KR102243211B1 - adhesion sheet and laminate - Google Patents

Abstract

It provides a pressure-sensitive adhesive sheet and a laminate having a pressure-sensitive adhesive layer that uses a pressure-sensitive adhesive material that does not contain a carboxyl group substantially, has excellent step-following properties, and has excellent moisture-heat whitening resistance and durability.
A (meth)acrylic acid ester copolymer (A) having a weight average molecular weight of 200,000 to 900,000, containing 15 to 30% by mass of a monomer having a hydroxyl group as a monomer unit constituting the polymer, and not containing a monomer having a carboxyl group, and , An active energy ray-curable component (B) and a pressure-sensitive adhesive composition containing a crosslinking agent (C) are thermally crosslinked to have a pressure-sensitive adhesive layer 11 having a thickness of 50 to 400 μm.

Description

Adhesive sheet and laminate {adhesion sheet and laminate}

The present invention relates to a pressure-sensitive adhesive sheet having an active energy ray-curable pressure-sensitive adhesive layer, and a laminate obtained by using the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet.

In recent years, various mobile electronic devices such as mobile phones and tablet terminals are equipped with displays using display modules including liquid crystal devices, light-emitting diodes (LED devices), organic electroluminescent (organic EL) devices, and the like.

In such a display, a protective panel is usually provided on the surface side of the display module. A gap is provided between the protection panel and the display module so that the deformed protection panel does not collide with the display module even when the protection panel is deformed by an external force.

However, if the above air gap, that is, an air layer, exists, there is a problem that the image quality of the display is deteriorated because the reflection loss of light is large due to the difference in refractive index between the protection panel and the air layer and the difference in refractive index between the air layer and the display module. have.

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer. However, on the display module side of the protective panel, there is a case where a frame-shaped print layer exists as a step difference. If the pressure-sensitive adhesive layer does not follow the level difference, the pressure-sensitive adhesive layer is lifted in the vicinity of the level difference, thereby causing reflection loss of light. Therefore, the pressure-sensitive adhesive layer is required to have a step-following property.

In order to solve the above problems, Patent Document 1 is a pressure-sensitive adhesive layer that fills the gap between the protective panel and the display module, and the shear storage modulus (G') at 25°C and 1 Hz is 1.0×10 ⁵ Pa or less, Further, a pressure-sensitive adhesive layer having a gel fraction of 40% or more is disclosed.

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-97070

In Patent Document 1, by lowering the storage modulus at room temperature in the pressure-sensitive adhesive layer, it is attempted to improve the level difference followability. However, if the storage modulus at room temperature is lowered as described above, the storage modulus at high temperature decreases more than necessary, and a problem occurs under durable conditions. For example, when returning to room temperature and humidity after performing high temperature and high humidity conditions, there arises a problem that the pressure-sensitive adhesive layer is whitened or bubbles are generated in the vicinity of the step.

On the other hand, the pressure-sensitive adhesive layer as described above may be attached to a transparent conductive film or metal wiring. In this case, when the pressure-sensitive adhesive contains carboxylic acid, and specifically, if the adhesive main material contains a carboxyl group, there arises a problem that the transparent conductive film or metal wiring is corroded or the resistance value of the transparent conductive film is changed. Therefore, the pressure-sensitive adhesive used for such a purpose is required to be free of carboxylic acid. However, in general, with a carboxylic acid-free adhesive, it is difficult to secure a desired adhesive force, and it is more difficult to obtain sufficient durability.

The present invention has been made in view of these facts, and provides a pressure-sensitive adhesive sheet and a laminate having an adhesive layer having excellent step-tracking properties and excellent moisture-heat whitening resistance and durability by using an adhesive material that does not contain a carboxyl group substantially. It aims to do.

In order to achieve the above object, the first invention has a weight average molecular weight of 200,000 to 900,000, contains 15 to 30 mass% of a monomer having a hydroxyl group as a monomer unit constituting the polymer, and contains a monomer having a carboxyl group. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 50 to 400 μm, obtained by thermal crosslinking an adhesive composition containing a non-(meth)acrylic acid ester copolymer (A), an active energy ray-curable component (B), and a crosslinking agent (C). Provides (Invention 1).

In the above invention (invention 1), the pressure-sensitive adhesive layer obtained by thermally crosslinking an adhesive composition containing a (meth)acrylic acid ester copolymer having a small weight average molecular weight and containing a predetermined amount of hydroxyl groups has excellent step-following properties and moisture-heat whitening resistance. At the same time, it has suitable durability. Further, since the adhesive composition contains an active energy ray-curable component, the adhesive layer is cured by irradiation with an active energy ray, and the adhesive layer thus cured is excellent in durability. In addition, since the (meth)acrylic acid ester copolymer substantially does not contain a carboxyl group, the pressure-sensitive adhesive layer can suppress corrosion of the transparent conductive film or metal wiring as an adherend, or changing the resistance value of the transparent conductive film.

In the above invention (invention 1), the content of the active energy ray-curable component (B) in the adhesive composition is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). (Invention 2).

In the above invention (Inventions 1 and 2), the content of the crosslinking agent (C) in the adhesive composition is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A) (Invention 3).

In the above inventions (Inventions 1 to 3), the ratio of the storage modulus at 23°C after irradiating the pressure-sensitive adhesive layer with active energy rays to the storage modulus at 23°C before irradiating the pressure-sensitive adhesive layer with active energy rays It is preferably 1.1 to 10 (Invention 4).

In the above inventions (Inventions 1 to 4), the ratio of the storage modulus at 85°C after irradiating the pressure-sensitive adhesive layer with active energy rays to the storage modulus at 85°C before irradiating the pressure-sensitive adhesive layer with active energy rays It is preferably 1.1 to 10 (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the pressure-sensitive adhesive sheet is provided with two release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to contact the release surfaces of the two release sheets (invention 6). ).

The second invention is a laminate comprising two hard plates and a pressure-sensitive adhesive layer sandwiched between the two hard plates, wherein the pressure-sensitive adhesive layer is irradiated with active energy rays on the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets (Inventions 1 to 6). It provides a laminated body characterized by being cured by (invention 7).

In the above invention (invention 7), it is preferable that at least one of the hard plates has a step on the side of the pressure-sensitive adhesive layer (invention 8).

In the above invention (invention 8), it is preferable that the step is a level difference due to the presence or absence of a printed layer (invention 9).

In the above inventions (inventions 7 to 9), it is preferable that at least one of the hard plates includes a polarizing plate (invention 10).

In the above inventions (inventions 7 to 10), it is preferable that at least one of the hard plates includes a glass plate or a plastic plate (invention 11).

In the above inventions (inventions 7 to 9), one of the two hard plates is a display module or a part thereof, and the other side of the two hard plates has a frame frame-shaped step on the side of the pressure-sensitive adhesive layer. It is preferable that it is (Invention 12).

In the above inventions (inventions 7 to 12), it is preferable that the total light transmittance of the pressure-sensitive adhesive layer is 80% or more (invention 13).

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present invention is excellent in step-following property, and after irradiation with active energy rays, it has excellent moisture-heat whitening resistance and durability. In the laminate obtained by using such a pressure-sensitive adhesive sheet, even if there is a step on the side of the pressure-sensitive adhesive layer, since the pressure-sensitive adhesive layer follows the step, there are no lifts or bubbles in the vicinity of the step. In addition, the pressure-sensitive adhesive layer in the laminate after irradiation with active energy rays has excellent moisture-heat whitening resistance and durability. Further, even when the pressure-sensitive adhesive layer is affixed to a transparent conductive film or metal wiring, it is possible to suppress corrosion of the transparent conductive film or metal wiring or changing the resistance value of the transparent conductive film.

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

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

[Adhesive sheet]

As shown in Fig. 1, the pressure-sensitive adhesive sheet 1 according to the present embodiment includes two release sheets 12a, 12b, and two release sheets so as to be in contact with the release surfaces of the two release sheets 12a, 12b. It is composed of the pressure-sensitive adhesive layer 11 sandwiched between (12a, 12b). In addition, the peeling surface of the release sheet in the present specification refers to a surface having peelability in the release sheet, and includes both a surface subjected to a peeling treatment and a surface exhibiting peelability even if no peeling treatment is performed.

1. Adhesive layer

The pressure-sensitive adhesive layer 11 has a weight average molecular weight of 200,000 to 900,000, contains 15 to 30 mass% of a monomer having a hydroxyl group (a hydroxyl group-containing monomer) as a monomer unit constituting the polymer, and a monomer having a carboxyl group (containing a carboxyl group). A pressure-sensitive adhesive composition containing a (meth)acrylic acid ester copolymer (A) that does not contain a monomer), an active energy ray-curable component (B), and a crosslinking agent (C) (hereinafter referred to as “adhesive composition P” in some cases. ) Is thermally crosslinked to form an active energy ray-curable pressure-sensitive adhesive layer. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same goes for other similar terms.

The pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheet 1 is formed by thermally crosslinking the pressure-sensitive adhesive composition P, specifically, the (meth)acrylic acid ester copolymer (A) is crosslinked with a crosslinking agent (C). have. On the other hand, the active energy ray-curable component (B) has not yet been cured and is present in the pressure-sensitive adhesive layer 11 in a state as it is blended in the pressure-sensitive adhesive composition P. This active energy ray-curable component (B) is polymerized and cured when the pressure-sensitive adhesive layer 11 is irradiated with active energy rays when the pressure-sensitive adhesive sheet 1 is used (when bonding the adherend).

(1) (meth)acrylic acid ester copolymer (A)

The (meth)acrylic acid ester copolymer (A) is an adhesive subject in the adhesive composition P. The (meth)acrylic acid ester copolymer (A) contains 15 to 30% by mass, preferably 17 to 28% by mass, and particularly preferably 20 to 25% by mass of a hydroxyl group-containing monomer as a monomer unit constituting the polymer. % Contains. When the content of the hydroxyl group-containing monomer is in the above range, the crosslinked structure formed by the (meth)acrylic acid ester copolymer (A) and the crosslinking agent (C) becomes good, and the pressure-sensitive adhesive layer 11 has suitable durability. . In addition, the pressure-sensitive adhesive layer 11 obtained from the pressure-sensitive adhesive composition P containing the (meth)acrylic acid ester copolymer (A) in which the content of the hydroxyl group-containing monomer is within the above range was cured at high temperature and high humidity. After carrying out the conditions (for example, under the conditions of 85°C and 85%RH for 240 hours), whitening when returned to room temperature and humidity is suppressed, that is, excellent moist heat whitening resistance. When the (meth)acrylic acid ester copolymer (A) contains a hydroxyl group-containing monomer in the above amount as a monomer unit, a predetermined amount of hydroxyl groups will remain in the obtained pressure-sensitive adhesive. The hydroxyl group is a hydrophilic group, and if such a hydrophilic group is present in the pressure-sensitive adhesive in a predetermined amount, even when the pressure-sensitive adhesive is placed under high temperature and high humidity conditions, it becomes easy to escape from the pressure-sensitive adhesive when the moisture infiltrating the pressure-sensitive adhesive is returned to room temperature and humidity under the high-temperature and high-humidity conditions. It is estimated, and as a result, whitening of the pressure-sensitive adhesive is suppressed.

When the content of the hydroxyl group-containing monomer as a monomer unit in the (meth)acrylic acid ester copolymer (A) is less than 15% by mass, the pressure-sensitive adhesive layer 11 is particularly poor in moist heat whitening resistance. On the other hand, when the content of the hydroxyl group-containing monomer exceeds 30% by mass, the coatability of the adhesive composition P deteriorates.

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

The (meth)acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Thereby, even when the obtained pressure-sensitive adhesive causes discomfort due to acid, for example, when it is attached to a transparent conductive film or metal wiring, it is possible to suppress the discomfort caused by acid. For example, it is possible to suppress corrosion of the transparent conductive film or metal wiring or changing the resistance value of the transparent conductive film.

Here, ``no monomer having a carboxyl group'' means substantially not containing a monomer having a carboxyl group, and in addition to not containing a carboxyl group-containing monomer at all, corrosion such as a transparent conductive film or metal wiring due to a carboxyl group It is to allow containing the carboxyl group-containing monomer to the extent that it does not occur. Specifically, it is allowed to contain a carboxyl group-containing monomer in an amount of 0.01% by mass or less, preferably 0.001% by mass or less as a monomer unit in the (meth)acrylic acid ester polymer (A).

The (meth)acrylic acid ester copolymer (A) preferably contains a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer, and particularly preferably as a main component. Thereby, the obtained adhesive can express preferable adhesiveness.

Examples of the (meth)acrylate alkyl ester having 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, (meth) Acrylic acid n-pentyl, (meth) acrylic acid n-hexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid isooctyl, (meth) acrylic acid n-decyl, (meth) acrylic acid n-dodecyl, (meth) acrylic acid Myristyl, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. are mentioned. Among them, from the viewpoint of further improving the adhesiveness, (meth)acrylic acid ester having 1 to 8 carbon atoms of the alkyl group is preferable, and methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate This is particularly preferred. Moreover, these may be used individually and may be used in combination of 2 or more types.

The (meth)acrylic acid ester copolymer (A) preferably contains 60 to 85% by mass of a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer, and particularly 72 to 83 It is preferable to contain it in mass %, and it is more preferable to contain it in 75 to 80 mass %.

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

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

The weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is 200,000 to 900,000, preferably 250,000 to 800,000, and more preferably 450,000 to 700,000. In addition, the weight average molecular weight in this specification is a value in terms of polystyrene measured by the gel permeation chromatography (GPC) method.

When the weight average molecular weight of the (meth)acrylic acid ester copolymer (A), which is the main component of the adhesive composition P, is relatively small as described above, the adhesive layer 11 obtained by thermally crosslinking the adhesive composition P becomes excellent in step followability. When the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) exceeds 900,000, the level difference followability is deteriorated. On the other hand, if the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is less than 200,000, the pressure-sensitive adhesive layer 11 after irradiation with active energy rays will have poor durability.

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

(2) Active energy ray-curable component (B)

When the adhesive composition P contains the active energy ray-curable component (B), the formed adhesive layer 11 becomes an active energy ray-curable adhesive layer. When this pressure-sensitive adhesive layer 11 contains the active energy ray-curable component (B), it becomes excellent in step-following property and durability.

The active energy ray-curable component (B) is not particularly limited as long as it is a component that is cured by irradiation with an active energy ray without interfering with the effects of the present invention, and may be a monomer, oligomer, or polymer, or a mixture thereof. Among them, a polyfunctional acrylate monomer having a molecular weight of less than 1000, which is excellent in compatibility with the (meth)acrylic acid ester copolymer (A) and the like, is preferably mentioned.

Examples of polyfunctional acrylate monomers having a molecular weight of less than 1000 include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylic. Rate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypibaric acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone Bifunctional types such as modified dicyclopentenyl di(meth)acrylate, ethylene oxide modified phosphoric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, and arylated cyclohexyl di(meth)acrylate; Trimethyrolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimester Trifunctional types such as tyrolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris(2-(meth)acryloxyethyl)isocyanurate; Tetrafunctional types such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; 5-functional types, such as propionic acid-modified dipentaerythritol penta (meth) acrylate; 6-functional types, such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. are mentioned. These may be used individually by 1 type, and may be used in combination of 2 or more types.

As the active energy ray-curable component (B), an active energy ray-curable acrylate oligomer can also be used. It is preferable that this acrylate oligomer has a weight average molecular weight of 50,000 or less. Examples of such acrylate oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate.

Here, the polyester acrylate oligomer is, for example, by esterifying the hydroxyl group of a polyester oligomer having hydroxyl groups at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth)acrylic acid, or It can be obtained by adding an alkylene oxide to the main acid and esterifying the hydroxyl group at the terminal of the oligomer with (meth)acrylic acid. Epoxy acrylate oligomers can be obtained, for example, by reacting an oxirane ring of a bisphenol-type epoxy resin or a novolac-type epoxy resin with (meth)acrylic acid for esterification. Further, a carboxyl-modified epoxy acrylate oligomer obtained by partially modifying this epoxy acrylate oligomer with dibasic carboxylic anhydride can also be used. The urethane acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of a polyether polyol or a polyester polyol with a polyisocyanate with (meth)acrylic acid. The polyol acrylate oligomer can be obtained by esterifying the hydroxyl group of a polyether polyol with (meth)acrylic acid.

The weight average molecular weight of the acrylate oligomer is preferably 50,000 or less, particularly preferably 500 to 50,000, and more preferably 3,000 to 40,000. These acrylate oligomers may be used singly or in combination of two or more.

Further, as the active energy ray-curable component (B), an adduct acrylate polymer in which a group having a (meth)acryloyl group is introduced into the side chain can also be used. Such an adduct acrylate polymer uses a copolymer of a (meth)acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and in part of the crosslinkable functional group of the copolymer, a (meth)acryloyl group and It can be obtained by reacting a compound having a group reacting with a crosslinkable functional group.

As the (meth)acrylic acid ester, it is preferable to contain a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group. For example, methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic acid Profile, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, ( Dodecyl meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. are mentioned. These may be used alone or in combination of two or more.

It is preferable that the monomer having a crosslinkable functional group in the molecule contains at least one selected from a hydroxyl group, a carboxyl group, an amino group and an amide group as the functional group. Examples of such monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, ( (Meth)acrylic acid hydroxyalkyl esters such as meth)acrylic acid 3-hydroxybutyl and (meth)acrylic acid 4-hydroxybutyl; Acrylamides such as N-methylol methacrylamide; Monoalkylaminoalkyl (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate; And ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid. These monomers may be used alone or in combination of two or more.

As a compound having a group reacting with a (meth)acryloyl group and a crosslinkable functional group, for example, 2-methacryloyloxyethyl isocyanate, methacrylic acid 2-(0-[1'-methylpropylideneamino] Carboxyamino)ethyl, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-acryloyloxyethyl succinate, 2-acryloyloxyethyl hexahydrophthalimide, ω-carboxy-polycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, 2-hydroxy-3- Phenoxypropyl acrylate etc. are mentioned preferably. These compounds may be used alone or in combination of two or more.

The weight average molecular weight of the adduct acrylate polymer is preferably about 50,000 to 900,000, particularly preferably about 100,000 to 300,000.

The active energy ray-curable component (B) may be used by selecting one of the above-described polyfunctional acrylate monomers, acrylate oligomers and adduct acrylate polymers, or in combination of two or more, It can also be used in combination with other active energy ray-curable components.

The content of the active energy ray-curable component (B) in the adhesive composition P is preferably 1 to 50 parts by mass, and particularly preferably 2 to 45 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). And, it is more preferable that it is 3-40 mass parts. If the content of the active energy ray-curable component (B) is less than 1 part by mass, there is a concern that the durability of the pressure-sensitive adhesive layer 11 after irradiation with an active energy ray may decrease. When the content of the active energy ray-curable component (B) exceeds 50 parts by mass, there is a concern that the moist heat whitening resistance of the pressure-sensitive adhesive layer 11 after irradiation with the active energy ray may deteriorate.

Here, for example, as a protective plate for a display module, a plastic plate may be used instead of a glass plate. In a high-temperature environment, gas (out gas) may be generated from this plastic plate. When such a plastic plate is used as the adherend of the pressure-sensitive adhesive sheet, bubbles, lifting or peeling may occur in the pressure-sensitive adhesive layer due to the outgas described above, and this is called a blister. When the plastic plate generating outgassing is used as an adherend in this way, the content of the active energy ray-curable component (B) in the adhesive composition P is 10 to 50 based on 100 parts by mass of the (meth)acrylic acid ester copolymer (A). It is preferable that it is a mass part, it is especially preferable that it is 15 to 45 mass parts, and it is more preferable that it is 25 to 40 mass parts. Since the content of the active energy ray-curable component (B) is 10 parts by mass or more, the cohesive force of the pressure-sensitive adhesive layer 11 after irradiation with the active energy ray is improved, and bubbles, lifting and peeling are suppressed even in a high-temperature environment, thereby preventing blister resistance. This becomes excellent. In addition, since the pressure-sensitive adhesive layer 11 after irradiation with active energy rays has an adhesive force (with respect to a glass substrate) of about 10 N/25 mm or more, it is possible to firmly maintain the bonded state of the hard plates.

(3) Crosslinking agent (C)

By containing the crosslinking agent (C), the adhesive composition P crosslinks the (meth)acrylic acid ester copolymer (A) to form a three-dimensional network structure, and improves the cohesive strength of the obtained adhesive. Moreover, after irradiation with an active energy ray, durability can also be imparted to the adhesive.

The crosslinking agent (C) may be any one that reacts with a reactive group (a hydroxyl group of a hydroxyl group-containing monomer that is a monomer unit) of the (meth)acrylic acid ester copolymer (A). For example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based Cross-linking agents, melamine-based cross-linking agents, aziridine-based cross-linking agents, hydrazine-based cross-linking agents, aldehyde-based cross-linking agents, oxazoline-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents and ammonium salt-based cross-linking agents. Among the above, it is preferable to use an isocyanate-based crosslinking agent excellent in reactivity with a hydroxyl group. Further, the crosslinking agent (C) may be used alone or in combination of two or more.

The isocyanate crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated diisocyanate. Alicyclic polyisocyanates, such as phenylmethane diisocyanate, and their biuret, isocyanurate, and low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc. The adduct body etc. which are reactants are mentioned.

The content of the crosslinking agent (C) in the adhesive composition P is preferably 0.01 to 5 parts by mass, particularly preferably 0.05 to 1 parts by mass, and also 0.1 to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). It is more preferably 0.4 parts by mass. When the content of the crosslinking agent (C) is 0.01 parts by mass or more, an effect of improving durability can be imparted to the pressure-sensitive adhesive after irradiation with active energy rays. When the content of the crosslinking agent (C) exceeds 5 parts by mass, the degree of crosslinking becomes excessive, and there is a concern that the level difference followability of the obtained pressure-sensitive adhesive is deteriorated. In addition, there is a fear that the hydroxyl groups of the (meth)acrylic acid ester copolymer (A) react with the crosslinking agent (C) in a large amount, and the amount of the hydroxyl groups remaining in the pressure-sensitive adhesive decreases, so that the above-described moist heat whitening resistance may decrease.

(4) Photopolymerization initiator (D)

When ultraviolet rays are used as active energy rays irradiated to the pressure-sensitive adhesive layer 11, it is preferable that the pressure-sensitive adhesive composition P further contains a photopolymerization initiator (D). By containing the photoinitiator (D) in this manner, the active energy ray-curable component (B) can be cured efficiently, and the polymerization curing time and the irradiation amount of the active energy ray can be reduced.

As such a photoinitiator (D), for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoaceto Phenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl propan-1-one, 1-hydroxy Cyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy- 2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methyl thioxanthone, 2-ethyl thioxanthone, 2-chloro thioxanthone, 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone, benzyl dimethyl ketal, Acetophenone dimethyl ketal, p-dimethylamino benzoic acid ester, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], 2,4,6-trimethylbenzoyl-di And phenyl-phosphine oxide. These may be used alone or in combination of two or more.

The photoinitiator (D) is preferably used in an amount ranging from 2 to 15 parts by mass, particularly 4 to 12 parts by mass, based on 100 parts by mass of the active energy ray-curable component (B).

(5) Various additives

To the adhesive composition P, as desired, various additives commonly used in acrylic adhesives, such as a silane coupling agent, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, a softener, a filler, a refractive index adjuster, etc., are added. I can do it.

In particular, from the viewpoint of improving durability, it is preferable that a silane coupling agent is added to the adhesive composition P as an additive. The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, and it is preferable that it has good compatibility with the (meth)acrylic acid ester copolymer (A). Moreover, when the adhesive sheet 1 is for optical use, a silane coupling agent having light transmittance is suitable.

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

The amount of the silane coupling agent added is preferably 0.01 to 1.0 parts by mass, and particularly preferably 0.05 to 0.5 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A).

(6) Preparation of adhesive composition

The adhesive composition P was prepared by preparing a (meth)acrylic acid ester copolymer (A), and mixing the obtained (meth)acrylic acid ester copolymer (A), an active energy ray-curable component (B), and a crosslinking agent (C). , If desired, it can be produced by adding a photoinitiator (D) and/or an additive.

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

Examples of the polymerization initiator include an azo compound and an organic peroxide, and two or more types may be used in combination. Examples of azo-based compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane 1- Carbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2' -Azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2' -Azobis[2-(2-imidazolin-2-yl)propane] etc. are mentioned.

As an organic peroxide, for example, benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydi Carbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, diacetyl peroxide, and the like.

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

After the (meth)acrylic acid ester copolymer (A) was obtained, in a solution of the (meth)acrylic acid ester copolymer (A), an active energy ray-curable component (B), a crosslinking agent (C), and optionally a photopolymerization initiator (D) ), an additive is added, and the adhesive composition P is obtained by sufficiently mixing.

(7) Formation of pressure-sensitive adhesive layer

The pressure-sensitive adhesive layer 11 is formed by thermally crosslinking the pressure-sensitive adhesive composition P. That is, crosslinking of the adhesive composition P is performed by heat treatment. In addition, this heat treatment can also serve as a drying treatment after application of the adhesive composition P.

The heating temperature of the heat treatment is preferably 50 to 150°C, and particularly preferably 70 to 120°C. In addition, the heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be set at room temperature (for example, 23°C, 50%RH). When this curing period is necessary, after the curing period has elapsed, and when the curing period is not necessary, after the heat treatment is completed, a pressure-sensitive adhesive layer is formed.

By the above heat treatment (and curing), the (meth)acrylic acid ester copolymer (A) is satisfactorily crosslinked through the crosslinking agent (C).

The thickness of the pressure-sensitive adhesive layer 11 to be formed (measured in accordance with JIS K7130) is 50 to 400 µm, preferably 70 to 300 µm, and particularly preferably 90 to 250 µm. Further, the pressure-sensitive adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

If the thickness of the pressure-sensitive adhesive layer 11 is less than 50 µm, sufficient level difference followability cannot be obtained, and if the thickness of the pressure-sensitive adhesive layer 11 exceeds 400 µm, workability is inferior.

2. Release sheet

As the release sheets 12a and 12b, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene Naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, poly Carbonate film, polyimide film, fluororesin film, and the like are used. Moreover, these crosslinked films are also used. Moreover, these laminated films may be sufficient.

It is preferable that the peeling treatment is applied to the peeling surface of the peeling sheets 12a and 12b (especially the surface in contact with the pressure-sensitive adhesive layer 11). Examples of the releasing agent used in the releasing treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based releasing agents. In addition, it is preferable that one of the release sheets 12a and 12b be used as a medium-release type release sheet having a high peeling force, and the other release sheet be used as a light-release type release sheet having a small peeling force.

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

3. Preparation of adhesive sheet

As one example of preparation of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the peeling surface of one release sheet 12a (or 12b), followed by heat treatment to thermally crosslink the adhesive composition P. After forming the coating layer, the peeling surface of the other peeling sheet 12b (or 12a) is superimposed on the coating layer. When a curing period is required, a curing period is provided. When a curing period is not required, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the adhesive sheet 1 is obtained. In addition, irradiation of active energy rays is not performed at this stage.

As another example of manufacture of the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the peeling surface of one release sheet 12a, followed by heat treatment to heat-crosslink the adhesive composition P to form a coating layer. Thus, a release sheet 12a with a coating layer is obtained. Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, followed by heat treatment to heat-crosslink the adhesive composition P to form a coating layer, and the release sheet 12b with a coating layer ). Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded together so that both coating layers are in contact with each other. When a curing period is required, a curing period is provided. When a curing period is not required, the laminated coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the adhesive sheet 1 is obtained. According to this manufacturing example, even when the pressure-sensitive adhesive layer 11 is thick, it becomes possible to stably manufacture.

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

4. Physical properties

The ratio of the storage modulus at 23° C. after irradiating the pressure-sensitive adhesive layer 11 with active energy rays to the storage modulus at 23° C. before irradiating the pressure-sensitive adhesive layer 11 with active energy rays (after irradiation with active energy rays) The storage modulus/storage modulus before irradiation with active energy rays) is preferably 1.1 to 10, and particularly preferably 1.2 to 6. In addition, the storage modulus in this specification is a value measured by a torsional shear method at a measurement frequency of 1 Hz in accordance with JIS K7244-6.

As described above, by increasing the storage modulus of the pressure-sensitive adhesive layer 11 at 23° C. after irradiation with active energy rays (after curing), the cured pressure-sensitive adhesive layer 11 is excellent in both durability and step followability.

In addition, the ratio of the storage modulus at 85°C after irradiating the adhesive layer 11 with active energy rays to the storage modulus at 85°C before irradiating the pressure sensitive adhesive layer 11 with active energy rays (active energy ray Storage modulus after irradiation/storage modulus before active energy ray irradiation) is preferably 1.1 to 10, particularly preferably 1.3 to 6, and more preferably 1.4 to 5.

As described above, the storage modulus of the pressure-sensitive adhesive layer 11 at 85° C. increases after irradiation with active energy rays (after curing), so that the cured pressure-sensitive adhesive layer 11 is particularly excellent in durability.

If the ratio of the storage modulus at 23°C or 85°C is less than 1.1, the above-described durability improvement effect may not be obtained. On the other hand, when the ratio of the storage modulus at 23°C or 85°C exceeds 10, the adhesive strength of the cured pressure-sensitive adhesive layer 11 may decrease, and sufficient durability may not be obtained.

The storage modulus at 23° C. of the pressure-sensitive adhesive layer 11 before irradiation with active energy rays is preferably 0.01 to 0.2 MPa, particularly preferably 0.04 to 0.15 MPa, and more preferably 0.07 to 0.1 MPa. In addition, the storage modulus at 85°C of the pressure-sensitive adhesive layer 11 before irradiation with active energy rays is preferably 0.01 to 0.1 MPa, particularly preferably 0.01 to 0.06 MPa, and more preferably 0.02 to 0.04 MPa. Do. The pressure-sensitive adhesive layer 11 before irradiation with active energy rays has the same storage modulus as described above, and is thus excellent in step followability.

The storage modulus at 23° C. of the pressure-sensitive adhesive layer 11 after irradiation with active energy rays is preferably 0.02 to 2 MPa, particularly preferably 0.05 to 1 MPa, and more preferably 0.09 to 0.6 MPa. Further, the storage modulus at 85°C of the pressure-sensitive adhesive layer 11 after irradiation with active energy rays is preferably 0.02 to 0.2 MPa, and particularly preferably 0.03 to 0.15 MPa. The pressure-sensitive adhesive layer 11 after irradiation with active energy rays has the storage modulus as described above, and thus has excellent durability.

In the above pressure-sensitive adhesive sheet 1, since the pressure-sensitive adhesive layer 11 before irradiation with active energy rays has excellent step-following properties, even when there is a step difference in the adherend, voids or bubbles are well formed between the step and the pressure-sensitive adhesive layer 11. It does not occur, and the pressure-sensitive adhesive layer 11 can fill the step. In addition, the pressure-sensitive adhesive layer 11 is cured by irradiation with active energy rays, so that it has excellent moist heat whitening resistance and durability.

As will be described later, the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably used to bond two hard plates to each other.

[Laminate]

As shown in Fig. 2, the laminate 2 according to the present embodiment includes a first hard plate 21, a second hard plate 22, and a first hard plate 21 positioned between them. ) And a pressure-sensitive adhesive layer 11 sandwiched between the second hard plate 22. In addition, in the layered product 2 according to the present embodiment, the first hard plate 21 has a step on the side of the pressure-sensitive adhesive layer 11, and specifically, due to the presence or absence of the printing layer 3 It has a step difference.

The first hard plate 21 and the second hard plate 22 are not particularly limited as long as the pressure-sensitive adhesive layer 11 is adhesive. Further, the first hard plate 21 and the second hard plate 22 may be the same material or different materials.

As the first hard plate 21 and the second hard plate 22, for example, in addition to a glass plate, a plastic plate, a metal plate, a semiconductor plate, etc., a laminated body thereof, or a display module, a solar cell module, etc. And plate-shaped hard products. At least one of the first hard plate 21 and the second hard plate 22 preferably includes a glass plate or a plastic plate.

The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, and the like. I can. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, preferably 0.2 to 2 mm.

It does not specifically limit as said plastic plate, For example, an acrylic plate, a polycarbonate plate, etc. are mentioned. The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5 mm, preferably 0.4 to 3 mm.

Further, on one or both sides of the glass plate or plastic plate, various functional layers (transparent conductive film, metal layer, silica layer, hard coating layer, anti-glare layer, etc.) may be provided, metal wiring may be formed, and optical member May be stacked. Since the pressure-sensitive adhesive layer 11 in the present embodiment is free of carboxylic acid, even if there is a case in which discomfort such as corrosion occurs due to an acid in the adherend, the discomfort can be suppressed.

As the optical member, for example, a polarizing plate (polarizing film), a polarizer, a retardation plate (phase difference film), a viewing angle compensation film, a brightness enhancing film, a contrast enhancing film, a liquid crystal polymer film, a diffusion film, a hard coating film, And semi-transmissive and reflective films.

Further, examples of the display module include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper. In addition, in these display module, the above-described glass plate, plastic plate, optical member, etc. are usually laminated. For example, a polarizing plate is laminated on an LCD module, and the polarizing plate forms one surface of the LCD module.

In the laminate 2 according to the present embodiment, it is preferable that at least one of the first hard plate 21 and the second hard plate 22 has a polarizing plate. In addition, the second hard plate 22 in the laminate 2 according to the present embodiment is a display module or a part thereof (for example, an optical member such as a polarizing plate), and the first hard plate 21 It is preferably a protective plate made of a silver glass plate or the like. In this case, the printing layer 3 is generally formed in the shape of a frame frame on the side of the pressure-sensitive adhesive layer 11 in the first hard plate 21.

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

In addition, the thickness (height of the step) of the printing layer 3 is preferably 3 to 30% of the thickness of the pressure-sensitive adhesive layer 11, particularly preferably 3.2 to 20%, and more preferably 3.5 to 15%. desirable. Thereby, the pressure-sensitive adhesive layer 11 reliably follows the level difference caused by the printing layer 3, so that lift or air bubbles do not occur in the vicinity of the level difference.

The pressure-sensitive adhesive layer 11 of the laminate 2 according to the present embodiment is obtained by curing the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above by irradiation with active energy rays. Here, the active energy ray refers to a substance having both energy among electromagnetic waves or charged particle rays, and specifically, ultraviolet rays, electron beams, and the like are exemplified. Among the active energy rays, ultraviolet rays that are easy to handle are particularly preferred.

The irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or the like, and the irradiation amount of ultraviolet rays is preferably about ^{50 to 1000 mW/cm 2.} In addition, the amount of light ^{is preferably 50 to 10000 mJ/cm 2} , more preferably 80 to 5000 mJ/cm ² , and particularly preferably 200 to 2000 mJ/cm ^2. On the other hand, the electron beam irradiation can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 10 to 1000 krad.

When the pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheet 1 is irradiated with an active energy ray, the active energy-ray-curable component (B) is polymerized and cured. The pressure-sensitive adhesive layer 11 cured by irradiation with active energy rays is excellent in durability and moisture-heat whitening resistance.

In order to manufacture the laminate 2, as an example, first, one peeling sheet 12a (or 12b) of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 and the agent of the adhesive sheet 1 are removed. The 1 hard plate 21 (or the 2nd hard plate 22) is attached|attached. Then, the other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 and the second hard The plate 22 (or the 1st hard plate 21) is attached|attached.

When bonding the pressure-sensitive adhesive layer 11 and the first hard plate 21 in the above process, since the pressure-sensitive adhesive layer 11 has excellent step-following properties, the difference between the step by the printing layer 3 and the pressure-sensitive adhesive layer 11 Since voids are hardly generated, the pressure-sensitive adhesive layer 11 can fill the gap.

After that, the pressure-sensitive adhesive layer 11 is irradiated with active energy rays from either side of the first hard plate 21 or the second hard plate 22 to cure the pressure-sensitive adhesive layer 11. At this time, the hard plate on the side to which the active energy ray is irradiated needs to be transparent to the active energy ray.

In the above-described laminate 2, since the pressure-sensitive adhesive layer 11 before irradiation with active energy rays has excellent step-following properties, voids or air bubbles are hardly generated between the step difference due to the printing layer 3 and the pressure-sensitive adhesive layer 11. In addition, the pressure-sensitive adhesive layer 11 cured by irradiation with active energy rays is suppressed from whitening when returned to room temperature after performing high temperature and high humidity conditions, and is excellent in moist heat whitening resistance. Further, even when the pressure-sensitive adhesive layer 11 irradiated with active energy rays is subjected to a high-temperature, high-humidity condition, bubbles or the like are prevented from being generated in the vicinity of the step and are excellent in durability.

The excellent moist heat whitening resistance of the pressure-sensitive adhesive layer 11 cured by irradiation of active energy rays can be evaluated as follows. For example, both sides of the pressure-sensitive adhesive layer 11 are sandwiched between two sheets of 1.1 mm-thick alkali-free glass and laminated by irradiating active energy rays of the above-described illuminance and light quantity from at least one side beyond the alkali-free glass. Get a sieve The laminate was stored for 240 hours at 85°C and 85%RH (moist heat condition), and then taken out at 23°C and 50%RH at room temperature and humidity. At this time, it is confirmed that the degree of whitening of the pressure-sensitive adhesive layer 11 is small.

The degree of whitening can also be quantitatively evaluated by haze value. Specifically, the value obtained by subtracting the haze value (%) before the moist heat condition from the haze value (%) after the moist heat condition in the laminate (measured in accordance with JIS K7136:2000, as follows) (the haze value after the moist heat condition) is subtracted from the haze value (%) before the moist heat condition. It can be evaluated by rising). It is preferable that the haze value rise after a moist heat condition is less than 5.0 point, and it is especially preferable that it is less than 1.0 point. In addition, for the evaluation, it is preferable to use the alkali-free glass having a haze value of about 0%. Further, the haze value of the pressure-sensitive adhesive layer after the moist heat condition is preferably 1.0% or less, particularly preferably 0.9% or less, and further preferably 0.8% or less.

In addition, the pressure-sensitive adhesive layer 11 preferably has a total light transmittance (measured in accordance with JIS K7361-1:1997) of 80% or more, particularly preferably 90% or more, and more preferably 99% or more. . When the total light transmittance is 80% or more, transparency is high and it is suitable for optical use. In addition, the total light transmittance of the pressure-sensitive adhesive layer 11 hardly changes before and after irradiation with active energy rays.

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

For example, either of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted. Moreover, the 1st hard plate 21 may have a level difference other than the printing layer 3, and may not have a level difference. In addition, not only the first hard plate 21 but also the second hard plate 22 may have a step on the pressure-sensitive adhesive layer 11 side.

Example

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

[Example 1]

1. Preparation of (meth)acrylic acid ester copolymer

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)acrylic acid ester copolymer (A). When the molecular weight of this (meth)acrylic acid ester copolymer (A) was measured by the method described later, it was 700,000 in weight average molecular weight.

2. Preparation of adhesive composition

100 parts by mass of the (meth)acrylic acid ester copolymer (A) obtained in the above step (1) (in terms of solid content; the same as below) and polyethylene glycol diacrylate (manufactured by Shinnakamura Chemical Co., Ltd.) as an active energy ray-curable component (B) , 5 parts by mass of the product name ``NK ester A-400'') and 0.23 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane, product name ``Colonate L'') as an isocyanate-based crosslinking agent (C), 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") as a silane coupling agent, and 1-hydroxycyclohexylphenylketone (manufactured by BASF) as a photoinitiator (D) , Product name "Igacura 184") 0.5 parts by mass, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition having a solid content concentration of 33% by mass.

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

[(Meth)acrylic acid ester copolymer]

2EHA: 2-ethylhexyl acrylic acid

BA: n-butyl acrylate

MA: methyl acrylate

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylic acid

[Active energy ray-curable component]

A400: Polyethylene glycol diacrylate (manufactured by Shinnakamura Chemical, product name ``NK Ester A-400'')

A9300-1CL: ε-caprolactone-modified tris (2-acryloxyethyl) isocyanurate (Shin-Nakamura Chemical Co., Ltd., product name ``A-9300-1CL'')

ADPH: Dipentaerythritol hexaacrylate (manufactured by Shinnakamura Chemical Co., Ltd., product name "A-DPH")

3. Preparation of adhesive sheet

The obtained adhesive composition coating solution was applied to the peel-treated side of a heavy-release type release sheet (manufactured by Lintec, product name “SP-PET752150”) in which one side of a polyethylene terephthalate film was peeled off with a silicone-based release agent, and the thickness after drying was 100 μm. After coating with a knife coater as much as possible, heat treatment was performed at 100° C. for 4 minutes to form a coating layer. Similarly, the obtained adhesive composition coating solution was applied to the peel-treated side of a light-release type release sheet (manufactured by Lintec, product name ``SP-PET382120'') in which one side of a polyethylene terephthalate film was peeled off with a silicone-based release agent, and the thickness after drying was After coating with a knife coater so as to be 100 µm, heat treatment was performed at 100° C. for 4 minutes to form a coating layer.

Then, the heavy-release type release sheet with the coating layer obtained above and the light-release type release sheet with the coating layer obtained above are bonded so that both coating layers are in contact with each other, and cured for 7 days under conditions of 23°C and 50% RH. , A pressure-sensitive adhesive sheet consisting of a medium-release type release sheet/adhesive layer (thickness: 200 μm)/a light-release type release sheet was prepared. In addition, the thickness of the pressure-sensitive adhesive layer is a value measured using a static pressure thickness meter (manufactured by Techrock, product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 9, Comparative Examples 1 to 3]

The ratio of each monomer constituting the (meth)acrylic acid ester copolymer (A), the weight average molecular weight of the (meth)acrylic acid ester copolymer (A), the type and amount of active energy ray-curable component (B), crosslinking agent (C) A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the blending amount of the photopolymerization initiator (D), the blending amount of the silane coupling agent, and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. Further, for Example 7, a pressure-sensitive adhesive sheet was prepared in which the thickness of each of the coating layers in the heavy-release type release sheet with the coating layer and the light-release type release sheet with the coating layer was 75 µm and the thickness of the pressure-sensitive adhesive layer was 150 µm.

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

<Measurement conditions>

GPC measuring device: HLC-8020 manufactured by Tosoh Corporation

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

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

·Measurement solvent: Tetrahydrofuran

·Measurement temperature: 40℃

[Test Example 1] (Measurement of storage modulus)

The light-release type release sheet and the medium-release type release sheet were peeled from the PSA sheet obtained in Examples or Comparative Examples, and a plurality of layers of the PSA layer were laminated so as to have a thickness of 0.6 mm. From the obtained laminate of the pressure-sensitive adhesive layer, a cylindrical body (0.6 mm in height) having a diameter of 8 mm was punched out, and this was used as a sample (a sample before ultraviolet irradiation).

With respect to the sample, the storage modulus (MPa) was measured under the following conditions by a torsional shearing method using a viscoelasticity measuring device (manufactured by Physica, MCR300) in accordance with JIS K7244-6.

Measurement frequency: 1Hz

Measurement temperature: 23℃, 85℃

In addition, for the same sample as above, by irradiating the adhesive layer with ultraviolet rays under the following conditions with an ultraviolet irradiation device (manufactured by Eye Graphics, product name ``Igrantage ECS-401 GX type''), the sample after ultraviolet irradiation was Got it. About the obtained sample after ultraviolet irradiation, it carried out similarly to the sample before ultraviolet irradiation, and measured the storage modulus (MPa).

[Ultraviolet irradiation conditions]

·Light source: high pressure mercury lamp

Light intensity: 1000mJ/cm ²

·Illuminance: 200mW/cm ²

From the above measurement results, the ratio of the storage modulus after ultraviolet irradiation to the storage modulus before ultraviolet irradiation at 23°C and 85°C (storage modulus after ultraviolet irradiation/storage modulus before ultraviolet irradiation) was calculated. Table 2 shows the measurement results and calculation results.

[Test Example 2] (Evaluation of processability)

The light-release type release sheet was peeled from the adhesive sheet obtained in Examples or Comparative Examples, and the peeling condition of the light-release type release sheet at this time was evaluated as workability. It was evaluated that the light peelable release sheet was able to gently peel from the pressure-sensitive adhesive layer as good workability (○), and that the pressure-sensitive adhesive layer was destroyed with the peeling of the light-peelable release sheet was evaluated as poor workability (x). Table 2 shows the results.

[Test Example 3] (Moisture heat whitening evaluation)

A laminate was obtained by sandwiching the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples on two sheets of 1.1 mm-thick alkali-free glass, and irradiating ultraviolet rays over one glass under the ultraviolet irradiation conditions of Test Example 1. With respect to the laminate, the haze value (%) was measured in accordance with JIS K7136:2000 using a haze meter (manufactured by Nippon Denshoku Co., Ltd., product name "NDH2000").

Next, the laminate was stored for 240 hours under a humid heat condition of 85°C and 85%RH. After that, it is returned to the normal temperature and humidity of 23°C and 50%RH, and the haze value (%) according to JIS K7136:2000 using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name "NDH2000") Was measured. In addition, the haze value was measured within 30 minutes after returning the laminate to room temperature and humidity.

Based on the above result, the haze value before the moist heat condition was subtracted from the haze value after the moist heat condition, and the haze value increase (point) after the moist heat condition was calculated. Moisture heat whitening resistance is good (○) for those whose haze value rise after moist heat condition is less than 1.0 point, and those whose haze value rise after moist heat condition is 1.0 point or more and less than 5.0 point within the suitable value of moist heat whitening resistance (△), haze after moist heat condition Those with a value increase of 5.0 points or more were evaluated as poor moist heat whitening resistance (x). Table 2 shows the results.

[Test Example 4] (Step followability/durability test)

(a) Preparation of sample for evaluation

UV-curable ink (manufactured by Teikoku Ink, product name ``POS-911 Sumi'') is applied to the surface of a glass plate (manufactured by NSG Flashzone, product name ``Corning Glass Eagle XG'', 90mm long x 50mm wide x 0.5mm thick). Screen printing was performed in the shape of a frame frame (outer shape: length 90 mm x width 50 mm, width 5 mm) so as to be 8 µm and 15 µm. Then, ultraviolet rays are irradiated (80 W/cm ² , metal halide lamp 2 lamp, lamp height 15 cm, belt speed 10 to 15 m/min), the printed ultraviolet curable ink is cured, and the step by printing A glass plate with steps having (step height: 8 µm and 15 µm) was produced.

The pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples was cut into a shape of 90 mm in length x 50 mm in width, and the light-peelable release sheet was removed to expose the pressure-sensitive adhesive layer. Then, using a laminator (manufactured by Fujipla, product name "LPD3214"), the pressure-sensitive adhesive sheet was laminated to the stepped glass plate so that the pressure-sensitive adhesive layer covers the entire surface of the frame-shaped print.

Then, samples for evaluation of the following (1) and (2) were produced, respectively.

(1) After the lamination, the heavy peeling type release sheet was peeled off, and a glass plate (manufactured by NSG Flashzone, product name ``Corning Glass Eagle XG'', 90 mm long x 50 mm wide x 0.5 mm thick) was laminated with the laminator on the exposed pressure-sensitive adhesive layer surface. Then, a sample for evaluation was produced.

(2) A hard plate on which a polarizing plate was laminated was prepared separately on a glass plate (manufactured by NSG Flashzone, product name "Corning Glass Eagle XG", 90 mm long x 50 mm wide x 0.5 mm thick) through a pressure-sensitive adhesive. Then, the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet laminated on the stepped glass plate obtained in the above step is peeled and the exposed pressure-sensitive adhesive layer surface and the polarizing plate surface of the hard plate are laminated with the laminator to obtain a sample for evaluation. Made.

(b) Evaluation of step followability (initial)

The obtained evaluation samples (1) and (2) were pressurized at 0.5 MPa and 50°C for 30 minutes in an autoclave manufactured by Kurihara Seisakusho. After that, it was visually checked whether or not there were air bubbles in the pressure-sensitive adhesive layer (especially in the vicinity of the step by the printing layer). As a result, it was evaluated as ⊚ that there were no bubbles, (circle) that there were almost no bubbles, and × that there were bubbles (evaluation of initial step followability). Table 2 shows the results.

(c) Evaluation of durability (step followability after durability)

Next, the evaluation samples (1) and (2) were stored for 240 hours under a humid heat condition of 85°C and 85%RH. After that, it was visually checked whether or not there were air bubbles in the pressure-sensitive adhesive layer (especially in the vicinity of the step by the printing layer). As a result, it was evaluated as (double-circle) that there were no bubbles, (circle) that there were almost no bubbles, and × (evaluation of durability (step difference followability after durability)). Table 2 shows the results.

[Test Example 5] (Total light transmittance measurement)

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples was bonded to glass, and this was used as a sample for measurement. After performing background measurement with glass, the total light transmittance (%) was measured using a haze meter (manufactured by Nippon Denshoku Kogyo, NDH-2000) in accordance with JIS K7361-1:1997 about the sample for measurement. . Table 2 shows the results.

[Test Example 6] (Evaluation of blister resistance)

By sputtering, a 125-micrometer-thick polyethylene terephthalate film (manufactured by Oike Co., Ltd., ITO film) was prepared with a transparent conductive film made of tin-doped indium oxide (ITO) on one side.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples was sandwiched between the transparent conductive film of the ITO film and a polycarbonate plate having a thickness of 1 mm (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name ``Upiron Sheet MR58''), and polycarbonate A laminate was obtained by irradiating ultraviolet rays over the plate under the ultraviolet irradiation conditions of Test Example 1.

The obtained laminate was subjected to an autoclave treatment at 50° C. and 0.5 MPa for 30 minutes, and then allowed to stand for 15 hours. Then, it was stored for 72 hours under a durable condition of 85°C and 85%RH. After that, it was visually checked whether or not there were air bubbles, lifting or peeling in the pressure-sensitive adhesive layer. As a result, it was evaluated as ⊚ that there was no air bubbles or lifted or peeled off, ○ that there was almost no air bubbles or lifted or peeled off, and that bubbles or lifted or peeled off occurred as x (evaluation of blister resistance). Table 2 shows the results.

(Meth)acrylic acid ester copolymer (A)
Active energy ray-curable component (B)
Crosslinking agent (C)
[Parts by mass]
Light polymerization
Initiator
(D)
[Parts by mass] Silane
Coupling agent
[Parts by mass] adhesive
thickness
(㎛) 2EHA BA MA MMA HEA Mw Mass part Kinds Mass part Example 1 60 - - 20 20 700,000 100 A400 5 0.23 0.5 0.2 200 Example 2 60 - - 20 20 700,000 100 A400 25 0.23 2.5 0.2 200 Example 3 60 - - 20 20 700,000 100 A400 25 0.5 2.5 0.2 200 Example 4 60 - - 20 20 600,000 100 A400 25 0.23 2.5 0 200 Example 5 - 60 20 - 20 600,000 100 A400 5 0.23 0.5 0.2 200 Example 6 80 - - - 20 600,000 100 A400 5 0.5 0.5 0.2 200 Example 7 60 - - 20 20 700,000 100 A400 5 0.5 0.5 0.2 200 Example 8 60 - - 20 20 700,000 100 A9300-1CL 10 0.2 One 0.2 200 Example 9 60 - - 20 20 700,000 100 ADPH 5 0.2 0.5 0.2 200 Comparative Example 1 60 - - 20 20 700,000 100 - - 0.23 - 0.2 200 Comparative Example 2 60 - - 20 20 700,000 100 A400 70 0.23 7 0.2 200 Comparative Example 3 70 - - 20 10 700,000 100 A400 5 0.23 0.5 0.2 200

As can be seen from Table 2, the pressure-sensitive adhesive sheet obtained in Examples was excellent in processability. Further, the pressure-sensitive adhesive layer obtained in Examples was excellent in step-following properties before ultraviolet irradiation, and excellent in moist heat whitening resistance, durability, and blister resistance after ultraviolet irradiation.

The pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for bonding a display module and a protective plate having a step difference.

One… Adhesive sheet
11... Adhesive layer
12a, 12b... Release sheet
2… Laminate
21... 1st hard plate
22... 2nd hard plate
3… Printed layer

Claims (13)

A (meth)acrylic acid ester copolymer (A) having a weight average molecular weight of 200,000 to 900,000, containing 15 to 30% by mass of a monomer having a hydroxyl group as a monomer unit constituting the polymer, and not containing a monomer having a carboxyl group, and ,
An active energy ray-curable component (B),
Crosslinking agent (C)
As a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 50 to 400 μm obtained by thermal crosslinking an adhesive composition for bonding two hard plates containing each other,
The adhesive sheet, wherein the adhesive composition contains only one or two of a polyfunctional acrylate monomer, an acrylate oligomer, and an adduct acrylate polymer as the active energy ray-curable component (B). The method of claim 1,
The content of the active energy ray-curable component (B) in the adhesive composition is 1 to 50 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). The method of claim 1,
The content of the crosslinking agent (C) in the adhesive composition is 0.01 to 5 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). The method of claim 1,
The pressure-sensitive adhesive sheet, characterized in that the ratio of the storage modulus at 23° C. after irradiating the pressure-sensitive adhesive layer with active energy rays to the storage modulus at 23° C. before irradiating the pressure-sensitive adhesive layer with active energy rays is 1.1 to 10 . The method of claim 1,
The pressure-sensitive adhesive sheet, characterized in that the ratio of the storage modulus at 85° C. after irradiating the pressure-sensitive adhesive layer with active energy rays to the storage modulus at 85° C. before irradiating the pressure-sensitive adhesive layer with active energy rays is 1.1 to 10 . The method of claim 1,
The adhesive sheet has two release sheets,
The pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is fitted to the release sheet so as to contact the release surfaces of the two release sheets. With two hard plates,
As a laminate having an adhesive layer sandwiched between the two hard plates,
The pressure-sensitive adhesive layer is a laminate, characterized in that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 is cured by irradiation with active energy rays. The method of claim 7,
A laminate, characterized in that at least one of the hard plates has a step on the side of the pressure-sensitive adhesive layer. The method of claim 8,
The step difference is a laminate, characterized in that the step difference due to the presence or absence of a printed layer. The method of claim 7,
A laminate, characterized in that at least one of the hard plates includes a polarizing plate. The method of claim 7,
A laminate, characterized in that at least one of the hard plates comprises a glass plate or a plastic plate. The method of claim 7,
One of the above two hard plates is a display module or a part thereof,
A laminate, characterized in that the other side of the two hard plates is a protective plate having a frame frame-shaped step on the side of the pressure-sensitive adhesive layer. The method of claim 7,
A laminate, characterized in that the total light transmittance of the pressure-sensitive adhesive layer is 80% or more.

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