JP3394682B2 - Optical anisotropic film and liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical anisotropic film used for a non-linear optical element, a liquid crystal display device and the like, and a liquid crystal display device using the optical anisotropic film.

[0002]

2. Description of the Related Art A retardation film is obtained by uniaxially stretching a transparent thermoplastic polymer film, and is a liquid crystal display device, particularly, a super-screw nematic (hereinafter sometimes referred to as STN) type liquid crystal display device or. An optical compensator (hereinafter, color) for compensating for coloring of an electric field control birefringence (hereinafter, also referred to as ECB) type liquid crystal display element (hereinafter, sometimes referred to as LCD) to improve display quality. Sometimes referred to as a compensator.) A liquid crystal display device using the retardation film has advantages such as light weight, thinness, and low cost. However, STN type LCDs have a problem that the response speed is low, and improvement studies are underway. To improve the response speed, it is effective to use a liquid crystal having a large birefringence Δn to reduce the cell gap. However, since a liquid crystal having a large Δn generally has a large wavelength dependence of Δn, a retardation film used together with a liquid crystal cell also has a large wavelength dependence of Δn, that is, a retardation film having a large wavelength dependence of retardation. Is known to be effective. When a liquid crystal cell having a high response speed, that is, a liquid crystal having a large Δn and a conventional retardation film are used, a liquid crystal display device having a high contrast cannot be obtained. Therefore, it is used for a high-speed response STN type liquid crystal display device. There is a need for a retardation film having wavelength dispersion characteristics that match the wavelength dispersion characteristics of birefringence of liquid crystal materials.

As a method for improving the wavelength dispersibility of a retardation film, Japanese Patent Laid-Open No. 5-107413 discloses a retardation film using polysulfone (hereinafter sometimes referred to as PSf) having high wavelength dispersion. It is disclosed. Similarly, JP-A-6-174923 discloses the use of polyarylate having high wavelength dispersion. However, since polysulfone and polyarylate have high glass transition temperatures, they are difficult to process and have a problem in industrial production. Further, since the wavelength dispersion characteristic of retardation differs depending on the liquid crystal material used for the liquid crystal cell, it may be necessary to control the wavelength dispersion of the retardation film.
JP-A-5-27119 and JP-A-6-13022
Japanese Unexamined Patent Publication No. 27 discloses that chromatic dispersion is controlled by a combination of optical anisotropic bodies having different chromatic dispersion values.

Next, in JP-A-4-500284, a side chain type liquid crystal polymer having a linear or cyclic main chain is used, and the same temperature dependence and liquid crystal molecules as those used in a liquid crystal cell are obtained. A retardation film having wavelength dependence is exemplified. It is disclosed that an aligned liquid crystal polymer film can be obtained by forming a liquid crystal polymer on the alignment film or applying an external field such as an electric field or a magnetic field to the liquid crystal polymer film. However, liquid crystal polymers have large refractive index anisotropy regardless of the main chain type or side chain type, and in order to obtain a retardation film with uniform retardation, strict control of the film thickness is required, so a large area is required. Was difficult to produce. In JP-A-5-257013, liquid crystal molecules are dispersed in a polymer film and stretched together with the polymer film to obtain wavelength dispersion with the same refractive index anisotropy as the liquid crystal molecules used in the liquid crystal cell. The retardation film that has been described. However, there is no description of specifically preferable wavelength dispersibility, and what kind of physical properties and structure of liquid crystal should be dispersed to what extent.

In Example 6 of Japanese Patent Publication No. 7-13683, there is shown an example in which a liquid crystal compound is blended with polyvinyl chloride to enhance wavelength dispersion. A substance having a low point cannot be used because of deformation and deterioration of optical properties when used in a high temperature environment. Further, Japanese Patent Laid-Open No. 7-13023 discloses a method of adjusting wavelength dispersion by adding a plasticizer to polycarbonate or polyarylate, but there is no description regarding addition of a dye that absorbs ultraviolet rays.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical anisotropic film having a high retardation wavelength dispersion and a liquid crystal display device using the optical anisotropic film, which can provide excellent black and white display. Especially.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a polymer (hereinafter sometimes referred to as a matrix polymer or simply a matrix) satisfies a specific condition. By mixing a dye or mixing a polymer liquid crystal and a dye in a polymer, an optically anisotropic film having a large wavelength dependence of retardation can be easily obtained without using a polymer having a large wavelength dispersion of retardation. The present invention has been completed and the present invention has been completed. That is, the present invention is an optically anisotropic film obtained by mixing [1] a polymer and a dye, the dye having no absorption peak in the visible region and an absorption peak in the ultraviolet region, and having an aspect ratio of Is defined as the ratio obtained by dividing the length of the long axis of the dye molecule by the length of the short axis of the dye molecule,
The aspect ratio of the dye molecule is 1.5 or more, and the retardation of the optically anisotropic film (measurement wavelength 546n
m) relates to an optically anisotropic film having a thickness of 50 to 3000 nm (hereinafter sometimes referred to as the first invention).
Furthermore, the present invention is [2] an optically anisotropic film obtained by mixing a polymer and a dye, wherein the dye does not have an absorption peak in the visible region and has an absorption peak in the ultraviolet region, And the retardation (measurement wavelength 546 nm) of the optically anisotropic film is 50 to 3000 nm (hereinafter sometimes referred to as the second invention). The present invention also provides [3] an optically anisotropic film obtained by mixing a polymer, a dye and a polymer liquid crystal, wherein the dye has no absorption peak in the visible region and has an absorption peak in the ultraviolet region. And the aspect ratio defined in claim 1 of the dye molecule is 1.5 or more, and the retardation (measurement wavelength 546 nm) of the optically anisotropic film is 5
It relates to an optically anisotropic film having a thickness of 0 to 3000 nm (hereinafter sometimes referred to as a third invention). Furthermore, the present invention is [4] an optically anisotropic film formed by mixing a polymer, a dye and a polymer liquid crystal, wherein the dye has no absorption peak in the visible region and has an absorption peak in the ultraviolet region. And an optical anisotropic film having dichroism and having a retardation (measurement wavelength 546 nm) of 50 to 3000 nm of the optically anisotropic film (hereinafter referred to as the fourth invention. is there). Further, in the present invention, the dye [5] is phase-separated from the polymer to form a domain, and the value of α defined by the following general formula (1) of the optically anisotropic film exceeds 1.06. It relates to the optically anisotropic film as described in [1] or [2].

## EQU3 ## α = R _F / R _D (1) [wherein, R _F is the value of the retardation measured with hydrogen F line (wavelength 486 nm), and R _D is sodium D line. It is the value of the retardation measured at (wavelength 589 nm). Further, in the present invention, the [6] dye and the polymer liquid crystal are phase-separated from the polymer to form a domain, and the value of α defined in [5] of the optically anisotropic film is 1.06. The optical anisotropic film according to [3] or [4]. Further, in the present invention, the [7] dye is compatible with a polymer, and the value of α defined in claim 5 of the optically anisotropic film exceeds 1.06 [1] or [2]. Of the optically anisotropic film. Further, the present invention provides
[8] The dye is compatible with a mixture of a polymer and a polymer liquid crystal, and the value of α defined in [5] of the optically anisotropic film exceeds 1.06 [3] or [4]. It relates to the optically anisotropic film described. Further, the present invention is characterized in that the [9] dye is adsorbed and oriented on a stretched polymer, and the value of α defined in [5] of the optically anisotropic film exceeds 1.06. It relates to the optically anisotropic film as described in [1] or [2]. Furthermore, the present invention provides [1
[0] The dye is adsorbed and oriented in a mixture of stretched polymer and polymer liquid crystal, and the value of α defined in [5] of the optically anisotropic film exceeds 1.06. [3]
Alternatively, it relates to the optically anisotropic film described in [4]. Further, the present invention provides the optical anisotropic body according to any one of [1] to [10], in which the retardation ratio (R ₄₀ / R ₀ ) of the [11] optical anisotropic film satisfies the following formula (2). It relates to a film.

Equation 4] _{0.900 <R 40 / R 0 <} 1.100 ··· (2) [ wherein, R ₀ is the measured film normal direction by using the Senarmont method (measuring wavelength 546 nm) with a polarizing microscope And R40 is the retardation measured when the film is tilted by 40 ° from the horizontal with the slow axis of the film as the rotation axis. The present invention also relates to [12] a liquid crystal display device using the optically anisotropic film according to any one of [1] to [11].

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the matrix polymer used in the present invention for explaining the present invention in detail will be explained. The polymer used in the matrix of the optically anisotropic film of the first invention or the second invention has an optical property or shape when the optically anisotropic film is used at a high temperature or at the temperature of the step of bonding with the liquid crystal cell. The polymer which does not change is preferably used, and the thermoplastic engineering polymer whose glass transition temperature is high to some extent, or the polymer to which a plasticizer is added, which has a certain high flow temperature is preferably used. The glass transition temperature or softening temperature of the polymer of the matrix is determined as the lower limit so that there is no deformation such as change of optical properties or shrinkage of the film within the temperature range in which the liquid crystal display is used, and it is considered as an optically anisotropic film. At this time, it is necessary to stretch while heating, and therefore, if the glass transition temperature is too high, it is industrially unfavorable, so the upper limit is determined.

The glass transition temperature or softening temperature required for the matrix is preferably 80 to 250 ° C.,
90 to 230 ° C. is more preferable, and 100 is particularly preferable.
~ 200 ° C.

Polymers satisfying these conditions include polycarbonate, polyarylate, cellulose diacetate,
Examples thereof include cellulose triacetate and ethylene vinyl alcohol copolymer, and preferably polycarbonate, polyarylate, and cellulose triacetate.

Next, when the polymer used for the matrix of the optically anisotropic film of the third or fourth invention, that is, when the dye and the polymer liquid crystal are mixed with the matrix, other than the above-mentioned polymer, A polymer having a small retardation may be used. In the optically anisotropic film of the third invention or the fourth invention, it was measured using the Senarmont method of a polymer film produced under the same conditions as the optically anisotropic film except that no dye or polymer liquid crystal was contained. Consider retardation as a matrix retardation.

The retardation of the matrix is represented by the product Δnd of the birefringence Δn of the matrix polymer and the film thickness d. It is not preferable to reduce the thickness of the film in order to reduce the retardation, since it adversely affects the handling of the film and the optical properties of the resulting optically anisotropic film. In order to reduce the retardation, it is preferable to reduce the birefringence of the matrix. Generally, the birefringence Δn due to the orientation of the polymer is expressed by the following equation (3) using the intrinsic birefringence Δn ⁰ of the polymer and the orientation function f.

## EQU5 ## Δn = Δn ⁰ × f (3) As a method of reducing the birefringence of a polymer, a polymer having a small intrinsic birefringence is used, or a polymer having a positive intrinsic birefringence and a polymer having a negative intrinsic birefringence are used. Examples of the method include a method of mixing the above polymers to reduce the apparent intrinsic birefringence and a method of reducing the orientation function.

As a polymer having a small intrinsic birefringence, polymethacrylic acid derivatives such as polymethylmethacrylate, poly-n-butylmethacrylate, poly-t-butylmethacrylate and polyglycolmethacrylate, polyacrylic acid, polymethylacrylate and polyethyl. Polyacrylic acid derivatives such as acrylate, polyvinyl acetate, polyvinyl butyrate, polyoxymethylphenylsilylene, etc., norbornene-ethylene copolymer (Mitsui Petrochemical Co., Ltd .: trade name APEL, etc.), norbornene resin (Nippon Synthetic) Rubber Co., Ltd .: Product name ART
ON), amorphous polyolefin (manufactured by Nippon Zeon Co., Ltd .: trade name ZEONEX, etc.), optical polyester resin (manufactured by Kanebo Co., Ltd.), acrylic-butadiene-styrene copolymer (manufactured by Toray Co., Ltd .: trade name Toyolac) Transparent grade, etc.) and the like. Among these, polymethylmethacrylate, poly-n-butylmethacrylate, poly-t-butylmethacrylate, norbornene-ethylene copolymer, optical polyester resin, amorphous polyolefin, and acryl-butadiene-styrene copolymer are preferable.

Next, when a polymer having a positive intrinsic birefringence and a polymer having a negative intrinsic birefringence are mixed and used as a matrix of the optically anisotropic film, it has a positive intrinsic birefringence. Examples of the polymer include polyvinyl chloride, polyvinylidene fluoride, vinylidene fluoride / trifluoroethylene copolymer, polyethylene oxide, polyphenylene oxide, and polycarbonate.Polymers having a negative intrinsic birefringence include poly Examples include methyl methacrylate and polystyrene.

A polymer having a positive or negative intrinsic birefringence, and a mixing ratio (weight ratio) in which the combination of compatible polymers and the apparent intrinsic birefringence are small is 20: polyphenylene oxide and polystyrene. 80-3
0:70, 30: 70-40: 60 for polyethylene oxide and polymethylmethacrylate, 5: 95-15: 85 for vinylidene fluoride / trifluoroethylene copolymer and polymethylmethacrylate, polyvinylidene fluoride and polymethylmethacrylate. Then 15:85 to 25: 7
5, 1 for polyvinyl chloride and polymethylmethacrylate
Examples are 5:85 to 25:75. Of these, combinations of polyphenylene oxide and polystyrene, which are easily soluble in a solvent, and combinations of polyethylene oxide and polymethylmethacrylate are preferred.

As a method for reducing the orientation function, a film obtained by mixing a dye, a polymer liquid crystal and a polymer is heated at a temperature above the glass transition temperature or softening point of the polymer and below the melting temperature of the polymer. A method of stretching is mentioned. Examples of polymers suitable for the method include polycarbonate, cellulose diacetate, cellulose triacetate, polystyrene, ethylene vinyl alcohol copolymer, polyethylene terephthalate, polyethylene naphthalate, and the like, preferably polycarbonate, cellulose triacetate, polyethylene terephthalate. , Polystyrene is exemplified.

Additives may be used for the purpose of imparting mechanical strength to these matrix polymers or improving the adhesiveness when they are laminated to LCD cells. The kind and amount of the additive are not particularly limited as long as they do not impair the object of the present invention.

In general, a substance having a unique color by strongly selectively absorbing or reflecting visible light is called a dye, but in the present invention, a compound having no absorption peak in the visible region and having an absorption in the ultraviolet region is called a dye. The dye used in the present invention is
It is essential that it has no absorption peak in the visible region and has absorption in the ultraviolet region. The absorption peak wavelength of the dye is 300 to
It is preferably in the range of 400 nm, more preferably 330 to 380 nm. Further, the dye used in the first invention or the third invention is a dye, when the aspect ratio is defined as a ratio obtained by dividing the length of the long axis of the dye molecule by the length of the short axis of the dye molecule. The aspect ratio of the molecule is 1.5 or more. The aspect ratio can be obtained by drawing a molecular structure so that the interatomic distance becomes a correct distance. In order to obtain the molecular structure, a molecular mechanics calculation using a computer is performed to optimize the drawn molecular structure, and then the long axis and the short axis of the molecule are obtained. The length of the long axis of the molecule in the present invention is defined as the interatomic distance between the atoms having the longest distance in the optimized molecular structure, and the length of the short axis of the molecule is orthogonal to the long axis of the molecule. It is defined as the distance between the atoms with the longest distance in the direction. In the present invention, to obtain the molecular structure, Chem 3D is used.
3.0 (Cambridge Scientific
Computing Inc. Company) is used. As a program used for optimizing the molecular structure, MOPAC
93 (manufactured by Fujitsu) is used, AM1 is used as a Hamiltonian parameter, and the default value is used as the convergence condition. Further, the dye used in the second invention or the fourth invention has dichroism in the ultraviolet region. The dichroic ratio of the dye is
It is defined as the ratio of the absorbance at the maximum absorption wavelength in the major axis direction of the dye molecule to the absorbance in the minor axis direction. The dichroic ratio can be determined by orienting the dye so that the order parameter is 0.8 or more, and measuring the absorbance in the alignment direction of the dye and the absorbance in the direction perpendicular to the alignment direction. First
The optically anisotropic film of the invention and the optically anisotropic film of the second invention substantially overlap. Similarly, the optically anisotropic film of the third invention and the optically anisotropic film of the fourth invention substantially overlap. In particular, when it is difficult to orient the dye and dichroism is not easily observed even when measuring the absorption spectrum, the aspect ratio obtained by dividing the length of the molecular long axis by the length of the molecular short axis. Can define the dye that can be used in the present invention. The dye that can be used in the present invention preferably has a dichroic ratio or an aspect ratio satisfying the following conditions. That is, the aspect ratio is 1.5 or more and 20 or less, preferably 1.8 or more and 15 or less. The dichroic ratio is preferably 2 or more and 50 or less, more preferably 5 or more and 30 or less.

The dyes which satisfy these conditions are not particularly limited, but may be Benzotriazol type, Benzophenon type, Pyr
Azoline, Diphenyl polyene, Binaphthyl polyen
e type, Biphenanthrenyl polyene type, Styrylbenzoxa
zol series, Stilbene series, Benzidine series, Benzothiazole
Series, Benzoxazole series, Benzimidazole series, Hydroxyaz
obenzene type, Aminoazobenzene type, Coumarin type, Nit
Examples include rodiphenylamine dyes and derivatives of these series of dyes. Further, a dye used as a fluorescent whitening agent, a fluorescent pigment or an ultraviolet absorber is also suitably used. Any dye that satisfies the above conditions can be used in the present invention. An example of a dye that can be used in the present invention is a dye handbook (Shin Okawara, Teijiro Kitao, Tsuneaki Hirashima, Ken Matsuoka, edited by Kodansha Scientific:
The dye numbers described in 1986, 1st edition) are shown in Table 1.

[0020]

[Table 1]

Next, the polymer liquid crystal used in the optically anisotropic film of the third or fourth invention, that is, the optically anisotropic film formed by mixing the dye, the polymer liquid crystal and the polymer will be described. The polymer liquid crystal preferably exhibits a nematic phase or a smectic phase. The temperature range showing the nematic phase or the smectic phase is preferably -30 ° C to 200 ° C, more preferably -30 to 150 ° C.
C., particularly preferably -30.degree. C. to 120.degree. A liquid crystal satisfying the above temperature range may be used alone, or two or more kinds of polymer liquid crystals may be mixed and used in order to keep the temperature range within the above range.

The high molecular weight liquid crystal used in the present invention is a liquid crystal having a high molecular weight, and includes what is called a liquid crystal oligomer. The preferable lower limit of the molecular weight or the degree of polymerization of the polymer liquid crystal is determined from the viewpoint of phase separation from the matrix polymer, and the preferable upper limit of the molecular weight or the degree of polymerization is determined from the viewpoint of light scattering. That is, if the molecular weight is too large, the particle size of the phase-separated polymer liquid crystal becomes longer than the wavelength of light in the matrix, and light scattering occurs, and if the molecular weight is too small, phase separation is difficult to occur and liquid crystal alignment does not occur. It is not preferable. The polymer liquid crystal used in the present invention preferably has a number average molecular weight of 1200 to 10,000,
The molecular weight of 1500 to 6000 is more preferable.

The polymer liquid crystal used in the present invention includes
Side chain type polymer liquid crystals and main chain type polymer liquid crystals are exemplified,
A side chain type polymer liquid crystal is preferable from the viewpoint of easy control of the molecular weight.

Examples of the side chain type polymer liquid crystal include those represented by the following general formula (4).

[Chemical 1] [In the formula, A is a group represented by the following general formula (5) or (6). In the general formula (5), —Si—O— is the main chain of the general formula (4), and may be cyclic or linear. In the general formula (6), —C—CH ₂ — is the main chain of the general formula (4), and the COO group is bonded to Sp ₁ . In the general formula (4), when A is the general formula (5),
R is an alkyl group having 1 to 6 carbon atoms or a phenylene group, and in the general formula (4), when A is the general formula (6), R
Is an alkyl group or an alkoxy group having 1 to 6 carbon atoms. In the general formula (4), Ar ₁ , Ar ₂ and Ar ₃ are
They are each independently a 1,4-phenylene group, a 1,4-cyclohexylene group, a pyridine-2,5-diyl group, a pyrimidine-2,5-diyl group or a derivative of these groups. Sp1 is an alkyl group or an alkoxy group having 2 to 8 carbon atoms. Sp ₂ and Sp ₃ are independently -CO
O -, - OCO -, - NCH -, - CHN -, - CH 2
_{-CH 2 -, - CH 2 -O} -, - O-CH 2 -, - N = N
-, A single bond (corresponding to a direct bond between Ar ₁ and Ar ₂ , or Ar ₂ and Ar ₃ ), or the following general formula (7)
Is a group represented by. k is an integer of 0 or 1 (corresponding to direct bonding of Ar ₂ and B when k is 0). B is a cyano group, a halogen, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, an acrylate group or a methacrylate group. ]

[0025]

[Chemical 2]

[Chemical 3]

[Chemical 4]

These side chain type polymer liquid crystals may be used alone or in a mixture. The side chain type polymer liquid crystal need not have a single side chain group, and may be a copolymerized polymer liquid crystal having different side chains.

As for the mixing ratio of the dye or polymer liquid crystal to the polymer matrix, if the ratio of the dye or the dye and the polymer liquid crystal is too large, the mechanical strength of the optically anisotropic film decreases and it becomes difficult to handle. There is an upper limit. On the other hand, if the ratio of the dye or the dye and the polymer liquid crystal is too small, the optical properties of the optically anisotropic film are difficult to develop, which is not preferable.

When the dye is mixed with the matrix polymer, the concentration of the dye [dye / (sum of dye and matrix polymer)] is preferably 0.01 to 20% by weight, more preferably 0.1 to 15% by weight. %, Particularly preferably 0.5 to 12% by weight. When the dye and the polymer liquid crystal are mixed in the polymer matrix, the concentration of the dye is preferably [dye / (sum of dye, polymer liquid crystal and matrix polymer)] and 0.01 to 20% by weight, More preferably 0.1 to 15% by weight, and particularly preferably 0.1.
The concentration of the polymer liquid crystal is [polymer liquid crystal / (sum of dye, polymer liquid crystal and matrix polymer)], preferably 0.01 to 20 wt%, and more preferably 0.1 to 20 wt%. -15% by weight, particularly preferably 0.5-1
It is 2% by weight.

Next, the forms of the dye or the dye and the polymer liquid crystal in the optically anisotropic film of the present invention will be described. In the optically anisotropic film of the present invention, the dye or the dye and the polymer liquid crystal may be phase-separated from the polymer matrix to form a domain or may be compatible with each other. The dye may be adsorbed on the polymer or the polymer and the polymer liquid crystal. Whether they are phase-separated, compatible or adsorbed is determined by the combination of the dye used and the polymer or polymer liquid crystal used. In the optically anisotropic film of the present invention, when the dye or the dye and the polymer liquid crystal are phase-separated from the matrix, visible light scattering occurs at the interface between the dye or the mixture of the dye and the polymer liquid crystal and the matrix. there is a possibility. In the optically anisotropic film of the present invention, it is preferable that internal scattering due to scattering at these interfaces is small. This is because the scattered light generally changes its polarization state, so that the characteristics may deteriorate in the case of an optically anisotropic film having large internal scattering, and the visible light transmittance may deteriorate. When it is desired to make the dye or the dye and the polymer liquid crystal compatible with each other in the optically anisotropic film of the present invention, or to adsorb the dye to the polymer or polymer and the polymer liquid crystal, a known compatibilizer or the like is used. May be.

In the optically anisotropic film of the present invention, when the dye or the dye-polymer liquid crystal domain is formed, the major axis length of the dye or the dye-polymer liquid crystal domain is 20 to 500 nm. Is preferred and 3
0 to 400 nm is more preferable.

Retardation observed from the direction normal to the optically anisotropic film of the present invention (measurement wavelength 546 nm)
Is 50 to 3000 nm, preferably 100 to 2
It is 500 nm.

As an index showing the wavelength dispersion of the retardation of the optically anisotropic film of the present invention, the F line of hydrogen (wavelength 486n is used by using the Senarmont method from the normal direction of the film.
Retardation R _F measured in m) and D of sodium
The ratio α = R _F / R _D of the retardation R _D measured with the line (wavelength 589 nm) is used. In the present invention, the index α indicating chromatic dispersion is preferably 1.061 to 1.300,
An optically anisotropic film having a thickness of 1.065 to 1.250 is more preferably used.

As an index showing the characteristics of the optically anisotropic film exhibiting a good viewing angle characteristic, the retardation (R measured by the light of 546 nm in the normal direction of the film) is used.
₀ ) and the ratio R ₄₀ / R _{0 of the} retardation (R ₄₀ ) when the film is inclined 40 degrees from the horizontal plane around the slow axis of the film. In the optically anisotropic film of the present invention, the ratio is preferably larger than 0.900 and smaller than 1.100. The ratio can be appropriately selected depending on the viewing angle dependence of liquid crystal cells used in combination.

Next, the method for producing the optically anisotropic film of the present invention will be described. The optically anisotropic film of the present invention is obtained by mixing a polymer and a dye or a polymer liquid crystal and a dye and a polymer liquid crystal, forming the film, and then stretching the film (hereinafter referred to as the first production method). I have something to say). It is also obtained by mixing a polymer or a polymer and a polymer liquid crystal, forming a film, stretching the film, and adsorbing a dye on the stretched film (hereinafter,
It may be called the second manufacturing method). As the method for mixing the dye or the mixture of the dye and the polymer liquid crystal and the matrix polymer of the first production method, it is preferable to mix them in a solution state in order to uniformly mix them. Specifically, a method may be mentioned in which a polymer is suspended or dissolved in a solvent, and a dye or a dye and a polymer liquid crystal are suspended or dissolved and mixed. The solvent used in the present invention preferably has a high solubility in the polymer.

Regarding the film formation method of a film comprising a dye and a matrix or a dye, a liquid crystal and a matrix, a solvent casting method in which a dye, a liquid crystal or a matrix polymer is cast in a solvent, a kneading in a solid state and an extruded film from a die or the like Examples thereof include an extrusion molding method, a calendering method in which a film is kneaded in a solid state and then a calendar roll is used, and a press molding method in which a film is pressed by a press or the like. Among these, the solvent casting method, which is excellent in film thickness accuracy, is preferable. The thickness of the film after film formation is not particularly limited,
If it is too thin, the mechanical strength is adversely affected, and if it is too thick, the evaporation rate of the solvent when the film is formed by the solvent casting method is slowed and the productivity is deteriorated. As the thickness of the film after film formation,
20 to 500 μm is preferable, and 50 to 3 is more preferable.
It is 00 μm.

The second embodiment of the optically anisotropic film of the present invention
As the production method of (3), the dye may be adsorbed on the film formed and stretched by the same method as the first production method except that the dye is not mixed. Regarding the method for adsorbing the dye, for example, a method of dissolving the dye in a good solvent for the dye in a poor solvent for the stretched film, impregnating the stretched film with the dye in the dye solution, or a softening temperature of the film or less than a melting point of the dye or more Examples thereof include a method of melting a dye at a temperature and impregnating the stretched film with the dye in the dye melt, and a method of impregnating the stretched film with a dye in a powder form.

As the stretching method when the film is stretched while being heated after the film formation, the same method can be used except for the optically anisotropic film described in [11]. The tenter stretching method, the inter-roll stretching method, and the inter-roll compression stretching. The law is exemplified. The tenter stretching method and the inter-roll stretching method are preferable from the viewpoint of uniformity of the film surface. The method of heating the film is not particularly limited.

A known method can be used as a stretching method for obtaining the optically anisotropic film described in [11]. For example, (A) when the film formed in the film forming step is uniaxially stretched and heat-relaxed at a glass transition temperature or a softening temperature or higher, as shown in JP-A-6-3009116, the film is parallel to the film surface. And a method of shrinking the stretching axis direction while suppressing the elongation in the direction perpendicular to the stretching axis, (B) uniaxially stretching the film prepared in the film forming step, and forming a film having heat shrinkability on at least one surface thereof. A method of laminating the heat-shrinkable film so that the heat-shrinking axis of the film is orthogonal to the stretching axis of the uniaxially stretched polymer film, and heating the obtained bonded body to heat-shrink, or (C ) As shown in JP-A-5-157911, a film having heat shrinkability on at least one side of the film prepared in the film preparing step is
Laminating the heat-shrinkable film so that the heat-shrinkable axis is orthogonal to the stretch axis of the uniaxially stretched polymer film,
Examples include a method of stretching the obtained bonded body. Among these, the methods (A) and (B) are preferable in terms of mass productivity and cost.

The method for uniaxially stretching the film is as follows.
Although any of the above methods may be used, a method of uniaxially stretching by a roll-roll stretching method or a tenter stretching method is preferable in terms of controllability of the refractive index in the thickness direction and uniformity of retardation in the film plane. .

The heating temperature for stretching the film by these stretching methods is appropriately selected depending on the softening temperature of the matrix polymer used and the transition temperature of the dye or liquid crystal. Regarding the draw ratio, if the draw ratio is low, the orientation of the dye or liquid crystal becomes insufficient, and if it is too high, the film thickness becomes too thin and the handling becomes difficult, which is not preferable. Specifically, it is preferably 1.1 to 20 times, more preferably 1.2 to 15 times. The stretching speed and the cooling rate after stretching are not particularly limited.

[0041]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Polymer liquid crystals are used for elemental analysis, infrared absorption spectrum, ¹ H-NM
The structure was confirmed from the R spectrum, and the molecular weight was confirmed from gel permeation chromatography (GPC). The absorption peak wavelength of the dye is measured by a spectrophotometer (U
-350) was used to directly measure the transmission spectrum of the dye / polymer mixed film. When the absorbance of the film was too large and the absorption peak wavelength was unknown, 1 part by weight of the dye was mixed with 99 parts by weight of KBr powder, and the mixture was pressurized to form a pellet having a thickness of about 1 mm, and then the transmission spectrum was measured. . The aspect ratio of the dye is the chemical structure drawing software (Cambridge S
ChemDraw 2.1.3 and Chem 3D 3.0 from Scientific Computing Inc.) and draw MO as described above.
The structure was optimized using PAC93, the obtained results were drawn in Chem 3D 3.0, and the length of the major axis of the molecule was calculated by dividing the length of the major axis by the length of the minor axis. The retardation of the optically anisotropic film of the present invention is 400, 420, 44.
0, 460, 480, 500, 525, 550, 57
Polarization microscope equipped with a spectroscope using a λ / 4 plate of 5, 600, 650, 700, 800 nm [Oak Seisakusho Co., Ltd.
Manufactured by TFM120-AFT] using the Senarmont method. The value of α defined by the general formula (1), which indicates the wavelength dispersion of the optically anisotropic film, is the retardation measured by the Senarmont method, and is represented by a graph drawing software (WaveMe
Curve fitting was performed using the Lorentz equation (Equation 8 below) with Igol Pro3.0 manufactured by trics, and using the fitting coefficient obtained as a result of the fitting, 48
Retardation values at 6 nm and 589 nm were calculated using the formula (8), and calculated from the formula (1).

[Equation 6] [In Expression (8), λ is the measurement wavelength, R (λ) is the retardation at the measurement wavelength, and A, B, and λ ₀ are fitting coefficients. The viewing angle dependence of the optically anisotropic film is the retardation and the slow axis around the retardation axis of the film observed with the light having a wavelength of 546 nm using the Senarmont method using a polarization microscope equipped with a tilting jig. The film was evaluated by measuring the retardation when the film was tilted.

Example 1 A cyclic siloxane oligomer (having a nematic phase, a nematic / isotropic phase transition temperature of 121 ° C., and a polystyrene-equivalent number average molecular weight of 2030) and a fluorescent whitening agent (manufactured by Sumitomo Chemical Co., Ltd., Product name Whitefluor P
HR, absorption peak wavelength 375 nm, aspect ratio 4.
6) and polymethyl methacrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumipex MHF, glass transition temperature 122 ° C.), liquid crystal oligomer: dye: polymethyl methacrylate = 0.9: 10: 90 (weight ratio). When the mixture was mixed with and stretched at 100 ° C. by a factor of 2, an optically anisotropic film having α = 1.102 defined by the above formula 1 was obtained. When the obtained optically anisotropic film is used in combination with an STN cell, a good black and white display is obtained.

Comparative Example 1 An optically anisotropic film was obtained in the same manner as in Example 1 except that the optical brightener was not mixed. The value of α of the obtained optically anisotropic film was 1.082, which showed smaller wavelength dispersion as compared with Example 1 in which a dye was mixed.

Example 2 Optical brightening agent (trade name: White, manufactured by Sumitomo Chemical Co., Ltd.)
10 parts by weight of Fluor B, absorption peak wavelength of 369 nm, aspect ratio of 1.9) and 90 parts by weight of a polycarbonate resin (trade name: Panlite C-1400 manufactured by Teijin Ltd.) were dissolved in methylene chloride to a concentration of 20% by weight. Mixed. The solution obtained is cast on a glass plate to a thickness of 100.
A film of μm was obtained. When the obtained film was stretched 1.5 times at 130 ° C., an optically anisotropic film with α = 1.075 was obtained. When the obtained optically anisotropic film is used in combination with an STN cell, a good black and white display is obtained.

Comparative Example 2 The retardation wavelength dispersion of a polycarbonate retardation film (Sumitomo Chemical Co., Ltd., trade name SEF480430) was α = 1.060. Further, when the wavelength dispersion of the retardation of the polysulfone retardation film was measured, α = 1.099
Met.

Example 3 UV absorber (Sumitomo Chemical Co., Ltd., trade name Sumi
Sorb 310, absorption peak wavelength 345 nm, aspect ratio 3.5) 10 parts by weight and polycarbonate resin (manufactured by Teijin Ltd., trade name Panlite C-1400) 90 parts by weight are dissolved in methylene chloride to 20% by weight. Mixed. The solution obtained is cast on a glass plate to give a thickness of 10
A 0 μm film was obtained. The obtained film is 140 ° C
When the film was stretched 1.5 times with, an optically anisotropic film with α = 1.078 was obtained. When the obtained optically anisotropic film is used in combination with an STN cell, a good black and white display is obtained.

Example 4 UV absorber (Sumitomo Chemical Co., Ltd., trade name Sumi
Sorb 310, absorption peak wavelength 345 nm, aspect ratio 3.5) 10 parts by weight and polyarylate resin (manufactured by Unitika Ltd., trade name U-100) 90 parts by weight are dissolved and mixed in methylene chloride to 20% by weight. did. The obtained solution was cast on a glass plate to obtain a film having a thickness of 100 μm. When the obtained film was stretched 1.2 times at 195 ° C., an optically anisotropic film with α = 1.086 was obtained. When the obtained optically anisotropic film is used in combination with an STN cell, a good black and white display is obtained.

[0048]

EFFECT OF THE INVENTION The optically anisotropic film of the present invention has a large wavelength dispersion of retardation, and when used in combination with a high-speed STN type liquid crystal cell, a liquid crystal display device exhibiting excellent black and white display can be obtained. Further, the optically anisotropic film of the present invention is easier to manufacture than conventional retardation films made of polysulfone or polyarylate.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09K 19/60 C09K 19/60 G02F 1/133 500 G02F 1/133 500 1/1335 510 1/1335 510 // B29L 7:00 B29L 7:00 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 5/30

Claims (14)

(57) [Claims] 1. An optically anisotropic film formed by mixing a polymer and a dye, the dye having no absorption peak in the visible region and an absorption peak in the ultraviolet region, and having an aspect ratio of When defined as a ratio obtained by dividing the length of the major axis by the length of the minor axis of the dye molecule, the aspect ratio of the dye molecule is 1.5 or more, and the retardation of the optically anisotropic film. (Measurement wavelength 546 nm) is 50 to 3000 nm
Der is, dye to form a polymer and phase separation to domain
And is defined by the following general formula (1) of the optically anisotropic film.
Optically anisotropic film in which the value of α is to wherein Rukoto exceed 1.06. α = R _F / R _D (1) [ wherein , R _F was measured by hydrogen F line (wavelength 486 nm)
Retardation value, R _D is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 2. An optically anisotropic film obtained by mixing a polymer and a dye, wherein the dye has no absorption peak in the visible region and has an absorption peak in the ultraviolet region and has dichroism. and, retardation of the optical anisotropic film (measurement wavelength 546nm) is Ri 50~3000nm der, a dye
Optically anisotropic because it forms a domain by phase separation with a polymer
The value of α defined by the following general formula (1) of the body film is
Optically anisotropic film characterized Rukoto exceed 1.06. α = R _F / R _D (1) [ wherein , R _F was measured by hydrogen F line (wavelength 486 nm)
Retardation value, R _D is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 3. An optically anisotropic film formed by mixing a polymer, a dye and a polymer liquid crystal, wherein the dye has no absorption peak in the visible region and has an absorption peak in the ultraviolet region. and an aspect ratio as defined in claim 1 molecule of 1.5 or more, retardation of the optical anisotropic film (wavelength 546 nm) is Ri 50~3000nm der,
The dye and polymer liquid crystal phase-separate from the polymer to form domains.
The following general formula (1) of the optically anisotropic film is formed.
Optically anisotropic film in which the value of α in the definition is characterized Rukoto exceed 1.06. α = R _F / R _D (1) [ wherein , R _F was measured by hydrogen F line (wavelength 486 nm)
Retardation value, R _D is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 4. An optically anisotropic film formed by mixing a polymer, a dye and a polymer liquid crystal, wherein the dye does not have an absorption peak in the visible region but has an absorption peak in the ultraviolet region, and it has two colors. And the retardation (measurement wavelength 546 nm) of the optically anisotropic film is 50 to 3000 nm.
The dye and polymer liquid crystal phase-separate from the polymer,
The following general formula of the optically anisotropic film
Optically anisotropic film in which the value of α defined by (1), characterized in Rukoto exceed 1.06. α = R _F / R _D (1) [ wherein , R _F was measured by hydrogen F line (wavelength 486 nm)
Retardation value, R _D is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 5. Optical anisotropic body made by mixing polymer and dye
It is a film, and the dye has an absorption peak in the visible region.
, Has an absorption peak in the ultraviolet region, and has an aspect ratio
Divide the length of the long axis of the dye molecule by the length of the short axis of the dye molecule
Aspect ratio of the dye molecule, defined as the ratio obtained
Is 1.5 or more, and the letter difference of the optically anisotropic film is
(Measurement wavelength 546 nm) is 50 to 3000 nm
, The dye is compatible with the polymer, and
The value of α defined by Rum's general formula (1) is 1.06.
Optical anisotropic film characterized by exceeding. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 6. Optical anisotropic body made by mixing polymer and dye
It is a film, and the dye has an absorption peak in the visible region.
It has an absorption peak in the ultraviolet region and has dichroism
And the retardation of the optically anisotropic film (measurement
Wavelength 546nm ) Is 50 to 3000 nm, and the dye is
It is compatible with polymers and is generally
If the value of α defined by equation (1) exceeds 1.06,
A characteristic optical anisotropic film. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 7. Do not mix polymer, dye and polymer liquid crystal.
It is an optically anisotropic film that absorbs the dye in the visible region.
Has no peaks and has an absorption peak in the ultraviolet region,
The aspect ratio defined in claim 1 of the elementary molecule is 1.5 or more.
The above is the retardation of the optically anisotropic film.
(Measurement wavelength 546 nm) is 50 to 3000 nm,
The dye is compatible with the mixture of polymer and polymer liquid crystal,
The α of the anisotropic film defined by the following general formula (1)
An optical anisotropic fiber characterized by a value exceeding 1.06
Rum. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 8. Do not mix polymer, dye and polymer liquid crystal.
It is an optically anisotropic film that absorbs the dye in the visible region.
Has no peaks, has an absorption peak in the ultraviolet region, and has two colors
Of the optically anisotropic film,
(Measurement wavelength 546 nm) is 50 to 3000 nm
The dye is compatible with the polymer and polymer liquid crystal mixture.
Is defined by the following general formula (1) of the optically anisotropic film.
Optical anisotropy characterized in that the value of α exceeds 1.06
Body film. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 9. An optical anisotropic body prepared by mixing a polymer and a dye.
A film, the dye have an absorption peak in the visible region
, Has an absorption peak in the ultraviolet region, and has an aspect ratio
Divide the length of the long axis of the dye molecule by the length of the short axis of the dye molecule
Aspect ratio of the dye molecule, defined as the ratio obtained
Is 1.5 or more, and the letter difference of the optically anisotropic film is
(Measurement wavelength 546 nm) is 50 to 3000 nm
And the dye is adsorbed and oriented on the stretched polymer,
Α defined in the following general formula (1) of the optically anisotropic film
Optical anisotropic body characterized in that the value of exceeds 1.06.
Film. α = R _F / R _D (1) [ wherein , R _F was measured by hydrogen F line (wavelength 486 nm)
Retardation value, R _D is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 10. Optical anisotropy formed by mixing polymer and dye
Body film, the dye has an absorption peak in the visible region
It has an absorption peak in the ultraviolet region and has dichroism
And the retardation of the optically anisotropic film (measurement
Wavelength 546 nm) is 50 to 3000 nm, and the dye is
It is adsorbed and oriented on the stretched polymer, and
The value of α defined by Rum's general formula (1) is 1.06.
Optical anisotropic film characterized by exceeding. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 11. Mixing polymer, dye and polymer liquid crystal
Is an optically anisotropic film, and the dye absorbs in the visible range.
It has no peak but an absorption peak in the ultraviolet region.
The aspect ratio defined in claim 1 of the dye molecule is 1.5.
The above is the retardation of the optically anisotropic film.
(Measurement wavelength 546 nm) is 50 to 3000 nm,
Adsorption on a mixture of polymer and polymer liquid crystal in which the dye is stretched
The following general formula (1) of the optically anisotropic film
Characterized in that the value of α defined exceeds 1.06
Optical anisotropic film. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 12. The method according to claim 12, Mixing polymer, dye and polymer liquid crystal
Is an optically anisotropic film, and the dye absorbs in the visible range.
It has no peak and has an absorption peak in the ultraviolet region.
It has chromaticity, and the letter day of the optically anisotropic film
(Measurement wavelength 546 nm) is 50-3000 nm
Yes, in a mixture of polymer and polymer liquid crystal with stretched dye
Adsorbed and oriented, the following general formula of optically anisotropic film
The value of α defined in (1) exceeds 1.06.
Optical anisotropic film to be used. α = R _F / R _D ... (1) [In the formula, R _F Was measured with hydrogen F line (wavelength 486 nm)
Retardation value, R _D Is sodium D line
Retardation value measured at (wavelength 589 nm)
is there. ] 13. The optical anisotropic film according to any one of claims 1 to 12, the retardation ratio of optically anisotropic film (R ₄₀ / R ₀₎ is characterized by satisfying the following formula (2) . 0.900 <R ₄₀ / R ₀ <1.100 (2) [wherein R ₀ is a letter measured from the film normal direction using the Senarmont method (measurement wavelength 546 nm) with a polarization microscope. R ₄₀ is the retardation when measured with the slow axis of the film as the axis of rotation and the film inclined at 40 ° from the horizontal. ] 14. A liquid crystal display device using the optically anisotropic film according to any one of claims 1 to 13 .