JP2013213214A - Photocurable adhesive composition, polarizing plate and method for producing the same, optical member and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable adhesive composition that can adhere to a polarizer in sufficiently high strength in a short time even in the case of using a protective film consisting of a resin film of low moisture permeability selected from a polyester resin, polycarbonate resin and acrylic resin, and to provide a polarizing plate with a polarizer laminated with such a protective film using the adhesive.SOLUTION: When a protective film consisting of the low-moisture-permeable resin film is bonded to a polarizer composed of a polyvinyl alcohol-based resin film, a photocurable adhesive composition is used which comprises: (A) an epoxy compound having in the molecule at least two epoxy groups; (B) an oxetane compound having in the molecule at least one oxetanyl group; (C) a photocationic polymerization initiator; and (F) a methyl methacrylate polymer with a glass transition temperature of 70°C or higher, wherein the weight ratio of the epoxy compound (A) to the oxetane compound (B) is 90/10 to 10/90, and the content of the photocationic polymerization initiator (C) is 0.5-20 wt.% in this composition.

Description

  The present invention relates to a photocurable adhesive composition used for bonding a polarizer and a protective film in a polarizing plate, a polarizing plate in which a protective film is bonded to a polarizer using the adhesive composition, and the polarizing plate. It is related with the manufacturing method. The present invention also relates to an optical member and a liquid crystal display device using the polarizing plate.

  The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. The polarizing plate is usually used by being incorporated in a liquid crystal display device in a state where protective films are laminated on both sides of the polarizer. It is also known that a protective film is provided only on one side of the polarizer, but in many cases, the other side is not merely a protective film, but a layer having another optical function also serves as the protective film. It will be pasted. Further, as a method for producing a polarizer, a method in which a uniaxially stretched polyvinyl alcohol resin film dyed with a dichroic dye is treated with boric acid, washed with water and dried is widely known.

  Usually, a protective film is bonded to the polarizer immediately after washing with water and drying. This is because the dried polarizer has a low physical strength, and once it is wound, problems such as tearing in the processing direction occur. Therefore, the polarizer after drying is usually applied immediately after applying an aqueous adhesive, and then a protective film is simultaneously bonded on both sides via this adhesive. Usually, a triacetyl cellulose film having a thickness of 30 to 120 μm is used as the protective film.

  For adhesion between a polarizer and a protective film, in particular, a protective film made of a triacetyl cellulose film, a polyvinyl alcohol-based adhesive is often used, but there is an attempt to use a urethane-based adhesive instead. For example, in JP-A-7-120617 (Patent Document 1), a urethane prepolymer is used as an adhesive, and a polarizer having a high water content is bonded to a cellulose acetate-based protective film such as a triacetylcellulose film. Have been described.

  On the other hand, since triacetyl cellulose has high moisture permeability, a polarizing plate bonded with this resin film as a protective film causes deterioration under wet heat, for example, at a temperature of 70 ° C. and a relative humidity of 90%. There was a problem. Therefore, a method for solving such a problem by using a resin film having a moisture permeability lower than that of a triacetyl cellulose film as a protective film has been proposed. For example, it is known that an amorphous polyolefin-based resin is used as a protective film. It has been. Specifically, JP-A-6-511117 (Patent Document 2) describes that a thermoplastic saturated norbornene resin sheet is laminated on at least one surface of a polarizer as a protective film.

  When pasting such a protective film with low moisture permeability with a conventional apparatus, an adhesive mainly containing water, for example, an aqueous polyvinyl alcohol solution is used, and the protective film is pasted on a polyvinyl alcohol polarizer. In the so-called wet lamination in which the solvent is dried after the combination, there are problems such as insufficient adhesive strength being obtained and the appearance being deteriorated. This is because a film having a low moisture permeability is generally more hydrophobic than a triacetyl cellulose film, and because the moisture permeability is low, water as a solvent cannot be sufficiently dried.

  Therefore, JP 2000-32432 A (Patent Document 3) proposes that a polyvinyl alcohol polarizer and a protective film made of a thermoplastic saturated norbornene resin are bonded with a polyurethane adhesive. Yes. However, the polyurethane adhesive has a problem that it takes a long time to cure, and the adhesive strength is not necessarily sufficient.

  On the other hand, it is also known to bond different types of protective films on both sides of a polarizer. For example, JP 2002-174729 A (PTL 4) discloses a polarizer made of a polyvinyl alcohol-based resin film. A protective film made of an amorphous polyolefin resin is bonded to one surface of the resin, and a protective film made of a resin different from the amorphous polyolefin resin, for example, triacetylcellulose, is bonded to the other surface. In JP 2005-208456 (Patent Document 5), a water-based first adhesive containing a specific urethane resin is interposed on one surface of a polarizing film made of a polyvinyl alcohol-based resin. A cycloolefin-based resin film and an aqueous second adhesive different from the first adhesive on the other surface, for example, an aqueous solution of a polyvinyl alcohol-based resin. Through be laminated cellulose acetate-based resin film has been proposed.

  What is called an amorphous polyolefin resin in Patent Document 4 and also called a cycloolefin resin in Patent Document 5 is a polycyclic compound such as norbornene, a derivative thereof, or dimethanooctahydronaphthalene. When a double bond remains as in a ring-opening polymer, a thermoplastic resin hydrogenated therewith is preferably used.

  JP-A-2004-245925 (Patent Document 6) discloses an adhesive mainly composed of an epoxy resin that does not contain an aromatic ring. The adhesive is irradiated with active energy rays to perform cationic polymerization. Thus, a method of bonding the polarizer and the protective film has been proposed. The epoxy adhesive disclosed herein is particularly effective for bonding various transparent resin films including amorphous polyolefin resin and cellulose resin to a polarizer. In the case of a protective film, it has become clear that the adhesive force is not always sufficient.

JP-A-7-120617 JP-A-6-511117 JP 2000-32432 A JP 2002-174729 A JP-A-2005-208456 JP 2004-245925 A

  In order to solve the problem when laminating a polyvinyl alcohol-based polarizer and a protective film with low moisture permeability by wet lamination, it may be possible to increase the drying oven length after laminating and increase the drying time, If the length of the drying oven is simply increased, there arises a problem that discoloration is likely to occur due to thermal deterioration of the polarizer. Therefore, it is conceivable to lower the drying temperature so as not to cause thermal deterioration of the polarizer. In this case, it is necessary to further increase the drying furnace length in order to sufficiently dry, and the capital investment is enormous. There is a problem of becoming. In addition, when different types of protective films are bonded to both sides of the polarizer, the shrinkage ratios of the protective films due to heat are different, so the protective films on both sides are bonded to the polarizer in different amounts. After drying, there is a problem that curling tends to occur on the polarizing plate when it is returned to room temperature.

  In order to improve such a problem, it is conceivable to employ a bonding method by dry lamination. However, because the adhesive having dry lamination suitability is extremely high in viscosity, the physical strength of the polarizer is weak, so the method of bonding the polarizer and the protective film is to apply the adhesive to the protective film, and then It is limited to the method of pasting to the child. In this method, if a foreign object adheres to the coated surface of the adhesive before bonding, the foreign object cannot be concealed, and after bonding, bubbles are generated between the adhesive layer and the polarizer starting from the foreign object. Cause bright spot defects.

  The inventors of the present invention provide a photocurable adhesive that exhibits a good adhesive force in a short time when a resin film having a low moisture permeability selected from a polyester resin, a polycarbonate resin, and an acrylic resin is used as a protective film for a polarizer. As a result of intensive studies to develop the film, it was found that these protective films can be bonded in a short time by using a specific photo-curable adhesive. And this adhesive gives a high adhesive force with the polarizer even when the acrylic resin film is used as a protective film, and also has an excellent adhesive force even when a polyester resin film or a polycarbonate resin film is used as the protective film. I found out that it works.

  Therefore, the object of the present invention is to adhere to a polarizer with sufficient adhesive strength in a short time even when a resin film with low moisture permeability selected from polyester resin, polycarbonate resin and acrylic resin is used as a protective film. An object of the present invention is to provide a photocurable adhesive that does not cause problems such as poor appearance and to provide a polarizing plate in which a protective film is bonded to a polarizer using the adhesive. Another object of the present invention is to provide an optical member capable of forming a liquid crystal display device having excellent reliability using this polarizing plate, and to apply the same to a liquid crystal display device.

  That is, according to the present invention, from a transparent resin film selected from the group consisting of a polyester resin, a polycarbonate resin, and an acrylic resin to a polarizer composed of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. An adhesive composition for adhering a protective film comprising: (A) an epoxy compound having at least two epoxy groups in the molecule; (B) an oxetane compound having at least one oxetanyl group in the molecule; And (C) a photocationic polymerization initiator, the weight ratio (A) / (B) of the epoxy compound (A) to the oxetane compound (B) is about 90/10 to 10/90, A photocurable adhesive composition is provided wherein the amount of the photocationic polymerization initiator (C) is about 0.5 to 20% by weight in the composition.

  In this photocurable adhesive composition, the epoxy compound (A) preferably contains a compound having at least two epoxy groups and at least one aromatic ring in the molecule. The epoxy compound (A) more preferably contains one or more selected from the group consisting of glycidyl ethers and glycidyl esters of aromatic compounds.

  On the other hand, examples of the oxetane compound (B) are preferably a compound having one oxetanyl group and at least one aromatic ring in the molecule, or a compound having two oxetanyl groups in the molecule.

  These photocurable adhesive compositions can further contain an unsaturated compound having at least one ethylenically unsaturated bond in the molecule as the component (D). In this case, the unsaturated compound ( The amount of D) is generally 35% by weight or less in the composition, and preferably about 5 to 25% by weight. This unsaturated compound (D) is preferably a (meth) acrylic compound having at least one (meth) acryloyl group and at least one alicyclic skeleton or aromatic ring skeleton in the molecule. More preferably, it is di (meth) acrylate having a tricyclodecane skeleton.

  When the adhesive composition contains the above unsaturated compound (D), particularly a (meth) acrylic compound, it is preferable to contain a radical photopolymerization initiator as the component (E). The amount of the radical photopolymerization initiator (E) is preferably about 10% by weight or less in the composition.

  Furthermore, these photocurable adhesive compositions can contain other components which do not have polymerizability as the component (F). In this case, the amount of the other component (F) is in the composition. A ratio of about 10% by weight or less is usually preferable.

  Further, according to the present invention, a polarizer comprising a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye is selected from the group consisting of a polyester resin, a polycarbonate resin, and an acrylic resin via an adhesive. There is provided a polarizing plate formed by laminating a protective film made of a transparent resin film, the adhesive of which is formed from any one of the above photocurable adhesive compositions.

  This polarizing plate is polarized through an adhesive application step of applying any one of the photocurable adhesive compositions to at least one of the bonding surfaces of the polarizer and the protective film, and an adhesive layer obtained. Including a bonding step of bonding the child and the protective film, and a curing step of curing the photocurable adhesive composition in a state where the polarizer and the protective film are bonded via the adhesive layer. It can be manufactured by a method. Specifically, after applying the uncured photocurable adhesive composition to the polarizer, a protective film is bonded to the coated surface of the adhesive composition, and then the adhesive composition is cured. A method of forming an adhesive layer, after coating the uncured photocurable adhesive composition on a protective film, a polarizer is bonded to the coated surface of the adhesive composition, and then the adhesive composition is A method of forming an adhesive layer by curing, casting the uncured photocurable adhesive composition between the polarizer and the protective film, and sandwiching the bonded product of the polarizer and the protective film with a roll or the like For example, a method of forming an adhesive layer by curing the adhesive composition while uniformly spreading the adhesive composition and then curing the adhesive composition can be employed.

  Furthermore, according to this invention, the optical member by which the above-mentioned polarizing plate and the optical layer which shows another optical function are laminated | stacked is provided. In this case, the other optical layer preferably includes a retardation plate. There is also provided a liquid crystal display device in which this optical member is disposed on one side or both sides of a liquid crystal cell.

  The photocurable adhesive composition of the present invention is characterized by being easily cured by irradiation with active energy rays such as ultraviolet rays, and capable of firmly bonding the polarizer and the protective film in a short time. This adhesive composition is particularly useful when the protective film is made of an acrylic resin. A polarizing plate obtained by bonding a polarizer and a protective film through this adhesive composition can be produced with high productivity because the adhesive composition is cured in a short time. Furthermore, an optical member in which this polarizing plate is combined with another optical layer can form a liquid crystal display device with excellent reliability.

  Hereinafter, the present invention will be described in detail. In the present invention, a photocurable adhesive composition having a specific composition is used to adhere a protective film made of a transparent resin film to a polarizer made of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. Is used. Thus, a polarizing plate is obtained by bonding a polarizer and a protective film through a photocurable adhesive composition. This polarizing plate can be laminated with an optical layer having other optical functions to form an optical member. The optical member can be disposed on at least one side of the liquid crystal cell to form a liquid crystal display device. Hereinafter, description is advanced in order of a photocurable adhesive composition, a polarizing plate, the manufacturing method of a polarizing plate, an optical member, and a liquid crystal display device.

[Photocurable adhesive composition]
In this invention, in order to bond a polarizer and a protective film, the photocurable adhesive composition of a specific composition is used. Hereinafter, this photocurable adhesive composition may be simply referred to as “photocurable adhesive”. The photocurable adhesive of the present invention essentially contains the following three components (A), (B) and (C).

(A) an epoxy compound having at least two epoxy groups in the molecule;
(B) an oxetane compound having at least one oxetanyl group in the molecule, and (C) a photocationic polymerization initiator.

  The epoxy compound (A) is also simply referred to as “component (A)” or “epoxy compound (A)” in the present specification. Similarly, in this specification, the oxetane compound of (B) is also referred to as “component (B)” or “oxetane compound (B)”, and the photocationic polymerization initiator of (C) is referred to as “component (C)” or Also referred to as “photo cationic polymerization initiator (C)”.

  The (A) component epoxy compound and the (B) component oxetane compound preferably have a (A) / (B) weight ratio of about 90/10 to 10/90. Moreover, it is preferable to make it the ratio of about 0.5 to 20 weight% of (C) component radical photopolymerization initiator in a composition.

  This photocurable adhesive can optionally contain an unsaturated compound having at least one ethylenically unsaturated bond in the molecule as component (D), and contains such an unsaturated compound (D). When it does, it is preferable to contain radical photopolymerization initiator as (E) component. Furthermore, this photocurable adhesive agent can also contain the other component which does not have polymerizability as (F) component.

  The unsaturated compound (D) is also simply referred to herein as “component (D)” or “unsaturated compound (D)”. Similarly, in this specification, the photoradical polymerization initiator of (E) is also referred to as “(E) component” or “photoradical polymerization initiator (E)”, and (F) other component having no polymerizability. Is also referred to as “component (F)” or “other component (F) having no polymerizability”.

<Epoxy compound (A)>
In the photocurable adhesive of the present invention, the epoxy compound as the component (A) is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxies. Compounds can be used. As a preferred epoxy compound as the component (A), a compound having at least two epoxy groups and at least one aromatic ring in the molecule (hereinafter referred to as “aromatic epoxy compound”), or at least 2 in the molecule Compound having at least one epoxy group, at least one of which is formed between two adjacent carbon atoms constituting the alicyclic ring (hereinafter referred to as “alicyclic epoxy compound”) Etc. are mentioned as examples.

  The aromatic epoxy compound is not particularly limited as long as the effects of the present invention are not hindered, but bisphenol-type epoxy such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and brominated bisphenol A diglycidyl ether. Resin; novolac epoxy resin such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; biphenyl type epoxy resin, hydroquinone diglycidyl ether, resorcin diglycidyl ether, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester Of styrene-butadiene copolymer, styrene-isoprene copolymer epoxide, terminal carboxylic acid polybutadiene and bisphenol A type epoxy resin Pressurized reactant, etc. as an example.

  Here, the epoxy resin means a compound or polymer having an average of two or more epoxy groups in the molecule and cured by reaction. In accordance with the custom in this field, in this specification, a monomer may be referred to as an epoxy resin as long as it has two or more curable epoxy groups in the molecule.

  The alicyclic epoxy compound is not particularly limited as long as the effect of the present invention is not hindered, but dicyclopentadiene dioxide, limonene dioxide, 4-vinylcyclohexene dioxide, 3,4-epoxycyclohexylmethyl 3,4-epoxy. Examples include compounds having at least one epoxidized cyclohexyl group, such as cyclohexanecarboxylate and bis (3,4-epoxycyclohexylmethyl) adipate.

  In addition to the above, aliphatic epoxy compounds such as 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, and polytetramethylene glycol diglycidyl ether; hydrogenated bisphenol A An epoxy compound having a hydrogenated aromatic ring, such as diglycidyl ether; a compound in which both ends of polybutadiene having hydroxyl groups at both ends are glycidyl etherified, an internal epoxidized product of polybutadiene, and a double bond of styrene-butadiene copolymer A partially epoxidized compound (for example, “Epofriend” manufactured by Daicel Chemical Industries, Ltd.) and a compound in which the isoprene unit of a block copolymer of ethylene-butylene copolymer and polyisoprene is partially epoxidized ( Eg to such KRATON manufactured by the "L-207"), an epoxy compound of the polymer system, etc. also can be an epoxy compound of the component (A).

  Among these, the aromatic epoxy compound is preferable because it is excellent in durability and the like when used as a polarizing plate, and is particularly excellent in adhesion to a polarizer and a protective film. Furthermore, preferred examples of the aromatic epoxy compound include glycidyl ethers of aromatic compounds or glycidyl esters of aromatic compounds. Specific examples of glycidyl ethers of aromatic compounds include bisphenol-type epoxy resins; phenol novolac-type epoxy resins, and cresols, such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of brominated bisphenol A. Preferred examples include novolak type epoxy resins such as novolak type epoxy resins; biphenyl type epoxy resins; hydroquinone diglycidyl ether; resorcin diglycidyl ether. Specific examples of the glycidyl ester of the aromatic compound include terephthalic acid diglycidyl ester and phthalic acid diglycidyl ester.

  Among them, glycidyl ether of an aromatic compound is particularly preferable because it is more excellent in adhesion when a polarizer and a protective film are bonded and durability when used as a polarizing plate. Among the glycidyl ethers of aromatic compounds, particularly preferable compounds include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and phenol novolac type epoxy resin.

  (A) The epoxy compound of a component can also be used individually by 1 type, and can also be used in mixture of 2 or more types. For example, two or more types of aromatic epoxy compounds can be mixed and used, or an aromatic epoxy compound as a main component and an alicyclic epoxy compound can also be mixed.

<Oxetane compound (B)>
In the photocurable adhesive of the present invention, the oxetane compound as the component (B) is not particularly limited as long as it has at least one oxetanyl group in the molecule, and various compounds having an oxetanyl group are also used. be able to. As the oxetane compound (B), a compound having one oxetanyl group in the molecule (hereinafter referred to as “monofunctional oxetane”) and a compound having two or more oxetanyl groups in the molecule (hereinafter referred to as “polyfunctional oxetane”) Is a preferred example.

  The monofunctional oxetane includes an aromatic group-containing monofunctional group such as an alkoxyalkyl group-containing monofunctional oxetane such as 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane and 3-ethyl-3-phenoxymethyloxetane. Preferred examples include a hydroxyl group-containing monofunctional oxetane such as oxetane and 3-ethyl-3-hydroxymethyloxetane.

Examples of the polyfunctional oxetane include the following compounds.
3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane,
1,4-bis [(3-ethyloxetane-3-yl) methoxymethyl] benzene,
1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene,
1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene,
1,2-bis [(3-ethyloxetane-3-yl) methoxy] benzene,
4,4'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl,
2,2'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl,
3,3 ′, 5,5′-tetramethyl-4,4′-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl,
2,7-bis [(3-ethyloxetane-3-yl) methoxy] naphthalene,
Bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] methane,
Bis [2-{(3-ethyloxetane-3-yl) methoxy} phenyl] methane,
2,2-bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] propane,
Etherified modified product of novolac type phenol-formaldehyde resin with 3-chloromethyl-3-ethyloxetane,
3 (4), 8 (9) -bis [(3-ethyloxetane-3-yl) methoxymethyl] -tricyclo [5.2.1.0 ^2,6 ] decane,
2,3-bis [(3-ethyloxetane-3-yl) methoxymethyl] norbornane,
1,1,1-tris [(3-ethyloxetane-3-yl) methoxymethyl] propane,
1-butoxy-2,2-bis [(3-ethyloxetane-3-yl) methoxymethyl] butane,
1,2-bis [{2- (3-ethyloxetane-3-yl) methoxy} ethylthio] ethane,
Bis [{4- (3-ethyloxetane-3-yl) methylthio} phenyl] sulfide,
1,6-bis [(3-ethyloxetane-3-yl) methoxy] -2,2,3,3,4,4,5,5-octafluorohexane,
3-[(3-ethyloxetane-3-yl) methoxy] propyltriethoxysilane hydrolysis condensate,
Tetrakis [(3-ethyloxetane-3-yl) methyl] silicate condensate and the like.

  The oxetane compound as the component (B) is preferably liquid at room temperature having a molecular weight of 500 or less from the viewpoint of coating properties and adhesion to a protective film when a polarizing plate is used. Further, in terms of the durability of the polarizing plate, a monofunctional oxetane is more preferably an aromatic ring in the molecule or a polyfunctional oxetane. Examples of such particularly preferred oxetane compounds include 3-ethyl-3-phenoxymethyloxetane, 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, and 1,4-bis [ (3-ethyloxetane-3-yl) methoxymethyl] benzene and the like.

  The oxetane compound as the component (B) can be used alone or in combination of two or more.

<Ratio of epoxy compound (A) and oxetane compound (B)>
The proportion of the (A) component epoxy compound and the (B) component oxetane compound used is 90/10 to 10/90 in a weight ratio of (A) / (B). If this ratio is excessive or insufficient, the effect of curing in a short time, which is one of the important characteristics of the photocurable adhesive of the present invention, is not sufficiently exhibited. A suitable weight ratio of the two is about 70/30 to 20/80, since it has a low viscosity before curing and excellent coating properties, and can exhibit sufficient adhesion and flexibility after curing. The weight ratio is about 60/40 to 25/75.

<Photocationic polymerization initiator (C)>
The photocurable adhesive of the present invention contains the epoxy compound (A) and the oxetane compound (B) described above as the curing component, and these are all cured by cationic polymerization, so that the component (C) As a photocationic polymerization initiator. This cationic photopolymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and starts a polymerization reaction of an epoxy group or an oxetanyl group.

  By blending a cationic photopolymerization initiator as component (C), curing at room temperature becomes possible, reducing the need to consider the heat resistance of the polarizer and distortion due to expansion or contraction, and adhere the protective film well. be able to. Moreover, since a photocationic polymerization initiator acts catalytically by irradiation of an active energy ray, even if it mixes with an epoxy compound (A) and an oxetane compound (B), it is excellent in storage stability and workability | operativity. Examples of compounds that generate cation species and Lewis acids upon irradiation with active energy rays include onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes.

Examples of the aromatic diazonium salt include the following compounds.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of the aromatic iodonium salt include the following compounds.
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
Diphenyl [4- (phenylthio) phenyl] sulfonium hexafluorophosphate,
Diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate,
4,4'-bis (diphenylsulfonio) diphenyl sulfide bishexafluorophosphate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate,
4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Examples of the iron-allene complex include the following compounds.
Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron (II) -tris (trifluoromethylsulfonyl) methanide and the like.

  Each of these cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and therefore can provide a cured product having excellent curability and good mechanical strength and adhesive strength. It is done.

  As the cationic photopolymerization initiator, commercially available products can be easily obtained. For example, “Kayarad PCI-220” and “Kayarad PCI-620” (Nippon Kayaku Co., Ltd.) ), “UVI-6992” (manufactured by Dow Chemical Company), “Adekaoptomer SP-150”, “Adekaoptomer SP-170” (manufactured by ADEKA Corporation), “CI-5102”, “CIT” -1370 "," CIT-1682 "," CIP-1866S "," CIP-2048S "," CIP-2064S "(above, manufactured by Nippon Soda Co., Ltd.)," DPI-101 "," DPI-102 " “DPI-103”, “DPI-105”, “MPI-103”, “MPI-105”, “BBI-101”, “BBI-102”, “BBI-103”, “BBI” 105 ”,“ TPS-101 ”,“ TPS-102 ”,“ TPS-103 ”,“ TPS-105 ”,“ MDS-103 ”,“ MDS-105 ”,“ DTS-102 ”,“ DTS-103 ” (Midori Chemical Co., Ltd.), “PI-2074” (Rhodia Co., Ltd.), “Irgacure 250”, “Irgacure PAG103”, Irgacure PAG108 ”, Irgacure PAG121”, Irgacure PAG203 ”(above, Ciba) “CPI-100P”, “CPI-101A”, “CPI-200K”, “CPI-210S” (manufactured by San Apro Co., Ltd.) and the like, and in particular, diphenyl [4- (phenylthio) phenyl] sulfonium "UVI-6992" manufactured by Dow Chemical Co., Ltd. "CPI-100P" of, "CPI-101A", "CPI-200K", "CPI-210S" is preferable.

  (C) The mixture ratio of the photocationic polymerization initiator of a component shall be the range of 0.5-20 weight% on the basis of the whole photocurable adhesive agent. When the proportion is less than 0.5% by weight, the adhesive is not sufficiently cured, and the mechanical strength and adhesive strength are lowered. On the other hand, when the proportion exceeds 20% by weight, the ionic substance in the cured product is obtained. Since the hygroscopic property of the cured product is increased and the durability performance is likely to be lowered due to the increase in the amount of slag, it is not preferable.

<Unsaturated compound (D)>
The photocurable adhesive of this invention can contain the unsaturated compound which has an at least 1 ethylenically unsaturated bond in a molecule | numerator as (D) component as needed. A typical example of such an unsaturated compound (D) is a (meth) acrylic compound having at least one (meth) acryloyl group in the molecule.

  Although it does not specifically limit as a (meth) acrylic-type compound, For example, (meth) acrylates, (meth) acrylamides, (meth) acrylic acid, (meth) acryloylmorpholine, (meth) acrylaldehyde, etc. are mentioned.

  Although it does not specifically limit as (meth) acrylates (henceforth monofunctional (meth) acrylate) which has one (meth) acryloyl group in a molecule | numerator, For example, the following compounds are mentioned.

Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, Alkyl (meth) acrylates such as isooctyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate;
Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate;
Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1,4-cyclohexanedimethylol mono (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) Alicyclic monofunctional (meth) acrylates such as acrylates;
Benzyl (meth) acrylate, (meth) acrylate of p-cumylphenolalkylene oxide adduct, (meth) acrylate of o-phenylphenolalkylene oxide adduct, (meth) acrylate of phenolalkylene oxide adduct and nonylphenol alkylene oxide addition Monofunctional (meth) acrylates having an aromatic ring, such as (meth) acrylates of the product (wherein, alkylene oxides include ethylene oxide and propylene oxide);
Alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, and (meth) acrylates of alkylene oxide adducts of 2-ethylhexyl alcohol;
Mono (meth) acrylates of dihydric alcohols such as ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, pentanediol mono (meth) acrylate, and hexanediol mono (meth) acrylate;
Mono (meth) acrylate of diethylene glycol, mono (meth) acrylate of triethylene glycol, mono (meth) acrylate of tetraethylene glycol, mono (meth) acrylate of polyethylene glycol, mono (meth) acrylate of dipropylene glycol, tripropylene glycol Mono (meth) acrylates of polyalkylene glycols such as mono (meth) acrylates of polypropylene and mono (meth) acrylates of polypropylene glycol;
Glycidyl (meth) acrylate;
Tetrahydrofurfuryl (meth) acrylate;
Tetrahydrofurfuryl (meth) acrylates, such as caprolactone-modified tetrahydrofurfuryl (meth) acrylate;
3,4-epoxycyclohexylmethyl (meth) acrylate;
N, N-dimethylaminoethyl (meth) acrylate;
2- (meth) acryloyloxyethyl isocyanate and the like.

  Moreover, although it does not specifically limit as (meth) acrylates which have a 2 or more (meth) acryloyl group in a molecule | numerator, For example, the following compounds are mentioned.

Alicyclic such as tricyclodecane dimethylol di (meth) acrylate, 1,4-cyclohexane dimethylol di (meth) acrylate, norbornane dimethylol di (meth) acrylate, and di (meth) acrylate of hydrogenated bisphenol A Di (meth) acrylates having a ring;
Di (meth) acrylate of bisphenol A ethylene oxide adduct, and di (meth) acrylate of bisphenol A alkylene oxide adduct including di (meth) acrylate of bisphenol A propylene oxide adduct, and di (meth) acrylate of bisphenol A diglycidyl ether Di (meth) acrylates having an aromatic ring, such as (meth) acrylate;
Di (meth) acrylates of alkylene glycols such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, pentanediol di (meth) acrylate, and hexanediol di (meth) acrylate;
Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate And di (meth) acrylates of polyalkylene glycols such as polypropylene glycol di (meth) acrylate;
Di- or tri (meth) acrylates of glycerins, such as di- or tri (meth) acrylates of glycerin and di- or tri (meth) acrylates of diglycerin;
Di- or tri (meth) acrylates of alkylene oxide adducts of glycerol;
Di (meth) acrylates of bisphenol alkylene oxide adducts, such as di (meth) acrylates of bisphenol A alkylene oxide adducts, and di (meth) acrylates of bisphenol F alkylene oxide adducts;
Trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) Polyols poly (meth) acrylates such as acrylates and dipentaerythritol hexa (meth) acrylate;
Poly (meth) acrylates of alkylene oxide adducts of these polyols;
Di- or tri (meth) acrylates of isocyanuric acid alkylene oxide adducts;
1,3,5-tri (meth) acryloylhexahydro-s-triazine and the like.

  (Meth) acrylamides include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N- (3-N, N- Examples thereof include dimethylaminopropyl) (meth) acrylamide, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide.

  In addition, oligomers such as urethane (meth) acrylate, polyester (meth) acrylate and epoxy (meth) acrylate can also be used as the (meth) acrylic compound.

  Furthermore, a compound having an ethylenically unsaturated bond other than the (meth) acryloyl group can also be used as the (meth) acrylic compound, and specific examples thereof include allyl (meth) acrylate, N, N-diallyl (meth). Examples include acrylamide.

  Component (D) is not particularly limited, and in addition to the above (meth) acrylic compounds, vinyl compounds such as N-vinyl-2-pyrrolidone, divinyl adipate, and divinyl sebacate; triallyl isocyanurate Allyl compounds such as N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetraallylammonium salt, and allylamine; such as maleic acid and itaconic acid, Unsaturated carboxylic acids and the like can also be used.

  Of these unsaturated compounds of component (D), (meth) acrylic compounds are preferred. Furthermore, when a polarizer and a protective film are bonded via an adhesive containing the same to form a polarizing plate, at least one alicyclic skeleton is included in the molecule from the viewpoint of enhancing durability such as heat resistance. Alternatively, a (meth) acrylic compound having an aromatic ring skeleton is more preferable. Specific examples of the (meth) acrylic compound having at least one alicyclic skeleton or aromatic ring skeleton in the molecule include the above-described alicyclic monofunctional (meth) acrylates and monofunctional having an aromatic ring. Preferable examples include (meth) acrylates, di (meth) acrylates having an alicyclic ring, and di (meth) acrylates having an aromatic ring. Among these, di (meth) acrylate having a tricyclodecane skeleton is preferable, and specific examples of such a particularly preferable (meth) acrylic compound include tricyclodecane dimethylol di (meth) acrylate and the like. Can do.

  The unsaturated compound of component (D) can be used to adjust the curing speed, the adhesion between the polarizer and the protective film, the elastic modulus of the adhesive layer, the durability of the adhesive, and the like. (D) The unsaturated compound of a component can be used individually by 1 type or in mixture of 2 or more types.

  (D) When mix | blending the unsaturated compound of a component, it is preferable that the mixture ratio shall be 35 weight% or less on the basis of the whole composition. Thereby, the adhesiveness between the polarizer and the protective film becomes excellent. When the amount of the unsaturated compound (D) exceeds 35% by weight, it becomes difficult to obtain sufficient adhesive strength with the polarizer. Therefore, the blending ratio of the unsaturated compound (D) is more preferably 30% by weight or less, further preferably about 5 to 25% by weight, and more preferably about 10 to 20% by weight.

<Photoradical polymerization initiator (E)>
When the photocurable adhesive of the present invention contains the unsaturated compound of component (D), in order to promote the radical polymerizability and make the curing rate sufficient, photoradical polymerization is initiated as component (E). It is preferable to mix an agent.

  Although it does not specifically limit as a specific example of the radical photopolymerization initiator used as (E) component, For example, the following compounds can be mentioned.

4'-phenoxy-2,2-dichloroacetophenone, 4'-tert-butyl-2,2-dichloroacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-1- (4-methylthiophenyl)- 2-morpholinopropan-1-one, 1-hydroxycyclohexyl phenyl ketone, α, α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) 2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl]- 2-hydroxy-2-methylpropan-1-one and 2-benzyl-2-dimethylamino-1- ( - such as morpholinophenyl) butan-1-one, acetophenone photopolymerization initiators;
Benzoin ether photoinitiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether;
Benzophenone-based photopolymerization initiators such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 2,4,6-trimethylbenzophenone;
Thioxanthone photopolymerization initiators such as 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, and 1-chloro-4-propoxythioxanthone;
Such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide , Acylphosphine oxide photopolymerization initiators;
Oxime ester photopolymerization initiators such as 1,2-octanedione, 1- [4- (phenylthiophenyl)]-, 2- (O-benzoyloxime);
Camphorquinone, etc.

  (E) The radical photoinitiator of a component can be used individually by 1 type or 2 or more types according to desired performance. (E) When mix | blending the radical photopolymerization initiator of a component, 10 weight% or less is preferable on the basis of the whole composition, and about 0.1 to 3 weight% is more preferable. If the amount of the radical photopolymerization initiator (E) is too large, sufficient strength may not be obtained, and if the amount is insufficient, the adhesive may not be cured sufficiently.

<Other ingredients>
Furthermore, in the photocurable adhesive of this invention, the other component different from the said (A)-(E) component can be arbitrarily mix | blended in the range which does not impair the effect of this invention. As one type belonging to such other components, there can be mentioned compounds having cationic polymerizability other than the epoxy compound of component (A) and the oxetane compound of component (B), and specific examples thereof are particularly limited. Although not, an epoxy compound having one epoxy group in the molecule can be used. Moreover, the other component (F) which does not have polymerizability can be mentioned as another type which belongs to another component. When the other component (F) having no polymerizability is blended, the blending ratio is preferably about 10% by weight or less based on the whole composition.

  Although it does not specifically limit as an example of the other component (F) which does not have polymerizability, A photosensitizer is mentioned. By blending a photosensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

Specific photosensitizers are not particularly limited, and examples thereof include the following compounds.
Benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone;
Benzophenone derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, and 4,4'-bis (diethylamino) benzophenone;
Thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone;
Anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone;
Acridone derivatives such as N-methylacridone and N-butylacridone;
In addition, α, α-diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compound, halogen compound and the like.

  Among these, there is a compound corresponding to the photoradical polymerization initiator of the component (E), but the photosensitizer here functions as a sensitizer for the photocationic polymerization initiator of the component (C). If it does, it will not specifically limit. These may be used alone or in combination of two or more.

  The photosensitizer is a cationic polymerizable monomer in the photo-curable adhesive of the present invention [comprising the above-mentioned epoxy compound (A) and oxetane compound (B), and the other cationic polymerizable compounds described above. If the total amount is 100 parts by weight, the content is preferably in the range of 0.1 to 20 parts by weight.

  Moreover, a thermal cationic polymerization initiator can also be used as another component (F) which does not have polymerizability. Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These initiators can be easily obtained as commercial products. For example, both of them are indicated by trade names, “Adeka Opton CP77” and “Adeka Opton CP66” (above, manufactured by ADEKA Corporation), “CI” -2639 "and" CI-2624 "(manufactured by Nippon Soda Co., Ltd.)," Sun-Aid SI-60L "," Sun-Aid SI-80L "and" Sun-Aid SI-100L "(Sanshin Chemical Industry Co., Ltd.) Manufactured) and the like.

  Since polyols have the property of promoting cationic polymerization, they can also be used as other components (F) that do not have polymerizability. As the polyols, those having no acidic group other than phenolic hydroxyl groups are preferable. For example, polyol compounds having no functional groups other than hydroxyl groups, polyester polyol compounds, polycaprolactone polyol compounds, polyol compounds having phenolic hydroxyl groups, polycarbonates A polyol compound etc. can be mentioned.

  Furthermore, as long as the effects of the present invention are not impaired, the other component (F) having no polymerizability includes a silane coupling agent, an ion trap agent, an antioxidant, a light stabilizer, a chain transfer agent, a sensitizer, and tackifying. An agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, a leveling agent, a dye, an organic solvent, and the like can also be blended. It is also effective to add a thermoplastic resin as another component (F) having no polymerizability for the purpose of further improving the adhesion to the protective film. As the thermoplastic resin, those having a glass transition temperature of 70 ° C. or higher are preferable from the viewpoint of enhancing the durability of the polarizer, and particularly preferred examples include a methyl methacrylate polymer.

[Polarizer]
The photocurable adhesive described above is used for adhering a protective film to a polarizer made of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye, and thus the protective film is provided on the polarizer. Bonded to become a polarizing plate. That is, the polarizing plate according to the present invention is not particularly limited as long as a protective film is bonded to a polarizer made of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. The protective film may be bonded only to one side of the polarizer, or may be bonded to both sides of the polarizer. When a protective film is bonded to both surfaces of the polarizer, each protective film may be made of the same type of resin, or may be made of a different type of resin.

<Polarizer>
The polyvinyl alcohol resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. Although the saponification degree of a polyvinyl alcohol-type resin is not specifically limited, Usually, it is 85-100 mol%, and the range of 98-100 mol% is preferable. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is usually 1,000 to 10,000, and preferably in the range of 1,500 to 10,000.

  The polarizing plate is a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye, and adsorbing the dichroic dye, and the dichroic dye is adsorbed. A step of treating the polyvinyl alcohol resin film with an aqueous boric acid solution, a step of washing with water after the treatment with the boric acid aqueous solution, and a uniaxially stretched polyvinyl alcohol resin film in which these steps are applied to adsorb and orient the dichroic dye It is manufactured through a process of pasting a protective film.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing with a dichroic dye, or may be performed after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing with a dichroic dye, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in these plural stages. For uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or uniaxially stretched using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is not particularly limited, but is usually about 4 to 8 times.

  In order to dye the polyvinyl alcohol resin film with the dichroic dye, for example, the polyvinyl alcohol resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is not particularly limited, but is usually about 0.01 to 0.5 parts by weight per 100 parts by weight of water, and the content of potassium iodide is not particularly limited. About 0.5 to 10 parts by weight per part. Although the temperature of this aqueous solution is not specifically limited, Usually, it is about 20-40 degreeC, Moreover, the immersion time in this aqueous solution is although it does not specifically limit, Usually, it is about 30-300 second.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is not particularly limited, but is usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. Although the temperature of this aqueous solution is not specifically limited, Usually, it is about 20-80 degreeC, and the immersion time in this aqueous solution is although it does not specifically limit, Usually, it is about 30-300 second.

  The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol resin film in an aqueous boric acid solution. The boric acid content in the boric acid aqueous solution is not particularly limited, but is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, this aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is not particularly limited, but is usually about 2 to 20 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of water. The immersion time in the boric acid aqueous solution is not particularly limited, but is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. Although the temperature of boric acid aqueous solution is not specifically limited, Usually, it is 50 degreeC or more, Preferably it is 50-85 degreeC.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. After washing with water, a drying process is performed to obtain a polarizer. The temperature of water in the water washing treatment is not particularly limited, but is usually about 5 to 40 ° C., and the immersion time is not particularly limited, but is usually about 2 to 120 seconds. The drying process performed thereafter is usually performed using a hot air dryer or a far infrared heater. Although a drying temperature is not specifically limited, Usually, it is 40-100 degreeC. Although the processing time in a drying process is not specifically limited, Usually, it is about 120 to 600 seconds.

  Thus, a polarizer comprising a polyvinyl alcohol-based resin film on which iodine or dichroic dye as a dichroic dye is adsorbed and oriented is obtained.

<Protective film>
Next, a protective film is bonded to one side or both sides of the polarizer using the photocurable adhesive described above. Triacetyl cellulose film is widely employed conventionally as a protective film of the polarizer has a generally moisture permeability of approximately 400g ^/ m 2 / 24hr, the present invention is stuck on at least one surface of the polarizer As the protective film, a resin having a moisture permeability lower than that of triacetyl cellulose, and a polyester resin, a polycarbonate resin, or an acrylic resin is employed.

  The type of polyester resin used for the protective film is not particularly limited, but polyethylene terephthalate is particularly preferable in terms of mechanical properties, solvent resistance, scratch resistance, cost, and the like. Polyethylene terephthalate means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components. Other copolymer components include isophthalic acid, p-β-hydroxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, and 1,4-dicarboxycyclohexane; propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol Preferred examples include diol components such as polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can also be used in combination of two or more as required. In addition, a hydroxycarboxylic acid such as p-hydroxybenzoic acid can be used in combination with the dicarboxylic acid component and the diol component. As other copolymerization component, a small amount of a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used.

  The polyester resin can be produced by directly reacting terephthalic acid and ethylene glycol (and other dicarboxylic acids and / or other diols if necessary), so-called direct polymerization method, dimethyl ester of terephthalic acid and ethylene glycol ( Furthermore, if necessary, an arbitrary method such as a so-called transesterification method in which a dimethyl ester of another dicarboxylic acid and / or another diol) is transesterified can be employed. Moreover, the polyester resin may contain a well-known additive as needed. The additive that can be contained is not particularly limited, and examples thereof include a lubricant, an anti-blocking agent, a thermal stabilizer, an antioxidant, an antistatic agent, a light-resistant agent, and an impact resistance improving agent. However, since transparency is required as a protective film laminated on the polarizing film, it is preferable to keep the amount of these additives to a minimum.

  A protective film made of a stretched polyester resin can be produced by forming the raw material resin into a film and subjecting it to uniaxial stretching or biaxial stretching. By performing the stretching treatment, a film having high mechanical strength can be obtained. The method for producing the stretched polyester resin film is arbitrary and is not particularly limited. However, the non-oriented film obtained by melting the raw material resin and extruding it into a sheet is formed at a temperature above the glass transition temperature. And a method of performing heat setting after transverse stretching.

  The polycarbonate resin used for the protective film is preferably a polyester formed from carbonic acid and glycol or bisphenol. Among these, an aromatic polycarbonate having a diphenylalkane in the molecular chain is preferably used because it is excellent in heat resistance, weather resistance and acid resistance. Such polycarbonates include 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, Illustrative are polycarbonates derived from bisphenols, such as 1,1-bis (4-hydroxyphenyl) isobutane or 1,1-bis (4-hydroxyphenyl) ethane.

  As a method for producing a polycarbonate resin film, any method such as a casting film forming method or a melt extrusion method may be used. As an example of a specific production method, a polycarbonate resin is dissolved in an appropriate organic solvent to form a polycarbonate resin solution, which is cast on a metal support to form a web, and the web is peeled off from the metal support. A method of obtaining a film by drying the peeled web with hot air after taking off can be mentioned.

  The acrylic resin used for the protective film is also not particularly limited, but generally a copolymer in which a methacrylic acid ester as a main component is copolymerized with a small amount of other comonomer components is preferable. As the methacrylic acid ester as the main component of the acrylic resin, alkyl methacrylate is preferably exemplified, and methyl methacrylate is particularly preferably used. The comonomer component is not particularly limited, but methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl-hexyl acrylate and the like are generally used. Further, an aromatic vinyl compound such as styrene, a vinyl cyanide compound such as acrylonitrile, or the like may be used as a comonomer component.

  As a method for producing the acrylic resin, any method such as ordinary bulk polymerization, suspension polymerization, emulsion polymerization, etc. can be employed. Among these, bulk polymerization in which no water-soluble component is present in the polymerization system is particularly preferably employed. Moreover, in order to obtain a suitable glass transition temperature or to obtain a viscosity exhibiting moldability to a suitable film, it is preferable to use a chain transfer agent during polymerization. What is necessary is just to determine the quantity of a chain transfer agent suitably according to the kind and composition of a monomer. Moreover, the acrylic resin may contain a well-known additive as needed. Known additives include, for example, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers, surfactants and the like. However, since transparency is required as a protective film laminated on the polarizing film, it is preferable to keep the amount of these additives to a minimum.

  As a method for producing the acrylic resin film, any method such as a melt casting method, a melt extrusion method such as a T-die method or an inflation method, or a calendar method may be used. Especially, the method of melt-extruding raw material resin, for example from a T die, and making a film by making at least one side of the film-form thing contact a roll or a belt is preferable at the point from which a surface property favorable film | membrane is obtained.

  The acrylic resin may contain acrylic rubber particles that are impact modifiers from the viewpoint of film-forming properties on the film and impact resistance of the film. The acrylic rubber particles herein are not particularly limited as long as they are particles containing an elastic polymer mainly composed of an acrylate ester as an essential component, and those having a single layer structure consisting essentially only of this elastic polymer, As an example, a multilayer structure having this elastic polymer as one layer can be given. An example of such an elastic polymer is a cross-linked elastic copolymer obtained by copolymerizing an alkyl acrylate as a main component with another vinyl monomer and a cross-linkable monomer copolymerizable therewith. Examples of the alkyl acrylate as the main component of the elastic polymer include those having about 1 to 8 carbon atoms in the alkyl group, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. An acrylate having an alkyl group of several 4 or more is preferably used. Examples of the other vinyl monomer copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid such as methyl methacrylate. Examples thereof include aromatic vinyl compounds such as esters and styrene, and vinylcyan compounds such as acrylonitrile. Examples of the crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate and butanediol. Examples include (meth) acrylates of polyhydric alcohols such as di (meth) acrylate, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate, and divinylbenzene.

  Furthermore, a laminate of a film made of an acrylic resin not containing rubber particles and a film made of an acrylic resin containing rubber particles can be used as a protective film.

  In the polarizing plate used on the viewing side of the liquid crystal display device, an antiglare property can be imparted to the protective film disposed on the viewing side, that is, on the side opposite to the liquid crystal cell. In this case, an antiglare layer having surface irregularities is generally provided on the surface on the viewing side of the protective film, that is, the surface opposite to the surface to be bonded to the polarizer. In general, the antiglare layer imparts irregularities to the active energy ray-curable resin by an embossing method, or imparts irregularities by blending and curing the active energy ray-curable resin with fine particles having a refractive index different from that. It is formed by the method. When the protective film is made of an acrylic resin, a light diffusing layer in which fine particles having a refractive index different from that in the acrylic resin as a binder are mixed, and a transparent layer made of an acrylic resin in which such fine particles are not mixed, It is also effective to form a protective film with the laminated film. In this case, a laminated film composed of two layers, the light diffusion layer and the transparent layer, is bonded to the polarizer on the light diffusion layer side, and both surfaces of the light diffusion layer are the transparent layers. The form etc. which paste the laminated film of the 3 layer structure pinched | interposed into the polarizer with the one transparent layer are employable. Furthermore, even when an acrylic resin laminated film imparted with antiglare properties by including such a light diffusing layer is used as a protective film, the surface on the viewing side, that is, the surface to be bonded to the polarizer is It is also effective to further improve the antiglare performance by providing the antiglare layer as described above on the opposite surface.

  As described above, in particular, when an acrylic resin film is used as a protective film, the epoxy resin alone, which does not contain an aromatic ring as shown in the above Patent Document 6 (Japanese Patent Application Laid-Open No. 2004-245925), does not necessarily have sufficient adhesion. However, the photocurable adhesive of the present invention gives good adhesive force even when such an acrylic resin film is used as a protective film. Therefore, the present invention is particularly useful when an acrylic resin film is used as a protective film. In this case, it is more preferable that the photocurable adhesive contains the unsaturated compound of the component (D) described above, particularly an acrylic compound.

  In this invention, the protective film which consists of a transparent resin film chosen from the polyester resin demonstrated above, a polycarbonate resin, and an acrylic resin on at least one surface of a polarizer is bonded through the photocurable adhesive previously demonstrated. Is done. When bonding a protective film only to one side of a polarizer, for example, it may take a form such as directly providing an adhesive layer for bonding to another member such as a liquid crystal cell on the other side of the polarizer. it can.

  On the other hand, when a protective film is bonded to both surfaces of the polarizer, the respective protective films may be the same type or different types. Specifically, for example, a form in which a polyester resin film is bonded as a protective film on both sides of a polarizer, a form in which a polycarbonate resin is bonded as a protective film on both sides of a polarizer, and an acrylic resin as a protective film on both sides of the polarizer Form of bonding, one transparent resin film selected from polyester resin, polycarbonate resin and acrylic resin is bonded as a protective film on one side of the polarizer, and on the other side of the polarizer, polyester resin, polycarbonate resin and It is any one selected from acrylic resins, and a mode in which a transparent resin film different from the above-described one-side protective film is bonded as a protective film can be preferably employed. Further, a transparent resin film selected from a polyester resin, a polycarbonate resin, and an acrylic resin is bonded to one surface of the polarizer as a protective film, and a polyester resin, a polycarbonate resin, and an acrylic resin are bonded to the other surface of the polarizer. It is also possible to adopt a form in which a transparent resin film different from any of them is bonded as a protective film. When bonding a protective film on both surfaces of a polarizer, two protective films may be bonded one step at a time, or both surfaces may be bonded in one step.

  When a protective film is bonded to both sides of a polarizer, and one of them is a resin film different from a polyester resin, a polycarbonate resin and an acrylic resin, as a suitable example of the other resin, Cellulose resins and amorphous polyolefin resins can be mentioned as examples. In addition, the protective film made of polyester resin, polycarbonate resin, or acrylic resin bonded to one surface of the polarizer is bonded through the photocurable adhesive described above according to the present invention. The protective film bonded to the other surface of the film may be bonded via another adhesive. For example, when a protective film made of a resin film having a relatively high moisture permeability such as a cellulose resin film is provided on one surface of the polarizer, a polyvinyl alcohol-based adhesive is attached to the bonding surface of the resin film having a high moisture permeability. You may use adhesives other than an epoxy type, such as an agent. However, since the photocurable adhesive according to the present invention gives a high adhesive force to the cellulose resin film and the amorphous polyolefin resin film exemplified here, it is better to use the same adhesive on both sides of the polarizer. This is advantageous because the operation becomes simple.

  The cellulose-based resin that can be used as one protective film is a cellulose partial or completely esterified product, and examples thereof include cellulose acetate, propionate, butyrate, and mixed esters thereof. Specific examples include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Examples of commercially available films made of such cellulose ester resins include, but are not limited to, “Fujitac TD80”, “Fujitac TD80UF” and “Fujitac TD80UZ” manufactured by Fuji Film Co., Ltd., Konica Minolta Opto Corporation "KC8UX2M", "KC8UY", etc. Moreover, the cellulose resin film provided with the optical compensation function can also be used. The optical compensation film is not particularly limited. For example, a film in which a compound having a retardation adjusting function is contained in a cellulose resin, or a film having a retardation adjusting function applied to the surface of a cellulose resin film. And a film obtained by stretching a cellulose resin film uniaxially or biaxially. Examples of commercially available cellulose-based optical compensation films include “Wide View Film WV BZ 438” and “Wide View Film WV EA” manufactured by FUJIFILM Corporation, and “KC4FR” manufactured by Konica Minolta Opto Co., Ltd. -1 "and" KC4HR-1 "are preferred.

  Examples of transparent resins with low moisture permeability that can be used as one of the protective films, which are different from polyester resins, polycarbonate resins, and acrylic resins, include, but are not limited to, amorphous polyolefin resins, polysulfone Examples thereof include resins and alicyclic polyimide resins. Among these, a film made of an amorphous polyolefin-based resin is a film excellent in mechanical properties, solvent resistance, scratch resistance, cost, and the like, and is particularly preferably used.

  Amorphous polyolefin-based resins usually have polymerized units derived from polycyclic cyclic olefins such as norbornene, derivatives thereof, and dimethanooctahydronaphthalene, and have double bonds like ring-opening polymers. If remaining, a hydrogenated thermoplastic resin is preferred. The amorphous polyolefin-based resin may be a copolymer of a cyclic olefin and a chain olefin, or a polar group may be introduced. Among them, a typical example is a thermoplastic saturated norbornene resin. Examples of commercially available amorphous polyolefin resins include “Arton” from JSR Corporation, “ZEONEX” and “ZEONOR” from Nippon Zeon Corporation, “APO” and “APO” from Mitsui Chemicals, Inc. Appel "etc. When the amorphous polyolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used for forming the film.

  Prior to bonding to the polarizer, the protective film may be subjected to easy adhesion treatment such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment on the bonding surface. Moreover, you may have various process layers, such as a hard-coat layer, an antireflection layer, an anti-glare layer, in the surface on the opposite side to the bonding surface to the polarizer of a protective film. Although the thickness of a protective film is not specifically limited, Usually, it is the range of about 5-200 micrometers, Preferably it is 10-120 micrometers, More preferably, it is 10-85 micrometers.

[Production method of polarizing plate]
The polarizing plate of the present invention is the photocuring described above on at least one of the bonding surfaces of the polarizer described above and a protective film made of a transparent resin film selected from polyester resin, polycarbonate resin, and acrylic resin. The adhesive application step for applying the adhesive, the bonding step for bonding the polarizer and the protective film through the obtained adhesive layer, and the polarizer and the protective film applied through this adhesive layer And a curing step of curing the photocurable adhesive in a combined state.

<Adhesive application process>
In the adhesive application step, the above-described photocurable adhesive is applied to at least one of the bonding surfaces of the polarizer and the protective film. When the photocurable adhesive is directly applied to the surface of the polarizer or the protective film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting the photocurable adhesive demonstrated previously between a polarizer and a protective film, the method of pressurizing with a roll etc. and spreading uniformly can also be utilized.

<Bonding process>
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, a protective film is superimposed thereon, and in the previous application step, the surface of the protective film is photocurable. When an adhesive is applied, a polarizer is superimposed thereon. Further, when a photocurable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film are superposed in that state. When a protective film is pasted on both sides of a polarizer, and the photocurable adhesive of the present invention is used on both sides, the protective film is superimposed on each side of the polarizer via a photocurable adhesive. Is done. Usually, in this state, both sides (when a protective film is placed on one side of the polarizer, the polarizer side and the protective film side, and when a protective film is placed on both sides of the polarizer, both sides are protected. The pressure is sandwiched between rolls from the membrane side). Here, metal, rubber, or the like can be used as the material of the roll. The rolls arranged on both sides may be the same material or different materials.

<Curing process>
As described above, the one in which the polarizer and the protective film are bonded through the uncured photocurable adhesive is then subjected to a curing step. In this curing step, the photocurable adhesive is irradiated with active energy rays to cure the adhesive layer containing the epoxy compound or the oxetane compound, thereby bonding the polarizer and the protective film. When a protective film is bonded to one side of the polarizer, the active energy ray may be irradiated from either the polarizer side or the protective film side. Moreover, when sticking a protective film on both surfaces of a polarizer, in the state which bonded the protective film on both surfaces of the polarizer through the photocurable adhesive agent, respectively, an active energy ray from either one of the protective films side It is advantageous to simultaneously cure the photocurable adhesive on both sides. However, when either one of the protective films contains an ultraviolet absorber (for example, when a cellulose-based resin film containing an ultraviolet absorber is used as one protective film), the active energy rays are ultraviolet rays. In this case, the ultraviolet ray is usually irradiated from the side of the protective film not containing the other ultraviolet absorbent.

  Visible light, ultraviolet rays, X-rays, electron beams, and the like can be used as the active energy rays, but ultraviolet rays are generally preferably used because they are easy to handle and have a sufficient curing rate. The light source of the active energy ray is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp. An LED lamp or the like can be used.

The light irradiation intensity to the photocurable adhesive is determined for each target composition and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is UV. -B (middle wavelength region ultraviolet ray of 280 to 320 nm) is preferably set to be 1 to 3,000 mW / cm ² . If the irradiation intensity is less than 1 mW / cm ² , the reaction time becomes too long, while if the irradiation intensity exceeds 3,000 mW / cm ² , the heat radiated from the lamp and the polymerization of the photocurable adhesive The heat generation may cause yellowing of the photocurable adhesive and deterioration of the polarizer.

The light irradiation time to the photocurable adhesive is controlled for each composition to be cured and is not particularly limited, but the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 5, It is preferably set to be 000 mJ / cm ² . If the integrated light amount is less than 10 mJ / cm ² , the active species derived from the polymerization initiator is not sufficiently generated, and the adhesive layer may be insufficiently cured, while the integrated light amount is 5,000 mJ. If it exceeds / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

  When curing the photocurable adhesive by irradiating with active energy rays, it should be cured under conditions that do not deteriorate the functions of the polarizing plate, such as the degree of polarization of the polarizer, the transmittance and hue, and the transparency of the protective film. Is preferred.

  In the polarizing plate thus obtained, the thickness of the adhesive layer is not particularly limited, but is usually 50 μm or less, preferably 20 μm or less, and more preferably 10 μm or less.

[Optical member]
When using a polarizing plate, it can also be set as the optical member which laminated | stacked the optical layer which shows optical functions other than a polarization function on the one side. The optical layer laminated on the polarizing plate for the purpose of forming an optical member is not particularly limited. For example, a reflective layer, a transflective reflective layer, a light diffusing layer, a retardation plate, a condensing plate, a brightness enhancement film, a liquid crystal, etc. Various types used for forming a display device or the like can be given. The reflective layer, transflective reflective layer, and light diffusing layer are used when forming an optical member comprising a reflective or transflective type, diffusive type, or a polarizing plate of both types.

  The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the viewing side. Since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective polarizing plate is used for a liquid crystal display device that displays as a reflective type in a bright place and displays using a light source such as a backlight in a dark place. An optical member as a reflective polarizing plate can form a reflective layer by attaching a foil or a vapor deposition film made of a metal such as aluminum to a protective film on a polarizer, for example. The optical member as a transflective polarizing plate can be formed by using the reflective layer as a half mirror, or by adhering a reflective plate exhibiting light transmittance by containing a pearl pigment or the like to the polarizing plate. On the other hand, an optical member as a diffusion type polarizing plate is subjected to various methods such as a method of performing a mat treatment on a protective film on a polarizing plate, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles. Use to form a fine relief structure on the surface.

  Furthermore, the optical member as a polarizing plate for both reflection and diffusion can be formed by, for example, a method of providing a reflective layer reflecting the concavo-convex structure on the fine concavo-convex structure surface of the diffusion polarizing plate. The reflective layer having a fine concavo-convex structure has the advantage that incident light can be diffused by irregular reflection, directivity and glare can be prevented, and uneven brightness can be suppressed. In addition, the resin layer or film containing fine particles has an advantage that incident light and its reflected light are diffused when passing through the fine particle-containing layer, and uneven brightness can be further suppressed. The reflective layer reflecting the surface fine concavo-convex structure can be formed by, for example, attaching a metal directly to the surface of the fine concavo-convex structure by a method such as vacuum deposition, ion plating, sputtering or other vapor deposition or plating. The fine particles to be blended to form the surface fine concavo-convex structure include, for example, silica having an average particle diameter of 0.1 to 30 μm, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like. Inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like can be used.

  On the other hand, the above-described retardation plate as an optical layer is used for the purpose of compensation of retardation by a liquid crystal cell. Examples thereof include, but are not limited to, birefringent films made of stretched films of various plastics, films in which discotic liquid crystals and nematic liquid crystals are aligned and fixed, and the above liquid crystal layer formed on a film substrate Etc. In this case, the film substrate for supporting the alignment liquid crystal layer is not particularly limited, but a cellulose-based film such as triacetyl cellulose is preferably used.

  The plastic forming the birefringent film is not particularly limited, and examples thereof include polyolefins such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, and polypropylene, polyarylate, polyamide, and amorphous polyolefin resin. . The stretched film may be processed by an appropriate method such as uniaxial or biaxial. Moreover, the birefringent film which controlled the refractive index of the thickness direction of a film by applying shrinkage force and / or extending | stretching force under adhesion | attachment with a heat-shrinkable film may be sufficient. Note that two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as broadening the bandwidth.

  The condensing plate is used for the purpose of optical path control and can be formed as a prism array sheet, a lens array sheet, a dot-attached sheet, or the like.

  The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device or the like. For example, a plurality of thin film films having different refractive index anisotropies are laminated to make the reflectance anisotropy. Examples thereof include a reflection-type linearly polarized light separating sheet designed so as to occur, an oriented film of cholesteric liquid crystal polymer, and a circularly polarized light separating sheet having the oriented liquid crystal layer supported on a film substrate.

  The optical member is selected from the polarizing plate, the reflective layer or the semi-transmissive reflective layer, the light diffusion layer, the retardation plate, the light collector, the brightness enhancement film, etc. These optical layers can be combined to form a laminate of two layers or three or more layers. In that case, two or more optical layers such as a light diffusion layer, a phase difference plate, a light collecting plate, and a brightness enhancement film may be arranged. In addition, there is no limitation in particular in arrangement | positioning of each optical layer.

  The various optical layers that form the optical member are integrated with the polarizing plate using an adhesive, but the adhesive used for this purpose is not particularly limited as long as the adhesive layer is well formed. It is preferable to use a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) from the viewpoint of easy bonding work and prevention of optical distortion. As the pressure-sensitive adhesive, an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or the like can be used as a base polymer. Above all, like acrylic pressure-sensitive adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to substrates, and has weather resistance, heat resistance, etc. It is preferable to select and use one that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl group, ethyl group, butyl group, (meth) acrylic acid, hydroxyethyl (meth) acrylate, etc. An acrylic copolymer having a weight average molecular weight of 100,000 or more, which was polymerized with a functional group-containing acrylic monomer comprising a polymer having a glass transition temperature of preferably 25 ° C. or lower, more preferably 0 ° C. or lower. The coalescence is useful as a base polymer.

  The pressure-sensitive adhesive layer is formed on the polarizing plate by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a liquid having a solid content concentration of 10 to 40% by weight. By directly coating on the adhesive layer to form a pressure-sensitive adhesive layer, or by previously forming a pressure-sensitive adhesive layer on a separate film and transferring it onto a polarizing plate, etc. ,It can be carried out. Although the thickness of an adhesive layer is determined according to the adhesive force etc., the range of about 1-50 micrometers is suitable.

  In addition, the adhesive layer is blended with fillers made of glass fibers, glass beads, resin beads, metal powders and other inorganic powders, pigments, colorants, antioxidants, UV absorbers, etc., as necessary. May be. Although it does not specifically limit as an ultraviolet absorber, A salicylic acid ester type compound, a benzophenone type compound, a benzotriazole type compound, a cyanoacrylate type compound, a nickel complex salt type compound, etc. are mentioned.

[Liquid Crystal Display]
The above optical members can be arranged on one side or both sides of the liquid crystal cell to form a liquid crystal display device. The liquid crystal cell to be used is arbitrary. For example, a liquid crystal display device using various liquid crystal cells such as an active matrix driving type typified by a thin film transistor type and a simple matrix driving type typified by a super twisted nematic type. Can be formed. The optical members provided on both sides of the liquid crystal cell may be the same or different.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the examples,% indicating the amount used or the content is based on weight unless otherwise specified.

  In the examples and comparative examples, each component used for the preparation of the adhesive composition is as follows, and hereinafter, each symbol (trade name itself or a part thereof) is indicated.

(A) Component : Epoxy compound jER-828: Bisphenol A type epoxy resin, “jER-828” manufactured by Japan Epoxy Resin Co., Ltd.
jER-152: A phenol novolac type epoxy resin, “jER-152” manufactured by Japan Epoxy Resin Co., Ltd.
ECC: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate.

(B) Component : Oxetane compound OXT-211: 3-ethyl-3-phenoxymethyloxetane, “Aron oxetane OXT-211” manufactured by Toagosei Co., Ltd.
OXT-221: 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, “Aron oxetane OXT-221” manufactured by Toagosei Co., Ltd.
OXT-121: A bifunctional oxetane compound having a xylylene skeleton mainly composed of 1,4-bis [(3-ethyloxetane-3-yl) methoxymethyl] benzene, “Alonoxetane OXT-” manufactured by Toagosei Co., Ltd. 121 ".

  The structures of these oxetane compounds are shown below.

Component (C) : Photocationic polymerization initiator UVI-6992: Propylene carbonate solution containing 50% active ingredient mainly composed of triarylsulfonium hexafluorophosphate, “UVI-6992” manufactured by Dow Chemical.

(D) Component : Acrylic unsaturated compound M-203S: Tricyclodecane dimethylol diacrylate, “Aronix M-203S” manufactured by Toagosei Co., Ltd.

(E) Component : Photoradical polymerization initiator Irg184: 1-hydroxycyclohexyl phenyl ketone, “Irgacure 184” manufactured by Ciba.

Component (F) : Other component having no polymerizability BR-60: Methyl methacrylate copolymer, “Dianal BR-60” manufactured by Mitsubishi Rayon Co., Ltd.

[Preparation of adhesive composition]
Each component shown in Table 1 and Table 2 was mix | blended in each ratio, and it stirred and mixed according to the conventional method, and prepared the photocurable adhesive composition. In addition, since "UVI-6992" used as the component (C) is a propylene carbonate solution containing 50% of the active ingredient, the component (C) and propylene carbonate are shown separately in the table. That is, the blending amount of “UVI-6992” in the table means the ratio of solid content, and the blending amount of “UVI-6992” itself is the amount shown in the column of component (C) and the column of propylene carbonate. The combined amount is 6%.

[Production of Polarizing Plate (1)]
Here, the following two types of films were used as protective films.
Stretched norbornene-based resin film: thickness 70 μm, trade name “ZEONOR film”, manufactured by Nippon Zeon Co., Ltd. The film was subjected to corona discharge treatment and then subjected to bonding with a polarizer.
Biaxially stretched polyethylene terephthalate film: thickness 50 μm, trade name “E5001”, manufactured by Toyobo Co., Ltd. This film was also subjected to corona discharge treatment and then subjected to bonding with a polarizer.

The adhesive composition prepared above is applied to the corona discharge-treated surface of the stretched norbornene-based resin film to a thickness of 3 μm with a bar coater, and a polarizer on which iodine is adsorbed and oriented is bonded to polyvinyl alcohol. did. Separately, the same adhesive was applied to the above-mentioned biaxially stretched polyethylene terephthalate film with a bar coater to a thickness of 3 μm, and was bonded to the opposite side of the norbornene-based resin film of the polarizer previously bonded with the norbornene-based resin film. . In this way, the polarizer with the protective film bonded on both sides is irradiated with UV light from one surface with an integrated light amount of 300 mJ / cm ² using a UV irradiation device with a belt conveyor (using a “Fusion H bulb” manufactured by Fusion). Then, it was left at room temperature for 1 hour to produce a polarizing plate (1) in which a protective film made of a polyethylene terephthalate film was bonded to one side and a stretched norbornene resin film was bonded to the other side.

[Production of Polarizing Plate (2)]
The biaxially stretched polyethylene terephthalate film was changed to an acrylic resin film (thickness 80 μm, trade name “Technoloy S001”, manufactured by Sumitomo Chemical Co., Ltd.). The protective film which consists of a resin film was bonded, and the polarizing plate (2) by which the extending | stretched norbornene-type resin film was bonded to the other surface was produced.

[Evaluation test]
About each obtained polarizing plate, sclerosis | hardenability, adhesiveness, and durability were evaluated with the following method, and a result is shown in Table 1 and Table 2.

<Curing property>
Attempt to peel off the polarizer and polyethylene terephthalate film or acrylic resin film by hand, and it cannot be peeled off completely, or even if peeled off, tackiness (tackiness due to uncured adhesive) remains on the part Those not present were evaluated as “◯”, and those that peeled off and remained tacky were evaluated as “x”.

<Adhesiveness>
When the blade of the cutter knife is inserted obliquely from above the polyethylene terephthalate film or acrylic resin film, the film peels off from the polarizer and the blade enters between the polyethylene terephthalate film or acrylic resin film and the polarizer, Rated as the worst “×”. When it did not peel in this test, the following evaluation was further performed. That is, the polarizing plate is cut into a 1 cm wide strip with the stretching direction as the long side, and a shallow cut is made with a cutter knife in the direction perpendicular to the stretching direction from the surface of the polyethylene terephthalate film or acrylic resin film, and this cut is made outside. Then, the degree of peeling from the end portion when it was folded into a “ku” shape was observed. When an edge part peeled here, peeling was tried from the peeling part by hand, and it evaluated by peeling progressing or whether a film destroyed material. According to the evaluation result, the determination was performed as follows.

(Triangle | delta): The peeling of an edge part is large when bent, and peeling advances easily by hand.
○: The edge part peels around 1 mm when bent, but if the peeling is further attempted by hand, the film breaks the material.
A: Almost no peeling when folded, and if the peeling is attempted by hand, the film breaks the material.

<durability>
For a good sample having an adhesion of “◯” or more, a thermal shock cycle test in which a cycle of placing at −35 ° C. for 60 minutes and then placing at + 70 ° C. for 60 minutes was repeated 300 times with a diagonal of 15 inches (about 38 cm) The test was carried out with two sample sizes of 5 inches (about 13 cm) and evaluated as follows.

○: 15 inches without appearance defects.
Δ: Some appearance defects at 15 inches, but no appearance defects at 5 inches.
X: Appearance is poor even at 5 inches.

  As shown in Table 1, the polarizing plates of Examples 1 to 7 produced using the photocurable adhesive composition of the present invention have good adhesion between the polarizer and the protective film, and good curability. Met. Among these, in Examples 1 to 3, in which “OXT-211” having one oxetanyl group and one aromatic ring in the molecule is used as the oxetane compound of the component (B), the adhesiveness is particularly good. Met. In Example 3 containing 18% of the acrylic unsaturated compound “M-203S” having an alicyclic skeleton as the component (D), in addition to good adhesiveness, durability was also good. In addition, Examples 4 to 7 using an oxetane compound “OXT-221” which has two oxetanyl groups in the molecule and is liquid at room temperature and has a molecular weight of 500 or less (in Example 4, “OXT-121” is used in combination). ) Was excellent in the balance between adhesion and durability. Among them, Examples 4 and 5 containing 18% of the acrylic unsaturated compound “M-203S” had particularly good adhesiveness.

  On the other hand, as shown in Table 2, Comparative Examples 1 and 2 not containing the oxetane compound as the component (B) had poor adhesion. In particular, Comparative Example 2 in which 43% of the (D) component acrylic unsaturated compound was blended had poor adhesion to both the polyethylene terephthalate film and the acrylic resin film. Moreover, the comparative example 3 which does not contain the epoxy compound of (A) component was bad in sclerosis | hardenability and adhesiveness.

  The photocurable adhesive composition of the present invention is easily cured by irradiation with active energy rays such as ultraviolet rays, and is useful for firmly bonding a polarizer and a protective film in a short time.

That is, according to the present invention, from a transparent resin film selected from the group consisting of a polyester resin, a polycarbonate resin, and an acrylic resin to a polarizer composed of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. An adhesive composition for adhering a protective film comprising: (A) an epoxy compound having at least two epoxy groups in the molecule; (B) an oxetane compound having at least one oxetanyl group in the molecule ; (C) a photocationic polymerization initiator , and (F) a methyl methacrylate polymer having a glass transition temperature of 70 ° C. or higher, and a weight ratio (A) between the epoxy compound (A) and the oxetane compound (B). / (B) is about 90/10 to 10/90, and the amount of the photocationic polymerization initiator (C) is about A photocurable adhesive composition is provided that is 0.5 to 20 wt%.

The amount of the methyl methacrylate polymer (F) having a glass transition temperature of 70 ° C. or higher is usually preferably about 10% by weight or less in the composition. Furthermore, these photocurable adhesive compositions can contain other components that are not polymerizable as the component (G), and in this case, the amount of the other component (G) is also included in the composition. Usually, a ratio of about 10% by weight or less is preferable.

[Photocurable adhesive composition]
In this invention, in order to bond a polarizer and a protective film, the photocurable adhesive composition of a specific composition is used. Hereinafter, this photocurable adhesive composition may be simply referred to as “photocurable adhesive”. The photocurable adhesive of the present invention essentially contains the following four components (A), (B) , (C) and (F) .

(A) an epoxy compound having at least two epoxy groups in the molecule;
(B) an oxetane compound having at least one oxetanyl group in the molecule ,
(C) a cationic photopolymerization initiator , and
(F) A methyl methacrylate polymer having a glass transition temperature of 70 ° C. or higher .

The epoxy compound (A) is also simply referred to as “component (A)” or “epoxy compound (A)” in the present specification. Similarly, in this specification, the oxetane compound of (B) is also referred to as “component (B)” or “oxetane compound (B)”, and the photocationic polymerization initiator of (C) is referred to as “component (C)” or call as "cationic photoinitiator (C)", hump as "component (F)" a methyl methacrylate-based polymer (F).

This photocurable adhesive can optionally contain an unsaturated compound having at least one ethylenically unsaturated bond in the molecule as component (D), and contains such an unsaturated compound (D). When it does, it is preferable to contain radical photopolymerization initiator as (E) component. Furthermore, this photocurable adhesive agent can also contain the other component which does not have polymerizability as (G) component.

The unsaturated compound (D) is also simply referred to herein as “component (D)” or “unsaturated compound (D)”. Similarly herein, the photoradical polymerization initiator, also referred to as "component (E)" or "photo-radical polymerization initiator (E)", polymerizable other without the (G) (E) The component is also referred to as “ (G) component” or “other component (G) having no polymerizability”.

<Other ingredients>
Furthermore, the photocurable adhesive of the present invention is added to the above components (A) to (C), or in addition to the (D) component and / or (E) component that is optionally blended, (F) As a component, for the purpose of further improving the adhesion to the protective film, a methyl methacrylate polymer having a glass transition temperature of 70 ° C. or higher is contained from the viewpoint of enhancing the durability of the thermoplastic resin, particularly the polarizer. (F) It is preferable that the mixture ratio of a component shall be about 10 weight% or less on the basis of the whole composition. In the adhesive, other components different from the components (A) to (F) can be arbitrarily blended as long as the effects of the present invention are not impaired. As one type belonging to such other components, there can be mentioned compounds having cationic polymerizability other than the epoxy compound of component (A) and the oxetane compound of component (B), and specific examples thereof are particularly limited. Although not, an epoxy compound having one epoxy group in the molecule can be used. Moreover, the other component (G) which does not have polymerizability can be mentioned as another type which belongs to another component. When the other component (G) having no polymerizability is blended, the blending ratio is preferably about 10% by weight or less based on the entire composition.

Although it does not specifically limit as an example of the other component (G) which does not have polymerizability, A photosensitizer is mentioned. By blending a photosensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

Moreover, a thermal cationic polymerization initiator can also be used as another component (G) which does not have polymerizability. Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These initiators can be easily obtained as commercial products. For example, both of them are indicated by trade names, “Adeka Opton CP77” and “Adeka Opton CP66” (above, manufactured by ADEKA Corporation), “CI” -2639 "and" CI-2624 "(manufactured by Nippon Soda Co., Ltd.)," Sun-Aid SI-60L "," Sun-Aid SI-80L "and" Sun-Aid SI-100L "(Sanshin Chemical Industry Co., Ltd.) Manufactured) and the like.

Since polyols have the property of promoting cationic polymerization, they can be used as other components (G) that also have no polymerizability. As the polyols, those having no acidic group other than phenolic hydroxyl groups are preferable. For example, polyol compounds having no functional groups other than hydroxyl groups, polyester polyol compounds, polycaprolactone polyol compounds, polyol compounds having phenolic hydroxyl groups, polycarbonates A polyol compound etc. can be mentioned.

Furthermore, as long as the effects of the present invention are not impaired, the other component (G) having no polymerizability includes a silane coupling agent, an ion trap agent, an antioxidant, a light stabilizer, a chain transfer agent, a sensitizer, and tackifying. Agents , fillers, flow regulators, plasticizers, antifoaming agents, leveling agents, dyes, organic solvents, and the like can also be blended .

Claims (16)

For adhering a protective film made of a transparent resin film selected from the group consisting of a polyester resin, a polycarbonate resin and an acrylic resin to a polarizer made of a polyvinyl alcohol resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. An adhesive composition comprising:
(A) an epoxy compound having at least two epoxy groups in the molecule;
(B) an oxetane compound having at least one oxetanyl group in the molecule ,
(C) a cationic photopolymerization initiator , and
(F) a methyl methacrylate polymer having a glass transition temperature of 70C or higher ,
The weight ratio (A) / (B) between the epoxy compound (A) and the oxetane compound (B) is 90/10 to 10/90,
The amount of the photocationic polymerization initiator (C) is 0.5 to 20% by weight in the composition,
Photo-curable adhesive composition.   The photocurable adhesive composition according to claim 1, wherein the epoxy compound (A) comprises a compound having at least two epoxy groups and at least one aromatic ring in the molecule.   The photocurable adhesive composition according to claim 1, wherein the epoxy compound (A) contains one or more selected from the group consisting of glycidyl ethers and glycidyl esters of aromatic compounds.   The photocurable adhesive composition according to any one of claims 1 to 3, wherein the oxetane compound (B) contains a compound having one oxetanyl group and at least one aromatic ring in the molecule.   The photocurable adhesive composition according to any one of claims 1 to 3, wherein the oxetane compound (B) contains a compound having two oxetanyl groups in the molecule.   Furthermore, (D) The photocuring in any one of Claims 1-5 which contain the unsaturated compound which has an at least 1 ethylenically unsaturated bond in a molecule | numerator in the ratio of 35 weight% or less. Adhesive composition.   The photocurable adhesive composition of Claim 6 which contains an unsaturated compound (D) in the ratio of 5 to 25 weight% in a composition.   The unsaturated compound (D) is a (meth) acrylic compound having at least one (meth) acryloyl group and at least one alicyclic skeleton or aromatic ring skeleton in the molecule. A photocurable adhesive composition.   The photocurable adhesive composition according to claim 8, wherein the unsaturated compound (D) is a di (meth) acrylate having a tricyclodecane skeleton.   Furthermore, the photocurable adhesive composition in any one of Claims 6-9 which contains (E) radical photopolymerization initiator in the ratio of 10 weight% or less in a composition. The photocurable adhesive composition according to any one of claims 1 to 10 , wherein the amount of the methyl methacrylate polymer (F) is 10% by weight or less in the composition.   Protection comprising a transparent resin film selected from the group consisting of a polyester resin, a polycarbonate resin, and an acrylic resin via an adhesive on a polarizer composed of a polyvinyl alcohol resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. It is a polarizing plate by which a film | membrane is bonded, Comprising: The said adhesive agent is formed from the photocurable adhesive composition in any one of Claims 1-11, The polarizing plate characterized by the above-mentioned. Protection comprising a transparent resin film selected from the group consisting of a polyester resin, a polycarbonate resin, and an acrylic resin via an adhesive on a polarizer composed of a polyvinyl alcohol resin film that is uniaxially stretched and adsorbed and oriented with a dichroic dye. A method of bonding a film and manufacturing a polarizing plate,
The adhesive application process which apply | coats the photocurable adhesive composition in any one of Claims 1-11 to at least one among the bonding surfaces of the said polarizer and the said protective film,
A bonding step of bonding the polarizer and the protective film through the resulting adhesive layer;
The manufacturing method of the polarizing plate characterized by including the hardening process which hardens the said photocurable adhesive composition in the state in which the polarizer and the protective film were bonded through the said adhesive bond layer.   An optical member, wherein another optical layer is laminated on the polarizing plate according to claim 12.   The optical member according to claim 14, wherein the other optical layer includes a retardation plate.   16. A liquid crystal display device, wherein the optical member according to claim 14 or 15 is disposed on one side or both sides of a liquid crystal cell.