JP2012131847A - Active energy ray-curing adhesive agent composition, adhesive sheet, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active energy ray-curing adhesive agent composition, from which an adhesive sheet good in punching processability can be produced highly productively and in a uniform thickness.SOLUTION: The active energy ray-curing adhesive agent composition includes a urethane prepolymer (A) having one ethylenically unsaturated group on one terminal of the molecule and two ethylenically unsaturated groups on the other terminal.

Description

  The present invention relates to a urethane-based active energy ray-curable pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet produced by curing the composition, and a display device using the pressure-sensitive adhesive sheet. More specifically, the present invention relates to a pressure-sensitive adhesive sheet having good punching processability, and an active energy ray-curable pressure-sensitive adhesive composition for obtaining the pressure-sensitive adhesive sheet.

  Adhesive sheets are widely used for various optical system applications. Examples of the pressure-sensitive adhesive sheet for optical systems include a pressure-sensitive adhesive sheet for attaching an optical filter disposed on the front surface of a display device such as a liquid crystal display, an organic EL display, and a plasma display to the display, a mobile phone, and a tablet. There are adhesive sheets for filling the gaps between the components (display panels, touch panels, transparent protective plates, etc.) of display devices such as PCs, car navigation systems, personal computers, ticket vending machines, and bank terminals. Are known. The latter application is described in Patent Documents 1 to 5, for example.

  On the other hand, urethane-based pressure-sensitive adhesive sheets obtained by curing an active energy ray-curable pressure-sensitive adhesive composition such as ultraviolet rays or electron beams are known as pressure-sensitive adhesive sheets (for example, Patent Documents 6 to 9).

Japanese Patent Laid-Open No. 2004-212521 JP 2008-169331 A JP 2008-266473 A JP 2009-98324 A JP 2009-155503 A JP 2006-171261 A JP 2007-254705 A JP 2008-31246 A JP 2008-184538 A

  The pressure-sensitive adhesive sheet used for filling the gaps between the members of the above-described display device and bringing the members into close contact with each other is designed to have a relatively large thickness. In addition, a relatively thick adhesive sheet may be used to impart shock absorption to the optical filter disposed on the display front surface of the display device described above.

  When the thickness of the pressure-sensitive adhesive sheet is increased (for example, the thickness is 50 μm or more, and further 100 μm or more), the handleability and punching workability may be a problem.

  The pressure-sensitive adhesive sheet used in the display device is often punched into sheets according to the screen size of the display device, and preferably has good punchability. When punching processability is poor, the cut part cannot be reattached and separated, the adhesive sticks to the punching blade, and the edge of the punched sheet adhesive sheet is raised and recessed, resulting in flatness The problem of getting worse. The deterioration of the flatness may cause a disadvantage that bubbles are generated when applied to a display device.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet, there are known a thermosetting type and a photo-curing type (active energy ray curable type such as ultraviolet rays). When a thermosetting pressure-sensitive adhesive composition is applied to a release PET film and then thermally cured, the release film may be wrinkled or deformed due to heat, resulting in a uniform coating film. There is a problem that cannot be obtained. When the display panel and the transparent protective plate are bonded together using an adhesive sheet having a non-uniform thickness, there arises a problem that bubbles are mixed.

  In addition, rubber-based and elastomer-based pressure-sensitive adhesives are known as pressure-sensitive adhesives constituting the pressure-sensitive adhesive sheet, but these pressure-sensitive adhesives require a heat-melting step and a cooling step after molding, and are inferior in productivity. There's a problem.

  Accordingly, an object of the present invention is to provide an active energy ray-curable pressure-sensitive adhesive composition capable of producing a pressure-sensitive adhesive sheet with good punching processability and a uniform thickness in view of the above-mentioned problems of the prior art. It is to provide. Another object of the present invention is to provide a pressure-sensitive adhesive sheet comprising the active energy ray-curable pressure-sensitive adhesive composition, and still another object is to provide a display device using the pressure-sensitive adhesive sheet. is there.

The above object of the present invention has been basically achieved by the following invention.
1) an activity characterized by containing a urethane prepolymer (A) having one ethylenically unsaturated group at one end of the molecule and two ethylenically unsaturated groups at the other end Energy ray-curable pressure-sensitive adhesive composition.
2) The active energy ray-curable pressure-sensitive adhesive composition according to 1), further comprising a urethane prepolymer (B) having one ethylenically unsaturated group only at both ends of the molecule.
3) The activity of 1) or 2) further comprising a urethane prepolymer (C) having 1 to 2 ethylenically unsaturated groups at one end of the molecule and having a hydroxyl group at the other end Energy ray-curable pressure-sensitive adhesive composition.
4) The active energy ray-curable pressure-sensitive adhesive composition according to any one of 1) to 3), further comprising a polymerizable monomer.
5) The active energy ray-curable composition according to any one of 1) to 4), further comprising a polymerization initiator.
6) The active energy ray-curable pressure-sensitive adhesive composition according to any one of 1) to 5), which contains substantially no organic solvent.
7) A pressure-sensitive adhesive sheet obtained by curing the active energy ray-curable pressure-sensitive adhesive composition according to any one of 1) to 6).
8) The pressure-sensitive adhesive sheet according to 7), which does not substantially contain a component having a carboxyl group.
9) The pressure-sensitive adhesive sheet according to 7) or 8), wherein the thickness is 50 to 1000 μm.
10) A display device having a display panel and a transparent protective plate, wherein the display panel and the transparent protective plate are in close contact with each other through the pressure-sensitive adhesive sheet of any one of 7) to 9).
11) A display device in which a display panel, a touch panel, and a transparent protective plate are arranged in this order, and the display panel and the touch panel or the touch panel and the touch panel are interposed via the adhesive sheet according to any one of 7) to 9). A display device in which a transparent protective plate is closely attached.
12) The display device according to 10) or 11), wherein a decorative layer is provided on a surface of the transparent protective plate on the display panel side.

  The pressure-sensitive adhesive sheet produced by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention has good punchability. Specifically, when the pressure-sensitive adhesive sheet of the present invention is punched, the punched piece (sheet-fed pressure-sensitive adhesive sheet) can be smoothly separated without reattachment of the cut portion after punching. The flatness of the piece (single-sheet adhesive sheet) is good (no bulge or dent at the end), and adhesion of adhesive (adhesive) to the punching blade is improved.

  The active energy ray-curable pressure-sensitive adhesive composition is suitable for the production of a pressure-sensitive adhesive sheet having a relatively large thickness, and improves productivity and thickness uniformity. Similarly, the active energy ray-curable pressure-sensitive adhesive composition of the present invention is also suitable for producing a pressure-sensitive adhesive sheet having a relatively large thickness. Furthermore, by using a solventless active energy ray-curable pressure-sensitive adhesive composition which is a preferred embodiment of the present invention, the productivity is further improved.

  Moreover, according to the preferable aspect of this invention, generation | occurrence | production of the bubble when it applies to a display apparatus is suppressed. Specifically, the generation of bubbles is suppressed by using the pressure-sensitive adhesive sheet of the present invention in order to close and close the gap between the display panel or touch panel of the display device and the transparent protective plate. In particular, by using the pressure-sensitive adhesive sheet of the present invention, it is possible to effectively suppress the generation of bubbles when the transparent protective plate provided with a decorative layer (black print layer) on the display panel side and the display panel or touch panel are brought into close contact with each other. be able to.

  Furthermore, according to the preferable aspect of this invention, the corrosivity of the transparent conductive film of a touchscreen is improved.

The schematic cross section which shows an example of the display apparatus which adhered the display panel and the transparent protective plate with the adhesive sheet of this invention. The schematic cross section which shows an example of the display apparatus which closely_contact | adhered the display panel, the touch panel, the touch panel, and the transparent protective plate with the adhesive sheet of this invention.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention comprises a urethane prepolymer having one ethylenically unsaturated group at one end of a molecule and two ethylenically unsaturated groups at the other end ( A) is contained. Here, the active energy ray-curable pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition that is cured by irradiating an active energy ray such as an electron beam or ultraviolet rays. After being molded or coated to a thickness of 1, the adhesive sheet of the present invention is obtained by curing.

  The pressure-sensitive adhesive sheet of the present invention obtained from the active energy ray-curable pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive sheet having an appropriate hardness and an appropriate adhesive force, and is excellent in punching workability and each of the display devices. It has the adhesion required to adhere the members.

  Hereinafter, urethane prepolymer (A) having one ethylenically unsaturated group at one end of the molecule and two ethylenically unsaturated groups at the other end (hereinafter referred to as urethane prepolymer (A)) (Abbreviated) will be described in detail.

  The urethane prepolymer (A) preferably does not have an ethylenically unsaturated group in the side chain of the molecule, but has an ethylenically unsaturated group only at both ends of the molecule. Here, examples of the ethylenically unsaturated group include a vinyl group, an allyl group, an acrylic group, and a methacryl group.

  The weight average molecular weight of the urethane prepolymer (A) is preferably 10,000 or more, more preferably 20,000 or more, further preferably 25,000 or more, and particularly preferably 30,000 or more from the viewpoint of improving the punching processability. The upper limit of the weight average molecular weight of the urethane polymer (A) is preferably 60000 or less, more preferably 55000 or less from the viewpoint of suppressing the increase in viscosity of the active energy ray-curable pressure-sensitive adhesive composition and ensuring good coatability. In particular, 50000 or less is preferable.

  The urethane prepolymer (A) includes, for example, a urethane prepolymer (a) having isocyanate groups at both ends of the molecule, a compound (b1) having a functional group capable of reacting with an isocyanate group and one ethylenically unsaturated group. And a functional group capable of reacting with an isocyanate group and a compound (b2) having two ethylenically unsaturated groups. Here, as a functional group which can react with an isocyanate group, a hydroxyl group, a carboxyl group, an amino group, an amide group etc. are mentioned, for example, Among these, a hydroxyl group is especially preferable.

  The urethane prepolymer (a) having an isocyanate group at both ends of the molecule can be synthesized by reacting a polyol and an isocyanate compound. Examples of the polyol include polyester polyol, polyether polyol, polycaprolactone polyol, and polycarbonate polyol. Among these, polyester polyol, polyether polyol, and polycaprolactone polyol are preferable, and polyether polyol is particularly preferable. A urethane polymer obtained using a polyether polyol as a raw material is preferable because it can be maintained without deteriorating the adhesion under high humidity.

  The polyester polyol can be obtained by esterifying a polyvalent carboxylic acid and a polyhydric alcohol. Such polycarboxylic acids include adipic acid, sebacic acid, succinic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, fumaric acid, maleic acid, maleic anhydride, itacone Examples include acids, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, lactic acid, dimer acid, and the like. Of these, adipic acid, sebacic acid, pyrrolimetic acid, and dimer acid are preferable.

  Polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, polyethylene glycol, polybutylene glycol, polypropylene glycol, 1,4-butanediol, 1,6 -Hexanediol, 3-methyl 1,5-pentanediol, ethylene oxide or propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, etc. can be used. Bifunctional alcohols such as 4-butanediol are preferred.

  The polyether polyol can be obtained by an etherification reaction of a polyhydric alcohol. As a polyhydric alcohol used here, the thing similar to the polyhydric alcohol used for manufacture of the said polyester polyol can be used.

  The polycaprolactone polyol is ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, ethylene oxide of bisphenol A, or Examples include propylene oxide adducts, glycerin, trimethylolpropane, trimethylolethane, and ε-caprolactone adducts of known and commonly used polyhydric alcohols such as pentaerythritol.

  Examples of the polycarbonate polyol include a dehydrochlorination reaction between the polyhydric alcohol and phosgene used in the synthesis of the polyester polyol, or a transesterification reaction between the polyhydric alcohol and diethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and the like. What is obtained is mentioned.

  Examples of the isocyanate compound used for the synthesis of the urethane pre-prepolymer (a) having an isocyanate group at both ends of the molecule include tolylene diisocyanate, hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, lysine diisocyanate, naphthalene diisocyanate, hexa Diisocyanate compounds such as methylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and hydrogenated xylylene diisocyanate are preferably used.

  Examples of the compound (b1) having one functional group capable of reacting with an isocyanate group and one ethylenically unsaturated group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl ( (Meth) acrylate, butanediol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, ethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, tetramethylene glycol mono (meth) acrylate, neopentyl glycol Mono (meth) acrylate, hydroxyl group-containing (meth) acrylate such as 2-hydroxyethyl (meth) acrylate modified with caprolactone, (meth) acrylic acid, carboxyethyl (meth) acrylate Carboxyl group-containing (meth) acrylates such as carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, amino group-containing (meth) acrylates such as N, N-diethylaminoethyl (meth) acrylate, (meta ) Amide group-containing (meth) acrylates such as acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide and the like. . Among these, a hydroxyl group-containing (meth) acrylate compound is particularly preferably used.

  Examples of the compound (b2) having two functional groups capable of reacting with an isocyanate group and two ethylenically unsaturated groups include 2-hydroxyethyl di (meth) acrylate, 1-hydroxypropyl di (meth) acrylate, and 1-hydroxyl. Butyl di (meth) acrylate, 4-hydroxybutyl di (meth) acrylate, 2-hydroxypentyl di (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane (meth) A hydroxyl group-containing bifunctional (meth) acrylate compound such as acrylate is preferably used.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention further has a urethane prepolymer (B) having one ethylenically unsaturated group only at both ends of the molecule (hereinafter simply referred to as urethane prepolymer (B)). ) Is preferably contained.

By including the urethane prepolymer (B) in addition to the urethane prepolymer (A), it is possible to suppress the hardness of the pressure-sensitive adhesive sheet from becoming too high and ensure an appropriate adhesion.
The content ratio (molar ratio) of the urethane prepolymer (A) and the urethane prepolymer (B) is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 8: 2, and further 3: The range of 7-7: 3 is preferred.

  The urethane prepolymer (B) has, for example, a urethane prepolymer (a) having isocyanate groups at both ends of the molecule, a functional group capable of reacting with the isocyanate group, and one ethylenically unsaturated group. It can be obtained by reacting with compound (b1). As the urethane prepolymer (a) and the compound (b1), the same compounds as described above can be used.

  Two types of urethane prepolymer (A) and urethane prepolymer (B) can be synthesized simultaneously in one synthesis process. For example, by adjusting the charging ratio of the compound (b1) and the compound (b2) to be reacted with the urethane prepolymer (a) having an isocyanate group at both ends of the molecule, or by adjusting the charging order and charging time, The above two types can be synthesized simultaneously.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention further comprises a urethane prepolymer (C) having 1 to 2 ethylenically unsaturated groups at one end of the molecule and a hydroxyl group at the other end ( Hereinafter, it is preferable to contain a urethane prepolymer (C)).

  It is preferable that said urethane prepolymer (C) does not have an ethylenically unsaturated group in the side chain of a molecule | numerator. The urethane prepolymer (C) preferably has 1 to 2 ethylenically unsaturated groups at one end of the molecule and 1 to 2 hydroxyl groups at the other end. Those having one ethylenically unsaturated group at one end and one or two hydroxyl groups at the other end are preferred, particularly having one ethylenically unsaturated group at one end of the molecule. And one having one hydroxyl group at the other end is preferred.

By containing the urethane prepolymer (C) in addition to the urethane prepolymer (A), it is possible to suppress the hardness of the pressure-sensitive adhesive sheet from becoming too high, and to appropriately increase the adhesion.
The content ratio (molar ratio) of the urethane prepolymer (A) and the urethane prepolymer (C) is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 8: 2, and further 3: The range of 7-7: 3 is preferred.

  The urethane prepolymer (C) has, for example, a urethane prepolymer (a) having isocyanate groups at both ends of the molecule, a functional group capable of reacting with the isocyanate group and one ethylenically unsaturated group. The compound (b2) or the compound (b2) having two functional groups capable of reacting with an isocyanate group and two ethylenically unsaturated groups is reacted with the compound (c) having a functional group capable of reacting with an isocyanate group and a hydroxyl group. Can be obtained. As the urethane prepolymer (a), the compound (b1), and the compound (b2), the same compounds as described above can be used.

  Examples of the compound (c) having a functional group capable of reacting with an isocyanate group and a hydroxyl group include polyvalent carboxylic acids, oxycarboxylic acids, and polyhydric alcohols.

  Examples of the polyvalent carboxylic acid include adipic acid, sebacic acid, malonic acid, succinic acid, glutaric acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, and fumaric acid. , Maleic acid, maleic anhydride, itaconic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, dimer acid, ethane-1,1,2-tricarboxylic acid, hexane-2,3,5 -Known and commonly used organic acids such as tricarboxylic acids are preferably used, but dicarboxylic acids are preferred from the standpoint of compatibility with other components.

  As said oxycarboxylic acid, well-known and usual organic acids, such as lactic acid, glycolic acid, trioxybutyric acid, trioxyvaleric acid, trioxyhexanoic acid, gluconic acid, are used suitably, for example.

  Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, polyethylene glycol, polybutylene glycol, polypropylene glycol, and 1,3-butanediol. 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, bisphenol A ethylene oxide or propylene oxide adduct, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, etc. A polyhydric alcohol can be preferably used. Among them, diols such as 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol are preferable from the viewpoint of compatibility with other components and water absorption stability. Particularly preferred.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention preferably contains a urethane prepolymer (A), a urethane prepolymer (B) and / or a urethane prepolymer (C). ), Urethane prepolymer (B) and urethane prepolymer (C).

  Three types of urethane prepolymer (A), urethane polymer (B), and urethane prepolymer (C) can be synthesized simultaneously in one synthesis process. For example, by adjusting the charging ratio of the compound (b1), the compound (b2), and the compound (c) to be reacted with the urethane prepolymer (a) having an isocyanate group at both ends of the molecule, or the charging order or charging time By adjusting the above, the above three types can be synthesized simultaneously.

  In the active energy ray-curable adhesive composition of the present invention, the content of the urethane prepolymer (A) is preferably 5% by mass or more with respect to 100% by mass of the total solid content of the active energy ray-curable adhesive composition. 10 mass% or more is more preferable, and especially 15 mass% or more is preferable. The upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less. Here, the total solid content of the active energy ray-curable pressure-sensitive adhesive composition means all components other than the organic solvent, and is a polymerizable monomer that is liquid at room temperature (for example, low as used as a reactive diluent). Molecular weight monomer) is included in the solid content.

  A preferred embodiment of the active energy ray-curable pressure-sensitive adhesive composition of the present invention is an embodiment containing a urethane prepolymer (A), a urethane prepolymer (B) and / or a urethane prepolymer (C). The total content of the urethane prepolymer (A), the urethane prepolymer (B) and the urethane prepolymer (C) is 40% by mass or more with respect to 100% by mass of the total solid content of the active energy ray-curable pressure-sensitive adhesive composition. Is preferable, 50 mass% or more is more preferable, and 60 mass% or more is particularly preferable. The upper limit is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention is a polymer other than the above-described urethane prepolymer (A), urethane prepolymer (B) and urethane prepolymer (C), such as an acrylic polymer and a urethane polymer. , Ester polymers, silicon polymers and the like can be contained. It is preferable that content of said other polymer is 30 mass parts or less with respect to 100 mass parts of total amounts of a urethane prepolymer (A), a urethane prepolymer (B), and a urethane prepolymer (C), 20 masses The amount is more preferably at most 10 parts by weight, particularly preferably at most 10 parts by weight.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention preferably further contains a polymerizable monomer. As such a polymerizable monomer, those known as reactive diluents can be used. For example, styrene, vinyl toluene, vinyl acetate, N-vinyl pyrrolidone, N-vinyl formamide, N-vinyl caprolactam, (meth) acryloylmorpholine, cyclohexyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-ethylhexyl ( Monofunctional vinyl monomers and acrylic monomers such as (meth) acrylate, n-hexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol Diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol Lumpur triacrylate, pentaerythritol tetraacrylate, polyfunctional acrylic monomers such as dipentaerythritol hexaacrylate. Among these, monofunctional polymerizable monomers are preferably used.

In the present invention, the following polymerizable monomers are particularly preferably used from the viewpoint of imparting relatively large adhesion to the pressure-sensitive adhesive sheet.
A) a polymerizable monomer having a hydroxyl group, b) a polymerizable monomer having an oxygen atom-containing heterocyclic ring, and c) a polymerizable monomer having a phenyloxy group are preferably used.

  Examples of the polymerizable monomer containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 5-hydroxypentyl (meta). ) Acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, caprolactone modified 2-hydroxyethyl (meth) acrylate, diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, N-methylol (meth) ) Acrylamide, 3-chloro-2-hydroxypropyl (meth) acrylate, 2,2-dimethyl-2-hydroxyethyl (meth) acrylate, and the like.

  (B) The polymerizable monomer having an oxygen atom-containing heterocycle includes monomers having an oxygen atom-containing heterocycle such as furfuryl, morpholine, caprolactan, and examples thereof include tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfur. Examples include furyl (meth) acrylate, N- (meth) acryloylmorpholine, vinyl caprolactam, and the like.

  Examples of the polymerizable monomer having a phenyloxy group described above include, for example, phenoxy (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxy-polyethylene glycol (meth) acrylate, 2-hydroxy- Examples thereof include 3-phenoxypropyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate.

  The total content of polymerizable monomers in the active energy ray-curable pressure-sensitive adhesive composition is preferably in the range of 1 to 50% by mass with respect to 100% by mass of the total solid content of the active energy ray-curable adhesive composition. The range of -40 mass% is more preferable, and the range of 5-30 mass% is particularly preferable.

  The active energy ray-curable pressure-sensitive adhesive composition preferably further contains a polymerization initiator. Commercially available products can be widely used as such polymerization initiators, but the following polymerization initiators are preferably used. Examples include acetophenones such as diethoxyacetophenone and benzyldimethyl ketal, benzoin ethers such as benzoin and benzoin methyl ether, benzophenones such as benzophenone and methyl o-benzoylbenzoate, and hydroxy such as 1-hydroxy-cyclohexyl-phenyl-ketone. Examples include alkylphenones, thioxanthones such as 2-isopropylthioxanthone and 2,4-dimethylthioxanthone, and amines such as triethanolamine and ethyl 4-dimethylbenzoate.

  The content of the polymerization initiator is suitably in the range of 0.05 to 5% by mass with respect to the total solid content of 100% by mass of the active energy ray-curable pressure-sensitive adhesive composition, and is 0.1 to 3% by mass. A range is preferred.

  The pressure-sensitive adhesive sheet of the present invention obtained by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention preferably does not substantially contain a component having a carboxyl group. When the pressure-sensitive adhesive sheet contains a component having a carboxyl group, there may be a problem that the transparent conductive layer constituting the touch panel of the display device is corroded.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention is that the pressure-sensitive adhesive sheet of the present invention obtained by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention does not substantially contain a component having a carboxyl group. Urethane prepolymers (urethane prepolymer (A), urethane prepolymer (B) and urethane prepolymer (C)), polymerizable monomers, and other urethane prepolymers used as necessary A polymer means that it does not have a carboxyl group in the molecule.

  The active energy ray-curable pressure-sensitive adhesive composition is preferably a so-called solventless type that does not substantially contain an organic solvent. Here, the active energy ray-curable pressure-sensitive adhesive composition substantially does not contain an organic solvent means that the amount of the organic solvent contained in 100% by mass of the active energy ray-curable pressure-sensitive adhesive composition is 5% by mass or less. The amount of the organic solvent is preferably 3% by mass or less, more preferably the amount of the organic solvent is 1% by mass or less, and particularly preferably no organic solvent is contained.

  The organic solvent is a highly volatile organic solvent such as methyl ethyl ketone, methyl isobutyl ketone, toluene, butyl acetate, ethanol, and methanol, and particularly an organic solvent having a boiling point of 130 ° C. or less.

  The organic solvent does not include a liquid polymerizable monomer (for example, a low-molecular (meth) acrylate monomer used as a reactive diluent).

  By making the active energy ray-curable pressure-sensitive adhesive composition a solvent-free type, the safety and environmental performance in the production process are improved, and the residual solvent of the obtained pressure-sensitive adhesive is greatly reduced. In addition, the solvent-free type is preferable because the drying process at the time of producing the pressure-sensitive adhesive sheet can be omitted, so that the production process is shortened and the production efficiency is improved.

  The active energy ray-curable pressure-sensitive adhesive composition preferably contains an antioxidant or a light stabilizer in order to prevent yellowing.

  As the antioxidant, a hindered phenol antioxidant and a phosphorus antioxidant are preferably used. As the light stabilizer, a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group is preferably used.

  Examples of the hindered phenol antioxidant include triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], ethylenebis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate], hexamethylene-bis [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], isooctyl-3- 3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis ( 3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, diethyl [(3 5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl] phosphate, 3,5-di-tert-butyl-4-hydroxybenzyl phosphonate-diethyl ester, 3,3 ′, 3 ″ , 5,5 ′, 5 ″ -hexa-t-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, 1,1,3-tris ( 2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5- Tris (4-sec-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-neopentyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 2,2 ′ -Methylenebis (4 -Methyl-6-t-butylphenol), 4,4'-butylidenebis (4-methyl-6-t-butylphenol), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, Tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, polycondensate of p-chloromethylstyrene and p-cresol, polycondensate of p-chloromethylstyrene and divinylbenzene, p -An isobutylene reaction product of cresol and divinylbenzene polycondensate, and the like.

  Among the above compounds, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], ethylenebis (oxyethylene) bis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate], hexamethylene-bis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], isooctyl-3- (3,5-di-t-butyl-4- Hydroxyphenyl) propionate compounds such propionate are preferably used.

  Examples of phosphorus antioxidants include triphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, diphenyl octyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tetrakis (2, 4-di-t-butylphenyl) -4,4'-biphenylene phosphite, trisnonylphenyl phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphos Phyto, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4- Dicumylphenyl) pentaerythrito Ru-diphosphite, tetrakis (2,4-di-t-butylphenyl) (1,1-biphenyl) -4,4'-diylbisphosphonite, di-t-butyl-m-cresyl-phosphonite, distearyl penta Erythritol diphosphite, di (2,4-di-t-butylphenyl) -pentaerythryl diphosphite, di (2,6-di-t-butyl-4-methylphenyl) -pentaerythryl diphosphite 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl-ditridecyl) phosphite, cyclic neopentanetetrayl (octadecyl phosphite), diisodecyl pentaerythritol diphosphite, 2,2-methylene bis (4,6-di-t-butylphenyl) octyl phosphite, bis (tridecyl ) Pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, hydrogenated bisphenol A pentaerythritol phosphite polymer, hydrogenated bisphenol A phosphite polymer, tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite, tetra ( Tridecyl) -4,4′-isopropylidene diphenyl diphosphite, tetraphenyl dipropylene glycol diphosphite and the like.

  Among these, triphenyl phosphites such as triphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, diphenyl octyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, diphenyl alkyl phosphite, etc. Phytes and monophenyl dialkyl phosphites are preferably used.

  A monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group that can be used in the present invention will be described. The sterically hindered piperidyl group in such a monomer is one having 1 to 2 alkyl groups at the 2-position and 6-position of the piperidyl group, respectively. The ethylenically unsaturated group is an acryl group (acryloyl group), A methacryl group (methacryloyl group), a crotonoyl group, a vinyl group, an allyl group, etc., and an ethylenically unsaturated group is directly or directly at the 1-position and / or 4-position of a sterically hindered piperidyl group, or a linking group such as an oxygen atom or imino group It is a compound bound via

  Monomers having a sterically hindered piperidyl group and an ethylenically unsaturated group that are preferably used in the present invention can be represented by the following general formulas (1) and (2).

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ^{2 to} R ⁵ each independently represents an alkyl group having 1 to 4 carbon atoms, and R ⁶ represents a hydrogen atom or a cyano group. R ⁷ and R ⁸ each independently represents a hydrogen atom or a methyl group, and X ¹ represents an oxygen atom or an imino group.)

(Wherein R ^{12 to} R ¹⁵ each independently represents an alkyl group having 1 to 4 carbon atoms, R ¹⁶ represents a hydrogen atom or a cyano group, and R ^{17 to} R ²⁰ each independently represents a hydrogen atom or methyl) And X ² represents an oxygen atom or an imino group.

  Examples of the compound represented by the general formula (1) include 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6. -Tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4 -Cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2 , 6,6-tetramethylpiperidine and the like.

  Examples of the compound represented by the general formula (2) include 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4. -Cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine and the like.

  Among the compounds described above, the compound represented by the general formula (1) is preferable, and 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1, 2,2,6,6-pentamethylpiperidine is preferably used.

  The content ratio of the hindered phenol antioxidant, the phosphorus antioxidant, and the monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group is the solid content of the active energy ray-curable composition. The range of 0.05-5 mass% is preferable with respect to the total amount of 100 mass%, and the range of 0.1-3 mass% is more preferable.

  The active energy ray-curable pressure-sensitive adhesive composition can further contain a polymerization inhibitor. As such a polymerization inhibitor, hydroquinone, hydroquinone monomethyl ether, benzoquinone, pt-butylcatechol, 2,6-dibutyl-4-methylphenol and the like can be used.

  The active energy ray-curable pressure-sensitive adhesive composition includes various additives other than those described above as necessary, for example, antioxidants, antifoaming agents, leveling agents, light stabilizers, ultraviolet absorbers, anti-coloring agents, A pigment, a tackifier (tackifier), and the like can be contained.

  The pressure-sensitive adhesive sheet obtained by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention is obtained by molding or coating the above-described active energy ray-curable pressure-sensitive adhesive composition of the present invention to a predetermined thickness, and then active energy. Manufactured by irradiating a wire to cure. Specifically, after an active energy ray-curable pressure-sensitive adhesive composition is applied to a release sheet (for example, a release PET film) to a predetermined thickness, the active energy ray is irradiated and cured, thereby causing the pressure-sensitive adhesive. A sheet is produced.

  Examples of the active energy rays include ultraviolet rays, electron beams, and radiation (α rays, β rays, γ rays, etc.). In practice, ultraviolet rays are simple and preferable. As the ultraviolet ray source, an ultraviolet fluorescent lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a xenon lamp, a carbon arc lamp, or the like can be used. Further, when irradiating active energy rays, it is preferable to irradiate under a low oxygen concentration because it can be cured efficiently.

  When irradiating active energy rays, it is preferable to irradiate in an atmosphere having a low oxygen concentration. Thereby, yellowing of the obtained pressure-sensitive adhesive sheet can be suppressed and can be cured efficiently.

  The oxygen concentration when irradiated with active energy rays is preferably 3000 ppm or less, more preferably 1000 ppm or less, and particularly preferably 500 ppm or less. The lower limit of the oxygen concentration is about 50 ppm from an economical viewpoint.

  As a method of reducing the oxygen concentration, a method of injecting an inert gas such as nitrogen gas and replacing it with oxygen is preferably used. In this case, it is preferable to seal as much as possible so that the outside air does not enter the active energy ray irradiating apparatus, and to blow an inert gas such as nitrogen gas therein to lower the oxygen concentration.

  Further, as a method of irradiating active energy rays in an atmosphere having a low oxygen concentration, another release sheet (on the active energy ray-curable pressure-sensitive adhesive composition coated on a release sheet (for example, a release PET film)) ( For example, a method of irradiating active energy rays in a state where oxygen is blocked by laminating a release PET film or the like can also be preferably used.

  The pressure-sensitive adhesive sheet of the present invention obtained by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention is suitable for optical system applications. For example, the pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet disposed between the display panel of the display device and the transparent protective plate.

  The mode in which the pressure-sensitive adhesive sheet of the present invention is disposed between the display panel and the transparent protective plate is as follows: a) a mode in which the pressure-sensitive adhesive sheet of the present invention is used to adhere the display panel and the transparent protective plate; A mode in which the pressure-sensitive adhesive sheet of the present invention is used to bring the display panel and the touch panel into close contact with each other when the touch panel is disposed between the display panel and the transparent protective plate. C) The touch panel is disposed between the display panel and the transparent protective plate. The mode which uses the pressure sensitive adhesive sheet of the present invention in order to stick a touch panel and a transparent protective board in the case of being carried out is mentioned.

  FIG. 1 is a schematic cross-sectional view showing an example of a display device in which a display panel and a transparent protective plate are in close contact with each other by the pressure-sensitive adhesive sheet of the present invention, and shows the above-mentioned aspect (a). The display panel 3 and the transparent protective plate 1 are in close contact via the adhesive sheet 2 of the present invention. A decorative layer (black print layer) 4 for fringing the image display area is provided on the outer peripheral edge of the surface of the transparent protective plate 1 on the display panel 3 side.

  FIG. 2 is a schematic cross-sectional view showing an example of a display device in which a display panel, a touch panel, a touch panel, and a transparent protective plate are in close contact with each other by the pressure-sensitive adhesive sheet of the present invention, and shows the above aspects b) and c). . The display panel 3 and the touch panel 5 and the touch panel 5 and the transparent protective plate 1 are in close contact with each other via the adhesive sheet 2 of the present invention. A decorative layer (black print layer) 4 for fringing the image display area is provided on the outer peripheral edge of the surface of the transparent protective plate 1 on the display panel 3 side.

  In FIG. 2, the above aspects b) and c) are carried out together, but they may be carried out independently. That is, the pressure-sensitive adhesive sheet 2 of the present invention may be used only between the display panel 3 and the touch panel 5, or the pressure-sensitive adhesive sheet 2 of the present invention may be used only between the touch panel 5 and the transparent protective plate 1.

  Examples of the display panel include a liquid crystal display panel and an organic EL display panel. Examples of the touch panel include a capacitive touch panel formed of a transparent conductive member in which a transparent conductive film such as an ITO film is laminated. Examples of the transparent protective plate include a glass plate and a plastic resin plate (for example, an acrylic resin plate, a polycarbonate resin plate, a polyester resin plate, etc.). The thickness of the transparent protective plate is generally about 0.3 to 3 mm, and more specifically in the range of 0.5 to 2 mm.

  The decorative layer provided on the transparent protective plate is, for example, a colored layer for bordering a region corresponding to the image display region of the display panel, and is provided on the outer periphery of the transparent protective plate by printing or the like. The decorative layer preferably does not transmit light, and therefore the color of the decorative layer is preferably black, and the thickness is preferably relatively large.

  From the above viewpoint, the thickness of the decorative layer is preferably 5 μm or more, more preferably 10 μm or more, and particularly preferably 15 μm or more. The upper limit is about 40 μm.

  The thickness of the pressure-sensitive adhesive sheet used in the display device described above is sufficient to fill the gaps between the display panel, touch panel, and transparent protective plate without gaps, or to sufficiently fill the step at the edge of the decorative layer of the transparent protective plate. Therefore, it is designed relatively large. Specifically, the thickness of the pressure-sensitive adhesive sheet is preferably 50 μm or more, more preferably 100 μm or more, further preferably 120 μm or more, and particularly preferably 150 μm or more. The upper limit of the thickness is about 1000 μm.

  Accordingly, the thickness of the pressure-sensitive adhesive sheet of the present invention is also preferably 50 μm or more, more preferably 100 μm or more, further preferably 120 μm or more, and particularly preferably 150 μm or more. The upper limit of the thickness is about 1000 μm.

  The pressure-sensitive adhesive sheet used in the above display device is often punched into sheets in accordance with the screen size of the display device, and preferably has good punchability. When punching processability is poor, the problem is that the cut part cannot be reattached and separated, the problem that the adhesive adheres to the punching blade, the edge of the punched sheet adhesive sheet is deformed, and the flatness is deteriorated. Problems arise. The deterioration of the flatness may cause a disadvantage that bubbles are generated when applied to a display device.

  Since the punching processability of the pressure-sensitive adhesive sheet tends to deteriorate as the thickness of the pressure-sensitive adhesive sheet increases, the punching processability of the pressure-sensitive adhesive sheet used in the display device is important. Since the pressure-sensitive adhesive sheet of the present invention is excellent in punching workability, it is suitable for the display device.

  From the viewpoint of improving the punching workability, the adhesive sheet preferably has a higher hardness. As described above, when the active energy ray-curable pressure-sensitive adhesive composition contains the urethane prepolymer (A), a pressure-sensitive adhesive sheet having a relatively large hardness can be obtained.

  The hardness of an adhesive sheet can be represented by Asker C hardness, for example. The Asker C hardness of the pressure-sensitive adhesive sheet of the present invention is preferably 15 or more, more preferably 18 or more, further preferably 20 or more, and particularly preferably 22 or more. The upper limit is preferably 50 or less, more preferably 45 or less, still more preferably 40 or less, and particularly preferably 35 or less. By setting the Asker C hardness of the pressure-sensitive adhesive sheet within the above range, the punching processability is improved.

  Further, as described above, when the decorative layer is provided on the transparent protective plate, when the display panel and the transparent protective plate, or the touch panel and the transparent protective plate are brought into close contact with each other via the adhesive sheet, Air bubbles are likely to be generated at the stepped portion of the decorative layer. In particular, when the thickness of the decorative layer becomes relatively large as described above, the generation of bubbles is promoted.

  In order to suppress the generation of bubbles, it is effective that the adhesive sheet has a larger initial adhesion. Here, the initial adhesion is an adhesion after 5 minutes after the pressure-sensitive adhesive sheet is bonded to the soda glass plate.

  In general, the adhesive strength of the pressure-sensitive adhesive sheet tends to increase with the lapse of time after bonding, but the initial adhesive strength is important for suppressing the generation of bubbles.

  The initial adhesive strength of the pressure-sensitive adhesive sheet of the present invention is preferably 8 N / 25 mm or more, more preferably 10 N / 25 mm or more, further preferably 11 N / 25 mm or more, and particularly preferably 12 N / 25 mm or more. The upper limit is about 50 N / 25 mm. Generation of bubbles is suppressed by setting the initial adhesive force of the pressure-sensitive adhesive sheet within the above range.

  The pressure-sensitive adhesive sheet of the present invention preferably has a shear modulus of 0.5 MPa or less, more preferably 0.4 MPa or less, and particularly preferably 0.3 MPa or less. The lower limit of the shear modulus is preferably 0.05 MPa or more, more preferably 0.08 MPa or more, and particularly preferably 0.1 MPa or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. In addition, the measuring method and evaluation method in a present Example are shown below.

1) Measurement of Asker C hardness An adhesive sheet was laminated so that the total thickness was about 6 mm, and a measurement sample was prepared. In accordance with SRIS0101 (Japan Rubber Association standard), the measurement was performed using an Asker C hardness meter (Digital Rubber Hardness Tester DD2-C type, Polymer Measuring Instruments Co., Ltd.), with an ambient temperature and humidity of 23 ± 2 ° C., 50 Performed at ± 5% RH. The measurement was performed 5 times, and the measurement data of 3 times excluding the maximum value and the minimum value were averaged.

2) Measurement of initial adhesive strength After the adhesive sheet prepared in this example was cut to a width of 25 mm and one release PET film was peeled off, it was pasted on a 100 μm thick polyethylene terephthalate film and measured after 24 hours. A sample was prepared.
The other release PET film of the above measurement sample was peeled off at an ambient temperature and humidity of 23 ± 2 ° C. and 50 ± 5% RH, and held on a polyethylene glass terephthalate film on a 1.8 mm thick soda glass plate. The pressure-sensitive adhesive sheet was affixed, and a rubber roller having a weight of 2 kg was reciprocated once and pressed. After a lapse of 5 minutes after the pressure bonding, a 180 degree peel test was conducted using Tensilon RTM-100 (Orientec Co., Ltd.) at a peel rate of 300 mm / min. The measurement was performed 5 times, and the measurement data of 3 times excluding the maximum value and the minimum value were averaged. The glass plate was washed with methyl ethyl ketone and then washed with ethyl alcohol.

3) Evaluation of punching workability When the pressure-sensitive adhesive sheet prepared in this example (laminated with a release PET film on both sides of the pressure-sensitive adhesive sheet) was punched into a sheet size of 22 cm × 17 cm with a mold. The situation was mainly observed at the following points A) and B) and evaluated according to the following criteria.
A) Whether it can be easily separated without reattachment of the cut portion.
B) Whether the edge of the punched sheet adhesive sheet is kept flat without being deformed.
○: The number of sheets that cannot be separated is less than 10 out of 100 sheets, and the number of sheets in which the edge of the punched sheet adhesive sheet is deformed is less than 10.
Δ: In 100 sheets, the number of sheets that cannot be separated is 10 or more and less than 20, or the number of the deformed end portions of the punched sheet adhesive sheet is 10 or more and less than 20.
X: When the number of sheets that cannot be separated is 20 or more out of 100 sheets, or the number of sheets in which the edge of the punched sheet adhesive sheet is deformed is 20 or more.

4) Evaluation of bubble generation Using the pressure-sensitive adhesive sheet produced in this example, the touch panel of the display device shown in FIG. 2 and a transparent protective plate (having a decorative layer around a glass plate having a thickness of 0.7 mm). After adhering, it was observed whether bubbles were generated near the decorative layer (thickness 20 μm black print layer) of the transparent protective plate, and evaluated according to the following criteria. The area of the image display area of this display device is 300 cm ² (20 cm × 15 cm).
○: No bubbles are generated.
X: Bubbles are generated.

5) Measuring method of weight average molecular weight The weight average molecular weight of the urethane prepolymer was measured by GPC. For measurement, WALTERS GPC-150C Plus (manufactured by Japan WALTERS) was used under the following conditions.
Detector: WALTERS 2410
・ Solvent: Tetrahydrofuran ・ Column: 2 HR4, 1 HR4E (7.5 mm × 300 mm)
・ Temperature: 40 ℃
・ Concentration: 0.2%
・ Injection volume: 100 μl
・ Flow velocity: 1.0m / m
-N number: 3.

<Synthesis of Urethane Prepolymer 1>
In a flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, 97.98 parts by mass of polypropylene glycol (“Exenol 3020” manufactured by Asahi Glass Urethane Co., Ltd., number average molecular weight 3200), dibutyltin dilaurate 11 parts by mass were charged. Next, the temperature inside the system was raised to 70 ° C. while blowing nitrogen gas, and after dissolving uniformly, 7.38 parts by mass of isophorone diisocyanate was added, and the temperature was kept while stirring for 3 hours. Thus, a urethane prepolymer (a1) having isocyanate groups at both ends of the molecule was synthesized. Subsequently, while blowing oxygen gas and nitrogen gas, 0.551 parts by mass of 4-hydroxybutyl acrylate, 0.153 parts by mass of glycerin diacrylate, and 0.047 parts by mass of 1,3-butanediol were sequentially added and stirred for 3 hours. While maintaining the temperature while measuring the molecular weight every 30 minutes, it was confirmed that the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was constant at 1.5, and the reaction was terminated. Prepolymer 1 (weight average molecular weight 41500) was obtained. This urethane prepolymer 1 includes a urethane prepolymer (A) having one ethylenically unsaturated group at one end of the molecule and two ethylenically unsaturated groups at the other end, Urethane prepolymer (B) having one ethylenically unsaturated group at each end, and urethane prepolymer having a hydroxyl group at one end of the molecule and one ethylenically unsaturated group at the other end (C) in a ratio of 3: 5: 2 (molar ratio).

<Synthesis of Urethane Prepolymer 2>
In a flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 91.86 parts by mass of “Kuraray polyol P-3010” [polyester polyol (diol type, number average molecular weight 3000) manufactured by Kuraray Co., Ltd.] Then, 0.11 part by mass of dibutyltin dilaurate was charged. Next, the temperature inside the system was raised to 70 ° C. while blowing nitrogen gas, and after uniformly dissolving, 8.65 parts by mass of isophorone diisocyanate was added, and the temperature was kept while stirring for 3 hours. Thus, a urethane prepolymer (a2) having isocyanate groups at both ends of the molecule was synthesized. Subsequently, while blowing oxygen gas and nitrogen gas, 1.27 parts by mass of 2-hydroxyethyl acrylate and 0.42 parts by mass of 1,3-butanediol were sequentially added and kept warm for 3 hours while stirring. As a result of molecular weight measurement, it was confirmed that the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was constant at 1.5, and the reaction was terminated. Urethane prepolymer 2 (weight average molecular weight 22000) Got. The urethane prepolymer 2 includes a urethane prepolymer (B) having one ethylenically unsaturated group at each of both ends of the molecule, and one ethylenically unsaturated group at one end of the molecule and the other. The urethane prepolymer (C) having one hydroxyl group at the terminal thereof is contained at a ratio of 4: 6 (molar ratio).

<Synthesis of urethane prepolymer 3>
In a flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 97.98 parts by mass of “Exenol 3020” [polypropylene glycol (number average molecular weight 3200) manufactured by Asahi Glass Urethane Co., Ltd.], dilauric acid 0.11 part by mass of dibutyltin was charged. Next, the temperature inside the system was raised to 70 ° C. while blowing nitrogen gas, and after uniformly dissolving, 8.65 parts by mass of isophorone diisocyanate was added, and the temperature was kept while stirring for 3 hours. Thus, a urethane prepolymer (a3) having isocyanate groups at both ends of the molecule was synthesized. Subsequently, 0.9 parts by mass of 2-hydroxyethyl acrylate and 0.7 parts by mass of 1,3-butanediol were sequentially added while blowing oxygen gas and nitrogen gas, and the mixture was kept warm for 3 hours while stirring. As a result of molecular weight measurement, it was confirmed that the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was constant at 1.5, and the reaction was terminated. Urethane prepolymer 3 (weight average molecular weight 24000) Got. This urethane prepolymer 3 is a urethane prepolymer (C) having one ethylenically unsaturated group at one end of the molecule and one hydroxyl group at the other end.

<Synthesis of urethane prepolymer 4>
In a flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 97.98 parts by mass of “Exenol 3020” [polypropylene glycol (number average molecular weight 3200) manufactured by Asahi Glass Urethane Co., Ltd.], dilauric acid 0.11 part by mass of dibutyltin was charged. Next, the temperature inside the system was raised to 70 ° C. while blowing nitrogen gas, and after uniformly dissolving, 8.65 parts by mass of isophorone diisocyanate was added, and the mixture was kept warm with stirring for 3 hours. A urethane prepolymer (a4) was obtained. 200 parts by mass of this urethane prepolymer (a4) was charged into a flask equipped with a stirrer, a thermometer and a reflux condenser, the temperature inside the system was raised to 80 ° C., 3.69 parts of 2-hydroxyethyl acrylate, hydroquinone 0.22 part of monomethyl ether was added, and the mixture was kept warm for 3 hours while stirring, and as a result of IR measurement, it was confirmed that the isocyanate group had disappeared, and the reaction was terminated to obtain urethane prepolymer 4 (weight average molecular weight 24000). This urethane prepolymer 4 is a urethane prepolymer (B) having one ethylenically unsaturated group at each end of the molecule.

<Synthesis of urethane polymer 5>
In a flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, 91.86 parts of “Kuraray polyol P-3010” [polyester polyol (diol type, number average molecular weight 3000) manufactured by Kuraray Co., Ltd.] 0.11 part of dibutyltin dilaurate was charged. Next, while nitrogen gas was blown into the system, the temperature in the system was raised to 70 ° C. and dissolved uniformly, and then 8.65 parts of isophorone diisocyanate was added, and the temperature was kept while stirring for 3 hours. Thus, a urethane prepolymer (a2) having isocyanate groups at both ends of the molecule was synthesized. Subsequently, 1.4 parts of 1,3-butanediol was added while blowing oxygen gas and nitrogen gas, and the mixture was kept warm for 3 hours while stirring. As a result of GPC measurement every 30 minutes, the weight average molecular weight (Mw) and number average After confirming that the ratio Mw / Mn of the molecular weight (Mn) was constant at 1.5, the reaction was terminated, and urethane polymer 5 (weight average molecular weight 22000) was obtained. This urethane polymer 5 is a urethane polymer having hydroxyl groups at both ends of the molecule.

Example 1
A pressure-sensitive adhesive sheet was prepared in the following manner.
<Preparation of solvent-free active energy ray-curable pressure-sensitive adhesive composition>
90 parts by mass of the urethane prepolymer 1, 14 parts by mass of 4-hydroxybutyl acrylate as a polymerizable monomer, 10 parts by mass of phenoxyethyl acrylate, and a hydroxyalkylphenone photopolymerization initiator (Ciba Specialty Chemicals ( Co., Ltd. "Irgacure 184") 0.7 parts by mass, triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] as a hindered phenol antioxidant 1 part by mass, 0.5 part by mass of triphenyl phosphite as a phosphorus-based antioxidant, 4- (meth) acryloyloxy-1,2, as a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group Add 0.5 parts by mass of 2,6,6-pentamethylpiperidine and mix uniformly The Rukoto, solventless actinic radiation-curable adhesive composition of (UV-curable composition) was prepared.

<Production of pressure-sensitive adhesive sheet>
The above active energy ray-curable pressure-sensitive adhesive composition is coated on a release PET film (Therapy (registered trademark) manufactured by Toray Film Processing Co., Ltd.) with a slit die coater, and then oxygenated by blowing nitrogen gas. In a state where the concentration is 300 ppm, an adhesive layer is formed by irradiating with a metal halide lamp with an ultraviolet ray (integrated light amount 1500 mJ / cm ² ), and a release PET film (manufactured by Toray Film Processing Co., Ltd.) is formed on the adhesive layer. The pressure-sensitive adhesive sheet was prepared by laminating therapy (registered trademark). The thickness of the obtained pressure-sensitive adhesive sheet was 175 μm (excluding the release PET film).

(Comparative Example 1)
<Preparation of solvent-free active energy ray-curable pressure-sensitive adhesive composition>
82 parts by mass of the urethane prepolymer 2, 7 parts by mass of 2-ethylhexyl acrylate as a polymerizable monomer, 6 parts by mass of 2-acryloyloxyethyl-succinic acid, and a hydroxyalkylphenone photopolymerization initiator ( 1 part by weight of Ciba Specialty Chemicals Co., Ltd. “Irgacure 184”) and triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) as a hindered phenol antioxidant 1 part by weight of propionate], 0.5 part by weight of triphenyl phosphite as a phosphorus antioxidant, and 4- (meth) acryloyloxy-1 as a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group , 2,2,6,6-pentamethylpiperidine is added in an amount of 0.5 parts by mass and mixed uniformly. By solvent-free active energy ray-curable pressure-sensitive adhesive composition of the (UV curable compositions) were prepared.

<Production of pressure-sensitive adhesive sheet>
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the solventless active energy ray-curable pressure-sensitive adhesive composition was used.

(Comparative Example 2)
In the preparation of the solventless active energy ray-curable pressure-sensitive adhesive composition of Comparative Example 1, a solventless active energy ray was obtained in the same manner as in Comparative Example 1 except that the urethane prepolymer 2 was changed to the urethane prepolymer 3. A curable adhesive composition was prepared, and an adhesive sheet was prepared in the same manner as in Comparative Example 1.

(Comparative Example 3)
<Preparation of solvent-free active energy ray-curable pressure-sensitive adhesive composition>
30 parts by mass of the urethane prepolymer 4, 30 parts by mass of the urethane polymer 5, 20 parts by mass of 2-hydroxyethyl acrylate as a polymerizable monomer, 20 parts by mass of styrene, and a hydroxyalkylphenone photopolymerization as a polymerization initiator 1 part by weight of an agent (Ciba Specialty Chemicals Co., Ltd. “Irgacure 184”), triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxy) as a hindered phenol-based antioxidant 1) parts by weight of phenyl) propionate], 0.5 parts by weight of triphenyl phosphite as a phosphorus antioxidant, and 4- (meth) acryloyloxy as a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group -Add 0.5 parts by mass of 1,2,2,6,6-pentamethylpiperidine By homogeneously mixing, solvent-free active energy ray-curable pressure-sensitive adhesive composition of the (UV curable compositions) were prepared.

<Production of pressure-sensitive adhesive sheet>
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the solventless active energy ray-curable pressure-sensitive adhesive composition was used.

<Evaluation>
About each adhesive sheet produced above, punching workability, bubble generation, Asker C hardness and initial adhesion were evaluated. The results are shown in Table 1.

  The examples of the present invention have good punchability and no generation of bubbles.

  On the other hand, in Comparative Example 1, bubbles are generated because the initial adhesion is small. Since Comparative Example 2 has a low hardness, the punching workability is inferior. In Comparative Example 3, bubbles are generated because the initial adhesion is small.

  Moreover, since the comparative examples 1 and 2 contain the monomer (2-acryloyloxyethyl-succinic acid) which has a carboxyl group as a polymerizable monomer in an active energy ray hardening adhesive composition, the transparent conductivity of a touch panel is included. The film was corroded.

DESCRIPTION OF SYMBOLS 1 Transparent protective board 2 Adhesive sheet of this invention 3 Display panel 4 Decorating layer of a transparent protective board 5 Touch panel

Claims (12)

  An active energy ray comprising a urethane prepolymer (A) having one ethylenically unsaturated group at one end of the molecule and two ethylenically unsaturated groups at the other end Curable adhesive composition.   The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, further comprising a urethane prepolymer (B) having one ethylenically unsaturated group only at both ends of the molecule. The active energy ray curing according to claim 1 or 2, further comprising a urethane prepolymer (C) having 1 to 2 ethylenically unsaturated groups at one end of the molecule and a hydroxyl group at the other end. Adhesive composition. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, further comprising a polymerizable monomer.   Furthermore, the active energy ray curable composition in any one of Claims 1-4 containing a polymerization initiator.   The active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 5, which contains substantially no organic solvent.   A pressure-sensitive adhesive sheet obtained by curing the active energy ray-curable pressure-sensitive adhesive composition according to claim 1.   The pressure-sensitive adhesive sheet according to claim 7, which contains substantially no component having a carboxyl group. The pressure-sensitive adhesive sheet according to claim 7 or 8, wherein the thickness is 50 to 1000 µm. A display device having a display panel and a transparent protective plate, wherein the display panel and the transparent protective plate are in close contact with each other through the pressure-sensitive adhesive sheet according to claim 7. A display device in which a display panel, a touch panel, and a transparent protective plate are arranged in this order, and the display panel and the touch panel or the touch panel and the transparent protective plate via the adhesive sheet according to claim 7. Is a display device that is closely attached. The display device according to claim 10 or 11, wherein a decoration layer is provided on a surface of the transparent protective plate on the display panel side.

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