JP2003344657A - Birefringence film, manufacturing method thereof optical compensation layer integral polarizing plate, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxial birefringence film which can form a liquid crystal display device or the like which excels in optical compensation performance, and which has a negative birefringence characteristics, while it realizes the thinness of a retardation film, laminated polarizing plate and a liquid crystal display device or the like. <P>SOLUTION: A solution which has at least one kind of polymer chosen from the group consists of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyetherimide dissolved in a solvent is coated on a base material. This birefringence film is formed after drying by using a base material which goes through a dimensional change in the process to be made into a film. Its birefringence is within the range of 0.0005 to 0.5, and also this birefringence satisfies all the formulas from (1) to (3): nx, ny is a main refraction factor in a flat surface of a film, nz is a refractive index of the thickness direction of a film, and (d) is the thickness of a film. Where, the following inequalities are satisfied: nx>ny>nz (1) 3nm≤(nx-ny)×d (2) (nx-nz)/(nx-ny)>1 (3). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a retardation plate suitable for optical compensation of a liquid crystal cell, and a birefringent film capable of forming a laminated polarizing plate and a liquid crystal display device using the retardation plate.

[0002]

2. Description of the Related Art Conventionally, biaxial retardation plates for optical compensation of various liquid crystal display devices have been produced by using a polymer film stretching technique. For example, a stretching method between rolls, a compression stretching method between rolls, a method of producing by a tenter transverse uniaxial stretching method (Japanese Patent Laid-Open No. 3-33719), a film strength, and an anisotropic condition are used. A method of obtaining a retardation plate by axial stretching (Japanese Patent Laid-Open No. 3-24502) and the like are disclosed. Further, a uniaxially stretched polymer film having a positive optical anisotropy and a biaxially stretched polymer film having a negative optical anisotropy with a small in-plane retardation value are used together and arranged as an optical compensation plate. There is also a method of setting (JP-A-4-
194820). Using such stretching technique, etc., nx
A retardation film having a characteristic of ≧ ny> nz is produced, and the retardation film is arranged between a driving cell and a polarizer to form a liquid crystal display device in which the liquid crystal cell has a viewing angle compensation.

However, the above-described stretching technique requires a precise stretching operation, and requires detailed setting of the stretching conditions such as the stretching ratio and axis and precise control.
It is also necessary to solve the Boeing phenomenon. For further stretching, the film cannot be stretched unless the film has a certain thickness, which causes a problem that the stretched retardation film or the liquid crystal display device becomes thicker.

On the other hand, conventionally, as a retardation plate for optical compensation of various liquid crystal display devices, a polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide,
It has been made by coating on an inorganic compound (SUS belt, thin copper plate, glass, Si wafer, etc.). For example, U.S. Pat. Nos. 5,344,916, 5,395,918 (Tokukaihei 8-511812), and 5,48.
No. 0,964 discloses a method of coating a Si wafer with polyimide to form a negative birefringent film, and the like. In US Pat. No. 5,580,950, a film of polyimide is used to form a negative birefringent film (nx≈ny> n).
A method of making z) is also disclosed.

Also, US Pat. No. 6,074,709 discloses a negative compound obtained by laminating a polyimide layer on glass, an optically isotropic polymer layer, an anisotropic polymer layer or an anisotropic ceramic layer. A wide-angle layer having a refraction layer (nx≈ny> nz) is disclosed.

As described above, conventionally, a retardation film is produced by coating a polymer solution made of polyimide or the like on an inorganic compound or laminating a polyimide layer on a support made of glass, polymer or ceramic. Then, by disposing this between the drive cell and the polarizer, a liquid crystal display device in which the viewing angle of the liquid crystal cell is compensated is formed.

[0007]

However, when the retardation film produced by these methods is used as an optical film, it is transferred to an intended use after being coated once on an inorganic compound. Since it is necessary to go through several steps such as winding as a self-supporting film, there is a problem that mass productivity is poor. There is also a problem that the cost of the inorganic compound used as the base material is high. Also,
The above-mentioned Japanese Patent Publication No. 8-511812 discloses a uniaxial retardation plate using polyimide. In this case, 0n
There is a problem that only a negative birefringent retardation plate having the characteristic of m≈ (nx−ny) · d can be produced.

The present invention has been made in view of the above-mentioned problems of the prior art. A liquid crystal display device, etc., which is excellent in optical compensation performance while enabling the thickness reduction of a retardation plate, a laminated polarizing plate, a liquid crystal display device, etc. It is an object of the present invention to provide a biaxial birefringent film having a negative birefringence capable of forming a film, an optical compensation layer-integrated polarizing plate using the same, and a method for producing the birefringent film.

[0009]

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive studies by the present inventors, at least one selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide. It was found that a thin biaxial birefringent film can be obtained by coating, drying and film-forming the polymer of (1) on a substrate whose dimension changes, and completed the present invention.

That is, according to the present invention, a solution prepared by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent is applied to a substrate, After drying, in the process of forming a film,
A birefringent film formed using a dimensional-change base material, the birefringence of which is in the range of 0.0005 to 0.5 and which satisfies all of the following formulas (1) to (3). The present invention provides a birefringent film characterized by the above. nx>ny> nz (1) 3 nm ≦ (nx-ny) · d (2) (nx-nz) / (nx-ny)> 1 (3) (where nx, ny in formulas (1) to (3)) Is the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction,
d is the film thickness. )

In the birefringent film, it is preferable that the maximum dimensional change rate of the base material when dried is 1% or more.

In the birefringent film, the base material may be a protective film material for a polarizing plate, or the base material may be a polarizer formed by stretching a polyvinyl alcohol film.

The present invention also provides a polarizing plate integrated with an optical compensation layer, which is a combination of the above birefringent film and a polarizer or a polarizing plate.

The present invention also provides a liquid crystal display device characterized in that the birefringent film or the polarizing plate integrated with an optical compensation layer is arranged on at least one side of a liquid crystal cell, and the birefringent film or the optical compensation film. A self-luminous display device using a layer-integrated polarizing plate.

Further, in the present invention, a solution prepared by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent is applied to a substrate, A method for producing a birefringent film which is formed into a film after drying, wherein the dimensional change rate of the substrate from immediately after coating to immediately after drying is 1% or more. To do. According to this manufacturing method, a birefringent film having a refractive index relationship of nx>ny> nz can be easily manufactured.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The birefringent film of the present invention is based on a solution prepared by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent. A birefringent film having a birefringence of 0.0005, which is formed by using a base material that changes in dimension in a process of coating the material, drying it, and forming a film.
Is in the range of 0.5 to 0.5 and the following equations (1) to (3)
It satisfies all of the above. nx>ny> nz (1) 3 nm ≦ (nx-ny) · d (2) (nx-nz) / (nx-ny)> 1 (3) (where nx, ny in formulas (1) to (3)) Is the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction,
d is the film thickness. )

The birefringent film produced by the method of the present invention, as shown in FIG. 4, extends in the direction perpendicular to the axis in the thickness direction of the film and is contained in the thickness of the film. The axis extending in the direction showing the maximum value among the refractive indexes along the axis is the main axis, the refractive index in the main axis direction is nx, and the refractive index in the direction perpendicular to both the main axis and the axis in the thickness direction. Is ny, and the refractive index along the thickness axis is n.
where z is z and the film thickness is d, the characteristics represented by the formula (1); nx>ny> nz, and the relation of the formula (2); 3 nm ≦ (nx−ny) · d, Relationship of equation (3);
(Nx-nz) / (nx-ny)> 1 are all satisfied. By using this method, a biaxial retardation plate can be easily obtained.

In the method described in Japanese Patent Publication No. 8-511812 mentioned above, a uniaxial retardation plate using polyimide is disclosed. Here, 0 nm≈ (nx-ny) .d.
Only a negative birefringent retardation plate having the above characteristic can be produced. On the other hand, the birefringent film of the present invention has the formula (1)
It is a biaxial retardation plate having the above characteristics, and has an advantage that it can be easily manufactured by using the method of the present invention.

In the present invention, the birefringence (Δn)
Is defined by the following equation. Δn = (nx−nz) · d / thickness

In the present invention, the value of the birefringence (Δn) of the birefringent film is preferably in the range of 0.0005 to 0.5, and when it is less than 0.0005, it is a thick retardation plate. When it exceeds 0.5, a thin retardation plate is obtained and it becomes difficult to control the retardation. Therefore, in order to obtain a thin biaxial retardation plate with excellent productivity, the value of Δn is preferably 0.001 to 0.2, more preferably 0.002 to 0.
It is preferably in the range of 15.

The thickness of the birefringent film is not particularly limited, but from the viewpoint of providing a film which is excellent in the viewing angle compensation function and uniform, while achieving a thin liquid crystal display device,
The thickness is preferably 1 to 50 μm, more preferably 0.5 to 30 μm, and further preferably 1 to 20 μm.

When the birefringent film of the present invention is formed,
As materials, polyamide, polyimide, polyester,
At least one polymer selected from the group consisting of polyetherketone, polyamideimide and polyesterimide is used. These polymers are suitable as a material for the biaxial retardation plate because they have excellent heat resistance and chemical resistance, are highly rigid, and have excellent transparency.

The above-mentioned polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide are not particularly limited, and any conventionally known polymer material may be used as long as it satisfies the birefringent film characteristics of the present invention. They can be used and can be used alone or in any combination. The molecular weight of these polymers is not particularly limited, but the weight average molecular weight (Mw) is 1,0.
The range of 00 to 1,000,000 is preferable, and the range of 2,000 to 500,000 is more preferable.

The polyimide used as the polymer material is 0.001 used in the negative birefringent layer of the liquid crystal display described in JP-A-8-511812.
Prepared from an aromatic dianhydride and a polyaromatic diamine represented by the following general formula, having a negative birefringence value of
Soluble polyimide that is soluble in a solvent is preferably used.

[0025]

[Chemical 1]

[Wherein G and G ′ are covalent bonds, CH ₂
Group, C (CH ₃ ) ₂ group, C (CX ₃ ) ₂ group (X is halogen), CO group, O atom, S atom, SO ₂ group, Si
(R) ₂ groups (R is H, independently selected from the group consisting of phenyl having 1 to 20 carbon atoms, substituted phenyl, alkyl and substituted alkyl), and N (R) groups (R groups are as defined above. And A is hydrogen, halogen, nitro, cyano or alkyl having 1 to 20 carbon atoms, substituted alkyl, thioalkyl, alkoxy, substituted alkoxy, aryl, substituted aryl, aliphatic or aromatic ester. And a mixture thereof; B is halogen, C _1-3 alkyl, C _1-3 alkyl halide, phenyl or substituted phenyl (substituents on the phenyl ring are halogen, C _1-3 alkyl, C _{1- 3}
Selected from the group consisting of alkyl halides and mixtures thereof; z is an integer from 0 to 3; n is an integer from 0 to 4; and p and q are 0 to 3 and 1 to 3, respectively.
Is a whole number, and when p and q are greater than 1, the linking group between the benzyl or substituted benzyl groups is G ′; and the negative birefringence value of the film is G, G ′, B and A, and n,
The degree of in-plane orientation, which is determined by controlling the degree of in-plane orientation of the polyimide by selecting the values of p, q, and z, affects the rigidity and linearity of the polyimide main chain, And the higher the linearity, the higher the negative birefringence value of the polyimide. ]

As the above-mentioned dianhydride and aromatic diamine, those described in JP-A-8-511812 can be appropriately used.

Further, as the polyether ketone used as the polymer material, there is polyaryl ether ketone. The polyaryletherketone is one having an ether group (-O-) and a ketone group (C (= O)) in a repeating unit, and these are linked by an aryl group,
The general formula is represented by the following formula (Formula 2).

[0029]

[Chemical 2] (In the formula, F is a fluorine atom, A ′ is a halogen atom,
A lower alkyl group or a lower alkoxy group, x and y are integers from 0 to 4, and m is 0 or 1. Also,
r represents the degree of polymerization, and R ¹ is a group represented by the general formula (Formula 3). )

[0030]

[Chemical 3] (In the formula, z and x ′ are integers of 0 to 4, s is 0 or 1, and R ² is a divalent aromatic group. A ′ and F
Is the same as (Chemical Formula 2). )

Among them, in the general formula (Formula 2), y = 0 is preferable, and y = 0 and x ′ = 0 is more preferable.

In the above general formula (Formula 3), 2
The valent aromatic group (R ² ) is preferably any of the following 6 kinds.

[0033]

[Chemical 4]

Specific examples of such preferable polyaryl ether ketones include those represented by the following structural formula (Formula 5) or (Formula 6). r is the degree of polymerization.

[0035]

[Chemical 5]

[0036]

[Chemical 6]

When the birefringent film of the present invention is produced,
Applying a polymer material such as polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide on a base material that changes in dimension and drying, by utilizing the difference in shrinkage within the surface of the base material. The in-plane refractive index difference is given to the polymer material. The base material preferably has a dimensional change rate of 1% or more when dried, and is preferably 3% or more, and more preferably 5% or more in order to obtain a uniform optical compensation film. After coating, the substrate is fixed or stretched in at least one direction, or is dried without fixing the substrate.

In the present invention, the dimensional change rate of the substrate is the maximum dimensional change rate from immediately after coating to immediately after drying and is expressed as follows. Dimensional change rate (%) = | 1-maximum dimension due to heat treatment / initial dimension | x 100

As the above-mentioned substrate, a glass transition point (T
Polymer film with low g), polymer film with high elastic modulus, base material with linear expansion equal to or larger than that of the material, base material with high heat transfer coefficient, base material with high aspect ratio, thin base material and so on. A plastic base material is preferable as the base material because the dimensional change rate can be easily controlled.

To give the substrate shrinkage, for example,
A method of drying without fixing the base material to give shrinkage in all directions, a method of fixing at least one direction or more to have shrinkage, a method of utilizing linear expansion of a metal belt,
A method of controlling shrinkage by fixing the tenter during film transport,
The method is not limited, such as a method of expanding the substrate in advance to increase the shrinkage rate by drying, a method of stretching the substrate before the drying step to cure and shrink it.

Here, as the plastic substrate, an appropriate material can be used, but a film made of a polymer having excellent transparency is preferable. Examples of the polymer, acetate resin such as triacetyl cellulose, polyester resin, polyether sulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, Examples thereof include polynorbornene-based resins, cellulose-based resins, polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polyacrylic-based resins, and liquid crystal polymer-based resins.

The plastic base material may be a single-layered product, or a multi-layered product such as a film laminated with different polymers for various purposes such as improvement of strength, heat resistance and adhesion of polymer. It may be. Further, it may be one that does not cause a phase difference due to birefringence, or one that causes a phase difference due to birefringence.

The thickness of the plastic substrate can be appropriately determined according to the purpose of use, etc., but from the viewpoint of strength and thinning, it is preferably 5 to 500 μm, more preferably 10 to 200 μm. , Particularly preferably 15 to
The range is preferably 150 μm.

The birefringent film of the present invention can be produced by casting or coating a polymer solution prepared by dissolving a polymer material in a solvent and drying the coating film. For example, the solvent to dissolve the polyimide is not particularly limited as long as it can dissolve the polyimide, for example, chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, halogenated hydrocarbon such as orthodichlorobenzene. Kinds; Phenols such as phenol and valachlorophenol; Benzene, toluene, xylene, methoxybenzene, 1,2-
Aromatic hydrocarbons such as dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone,
Ketone solvents such as N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, di Alcohol solvents such as propylene glycol and 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; diethyl ether, dibutyl ether and tetrahydrofuran. Ethereal solvents such as:
Alternatively, carbon disulfide, ethyl cellosolve, butyl cellosolve and the like can be used alone or in combination. When applied as a polymer solution, 5 to 5 parts of the above polymer is added to 100 parts by weight of the solvent in terms of viscosity.
It is advisable to mix 0 part by weight, preferably 10 to 40 parts by weight.

The coating treatment may be carried out by an appropriate method such as a spin coating method, a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method or a gravure printing method. it can. At the time of coating, a superposition method of polymer layers and the like can be adopted if necessary.

After coating, air drying or 60 to 20
By heating at 0 ° C., the polymer is immobilized on the base material to form a polymer layer on the base material. The obtained birefringent film may be used in the form of a laminate as an integral body with a supporting base material, or may be used as a birefringent film by peeling the polymer layer from the base material. When forming the polymer layer, various additives such as stabilizers, plasticizers and metals can be blended as necessary.

As shown in FIG. 1, the birefringent film (1)
Can be put to practical use as an optical compensation integrated type polarizing plate with the polarizer (2) adhered via an adhesive layer if necessary. In the case of the illustrated example, the protective film (3) is adhered to the outside of the polarizer (2). Also, as shown in FIG.
If necessary, the polarizing plate (11) can be put to practical use as a polarizing plate integrated with optical compensation, with the polarizing plate (11) being bonded via an adhesive layer. In the case of the polarizing plate shown in the figure, protective films (3) are adhered to both sides of the polarizer (2). Further, as shown in FIG. 3, a liquid crystal cell (21) may be bonded to the side having the birefringent film (1) through an adhesive layer (not shown) to provide a practical form. By integrating with such a polarizer or a polarizing plate, the workability of handling can be further improved, and the assembly process of the liquid crystal display device or the like can be simplified.

The polarizing plate used in the present invention is not particularly limited, but its basic constitution is such that a suitable adhesive layer is provided on one side or both sides of a polarizer made of a polyvinyl alcohol-based polarizing film containing a dichroic substance. For example, a transparent protective film serving as a protective layer is adhered via an adhesive layer made of vinyl alcohol polymer or the like.

As the polarizer (polarizing film), for example, a film made of a vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol is dyed with a dichroic substance such as iodine or a dichroic dye, and stretched. Appropriate treatments such as treatments and cross-linking treatments performed in an appropriate order or method and capable of transmitting linearly polarized light when natural light is incident can be used. A polarizing film formed of a polyene oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride may be used. Among them, a polyvinyl alcohol-based film in which iodine or a dichroic dye is adsorbed and oriented is preferable. In particular, those having excellent light transmittance and polarization degree are preferable. The thickness of the polarizing film is generally 1 to 80 μm, but is not limited to this.

An appropriate transparent film can be used as the protective film material which is a transparent protective layer provided on one side or both sides of the polarizer (polarizing film). Above all, a film made of a polymer having excellent transparency, mechanical strength, thermal stability, moisture shielding property and the like is preferably used. Examples of the polymer include acetate resins such as triacetyl cellulose, polyester resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polynorbornene resins, polyolefin resins, polyacrylic resins. Examples thereof include resins, but are not limited thereto. A transparent protective film that can be particularly preferably used in terms of polarization characteristics and durability is a triacetyl cellulose film whose surface is saponified with an alkali or the like. The thickness of the transparent protective film is arbitrary, but generally 500 μm or less, preferably 5 to 300 μm for the purpose of thinning the polarizing plate.
m, particularly preferably 5 to 150 μm. When the transparent protective films are provided on both sides of the polarizing film, the transparent protective films made of different polymers may be used on the front and back.

The transparent protective film used for the protective layer is
As long as the object of the present invention is not impaired, a hard coat treatment, an antireflection treatment, a treatment for the purpose of preventing sticking, diffusion or antiglare, or the like may be applied. The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate.
It is possible to form a cured skin film, which is made of a suitable ultraviolet-curable resin such as urethane-based, acrylic-based, or epoxy-based resin, and has excellent hardness and slipperiness, by a method of adding it to the surface of the transparent protective film.

On the other hand, the antireflection treatment is carried out for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art. In addition, anti-sticking is performed for the purpose of preventing adhesion with an adjacent layer, and anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering visual recognition of light transmitted through the polarizing plate. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a surface roughening method such as a sandblasting method or an embossing method or a method of blending transparent fine particles.

Examples of the transparent fine particles include silica and alumina having an average particle diameter of 0.5 to 20 μm, titania and zirconia, tin oxide and indium oxide, cadmium oxide and antimony oxide. Fine particles may be used, or organic fine particles made of crosslinked or non-crosslinked polymer particles may be used.
The amount of transparent fine particles used is 2 per 100 parts by weight of transparent resin.
It is generally 70 to 70 parts by weight, especially 5 to 50 parts by weight.

The antiglare layer containing transparent fine particles can be provided as the transparent protective film itself or as a coating layer on the surface of the transparent protective film. The anti-glare layer may also serve as a diffusion layer (viewing angle compensation function or the like) for diffusing light transmitted through the polarizing plate and expanding the viewing angle. The antireflection layer, the sticking prevention layer, the diffusion layer, the antiglare layer, and the like may be provided as an optical layer formed of a sheet provided with these layers, separately from the transparent protective film.

The adhesion treatment of the polarizer and the transparent protective film as the protective layer is not particularly limited, but for example, an adhesive made of an acrylic polymer or a vinyl alcohol polymer, or boric acid or borax. Alternatively, it can be carried out via an adhesive or the like made of at least a water-soluble crosslinking agent of a vinyl alcohol polymer such as glutaraldehyde, melamine, and oxalic acid. This makes it difficult to peel off due to the influence of humidity and heat, and makes it possible to provide excellent light transmittance and polarization degree. Such an adhesive layer is formed as a coating dry layer of an aqueous solution or the like, but other additives and a catalyst such as an acid can be added as necessary when preparing the aqueous solution. In particular, it is preferable to use an adhesive made of polyvinyl alcohol because of its excellent adhesion to the PVA film.

When a polarizing plate and a birefringent film are laminated to form a laminated polarizing plate, both can be laminated using an appropriate adhesive means such as an adhesive layer, but the invention is not limited thereto. . For example, it is also possible to use a polymer film such as triacetyl cellulose used as a protective layer of a polarizing plate as a substrate and form a polymer layer (birefringent layer) on the substrate. Then, a polymer film such as triacetyl cellulose may be adhered to the polarizer, and only the polymer film such as triacetyl cellulose may be adhered to the other side of the polarizer. When laminating by such a method, the birefringent film supporting substrate can be used as a protective film on one side of the polarizing plate.

The pressure-sensitive adhesive layer used for lamination is not particularly limited, and a suitable pressure-sensitive adhesive such as an acrylic, silicone, polyester, polyurethane, polyether, rubber or other transparent pressure-sensitive adhesive is used. Can be used. From the viewpoint of preventing changes in optical properties of optical films and the like, those that do not require a high temperature process at the time of curing or drying are preferable, and those that do not require a long curing treatment or drying time are desirable. Further, those which do not cause peeling under heating or humidifying conditions are preferably used.

The birefringent film of the present invention can also be used in combination with various retardation plates, diffusion control films, brightness enhancement films and the like. Examples of the retardation plate include a uniaxially stretched polymer, a biaxially stretched polymer, a Z-axis oriented treatment product, and a liquid crystal polymer-coated product. As the diffusion control film, a film using diffusion, scattering, and refraction for controlling the viewing angle, a film using diffusion, scattering, and refraction for controlling glare related to resolution, scattered light, and the like can be used. The brightness enhancement film
A brightness enhancement film using selective reflection of cholesteric liquid crystal and a λ / 4 plate, a scattering film utilizing anisotropic scattering depending on the polarization direction, and the like can be used. Further, it may be used in combination with a wire grid polarizer.

The birefringent film and the polarizing plate integrated with an optical compensation layer according to the present invention can be preferably used for forming various liquid crystal display devices, etc., but in the application thereof, the above-mentioned pressure-sensitive adhesive layer or the like may be optionally used. One or more layers of other optical layers such as a polarizing plate, a reflection plate, a semi-transmissive reflection plate, and a brightness enhancement film can be laminated. In particular, the laminated polarizing plate in which the polarizing plate and the birefringent film of the present invention are laminated is used as a polarizing plate having an optical compensation function (optical compensation layer integrated polarizing plate).

The above-mentioned reflection plate is provided on a polarizing plate to form a reflection type polarizing plate. The reflective polarizing plate is usually placed on the back side of the liquid crystal cell and is on the viewing side (display side).
A liquid crystal display device (reflection-type liquid crystal display device) of a type that reflects and displays incident light from the device is formed. The reflective polarizing plate has an advantage that a light source such as a backlight can be omitted and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate. Specific examples thereof include a transparent protective film that is mat-treated if necessary, and a reflective layer formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum to one surface of the transparent protective film.

Further, there may be mentioned a reflection type polarizing plate having a reflective layer reflecting the fine concavo-convex structure on the transparent protective film containing fine particles and having a fine concavo-convex structure on the surface. The reflective layer having a fine surface irregularity structure has an advantage of diffusing incident light by diffuse reflection, preventing directivity and glare, and suppressing uneven brightness. The transparent protective film can be formed by a method of directly attaching a metal to the surface of the transparent protective film by an appropriate method such as a vacuum vapor deposition method, an ion plating method, a vapor deposition method such as a sputtering method or a plating method. .

Further, the reflection plate may be used as a reflection sheet in which a reflection layer is provided on an appropriate film according to the transparent protective film instead of the method of directly attaching to the transparent protective film of the polarizing plate. it can. Since the reflective layer of the reflective plate is usually made of metal, the use form in which the reflective surface is covered with a film or a polarizing plate is to prevent reduction of the reflectance due to oxidation, and thus to maintain the initial reflectance for a long time. Also, it is preferable from the viewpoint of avoiding the additional provision of the protective layer.

The semi-transmissive polarizing plate is a semi-transmissive reflective layer in the reflective polarizing plate described above, and examples thereof include a half mirror that reflects and transmits light at the reflective layer.
The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when a liquid crystal display device is used in a relatively bright atmosphere, it reflects incident light from the viewing side (display side) to display an image. In a relatively dark atmosphere, a liquid crystal display device of the type that displays an image using a built-in light source such as a backlight built in the back side of a semi-transmissive polarizing plate is formed. That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

Further, as the above brightness enhancement film,
For example, a dielectric multi-layered thin film or a multi-layered laminate of thin films having different refractive index anisotropies, which shows the property of transmitting linearly polarized light of a predetermined polarization axis and reflecting other light (“D” manufactured by 3M). -BEF ", etc.), a cholesteric liquid crystal layer, especially an oriented film of a cholesteric liquid crystal polymer, or one having an oriented liquid crystal layer supported on a film substrate (Nitto Denko Corporation" P
CF350 ", Merck" Transmax ")
As described above, an appropriate one can be used, such as one having a characteristic of reflecting either left-handed or right-handed circularly polarized light and transmitting other light.

The above-mentioned optical member in which two or more optical layers are laminated can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. The optical member is excellent in quality stability and assembling workability, and has an advantage that the manufacturing efficiency of the liquid crystal display device can be improved. In addition, for stacking,
Appropriate adhesion means such as the above-mentioned adhesive layer can be used.

The birefringent film (biaxial retardation plate), the optical compensation layer-integrated polarizing plate or the like of the present invention is provided with an adhesive layer or the like for adhering to other optical layers or other members such as liquid crystal cells. You can also The pressure-sensitive adhesive layer can be appropriately formed by using a conventionally known pressure-sensitive adhesive such as acrylic resin. Above all,
In order to prevent foaming phenomenon and peeling phenomenon due to moisture absorption, deterioration of optical properties due to thermal expansion difference, prevention of warp of liquid crystal cell, and further formability of liquid crystal display device with high quality and durability, the moisture absorption rate is low. It is preferable that the adhesive layer has excellent heat resistance. Further, an adhesive layer or the like which contains fine particles and exhibits a light diffusing property can be used. The adhesive layer may be provided on a required surface as needed. The thickness of the adhesive layer can be appropriately determined according to the purpose of use and the adhesive strength, and is generally 1 to 500 μm.
And preferably 5 to 200 μm, particularly 10 to 100
μm is preferred.

When the pressure-sensitive adhesive layer provided on the birefringent film (biaxial retardation plate), the optical compensation layer-integrated polarizing plate, etc. is exposed on the surface, contamination prevention is performed until the pressure-sensitive adhesive layer is put into practical use. It is preferable to temporarily cover with a separator for such purposes. The separator is formed by, for example, a method in which an appropriate thin sheet conforming to the above-mentioned transparent protective film or the like is provided with a release coat with an appropriate release agent such as a silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide as necessary. be able to.

Each layer such as the polarizer, the transparent protective film and the adhesive (adhesion) layer which compose the birefringent film or the polarizing plate integrated with the optical compensation layer may be, for example, a salicylate compound, a benzophenone compound or a benzophenone compound. It may be one having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorber such as a triazole compound, a cyanoacrylate compound, a nickel complex salt compound or the like.

The birefringent film of the present invention is a laminate comprising the film alone or, if necessary, in combination with other birefringent films such as other retardation film, liquid crystal film, light scattering film, diffractive film, polarizing film and the like. Can be used for various optical applications, specifically, as an optical compensation member for various liquid crystal display elements. For example, a polarizing plate having a function of compensating and adjusting the birefringence of a liquid crystal display element can be obtained by combining an industrially produced iodine-based or dye-based polarizing film with a birefringent film.

The liquid crystal display element referred to here is, for example, ST
N (Super Twisted Nematic) cell, TN (Twisted Nem)
atic) cell, IPS (In-Plane Switching) cell, V
A (Vertical Alighned) cell, OCB (Optically Ali)
ghned birefringence) cell, HAN (Hybrid Alighned)
Nematic) cell, ASM (Axially Symmetric Alighned)
Microcells), ferroelectric / antiferroelectric cells, and various types of cells such as those having regular orientation division and those having random orientation division. The birefringent film of the present invention is very excellent in optical compensation of a VA (Vertical Alighned) cell.

The birefringent film of the present invention is VA
Since it is very excellent in optical compensation of a (Vertical Alighned) cell, it can be most suitably used as a viewing angle compensation film for a VA mode liquid crystal display device.

It is possible to form a suitable liquid crystal display device such as a liquid crystal display device in which the above-mentioned optical element is arranged on one side or both sides of a liquid crystal cell or a liquid crystal display device using a backlight or a reflector in an illumination system. In that case, the birefringent film according to the present invention can be arranged on one side or both sides of the liquid crystal cell. When birefringent films are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array sheet, a lens array sheet, a light diffusion plate, a back light, and other appropriate components are formed in a single layer at appropriate positions. Alternatively, two or more layers can be arranged.

Further, the birefringent film and the optical compensation layer-integrated polarizing plate of the present invention can be used in a self-luminous display device such as an organic EL display in the same manner as a liquid crystal display device.

[0074]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The characteristics of the optical film were evaluated by the following methods.

(Measurement of Phase Difference and Alignment Axis Accuracy) It was measured using a phase difference meter (KOBRA21ADH manufactured by Oji Scientific Instruments).

(Measurement of Refractive Index) KOBR manufactured by Oji Scientific Instruments
The refractive index at 590 nm was measured using A21ADH.

(Measurement of Membrane Pressure) The film pressure was measured using an Anritsu Digital Micrometer Model K-351C.

(Example 1) 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis (trifluoromethyl) -4,4 ' -Thickness of a polyimide prepared from diaminobiphenyl (TFMB) having a weight average molecular weight (Mw) of 70,000 and a Δn of about 0.04 to 25 wt% using cyclohexanone as a solvent, fixed on the vertical axis. 80
Coated on μm triacetyl cellulose. Then 1
After heat treatment at 50 ° C. for 5 minutes, a completely transparent and smooth film was obtained. The rate of dimensional change in the lateral direction of the substrate used at this time at 150 ° C. for 5 minutes was 4%. Also, the film is nx> ny
It was a retardation plate having a birefringent layer of> nz.

Example 2 The same solution as in Example 1 was used, and this solution was applied onto polyethylene terephthalate having a thickness of 75 μm and fixed on the vertical axis. Then, after heat treatment at 150 ° C. for 5 minutes, a completely transparent and peeled smooth film was obtained. The rate of dimensional change in the lateral direction of the substrate used at this time at 150 ° C. for 5 minutes was 2%. The film was a retardation plate having a birefringent layer of nx>ny> nz.

Example 3 The same solution as in Example 1 was used, and this solution was applied onto triacetyl cellulose. Then, after heat treatment at 150 ° C. for 5 minutes, a completely transparent and peeled smooth film was obtained. The rate of dimensional change in the longitudinal direction of the substrate used at this time at 150 ° C. for 5 minutes was 1.5%, and the rate of dimensional change in the lateral direction was 1%. The film was a retardation plate having a birefringent layer of nx>ny> nz.

(Example 4) 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis (trifluoromethyl) -4,4 ' -A solution of polyimide prepared from diaminobiphenyl (TFMB) and having Δn of about 0.005 at 25 wt% using cyclohexanone as a solvent was fixed on the base material used in Example 1 in the same manner. Applied. Then, after heat treatment at 150 ° C. for 5 minutes, a completely transparent and smooth film was obtained. The rate of dimensional change in the lateral direction of the substrate used at this time at 150 ° C. for 5 minutes was 4%. The film was a retardation plate having a birefringent layer of nx>ny> nz.

Example 5 A solution prepared by using MIBK as a solvent in a polyaryletherketone A (manufactured by Nippon Shokubai Co., Ltd.) represented by the following structural formula (Formula 7) to adjust its concentration to 20% is the same as in Example 1. It was applied to the base material fixed on the substrate and then heat-treated at 150 ° C. for 5 minutes to obtain a completely transparent and smooth film. The rate of dimensional change in the lateral direction of the substrate used at this time at 150 ° C. for 5 minutes was 4%. The film is nx>
The retardation plate had a birefringent layer of ny> nz.

[0083]

[Chemical 7]

Comparative Example 1 The solution used in Example 1 was used, and this solution was applied onto triacetyl cellulose fixed in length and width, and after heat treatment at 150 ° C. for 5 minutes, a completely transparent and smooth film was obtained. . The rate of dimensional change in the lateral direction of the substrate used at this time at 150 ° C. for 5 minutes was 0.02%. The film was a retardation plate having a birefringent layer of nx≅ny> nz.

Comparative Example 2 The same solution as in Example 1 was used, and this solution was applied onto a glass plate. Then 1 at 100 ℃
After heat treatment for 0 minutes, a completely transparent film was obtained after peeling. This film was a retardation plate having a birefringent layer of nx≈ny> nz.

With respect to the retardation plates obtained in the above Examples and Comparative Examples, from the values of nx, ny and nz, (nx-n
y) * d, (nx-nz) * d, (nx-nz) / (n
The value of x-ny) was calculated. The results and the thickness of the obtained birefringent film are summarized in Table 1.

[0087]

[Table 1] △ n (nx-ny) ・ d (nx-nz) ・ d (nx-nz) Thickness Base material dimensions (Nm) (nm) / (nx-ny) (μm) Change rate (%) Example 1 0.04 135 280 2 10 4 Example 2 0.04 45 200 4 6 2 Example 3 0.04 50 280 6 10 1.5, 1 Implementation Example 4 0.005 100 150 2 6 4 Example 5 0.021 60 140 2 10 4 Comparative Example 1-0.2 220 1100 6 0.02 Comparative Example 2-0.2 275 1375 10 0

From the above results, the optical characteristics of the birefringent film of the present invention have a value of (nx-ny) × d of 3 nm or more,
In addition, (nx-nz) / (nx-ny)> 1, which means that the film is a thin film.

Next, the retardation plate and the polarizing plate manufactured in Example 1 above (trade name “HEG1425D” manufactured by Nitto Denko Corporation) are used.
U ”) was laminated via an acrylic adhesive to obtain an optical compensation layer-integrated polarizing plate. This was adhered to the backlight side of the liquid crystal cell so that the polarizing plate was on the outer side to produce a liquid crystal display device. When the display characteristics were examined, it was found that the contrast and display uniformity were excellent and the display quality was good in a wide viewing angle range of the front and squint.

[0090]

As described above, according to the present invention, at least one polymer selected from the group consisting of polyamides, polyimides, polyesters, polyetherketones, polyamideimides and polyesterimides is brought into a solution state, and a dimensional change occurs during drying. 3 nm <(nx-ny) d and (nx-nz) /
A biaxial retardation film satisfying (nx-ny)> 1 can be easily obtained. The obtained film is a thin layer and is a retardation plate having a characteristic of nx>ny> nz, which is uniform and transparent and has extremely excellent optical properties, and can form a liquid crystal display device in which the viewing angle of a liquid crystal cell is compensated. .

Further, the birefringent film of the present invention or the polarizing plate integrated with an optical compensation layer, which is obtained by laminating the birefringent film on a polarizer or a polarizing plate, is disposed on at least one side of a liquid crystal cell or used for a self-luminous display device. As a result, it is possible to realize a thin display device having excellent display quality in a wide viewing angle range of the front and squint.

According to the method for producing a birefringent film of the present invention, the birefringence is in the range of 0.0005 to 0.5, and the optical characteristics are nx>ny> nz (where nx,
A birefringent film satisfying ny is the main refractive index in the plane of the film and nz is the refractive index in the film thickness direction) can be easily manufactured with high production efficiency, and is excellent in mass productivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a polarizing plate integrated with an optical compensation layer of the present invention.

FIG. 2 is a schematic sectional view showing an example of an optical compensation layer-integrated polarizing plate of the present invention.

FIG. 3 is a schematic sectional view showing an example of a liquid crystal display device of the present invention.

FIG. 4 is a diagram showing an axial direction of the optical film of the present invention.

[Explanation of symbols]

1: Birefringent film 2: Polarizer 3: Protective film 11: Polarizing plate 21: Liquid crystal cell nx, ny, nz ... The thickness direction is the Z axis, the drawing direction in the plane perpendicular to the Z axis is the X axis, Refractive index of each axis when the direction perpendicular to the X and Z axes is the Y axis

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) // B29L 7:00 B29L 7:00 (72) Inventor Yuichi Nishikoji 1-chome Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Co., Ltd. (72) Inventor Masaki Hayashi 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture F-term (reference) within Nitto Denko Corporation 2H049 BA02 BA06 BA42 BB03 BB43 BC01 BC03 BC22 2H091 FA08X FA08Z FA11X FA11Z FB02 GA16 LA12 4F205 AA24 AA29 AA32 AA40 AG01 AH73 AJ03 GA06 GB01 GN28

Claims (8)

[Claims] 1. A film obtained by applying a solution prepared by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent to a substrate, and drying it. A birefringent film formed by using a base material that changes in dimension in the step of converting into a birefringent film having a birefringence index in the range of 0.0005 to 0.5 and the following formula (1) ( A birefringent film satisfying all of 3). nx>ny> nz (1) 3 nm ≦ (nx-ny) · d (2) (nx-nz) / (nx-ny)> 1 (3) (where nx, ny in formulas (1) to (3)) Is the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction,
d is the film thickness. ) 2. The birefringent film according to claim 1, wherein the maximum dimensional change rate of the substrate when dried is 1% or more. 3. The birefringent film according to claim 1, wherein the base material is a protective film material for a polarizing plate. 4. The birefringent film according to claim 1, wherein the base material is a polarizer formed by stretching a polyvinyl alcohol film. 5. An optical compensation layer-integrated polarizing plate comprising a combination of the birefringent film according to claim 1 and a polarizer or a polarizing plate. 6. A liquid crystal display, wherein the birefringent film according to any one of claims 1 to 4 or the polarizing plate with an optical compensation layer according to claim 5 is arranged on at least one side of a liquid crystal cell. apparatus. 7. A self-luminous display device comprising the birefringent film according to claim 1 or the polarizing plate with an optical compensation layer according to claim 5. 8. A film obtained by applying a solution prepared by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent to a substrate, and drying it. A method for producing a birefringent film, wherein the dimensional change rate of the substrate from immediately after coating to immediately after drying is 1% or more.