KR102609663B1 - Adhesive composition, adhesive, adhesive sheet, and display - Google Patents

Abstract

[Problem] To provide an adhesive composition, adhesive, adhesive sheet, and display body in which the adhesive layer has excellent step followability and can exhibit high film strength.
[Solution] As monomer units constituting the polymer, a (meth)acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer and an alicyclic structure-containing monomer, and a polyrotaxane compound (B) having a cyclic oligosaccharide as a cyclic molecule, and , an adhesive composition containing an isocyanate-based crosslinking agent (C).

Description

Adhesive composition, adhesive, adhesive sheet and indicator {ADHESIVE COMPOSITION, ADHESIVE, ADHESIVE SHEET, AND DISPLAY}

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

Various mobile electronic devices such as recent smartphones and tablet terminals are equipped with displays using display modules having liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescence (organic EL) elements, etc. Increasingly, displays are becoming touch panels.

In displays such as the above, a protection panel is usually installed on the surface side of the display module. As electronic devices become thinner and lighter, the protective panel is being changed from a conventional glass plate to a plastic plate such as an acrylic plate or polycarbonate plate.

Here, 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 the above-mentioned air gap, or air layer, exists, the reflection loss of light resulting from 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 is large, causing a problem that the image quality of the display deteriorates.

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protection panel and the display module with an adhesive layer. However, on the display module side of the protection panel, the printed layer on the frame may exist as a step. If the adhesive layer does not follow the step, the adhesive layer floats near the step, resulting in light reflection loss. Therefore, the adhesive layer is required to have step followability.

In order to solve the above problem, Patent Document 1 is an adhesive layer that fills the gap between the protection panel and the display module, and has a shear storage modulus (G') at 25°C and 1 Hz of 1.0×10 ⁵ Pa or less. , also discloses an adhesive layer with a gel fraction of 40% or more.

Japanese Patent Publication No. 2010-97070

In Patent Document 1, an attempt is made to improve step followability by lowering the storage modulus of the adhesive layer at room temperature. However, if the storage modulus is lowered as such, the film strength of the adhesive layer decreases and processability deteriorates. For example, when punching an adhesive sheet, problems such as the adhesive sticking to the blade and part of the adhesive layer falling off occur. Additionally, a problem occurs in which the adhesive oozes out from the adhesive layer, such as when storing the adhesive sheet.

The present invention was made in consideration of such actual conditions, and its purpose is to provide an adhesive composition, adhesive, adhesive sheet, and display body in which the adhesive layer has excellent step followability and can exhibit high film strength.

In order to achieve the above object, the present invention firstly provides a (meth)acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer and an alicyclic structure-containing monomer as monomer units constituting the polymer, and a cyclic oligosaccharide as a cyclic molecule. Provided is an adhesive composition characterized by containing a polyrotaxane compound (B) having a and an isocyanate-based crosslinking agent (C) (invention 1).

The adhesive layer made of an adhesive obtained by crosslinking the adhesive composition according to the above invention (invention 1) is, in particular, the adhesive composition contains a polyrotaxane compound (B), and the (meth)acrylic acid ester polymer (A) constitutes the polymer. By including an alicyclic structure-containing monomer as the monomer unit, it is possible to exhibit excellent step followability and high film strength.

In the above invention (invention 1), the (meth)acrylic acid ester polymer (A) is a monomer unit constituting the polymer, and in addition to the hydroxyl group-containing monomer and the alicyclic structure-containing monomer, the alkyl group has 5 to 20 carbon atoms. It is preferable to contain 10% by mass or more and 90% by mass or less of alkyl (meth)acrylate (invention 2).

In the above inventions (inventions 1 and 2), the (meth)acrylic acid ester polymer (A) preferably contains 3% by mass or more and 30% by mass or less of the hydroxyl group-containing monomer as a monomer unit constituting the polymer. Do (Invention 3).

In the above inventions (inventions 1 to 3), the (meth)acrylic acid ester polymer (A) contains 1% by mass or more and 50% by mass or less of the alicyclic structure-containing monomer as a monomer unit constituting the polymer. It is preferable (invention 4).

In the above inventions (inventions 1 to 4), the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 or more and 900,000 or less (invention 5).

In the above inventions (inventions 1 to 5), the content of the polyrotaxane compound (B) in the adhesive composition is 3 parts by mass or more, 30 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A). It is preferable that it is the following (invention 6).

Second, the present invention provides an adhesive obtained by crosslinking the above adhesive compositions (Inventions 1 to 6) (Invention 7).

Thirdly, the present invention is a pressure-sensitive adhesive sheet having one display body member having a step at least on the side to be joined, and an adhesive layer for bonding the other display body members, wherein the pressure-sensitive adhesive layer contains the pressure-sensitive adhesive (invention 7) An adhesive sheet is provided (invention 8).

In the above invention (invention 8), the adhesive sheet is provided with two release sheets, and the adhesive layer is preferably sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets ( Invention 9).

Fourthly, the present invention provides a method for bonding one display structural member and another display structural member having a step at least on the surface of the side to be joined, and bonding the one display structural member and the other display structural member to each other. A display body provided with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Inventions 8 and 9) (Invention 10).

The adhesive layer obtained from the adhesive composition and adhesive according to the present invention, and the adhesive layer of the adhesive sheet and display body according to the present invention, are excellent in step followability and can exhibit high film strength.

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

Hereinafter, embodiments of the present invention will be described.

[Adhesive composition]

The adhesive composition (hereinafter sometimes referred to as “adhesive composition P”) according to the present embodiment is a monomer unit constituting a polymer, which includes a hydroxyl group-containing monomer (monomer containing a hydroxyl group in the molecule) and an alicyclic structure-containing monomer (molecule It contains a (meth)acrylic acid ester polymer (A) containing a monomer containing an alicyclic structure therein, a polyrotaxane compound (B) having a cyclic oligosaccharide as a cyclic molecule, and an isocyanate-based crosslinking agent (C). In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same goes for other similar terms. In addition, “polymer” shall also include the concept of “copolymer.”

When the adhesive composition P according to the present embodiment is crosslinked, the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth)acrylic acid ester polymer (A) and the isocyanate group of the isocyanate-based crosslinking agent (C) react to form a three-dimensional network structure, An adhesive having a predetermined cohesive force is obtained. The polyrotaxane compound (B) has a mechanical bond between a cyclic molecule and a linear molecule penetrating it, and the cyclic molecule can freely move on the linear molecule. With this structure, the polyrotaxane compound (B) can provide excellent stress relaxation properties to the obtained adhesive. In addition, since the monomer containing an alicyclic structure has a large volume, it is assumed that by making it present in the polymer, the gap between the polymers is widened, and the obtained adhesive can be made to have excellent flexibility. Therefore, the adhesive composition P contains the polyrotaxane compound (B) and the (meth)acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a constituent monomer unit, so that the adhesive composition P is crosslinked. becomes excellent in step followability.

For example, when the adhesive sheet obtained using the adhesive composition P according to the present embodiment is affixed to a display member having a step, the adhesive layer tends to follow the step, and gaps, lifting, etc. occur near the step. It is suppressed. In addition, even when left in that state under high temperature and high humidity conditions, for example, 85°C and 85%RH for 72 hours, the occurrence of bubbles, floatation, peeling, etc. in the vicinity of the steps is suppressed.

Since the excellent level difference followability is obtained without lowering the storage modulus of the adhesive, the adhesive layer formed from the adhesive obtained by crosslinking the adhesive composition P can exhibit high film strength. Therefore, for example, when punching an adhesive sheet, problems such as the adhesive sticking to the blade and a part of the adhesive layer falling off are suppressed. Additionally, oozing of the adhesive from the adhesive layer, such as during storage of the adhesive sheet, is suppressed.

Here, when the cyclic molecule of the polyrotaxane compound (B) is a cyclic oligosaccharide having a hydroxyl group as a reactive group, the following effects are especially exhibited. That is, when the adhesive composition P according to the present embodiment is crosslinked, the isocyanate group of the isocyanate-based crosslinking agent (C) reacts with the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth)acrylic acid ester polymer (A). The isocyanate group of the crosslinking agent (C) reacts with the hydroxyl group of the cyclic molecule of the polyrotaxane compound (B). As a result, the (meth)acrylic acid ester polymer (A) is bonded to one cyclic molecule of the polyrotaxane compound (B) via the isocyanate-based crosslinking agent (C) through a hydroxyl group, and similarly, another (meth)acrylic acid ester It is presumed that the polymer (A) is bonded to other cyclic molecules of the polyrotaxane compound (B). As a result, it is presumed that the plurality of (meth)acrylic acid ester polymers (A) form a higher-order structure such as a three-dimensional network structure mechanically bonded to each other by the polyrotaxane compound (B). With this higher-order structure, the film strength can be made higher without deteriorating stress relaxation properties (while retaining step followability) compared to the same higher-order structure except that it does not contain the polyrotaxane compound (B).

In addition, not all of the obtained adhesives need to have the above estimated structure, and the two (meth)acrylic acid ester polymers (A) are directly bonded by the isocyanate-based crosslinking agent (C) without the polyrotaxane compound (B) intervening. It may include existing structures, etc.

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

The (meth)acrylic acid ester polymer (A) in this embodiment includes a hydroxyl group-containing monomer and an alicyclic structure-containing monomer as monomer units constituting the polymer.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and (meth)acrylic acid. ) (meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate. Among them, in terms of the reactivity of the hydroxyl group in the obtained (meth)acrylic acid ester polymer (A) with the isocyanate-based crosslinking agent (C) and copolymerizability with other monomers, 2-hydroxyethyl (meth)acrylic acid or (meth)acrylic acid 4-Hydroxybutyl is preferred. These may be used individually, or two or more types may be used in combination.

The (meth)acrylic acid ester polymer (A), as a monomer unit constituting the polymer, preferably contains 3% by mass or more of a hydroxyl group-containing monomer as a lower limit, and especially preferably contains 5% by mass or more, and further preferably contains It is preferable to contain 10% by mass or more. If the content of the hydroxyl group-containing monomer is 3% by mass or more, the cohesive force of the obtained adhesive is improved, thereby resulting in a higher film strength. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 30% by mass or less of hydroxyl group-containing monomer as the upper limit as a monomer unit constituting the polymer, and especially preferably contains 25% by mass or less, and further. It is preferable to contain 20% by mass or less. If the content of the hydroxyl-containing monomer is 30% by mass or less, it becomes easy to obtain appropriate adhesiveness, the adhesive is suppressed from becoming too hard, and the step followability becomes more excellent.

The carbocyclic ring of the alicyclic structure in the alicyclic structure-containing monomer may have a saturated structure or may have a part of an unsaturated bond. In addition, the alicyclic structure may be a monocyclic alicyclic structure, or may be a polycyclic alicyclic structure such as 2 or 3 rings. From the viewpoint of providing an appropriate distance between the resulting (meth)acrylic acid ester polymers (A) and providing higher stress relaxation properties to the adhesive, the alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). . In addition, considering the compatibility of the (meth)acrylic acid ester polymer (A) and other components, it is particularly preferable that the polycyclic structure has 2 to 4 rings. Also, in the same manner as above, from the viewpoint of imparting stress relaxation properties, the number of carbon atoms in the alicyclic structure (refers to all carbon atoms in the portion forming the ring, and when multiple rings exist independently, refers to the total carbon number) is: Usually, it is preferable that it is 5 or more, and it is especially preferable that it is 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 similarly to the above, from the viewpoint of compatibility, it is preferably 15 or less, and particularly preferably 10 or less.

Specific examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. , dicyclopentenyloxyethyl (meth)acrylate, etc., and among them, dicyclopentanyl (meth)acrylate (carbon number of alicyclic structure: 10), (meth), which exhibits better step followability under moist heat conditions. Adamantyl acrylate (alicyclic carbon number: 10) or isobornyl (meth)acrylate (alicyclic carbon number: 7) is preferable, and isobornyl (meth)acrylate is particularly preferable. These may be used individually by 1 type, or may be used in combination of 2 or more types.

The (meth)acrylic acid ester polymer (A), as a monomer unit constituting the polymer, preferably contains 1% by mass or more of an alicyclic structure-containing monomer, especially preferably 5% by mass or more, and further preferably contains 10% by mass or more. It is preferable to contain it in mass% or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 50% by mass or less of an alicyclic structure-containing monomer as a monomer unit constituting the polymer, and especially preferably contains 40% by mass or less, and further It is preferable to contain 30% by mass or less. If the content of the alicyclic structure-containing monomer is within the above range, the obtained pressure-sensitive adhesive has better step followability and sufficiently exhibits excellent adhesion to transparent conductive films and plastics.

The (meth)acrylic acid ester polymer (A) is a monomer unit constituting the polymer, and in addition to the hydroxyl group-containing monomer and the alicyclic structure-containing monomer, an alkyl (meth)acrylate having an alkyl group having 5 to 20 carbon atoms, especially 8 to 15 carbon atoms. It is preferable to contain an ester (one that does not contain an alicyclic structure). As a result, desirable adhesiveness can be achieved without reducing compatibility with the polyrotaxane compound (B). Additionally, flexibility can be provided to the obtained adhesive, making it excellent in step followability. Additionally, the alkyl group may be either linear or branched.

From the above viewpoint, the (meth)acrylic acid ester polymer (A) preferably contains 10% by mass or more of an alkyl (meth)acrylic acid ester with an alkyl group having 5 to 20 carbon atoms as the monomer unit constituting the polymer, especially It is preferable to contain 20 mass% or more, and more preferably 50 mass% or more. When the above-mentioned (meth)acrylic acid alkyl ester is contained in an amount of 10% by mass or more, the resulting adhesive can exhibit desirable adhesiveness and better step followability. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 90% by mass or less of an alkyl (meth)acrylic acid ester with an alkyl group having 5 to 20 carbon atoms as the monomer unit constituting the polymer, especially 80% by mass. It is preferable to contain it below, and it is further preferable to contain it at 70% by mass or less. By setting the above-mentioned (meth)acrylic acid alkyl ester to 90% by mass or less, other monomer components can be introduced in a suitable amount into the (meth)acrylic acid ester polymer (A).

Examples of (meth)acrylic acid alkyl esters in which the alkyl group has 5 to 20 carbon atoms include n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate. , n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, etc. Among them, 2-ethylhexyl (meth)acrylate is preferable from the viewpoint of further improving adhesiveness and compatibility with the polyrotaxane compound (B). These may be used individually, or two or more types may be used in combination.

On the other hand, the (meth)acrylic acid ester polymer (A) contains, as a monomer unit constituting the polymer, an alkyl (meth)acrylic acid ester with an alkyl group having 4 or less carbon atoms, or less than 60% by mass, preferably 50% by mass. It is also preferable to contain it in an amount of 30% by mass or less, particularly preferably. Thereby, other monomer components can be introduced in a suitable amount into the (meth)acrylic acid ester polymer (A).

The (meth)acrylic acid ester polymer (A) also preferably contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By allowing a nitrogen atom-containing monomer to exist as a structural unit in the polymer, a predetermined polarity can be imparted to the adhesive, making it excellent in affinity even for an adherend having a certain degree of polarity, such as glass. Examples of the nitrogen atom-containing monomer include monomers having an amino group, monomers having an amide group, monomers having a nitrogen-containing heterocycle, and the like. Among these, the viewpoint of providing appropriate rigidity to the (meth)acrylic acid ester polymer (A) In, monomers having nitrogen-containing heterocycles are preferred.

Examples of monomers having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, and N-(meth)acryl. Roylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinyl Examples include pyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide. Among them, N-(meth)acryloylmorpholine, which exhibits superior adhesive strength, is preferable, especially N-acryloylmorpholine is preferred.

In addition, examples of nitrogen atom-containing monomers include (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, N-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, monomethylaminopropyl (meth)acrylate, monoethylamino (meth)acrylate Propyl, dimethylaminoethyl (meth)acrylate, etc. can also be used.

The above nitrogen atom-containing monomers may be used individually, or may be used in combination of two or more types.

When the (meth)acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer, it preferably contains 0.5% by mass or more of the nitrogen atom-containing monomer, especially 1% by mass or more. It is preferable to contain it, and it is further preferable to contain it at 3% by mass or more. In addition, the (meth)acrylic acid ester polymer (A) preferably contains 20% by mass or less of the nitrogen atom-containing monomer as a monomer unit constituting the polymer, and especially preferably contains 15% by mass or less, and further It is preferable to contain 8% by mass or less. If the content of the nitrogen atom-containing monomer is within the above range, the resulting pressure-sensitive adhesive can sufficiently exhibit excellent adhesion to glass.

In addition, the (meth)acrylic acid ester polymer (A) preferably contains a hard monomer having a glass transition temperature (Tg) of 0°C or higher as a homopolymer as a monomer unit constituting the polymer. Additionally, this hard monomer may also contain the various monomers described above. By containing the hard monomer as the monomer unit constituting the (meth)acrylic acid ester polymer (A), the resulting pressure-sensitive adhesive has improved cohesion and higher film strength. In particular, when using an alkyl (meth)acrylic acid ester (for example, 2-ethylhexyl (meth)acrylic acid) whose alkyl group has 5 to 20 carbon atoms as the monomer unit constituting the (meth)acrylic acid ester polymer (A) Since cohesion tends to be low, it is preferable to use the hard monomer. The glass transition temperature (Tg) of the hard monomer as a homopolymer is preferably 15°C or higher as a lower limit, and particularly preferably 80°C or higher. Moreover, the glass transition temperature (Tg) is preferably 200°C or lower as an upper limit, and is particularly preferably 180°C or lower.

Examples of the hard monomer include methyl acrylate (Tg 10°C), methyl methacrylate (Tg 105°C), isobornyl acrylate (Tg 94°C), isobornyl methacrylate (Tg 180°C), and acrylic acid. Examples include damantyl (Tg 115°C), adamantyl methacrylate (Tg 141°C), acryloylmorpholine (Tg 145°C), and cyclohexyl acrylate (Tg 19°C). These may be used individually, or two or more types may be used in combination.

When the (meth)acrylic acid ester polymer (A) contains the hard monomer as a monomer unit constituting the polymer, it is preferable to contain 5% by mass or more of the hard monomer, and it is particularly preferable to contain 10% by mass or more. do. By containing 5% by mass or more of the hard monomer, film strength can be further improved. Moreover, the (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or less of the hard monomer as a monomer unit constituting the polymer, and particularly preferably contains 30% by mass or less. By setting the content of the hard monomer to 40% by mass or less, the relative deficiency of other monomer units in the (meth)acrylic acid ester polymer (A) can be prevented, and the obtained adhesive can be excellent in adhesion and step followability. .

The (meth)acrylic acid ester polymer (A) may, as desired, contain other monomers as monomer units constituting the polymer. The other monomer may be a monomer containing a reactive functional group (excluding a hydroxyl group), or may be a monomer that does not contain a reactive functional group.

As a monomer containing a reactive functional group, a carboxyl group-containing monomer is preferably used. Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferable in terms of its influence on the reaction between the hydroxyl group derived from the hydroxyl group-containing monomer and the isocyanate-based crosslinking agent (C), and its copolymerizability with other monomers. These may be used individually, or two or more types may be used in combination.

When the (meth)acrylic acid ester polymer (A) contains a carboxyl group-containing monomer as a monomer unit constituting the polymer, its content is preferably 0.5% by mass or more as a lower limit, and especially preferably 1% by mass or more. Moreover, as an upper limit, it is preferable that it is 20 mass % or less, and it is especially preferable that it is 10 mass % or less.

Additionally, from the viewpoint of facilitating control of the crosslinked structure of the resulting pressure-sensitive adhesive, it is also preferable that the monomer containing a reactive functional group be solely the above-mentioned hydroxyl group-containing monomer.

On the other hand, examples of monomers that do not contain a reactive functional group include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. . These may be used individually, or two or more types may be used in combination.

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

The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 or more as a lower limit, especially preferably 200,000 or more, and more preferably 300,000 or more. If the lower limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is more than the above, the film strength of the obtained adhesive will be higher. Moreover, the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 900,000 or less as an upper limit, especially preferably 800,000 or less, and more preferably 700,000 or less. If the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is the above or less, the resulting pressure-sensitive adhesive will have better step followability. In addition, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by gel permeation chromatography (GPC) method.

In the adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used individually or in combination of two or more types.

(2) Polyrotaxane compound (B)

The polyrotaxane compound (B) is a compound in which a linear molecule passes through the openings of at least two cyclic molecules and has block groups at both ends of the linear molecule. In this polyrotaxane compound (B), the cyclic molecule can move freely on the linear molecule, but the blocking group has a structure in which the cyclic molecule cannot escape from the linear molecule. That is, linear molecules and cyclic molecules maintain their shape not by chemical bonds such as covalent bonds, but by so-called mechanical bonds. When the adhesive composition P according to the present embodiment contains the polyrotaxane compound (B) having such a mechanical bond, the resulting adhesive exhibits high stress relaxation properties and is excellent in step followability. In particular, when the cyclic molecule of the polyrotaxane compound (B) is a cyclic oligosaccharide having a hydroxyl group as a reactive group, the (meth)acrylic acid ester polymer (A) and the polyrotaxane compound ( B) (cyclic molecule) is crosslinked, and the cyclic molecule freely moves on the linear molecule in the polyrotaxane compound (B), thereby significantly improving the flexibility of the crosslinked product. As a result, the obtained adhesive exhibits extremely high stress relaxation properties and has superior level difference followability.

The polyrotaxane compound (B) in this embodiment has a cyclic oligosaccharide as a cyclic molecule. By using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (B), it becomes possible to select an appropriate ring diameter, thereby easily exhibiting the effect of the cyclic molecule moving on a linear molecule. Additionally, if the cyclic oligosaccharide has a hydroxyl group as a reactive group, reaction with the isocyanate-based crosslinking agent (C) is easy. In addition, it is easy to introduce various substituents, etc., thereby making it possible to adjust the compatibility of the polyrotaxane compound (B) with other components by using the polyrotaxane compound (B). Additionally, cyclic oligosaccharides have the advantage of being easy to obtain. In addition, in this specification, “cyclic” in “cyclic molecule” or “cyclic oligosaccharide” means substantially “cyclic.” In other words, as long as it can move on a linear molecule, the cyclic molecule does not have to be completely ring-closed and, for example, may have a helical structure.

Preferred examples of cyclic oligosaccharides include cyclodextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and among these, α-cyclodextrin is particularly preferred. Two or more types of cyclic molecules of the polyrotaxane compound (B) may be mixed in the polyrotaxane compound (B) or in the adhesive composition P.

When the cyclic molecule (cyclic oligosaccharide) of the polyrotaxane compound (B) has a hydroxyl group as a reactive group, the hydroxyl group may be a hydroxyl group originally (referring to the state before modification) of the cyclic oligosaccharide, or may be a hydroxyl group introduced as a substituent into the cyclic oligosaccharide. Hydroxyl acid contribution is also possible.

The lower limit of the hydroxyl value of the cyclic molecule is preferably 10 mgKOH/g or more, more preferably 30 mgKOH/g or more, and particularly preferably 50 mgKOH/g or more. If the lower limit of the hydroxyl value is more than the above, the polyrotaxane compound (B) can sufficiently react with the isocyanate-based crosslinking agent (C). Moreover, the upper limit of the hydroxyl value of the cyclic molecule is preferably 1000 mgKOH/g or less, more preferably 200 mgKOH/g or less, and especially preferably 100 mgKOH/g or less. If the upper limit of the hydroxyl value exceeds the above value, a large number of crosslinks occur in the same cyclic molecule, and the cyclic molecule itself becomes a crosslinking point, making it impossible to exert the crosslinking point effect as the polyrotaxane compound (B) as a whole, As a result, it is thought that the effect of improving the film strength through the addition of the polyrotaxane compound (B) in the step followability as is is not sufficient.

The linear molecule of the polyrotaxane compound (B) is a molecule or substance that is enclosed in a cyclic molecule and can be integrated by mechanical bonds rather than chemical bonds such as covalent bonds, and is not particularly limited as long as it is linear. In addition, in this specification, “linear” in “linear molecule” means substantially “linear”. That is, as long as the cyclic molecule can move on the linear molecule, the linear molecule may have branched chains.

Examples of linear molecules of the polyrotaxane compound (B) include polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylic acid ester, polydimethylsiloxane, polyethylene, poly Propylene and the like are preferable, and two or more of these linear molecules may be mixed in the adhesive composition P.

The number average molecular weight of the linear molecules of the polyrotaxane compound (B) is preferably 3,000 or more as a lower limit, especially preferably 10,000 or more, and more preferably 20,000 or more. If the lower limit of the number average molecular weight is more than the above, the amount of movement of the cyclic molecules on the linear molecules is ensured, and the stress relaxation property of the adhesive is sufficiently obtained. Additionally, the number average molecular weight of the linear molecules of the polyrotaxane compound (B) is preferably 300,000 or less as an upper limit, particularly preferably 200,000 or less, and more preferably 100,000 or less. If the upper limit of the number average molecular weight is the above or less, the solubility of the polyrotaxane compound (B) in the solvent and compatibility with the (meth)acrylic acid ester polymer (A) become good.

The block group of the polyrotaxane compound (B) is not particularly limited as long as it is a group that can maintain the skewed form of the cyclic molecule by linear molecules. Examples of such groups include bulky groups, ionic groups, and the like.

Specifically, the block group of the polyrotaxane compound (B) is dinitrophenyl group, cyclodextrin group, adamantane group, trityl group, fluorescein group, pyrene group, anthracene group, etc., or has a number average molecular weight of 1,000 to 1,000. A polymer main chain or side chain of 1,000,000 is preferable, and two or more of these block groups may be mixed in the polyrotaxane compound (B) or in the adhesive composition P.

The polyrotaxane compound (B) described above can be obtained by a conventionally known method (for example, the method described in Japanese Patent Application Laid-Open No. 2005-154675).

The content of the polyrotaxane compound (B) in the adhesive composition P according to the present embodiment is preferably 3 parts by mass or more as a lower limit with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially 5 parts by mass. It is preferable that it is more than 7 parts by mass or more. When the content of the polyrotaxane compound (B) is 3 parts by mass or more, the film strength of the obtained adhesive increases and the processability becomes more excellent. Moreover, when the content of the polyrotaxane compound (B) is 7 parts by mass or more, the level difference followability of the obtained pressure-sensitive adhesive is also improved. Moreover, the upper limit of the content of the polyrotaxane compound (B) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, especially preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. When the content of the polyrotaxane compound (B) is 30 parts by mass or less, the processability of the obtained adhesive becomes more excellent, compatibility with the (meth)acrylic acid ester polymer (A) is maintained well, and the haze value of the obtained adhesive is maintained well. It can be suppressed to a low level. Moreover, if the content of the polyrotaxane compound (B) is 15 parts by mass or less, the level difference followability of the obtained pressure-sensitive adhesive is also improved.

(3) Isocyanate-based crosslinking agent (C)

The isocyanate-based crosslinking agent (C) has excellent reactivity with the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth)acrylic acid ester polymer (A) and the hydroxyl group of the cyclic oligosaccharide, which is a cyclic molecule of the polyrotaxane compound (B). .

The isocyanate-based crosslinking agent (C) contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane diisocyanate. alicyclic polyisocyanates, etc., and their biuret and isocyanurate forms, as well as adducts that are reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Sieves, etc. may be mentioned. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates, especially trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable. In addition, the isocyanate-based crosslinking agent (C) can be used individually or in combination of two or more types.

The content of the isocyanate-based crosslinking agent (C) in the adhesive composition P is preferably 0.05 parts by mass or more as a lower limit with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially preferably 0.1 parts by mass or more. is preferably 0.2 parts by mass or more. If the lower limit of the content of the isocyanate-based crosslinking agent (C) is more than the above, it is presumed that the above-mentioned higher-order structure can be formed satisfactorily, and the resulting pressure-sensitive adhesive has better step followability under high temperature and high humidity. Moreover, the content of the isocyanate-based crosslinking agent (C) is preferably 3 parts by mass or less as an upper limit for 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially preferably 2 parts by mass or less, and furthermore, 1 part by mass. It is preferable that it is below. If the upper limit of the content of the isocyanate-based crosslinking agent (C) is below the above, the degree of crosslinking can be made appropriate, and the level difference followability of the obtained pressure-sensitive adhesive can be ensured well.

(4) Various additives

The adhesive composition P contains various additives commonly used in acrylic adhesives as desired, such as silane coupling agents, reaction accelerators, reaction inhibitors, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, A refractive index regulator, etc. may be added. In addition, the polymerization solvent and dilution solvent described later are not included in the additives constituting the adhesive composition P.

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

Examples of such silane coupling agents include silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane; Silicon compounds having an epoxy structure such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyl Mercapto group-containing silicon compounds such as dimethoxymethylsilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3 -Silicon compounds containing amino groups such as aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, or at least one of these, methyltriethoxysilane, and ethyltriethoxysilane. , condensates of alkyl group-containing silicon compounds such as methyltrimethoxysilane and ethyltrimethoxysilane. These may be used individually by 1 type, or may be used in combination of 2 or more types.

When the adhesive composition P contains a silane coupling agent, the content is preferably 0.01 parts by mass or more as a lower limit for 100 parts by mass of the (meth)acrylic acid ester polymer (A), and especially preferably 0.05 parts by mass or more, and further. It is preferable that it is 0.1 mass part or more. Moreover, the content of the silane coupling agent is preferably 1 part by mass or less as an upper limit, especially preferably 0.5 part by mass or less, and more preferably 0.3 part by mass or less.

(5) Preparation of adhesive composition

Adhesive composition P is prepared by preparing a (meth)acrylic acid ester polymer (A), mixing the obtained (meth)acrylic acid ester polymer (A), a polyrotaxane compound (B), and an isocyanate-based crosslinking agent (C). , can be prepared by adding additives as desired.

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

Examples of polymerization initiators include azo-based compounds and organic peroxides, and two or more types may be used in combination. Examples of azo compounds 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), dimethyl2,2'-azo Bis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azo Bis[2-(2-imidazoline-2-yl)propane] etc. can be mentioned.

Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide, etc.

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

Once the (meth)acrylic acid ester polymer (A) has been obtained, add a polyrotaxane compound (B), an isocyanate-based crosslinking agent (C), and a diluting solvent and additives as desired to the solution of the (meth)acrylic acid ester polymer (A). By adding and thoroughly mixing, adhesive composition P (application solution) diluted with a solvent is obtained. In addition, when any of the above components is used in solid form or when precipitation occurs when mixed with other components in an undiluted state, the component must be dissolved or diluted individually in a diluting solvent beforehand. , may be mixed with other ingredients.

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, and 1-methoxy. -Alcohols such as 2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve-based solvents such as ethyl cellosolve. It is used.

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

〔adhesive〕

The adhesive according to the present embodiment is obtained by crosslinking the adhesive composition P. Crosslinking of the adhesive composition P can usually be performed by heat treatment. Additionally, this heat treatment can also serve as a drying treatment for volatilizing a diluting solvent or the like from a film of the adhesive composition P applied to a desired object.

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

After heat treatment, a curing period of about 1 to 2 weeks may be set at room temperature (for example, 23°C, 50%RH) as needed. If this curing period is necessary, the adhesive is formed after the curing period has elapsed. If the curing period is not necessary, the adhesive is formed after the heat treatment is completed.

By the heat treatment (and curing), the (meth)acrylic acid ester polymer (A) (and polyrotaxane compound (B)) is sufficiently crosslinked via the isocyanate-based crosslinking agent (C). The adhesive obtained in this way is excellent in step followability and can also exhibit high film strength.

The lower limit of the gel fraction of the adhesive according to the present embodiment is preferably 40% or more, more preferably 45% or more, particularly preferably 50% or more, and still more preferably 60% or more. If the lower limit of the gel fraction of the adhesive is greater than the above, the cohesive force of the adhesive increases and the film strength becomes higher. Moreover, the gel fraction of the adhesive according to the present embodiment is preferably 90% or less as an upper limit, especially preferably 85% or less, and more preferably 80% or less. If the upper limit of the gel fraction of the adhesive is the above or less, the adhesive does not become too hard and has better step followability. Here, the method for measuring the gel fraction of the adhesive is as shown in the test example described later.

The 1000% modulus of the adhesive when a tensile test was performed at 23°C for the adhesive related to this embodiment (the modulus at fracture when fractured before reaching 1000% elongation; hereinafter simply referred to as “modulus at fracture”) In some cases, the lower limit is preferably 0.22 MPa or more, especially 0.25 MPa or more, and more preferably 0.27 MPa or more. When the lower limit of the 1000% modulus (or modulus at break) is above, the film strength as an adhesive layer is high and processability is excellent. For example, when punching an adhesive sheet, the occurrence of problems such as the adhesive sticking to the blade and part of the adhesive layer falling off is suppressed. Additionally, oozing of the adhesive from the adhesive layer, such as during storage of the adhesive sheet, is suppressed. The above 1000% modulus (or modulus at break) can be sufficiently achieved by using the adhesive composition P according to the present embodiment. Additionally, the upper limit of the 1000% modulus (or modulus at break) is not particularly limited, but is usually preferably 2.0 MPa or less, and especially 1.0 MPa or less. Here, the details of the tensile test are as shown in the test examples described later.

[Adhesive sheet]

The pressure-sensitive adhesive sheet according to the present embodiment has at least one display body member having a step on the surface on the side to be bonded, and an adhesive layer for bonding the other display body members, and the pressure-sensitive adhesive layer is made of the above-described pressure-sensitive adhesive. It will come true.

A specific configuration as an example of the adhesive sheet according to this embodiment is shown in FIG. 1.

As shown in FIG. 1, the adhesive sheet 1 according to one embodiment includes two peeling sheets 12a and 12b, and the two peeling sheets 12a and 12b are peeled off so as to contact the peeling surfaces of the two peeling sheets 12a and 12b. It is composed of an adhesive layer 11 sandwiched between sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to the surface of the release sheet that has peelability, and includes both a surface that has been subjected to a peeling treatment and a surface that exhibits peelability even without performing a peeling treatment.

(1) Adhesive layer

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

The thickness of the adhesive layer 11 in the adhesive sheet 1 according to the present embodiment (value measured according to JIS K7130) is preferably 10 μm or more as a lower limit, more preferably 25 μm or more, and especially 50 μm or more. It is preferable to be ㎛ or more. If the lower limit of the thickness of the adhesive layer 11 is more than the above, the desired adhesive strength can be easily achieved, and sufficient level difference followability can be ensured with respect to the normal level differences of the display body constituent members. Moreover, the upper limit of the thickness of the adhesive layer 11 is preferably 1000 μm or less, more preferably 400 μm or less, and especially preferably 300 μm or less. If the upper limit of the thickness of the adhesive layer 11 is equal to or less than the above, the processability is good. Additionally, the adhesive layer 11 may be formed as a single layer or may be formed by laminating multiple layers.

(2) Release sheet

The release sheets 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive 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 polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, and polyethylene film. Phthalate 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, polycarbonate Films, polyimide films, fluororesin films, etc. are used. Additionally, these crosslinked films are also used. Additionally, these laminated films may be used.

It is preferable that the peeling surface of the peeling sheets 12a and 12b (particularly the surface in contact with the adhesive layer 11) is subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Furthermore, among the release sheets 12a and 12b, it is preferable that one of the release sheets is a heavy release type release sheet with a large release force, and that the other release sheet is a light release type release sheet with a small release force.

There is no particular limitation on the thickness of the release sheets 12a and 12b, but it is usually about 20 to 150 μm.

(3) Physical properties

(3-1) Step tracking rate

The pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment preferably has a step tracking ratio (%) expressed by the following formula of 30% or more as a lower limit, especially preferably 40% or more, and furthermore 50%. It is preferable that it is % or more. Moreover, the upper limit of the step tracking rate is not particularly limited, but is usually preferably 80% or less, and especially 70% or less.

Step follow-up rate (%) = {(Height of step (㎛) in which there are no bubbles, lifting, peeling, etc. after the prescribed durability test and the buried state is maintained) / (thickness of adhesive layer)} × 100

In addition, the test method for the step tracking ratio is as shown in the test example described later.

As described above, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment is made by bonding display structural members having steps on the surface on the side to be bonded. When the level difference tracking rate of the adhesive layer is within the above range, the adhesive layer follows well the level difference of the display member, and the occurrence of bubbles, lifting, peeling, etc. near the level difference is suppressed even after an endurance test, This suppresses reflection loss of light.

(3-2) Haze value

The haze value of the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and still more preferably 0.7% or less. do. If the haze value of the adhesive layer 11 is 5% or less, transparency is very high and it is preferable for optical use (for display). In addition, the haze value in this specification is a value measured according to JIS K7136:2000.

(3-3) Adhesion

The lower limit of the adhesive force of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 5 N/25 mm or more, particularly preferably 10 N/25 mm or more, and further preferably 15 N/25 mm or more. . If the adhesive force of the adhesive sheet 1 is 5 N/25 mm or more, the level difference followability under high temperature and high humidity becomes more excellent. In addition, the upper limit of the adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 50 N/25 mm or less, more preferably 40 N/25 mm or less, and particularly preferably 35 N/25 mm or less. And, it is more preferable that it is 25N/25mm or less. If the adhesive force of the adhesive sheet 1 is 50 N/25 mm or less, it is possible to prevent the adhesive from adhering to the blade during cutting, and if it is 25 N/25 mm or less, good reworkability is obtained, preventing bonding errors from occurring. In this case, it becomes possible to reuse expensive display structural members.

Here, the adhesive force in this specification basically refers to the adhesive force measured by the 180 degree peeling method according to JIS Z0237:2009. The measurement sample is 25 mm wide and 100 mm long, and the measurement sample is the adherend. , pressurized at 0.5 MPa and 50°C for 20 minutes, left for 24 hours under conditions of normal pressure, 23°C and 50%RH, and then measured at a peeling speed of 300 mm/min.

(4) Manufacturing of adhesive sheets

As an example of manufacturing the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one release sheet 12a (or 12b), heat treatment is performed to heat-crosslink the adhesive composition P, and then applied. After forming the layer, the peeling surface of the other peeling sheet 12b (or 12a) is overlaid on the applied layer. When a curing period is necessary, a curing period is provided, and when a curing period is not necessary, the application layer becomes the adhesive layer 11 as is. As a result, the pressure-sensitive adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another manufacturing example of the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one release sheet 12a, heat treatment is performed to heat crosslink the adhesive composition P, and an application layer is formed, A release sheet 12a with an application layer formed thereon is obtained. Additionally, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat treatment is performed to heat crosslink the adhesive composition P, and an application layer is formed, and the release sheet 12b with the application layer is formed. ) to get Then, the release sheet 12a with the application layer and the release sheet 12b with the application layer are bonded so that both application layers contact each other. When a curing period is necessary, a curing period is provided, and when a curing period is not necessary, the laminated application layer becomes the adhesive layer 11 as is. As a result, the pressure-sensitive adhesive sheet 1 is obtained. According to this manufacturing example, even when the adhesive layer 11 is thick, it can be manufactured stably.

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

In the adhesive sheet 1 according to the present embodiment, the film strength of the adhesive layer 11 is high, so that when the adhesive sheet 1 is punched or processed, the adhesive adheres to the blade and a portion of the adhesive layer 11 is formed. Problems such as falling out are suppressed. Additionally, oozing of the adhesive from the adhesive layer 11, such as when storing the adhesive sheet 1, is also suppressed.

〔Display type〕

As shown in FIG. 2, the display body 2 according to the present embodiment includes a first display body member 21 (one display body member) having a step at least on the surface on the side to be joined, and a second display body member 21. A display structural member 22 (another display structural member) and an adhesive layer 11 located between them and bonding the first display structural member 21 and the second display structural member 22 to each other. It is comprised of: In the display body 2 according to the present embodiment, the first display body member 21 has a step on the surface on the adhesive layer 11 side, and specifically has a step due to the printing layer 3. there is.

The adhesive layer 11 in the display body 2 is the adhesive layer 11 of the adhesive sheet 1 described above.

Examples of the display body 2 include liquid crystal (LCD) displays, light emitting diode (LED) displays, organic electroluminescence (organic EL) displays, electronic paper, etc., and may be a touch panel. Additionally, the display body 2 may be a member constituting a part of them.

The first display structural member 21 is preferably a protection panel made of a glass plate, a plastic plate, etc., as well as a laminate containing them. In this case, the printing layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the first display body member 21.

The glass plate is not particularly limited and includes, for example, chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, glass containing barium/strontium, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, etc. You can. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, and preferably 0.2 to 2 mm.

The plastic plate is not particularly limited, and examples include acrylic plates and polycarbonate plates. The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5 mm, and preferably 0.4 to 3 mm.

Additionally, 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, and optical members may be laminated. Additionally, the transparent conductive film and metal layer may be patterned.

The second display structural member 22 is an optical member to be attached to the first display structural member 21, a display module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electrolyte It is preferable that it is a laminate containing a luminescence (organic EL) module, etc.), an optical member as part of a display module, or a display module.

Examples of the optical member include an anti-shatter film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a transflective reflective film. , transparent conductive films, etc. Examples of the anti-scattering film include a hard coat film in which a hard coat layer is formed on one side of a base film.

The material constituting the printing layer 3 is not particularly limited, and known materials for printing are used. The lower limit of the thickness of the printed layer 3, that is, the height of the step, 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 greater than or equal to the above, sufficient concealment, such as making the electric wiring invisible from the viewer, can be ensured. Moreover, the upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and still more preferably 20 μm or less. When the upper limit is below the above, it is possible to prevent deterioration of the level difference followability of the adhesive layer 11 with respect to the printing layer 3.

In order to manufacture the display body 2, as an example, one release sheet 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is used to form the first display body. It is bonded to the surface of the member 21 on the side where the printed layer 3 is present. At this time, since the adhesive layer 11 has excellent level difference followability, the occurrence of gaps or floaters near the level difference caused by the printing layer 3 is suppressed.

Thereafter, the other release sheet 12b is peeled from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 and the second display body member 22 are separated. Join together. As another example, the order of joining the first display body member 21 and the second display body member 22 may be changed.

In the above display body 2, since the pressure-sensitive adhesive layer 11 has excellent step followability even under high temperature and high humidity conditions, the display body 2 can be used under high temperature and high humidity conditions (e.g., 85° C., 85° C. Even when placed at %RH), the occurrence of bubbles, lifting, peeling, etc. near the level difference is suppressed.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within 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. Additionally, the first display body member 21 may have steps other than those of the printing layer 3. Furthermore, not only the first display body member 21 but also the second display body member 22 may have a step on the adhesive layer 11 side.

[Example]

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

[Example 1]

1. Preparation of (meth)acrylic acid ester polymer

60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of isobornyl acrylate, 5 parts by mass of 4-acryloylmorpholine, and 15 parts by mass of 2-hydroxyethyl acrylate were copolymerized to produce (meth)acrylic acid ester polymer (A). It was prepared. The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was 600,000.

2. Preparation of adhesive composition

100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in the above step 1 (solid content conversion value; the same below), and polyrotaxane compound (B) (manufactured by Advanced Soft Materials, product name "Serum Superpolymer SH3400P", Straight chain molecule: polyethylene glycol, cyclic molecule: α-cyclodextrin with hydroxypropyl group and caprolactone chain, block group: adamantane group, weight average molecular weight (Mw) 700,000, hydroxyl group 72 mgKOH/g) 3.0 parts by mass, 0.25 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Corporation, product name “Coronate L”) as an isocyanate-based crosslinking agent (C), and 3-glycidoxypropyltrimethoxy as a silane coupling agent. 0.25 parts by mass of silane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") was mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition with a solid content concentration of 40% by mass.

Here, Table 1 shows each formulation (solid content conversion value) of the adhesive composition when the (meth)acrylic acid ester polymer (A) is 100 parts by mass (solid content conversion value). In addition, details such as the abbreviations listed in Table 1 are as follows.

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

2EHA: 2-ethylhexyl acrylate

IBXA: Isobornyl acrylate

ACMO: 4-acryloylmorpholine

HEA: 2-hydroxyethyl acrylate

BA: n-butyl acrylate

MMA: Methyl methacrylate

CHA: Cyclohexyl acrylate

MA: Methyl acrylate

[Isocyanate-based crosslinking agent (C)]

TDI: Trimethylolpropane modified tolylene diisocyanate (manufactured by Nippon Polyurethane Corporation, product name “Coronate L”)

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

3. Preparation of adhesive sheet

The coating solution of the adhesive composition obtained in step 2 above was applied to the peeled surface of a medium-release type release sheet (manufactured by Lintec, product name "SP-PET752150"), where one side of the polyethylene terephthalate film was peeled with a silicone-based release agent, using a knife coater. applied. Then, the application layer was heat treated at 90°C for 1 minute to form an application layer.

Next, the application layer on the heavy release type release sheet obtained above and one side of the polyethylene terephthalate film were treated to release with a silicone-based release agent (manufactured by Lintec, product name "SP-PET382120"), and the light release type release sheet was prepared. The product consists of a heavy release type release sheet/adhesive layer (thickness: 25㎛)/light release type release sheet by bonding the release treatment surface in contact with the application layer and curing for 7 days under conditions of 23°C and 50%RH. 1 An adhesive sheet was produced.

In addition, the coating solution of the adhesive composition obtained in step 2 above was applied to the peeling surface of a medium-release type release sheet (manufactured by Lintec, product name "SP-PET752150"), where one side of the polyethylene terephthalate film was peeled with a silicone-based release agent, using a knife. After application with a coater, heat treatment was performed at 90°C for 1 minute to form an application layer (thickness: 25 μm). Similarly, the coating solution of the adhesive composition obtained in Step 2 above was applied to the peeling surface of a light release type release sheet (manufactured by Lintec, product name "SP-PET382120"), where one side of a polyethylene terephthalate film was peeled with a silicone-based release agent, using a knife. After applying with a coater, heat treatment was performed at 90°C for 1 minute to form an application layer (thickness: 25 μm).

Next, the heavy release type release sheet with the application layer obtained above and the light release type release sheet with the application layer obtained above are bonded so that both application layers are in contact with each other, and cured for 7 days under conditions of 23° C. and 50% RH. By doing this, a second adhesive sheet consisting of a heavy release type release sheet/adhesive layer (thickness: 50 μm)/light release 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 Teclac Co., Ltd.) in accordance with JIS K7130.

[Examples 2 to 15, Comparative Examples 1 to 5]

The type and ratio of each monomer constituting the (meth)acrylic acid ester polymer (A), the weight average molecular weight of the (meth)acrylic acid ester polymer (A), the compounding amount of the polyrotaxane compound (B), and the isocyanate-based crosslinking agent (C) An adhesive sheet was manufactured in the same manner as in Example 1, except that the type, mixing amount, and mixing amount of the silane coupling agent were changed as shown in Table 1.

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

＜Measurement conditions＞

· GPC measurement device: HLC-8020 manufactured by Tosoh Corporation

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

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

· Measurement solvent: tetrahydrofuran

· Measurement temperature: 40℃

[Test Example 1] (Measurement of gel fraction)

The first adhesive sheet (thickness of the adhesive layer: 25 μm) obtained in the examples and comparative examples was cut into a size of 80 mm × 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was was weighed using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is set to 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, air-dried for 24 hours in an environment with 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 using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is set to M2. The gel fraction (%) is expressed as (M2/M1) x 100. The results are shown in Table 2.

[Test Example 2] (Measurement of haze value)

For the adhesive layer of the first adhesive sheet (thickness of the adhesive layer: 25 μm) obtained in the examples and comparative examples, a haze meter (manufactured by Nippon Denshoku Kogyo, product name “NDH-2000”) was measured in accordance with JIS K7136:2000. The haze value (%) was measured using The results are shown in Table 2.

[Test Example 3] (Measurement of 1000% modulus (or modulus at break))

The adhesive layer of the second adhesive sheet (thickness of adhesive layer: 50 μm) obtained in the examples and comparative examples was laminated in multiple layers to a total thickness of 600 μm, and then a sample of 10 mm width × 75 mm length was cut. The sample was set in a tensile tester (manufactured by Orientec, product name "Tensilon") so that the sample measurement area was 10 mm wide x 20 mm long (in the direction of elongation), and tested on the tensile tester in an environment of 23°C and 50%RH. was stretched at a tensile speed of 200 mm/min, and the stress value at which the elongation rate was 1000% was measured as 1000% modulus (MPa). In addition, when the material fractured before the elongation reached 1000%, the stress value at the time of fracture was measured (modulus at the time of fracture). The results are shown in Table 2 (in Table 2, the modulus at break is indicated in parentheses).

[Test Example 4] (Measurement of adhesive force)

The light-release type release sheet was peeled from the first adhesive sheet (thickness of the adhesive layer: 25 μm) obtained in the examples and comparative examples, and the exposed adhesive layer was replaced with a polyethylene terephthalate (PET) film (Toyobo Co., Ltd.) having an easy-adhesion layer. It was bonded to an easy-adhesion layer (manufactured, product name: “PET A4300”, thickness: 100 μm) to obtain a laminate of release sheet/adhesive layer/PET film. The obtained laminate was cut to 25 mm in width and 100 mm in length, and this was used as a sample.

In an environment of 23°C and 50%RH, the medium-release type release sheet was peeled from the sample, the exposed adhesive layer was attached to soda-lime glass (manufactured by Nippon Plate Glass Co., Ltd.), and then placed in an autoclave manufactured by Kurihara Seisakusho Co., Ltd. for 0.5 degrees Celsius. It was pressurized at MPa and 50°C for 20 minutes. Afterwards, after leaving it for 24 hours under the conditions of 23°C and 50%RH, the adhesive force (N/ 25 mm) was measured. Conditions other than those described here were measured in accordance with JIS Z 0237:2009. The results are shown in Table 2.

[Test Example 5] (Measurement of step tracking rate)

Apply ultraviolet curable ink (manufactured by Teikoku Ink, product name “POS-911 Ink”) to the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle It was screen-printed on a frame (outer shape: 90 mm long x 50 mm wide, 5 mm wide) so that the application thickness was one of 5 ㎛, 10 ㎛, 15 ㎛, 20 ㎛, and 25 ㎛. Next, ultraviolet rays are irradiated (80 W/cm2, metal halide lamp 2 lights, lamp height 15 cm, belt speed 10 to 15 m/min) to cure the printed ultraviolet curable ink, thereby reducing the level difference caused by printing. A glass plate with a step height of 5㎛, 10㎛, 15㎛, 20㎛, and 25㎛ was produced.

The light release type release sheet was peeled from the second adhesive sheet (thickness of the adhesive layer: 50 μm) obtained in the examples and comparative examples, and the exposed adhesive layer was replaced with a polyethylene terephthalate film (manufactured by Toyobo Corporation, product name) having an easy-adhesion layer. It was bonded to an easy-adhesion layer of "PET A4300" (thickness: 100 μm). Next, the heavy release type release sheet was peeled off, and the adhesive layer was exposed. Then, using a laminator (manufactured by Fuji Plastics, product name "LPD3214"), the above-mentioned laminate was laminated on a glass plate on which each step was formed so that the adhesive layer covered the entire printed surface on the frame, and this was used as a sample for evaluation.

The obtained evaluation sample was autoclaved for 30 minutes at 50°C and 0.5 MPa, and then left at normal pressure, 23°C, and 50%RH for 24 hours. Next, it was stored under high temperature and high humidity conditions of 85°C and 85%RH for 72 hours (durability test), and then the level difference followability was evaluated. Step followability is judged by whether or not the printing step is completely buried by the adhesive layer. If bubbles, lifting, peeling, etc. are observed at the interface between the printing step and the adhesive layer, it is judged that the printing step cannot be followed. . Here, step followability was evaluated as step followability (%) expressed by the following formula. The results are shown in Table 2.

Step tracking rate (%) = {(After the durability test, there are no bubbles, lifting, peeling, etc., and the height of the step that remains embedded (㎛)) / (Thickness of adhesive layer: 50㎛)} × 100

[Test Example 6] (Evaluation of cut aptitude)

Multiple layers of the adhesive layer of the second adhesive sheet (thickness of the adhesive layer: 50 μm) obtained in the examples and comparative examples were laminated to obtain a laminate with a total thickness of 1 mm. The laminate was cut using a cutting device (product name "Super Cutter PN1-600", manufactured by Ogi no Seisakusho Co., Ltd.). The cut surface (length: 100 mm) of the adhesive layer after cutting was visually confirmed, and the cut suitability was evaluated based on the following standards. The results are shown in Table 2.

○: No peeling of the adhesive layer on the cut surface.

△: There is some peeling of the adhesive layer on the cut surface (less than 10% of the cut surface).

×: Adhesive layer is missing from the cut surface (10% or more of the cut surface)

As can be seen from Table 2, the pressure-sensitive adhesive sheets obtained in the examples had excellent step followability and good cut aptitude, that is, high film strength.

The adhesive sheet of the present invention can be suitably used, for example, for bonding a protective panel having steps and a desired display body member.

1: Adhesive sheet
11: Adhesive layer
12a, 12b: release sheet
2: indicator
21: First display member
22: Second display member
3: Printing layer

Claims (10)

As a monomer unit constituting the polymer, a (meth)acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer and an alicyclic structure-containing monomer,
A polyrotaxane compound (B) having a cyclic oligosaccharide as a cyclic molecule,
Isocyanate-based crosslinking agent (C)
Contains,
An adhesive composition characterized in that the alicyclic structure-containing monomer has a polycyclic alicyclic structure. The (meth)acrylic acid ester polymer (A) according to claim 1, wherein the monomer unit constituting the polymer is (meth) whose alkyl group has 5 to 20 carbon atoms in addition to the hydroxyl group-containing monomer and the alicyclic structure-containing monomer. An adhesive composition characterized by containing 10% by mass or more and 90% by mass or less of an acrylic acid alkyl ester. The adhesive composition according to claim 1, wherein the (meth)acrylic acid ester polymer (A) contains 3% by mass or more and 30% by mass or less of the hydroxyl group-containing monomer as a monomer unit constituting the polymer. The adhesive according to claim 1, wherein the (meth)acrylic acid ester polymer (A) contains 1% by mass or more and 50% by mass or less of the alicyclic structure-containing monomer as a monomer unit constituting the polymer. Composition. The adhesive composition according to claim 1, wherein the (meth)acrylic acid ester polymer (A) has a weight average molecular weight of 100,000 or more and 900,000 or less. The content of the polyrotaxane compound (B) in the adhesive composition according to claim 1, wherein the content of the polyrotaxane compound (B) is 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A). Adhesive composition. An adhesive obtained by crosslinking the adhesive composition according to any one of claims 1 to 6. An adhesive sheet having one display component having a step at least on the side to be bonded, and an adhesive layer for bonding the other display component,
The adhesive layer is made of the adhesive according to claim 7.
An adhesive sheet characterized in that. The adhesive sheet according to claim 8, wherein the adhesive sheet includes two release sheets,
The adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets.
An adhesive sheet characterized in that. One display body member having a step at least on the surface of the side to be joined,
Other indicator constituent members,
An adhesive layer that bonds the one display member and the other display member to each other.
As a display body provided with,
The adhesive layer is an adhesive layer of the adhesive sheet according to claim 8.
A display body characterized by: