring type, and an electron beam curing type can be used without any problem as long as it has optical isotropy.

The transfer of the compensation film of the present invention to a second substrate suitable for a liquid crystal display device can be carried out by peeling the oriented substrate at the interface with the film after bonding. As described above, the method of peeling is a method of mechanical peeling using a roll or the like, a method of mechanically peeling after immersing in a poor solvent for all structural materials, and a peeling by applying ultrasonic waves in a poor solvent. Examples of the method include a method of performing separation by giving a temperature change using a difference in thermal expansion coefficient between an oriented substrate and the film, a method of dissolving and removing an oriented substrate itself or an oriented film on an oriented substrate, and the like. it can. Since the releasability depends on the type (composition and the like) of the positive uniaxial liquid crystalline polymer to be used and the adhesion to the alignment substrate, a method most suitable for the system should be adopted. The compensation film of the present invention may be provided with a protective layer such as a transparent plastic film for the purpose of protecting the surface, increasing the strength, and improving environmental reliability.

The compensation film thus obtained is
The TN-LCD has a particularly excellent viewing angle compensation effect. The thickness of the compensation film is such that the film exhibits a more suitable compensation effect for various TN-LCDs.
Since it depends on the target TN-LCD system and various optical parameters, it cannot be said unconditionally.
In the range of not less than 20 μm and more preferably not more than 0.2 μm.
μm or more and 10 μm or less, particularly preferably 0.3 μm
m and 5 μm or less. When the film thickness is less than 0.1 μm, there is a possibility that a sufficient compensation effect cannot be obtained. If the thickness exceeds 20 μm, the display may be unnecessarily colored. However, in order to bring out the performance of the compensating film of the present invention, it is desirable to consider the optical parameters and the axial arrangement of the compensating film in more detail. This will be individually described below.

First, the in-plane apparent retardation value when viewed from the normal direction of the film will be described.
In a film having a nematic hybrid orientation, a refractive index in a direction parallel to the director (hereinafter referred to as ne) and a refractive index in a direction perpendicular to the director (hereinafter referred to as no) are different. n
When the value obtained by subtracting no from e is the apparent birefringence, the apparent retardation value is given by the product of the apparent birefringence and the absolute film thickness. This apparent retardation value can be easily obtained by polarization optical measurement such as ellipsometry. The apparent retardation value of the compensation film of the present invention is usually in the range of 5 nm to 500 nm, more preferably in the range of 10 nm to 300 nm, and particularly preferably in the range of 15 nm to 150 nm for 550 nm monochromatic light. When the apparent retardation value is less than 5 nm, there is a possibility that substantially no homeotropic alignment is obtained and a sufficient viewing angle enlarging effect cannot be obtained. On the other hand, if it is larger than 500 nm, unnecessary coloring may occur on the liquid crystal display when viewed obliquely.

Next, the angle of the director will be described. The angle range of the director in the film thickness direction of the nematic hybrid oriented film is the acute angle formed by the director of the positive uniaxial liquid crystalline polymer at the film interface and the projected component of the director onto the film interface. However, on one of the upper surface and the lower surface of the film, the angle is usually 60 degrees or more and 90 degrees or less, and on the opposite surface of the film, it is usually 0 degrees or more and 50 degrees or less. More preferably, the absolute value of one angle is 80 degrees or more and 90 degrees or less, and the absolute value of the other angle is 0 degrees or more and 30 degrees or less.

Next, the average tilt angle will be described. In the present invention, an average value in the film thickness direction of an angle formed by a director of a positive uniaxial liquid crystalline polymer and a component projected by the director onto a substrate plane is defined as an average tilt angle.
The average tilt angle can be obtained by applying a crystal rotation method. The average tilt angle of the compensation film of the present invention is in the range of 10 degrees to 60 degrees, preferably 2 degrees.
It is in the range of 0 to 50 degrees. When the average tilt angle is smaller than 10 degrees or larger than 60 degrees, a certain viewing angle expanding effect is recognized but a satisfactory effect may not be obtained.

Next, the TN-LC
The arrangement when used for expanding the viewing angle of D will be specifically described. The position of the compensation film may be any position between the polarizing plate and the liquid crystal cell, and one or more compensation films can be arranged. In the present invention, it is practically preferable to perform viewing angle compensation using one or two compensation films. Even if three or more compensation films are used,
Although viewing angle compensation is possible, it is not very preferable because it leads to an increase in cost. An example of a specific arrangement position is as follows. However, these are merely typical arrangement positions, and the present invention is not limited to these.

First, the upper and lower surfaces of the present compensation film are defined as follows. The plane where the angle between the director of the liquid crystalline polymer having optically positive uniaxiality and the plane of the film forms an angle of 60 degrees or more and 90 degrees or less on the acute angle side is referred to as a b-plane. A plane in which the angle forms an angle of 0 ° or more and 50 ° or less on the acute angle side is referred to as a c-plane. Next, the tilt direction of the present compensation film is defined as follows. When viewing the c-plane from the b-plane of the compensation film through the liquid crystal layer, the direction in which the angle between the director and the projection component on the c-plane of the director is an acute angle and the direction parallel to the projection component is the tilt of the compensation film. Defined as direction. Next, the pretilt direction of the liquid crystal cell is defined as follows. Usually, at the liquid crystal cell interface, the driving low-molecular liquid crystal is not parallel to the cell interface but is inclined at an angle. This is called a pretilt angle. The direction in which the angle formed by the director of the liquid crystal at the cell interface and the projected component on the interface of the director is an acute angle, and the direction parallel to the projected component of the director is defined as the pretilt direction of the liquid crystal cell.

Based on the above definition, 1 of the present compensation film
A case in which a TN-LCD is used will be described. The compensation film is disposed between the polarizing plate and the liquid crystal cell, and may be on the upper surface side or the lower surface side of the cell. It is preferable that the tilt direction of the compensation film and the pretilt direction of the liquid crystal of the cell at the interface of the liquid crystal cell not adjacent to each other substantially coincide. The angle between the tilt direction and the pretilt direction is preferably in the range of 0 to 15 degrees, more preferably in the range of 0 to 10 degrees, and particularly preferably in the range of 0 to 5 degrees. If the angle between them is 15 degrees or more, a sufficient viewing angle compensation effect may not be obtained. Next, a case where two compensating films are used for a TN-LCD will be described. The two compensation films are arranged on the upper or lower surface of a liquid crystal cell sandwiched between a pair of upper and lower polarizing plates. When arranging, two compensating films may be on the same side, or one each may be above and below. The two compensation films may have the same parameter or different parameters.

In the present invention, when two compensating films are separately arranged above and below a liquid crystal cell, it is preferable that each compensating film is arranged in the same manner as when only one compensating film is used. That is, it is preferable that the tilt direction of the liquid crystalline polymer in each compensation film and the pretilt direction of the cell liquid crystal at the interface of the liquid crystal cell not adjacent to each other substantially coincide. The angle between the tilt direction and the pretilt direction is preferably in the range of 0 to 15 degrees, more preferably in the range of 0 to 10 degrees, and particularly preferably in the range of 0 to 5 degrees. When two compensating films are arranged on either the upper surface or the lower surface of the liquid crystal cell, the compensating film on the side closer to the liquid crystal cell is arranged in the same manner as when one compensating film is used. That is, it is preferable that the tilt direction of the compensating film and the pretilt direction of the nematic liquid crystal at the liquid crystal cell interface not adjacent to each other are arranged so as to substantially coincide with each other. The angle between the tilt direction and the pretilt direction is preferably in the range of 0 to 15 degrees, more preferably in the range of 0 to 10 degrees, and particularly preferably in the range of 0 to 5 degrees. The second compensation film is to be arranged between the first compensation film and the polarizing plate,
It is preferable that the pre-tilt direction of the nematic liquid crystal at the liquid crystal cell interface adjacent to the first compensation film and the tilt direction of the second compensation film are substantially aligned.

Further, since the compensation film of the present invention has a nematic hybrid orientation, the top and bottom of the compensation film are not equivalent. Therefore, when the compensation film is mounted on a liquid crystal cell, a slight difference in the compensation effect is seen depending on which surface is closer to the liquid crystal cell. When the compensating film of the present invention is actually incorporated in a TN-LCD, the surface formed by the director of the liquid crystalline polymer with the film plane has a larger angle (the surface having an angle of 60 degrees or more and 90 degrees or less).
It is more desirable to dispose the liquid crystal near the liquid crystal cell and far from the polarizing plate. Finally, the arrangement of the polarizing plates will be described. Normally, in a TN-LCD, there are cases where the transmission axes of the upper and lower polarizers are arranged so as to be orthogonal to each other and where they are arranged so as to be parallel. Further, when the transmission axes of the upper and lower polarizing plates are orthogonal to each other, the transmission axis of the polarizing plate and the rubbing direction of the liquid crystal cell closer to the polarizing plate may be parallel or vertical, or may form an angle of 45 degrees. . When a polarizing plate is mounted on the compensating film of the present invention, the arrangement of the polarizing plate can obtain a viewing angle expanding effect in any of the above arrangements, but the transmission axes of the upper and lower polarizing plates are orthogonal to each other and the polarizing plate has An arrangement in which the transmission axis and the rubbing direction of the liquid crystal cell on the side closer to the polarizing plate are parallel is most preferable. The compensation film of the present invention described above is a TN-LC using a TFT element or a MIM element.
D has a tremendous effect on the improvement of the viewing angle, and the production of the optically positive uniaxial liquid crystalline polymer as the raw material of the compensation film and the production of the film itself are simple. The value is very large.

[0099]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. In addition, each analysis method used in the Example is as follows. (1) Determination of Composition of Liquid Crystalline Polymer The polymer was dissolved in deuterated chloroform or deuterated trifluoroacetic acid, and determined by 400 NH ¹ H-NMR (JNM-GX400 manufactured by JEOL Ltd.). (2) Measurement of logarithmic viscosity The viscosity was measured at 30 ° C. in a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent using an Ubbelohde viscometer. (3) Determination of liquid crystal phase series Determined by DSC (Perkin Elmer DSC-7) measurement and observation with an optical microscope (BH2 polarizing microscope manufactured by Olympus Optical Co., Ltd.). (4) Measurement of Refractive Index The refractive index was measured using an Appe refractometer (Type-4, manufactured by Atago Co., Ltd.). (5) Polarization analysis Ellipsometer DVA-36V manufactured by Mizojiri Optical Co., Ltd.
Performed using WLD. (6) Film thickness measurement Kosaka Laboratory Co., Ltd. high-precision thin film step measuring device ET-1
0 was used. In addition, a method of determining the film thickness from the data of the refractive index and the interference wave measurement (UV-visible / near-infrared spectrophotometer V-570 manufactured by JASCO Corporation) was also used.

Example 1 100 mmol of 6-hydroxy-2-naphthoic acid, 100 mmol of terephthalic acid, and 5 of chlorohydroquinone
0 mmol, tert-butylcatechol 50 mmol
1 and 600 mmol of acetic anhydride under a nitrogen atmosphere at 140 ° C. for 2 hours to perform an acetylation reaction. Subsequently, polymerization was performed at 270 ° C. for 2 hours, 280 ° C. for 2 hours, and 300 ° C. for 2 hours. Next, the obtained reaction product was dissolved in tetrachloroethane, and then purified by reprecipitation with methanol to obtain a liquid crystalline polyester (formula (52)).
0 g was obtained. The logarithmic viscosity of this liquid crystalline polyester is 0.1.
35, having a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 300 ° C. or more, and a glass transition point of 135 ° C. Using this liquid crystalline polyester, a phenol / tetrachloroethane mixed solvent of 10 wt% (6/4 weight ratio)
A solution was prepared. This solution was applied on a soda glass plate by a screen printing method, dried, and heated at 230 ° C. for 30 minutes.
After the heat treatment, it was cooled and fixed at room temperature. Film thickness 2
A 0 μm uniformly oriented compensation film was obtained. Conoscopic observation revealed that the liquid crystalline polyester had optically positive uniaxiality.

[0101]

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Next, the liquid crystalline polyester 8 of the formula (52)
A wt% tetrachloroethane solution was prepared, applied to a glass having a rubbing polyimide film by spin coating, dried, heat-treated at 250 ° C. for 30 minutes, air-cooled and fixed to obtain a compensation film. The obtained compensation film on the substrate was transparent, had no alignment defects, was uniform, and had a thickness of 2.0 μm.

Using the optical measuring system shown in FIGS. 1 and 2,
The compensation film was tilted in the rubbing direction of the substrate, and the retardation value was measured. As a result, as shown in FIG. 3, a result was obtained in which there was no left-right asymmetric and no angle at which the retardation value was 0. From this result, it was found that the director of the liquid crystalline polyester was inclined with respect to the substrate and was not in a uniform tilt orientation (the angle between the director and the substrate surface was not constant in the film thickness direction). Next, the compensation film on the substrate was cut into five pieces, each of which was immersed in a methanol solution containing 5 wt% of chloroform for a certain period of time, and eluted from the upper surface of the liquid crystal layer. Immersion time was 15 seconds, 30 seconds, 1 minute,
In the case of 2 minutes and 5 minutes, the thickness of the liquid crystal layer remaining without being eluted is 1.5 μm, 1.2 μm, 1.0 μm,
0.8 μm and 0.5 μm. The retardation value (front retardation value) at θ = 0 degrees was measured using the optical system of FIGS. 1 and 2, and the relationship between the film thickness and the retardation value of FIG. 4 was obtained. As can be seen from FIG. 4, the film thickness and the retardation value do not have a linear relationship, and this also indicates that the film is not in a uniform tilt orientation. The dotted line in the figure is a straight line observed in a film having a uniform tilt orientation.
Next, a liquid crystal polyester of the formula (52) was coated with a high refractive index glass substrate having a rubbing polyimide film (refractive index: 1.8).
4) On top, oriented and fixed using the same method as above,
A compensation film was prepared, and a refractive index was measured using the compensation film. When the glass substrate is placed in contact with the prism surface of the refractometer and the compensation film is arranged so that the substrate interface side is lower than the air interface side, the refractive index in the film surface is anisotropic and perpendicular to the rubbing direction. The in-plane refractive index is 1.5
6. The refractive index in the parallel plane was 1.73, and the refractive index in the film thickness direction was constant at 1.56 regardless of the direction of the sample.
From this, it was found that on the glass substrate side, rod-like liquid crystal molecules constituting the liquid crystalline polyester were planarly oriented parallel to the substrate. Next, when the compensating film is arranged so that the air interface side is in contact with the prism surface of the refractometer, the in-plane refractive index has no anisotropy, the refractive index is constant at 1.56, and the refractive index in the film thickness direction is constant. Is 1.7 regardless of the direction of the material
It was constant at 3. From this, it was found that rod-like liquid crystal molecules constituting the liquid crystalline polyester were oriented perpendicular to the substrate plane on the air interface side.

As described above, the compensation film formed of the uniaxial nematic liquid crystal forms a nematic hybrid orientation, and the rubbing force at the substrate interface and the air force at the air interface as shown in FIG. I suspected that. Next, the following operation was performed in order to more accurately determine the direction angle of the director at the substrate interface. Another glass substrate having a rubbing polyimide film was placed over and adhered to the compensation film formed on the high refractive glass substrate having the rubbing polyimide film. That is, the compensation film was sandwiched between two rubbing polyimide films. At this time, the upper and lower rubbing films were arranged such that the rubbing directions were 180 degrees with respect to each other. In this state, heat treatment was performed at 230 ° C. for 30 minutes. The sample thus obtained was subjected to refractive index measurement and ellipsometry. As a result of the refractive index measurement, the same value was obtained for the top and bottom of the compensating film, and the in-plane contact ratio of the film was 1.56 in a plane perpendicular to the rubbing direction and 1.7 in a plane parallel to the rubbing direction.
3. It was 1.56 in the film thickness direction of the film. This indicates that the director is substantially parallel to the substrate plane both above and below the compensation film near the interface of the substrate. Furthermore, as a result of polarization analysis, the refractive index structure is almost positive uniaxial, and as a result of detailed analysis based on the crystal rotation method, the director has a slight inclination near the substrate interface, and the director plane and the director The angle formed was about 3 degrees. The direction in which the director was inclined coincided with the rubbing direction (the tilt direction and the rubbing direction of the compensation film coincided with each other). From the above, considering that the director orientation at the substrate interface is almost determined by the interaction between the liquid crystalline polyester and the alignment substrate interface, the nematic hybrid alignment structure of the compensation film formed on one alignment substrate described above is considered. Is estimated to be 3 degrees at the substrate interface.

Embodiment 2

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A liquid crystalline polyester of the formula (53) was synthesized in the same manner as in Example 1. This liquid crystalline polyester had a logarithmic viscosity of 0.20, a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 300 ° C. or higher, and a glass transition point of 115 ° C. As a result of the same orientation test as in Example 1, it was found that the liquid crystalline polyester had homeotropic orientation and exhibited optically positive uniaxiality. 5 wt% of the liquid crystalline polyester of the formula (53)
Of tetrachloroethane was prepared. The solution was applied to glass having a dielectric constant of a rubbing polyimide film by a spin coating method and dried. After drying, heat treatment was performed at 250 ° C. for 30 minutes, followed by cooling and fixing to obtain a compensation film. The obtained compensation film on the substrate was transparent, uniform without any alignment defects, had a film thickness of 0.9 μm, and had an average tilt angle of 45 degrees in the film thickness direction. The axial arrangement of each optical element is the arrangement shown in FIG. 6, and one compensation film is arranged above and below the liquid crystal cell so that the air interface side of the compensation film is closer to the liquid crystal cell. The liquid crystal cell used was ZL as the liquid crystal material.
Using I-4792, the cell parameters are a cell gap of 4.8 μm, a twist angle of 90 ° (left twist), and a pretilt angle of 4 °. A voltage was applied to the liquid crystal cell with a rectangular wave of 300 Hz. Hamamatsu Photonics Co., Ltd. measures the contrast ratio from all directions with the ratio of the transmittance of white display 0 V and black display 6 V (white display) / (black display) as the contrast ratio.
An isocontrast curve was drawn using an FFP optical system DVS-3000 manufactured by Toshiba Corporation. FIG. 7 shows the result. In the arrangement shown in FIG. 6, a voltage that divides the difference between the transmittances of the white display and the black display into eight is applied to the liquid crystal cell, and the gradation characteristics in the horizontal direction (0-180 degrees) are obtained. The measurement was performed using a color luminance meter BM-5. FIG. 8 shows the results.

Embodiment 3

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A liquid crystalline polyester of the formula (54) was synthesized. It had a logarithmic viscosity of 0.25, a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 300 ° C. or higher, and a glass transition point of 95 ° C. Using this liquid crystalline polyester, an 8 wt% phenol / tetrachloroethane mixed solvent (6/4 weight ratio) solution was prepared, applied to various orientation test substrates by screen printing, dried, and dried.
Heat treatment was performed at 0 ° C. for 10 minutes. Soda glass, borosilicate glass, polyethylene terephthalate film, polyimide film, polyether imide film, polyether ether ketone film, and polyether sulfone film were used as substrates, but the schlieren structure was obtained by microscopic observation of the liquid crystal phase on any substrate. It was found that this liquid crystalline polyester had a homogeneous orientation. A 5 wt% tetrachloroethane solution of an optically positive uniaxial liquid crystal polyester composition containing the liquid crystal polyester of the formula (53) and the liquid crystal polyester of the formula (54) in a weight ratio of 90:10 was prepared. .
Coating, drying and heat treatment were performed under the same conditions as in Example 2 to obtain a compensation film having a thickness of 0.9 μm. The average tilt angle in the film thickness direction of this film was 25 degrees. The contrast ratio was measured from all directions in the same manner as in Example 2. FIG. 9 shows the result.

Comparative Example 1 The same TN type liquid crystal cell as in Example 2 was used, and the arrangement of the polarizing plates was the same as that in FIG. 6 without the compensation film attached. The contrast ratio was measured, and the gradation characteristics in the horizontal direction (0-180 degrees) were measured. The results are shown in FIGS.

Embodiment 4

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[0111]

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The liquid crystalline polyesters of the formulas (55) and (56) were synthesized. The logarithmic viscosity was 0.12, the liquid crystal phase had a nematic phase, and the isotropic phase-liquid crystal phase transition temperature was 300 ° C. or more. As a result of the same orientation test as in Example 1, it was found that the liquid crystalline polyester represented by the formula (55) had homeotropic orientation and showed optically positive uniaxiality. The liquid crystalline polyester of the formula (56) had a logarithmic viscosity of 0.24, had a nematic phase as a liquid crystal phase, and had a crystal phase on a lower temperature side than the nematic phase. As a result of conducting an orientation test in the same manner as in Example 3, it was found that this polymer had a homogeneous orientation. Equation (55), Equation (56)
4 wt% of an optically positive uniaxial liquid crystal polyester composition containing the liquid crystal polyester of the formula (1) in a weight ratio of 8: 2.
% Chloroform solution was prepared. The solution was applied on a polyethylene terephthalate film having a rubbing polyimide film by a printing method and dried. After drying, 180 ° C
As a result of performing heat treatment for 45 minutes and cooling and fixing, a compensation film was obtained. A triacetyl cellulose film having an adhesive was adhered to the surface of the obtained compensation film via the adhesive, then the polyethylene terephthalate film was peeled off, and the compensation film was transferred to the triacetyl cellulose film. The thickness of the compensation film is 0.7μ
m, the average tilt angle in the film thickness direction was 35 degrees. The axial arrangement of each optical element was as shown in FIG. 6, and one compensation film was arranged above and below the liquid crystal cell such that the triacetyl cellulose film of the compensation film was on the side closer to the liquid crystal cell. The contrast ratio was measured in all directions by the same method as in Example 2. The result is shown in FIG.

Embodiment 5

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A liquid crystalline polyester of the formula (57) was synthesized. The logarithmic viscosity was 0.23, the liquid crystal phase had a nematic phase, and the isotropic phase-liquid crystal phase transition temperature was 300 ° C. or more.
As a result of an orientation test, it was found that this liquid crystalline polyester exhibited homeotropic properties and exhibited optically positive uniaxiality. A 10 wt% phenol / tetrachloroethane mixed solvent (6/4 weight ratio) solution of this liquid crystalline polyester was prepared and applied to a rubbed polyimide film substrate by a die coater over a width of 50 cm and a length of 20 m. After coating, hot air drying at 120 ° C, 230 ° C
As a result, a compensation film was obtained. Next, apply an ultraviolet curable adhesive on the surface of the compensation film,
A polycarbonate film having a retardation of 180 nm was bonded via an adhesive. After irradiating ultraviolet rays to cure the adhesive, the polyimide film was peeled off, and the compensation film was transferred onto a polycarbonate film.
The thickness of the compensation film was 1.4 μm, and the average tilt angle in the thickness direction was 45 degrees. The axial arrangement of each optical element was as shown in FIG. 13, and one compensation film was arranged above and below the liquid crystal cell such that the polycarbonate film of the compensation film was on the side closer to the liquid crystal cell. The contrast ratio was measured in all directions by the same method as in Example 2. FIG. 14 shows the results.

Embodiment 6

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[0116]

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The liquid crystalline polyesters of the formulas (58) and (59) were synthesized. The logarithmic viscosity of the liquid crystalline polyester of the formula (58) was 0.15, the liquid crystal phase had a nematic phase, and the isotropic phase-liquid crystal phase transition temperature was 300 ° C. or more. As a result of an orientation test, it was found that this liquid crystalline polyester exhibited homeotropic orientation and exhibited optically positive uniaxiality. The liquid crystalline polyester of the formula (59) had a logarithmic viscosity of 0.12, a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 200 ° C., and was homogeneously oriented. 10 wt% of N-methyl-2 of an optically positive uniaxial liquid crystal polyester composition containing the liquid crystal polyesters of the formulas (58) and (59) in a weight ratio of 8: 2.
-A pyrrolidone solution was prepared and applied on a polyarylate film having a rubbing polyimide film by a roll coater. After applying, it is dried with hot air at 100 ° C.
As a result of performing heat treatment at 00 ° C. for 5 minutes, a compensation film was obtained. The film thickness of the obtained compensation film was 0.4 μm, and the average tilt angle in the film thickness direction was 35 degrees. Remove the polarizing plate of the liquid crystal color television 6E-A3 manufactured by Sharp Corporation so that the air interface side of the compensation film is closer to the liquid crystal cell.
One compensating film was attached to each of the upper and lower sides of the liquid crystal cell. Thereafter, a polarizing plate was attached to the polyarylate film one by one at the top and at the bottom. The axial arrangement of each optical element was the same as the arrangement shown in FIG. The contrast ratio in all directions was measured in the same manner as in Example 2. The result is shown in FIG.

Comparative Example 2 The contrast ratio in all directions when the compensation film was not mounted on the TFT liquid crystal color television manufactured by Sharp Corporation of Example 6 was measured. FIG. 16 shows the results.

Embodiment 7

[0120]

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[0121]

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The liquid crystalline polyesters of the formulas (60) and (61) were synthesized. The logarithmic viscosity of the liquid crystalline polyester of the formula (60) was 0.15, the liquid crystal phase had a nematic phase, and the isotropic phase-liquid crystal phase transition temperature was 180 ° C. Next, when an orientation test was performed, it was found that the liquid crystalline polyester had homeotropic orientation and exhibited optically positive uniaxiality. The liquid crystalline polyester of the formula (61) had a logarithmic viscosity of 0.20, a nematic phase as a liquid crystal phase, an isotropic phase-liquid crystal phase transition temperature of 300 ° C. or higher, and was homogeneously oriented. An optically positive uniaxial liquid crystalline polyester composition containing the liquid crystalline polyesters of formulas (58) and (59) in a weight ratio of 8: 2, and 10 wt% of a phenol / tetrachloroethane mixed solvent (6 / 4 weight ratio)
A solution was prepared and applied on polyethersulfone rubbed with a die coater. After applying, 12
Hot air drying was performed at 0 ° C., and heat treatment was performed at 220 ° C. for 10 minutes. As a result, a compensation film was obtained. The film thickness of the obtained compensation film was 0.7 μm, and the average tilt angle in the film thickness direction was 45 degrees. Epson LCD color television EP-W
The polarizing plate of 7000 was peeled off, and one compensating film was attached to each of the upper and lower sides of the liquid crystal cell such that the air interface side of the compensating film was closer to the liquid crystal cell. Thereafter, a polarizing plate was attached to polyether sulfone one by one at the top and at the bottom. The axial arrangement of each optical element was the same as the arrangement shown in FIG. The contrast ratio in all directions was measured in the same manner as in Example 2. The result is shown in FIG.

Comparative Example 3 The contrast ratio in all directions when the compensation film was not mounted on the liquid crystal color television manufactured by Epson Corporation of Example 7 was measured. The results are shown in FIG.

[Brief description of the drawings]

FIG. 1 is a layout diagram of an optical measurement system used for measuring a tilt angle of a compensation film of the present invention.

FIG. 2 shows the relationship between the axial orientation of a sample of an optical measurement system used for measuring the tilt angle of the compensation film of the present invention and the polarizing plate.

FIG. 3 shows a relationship between an apparent retardation value measured while being tilted along a rubbing direction of a substrate and a tilt angle of a sample in Example 1.

FIG. 4 shows a measurement result of a film thickness after immersion of a compensation film and an apparent retardation value in front of a sample in Example 1.

FIG. 5 is a conceptual diagram of an orientation structure of a compensation film of the present invention.

FIG. 6 shows the axial arrangement of each optical element in the second embodiment.

FIG. 7 shows an isocontrast curve of Example 2.

FIG. 8 shows a measurement result of a gradation characteristic in a horizontal direction in Example 2.

FIG. 9 shows an isocontrast curve of Example 3.

FIG. 10 shows an isocontrast curve of Comparative Example 1.

FIG. 11 shows the gradation characteristics in the horizontal direction of Comparative Example 1.

FIG. 12 shows an isocontrast curve of Example 4.

FIG. 13 shows the axial arrangement of each optical element in the fifth embodiment.

FIG. 14 shows an isocontrast curve of Example 5.

FIG. 15 shows an isocontrast curve of Example 6.

16 shows an isocontrast curve of Comparative Example 2. FIG.

FIG. 17 shows an isocontrast curve of Example 7.

FIG. 18 shows an isocontrast curve of Comparative Example 3.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yosuke Numao 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Nippon Oil & Oil Co., Ltd.

Claims (2)

[Claims] 1. A liquid crystal substantially formed of a liquid crystalline polymer having optically positive uniaxiality, wherein the liquid crystalline polymer fixes a nematic hybrid alignment formed in a liquid crystal state. Optical compensation film for display devices. 2. A twisted nematic liquid crystal display comprising at least a driving liquid crystal cell comprising a pair of transparent substrates provided with electrodes and a nematic liquid crystal, and upper and lower polarizing plates disposed above and below the substrate. An apparatus, wherein the optical compensation film for a liquid crystal display element according to claim 1, between the substrate and either one of the upper or lower polarizing plate or between the substrate and the upper and lower polarizing plates. A twisted nematic liquid crystal display device comprising at least one sheet.