JP5518370B2 - Method for producing water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, water-dispersed acrylic pressure-sensitive adhesive composition for re-peeling, pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to a method for producing a water-dispersed acrylic pressure-sensitive adhesive composition that can form a re-peelable pressure-sensitive adhesive layer. Specifically, a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling that can form a pressure-sensitive adhesive layer that is excellent in appearance characteristics without appearance defects such as dents, and that has excellent deterrence or prevention of an increase in adhesive strength over time. It relates to the manufacturing method. Moreover, it is related with the water-dispersed acrylic adhesive composition for re-peeling obtained by this manufacturing method. Furthermore, it is related with the adhesive layer which consists of this adhesive composition, and the adhesive sheet which has this adhesive layer.

  In the manufacturing and processing processes of optical members (optical materials) including optical films such as polarizing plates, retardation plates, and antireflection plates, for the purpose of surface scratches, dirt prevention, cutting workability improvement, crack suppression, etc. A surface protective film is used by being attached to the surface of an optical member (see Patent Documents 1 and 2). As these surface protective films, a removable pressure-sensitive adhesive sheet in which a removable pressure-sensitive adhesive layer is provided on the surface of a plastic film substrate is generally used.

  Conventionally, solvent-type acrylic pressure-sensitive adhesives have been used for these surface protective film applications (see Patent Documents 1 and 2). However, since these solvent-type acrylic pressure-sensitive adhesives are synthesized in an organic solvent, they are coated. Volatilization of the solvent during construction is an environmental problem, and conversion to a water-dispersed acrylic pressure-sensitive adhesive has been attempted (see Patent Documents 3 to 5).

  These surface protective films are required to exhibit sufficient adhesiveness while being attached to the optical member. Furthermore, since it peels after using in the manufacturing process of an optical member, etc., the outstanding peelability (removability) is calculated | required. In addition, in order to have excellent removability, in addition to having a small peel force (light peel), the adhesive strength (peel force) does not increase over time after being attached to an adherend such as an optical member ( Adhesive strength prevention property) is required.

  In order to obtain characteristics such as light peeling and prevention of increase in adhesive strength, it is effective to use a water-insoluble crosslinking agent for the adhesive (or adhesive composition). As a pressure-sensitive adhesive composition using a water-insoluble crosslinking agent, for example, a re-peeling water-dispersed acrylic pressure-sensitive adhesive composition containing an oil-soluble crosslinking agent is known (see Patent Documents 6 and 7).

  However, like the above-mentioned pressure-sensitive adhesive composition, the water-dispersed acrylic pressure-sensitive adhesive composition using a water-insoluble crosslinking agent does not sufficiently disperse large particles of the water-insoluble crosslinking agent in the pressure-sensitive adhesive composition. Due to this, when forming the pressure-sensitive adhesive layer, appearance defects such as “dents” are likely to occur on the surface of the pressure-sensitive adhesive layer. For this reason, especially when using as an adhesive layer etc. of a surface protection film, the problem that it becomes difficult to carry out the test | inspection of a to-be-adhered body with the surface protection film affixed may arise.

  Therefore, it is excellent in adhesiveness and removability (especially, prevention of increase in adhesive strength), and is a removable water-dispersible acrylic that can form a pressure-sensitive adhesive layer with excellent appearance characteristics such as “dents” that do not cause poor appearance. The present condition is that the adhesive is not obtained.

  Furthermore, in surface protective film applications (especially for optical member surface protective film applications), adhesive residue (so-called “glue residue”) remains on the surface of the adherend (optical member, etc.) when the adhesive sheet is peeled off. Contamination of the adherend surface due to transfer of components contained in the adhesive layer to the adherend surface causes problems such as an adverse effect on the optical characteristics of the optical member. For this reason, the low adhesiveness with respect to a to-be-adhered body is strongly calculated | required by the adhesive and the adhesive layer.

Japanese Patent Laid-Open No. 11-961 JP 2001-64607 A JP 2001-131512 A JP 2003-27026 A Japanese Patent No. 3810490 JP 2004-91563 A JP 2006-169596 A

  An object of the present invention is a pressure-sensitive adhesive layer that can be re-peeled, and is particularly excellent in the ability to prevent an increase in adhesive strength over time, and also has excellent appearance characteristics (no appearance defects such as dents). Is to provide a method for producing a water-dispersed acrylic pressure-sensitive adhesive composition. Furthermore, another object of the present invention is to form a pressure-sensitive adhesive layer that is excellent in low contamination to the adherend, and particularly in prevention of whitening contamination (whitening contamination prevention) generated on the adherend in a high humidity environment. Another object of the present invention is to provide a method for producing a pressure-sensitive adhesive composition. Moreover, it is providing the adhesive composition obtained by this manufacturing method, the adhesive layer which consists of this adhesive composition, and the adhesive sheet which has this adhesive layer.

  As a result of intensive studies to achieve the above object, the inventors of the present invention mixed an acrylic emulsion polymer and a water-insoluble crosslinking agent at a specific ratio to obtain a mixed solution, and then added the mixed solution again. Adhesive with excellent anti-adhesiveness and appearance characteristics by mixing acrylic emulsion polymer so that acrylic emulsion polymer and water-insoluble crosslinking agent in the entire system have a specific blending ratio. It discovered that the water-dispersed acrylic adhesive composition which can form an agent layer was obtained, and completed this invention. Furthermore, by using an acrylic emulsion polymer polymerized with a reactive emulsifier, it is excellent in low contamination to the adherend, especially the occurrence of whitening contamination in a high humidity environment on the adherend. The present invention was completed by finding that a water-dispersed acrylic pressure-sensitive adhesive composition capable of forming an excellent pressure-sensitive adhesive layer that can be reduced is obtained.

That is, the present invention provides an acrylic emulsion comprising an aqueous dispersion of an acrylic emulsion polymer (A1) and a water-insoluble crosslinking agent (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule. After mixing the water-insoluble crosslinking agent (B) with respect to the polymer (A1) at a weight ratio [(B) / (A1)] (weight ratio) of 0.5 to 5 to obtain a mixed solution A method for producing a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, comprising mixing the mixed solution and an aqueous dispersion of an acrylic emulsion-based polymer (A2) having a carboxyl group, which is a water-insoluble crosslinking agent. (B) not more than the solubility of 5 parts by weight with respect to 100 parts by weight of water at 25 ° C., and the carboxyl group of the carboxyl group and the acrylic emulsion polymer (A2) having the acrylic emulsion polymer (A1) The ratio of the number of moles of the functional group capable of reacting with the carboxyl group of the water-insoluble crosslinking agent (B) to the total number of moles [functional group / carboxyl group capable of reacting with the carboxyl group] (molar ratio) is 0.5 to Water-removable acrylic adhesive for re-peeling, characterized by blending acrylic emulsion polymer (A1), acrylic emulsion polymer (A2) and water-insoluble crosslinking agent (B) at a ratio of 1.3 The manufacturing method of an agent composition is provided. [In the above, when (A1) does not have a carboxyl group, “the number of moles of the carboxyl group (A1)” is set to 0. ]

  Furthermore, the present invention is a polymer obtained by polymerizing an acrylic emulsion polymer (A1) and an acrylic emulsion polymer (A2) using a reactive emulsifier having a radical polymerizable functional group introduced in the molecule. A method for producing a re-peeling water-dispersed acrylic pressure-sensitive adhesive composition is provided.

  The present invention also provides a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling obtained by the above production method.

The present invention also relates to an adhesive layer formed from the above-mentioned water-dispersible acrylic adhesive composition for re-peeling, wherein the adhesive layer has an elongation at break of 200% or less. Providing an agent layer.
Elongation at break: It is determined by conducting a tensile test on a cylindrical pressure-sensitive adhesive layer sample having a length of 50 mm and a cross-sectional area of 1 mm ² under a tensile speed of 50 mm / min.

  Moreover, this invention provides the adhesive sheet which has the said adhesive layer on the at least single side | surface side of a base material.

Furthermore, this invention provides the said adhesive sheet which is a surface protection film for optical members.
Furthermore, this invention provides the optical member with which the said adhesive sheet is affixed.

  The pressure-sensitive adhesive composition obtained by the production method of the present invention is a water-dispersed type, and further comprises an acrylic emulsion polymer having a specific blending ratio and a water-insoluble crosslinking agent. Therefore, the pressure-sensitive adhesive composition formed from the pressure-sensitive adhesive composition The agent layer has excellent adhesion and removability. In particular, it is excellent in the prevention of an increase in adhesive strength with the adherend over time. Furthermore, since the production method of the present invention mixes the acrylic emulsion polymer and the water-insoluble cross-linking agent in a multi-stage at a specific ratio, the obtained pressure-sensitive adhesive composition is excellent in having no appearance defects such as dents. An adhesive layer having appearance characteristics can be formed. In addition, by using an acrylic emulsion polymer polymerized with a reactive emulsifier, it is possible to form a pressure-sensitive adhesive layer that is excellent in low contamination, particularly whitening contamination prevention when stored in a high humidity environment. An agent composition can be obtained. For this reason, the adhesive composition by the manufacturing method of this invention is especially useful as a surface protection use of an optical film.

  The present invention relates to an acrylic emulsion polymer (A1), an acrylic emulsion polymer (A2) having a carboxyl group, and a water-insoluble crosslinking agent (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule. ) Is an essential constituent component and is a method for producing a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling (hereinafter sometimes simply referred to as “pressure-sensitive adhesive composition”) (hereinafter simply referred to as “the production method of the present invention”). "). In the present specification, “acryl emulsion polymer (A1)” is simply “(A1)”, and “acryl emulsion polymer having carboxyl group (A2)” is simply “acryl emulsion polymer (A2)”. ) ”Or“ (A2) ”,“ water-insoluble crosslinking agent (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule ”simply“ water-insoluble crosslinking agent (B) ”or“ (B) ". Further, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition in the present invention may be simply referred to as “pressure-sensitive adhesive layer”, and the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer may be simply referred to as “pressure-sensitive adhesive sheet”.

  In the production method of the present invention, an aqueous dispersion of an acrylic emulsion polymer (A1) and a water-insoluble crosslinking agent (B) are added to the weight of the water-insoluble crosslinking agent (B) with respect to the acrylic emulsion polymer (A1). A first step of mixing at a ratio [(B) / (A1)] (weight ratio) of 0.5 to 5 to obtain a mixed solution (hereinafter sometimes simply referred to as “first step”); After the first step, the second step of mixing the mixed liquid obtained in the first step and the aqueous dispersion of the acrylic emulsion polymer (A2) (hereinafter sometimes simply referred to as “second step”). It is included as an essential process.

  In the production method of the present invention, the number of moles of the carboxyl group of the acrylic emulsion polymer (A1) [when (A1) does not have a carboxyl group, the number of moles of the carboxyl group of (A1)] is 0. And ] And the ratio of the number of moles of functional groups capable of reacting with the carboxyl group of the water-insoluble crosslinking agent (B) to the total number of moles of the carboxyl group of the acrylic emulsion polymer (A2) [with the carboxyl group and The acrylic emulsion polymer (A1), the acrylic emulsion polymer (A2), and the water-insoluble cross-linking agent (reactive functional group / carboxyl group) (molar ratio) are 0.5 to 1.3. B) is blended.

[Acrylic emulsion polymer (A1), Acrylic emulsion polymer (A2)]
The acrylic emulsion polymer (A2) in the production method of the present invention is an acrylic polymer having a carboxyl group in the molecule. The acrylic emulsion polymer (A1) is not particularly limited as long as it is an acrylic polymer, and may or may not have a carboxyl group in the molecule. When the acrylic emulsion polymer (A1) is an acrylic polymer having a carboxyl group in the molecule, the acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2) may be the same. Although they may be different, they are preferably the same from the viewpoint of production efficiency. In the following, the acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2) may be collectively referred to as “acrylic emulsion polymer (A)”.

  The acrylic emulsion polymer (A) [acrylic emulsion polymer (A1), acrylic emulsion polymer (A2)] in the production method of the present invention is a polymer polymerized by emulsion polymerization. When the acrylic emulsion polymer (A) has a carboxyl group, a protective layer is formed on the surface of the emulsion particles due to the effect of the carboxyl group, thereby preventing shear fracture of the particles.

  The acrylic emulsion polymer (A1) is not particularly limited, but is preferably a polymer composed of (meth) acrylic acid alkyl ester as an essential monomer component (raw material monomer). That is, the acrylic emulsion polymer (A1) is preferably a polymer obtained from a monomer mixture containing (meth) acrylic acid alkyl ester as an essential component. The acrylic emulsion polymer (A1) can be used alone or in combination of two or more. “(Meth) acryl” means “acryl” and / or “methacryl”, and the same applies to the following.

  The acrylic emulsion polymer (A2) is not particularly limited, but is preferably a polymer composed of (meth) acrylic acid alkyl ester and carboxyl group-containing unsaturated monomer as essential monomer components (raw material monomers). is there. That is, the acrylic emulsion polymer (A2) is preferably a polymer obtained from a monomer mixture containing (meth) acrylic acid alkyl ester and a carboxyl group-containing unsaturated monomer as essential components. The acrylic emulsion polymer (A2) can be used alone or in combination of two or more.

  The (meth) acrylic acid alkyl ester is used as a main monomer component in the acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2), and is mainly a pressure-sensitive adhesive (or pressure-sensitive adhesive) such as adhesiveness and peelability. It plays a role to express basic characteristics as a layer. Among them, the alkyl acrylate ester imparts flexibility to the polymer forming the pressure-sensitive adhesive layer, and easily exerts the effect of causing the pressure-sensitive adhesive layer to exhibit adhesion and adhesion. The alkyl methacrylate ester forms the pressure-sensitive adhesive layer. It is easy to exert the effect of giving hardness to the polymer and adjusting the removability of the pressure-sensitive adhesive layer. Although it does not specifically limit as said (meth) acrylic-acid alkylester, The carbon number of an alkyl group is 2-16, More preferably, it is 2-10, More preferably, it is 4-8, linear, branched or cyclic. And (meth) acrylic acid alkyl esters having the following alkyl groups.

  Among them, as the alkyl acrylate ester, for example, an alkyl acrylate ester having an alkyl group having 2 to 14 carbon atoms (more preferably 4 to 8) is preferable, such as n-butyl acrylate, isobutyl acrylate, acrylic acid s. -Acrylic acid alkyl ester having a linear or branched alkyl group such as butyl, isoamyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, isononyl acrylate, etc. Etc. Among these, 2-ethylhexyl acrylate and n-butyl acrylate are preferable.

  Further, as the alkyl methacrylate, for example, alkyl methacrylate having an alkyl group having 2 to 16 carbon atoms (more preferably 2 to 8) is preferable, such as ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, methacrylic acid. Methacrylic acid alkyl ester or cyclohexyl methacrylate, bornyl methacrylate, bornyl methacrylate, isobornyl methacrylate such as n-butyl acid, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, etc. And an alicyclic methacrylic acid alkyl ester. Of these, n-butyl methacrylate is preferable.

  As said (meth) acrylic-acid alkylester, it can select suitably according to the target adhesiveness etc., and can be used individually or in combination of 2 or more types.

  In the acrylic emulsion polymer (A1), the content of the alkyl (meth) acrylate is 70 to 100 with respect to the total amount (100% by weight) of monomer components constituting the acrylic emulsion polymer (A1). % By weight is preferable, more preferably 70 to 99.5% by weight, more preferably 85 to 99% by weight, and still more preferably 90 to 97% by weight. If the content exceeds 99.5% by weight, the content of the carboxyl group-containing unsaturated monomer may decrease, and the stability of the emulsion may decrease. If the content is less than 70% by weight, Adhesiveness and removability may be reduced. When 2 or more types of (meth) acrylic-acid alkylesters are used, the total amount of all the (meth) acrylic-acid alkylesters should just satisfy the said range. In addition, the content ratio (acrylic acid alkyl ester: methacrylic acid alkyl ester) of alkyl acrylate and alkyl methacrylate in the (meth) acrylic acid alkyl ester is not particularly limited, but is 100: 0 to 30:70 (weight). Ratio) is preferred, more preferably 100: 0 to 50:50.

  In the acrylic emulsion polymer (A2), the content of the alkyl (meth) acrylate is 70 to 99 with respect to the total amount (100% by weight) of monomer components constituting the acrylic emulsion polymer (A2). 0.5% by weight is preferable, more preferably 85-99% by weight, and still more preferably 90-97% by weight. When the content exceeds 99.5% by weight, the content of the carboxyl group-containing unsaturated monomer decreases, so that the stability of the emulsion and the anchoring property of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition are low. If the amount is less than 70% by weight, the adhesiveness and removability of the pressure-sensitive adhesive layer may be lowered. When 2 or more types of (meth) acrylic-acid alkylesters are used, the total amount of all the (meth) acrylic-acid alkylesters should just satisfy the said range. In addition, the content ratio (acrylic acid alkyl ester: methacrylic acid alkyl ester) of alkyl acrylate and alkyl methacrylate in the (meth) acrylic acid alkyl ester is not particularly limited, but is 100: 0 to 30:70 (weight). Ratio) is preferred, more preferably 100: 0 to 50:50.

  The carboxyl group-containing unsaturated monomer forms a protective layer on the surface of the emulsion particles made of the acrylic emulsion polymer (A), and prevents the particles from shearing. This is further improved by neutralizing the carboxyl group with a base. The stability of the particles against shear fracture is more generally referred to as mechanical stability. Moreover, by mixing with the polyfunctional compound (water-insoluble crosslinking agent (B)) which reacts with a carboxyl group, it acts also as a crosslinking point in the adhesive layer formation stage by water removal. Furthermore, in the case of the pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on the base material, the adhesion (throwing property) with the base material is improved via the water-insoluble crosslinking agent (B). Examples of such carboxyl group-containing unsaturated monomers include (meth) acrylic acid (acrylic acid, methacrylic acid), itaconic acid, maleic acid, fumaric acid, crotonic acid, carboxyethyl acrylate, carboxypentyl acrylate, and the like. Can be mentioned. The carboxyl group-containing unsaturated monomer includes acid anhydride group-containing unsaturated monomers such as maleic anhydride and itaconic anhydride. Among these, acrylic acid is preferable because it has a high relative concentration on the surface of the emulsion particles and can easily form a higher-density protective layer.

  As the monomer component (raw material monomer) constituting the acrylic emulsion polymer (A1), a carboxyl group-containing unsaturated monomer may be used. In the acrylic emulsion polymer (A1), the content of the carboxyl group-containing unsaturated monomer is 0 to the total amount of monomer components (100% by weight) constituting the acrylic emulsion polymer (A1). 10 weight% is preferable, More preferably, it is 0.5-10 weight%, More preferably, it is 1-5 weight%, More preferably, it is 2-4 weight%. When the content exceeds 10% by weight, the carboxyl group-containing unsaturated monomer (for example, acrylic acid) is generally water-soluble, so that it is polymerized in water to form the acrylic emulsion polymer (A1). It may cause thickening (increase in viscosity) during polymerization. Furthermore, after forming the pressure-sensitive adhesive layer, the interaction with the functional group on the surface of the adherend (for example, a polarizing plate) increases, and the adhesive force increases with time, and peeling may become difficult. . Since the acrylic emulsion polymer (A1) is usually used in a small amount compared to the acrylic emulsion polymer (A2) and has a small influence on the adhesive force, the monomer component constituting the acrylic emulsion polymer (A1) is: The carboxyl group-containing unsaturated monomer may not be used, but when the content is less than 0.5% by weight, the mechanical stability of the emulsion particles may be lowered.

  In the acrylic emulsion polymer (A2), the content of the carboxyl group-containing unsaturated monomer is 0. 0% relative to the total amount of monomer components (100% by weight) constituting the acrylic emulsion polymer (A2). 5 to 10 weight% is preferable, More preferably, it is 1 to 5 weight%, More preferably, it is 2 to 4 weight%. When the content exceeds 10% by weight, the carboxyl group-containing unsaturated monomer (for example, acrylic acid) is generally water-soluble, so that it is polymerized in water to form the acrylic emulsion polymer (A2). It may cause thickening (increase in viscosity) during polymerization. Furthermore, after forming the pressure-sensitive adhesive layer, the interaction with the functional group on the surface of the adherend (for example, a polarizing plate) increases, and the adhesive force increases with time, and peeling may become difficult. . On the other hand, if it is less than 0.5% by weight, the mechanical stability of the emulsion particles may be lowered. Further, in the pressure-sensitive adhesive sheet, the adhesiveness (throwing property) between the pressure-sensitive adhesive layer and the base material is lowered, which may cause adhesive residue.

  In the acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2), as a monomer component (raw material monomer) constituting the acrylic emulsion polymer (A), the above ( Other monomer components other than the (meth) acrylic acid alkyl ester and the carboxyl group-containing unsaturated monomer may be used in combination. As such a monomer component, for example, an amide group-containing monomer such as N, N-diethylacrylamide or N-isopropylacrylamide may be added (used) for the purpose of improving cohesion. Good. In addition, for purposes such as refractive index adjustment and reworkability, (meth) acrylic acid aryl esters such as phenyl (meth) acrylate; vinyl esters such as vinyl acetate and vinyl propionate; styrene monomers such as styrene, About 0.1 to 5% by weight may be added. Furthermore, for the purpose of crosslinking in emulsion particles and improving cohesive strength, epoxy group-containing monomers such as glycidyl (meth) acrylate; polyfunctional monomers such as trimethylolpropane tri (meth) acrylate and divinylbenzene are each added in an amount of 0.01 to About 2.0% by weight may be added. Furthermore, in order to form hydrazide bridge | crosslinking in combination with a hydrazide type | system | group crosslinking agent and to improve especially low pollution property, diacetone acrylamide (DAAM), allyl acetoacetate, 2- (acetoacetoxy) ethyl (meth) acrylate, etc. About 0.1 to 10% by weight (preferably 0.5 to 5% by weight) of a keto group-containing unsaturated monomer may be added. In addition, the said addition amount (use amount) is content with respect to the total amount (100 weight%) of the monomer component which comprises an acrylic emulsion type polymer (A).

  As the other monomer component, it is preferable that the hydroxyl group-containing unsaturated monomer such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate is added in a smaller amount from the viewpoint of further reducing whitening contamination. Specifically, the addition amount of the hydroxyl group-containing unsaturated monomer (content with respect to the total amount (100% by weight) of monomer components constituting the acrylic emulsion polymer (A)) is preferably less than 1% by weight, More preferably, it is less than 0.1% by weight, more preferably it is substantially free (for example, less than 0.05% by weight). However, when the purpose is to introduce a crosslinking point such as crosslinking of a hydroxyl group and an isocyanate group or crosslinking of a metal bridge, about 0.01 to 10% by weight may be added.

  The acrylic emulsion polymer (A) [acrylic emulsion polymer (A1) and acrylic emulsion polymer (A2)] in the present invention is prepared by, for example, using the above-described monomer component (monomer mixture) as an emulsifier and a polymerization initiator. Obtained by emulsion polymerization.

  As the emulsifier used for emulsion polymerization of the acrylic emulsion polymer (A), it is preferable to use a reactive emulsifier having a radical polymerizable functional group introduced into the molecule (a reactive emulsifier containing a radical polymerizable functional group). That is, the acrylic emulsion polymer (A) [acrylic emulsion polymer (A1) and acrylic emulsion polymer (A2)] is polymerized using a reactive emulsifier having a radical polymerizable functional group introduced in the molecule. It is preferable that the polymer is a polymer. The above emulsifiers may be used alone or in combination of two or more.

  The reactive emulsifier containing the radical polymerizable functional group (hereinafter may be referred to as “reactive emulsifier”) is not particularly limited, and vinyl group, propenyl group, isopropenyl group, vinyl ether group (vinyloxy group), One or two or more kinds of reactive emulsifiers having a radical polymerizable functional group such as an allyl ether group (allyloxy group) can be selected and used. Use of the reactive emulsifier is preferable because the emulsifier is incorporated into the polymer (acrylic emulsion polymer (A)), and contamination from the emulsifier is reduced.

  Examples of the reactive emulsifier include nonionic anionic emulsifiers such as sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl sulfosuccinate (nonionic). A reactive emulsifier having a form in which a radical polymerizable functional group (radical reactive group) such as a propenyl group or an allyl ether group is introduced into an anionic emulsifier having a hydrophilic hydrophilic group) (or corresponding to the form) Can be mentioned. Hereinafter, a reactive emulsifier having a form in which a radical polymerizable functional group is introduced into an anionic emulsifier may be referred to as an “anionic reactive emulsifier”. A reactive emulsifier having a form in which a radical polymerizable functional group is introduced into a nonionic anionic emulsifier may be referred to as a “nonionic anionic reactive emulsifier”.

  In particular, when an anionic reactive emulsifier (particularly, a nonionic anionic reactive emulsifier) is used, the emulsifier is incorporated into the polymer, so that the low contamination property can be improved. Furthermore, when the water-insoluble crosslinking agent (B) is a polyfunctional epoxy-based crosslinking agent having an epoxy group, the reactivity of the crosslinking agent can be improved by its catalytic action. When an anionic reactive emulsifier is not used, the crosslinking reaction is not completed by aging, and the adhesive force of the pressure-sensitive adhesive layer may change over time. Furthermore, there may be a problem that the adhesive force with the adherend increases with time due to unreacted carboxyl groups. In addition, since the anionic reactive emulsifier is incorporated in the polymer, it is generally used as a catalyst for an epoxy crosslinking agent, such as a quaternary ammonium compound (for example, see JP-A-2007-31585). In addition, since it does not precipitate on the surface of the adherend, it cannot cause whitening contamination, which is preferable.

  Examples of the reactive emulsifier include trade name “ADEKA rear soap SE-10N” (manufactured by ADEKA Corporation), trade name “AQUALON HS-10” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and trade name “AQUALON HS-”. Commercial products such as “05” (Daiichi Kogyo Seiyaku Co., Ltd.) can also be used.

In particular, since impurity ions may become a problem, it is desirable to remove the impurity ions and use an emulsifier having an SO ₄ ^2- ion concentration of 100 μg / g or less. In the case of an anionic emulsifier, it is desirable to use an ammonium salt emulsifier. As a method for removing impurities from the emulsifier, an appropriate method such as an ion exchange resin method, a membrane separation method, or a precipitation filtration method for impurities using alcohol can be used.

  The use amount (blending amount) of the reactive emulsifier used for emulsion polymerization of the acrylic emulsion polymer (A) is 0. 0 parts by weight relative to 100 parts by weight of the total amount of monomer components constituting the acrylic emulsion polymer (A). 1-5 weight part is preferable, More preferably, it is about 0.5-3 weight part. If the blending amount exceeds 5 parts by weight, the cohesive force of the pressure-sensitive adhesive layer may be reduced to increase the amount of contamination on the adherend, and contamination with an emulsifier may occur. On the other hand, if the blending amount is less than 0.1 parts by weight, stable emulsification may not be maintained.

  The polymerization initiator used for emulsion polymerization of the acrylic emulsion polymer (A) is not particularly limited, and examples thereof include 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-amidinopropane). ) Dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2, Azo polymerization initiators such as 2'-azobis (N, N'-dimethyleneisobutylamidine); persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, hydrogen peroxide, etc. Peroxide-based polymerization initiators; redox initiators in combination with peroxides and reducing agents, such as peroxides Combination with scorbic acid (combination of hydrogen peroxide and ascorbic acid), combination of peroxide and iron (II) salt (combination of hydrogen peroxide and iron (II) salt), persulfate A redox polymerization initiator based on a combination of a salt and sodium hydrogen sulfite can be used.

  The amount (blending amount) of the polymerization initiator used for the emulsion polymerization of the acrylic emulsion polymer (A) can be appropriately determined according to the type of the initiator and the monomer component, and is not particularly limited. The amount is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of the total amount of the monomer components constituting the emulsion polymer (A).

  For the emulsion polymerization of the acrylic emulsion polymer (A), any method such as general batch polymerization, continuous dropping polymerization, and divided dropping polymerization can be used, and the method is not particularly limited. From the viewpoint of reducing contamination, it is desirable to perform polymerization at the same time and at a low temperature (for example, 55 ° C. or less, preferably 30 ° C. or less). When polymerization is performed under such conditions, it is presumed that contamination is reduced because high molecular weight products are easily obtained and low molecular weight products are reduced.

[Water-insoluble crosslinking agent (B)]
The water-insoluble crosslinking agent (B) in the production method of the present invention is a water-insoluble compound, and a compound having two or more (for example, 2 to 6) functional groups capable of reacting with a carboxyl group in one molecule. It is. The number of functional groups capable of reacting with a carboxyl group in one molecule is preferably 3-5. As the number of functional groups capable of reacting with a carboxyl group in one molecule increases, the pressure-sensitive adhesive composition crosslinks densely (that is, the cross-linked structure of the polymer forming the pressure-sensitive adhesive layer becomes dense). For this reason, it becomes possible to prevent the wetting and spreading of the pressure-sensitive adhesive layer after forming the pressure-sensitive adhesive layer. In addition, since the polymer forming the pressure-sensitive adhesive layer is constrained, the functional group (carboxyl group) in the pressure-sensitive adhesive layer is segregated on the adherend surface, thereby preventing the adhesive force with the adherend from increasing with time. It becomes possible. On the other hand, when the number of functional groups capable of reacting with a carboxyl group in one molecule exceeds 6 and is too large, a gelled product may be formed.

  Although it does not specifically limit as a functional group which can react with the carboxyl group in the said water-insoluble crosslinking agent (B), For example, an epoxy group, an isocyanate group, a carbodiimide group etc. are mentioned. Among these, an epoxy group is preferable from the viewpoint of reactivity. Furthermore, since the reactivity is high, unreacted substances in the cross-linking reaction are less likely to remain, which is advantageous for low contamination. The unreacted carboxyl group in the pressure-sensitive adhesive layer increases the adhesive strength with the adherend over time. From the viewpoint that it can be suppressed, a glycidylamino group is preferred. That is, as the water-insoluble crosslinking agent (B), an epoxy-based crosslinking agent having an epoxy group is preferable, and among them, a crosslinking agent having a glycidylamino group is preferable. When the water-insoluble crosslinking agent (B) is an epoxy crosslinking agent (especially a crosslinking agent having a glycidylamino group), the number of epoxy groups (especially glycidylamino groups) in one molecule is 2 or more ( For example, 2 to 6), and 3 to 5 is preferable.

  The water-insoluble crosslinking agent (B) in the production method of the present invention is a water-insoluble compound. “Water-insoluble” means that the solubility in 100 parts by weight of water at 25 ° C. (the weight of the compound (crosslinker) soluble in 100 parts by weight of water) is 5 parts by weight or less, preferably 3 The amount is not more than parts by weight, more preferably not more than 2 parts by weight. By using a water-insoluble cross-linking agent, the cross-linking agent remaining without cross-linking is unlikely to cause whitening contamination generated on the adherend in a high-humidity environment, and the low-contamination property is improved. In the case of a water-soluble cross-linking agent, in a high humidity environment, the remaining cross-linking agent dissolves in water and is easily transferred to an adherend, and thus easily causes whitening contamination. In addition, the water-insoluble cross-linking agent has a higher contribution to the cross-linking reaction (reaction with a carboxyl group) than the water-soluble cross-linking agent, and has a high effect of preventing the adhesive force from increasing with time. Furthermore, since the water-insoluble crosslinking agent has a high crosslinking reaction reactivity, the crosslinking reaction proceeds promptly by aging, and the adhesive force with the adherend increases with time due to unreacted carboxyl groups in the adhesive layer. Can be suppressed.

In addition, the solubility with respect to water of said crosslinking agent can be measured as follows, for example.
(Measurement method of water solubility)
The same weight of water (25 ° C.) and the crosslinking agent are mixed using a stirrer at a rotation speed of 300 rpm for 10 minutes, and separated into an aqueous phase and an oil phase by centrifugation. Next, the aqueous phase is collected and dried at 120 ° C. for 1 hour, and the nonvolatile content in the aqueous phase (parts by weight of nonvolatile components relative to 100 parts by weight of water) is determined from the loss on drying.

  Specifically, as the water-insoluble crosslinking agent (B), 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (for example, trade name “TETRAD-C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) Etc.] [Solubility of 2 parts by weight or less with respect to 100 parts by weight of water at 25 ° C.] 1,3-bis (N, N-diglycidylaminomethyl) benzene (for example, trade name “TETRAD-” manufactured by Mitsubishi Gas Chemical Co., Ltd.) X "etc.) [cross-linking agent having a glycidylamino group such as [solubility of 2 parts by weight or less with respect to 100 parts by weight of water at 25 ° C.]; Tris (2,3-epoxypropyl) isocyanurate (for example, manufactured by Nissan Chemical Industries, Ltd., product) Other epoxy-based cross-linking agents such as “TEPIC-G” and the like [solubility of 0.9 parts by weight with respect to 100 parts by weight of water at 25 ° C.] are exemplified.

[First step]
The first step in the production method of the present invention is a step of mixing the aqueous dispersion of the acrylic emulsion polymer (A1) and the water-insoluble crosslinking agent (B) to obtain a mixed solution.

  In the first step, the acrylic emulsion polymer (A1) is mixed with the water-insoluble crosslinking agent (B) in the form of an aqueous dispersion. The aqueous dispersion of the acrylic emulsion polymer (A1) is not particularly limited, and for example, an aqueous dispersion obtained by emulsion polymerization of the acrylic emulsion polymer (A1) or water added to the aqueous dispersion. An aqueous dispersion having a controlled concentration can be used. Alternatively, an aqueous dispersion may be prepared by dispersing the acrylic emulsion polymer (A1) obtained in advance in water. The concentration (content) of the acrylic emulsion polymer (A1) in the aqueous dispersion of the acrylic emulsion polymer (A1) is not particularly limited, but is preferably 30 to 50% by weight from the viewpoint of production efficiency. Preferably it is 35 to 45% by weight.

  On the other hand, as the water-insoluble crosslinking agent (B), the liquid water-insoluble crosslinking agent (B) may be added as it is, or may be added after being dissolved and / or diluted with an organic solvent (however, organic The amount of solvent used is preferably as small as possible). A method of emulsifying the water-insoluble crosslinking agent (B) with an emulsifier is not preferable because the emulsifier bleeds and easily causes contamination (particularly whitening contamination).

  In the first step, the weight ratio [(B) / (A1)] (weight ratio) of the water-insoluble crosslinking agent (B) to the acrylic emulsion polymer (A1) is 0.5 to 5 (preferably 0). .5 to 3) are mixed. That is, with respect to 1 part by weight of the acrylic emulsion polymer (A1), the water-insoluble crosslinking agent (B) is mixed at a blending ratio of 0.5 to 5 parts by weight (preferably 0.5 to 3 parts by weight). To do. If [(B) / (A1)] is less than 0.5, the effect of providing the first step is not substantially obtained, and if it exceeds 5, the acrylic emulsion polymer (A1) contains a carboxyl group. In this case, the reactivity between the acrylic emulsion polymer (A1) and the water-insoluble crosslinking agent (B) is increased, and aggregates are generated in the pressure-sensitive adhesive composition to cause poor appearance.

  The mixing method in the first step may be a known and common emulsion mixing method, and is not particularly limited. For example, stirring using a stirrer is preferable. Although stirring conditions are not specifically limited, For example, as for temperature, 10-50 degreeC is preferable, More preferably, it is 20-35 degreeC. The stirring time is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. The stirring rotation speed is preferably 10 to 2000 rpm, more preferably 30 to 1000 rpm.

  By the said 1st process, the liquid mixture of the water dispersion of an acrylic emulsion polymer (A1) and a water-insoluble crosslinking agent (B) is obtained.

[Second step]
The second step in the production method of the present invention is a step of mixing the mixed liquid obtained in the first step and the aqueous dispersion of the acrylic emulsion polymer (A2).

  In the second step, the acrylic emulsion polymer (A2) is mixed with the liquid mixture obtained in the first step in the state of an aqueous dispersion. The aqueous dispersion of the acrylic emulsion polymer (A2) is not particularly limited. For example, the aqueous dispersion obtained by emulsion polymerization of the acrylic emulsion polymer (A2) or water is further added thereto. An aqueous dispersion having a controlled concentration can be used. Further, an aqueous dispersion may be prepared by dispersing the acrylic emulsion polymer (A2) obtained in advance in water. The concentration (content) of the acrylic emulsion polymer (A2) in the aqueous dispersion of the acrylic emulsion polymer (A2) is not particularly limited, but is preferably 30 to 50% by weight from the viewpoint of production efficiency. Preferably it is 35 to 45% by weight.

  The mixing method in the second step may be a known and common emulsion mixing method, and is not particularly limited. For example, stirring using a stirrer is preferable. Although stirring conditions are not specifically limited, For example, as for temperature, 10-50 degreeC is preferable, More preferably, it is 20-35 degreeC. The stirring time is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. The stirring rotation speed is preferably 10 to 2000 rpm, more preferably 30 to 1000 rpm.

  In the second step, the mixed liquid obtained in the first step and the aqueous dispersion of the acrylic emulsion polymer (A2) are preferably mixed at a time from the viewpoint of production efficiency, but are particularly limited. For example, the aqueous dispersion of the acrylic emulsion polymer (A2) may be divided into multiple stages and mixed with the liquid mixture obtained in the first step. Further, when the acrylic emulsion polymer (A2) is a mixture of two or more kinds of polymers [for example, when (A2) is a mixture of (A2-1) and (A2-2)] The step of mixing the aqueous dispersion of (A2-2) after mixing the mixed solution obtained in the first step and the aqueous dispersion of (A2-1) is also included in the second step.

  In the production method of the present invention, “non-water-soluble” with respect to “the total number of moles of the carboxyl group of the acrylic emulsion polymer (A1) and the number of moles of the carboxyl group of the acrylic emulsion polymer (A2)”. Ratio of [number of moles of functional group capable of reacting with carboxyl group possessed by reactive crosslinking agent (B)] [functional group capable of reacting with carboxyl group / carboxyl group] (molar ratio) of 0.5 to 1.3 Therefore, it is necessary to blend the acrylic emulsion polymer (A1), the acrylic emulsion polymer (A2), and the water-insoluble crosslinking agent (B). That is, the water-insoluble crosslinking agent (B) is used for the total number of moles of 1 mole of the carboxyl groups of the acrylic emulsion polymer (A1) and the moles of the carboxyl groups of the acrylic emulsion polymer (A2). ) In the compounding ratio in which the number of moles of the functional group capable of reacting with the carboxyl group is 0.5 to 1.3 mol. [Functional group capable of reacting with carboxyl group / carboxyl group] is preferably 0.6 to 1.1, and more preferably 0.7 to 1.0. When [functional group / carboxyl group that can react with carboxyl group] is less than 0.5, there are many unreacted carboxyl groups in the pressure-sensitive adhesive layer, and due to the interaction between the carboxyl group and the adherend, Increase in adhesive strength is likely to occur. Moreover, when it exceeds 1.3, many unreacted water-insoluble crosslinking agents (B) exist in an adhesive layer, and it will become easy to produce the appearance defect. In the above, when the acrylic emulsion polymer (A1) does not have a carboxyl group, “the number of moles of carboxyl groups of the acrylic emulsion polymer (A1)” is set to zero.

  In particular, when the water-insoluble crosslinking agent (B) is an epoxy crosslinking agent, [epoxy group / carboxyl group] (molar ratio) is 0.5 to 1.3, preferably 0.6 to 1.1, More preferably, it is 0.7-1.0. Furthermore, when the water-insoluble crosslinking agent (B) is a crosslinking agent having a glycidylamino group, [glycidylamino group / carboxyl group] (molar ratio) preferably satisfies the above range.

  The acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2) are composed of the aforementioned (meth) acrylic acid alkyl ester and carboxyl group-containing unsaturated monomer as essential monomer components (raw material monomers). In general, the carboxyl group of the carboxyl group-containing unsaturated monomer used as the monomer component of the acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2) The total number of moles of the functional group capable of reacting with the carboxyl group of the water-insoluble crosslinking agent (B) is 0.5 to 1.3 (preferably 0.6 to 1.1, more preferably 0.00). 7-1.0) Acrylic emulsion polymer (A1), acrylic emulsion polymer (A2) and water-insoluble crosslinking agent (B) It is sufficient if. The same applies when the acrylic emulsion polymer (A1) does not have a carboxyl group.

For example, when 4 g of a water-insoluble crosslinking agent (B) having a functional group equivalent to a carboxyl group of 110 (g / eq) is added (blended), the water-insoluble crosslinking agent (B) The number of moles of the functional group that can react with the carboxyl group it has can be calculated as follows, for example.
Number of moles of functional group capable of reacting with carboxyl group of water-insoluble crosslinking agent (B) = [blending amount of water-insoluble crosslinking agent (B) (addition amount)] / [functional group equivalent] = 4/110
For example, when 4 g of an epoxy-based crosslinking agent having an epoxy equivalent of 110 (g / eq) is added (blended) as the water-insoluble crosslinking agent (B), the number of moles of epoxy groups possessed by the epoxy-based crosslinking agent is, for example, It can be calculated as follows.
Number of moles of epoxy group possessed by epoxy-based crosslinking agent = [blending amount (addition amount) of epoxy-based crosslinking agent] / [epoxy equivalent] = 4/110

  In the production method of the present invention, so-called non-reactive (non-reactive) other than reactive (polymerizable) components incorporated into a polymer that forms an adhesive layer by reacting (polymerizing) with the acrylic emulsion polymer (A) or the like. It is preferable not to add a polymerizable component (excluding components such as water that volatilizes by drying and does not remain in the pressure-sensitive adhesive layer). If non-reactive components remain in the pressure-sensitive adhesive layer, these components may be transferred to the adherend and cause whitening contamination. Therefore, it is preferable that the pressure-sensitive adhesive composition of the present invention does not substantially contain the non-reactive component. “Substantially free” means that it is not actively added unless it is inevitably mixed. Specifically, the pressure-sensitive adhesive composition of these non-reactive components (non-volatile content) It is preferable that content in it is less than 1 weight%, More preferably, it is less than 0.1 weight%, More preferably, it is less than 0.005 weight%.

  Examples of the non-reactive component include a component that bleeds to the surface of the pressure-sensitive adhesive layer such as a phosphate ester compound used in JP-A-2006-45412 to impart releasability. Non-reactive emulsifiers such as sodium lauryl sulfate and ammonium lauryl sulfate are also included.

  In particular, in the production method of the present invention, from the viewpoint of low contamination, it is preferable not to add a quaternary ammonium salt, and it is preferable not to add a quaternary ammonium compound. Therefore, the pressure-sensitive adhesive composition of the present invention preferably does not substantially contain a quaternary ammonium salt, and preferably does not substantially contain a quaternary ammonium compound. These compounds are generally used as a catalyst for improving the reactivity of the epoxy crosslinking agent. However, these compounds are not incorporated into the polymer forming the pressure-sensitive adhesive layer, and can move freely in the pressure-sensitive adhesive layer, so that they easily deposit on the surface of the adherend, and these compounds are contained in the pressure-sensitive adhesive composition. If this occurs, whitening contamination is likely to occur, and low contamination cannot be achieved. Specifically, the content of the quaternary ammonium salt in the pressure-sensitive adhesive composition of the present invention is preferably less than 0.1% by weight, more preferably 100% by weight of the pressure-sensitive adhesive composition (nonvolatile content). Is less than 0.01% by weight, more preferably less than 0.005% by weight. Furthermore, it is preferable that the content of the quaternary ammonium compound satisfies the above range.

  In addition, although a quaternary ammonium salt is not specifically limited, Specifically, it is a compound represented, for example by a following formula.

In the above formula, R ¹ , R ² , R ³ , and R ⁴ represent an alkyl group, an aryl group, or a group derived therefrom (excluding a hydrogen atom, such as an alkyl group or an aryl group having a substituent). . X ⁻ represents a counter ion.

  The quaternary ammonium salt and the quaternary ammonium compound are not particularly limited, but for example, water such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. Alkylammonium oxide and its salts, arylammonium hydroxide such as tetraphenylammonium hydroxide and its salts, trilaurylmethylammonium ion, didecyldimethylammonium ion, dicocoyldimethylammonium ion, distearyldimethylammonium ion, dioleyldimethylammonium ion Ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, behenyltrimethylammonium ion, cocoylbis (2-hydride) Xylethyl) methylammonium ion, polyoxyethylene (15) cocostearylmethylammonium ion, oleylbis (2-hydroxyethyl) methylammonium ion, cocobenzyldimethylammonium ion, laurylbis (2-hydroxyethyl) methylammonium ion, decylbis (2- And a base having hydroxyethyl) methylammonium ion as a cation and salts thereof.

  Furthermore, in the production method of the present invention, from the viewpoint of low contamination, a catalyst for improving the reactivity of the epoxy-based crosslinking agent, etc., like the above quaternary ammonium salt (or quaternary ammonium compound), etc. It is preferable not to add a tertiary amine and an imidazole compound that are generally used. Therefore, it is preferable that the pressure-sensitive adhesive composition of the present invention does not substantially contain a tertiary amine and an imidazole compound. Specifically, the content of the tertiary amine and the imidazole compound in the pressure-sensitive adhesive composition of the present invention (the total content of the tertiary amine and the imidazole compound) is 100% by weight of the pressure-sensitive adhesive composition (nonvolatile content). % Is preferably less than 0.1% by weight, more preferably less than 0.01% by weight, and still more preferably less than 0.005% by weight.

  Examples of the tertiary amine include tertiary amine compounds such as triethylamine, benzyldimethylamine, and α-methylbenzyl-dimethylamine. Examples of the imidazole compound include 2-methylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 4-ethylimidazole, 4-dodecylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4- Examples thereof include hydroxymethylimidazole, 1-cyanoethyl-4-methylimidazole and 2-phenyl-4,5-dihydroxymethylimidazole.

  By the production method of the present invention, a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling is obtained. In the production method of the present invention, after the aqueous dispersion of the acrylic emulsion polymer (A1) and the water-insoluble crosslinking agent (B) are preliminarily mixed (preliminary stirring) at a specific ratio in the first step, It is characterized by multistage mixing (at least two stages) in which it is mixed with the aqueous dispersion of the acrylic emulsion polymer (A2) again. Thereby, even when a water-insoluble crosslinking agent is used in the water-dispersed acrylic pressure-sensitive adhesive composition, appearance defects such as “dents” at the time of forming the pressure-sensitive adhesive layer can be prevented. The appearance characteristics of the pressure-sensitive adhesive sheet are improved. Although the detailed principle by which such an effect is obtained is not clear, it is presumed that the water-insoluble crosslinking agent (B) can be finely dispersed in the aqueous dispersion by premixing. For example, when the total amount of the aqueous dispersion of the acrylic emulsion polymer (A) and the total amount of the water-insoluble crosslinking agent (B) are directly mixed in one step without performing multistage mixing as in the present invention, Large dispersed particles of the water-soluble crosslinking agent remain, and when the pressure-sensitive adhesive composition is used to form the pressure-sensitive adhesive layer, appearance defects such as “dents” tend to occur on the pressure-sensitive adhesive layer surface (glue surface). In addition, in order to prevent the above-mentioned poor appearance, there is a method of adding a surfactant to an aqueous dispersion of an acrylic emulsion polymer or emulsifying a water-insoluble crosslinking agent in advance, but in such a method, Undesirably, whitening contamination due to a surfactant or an emulsifier tends to occur.

[Re-peeling water-dispersed acrylic pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, pressure-sensitive adhesive sheet]
The water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling of the present invention obtained by the production method of the present invention comprises an acrylic emulsion polymer (A1), an acrylic emulsion polymer (A2), and a water-insoluble crosslink. An agent (B) is comprised as an essential component.

  The pressure-sensitive adhesive composition of the present invention is a water-dispersed pressure-sensitive adhesive composition. The “water-dispersed type” means that it can be dispersed in an aqueous medium, that is, the pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition that can be dispersed in an aqueous medium. The aqueous medium is a medium (dispersion medium) containing water as an essential component. In addition to water alone, the aqueous medium may partially contain a water-soluble solvent. The pressure-sensitive adhesive composition of the present invention may be a dispersion using the above aqueous medium or the like.

  A pressure-sensitive adhesive layer can be formed from the pressure-sensitive adhesive composition of the present invention. The formation method of an adhesive layer is not specifically limited, The formation method of a well-known and usual adhesive layer can be used. For example, the pressure-sensitive adhesive composition of the present invention can be formed by applying (coating) the pressure-sensitive adhesive composition of the present invention onto a substrate or a release liner, and drying and / or curing as necessary. . Crosslinking is performed by dehydrating in the drying step, heating the pressure-sensitive adhesive layer after drying, or the like.

  In addition, a known coating method can be used for coating (coating) in the method for forming the pressure-sensitive adhesive layer, and a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, or a dip coater can be used. A roll coater, bar coater, knife coater, spray coater, comma coater, direct coater or the like can be used.

  As for the thickness of the adhesive layer of this invention, 1-35 micrometers is preferable, More preferably, it is 3-25 micrometers.

  The elongation at break (elongation at break) in the tensile test of the pressure-sensitive adhesive layer of the present invention is preferably 200% or less, more preferably 10 to 100%, from the viewpoint of the degree of crosslinking of the pressure-sensitive adhesive layer. The elongation at break is a measure of the degree of crosslinking of the pressure-sensitive adhesive layer, and if it is 200% or less, the crosslinked structure of the polymer forming the pressure-sensitive adhesive layer is dense. For this reason, it becomes possible to prevent the wetting and spreading of the pressure-sensitive adhesive layer after forming the pressure-sensitive adhesive layer. In addition, since the polymer forming the pressure-sensitive adhesive layer is constrained, the functional group (carboxyl group) in the pressure-sensitive adhesive layer is segregated on the adherend surface, thereby preventing the adhesive force with the adherend from increasing with time. It becomes possible.

  By providing the pressure-sensitive adhesive layer of the present invention on at least one surface of the substrate, a pressure-sensitive adhesive sheet (pressure-sensitive adhesive sheet with a substrate) can be obtained. Further, the pressure-sensitive adhesive layer of the present invention can be used as a substrate-less pressure-sensitive adhesive sheet by itself. The pressure-sensitive adhesive sheet with a base material, for example, applies the pressure-sensitive adhesive composition of the present invention to the surface on at least one side of the base material, and if necessary, dries to form a pressure-sensitive adhesive layer on at least one side of the base material. It is obtained by forming (direct copy method). Alternatively, a pressure-sensitive adhesive sheet can be obtained by once providing a pressure-sensitive adhesive layer on a release liner and then transferring the pressure-sensitive adhesive layer onto a substrate (transfer method). Although not particularly limited, the direct copy method is preferable from the viewpoint of anchoring property (adhesion) with the substrate.

  As a base material in said adhesive sheet, a plastic base material (for example, a plastic film and a plastic sheet) is preferable from a viewpoint from which the adhesive sheet which has high transparency is obtained. Although it does not specifically limit as a raw material of a plastic substrate, For example, polyolefin resin, such as a polypropylene and polyethylene, polyester resins, such as a polyethylene terephthalate (PET), polycarbonate, polyamide, a polyimide, an acryl, polystyrene, acetate, polyether sulfone A transparent resin such as triacetylcellulose is used. These resins may be used alone or in combination of two or more. Among these, although not particularly limited, polyester resins and polyolefin resins are preferable, and PET, polypropylene, and polyethylene are preferably used from the viewpoints of productivity and moldability. That is, the base material is preferably a polyester film or a polyolefin film, and more preferably a PET film, a polypropylene film or a polyethylene film. Although it does not specifically limit as said polypropylene, The homotype which is a homopolymer, the random type which is an alpha-olefin random copolymer, and the block type thing which is an alpha-olefin block copolymer are mentioned. Examples of polyethylene include low density polyethylene (LDPE), high density polyethylene (HDPE), and linear low density polyethylene (L-LDPE). These may be used singly or in combination of two or more. Although the thickness of the said base material is not specifically limited, 10-150 micrometers is preferable, More preferably, it is 30-100 micrometers.

  The arithmetic average roughness (Ra) of the surface of the substrate on the side where the pressure-sensitive adhesive layer is provided is preferably 0.001 to 1 μm, more preferably 0.01 to 0.7 μm. Since the pressure-sensitive adhesive layer of the present invention has a high solvent-insoluble content, when the Ra of the base material exceeds 1 μm, the thickness accuracy of the coated surface (glue surface) decreases or the pressure-sensitive adhesive is on the base material surface (for example, the film surface). ), The contact area is reduced and the anchoring property of the pressure-sensitive adhesive layer and the substrate is lowered. If it is less than 0.001 μm, blocking may easily occur, handling properties may decrease, and industrial production may be difficult.

  In addition, the surface of the substrate on the side where the pressure-sensitive adhesive layer is provided, for the purpose of improving the adhesion with the pressure-sensitive adhesive layer, etc., physical treatment such as corona treatment and plasma treatment, chemical treatment such as primer, etc. It is preferable that an appropriate surface treatment is performed. Moreover, you may provide an intermediate | middle layer between a base material and an adhesive layer. The thickness of the intermediate layer is preferably, for example, 0.05 to 1 μm, more preferably about 0.1 to 1 μm.

  The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention has a pressure-sensitive adhesive force (180) with respect to a polarizing plate (triacetylcellulose (TAC) plate) (with a surface arithmetic average roughness Ra of 50 nm or less) at a tensile rate of 0.3 m / min. ° Peel test) (peeling force when peeling the adhesive sheet attached to the polarizing plate) is preferably 0.01 to 6 N / 25 mm, more preferably 0.05 to 5 N / 25 mm. When the adhesive force exceeds 6 N / 25 mm, it is difficult to peel off the adhesive sheet in the manufacturing process of the polarizing plate or the liquid crystal display device, and productivity and handleability may be deteriorated. If it is less than 0.01 N / 25 mm, the pressure sensitive adhesive sheet may float or peel off during the production process, and the protective function as a pressure sensitive adhesive sheet for surface protection may be reduced. The arithmetic average roughness Ra can be measured using, for example, P-15 (contact type surface shape measuring device) manufactured by KLA Tencor. The measurement conditions of the surface roughness (arithmetic average roughness Ra) are not particularly limited, but for example, the measurement can be performed with a measurement length of 1000 μm, a scanning speed of 50 μm / second, a scanning frequency of once, and a load of 2 mg.

  The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention is preferably excellent in the whitening contamination inhibiting property of the adherend. The whitening contamination deterrence can be evaluated, for example, as follows. The pressure-sensitive adhesive sheet was bonded to a polarizing plate (triacetylcellulose (TAC) plate) (with a surface arithmetic average roughness Ra of 50 nm or less) under the conditions of 0.25 MPa, 0.3 m / min, and 4 at 80 ° C. After standing for a period of time, the adhesive sheet is peeled off. The polarizing plate after the pressure-sensitive adhesive sheet is peeled is further left for 12 hours in an environment of 23 ° C. and 90% RH, and then the surface is observed. At this time, it is preferable that no whitening is observed on the surface of the polarizing plate. When whitening occurs on the polarizing plate as an adherend under humidification conditions (high humidity conditions) after sticking / peeling the pressure-sensitive adhesive sheet, low contamination is not sufficient for use as a surface protective film for optical members.

  The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention can be a wound body, and can be wound up in a roll shape with the pressure-sensitive adhesive layer protected by a release film (separator). When the release film is not used, the back surface of the pressure-sensitive adhesive sheet may be subjected to a back treatment with a release treatment agent such as a silicone release agent or a long-chain alkyl release agent. As the pressure-sensitive adhesive sheet, the latter pressure-sensitive adhesive layer / base material / back treatment layer is preferable. Further, the back surface of the pressure-sensitive adhesive sheet is composed of a surfactant (anionic, cationic, nonionic low molecular weight or high molecular weight), a polymer electrolyte, or the like in addition to or replacing the release processing agent. An antistatic agent layer can also be provided.

  The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition that is excellent in adhesiveness and removability (easy releasability) and can form a releasable pressure-sensitive adhesive layer, and is used for re-peeling applications. Used to form an adhesive layer (for re-peeling). That is, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention or a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer is used again [for example, a masking tape for building curing, a masking tape for automobile coating, an electronic component (lead Masking tape for frame, printed circuit board), masking tape for sandblasting, surface protection film for aluminum sash, surface protection film for optical plastic, surface protection film for optical glass, surface protection film for automobile protection, for metal plate For surface protection film such as surface protection film, back grinding tape, pellicle fixing tape, dicing tape, lead frame fixing tape, cleaning tape, dust removal tape, carrier tape, cover tape, etc. Adhesive tape, electric Packing tapes of equipment and electronic parts, tacking tapes during transport, bundling tapes, used to label such], and the like.

  The pressure-sensitive adhesive layer of the present invention has no appearance defects such as “dents” and has excellent appearance characteristics. Further, by using a reactive emulsifier for the polymerization of the acrylic emulsion polymer (A) or not using a quaternary ammonium salt (or quaternary ammonium compound) for the production of the pressure-sensitive adhesive composition, Contamination such as whitening contamination does not occur, and particularly low contamination is excellent. For this reason, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention or the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer are liquid crystal displays, Optical members (optical plastic, optical glass, optical film, etc.) such as polarizing plates, retardation plates, antireflection plates, wave plates, optical compensation films, brightness enhancement films, etc. constituting panels such as electroluminescence (organic EL) and field emission displays ) Is preferably used for surface protection (surface protective film, etc.). However, the application is not limited to this. Surface protection and damage prevention in the manufacture of microfabricated parts such as semiconductors, circuits, various printed boards, various masks, and lead frames, or removal of foreign substances, masking, etc. Can also be used.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

Example 1
[Preparation of acrylic emulsion polymer]
In a container, 90 parts by weight of water and 96 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of acrylic acid (AA), ether sulfate type reactive nonionic anionic emulsifier (stock) After blending 3 parts by weight of a trade name “ADEKA rear soap SE-10N” manufactured by ADEKA, a monomer emulsion was prepared by stirring and mixing with a homomixer.
Next, in a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 50 parts by weight of water, 0.01 part by weight of a polymerization initiator (ammonium persulfate), and 10% of the monomer emulsion prepared above % Was added, and emulsion polymerization was carried out at 65 ° C. for 1 hour with stirring. Thereafter, 0.05 parts by weight of a polymerization initiator (ammonium persulfate) was further added, and then all of the remaining monomer emulsion (amount corresponding to 90% by weight) was added over 3 hours with stirring. The reaction was carried out at 0 ° C. for 3 hours. Next, this was cooled to 30 ° C. and adjusted to pH 8 by adding ammonia water having a concentration of 10% by weight to prepare an aqueous dispersion of an acrylic emulsion polymer.

[Preparation of re-peeling water-dispersed acrylic pressure-sensitive adhesive composition]
(First step)
An aqueous dispersion of the acrylic emulsion polymer obtained above and an epoxy crosslinking agent having a glycidylamino group which is a water-insoluble crosslinking agent [Made by Mitsubishi Gas Chemical Co., Ltd., trade name “Tetrad-C”, 1 , 3-bis (N, N-diglycidylaminomethyl) cyclohexane, epoxy equivalent: 110, number of functional groups: about 4] with a stirrer under stirring conditions at 23 ° C., 300 rpm, 10 minutes, A mixture was prepared. Said mixing was performed in the ratio from which an epoxy-type crosslinking agent (Tetrad-C) will be 4 weight part with respect to 1.6 weight part of acrylic emulsion type polymers in an aqueous dispersion. That is, the weight ratio [epoxy crosslinking agent / acryl emulsion polymer] (weight ratio) of the epoxy crosslinking agent to the acrylic emulsion polymer in the mixing is 2.5.
(Second step)
Next, the liquid mixture obtained above is added to the aqueous dispersion of the acrylic emulsion polymer obtained above, and the mixture is stirred and mixed using a stirrer at 23 ° C., 300 rpm for 10 minutes. A water-dispersed acrylic pressure-sensitive adhesive composition for re-peeling was prepared. In the above mixing, a mixed liquid containing 1.6 parts by weight of an acrylic emulsion polymer and 4 parts by weight of an epoxy crosslinking agent (Tetrad-C) is converted into an aqueous dispersion containing 98.4 parts by weight of an acrylic emulsion polymer. This was done by adding.
That is, in the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, 4 parts by weight of an epoxy crosslinking agent (Tetrad-C) is blended with 100 parts by weight of the acrylic emulsion polymer. The ratio [epoxy group / carboxyl group] (molar ratio) of the number of moles of the epoxy group (glycidylamino group) of the epoxy crosslinking agent to the number of moles of the carboxyl group of the acrylic emulsion polymer is 0.7.

[Formation of pressure-sensitive adhesive layer, production of pressure-sensitive adhesive sheet]
The water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling obtained above is applied to a tester industry on the corona-treated surface of a PET film (Mitsubishi Resin Co., Ltd., trade name “T100-N”, thickness: 38 μm). Using an applicator manufactured by Co., Ltd., the coating was dried to a thickness of 15 μm, and then dried in a hot air circulating oven at 120 ° C. for 2 minutes, followed by curing at 50 ° C. for 3 days. A sheet was obtained.
In Example 1, the same acrylic emulsion polymer aqueous dispersion was used in the first step and the second step. The same applies to Example 2 and Comparative Examples 1 and 3 to 5.

Example 2
As shown in Table 1, the weight ratio of the epoxy crosslinking agent (Tetrad-C) to the acrylic emulsion polymer in the first step [epoxy crosslinking agent / acryl emulsion polymer] (weight ratio), water dispersion for re-peeling Acrylic emulsion polymer, water-dispersible acrylic adhesive for re-peeling in the same manner as in Example 1 except that the blending amount of the acrylic emulsion polymer and the epoxy crosslinking agent in the acrylic adhesive composition is changed. An agent composition and an adhesive sheet were obtained.

Comparative Example 1
As shown in Table 1, except that the weight ratio of the epoxy-based crosslinking agent (Tetrad-C) to the acrylic emulsion-based polymer in the first step [epoxy-based crosslinking agent / acrylic emulsion-based polymer] (weight ratio) is changed. In the same manner as in Example 2, an acrylic emulsion polymer, a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, and a pressure-sensitive adhesive sheet were obtained.

Comparative Example 2
In the same manner as in Example 1, an aqueous dispersion of an acrylic emulsion polymer was prepared.
Next, the aqueous dispersion of the acrylic emulsion polymer obtained above and the epoxy crosslinking agent (Tetrad-C) were directly mixed in one step. To an aqueous dispersion of the acrylic emulsion polymer obtained above, 3 parts by weight of an epoxy crosslinking agent (Tetrad-C) is added to 100 parts by weight of the acrylic emulsion polymer, and a stirrer is used. The mixture was stirred and mixed at 23 ° C., 300 rpm, and 10 minutes to prepare a re-peeling water-dispersed acrylic pressure-sensitive adhesive composition.
Furthermore, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 using the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling obtained above.

Comparative Example 3
As shown in Table 1, in place of the epoxy-based crosslinking agent (Tetrad-C), which is a water-insoluble crosslinking agent, a water-soluble epoxy-based crosslinking agent [trade name “Denacol EX-512, manufactured by Nagase ChemteX Corporation”. (Polyglycerol Polyglycidyl Ether, epoxy equivalent: 168, functional group number: about 4)] as a crosslinking agent, and the weight ratio of the epoxy crosslinking agent to the acrylic emulsion polymer in the first step [epoxy crosslinking agent / acrylic Emulsion polymer] (weight ratio), the amount of the acrylic emulsion polymer and the epoxy cross-linking agent in the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, etc. A polymer, a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, and a pressure-sensitive adhesive sheet were obtained.

Comparative Examples 4 and 5
As shown in Table 1, the acrylic emulsion system was the same as in Example 2 except that the blending amount of the acrylic emulsion polymer and the epoxy crosslinking agent in the water-dispersible acrylic adhesive composition for re-peeling was changed. A polymer, a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, and a pressure-sensitive adhesive sheet were obtained.

[Evaluation]
The re-peeling water-dispersed acrylic pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples were evaluated by the following measurement method or evaluation method. The evaluation results are shown in Table 1.

(1) Elongation at break (elongation at break) [Tensile test]
After drying, the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling obtained in Examples and Comparative Examples was dried on the silicone-treated surface of a PET film (Mitsubishi Resin Co., Ltd., “MRF38”) whose surface was silicone-treated. The film was coated to a thickness of 50 μm, then dried in a hot air circulation oven at 120 ° C. for 2 minutes, and cured at 50 ° C. for 3 days to obtain an adhesive layer.
Subsequently, the said adhesive layer was rolled up and the column-shaped adhesive layer sample (length 50mm, cross-sectional area 1mm < ² >) was produced.
Measurement was performed using a tensile tester. The chuck was set so that the initial length of measurement (chuck interval) was 10 mm, a tensile test was performed under the condition of a tensile speed of 50 mm / min, and the elongation at break (elongation at break) was measured.
The elongation at break (elongation at break) represents the elongation when the test piece (adhesive layer sample) broke in a tensile test, and is calculated by the following equation.
“Elongation at break (Elongation at break)” (%) = (“Length of test piece at break” − “Initial length (10 mm)”) ÷ “Initial length (10 mm)” × 100

(2) Appearance (with or without dents)
The state of the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was visually observed. The number of defects (dents) within the observation range of 10 cm long × 10 cm wide was measured and evaluated according to the following criteria.
Number of defects is 0 to 10: Appearance is good (◯).
Number of defects is 11 to 100: Appearance is slightly bad (Δ).
The number of defects is 101 or more: Appearance is poor (x).

(3) Contamination (whitening) [humidification test]
The pressure-sensitive adhesive sheets (sample size: 25 mm width × 100 mm length) obtained in the examples and comparative examples were 0.25 MPa, 0.00 mm using a bonding machine (manufactured by Tester Sangyo Co., Ltd., a small bonding machine). Under conditions of 3 m / min, a polarizing plate [material: triacetylcellulose (TAC), size: 35 mm width × 50 mm length, surface arithmetic average roughness Ra is about 21 nm in the MD direction (flow direction), TD direction (width Direction) is about 31 nm, and the average of MD direction and TD direction is about 26 nm].
In addition, arithmetic mean roughness Ra of the said polarizing plate was measured using the contact-type surface shape measuring apparatus [KLA Tencor (P-15 by KLA Tencor) company] (The following is also the same.). The Ra measurement method and measurement conditions using P-15 manufactured by KLA-Tencor are as follows. The sample size of the Ra measurement sample was 50 mm (MD direction) × 20 mm (TD direction), and the measurement was performed at an arbitrary position inside 5 mm from the outermost end of the sample in both the MD direction and the TD direction. The sample was fixed on a glass plate, and at the above arbitrary position, the measurement length was 1000 μm and the scanning speed was 50 μm / sec. The number of scans was 1 and the load was 2 mg.
The polarizing plate on which the pressure-sensitive adhesive sheet was bonded was allowed to stand at 80 ° C. for 4 hours while the pressure-sensitive adhesive sheet was bonded, and then the pressure-sensitive adhesive sheet was peeled off. Then, the polarizing plate from which the pressure-sensitive adhesive sheet was peeled was allowed to stand for 12 hours in a humidified environment (23 ° C., 90% RH), the surface of the polarizing plate was visually observed, and the contamination was evaluated according to the following criteria.
Good low contamination (◯): No change was observed between the part with and without the adhesive sheet.
Usable level (Δ): Slight whitening was observed at the part where the adhesive sheet was applied.
Low contamination resistance (×): The part where the adhesive sheet is pasted is severely whitened.

(4) Prevention of adhesive strength increase (initial adhesive strength, adhesive strength after storage at 40 ° C for 1 week)
The pressure-sensitive adhesive sheet (sample size: 25 mm width × 100 mm length) obtained in Examples and Comparative Examples was bonded to the surface of the pressure-sensitive adhesive sheet on the pressure-sensitive adhesive layer side, a small bonding machine manufactured by Tester Sangyo Co., Ltd. ) Under the conditions of 0.25 MPa and 0.3 m / min, the polarizing plate [material: triacetyl cellulose (TAC), surface arithmetic average roughness (Ra) is about 21 nm in the MD direction and about TD in the TD direction] About 31 nm, and the average of MD direction and TD direction is about 26 nm].
Using the above-mentioned sample of the pressure-sensitive adhesive sheet and the polarizing plate, after leaving for 20 minutes in an environment of 23 ° C. and 60% RH, a 180 ° peel test is performed according to the following conditions to N / 25 mm) and measured as “initial adhesive strength”.
Further, the above-mentioned sample of the pressure-sensitive adhesive sheet and polarizing plate was stored in a 40 ° C. environment for 1 week and then left in a 23 ° C., 60% RH environment for 2 hours. A peel test was performed, and the adhesive strength (N / 25 mm) of the pressure-sensitive adhesive sheet to the polarizing plate was measured.
The 180 ° peel test was performed using a tensile tester in accordance with JIS Z 0237 and at a tensile rate of 0.3 m / min in an environment of 23 ° C. and 60% RH.
If the difference between the initial adhesive strength and the adhesive strength after storage at 40 ° C. for 1 week [(Adhesive strength after storage at 40 ° C. for 1 week) − (initial adhesive strength)] is 0.10 N / 25 mm or less, the increase in adhesive strength is prevented. It can be judged that the property is excellent.

The abbreviations used in Table 1 are as follows.
2EHA: 2-ethylhexyl acrylate AA: acrylic acid SE-10N: manufactured by ADEKA Co., Ltd., trade name “ADEKA rear soap SE-10N”
Tetrad-C: manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name “TETRAD-C” (1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, epoxy equivalent: 110, number of functional groups: about 4)
Denacol EX-512: manufactured by Nagase ChemteX Corporation, trade name “Denacol EX-512” (Polyglycerol Polyglycidyl Ether, epoxy equivalent: 168, number of functional groups: about 4)

As is clear from the results in Table 1, the pressure-sensitive adhesive layer formed from the re-peeling water-dispersed acrylic pressure-sensitive adhesive composition produced by the production method of the present invention is excellent in preventing an increase in adhesive force, and has a dent, etc. The appearance characteristics are excellent and the appearance characteristics are excellent.
On the other hand, when the aqueous dispersion of the acrylic emulsion polymer and the water-insoluble crosslinking agent were directly mixed in one stage (Comparative Example 2), appearance defects such as dents occurred in the pressure-sensitive adhesive layer. In the first step, when the weight ratio of the water-insoluble crosslinking agent to the acrylic emulsion polymer is mixed at a ratio exceeding 5 (Comparative Example 1), an agglomerate is generated in the pressure-sensitive adhesive layer due to poor mixing. Appearance characteristics deteriorated. Moreover, when a water-soluble crosslinking agent was used instead of the water-insoluble crosslinking agent (Comparative Example 3), the prevention of increase in adhesive strength was reduced and the low contamination property was deteriorated. Furthermore, when [functional group (epoxy group) / carboxyl group that can react with carboxyl group] (molar ratio) is too small (Comparative Example 4), the ability to prevent increase in adhesive strength with time decreases and is too large ( In Comparative Example 5), appearance defects such as dents occurred in the pressure-sensitive adhesive layer.

Claims (7)

An acrylic emulsion polymer (A1) comprising an aqueous dispersion of an acrylic emulsion polymer (A1) and a water-insoluble crosslinking agent (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule. After mixing the water-insoluble crosslinking agent (B) with respect to the weight ratio [(B) / (A1)] (weight ratio) of 0.5 to 5 to obtain a mixed solution,
A method for producing a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling, comprising mixing the mixed solution and an aqueous dispersion of an acrylic emulsion-based polymer (A2) having a carboxyl group,
The solubility of the water-insoluble crosslinking agent (B) in 100 parts by weight of water at 25 ° C. is 5 parts by weight or less,
The functional group capable of reacting with the carboxyl group of the water-insoluble crosslinking agent (B) with respect to the total number of moles of the carboxyl group of the acrylic emulsion polymer (A1) and the carboxyl group of the acrylic emulsion polymer (A2) Acrylic emulsion polymer (A1) and acrylic emulsion polymer (A2) in such a proportion that the molar ratio [functional group / carboxyl group capable of reacting with carboxyl group] (molar ratio) is 0.5 to 1.3. ) And a water-insoluble crosslinking agent (B). A method for producing a water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling.   The acrylic emulsion polymer (A1) and the acrylic emulsion polymer (A2) are polymers polymerized using a reactive emulsifier having a radical polymerizable functional group introduced in the molecule. A method for producing a water-dispersible acrylic pressure-sensitive adhesive composition for peeling.   A water-dispersed acrylic pressure-sensitive adhesive composition for re-peeling obtained by the production method according to claim 1 or 2. A pressure-sensitive adhesive layer formed from the water-dispersible acrylic pressure-sensitive adhesive composition for re-peeling according to claim 3, wherein the pressure-sensitive adhesive layer has an elongation at break of 200% or less. .
Elongation at break: It is determined by conducting a tensile test on a cylindrical pressure-sensitive adhesive layer sample having a length of 50 mm and a cross-sectional area of 1 mm ² under a tensile speed of 50 mm / min.   The adhesive sheet which has an adhesive layer of Claim 4 in the at least single side | surface side of a base material.   The pressure-sensitive adhesive sheet according to claim 5, which is a surface protective film for an optical member. An optical member to which the pressure-sensitive adhesive sheet according to claim 6 is attached.