Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/062—Copolymers with monomers not covered by C09J133/06
  • C09J133/066—Copolymers with monomers not covered by C09J133/06 containing -OH groups
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/08—Macromolecular additives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
  • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C09J7/385—Acrylic polymers

Definitions

• the present invention relates to an adhesive composition.
• the present invention also relates to an adhesive tape having an adhesive layer containing the adhesive composition.
• adhesive tapes are used for assembly (e.g., Patent Documents 1 and 2).
• Adhesive tapes are also used for bonding optical components (e.g., Patent Document 3).
• Adhesive compositions and adhesive tapes used to fix optical components are required to have both adhesive strength and optical transparency.
• adhesive compositions and thinner adhesive tapes there has been a demand for thinner adhesive compositions and thinner adhesive tapes.
• conventional adhesive compositions could not exert sufficient adhesive strength.
• adhesive compositions and adhesive tapes have been improved in adhesive strength by including a tackifier resin, but when the adhesive composition or adhesive tape contains a tackifier resin, it can cause turbidity or yellowing, making it difficult to obtain optical transparency.
• the present invention aims to provide a pressure-sensitive adhesive composition that can achieve both excellent adhesive strength and excellent optical transparency even when the applied thickness is thin.
• the present invention aims to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition.
• the present disclosure 1 relates to a pressure-sensitive adhesive composition that contains an acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and that satisfies at least one constitution selected from the group consisting of the following first constitution and the following second constitution:
• the acrylic copolymer has a constituent unit derived from a polar functional group-containing monomer, and the acrylic copolymer is an acrylic (meth)acrylate.
• Disclosure 2 is a pressure-sensitive adhesive composition according to Disclosure 1, in which in the above-mentioned first configuration, the acrylic copolymer has a constituent unit derived from an alkyl (meth)acrylate ester, in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 4 or less carbon atoms, and in the acrylic copolymer, the content of the constituent unit derived from an alkyl (meth)acrylate ester, in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 4 or less carbon atoms, is 30% by mass or more and 90% by mass or less, and the composition does not contain a tackifier resin, or contains a tackifier resin, and in the case of containing a tackifier resin, the content of the tackifier resin
• the present disclosure 3 is a pressure-sensitive adhesive composition according to the present disclosure 1 or 2, wherein the constituent unit derived from the polar functional group-containing monomer includes at least one constituent unit selected from the group consisting of a constituent unit derived from a carboxy group-containing monomer and a constituent unit derived from a hydroxyl group-containing monomer.
• the present disclosure 4 relates to the pressure-sensitive adhesive composition of the present disclosure 3, wherein the constitutional unit derived from the polar functional group-containing monomer includes a constitutional unit derived from the carboxy group-containing monomer.
• the present disclosure 5 is the pressure-sensitive adhesive composition according to the present disclosure 4, wherein, in the second configuration, the content of the structural unit derived from the carboxy group-containing monomer in the acrylic copolymer is 10 mass% or less.
• the present disclosure 6 is the pressure-sensitive adhesive composition according to the present disclosure 4 or 5, wherein the content of the structural unit derived from the carboxy group-containing monomer in the acrylic copolymer is 1 mass% or less.
• the present disclosure 7 is the pressure-sensitive adhesive composition according to the present disclosure 3, 4, 5, or 6, wherein the structural unit derived from the polar functional group-containing monomer includes a structural unit derived from the hydroxyl group-containing monomer.
• the present disclosure 8 is the pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, or 7, in the first configuration, wherein the tackifier resin T1 contains the hydrogenated terpene phenol resin.
• the present disclosure 9 is directed to the second configuration, wherein the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 2 or less,
• the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the content of structural units derived from an alkyl (meth)acrylate ester in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 2 or less carbon atoms in the acrylic copolymer is 10% by mass or more and 60% by mass or less.
• the present disclosure 10 relates to the second configuration, wherein the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 3 or more and 4 or less,
• the present disclosure 11 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.
• the present disclosure 12 is the pressure-sensitive adhesive tape of the present disclosure 11, wherein the pressure-sensitive adhesive layer has a gel fraction of 10 mass % or more and 80 mass % or less.
• the present disclosure 13 is the pressure-sensitive adhesive tape of the present disclosure 11 or 12, wherein the pressure-sensitive adhesive layer has a thickness of 15 ⁇ m or less.
• Disclosure 14 is the pressure-sensitive adhesive tape of Disclosure 13, which has a 180° peel strength from glass at 23° C. of 9 N/inch or more after being left at 23° C. for 24 hours after application.
• the present disclosure 15 is the pressure-sensitive adhesive tape of the present disclosure 11, 12, 13, or 14, having a haze at 23° C. of 1.0% or less.
• the present disclosure 16 is a pressure-sensitive adhesive tape according to the present disclosure 11, 12, 13, 14, or 15, which does not have a substrate. The present invention will be described in detail below. In addition, matters common to the first configuration and the second configuration will be described without being particularly specified.
• the inventors have studied the composition of the adhesive composition, included an acrylic copolymer having a specific structure, and studied the content and type of tackifier resin to be included in the adhesive composition. As a result, they have found that it is possible to obtain an adhesive composition that can achieve both excellent adhesive strength and excellent optical transparency even when the applied thickness is thin, and have completed the present invention.
• the pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond.
• (meth)acrylic means acrylic or methacrylic.
• the acrylic copolymer has a structure in which the structural units derived from an olefin polymer having a polymerizable unsaturated double bond at the end are aggregated by interaction to form pseudo-crosslinking points. When the acrylic copolymer has such a structure, the pressure-sensitive adhesive composition exhibits hard properties like a crosslinked pressure-sensitive adhesive composition when strain is small, and the holding power is improved.
• the above-mentioned (meth)acrylic acid alkyl esters include, for example, (meth)acrylic acid alkyl esters obtained by dehydration condensation of (meth)acrylic acid and an alcohol having a linear or branched alkyl group having 1 to 24 carbon atoms.
• alkyl esters include octyl, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acryl
• the preferred lower limit of the content of the structural units derived from the (meth)acrylic acid alkyl ester is 50% by mass, and the preferred upper limit is 95% by mass.
• the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved.
• a more preferred lower limit of the content of the structural units derived from the (meth)acrylic acid alkyl ester is 60% by mass, and an even more preferred lower limit is 70% by mass, and a more preferred upper limit is 90% by mass, and an even more preferred upper limit is 85% by mass.
• the olefin polymer having a polymerizable unsaturated double bond at the terminal may have a polymerizable unsaturated double bond at one terminal, or may have polymerizable unsaturated double bonds at both terminals.
• an olefin polymer having a polymerizable unsaturated double bond at one terminal is preferred from the viewpoint of facilitating the formation of an appropriate number of pseudo crosslinks.
• Examples of the olefin polymer having a polymerizable unsaturated double bond at one end include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, butylene polymers, etc., each of which has a group having a polymerizable unsaturated double bond at one end or both ends.
• These olefin polymers having a polymerizable unsaturated double bond at the terminal may be used alone or in combination of two or more kinds.
• Examples of the group having a polymerizable unsaturated double bond include a (meth)acryloyl group, a vinyl ether group, and a styryl group.
• a (meth)acryloyl group is preferred because of its excellent copolymerizability with the (meth)acrylic acid alkyl ester.
• Examples of the olefin polymer having a (meth)acryloyl group at the end include an ethylene macromonomer having a (meth)acryloyl group at one end, a propylene macromonomer having a (meth)acryloyl group at one end, an ethylene-butylene macromonomer having a (meth)acryloyl group at one end, an ethylene-propylene macromonomer having a (meth)acryloyl group at one end, etc.
• an ethylene-butylene macromonomer having a (meth)acryloyl group at one end and an ethylene-propylene macromonomer having a (meth)acryloyl group at one end are preferred.
• the term "macromonomer” refers to a monomer having a polymerizable functional group and a weight average molecular weight of about 1,000 to 100,000.
• the preferred lower limit of the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass, and the preferred upper limit is 30% by mass.
• the acrylic copolymer forms an appropriate number of pseudo crosslinks, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved.
• the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 30% by mass or less, the cohesive failure of the pressure-sensitive adhesive composition can be further suppressed.
• the more preferred lower limit of the content of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal is 8% by mass, and even more preferred lower limit is 10% by mass, and more preferred upper limit is 27% by mass, and even more preferred upper limit is 25% by mass.
• the pressure-sensitive adhesive composition of the present invention satisfies at least one constitution selected from the group consisting of the following first constitution and the following second constitution.
• First configuration the composition contains at least one tackifier resin T1 selected from the group consisting of a terpene phenol resin, a hydrogenated terpene phenol resin, and a xylene resin, and the content of the tackifier resin T1 is 5 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the acrylic copolymer, and does not contain a tackifier resin T2 different from the terpene phenol resin, the hydrogenated terpene phenol resin, and the xylene resin, or contains the tackifier resin T2, and when the tackifier resin T2 is contained, the content of the tackifier resin T2 is 10 parts by mass or less relative to 100 parts by mass of the acrylic copolymer.
• the acrylic copolymer has a constituent unit derived from a polar functional group-containing monomer, and the acrylic copolymer has an ester bond. in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, and in the acrylic copolymer, the content of structural units derived from (meth)acrylic acid alkyl esters, in which the carbon number of the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less, is 30% by mass or more and 90% by mass or less, and the pressure-sensitive adhesive composition of the present invention does not contain a tackifier resin or contains a tackifier resin, and in the case of containing a tackifier resin, the content of the tackifier resin is 5 parts by mass or less per 100 parts by mass of the acrylic copolymer.
• the acrylic copolymer preferably has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 8.
• the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4, the polarity of the acrylic copolymer becomes greater, and the interaction with the adherend is enhanced, thereby further improving the adhesive strength of the pressure-sensitive adhesive composition.
• the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 4 to 8, the glass transition temperature described below is easily adjusted to an appropriate range, and the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• the structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group bonded to the oxygen atom of the ester bond has 1 or more and 8 or less carbon atoms may be used alone or in combination of two or more kinds.
• the acrylic copolymer has a structural unit derived from an alkyl (meth)acrylate ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less.
• the acrylic copolymer having a structural unit derived from an alkyl (meth)acrylate ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 or more and 4 or less the polarity of the acrylic copolymer is increased, and the interaction with the adherend is enhanced, thereby improving the adhesive strength of the pressure-sensitive adhesive composition.
• the lower limit of the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 30% by mass
• the upper limit is 90% by mass.
• the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 90% by mass or less
• the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the end in the acrylic copolymer can form a pseudo crosslinking point with high cohesive strength.
• the adhesive strength and holding strength of the pressure-sensitive adhesive composition are improved.
• the preferred lower limit of the content of structural units derived from (meth)acrylic acid alkyl esters in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4 is 40% by mass, more preferably 50% by mass, and the preferred upper limit is 85% by mass, more preferably 80% by mass.
• Examples of (meth)acrylic acid alkyl esters in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4 include (meth)acrylic acid alkyl esters obtained by dehydration condensation of (meth)acrylic acid and an alcohol having a linear or branched alkyl group with 1 to 4 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, and isobutyl (meth)acrylate.
• the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 2.
• the preferred lower limit of the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 2 is 10% by mass, and the preferred upper limit is 60% by mass.
• the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 10% by mass or more, the polarity of the acrylic copolymer becomes greater, and the interaction with the adherend is enhanced, thereby further improving the adhesive strength of the pressure-sensitive adhesive composition.
• the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 60% by mass or less, it becomes easier to adjust the glass transition temperature of the acrylic copolymer described later within an appropriate range, and the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• a more preferred lower limit of the content of structural units derived from (meth)acrylic acid alkyl esters in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 2 is 15% by mass, and an even more preferred lower limit is 30% by mass.
• the acrylic copolymer preferably has a structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 3 to 4.
• the preferred lower limit of the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 3 to 4 is 60 mass%.
• the pseudo crosslinking point formed by aggregation of the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the terminal becomes smaller, and the optical transparency of the pressure-sensitive adhesive composition is further improved.
• the more preferred lower limit of the content of the structural unit derived from a (meth)acrylic acid alkyl ester in which the number of carbon atoms of the alkyl group bonded to the oxygen atom of the ester bond is 3 to 4 is 70 mass%, and the even more preferred lower limit is 75 mass%.
• the preferred upper limit of the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 3 to 4 is 90% by mass.
• the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 3 to 4 is 90% by mass or less, thereby further improving the adhesive strength.
• the more preferred upper limit of the content of the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 85% by mass, and even more preferred upper limit is 80% by mass.
• the structural unit derived from the (meth)acrylic acid alkyl ester in which the number of carbon atoms in the alkyl group bonded to the oxygen atom of the ester bond is 1 to 4 may be used alone or in combination of two or more.
• the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• the acrylic copolymer has a constituent unit derived from a polar functional group-containing monomer.
• the acrylic copolymer has a constituent unit derived from the polar functional group-containing monomer, which enhances the interaction with the adherend, thereby improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the pressure-sensitive adhesive composition contains a crosslinking agent described below, the acrylic copolymer is crosslinked via the crosslinking agent, thereby improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the acrylic copolymer preferably has a structural unit derived from a polar functional group-containing monomer.
• the acrylic copolymer has a structural unit derived from the polar functional group-containing monomer, which enhances the interaction with the adherend, thereby improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the pressure-sensitive adhesive composition contains a crosslinking agent described below
• the acrylic copolymer is crosslinked via the crosslinking agent, thereby improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the gel fraction of the pressure-sensitive adhesive layer described below can be adjusted to an appropriate range.
• the polar functional group-containing monomer examples include a carboxy group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, and an amino group-containing monomer.
• the polar functional group-containing monomer preferably includes at least one selected from the group consisting of a carboxy group-containing monomer and a hydroxyl group-containing monomer. That is, the constitutional unit derived from the polar functional group-containing monomer preferably includes at least one constitutional unit selected from the group consisting of a constitutional unit derived from a carboxy group-containing monomer and a constitutional unit derived from a hydroxyl group-containing monomer.
• These polar functional group-containing monomers may be used alone or in combination of two or more kinds.
• the acrylic copolymer has a constituent unit derived from the carboxy group-containing monomer, which enhances the interaction with the adherend, thereby further improving the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the carboxy group-containing monomer include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.
• the content of the structural unit derived from the carboxyl group-containing monomer in the acrylic copolymer is preferably 1% by mass.
• the content of the structural unit derived from the carboxyl group-containing monomer is 1% by mass or less, so that the metal corrosiveness of the pressure-sensitive adhesive composition is further reduced.
• the content of the structural unit derived from the carboxyl group-containing monomer is more preferably 0.5% by mass. From the viewpoint of metal corrosiveness, it is preferable that the acrylic copolymer does not have any structural units derived from the carboxy group-containing monomer.
• the content of the structural unit derived from the carboxyl group-containing monomer in the acrylic copolymer is preferably 10% by mass.
• the content of the structural unit derived from the carboxyl group-containing monomer is 10% by mass or less, so that the metal corrosiveness of the pressure-sensitive adhesive composition is further reduced.
• the content of the structural unit derived from the carboxyl group-containing monomer is more preferably 1% by mass. From the viewpoint of metal corrosiveness, it is preferable that the acrylic copolymer does not have any structural units derived from the carboxy group-containing monomer.
• the acrylic copolymer has a structural unit derived from the hydroxyl group-containing monomer, crosslinking between the acrylic copolymer and the adherend molecules via the crosslinking agent occurs more easily, and the adhesive strength and holding strength of the pressure-sensitive adhesive composition are further improved.
• the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.
• the preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer is 0.01% by mass, and the preferred upper limit is 2% by mass.
• the content of the structural unit derived from the hydroxyl group-containing monomer is 0.01% by mass or more, crosslinking of the acrylic copolymer via the crosslinking agent occurs more easily, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved.
• the content of the structural unit derived from the hydroxyl group-containing monomer is 2% by mass or less, the acrylic copolymer does not become too hard, and the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• the more preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer is 0.05% by mass, and the more preferred upper limit is 1% by mass.
• amide group-containing monomer examples include N-vinyl-2-pyrrolidone, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide.
• amino group-containing monomer examples include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.
• the preferred lower limit of the total content of the constituent units derived from the polar functional group-containing monomer is 0.1% by mass, and the preferred upper limit is 10% by mass.
• the total content of the constituent units derived from the polar functional group-containing monomer is 0.1% by mass or more, the interaction between the acrylic copolymer and the adherend is enhanced, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved.
• the pressure-sensitive adhesive composition contains a crosslinking agent described later, crosslinking of the acrylic copolymer via the crosslinking agent occurs more easily, and the adhesive strength and holding power of the pressure-sensitive adhesive composition are further improved.
• the acrylic copolymer does not become too hard, and the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• a more preferred lower limit of the total content of the constituent units derived from the polar functional group-containing monomer is 1% by mass, an even more preferred lower limit is 3% by mass, and a more preferred upper limit is 8% by mass, and an even more preferred upper limit is 6% by mass.
• the glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of -100°C or more and 200°C or less, and more preferably -20°C or less.
• Tg glass transition temperature
• a more preferable upper limit of the glass transition temperature of the acrylic copolymer is -30°C, and a particularly preferable upper limit is -35°C.
• the pressure-sensitive adhesive composition contains a plurality of the acrylic copolymers, it is preferable that the glass transition temperatures of all the acrylic copolymers contained in the pressure-sensitive adhesive composition are -20°C or less.
• the glass transition temperature of the acrylic copolymer can be measured by differential scanning calorimetry. More specifically, the glass transition temperature of the acrylic copolymer can be measured by a method conforming to JIS K6240:2011 using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., "220C” or the like) under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL/min) at a measurement temperature of -100°C to 200°C and a temperature rise rate of 10°C/min.
• a differential scanning calorimeter manufactured by Seiko Instruments Inc., "220C” or the like
• the glass transition temperature of the acrylic copolymer can be adjusted by the type and amount of monomers that are the raw materials for the acrylic copolymer.
• the preferred lower limit of the weight average molecular weight (Mw) of the acrylic copolymer is 500,000, and the preferred upper limit is 2,000,000.
• Mw weight average molecular weight
• the more preferred lower limit of the weight average molecular weight of the acrylic copolymer is 650,000, and the more preferred upper limit is 1,500,000.
• the polydispersity of the acrylic copolymer is preferably 1.0 at its lower limit and 6.0 at its upper limit.
• the polydispersity of the acrylic copolymer within the above range further improves the adhesive strength and holding power of the pressure-sensitive adhesive composition.
• the polydispersity of the acrylic copolymer is more preferably 1.5 at its lower limit and 4.5 at its upper limit.
• the polydispersity refers to the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn).
• the weight average molecular weight, the number average molecular weight, and the polydispersity can be determined from the molecular weight distribution in terms of polystyrene measured using gel permeation chromatography (GPC). Specifically, for example, they can be determined by measuring under the following conditions using gel permeation chromatography (Waters Corporation, "2690 Separations Module", etc.).
• Solvent Tetrahydrofuran Sample flow rate: 1 mL/min Detector: Differential refractometer RI Column: GPC KF-806L (Showa Denko) Column temperature (measurement temperature): 40°C Injection volume: 20 ⁇ L
• the content of the acrylic copolymer in the pressure-sensitive adhesive composition is not particularly limited, but it is preferably more than 50% by mass in the pressure-sensitive adhesive composition (i.e., it is the main component in the pressure-sensitive adhesive composition).
• the content of the acrylic copolymer is more than 50% by mass, the pressure-sensitive adhesive composition becomes more transparent, and the optical transparency of the pressure-sensitive adhesive composition is further improved.
• the pressure-sensitive adhesive composition of the present invention contains a tackifier resin T1.
• the tackifier resin T1 is at least one type of tackifier resin selected from the group consisting of terpene phenol resins, hydrogenated terpene phenol resins, and xylene resins.
• the tackifier resin T1 has a relatively high polarity and good compatibility with the acrylic copolymer, so it is easily incorporated into the acrylic copolymer.
• the tackifier resin T1 is easily incorporated into the acrylic copolymer, the pressure-sensitive adhesive composition can be suppressed from becoming turbid and has excellent optical transparency.
• the tackifier resin T1 does not have a polymerizable unsaturated double bond in its molecular structure and has a property of being difficult to oxidize, the pressure-sensitive adhesive composition can be suppressed from yellowing and is unlikely to lose optical transparency even after long-term use.
• the tackifier resin T1 may be used alone or in combination of two or more kinds.
• the tackifier resin T1 preferably contains at least one selected from the group consisting of the terpene phenol resin and the hydrogenated terpene phenol resin.
• the tackifier resin T1 has a hydroxyl group, and the interaction with the adherend is further enhanced, thereby further improving the adhesive strength of the pressure-sensitive adhesive composition.
• the hydrogenated terpene phenol resin is more preferred from the viewpoint of the resin having a light color and excellent optical transparency.
• the terpene phenol resin is a resin obtained by polymerizing a terpene compound in the presence of a phenol compound.
• the phenol compound include phenol, cresol, xylenol, propylphenol, norylphenol, methoxyphenol, bromophenol, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalene, resorcinol, pyrocatechol, hydroquinone, pyrogallol, 1,2,4-trihydroxybenzene, and phloroglucinol.
• terpene compounds examples include ⁇ -pinene, ⁇ -pinene, limonene, dipentene, ⁇ -3-carene, dimethyloctatriene, alloocimene, myrcene, ocimene, linalool, and cosmene.
• other compounds may be further polymerized in the terpene phenol resin.
• the phenol compounds, the terpene compounds, and the other compounds may each be used alone or in combination of two or more kinds.
• the above terpene phenol resin may be a commercially available product, such as YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.).
• the hydrogenated terpene phenol resin is a resin in which the unsaturated bonds in the terpene phenol resin are reduced to saturated bonds by hydrogenation.
• the benzene rings in the terpene phenol resin are converted to cyclohexane rings by hydrogenation.
• Examples of the method for hydrogenating the terpene phenol resin include the following methods.
• the terpene phenol resin is dissolved in purified and dried cyclohexane so that the polymer concentration becomes 5% by mass, and then the hydrogenation reaction is started under stirring at a hydrogen gas supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80° C., and when the absorption of hydrogen is completed, the reaction solution is returned to normal temperature and pressure, and the reaction solution is withdrawn from the reactor to obtain the hydrogenated terpene phenol resin.
• the hydrogenated terpene phenol resin may be a commercially available product, such as YS Polystar UH115 (manufactured by Yasuhara Chemical Co., Ltd.).
• the xylene resin is a resin obtained by reacting and polymerizing m-xylene with formaldehyde in the presence of an acid catalyst.
• the xylene resin may further contain other compounds, and it is preferable that a phenol compound is polymerized in the xylene resin.
• a phenol compound is polymerized in the xylene resin.
• the polarity of the tackifier resin T1 becomes larger, and the compatibility with the acrylic copolymer becomes better, so that the adhesive strength of the pressure-sensitive adhesive composition is further improved.
• the phenol compound polymerized in the xylene resin the same phenol compound as that polymerized in the terpene phenol resin can be used.
• the other compounds may be used alone or in combination of two or more kinds.
• the xylene resin may be a commercially available product, such as GHP-150 (manufactured by Fudow Co., Ltd.).
• the lower limit of the content of the tackifier resin T1 is 5 parts by mass, and the upper limit is 50 parts by mass.
• the adhesive strength of the adhesive composition is improved.
• the content of the tackifier resin T1 is 50 parts by mass or less, the adhesive composition does not become too hard, and the adhesive strength of the adhesive composition is improved.
• the preferred lower limit of the content of the tackifier resin T1 is 10 parts by mass, more preferably 15 parts by mass, and the preferred upper limit is 45 parts by mass, more preferably 40 parts by mass.
• the adhesive composition of the present invention does not contain a tackifier resin T2 different from a terpene phenol resin, a hydrogenated terpene phenol resin, and a xylene resin, or contains the tackifier resin T2, and when the tackifier resin T2 is contained, the upper limit of the content of the tackifier resin T2 is 10 parts by mass relative to 100 parts by mass of the acrylic copolymer.
• the adhesive composition of the present invention does not contain the tackifier resin T2, or contains the tackifier resin T2 and contains the tackifier resin T2
• the content of the tackifier resin T2 is 10 parts by mass or less, so that the adhesive composition can suppress turbidity and yellowing and has excellent optical transparency.
• the preferred upper limit of the content of the tackifier resin T2 is 5 parts by mass.
• the content of the tackifier resin T1 is preferably greater than the content of the tackifier resin T2.
• the pressure-sensitive adhesive composition has superior optical transparency.
• the adhesive composition of the present invention does not contain a tackifier resin, or contains a tackifier resin, and when it contains a tackifier resin, the upper limit of the tackifier resin content is 5 parts by mass per 100 parts by mass of the acrylic copolymer.
• the tackifier resin content is 5 parts by mass or less, so that the adhesive composition can further suppress turbidity and yellowing, and has excellent optical transparency.
• the preferred upper limit of the tackifier resin content is 4 parts by mass.
• the tackifier resin examples include terpene phenol resin, hydrogenated terpene phenol resin, xylene resin, etc.
• hydrogenated terpene phenol resin is preferred from the viewpoint of the light color of the resin and excellent optical transparency.
• the pressure-sensitive adhesive composition preferably contains a crosslinking agent.
• the acrylic copolymer is crosslinked via the crosslinking agent.
• the gel fraction of the pressure-sensitive adhesive layer described below can be adjusted within an appropriate range.
• the acrylic copolymer it is preferable that the acrylic copolymer has a constituent unit derived from the polar functional group-containing monomer.
• crosslinking agent examples include epoxy-based crosslinking agents and isocyanate-based crosslinking agents.
• isocyanate-based crosslinking agents are preferred because they make it easier to adjust the gel fraction of the adhesive layer (described below) within an appropriate range, and further improve the adhesive strength and holding power of the adhesive tape having the adhesive layer.
• the preferred lower limit of the content of the crosslinking agent is 0.05 parts by mass, and the preferred upper limit is 5 parts by mass, relative to 100 parts by mass of the acrylic copolymer.
• the above-mentioned adhesive composition may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as necessary.
• the present invention also includes a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present invention.
• the pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition, and thus can achieve both excellent adhesive strength and excellent optical transparency even when the tape is thin.
• the preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, and the preferred upper limit is 80% by mass.
• the gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more, the pressure-sensitive adhesive layer becomes hard, and the holding power of the pressure-sensitive adhesive tape is further improved.
• the bulk cohesive force of the pressure-sensitive adhesive layer becomes larger, and the heat resistance of the pressure-sensitive adhesive tape is further improved.
• the gel fraction of the pressure-sensitive adhesive layer is 80% by mass or less, the pressure-sensitive adhesive layer becomes more easily stretched, and the adhesive strength of the pressure-sensitive adhesive tape is further improved.
• the more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 15% by mass, and the more preferred upper limit is 75% by mass.
• the gel fraction of the pressure-sensitive adhesive layer can be measured by the following method. That is, the pressure-sensitive adhesive layer W 0 (g) is collected, the collected pressure-sensitive adhesive layer is immersed in 50 mL of tetrahydrofuran, and shaken with a shaker at a temperature of 23° C. and 200 rpm for 24 hours. After shaking, the pressure-sensitive adhesive layer that has absorbed and swollen with tetrahydrofuran is filtered using a metal mesh (opening #200 mesh, mass: W 1 (g)). The separated pressure-sensitive adhesive layer is dried under a condition of 110° C. for 1 hour, and then the mass W 2 (g) of the pressure-sensitive adhesive layer including the metal mesh is measured.
• the gel fraction can be measured by a method of calculating the gel fraction from the following formula (1) using the obtained W 0 , W 1 , and W 2 .
• Gel fraction (mass%) 100 ⁇ (W 2 ⁇ W 1 )/W 0 (1) (W 0 : initial mass of adhesive layer, W 1 : initial mass of metal mesh, W 2 : mass of adhesive layer including metal mesh after drying)
• the preferred upper limit of the thickness of the pressure-sensitive adhesive layer is 15 ⁇ m.
• the pressure-sensitive adhesive tape can be suitably used for fixing small or thin electronic devices, etc.
• the more preferred upper limit of the thickness of the pressure-sensitive adhesive layer is 10 ⁇ m, and the even more preferred upper limit is 5 ⁇ m.
• the adhesive tape may be a non-support type that does not have a substrate, or a supported type in which the adhesive layer is formed on a substrate.
• the adhesive tape is preferably a non-support type that does not have a substrate. By not having a substrate, the adhesive tape becomes thinner and has better optical transparency, so that the adhesive tape can be suitably used for fixing small or thin electronic devices, devices, etc.
• the adhesive tape When the adhesive tape has a substrate, it may be a single-sided adhesive tape having the adhesive layer on one side of the substrate, or a double-sided adhesive tape having the adhesive layer on both sides.
• the substrate examples include sheets made of resins such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide, sheets with a mesh structure, and sheets with holes.
• resins such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, and polyimide
• the preferred lower limit of the thickness of the substrate is 5 ⁇ m, and the preferred upper limit is 10 ⁇ m.
• the adhesive tape has appropriate stiffness and excellent handling properties.
• the adhesive tape can be suitably used for fixing small or thin electronic devices, devices, etc.
• the preferred upper limit of the haze of the substrate at 23° C. is 0.5%.
• the pressure-sensitive adhesive tape has better optical transparency.
• the more preferred upper limit of the haze of the substrate at 23° C. is 0.3%.
• the haze of the substrate can be measured, for example, by using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., "NDH4000" or the like).
• the above adhesive tape may further have other layers as long as the effects of the present invention are not impaired.
• the method for producing the adhesive tape is not particularly limited, and a conventionally known method can be used. For example, first, the (meth)acrylic acid alkyl ester, the olefin polymer having a polymerizable unsaturated double bond at the end, and, if necessary, a polar functional group monomer or the like are copolymerized in a conventional manner to obtain the acrylic copolymer. Next, a solution containing an adhesive composition containing the obtained acrylic copolymer, if necessary, a tackifier resin such as the tackifier resin T1 or the tackifier resin T2, and other additives is applied to a film that has been subjected to a release treatment, and then dried to produce the adhesive tape.
• the adhesive tape produced by the above-mentioned method can be laminated to a substrate as an adhesive layer to produce a support-type adhesive tape.
• the preferred lower limit of the 180° peel strength from glass at 23° C. after the pressure-sensitive adhesive tape is applied and left to stand at 23° C. for 24 hours is 9 N/inch. Since the 180° peel strength from glass at 23° C. after the pressure-sensitive adhesive layer is applied and left to stand at 23° C. for 24 hours is 9 N/inch or more, the pressure-sensitive adhesive tape can be more suitably used for fixing small or thin electronic devices, etc. The more preferred lower limit of the 180° peel strength from glass at 23° C. after the pressure-sensitive adhesive tape is applied and left to stand at 23° C. for 24 hours is 10 N/inch. There is no particular upper limit to the 180° peel strength from glass at 23° C.
• the 180° peel strength from glass at 23° C. can be measured by the following method. That is, the pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer is cut into a flat rectangular shape of 25 mm wide x 60 mm long to prepare a test piece, and the obtained test piece is attached to a glass plate ("Large slide glass white edge polished No. 2" manufactured by Matsunami Glass Industrial Co., Ltd.) using a 2 kg hand roller.
• the obtained measurement sample is subjected to a 180 ° peel test using a tensile tester (manufactured by A & D Co., Ltd., "RTI-1310" etc.) in accordance with JIS Z0237:2009 under conditions of 23 ° C and a tensile speed of 300 mm / min, and the 180 ° peel force against glass at 23 ° C after leaving it at 23 ° C for 24 hours after attachment can be measured by a method such as measuring.
• a tensile tester manufactured by A & D Co., Ltd., "RTI-1310" etc.
• the upper limit of the haze of the pressure-sensitive adhesive tape at 23° C. is preferably 1.0%. If the haze of the pressure-sensitive adhesive tape at 23° C. is 1.0% or less, the pressure-sensitive adhesive tape has better optical transparency.
• the upper limit of the haze of the pressure-sensitive adhesive tape at 23° C. is more preferably 0.5%, and even more preferably 0.3%.
• there is no particular preferred lower limit for the haze of the pressure-sensitive adhesive tape at 23° C. but from the viewpoint of the optical transparency of the pressure-sensitive adhesive tape, the closer to 0%, the more preferable.
• the haze of the pressure-sensitive adhesive tape at 23° C. can be measured by the following method.
• the above-mentioned adhesive tape (adhesive layer thickness: 5 ⁇ m) is cut into a flat rectangular shape of 40 mm ⁇ 40 mm, and then the polyethylene terephthalate film on one side of the cut adhesive tape is peeled off and pasted onto soda glass (0.7 mm ⁇ 56 mm ⁇ 86.6 mm) using a 2 kg hand roller. Thereafter, the polyethylene terephthalate film on the other side of the pasted adhesive tape is peeled off, and the light transmitted from the single-layer sheet surface to the soda glass surface can be measured at room temperature (23 ° C.) using a spectrophotometer (Konica Minolta, Inc., "CM-3700", etc.) by the SCI method.
• a spectrophotometer Konica Minolta, Inc., "CM-3700", etc.
• the preferred upper limit of the yellowing index b * of the pressure-sensitive adhesive tape at 23° C. is 0.4.
• the pressure-sensitive adhesive tape has better optical transparency.
• the more preferred upper limit of the yellowing index b * of the pressure-sensitive adhesive tape at 23° C. is 0.2.
• the yellowing index b * of the pressure-sensitive adhesive tape at 23° C. can be measured by the following method.
• the above-mentioned adhesive tape (adhesive layer thickness: 15 ⁇ m) is cut into a flat rectangular shape of 40 mm ⁇ 40 mm, and then the polyethylene terephthalate film on one side of the cut adhesive tape is peeled off and pasted onto soda glass (0.7 mm ⁇ 56 mm ⁇ 86.6 mm) using a 2 kg hand roller.
• the polyethylene terephthalate film on the other side of the pasted adhesive tape is peeled off, and the light transmitted from the single-layer sheet surface to the soda glass surface can be measured at room temperature (23 ° C.) using a spectrophotometer (manufactured by Konica Minolta, Inc., "CM-3700", etc.) by the SCI method.
• a spectrophotometer manufactured by Konica Minolta, Inc., "CM-3700", etc.
• the preferred upper limit of the yellowing index b * of the pressure-sensitive adhesive tape after heating at 85° C. for 500 hours is 0.4.
• the pressure-sensitive adhesive tape after heating at 85° C. for 500 hours is 0.4 or less, the pressure-sensitive adhesive tape has better optical transparency. In addition, the pressure-sensitive adhesive tape is less likely to lose optical transparency even after long-term use.
• the more preferred upper limit of the yellowing index b * of the pressure-sensitive adhesive tape after heating at 85° C. for 500 hours is 0.2.
• the yellowing index b * of the pressure-sensitive adhesive tape after heating at 85° C. for 500 hours can be measured by the following method.
• the above-mentioned adhesive tape (adhesive layer thickness: 15 ⁇ m) is cut into a flat rectangular shape of 40 mm ⁇ 40 mm, and the cut adhesive tape is heated in an oven at 85 ° C. for 500 hours. After that, the heated adhesive tape is cooled naturally to room temperature (23 ° C.), and then the polyethylene terephthalate film on one side is peeled off and pasted on soda glass (0.7 mm ⁇ 56 mm ⁇ 86.6 mm) with a hand roller.
• the polyethylene terephthalate film on the other side of the pasted adhesive tape is peeled off, and the light transmitted from the single-layer sheet surface to the soda glass surface can be measured at room temperature (23 ° C.) using a spectrophotometer (manufactured by Konica Minolta, "CM-3700", etc.) by a method of evaluating the light by the SCI method.
• a spectrophotometer manufactured by Konica Minolta, "CM-3700", etc.
• the adhesive tape of the present invention is not particularly limited in its applications, but since it has excellent adhesive strength and excellent optical transparency, it is preferably used for bonding optical components of electronic devices and devices.
• the adhesive tape of the present invention can exhibit excellent adhesive strength and excellent optical transparency even when the adhesive layer is thin, it can be preferably used for fixing small or thin electronic devices and devices.
• a pressure-sensitive adhesive composition that can achieve both excellent adhesive strength and excellent optical transparency even when the applied thickness is thin. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer that contains the pressure-sensitive adhesive composition.
• the molecular weight distribution of the obtained acrylic copolymer was measured in terms of polystyrene using gel permeation chromatography (GPC) (Waters Corporation, "2690 Separations Module”) under the following conditions.
• the weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity (Mw/Mn) of the acrylic copolymer were determined from the obtained molecular weight distribution curve.
• GPC Measurement Conditions> Solvent: Tetrahydrofuran Sample flow rate: 1 mL/min Detector: Differential refractometer RI Column: GPC KF-806L (Showa Denko) Column temperature (measurement temperature): 40°C Injection volume: 20 ⁇ L
• Adhesive force After preparing an adhesive tape having an adhesive layer thickness of 15 ⁇ m by the method described in "(2) Preparation of adhesive tape", the obtained adhesive tape was cut into a flat rectangular shape having a width of 25 mm and a length of 60 mm to prepare a test piece. Next, the obtained test piece was attached to a glass plate ("Large slide glass white edge polished No. 2" manufactured by Matsunami Glass Industry Co., Ltd.) by moving a 2 kg hand roller back and forth at a speed of 300 mm/min. Then, after leaving it at 23 ° C.
• the obtained measurement sample was subjected to a 180 ° peel test using a tensile tester (manufactured by A & D Co., Ltd., "RTI-1310") in accordance with JIS Z0237:2009 under the conditions of 23 ° C. and a tensile speed of 300 mm/min, and the 180 ° peel force against the glass at 23 ° C. was measured after leaving it at 23 ° C. for 24 hours after application of the adhesive tape.
• a tensile tester manufactured by A & D Co., Ltd., "RTI-1310"
• the adhesive strength of the adhesive tape was evaluated as follows when the 180° peel strength from glass at 23°C after leaving it for 24 hours at 23°C was 10 N/inch or more: " ⁇ "; when it was 9 N/inch or more and less than 10 N/inch: " ⁇ "; when it was 8 N/inch or more and less than 9 N/inch: " ⁇ "; and when it was less than 8 N/inch: "X".
• the same method was also used for an adhesive tape having an adhesive layer thickness of 5 ⁇ m. After the adhesive tape was applied and left to stand at 23° C. for 24 hours, the 180° peel force from glass at 23° C. was measured to evaluate the adhesive strength of the adhesive tape.
• the polyethylene terephthalate film on the other side of the laminated adhesive tape was peeled off, and the haze of the adhesive tape at 23°C was measured by evaluating the light transmitted from the single-layer sheet surface to the soda glass surface by the SCI method using a spectrophotometer (manufactured by Konica Minolta, "CM-3700") at room temperature (23°C).
• CM-3700 spectrophotometer
• the optical transparency of the adhesive tape was evaluated as follows: if the haze at 23°C was 0.5% or less, it was marked “ ⁇ ”; if it was greater than 0.5% and less than 1.0%, it was marked “ ⁇ ”; if it was greater than 1.0% and less than 1.5%, it was marked “ ⁇ ”; and if it was greater than 1.5%, it was marked "X”.
• the optical transparency of the pressure-sensitive adhesive tape was evaluated as follows: when the obtained yellowing index b * at 23°C was 0.2 or less, it was marked as " ⁇ "; when it was more than 0.2 and 0.4 or less, it was marked as " ⁇ "; when it was more than 0.4 and 0.5 or less, it was marked as " ⁇ "; and when it was more than 0.5, it was marked as " ⁇ ".
• the polyethylene terephthalate film on the other side of the attached adhesive tape was peeled off, and the yellowing degree b * after heating at 85 ° C. for 500 hours was measured by evaluating the light transmitted from the single layer sheet surface to the soda glass surface by the SCI method using a spectrophotometer (manufactured by Konica Minolta, "CM-3700" ) at room temperature (23 ° C.).
• the optical transparency of the pressure-sensitive adhesive tape was evaluated as follows: if the yellowing index b * after heating at 85°C for 500 hours was 0.2 or less, it was marked as " ⁇ "; if it was more than 0.2 and 0.4 or less, it was marked as " ⁇ ”; if it was more than 0.4 and 0.5 or less, it was marked as " ⁇ "; and if it was more than 0.5, it was marked as " ⁇ ".
• a pressure-sensitive adhesive composition that can achieve both excellent adhesive strength and excellent optical transparency even when the applied thickness is thin. Also, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition.

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