JP2017149980A - Double-sided pressure-sensitive adhesive sheet and portable electronic device - Google Patents

Abstract

The present invention provides a double-sided pressure-sensitive adhesive sheet excellent in pressure adhesion and drop impact resistance.
A double-sided pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer having an acrylic polymer (A) containing 9 to 30% by mass of a structural unit derived from a polar monomer.
[Selection] Figure 1

Description

  The present invention relates to a double-sided pressure-sensitive adhesive sheet and a portable electronic device.

  Conventionally, double-sided pressure-sensitive adhesive sheets have been used in various technical fields. For example, in the field of portable electronic devices such as mobile phones and portable information terminals, double-sided pressure-sensitive adhesive sheets are used for fixing between various members. As an example, Patent Document 1 discloses that a protective panel (lens) that protects a display unit of a portable electronic device is fixed to a housing using a double-sided adhesive sheet. The double-sided pressure-sensitive adhesive sheet is bonded to these members and fixed to each other while being sandwiched between the protective panel and the housing.

JP 2009-108314 A

  In this type of double-sided PSA sheet, not only in a normal use state where the mobile electronic device is not deformed, but also in a state where the mobile electronic device is subjected to external force and is distorted (deformed), the members are excellent Adhesive strength that can be fixed is required. As a case where distortion occurs in each member, for example, when the user sits on a chair with the portable electronic device stored in the back pocket of the pants, the portable electronic device is pressed by the user's buttocks, etc. Is mentioned. Even in such a case, the double-sided PSA sheet is required to have an adhesive force that keeps the members fixed.

  By the way, in recent years, parts to be fixed by the double-sided pressure-sensitive adhesive sheet have also been enlarged due to an increase in the size of display portions of portable electronic devices. That is, the mass of the member that the double-sided PSA sheet must be fixed and supported has been increasing in recent years. In addition, for the purpose of improving design and the like, the adhesion area (fixed area) of the double-sided pressure-sensitive adhesive sheet tends to be narrowed against the increase in size of the member. Therefore, the double-sided pressure-sensitive adhesive sheet is required to exhibit a sufficient adhesive force with a small adhesion area. Under such circumstances, in recent years, this type of double-sided pressure-sensitive adhesive sheet is required to have higher adhesive strength.

  Further, as shown in Patent Document 1, the double-sided pressure-sensitive adhesive sheet is a member that is fixed even when a large impact is momentarily applied when the portable electronic device is dropped as an adhesive performance other than the above-described adhesive force. There is also a need for a drop impact resistance property that does not drop off.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a double-sided pressure-sensitive adhesive sheet and the like that are excellent in pressure adhesion and drop impact resistance.

  As a result of intensive studies to achieve the above object, the present inventor has a double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer having an acrylic polymer (A) containing 9 to 30% by mass of a structural unit derived from a polar monomer, It has been found that it has an excellent pressure-adhesive force and an excellent drop impact resistance, and has completed the present invention.

  The double-sided pressure-sensitive adhesive sheet may be used for fixing a member constituting a portable electronic device.

  In the double-sided pressure-sensitive adhesive sheet, the shape when viewed in plan may be any one selected from the group consisting of a tape shape, a strip shape, a U shape, an L shape, and a frame shape.

  In the double-sided pressure-sensitive adhesive sheet, the acrylic polymer (A) may include a structural unit derived from a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms. Good.

  In the double-sided pressure-sensitive adhesive sheet, the polar monomer may be at least one selected from the group consisting of a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, and a heterocyclic ring-containing vinyl monomer.

  In the double-sided pressure-sensitive adhesive sheet, the acrylic polymer (A) may include a structural unit derived from a polyfunctional monomer having two or more polymerizable functional groups.

  In the double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer may have a bubble content of 3% by volume or less.

  In the double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer may have a thickness of 90 μm to 1,500 μm.

  In the double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer may further contain a thermal foaming agent.

  In the portable electronic device according to the present invention, members constituting the portable electronic device may be fixed via the double-sided pressure-sensitive adhesive sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the conventional problems can be solved and the double-sided adhesive sheet etc. which are excellent in press adhesive force and a drop impact resistance characteristic can be provided.

Schematic sectional view of the double-sided PSA sheet of Reference Example 1 Schematic top view of a sample for evaluation used when measuring pressure adhesion A-A 'line sectional view of FIG. Schematic cross-sectional view showing the method for measuring pressure adhesion Schematic top view of an evaluation sample used when evaluating drop impact resistance B-B 'line sectional view of FIG. Schematic cross section showing the evaluation method of drop impact resistance

  The double-sided pressure-sensitive adhesive sheet according to this embodiment is a double-sided pressure-sensitive adhesive sheet having at least one acrylic pressure-sensitive adhesive layer (hereinafter sometimes referred to as a pressure-sensitive adhesive layer). In general, “double-sided pressure-sensitive adhesive sheet” is sometimes called with a name different from “double-sided pressure-sensitive adhesive tape”, “double-sided pressure-sensitive adhesive film”, etc., but in this specification, the expression is unified to “double-sided pressure-sensitive adhesive sheet”. . Further, the surface of the pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive sheet may be referred to as “pressure-sensitive adhesive surface”.

  As a form of the double-sided pressure-sensitive adhesive sheet, it may be a so-called base-less double-sided pressure-sensitive adhesive sheet that does not include a base material (support), or a so-called double-sided pressure-sensitive adhesive sheet with a base material that includes a base material. Also good. Examples of the substrate-less double-sided pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer. On the other hand, as a double-sided adhesive sheet with a base material, the double-sided adhesive sheet which respectively has an adhesive layer on the both surfaces side of a base material is mentioned, for example. However, as the base material, a base material other than the foam base material (a non-foam base material that does not include a hollow portion such as bubbles) is preferably used.

  In addition, the double-sided pressure-sensitive adhesive sheet of the present embodiment may include other layers (for example, an intermediate layer and an undercoat layer) as long as the object of the present invention can be achieved, in addition to the pressure-sensitive adhesive layer and the base material. As the double-sided pressure-sensitive adhesive sheet of the present embodiment, a so-called base-less double-sided pressure-sensitive adhesive sheet consisting only of a pressure-sensitive adhesive layer is preferable from the standpoint of easily exhibiting excellent pressing adhesive force, drop impact resistance and the like. Hereinafter, the pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet will be described.

(Acrylic adhesive layer)
The pressure-sensitive adhesive layer is a layer that provides a pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet, and mainly includes an acrylic polymer (A). Moreover, in an adhesive layer, another component may be contained as needed. Hereinafter, the acrylic polymer (A) and other components will be described.

<Acrylic polymer (A)>
The pressure-sensitive adhesive layer contains the acrylic polymer (A) as the base polymer (main component), and specifically, the pressure-sensitive adhesive layer preferably contains 50% by mass or more, more preferably 60% by mass or more. More preferably 75% by mass or more, and still more preferably 85% by mass or more. The upper limit is not particularly limited, but is 100% by mass or less, preferably 95% by mass or less.

  The acrylic polymer (A) contains 9 to 30% by mass of a structural unit derived from the polar monomer (a2). The acrylic polymer (A) is a (meth) acrylic acid alkyl ester (a1) (hereinafter referred to as a (meth) acrylic acid alkyl ester (a1) having a linear or branched alkyl group having 1 to 20 carbon atoms. And a structural unit derived from).

The proportion (mass%) of the structural unit derived from the (meth) acrylic acid alkyl ester (a1) contained in the acrylic polymer (A) is preferably 65 to 91 mass%, more preferably 68 to 91 mass%. More preferably, it is 70-91 mass%.
In addition, 65-91 mass% is preferable with respect to the mass of all the monomer components utilized for formation of an acrylic polymer (A), and the usage-amount (mass%) of the (meth) acrylic-acid alkylester (a1), More preferably, it is 68-91 mass%, More preferably, it is 70-91 mass%.

  Examples of the (meth) acrylic acid alkyl ester (a1) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic acid n- Butyl, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, (meth ) Heptyl acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, ( (Meth) acrylic acid isodecyl, (meth) acrylic acid undecyl, (meth) acrylic acid Decyl, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate And eicosyl (meth) acrylate. The (meth) acrylic acid alkyl ester (a1) may be used alone or in combination of two or more. In this specification, “(meth) acryl” represents “acryl” and / or “methacryl” (one or both of “acryl” and “methacryl”).

  The (meth) acrylic acid alkyl ester (a1) is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, more preferably n-butyl acrylate (BA) or acrylic acid. Examples include 2-ethylhexyl (2EHA), isooctyl acrylate, isononyl acrylate, and the like.

  The polar monomer (a2) is a monomer having at least one polar group and containing a polymerizable unsaturated bond.

Double-sided pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) obtained when the proportion (% by mass) of the structural unit derived from the polar monomer (a2) contained in the acrylic polymer (A) is 9 to 30% by mass. The pressure adhesion strength and the drop impact resistance are excellent.
In addition, the usage-amount (mass%) of polar monomer (a2) is 9-30 mass% with respect to the mass of all the monomer components utilized for formation of an acrylic polymer (A).

  Examples of the polar monomer (a2) include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and acid anhydrides thereof (for example, acid anhydrides such as maleic anhydride and itaconic anhydride). Carboxyl group-containing monomers, such as product-containing monomers; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate Hydroxyl group-containing monomers such as vinyl alcohol and allyl alcohol; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N- Butoxymethyl (meth) acrylamide, N-hy Amide group-containing monomers such as roxyethyl (meth) acrylamide; Amino group-containing monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; (meth) acrylic Epoxy group-containing monomers such as glycidyl acid and methyl glycidyl (meth) acrylate; Cyano group-containing monomers such as acrylonitrile and methacrylonitrile; N-vinyl-2-pyrrolidone, (meth) acryloylmorpholine, N-vinylpiperidone, N-vinyl Heterocycle-containing vinyl monomers such as piperazine, N-vinylpyrrole, N-vinylimidazole; sulfonic acid group-containing monomers such as sodium vinylsulfonate; phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate; Hexyl maleimide, imide group-containing monomers such as isopropyl maleimide; isocyanate group-containing monomers such as 2-methacryloyloxyethyl isocyanate. The polar monomer (a2) may be used alone or in combination of two or more.

  The polar monomer (a2) is preferably a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, or a heterocyclic ring-containing vinyl monomer, more preferably acrylic acid (AA) or 2-hydroxyethyl acrylate ( HEA), N-hydroxyethylacrylamide (HEAA), N-vinyl-2-pyrrolidone (NVP) and the like.

  Further, as a preferred embodiment, one or more acidic group-containing monomers selected from the group consisting of a carboxyl group-containing monomer and a hydroxyl group-containing monomer, a group consisting of an amide group-containing monomer and a heterocyclic ring-containing vinyl monomer In combination with any one or more basic group-containing monomers selected from:

  The acrylic polymer (A) is a kind of copolymerizable monomer, and is a polyfunctional monomer (a3) having two or more polymerizable functional groups containing an unsaturated double bond (hereinafter referred to as a polyfunctional monomer). A structural unit derived from (referred to as (a3)) may be included.

  Examples of the polyfunctional monomer (a3) include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, Neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methanetri (meth) Examples include acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, and urethane acrylate. The polyfunctional monomer (a3) may be used alone or in combination of two or more. In addition, as said polyfunctional monomer (a3), polyfunctional (meth) acrylate is preferable.

The proportion (mass%) of the mass of the structural unit derived from the polyfunctional monomer (a3) contained in the acrylic polymer (A) is preferably 0.01 to 0.5 mass%, more preferably 0.00. It is 02-0.3 mass%. When the ratio of the polyfunctional monomer (a3) is 0.01 to 0.5% by mass, appropriate cohesiveness of the pressure-sensitive adhesive layer can be obtained, and the deterioration of the pressure adhesive force and the drop impact resistance can be suppressed. .
In addition, the usage-amount (mass%) of a polyfunctional monomer (a3) has preferable 0.01-0.5 mass% with respect to the mass of all the monomer components utilized for formation of an acrylic polymer (A). More preferably, it is 0.02-0.3 mass%.

  When the acrylic polymer (A) contains a structural unit derived from the polyfunctional monomer (a3), the acrylic polymer (A) contains a cross-linked acrylic polymer, and is adhesive. The cohesiveness and adhesive strength of the agent layer are improved.

  Further, a copolymerizable monomer other than the polyfunctional monomer (a3) may be used as a monomer component for forming the acrylic polymer (A). Examples of the copolymerizable monomer include (meth) acrylic acid esters having an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate, and phenyl (meth) acrylate. (Meth) acrylic acid esters other than the above (a1) such as (meth) acrylic acid esters having an aromatic hydrocarbon group such as, vinyl esters such as vinyl acetate and vinyl propionate, and aromatics such as styrene and vinyltoluene Examples thereof include vinyl compounds, olefins or dienes such as ethylene, butadiene, isoprene, and isobutylene, vinyl ethers such as vinyl alkyl ether, and vinyl chloride.

  Content (mass%) of the acrylic polymer (A) in an adhesive layer is 50-100 mass%.

  The acrylic polymer (A) can be prepared using a known or conventional polymerization method. Examples of the polymerization method include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a photopolymerization method. Among these, in preparing the acrylic polymer (A), it is preferable to use a curing reaction by heat or active energy rays (for example, ultraviolet rays) using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator. In particular, it is preferable to use a curing reaction using a photopolymerization initiator because it has advantages such as shortening the polymerization time.

  For example, the acrylic polymer (A) can be prepared by irradiating an active energy ray (for example, ultraviolet rays) to a monomer composition containing a photopolymerization initiator to polymerize the monomer. Moreover, you may mix | blend the other component included in an adhesive layer with a polymerization initiator at the time of preparation of an acrylic polymer (A). In addition, you may use polymerization initiators, such as a thermal-polymerization initiator and a photoinitiator, which are utilized for preparation of an acrylic polymer (A) individually or in combination of 2 or more types.

  Examples of the thermal polymerization initiator include azo polymerization initiators [for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis. (2-methylpropionic acid) dimethyl, 4,4′-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [ 2- (5-Methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-di) Methyleneisobutylamidine) dihydrochloride, etc.], peroxide polymerization initiators (for example, dibenzoyl peroxide, t-butylpermaleate, lauro peroxide) Le etc.), redox polymerization initiators, and the like. The amount of the thermal polymerization initiator used is not particularly limited as long as it can be conventionally used as a thermal polymerization initiator.

  Examples of the photopolymerization initiator include benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, and photoactive oxime photopolymerization initiator. Initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, thioxanthone photopolymerization initiators, acylphosphine oxide photopolymerization initiators, and the like It is done.

  Examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one [ BASF, trade name: Irgacure 651], anisole methyl ether, and the like. Examples of the acetophenone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone [manufactured by BASF, trade name: Irgacure 184], 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one [manufactured by BASF, trade name: Irgacure 2959], 2-hydroxy-2-methyl-1-phenyl-propane Examples include -1-one [manufactured by BASF, trade name: Darocur 1173], methoxyacetophenone, and the like. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1 -ON etc. are mentioned.

  Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzyl photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone. 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like.

  Examples of the acylphosphine photopolymerization initiator include bis (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -n-butylphosphine oxide, bis (2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl)-(1 -Methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -t-butylphosphine oxide, bis (2,6-dimethoxybenzoyl) cyclohexylphosphine oxide, bis (2,6-dimethoxybenzoyl) octyl Phosphine oxide, bis (2 Methoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2-methoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (2-methyl Propan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-dibutoxybenzoyl) (2-methylpropane-1- Yl) phosphine oxide, bis (2,4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) (2,4-dipentoxyphenyl) phosphine oxide Bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bi (2,6-dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine Oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diisopropylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2-methylphenylphosphine oxide, Bis (2,4,6-trimethylbenzoyl) -4-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) ) -2,3,5,6-tetramethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl Phosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4 , 6-Trimethylbenzoyl-n-butylphosphine Sid, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dibutoxyphenylphosphine oxide, 1,10-bis [bis (2,4 , 6-trimethylbenzoyl) phosphine oxide] decane, tri (2-methylbenzoyl) phosphine oxide, and the like.

  Although the usage-amount of a photoinitiator will not be restrict | limited especially if an acrylic polymer (A) can be formed by a photopolymerization reaction, For example, all the monomer components utilized in order to form an acrylic polymer (A) 0.01-5 mass parts is preferable with respect to 100 mass parts, More preferably, it is 0.03-3 mass part, More preferably, it is 0.05-2 mass part.

  A polymerization reaction can fully be performed as the usage-amount of a photoinitiator is 0.01-5 mass parts, and the fall of the molecular weight of the polymer to produce | generate can be suppressed. As a result, the cohesive strength of the formed pressure-sensitive adhesive layer is ensured.

  In activating the photopolymerization initiator, it is important to irradiate the monomer composition containing the photopolymerization initiator with active energy rays. Examples of such active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, and ultraviolet rays, and ultraviolet rays are particularly preferable. The irradiation energy, irradiation time, irradiation method, and the like of the active energy ray are not particularly limited as long as the photopolymerization initiator can be activated to cause the monomer component to react.

  The weight average molecular weight (Mw) of the acrylic polymer (A) is, for example, 100,000 to 5,000,000. The measurement of the weight average molecular weight of an acrylic polymer (A) is calculated | required in polystyrene conversion by GPC (gel permeation chromatography) method. Specifically, TSKgelGMH-H (20) × 2 columns are used in HPLC 8020 manufactured by Tosoh Corporation, and measurement is performed with a tetrahydrofuran solvent under a flow rate of 0.5 ml / min.

<Other ingredients>
[Acrylic polymer (B)]
The pressure-sensitive adhesive layer may contain an acrylic polymer (B) as a component other than the acrylic polymer (A). This acrylic polymer (B) is a polymer having a weight average molecular weight smaller than that of the acrylic polymer (A), and includes a structural unit derived from a (meth) acrylic acid ester.

  Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and (meth) acrylic. Carbon such as pentyl acid, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate A linear or branched (meth) acrylic acid alkyl ester having a number of 1 to 12 and an ester with an alicyclic alcohol of (meth) acrylic acid such as cyclohexyl (meth) acrylate or isobornyl (meth) acrylate, (Meth) acrylic acid aryl ester such as phenyl (meth) acrylate and benzyl (meth) acrylate Tel and the like. The (meth) acrylic acid esters may be used alone or in combination of two or more.

  As a monomer component (monomer unit) constituting the acrylic polymer (B), a (meth) acrylic acid ester containing an alicyclic hydrocarbon group (for example, cyclohexyl methacrylate (CHMA), dicyclopentanyl methacrylate (DCPMA), Dicyclopentanyl acrylate (DCPA)) or a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 12 carbon atoms (more preferably, isobutyl methacrylate has a carbon number such as isobutyl methacrylate). (Meth) acrylic acid alkyl ester having 1 to 8 alkyl groups) and the like can be suitably used.

  The acrylic polymer (B) is obtained by copolymerizing a covalent monomer having a polymerizable unsaturated bond copolymerizable with the (meth) acrylic acid ester in addition to the above-mentioned (meth) acrylic acid ester. It is also possible.

The ratio (mass%) of the mass of the (meth) acrylic acid ester in the acrylic polymer (B) is preferably 90 to 100 mass%, more preferably 95 to 100 mass%.
In addition, the usage-amount (mass%) of (meth) acrylic acid ester becomes like this. Preferably it is 90-100 mass% with respect to the mass of all the monomer components utilized for formation of an acrylic polymer (B), More preferably Is 95 to 100% by mass.

  Examples of the acrylic polymer (B) include a copolymer of cyclohexyl methacrylate (CHMA) and isobutyl methacrylate (IBMA), a copolymer of cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBXMA), and cyclohexyl methacrylate (CHMA). And a copolymer of acryloylmorpholine (ACMO), a copolymer of cyclohexyl methacrylate (CHMA) and diethylacrylamide (DEAA), a copolymer of dicyclopentanyl methacrylate (DCPMA) and methyl methacrylate (MMA) are preferably used. .

In the acrylic polymer (B), the mass ratio (mass%) of the (meth) acrylic acid ester (for example, CHMA, DCPMA) containing an alicyclic hydrocarbon group is preferably 50 to 85 mass%, more preferably. Is 55-75 mass%.
In addition, the usage-amount (mass%) of the (meth) acrylic acid ester containing an alicyclic hydrocarbon group is 50-85 with respect to the mass of all the monomer components utilized for formation of an acrylic polymer (B). % By mass is preferable, and more preferably 55 to 75% by mass.

  The weight average molecular weight of the acrylic polymer (B) is preferably 1,000 to 30,000, more preferably 2,500 to 15,000, and still more preferably 3,000 to 10,000.

  When the weight average molecular weight of the acrylic polymer (B) is 1,000 to 30,000, compatibility with the acrylic polymer (A) is secured, and the pressure-sensitive adhesive performance (adhesion performance) and retention of the resulting pressure-sensitive adhesive layer are maintained. Performance is ensured.

  The measurement of the weight average molecular weight of an acrylic polymer (B) is calculated | required in polystyrene conversion by GPC method. Specifically, TSKgelGMH-H (20) × 2 columns are used in HPLC 8020 manufactured by Tosoh Corporation, and measurement is performed with a tetrahydrofuran solvent under a flow rate of 0.5 ml / min.

  The usage-amount of an acrylic polymer (B) is 10-40 mass parts with respect to 100 mass parts of all the monomer components utilized in order to form an acrylic polymer (A), Preferably 5-35 mass parts is used. It is. When the amount of the acrylic polymer (B) used is 10 to 40 parts by mass, compatibility with the acrylic polymer (A) is ensured, and the adhesive performance (adhesion performance) and retention performance of the resulting adhesive layer are improved. Secured.

  The glass transition temperature (Tg) of the acrylic polymer (B) is preferably 40 to 300 ° C. When the glass transition temperature (Tg) is 40 to 300 ° C., cohesive force at room temperature or higher is ensured, and holding performance and high-temperature adhesion performance are also ensured.

The glass transition temperature (Tg) of the acrylic polymer (B) is obtained from a nominal value described in literatures, catalogs, etc., or a calculated value based on the following formula (Fox formula).
<Formula> 1 / Tg = Σ (Wi / Tgi)
In the above formula, Tg is the glass transition temperature (unit: K) of the acrylic polymer (B), Tgi is the glass transition temperature (unit: K) of the homopolymer composed of the monomer i, and Wi is the total monomer of the monomer i. Represents the mass fraction in the component (i = 1, 2,... N). The above formula is a calculation formula when the acrylic polymer (B) is composed of n types of monomer components of monomer 1, monomer 2,.

  For the acrylic polymer (B), for example, a monomer component such as (meth) acrylic acid ester is used by a known or conventional polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization, or a bulk polymerization. Prepared.

  In order to adjust the molecular weight of the acrylic polymer (B), a chain transfer agent may be used in the polymerization system. Examples of chain transfer agents used include compounds having a mercapto group such as octyl mercaptan, dodecyl mercaptan, t-dodecyl mercaptan; thioglycolic acid, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, thioglycolic acid t-butyl, 2-ethylhexyl thioglycolate, octyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, thioglycolate ester of ethylene glycol, thioglycolate ester of neopentyl glycol, thioglycolate ester of pentaerythritol Is mentioned. Among chain transfer agents, thioglycolic acids can be particularly preferably used.

  Although the usage-amount of a chain transfer agent is not restrict | limited in particular, Usually, 0.1-20 mass parts of chain transfer agents are used with respect to 100 mass parts of all the monomer components utilized in order to form an acrylic polymer (B). The amount is preferably 0.2 to 15 parts by mass, more preferably 0.3 to 10 parts by mass. Thus, the acrylic polymer (B) of a suitable molecular weight can be obtained by adjusting the usage-amount of a chain transfer agent.

  The method for containing the acrylic polymer (B) in the pressure-sensitive adhesive layer is not particularly limited. For example, in the monomer composition used for producing the acrylic polymer (A), together with the polymerization initiator, A method of mixing the acrylic polymer (B) is preferable.

[Hydrogenated tackifying resin]
The pressure-sensitive adhesive layer may contain various tackifying resins such as a hydrogenated tackifying resin as a component other than the acrylic polymer (A). Examples of the hydrogenated tackifying resin include derivatives obtained by hydrogenating tackifying resins such as petroleum resins, terpene resins, coumarone / indene resins, styrene resins, rosin resins, alkylphenol resins, and xylene resins. be able to. For example, the hydrogenated petroleum resin is appropriately selected from aromatic, dicyclopentadiene, aliphatic, and aromatic-dicyclopentadiene copolymer. Further, the hydrogenated terpene resin is appropriately selected from terpene phenol resin, aromatic terpene resin and the like. Among these, it is particularly preferable to use a hydrogenated petroleum resin or a hydrogenated terpene resin as the hydrogenated tackifier resin.

  The softening point of the hydrogenated tackifying resin is preferably 80 to 200 ° C, more preferably 100 to 200 ° C. When the softening point of the hydrogenated tackifying resin is 80 to 200 ° C., a high cohesive force can be obtained.

  The amount of the hydrogenated tackifying resin used is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts per 100 parts by mass of all monomer components used to form the acrylic polymer (A). It is a mass part, More preferably, it is 3-30 mass parts. When the usage-amount of hydrogenation-type tackifying resin is 1-50 mass parts, the cohesive force of an adhesive layer is ensured, and the adhesive performance (adhesion performance) of an adhesive layer improves.

  Examples of commercially available hydrogenated tackifier resins include, for example, trade name “Arcon P125 (hydrogenated petroleum-based resin)” (Arakawa Chemical Co., Ltd.), trade name “YS Polystar TH130 (hydrogenated terpene). Ferrule resin) "(Yasuhara Chemical Co., Ltd.) and the like.

[Additive]
The pressure-sensitive adhesive layer may contain an additive as a component other than the acrylic polymer (A). An additive is mix | blended with an adhesive layer in order to improve various performances, such as reinforcement, workability, handleability, and adhesiveness, as needed. Although it does not specifically limit as an additive, For example, metal powders, such as copper, nickel, aluminum, chromium, iron, stainless steel, calcium carbonate (for example, heavy calcium carbonate, light calcium carbonate), magnesium carbonate, sodium carbonate, carbonate Examples thereof include carbonates such as potassium, hydroxides such as aluminum hydroxide and magnesium hydroxide, talc, mica, clay, bentonite, silica, alumina, aluminum silicate, titanium oxide, and hollow microspheres. These additives may be used alone or in combination of two or more.

  Examples of the hollow microspheres include inorganic hollow microspheres and organic hollow microspheres. Specific examples of inorganic hollow microspheres include glass hollow balloons such as hollow glass balloons, metal compound hollow balloons such as hollow alumina balloons, and porcelain hollow balloons such as hollow ceramic balloons. It is done. Specific examples of organic hollow microspheres include resin hollow balloons such as hollow acrylic balloons and hollow vinylidene chloride balloons. The hollow microspheres may be used alone or in combination of two or more.

  Among the hollow microspheres, inorganic hollow microspheres are preferable, and hollow glass balloons are particularly preferable from the viewpoints of polymerization efficiency by active energy rays (particularly ultraviolet rays) and weight. If a hollow glass balloon is used as the hollow microsphere, the adhesive performance of the pressure-sensitive adhesive layer can be improved without impairing other properties such as shearing force and holding force. Examples of commercially available hollow glass balloons include, for example, trade name “Fuji Balloon H-40” (manufactured by Fuji Silysia Chemical Co., Ltd.), trade name “Sphericel (registered trademark) 25P45 (silicate glass)” (Potters Barotini Co., Ltd.). The surface of the hollow microspheres may be subjected to various surface treatments (for example, a low surface tension treatment with a silicone compound or a fluorine compound).

  Although the particle diameter (average particle diameter) of an additive is not specifically limited, 0.1 micrometer-500 micrometers are preferable, More preferably, they are 0.1 micrometer-200 micrometers, More preferably, they are 0.1 micrometer-80 micrometers.

The specific gravity of the additive (true density) is not particularly ^limited, but ^is preferably ^{0.1g / cm 3 ~5.0g / cm 3} , more preferably ^{0.15g / cm 3 ~3.0g / cm 3} . Additives (in particular, hollow microspheres) the specific gravity of is ^{0.1g / cm 3 ~3.0g / cm 3} , floating in formulating the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer This is preferable because it is suppressed and easily dispersed uniformly in the pressure-sensitive adhesive composition.

  The usage-amount of an additive is 0.1-100 mass parts with respect to 100 mass parts of all the monomer components utilized in order to form an acrylic polymer (A), Preferably it is 1-90 mass parts. . It can mix and disperse | distribute in the adhesive composition for forming an adhesive layer in the usage-amount of an additive being 0.1-100 mass parts.

  In addition, the adhesive layer is blended with a thermal foaming agent to give the double-sided PSA sheet re-pasteability (repair workability) during use and separation / disassembly of the joints (easy peelability). Also good. As the thermal foaming agent, for example, microspheres having thermal expansibility (hereinafter, thermal expansible microspheres) are preferable.

  Thermally expandable microspheres are microspheres that expand and / or foam upon heating. When the pressure-sensitive adhesive layer contains thermally expandable microspheres, it is possible to obtain a property of separation or disassembly at the interface between the adherend and the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet during heating. Such a characteristic is that the thermally expandable microspheres in the pressure-sensitive adhesive layer expand and / or foam by heating, and the pressure-sensitive adhesive layer expands and deforms to deform into an uneven shape, and the adherend and the pressure-sensitive adhesive. This is because peeling occurs at the interface with the layer. In addition, depending on the type of material of the adherend, the above characteristics may be caused by the expansion and / or foaming of the heat-expandable microspheres in the pressure-sensitive adhesive layer, which causes the pressure-sensitive adhesive layer to expand and deform. In some cases, the adhesive strength is reduced or the adhesive strength is lost, and peeling occurs at the interface between the adherend and the pressure-sensitive adhesive layer.

  The heat treatment can be performed by appropriately using a heating means such as a hot plate, a hot air dryer, a near infrared lamp, an air dryer, for example. The heating temperature may be higher than the expansion start temperature of the thermally expandable microsphere, but the surface state of the adherend, the type of the microsphere, the heat resistance of the adherend, the heating method (heat capacity, heating means, etc.) ) And the like. Typical heat treatment conditions are, for example, a temperature of 100 to 250 ° C., 5 to 90 seconds (hot plate or the like), or 5 to 15 minutes (hot air dryer or the like).

  The heat-expandable microspheres used in the pressure-sensitive adhesive layer are not particularly limited as long as they have the property of expanding and / or foaming by heating. For example, known heat-expandable microspheres can be appropriately selected and used. it can. Among these, microencapsulated thermally expandable microspheres can be suitably used. Examples of such microencapsulated thermally expandable microspheres include microspheres in which a material that easily expands by gasification by heating, such as isobutane, propane, or pentane, is encapsulated in an elastic shell. Can be mentioned.

  Usually, the shell of the thermally expandable microsphere is often formed of a thermoplastic material, a thermally meltable material, a material that bursts due to thermal expansion, or the like. Examples of the substance that forms the shell of the thermally expandable microsphere include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone. Thermally expandable microspheres can be produced by conventional methods (eg, coacervation method, interfacial polymerization method, etc.).

  As the thermally expandable microspheres, commercially available products of thermally expandable microspheres can also be used. Commercially available products of such thermally expandable microspheres are not particularly limited, and examples thereof include trade names “Matsumoto Microsphere F-30D”, “Matsumoto Microsphere F-50D”, “Matsumoto Microsphere F-80SD”, Examples include “Matsumoto Microsphere F-48D *” (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.); trade name “Expansel 051DU40” (manufactured by EXPANCEL).

  The average particle diameter of the heat-expandable microspheres is not particularly limited, but is preferably 1 μm to 80 μm, and more preferably 3 μm to 50 μm from the viewpoint of dispersibility, thin layer formability, and the like.

  Further, as the thermally expandable microsphere, in order to efficiently reduce the adhesive strength of the pressure-sensitive adhesive layer by heat treatment, those having an appropriate strength that does not rupture until the volume expansion coefficient is 5 times or more, particularly 10 times or more. preferable. When microspheres that burst at a low expansion rate are used, or when microspheres that are not microencapsulated are used, the adhesive area between the pressure-sensitive adhesive layer and the adherend is not sufficiently reduced. In some cases, the peelability cannot be obtained, and the characteristics of separation / disassembly by heating (for example, the characteristics of disassembly at the interface between the pressure-sensitive adhesive layer and the peelable film layer) may decrease.

  Although the compounding quantity of a thermally expansible microsphere changes also with the kind, 5-200 mass parts is preferable with respect to 100 mass parts of all the monomer components utilized in order to form an acrylic polymer (A), for example. 8 to 125 parts by mass, more preferably 10 to 100 parts by mass, still more preferably 15 to 70 parts by mass, and particularly preferably 20 to 50 parts by mass. When the blending amount of the heat-expandable microspheres is within such a range, the adhesive layer after the heat treatment can be sufficiently expanded and deformed without causing cohesive failure, and separation / disassembly by heating can be performed.

  Moreover, as another thermal foaming agent used for an adhesive layer, various inorganic type foaming agents and organic type foaming agents are mentioned, for example. Typical examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, azides and the like. Representative examples of organic foaming agents include water; chlorofluorinated alkanes such as trichloromonofluoromethane and dichloromonofluoromethane; azo series such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarboxylate. Compounds: Hydrazine compounds such as paratoluenesulfonyl hydrazide, diphenylsulfone-3,3′-disulfonyl hydrazide, 4,4′-oxybis (benzenesulfonyl hydrazide), allyl bis (sulfonyl hydrazide); p-toluylene sulfonyl semicarbazide, 4 Semicarbazide compounds such as 4,4'-oxybis (benzenesulfonyl semicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; N, N'-dinitrosopentamethylenetetramine, N, N - dimethyl -N, N-nitroso compounds such as N'- dinitrosoterephthalamide, and the like.

  A thermal foaming agent can be used individually or in combination of 2 or more types. Furthermore, the pressure-sensitive adhesive layer may contain a foaming aid as necessary.

[Crosslinking agent]
The pressure-sensitive adhesive layer may contain a crosslinking agent as a component other than the acrylic polymer (A) depending on the use of the double-sided pressure-sensitive adhesive sheet. The crosslinking agent is used for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive layer. Examples of the crosslinking agent include an epoxy crosslinking agent, an isocyanate crosslinking agent, a silicone crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a silane crosslinking agent, an alkyl etherified melamine crosslinking agent, a metal chelate crosslinking agent, and the like. Can be mentioned. In particular, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent can be preferably used.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, and triphenyl. Mention may be made of adducts of methane triisocyanate, polymethylene polyphenyl isocyanate and polyols such as trimethylolpropane.

  Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane. Triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane and the like Can be mentioned.

[Others]
The pressure-sensitive adhesive layer has a crosslinking accelerator, a silane coupling agent, an anti-aging agent, a colorant (pigment, dye, etc.), an ultraviolet absorber, an antioxidant, a chain transfer as long as the object of the present invention can be achieved. An agent, a plasticizer, a softener, an antistatic agent, a solvent and the like may be added. These components may be used alone or in combination of two or more.

  In addition, the said colorant may be mix | blended suitably with an adhesive layer in order to provide an optical characteristic (for example, light-shielding property), designability, etc. In particular, when the light-shielding property is imparted to the pressure-sensitive adhesive layer, it is preferable to use carbon black (for example, acetylene black, ketjen black, furnace black, channel black, thermal black) which is a black pigment. The amount of carbon black used is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of all monomer components used to form the acrylic polymer (A). Part.

  In the pressure-sensitive adhesive layer, for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyamide-based pressure-sensitive adhesive are within the range where the object of the present invention can be achieved. Other pressure-sensitive adhesives such as an adhesive, a urethane-based pressure-sensitive adhesive, a fluorine-based pressure-sensitive adhesive, and an epoxy-based pressure-sensitive adhesive may be contained. These may be used alone or in combination of two or more.

<Structure substantially free of bubbles>
The pressure-sensitive adhesive layer preferably has a structure that does not substantially contain bubbles. In the present specification, “substantially free of bubbles” means that the bubbles are not actively formed in the pressure-sensitive adhesive layer except when inevitably mixed. The bubble content in such an adhesive layer is ideally zero. In addition, the bubble content rate in the actual pressure-sensitive adhesive layer is preferably 3% by volume or less, more preferably 1% by volume or less, with respect to the total volume (100% by volume) of the pressure-sensitive adhesive layer. When the air bubbles are 3% by volume or less in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer becomes hard and the strength against deformation becomes excellent.

In addition, the content rate (volume%) of the bubble in an adhesive layer can be measured with the following method.
(Measuring method)
(1) The pressure-sensitive adhesive layer is cut in the thickness direction to produce a measurement sample in a state where damage to the cut surface is suppressed as much as possible. In addition, after immersing an adhesive layer in liquid nitrogen, the said adhesive layer may be fractured | ruptured and a measurement sample may be produced.
(2) Next, the cross section (cut surface, fracture surface) of the obtained measurement sample was increased 100 times by a field emission scanning electron microscope (FE-SEM) (manufactured by Hitachi High-Technologies Corporation, model: S-4800). Zoom in.
(3) Then, in the enlarged cross-section, a square portion surrounded by (width 1 mm) × (thickness of the adhesive layer) is defined as a reference area S1, and the total area S2 of the bubble portions included in the S1 Ask for.
(4) The bubble ratio (%) in the cross section is obtained by (S2 / S1) × 100.
(5) By repeating the operations (1) to (4) described above, the pressure-sensitive adhesive layer was sampled at a total of five locations at regular intervals along one direction. Adopted as the bubble content (volume%) in the agent layer.

(Method for forming pressure-sensitive adhesive layer)
The pressure-sensitive adhesive layer used in the double-sided pressure-sensitive adhesive sheet of the present embodiment is formed using, for example, a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition is not particularly limited as long as it can form the above-described pressure-sensitive adhesive layer of the present embodiment, and is appropriately selected according to the purpose. As the pressure-sensitive adhesive composition, from the viewpoint of workability and the like, a monomer composition composed of each monomer component used for forming the acrylic polymer (A) and a polymerization initiator for polymerizing the monomer component It is preferable to use a curable pressure-sensitive adhesive composition containing a mixture of other components added as necessary. In particular, the pressure-sensitive adhesive composition is preferably a photocurable pressure-sensitive adhesive composition using a photopolymerization initiator as the polymerization initiator. The curable pressure-sensitive adhesive composition is a so-called solventless pressure-sensitive adhesive composition, and is prepared by mixing the polymerization initiator and the like with the monomer composition.

  The monomer composition usually comprises a mixture of monomer components such as (meth) acrylic acid alkyl ester (a1) and polar monomer (a2). Although the said monomer composition changes with the kind of monomer component, a composition ratio, etc., normally it has comprised the liquid state. Therefore, for the purpose of increasing the viscosity of the monomer composition and improving workability (handleability), etc., the monomer component contained in the monomer composition is partially polymerized to obtain a partial weight. A coalescence may be formed. The monomer composition containing the partial polymer is in a syrup state. The unreacted monomer component is appropriately polymerized after the curable pressure-sensitive adhesive composition is prepared.

  For the polymerization of the partial polymer, a known or conventional polymerization method can be used. For example, the monomer component in the monomer composition may be appropriately polymerized using various polymerization initiators (for example, photopolymerization initiator) exemplified in the item of the acrylic polymer (A). In addition, the polymerization rate of the said partial polymer is adjusted to 5-15 mass%, for example, Preferably it is 7-10 mass%. As for the polymerization rate of the partial polymer, for example, the correlation between the viscosity of the monomer composition and the polymerization rate of the partial polymer is grasped in advance, and the viscosity of the monomer composition is adjusted based on the correlation. Can be adjusted accordingly. In addition, the said partial polymer is finally contained in an adhesive layer as a part of acrylic polymer (A).

  In addition, when using a polyfunctional monomer as a monomer component utilized in order to form an acrylic polymer (A), a polyfunctional monomer is mix | blended with the said monomer composition before the said partial polymer is formed. It may be blended with the monomer composition after the partial polymer is formed. However, from the viewpoint of forming a cross-linked acrylic polymer and reliably increasing the cohesiveness of the pressure-sensitive adhesive layer, the polyfunctional monomer is blended in the monomer composition after the partial polymer is formed. It is preferable.

  The curable pressure-sensitive adhesive composition after the preparation is applied in a layer form on a suitable support such as a substrate or a release liner. Thereafter, a curing step is performed on the layered pressure-sensitive adhesive composition. Moreover, a drying process is given before and after a hardening process as needed. When the pressure-sensitive adhesive composition contains a thermal polymerization initiator as a polymerization initiator, the pressure-sensitive adhesive composition is cured by starting a polymerization reaction by heating. On the other hand, when the pressure-sensitive adhesive composition contains a photopolymerization initiator as a polymerization initiator, the pressure-sensitive adhesive composition is cured by being irradiated with an active energy ray such as ultraviolet rays, and cured ( Photocured). Irradiation of active energy rays may be performed from one side of the layered pressure-sensitive adhesive composition or from both sides. Thus, when the said adhesive composition is hardened | cured, the adhesive layer which can be utilized for the double-sided adhesive sheet of this embodiment is obtained.

  In addition, when performing curing (photocuring) with active energy rays, a known or conventional oxygen blocking method (for example, the layered pressure-sensitive adhesive composition (pressure-sensitive adhesive layer)) is used so that the polymerization reaction is not inhibited by oxygen in the air. An appropriate support such as a release liner or a substrate may be bonded to the top, and a photocuring reaction may be performed in a nitrogen atmosphere).

  In addition, for the application (coating) of the pressure-sensitive adhesive composition, a known or common coating method can be used, and a general coater (for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip coater). Roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, direct coaters, etc.) can be used.

  Further, the pressure-sensitive adhesive layer may be a pressure-sensitive adhesive composition other than the above-described curable pressure-sensitive adhesive composition (for example, a solvent-type pressure-sensitive adhesive composition, an emulsion-type pressure-sensitive adhesive) as long as the object of the present invention can be achieved. It may be formed using a composition).

(Adhesive layer thickness)
The thickness of the pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive sheet is preferably 90 μm to 1,500 μm, more preferably 90 μm to 800 μm, and still more preferably 90 μm, from the viewpoint of ensuring high pressure adhesion and excellent impact resistance. ˜600 μm, particularly preferably 90 μm to 400 μm. The thickness of the pressure-sensitive adhesive layer is preferably 90 μm to 1,500 μm from the viewpoint of followability to the adhesive surface. Furthermore, when the thickness of the pressure-sensitive adhesive layer is 90 μm to 800 μm, it is preferable from the viewpoint of ease of production of the double-sided pressure-sensitive adhesive sheet (including reactivity), and particularly when the thickness of the pressure-sensitive adhesive layer is 90 μm to 600 μm. This is particularly preferable from the viewpoint that the pressure-sensitive adhesive layer is hardly distorted.

(Release liner)
The surface (adhesive surface) of the pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive sheet may be protected by a release liner until use. In the double-sided pressure-sensitive adhesive sheet, each pressure-sensitive adhesive surface may be protected by a separate release liner, or each pressure-sensitive adhesive surface may be protected by a single release liner in a form wound in a roll. The release liner is used as a protective material for the adhesive surface, and is peeled off when it is attached to an adherend. Moreover, when the double-sided pressure-sensitive adhesive sheet is a substrate-less double-sided pressure-sensitive adhesive sheet, the release liner also serves as a support. The release liner is not necessarily provided on the double-sided pressure-sensitive adhesive sheet.

A conventional release paper or the like can be used as the release liner, and is not particularly limited. As the release liner, for example, a substrate having a release treatment layer, a low adhesive substrate made of a fluoropolymer, a low adhesive substrate made of a nonpolar polymer, or the like can be used. As a base material which has the said peeling process layer, the base material surface-treated by peeling processing agents, such as a silicone type, a long-chain alkyl type, a fluorine type, molybdenum sulfide, is mentioned, for example. Examples of the fluorine-based polymer in the low-adhesive substrate made of the fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chloro Examples include fluoroethylene-vinylidene fluoride copolymer. Examples of the nonpolar polymer include olefinic resins (for example, polyethylene and polypropylene).
Examples of the substrate to be surface-treated with the release treatment agent include polyester films such as polyethylene terephthalate; olefin resin films such as polyethylene films and polypropylene films; polyvinyl chloride films; polyimide films; polyamide films such as nylon films; Examples thereof include plastic films such as rayon film, and papers such as high-quality paper, Japanese paper, kraft paper, glassine paper, synthetic paper, and top coat paper. Among these, from the viewpoint of processability, a polyester film or paper is preferable, and polyethylene terephthalate is more preferable.
The release liner can be formed by a known or conventional method. Further, the thickness of the release liner is not particularly limited.

(Base material)
In the case where the double-sided pressure-sensitive adhesive sheet has a base material, the base material is preferably a base material other than the foam base material (a non-foam base material that does not include hollow portions such as bubbles). As the base material, for example, a plastic film base material (hereinafter referred to as a plastic film base material) is used. The material of the plastic film substrate is not particularly limited. For example, a polyester resin such as polyethylene terephthalate, an acrylic resin such as polymethyl methacrylate, polycarbonate, triacetyl cellulose, polysulfone, polyarylate, polyimide, polyvinyl chloride, poly Cyclic olefin polymers such as vinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, trade name “ARTON (cyclic olefin polymer, manufactured by JSR)”, trade name “ZEONOR (cyclic olefin polymer, manufactured by Nippon Zeon)” For example, plastic materials such as In addition, you may use these plastic materials individually or in combination of 2 or more types. In addition, the “base material” is a portion that is attached to the adherend together with the adhesive layer when the double-sided adhesive sheet is used (attached). The release liner that is peeled off when the double-sided PSA sheet is used (attached) is not included in the “base material”.

(Double-sided adhesive sheet)
The double-sided pressure-sensitive adhesive sheet of this embodiment has at least one pressure-sensitive adhesive layer as described above, and can be produced using a known or conventional method. The total thickness of the double-sided PSA sheet is preferably 90 μm to 1,500 μm, more preferably 90 μm to 800 μm, still more preferably 90 μm to 600 μm, and particularly preferably 90 μm to 400 μm, regardless of the presence or absence of the substrate. .

  The shape of the double-sided pressure-sensitive adhesive sheet is appropriately set depending on the application. Specific shapes of the double-sided pressure-sensitive adhesive sheet include various shapes such as a tape shape (strip shape), a strip shape, a U shape (a U shape), an L shape, and a frame shape (loop shape) when viewed in plan. The shape is mentioned. The tape-like (band-like) double-sided pressure-sensitive adhesive sheet has a narrow shape having a predetermined length. The strip-like double-sided pressure-sensitive adhesive sheet is usually narrow and shorter than the tape-like one, and has an I-shape. The U-shaped double-sided pressure-sensitive adhesive sheet has such a shape that other strip-like double-sided pressure-sensitive adhesive sheets are respectively extended in substantially the same direction at both ends of the strip-shaped double-sided pressure-sensitive adhesive sheet. The U-shaped double-sided pressure-sensitive adhesive sheet may be one having rounded corners, or one having corners intersecting substantially at right angles (so-called U-shape). The L-shaped double-sided pressure-sensitive adhesive sheet has a shape such that the two strip-shaped double-sided pressure-sensitive adhesive sheets intersect at a substantially right angle. The frame-like double-sided pressure-sensitive adhesive sheet has a shape in which narrow linear portions are connected in a ring-like state without a seam. As the frame shape, the corners may be rounded, or the corners may intersect at a substantially right angle. A typical example of the frame shape is a shape in which four narrow linear portions are connected in a seamless state so as to form a square or a rectangle.

When the double-sided pressure-sensitive adhesive sheet is used for a small electronic device such as a mobile phone, for example, the preferred form (shape) is preferably a line width of 0.5 mm to 20 mm, and 0.8 to 20 mm. More preferably.
Moreover, when using for medium-sized electronic devices, such as tablet PC, as a preferable form (shape), it is preferable that line width is 0.5 mm-50 mm, and it is more preferable that it is 0.8 mm-30 mm.

(Press adhesive strength)
The double-sided pressure-sensitive adhesive sheet of the present embodiment has a pressure adhesive force of 25.0 N / cm ² or more, preferably 28.0 N / cm ² or more. The pressure adhesive force is, for example, “measurement obtained by laminating a polycarbonate plate and an acrylic plate with a predetermined compression load using a window frame-shaped double-sided pressure-sensitive adhesive sheet having a width of 40 mm, a length of 60 mm, and a width of 1 mm. The sample is defined as “the maximum stress until the acrylic plate and the polycarbonate plate are separated by pressing the acrylic plate at 10 mm / min from the inside toward the outside in the thickness direction of the acrylic plate”.

When the double-sided pressure-sensitive adhesive sheet has a pressure adhesive force as defined above of 25.0 N / cm ² or more, for example, the members fixed by the double-sided pressure-sensitive adhesive sheet receive external force and are bent or distorted by the members. Even when such deformation occurs, the double-sided PSA sheet can continue to fix the members together.

(Drop impact resistance)
Moreover, the double-sided pressure-sensitive adhesive sheet of the present embodiment has a drop impact resistance property under normal temperature (23 ° C.) conditions. This anti-drop impact property means that when a device (for example, a portable electronic device) incorporating a double-sided pressure-sensitive adhesive sheet is subjected to an impact due to a drop, it is difficult to cause peeling due to dropping between the members bonded together by the impact. Say. Since the double-sided pressure-sensitive adhesive sheet of the present embodiment has a drop impact resistance characteristic, even if a large impact is momentarily applied when the portable electronic device is dropped, the double-sided pressure-sensitive adhesive sheet can be peeled off from the member or double-sided pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) It is suppressed that the device itself is destroyed, and it is possible to continue to hold the fixed member.

(Other characteristics)
Moreover, the double-sided pressure-sensitive adhesive sheet of the present embodiment has characteristics such as cutting (punching) workability, workability (handling property), adhesiveness (adhesiveness to an adherend), durability, and weather resistance. Such a double-sided pressure-sensitive adhesive sheet of this embodiment can be used for various applications.

(Use of double-sided PSA sheet)
The double-sided pressure-sensitive adhesive sheet of the present embodiment is used, for example, when fixing various members and modules constituting a mobile electronic device. Examples of such portable electronic devices include mobile phones, PHS, smartphones, tablets (tablet computers), mobile computers (mobile PCs), personal digital assistants (PDAs), electronic notebooks, portable televisions, portable radios, and the like. Mobile broadcast receivers, portable game machines, portable audio players, digital camera cameras, camcorder video cameras, and the like.

  Specific usage modes of the double-sided pressure-sensitive adhesive sheet are not particularly limited. For example, a lens (especially a glass lens) is fixed to a casing, a display panel is fixed to the casing, an input device such as a sheet keyboard or a touch panel To the housing, bonding the protective panel of the information display unit to the housing, bonding of the housings, bonding of the housing to the decorative sheet, various members and modules that make up the portable electronic device Fixing and the like.

  In addition, the “lens” in the present specification is a concept including both a transparent body showing a light refraction action and a transparent body having no light refraction action. In other words, the “lens” in the present specification includes a simple window panel having no refractive action.

  Moreover, as a member of the preferable portable electronic device fixed using a double-sided adhesive sheet, an optical member is mentioned, for example. For example, the double-sided pressure-sensitive adhesive sheet is preferably used for attaching optical members constituting a portable electronic device to each other, fixing an optical member constituting the portable electronic device to a housing, and the like.

  The optical member is a member having optical characteristics (for example, polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). Say. The optical member is not particularly limited as long as it is a member having optical characteristics, for example, a polarizing plate, a wavelength plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light guide plate, a reflective film, an antireflection film, Examples thereof include a transparent conductive film (ITO form), a design film, a decorative film, a surface protective plate, a prism, a lens, a color filter, a transparent substrate, and a laminate thereof. The above-mentioned “plate” and “film” include plates, films, sheets, and the like. For example, “polarizing film” includes “polarizing plate” and “polarizing sheet”.

  Although it does not specifically limit as a raw material which comprises the said optical member, For example, plastic materials, such as an acrylic resin, polycarbonate resin, a polyethylene terephthalate, glass, a metal (a metal oxide is included) etc. are mentioned. In particular, the double-sided pressure-sensitive adhesive sheet of the present invention is particularly preferably used for optical members made of plastic (particularly acrylic or polycarbonate).

The double-sided pressure-sensitive adhesive sheet of the present embodiment has particularly excellent pressure-bonding strength and excellent drop impact resistance. Therefore, the double-sided pressure-sensitive adhesive sheet of the present embodiment constitutes a mobile electronic device having a screen area of 35 cm ² or more (for example, 35 cm ^{2 to} 650 cm ² ) in addition to various members and modules constituting a mobile electronic device having a small screen area. It is preferably used for fixing and bonding various members and modules, particularly various members and modules constituting a mobile electronic device having a screen area of 40 cm ² or more (for example, 40 cm ^{2 to} 650 cm ² ).

  Moreover, the double-sided pressure-sensitive adhesive sheet of this embodiment may be used for fixing various components and various modules in apparatuses other than the above-described portable electronic device. Examples of devices other than the portable electronic device include a display device (image display device) and an input device. Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, and a PDP ( Plasma display panel) and electronic paper. Examples of the input device include a touch panel.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited at all by these Examples.

[Reference Example 1]
(Production of syrup I)
As a monomer component, a product name “Irgacure 651” is used as a photopolymerization initiator in a liquid monomer mixture (monomer composition) obtained by mixing 90 parts by mass of 2-ethylhexyl acrylate (2EHA) and 10 parts by mass of acrylic acid (AA). (2,2-dimethoxy-1,2-diphenylethane-1-one) "(BASF Japan Ltd.) 0.05 parts by mass and trade name" Irgacure 184 (1-hydroxycyclohexyl phenyl ketone) "(BASF Japan Stock) After the addition of 0.05 part by mass), ultraviolet rays were irradiated until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) reached about 15 Pa · s. Syrup I (2EHA / AA = 90 /) containing a partial polymer obtained by polymerization of a part (polymerization rate: about 10% by mass) 0) was obtained.

(Preparation of pressure-sensitive adhesive composition)
To 100 parts by mass of syrup I, 0.07 part by mass of 1,6-hexanediol diacrylate (HDDA) and a hollow glass balloon (average particle size 45 μm, specific gravity 0.25 g / cm ³ , trade name “Sphericel (registered trademark) ) 25P45 (silicate glass) "(Potters Barotini Co., Ltd.) 9 parts by mass was added to obtain a mixture of the syrup. Nox 1010 "(manufactured by BASF Japan Ltd.) was added in an amount of 0.5 parts by mass, and by sufficiently mixing these, pressure-sensitive adhesive composition 1 was obtained, and acrylic contained in pressure-sensitive adhesive composition 1 The polymer (A) contains 10.0% by mass of a structural unit derived from a polar monomer (total amount for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 10 parts by mass).

(Production of double-sided PSA sheet)
The pressure-sensitive adhesive composition 1 was applied to the release-treated surface of the release liner to obtain a coating layer. Then, another release liner was bonded onto the coating layer in a form in which the coating layer and the pharmacological treatment surface of the release liner were in contact with each other. In addition, as the release liner, a polyethylene terephthalate base material (trade name “MRF”, manufactured by Mitsubishi Polyester Film Co., Ltd., or product name “MRN”, manufactured by Mitsubishi Polyester Film Co., Ltd.) whose one side is peeled is used. did.

Next, the coating layer was irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² from both sides for 3 minutes to cure the coating layer to obtain a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) having a thickness of 200 μm. In addition, “Black Light” manufactured by Toshiba Corporation was used as a source of ultraviolet rays. The illuminance of ultraviolet rays was adjusted using a UV checker (trade name “UVR-T1”, manufactured by Topcon Corporation, maximum sensitivity: measured at 350 nm).

  As described above, the double-sided pressure-sensitive adhesive sheet 100 of Reference Example 1 (baseless-less double-sided pressure-sensitive adhesive sheet having a laminate structure of release liner 120 / adhesive layer 110 / release liner 130) 100 was obtained. FIG. 1 is a schematic view of a double-sided pressure-sensitive adhesive sheet 100 of Reference Example 1. The thickness d of the pressure-sensitive adhesive layer 100 was 200 μm.

  In addition, the solvent insoluble content rate (mass%) of the adhesive layer 110 with which the obtained double-sided adhesive sheet 100 was provided was 63 mass%. This solvent-insoluble fraction (mass%) was determined by the following method.

(Measurement of solvent insoluble fraction)
A predetermined amount of the pressure-sensitive adhesive layer (initial mass W1) was immersed in an ethyl acetate solution and allowed to stand at room temperature for 1 week. Then, the insoluble matter was taken out and dried, and the mass (W2) was measured. Asking.
Solvent insoluble fraction = (W2 / W1) × 100

[Example 2]
(Production of syrup II)
As monomer components, 2-ethylhexyl acrylate (2EHA) 80 parts by mass, 2-methoxyethyl acrylate (2MEA) 11.5 parts by mass, N-vinyl-2-pyrrolidone (NVP) 7 parts by mass and N- (2-hydroxyethyl) The product name “Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane) is used as a photopolymerization initiator in a liquid monomer mixture (monomer composition) obtained by mixing 1.5 parts by mass of acrylamide (HEAA). -1-one) "(BASF Japan Ltd.) 0.05 parts by mass and trade name" Irgacure 184 (1-hydroxycyclohexyl phenyl ketone) "(BASF Japan Ltd.) 0.05 parts by mass, Viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) is about 15 Pa Syrup II (2EHA / 2MEA / NVP / HEAA = 80/11. 2) containing a partial polymer (polymerization rate: about 10% by mass) obtained by irradiating ultraviolet rays until s is reached and polymerizing a part of the monomer component. 5/7 / 1.5) was obtained.

(Preparation of pressure-sensitive adhesive composition)
To 100 parts by mass of Syrup II, 3 parts by mass of acrylic acid (AA), 0.12 parts by mass of 1,6-hexanediol diacrylate (HDDA), and 10 parts by mass of the first polymer (B) are added, By sufficiently mixing these, the pressure-sensitive adhesive composition 2 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 2 contains 11.2% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 11.5 parts by mass).

(Production of double-sided PSA sheet)
A pressure-sensitive adhesive layer (thickness: 200 μm) comprising the pressure-sensitive adhesive composition 2 is provided in the same manner as in Reference Example 1 except that the pressure-sensitive adhesive composition 2 is used instead of the pressure-sensitive adhesive composition 1, and a reference example. A double-sided PSA sheet having the same laminated structure as in No. 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 2 was 62 mass%.

In addition, the preparation method of the said 1st polymer (B) is as follows.
(Preparation of first polymer (B))
100 parts by mass of toluene, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA) (trade name “FA-513M”, manufactured by Hitachi Chemical Co., Ltd.), 40 parts by mass of methyl methacrylate (MMA), and thioglycolic acid as a chain transfer agent 3 parts by mass of (GSH acid) was charged into a four-necked flask. Then, after stirring for 1 hour at 70 ° C. in a nitrogen atmosphere, 0.2 part by mass of azobisisobutyronitrile as a thermal polymerization initiator was added and reacted for 2 hours at 70 ° C., followed by 2 at 80 ° C. Reacted for hours. Thereafter, the reaction solution was put into a temperature atmosphere of 130 ° C., and toluene, chain transfer agent and unreacted monomer were removed by drying, and a solid (meth) acrylic polymer (first polymer (B), DCPMA / MMA = 60/40).

  The weight average molecular weight (Mw) of the obtained first polymer (B) was 5,500. Moreover, the glass transition temperature (Tg) of the obtained 1st polymer (B) was 144 degreeC.

Example 3
To 100 parts by mass of Syrup II, 3 parts by mass of acrylic acid (AA), 0.12 parts by mass of 1,6-hexanediol diacrylate (HDDA), and 15 parts by mass of the first polymer (B) are added, By fully mixing these, the pressure-sensitive adhesive composition 3 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 3 contains 11.2% by mass of a structural unit derived from a polar monomer (all monomers for forming the acrylic polymer (A)). Component: 103 parts by mass, polar monomer component: 11.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 145 micrometers) which consists of an adhesive composition 3 similarly to the reference example 1 except having utilized the adhesive composition 3. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 3 was 55 mass%.

Example 4
In place of 10 parts by mass of the first polymer (B), the trade name “heavy calcium carbonate (natural heavy calcium carbonate, average particle size 3.2 to 12 μm, specific gravity 2.71 g / cm ³ )” (Maruo Calcium Co., Ltd.) Manufactured) Adhesive composition 4 was prepared in the same manner as in Example 2 except that 80 parts by mass was added to 100 parts by mass of syrup II. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 4 contains 11.2% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 11.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 156 micrometers) which consists of an adhesive composition 4 like the reference example 1 except having utilized the adhesive composition 4. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 4 was 94 mass%.

Example 5
By adding 3 parts by weight of acrylic acid (AA) and 0.025 parts by weight of 1,6-hexanediol diacrylate (HDDA) to 100 parts by weight of syrup II, the pressure-sensitive adhesive composition is sufficiently mixed. Product 5 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 5 contains 11.2% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 11.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 140 micrometers) which consists of the adhesive composition 5 similarly to the reference example 1 except having utilized the adhesive composition 5. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 5 was 60 mass%.

Example 6
To 100 parts by mass of Syrup II, 3 parts by mass of acrylic acid (AA), 0.12 parts by mass of 1,6-hexanediol diacrylate (HDDA), and 15 parts by mass of the second polymer (B) are added, By fully mixing these, the pressure-sensitive adhesive composition 6 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 6 contains 11.2% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 11.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 145 micrometers) which consists of an adhesive composition 6 similarly to the reference example 1 except having utilized the adhesive composition 6. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 6 was 77 mass%.

In addition, the preparation method of the said 2nd polymer (B) is as follows.
(Preparation of second polymer (B))
Nitrogen gas was blown into a mixture in which 60 parts by mass of cyclohexyl methacrylate (CHMA), 40 parts by mass of isobutyl methacrylate (IBMA) and 4 parts by mass of thioglycolic acid were mixed to remove dissolved oxygen in the mixture. Thereafter, when the temperature of the mixture was raised to 90 ° C., 0.05 part by mass of a product name “Perhexyl O (t-hexylperoxy 2-ethylhexanoate)” (manufactured by NOF Corporation) and a product as a polymerization initiator The name "perhexyl D (di-t-hexyl peroxide)" (manufactured by NOF Corporation) was blended in an amount of 0.01 parts by mass to the mixture. Next, the mixture was stirred at 90 ° C. for 1 hour, then heated to 150 ° C. over 1 hour, and further stirred at 150 ° C. for 1 hour. Thereafter, the mixture was heated to 170 ° C. over 1 hour and further stirred at 170 ° C. for 1 hour.

  Next, the mixture was depressurized at 170 ° C., and stirred for 1 hour to remove residual monomer, whereby a second polymer (B) (CHMA / IBMA = 60/40) was obtained. The weight average molecular weight (Mw) of the obtained second polymer (B) was 3,500. Moreover, the glass transition temperature (Tg) of the obtained 2nd polymer (B) was 59 degreeC.

Example 7
In the same manner as in Example 2, except that 5 parts by mass of the first polymer (B) was added to 100 parts by mass of syrup II instead of 10 parts by mass of the first polymer (B). Produced. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 7 contains 11.2% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 11.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 148 micrometers) which consists of an adhesive composition 7 similarly to the reference example 1 except having utilized the adhesive composition 7. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 7 was 79 mass%.

Example 8
A pressure-sensitive adhesive composition 8 was prepared in the same manner as in Example 5 except that 4 parts by mass of acrylic acid (AA) was added to 100 parts by mass of syrup II instead of 3 parts by mass of acrylic acid (AA). . The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 8 contains 12.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 12.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 146 micrometers) which consists of the adhesive composition 8 similarly to the reference example 1 except having utilized the adhesive composition 8. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 8 was 59 mass%.

Example 9
Instead of 3 parts by mass of acrylic acid (AA), 5 parts by mass of acrylic acid (AA) is added to 100 parts by mass of syrup II, and 0.12 part by mass of 1,6-hexanediol diacrylate (HDDA). Instead, an adhesive composition 9 was prepared in the same manner as in Example 5 except that 0.05 part by mass of dipentaerythritol hexaacrylate (DPHA) was added to the syrup II. In addition, the acrylic polymer (A) contained in the pressure-sensitive adhesive composition 9 contains 12.9% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 105 parts by mass, polar monomer component: 13.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 204 micrometers) which consists of an adhesive composition 9 similarly to the reference example 1 except having utilized the adhesive composition 9. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 9 was 66 mass%.

Example 10
It replaced with 3 mass parts of acrylic acid (AA), and produced the adhesive composition 10 like Example 5 except adding 5 mass parts of acrylic acid (AA) to 100 mass parts syrup II. . The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 10 contains 12.9% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 105 parts by mass, polar monomer component: 13.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 138 micrometers) which consists of an adhesive composition 10 similarly to the reference example 1 except having utilized the adhesive composition 10. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 10 was 60 mass%.

Example 11
To 100 parts by mass of syrup II, 5 parts by mass of acrylic acid (AA), 0.05 parts by mass of dipentaerythritol hexaacrylate (DPHA), and the trade name “Shiraka Hana CC-R (synthetic light calcium carbonate, average grain) The pressure-sensitive adhesive composition 11 was obtained by adding 40 parts by mass of 80 μm in diameter and a specific gravity of 2.52 g / cm ³ ) ”(manufactured by Shiraishi Calcium Co., Ltd.) and mixing them sufficiently. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 11 contains 12.9% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 105 parts by mass, polar monomer component: 13.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 217 micrometers) which consists of the adhesive composition 11 similarly to the reference example 1 except having utilized the adhesive composition 11. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 11 was 76 mass%.

Example 12
To 100 parts by mass of syrup I, 4 parts by mass of N-vinyl-2-pyrrolidone (NVP) and 0.035 parts by mass of 1,6-hexanediol diacrylate (HDDA) are added and mixed sufficiently. Thus, a pressure-sensitive adhesive composition 12 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 12 contains 13.5% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 14 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 194 micrometers) which consists of an adhesive composition 12 similarly to the reference example 1 except having utilized the adhesive composition 12. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 12 was 75 mass%.

Example 13
Instead of 4 parts by mass of N-vinyl-2-pyrrolidone (NVP), the same procedure as in Example 12 was conducted except that 8 parts by mass of N-vinyl-2-pyrrolidone (NVP) was added to 100 parts by mass of syrup I. Thus, a pressure-sensitive adhesive composition 13 was produced. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 13 contains 16.7% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 108 parts by mass, polar monomer component: 18 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 194 micrometers) which consists of an adhesive composition 13 similarly to the reference example 1 except having utilized the adhesive composition 13. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 13 was 76 mass%.

[Reference Example 14]
(Production of syrup III)
A liquid monomer mixture in which 78 parts by mass of 2-ethylhexyl acrylate (2EHA), 18 parts by mass of N-vinyl-2-pyrrolidone (NVP) and 4 parts by mass of 2-hydroxyethyl acrylate (HEA) are mixed as a monomer component ( Monomer composition) as a photopolymerization initiator, trade name “Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane-1-one)” (manufactured by BASF Japan Ltd.) 0.05 parts by mass and product After blending 0.05 part by mass of the name “Irgacure 184 (1-hydroxycyclohexyl phenyl ketone)” (manufactured by BASF Japan Ltd.), the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) is about A portion formed by polymerizing a part of the monomer component by irradiating with ultraviolet rays until reaching 15 Pa · s Polymer (polymerization ratio: 10 wt%) was obtained syrup III (2EHA / NVP / HEA = 78/18/4) containing.

(Preparation of pressure-sensitive adhesive composition)
0.12 parts by mass of 1,6-hexanediol diacrylate (HDDA) was added to 100 parts by mass of syrup III, and these were sufficiently mixed to obtain an adhesive composition 14. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 14 contains 22.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 22 parts by mass).

(Production of double-sided PSA sheet)
In addition to the use of the pressure-sensitive adhesive composition 14 instead of the pressure-sensitive adhesive composition 1, a pressure-sensitive adhesive layer (thickness: 144 μm) comprising the pressure-sensitive adhesive composition 14 was provided in the same manner as in Reference Example 1, and the examples A double-sided PSA sheet having the same laminated structure as in No. 1 was obtained. In addition, the solvent insoluble fraction of the pressure-sensitive adhesive layer in Reference Example 14 was 82% by mass.

Example 15
An adhesive composition is prepared by adding 1 part by mass of acrylic acid (AA) and 0.025 part by mass of 1,6-hexanediol diacrylate (HDDA) to 100 parts by mass of syrup III and mixing them sufficiently. 15 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 15 contains 22.8% by mass of a structural unit in the polar monomer (all monomer components for forming the acrylic polymer (A)). : 101 parts by mass, polar monomer component: 23 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 149 micrometers) which consists of an adhesive composition 15 similarly to the reference example 1 except having utilized the adhesive composition 15. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 15 was 80 mass%.

Example 16
It replaced with 1 mass part of acrylic acid (AA), and produced the adhesive composition 16 like Example 15 except adding 2 mass parts of acrylic acid (AA) to 100 mass parts syrup III. . The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 16 contains 23.5% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 102 parts by mass, polar monomer component: 24 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 143 micrometers) which consists of an adhesive composition 16 similarly to the reference example 1 except having utilized the adhesive composition 16. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 16 was 83 mass%.

Example 17
A pressure-sensitive adhesive composition 17 was produced in the same manner as in Example 15 except that 3 parts by mass of acrylic acid (AA) was added to 100 parts by mass of syrup III instead of 1 part by mass of acrylic acid (AA). . The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 17 contains 24.3% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 103 parts by mass, polar monomer component: 25 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 143 micrometers) which consists of an adhesive composition 17 similarly to the reference example 1 except having utilized the adhesive composition 17. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 17 was 81 mass%.

Example 18
A pressure-sensitive adhesive composition 18 was produced in the same manner as in Example 15 except that 4 parts by mass of acrylic acid (AA) was added to 100 parts by mass of syrup III instead of 1 part by mass of acrylic acid (AA). . The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 18 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 145 micrometers) which consists of an adhesive composition 18 similarly to the reference example 1 except having utilized the adhesive composition 18. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 18 was 82 mass%.

Example 19
To 100 parts by mass of syrup III, 4 parts by mass of acrylic acid (AA) and 0.025 parts by mass of 1,6-hexanediol diacrylate (HDDA) were added to obtain a mixture of the syrup. Furthermore, as a photopolymerization initiator for an additional amount, a trade name “Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane-1-one)” (manufactured by BASF Japan Ltd.) 0.5 mass Parts were added. Thereafter, 0.3 parts by mass of a trade name “AT DN101 Black” (manufactured by Dainichi Seika Kogyo Co., Ltd.) as a black pigment was added to the mixture as another additive component. And the adhesive composition 19 was obtained by fully mixing these. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 19 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of an adhesive composition 19 similarly to the reference example 1 except having utilized the adhesive composition 19. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 19 was 35 mass%.

Moreover, the haze and total light transmittance of the double-sided pressure-sensitive adhesive sheet in Example 19 were measured. As a result of the measurement, haze was 44% and total light transmittance was 18%. The measuring method of haze and total light transmittance is based on JISK7361, and the specific content is as follows.
(Method for measuring haze and total light transmittance)
The double-sided pressure-sensitive adhesive sheet is bonded to a slide glass (manufactured by Matsunami Glass Industrial Co., Ltd., trade name “S-1111”, total light transmittance 91.8%, haze 0.4%) except for one release liner. Except for one release liner, a test piece [(adhesive sheet) / (slide glass) configuration] was obtained. The haze and total light transmittance of the test piece were measured using a haze meter (“Murakami Color Research Laboratory, trade name“ HM-150 ”).

Example 20
Use 0.8 parts by weight of black pigment instead of 0.3 parts by weight of black pigment, use 0.03 parts by weight of HDDA instead of 0.025 parts by weight of HDDA, and additional photopolymerization initiator (Irgacure 651) In place of 0.5 part by mass, an additional photopolymerization initiator (Irgacure 651) was used in the same manner as in Example 19 except that 0.3 part by mass was used. Agent composition 20 was prepared. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 20 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 207 micrometers) which consists of the adhesive composition 20 similarly to the reference example 1 except having utilized the adhesive composition 20. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 20 was 41 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 20 was 66%, and the total light transmittance was 2.9%.

Example 21
Use 1 part by weight of black pigment instead of 0.3 part by weight of black pigment, use 0.03 part by weight of HDDA instead of 0.025 part by weight of HDDA, and add photopolymerization initiator (Irgacure 651) A pressure-sensitive adhesive composition using syrup III in the same manner as in Example 19 except that 0.3 parts by mass of an additional photopolymerization initiator (Irgacure 651) is used instead of 0.5 parts by mass. Product 21 was prepared. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 21 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 207 micrometers) which consists of an adhesive composition 21 similarly to the reference example 1 except having utilized the adhesive composition 21. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 21 was 14 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 21 was 72%, and the total light transmittance was 1.8%.

[Example 22]
The same procedure as in Example 19 except that 1 part by weight of black pigment was used instead of 0.3 part by weight of black pigment, and 0.05 part by weight of HDDA was used instead of 0.025 part by weight of HDDA. An adhesive composition 22 was prepared using syrup III. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 22 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 206 micrometers) which consists of an adhesive composition 22 similarly to the reference example 1 except having utilized the adhesive composition 22. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 22 was 41 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 22 was 71%, and the total light transmittance was 1.7%.

Example 23
Use 1 part by weight of black pigment instead of 0.3 part by weight of black pigment, use 0.07 part by weight of HDDA instead of 0.025 part by weight of HDDA, and add photopolymerization initiator (Irgacure 651) A pressure-sensitive adhesive composition using syrup III in the same manner as in Example 19 except that 0.7 parts by mass of an additional photopolymerization initiator (Irgacure 651) was used instead of 0.5 parts by mass. Article 23 was prepared. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 23 contains 25.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 209 micrometers) which consists of an adhesive composition 23 similarly to the reference example 1 except having utilized the adhesive composition 23, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 23 was 55 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 23 was 69%, and the total light transmittance was 1.3%.

Example 24
In place of 0.3 part by weight of black pigment, 0.8 part by weight of black pigment is used. In place of 0.025 part by weight of HDDA, 0.056 part by weight of HDDA is used. Irgacure 651) Instead of 0.5 part by mass, an additional part of the photopolymerization initiator (Irgacure 651) 0.7 part by mass is used, and a hollow glass balloon (average particle size 45 μm, specific gravity 0.25 g / cm ³⁾ Adhesion using syrup III in the same manner as in Example 19 except that 4 parts by mass of trade name “Sphericel® 25P45 (silicate glass)” (manufactured by Potters Barotini Co., Ltd.) was added. An adhesive composition 24 was prepared, and the acrylic polymer (A) contained in the pressure-sensitive adhesive composition 24 contained 25.0% by mass of a structural unit derived from a polar monomer. (Total monomer component for forming acrylic polymer (A): 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 212 micrometers) which consists of an adhesive composition 24 similarly to the reference example 1 except having utilized the adhesive composition 24, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 24 was 56 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 24 was 80%, and the total light transmittance was 2.0%.

Example 25
In place of 0.3 part by weight of black pigment, 0.8 part by weight of black pigment is used. In place of 0.025 part by weight of HDDA, 0.03 part by weight of HDDA is used. Irgacure 651) Instead of 0.5 part by mass, an additional amount of photopolymerization initiator (Irgacure 651) 0.7 part by mass is used, and aluminum hydroxide (average particle size 18 μm, specific gravity 0.9 g / cm ³⁾ A pressure-sensitive adhesive composition 25 was prepared using syrup III in the same manner as in Example 19 except that 10 parts by mass of the trade name “H31 (Hijilite)” (manufactured by Showa Denko KK) was added. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 25 contains 25.0% by mass of a structural unit derived from a polar monomer (all monomers for forming the acrylic polymer (A)). Component: 104 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 205 micrometers) which consists of an adhesive composition 25 like the reference example 1 except having utilized the adhesive composition 25, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 25 was 23 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 25 was 93%, and the total light transmittance was 2.8%.

Example 26
In place of 0.3 part by weight of black pigment, 0.8 part by weight of black pigment is used. In place of 0.025 part by weight of HDDA, 0.08 part by weight of HDDA is used. Irgacure 651) Instead of 0.5 part by mass, an additional photopolymerization initiator (Irgacure 651) 0.7 part by mass and hydrogenated petroleum resin (softening point 125 ° C., trade name “Alcon P125”) (Arakawa Chemical Industries, Ltd.) A pressure-sensitive adhesive composition 26 was produced using syrup III in the same manner as in Example 19 except that 10 parts by mass was added. The acrylic polymer (A) contains 25.0% by mass of a structural unit derived from a polar monomer (total monomer components for forming the acrylic polymer (A): 104 parts by mass, polar monomer Minute: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 204 micrometers) which consists of an adhesive composition 26 similarly to the reference example 1 except having utilized the adhesive composition 26, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 26 was 57 mass%. Moreover, the haze of the double-sided pressure-sensitive adhesive sheet in Example 26 was 85%, and the total light transmittance was 3.4%.

Example 27
To 100 parts by mass of syrup III, 3 parts by mass of acrylic acid (AA), 5 parts by mass of 2-hydroxyethyl acrylate (HEA) and 0.025 parts by mass of HDDA are added, and these are mixed sufficiently to produce a pressure-sensitive adhesive composition. Product 27 was obtained. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 27 contains 27.8% by mass of structural units derived from polar monomers (all for forming the acrylic polymer (A)). Monomer component: 108 parts by mass, polar monomer component: 26 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of the adhesive composition 27 similarly to the reference example 1 except having utilized the adhesive composition 27, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 27 was 68 mass%.

Example 28
40 parts by mass of syrup I, 17 parts by mass of N-vinyl-2-pyrrolidone (NVP), 4 parts by mass of 2-hydroxyethyl acrylate (HEA), 39 parts by mass of 2-ethylhexyl acrylate (2EHA), 0.07 part by mass of 6-hexanediol diacrylate (HDDA) was added to obtain a mixture of the syrup. Further, as an additional photopolymerization initiator, the product name “Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane-1-one)” (manufactured by BASF Japan Ltd.) 0.7 mass Parts were added. Thereafter, as the other additive component, 1 part by mass of trade name “AT DN101 Black” (manufactured by Dainichi Seika Kogyo Co., Ltd.) was added to the mixture as a black pigment. And the adhesive composition 28 was obtained by fully mixing these.
The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 28 contains 21.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 25 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of an adhesive composition 28 similarly to the reference example 1 except having utilized the adhesive composition 28, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. The solvent insoluble fraction of the pressure-sensitive adhesive layer in Example 28 was 61% by mass.

Example 29
(Production of syrup IV)
As a monomer component, a product name “Irgacure 651” is used as a photopolymerization initiator in a liquid monomer mixture (monomer composition) in which 94 parts by mass of 2-ethylhexyl acrylate (2EHA) and 6 parts by mass of acrylic acid (AA) are mixed. (2,2-dimethoxy-1,2-diphenylethane-1-one) "(BASF Japan Ltd.) 0.05 parts by mass and trade name" Irgacure 184 (1-hydroxycyclohexyl phenyl ketone) "(BASF Japan Stock) After the addition of 0.05 part by mass), ultraviolet rays were irradiated until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) reached about 15 Pa · s. Syrup IV (2EHA / AA = 94 /) containing a partial polymer obtained by polymerization of a part (polymerization rate: about 10% by mass) ) Was obtained.

(Preparation of pressure-sensitive adhesive composition)
66.7 parts by mass of syrup IV, 17 parts by mass of N-vinyl-2-pyrrolidone (NVP), 4 parts by mass of 2-hydroxyethyl acrylate (HEA), and 12.3 parts by mass of 2-ethylhexyl acrylate (2EHA) Then, 0.07 part by mass of 1,6-hexanediol diacrylate (HDDA) was added to obtain a mixture of the syrup. Further, as an additional photopolymerization initiator, the product name “Irgacure 651 (2,2-dimethoxy-1,2-diphenylethane-1-one)” (manufactured by BASF Japan Ltd.) 0.7 mass Parts were added. Thereafter, as the other additive component, 1 part by mass of trade name “AT DN101 Black” (manufactured by Dainichi Seika Kogyo Co., Ltd.) was added to the mixture as a black pigment. And the adhesive composition 29 was obtained by fully mixing these.
The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 29 contains 21.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 25 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of an adhesive composition 29 similarly to the reference example 1 except having utilized the adhesive composition 29, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in Example 29 was 59 mass%.

[Reference Example 30]
100 parts by mass of syrup I, 30 parts by mass of thermal foaming agent 1 (thermally expandable microsphere, trade name “thermally expandable microsphere 051DU40” manufactured by EXPANCEL), 0.2 part by mass of trimethylolpropane triacrylate (TMPTA) Was added and sufficiently mixed to obtain a pressure-sensitive adhesive composition 30 containing the thermal foaming agent 1. The acrylic polymer (A) contained in the pressure-sensitive adhesive composition 30 contains 10.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 10.0 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of the adhesive composition 30 like the reference example 1 except having utilized the adhesive composition 30, A heat-expandable double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble fraction of the pressure-sensitive adhesive layer in Reference Example 30 was 89% by mass.

[Reference Example 31]
A heat-expandable double-sided pressure-sensitive adhesive sheet having a laminated structure similar to that of Reference Example 30 was obtained in the same manner as Reference Example 30, except that the thickness of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition 30 was 150 μm. The solvent insoluble fraction of the pressure-sensitive adhesive layer in Reference Example 31 was 89% by mass.

[Reference Example 32]
To 100 parts by mass of syrup I, 30 parts by mass of thermal foaming agent 2 (thermally expandable microsphere, trade name “Matsumoto Microsphere F-48D *” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), trimethylolpropane triacrylate (TMPTA) 0 The pressure-sensitive adhesive composition 32 containing the thermal foaming agent 2 was obtained by adding 2 parts by mass and mixing them sufficiently. In addition, the acrylic polymer (A) contained in the pressure-sensitive adhesive composition 32 contains 10.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 10.0 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of the adhesive composition 32 similarly to the reference example 1 except having utilized the adhesive composition 32, A heat-expandable double-sided pressure-sensitive adhesive sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble fraction of the pressure-sensitive adhesive layer in Reference Example 32 was 86% by mass.

[Reference Example 33]
In 100 parts by mass of syrup I, 20 parts by mass of thermal foaming agent 2 (thermally expandable microsphere, trade name “Matsumoto Microsphere F-48D *” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), trimethylolpropane triacrylate (TMPTA) 0 The pressure-sensitive adhesive composition 33 containing the thermal foaming agent 2 was obtained by adding 2 parts by mass and mixing them sufficiently. In addition, the acrylic polymer (A) contained in the pressure-sensitive adhesive composition 33 contains 10.0% by mass of a structural unit derived from a polar monomer (all for forming the acrylic polymer (A)). Monomer component: 100 parts by mass, polar monomer component: 10.0 parts by mass).
Further, a heat-expandable double-sided pressure-sensitive adhesive sheet having a laminated structure similar to that of Reference Example 32 is obtained in the same manner as Reference Example 32 except that the thickness of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition 33 is 94 μm. It was. In addition, the solvent insoluble content rate of the adhesive layer was 86 mass%.
Further, the release liner was peeled off from one side of the obtained double-sided pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer), and the double-sided pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) was replaced with a polyester film (trade name “Lumirror S-10”, thickness And 12 μm, manufactured by Toray Industries, Inc.) with a hand roller to obtain a heat-expandable double-sided pressure-sensitive adhesive sheet containing a PET base material in Reference Example 33.

[Comparative Example 1]
To 100 parts by mass of syrup II, 0.05 part by mass of DPHA was added, and these were sufficiently mixed to obtain an adhesive composition C1. The acrylic polymer contained in the pressure-sensitive adhesive composition C1 contains 8.5% by mass of a structural unit derived from a polar monomer (total monomer components for forming an acrylic polymer: 100 parts by mass) , Polar monomer component: 8.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of adhesive composition C1 similarly to the reference example 1 except having utilized the adhesive composition C1. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in the comparative example 1 was 69 mass%.

[Comparative Example 2]
To 100 parts by mass of syrup II, 0.025 parts by mass of DPHA and a trade name “heavy calcium carbonate (natural heavy calcium carbonate, average particle size 3.2 to 12 μm, specific gravity 2.71 g / cm ³ )” (Maruo Calcium 40 parts by mass) were added, and these were mixed sufficiently to obtain an adhesive composition C2. The acrylic polymer contained in the pressure-sensitive adhesive composition C2 contains 8.5% by mass of a structural unit derived from a polar monomer (total monomer components for forming an acrylic polymer: 100 parts by mass) , Polar monomer component: 8.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 217 micrometers) which consists of adhesive composition C2 similarly to the reference example 1 except having utilized the adhesive composition C2. A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in the comparative example 2 was 57 mass%.

[Comparative Example 3]
To 100 parts by mass of syrup II, 0.05 parts by mass of DPHA and a hollow glass balloon (average particle size 45 μm, specific gravity 0.25 g / cm ³ , trade name “Sphericel® 25P45 (silicate glass)” (potter And 20 parts by mass), and sufficiently mixing them, pressure-sensitive adhesive composition C3 was obtained, and the acrylic polymer contained in pressure-sensitive adhesive composition C3 contains polar monomers. Is contained in an amount of 8.5 mass% (total monomer components for forming acrylic polymer: 100 parts by mass, polar monomer components: 8.5 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 210 micrometers) which consists of adhesive composition C3 similarly to the reference example 1 except having utilized the adhesive composition C3, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in the comparative example 3 was 68 mass%.

[Comparative Example 4]
By adding 0.025 parts by weight of HDDA, 15 parts by weight of acrylic acid (AA), and 16.5 parts by weight of 2-hydroxyethyl acrylate (HEA) to 100 parts by weight of Syrup II, and mixing them sufficiently An adhesive composition C4 was obtained. The acrylic polymer contained in the pressure-sensitive adhesive composition C4 contains 30.4% by mass of a structural unit derived from a polar monomer (total monomer components for forming an acrylic polymer: 131.5 Parts by mass, polar monomer component: 40 parts by mass).
Moreover, it replaced with the adhesive composition 1 and was equipped with the adhesive layer (thickness: 200 micrometers) which consists of adhesive composition C4 similarly to the reference example 1 except having utilized the adhesive composition C4, A double-sided PSA sheet having the same laminated structure as in Reference Example 1 was obtained. In addition, the solvent insoluble content rate of the adhesive layer in the comparative example 4 was 78 mass%.

(Evaluation test)
About each Example, each reference example, and Comparative Examples 1-4, the evaluation test of the press adhesive force of each double-sided adhesive sheet and a drop impact resistance characteristic (room temperature conditions) was done.
In addition, for Reference Examples 30 to 33, the pressure adhesion strength and drop impact resistance characteristics (under normal temperature conditions) were similarly evaluated, and the 180 ° peel adhesion was initially (before heating) and after heating. The measurement was performed under the conditions described above, and the tackiness (adhesiveness) and the separation / disassembly (easy peelability) were evaluated.

<Evaluation 1: Press adhesive strength>
FIG. 2 is a schematic view (top view) of a sample for evaluation used when measuring the pressure adhesive force. The produced double-sided PSA sheet was cut into a window frame shape (frame shape) having a width of 1 mm as shown in FIG. 2 (width: 40 mm, length: 60 mm) to obtain a window frame-like double-sided PSA sheet. Using the window frame-shaped double-sided pressure-sensitive adhesive sheet, an acrylic plate (acrylic lens, width: 40 mm, length: 60 mm, thickness: 1 mm) and a polycarbonate plate (PC plate) with a through hole having a diameter of 15 mm in the center (width) : 70 mm, length: 80 mm, thickness: 2 mm) were bonded together under pressure and reciprocation conditions of a roller with a predetermined pressure load (2 kg) to obtain an evaluation sample. 3 is a cross-sectional view taken along line AA ′ of FIG. 2 and 3, 1 is a polycarbonate plate, 2 is a window frame-shaped double-sided pressure-sensitive adhesive sheet, 3 is an acrylic plate, and 4 is a through hole of the polycarbonate plate.

  Next, these evaluation samples are set in a universal tensile compression tester (device name “Tensile compression tester, TG-1kN” manufactured by Minebea Co., Ltd.), and the round bar is passed through the through hole of the polycarbonate plate. The acrylic plate was pressed with a round bar (diameter: 10 mm) under the condition of 10 mm / min, and the maximum stress until the acrylic plate and the polycarbonate plate were separated was measured as the pressing adhesive force. The measurement was performed at room temperature (23 ° C.).

  FIG. 4 is a schematic cross-sectional view showing a method for measuring the pressing adhesive force. In FIG. 4, 1 is a polycarbonate plate, 2 is a window frame-shaped double-sided pressure-sensitive adhesive sheet, 3 is an acrylic plate, 21 is a round bar, and 22 is a support base. The evaluation sample is fixed to the support base 22 of the tensile and compression tester as shown in FIG. 4, and the evaluation sample acrylic plate 3 is pressed by the round bar 21 that has passed through the through hole of the polycarbonate plate 1. In the sample for evaluation, the polycarbonate plate 1 was subjected to a load when the acrylic plate was pressed, and was not bent or damaged.

<Evaluation 2: Drop impact resistance at normal temperature>
FIG. 5 is a schematic view (top view) of a sample for evaluation used in evaluating the drop impact resistance characteristics. The produced double-sided PSA sheet was cut into a window frame shape (frame shape) having a width of 1 mm as shown in FIG. 5 (width: 40 mm, length: 60 mm) to obtain a window frame-type double-sided PSA sheet. Using the window frame-shaped double-sided pressure-sensitive adhesive sheet, an acrylic plate (acrylic lens, width: 40 mm, length: 60 mm, thickness: 1 mm) and a polycarbonate plate (PC plate) (width: 70 mm, length: 80 mm, thickness: 2 mm) Were bonded together by pressure bonding under the condition of one reciprocation of a 2 kg roller to obtain a sample for evaluation. 6 is a cross-sectional view taken along line BB ′ of FIG. 5 and 6, 31 is a polycarbonate plate, 32 is a window frame-shaped double-sided pressure-sensitive adhesive sheet, and 33 is an acrylic plate (acrylic lens).

  FIG. 7 is a schematic cross-sectional view illustrating a method for evaluating a drop impact resistance characteristic. After attaching the weight 34 to the obtained sample for evaluation and making the total mass 110 g, the sample for evaluation is freely dropped from a height of 1.2 m onto the concrete plate 35 (see FIG. 7) to evaluate the drop impact resistance characteristics. did. The evaluation of the drop impact resistance was performed by free-falling 12 times at room temperature (23 ° C.).

  The free fall of the evaluation sample is the first time (falling from the plate surface on the weight 34 side of the polycarbonate plate 31), the second time (falling from the plate surface of the polycarbonate plate 31 on the acrylic plate 33 side), and the third time (polycarbonate plate). Drop from one longitudinal end face of the plate 31), 4th (fall from the other longitudinal end face of the polycarbonate plate 31), 5th (fall from one lateral end face of the polycarbonate plate 31), 6th ( This was performed in the order of dropping from the other side end face of the polycarbonate plate 31. In other words, the drop impact resistance was evaluated by repeating the six drops twice. The evaluation criteria are as follows.

[Evaluation criteria]
Good: “Acrylic plate was not peeled off after 12 free drops at room temperature, and the acrylic plate was held”
Defect: “Acrylic plate peeled off due to free fall at room temperature”, the number of times the acrylic plate was dropped

<Evaluation 3: 180 degree peeling adhesive strength>
After bonding a polyester film (trade name “Lumirror S-10”, thickness: 50 μm, manufactured by Toray Industries, Inc.) as a backing substrate on one side of the heat-expandable double-sided PSA sheet obtained in Reference Examples 30 to 33 It was cut into a width of 20 mm. Thereafter, the release liner attached to the double-sided pressure-sensitive adhesive sheet was peeled off, and a pressure-sensitive adhesive pressure measurement polycarbonate plate (PC plate) was pressure-bonded under the condition of 2 kg roller and 1 reciprocation as an evaluation sample. In addition, the evaluation sample prepared the thing for measuring initial adhesive force (after-mentioned) about the double-sided adhesive tape of each reference examples 30-33, and the thing for measuring post-heating adhesive force (after-mentioned), respectively. .

(Initial (before heating) adhesive strength)
The evaluation sample prepared as described above was left for 30 minutes after pressure bonding. Thereafter, both surfaces of the evaluation sample are evaluated under conditions of a tensile speed of 300 mm / min and a peeling angle of 180 ° using a tensile tester (trade name “TG-1kN” manufactured by Minebea) in an atmosphere of 23 ° C. By peeling off the pressure-sensitive adhesive sheet, the peel adhesive strength of each evaluation sample was measured. The measured peel adhesive strength was defined as initial adhesive strength (20 / mm). In addition, based on the measured initial adhesive force (20 / mm), the adhesiveness (adhesiveness) of each evaluation sample of Reference Examples 30 to 33 was evaluated according to the following evaluation criteria.
[Evaluation criteria]
○: Adhesiveness to the adherend (PC board) of the double-sided PSA sheet is sufficient (5.0 [N / 20 mm] or more).
Δ: Adhesiveness of the double-sided PSA sheet to the adherend (PC board) is slightly inferior (2.5 [N / 20 mm] or more and less than 5.0 [N / 20 mm]).
X: Adhesiveness to the adherend (PC board) of the double-sided PSA sheet is insufficient (less than 2.5 [N / 20 mm]).

(Adhesive strength after heating)
The evaluation sample prepared as described above was left for 30 minutes after pressure bonding. Thereafter, each evaluation sample was put into a hot air drier at a predetermined temperature (see Table 4 described later) for 10 minutes to perform heat treatment. After the heat treatment, the sample was left for 2 hours in an atmosphere at 23 ° C., and then peeled off from the double-sided pressure-sensitive adhesive sheet of the evaluation sample by the same method as the measurement of the initial adhesive strength, and the adhesive strength was measured. The measured peel adhesive strength was defined as adhesive strength after heating (20 / mm). And based on the measured post-heating adhesive force (20 / mm), according to the following evaluation criteria, the separation / disassembly property (easy peelability) of each sample for evaluation of Reference Examples 30 to 33 was evaluated.
[Evaluation criteria]
(Circle): A double-sided adhesive sheet peels naturally with a weak force from a to-be-adhered body (PC board) (less than 0.5 [N / 20mm]).
Δ: The double-sided pressure-sensitive adhesive sheet is easily peeled from the adherend (PC board) with a force of being pulled by hand (0.5 [N / 20 mm] or more and less than 2.0 [N / 20 mm]).
X: It cannot peel easily or cannot peel (2.0 [N / 20mm] or more).

The results of the evaluation tests described above are shown in Tables 1 to 3 and Table 4 below. In addition, in each table | surface, the component of the adhesive composition used by each Example, each reference example, and Comparative Examples 1-4 was also shown collectively. “Part” in each table means part by mass, and “−” in each table means none (zero). The meanings of the abbreviations shown in the table are as follows.
AA: acrylic acid NVP: N-vinyl-2-pyrrolidone HEA: 2-hydroxyethyl acrylate HDDA: 1,6-hexanediol diacrylate DPHA: dipentaerythritol hexaacrylate TMPTA: trimethylolpropane triacrylate GB: hollow glass balloon ( Product name "Sphericel (registered trademark) 25P45")
Heavy coal: Natural heavy calcium carbonate (trade name “heavy calcium carbonate”)
Light coal: Synthetic light calcium carbonate (Brand name “Shiroka Hana CC-R”)
Black pigment: Trade name “AT DN101 Black”
Hydrogenated resin: Hydrogenated petroleum resin (trade name “ALCON P125”)
H31: Aluminum hydroxide (trade name “H31 Hydrite”)
Thermal foaming agent 1: Thermally expandable microsphere (trade name “thermally expandable microsphere 051DU40”)
Thermal foaming agent 2: Thermally expandable microsphere (trade name “Matsumoto Microsphere F-48D *”)

As shown in Tables 1 and 2, double-sided pressure-sensitive adhesive sheets such as Example 2 provided with a pressure-sensitive adhesive layer having an acrylic polymer (A) containing 9 to 30% by mass of a structural unit derived from a polar monomer are all used. It was confirmed that it had excellent pressure adhesion and excellent drop impact resistance (23 ° C condition).
On the other hand, it is confirmed that the double-sided PSA sheets of Comparative Examples 1 to 3 having a structural unit derived from a polar monomer of less than 9% by mass do not have sufficient pressure-adhesive force although they have excellent drop impact resistance. It was. Moreover, although the press adhesive force was excellent about the comparative example 4 from which the structural unit derived from a polar monomer exceeds 30 mass%, it was confirmed that it is not equipped with sufficient drop impact resistance property.

  As described above, the double-sided PSA sheet of Example 26 had a haze of 85% and a total light transmittance of 3.4%. In addition to the acrylic polymer (A) (base polymer), the pressure-sensitive adhesive composition 26 used for forming the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet includes hydrogenated petroleum resin (softening point 125 ° C., trade name “Alcon P125”). (Made by Arakawa Chemical Co., Ltd.) This hydrogenated petroleum resin is poorly compatible with the acrylic polymer (A), so it is phase-separated from the acrylic polymer (A). The polymer (A) is diffused (dispersed), that is, when a predetermined amount of hydrogenated petroleum resin is added to the acrylic polymer (A), the light diffusibility is improved. As a result, the concealability (light-shielding property) of the resulting pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive sheet) is improved.In this way, hydrogenated petroleum resin is blended in the pressure-sensitive adhesive composition, and diffusibility is achieved by phase separation. To increase the pressure-sensitive adhesive It may be increased (double-sided pressure-sensitive adhesive sheet) of the hiding property (light-shielding).

As shown in Table 1, the pressure adhesive force of the double-sided pressure-sensitive adhesive sheet of Reference Example 1 was 28 N / cm ² . The pressure-sensitive adhesive composition 1 of Reference Example 1 is prepared from syrup I and contains acrylic acid as a polar monomer.
In contrast, the push-out adhesive force in each double-sided pressure-sensitive adhesive sheets of Examples 12 and 13, as shown in Table 1, were respectively ^{29N / cm 2, 41N / cm} 2. The pressure-sensitive adhesive compositions 12 and 13 of Examples 12 and 13 are made by adding N-vinyl-2-pyrrolidone (NVP) to syrup I, respectively. Therefore, each adhesive composition 12 and 13 contains NVP other than acrylic acid as a polar monomer. That is, in Examples 12 and 13, acrylic acid (an example of a carboxyl group-containing monomer) and NVP (an example of a heterocyclic ring-containing vinyl monomer) are used in combination as polar monomers. As described above, when acrylic acid and NVP are used in combination as polar monomers, the pressure adhesive strength of the obtained double-sided PSA sheet (adhesive layer) is higher than when not used together (when only acrylic acid is used). It can be said that it is preferable.

  In Reference Example 1, only acrylic acid (AA) is used as a polar monomer. In Examples 2 to 11, NVP, HEAA, and acrylic acid (AA) are used in combination as polar monomers. In Examples 12 and 13, acrylic acid (AA) and NVP are used in combination as described above. In Reference Example 14, NVP and HEA are used in combination as polar monomers. In Examples 15 to 26, NVP, HEA, and acrylic acid (AA) are used in combination as polar monomers. In Example 27, NVP and HEA are used in combination as polar monomers. In Example 28, acrylic acid (AA), NVP, and HEA are used in combination as polar monomers. In Example 29, acrylic acid (AA), NVP, and HEA are used in combination as polar monomers.

  The pressure-sensitive adhesive composition 28 of Example 28 is composed of 40 parts by mass of syrup I (2EHA / AA = 90/10) with NVP 17 parts by mass, HEA 4 parts by mass, and 2EHA 39 parts by mass as monomer components. . In contrast, the pressure-sensitive adhesive composition 29 of Example 29 was prepared by adding 66.7 parts by mass of syrup IV (2EHA / AA = 94/6), NVP 17 parts by mass, HEA 4 parts by mass and 2EHA12.3 as monomer components. It consists of a mass part added. In Example 28 and Example 29, the syrup used was different, but the component ratio (mass ratio) in each composition 28, 29 was 2EHA / AA / HEA / NVP = 75/4/4. / 17. As shown in Table 2, the double-sided pressure-sensitive adhesive sheet of Example 28 and the double-sided pressure-sensitive adhesive sheet of Example 29 both have the same performance (press adhesive strength, drop impact resistance). In other words, when preparing the pressure-sensitive adhesive composition, the physical properties of the pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive sheet) are hardly affected even if the monomer addition method is different as in Examples 28 and 29. It was confirmed.

  As shown in Table 4, each double-sided pressure-sensitive adhesive sheet of Reference Examples 30 to 33 in which the pressure-sensitive adhesive layer contains the thermal foaming agent 1 or the thermal foaming agent 2 has excellent press adhesive strength and excellent drop impact resistance. (23 ° C. condition). Moreover, each double-sided pressure-sensitive adhesive sheet of Reference Examples 30 to 33 is provided with excellent adhesive strength (180 ° peeling adhesive strength) in the state before heating (initial state), and in the state after heating, excellent separation / It was confirmed that it had dismantling properties (easy peelability).

(Bubble content)
In addition, all the bubble content rate of each adhesive layer in each double-sided adhesive sheet of each Example, each reference example, and Comparative Examples 1-4 was 1 volume% or less.
Moreover, the bubble content rate (before heat processing) of each adhesive layer in each double-sided adhesive sheet of Reference Examples 30 to 33 was 1% by volume or less.

  DESCRIPTION OF SYMBOLS 100 ... Double-sided adhesive sheet, 110 ... Adhesive layer, 120, 130 ... Release liner, 1 ... Polycarbonate board, 2 ... Window frame-shaped double-sided adhesive sheet, 3 ... Acrylic board, 4 ... Through-hole of polycarbonate board

Claims (10)

A pressure-sensitive adhesive layer having an acrylic polymer (A) containing 9 to 30% by weight of a polar monomer is provided,
The acrylic polymer (A) contains 78 to 91% by mass of a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms,
The polar monomer is a double-sided pressure-sensitive adhesive sheet comprising a hydroxyl group-containing monomer and a heterocyclic ring-containing vinyl monomer.   The double-sided pressure-sensitive adhesive sheet according to claim 1, which contains substantially no carboxyl group-containing monomer as the polar monomer.   The hydroxyl group-containing monomer is 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, vinyl alcohol, or The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, which is allyl alcohol.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the hydroxyl group-containing monomer contains at least one of 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the hydroxyl group-containing monomer includes 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.   The heterocyclic ring-containing vinyl monomer is N-vinyl-2-pyrrolidone, (meth) acryloylmorpholine, N-vinyl piperidone, N-vinyl piperazine, N-vinyl pyrrole, or N-vinyl imidazole. The double-sided pressure-sensitive adhesive sheet according to any one of the above.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the heterocyclic ring-containing vinyl monomer is N-vinyl-2-pyrrolidone.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive layer further contains a black pigment.   The double-sided pressure-sensitive adhesive sheet according to claim 8, wherein the black pigment is contained in an amount of 0.01 to 10 parts by mass with respect to 100 parts by mass of all monomer components of the acrylic polymer (A).   The double-sided pressure-sensitive adhesive sheet according to claim 8 or 9, wherein the black pigment is carbon black.

Images