TWI668281B - Adhesive and adhesive sheet - Google Patents

Abstract

The invention provides an adhesive and an adhesive sheet. The adhesive system of the present invention is obtained by crosslinking the adhesive composition. The adhesive composition contains: (meth) acrylate polymer (A), which is a monomer unit constituting the polymer and contains 8 to 30 masses. % Of a monomer having a reactive functional group; and a rosin acid ester-based tackifying liquid (B), and the gel fraction of the adhesive is 30 to 95%. This kind of adhesive is excellent in both anti-foaming property and step-following property.

Description

Adhesive and adhesive sheet

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

In recent years, various mobile electronic devices such as mobile phones and tablet computers include displays using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. The situation of touch panels is also increasing.

In the above display, a protective panel is usually provided on the surface side of the display body module. With the reduction in thickness and weight of electronic devices, the protective panel has been gradually changed from a conventional glass plate to a plastic plate such as an acrylic plate and a polycarbonate plate.

Here, a gap is provided between the protective panel and the display body module, so that when the protective panel is deformed by an external force, the deformed protective panel does not collide with the display body module.

However, if there is an air layer such as the above-mentioned gap, the reflection loss of light caused by the refractive index difference between the protective panel and the air layer, and the refractive index difference between the air layer and the display module increases, and the picture quality of the display exists The problem of decline.

Therefore, it is proposed to improve the image quality of the display by filling the gap between the protective panel and the display body module with an adhesive layer. However, the frame-shaped printing layer may exist in a stepped manner on the display body module side of the protective panel. If stuck If the agent layer does not follow the step, the adhesive layer will be lifted near the step, thereby generating a reflection loss of light. Therefore, a step followability is required for the above-mentioned adhesive layer.

In order to solve the above-mentioned problems, Patent Document 1 discloses a shear storage modulus (G ') of 1.0 at 25 ° C and 1 Hz as an adhesive layer for filling a gap between a protection panel and a display body module. × 10 ⁵ Pa or less, and an adhesive layer having a gel fraction of 40% or more.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2010-97070

In Patent Document 1, it is intended to improve the step-followability by reducing the storage elastic modulus at room temperature in the adhesive layer. However, if the storage elastic modulus at room temperature is reduced as described above, the storage elastic modulus at high temperature is excessively reduced, and problems may occur under durable conditions. For example, when high-temperature and high-humidity conditions are applied, problems such as generation of bubbles in the vicinity of the step difference, or generation of air leakage from a plastic plate as a protective panel, and generation of bubbles such as bubbles, lifting, and peeling, may occur. On the other hand, if the adhesive layer is hardened in order to improve the anti-foaming resistance, the step-following property is reduced.

The present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide an adhesive and an adhesive sheet excellent in both anti-foaming property and step followability.

In order to achieve the above object, first, the present invention provides an adhesive, which is obtained by cross-linking an adhesive composition. The aforementioned adhesive composition contains: (a Group) an acrylate polymer (A), as a monomer unit constituting the polymer, containing 8 to 30% by mass of a monomer having a reactive functional group; and a rosin acid ester-based thickening liquid (B), and The gel fraction of the adhesive is 30 to 95% (Invention 1).

In the above invention (Invention 1), the rosin acid ester-based viscosity increase The wettability-improving effect of the liquid (B) interacts with the reactive functional group of the (meth) acrylate polymer (A) and the rosin acid ester-based thickening liquid (B). The adhesion of the material is improved, and it becomes an excellent anti-foaming property. In addition, it is not necessary to make the adhesive hard to improve the anti-foaming resistance, and the gel fraction is within the above range, and the step-following property of the adhesive layer composed of the adhesive is also excellent.

In the above invention (Invention 1), the (meth) acrylate poly In the compound (A), as a monomer unit constituting the polymer, it is preferable to include a hard monomer having a glass transition temperature of 70 ° C. or higher as a homopolymer (Invention 2).

In the invention (Inventions 1, 2), the (meth) acrylic acid The ester polymer (A) preferably contains 2-ethylhexyl (meth) acrylate as a monomer unit constituting the polymer (Invention 3).

In the above inventions (Inventions 1 to 3), the (meth) acrylic acid The weight average molecular weight of the acid ester polymer (A) is preferably 200,000 to 1.2 million (Invention 4).

In the above inventions (Inventions 1 to 4), in the adhesive composition It is more preferable to further contain a crosslinking agent (C) (Invention 5).

Second, the present invention provides an adhesive sheet comprising two pieces of peeling Sheet; and an adhesive layer, which is held by the release sheet so as to be in contact with the release surfaces of the two release sheets, and the adhesive layer is composed of the adhesive (Inventions 1 to 5) Composition (Invention 6).

In the above invention (Invention 6), the aforementioned adhesive layer is preferably disposed between two patterned transparent conductive films, or between the patterned transparent conductive film and a cover material or a display body module (Invention 7) ).

The adhesive and the adhesive sheet of the present invention are excellent in both anti-foaming property and step-following property.

1‧‧‧ adhesive sheet

11‧‧‧ Adhesive layer

12a, 12b ‧‧‧ peeling sheet

2‧‧‧ touch panel

3‧‧‧Display Module

4a, 4b‧‧‧Adhesive layer

5a‧‧‧1st thin film sensor

5b‧‧‧ 2nd thin film sensor

51‧‧‧ substrate film

52‧‧‧Transparent conductive film

6‧‧‧ Covering 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 is formed by crosslinking an adhesive composition (hereinafter sometimes referred to as "adhesive composition P"). The adhesive composition contains: (meth) acrylate polymer (A), As a monomer unit constituting the polymer, it contains 8 to 30% by mass of a monomer having a reactive functional group (reactive functional group-containing monomer); and a rosin acid ester-based viscosity-increasing liquid (B), and the The gel rate of the adhesive is 30 ~ 95%. It is preferable that the adhesive composition P further contains a crosslinking agent (C).

In addition, in this specification, (meth) acrylate means both an acrylate and a methacrylate. Other similar terms are the same. The term "polymer" also includes the concept of "copolymer".

The rosin acid ester-based thickening liquid (B) is a liquid at normal temperature. With There is an adhesive obtained by cross-linking the adhesive composition P of the rosin acid ester-based viscosity-increasing liquid (B), the wettability of which is improved, and the adhesion to the adherend is improved. In addition, the (meth) acrylate polymer (A) contains a large number of reactive functional group-containing monomers as the monomer units constituting the polymer as described above, and the reactive functional group and rosin acid ester system are generated. The interaction of the thickening liquid (B) further improves the adhesion to the adherend. Thereby, the adhesive layer which consists of this adhesive becomes an excellent foam resistance. In addition, it is not necessary to make the adhesive hard to improve the anti-foaming resistance, and the gel fraction is within the above range, and the step-following property of the adhesive layer composed of the adhesive is also excellent. That is, the adhesive according to this embodiment can balance the anti-foaming property and the step-following property which are usually in a trade-off relationship.

Therefore, as an example, when an adhesive composed of the above-mentioned adhesive is used When the adhesive layer is attached to the surface of one side of the plastic plate where the step is present, the adhesive layer follows the step, so that there is no warp or bubbles near the step. In addition, even if the laminated body of the adhesive layer and the plastic plate is placed under a durable condition, generation of bubbles and the like near the step can be suppressed, and even if air leakage occurs from the plastic plate, generation of bubbles, lifting, and peeling can be suppressed Wait for blistering.

(1) (meth) acrylate polymer (A)

As the reactive functional group-containing monomer contained in the (meth) acrylate polymer (A) as a monomer unit constituting the polymer, a monomer having a hydroxyl group in the molecule (a hydroxyl group-containing monomer) is preferably used. Monomer), a monomer having a carboxyl group in the molecule (carboxyl-containing monomer), a monomer having an amino group in the molecule (amino-containing monomer), and the like. Among these, a hydroxyl-containing monomer and a carboxyl-containing monomer are preferred, and a hydroxyl-containing monomer is particularly preferred. By using hydroxyl-containing monomers, especially by combining hydroxyl-containing monomers And the isocyanate-based crosslinking agent described later as the crosslinking agent (C), and the obtained adhesive becomes more excellent in foam resistance.

Examples of the hydroxyl group-containing monomer include (meth) acrylic acid. 2-hydroxyethyl enoate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate Esters, hydroxyalkyl (meth) acrylate and the like, such as 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 cross-linking agent (C) and copolymerizability with other monomers. Hydroxyethyl esters are preferred. These substances may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferred from the viewpoints of the reactivity of the carboxyl group with the crosslinking agent (C) in the obtained (meth) acrylate polymer (A) and the cross-linking agent (C). These can be used alone or in combination of two or more.

Examples of the amino-containing monomer include aminoethyl (meth) acrylate and n-butylaminoethyl (meth) acrylate. These can be used alone or in combination of two or more.

As described above, the (meth) acrylate polymer (A) contains, as a monomer unit constituting the polymer, 8 to 30% by mass of a reactive functional group-containing monomer. When the content of the reactive functional group-containing monomer is less than 8% by mass, it is difficult to cause interaction with the rosin acid ester-based viscosity-increasing liquid (B), and the obtained adhesive becomes poor in foam resistance. On the other hand, if the content of the reactive functional group-containing monomer exceeds 30% by mass, desired adhesiveness cannot be obtained.

When the (meth) acrylate polymer (A) contains a hydroxyl-containing monomer When the polymer is a reactive functional group-containing monomer constituting the polymer, the content thereof is preferably 10 to 25% by mass, and particularly preferably 15 to 20% by mass. In addition, when the (meth) acrylate polymer (A) contains a carboxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content is preferably 8 to 25% by mass, and 10 to 15 Mass% is particularly preferred.

Here, if the touch panel or the like is placed in a high temperature and high humidity environment, Then, moisture is immersed in the adhesive layer, and when the touch panel or the like is returned to normal temperature, there is a problem of "wet heat whitening" in which the adhesive layer is whitened and the transparency is decreased. When the (meth) acrylate polymer (A) contains the reactive functional group-containing monomer in the above range, a predetermined amount of the reactive functional group remains in the adhesive layer. The reactive functional group is usually a hydrophilic group. If a certain amount of the hydrophilic group is present in the adhesive layer, even when the adhesive layer is placed under high temperature and high humidity conditions, Under the conditions, the compatibility of the water immersed in the adhesive layer is also good. As a result, the whitening of the adhesive layer is suppressed, and the adhesive layer becomes excellent in moisture and heat whitening resistance.

In the (meth) acrylate polymer (A), as the polymer The monomer unit of the compound is preferably an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group. Thereby, the obtained adhesive can exhibit better adhesion. In addition, a hard monomer described later is removed from the alkyl (meth) acrylate.

(Meth) acrylic alkyl groups having 1 to 20 carbon atoms as an alkyl group Examples of the ester include methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-amyl (meth) acrylate, and n-hexyl (meth) acrylate Ester, 2-ethylhexyl (meth) acrylate, (meth) Isooctyl acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, tetradecyl (meth) acrylate, cetyl (meth) acrylate, (methyl) ) Stearyl acrylate and the like. Among them, from the viewpoint of further improving the adhesion, (meth) acrylic acid esters having 1 to 8 carbon atoms are preferred, and n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferred. Esters are particularly preferred, and 2-ethylhexyl (meth) acrylate is further preferred. 2-Ethylhexyl (meth) acrylate can reduce the dielectric constant of the obtained adhesive, and can improve the response accuracy of the touch panel. These may be used alone or in combination of two or more.

In the (meth) acrylate polymer (A), The monomer unit of the polymer is preferably 30 to 90% by mass of an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group, more preferably 40 to 75% by mass, and 50 to 65% by mass. Is even better.

In the (meth) acrylate polymer (A), The monomer unit forming the polymer preferably contains a hard monomer having a glass transition temperature (Tg) of 70 ° C or higher as a homopolymer. By containing the above-mentioned hard monomer as a monomer unit constituting the (meth) acrylate polymer (A), the cohesive force of the obtained adhesive is further improved, and the foaming resistance is further improved. In particular, when 2-ethylhexyl (meth) acrylate is used as a monomer unit constituting the (meth) acrylate polymer (A), the cohesive force tends to decrease. Therefore, it is preferable to use the above-mentioned hard monomer. The glass transition temperature (Tg) of the homopolymer as the hard monomer is preferably 75 to 200 ° C, and particularly preferably 80 to 180 ° C.

Examples of the hard monomer include methyl methacrylate (Tg105 ℃), isobornyl acrylate (Tg94 ℃), isobornyl methacrylate Tablets (Tg180 ° C), Acrylic morpholine (Tg145 ° C), Amantadyl acrylate (Tg115 ° C), Amantadyl methacrylate (Tg141 ° C), Dimethacrylamide (Tg89 ° C), Acrylamid (Tg165 ° C) and the like. These can be used alone or in combination of two or more.

Among the above-mentioned hard monomers, the prevention of adhesion and transparency, etc. From the viewpoint of further exerting the properties of the hard monomer while adversely affecting the characteristics, methyl methacrylate, isobornyl acrylate and acrylomorpholine are more preferred, and methyl methacrylate is particularly preferred.

In the (meth) acrylate polymer (A), as the polymer The monomer unit of the composition is preferably 10 to 45% by mass of the above-mentioned hard monomer, and more preferably 15 to 30% by mass. By containing the above-mentioned hard monomer in an amount of 10% by mass or more, the effect of improving foaming resistance based on the monomer unit can be expected. On the other hand, by setting the content of the hard monomer to 45% by mass or less, it is possible to prevent the relative shortage of other monomer units in the (meth) acrylate polymer (A) and to make the obtained adhesion The agent becomes excellent in adhesiveness and step followability.

The (meth) acrylate polymer (A) may contain as needed Other monomers as monomer units constituting the polymer. As the other monomer, a monomer having a reactive functional group is not contained so as not to impair the function of the reactive functional group-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 acid esters having aliphatic rings, non-crosslinked (meth) acrylic acid-N, N-dimethylaminoethyl ester, (meth) acrylic acid-N, N-dimethylaminopropyl ester, etc. (Meth) acrylates of tertiary amino groups, vinyl acetate, styrene, etc. These substances can be used alone or Two or more kinds can be used in combination.

The polymerization state of the (meth) acrylate polymer (A) may be A regular copolymer may also be a block copolymer.

Weight average molecular weight of (meth) acrylate polymer (A) It is preferably 200,000 to 1.2 million, particularly 300,000 to 900,000, and 400,000 to 700,000 is even better. In addition, the weight average molecular weight in this specification is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

By weight average of (meth) acrylate polymer (A) As described above, in a relatively low range, an adhesive having excellent foam resistance and step-followability can be obtained. If the weight average molecular weight of the (meth) acrylate polymer (A) is less than 200,000, foam resistance may be deteriorated. If the weight average molecular weight of the (meth) acrylate polymer (A) exceeds 1.2 million, The followability of the step may be deteriorated.

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

(2) Rosin acid ester thickening liquid (B)

The rosin acid ester-based thickening liquid (B) in this embodiment means a rosin acid ester having a melting point of 20 ° C or lower. As a result, the rosin acid ester-based viscosity-increasing liquid (B) becomes a liquid at normal temperature, and can exhibit the aforementioned wettability-improving effect and interaction with the reactive functional group of the (meth) acrylate polymer (A). The effect of improving the adhesion is achieved, thereby achieving excellent anti-foaming properties. From this viewpoint, the melting point of the rosin acid ester-based thickening liquid (B) is preferably 0 ° C or lower.

As the rosin acid ester-based viscosity-increasing liquid (B) having the melting point described above, for example, Arakawa Chemical Industries, Ltd. "PINE CRYSTAL ME-G" (trade name), etc. The rosin acid ester-based viscosity-increasing liquid (B) may be used singly or in combination of two or more kinds.

Rosin acid ester based thickening liquid in adhesive composition P (B) The content is preferably 5 to 25 parts by mass, more preferably 7 to 20 parts by mass, and even more preferably 10 to 15 parts by mass based on 100 parts by mass of the (meth) acrylate polymer (A). When the content of the rosin acid ester-based viscosity-increasing liquid (B) is 5 parts by mass or more, the above-mentioned adhesion-improving effect can be exerted, and the obtained adhesive becomes excellent in foam resistance. In addition, when the content of the rosin acid ester-based thickening liquid (B) is 25 parts by mass or less, the obtained adhesive becomes a cohesive force, and the obtained adhesive becomes a durability agent.

(3) Crosslinking agent (C)

It is preferable that the adhesive composition P further contains a crosslinking agent (C). When the adhesive composition P is heated or the like, the cross-linking agent (C) reacts with the reactive functional group of the (meth) acrylate polymer (A). Thereby, the (meth) acrylic acid ester polymer (A) is crosslinked by the crosslinking agent (C), and the cohesive force of the obtained adhesive is improved, and it becomes a person with more excellent foaming resistance.

As the crosslinking agent (C), as long as it is polymerized with (meth) acrylate The reactive functional group possessed by the compound (A) can be any one, and examples thereof include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based crosslinking agent, a melamine-based crosslinking agent, and an aziridine-based crosslinking agent. Crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, ammonium salt Crosslinking agent and so on. Among the above, when the reactive functional group of the (meth) acrylate polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group. When (meth) acrylic acid is used, Ester When the reactive functional group of the compound (A) is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group. The crosslinking agent (C) may be used alone or in combination of two or more thereof.

Isocyanate-based crosslinking agent contains at least polyisocyanate compound By. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; isophorone diisocyanate; and hydrogenation. Alicyclic polyisocyanates, such as diphenylmethane diisocyanate, etc., and biurets, isocyanurates, etc., as well as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, Adducts of reactants containing low-molecular active hydrogen compounds such as castor oil. Among them, from the viewpoint of reactivity with a hydroxyl group, trimethylolpropane-modified aromatic polyisocyanates, especially trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylene diisocyanate, are preferred. good.

Examples of the epoxy-based crosslinking agent include 1,3-bis (N, N'- Diglycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl Glyceryl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine, and the like.

The content of the cross-linking agent (C) in the adhesive composition P is higher than 100) parts by mass of the acrylate polymer (A) is preferably 0.001 to 10 parts by mass, particularly preferably 0.01 to 5 parts by mass, and still more preferably 0.02 to 1 part by mass.

When the content of the cross-linking agent (C) is within the above range, it does not hinder The obtained adhesive has a step-following property to improve the anti-foaming property.

(4) Various additives

To the adhesive composition P, various additives commonly used as propylene-based adhesives can be added as needed, for example, a silane coupling agent, a refractive index adjuster, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, and a light. Stabilizers, softeners, fillers, etc.

(5) Production of adhesive composition

The adhesive composition P can be produced by adding a (meth) acrylate polymer (A) to the obtained (meth) acrylate polymer (A), and adding a rosinate-based viscosity-increasing liquid (B), and It is produced by adding a cross-linking agent (C) and additives as necessary.

Polymer is formed by polymerization using a general radical polymerization method It is a mixture of monomer units, so that a (meth) acrylate polymer (A) can be manufactured. If necessary, the polymerization of the (meth) acrylate polymer (A) can be performed by a solution polymerization method or the like 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 an azo compound and an organic solvent. Two or more oxides may be used in combination. Examples of the azo-based compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), and 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 hydroperoxide, diisopropyl peroxy dicarbonate, di-N-propyl peroxy dicarbonate, bis (2-ethoxyethyl) peroxy di Carbonate, tert-butyl peroxy neodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl) peroxide, dipropylammonium peroxide, diethylammonium peroxide Wait.

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

After the (meth) acrylate polymer (A) is obtained, The acrylate polymer (A) is added with a rosin acid ester-based viscosity-increasing liquid (B), and a cross-linking agent (C), an additive, and a diluting solvent are added and mixed as needed to obtain a solution diluted with a solvent Adhesive composition P (coating solution).

As the above-mentioned diluting solvent, for example, hexane, heptane, cyclic Aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane and dichloroethane, methanol, ethanol, propanol, butanol, 1-methoxy-2-propene Alcohols such as alcohols, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve, etc. .

As the concentration and viscosity of the coating solution thus prepared, The applicable range is not particularly limited, 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 diluting solvent.

(6) Manufacturing of adhesives

The adhesive of this embodiment is constituted by crosslinking the adhesive composition P. Crosslinking of the adhesive composition P is usually performed by heat treatment. Moreover, the said heat processing can be combined with the drying process at the time of volatilizing the diluent solvent, etc. of the adhesive composition P.

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

By the above heat treatment (and health preservation), (meth) acrylic acid The ester polymer (A) is sufficiently cross-linked to exhibit excellent foam resistance.

(7) Gel fraction

The gel fraction of the adhesive in this embodiment is 30 to 95%, more preferably 40 to 80%, and most preferably 45 to 70%. If the gel fraction is less than 30%, the cohesive force of the adhesive is insufficient, and the foam resistance is reduced. On the other hand, when the gel fraction exceeds 95%, the adhesive force becomes too low, and the durability decreases or the step-following performance decreases. The method of measuring the gel fraction is shown in the test examples described later.

[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 refers to a material having release properties in the release sheet. The surface includes any one of a surface subjected to a peeling treatment and a surface that can exhibit peelability even without a peeling treatment.

(1) Adhesive layer

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

Thickness of the adhesive layer 11 (measured based on JIS K7130 Value) depends on the height of the step, 10 to 400 μm is more preferred, 20 to 300 μm is particularly preferred, and 50 to 250 μm is more preferred. Since the thickness of the adhesive layer 11 is 10 μm or more, good step-followability can be exhibited, and since the thickness of the adhesive layer 11 is 400 μm or less, processability 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

The release sheets 12a and 12b are not particularly limited, and a known plastic film can be used. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film can be used , Polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene- (meth) acrylic copolymer film, ethylene- (methyl ) Acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Moreover, such a crosslinked film can also be used. In addition, such a laminated film may be used.

The release surfaces of the release sheets 12a and 12b (especially with the adhesive layer) 11 contact surface) is preferably subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, Release agents such as polyolefins and waxes. 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.

There is no particular limitation on the thickness of the release sheets 12a, 12b, and usually It is 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 form After the application layer, the release surface of the other release sheet 12b (or 12a) is superposed on the application layer. When a health period is required, a health period is set in advance. When a health period is not required, the coating layer directly becomes the adhesive layer 11. Thereby, the above-mentioned adhesive sheet 1 can be obtained. Regarding the heat treatment and health conditions, it is as described above.

As another manufacturing example of the adhesive sheet 1, a release sheet 12a is provided on one side The coating liquid of the above-mentioned adhesive composition P is coated on the peeling surface, and heat treatment is performed to crosslink the adhesive composition P to form a coating layer, thereby obtaining a release sheet 12a with a coating layer. 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 health period is required, a health period is set in advance. When a health 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 above-mentioned adhesive composition P, For example, a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, and the like can be used.

(4) Haze value

The haze value (value measured in accordance with JIS K7136: 2000) of the adhesive layer 11 in this embodiment is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. If the haze value is 3% or less, it will be very transparent and suitable for optical applications.

(5) Total light transmittance

The total light transmittance (value measured in accordance with JIS K7105: 1981) of the adhesive layer 11 in this embodiment is preferably 90% or more, more preferably 95% or more, and more preferably 98% or more. If the total light transmittance is 98% or more, it will be highly transparent and suitable for optical applications.

(6) Use of adhesive sheet

By using the above-mentioned adhesive sheet 1, for example, a touch panel 2 of the electrostatic capacitance 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, which is laminated on the display body module 3 via an adhesive layer 4a; and a second thin film sensor 5b, which passes through an adhesive layer 4b. It is laminated on the first thin-film sensor 5a; the cover material 6 is laminated on the second thin-film sensor 5b via the adhesive layer 11.

The adhesive layer 11 in the touch panel 2 is the adhesive layer 11 of the adhesive sheet 1.

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

The adhesive layers 4a and 4b may be the adhesive layers of the adhesive sheet 1 described above. 11 is formed, can also 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 polyvinyl ether-based adhesives. Among them, propylene-based adhesives are preferred.

The first thin film sensor 5a and the second thin film sensor 5b are usually Each is composed of a base film 51 and a patterned transparent conductive film 52. The base film 51 is not particularly limited, and examples thereof include a polyethylene terephthalate film, an acrylic film, and a polycarbonate film.

Examples of the transparent conductive film 52 include platinum, gold, silver, Metals such as copper, oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide, zinc dioxide, tin doped indium oxide (ITO), zinc oxide doped indium oxide, fluorine doped indium oxide, antimony doped tin oxide , Fluorine-doped tin oxide, aluminum-doped zinc oxide and other composite oxides, chalcogenides, lanthanum hexaboride, titanium nitride, titanium carbide and other non-oxidizing compounds, etc., which is composed of tin-doped indium oxide (ITO) Which is better.

The transparent conductive film 52 of the first thin film sensor 5a and the second thin film Generally, one of the transparent conductive films 52 of the 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 second thin film sensor 5b in this embodiment is The transparent conductive film 52 is located on the upper side of the second thin film sensor 5b, but it is not limited to this, and may be located on the lower side of the second thin film sensor 5a. In addition, in FIG. 2, the transparent conductive film 52 of the first thin-film sensor 5 a is located on the upper side of the first thin-film sensor 5 a, but it is not limited to this, and may be located on the first thin-film sensor. 5a's underside.

The cover material 6 is usually a glass plate or a plastic plate as a main body. As 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 acid, lead glass, borosilicate glass, and barium borosilicate Acid glass and so on. The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate made of polymethyl methacrylate and the like.

In addition, one or both sides of the glass plate or plastic plate can be set With hard coating, anti-reflection layer, anti-glare layer and other functional layers, optical components such as hard coating film, anti-reflection film and anti-glare film can also be laminated.

In this embodiment, the covering material 6 is on the side of the adhesive layer 11 The surface has a step, specifically, a step formed by the presence or absence of the print 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 printing can be used Well-known materials 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.

The thickness (step height) of the printed layer 7 is an adhesive layer. The thickness of 11 is preferably from 3 to 30%, more preferably from 3.2 to 20%, and further from 3.5 to 15%. This makes it easy for the adhesive layer 11 to follow the step difference formed by the printing layer 7, and it is possible to suppress the occurrence of floating or bubbles in the vicinity of the step difference.

Hereinafter, an example of the method for manufacturing the touch panel 2 will be described. Instructions.

A peeling sheet 12 a is peeled from the adhesive sheet 1 to expose the adhesive layer 11 The second thin film sensor 5b is bonded to the second thin film sensor 5b so as to be in contact with the patterned transparent conductive film 52. On the other hand, the adhesive layer 4b provided on the release sheet is bonded to the first thin film sensor 5a so as to be in contact with the patterned transparent conductive film 52 of the first thin film sensor 5a.

Then, the release film remaining on the adhesive layer 4b is peeled to expose The exposed adhesive layer 4b is in contact with the surface of the second film sensor 5b on the side opposite to the side where the adhesive layer 11 is laminated (the exposed surface of the base film 51 of the second film sensor 5b). The way fits both. Thereby, a laminated body in which the release sheet 12b, the adhesive layer 11, the second thin film sensor 5b, the adhesive layer 4b, and the first thin film sensor 5a are sequentially laminated is obtained.

Next, the surface of the laminated body on the side of the first thin film sensor 5a The surface (the exposed surface of the base film 51 of the first film sensor 5a) is adhered to the adhesive layer 4a provided on the release sheet. Next, the other peeling sheet 12b is peeled from the laminated body, and the exposed adhesive layer 11 is bonded to the cover material 6 so that the printed layer 7 side of the cover material 6 is in contact with the adhesive layer 11. Thereby, the structure which laminated | stacked the cover material 6, the adhesive layer 11, the 2nd thin film sensor 5b, the adhesive layer 4b, the 1st thin film sensor 5a, the adhesive layer 4a, and the peeling sheet in this order was obtained.

Finally, the release sheet is peeled from the above-mentioned structure, and the exposed adhesive is used. In a manner that the adhesive layer 4 a is in contact with the display module 3, the structure is bonded to the display module 3. Thereby, the touch panel 2 shown in FIG. 2 can be manufactured.

When the adhesive layer 11 and the cover material 6 are laminated in the above process In this case, since the step difference of the adhesive layer 11 is excellent, it is difficult to form a gap between the step difference generated by the printing layer 7 and the adhesive layer 11, and the adhesive layer 11 can fill the step. Moreover, even when the touch panel 2 is placed in a high temperature and high humidity condition, It is also possible to prevent bubbles, warping, peeling, etc. from occurring near the step.

In addition, when the covering material 6 is a plastic plate, even under high temperature and high humidity Air leakage occurs from the plastic plate under the conditions, and since the above-mentioned adhesive layer 11 is excellent in foam resistance, it is also possible to suppress generation of bubbles such as bubbles, lifting, and peeling.

In addition, the above-mentioned adhesive layer 11 is excellent in moist heat and whitening resistance. Therefore, after the touch panel 2 is placed in a high-temperature and high-humidity condition, whitening when the touch panel 2 returns to normal temperature is suppressed.

The embodiments described above are described for easy understanding of the present invention. The carrier is not described to limit 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, the release sheets 12a and 12b in the adhesive sheet 1 may be omitted. Either side.

[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 polymer

60 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 polymer (A). As a result of measuring the molecular weight of this (meth) acrylate polymer (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 polymer (A) obtained in the above process (1) (solid content conversion value; the same applies hereinafter) as a rosin acid ester-based thickening liquid (B) (thickener) 10 parts by mass of a rosin ester compound (manufactured by Arakawa Chemical Industries, Ltd., product name "PINE CRYSTAL ME-G"), and a toluene diisocyanate compound (TOYOCHEM Co., Ltd.) as a cross-linking agent (C). (Product name: "BHS8515") was 0.25 parts by mass, fully stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 36% by mass.

Table 1 shows the blending of the adhesive composition. The details of the abbreviations and the like described in Table 1 are as follows.

[(Meth) acrylate polymer (A)]

2EHA: 2-ethylhexyl acrylate

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylate

BA: n-butyl acrylate

AA: Acrylic

MA: methyl acrylate

[Crosslinking agent (C)]

Isocyanate-based: toluene diisocyanate-based compound (manufactured by TOYOCHEM Co., Ltd., product name "BHS8515")

Epoxy: 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by TAISEI KAYAKU CO., Ltd., product name "TC-5")

3. Manufacturing of adhesive sheet

With a thickness of 25 μm after drying, The obtained coating solution of the adhesive composition was applied to a heavy release type peeling sheet (manufactured by Lintec Corporation, product name " SP-PET752150 ") after peeling the treated surface, heat treatment was performed at 90 ° C for 1 minute to form a coating layer. Similarly, the coating solution of the obtained adhesive composition was applied to a polyethylene terephthalate using a doctor blade coater so that the thickness after drying became 25 μm. After the release-treated surface of a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") of which one side of the ester film was peeled off, the heat treatment was performed at 90 ° C for 1 minute to form a coating layer.

Next, the heavy-peeling type with the coating layer obtained above was peeled Sheet and the light-peeling release sheet with coating layer obtained above were bonded in such a way that the two coating layers were in contact with each other, and were cured at 23 ° C and 50% RH for 7 days. 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 3, Comparative Examples 1 to 4]

The ratio of each monomer constituting the (meth) acrylate polymer (A), the weight average molecular weight (Mw) of the (meth) acrylate polymer (A), and the type of the tackifier were changed as shown in Table 1. A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the amount and the blending amount, and the type and the blending amount of the crosslinking agent (C).

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

<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 gel fraction)

The adhesive sheets obtained in the examples and comparative examples were cut to a size of 80 mm × 80 mm, and the adhesive layer was wrapped in a polyester mesh (mesh size 200). The mass was taken by a precision balance and subtracted The individual masses of the above meshes are used to calculate the mass of the adhesive itself. Let the mass at this time be M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C) for 24 hours. After that, the adhesive was taken out and air-dried in an environment at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours, and dried in an oven at 80 ° C. for 12 hours. After drying, the weight of the adhesive is calculated by subtracting the mass of the above net by a precision balance scale. Let the mass at this time be M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Evaluation of anti-foaming properties)

A polyethylene terephthalate film (made by OIKE & Co., Ltd.) with a transparent conductive film made of tin-doped indium oxide (ITO) on one side, an ITO film, thick Degree: 125 μm), a transparent conductive film and an acrylic plate (manufactured by Mitsubishi Gas Chemical Company, IUPILON SHEET MR200, thickness: 1 mm) made of polymethyl methacrylate (PMMA) sandwiched the adhesive sheets obtained in the examples and comparative examples. Layer of adhesive to obtain a laminate.

Under the conditions of 50 ° C and 0.5 MPa, After the autoclave treatment was carried out for 30 minutes, it was left at normal pressure, 23 ° C., and 50% RH for 24 hours. Then, it was stored for 72 hours under the durable conditions of 85 ° C. and 85% RH. Thereafter, it was visually confirmed whether there were bubbles, lifting or peeling in the adhesive layer, and the anti-foaming property was evaluated by the following criteria. The results are shown in Table 2.

(Double-circle): There are no bubbles, lifting, and peeling at all.

：: Only bubbles having a diameter of 0.1 mm or less were generated.

×: Bubbles exceeding 0.1 mm in diameter were generated, raised or peeled.

[Experimental Example 3] (Evaluation of Step Followability) (a) Preparation of evaluation samples

A glass plate (manufactured by NSG Precision Co, Ltd., product name "Corning glass Eagle XG", 90 mm in length x 50 mm in width x 0.5 mm in thickness) was applied on the surface to a thickness of any of 5 μm, 10 μm, 15 μm, and 20 μm. In one method, an ultraviolet curable ink (manufactured by Teikoku Printing Inks Mfg. Co., Ltd., product name "POS-911 Ink") is screen-printed (frame shape: 90 mm in length x 50 mm in width, 5 mm in width) in a frame shape. Next, ultraviolet rays were irradiated (80 W / cm ² , two metal halide lamps, a lamp height of 15 cm, and a belt speed of 10 to 15 m / min) to harden the above-mentioned ultraviolet curable ink for printing to produce a step (step difference) caused by printing. Height: any of 5 μm, 10 μm, 15 μm, and 20 μm).

Peel off easily from the adhesive sheets obtained in Examples and Comparative Examples Type release sheet, and the exposed adhesive layer was bonded to an easy-adhesion layer of a polyethylene terephthalate film (manufactured by TOYOBO Co., Ltd., PET A4300, thickness: 100 μm) having an easy-adhesion layer. Next, the heavy release-type release sheet is peeled off to expose the adhesive layer. Then, using a laminating machine (product name "LPD3214" manufactured by FUJIPLA Inc.), the above-mentioned laminated volume layer was laminated on each band-difference glass plate so that the adhesive layer covered the entire frame-shaped printing surface, and this was used as an evaluation sample. .

(b) Evaluation of evaluation samples

The sample for evaluation was subjected to an autoclave treatment at 50 ° C and 0.5 MPa for 30 minutes, and then left at normal pressure, 23 ° C, and 50% RH for 24 hours. Next, after storing for 72 hours in a hot and humid condition at 85 ° C. and 85% RH, the step followability was evaluated. The followability of the step difference is judged based on whether the printing step difference is completely filled by the adhesive layer. When a gap or a bubble is observed at the interface between the printing step difference and the adhesive layer, it is determined that the printing step difference cannot be accompanied. Here, the step followability is evaluated as a step follow-up rate (%) according to the following criteria. The results are shown in Table 2.

Step-following rate (%) = {(height of printing step (μm) filled with no gaps or bubbles) / (thickness of adhesive layer: 50 μm)} × 100

◎: 40% follow-up rate

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

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

[Test Example 4] (Measurement of optical characteristics)

For the adhesive layer of the adhesive sheet obtained in the examples and comparative examples, a haze meter (NIPPON DENSHOKU) was used in accordance with JIS K7361-1: 1997. INDUSTRIES Co., Ltd., NDH-2000) measured the haze value (%) and the total light transmittance (%). The results are shown in Table 2.

As can be seen from Table 2, the step difference of the adhesive sheet obtained in the example follows Both of these properties are excellent in resistance and anti-foaming property, and have good optical characteristics.

[Industrial availability]

The adhesive agent and the adhesive sheet of the present invention can be used, for example, for bonding a display body module in a touch panel and a cover material having a step difference, especially a plastic plate.

Claims (7)

An adhesive is obtained by cross-linking an adhesive composition. The aforementioned adhesive composition contains (meth) acrylate polymer (A), which is a monomer unit constituting the polymer and contains 8 to 30% by mass of A monomer having a reactive functional group; and a rosin acid ester-based thickening liquid (B), which is characterized by a gel fraction of 30 to 95%. The adhesive according to item 1 of the scope of the patent application, wherein the (meth) acrylate polymer (A) contains, as a monomer unit constituting the polymer, a glass transition temperature as a homopolymer of Hard monomer above 70 ° C. The adhesive according to item 1 of the scope of patent application, wherein the (meth) acrylate polymer (A) contains 2-ethylhexyl (meth) acrylate as a monomer unit constituting the polymer. ester. The adhesive according to item 1 of the patent application range, wherein the weight average molecular weight of the (meth) acrylate polymer (A) is 200,000 to 1.2 million. The adhesive according to item 1 of the scope of patent application, wherein the adhesive composition further contains a crosslinking agent (C). An adhesive sheet is characterized by comprising: two release sheets; and an adhesive layer, which is held by the aforementioned release sheet so as to be in contact with the release surfaces of the aforementioned two release sheets. The adhesive composition according to any one of items 5 to 5. The adhesive sheet according to item 6 of the patent application scope, wherein the aforementioned adhesive layer is disposed between two patterned transparent conductive films, or between the patterned transparent conductive film and a cover material or a display module. between.