JP2019048920A - Adhesive composition, manufacturing method therefor, adhesive sheet and manufacturing method thereof - Google Patents

Abstract

To provide an adhesive composition which is suitable as a material for an adhesive sheet capable of providing sufficient high adhesive force even with thin thickness, and maintaining high peeling resistance even when used under a high temperature for long time.SOLUTION: There is provided an adhesive composition containing a (meth)acrylic resin A, a (meth)acrylic resin B, and a curing agent C, in which the (meth)acrylic resin A contains a constitutional unit a1 derived from (meth)acrylate containing an amide bond, and a constitutional unit a2 containing a functional group having a reactivity to a functional group contained in the curing agent C, the (meth)acrylic resin B contains a constitutional unit b1 derived from the (meth)acrylate having the amide bond, and a constitutional unit b2 containing the functional group having reactivity to the functional group contained in the curing agent C, and the curing agent C has a plurality of functional groups selected from a group consisting of an isocyanato group, an epoxy group, a hydroxy group, a carboxyl group, an amino group and an aziridine group.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition and a method for producing the same, and a pressure-sensitive adhesive sheet and a method for producing the same, and more particularly to a pressure-sensitive adhesive composition containing a (meth) acrylic resin and a method for producing the same and a pressure-sensitive adhesive sheet and a method for producing the same.

  In recent years, pressure-sensitive adhesive sheets are used in various product fields. As a typical product in which the adhesive sheet is used, there is an electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device. Specifically, an adhesive sheet is used to adhere the optical film of the touch panel module or the display panel module to the cover panel that protects the surface of the electronic device. An adhesive sheet is also used to bond the touch panel module and the display panel module.

  As an adhesive tape used for fixing an optical film, there is an adhesive tape having an adhesive layer containing a polymer component containing an acrylic polymer obtained by living radical polymerization of a specific monomer mixture and a crosslinking agent ( For example, refer to Patent Document 1).

Unexamined-Japanese-Patent No. 2016-210892

In the electronic devices, further downsizing, thinning and weight saving are required. Therefore, as an adhesive sheet used for an electronic device, what can acquire adhesive strength high enough even if thickness is thin is calculated | required.
Moreover, the adhesive sheet with which the electronic device is equipped may be exposed to high temperature by heat_generation | fever of an electronic device. Therefore, as an adhesive sheet used for an electronic device, what can maintain high exfoliation resistance is called for, even if it is used under high temperature for a long period of time.

The present invention has been made in view of the above circumstances, and a material of a pressure-sensitive adhesive sheet capable of obtaining sufficiently high adhesion even with a small thickness and maintaining high peel resistance even when used for a long time under high temperature It is an object of the present invention to provide a pressure-sensitive adhesive composition suitable as
In addition, the present invention contains a cured product of the pressure-sensitive adhesive composition of the present invention, and even with a small thickness, sufficiently high adhesion can be obtained, and high peel resistance can be maintained even when used for a long time under high temperature. An object of the present invention is to provide an adhesive sheet and a method for producing the same.

The configuration of the present invention for solving the above problems is as follows.
[1] A (meth) acrylic resin A, a (meth) acrylic resin B, and a curing agent C, wherein the (meth) acrylic resin A contains all the structural units constituting the (meth) acrylic resin A. And 25 to 50 mol% of a structural unit a1 derived from (meth) acrylate containing an amide bond, and 0.5 to 10 mol of a structural unit a2 containing a functional group having reactivity with a functional group contained in the curing agent C. % And the (meth) acrylic resin B contains 5 to 24 mol% of a (meth) acrylate-derived structural unit b1 containing an amide bond in all the structural units constituting the (meth) acrylic resin B, and the curing Containing 0.5 to 10 mol% of a structural unit b2 containing a functional group having reactivity with a functional group contained in the agent C, and the curing agent C is an isocyanate group, an epoxy group, a hydroxy group, a carboco The (meth) acrylic resin A has a plurality of functional groups selected from the group consisting of an amino group, an amino group and an aziridine group, relative to the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B The content is 30 to 80% by mass, and the curing agent C is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B A pressure-sensitive adhesive composition characterized by

[2] The pressure-sensitive adhesive composition according to [1], wherein the weight average molecular weight of the (meth) acrylic resin A is 500,000 to 1,500,000.
[3] The pressure-sensitive adhesive composition as described in [1] or [2], wherein the weight average molecular weight of the (meth) acrylic resin B is 500,000 to 1,500,000.
[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the structural unit a1 is a structural unit derived from an N, N-dialkyl (meth) acrylamide monomer.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the structural unit a1 comprises N, N-diethylacrylamide, and the structural unit b1 comprises N, N-dimethylacrylamide.
[6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the functional group contained in the curing agent C is at least one selected from the group consisting of an isocyanato group and an epoxy group.
[7] The structural unit a2 is at least one selected from the group consisting of a structural unit derived from a (meth) acrylate containing a hydroxy group and a structural unit derived from acrylic acid [1] to [6] The adhesive composition as described.
The adhesive sheet containing the hardened | cured material of the adhesive composition in any one of [8] [1]-[7].

[9] A method for producing a pressure-sensitive adhesive composition in which a (meth) acrylic resin A, a (meth) acrylic resin B, and a curing agent C are mixed, wherein the (meth) acrylic resin A is the (meth) acrylic resin. A functional group having reactivity to a functional group contained in 25 to 50 mol% of a structural unit a1 derived from (meth) acrylate containing an amide bond in all the structural units constituting the acrylic resin A, and a functional group contained in the curing agent C The (meth) acrylic resin B contains an amide bond in all the structural units constituting the (meth) acrylic resin B, and contains 0.5 to 10 mol% of the structural unit a2 containing Containing 5 to 24 mol% of the unit b1 and 0.5 to 10 mol% of a constituent unit b2 containing a functional group having reactivity to a functional group contained in the curing agent C, wherein the curing agent C is an isocyanate group It has a plurality of functional groups selected from the group consisting of an epoxy group, a hydroxy group, a carboxy group, an amino group and an aziridine group, and the above with respect to the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B The amount of addition of the meta) acrylic resin A is 30 to 80 mass%, and the curing agent C is used in an amount of 0. 0 based on 100 parts by mass of the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B. The method for producing a pressure-sensitive adhesive composition, which is added in an amount of 1 to 10 parts by mass.
The manufacturing method of the adhesive sheet including the process of hardening the adhesive composition obtained by the manufacturing method as described in [10] [9].

The pressure-sensitive adhesive sheet containing the cured product of the pressure-sensitive adhesive composition of the present invention can obtain sufficiently high adhesion even with a small thickness, and can maintain high peel resistance even when used for a long time under high temperature.
According to the method for producing a pressure-sensitive adhesive composition of the present invention, a sufficiently high adhesive strength can be obtained even if the thickness is thin, and as a material of a pressure-sensitive adhesive sheet which can maintain high peel resistance even when used for a long time under high temperature A suitable pressure-sensitive adhesive composition is obtained.

Hereinafter, embodiments of the pressure-sensitive adhesive composition of the present invention and the method for producing the same, and the pressure-sensitive adhesive sheet and the method for producing the same will be described in detail. The present invention is not limited to only the embodiments shown below.
In the following description, "(meth) acrylic" means acrylic or methacrylic or both of them. "(Meth) acrylate" means acrylate or methacrylate or both of them.
Moreover, "(meth) acrylic resin" is a polymer which has (meth) acrylate as a main component of a monomer, and content of the structural unit derived from (meth) acrylate in all the structural units of a polymer exceeds 50 mol% Means to be. The term "constituent unit" means a unit corresponding to one monomer.

<1. Adhesive composition>
The pressure-sensitive adhesive composition of the present embodiment contains a resin component containing (meth) acrylic resin A and (meth) acrylic resin B, and a curing agent C. The (meth) acrylic resin A and the (meth) acrylic resin B differ in the ratio (mol%) of the structural unit derived from the (meth) acrylate monomer containing an amide bond in all the structural units of the polymer. That is, in the distribution chart of the proportion (mol%) of the structural unit derived from the (meth) acrylate monomer containing an amide bond in the pressure-sensitive adhesive composition, two peaks are present at 24.5 mol% as a boundary. The details of the configuration of each of (meth) acrylic resin A, (meth) acrylic resin B and curing agent C will be described later.

  The content of (meth) acrylic resin A is 30 to 80% by mass with respect to the total amount of (meth) acrylic resin A and (meth) acrylic resin B. The adhesive composition which has the outstanding adhesiveness under high temperature as the said content of (meth) acrylic resin A is 30 mass% or more is obtained. Moreover, since content of (meth) acrylic resin B can fully be ensured as said content of (meth) acrylic resin A is 80 mass% or less, the adhesive composition which has high peeling resistance is obtained. Be The content of the (meth) acrylic resin A is preferably 40 to 80% by mass, and more preferably 50 to 70% by mass.

  The content of the (meth) acrylic resin B is 20 to 70% by mass with respect to the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B. The adhesive composition excellent in the peeling resistance with respect to constant load load is obtained as said content of (meth) acrylic resin B is 20 mass% or more. Moreover, since content of (meth) acrylic resin A can fully be ensured as said content of (meth) acrylic resin B is 70 mass% or less, the adhesive composition which has the outstanding adhesiveness under high temperature The thing is obtained. The content of the (meth) acrylic resin B is preferably 20 to 60% by mass, and more preferably 30 to 50% by mass.

  The content of the curing agent C is 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of (meth) acrylic resin A and (meth) acrylic resin B. As a result, a pressure-sensitive adhesive composition having excellent cohesion can be obtained. The content of the curing agent C is preferably 0.2 to 8 parts by mass, and more preferably 0.5 to 5 parts by mass.

  The pressure-sensitive adhesive composition of the present embodiment may optionally contain, in addition to the (meth) acrylic resin A, the (meth) acrylic resin B, and the curing agent C, a tackifier, a plasticizer, a surface lubricant, and a leveling agent. Various additives such as an agent, a softener, an antioxidant, an antioxidant, an ultraviolet absorber, a polymerization inhibitor, a light stabilizer, a flame retardant, a surfactant, and an antistatic agent may be included.

  Hereinafter, each component of the (meth) acrylic resin A, the (meth) acrylic resin B, and the curing agent C which comprise the adhesive composition of this embodiment is demonstrated.

<1-1. (Meth) acrylic resin A>
The (meth) acrylic resin A contains a constituent unit a1 derived from a (meth) acrylate monomer containing an amide bond, and a constituent unit a2 containing a functional group having reactivity with a functional group contained in the curing agent C. . Furthermore, you may contain the structural unit a3 derived from the (meth) acrylate monomer other than structural unit a1 and a2.

  The (meth) acrylic resin A is a copolymer. The (meth) acrylic resin A may be any of a random copolymer, an alternating copolymer, and a block copolymer. The (meth) acrylic resin A is preferably a random copolymer or an alternating copolymer because it is preferable that the functional group is dispersed in the molecular chain. In consideration of ease of production, (meth) acrylic resin A is preferably a random copolymer.

  The structural unit a1 derived from (meth) acrylate containing an amide bond is contained in an amount of 25 to 50 mol%, preferably 30 to 45 mol%, in all the structural units constituting the (meth) acrylic resin A, more preferably 30 to 45 40 mol% is included. When the content of the structural unit a1 in all the structural units is in the above range, an effect of obtaining high adhesiveness at high temperature can be obtained.

Examples of (meth) acrylates containing an amide bond to be the structural unit a1 include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, (meth) acryloyl morpholine, etc. There is no limitation to these. Among these, N, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, etc. are suitably used because they are excellent in adhesion to various optical films. Be Among them, particularly preferred is N, N-dialkyl (meth) acrylamide in which the alkyl group has 1 to 5 carbon atoms.
The monomer that forms the structural unit a1 may be one type, or two or more types.

  The constituent unit a2 containing a functional group having reactivity to the functional group contained in the curing agent C is contained in an amount of 0.5 to 10 mol% in all constituent units constituting the (meth) acrylic resin A, preferably 1 It is contained at -7 mol%, more preferably at 1 to 6 mol%. When the content of the structural unit a2 in all the structural units is 0.5 to 10 mol%, the reaction with the curing agent C can be easily advanced.

  The structural unit containing an amide bond and containing a functional group having reactivity with the functional group contained in the curing agent C belongs to both of the structural units a1 and a2. For example, with respect to a functional group having an amide bond and having an amide bond and having an amide bond, the structural unit a11 having an amide bond but not having a functional group having a reactivity to the functional group contained in the curing agent C Since the structural unit a1 is 30 mol% and the structural unit a2 is 7 mol% when 7 mol% of the structural unit a12 having a functional group having reactivity is included, the requirement of the (meth) acrylic resin A of this embodiment is Fulfill.

  Moreover, even if it is a structural unit containing the said functional group, depending on the kind of hardening | curing agent C, the functional group contained in a structural unit may not have the reactivity with respect to the functional group contained in the hardening agent C. . In that case, the structural unit is not the structural unit a2.

  The structural unit a2 is preferably a structural unit derived from a (meth) acrylate monomer. As a functional group which has reactivity with respect to the functional group contained in the hardening agent C, a hydroxy group, a carboxy group, an epoxy group etc. are mentioned, for example.

  As a monomer containing a hydroxy group to be the structural unit a2, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,3-butanediol mono ( Examples include meta) acrylate, 1,4-butanediol mono (meth) acrylate, 1,6-hexanediol mono (meth) acrylate, 3-methylpentanediol mono (meth) acrylate and the like.

  As a monomer containing the carboxy group used as the structural unit a2, (meth) acrylic acid, (beta) -carboxyethyl (meth) acrylate etc. are mentioned, for example. As a monomer containing the epoxy group used as the structural unit a2, a glycidyl (meth) acrylate etc. are mentioned, for example. The monomers for forming the structural unit a2 are not limited to those listed above. The monomer that forms the structural unit a2 may be of one type or may include two or more types.

  For example, when the curing agent C is an isocyanate compound, the structural unit a2 is preferably one containing a hydroxy group but not containing a carboxy group, or one containing a hydroxy group and a carboxy group. In particular, when the curing agent C is an isocyanate compound, (meth) acrylate containing a hydroxy group but not containing a carboxy group as a monomer for forming the structural unit a2 and (meth) acrylate containing a hydroxy group and a carboxy group It is preferable to use one or both of the above.

  Examples of the (meth) acrylate monomer that forms the structural unit a3 include alkyl (meth) acrylate, cyclic alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, alkoxy (poly) alkylene glycol (meth) acrylate, N, N -Dialkylaminoalkyl (meth) acrylate, (meth) acrylate containing a sulfo group, fluorinated alkyl (meth) acrylate, dimethylsiloxane group-containing (meth) acrylate and the like.

  As the alkyl (meth) acrylate, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) Acrylate, isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, isodecyl (meth) acrylate, stearyl (meth) acrylate, tridecyl ( Meta) acrylate, isostearyl (meth) acrylate, etc. are mentioned.

  Examples of cyclic alkyl (meth) acrylates include cyclohexyl (meth) acrylate, norbornyl (meth) acrylate, isobornyl (meth) acrylate, norbornanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyl oxyethyl (meth) ) Acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate and the like.

  As the alkoxyalkyl (meth) acrylate, for example, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, 2-methoxyethoxyethyl (meth) acrylate, 2-ethoxyethoxyethyl (meth) An acrylate etc. are mentioned.

  Examples of the alkoxy (poly) alkylene glycol (meth) acrylate include methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate and the like.

Examples of N, N-dialkylaminoalkyl (meth) acrylates include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate and the like.
As (meth) acrylate containing a sulfonic acid group, 2-sulfoethyl (meth) acrylate etc. are mentioned, for example.

Examples of fluorinated alkyl (meth) acrylates include octafluoropentyl (meth) acrylate and the like.
Examples of the dimethylsiloxane group-containing (meth) acrylate include α-butyl-ω- (3- (meth) acryloxypropyl) polydimethylsiloxane and the like.

The monomers for forming the structural unit a3 are not limited to those listed above. The monomer for forming the structural unit a3 may be of one type, or may include two or more types.
In addition, even if it is the monomer mentioned as a specific example of the monomer which forms the structural unit a3, depending on how to choose the curing agent C, a functional group having reactivity to the functional group contained in the curing agent C is included. There is a case. In that case, the structural unit derived from the monomer is the structural unit a2.

  The (meth) acrylic resin A can contain a structural unit derived from a polymerizable monomer other than the structural units a1, a2, and a3 as a copolymerization component, as long as the polymerizability is not impaired. As such polymerizable monomers, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone And itaconic acid dialkyl esters, fumaric acid dialkyl esters, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyltrimethyl ammonium chloride, dimethylallyl vinyl ketone and the like.

The weight average molecular weight of the (meth) acrylic resin A is preferably 50 to 150,000, more preferably 600 to 1,300,000, and still more preferably 70 to 1,000,000. When the weight average molecular weight of the (meth) acrylic resin A is 500,000 or more, a pressure-sensitive adhesive composition having a larger cohesive force is obtained. In addition, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin A having a weight average molecular weight of 500,000 or more, a pressure-sensitive adhesive sheet in which adhesive residue after peeling is suppressed. And is preferable. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin A having a weight average molecular weight of 1,500,000 or less, a pressure-sensitive adhesive sheet having higher adhesive strength is obtained.
The weight average molecular weight of (meth) acrylic resin A can be measured, for example, by GPC (gel permeation chromatography) or the like.

The glass transition temperature Tg of (meth) acrylic resin A is preferably -40 to -10 ° C, more preferably -30 to -10 ° C, and still more preferably -30 to -15 ° C. When the Tg of (meth) acrylic resin A is −40 ° C. or higher, a pressure-sensitive adhesive composition having a larger cohesive force is obtained. In addition, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin A having a Tg of -40 ° C or higher, a pressure-sensitive adhesive sheet capable of obtaining higher peel resistance Become. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin A having a Tg of −10 ° C. or less, the pressure-sensitive adhesive sheet in which zipping at the time of peeling is suppressed Become. The Tg of the (meth) acrylic resin A can be adjusted by appropriately changing the type and composition ratio of the monomers constituting the (meth) acrylic resin A.
The glass transition temperature Tg of the (meth) acrylic resin A can be measured, for example, by a differential scanning calorimeter (DSC) or the like.

<1-2. (Meth) acrylic resin B>
The (meth) acrylic resin B contains a constituent unit b1 derived from a (meth) acrylate monomer containing an amide bond, and a constituent unit b2 containing a functional group having reactivity with a functional group contained in the curing agent C. . Furthermore, you may contain the structural unit b3 derived from the (meth) acrylate monomer other than structural unit b1 and b2.

  The (meth) acrylic resin B is a copolymer. The (meth) acrylic resin B may be any of a random copolymer, an alternating copolymer, and a block copolymer. The (meth) acrylic resin B is preferably a random copolymer or an alternating copolymer because it is preferable that the functional group is dispersed in the molecular chain. In consideration of ease of production, (meth) acrylic resin B is preferably a random copolymer.

  The structural unit b1 derived from (meth) acrylate containing an amide bond is contained in an amount of 5 to 24 mol%, preferably 8 to 20 mol%, in all the structural units constituting the (meth) acrylic resin B, more preferably 10 to 10 It contains 20 mol%. When the content of the structural unit b1 in all the structural units is in the above range, an effect of excellent adhesion to the adherend can be obtained.

Examples of the (meth) acrylate containing an amide bond to be the structural unit b1 include those used as a (meth) acrylate containing an amide bond to be the structural unit a1 described above. Examples of (meth) acrylates containing an amide bond to be the structural unit b1 include various optical films of N, N-dialkyl (meth) acrylamide such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide. It is suitably used because of its excellent adhesion to the skin.
The monomer that forms the structural unit b1 may be one type, or two or more types. The structural unit b1 and the structural unit a1 may be the same, may be different, or may be partially the same.

  The constituent unit b2 containing a functional group having reactivity to the functional group contained in the curing agent C is contained in an amount of 0.5 to 10 mol% in all constituent units constituting the (meth) acrylic resin B, preferably 1 It is contained at -7 mol%, more preferably at 1 to 6 mol%. When the content of the structural unit b2 in all the structural units is 0.5 to 10 mol%, the reaction with the curing agent C can be easily advanced.

  A structural unit containing an amide bond and containing a functional group having reactivity with the functional group contained in the curing agent C belongs to both of the structural units b1 and b2. Moreover, even if it is a structural unit containing the said functional group, depending on the kind of hardening | curing agent C, the functional group contained in a structural unit may not have the reactivity with respect to the functional group contained in the hardening agent C. . In that case, the structural unit is not the structural unit b2.

  The structural unit b2 is preferably a structural unit derived from a (meth) acrylate monomer. As a functional group which has reactivity with respect to the functional group contained in the hardening agent C, a hydroxy group, a carboxy group, an epoxy group etc. are mentioned, for example.

  Examples of the monomer containing a functional group having reactivity with the functional group contained in the curing agent C to be the structural unit b2 include those used as the monomer to be the structural unit a2 described above. The structural unit b2 and the structural unit a2 may be the same, may be different, or may be partially the same. The monomers for forming the structural unit b2 are not limited to those listed above. The monomer that forms the structural unit b2 may be of one type or may include two or more types.

  When, for example, the curing agent C is an isocyanate compound, the structural unit b2 is preferably one containing a hydroxy group but not containing a carboxy group, or one containing a hydroxy group and a carboxy group. In particular, when the curing agent C is an isocyanate compound, (meth) acrylate containing a hydroxy group but not containing a carboxy group as a monomer for forming the structural unit b2 and (meth) acrylate containing a hydroxy group and a carboxy group It is preferable to use one or both of the above.

  As a monomer which forms the structural unit b3, what is used as a monomer which forms the structural unit a3 mentioned above is mentioned. The structural unit b3 and the structural unit a3 may be the same, may be different, or may be partially the same.

The monomers for forming the structural unit b3 are not limited to those listed above. The monomer for forming the structural unit b3 may be of one type, or may include two or more types.
In addition, even if it is the monomer mentioned as a specific example of the monomer which forms the structural unit b3, depending on how to choose the curing agent C, a functional group having reactivity to the functional group contained in the curing agent C is included. There is a case. In this case, the structural unit derived from the monomer is referred to as structural unit b2.

  The (meth) acrylic resin B can contain a structural unit derived from a polymerizable monomer other than the structural units b1, b2 and b3 as a copolymerization component, as long as the polymerizability is not impaired. Examples of such polymerizable monomers include polymerizable monomers other than the structural units a1, a2, and a3 used in the (meth) acrylic resin A. The polymerizable monomer used in the (meth) acrylic resin B and the polymerizable monomer used in the (meth) acrylic resin A may be the same, may be different, or may be only part of the same. Good.

The weight average molecular weight of the (meth) acrylic resin B is preferably 50 to 150,000, more preferably 600 to 1,300,000, and still more preferably 70 to 1,000,000. When the weight average molecular weight of the (meth) acrylic resin B is 500,000 or more, a pressure-sensitive adhesive composition having a larger cohesive force is obtained. In addition, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin B having a weight average molecular weight of 500,000 or more, a pressure-sensitive adhesive sheet in which the adhesive residue after peeling is suppressed. And is preferable. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing a (meth) acrylic resin B having a weight average molecular weight of 1,500,000 or less, a pressure-sensitive adhesive sheet having higher adhesive strength is obtained.
The weight average molecular weight of (meth) acrylic resin B can be measured, for example, by GPC (gel permeation chromatography) or the like.

The glass transition temperature Tg of (meth) acrylic resin B is preferably -40 to -10 ° C, more preferably -30 to -10 ° C, and still more preferably -30 to -15 ° C. It becomes an adhesive composition which has larger cohesive force as Tg of (meth) acrylic resin B is -40 degreeC or more. In addition, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin B having a Tg of -40 ° C or higher, a pressure-sensitive adhesive sheet capable of obtaining higher peel resistance Become. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of a cured product of a pressure-sensitive adhesive composition containing (meth) acrylic resin B having a Tg of −10 ° C. or less, a pressure-sensitive adhesive sheet in which zipping at the time of peeling is suppressed Become. The Tg of the (meth) acrylic resin B can be adjusted by appropriately changing the type and composition ratio of the monomers constituting the (meth) acrylic resin B.
The glass transition temperature Tg of (meth) acrylic resin B can be measured, for example, by a differential scanning calorimeter (DSC) or the like.

<1-3. Hardener C>
The curing agent C is an isocyanato group (biuret) as a functional group having reactivity with a functional group contained in the structural unit a2 of the (meth) acrylic resin A and a functional group contained in the structural unit b2 of the (meth) acrylic resin B And a plurality of functional groups selected from the group consisting of an epoxy group, a hydroxy group, a carboxy group, an amino group, and an aziridine group. The plurality of functional groups may be of one type or of multiple types. Preferred functional groups are an isocyanate group and an epoxy group from the viewpoint of reactivity. As a curing agent C, an isocyanate type compound, an epoxy resin, an epoxy type compound, an aziridine type compound, a melamine type compound etc. are mentioned, for example. The curing agent C may be only one kind of compound or may contain two or more kinds of compounds.

  Examples of isocyanate compounds include hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, Diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethyl xylylene diisocyanate, 1,5-naphthalene diisocyanate, and their biuret, isocyanurate, trimethylolpropane Tolylene diisocyanate adduct, xylylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, methylene bis (4-phenyl) Tan) triisocyanate, and the like. Among these, isocyanurate of hexamethylene diisocyanate is preferable from the viewpoint of heat resistance.

As an epoxy resin, the epoxy resin of bisphenol A * epichlorohydrin type is mentioned, for example.
Examples of epoxy compounds include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,1 6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether and the like. Among these, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane is preferable from the viewpoint of heat resistance.

  Examples of aziridine compounds include, for example, tetramethylolmethane-tri-β-aziridinyl propionate, trimethylolpropane-tri-β-aziridinyl propionate, N, N'-diphenylmethane-4,4'- Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like can be mentioned.

  Examples of the melamine compound include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine and the like.

<2. Method of producing pressure-sensitive adhesive composition>
<2-1. Synthesis of (meth) acrylic resin A and (meth) acrylic resin B>
In the present embodiment, there is no need to distinguish between the method of synthesizing the (meth) acrylic resin A and the method of synthesizing the (meth) acrylic resin B. Therefore, hereinafter, the method of synthesizing (meth) acrylic resin A and the method of synthesizing (meth) acrylic resin B will be collectively described as a method of synthesizing (meth) acrylic resin. The (meth) acrylic resin A and the (meth) acrylic resin B may be synthesized using the same method, or may be synthesized using different methods.

When synthesizing (meth) acrylic resin A, (meth) acrylate containing an amide bond that forms structural unit a1 of (meth) acrylic resin A as a monomer, a monomer that forms structural unit a2, and necessary Accordingly, (meth) acrylate monomer is used to form the structural unit a3.
When synthesizing (meth) acrylic resin B, (meth) acrylate containing an amide bond that forms structural unit b1 of (meth) acrylic resin B as a monomer, a monomer that forms structural unit b2, and necessary Accordingly, (meth) acrylate monomer is used to form the structural unit b3.

  Although the synthesis method of the (meth) acrylic resin is not limited, it is preferable to synthesize the above-mentioned monomer by ion polymerization or radical polymerization. When using ion polymerization, even if it is a trace amount of impurities, a large-scale installation is needed for the reason of superposition | polymerization stopping. For this reason, in mass production etc., it is more preferable to synthesize | combine a (meth) acrylic resin by radical polymerization.

  The polymerization initiator to be used when synthesizing a (meth) acrylic resin by radical polymerization is not particularly limited, and, for example, an oil-soluble polymerization initiator such as an azo polymerization initiator or a peroxide polymerization initiator is used. Is preferred. Only one type of polymerization initiator may be used, or two or more types may be used in combination.

  As an azo polymerization initiator, for example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2) 2,4-Dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2,4,4 4-trimethylpentane), dimethyl-2,2'-azobis (2-methyl propionate) and the like.

  As a peroxide type polymerization initiator, for example, benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis (t -Butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclododecane and the like.

  The use amount of the polymerization initiator is not particularly limited, but preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of all the monomers used for the synthesis of the (meth) acrylic resin, for example. The content is more preferably 4 parts by mass, further preferably 0.03 to 3 parts by mass. The molecular weight of the (meth) acrylic resin synthesized can be adjusted by adjusting the amount of the polymerization initiator used. When the amount of the polymerization initiator used is increased, the molecular weight of the (meth) acrylic resin tends to decrease. When the amount of the polymerization initiator used is reduced, the molecular weight of the (meth) acrylic resin tends to increase.

  As a polymerization method of the (meth) acrylic resin, methods such as solution polymerization, emulsion polymerization, bulk polymerization and suspension polymerization can be used. Among these polymerization methods, it is particularly preferable to use solution polymerization because a (meth) acrylic resin containing no impurities such as an emulsifier is obtained.

  The solvent used when the synthesis of the (meth) acrylic resin is carried out by solution polymerization can be appropriately selected according to the type of monomer and the like. For example, as a solvent, esters such as ethyl acetate, n-propyl acetate and n-butyl acetate, aromatic hydrocarbons such as toluene and benzene, aliphatic hydrocarbons such as n-hexane and n-heptane, cyclohexane, methylcyclohexane and the like Organic solvents such as alicyclic hydrocarbons and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone. These solvents may be used alone or in combination of two or more.

2-2. Method of mixing each component>
The pressure-sensitive adhesive composition of the present embodiment is prepared by mixing a resin component containing (meth) acrylic resin A and (meth) acrylic resin B, a curing agent C, and an additive optionally contained. can get.
When mixing the materials of the pressure-sensitive adhesive composition, it is preferable to carry out in a solvent or a dispersion medium because a pressure-sensitive adhesive composition in which each component is uniformly mixed is easily obtained. Specifically, in the solution containing the resin solution obtained after solution polymerization of (meth) acrylic resin A and / or the resin solution obtained after solution polymerization of (meth) acrylic resin B, mixing of each component is carried out It is preferred to do.
When it is not preferable to mix in a solution depending on conditions of the pressure-sensitive adhesive composition, cost, manufacturing equipment and the like, other mixing methods can be appropriately selected.

  Hereinafter, as a method for producing the pressure-sensitive adhesive composition of the present embodiment, a case where (meth) acrylic resin A, (meth) acrylic resin B, and curing agent C are mixed in a solution will be described as an example. The mixing method of each component used as the adhesive composition of this embodiment is not restricted to the method mentioned below.

When (meth) acrylic resin A is synthesized by solution polymerization, a resin solution containing (meth) acrylic resin A is obtained after polymerization. Similarly, when (meth) acrylic resin B is synthesized by solution polymerization, a resin solution containing (meth) acrylic resin B can be obtained after polymerization.
In this embodiment, a pressure-sensitive adhesive composition is produced by mixing a resin solution containing (meth) acrylic resin A obtained after polymerization, a resin solution containing (meth) acrylic resin B, and a curing agent C. It is preferable to do.

  The resin solution containing (meth) acrylic resin A obtained after polymerization and / or the resin solution containing (meth) acrylic resin B obtained after polymerization may be used as it is as a material of the pressure-sensitive adhesive composition, or Before mixing with each component to be the agent composition, the solvent may be volatilized and concentration may be performed or the solvent may be additionally diluted, if necessary.

When mixing the curing agent C with each component to be the pressure-sensitive adhesive composition, the curing agent C may be mixed in advance in the form of a solution in which the curing agent C is dissolved in a solvent or dispersed in a dispersion medium.
When mixing each component used as a pressure sensitive adhesive composition, all the components may be added simultaneously and mixed, and the timing to add for every component is suitably determined in consideration of the nature, reactivity, etc. of each component. May be
When mixing with each component used as an adhesive composition, you may stir as needed.
In the present embodiment, the pressure-sensitive adhesive composition obtained by mixing the components to be the pressure-sensitive adhesive composition may be concentrated or diluted as necessary.

<3. Adhesive sheet>
The pressure-sensitive adhesive sheet of the present embodiment has a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition of the present embodiment. The pressure-sensitive adhesive sheet of the present embodiment may have a pressure-sensitive adhesive layer on one side or both sides of a substrate, or may be formed only of a pressure-sensitive adhesive layer not having a substrate.
Hereinafter, as a pressure-sensitive adhesive sheet of the present embodiment, a pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive sheet having no substrate will be described by way of examples. In addition, the manufacturing method of the adhesive sheet which has a base material demonstrated below and the adhesive sheet which does not have a base material is only an example, and if the same adhesive sheet is obtained, even if it uses another manufacturing method. Good.

<3-1. Adhesive sheet having a substrate>
The pressure-sensitive adhesive sheet having a substrate has a substrate and a pressure-sensitive adhesive layer formed on one side or both sides of the substrate. An adhesive layer contains the hardened | cured material of the adhesive composition of this embodiment.
The thickness of the pressure-sensitive adhesive layer can be appropriately adjusted according to the purpose of use of the pressure-sensitive adhesive sheet, the use environment, and the like. The thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm. When the thickness of the pressure-sensitive adhesive layer is 3 μm or more, a sufficiently high adhesive strength to an adherend can be obtained, and the peel resistance to a constant load can be improved, which is preferable. When the thickness of the pressure-sensitive adhesive layer is 100 μm or less, the thickness becomes preferable as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet used for the electronic device. The thickness of the pressure-sensitive adhesive layer is more preferably 5 to 50 μm, further preferably 10 to 30 μm.

  The thickness of the substrate used for the pressure-sensitive adhesive sheet can be appropriately set depending on the material of the substrate, the use of the pressure-sensitive adhesive sheet, and the like. For example, when a resin film is used as the substrate, the thickness of the substrate is preferably 5 to 200 μm, and more preferably 10 to 100 μm, because the strength and flexibility of the substrate are appropriate.

Although the material of the base material used for an adhesive sheet is not specifically limited, For example, a resin film, a resin foam, paper, a nonwoven fabric etc. are mentioned.
As a resin film used as a base material, For example, Polyolefin resin films, such as a polyethylene film and a polypropylene film, Polyester resin films, such as a PET (polyethylene terephthalate) film, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester Examples thereof include modified olefin resin films such as copolymers, polyvinyl chloride resin films, polyurethane resin films, cycloolefin polymer resin films and the like.
As a resin foam used for a base material, a polyethylene foam, a polypropylene foam, an acrylic foam, a urethane foam, an ethylene propylene rubber foam etc. are mentioned, for example.

  On the surface of the substrate on which the pressure-sensitive adhesive layer is formed, if necessary, the pressure-sensitive adhesive layer is formed by antifouling treatment, acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, ultraviolet light treatment, ozone treatment, etc. A surface treatment may be applied to fix on the surface of the material.

  When the adhesive sheet is a double-sided tape used for assembling a display module, as a substrate, for example, a film printed black for preventing light transmission, a film printed white for improving light reflectivity, metal deposition Can be used.

In the present embodiment, it is preferable that a separator be attached to the surface (adhesive surface) opposite to the substrate in the pressure-sensitive adhesive layer formed on one side or both sides of the substrate. By sticking the separator, the adhesive surface of the adhesive layer can be protected from moisture, dust and the like.
As a material of a separator, the resin film etc. which are used as a base material mentioned above are mentioned, for example. It is preferable that the surface facing the adhesive surface of the resin film used as a separator is subjected to easy peeling treatment. As a peeling process, the process etc. which apply | coat a silicone compound, a fluorine compound, etc. are mentioned to the opposing surface with the adhesive surface of a resin film, for example. The separator is peeled off from the pressure-sensitive adhesive layer when using the pressure-sensitive adhesive sheet.

<3-2. Method for Producing Pressure-Sensitive Adhesive Sheet Having Base Material>
As a method for producing a pressure-sensitive adhesive sheet having a substrate, for example, the pressure-sensitive adhesive composition is applied to one side or both sides of the substrate and dried to remove the solvent, and the pressure-sensitive adhesive composition is further cured by heating or the like. And the method of forming the adhesive layer which consists of hardened | cured material of an adhesive composition. The pressure-sensitive adhesive layer obtained after drying by heating may be further aged at 20 to 60 ° C. for 24 to 100 hours, if necessary. By aging, an effect is obtained that the crosslinking by the curing agent proceeds more.

  The method for applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and can be appropriately selected. For example, as a method for applying a pressure-sensitive adhesive composition to a substrate, various coaters such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, direct coater, etc. The method used, the screen printing method, etc. may be mentioned.

  The pressure-sensitive adhesive composition to be applied to the substrate may be diluted with an organic solvent for the purpose of viscosity adjustment, depending on the application method, application conditions, and the like. Examples of the organic solvent used for dilution include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol, isopropanol, n-propyl acetate and the like. These organic solvents may be used alone or in combination of two or more. The organic solvent used for dilution is removed by drying after applying the pressure-sensitive adhesive composition to a substrate.

  In the present embodiment, after the pressure-sensitive adhesive layer is formed on one side or both sides of the substrate, the separator may be attached to the surface (pressure-sensitive adhesive surface) opposite to the substrate of the pressure-sensitive adhesive layer.

<3-3. Modified Example of Method of Manufacturing Pressure-Sensitive Adhesive Sheet Having Substrate>
As another method of producing a pressure-sensitive adhesive sheet having a substrate, for example, the pressure-sensitive adhesive composition is applied onto a first substrate and dried to remove the solvent, and the pressure-sensitive adhesive composition is cured by heating or the like. After forming the pressure-sensitive adhesive layer, there is a method of transferring the obtained pressure-sensitive adhesive layer from the first base material to the second base material. The pressure-sensitive adhesive layer may be transferred onto only one side of the second base, or may be transferred onto both sides of the second base.

As a material of a 1st base material, the thing similar to the base material mentioned above and the separator mentioned above can be used, and it is preferable to use the resin film used as a base material mentioned above.
It is preferable that the surface on which the pressure-sensitive adhesive composition of the first base material is applied be subjected to the easy peeling treatment, as in the case of the surface facing the pressure-sensitive adhesive surface of the separator described above. When the surface to which the pressure-sensitive adhesive composition of the first base material is applied is subjected to peeling treatment, the pressure-sensitive adhesive layer can be efficiently peeled from the first base material when the pressure-sensitive adhesive layer is transferred onto the second base material. .

  The example of the method of apply | coating an adhesive composition to a 1st base material is as having illustrated by the manufacturing method of the adhesive sheet which has the base material mentioned above. The pressure-sensitive adhesive composition may be appropriately diluted, for example, using the organic solvent used for the dilution exemplified above, before being applied to the first substrate.

As a material of a 2nd base material, the thing similar to the base material mentioned above can be used.
The surface of the second substrate on which the pressure-sensitive adhesive layer is transferred is subjected to surface treatment for fixing the pressure-sensitive adhesive layer to the surface of the substrate, similarly to the surface on which the pressure-sensitive adhesive layer of the substrate is formed. It may be done. When the surface of the second substrate on which the pressure-sensitive adhesive layer is to be transferred is surface-treated, the pressure-sensitive adhesive layer can be more reliably transferred to the second substrate. The example of surface treatment is as surface treatment of the base material described in the manufacturing method of the adhesive sheet which has the base material mentioned above.
The material of the first base material may be the same as or different from the material of the second base material.

In the present embodiment, after the pressure-sensitive adhesive layer is transferred to the second base material, the first base material is peeled off from the pressure-sensitive adhesive layer to expose the pressure-sensitive adhesive layer. Thereafter, a separator may be attached to the surface (adhesive surface) opposite to the second substrate in the exposed pressure-sensitive adhesive layer.
In this manufacturing method, after the pressure-sensitive adhesive layer formed on the first base material is attached to the second base material, the first base material is not peeled off from the pressure-sensitive adhesive layer, and the first base material is used as it is as a separator May be

<3-4. Adhesive sheet without substrate>
The adhesive sheet which does not have a base material is an adhesive layer containing the hardened | cured material of an adhesive composition. The thickness of the pressure-sensitive adhesive layer is the same as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet having a substrate.

<3-5. Method for Producing Pressure-Sensitive Adhesive Sheet Having No Substrate>
As a method for producing a pressure-sensitive adhesive sheet having no substrate, for example, the pressure-sensitive adhesive composition is applied on a substrate and dried to remove the solvent, and the pressure-sensitive adhesive composition is further cured by heating or the like. The method of forming the adhesive layer which consists of hardened | cured material of an adhesive composition, and peeling this from a base material is mentioned.
The pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) having no substrate produced may be subjected to aging at 20 to 60 ° C. for 24 to 100 hours, as necessary, before or after peeling from the substrate.

A separator may be attached to the surface of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) having no substrate. As a separator, the base used when forming an adhesive layer may be used without peeling from the adhesive layer.
When separators are provided on both sides of the pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer, the substrate used when forming the pressure-sensitive adhesive layer is used without peeling as a separator on one side of the pressure-sensitive adhesive layer. A separator prepared separately from the substrate may be attached as the separator on the other side. Moreover, when providing a separator on both surfaces of the adhesive sheet which consists of an adhesive layer, you may each stick the separator prepared separately from the base material on both surfaces of the adhesive layer peeled from the base material.
A separator is exfoliated at the time of use of an adhesive sheet.

Hereinafter, examples of the present invention will be described. The following examples are representative examples of the present invention, and the present invention is not limited to these examples.
<1. Synthesis of (meth) acrylic resin>
Using the monomers shown in Table 1 in the proportions shown in Table 1, (meth) acrylic resins of A1 to A4, AC, B1 and BC were synthesized by the synthesis method shown below. The weight average molecular weight and glass transition temperature of the synthesized (meth) acrylic resins A1 to A4, AC, B1 and BC were measured by the methods described below. The results are shown in Table 1.

[Measurement of weight average molecular weight of (meth) acrylic resin]
The weight average molecular weight was measured using gel permeation chromatography (manufactured by Showa Denko KK, Showdex (registered trademark) GPC-101) under the following conditions, and calculated in terms of polystyrene.
Column: Showdex (registered trademark) LF-804 manufactured by Showa Denko KK
Column temperature: 40 ° C
Sample: 0.2% by mass solution of (meth) acrylic resin in tetrahydrofuran Flow rate: 1 ml / min Eluent: tetrahydrofuran Detector: RI detector (differential refractive index detector)

[Measurement of glass transition temperature of (meth) acrylic resin]
A 10 mg sample of (meth) acrylic resin was packed in a sample pan made of aluminum to prepare a sample. This sample was subjected to differential scanning calorimetry by changing the temperature from -60 ° C to 150 ° C at a heating rate of 10 ° C / min using a differential scanning calorimeter (DSC), and the endothermic start temperature Tg due to glass transition Was measured. In addition, when two Tg was observed, the simple average value of two Tg was made into the glass transition temperature.

[(Meth) acrylic resin A1]
In a reactor provided with a stirrer, a temperature controller, a reflux condenser, a dropping funnel, and a thermometer, as a monomer, 39 mol% of N, N-dimethyl acrylamide, 1 mol% of 2-hydroxyethyl acrylate, 1 mol% of acrylic acid, n-butyl 59 mol% of acrylate was charged, and 100 parts by mass of ethyl acetate was charged as a solvent with respect to 100 parts by mass of the monomer.
After heating the solution in the reactor to start refluxing, 0.07 parts by mass of azobisisobutyronitrile as a polymerization initiator was added to 100 parts by mass of the monomer. Thereafter, the monomers were polymerized at reflux temperature of ethyl acetate for 8 hours to obtain (meth) acrylic resin A1.
The (meth) acrylic resin A1 synthesized had a weight average molecular weight of 650,000 and a glass transition temperature of -14 ° C. In addition, content (mol%) of the structural unit derived from each monomer of (meth) acrylic resin A1 is regarded as the ratio (mol%) of the charged monomer. The same applies to (meth) acrylic resins A2 to A4, AC, B1 and BC described below.

[(Meth) acrylic resins A2 to A4, AC, B1, BC]
The (meth) acrylic resins A2 to A4, AC, B1, and BC were synthesized in the same manner as the (meth) acrylic resin A1 except that monomers were charged as shown in Table 1. The weight average molecular weights and glass transition temperatures of the obtained (meth) acrylic resins A2 to A4, AC, B1 and BC are as shown in Table 1.

<2. Preparation of adhesive composition>
At a ratio shown in Table 2, one of (meth) acrylic resins A1 to A4 and AC, (meth) acrylic resin B1 or BC, and Coronate HX as a curing agent (based on hexamethylene diisocyanate manufactured by Tosoh Corp. Polyisocyanurate type) or Tetrad C (Mitsubishi Gas Chemical Co., Ltd., epoxy compound (1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane)) is mixed, and the solid content concentration is 30% by mass. The mixture was diluted with ethyl acetate and stirred at 25 ° C. using a disper. As a result, ethyl acetate solutions (hereinafter sometimes referred to as “composition solutions”) of the pressure-sensitive adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 4 were obtained.

In Examples 1 to 5 and Comparative Examples 1 to 4, the (meth) acrylic resin synthesized from the amounts of the monomers and solvents used for the synthesis of (meth) acrylic resins A1 to A4, AC, B1, and BC is included. The solid content concentration of the resin solution was calculated. Furthermore, the amount of ethyl acetate necessary to obtain a composition solution having a solid content of 30% by mass was calculated from the solid content concentration of the resin solution containing the (meth) acrylic resin and the amount of the curing agent. In addition, as for the resin solution containing (meth) acrylic resin, all are solid content concentration 50 mass%. The amount of the curing agent added to the total 100 parts by mass of the resin solution containing two types of (meth) acrylic resins shown in Table 2 was 0. 0 in all of Examples 1 to 5 and Comparative Examples 1 to 4. 5 parts by mass.
Therefore, when obtaining the composition solutions of Examples 1 to 5 and Comparative Examples 1 to 4 having a solid content concentration of 30% by mass, a total of 100 parts by mass of resin solutions containing two types of (meth) acrylic resins To this was added 68 parts by weight of ethyl acetate.

<3. Evaluation of adhesive composition>
The adhesive sheet was produced by the method shown below using the composition solution of Examples 1-5 and Comparative Examples 1-4, and the method shown below evaluated. The results are shown in Table 2.

[Production method of adhesive sheet]
The composition solution is cast on one side of a 50 μm-thick PET film so that the thickness of the coating layer is 35 μm, and dried by heating at 80 ° C. for 5 minutes to obtain a thickness of a cured product of the pressure-sensitive adhesive composition. A 10 μm thick adhesive layer was formed. Thereafter, the surface of the pressure-sensitive adhesive layer was bonded to the surface of the separator subjected to peeling treatment so as to face each other, and aging was performed at 40 ° C. for 72 hours. As a separator, a 25 μm-thick PET film having a release treatment for applying a silicone compound on one side was used.
By the above process, the adhesive layer was provided on the base material, and the adhesive sheet by which the separator was stuck on the surface of the adhesive layer was obtained.

[Measurement of adhesive strength]
The adhesive sheet was cut into a size of 25 mm × 150 mm, and the separator was peeled off. Thereafter, the entire surface of the exposed pressure-sensitive adhesive layer (measurement surface) is attached to a test plate made of glass, and the rubber roller (diameter: 85 mm, width: 50 mm) having a mass of 2 kg (load 19.6 N) is reciprocated once. , And a sample for measurement.

The obtained measurement sample was left for 30 minutes in an environment of a temperature of 23 ° C. and a relative humidity of 50%. Thereafter, according to JIS K 6854-2, a tensile test in the direction of 180 ° was performed at a peeling speed of 0.3 m / min to measure the adhesion (N / 25 mm) of the pressure-sensitive adhesive layer to the glass plate.
After measurement, the average value of the adhesive strength in the curve showing the adhesive strength-peeling distance is calculated over the peeling length of 25 mm to 125 mm from the peeling start point (0 mm), and this is the adhesive strength of the adhesive layer to the glass plate (N / 25 mm).

[Evaluation of peeling resistance to constant load load for a long time under high temperature]
The separator was peeled off from the pressure-sensitive adhesive sheet having a size of 20 mm × 50 mm in width to expose the pressure-sensitive adhesive layer. Then, the exposed surface of the pressure-sensitive adhesive layer was attached to a glass plate, and was left for 24 hours under conditions of a temperature of 23 ° C. and a humidity of 50%. Thereafter, the temperature of the glass plate and the pressure-sensitive adhesive sheet was set to 60 ° C., and a load of 0.49 N was applied in the direction of 90 ° for 30 minutes, and the peeling distance (the length of the peeled glass plate of the pressure-sensitive adhesive sheet) was measured. The measurement results were evaluated according to the following criteria.

:: Peeling distance is 5 mm or less ○: Peeling distance is more than 5 mm and more than 10 mm Δ: Peeling distance is more than 10 mm and 15 mm or less ×: Peeling distance is more than 15 mm

<4. Evaluation result of adhesive composition>
As shown in Table 2, it is confirmed that the adhesive sheets of Examples 1 to 5 can obtain sufficiently high adhesive strength even if the thickness is thin, and can maintain high peel resistance even when used for a long time under high temperature did it.

On the other hand, the pressure-sensitive adhesive composition of Comparative Example 1 includes (meth) acrylic resin BC in which the proportion of the structural unit b1 derived from (meth) acrylate containing an amide bond is low. The pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of Comparative Example 1 was not sufficiently resistant to peeling under a constant load load for a long time under high temperature.
Moreover, the adhesive composition of the comparative example 2 contains (meth) acrylic resin AC with a high ratio of the structural unit a1 derived from the (meth) acrylate containing an amide bond. The pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of Comparative Example 2 also did not have sufficient peel resistance to constant load load for a long time under high temperature.

The pressure-sensitive adhesive composition of Comparative Example 3 contains (meth) acrylic resin A1 in excess, in which the proportion of constituent units derived from (meth) acrylate containing an amide bond is high. The pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of Comparative Example 3 was insufficient in peel resistance to constant load load for a long time under high temperature.
The pressure-sensitive adhesive composition of Comparative Example 4 contains (meth) acrylic resin B1 in excess, in which the proportion of structural units derived from (meth) acrylate containing an amide bond is low. The pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition of Comparative Example 4 was insufficient in peel resistance to a constant load load for a long time under high temperature. Moreover, the adhesive force using the adhesive sheet of the comparative example 4 was also inadequate.

Claims (10)

(Meth) acrylic resin A, (meth) acrylic resin B, and curing agent C, and
The (meth) acrylic resin A contains 25 to 50 mol% of a (meth) acrylate-derived structural unit a1 containing an amide bond in all the structural units constituting the (meth) acrylic resin A, and the curing agent C 0.5 to 10 mol% of a structural unit a2 containing a functional group having reactivity with the functional group contained,
The (meth) acrylic resin B contains 5 to 24 mol% of a (meth) acrylate-derived structural unit b1 containing an amide bond in all the structural units constituting the (meth) acrylic resin B, and the curing agent C 0.5 to 10 mol% of a structural unit b2 containing a functional group having reactivity with the functional group contained,
The curing agent C has a plurality of functional groups selected from the group consisting of isocyanato groups, epoxy groups, hydroxy groups, carboxy groups, amino groups and aziridine groups,
The content of the (meth) acrylic resin A with respect to the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B is 30 to 80 mass%,
The adhesive composition characterized in that the curing agent C is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of a total amount of the (meth) acrylic resin A and the (meth) acrylic resin B.   The pressure-sensitive adhesive composition according to claim 1, wherein the weight average molecular weight of the (meth) acrylic resin A is 500,000 to 1,500,000.   The pressure-sensitive adhesive composition according to claim 1, wherein a weight average molecular weight of the (meth) acrylic resin B is 500,000 to 1,500,000.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the structural unit a1 is a structural unit derived from an N, N-dialkyl (meth) acrylamide monomer. The structural unit a1 comprises N, N-diethylacrylamide,
The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the structural unit b1 comprises N, N-dimethyl acrylamide.   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the functional group contained in the curing agent C is at least one selected from the group consisting of an isocyanate group and an epoxy group.   The adhesion according to any one of claims 1 to 6, wherein the structural unit a2 is at least one selected from the group consisting of a structural unit derived from a (meth) acrylate containing a hydroxy group and a structural unit derived from acrylic acid. Agent composition.   The adhesive sheet containing the hardened | cured material of the adhesive composition as described in any one of Claims 1-7. A method for producing a pressure-sensitive adhesive composition, which comprises mixing (meth) acrylic resin A, (meth) acrylic resin B, and a curing agent C,
The (meth) acrylic resin A contains 25 to 50 mol% of a (meth) acrylate-derived structural unit a1 containing an amide bond in all the structural units constituting the (meth) acrylic resin A, and the curing agent C 0.5 to 10 mol% of a structural unit a2 containing a functional group having reactivity with the functional group contained,
The (meth) acrylic resin B contains 5 to 24 mol% of a (meth) acrylate-derived structural unit b1 containing an amide bond in all the structural units constituting the (meth) acrylic resin B, and the curing agent C 0.5 to 10 mol% of a structural unit b2 containing a functional group having reactivity with the functional group contained,
The curing agent C has a plurality of functional groups selected from the group consisting of isocyanato groups, epoxy groups, hydroxy groups, carboxy groups, amino groups and aziridine groups,
The addition amount of the (meth) acrylic resin A is 30 to 80% by mass with respect to the total amount of the (meth) acrylic resin A and the (meth) acrylic resin B,
0.1 to 10 parts by mass of the curing agent C is added to 100 parts by mass of the total of the (meth) acrylic resin A and the (meth) acrylic resin B. Manufacturing method.   A method for producing a pressure-sensitive adhesive sheet, comprising the step of curing the pressure-sensitive adhesive composition obtained by the method according to claim 9.