JP2007193045A - Retardation plate, optical film, liquid crystal panel and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation plate which is excellent in thickness reduction and weight reduction and which shows flat wavelength dispersion in a visible light region. <P>SOLUTION: The retardation plate has a coating film which is obtained by applying a solution containing polyamidoimide with a repeating unit expressed by a general formula (I) and modified polystyrene with a carboxyl group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a retardation plate that exhibits flat wavelength dispersion characteristics and is excellent in thinness and weight reduction, an optical film including the retardation plate, and the like.

The retardation plate is an important optical member that realizes an improvement in contrast and an expansion of the viewing angle range in an image display device such as a liquid crystal display device by optical compensation. Known retardation films include those obtained by stretching a polymer film to impart optical anisotropy, and those obtained by coating a liquid crystal compound on a substrate such as glass or a polymer film.
By the way, the wavelength dispersion characteristic is an important factor in designing the retardation plate. Normally, the wavelength dispersion of the retardation plate is positive wavelength dispersion in which the retardation in the thickness direction in the visible light region is shorter on the short wavelength side, and the flat wavelength in which the retardation in the thickness direction is substantially uniform in the visible light region. Dispersion is roughly classified into reverse wavelength dispersion in which the retardation in the thickness direction in the visible light region is smaller on the shorter wavelength side.

As a retardation plate exhibiting such flat wavelength dispersion, a retardation plate made of a norbornene film has been conventionally known (Patent Document 1).
However, a retardation film made of a film has a large film thickness, and thus it is difficult to reduce the thickness and weight.

JP-A-2005-43740

  Therefore, the present invention provides a retardation plate that is excellent in thin and light weight and exhibits flat wavelength dispersion in the visible light region, and an optical film, a liquid crystal panel, and an image display device including the retardation plate. Let it be an issue.

  The present invention applies a solution containing a polyamideimide having at least one repeating unit represented by the following general formula (I) or general formula (II) and a modified polystyrene containing a carboxyl group. A retardation film having a coating film obtained by processing is provided.

  In the general formulas (I) and (II), A, B, and D each represent a substituent, and a, b, and d on the side indicate the number of substitutions. A, B and D are the same or different and are atoms or groups selected from halogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, nitro group, cyano group, hydroxyl group and thiol group. is there. a is an integer of 0 to 3, and b and d are integers of 0 to 4. When A, B, and D are composed of a plurality of substituents, each substituent may be the same or different. X is a single bond, or an atom or group selected from oxygen, sulfur, a carbonyl group, an alkylene group, and a substituted alkylene group. p1 and p2 are integers of 1 or more.

Since the modified polystyrene containing the specific polyamideimide and the carboxyl group are excellent in solubility to each other, the coating film obtained by coating a solution containing both is very excellent in transparency.
Further, the coating film exhibits flat wavelength dispersion in the visible light region. Although this principle is not clear, polyamideimide shows positive wavelength dispersion, modified polystyrene containing carboxyl groups shows reverse wavelength dispersion, and the normal wavelength dispersion and reverse wavelength dispersion cancel each other, resulting in flat wavelength dispersion. It is thought that it shows.
Furthermore, the coating film obtained by coating the solution can be formed with a smaller film thickness than the film.

Furthermore, this invention provides an optical film provided with the said phase difference plate.
Moreover, this invention provides a liquid crystal panel provided with the said phase difference plate or an optical film.
Furthermore, this invention provides an image display apparatus provided with the said phase difference plate or an optical film.

  According to the present invention, a flat retardation can be provided in the visible light region, and a thin retardation plate can be provided.

The retardation plate of the present invention has a coating film obtained by coating a base material with a solution containing a specific polyamideimide and a modified polystyrene containing a carboxyl group.
The retardation plate of the present invention may be formed by peeling a coating film from a substrate and using a single layer of the coating film as a retardation plate, or by laminating a coating film laminated on a substrate. You may use as a phase difference plate.

(Polymer used)
The polyamideimide used in the present invention is a polymer containing a repeating unit represented by the general formula (I) or (II).

  In the general formulas (I) and (II), A, B, and D each represent a substituent, and a, b, and d on the side indicate the number of substitutions. A, B and D are the same or different and are atoms or groups selected from halogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, nitro group, cyano group, hydroxyl group and thiol group. is there. a is an integer of 0 to 3, and b and d are integers of 0 to 4. When A, B, and D are composed of a plurality of substituents, each substituent may be the same or different. X is a single bond, or an atom or group selected from oxygen, sulfur, a carbonyl group, an alkylene group, and a substituted alkylene group. p1 and p2 are integers of 1 or more.

In general formulas (I) and (II), the alkyl group, substituted alkyl group, and alkoxy group preferably have 1 to 6 carbon atoms and 1 to 4 carbon atoms, and preferably have 1 to 3 carbon atoms. More preferred. As the substituted alkyl group, a halogenated alkyl group is preferable.
The aryl group and substituted aryl group preferably have 1 to 3 rings, and more preferably have 1 to 2 rings. The alkylene group and substituted alkylene group preferably have 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. As the substituted alkylene, a halogenated alkylene group is preferred.
Among the repeating units represented by the general formulas (I) and (II), the most preferred specific examples are those represented by the following formulas (III) and (IV).

  Furthermore, the polyamideimide used in the present invention is preferably a polymer containing a repeating unit represented by the above general formula (I) or (II) and a repeating unit represented by the following general formula (V).

  In the general formula (V), E, G, and H each represent a substituent, and e, g, and h on the side indicate the number of substitutions. E, G and H are the same or different and are atoms or groups selected from halogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, nitro group, cyano group, hydroxyl group and thiol group. is there. e is an integer of 0 to 3, and g and h are integers of 0 to 4. When E, G, and H are composed of a plurality of substituents, each substituent may be the same or different. Y and X are the same or different and each represents a single bond or an atom or group selected from oxygen, sulfur, a carbonyl group, an alkylene group, and a substituted alkylene group. q1 and q2 are integers of 1 or more.

In the general formula (V), the alkyl group, substituted alkyl group, and alkoxy group preferably have 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms. As the substituted alkyl group, a halogenated alkyl group is preferable.
The aryl group and substituted aryl group preferably have 1 to 3 rings, and more preferably have 1 to 2 rings. The alkylene group and substituted alkylene group preferably have 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. As the substituted alkylene, a halogenated alkylene group is preferred.

  Among the repeating units represented by the general formula (V), the most preferred specific examples are those represented by the following formula (VI).

  Specific examples of the polyamideimide containing the repeating unit represented by the general formula (I) or (II) and the repeating unit represented by the following general formula (V) include the following general formula (VII) or (VIII) The thing represented by these is preferable.

  In the general formulas (VII) and (VIII), m is 30 to 70 mol%, and n is 30 to 70 mol% when the total repeating units constituting the polyamideimide are 100 mol%.

In the present invention, any one of the polyamideimides represented by the above general formulas (VII) and (VIII) or a mixture of both polyamideimides can be used. The ratio of the mixture is not particularly limited, and the polyamide imide represented by the general formula (VII) and the polyamide imide represented by the general formula (VIII) may be mixed in an equal amount, and either one is more It may be mixed.
The molecular weight of the polyamideimide is not particularly limited, but a coating film excellent in strength can be obtained, so that a weight average molecular weight of 10,000 or more, more preferably 20,000 or more is preferable. From the viewpoint of solvent solubility, those having a weight average molecular weight of 1,000,000 or less and more preferably 500,000 or less are preferred.

  Next, examples of the modified polystyrene containing a carboxyl group include unsaturated mono (di) carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, phthalic acid, and itaconic acid, or a carboxyl group that is an alkyl group or a substituted alkyl. And an unsaturated mono (di) carboxylic acid substituted with a group and an aromatic vinyl monomer such as styrene, α-methylstyrene, and vinyltoluene. In particular, it is preferable to use a modified polystyrene containing a repeating unit represented by the following general formula (IX) because a coating film having excellent compatibility with the polyamideimide and high transparency can be obtained.

一般式（IX）において、Ｊは、それぞれ置換基を示し、その横のｊは、置換数を示す。Ｊは、ハロゲン、アルキル基、置換アルキル基、アルコキシ基、アリール基、置換アリール基、ニトロ基、シアノ基、水酸基、チオール基から選択される原子または基である。ｊは、０〜５の整数である。Ｊが複数の置換基からなる場合、各置換基は、それぞれ同一又は異なるものでもよい。Ｒは、水素原子、炭素数１〜４のアルキル基、炭素数１〜４の置換アルキル基である。

In general formula (IX), J represents a substituent, and j on the side represents the number of substitutions. J is an atom or group selected from halogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, nitro group, cyano group, hydroxyl group and thiol group. j is an integer of 0-5. When J consists of a plurality of substituents, each substituent may be the same or different. R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a substituted alkyl group having 1 to 4 carbon atoms.

In general formula (IX), the alkyl group, substituted alkyl group, and alkoxy group preferably have 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms.
The aryl group and substituted aryl group preferably have 1 to 3 rings, and more preferably have 1 to 2 rings. The alkylene group and substituted alkylene group preferably have 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.
Of the modified polystyrenes contained in the above general formula (IX), those having no substituent on the benzene ring (j being 0) and R being a hydrogen atom, a methyl group or an ethyl group are preferred.

  Among the repeating units represented by the general formula (IX), the most preferred specific examples are those represented by the following formula (X).

The modified polystyrene preferably contains 95 mol% or more of the repeating unit represented by the above general formula (IX) when the total repeating unit is 100 mol%.
Further, the molecular weight of the modified polystyrene is not particularly limited, but usually, the weight average molecular weight is preferably 100,000 to 500,000, and more preferably about 100,000 to 300,000.

(Preparation of coating film)
A polymer material containing the polyamideimide and modified polystyrene is dissolved in a solvent to prepare a solution.
In addition, as long as the optical properties of the obtained coating film are not impaired, a polymer material can be prepared by blending other polymers other than the polyamideimide and modified polystyrene. You may mix | blend various additives, such as a ultraviolet absorber, a stabilizer, a plasticizer, an antistatic agent, with a polymer material, for example.

As the blending ratio of polyamideimide and modified polystyrene, from the point of obtaining a coating film exhibiting flat wavelength dispersion and the point of obtaining a transparent coating film, 10 to 150 parts by mass of modified polystyrene with respect to 100 parts by mass of polyamideimide. It is preferable to mix | blend, and it is preferable to mix | blend 10-100 mass parts of modified polystyrene especially.
The blending ratio of the polymer material or the like with respect to the solvent is preferably 5 to 30% by mass in terms of solid content from the viewpoint of adjusting to a viscosity suitable for coating workability.

  The solvent is not particularly limited as long as it can dissolve the polymer material and the like, and a conventionally known organic solvent can be appropriately selected and used. Specifically, examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol; benzene Aromatic hydrocarbons such as toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone Solvents; Ester solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethyl Alcohol solvents such as dimethyl glycol ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; Ether solvents such as diethyl ether, dibutyl ether and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve and the like. One type of these solvents may be used, or two or more types may be used in combination. Among these solvents, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, dichloromethane, trichloroethylene, tetrachloroethane, cyclohexanone, cyclopentanone, methyl isobutyl ketone, methyl isobutyl ketone, diethylene glycol dimethyl ether, toluene, ethyl acetate, tetrahydrofuran Is preferred, and methyl isobutyl ketone is particularly preferred.

A solution containing the polymer material is applied to a substrate to form a coating film.
The base material to which the polymer solution is applied is not particularly limited, and for example, a synthetic resin base material or a base material of an inorganic compound such as a glass base material or a silicon wafer may be used. Examples of the synthetic resin substrate include those prepared by a casting method and those prepared by forming a molten polymer and then subjecting it to a stretching treatment. Among these, a precise coating having excellent mechanical strength is provided. A synthetic resin base material that has been subjected to a stretching treatment is preferable because of its work accuracy.

  Moreover, as a base material, the transparent film formed from the synthetic resin which is excellent in transparency, for example is preferable. This is because with such a base material, a laminate in which a coating film is laminated on the base material can be used as it is as a retardation plate.

  As such a transparent film substrate, for example, acetate resin such as triacetyl cellulose (TAC), polyester resin such as polyethylene terephthalate, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, Examples thereof include acrylic resins, polynorbornene resins, cellulose resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyacryl resins, and mixtures thereof. A liquid crystal polymer or the like can also be used.

  The thickness of the substrate is, for example, 12 μm or more and 200 μm or less, preferably 20 μm or more and 150 μm or less, and more preferably 25 μm or more and 100 μm or less. If the thickness is too thin, the coating accuracy of the solution may be lowered. On the other hand, if the thickness is too thick, the retardation plate constituted by the laminate of the base material and the coating film becomes too thick.

  The polymer solution can be applied by an appropriate method such as spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, or gravure printing. it can.

Next, the coating film formed on the base material is subjected to a drying process to fix the coating film.
The drying temperature is, for example, 50 to 250 ° C, preferably 80 to 200 ° C, more preferably 100 to 180 ° C. The drying time is, for example, 1 minute to 60 minutes, preferably 5 minutes to 50 minutes, more preferably 10 to 40 minutes.
The drying process can be performed in a plurality of times.
After drying, the amount of residual solvent in the obtained coating film is 3% by mass or less, preferably 2% by mass or less, more preferably 1% by mass or less.
The thickness of the coating film after drying is, for example, 1 to 20 μm, preferably 2 to 15 μm, and more preferably 2 to 10 μm.

The coating film obtained as described above exhibits birefringence of nx> nz and ny> nz, and the retardation in the thickness direction at least at a wavelength of 500 to 750 nm is 0.99 <Rth (W). / Rth (590 nm) <1.01 is satisfied, and flat chromatic dispersion is exhibited.
Here, Rth (W) represents a phase difference at a wavelength Wnm (however, in a range of 500 nm to 750 nm), Rth (590) represents a thickness direction retardation at a wavelength of 590 nm, and each Rth = It is determined by (nx−nz) × d. nx, ny, and nz respectively indicate the refractive indexes in the X-axis, Y-axis, and Z-axis directions of the coating film, and the X-axis is an axial direction that indicates the maximum refractive index in the plane of the coating film, The Y axis is an axial direction perpendicular to the X axis in the plane of the coating film, and the Z axis is a thickness direction perpendicular to the plane of the coating film (perpendicular to the X axis and the Y axis). Indicates. d represents the thickness of the coating film.
Furthermore, the coating film can be formed with a birefringence (nx-nz) in the thickness direction of 0.03 or more, preferably 0.04 or more, and a desired retardation can be obtained with a relatively small film thickness. it can.

  Moreover, you may extend | stretch the coating film which shows the birefringence obtained by solidifying further. By performing the stretching treatment in this way, the birefringence of the coating film can be changed. Specifically, as described above, a coating film exhibiting optical uniaxiality (nx> nz, ny> nz) is optically biaxial (nx> ny> nz) and birefringent. can do. By such a stretching process, the in-plane birefringence (Δnxy) and the in-plane retardation (Δnd = (nx−ny) · d) can be controlled.

These treatments may be performed simultaneously with the drying treatment or after the drying step. Examples of the stretching method include a method of uniaxial stretching in the longitudinal direction of the base material, a method of uniaxial stretching in the width direction while fixing the longitudinal direction of the base material, and simultaneous biaxial stretching for stretching in both the longitudinal direction and the width direction. The method etc. are mentioned. The stretching treatment may be performed, for example, by stretching both the base material and the coating film, but only the base material may be stretched. Even when only the base material is stretched, the coating film is stretched indirectly and uniformly by the tension generated in the base material.
The stretching conditions are not particularly limited, and for example, the stretching ratio is preferably more than 1 time and 5 times or less, more preferably more than 1 time and 4 times or less, particularly preferably more than 1 time and 3 times. It is as follows.

(Example of use of retardation plate)
The said coating film can peel from a base material and can be used independently as a phase difference plate. Moreover, it can also be used as a phase difference plate in the state of the laminated body which laminated | stacked the coating film on the base material.
The retardation plate can be used as an optical member as it is, but can be used for various optical film applications in combination with other optical members as required.

  An example of the optical film is a laminated polarizing plate in which a polarizer is laminated on the retardation plate of the present invention. The configuration of such a polarizing plate is not particularly limited, and examples thereof include those having the retardation plate of the present invention and a polarizer, and transparent protective layers laminated on both sides of the polarizer. A transparent protective layer may be laminated | stacked on both sides of a polarizer, and may be laminated | stacked only on either one surface. Moreover, when laminating | stacking a transparent protective layer on both surfaces, you may use the same kind of transparent protective layer, for example, or a different kind of transparent protective layer.

  In addition, when the phase difference plate of this invention consists of a laminated body of a base material and a coating film, any surface of a coating film and a base material may face a polarizer. However, by disposing the polarizer so that the polarizer faces the substrate side of the retardation plate, the substrate can also be used as a transparent protective layer for the polarizer. That is, instead of laminating a transparent protective layer on both sides of the polarizer as described above, a transparent protective layer is disposed on one side of the polarizer, and the substrate of the retardation plate is provided on the other side of the polarizer. By arranging so as to face each other, the substrate of the retardation plate also serves as the other transparent protective layer of the polarizer. Accordingly, a polarizing plate that is thinner and lighter can be obtained.

  The polarizer is not particularly limited, and is prepared, for example, by adsorbing and dying dichroic substances such as iodine and dichroic dyes on various films, crosslinking, stretching and drying by a conventionally known method. Can be used. Among these, a film that transmits linearly polarized light when natural light is incident is preferable, and a film that is excellent in light transmittance and degree of polarization is preferable. Examples of the various films that adsorb the dichroic substance include high hydrophilicity such as polyvinyl alcohol (PVA) film, partially formalized PVA film, ethylene / vinyl acetate copolymer partially saponified film, and cellulose film. In addition to these, for example, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products can be used. Among these, PVA film is preferable. Moreover, although the thickness of a polarizer is the range of 1-80 micrometers normally, it is not limited to this.

  The transparent protective layer is not particularly limited, and a conventionally known transparent resin can be used. For example, a transparent protective layer having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. Specific examples of the material of such a transparent protective layer include those having excellent transparency, for example, cellulose resins such as triacetyl cellulose (TAC), polyester resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfones. Examples thereof include resins, polysulfone resins, polystyrene resins, norbornene resins, polyolefin resins, acrylic resins, acetate resins, polymethyl methacrylate resins, and the like. Note that the transparent protective layer may be made of the same material as the base material.

The thickness of the transparent protective layer is not particularly limited, and can be appropriately determined according to, for example, the phase difference or the protective strength, but is usually 500 μm or less, preferably 5 to 300 μm, more preferably 5 to 150 μm. The certain transparent protective layer can be appropriately formed by a conventionally known method such as a method of applying the transparent resin to a polarizer or a method of laminating the transparent resin film on the polarizer.

The transparent protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, a treatment for preventing sticking or diffusion, antiglare, and the like.
The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, and for example, is a treatment for forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective layer.
As the curable resin, for example, a silicone-based, urethane-based, acrylic-based, or epoxy-based ultraviolet curable resin can be used, and the treatment can be performed by a conventionally known method. The purpose of preventing sticking is to prevent adhesion between adjacent layers.
The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be performed by forming a conventionally known antireflection layer or the like.

The anti-glare treatment is intended to prevent visual interference of light transmitted through the polarizing plate due to reflection of external light on the surface of the polarizing plate. For example, the surface of the transparent protective layer may be finely uneven by a conventionally known method. This can be done by forming a structure. Examples of a method for forming such a concavo-convex structure include a surface roughening method by sandblasting or embossing, a method of forming a transparent protective layer by blending transparent fine particles in the transparent resin as described above, and the like. .
Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like. In addition, inorganic fine particles having conductivity, crosslinked or uncrosslinked polymer, and the like. Organic fine particles composed of granular materials or the like can also be used. The average particle diameter of the transparent fine particles is not particularly limited, but is, for example, in the range of 0.5 to 20 μm. Further, the blending ratio of the transparent fine particles is not particularly limited, but in general, the range of 2 to 70 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of the transparent resin as described above.

  The antiglare layer containing the transparent fine particles can be used as, for example, the transparent protective layer itself, or may be formed as a coating layer on the surface of the transparent protective layer. Furthermore, the anti-glare layer may also serve as a diffusion layer (visual compensation function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, etc. are laminated on the polarizing plate separately from the transparent protective layer, for example, as an optical layer comprising a sheet provided with these layers. May be.

  The optical film of the present invention preferably further has at least one of an adhesive layer and a pressure-sensitive adhesive layer. This is because adhesion between the optical film of the present invention and other members such as other optical members and liquid crystal cells is facilitated, and peeling of the optical film of the present invention can be prevented. Therefore, the adhesive layer and the pressure-sensitive adhesive layer are excellent in optical transparency. The adhesive layer and the pressure-sensitive adhesive layer are preferably laminated on the outermost layer of the optical film, and may be one outermost layer of the optical film or may be laminated on both outermost layers.

  The material of the adhesive layer is not particularly limited. For example, a pressure sensitive adhesive made of a polymer such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, or polyether, or a rubber pressure sensitive adhesive. Etc. can be used. Examples of the material of the pressure-sensitive adhesive layer include rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, polyurethane-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives. Among these, acrylic pressure-sensitive adhesives The base polymer preferably has a weight average molecular weight of about 300,000 to 2.5 million. Although the thickness of an adhesive bond layer or an adhesive layer is not specifically limited, It is preferable to set it as about 10-40 micrometers. Alternatively, these materials may contain fine particles to form a layer exhibiting light diffusibility. Among these, for example, a material excellent in hygroscopicity and heat resistance is preferable. With such a property, for example, when used in a liquid crystal display device, it can prevent foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, warpage of the liquid crystal cell, etc., and high quality and durability. The image display device is also excellent.

The method for laminating the optical members (retardation plate, polarizer, transparent protective layer, etc.) is not particularly limited, and can be performed by a conventionally known method. In general, the same pressure-sensitive adhesives and adhesives as described above can be used, and the type thereof can be appropriately determined depending on the material of each component.
These adhesives and pressure-sensitive adhesives may be applied to the surface of the polarizer or the transparent protective layer as they are, for example, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed between the optical members. May be.

  The retardation plate of the present invention is used as an optical film in combination with conventionally known optical members such as other retardation plates, diffusion control films, brightness enhancement films, etc. in addition to the polarizer as described above. You can also Examples of the other retardation plate include those obtained by uniaxially or biaxially stretching a polymer film, those obtained by Z-axis alignment treatment, and coating films of liquid crystalline polymers. Examples of the diffusion control film include films utilizing diffusion, scattering, and refraction, and these can be used for, for example, control of viewing angle, glare related to resolution, and control of scattered light.

  The laminated polarizing plate of the present invention may further contain other optical layers in practical use. Examples of the optical layer include various conventionally known optical layers used for forming liquid crystal display devices such as a reflector, a semi-transmissive reflector, and a brightness enhancement film as shown below. One kind of these optical layers may be used, two or more kinds may be used in combination, one layer may be used, or two or more layers may be laminated. A laminated polarizing plate including such an optical layer is preferably used as an integrated polarizing plate having an optical compensation function, for example, and is suitable for use in various image display devices such as being disposed on the surface of a liquid crystal cell. Yes.

  First, an example of a reflective polarizing plate or a transflective polarizing plate will be described. In the reflective polarizing plate, a reflective plate is further laminated on the laminated polarizing plate of the present invention, and in the transflective polarizing plate, a semi-transmissive reflective plate is further laminated on the laminated polarizing plate of the present invention.

  The reflective polarizing plate is usually disposed on the back side of the liquid crystal cell, and can be used for a liquid crystal display device (reflective liquid crystal display device) of a type that reflects incident light from the viewing side (display side). Such a reflective polarizing plate, for example, has an advantage that the liquid crystal display device can be thinned because the built-in light source such as a backlight can be omitted.

  The reflective polarizing plate can be produced by a conventionally known method such as a method of forming a reflective plate made of metal or the like on one surface of the polarizing plate. Specifically, for example, one surface (exposed surface) of the transparent protective layer in the polarizing plate is mat-treated as necessary, and a metal foil or a vapor deposition film made of a reflective metal such as aluminum is used as a reflector on the surface. Examples include the formed reflective polarizing plate.

  In addition, as described above, a reflective polarizing plate, etc., in which a reflecting plate reflecting the fine uneven structure is formed on a transparent protective layer containing fine particles in various transparent resins and having a fine uneven structure on the surface. It is done. A reflector having a fine concavo-convex structure on its surface has an advantage that, for example, incident light can be diffused by irregular reflection to prevent directivity and glaring appearance and to suppress uneven brightness. Such a reflector is, for example, directly on the uneven surface of the transparent protective layer by a conventionally known method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can form as a metal vapor deposition film.

  On the other hand, the transflective polarizing plate has a transflective reflective plate instead of the reflective plate in the reflective polarizing plate. Examples of the semi-transmissive reflector include a half mirror that reflects light through a reflective layer and transmits light.

  The transflective polarizing plate is usually provided on the back side of the liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. In a relatively dark atmosphere, it can be used for a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. That is, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and can be used with the built-in light source in a relatively dark atmosphere. It is useful for the formation of etc.

  Next, an example of a polarizing plate in which a brightness enhancement film is laminated on the laminated polarizing plate of the present invention will be described. The brightness enhancement film is not particularly limited. For example, it transmits linearly polarized light having a predetermined polarization axis, such as a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy, and the like. For example, the light having the characteristic of reflecting can be used. As such a brightness enhancement film, for example, trade name “D-BEF” manufactured by 3M Co., Ltd. may be mentioned. Also, a cholesteric liquid crystal layer, in particular an oriented film of a cholesteric liquid crystal polymer, or a film in which the oriented liquid crystal layer is supported on a film substrate can be used. These reflect the right and left circularly polarized light and transmit the other light. For example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name “Transmax” manufactured by Merck, etc. can give.

Various polarizing plates having an optical layer such as the reflection plate, transflective plate, and brightness enhancement film can be easily laminated on other members such as a liquid crystal cell. It is preferable to have. These can be arranged on one side or both sides of the polarizing plate. As materials for the pressure-sensitive adhesive layer and the adhesive layer, those exemplified above can be used.
In practical use, the pressure-sensitive adhesive layer is preferably covered with a separator. This separator can be formed on a suitable film or paper by a method of providing one or more release coats with a release agent such as silicone, long chain alkyl, fluorine, and molybdenum sulfide, if necessary.

  As described above, the optical film such as the laminated polarizing plate of the present invention can be attached to a liquid crystal cell and used in the form of a liquid crystal panel, or used in various image display devices such as a liquid crystal display device incorporating the same. be able to. For example, an optical film such as a laminated polarizing plate of the present invention is disposed on one side or both sides of a liquid crystal cell to form a liquid crystal panel, which can be used for a liquid crystal display device such as a reflection type, a transflective type, or a transmission / reflection type. .

  The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected. For example, an active matrix driving type represented by a thin film transistor type, a simple matrix driving type represented by a twist nematic type or a super twist nematic type, and the like. Various types of liquid crystal cells can be used.

  The liquid crystal cell is usually a structure in which liquid crystal is injected into the gap between the opposing liquid crystal cell substrates. The liquid crystal cell substrate is not particularly limited, and for example, a glass substrate or a plastic substrate can be used. The material for the plastic substrate is not particularly limited, and conventionally known materials can be used.

  Moreover, when providing the optical film of this invention on both surfaces of a liquid crystal cell, they may be the same kind and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged in one or more layers at appropriate positions.

  Furthermore, the liquid crystal display device of the present invention includes the liquid crystal panel of the present invention, and is not particularly limited except that the liquid crystal panel is used. In the case of including a light source, the light source is not particularly limited. However, for example, a plane light source that emits polarized light is preferable because the energy of light can be used effectively.

  In the liquid crystal display device of the present invention, for example, a diffusion plate, an antiglare layer, an antireflection film, a protective layer and a protective plate are further arranged on the viewing-side optical film (laminated polarizing plate), or the liquid crystal in the liquid crystal panel. A compensation retardation plate or the like can be appropriately disposed between the cell and the polarizing plate.

  The optical film such as the laminated polarizing plate of the present invention is not limited to the use of the liquid crystal display device as described above. For example, a self-luminous image display device such as an organic electroluminescence (EL) display, PDP, or FED. Can also be used.

  Next, the retardation plate of the present invention will be described in more detail based on the following examples, but the present invention is not limited to only these examples.

(Polyamideimide structure)
The structure was specified using FT-NMR (manufactured by JEOL Ltd., LA400) and FT-IR (manufactured by Thermo Nicolet, Magna750).

(Measurement of molecular weight)
Measurement was performed using HLC-8120GPC manufactured by Tosoh Corporation.

(Measurement of birefringence and thickness direction retardation)
Using an automatic phase difference meter (manufactured by Oji Scientific Instruments Co., Ltd., trade name: KOBRA-21ADH), the thickness direction retardation value (Rth) at wavelengths of 480 nm to 800 nm was measured. This retardation value was measured with respect to incident light from a direction inclined by 40 degrees from the normal line of the retardation plate (coating film).

(Film thickness measurement)
The film thickness of the coating film was measured using MCPD-2000 from Otsuka Electronics Co., Ltd.

Example 1
2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), trimellitic anhydride (TMA), 2,2′-bis (trifluoromethyl) -4, Polyamideimide synthesized by 4′-diaminobiphenyl (TFMB) was used. The polyamideimide has a weight average molecular weight of about 100,000, and two types of polyamideimides represented by the above general formulas (VII) and (VIII) (“m” in the above general formulas (VII) and (VIII) are 50 mol%, and “n” is 50 mol%).
These two types of polyamideimide mixture and modified polystyrene (trade name: ARASTOR 700, manufactured by Arakawa Chemical Co., Ltd.) are mixed at 10: 3 by mass, dissolved in methyl isobutyl ketone, and a solid content concentration of 10% by mass. Was prepared.
This prepared solution was applied to one side of a 75 μm thick polyethylene terephthalate biaxially stretched film (trade name: S-27, manufactured by Toray Industries, Inc.) by spin coating to a thickness of about 80 μm, and then dried at 150 ° C. for 30 minutes. And solidified to form a coating film having a thickness of 8 μm. The coated film was peeled from the PET film to obtain the retardation plate of Example 1.

Example 2
A coating film having a thickness of 8 μm was formed in the same manner as in Example 1 except that the blending ratio of the polyamideimide mixture and the modified polystyrene was changed to 10: 7 by mass, and this was carried out by peeling the film from the PET film. The retardation plate of Example 2 was obtained.

Comparative Example 1
A coating film was formed on a PET film in the same manner as in Example 1 except that general-purpose polystyrene (manufactured by PS Japan, trade name: SGP-10) was used instead of modified polystyrene.

Comparative Example 2
Synthesized with 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (TFMB) A coated film was formed on a PET film in the same manner as in Example 1 except that the polyimide used was used.
This polyimide has a weight average molecular weight of about 100,000 and is made of a polymer consisting only of the repeating unit represented by the general formula (VI).

Comparative Example 3
A coating film was formed on a PET film in the same manner as in Example 1 except that the polyimide used in Comparative Example 2 and the general-purpose polystyrene used in Comparative Example 1 were blended at 10: 3 by mass.

Comparative Example 4
Only the polyamideimide used in Example 1 was dissolved in methyl isobutyl ketone to prepare a solution having a solid concentration of 10% by mass. A coating film having a thickness of 8 μm was formed in the same manner as in Example 1 except that this solution was used, and this was peeled from the PET film to obtain a retardation film of Comparative Example 4.

Comparative Example 5
Only the polyimide used in Comparative Example 2 was dissolved in methyl isobutyl ketone to prepare a solution having a solid concentration of 10% by mass. A coating film having a thickness of 8 μm was formed in the same manner as in Example 1 except that this solution was used, and this was peeled from the PET film to obtain a retardation plate of Comparative Example 5.

(State of solution and coating film)
When the polymer solutions of Examples 1 and 2 and Comparative Examples 4 and 5 were visually confirmed, they were very excellent in transparency, but the polymer solutions of Comparative Examples 1 to 3 were clearly cloudy. Further, when the obtained coating films were visually confirmed, the coating films of Examples 1 and 2 and Comparative Examples 4 and 5 were very excellent in transparency, but the polymers of Comparative Examples 1 to 3 were used. The solution was clearly cloudy.

(Birefringence and wavelength dispersion characteristics)
Table 1 shows the birefringence in the thickness direction and the ratio of retardation values at wavelengths of 480 nm and 590 nm for the coating films of Examples 1 and 2 and Comparative Examples 4 and 5.
Further, for the coating films of Examples 1 and 2 and Comparative Examples 4 and 5, the ratio of the retardation value in the thickness direction at each wavelength to the retardation value in the thickness direction at wavelength 590 (Rth (W) / Rth (590 nm)) is shown in the graph of FIG.
From the above results, it was confirmed that the coating films of Examples 1 and 2 satisfied the relationship of 0.99 <Rth (W) / Rth (590 nm) <1.01 and exhibited flat wavelength dispersion. . On the other hand, the coating films of Comparative Examples 4 and 5 showed positive chromatic dispersion in which the retardation in the thickness direction was larger toward the shorter wavelength side.
Note that the coating films of Comparative Examples 1 to 3 that were clearly cloudy and could not be used as optical members could not measure the birefringence or the phase difference at each wavelength.

The graph which shows the wavelength dispersion characteristic of Examples 1 and 2 and Comparative Examples 4 and 5. FIG.

Claims (13)

Obtained by coating a solution containing polyamideimide having at least one repeating unit represented by the following general formula (I) or general formula (II) and a modified polystyrene containing a carboxyl group A retardation plate having a coated film.

(In general formulas (I) and (II), A, B, and D each represent a substituent, and a, b, and d next to it represent the number of substitutions. A, B, and D are the same. Or, each of them is an atom or group selected from a halogen, an alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a nitro group, a cyano group, a hydroxyl group, and a thiol group, where a is 0 to 3. And b and d are integers of 0 to 4. When A, B and D are composed of a plurality of substituents, each substituent may be the same or different, and X is a single bond, or (It is an atom or group selected from oxygen, sulfur, a carbonyl group, an alkylene group, and a substituted alkylene group. P1 and p2 are integers of 1 or more.) The retardation plate according to claim 1, wherein the repeating unit represented by the general formula (I) is represented by the following formula (III).

The retardation plate according to claim 1, wherein the repeating unit represented by the general formula (II) is represented by the following formula (IV).

The phase difference plate according to claim 1, wherein the polyamideimide further has a repeating unit represented by the following general formula (V).

(In general formula (V), E, G, and H each represent a substituent, and e, g, and h next to it represent the number of substitutions. E, G, and H are the same or different. And an atom or group selected from a halogen, an alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a nitro group, a cyano group, a hydroxyl group, and a thiol group, e is an integer of 0 to 3, g And h is an integer of 0 to 4. When E, G, and H are composed of a plurality of substituents, each substituent may be the same or different, and Y and X are the same or different, A bond or an atom or group selected from oxygen, sulfur, carbonyl group, alkylene group, substituted alkylene group, q1 and q2 are integers of 1 or more.) The retardation plate according to claim 4, wherein the repeating unit represented by the general formula (V) is represented by the following formula (VI).

The phase difference plate according to claim 1, wherein the polyamideimide contains at least one of copolymers represented by the following general formula (VII) or general formula (VIII).

(In the general formulas (VII) and (VIII), m represents 30 to 70 mol% and n represents 30 to 70 mol% when the total repeating units constituting the polyamideimide are 100 mol%) The retardation plate according to claim 1, wherein the modified polystyrene has a repeating unit represented by the following general formula (IX).

(In general formula (IX), J represents a substituent, and j beside it represents the number of substitutions. J represents a halogen, an alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, An atom or group selected from a nitro group, a cyano group, a hydroxyl group, and a thiol group, j is an integer of 0 to 5. When J comprises a plurality of substituents, each substituent is the same or different. R may be a hydrogen atom, an alkyl group or a substituted alkyl group.) The retardation plate according to claim 7, wherein the repeating unit represented by the general formula (IX) is represented by the following formula (X).

  The retardation plate according to claim 1, wherein 10 to 150 parts by mass of the modified polystyrene is blended with respect to 100 parts by mass of the polyamideimide. The phase according to any one of claims 1 to 9, wherein the thickness direction retardation at least at a wavelength of 500 to 750 nm satisfies a relationship of 0.99 <Rth (W) / Rth (590) <1.01. Phase difference plate.
(Rth (W) represents a phase difference at a wavelength Wnm, Rth (590) represents a phase difference at a wavelength of 590 nm, and each Rth is defined by (nx−nz) × d, where nx is ) Represents the maximum refractive index in the plane, nz represents the refractive index in the thickness direction, and d represents the thickness of the retardation plate.   An optical film provided with the phase difference plate in any one of Claims 1-10.   A liquid crystal panel comprising the retardation plate according to claim 1 or the optical film according to claim 11. An image display apparatus provided with the phase difference plate in any one of Claims 1-10, or the optical film of Claim 11.

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