JP2008216782A - Optical laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical laminate in which the adverse influence on optical characteristics is suppressed and the adhesion between a retardation layer and a base material is excellent. <P>SOLUTION: The optical laminate has the base material, an alignment layer and the retardation layer in this order. The alignment layer is formed of a silane coupling coating and a silica sol and the retardation layer is a solidification layer or a hardening layer of a liquid crystalline composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical laminate, a polarizing element using the optical laminate, and an image display device. More specifically, the present invention relates to an optical laminate that can be excellent in adhesion between a retardation layer and a substrate and can suppress the generation of haze.

  In various image display devices such as a liquid crystal display device and an electroluminescence (EL) display, a retardation layer is generally used for optical compensation.

The retardation layer includes, for example, a layer formed by fixing the alignment state of the liquid crystal material (see, for example, Patent Document 1). However, when such a retardation layer is used, there is a problem in that the optical properties are adversely affected (for example, haze occurs), and the adhesion with an adjacent layer (base material) is poor.
JP 2002-333642 A

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an optical laminate that suppresses adverse effects on optical properties and is excellent in adhesion between a retardation layer and a substrate. It is.

  The optical layered body of the present invention comprises a substrate, an alignment film, and a retardation layer in this order, the alignment film is formed from a silane coupling agent and silica sol, and the retardation layer is a solidified liquid crystalline composition. Layer or hardened layer.

  In preferable embodiment, the said base material contains norbornene-type resin.

  In a preferred embodiment, the refractive index ellipsoid of the substrate has a relationship of nx> ny = nz.

  In a preferred embodiment, the refractive index ellipsoid of the substrate has a relationship of nx> ny> nz.

  In a preferred embodiment, the alignment film has a thickness of 1 nm to 20 μm.

  In a preferred embodiment, the alignment film is formed from 1 to 100 parts by weight of the silica sol (solid content) with respect to 100 parts by weight of the silane coupling agent.

ここで、Ｒ_１、Ｒ_２およびＲ_３は、それぞれ独立して、水素原子、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｓｅｃ−ブチル基またはｔｅｒｔ−ブチル基であり、Ｘは、アクリルエステル基、ビニル基、メタクリル基、ウレイド基、イソシアネート基およびエポキシ基からなる群より選ばれた少なくとも１種の官能基である。 In preferable embodiment, the said silane coupling agent contains the compound represented with the following general formula (I).

Here, R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group or tert-butyl. X is at least one functional group selected from the group consisting of an acrylic ester group, a vinyl group, a methacryl group, a ureido group, an isocyanate group and an epoxy group.

  In a preferred embodiment, the refractive index ellipsoid of the retardation layer has a relationship of nz> nx = ny.

  In a preferred embodiment, the retardation Rth in the thickness direction of the retardation layer is −20 to −200 nm.

  In a preferred embodiment, the liquid crystal composition includes a liquid crystal compound having a polymerizable functional group.

  According to another aspect of the present invention, a polarizing element is provided. The polarizing element includes the optical layered body and a polarizer.

  In preferable embodiment, the said polarizer is arrange | positioned at the base-material side of the said optical laminated body.

  In a preferred embodiment, the absorption axis of the polarizer and the slow axis of the substrate are orthogonal to each other.

  According to another aspect of the present invention, an image display device is provided. The image display device includes the polarizing element.

  According to the present invention, by providing an alignment film formed from a silane coupling agent and a silica sol, an optical laminate capable of excellent adhesion between the base material and the retardation layer and suppressing adverse effects on optical properties. The body can be provided.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

(Definition of terms and symbols)
The definitions of terms and symbols in this specification are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), “ny” is the refractive index in the direction perpendicular to the slow axis in the plane, and “nz” "Is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
The in-plane retardation (Re) means an in-plane retardation value of a layer (film) at 23 ° C., and a wavelength of 590 nm unless otherwise specified. Re is obtained by Re = (nx−ny) × d, where d (nm) is the thickness of the layer (film). In this specification, when Re (550) is indicated, it means an in-plane retardation of a layer (film) at a wavelength of 550 nm.
(3) Thickness direction retardation (Rth)
Thickness direction retardation (Rth) is a retardation value in the thickness direction of a layer (film) at a wavelength of 590 nm unless otherwise specified. Rth is determined by Rth = (nx−nz) × d, where d (nm) is the thickness of the layer (film). In addition, in this specification, when Rth (550) is shown, it means the retardation in the thickness direction of the layer (film) at a wavelength of 550 nm.
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.

A. FIG. 1 is a schematic cross-sectional view of an optical laminate according to a preferred embodiment of the present invention. The optical laminate 10 includes a base material 11, an alignment film 12, and a retardation layer 13 in this order. Although not shown, other optical elements may be provided as necessary. As the other optical element, any appropriate optical element can be adopted depending on the purpose. For example, a liquid crystal film, a light scattering film, a diffraction film, and another retardation film are mentioned. Hereinafter, each layer will be described.

A-1. Base Material The base material 11 is formed of any appropriate material that can be used as an optical element. A specific example is a polymer film. The substrate may be a single layer of a polymer film or a laminate of polymer films. The base material may be a polymer film that has been subjected to a stretching treatment. Materials for forming the polymer film include norbornene resins, polycarbonate resins, cellulose resins, (meth) acrylic resins, polyester resins, nylon resins, polyolefin resins such as polypropylene, vinyl resins, maleic acid Resin, phthalic acid resin and the like. A norbornene resin is preferable.

  The substrate may be optically isotropic or optically anisotropic (birefringent). When a base material has optical anisotropy, the base material can also function as an optical compensation layer (retardation layer). Here, “optically isotropic” includes a case where the optically isotropic property is substantially achieved. “Substantially optically isotropic” means that Re is less than 10 nm and the absolute value of Rth is less than 10 nm. When the substrate has optical anisotropy, its optical characteristics (for example, Re, Rth) can be set to any appropriate value depending on, for example, the driving mode of the liquid crystal cell to be compensated. In one embodiment, the substrate has a refractive index ellipsoid of nx> ny = nz. Here, “ny = nz” includes not only the case where ny and nz are exactly equal, but also the case where ny and nz are substantially equal. That is, the Nz coefficient (Rth / Re) is more than 0.9 and less than 1.1. In another embodiment, the substrate has a refractive index ellipsoid of nx> ny> nz. In this case, the Nz coefficient is preferably 1 <Nz <1.5. Such optical characteristics can be controlled by appropriately setting the conditions for the stretching treatment (for example, stretching ratio, stretching temperature, stretching method, stretching direction).

  The thickness of the base material can be set to any appropriate value depending on the purpose. Typically, it is 5-500 micrometers, Preferably it is 10-250 micrometers, More preferably, it is 10-150 micrometers.

A-2. Alignment film The alignment film 12 is formed of a silane coupling agent and silica sol. By providing such an alignment film, adhesion between the base material and a retardation layer described later can be improved, and adverse effects on optical characteristics, for example, generation of haze can be suppressed. In addition, it is thought that by providing the alignment layer, the alignment state of the liquid crystal material forming the retardation layer can be improved, and as a result, adverse effects on the optical characteristics are suppressed.

The silane coupling agent includes, for example, a compound represented by the following general formula (I).

In the above formula (I), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group. Or it is a tert-butyl group. In the above formula (I), X is at least one functional group selected from the group consisting of an acrylic ester group, a vinyl group, a methacryl group, a ureido group, an isocyanate group, and an epoxy group. X is preferably an acrylic ester group.

In one embodiment, the silica sol is at least one hydrolysis or condensate selected from tetraalkoxysilane, a partial hydrolyzate of tetraalkoxysilane, and an oligomer that is a condensate of tetraalkoxysilane. Tetraalkoxysilane is a compound represented by Si (OR) ₄ . R in the formula can be any suitable alkyl group. Preferably, it is an alkyl group having 1 to 4 carbon atoms. In addition, as a silica sol, a commercial item can be used as it is. Examples of commercially available products include “Colcoat P” (manufactured by Colcoat Co., Ltd.), which is an alcoholic silica sol. Such a silica sol can form polysiloxane by being coated on the base material together with the silane coupling agent and dried.

  The blending ratio of the silane coupling agent and the silica sol (solid content) is preferably 1 to 100 parts by weight, more preferably 1 to 80 parts by weight of silica sol (solid content) with respect to 100 parts by weight of the silane coupling agent. More preferably, it is 1 to 50 parts by weight, particularly preferably 1 to 30 parts by weight, and most preferably 1 to 20 parts by weight.

  In one embodiment, the alignment film can be obtained by applying a coating solution containing a silane coupling agent and silica sol onto the substrate and removing the solvent by drying. Any appropriate solvent can be adopted as the solvent as long as it can dissolve the silane coupling agent and disperse the silica sol. Preferably, alcohols such as isopropyl alcohol, methanol and ethanol, ketones, ethers and the like can be mentioned. The amount of the solvent can be set to any appropriate value as long as the silane coupling agent can be dissolved and the silica sol can be dispersed.

  Any appropriate coating means can be used for the coating. Preferably, a wire bar, a curtain coater, a roll coater, a gravure coater, etc. are mentioned. The drying temperature is typically 40 to 160 ° C, preferably 50 to 150 ° C, and more preferably 65 to 120 ° C. The drying time is typically 30 seconds to 1 hour, preferably 30 seconds to 30 minutes, and particularly preferably 30 seconds to 10 minutes.

  The thickness of the alignment film can be set to any appropriate thickness. Preferably they are 1 nm-20 micrometers, More preferably, they are 1 nm-10 micrometers, Most preferably, they are 1 nm-5 micrometers.

A-3. Retardation layer The retardation layer 13 is a solidified layer or a cured layer of a liquid crystalline composition. In the present specification, the “solidified layer” refers to a softened, melted or solution liquid crystalline composition that has been cooled and solidified. The “cured layer” refers to a liquid crystal composition that has been cross-linked by heat, catalyst, light, and / or radiation to be in a stable state of infusibility or insolubility. In addition, the hardened layer includes a hardened layer formed through a solidified layer of the liquid crystal composition.

  Specific examples of the retardation layer include a film containing a liquid crystal material fixed (solidified or cured) in homeotropic alignment. In this specification, “homeotropic alignment” refers to an alignment state in which the major axis direction of the liquid crystal material (liquid crystal compound) contained in the liquid crystal composition is 60 to 90 ° with respect to the substrate surface. In other words, “homeotropic alignment” includes not only pure vertical alignment but also predetermined tilted alignment. Note that the tilt angle of the tilted orientation can be obtained by the procedure described in Journal of Applied Physics, Vol. 38 (1999), P.748, for example. Another specific example is a film obtained by in-plane orientation of a material exhibiting negative birefringence such as polystyrene. These films can have a refractive index profile of nz> nx = ny and can function as so-called positive C plates. Here, “nx = ny” includes not only the case where nx and ny are exactly equal, but also the case where nx and ny are substantially equal. That is, Re is less than 10 nm. The thickness direction retardation Rth of the film is preferably −20 to −200 nm, more preferably −40 to −180 nm, and particularly preferably −40 to −160 nm. The thickness of the film from which such Rth can be obtained can vary depending on the material used. Preferably it is 0.5-60 micrometers, More preferably, it is 0.5-50 micrometers, Most preferably, it is 0.5-40 micrometers.

  The liquid crystal material (liquid crystal compound) capable of forming the homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Examples of typical liquid crystal compounds include nematic liquid crystal compounds. An outline of such a liquid crystal compound alignment technique is described in, for example, Chemical Review 44 (Surface Modification, Edited by Chemical Society of Japan, pages 156 to 163).

  Another specific example of the liquid crystal material capable of forming homeotropic alignment is a side containing a monomer unit (a) containing a liquid crystalline fragment side chain and a monomer unit (b) containing a non-liquid crystalline fragment side chain. A chain type liquid crystal polymer is mentioned. Such a side-chain liquid crystal polymer can realize homeotropic alignment without using a vertical alignment agent or a vertical alignment film. The side chain type liquid crystal polymer is a monomer unit containing a non-liquid crystalline fragment side chain having an alkyl chain in addition to the monomer unit (a) containing a liquid crystalline fragment side chain of a normal side chain type liquid crystal polymer. (B) Due to the action of the monomer unit (b) containing the non-liquid crystalline fragment side chain, a liquid crystal state (for example, a nematic liquid crystal phase) can be expressed by, for example, heat treatment without using a vertical alignment agent or a vertical alignment film. It is speculated that homeotropic alignment can be realized.

  The monomer unit (a) has a side chain having nematic liquid crystallinity, and examples thereof include a monomer unit represented by the general formula (a).

In the formula (a), R ¹ is a hydrogen atom or a methyl group, a is a positive integer of 1 to 6, X ¹ is a —CO ₂ — group or a —OCO— group, and R ² is cyano. A group, an alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, and b and c each represent an integer of 1 or 2.

  The monomer unit (b) has a linear side chain, and examples thereof include a monomer unit represented by the general formula (b).

In the above formula (b), R ³ is a hydrogen atom or a methyl group, and R ⁴ is represented by an alkyl group having 1 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or the general formula (b1). It is a group.

In the above formula (b1), d is a positive integer from 1 to 6, ^{R 5} is an alkyl group having 1 to 6 carbon atoms.

  The ratio of the monomer unit (a) and the monomer unit (b) can be appropriately set according to the purpose and the type of the monomer unit. (B) / {(a) + (b)} is preferably 0.01 to 0.8 (molar ratio), more preferably 0.1 to 0.5 (molar ratio). This is because when the proportion of the monomer unit (b) increases, the side chain type liquid crystal polymer often does not exhibit liquid crystal monodomain alignment.

  As another specific example of the liquid crystal material capable of forming homeotropic alignment, a monomer unit (a) containing the liquid crystalline fragment side chain and a monomer unit containing a liquid crystalline fragment side chain having an alicyclic ring structure ( and a side chain type liquid crystal polymer containing c). Such a side-chain liquid crystal polymer can also realize homeotropic alignment without using a vertical alignment agent or a vertical alignment film. The side chain type liquid crystal polymer is a monomer containing a liquid crystalline fragment side chain having an alicyclic ring structure in addition to the monomer unit (a) containing a liquid crystalline fragment side chain of a normal side chain type liquid crystal polymer. It has a unit (c). Due to the action of the monomer unit (c), a liquid crystal state (for example, a nematic liquid crystal phase) can be expressed by, for example, heat treatment without using a vertical alignment film, and it is assumed that homeotropic alignment can be realized. The

  The monomer unit (c) has a side chain having nematic liquid crystallinity, and examples thereof include a monomer unit represented by the general formula (c).

In the above formula (c), R ⁶ is a hydrogen atom or a methyl group, h is a positive integer of 1 to 6, X ² is a —CO ₂ — group or a —OCO— group, and e and g are , Each is an integer of 1 or 2, f is an integer of 0 to 2, and R ⁷ is a cyano group or an alkyl group having 1 to 12 carbon atoms.

  The ratio of the monomer unit (a) to the monomer unit (c) can be appropriately set according to the purpose and the type of monomer unit. (C) / {(a) + (c)} is preferably 0.01 to 0.8 (molar ratio), more preferably 0.1 to 0.6 (molar ratio). This is because when the proportion of the monomer unit (b) increases, the side chain type liquid crystal polymer often does not exhibit liquid crystal monodomain alignment.

  The above monomer units are merely examples, and it goes without saying that the liquid crystal polymer capable of forming homeotropic alignment is not limited to those having the above monomer units. Moreover, the said exemplary monomer unit can be combined suitably.

  The weight average molecular weight of the side chain type liquid crystal polymer is preferably 2,000 to 100,000. By adjusting the weight average molecular weight to such a range, the performance as a liquid crystal polymer can be satisfactorily exhibited. The weight average molecular weight is more preferably 2,500 to 50,000. Within such a range, the alignment layer is excellent in film formability and a uniform alignment state can be formed.

  The exemplified side chain type liquid crystal polymer can be prepared by copolymerizing an acrylic monomer or a methacrylic monomer corresponding to the monomer unit (a), the monomer unit (b) or the monomer unit (c). The monomer corresponding to the monomer unit (a), the monomer unit (b) or the monomer unit (c) can be synthesized by any appropriate method. The copolymer can be prepared according to any appropriate polymerization method such as an acrylic monomer (for example, radical polymerization method, cationic polymerization method, anion polymerization method). In addition, when applying radical polymerization system, various polymerization initiators can be used. Preferred polymerization initiators include azobisisobutyronitrile or benzoyl peroxide. This is because the polymerization can be started with an appropriate mechanism and speed because it can be decomposed at an appropriate temperature (not high or low).

The homeotropic alignment can also be formed from a liquid crystalline composition containing the side chain liquid crystal polymer. Such a liquid crystal composition may contain a polymerizable liquid crystal compound (typically, a photopolymerizable liquid crystal compound) in addition to the polymer. The polymerizable liquid crystal compound is a liquid crystal compound having at least one polymerizable functional group (for example, a photopolymerizable functional group such as an unsaturated double bond such as an acryloyl group or a methacryloyl group). Those exhibiting nematic liquid crystallinity are preferred. Specific examples of such a photopolymerizable liquid crystal compound include acrylates and methacrylates that can also be used as the monomer unit (a). Further preferred photopolymerizable liquid crystal compounds have two or more photopolymerizable functional groups. It is because durability of the film obtained can be improved. Examples of such a photopolymerizable liquid crystal compound include a crosslinked nematic liquid crystal monomer represented by the following formula. Examples of the photopolymerizable liquid crystal compound include compounds in which the terminal “H ₂ C═CR—CO ₂ —” in the following formula is substituted with a vinyl ether group or an epoxy group, “— (CH ₂ ) _m —” and / or Alternatively, “— (CH ₂ ) _n —” is replaced with “— (CH ₂ ) ₃ —C ^* H (CH ₃ ) — (CH ₂ ) ₂ —” or “— (CH ₂ ) ₂ —C ^* H (CH ₃ )”. A compound substituted with “— (CH ₂ ) ₃ —” can be exemplified.

In the above formula, R ⁸ is a hydrogen atom or a methyl group, A and D are each independently a 1,4-phenylene group or a 1,4-cyclohexylene group, and Y is each independently —COO— group, —OCO— group or —O— group, and B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4′-biphenylene group or 4,4′-bicyclohexylene. And m and n each independently represents an integer of 2 to 6.

  The photopolymerizable liquid crystal compound can be brought into a liquid crystal state by heat treatment, for example, to exhibit a nematic liquid crystal phase and to be homeotropically aligned with the side chain liquid crystal polymer. Next, the durability of the homeotropic alignment liquid crystal film can be further improved by polymerizing or crosslinking the photopolymerizable liquid crystal compound to fix the homeotropic alignment.

  The ratio of the photopolymerizable liquid crystal compound to the side chain type liquid crystal polymer in the liquid crystal composition is the purpose, the type of the side chain type liquid crystal polymer and the photopolymerizable liquid crystal compound used, and the durability of the resulting homeotropic alignment liquid crystal film. It can be set as appropriate in consideration of the characteristics. Specifically, the photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) is preferably about 0.1: 1 to 30: 1, more preferably 0.5: 1 to 20: 1. Yes, most preferably 1: 1 to 10: 1.

  The liquid crystalline composition may further contain a photopolymerization initiator. Any appropriate photopolymerization initiator can be adopted as the photopolymerization initiator. Specific examples include Irgacure 907, 184, 651, and 369 manufactured by Ciba Specialty Chemicals. The content of the photopolymerization initiator can be adjusted to such an extent that the homeotropic orientation of the liquid crystalline composition is not disturbed in consideration of the kind of the photopolymerizable liquid crystal compound, the blending ratio of the liquid crystalline composition, and the like. Typically, the content of the photopolymerization initiator is preferably about 0.5 to 30 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the photopolymerizable liquid crystal compound. is there.

  When the retardation layer is a film containing a liquid crystal material fixed in a homeotropic alignment, by providing the alignment film, the homeotropic alignment state of the liquid crystal material can be satisfactorily maintained. Can be suppressed. Note that the haze can be manifested when the liquid crystal material is not well and uniformly aligned and a microdomain or the like is formed.

A-4. Manufacturing Method The manufacturing method in one embodiment of the optical layered body of the present invention includes a step of forming the alignment film on the substrate and a step of forming a retardation layer on the alignment film. Specific examples of the method for forming the alignment film are as described in the above section A-2. Hereinafter, a method for forming the retardation layer will be described using a film containing a liquid crystal material fixed in the above-described homeotropic alignment as an example.

  A film containing a liquid crystal material fixed in the homeotropic alignment is obtained by applying the liquid crystal material (liquid crystal monomer or liquid crystal polymer) or the liquid crystalline composition described in the above section A-3 onto an alignment film, The film is formed by homeotropic orientation in a state of exhibiting and fixing in a state in which the orientation is maintained. Hereinafter, a detailed production procedure of the film will be described.

  As a method for coating the liquid crystal material (liquid crystal monomer or liquid crystal polymer) or liquid crystalline composition on the alignment film, a solution coating method using a solution obtained by dissolving the liquid crystal material or liquid crystalline composition in a solvent, or Examples include a method of melting and applying a liquid crystal material or a liquid crystal composition. A solution coating method is preferred. This is because homeotropic alignment can be realized precisely and easily.

  As a solvent used in the solution coating method, any appropriate solvent capable of dissolving the liquid crystal material or the liquid crystal composition may be employed. Specific examples include halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, xylene, methoxybenzene, 1,2- Aromatic hydrocarbons such as dimethobenzene, acetone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve, butyl cellosolve, 2 -Pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetate Amides, dimethyl sulfoxide, acetonitrile, butyronitrile, carbon disulfide, cyclohexanone, cyclopentane and the like. The concentration of the solution can be set to any appropriate value depending on the type (solubility) of the liquid crystal material used, the target thickness, and the like. Preferably it is 3 to 50 weight%, More preferably, it is 7 to 30 weight%.

  Examples of the method for applying the solution to the alignment film include a roll coating method, a gravure coating method, a spin coating method, and a bar coating method. A gravure coating method and a bar coating method are preferred. This is because it is easy to coat a large area uniformly. After coating, the solvent is removed, and a liquid crystal material layer (liquid crystalline composition layer) is formed on the substrate. The conditions for removing the solvent are not particularly limited, as long as the solvent can be substantially removed and the liquid crystal material layer or the liquid crystal composition layer does not flow or even flows down. Usually, the solvent is removed by drying at room temperature, drying in a drying furnace, heating on a hot plate, or the like.

  Next, the liquid crystal material layer (liquid crystal composition layer) formed on the alignment film is brought into a liquid crystal state and homeotropically aligned. For example, the liquid crystal polymer (liquid crystalline composition) is heat-treated so as to have a temperature in a liquid crystal state, and homeotropic alignment is performed in the liquid crystal state. As the heat treatment method, the above drying method can be adopted. The heat treatment temperature and the heat treatment time can vary depending on the type of liquid crystal material or liquid crystal composition used and the alignment film. The heat treatment temperature is preferably 40 to 300 ° C, more preferably 45 to 200 ° C, and most preferably 50 to 150 ° C. The heat treatment time is preferably 10 seconds to 2 hours, more preferably 20 seconds to 30 minutes, and most preferably 30 seconds to 10 minutes. When the heat treatment time is shorter than 10 seconds, homeotropic alignment formation may not sufficiently proceed. When the heat treatment time is longer than 2 hours, homeotropic alignment formation often does not proceed any more, which is not preferable in terms of workability and mass productivity.

  Cooling is performed after the heat treatment. The orientation of the homeotropic alignment liquid crystal film is fixed by being cooled below the glass transition temperature of the liquid crystal material. As the cooling operation, for example, the homeotropic alignment liquid crystal film after the heat treatment is taken out from the heating atmosphere in the heat treatment operation to room temperature. You may perform forced cooling, such as air cooling and water cooling.

When using a liquid crystalline composition, the homeotropic liquid crystal alignment film fixed as described above is irradiated with light or ultraviolet rays to polymerize or crosslink the photopolymerizable liquid crystal compound, thereby making it photopolymerizable. The durability can be further improved by fixing the liquid crystal compound. The ultraviolet irradiation is preferably performed in an inert gas atmosphere in order to sufficiently accelerate the polymerization or the crosslinking reaction. As the ultraviolet irradiation means, a high-pressure mercury ultraviolet lamp having an illuminance of about 80 to 160 mW / cm ² is typically used. It is also possible to use another type of lamp such as a metahalide UV lamp or an incandescent tube. In addition, it is preferable to adjust the temperature so that the surface temperature of the liquid crystal layer during ultraviolet irradiation is in a temperature range that exhibits a liquid crystal state. Examples of temperature control methods include cold mirrors, water cooling and other cooling processes, or increasing the line speed.

B. Polarizing Element FIG. 2 is a schematic cross-sectional view of a polarizing element according to a preferred embodiment of the present invention. The polarizing element 100 includes an optical laminate 10 and a polarizer 20. Although not shown, a first protective layer is provided between the polarizer 20 and the optical laminate 10 as necessary, and a second protective layer is provided on the opposite side of the polarizer 20 from the optical laminate 10. . In the illustrated example, the polarizer 20 is disposed on the base material side 11 of the optical laminate 10, but may be disposed on the retardation layer 13 side. Preferably, as shown in FIG. 2, the polarizer is disposed on the base side of the optical laminate.

  When the substrate has a substantially in-plane retardation Re, the optical laminate 20 is laminated such that the slow axis of the substrate 11 is orthogonal to the absorption axis of the polarizer 10. In the present specification, the term “orthogonal” includes a case of being substantially orthogonal. Here, “substantially orthogonal” includes the case of 90 ° ± 3.0 °, preferably 90 ° ± 1.0 °, more preferably 90 ° ± 0.5 °.

B-1. Polarizer Any appropriate polarizer may be adopted as the polarizer 20 depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

  A polarizer uniaxially stretched by adsorbing iodine to a polyvinyl alcohol film can be produced by, for example, dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. . If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing.

  By washing the polyvinyl alcohol film with water, not only can the surface of the polyvinyl alcohol film be cleaned and the anti-blocking agent can be washed, but also the effect of preventing unevenness such as uneven dyeing can be obtained by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

B-2. Protective layer The said protective layer (a 1st protective layer and a 2nd protective layer) is formed with arbitrary appropriate films which can be used as a protective film of a polarizing plate. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

  As said (meth) acrylic-type resin, Tg (glass transition temperature) becomes like this. Preferably it is 115 degreeC or more, More preferably, it is 120 degreeC or more, More preferably, it is 125 degreeC or more, Most preferably, it is 130 degreeC or more. It is because it can be excellent in durability. The upper limit value of Tg of the (meth) acrylic resin is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

As said (meth) acrylic-type resin, arbitrary appropriate (meth) acrylic-type resins can be employ | adopted within the range which does not impair the effect of this invention. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  Specific examples of the (meth) acrylic resin include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. Examples of the resin include high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure is particularly preferable in that it has high heat resistance, high transparency, and high mechanical strength.

  Examples of the (meth) acrylic resin having the lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in JP-A-146084.

  The (meth) acrylic resin having the lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and still more preferably 10,000 to 500,000. Preferably it is 50000-500000.

  The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C., most preferably. Is 140 ° C. or higher. It is because it can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  In the present specification, “(meth) acrylic” refers to acrylic and / or methacrylic.

  The protective layer is preferably transparent and has no color. The thickness direction retardation Rth of the protective layer is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and still more preferably −70 nm to +70 nm.

  As the thickness of the protective layer, any appropriate thickness can be adopted as long as the above preferred thickness direction retardation Rth can be obtained. The thickness of the second protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 to 500 μm, and still more preferably 5 to 150 μm.

  On the opposite side of the second protective layer from the polarizer, a hard coat treatment, an antireflection treatment, an antisticking treatment, an antiglare treatment, or the like can be performed as necessary.

  The thickness direction retardation (Rth) of the first protective layer provided between the polarizer 20 and the optical layered body 10 is preferably smaller than the preferable value. As described above, in the case of a cellulose film generally used as a protective film, for example, a triacetyl cellulose film, the thickness direction retardation (Rth) is about 60 nm at a thickness of 80 μm. Therefore, the first protective layer can be suitably obtained by subjecting the cellulose-based film having a large thickness direction retardation (Rth) to appropriate treatment for reducing the thickness direction retardation (Rth). .

  Any appropriate treatment method can be adopted as the treatment for reducing the retardation (Rth) in the thickness direction. For example, a base material such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, about 80 to 150 ° C. for 3 to 10 minutes) After removing the base film, a solution obtained by dissolving norbornene resin, acrylic resin or the like in a solvent such as cyclopentanone or methyl ethyl ketone is applied to a general cellulose film and dried by heating (for example, And a method of peeling the coated film after about 3 to 10 minutes at about 80 to 150 ° C.).

  The material constituting the cellulose film is preferably a fatty acid-substituted cellulose polymer such as diacetyl cellulose or triacetyl cellulose. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8, preferably an acetic acid substitution degree of 1.8 to 2.7, more preferably a propionic acid substitution degree of 0.1 to 2.7. By controlling to 1, the thickness direction retardation (Rth) can be controlled to be small.

  By adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, and acetyltriethyl citrate to the fatty acid-substituted cellulose polymer, the thickness direction retardation (Rth) can be controlled small. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid-substituted cellulose polymer.

  The processes for reducing the thickness direction retardation (Rth) may be used in appropriate combination. The thickness direction retardation Rth (550) of the first protective layer obtained by performing such treatment is preferably −20 nm to +20 nm, more preferably −10 nm to +10 nm, still more preferably −6 nm to +6 nm, particularly Preferably, it is −3 nm to +3 nm. The in-plane retardation Re (550) of the first protective layer is preferably 0 nm to 10 nm, more preferably 0 nm to 6 nm, and still more preferably 0 nm to 3 nm.

  As the thickness of the first protective layer, any appropriate thickness can be adopted as long as the preferable thickness direction retardation Rth can be obtained. The thickness of the first protective layer is preferably 20 to 200 μm, more preferably 20 to 100 μm, and still more preferably 20 to 95 μm.

  Any appropriate method can be adopted as a method of laminating each layer (polarizer, optical laminate, and protective layer as necessary). Typically, it is laminated via any appropriate pressure-sensitive adhesive layer or adhesive layer.

C. Image Display Device An image display device of the present invention includes the polarizing element. In one embodiment, the image display device is a liquid crystal display device. The liquid crystal display device includes a liquid crystal cell and the polarizing element. The polarizing element is typically disposed on one side or both sides of the liquid crystal cell. Further, typically, the polarizing element is arranged so that the optical layered body is on the liquid crystal cell side. Any appropriate method can be adopted as a method of laminating the liquid crystal cell and the polarizing element. Typically, it is laminated via any appropriate pressure-sensitive adhesive layer or adhesive layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

[Example 1]
(Formation of alignment film)
A silane coupling agent (3-acryloxypropyltrimethoxysilane, product name: KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with isopropyl alcohol to 2% by weight. To 90 parts by weight of this diluted silane coupling agent solution, 10 parts by weight of Colcoat P (product name, alcoholic silica sol, solid content 2% by weight, manufactured by Colcoat Co., Ltd.) was added to prepare a coating solution. And after apply | coating the said coating solution with a bar-coater on a base material (norbornene-type resin film, product name: ZEONOR), the oriented film was formed by heat-drying for 3 minutes at 80 degreeC. The thickness of the obtained alignment film was 10 nm.

(Formation of retardation layer)
20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (1) (numbers 65 and 35 in the formula indicate mol% of the monomer units and are represented by block polymer for convenience: weight average molecular weight 5000), A polymerizable liquid crystal exhibiting a nematic liquid crystal phase (BASF, trade name: Paliocolor LC242) and 80 parts by weight of a photopolymerization initiator (Ciba Specialty Chemicals, trade name: Irgacure 907) are dissolved in 200 parts by weight of cyclopentanone. A liquid crystal coating solution was prepared. And after apply | coating the said coating liquid with the bar coater on the alignment film obtained above, the liquid crystal was orientated by heating and drying at 80 degreeC for 4 minute (s). The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby forming a film on the alignment film. In this way, an optical laminate was obtained.

[Example 2]
An optical laminate was obtained in the same manner as in Example 1 except that 20 parts by weight of Colcoat P was added to 80 parts by weight of the diluted silane coupling agent solution to prepare a coating solution for forming an alignment film.

[Example 3]
An optical laminate was obtained in the same manner as in Example 1 except that 50 parts by weight of Colcoat P was added to 50 parts by weight of the diluted silane coupling agent solution to prepare a coating solution for forming an alignment film.

(Comparative Example 1)
An optical laminate was obtained in the same manner as in Example 1 except that the retardation layer was formed on the substrate without providing the alignment film.

(Comparative Example 2)
An optical laminate was obtained in the same manner as in Example 1 except that Colcoat P was used as the coating solution for forming the alignment film.

(Comparative Example 3)
An optical layered body was obtained in the same manner as in Example 1 except that the diluted silane coupling agent solution was used as the coating solution for forming the alignment film.

The following evaluation was performed about the optical laminated body obtained by each Example and each comparative example. The evaluation results are summarized in Table 1.
1. Haze value Using a haze meter HM-150 (manufactured by Murakami Color Research Laboratory), the haze value of each optical laminate was measured three times (the average value of the three times is shown in Table 1).
2. Adhesiveness It evaluated by the board | substrate peeling method. Specifically, a 1 mm square base notch cut was made with a sharp blade on the surface (retardation layer side) of the optical laminate, and then a cellophane adhesive tape (24 mm width, JIS Z1522) was adhered. Thereafter, the adhesive tape was peeled off, and the number of small pieces of the film adhered to the adhesive tape was counted in the 100th cut.
<Evaluation results>
○: not peeled off at all (100/100)
Δ: Some peeled off was confirmed (60-80 / 100)
X: All peeled off (0/100)

  As is clear from Table 1, in Examples 1 to 3, the occurrence of haze was suppressed and the adhesion was also good. On the other hand, Comparative Example 1 in which no alignment film was provided and Comparative Example 2 in which no silane coupling agent was used had poor adhesion. The comparative example 3 which did not use a silica sol had a high haze value. From this, it can be said that coexistence of adhesion and haze suppression can be achieved by providing an alignment film formed of a silane coupling agent and silica sol.

  The optical laminate and the polarizing element of the present invention can be suitably applied to various image display devices. The application of the image display device of the present invention is not particularly limited. Specifically, OA devices such as personal computer monitors, notebook computers, and copy machines; mobile devices such as mobile phones, watches, digital cameras, personal digital assistants (PDAs), and portable game machines; video cameras, liquid crystal televisions, microwave ovens, etc. Household electrical equipment; back monitors, car navigation system monitors, in-car equipment such as car audio; exhibition equipment such as information monitors for commercial stores; security equipment such as monitoring monitors; nursing monitors, medical monitors, etc. It can be used for nursing care and medical equipment.

1 is a schematic cross-sectional view of an optical laminate according to one preferred embodiment of the present invention. 1 is a schematic cross-sectional view of a polarizing element according to one preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical laminated body 11 Base material 12 Orientation film 13 Phase difference layer 20 Polarizer 100 Polarizing element

Claims (14)

A substrate, an alignment film, and a retardation layer are provided in this order,
The alignment film is formed from a silane coupling agent and silica sol,
An optical laminate, wherein the retardation layer is a solidified layer or a cured layer of a liquid crystalline composition.   The optical laminate according to claim 1, wherein the base material contains a norbornene-based resin.   The optical laminated body according to claim 1 or 2, wherein the refractive index ellipsoid of the base material has a relationship of nx> ny = nz.   The optical laminated body according to claim 1 or 2, wherein the refractive index ellipsoid of the substrate has a relationship of nx> ny> nz.   The optical laminate according to claim 1, wherein the alignment film has a thickness of 1 nm to 20 μm.   The optical laminated body according to any one of claims 1 to 5, wherein the alignment film is formed from 1 to 100 parts by weight of the silica sol (solid content) with respect to 100 parts by weight of the silane coupling agent. The optical laminate according to any one of claims 1 to 6, wherein the silane coupling agent contains a compound represented by the following general formula (I):

Here, R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group or tert-butyl. X is at least one functional group selected from the group consisting of an acrylic ester group, a vinyl group, a methacryl group, a ureido group, an isocyanate group and an epoxy group.   The optical layered body according to claim 1, wherein the refractive index ellipsoid of the retardation layer has a relationship of nz> nx = ny.   The optical layered body according to any one of claims 1 to 8, wherein a retardation Rth in a thickness direction of the retardation layer is -20 to -200 nm.   The optical layered product according to any one of claims 1 to 9, wherein the liquid crystalline composition contains a liquid crystal compound having a polymerizable functional group.   A polarizing element provided with the optical laminated body in any one of Claim 1 to 10, and a polarizer.   The polarizing element of Claim 11 with which the said polarizer is arrange | positioned at the base-material side of the said optical laminated body.   The polarizing element according to claim 11 or 12, wherein an absorption axis of the polarizer and a slow axis of the substrate are orthogonal to each other.   An image display device comprising the polarizing element according to claim 11.

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