TWI727920B - Adhesive sheet - Google Patents

Abstract

The present invention provides an adhesive and an adhesive sheet. The adhesive of the present invention is formed by cross-linking an adhesive composition. The adhesive composition contains: (meth)acrylate polymer (A), the weight of which is average The molecular weight is 200,000 to 900,000. As the monomer unit constituting the polymer, it contains more than 10% by mass and 30% by mass or less of monomers with hydroxyl groups; crosslinking agent (B); and crosslinking accelerator (C), Among them, the gel ratio of the aforementioned adhesive is 40 to 90%. The adhesive layer composed of this type of adhesive is excellent in both anti-foaming properties and step-following properties.

Description

Adhesive sheet

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

In recent years, various mobile electronic devices such as mobile phones or tablet computers include displays using display modules. The aforementioned display molds include liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescence (organic EL) elements, etc. The number of cases where the display becomes a touch panel is gradually increasing.

In the above-mentioned display, a protective panel is usually provided on the surface side of the display module. With the thinning and weight reduction of electronic devices, the above-mentioned protective panels are gradually changed from conventional glass plates to plastic plates such as acrylic plates or polycarbonate plates.

Here, a gap is provided between the protection panel and the display module, so that when the protection panel is deformed due to external force, the deformed protection panel will not touch the display module.

However, if there is an air layer as the above-mentioned void, the light reflection loss caused by the refractive index difference between the protective panel and the air layer, and the refractive index difference between the air layer and the display module becomes larger, and the display is The problem of image quality degradation.

Therefore, it is proposed to fill the protective panel and The gap between the display modules improves the image quality of the display. However, sometimes there is a frame-shaped printed layer as a step on the display module side of the protection panel. If the adhesive layer does not follow the level difference, it will cause the adhesive layer to lift up near the level difference, thereby causing light reflection loss. Therefore, the level difference followability is required for the above-mentioned adhesive layer.

In order to solve the above-mentioned problems, Patent Document 1 discloses the following adhesive layer as an adhesive layer filling the gap between the protective panel and the display module, and the shear storage modulus (G ') is 1.0×10 ⁵ Pa or less, and the gel fraction is 40% or more.

【Prior Technical Literature】 【Patent Literature】

[Patent Document 1] JP 2010-97070 A

In Patent Document 1, it is desired to improve the step followability by reducing the storage elastic modulus at room temperature in the adhesive layer. However, if the storage elastic modulus at normal temperature is reduced as described above, the storage elastic modulus at high temperature is reduced to more than a required value, which causes a problem under durable conditions. For example, when high-temperature and high-humidity conditions are applied, air bubbles are generated near the step difference, or air leakage from the plastic plate as the protective panel causes air bubbles, warping, peeling, and other expansion problems. On the other hand, if the adhesive layer is hardened in order to improve the anti-foaming property, the step followability decreases.

The present invention was completed in view of the above-mentioned actual situation, and its purpose is to provide an adhesive and an adhesive sheet that are excellent in both anti-foaming properties and step-following properties.

In order to achieve the above object, firstly, the present invention provides an adhesive, which is formed by cross-linking an adhesive composition. The adhesive composition contains: (meth)acrylate polymer (A) with a weight average molecular weight of 20 10,000 to 900,000, as the monomer unit constituting the polymer, containing more than 10% by mass and 30% by mass or less of a monomer having a hydroxyl group; a crosslinking agent (B); and a crosslinking accelerator (C), wherein The glue ratio is 40~90% (Invention 1).

In the above invention (Invention 1), the crosslinking agent (B) is activated by the catalytic action of the crosslinking accelerator (C), the (meth)acrylate polymer (A) and the crosslinking agent (B) The cross-linking reaction proceeds effectively, and the cohesive force of the obtained adhesive is improved. The adhesive layer with this kind of strong cohesive force and composed of an adhesive cross-linked with the gel ratio within the above range has excellent anti-foaming properties and is not easy to become too hard, so the step followability is also excellent . That is, the adhesive according to the above invention (Invention 1) can usually achieve the two properties of anti-foaming property and step-following property in a trade-off relationship.

In the above invention (Invention 1), the content of the crosslinking accelerator (C) in the adhesive composition is 0.001 to 1 mass relative to 100 parts by mass of the (meth)acrylate polymer (A) Parts are better (Invention 2).

In the above invention (Invention 1), it is preferable that the aforementioned crosslinking accelerator (C) is an organotin compound (Invention 3).

In the above inventions (Inventions 1 to 3), in the (meth)acrylate polymer (A), it is preferable that the monomer unit constituting the polymer does not contain a monomer having a carboxyl group (Invention 4).

In the above inventions (Inventions 1 to 4), the aforementioned crosslinking agent (B) is An isocyanate-based crosslinking agent is preferable (Invention 5).

In the above inventions (Inventions 1 to 5), the (meth)acrylate polymer (A) contains a homopolymer having a glass transition temperature of 70°C or higher as a monomer unit constituting the polymer Hard monomers are preferred (Invention 6).

In the above inventions (Inventions 1 to 6), in the (meth)acrylate polymer (A), it is preferable to contain 2-ethylhexyl (meth)acrylate as a monomer unit constituting the polymer (Invention 7).

In the above inventions (Inventions 1 to 7), it is preferable that the adhesive composition further contains a silane coupling agent (D) (Invention 8).

Secondly, the present invention provides an adhesive sheet. The adhesive sheet is characterized by: comprising: two release sheets; and an adhesive layer sandwiched by the release sheet so as to contact the release surfaces of the two release sheets, and The adhesive layer is composed of the adhesive (Inventions 1 to 8) (Invention 9).

In the above invention (Invention 9), it is preferable that the aforementioned adhesive layer is arranged between two patterned transparent conductive films, or between the patterned transparent conductive film and the cover material or the display module (Invention 10).

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

1‧‧‧Adhesive sheet

11‧‧‧Adhesive layer

12a、12b‧‧‧Release sheet

2‧‧‧Touch Panel

3‧‧‧Display module

4a, 4b‧‧‧Adhesive layer

5a‧‧‧The first thin film sensor

5b‧‧‧The second thin film sensor

51‧‧‧Substrate film

52‧‧‧Transparent conductive film

6‧‧‧Cover material

7‧‧‧Printing layer

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

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

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

〔Adhesive〕

The adhesive of this embodiment is formed by cross-linking an adhesive composition (hereinafter sometimes referred to as "adhesive composition P"), and the aforementioned adhesive composition contains: (meth)acrylate polymer (A), which The weight average molecular weight is 200,000 to 900,000, as the monomer unit constituting the polymer, containing more than 10% by mass and 30% by mass or less of monomers having hydroxyl groups (hydroxyl-containing monomers); crosslinking agent (B); and Crosslinking accelerator (C), the gel rate of the aforementioned adhesive is 40~90%. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. Other similar terms are also the same. In addition, "polymer" also includes the concept of "copolymer".

In the adhesive formed by cross-linking the above-mentioned adhesive composition P, the cross-linking agent (B) is activated by the catalytic action of the cross-linking accelerator (C), and the (meth)acrylate polymer ( The crosslinking reaction between A) and the crosslinking agent (B) proceeds efficiently. The compound as the crosslinking agent (B) has a plurality of functional groups in one molecule. In a normal reaction, several functional groups in one molecule do not react and remain. However, due to the presence of the crosslinking accelerator (C), it can be estimated All the functional groups in one molecule of the above-mentioned compound are those capable of reacting with the reactive functional groups (hydroxyl groups) of the (meth)acrylate polymer (A). Therefore, it becomes a stronger cross-linked structure, and the cohesive force of the obtained adhesive is improved. With this kind of strong cohesive force, and the adhesive layer composed of the adhesive cross-linked with the gel ratio within the above range, the adhesive layer is excellent in anti-foaming properties, and is not too hard, so the step followability is also excellent. That is, the adhesive according to the present embodiment can have both anti-foaming properties and step-following properties that are usually in a trade-off relationship.

Therefore, as an example, when the adhesive layer composed of the above-mentioned adhesive is applied to the surface of the plastic plate on the side where the level difference exists, the adhesive layer follows the level difference, so there is no warpage or bubbles near the level difference. In addition, even if the laminate of the adhesive layer and the plastic plate is placed under durable conditions, the generation of bubbles near the step difference can be suppressed, and even if air leakage occurs from the plastic plate, the generation of bubbles, warping, and peeling can be suppressed Wait for expansion.

(1) (Meth) acrylate polymer (A)

Examples of the (meth)acrylate polymer (A) contained in the monomer unit constituting the polymer, that is, a hydroxyl group-containing monomer, include, for example, 2-hydroxyethyl (meth)acrylate, (meth) 2-hydroxypropyl acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate Etc. (meth) hydroxyalkyl acrylate and so on. Among them, from the viewpoint of the reactivity of the hydroxyl group in the obtained (meth)acrylate polymer (A) with the crosslinking agent (B) and the copolymerizability of other monomers, the (meth)acrylic acid 2-hydroxyl Ethyl ester is preferred. These can be used alone or in combination of two or more.

As described above, in the (meth)acrylate polymer (A), as a monomer constituting the polymer, more than 10% by mass and 30% by mass or less of hydroxyl-containing monomer units are contained. If the content of the hydroxyl group-containing monomer is 10% by mass or less, the aforementioned strong cross-linked structure will not be formed, and the resulting adhesive will have poor anti-foaming properties. On the other hand, if the content of the hydroxyl group-containing monomer exceeds 30% by mass, the desired adhesiveness cannot be obtained.

Here, if the touch panel or the like is placed in a high-temperature and high-humidity environment, water will penetrate into the adhesive layer, and when the touch panel or the like is restored to normal temperature, There is a problem of "damp heat whitening" in which the adhesive layer whitens and the transparency decreases. If the (meth)acrylate polymer (A) contains a hydroxyl group-containing monomer in the above-mentioned range, a predetermined amount of hydroxyl groups will remain in the adhesive layer. The hydroxyl group is a hydrophilic group. If a predetermined amount of this hydrophilic group is present in the adhesive layer, even when the adhesive layer is placed under high temperature and high humidity conditions, it will be immersed in the adhesive under the high temperature and high humidity conditions. The compatibility of the water in the agent layer is also good. As a result, the whitening of the adhesive layer is suppressed, and the adhesive layer has excellent heat and humidity resistance to whitening.

From the above point of view, in the (meth)acrylate polymer (A), it is preferable to contain 12-25% by mass of a hydroxyl-containing monomer as a monomer unit constituting the polymer, and it is particularly preferable to contain 15-20% by mass. .

In the (meth)acrylate polymer (A), it is preferable that the monomer unit constituting the polymer does not contain a carboxyl group-containing monomer. The carboxyl group (acid) has a tendency to reduce the catalytic effect of the crosslinking accelerator (C), but since the (meth)acrylate polymer (A) does not have a carboxyl group, it can fully exert the catalysis of the crosslinking accelerator (C) effect. In addition, since the (meth)acrylate polymer (A) does not have a carboxyl group, even if the obtained adhesive is applied to a problem caused by acid, for example, in the case of a transparent conductive film or metal wiring, It can also suppress the aforementioned disadvantages caused by acid. For example, it is possible to suppress corrosion of the transparent conductive film or metal wiring, or to change the resistance value of the transparent conductive film.

Here, "does not contain a monomer having a carboxyl group" means that it does not actually contain a monomer having a carboxyl group. In addition to not containing a carboxyl group-containing monomer at all, it is allowed to reduce the catalytic effect of the crosslinking accelerator (C) based on the carboxyl group. Alternatively, a carboxyl group-containing monomer is contained to such an extent that defects such as a transparent conductive film or metal wiring do not cause problems. Specifically, in the (meth)acrylate polymer (A), as a monomer unit, The carboxyl group-containing monomer is contained in an amount of 0.1% by mass or less, preferably in an amount of 0.01% by mass or less.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, an alkyl (meth)acrylate having 1 to 20 carbon atoms containing an alkyl group is preferred. With this, the obtained adhesive can show better adhesiveness. In addition, the hard monomer mentioned later is removed from this alkyl (meth)acrylate.

Examples of alkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and n-(meth)acrylate. Butyl ester, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, N-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmitoyl (meth)acrylate, stearyl (meth)acrylate, and the like. Among them, from the viewpoint of further improving the adhesiveness, (meth)acrylates having an alkyl group of 1 to 8 carbon atoms are preferred, and n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred. Esters are particularly preferred, and 2-ethylhexyl (meth)acrylate is even more preferred. According to 2-ethylhexyl (meth)acrylate, the dielectric constant of the obtained adhesive can be reduced, and the response accuracy of the touch panel can be improved. In addition, these can be used individually or in combination of 2 or more types.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, 30 to 85% by mass of alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms is more Preferably, 40 to 75% by mass is more preferable, and 50 to 65% by mass is more preferable.

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

As the above-mentioned hard monomers, for example, methyl methacrylate (Tg105°C), isobornyl acrylate (Tg94°C), isobornyl methacrylate (Tg180°C), acrylomorpholine (Tg145°C) , Adamantyl acrylate (Tg115°C), adamantyl methacrylate (Tg141°C), dimethyl acrylamide (Tg89°C), acrylamide (Tg165°C), etc. These substances can be used alone or in combination of two or more.

Among the above-mentioned hard monomers, from the viewpoint of further exerting the performance of the hard monomers while preventing adverse effects on other properties such as adhesion and transparency, methyl methacrylate, isobornyl acrylate and acrylomorpholine are more preferred. Preferably, methyl methacrylate is particularly preferred.

In the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, 10 to 45% by mass of the above-mentioned hard monomer is preferably contained, and 15 to 30% by mass is particularly preferred. By containing 10% by mass or more of the above-mentioned hard monomer, the effect of improving the anti-foaming property based on the monomer unit can be expected. On the other hand, by setting the above-mentioned hard monomers to a content of 45% by mass or less, it is possible to prevent the other monomer units in the (meth)acrylate polymer (A) from being relatively insufficient, thereby enabling Enough to make the obtained adhesives have excellent adhesion and step followability.

The (meth)acrylate polymer (A) may contain other monomers as monomer units constituting the polymer as necessary. As other monomers, monomers that do not contain reactive functional groups are preferred in order not to impair the function of the hydroxyl-containing monomers. As the other monomers, for example, alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, and cyclohexyl (meth)acrylate (Meth)acrylates with aliphatic rings, (meth)acrylic acid-N,N-dimethylaminoethyl, (meth)acrylic acid-N,N-dimethylaminopropyl ester, etc. have non-crosslinking (Meth) acrylate of tertiary amino group, vinyl acetate, styrene, etc. These substances can be used alone or in combination of two or more.

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

The weight average molecular weight of the (meth)acrylate polymer (A) is 200,000 to 900,000, preferably 300,000 to 800,000, and particularly preferably 400,000 to 600,000. In addition, the weight average molecular weight in this specification is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method.

When the weight average molecular weight of the (meth)acrylate polymer (A) is in the relatively low range as described above, an adhesive that is excellent in both anti-foaming properties and step-following properties can be obtained. If the weight average molecular weight of the (meth)acrylate polymer (A) is less than 200,000, the foam resistance is poor, and if the weight average molecular weight of the (meth)acrylate polymer (A) exceeds 900,000, then Become a poor follower of the gap.

In addition, in the adhesive composition P, (meth)acrylate is polymerized The substance (A) may be used alone or in combination of two or more kinds.

(2) Crosslinking agent (B)

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

As the crosslinking agent (B), it is sufficient to react with the reactive group (the hydroxyl group of the hydroxyl-containing monomer as a monomer unit) possessed by the (meth)acrylate polymer (A), for example, isocyanate Crosslinking agent, epoxy crosslinking agent, amine crosslinking agent, melamine crosslinking agent, aziridine crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent , Metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents, etc. Among the above-mentioned substances, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with a hydroxyl group and can exhibit an excellent catalytic effect of the crosslinking accelerator (C). Moreover, the crosslinking agent (B) can be used individually by 1 type, or in combination of 2 or more types.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. As the polyisocyanate compound, for example, aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; isophorone diisocyanate, Hydrogenated diphenylmethane diisocyanate and other alicyclic polyisocyanates; and their biuret and isocyanurate; further examples include ethylene glycol, propylene glycol, neopentyl glycol, trimethylol Propane, castor oil and other reactants containing low-molecular-weight active hydrogen compounds are also adducts. Among them, from the viewpoint of the reactivity with the hydroxyl group and the catalytic effect of the crosslinking accelerator (C), the trimethylolpropane modified aromatic Fragrance polyisocyanate is preferred, and trimethylolpropane modified toluene diisocyanate is particularly preferred.

One molecule of the above-mentioned polyisocyanate compound has a plurality of isocyanate groups. In the adhesive of this embodiment, since the adhesive composition P contains the crosslinking accelerator (C), it can be estimated that all the isocyanate genes and the (meth)acrylate polymer possessed by one molecule of the polyisocyanate compound The reactive functional group (hydroxyl group) of (A) reacts to increase the cohesion, and is excellent in both anti-foaming properties and step-following properties.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 2 parts by mass relative to 100 parts by mass of the (meth)acrylate polymer (A), particularly preferably 0.05 to 1 part by mass , 0.10~0.20 parts by mass is further preferred. If the content of the crosslinking agent (B) is within the above range, the obtained adhesive will be excellent in both the anti-foaming properties and the step following properties.

(3) Crosslinking accelerator (C)

The crosslinking accelerator (C) is not particularly limited as long as it can activate the crosslinking agent (B) and improve the reaction efficiency of the (meth)acrylate polymer (A) and the crosslinking agent (B). As the crosslinking accelerator (C), for example, organic tin compounds; amino compounds such as N,N,N',N'-tetramethylhexamethylenediamine, triethylamine, imidazole, etc.; metals such as aluminum complexes Complexes; acid catalysts such as p-toluenesulfonic acid, phosphoric acid, hydrochloric acid, ammonium chloride, etc. Among them, from the viewpoint of catalytic action, organotin compounds are preferred.

As the organotin compound, for example, an organotin compound such as dimethyl tin dichloride; dimethyl tin dilaurate, dimethyl tin di(2-ethylhexanoic acid), and dimethyl diacetate may be mentioned. Tin, dibutyltin dilaurate, dihexyl diacetate Fatty acid salts of organotin compounds such as methyltin and dioctyltin dilaurate; dimethyltin bis(isooctyl thioglycolate) salt, dioctyltin bis(isooctyl thioglycolate) salt, etc. Thioglycolic acid ester salts of organotin compounds; metal soaps such as tin octylate and tin decanoate, etc. Among them, from the viewpoint of catalysis, fatty acid salts of organotin compounds are preferred, and dibutyltin dilaurate is particularly preferred. Moreover, a crosslinking accelerator (C) may be used individually by 1 type, and may be used in combination of 2 or more types.

The content of the crosslinking accelerator (C) in the adhesive composition P is preferably 0.001 to 1 part by mass relative to 100 parts by mass of the (meth)acrylate polymer (A), 0.005 to 0.8 part by mass Particularly preferred, 0.01 to 0.7 parts by mass is further preferred. Since the content of the cross-linking accelerator (C) is within the above range, the catalytic effect based on the cross-linking accelerator (C) can be effectively exerted without hindering adhesion.

(4) Silane coupling agent (D)

It is preferable that the adhesive composition P further contains a silane coupling agent (D). Therefore, if the glass member is present in the adherend, the adhesion of the obtained adhesive to the glass member is improved. In addition, even if the object to be adhered is a plastic plate, the adhesion of the obtained adhesive to the plastic plate is improved, and the foaming resistance is more excellent.

As the silane coupling agent (D), an organosilicon compound having at least one alkoxysilyl group in the molecule has good compatibility with the (meth)acrylate polymer (A) and has light transmittance.

As the silane coupling agent (D), for example, vinyl trimethoxy silane, vinyl triethoxy silane, methacryloxypropyl trimethoxy silane, and other polymerizable unsaturated group-containing silicon compounds can be mentioned. , 3-glycidyl ether propyl trimethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane and other epoxy Structured silicon compounds, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane and other mercapto-containing silicon compounds, 3-aminopropyltrimethyl Amino-containing silicon such as oxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, etc. Compound, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these and methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane Condensates of alkyl-containing silicon compounds such as silane and ethyltrimethoxysilane. One of these substances may be used alone, or two or more of them may be used in combination.

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

(5) Various additives

In the adhesive composition P, various additives commonly used as acrylic adhesives can be added as needed, such as reaction inhibitors, refractive index modifiers, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, light Stabilizers, softeners, fillers, etc.

In the adhesive composition P in this embodiment, the (meth)acrylate polymer (A) and the cross-linking agent (B) easily react due to the catalytic action of the cross-linking accelerator (C), so It is better to contain a reaction inhibitor to ensure the pot life.

As the reaction inhibitor, for example, acetone, ethyl acetone, octanediol, etc. may be mentioned. Among them, acetone is preferred. These can be used alone One type or two or more types may be used in combination. In addition, the above-mentioned reaction inhibitor usually volatilizes during the drying process when the adhesive layer is formed.

The content of the reaction inhibitor in the adhesive composition P is preferably 0.01-10 parts by mass relative to 100 parts by mass of the (meth)acrylate polymer (A), particularly preferably 0.05-8 parts by mass, and 0.1~ 5 parts by mass is more preferable.

(6) Manufacturing of adhesive composition

Manufacture the (meth)acrylate polymer (A), and add a crosslinking agent (B), a crosslinking accelerator (C), and if necessary, to the obtained (meth)acrylate polymer (A) The silane coupling agent (D) and additives can produce the adhesive composition P.

The (meth)acrylate polymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by a normal radical polymerization method. If necessary, the (meth)acrylate polymer (A) can be polymerized by a solution polymerization method or the like using a polymerization initiator. As the polymerization solvent, for example, ethyl acetate, n-butyl acetate, n-isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc. may be mentioned, and two or more kinds may be used in combination.

As a polymerization initiator, an azo compound, an organic peroxide, etc. may be mentioned, and 2 or more types may be used together. As the azo compound, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane- 1-carboxynitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile) ), 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethyl Base propionitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] and the like.

As the organic peroxide, for example, benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxy dicarbonate, di-N-propyl peroxy dicarbonate, Carbonate, bis(2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl) ) Peroxide, dipropylene peroxide, diacetyl peroxide, etc.

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

If the (meth)acrylate polymer (A) is obtained, add a crosslinking agent (B), a crosslinking accelerator (C), and if necessary, to the solution of the (meth)acrylate polymer (A) Silane coupling agent (D), diluting solvent and additives are mixed thoroughly to obtain adhesive composition P (coating solution) diluted with solvent.

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

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as the coating solution is within a range that can be applied, and can be appropriately selected according to the situation. For example, it is diluted so that the concentration of the adhesive composition P becomes 10-60% by mass. In addition, when a coating solution is obtained, the addition of a dilution solvent or the like is not a necessary condition, and if the adhesive composition P has a viscosity or the like that can be applied, the dilution solvent may not be added. In this case, the adhesive composition P will directly combine (methyl)acrylic acid The polymerization solvent of the acrylic acid ester polymer (A) is used as the coating solution of the dilution solvent.

(7) Manufacturing of adhesive

The adhesive of this embodiment is preferably constituted by crosslinking the adhesive composition P. The crosslinking of the adhesive composition P is usually performed by heat treatment. In addition, the drying treatment when the diluent solvent or the like of the adhesive composition P is volatilized can also be used as the aforementioned heating treatment.

When heat treatment is performed, the heating temperature is preferably 50 to 150°C, and 70 to 120°C is particularly preferred. In addition, the heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, it can also be set to a normal temperature (for example, 23° C., 50% RH) and a regimen period of about 1 to 2 weeks. When the regimen period is required, the adhesive is formed after the regimen period has elapsed, and when the regimen period is not required, the adhesive agent is formed after the end of the heat treatment.

Through the above-mentioned heat treatment (and health maintenance), the (meth)acrylate polymer (A) is sufficiently cross-linked via the cross-linking agent (B), and the aforementioned effects can be exerted.

(8) Gel rate

The gel ratio of the adhesive of this embodiment is 40~90%, 50~85% is preferred, and 60~80% is particularly preferred. If the gel ratio is less than 40%, the cohesive force of the adhesive is insufficient, and the foaming resistance is reduced. On the other hand, if the gel fraction exceeds 90%, the adhesive force becomes too low, resulting in a decrease in durability or a decrease in the step-following performance. In addition, the measuring method of the gel fraction is as shown in the test example mentioned later.

〔Adhesive sheet〕

As shown in Figure 1, the adhesive sheet 1 of this embodiment consists of two release sheets 12a, 12b is composed of an adhesive layer 11 sandwiched between the two peeling sheets 12a, 12b so as to be in contact with the peeling surfaces of the two peeling sheets 12a, 12b. In addition, the peeling surface of the peeling sheet in this specification refers to the surface which has peelability in a peeling sheet, and includes any one of the surface to which the peeling process was performed, and the surface which can show peelability even if a peeling process is not performed.

(1) Adhesive layer

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

The thickness of the adhesive layer 11 (value measured based on JIS K7130) depends on the step height, and is preferably 10 to 400 μm, particularly preferably 20 to 300 μm, and even more preferably 50 to 250 μm. Since the thickness of the adhesive layer 11 is 10 μm or more, good step followability can be exerted, and since the thickness of the adhesive layer 11 is 400 μm or less, the workability is good. In addition, the adhesive layer 11 may be formed in a single layer, or may be formed by stacking a plurality of layers.

(2) Peeling sheet

There are no particular limitations on the release sheets 12a and 12b, and a known plastic film can be used. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film can be used. Film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid copolymer film, ethylene -(Meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Moreover, these crosslinked films can also be used. Furthermore, these laminated films can also be used.

It is preferable that the peeling surface (especially the surface contacting the adhesive layer 11) of the said peeling sheet 12a, 12b is given a peeling process. As the release agent used in the release treatment, for example, an alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agent may be mentioned. In addition, among the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release type with a large release force, and the other release sheet is a light release type with a small release force.

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

(3) Manufacturing of adhesive sheet

As an example of the production of the adhesive sheet 1, the above-mentioned coating liquid of the adhesive composition P is applied to the release surface of one of the release sheets 12a (or 12b), and heat treatment is performed to crosslink the adhesive composition P to form After the coating layer, the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. When a health period is required, the health period is set in advance, and when the health period is not required, the above-mentioned coating layer directly becomes the adhesive layer 11. In this way, the above-mentioned adhesive sheet 1 can be obtained. The conditions for heat treatment and health preservation are the same as described above.

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

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

(4) Adhesion

The adhesive layer 11 is laminated on a substrate made of a polyethylene terephthalate film with a thickness of 100 μm on the adhesive layer 11 side of the laminate, and the adhesive layer 11 is pasted on the surface of the laminate provided with tin doped indium oxide (ITO ) In the case of the transparent conductive film constituting the transparent conductive film of the transparent conductive film, the adhesive force of the laminate to the transparent conductive film is preferably 5~80N/25mm, especially 10~70N/25mm, 15 ~50N/25mm is further preferred. Since the adhesive force is within the above range, for example, the constituent components of the touch panel can be reliably bonded.

In addition, the so-called adhesive force here basically refers to the adhesive force measured by the 180° peeling method based on JIS Z0237:2009. The measurement sample is set to 25 mm in width and 100 mm in length, and the measurement sample faces the object. After applying pressure at 0.5 MPa and 50°C for 20 minutes to perform the pasting, it was left under normal pressure, 23°C, and 50% RH conditions for 24 hours, and then the measurement was performed at a peeling speed of 300 mm/min.

(5) Use of adhesive sheet

By using the adhesive sheet 1 described above, it is possible to manufacture, for example, a capacitive touch panel 2 as shown in FIG. 2. The touch panel 2 is configured to include: a display module 3; a first film sensor 5a, which is laminated on the display module via an adhesive layer 4a 3 on; the second film sensor 5b, which is laminated on the first film sensor 5a via the adhesive layer 4b; the cover material 6, which is laminated on the second film sensor 5b via the adhesive layer 11.

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

As the above-mentioned display module 3, for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, electronic paper, etc. may be mentioned.

The adhesive layers 4a, 4b may be formed by the adhesive layer 11 of the above-mentioned adhesive sheet 1, or may be formed by other adhesives or adhesive sheets. In the latter case, as the adhesive constituting the adhesive layer 4, acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyethylene Among ether-based adhesives and the like, acrylic-based adhesives are preferred.

The first thin film sensor 5a and the second thin film sensor 5b are usually composed of a base film 51 and a patterned transparent conductive film 52, respectively. The base film 51 is not particularly limited, and for example, a polyethylene terephthalate film, an acrylic film, a polycarbonate film, etc. can be used.

Examples of the transparent conductive film 52 include metals such as platinum, gold, silver, and copper, oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide, and zinc dioxide, tin-doped indium oxide (ITO), and zinc oxide. Doped indium oxide, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide and other composite oxides, chalcogenides, lanthanum hexaboride, titanium nitride, titanium carbide, etc. Among them, oxide compounds and the like are preferably composed of tin-doped indium oxide (ITO).

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

In Figure 2, the transparent conductive film 52 of the second thin film sensor 5b in this embodiment is located on the upper side of the second thin film sensor 5b, but it is not limited to this, and may be located on the second thin film sensor. The lower side of the device 5a. In addition, in Figure 2, the transparent conductive film 52 of the first thin film sensor 5a is located on the upper side of the first thin film sensor 5a, but it is not limited to this, and may be located on the first thin film sensor 5a. Down side.

The covering material 6 usually takes a glass plate or a plastic plate as the main body. The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium-containing strontium glass, aluminosilicate glass acid, lead glass, borosilicate glass, barium borosilicate Salt glass and so on. It does not specifically limit as a plastic board, For example, the acrylic board which consists of polymethyl methacrylate etc., a polycarbonate board, etc. are mentioned.

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

In this embodiment, the cover material 6 has a level difference on the surface of the adhesive layer 11 side, and specifically, has a level difference formed by the presence or absence of the printed layer 7. The printing layer 7 is generally formed in a frame shape on the side of the adhesive layer 11 in the cover material 6.

The material constituting the printing layer 7 is not particularly limited, and known materials for printing can be used. The thickness of the printed layer 7, that is, the step height is preferably 3~45μm, 5~35μm is more preferred, 7~25μm is especially preferred, and 7~15μm is further Better.

In addition, the thickness of the printed layer 7 (the height of the step) is preferably 3-30% of the thickness of the adhesive layer 11, 3.2-20% is particularly preferred, and 3.5-15% is further preferred. As a result, the adhesive layer 11 easily follows the step formed by the printed layer 7, and it is possible to suppress the occurrence of floating or bubbles in the vicinity of the step.

Hereinafter, an example of a method of manufacturing the above-mentioned touch panel 2 will be described.

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

Then, the peeling film remaining on the adhesive layer 4b is peeled to expose the adhesive layer 4b and the surface of the second film sensor 5b on the side opposite to the side where the adhesive layer 11 is laminated (the first 2) The exposed surface of the base film 51 of the film sensor 5b) is bonded to each other so that they are in contact with each other. In this way, a laminate in which the release sheet 12b, the adhesive layer 11, the second film sensor 5b, the adhesive layer 4b, and the first film sensor 5a are laminated in this order is obtained.

Next, the adhesive layer 4a provided on the release sheet is bonded to the surface on the side of the first film sensor 5a of the laminate (the exposed surface of the base film 51 of the first film sensor 5a). Next, the other release sheet 12b is peeled from the laminate, and the cover material 6 is bonded to the exposed adhesive layer 11 so that the printed layer 7 side of the cover material 6 is in contact with the adhesive layer 11. In this way, the covering material 6, the adhesive layer 11, the second film sensor 5b, the adhesive layer 4b, and the first film sensor are obtained. The measuring device 5a, the adhesive layer 4a, and the release sheet are laminated in this order.

Finally, the release sheet is peeled from the above-mentioned structure, and the structure is attached to the display module 3 so that the exposed adhesive layer 4a is in contact with the display module 3. In this way, the touch panel 2 shown in Fig. 2 can be manufactured.

In the above process, when the adhesive layer 11 and the cover material 6 are bonded together, since the adhesive layer 11 has excellent step-following properties, it is difficult to generate voids between the step formed by the printed layer 7 and the adhesive layer 11 , The adhesive layer 11 can fill the step. In addition, when the touch panel 2 is placed under high-temperature and high-humidity conditions, it is also possible to prevent bubbles, warping, peeling, etc. near the step.

In addition, when the covering material 6 is a plastic plate, even if air leakage occurs from the plastic plate under high temperature and high humidity conditions, the adhesive layer 11 has excellent anti-foaming properties, so it is possible to suppress the generation of bubbles, warping, and peeling. Wait for expansion.

The embodiments described above are described in order to facilitate the understanding of the present invention, and are not described in order to limit the present invention. Therefore, each element disclosed in the above-mentioned embodiment includes all design changes or equivalent substances belonging to the technical scope of the present invention.

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

[Examples]

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

[Example 1]

1. Preparation of (meth)acrylate copolymer

Make 62.5 parts by mass of 2-ethylhexyl acrylate and 22.5 parts of methyl methacrylate Part by mass and 15 parts by mass of 2-hydroxyethyl acrylate were copolymerized to prepare a (meth)acrylate polymer (A). As a result of measuring the molecular weight of the (meth)acrylate polymer (A) by the method described later, the weight average molecular weight (Mw) was 500,000.

2. Preparation of adhesive composition

100 parts by mass of the (meth)acrylate polymer (A) obtained in the above process (1) (solid content conversion value; the same below), and trimethylolpropane modified toluene as a crosslinking agent (B) 0.23 parts by mass of isocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "CORONATE L"), dibutyltin dilaurate (manufactured by Toyokemu Co., Ltd., product name "BXX3778) as a crosslinking accelerator (C) -10") 0.005 parts by mass, 0.25 parts by mass of 3-glycidyl ether propyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") as the silane coupling agent (D) , 2.5 parts by mass of acetone as a reaction inhibitor, fully stirred, and diluted with methyl ethyl ketone, thereby obtaining a coating solution of an adhesive composition with a solid content concentration of 36% by mass.

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

[(Meth)acrylate polymer (A)]

2EHA: 2-ethylhexyl acrylate

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylate

3. Adhesive sheet manufacturing

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

Next, the above-obtained heavy release release sheet with a coating layer and the above-obtained light release release sheet with a coating layer are bonded together so that the two coating layers are in contact with each other, and then After curing for 7 days under the conditions of ℃ and 50% RH, an adhesive sheet composed of a heavy peeling peeling sheet/adhesive layer (thickness: 50 μm)/light peeling peeling sheet was produced. In addition, the thickness of the adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring device (manufactured by TECLOCK Company Inc., product name "PG-02").

[Examples 2~6, Comparative Examples 1~2]

The adhesive sheet was manufactured in the same manner as in Example 1, except that the blending amounts of the crosslinking agent (B), the crosslinking accelerator (C), and the silane coupling agent (D) were changed as shown in Table 1.

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

<Measurement conditions>

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

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

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

‧Measuring solvent: Tetrahydrofuran

‧Measuring temperature: 40℃

[Test Example 1] (Measurement of Adhesion)

The light-peelable release sheet was peeled off from the adhesive sheets obtained in the examples and comparative examples, and the exposed adhesive layer was attached to a polyethylene terephthalate film (Toyobo Co., Ltd.) with an easy-adhesive layer. Made, PET A4300, thickness: 100μm) easy-to-bond layer. This laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample. The heavy peelable release sheet was peeled from the sample, and the exposed adhesive layer was attached to a polyethylene terephthalate film (Oike Industry) with a transparent conductive film made of tin-doped indium oxide (ITO) on one side. Co., Ltd., ITO thin film, thickness: 125 μm) transparent conductive film.

Then, after leaving for 24 hours under the conditions of normal pressure, 23°C, and 50% RH, a tensile tester (manufactured by Orientec Company Inc., Tensilon) was used, based on JIS Z0237:2009, at a peeling speed of 300 mm/min. , Measure the adhesive force (N/25mm) under the condition of peeling angle of 180°. The results are shown in Table 1.

[Test Example 2] (Measurement of Gel Ratio)

Cut the adhesive sheets obtained in the Examples and Comparative Examples into 80mm×80mm The size of the adhesive layer is surrounded by polyester mesh (mesh size 200), and its mass is weighed with a precision balance. By subtracting the individual mass of the above mesh, only the adhesion is calculated The quality of the agent. Let the mass at this time be M1.

Next, the adhesive surrounded by the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. Then, the adhesive was taken out and dried in the air for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, and then dried in an oven at 80°C for 12 hours. After drying, use a precision balance to weigh the mass, and subtract the mass of the above-mentioned mesh alone to calculate only the mass of the adhesive. Let the mass at this time be M2. Use (M2/M1)×100 to express the gel rate (%). The results are shown in Table 1.

[Test Example 3] (Evaluation of the followability of the step difference)

(a) Preparation of evaluation samples

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

The light-peelable release sheet was peeled off from the adhesive sheets obtained in the examples and comparative examples, and the exposed adhesive layer was attached to a polyethylene terephthalate film (Toyobo Co., Ltd.) with an easy-adhesive layer. Made, PET A4300, thickness: 100μm) easy to bond layer. Next, peel off the heavy-peelable release sheet to expose the adhesive layer. And, using a laminator (manufactured by Fujipura Company Inc., product name "LPD3214"), the above-mentioned laminate was laminated on each glass plate with stepped difference in such a way that the adhesive layer covers the entire printed surface of the frame shape, and the ratio was used as an evaluation Use samples.

(b) Evaluation of evaluation samples

After autoclave treatment of the obtained sample for evaluation under conditions of 50°C and 0.5 MPa for 30 minutes, it was stored under humid heat conditions of 85°C and 85% RH for 72 hours. Then, the adhesive layer (especially, the vicinity of the step caused by the printed layer) was confirmed visually, and the step followability was evaluated based on the following criteria. The results are shown in Table 1.

⊚: There are no bubbles, lifting, and peeling at all.

○: Only bubbles with a diameter of 0.1 mm or less are generated.

△: Bubbles with a diameter exceeding 0.1 mm are generated, and the diameter of the largest bubble is 0.2 mm or less.

×: A bubble with a diameter of more than 0.2 mm is generated, lifted, or peeled.

[Test Example 4] (Evaluation of anti-foaming property)

The adhesive layer of the adhesive sheet obtained in the Examples and Comparative Examples was used with a polyethylene terephthalate film (Oike Industry Co.) provided with a transparent conductive film composed of tin-doped indium oxide (ITO) on one side. , Ltd., ITO film, thickness: 125μm) transparent conductive film, and polycarbonate (PC) board (Mitsubishi Gas Chemical Co., Ltd., IUPILON SHEET MR58, thickness: 1mm) or made of polymethacrylic acid Acrylic sheet composed of methyl ester (PMMA) (manufactured by Mitsubishi Gas Chemical Co., Ltd., IUPILON SHEET MR200, thickness: 1mm) To clamp and obtain a laminate.

After autoclave treatment of the obtained laminate under the conditions of 50° C. and 0.5 MPa for 30 minutes, it was left under normal pressure, 23° C., and 50% RH for 15 hours. Next, store for 72 hours under durable conditions of 85°C and 85% RH. Thereafter, the presence or absence of bubbles, lifting, or peeling in the adhesive layer was confirmed visually, and the foaming resistance was evaluated based on the following criteria. The results are shown in Table 1.

⊚: There are no bubbles, lifting, and peeling at all.

○: Only bubbles with a diameter of 0.1 mm or less are generated.

×: Bubbles with a diameter of more than 0.1 mm, lifting, or peeling are generated.

It can be seen from Table 1 that the adhesive sheets obtained in the examples have excellent step-following properties and anti-foaming properties.

[Industrial availability]

The adhesive sheet of the present invention can be suitable for use in, for example, a display module in a touch panel and a cover material with a step difference, especially for bonding with a plastic board.

1‧‧‧Adhesive sheet

11‧‧‧Adhesive layer

12a、12b‧‧‧Release sheet

Claims (8)

An adhesive sheet, characterized by comprising: two peeling sheets; and an adhesive layer, which is sandwiched by the peeling sheet so as to contact the peeling surfaces of the two peeling sheets, and the adhesive layer is composed of an adhesive. The aforementioned adhesive is formed by cross-linking an adhesive composition, and the aforementioned adhesive composition contains: (meth)acrylate polymer (A), with a weight average molecular weight of 200,000 to 900,000, as the composition The monomer unit of the polymer contains more than 10% by mass and 30% by mass or less of monomers having hydroxyl groups; crosslinking agent (B); and crosslinking accelerator (C), and is relative to the aforementioned (meth)acrylic acid 100 parts by mass of the ester polymer (A) is 0.005 to 0.03 parts by mass, contains the aforementioned cross-linking accelerator (C), the gel fraction of the aforementioned adhesive is 40-90%, and the ratio of the aforementioned adhesive layer to the transparent conductive film The adhesive force is 10N/25mm or more. The adhesive sheet according to the first item of the scope of patent application, wherein the crosslinking accelerator (C) is an organotin compound. The pressure-sensitive adhesive sheet described in claim 1, wherein the (meth)acrylate polymer (A) does not contain a monomer having a carboxyl group as a monomer unit constituting the polymer. The pressure-sensitive adhesive sheet described in claim 1, wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent. The pressure-sensitive adhesive sheet described in claim 1, wherein the (meth)acrylate polymer (A), as a monomer unit constituting the polymer, contains a homopolymer with a glass transition temperature of Hard monomer above 70°C. The pressure-sensitive adhesive sheet described in claim 1, wherein the (meth)acrylate polymer (A) contains 2-ethylhexyl (meth)acrylate as a monomer unit constituting the polymer ester. The adhesive sheet according to the first item of the patent application, wherein the adhesive composition further contains a silane coupling agent (D). The adhesive sheet according to any one of items 1 to 7 in the scope of the patent application, wherein, after peeling off the two release sheets, the adhesive layer is used to be arranged between two patterned transparent conductive films , Or between the patterned transparent conductive film and the cover material or the display module.

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