JP2012251030A - Adhesive sheet, electrostatic capacity-type touch panel with surface protective layer, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet for an electrostatic capacity-type touch panel, capable of preventing detection sensitivity from degrading in the electrostatic capacity-type touch panel.SOLUTION: The adhesive sheet is arranged between the electrostatic capacity-type touch panel and a surface protective layer, wherein relative permittivity is ≥5.0.

Description

  The present invention relates to an adhesive sheet used for adhesion between a capacitive touch panel and a surface protective layer, a capacitive touch panel with a surface protective layer using the adhesive sheet, and a display device.

  In recent years, electronic devices such as mobile phones / smartphones, car navigation systems, personal computers, ticket vending machines and the like equipped with touch panels are increasing. Examples of the main touch panel operation method include a resistance film type, a capacitance type, an optical type, an ultrasonic type, and an electromagnetic induction type. Among these, the resistive film type is widely adopted from the viewpoint of manufacturing cost. In recent years, capacitive touch panels have been widely used for smartphones and tablet-type personal computers, and the demand is increasing as these markets expand.

  In general, there are many cases where a surface protective layer such as a glass plate is provided on the surface of the touch panel, and the surface protective layer is attached to the touch panel via an air layer (void) or an adhesive (adhesive sheet). . For example, Patent Documents 1 to 3 disclose that a surface protective layer is attached to a touch panel via an adhesive.

  Patent Documents 1 to 3 propose that the surface protective layer and the touch panel are closely integrated with an acrylic adhesive or a silicone adhesive.

  On the other hand, a glass plate is generally used as a material for the surface protective layer, but as a display device having a relatively large display screen such as a tablet-type personal computer becomes widespread, the weight of the display device is required. . As one means for reducing the weight of the display device, it is desired to change the surface protective layer to a relatively lightweight resin plate or resin film such as an acrylic resin or a polycarbonate resin.

JP 2009-120675 A JP 2010-163591 A JP 2011-74308 A

  In the capacitive touch panel, when an insulator such as a surface protective layer, an air layer, or an adhesive is interposed between the finger and the touch panel electrode when inputting with a finger, the electrostatic capacity becomes small, Detection sensitivity at the time of input may decrease, and operability may decrease.

  Further, when the surface protective layer is changed from a glass plate to a resin plate such as an acrylic resin plate or a polycarbonate resin plate, there is a problem that the detection sensitivity is further lowered and the operability is lowered.

  Accordingly, an object of the present invention is to provide an adhesive sheet for a capacitive touch panel that can suppress a decrease in detection sensitivity in the capacitive touch panel in view of the above problems. Another object of the present invention is to provide a capacitive touch panel with a surface protective layer in which the capacitive touch panel and the surface protective layer are in close contact using the adhesive sheet of the present invention and a display device using the same. There is to do.

The above object of the present invention has been basically achieved by the following invention.
1) A pressure-sensitive adhesive sheet disposed between a capacitive touch panel and a surface protective layer, and having a relative dielectric constant of 5.0 or more.
2) The pressure-sensitive adhesive sheet according to 1), wherein the pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer made of a urethane-based pressure-sensitive adhesive.
3) The pressure-sensitive adhesive sheet according to 2), wherein the urethane-based pressure-sensitive adhesive is an active energy ray-curable pressure-sensitive adhesive.
4) The pressure-sensitive adhesive sheet according to any one of 1) to 3), wherein the thickness is 50 to 1000 μm.
5) A touch panel with a surface protective layer, wherein the capacitive touch panel and the surface protective layer are in close contact with each other through the pressure-sensitive adhesive sheet of any one of 1) to 4).
6) The display apparatus provided with the touchscreen with a surface protective layer of said 5).

  By disposing the adhesive sheet of the present invention between the capacitive touch panel and the surface protective layer, it is possible to suppress a decrease in detection sensitivity at the time of input. In particular, in order to reduce the weight of a touch panel with a surface protective layer and a display device using the touch panel, the reduction in detection sensitivity that occurs when the surface protective layer is changed from a glass plate to a resin plate, a resin film, etc. It is suppressed by using the adhesive sheet.

The schematic cross section which shows an example of the capacitive touch panel with a surface protective layer using the adhesive sheet of this invention. The schematic cross section which shows an example of the display apparatus provided with the electrostatic capacitance type touch panel with a surface protective layer of this invention.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet disposed between a capacitive touch panel and a surface protective layer. Furthermore, it is preferable that the pressure-sensitive adhesive sheet of the present invention is used for bringing a capacitive touch panel and a surface protective layer into close contact. That is, it is preferable to adhere both using the adhesive sheet of the present invention so that an air layer is not interposed between the capacitive touch panel and the surface protective layer. In the following description, the capacitive touch panel may be simply referred to as a touch panel.

FIG. 1 is a schematic cross-sectional view showing an example of a capacitive touch panel with a surface protective layer using the pressure-sensitive adhesive sheet of the present invention. The capacitive touch panel 10 with a surface protective layer has a configuration in which the touch panel 1 and the surface protective layer 3 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 surface protective layer 3 on the touch panel 1 side.
FIG. 2 is a schematic cross-sectional view showing an example of a display device provided with the capacitive touch panel with a surface protective layer of the present invention shown in FIG. In the display device 20, the capacitive touch panel 10 with a surface protective layer is mounted on the display panel 5 via the adhesive sheet 6. The pressure-sensitive adhesive sheet 6 is not particularly limited, and the pressure-sensitive adhesive sheet of the present invention may be used, or a pressure-sensitive adhesive sheet other than the present invention may be used, but the pressure-sensitive adhesive sheet of the present invention is preferably used.

  The capacitive touch panel detects an input position by reading a change in capacitance between a finger and a transparent conductive film constituting the touch panel in an input operation. Capacitive touch panels are roughly classified into a surface type and a projection type depending on the operation method.

  A surface-type capacitive touch panel has a uniform electric field formed by a transparent conductive film provided on a substrate. When touched with a finger, the capacitance changes according to the distance between the electrode at the four corners of the substrate and the finger. This is a method for determining the input position. A projected capacitive touch panel is a system in which an X electrode and a Y electrode are provided on a glass substrate or a resin substrate, and the change in capacitance caused by touching with a finger is read from each of the X electrode and the Y electrode to detect the position. It is.

  The above-mentioned electrostatic capacitance type touch panel often has a surface protective layer disposed on the outermost surface, and the pressure-sensitive adhesive sheet of the present invention is disposed between the touch panel and the surface protective layer, particularly the touch panel and the surface protection. It is suitable for use in close contact with the layer. The pressure-sensitive adhesive sheet of the present invention is particularly preferably applied to a projection type capacitive touch panel.

  Examples of the surface protective layer according to the present invention include a glass plate, a plastic resin plate (for example, an acrylic resin plate, a polycarbonate resin plate, a polyester resin plate, etc.), a plastic resin film (a polyester resin film, an acrylic resin film, a polycarbonate resin film, a cellulose resin). Films, polyolefin resin films, polyamide resin films, etc.), organic / inorganic hybrid plates and films (eg “Silplus” from Nippon Steel Chemical Co., Ltd., “HD Film” from Gunze Co., Ltd.), etc. be able to.

  Among the materials constituting the surface protective layer, a plastic resin plate, a plastic resin film, an organic / inorganic hybrid plate or film are preferable from the viewpoint of reducing the weight of the touch panel with the surface protective layer and the display device.

  The thickness of the surface protective layer is generally about 0.05 to 3 mm, preferably 0.1 to 2.5 μm, more preferably 0.3 to 2 mm, particularly 0.5 to 1.5 mm. The range of is preferable. When the thickness of the surface protective layer is too thin, the function as the protective layer may not be sufficiently exhibited. On the other hand, when the thickness is too thick, the detection sensitivity of the input position may be lowered, and the operability of the touch panel may be deteriorated.

  The surface protective layer is preferably provided with a decorative layer. The decorative layer is, for example, a colored layer for bordering an area corresponding to the image display area of the display panel, and can be directly provided on the outer periphery of the surface protective layer by printing or the like. Or you may make the film etc. which provided the decoration layer closely_contact | adhered to a surface protective layer.

  Further, the surface protective layer may be provided with a functional layer such as an antireflection layer or a hard coat layer. These functional layers may be directly laminated on the surface protective layer, or a film provided with a functional layer may be laminated on the surface protective layer.

  Examples of the display panel constituting the display device according to the present invention include a liquid crystal display panel, an organic EL display panel, and a plasma display panel.

  As described above, when an insulator such as a surface protective layer, an air layer, or an adhesive sheet is disposed on the touch panel, the detection sensitivity of the touch panel decreases. For this reason, conventionally, it is necessary to design the touch panel itself with high detection sensitivity, which affects the complexity of the touch panel configuration and the manufacturing cost. Examples of factors that affect the detection sensitivity of the touch panel include the arrangement and pattern of electrodes constituting the touch panel, the electrical characteristics of the transparent conductive layer constituting the electrodes, and the performance of the IC controller.

  The configuration in which the surface protective layer is arranged on the touch panel via the air layer has a problem that the contrast and the luminance are reduced because light scattering occurs due to the presence of the air layer.

  Therefore, it is important to suppress a decrease in detection sensitivity in the configuration in which the surface protective layer is in close contact with the touch panel via the adhesive sheet. As a result of studying the present invention to solve the above-mentioned problems, it has been found that a decrease in detection sensitivity is suppressed by using an adhesive sheet having a relative dielectric constant of 5.0 or more.

  In addition, if the glass plate that has been conventionally used as a surface protective layer is changed to a resin plate, a resin film, or a plate or film made of an organic / inorganic hybrid, the detection sensitivity further decreases. By using this, it is possible to suppress a decrease in detection sensitivity.

  In other words, by using the pressure-sensitive adhesive sheet of the present invention, it is possible to use a resin plate, a resin film, or an organic / inorganic hybrid plate or film as a surface protective layer without reducing the detection sensitivity. The touch panel and the display device can be reduced in weight.

  Hereinafter, the pressure-sensitive adhesive sheet of the present invention will be described in detail.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a relative dielectric constant of 5.0 or more. The pressure-sensitive adhesive sheet of the present invention preferably has a relative dielectric constant of 5.5 or more, more preferably has a relative dielectric constant of 6.0 or more, and particularly preferably has a relative dielectric constant of 6.5 or more. . The upper limit of the relative dielectric constant in the pressure-sensitive adhesive sheet of the present invention is preferably 12.0 or less, more preferably 11.0 or less, and particularly preferably 10.0 or less. If the relative dielectric constant of the pressure-sensitive adhesive sheet becomes too large, malfunction may be caused.

  A pressure-sensitive adhesive sheet made of an acrylic pressure-sensitive adhesive generally used has a relative dielectric constant of about 3 to 4, and cannot sufficiently suppress a decrease in detection sensitivity of the touch panel. Moreover, the relative dielectric constant of the silicone-based pressure-sensitive adhesive is generally about 3 to 4, and a decrease in the detection sensitivity of the touch panel cannot be sufficiently suppressed.

  The pressure-sensitive adhesive sheet of the present invention may be composed of (a) a single pressure-sensitive adhesive layer, (b) a structure in which a plurality of pressure-sensitive adhesive layers are laminated, or (c) 1 The structure (what is called a double-sided adhesive sheet) which laminated | stacked the adhesive layer on both surfaces of the base material of a sheet | seat may be sufficient.

  When the pressure-sensitive adhesive sheet of the present invention is composed of (a) a single pressure-sensitive adhesive layer, the relative dielectric constant of the pressure-sensitive adhesive layer is directly used as the relative dielectric constant of the pressure-sensitive adhesive sheet, so that the relative dielectric constant is 5.0 or more. It is essential to use an adhesive layer.

  In the case where the pressure-sensitive adhesive sheet of the present invention has a configuration in which (b) a plurality of pressure-sensitive adhesive layers are laminated, the relative dielectric constant of at least one pressure-sensitive adhesive layer is set to 5.0 or more. Is required to be 5.0 or more.

  In the case where the pressure-sensitive adhesive sheet of the present invention has a structure in which (c) pressure-sensitive adhesive layers are laminated on both surfaces of a single base material, at least 1 is required to set the relative dielectric constant of the pressure-sensitive adhesive sheet to 5.0 or more. It is essential that the relative dielectric constant of one adhesive layer or the substrate is 5.0 or more.

  The pressure-sensitive adhesive sheet of the present invention preferably includes at least a pressure-sensitive adhesive layer having a relative dielectric constant of 5.0 or more, and is preferably composed of a single pressure-sensitive adhesive layer having a relative dielectric constant of 5.0 or more. .

  The adhesive having a relative dielectric constant of 5.0 or more used in the present invention is not particularly limited. For example, by mixing an acrylic adhesive having a relative dielectric constant of about 3 to 4 with a material having a large relative dielectric constant such as urea resin, urea formaldehyde resin, urethane resin, titanium dioxide, the relative dielectric constant is 5 It is possible to use a pressure-sensitive adhesive having a viscosity of 0.0 or more. However, when a material with a large relative dielectric constant as described above is mixed with an acrylic pressure-sensitive adhesive, compatibility problems, adhesive force change problems, weather resistance problems (yellowing, etc.), and transparency reduction problems may occur. There is a need to scrutinize thoroughly.

  Therefore, in view of the above problems, the pressure-sensitive adhesive sheet of the present invention preferably includes a pressure-sensitive adhesive layer made of a urethane-based pressure-sensitive adhesive having a relative dielectric constant of 5.0 or more. In particular, the pressure-sensitive adhesive sheet is preferably composed of a single layer composed only of a pressure-sensitive adhesive layer made of a urethane-based pressure-sensitive adhesive having a relative dielectric constant of 5.0 or more. Hereinafter, the urethane type adhesive preferably used for the adhesive sheet of this invention is demonstrated in detail.

  The urethane-based pressure-sensitive adhesive means that the urethane resin contains 50% by mass or more with respect to 100% by mass of the total solid content of the urethane-based pressure-sensitive adhesive. Preferably, the urethane resin is contained in an amount of 60% by mass or more based on 100% by mass of the solid content of the urethane-based adhesive, and more preferably 70% by mass of 100% by mass of the solid content of the urethane-based adhesive. % Or more. The upper limit is preferably 98% by mass or less, and more preferably 95% by mass or less.

  The urethane-based pressure-sensitive adhesive is preferably a thermosetting pressure-sensitive adhesive or an active energy ray-curable pressure-sensitive adhesive, and particularly preferably an active energy ray-curable pressure-sensitive adhesive. As described later, the pressure-sensitive adhesive sheet of the present invention preferably has a relatively large thickness, and an active energy ray-curable pressure-sensitive adhesive is preferable from the viewpoint that a pressure-sensitive adhesive sheet having a relatively large thickness can be produced uniformly with high productivity. .

  The active energy ray-curable pressure-sensitive adhesive is a pressure-sensitive adhesive formed by being cured by an active energy ray such as an electron beam or ultraviolet rays. Hereinafter, the active energy ray-curable urethane pressure-sensitive adhesive preferably used in the present invention will be described in detail.

  Such an active energy ray-curable urethane-based pressure-sensitive adhesive is preferably obtained by curing an active energy ray-curable composition containing at least a urethane polymer.

  The urethane polymer contained in the active energy ray-curable composition preferably includes at least a polymerizable urethane polymer. As such a polymerizable urethane polymer, those having an ethylenically unsaturated group in the molecule are preferable. 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 polymerizable urethane polymer is preferably 20000 or more, more preferably 30000 or more, and particularly preferably 35000 or more from the viewpoint of increasing the initial adhesion of the pressure-sensitive adhesive sheet. The upper limit of the weight average molecular weight of the urethane polymer is preferably 60000 or less, more preferably 55000 or less, particularly preferably 50000 or less, from the viewpoint of suppressing the increase in viscosity of the active energy ray-curable composition and ensuring good coating properties. preferable.

  As the polymerizable urethane polymer, a urethane prepolymer having an ethylenically unsaturated group at least at one end of the molecule is preferably used. In particular, the following polymerizable urethane polymer (A) or polymerizable urethane polymer (B) is preferably used.

  The polymerizable urethane polymer (A) is a urethane polymer having ethylenically unsaturated groups at both ends of the molecule.

  The polymerizable urethane polymer (B) is a urethane polymer having a hydroxyl group at one end of the molecule and an ethylenically unsaturated group at the other end.

  Both the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) preferably have no ethylenically unsaturated group in the side chain of the molecule.

  The polymerizable urethane polymer (B) is preferably a urethane polymer having one hydroxyl group at one end of the molecule and one ethylenically unsaturated group at the other end.

  The active energy ray-curable composition preferably contains both the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B). The content ratio (molar ratio) of the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 8: 2. The range of 3: 7 to 7: 3 is preferred.

  The polymerizable urethane polymer (A) has a polymerizable urethane polymer (A1) having one ethylenically unsaturated group at both ends of the molecule and one ethylenically unsaturated group at one end of the molecule. And a polymerizable urethane polymer (A2) having two ethylenically unsaturated groups at the other end. The content ratio (molar ratio) of the polymerizable urethane polymer (A1) and the polymerizable urethane polymer (A2) is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 8: 2. The range of 3: 7 to 7: 3 is preferred.

  The active energy ray-curable composition can contain a urethane polymer other than the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) as the urethane polymer. In this case, the content ratio of the other urethane polymer is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less with respect to 100% by mass of the urethane polymer.

  The active energy ray-curable composition can contain a polymer other than the urethane polymer, such as an acrylic polymer, an ester polymer, and a silicon polymer. The content of the polymer other than the urethane polymer is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less with respect to 100 parts by mass of the urethane polymer. preferable.

  The polymerizable urethane polymer (A) reacts, for example, a urethane prepolymer (a) having an isocyanate group at a molecular terminal, a functional group capable of reacting with an isocyanate group, and a compound (b) having an ethylenically unsaturated group. Can be obtained.

  The polymerizable urethane polymer (B) includes, for example, a urethane prepolymer (a) having an isocyanate group at a molecular terminal, a compound (b) having an ethylenically unsaturated group and a functional group capable of reacting with an isocyanate group, and an isocyanate group. It can be obtained by reacting a functional group capable of reacting with a compound (c) having a hydroxyl group.

  Examples of the functional group capable of reacting with the isocyanate group in the compounds (b) and (c) include a hydroxyl group, a carboxyl group, an amino group, an amide group, and the like, and among these, a hydroxyl group is particularly preferable.

  Moreover, in the synthesis | combination of the said polymeric urethane polymer (B), by adjusting the preparation ratio of the said compound (b) and the said compound (c), or adjusting the preparation order and preparation time, polymerizable urethane polymer (B) and the polymerizable urethane polymer (A) can be synthesized simultaneously.

  That is, the above synthesis method is a synthesis method capable of simultaneously producing the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) in one synthesis process, and the polymerizable urethane polymer used in the present invention is For the synthesis, the above synthesis method is preferably used. All terminals of all molecules of the polymerizable urethane polymer obtained by this synthesis method are substituted with ethylenically unsaturated groups or hydroxyl groups, and the ratio of the terminals substituted with ethylenically unsaturated groups (hereinafter referred to as acrylate terminals). The ratio) is preferably 60 to 90% with respect to all terminals of the polymerizable urethane polymer.

  The acrylate terminal ratio can be calculated from the hydroxyl group value and molecular weight obtained by determining the hydroxyl group value of the polymerizable urethane polymer by a titration method or the like.

  When the acrylate terminal ratio of the polymerizable urethane polymer obtained by the above synthesis method is 60%, for example, the content ratio of the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) is 20:80 in terms of molar ratio. Become. Similarly, when the acrylate terminal ratio is 70%, the ratio is 40:60. Similarly, when the acrylate terminal ratio is 80%, the ratio is 60:40. Similarly, when the acrylate terminal ratio is 90%, the ratio is 80:20. It becomes a ratio.

  The compounds used for the synthesis of the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) will be described below.

  The urethane prepolymer (a) having an isocyanate group at the molecular end 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.

  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.

  The isocyanate compound used for the synthesis of the urethane pre-prepolymer (a) having an isocyanate group at the molecular end includes tolylene diisocyanate, hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, lysine diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate. Diisocyanate compounds such as isophorone diisocyanate, xylene diisocyanate and hydrogenated xylylene diisocyanate are preferably used.

  As the urethane prepolymer (a), those having isocyanate groups at both ends of the molecule are preferable.

  Next, the compound (b) to be reacted with the urethane prepolymer (a) in order to synthesize the polymerizable urethane polymer (A) and the polymerizable urethane polymer (B) will be described. The compound (b) is a compound having a functional group capable of reacting with an isocyanate group and an ethylenically unsaturated group.

  Examples of the compound (b) 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, 2-hydroxyethyl (meth) acrylate modified caprolactone Such as hydroxyl group-containing (meth) acrylate, (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxy Carboxyl group-containing (meth) acrylates such as ethyl succinic acid, amino group-containing (meth) acrylates such as N, N-diethylaminoethyl (meth) acrylate, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl Amide group containing (meth) acrylates, such as (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, etc. are mentioned. Among these, a hydroxyl group-containing (meth) acrylate compound is particularly preferably used.

  The polymerizable urethane polymer (A2) (polymerizable urethane polymer having one ethylenically unsaturated group at one end of the molecule and two ethylenically unsaturated groups at the other end) is the compound In addition to (b), the compound can be synthesized by using a compound (d) having a functional group capable of reacting with an isocyanate group and two ethylenically unsaturated groups.

  Examples of the compound (d) include 2-hydroxyethyl di (meth) acrylate, 1-hydroxypropyl di (meth) acrylate, 1-hydroxybutyl di (meth) acrylate, 4-hydroxybutyl di (meth) acrylate, Examples thereof include hydroxyl group-containing bifunctional (meth) acrylate compounds such as 2-hydroxypentyl di (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, and trimethylolethanedi (meth) acrylate. .

  Next, the compound (c) to be reacted with the urethane prepolymer (a) in order to synthesize the polymerizable urethane polymer (B) will be described. Examples of the compound (c) include oxycarboxylic acids and polyhydric alcohols, with polyhydric alcohols being preferred.

  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 composition 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 such as (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and phenoxyethyl (meth) acrylate, (meth) acrylic monomers, diethylene glycol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tripropylene glycol Multifunctional (meth) acrylic monomers such as di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Can be mentioned. 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 the polymerizable monomers in the active energy ray-curable composition is preferably in the range of 1 to 50% by mass, preferably 2 to 40% by mass, relative to 100% by mass of the total solid content of the active energy ray-curable composition. Is more preferable, and a range of 5 to 30% by mass is particularly preferable.

  The active energy ray-curable 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 amount of the polymerization initiator used is suitably in the range of 0.05 to 5% by mass and in the range of 0.1 to 3% by mass with respect to 100% by mass of the total solid content of the active energy ray-curable composition. preferable.

  The pressure-sensitive adhesive sheet of the present invention obtained by curing the active energy ray curing agent 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 is corroded.

  The pressure-sensitive adhesive sheet of the present invention obtained by curing the active energy ray-curable composition of the present invention substantially does not contain a component having a carboxyl group, which constitutes the active energy ray-curable composition of the present invention. It means that the resin component such as the aforementioned urethane polymer and other polymers used as necessary, and the polymerizable monomer do not have a carboxyl group in the molecule.

  The active energy ray-curable composition is preferably a so-called solventless type that does not substantially contain an organic solvent. Here, that the active energy ray-curable composition does not substantially contain an organic solvent means that the amount of the organic solvent contained in 100% by mass of the active energy ray-curable 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 above-mentioned active energy ray-curable composition solvent-free, the safety and environmental performance in the production process are improved, and the residual solvent of the obtained adhesive can be 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, and the production process is shortened. Moreover, there exists an advantage that a comparatively large adhesive sheet can be manufactured with sufficient production efficiency by setting it as a solventless type.

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

  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 vinyl group, an allyl group, etc., and an ethylenically unsaturated group is directly or via a linking group such as an oxygen atom or imino group at the 1-position and / or 4-position of a sterically hindered piperidyl group It is a bound compound.

  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 composition can further contain a plasticizer. Such plasticizers include benzyl benzoate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, dibutyl benzyl phthalate, dioctyl phthalate Phthalic acid compounds such as butyl phthalyl butyl glycolate, diisobutyl adipate, diisononyl adipate, diisodecyl adipate, dibutoxyethyl adipate, dibutyl sebacate, di-2-ethylhexyl sebacate, etc. Sebacic acid compounds such as triethylene phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresylphenyl phosphate, dioctyl sebacate, methylacetylricinolate Any fatty acid compound, epoxy compound such as diisodecyl-4,5-epoxytetrahydrophthalate, trimellit such as tributyl trimellitic acid, tri-2-ethylhexyl trimellitic acid, tri-n-octyl trimellitic acid, triisodecyl trimellitic acid Examples include acid compounds, butyl oleate, chlorinated paraffin, polyoxypropylene glycol, polyoxytetramethylene glycol, polybutene, and polyisobutylene.

  The amount of the plasticizer used is preferably in the range of 1 to 20% by mass with respect to 100% by mass of the total solid content of the active energy ray-curable composition.

  The active energy ray curable composition may 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.

  In addition, the active energy ray-curable composition may contain various additives other than those described above, for example, an antifoaming agent, a leveling agent, an ultraviolet absorber, and a pigment as necessary.

  The pressure-sensitive adhesive layer made of the active energy ray-curable pressure-sensitive adhesive can be produced by molding or coating the above-described active energy ray-curable composition to a predetermined thickness and then irradiating and curing the active energy ray. it can. Specifically, after applying the above-mentioned active energy ray-curable composition to a predetermined thickness on a release-treated substrate film such as a release PET film, the active energy ray is irradiated and cured. Can be manufactured by. The above release film is peeled off when applied to a touch panel.

  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.

  Although the thickness of the adhesive sheet of this invention is suitably set according to the design specification of the electrostatic capacitance type touch panel in which the adhesive sheet of this invention is used, generally it is the range of 50-1000 micrometers.

  A capacitive touch panel generally requires a flexible printed circuit board (FPC) and a controller IC, and these members may be disposed between the touch panel and the surface protective layer. In such a specification, since the distance between the touch penel and the surface protective layer is designed to be larger than that of the above member, the thickness of the pressure-sensitive adhesive sheet of the present invention used for closely attaching the touch panel and the surface protective layer is also in accordance therewith. Is relatively large.

  In addition, as described above, the surface protective layer is generally provided with a decorative layer, and the thickness of the pressure-sensitive adhesive sheet is preferably designed to be larger in order to sufficiently fill the step of the decorative layer. .

  From the above viewpoint, the thickness of the pressure-sensitive adhesive sheet of the present invention 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. If the thickness of the pressure-sensitive adhesive sheet is too small, the gap between the touch panel and the surface protective layer cannot be sufficiently filled, and there is an air layer, or the step of the decorative layer of the surface protective layer may be sufficiently filled. There is a case where bubbles are generated in the stepped portion without being able to be performed. On the other hand, when the thickness of the pressure-sensitive adhesive sheet is too large, inconveniences such as a decrease in detection sensitivity of the touch panel and an increase in the total thickness of the final product may occur.

  As described above, when the distance between the touch panel and the surface protective layer is relatively large, the detection sensitivity of the touch panel decreases, but the use of the pressure-sensitive adhesive sheet of the present invention can suppress the decrease in detection sensitivity.

  The pressure-sensitive adhesive sheet of the present invention preferably has an initial adhesion strength of 8 N / 25 mm or more. When the touch panel and the surface protective layer are adhered with the adhesive sheet, there is a problem that bubbles are likely to be generated in the stepped portion of the decorative layer provided on the surface protective layer, but the initial adhesive force of the adhesive sheet is 8 N / 25 mm or more. Thus, the generation of the bubbles is suppressed. 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 the suppression of the generation of bubbles.

  The initial adhesive strength of the pressure-sensitive adhesive sheet is more preferably 10 N / 25 mm or more, and particularly preferably 11 N / 25 mm or more. The upper limit is about 50 N / 25 mm. Here, the initial adhesion is an adhesion after 5 minutes after the adhesive sheet is bonded to the soda glass plate.

  The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet of the present invention preferably has an Asker C hardness of 15 or higher, more preferably 18 or higher, and further preferably 20 or higher. 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 layer constituting the pressure-sensitive adhesive sheet to 10 N / 25 mm or more, the punching processability is improved.

  The pressure-sensitive adhesive sheet according to the present invention is often punched into sheets in accordance with the screen size of a touch panel or a display device, and preferably has good punchability. If the punching processability is poor, the cutting part will reattach to the punching blade and cannot be separated, the adhesive will stick to the punching blade, the edge of the punched sheet adhesive sheet will be deformed and the flatness will deteriorate Problem occurs. The deterioration of the flatness may cause inconvenience that bubbles are generated when the touch panel and the surface protective layer are brought into close contact with each other.

As described above, the pressure-sensitive adhesive sheet of the present invention can employ the following configuration.
(A) Configuration with a single PSA layer (B) Configuration with multiple PSA layers laminated (C) Configuration with PSA layers laminated on both sides of a single substrate (so-called double-sided PSA sheet) .

  When the pressure-sensitive adhesive sheet of the present invention has the above-mentioned configuration (A), the relative dielectric constant of the pressure-sensitive adhesive layer becomes the relative dielectric constant of the pressure-sensitive adhesive sheet as it is, and therefore a pressure-sensitive adhesive layer having a relative dielectric constant of 5.0 or more is used. Is essential.

  When the pressure-sensitive adhesive sheet of the present invention has the configuration (b) above, it is essential that the relative dielectric constant of at least one pressure-sensitive adhesive layer is 5 or more in order to make the pressure-sensitive adhesive sheet have a dielectric constant of 5.0 or more. It is. In the configuration of (b), if the relative dielectric constant of one pressure-sensitive adhesive layer is 5.0 or more and the relative dielectric constant of the other pressure-sensitive adhesive layer is less than 5.0, the ratio of the pressure-sensitive adhesive sheet Since the dielectric constant may be less than 5.0, the thickness of the pressure-sensitive adhesive layer having a relative dielectric constant of 5.0 or more is relatively large, and the thickness of the pressure-sensitive adhesive layer having a relative dielectric constant of less than 5 is relatively small. There is a need to.

  When the pressure-sensitive adhesive sheet of the present invention has the above-mentioned configuration (c), in order to set the relative dielectric constant of the pressure-sensitive adhesive sheet to 5.0 or higher, the relative dielectric constant of at least one pressure-sensitive adhesive layer or substrate is 5.0 or higher. It is essential. Even in the configuration of (c), when the relative dielectric constant is less than 5 as described above, the adhesive sheet may have a relative dielectric constant of less than 5.0, so the thickness of the structural member is adjusted. There is a need.

  When the pressure-sensitive adhesive sheet of the present invention has the above configuration (c), it is preferable that the dielectric constant of at least one pressure-sensitive adhesive layer is 5.0 or more and the dielectric constant of the substrate is 5.0 or more.

  When the pressure-sensitive adhesive sheet is composed of a plurality of layers (members) as in (b) and (c) above, the approximate relative dielectric constant of the pressure-sensitive adhesive sheet is the ratio of the plurality of pressure-sensitive adhesive layers (or base materials) to be laminated. It can be obtained by calculation from the dielectric constant and thickness, and can be used as a reference for designing a laminated type adhesive sheet.

For example, when the pressure-sensitive adhesive sheet is a laminated type of the pressure-sensitive adhesive layer 1 and the pressure-sensitive adhesive layer 2, the capacitance C ₁₂ when the pressure-sensitive adhesive sheet is interposed between the electrodes is the capacitance C 1 of the pressure-sensitive adhesive layer _1. and the capacitance _{C 2} of the pressure-sensitive adhesive layer 2 becomes synthesis of when is connected in _{series, 1 / C 12 = 1 /} C 1 + 1 / C 2 ··· represented by the formula: (1) (1) .

  Here, the general formula of the capacitor is represented by the following formula (2).

C = ε _r ε ₀ A / d (2)
In Equation 2, C is a capacitance, ε _r is a relative dielectric constant, ε ₀ is a vacuum dielectric constant (= 8.854 × 10 ⁻¹² (F / m)), A is an electrode area, and d is a distance between electrodes. Represents.

From the above formulas (1) and (2), the relative dielectric constant of the pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer 1 and the pressure-sensitive adhesive layer 2 can be calculated from the following formula (3): ε _r12 = ε _r1 ε _r2 (d ₁ + d ₂ ) / (Ε _r1 d ₂ + ε _r2 d ₁ ) (3)
In formula (3), ε _r1 is the dielectric constant of the pressure-sensitive adhesive layer 1, ε _r2 is the dielectric constant of the pressure-sensitive adhesive layer 2, d ₁ is the thickness of the pressure-sensitive adhesive layer 1, d ₂ is the thickness of the pressure-sensitive adhesive layer 2, ε _r12 represents the relative dielectric constant of the adhesive sheet.

  In the projected capacitive touch panel, two transparent conductive films of an X electrode and a Y electrode are required. The two transparent conductive films of the X electrode and the Y electrode are of a type that is laminated on both sides of a single substrate, a type that is sequentially laminated on the same surface of a single substrate, or a substrate on which an X electrode is formed and Y There is a type in which a substrate on which an electrode is formed is laminated. In the type in which the substrate on which the X electrode is formed and the substrate on which the Y electrode is formed, the pressure-sensitive adhesive sheet of the present invention is preferably used to laminate and adhere the two substrates. In this case, the thickness of the pressure-sensitive adhesive sheet is suitably in the range of 5 to 50 μm.

  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 relative dielectric constant For the pressure-sensitive adhesive sheet prepared in this example, the capacity (C _p ) was measured at 100 kHz by the flat plate contact method using an LCR meter manufactured by Agilent Technologies, and the ratio of the measurement sample from the following formula: The dielectric constant was calculated. The measurement environment is 23 ± 2 ° C. and 50 ± 5% RH.
ε _r = (t _a × C _p ) / (A × ε ₀ )
ε _r : relative dielectric constant t _{a of} measurement sample: thickness of measurement sample (m)
C _p : Capacity (F)
A: Area of main electrode (m ² )
ε ₀ : relative permittivity of vacuum (= 8.854 × 10 ⁻¹² (F / m)).

2) Sensory evaluation of touch panel detection sensitivity <Production of evaluation sample>
Apple's iPhone 3G was used as the touch panel. First, the ready-made surface protective layer (tempered glass) of iPhone3G was removed, and an acrylic resin plate (thickness 0.8 mm) was used as the surface protective layer instead. The touch panel surface and the acrylic resin plate were adhered to each other with the pressure-sensitive adhesive sheet prepared in this example, and an evaluation sample was prepared. A decorative layer (black printing layer) for bordering the image display area is provided on the peripheral edge of the acrylic resin plate.
In addition, about the lamination type adhesive sheet produced in Example 5, 6 and the comparative example 2, it has arrange | positioned so that a urethane type adhesive layer may become the surface protective layer side.
<Evaluation>
A blank was prepared by mounting an acrylic resin plate on a touch panel without interposing an adhesive sheet. Ten evaluators were allowed to operate the blank and the evaluation sample with their fingers, and the touch panel detection sensitivity was evaluated in the following five stages from the viewpoint of operability during input. The average score of the 10 evaluation points was taken as the evaluation result of the detection sensitivity of the touch panel.
5; I felt that the operability was very good compared to the blank.
4: It was clearly felt that the operability was better than that of the blank.
3; I felt that the operability was slightly better than that of the blank.
2: I felt it was almost the same as the blank.
1: I felt that operability was worse than blank.

3) Measurement of initial adhesion strength After the adhesive sheet prepared in this example was cut to a width of 25 mm and one of the release PET films was peeled off, it was pasted on a 100 μm-thick polyethylene terephthalate film and measured for 24 hours. A sample was used.
The other release PET film of the above measurement sample is peeled off, an adhesive sheet held on a polyethylene terephthalate film is pasted on a soda glass plate having a thickness of 1.8 mm, and a rubber roller having a weight of 2 kg is reciprocated once. Crimped. 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 series of operations described above was performed in an environment of 23 ± 2 ° C. and 50 ± 5% RH. The glass plate used was washed with methyl ethyl ketone and then washed with ethyl alcohol.
Moreover, about the lamination type adhesive sheet produced in Example 5, 6, the urethane type adhesive layer side was affixed on the soda glass plate, and it measured.

4) Measurement of Asker C hardness An adhesive sheet was laminated so that the total thickness was about 6 mm to prepare a measurement sample. The measurement was performed using an Asker C hardness meter (digital rubber hardness meter DD2-C type of Polymer Measuring Instruments Co., Ltd.) according to SRIS0101 (Japan Rubber Association Standard). The measurement was performed 5 times, and the measurement data of 3 times excluding the maximum value and the minimum value were averaged. The series of operations described above was performed in an environment of 23 ± 2 ° C. and 50 ± 5% RH.

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-150CPplus (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.

6) Method for measuring acrylate terminal ratio of polymerizable urethane polymer The acrylate terminal ratio of the polymerizable urethane polymer is based on JISK-1557, by dissolving the resin in chloroform, adding acetic anhydride, and titrating with KOH. The acrylate terminal ratio was calculated from the hydroxyl value and the weight average molecular weight.

<Synthesis of polymerizable urethane polymer 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. Urethane polymer 1 (weight average molecular weight 41500) was obtained. This polymerizable urethane polymer 1 has a polymerizable urethane polymer (A1) having one ethylenically unsaturated group at both ends of the molecule and one ethylenically unsaturated group at one end of the molecule. And a polymerizable urethane polymer (A2) having two ethylenically unsaturated groups at the other end, a hydroxyl group at one end of the molecule, and one ethylenically unsaturated group at the other end The polymerizable urethane polymer (B) is included at a ratio of 50:30:20 (molar ratio).

<Synthesis of polymerizable urethane polymer 2>
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, 0.415 parts by mass of 2-hydroxyethyl acrylate was added while blowing oxygen gas and nitrogen gas, then 0.15 part by mass of 1,3-butanediol was added, and the mixture was kept warm for 3 hours while stirring for 30 minutes. As a result of measuring the molecular weight of each, it was confirmed that the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) was constant at 1.5, the reaction was terminated, and the polymerizable urethane polymer 2 (weight average Molecular weight 41500) was obtained. This polymerizable urethane polymer 2 has an acrylate terminal ratio of 70%, a polymerizable urethane polymer (A1) having one ethylenically unsaturated group at both ends of the molecule, and one hydroxyl at one terminal of the molecule. A polymerizable urethane polymer (B) having a group and having one ethylenically unsaturated group at the other end is contained in a molar ratio of 40:60.

<Synthesis of polymerizable urethane polymer 3>
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. Polymerizable urethane polymer 3 (weight average molecular weight 22000 ) This polymerizable urethane polymer 3 has an acrylate terminal ratio of 70%, a polymerizable urethane polymer (A1) having one ethylenically unsaturated group at each end of the molecule, and one at one end of the molecule. The polymerizable urethane polymer (B) having a hydroxyl group and having one ethylenically unsaturated group at the other end is contained in a ratio of 40:60 (molar ratio).

<Synthesis of polymerizable urethane polymer 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 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. Polymerizable urethane polymer 4 (weight average molecular weight 24000) ) This polymerizable urethane polymer 4 is a polymerizable urethane polymer (B) having one hydroxyl group at one end of the molecule and one ethylenically unsaturated group at the other end.

Example 1
A pressure-sensitive adhesive sheet was prepared in the following manner.
<Preparation of solvent-free active energy ray-curable composition>
90 parts by mass of the polymerizable urethane polymer 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) as a polymerization initiator 0.7 parts by mass of “Irgacure 184”), triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] as a hindered phenol-based antioxidant 1 part by weight, 0.5 parts by weight of triphenyl phosphite as a phosphorus antioxidant, and 4- (meth) acryloyloxy-1,2 as a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group , 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 composition of the (UV curable compositions) were prepared.
<Production of adhesive sheet>
The above active energy ray-curable composition is applied onto a release PET film (Therapy (registered trademark) manufactured by Toray Film Processing Co., Ltd.) with a slit die coater, and then the oxygen concentration is increased by blowing nitrogen gas. In the state of 300 ppm, a metal halide lamp is used to irradiate with ultraviolet rays (integrated light quantity 1500 mJ / cm ² ) to form an adhesive layer, and a release PET film (Toray Film Processing Co., Ltd. (Registered trademark)) was laminated to produce an adhesive sheet. The thickness of the obtained pressure-sensitive adhesive sheet was 175 μm (excluding the release PET film).

(Example 2)
<Preparation of solvent-free active energy ray-curable composition>
A solventless active energy ray-curable composition (ultraviolet curable composition) was prepared in the same manner as in Example 1 except that the polymerizable urethane polymer 1 of Example 1 was changed to the polymerizable urethane polymer 2.
<Production of adhesive sheet>
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the solventless active energy ray-curable composition was used.

(Example 3)
<Preparation of solvent-free active energy ray-curable composition>
82 parts by mass of the polymerizable urethane polymer 3, 13 parts by mass of 2-ethylhexyl acrylate as a polymerizable monomer, and a hydroxyalkylphenone photopolymerization initiator (“Irgacure 184”) as a polymerization initiator 1 part by mass, 1 part by mass of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] as a hindered phenol antioxidant, tri 0.5 parts by mass of phenyl phosphite, and 0 as 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine as a monomer having a sterically hindered piperidyl group and an ethylenically unsaturated group .5 parts by mass added and mixed uniformly, solvent-free active energy ray curable group Objects (the UV-curable composition) was prepared.
<Production of adhesive sheet>
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the solventless active energy ray-curable composition was used.

Example 4
<Preparation of solvent-free active energy ray-curable composition>
Solventless active energy ray curable in the same manner as in Example 3 except that the polymerizable urethane polymer 3 is changed to the polymerizable urethane polymer 4 in the preparation of the solventless active energy ray curable composition of Example 3. Composition (ultraviolet curable composition) was prepared.
<Production of adhesive sheet>
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the solventless active energy ray-curable composition was used.

(Example 5)
100 parts by mass of solvent-based thermosetting acrylic pressure-sensitive adhesive (trade name “BPS6271” manufactured by Toyo Ink Manufacturing Co., Ltd.) and isocyanate-based crosslinking agent (trade name “BXX6105” manufactured by Toyo Ink Manufacturing Co., Ltd.) 1 A pressure-sensitive adhesive composition was prepared by mixing 5 parts by mass.
The pressure-sensitive adhesive composition was coated on a release PET film (Tracel (registered trademark) manufactured by Toray Film Processing Co., Ltd.) with a slot die coater so as to have a dry thickness of 50 μm, and dried to form a pressure-sensitive adhesive layer. And aged at 40 ° C. for 2 days.
Next, the solventless active energy ray-curable composition (ultraviolet curable composition) of Example 1 is slit on the pressure-sensitive adhesive layer obtained above so that the thickness after curing becomes 125 μm. After coating with a die coater, the pressure-sensitive adhesive layer was laminated by irradiating with ultraviolet rays (integrated light amount 1500 mJ / cm ² ) using a metal halide lamp in a state where the oxygen concentration was 300 ppm by blowing nitrogen gas. Further, a release PET film (Toray Film Processing Co., Ltd. Therapy (registered trademark)) was laminated on the pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive sheet.
The pressure-sensitive adhesive sheet thus obtained is a pressure-sensitive adhesive sheet having a laminated structure of an acrylic pressure-sensitive adhesive layer (thickness 50 μm) and a urethane-based pressure-sensitive adhesive layer (thickness 125 μm).

(Example 6)
In Example 5, a pressure-sensitive adhesive sheet having a laminated structure was produced in the same manner as in Example 5 except that the thickness of the acrylic pressure-sensitive adhesive layer was changed to 25 μm and the thickness of the urethane pressure-sensitive adhesive layer was changed to 150 μm.

(Comparative Example 1)
As an adhesive sheet made of an acrylic adhesive, “OCA (Optically Clear Adhesive) 8187” (thickness: 175 μm) manufactured by 3M was used.

(Comparative Example 2)
In Example 5, a laminated pressure-sensitive adhesive sheet was produced in the same manner as in Example 5 except that the thickness of the acrylic pressure-sensitive adhesive layer was changed to 88 μm and the thickness of the urethane-based pressure-sensitive adhesive layer was changed to 88 μm.
<Evaluation>
Detection sensitivity was evaluated about the adhesive sheet of the Example produced above and a comparative example. The results are shown in Table 1.

  Since Examples 1-6 of the present invention use an adhesive sheet having a relative dielectric constant of 5.0 or more, the detection sensitivity of the touch panel was good. On the other hand, Comparative Example 1 and Comparative Example 2 were inferior in detection sensitivity because an adhesive sheet having a dielectric constant of less than 5.0 was used.

  Next, Table 2 shows the results of measuring the initial adhesion and Asker C hardness for Examples 1 to 6.

  In Examples 1, 2, 4, 5, and 6 having an initial adhesion strength of 8 N / 25 mm or more, no bubbles were generated at the step portion of the decorative layer (black print layer) provided on the surface protective layer. In Example 3, the initial adhesion was less than 8 N / 25 mm, and the generation of bubbles was slightly observed.

  Examples 1, 3, 5, and 6 having Asker C hardness of 15 or more have no problem that the cut portion cannot be reattached to the punching blade at the time of punching and cannot be separated and the adhesive adheres to the punching blade. Punching workability was good. In Examples 2 and 4, the Asker C hardness was less than 15, and it often occurred that the cut portion reattached to the punching blade and could not be separated during the punching process.

DESCRIPTION OF SYMBOLS 1 Capacitive touch panel 2 Adhesive sheet of this invention 3 Surface protective layer 4 Decoration layer 5 Display panel 6 Adhesive sheet 10 Capacitive touch panel with surface protective layer 20 Display apparatus

Claims (6)

  A pressure-sensitive adhesive sheet disposed between a capacitive touch panel and a surface protective layer, wherein the pressure-sensitive adhesive sheet has a relative dielectric constant of 5.0 or more.   The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer made of a urethane-based pressure-sensitive adhesive.   The pressure-sensitive adhesive sheet according to claim 2, wherein the urethane-based pressure-sensitive adhesive is an active energy ray-curable pressure-sensitive adhesive.   The adhesive sheet in any one of Claims 1-3 whose thickness is 50-1000 micrometers.   A touch panel with a surface protective layer, wherein the capacitive touch panel and the surface protective layer are in close contact via the pressure-sensitive adhesive sheet according to claim 1.   A display device comprising the touch panel with a surface protective layer according to claim 5.

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