JP5721917B1 - Adhesive tape - Google Patents

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive tape that is difficult to peel off even if it is a thin pressure-sensitive adhesive tape and can exhibit high constant load peelability and pressure-sensitive adhesive cohesive strength with respect to an adherend. The present invention provides 60% by weight or more of an acrylic polymer obtained by living radical polymerization and having a crosslinkable functional group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. The pressure-sensitive adhesive tape contains a pressure-sensitive adhesive layer containing a polymer component and a crosslinking agent, and the pressure-sensitive adhesive layer has a gel fraction of 15% by weight or less.

Description

The present invention relates to a pressure-sensitive adhesive tape that is difficult to peel off even with a thin pressure-sensitive adhesive tape and can exhibit high constant load peelability and pressure-sensitive adhesive cohesive force with respect to an adherend.

Adhesive tapes are used in various industrial fields because they can be easily joined. Temporary fixing of curing sheets and bonding of interior materials in the construction field, fixing of interior parts such as seats and sensors, fixing of exterior parts such as side moldings and side visors in the automotive field, module assembly in the electrical and electronic field, Adhesive tape is used for attaching the module to the housing.

In recent years, there has been a demand for adhesive tapes that are thinner than conventional ones in accordance with the increasing needs for miniaturization, thinning or lightening of parts, and resource saving. However, there is a problem that a thin adhesive tape cannot provide sufficient adhesive force and is easily peeled off when a constant load is applied.

On the other hand, polymers obtained by polymerizing radically polymerizable monomers such as vinyl monomers and acrylic monomers are frequently used as adhesives for adhesive tapes. As a type of radical polymerization, free radical polymerization is common. However, free radical polymerization cannot sufficiently control the molecular weight, molecular weight distribution, copolymer composition, etc., and low molecular weight components are produced, and even in the case of copolymerization, homopolymers are produced. This component has disadvantages such as lowering the heat resistance and cohesive strength of the pressure-sensitive adhesive tape, and making it easier to peel off the pressure-sensitive adhesive tape.

On the other hand, living radical polymerization has been studied as a more controlled 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. Generation of low molecular weight components and the like can be suppressed.

Patent Document 1 describes a pressure-sensitive adhesive containing a copolymer obtained by copolymerizing monomers by a living radical polymerization method using an organic tellurium compound as a polymerization initiator. It describes that it exhibits an excellent effect.

Japanese Patent No. 5256515

In Patent Document 1, in a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a living radical polymerization acrylic polymer as a polymer component, the adhesive force is reduced when the gel fraction is 80% by weight or more, and no adhesive remains at the time of peeling. It is described that the performance is demonstrated. This means that the adhesive strength increases when the gel fraction is less than 80% by weight. However, in a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a living radical polymerization acrylic polymer as a polymer component, it is difficult to peel off even if it is thin with respect to the adherend by making it within a specific gel fraction range. However, the range of the gel fraction that can exhibit high constant load peelability and high adhesive cohesive strength is not known, and sufficient adhesive strength to adherends with a thin adhesive tape as requested in recent years It was difficult to obtain and further improvement was required.

An object of the present invention is to provide a pressure-sensitive adhesive tape that is difficult to peel off even if it is a thin pressure-sensitive adhesive tape and can exhibit high constant load peelability and pressure-sensitive adhesive cohesive strength with respect to an adherend.

The present invention provides 60% by weight or more of an acrylic polymer obtained by living radical polymerization and having a crosslinkable functional group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. The pressure-sensitive adhesive tape contains a pressure-sensitive adhesive layer containing a polymer component and a crosslinking agent, and the pressure-sensitive adhesive layer has a gel fraction of 15% by weight or less.
The present invention is described in detail below.

The present inventors are mainly composed of an acrylic polymer obtained by living radical polymerization and having a crosslinkable functional group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. In addition, by using a cross-linking agent and setting the gel fraction of the pressure-sensitive adhesive layer to 15% by weight or less, even if it is a thin pressure-sensitive adhesive tape, it is difficult to peel off and has a high constant load peelability and pressure-sensitive adhesive. It has been found that an adhesive tape capable of exhibiting cohesive force can be obtained, and the present invention has been completed.

The pressure-sensitive adhesive tape of the present invention is an acrylic polymer having a crosslinkable functional group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5, obtained by living radical polymerization. It has a pressure-sensitive adhesive layer containing a polymer component containing 60% by weight or more of “living radical polymerization crosslinkable acrylic polymer” in the specification.
When the pressure-sensitive adhesive layer contains the living radical polymerization crosslinkable acrylic polymer, the pressure-sensitive adhesive tape of the present invention is not easily peeled even if it is a thin pressure-sensitive adhesive tape, and has high constant load peelability and adhesion to the adherend. The agent cohesive force can be exhibited.

The above-mentioned living radical polymerization crosslinkable acrylic polymer is obtained by living radical polymerization using an acrylic monomer such as (meth) acrylic acid ester or (meth) acrylic acid as a raw material, preferably living radical polymerization using an organic tellurium polymerization initiator. It is the obtained acrylic polymer.
Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. According to living radical polymerization, for example, a polymer having a more uniform molecular weight and composition than that of free radical polymerization or the like can be obtained, and the production of low molecular weight components and the like can be suppressed. The constant load peelability to the body is improved.

FIG. 1 shows a schematic diagram for explaining living radical polymerization. Living radical polymerization is polymerization in which molecular chains grow without the polymerization reaction being hindered by side reactions such as termination reactions or chain transfer reactions. In living radical polymerization, the reaction proceeds without the growth terminal radicals being deactivated and without generating new radical species during the reaction. In the middle of the reaction, all polymer chains are polymerized while uniformly reacting with the monomer, and the composition of all polymers approaches uniform. Therefore, the crosslinkable functional group-containing monomer 12 is included in all polymers of the living radical polymerization crosslinkable acrylic polymer 1. When such a living radical polymerization crosslinkable acrylic polymer 1 is crosslinked using a crosslinking agent, almost all polymers can participate in crosslinking between polymer chains. In particular, since there are few low molecular weight components that do not contain a crosslinkable functional group-containing monomer, the probability that all polymer chains are involved in crosslinking is improved even with fine crosslinking with a gel fraction of 15% by weight or less. FIG. 2 is a schematic diagram illustrating a case where a living radical polymerization crosslinkable acrylic polymer is crosslinked. In the living radical polymerization crosslinkable acrylic polymer, the composition of all polymers is uniform, and since the crosslinkable functional group-containing monomer is included, all polymer chains are involved in crosslinking. In FIG. 2, a hydroxyl group is shown as an example of the crosslinkable functional group. In this way, almost all polymers can participate in the cross-linking between polymer chains, so even thin adhesive tapes are difficult to peel off, exhibiting high constant load releasability and adhesive cohesion on adherends. An adhesive tape that can be obtained can be obtained.

The effect of the present invention cannot be obtained even when an acrylic polymer obtained by conventional free radical polymerization is used.
FIG. 3 is a schematic diagram for explaining free radical polymerization. In free radical polymerization, radical species are continuously generated during the reaction and added to the monomer, and the polymerization proceeds. Therefore, in the free radical polymerization, a polymer 23 in which the growing terminal radical is deactivated during the reaction and a polymer 24 grown by the radical species newly generated during the reaction are generated. Therefore, when an acrylic polymer containing a crosslinkable functional group is produced by free radical polymerization, a polymer containing no relatively low molecular weight crosslinkable functional group-containing monomer is produced. Even if such a free radical polymerization crosslinkable acrylic polymer 2 is cross-linked using a cross-linking agent, a polymer that does not contain a crosslinkable functional group-containing monomer cannot participate in cross-linking between polymer chains. FIG. 4 is a schematic diagram for explaining a case where a free radical polymerization crosslinkable acrylic polymer is crosslinked. In the free radical polymerization crosslinkable acrylic polymer, the composition of the polymer is non-uniform, and since the polymer does not include a relatively low molecular weight crosslinkable functional group-containing monomer, a polymer chain that cannot participate in crosslinking exists. In FIG. 4, a hydroxyl group is shown as an example of the crosslinkable functional group. When a load is applied by attaching to an adherend as a thin adhesive tape, peeling occurs from a site that does not contain a crosslinkable functional group-containing monomer that cannot participate in crosslinking. The peelability cannot be exhibited.

Among living radical polymerizations, living radical polymerization using an organic tellurium polymerization initiator has a crosslinkable functional group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, and a nitrile group unlike other living radical polymerizations. Without protecting any radically polymerizable 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 radically polymerizable monomer which has a crosslinkable 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.

The living radical polymerization crosslinkable acrylic polymer contains a crosslinkable functional group.
Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, and a nitrile group. Especially, since adjustment of the gel fraction of the said adhesive layer is easy, a hydroxyl group or a carboxyl group is preferable and a hydroxyl group is more preferable.

A monomer having a crosslinkable functional group is blended as a monomer to be polymerized in the living radical polymerization.
Examples of the monomer having a hydroxyl group include (meth) acrylic acid esters having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.
Examples of the monomer having a carboxyl group include (meth) acrylic acid. Of these, acrylic acid is preferred.
Examples of the monomer having a glycidyl group include glycidyl (meth) acrylate.
Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, dimethylaminopropyl acrylamide, and the like.
Examples of the monomer having a nitrile group include acrylonitrile.

When the (meth) acrylic acid ester having a hydroxyl group is used, the content is not particularly limited, but a preferable upper limit in the radical polymerizable monomer to be polymerized in the living radical polymerization is 30% by weight. When the content exceeds 30% by weight, the gel fraction of the pressure-sensitive adhesive layer becomes too high and the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered.

When the acrylic monomer having a carboxyl group is used, the content thereof is not particularly limited, but the preferable lower limit in the radical polymerizable monomer polymerized in the living radical polymerization is 0.1% by weight, and the preferable upper limit is 10% by weight. is there. When the content is less than 0.1% by weight, the pressure-sensitive adhesive layer becomes too soft and heat resistance may be lowered. When the content exceeds 10% by weight, the pressure-sensitive adhesive layer may become too hard and the pressure-sensitive adhesive tape may be easily peeled off.

As the acrylic monomer that is polymerized in the living radical polymerization, other radical polymerizable monomers other than the acrylic monomer having a crosslinkable functional group may be used. As said other radically polymerizable monomer, other (meth) acrylic acid ester is mentioned, for example. In addition to the acrylic monomer, a vinyl compound may be used as a monomer.

The other (meth) acrylic acid esters are not particularly limited, and are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2 -(Meth) acrylic acid alkyl esters such as ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isomyristyl (meth) acrylate, stearyl (meth) acrylate, Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate, polypropylene glycol mono (meth) acrylate. These (meth) acrylic acid esters may be used alone or in combination of two or more.

The said vinyl compound is not specifically limited, For example, N-vinyl pyrrolidone, N-vinyl caprolactam, N-acryloyl morpholine, styrene, vinyl acetate etc. are mentioned. These vinyl compounds may be used alone or in combination of two or more.

In the living radical polymerization, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and polyethylene glycol.
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 living radical polymerization crosslinkable acrylic polymer has a weight-average molecular weight (Mw) lower limit of 300,000 and an upper limit of 2 million. When the weight average molecular weight is less than 300,000, the pressure-sensitive adhesive layer becomes too soft and heat resistance is lowered. If the weight average molecular weight exceeds 2,000,000, the viscosity at the time of coating becomes too high to be applied, which may cause uneven thickness of the pressure-sensitive adhesive layer. The minimum with a preferable weight average molecular weight (Mw) of the said living radical polymerization crosslinkable acrylic polymer is 400,000, and a preferable upper limit is 1.5 million.

The living radical polymerization crosslinkable acrylic polymer has a molecular weight distribution (Mw / Mn) of 1.05 to 2.5. When the molecular weight distribution exceeds 2.5, the low molecular weight components and the like generated in the living radical polymerization increase, so that the pressure-sensitive adhesive tape is easily peeled off and the constant load peelability to the adherend is lowered. A preferable upper limit of the molecular weight distribution is 2.0, a more preferable upper limit is 1.8, and a further preferable upper limit is 1.7.

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) are obtained by filtering a diluted solution obtained by diluting a living radical polymerization crosslinkable acrylic polymer with tetrahydrofuran (THF) 50 times with a filter, It is measured as a polystyrene-converted molecular weight by the GPC method using the obtained filtrate. In the GPC method, for example, 2690 Separations Model (manufactured by Waters) or the like can be used.

The polymer component may contain a polymer other than the living radical polymerization crosslinkable acrylic polymer, for example, a polymer obtained by free radical polymerization.
However, the lower limit of the content of the living radical polymerization crosslinkable acrylic polymer in the polymer component is 60% by weight, and the total amount of the polymer component (100% by weight) is the living radical polymerization crosslinkable acrylic polymer. Is preferred. By making the content of the above-mentioned living radical polymerization crosslinkable acrylic polymer in the polymer component 60% by weight or more, it is difficult to peel off even if it is thin, and adheres to adherends such as polycarbonate (PC) plates and polypropylene (PP) plates. An adhesive tape capable of exhibiting high constant load peelability can be obtained.
In addition, the tackifier resin mentioned later is not included in the polymer component.

The pressure-sensitive adhesive layer has a gel fraction of 15% by weight or less.
In the pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a free radical polymerization acrylic polymer as a polymer component, if the gel fraction is lowered, the constant load peelability is improved. . On the other hand, when the gel fraction is increased, the adhesive cohesion is improved, but the constant load peelability is lowered. For this reason, in a pressure-sensitive adhesive layer containing a free radical polymerization crosslinkable acrylic polymer as a polymer component, it is common to adjust the gel fraction to 15 to 35% by weight to achieve both constant load peelability and pressure-sensitive adhesive cohesive strength. Is.
On the other hand, in the pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a living radical polymerization acrylic polymer as a polymer component, the adhesive strength is reduced when the gel fraction is 80% by weight or more, and the performance that no adhesive remains at the time of peeling is exhibited. It is known that This means that the adhesive strength increases when the gel fraction is less than 80% by weight. However, in adhesive tapes having an adhesive layer containing living radical polymerization acrylic polymer as a polymer component, it is difficult to peel off even if it is thin, and it is known about the range of gel fraction that can exhibit high constant load peelability to the adherend. It was not done.

As a result of intensive studies, the present inventors have made the gel fraction of the pressure-sensitive adhesive layer 15% by weight or less, so that even if it is thin, it is difficult to peel off and has high constant load peelability and pressure-sensitive adhesive cohesive strength. It was found that can be demonstrated. This is because the living radical polymerization crosslinkable acrylic polymer has a uniform composition of all polymers contained therein and has a crosslinkable functional group, so that all polymers can participate in crosslinking between polymer chains. Both are considered to be able to exhibit sufficient adhesive cohesive force and improve the constant load peel force.
When the gel fraction exceeds 15% by weight, the pressure-sensitive adhesive layer becomes hard and the constant load peelability to the adherend is lowered. The gel fraction is preferably 10% by weight or less, and more preferably 5% by weight or less.

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)

In order to obtain a pressure-sensitive adhesive layer having a gel fraction in the above range, the pressure-sensitive adhesive layer contains a crosslinking agent. 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 crosslinking agent is not particularly limited, and may be, for example, an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, or a metal chelate crosslinking agent depending on the type of crosslinking functional group of the living radical polymerization crosslinking acrylic polymer. Etc. are selected and used.
For example, when the living radical polymerization crosslinkable acrylic polymer has a hydroxyl group as a crosslinkable functional group, the living radical polymerization crosslinkable acrylic polymer can be crosslinked by using, for example, an isocyanate crosslinking agent as a crosslinking agent. In addition, when the living radical polymerization crosslinkable acrylic polymer has a carboxyl group as a crosslinkable functional group, the living radical polymerization crosslinkable acrylic polymer crosslink can be obtained by using, for example, an epoxy crosslinking agent or an aziridine crosslinking agent as a crosslinking agent. Can be made. Since the living radical polymerization crosslinkable acrylic polymer has a uniform composition of all the polymers contained and has a crosslinkable functional group, all the polymers can participate in crosslinking between polymer chains. For this reason, even if it is a thin adhesive tape, it is hard to peel off and the adhesive tape which can exhibit high constant load peelability and adhesive cohesive force with respect to a to-be-adhered body can be obtained.
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).

The blending amount of the crosslinking agent is preferably 0.01 to 5 parts by weight and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the living radical polymerization crosslinkable acrylic polymer. Within this range, the gel fraction of the pressure-sensitive adhesive layer can be adjusted to 15% by weight or less.

The pressure-sensitive adhesive layer preferably further contains a tackifier resin. When the said adhesive layer contains tackifying resin, the constant load peelability with respect to the adherend of an adhesive tape improves. Especially, when using the tackifier which has a crosslinkable functional group, it can be bridge | crosslinked with the said living radical polymerization crosslinkable acrylic polymer via a crosslinking agent.

The tackifying resin has a preferred lower limit of hydroxyl value of 25 and a preferred upper limit of 55. When the hydroxyl value is out of the above range, the constant load peelability of the adhesive tape to the adherend may be lowered. A more preferred lower limit of the hydroxyl value is 30, and a more preferred upper limit is 50.
The hydroxyl value can be measured by JIS K1557 (phthalic anhydride method).

The tackifying resin has a preferable lower limit of the softening temperature of 70 ° C and a preferable upper limit of 170 ° C. When the softening temperature is less than 70 ° C., the tackifying resin may be too soft and the constant load peelability may be lowered. When the softening temperature exceeds 170 ° C., the pressure-sensitive adhesive layer becomes too hard, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. A more preferable lower limit of the softening temperature is 120 ° C.
The softening temperature is a softening temperature measured by the JIS K2207 ring and ball method.

The tackifying resin is not particularly limited, and examples thereof include rosin resins such as rosin ester resins, terpene resins such as terpene phenol resins, and petroleum resins. Of these, rosin ester resins and terpene phenol resins are preferable.
The above-mentioned rosin ester resins are rosin resins mainly composed of abietic acid, disproportionated rosin resins and hydrogenated rosin resins, dimers of polymer acids such as abietic acid (polymerized rosin resins), etc. It is the resin obtained by making it. A part of the hydroxyl group of the alcohol used for esterification is contained in the resin without being used for esterification, so that the hydroxyl value is adjusted to the above range. Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.
Resin esterified rosin resin is rosin ester resin, disproportionated rosin resin esterified disproportionated rosin ester resin, hydrogenated rosin resin esterified resin is hydrogenated rosin ester resin, polymerized rosin A resin obtained by esterifying the resin is a polymerized rosin ester resin.
The terpene phenol resin is a resin obtained by polymerizing terpene in the presence of phenol.

Examples of the disproportionated rosin ester resin include Superester A75 (hydroxyl value 23, softening temperature 75 ° C.) manufactured by Arakawa Chemical Industries, Superester A100 (hydroxyl value 16, softening temperature 100 ° C.) manufactured by Arakawa Chemical Co., Ltd. Examples thereof include ester A115 (hydroxyl value 19, softening temperature 115 ° C.), super ester A125 (hydroxyl value 15, softening temperature 125 ° C.) manufactured by the same company. Examples of the hydrogenated rosin ester resin include Pine Crystal KE-359 (hydroxyl value 42, softening temperature 100 ° C.) manufactured by Arakawa Chemical Industries, and ester gum H (hydroxyl value 29, softening temperature 70 ° C.) manufactured by the same company. It is done. Examples of the polymerized rosin ester resin include Pencel D135 (Hydroxyl value 45, softening temperature 135 ° C.) manufactured by Arakawa Chemical Industries, Pencel D125 (Hydroxyl value 34, softening temperature 125 ° C.) manufactured by Arakawa Chemical Co., Ltd. 42, softening temperature 160 ° C.) and the like.
Examples of the terpene resin include YS Polystar G150 (softening point 150 ° C.) manufactured by Yasuhara Chemical Co., Ltd. YS Polyster T100 (softening point 100 ° C.) manufactured by Yasuhara Chemical Co., Ltd. YS Polystar G125 (softening point 125 ° C.) Examples thereof include T115 (softening point 115 ° C.), YS Polystar T130 (softening point 130 ° C.) manufactured by the same company.
These tackifier resins may be used alone or in combination of two or more.

The content of the tackifying resin is preferably 5 parts by weight with respect to 100 parts by weight of the living radical polymerization crosslinkable acrylic polymer, and 40 parts by weight with a preferable upper limit. When the content is less than 5 parts by weight, the adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. Even if the content exceeds 40 parts by weight, the pressure-sensitive adhesive layer may become too hard due to an increase in the glass transition temperature (Tg), and the pressure-sensitive adhesive tape may be easily peeled off.

The pressure-sensitive adhesive layer may contain other resins such as additives such as a plasticizer, an emulsifier, a softener, a filler, a pigment, a dye, a silane coupling agent, and an antioxidant, if necessary. Good.

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. When the thickness is less than 1 μm, the pressure-sensitive adhesive tape is easily peeled off, and the constant load peelability to the adherend may be lowered. When the said thickness exceeds 100 micrometers, a thin adhesive tape may not be obtained. The more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 3 μm, the more preferable upper limit is 75 μm, the still more preferable lower limit is 5 μm, and the still more preferable upper limit is 25 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.

Although the said base material is not specifically limited, A resin film, a resin foam, paper, a nonwoven fabric, a yarn cloth cloth etc. are mentioned.
Examples of the resin film include polyolefin resin films such as polyethylene films and polypropylene films, polyester resin films such as PET films, and modified olefins such as ethylene-vinyl acetate copolymers and ethylene-acrylic acid ester copolymers. Examples thereof include a resin film, a polyvinyl chloride resin film, a polyurethane resin film, and a cycloolefin polymer resin film.
Examples of the resin foam include polyethylene foam, polypropylene foam, acrylic foam, urethane foam, and ethylene propylene rubber foam.
Examples of the yarn cloth cloth include a woven polyethylene flat yarn and a laminate of a resin film on the surface thereof.
Especially in the case of double-sided tapes used in the assembly of display modules, black-printed substrates to prevent light transmission, white-printed substrates to improve light reflectivity, metal-deposited film substrates, etc. Can also be used.

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 living radical polymerization crosslinkable acrylic polymer is mixed with other compounding components such as the tackifying resin and the crosslinking agent as necessary, and stirred. Then, the pressure-sensitive adhesive solution is prepared, and subsequently this pressure-sensitive adhesive solution is applied to a release-treated PET film and dried to form a pressure-sensitive adhesive layer. The resulting pressure-sensitive adhesive layer is applied to one or both sides of the substrate. Examples thereof include a method of transferring 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.

The use of the adhesive tape of the present invention is not particularly limited, but it is 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, assembling and fixing automobile parts, and the like. Is preferred.

ADVANTAGE OF THE INVENTION According to this invention, even if it is a thin adhesive tape, it is hard to peel and can provide the adhesive tape which can exhibit high constant load peelability and adhesive cohesive force with respect to a to-be-adhered body.

It is a schematic diagram explaining living radical polymerization. It is a schematic diagram explaining the case where a living radical polymerization crosslinkable acrylic polymer is bridge | crosslinked. It is a schematic diagram explaining free radical polymerization. It is a schematic diagram explaining the case where a free radical polymerization crosslinkable acrylic polymer is bridge | crosslinked.

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

(Radical polymerization polymer)
(Synthesis 1)
(Synthesis 1-1)
Tellurium (40 mesh, metal tellurium, manufactured by Aldrich) 6.38 g (50 mmol) was suspended in tetrahydrofuran (THF) 50 mL, and 1.6 mol / L n-butyllithium / hexane solution (Aldrich) 34 was added thereto. 4 mL (55 mmol) 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.

(Synthesis 1-2)
In a glove box substituted with argon, in a reaction vessel, 38 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis Example 1-1, V-60 (2,2′-azobisisobutyro (Nitrile, manufactured by Wako Pure Chemical Industries, Ltd.) 2.8 mg and ethyl acetate 1 mL 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 (BA: butyl acrylate, Aac: acrylic acid, HEA: 2-hydroxyethyl acrylate) shown in Table 1 was added into the reaction vessel, and acetic acid as the polymerization solvent. 66.5 g of ethyl was added, and a polymerization reaction was performed at 60 ° C. for 20 hours to obtain a living radical polymerization crosslinkable acrylic polymer-containing solution.
The resulting living radical polymerization crosslinkable acrylic polymer was diluted 50 times 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), and 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. The weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) were determined. GPC KF-806L (Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(Synthesis 2)
58 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1, 4.2 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) A living radical polymerization polymer-containing solution was obtained in the same manner as in Synthesis 1-2 except that the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 3)
12 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1, 0.9 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) A living radical polymerization polymer-containing solution was obtained in the same manner as in Synthesis 1-2 except that the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 4)
230 μL of ethyl 2-methyl-2-n-butylterranyl-propionate prepared in Synthesis 1-1 and 17 mg of V-60 (2,2′-azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) were changed. Except for the above, a living radical polymerization polymer-containing solution was obtained in the same manner as in Synthesis 1-2, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined.

(Synthesis 5)
50 g of ethyl acetate was added as a polymerization solvent in the 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 polymerization reaction was carried out for 4 hours to obtain a free radical polymerization polymer-containing solution.
In the same manner as in Synthesis 1, the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) were determined.

(Examples 1-5, Comparative Examples 1-6)
To the radical polymerization crosslinkable polymer-containing solution obtained above, ethyl acetate is added to 100 parts by weight of the non-volatile content and stirred. Coronate L (isocyanate-based crosslinking agent, manufactured by Nippon Polyurethane Co., Ltd.) or Tetrad- A predetermined amount of X (epoxy crosslinking agent, manufactured by Mitsubishi Gas Chemical Co., Inc.) shown in Table 2 was added and stirred to obtain an adhesive solution having a nonvolatile content of 30% by weight. The obtained pressure-sensitive adhesive solution was applied to a PET film having a thickness of 50 μm which had been subjected to a release treatment so as to have the tape thickness shown in Table 2 after drying, and then dried at 70 ° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer.

The obtained adhesive tape was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece, and the release film was peeled off. The test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, then taken out from the ethyl acetate and dried at 110 ° C. for 1 hour. The weight of the test piece after drying was measured, and the gel fraction was calculated using the following formula (1).
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)

(Examples 6-8, Comparative Example 7)
To the radical polymerization crosslinkable polymer-containing solution obtained above, ethyl acetate is added to 100 parts by weight of the nonvolatile content and stirred, and coronate L (isocyanate-based crosslinker, manufactured by Nippon Polyurethane Co., Ltd.) as a crosslinker is added. Pencel D135 (polymerized rosin ester, manufactured by Arakawa Chemical Co., Ltd.) as a resin was added in a predetermined amount as shown in Table 2 and stirred to obtain an adhesive solution having a nonvolatile content of 30% by weight. The obtained pressure-sensitive adhesive solution was applied to a PET film having a thickness of 50 μm which had been subjected to a release treatment so as to have the tape thickness shown in Table 2 after drying, and then dried at 70 ° C. for 10 minutes to obtain a pressure-sensitive adhesive tape. In addition, the release film for protecting an adhesive layer was laminated | stacked on the surface of the both sides of an adhesive layer. The gel fraction of the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive tape was measured by the same method as in Example 1.

(Evaluation)
The following evaluation was performed about the adhesive tape obtained by the Example and the comparative example. The results are shown in Table 2.

(1) Constant load peelability for polycarbonate (PC) plate Affixed with a backing adhesive tape with a width of 20mm x 50mm on a polycarbonate (PC) plate, cured at 23 ° C and 50% humidity overnight, then at 85 ° C and 90 ° direction A 50 g load was applied to the film, and the peeling time was measured. Based on the obtained peeling time, the constant load peelability was evaluated according to the following criteria.
◎: Peeling time is 1 hour or more ○: Peeling time is 30 minutes or more, less than 1 hour Δ: Peeling time is 15 minutes or more, less than 30 minutes ×: Peeling time is less than 15 minutes

(2) Adhesive adhesive cohesive force A backing adhesive tape having a width of 10 mm × 10 mm was attached to a stainless steel plate, a load of 200 g was applied in the direction of 180 ° at 23 ° C., and the amount of deviation after 3 minutes was measured. Based on the obtained shift amount, the adhesive cohesive strength was evaluated according to the following criteria.
A: Deviation amount is 15 μm or less B: Deviation amount exceeds 15 μm, 30 μm or less X: Deviation amount exceeds 30 μm

ADVANTAGE OF THE INVENTION According to this invention, even if it is a thin adhesive tape, it is hard to peel and can provide the adhesive tape which can exhibit high constant load peelability and adhesive cohesive force with respect to a to-be-adhered body.

DESCRIPTION OF SYMBOLS 1 Living radical polymerization crosslinkable acrylic polymer 11 Monomer which does not contain a crosslinkable functional group 12 Crosslinkable functional group containing monomer 2 Free radical polymerization crosslinkable acrylic polymer 21 Monomer which does not contain a crosslinkable functional group 22 Crosslinkable functional group containing monomer 23 Polymer whose growth terminal radical is deactivated during the reaction 24 Polymer grown by the radical species newly generated during the reaction

Claims (3)

Polymer component containing 60% by weight or more of an acrylic polymer having a crosslinkable functional group having a weight average molecular weight of 300,000 to 2,000,000 and a molecular weight distribution (Mw / Mn) of 1.05 to 2.5, obtained by living radical polymerization A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer containing a crosslinking agent and a gel fraction of the pressure-sensitive adhesive layer of 15% by weight or less. The pressure-sensitive adhesive tape according to claim 1, wherein the crosslinkable functional group contains a hydroxyl group, and the crosslinking agent contains an isocyanate-based crosslinking agent. The pressure-sensitive adhesive tape according to claim 1, wherein the crosslinkable functional group contains a carboxyl group, and the crosslinking agent contains an epoxy-based crosslinking agent or an aziridine-based crosslinking agent.

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