JP5406456B2 - Ionizing radiation curable adhesive composition for re-peeling and use thereof - Google Patents

Description

The present invention relates to an ionizing radiation curable pressure-sensitive adhesive composition for re-peeling and its use. More specifically, an ionizing radiation-curable releasable pressure-sensitive adhesive composition that can be suitably used for forming an adhesive film or the like that protects an optical member, a laminate obtained by curing the composition, and the laminate And an optical member formed by sticking the adhesive film.

The ionizing radiation curable pressure-sensitive adhesive composition for re-peeling is intended to produce a pressure-sensitive adhesive film that can be used as a re-peelable surface protective film (surface protective sheet) having the ability to be cured by ionizing radiation such as UV and EB. It becomes the raw material of A re-peelable surface protective film is a film that is temporarily affixed during processing, transportation, inspection, etc., in order to suppress scratches and dirt during the process in the production of optical members, etc. Usually, it is finally peeled off and discarded. In recent years, the demand for a film for protecting the surface of an optical member or the like has increased rapidly, and a film suitable for protecting an optical member is particularly desired.

As a pressure-sensitive adhesive film used to protect the surface of an optical member, a viewpoint that prevents problems such as disorder of alignment of the optical member and liquid crystal cell and expansion of a cell gap due to distortion generated at the time of peeling, and a productivity viewpoint Therefore, it is desirable that the adhesive force (high-speed adhesive force) at the time of high-speed peeling is sufficiently low. Moreover, it is desirable that not only the high-speed adhesive force is low, but also the property (familiarity) of quickly getting wet to the adherend by the weight of the adhesive film is excellent. If the conformability is excellent, even if the adhesive film is peeled off due to some trouble during the process, it can be re-adhered to the adherend by the weight of the adhesive film, and the surface of the optical member may be damaged during the process. It is because it can suppress more effectively.

As a method for reducing the high-speed adhesive strength of the adhesive film, for example, increasing the crosslinking density of the polymer constituting the adhesive film is conceivable. However, if the crosslink density of the polymer is increased to reduce the high-speed adhesive force of the adhesive film, the adhesive strength with the adherend will also be reduced, and the protective film may be peeled off during the manufacturing process, or floating may occur during autoclave processing. There is a possibility that a problem such as failure may occur, and a problem such as a decrease in conformability will occur. In particular, when a member having fine irregularities on the surface (for example, an optical member such as an antiglare-treated polarizing plate) is used as an adherend, these problems are significant.

Thus, lowering the adhesive strength (high-speed adhesive strength) when peeled at a high speed and improving the conformability and the like are mutually contradictory physical properties, and the conventional adhesive film is compatible with both. It was not a thing. Therefore, a pressure-sensitive adhesive film that simultaneously satisfies these physical properties at a high level and a pressure-sensitive adhesive composition for re-peeling that can form such a pressure-sensitive adhesive film have been demanded. It has also been desired that the adhesive film can be used for an adherend having fine irregularities on the surface.

As a conventional re-peeling pressure-sensitive adhesive composition, for example, as a main component of a re-peelable pressure-sensitive adhesive, an acrylate monomer having a glass transition temperature of -15 ° C. or less of a homopolymer is 50 to 90 mass. %, A monomer mixture essentially comprising an acrylate monomer having a glass transition temperature of 0 to 120 ° C. of 0 to 120 ° C. and an acid group-containing monomer of 5 to 0.1% by mass. Obtained by polymerization in an aqueous medium using 0.2 to 4% by mass of a reactive nonionic surfactant and 0.1 to 2% by mass of an anionic surfactant per 100% by mass of the monomer mixture. In which a water-soluble acrylic copolymer is used, the solvent-soluble content of the pressure-sensitive adhesive is set to 40% or less, and the elastic modulus is set to a range of 1 to 40 kg / cm ² . (For example, refer to Patent Document 1). This technique proposes that an acrylic pressure-sensitive adhesive contains a component having a high glass transition temperature (0 to 120 ° C.) to weaken the adhesive force and impart removability. However, since the adhesive strength is too high, there is room for further improvement in removability. Furthermore, it is possible to lower the adhesive strength by increasing the crosslink density, but it is impossible to achieve compatibility with the compatibility, and it is possible to achieve both low adhesion and compatibility with high speed peeling. There was room.

Moreover, (meth) acrylic acid alkylene oxide adduct 51-100 mass%, (meth) acrylic monomers other than the above 0-49 mass%, and other polymerizable monomers 0-49 mass% are monomer components. A pressure-sensitive adhesive composition comprising a (meth) acrylic (co) polymer and a crosslinking agent is disclosed (see, for example, Patent Document 2). This technology improves wettability by using an acrylic polymer obtained by crosslinking 51 to 100% by mass of an (meth) acrylic acid alkylene oxide adduct with an epoxy compound or an isocyanate compound, thereby enabling high-speed peeling. It is intended to reduce the adhesive strength at the time. However, in order to achieve both compatibility and high-speed peelability, a large amount of an alkylene oxide adduct must be used, but this monomer is expensive and unsuitable for industrial use. Further, since the alkylene oxide portion is easily subjected to extraction by radicals, there is a problem that gelation is likely to occur during polymerization.

Furthermore, the main component is a radiation-reactive polymer having one carbon-carbon double bond and a molecular inner chain with a chain length of 6 or more atoms, and shrinkage force generated by a curing reaction by irradiation. A re-peelable pressure-sensitive adhesive having a viscosity of 30 MPa or less is disclosed (for example, see Patent Document 3). This technology is a re-peelable pressure-sensitive adhesive composed of a radiation-reactive polymer having one carbon-carbon double bond and a radiation-reactive oligomer, and suppresses the warping of the adherend due to shrinkage generated by the curing reaction to a low level. The purpose is to do. However, it is intended for dicing tapes used in semiconductor manufacturing, and adhesive tape that has been cross-linked with isocyanate in advance is affixed to a silicon wafer and UV cured for the purpose of reducing the adhesive strength at the time of peeling. Is sufficiently low, but is conscious only of low adhesiveness at the time of peeling, and has problems such as incompatibility.

As a conventional radiation curable pressure-sensitive adhesive, 75 to 95% by mass of a radiation curable prepolymer having a molecular weight of 5000 to 50000 (meth) acryloyl group in the molecule and a (meth) acryloyl group having a molecular weight of 500 to 3000 at both ends. Drawing process surface protective film comprising a mixture of radiation curable oligomers 5 to 25% by mass and blending polyfunctional thiol 0.2 to 2.0% by mass and an acrylic monomer having an acidic group 50 to 100% by mass Radiation curable pressure sensitive adhesives are disclosed (for example, see Patent Document 4). However, this technique is used for a highly polar adherend such as a metal plate or a glass plate, and is not suitable for use in a low polarity polymer material or the like. Moreover, 50-100 mass% and a large amount of acidic group containing monomer are essential as a component, and adhesive force was too high and it was not compatible with adhesive force level and conformability.

Further, a (meth) acrylate copolymer polymer having a glass transition temperature (Tg) of −20 ° C. or lower and a melt viscosity at 130 ° C. of 50,000 to 500,000 (mPa · S), and a hydrogen abstraction type A transparent pressure-sensitive adhesive sheet comprising a single layer containing a photoinitiator, wherein the pressure-sensitive adhesive strength of the sheet surface on one side and the pressure-sensitive adhesive force on the other surface are different. Is disclosed (for example, see Patent Document 5). This technology uses a hydrogen abstraction type initiator having an absorption wavelength region that approximates that of PET film or soda lime glass, so that the adhesiveness on the side irradiated with ultraviolet rays through the PET film or soda lime glass is higher than that on the opposite side. By doing this, it is intended to obtain pressure-sensitive adhesive sheets having different adhesive properties on the front and back sides. However, this technique has problems such as low curability of the surface irradiated through the PET film and soda lime glass, and too high adhesive strength.
JP-A-8-85779 (page 1-2) JP-2005-200540 (page 1-2) JP 2000-355678 A (page 1-2) JP-A-61-207476 (page 1-2) JP 2006-299053 A (page 1-2)

The present invention has been made in view of the above-mentioned present situation, and is capable of being used suitably as an adhesive film or the like that protects an optical member while achieving both low adhesiveness and conformability at high speed at a high level. It aims at providing the adhesive composition for curable re-peeling, and its use.

The inventors of the present invention have studied various ionizing radiation curable compositions for use in the application of the re-peeling pressure-sensitive adhesive. As a result, the polyfunctional monomer (B) is used with respect to 100% by mass of the acrylic polymer (A). ) In a composition containing 1 to 50% by mass, the acrylic polymer (A) is obtained by polymerizing a monomer component essentially comprising an alkyl acrylate ester having 8 to 14 carbon atoms in the alkyl group. And a side chain unsaturated bond-containing polymer having an unsaturated bond of 0 to 0.200 mmol / g as a monomer component constituting the acrylic polymer (A). Use an acrylic acid alkyl ester having 8 to 14 carbon atoms, a monomer having a hydroxyl group and / or a carboxyl group, and other vinyl monomers, and use amounts of these monomers within a specific range. By special Even without using a monomer, it is possible to achieve both low adhesion and conformability at high speeds at a high level, and it becomes a raw material for a protective film that can be suitably used for adherends having fine irregularities on the surface. As a result, they have come up with the idea that the above problems can be solved brilliantly.

That is, the present invention is an ionizing radiation curable releasable pressure-sensitive adhesive composition containing 1 to 50% by mass of the polyfunctional monomer (B) with respect to 100% by mass of the acrylic polymer (A), The acrylic polymer (A) is obtained by polymerizing a monomer component essentially comprising an alkyl acrylate ester having 8 to 14 carbon atoms in the alkyl group, and the unsaturated bond in the side chain is 0. It is a polymer containing a side chain unsaturated bond of ˜0.200 mmol / g, and the monomer component is an acrylic acid having 8 to 14 carbon atoms in the alkyl group, assuming that the total amount of the monomer is 100% by mass. Ionizing radiation curable re-peeling in which the alkyl ester is 50 to 100% by mass, the monomer having a hydroxyl group and / or a carboxyl group is 0 to 10% by mass, and the other vinyl monomers are 0 to 50% by mass. It is a pressure-sensitive adhesive composition.
The present invention is described in detail below.

The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling of the present invention contains 1 to 50% by mass of the polyfunctional monomer (B) with respect to 100% by mass of the acrylic polymer (A).
By including 1-50 mass% of polyfunctional monomers, the initial tack, adhesive force, and cohesive force required as an adhesive will be expressed. The polyfunctional monomer increases the crosslink density of the pressure-sensitive adhesive, suppresses the movement of the polymer main chain, and adjusts the removability by adjusting the conformability and adhesion to the adherend. The physical properties necessary for the surface protective film will be developed.

It is preferable to change the usage-amount of the said polyfunctional monomer according to the amount of unsaturated double bonds of the side chain which an acrylic polymer (A) has. When the amount of unsaturated double bonds is large, the amount of polyfunctional monomer used is small. Conversely, when the amount of unsaturated double bonds is small, the amount of polyfunctional monomer used is increased. An adhesive is obtained. The usage-amount of a polyfunctional monomer is 50 mass% or less with respect to 100 mass% of an acrylic polymer (A). If it exceeds 50% by mass, the conformability may be insufficient. As the usage-amount of a polyfunctional monomer (B), it is preferable that it is 2-40 mass% with respect to 100 mass% of acrylic polymers (A). More preferably, it is 3-30 mass%. When the usage-amount of a polyfunctional monomer (B) is such a preferable range, the balance with adhesive force and conformability will be further excellent.

The polyfunctional monomer (B) is a monomer having two or more functional groups. The polyfunctional monomer (B) is preferably a monomer having two or more radical polymerizable groups. More preferably, it is a bifunctional or higher functional (meth) acrylate having two or more (meth) acryloyl groups, and more preferably a monomer having three or more radical polymerizable groups. Particularly preferred is a trifunctional or higher functional (meth) acrylate having three or more (meth) acryloyl groups. In the present specification, a monomer having three radical polymerizable groups is also referred to as a trifunctional monomer (trifunctional monomer).

Examples of the bifunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and propylene glycol di (meth). Acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide modified bisphenol A type di (meth) acrylate, propylene oxide Modified bisphenol A type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) a Relate, tricyclodecane dimethanol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, phthalate Acid diglycidyl ester di (meth) acrylate, hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate, 2- (vinyloxyethoxy) ethyl acrylate (VEEA), 2- (vinyloxyethoxy) ethyl methacrylate and the like It is done.

Examples of the trifunctional or higher functional (meth) acrylate include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipenta Examples include erythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, and glycerin polyglycidyl ether poly (meth) acrylate.
As other polyfunctional (meth) acrylates, epoxy (meth) acrylates and urethane (meth) acrylates can be used as appropriate.

Among the polyfunctional monomers, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate and tri (meth) acryloyloxyethoxytrimethylolpropane which are trifunctional (meth) acrylates are preferable, and trimethylolpropane is preferred. Tri (meth) acrylate is particularly preferred. Most preferred is trimethylolpropane tri (meth) acrylate.

The ionizing radiation curable releasable pressure-sensitive adhesive composition can be used in combination with a monofunctional monomer, if necessary, in addition to the polyfunctional monomer. Thereby, the pressure-sensitive adhesive composition for ionizing radiation curable re-peeling can be finely adjusted so as to have desired pressure-sensitive adhesive properties. As addition amount of a monofunctional monomer, 50 mass% or less is preferable with respect to 100 mass% of polymers. If it exceeds 50 mass%, the curability may be lowered. As the usage-amount of a monofunctional monomer, it is preferable that it is 0-30 mass% with respect to 100 mass% of acrylic polymers (A), for example. More preferably, it is 0-25 mass%, More preferably, it is 0-20 mass%. When the usage amount of the monofunctional monomer is within such a preferable range, desired adhesive properties can be imparted without lowering curability.

The monofunctional monomer is a compound having one functional group. The monofunctional monomer is preferably a compound having one radical polymerizable group. Examples of the monofunctional monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, (Meth) acrylates such as isodecyl (meth) acrylate, n-lauryl (meth) acrylate, tridecyl (meth) acrylate, n-stearyl (meth) acrylate, and 2-ethylhexyl-diglycol acrylate can be used. Among these, 2-ethylhexyl (meth) acrylate and 2-ethylhexyl-diglycol acrylate are preferable.

The acrylic polymer (A) contained in the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling of the present invention is a monomer component essentially comprising an alkyl acrylate ester having 8 to 14 carbon atoms in the alkyl group. It is a polymer containing a side chain unsaturated bond obtained by polymerization and having a side chain unsaturated bond of 0 to 0.200 mmol / g.
Below, the monomer component and polymerization process for obtaining an acrylic polymer (A) are demonstrated.

If the alkyl group having 8 to 14 carbon atoms in the alkyl group is represented by a general formula, the following general formula (1);

(Wherein R ¹ represents an alkyl group having 8 to 14 carbon atoms). R ¹ may be linear or branched.
Examples of the compound represented by the general formula (1) include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, tridecyl acrylate, and isomyristyl acrylate. These 1 type (s) or 2 or more types can be used.
R ¹ is preferably an alkyl group having 8 to 12 carbon atoms. More preferably, it is an 8-9 alkyl group. Among the compounds in which R ¹ is an alkyl group having 8 to 9, it is particularly preferable to use 2-ethylhexyl acrylate or isononyl acrylate.

In the said acrylic polymer (A), the usage-amount of the acrylic acid alkylester whose carbon number of an alkyl group is 8-14 is 50-100 mass% when all the monomer components are 100 mass%. . If the amount of the alkyl alkyl ester having 8 to 14 carbon atoms in the alkyl group is less than 50% by mass, the compatibility may be insufficient. It is preferable that the usage-amount of the acrylic acid alkylester whose carbon number of an alkyl group is 8-14 is 55-95 mass%. More preferably, it is 57-90 mass%. If the amount of the acrylic acid alkyl ester used is within such a preferable range, the conformability will be more excellent.

The above-mentioned adaptability is the performance in which the adhesive wets the adherend only by the weight of the tape when the protective film is lightly placed on an optical member such as a polarizing plate. Even if the protective film is peeled off due to such trouble, if the compatibility is excellent, it will be re-adhered only by the weight of the tape, so the performance required to suppress damage to the surface of the optical member is there.
Some polarizing plates have been subjected to a so-called anti-glare treatment in which reflection of light is suppressed by providing fine irregularities on the surface in order to suppress glare in the display portion. This antiglare-treated polarizing plate has a drawback that the wettability of the pressure-sensitive adhesive is poor due to fine unevenness. In general, a protective film having a high crosslinking density and satisfying high-speed peelability has poor conformability, and it is difficult to achieve both physical properties. The pressure-sensitive adhesive film obtained by using the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling according to the present invention has excellent conformability and low-tackiness at high-speed peeling, and is as fine as an anti-glare-treated polarizing plate. It can also be suitably used for an optical member having irregularities. The fine unevenness here means that the unevenness of the unevenness is about 0.1 to 10 μm, and as an adherend having such fine unevenness, an AG (anti-glare, anti-glare) treated film, AR (Antireflection) film, electromagnetic wave shielding film and the like.
The uneven height difference is a numerical value represented by a ten-point average roughness (Rz) measured according to JIS B0601. For example, a laser microscope VK-9710 manufactured by Keyence Co., Ltd. can be used to measure the uneven height difference of the adherend surface.

The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling of the present invention is a group comprising a monomer having a hydroxyl group and / or a carboxyl group as a monomer constituting the acrylic polymer (A). Adhesiveness with the material can be improved, and it can be used as a reaction point when a compound having an unsaturated double bond and a functional group described later is added to the polymer side chain. In order to use as a reaction point when using an isocyanate group-containing compound as a compound having an unsaturated double bond and a functional group, it is preferable to use a monomer having a hydroxyl group. Moreover, in order to make it a reaction point at the time of using a glycidyl group containing compound or an oxazoline monomer as a compound which has an unsaturated double bond and a functional group, it is preferable to use the monomer which has a carboxyl group. Moreover, as a monomer which has a hydroxyl group and / or a carboxyl group, it is preferable to use either the monomer which has a hydroxyl group, or the monomer which has a carboxyl group. When a monomer having a hydroxyl group and a monomer having a carboxyl group are copolymerized, the hydroxyl group reacts with the carboxyl group, which serves as a reaction point when an unsaturated double bond is added to the polymer side chain. Because it becomes impossible.

Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. These 1 type (s) or 2 or more types can be used.
The monomer having a hydroxyl group is preferably a (meth) acrylic acid alkyl ester having a hydroxyalkyl group. More preferably, it is a (meth) acrylic acid alkyl ester having a C1-C6 hydroxyalkyl group, and more preferably a (meth) acrylic acid alkyl ester having a C2-C4 hydroxyalkyl group. Moreover, it is especially preferable to use 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate among (meth) acrylic acid alkyl esters having a C2-C4 hydroxyalkyl group.

Examples of the monomer having a carboxyl group include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2- (meth) acryloyloxyethyl succinic acid, and 2- (meth) acryloyl. Examples include loxyethyl phthalic acid and 2- (meth) acryloyloxyethyl hexahydrophthalic acid, and one or more of these can be used.
The monomer having a carboxyl group is preferably (meth) acrylic acid.

In the said acrylic polymer (A), the usage-amount of the monomer which has a hydroxyl group and / or a carboxyl group is 0-10 mass% when all the monomer components are 100 mass%. If it exceeds 10% by mass, the conformability may be insufficient. It is preferable that the usage-amount of the monomer which has a hydroxyl group and / or a carboxyl group is 0-8 mass%. More preferably, it is 0-7.0 mass%, More preferably, it is 0-6.0 mass%.

The other vinyl-based monomer is a compound that does not correspond to any one of the alkyl ester having 8 to 14 carbon atoms in the alkyl group and the monomer having a hydroxyl group and / or a carboxyl group, It is a vinyl group-containing monomer copolymerizable with these.
Other vinyl monomers include, for example, alkyl acrylates having 1 to 7 carbon atoms in the alkyl group, alkyl methacrylates having 1 to 18 carbon atoms in the alkyl group, vinyl acetate, vinyl toluene, and Styrene etc. are mentioned, These 1 type (s) or 2 or more types can be used.

The other vinyl monomers are more preferably alkyl acrylates having 1 to 7 carbon atoms in the alkyl group and alkyl methacrylates having 1 to 18 carbon atoms in the alkyl group.

In the acrylic polymer (A), the amount of other vinyl monomers used is 0 to 50% by mass when the total monomer components are 100% by mass. When the amount of the other vinyl monomer used exceeds 50% by mass, the amount of the alkyl alkyl ester having 8 to 14 carbon atoms in the alkyl group is too small, and the conformability becomes insufficient. The amount of other vinyl monomers used is preferably 0 to 45% by mass. More preferably, it is 0-40 mass%, More preferably, it is 0-35 mass%.

The acrylic polymer (A) is a side chain unsaturated bond-containing polymer having a side chain unsaturated bond of 0 to 0.200 mmol / g, but the side chain unsaturated bond is 0 to 0.0. It is preferable that it is 180 mmol / g. More preferably, it is 0-0.160 mmol / g.
As the polymer having an unsaturated bond in the side chain, (i) polymerization is performed using a monomer having a portion that becomes a side chain unsaturated bond, or (ii) the side chain is prepared after preparing the polymer. An unsaturated bond may be introduced into. Among these methods, the method (ii) is preferable.
As a method of introducing an unsaturated double bond into the side chain of the polymer as in (ii) above, a compound having an unsaturated group double bond and a functional group is the basis of the acrylic polymer (A). A method of adding to a polymer (performing an addition reaction step) can be mentioned. In addition, even if the unsaturated bond of a side chain is substantially 0 mmol / g, the effect of this invention can be show | played by specifying the usage-amount of a polyfunctional monomer as mentioned above.

The polymerization step for obtaining the acrylic polymer (A) can be performed by various methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but there is no mixing of a dispersant or an emulsifier. Bulk polymerization or solution polymerization is preferred.

The solvent used in the polymerization step for obtaining the acrylic polymer (A) is preferably inactive to the polymerization reaction. Moreover, it is preferable to use the solvent used when setting it as the ionizing radiation-curable re-peeling pressure-sensitive adhesive composition. Thereby, an ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling can be efficiently prepared. In addition, it is suitable to set a solvent suitably according to superposition | polymerization conditions, such as superposition | polymerization mechanism, the kind and quantity of the monomer to be used, superposition | polymerization temperature, superposition | polymerization density | concentration.

Examples of the solvent include monoalcohols such as methanol, ethanol, isopropanol, n-butanol and sec-butanol; glycols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl ether; Glycol monoethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether and 3-methoxybutanol Ethylene glycol dimethyl ester Ter, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether and other glycol ethers; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol Esters of glycol monoethers such as noethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, 3-methoxybutyl acetate; Ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl lactate, ethyl lactate, butyl lactate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxy Alkyl esters such as methyl propionate, ethyl 3-ethoxypropionate, methyl acetoacetate, ethyl acetoacetate; acetone, methyl Ketones such as ruethylketone, methylisobutylketone and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; aliphatic hydrocarbons such as hexane, cyclohexane and octane; dimethylformamide, dimethylacetamide and N-methylpyrrolidone Amides and the like. These may be used alone or in combination of two or more. As a usage-amount of a solvent, 40-1000 mass% is preferable with respect to 100 mass% of all the monomer components. More preferably, it is 100-400 mass%.

In the polymerization step, it is preferable to use a polymerization initiator.
Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy octoate, t-butyl peroxybenzoate, cumene Organic peroxides such as hydroperoxide, cyclohexanone peroxide, dicumyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate;
Examples include azo compounds such as 2,2'-azobis- (2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile. . These may be used alone or in combination of two or more.

The addition amount of the polymerization initiator in the polymerization step is not limited as long as the polymerization reaction can be performed sufficiently and sufficiently. For example, when the total mass of the polymerization solution is 100% by mass, the addition amount is 0.01 to 1.0% by mass. Preferably there is. More preferably, it is 0.01-1.0 mass%, More preferably, it is 0.02-0.5 mass%. When the addition amount of the polymerization initiator exceeds 1.0% by mass, the storage stability may not be sufficient.

The polymerization step is preferably performed by adding a chain transfer agent as necessary. Thereby, a polymer having a desired average molecular weight can be obtained. As the chain transfer agent, various known chain transfer agents can be used, but a thiol compound is most preferable because the polymerization reaction of the monomer component can be controlled very easily.

Examples of the thiol compound include alkyl mercaptans such as t-butyl mercaptan, n-octyl mercaptan and n-dodecyl mercaptan; aromatic mercaptans such as thiophenol and thionaphthol; thioglycolic acid; octyl thioglycolate, ethylene glycol dithiol. Thioglycolic acid alkyl esters such as glycolate, trimethylolpropane tris- (thioglycolate), pentaerythritol tetrakis- (thioglycolate); β-mercaptopropionic acid; octyl β-mercaptopropionic acid, 1,4-butanediol Β-mercaptopropi such as di (β-thiopropionate), trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakis- (β-thiopropionate) Phosphate esters, and the like. These may be used alone or in combination of two or more. Among these, alkyl mercaptans are preferable.

What is necessary is just to set the usage-amount of the said chain transfer agent according to the kind of this chain transfer agent, a monomer composition, etc., and it exists in the range of 0.01-4 mass% with respect to 100 mass% of monomer components. Is preferred. More preferably, it is in the range of 0.02 to 3% by mass, and still more preferably in the range of 0.03 to 2% by mass.

The polymerization temperature in the polymerization step is preferably 50 to 200 ° C., for example. When the temperature is lower than 50 ° C., it is necessary to use an initiator having a low decomposition temperature, which may be disadvantageous for industrial production, for example, a facility for cooling and storing the initiator is required. If it exceeds 200 ° C., the monomer component may start to undergo thermal polymerization before reaching the decomposition temperature of the initiator. Preferably, it is 60-150 degreeC. The polymerization temperature is preferably set as appropriate according to the type of initiator.

The reaction time in the polymerization step may be appropriately adjusted depending on other reaction conditions such as reaction temperature and the physical properties of the monomer, but is preferably 0.1 to 48 hours. More preferably, it is 0.1 to 24 hours. If the reaction time is less than 0.1 hour, the monomer may not be sufficiently polymerized, and the reaction process may be economically inefficient. If the reaction time exceeds 48 hours, gelation may occur.
Then, the process (addition reaction process) of adding the compound which has an unsaturated group double bond and a functional group to the polymer used as the basis of an acrylic polymer (A) is demonstrated.

Examples of the method of the addition reaction step include: (a) a method in which an isocyanate group-containing (meth) acrylic ester is reacted with a polymer obtained by copolymerizing a monomer having a carboxyl group and / or a hydroxyl group; Examples thereof include a method in which a polymer obtained by copolymerizing a monomer having a group is reacted with an epoxy group-containing monomer such as glycidyl methacrylate and / or an oxazoline monomer such as isopropenyl oxazoline. Among these methods, the method (a) is particularly preferable because the reaction rate is high and the reaction rate is high.

The isocyanate group-containing (meth) acrylic acid ester used in the introduction method (a) is preferably a monoisocyanate having one isocyanate group in the molecule. If a polyvalent isocyanate compound is used, cross-linking between molecules occurs during synthesis, and there is a possibility of gelation.

The isocyanate group-containing (meth) acrylic acid ester having one isocyanate group in the molecule is represented by the following general formula (2):

(Wherein R ² represents a hydrogen atom or a methyl group. R ³ represents a group in which one hydrogen atom of an alkyl group is substituted with an isocyanate group).
In the compound represented by the general formula (2), R ³ is preferably a group in which one hydrogen atom of an alkyl group having 1 to 5 carbon atoms is substituted with an isocyanate group. More preferably, it is a group in which one hydrogen atom of an alkyl group having 1 to 3 carbon atoms is substituted with an isocyanate group. R ³ may be linear or branched. Also, isocyanate groups of the R ³ may be blocked.

Examples of the compound represented by the general formula (2) include (meth) acryloyloxymethyl isocyanate, 2- (meth) acryloyloxyethyl isocyanate, and 3- (meth) acryloyloxypropyl isocyanate. Species or two or more can be used.
Among these compounds, (meth) acryloyloxymethyl isocyanate and 2- (meth) acryloyloxyethyl isocyanate are preferable. More preferred is 2- (meth) acryloyloxyethyl isocyanate.
As such an isocyanate group-containing (meth) acrylic acid ester, for example, Karenz series (manufactured by Showa Denko KK) can be used.

The epoxy group-containing monomer used in the introduction method (b) is a compound having an epoxy group and a double bond. Examples of the epoxy group include 1,2-epoxide group (oxirane group), 1,3-epoxide group (oxetanyl group), 1,4-epoxide group (tetrahydrofuranyl group), 1,5-epoxide group (tetrahydropyrani group). Group).
Examples of such compounds include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, β-ethylglycidyl (meth) acrylate, allyl (meth) acrylate, vinylbenzyl glycidyl ether, allyl glycidyl ether, and the like. Monomer having an aliphatic 1,2-epoxide group, 3- (meth) acryloxymethyloxetane, 3-methyl-3- (meth) acryloxymethyloxetane, 3-ethyl-3- (meth) acryloxy Monomers having an aliphatic 1,3-epoxide group such as methyl oxetane, and alicyclic 1,2-epoxide groups such as (meth) acrylic acid (3,4-epoxycyclohexyl) methyl, vinylcyclohexene oxide, etc. A monomer is mentioned.
Among these, a monomer having an aliphatic 1,2-epoxide group is preferable because it is excellent in terms of reactivity to a carboxyl group and economy. Particularly preferred is glycidyl (meth) acrylate. Most preferred is glycidyl methacrylate.
As such an epoxy group-containing monomer, BLEMMER G (trade name, manufactured by NOF Corporation) and the like can be used.

The oxazoline monomer used in the introduction method (b) is a compound having a vinyl group and an oxazoline group. Examples of the oxazoline monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and one or more of these Can be used. Among these, 2-isopropenyl-2-oxazoline is preferable because it is excellent in terms of reactivity and availability.

It is preferable to perform the said addition reaction process in the temperature range of 50-100 degreeC. In this case, the polymerization is usually performed by mixing the polymer that is the basis of the acrylic polymer (A), the compound having an unsaturated group double bond and a functional group, a solvent, and an addition catalyst.
More preferably, it is 55-90 degreeC as said temperature, More preferably, it carries out at 60-80 degreeC. If the temperature is lower than 50 ° C., the reaction may take a long time or the reaction rate may decrease. When temperature exceeds 100 degreeC, it will become easy to gelatinize a polymer during reaction. In order to prevent gelation, it is desirable to further mix a polymerization inhibitor and perform in the presence of a molecular oxygen-containing gas. As the molecular oxygen-containing gas, air or oxygen gas diluted with an inert gas such as nitrogen is usually used and blown into the reaction vessel.

The reaction time in the addition reaction step is preferably continued until the reaction rate of the compound having an unsaturated group double bond and a functional group reaches 80% or more. More preferably, it is continued until 90% or more is reached, and further preferably, it is continued until 95% or more is reached.
As a result, effects such as introducing a sufficient amount of unsaturated bonds into the side chain and sufficiently reducing highly toxic isocyanate-containing monomers and epoxy group-containing monomers are exhibited. The reaction rate can be confirmed by quantification of the amount of unreacted functional groups by FT-IR, quantification of the acid value of the reaction solution, quantification of the residual amount of an epoxy group-containing monomer or the like using gas or liquid chromatography. .

As the solvent used in the above addition reaction step, those mentioned as the solvent used in the polymerization can be used, and one kind or two or more kinds may be used. It is efficient and preferable to synthesize the polymer using a solvent and to use the solvent of the obtained polymer solution as it is as a solvent for the addition reaction step.

As for the usage-amount of the solvent in the said addition reaction process, it is preferable that a polymer concentration is 10-80 mass% when the total mass of a polymer solution is 100 mass%. By carrying out within the above range, the reaction time can be shortened and it is economical, and since the viscosity of the system is relatively low, it is difficult to gel, and the temperature can be easily controlled. A more preferable concentration is 15 to 70% by mass, and a further preferable concentration is 20 to 60% by mass.

As the addition catalyst used in the introduction method (a), for example, a tin compound or a known urethane cleavage catalyst can be used. Among these, it is preferable to use dibutyltin dilaurate because there are few side reactions.

The amount of the catalyst used in the introduction method (a) is 0 when the total mass of the polymer based on the acrylic polymer (A) and the isocyanate group-containing (meth) acrylic acid ester is 100% by weight. It is preferable that it is 0.01-0.5 mass%. More preferably, it is 0.02-0.1 mass%. By performing in the said range, reaction time can be shortened and it is economical, and storage stability can be improved more.

As the addition catalyst used in the introduction method (b), known basic catalysts for esterification or transesterification and acidic catalysts can be used. Among these, it is preferable to use a basic catalyst because there are few side reactions.
Examples of the basic catalyst include tertiary amines such as dimethylbenzylamine, triethylamine, tri-n-octylamine and tetramethylethylenediamine, tetramethylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, and n-dodecyltrimethylammonium. Quaternary ammonium salts such as chloride, urea compounds such as tetramethylurea, alkylguanidines such as tetramethylguanidine, amide compounds such as dimethylformamide and dimethylacetamide, tertiary phosphines such as triphenylphosphine and tributylphosphine, tetraphenylphosphonium bromide And quaternary phosphonium salts such as benzyltriphenylphosphonium bromide. These catalysts may be used alone or in combination of two or more.
Among these, dimethylbenzylamine, triethylamine, tetramethylurea, and triphenylphosphine are preferable in terms of reactivity, handling properties, and halogen-free.

The amount of the catalyst used in the introduction method (b) is 0 when the total mass of the polymer based on the acrylic polymer (A), the epoxy group-containing monomer and the oxazoline compound is 100% by weight. It is preferable that it is 0.01-5.0 mass%. More preferably, it is 0.1-3.0 mass%. By performing in the said range, reaction time can be shortened and it is economical, and storage stability can be improved more.

The addition reaction step is preferably performed by adding a polymerization inhibitor.
As the polymerization inhibitor, a known polymerization inhibitor for radical polymerizable monomers can be used. Examples of the polymerization inhibitor for radical polymerizable monomers include hydroquinone, methylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, methoquinone, 6-t-butyl-2,4-xylenol, and 2,6-di-t-. Mention phenolic inhibitors such as butylphenol, 2,6-di-t-butyl-4-methoxyphenol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), organic acid copper salts and phenothiazines Can do. Among these, phenol-based inhibitors are preferable from the viewpoint of low coloring and ability to prevent polymerization. Among them, methoquinone, 6-t-butyl-2,4-xylenol, 2,6-di-t are particularly preferable in view of availability and economy. -Butylphenol and 2,2'-methylenebis (4-methyl-6-t-butylphenol) are preferred. More preferably, it is 2,2′-methylenebis (4-methyl-6-tert-butylphenol). These polymerization inhibitors may be used alone or in combination of two or more.

As the usage-amount of the said polymerization inhibitor, when the total mass of all the monomer components and the compound which has an unsaturated group double bond and a functional group is 100 mass%, it is 0.001-1.0 mass%. Preferably there is. More preferably, it is 0.005-0.5 mass%. By carrying out in the above range, it is possible to expect compatibility between prevention of gelation in the addition reaction step and sufficient curability when formed into a composition.

As the acrylic polymer (A), those having a weight average molecular weight of 10,000 to 1,000,000 can be used. If the weight average molecular weight exceeds 1,000,000, the coatability may be deteriorated. The weight average molecular weight is preferably 20,000 to 800,000. More preferably, it is 30,000 to 600,000.

The weight average molecular weight is preferably measured using the following gel permeation chromatography (GPC) apparatus and conditions.
Apparatus: HLC-8220GPC (trade name, manufactured by Tosoh Corporation)
Elution solvent: Tetrahydrofuran standard substance: Standard polystyrene separation column made by Tosoh Corporation: TSKgel SuperHZM-M

The glass transition temperature of the acrylic polymer (A) is preferably -100 to -20 ° C. When the glass transition temperature is −100 to −20 ° C., sufficient conformability can be imparted. The glass transition temperature is more preferably -100 to -30 ° C, still more preferably -100 to -40 ° C, and particularly preferably -100 to -50 ° C.

The glass transition temperature of the acrylic polymer (A) can be determined by DSC (differential scanning calorimeter), DTA (differential thermal analyzer), and TMA (thermomechanical analyzer). Moreover, since Tg (K) of homopolymer is described in various documents (for example, polymer handbook etc.), Tg (K) of copolymer is different from Tgn (K) of various homopolymers and mass fraction of monomer ( Wn) can also be obtained from the following equation.

Here, the abbreviations represent the following.
Wn: Mass fraction of each monomer Tgn: Tg (K) of homopolymer of each monomer
Subsequently, the polyfunctional monomer (B) will be described.

It is a preferred embodiment of the present invention that the ionizing radiation curable releasable pressure-sensitive adhesive composition further comprises a hydrogen abstraction type photopolymerization initiator (C) and is cured by ultraviolet irradiation. One.
Initiators used for ultraviolet (UV) curing include a hydrogen abstraction type and a self-cleavage type. In the present invention, it is preferable to use a hydrogen abstraction type photoinitiator. When a hydrogen abstraction type initiator is used, the initiator abstracts hydrogen radicals from the adhesive resin, and the radicals on this polymer react with side chain unsaturated bonds of other polymer molecules (intermediately via the polyfunctional monomer). In some cases, a crosslinked structure is formed. Since this reaction starts from a polymer radical, the crosslinking efficiency is high, and as a result, it is presumed that both high-speed peelability and conformability can be achieved. On the other hand, in the self-cleaving type, the initiator is cleaved into two radical molecules, and this radical first reacts with a side chain unsaturated bond of one polymer molecule, and further reacts with another polymer molecule to form a crosslinked structure. Compared with the above-described hydrogen abstraction mold, the step until the formation of a crosslinked structure becomes longer, so that the crosslinking efficiency is considered to be poor. In fact, compared to hydrogen abstraction type initiators, high-speed adhesive force is less likely to decrease, and it is possible to reduce high-speed adhesive force by increasing the amount of unsaturated double bonds and the amount of polyfunctional monomers in the adhesive resin side chain. , Balance with familiarity is not possible. In order to obtain high-speed peelability, it is necessary to raise the degree of crosslinking as a whole. However, the self-cleavage type requires excessive crosslinking because of poor crosslinking efficiency. For this reason, there are places where the crosslinking density is too high, and as a result, the balance between high-speed peelability and conformability is considered to be poor.

Examples of the hydrogen abstraction type initiator include benzophenone, methylbenzophenone, trimethylbenzophenone, o-benzoylbenzoic acid, methyl o-benzoylbenzoate, 4-chlorobenzophenone, 4,4′-dichlorobenzophenone, 4-fluorobenzophenone, 4, Benzophenones such as 4′-difluorobenzophenone, tetra (t-butylperoxycarbonyl) benzophenone, [4- (methylphenylthio) phenyl] phenylmethanone; thioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, etc. Examples include thioxanthones, 3-ketocoumarin, 2-ethylanthraquinone, camphorquinone, Michler's ketone, and the like, and one or more of these can be used.

Among the hydrogen abstraction type photoinitiators, it is preferable to use benzophenones. Benzophenones are compounds having a benzophenone group. More preferred is benzophenone.
Moreover, it is preferable that the addition amount of a hydrogen abstraction type photoinitiator is 0.1-10 mass% when the total mass of the ionizing radiation-curable re-peeling pressure-sensitive adhesive composition is 100 mass%. More preferably, it is 0.2-8 mass%, and is 0.3-6 mass%.

In the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling of the present invention, a self-cleavage photoinitiator can be used in combination with a hydrogen abstraction photoinitiator. By using the self-cleaving photoinitiator, the unreacted amount of the monofunctional monomer can be reduced. However, the addition amount of the self-cleaving photoinitiator is preferably 5% by mass or less when the total mass of the composition is 100% by mass. This is because the self-cleaving initiator also has a function of reducing the crosslinking efficiency.

Examples of the self-cleaving photoinitiator include benzoins such as benzoin and benzoin isobutyl ether; dimethylbenzyl ketal, 2,2-dimethoxyphenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1 -Acetophenones such as phenylpropan-1-one; acylphosphine oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. These 1 type (s) or 2 or more types can be used.

In the case of curing the ionizing radiation-curable releasable pressure-sensitive adhesive composition by ultraviolet irradiation, examples of the UV light source include black light, low-pressure mercury lamp, high-pressure mercury lamp, ultrahigh-pressure mercury lamp, metal halide lamp, and xenon lamp.
As UV irradiation intensity | strength, an adhesive composition should just be hardened enough, for example, 50-1000 mW / cm < ² > is preferable. If the irradiation intensity is too weak, curing may take too long.
As a UV irradiation amount, for example, 10 to 1000 mJ / cm ² is preferable. If the irradiation amount is too small, the curing may be insufficient and the high-speed adhesive force may be too high, and if it is too large, the conformability may be insufficient due to excessive curing.

The difference between the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling of the present invention and a conventional pressure-sensitive adhesive composition for re-peeling comprising an isocyanate crosslinking agent will be described below.
The re-peelable pressure-sensitive adhesive needs to have a higher cross-linking density than that of a normal pressure-sensitive adhesive for the purpose of suppressing the adhesive force to a low level and suppressing an increase in the adhesive strength with time after pasting. For this purpose, the pressure-sensitive adhesive resin having more crosslinking points than usual is crosslinked with a large amount of crosslinking agent. In the generally used isocyanate cross-linking system, many high-polar urethane bonds are formed as cross-linking points, and this reduces the tack and wettability of the adhesive layer, making it difficult to express the conformability. Become. On the other hand, in the case of ionizing radiation curing, since the cross-linked portion is a nonpolar alkyl group, it is flexible and easily adaptable.
In addition, in the case of isocyanate cross-linking, since a large amount of cross-linking points are reacted with a large amount of cross-linking agent, other than problems such as easy distribution of cross-linking density, and the intended polymer cross-linking points and reaction of isocyanate compounds (urethane bonds) In addition, side reactions such as reactions between isocyanates (allophanate bonds) and reactions with moisture present in the system also occur, so that the crosslinked structure is complicated and considered to be non-uniform. On the other hand, in the case of ionizing radiation curing, the unsaturated double bond reacts with the radical to form a crosslink, so there is no side reaction such as isocyanate, and the crosslink density is relatively uniform. It is considered that the balance of conformability is excellent.
For these reasons, the content of the crosslinking agent such as an isocyanate crosslinking agent and an epoxy compound that may be included in the ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling of the present invention may be within the range described below. This is a preferred form.

It is one of the preferred embodiments of the present invention that the ionizing radiation curable releasable pressure-sensitive adhesive composition is cured by electron beam irradiation.
When cured by electron beam irradiation, since all starting species are polymer radicals, the balance between high-speed peelability and conformability is further improved. Further, electron beam (EB) curing has the same mechanism as ultraviolet (UV) curing using a hydrogen abstraction type initiator since it starts from generation of polymer radicals by electron beam irradiation. Strictly speaking, UV curing using a hydrogen abstraction type initiator is initiated by two types of polymer radicals and initiator radicals (in which the initiator extracts hydrogen radicals from the polymer). A polymer radical is a more preferable form because it becomes a starting species.

The curing by the electron beam irradiation may use an electron beam having an acceleration voltage of 300 kV or less. More preferably, an electron beam of 250 kV or less is used. If the acceleration voltage exceeds 300 kV, the electron beam that has passed through the composition may deteriorate the substrate. In the electron beam irradiation, the higher the acceleration voltage, the greater the electron beam transmission capability. Therefore, by selecting the accelerating voltage so that the penetration depth of the electron beam and the thickness of the resin layer are substantially equal, it is possible to suppress the irradiation of the extra electron beam to the base sheet, and the excess electron beam It is possible to minimize the deterioration of the base sheet due to the above. Thus, the optimum acceleration voltage depends on the thickness of the resin layer. Therefore, when the thickness after curing is about 5 to 50 μm, which is a preferable range, the acceleration voltage is in the range of 50 to 200 kV. preferable.
The irradiation dose is preferably adjusted to an amount that saturates the crosslinking density of the resin layer, and is usually adjusted to 5 to 300 kGy. The irradiation dose is preferably 10 to 250 kGy, more preferably 20 to 200 kGy.
As an electron beam source in the above-mentioned electron beam irradiation, for example, various electron beam accelerators such as a Cockloft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type are used. be able to.

As the ionizing radiation used when the ionizing radiation curable releasable pressure-sensitive adhesive composition is cured, it is particularly preferable to use electron beam irradiation among ultraviolet (UV) irradiation and electron beam (EB) irradiation. Compared with ultraviolet rays, the number of irradiations can be reduced, and as a result, productivity can be improved with respect to the production of adhesive films and the like. In general, electron beam curing does not require a photoinitiator unlike curing by ultraviolet irradiation, so the ionizing radiation curable adhesive composition for re-peeling has good storage stability and improves coating workability, etc. Can be made.

It is preferable that the ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling further comprises 0.1 to 10% by mass of the mercaptan compound (D) with respect to 100% by mass of the pressure-sensitive adhesive composition. It is one of the embodiments.
By containing 0.1 to 10% by mass of the mercaptan compound (D), it is possible to effectively suppress the inhibition of curing by oxygen and to effectively suppress the local excess of the crosslinking density by the chain transfer effect. The property can be further improved.
The effect of suppressing curing inhibition by oxygen is obtained by converting a peroxy radical having no polymerization activity formed by the combination of oxygen and a radical into a thiyl radical having a polymerization activity by extracting hydrogen from the mercaptan. The conformability improving effect is considered to be obtained by controlling the local high crosslink density during ionizing radiation curing by chain transfer using a mercapto group.
If the addition amount of the mercaptan compound is less than 0.1% by mass, the effect of addition may not be obtained, and if it exceeds 10% by mass, the curability may be lowered.

The content of the mercaptan compound (D) is preferably 0.1 to 9% by mass when the acrylic polymer (A) is 100% by mass. The addition amount of the mercaptan compound is more preferably 0.1 to 8% by mass with respect to 100% by mass of the polymer, and further preferably 0.1 to 7% by mass with respect to 100% by mass of the polymer.
The addition amount of the mercaptan compound (D) is an amount including the residue of the mercaptan chain transfer agent added in the polymerization step for obtaining the acrylic polymer (A).

The mercaptan compound is a compound having at least one mercapto group.
Examples of mercaptan compounds include monofunctional mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, octyl thioglycolate, β-mercaptopropionic acid, octyl β-mercaptopropionic acid; 1,4-butane Diol dithioglycolate, 1,4-butanediol di (β-mercaptopropionate), trimethylolpropane tristhioglycolate, trimethylolpropane tris (β-mercaptopropionate), pentaerythritol tetrakisthioglycolate, penta Erythritol tetrakis (β-mercaptopropionate), dipentaerythritol hexakispentaerythritol tetrakisthioglycolate, dipentaerythritol hexakispentaerythritol Multifunctional mercaptans such as trakis (β-mercaptopropionate) are exemplified. From the viewpoint of volatility and odor, polyfunctional mercaptans are preferable.
Polyfunctional mercaptans are compounds having two or more mercapto groups per molecule.

The ionizing radiation-curable re-peeling pressure-sensitive adhesive composition of the present invention further includes an inorganic filler, a non-reactive resin (for example, an acrylic polymer, polyester, polyurethane, polystyrene, polyvinyl chloride, etc.) as an additive, if necessary. ), Coloring pigments, plasticizers, UV absorbers, antioxidants, matting agents, dyes, antifoaming agents, leveling agents, antistatic agents, dispersants, slip agents, surface modifiers, tackifiers, etc. Can be used. Moreover, these additives may be used independently and may use 2 or more types together.

The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling of the present invention is a functional group possessed by an acrylic polymer (A) such as an isocyanate compound or an epoxy compound for reasons such as improving the adhesion between the substrate and the adhesive layer. A crosslinking agent capable of reacting with can be used in combination.
Examples of the isocyanate-containing compound include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate. Diisocyanate compounds such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; Burette polyisocyanate compounds such as “Sumijoule N” (manufactured by Sumitomo Bayer Urethane Co., Ltd.); G. Co., Ltd.), “Coronate EH” (manufactured by Nippon Polyurethane Industry Co., Ltd.), and other polyisocyanates having an isocyanurate ring Nate compounds; adduct polyisocyanate compounds such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.); polyisocyanate compounds such as “deyuranate D201” (manufactured by Asahi Kasei Co., Ltd.), and the like. These can be used alone or in combination of two or more.

Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A type epoxy resin, N, N, N ′, N′-tetraglycidyl-m-xylene. Examples include diamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine, and the like.
The content of these isocyanate compounds and epoxy compounds is preferably 0.5% by mass or less when the acrylic polymer (A) is 100% by mass. More preferably, it is 0.4 mass% or less, More preferably, it is 0.3 mass% or less. When the addition amount of the isocyanate compound or the epoxy compound exceeds the above range, the conformability may be lowered.

The ionizing radiation-curable re-peelable pressure-sensitive adhesive composition is suitable for uses such as a pressure-sensitive adhesive film that protects an optical member that the obtained pressure-sensitive adhesive sheet (pressure-sensitive adhesive film) has the following physical properties, It can be said that this is a preferred embodiment in the present invention. In order to express such physical properties, it is possible to achieve by adopting the configuration of the present invention described above and adopting a preferable form as appropriate.
That is, it is preferable that the obtained adhesive sheet (adhesive film) has a low-speed adhesive strength of 0.1 N / 25 mm or more. When the low-speed adhesive force is 0.1 N / 25 mm or more, peeling during the process, floating during autoclave treatment, and the like can be further suppressed. In addition, in this specification, a low-speed adhesive force means the adhesive force at the time of peeling 180 degree | times at peeling speed 0.3m / min, and is a value obtained by the below-mentioned measuring method.
More preferably, the low-speed adhesive strength is 0.12 N / 25 mm or more. More preferably, it is 0.15 N / 25 mm or more, Especially preferably, it is 0.17 N / 25 mm or more, Most preferably, it is 0.20 N / 25 mm or more.

From the viewpoint of reducing damage to the adherend during peeling, the ionizing radiation curable re-peeling pressure-sensitive adhesive composition requires a force required to peel the pressure-sensitive adhesive sheet from the adherend at high speed, that is, high-speed adhesive. It is preferable that the force is sufficiently low. Specifically, it is preferably 2.0 N / 25 mm or less. In addition, in this specification, high-speed adhesive force means the adhesive force at the time of 180 degree peeling at the peeling speed of 30 m / min, and is a value obtained by the measurement method mentioned later.
More preferably, the high-speed adhesive strength is 1.7 N / 25 mm or less. More preferably, it is 1.5 N / 25 mm or less, Most preferably, it is 1.2 N / 25 mm or less, Most preferably, it is 1.0 N / 25 mm or less.

The low-speed adhesive force and the high-speed adhesive force are obtained by applying an adhesive sheet obtained by applying the composition of the present invention to a PET film having a thickness of 38 μm so that the paste thickness after drying is 20 μm and curing the adhesive sheet on a PMMA plate. It is preferable to measure using the attached one. In this case, the sample for measurement is obtained, for example, by cutting the cured adhesive sheet into a size of 25 mm × 150 mm, affixing it to a PMMA plate (manufactured by Engineering Test Service), and pressing it once with a 2 kg roller. .
The low-speed adhesive force is obtained by measuring the adhesive force when peeled in the 180 ° direction at a peeling speed of 0.3 m / min after 1 hour of pressure bonding. Moreover, a high-speed adhesive force is obtained by measuring the adhesive force when peeled in the 180 ° direction at a peeling speed of 30 m / min after 1 hour of pressure bonding.

It is preferable that the pressure-sensitive adhesive sheet (pressure-sensitive adhesive film) obtained by curing the ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling of the present invention satisfies both the low-speed pressure-sensitive adhesive force and the high-speed pressure-sensitive adhesive force.
That is, the pressure-sensitive adhesive sheet obtained by curing the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling is attached to an adherend, and has a pressure-sensitive adhesive strength of 0.1 N / min when peeled 180 ° at 0.3 m / min. It is one of the preferred embodiments of the present invention that the adhesive strength when it is 25 mm or more and peeled 180 ° at 30 m / min is 1.5 N / 25 mm or less.

In the ionizing radiation curable re-peeling pressure-sensitive adhesive composition, the value obtained by dividing the low-speed adhesive force by the high-speed adhesive force (hereinafter, this value is referred to as peeling rate dependency) is preferably 15 or less. As a result, the low-speed adhesive force with respect to the high-speed adhesive force becomes relatively large enough to exhibit sufficient performance as a protective film.
The peeling rate dependency is preferably 14 or less. More preferably, it is 13 or less, More preferably, it is 12 or less, Most preferably, it is 11 or less. Most preferably, it is 10 or less.

A pressure-sensitive adhesive sheet obtained by curing the ionizing radiation-curable re-peelable pressure-sensitive adhesive composition is cut into an area of 40 mm × 40 mm, and has an uneven height difference of 0.1 to 10 μm on an adherend. One of the preferred embodiments of the present invention is that the time required for the entire surface to get wet after starting standing (hereinafter referred to as the wet time) is within 180 seconds.
If the wetting time is in the above range, it can be said that the conformability is excellent, and the adhesive film can be peeled off more efficiently, and the productivity is excellent. In order to express such physical properties, it is possible to achieve by adopting the configuration of the present invention described above and adopting a preferable form as appropriate.

The wetting time is preferably within 150 seconds. More preferably, it is within 120 seconds, still more preferably within 90 seconds, and particularly preferably within 60 seconds.

The wetting time is a value calculated under the following measurement conditions.
As an adherend having a fine uneven surface, an anti-glare film (trade name “BOF-H141S”, a liquid crystal protective film manufactured by BUFFALO) having an uneven height difference of 5.7 μm and a surface roughness (Ra) of 0.31 μm is used. An adhesive film obtained by applying the composition of the present invention to a PET film having a thickness of 38 μm so as to have a paste thickness after drying of 20 μm and curing the composition (used for the measurement of the low-speed adhesive force and the high-speed adhesive force). The same sample) was cut into a size of 40 mm × 40 mm and placed gently with the adhesive side down. Then, the time required for the entire surface of the sample to get wet (accommodate) is measured after the adhesive film starts to get wet with the anti-glare treatment film (after it starts to adapt).
Then, the laminated body of this invention, an adhesive film, an adhesive film roll, and an optical member are demonstrated.

This invention is also a laminated body obtained by apply | coating the said ionizing radiation-curable adhesive composition for re-peeling to a base material, and making it harden | cure by ionizing radiation irradiation.
The laminate preferably includes a support such as a film imparted with hard coat performance and a surface protective film for optical members. A hard coat is a coating film excellent in abrasion resistance obtained by irradiating a liquid coating film applied on an upper layer of a resin (base material) such as a film with ultraviolet rays or an electron beam. The surface protective film for optical members is a film that protects a base material from factors such as scratches and contamination on optical members and films (polarizing plates, antireflection films, etc.) used for liquid crystal display panels.

The thickness after curing of the pressure-sensitive adhesive composition for ionizing radiation curable re-peeling of the present invention is usually 0.5 to 500 μm. Preferably, it coats so that it may become 1-300 micrometers, more preferably 3-200 micrometers. Particularly when used as an adhesive, a thickness of 5 to 50 μm is preferred. Assuming that the ionizing radiation-curable adhesive composition for re-peeling used in the present invention is used for pressure-sensitive adhesives, the coating liquid reacts when a non-reactive diluent such as an organic solvent is not contained. The coating thickness of the pressure-sensitive adhesive composition for ionizing radiation curable re-peeling and after curing is not a significant decrease in thickness due to electron beam curing. The thickness of the resin layer is almost the same.

As a method for applying the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling onto a support, a conventional coating method can be employed. For example, the method of apply | coating using a roll coater, a die coater, a bar coater, a knife coater, a gravure coater, a Mayer bar coater etc. is mentioned.
The laminate of the present invention is usually formed by applying the pressure-sensitive adhesive layer on one side or both sides of various supports made of a plastic film such as a polyester film, a porous material such as paper and nonwoven fabric, and the like. Or in the form of a tape. The thickness of the support constituting the pressure-sensitive adhesive film using the ionizing radiation-curable releasable pressure-sensitive adhesive composition of the present invention is usually 5 to 200 μm, preferably 10 to 100 μm.

Known release agents used for the support include silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based. Also, anti-static treatment such as mold release and antifouling treatment with silica powder, acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, UV treatment, etc., coating type, kneading type, vapor deposition type, etc. It can also be processed.
Moreover, it is preferable that the said support body is a plastic base material which has heat resistance and solvent resistance, and has flexibility. When the support is flexible, the pressure-sensitive adhesive composition can be applied by a roll coater or the like, and can be wound into a roll.
The plastic substrate may be any material that can be formed into a sheet or film, for example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, an ethylene / propylene copolymer, Polyolefin films such as ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer, polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate Film, polyacrylate film, polystyrene film, nylon 6, nylon 6,6, polyamide film such as partially aromatic polyamide, polyvinyl chloride film, polyvinylidene chloride film, polycarbonate film, etc. It is.

As the plastic substrate having heat resistance and solvent resistance and flexibility, in addition to those described above, for example, a polymer having a hydroxyl group and an ester group in a molecular chain is subjected to a lactone cyclocondensation reaction. A lactone ring-containing polymer represented by the following general formula (3) is known. In addition, the thermoplastic resin containing the lactone ring-containing polymer as a main component is excellent in optical properties such as transparency and optical isotropy and heat resistance, and is an optical planar thermoplastic resin molded body (sheet, film, etc.). And can be suitably used as a support for the ionizing radiation-curable adhesive composition for re-peeling.
The lactone ring-containing polymer is the following general formula (3);

(Wherein R ⁴ , R ⁵ and R ⁶ are the same or different and represent a hydrogen atom or an organic group having 1 to 20 carbon atoms). Note that R ⁴ , R ⁵ and R ⁶ may contain an oxygen atom.

This invention is also an adhesive film comprised by the said laminated body.
The pressure-sensitive adhesive film composed of the laminate of the present invention has a sufficiently low peel rate dependency, and can be suitably used for various substrates as a re-peelable surface protective film. As said base material, it can use with respect to products, such as an optical member, a metal plate, a glass plate, a plastic plate, a resin coating copper plate, a window glass, furniture, a car, for example. Among these, it is preferable to use for an optical member.
The pressure-sensitive adhesive film is coated with a known release agent on the back of the support and wound into a roll (so-called separator-free), or a known release agent is coated on the exposed surface of the formed radiation-cured pressure-sensitive adhesive layer. It may be covered with a separator and wound into a roll.

Furthermore, this invention is an adhesive film roll comprised by the said laminated body, Comprising: The said adhesive film roll is also an adhesive film roll wound without interposing a separator.
The pressure-sensitive adhesive film constituted by the laminate of the present invention has a sufficiently low release rate dependency, and is particularly preferably a separator-free film roll. In the surface protection film application, the form of winding in a roll-free manner with a separator free is preferable because it reduces cost and eliminates the disposal of the separated separator, and thus does not adversely affect the environment and enables efficient industrial production.

The pressure-sensitive adhesive film roll is a step of coating a base film with an ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling, and a step of crosslinking the ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling by irradiation with ultraviolet rays or radiation. And it is preferable that it is a thing obtained by the manufacturing method including the process wound up in roll shape without interposing a separator between the adhesive layer after bridge | crosslinking, and a support body back surface.
Such a method for producing an adhesive film roll is also one aspect of the present invention.

The present invention is further a surface protective film constituted by the pressure-sensitive adhesive film, and the surface protective film is also a surface protective film used for an adherend having a surface unevenness height difference of 0.1 to 10 μm.
The uneven height difference is a numerical value represented by a ten-point average roughness (Rz) measured according to JIS B0601. The adherend preferably has a surface unevenness height difference of 1.0 to 9.0 μm. More preferably, it is 2.0-8.0 micrometers.
When the surface protective film of the present invention is used for such an adherend, the effect of achieving both low adhesiveness and conformability during high-speed peeling is further exhibited.

The present invention is further a surface protective film constituted by the pressure-sensitive adhesive film, and the surface protective film is also a surface protective film used for an optical member subjected to antiglare treatment.
Anti-glare treatment performed on optical members includes, for example, a method of scattering fine light by spraying fine powder of silica on the surface of a liquid crystal display device, etc., inorganic filler such as silica, melamine, acrylic, etc. A method of coating a resin solution containing an organic filler made of plastic beads and forming fine irregularities on the surface by drying the solvent to scatter light, and a transparent thin film on the surface of a liquid crystal display device, etc. And AR coating that generates light interference (cancels outside light). Among these, for example, it is particularly preferable to use the surface protective film of the present invention for an optical member that has been antiglare-treated by a method of applying an inorganic or organic filler-containing resin solution. Moreover, it is preferable that the unevenness height difference of the surface of the optical member subjected to the antiglare treatment is the same as the unevenness height difference of the adherend. Furthermore, the optical member is preferably a polarizing plate.
When the surface protective film of the present invention is used for an optical member having such a form, the effect of achieving both low adhesiveness and conformability during high-speed peeling will be exhibited more remarkably.
In addition, it is preferable that the surface protection film of this invention is comprised using the adhesive film roll of this invention. As a result, advantageous effects such as more efficient surface protection of the adherend such as an optical member can be exhibited.

The present invention is also an optical member formed by attaching the above adhesive film.
As said optical member, optical films, such as a polarizing plate, a phase difference plate, a brightness improvement film which comprise a liquid crystal display, an AR film which comprises a plasma display, an electromagnetic wave shield film, IR cut film, etc. are mentioned, for example. An optical member having a fine uneven surface is particularly suitable.

The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling according to the present invention and the use thereof are composed of the above-described constitution, and are a pressure-sensitive adhesive film that protects an optical member with both low-tackiness and conformability at high speed peeling at a high level. Etc., which can be suitably used.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.

In the following examples and comparative examples, the measurement was performed by the following method.
[Adaptability to fine uneven surface]
As an adherend having a fine uneven surface, an anti-glare film (trade name “BOF-H141S”, a liquid crystal protective film manufactured by BUFFALO) having an uneven height difference of 5.7 μm and a surface roughness (Ra) of 0.31 μm is used. Then, an adhesive film cut into a size of 40 mm × 40 mm was gently placed with the adhesive side down. Then, the time required for the entire surface of the sample to get wet (accommodate) was measured after the adhesive film began to get wet with the anti-glare treatment film (after it started to adapt).

[Synthesis Example 1]
Polymerization example of acrylic polymer (resin A1)
In a reactor equipped with a thermometer, a cooler, a nitrogen gas inlet tube, and a stirrer, 143.85 parts of 2-ethylhexyl acrylate, 63 parts of butyl acrylate, 3.2 parts of 2-hydroxyethyl methacrylate, n- as a chain transfer agent After charging 0.21 part of dodecyl mercaptan and 280.6 parts of ethyl acetate as a solvent, the reactor was replaced with nitrogen gas. Next, the internal temperature was raised to 85 ° C. while stirring the above mixture, and then 2,2′-azobis- (2-methylbutyronitrile) (trade name “ABN-E”; Japan as a polymerization initiator. The reaction was started by adding 0.175 parts (manufactured by Hydrazine Kogyo Co., Ltd.) and 3.15 parts ethyl acetate as a solvent. 10 minutes after the start of polymerization, a mixture of 335.65 parts of 2-ethylhexyl acrylate, 147 parts of butyl acrylate, 7.35 parts of 2-hydroxyethyl methacrylate, and 0.49 part of n-dodecyl mercaptan as a chain transfer agent was added from the dropping funnel to 60. It was added dropwise over a period of minutes. Further, 0.175 part of ABN-E as a polymerization initiator and 14 parts of ethyl acetate as a solvent were similarly dropped from another dropping funnel. After completion of dropping, 119 parts of ethyl acetate was added to the reactor while washing the dropping funnel. Then, after making it react at reflux temperature for 5 hours, it diluted with 105 parts of ethyl acetate, and obtained the solution of the acrylic polymer (resin A1) whose non volatile matter density | concentration 53.9% and weight average molecular weight 210,000.

[Synthesis Examples 2 to 6]
Polymerization example of acrylic polymer (resins A2 to A6)
Except having changed the monomer composition into the ratio of Table 1, operation similar to resin A1 was performed and resin A2-A5 was obtained. Table 1 shows the non-volatile concentration and the weight average molecular weight of the resins A2 to A5.

In Table 1 above, abbreviations indicate the following.
2EHA: 2-ethylhexyl acrylate BA: butyl acrylate INA: isononyl acrylate HEMA: 2-hydroxyethyl methacrylate HEA: 2-hydroxyethyl acrylate

[Synthesis Example 7]
Production example of acrylic polymer having unsaturated double bond in side chain (resin B1)
In a reactor equipped with a thermometer, a cooler, a nitrogen gas inlet tube, and a stirrer, 100 parts of the resin A1 solution in terms of solid content and 2,2′-methylenebis (4-methyl-6-t-) as a polymerization inhibitor Butylphenol) (trade name “ANTAGE W-400”; manufactured by Kawaguchi Chemical Co., Ltd.) 0.06 part, 2-acryloyloxyethyl isocyanate (trade name “Karenz AOI”; manufactured by Showa Denko Co., Ltd.) 0.18 part, and nitrogen was added. Stirring was performed while bubbling a mixed gas of / air = 2/1, and the internal temperature was raised to 70 ° C. Thereafter, 0.04 part of dibutyltin dilaurate was added as a catalyst and reacted at 70 ° C. for 3 hours. Then, disappearance of the 2273 cm ⁻¹ peak derived from the isocyanate group was confirmed by FT-IR analysis. An acrylic polymer (resin B1) having an unsaturated double bond of .013 mmol / g was obtained.

[Synthesis Examples 8 to 12]
Example of production of acrylic polymer having unsaturated double bond in side chain (resins B2 to B6)
Resins B2 to B6 were obtained in the same manner as in resin B1 except that the acrylic polymer and the amount of Karenz AOI used were changed as shown in Table 2. Table 2 shows the amount of unsaturated double bonds introduced and the weight average molecular weight of resins B1 to B6. In addition, DBTDL of the following Table 2 represents dibutyltin dilaurate.

Example 1
23.5 parts of trimethylolpropane triacrylate, 2.5 parts of benzophenone as a photoinitiator, and pentaerythritol tetrakis (β-mercaptopropionate) as a mercaptan with respect to 100 parts (in terms of solid content) of the adhesive resin A1 : PEMP; manufactured by Sakai Chemical Industry Co., Ltd.) 1.2 parts was added to obtain a UV curable adhesive composition.
This pressure-sensitive adhesive composition was applied to a PET film having a thickness of 38 μm with an applicator so that the paste thickness after drying was 20 μm, and was dried in a hot air circulating oven at 80 ° C. for 3 minutes. Next, this dried product was irradiated with UV under a condition of a peak illuminance of 168 mW / cm ² and an irradiation amount of 100 mJ / cm ² with a UV irradiator having a high-pressure mercury lamp, to prepare a UV curable pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet obtained in Example 1 was evaluated by the following evaluation method.
[Measurement method of low-speed adhesive strength]
The cured pressure-sensitive adhesive sheet was cut into a size of 25 mm × 150 mm, attached to a PMMA plate (manufactured by Engineering Test Service Co., Ltd.), and pressed once and reciprocally with a 2 kg roller. One hour after the pressure bonding, the adhesive strength when peeled in the 180 ° direction at a peeling speed of 0.3 m / min was measured. The low-speed adhesive force is preferably high from the viewpoint of suppressing peeling during the process and floating during autoclaving, and specifically 0.1 N / 25 mm or more.

[High-speed adhesive strength measurement method]
The cured pressure-sensitive adhesive sheet was cut into a size of 25 mm × 150 mm, attached to a PMMA plate (manufactured by Engineering Test Service Co., Ltd.), and pressed once and reciprocally with a 2 kg roller. One hour after the pressure bonding, the adhesive strength when peeled in the 180 ° direction at a peeling speed of 30 m / min was measured. The high-speed adhesive force is preferably as low as possible from the viewpoint of reducing damage to the adherend during peeling, and specifically, it is preferably 1.5 N / 25 mm or less.

[Peeling speed dependence]
The peeling speed dependency is obtained by dividing the above high-speed adhesive force by the low-speed adhesive force, but it is desirable to increase the low-speed adhesive force and reduce the high-speed adhesive force, so that it is preferably as small as possible. Specifically, it can be said that the peeling rate dependency is preferably 10 or less.

[Adaptability to fine uneven surface]
As an adherend having a fine uneven surface, ten-point average roughness (Rz) 6.74 μm, arithmetic average roughness (Ra) 0.31 μm (Keyence laser microscope VK-9710 was used, in accordance with JIS B0601. Measurement) is an anti-glare treatment film (trade name “BOF-H141S”, a liquid crystal protective film manufactured by BUFFALO), and the adhesive sheet is cut into a size of 40 mm × 40 mm. Put it on. And after the adhesive sheet began to get wet with the anti-glare film (after it started to fit), the time required for the entire surface of the sample to get wet (fit) was measured and judged according to the following criteria.
Judgment Criteria ◎: The entire surface is adapted within 60 seconds. ○: The entire surface is adapted within 60 to 180 seconds. X: The entire surface is adapted to exceed 180 seconds.

Examples 2 to 22 and Comparative Examples 3 to 6
A UV-curable pressure-sensitive adhesive sheet was prepared by performing the same operation as in Example 1 except that the pressure-sensitive adhesive resin, polyfunctional monomer, monofunctional monomer, photoinitiator, and mercaptan were changed as shown in Table 3. And the low speed adhesive force measuring method, the high speed adhesive force measuring method, the peeling rate dependence, and the conformability to a fine uneven surface were measured by the same evaluation method as Example 1.

Comparative Examples 1-2
To the adhesive resin A6, “Deyuranate D-201” (produced by Asahi Kasei Co., Ltd.), which is an isocyanate crosslinking agent, and dibutyltin dilaurate, which is a curing catalyst, are added at a blending ratio shown in Table 3 to obtain an isocyanate curable adhesive composition. It was.
This pressure-sensitive adhesive composition was applied to a PET film having a thickness of 38 μm with an applicator so that the paste thickness after drying was 20 μm, and was dried in a hot air circulating oven at 80 ° C. for 3 minutes. Next, this dried product was cured for 1 week under the conditions of 23 ° C. and 65% RH to prepare an isocyanate curable pressure-sensitive adhesive sheet.

Reference Examples 23-27
Trimethylolpropane triacrylate and mercaptan were added at a blending ratio shown in Table 3 to 100 parts of the adhesive resin B3 (in terms of solid content) to obtain an EB curable adhesive composition.
This pressure-sensitive adhesive composition was applied to a PET film having a thickness of 38 μm with an applicator so that the paste thickness after drying was 20 μm, and was dried in a hot air circulating oven at 80 ° C. for 3 minutes. Subsequently, this dried product was irradiated with EB under the conditions of an acceleration voltage of 130 kV and an irradiation dose of 60 kGy with an EB irradiator to prepare an EB curable pressure-sensitive adhesive sheet.
The results of these Examples , Reference Examples and Comparative Examples are shown in Table 3 and Table 4 below.

In Table 3 and Table 4, abbreviations indicate the following.
A-TMPT: trimethylolpropane triacrylate EHDG: 2-ethylhexyl-diglycol acrylate BP: benzophenone MBB: O-benzoylbenzoic acid 4-ClBP: 4-chlorobenzophenone DETX-S: 2,4-diethylthioxanthone IRG184: Irgacure 184 (1-hydroxycyclohexyl phenyl ketone)
IRG651: Irgacure 651 (2,2-dimethoxy-1,2-diphenylmethane-1-one)
IRG819: Irgacure 819 [bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide]
PEMP: Pentaerythritol tetrakis (β-mercaptopropionate)
n-DM: n-dodecyl mercaptan TMMP: trimethylolpropane tris (β-mercaptopropionate)
A-HD: 1,6-hexanediol diacrylate A-NOD: 1,9-nonanediol diacrylate

From the above Examples , Reference Examples and Comparative Examples, it was found that the following can be said.
The UV curable pressure-sensitive adhesive sheet of Example 1 satisfies a low-speed adhesive strength of 0.1 N / 25 mm or more, a high-speed adhesive strength of 1.5 N / 25 mm or less, a peeling rate dependency of 10 or less, and a conformability to fine uneven surfaces. Thus, it can be seen that the pressure-sensitive adhesive sheet has both high-speed peelability and conformability.
On the other hand, Comparative Example 1 is an isocyanate-curing type pressure-sensitive adhesive sheet. Although the conformability is acceptable, the high-speed adhesive strength exceeds 1.5 N / 25 mm, and both the high-speed peelability and the conformability cannot be achieved. In Comparative Example 2 in which the addition amount of the isocyanate crosslinking agent was further increased in order to lower the high-speed adhesive force, the high-speed adhesive force managed to satisfy 1.5 N / 25 mm. Are not compatible.

In Examples 1 to 6 and Comparative Example 3, the double bond introduction amount of the UV curable pressure-sensitive adhesive resin was changed stepwise from 0 to 0.300 mmol / g. By reducing the amount of polyfunctional monomer as the amount of double bonds increases, the adhesive resin with a double bond introduction amount of 0 to 0.200 mmol / g has low speed, high speed adhesive force and compatibility with fine uneven surfaces. It becomes a compatible adhesive sheet. On the other hand, if the double bond introduction amount is too large, 0.300 mmol / g, it becomes impossible to achieve both high-speed adhesive force and conformability.

Moreover, Examples 7-9 and Comparative Example 4 are the results of changing the monomer composition of the UV curable adhesive resin. In Examples 7 to 9 containing 50 mass% or more of an alkyl acrylate having 9 to 14 carbon atoms in the alkyl group, both high-speed peelability and compatibility with fine uneven surfaces can be achieved. In Comparative Example 4 in which the amount of alkyl ester of 9 to 14 is less than 50% by mass, both high-speed peelability and compatibility with fine uneven surfaces cannot be achieved.

Examples 10 to 13 are results showing the effect of adding mercaptans to the UV curable pressure-sensitive adhesive composition. In Example 10 which does not contain a mercaptan, both high-speed peelability and compatibility with fine uneven surfaces can be achieved, but in Examples 11 to 13 to which mercaptan is added, the compatibility is greatly improved.

Furthermore, Examples 14 and 15 are the results of using a trifunctional monomer and a bifunctional monomer in combination as the polyfunctional monomer of the UV curable adhesive composition. Thus, even when a functional monomer and a bifunctional monomer are used in combination, high-speed peelability and compatibility with a fine uneven surface can be achieved.

Examples 16 to 19 and Comparative Examples 5 and 6 were carried out by changing the type of photoinitiator of the UV curable adhesive composition. In Examples 16 to 19 using a hydrogen abstraction type initiator, both high-speed peelability and compatibility with a fine uneven surface are compatible, but in Comparative Examples 5 and 6 using a self-cleavage type initiator, high-speed adhesion is achieved. Although the power is high, the conformability deteriorates, indicating that the crosslinking efficiency is poor.

Examples 20 and 21 are the results of blending UV curable adhesive resin with and without an introduced double bond. It can be seen that even when blended in this way, both high-speed peelability and compatibility with fine uneven surfaces can be achieved.

Example 22 is the result of the combined use of a monofunctional monomer of the UV curable pressure-sensitive adhesive composition. When the irradiation amount is small, unreacted monofunctional monomer tends to remain, but the residual monomer can be reduced by using a small amount of a self-cleaving initiator. Further, even when a monofunctional monomer and a self-cleaving initiator are used in combination, high-speed peelability and compatibility with fine uneven surfaces can be achieved.

Reference Examples 23 to 27 are results of the EB curable pressure-sensitive adhesive composition. As with UV curable adhesive compositions, both high-speed peelability and compatibility with fine uneven surfaces can be achieved, and it is possible to further reduce high-speed adhesive strength while maintaining high compatibility. . This is probably because EB curing has better crosslinking efficiency than UV curing.

Claims (10)

An ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling containing 1 to 50% by mass of the polyfunctional monomer (B) with respect to 100% by mass of the acrylic polymer (A),
The acrylic polymer (A) is obtained by polymerizing a monomer component essentially comprising an alkyl acrylate ester having 8 to 14 carbon atoms in the alkyl group, and has zero side chain unsaturated bonds. A side chain unsaturated bond-containing polymer of ˜0.200 mmol / g,
The monomer component is a single monomer having 50 to 100% by mass of an alkyl acrylate ester having 8 to 14 carbon atoms in the alkyl group and a hydroxyl group and / or a carboxyl group, assuming that the total amount of the monomer is 100% by mass. body 0 to 10% by weight, as well as, other vinyl monomer is Ri 0-50% by mass,
The ionizing radiation-curable releasable pressure-sensitive adhesive composition further comprises a hydrogen abstraction type photopolymerization initiator (C) and is cured by irradiation with ultraviolet rays, and is based on 100% by mass of the pressure-sensitive adhesive composition. An ionizing radiation-curable pressure-sensitive adhesive composition for re-peeling comprising 0.1 to 10% by mass of a mercaptan compound (D) . The ionizing radiation-curable releasable pressure-sensitive adhesive composition according to claim 1, wherein the ionizing radiation-curable releasable pressure-sensitive adhesive composition is cured by electron beam irradiation. The pressure-sensitive adhesive composition for re-peeling ionizing radiation curable adhesive sheet obtained by curing the pressure-sensitive adhesive composition for re-peeling ionizing radiation is attached to an adherend, and 180 ° at 0.3 m / min. adhesion at the time of peeling is at 0.1 N / 25 mm or more, and, 30 m / adhesive force when the 180 ° peel at a minute to claim 1 or 2, characterized in that not more than 2.0 N / 25 mm The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling described. The pressure-sensitive adhesive composition for ionizing radiation curable re-peeling is a pressure-sensitive adhesive sheet obtained by curing a pressure-sensitive adhesive composition for ionizing radiation-curable re-peeling, and has an uneven height difference of 0.1 to 10 μm on the surface. 4. The ionizing radiation curable releasable pressure-sensitive adhesive according to any one of claims 1 to 3 , wherein the time required for the entire surface to become wet from the beginning of wetting when left on the body is within 180 seconds. Composition. A laminate obtained by applying the ionizing radiation curable pressure-sensitive adhesive composition for re-peeling according to any one of claims 1 to 4 to a substrate and curing it by irradiation with ionizing radiation. An adhesive film comprising the laminate according to claim 5 . It is an adhesive film roll comprised by the laminated body of Claim 5 , Comprising: This adhesive film roll was wound without interposing a separator, The adhesive film roll characterized by the above-mentioned. It is a surface protection film comprised by the adhesive film of Claim 6 , Comprising:
The surface protective film is used for an adherend having a surface unevenness height difference of 0.1 to 10 μm. It is a surface protection film comprised by the adhesive film of Claim 6 , Comprising:
The surface protective film is used for an antiglare-processed optical member. An optical member comprising the adhesive film according to claim 6 attached thereto.