JP6368410B2 - Touch panel - Google Patents

Description

  The present invention relates to a touch panel using an adhesive and an adhesive sheet.

  In various mobile electronic devices such as smartphones and tablet terminals in recent years, a capacitive touch panel is often used as a display.

  There are various configurations of capacitive touch panels. As a typical example, a display module such as a liquid crystal module, a first film sensor laminated thereon with an adhesive layer thereon, The structure provided with the 2nd film sensor laminated | stacked through the adhesive layer and the cover material laminated | stacked through the adhesive layer on it is mentioned.

  Here, a frame-like printed layer may exist as a step on the display module side of the cover material. If the pressure-sensitive adhesive layer does not follow the step, the pressure-sensitive adhesive layer floats in the vicinity of the step, thereby causing light reflection loss. For this reason, the pressure-sensitive adhesive layer is required to have a step following ability.

  On the other hand, the film sensor is generally composed of a base film and a transparent conductive film made of patterned tin-doped indium oxide (ITO). Here, when the adhesive of the adhesive layer in contact with the transparent conductive film contains carboxylic acid (carboxyl group), there arises a problem that the transparent conductive film is corroded or the resistance value of the transparent conductive film is changed.

  In addition, in the touch panel having the patterned transparent conductive film as described above, there is a so-called bone appearance problem in which the circuit pattern of the transparent conductive film is visible and the appearance is impaired. This problem tends to occur particularly noticeably when the touch panel is placed at a high temperature.

  In order to solve the above-mentioned problem of bone appearance, Patent Document 1 proposes a pressure-sensitive adhesive having a storage elastic modulus at 23 ° C., and Patent Document 2 has a pressure-sensitive adhesive having a storage elastic modulus and adhesive strength at 120 ° C. is suggesting. Patent Document 3 proposes a pressure-sensitive adhesive layer in which an acrylic pressure-sensitive adhesive composition containing a predetermined amount of an acrylic polymer and a styrene-based oligomer is used and the refractive index and haze are defined.

JP 2012-128629 A JP2012-238467A JP 2013-116992 A

  However, with the adhesives of Patent Documents 1 to 3, it has been difficult to sufficiently satisfy both the effects of suppressing the appearance of bone and the ability to follow a step. Moreover, since the acrylic polymer of the adhesive used in the example of Patent Document 2 uses acrylic acid as a constituent monomer, it adversely affects the transparent conductive film.

  The present invention has been made in view of the above circumstances, can make it difficult to see the circuit pattern of the transparent conductive film, has excellent step following ability, and adversely affects the transparent conductive film due to the carboxyl group. It is an object of the present invention to provide a capacitance type touch panel provided with an adhesive layer having no adhesive.

In order to achieve the above object, first, the present invention comprises two transparent conductive films, or a transparent conductive film and a cover material, and between the two transparent conductive films or between the transparent conductive film and the cover material. A capacitive touch panel further comprising an adhesive layer positioned therebetween, wherein the adhesive layer has a refractive index of 1.47 to 1.54 and a storage elastic modulus at 80 ° C. of 0.02 to Provided is a touch panel that is made of an adhesive that does not contain a component having a carboxyl group at 0.10 MPa (Invention 1).
Moreover, this invention is an adhesive used between a 2 transparent conductive films or between a transparent conductive film, and a cover material in a capacitive touch panel, Comprising: A refractive index is 1.45-1. The pressure-sensitive adhesive has a storage elastic modulus at 80 ° C. of 0.02 to 0.10 MPa and does not contain a component having a carboxyl group.

  According to the above invention, the refractive index and the storage elastic modulus are defined as described above, so that it is difficult to see the circuit pattern of the transparent conductive film in the capacitive touch panel. The effect is also exhibited when placed under high temperature. In addition, since the refractive index and the storage elastic modulus are defined as described above, the step followability with respect to the printing step or the like of the cover material is excellent. Furthermore, by not containing the component which has a carboxyl group, it can suppress that a transparent conductive film is corroded or changing the resistance value of a transparent conductive film.

In the said invention (invention 1), it is preferable that the said adhesive is an acrylic adhesive (invention 2), and the said acrylic adhesive does not contain the monomer which has a carboxyl group as a monomer unit which comprises a polymer ( It is preferable to crosslink the adhesive composition containing a (meth) acrylic acid ester copolymer (A) and a crosslinking agent (B) (Invention 3).
In the said invention (invention 3), the said (meth) acrylic acid ester copolymer (A) is 5-30 mass% of monomers which have a hydroxyl group as a monomer unit which comprises the said polymer, and the glass transition as a homopolymer It is preferable that 5-40 mass% of hard monomers which do not have an aromatic ring whose temperature is 70 degreeC or more are contained (invention 4).

  In the said invention (invention 4), the said (meth) acrylic acid ester copolymer (A) consists of methyl methacrylate, isobornyl acrylate, and acryloyl morpholine as said hard monomer which is a monomer unit which comprises the said polymer. It is preferable to contain at least one selected from the group (Invention 5).

  In the said invention (invention 3-5), it is preferable that the weight average molecular weights of the said (meth) acrylic acid ester copolymer (A) are 200,000-1 million (invention 6).

  In the said invention (invention 1-6), it is preferable that the said adhesive contains a silane coupling agent (C) further (invention 7).

  Secondly, the present invention is an adhesive sheet used for adhesion of two transparent conductive films in a capacitive touch panel, or adhesion between a transparent conductive film and a cover material, the two release sheets, There is provided a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer sandwiched between the release sheets so as to be in contact with release surfaces of two release sheets, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive.

  In the said invention (invention 1-7), it is preferable that the thickness of the said adhesive layer is 10-400 micrometers (invention 8).

  In the above inventions (Inventions 1 to 8), when the pressure-sensitive adhesive layer side surface of the laminate obtained by laminating the pressure-sensitive adhesive layer on a substrate made of a polyethylene terephthalate film having a thickness of 100 μm is attached to soda lime glass, The adhesion of the laminate to the soda lime glass is preferably 5 to 50 N / 25 mm.

  According to the pressure-sensitive adhesive layer of the touch panel according to the present invention, it is possible to make it difficult to see the circuit pattern of the transparent conductive film on the capacitive touch panel, especially when the touch panel is placed at a high temperature such as 80 ° C. , The effect is demonstrated. In addition, the pressure-sensitive adhesive according to the present invention and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet are excellent in step following ability and do not contain a component having a carboxyl group, so that the transparent conductive film is corroded or the resistance value of the transparent conductive film is reduced. It can suppress changing.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing which shows one structural example of a touchscreen.

Hereinafter, embodiments of the present invention will be described.
[Adhesive]
The pressure-sensitive adhesive according to this embodiment has a refractive index of 1.45 to 1.54, a storage elastic modulus at 80 ° C. of 0.02 to 0.10 MPa, and does not contain a component having a carboxyl group. . This adhesive is used between two transparent conductive films or between a transparent conductive film and a cover material in a capacitive touch panel.

  The pressure-sensitive adhesive according to the present embodiment makes it difficult to see the circuit pattern of the transparent conductive film on the capacitive touch panel because the refractive index and the storage elastic modulus at 80 ° C. are in the above-described range. In particular, the effect is exhibited even when the touch panel is placed at a high temperature such as 80 ° C. Moreover, the adhesive which concerns on this embodiment is excellent also in level | step difference followability by having a refractive index and the storage elastic modulus in 80 degreeC in said range. Therefore, even if the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is attached to a cover material having a step due to a printed layer or the like, it is difficult to form a gap or a bubble between the step and the pressure-sensitive adhesive layer. Moreover, even when the laminate is placed at a high temperature such as 80 ° C., bubbles and the like are prevented from being generated in the vicinity of the step. Furthermore, since the adhesive which concerns on this embodiment does not contain the component which has a carboxyl group, it can suppress corroding a transparent conductive film or changing the resistance value of a transparent conductive film.

  When the refractive index of the pressure-sensitive adhesive is less than 1.45, the circuit pattern of the transparent conductive film is easily visible. On the other hand, when the refractive index of the pressure-sensitive adhesive is more than 1.54, the step following ability is poor. Further, when the storage elastic modulus at 80 ° C. is less than 0.02 MPa, the circuit pattern of the transparent conductive film becomes easy to see, and the visibility becomes particularly noticeable when placed at a high temperature such as 80 ° C. On the other hand, when the storage elastic modulus at 80 ° C. of the pressure-sensitive adhesive exceeds 0.10 MPa, the step following ability is inferior.

  From the above viewpoint, the refractive index of the pressure-sensitive adhesive is preferably 1.46 to 1.52, and particularly preferably 1.47 to 1.50. Moreover, it is preferable that the storage elastic modulus in 80 degreeC of an adhesive is 0.015-0.09 MPa, and it is especially preferable that it is 0.02-0.07 MPa.

  In addition, the refractive index in this specification is a value measured according to JIS K0062-1992 using an Abbe refractometer. The storage elastic modulus at 80 ° C. is a value measured by a torsional shear method shown in a test example described later.

  Although the adhesive which concerns on this embodiment should just satisfy | fill said physical property, as a monomer unit which comprises a polymer, the monomer (hydroxyl group containing monomer) 5-30 mass% which has a hydroxyl group, and as a homopolymer A (meth) acrylic acid ester copolymer (A) containing a hard monomer having an aromatic ring having a glass transition temperature (Tg) of 70 ° C. or higher and 5 to 40% by mass and containing no monomer having a carboxyl group; A pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition (hereinafter sometimes referred to as “pressure-sensitive adhesive composition P”) containing a crosslinking agent (B) and preferably a silane coupling agent (C) is preferred. According to this pressure-sensitive adhesive, the above physical properties (refractive index and storage elastic modulus) can be satisfied. In the present specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

(1) (Meth) acrylic acid ester copolymer (A)
The adhesive composition P preferably contains the (meth) acrylic acid ester copolymer (A) as an adhesive main agent. In the (meth) acrylic acid ester copolymer (A), the content of the hydroxyl group-containing monomer and the hard monomer is in the range described above, so that the pressure-sensitive adhesive contains the (meth) acrylic acid ester copolymer (A). The pressure-sensitive adhesive obtained from the composition P easily satisfies the above-described refractive index and storage elastic modulus.

  In addition, the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P containing the (meth) acrylic acid ester copolymer (A) having a hydroxyl group-containing monomer content in the above range can be used under high temperature and high humidity conditions (for example, 85 Whitening is suppressed when the temperature is returned to room temperature and normal humidity, that is, excellent in heat-and-moisture whitening resistance. When the (meth) acrylic acid ester copolymer (A) contains a hydroxyl group-containing monomer in the above amount as a monomer unit, a predetermined amount of hydroxyl group remains in the resulting adhesive. A hydroxyl group is a hydrophilic group, and when such a hydrophilic group is present in a pressure-sensitive adhesive, even if the pressure-sensitive adhesive is placed under a high temperature and high humidity condition, it penetrates into the pressure sensitive adhesive under the high temperature and high humidity condition. As a result, the whitening of the pressure-sensitive adhesive is suppressed.

  If the content of the hydroxyl group-containing monomer as the monomer unit in the (meth) acrylic acid ester copolymer (A) is less than 5% by mass, the wet heat and whitening resistance may be lowered, while the hydroxyl group-containing monomer is contained. When the amount exceeds 30% by mass, the adhesion to the adherend is lowered, the durability may be lowered, and a desired adhesive force may not be obtained.

  Moreover, the refractive index and storage elastic modulus of an adhesive will become lower than the said range as content of the said hard monomer as a monomer unit in a (meth) acrylic acid ester copolymer (A) is less than 5 mass%. On the other hand, if the content of the hard monomer exceeds 40% by mass, the step following ability may be deteriorated or a desired adhesive force may not be obtained.

  From the above viewpoint, the (meth) acrylic acid ester copolymer (A) preferably contains 5 to 30% by mass of a hydroxyl group-containing monomer as the monomer unit constituting the polymer, particularly 10 to 25% by mass. It is preferable to contain. The (meth) acrylic acid ester copolymer (A) preferably contains 5 to 50% by mass of the hard monomer as a monomer unit constituting the polymer, and particularly 10 to 30% by mass. Is preferred.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate is preferred from the viewpoint of the reactivity of the hydroxyl group in the resulting (meth) acrylic acid ester polymer (A) with the crosslinking agent (B) and the copolymerizability with other monomers. Is preferred. These may be used alone or in combination of two or more.

  The hard monomer is a monomer that does not contain an aromatic ring, and has a glass transition temperature of 70 ° C. or higher, preferably 75 to 200 ° C., particularly preferably 80 to 200 ° C. as a homopolymer obtained by polymerizing only the hard monomer. It is a monomer at 180 ° C.

  The hard monomer is preferably an acrylic monomer. For example, methyl methacrylate (Tg 105 ° C.), isobornyl acrylate (Tg 94 ° C.), isobornyl methacrylate (Tg 180 ° C.), acryloylmorpholine (Tg 145 ° C.), acrylic acid Examples thereof include adamantyl (Tg 115 ° C.), adamantyl methacrylate (Tg 141 ° C.), dimethylacrylamide (Tg 89 ° C.), and acrylamide (Tg 165 ° C.). These may be used alone or in combination of two or more.

  Among the hard monomers, methyl methacrylate, isobornyl acrylate, and acryloylmorpholine are particularly preferable. That is, the (meth) acrylic acid ester copolymer (A) is at least one selected from the group consisting of methyl methacrylate, isobornyl acrylate and acryloylmorpholine as the hard monomer which is a monomer unit constituting the polymer. It is preferable to contain.

  The (meth) acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Thereby, even if the obtained adhesive is affixed on a transparent conductive film, those malfunctions by an acid can be suppressed. For example, it can suppress corroding the transparent conductive film or changing the resistance value of the transparent conductive film.

  Here, “does not contain a component having a carboxyl group” or “does not contain a monomer having a carboxyl group” means that the component or monomer having a carboxyl group is substantially not contained, and the component or monomer containing a carboxyl group In addition to containing no carboxyl group, it is allowed to contain a carboxyl group-containing component or monomer to such an extent that corrosion of the transparent conductive film due to the carboxyl group does not occur. Specifically, the (meth) acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit in an amount of 0.1% by mass or less, preferably 0.01% by mass or less. It is acceptable.

  The (meth) acrylic acid ester copolymer (A) is a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group (excluding the hard monomer described above) as a monomer unit constituting the polymer. It is preferable to contain. Thereby, the obtained adhesive can express preferable adhesiveness.

  Examples of the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, ( N-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate , Myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid esters having 2 to 8 carbon atoms in the alkyl group are preferable, and n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are particularly preferable. . In addition, these may be used independently and may be used in combination of 2 or more type.

  The (meth) acrylic acid ester copolymer (A) contains 10 to 90% by mass of a (meth) acrylic acid alkyl ester having 2 to 20 carbon atoms as the monomer unit constituting the polymer. It is preferable to contain 20-85 mass% especially, and it is further preferable to contain 30-80 mass%.

  The (meth) acrylic acid ester copolymer (A) may be referred to as a monomer that can increase the refractive index of the resulting pressure-sensitive adhesive (hereinafter referred to as “high refractive index monomer”) as a monomer unit constituting the polymer. .) May be contained.

  The high refractive index monomer is preferably a monomer containing an aromatic ring, and examples thereof include an aromatic monomer having one or more aromatic rings, a monomer having a polycyclic aromatic skeleton, and the like. Examples of the aromatic monomer containing one aromatic ring include benzyl (meth) acrylate, 2-phenoxyethyl acrylate, nonylphenoxypolyethylene glycol acrylate, styryl (meth) acrylate, and the like.

  Examples of the aromatic monomer containing two or more aromatic rings include a biphenyl group-containing monomer, a bisphenol A monomer, and the like. From the viewpoint of handling, a biphenyl group-containing monomer is preferable. The biphenyl group-containing monomer is preferably a biphenyl group-containing monofunctional acrylate. Examples of such biphenyl group-containing monomers include ethoxylated o-phenylphenol acrylate and o-biphenyl (meth) acrylate.

  Examples of the monomer having a polycyclic aromatic skeleton include a naphthalene skeleton, anthracene skeleton, triphenylene skeleton, tetraphen skeleton, tetracene skeleton, chrysene skeleton, pyrene skeleton, pentacene skeleton, hexacene skeleton, heptacene skeleton, coronene skeleton, and keklen skeleton. Monomer. From the viewpoint of handling, a monomer having a naphthalene skeleton or an anthracene skeleton is preferable as the polycyclic aromatic skeleton, and a monomer having a naphthalene skeleton is more preferable.

  Examples of the monomer having a naphthalene skeleton include 1-naphthyl (meth) acrylate, 2-naphthyl (meth) acrylate, 2- (1-naphthyloxy) ethyl acrylate, (4-methoxynaphthylene) -1-acrylate, vinyl naphthalene, and the like. Is mentioned.

  Among the above-described high refractive index monomers, benzyl (meth) acrylate and ethoxylated o-phenylphenol acrylate are particularly preferable from the viewpoints of exhibiting a high refractive index and obtaining desired stickability and handling properties. In addition, the said high refractive index monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

  When the (meth) acrylic acid ester copolymer (A) contains a high refractive index monomer as a monomer unit constituting the polymer, the content is preferably 1 to 30% by mass, particularly 2 to 2. It is preferably 20% by mass.

  The (meth) acrylic acid ester copolymer (A) may contain other monomers as monomer units constituting the polymer, if desired. The other monomer is preferably a monomer that does not contain a reactive functional group in order not to interfere with the action of the hydroxyl group-containing monomer. Such other monomers include, for example, (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and aliphatic rings such as cyclohexyl (meth) acrylate (meta ) Acrylic acid ester, (meth) acrylic acid N, N-dimethylaminoethyl, (meth) acrylic acid N, N-dimethylaminopropyl, etc. (meth) acrylic acid ester having acetic acid tertiary amino group, acetic acid Examples include vinyl and styrene. These may be used alone or in combination of two or more.

  The polymerization aspect of the (meth) acrylic acid ester copolymer (A) may be a random copolymer or a block copolymer.

  The (meth) acrylic acid ester copolymer (A) preferably has a weight average molecular weight of 200,000 to 1,000,000, particularly preferably 300,000 to 900,000, and more preferably 400,000 to 800,000. Is preferred. In addition, the weight average molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  When the weight average molecular weight of the (meth) acrylic acid ester copolymer (A) is within the above range, the obtained pressure-sensitive adhesive easily satisfies the storage elastic modulus described above.

  In the adhesive composition P, the (meth) acrylic ester copolymer (A) may be used alone or in combination of two or more.

(2) Crosslinking agent (B)
When the adhesive composition P is crosslinked, the crosslinking agent (B) reacts with a hydroxyl group derived from a hydroxyl group-containing monomer constituting the (meth) acrylic acid ester copolymer (A). Thereby, the structure where the (meth) acrylic acid ester copolymer (A) was bridge | crosslinked with the crosslinking agent (B) is formed.

  Any crosslinking agent (B) may be used as long as it reacts with the reactive group (hydroxyl group of the hydroxyl group-containing monomer that is a monomer unit) of the (meth) acrylic acid ester copolymer (A). Agent, epoxy crosslinking agent, amine crosslinking agent, melamine crosslinking agent, aziridine crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal A salt type crosslinking agent, an ammonium salt type crosslinking agent, etc. are mentioned. Among the above, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with a hydroxyl group. In addition, a crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, etc. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferable from the viewpoint of reactivity with hydroxyl groups.

  The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). The amount is preferably 0.05 to 1 part by mass, more preferably 0.1 to 0.5 part by mass. When the content of the crosslinking agent (B) is within the above range, the obtained pressure-sensitive adhesive easily satisfies the refractive index and storage elastic modulus described above.

(3) Silane coupling agent (C)
The adhesive composition P preferably contains a silane coupling agent (C) from the viewpoint of improving the adhesive strength of the obtained adhesive. The silane coupling agent (C) is an organosilicon compound having at least one alkoxysilyl group in the molecule, has good compatibility with the (meth) acrylic acid ester copolymer (A), and is light transmissive. Those having the following are preferred.

  Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, Mercapto groups such as silicon compounds having an epoxy structure such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane Contains amino groups such as silicon compounds, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Silicon compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of them, and alkyl groups such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane Examples include condensates with silicon compounds. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the silane coupling agent (C) in the adhesive composition P is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the (meth) acrylic acid ester copolymer (A). In particular, the amount is preferably 0.05 to 0.5 parts by mass, and more preferably 0.1 to 0.3 parts by mass.

(4) Various additives For the adhesive composition P, various additives usually used for acrylic pressure-sensitive adhesives, for example, refractive index adjusters, antistatic agents, tackifiers, antioxidants, ultraviolet rays, as desired. Absorbers, light stabilizers, softeners, fillers and the like can be added.

  Examples of the refractive index adjuster include benzyl benzoate, diphenyl sulfide, triphenyl phosphate, benzyl-n-butyl phthalate, diphenyl phthalate, diphenyl, diphenylmethane, tricresyl phosphate, diphenyl sulfoxide and the like.

  When the adhesive composition P contains a refractive index adjuster, the content thereof is preferably 1 to 30 parts by mass, particularly 5 to 5 parts by mass with respect to 100 parts by mass of the acrylate copolymer (A). It is preferably 20 parts by mass.

(5) Manufacture of adhesive composition Adhesive composition P manufactured (meth) acrylic acid ester copolymer (A), and crosslinked to the obtained (meth) acrylic acid ester copolymer (A). It can be produced by adding the agent (B) and, if desired, the silane coupling agent (C) and additives.

  The (meth) acrylic acid ester copolymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylic acid ester copolymer (A) can be carried out by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like. Two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  When the (meth) acrylic acid ester copolymer (A) is obtained, the solution of the (meth) acrylic acid ester copolymer (A) is added to the crosslinking agent (B), and optionally the silane coupling agent (C), A diluting solvent and an additive are added and mixed well to obtain an adhesive composition P (coating solution) diluted with a solvent.

  Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may be 10-60 mass%. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as a dilution solvent.

(6) Production of pressure-sensitive adhesive The pressure-sensitive adhesive according to the present embodiment is preferably one obtained by crosslinking the pressure-sensitive adhesive composition P. The crosslinking of the pressure-sensitive adhesive composition P can be usually performed by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing the dilution solvent of the adhesive composition P, etc.

  When performing heat processing, it is preferable that heating temperature is 50-150 degreeC, and it is especially preferable that it is 70-120 degreeC. The heating time is preferably 30 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH). When this curing period is necessary, after the curing period has elapsed, and when the curing period is unnecessary, an adhesive is formed after the heat treatment.

  By the heat treatment (and curing), the (meth) acrylic acid ester copolymer (A) is well crosslinked through the crosslinking agent (B), and the above-described physical properties can be exhibited.

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to this embodiment includes two release sheets 12a and 12b and the two release sheets 12a so as to be in contact with the release surfaces of the two release sheets 12a and 12b. , 12b and an adhesive layer 11 sandwiched between the two layers. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

(1) Adhesive layer The adhesive layer 11 is comprised from the adhesive mentioned above, Preferably it is comprised from the adhesive formed by bridge | crosslinking the adhesive composition P. FIG.

  The thickness of the pressure-sensitive adhesive layer 11 (measured according to JIS K7130) is preferably 10 to 400 μm, particularly preferably 20 to 300 μm, and more preferably 25, depending on the height of the step. It is preferable that it is -250 micrometers. When the thickness of the pressure-sensitive adhesive layer 11 is 10 μm or more, good step followability is exhibited, and when the thickness of the pressure-sensitive adhesive layer 11 is 400 μm or less, workability is improved. The pressure-sensitive adhesive layer 11 may be formed as a single layer or may be formed by laminating a plurality of layers.

(2) Release sheet Examples of the release sheets 12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate. Phthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film A polyimide film, a fluororesin film, or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  It is preferable that the peeling surface (especially the surface in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b is subjected to a peeling treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Of the release sheets 12a and 12b, one release sheet is preferably a heavy release release sheet having a high release force, and the other release sheet is preferably a light release release sheet having a low release force.

  Although there is no restriction | limiting in particular about the thickness of release sheet 12a, 12b, Usually, it is about 20-150 micrometers.

(3) Production of pressure-sensitive adhesive sheet As one production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and heat treatment is performed for adhesion. After cross-linking the composition P and forming a coating layer, the release surface of the other release sheet 12b (or 12a) is overlaid on the coating layer. When a curing period is required, a curing period is set, and when the curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

  As another production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12 a, a heat treatment is performed to cross-link the pressure-sensitive adhesive composition P, and a coating layer To obtain a release sheet 12a with a coating layer. Moreover, the coating liquid of the said adhesive composition P is apply | coated to the peeling surface of the other peeling sheet 12b, heat processing is performed, the adhesive composition P is bridge | crosslinked, an application layer is formed, and an application layer is attached. A release sheet 12b is obtained. And the peeling sheet 12a with an application layer and the peeling sheet 12b with an application layer are bonded together so that both application layers may mutually contact. When the curing period is necessary, the curing period is set, and when the curing period is unnecessary, the above-mentioned laminated application layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, it can be stably produced.

  For example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used as a method for applying the coating solution of the adhesive composition P.

(4) Adhesive strength A transparent conductive film made of tin-doped indium oxide (ITO) is provided on the pressure-sensitive adhesive layer 11 side of the laminate obtained by laminating the pressure-sensitive adhesive layer 11 on a base material made of a polyethylene terephthalate film having a thickness of 100 μm. When the obtained transparent conductive film is attached to the transparent conductive film, the adhesive strength of the laminate to the transparent conductive film is preferably 5 to 80 N / 25 mm, particularly 10 to 70 N / 25 mm. It is preferable that it is 15-50 N / 25mm. When the adhesive force is in the above range, the constituent members of the touch panel are securely bonded.

  In addition, although the adhesive force here means the adhesive force measured by the 180 degree peeling method according to JIS Z0237: 2009, the measurement sample has a width of 25 mm and a length of 100 mm, and the measurement sample is attached. After being applied to the body by applying pressure at 0.5 MPa and 50 ° C. for 20 minutes, the sample was left for 24 hours under conditions of normal pressure, 23 ° C. and 50% RH, and then measured at a peeling rate of 300 mm / min. To do.

(5) Use of pressure-sensitive adhesive sheet By using the pressure-sensitive adhesive sheet 1, for example, the capacitive touch panel 2 shown in FIG. 2 can be manufactured. The touch panel 2 includes a display module 3, a first film sensor 5 a laminated thereon via an adhesive layer 4, and a second film sensor 5 b laminated thereon via an adhesive layer 11. And the cover material 6 laminated | stacked through the adhesive layer 11 on it is comprised.

  The two pressure-sensitive adhesive layers 11 in the touch panel 2 are the pressure-sensitive adhesive layers 11 of the pressure-sensitive adhesive sheet 1.

  Examples of the display module 3 include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper.

  The pressure-sensitive adhesive layer 4 may be formed by the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 or may be formed by another pressure-sensitive adhesive or pressure-sensitive adhesive sheet. In the latter case, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 4 includes an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyvinyl ether-based pressure-sensitive adhesive. However, among them, an acrylic pressure-sensitive adhesive is preferable.

  The 1st film sensor 5a and the 2nd film sensor 5b are normally comprised from the base film 51 and the patterned transparent conductive film 52, respectively. Although it does not specifically limit as the base film 51, For example, a polyethylene terephthalate film, a polycarbonate film, a polymethylmethacrylate film, a polycycloolefin film, a polyolefin film, a triacetylcellulose film etc. are used.

  Examples of the transparent conductive film 52 include metals such as platinum, gold, silver and copper, oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide and zinc dioxide, tin-doped indium oxide (ITO), and zinc oxide-doped oxide. Examples include composite oxides such as indium, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide, and non-oxidized compounds such as chalcogenide, lanthanum hexaboride, titanium nitride, and titanium carbide. Among these, those made of tin-doped indium oxide (ITO) are preferable.

  One of the transparent conductive film 52 of the first film sensor 5a and the transparent conductive film 52 of the second film sensor 5b normally constitutes a circuit pattern in the X-axis direction, and the other constitutes a circuit pattern in the Y-axis direction. .

  The transparent conductive film 52 of the first film sensor 5a in the present embodiment is located on the upper side (the cover material 6 side) of the first film sensor 5a in FIG. 2, but is not limited thereto. The first film sensor 5a may be located below (the display module 3 side). Further, the transparent conductive film 52 of the second film sensor 5b is located below the second film sensor 5b in FIG. 2, but the present invention is not limited to this, and the second film sensor 5b. It may be located above.

  The cover material 6 is mainly composed of a glass plate or a plastic plate. The glass plate is not particularly limited. For example, chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass. Etc. The plastic plate is not particularly limited, and examples thereof include an acrylic plate made of polymethyl methacrylate and the like, and a polycarbonate plate.

  In addition, a functional layer such as a hard coat layer, an antireflection layer, or an antiglare layer may be provided on one side or both sides of the glass plate or plastic plate, or a hard coat film, an antireflection film, or an antiglare film. Such optical members may be laminated.

  In the present embodiment, the cover material 6 has a step on the surface on the pressure-sensitive adhesive layer 11 side, and specifically has a step due to the presence or absence of the printing layer 7. The print layer 7 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the cover material 6.

  The material which comprises the printing layer 7 is not specifically limited, The well-known material for printing is used. The thickness of the printing layer 7, that is, the height of the step, is preferably 3 to 45 μm, more preferably 5 to 35 μm, particularly preferably 7 to 25 μm, and preferably 7 to 15 μm. Further preferred.

  Further, the thickness of the printing layer 7 (height of the step) is preferably 3 to 30% of the thickness of the pressure-sensitive adhesive layer 11, particularly preferably 3.2 to 20%, and more preferably 3 It is preferable that it is 5 to 15%. As a result, the pressure-sensitive adhesive layer 11 follows the step due to the printing layer 7 well, and the occurrence of floating, bubbles, etc. in the vicinity of the step is suppressed.

An example of the manufacturing method of the touch panel 2 will be described below.
One release sheet 12a (or 12b) is peeled from the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 is bonded to the film sensor 5a so as to be in contact with the patterned transparent conductive film 52 of the film sensor 5a. Next, the other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 is attached to the film sensor 5b so as to be in contact with the patterned transparent conductive film 52 of the film sensor 5b. Match. Thereby, the laminated body by which the film sensor 5a, the adhesive layer 11, and the film sensor 5b are laminated | stacked one by one is obtained.

  Next, the pressure-sensitive adhesive layer 4 provided on the release sheet is bonded to the surface of the laminated body on the film sensor 5a side (exposed surface of the base film 51 of the film sensor 5a). Moreover, the adhesive sheet 1 different from the said adhesive sheet 1 is prepared, one peeling sheet 12a (or 12b) is peeled from the said adhesive sheet 1, and the exposed adhesive layer 11 is adhesive with the said laminated body. It is bonded to the surface opposite to the side on which the layer 4 is laminated (exposed surface of the base film 51 of the film sensor 5b).

  Thereafter, the other release sheet 12b (or 12a) is peeled from the other adhesive sheet 1, and the printed layer 7 side of the cover material 6 is in contact with the adhesive layer 11 with respect to the exposed adhesive layer 11. The cover material 6 is bonded. Thereby, the structure by which the cover material 6, the adhesive layer 11, the film sensor 5b, the adhesive layer 11, the film sensor 5a, the adhesive layer 4, and a peeling sheet are laminated | stacked one by one is obtained.

  Finally, the release sheet is peeled from the structure, and the structure is bonded to the display module 3 so that the exposed adhesive layer 4 is in contact with the display module 3. Thereby, the touch panel 2 shown in FIG. 2 is manufactured.

  When the pressure-sensitive adhesive layer 11 and the cover material 6 are bonded in the above process, since the pressure-sensitive adhesive layer 11 is excellent in step following ability, it is difficult to form a gap between the step formed by the printing layer 7 and the pressure-sensitive adhesive layer 11. The agent layer 11 can fill the step.

  In the touch panel 2 described above, since the adhesive layer 11 has a predetermined refractive index and storage elastic modulus, it is difficult to see the circuit pattern of the transparent conductive film 52. In particular, the touch panel 2 has a high temperature such as 80 ° C. The effect is also demonstrated when placed underneath. Moreover, in the said touch panel 2, since the adhesive layer 11 is excellent in level | step difference followable | trackability, a space | gap or a bubble is hard to be made between the level | step difference by the printing layer 7, and the adhesive layer 11, and also the touch panel 2 is high-temperature, high-humidity conditions. Even when placed, bubbles and the like are prevented from being generated in the vicinity of the step. Moreover, in the said touch panel 2, since the adhesive layer 11 does not contain the component which has a carboxyl group, the transparent conductive film 52 which the adhesive layer 11 contacts is corroded, or the resistance value of the transparent conductive film 52 is changed. Is suppressed. Further, when the pressure-sensitive adhesive layer 11 is formed by crosslinking the pressure-sensitive adhesive composition P, the pressure-sensitive adhesive layer 11 is excellent in moisture and heat whitening resistance, and returns to room temperature after the touch panel 2 is placed in a high temperature and high humidity condition. Whitening at the time is suppressed. Moreover, when the cover material 6 is a plastic plate, the pressure-sensitive adhesive layer 11 has the above-described storage elastic modulus and has cohesive strength derived from the hard monomer in the (meth) acrylic acid ester copolymer (A). In addition, foaming of the pressure-sensitive adhesive layer 11 due to outgas generated from the cover material 6 and bubble mixing (blister) are suppressed.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, one of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
1. Preparation of (meth) acrylic acid ester copolymer 30 parts by mass of butyl acrylate, 30 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized ( A (meth) acrylic acid ester copolymer (A) was prepared. When the molecular weight of this (meth) acrylic acid ester copolymer (A) was measured by the method mentioned later, it was weight average molecular weight (Mw) 600,000.

2. Preparation of adhesive composition (Meth) acrylate copolymer (A) 100 parts by mass (in terms of solid content; the same applies hereinafter) obtained in the above step (1), and trimethylol as a crosslinking agent (B) 0.25 parts by mass of propane-modified tolylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name “L-45”) and 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name) as a silane coupling agent “KBM-403”) was mixed with 0.2 parts by mass, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 40% by mass.

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[(Meth) acrylic ester copolymer (A)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate (hard monomer)
HEA: 2-hydroxyethyl acrylate IBXA: Isobornyl acrylate (hard monomer)
ACMO: acryloylmorpholine (hard monomer)
A-LEN: Ethoxylated o-phenylphenol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
BzA: benzyl acrylate AA: acrylic acid V-3F: 2,2,2-trifluoroethyl acrylate
[Crosslinking agent (B)]
TDI: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name “L-45”)
XDI: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name “TD-75”)
Epoxy: 1,3-bis (diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, product name “TETRAD-C”)

3. Production of pressure-sensitive adhesive sheet Peeling of a heavy-peelable release sheet (product name "SP-PET752150", manufactured by Lintec Corporation), in which one side of a polyethylene terephthalate film was subjected to a release treatment with a silicone-based release agent The treated surface was coated with a knife coater so that the thickness after drying was 25 μm, and then heated at 100 ° C. for 4 minutes to form a coated layer. Similarly, a release treatment of a light release release sheet (product name “SP-PET382120” manufactured by Lintec Corporation) in which one side of a polyethylene terephthalate film was release-treated with a silicone-based release agent was applied to the obtained adhesive composition coating solution. The surface was coated with a knife coater so that the thickness after drying was 25 μm, and then heated at 100 ° C. for 4 minutes to form a coating layer.

  Subsequently, the heavy release type release sheet with the coating layer obtained above and the light release type release sheet with the coating layer obtained above were bonded so that both coating layers were in contact with each other. By curing for 7 days under the condition of 50% RH, a pressure-sensitive adhesive sheet having a structure of heavy release type release sheet / pressure-sensitive adhesive layer (thickness: 50 μm) / light release type release sheet was produced. The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring instrument (manufactured by Teclock, product name “PG-02”) in accordance with JIS K7130.

[Examples 2 to 24, Comparative Examples 1 to 4]
Kind of each monomer constituting the (meth) acrylic acid ester copolymer (A), ratio and polymerization average molecular weight (Mw), kind and blending amount of the crosslinking agent (B), and blending of the silane coupling agent (C) A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the amount was changed as shown in Table 1. In addition, about Examples 7-9, the benzyl benzoate (made by Tokyo Chemical Industry Co., Ltd.) as a refractive index regulator was further mix | blended with the adhesive composition. The blending amounts are as shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Measurement of adhesive strength)
The light-release type release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was easily adhered to a polyethylene terephthalate film (Toyobo Co., Ltd., PETA4300, thickness: 100 μm) having an easy-adhesion layer. Bonded to the layer. The laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

  On the other hand, a transparent conductive film (Oike Industry Co., Ltd., ITO film, thickness: 125 μm) in which a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) is provided on one side of a polyethylene terephthalate (PET) film The PET film was fixed to the glass plate so that the PET film side was in contact with the glass plate.

  The heavy release release sheet was peeled off from the sample, and the exposed adhesive layer was attached to the transparent conductive film. This pasting was performed by pressurizing at a pressure of 0.5 MPa for 20 minutes under a temperature condition of 50 ° C.

  Then, after leaving for 24 hours under conditions of normal pressure, 23 ° C., and 50% RH, using a tensile tester (Orientec, Tensilon), according to JIS Z0237: 2009, a peeling rate of 300 mm / min, The adhesive strength (N / 25 mm) was measured under the condition of a peeling angle of 180 °. The results are shown in Table 2.

[Test Example 2] (Measurement of storage elastic modulus)
The release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and a plurality of pressure-sensitive adhesive layers were laminated so as to have a thickness of 3 mm. A cylindrical body (height 3 mm) having a diameter of 8 mm was punched out from the obtained laminate of the pressure-sensitive adhesive layer, and this was used as a sample.

About the said sample, based on JISK7244-6, the storage elastic modulus (MPa) was measured on condition of the following by the torsional shear method using the viscoelasticity measuring device (the REOMETRIC company make, DYNAMIC ANALAYZER). The results are shown in Table 2.
Measurement frequency: 1Hz
Measurement temperature: 80 ° C

[Test Example 3] (Measurement of refractive index)
Using the Abbe refractometer (Atago Co., Ltd., product name “Abbe refractometer DR-M2”, Na light source, wavelength: 589 nm), the refractive index of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples, It measured according to JIS K0062-1992. The results are shown in Table 2.

[Test Example 4] (Evaluation of pattern visibility)
On the ITO film of a transparent conductive film (Oike Industry Co., Ltd., ITO film) in which a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) is provided on one side of a 125 μm thick PET film, A polyimide adhesive tape (width 1 cm) was bonded so as to be arranged in parallel at intervals of 1 cm.

  The obtained laminate was dipped in hydrochloric acid adjusted to 1 mol / l for 2 minutes to etch the ITO film portion on which the polyimide adhesive tape was not applied. Subsequently, the laminate was sufficiently washed with ion-exchanged water, dried at 120 ° C. for 10 minutes, and then the polyimide adhesive tape was peeled off from the transparent conductive film. As a result, a transparent conductive film was obtained in which the ITO film was patterned so that the 1 cm wide ITO film portion and the 1 cm wide ITO film non-existing portion were alternately repeated.

  Next, the transparent conductive film patterned with the ITO film as described above was annealed at 150 ° C. for 90 minutes to crystallize the patterned ITO film.

  On the other hand, the light release type release sheet was peeled from the pressure sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure sensitive adhesive layer was laminated on a PET film having a thickness of 100 μm. Then, the heavy release release sheet is peeled from the pressure-sensitive adhesive layer laminated on the PET film (thickness 100 μm), and the exposed pressure-sensitive adhesive layer is replaced with the patterned ITO film (crystals) of the transparent conductive film obtained above. Pasted together. Thus, an evaluation sample having a configuration of PET film (thickness 125 μm) / patterned ITO film / adhesive layer / PET film (thickness 100 μm) was obtained.

By visually observing the patterned ITO film under the fluorescent lamp from the transparent conductive film side of the obtained evaluation sample, that is, the PET film side having a thickness of 125 μm, the pattern visibility by the pressure-sensitive adhesive layer according to the following criteria ( The difficulty in viewing the pattern of the transparent conductive film) was evaluated. The results are shown in Table 2.
A: The pattern is not visible.
○: The pattern is slightly visible.
X: A pattern is visible.

[Test Example 5] (Evaluation of step following ability)
(A) Preparation of sample for evaluation On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), an ultraviolet curable ink (made by Teikoku Ink, The product name “POS-911 Black”) was screen-printed in a frame shape (outside: 90 mm long × 50 mm wide, 5 mm wide) so that the coating thickness was 5 μm, 10 μm, 15 μm, and 20 μm. Next, irradiation with ultraviolet rays (80 W / cm ² , ^two metal halide lamps, lamp height of 15 cm, belt speed of 10 to 15 m / min) is performed to cure the printed ultraviolet curable ink, and a level difference due to printing (level difference) Stepped glass plates having a thickness of 5 μm, 10 μm, 15 μm and 20 μm) were produced.

  The light release type release sheet was peeled off from the pressure sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure sensitive adhesive layer was easily adhered to a polyethylene terephthalate film (PET100A4300, Toyobo Co., Ltd., thickness: 100 μm) having an easy adhesion layer. Bonded to the layer. Next, the heavy release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (product name “LPD3214”, manufactured by Fuji Pla Co., Ltd.), the laminate is laminated on each stepped glass plate so that the pressure-sensitive adhesive layer covers the entire surface of the frame-like printing, and autoclave treatment (50 The sample for evaluation was obtained by carrying out (C, 0.5MPa, 30 minutes).

(B) Evaluation of Evaluation Sample For the evaluation sample, first, the step following property at the stage where the evaluation sample was obtained was evaluated as “initial”. Step followability is determined by whether or not the printing step is completely filled with the adhesive layer, and if gaps or bubbles are observed at the interface between the printing step and the adhesive layer, it cannot follow the printing step. It is judged that Here, the step following property was evaluated as a step following rate (%) according to the following criteria.

  Next, the sample for evaluation was put in an environment of 85 ° C. and 85% RH for 72 hours. Then, it returned to normal temperature normal humidity of 23 degreeC and 50% RH, and evaluated the level | step difference followability of the said sample for evaluation as "after the endurance" similarly to the above. The respective evaluation results are shown in Table 2.

Step follow-up rate% = {(height of printed step filled without gaps or bubbles (μm)) / (thickness of adhesive layer: 50 μm)} × 100
A: Step following rate 40%
○: Step following rate 10% to 30%
×: Step following rate less than 10%

[Test Example 6] (Moisture and heat whitening evaluation)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were sandwiched between two soda lime glasses (thickness: 1.1 mm) to obtain a laminate. About the laminated body, haze value (%) was measured according to JISK7136: 2000 using the haze meter (The Nippon Denshoku Industries Co., Ltd. make, product name "NDH2000").

  Next, the laminate was stored for 72 hours under wet heat conditions of 85 ° C. and 85% RH. Thereafter, the temperature was returned to room temperature and normal humidity of 23 ° C. and 50% RH, and the laminate was subjected to a haze value according to JIS K7136: 2000 using a haze meter (product name “NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd.). %). In addition, the said haze value was measured within 30 minutes after returning a laminated body to normal temperature normal humidity.

  Based on the above results, a haze value increase (points) after the wet heat condition was calculated by subtracting the haze value before the wet heat condition from the haze value after the wet heat condition. Humidity and heat-whitening resistance is good when the haze value rises after a moist heat condition is less than 1.0 point (A), and heat haze resistance increases when the haze value rise after a moist heat condition is 1.0 point or more and less than 5.0 points Those having an increase in haze value of 5.0 points or more within the suitability value (◯) and wet heat conditions were evaluated as poor heat and heat whitening resistance (x). The results are shown in Table 2.

[Test Example 7] (Blister resistance evaluation)
The adhesive layer of the adhesive sheets obtained in the examples and comparative examples is made of a transparent conductive film (made by Oike Kogyo Co., Ltd., ITO film) provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side of a PET film. , Thickness: 125 μm) and a polycarbonate plate (Mitsubishi Gas Chemical Co., Ltd., Iupilon sheet MR58, thickness: 1 mm) to obtain a laminate.

  The obtained laminate was autoclaved for 30 minutes at 50 ° C. and 0.5 MPa, and then allowed to stand for 15 hours. Subsequently, it was stored for 72 hours under 85 ° C. and 85% RH durability conditions. Thereafter, it was visually confirmed whether or not the pressure-sensitive adhesive layer had bubbles, floats or peeling. As a result, no bubble, no lift or peeling was evaluated as 、, only a bubble having a diameter of 0.2 mm or less was generated, ○, a bubble having a diameter of more than 0.2 mm, float or peeling was evaluated as ×. (Evaluation of blister resistance). The results are shown in Table 2.

  As can be seen from Table 2, according to the pressure-sensitive adhesive sheets obtained in the examples, it was difficult to see the pattern of the transparent conductive film, and excellent level difference followability and blister resistance were achieved. In particular, the pressure-sensitive adhesive sheets obtained in Examples 1 to 23 were excellent in moisture and heat whitening resistance, and the pressure-sensitive adhesive sheets obtained in Examples 1 to 22 and 24 also had excellent adhesive strength. .

  The pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention are very useful for forming a pressure-sensitive adhesive layer used in a capacitive touch panel.

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Touch panel 3 ... Display body module 4 ... Adhesive layer 5a ... 1st film sensor 5b ... 2nd film sensor 51 ... Base film 52 ... Transparent Conductive film 6 ... Cover material 7 ... Print layer

Claims (8)

Capacitance method comprising two transparent conductive films, or a transparent conductive film and a cover material, and further comprising an adhesive layer positioned between the two transparent conductive films or between the transparent conductive film and the cover material Touch panel,
The pressure-sensitive adhesive layer is
The refractive index is 1.47 to 1.54,
The storage elastic modulus at 80 ° C. is 0.02 to 0.10 MPa,
A touch panel comprising an adhesive that does not contain a component having a carboxyl group.   The touch panel according to claim 1, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive. The acrylic adhesive is
(Meth) acrylic acid ester copolymer (A) not containing a monomer having a carboxyl group as a monomer unit constituting the polymer;
The touch panel according to claim 2, wherein the pressure-sensitive adhesive composition containing the crosslinking agent (B) is crosslinked.   The (meth) acrylic acid ester copolymer (A) is an aromatic having a monomer unit constituting the polymer of 5 to 30% by mass of a monomer having a hydroxyl group and a glass transition temperature of 70 ° C. or more as a homopolymer. The touch panel according to claim 3, comprising 5 to 40% by mass of a hard monomer having no ring.   The (meth) acrylic acid ester copolymer (A) contains at least one selected from the group consisting of methyl methacrylate, isobornyl acrylate and acryloylmorpholine as the hard monomer which is a monomer unit constituting the polymer. It contains, The touchscreen of Claim 4 characterized by the above-mentioned.   The touch panel according to any one of claims 3 to 5, wherein the (meth) acrylic acid ester copolymer (A) has a weight average molecular weight of 200,000 to 1,000,000.   The touch panel according to claim 1, wherein the pressure-sensitive adhesive further contains a silane coupling agent (C).   The thickness of the said adhesive layer is 10-400 micrometers, The touch panel as described in any one of Claims 1-7 characterized by the above-mentioned.

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