TW201816038A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

The present invention addresses the problem of providing a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive sheet which has excellent conformability to rugged portions and generates few delayed bubbles. The present invention relates to a pressure-sensitive adhesive composition which comprises a (meth)acrylic acid ester polymer (A) having a weight-average molecular weight less than 1,000,000, a hydrogen abstraction type photopolymerization initiator (B) that reacts with the (meth)acrylic acid ester polymer (A), and a solvent (C), the content of any photopolymerization initiators other than the hydrogen abstraction type photopolymerization initiator (B) being not higher than 0.1 mass%.

Description

   Adhesive sheet   

The present invention relates to an adhesive sheet.

In recent years, a display device module such as a liquid crystal display (LCD) or an input device such as a touch panel has been widely used in various fields. In the manufacture of such display devices or input devices, a transparent adhesive sheet is used for the purpose of bonding optical members. For such an adhesive sheet, not only the function of firmly bonding the optical members is required, but also durability is required.

Furthermore, when the optical member is a member having a step, the step followability is required for the adhesive sheet. In order to balance adhesion, durability, and unevenness followability, it has been proposed to use an adhesive sheet having after cure (for example, Patent Document 1). In the case of using such an adhesive sheet having post-curing properties, first, the adhesive sheet in a semi-hardened state is adhered to the adherend, so that it sufficiently follows the uneven shape. Then, in this state, it is irradiated with active energy rays to thereby completely harden it, and exhibits strong adhesion and durability.

The conventional adhesive sheet with post-curing properties is a low-molecular photoreactive monomer. Therefore, in the step of evaporating the solvent during the formation of the adhesive sheet, a problem arises in that the photoreactive monomer is volatilized together with the solvent. The volatilization of such photoreactive monomers causes problems due to quality deviation of the adhesive sheet or contamination of the applicator. In the case where a low-molecular photoreactive monomer is blended, the photoreactive monomer is not completely polymerized and becomes a residual monomer even after it is completely cured, which may cause problems such as ozone generation or health hazards.

In order to solve such a problem, a method of adding a photoreactive oligomer in place of the photoreactive monomer is considered. However, oligomers are generally not compatible with other polymers due to their high molecular weights, and there may be cases where the adhesive sheet is cloudy, which is not suitable for optical applications.

Therefore, Patent Document 2 proposes an adhesive composition and an adhesive sheet, which is an adhesive composition that does not contain a photoreactive monomer or a photoreactive oligomer, and contains an acrylic resin and a photopolymerization initiator. Here, the problems of volatilization or quality deviation of the photoreactive monomer as described above are solved.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2010-261029

[Patent Document 2] Japanese Patent Laid-Open No. 2007-191671

However, since the adhesive composition described in Patent Document 2 contains an isocyanate, the gel fraction increases with time, the step-following property, or the delay bubble resistance is deteriorated. In addition, Patent Document 2 does not describe the post-adhesiveness of the adhesive sheet.

Therefore, in order to solve such a problem of the conventional technology, the inventors of the present invention have provided an adhesive sheet which can suppress the volatility of photoreactive monomers or the quality variation concurrently produced, and has excellent step followability and delayed bubble resistance. The purpose of the adhesive composition was reviewed. In addition, the inventors of this case also conducted a review with the purpose of providing an adhesive composition that can form an adhesive sheet with post-curing properties.

In order to solve the above problems, intensive research was conducted. As a result, the inventors of the present invention found that a dehydrogenation type photopolymerization initiator was separately formulated as a photopolymerization initiator in the adhesive composition, and the molecular weight of the acrylate polymer was set to a predetermined Within this range, it is possible to obtain an adhesive sheet having excellent step followability and delayed bubble resistance, and having post-hardening properties.

Specifically, the present invention has the following configuration.

[1] An adhesive composition containing a (meth) acrylate polymer (A) having a weight-average molecular weight of less than 1 million, and a dehydrogenated light that reacts with the (meth) acrylate polymer (A) Contents of the polymerization initiator (B) and the solvent (C) with respect to 100 parts by mass of the (meth) acrylate polymer (A), a content of a photopolymerization initiator other than the dehydrogenated photopolymerization initiator (B) It is 0.1 parts by mass or less.

[2] The adhesive composition according to [1], wherein the (meth) acrylate polymer (A) is a non-crosslinkable (meth) acrylate containing an alkyl group having 1 to 10 carbon atoms unit.

[3] The adhesive composition according to [1] or [2], wherein the dehydrogenation type photopolymerization initiator (B) contains a compound selected from the group consisting of diphenyl ketone, 4-methyldiphenyl ketone, and 2, At least one kind of 4,6-trimethyldiphenyl ketone.

[4] The adhesive composition according to any one of [1] to [3], wherein the content of the dehydrogenated photopolymerization initiator (B) is relative to the (meth) acrylate polymer (A) 100 parts by mass, from 0.5 parts by mass to 5.0 parts by mass.

[5] An adhesive sheet containing an adhesive layer hardened by the adhesive composition of any one of [1] to [4], and the gel fraction of the adhesive layer is 0.1% to 80% the following.

[6] The adhesive sheet according to [5], wherein the thickness of the adhesive layer is 5 μm or more and 300 μm or less.

[7] The adhesive sheet according to [5] or [6], which is a double-sided adhesive sheet.

[8] A method for manufacturing a laminated body, which comprises contacting the adhesive layer of the adhesive sheet according to any one of [5] to [7] to the surface of an adherend, and in this state, irradiating active energy rays to harden the adhesive layer A step of.

[9] A method for using an adhesive sheet, in which the adhesive layer of the adhesive sheet according to any one of [5] to [7] is brought into contact with the surface of an adherend, and in this state, active energy rays are irradiated to harden the adhesive layer.

According to the present invention, an adhesive sheet having excellent step-following property and delayed bubble resistance can be obtained. Furthermore, according to the present invention, an adhesive sheet having post-curing properties can be produced without using a photoreactive monomer.

1‧‧‧ Adhesive sheet with release sheet

11‧‧‧ Adhesive sheet (adhesive layer)

12a, 12b ‧‧‧ peeling sheet

FIG. 1 is a cross-sectional view showing an example of the configuration of an adhesive sheet having a release sheet.

The present invention is explained in detail below. The description of the constituent elements described below is based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

    (Adhesive composition)    

The present invention relates to a dehydrogenated photopolymerization initiator (B) containing a (meth) acrylate polymer (A) having a weight-average molecular weight of less than 1 million and reacting with the (meth) acrylate polymer (A). ), And an adhesive composition of a solvent (C). The content of the photopolymerization initiator other than the dehydrogenation type photopolymerization initiator (B) in the adhesive composition of the present invention is 0.1 parts by mass based on 100 parts by mass of the (meth) acrylate polymer (A). the following. Here, the content of the photopolymerization initiator other than the dehydrogenation type photopolymerization initiator (B) in the adhesive composition is 0.1 part by mass or less with respect to 100 parts by mass of the (meth) acrylate polymer (A). It means that a dehydrogenation type photopolymerization initiator is used alone as a photopolymerization initiator in the adhesive composition, and it means that a photopolymerization initiator other than the dehydrogenation type photopolymerization initiator is not intentionally added.

Since the adhesive composition of the present invention has the above-mentioned structure, it is possible to form an adhesive sheet excellent in step-followability and delayed bubble resistance. Here, the term "resistance to delayed bubbles" refers to bubbles that reoccur at the interface between the adhesive layer and the adherend after the bubbles have been removed by an autoclave treatment or the like. In the case where the adhesive sheet has excellent delayed bubble resistance, even if the laminated body to which the adhesive sheet is adhered is placed under high temperature conditions, the occurrence of delayed bubbles or the peeling of the adhesive sheet accompanied by the occurrence of delayed bubbles is suppressed.

Moreover, when using the adhesive composition of this invention, even if a photoreactive monomer is not used, the adhesive sheet which has post-hardening property can be manufactured. If the adhesive sheet is post-hardening, after the adhesive sheet is adhered to the adherend and fully follows the uneven shape, it can be completely hardened, and both the firm adhesion and the step-following can be taken into account.

    <(Meth) acrylate polymer (A)>    

The (meth) acrylate polymer (A) may be a polymer composed of only a non-crosslinkable (meth) acrylate unit (a1). However, the (meth) acrylate polymer (A) preferably contains a non-crosslinkable (meth) acrylic acid in order to easily adjust the glass transition temperature (Tg) to a desired range and to easily control the physical properties of the adhesive sheet. A (meth) acrylic acid ester copolymer of an ester unit (a1) and a (meth) acrylic monomer unit (a2) having a crosslinkable functional group. In the present specification, "unit" means a repeating unit (monomer unit) constituting a polymer.

The (meth) acrylate polymer (A) preferably has transparency to such an extent that the visibility of the display device is reduced.

The weight average molecular weight of the (meth) acrylate polymer (A) is preferably 100,000 or more, more preferably 200,000 or more, and still more preferably 250,000 or more. The weight average molecular weight of the (meth) acrylate polymer (A) may be less than 1 million, and is preferably 850,000 or less, more preferably 750,000 or less, and still more preferably 650,000 or less. By setting the weight average molecular weight of the (meth) acrylate polymer (A) within the above-mentioned range, an adhesive sheet excellent in step-following property and delayed bubble resistance can be formed. Furthermore, the adhesion or durability of the adhesive sheet can be improved.

The weight average molecular weight of the (meth) acrylate polymer (A) is measured by gel permeation chromatography (GPC), and is a value determined on the basis of polystyrene. The measurement conditions of gel permeation chromatography (GPC) are as follows.

Solvent: Tetrahydrofuran

Columns: Shodex KF801, KF803L, KF800L, KF800D (use 4 connected Showa Denko Corporation)

Column temperature: 40 ℃

Sample concentration: 0.5% by mass

Detector: RI-2031plus (manufactured by JASCO)

Pump: RI-2080plus (manufactured by JASCO)

Flow (flow rate): 0.8ml / min

Injection volume: 10 μl

Standard curve: A standard curve obtained using 10 samples of standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko Corporation) Mw = 1320-2,500,000.

The content of the (meth) acrylate polymer (A) is based on the total mass of the adhesive composition, and is preferably 75% by mass or more, more preferably 80% by mass or more, and still more preferably 85% by mass or more. The content of the (meth) acrylate polymer (A) is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

    <Non-crosslinkable (meth) acrylate unit (a1)>    

The non-crosslinkable (meth) acrylate unit (a1) is preferably derived from a repeating unit of an alkyl (meth) acrylate having an alkyl group, and more preferably is derived from an (meth) acrylic acid alkyl group having a branched alkyl group. Repeating unit of the base ester. When the non-crosslinkable (meth) acrylate unit (a1) has an alkyl group, the number of alkyl carbons is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, even more preferably 3 or more It is 10 or less, and more preferably 3 or more and 9 or less.

Examples of such an alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (methyl) Base) n-butyl acrylate, isobutyl (meth) acrylate, third butyl (meth) acrylate, n-amyl (meth) acrylate, iso-amyl (meth) acrylate, n-hexyl (meth) acrylate Ester, isohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isoheptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, N-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, iso-decyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) N-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) Benzyl acrylate and the like. Among them, as the non-crosslinkable (meth) acrylate unit, n-butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate is preferably used.

The content of the unit (a1) derived from the non-crosslinkable (meth) acrylate in the (meth) acrylate polymer (A) is relative to the total mass of the (meth) acrylate polymer (A), It is preferably at least 40% by mass, more preferably at least 50% by mass, and even more preferably at least 60% by mass. The content of the unit (a1) is preferably 90% by mass or less, and more preferably 85% by mass or less.

    <(Meth) acrylic monomer unit (a2) having a crosslinkable functional group>    

Examples of the (meth) acrylic monomer unit (a2) having a crosslinkable functional group include a monomer unit containing a hydroxyl group, a monomer unit containing an amine group, a monomer unit containing an epoxy group, and Carboxyl monomer unit. These monomer units may be one type or two or more types.

The hydroxyl-containing monomer unit is a repeating unit derived from a hydroxyl-containing monomer. Examples of the hydroxyl-containing monomer include (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Hydroxyalkyl esters; (meth) acrylic acid [(mono, di, or poly) alkylene glycols], such as mono (diethylene glycol) (meth) acrylates; monocaprolactone (meth) acrylates, etc. ( (Meth) acrylate.

The amine-group-containing monomer unit may be, for example, a repeating unit derived from an amine-group-containing monomer such as (meth) acrylamidoamine or allylamine.

Examples of the glycidyl group-containing monomer unit include repeating units derived from a glycidyl group-containing monomer such as glycidyl (meth) acrylate.

Examples of the carboxyl group-containing monomer unit include acrylic acid and methacrylic acid.

The content of the (meth) acrylic monomer unit (a2) having a crosslinkable functional group in the (meth) acrylate polymer (A) is relative to that of the (meth) acrylate polymer (A). The total mass is preferably 0.01% by mass or more, and more preferably 0.5% by mass or more. The content of the unit (a2) is preferably 40% by mass or less, and more preferably 35% by mass or less.

    <Other individual units>    

The (meth) acrylate polymer (A) may optionally have a non-crosslinkable (meth) acrylate unit (a1) and a (meth) acrylic monomer unit (a2) having a crosslinkable functional group. ) Other monomer units. Other monomers may be those that can be copolymerized with a non-crosslinkable (meth) acrylate and an acrylic monomer having a crosslinkable functional group, and examples thereof include (meth) acrylonitrile and vinyl acetate. Esters, styrene, vinyl chloride, vinyl pyrrolidone, vinyl pyridine and the like.

The content of other monomer units is preferably 20% by mass or less, and more preferably 15% by mass or less.

    <Dehydrogenated photopolymerization initiator (B)>    

The dehydrogenation type photopolymerization initiator (B) is a starter of a polymerization reaction of the (meth) acrylate polymer (A) by irradiation with active energy rays. Examples of the dehydrogenation-type photopolymerization initiator include diphenyl ketone, benzamyl benzoic acid, methyl benzamyl benzoate, 4-phenyldiphenyl ketone, hydroxydiphenyl ketone, 3 , 3'-dimethyl-4-methoxydiphenyl ketone, 2,4,6-trimethyldiphenyl ketone, 4-methyldiphenyl ketone, 9-oxysulfur , 2-chloro9-oxysulfur 2-methyl 9-oxysulfur 2,4-dimethyl 9-oxosulfur Isopropyl 9-oxysulfur , Camphorquinone, dibenzocycloheptanone, 2-ethylanthrone, 3,3 ', 4,4'-tetrakis (third butylperoxycarbonyl) diphenyl ketone, benzyl, 9,10- Phenanthrenequinone and so on. Among them, the dehydrogenation type photopolymerization initiator (B) preferably contains at least 1 selected from the group consisting of diphenyl ketone, 4-methyldiphenyl ketone, and 2,4,6-trimethyldiphenyl ketone. Species, more preferably containing 4-methyldiphenyl ketone.

The content of the dehydrogenation type photopolymerization initiator of the adhesive composition is preferably 0.5 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the (meth) acrylate polymer (A). 0.5 mass parts or more and 3.0 mass parts or less.

In the adhesive composition of the present invention, a polymerization initiator other than the above-mentioned dehydrogenated photopolymerization initiator is 100 parts by mass of the (meth) acrylate polymer (A), and preferably 0.1 parts by mass or less , And preferably is substantially free of. That is, in the present invention, it is preferred to use a dehydrogenation type photopolymerization initiator as the polymerization initiator alone.

Since the dehydrogenation type photopolymerization initiator can also be used as a repeating reaction initiator by light irradiation, it can also cause post-curing to the adhesive sheet of the present invention.

    <Solvent (C)>    

The adhesive composition system contains a solvent (C). That is, the adhesive composition is preferably a solvent-based adhesive composition, and the adhesive sheet of the present invention is formed by coating the solvent-based adhesive composition and volatilizing the solvent.

Examples of the solvent (C) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; methylene chloride, trichloroethane, and trichloromethane. Halogenated hydrocarbons such as vinyl chloride, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and diacetone alcohol; diethyl ether, diisopropyl ether, and two Ethers such as alkane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, Polyesters such as ethyl butyrate; glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, and the like derivative.

The solvent (C) may be used singly or in combination of two or more kinds. The content of the solvent (C) in the adhesive composition is not particularly limited, and may be 25 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the (meth) acrylate polymer (A). It can be 30 mass parts or more and 400 mass parts or less.

The content of the solvent (C) is 10% by mass or more and 90% by mass or less with respect to the total mass of the adhesive composition, and may be 20% by mass or more and 80% by mass or less.

    <Other ingredients>    

The content of the crosslinking agent in the adhesive composition is preferably 0.01 parts by mass or less based on 100 parts by mass of the (meth) acrylate polymer (A). That is, it is preferable that the adhesive composition is substantially free of a crosslinking agent. As the crosslinking agent, isocyanate compounds, epoxy compounds, A well-known crosslinking agent such as an oxazoline compound, an aziridine compound, a metal chelate compound, a butylated melamine compound, etc. is not intentionally added to the adhesive composition.

The adhesive composition is within a range that does not impair the effect of the present invention, and may contain other components than the above. As other components, if necessary, it can select from well-known components as an additive for adhesives, for example, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, etc.

Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. These antioxidants may be used individually by 1 type, and may use 2 or more types together.

Examples of the metal corrosion preventing agent include benzotriazole-based resins.

Examples of the tackifier system include turpentine resin, terpene resin, terpene phenol resin, coumarone-indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin.

Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto-substituted alkoxy oligomer).

Examples of the ultraviolet absorber include benzotriazole-based compounds, diphenylketone-based compounds, and hindered amine-based compounds. Among them, in the case where ultraviolet rays are used as the active energy rays during curing, they must be added within a range that does not hinder the polymerization reaction.

Furthermore, the adhesive composition may contain a plasticizer. As the plasticizer, a non-functional acrylic polymer can be used. The "non-functional acrylic polymer" refers to a polymer composed of only acrylic monomer units having no functional group other than an acrylate group, or an acrylic monomer having no functional group other than an acrylate group. A unit composed of a unit and a non-acrylic monomer unit having no functional group.

Examples of the acrylic monomer unit having no functional group other than an acrylate group are the same as those of the non-crosslinkable (meth) acrylate unit (a1).

Examples of non-acrylic monomer units having no functional group include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, and myristic acid. Vinyl esters, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl carboxylates such as vinyl benzoate, or styrene.

    (Adhesive sheet)    

The present invention may also be an adhesive sheet containing an adhesive layer obtained by curing the above-mentioned adhesive composition. The adhesive sheet of the present invention contains a (meth) acrylate polymer (A) having a weight average molecular weight of less than 1 million, and a dehydrogenation type photopolymerization reaction that reacts with the (meth) acrylate polymer (A). Agent (B), and the content of the photopolymerization initiator other than the dehydrogenation type photopolymerization initiator (B) is 0.1% by mass or less. The gel fraction of the adhesive layer of the adhesive sheet of the present invention is 0.1% to 80%.

The gel fraction of the adhesive layer of the adhesive sheet may be 0.1% or more, preferably 20% or more, and more preferably 30% or more. The gel fraction may be 80% or less, and is preferably 75% or less. In addition, the above-mentioned gel fraction is a gel fraction obtained by using a high-pressure mercury lamp for the adhesive sheet and irradiating ultraviolet rays so that the accumulated light amount becomes 1000 mJ / cm ² , and then left in an environment at 23 ° C. and a relative humidity of 50% for 7 days.

In the pressure-sensitive adhesive sheet of the present invention, by setting the gel fraction of the pressure-sensitive adhesive layer within the above-mentioned range, the step-following property and the delayed bubble resistance can be improved, and the pressure-sensitive adhesive sheet can be post-cured.

In the adhesive sheet of the present invention, it is preferred that the gel fraction of the adhesive layer be irradiated with an active energy ray such that the cumulative light amount becomes 1000 mJ / cm ² when the active energy ray is irradiated once, and 30 minutes have elapsed. Also within the above range. Generally, the curing step usually takes a few days, such as 3 days at 40 ° C or 7 days at 23 ° C. However, there are problems that it takes time until the adhesive sheet is shipped, or it cannot be used immediately after the adhesive sheet is manufactured. The adhesive sheet of the present invention can exhibit better adhesive properties even without undergoing such an aging step. Since the adhesive sheet of the present invention can be adhered to the adherend after a single hardening treatment, the operability is easy and the cost competitiveness is also superior.

The gel fraction of the adhesive layer can be calculated by performing the following treatment after the aging treatment or 30 minutes after the completion of the primary hardening treatment. Specifically, the adhesive sheet was covered with a metal mesh (150 mesh), immersed in ethyl acetate, and left at 40 ° C for 24 hours. The removed adhesive sheet was dried at 100 ° C. for 1 hour, and the weight ratio before and after dipping with ethyl acetate was calculated, and the gel fraction was obtained from the following formula.

Gel fraction (%) = weight of adhesive sheet after ethyl acetate impregnation / weight of adhesive sheet before ethyl acetate impregnation × 100

The adhesive sheet of the present invention is an adhesive sheet before it is formally hardened. The adhesive sheet before formal hardening refers to an adhesive sheet that has room for further active energy ray hardening. That is, the adhesive sheet of the present invention is preferably one having an active energy ray hardening ability. Such an adhesive sheet with active energy ray hardening ability can also be said to have post-hardening properties. In the case where the adhesive sheet is post-cured, the adhesive layer is in a semi-hardened state. After the adhesive sheet having such an adhesive layer is pasted to the adherend, the adhesive layer is formally hardened by irradiating an active energy ray. The adhesive layer in the semi-hardened state can follow the uneven structure of the adherend, and through the formal hardening, the adhesive layer is completely hardened and can exert a strong bonding force.

Here, the "semi-hardened state" refers to a state in which the dynamic viscoelasticity after hardening by irradiation with active energy rays becomes 1.5 times or more. The dynamic viscoelasticity is preferably 1.5 times to 1000 times, more preferably 2 times to 100 times. In the semi-hardened state of the present invention, the dynamic viscoelasticity of the adhesive layer is preferably 1.0 × 10 ⁶ Pa or less, more preferably 8.0 × 10 ⁵ Pa or less, and particularly preferably 5.0 × 10 ⁵ Pa or less. The "formal hardening" means that the adhesive layer is further hardened by active energy rays after primary hardening.

Moreover, in the present invention, it is preferable that the active energy ray is irradiated in any of the primary hardening step and the formal hardening step. In the present invention, it may be divided into a plurality of hardening steps, or a plurality of steps of hardening in order to achieve a full hardened state.

The adhesive sheet of the present invention has an adhesive layer. The adhesive sheet may be a single-layer adhesive sheet composed of only an adhesive layer. In addition, the adhesive sheet of the present invention may be a single-sided adhesive sheet or a double-sided adhesive sheet.

Examples of the single-sided adhesive sheet include a multilayer sheet in which an adhesive layer is laminated on a support. Alternatively, another layer may be provided between the support and the adhesive layer.

As the double-sided adhesive sheet, for example, a single-layer adhesive sheet composed of an adhesive layer, a plurality of multilayer adhesive sheets laminated with an adhesive layer, and other adhesive layers laminated between the adhesive layer and the adhesive layer The multilayer adhesive sheet is a multilayer adhesive sheet in which a support is laminated between the adhesive layer and the adhesive layer. When the double-sided adhesive sheet has a support, it is preferable to use a transparent support as the support. Since such a double-sided adhesive sheet is also excellent in transparency of the entire adhesive sheet, it is suitable for bonding optical members to each other.

The adhesive sheet of the present invention is among the above, preferably a carrierless type without a support, more preferably a single-layer adhesive sheet composed of an adhesive layer, or a multilayer adhesive sheet in which a plurality of adhesive layers are laminated. Particularly preferred is a single-layer double-sided adhesive sheet composed of an adhesive layer.

When the adhesive sheet of the present invention has a support, examples of the support include polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, and polyetheretherketone. , Triethylfluorinated cellulose and other plastic films; anti-reflective films, electromagnetic wave shielding films, and other optical films; etc.

The surface of the adhesive layer of the present invention is preferably covered with a release sheet. That is, the present invention may also be an adhesive sheet having a release sheet.

FIG. 1 is a cross-sectional view showing an example of the configuration of an adhesive sheet having a release sheet. The adhesive sheet 11 shown in FIG. 1 has a release sheet (12a, 12b). In addition, the adhesive sheet 11 in FIG. 1 is a single-layer adhesive sheet without a carrier type, and is a double-sided adhesive sheet.

Examples of the release sheet include: a release sheet substrate, a release laminate sheet having a release agent layer provided on one side of the release sheet substrate, and a polyethylene film or polypropylene as a low-polarity substrate. Polyolefin films such as films.

As the base material for a release sheet in the release laminated sheet, paper or a polymer film can be used. As the release agent system constituting the release agent layer, for example, a general-purpose addition or condensation type silicone release agent or a compound containing a long-chain alkyl group can be used. Particularly preferred is the use of a highly reactive additive silicone release agent.

Specific examples of the silicone release agent include: BY24-4527, SD-7220, etc. manufactured by Toray Dow Corning Silicone; or KS-3600, KS-774, X62-2600, manufactured by Shin-Etsu Chemical Industry Co., Ltd. Wait. In addition, it is preferable that the polysiloxane-based release agent contains an organic silicon compound having SiO ₂ units and (CH ₃ ) ₃ SiO _1/2 units, or CH ₂ = CH (CH ₃ ) SiO _1/2 units. Silicone resin. Specific examples of the silicone resin include BY24-843, SD-7292, and SHR-1404 manufactured by Toray Dow Corning Silicone, or KS-3800 and X92-183 manufactured by Shin-Etsu Chemical Industry Co., Ltd.

In order to make a peeling sheet easy to peel in the peeling sheet 12, it is preferable to set it as the thing whose peelability is different from the peeling sheet 12a and the peeling sheet 12b. That is, if the releasability of one of them is different from the releasability of the other, only the peeling sheet 12 with high releasability can be easily peeled first. In this case, the peelability of the release sheet 12 of the release sheet 12a and the release sheet 12b may be adjusted in accordance with the bonding method or the bonding order.

The thickness of the adhesive layer of the adhesive sheet of the present invention is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. The thickness of the adhesive layer is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less. The thickness of the entire adhesive sheet is preferably within the above range. By setting the thickness of the adhesive layer within the above range, adhesion and durability can be improved. In addition, by setting the thickness of the adhesive layer within the above range, the unevenness followability is also improved.

The adhesive force of the adhesive layer of the adhesive sheet of the present invention is preferably 3N / 25mm or more, and more preferably 5N / 25mm or more. The adhesive force is an adhesive force after 30 minutes from the start of the primary hardening treatment.

In addition, the adhesive force of the adhesive layer to the adherend is determined by pulling and peeling each adherend at 180 ° according to JIS Z 0237.

The adhesive sheet of the present invention preferably has a haze value of 2% or less, more preferably 1.5% or less, and still more preferably 1% or less under an environment of 23 ° C and a relative humidity of 50%. When the haze value is within the above range, the transparency required when the adhesive sheet is used for an optical member can be satisfied. When the haze value is 2% or less, it is suitable for optical applications. The haze value can be measured in accordance with JIS K 7136: 2000.

The adhesive sheet of the present invention preferably has a total light transmittance (value measured in accordance with JIS K 7361-1: 1997) of 80% or more, more preferably 90% or more under an environment of 23 ° C and a relative humidity of 50%. When the total light transmittance is within the above range, the transparency is high and it is suitable for optical applications.

    (Manufacturing method of adhesive sheet)    

The method for producing an adhesive sheet according to the present invention includes the steps of applying the above-mentioned adhesive composition and semi-hardening (primary curing) by irradiating active energy rays. This step includes a step of applying a pressure-sensitive adhesive composition on a release sheet to form a coating film; and a step of irradiating the coating film with active energy rays to form a cured product. Prior to the step of irradiating the coating with an active energy ray to form a cured product, it is preferred to provide a heating and drying step in order to volatilize the solvent (C).

The application of the adhesive composition can be performed using a known coating device. Examples of the coating device include a blade coater, an air knife coater, a roll coater, a rod coater, a gravure coater, a microgravure coater, a rod leaf coater, a lip coater, Die coating machine, shower coating machine, etc.

The heating and drying step of the coating film can be performed using a known heating device such as a heating furnace or an infrared lamp. For example, drying is performed in an air-circulating thermostatic oven at a temperature of 50 ° C. to 150 ° C. for 10 seconds to 10 minutes.

In the step of irradiating the coating film with an active energy ray to form a semi-hardened material, examples of the active energy ray include ultraviolet rays, electron beams, visible rays, X-rays, and ion rays. Among them, it is preferable to use ultraviolet rays or electron beams as the active energy rays, and it is more preferable to use ultraviolet rays.

It is preferable that the irradiation output of ultraviolet rays is that the accumulated light amount is 100 mJ / cm ² or more and 10000 mJ / cm ² or less, and more preferably that the cumulative light amount is 500 mJ / cm ² or more and 5000 mJ / cm ² or less.

    (How to use the adhesive sheet)    

The adhesive sheet of the present invention can firmly adhere the adhesive layer to the surface of the adherend even if no curing step is provided after the primary hardening of the adhesive layer. In addition, the adhesive layer of the adhesive sheet is brought into contact with the surface of the adherend, and active energy rays are irradiated in this state to completely harden the adhesive layer. At this time, before the active energy ray is irradiated, since the adhesive layer of the adhesive sheet is in a semi-hardened state, even if the adherend has a stepped portion, the adhesive layer can still follow its unevenness.

Examples of the active energy rays include ultraviolet rays, electron beams, visible rays, X-rays, and ion rays. Among these, from the viewpoint of versatility, ultraviolet rays, electron beams, and particularly preferred ultraviolet rays are preferred.

As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used.

As the electron beam, for example, a Cockroft-Walton type, a Van-de-Graaff type, a resonant transformer type, an insulated core transformer type, a linear type, Electron beams emitted by various electron beam accelerators such as Dynamitron type and high frequency type.

    (Laminated body)    

This invention relates to the laminated body which has an adherend on at least one side of the said adhesive sheet. The laminated system of the present invention is obtained by the steps of bringing the adhesive layer of the adhesive sheet into contact with the surface of the adherend, and irradiating active energy rays in this state to completely harden the adhesive layer.

The adherend is preferably an optical member. Examples of the optical member include each constituent member in an optical product such as a touch panel or an image display device. As a constituent member of the touch panel, for example, an ITO film provided with an ITO film on a transparent resin film, an ITO glass provided with an ITO film on the surface of a glass plate, and a transparent conductive film coated with a conductive polymer Film, hard coating film, fingerprint resistant film, etc. As a constituent member of the image display device, for example, an anti-reflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used in a liquid crystal display device can be mentioned.

Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, and triethylpyrene. Cellulose, polyimide, cellulose halide and the like.

In the case where the adhesive sheet of the present invention is a double-sided adhesive sheet, it can be used for bonding two adherends. At this time, the adhesive sheet of the present invention is used for the bonding of ITO films inside the touch panel, the bonding of ITO film and ITO glass, the bonding of ITO film of touch panel and liquid crystal panel, and protective glass and ITO film. Lamination, protection glass and decorative glass.

    (Manufacturing method of laminated body)    

The invention also relates to a method for manufacturing a laminated body. The manufacturing method of the laminated body of the present invention includes the steps of bringing the adhesive sheet in the semi-hardened state into contact with the surface of the adherend, and irradiating active energy rays in this state to formally harden the adhesive layer. In the present invention, the step of formal hardening may be performed immediately after 30 minutes of primary hardening of the adhesive layer, or after 30 minutes of primary hardening treatment of the adhesive layer, the adhesive layer and the surface of the adherend Contact, adhere the adhesive layer to the adherend.

Examples of the active energy ray include the aforementioned energy ray, preferably ultraviolet rays or electron beams, and particularly preferably ultraviolet rays.

It is preferable that the irradiation output of ultraviolet rays is that the accumulated light amount is 100 mJ / cm ² or more and 10000 mJ / cm ² or less, and more preferably that the cumulative light amount is 500 mJ / cm ² or more and 5000 mJ / cm ² or less.

In the manufacturing method of the laminated body of the present invention, the adhesive layer of the adhesive sheet is an adhesive sheet before it is formally hardened, and is further an adhesive sheet in a space where active energy rays are hardened. Therefore, even if the adherend has a stepped portion, the adhesive layer Can follow its unevenness. In this way, after bonding the adhesive sheet to follow the unevenness, the adhesive layer is hardened formally by active energy rays, thereby improving the cohesive force of the adhesive layer and the adhesion to the adherend.

    [Example]    

Examples and comparative examples are listed below to describe the features of the present invention in more detail. The materials, usage amounts, proportions, processing contents, processing order, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited to the specific examples shown below.

    [Manufacture of acrylate copolymer]         <Synthesis of Acrylate Copolymer (A-1)>    

In a reaction device including a stirrer, a reflux cooler, a thermometer, and a nitrogen introduction tube, 100 parts by mass of butyl acrylate (BA), 40 parts by mass of 2-hydroxyethyl acrylate (2HEA), and 150 parts of ethyl acetate (EtAc) were charged. Parts by mass and 20 parts by mass of methyl ethyl ketone (MEK) were heated to 70 ° C. while introducing nitrogen gas. Next, 0.05 parts by mass of azobisisobutyronitrile (AIBN) was added, and a polymerization reaction was performed at 70 ° C. for 8 hours under a nitrogen environment. After the reaction, the solid content concentration was diluted to 35 mass% with ethyl acetate (EtAc) to obtain a (meth) acrylate copolymer (A-1) having a weight average molecular weight of 500,000. The weight average molecular weight (Mw) of the (meth) acrylate copolymer (A-1) was measured by GPC (gel permeation chromatography) using a sample in which THF (tetrahydrofuran) was dissolved.

    <Synthesis of Acrylate Copolymer (A-2)>    

In a reaction apparatus including a stirrer, a reflux cooler, a thermometer, and a nitrogen introduction tube, 100 parts by mass of butyl acrylate (BA), 1 part by mass of 2-hydroxyethyl acrylate (2HEA), and 0.1 part by mass of acrylic acid (AAc) were charged. 0.5 parts by mass of acrylamide (AM), 150 parts by mass of ethyl acetate (EtAc), and 20 parts by mass of methyl ethyl ketone (MEK). While introducing nitrogen, the temperature was raised to 70 ° C. Next, 0.05 parts by mass of azobisisobutyronitrile (AIBN) was added, and a polymerization reaction was performed at 70 ° C. for 8 hours under a nitrogen environment. After the reaction, the solid content concentration was diluted with ethyl acetate (EtAc) to 15% by mass, and a (meth) acrylate copolymer (A-2) having a weight average molecular weight of 1.8 million was obtained.

    <Synthesis of Acrylate Copolymer (A-3)>    

In a reaction apparatus equipped with a stirrer, a reflux cooler, a thermometer, and a nitrogen introduction tube, 100 parts by mass of 2-ethylhexyl acrylate (2EHA), 35 parts by mass of acrylamide (AM), and 7 parts by mass of acrylic acid (AAc) were charged. Parts, 150 parts by mass of ethyl acetate (EtAc), and 20 parts by mass of methyl ethyl ketone (MEK). While introducing nitrogen gas, the temperature was raised to 70 ° C. Next, 0.05 parts by mass of azobisisobutyronitrile (AIBN) was added, and a polymerization reaction was performed at 70 ° C. for 8 hours under a nitrogen environment. After the reaction, the solid content concentration was diluted with ethyl acetate (EtAc) to 56% by mass, and a (meth) acrylate copolymer (A-3) having a weight average molecular weight of 300,000 was obtained.

    (Example 1)         [Preparation of adhesive composition]    

With respect to 100 parts by mass of the solid content of the acrylate copolymer (A-1) obtained as described above, 1.0 part by mass of a dehydrogenated photopolymerization initiator (4-methyldiphenyl ketone (4MBP)) was added, and a silane type was added. 0.1 mass part of compound (KBM403) was diluted and stirred with ethyl acetate to obtain a solution having a solid content concentration of 30 mass% to prepare an adhesive composition.

    [Production of adhesive sheet]    

A 38 μm-thick polyethylene terephthalate film (first release sheet) was provided with the adhesive composition prepared as described above, which had a release agent layer treated with a polysiloxane-based release agent (Prince F -The surface of 38RL-07 (2) manufactured by TEX Co. is uniformly coated with a dripper so that the coating amount becomes 20 μm / m ² after drying, and it is dried in a 100 ° C air-circulating constant temperature furnace for 3 minutes. An adhesive layer was formed on the surface of the first release sheet. Next, a second peeling sheet (manufactured by Oji F-TEX Co., Ltd., 38RL-07 (L)) having a thickness of 38 μm was bonded to the surface of the adhesive layer. In this way, an adhesive sheet having a configuration of a first release sheet, an adhesive layer, and a second release sheet is obtained, which is held by a pair of release sheets having different peeling forces of the adhesive layer. Furthermore, the adhesive sheet was irradiated with ultraviolet rays of 1000 mJ / cm ² by a high-pressure mercury lamp.

    (Example 2)    

Except having changed the acrylate copolymer (A-1) into the acrylate copolymer (A-3) obtained as mentioned above, it carried out similarly to Example 1, and produced the adhesive composition and the adhesive sheet of Example 2.

    (Comparative example 1)    

Except having changed the acrylate copolymer (A-1) into the acrylate copolymer (A-2) obtained as mentioned above, it carried out similarly to Example 1, and produced the adhesive composition and the adhesive sheet of the comparative example 1.

    (Comparative example 2)    

In addition to setting the addition amount of the dehydrogenation type photopolymerization initiator (4MBP) to 0.5 parts by mass, and adding 0.5 parts by mass of the self-cracking type photoinitiator (IRGACURE) and 1.0 part by mass of the crosslinking agent (CORONATE L), Except for the adhesive composition, the rest were carried out in the same manner as in Example 1 to prepare an adhesive composition and an adhesive sheet of Comparative Example 2.

    (Comparative example 3)    

In addition to setting the addition amount of the dehydrogenation type photopolymerization initiator (4MBP) to 0.5 parts by mass, and adding 0.5 parts by mass of the self-cracking type photoinitiator (IRGACURE) and 1.0 part by mass of the crosslinking agent (CORONATE L), Except for the adhesive composition, the rest were carried out in the same manner as in Example 2 to prepare an adhesive composition and an adhesive sheet of Comparative Example 3.

    (Comparative Example 4)    

An adhesive composition was prepared in the same manner as in Example 1 except that a dehydrogenated photopolymerization initiator (4MBP) was not added, and 1.0 part by mass of a crosslinking agent (CORONATE L) was added to prepare an adhesive composition. Composition and adhesive sheet.

    (Comparative example 5)    

The adhesive composition was prepared in the same manner as in Comparative Example 1 except that a dehydrogenation-type photopolymerization initiator was not added, and 1.0 part by mass of a crosslinking agent (CORONATE L) was added to prepare an adhesive composition. Adhesive sheet.

    (Comparative Example 6)    

The adhesive composition was prepared in the same manner as in Example 2 except that a dehydrogenation-type photopolymerization initiator was not added, and 1.0 part by mass of a cross-linking agent (CORONATE L) was added to prepare an adhesive composition. Adhesive sheet.

    (Evaluation and analysis)         (Gel fraction)    

The adhesive sheets obtained in the examples and comparative examples were irradiated with ultraviolet rays using a high-pressure mercury lamp so that the accumulated light amount became 1000 mJ / cm ² , and then left for 7 days in an environment of 23 ° C. and a relative humidity of 50%. This adhesive sheet was covered with a metal mesh (150 mesh), immersed in ethyl acetate, and left at 40 ° C for 24 hours. The removed adhesive sheet was dried at 100 ° C. for 1 hour, and the weight ratio before and after dipping with ethyl acetate was calculated, and the gel fraction was obtained from the following formula.

Gel fraction (%) = weight of adhesive sheet after ethyl acetate impregnation / weight of adhesive sheet before ethyl acetate impregnation × 100

    (Segment Followability)    

UV-curable ink was screen-printed on the surface of glass plate A (120 mm in height × 70 mm in width × 0.7 mm in thickness) so that the coating thickness became 5 μm (inner edge size: 90 mm in length × 50 mm in width × width) 5mm). Next, the printed UV-curable ink is cured by irradiating ultraviolet rays. This step was repeated 5 times to obtain a printing step glass plate having a step difference of 25 μm.

The laminated adhesive sheets obtained in the examples and comparative examples were cut into a shape of 94 mm in length by 54 mm in width, and the first release sheet was peeled off, and then laminated to a PET film (A4300 using a laminator (IKO-650EMT, manufactured by Youbon Corporation). # 100μm). Thereafter, the second release sheet was peeled off, and the frame-shaped printing covering the printing step glass was fully bonded, and then subjected to an autoclave treatment (40 ° C, 0.5 MPa, 30 minutes). Next, a laminated body was obtained by irradiating an ultraviolet ray from the glass plate A side by an ultraviolet ray irradiator (ECS-301G1, manufactured by EYE GRAPHICS) so that the accumulated light amount became 2,000 mJ / cm ² .

The printing step difference portion of the laminated body was visually observed, and the followability of the step difference of the laminated adhesive sheet was evaluated according to the following criteria.

○: No foaming or peeling was observed at all.

×: Foaming or peeling was seen.

    (Delayed bubbles)    

The laminated body was treated at 85 ° C for 24 hours. After the treatment, the printed step difference of the laminated body was visually observed, and the delayed bubble resistance was evaluated according to the following criteria.

○: No foaming or peeling was observed at all, and the delayed bubble resistance was excellent.

Δ: Foam or peeling was observed when the diameter was less than 0.5 mm, and the delayed bubble resistance was slightly inferior.

×: A plurality of foaming or peeling was observed, or one or more foaming or peeling having a diameter of 0.5 mm or more was observed, and the delayed bubble resistance was not good.

It can be seen from Table 1 that the adhesive sheet formed by the adhesive composition obtained in the examples has excellent step-followability and delayed bubble resistance. In addition, the adhesive composition obtained in Examples can be hardened in multiple stages.

Claims (9)

    An adhesive composition comprising a (meth) acrylate polymer (A) having a weight average molecular weight of less than 1 million, and a dehydrogenation type photopolymerization that reacts with the (meth) acrylate polymer (A) The content of the initiator (B) and the solvent (C) other than the above-mentioned dehydrogenated photopolymerization initiator (B) is 0.1% by mass or less.         The adhesive composition according to claim 1, wherein the (meth) acrylate polymer (A) is a non-crosslinkable (meth) acrylate unit having an alkyl group having 1 to 10 carbon atoms.         The adhesive composition according to claim 1 or 2, wherein the dehydrogenated photopolymerization initiator (B) contains a compound selected from the group consisting of diphenyl ketone, 4-methyldiphenyl ketone, and 2,4,6- At least one kind of trimethyldiphenyl ketone.         The adhesive composition according to claim 1 or 2, wherein the content of the dehydrogenated photopolymerization initiator (B) is 0.5 mass based on 100 mass parts of the (meth) acrylate polymer (A). At least 5.0 parts by mass.         An adhesive sheet includes an adhesive layer formed by hardening the adhesive composition of any one of claims 1 to 4, and the gel fraction of the adhesive layer is 0.1% to 80%.         The adhesive sheet according to claim 5, wherein the thickness of the adhesive layer is 5 μm or more and 300 μm or less.         If the adhesive sheet of claim 5 or 6 is a double-sided adhesive sheet.         A laminated body manufacturing method includes the steps of contacting the adhesive layer of the adhesive sheet of any one of claims 5 to 7 to the surface of the adherend, and irradiating active energy rays in this state to harden the adhesive layer.         A method for using an adhesive sheet is to contact the adhesive layer of the adhesive sheet according to any one of claims 5 to 7 to the surface of an adherend, and in this state, irradiate active energy rays to harden the adhesive layer.