TWI642739B - Touch panel - Google Patents

Abstract

The present invention provides an adhesive and an adhesive sheet. The adhesive of the present invention is used between two transparent conductive films or between a transparent conductive film and a cover material in a touch panel of an electrostatic capacity method. The refractive index of the adhesive is 1.45 ~ 1.54, the storage elastic modulus at 80 ° C is 0.02 ~ 0.10MPa, and does not contain a component having a carboxyl group. The aforementioned adhesive sheet (1) includes an adhesive layer (11) composed of an adhesive. According to these adhesives and the adhesive sheet (1), the circuit pattern of the transparent conductive film can be made inconspicuous, and the step followability is excellent, and the transparent conductive film will not be adversely affected by the carboxyl group.

Description

Touch panel

The present invention relates to an adhesive and an adhesive sheet that can be used in a touch panel and the like.

In recent years, in various mobile electronic devices such as smart phones and tablet computers, the use of a capacitive touch panel as a display has been increasing.

There are a plurality of structures in a touch panel of an electrostatic capacity type. As a typical example, the following structures can be exemplified, which include a display module such as a liquid crystal module, and a first thin film sensor, which is laminated through an adhesive On the display body module; the second thin film sensor is laminated on the first thin film sensor through an adhesive; and the cover material is laminated on the second thin film sensor through the adhesive.

Here, the frame-shaped printed layer may exist as a step on the display body module side of the cover material. If the adhesive layer does not follow the step, it will cause the adhesive layer to float near the step, thereby causing loss of light reflection. Therefore, a step followability is required for the above-mentioned adhesive layer.

On the other hand, in general, the above-mentioned thin film sensor is composed of a base film and a transparent conductive film composed of a patterned tin-doped indium oxide (ITO). Here, if the adhesive of the adhesive layer in contact with the transparent conductive film contains a hydroxy acid (carboxyl group), corrosion of the transparent conductive film or change in the resistance value of the transparent conductive film may occur. problem.

In addition, in a touch panel having the patterned transparent conductive film as described above, there is a problem of a so-called pattern visualization that affects the appearance by seeing the circuit pattern of the transparent conductive film. When the touch panel is placed at a high temperature, this problem tends to occur particularly remarkably.

In order to solve the above-mentioned pattern visualization problem, Patent Document 1 proposes an adhesive that specifies a storage elastic modulus at 23 ° C, and Patent Document 2 proposes a predetermined adhesive that specifies a storage elastic modulus at 120 ° C and an adhesive force. Agent. In addition, Patent Document 3 proposes an adhesive layer that uses a propylene-based adhesive composition containing a predetermined amount of a propylene-based polymer and a styrene-based oligomer, and specifies a refractive index and a haze.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2012-128629

[Patent Document 2] Japanese Patent Laid-Open No. 2012-238467

[Patent Document 3] Japanese Patent Laid-Open No. 2013-116992

However, with the adhesives of Patent Documents 1 to 3, it is not easy to sufficiently satisfy the effects of both of the pattern visualization suppression performance and the step followability. In addition, since the propylene 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 actual situation as described above. The purpose is to provide an adhesive and an adhesive sheet capable of making the circuit pattern of the transparent conductive film inconspicuous, having excellent step followability, and not adversely affecting the transparent conductive film due to a carboxyl group in a touch panel of a capacitance method.

In order to achieve the above object, the first invention of the present invention provides an adhesive for use in a capacitive touch panel between two transparent conductive films, or between a transparent conductive film and a cover material, wherein the refractive index is It is 1.45 to 1.54, the storage elastic modulus at 80 ° C is 0.02 to 0.10 MPa, and it does not contain a component having a carboxyl group (Invention 1).

According to the above-mentioned invention (Invention 1), by specifying the refractive index and the storage elastic modulus as described above, the circuit pattern of the transparent conductive film can be made inconspicuous in the touch panel of the electrostatic capacity method, and in particular, the touch panel is placed at 80 ° C. The effect can also be exerted at high temperatures. In addition, by specifying the refractive index and the storage elastic modulus as described above, it is also excellent in followability of steps such as printing steps of the cover material. In addition, since it does not contain a component having a carboxyl group, it is possible to suppress corrosion of the transparent conductive film or change in the resistance value of the transparent conductive film.

In the above-mentioned invention (Invention 1), the adhesive is preferably formed by crosslinking an adhesive composition containing a (meth) acrylate copolymer (A) and a crosslinking agent (B), In the aforementioned (meth) acrylate copolymer (A), the monomer unit constituting the polymer contains 5 to 30% by mass of the monomer having a hydroxyl group, and the glass transition temperature of the homopolymer is 70 ° C. or higher. 5 to 40% by mass of the hard monomer having no aromatic ring, and containing no monomer having a carboxyl group (Invention 2).

In the said invention (invention 2), the said (meth) acrylate The weight average molecular weight of the copolymer (A) is preferably 200,000 to 1 million (Invention 3).

In the above invention (Inventions 2, 3), the aforementioned (meth) acrylate copolymer (A) is a monomer unit constituting the polymer, that is, the aforementioned hard monomer, and contains a material selected from the group consisting of methyl methacrylate and acrylic acid. At least one of the group consisting of bornyl ester and acrylmorpholine is preferred (Invention 4).

In the above inventions (Inventions 2 to 4), it is preferable that the adhesive further contains a silane coupling agent (C) (Invention 5).

A second aspect of the present invention provides an adhesive sheet used for bonding two transparent conductive films in a capacitive touch panel, or bonding a transparent conductive film and a cover material, including two release sheets and a The pressure-sensitive adhesive layer sandwiched between the two release sheets of the two release sheets is sandwiched by the release sheet, and the pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesive (Inventions 1 to 5) (Invention 6).

In the above invention (Invention 6), the thickness of the adhesive layer is preferably 10 to 400 μm (Invention 7).

In the above-mentioned inventions (Inventions 6, 7), the adhesive is laminated on the surface of the adhesive layer side of a laminate on a substrate made of a polyethylene terephthalate film having a thickness of 100 μm, and adhered. In the case of soda-lime glass, the adhesion of the laminated body to the soda-lime glass is preferably 5 to 50 N / 25 mm (Invention 8).

According to the adhesive agent and the adhesive layer of the adhesive sheet of the present invention, the circuit pattern of the transparent conductive film can be made inconspicuous in a touch panel of an electrostatic capacity method, especially when the touch panel is placed at a high temperature such as 80 ° C. effect fruit. In addition, the adhesive layer and the adhesive layer of the adhesive sheet of the present invention are also excellent in followability of steps, and because they do not contain a component having a carboxyl group, it is possible to suppress corrosion of the transparent conductive film or change in resistance value of the transparent conductive film.

1‧‧‧ adhesive sheet

11‧‧‧ Adhesive layer

12a, 12b ‧‧‧ peeling sheet

2‧‧‧ touch panel

3‧‧‧Display Module

4‧‧‧ Adhesive layer

5a‧‧‧1st thin film sensor

5b‧‧‧ 2nd thin film sensor

51‧‧‧ substrate film

52‧‧‧Transparent conductive film

6‧‧‧ cover material

7‧‧‧print layer

FIG. 1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of the configuration of a touch panel.

Hereinafter, embodiments of the present invention will be described.

[Adhesive]

The adhesive of 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. The adhesive is used between two transparent conductive films or between a transparent conductive film and a cover material in a touch panel of an electrostatic capacity method.

The refractive index of the adhesive of this embodiment and the storage elastic modulus at 80 ° C. are within the above ranges, thereby making it possible to make the circuit pattern of the transparent conductive film inconspicuous (not easy to observe) in the touch panel of the electrostatic capacity method, In particular, the effect can be exhibited when the touch panel is placed at a high temperature such as 80 ° C. In addition, the refractive index of the adhesive of this embodiment and the storage elastic modulus at 80 ° C. are within the above-mentioned ranges, so that the step followability is also excellent. Therefore, even if an adhesive layer composed of the adhesive is adhered to a cover material having a step difference formed by a printing layer or the like, it is not easy to generate voids or bubbles between the step difference and the adhesive layer. In addition, even when the laminated body is placed at a high temperature such as 80 ° C, bubbles and the like can be prevented from being generated near the step. In addition, since the adhesive of this embodiment does not contain a component having a carboxyl group, It is possible to suppress corrosion of the transparent conductive film or change in the resistance value of the transparent conductive film.

If the refractive index of the adhesive is less than 1.45, the circuit pattern of the transparent conductive film can be easily seen. On the other hand, if the refractive index of the adhesive exceeds 1.54, the step-followability deteriorates. In addition, if the storage elastic modulus at 80 ° C. is less than 0.02 MPa, the circuit pattern of the transparent conductive film is easy to see, and is particularly visible when placed at a high temperature such as 80 ° C. On the other hand, if the storage elastic modulus of the adhesive at 80 ° C. exceeds 0.10 MPa, the step-followability becomes worse.

From the above point of view, the refractive index of the adhesive is preferably 1.46 to 1.52, and particularly preferably 1.47 to 1.50. In addition, the storage elastic modulus of the adhesive at 80 ° C. is preferably 0.015 to 0.09 MPa, and particularly preferably 0.02 to 0.07 MPa.

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

The adhesive of this embodiment is only required to satisfy the above-mentioned physical properties. However, the adhesive composition contains a (meth) acrylate copolymer (A), a crosslinking agent (B), and a silane coupling agent (C). (Hereinafter, it may be referred to as "adhesive composition P.") A cross-linked adhesive is preferred. In the aforementioned (meth) acrylate copolymer (A), a monomer unit constituting a polymer is preferred. It contains 5 to 30% by mass of a monomer having a hydroxyl group (hydroxyl-containing monomer), and 5 to 40% by mass of a hard monomer having no aromatic ring and a glass transition temperature (Tg) of 70 ° C or more as a homopolymer. %, And does not contain a monomer having a carboxyl group. According to this adhesive, the above-mentioned physical properties (refractive index and storage elastic modulus) can be satisfied. In addition, in this specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

(1) (meth) acrylate copolymer (A)

The adhesive composition P preferably contains a (meth) acrylate copolymer (A) as a main adhesive. In the (meth) acrylic acid ester copolymer (A), the content of the hydroxyl-containing monomer and the hard monomer is within the aforementioned range, and the adhesive composition P containing the (meth) acrylic acid ester copolymer (A) is thereby contained. The obtained adhesive easily meets the aforementioned refractive index and storage elastic modulus.

In addition, the adhesive obtained from the adhesive composition P containing the (meth) acrylate copolymer (A) having a hydroxyl group-containing monomer content within the above range is set under high temperature and high humidity conditions (for example, 85 ° C, 85 After 72 hours under the condition of% RH), whitening is suppressed when the temperature is returned to normal temperature and humidity, that is, those having excellent moist heat and whitening resistance. When the (meth) acrylate copolymer (A) contains a hydroxyl-containing monomer as a monomer unit in the above-mentioned amount, a predetermined amount of hydroxyl groups remain in the obtained adhesive. The hydroxyl group is a hydrophilic group. Therefore, if the predetermined amount of the hydrophilic group is present in the adhesive, even if the adhesive is placed under high temperature and high humidity conditions, the adhesive is immersed in the adhesive under the high temperature and high humidity conditions. The compatibility with water is also good, and as a result, whitening of the adhesive is suppressed.

In the (meth) acrylic acid ester copolymer (A), if the content of the hydroxyl-containing monomer as a monomer unit is less than 5% by mass, the moisture-heat whitening resistance may be reduced. When the content is more than 30% by mass, the adherence to the adherend may be reduced, the durability may be reduced, or a desired adhesive force may not be obtained.

In addition, in the (meth) acrylate copolymer (A), if the content of the hard monomer as a monomer unit is less than 5% by mass, the refractive index and storage elastic modulus of the adhesive may be lower than the above ranges. , On the other hand, if hard If the content of the monomer exceeds 40% by mass, the step-followability is reduced, or a desired adhesive force cannot be obtained.

From the viewpoints described above, in the (meth) acrylate copolymer (A), it is preferable to contain 5 to 30% by mass of a hydroxyl-containing monomer as a monomer unit constituting the polymer, and it is more preferable to contain 10 to 25% by mass. . In the (meth) acrylic acid ester copolymer (A), as a monomer unit constituting the polymer, the hard monomer is preferably contained in an amount of 5 to 50% by mass, and more preferably 10 to 30% by mass.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and (meth) acrylic acid. 2-hydroxybutyl (hydroxy) (meth) acrylate and the like, such as 2-hydroxybutyl, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, (meth) acrylic acid 2- (meth) acrylic acid ester polymer (A) is considered in terms of its reactivity with a hydroxyl group and a crosslinking agent (B) and copolymerizability with other monomers. Hydroxyethyl esters are preferred. These substances may be used alone or in combination of two or more.

The above-mentioned hard monomer is a monomer which does not contain an aromatic ring, and the glass transition temperature of the homopolymer obtained by polymerizing only the aforementioned hard monomer is 70 ° C or higher, preferably 75 to 200 ° C, and particularly 80 to 180 ° C. good.

The hard monomer is preferably a propylene-based monomer, and examples thereof include methyl methacrylate (Tg 105 ° C), isobornyl acrylate (Tg 94 ° C), isobornyl methacrylate (Tg 180 ° C), and propylene. Morpholine (Tg 145 ° C), adamantyl acrylate (Tg 115 ° C), adamantyl methacrylate (Tg141 ° C), dimethylacrylamide (Tg89 ° C), acrylamide (Tg165 ° C) and the like. These substances may be used alone or in combination of two or more.

Among the above hard monomers, methyl methacrylate, isobornyl acrylate, and acrylomorpholine are particularly preferred. That is, the (meth) acrylic acid ester copolymer (A) contains a group selected from the group consisting of methyl methacrylate, isobornyl acrylate, and propylene morpholine, which are monomer units constituting the polymer, that is, the above-mentioned hard monomer. At least one of them is preferred.

The (meth) acrylate polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Thereby, even if the obtained adhesive is adhered to the transparent conductive film, it is possible to suppress a bad condition caused by an acid. For example, it is possible to suppress corrosion of the transparent conductive film or change in the resistance value of the transparent conductive film.

Here, "containing no component having a carboxyl group" and "containing no monomer having a carboxyl group" means that the component or monomer having a carboxyl group is practically not included, except that the component or monomer having a carboxyl group is not contained at all. A degree of corrosion of the transparent conductive film due to a carboxyl group allows a carboxyl group-containing component or a monomer to be contained. Specifically, in the (meth) acrylate polymer (A), an amount of 0.1% by mass or less of a carboxyl group-containing monomer is allowed as a monomer unit, and an amount of 0.01% by mass or less is preferable.

In the (meth) acrylate copolymer (A), as a monomer unit constituting the polymer, an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group (except for the aforementioned hard monomer) Other than) is preferred. Thereby, the obtained adhesive can show better adhesion.

Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, ( N-butyl (meth) acrylate, n-amyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Ester, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, tetradecyl (meth) acrylate, cetyl (meth) acrylate Alkyl esters, octadecyl (meth) acrylate, and the like. Among them, (meth) acrylates having 2 to 8 carbon atoms in the alkyl group are preferred from the viewpoint of further improving the adhesion, and n-butyl (meth) acrylate and 2-ethyl (meth) acrylate are preferred. Hexyl esters are particularly preferred. These substances may be used alone or in combination of two or more.

In the (meth) acrylate copolymer (A), as a monomer unit constituting the polymer, 10 to 90% by mass of the (meth) acrylic acid alkyl ester having 2 to 20 carbon atoms in the alkyl group is It is more preferable to contain 20 to 85% by mass, and it is more preferable to contain 30 to 80% by mass.

In the (meth) acrylate copolymer (A), as a monomer unit constituting the polymer, a monomer (hereinafter, sometimes referred to as “high refractive index”) which can increase the refractive index of the obtained adhesive may be contained. Rate monomer ".).

As the high refractive index monomer, a monomer containing an aromatic ring is preferable, and examples thereof include an aromatic monomer containing 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, nonylphenoxy polyethylene glycol acrylate, and (meth) Acrylic styrene and the like.

Examples of the aromatic monomer containing two or more aromatic rings include a biphenyl-containing monomer, a bisphenol A-type monomer, and the like, and a biphenyl-containing monomer is preferred from the viewpoint of handling. As the biphenyl-containing monomer, a biphenyl-containing monofunctional acrylate is preferred. Examples of such biphenyl-containing monomers include ethoxylated o-phenylbenzene Phenol acrylate, o-biphenyl (meth) acrylate and the like.

Examples of the monomer having a polycyclic aromatic skeleton include a naphthalene skeleton, an anthracene skeleton, a triphenylene skeleton, a benzoanthracene skeleton, a tetracene skeleton, a flexion skeleton, a pyrene skeleton, a pentacene skeleton, and hexacene. A monomer such as a skeleton, a heptacene skeleton, a halobenzene skeleton, a kekulene skeleton, and the like. From the viewpoint of handling, a monomer having a naphthalene skeleton or an anthracene skeleton as a polycyclic aromatic skeleton is preferable, 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 -Methoxy-naphthylene) -1-acrylate, vinylnaphthalene, and the like.

Among the above-mentioned high-refractive index monomers, benzyl (meth) acrylate and ethoxylated o-phenylphenol acrylate are particularly preferred from the viewpoint of exhibiting a high refractive index and obtaining desired adhesive applicability and handling properties. . The high refractive index monomers may be used singly or in combination of two or more kinds.

When the (meth) acrylate copolymer (A) contains a high refractive index monomer as a monomer unit constituting the polymer, the content thereof is preferably 1 to 30% by mass, and particularly 2 to 20% by mass. good.

The (meth) acrylate copolymer (A) may contain other monomer as a monomer unit which comprises this polymer as needed. As the other monomer, a monomer having no reactive functional group is preferred so as not to impair the effect of the hydroxyl-containing monomer. Examples of the other monomers include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and cyclohexyl (meth) acrylate. (Meth) acrylic esters having aliphatic rings such as esters, (N) N-N-dimethylaminoethyl (meth) acrylate, (meth) acrylic acid (Meth) acrylates having non-crosslinkable tertiary amino groups such as acid-N, N-dimethylaminopropyl, vinyl acetate, styrene and the like. These substances may be used alone or in combination of two or more.

The polymerization state of the (meth) acrylate copolymer (A) may be a random copolymer or a block copolymer.

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

Since the weight average molecular weight of the (meth) acrylate copolymer (A) is within the above range, the obtained adhesive easily meets the aforementioned storage elastic modulus.

In addition, in the adhesive composition P, a (meth) acrylate copolymer (A) may be used individually by 1 type, and may use 2 or more types together.

(2) Crosslinking agent (B)

When the adhesive composition P is crosslinked, the crosslinking agent (B) reacts with the hydroxyl group derived from the hydroxyl group-containing monomer constituting the (meth) acrylate copolymer (A). Thereby, a structure in which the (meth) acrylate copolymer (A) is crosslinked by the crosslinking agent (B) is formed.

The cross-linking agent (B) may be any one that reacts with a reactive group (a hydroxyl group of a hydroxyl-containing monomer as a monomer unit) in the (meth) acrylate copolymer (A). For example, isocyanate-based cross-linking Agent, epoxy-based crosslinking agent, amine-based crosslinking agent, melamine-based crosslinking agent, aziridine-based crosslinking agent, hydrazine-based crosslinking agent, aldehyde-based crosslinking agent, oxazoline-based crosslinking agent, metal Crosslinker for alkoxide system, metal chelate Cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents, and the like. It is preferable to use the isocyanate-type crosslinking agent excellent in the reactivity with a hydroxyl group among the said substances. Moreover, a crosslinking agent (B) can be used individually by 1 type, or can use 2 or more types together.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and isophorone diisocyanate. Alicyclic polyisocyanates, such as hydrogenated diphenylmethane diisocyanate, etc., and biuret bodies, isocyanurate bodies of the substances, and ethylene glycol, propylene glycol, neopentyl glycol, and trimethylol The reactants of low-molecular active hydrogen-containing compounds such as propane and castor oil are adducts. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferred from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylene xylene are preferred. Isocyanates are particularly preferred.

The content of the cross-linking agent (B) in the adhesive composition P is preferably 0.01 to 2 parts by mass relative to 100 parts by mass of the (meth) acrylate copolymer (A), and more preferably 0.05 to 1 part by mass, 0.1 to 0.1 parts by mass. 0.5 part by mass is more preferable. When the content of the crosslinking agent (B) is within the above range, the obtained adhesive can easily satisfy the aforementioned refractive index and storage elastic modulus.

(3) Silane coupling agent (C)

From the viewpoint of improving the adhesion of the obtained adhesive, it is preferable that the adhesive composition P contains a silane coupling agent (C). As the silane coupling agent (C), an organosilicon compound having at least one alkoxysilyl group in the molecule has good compatibility with the (meth) acrylate copolymer (A), and it is preferable that it has translucency.

Examples of such a silane coupling agent (C) include a polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrylidine, and 3-glycidyl ether propyl. Silicon compounds with epoxy structures such as trimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxy Mercapto-containing silicon compounds such as silane, 3-mercaptopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane , N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and other amino-containing silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, Or these at least one kind of condensate with an alkyl silicon-containing compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, and the like. These substances may be used singly or in combination of two or more kinds.

The content of the silane coupling agent (C) in the adhesive composition P is preferably 0.01 to 1 part by mass relative to 100 parts by mass of the (meth) acrylate copolymer (A), more preferably 0.05 to 0.5 parts by mass, and 0.1 ~ 0.3 parts by mass is further preferred.

(4) Various additives

In the adhesive composition P, various additives commonly used as propylene-based adhesives, such as a refractive index adjuster, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, and a softening agent can be added as needed. Agents, fillers, etc.

Examples of the refractive index adjusting agent include benzyl benzoate, diphenyl sulfide, triphenyl phosphate, n-butyl benzyl phthalate, diphenyl phthalate, biphenyl, and diphenylmethane. , Tricresyl phosphate, diphenyl sulfoxide, etc.

When the adhesive composition P contains a refractive index modifier, The content thereof is preferably 1 to 30 parts by mass, and more preferably 5 to 20 parts by mass based on 100 parts by mass of the acrylate copolymer (A).

(5) Production of adhesive composition

Producing a (meth) acrylate copolymer (A), adding a crosslinking agent (B) to the obtained (meth) acrylate copolymer (A), and adding a silane coupling agent (C) and additives as necessary, As a result, an adhesive composition P can be produced.

A (meth) acrylate copolymer (A) can be manufactured by polymerizing the mixture of the monomer unit which comprises a polymer by a normal radical polymerization method. If necessary, the polymerization of the (meth) acrylate copolymer (A) can be performed by a solution polymerization method using a polymerization initiator. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, n-isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

Examples of the polymerization initiator include azo compounds, organic peroxides, and the like, and two or more of them may be used in combination. As the azo-based compound, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane- 1-carboxonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile) ), 2,2'-azobis (2-methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethyl) Propionitrile), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] and the like.

Examples of the organic peroxide include benzamidine peroxide, tert-butyl perbenzoate, cumene hydrogen peroxide, diisopropylperoxydicarbonate, and di-N-propylperoxydioxide. Carbonate, bis (2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl) ) Peroxide, dipropylammonium peroxide, diethylammonium peroxide, and the like.

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

After the (meth) acrylate copolymer (A) is obtained, a crosslinking agent (B) is added to the (meth) acrylate copolymer (A) solution, and a silane coupling agent (C), a diluting solvent, The additive is mixed thoroughly to obtain an adhesive composition P (coating solution) diluted with a solvent.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; chlorinated hydrocarbons such as dichloromethane and dichloroethane; and methanol and ethanol. , Alcohols such as propanol, butanol, 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone, ethyl acetate, butyrate Ester such as ester, cellosolvent solvent such as ethyl cellosolve, etc.

The viscosity of the thickener of the coating solution prepared in this manner is not particularly limited as long as it is within a range in which it can be applied, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may become 10-60 mass%. In addition, when a coating solution is obtained, the addition of a diluent solvent or the like is not necessary, and if the adhesive composition P has a coatable viscosity or the like, the diluent solvent may not be added. In this case, the adhesive composition P becomes a coating solution in which a polymerization solvent of the (meth) acrylate polymer (A) is directly used as a diluent.

(6) Manufacturing of adhesives

The adhesive of this embodiment is preferably constituted by crosslinking the adhesive composition P. Crosslinking of the adhesive composition P is usually performed by heat treatment. The heat treatment may be combined with the drying treatment when the diluent solvent and the like of the adhesive composition P are volatilized.

When the heat treatment is performed, the heating temperature is preferably 50 to 150 ° C, and more preferably 70 to 120 ° C. The heating time is preferably 30 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks at a normal temperature (for example, 23 ° C., 50% RH) may be set. When the curing period is required, an adhesive is formed after the curing period has elapsed, and when the curing period is not required, an adhesive is formed after the heat treatment is completed.

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

[Adhesive sheet]

As shown in FIG. 1, the adhesive sheet 1 of this embodiment is sandwiched between the two peeling sheets 12a, 12b and the two peeling sheets 12a so as to contact the peeling surfaces of the two peeling sheets 12a, 12b. 12b is composed of the adhesive layer 11. In addition, the release surface of the release sheet in this specification means the surface which has peelability in a release sheet, and includes any of the surface which performed the peeling process, and the surface which can exhibit peelability even if a peeling process is not performed.

(1) Adhesive layer

The adhesive layer 11 is composed of the aforementioned adhesive, and is preferably composed of an adhesive formed by crosslinking the adhesive composition P.

The thickness of the adhesive layer 11 (value measured based on JIS K7130) depends on the height of the step, preferably 10 to 400 μm, more preferably 20 to 300 μm, and even more preferably 25 to 250 μm. Since the thickness of the adhesive layer 11 is 10 μm or more, it can exhibit good followability of the step, and because the thickness of the adhesive layer 11 is Since the thickness is 400 μm or less, the workability is good. In addition, the adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

(2) Release sheet

As the release sheet 12a, 12b, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, or a polypair Ethylene phthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic copolymer film , Ethylene / (meth) acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. In addition, a crosslinked film of these materials may be used. A laminated film of these materials may be used.

It is preferable that the peeling surface (particularly the surface which contacts the adhesive layer 11) of the said peeling sheet 12a, 12b is peeled. Examples of the release agent used for the release treatment include release agents such as alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Among the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release-type release sheet having a large release force, and the other release sheet is a light-release type release sheet having a small release force.

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

(3) Manufacturing of adhesive sheet

As a manufacturing example of the adhesive sheet 1, the coating liquid of the said adhesive composition P is apply | coated to the peeling surface of one release sheet 12a (or 12b), and heat processing is performed so that the adhesive composition P may be bridge | crosslinked, and it will be formed. After applying the layer, peel the other side The release surface of the sheet 12b (or 12a) is superposed on the coating layer. When a curing period is required, a curing period is set in advance. When a curing period is not required, the coating layer directly becomes the adhesive layer 11. Thereby, the above-mentioned adhesive sheet 1 can be obtained. The conditions for heat treatment and curing are the same as described above.

As another manufacturing example of the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the release surface of one release sheet 12a, and heat treatment is performed to crosslink the adhesive composition P to form a coating layer. A release sheet 12a with a coating layer was obtained. Then, the coating liquid of the adhesive composition P is coated on the release surface of the other release sheet 12b, and heat treatment is performed to crosslink the adhesive composition P to form a coating layer, thereby obtaining a coating layer with a coating layer. The release sheet 12b. Then, the release sheet 12a with a coating layer and the release sheet 12b with a coating layer are bonded together so that the two coating layers are in contact with each other. When a curing period is required, a curing period is set in advance. When a curing period is not required, the coating layer of the above-mentioned laminated layer directly becomes the adhesive layer 11. Thereby, the above-mentioned adhesive sheet 1 can be obtained. According to this manufacturing example, it is possible to stably manufacture even when the adhesive layer 11 is thick.

As a method for applying the coating liquid of the adhesive composition P, for example, a bar coating method, a blade coating method, a roll coating method, a blade coating method, a mold coating method, a gravure coating method, or the like can be used. .

(4) Adhesion

The adhesive layer 11 was laminated on the side of the adhesive layer 11 of the laminated body on a substrate made of a polyethylene terephthalate film having a thickness of 100 μm, and adhered to a layer provided with tin-doped indium oxide (ITO). In the case of the transparent conductive film of the transparent conductive film constituted by the transparent conductive film, the adhesion of the laminated body to the transparent conductive film is preferably 5 to 80 N / 25 mm, and particularly preferably 10 to 70 N / 25 mm. 15 ~ 50N / 25mm is more preferable. Since the adhesive force is within the above range, the constituent components of the touch panel can be reliably attached.

In addition, the term "adhesive force" as used herein refers to basically JIS Z0237: 2009 as the standard and the adhesive force measured by the 180 ° peeling method. The measurement sample was set to 25 mm in width and 100 mm in length. The measurement sample was adhered to the adherend at 0.5 MPa and 50 ° C for 20 minutes to adhere. After that, it was left for 24 hours under the conditions of normal pressure, 23 ° C., and 50% RH, and then measured at a peeling speed of 300 mm / min.

(5) Use of adhesive sheet

By using the above-mentioned pressure-sensitive adhesive sheet 1, for example, a touch panel 2 of the electrostatic capacity type shown in FIG. 2 can be manufactured. The touch panel 2 is configured to include: a display body module 3; a first thin film sensor 5a laminated on the display body module 3 via an adhesive layer 4; and a second thin film sensor 5b laminated on the display body module 3 via an adhesive layer 11 The first thin-film sensor 5a and the cover material 6 are laminated on the second thin-film sensor 5b via the adhesive layer 11.

The two adhesive layers 11 in the touch panel 2 are the adhesive layers 11 of the 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 adhesive layer 4 may be formed by the above-mentioned adhesive layer 11 of the adhesive sheet 1, or may be formed by other adhesives or adhesive sheets. In the latter case, examples of the adhesive constituting the adhesive layer 4 include propylene-based adhesives, rubber-based adhesives, silicone-based adhesives, polyurethane-based adhesives, polyester-based adhesives, and polyethylene. Among the ether-based adhesives, propylene-based adhesives are preferred.

The first thin-film sensor 5a and the second thin-film sensor 5b are generally composed of a base film 51 and a patterned transparent conductive film 52, respectively. The base film 51 is not particularly limited. For example, a polyethylene terephthalate film, a polycarbonate film, a polymethyl methacrylate film, a polycycloolefin film, a polyolefin film, or a cellulose triacetate film can be 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; and tin-doped indium oxide (ITO) and zinc oxide Doped indium oxide, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide and other complex oxides, chalcogenides, lanthanum hexaboride, titanium nitride, titanium carbide and other non- Among the oxide compounds, tin-doped indium oxide (ITO) is preferred.

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

In FIG. 2, the transparent conductive film 52 of the first thin-film sensor 5 a of this embodiment is located on the upper side (the cover material 6 side) of the first thin-film sensor 5 a, but it is not limited to this, and may be located on the first side. The lower side of the thin film sensor 5a (showing the module 3 side). In addition, in FIG. 2, the transparent conductive film 52 of the second thin-film sensor 5 b is located on the lower side of the second thin-film sensor 5 b, but it is not limited to this, and may be located on the upper side of the second thin-film sensor 5 b. .

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

In addition, one or both sides of the glass plate or plastic plate may be provided with functional layers such as a hard coat layer, an anti-reflection layer, and an anti-glare layer, and optical components such as a hard coat film, an anti-reflection film, and an anti-glare film may also be laminated.

In this embodiment, the surface of the cover material 6 on the side of the adhesive layer 11 has a step, and specifically, has a step formed by 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 adhesive layer 11 in the cover material 6.

The material constituting the printing layer 7 is not particularly limited, and a known material for printing can be used. The thickness of the printing layer 7, that is, the step height is preferably 3 to 45 μm, more preferably 5 to 35 μm, particularly preferably 7 to 25 μm, and 7 to 15 μm is more preferable.

In addition, the thickness (step height) of the printing layer 7 is preferably 3 to 30% of the thickness of the adhesive layer 11, more preferably 3.2 to 20%, and even more preferably 3.5 to 15%. Thereby, the adhesive layer 11 can follow the step difference formed by the printing layer 7 well, and can suppress generation | occurrence | production of a float, a bubble, etc. in the vicinity of a step difference.

An example of the method of manufacturing the touch panel 2 will be described below.

One peeling sheet 12a (or 12b) is peeled from the adhesive sheet 1, and the exposed adhesive layer 11 is attached to the thin film sensor 5a so as to be in contact with the patterned transparent conductive film 52 of the thin film sensor 5a. Next, the other peeling sheet 12b (or 12a) is peeled from the above-mentioned adhesive sheet 1, and the exposed adhesive layer 11 is attached to the thin film sensor 5b so as to be in contact with the patterned transparent conductive film 52 Sensor 5b. Thereby, a laminated body in which the thin film sensor 5a, the adhesive layer 11 and the thin film sensor 5b are laminated in this order can be obtained.

Next, the adhesive layer 4 provided on the release sheet is bonded to the surface of the film sensor 5a side of the laminated body (the exposed surface of the base film 51 of the film sensor 5a). In addition, an adhesive sheet 1 different from the above-mentioned adhesive sheet 1 is prepared, and one peeling sheet 12a (or 12b) is peeled off from the adhesive sheet 1, and the exposed adhesive layer 11 is bonded to the laminated body in which the adhesive layer 4 is laminated. The surface opposite to one side (the exposed surface of the base film 51 of the thin film sensor 5b).

Thereafter, the other peeling sheet 12b (or 12a) is peeled from the other adhesive sheet 1 and the cover material 6 is adhered to the exposed side so that the printed layer 7 side of the cover material 6 is in contact with the adhesive layer 11.胶 胶剂 层 11。 Adhesive layer 11. As a result, a structure including a cover material 6, an adhesive layer 11, a thin film sensor 5b, an adhesive layer 11, a thin film sensor 5a, an adhesive layer 4, and a release sheet laminated in this order can be obtained.

Finally, the peeling sheet is peeled from the above-mentioned 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 can be manufactured.

In the above process, when the adhesive layer 11 and the cover material 6 are adhered, since the step difference of the adhesive layer 11 is excellent in followability, it is difficult to generate a gap between the step difference formed by the printing layer 7 and the adhesive layer 11. The adhesive layer 11 can fill the step.

In the above touch panel 2, the adhesive layer 11 has a predetermined refractive index and a storage elastic modulus, whereby the circuit pattern of the transparent conductive film 52 is not obvious. In particular, the touch panel 2 may be placed at a high temperature such as 80 ° C. Exert its effect. In addition, in the touch panel 2 described above, the step difference of the adhesive layer 11 is excellent. Therefore, it is difficult to generate voids or bubbles between the step difference formed by the printing layer 7 and the adhesive layer 11. In addition, when the touch panel 2 is placed under high temperature and high humidity conditions, bubbles can be prevented from being generated near the step difference. . In addition, in the touch panel 2 described above, the adhesive layer 11 does not contain a component having a carboxyl group, so that the transparent conductive film 52 contacted by the adhesive layer 11 can be prevented from being corroded or the resistance value of the transparent conductive film 52 changing. In addition, when the adhesive layer 11 is formed by cross-linking the adhesive composition P, the adhesive layer 11 is excellent in moisture and heat whitening resistance, and the touch panel 2 is restored under high temperature and high humidity conditions. Whitening at room temperature is suppressed. In addition, when the cover material 6 is a plastic plate, the adhesive layer 11 has the aforementioned storage elastic modulus and has the cohesive force derived from the hard monomer in the (meth) acrylate copolymer (A). The foaming of the pressure-sensitive adhesive layer 11 caused by the outgassing or the like generated from the cover material 6 is suppressed (blistering).

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each of the elements disclosed in the above embodiments is intended to include all design changes or equivalents belonging to the technical scope of the present invention.

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

[Example]

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

[Example 1]

1. Preparation of (meth) acrylate 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 were copolymerized to prepare a (meth) acrylate copolymer物 (A). As a result of measuring the molecular weight of this (meth) acrylate copolymer (A) by the method mentioned later, the weight average molecular weight (Mw) was 600,000.

2. Preparation of adhesive composition

100 parts by mass of the (meth) acrylate copolymer (A) obtained in the above process (1) (solid content conversion value; the same applies hereinafter), and trimethylolpropane-modified toluene as a crosslinking agent (B) 0.25 parts by mass of diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "L-45"), 3-glycidyl ether propyltrimethoxysilane, a silane coupling agent (Shin-Etsu Chemical Co., Ltd., product name "KBM-403") 0.2 parts by mass were mixed and stirred sufficiently, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 40% by mass.

The mixing | blending of this adhesive composition is shown in Table 1. The details of the abbreviations and the like described in Table 1 are as follows.

[(Meth) acrylate 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: Acrylic morpholine (hard monomer)

A-LEN: ethoxylated o-phenylphenol acrylate (Shin-Nakamura (Manufactured by Chemical Industry Co., Ltd.)

BzA: benzyl acrylate

AA: Acrylic

V-3F: 2,2,2-trifluoroethyl acrylate

[Crosslinking agent (B)]

TDI: Trimethylolpropane modified toluene diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "L-45")

XDI: Trimethylolpropane modified xylylene diisocyanate (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75")

Epoxy: 1,3-bis (glycidyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company Inc., product name "TETRAD-C")

3. Manufacturing of adhesive sheet

The coating solution of the obtained adhesive composition was applied with a doctor blade coater so that the thickness after drying became 25 μm. After the release-treated surface of a heavy release-type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") on which the surface was subjected to release treatment, a heat treatment was performed at 100 ° C for 4 minutes to form a coating layer. Similarly, the coating solution of the obtained adhesive composition was applied with a doctor blade coater so that the thickness after drying became 25 μm to a polyethylene terephthalate using a silicone release agent. After the release-treated surface of a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") on one side of the ester film was peeled off, the heat treatment was performed at 100 ° C for 4 minutes to form a coating layer.

Next, the heavy-peeling type with the coating layer obtained above was peeled The sheet and the light-peeling release sheet with a coating layer obtained above were bonded so that the two coating layers were in contact with each other, and cured for 7 days at 23 ° C. and 50% RH to produce An adhesive sheet composed of a heavy release type release sheet / adhesive layer (thickness: 50 μm) / light release type release sheet was produced. The thickness of the adhesive layer is a value measured in accordance with JIS K7130 using a constant-pressure thickness measuring device (manufactured by TECLOCK Company Inc., product name "PG-02").

[Examples 2 to 24, Comparative Examples 1 to 4]

The type and ratio of each monomer constituting the (meth) acrylate copolymer (A), the polymerization average molecular weight (Mw), the type and amount of the crosslinking agent (B), and the compounding of the silane coupling agent (C) An adhesive sheet was produced in the same manner as in Example 1 except that the amounts were changed as shown in Table 1. In addition, regarding Examples 7 to 9, benzyl benzoate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a refractive index adjuster was further blended to the adhesive composition. The blending amount is shown in Table 1.

Here, the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement).

<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

‧Determination solvent: tetrahydrofuran

‧Measuring temperature: 40 ℃

[Test Example 1] (Measurement of Adhesion)

The light-peeling type peeling sheet was peeled from the adhesive sheet obtained in the Example and the comparative example, and the exposed adhesive layer was stuck to the polyethylene terephthalate film (made by Toyobo Co., Ltd.) which has an easy adhesion layer. , PETA4300, thickness: 100 μm). The laminated body was cut into a width of 25 mm and a length of 100 mm as samples.

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

The heavy release type peeling sheet was peeled from the sample, and the exposed adhesive layer was bonded to the transparent conductive film. The above-mentioned sticking was performed under a temperature condition of 50 ° C. under a pressure of 0.5 MPa for 20 minutes.

After that, it was left for 24 hours under the conditions of normal pressure, 23 ° C. and 50% RH, and then a tensile tester (Tensilon, manufactured by Orientec Company Inc.), based on JIS Z0237: 2009, was used at a peeling speed of 300 mm / min. The adhesive force (N / 25mm) was measured under the conditions of a peeling angle of 180 °. The results are shown in Table 2.

[Test Example 2] (Measurement of storage elastic modulus)

The peeling and peeling sheet was peeled from the adhesive sheet obtained in the Example and the comparative example, and several layers were laminated so that the adhesive layer might become 3 mm thickness. A cylindrical body (height 3 mm) having a diameter of 8 mm was punched from the laminated body of the obtained adhesive layer, and this was used as a sample.

Regarding the above-mentioned samples, the storage elastic modulus (MPa) was measured under the following conditions by a torsional shear method using a viscoelasticity measuring device (DYNAMIC ANALAYZER manufactured by REOMETRIC) based on JIS K7244-6. The results are shown in Table 2.

Measurement frequency: 1Hz

Measurement temperature: 80 ℃

[Test Example 3] (Measurement of refractive index)

An Abbe refractometer (manufactured by Atago, Company Inc., product name "Abe Refractometer DR-M2", Na light source, wavelength: 589 nm) was used, and the values obtained in Examples and Comparative Examples were based on JIS K0062-1992. The refractive index of the adhesive layer of the adhesive sheet was measured. The results are shown in Table 2.

[Test Example 4] (Evaluation of Pattern Recognition)

An ITO film of a transparent conductive film (ITO film made by Oike Industry Co., Ltd.) of a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) is provided on one side of a PET film having a thickness of 125 μm. On the top, a plurality of polyimide adhesive tapes (1 cm in width) were attached in a parallel arrangement at 1 cm intervals.

The obtained laminated body was immersed in hydrochloric acid adjusted to 1 mol / l for 2 minutes, and the ITO film portion to which the aforementioned polyimide adhesive tape was not etched was etched. Next, the laminated body was sufficiently washed with ion-exchanged water, and then dried at 120 ° C. for 10 minutes, and then the polyimide adhesive tape was peeled from the transparent conductive film. Thereby, a transparent conductive film in which the ITO film is patterned in such a manner that the ITO film portion having a width of 1 cm and the non-existing portion of the ITO film having a width of 1 cm are repeatedly repeated is obtained.

Next, the transparent conductive film in which the ITO film was patterned as described above was subjected to an annealing treatment at 150 ° C for 90 minutes to pattern the pattern. The ITO film crystallized.

On the other hand, a light release type peeling sheet was peeled from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive was laminated on a PET film having a thickness of 100 μm. Then, the heavy-peeling release sheet was peeled from the adhesive layer laminated on the PET film (thickness: 100 μm), and the exposed adhesive layer was bonded to the patterned ITO film (crystal of the transparent conductive film obtained above)化). Thereby, an evaluation sample composed of a structure of a PET film (thickness 125 μm) / patterned ITO film / adhesive layer / PET film (thickness 100 μm) was obtained.

From the transparent conductive film side of the obtained evaluation sample, that is, the PET film side with a thickness of 125 μm, the patterned ITO film was visually observed under a fluorescent lamp, thereby evaluating the pattern recognition of the adhesive layer with the following criteria. (The visibility of the pattern of the transparent conductive film). The results are shown in Table 2.

：: Graphics are not visible.

○: The figure is faintly visible.

×: The figure is visible.

[Experimental Example 5] (Evaluation of Followability of Steps)

(a) Preparation of evaluation samples

On the surface of a glass plate (product name: "Corning Glass Eagle XG", manufactured by NSG Precision Company Inc., 90mm in length x 50mm in width x 0.5mm in thickness), a thickness of 5 μm, 10 μm, 15 μm, and 20 μm is applied. An ultraviolet curable ink (manufactured by Teikoku Ink Mfg. Co., Ltd., product name "POS-911 ink") was screen-printed in a frame shape (outer shape: 90 mm in length × 50 mm in width and 5 mm in width). Next, ultraviolet light was irradiated (80 W / cm ² , two metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min) to harden the above-mentioned ultraviolet curable ink for printing, and a step (step height) based on printing was produced. : 5 μm, 10 μm, 15 μm, and 20 μm) stepped glass plates.

The light release type peeling sheet was peeled from the adhesive sheet obtained in the Example and the comparative example, and the exposed adhesive layer was adhered to a polyethylene terephthalate film (Toyobo Co., Ltd. Made of PET100A4300, thickness: 100 μm). Next, the heavy release type peeling sheet was peeled to expose the adhesive layer. Then, using a laminator (manufactured by Fujipura Company Inc., product name "LPD3214"), the above-mentioned laminated body was laminated on each band-difference glass plate with the adhesive layer covering the entire printed surface of the frame shape, and then pressed by heat. Treatment (50 ° C, 0.5 MPa, 30 minutes) yielded a sample for evaluation.

(b) Evaluation of evaluation samples

Regarding the above-mentioned evaluation sample, first, the step followability of the evaluation sample stage was obtained and evaluated. The followability of the step difference is judged by whether or not the adhesive layer is completely filled in the printing step difference. When a gap or a bubble is observed at the interface between the printing step and the adhesive layer, it is determined that it cannot follow the printing step difference. Here, the step followability is evaluated as a step follow-up rate (%) according to the following criteria.

Next, the sample for evaluation was left in an environment of 85 ° C. and 85% RH for 72 hours. Then, it returned to the normal temperature and normal humidity state of 23 degreeC and 50% RH, and evaluated the follow-up of this step sample as "after durability" in the same way as the above. The evaluation results are shown in Table 2.

Follow-up rate of step difference% = {(the height of the printed step difference without gaps and bubbles and being filled (μm)) / (thickness of the adhesive layer: 50 μm)} × 100

◎: 40% follow-up rate

○: Follow-up rate of step difference 10% ~ 30%

×: Follow-up rate of step difference is less than 10%

[Test Example 6] (Moisture and whitening resistance evaluation)

The adhesive layer of the adhesive sheet obtained in the Example and the comparative example was sandwiched between two sheets of soda-lime glass (thickness: 1.1 mm), and the laminated body was obtained. About this laminated body, the haze value (%) was measured using the haze meter (made by Nippon Denshoku Industries Co., Ltd., product name "NDH2000") based on JIS K7136: 2000.

Next, the laminated body was stored under a humid heat condition of 85 ° C. and 85% RH for 72 hours. Thereafter, the temperature was returned to normal temperature and normal humidity of 23 ° C. and 50% RH. For this laminate, a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name “NDH2000”) was used, based on JIS K7136: 2000. The haze value (%) was measured. The haze value was measured within 30 minutes after the laminate was returned to normal temperature and humidity.

Based on the above results, the haze value before the moist heat condition is subtracted from the haze value after the moist heat condition, thereby calculating the increase (point) of the haze value after the moist heat condition. Those with a haze value increase of less than 1.0 after moist-heat conditions are evaluated as having good moist-heat whitening resistance (◎), and those with a haze value after moist-heat conditions are increased by 1.0 points or more and less than 5.0 points are evaluated as being within the proper value (○) The one whose haze value after the moist heat condition rises to 5.0 points or more is evaluated as poor moist heat whitening resistance (×). The results are shown in Table 2.

[Test Example 7] (Evaluation of foam resistance)

The adhesive layer of the adhesive sheet obtained in the examples and comparative examples was used as a transparent conductive film (Oike Industry Co., Ltd.) provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side of a PET film. Ltd., thin ITO A film, a transparent conductive film having a thickness of 125 μm), and a polycarbonate plate (Mitsubishi Gas Chemical Company, Jupilon Sheet MR58, thickness: 1 mm) were sandwiched to obtain a laminated body.

The obtained laminated body was heat-pressed under conditions of 50 ° C. and 0.5 MPa for 30 minutes, and then left for 15 hours. Then, it was stored for 72 hours under the durable conditions of 85 ° C. and 85% RH. Thereafter, the presence or absence of air bubbles, floating, or peeling in the adhesive layer was confirmed by visual observation. As a result, those who were completely free of bubbles, floating and peeling were evaluated as ◎, those who only produced bubbles having a diameter of 0.2 mm or less were evaluated as ○, and those having a diameter exceeding 0.2 mm, which were floating or peeling were evaluated as × (resistant Evaluation of foaming properties). The results are shown in Table 2.

【Table 1】

【Table 2】

As can be seen from Table 2, according to the adhesive sheet obtained in the examples, the pattern of the transparent conductive film is not obvious, and excellent step-following and foaming resistance are achieved. In particular, the adhesive sheets obtained in Examples 1 to 23 are also excellent in moisture and heat whitening resistance, and the adhesive sheets obtained in Examples 1 to 22 and 24 also have excellent adhesive power.

[Industrial availability]

The adhesive and the adhesive sheet of the present invention are very useful in forming an adhesive layer used in a touch panel of an electrostatic capacity method.

Claims (7)

A touch panel is provided with two transparent conductive films, or a transparent conductive film and a cover material, and an adhesive is further provided between the two transparent conductive films or between the transparent conductive film and the cover material. The touch panel of the electrostatic capacity type is characterized in that the transparent conductive film has a circuit pattern, and the adhesive layer is formed of an adhesive having the following characteristics: a refractive index of 1.47 to 1.54, and a storage elasticity at 80 ° C. The modulus is 0.02 to 0.10 MPa, and it does not contain a component having a carboxyl group. The touch panel according to item 1 of the scope of patent application, wherein the adhesive is obtained by crosslinking an adhesive composition containing a (meth) acrylate copolymer (A) and a crosslinking agent (B). The constituent includes, as a monomer unit constituting the (meth) acrylate copolymer (A), 5 to 30% by mass of a monomer having a hydroxyl group, and a homopolymer having a glass transition temperature of 70 ° C. or higher. The hard monomer having an aromatic ring is 5 to 40% by mass, and the monomer having a carboxyl group is not contained. The touch panel according to item 2 of the scope of patent application, wherein the weight average molecular weight of the (meth) acrylate copolymer (A) is 200,000 to 1 million. The touch panel according to item 2 of the scope of patent application, wherein the hard monomer as a monomer unit constituting the (meth) acrylate copolymer (A) contains a material selected from the group consisting of methyl methacrylate and acrylic acid isocyanate. At least one of the group consisting of borneol and acrylomorphine. The touch panel according to item 2 of the patent application range, wherein the adhesive further contains a silane coupling agent (C). The touch panel according to item 1 of the scope of patent application, wherein the thickness of the aforementioned adhesive layer is 10 to 400 μm. The touch panel according to item 1 of the scope of patent application, wherein the adhesive is laminated on the adhesive layer side of a laminate on a substrate composed of a polyethylene terephthalate film having a thickness of 100 μm. In the case where the surface is adhered to the soda lime glass, the adhesion force of the laminated body to the soda lime glass is 5 to 50 N / 25 mm.