JP5448024B2 - Photocurable adhesive, polarizing plate using the photocurable adhesive, method for producing the same, optical member, and liquid crystal display device - Google Patents

Description

  The present invention relates to a specific photocurable adhesive, a polarizing plate formed by laminating a protective film on one or both sides of a polarizer using the photocurable adhesive, a method for producing the same, and the polarizing plate. The present invention relates to an optical member and a liquid crystal display device.

  The polarizing plate is useful as one of the optical components constituting the liquid crystal display device. A polarizing plate usually has a structure in which protective films are laminated on both sides of a polarizer, and is used by being incorporated in a liquid crystal display device. It is also known that a protective film is provided only on one side of the polarizer, but in many cases, a layer having an optical function as another function is not provided on the other side. It is also 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 weak physical strength, and once it is wound, there is a problem such as tearing in the processing direction. Therefore, usually, a water-based adhesive is immediately applied to the dried polarizer, and protective films are simultaneously bonded to both sides of the polarizer 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 the polarizer and the protective film, particularly a protective film made of a triacetyl cellulose film, a polyvinyl alcohol-based adhesive is often used, but instead, an attempt is made to use a urethane-based adhesive. 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. It is described.

  However, the moisture permeability of triacetyl cellulose is high, and the polarizing plate bonded as a protective film has problems such as causing deterioration under wet heat, for example, at a temperature of 70 ° C. and a relative humidity of 90%. It was.

  Therefore, a method for solving such a problem by using a resin film having a moisture permeability lower than that of a triacetyl cellulose resin film as a protective film has been proposed. For example, it is known that an amorphous polyolefin 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 so-called wet lamination in which the solvent is dried after combining, there are problems such as insufficient adhesive strength and poor appearance. 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.

  Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 4) discloses an adhesive mainly composed of an epoxy resin not containing an aromatic ring, and an adhesion method by cationic polymerization by heating or irradiation of active energy rays. Has been proposed. However, in order to increase the efficiency of polarizing plate production, further time reduction in the bonding process is required, and prevention of discoloration of the adhesive is also required.

  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 (Patent Document 5) 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. It has been proposed to do.

Amorphous polyolefin-based resins are, for example, “Chemical Industry” February 1991 (Chemical Industry), pages 20 to 26 (Non-Patent Document 1), “Functional Materials” January 1993 (Vol. 13). , No. 1) (CMC), pp. 40-52 (Non-patent Document 2) and the like.
JP-A-7-120617 JP-A-6-511117 JP 2000-32432 A JP 2004-245925 A JP 2002-174729 A "Chemical Industry" February 1991 (Chemical Industry), pp. 20-26 "Functional Materials" January 1993 (Vol. 13, No. 1) (CMC), pp. 40-52

  In order to solve problems such as insufficient adhesive strength and poor appearance when bonding polyvinyl alcohol polarizers and protective films with low moisture permeability by wet lamination, the drying oven length after bonding may be extended. Although it is conceivable, there is a problem that discoloration due to thermal deterioration of the polarizer and the adhesive tends to occur when the drying oven length is simply increased. Therefore, if the drying temperature is lowered so as not to cause thermal deterioration of the polarizer and the adhesive, it is necessary to further extend the drying furnace length in order to sufficiently dry, and the capital investment becomes enormous. There is.

  In addition, when different types of protective films are used for one surface and the other surface of the polarizer, the protective film has a different shrinkage rate due to heat. There is a problem that the polarizing plate curls when it returns to room temperature after drying.

Therefore, it is conceivable to adopt a bonding method by dry lamination in order to improve such a problem. However, an adhesive having dry lamination suitability has a very high viscosity.
Therefore, from the problem that the physical strength of the polarizer is weak, the method of bonding the polarizer and the protective film is to apply an adhesive to the protective film and then paste the protective film to the polarizer. Limited.
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. Therefore, it causes a bright spot defect. In this method, the thickness and thickness distribution of the coating layer are greatly affected by the viscosity of the adhesive, and the smaller the change in viscosity with time, the more uniform the thickness and thickness distribution of the coating layer. Therefore, there is a demand for an adhesive having excellent storage stability in which the increase in viscosity due to curing during storage is suppressed while maintaining the curing rate at or above a desired level.

  An object of the present invention is a photocurable adhesive that has excellent storage stability, can suppress discoloration of the adhesive itself and an object to be bonded at the time of curing, has a high curing rate, and provides good adhesiveness, and A polarizing plate formed using the curable adhesive and having a good appearance, a method for producing the same, an optical member capable of forming a liquid crystal display device having excellent reliability using the polarizing plate, and a liquid crystal provided with the optical member It is to provide a display device.

  The present invention is an adhesive for bonding a protective film to a polarizer composed of a polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented, and has two or more epoxy groups in the molecule. And 100 parts by mass of the epoxy resin (A) in which at least one of the epoxy groups is an alicyclic epoxy group, and having two or more epoxy groups in the molecule and substantially comprising the alicyclic epoxy group It is related with the photocurable adhesive agent containing 5-1000 mass parts of epoxy resin (B) which does not have, and 0.5-20 mass parts of a photocationic polymerization initiator (C).

  The photocurable adhesive of this invention can further contain a polymerizable monomer (D) at 100 mass parts or less.

  In the photocurable adhesive of the present invention, it is preferable that the epoxy resin (A) and the epoxy resin (B) are resins having substantially no aromatic ring.

  In the photocurable adhesive of the present invention, the epoxy resin (B) is preferably a resin that does not substantially have an alicyclic ring.

  The photocurable adhesive of the present invention comprises 100 parts by mass of the epoxy resin (A), 5 to 1000 parts by mass of the epoxy resin (B), and 0.5 to 20 parts by mass of the cationic photopolymerization initiator (C). And 0 to 100 parts by mass of the polymerizable monomer (D) and 0 to 1000 parts by mass of the additive component (E).

  The photocurable adhesive of the present invention can contain, as an additive component (E), a photosensitizer (P) having a sensitizing ability for light longer than 380 nm in an amount of 250 parts by mass or less. Examples of the agent (P) include anthracene compounds represented by the following general formula (I).

(In the formula, R and R ′ represent an alkyl group having 1 to 18 carbon atoms or an ether group having 2 to 18 carbon atoms, and R ″ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.)
In the present invention, a protective film is bonded to one or both sides of a polarizer composed of a polyvinyl alcohol-based resin film adsorbed and oriented with iodine or a dichroic dye via an adhesive. The polarizing plate which is a hardened | cured material of the photocurable adhesive agent in any one of.

  The polarizing plate of the present invention can take a form in which an acetylcellulose-based resin film is bonded to at least one surface of a polarizer as a protective film.

  Moreover, the polarizing plate of this invention can take the form by which the film of the transparent resin whose moisture permeability is lower than a triacetyl cellulose was bonded to the at least single side | surface of a polarizer as a protective film.

  Furthermore, the polarizing plate of the present invention has at least one transparent selected from an amorphous polyolefin resin, a polyester resin, an acrylic resin, a polycarbonate resin, a polysulfone resin, and an alicyclic polyimide resin as a protective film. It can take the form in which a resin film is bonded to at least one surface of a polarizer.

  Furthermore, in the polarizing plate of the present invention, as a protective film, a film of an acetylcellulose-based resin is provided on one side of the polarizer, and a transparent resin film having a lower moisture permeability than triacetylcellulose is provided on the other side of the polarizer. However, it can also take the form each bonded.

  The present invention is also a method for producing a polarizing plate by laminating a protective film via an adhesive on one or both sides of a polarizer comprising a polyvinyl alcohol resin film adsorbed and oriented with iodine or a dichroic dye. Then, a coating process for coating one side of the protective film with the photocurable adhesive described above to form an adhesive coated surface, and the polarizer on the adhesive coated surface of the protective film It is related with the manufacturing method of a polarizing plate including the bonding process to bond and the hardening process to harden a photocurable adhesive agent.

  The present invention also relates to an optical member comprising a laminate of any one of the polarizing plates described above and an optical layer.

In the optical member of the present invention, the optical layer preferably includes a retardation plate.
The present invention also relates to a liquid crystal display device in which any one of the optical members described above is disposed on one side or both sides of a liquid crystal cell.

  According to the present invention, it is possible to obtain a photocurable adhesive that is excellent in storage stability, can suppress discoloration of the adhesive itself and an object to be bonded at the time of curing, has a high curing speed, and provides good adhesiveness. Therefore, by using the curable adhesive, a polarizing plate having a good appearance can be obtained even when, for example, a resin film having low moisture permeability is used as a protective film. Further, by using the polarizing plate, it is possible to provide an optical member capable of forming a liquid crystal display device with excellent reliability and a liquid crystal display device provided with the optical member.

[Photocurable adhesive]
The present invention relates to an epoxy resin (A) having two or more epoxy groups in the molecule and at least one of the epoxy groups being an alicyclic epoxy group (hereinafter also simply referred to as epoxy resin (A)). And an epoxy resin (B) having two or more epoxy groups in the molecule and substantially not having an alicyclic epoxy group (hereinafter also simply referred to as an epoxy resin (B)). ) 5 to 1000 parts by mass and a photocationic polymerization initiator (C) 0.5 to 20 parts by mass.

  In the present invention, the photocationic polymerization initiator (C) is used as a cationic polymerization initiator for curing the epoxy resin (A) and the epoxy resin (B). As a result, curing during storage of the adhesive is suppressed, excellent storage stability is imparted, and, for example, the adhesive itself and adhesion that occur due to heat history when using a thermosetting polymerization initiator is used. Deterioration and discoloration of the object can be prevented. Further, deformation due to thermal shrinkage of the bonding target due to the thermal history can be prevented.

  In the present invention, by using the epoxy resin (A) and the epoxy resin (B) in combination, an adhesive having a sufficiently high curing rate in photocuring and excellent adhesiveness can be obtained.

  Therefore, when the photocurable adhesive of the present invention is used for optical applications such as a polarizing plate, it is possible to achieve both excellent appearance and physical strength.

  Since the photocurable adhesive of the present invention has a high curing rate and excellent storage stability, for example, a polarizing plate formed by bonding a polyvinyl alcohol polarizer and a protective film that is a resin film having low moisture permeability. Even when used for forming, excellent adhesion strength and appearance are imparted.

  The photocurable adhesive of the present invention is typically suitably used for bonding between a polarizer and a protective film. In the present invention, the epoxy resin means a compound or polymer having an average of two or more epoxy groups in the molecule and capable of curing reaction. In accordance with the practice in this field, in the present invention, any monomer having two or more curable epoxy groups in the molecule is referred to as an epoxy resin.

<Epoxy resin (A)>
As an epoxy resin (A) which is an essential component of the photocurable adhesive of the present invention and has two or more epoxy groups in the molecule and at least one of the epoxy groups is an alicyclic epoxy group A well-known general epoxy compound can be used. The epoxy resin (A) containing an alicyclic epoxy group contributes to an improvement in adhesive strength in the photocurable adhesive of the present invention.

  The epoxy resin (A) is preferably a resin that has substantially no aromatic ring. In this case, it is possible to obtain a photocurable adhesive capable of shortening the curing time due to good photocurability and capable of providing an adhesive layer having good weather resistance and refractive index. In the present invention, “substantially free” means that it is not contained other than those inevitably left, for example, by the manufacturing process.

  In the present invention, at least one of the two or more epoxy groups of the epoxy resin (A) in the molecule may be an alicyclic epoxy group, but all the epoxy groups are alicyclic epoxy groups. Is more preferable. In this case, the improvement effect of the adhesive strength by combining an epoxy resin (A) is exhibited more favorably.

  As the epoxy resin (A), those having two epoxy groups in the molecule and both of the two epoxy groups being alicyclic epoxy groups are particularly preferred. This is particularly advantageous in terms of adhesive strength.

  Carbon number of the alicyclic ring which comprises the alicyclic epoxy group in an epoxy resin (A) is in the range of 5-7 normally. An alicyclic epoxy group (epoxycyclohexyl group) having a cyclohexane ring having 6 carbon atoms in the alicyclic ring is particularly preferred because it is inexpensive and easily available.

  In addition, the alicyclic ring may have a substituent, and typical examples include those having an alkyl group as a substituent. In terms of curing speed and adhesive strength, the alkyl group preferably has 20 or less carbon atoms.

  Examples of the structural portion other than the epoxy group of the epoxy resin (A) include saturated hydrocarbons, unsaturated hydrocarbons, alicyclic rings, esters, ethers, ketones, carbonates, and the like. The carbon number of the structural part other than the epoxy group can be set to 8 or less, for example. In this case, since the viscosity of the epoxy resin (A) is low, there is an advantage that it is easy to handle when producing the photocurable adhesive or when applying the resulting photocurable adhesive.

  As the epoxy resin (A), for example, those represented by the following general formulas (1) to (22) can be particularly preferably exemplified. These resins are preferable in terms of particularly good photocurability.

In the general formulas (1) to (22), R ^{1 to} R ⁴⁴ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. When R ^{1 to} R ⁴⁴ are alkyl groups, the position bonded to the alicyclic ring is any position from the 1st to 6th positions. The alkyl group having 1 to 6 carbon atoms may be a straight chain, may have a branch, or may have an alicyclic ring. When the carbon number is 6 or less, it is advantageous in terms of curing speed.

Y ¹ represents an oxygen atom or an alkanediyl group, and Y ^{2 to} Y ²² each independently may be a straight chain, may have a branch, or may have an alicyclic ring. Represents. The number of carbon atoms of the alkanediyl group is Y ² , Y ⁴ , Y ⁹ , Y ¹⁰ , Y ¹¹ , Y ¹² , Y ¹³ , Y ¹⁴ , Y ¹⁵ , Y ¹⁸ , Y ¹⁹ , Y ²⁰ , Y ²¹ . 20, Y ¹ , Y ³ , Y ⁵ , Y ⁶ , Y ⁷ , Y ⁸ , Y ¹⁷ , Y ¹⁸ are 2-20. When the carbon number of Y ^{2 to} Y ²² is 20 or less, it is advantageous in that the viscosity is lowered.

Z ^{1 to} Z ² each independently represents a straight chain, may have a branch, or represents an alkanetriyl group that may have an alicyclic ring. The number of carbon atoms of alkanetriyl groups, Z ¹ is 2 to 20, Z ² is from 1 to 20. When the carbon number of Z ^{1 to} Z ² is 20 or less, it is advantageous in that the viscosity is lowered.

T ¹ represents a C 1-20 alkanetetrayl group which may be a straight chain, may be branched, or may have an alicyclic ring. When the carbon number is 20 or less, it is advantageous in that the viscosity is lowered.

  a to r represent an integer of 0 to 20. When a to r are 20 or less, it is advantageous in that the viscosity is lowered.

  As the epoxy resin (A), one type of resin or a mixture of two or more types of resins can be used.

<Epoxy resin (B)>
The epoxy resin (B), which is an essential component of the photocurable adhesive of the present invention, has two or more epoxy groups in the molecule and substantially does not have an alicyclic epoxy group, Epoxy compounds can be used. In addition, the epoxy resin which does not have an alicyclic epoxy group substantially can be paraphrased with the epoxy resin in which the epoxy group in a molecule | numerator consists of an aliphatic epoxy group.

  The epoxy resin (B) substantially not having an alicyclic epoxy group contributes to improving the flexibility of the adhesive layer after curing in the photocurable adhesive of the present invention.

  Examples of the epoxy resin (B) include bisphenol-type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; phenol novolac epoxy resin; cresol novolac epoxy resin; hydroxybenzaldehyde phenol Novolak-type epoxy resins such as novolak epoxy resins; aromatic epoxy resins such as polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol; Polyglycidyl ether of polyhydric alcohol; polyglycidyl ether of alkylene oxide adduct of aliphatic polyhydric alcohol; aliphatic polyhydric alcohol Polyglycidyl ether of a polyester polyol of a polyol and an aliphatic polycarboxylic acid; Polyglycidyl ester of an aliphatic polyhydric carboxylic acid; Polyglycidyl of a polyester polycarboxylic acid of an aliphatic polyhydric alcohol and an aliphatic polycarboxylic acid Dimers, oligomers and polymers obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate; oligomers and polymers obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate and other vinyl monomers; epoxidized vegetable oils; transesterification of epoxidized vegetable oils Body; epoxidized polybutadiene, and the like.

  Examples of the aliphatic polyhydric alcohol include those having 2 to 20 carbon atoms. More specifically, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2- Methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, Aliphatic diols such as 2-methyl-1,8-octanediol, 1,9-nonanediol and 1,10-decanediol; cyclohexane Alicyclic diols such as methanol, cyclohexanediol, hydrogenated bisphenol A, hydrogenated bisphenol F; trimethylolethane, trimethylolpropane, hexitols, pentitols, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, tetramethylol And trivalent or higher polyols such as propane.

  Specific examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and the like.

  More specifically, examples of the aliphatic polycarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, and 2-methylsuccinic acid. Acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, 1,20- Eicosamethylenedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1, 4-dicarboxylmethylenecyclohexane, 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanthate Carboxylic acid, 1,2,3,4-cyclobutane tetracarboxylic acid.

Examples of the epoxidized vegetable oil include epoxidized soybean oil and epoxidized linseed oil.
When the epoxy resin (B) is a resin that does not substantially have an aromatic ring, the photocurability is good, so that the curing time can be shortened, and the adhesive layer has good weather resistance and refractive index. It is preferable at the point which can obtain the photocurable adhesive agent which can give. In addition, if the epoxy resin (B) is made of a resin that does not substantially have an alicyclic ring, it is preferable for further improving the adhesion between the polarizer, which is an adherend, and the protective layer.

  In the present invention, it is particularly preferable that both the epoxy resin (A) and the epoxy resin (B) are resins substantially free of an aromatic ring. In this case, it is possible to obtain a photocurable adhesive capable of providing an adhesive layer having particularly good effects of shortening the curing time and having particularly good weather resistance and refractive index.

  As the epoxy resin (B), one type of resin or a mixture of two or more types of resins can be used. In this invention, the usage-amount of an epoxy resin (B) is 5-1000 mass parts with respect to 100 mass parts of above-mentioned epoxy resins (A). If this ratio is excessive or insufficient, the effect of shortening the curing time, which is a characteristic of the photocurable adhesive of the present invention, cannot be obtained sufficiently. A suitable amount of use of the epoxy resin (B) is 10 to 500 parts by mass with respect to 100 parts by mass of the epoxy resin (A) in order to develop sufficient adhesion and flexibility after curing. A suitable usage-amount is 10-250 mass parts with respect to 100 mass parts of epoxy resins (A).

<Photocationic polymerization initiator (C)>
The cationic photopolymerization initiator (C), which is an essential component of the photocurable adhesive of the present invention, releases a substance that initiates cationic polymerization by light irradiation, more specifically, irradiation of active energy rays as described later. It is a compound that can be used. In the present invention, since the cationic photopolymerization initiator (C) is used as the cationic polymerization initiator for curing the epoxy resin (A) and the epoxy resin (B), deterioration of the adhesive itself and the adhesion target object during curing. And an adhesive capable of preventing discoloration can be obtained.

Particularly preferred as the cationic photopolymerization initiator (C) is a double salt that is an onium salt that releases a Lewis acid by light irradiation, or a derivative thereof. A typical example of such a compound is a salt of a cation and an anion represented by the general formula [A] ^{y +} [B] ^y- .

Here, the cation A ^{y +} is preferably onium, and the structure thereof can be represented by, for example, [(R ⁴⁵ ) _x Q] ^{y +} .

Further, here, R ⁴⁵ is an organic group having 1 to 60 carbon atoms and may contain any number of atoms other than carbon, and x is an integer of 1 to 5. The x R ^{45 s} are independent and may be the same or different. In addition, at least one of the x R ⁴⁵ is preferably an aromatic group. Q is an atom or atomic group selected from the group consisting of S, N, Se, Te, P, As, Sb, Bi, O, I, Br, Cl, F, and N = N. Further, when the valence of Q in the cation A ^{y +} is z, it is necessary that the relationship y = x−z holds.

The anion B ^y− is preferably a halide complex, and its structure can be represented by, for example, [LX _s ] ^y− .

Further, L is a metal or metalloid which is a central atom of a halide complex, and B, P, As, Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Sc, V, Cr, Mn, Co and the like. X is a halogen. s is an integer of 3-7. Further, when the valence of L in the anion B ^y− is t, it is necessary that the relationship y = s−t holds.

Specific examples of the anion [LX _s ] ^y− of the above general formula include tetrafluoroborate (BF ₄ ) ⁻ , hexafluorophosphate (PF ₆ ) ⁻ , hexafluoroantimonate (SbF ₆ ) ⁻ , hexafluoroarsenate. (AsF ₆ ) ⁻ , hexachloroantimonate (SbC 1 ₆ ) ^{− and the} like.

Further, as the anion B ^y− , one having a structure represented by [LX _s ⁻¹ (OH)] ^y− can be preferably used. L, X, and s are the same as described above. Other anions that can be used include perchlorate ion (ClO ₄ ) ⁻ , trifluoromethyl sulfite ion (CF ₃ SO ₃ ) ⁻ , fluorosulfonate ion (FSO ₃ ) ⁻ , and toluenesulfone anion ion. And trinitrobenzenesulfonic acid anion.

Further, tetrakis (pentafluorophenyl) borate can also be preferably used as the anion ^By- .

  In the present invention, it is particularly effective to use an aromatic onium salt among such onium salts. Of these, aromatic halonium salts described in JP-A-50-151997, JP-A-50-158680, JP-A-50-151997, JP-A-52-30899, JP-A-56- No. 55420, JP-A No. 55-125105, etc., Group VIA aromatic onium salts, JP-A No. 50-158698, Group VA aromatic onium salts, JP-A No. 56-8428, Oxosulfoxonium salts described in JP-A-56-149402, JP-A-57-192429, etc., aromatic diazonium salts described in JP-A-49-17040, US Pat. No. 4,139,655 The thiopyrylium salt described in 1 is preferable.

  Particularly preferred among these aromatic onium salts are compounds having a sulfonium cation having the following structure,

(Wherein R ^{46 to} R ⁵⁹ are the same or different from each other, a hydrogen atom, a halogen atom, an oxygen atom or a hydrocarbon group that may contain a halogen atom, or an alkoxy group that may have a substituent, Ar is One or more hydrogen atoms may be substituted.), And (tricumyl) iodonium, bis (tertiarybutylphenyl) iodonium, triphenylsulfonium, and the like.

  For example, 4- (4-benzoyl-phenylthio) phenyl-di- (4-fluorophenyl) sulfonium hexafluorophosphate, 4,4′-bis [bis ((β-hydroxyethoxy) phenyl) sulfonio] phenyl sulfide-bis- Hexafluorophosphate, 4,4′-bis [bis ((β-hydroxyethoxy) phenyl) sulfonio] phenyl sulfide-bis-hexafluoroantimonate, 4,4′-bis [bis (fluorophenyl) sulfonio] phenyl sulfide— Bis-hexafluorophosphate, 4,4′-bis [bis (fluorophenyl) sulfonio] phenyl sulfide-bis-hexafluoroantimonate, 4,4′-bis (diphenylsulfonio) phenyl sulfide-bis-hexafluorophos Fate, 4,4′-bis (diphenylsulfonio) phenyl sulfide-bis-hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-di- (4- (β-hydroxyethoxy) phenyl) sulfonium hexafluoro Phosphate, 4- (4-benzoylphenylthio) phenyl-di- (4- (β-hydroxyethoxy) phenyl) sulfonium hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-di- (4-fluorophenyl) ) Sulfonium hexafluorophosphate, 4- (4-benzoylphenylthio) phenyl-di- (4-fluorophenyl) sulfonium hexafluoroantimonate, 4- (4-benzoylphenylthio) phenyl-diphenylsulfonium hexaful Orophosphate, 4- (4-benzoylphenylthio) phenyl-diphenylsulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-di- (4- (β-hydroxyethoxy) phenyl) sulfonium hexafluorophosphate, 4- (phenylthio) ) Phenyl-di- (4- (β-hydroxyethoxy) phenyl) sulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-di- (4-fluorophenyl) sulfonium hexafluorophosphate, 4- (phenylthio) phenyl-di -(4-fluorophenyl) sulfonium hexafluoroantimonate, 4- (phenylthio) phenyl-diphenylsulfonium hexafluorophosphate, 4- (phenylthio) phenyl-diphenyls Rufonium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenylbis (4-fluorophenyl) sulfonium hexafluorophosphate, 4- (2-chloro-4-benzoylphenylthio) phenylbis (4 -Fluorophenyl) sulfonium hexafluoroantimonate, 4- (2-chloro-4-benzoylphenylthio) phenyldiphenylsulfonium hexafluorophosphate, 4- (2-chloro-4-benzoylphenylthio) phenyldiphenylsulfonium hexafluoroantimonate 4- (2-chloro-4-benzoylphenylthio) phenylbis (4-hydroxyphenyl) sulfonium hexafluorophosphate, 4- (2-chloro-4-benzoylphenylthio) Phenylbis (4-hydroxyphenyl) sulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, (tolylcumyl) iodonium hexafluorophosphate, (tolylcumyl) iodonium hexafluoroantimonate, (tolylcumyl) iodonium tetrakis (Pentafluorophenyl) borate, bis (tertiarybutylphenyl) iodonium hexafluorophosphate, bis (tertiarybutylphenyl) iodonium hexafluoroantimonate, bis (tertiarybutylphenyl) iodonium tetrakis (pentafluorophenyl) borate, benzyl- 4-hydroxyphenylmethylsulfonium hexa Fluorophosphate, benzyl-4-hydroxyphenylmethylsulfonium hexafluoroantimonate, benzyldimethylsulfonium hexafluorophosphate, benzyldimethylsulfonium hexafluoroantimonate, p-chlorobenzyl-4-hydroxyphenylmethylsulfonium hexafluorophosphate, p-chloro Benzyl-4-hydroxyphenylmethylsulfonium hexafluoroantimonate, 4-acetoxyphenyldimethylsulfonium hexafluorophosphate, 4-acetoxyphenyldimethylsulfonium hexafluoroantimonate, 4-methoxycarbonyloxyphenyldimethylsulfonium hexafluorophosphate, 4-methoxycarbonyl Oxyphenyl dimethyl sul Fonium hexafluoroantimonate, 4-ethoxycarbonyloxyphenyldimethylsulfonium hexafluorophosphate, 4-ethoxycarbonyloxyphenyldimethylsulfonium hexafluoroantimonate, α-naphthylmethyldimethylsulfonium hexafluorophosphate, α-naphthylmethyldimethylsulfonium hexafluoro Antimonate, α-naphthylmethyltetrahydrothiophenium hexafluorophosphate, α-naphthylmethyltetrahydrothiophenium hexafluoroantimonate, cinnamyldimethylsulfonium hexafluorophosphate, cinnamyldimethylsulfonium hexafluoroantimonate, cinnamyltetrahydrothiophene Ni-hexafluorophosphate Cinnamyl tetrahydrothiophenium hexafluoroantimonate, N- (α-phenylbenzyl) cyanopyridinium hexafluorophosphate, N- (α-phenylbenzyl) -2-cyanopyridinium hexafluoroantimonate, N-cinnamyl-2- Cyanopyridinium hexafluorophosphate, N-cinnamyl-2-cyanopyridinium hexafluoroantimonate, N- (α-naphthylmethyl) -2-cyanopyridinium hexafluorophosphate, N- (α-naphthylmethyl) -2-cyanopyridinium hexa Examples thereof include fluoroantimonate, N-benzyl-2-cyanopyridinium hexafluorophosphate, and N-benzyl-2-cyanopyridinium hexafluoroantimonate.

  Other preferable examples include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) -tris ( Examples thereof include iron / allene complexes such as (trifluoromethylsulfonyl) methanide, aluminum complexes / photolytic silicon compound-based initiators, and the like.

  A photocationic polymerization initiator (C) can be used individually by 1 type or in mixture of 2 or more types. The usage-amount of a photocationic polymerization initiator (C) is 0.5-50 mass parts with respect to 100 mass parts of above-mentioned epoxy resins (A). When the amount used is less than 0.5 parts by mass, the photocurable adhesive is not sufficiently cured and sufficient adhesive strength cannot be obtained. When the amount used exceeds 50 parts by mass, the content of the ionic substance in the adhesive layer formed by curing the photo-curable adhesive increases, so that the hygroscopicity of the adhesive layer increases, and the adhesive The durability of the layer cannot be obtained sufficiently. The more preferable usage-amount of a photocationic polymerization initiator (C) is 1 mass part-25 mass parts with respect to 100 mass parts of epoxy resins (A).

<Polymerizable monomer (D)>
The photocurable adhesive of the present invention may further contain a polymerizable monomer (D). In the present invention, as described above, any monomer having two or more curable epoxy groups in its molecule is called an epoxy resin. Therefore, in this invention, a polymerizable monomer (D) shall mean the polymerizable monomer which is not contained in the concept of an epoxy resin (A) and an epoxy resin (B). Examples of the polymerizable monomer (D) include a cationic polymerizable monomer and a radical polymerizable monomer.

  Examples of the cationic polymerizable monomer include oxetanes. Oxetanes are compounds having a 4-membered ring ether in the molecule, such as 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3 -Ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, phenol novolac oxetane and the like. Commercially available products can be easily obtained as these oxetane compounds. For example, “Aron Oxetane OXT-101”, “Aron Oxetane OXT-121”, and “Aron Oxetane OXT-211” are all trade names. "Aron oxetane OXT-221", "Aron oxetane OXT-212" (manufactured by Toagosei Co., Ltd.) and the like.

  The above cationic polymerizable monomer has an effect of improving the adhesiveness after curing of the adhesive, and is used in a range that does not affect the weather resistance and photocurability as necessary.

  Examples of the radical polymerizable monomer include acrylate compounds, methacrylate compounds (hereinafter also referred to as (meth) acrylates in the meaning including both acrylates and methacrylates), allyl urethane compounds, unsaturated polyester compounds, and styrene compounds. It is done. When used in the photocurable adhesive of the present invention, (meth) acrylate is preferred because it is easily available and easy to handle. As (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, (poly) ester (meth) acrylate, (poly) ether (meth) acrylate, alcohol (meth) acrylate, other (meth) An acrylate is mentioned.

  The epoxy (meth) acrylate exemplified as the above (meth) acrylate compound is one type or two or more types of epoxy resin and acrylic acid or methacrylic acid (hereinafter also referred to as (meth) acrylic acid in the meaning of including both). And an ester compound. The ester-derived epoxy resin is not particularly limited, and has one or more epoxy groups in the molecule, such as aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, epoxy novolac resin, etc. Can be used.

  The urethane (meth) acrylate is a hydroxyl group containing an ester compound of (meth) acrylic acid and one or more (poly) ester polyols, (poly) ether polyols, polyols such as polyhydric alcohols, and the like ( (Meth) acrylates obtained by reacting (meth) acrylates with one or more (poly) isocyanate compounds; one or more (poly) ester polyols, (poly) ether polyols, many It is an ester compound having a urethane bond, such as (meth) acrylate obtained by reacting a polyol such as a monohydric alcohol, a hydroxyl group-containing (meth) acrylate and an isocyanate.

  Examples of the polyhydric alcohol for deriving the (poly) ester polyol include 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, neopentyl glycol, polyethylene glycol, and polypropylene. Examples include glycol, polybutylene glycol, trimethylolpropane, glycerin, pentaerythritol, and dipentaerythritol. Examples of the polycarboxylic acid from which the (poly) ester polyol is derived include adipic acid, terephthalic acid, phthalic anhydride, trimellitic acid, trimesic acid, and the like.

  Examples of the (poly) ether polyol include those obtained by adding an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide to the polyhydric alcohol described above. Examples of the (poly) isocyanate compound include monovalent or divalent isocyanates, and divalent or higher isocyanates are preferred.

  Divalent or higher isocyanates include 2,4- and / or 2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, 3 , 3′-dimethyldiphenyl-4,4′-diisocyanate, dianisidine diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, trans and / or cis-1,4-cyclohexane diisocyanate, Norbornene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4 and / or (2,4,4) -trimethylhexamethylene diisocyanate, lysine Isocyanate, triphenylmethane triisocyanate, 1-methyl-benzol-2,4,6-triisocyanate, dimethyl triphenylmethane tetra isocyanate.

  The (poly) ester (meth) acrylate is an ester compound of (poly) ester having (one) or two or more hydroxyl groups in the molecule and (meth) acrylic acid. (Poly) ester having one or more hydroxyl groups in the molecule is an ester compound of one or more polyhydric alcohols and one or more monocarboxylic acids or polycarboxylic acids. Is mentioned.

  Examples of the polyhydric alcohol for deriving a (poly) ester having one or two or more hydroxyl groups in the molecule include those described above, and examples of the monocarboxylic acid include formic acid, acetic acid, and propionic acid. , Butyric acid, isobutyric acid, valeric acid, caproic acid, caprylic acid, 2-ethylhexanoic acid, benzoic acid and the like. Examples of the polycarboxylic acid include the same compounds as those described above.

Moreover, (poly) ether (meth) acrylate is an ester compound of (poly) ether and (meth) acrylic acid having one or more hydroxyl groups in the molecule. (Poly) ether having 1 or 2 or more hydroxyl groups in the molecule, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, or one or more alkylene oxides added to polyhydric alcohol And the like obtained by doing so.
Examples of the polyhydric alcohol and alkylene oxide include the same compounds as those described above. Specifically, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene Examples thereof include oxide-modified trimethylolpropane tri (meth) acrylate and dipentaerythritol hexa (meth) acrylate.

  The (meth) acrylates of alcohols are ester compounds of alcohols (particularly aliphatic alcohols or aromatic alcohols) having one or more hydroxyl groups in the molecule and (meth) acrylates. For example, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, isoamyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isooctyl (meth) Acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate and the like.

  Other acrylates include ε-caprolactone-modified dipentaerythritol hexa (meth) acrylate, fluorene derivative di (meth) acrylate, carbazole derivative di (meth) acrylate, and the like.

The above radical polymerizable monomer can be used to adjust the curing rate.
When a radical polymerizable monomer is used as the polymerizable monomer (D), at least a photo radical polymerization initiator is used as an additive component (E) described later.

  Examples of the photo radical polymerization initiator include ketone compounds such as acetophenone compounds, benzyl compounds, benzophenone compounds, and thioxanthone compounds.

  Examples of the acetophenone compound include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4′-isopropyl-2-hydroxy-2-methylpropiophenone, 2-hydroxymethyl- 2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, p-dimethylaminoacetophenone, P-tertiarybutyldichloroacetophenone, p-tertiarybutyltrichloroacetophenone, p-azidoben Salacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) ) -Butanone-1, benzo , Benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether and the like. Examples of the benzyl compound include benzyl and anisyl. Examples of the benzophenone compound include Examples include benzophenone, methyl o-benzoylbenzoate, Michler's ketone, 4,4′-bisdiethylaminobenzophenone, 4,4′-dichlorobenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, and the thioxanthone compound includes thioxanthone. , 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone and the like.

  These radical photopolymerization initiators can be used alone or in combination of two or more according to the desired performance, and preferably 0.05 to 10% by mass with respect to the radical polymerizable monomer. More preferably, it is blended in an amount of 0.1 to 10% by mass. When the blending amount of the radical photopolymerization initiator with respect to the radical polymerizable monomer is 0.05% by mass or more, the curing of the photocurable adhesive can proceed more favorably, and when the blending amount is 10% by mass or less, The physical strength of the adhesive layer formed by curing the photocurable adhesive of the invention is good.

  The monomer used as the polymerizable monomer (D) may be one type or a mixture of two or more types. When the photocurable adhesive of this invention contains a polymerizable monomer (D), the usage-amount of a polymerizable monomer (D) is 100 mass parts or less with respect to 100 mass parts of above-mentioned epoxy resins (A). It is preferable. When the use amount of the polymerizable monomer (D) is 100 parts by mass or less, when producing a polarizing plate using the photocurable adhesive of the present invention, the adhesive strength between the polarizer and the protective film is improved. Can be maintained. The amount of the polymerizable monomer (D) used relative to 100 parts by mass of the epoxy resin (A) is more preferably 5 parts by mass or more, and in this case, the modification effect by the polymerizable monomer (D) can be favorably obtained. it can. The amount of the polymerizable monomer (D) used is more preferably 50 parts by mass or less.

<Additive component (E)>
Furthermore, the additive component (E) can be contained in the photocurable adhesive of the present invention as another component which is an optional component as long as the effects of the present invention are not impaired. As the additive component (E), in addition to the above-mentioned radical photopolymerization initiator, photosensitizer, thermal cationic polymerization initiator, polyols, ion trapping agent, antioxidant, light stabilizer, chain transfer agent, sensitizer Sensitizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, leveling agents, dyes, organic solvents and the like can be blended.

  When the additive component (E) is contained, the amount of the additive component (E) used is preferably 1000 parts by mass or less with respect to 100 parts by mass of the epoxy resin (A). When the amount used is 1000 parts by mass or less, storage stability is obtained by a combination of the epoxy resin (A), the epoxy resin (B) and the photocationic polymerization agent (C), which are essential components of the photocurable adhesive of the present invention. The effect of improving the property, preventing discoloration, improving the curing rate, and ensuring good adhesiveness can be exhibited well.

  Examples of the photosensitizer include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreducible dyes, and the like. Two or more types may be mixed and used. The photosensitizer is usually used in the photocurable resin of the present invention in an amount of 250 parts by weight or less, and when the total amount of the cationic polymerizable monomer in the photocurable adhesive of the present invention is 100 parts by weight, 0 is used. It is preferable to contain so that it may become the range of 0.1-20 weight part.

  Specific photosensitizers include, for example, anthracene compounds represented by the following general formula (I); pyrene; benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; Benzophenone derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone; 2-chlorothioxanthone, 2 A thioxanthone derivative such as isopropylthioxanthone; an anthraquinone derivative such as 2-chloroanthraquinone and 2-methylanthraquinone; an acridone derivative such as N-methylacridone and N-butylacridone; -Diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compound, halogen compound and the like. In the photocurable adhesive of the present invention, when the base material to be bonded contains an ultraviolet absorber or when light for curing is irradiated from the side of the layer containing the ultraviolet absorber, poor curing is avoided. Therefore, it is preferable to use a photosensitizer (P) having a sensitizing ability for light longer than 380 nm. Preferable examples of the photosensitizer (P) having a sensitizing ability for light longer than 380 nm include an anthracene compound represented by the following general formula (I).

(In the formula, R and R ′ represent an alkyl group having 1 to 18 carbon atoms or an ether group having 2 to 18 carbon atoms, and R ″ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.)
In the general formula (I), the alkyl group having 1 to 18 carbon atoms represented by R, R ′, and R ″ is methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, Amyl, isoamyl, tertiary amyl, hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 1-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl , 2-ethylhexyl, nonyl, isononyl, decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, and the ether group having 2 to 18 carbon atoms represented by R and R ′ includes 2- Methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-phenoxy Til, 2- (2-methoxyethoxy) ethyl, 3-methoxypropyl, 3-butoxypropyl, 3-phenoxypropyl, 2-methoxy-1-methylethyl, 2-methoxy-2-methylethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-phenoxyethyl, etc. As can be seen from the above examples, the ether group here is a hydrocarbon group having at least one ether bond, The concept includes an alkoxyalkyl group, an alkoxyalkoxyalkyl group, an aryloxyalkyl group, and the like.

  As the photosensitizer (P) used in the present invention, R and R ′ in the general formula (I) are alkyl groups having 1 to 4 carbon atoms, and R ″ is a hydrogen atom or alkyl having 1 to 4 carbon atoms. What is a group is more preferable because of good compatibility and excellent photosensitization ability.

  Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These initiators can be easily obtained as commercial products. For example, “ADEKA OPTON CP77” and “ADEKA OPTON CP66” (manufactured by ADEKA Co., Ltd.), “CI-2539” are available under the trade names. "CI-2624" (manufactured by Nippon Soda Co., Ltd.), "Sun-Aid SI-60L", "Sun-Aid SI-80L" and "Sun-Aid SI-100L" (manufactured by Sanshin Chemical Industry Co., Ltd.) Etc.

  In addition, it is preferable to control especially the usage-amount of a thermal cationic polymerization initiator so that the effect of this invention may not be impaired.

  In addition, polyols themselves are not polymerizable monomers, but can react with an epoxy resin to form a polymer. In the present invention, a polyol may be blended as the additive component (E). 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. And polycarbonate polyol.

  In addition, the organic solvent may be used for coating the photocurable adhesive of the present invention. As the organic solvent, an organic solvent that dissolves the photocurable adhesive of the present invention well without degrading the optical performance of the polarizer is preferably used, but there is no particular limitation on the type thereof. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate can be used.

  As a most typical example of the photocurable adhesive of the present invention, 100 parts by mass of the epoxy resin (A), 5 to 1000 parts by mass of the epoxy resin (B), and the photocationic polymerization initiator (C) Examples include an adhesive composed of 0.5 to 20 parts by mass, 0 to 100 parts by mass of the polymerizable monomer (D), and 0 to 1000 parts by mass of the additive component (E).

[Polarizer]
The present invention also provides a polarizing plate in which a protective film is bonded to one or both sides of a polarizer using the above-described photocurable adhesive. As the polarizer in the polarizing plate of the present invention, typically, a polarizer made of a polyvinyl alcohol-based resin film that is uniaxially stretched and adsorbed and oriented with iodine or a dichroic dye can be used. Hereinafter, a preferred embodiment of the polarizing plate according to the present invention will be described in the case of using a polarizer composed of a polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented.

  The polyvinyl alcohol resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate-based 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.

  The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 to 100 mol%. 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 resin is usually 1,000 to 10,000, preferably 1,500 to 10,000.

  A polarizer typically includes a step of uniaxially stretching the polyvinyl alcohol-based resin film, a dyeing of the polyvinyl alcohol-based resin film with a dichroic dye, and the dichroic dye into a polyvinyl alcohol-based resin film. It can be produced by a step of adsorbing, a step of treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with an aqueous boric acid solution.

  Uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with the dichroic dye, may be performed simultaneously with dyeing with the dichroic dye, or may be performed after dyeing with the dichroic dye. Good. 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. The method of uniaxial stretching is not limited, and may be uniaxially stretched between rolls having different peripheral speeds, or may be 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 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 can be used as the dichroic dye.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in this aqueous solution is usually about 0.01 to 0.5 parts by mass per 100 parts by mass of water, and the potassium iodide content is usually 0.5 to 10 parts by mass per 100 parts by mass of water. About a part. The temperature of this aqueous solution is usually about 20 to 40 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

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 usually about 1 × 10 ⁻³ to 1 × 10 ⁻² parts by mass per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate. The temperature of this aqueous solution is usually about 20 to 80 ° C., and the immersion time in this aqueous solution is usually about 30 to 300 seconds.

  The boric acid treatment after dyeing with the dichroic dye is performed, for example, 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 usually about 2 to 15 parts by mass, preferably about 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The content of potassium iodide in the boric acid aqueous solution is usually about 2 to 20 parts by mass, preferably 5 to 15 parts by mass per 100 parts by mass of water. The immersion time in the boric acid aqueous solution is usually about 100 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C.

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 usually about 5 to 40 ° C., and the immersion time is usually about 2 to 120 seconds.
The drying process performed after that is normally performed using a hot air dryer or a far-infrared heater. The drying temperature is usually 40 to 100 ° C. The processing time in the drying process is usually about 120 to 600 seconds.

  By the method as described above, a polarizer comprising a polyvinyl alcohol-based resin film on which iodine or a dichroic dye is adsorbed and oriented can be obtained. Then, this polarizer and a protective film are bonded together using the photocurable adhesive of this invention. In the polarizing plate of this invention, a protective film is bonded on the single side | surface or both surfaces of a polarizer.

  The polarizing plate of the present invention typically comprises a coating process in which the photocurable adhesive of the present invention is applied to a protective film in an uncured state to form an adhesive coated surface, and the adhesion of the protective film. It can manufacture by the method of including the bonding process which bonds a polarizer to the agent coating surface, and the hardening process which hardens a photocurable adhesive agent.

  As another method for producing the polarizer in the present invention, the photocurable adhesive of the present invention is dropped between the polarizer and the protective film in an uncured state, and then uniformly spread with a roll or the like. It is also possible to employ a method in which an adhesive layer is formed by pressure bonding while curing the above-described photocurable adhesive.

<Coating process>
In the present invention, there is no particular limitation on the method of applying the photocurable adhesive to the protective film, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. . In addition, in the method in which the photocurable adhesive is dropped between the polarizer and the protective film and then uniformly spread by pressing with a roll or the like, it is possible to use metal or rubber as the material of the roll. is there. In addition, in the method of passing between the roll and the roll by dropping the photocurable adhesive between the polarizer and the protective film, and pressurizing and spreading, these rolls may be the same material, Different materials may be used.

  The thickness of the adhesive layer formed by curing the photocurable adhesive of the present invention is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. When the thickness of the adhesive layer is 50 μm or less, there is little risk of impairing the appearance of the polarizing plate. The thickness of the adhesive layer is usually 0.1 μm or more, preferably 0.5 μm or more.

<Bonding process>
When the photocurable adhesive of the present invention is applied to the protective film, a polarizer is then bonded to the adhesive-coated surface. Moreover, when a photocurable adhesive is applied between a polarizer and a protective film, both are bonded as it is. The protective film used in the polarizing plate of the present invention is typically a film having transparency. The protective film is not particularly limited, and specifically, a film of an acetyl cellulose resin such as triacetyl cellulose, which is currently most widely used as a protective film of a polarizing plate, or a transparent resin having a lower moisture permeability than triacetyl cellulose. The film can be used.

  In the polarizing plate of the present invention, typically, a film of an acetylcellulose-based resin or a transparent resin film having a moisture permeability lower than that of triacetylcellulose can be bonded to at least one surface of the polarizer.

In addition, the water vapor transmission rate of said triacetylcellulose is about 400 g / m < ² > / 24hr in general. 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.

  Examples of the acetylcellulose-based resin film include a diacetylcellulose film and an acetylbutylcellulose film in addition to the aforementioned triacetylcellulose film.

Examples of transparent resin films with lower moisture permeability than triacetyl cellulose include amorphous polyolefin resins, polyester resins represented by polyethylene terephthalate, acrylic resins, polycarbonate resins, polysulfone resins, alicyclic A film of at least one transparent resin selected from polyimide resins and the like can be mentioned. Among these, a film made of an amorphous polyolefin resin is particularly preferable. The amorphous polyolefin-based resin usually has a cyclic olefin polymerization unit such as norbornene or a polycyclic norbornene-based monomer, and may be a copolymer of a cyclic olefin and a chain olefin. Examples of such amorphous polyolefin-based resins include those described in Non-Patent Document 1 and Non-Patent Document 2 described above. Among them, a thermoplastic saturated norbornene resin is representative. Those having a polar group introduced are also effective. Commercially available amorphous polyolefin resins include “Arton” from JSR Corporation, “ZEONEX” and “ZEONOR” from Nippon Zeon Co., Ltd., “APO” and “Apel” from Mitsui Chemicals, Inc. 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. These amorphous polyolefin resin film has a generally less moisture permeability 300g / m ² / 24hr.

  In the present invention, when the protective film is bonded to both surfaces of the polarizer, the protective film bonded to one surface and the other surface of the polarizer may be the same type or different types. When bonding different types of protective films on both sides of the polarizer, for example, an acetylcellulose-based resin film is used as one protective film, and the moisture permeability is higher than that of triacetylcellulose as the other protective film. A low transparent resin film can be used. Conventionally, wet lamination using an adhesive using water as a solvent has been employed for bonding the acetylcellulose-based protective film and the polarizer. In this case, however, a long drying furnace is required. On the other hand, the present invention does not require any drying oven. Advantages in this case include, as described above, that there is no need for capital investment in the drying furnace, that the polarizer and / or adhesive layer does not thermally deteriorate, and that curling can be suppressed. Can be mentioned.

  More specifically, a triacetyl cellulose film, a diacetyl cellulose film, an acetyl butyl cellulose film or the like is used as one protective film, and an amorphous polyolefin-based resin film, a polyester-based resin film, an acrylic film is used as the other protective film. A form using a resin film with low moisture permeability such as a resin film, a polycarbonate resin film, a polysulfone resin film, and an alicyclic polyimide resin film can be employed.

  It is also effective to use a polyethylene terephthalate film or an acrylic resin film as one protective film and a film made of an amorphous polyolefin resin as the other protective film.

  In addition, when providing a relatively high moisture-permeable protective film such as an acetylcellulose-based resin film on one surface of the polarizer, on the bonding surface of the protective film and the polarizer, a polyvinyl alcohol-based adhesive, etc. An adhesive other than the photocurable adhesive of the present invention may be used.

  Prior to bonding with the polarizer, the surface to be bonded to the polarizer in the protective film is easy adhesion treatment such as saponification treatment, corona treatment, primer treatment, anchor coating treatment, plasma treatment, flame treatment, etc. May be applied. 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. The thickness of the protective film is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm.

<Curing process>
As described above, after the polarizer and the protective film are bonded via the uncured photocurable adhesive, the photocurable adhesive is cured by irradiating active energy rays, and the protective film is removed. Secure on the polarizer.

The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferable. The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW. / Cm ² is preferable. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, it is caused by heat radiated from the light source and heat generated during curing of the photocurable adhesive. There is little risk of yellowing of the epoxy resin and deterioration of the polarizer. The light irradiation time to the photocurable adhesive is controlled for each photocurable adhesive to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is It is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained.

  When curing a photocurable adhesive by irradiation with active energy rays, it is preferable to perform curing under conditions that do not deteriorate various functions of the polarizing plate such as the degree of polarization of the polarizer, the transmittance and the hue, and the transparency of the protective film. .

The polarizing plate of this invention can be manufactured by the above methods.
[Optical member]
The present invention also provides an optical member comprising a laminate of a polarizing plate and an optical layer. Typically, an optical member is formed by bonding and laminating a polarizing plate and an optical layer through a protective film of the polarizing plate. In the present invention, the optical layer typically indicates an optical function other than a polarizing function, and includes, for example, a reflective layer, a transflective reflective layer, a light diffusing layer, a retardation plate, a light collecting plate, and a luminance improvement. Examples include films used for forming liquid crystal display devices and the like. The reflective layer, the transflective reflective layer, and the light diffusing layer can be used in the case of forming either a reflective, transflective, or diffusing optical member or a dual-use optical member.

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

  Further, the optical member for both reflection and diffusion can be formed by a method of providing a reflective layer reflecting the fine concavo-convex structure on the fine concavo-convex structure surface of the polarizing plate formed by the above method, for example. . The reflective layer having a fine concavo-convex structure has advantages such as 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 also has an advantage that unevenness in brightness and darkness can be further suppressed by diffusion of incident light and its reflected light when passing through the fine particle-containing layer.

  The reflective layer reflecting the fine concavo-convex structure of the polarizing plate can be formed, for example, by directly attaching a metal to the surface of the fine concavo-convex structure using a method such as vapor deposition such as vacuum deposition, ion plating, sputtering, or plating.

  Examples of the fine particles to be blended to form the fine uneven structure on the polarizing plate surface include silica, aluminum oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium oxide, and oxide having an average particle size of 0.1 to 30 μm. Inorganic fine particles made of antimony or the like, organic fine particles made of a crosslinked or uncrosslinked polymer, or the like can be used.

  On the other hand, the above-described retardation plate as an optical layer is a typical optical layer used for the purpose of compensating for a retardation by a liquid crystal cell in a liquid crystal display device. Examples of retardation plates include birefringent films made of stretched films of various plastics, films in which discotic liquid crystals and nematic liquid crystals are oriented and fixed, and oriented liquid crystal layers such as discotic liquid crystals and nematic liquid crystals on a film substrate. In which is formed. In this case, a cellulose-based film such as triacetyl cellulose is preferably used as the film substrate that supports the oriented liquid crystal layer.

  Examples of the plastic forming the birefringent film include polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polyolefin such as polypropylene, polyarylate, polyamide, and the like. The stretched film may be processed by an appropriate method such as uniaxial stretching or biaxial stretching. Moreover, the birefringent film which controlled the refractive index of the thickness direction of a film by applying a shrinkage force and / or extending | stretching force under adhesion | attachment with a heat-shrinkable film may be sufficient. Two or more retardation plates may be used in combination for the purpose of controlling optical characteristics such as broadening the band.

  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 brightness in a liquid crystal display device or the like. Examples of brightness enhancement films include reflective polarization separation sheets and alignment films of cholesteric liquid crystal polymers designed to produce anisotropy in reflectance by laminating a plurality of thin film films having different refractive index anisotropies. And a circularly polarized light separating sheet in which an oriented liquid crystal layer of cholesteric liquid crystal is supported on a film substrate.

  The optical member is composed of a polarizing plate and one or more layers selected according to the purpose of use from the above-described reflective layer, transflective reflective layer, light diffusion layer, retardation plate, light collector, brightness enhancement film, and the like. It can be combined with an optical layer to form a laminate of two layers or three or more layers. In this case, the optical layers such as the light diffusion layer, the phase difference plate, the light collecting plate, and the brightness enhancement film may each be composed of two or more layers. In the present invention, the arrangement of each optical layer is not particularly limited.

  The various optical layers forming the optical member are typically integrated with the polarizing plate using an adhesive, but the adhesive used for the integration can form the adhesive layer satisfactorily. There is no particular limitation. 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, those based on an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or the like can be used. 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 a material that does not cause 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 with 20 or less carbon atoms, such as methyl, ethyl and butyl groups, and (meth) acrylic acid and hydroxy (meth) acrylic acid An acrylic copolymer having a weight average molecular weight of 100,000 or more, in which a functional group-containing acrylic monomer composed of ethyl or the like is blended so that the glass transition temperature is preferably 25 ° C. or less, more preferably 0 ° C. or less. 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 10 to 40% by mass solution, which is directly on the polarizing plate. Form a pressure-sensitive adhesive layer by coating, or form a pressure-sensitive adhesive layer on a polarizing plate by forming a pressure-sensitive adhesive layer on a protective film in advance and transferring the pressure-sensitive adhesive layer onto the polarizing plate This can be done by a method to do so. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength of the pressure-sensitive adhesive layer, but a range of about 1 to 50 μm is appropriate.

  In addition, the pressure-sensitive adhesive layer may be filled with glass fiber, glass beads, resin beads, metal powders, other inorganic powders, etc., if necessary, pigments, colorants, antioxidants, ultraviolet absorbers, etc. May be blended. Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

[Liquid Crystal Display]
The present invention also provides a liquid crystal display device in which any one of the optical members described above is disposed on one side or both sides of a liquid crystal cell. The liquid crystal cell used in the liquid crystal display device is arbitrary. For example, various liquid crystal cells such as an active matrix drive type represented by a thin film transistor type and a simple matrix drive type represented by a super twisted nematic type are used. Thus, a liquid crystal display device can be formed. When the optical members are arranged on both sides of the liquid crystal cell, the optical members on both sides may be the same or different.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  In addition, the number shown in <> in each table is the value (unit: parts by mass) obtained by converting the blending amount of each component into the amount with respect to 100 parts by mass of the epoxy resin (A) (however, the third decimal place is rounded off) Estimated value or estimated value with 3 significant figures).

[Examples 1 and 2, Comparative Examples 1 and 2]
After mixing each component of the mixing | blending of Table 1, it defoamed and obtained the adhesive which concerns on Examples 1 and 2 as a photocurable adhesive of this invention. The cationic photopolymerization initiator (C) was blended as a 50% by mass propylene carbonate solution. In addition, the epoxy resin (A), the epoxy resin (B), the photocationic polymerization initiator (C), the polymerizable monomer (D), and the additive component (E) in the following table are defined as described above in the present invention. Has the meaning of In addition, the epoxy resin (A) (namely, a-1, a-2, a-3, a-4) and the epoxy resin (B) (namely, b-1, b-2) used by the Example and the comparative example. , B-3, b-4, b-5) are shown in the following formula.

  On the other hand, after mixing each component of the mixing | blending of Table 1, it degas | defoamed and obtained the adhesive which concerns on Comparative Examples 1 and 2 as a thermosetting adhesive for a comparison. The thermal cationic polymerization initiator was blended as a 66 mass% propylene carbonate solution.

  The storage stability of the photocurable adhesive and thermosetting adhesive obtained above was evaluated. Specifically, the adhesive compounded above was allowed to stand at room temperature, and the function evaluation as an adhesive was performed by the following method 6 hours and 24 hours after compounding.

  That is, the adhesive obtained above is applied to a triacetyl cellulose (TAC) film (hereinafter also referred to as a TAC film) (trade name: Fujitac) manufactured by Fuji Film Co., Ltd. containing an ultraviolet absorber having a thickness of 80 μm serving as a protective film. Coating was performed with a 10 μm bar coater, and a polyvinyl alcohol-iodine polarizer was bonded thereon. Further, a 70 μm thick stretched norbornene resin film (hereinafter also referred to as a norbornene film) (trade name ZEONOR) (trade name ZEONOR) having a thickness of 70 μm whose surface has been subjected to corona discharge treatment is applied with a 10 μm bar coater. It coated and bonded to the surface on the opposite side to the surface which bonded the TAC film of the above-mentioned polarizer. The coatability when a protective film was bonded to both sides of the polarizer by the above method was evaluated.

c-3: 4,4'-bis (diphenylsulfonio) phenyl sulfide-bis-hexafluorophosphate c-4: 4- (phenylthio) phenyl-diphenylsulfonium hexafluorophosphate f-1: 3-methyl-2-butenyl Tetrahydrothiophenium hexafluorophosphate In Examples 1 and 2 coated with the photo-curable adhesive of the present invention, the adhesive can be applied uniformly both after 6 hours and after 24 hours. In Comparative Examples 1 and 2 where a comparative thermosetting adhesive was applied, curing gradually progressed from the time of mixing the resin in the preparation of the adhesive, and 6 hours from the blending. When applied later, the coated surface became non-uniform, and after 24 hours from compounding, the adhesive could not be applied due to gelation. From this result, it was found that the storage stability was significantly improved in the photocurable adhesive of the present invention as compared with the comparative thermosetting adhesive.

[Example 3, Comparative Examples 3 to 7]
After mixing each component described in Table 2, defoaming, the adhesive according to Example 3 as the photocurable adhesive of the present invention, and according to Comparative Examples 3 and 4 as the photocurable adhesive for comparison An adhesive was obtained. The cationic photopolymerization initiator (C) was blended as a 50% by mass propylene carbonate solution.

  Moreover, after mixing each component of the mixing | blending of Table 2, it defoamed and obtained the adhesive which concerns on Comparative Examples 5-7 as a thermosetting adhesive for a comparison. The thermal cationic polymerization initiator was blended as a 66 mass% propylene carbonate solution.

The photocurable adhesive and thermosetting adhesive obtained above were evaluated for colorability, which is a characteristic that greatly affects whether or not the photocurable adhesive and thermosetting adhesive can be applied to an optical film. In order to clarify the difference in color tone, each adhesive is sandwiched between glass plates with a thickness of 1.3 mm so that the thickness of the adhesive layer is 50 μm. For the photo-curable adhesive, Curing was performed with an energy of 2000 mJ / cm ² . The thermosetting adhesive was cured at 130 ° C. for 15 minutes. About the test piece produced by the above method, the color tone was measured with the color difference meter (made by Nippon Denshoku Industries Co., Ltd.).

  In addition, the photocurable adhesive and the thermosetting adhesive obtained above were coated with a 10 μm bar coater on a TAC film (trade name: Fujitac) manufactured by Fuji Film Co., Ltd. containing an ultraviolet absorber with a thickness of 80 μm serving as a protective film. And the polarizer of polyvinyl alcohol-iodine was bonded on it. In addition, each adhesive was coated with a 10 μm bar coater on a 70 μm-thick OPTES stretched norbornene film (trade name ZEONOR) whose surface was corona discharge treated, and the above-described polarizer TAC film was applied. It bonded to the surface on the opposite side to the surface which is bonding. The protective film was bonded on both surfaces of the polarizer by the above method.

About the thing using a photocurable adhesive agent, after irradiating an ultraviolet-ray with the ultraviolet irradiation apparatus with a belt conveyor (lamp: Fusion D lamp, integrated light quantity 1000mJ / cm < ² >), it was left to stand at room temperature for 1 hour. Moreover, about what used the thermosetting adhesive agent, 130 degreeC * 15 minute (s) hardening was performed. The polarizing plate by which the protective film was bonded on both surfaces of the polarizer by said method was obtained.

About each of the polarizing plate obtained above, the TAC film and norbornene film which are protective films were peeled off from the polarizer, and adhesiveness and curability were evaluated according to the following criteria.
Adhesiveness: When the TAC film and norbornene film are peeled off from the polarizer, if the film breaks without peeling off at the interface (◎), peeled off at the above interface without breaking the film (○), a situation where floating occurred immediately after curing and no adhesion occurred at all (×).
Curability: Check the adhesive touch on the peeled surface of the polarizer and TAC film or norbornene film, good curability when there is no stickiness (○), poor curability when there is stickiness ( X).

  In addition, sclerosis | hardenability evaluation was not performed considering that the said evaluation of adhesiveness was (double-circle) or (circle) that sclerosis | hardenability was also favorable.

c-3: 4,4'-bis (diphenylsulfonio) phenyl sulfide-bis-hexafluorophosphate c-4: 4- (phenylthio) phenyl-diphenylsulfonium hexafluorophosphate f-1: 3-methyl-2-but Tenyltetrahydrothiophenium hexafluorophosphate From the above results, in Comparative Examples 5 to 7 using a thermosetting adhesive, it was confirmed that the color tone of the polarizing plate was poor and that it was unsuitable for optical use. It was done. Moreover, in Comparative Examples 3 and 5 using only the epoxy resin (A) among the epoxy resin (A) and the epoxy resin (B), the adhesiveness is poor, and Comparative Example 4 using only the epoxy resin (B). In No. 7, the curability was poor. In the formulation shown in Table 2, only the example 3 using a photocurable adhesive satisfying the requirements of the present invention was satisfactory in all of color tone, adhesiveness and curability.

[Examples 4 to 24]
After mixing each component of the mixing | blending of Tables 3-9, it degas | defoamed and obtained the adhesive which concerns on Examples 4-24 as a photocurable adhesive agent of this invention. The cationic photopolymerization initiator (C) was blended as a 50% by mass propylene carbonate solution.

The adhesive obtained above was coated with a 10 μm bar coater on a TAC film (trade name Fujitac) manufactured by Fuji Film Co., Ltd. containing an ultraviolet absorber having a thickness of 80 μm serving as a protective film, and a polarization of polyvinyl alcohol-iodine on the TAC film. Pasted the child. In addition, each adhesive was coated with a 10 μm bar coater on a 70 μm-thick OPTES stretched norbornene film (trade name ZEONOR) whose surface was corona discharge treated, and the above-described polarizer TAC film was applied. It bonded with the surface on the opposite side to the surface currently bonded, and bonded the protective film on both surfaces of the polarizer. A polarizing plate in which a protective film is bonded to both sides of a polarizer by irradiating ultraviolet rays from the norbornene film side with an ultraviolet irradiation device with a belt conveyor (lamp: Fusion D lamp, integrated light quantity 1000 mJ / cm ² ) did. This was left at room temperature for 1 hour, and the TAC film and norbornene film as protective films were peeled off from the polarizer, and the adhesion and curability were evaluated according to the following criteria.
Adhesiveness: When the TAC film and norbornene film are peeled off from the polarizer, the adhesive is (◎) when the film breaks without peeling at the interface, and peeled at the above interface without breaking the film (○), a situation where floating occurred immediately after curing and no adhesion occurred at all (×).
Curability: When the TAC film and norbornene film are peeled off from the polarizer, the interface is confirmed by touch, the curability when there is no stickiness is good (○), and the curability when there is stickiness is poor (× ).

  In addition, sclerosis | hardenability evaluation was not performed considering that the said evaluation of adhesiveness was (double-circle) or (circle) that sclerosis | hardenability was also favorable.

  In Examples 4 to 24 using the photocurable adhesive of the present invention, the adhesiveness was good. Among them, in Examples 4 to 14, Examples 18 to 20, and Examples 22 to 24 in which the epoxy resin (B) does not have an alicyclic ring, the epoxy resin (B) has an alicyclic ring. Compared with Examples 15 to 17 and Example 21, the adhesion between the polarizer and the TAC film was particularly better.

[Comparative Examples 8 to 18]
After mixing each component of the mixing | blending of Table 3-7, 9, it defoamed and obtained the adhesive which concerns on Comparative Examples 8-18 as a photocurable adhesive for a comparison. The cationic photopolymerization initiator (C) was blended as a 50% by mass propylene carbonate solution. The obtained comparative photocurable adhesive was evaluated in the same manner as in Example 3 above. In Comparative Examples 9, 12, 13, 14, 15, 16, and 18, floating occurred immediately after curing, and the polarizer and the protective film were not adhered at all. However, in these comparative examples, there was no tack (stickiness) on the peeled surface.

  In Comparative Examples 8, 10, 11, and 17, all peeled off from the bonding surface of the protective film and the polarizer, and sufficient adhesiveness was not obtained. Furthermore, tack (stickiness) remained on the peeled surface. In these comparative examples, it is considered that the poor curability also affected the deterioration of adhesiveness.

  From the above Examples and Comparative Examples, in Examples 3 to 24 using the photocurable adhesive which is a representative example of the photocurable adhesive of the present invention, both the curing speed and the adhesive strength are sufficient. It could be confirmed. Furthermore, among them, in Examples 4 to 14, Examples 18 to 20, and Examples 22 to 24, the polarizer and the protective film cannot be peeled without breaking, and thus the adhesiveness is particularly excellent. It turned out to be. That is, when epoxy resin (B) does not have an alicyclic ring, it has confirmed that it was especially useful at the point of adhesiveness.

  Further, in Comparative Examples 3, 9, 12, 13, 14, 15, 16, and 18 using a comparative photo-curing adhesive, floating occurred immediately after curing, and the polarizer and the protective film were separated. There was no adhesion. However, there was no tack (stickiness) on the peeled surface. Therefore, in the above comparative example, it was confirmed that although the epoxy resin (B) was not used, the curability was good but the adhesion was poor. In each of Comparative Examples 4, 8, 10, 11, and 17, tack (stickiness) remained on the release surface, and it was confirmed that the curability was poor because the epoxy resin (A) was not used. The above-mentioned result is a result due to a difference in photocuring time under the same photocuring conditions, and the effect of the photocurable adhesive of the present invention can be confirmed.

c-1: 4,4'-bis [bis ((β-hydroxyethoxy) phenyl) sulfonio] phenyl sulfide-bis-hexafluorophosphate

c-2: 4- (2-chloro-4-benzoylphenylthio) phenylbis (4-fluorophenyl) sulfonium hexafluorophosphate

c-3: 4,4′-bis (diphenylsulfonio) phenyl sulfide-bis-hexafluorophosphate c-4: 4- (phenylthio) phenyl-diphenylsulfonium hexafluorophosphate

d-1: 3-ethyl-3-hydroxymethyloxetane

d-2: Diacrylate of ethylene oxide adduct of bisphenol A (ethylene oxide addition is 2 mol for each phenolic OH group of bisphenol, totaling 4 mol)
e-1: 1-hydroxycyclohexyl phenyl ketone [Examples 25 to 30]
50 parts by mass of a-1 as an epoxy resin (A), 50 parts by mass of b-4 as an epoxy resin (B), c-3 [4,4′-bis (diphenyl) as a cationic photopolymerization initiator (C) 1.75 parts by mass of sulfonio) phenyl sulfide-bis-hexafluorophosphate], 0.75 parts by mass of c-4 [4- (phenylthio) phenyl-diphenylsulfonium hexafluorophosphate], photosensitizer (P) As shown in Table 10, the mixture was defoamed and a photocurable adhesive was obtained. The cationic photopolymerization initiator (C) was blended as a 50% by mass propylene carbonate solution. The above-described Examples 4 to 24 were used except that the adhesive obtained as described above was irradiated with ultraviolet rays from the TAC film side. The same operation was performed to produce a polarizing plate and evaluated. The results are shown in Table 10.

  In Examples 25 to 30 using the photocurable adhesive containing the photosensitizer (P) of the present invention, both adhesiveness and curing were performed even if light irradiation from the TAC side containing an ultraviolet absorber was performed. The property was good.

[Examples 31 to 36]
As epoxy resin (A), epoxy resin (B) and photocationic polymerization initiator (C) listed in Table 11, 1.75 parts by mass of c-3 and 0.75 parts by mass of c-4 were mixed, and then removed. A photocurable adhesive was obtained by foaming. The photocurable adhesive used in Example 31 has the same composition as the photocurable adhesive used in Example 13.

The adhesive obtained above was coated on a uniaxially stretched PET (polyethylene terephthalate) film (trade name K1589) manufactured by Toyobo Co., Ltd. with a thickness of 38 μm serving as a protective film, and a polyvinyl alcohol-iodine polarized light was applied thereon. Pasted the child. Also, each of the adhesives was coated with a 10 μm bar coater on a 70 μm-thick OPTES stretched norbornene film (trade name ZEONOR) having a corona discharge treatment on the surface, and the above-described polarizer PET film was applied. It bonded with the surface on the opposite side to the surface currently bonded, and bonded the protective film on both surfaces of the polarizer. This is irradiated with ultraviolet rays from the norbornene film side with an ultraviolet irradiation device with a belt conveyor (lamp: Fusion D lamp, integrated light quantity 1000 mJ / cm ² ), heated at 80 ° C. for 1 minute, and a protective film is formed on both sides of the polarizer. It was set as the bonded polarizing plate. This was left at room temperature for 1 hour, the PET film as a protective film was peeled off from the polarizer, and the adhesion was evaluated according to the following criteria.
Adhesiveness: When the PET film is peeled off from the polarizer, the adhesiveness is (◎) when the film breaks without peeling off at the interface, and when the film is peeled off at the above interface without breaking the film (○ ), A situation in which floating occurred immediately after curing and no adhesion was observed (×).

  From the above results, it was confirmed that even when PET was used for the protective film, Examples 31 to 36 using the photocurable adhesive satisfying the requirements of the present invention showed sufficient adhesiveness.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The photocurable adhesive according to the present invention can be preferably applied to, for example, bonding of a polarizer and a protective film of a polarizing plate constituting an optical member in a liquid crystal display device or the like.

Claims (14)

An adhesive for bonding a protective film to a polarizer composed of a polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented,
100 parts by mass of the epoxy resin (A) having two or more epoxy groups in the molecule and at least one of the epoxy groups being an alicyclic epoxy group and having substantially no aromatic ring When,
5 to 1000 parts by mass of an epoxy resin (B) having two or more epoxy groups in the molecule and having substantially no alicyclic epoxy group, aromatic ring or alicyclic ring;
0.5 to 20 parts by mass of the cationic photopolymerization initiator (C);
Including photocurable adhesive (however, the following formula
HO— (R ¹ —O—CO—O) _m — (R ² —O—CO—O) _n —R ³ —OH
(In the formula, R ¹ and R ² each independently represents a divalent hydrocarbon group having 2 to 12 carbon atoms, R ³ represents the same structure as either R ¹ or R ² , and m is 2 to 150. , N is 0 to 150, and m + n is 2 to 200.), when polyoxypropylene glyceryl ether is included, and per 100 parts by mass of the epoxy resin (B) Except when the epoxy resin (A) is 50 parts by mass or less. ]   The photocurable adhesive according to claim 1, further comprising a polymerizable monomer (D) at 100 parts by mass or less.   100 parts by mass of the epoxy resin (A), 5 to 1000 parts by mass of the epoxy resin (B), 0.5 to 20 parts by mass of the cationic photopolymerization initiator (C), and the polymerizable monomer ( The photocurable adhesive according to claim 2, comprising 0 to 100 parts by mass of D) and 0 to 1000 parts by mass of the additive component (E).   The photocurable adhesive according to claim 3, comprising 250 parts by mass or less of a photosensitizer (P) having a sensitizing ability to light longer than 380 nm as an additive component (E). An adhesive for bonding a protective film to a polarizer composed of a polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented,
100 parts by mass of the epoxy resin (A) having two or more epoxy groups in the molecule and at least one of the epoxy groups being an alicyclic epoxy group and having substantially no aromatic ring When,
5 to 1000 parts by mass of an epoxy resin (B) having two or more epoxy groups in the molecule and having substantially no alicyclic epoxy group, aromatic ring or alicyclic ring;
0.5 to 20 parts by mass of the cationic photopolymerization initiator (C);
0 to 100 parts by mass of the polymerizable monomer (D);
It consists of 1000 parts by mass or less of the additive component (E),
The additive component (E) contains 250 parts by mass or less of a photosensitizer (P) having a sensitizing ability to light longer than 380 nm,
The photosensitizer (P) is an anthracene compound represented by the following formula (I), light curable adhesive.

(In the formula, R and R ′ represent an alkyl group having 1 to 18 carbon atoms or an ether group having 2 to 18 carbon atoms, and R ″ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.) A protective film is bonded via an adhesive to one or both sides of a polarizer composed of a polyvinyl alcohol resin film in which iodine or a dichroic dye is adsorbed and oriented,
The said adhesive agent is a polarizing plate which is the hardened | cured material of the photocurable adhesive agent in any one of Claims 1-5.   The polarizing plate according to claim 6, wherein an acetyl cellulose resin film is bonded to at least one surface of the polarizer as the protective film.   The polarizing plate according to claim 6, wherein a film of a transparent resin having a moisture permeability lower than that of triacetyl cellulose is bonded to at least one surface of the polarizer as the protective film.   As the protective film, a film of at least one transparent resin selected from an amorphous polyolefin resin, a polyester resin, an acrylic resin, a polycarbonate resin, a polysulfone resin, and an alicyclic polyimide resin is the polarizer. The polarizing plate according to claim 6, which is bonded to at least one side.   As the protective film, an acetylcellulose-based resin film is bonded to one surface of the polarizer, and a transparent resin film having a moisture permeability lower than that of triacetylcellulose is bonded to the other surface of the polarizer. The polarizing plate according to claim 6. A method for producing a polarizing plate by laminating a protective film via an adhesive on one or both sides of a polarizer comprising a polyvinyl alcohol-based resin film adsorbed and oriented with iodine or a dichroic dye,
On one side of the protective film, a coating step of coating the photocurable adhesive according to any one of claims 1 to 5 to form an adhesive coating surface;
A bonding step of bonding the polarizer to the adhesive coating surface of the protective film;
A curing step for curing the photocurable adhesive;
The manufacturing method of a polarizing plate containing.   The optical member which consists of a laminated body of the polarizing plate in any one of Claims 6-10, and an optical layer.   The optical member according to claim 12, wherein the optical layer includes a retardation plate.   A liquid crystal display device, wherein the optical member according to claim 12 or 13 is disposed on one side or both sides of a liquid crystal cell.