JP6688063B2 - Photocurable resin composition and laminate - Google Patents

Description

  The present invention relates to a photocurable resin composition used when a protective film is attached to a polarizer composed of a polyvinyl alcohol (hereinafter referred to as “PVA”) film, and an optical film laminate using the photocurable resin composition. .

  In optical films used for optical members and electronic devices, a polarizing film in which a protective film is attached to a polarizer, which is a PVA film in which iodine or a dye is adsorbed and stretched and oriented, is mainly composed of a water-based adhesive. Has been used for. As the protective film, a triacetyl cellulose (hereinafter referred to as “TAC”) film is mainly used, but its moisture permeability is high, so that it is likely to cause quality deterioration under moist heat (eg, temperature 70 ° C., relative humidity 90%). There was a problem such as.

  In order to improve moisture resistance against such quality problems, replacement with other than TAC film is in progress, and for example, a hydrophobic film represented by a cycloolefin polymer (hereinafter referred to as "COP") film is also used. In this case, the conventional water-based adhesive has a problem that sufficient drying is required at the time of laminating, productivity is lowered, and adhesive strength is weak.

Therefore, in order to improve such a problem, a polarizing film using a non-aqueous photocurable epoxy resin-based adhesive containing no organic solvent has been developed. For example, Japanese Patent No. 4306270 (Patent Document 1) proposes a method for manufacturing a polarizing plate using a resin composition containing a photocationic polymerization initiator containing an epoxy resin containing no aromatic ring as a main component. .

Further, in JP 2013-213214 A (Patent Document 2), an epoxy resin containing an alicyclic epoxy group and an alicyclic epoxy group are further used as an adhesive for bonding a protective film to a polarizer made of a PVA film. Photocurable adhesives containing epoxy resin and cationic photopolymerization initiator have been proposed

By using these non-aqueous adhesives, even if a film having a higher moisture resistance than the TAC film is used as a protective film for the polarizing film, the quality of the film is practically no problem. However, in terms of manufacturing a polarizing film, there is a need for further improvement in storage stability and adhesive strength of adhesives, and there is room for improvement.

Japanese Patent No. 4306270 JP, 2013-213214, A

  The problem to be solved by the present invention is that when a protective film is attached to a polarizer made of a PVA film which is adsorbed iodine or a dye and stretched and oriented, it has excellent storage stability, low moisture permeability, and sufficient adhesive strength. Another object of the present invention is to provide a photocurable resin composition that is resistant to color loss and an optical film laminate using the same.

The invention according to claim 1 includes an aromatic compound (A) having a plurality of epoxy groups in the molecule, an aliphatic compound (B) having a plurality of epoxy groups in the molecule, and an alicyclic epoxy (C). A photocationic polymerization initiator (D), the (A) contains bisphenol F diglycidyl ether and phthalic acid diglycidyl ester, and the (B) content is 30 parts by weight based on 100 parts by weight of the total composition. Provided is a photocurable resin composition which is not less than 60 parts by weight and not less than 60 parts by weight.

The invention according to claim 2 is characterized in that the compounding ratio of (A) bisphenol F diglycidyl ether: phthalic acid diglycidyl ester is 2.1 to 5.1: 1. Provide things .

The invention according to claim 3 provides an optical film laminate including at least the photocurable resin composition layer according to claim 1 or 2, a polarizer, and a protective film.

  The photocurable resin composition according to the present invention has excellent storage stability, and when a protective film is attached to a polarizer made of a PVA film, even if the protective film is a hydrophobic type film that is not a TAC type, it has sufficient strength. Since it has excellent moisture resistance, the optical film laminate adhered with the photocurable resin composition has the effect that quality problems such as "color loss" in which the color tone of the PVA film changes under moist heat are less likely to occur. is there.

  The present invention will be described in detail below.

  The composition of the present invention comprises an aromatic compound (A) having a plurality of epoxy groups in the molecule, an aliphatic compound (B) having a plurality of epoxy groups in the molecule, an alicyclic epoxy (C), It is a photocationic polymerization initiator (D).

  The aromatic compound (A) having a plurality of epoxy groups in the molecule used in the present invention has a plurality of epoxy groups which are ring-opened by a photocationic polymerization initiator to form a crosslinked structure and have a role of improving the curing degree. Carry. In particular, when the number of epoxy groups is two, the optimum balance between the curing degree and the peeling strength can be obtained. Examples of the aromatic compound having two epoxy groups include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, biphenyl diglycidyl ether, phthalic acid diglycidyl ester, hydrogenated phthalic acid diglycidyl ester, and diglycidyl-p-oxybenzoic acid. , 2,6-naphthalenecarboxylic acid glycidyl ester can be mentioned, and they can be used alone or in combination of two or more kinds. Commercially available products include EXA-830LVP (trade name: manufactured by DIC, bifunctional).

The epoxy equivalent of (A) is preferably 100 to 300, more preferably 100 to 200. When it is less than 100, the curing shrinkage is large and the skin sensitization is high, and when it exceeds 300, the curing rate is slow and the viscosity is high, so that the coating amount tends to be large.

The aliphatic compound (B) having a plurality of epoxy groups in the molecule used in the present invention has a plurality of epoxy groups which are ring-opened by a photocationic polymerization initiator to form a cross-linked structure and improve the peel strength. Carry. In particular, when the number of epoxy groups is two, the optimum balance between peeling strength and curing degree can be achieved. Examples of the aliphatic compound having two epoxy groups include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane diglycidyl ether, 1,6-hexanediol di Examples thereof include glycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and the like, which may be used alone or in combination of two or more kinds. Commercially available products include EX-214L (trade name: manufactured by Nagase Chemtex Corp., bifunctional).

The blending amount of 100 parts by weight of the total composition of (B) is 30 parts by weight or more and less than 60 parts by weight. If it is less than 30 parts by weight, the moisture resistance is lowered and color fading easily occurs, and if it is 60 parts by weight or more, it is curable. And the moisture resistance decreases. The epoxy equivalent is preferably 100 to 300, more preferably 100 to 200. If it is less than 100, the curing shrinkage is large and the skin sensitization is high, and if it exceeds 300, the curing rate is slow and the coating amount is large due to high viscosity.

The alicyclic epoxy (C) used in the present invention is a compound in which at least one epoxy group constitutes a part of a cyclic carbon skeleton, and is compounded for the purpose of accelerating the curing speed and increasing the cohesive force of the adhesive layer. In particular, when the number of epoxy groups in the molecule is two, the optimum balance between the curing speed and the cohesive force can be achieved. The preferred blending amount based on 100 parts by weight of the total composition is 4 to 20 parts by weight. If it is less than 4 parts by weight, the curing rate tends to be slow, so that the workability tends to decrease, and if it exceeds 20 parts by weight, the durability tends to decrease. For example, limonene monooxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, (3,3 ′, 4,4′-diepoxy) bicyclohexyl, limonenedioxide, etc. may be used. I can. Commercially available products include Celoxide 2021P and Celoxide 8000 (trade name: manufactured by Daicel) and the like, and these can be used alone or in combination of two or more kinds.

The photocationic polymerization initiator (D) used in the present invention is an initiator that generates a cation ion upon irradiation with an active energy ray such as visible light, ultraviolet ray, or electron beam. For example, the cation portion is an aromatic sulfonium, There are aromatic iodonium, aromatic diazonium, and the like, and the anion part can be used alone or in combination of two or more onium salts composed of BF4-, PF6-, SbF6-, B (C6F5) 4-, and the like. .

  The blending amount of (D) is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the total composition. If it is less than 0.5 part by weight, the curing will be insufficient, and if it exceeds 10 parts by weight, the storage stability of the composition will be poor. If it is less than 1 part by weight, the curing tends to be insufficient, and if it exceeds 8 parts by weight, the storage stability of the composition tends to be poor. Commercially available photocationic polymerization initiators of aromatic sulfonium salts include CPI-110P, CPI-210S, CPI-310B (trade name: manufactured by San Apro), Irgacure 270, Irgacure 290 (trade name: manufactured by BASF Japan). There is.

In addition to the above, if necessary, a polymerizable monomer, a sensitizer, a filler, a leveling agent, a defoaming agent, a curing accelerator, an antioxidant, a silane coupling agent, etc. may be added as long as the performance of the composition is not impaired. You can

Examples of the polymerizable monomer include oxetane compounds and vinyl ethers, which may be added in an amount of up to 20 parts by weight based on 100 parts by weight of the total of (A) and (B).

  As an example of the sensitizer, anthraquinone or the like which broadens the light absorption wavelength range and promotes the polymerization reaction may be blended up to 5 parts by weight with respect to 100 parts by weight of the total of (A) and (B). Examples of commercially available sensitizers include UVS-581 and UVS-1331 (trade name: manufactured by Kawasaki Kasei Kogyo Co., Ltd.).

  The film constituting the optical film laminate in the present invention is a PVA-based resin film in which iodine or a dye is adsorbed and stretched and oriented, and the present photocurable resin composition is applied to one side or both sides of the film to form a protective film. Stick together. Examples of the protective film include a TAC film and a COP-based film, and the laminate is not limited to 2 layers and 3 layers, and may have 4 layers or more depending on the structure of the product.

  Hereinafter, the photocurable resin composition according to the present application will be specifically described with reference to Examples and Comparative Examples, but specific examples are shown and the invention is not particularly limited thereto.

Reference example 1
In the light-shielding bottle, as the (A), EXA-830LVP (trade name: manufactured by DIC, bisphenol F diglycidyl ether, epoxy equivalent: 160), and as the (B), EX-214L (trade name: Nagase Chemtex). Cellulose 2021P (trade name: 3,4 epoxycyclohexylmethyl, 3,4 epoxycyclohexanecarboxylate, manufactured by Daicel Co., Ltd.) as butanediyl diglycidyl ether, epoxy equivalent: 120) as the (C). As (D) above, CPI-110P (trade name: manufactured by San-Apro Co., sulfonium salt-based photoacid generator) was added in an amount shown in Table 1, and stirred using a stirring defoamer until uniform. The photocurable resin composition of Example 1 was obtained.

Reference Example 2, Examples 3-10
In addition to the materials used in Reference Example 1, EX-721P (trade name: manufactured by Nagase Chemtex, phthalic acid glycidyl ester, epoxy equivalent: 154) is used as the (A), and EX-721P is used as the (B). 722P (trade name: manufactured by Nagase Chemtex, hydrogenated phthalic acid diglycidyl ester, epoxy equivalent: 158) is used as (C), Celoxide 8000 (trade name: manufactured by Daicel, (3, 3 ', 4, 4'-diepoxy) bicyclohexyl) in Table 1
The amount shown in was added, and the mixture was stirred using a stirring and defoaming device until it became uniform, to obtain the photocurable resin compositions of Examples 2 to 10.

Comparative Examples 1-8
In addition to the materials used in the examples, EX-211L (trade name: neopentyl glycol diglycidyl ether, epoxy equivalent: 130) manufactured by Nagase Chemtec Co., Ltd. as the monofunctional aliphatic epoxy was used as the (B). -121 (trade name: manufactured by Nagase Chemtech, 2-ethylhexyl glycidyl ester, epoxy equivalent: 187) was added in an amount shown in Table 1 and stirred until uniform using a stirring defoamer. A photocurable resin composition of No. 8 was obtained.

Evaluation items and evaluation methods

<Creation of test pieces>
A TAC film (manufactured by Fuji Film Co., 60 μm) and a COP film (manufactured by Nippon Zeon Co., Ltd., 50 μm), which are adherends of the photocurable resin composition, are treated with a corona surface modification evaluation device TEC-4AX manufactured by Kasugai Electric Co., Ltd. Irradiate corona until the contact angle of is saturated. The photocurable resin composition was dropped onto the TAC film which had been subjected to corona irradiation treatment, immediately the iodine-impregnated stretched and polarized PVA film was overlaid, and the photocurable resin composition was dropped onto the PVA film, and immediately. Laminate the COP film. In this state, from the COP film surface, using an electrodeless UV irradiation device F300S / LC-6B manufactured by Fusion UV Systems Japan, UV irradiation and curing were performed so that the output was 250 mW / cm2 with the D valve and the integrated light amount was 200 mJ / cm2. After that, it was cured in an incubator at 80 ° C. for 3 minutes to prepare a polarizing film, which was used as a test body.

Viscosity: Toki Sangyo E-type viscometer 550R was used, rotor 1 ° 34'R24, rotation speed 50 rpm, 2 min. It was measured at 25 ± 1 ° C.

Storage stability: 10 ml of the photocurable resin composition was placed in a closed glass bottle, and the viscosity after standing for 1500 hours in a constant temperature bath at 40 ° C. was measured. And

Peel strength: Using Minebea's tensile tester TGI-1kN, crosshead speed 200 mm / min. It was measured at. For the test piece, the test piece prepared above was cut into a size of 25 × 100 mm, the COP film surface and the movable measuring table were fixed with a double-sided tape, and the 90 ° peel strength between the TAC film and the PVA film was measured. . A peel strength of 0.5 N / 25 mm or more was evaluated as ◯.

Curing property: When the peeling strength was measured, the one having a sticky feel on the peeled surface with a finger was evaluated as x.

Heat resistance: Using a spectrophotometer SD6000 manufactured by Nippon Denshoku Industries, the test piece prepared above was cut into a size of 20 × 30 mm, and the test piece was put in an incubator at 80 ° C. for 500 hours. The change in b value afterward was measured, and the change value of 4 or less was designated as ◯.

Moisture resistance: A test piece prepared by cutting the test piece prepared above into a size of 20 × 30 mm is placed in a thermo-hygrostat at 60 ° C. and a relative humidity of 90% for 500 hours, and the appearance such as peeling, clouding, and color change is confirmed. However, those that did not change were rated as ◯, and those that changed were rated as x.

Water resistance: A sealed beaker of 100 ml was filled with water, and a test piece prepared by cutting the test body prepared above into a size of 20 × 30 mm was put into the beaker. The temperature was kept at 23 ° C. for 144 hours and at 60 ° C. for 48 hours. After leaving for a period of time, the appearance of each peeling, clouding, and color tone change was confirmed.

Evaluation results Table 2 shows the evaluation results.

  The evaluation results of the resin compositions of the examples were all good. On the other hand, in Comparative Examples 1, 2 and 3 not containing (A), the moisture resistance was evaluated as ×, and Comparative Examples 1 and 2 had a problem in storage stability, and Comparative Example 3 had a problem in curability and peel strength. was there. Further, Comparative Examples 4 and 5 in which the blending amount of (B) was less than 30 parts by weight had a problem in evaluation of moisture resistance, and particularly Comparative Example 5 was low in water resistance and peel strength and was not suitable for the present invention. . Further, Comparative Examples 7 and 8 in which the compounding amount of (B) exceeds 60 parts by weight have problems in moisture resistance and curability, and Comparative Example 6 not containing (C) has problems in moisture resistance and water resistance. It was not suitable for the invention.

The invention of the present application is excellent in long-term storage stability as a photocurable resin composition used in laminating a protective film to a polarizer in which iodine or a dye is adsorbed to a polyvinyl alcohol-based resin film and stretched and oriented, and The optical film laminate using the composition can provide excellent optical durability in which color loss is unlikely to occur.

Claims (3)

An aromatic compound (A) having a plurality of epoxy groups in the molecule, an aliphatic compound (B) having a plurality of epoxy groups in the molecule, an alicyclic epoxy (C), and a cationic photopolymerization initiator (D). ) And (A) contains bisphenol F diglycidyl ether and phthalic acid diglycidyl ester, and the content of (B) is 30 parts by weight or more and less than 60 parts by weight based on 100 parts by weight of the total composition. A photocurable resin composition. The photocurable resin composition, wherein the compounding ratio of (A) bisphenol F diglycidyl ether: phthalic acid diglycidyl ester is 2.1 to 5.1: 1. An optical film laminate comprising at least the photocurable resin composition layer according to claim 1 or 2, a polarizer, and a protective film.