JP5840200B2 - Transparent double-sided adhesive sheet and image display device with touch panel - Google Patents

Description

  The present invention relates to a transparent double-sided pressure-sensitive adhesive sheet that can be suitably used when sticking and fixing a touch panel and an image display panel or a touch panel and a surface protection panel, and an image display device with a touch panel provided with the transparent double-sided pressure-sensitive adhesive sheet.

  In recent years, with the spread of electronic devices such as personal digital assistants (PDAs) such as game machines, digital cameras, car navigation systems, televisions, personal computers, ATMs, ticket vending machines, mobile phones and mobile terminals, the market for image display devices with touch panels has increased. It is growing rapidly. Since an image display device with a touch panel is usually required to have impact resistance, many image display devices are provided with an air layer between the touch panel and the image display panel or between the touch panel and the surface protection panel. However, since an air layer with a certain thickness is required to obtain impact resistance, it has become difficult to meet the demand for thinning an image display device with a touch panel. In addition, when the air layer is present, there is a problem that reflection occurs at the interface between the panel and the air layer, and the visibility and luminance of the image are lowered.

As a method for solving these problems, it has been proposed that the touch panel and the image display panel or the touch panel and the surface protection panel are adhered and fixed with a transparent double-sided pressure-sensitive adhesive sheet to eliminate the air layer.
For example, Patent Document 1 proposes an adhesive sheet in which a plurality of adhesive layers having different viscoelastic behaviors are stacked and integrated. However, since such an adhesive sheet consists only of an adhesive layer, it has poor portability and punchability, and there is room for improvement. Further, when the adherend is a plastic resin such as an acrylic resin or a polycarbonate resin, there is a problem that foaming occurs due to outgas generated from the plastic resin.
Patent Document 2 discloses a double-sided PSA sheet in which PSA layers are formed on both sides of a transparent substrate such as a polyethylene terephthalate (PET) film in the Examples. However, such a double-sided PSA sheet has a problem in that since the refractive index of the PSA layer is different from that of the transparent substrate, reflection occurs at the interface and image visibility and brightness are lowered. In addition, since the transparent base material is a hard plastic material, there is a problem that the requirements for step absorbency and impact resistance cannot be satisfied.
Patent Document 3 proposes a double-sided pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is made of a (meth) acrylate block copolymer. However, even if this is applied as it is to a touch panel and an image display panel or a touch panel and a surface protection panel, in order to obtain step absorbency and impact resistance, for example, a transparent double-sided adhesive sheet having a thickness exceeding 250 μm, Then, the flexibility of the transparent double-sided pressure-sensitive adhesive sheet is increased and the shape cannot be maintained, and there is a problem that portability and punchability are deteriorated. In addition, when the adherend is a plastic resin such as an acrylic resin or a polycarbonate resin, foaming may occur due to outgas generated from the plastic resin.

International Publication No. 2010/044229 JP 2003-238915 A JP 2008-88395 A Japanese Patent Laid-Open No. 05-140244 JP-A-10-101748 Japanese Patent Laid-Open No. 07-188638 JP 2003-104712 A JP 2005-533918 A Japanese Patent Laid-Open No. 06-93060 Japanese National Patent Publication No. 05-507737 JP-A-11-335432

Macromolecular Chemistry and Physics, 2000, 201, p. 1108 to 1114

  Therefore, an object of the present invention is to provide a transparent double-sided pressure-sensitive adhesive sheet excellent in impact resistance and corrosion resistance. Moreover, the other object of this invention is to provide the image display apparatus with a touch panel excellent in visibility provided with the said transparent double-sided adhesive sheet.

According to the present invention, the above object is
[1] A polymer block (A) having a glass transition temperature of 50 ° C. or higher obtained by polymerizing at least one monomer selected from a methacrylic acid ester and an acrylic acid ester, and a methacrylic acid ester and an acrylic layer. A transparent double-sided pressure-sensitive adhesive sheet containing an acrylic block copolymer (0) containing a polymer block (B) having a glass transition temperature of 20 ° C. or lower obtained by polymerizing at least one monomer selected from acid esters;
[2] The transparent double-sided pressure-sensitive adhesive sheet according to [1], wherein each of the layers constituting the transparent double-sided pressure-sensitive adhesive sheet contains an acrylic block copolymer (0);
[3] The adhesive layer has the following general formula (II):
A3-B2-A4 (II)
(In the formula, A3 and A4 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B2 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
The weight average molecular weight (Mw) is 50,000 to 300,000, the content of the polymer block B2 is 77 to 95% by mass, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. [1] or [2] transparent double-sided pressure-sensitive adhesive sheet comprising 20% by mass or more of the acrylic block copolymer (II) which is .5;
[4] A base material layer having a storage tensile elastic modulus at 20 ° C. of 6.0 × 10 ⁶ Pa to 3.3 × 10 ⁹ Pa, and an adhesive layer (a) on one main surface of the base material layer, And an adhesive layer (b) is provided on the other main surface, and the refractive index difference between the adhesive layer (a) and the base material layer and the refractive index difference between the adhesive layer (b) and the base material layer are both 0. The transparent double-sided pressure-sensitive adhesive sheet of [1] to [3], which is 05 or less;
[5] The transparent of [4], wherein the refractive index of the adhesive layer (a) and the adhesive layer (b) is 1.45 to 1.65, and the refractive index of the base material layer is 1.46 to 1.65. Double-sided adhesive sheet.
[6] The transparent double-sided pressure-sensitive adhesive sheet according to [4] or [5], wherein at least one of the base material layer, the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) is formed by a hot melt molding method;
[7] The transparent double-sided pressure-sensitive adhesive sheet according to [4] to [6], wherein the base material layer contains the acrylic block copolymer (0);
[8] The base material layer has the following general formula (I);
A1-B1-A2 (I)
(In the formula, A1 and A2 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B1 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
The weight average molecular weight (Mw) is 50,000 to 300,000, the content of the polymer block B1 is 49 to 5% by mass, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. [4]-[7] transparent double-sided pressure-sensitive adhesive sheet comprising the acrylic block copolymer (I) being .5;
[9] The transparent both sides of [8], wherein the polymer block A1 and the polymer block A2 constituting the acrylic block copolymer (I) of the base material layer have a microphase separation structure that becomes a continuous phase. Adhesive sheet;
[10] The transparent double-sided pressure-sensitive adhesive sheet according to [1] to [9], having a thickness of 210 μm or more and 1000 μm or less;
[11] The transparent double-sided pressure-sensitive adhesive sheet of [1] to [10] for sticking and fixing the touch panel and the image display panel, or the touch panel and the surface protection panel;
[12] A member provided with a touch panel on one main surface of the transparent double-sided pressure-sensitive adhesive sheet of [1] to [11] and an image display panel or a surface protection panel on the other main surface;
[13] A touch panel member comprising the transparent double-sided pressure-sensitive adhesive sheet of [1] to [11], which is either an out-cell type, an in-cell type, an on-cell type, a cover glass integrated type, or a cover sheet integrated type;
[14] A touch panel member comprising the member of [12]; and
[15] An image display device comprising the touch panel member according to [13] or [14];
Is achieved by providing

 ADVANTAGE OF THE INVENTION According to this invention, the transparent double-sided adhesive sheet excellent as impact resistance and corrosion resistance useful as a transparent double-sided adhesive sheet for touchscreens can be provided.

It is the schematic which shows an example of the sample used for evaluation of the punchability of the transparent double-sided adhesive sheet of this invention.

Hereinafter, the present invention will be described in detail.
The transparent double-sided pressure-sensitive adhesive sheet of the present invention comprises a polymer block (A) having a glass transition temperature of 50 ° C. or higher, wherein the pressure-sensitive adhesive layer is obtained by polymerizing at least one monomer selected from methacrylic acid esters and acrylic acid esters. Containing an acrylic block copolymer (0) containing a polymer block (B) having a glass transition temperature of 20 ° C. or lower obtained by polymerizing at least one monomer selected from methacrylic acid esters and acrylic acid esters To do.

  Examples of the monomer used for the polymer block (A) include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, Methacrylic acid esters such as isobornyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate; methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate, etc. Examples include acrylic acid esters.

  Among these, from the viewpoint of improving the transparency and heat resistance of the transparent double-sided PSA sheet, methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, 2-methacrylic acid 2- Hydroxyethyl, methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenyl acrylate and 2-hydroxyethyl acrylate are preferred, and methyl methacrylate is more preferred. The polymer block (A) may be composed of one of these methacrylic acid esters and acrylic acid esters, or may be composed of two or more. The acrylic block copolymer (0) preferably contains two or more polymer blocks (A) from the viewpoint of enhancing durability. In that case, these polymer blocks (A) may be the same or different.

  Examples of the monomer used in the polymer block (B) include n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, and methacrylic acid. Methacrylic acid esters such as 2-ethylhexyl, pentadecyl methacrylate, dodecyl methacrylate, phenoxyethyl methacrylate, 2-methoxyethyl methacrylate; methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-acrylate -Butyl, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, Benzyl acrylic acid, phenoxyethyl acrylate and acrylic acid esters such as 2-methoxyethyl acrylate.

  Among these, from the viewpoint of improving the transparency, flexibility, cold resistance, and low temperature characteristics of the obtained transparent double-sided PSA sheet, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-acrylic acid 2- Acrylic esters such as ethylhexyl, dodecyl acrylate, phenoxyethyl acrylate, and 2-methoxyethyl acrylate are preferred. The polymer block (B) may be composed of one of these methacrylic acid esters and acrylic acid esters, or may be composed of two or more kinds. Moreover, when two or more polymer blocks (B) are contained in the acrylic block copolymer (0), the polymer blocks (B) may be the same or different.

  As long as the characteristics of the acrylic block copolymer (0) used in the present invention are not impaired, the monomer used for the polymer block (A) and the polymer block (B) further has methacrylic acid having a reactive group. Esters and acrylic esters may be used. Examples of the methacrylic acid ester and acrylic acid ester having a reactive group include glycidyl methacrylate, allyl methacrylate, glycidyl acrylate, and allyl acrylate. When these monomers are used, they are usually used in a small amount, but the amount is preferably 40% by mass or less, more preferably 20% by mass or less, based on the total mass of the monomers used for each polymer block. Used in.

  In addition, as long as the characteristics of the acrylic block copolymer (0) used in the present invention are not impaired, the monomer used for the polymer blocks (A) and (B) may be other monomers as necessary. May be used in combination.

  Examples of such other monomers include styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, butadiene, isoprene, octene, vinyl acetate, anhydrous Maleic acid, vinyl chloride, vinylidene chloride and the like can be mentioned. When these monomers are used, they are usually used in a small amount, but the amount is preferably 40% by mass or less, more preferably 20% by mass or less, based on the total mass of the monomers used for each polymer block. Used in.

The acrylic block copolymer (0) used in the present invention may have other polymer blocks as necessary in addition to the polymer block (A) and the polymer block (B).
Examples of such other polymer blocks include styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, acrylonitrile, methacrylonitrile, ethylene, propylene, isobutene, butadiene, isoprene, octene, vinyl acetate, anhydrous Examples thereof include a polymer block or copolymer block composed of maleic acid, vinyl chloride, vinylidene chloride and the like; a polymer block composed of polyethylene terephthalate, polylactic acid, polyurethane, polydimethylsiloxane, and the like. The polymer block also includes a hydrogenated polymer block containing a conjugated diene compound such as butadiene or isoprene.

  The glass transition temperatures of the polymer block (A) and the polymer block (B) in the present invention are observed in a curve obtained by measuring the acrylic block copolymer (0) with a differential scanning calorimeter (DSC). It is the extrapolation start temperature (Tgi) of the transition region of the polymer block (A) and the polymer block (B). As a specific measuring method, the method described in detail in Examples described later is adopted. As the glass transition temperature, literature values described in “Synthesis / design of acrylic resin and development of new applications” (published by Chubu Business Development Center, published in 1985) may be used.

Based on the curve obtained by the DSC measurement, in the acrylic block copolymer (0) used in the present invention, the plurality of glass transition temperatures derived from the polymer block (A) and the polymer block (B) are respectively Since the glass transition temperature of the polymer having the same chemical structure (monomer composition, stereoregularity, etc.) as that of the polymer block is the same as or close to that, these multiple glass transition temperatures originate from which polymer block It can be easily determined whether or not to do. The polymer having the same chemical structure as the polymer block (A) and the polymer block (B) is obtained by analyzing the acrylic block copolymer (0) by ¹ H-NMR, ¹³ C-NMR, etc. The chemical structure such as the monomer composition and stereoregularity of the polymer block (A) and the polymer block (B) can be obtained and polymerized appropriately so that the chemical structure is reproduced.

The structure of the acrylic block copolymer (0) includes, for example, formula (AB) _a , formula (AB) _b -A, formula (BA) _c -B, formula (AB) _m- Z and formula (BA) _m- Z [wherein A represents a polymer block (A), B represents a polymer block (B), and a, b and c are the same or different. May represent an integer of 1 to 10, m represents an integer of 3 to 30, and Z represents a coupling site (a coupling site after a coupling agent reacts with a polymer terminal to form a chemical bond). And the like. Examples of the acrylic block copolymer (0) include an AB diblock copolymer, an ABA triblock copolymer, and an ABAB tetrablock copolymer. , A-B-A-B-A or B-A-B-A-B pentablock copolymer, (A-B) _m- Z star-type block copolymer, and the like. Especially, it is preferable from a viewpoint of the heat resistance of the transparent double-sided adhesive sheet of this invention, mechanical strength, surface sticking, etc. to have the structure which the polymer block (A) couple | bonded with the both ends of the polymer block (B). Among them, an ABA triblock copolymer is more preferable. Moreover, the said acrylic block copolymer (0) may be contained only 1 type in the adhesion layer, and may be contained 2 or more types.

  The acrylic block copolymer (0) used for the pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet of the present invention includes functional groups having active hydrogen such as amino groups, thiol groups, and carboxyl groups, and sodium salts thereof. It is preferable not to have a metal salt; a functional group containing nitrogen such as a dimethylamino group or a diethylamino group; a functional group containing sulfur such as a thioether. Since the transparent double-sided pressure-sensitive adhesive sheet containing such an acrylic block copolymer (0) in the pressure-sensitive adhesive layer does not corrode ITO (indium tin oxide) forming the conductive film in the touch panel, the transparent double-sided pressure-sensitive adhesive sheet was used. The touch panel is excellent in durability.

As the acrylic block copolymer (0) contained in the adhesive layer, the following general formula (II):
A3-B2-A4 (II)
(In the formula, A3 and A4 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B2 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
It is particularly preferable to use an acrylic block copolymer (II) represented by

  In the acrylic block copolymer (II), the total content of the polymer block A3 and the polymer block A4 is 5 to 23 mass%, preferably 5 to 18 mass%, more preferably 10 to 18 mass%. preferable. In the acrylic block copolymer (II), the content of the polymer block B2 is 77 to 95% by mass, preferably 82 to 95% by mass, and 82 to 90% by mass. More preferred. If it is in the said range, it will be excellent by the level | step difference absorbability. When the total content of the polymer block A3 and the polymer block A4 is smaller than the above range, the shape-retaining property of the transparent double-sided PSA sheet may be deteriorated and the durability may be inferior. When the total content of the polymer block A3 and the polymer block A4 is larger than the above range, the flexibility of the acrylic block copolymer (II) is insufficient, and the adhesive physical properties tend to be inferior.

  The weight average molecular weight of the acrylic block copolymer (II) is 50,000 to 300,000 in terms of polystyrene calculated by gel permeation chromatography (GPC) measurement from the viewpoint of adhesive properties. It is preferable that it is 50,000-200,000. As a specific method for measuring the weight average molecular weight, the method described in detail in Examples described later is employed.

  The molecular weight distribution (weight average molecular weight / number average molecular weight) of the acrylic block copolymer (II) is 1.0 to 1.5 from the viewpoint of surface stickiness and transparency, and is 1.0 to 1.4. Preferably, it is 1.0 to 1.3, more preferably 1.0 to 1.2. When the molecular weight distribution is in the above range, the transparency, flexibility and durability are excellent. In addition, when the molecular weight distribution is within this range, the content of (meth) acrylic acid derived from the monomer (generated by hydrolysis of the remaining monomer) is so small that it can be ignored, so that it is resistant to ITO (indium tin oxide) corrosion. Is also preferable.

  When the acrylic block copolymer (II) is used for the pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet of the present invention, the content of the acrylic block copolymer (II) with respect to the total mass of the pressure-sensitive adhesive layer is 20% by mass or more. It is preferably 20% by mass to 100% by mass, more preferably 30% by mass to 100% by mass, and further preferably 50% by mass to 100% by mass.

  The adhesive layer may further contain an acrylic diblock copolymer having an AB structure. When the acrylic diblock copolymer is included, it is preferably 70% by mass or less, more preferably 10% by mass to 70% by mass, and more preferably 30% by mass to 60% by mass with respect to the total mass of the adhesive layer. % Is more preferable. When the acrylic diblock copolymer is included within the above range, the pressure-sensitive adhesive layer becomes highly viscous and has excellent tack and step absorbability.

  In the acrylic diblock copolymer, the content of the polymer block (A) is preferably from 3 to 70 mass%, more preferably from 5 to 55 mass%. In the acrylic diblock copolymer, the content of the polymer block B is preferably 30 to 97% by mass, and more preferably 45 to 95% by mass. When the content of the polymer block (A) is smaller than the above range, the durability tends to be inferior. When the content of the polymer block (A) is larger than the above range, the step absorbability, the adhesive properties, and the compatibility with the acrylic triblock copolymer tend to be inferior.

  As for the molecular weight of the acrylic diblock copolymer, the polystyrene equivalent weight average molecular weight determined by gel permeation chromatography (GPC) measurement is preferably 50,000 to 300,000, preferably 50,000 to 200, Is more preferably 50,000, more preferably 50,000 to 100,000, and particularly preferably 50,000 to 75,000. When the weight average molecular weight of the acrylic diblock copolymer is smaller than the above range, durability tends to be inferior. When the weight average molecular weight of the acrylic diblock copolymer is larger than the above range, the viscosity of the solution increases and the coating property tends to be inferior. As a specific method for measuring the weight average molecular weight, the method described in detail in Examples described later is employed.

  The pressure-sensitive adhesive layer constituting the transparent double-sided pressure-sensitive adhesive sheet of the present invention is a polymer, softener, curing agent, lubricant, plasticizer, pressure-sensitive adhesive, tackifying resin, and heat stabilizer as long as the effects of the present invention are not impaired. Further, additives such as an antioxidant, a light stabilizer, an antistatic agent, a flame retardant, a foaming agent, a coloring agent, a dyeing agent, a refractive index adjusting agent and a filler may be contained. These other polymers and additives may be included in one kind or in two or more kinds.

  Examples of the other polymer include acrylic resins such as polymethyl methacrylate and methacrylate ester copolymer; polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polybutene-1, poly-4-methylpentene- 1. Olefin resin such as polynorbornene; ethylene ionomer; styrene resin such as polystyrene, styrene-maleic anhydride copolymer, high impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, MBS resin Resin; Methyl methacrylate-styrene copolymer; Polyester resin such as polyethylene terephthalate, polybutylene terephthalate and polylactic acid; Polyamide such as nylon 6, nylon 66 and polyamide elastomer; Polycarbonate; Polyvinyl chloride; Polyvinyl alcohol; ethylene-vinyl alcohol copolymer; polyacetal; polyvinylidene fluoride; polyurethane; modified polyphenylene ether; polyphenylene sulfide; silicone rubber modified resin; acrylic rubber; silicone rubber; SEPS, SEBS, SIS Styrenic thermoplastic elastomers; olefinic rubbers such as IR, EPR and EPDM. Among these, from the viewpoint of compatibility with the acrylic block copolymer contained in the pressure-sensitive adhesive layer used in the transparent double-sided pressure-sensitive adhesive sheet, acrylic resin, ethylene-vinyl acetate copolymer, AS resin, polylactic acid, and polyfluoride are used. Vinylidene chloride is preferred.

Examples of the softening agent include mineral oils such as paraffinic process oil and naphthenic process oil.
Examples of the filler include inorganic fibers such as glass fibers and carbon fibers, and organic fibers; inorganic fillers such as calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, and magnesium carbonate. . When inorganic fiber and organic fiber are contained, a reinforcing effect is imparted to the resulting adhesive layer. When the inorganic filler is contained, heat resistance and weather resistance are imparted to the obtained adhesive layer.

  When the heat stabilizer or antioxidant is contained in the adhesive layer, the heat resistance and weather resistance are further improved, so that it is practically included in the adhesive layer used in the transparent double-sided pressure-sensitive adhesive sheet. preferable.

  Examples of the curing agent include photocuring agents such as UV curing agents, thermosetting agents, and the like, and examples include benzoins, benzoin ethers, benzophenones, anthraquinones, benzyls, acetophenones, and diacetyls. . Specifically, benzoin, α-methylol benzoin, α-t-butyl benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-n-propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, α-methylol benzoin methyl ether, α -Methoxybenzoin methyl ether, benzoin phenyl ether, benzophenone, 9,10-anthraquinone, 2-ethyl-9,10-anthraquinone, benzyl, 2,2-dimethoxy-1,2-diphenylethane-1-one (2,2 -Dimethoxy-2-phenylacetophenone), diacetyl and the like. A hardening | curing agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  From the viewpoint of enhancing the effect of the curing agent, a monomer may be added. Examples of these monomers include acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-halogenated acrylic acid, crotonic acid, cinnamic acid, sorbic acid, maleic acid, itaconic acid, and acrylic acid esters, methacrylic acid, Esters such as acid esters, crotonic acid esters and maleic acid esters; acrylamides; methacrylamides; acrylamide derivatives such as N-methylol acrylamide, N-hydroxyethyl acrylamide, N, N- (dihydroxyethyl) acrylamide; N-methylol methacrylamide; Methacrylamide derivatives such as N-hydroxyethyl methacrylamide and N, N- (dihydroxyethyl) methacrylamide; vinyl esters; vinyl ethers; mono-N-vinyl derivatives; styrene derivatives; The oligomer etc. which are included as a component are mentioned. From the viewpoint of enhancing durability without corroding a conductive layer such as ITO forming the conductive film in the touch panel, esters such as acrylic acid esters, methacrylic acid esters, crotonic acid esters, maleic acid esters; vinyl ethers; styrene derivatives; And the oligomer which contains the said monomer as a structural component is preferable. In addition to these monomers, a cross-linking agent composed of a bifunctional or higher functional monomer or oligomer may be added.

  The refractive index of the pressure-sensitive adhesive layer constituting the transparent double-sided pressure-sensitive adhesive sheet of the present invention is preferably 1.45 to 1.65 from the viewpoint of transparency. In addition, as a specific method for measuring the refractive index of the pressure-sensitive adhesive layer, the method described in detail in Examples described later is employed.

The adhesive layer requires an elastic modulus and flexibility that can maintain its form. Therefore, the adhesive layer of the transparent double-sided PSA sheet preferably has a storage shear modulus at 20 ° C. of 5.0 × 10 ³ Pa or more and 2.0 × 10 ⁶ Pa or less, and 2.0 × 10 ⁴ Pa. or more preferably 5.0 at × ¹⁰ 5 Pa or less, still more preferably not more than 6.0 × ¹⁰ 4 Pa or more 5.0 × ¹⁰ 5 Pa. When the storage shear modulus at 20 ° C. of the adhesive layer is larger than the above range, the adhesive property tends to be inferior due to insufficient flexibility. Conversely, when it is smaller than the above range, the durability tends to be inferior. In addition, as a specific method for measuring the storage shear modulus at 20 ° C., the method described in detail in Examples described later is employed.

  Although it does not specifically limit as a shaping | molding method of the adhesion layer of the transparent double-sided adhesive sheet of this invention, For example, the hot-melt-molding method mentioned later, the solution cast method, etc. are mentioned. Among these, the solution casting method is preferable from the viewpoint of high thickness accuracy.

The transparent double-sided pressure-sensitive adhesive sheet of the present invention may be composed of one pressure-sensitive adhesive layer, or may be composed of two or more layers having a base material layer and a pressure-sensitive adhesive layer. It is preferable that the acrylic block copolymer (0) is contained in all layers regardless of whether it is composed of one adhesive layer or two or more layers.
When the transparent double-sided pressure-sensitive adhesive sheet of the present invention comprises two or more layers, the base layer is provided with an adhesive layer (a) on one main surface and the other main surface is provided with an adhesive layer (b). Is preferred. With such a configuration, a transparent double-sided pressure-sensitive adhesive sheet having excellent durability such as portability and foam resistance is obtained.

When the transparent double-sided pressure-sensitive adhesive sheet of the present invention is provided with an adhesive layer (a) on one main surface of the base material layer and an adhesive layer (b) on the other main surface, the base material layer is 20 ° C. The storage tensile elastic modulus is preferably 6.0 × 10 ⁶ Pa or more and 3.3 × 10 ⁹ Pa or less, more preferably 2.0 × 10 ⁷ Pa or more and 3.3 × 10 ⁹ Pa or less. It is more preferable that it is 0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less. When the storage tensile elastic modulus at 20 ° C. of the base material layer is larger than the above range, the flexibility is insufficient and the step absorbability is inferior. Conversely, when it is smaller than the above range, the portability and foam resistance are poor. In addition, as a specific method for measuring the storage tensile elastic modulus at 20 ° C., the method described in detail in Examples described later is employed.

  In order to obtain the base material layer having the above storage tensile modulus, there are a method of adding a plasticizer to the base material layer, a method of changing a copolymerization ratio of a copolymer used for the base material layer, and the like.

  The material constituting the base layer of the transparent double-sided pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it satisfies the above-described range of the storage tensile modulus at 20 ° C. For example, an acrylic random copolymer, an acrylic block Acrylic resins such as copolymers and acrylic multilayer structures (see Patent Documents 4 and 5); olefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, polynorbornene; Ethylene ionomer; polystyrene, styrene-maleic anhydride copolymer, high impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, MBS resin, and other styrene resins; SIS, SBS, SEBS, SEPS, etc. Styrene thermoplastic elastomers; methyl methacrylate-styrene copolymer Polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polylactic acid; Polyamide resins such as nylon 6, nylon 66 and polyamide elastomer; Polyurethane resin; Ester polyurethane elastomer, Ether polyurethane elastomer, Non-yellowing ester polyurethane elastomer, None Polyurethane thermoplastic elastomers such as yellowing carbonate polyurethane elastomers; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, modified polyphenylene ether, polyphenylene sulfide, silicone rubber Modified resins, core-shell rubber, acrylic rubber, etc. and compositions containing these It is. 1 type may be sufficient as the said resin and it may combine 2 or more types. Among these, an acrylic resin and a composition containing an acrylic resin are preferable. Moreover, what can be hot-melt molded is preferable.

  From the viewpoint of improving transparency, punchability, etc., the material constituting the base layer of the transparent double-sided pressure-sensitive adhesive sheet of the present invention is an acrylic block copolymer among the acrylic resin and the composition containing the acrylic resin. A composition containing a polymer and an acrylic block copolymer is preferred. The resin other than the acrylic block copolymer contained in the composition includes an acrylic block copolymer different from the acrylic block copolymer; poly α-methylstyrene; polyvinyl acetal resin, polyvinyl butyral resin. And a copolymer thereof; a resin selected from a block copolymer containing an acrylic polymer block and a conjugated diene polymer block is preferred, and other acrylic resins such as an acrylic random copolymer are contained. May be.

  Among the acrylic block copolymers, a polymer block (A) having a glass transition temperature of 50 ° C. or higher obtained by polymerizing at least one monomer selected from methacrylic acid esters and acrylic acid esters, and methacrylic acid In the case of an acrylic block copolymer (0) containing a polymer block (B) having a glass transition temperature of 20 ° C. or lower obtained by polymerizing at least one monomer selected from an ester and an acrylate ester In particular, a substrate excellent in flexibility, light resistance and transparency can be obtained.

When the acrylic block copolymer (0) is contained in the base material layer, the following general formula (I) is used as the acrylic block copolymer (0) from the viewpoint of transparency, durability, flexibility and the like:
A1-B1-A2 (I)
(In the formula, A1 and A2 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B1 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
It is particularly preferable to use an acrylic block copolymer (I) represented by

  In the acrylic block copolymer (I), the total content of the polymer block A1 and the polymer block A2 is 51 to 95% by mass, and preferably 51 to 80% by mass. Moreover, in said acrylic block copolymer (I), content of polymer block B1 is 49-5 mass%, and it is preferable that it is 49-20 mass%. If it is in the said range, it is easy to make the storage tensile elasticity modulus of a base material layer into the range of this invention. When the total content of the polymer block A1 and the polymer block A2 is less than the above range, the shape retainability of the base material layer is lowered, and the shape retainability, portability and durability of the transparent double-sided pressure-sensitive adhesive sheet are lowered. To do. When the total content of the polymer block A1 and the polymer block A2 is more than the above range, the flexibility of the acrylic block copolymer is inferior.

  The weight average molecular weight of the acrylic block copolymer (I) is 50,000 to 300,000 in terms of polystyrene calculated by gel permeation chromatography (GPC) measurement from the viewpoint of moldability. 50,000 to 200,000 is preferable. As a specific method for measuring the weight average molecular weight, the methods described in detail in the following examples are employed.

  The molecular weight distribution (value of weight average molecular weight / number average molecular weight) of the acrylic block copolymer (I) is 1.0 to 1.5 from the viewpoint of surface stickiness and transparency. 4, more preferably 1.0 to 1.3, and even more preferably 1.0 to 1.2. When the molecular weight distribution is in the above range, transparency and durability are excellent.

Moreover, the base material layer containing the acrylic block copolymer (I) has a microphase separation structure. Such a microphase-separated structure usually varies depending on the mass ratio, volume ratio, degree of polymerization, etc. of each polymer block, but a spherical structure in which a spherical phase exists in the matrix phase, and a rod-like phase in the matrix phase. And a lamellar structure in which two or more phases overlap each other, a co-continuous structure different from the above three structures, and the like.
In the present invention, the co-continuous structure refers to a structure other than a spherical structure, a cylinder structure, and a lamella structure, and typically includes a gyroidal structure, a porous lamella structure, and the like.
As an observation method of the microphase separation structure, a transmission electron microscope (TEM), an atomic force microscope (AFM), or X-ray small angle scattering (SAXS) is used. It is possible to analyze which structure the base material layer has taken by analysis using these.

The transparent double-sided pressure-sensitive adhesive sheet of the present invention has a microphase separation structure in which the polymer block A1 and the polymer block A2 constituting the acrylic block copolymer (I) used for the base material layer are continuous phases. It is preferable. In order to form such a microphase separation structure, the polymer block (A) of the acrylic block copolymer (I), that is, the total of the polymer block A1 and the polymer block A2, and the polymer block (B), That is, the composition ratio (polymer block (A) / polymer block (B)) to the polymer block B1 is preferably 51/49 to 95/5 as a mass ratio. When the substrate layer has such a microphase separation structure, good flexibility and durability can be obtained.
In this case, the polymer block B1 may be a dispersed phase or a continuous phase, but both the polymer blocks A1 and A2 and the polymer block B1 are continuous phases. It is preferable. Typical examples of the structure include a cylinder structure, a co-continuous structure, and a lamella structure. From the viewpoint of flexibility and durability, a lamella structure is more preferable.

  When the acrylic block copolymer (I) is used for the base material layer in the transparent double-sided pressure-sensitive adhesive sheet, the content of the acrylic block copolymer (I) with respect to the total mass of the base material layer is 20% by mass or more. It is preferable that it is 20 mass%-100 mass%, and it is more preferable that it is 50 mass%-100 mass%.

  When the acrylic block copolymer (I) is contained in the base material layer used in the transparent double-sided pressure-sensitive adhesive sheet of the present invention, the base material layer may be composed of only the acrylic block copolymer (I). It may consist of a composition containing the system block copolymer (I). When the substrate layer is composed of a composition containing the acrylic block copolymer (I), an acrylic block copolymer or an acrylic random copolymer different from the acrylic block copolymer (I). Other acrylic resins may be contained. As other acrylic resins, acrylic resins mainly composed of methacrylic acid esters such as “Parapet GF” manufactured by Kuraray Co., Ltd. are preferable. In this case, the content contains the above acrylic block copolymer (I) It is preferable that it is 0.1-50 mass% in the composition to do. Here, “mainly” means, for example, containing 50 to 100% by mass of a methacrylic acid ester unit in an acrylic resin.

  Furthermore, when the base material layer used for the transparent double-sided pressure-sensitive adhesive sheet of the present invention is composed of a composition containing the acrylic block copolymer (I), as the resin that may be contained, in addition to the acrylic resin, Examples include resins selected from α-methylstyrene, polyvinyl acetal resins, polyvinyl butyral resins and copolymers thereof, block copolymers containing an acrylic polymer block and a conjugated diene polymer block, and the like. Among these, a polyvinyl acetal resin, a polyvinyl butyral resin and a copolymer thereof, and a block copolymer containing an acrylic polymer block and a conjugated diene polymer block are particularly preferable.

  The base material layer used for the transparent double-sided pressure-sensitive adhesive sheet of the present invention is within the range that does not impair the effects of the present invention, other polymers, softeners, plasticizers, tackifier resins, heat stabilizers, light stabilizers, antistatic agents. Additives such as flame retardants, foaming agents, coloring agents, dyeing agents, refractive index adjusting agents, fillers and the like may be included. These other polymers and additives may be included in one kind or in two or more kinds.

  Examples of the other polymer include acrylic rubbers; silicone rubbers; styrene thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin rubbers such as IR, EPR, and EPDM.

Examples of the softening agent include mineral oils such as paraffinic process oil and naphthenic process oil.
Examples of the filler include inorganic fibers such as glass fibers and carbon fibers, and organic fibers; inorganic fillers such as calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, and magnesium carbonate. . When inorganic fibers and organic fibers are contained, a reinforcing effect is imparted to the obtained base material layer. When the inorganic filler is contained, heat resistance and weather resistance are imparted to the obtained base material layer.

  When the heat stabilizer or the antioxidant is contained in the base material layer, the heat resistance and the weather resistance are further improved. Therefore, it is preferable for practical use to be contained in the base material layer.

  If necessary, the refractive index difference between the pressure-sensitive adhesive layer and the base material layer in the transparent double-sided pressure-sensitive adhesive sheet can be reduced by adding the refractive index adjusting agent to the base material layer used in the transparent double-sided pressure-sensitive adhesive sheet of the present invention. The visibility of the touch panel using the transparent double-sided pressure-sensitive adhesive sheet can be improved. Examples of the refractive index adjusting agent include aromatic organic phosphorus compounds, silica-containing composite oxide spherical fine particles, and the like (see Patent Documents 6 and 7). Of these, aromatic organophosphorus compounds are preferred from the viewpoint of transparency. Other methods for adjusting the refractive index include a method for selecting an appropriate monomer (see Patent Document 8).

As a base material layer, what was shape | molded by various shaping | molding methods, such as the hot-melt shaping | molding method mentioned later and the solution cast method, can be used for the said material. Moreover, as a base material layer, you may use a commercially available thing, for example, brand name "Acryprene" (Mitsubishi Rayon Co., Ltd., storage tensile elasticity modulus 1.2 * 10 < ⁹ > Pa, refractive index 1.49) etc. Can be used.

  The refractive index of the base material layer is preferably 1.46 to 1.65. Within this range, the range of the refractive index difference defined in the present invention is likely to be satisfied, and reflection at the interface of the adhesive layer / base material layer is reduced, so that the visibility tends to be excellent. In addition, as a specific method for measuring the refractive index of the base material layer, the method described in detail in Examples described later is employed.

  The thickness of the base material layer is preferably 20 μm or more and 950 μm or less, and more preferably 50 μm or more and 900 μm or less. When the thickness of the base material layer is within the above range, the step absorbability, impact resistance, punchability, portability, and foam resistance are excellent.

  When the transparent double-sided pressure-sensitive adhesive sheet of the present invention includes the pressure-sensitive adhesive layer (a) on one main surface of the base material layer and the pressure-sensitive adhesive layer (b) on the other main surface, the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer Either or both of (b) contain an acrylic block copolymer (0).

  As long as one of the above-mentioned adhesive layer (a) and adhesive layer (b) contains an acrylic block copolymer (0), the other does not have an acrylic block copolymer (0). May be. Examples of such other adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, polyurethane adhesives, and the like. Among these, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of transparency.

  Examples of the acrylic pressure-sensitive adhesive include an emulsion type, a solution type, a UV curing type, and a hot melt type. The polymers used for the above-mentioned types of acrylic pressure-sensitive adhesives include acrylic random copolymers, crosslinked acrylic random copolymers, and acrylic block copolymers other than acrylic block copolymers (0). Examples thereof include an acrylic polymer and an acrylic multilayer structure polymer. These may be used individually by 1 type, and may mix and use 2 or more types. Moreover, as an acrylic adhesive used for an adhesion layer, you may use a commercially available thing, for example, the "SK Dyne" series by Soken Chemical Co., Ltd. etc. are mentioned. Furthermore, you may use what was already shape | molded as an adhesive sheet for an adhesion layer. A commercially available product may be used for the adhesive layer, and examples thereof include “CS9621T” manufactured by Nitto Denko Corporation.

  When the acrylic block copolymer (0) is contained in either or both of the adhesive layer (a) and the adhesive layer (b), an acrylic block copolymer (0) is used as the acrylic block copolymer (0). It is preferred to use II).

  The above-mentioned pressure-sensitive adhesive layer (a) and pressure-sensitive adhesive layer (b) are within the range not impairing the effects of the present invention, and other polymers, softeners, curing agents, lubricants, plasticizers, pressure-sensitive adhesives, tackifying resins, and heat-stable An additive such as an agent, an antioxidant, a light stabilizer, an antistatic agent, a flame retardant, a foaming agent, a coloring agent, a dyeing agent, a refractive index adjusting agent, and a filler may be included. These other polymers and additives may be included in one kind or in two or more kinds. As these other polymers and additives, those similar to those contained in the above-mentioned adhesive layer can be used.

  When the refractive index adjuster is contained in either or both of the adhesive layer (a) and the adhesive layer (b) in the transparent double-sided adhesive sheet, the adhesive layer (a) or the adhesive layer (b) and the base The difference in refractive index with the material layer or the difference in refractive index between the adhesive layer and the adherend can be reduced, and the visibility of the touch panel using such a transparent double-sided adhesive sheet can be increased. Examples of the refractive index adjusting agent include aromatic organophosphorus compounds, silica-containing composite oxide spherical fine particles (see Patent Documents 6 and 7), and a tackifier resin excellent in compatibility with the adhesive layer. . Of these, aromatic organophosphorus compounds or tackifying resins are preferred from the viewpoint of transparency. Examples of such tackifying resins include rosins such as rosin, hydrogenated rosin, and disproportionated rosin; styrene resins and α-methylstyrene resins; terpene resins such as hydrogenated terpene resins and terpene phenols. Among them, rosins are preferable from the viewpoint of improving adhesiveness, and disproportionated or hydrogenated rosin purified by operations such as distillation, recrystallization, and extraction from the viewpoint of suppressing light deterioration, coloring, and generation of bubbles due to impurities. Are more preferred. Specific examples of the rosins include Pine Crystal KE-100, Pine Crystal KE-311, Pine Crystal KE-359, Pine Crystal KE-604, and Pine Crystal D-6250 (all manufactured by Arakawa Chemical Industries, Ltd.). It is done. Specific examples of the styrenic resin include FTR6000 series and FTR7000 series (manufactured by Mitsui Chemicals, Inc.). Specific examples of the terpene resin include Tamorol 901 (Arakawa Chemical Industries, Ltd.).

  The content of the refractive index adjusting agent in the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) can be adjusted according to the refractive index, but the cohesive force of the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) can be adjusted. From a viewpoint to hold | maintain, 1-30 mass% is preferable, and 3-20 mass% is more preferable.

  It is preferable that the refractive indexes of the above-described adhesive layer (a) and adhesive layer (b) are both 1.45 to 1.65. When the refractive index is within the above range, the range of the refractive index difference defined in the present invention is easily satisfied, and reflection at the interface of the adhesive layer / base material layer is reduced, which is preferable in terms of improving visibility. In addition, as a specific measuring method of the refractive index of the adhesion layer (a) and the adhesion layer (b), the method detailed in the below-mentioned Example is employ | adopted.

  The thicknesses of the adhesive layer (a) and the adhesive layer (b) are each preferably 10 μm or more and 200 μm or less, and are 25 μm from the viewpoint of balance between step absorbability, impact resistance, punching property, portability and foam resistance. More preferably, it is 100 μm or less. Here, the thickness of the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) constituting the transparent double-sided pressure-sensitive adhesive sheet of the present invention is to selectively thicken the pressure-sensitive adhesive layer to be bonded to the stepped surface. It is preferable at the point which can thin the thickness of the whole transparent double-sided adhesive sheet.

  In order to improve the step absorbability when bonding the transparent double-sided pressure-sensitive adhesive sheet of the present invention to a stepped surface, in addition to increasing the thickness of the pressure-sensitive adhesive layer on the side to be bonded to the stepped surface, The storage shear modulus of the adhesive layer on the side to be bonded to the stepped surface may be lowered.

  When the transparent double-sided pressure-sensitive adhesive sheet of the present invention is provided with the pressure-sensitive adhesive layer (a) on one main surface of the base material layer and the pressure-sensitive adhesive layer (b) on the other main surface, the transparent double-sided pressure-sensitive adhesive having such a three-layer structure Two or more sheets may be stacked. A three-layer structure is preferable from the viewpoint of enhancing the step absorbability and improving the productivity. Moreover, you may interpose the layer (for example, outgas barrier layer etc.) which has another function between the adhesion layer and a base material layer.

  Of the adhesive layer (a) and the adhesive layer (b), at least one of the adhesive layer (a) and the adhesive layer (b) contains the acrylic block copolymer (0). (0) may be contained in both the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b), or may be contained in any one of the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) and the base material layer. Also good. It is preferable that the acrylic block copolymer (0) is contained in two or more layers, and when all the layers contain the acrylic block copolymer (0), the interlayer adhesion is high and the reworkability is excellent. And it is more preferable from the viewpoint of excellent transparency.

  In the transparent double-sided pressure-sensitive adhesive sheet of the present invention, the refractive index difference between the pressure-sensitive adhesive layer (a) and the base material layer and the refractive index difference between the pressure-sensitive adhesive layer (b) and the base material layer are both 0.05 or less. When the refractive index difference is within this range, light scattering at the interface between layers is suppressed, and high transparency is obtained.

  In order to obtain the pressure-sensitive adhesive layer and the base material layer having the above refractive index difference, the refractive index adjusting agent described above is added to either or both of the pressure-sensitive adhesive layer and the base material layer in accordance with the pressure-sensitive adhesive layer or the base material layer to be used. (See Patent Documents 6 and 7) or a method of selecting an appropriate monomer (see Patent Document 8).

  The acrylic block copolymer (0) used for the transparent double-sided pressure-sensitive adhesive sheet of the present invention preferably has the optical characteristics described above. In order to have such optical characteristics, the molecular weight distribution of the acrylic block copolymer (0) is preferably close to 1.0. As a method for producing such an acrylic block copolymer (0), a living polymerization method capable of highly controlling the molecular structure is preferable.

  Living polymerization refers to polymerizing the monomer of the polymer block that constitutes the block copolymer, and then synthesizing the block copolymer by polymerizing other monomers before the polymerization is deactivated or stopped. For example, a method of living polymerization using an organic rare earth metal complex as a polymerization initiator (see Patent Document 9), and a mineral acid salt such as an alkali metal or alkaline earth metal salt using an organic alkali metal compound as a polymerization initiator A living anion polymerization in the presence of (see Patent Document 10), a living anion polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound (see Patent Document 11), an atom transfer radical Examples thereof include a polymerization method (ATRP) (see Non-Patent Document 1).

  Among the above production methods, in the case of living anion polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound, there is little deactivation during the polymerization, so there is little mixing of the deactivating component homopolymer. As a result, the acrylic block copolymer (0) obtained has high transparency. Further, since the polymerization conversion rate of the monomer is high, the residual monomer is small and the odor is suppressed. Furthermore, when the monomer which comprises a polymer block (A) is a methacrylic ester, the molecular structure of the polymer block (A) obtained becomes high syndiotactic, and there exists an effect which improves heat resistance. And, since living polymerization is possible under relatively mild temperature conditions, there is a tendency for environmental load (mainly energy required for a refrigerator to control the polymerization temperature) to be reduced in industrial production. There is. From the above points, the acrylic block copolymer is preferably produced by a method of living anion polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound.

As the above-mentioned organoaluminum compound, for example, the following general formula (III)
AlR ¹ R ² R ³ (III)
(In the above formula (III), R ¹ , R ² and R ³ are each independently an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or a substituent. An aryl group which may have a substituent, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent, a substituent An optionally substituted N, N-disubstituted amino group or a halogen atom, wherein R ¹ represents the group described above, and ^two of R ² and R ³ are bonded to each other to form a substituent; An arylene alkyl group which may have, an alkylenedioxy group which may have a substituent, and an aryleneoxy group which may have a substituent may be formed.
The compound shown by these is mentioned.

  Examples of the organoaluminum compound represented by the above formula (III) include trialkylaluminum such as trimethylaluminum and triisobutylaluminum; dimethyl (2,6-di-tert-butylphenoxy) aluminum, diisobutyl (2,6-dioxy). -Tert-butylphenoxy) aluminum, dialkylphenoxyaluminum such as diisobutyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum; methylbis (2,6-di-tert-butylphenoxy) aluminum, isobutylbis ( 2,6-di-tert-butylphenoxy) aluminum, isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutyl [2,2′-methylenebis (4-methyl-6-t) rt-butylphenoxy)] alkyldiphenoxyaluminum such as aluminum; alkoxydiphenoxyaluminum such as methoxybis (2,6-di-tert-butylphenoxy) aluminum; tris (2,6-di-tert-butyl-4-methyl) And phenoxy) aluminum and triphenoxyaluminum such as tris (2,6-diphenylphenoxy) aluminum.

  Among the organoaluminum compounds described above, isobutyl bis (2,6-di-tert-butylphenoxy) aluminum, isobutyl bis (2,6-di-tert) are preferred from the viewpoints of high living property of polymerization and easy handling. -Butyl-4-methylphenoxy) aluminum and isobutyl [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum are preferred.

  As the organic alkali metal compound, an organic lithium compound can be preferably used. Examples of the organolithium compound include alkyllithium or alkylenedilithium such as n-butyllithium, sec-butyllithium, isobutyllithium, t-butyllithium and tetramethylenedilithium; aryllithium such as phenyllithium and xylyllithium. Alternatively, aryl dilithium; aralkyl lithium such as dilithium produced by the reaction of benzyl lithium, diisopropenylbenzene and butyl lithium or aralkyl dilithium; lithium amide such as lithium diisopropylamide; lithium alkoxide such as lithium methoxide;

  Among the organic alkali metal compounds, t-butyllithium and sec-butyllithium are preferable because of high polymerization initiation efficiency, and sec-butyllithium is more preferable.

  In addition to the above organoaluminum compounds, if necessary, ethers such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4; triethylamine, N, N, N ′, N′-tetramethylethylenediamine, N , N, N ', N ", N" -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, nitrogen-containing compounds such as 2,2'-dipyridyl The acrylic block copolymer (0) may be synthesized by further existing in the system.

  The living anion polymerization is usually performed in the presence of a solvent inert to the polymerization reaction. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as chloroform, methylene chloride, and carbon tetrachloride; ethers such as tetrahydrofuran and diethyl ether.

  The method for producing the acrylic block copolymer (0) by living anionic polymerization in the presence of an organoaluminum compound is further specifically exemplified. For example, in the presence of an organoaluminum compound, a first step of polymerizing a monomer that forms a polymer block (A) with a polymerization initiator composed of an organic alkali metal compound, a single amount that forms a polymer block (B) The acrylic block copolymer (0) is subjected to a plurality of polymerization steps including a second step of polymerizing the polymer and a third step of polymerizing the monomer that forms the polymer block (A) if necessary. ) Can be manufactured.

  In the said manufacturing method, a desired polymer block will be formed at the living polymer terminal produced | generated at each process at the next process. Therefore, for example, the polymer block (A)-is obtained by continuously reacting the active terminal of the obtained polymer with an alcohol or the like through the above-described two-stage or three-stage polymerization step and stopping the polymerization reaction. A binary block (diblock) copolymer comprising a polymer block (B) and a ternary block (triblock) comprising a polymer block (A) -polymer block (B) -polymer block (A) A polymer can be produced. Here, the quaternary block copolymer is a desired polymer block (polymer block (A), polymer block (B), etc.) obtained by polymerizing monomers in addition to the above three-step process. Can be produced by adding the desired number of steps, reacting the active terminal of the obtained polymer with alcohol or the like, and stopping the polymerization reaction.

  Here, as polymerization temperature, when forming a polymer block (A), 0-100 degreeC is preferable, and when forming a polymer block (B), -50-50 degreeC is preferable. When the polymerization temperature is lower than the above range, the progress of the reaction is slow, and it takes a long time to complete the reaction. On the other hand, when the polymerization temperature is higher than the above range, deactivation increases, the molecular weight distribution becomes wide, and a desired block copolymer cannot be obtained. The polymer block (A) and the polymer block (B) can be polymerized in the range of 1 second to 20 hours, respectively.

  The pressure-sensitive adhesive layer of the transparent double-sided pressure-sensitive adhesive sheet of the present invention can be produced by a hot melt molding method, a solution casting method, or the like. When the transparent double-sided pressure-sensitive adhesive sheet of the present invention includes a base material layer, the base material layer can also be produced by the same method. When the transparent double-sided pressure-sensitive adhesive sheet of the present invention includes three layers of a base material layer, a pressure-sensitive adhesive layer (a) and a pressure-sensitive adhesive layer (b), at least one of them is obtained by a hot melt molding method. May be. At this time, the layer obtained by the hot melt molding method may be an adhesive layer or a base material layer. Further, all three layers of the adhesive layer (a), the base material layer, and the adhesive layer (b) may be obtained by a solution casting method.

  Since the transparent double-sided pressure-sensitive adhesive sheet of the present invention does not rely only on the solution casting method, it can be easily obtained with a thick, easy-to-carry, punchable, foam-resistant, and transparent material having different thicknesses. It is easy. In particular, from the viewpoint of step absorbability and impact resistance, a thickness of 210 μm or more is preferable, and a thickness of 210 μm or more and 1000 μm or less is more preferable. Moreover, when impact resistance is calculated | required, the thickness of 300 micrometers or more and 1000 micrometers or less is preferable, and the thickness of 500 micrometers or more and 1000 micrometers or less is more preferable.

  The hot melt molding method is a method in which a resin is melted by heat to form, for example, a hot melt coating method, a T-die extrusion method, an inflation method, a calender molding method, etc. The T die method or the inflation method is preferable from the viewpoint of processability and cost, and the T die method is more preferable from the viewpoint of excellent productivity and thickness accuracy.

  When manufacturing the adhesive layer or base material layer of the said transparent double-sided adhesive sheet by T-die method, the said composition containing an acrylic block copolymer (0) is fuse | melted in an extruder, for example, the said extruder The sheet or film is extruded from a die attached to the sheet, and the extruded sheet or film is taken into close contact with at least one cooling drum. In the case of multiple layers, the layer structure may be formed at a time by co-extrusion of the adhesive layer and the base material layer.

  The die is not particularly limited, and examples thereof include known dies such as a T die and a coat hanger die. Examples of the material of the die include, but are not limited to, SCM steel and stainless steel such as SUS.

  As said solution casting method, the general method used for manufacture of a film-like or sheet-like member can be used. Specifically, a heat resistant material such as polyethylene terephthalate or a flat plate or roll such as a steel belt is used as a support, and a bar coater, roll coater, die coater, comma coater, or the like is used on these. Examples include a method of applying a solution obtained by dissolving a composition containing the polymer (0) or the acrylic block copolymer (0) in a solvent, and removing the solvent by drying.

  The method for removing the solvent by drying is not particularly limited, and a conventionally known method can be used, but it is preferable to perform drying in a plurality of stages. When drying is performed in a plurality of stages, the first stage of drying is performed at a relatively low temperature in order to suppress foaming due to rapid volatilization of the solvent. In order to remove the solvent, a method of drying at a high temperature is more preferable.

  In the solution casting method, examples of the solvent used for dissolving the acrylic block copolymer (0) or the composition containing the acrylic block copolymer (0) include toluene, ethyl acetate, ethylbenzene, methylene chloride, Examples include chloroform, tetrahydrofuran, methyl ethyl ketone, dimethyl sulfoxide, toluene-ethanol mixed solvent, and the like. Of these, toluene, ethylbenzene, ethyl acetate, and methyl ethyl ketone are preferable.

  The concentration of the composition containing the acrylic block copolymer (0) or the acrylic block copolymer (0) in the solution is such that the acrylic block copolymer (0) or the acrylic block copolymer (0). Is suitably determined in consideration of the solubility of the composition containing the solvent in the solvent, the viscosity of the obtained solution, and the like, but a preferable lower limit is 5% by mass and a preferable upper limit is 50% by mass.

  The method for laminating the pressure-sensitive adhesive layer and the base material layer obtained by the above method is not particularly limited. For example, after each of the three layers of the pressure-sensitive adhesive layer (a), the base material layer, and the pressure-sensitive adhesive layer (b) is obtained by the above method. Once each is wound on a roll, each layer may be unwound from each roll, and may be wound on a roll while laminating an adhesive surface on both sides of the base material layer. After obtaining each of the three layers of the material layer and the pressure-sensitive adhesive layer (b) by the above method, it may be obtained by cutting out to a required size and laminating the pressure-sensitive adhesive surfaces on both surfaces of the base material layer. In addition, after each of the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) is obtained by the above-described method, each of the pressure-sensitive adhesive layers is wound around a roll, and then the pressure-sensitive adhesive layer is unwound from each roll, and a hot melt extrusion molding method. May be wound on a roll while being laminated on both sides of the substrate layer extruded from the die. There is also a method of directly obtaining a three-layer structure of an adhesive layer (a), a base material layer, and an adhesive layer (b) by a hot melt coextrusion molding method. Further, the obtained transparent double-sided PSA sheet may be further subjected to a curing step by light or heat as necessary.

  The transparent double-sided PSA sheet of the present invention can be used for various optical applications by utilizing its excellent transparency and flexibility. For example, it can be used for a flat or flexible image display device using an image display panel such as an LCD, EL, or PDP, such as electronic paper, PDA, TV, or game machine. Especially, it is useful for bonding of each layer in a touch panel member. For example, an adhesive layer is formed on a part or all of one surface or both surfaces of a surface protection panel, a touch panel, an image display panel, etc., and the panels are adhered to each other. be able to. Specifically, for example, a member provided with a touch panel on one main surface of the transparent double-sided pressure-sensitive adhesive sheet of the present invention and an image display panel or a surface protection panel on the other main surface can be obtained.

  The touch panel member is not limited to the above-described member having a touch panel on one main surface of the transparent double-sided pressure-sensitive adhesive sheet of the present invention and a member having an image display panel or a surface protection panel on the other main surface. . That is, the transparent double-sided pressure-sensitive adhesive sheet of the present invention can be used for sticking and fixing various layers of the touch panel member. Moreover, when each panel is formed by laminating a plurality of layers, they may be used for adhering and fixing those layers. Specifically, it can be used for sticking and fixing the following layers in the touch panel member. For example, surface protection layers such as anti-scattering films, glass, polycarbonate plates, and acrylic plates, surface protection layers such as surface protection sheets; transparent conductive films made of ITO films, conductive polymer films, etc., ITO and transparent electrodes Panels made of glass, polycarbonate plates, acrylic plates, etc. with patterning formed thereon, touch panel layers such as ITO protective layers; hard coat layers, polarizing plates, non-glare layers, antireflection layers, optical isotropic films, Layers that make up LCD panels such as color filters, sealing glass, LCD cells, organic EL cells, insulating films, electrodes, protective films; and layers that have these two or more functions at the same time, and other touch panel members It can be used for sticking and fixing any layer. Examples of the touch panel member include an out-cell type, an in-cell type, an on-cell type, a cover glass integrated type, a cover sheet integrated type, and any other touch panel members. Specifically, for example, the touch panel and the image display panel, or the surface protection panel and the touch panel may be integrated, or the panel portion may be formed of a film having each function. Moreover, there is no restriction | limiting in particular also about the technical system of a touchscreen member, For example, a resistive film type, an electrostatic capacitance type, an optical type, an ultrasonic type etc. are mentioned.

  In the present specification, “transparent” means having a level of transparency generally used as an optical film. Specifically, the total light transmittance of the transparent double-sided PSA sheet of the present invention is preferably 88% or more, and more preferably 90% or more. The wavelength at the time of measuring the total light transmittance of the transparent double-sided pressure-sensitive adhesive sheet can be appropriately set within the range of visible light (360 to 730 nm). The haze value of the transparent double-sided PSA sheet is preferably 3% or less, and more preferably 2% or less. The wavelength at the time of haze value measurement of the said transparent double-sided adhesive sheet can be suitably set in the range of visible light (360-730 nm). As a specific method for measuring the total light transmittance and the haze value, a method described in detail in Examples described later is employed.

Hereinafter, the present invention will be described more specifically based on examples and the like, but the present invention is not limited to the following examples.
Various physical properties of Examples and Comparative Examples were measured or evaluated by the following methods.
(1) Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of acrylic block copolymers (I), (II) and (0-1)
It was determined as a molecular weight in terms of standard polystyrene by gel permeation chromatography (hereinafter abbreviated as GPC).
・ Equipment: GPC equipment “HLC-8020” manufactured by Tosoh Corporation
・ Separation column: “TSKgel GMHXL”, “G4000HXL” and “G5000HXL” manufactured by Tosoh Corporation are connected in series. ・ Eluent: Tetrahydrofuran ・ Eluent flow rate: 1.0 ml / min ・ Column temperature: 40 ° C.
・ Detection method: Differential refractive index (RI)
(2) Content of each polymer block in acrylic block copolymers (I), (II) and (0-1) It was determined by 1H-NMR measurement.
・ Device: JEM Nuclear Magnetic Resonance Device “JNM-LA400”
Solvent: In deuterated chloroform - IH-NMR spectrum, signals in the vicinity of 3.6ppm and 4.0ppm, respectively, the ester group of methyl methacrylate unit (-O-CH _3), and acrylic acid n- butyl Unit Ester group —O—CH ₂ —CH ₂ —CH ₂ —CH ₃ ), and the content of the copolymer component was determined by the ratio of the integral values.
(3) Glass transition temperature (Tg)
Under the following conditions, the extrapolation start temperature (Tgi) was defined as the glass transition temperature (Tg) in the curve obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121.
・ Equipment: “DSC-822” manufactured by METTLER TOLEDO
Condition: Temperature rising rate 10 ° C./min (4) Storage shear modulus In Examples 1 to 10 and Reference Examples 11 to 13 , the acrylic block copolymer (II) (or (II) used in the adhesive layer Composition) and an acrylic adhesive sheet (C-1) used for the adhesive layer in the comparative example was prepared in the same manner as in Reference Example 12 described later. The laminate thus laminated was used as a test piece, the dynamic viscoelasticity was measured under torsional vibration under the following conditions, and the value of the storage shear modulus (G ′) at 20 ° C. was adopted.
-Equipment: “Advanced Rheometric Expansion System” manufactured by Rhemetric Scientific
・ Parallel plate: Diameter 8mm
・ Vibration mode: Torsional vibration ・ Frequency: 6.28 rad / sec ・ Measurement temperature range: −50 ° C. to 250 ° C.
-Temperature rising rate: 3 ° C / min-Strain: 0.05% (-50 ° C to -37 ° C), 1.0% (-37 ° C to -15 ° C), 5.0% (-15 ° C to 250 ° C) ℃)
(5) Storage tensile elastic modulus The base layer film produced in the examples and comparative examples was punched into a strip shape having a length of 20 mm and a width of 5 mm to create a test piece, and dynamic under tensile vibration under the following conditions: The viscoelasticity was measured, and the value of the storage tensile modulus (E ′) at 20 ° C. was adopted.
・ Equipment: Wide-area dynamic viscoelasticity measurement equipment (forced vibration non-resonance method)
“PVE-V4 FT Leospectrer” manufactured by Rheology Co., Ltd.
・ Frequency: 11Hz
・ Vibration mode: Tensile vibration ・ Measurement temperature range: 20 ℃ ～ 200 ℃
-Temperature increase rate: 3 ° C / min-Strain: 0.03%
(6) Refractive index A test piece of 8 mm × 20 mm was cut out from the adhesive layer film and the base layer film prepared in Examples and Comparative Examples, and the refractive index was measured according to JIS K7142.
・ Device: "Multi-wavelength Abbe refractometer DR-M2" manufactured by Atago Co., Ltd.
・ Measurement temperature: 25 ℃
・ Light source wavelength: D line (589 nm)
(7) Total light transmittance and haze A test piece of 50 mm × 50 mm was cut out from the transparent double-sided pressure-sensitive adhesive sheet (having a release polyethylene terephthalate (PET) film on both sides) prepared in Examples or Comparative Examples. Subsequently, the release PET films on both sides of the test piece were peeled off and attached to a haze meter, and the total light transmittance and haze were measured in the thickness direction in accordance with JIS K7361 and JIS K7136.
・ Device: Nippon Denshoku Industries Co., Ltd. Haze meter “NDH5000”
・ Temperature: 20 ℃
・ Light source: White LED
(8) Adhesive strength and adhesive residue The release PET film on one side of the transparent double-sided pressure-sensitive adhesive sheet (provided with a release PET film on both sides) prepared in the examples or comparative examples is peeled off to obtain a PET film (manufactured by Toyobo Co., Ltd.). After bonding with Cosmo Shine A4300 (thickness 50 μm), a test piece 25 mm wide × 200 mm long was cut out. Subsequently, the release PET film on the other side of the test piece is peeled off and adhered to the glass plate or polycarbonate plate, which is an adherend, by reciprocating twice at a speed of 10 mm / second using a rubber roller with a load of 2 kg. I let you. This was stored for 24 hours at 23 ° C., 50% RH and atmospheric pressure, and then conditioned, and then peeled off at a peeling angle of 180 ° at a peeling speed of 30 mm / min and 300 mm / min in accordance with JIS Z0237. The adhesion was measured.
In the measurement of the 180 ° peeling adhesive strength, after peeling, whether or not the adhesive remains on the glass plate or the polycarbonate plate as the adherend is visually observed. A case where there was no adhesive residue was evaluated, and a case where the adhesive was peeled off without remaining, was evaluated as “no adhesive residue”.
(9) Wet heat durability A test piece having a width of 25 mm and a length of 80 mm was cut out from the transparent double-sided pressure-sensitive adhesive sheet (having a release PET film on both sides) prepared in Examples or Comparative Examples. Subsequently, the release PET film on one side of the test piece was peeled off and adhered to a glass plate or a polycarbonate plate as an adherend by reciprocating twice at a speed of 10 mm / sec using a roller with a load of 2 kg. . Subsequently, this was autoclaved at 60 ° C. and 0.5 MPa for 30 minutes, stored in a constant temperature and humidity chamber at 60 ° C. and 95% RH for 200 hours, and then foamed using a calibrated loupe (10 times). The durability was evaluated based on the criteria described in Table 1.

(10) Probe tack One side of the release PET film of the transparent double-sided pressure-sensitive adhesive sheet (having a release PET film on both sides) prepared in the examples or comparative examples is peeled off, and then a PET film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) Then, a test piece having a width of 25 mm and a length of 100 mm was cut out. Subsequently, the release PET film on the other side of the test piece was peeled off, and the probe tack was measured according to ASTM D2979.
-Apparatus: “PMA-1000” manufactured by Chem Instruments
・ Probe area: 0.174 cm ²
・ Test speed: 1 cm / min
・ Peeling speed: 60 cm / min
(11) Rate of change in ITO resistance (ITO corrosivity)
A transparent conductive film “PG100-AB500H” (a film in which ITO is laminated on a PET film substrate) manufactured by Teijin Chemicals Limited was cut into a width of 70 mm and a length of 50 mm. A copper tape (made by Touch Panel Laboratories, made of copper foil and conductive acrylic adhesive, width 6 mm) having a conductive adhesive surface on one side was cut to a length of 80 mm on the surface on which this ITO was laminated. The thing was stuck so that 30 mm might protrude from one side of a transparent conductive film along two short sides. At this time, the protruding part of the copper tape was folded in two with the adhesive surface inside. Subsequently, in Examples 1 to 10 and Reference Examples 11 to 13 , using the acrylic block copolymer (II) (or the composition of (II)) used for the adhesive layer, the same as Reference Example 12 described later. The film having a thickness of 50 μm prepared by the above method and the acrylic pressure-sensitive adhesive sheet (C-1) used for the pressure-sensitive adhesive layer in the comparative example are laminated so as to have a thickness of 50 μm. The attached laminated body was prepared. The release PET film on one side is peeled off and bonded to a PET film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd., thickness 50 μm), then cut into a width of 70 mm and a length of 50 mm, and the other release PET film is removed. The test piece was obtained by peeling off and pasting on the surface of the transparent conductive film with the copper tape pasted thereon by reciprocating twice at a speed of 10 mm / second using a roller with a load of 2 kg. It was. The obtained test piece was autoclaved at 60 ° C. and 0.5 MPa for 30 minutes, and then stored in a constant temperature and humidity chamber at 85 ° C. and 85% RH for 200 hours. The rate of change in ITO resistance value was calculated by measuring the resistance value before and after storage for 200 hours in a constant temperature and humidity chamber using the portion of the copper tape protruding from the test piece ([after storage for 200 hours Resistance value—resistance value before storage for 200 hours] / resistance value before storage for 200 hours). It shows that it is excellent in corrosion resistance, so that the change rate of ITO resistance value is small.
(12) Initial Stress Value of Adhesive Layer A test piece was prepared in the same manner as in the above (4) storage shear modulus, and the initial stress value when stress was applied under the following conditions was measured.
・ Equipment: Wide-area dynamic viscoelasticity measurement equipment (forced vibration non-resonance method)
“PVE-V4 FT Leospectrer” manufactured by Rheology Co., Ltd.
・ Measurement temperature: 50 ℃
・ Sample length: 10mm
・ Displacement: 20%

(13) Punching property A test piece having a width of 30 mm and a length of 30 mm was cut out from the transparent double-sided pressure-sensitive adhesive sheet (having a release PET film on both sides) produced in Examples or Comparative Examples. Subsequently, this test piece was punched out using a punch (“FK-P17” manufactured by Fukui Kiko Co., Ltd., circular shape with an inner diameter of 5 mm), and the cross section of the transparent double-sided PSA sheet was observed.
The observation method will be described with reference to FIG. The length of the longest portion of the portions (c) and (c ′) protruding from the punched section (b) of the transparent double-sided pressure-sensitive adhesive sheet (a) (such as the stringing portion of the material constituting the pressure-sensitive adhesive layer or the base material). (C) is measured using a magnifying loupe (10 times), “◯” for 0.25 cm or less, “Δ” for 0.25 cm or more and less than 0.55 cm, or 0.55 cm or more Was marked “x”.
(14) Step absorbability A test piece having a width of 30 mm and a length of 30 mm was cut out from the transparent double-sided pressure-sensitive adhesive sheet (having a release PET film on both sides) prepared in Examples or Comparative Examples. The release PET film on one side of this test piece was peeled off, and the adhesive surface was layered on the PET film with a step of 10 μm, and a rubber roller with a load of 2 kg was reciprocated twice at a speed of 10 mm / second and adhered. Subsequently, after autoclaving at 60 ° C. and 0.5 MPa for 30 minutes, the width of the air layer generated in the stepped portion was observed with a scaled loupe (10 times).

<< Synthesis Example 1 >> [Synthesis of Acrylic Block Copolymer (I-1)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 1040 g of toluene and 100 g of 1,2-dimethoxyethane were added at room temperature, and then isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) 45.0 g of a toluene solution containing 30.0 mmol of aluminum was added, and 12.7 g of a mixed solution of cyclohexane and n-hexane containing 7.3 mmol of sec-butyllithium was further added. Subsequently, 64.0 g of methyl methacrylate was added to this mixed solution. The reaction mixture was initially colored yellow, but became colorless after 60 minutes of stirring at room temperature. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Next, the reaction mixture was cooled to −30 ° C., 184.0 g of n-butyl acrylate was added dropwise over 2 hours, and the mixture was stirred at −30 ° C. for 5 minutes after the completion of the addition. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Subsequently, 161.0 g of methyl methacrylate was added to the reaction mixture, and after stirring overnight at room temperature, 4.0 g of methanol was added to stop the polymerization reaction. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. The obtained reaction mixture was poured into 15 kg of methanol to precipitate a white precipitate. The white precipitate was collected by filtration and dried to obtain 405 g of a block copolymer [hereinafter referred to as “acrylic block copolymer (I-1)”].

(2) About the obtained acrylic block copolymer (I-1), as a result of performing ¹ H-NMR measurement and GPC measurement, it consists of polymethyl methacrylate-poly (n-butyl acrylate) -polymethyl methacrylate. It was a triblock copolymer, the weight average molecular weight (Mw) was 62,000, the number average molecular weight (Mn) was 56,000, and the molecular weight distribution (Mw / Mn) was 1.11. The content of each polymer block in the acrylic block copolymer (I-1) was 51.1% by mass for the methyl methacrylate polymer block and 48.9% for the n-butyl acrylate polymer block. %Met.

<< Synthesis Example 2 >> [Synthesis of Acrylic Block Copolymer (I-2)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 1040 g of toluene and 100 g of 1,2-dimethoxyethane were added at room temperature, and then isobutyl bis (2,6-di-tert-butyl-4-methylphenoxy) ) 48.0 g of a toluene solution containing 32.0 mmol of aluminum was added, and 14.0 g of a mixed solution of cyclohexane and n-hexane containing 8.10 mmol of sec-butyllithium was further added. Subsequently, 72.0 g of methyl methacrylate was added to this mixed solution. The reaction mixture was initially colored yellow, but became colorless after 60 minutes of stirring at room temperature. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Next, the reaction mixture was cooled to −30 ° C., 307.0 g of n-butyl acrylate was added dropwise over 2 hours, and the mixture was stirred at −30 ° C. for 5 minutes after the completion of the addition. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Subsequently, 72.0 g of methyl methacrylate was added to the reaction mixture, and after stirring overnight at room temperature, 4.0 g of methanol was added to stop the polymerization reaction. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. The obtained reaction mixture was poured into 15 kg of methanol to precipitate a white precipitate. The white precipitate was collected by filtration and dried to obtain 442 g of a block copolymer [hereinafter referred to as “acrylic block copolymer (I-2)”].

(2) The resulting acrylic block copolymer (I-2) was subjected to ¹ H-NMR measurement and GPC measurement. As a result, polymethyl methacrylate-b-polyacrylate n-butyl-b-polymethacrylate was obtained. It is a triblock copolymer consisting of methyl acid, the weight average molecular weight (Mw) is 62,000, the number average molecular weight (Mn) is 57,400, and the molecular weight distribution (Mw / Mn) is 1.08. . The content of each polymer block in the acrylic block copolymer (I-2) was 32.0% by mass for the methyl methacrylate polymer block and 68.0% for the n-butyl acrylate polymer block. %Met.

<< Synthesis Example 3 >> [Synthesis of Acrylic Block Copolymer (II-1)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 1048 g of toluene and 52.4 g of 1,2-dimethoxyethane were added at room temperature, and then isobutyl bis (2,6-di-tert-butyl-4-methyl) was added. 50.0 g of a toluene solution containing 10.9 mmol of phenoxy) aluminum was added, and 4.01 g of a mixed solution of cyclohexane and n-hexane containing 2.31 mmol of sec-butyllithium was further added. Subsequently, 18.0 g of methyl methacrylate was added to this mixed solution. The reaction mixture was initially colored yellow, but became colorless after 60 minutes of stirring at room temperature. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Next, the reaction mixture was cooled to −30 ° C., 221.2 g of n-butyl acrylate was added dropwise over 2 hours, and the mixture was stirred at −30 ° C. for 5 minutes after the completion of the addition. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Subsequently, 24.5 g of methyl methacrylate was added to the reaction mixture, and after stirring overnight at room temperature, 13 g of acetic acid water was added to stop the polymerization reaction. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. The obtained reaction mixture was poured into 15 kg of methanol to precipitate a white precipitate. The white precipitate was collected by filtration and dried to obtain 262 g of a block copolymer [hereinafter referred to as “acrylic block copolymer (II-1)”].

(2) As a result of performing ¹ H-NMR measurement and GPC measurement on the acrylic block copolymer (II-1), the triblock copolymer consisting of polymethyl methacrylate-poly (n-butyl acrylate) -polymethyl methacrylate was used. The polymer had a weight average molecular weight (Mw) of 155,000, a number average molecular weight (Mn) of 135,600, and a molecular weight distribution (Mw / Mn) of 1.14. Further, the content of each polymer block in the acrylic block copolymer (II-1) was 16.1% by mass for the methyl methacrylate polymer block and 83.9% by mass for the n-butyl acrylate polymer block. %Met.

<< Synthesis Example 4 >> [Synthesis of Acrylic Block Copolymer (II-2)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 1040 g of toluene and 52.0 g of 1,2-dimethoxyethane were added at room temperature, and then isobutyl bis (2,6-di-tert-butyl-4-methyl) was added. 60.0 g of a toluene solution containing 40.2 mmol of phenoxy) aluminum was added, and 5.17 g of a mixed solution of cyclohexane and n-hexane containing 2.98 mmol of sec-butyllithium was further added. Subsequently, 25.0 g of methyl methacrylate was added to this mixed solution. The reaction solution was initially colored yellow, but became colorless after stirring for 60 minutes at room temperature. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Next, the reaction mixture was cooled to −30 ° C., 204.0 g of n-butyl acrylate was added dropwise over 2 hours, and the mixture was stirred at −30 ° C. for 5 minutes after the completion of the addition. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Subsequently, 35.0 g of methyl methacrylate was added to the reaction mixture, and after stirring overnight at room temperature, 3.50 g of methanol was added to stop the polymerization reaction. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. The obtained reaction solution was poured into 15 kg of methanol to precipitate a white precipitate. The white precipitate was collected by filtration and dried to obtain 260 g of a block copolymer [hereinafter referred to as “acrylic block copolymer (II-2)”].

(2) About the obtained acrylic block copolymer (II-2), as a result of performing ¹ H-NMR measurement and GPC measurement, it consists of polymethyl methacrylate-poly (n-butyl acrylate) -polymethyl methacrylate. It was a triblock copolymer, the weight average molecular weight (Mw) was 115,000, the number average molecular weight (Mn) was 104,500, and the molecular weight distribution (Mw / Mn) was 1.10. In addition, the content of each polymer block in the acrylic block copolymer (II-2) was 22.5 mass% for the methyl methacrylate polymer block and 77.5 mass% for the n-butyl acrylate polymer block. %Met.

<< Synthesis Example 5 >> [Synthesis of Acrylic Block Copolymer (0-1)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 870 g of toluene and 44.0 g of 1,2-dimethoxyethane were added at room temperature, and then isobutyl bis (2,6-di-tert-butyl-4-methyl) was added. 30.9 g of a toluene solution containing 20.7 mmol of phenoxy) aluminum was added, and further 2.99 g of a mixed solution of cyclohexane and n-hexane containing 5.17 mmol of sec-butyllithium was added. Subsequently, 21.7 g of methyl methacrylate was added to this mixed solution. The reaction solution was initially colored yellow, but became colorless after stirring for 60 minutes at room temperature. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Next, the reaction mixture was cooled to −30 ° C., and 288.4 g of n-butyl acrylate was added dropwise over 2 hours. After completion of the addition, the mixture was stirred at −30 ° C. for 5 minutes, and then 3.5 g of methanol was added. The polymerization reaction was stopped. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Subsequently, the obtained reaction solution was poured into 15 kg of methanol to precipitate an oily precipitate. Thereafter, an oily precipitate was collected by decantation and dried to obtain 310 g of a block copolymer [hereinafter referred to as “acrylic block copolymer (0-1)]”.

(2) As a result of performing ¹ H-NMR measurement and GPC measurement on the obtained acrylic block copolymer (0-1), a diblock copolymer comprising polymethyl methacrylate-n-butyl polyacrylate The weight average molecular weight (Mw) was 67,000, the number average molecular weight (Mn) was 55,400, and the molecular weight distribution (Mw / Mn) was 1.21. The content of each polymer block in the acrylic block copolymer (0-1) was 6.9% by mass for the methyl methacrylate polymer block and 93.1% for the n-butyl acrylate polymer block. %Met.

  The physical property values of the acrylic block copolymers (I-1), (I-2), (II-1), (II-2) and (0-1) obtained in Synthesis Examples 1 to 5 above are shown. Table 2 below shows.

<< Synthesis Example 6 >> [Synthesis of Methacrylic Resin (E-1)]
A methacrylic resin (E-1) (weight average molecular weight (Mw) = 100,000) consisting of 91% by mass of methyl methacrylate and 9% by mass of methyl acrylate was obtained by a bulk polymerization method.

<< Synthesis Example 7 >> [Synthesis of Polyvinyl Butyral Resin (E-2)]
An aldehyde mixture of butyraldehyde: acetaldehyde = 50: 50 (molar ratio) and hydrochloric acid were added to an aqueous solution in which the polyvinyl alcohol resin was dissolved, and the mixture was stirred to acetalize to precipitate the resin. Wash with water until pH = 6 according to known methods. It was then added to an alkaline aqueous medium, suspended by stirring, and the resulting resin was washed with water until pH = 7. A polyvinyl butyral resin (E-2) was obtained by drying until the volatile content was 1.0%.

<< Synthesis Example 8 >> [Synthesis of Star Block Copolymer (E-3)]
Into a 1.5 L autoclave vessel with a stirrer, 694 ml of toluene was charged and purged with nitrogen for 20 minutes. Thereto, 2.77 ml of a cyclohexane solution of sec-butyllithium having a concentration of 1.3 mol / l and 112 ml of butadiene were added and reacted at 30 ° C. for 1.5 hours to obtain a reaction mixture containing a butadiene polymer. The resulting reaction mixture was cooled to −30 ° C. and 60 ml of a toluene solution containing 0.6 mol / l of isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum was added for 10 minutes. Stir to a homogeneous solution. While the solution was vigorously stirred, 144 ml of n-butyl acrylate was added and polymerized at −30 ° C. for 1 hour. Further, 2.4 ml of 1,6-hexanediol diacrylate was added and polymerization was performed for 2 hours. Then about 1 ml of methanol was added to stop the polymerization. The reaction mixture was reprecipitated in 8000 ml of methanol to obtain a star block copolymer (E-3) with a yield of almost 100%.

<< Synthesis Example 9 >> [Synthesis of Methacrylic Resin Composition (D-3)]
An autoclave with a stirrer and a sampling tube was charged with 57.8 parts by weight of methyl methacrylate, 3.0 parts by weight of methyl acrylate, and 35 parts by weight of toluene, and the star block copolymer (E- 3) 4.2 parts by mass was added and stirred at 30 ° C. for 8 hours to uniformly dissolve the star block copolymer (E-2). Subsequently, 0.0375 parts by mass of 1,1-di (tert-butylperoxy) cyclohexane (“Perhexa C” manufactured by Nippon Oil & Fats Co., Ltd., hydrogen abstraction ability: 35%, 1 hour half-life temperature: 111.1 ° C.) and After adding 0.1 part by mass of n-octyl mercaptan and dissolving uniformly, oxygen in the reaction system was removed with nitrogen. To this, 0.001 part by mass of 1,1-di (tert-butylperoxy) cyclohexane (“Perhexa C” manufactured by NOF Corporation, hydrogen abstraction capacity: 35%, 1 hour half-life temperature: 111.1 ° C.), 0.02 parts by mass of tert-butyl peroxybenzoate (“Perbutyl Z” manufactured by NOF Corporation, hydrogen abstraction ability: 56%, 1 hour half-life temperature: 124.7 ° C.) was added for polymerization. This polymerization solution was supplied to a twin screw extruder controlled at 260 ° C. at a constant flow rate, and the reaction product was extruded into a strand shape. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin composition (pellet shape) (D-3).

Example 1
(1) Acrylic block copolymer (I-1) obtained in Synthesis Example 1, acrylic block copolymer (I-2) obtained in Synthesis Example 2, and acrylic resin ("Kuraray Co., Ltd." Parapet GF ”, MFR: 15 g / 10 min (230 ° C., 37.3 N)) at a blending ratio of (I-1) :( I-2): acrylic resin = 50: 20: 30 (mass ratio). An acrylic thermoplastic resin composition (pellet shape) (D-1) was produced by melt-kneading at 230 ° C. with a shaft extruder. Further, this was subjected to extrusion molding at 190 ° C. to 210 ° C. using a T-die extruder to obtain a film for a substrate layer having a thickness of 125 μm.
(2) The acrylic block copolymer (II-1) obtained in Synthesis Example 3 was dissolved in a toluene solution to prepare a solution having a solid concentration of 35%, and this was formed into a release PET film (Teijin DuPont Film Co., Ltd.). After coating on company Purex A43 (thickness: 50 μm), it was dried at 60 ° C. for 30 minutes to obtain an adhesive layer (a) film having an adhesive layer thickness of 25 μm.
(3) A film for an adhesive layer (b) having an adhesive layer thickness of 25 μm was obtained in the same manner as in (2) above.
(4) The adhesive layer (a) film obtained in (2) above is applied to one side of the base layer film obtained in (1) above on a laminator (Laboratory Laminator LL-100, manufactured by Chem Instruments). ), And then the adhesive layer (b) film obtained in (3) above is bonded to the other side of the substrate film in the same manner, thereby releasing the PET film. A double-sided transparent adhesive sheet having a structure of / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film layer was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 2
(1) Using a pellet of the thermoplastic polymer composition (D-1) obtained in Example 1 (1), a base layer film having a thickness of 300 μm was prepared in the same manner as in Example 1 (1). Produced.
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), so that the release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film has a layer structure. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 3
(1) Using a pellet of the thermoplastic polymer composition (D-1) obtained in Example 1 (1), a film for a substrate layer having a thickness of 100 μm was obtained in the same manner as in Example 1 (1). Produced.
(2) The acrylic block copolymer (II-1) obtained in Synthesis Example 3 was dissolved in a toluene solution to prepare a pressure-sensitive adhesive solution having a solid content of 35%, and this was used as a release PET film (Teijin DuPont). After coating on Purex A43 manufactured by Film Co., Ltd., having a thickness of 50 μm, it was dried at 60 ° C. for 30 minutes to obtain a film for an adhesive layer (a) having an adhesive layer thickness of 50 μm.
(3) By the same method as in (2) above, a film for an adhesive layer (b) having an adhesive layer thickness of 50 μm was obtained.
(4) The film for adhesive layer (a) obtained in (2) above and the film for adhesive layer (b) obtained in (3) above are added to the film for base material layer obtained in (1) above. A double-sided transparent adhesive comprising a release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film layer structure by pasting together in the same manner as in Example 1 (4) A sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 4
(1) Adhesive layer (a) having an adhesive layer thickness of 25 μm in the same manner as in Example 1 (2) using the acrylic block copolymer (II-2) obtained in Synthesis Example 4 A film was obtained.
(2) A film for an adhesive layer (b) having an adhesive layer thickness of 25 μm was obtained by the same method as in (1) above.
(3) For the film for the base layer obtained in Example 1 (1), for the adhesive layer (a) obtained in (1) above and for the adhesive layer (b) obtained in (2) above By sticking the film together in the same manner as in Example 1 (4), a double-sided transparent film comprising the structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film An adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 5
(1) Using the acrylic block copolymer (I-1) obtained in Synthesis Example 1, T-die extrusion molding was carried out at 190 ° C. to 210 ° C. to produce a film for a substrate layer having a thickness of 125 μm. did.
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), thereby having a structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 6
(1) The acrylic block copolymer (I-1) obtained in Synthesis Example 1 is dissolved in a toluene solution to prepare a solution having a solid content concentration of 35%, and this is coated on the release PET film. Then, the film was dried at 60 ° C. for 30 minutes to prepare a film for a base material layer having a thickness of 50 μm.
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), thereby having a structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 7
(1) The acrylic block copolymer (I-1) obtained in Synthesis Example 1 is dissolved in a toluene solution to prepare a solution having a solid content concentration of 35%, and this is coated on the release PET film. Then, it was dried at 60 ° C. for 30 minutes to obtain a film for a base material layer having a thickness of 100 μm.
(2) The adhesive layer (b) obtained in Example 3 (3) and the adhesive layer (b) obtained in Example 3 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), so that the release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film has a layer structure. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 8
(1) The acrylic block copolymer (I-2) obtained in Synthesis Example 2 is dissolved in a toluene solution to prepare a solution having a solid content of 35%, and this is coated on the release PET film. Then, the film was dried at 60 ° C. for 30 minutes to obtain a film for a base material layer having a thickness of 125 μm.
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Is bonded in the same manner as in Example 1 (4), whereby a double-sided transparent film having a structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film. An adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 9
(1) 75% by mass of the methacrylic resin (E-1) obtained in Synthesis Example 5 and 25% by mass of the polyvinyl butyral resin (E-2) obtained in Synthesis Example 6 The mixture was melt-kneaded at 230 ° C. to produce an acrylic thermoplastic resin composition (pellet shape) (D-2). Using this pellet, a film for a substrate layer having a thickness of 125 μm was produced in the same manner as in Example 1 (1).
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), so that the release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film has a layer structure. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

Example 10
(1) Using the methacrylic resin composition (pellet shape) (D-3) obtained in Synthesis Example 8, a substrate layer film having a thickness of 125 μm was produced in the same manner as in Example 4 (1). .
(2) The film for the adhesive layer (a) obtained in Example 1 (2) and the adhesive layer (b) obtained in Example 1 (3) were added to the base layer film obtained in (1) above. ) Film is laminated in the same manner as in Example 1 (4), so that the release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film has a layer structure. A double-sided transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

<< Reference Example 11 >>
(1) A film for adhesive layer (a) obtained in Example 1 (2) and Example 1 (3) on a commercially available PET film (S100 manufactured by Mitsubishi Plastics, Inc., thickness 125 μm) (D-4) The film for the pressure-sensitive adhesive layer (b) obtained in 1 was bonded together in the same manner as in Example 1 (4), thereby releasing PET film / pressure-sensitive adhesive layer (a) / base material layer / pressure-sensitive adhesive layer (b) / A double-sided transparent adhesive sheet having a release PET film structure was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

<< Reference Example 12 >>
(1) The acrylic block copolymer (II-2) obtained in Synthesis Example 4 is dissolved in a toluene solution to prepare a solution having a solid concentration of 35%, and this is coated on the release PET film. Then, it was dried at 60 ° C. for 30 minutes to obtain a film for an adhesive layer (a) having an adhesive layer thickness of 200 μm.
(2) By attaching the release PET film to the adhesive layer (a) film obtained in (1) in the same manner as in Example 1 (4), a release PET film / adhesion layer ( a) A double-sided transparent adhesive sheet having a structure of a release PET film was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

<< Reference Example 13 >>
(1) The acrylic block copolymer (II-1) obtained in Synthesis Example 3 and the acrylic block copolymer (0-1) obtained in Synthesis Example 5 at a ratio of 50:50 A solution having a solid content concentration of 35% was prepared by dissolving in a toluene solution, and this was coated on the above-mentioned release PET film, and then dried at 60 ° C. for 30 minutes. The pressure-sensitive adhesive layer had a thickness of 175 μm. A film for layer (a) was obtained.
(2) By attaching the release PET film to the adhesive layer (a) film obtained in (1) in the same manner as in Example 1 (4), a release PET film / adhesion layer ( a) A double-sided transparent adhesive sheet having a structure of a release PET film was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

<< Comparative Example 1 >>
(1) Commercially available PET double-sided adhesive sheet (Nitto Denko Corporation CS9621T, thickness 25 μm) to commercially available PET film (S100, Mitsubishi Plastics, Inc., S100, thickness 125 μm) (D-4) (C-1) By bonding two sheets together in the same manner as in Example 1 (4), both surfaces having a structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film A transparent adhesive sheet was obtained. About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

<< Comparative Example 2 >>
(1) Two commercially available acrylic pressure-sensitive adhesive sheets (CS9621T manufactured by Nitto Denko Corporation, thickness 25 μm) (C-1) are used in the base layer film obtained in Example 5 (1). A double-sided transparent adhesive sheet having a layer structure of release PET film / adhesive layer (a) / base material layer / adhesive layer (b) / release PET film was obtained by pasting together in the same manner as (4). . About this double-sided transparent adhesive sheet, when various physical properties were measured or evaluated by the above-described method, they were as shown in Tables 3 to 5 below.

As seen in the results of Tables 3 to 5 above, the transparent double-sided PSA sheets of Examples 1 to 10 and Reference Examples 11 to 13 containing the acrylic block copolymer (II) in the adhesive layer have an ITO resistance value of The rate of change is small, the ITO corrosivity is small, and it is very excellent. On the other hand, Comparative Examples 1 and 2 using an adhesive layer containing no acrylic block copolymer (II) had a large rate of change in ITO resistance, that is, ITO corrosivity was large. Examples 1 to 5, 7 and Reference Example 12 containing the acrylic block copolymer (0) in each layer constituting the double-sided pressure-sensitive adhesive sheet are the adhesive residue on the adherend in the measurement of 180 ° peeling adhesive force. No reworkability. The transparent double-sided PSA sheets of Reference Examples 12 and 13 consisting of an adhesive layer containing the acrylic block copolymer (II) are excellent in step absorbability. The transparent double-sided PSA sheet of Reference Example 13 containing the acrylic block copolymers (II-1) and (0-1) in the adhesive layer contains the acrylic block copolymer (II-2) in the adhesive layer. Compared to the transparent double-sided pressure-sensitive adhesive sheet of Reference Example 12, the storage shear modulus is low, the probe tack is high, and the initial stress value is low, so the step absorbability is excellent. The transparent double-sided pressure-sensitive adhesive sheets of Examples 1 to 10 and Reference Example 11 having a base material layer are excellent in punchability and excellent in portability.

Furthermore, the transparent double-sided pressure-sensitive adhesive sheets of Examples 1 to 10 have a base material layer having a storage tensile modulus of 6.0 × 10 ⁶ Pa to 3.3 × 10 ⁹ Pa, and a storage shear modulus of 5.0. * 10 ³ Pa or more and 2.0 × 10 ⁶ Pa or less of the adhesive layer, and since the difference in refractive index between the base material layer and the adhesive layer is 0.05 or less, transparency, Excellent wet heat durability, punchability and step absorbability. On the other hand, Comparative Example 1 in which the adhesive layer does not contain the acrylic block copolymer (0) has low transparency. Moreover, the comparative example 2 is inferior to the wet heat durability with respect to a polycarbonate.

In particular, the transparent double-sided pressure-sensitive adhesive sheets of Examples 1 to 8 use the acrylic block copolymer having a storage tensile elastic modulus of 2.0 × 10 ⁷ Pa or more and 1.0 × 10 ⁹ Pa or less as a base material layer. Therefore, it has excellent wet heat durability. Furthermore, the transparent double-sided pressure-sensitive adhesive sheet of Example 1 has a pressure-sensitive adhesive layer made of an acrylic block copolymer (II-1) having a polymer block B2 content of 82% by mass or more. The wettability to the adherend is better than that of Example 4 having an adhesive layer made of an acrylic block copolymer (II-2) having a content of the combined block B2 of less than 82% by mass, and the wet heat durability is excellent. . Moreover, when the adhesion layer contains acrylic block copolymer (II-1), since an initial stress value is 6.1 * 10 < ⁴ > Pa and probe tack is high, it turns out that it is excellent in level | step difference absorbability.

In addition, the transparent double-sided PSA sheets of Examples 1 to 7 using an acrylic block copolymer for the base material layer have no reworkability because there is no transfer of the PSA layer to the adherend. On the other hand, in the transparent double-sided pressure-sensitive adhesive sheet of Example 9 using an acrylic thermoplastic resin composition as a base material layer and Example 10 using a methacrylic resin composition, the 180 ° peel adhesion measurement was performed at room temperature. Transfer of the pressure-sensitive adhesive layer to the adherend occurred, and adhesive residue was generated when measuring the adhesive force. Moreover, in the transparent double-sided adhesive sheets of Example 9 and Example 10, when glass was used for the adherend, some peeling was observed at the end in the wet heat durability test. When the adherend is polycarbonate, the transparent double-sided pressure-sensitive adhesive sheets of Example 9 and Example 10 have excellent wet heat durability and can be used in these configurations if reworkability is not required. Can be used without problems.
Moreover, since the transparent double-sided pressure-sensitive adhesive sheet of Reference Example 11 uses a PET film having a high refractive index and high storage tensile modulus for the base material layer, the transparency is low and the step absorbability is poor, but the wet heat durability is excellent. . Therefore, the transparent double-sided pressure-sensitive adhesive sheet having this configuration can be used in applications where wet heat durability is required more strongly than transparency and step absorbability.

  The transparent double-sided pressure-sensitive adhesive sheet of the present invention has excellent transparency, adhesive strength, foam resistance, impact resistance, and images such as LCD, EL, PDP, etc., such as electronic paper, PDA, TV, game machine, etc. It can be suitably used when an optical member used in a flat type or flexible image display device using a display panel is bonded and fixed. Moreover, since the transparent double-sided adhesive sheet of this invention is excellent in corrosion resistance, punching property, and level | step difference absorption, it can be used especially suitably when sticking and fixing a touch panel and an image display panel or a touch panel and a surface protection panel.

a Transparent double-sided adhesive sheet b Perforated section (circumference)
c Projection (thread pulling) part: longest part c 'Projection (thread pulling) part: part other than c

Claims (15)

From the polymer block (A) having a glass transition temperature of 50 ° C. or higher obtained by polymerizing at least one monomer selected from a methacrylic acid ester and an acrylic acid ester, and a methacrylic acid ester and an acrylic acid ester. A transparent double-sided pressure-sensitive adhesive sheet containing an acrylic block copolymer (0) containing a polymer block (B) having a glass transition temperature of 20 ° C. or lower obtained by polymerizing at least one selected monomer ,
A base material layer having a storage tensile elastic modulus at 20 ° C. of 6.0 × 10 ⁶ Pa to 3.3 × 10 ⁹ Pa, an adhesive layer (a) on one main surface of the base material layer, and A transparent double-sided pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer (b) on the other main surface, the refractive index difference between the pressure-sensitive adhesive layer (a) and the base material layer, and the refractive index of the pressure-sensitive adhesive layer (b) and the base material layer A transparent double-sided PSA sheet having a difference of 0.05 or less . The transparent double-sided pressure-sensitive adhesive sheet according to claim 1, wherein each of the layers constituting the transparent double-sided pressure-sensitive adhesive sheet contains an acrylic block copolymer (0). The adhesive layer has the following general formula (II):
A3-B2-A4 (II)
(In the formula, A3 and A4 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B2 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
The weight average molecular weight (Mw) is 50,000 to 300,000, the content of the polymer block B2 is 77 to 95% by mass, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. The transparent double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, comprising 20% by mass or more of the acrylic block copolymer (II) which is 0.5. A base material layer having a storage tensile elastic modulus at 20 ° C. of 6.0 × 10 ⁶ Pa or more and 1.0 × 10 ⁹ Pa or less, an adhesive layer (a) on one main surface of the base material layer, and transparent double-sided pressure-sensitive adhesive sheet comprising the adhesive layer on the other main surface (b). Any refractive index of the adhesive layer (a) and the adhesive layer (b) is 1.45 to 1.65 both, the refractive index of the base layer of claim 1 is from 1.46 to 1.65 transparent double-sided pressure-sensitive adhesive sheet according to any. The transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein at least one of the base material layer, the pressure-sensitive adhesive layer (a) and the pressure-sensitive adhesive layer (b) is formed by a hot melt molding method. The transparent double-sided adhesive sheet in any one of Claims 1-6 in which a base material layer contains an acryl-type block copolymer (0). The base material layer has the following general formula (I);
A1-B1-A2 (I)
(In the formula, A1 and A2 each independently represent a methacrylic ester polymer block having a glass transition temperature of 100 ° C. or higher, and B1 represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower.)
The weight average molecular weight (Mw) is 50,000 to 300,000, the content of the polymer block B1 is 49 to 5% by mass, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. The transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 7 , comprising an acrylic block copolymer (I) of 0.5 . Polymer block A1 and the polymer block A2 constituting the acrylic block copolymer of the base layer (I) has no micro-phase separation structure comprising a continuous phase, to any one of claims 1 to 8 The transparent double-sided pressure-sensitive adhesive sheet described. The transparent double-sided pressure-sensitive adhesive sheet according to claim 1, having a thickness of 210 μm or more and 1000 μm or less. The transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 10, which is used for sticking and fixing a touch panel and an image display panel, or a touch panel and a surface protection panel. The member which equips one main surface of the transparent double-sided adhesive sheet in any one of Claims 1-11 with a touch panel, and equips the other main surface with an image display panel or a surface protection panel. A touch panel member of any of an out-cell type, an in-cell type, an on-cell type, a cover glass integrated type, or a cover sheet integrated type, comprising the transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 11. A touch panel member comprising the member of claim 12. An image display device comprising the touch panel member according to claim 13.