KR102215672B1 - Double-sided adhesive sheet - Google Patents

Abstract

As a double-sided adhesive sheet 1 provided with an adhesive layer 2 disposed between two patterned transparent conductive films or between the patterned transparent conductive film and a cover material or display module, the adhesive layer 2 A double-sided pressure-sensitive adhesive sheet 1 comprising a pressure-sensitive adhesive comprising a component and an adhesive composition containing light-diffusion fine particles, and having a haze value of 2 to 40% of the pressure-sensitive adhesive layer 2. According to the pressure-sensitive adhesive layer 2 of such a double-sided pressure-sensitive adhesive sheet 1, it is possible to make the circuit pattern of the transparent conductive film invisible in a capacitive touch panel or the like.

Description

Double-sided adhesive sheet {DOUBLE-SIDED ADHESIVE SHEET}

The present invention relates to a double-sided adhesive sheet that can be used for a touch panel or the like.

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

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

The film sensor is usually composed of a base film and a transparent conductive film made of patterned tin-doped indium oxide (ITO). In the touch panel having such a patterned transparent conductive film, there is a problem of so-called pattern visibility, in which the circuit pattern of the transparent conductive film is seen and the appearance is deteriorated.

In order to solve the problem of pattern visibility, in Patent Document 1, an undercoat layer is formed between the film substrate and the transparent conductor layer, and the difference between the refractive index of the transparent conductor layer and the refractive index of the undercoat layer is used. It is intended to suppress the appearance of the pattern by reducing the difference in reflectance between the patterned portion and the non-patterned portion.

In addition, in Patent Document 2, an easily-adhesive layer and an optical adjustment layer that stipulate the content, refractive index, and thickness of the polyester resin are laminated between the polyester film and the transparent conductor layer to prevent optical interference by the easily-adhesive layer. By suppressing the influence, we are trying to suppress the appearance of the pattern.

Japanese Patent Laid-Open No. 2011-142089 Japanese Patent Laid-Open No. 2013-184431

However, in the invention described in Patent Document 1, it was difficult to control the film thickness of the undercoat layer as described above, and it was difficult to obtain a sufficient effect of suppressing pattern visibility. In addition, there is also a problem that the cost is increased by forming the undercoat layer. On the other hand, in the invention described in Patent Document 2, it was difficult to control the refractive index and film thickness of the easily adhesive layer, and it was difficult to obtain a sufficient effect of suppressing the appearance of the pattern.

The present invention has been made in view of the above realities, and an object of the present invention is to provide a double-sided pressure-sensitive adhesive sheet capable of making the circuit pattern of a transparent conductive film invisible by an adhesive layer in a capacitive touch panel or the like.

In order to achieve the above object, the first aspect of the present invention is a double-sided adhesive sheet having an adhesive layer disposed between two patterned transparent conductive films, or between the patterned transparent conductive film and a cover material or display module, Provided is a double-sided pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive comprising an adhesive component and an adhesive composition containing light-diffusion fine particles, and the pressure-sensitive adhesive layer has a haze value of 2 to 40% (Invention 1). .

When the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet according to the invention (invention 1) is disposed between two patterned transparent conductive films or between the patterned transparent conductive film and the cover material or display module, the haze value of the pressure-sensitive adhesive layer is By being in the above range, it is possible to make the circuit pattern of the transparent conductive film difficult to be seen while maintaining high light transmittance.

In the above invention (invention 1), the average particle diameter of the light-diffusing fine particles by centrifugal sedimentation light transmission is preferably 0.1 to 20 µm (invention 2).

In the above invention (inventions 1 and 2), it is preferable that the adhesive component contains a (meth)acrylic acid ester polymer (invention 3).

In the above invention (invention 3), it is preferable that the (meth)acrylic acid ester polymer is crosslinked with a crosslinking agent (invention 4).

In the above invention (Invention 3 and 4), the content of the light-diffusion fine particles is preferably 0.01 to 15 parts by mass per 100 parts by mass of the (meth)acrylic acid ester polymer (Invention 5).

In addition, the present invention is characterized in that a pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet (Inventions 1 to 5) is provided between the two patterned transparent conductive films or between the patterned transparent conductive film and the cover material or display module. It provides a laminated body. In this laminate, the pressure-sensitive adhesive layer may or may not be in direct contact with the transparent conductive film, the cover material, or the display module.

According to the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet according to the present invention, it is possible to make the circuit pattern of the transparent conductive film invisible while maintaining high light transmittance in a capacitive touch panel or the like.

1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a configuration example of a touch panel.

Hereinafter, an embodiment of the present invention will be described.

The double-sided pressure-sensitive adhesive sheet according to the present embodiment includes a pressure-sensitive adhesive layer disposed between two patterned transparent conductive films or between the patterned transparent conductive films and a cover material or a display module.

As shown in Fig. 1, the double-sided pressure-sensitive adhesive sheet 1 according to the present embodiment includes two release sheets 3a and 3b and the two release sheets 3a and 3b in contact with the release surfaces of the two release sheets 3a and 3b. It is composed of the pressure-sensitive adhesive layer 2 sandwiched between the release sheets 3a and 3b. However, in the double-sided adhesive sheet 1, the release sheets 3a and 3b are not essential components, and are peeled and removed when the double-sided adhesive sheet 1 is used. In addition, the peeling surface of a release sheet in this specification refers to the surface which has peelability in a peeling sheet, and includes both a peeling-treated surface and a surface exhibiting peelability even if no peeling treatment has been performed.

1. Adhesive layer

The pressure-sensitive adhesive layer 2 in the present embodiment is made of a pressure-sensitive adhesive formed from an adhesive composition containing an adhesive component and light-diffusion fine particles (hereinafter sometimes referred to as “adhesive composition P”), and has a haze value of 2 It is -40%. In the pressure-sensitive adhesive layer 2 in the present embodiment, by controlling the haze value using light-diffusion fine particles as described above, the circuit pattern of the transparent conductive film can be improved while maintaining high light transmittance in a capacitive touch panel or the like. It can be made invisible, and an excellent pattern suppression effect is exhibited.

When the haze value is less than 2%, the effect of suppressing the appearance of the pattern is not obtained, and the circuit pattern of the transparent conductive film is observed. In addition, even when the haze value exceeds 40%, the effect of suppressing the appearance of the pattern is not obtained. From such a viewpoint, the haze value of the pressure-sensitive adhesive layer 2 is preferably 3 to 30%, and particularly preferably 6 to 20%. In addition, the haze value in this specification is taken as a value measured according to JIS K7136:2000.

(1) adhesive component

The adhesive component is not particularly limited as long as it exhibits a desired adhesive force in a capacitive touch panel or the like, has light transmittance, and does not impair the effect of the light-diffusion fine particles. As such an adhesive component, an acrylic adhesive component, a rubber adhesive component, a silicone adhesive component, a polyurethane adhesive component, a polyester adhesive component, etc. are mentioned, for example, but an acrylic adhesive component is especially preferable from the said viewpoint.

As an acrylic adhesive component, it is preferable to contain a (meth)acrylic acid ester polymer (A), and a (meth)acrylic acid ester polymer (A) crosslinked with a crosslinking agent (B) is particularly preferable. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. Other similar terms are the same. In addition, in this specification, the concept of "copolymer" shall also be included in "polymer".

(1-1) (meth)acrylic acid ester polymer (A)

It is preferable that the (meth)acrylic acid ester polymer (A) contains an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group as a monomer constituting the polymer. Thereby, the obtained adhesive can express preferable adhesiveness. In addition, the (meth)acrylic acid ester polymer (A) includes a (meth)acrylate alkyl ester having 1 to 20 carbon atoms in the alkyl group, a monomer having a functional group reacting with the crosslinking agent (B) (reactive functional group-containing monomer), as desired. It is particularly preferred that it is a copolymer of other monomers used accordingly. In addition, the hard monomer mentioned later is excluded from the said alkyl (meth)acrylate.

Examples of alkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group include 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, (meth) ) Palmityl acrylate, stearyl (meth)acrylate, and the like. Among them, from the viewpoint of further improving the adhesiveness, (meth)acrylate esters having 1 to 8 carbon atoms in the alkyl group are preferred, and methyl acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are particularly preferred. Do. In addition, these may be used individually or may be used in combination of 2 or more types.

The (meth)acrylic acid ester polymer (A) preferably contains 30 to 90% by mass of an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer, and particularly 40 to 75% by mass It is preferable to contain it, and further it is preferable to contain 50-65 mass %.

As the reactive functional group-containing monomer, a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), etc. are preferably mentioned.

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

As a carboxyl group-containing monomer, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid, are mentioned, for example. Among them, acrylic acid is preferable from the viewpoint of reactivity of the carboxyl group in the obtained (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and copolymerization with other monomers. These may be used alone or in combination of two or more.

As an amino group-containing monomer, aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. are mentioned, for example. These may be used alone or in combination of two or more.

When the (meth)acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content is preferably 15 to 30% by mass from the viewpoint of level difference followability under durable conditions. In particular, it is preferably 17 to 28% by mass, and furthermore, it is preferably 20 to 25% by mass from the viewpoint of making the moist heat whitening resistance optimal in addition to the above viewpoint.

When the (meth)acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content is preferably 5 to 25% by mass from the viewpoint of level difference followability under durable conditions. In particular, it is preferably 7 to 20% by mass, and further, it is preferably 10 to 15% by mass from the viewpoint of making the moist heat whitening resistance optimal in addition to the above viewpoint.

Here, when the touch panel or the like is placed in an environment of high temperature and high humidity, moisture intrudes into the pressure-sensitive adhesive layer, and when the touch panel or the like returns to room temperature, there is a problem of "moist heat whitening" in which the pressure-sensitive adhesive layer whitens and decreases transparency. When the (meth)acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above range, a predetermined amount of reactive functional groups will remain in the pressure-sensitive adhesive layer. The reactive functional group is usually a hydrophilic group, and if such a hydrophilic group is present in a predetermined amount of the pressure-sensitive adhesive layer, even when the pressure-sensitive adhesive layer is placed under high temperature and high humidity conditions, compatibility with moisture infiltrating the pressure sensitive adhesive layer under the high temperature and high humidity conditions is good, as a result. Whitening of the pressure-sensitive adhesive layer is suppressed, and the pressure-sensitive adhesive layer 2 is excellent in moisture-heat whitening resistance.

It is preferable that the (meth)acrylic acid ester polymer (A) contains an acrylic acid ester-based hard monomer as a monomer unit constituting the polymer. Here, the hard monomer refers to a monomer having a glass transition temperature (Tg) of 70°C or higher, preferably 75 to 200°C, and particularly preferably 80 to 180°C, as a homopolymer obtained by polymerizing only the hard monomer. The pressure-sensitive adhesive obtained by containing the hard monomer as a monomer unit constituting the (meth)acrylic acid ester polymer (A) is excellent in durability and blister resistance. Therefore, even when the adherend is a plastic plate and outgas is generated from the plastic plate, generation of blisters such as bubbles, lifting, peeling, etc. is suppressed.

As the hard monomer, for example, methyl methacrylate (Tg 105°C), isobornyl acrylate (Tg 94°C), isobornyl methacrylate (Tg 180°C), acryloylmorpholine (Tg 145°C) , Adamantyl acrylate (Tg 115°C), adamantyl methacrylate (Tg 141°C), dimethylacrylamide (Tg 89°C), acrylamide (Tg 165°C), and the like. These may be used alone or in combination of two or more.

Among the hard monomers, methyl methacrylate, isobornyl acrylate, and acryloylmorpholine are more preferable from the viewpoint of more exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesiveness and transparency. Methyl acrylate is particularly preferred.

The (meth)acrylic acid ester polymer (A) preferably contains 10 to 45% by mass of the hard monomer, and particularly preferably 15 to 30% by mass, as a monomer unit constituting the polymer. By containing 10% by mass or more of the hard monomer, an effect of improving durability or blister resistance by the monomer unit can be expected. On the other hand, by making the content of the hard monomer 45% by mass or less, the relative shortage of other monomer units in the (meth)acrylic acid ester polymer (A) is prevented, and the adhesiveness, step followability, and moist heat resistance of the obtained pressure-sensitive adhesive are prevented. Mars can be made good.

It is preferable that the (meth)acrylic acid ester polymer (A) contains a hydroxyl-containing monomer and the hard monomer in the above-described ranges as monomer units constituting the polymer. Thereby, the obtained adhesive becomes what is more excellent in blister resistance.

The (meth)acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer, as desired. As the other monomer, a monomer that does not contain a reactive functional group is preferable in order not to interfere with the action of the hydroxyl group-containing monomer. Examples of such other monomers include (meth)acrylate alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, and (meth)acrylate esters having an aliphatic ring such as cyclohexyl (meth)acrylate. , (Meth)acrylic acid ester having a non-crosslinkable tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate, vinyl acetate, styrene, and the like. These may be used alone or in combination of two or more.

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

The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 to 1.5 million, particularly preferably 200,000 to 1.3 million, and further preferably 300,000 to 800,000. In addition, the weight average molecular weight in this specification is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method.

Moreover, in the adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used individually by 1 type, and may be used in combination of 2 or more types.

When the adhesive composition P contains a (meth)acrylic acid ester polymer (A) as an adhesive component, and the (meth)acrylic acid ester polymer (A) has the above-described predetermined composition and molecular weight, the obtained adhesive layer (2) is It is also excellent in step followability. Accordingly, even if the pressure-sensitive adhesive layer 2 is affixed to a cover material having a step difference due to a printing layer or the like, voids or bubbles are unlikely to occur between the step and the pressure-sensitive adhesive layer. Further, even when the laminate is placed under a high temperature such as 80°C, bubbles or the like are prevented from occurring in the vicinity of the step.

(1-2) crosslinking agent (B)

When the adhesive component of the adhesive composition P contains a (meth)acrylic acid ester polymer (A) containing a reactive functional group-containing monomer as a monomer unit constituting the polymer and a crosslinking agent (B), heating the adhesive composition P And the crosslinking agent (B) reacts with the reactive functional group of the reactive functional group-containing monomer constituting the (meth)acrylic acid ester polymer (A). Thereby, a structure in which the (meth)acrylic acid ester polymer (A) is crosslinked by the crosslinking agent (B) is formed, and the strength and durability of the pressure-sensitive adhesive layer 2 are improved.

As the crosslinking agent (B), any one that reacts with the reactive functional group possessed by the (meth)acrylic acid ester polymer (A) may be used. For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an amine crosslinking agent, a melamine crosslinking agent, an aziridine crosslinking agent, and hydrazine A crosslinking agent, an aldehyde type crosslinking agent, an oxazoline type crosslinking agent, a metal alkoxide type crosslinking agent, a metal chelate type crosslinking agent, a metal salt type crosslinking agent, an ammonium salt type crosslinking agent, and the like. Among the above, when the reactive functional group of the (meth)acrylic acid ester polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with a hydroxyl group, and the reactive functional group possessed by the (meth)acrylic acid ester polymer (A) When is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent excellent in reactivity with a carboxyl group. In addition, crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate 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, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate. Adducts that are reactants with low-molecular active hydrogen-containing compounds such as alicyclic polyisocyanates such as, and their biuret body, isocyanurate body, and further ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc. Sieves and the like. Among them, from the viewpoint of reactivity with a hydroxyl group, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferred.

As an epoxy crosslinking agent, for example, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, Ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidylamine, etc. are mentioned.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.001 to 10 parts by mass, particularly preferably 0.01 to 5 parts by mass, and further 0.02 to 100 parts by mass of the (meth)acrylic acid ester polymer (A). It is preferable that it is -1 mass part.

(2) light diffusion fine particles

As the light-diffusion fine particles, any one capable of making the haze value of the pressure-sensitive adhesive layer 2 within the above range, for example, inorganic fine particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide; Organic light-transmitting fine particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin; Fine particles made of a silicon-containing compound having an intermediate structure between inorganic and organic, such as a silicone resin (eg, Tospul series manufactured by Momentive Performance Materials Japan), and the like. Among them, acrylic resin fine particles and fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic are preferable because they have excellent dispersibility in the adhesive component and uniform optical properties can be obtained. The above light-diffusion fine particles may be used alone or in combination of two or more.

As the shape of the light-diffusion fine particles, spherical fine particles with uniform light diffusion are preferable. The average particle diameter of the light-diffusion fine particles by the centrifugal sedimentation light transmission method is preferably 0.1 to 20 µm, more preferably 1 to 10 µm. In particular, when the light-diffusion fine particles are fine particles composed of a silicon-containing compound, the average particle diameter by the centrifugal sedimentation light transmission method is preferably 1 to 10 µm. When the average particle diameter is within the above range, the haze value can be in the above-described range without disturbing the light transmittance of the pressure-sensitive adhesive layer 2.

In addition, as for the average particle diameter by the centrifugal sedimentation light transmission method, 1.2 g of fine particles and 98.8 g of isopropyl alcohol were sufficiently stirred as a sample for measurement, and a centrifugal automatic particle size distribution measuring device (manufactured by Horiba Seisakusho, CAPA- 700).

When the adhesive composition P contains the (meth)acrylic acid ester polymer (A) as an adhesive component, the content of the light-diffusion fine particles is preferably 0.01 to 15 parts by mass per 100 parts by mass of the (meth)acrylic acid ester polymer (A). It is more preferable that it is 0.1-4 mass parts. Furthermore, in the case of light-diffusion fine particles composed of a silicon-containing compound having an intermediate structure between organic and inorganic, such as a silicone resin, it is particularly preferably 0.2 to 1.5 parts by mass, most preferably 0.2 to 0.9 parts by mass, and organic In the case of the translucent fine particles, it is most preferably 0.3 to 3 parts by mass. When the content of the light-diffusion fine particles is within the above range, the haze value of the pressure-sensitive adhesive layer 2 can be set within the above-described range, and an excellent effect of suppressing the appearance of a pattern can be obtained. In addition, when the adhesive component is other than the acrylic adhesive component, the content of the light-diffusion fine particles is preferably within the above range with respect to 100 parts by mass of the adhesive component.

(3) Various additives

The adhesive composition P (the adhesive constituting the adhesive layer 2), as desired, includes various additives, such as a silane coupling agent, a refractive index adjuster, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, a softener, You may contain a filler or the like.

It is preferable that the adhesive composition P contains a silane coupling agent from the viewpoint of improving the adhesive force of the obtained adhesive. It is preferable that the silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, has good compatibility with an adhesive component, and has light transmittance.

Examples of such silane coupling agents include silicon compounds containing polymerizable unsaturated groups such as vinyl trimethoxysilane, vinyl triethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, Silicon compounds having an epoxy structure such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyl Mercapto group-containing silicon compounds such as dimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3 -Amino group-containing silicon compounds such as aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these, methyltriethoxysilane, ethyltriethoxysilane , A condensation product of an alkyl group-containing silicon compound such as methyl trimethoxysilane and ethyl trimethoxysilane. These may be used individually by 1 type, and may be used in combination of 2 or more types.

When the adhesive composition P contains the (meth)acrylic acid ester polymer (A) as an adhesive component, the content of the silane coupling agent is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the (meth)acrylic acid ester polymer (A). , Particularly preferably 0.05 to 5 parts by mass, and further preferably 0.1 to 1 parts by mass. Moreover, when the adhesive component is other than an acrylic adhesive component, it is preferable that content of a silane coupling agent is the said range with respect to 100 mass parts of adhesive components.

(4) Preparation of adhesive composition

The adhesive composition P can be produced by mixing an adhesive component, light-diffusion fine particles, and an additive as desired. When the adhesive component contains a (meth)acrylic acid ester polymer (A), first, a (meth)acrylic acid ester polymer (A) is prepared, and a crosslinking agent (B) is blended as desired.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by a conventional radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (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, and methyl ethyl ketone, and two or more types may be used in combination.

As a polymerization initiator, an azo compound, an organic peroxide, etc. are mentioned, You may use 2 or more types together. As an azo compound, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonitrile) ), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azo Bis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azo Bis[2-(2-imidazolin-2-yl)propane] and the like.

Examples of the organic peroxide include benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butylperoxyneodecanoate, t-butylperoxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, diacetyl peroxide, and the like.

In addition, in the polymerization step, by blending a chain transfer agent such as 2-mercaptoethanol, the weight average molecular weight of the obtained polymer can be adjusted.

When the (meth)acrylic acid ester polymer (A) is obtained, the light-diffusion fine particles, and optionally the crosslinking agent (B) and additives are added to the solution of the (meth)acrylic acid ester polymer (A), and sufficiently mixed to form a solvent. Diluted adhesive composition P (coating solution) is obtained.

Examples of the diluting 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, and 1-methoxy Alcohol such as -2-propanol, ketones such as 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, cellosolve solvents such as ethyl cellosolve, etc. Used.

The concentration and viscosity of the coating solution thus prepared may be within a range in which coating is possible, and is not particularly limited, and may be appropriately selected depending on the situation. For example, it is diluted so that the concentration of the adhesive composition P becomes 10-40 mass %. In addition, when obtaining a coating solution, addition of a diluting solvent etc. is not a necessary condition, and it is not necessary to add a diluting solvent as long as the adhesive composition P has a coatable viscosity or the like.

(5) formation of adhesive

The adhesive in this embodiment is formed from the adhesive composition P. Formation of the pressure-sensitive adhesive can usually be performed by subjecting the pressure-sensitive adhesive composition P to heat treatment. In addition, this heat treatment can also serve as a drying treatment when volatilizing the diluted solvent of the adhesive composition P or the like.

When the adhesive composition P contains the (meth)acrylic acid ester polymer (A), the heating temperature of the heat treatment is preferably 50 to 150°C, and particularly preferably 70 to 120°C. In addition, the heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be set at room temperature (eg, 23° C., 50% RH). When this curing period is necessary, after the curing period has elapsed, and when the curing period is unnecessary, after the heat treatment is completed, the adhesive is formed.

(6) thickness of the adhesive layer

The thickness of the pressure-sensitive adhesive layer 2 (value measured according to JIS K7130) is preferably 5 to 600 µm, particularly preferably 20 to 300 µm, and further preferably 50 to 150 µm. When the thickness of the pressure-sensitive adhesive layer 2 is 5 μm or more, good adhesion is exhibited. Moreover, when affixed to an adherend having a level difference, the level difference followability is exhibited. On the other hand, when the thickness of the pressure-sensitive adhesive layer 2 is 600 µm or less, workability becomes good. Further, the pressure-sensitive adhesive layer 2 may be formed as a single layer, or may be formed by laminating a plurality of layers.

2. Release sheet

Although it does not specifically limit as release sheets 12a, 12b, For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene tere Phthalate film, polyethylene naphthalate 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 films, polycarbonate films, polyimide films, fluororesin films, and the like are used. Moreover, these crosslinked films are also used. Moreover, these laminated films may be sufficient.

It is preferable that the peeling treatment is performed on the peeling surface (particularly the surface in contact with the pressure-sensitive adhesive layer 2) of the peeling sheets 12a and 12b. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. In addition, it is preferable that one of the release sheets 12a and 12b be used as a medium-release type release sheet having a large peeling force, and the other release sheet be used as a light-release type release sheet having a small peeling force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 µm.

3. Preparation of double-sided adhesive sheet

As an example of production of the double-sided adhesive sheet 1, after applying the coating liquid of the adhesive composition P to the release surface of one release sheet 12a (or 12b), performing heat treatment to form a coating layer, The peeling surface of the other peeling sheet 12b (or 12a) is superimposed on the coating layer. When a curing period is required, a curing period is provided, and when a curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 2 as it is. Thereby, the said double-sided adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another example of production of the double-sided adhesive sheet 1, a coating liquid of the adhesive composition P is applied to the release surface of one release sheet 12a, followed by heat treatment to form a coating layer, and a release sheet ( 12a). Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other peeling sheet 12b, followed by heat treatment to form a coating layer to obtain a peeling sheet 12b with a coating layer formed thereon. Then, the release sheet 12a on which the coating layer was formed and the release sheet 12b on which the coating layer was formed are bonded together so that both coating layers are in contact with each other. When a curing period is required, a curing period is provided, and when a curing period is unnecessary, the laminated coating layer becomes the pressure-sensitive adhesive layer 2 as it is. Thereby, the said double-sided adhesive sheet 1 is obtained. According to this manufacturing example, even when the adhesive layer 2 is thick, it becomes possible to manufacture stably.

As a method of applying the coating liquid of the adhesive composition P, 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.

4. Use of double-sided adhesive sheet

The double-sided pressure-sensitive adhesive sheet 1 according to the present embodiment can be used for a laminate having a circuit pattern of a transparent conductive film, and can be particularly suitably used for a capacitive touch panel. When the double-sided pressure-sensitive adhesive sheet 1 is used for a capacitive touch panel, the pressure-sensitive adhesive layer 2 may be present in any position as long as it is between the display module of the touch panel and the cover material. It may be positioned between the transparent conductive film, the transparent conductive film and the cover material, and between the transparent conductive film and the display module. Even if the pressure-sensitive adhesive layer 2 is present at any of these positions, the circuit pattern of the transparent conductive film is difficult to see due to the excellent pattern suppression effect of the pressure-sensitive adhesive layer 2.

By using the double-sided pressure-sensitive adhesive sheet 1 according to the present embodiment, for example, a touch panel 10 of a capacitive type shown in FIG. 2 can be manufactured. The touch panel 10 includes a display module 4, a first film sensor 5a stacked thereon through an adhesive layer 2, and a second film sensor 5a stacked thereon through an adhesive layer 2 It comprises a film sensor 5b and a cover member 6 laminated thereon via an adhesive layer 2.

The three pressure-sensitive adhesive layers 2 in the touch panel 10 are the pressure-sensitive adhesive layers 2 of the double-sided pressure-sensitive adhesive sheet 1, but are not limited thereto, and at least one pressure-sensitive adhesive layer 2 is The adhesive layer 2 of the double-sided adhesive sheet 1 may be sufficient. When one or two pressure-sensitive adhesive layers 2 in the touch panel 10 are the pressure-sensitive adhesive layer 2 of the double-sided pressure-sensitive adhesive sheet 1, the other pressure-sensitive adhesive layers are composed of a desired pressure-sensitive adhesive. As the desired pressure-sensitive adhesive, those that do not contain light-diffusion fine particles of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 2 can be exemplified.

Examples of the display module 4 include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper.

The first film sensor 5a and the second film sensor 5b are usually constituted by a base film 51 and a 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 polymethyl methacrylate film, a polycycloolefin film, a polyolefin film, a triacetyl cellulose 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. Compound oxides such as doped indium oxide, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide, non-oxidizing compounds such as chalcogenide, lanthanum hexaborate, titanium nitride, titanium carbide, etc. Among them, those made of tin-doped indium oxide (ITO) are preferable.

The transparent conductive film 52 of the first film sensor 5a and the transparent conductive film 52 of the second film sensor 5b are usually one of a circuit pattern in the X-axis direction and the other in the Y-axis direction. Construct a circuit pattern.

Although the transparent conductive film 52 of the 1st film sensor 5a in this embodiment is located above the 1st film sensor 5a in FIG. 2 (cover material 6 side), it is limited to this. It does not mean that it may be located below the first film sensor 5a (on the display module 4 side). In addition, although the transparent conductive film 52 of the 2nd film sensor 5b is located under the 2nd film sensor 5b in FIG. 2 (the display body module 4 side), it is not limited to this, You may be located above the 2nd film sensor 5b (cover material 6 side).

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

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

In the present embodiment, the cover member 6 has a level difference on the surface on the side of the pressure-sensitive adhesive layer 2, and specifically, has a level difference due to the presence or absence of the printing layer 7. The printing layer 7 is generally formed in a frame shape on the side of the pressure-sensitive adhesive layer 2 in the cover material 6.

The material constituting the printing layer 7 is not particularly limited, and a known material for printing is used. The thickness of the print 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 still more preferably 7 to 15 µm. .

In addition, the thickness (height of the step) of the printing layer 7 is preferably 50% or less of the thickness of the pressure-sensitive adhesive layer 2, particularly preferably 5 to 40%, and further preferably 10 to 30%. . When the thickness of the pressure-sensitive adhesive layer 2 satisfies the above relationship with the thickness of the print layer 7, the pressure-sensitive adhesive layer 2 satisfactorily follows the step difference caused by the print layer 7 and is lifted or air bubbles in the vicinity of the step difference. It is suppressed from occurring.

An example of a method of manufacturing the touch panel 10 will be described below.

As the double-sided adhesive sheet 1, first, second and third double-sided adhesive sheets 1 are prepared. First, one release sheet 3a (or 3b) is peeled from the first double-sided pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 2 is transferred to the patterned transparent conductive film 52 of the film sensor 5a. It bonds with the said film sensor 5a so that it may contact. Next, the other release sheet 3b (or 3a) is peeled from the first double-sided adhesive sheet 1, and the exposed adhesive layer 2 is brought into contact with the patterned transparent conductive film 52 of the film sensor 5b. It bonds with the said film sensor 5b so that it might be. Thereby, a laminate obtained by sequentially laminating the film sensor 5a, the pressure-sensitive adhesive layer 2 and the film sensor 5b is obtained.

Next, one release sheet 3a (or 3b) is peeled from the second double-sided pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 2 is placed on the side of the film sensor 5a of the laminate (film sensor). It adheres to the exposed surface of the base film 51 of (5a). In addition, one release sheet 3a (or 3b) is peeled from the third double-sided adhesive sheet 1, and the exposed adhesive layer 2 is separated from the side on which the adhesive layer 2 is laminated in the laminate. It adheres to the opposite side (exposed surface of the base film 51 of the film sensor 5b).

Thereafter, the other release sheet 3b (or 3a) is peeled from the third double-sided adhesive sheet 1, and the printed layer 7 side of the cover material 6 is applied to the exposed adhesive layer 2 The cover member 6 is bonded so as to be in contact with the pressure-sensitive adhesive layer 2. Thereby, the cover material 6, the adhesive layer 2, the film sensor 5b, the adhesive layer 2, the film sensor 5a, the adhesive layer 2, and the release sheet 3b (or 3a) are A structure formed by sequentially stacking is obtained.

Finally, the release sheet 3b (or 3a) is peeled off from the structure, and the structure is bonded to the display module 4 so that the exposed pressure-sensitive adhesive layer 2 contacts the display module 4. Thereby, the touch panel 10 shown in FIG. 2 is manufactured.

The pressure-sensitive adhesive layer (2) in contact with the cover material (6) is composed of an adhesive composition P containing a (meth)acrylic acid ester polymer (A) as an adhesive component, and the (meth)acrylic acid ester polymer (A) is defined above It has a composition and molecular weight of, and when the pressure-sensitive adhesive layer 2 has a predetermined thickness, the pressure-sensitive adhesive layer 2 is excellent in step followability. Therefore, when bonding the pressure-sensitive adhesive layer 2 and the cover material 6 in the above step, voids or bubbles are hardly generated between the step difference due to the printing layer 7 and the pressure-sensitive adhesive layer 2, and the pressure-sensitive adhesive layer ( 2) This step can be filled. Further, even when the touch panel 10 is placed in a high temperature and high humidity condition, generation of air bubbles or the like in the vicinity of the step is prevented.

In the above-described touch panel 10, since the pressure-sensitive adhesive layer 2 has a predetermined haze value, an excellent pattern visibility suppression effect is exhibited, and the circuit pattern of the transparent conductive film 52 is hardly seen. Further, since the pressure-sensitive adhesive layer 2 has high light transmittance, the screen of the display module 4 can be clearly displayed. In addition, when the adhesive layer 2 is composed of an adhesive composition P containing a (meth)acrylic acid ester polymer (A) as an adhesive component, and the (meth)acrylic acid ester polymer (A) has the predetermined composition described above, the The pressure-sensitive adhesive layer 2 is excellent in moist heat whitening resistance, and whitening when the touch panel 10 returns to room temperature after being placed in a high temperature and high humidity condition is suppressed.

Moreover, the touch panel 10 may be provided with a layer which exhibits other pattern visibility suppression effect in addition to the said layer. For example, a known refractive index adjusting layer (index matching layer) is provided between the base film 51 and the transparent conductive film 52 in the first film sensor 5a and/or the second film sensor 5b. You may have it.

Embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents falling within the technical scope of the present invention.

For example, any one of the release sheets 3a and 3b in the double-sided pressure-sensitive adhesive sheet 1 may be omitted.

Example

Hereinafter, the present invention will be described in more detail by examples and the like, but the scope of the present invention is not limited to these examples.

[Example 1]

1. Preparation of (meth)acrylic acid ester copolymer

90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid were copolymerized to prepare a (meth)acrylic acid ester polymer (A). When the molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described later, it was 400,000 in weight average molecular weight (Mw).

2. Preparation of adhesive composition

100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in the above step (1) (in terms of solid content; the same as below) and 1,3-bis(N,N'- as a crosslinking agent (B) (epoxy crosslinking agent)) Diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD C-5") 0.057 parts by mass and 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent Manufacturing, product name "KBM-403") 0.25 parts by mass and fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic as light-diffusion fine particles (manufactured by Momentive Performance Materials Japan, brand name "Tospearl 120" ", average particle diameter: 2.0 µm, refractive index: 1.42) 0.1 parts by mass was mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 34% by mass.

Here, the formulation of the adhesive composition is shown in Table 1. In addition, details, such as the abbreviation shown in Table 1, are as follows.

[(Meth)acrylic acid ester polymer (A)]

BA: n-butyl acrylate

AA: acrylic acid

2EHA: 2-ethylhexyl acrylic acid

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylic acid

[Crosslinking agent (B)]

Epoxy: 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD C-5")

Isocyanate: Xylylene diisocyanate-based crosslinking agent (manufactured by Toyo Ink Corporation, product name "BHS8515")

[Light diffusion fine particles]

Toss pearl 120: fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, brand name "Tos pearl 120", average particle diameter: 2.0 μm, refractive index: 1.43)

Toss Pearl 145: Fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, brand name "Tos Pearl 145", average particle diameter: 4.5 μm, refractive index: 1.43)

SSX102: Crosslinked acrylic resin beads (manufactured by Sekisuika Sehinkogyo Co., Ltd., brand name "SSX102", average particle diameter: 2.5 µm, refractive index: 1.49)

SSX104: Crosslinked acrylic resin beads (manufactured by Sekisuika Sehinko Co., Ltd., brand name "SSX104", average particle diameter: 4.0 µm, refractive index: 1.49)

3. Preparation of double-sided adhesive sheet

The thickness after drying was 25 μm on the peeling-treated side of the heavy-release type release sheet (manufactured by Lintec, product name “SP-PET752150”) obtained by applying the obtained adhesive composition coating solution to one side of the polyethylene terephthalate film with a silicone-based release agent. After coating with a knife coater as much as possible, heat treatment was performed at 90° C. for 1 minute to form a coating layer. Similarly, the applied solution of the obtained adhesive composition was applied to the peeling-treated surface of a light-peelable release sheet (manufactured by Lintec, product name ``SP-PET382120'') obtained by peeling off one side of a polyethylene terephthalate film with a silicone-based release agent. After coating with a knife coater so that it might become mu m, it heat-processed at 90 degreeC for 1 minute, and formed the coating layer.

Next, 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 are bonded so that both coating layers are in contact with each other, and cured for 7 days under conditions of 23°C and 50% RH. By doing this, a double-sided pressure-sensitive adhesive sheet comprising a medium-release type release sheet/adhesive layer (thickness: 50 μm)/a light release type release sheet was produced. In addition, the thickness of the pressure-sensitive adhesive layer is a value measured using a static pressure thickness meter (manufactured by Tekrox, product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 14, Comparative Examples 1 to 8]

As shown in Table 1, the type, ratio and polymerization average molecular weight (Mw) of each monomer constituting the (meth)acrylic acid ester polymer (A), the type and amount of crosslinking agent (B), and the type and amount of light-diffusion fine particles are shown in Table 1. Except changing, it carried out similarly to Example 1, and produced the double-sided adhesive sheet.

Here, the above-described weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).

<Measurement conditions>

GPC measuring device: manufactured by Tosoh Corporation, HLC-8020

GPC column (passed in the following order): manufactured by Tosoh Corporation

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Measurement solvent: tetrahydrofuran

·Measurement temperature: 40℃

[Test Example 1] (Measurement of haze value)

About the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples, a haze value (%) was measured according to JIS K 7136:2000 using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., NDH2000). The results are shown in Table 2.

[Test Example 2] (Evaluation of the effect of suppressing pattern visibility)

On the ITO film of a transparent conductive film (ITO film, manufactured by Oikeko Co., Ltd.) in which a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) is formed on one side of a 125 μm-thick polyethylene terephthalate film, a plurality of polyees The mid adhesive tapes (1 cm in width) were bonded together so as to be arranged in parallel at 1 cm intervals.

The obtained laminate was immersed in hydrochloric acid adjusted to 1 mol/L for 2 minutes, and the portion of the ITO film to which the polyimide adhesive tape was not affixed was etched. 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 in which an ITO film was patterned was obtained so that an ITO film portion having a width of 1 cm and an ITO film-free portion having a width of 1 cm were alternately repeated.

Subsequently, 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, after cutting the double-sided pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples into a width of 45 mm and a length of 70 mm, the light-release type release sheet was peeled off. The exposed pressure-sensitive adhesive layer was bonded to the patterned ITO film (crystallization) of the transparent conductive film obtained above. The heavy peeling type release sheet was peeled from the laminate, and the exposed pressure-sensitive adhesive layer was affixed to a 0.5 mm-thick glass plate made of alkali glass, and this was used as a sample.

The sample was pressurized in an autoclave at 0.5 MPa and 50° C. for 30 minutes, and then put in an environment of 85° C. and 85% RH for 72 hours. After that, it was confirmed whether or not the circuit pattern was visible from the side of the polyethylene terephthalate film with the naked eye, and the effect of suppressing the appearance of the pattern was evaluated according to the following criteria. The results are shown in Table 2.

◎: The pattern is not seen.

○: The pattern is seen faintly.

X: The pattern is seen.

[Test Example 3] (Evaluation of level difference followability)

(a) Preparation of sample for evaluation

On the surface of a glass plate (manufactured by NSG Flash Transfer, product name "Corning Glass Eagle XG", 90 mm long x 50 mm wide x 0.5 mm thick), UV-curable ink (manufactured by Teikoku Ink, product name "POS-911 Ink") Screen printing was performed in a frame shape (outer shape: 90 mm long x 50 mm wide, 5 mm wide) so that the coating thickness became any one of 5 µm, 10 µm, 15 µm and 20 µm. Subsequently, ultraviolet rays are irradiated (80 W/cm 2, metal halide lamp 2 lamp, lamp height 15 cm, belt speed 10 to 15 m/min), the printed ultraviolet curable ink is cured, and the step by printing (step difference A glass plate having a height of 5 µm, 10 µm, 15 µm, and 20 µm) was prepared.

The light-release type release sheet was peeled from the double-sided pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was applied to an easily-adhesive layer of a polyethylene terephthalate film (manufactured by Toyobo, PET A4300, thickness: 100 μm). Joined together. Then, the heavy peeling type release sheet was peeled off, and the pressure-sensitive adhesive layer was exposed. Then, using a laminator (manufactured by Fuji Plaza, product name "LPD3214"), the laminate was laminated on a glass plate having each step so that the pressure-sensitive adhesive layer covers the entire frame-shaped printing surface, and this was used as a sample for evaluation.

(b) Evaluation of the sample for evaluation

The obtained sample for evaluation was autoclaved for 30 minutes at 50° C. and 0.5 MPa, and then stored for 72 hours at 85° C. and 85% RH moist heat. After that, the pressure-sensitive adhesive layer (especially in the vicinity of the step difference due to the printing layer) was visually confirmed, and the step difference followability was evaluated according to the following criteria. The results are shown in Table 2.

◎: There were no air bubbles, lifting, and peeling.

○: Only bubbles with a diameter of 0.2 mm or less were generated.

X: Air bubbles having a diameter of more than 0.2 mm, lifting or peeling occurred.

[Test Example 4] (Evaluation of blister resistance)

The pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples is transparent of a polyethylene terephthalate film (manufactured by Oikeko Co., Ltd., ITO film, thickness: 125 μm) with a transparent conductive film made of tin-doped indium oxide (ITO) formed on one side. An acrylic plate made of a conductive film and polymethyl methacrylate (PMMA) (manufactured by Mitsubishi Gas Chemical Co., Ltd., Upiron sheet MR200, thickness: 1 mm) or polycarbonate (PC) plate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) Pylon sheet MR58, thickness: 1 mm) and sandwiched it, and obtained the laminated body.

The obtained laminate was subjected to an autoclave treatment at 50°C and 0.5 MPa for 30 minutes, and then allowed to stand at normal pressure, 23°C and 50% RH for 15 hours. Then, it stored for 72 hours under the durable conditions of 85 degreeC and 85%RH. After that, it was visually checked whether or not there were bubbles, lifting or peeling in the pressure-sensitive adhesive layer, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2.

○… There were no air bubbles, lifting and peeling, or only air bubbles with a diameter of 0.1 mm or less occurred.

×… Air bubbles having a diameter of more than 0.1 mm, lifting or peeling occurred.

[Test Example 5] (Moisture heat whitening evaluation)

Two polyethylene terephthalate films (made by Oikeko Co., Ltd., ITO film, thickness: 125 μm) formed with a transparent conductive film made of tin-doped indium oxide (ITO) on one side were prepared, and the transparent conductive films of these ITO films were examples or comparisons. In order to contact the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet obtained in the example, the pressure-sensitive adhesive layer was sandwiched, and the laminate was used as a sample.

First, the haze value (the haze value before the moist heat condition) of the obtained sample was measured. Next, the sample was stored for 72 hours under humid heat conditions of 85°C and 85% RH. Then, it returned to the atmosphere of 23 degreeC and 50% RH (room temperature and humidity), and the haze value (haze value after moist heat conditions) of the said sample was measured within 30 minutes. The haze value was measured using a haze meter (manufactured by Nippon Denshoku Co., Ltd., product name "NDH2000") according to JIS K7136:2000.

The haze value before the moist heat condition was subtracted from the haze value after the moist heat condition, and the haze value increase (point) after the moist heat condition was calculated. The results are shown in Table 2. If this haze value rise is less than 1.0 point, it can be said that the moist heat whitening resistance is good.

As can be seen from Table 2, the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet obtained in Examples had excellent pattern visibility suppression performance, good step tracking property and moist heat whitening resistance. Further, the pressure-sensitive adhesive layers of Examples 8 to 14 in which a hydroxyl-containing monomer and a hard monomer were used as monomer units constituting the (meth)acrylic acid ester polymer (A) were also excellent in blister resistance.

Industrial availability

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

1: double-sided adhesive sheet
2: adhesive layer
3a, 3b: release sheet
4: display module
5a: first film sensor
5b: second film sensor
51: base film
52: transparent conductive film
6: cover material
7: printing layer
10: touch panel

Claims (5)

As a double-sided adhesive sheet provided with an adhesive layer,
The pressure-sensitive adhesive layer is disposed between two patterned transparent conductive films, or between a patterned transparent conductive film and a cover material or a display module, and used,
The pressure-sensitive adhesive layer is composed of an adhesive formed of an adhesive composition containing an adhesive component and light-diffusion fine particles,
The haze value of the pressure-sensitive adhesive layer is 2 to 40%
Double-sided adhesive sheet, characterized in that. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the average particle diameter of the light-diffusing fine particles by centrifugal sedimentation light transmission method is 0.1 to 20 µm. The double-sided adhesive sheet according to claim 1, wherein the adhesive component contains a (meth)acrylic acid ester polymer. The double-sided adhesive sheet according to claim 3, wherein the (meth)acrylic acid ester polymer is crosslinked with a crosslinking agent. The double-sided pressure-sensitive adhesive sheet according to claim 3, wherein the content of the light-diffusion fine particles is 0.01 to 15 parts by mass based on 100 parts by mass of the (meth)acrylic acid ester polymer.

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