JP6979322B2 - 3-layer adhesive sheet - Google Patents

Description

The present invention relates to the composition of a three-layer type pressure-sensitive adhesive sheet formed by a plurality of pressure-sensitive adhesive layers having different compositions.

In recent years, a touch panel is generally arranged on the display device display unit of mobile mobile terminals and small personal computer tablet terminals.
It has been practiced for several years to improve visibility by filling a gap formed between a display device and a touch panel or tempered glass with an optical transparent adhesive or an optical transparent adhesive sheet.
In the case of a touch panel, black printing is generally applied to improve visibility and contrast, and the adhesive sheet used for this part has black printing on the part and the non-black printing part. It is required to be able to follow steps.
In recent years, a multi-layer adhesive layer has been developed in order to satisfy this step followability.

Apart from this, an accelerated test is conducted by the set maker to guarantee optical transparency, but even if an accelerated test such as a moisture resistance test or a QUV test is performed, the haze does not change and foaming does not occur. Required.

Further, if the set maker fails to attach the material, it is necessary to rework it, but at that time, reworkability is required in which no adhesive component remains on the adherend (no adhesive residue).

As a recent tendency of display devices, each member is thin-walled for thinning and weight reduction, and the optical transparent adhesive sheet is also required to be thinned to 100 μm or less.

Japanese Unexamined Patent Publication No. 2014-167634 Japanese Patent Application No. 2017-067046 International release 2015/174392

Patent Document 1 proposes a three-layer structure in order to satisfy the step followability.
As a procedure for producing a three-layer structure, a method is adopted in which each layer is sandwiched between two separator films (a PET film treated with silicone) to produce the three-layer structure, and then the three layers are bonded together. In this method, each layer is prepared once, and then the three layers are bonded together, so that the process time is long and the amount of waste of the separator film is considerable.
As part of shortening the process time and reducing the separator film, the surface (A) layer is coated on the PET film, the intermediate (B) layer is directly coated on it, and the surface (A) layer is directly coated on it. A method of working and finally covering with a PET film is desired.
By doing so, the number of separator films can be reduced by two, and the coating time can be reduced by about half.

In Patent Document 2, the present inventors apply the above-mentioned method having a three-layer structure (a surface (A) layer is coated on a PET film, an intermediate (B) layer is directly coated on the PET film, and further, from above. A method of directly coating the surface (A) layer and finally covering it with a PET film) was invented, but there was room for improvement in order to cope with a thin wall of 100 μm or less.

Patent Document 3 is a publication pursuing step followability due to a single-layer structure. There are two steps in which macromonomers are once produced, mixed and copolymerized again, and there is a process load, and there is room for improvement in order to cope with thinning of 100 μm or less.

To obtain a three-layer adhesive sheet that can obtain good step followability and a good appearance even after a moist heat resistance test and a QUV test even if the thickness of the three-layer adhesive sheet is 100 μm or less by the online method. Is.

The table (A) layer contains an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, and a hydrogen abstraction type photopolymerization initiator. , The intermediate (B) layer is an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, a hydrogen abstraction type photopolymerization initiator, and It is a three-layer type pressure-sensitive adhesive sheet containing a polyfunctional (meth) acrylic monomer and a thermosetting agent, and having a surface (A) layer on both sides of an intermediate (B) layer.

The three-layer adhesive sheet of the present invention has a sheet thickness of 100 μm or less, exhibits good step followability, and provides a good appearance even after a moisture resistance test and a QUV test.
In addition, there is no adhesive residue even after reworking.
Therefore, it is suitable for manufacturing optical members such as touch panels.

In the three-layer type pressure-sensitive adhesive sheet, the surface (A) layer is an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, and an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more. The intermediate (B) layer contains an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, and an acidic group-containing (meth) acrylic having a weight average molecular weight of 600,000 or more. A three-layer adhesive containing a polymer, a hydrogen abstraction type photopolymerization initiator, a polyfunctional (meth) acrylic monomer and a thermosetting agent, and having a surface (A) layer on both sides of an intermediate (B) layer. It is an agent sheet.

Raw material monomers of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer. Can select the monomers shown below.
The weight average molecular weight can be controlled by changing the amount of the thermal polymerization initiator.

The acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and the acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer are as follows. It can be selected from the monomers shown in.
The (meth) acrylic monomer constituting the (meth) acrylic polymer is not particularly limited, and is limited to methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and the like. n-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, n-octyl (meth) Acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) Acrylate, Pentadecyl (meth) acrylate, Hexadecyl (meth) acrylate, Heptadecyl (meth) acrylate, Stearyl (meth) acrylate, Behenyl (meth) acrylate, Isodecyl (meth) acrylate, Isomystylyl (meth) acrylate, Isostearyl (meth) acrylate Alkyl such as propylheptyl (meth) acrylate, isoundecyl (meth) acrylate, isododecyl (meth) acrylate, isotridecyl (meth) acrylate, isopentadecyl (meth) acrylate, isohexadecyl (meth) acrylate, isoheptadecyl (meth) acrylate. Examples thereof include a group-containing acrylic monomer, which may be used alone or in combination.

The acidic groups of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer. Examples of the monomers containing (meth) acrylic acid, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, (meth) acrylic acid dimer, maleic anhydride, Examples thereof include maleic acid, crotonic acid, itaconic acid, phthalic acid, mucon acid, citraconic acid and the like.
100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer. Among them, the monomer containing an acidic group is contained in an amount of 0.5 to 10 parts by weight.

The acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and the acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer are (meth). Meta) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, 4- (meth) acryloylmorpholine, diacetone (meth) acrylamide, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (Meta) acrylamide, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, Nn-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide , N-t-butyl (meth) acrylamide, N, N'-methylenebis (meth) acrylamide, N, N'-methylenebis (meth) acrylamide, N-methoxymethyl (meth) acrylamide and other nitrogen atom-containing (meth) acrylics. A monomer may be used in combination.

The acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and the acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more forming the table (A) layer and the intermediate (B) layer are 2 -Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy-3-chloropropyl (meth) acrylate, 2- A hydroxyl group-containing (meth) acrylic monomer such as hydroxy-3-phenoxypropyl (meth) acrylate may be used.

The (meth) acrylic polymer on the surface layer can be prepared by a conventionally known polymerization method such as solution polymerization, emulsion polymerization, or bulk polymerization, but the solution is considered in consideration of the weight average molecular weight of the obtained polymer and the processability into a pressure-sensitive adhesive sheet. Polymerization is preferred.

Solvents used for solution polymerization include methyl acetate, ethyl acetate, butyl acetate, benzene, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, n-hexane, isopropyl alcohol, n-butanol, propylene glycol monomethyl ether, propylene glycol. Examples thereof include organic solvents such as dimethyl ether, propylene glycol monomethyl ether acetate, and propylene carbonate. However, there is no problem even if a solvent other than these is used, and two or more kinds of solvents may be used in combination.

It is preferable to use a pyrolysis-type polymerization initiator as the thermal polymerization initiator for polymerizing the (meth) acrylic polymer forming the table (A) layer. 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl- 2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'- Azobis [N- (2-propenyl) -2-methoxypropionamide], 1-[(1-cyano-1-methylethyl) azo] formamide, 2,2'-azobis (N-butyl-2-methylpropionamide) ), 2,2'-azobis (N-cyclohexyl-2-methylpropionamide), [1,1'-azobis (1-acetoxy-1-phenylethane)], azo compounds such as lauroyl peroxide, octa. Noyl peroxide, benzoyl peroxide, ethyl methyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, cumylperoxyneodecanoate, t-hexylperoxyneodecanoate, t. -Butylperoxy-2-ethylhexanoate, dicumyl peroxide, isobutyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, t-butylperoxybenzoate, 25-dimethyl-25-di (T-Butylperoxy) hexane, di (2-ethylhexyl) peroxydicarbonate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3,3,5-trimethylcyclohexyl Organic oxide compounds such as sanoyl peroxide can be used. Further, the peroxide-based compound can be redox-polymerized by using a reducing agent such as N, N-dimethyltoluidine or N, N-diethyltoluidine in combination.

The thermal polymerization initiator is used in an amount of 0.05 to 3 parts by weight with respect to 100 parts by weight of the monomer. Increasing the amount of the thermal polymerization initiator used tends to reduce the weight average molecular weight of the obtained polymer, and decreasing the amount of the thermal polymerization initiator used tends to increase the weight average molecular weight of the obtained polymer.

The table (A) layer contains 20 to 60 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more with respect to 100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less. In addition to this, it contains 1 to 2 parts by weight of a hydrogen abstraction type photopolymerization initiator. As the hydrogen abstraction type photopolymerization initiator, for example, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and the like can be used.

Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-methylbenzophenone, Lumberti, trade name ESACURE TZT (mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone), o-benzoylmethyl benzoate, and the like. Examples thereof include 2-methylthioxanthone, 2-isopropylthioxanthone, and 2,4-dimethylthioxanthone.

In the intermediate (B) layer, in addition to an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less and an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, hydrogen extraction type photopolymerization is started. Contains an agent. As the hydrogen abstraction type photopolymerization initiator, the hydrogen abstraction type photopolymerization initiator listed in the table (A) layer can be used.

The intermediate (B) layer includes an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, and a hydrogen-drawing type photopolymerization initiator. It is also possible to add a cleavage type photopolymerization initiator or the like.

Cleavage type photopolymerization initiator, as a typical example, manufactured by BASF, trade name IRUGACURE651 (2,2-dimethoxy-1,2-diphenylethane-1-one), trade name IRUGACURE 184 (1-hydroxy-cyclohexyl-phenyl). -Ketone), trade name IRUGACURE1173 (2-hydroxy-2-methyl-1-phenyl-propan-1-one), trade name IRUGACURE2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy- 2-Methyl-1-propan-1-one), trade name IRUGACURE127 (2-hirodoxy-1-{4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl- Propane-1-one), trade name IRUGACURE907 (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one), trade name IRUGACURE369E (2-benzyl-2-dimethylamino-1-one) (4-Morphorinophenyl) -butanone-1), trade name IRUGACURE379EG (2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1 -Butanon) Trade name IRUGACURETPO (2,4,6-trimethylbenzoyl-diphenyl-phosphinoxide), trade name IRUGACURE819 (bis (2,4,6-trimethylbenzoyl) -phenylphosphinoxide), trade name IRUGACUREOXE01 (1.2) -Octandione, 1- [4- (Phenylthio)-, 2- (O-benzoyloxime)]), trade name IRUGACUREOXE02 (Etanon, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole) -3-yl]-, 1- (0-acetyloxime)), manufactured by Phenylberti, trade name ESACURECIP-150, trade name ESACURECIP-160 and the like.

The intermediate (B) layer contains 20 to 60 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more with respect to 100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less. In addition to 1 to 2 parts by weight of the hydrogen abstraction type photopolymerization initiator, 0.1 to 2 parts by weight of the thermosetting agent is contained. The thermosetting agent may be any compound as long as it is a component that reacts with the acidic group of the side chain of the (meth) acrylic polymer, and examples thereof include the following types of compounds.

Metals can be mentioned as a component that reacts with the acidic group of the side chain of the acrylic polymer. However, the metal itself is not preferable from the viewpoint of solubility, and it is preferable to use an organic metal. Examples of the organic metal include compounds such as soaps and complexes.
However, organometallics are generally colored in many cases and may not be applicable to transparent material laminating agents. In order to prevent coloring, a chelate compound may be mentioned, and specific examples thereof include Nihon Kagaku Sangyo Co., Ltd., trade name Nasem Aluminum, trade name Nasem Zinc and the like.

In addition, an epoxy resin can be mentioned as a component that reacts with the acidic group of the side chain of the acrylic polymer. However, the reaction between the acidic group and the epoxy group is difficult to proceed. Especially in this case, since nucleophilic addition is performed to the epoxy group of the acidic group in the side chain of the acrylic polymer, it is necessary to apply a temperature of 100 ° C. or higher, and oxidative yellowing occurs. It is highly possible that it is not very preferable.
As a means for reacting without applying a high temperature, an epoxy curing agent having both an epoxy group and a tertiary amine may be used. The tertiary amines in the epoxy hardener increase the nucleophilicity of the acidic groups in the side chains of the acrylic polymer and react with the epoxy groups in the hardener without high temperatures.
Specific examples of such an epoxy curing agent include Mitsubishi Gas Chemical Company, Inc., trade name TETRAD-X and the like.

A delayed curing agent can be added to the intermediate (B) layer to adjust the reactivity. Specific examples thereof include acetylacetone, which is a chelating ligand for nasem aluminum.

The intermediate (B) layer contains 20 to 60 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more with respect to 100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less. It contains 1 to 2 parts by weight of a hydrogen abstraction type photopolymerization initiator, 0.1 to 2 parts by weight of a thermosetting agent, and 1 to 20 parts by weight of a polyfunctional (meth) acrylic monomer. Examples of the polyfunctional monomer include bifunctional (meth) acrylate and trifunctional or higher (meth) acrylate. Examples of the bifunctional (meth) acrylate include ethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, and triethylene glycol di (meth). Acrylate, tetraethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, dicyclopentanyldi (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene di (meth) acrylate, triglycerol di (meth) Acrylate, neopentyl glycol-modified trimethylol propandi (meth) acrylate, allylated cyclohexyldi (meth) acrylate, methoxylated cyclohexyldi (meth) acrylate, acrylicized isocyanurate, bis (acryloxyneopentylglycol) adipate, bisphenol A Examples thereof include di (meth) acrylate, bisphenol S di (meth) acrylate, butanediol di (meth) acrylate and the like.
Examples of the trifunctional or higher (meth) acrylate include trimethylolpropane tri (meth) acrylate, trimethylol ethanetri (meth) acrylate, glycerol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol. Tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, ditrimethylolpropanetetra acrylate, alkyl-modified dipentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) Examples thereof include acrylate, dipentaerythritol penta (meth) acrylate, and the like. These polyfunctional (meth) acrylates may be used alone or in combination of two or more. It is also possible to use PET-30 (a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate) manufactured by Nippon Kayaku Co., Ltd.

The method for producing the three-layer adhesive sheet of the present invention is not particularly limited, but the surface (A) layer is applied to a base material having releasability in a solution state to volatilize the solvent, and then the intermediate (B) is further formed. A simple method is to apply a layer on it, volatilize the solvent, then apply it to another substrate, volatilize the solvent, and then bond the surface (A) layer. The three-layer adhesive sheet is cured by aging at 23 ° C. to become a practical three-layer adhesive sheet. The obtained three-layer adhesive sheet is used by being bonded to a transparent member, but after the bonding, it may be further cured by irradiating it with active energy rays such as ultraviolet rays.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but only specific examples thereof are shown, and the present invention is not particularly limited thereto. The number of copies is all by weight.

96 parts by weight of synthetic butyl acrylate (BA) of (meth) acrylic polymer 1, 1 part by weight of dimethylaminoethyl methacrylate (DMAEMA), 3 parts by weight of acrylic acid (AA), azobisdimethylvaleronitrile 1.0 as a thermal polymerization initiator A monomer mixed solution was prepared by mixing and dissolving 70 parts by weight and 70 parts by weight of ethyl acetate as a solvent. 20 parts by weight of ethyl acetate was added as a solvent to a separable flask equipped with a stirrer and a reflux condenser, the temperature was raised to 65 ° C., nitrogen gas was introduced for 30 minutes or more, and oxygen in the polymerization system was removed. Then, the monomer mixed solution was added dropwise over 3 hours while keeping the temperature at 65 ± 1 ° C., and the reaction was further carried out for 3 hours while keeping the temperature at 65 ± 1 ° C. Then, the reaction temperature was raised to 78 ° C. and kept at 78 ± 1 ° C. for 2 hours to complete the polymerization reaction. After completion of the reaction, the mixture was cooled to obtain a pale yellow transparent viscous liquid. The viscosity was 2000 mPa · s, the solid content was 52%, and the weight average molecular weight was 150,000.

The synthesis of the (meth) acrylic polymers 2 to 7 was carried out in the same manner as in the synthesis of the acrylic polymer 1 except that the composition of the monomer was changed as shown in Table 1, to obtain the (meth) acrylic polymers 2 to 7.
However, the (meth) acrylic polymers 2 and 3 contain 1.0 part by weight of the thermal polymerization initiator azobisdimethylvaleronitrile, and the (meth) acrylic polymer 4 contains the thermal polymerization initiator azobisdimethylvaleronitrile 0. 1 part by weight, the (meth) acrylic polymers 5 and 6 are 0.07 parts by weight of the thermal polymerization initiator azobisdimethylvaleronitrile, and the (meth) acrylic polymer 7 is the thermal polymerization initiator azobisdimethylvaleronitrile. The polymerization reaction was carried out at 0.25 parts by weight.
2HEA represents 2ethylhexyl acrylate, MMA represents methyl methacrylate, and VAc represents vinyl acetate.

Preparation of 3-layer adhesive sheet As shown in Tables 2 and 3, acrylic polymers 1 to 7, Irgacure 184 as a photopolymerization initiator, ESACURE TZT, acetylacetone as a curing retarder, and nursem aluminum as a thermosetting agent. TETRAD-X and PET-30 as a polyfunctional (meth) acrylic monomer were added and stirred uniformly to obtain each coating agent.
First, the surface (A) layer was applied on the separator film to the thicknesses of Tables 2 and 3, and heated at 90 ° C. for 5 minutes to volatilize the solvent.
Next, the intermediate (B) layer was coated on the surface (A) layer with the thickness of Tables 2 and 3, and then heated at 90 ° C. for 10 minutes to volatilize the solvent.
Separately, the pressure-sensitive adhesive composition separator film for the table (A) layer was coated with the thicknesses of Tables 2 and 3 and heated at 90 ° C. for 5 minutes to volatilize the solvent.
By adhering a separately prepared table (A) layer sheet on the intermediate (B) layer of the sheet in which the table (A) layer and the intermediate (B) layer are stacked, each of the three-layer type of the example and the comparative example An adhesive sheet was prepared. The three-layer adhesive sheet was left in an atmosphere of 23 ° C. and a relative humidity of 50% RH for 7 days to obtain each three-layer adhesive sheet.

Peeling strength before UV irradiation , reworkability Peel off one side of the release film of the 3-layer adhesive sheet and attach it to PET film (manufactured by Toyobo Co., Ltd., trade name A4100, thickness 50 μm), width 25 mm, length 100 mm. A piece of film was prepared. The release film of the film piece is peeled off, attached onto the glass in an atmosphere of 23 ° C. and 50% RH using a laminator, left in an atmosphere of 23 ° C. and a relative humidity of 50% RH for 1 day, and then the tensile speed. It was pulled in the 180 ° direction at 300 mm / min, and its center value was taken as the peel strength. At this time, those having no adhesive residue on the glass and not peeling between the surface (A) layer and the intermediate (B) layer had good reworkability (○), and those having adhesive residue on the glass or the surface (A). ) Layer-intermediate (B) stripped between layers was evaluated as reworkability (x). If the reworkability is good and the peel strength is 10 N / 25 mm or more, it does not peel off during use and has sufficient adhesive strength.

Step followability <br /> On glass, using silver ink, a silk screen coater with a width of 1 cm and a step of 30
Printing was performed so as to be μm, and a step-following test glass was produced. The release film on one side of each three-layer adhesive sheet was peeled off and attached to the printed surface of the step follow-up test glass at 23 ° C. and 50% RH atmosphere using a laminator. Next, the release film on the other surface was peeled off and attached to a glass plate using a laminator. This was treated in an autoclave at 50 ° C. and 0.5 MPa for 20 minutes, and immediately after being left in an environment of 23 ° C. and 50% RH for 24 hours, it was visually evaluated according to the following criteria. If the step is filled, the step followability is good (◯), and if the step is not filled, the step followability is poor (×).

After UV irradiation , peel off one side of the release film of the 3-layer adhesive sheet, attach it to a PET film (manufactured by Toyobo Co., Ltd., trade name A4100, thickness 50 μm), and attach a film piece with a width of 25 mm and a length of 100 mm. Made. The release film of the film piece is peeled off, attached on glass in an atmosphere of 23 ° C. and 50% RH using a laminator, left in an atmosphere of 23 ° C. and a relative humidity of 50% RH for one day, and then a high-pressure mercury lamp is used. Ultraviolet irradiation was performed at (irradiation intensity 150 mW / cm2, irradiation amount 2000 mJ / cm2). It was pulled in the 180 ° direction at a tensile speed of 300 mm / min, and its center value was taken as the peel strength.

Moisture resistance test The release film on one side of each three-layer adhesive sheet was peeled off and attached to the printed surface of the step follow-up test glass at 23 ° C. and 50% RH atmosphere using a laminator. Next, the release film on the other surface was peeled off and attached to a glass plate using a laminator. This was treated in an autoclave at 50 ° C. and 0.5 MPa for 20 minutes, and then left to stand in an environment of 23 ° C. and 50% RH for 24 hours. It was irradiated with ultraviolet rays at 2000 mJ / cm2). Next, after leaving it for 500 hours in an environment of 85 ° C. and 85% RH and cooling at 23 ° C. and 50% RH for 15 minutes, the haze was measured and the presence or absence of foaming was confirmed. The haze was measured using HAZE-GARDII manufactured by Toyo Seiki Seisakusho Co., Ltd. The evaluation criteria are as follows.
○: Haze is less than 1.5 ×: Haze is 1.5 or more ○: No foaming ×: Foaming

QUV test The release film on one side of each 3-layer adhesive sheet was peeled off and attached to a glass plate at 23 ° C. and 50% RH atmosphere using a laminator. Next, the release film on the other surface was peeled off and attached to a glass plate using a laminator. This was treated in an autoclave at 50 ° C. and 0.5 MPa for 20 minutes, and then left to stand in an environment of 23 ° C. and 50% RH for 24 hours, and this was left in a high-pressure mercury lamp (irradiation intensity 150 mW / cm2, irradiation amount 2000 mJ / cm2). Irradiated with ultraviolet rays. Next, it was set in a QUV weather resistance tester, and the conditions of 340 mm (irradiance illuminance 0.63 w / cm2), 60 ° C (irradiation for 4 hours) / 50 ° C dew condensation 4 hours) were rotated for 12 cycles, and 23 ° C, 50% RH. After cooling for 15 minutes, the presence or absence of foaming and peeling was confirmed. The evaluation criteria are as follows.
○: No foaming or peeling ×: Foaming or peeling

The table (A) layer contains an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, and a hydrogen abstraction type photopolymerization initiator. , The intermediate (B) layer is an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less, an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, a hydrogen-drawing type photopolymerization initiator, and many. Example 1 which contains a functional (meth) acrylic monomer and a thermosetting agent and has an adhesive composition structure in which the layers (surface (A) layer / intermediate (B) layer / surface (A) layer) are superposed. No. 4 had sufficient peeling strength before irradiation with ultraviolet rays, and there was no problem in reworkability and step followability.
In addition, it had sufficient peel strength after irradiation with ultraviolet rays, and there was no problem in appearance such as haze change and foaming after the moisture resistance test and the QUV test.

Comparative Example 1, Comparative Example 2, in which the layer (A) does not contain an acidic group-containing (meth) acrylic polymer having an average molecular weight of 250,000 or less or an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more. Comparative Example 3 containing only an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 500,000 and Comparative Example 6 containing no acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more in the intermediate (B) layer There was a problem in reworkability or step followability before UV irradiation, and in Comparative Example 6, the appearance after the QUV test after UV irradiation was also a problem.

Comparative Example 4 in which the intermediate (B) layer does not contain a thermosetting agent and Comparative Example 5 in which the intermediate (B) layer does not contain a polyfunctional (meth) acrylic monomer are after durability tests such as a moisture resistance test and a QUV test. The appearance was not good.

Comparative Example 7 in which the table (A) layer does not contain a hydrogen abstraction type photopolymerization initiator, and Comparative Example 8 in which the intermediate (B) layer contains a cleavage type photopolymerization initiator instead of a hydrogen abstraction type photopolymerization initiator. There was a problem in reworkability before UV irradiation, and Comparative Example 7 did not have a good appearance after durability tests such as a moist heat resistance test and a QUV test after UV irradiation.

Claims (1)

In a three-layer adhesive sheet with a sheet thickness of 100 μm or less,
The table (A) layer contains 20 to 60 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more with respect to 100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less. Contains and contains a hydrogen abstraction type photopolymerization initiator, and does not contain a thermosetting agent and / or a polyfunctional (meth) acrylate monomer.
The intermediate (B) layer contains 20 to 60 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 600,000 or more, while 100 parts by weight of an acidic group-containing (meth) acrylic polymer having a weight average molecular weight of 250,000 or less. wherein the hydrogen abstraction-type photopolymerization initiator contains a polyfunctional (meth) acrylic monomer and hardener,
A three-layer adhesive sheet having a surface (A) layer on both sides of the intermediate (B) layer.