JP6235346B2 - Adhesive composition, adhesive tape and laminate - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition having high transparency, a low dielectric constant, and excellent removability. Moreover, this invention relates to the adhesive tape and laminated body which were manufactured using this adhesive composition.

The adhesive used for optical applications is used, for example, when a display, a touch panel, or the like is bonded to a module housing in a portable information terminal. Since the display screen is required to be clear, a highly transparent adhesive is desired.

In addition, in order to prevent malfunction of a touch panel, particularly a thin touch panel in recent years, it is also desired that an adhesive used for optical applications has a low dielectric constant. Patent Documents 1 and 2 describe a low dielectric constant pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer containing a specific acrylic polymer.

On the other hand, when the pressure-sensitive adhesive is bonded to the adherend, bubbles or the like may enter the adhesion surface with the adherend, resulting in poor bonding. At this time, the adhesive can be peeled off from the adherend and reused (reworked) if there is no adhesive residue on the adherend, but if there is adhesive residue, the adherend must be discarded. Since optical members (for example, ITO films) are expensive, the pressure-sensitive adhesive used for optical applications also needs “removability” that can be easily peeled off from the adherend while reducing adhesive residue. ing.
The pressure-sensitive adhesive sheets described in Patent Documents 1 and 2 have a low dielectric constant, but are still insufficient from the viewpoint of such removability.

JP 2012-173354 A JP 2012-246477 A

An object of the present invention is to provide a pressure-sensitive adhesive composition having high transparency, a low dielectric constant, and excellent removability. Moreover, an object of this invention is to provide the adhesive tape and laminated body which were manufactured using this adhesive composition.

The present invention relates to a molecular weight obtained by copolymerizing a monomer mixture containing a) a nitrogen-containing monomer and b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms by living radical polymerization. The pressure-sensitive adhesive composition is mainly composed of a (meth) acrylic polymer having a distribution (Mw / Mn) of 1.05 to 2.5.
The present invention is described in detail below.

In general, a polymer obtained by polymerizing a radical polymerizable monomer such as a (meth) acryl monomer by “free radical polymerization” is used for the pressure-sensitive adhesive.
However, free radical polymerization cannot sufficiently control the molecular weight, molecular weight distribution, copolymer composition, etc., and has the disadvantage that a low molecular weight component is produced or a homopolymer is produced even in the case of copolymerization. is there. The present inventors considered that such low molecular weight components or homopolymers are responsible for adhesive residue. In particular, in order to obtain a low dielectric constant, it is generally preferable to use a monomer having a large carbon number. Since a monomer having a large carbon number has low reactivity and is difficult to be incorporated into a polymer molecule, it tends to remain as a low molecular weight component or a homopolymer. it is conceivable that. Further, it is considered that such a low molecular weight component or homopolymer, or a monomer having a large carbon number itself is not easily volatilized by heating and is likely to remain. Therefore, the present inventors examined the use of a polymer obtained by “living radical polymerization” instead of free radical polymerization.

Living radical polymerization is a polymerization in which a molecular chain grows without being hindered by a side reaction such as a termination reaction or a chain transfer reaction, so that it is easy to control the molecular weight and molecular weight distribution, copolymer composition, etc. Even when a monomer having a large carbon number is used, the generation of a low molecular weight component and the generation of a homopolymer that occurs without copolymerization can be suppressed.
The present inventors obtained by copolymerizing a monomer mixture containing a) a nitrogen-containing monomer and b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms by living radical polymerization. If the pressure-sensitive adhesive composition mainly comprises a (meth) acrylic polymer having a specific range of molecular weight distribution (Mw / Mn), it is found that the transparency is high, the dielectric constant is low, and the removability is excellent. The present invention has been completed.

The pressure-sensitive adhesive composition of the present invention is obtained by copolymerizing a monomer mixture containing a) a nitrogen-containing monomer and b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms by living radical polymerization. The main component is a (meth) acrylic polymer having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5.
In addition, (meth) acrylate means an acrylate and a methacrylate. In addition, the main component of the (meth) acrylic polymer means that the (meth) acrylic polymer occupies 50% by weight or more of the resin component constituting the pressure-sensitive adhesive composition of the present invention.

When the a) nitrogen-containing monomer is contained in the monomer mixture, the adhesive composition improves the adhesive force without increasing the dielectric constant.
Examples of the nitrogen-containing monomer a) include amino groups such as dimethylamino (meth) acrylate, diethylamino (meth) acrylate, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, and dimethylaminoethyl (meth) acrylate. Monomers, amide group-containing monomers such as diacetone acrylamide (diacetone acrylamide), N, N-dimethylacrylamide, N, N-diethylacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, acrylamide, methacrylamide, and vinyl Examples include pyrrolidone, N-vinylcaprolactam, N-vinylacetamide, N-acryloylmorpholine, acrylonitrile and the like. These a) nitrogen-containing monomers may be used alone or in combination of two or more. Of these, dimethylaminoethyl (meth) acrylate, diacetone acrylamide, and vinyl pyrrolidone are preferable.

When the monomer mixture contains b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms, the dielectric constant of the pressure-sensitive adhesive composition is lowered. The b) alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms has a branched chain alkyl group having 10 to 20 carbon atoms as an ester residue.
The b) alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms has a branched chain alkyl group having 10 to 20 carbon atoms instead of a linear or cyclic alkyl group. If it has, it will not specifically limit, For example, isostearyl (meth) acrylate, isodecyl (meth) acrylate, isolauryl (meth) acrylate, isoeicosyl (meth) acrylate, isotetradecyl (meth) acrylate etc. are mentioned. These b) alkyl (meth) acrylates having a branched chain alkyl group having 10 to 20 carbon atoms may be used alone or in combination of two or more. Of these, isostearyl acrylate is preferable.

In the monomer mixture, the blending ratio of the a) nitrogen-containing monomer is 10 to 30 parts by weight, and the blending ratio of the b) alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms is 10 to 10 parts by weight. It is preferable that it is 70 weight part. When the blending ratio of the nitrogen-containing monomer is less than the above range, the pressure-sensitive adhesive composition has insufficient adhesive strength and may be peeled off before re-peeling. If the blending ratio of the nitrogen-containing monomer is greater than the above range, the dielectric constant of the pressure-sensitive adhesive composition may increase.

The monomer mixture preferably further contains c) a carboxyl group and / or hydroxyl group-containing monomer. When the monomer mixture contains the c) carboxyl group and / or hydroxyl group-containing monomer, the cohesive force of the pressure-sensitive adhesive composition is improved, and the removability is improved.
Among the above-mentioned c) carboxyl group and / or hydroxyl group-containing monomers, examples of the carboxyl group-containing monomer include (meth) acrylic acid, phthalic acid, terephthalic acid, pyromellitic acid and the like. Of these, acrylic acid is preferred.
Examples of the hydroxyl group-containing monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol modified at one end with an acryloyl group, and one end at an acryloyl group. Examples thereof include modified polypropylene glycol. Of these, hydroxyethyl methacrylate and 4-hydroxybutyl acrylate are preferable.

In the monomer mixture, the blending ratio of the a) nitrogen-containing monomer is 10 to 30 parts by weight, and the blending ratio of the b) alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms is 10 to 10 parts by weight. When it is 70 parts by weight, the blending ratio of the above c) carboxyl group and / or hydroxyl group-containing monomer is preferably 0.1 to 5 parts by weight. When the blending ratio of the above-mentioned c) carboxyl group and / or hydroxyl group-containing monomer is less than 0.1 parts by weight, the cohesive force of the pressure-sensitive adhesive composition may be lowered, and the removability may be lowered. When the blending ratio of the above-mentioned c) carboxyl group and / or hydroxyl group-containing monomer exceeds 5 parts by weight, the gel fraction of the pressure-sensitive adhesive composition may become too high and easily peel off.

The monomer mixture preferably further includes d) other alkyl (meth) acrylates. When the monomer mixture contains the d) other alkyl (meth) acrylate, the cohesive force, initial adhesiveness, adhesion and the like of the pressure-sensitive adhesive composition are improved.
In addition, said d) other alkyl (meth) acrylate means alkyl (meth) acrylate other than said b) alkyl (meth) acrylate which has a C10-C20 branched chain alkyl group.

The d) other alkyl (meth) acrylates preferably include (meth) acrylates having a bicyclo ring structure.
The bicyclo ring structure is not particularly limited, and examples of the functional group having the bicyclo ring structure include a bicyclo [1.1.0] butyl group, a bicyclo [1.1.1] pentyl group, and a bicyclo [2.1. 0] pentyl group, bicyclo [3.1.0] hexyl group, bicyclo [2.1.1] hexyl group, bicyclo [2.2.0] hexyl group, bicyclo [2.2.1] heptyl group, bicyclo [3.1.1] heptyl group, bicyclo [3.2.0] heptyl group, bicyclo [4.1.0] heptyl group, bicyclo [2.2.2] octyl group, bicyclo [3.2.1] ] Octyl group, bicyclo [3.3.0] octyl group, bicyclo [4.1.1] octyl group, bicyclo [4.2.0] octyl group, bicyclo [5.1.0] octyl group, bicyclo [ 3.2.2] Nonyl group, bicyclo 3.3.1] Nonyl group, bicyclo [4.2.1] nonyl group, bicyclo [4.3.0] nonyl group, bicyclo [5.1.1] nonyl group, bicyclo [5.2.0] Nonyl group, bicyclo [6.1.0] nonyl group, bicyclo [4.3.1] decyl group, and a part of hydrogen atoms of these functional groups having a bicyclo ring structure may be a chain alkyl group or a cyclic alkyl group. And a functional group having a structure substituted with a group. In addition, the said substitution may be one place and may be multiple places. Of these, a norbornyl group and an isobornyl group are preferable, and an isobornyl group is particularly preferable. That is, the (meth) acrylate having the bicyclo ring structure is particularly preferably isobornyl (meth) acrylate having an isobornyl group and a (meth) acryloyl group.

In the above d) other alkyl (meth) acrylates other than the (meth) acrylate having the bicyclo ring structure, the alkyl group may be a long chain, a branched chain, or a ring. Examples of such alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, and 2-ethylhexyl. (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, stearyl (meth) acrylate, and the like. Moreover, the (meth) acrylate which has cyclic alkyl groups, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, is also mentioned. Among them, since a low-temperature elastic modulus and a high initial wettability pressure-sensitive adhesive composition are obtained, it is selected from the group consisting of 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate and butyl (meth) acrylate. At least one of these is preferred.

In the monomer mixture, the blending ratio of the a) nitrogen-containing monomer is 10 to 30 parts by weight, and the blending ratio of the b) alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms is 10 to 10 parts by weight. In the case of 70 parts by weight, the blending ratio of the above d) other alkyl (meth) acrylate is preferably 10 to 80 parts by weight.

The monomer mixture includes a) a nitrogen-containing monomer, b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms, c) a carboxyl group and / or a hydroxyl group-containing monomer, and In addition to the above d) other alkyl (meth) acrylates, monomers copolymerizable with these may be contained. The copolymerizable monomer is not particularly limited, and examples thereof include (meth) acrylic acid esters and vinyl compounds.
The (meth) acrylic acid ester is not particularly limited, and benzyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate And polypropylene glycol mono (meth) acrylate. These (meth) acrylic acid esters may be used alone or in combination of two or more.

The vinyl compound is not particularly limited, and examples thereof include styrene and vinyl acetate. These vinyl compounds may be used alone or in combination of two or more.

The (meth) acrylic polymer is a (meth) acrylic polymer obtained by copolymerizing the monomer mixture by living radical polymerization, preferably living radical polymerization using an organic tellurium polymerization initiator.
Living radical polymerization is a polymerization in which a molecular chain grows without being hindered by a side reaction such as a termination reaction or a chain transfer reaction, so that it is easy to control the molecular weight and molecular weight distribution, copolymer composition, etc. Even when a monomer having a large carbon number is used, the generation of a low molecular weight component and the generation of a homopolymer that occurs without copolymerization can be suppressed. For this reason, by mainly using the (meth) acrylic polymer, the pressure-sensitive adhesive composition of the present invention has high transparency, low dielectric constant, and excellent removability.

Among these, living radical polymerization using an organic tellurium polymerization initiator has a functional group such as a carboxyl group, a hydroxyl group, an epoxy group, an amino group, an isocyanate group, an amide group, and a nitrile group, unlike other living radical polymerizations. Without protecting any monomer, it is possible to obtain a polymer having a uniform molecular weight and composition by polymerizing with the same initiator. For this reason, the monomer which has such a functional group can be copolymerized easily.

The organic tellurium polymerization initiator is not particularly limited as long as it is generally used for living radical polymerization, and examples thereof include organic tellurium compounds and organic telluride compounds.
Examples of the organic tellurium compound include (methylterranyl-methyl) benzene, (1-methylterranyl-ethyl) benzene, (2-methylterranyl-propyl) benzene, 1-chloro-4- (methylterranyl-methyl) benzene, 1-hydroxy- 4- (methylterranyl-methyl) benzene, 1-methoxy-4- (methylterranyl-methyl) benzene, 1-amino-4- (methylterranyl-methyl) benzene, 1-nitro-4- (methylterranyl-methyl) benzene, 1- Cyano-4- (methylterranyl-methyl) benzene, 1-methylcarbonyl-4- (methylterranyl-methyl) benzene, 1-phenylcarbonyl-4- (methylterranyl-methyl) benzene, 1-methoxycarbonyl-4- (methylterranyl-methyl) ) Benzene, 1- Enoxycarbonyl-4- (methylterranyl-methyl) benzene, 1-sulfonyl-4- (methylterranyl-methyl) benzene, 1-trifluoromethyl-4- (methylterranyl-methyl) benzene, 1-chloro-4- (1 -Methyl terranyl-ethyl) benzene, 1-hydroxy-4- (1-methyl terranyl-ethyl) benzene, 1-methoxy-4- (1-methyl teranyl-ethyl) benzene, 1-amino-4- (1-methyl terranyl-ethyl) Benzene, 1-nitro-4- (1-methylterranyl-ethyl) benzene, 1-cyano-4- (1-methylterranyl-ethyl) benzene, 1-methylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1- Phenylcarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-meth Sicarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-phenoxycarbonyl-4- (1-methylterranyl-ethyl) benzene, 1-sulfonyl-4- (1-methylterranyl-ethyl) benzene, 1-trifluoromethyl -4- (1-methylteranyl-ethyl) benzene, 1-chloro-4- (2-methylterranyl-propyl) benzene, 1-hydroxy-4- (2-methylterranyl-propyl) benzene, 1-methoxy-4- (2 -Methyl teranyl-propyl) benzene, 1-amino-4- (2-methyl teranyl-propyl) benzene, 1-nitro-4- (2-methyl teranyl-propyl) benzene, 1-cyano-4- (2-methyl teranyl-propyl) Benzene, 1-methylcarbonyl-4- (2-methylterranyl-propyl ) Benzene, 1-phenylcarbonyl-4- (2-methylterranyl-propyl) benzene, 1-methoxycarbonyl-4- (2-methylterranyl-propyl) benzene, 1-phenoxycarbonyl-4- (2-methylterranyl-propyl) benzene 1-sulfonyl-4- (2-methylterranyl-propyl) benzene, 1-trifluoromethyl-4- (2-methylterranyl-propyl) benzene, 2- (methylterranyl-methyl) pyridine, 2- (1-methylterranyl-ethyl) ) Pyridine, 2- (2-methylterranyl-propyl) pyridine, 2-methylterranyl-methyl ethanoate, methyl 2-methylterranyl-propionate, methyl 2-methylterranyl-2-methylpropionate, 2-methylterranyl-ethyl ethanoate, 2 -Methylterranil Ethyl propionate, 2-Mechiruteraniru -2-methylpropionic acid ethyl, 2-methyl-Terra alkylsulfonyl acetonitrile, 2-methyl-Terra sulfonyl propionitrile, 2-methyl-2-methyl-Terra sulfonyl propionitrile, and the like. The methyl terranyl group in these organic tellurium compounds may be an ethyl terranyl group, n-propyl terranyl group, isopropyl terranyl group, n-butyl terranyl group, isobutyl terranyl group, t-butyl terranyl group, phenyl terranyl group, etc. These organic tellurium compounds may be used alone or in combination of two or more.

Examples of the organic telluride compound include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n-butyl ditelluride, di-sec-butyl ditelluride. , Di-tert-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis- (p-methoxyphenyl) ditelluride, bis- (p-aminophenyl) ditelluride, bis- (p-nitrophenyl) ditelluride, bis -(P-cyanophenyl) ditelluride, bis- (p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, dipyridyl ditelluride and the like can be mentioned. These organic telluride compounds may be used alone or in combination of two or more. Of these, dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, di-n-butyl ditelluride and diphenyl ditelluride are preferable.

In addition, within the range which does not impair the effect of this invention, in addition to the said organic tellurium polymerization initiator, you may use an azo compound as a polymerization initiator for the purpose of acceleration | stimulation of a polymerization rate.
The azo compound is not particularly limited as long as it is generally used for radical polymerization. For example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2-methylbutyronitrile) ), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis (cyclohexane-1-carbonitrile) ), 1-[(1-cyano-1-methylethyl) azo] formamide, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobis (2-methylpropionate), Dimethyl-1,1′-azobis (1-cyclohexanecarboxylate), 2,2′-azobis {2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl Propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2 , 2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazoline-2 -Yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis [2 -(2-imidazolin-2-yl) propane], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionami Tetrahydrate, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis (2,4,4-trimethylpentane) and the like. It is done. These azo compounds may be used alone or in combination of two or more.

As the living radical polymerization method, conventionally known methods are used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
When a polymerization solvent is used in the living radical polymerization, the polymerization solvent is not particularly limited. For example, a nonpolar solvent such as hexane, cyclohexane, octane, toluene, xylene, water, methanol, ethanol, propanol, butanol, acetone, Highly polar solvents such as methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, N, N-dimethylformamide can be used. These polymerization solvents may be used alone or in combination of two or more.
The polymerization temperature is preferably 0 to 110 ° C. from the viewpoint of the polymerization rate.

The (meth) acrylic polymer has a molecular weight distribution (Mw / Mn) of 1.05 to 2.5.
If the molecular weight distribution exceeds 2.5, the low molecular weight components and the like generated in the living radical polymerization increase, and thus the removability of the pressure-sensitive adhesive composition decreases. A more preferable upper limit of the molecular weight distribution is 2.0, and a further preferable upper limit is 1.8.

The said (meth) acrylic polymer has a preferable lower limit of 100,000 and a preferable upper limit of 2 million of a weight average molecular weight (Mw). When the weight average molecular weight is less than 100,000, the cohesive force of the pressure-sensitive adhesive composition is lowered, and may not be peeled cleanly when re-peeling. In addition, when the said weight average molecular weight exceeds 2 million, the viscosity at the time of coating will be too high, and it will become difficult to apply, and the thickness nonuniformity of the coated adhesive composition may generate | occur | produce. The more preferable lower limit of the weight average molecular weight is 200,000.

The molecular weight distribution (Mw / Mn) is a ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
A weight average molecular weight (Mw) and a number average molecular weight (Mn) are measured as a polystyrene conversion molecular weight by the gel permeation chromatography (GPC) method. Specifically, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were obtained by filtering a diluted solution obtained by diluting a (meth) acrylic polymer with tetrahydrofuran (THF) 50 times through a filter. It is measured as polystyrene-reduced molecular weight by the GPC method using the filtrate. In the GPC method, for example, 2690 Separations Model (manufactured by Waters) or the like can be used.

The pressure-sensitive adhesive composition of the present invention may further contain a tackifier resin.
Examples of the tackifying resin include a hydrogenated rosin ester resin and a hydrogenated terpene phenol resin.

The pressure-sensitive adhesive composition of the present invention is, as necessary, a plasticizer, an emulsifier, a softener, a fine particle, a filler, a pigment, a dye, a silane coupling agent, an antioxidant, an interface within a range that does not impair transparency. You may contain well-known additives, such as an activator and a wax.

The pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is also one aspect of the present invention.

The pressure-sensitive adhesive layer preferably has a gel fraction of 70 to 95% by weight. If the gel fraction is less than 70% by weight, the pressure-sensitive adhesive composition may become too soft and difficult to re-peel. When the said gel fraction exceeds 95 weight%, the adhesive force of an adhesive composition may be insufficient. A more preferable lower limit of the gel fraction is 80% by weight, and a more preferable upper limit is 93% by weight.
The gel fraction is measured as follows. First, the adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After the test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate and subjected to a condition of 110 ° C. For 1 hour. The weight of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). In addition, the release film for protecting an adhesive layer shall not be laminated | stacked on the test piece.
Gel fraction (% by weight) = 100 × (W2-W0) / (W1-W0) (1)
(W0: weight of substrate, W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

As a method for obtaining a pressure-sensitive adhesive layer having a gel fraction in the above range, a method of adding a crosslinking agent to form a crosslinked structure between the main chains of the resin constituting the pressure-sensitive adhesive layer is preferable. By appropriately adjusting the type or amount of the crosslinking agent, the gel fraction of the pressure-sensitive adhesive layer can be easily adjusted to the above range.

The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Especially, since it is excellent in the adhesive stability with respect to a base material, an isocyanate type crosslinking agent is preferable. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation).
0.01-5 weight part is preferable with respect to 100 weight part of said (meth) acrylic polymers, and, as for the compounding quantity of the said crosslinking agent, 0.1-3 weight part is more preferable.

Since the pressure-sensitive adhesive tape of the present invention is difficult to peel off even if it is a thin pressure-sensitive adhesive tape, the pressure-sensitive adhesive layer and the substrate described later can be made thin according to the application.
The thickness of the pressure-sensitive adhesive layer is not particularly limited because it is set depending on the application, but a preferred lower limit is 1 μm and a preferred upper limit is 100 μm. If the thickness is less than 1 μm, the adhesive tape may be easily peeled off. When the said thickness exceeds 100 micrometers, a thin adhesive tape may not be obtained. The more preferable lower limit of the thickness is 25 μm, and the more preferable upper limit is 75 μm.

The pressure-sensitive adhesive tape of the present invention may be a support type having a base material or a non-support type having no base material. In the case of the support type, the pressure-sensitive adhesive layer may be formed on one side of the substrate, or the pressure-sensitive adhesive layer may be formed on both sides.

The base material is not particularly limited as long as it is a transparent base material. For example, acrylic resin, polyolefin resin, polycarbonate, polyvinyl chloride, acrylonitrile vitadiene styrene (ABS), polyethylene terephthalate (PET), polyethylene naphthalate. (PEN), the base material which consists of nylon, a polyurethane, a polyimide etc. is mentioned. The base material may be a base material having a network structure, or a base material with holes formed therein.

The thickness of the substrate is not particularly limited because it is set depending on the application, but for example, in the case of a film substrate, 1 to 100 μm is preferable, and 5 to 75 μm is more preferable. When the thickness of the substrate is less than 1 μm, the mechanical strength of the adhesive tape may be lowered. If the thickness of the base material exceeds 100 μm, the adhesive tape may become too stiff and it may be difficult to adhere and adhere together along the shape of the adherend.

The production method of the pressure-sensitive adhesive tape of the present invention is not particularly limited. For example, the (meth) acrylic polymer is mixed with other compounding components such as the tackifying resin and the crosslinking agent as necessary, and stirred to adhere. An adhesive solution is prepared, and subsequently this adhesive solution is coated and dried on a release-treated PET film to form an adhesive layer, and the resulting adhesive layer is transferred to one or both sides of the substrate. Examples thereof include a method and a method of directly coating and drying the substrate. The pressure-sensitive adhesive layer formed by coating and drying the PET film obtained by releasing the pressure-sensitive adhesive solution may be used as a non-support type pressure-sensitive adhesive tape without a substrate.

Applications of the pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive tape of the present invention are not particularly limited, but optical applications are preferred. Specifically, for example, it is preferably used for assembling an electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device. Among them, the pressure-sensitive adhesive composition of the present invention is used for bonding a surface protective plate and a display when manufacturing an image display device such as a portable information terminal, or manufacturing an input device such as a portable information terminal. It can be used to bond the touch panel and the display together.
A laminate in which an adhesive layer is disposed between at least two adherends (for example, members constituting the electronic device), and at least one of the adherends is a transparent adherend, The laminated body in which the said adhesive layer is formed from the adhesive composition of this invention is also one of this invention.

According to the present invention, a pressure-sensitive adhesive composition having high transparency, a low dielectric constant, and excellent removability can be provided. Moreover, according to this invention, the adhesive tape and laminated body manufactured using this adhesive composition can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Examples 1-4, Comparative Example 1)
(1) Synthesis of living radical polymerization polymer (LRP) 6.38 g (50 mmol) of Tellurium (40 mesh, metal tellurium, manufactured by Aldrich) was suspended in 50 mL of tetrahydrofuran (THF), and 1.6 mol / L of n was added thereto. -34.4 mL (55 mmol) of butyl lithium / hexane solution (manufactured by Aldrich) was slowly added dropwise at room temperature. The reaction solution was stirred until the metal tellurium disappeared completely. To this reaction solution, 10.7 g (55 mmol) of ethyl-2-bromo-isobutyrate was added at room temperature and stirred for 2 hours. After completion of the reaction, the solvent was concentrated under reduced pressure, followed by distillation under reduced pressure to obtain a yellow oily ethyl 2-methyl-2-n-butylteranyl-propionate.

In a glove box substituted with argon, 38 μL of ethyl 2-methyl-2-n-butylterranyl-propionate obtained above, V-60 (2,2′-azobisisobutyronitrile, 2.8 mg (manufactured by Kosei Pharmaceutical Co., Ltd.) and 1 mL of ethyl acetate were added, the reaction vessel was sealed, and the reaction vessel was taken out of the glove box. Subsequently, while flowing argon gas into the reaction vessel, a total of 100 g of the monomers shown in Table 1 and 66.5 g of ethyl acetate as a polymerization solvent were charged into the reaction vessel, and a polymerization reaction was performed at 60 ° C. for 20 hours. A solution containing a radical polymerization polymer (LRP) was obtained.
The obtained living radical polymerization polymer (LRP) was diluted 50-fold with tetrahydrofuran (THF), and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). The filtrate was supplied to a gel permeation chromatograph (manufactured by Waters, 2690 Separations Model), GPC measurement was performed under the conditions of a sample flow rate of 1 ml / min, and a column temperature of 40 ° C., and the polystyrene equivalent molecular weight of the polymer was measured. Molecular weight distribution (Mw / Mn) was determined. GPC KF-806L (Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(2) Manufacture of double-sided adhesive tape In the living radical polymerization polymer (LRP) -containing solution obtained above, Maitec NY260A (Mitsubishi Gas Chemical Co., Ltd.), which is a cross-linking agent, with respect to 100 parts by weight of copolymer solid content After adding 1.5 parts by weight and stirring, it was coated on the release-treated surface of a release polyethylene terephthalate (PET) film and dried at 110 ° C. for 10 minutes to remove ethyl acetate, and the thickness was 50 μm. The pressure-sensitive adhesive layer was formed. In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer.

(Comparative Example 2)
(1) Synthesis of Free Radical Polymerization Polymer (FRP) 50 g of ethyl acetate was added as a polymerization solvent in a reaction vessel, and after bubbling with nitrogen, the reaction vessel was heated while flowing nitrogen and refluxing was started. Subsequently, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10-fold with ethyl acetate was placed in the reaction vessel. A total of 100 g of the monomers shown in Table 1 was added dropwise over 2 hours. After completion of dropping, a polymerization initiator solution in which 0.15 g of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was diluted 10 times with ethyl acetate was added to the reaction vessel. The polymer was again charged and subjected to a polymerization reaction for 4 hours to obtain a free radical polymerization polymer (FRP) -containing solution. The molecular weight distribution (Mw / Mn) was determined in the same manner as in the case of the living radical polymerization polymer (LRP).

(2) Production of double-sided pressure-sensitive adhesive tape A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in the case of the living radical polymerization polymer (LRP).

<Evaluation>
The following evaluation was performed about the double-sided adhesive tape obtained by the Example and the comparative example. The results are shown in Table 1.

(1) The dielectric constant double-sided adhesive tape was cut so as to have a planar shape of 30 mm × 30 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape was peeled off and bonded to a copper foil (thickness 50 μm). Furthermore, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape was peeled off and bonded to a copper foil (thickness 50 μm) to obtain a laminated sample in which the copper foil was bonded to both sides of the pressure-sensitive adhesive layer. The obtained laminated sample was sandwiched between circular electrodes using an impedance analyzer (SI1260 type, manufactured by Toyo Corporation). In this state, the relative dielectric constant at a frequency of 1 MHz was measured according to JIS K 6911. The relative dielectric constant was determined according to the following criteria.
[Criteria for relative permittivity]
○: Dielectric constant is less than 3.0 x: Dielectric constant is 3.0 or more

(2) The transparent double-sided pressure-sensitive adhesive tape was cut so as to have a planar shape of 45 mm × 60 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape is peeled off and bonded to a slide glass (trade name “S-1214” manufactured by MATSUNAMI), and a test piece having a double-sided pressure-sensitive adhesive tape / slide glass layer structure. Was made. The haze value (%) of the test piece was measured according to JIS K 7105 using a haze meter, and the Δ haze value was calculated by the following formula (2).
ΔHaze value (%) = {Haze value of test piece (%)} − {Haze value of slide glass (%)} (2)
○: Δhaze value is 0.3 or less (transparent)
X: Δhaze value exceeds 0.3 (white turbidity)

(3) The removable double-sided adhesive tape was cut into a width of 25 mm and a length of 100 mm. One release polyethylene terephthalate film of the cut double-sided pressure-sensitive adhesive tape was peeled off and bonded to a polyethylene terephthalate film (thickness 25 μm). Further, the other release polyethylene terephthalate film of the double-sided pressure-sensitive adhesive tape was peeled off and bonded to a cover glass (reinforced alkali glass, Corning gorilla glass) by reciprocating once with a 2 kg rubber roller. It was left for 24 hours at 50% relative humidity. Then, the double-sided adhesive tape was peeled off from the cover glass by hand, and the adhesive residue on the cover glass was determined according to the following criteria.
[Judgment criteria for removability]
○: There is no adhesive residue on the cover glass. Δ: Adhesive residue is generated on part of the cover glass. ×: There is adhesive residue on the cover glass.

According to the present invention, a pressure-sensitive adhesive composition having high transparency, a low dielectric constant, and excellent removability can be provided. Moreover, according to this invention, the adhesive tape and laminated body manufactured using this adhesive composition can be provided.

Claims (4)

a) a nitrogen-containing monomer, b) an alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms, c) 0.1 to 5 parts by weight of a carboxyl group and / or hydroxyl group-containing monomer, and d ) A (meth) acrylic polymer having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5 obtained by copolymerizing a monomer mixture containing 10 to 80 parts by weight of other alkyl (meth) acrylates by living radical polymerization. it characterized by mainly viscous Chakuzai composition. The blending ratio of the nitrogen-containing monomer in the monomer mixture is 10 to 30 parts by weight, and b) the blending ratio of the alkyl (meth) acrylate having a branched chain alkyl group having 10 to 20 carbon atoms is 10 to 70 parts by weight. The pressure-sensitive adhesive composition according to claim 1. A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 . It is a laminated body which has arrange | positioned the adhesive layer between at least 2 to-be-adhered bodies, Comprising: At least 1 is an adherend which is transparent among the said adherends, The said adhesive layer is Claim 1 or 2. A laminate comprising an adhesive composition.