KR102518563B1 - Adhesive composition, adhesive, adhesive sheet, and display - Google Patents

Abstract

(Problem) To provide an adhesive composition, an adhesive, an adhesive sheet, and a display body having excellent reworkability while maintaining performance as an adhesive for display bodies.
(Solution) As an adhesive composition for forming an adhesive layer for bonding one display body constituent member and another display body constituent member, (meth)acrylic acid ester copolymer (A), a crosslinking agent (B), and a compound (C ), and the (meth)acrylic acid ester copolymer (A) contains a reactive group-containing monomer having a reactive group that reacts with the crosslinking agent (B) in the molecule as a monomer unit constituting the polymer, and has a weight average molecular weight It is 400,000 or more and 1,300,000 or less, and the compound (C) has an alkylene oxide moiety and has no or one reactive group that reacts with the crosslinking agent (B).

Description

Adhesive composition, adhesive, adhesive sheet and display

The present invention relates to an adhesive composition, an adhesive and an adhesive sheet for bonding display body constituent members, and a display body obtained by using the adhesive layer of the adhesive sheet.

Recently, various mobile electronic devices such as mobile phones, smart phones, and tablet terminals are display bodies using display modules having liquid crystal elements, light emitting diodes (LED elements), organic electroluminescence (organic EL) elements, and the like. ) is provided.

In such a display, a protection panel is usually formed on the surface side of the display module. A gap is formed 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 there is such a gap, that is, the air layer, there is a problem in that the image quality of the display deteriorates due to the large reflection loss of light due to the difference in refractive index between the protective panel and the air layer and the difference in refractive index between the air layer and the display module.

Therefore, it has been proposed to improve the image quality of a display by filling the gap between the protection panel and the display module with an adhesive layer. However, in some cases, a frame-shaped printed layer exists as a step on the display module side of the protection panel. If the pressure-sensitive adhesive layer does not follow the level difference, the pressure-sensitive adhesive layer floats in the vicinity of the level difference, thereby causing reflection loss of light. Therefore, level conformability is required for the pressure-sensitive adhesive layer.

In order to solve the above problems, Patent Document 1 is a pressure-sensitive adhesive layer filling 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, Also, a pressure-sensitive adhesive layer having a gel fraction of 40% or more is disclosed.

Patent Document 1: Japanese Unexamined Patent Publication No. 2010-97070

In Patent Literature 1, it is intended to improve level conformability by lowering the storage elastic modulus at room temperature in the pressure-sensitive adhesive layer. However, if the storage modulus at room temperature is lowered as described above, the storage modulus at high temperature is lowered than necessary, causing problems under durability conditions. For example, when high temperature and high humidity conditions are applied, problems such as generation of air bubbles in the vicinity of the level difference occur.

Moreover, bonding of a protection panel and a display body module is often performed using the adhesive sheet which has the above adhesive layer. In this bonding, a shift may occur in the bonding position. In particular, bonding hard materials (hard bodies) such as protection panels and display modules to each other using an adhesive sheet is more difficult than bonding films to each other or films and hard bodies, and the yield at the time of bonding tends to decrease.

Since the display module is expensive, the production cost can be reduced if only the display module side can be reused when the problem of the above pasting shift occurs. Therefore, the reworkability which can peel two hard bodies bonded by the said adhesive sheet so that at least an indicator module can be reused is expected to the adhesive sheet as described above.

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide an adhesive composition, an adhesive, an adhesive sheet, and an indicator having excellent reworkability while maintaining performance as an adhesive for display bodies.

In order to achieve the above object, first, the present invention is an adhesive composition for forming an adhesive layer for bonding one display body constituent member and another display body constituent member, (meth)acrylic acid ester copolymer (A) and a crosslinking agent (B) and a compound (C), wherein the (meth)acrylic acid ester copolymer (A) contains a reactive group having in its molecule a reactive group that reacts with the crosslinking agent (B) as a monomer unit constituting the polymer It contains a monomer, has a weight average molecular weight of 400,000 or more and 1,300,000 or less, the compound (C) has an alkylene oxide moiety, and does not have or has one reactive group that reacts with the crosslinking agent (B) Provided is an adhesive composition characterized by (Invention 1).

The pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the above invention (Invention 1) exhibits good flexibility due to the (meth)acrylic acid ester copolymer (A) having a weight average molecular weight in a relatively low range, and is excellent in level conformability. Moreover, the said adhesive becomes what was excellent in reworkability, maintaining the performance as an adhesive for display bodies, by containing compound (C).

In the above invention (Invention 1), the compound (C) has a linear structure and has an alkyl group at both ends or at one end (Invention 2), or the compound (C) has a linear structure, It is preferable to have a (meth)acryloyl group at both ends or at one end (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable that the compound (C) is contained in an amount of 0.2 parts by mass or more and less than 10 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A) ( invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the (meth)acrylic acid ester copolymer (A) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the one display body constituent member and the other display body constituent member are rigid (Invention 6).

In the above inventions (Inventions 1 to 6), it is preferable that the one display body constituent member has a step at least on the surface to be bonded (Invention 7).

Second, the present invention provides a pressure-sensitive adhesive obtained by crosslinking the above-mentioned adhesive composition (Invention 1 to 7) (Invention 8).

Thirdly, the present invention provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding one display body constituent member to another display body constituent member, wherein the pressure-sensitive adhesive layer is composed of the above-mentioned pressure-sensitive adhesive (Invention 8). (Invention 9).

In the above invention (invention 9), it is preferable that the thickness of the pressure-sensitive adhesive layer is 20 μm or more and 500 μm or less (invention 10).

In the above inventions (Inventions 9 and 10), it is preferable that the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is held by the release sheets so as to contact the release surfaces of the two release sheets ( Invention 11).

Fourth, the present invention is a display body provided with one display body constituent member, another display body constituent member, and an adhesive layer for bonding the one display body constituent member and the other display body constituent member together, wherein the adhesive layer A display body characterized by being the pressure-sensitive adhesive layer of the above-mentioned pressure-sensitive adhesive sheet (Invention 9 to 11) is provided (Invention 12).

In addition, the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding one display body constituent member and another display body constituent member, wherein the pressure-sensitive adhesive layer comprises a (meth)acrylic acid ester copolymer (A) and a crosslinking agent (B) and a pressure-sensitive adhesive obtained by crosslinking an adhesive composition containing the compound (C), wherein the (meth)acrylic acid ester copolymer (A) reacts with the crosslinking agent (B) as a monomer unit constituting the polymer A compound containing a reactive group-containing monomer having a group in its molecule, the compound (C) having an alkylene oxide moiety, and having no or one reactive group that reacts with the crosslinking agent (B), and the thickness of the pressure-sensitive adhesive layer It provides an adhesive sheet characterized in that it is 20 μm or more and 500 μm or less.

The adhesive composition, the adhesive, the adhesive sheet, and the display body according to the present invention are excellent in reworkability while maintaining performance as an adhesive for display bodies.

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.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described.

[Adhesive composition]

The adhesive composition (hereinafter sometimes referred to as "adhesive composition (P)") according to the present embodiment is an adhesive composition for forming a pressure-sensitive adhesive layer to which one display body constituent member is bonded to another display body constituent member. The display body and display body constituent members will be described later.

The adhesive composition (P) contains a (meth)acrylic acid ester copolymer (A), a crosslinking agent (B), and a compound (C), and preferably further contains a silane coupling agent (D). In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. Other similar terms are also the same.

The (meth)acrylic acid ester copolymer (A) contains a reactive group-containing monomer having a reactive group that reacts with the crosslinking agent (B) as a monomer unit constituting the polymer, and has a weight average molecular weight of 400,000 or more and 1,300,000 or less. am. In addition, the compound (C) is a compound having an alkylene oxide moiety and having no or one reactive group that reacts with the crosslinking agent (B).

When the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is in a relatively low range as described above, the resulting pressure-sensitive adhesive exhibits good flexibility and is excellent in level conformability. In addition, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

In addition, when the adhesive composition (P) contains the compound (C), the adhesive obtained by crosslinking the adhesive composition (P) is excellent in reworkability while maintaining performance as an adhesive for display bodies. In particular, when the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is relatively low as described above, the resulting adhesive tends to be soft and has poor reworkability, but in the present embodiment, the compound (C) is used. By doing so, excellent reworkability is obtained. That is, in the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition (P), the compound (C) acts as an excellent rework agent. Therefore, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive can be easily peeled off from the display body constituent member even after once attached to the display body constituent member, and the display body constituent member can be reused.

It is thought that the excellent reworkability described above is mainly exhibited by the alkylene oxide moiety possessed by the compound (C). Moreover, compatibility with a (meth)acrylic acid ester copolymer (A) is maintained because a compound (C) does not have a reactive group which reacts with a crosslinking agent (B) or has one. Furthermore, the reaction between the (meth)acrylic acid ester copolymer (A) and the crosslinking agent (B) is not inhibited by the compound (C), a good crosslinked structure is formed, and the resulting adhesive exhibits desired cohesive force. Therefore, performance as a pressure-sensitive adhesive for display bodies is maintained, and in particular, step followability under high temperature and high humidity conditions is well exhibited.

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

The (meth)acrylic acid ester copolymer (A) contains a reactive group-containing monomer having in its molecule a reactive group that reacts with the crosslinking agent (B) as a monomer unit constituting the polymer. The reactive group derived from this reactive group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), and a pressure-sensitive adhesive having desired cohesive force is obtained.

Preferable examples of the reactive group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). . Among these, hydroxyl group-containing monomers that are excellent in reactivity with the crosslinking agent (B) and have little adverse effect on adherends are particularly preferred. Moreover, even if the weight average molecular weight of a (meth)acrylic acid ester copolymer (A) is comparatively low, a carboxyl group-containing monomer is preferable from a viewpoint in which desired cohesion force is exhibited.

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

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Especially, acrylic acid is preferable from the viewpoint of the reactivity of the carboxyl group in the obtained (meth)acrylic acid ester copolymer (A) with the crosslinking agent (B) and copolymerizability with other monomers. These may be used independently and may be used in combination of 2 or more type.

Examples of the amino group-containing monomer include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester copolymer (A) preferably contains 3% by mass or more of a hydroxyl group-containing monomer as a lower limit as a monomer unit constituting the polymer, particularly preferably 10% by mass or more, and further preferably 15% by mass or more. It is preferable to contain more than mass %. Further, the (meth)acrylic acid ester copolymer (A) preferably contains, as a monomer unit constituting the polymer, 35% by mass or less of a hydroxyl group-containing monomer as an upper limit, particularly preferably 30% by mass or less, and furthermore It is preferable to contain 25 mass % or less. When the (meth)acrylic acid ester copolymer (A) contains a hydroxyl group-containing monomer in the above amount as a monomer unit, a good crosslinked structure is formed in the resulting adhesive, desired cohesive force is obtained, and a predetermined amount of hydroxyl groups in the adhesive will remain The hydroxyl group is a hydrophilic group, and if such a hydrophilic group is present in the adhesive in a predetermined amount, even when the adhesive is placed under high temperature and high humidity conditions, compatibility with moisture penetrating into the adhesive under the high temperature and high humidity conditions is good, and as a result, when returned to room temperature and normal humidity, The whitening of the adhesive at the time of application is suppressed (it is excellent in heat-and-moisture whitening resistance).

When the (meth)acrylic acid ester copolymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, the (meth)acrylic acid ester copolymer (A) uses the carboxyl group-containing monomer as a lower limit of 5% by mass or more It is preferable to contain, it is preferable to contain especially 7 mass % or more, and also it is preferable to contain 10 mass % or more. Further, the (meth)acrylic acid ester copolymer (A) preferably contains, as a monomer unit constituting the polymer, 30% by mass or less of a carboxyl group-containing monomer as an upper limit, particularly preferably 20% by mass or less, and furthermore It is preferable to contain 15 mass % or less. When the (meth)acrylic acid ester copolymer (A) contains a carboxyl group-containing monomer in the above amount as a monomer unit, a good crosslinked structure is formed in the resulting adhesive, and desired cohesive force is obtained.

Moreover, it is also preferable that the (meth)acrylic acid ester copolymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, by not containing a carboxyl group-containing monomer, problems arise due to acid on the target to which the adhesive is attached, for example, a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film exists. Even in this case, such problems (corrosion, change in resistance value, etc.) caused by acid can be suppressed. However, it is permissible to contain a carboxyl group-containing monomer in a predetermined amount to the extent that such a problem does not occur. Specifically, in the (meth)acrylic acid ester copolymer (A), the amount of the carboxyl group-containing monomer as a monomer unit is less than 5% by mass, preferably 2% by mass or less, particularly preferably 0.1% by mass or less. allowed

The (meth)acrylic acid ester copolymer (A) can express desirable adhesiveness by containing a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in an alkyl group in the monomer unit constituting the polymer. Examples of (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. n-pentyl acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, (meth)acrylic acid Myristyl, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. are mentioned. Among them, (meth)acrylic acid esters having 1 to 8 carbon atoms in the alkyl group are preferable, and n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate is particularly preferable from the viewpoint of further improving the adhesiveness. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester copolymer (A) preferably contains 40% by mass or more 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 50% by mass or more. It is preferable to contain, and also it is preferable to contain 60 mass % or more. When 40 mass % or more of (meth)acrylic-acid alkylesters are contained, favorable adhesiveness can be provided to a (meth)acrylic-acid ester copolymer (A). In addition, it is preferable to contain 90% by mass or less of (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, particularly preferably 80% by mass or less, and more preferably 70% by mass or less. When the content of the (meth)acrylic acid alkyl ester is 90% by mass or less, other monomer components can be introduced in a desired amount into the (meth)acrylic acid ester copolymer (A).

It is also preferable that the (meth)acrylic acid ester copolymer (A) contains a monomer having an alicyclic structure in the molecule (an alicyclic structure-containing monomer) as a monomer unit constituting the copolymer. Since an alicyclic structure-containing monomer is bulky, the space|interval between polymers widens by making it exist in a polymer. Then, the compound (C) becomes easy to move within the polymer, and thereby easily appears on the surface of the pressure-sensitive adhesive. As a result, the action of the compound (C) as a rework agent is effectively exerted, and the reworkability of the resulting adhesive is further improved.

The carbocycle of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may partially have an unsaturated bond. In addition, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as bicyclic or tricyclic. From the viewpoint of increasing the distance between the obtained (meth)acrylic acid ester copolymers (A) and effectively exhibiting the action of the compound (C) as a rework agent, the alicyclic structure is a polycyclic alicyclic structure (polycyclic structure). it is desirable Further, in consideration of compatibility between the (meth)acrylic acid ester copolymer (A) and other components, it is particularly preferred that the polycyclic structure is bicyclic or tetracyclic. In addition, similar to the above, from the viewpoint of effectively exhibiting the action of the compound (C) as a rework agent, the number of carbon atoms in the alicyclic structure (refers to all carbon atoms in the portion forming the ring, when a plurality of rings exist independently, It refers to the total number of carbon atoms) is usually preferably 5 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but is preferably 15 or less, particularly preferably 10 or less, from the viewpoint of compatibility as described above.

Examples of the alicyclic structure include cyclohexyl skeleton, dicyclopentadiene skeleton, adamantane skeleton, isobornyl skeleton, cycloalkane skeleton (cycloheptane skeleton, cyclooctane skeleton, cyclononane skeleton, cyclodecane skeleton, cycloundecane skeleton, cyclododecane skeleton, etc.), cycloalkene skeleton (cycloheptene skeleton, cyclooctene skeleton, etc.), norbornene skeleton, norbornadiene skeleton, cubane skeleton, basketane skeleton, housein skeleton, spiro Examples include those containing skeletons and the like, and among them, dicyclopentadiene skeletons (carbon atoms in an alicyclic structure: 10), adamantane skeletons (carbon atoms in an alicyclic structure: 10), or isobornyl, which exhibit superior durability. It is preferable to include a skeleton (carbon number of the alicyclic structure: 7), and particularly preferably to include an isobornyl skeleton.

As the alicyclic structure-containing monomer, a (meth)acrylic acid ester monomer having the above skeleton is preferable, and specifically, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamane (meth)acrylate. ethyl, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc., among which dicyclopentanyl (meth)acrylate exhibits superior durability , Adamantyl (meth)acrylate or isobornyl (meth)acrylate is preferred, and isobornyl (meth)acrylate is particularly preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the (meth)acrylic acid ester copolymer (A) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the (meth)acrylic acid ester copolymer (A) contains 5 masses of the alicyclic structure-containing monomer It is preferable to contain % or more, it is preferable to contain 8 mass % or more especially, and also it is preferable to contain 11 mass % or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 40% by mass or less of an alicyclic structure-containing monomer as a monomer unit constituting the polymer, particularly preferably 30% by mass or less, and furthermore It is preferable to contain 25 mass % or less. When the content of the alicyclic structure-containing monomer is within the above range, the action of the compound (C) as a rework agent is effectively exhibited, and the resulting adhesive has better reworkability.

It is also preferable that the (meth)acrylic acid ester copolymer (A) contains a monomer having a nitrogen atom in the molecule (nitrogen atom-containing monomer) as a monomer unit constituting the copolymer. When the nitrogen atom-containing monomer is present in the polymer as a constituent unit, the reaction between the acrylic acid ester copolymer (A) and the crosslinking agent (B) can be promoted, polarity can be imparted to the pressure-sensitive adhesive, and the cohesive force of the pressure-sensitive adhesive itself can be increased.

Examples of the nitrogen atom-containing monomer include a monomer having an amino group, a monomer having an amide group, a monomer having a nitrogen-containing heterocycle, and the like, and among these, a monomer having a nitrogen-containing heterocycle is preferable.

Examples of the monomer having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, and N-(meth)acryloylmorpholine. ) Acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl(meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2 -Vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. are exemplified, among which N-(meth)acryloylmorpholine, which exhibits more excellent adhesive strength, is preferred. , N-acryloylmorpholine is particularly preferred.

In addition, examples of nitrogen atom-containing monomers other than the monomers having a nitrogen-containing heterocycle described above include (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylol(meth)acrylamide. -tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-ethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-isopropyl ( Meth)acrylamide, N-phenyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, N-vinylcaprolactam, monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, (meth) Monomethylaminopropyl acrylate, monoethylaminopropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and the like can also be used.

The above nitrogen atom-containing monomers may be used individually by 1 type, or may be used in combination of 2 or more type.

When the (meth)acrylic acid ester copolymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the (meth)acrylic acid ester copolymer (A) contains 1% by mass or more of the nitrogen atom-containing monomer It is preferable to do it, and it is preferable to contain 2 mass % or more especially, and also it is preferable to contain 4 mass % or more. In addition, the (meth)acrylic acid ester copolymer (A) preferably contains 40% by mass or less of a nitrogen atom-containing monomer as a monomer unit constituting the polymer, particularly preferably 25% by mass or less, and furthermore It is preferable to contain 14 mass % or less. When the content of the nitrogen atom-containing monomer is within the above range, the cohesive force of the pressure-sensitive adhesive obtained is effectively improved.

The (meth)acrylic acid ester copolymer (A) may contain other monomers as a monomer unit constituting the polymer as desired. As another monomer, the monomer which does not contain a reactive functional group is preferable. Examples of such other monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used independently and may be used in combination of 2 or more type.

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

As described above, the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is 400,000 or more, preferably 450,000 or more, and particularly preferably 500,000 or more. When the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is greater than or equal to the above, the reworkability of the pressure-sensitive adhesive obtained and the step conformability under high-temperature, high-humidity conditions can be ensured satisfactorily. Moreover, the said weight average molecular weight is 1.3 million or less as mentioned above, It is preferable that it is 1 million or less, and it is especially preferable that it is 900,000 or less. When the weight average molecular weight of the (meth)acrylic acid ester copolymer (A) is below the above, the resulting pressure-sensitive adhesive exhibits good flexibility and has excellent conformability to initial level differences.

In addition, in the adhesive composition (P), the (meth)acrylic acid ester copolymer (A) may be used alone or in combination of two or more.

(2) crosslinking agent (B)

When the adhesive composition (P) containing the crosslinking agent (B) is heated, the crosslinking agent (B) crosslinks the (meth)acrylic acid ester copolymer (A) to form a three-dimensional network structure. Thereby, the cohesion force of the adhesive obtained improves, and it becomes what is excellent in level difference followability, for example under high temperature, high humidity conditions.

The crosslinking agent (B) may be one that reacts with the reactive group of the (meth)acrylic acid ester copolymer (A), and examples thereof include an isocyanate crosslinking agent, an epoxy crosslinking agent, an amine crosslinking agent, a melamine crosslinking agent, an aziridine crosslinking agent, A hydrazine type crosslinking agent, an aldehyde type crosslinking agent, an oxazoline type crosslinking agent, a metal alkoxide type crosslinking agent, a metal chelate type crosslinking agent, a metal salt type crosslinking agent, an ammonium salt type crosslinking agent, etc. are mentioned. Among the above, when the reactive group of the (meth)acrylic acid ester copolymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with hydroxyl groups, and the reactivity of the (meth)acrylic acid ester copolymer (A) When the group is a carboxyl group, it is preferable to use an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group. In addition, a 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. 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 diphenylmethane. Alicyclic polyisocyanates such as diisocyanates, and their biurets, isocyanurates, and further, reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. An adduct body etc. are mentioned. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylol-propane-modified xylylene diisocyanate, are preferable.

As the epoxy-based crosslinking agent, for example, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylene diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. Especially, from a reactive viewpoint with a carboxyl group, 1, 3-bis (N, N'-diglycidylaminomethyl) cyclohexane is preferable.

The content of the crosslinking agent (B) in the adhesive composition (P) is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). It is preferable that it is 0.1 mass part or more. Moreover, it is preferable that the said content is 10 mass parts or less, It is especially preferable that it is 5 mass parts or less, Furthermore, it is preferable that it is 0.4 mass parts or less. When the content of the crosslinking agent (B) is within the above range, the resulting pressure-sensitive adhesive exhibits good cohesive force, and conformability to level differences under high temperature and high humidity conditions becomes more excellent.

(3) Compound (C)

The compound (C) is a compound having an alkylene oxide moiety and having no or one reactive group that reacts with the crosslinking agent (B). As described above, in the adhesive obtained from the adhesive composition (P), the compound (C) acts as an excellent rework agent. Specifically, when the compound (C) is a compound having an alkylene oxide moiety, the resulting adhesive exhibits excellent reworkability. Moreover, compatibility with a (meth)acrylic acid ester copolymer (A) is maintained because a compound (C) does not have a reactive group which reacts with a crosslinking agent (B) or has one. In addition, the reaction between the (meth)acrylic acid ester copolymer (A) and the crosslinking agent (B) is not inhibited by the compound (C), a good crosslinked structure is formed, and the resulting adhesive exhibits desired cohesive force. Furthermore, since the compound having the above structure is different from the surfactant, bubbles are less likely to be generated when the adhesive composition (P) is prepared, and even if they are generated, they are easily eliminated. Therefore, a bubble-free pressure-sensitive adhesive layer can be easily formed.

It is preferable that compound (C) has a linear structure. By having a linear structure, the compound (C) becomes easy to move within (crosslinked structure) of the (meth)acrylic acid ester copolymer (A) in the pressure-sensitive adhesive layer formation process such as a drying process. As a result, the compound (C) is easily expressed on the surface of the pressure-sensitive adhesive, the action as a rework agent is exhibited effectively, and the reworkability of the resulting pressure-sensitive adhesive is further improved. In addition, in this specification, "straight chain" of "linear structure" means "straight chain" substantially. That is, the linear structure may have a branched chain, as long as the action and effect of the compound (C) as a rework agent are exhibited satisfactorily.

The compound (C) is preferably not a silicone compound, that is, a compound having no siloxane bond in the molecule. When the adhesive composition (P) contains a silicone compound, the interaction between the pressure-sensitive adhesive layer of the pressure-sensitive adhesive obtained and the release sheet in contact with the pressure-sensitive adhesive layer may become strong, and the release sheet may become heavy. In addition, a silicone compound cannot exhibit a sufficient action as a rework agent.

As the alkylene oxide of the alkylene oxide moiety, an alkylene oxide having 2 to 4 carbon atoms is preferable, and examples thereof include preferably ethylene oxide, propylene oxide, butylene oxide, etc. Among them, ethylene oxide is desirable. Moreover, as a reactive group which reacts with the said crosslinking agent (B), a hydroxyl group, a carboxyl group, and an amino group are mentioned.

It is preferable that the compound (C) has a linear structure and has a non-reactive group that does not react with the crosslinking agent (B) at both ends or one end thereof. It is preferable that this non-reactive group is an alkyl group or a (meth)acryloyl group. That is, the compound (C) preferably has a linear structure and has an alkyl group at both ends or at one end, or preferably has a (meth)acryloyl group at both ends or at one end. Moreover, the compound (C) has a linear structure and may have an alkyl group at one terminal and a (meth)acryloyl group at the other terminal.

It is preferable that the carbon number of the said alkyl group is 1 or more. Moreover, it is preferable that carbon number of the said alkyl group is 10 or less, and it is especially preferable that it is 5 or less. As the alkyl group, specifically, a methyl group, an ethyl group, a propyl group, etc. are preferable, and a methyl group is particularly preferable from the viewpoint of the polarity of the compound.

The (meth)acryloyl group does not react with the crosslinking agent (B) and remains in the pressure-sensitive adhesive as it is. The compound (C) has a linear structure and has a (meth)acryloyl group at both ends or at one end, so that the compatibility with the (meth)acrylic acid ester copolymer (A) becomes better, and the adhesive obtained Adhesion and reworkability are stably obtained.

The compound (C) preferably has a glycol ether skeleton from the viewpoint of the reworkability exhibited, and among these, monoethylene glycol ether, diethylene glycol ether, triethylene glycol ether, tetraethylene glycol ether, polyethylene glycol ether, etc. It is preferable that it has a skeleton of.

Compound (C) is specifically, tetraethylene glycol alkyl ether, tetraethylene glycol dialkyl ether, polyethylene glycol alkyl ether, polyethylene glycol dialkyl ether, alkoxy polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acryl A rate etc. are mentioned preferably. Among the above, tetraethylene glycol dimethyl ether, polyethylene glycol methyl ether, methoxy polyethylene glycol (meth)acrylate, and polyethylene glycol di(meth)acrylate are particularly preferred from the viewpoint of the reworkability exhibited. In addition, compound (C) can be used individually by 1 type or in combination of 2 or more types.

The number average molecular weight of the compound (C) is preferably 100 or more, particularly preferably 200 or more, and more preferably 300 or more. In addition, the number average molecular weight is preferably 2000 or less, particularly preferably 1500 or less, and more preferably 1000 or less. When the number average molecular weight of the compound as the compound (C) is within the above range, the compound (C) becomes easy to move within (the crosslinked structure of) the (meth)acrylic acid ester copolymer (A), and thereby appears on the surface of the pressure-sensitive adhesive. It becomes easy to do, and the reworkability of the adhesive obtained becomes what is further excellent. In addition, the number average molecular weight in this specification is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

The content of the compound (C) in the adhesive composition (P) is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and 1.0 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester copolymer (A). Part or more is particularly preferable, and it is more preferable that it is 1.5 parts by mass or more. When the content of the compound (C) is equal to or greater than the above, the effect of the compound (C) as a rework agent is effectively exhibited, and the resulting pressure-sensitive adhesive has more excellent rework properties. The content of the compound (C) is preferably less than 10 parts by mass, particularly preferably 8 parts by mass or less, and more preferably 5 parts by mass or less. If the content of the compound (C) is below the above, the adhesive strength as the pressure-sensitive adhesive for display bodies becomes more excellent.

(4) Silane coupling agent (D)

It is preferable that the adhesive composition (P) further contains a silane coupling agent (D). Thereby, if the adherend has a glass member, the resulting adhesive has improved adhesion with the glass member. Moreover, even if the adherend is a plastic plate, the adhesiveness obtained with the plastic plate improves. As a result, the resulting pressure-sensitive adhesive becomes more excellent in conformability to level differences under high-temperature, high-humidity conditions.

The silane coupling agent (D) is preferably an organosilicon compound having at least one alkoxysilyl group in its molecule, having good compatibility with the (meth)acrylic acid ester copolymer (A) and having light transmittance.

Examples of such a silane coupling agent (D) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; and 3-glycidoxypropyltri Silicon compounds having an epoxy structure such as methoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3 -mercapto group-containing silicon compounds such as mercaptopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-amino Amino group-containing silicon compounds such as ethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these, methyltriethoxysilane, and ethyl and condensates of alkyl group-containing silicon compounds such as triethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the silane coupling agent (D) in the adhesive composition (P) is preferably 0.01 part by mass or more, particularly preferably 0.05 part by mass or more, based on 100 parts by mass of the (meth)acrylic acid ester copolymer (A). Furthermore, it is preferable that it is 0.1 mass part or more. Moreover, it is preferable that the said content is 1 mass part or less, It is especially preferable that it is 0.5 mass part or less, Furthermore, it is preferable that it is 0.3 mass part or less.

(5) Various additives

To the adhesive composition (P), various additives commonly used in acrylic adhesives such as ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index adjusters, etc. can be added as desired to the adhesive composition (P). there is. In addition, the polymerization solvent and the dilution solvent mentioned later shall not be included in the additives constituting the adhesive composition (P).

(6) Preparation of adhesive composition

The adhesive composition (P) is prepared by preparing a (meth)acrylic acid ester copolymer (A), mixing the obtained (meth)acrylic acid ester copolymer (A), a crosslinking agent (B), and a compound (C), as desired Therefore, it can manufacture by adding a silane coupling agent (D) and 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. Polymerization of the (meth)acrylic acid ester copolymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. As a polymerization solvent, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone etc. are mentioned, for example, You may use 2 or more types together.

As a polymerization initiator, an azo compound, an organic peroxide, etc. are mentioned, You may use 2 or more types together. Examples of the azo-based compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 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.

Examples of organic peroxides include benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydi Carbonate, t-butylperoxyneodecanoate, t-butylperoxypivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide, etc. are mentioned.

Moreover, in the said polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix|blending a chain transfer agent, such as 2-mercaptoethanol.

When the (meth)acrylic acid ester copolymer (A) is obtained, to the solution of the (meth)acrylic acid ester copolymer (A), a crosslinking agent (B), a compound (C), and, if desired, a silane coupling agent (D) and an additive and a diluting solvent are added and thoroughly mixed to obtain an adhesive composition (P) (coating solution) diluted with a solvent. Here, since the compound (C) used in the present embodiment is different from the surfactant, it is difficult to generate air bubbles when preparing the adhesive composition (P), and even if they are generated, they are easy to remove. Therefore, a bubble-free pressure-sensitive adhesive layer can be easily formed.

In addition, when using any one of the above components in a solid state, or when precipitation occurs when mixed with other components in an undiluted state, dissolve or dilute the component alone in a dilution solvent in advance, , You may mix with other components.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, 1- Alcohols such as methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, cellosolve solvents such as ethyl cellosolve etc. are used.

The concentration and viscosity of the coating solution prepared in this way are not particularly limited as long as they are within the coating range, and can be appropriately selected according to the situation. For example, it is diluted so that the density|concentration of adhesive composition (P) may become 10-60 mass %. In addition, when obtaining a coating solution, addition of a diluting solvent etc. is not a necessary condition, and if the adhesive composition (P) has the viscosity etc. which can be coated, it is not necessary to add a diluting solvent. In this case, the adhesive composition (P) becomes a coating solution in which the polymerization solvent of the (meth)acrylic acid ester copolymer (A) is used as a diluting solvent as it is.

〔adhesive〕

The pressure-sensitive adhesive according to the present embodiment is formed by crosslinking the pressure-sensitive adhesive composition (P). Crosslinking of the adhesive composition (P) can usually be performed by heat treatment. In addition, this heat treatment can also serve as a drying treatment when volatilizing a diluting solvent or the like from a coating film of the adhesive composition (P) applied to a desired object.

The heating temperature of the heat treatment is preferably 50 to 150°C, particularly preferably 70 to 120°C. Further, the heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23°C, 50% RH) as needed. When this curing period is required, the adhesive is formed after the curing period has elapsed, and when the curing period is unnecessary, after the heat treatment is completed.

By the heat treatment (and curing) described above, the (meth)acrylic acid ester copolymer (A) is sufficiently crosslinked via the crosslinking agent (B), and the compound (C) exists in the crosslinked structure and on the surface of the crosslinked structure. The pressure-sensitive adhesive obtained in this way maintains performance as an adhesive for display bodies, has good step followability under high temperature and high humidity conditions, and is excellent in reworkability.

As a lower limit, the gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more. If the lower limit of the gel fraction of the pressure-sensitive adhesive is equal to or greater than the above, the cohesive force of the pressure-sensitive adhesive increases, and conformability to level differences under high temperature and high humidity conditions becomes more excellent. The upper limit of the gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 90% or less, particularly preferably 85% or less, and more preferably 80% or less. When the upper limit of the gel fraction of the pressure-sensitive adhesive is the above or less, the pressure-sensitive adhesive does not harden too much, and the conformability to level difference in the initial stage becomes more excellent. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in the test examples to be described later.

[adhesive sheet]

The pressure-sensitive adhesive sheet according to the present embodiment has a pressure-sensitive adhesive layer for bonding one display body constituent member to another display body constituent member, and the pressure-sensitive adhesive layer is made of the above-mentioned pressure-sensitive adhesive.

Fig. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment.

As shown in FIG. 1 , the pressure-sensitive adhesive sheet 1 according to one embodiment includes two release sheets 12a and 12b, and the two release sheets 12a and 12b are peeled so as to come into contact with the release surfaces of the two release sheets 12a and 12b. It is comprised by the adhesive layer 11 clamped by the sheet|seat 12a, 12b. In addition, the release surface of a release sheet in this specification refers to the surface which has release property in a release sheet, and includes both the surface which has been subjected to the release treatment and the surface which exhibits release property even without the release treatment.

(1) adhesive layer

The pressure-sensitive adhesive layer 11 is composed of the above-mentioned pressure-sensitive adhesive, that is, a pressure-sensitive adhesive formed by crosslinking the pressure-sensitive adhesive composition (P).

The lower limit of the thickness of the pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheet 1 according to the present embodiment (value measured according to JIS K 7130) is preferably 20 μm or more, more preferably 25 μm or more, and particularly 30 μm or more. It is preferable that it is micrometer or more, and also it is preferable that it is 50 micrometer or more. If the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is 20 μm or more, it is easy to exhibit desired adhesive strength. In addition, when the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is 30 µm or more, sufficient conformability to the level difference can be ensured with respect to the normal level difference of the display member.

In addition, as an upper limit, the thickness of the pressure-sensitive adhesive layer 11 is preferably 500 μm or less, more preferably 400 μm or less, and particularly preferably 300 μm or less. When the upper limit of the thickness of the pressure-sensitive adhesive layer 11 is below the above, workability becomes good. In addition, the pressure-sensitive adhesive layer 11 may be formed as a single layer or may be formed by laminating a plurality of layers.

(2) release sheet

The release sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the time of use of the pressure-sensitive adhesive sheet 1, and are peeled off when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the PSA sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

Examples of the release sheets 12a and 12b include 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, and 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 A carbonate film, a polyimide film, a fluororesin film or the like is used. Moreover, these crosslinked films are also used. And these laminated|multilayer films may be sufficient.

It is preferable that peeling treatment is given to the peeling surface (particularly, the surface in contact with the pressure-sensitive adhesive layer 11) of the above-mentioned peeling sheet 12a, 12b. Examples of the release agent used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Among the release sheets 12a and 12b, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is a light release type release sheet having a small release force.

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

(3) physical properties

(3-1) Step tracking rate

In the PSA layer 11 of the PSA sheet 1 according to the present embodiment, the level conformance rate (%) represented by the following formula is preferably 20% or more as a lower limit, particularly preferably 25% or more, and further preferably 30% It is preferable to be more than In addition, the upper limit of the step conformance rate is not particularly limited, but is usually preferably 80% or less, and particularly preferably 70% or less.

Step follow-up rate (%) = {(height of the step where the filled state was maintained without bubbles, lifting, peeling, etc. after a predetermined durability test (μm))/(thickness of the pressure-sensitive adhesive layer)} × 100

In addition, the step follow-up ratio test method is as shown in the test example described later.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment is suitable for bonding a display body constituent member having a level difference to the surface to be bonded. When the level difference follow-up rate of the pressure-sensitive adhesive layer is within the above range, the pressure-sensitive adhesive layer follows the level difference of the display body constituent member well, and even after passing an endurance test, the occurrence of air bubbles, lifting, peeling, etc. in the vicinity of the level difference is suppressed. , whereby the reflection loss of light is suppressed. Even if the pressure-sensitive adhesive contains the compound (C), the level conformance rate within the above range is achieved.

(3-2) Heizechi

The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 5% or less, particularly preferably 3% or less, and more preferably 1% or less. When the haze value of the pressure-sensitive adhesive layer 11 is 5% or less, transparency is very high, and it is suitable for optical applications (for display bodies). In addition, the haze value in this specification is taken as the value measured according to JISK7136:2000.

(3-3) Adhesion

The lower limit of the adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 1 N/25 mm or more, particularly preferably 2 N/25 mm or more, and more preferably 5 N/25 mm or more. If the adhesive force of the adhesive sheet 1 is 1 N/25 mm or more, it becomes more excellent in conformability to a step under high-temperature, high-humidity conditions. The upper limit of the adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 35 N/25 mm or less, more preferably 30 N/25 mm or less, and particularly preferably 25 N/25 mm or less. . If the adhesive strength of the adhesive sheet 1 is 35 N/25 mm or less, it can be said that the rework property is excellent. Thereby, even when a bonding error to the display body constituent member occurs, the pressure-sensitive adhesive layer can be easily peeled off from the display body constituent member, and reuse of the expensive display body constituent member becomes possible.

Here, the adhesive force in this specification basically refers to the adhesive force measured by the 180-degree peeling method conforming to JIS Z 0237:2009, but the measurement sample was set to a width of 25 mm and a length of 100 mm, and the measurement sample was avoided. After attaching to the complex, pressurizing at 0.5 MPa and 50°C for 20 minutes, leaving it to stand for 24 hours under conditions of normal pressure, 23°C and 50% RH, and then measuring the peeling rate at 300 mm/min.

(3-4) Peel force

The peeling force at the time of peeling the pressure-sensitive adhesive layer 11 (the laminate of the substrate and the pressure-sensitive adhesive layer 11) according to the present embodiment from the release sheet 12a or 12b is preferably 30 mN/25 mm or more as a lower limit, particularly It is preferable that it is 50 mN/25 mm or more, and also it is preferable that it is 80 mN/25 mm or more. If the said peeling force is 30 mN/25 mm or more, it can suppress that peeling sheet 12a or 12b unintentionally peels from the adhesive layer 11. Further, the peeling force at the time of peeling the pressure-sensitive adhesive layer 11 (the laminate of the base material and the pressure-sensitive adhesive layer 11) according to the present embodiment from the release sheet 12a or 12b is preferably 300 mN/25 mm or less as an upper limit. , It is more preferable that it is 200 mN/25 mm or less, and it is especially preferable that it is 150 mN/25 mm or less. If the said peeling force is 150 mN/25 mm or less, peeling sheet 12a or 12b can be peeled from the adhesive layer 11 easily.

Here, the peel force in this specification basically refers to the adhesive force measured by the 180-degree peel method conforming to JIS Z 0237:2009, but is as specifically shown in the test examples described later.

(4) Manufacture of adhesive sheet

In one production example of the PSA sheet 1, a coating liquid of the PSA composition (P) is applied to the release surface of one of the release sheets 12a (or 12b), and heat treatment is performed to obtain the PSA composition (P). is thermally crosslinked to form a coating layer, and then the release surface of the other release sheet 12b (or 12a) is overlaid on the coating layer. When a curing period is required, a curing period is given, and when a curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. In this way, the pressure-sensitive adhesive sheet 1 is obtained. The heat treatment and curing conditions are as described above.

In another production example of the PSA sheet 1, a coating liquid of the PSA composition (P) is applied to the release surface of one release sheet 12a, heat treatment is performed, and the PSA composition (P) is thermally cross-linked. , a coating layer is formed to obtain a release sheet 12a with a coating layer. Further, a coating liquid of the above-mentioned adhesive composition (P) is applied to the release surface of the other release sheet 12b, heat treatment is performed to thermally crosslink the adhesive composition (P), and a coating layer is formed. The formed release sheet 12b is obtained. And the release sheet 12a with an application layer and the release sheet 12b with an application layer are bonded together so that both application layers may contact each other. When a curing period is required, a curing period is given, and when a curing period is unnecessary, the laminated coating layer becomes the pressure-sensitive adhesive layer 11 as it is. In this way, the pressure-sensitive adhesive sheet 1 is obtained. According to this manufacturing example, even when the adhesive layer 11 is thick, it becomes possible to manufacture 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, or the like can be used.

[display body]

As shown in Fig. 2, the display body 2 according to the present embodiment includes a first display body constituent member 21 (one display body constituent member) and a second display body constituent member 22 (another display member). body constituent member), and an adhesive layer 11 positioned between them and bonding the first display body constituent member 21 and the second display body constituent member 22 to each other.

The pressure-sensitive adhesive layer 11 of the display body 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above.

It is preferable that the 1st display body structural member 21 and the 2nd display body structural member 22 are hard bodies. Bonding of hard bodies together by means of an adhesive layer is more difficult than bonding films to each other or between films and hard bodies, and the yield at the time of bonding tends to decrease. Therefore, in this case, there is a high need to separate the two hard bodies so that the first display member 21 and/or the second display member 22 (particularly the expensive display module) can be reused. In the case of using a normal pressure-sensitive adhesive layer, it is very difficult to separate the two hard bodies. In contrast, by using the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment, the two hard bodies can be easily separated, and the first display body constituent member 21 and/or the second display body Reuse of the constituent member 22 becomes possible.

In addition, the "hard body" in this specification means the thing whose Young's modulus measured based on JISK 7127:1999 is 10 GPa or more. The rigid body may consist of a single layer or a single member, or may consist of a plurality of layers or a plurality of members. In the latter case, a product composed of a plurality of layers or a plurality of members, if the above Young's modulus is satisfied, the product can be said to be a rigid body even if some of the layers or members of the product do not satisfy the Young's modulus.

It is preferable that the 1st display body structural member 21 (one display body structural member) has a level|step difference in the surface of the side to which it is bonded at least. In the display body 2 according to the present embodiment, the first display body constituent member 21 has a level difference on the surface on the pressure-sensitive adhesive layer 11 side, and specifically, has a level difference caused by the printed layer 3 there is. Since the PSA layer 11 of the PSA sheet 1 according to the present embodiment is excellent in level conformability (initial level conformability and level conformability under high-temperature, high-humidity conditions), the PSA sheet 1 is used as a constituent member of the first display body. When affixed to (21), the pressure-sensitive adhesive layer 11 easily follows the level difference, and the occurrence of gaps, floating, etc. in the vicinity of the level difference is suppressed. Moreover, even when it is placed under high temperature and high humidity conditions in that state, the occurrence of bubbles, floating, peeling, etc. in the vicinity of the step is suppressed.

As the display body 2, a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, etc. are mentioned, for example, A touch panel may be sufficient as it. Moreover, as the display body 2, the member which comprises one part of them may be sufficient.

It is preferable that the 1st display body structural member 21 is a protective panel which consists of a laminated body etc. which contain them other than a glass plate, a plastic plate, etc. In this case, it is common that the printed layer 3 is formed in a frame shape on the side of the pressure-sensitive adhesive layer 11 in the first display body constituent member 21 .

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. can be heard 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 board, For example, an acrylic board, a polycarbonate board, 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.

In addition, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, etc.) may be formed on one side or both sides of the glass plate or plastic plate, or optical members may be laminated. Moreover, the transparent conductive film and the metal layer may be patterned.

The second display member 22 is an optical member to be attached to the first display member 21, a display module (e.g., a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescent Necess (organic EL) module, etc.), an optical member as a part of the display module, or a laminate comprising the display module is preferable.

Examples of the optical member include an anti-shattering film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a luminance enhancing film, a contrast enhancing film, a liquid crystal polymer film, a diffusion film, and a transflective film. A reflective film, a transparent conductive film, etc. are mentioned. Examples of the anti-scattering film include a hard coat film formed by forming a hard coat layer on one side of a base film.

The material constituting the print layer 3 is not particularly limited, and a known material for printing is used. The thickness of the printed layer 3, that is, the lower limit of the step height is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. When the lower limit is equal to or greater than the above, the concealment property such as making the electric wiring invisible from the viewer side can be sufficiently secured. The upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. When the upper limit is equal to or less than the above, deterioration in level conformability of the pressure-sensitive adhesive layer 11 to the printed layer 3 can be prevented.

In order to manufacture the display body 2, as an example, one release sheet 12a of the PSA sheet 1 is peeled off, and the exposed PSA layer 11 of the PSA sheet 1 is removed as a first display body constituent member. It is bonded to the surface on the side where the printed layer 3 of (21) exists. At this time, since the pressure-sensitive adhesive layer 11 has excellent conformability to the level difference, the occurrence of gaps or lifting in the vicinity of the level difference by the printed layer 3 is suppressed.

Thereafter, the other release sheet 12b is peeled off 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 display member 22 are removed. It bonds together and obtains the display body (2). Moreover, as another example, you may exchange the bonding order of the 1st display body structural member 21 and the 2nd display body structural member 22. At this time, even if the bonding position of the second display body constituent member 22 is shifted, since the adhesive layer 11 is excellent in reworkability, from the second display body constituent member 22, the adhesive layer 11 and The laminated body of the 1st display body constituent member 21 can be peeled easily. In particular, even if they are hard bodies, they can be easily separated. In this way, reuse of at least the second display member constituent member 22 becomes possible.

In the above display body (2), since the pressure-sensitive adhesive layer 11 is excellent in level conformability even under high temperature and high humidity conditions, the display body 2 is suitable for example under high temperature and high humidity conditions (e.g., 85°C, 85 °C). %RH), the occurrence of air bubbles, floating, peeling, etc. in the vicinity of the step is suppressed.

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

For example, one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12a and/or 12b. Moreover, the 1st display body structural member 21 may have a level difference other than the printing layer 3. Furthermore, not only the first display body constituent member 21 but also the second display body constituent member 22 may have a step on the pressure-sensitive adhesive layer 11 side.

Example

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

[Example 1]

1. Preparation of (meth)acrylic acid ester copolymer

A (meth)acrylic acid ester copolymer (A ) was prepared. As a result of measuring the molecular weight of this (meth)acrylic acid ester copolymer (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)acrylic acid ester copolymer (A) obtained in the above step 1 (solid content equivalent; hereinafter the same), and trimethylolpropane-modified tolylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "L-45) as a crosslinking agent (B) ") 0.2 parts by mass, and 0.5 parts by mass of tetraethylene glycol dimethyl ether (manufactured by Toho Chemical Industry Co., Ltd., product name "Hisolve MTEM") as a compound (C), and 3-glycidoxypropyl trime as a silane coupling agent (D) A coating solution of an adhesive composition having a solid content concentration of 45% by mass was obtained by mixing 0.2 parts by mass of toxoxysilane (manufactured by Shin-Etsu Chemical Industry, product name "KBM403"), sufficiently stirring, and diluting with methyl ethyl ketone.

3. Manufacture of adhesive sheet

The coating solution of the obtained adhesive composition was applied with a knife coater to the release-treated surface of a heavy release type release sheet (manufactured by Lintec, product name "SP-PET752150") in which one side of a polyethylene terephthalate film was subjected to release treatment with a silicone-based release agent. Then, the coated layer was subjected to heat treatment at 90°C for 1 minute to form an coated layer.

Next, an easy-peelable release sheet (manufactured by Lintec, product name "SP-PET382120") in which the coating layer on the heavy-peelable release sheet obtained above and one side of the polyethylene terephthalate film were subjected to a peeling treatment with a silicone-based release agent, and the easy-peelable release sheet was peeled off. An adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 25 μm, that is, a heavy release type release sheet / pressure-sensitive adhesive layer (thickness: 25 μm) / A PSA sheet (first PSA sheet) composed of a light-peelable release sheet was produced. In addition, the solid content concentration of the coating solution of the adhesive composition was changed to 55% by mass, and the thickness of the adhesive layer was changed to 50 μm, in the same manner as above, an adhesive sheet having an adhesive layer with a thickness of 50 μm, that is, a heavy release type A pressure-sensitive adhesive sheet (second pressure-sensitive adhesive sheet) composed of a release sheet/a pressure-sensitive adhesive layer (thickness: 50 µm)/an easy-to-peel type release sheet was produced. In addition, the thickness of the adhesive layer is a value measured using a static pressure thickness meter (product name "PG-02" manufactured by Teklock Co., Ltd.) in accordance with JIS K 7130.

Here, Table 1 shows each formulation (value in terms of solid content) of the adhesive composition when the (meth)acrylic acid ester copolymer (A) is 100 parts by mass (value in terms of solid content). In addition, the details of the abbreviation etc. described in Table 1 are as follows.

[(meth)acrylic acid ester copolymer (A)]

2EHA: 2-ethylhexyl acrylate

IBXA: isobornyl acrylate

ACMO: N-Acryloylmorpholine

HEA: 2-hydroxyethyl acrylate

MMA: methyl methacrylate

BA: n-butyl acrylate

MA: methyl acrylate

AA: acrylic acid

[Crosslinking agent (B)]

TDI: trimethylolpropane modified tolylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "L-45")

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

Epoxy: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD-C")

[Compound (C)]

HiSolve MTEM: Tetraethylene glycol dimethyl ether (manufactured by Toho Chemical Industry Co., Ltd., product name "HiSolve MTEM")

PEGME: Polyethylene glycol methyl ether (manufactured by ALDRICH, number average molecular weight 550)

A-400: Polyethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name "A-400", number average molecular weight 400)

M-130G: methoxy polyethylene glycol acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name "M-130G", number average molecular weight 550)

KF6000: Reactive silicone oil modified with carbinol at both ends (manufactured by Shin-Etsu Chemical Co., Ltd., product name “KF6000”)

KF2012: Reactive silicone oil modified with one end of methacrylic acid (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF2012")

KF8010: Amino-modified reactive silicone oil sock end (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF8010")

PEG (1000): Polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight: 1000)

[Examples 2 to 22, Comparative Examples 1 to 5]

Type and ratio of each monomer constituting the (meth)acrylic acid ester copolymer (A), weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer (A), type and compounding amount of the crosslinking agent (B), compound (C ), and the blending amount of the silane coupling agent (D) were changed as shown in Table 1, and PSA sheets (first PSA sheet and second PSA sheet) were prepared in the same manner as in Example 1. .

[Test Example 1] (Evaluation of bubble release property)

The coating solution of the adhesive composition prepared in Examples and Comparative Examples was stirred for 15 minutes under normal temperature and 1500 rpm conditions using a high-speed disperser (manufactured by Primix, product name "Homodisper 2.5 type"). Then, using a desiccator (manufactured by As One, product name "Stainless Vacuum Desiccator DVS-310"), vacuum degassing was performed at room temperature at -0.06 MPa on a vacuum gauge scale for 20 minutes. The coating solution in that state was visually confirmed, and it was judged that the bubble release property was good (○) when air bubbles completely fell out, and the air bubble release property was judged to be poor (x) when air bubbles did not come off. A result is shown in Table 2.

[Test Example 2] (Measurement of gel fraction)

The PSA sheet (first PSA sheet) obtained in Examples and Comparative Examples was cut to a size of 80 mm × 80 mm, the PSA layer was wrapped in a polyester mesh (mesh size 200), and its mass was weighed with a precision balance. And, the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. Let the mass at this time be M1.

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

[Test Example 3] (Measurement of haze value)

For the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (first pressure-sensitive adhesive sheet) obtained in Examples and Comparative Examples, haze value ( %) was measured. A result is shown in Table 2.

[Test Example 4] (Measurement of adhesive strength)

The easy-peelable release sheet was peeled off from the PSA sheets (first PSA sheet and second PSA sheet) obtained in Examples and Comparative Examples, and the exposed PSA layer was replaced with a polyethylene terephthalate (PET) film having an easily adhesive layer (manufactured by Toyobo Co., Ltd.). , product name "PETA4300", thickness: 100 µm), and bonded to an easily bonding layer to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

In an environment of 23° C. and 50% RH, the heavy release type release sheet is peeled off from the sample, and the exposed pressure-sensitive adhesive layer is affixed to alkali-free glass (manufactured by Corning, product name “Eagle XG”), followed by autoclave manufactured by Kurihara Manufacturing Co., Ltd. was pressurized at 0.5 MPa and 50°C for 20 minutes. Then, after leaving it to stand for 24 hours under conditions of 23°C and 50% RH, a peeling speed of 300 mm/min and a peeling angle of 180 degrees were obtained using a universal tensile tester (manufactured by Orientec, product name "Tensilon UTM-4-100"). Adhesion (N/25 mm) was measured under the conditions shown in the figure. Conditions other than those described here were measured based on JIS Z 0237:2009. A result is shown in Table 2.

[Test Example 5] (Measurement of Peel Force)

About the PSA sheet (1st PSA sheet) obtained by the Example and the comparative example, it carried out similarly to Test Example 3, and produced the sample. The release sheet side of the sample was bonded to a stainless steel plate using double-sided adhesive tape, and fixed to a universal tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon UTM-4-100"). In accordance with JIS Z 0237:2009 under conditions of a temperature of 23°C and 50% RH, the PET film of the sample was pulled in the direction of 180° at a tensile speed of 300 mm/min to obtain a laminate of the PET film and the pressure-sensitive adhesive layer from the release sheet. The force at the time of peeling was measured and this was made into peeling force (mN/25mm). A result is shown in Table 2.

[Test Example 6] (Evaluation of reworkability by pool retention)

After measuring the adhesive force according to Test Example 3, peeling off the PSA sheet as a sample (first PSA sheet), measuring the remaining area of the paste on the surface of the alkali-free glass as an adherend (bonding surface of the PSA), Reworkability (normal temperature) was evaluated according to the following criteria. A result is shown in Table 2.

○ … There was no grass residue at all.

△ … There was paste retention in an area of less than 30% of the bonded area.

× … There was paste residue in an area of 30% or more of the bonding area.

Further, as shown in Test Example 3, after bonding the PSA sheet as a sample (first PSA sheet) to alkali-free glass and pressurizing, it was left to stand for 24 hours under conditions of 23°C and 50% RH, followed by 60°C , and left for 24 hours under conditions of 90% RH (accelerated conditions). Thereafter, the PSA sheet (first PSA sheet) was peeled by the method shown in Test Example 3, and the reworkability (after accelerating conditions) was evaluated on the basis of the above. A result is shown in Table 2.

[Test Example 7] (Measurement of step tracking rate)

On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), an ultraviolet curable ink (manufactured by Teikoku Ink Co., product name “POS-911 Black”) was applied. ) was screen-printed in a frame shape (external shape: length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was any one of 5 μm, 10 μm, 15 μm and 20 μm. Subsequently, the UV curable ink printed by irradiation with ultraviolet rays (80 W/cm 2 , 2 metal halide lamps, lamp height 15 cm, belt speed 10-15 m/min) is cured, and the step by printing (step difference) Height: any one of 5 μm, 10 μm, 15 μm, and 20 μm) was prepared as a stepped glass plate.

The easy-to-peel type release sheet was peeled off from the PSA sheet (second PSA sheet) obtained in Examples and Comparative Examples, and the exposed PSA layer was replaced with a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "PETA4300", thickness: 100) having an easy-adhesive layer. μm) was bonded to the easy-adhesive layer. Then, the heavy release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (manufactured by Fujipla Co., Ltd., product name "LPD3214"), the laminate was laminated on each stepped glass plate so that the pressure-sensitive adhesive layer covered the entire frame-shaped printing surface, and this was used as an evaluation sample.

The obtained sample for evaluation was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa, and then left to stand for 24 hours at normal pressure, 23°C, and 50% RH. Subsequently, it was stored for 72 hours under high temperature and high humidity conditions of 85°C and 85% RH (endurance test), and then the step followability was evaluated. The level difference followability is determined by whether or not the printing level difference is completely filled by the pressure-sensitive adhesive layer, and when air bubbles, lifting, peeling, etc. are observed at the interface between the printing level difference and the pressure-sensitive adhesive layer, it is determined that the printing level difference could not be followed. Here, the step followability was evaluated as a step follow rate (%) represented by the following formula. A result is shown in Table 2.

Step follow-up rate (%) = {(height of a step maintained in a filled state without bubbles, lifting, peeling, etc. after durability test (μm))/(thickness of adhesive layer: 50 μm)} × 100

As can be seen from Table 2, the PSA sheets obtained in Examples had adhesive strength that was not too high, and were excellent in reworkability in that there was little adhesive residue when peeled off from the adherend. In addition, the PSA sheets obtained in Examples had sufficient peeling strength and were also excellent in conformability to level difference (under high temperature and high humidity conditions).

The pressure-sensitive adhesive sheet of the present invention can be suitably used for, for example, bonding between a stepped protection panel and a desired display member.

One … adhesive sheet
11 … adhesive layer
12a, 12b... release sheet
2 … display body
21 … 1st display body constituent member
22 … 2nd display body constituent member
3 … printed layer

Claims (12)

An adhesive composition for forming an adhesive layer for bonding one display body constituent member to another display body constituent member, comprising (meth)acrylic acid ester copolymer (A), a crosslinking agent (B), and a compound (C) , The (meth)acrylic acid ester copolymer (A) contains a reactive group-containing monomer having a reactive group that reacts with the crosslinking agent (B) in the molecule as a monomer unit constituting the polymer, and does not contain a carboxyl group-containing monomer, and a weight average molecular weight of 400,000 or more and 1,300,000 or less, the compound (C) has an alkylene oxide moiety, and has no or one reactive group that reacts with the crosslinking agent (B). composition. The adhesive composition according to claim 1, wherein the compound (C) has a linear structure and has an alkyl group at both ends or at one end. The adhesive composition according to claim 1, wherein the compound (C) has a linear structure and has (meth)acryloyl groups at both ends or at one end. The adhesive composition according to claim 1, wherein the compound (C) is contained in an amount of 0.2 parts by mass or more and less than 10 parts by mass based on 100 parts by mass of the (meth)acrylic acid ester copolymer (A). The adhesive composition according to claim 1, wherein the (meth)acrylic acid ester copolymer (A) contains an alicyclic structure-containing monomer as a monomer unit constituting the polymer. The adhesive composition according to claim 1, wherein the one display body constituent member and the other display body constituent member are hard bodies. The adhesive composition according to claim 1, wherein the one display body constituent member has a step on at least a surface to be bonded. A pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to any one of claims 1 to 7. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding one display body constituent member to another display body constituent member, wherein the pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive according to claim 8. The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive layer has a thickness of 20 μm or more and 500 μm or less. 10. The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is held by the release sheets so as to come into contact with the release surfaces of the two release sheets. A display body comprising one display body constituent member, another display body constituent member, and a pressure-sensitive adhesive layer for bonding the one display body constituent member and the other display body constituent member together, wherein the pressure-sensitive adhesive layer according to claim 9 A display body characterized by being a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet described above.

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