JP6805014B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive and an adhesive sheet, and more particularly to an adhesive and an adhesive sheet suitable for adhering display body constituent members.

In recent years, a liquid crystal panel is often used as a display body (display). In such a liquid crystal panel, a light diffusing member that diffuses the light of the light source is required in order to make the brightness of the backlight uniform. Further, in recent liquid crystal panels, problems such as glare, moire, and uneven liquid crystal are likely to occur due to the demand for high-definition image quality. From the viewpoint of solving such a problem with the pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer having light diffusivity is attracting attention.

As such a light-diffusing pressure-sensitive adhesive layer, for example, Patent Document 1 has (A) (a) (meth) acrylic acid ester-based copolymer and (b) a polymerizable unsaturated group in the side chain (b). A tacky resin component obtained by curing a mixture for forming a tacky resin containing (meth) an acrylic acid ester-based copolymer and (c) an energy ray-curable compound, and (B) an average particle size of 0.1 to 20 μm. A pressure-sensitive adhesive containing fine particles and having a storage elasticity (G') at 23 ° C. of 2 MPa or more and 20 MPa or less is disclosed.

Further, Patent Document 2 contains at least one type of alkyl (meth) acrylate monomer having an alkyl group having C1 to C14 carbon atoms, a hydroxyl group-containing copolymerizable monomer as a copolymerizable functional group-containing monomer, and a carboxyl group. A pressure-sensitive adhesive composition containing a copolymer containing at least one selected from the group consisting of a copolymerizable monomer, a nitrogen-containing vinyl monomer, and an aromatic-containing monomer, a cross-linking agent, and silicon-based particles (fine particles). A light diffusing pressure-sensitive adhesive layer formed from an object is disclosed.

Furthermore, Patent Document 3, (meth) acrylic polymer to (A), the refractive index n _b when the homopolymer is larger than the refractive index n _a of the (meth) acrylic polymer (A) A modified (meth) acrylate-based copolymer (B) obtained by blending and polymerizing a radically polymerizable monomer, specifically a monomer having an aromatic group such as a styrene monomer, a benzyl acrylate, or a phenoxyethyl acrylate; And a photodiffusive pressure-sensitive adhesive layer obtained by cross-linking a photodiffusive pressure-sensitive adhesive composition containing a cross-linking agent is disclosed.

Japanese Patent No. 5149533 JP-A-2015-86297 Japanese Unexamined Patent Publication No. 2010-159333

By the way, the liquid crystal panel usually includes a liquid crystal module and a protective panel for protecting the liquid crystal module. A gap is provided between the liquid crystal module and the protective panel so that the deformed protective panel does not collide with the display module even when the protective panel is deformed by an external force.

However, in the presence of the above-mentioned voids, that is, the air layer, the difference in the refractive index between the protective panel and the air layer and the difference in the refractive index between the air layer and the liquid crystal module cause a large loss of light reflection, and the image quality of the display There is a problem that

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the liquid crystal module with an adhesive layer. However, a frame-shaped print layer may exist as a step on the liquid crystal module side of the protective panel. If the pressure-sensitive adhesive layer does not follow the step, the pressure-sensitive adhesive layer floats in the vicinity of the step, which causes a loss of light reflection. Therefore, the pressure-sensitive adhesive layer is required to have a step followability.

When the pressure-sensitive adhesive layer disclosed in Patent Document 1 is used between the protective panel and the liquid crystal module, the pressure-sensitive adhesive layer has a high storage elastic modulus (G') of 2 MPa or more and 20 MPa or less, and is hard. , Not suitable for applications that require step followability as described above. Like the pressure-sensitive adhesive layer disclosed in Patent Document 1, the pressure-sensitive adhesive layer disclosed in Patent Document 2 also becomes hard due to the inclusion of fine particles, so that it is difficult to follow the step and the required step-following property is required. It is difficult to meet.

Further, when the pressure-sensitive adhesive contains fine particles as in Patent Documents 1 and 2, it is necessary to use a dedicated pipe or a dedicated pot when manufacturing the pressure-sensitive adhesive, and to other products that do not contain fine particles. There is also a risk of contamination. Further, it is necessary to disperse the fine particles in the pressure-sensitive adhesive, which causes not only the raw material cost of the fine particles but also the manufacturing cost to increase.

On the other hand, the pressure-sensitive adhesive layer that does not use fine particles of Patent Document 3 is preferable from the viewpoint that the above problems do not occur. However, since the pressure-sensitive adhesive layer becomes hard due to the modified (meth) acrylate-based copolymer (B) formed by polymerizing a monomer having an aromatic group, the step followability is also inferior.

The present invention has been made in view of the above-mentioned actual conditions, and an object of the present invention is to provide an adhesive and an adhesive sheet having excellent both light diffusivity and step followability.

In order to achieve the above object, firstly, the present invention comprises a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 300,000 or more and less than 1.5 million, a polyrotaxane compound (B), and a cross-linking agent. A pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition containing (C), wherein the (meth) acrylic acid ester polymer (A) is a hydroxyl group-containing monomer and a hydroxyl group-containing monomer as a monomer unit constituting the polymer. When at least one kind of carboxy group-containing monomer is contained and the hydroxyl group-containing monomer is contained, the hydroxyl group-containing monomer is contained in a content of less than 20% by mass, and when the carboxy group-containing monomer is contained. , The carboxy group is contained in a content of less than 15% by mass, the polyrotaxane compound (B) has a cyclic molecule containing a reactive group, and the gel content of the pressure-sensitive adhesive is 20% or more. Provided is a pressure-sensitive adhesive having a content of 99% or less (Invention 1).

In the above invention (Invention 1), the cross-linking agent adduct is obtained by reacting the reactive group of the cross-linking agent (C) with the reactive group of the cyclic molecule of the polyrotaxane compound (B). Since this cross-linking agent adduct has low compatibility with the (meth) acrylic acid ester polymer (A), the haze value of the obtained pressure-sensitive adhesive increases, whereby the pressure-sensitive adhesive has excellent light diffusivity. It becomes. In addition, the cross-linking agent adduct then reacts with the hydroxyl group or carboxy group of the (meth) acrylic acid ester polymer (A) to form a cross-linked structure. The pressure-sensitive adhesive having such a crosslinked structure has excellent flexibility due to the free movement of each cyclic molecule of the polyrotaxane compound (B) on the linear molecule, so that the obtained pressure-sensitive adhesive has excellent step-following property. It becomes a thing.

In the above invention (Invention 1), the content of the polyrotaxane compound (B) in the adhesive composition is 1 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). , 30 parts by mass or less is preferable (Invention 2).

In the above inventions (Inventions 1 and 2), the (meth) acrylic acid ester polymer (A) is a (meth) acrylic acid having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. It is preferable that the alkyl ester is contained in an amount of 30% by mass or more and 99% by mass or less (Invention 3).

In the above inventions (Inventions 1 to 3), the cross-linking agent (C) is preferably an isocyanate-based cross-linking agent (Invention 4).

The pressure-sensitive adhesive according to the above inventions (Inventions 1 to 4) preferably does not contain a filler.

Secondly, the present invention is an adhesive sheet comprising two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. Provided is a pressure-sensitive adhesive sheet, wherein the layer is made of the pressure-sensitive adhesive (Invention 1 to 4) (Invention 5).

In the above invention (Invention 5), the haze value of the pressure-sensitive adhesive layer is preferably 30% or more and 90% or less (Invention 6).

The pressure-sensitive adhesive and the pressure-sensitive adhesive sheet according to the present invention are excellent in both light diffusivity and step-following property.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing of the display body which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive]
The pressure-sensitive adhesive according to the present embodiment contains a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 300,000 or more and less than 1.5 million, a polyrotaxane compound (B), and a cross-linking agent (C). This is a pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition (hereinafter, may be referred to as “sticky composition P”). The (meth) acrylic acid ester polymer (A) contains at least one of a hydroxyl group-containing monomer and a carboxy group-containing monomer as a monomer unit constituting the polymer, and when the hydroxyl group-containing monomer is contained, the said The hydroxyl group-containing monomer is contained in a content of less than 20% by mass, and when the carboxy group-containing monomer is contained, the carboxy group is contained in a content of less than 15% by mass. The polyrotaxane compound (B) has a cyclic molecule containing a reactive group. The gel fraction of the pressure-sensitive adhesive is 20% or more and 99% or less. In addition, in this specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the concept of "polymer" shall be included in "polymer".

When the adhesive composition P is crosslinked, the reactive group of the crosslinking agent (C) reacts with the reactive group of the cyclic molecule of the polyrotaxane compound (B). Since the cross-linking agent adduct formed by the reaction has low compatibility with the (meth) acrylic acid ester polymer (A), the haze value of the obtained pressure-sensitive adhesive is increased. The other reactive group of the cross-linking agent (C) added to the cross-linking agent addition is subsequently a hydroxyl group derived from the hydroxyl group-containing monomer of the (meth) acrylic acid ester polymer (A) or a carboxy group derived from the carboxy group-containing monomer. Also reacts to form a crosslinked structure. Since the contents of the hydroxyl group-containing monomer and the carboxy group-containing monomer are relatively small, the (meth) acrylic acid ester polymers (A) are reactive groups of the cross-linking agent (C) without interposing the polyrotaxane compound (B). It is presumed that the cross-linking agent adduct of the above-mentioned polyrotaxane compound (B) is preferentially formed rather than directly reacting with, whereby the haze value of the obtained pressure-sensitive adhesive is increased.

Here, the polyrotaxane compound (B) has a mechanical bond between the cyclic molecule and the linear molecule penetrating the cyclic molecule, and the cyclic molecule can freely move on the linear molecule. ing. The (meth) acrylic acid ester polymer (A) is bonded to one cyclic molecule of the polyrotaxane compound (B) via the cross-linking agent (C) in the cross-linking agent adduct by the hydroxyl group or carboxy group of the polymer. Similarly, it is presumed that another (meth) acrylic acid ester polymer (A) binds to another cyclic molecule of the polyrotaxane compound (B). As a result, a structure (crosslinked structure) in which the plurality of (meth) acrylic acid ester polymers (A) are crosslinked via the polyrotaxane compound (B) having the above mechanical bond is formed. The pressure-sensitive adhesive according to the present embodiment can be designed to be soft because it does not require fine particles, and by including the above-mentioned crosslinked structure, it is excellent in stress relaxation property and step followability.

It is not necessary that all of the obtained pressure-sensitive adhesives have the above-mentioned structure, and the two (meth) acrylic acid ester polymers (A) are directly bonded by the cross-linking agent (C) without the intervention of the polyrotaxane compound (B). It may include a structure or the like.

As described above, the pressure-sensitive adhesive according to the present embodiment having the above composition and gel fraction is excellent in both light diffusivity and step-following property because it has a high haze value and can be designed softly. Specifically, the pressure-sensitive adhesive according to this embodiment can achieve a haze value of 30% or more. Further, when the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive according to the present embodiment is attached to a display body component having a step, it easily follows the step, and it is possible to prevent gaps, floats, etc. from occurring in the vicinity of the step. .. Further, even when the product is left in that state under high temperature and high humidity conditions, for example, 85 ° C. and 85% RH conditions for 72 hours, the occurrence of bubbles, floats, peeling, etc. in the vicinity of the step is suppressed.

In addition, according to the adhesive according to the present embodiment, a high haze value can be obtained without using fine particles, so that it is not necessary to use a dedicated pipe or a dedicated kettle, and the adhesive does not contain fine particles. There is no risk of product contamination. Further, since it is not necessary to disperse the fine particles as a raw material in the pressure-sensitive adhesive, the cost can be reduced.

(1) Each component (1-1) (meth) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) in the present embodiment contains at least one of a hydroxyl group-containing monomer and a carboxy group-containing monomer as a monomer unit constituting the polymer.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth). ) (Meta) Acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, it is reactive with the cross-linking agent (C) and with other monomers among the above. 2-Hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is preferable from the viewpoint of copolymerizability. These may be used alone or in combination of two or more.

When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, the content thereof is less than 20% by mass, preferably 18% by mass or less. , Particularly preferably 15% by mass or less. When the content of the hydroxyl group-containing monomer is 20% by mass or more, the hydroxyl group of the hydroxyl group-containing monomer reacts with the reactive group of the cross-linking agent (C) and the reactive group of the cyclic molecule of the polyrotaxane compound (B). It interferes with the increase in haze value due to the cross-linking agent addition of the polyrotaxane compound (B). Further, from the viewpoint of obtaining a higher haze value while maintaining good step followability of the obtained pressure-sensitive adhesive, the content of the hydroxyl group-containing monomer is more preferably 10% by mass or less, and more preferably 4% by mass or less. It is more preferable, and it is particularly preferable that it is 2% by mass or less.

When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, the content thereof is preferably 0.1% by mass or more, particularly. It is preferably 0.3% by mass or more, and more preferably 0.5% by mass or more. When the content of the hydroxyl group-containing monomer is 0.1% by mass or more, the above-mentioned crosslinked structure is formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive has excellent cohesive power while maintaining stress relaxation property.

Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. When the (meth) acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the polymer, among the above, from the viewpoint of the adhesive strength of the obtained pressure-sensitive adhesive, the cross-linking agent (C) Acrylic acid is preferable from the viewpoint of reactivity with and the effect on the reaction between the hydroxyl group derived from the hydroxyl group-containing monomer and the cross-linking agent (C), and copolymerizability with other monomers. These may be used alone or in combination of two or more.

When the (meth) acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the polymer, the content thereof shall be less than 15% by mass and 10% by mass or less. Is preferable, and particularly preferably 5% by mass or less. When the content of the carboxy group-containing monomer is 15% by mass or more, the carboxy group of the carboxy group-containing monomer becomes the reactive group of the cross-linking agent (C) and the reactive group of the cyclic molecule of the polyrotaxane compound (B). This will interfere with the reaction of the polyrotaxane compound (B) and inhibit the increase in haze value due to the formation of the cross-linking agent adduct of the polyrotaxane compound (B).

When the (meth) acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the polymer, the content thereof is preferably 0.1% by mass or more. In particular, it is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. When the content of the carboxy group-containing monomer is 0.1% by mass or more, the above-mentioned crosslinked structure is formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive has excellent cohesive power while maintaining stress relaxation property.

The (meth) acrylic acid ester polymer (A) preferably contains a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. It is possible to develop preferable stickiness. The alkyl group may be linear or branched chain, or may have a cyclic structure.

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, and n- (meth) acrylic acid. Butyl, n-pentyl (meth) acrylic acid, n-hexyl (meth) acrylic acid, 2-ethylhexyl (meth) acrylic acid, isooctyl (meth) acrylic acid, n-decyl (meth) acrylic acid, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate. These may be used alone or in combination of two or more.

Among the above, the (meth) acrylic acid ester polymer (A) preferably contains a (meth) acrylic acid alkyl ester having an alkyl group having 5 to 20 carbon atoms as a monomer unit constituting the polymer. .. By including the (meth) acrylic acid alkyl ester having a large number of carbon atoms as a constituent monomer unit, the hydrophobicity of the (meth) acrylic acid ester polymer (A) is increased, and a cross-linking agent is added to the polyrotaxane compound (B). The compatibility with the substance is further reduced, and the haze value of the obtained adhesive is further improved.

Among the (meth) acrylic acid alkyl esters having 5 to 20 carbon atoms in the alkyl group, a monomer (hard monomer) having a glass transition temperature (Tg) exceeding 0 ° C. as a homopolymer and a glass transition as a homopolymer are particularly present. It is preferable to use it in combination with a monomer (soft monomer) having a temperature (Tg) of 0 ° C. or lower. This is because the cohesive force can be improved with the hard monomer while ensuring the adhesiveness and flexibility with the soft monomer, so that the step followability under high temperature and high humidity conditions can be further improved. In this case, the mass ratio of the hard monomer to the soft monomer is preferably 5:95 to 40:60, and particularly preferably 20:80 to 30:70.

As the hard monomer, a (meth) acrylic acid alkyl ester having an alicyclic structure in the molecule is preferable, and a (meth) acrylic acid alkyl ester having a plurality of alicyclic structures is more preferable. For example, isobornyl acrylate (Tg 94 ° C.), isobornyl methacrylate (Tg 180 ° C.), adamantyl acrylate (Tg 115 ° C.), adamantyl methacrylate (Tg 141 ° C.) and the like can be mentioned. Among the above-mentioned hard monomers, isobornyl acrylate is preferable from the viewpoint of further exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesiveness.

As the soft monomer, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group is preferably mentioned. Specifically, 2-ethylhexyl acrylate (Tg-70 ° C.) is particularly preferable. That is, as a combination of the hard monomer and the soft monomer, a combination of isobornyl acrylate and 2-ethylhexyl acrylate is particularly preferable.

The (meth) acrylic acid ester polymer (A) preferably contains 30% by mass or more of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. In particular, it is preferably contained in an amount of 50% by mass or more, and more preferably 80% by mass or more. When the (meth) acrylic acid alkyl ester is contained in an amount of 30% by mass or more, the (meth) acrylic acid ester polymer (A) can exhibit suitable adhesiveness. Further, the (meth) acrylic acid ester polymer (A) contains 99% by mass or less of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. Is preferable, and it is particularly preferable to contain 98% by mass or less, and further preferably 96% by mass or less. By adjusting the amount of the (meth) acrylic acid alkyl ester to 99% by mass or less, a suitable amount of other monomer components can be introduced into the (meth) acrylic acid ester polymer (A).

Further, the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms preferably contains a (meth) acrylic acid alkyl ester having an alkyl group having 5 to 20 carbon atoms. When a (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms is contained in the alkyl group, the alkyl group has 5 carbon atoms in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms. The content ratio of the (meth) acrylic acid alkyl ester of ~ 20 is preferably 5% by mass or more, particularly preferably 20% by mass or more, and further preferably 40% by mass or more. As a result, the above-mentioned haze value improving effect is satisfactorily exhibited as well as the adhesiveness. On the other hand, the content ratio is preferably 100% by mass or less, particularly preferably 95% by mass or less, and further preferably 70% by mass or less. When the content ratio is 95% by mass or less, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms can be contained. Thereby, the (meth) acrylic acid ester polymer (A) can be made hard and the hydrophobicity can be finely adjusted. In particular, when only the above-mentioned soft monomer is used as the (meth) acrylic acid alkyl ester having an alkyl group having 5 to 20 carbon atoms, the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms coexists. It is preferable to let it.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. As the other monomer, a monomer containing no functional group having reactivity is preferable so as not to inhibit the action of the above-mentioned hydroxyl group-containing monomer and carboxy group-containing monomer. Examples of the functional group-free monomer having such reactivity include (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and vinyl acetate. These may be used alone or in combination of two or more.

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 300,000 or more and less than 1.5 million. When the weight average molecular weight is 1.5 million or more, the obtained adhesive becomes hard and the step followability is lowered. Further, when the weight average molecular weight is less than 300,000, the cohesive force of the obtained adhesive is lowered, and the step followability under high temperature and high humidity conditions is lowered.

From this point of view, the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 400,000 or more, and particularly preferably 500,000 or more. The weight average molecular weight is preferably 1.3 million or less, and particularly preferably 900,000 or less. Here, the weight average molecular weight in the present specification is a standard polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method.

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

The content of the (meth) acrylic acid ester polymer (A) in the adhesive composition P according to the present embodiment is preferably 60% by mass or more, particularly 70% by mass or more, as a lower limit value. Is preferable, and more preferably 80% by mass or more. When the lower limit of the content of the (meth) acrylic acid ester polymer (A) is as described above, the adhesive strength of the obtained pressure-sensitive adhesive becomes good. The content of the (meth) acrylic acid ester polymer (A) is preferably 99% by mass or less, particularly preferably 98% by mass or less, and further 95% by mass or less as the upper limit value. It is preferable to have. Since the upper limit of the content of the (meth) acrylic acid ester polymer (A) is as described above, the haze value of the adhesive obtained by ensuring the contents of the polyrotaxane compound (B) and the cross-linking agent (C). Can be effectively improved.

(1-2) Polyrotaxane compound (B)
The polyrotaxane compound (B) is a compound in which a linear molecule penetrates 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 freely move on the linear molecule, but the cyclic molecule has a structure in which the cyclic molecule cannot escape from the linear molecule due to the block group. That is, the linear molecule and the cyclic molecule maintain their morphology not by a chemical bond such as a covalent bond but by a so-called mechanical bond.

The polyrotaxane compound (B) in this embodiment has a cyclic molecule containing a reactive group. When the adhesive composition P is crosslinked, as described above, the reactive group of the cyclic molecule of the polyrotaxane compound (B) reacts with the reactive group of the crosslinking agent (C) to cause (meth) acrylic acid. A cross-linking agent adduct having low reactivity with the ester polymer (A) is formed. The cross-linking agent adduct increases the haze value of the resulting pressure-sensitive adhesive. In addition, the cross-linking agent adduct cross-links (meth) acrylic acid ester polymers (A) having a hydroxyl group or a carboxy group. The cross-linking agent adduct used for this cross-linking is cross-linked by the (meth) acrylic acid ester polymer (A) by allowing each cyclic molecule of the polyrotaxane compound (B) to freely move on the linear molecule. In order to impart flexibility to the structure, the obtained pressure-sensitive adhesive exhibits high stress relaxation properties while having sufficient cohesive force, and is excellent in step followability.

The reactive group contained in the cyclic molecule of the polyrotaxane compound (B) is not particularly limited as long as it can react with the reactive group of the cross-linking agent (C), and examples thereof include a hydroxyl group and a carboxy group. Hydroxyl groups are preferred.

The polyrotaxane compound (B) in the present embodiment preferably has a cyclic oligosaccharide as a cyclic molecule. The cyclic oligosaccharide has a hydroxyl group as a reactive group in an unmodified state. Further, by using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (B), it is possible to select an appropriate ring diameter, and thereby the effect of moving the cyclic molecule on the linear molecule is exhibited. Cheap. Furthermore, it is easy to introduce various substituents and the like, which makes it possible to adjust the physical properties of the obtained pressure-sensitive adhesive. Further, the cyclic oligosaccharide has an advantage that it is easily available. In addition, in this specification, "cyclic" of "cyclic molecule" or "cyclic oligosaccharide" means substantially "cyclic". That is, the cyclic molecule does not have to be completely ring-closed, and may have a helical structure, for example, as long as it can move on the linear molecule.

Examples of the cyclic oligosaccharide include cyclodextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and α-cyclodextrin is particularly preferable. Two or more kinds of cyclic molecules of the polyrotaxane compound (B) may be mixed in the polyrotaxane compound (B) or in the adhesive composition P.

The hydroxyl group of the cyclic oligosaccharide as a reactive group may be the hydroxyl group originally possessed by the cyclic oligosaccharide (meaning the state before modification), or the hydroxyl group introduced into the cyclic oligosaccharide as a substituent. You may.

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 as the lower limit value. When the lower limit of the hydroxyl value is as described above, the polyrotaxane compound (B) can sufficiently react with the cross-linking agent (C). The hydroxyl value of the cyclic molecule is preferably 1000 mgKOH / g or less, more preferably 200 mgKOH / g or less, and particularly preferably 100 mgKOH / g or less as the upper limit value. When the upper limit of the hydroxyl value exceeds the above value, a large number of crosslinks occur in the same cyclic molecule, so that the cyclic molecule itself becomes a crosslink point, and the effect of the crosslink point of the polyrotaxane compound (B) as a whole can be exhibited. As a result, sufficient flexibility may not be ensured in the obtained adhesive.

The linear molecule of the polyrotaxane compound (B) is a molecule or substance that is encapsulated in a cyclic molecule and can be integrated by a mechanical bond rather than a chemical bond such as a covalent bond, and is linear. If so, there is no particular limitation. In addition, in this specification, a "straight line" of a "linear molecule" means substantially a "straight line". That is, the linear molecule may have a branched chain as long as the cyclic molecule can move on the linear molecule.

As the linear molecule of the polyrotaxane compound (B), for example, polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylic acid ester, polydimethylsiloxane, polyethylene, polypropylene and the like are preferable. Two or more kinds of 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 value, particularly preferably 10,000 or more, and further preferably 20,000 or more. preferable. When the lower limit of the number average molecular weight is the above, the amount of movement of the cyclic molecule on the linear molecule is secured, and the flexibility of the crosslinked structure due to the polyrotaxane compound (B) can be sufficiently obtained. The number average molecular weight of the linear molecules of the polyrotaxane compound (B) is preferably 300,000 or less, particularly preferably 200,000 or less, and further 100,000 or less as an upper limit value. Is preferable. When the upper limit of the number average molecular weight is the above, the solubility of the polyrotaxane compound (B) in the solvent becomes good.

The blocking group of the polyrotaxane compound (B) is not particularly limited as long as it is a group capable of retaining the skewered form of the cyclic molecule by the linear molecule. Examples of such a group include a bulky group and an ionic group.

Specifically, the blocking group of the polyrotaxane compound (B) includes dinitrophenyl groups, cyclodextrins, adamantan groups, trityl groups, fluoresceins, pyrenes, anthracenes, etc., or a number average molecular weight of 1,000. The main chain or side chain of a polymer of ~ 1,000,000 is preferable, and two or more of these blocking 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 JP-A-2005-154675).

The content of the polyrotaxane compound (B) in the adhesive composition P according to the present embodiment shall be 1 part by mass or more as a lower limit with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). Is preferable, and in particular, it is preferably 2 parts by mass or more, and further preferably 5 parts by mass or more. When the lower limit of the content of the polyrotaxane compound (B) is as described above, the haze value of the obtained pressure-sensitive adhesive can be satisfactorily improved. The content of the polyrotaxane compound (B) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less as an upper limit value. When the upper limit of the content of the polyrotaxane compound (B) is as described above, the adhesive strength of the obtained pressure-sensitive adhesive can be made sufficient.

(1-3) Crosslinking agent (C)
The cross-linking agent (C) has a reactive group. The reactive group may be any as long as it can react with the hydroxyl group or carboxy group of the (meth) acrylic acid ester polymer (A) and the reactive group of the cyclic molecule of the polyrotaxane compound (B). Such a cross-linking agent (C) forms a cross-linking agent adduct with the polyrotaxane compound (B). Then, the cross-linking agent adduct cross-links the (meth) acrylic acid ester polymers (A) with each other.

Examples of the reactive group contained in the cross-linking agent (C) include an isocyanate group, an epoxy group, an amino group, a vinyl sulfone group, and an organic metal. Examples of the cross-linking agent (C) having such a reactive group include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an amine-based cross-linking agent, a vinyl sulfone-based cross-linking agent, and an organic titanium / zirconium compound. Among these, an isocyanate-based cross-linking agent having high reactivity with a hydroxyl group is preferable. According to the isocyanate-based cross-linking agent, the cross-linking agent of the polyrotaxane compound (B) having a hydroxyl group as a reactive group can be sufficiently added, whereby the haze value of the obtained pressure-sensitive adhesive can be effectively increased. it can. As the cross-linking agent (C), one type can be used alone, or two or more types can be used in combination.

The isocyanate-based cross-linking 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 diisocyanates, and alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate. , And their biurets, isocyanurates, and adducts, which are reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Of these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable from the viewpoint of reactivity with hydroxyl groups.

When the (meth) acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the polymer without containing a hydroxyl group-containing monomer, it is used as a cross-linking agent (C). It is also preferable to use an epoxy-based cross-linking agent having high reactivity with a carboxy group.

Examples of the epoxy-based cross-linking agent include 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylene diamine, and ethylene glycol diglycidyl ether. , 1,6-Hexanediol diglycidyl ether, trimethylpropan diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. Of these, N, N, N', N'-tetraglycidyl-m-xylylenediamine are preferable from the viewpoint of reactivity with the carboxy group.

The content of the cross-linking agent (C) in the adhesive composition P is preferably 0.5 parts by mass or more as a lower limit value with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). In particular, it is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more. When the lower limit of the content of the cross-linking agent (C) is as described above, the cross-linking agent adduct of the above-mentioned polyrotaxane compound (B) can be satisfactorily formed, and the haze value of the obtained pressure-sensitive adhesive can be effectively improved. Can be made to. The content of the cross-linking agent (C) is preferably 30 parts by mass or less, particularly 25 parts by mass or less, as an upper limit value with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferable that the amount is 20 parts by mass or less. When the upper limit of the content of the cross-linking agent (C) is as described above, the degree of cross-linking can be made appropriate, and the step-following property of the obtained adhesive can be satisfactorily secured. Further, from the viewpoint of making the step followability more excellent, the upper limit value of the cross-linking agent (C) is more preferably 14 parts by mass or less, and particularly preferably 6 parts by mass or less.

Further, when the cross-linking agent (C) is an isocyanate-based cross-linking agent, if the hydroxyl groups of the (meth) acrylic acid ester polymer (A) are too large with respect to the reactive groups (isocyanate groups) of the cross-linking agent (C). , The cross-linking agent (C) is more likely to be consumed in the cross-linking reaction with the (meth) acrylic acid ester polymer (A), and the probability of forming a cross-linking agent adduct with the polyrotaxane compound (B) is reduced. On the other hand, if the hydroxyl group of the (meth) acrylic acid ester polymer (A) is too small with respect to the reactive group of the cross-linking agent (C), the cross-linked structure of the obtained adhesive becomes too dense, and the step-following property May be insufficient. From this point of view, the ratio of the number of moles of the hydroxyl group of the (meth) acrylic acid ester polymer (A) to the number of moles of the reactive group of the cross-linking agent (C) is preferably 5 or less, preferably 3 or less. It is more preferably 1 or less, and even more preferably 0.5 or less. The ratio of the number of moles is preferably 0.01 or more, more preferably 0.04 or more, particularly preferably 0.08 or more, and further preferably 0.16 or more. preferable.

(1-4) Various Additives The tacky composition P contains various additives usually used for acrylic pressure-sensitive adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, and tackifiers, if desired. , Antioxidants, light stabilizers, softeners, refractive index adjusters, rust preventives and the like can be added. The polymerization solvent and the dilution solvent described later are not included in the additives constituting the adhesive composition P.

On the other hand, the adhesive composition P preferably does not contain a filler such as fine particles. According to the pressure-sensitive adhesive according to the present embodiment, a high haze value can be obtained without using fine particles. If it does not contain a filler, there is no need to use a dedicated pipe or a dedicated kettle, and there is no risk of contamination with other products that do not contain a filler. Further, since the filler as a raw material and the work of dispersing the filler in the pressure-sensitive adhesive are not required, the cost can be reduced.

(2) Production of Adhesive Composition The adhesive composition P produced a (meth) acrylic acid ester polymer (A), and the obtained (meth) acrylic acid ester polymer (A) and a polyrotaxane compound ( It can be produced by mixing B) and the cross-linking agent (C) and, if desired, adding an additive.

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

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), and 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] and the like.

Examples of the organic peroxide include benzoyl peroxide, t-butylperbenzoate, cumenehydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butylperoxyneodecanoate, t-butylperoxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

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

Once the (meth) acrylic acid ester polymer (A) is obtained, the polyrotaxane compound (B), the cross-linking agent (C), and optionally a diluting solvent and addition are added to the solution of the (meth) acrylic acid ester polymer (A). The agent is added and mixed thoroughly to obtain a tacky composition P (coating solution) diluted with a solvent. If any of the above components is in the form of a solid, or if precipitation occurs when the component is mixed with another component in an undiluted state, the component is used alone as a diluting solvent in advance. It may be dissolved or diluted and then 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 and butanol. Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

The concentration and viscosity of the coating solution prepared in this manner may be any range as long as it can be coated, and is not particularly limited and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted so as to have a concentration of 10 to 60% by mass. It should be noted that the addition of a diluting solvent or the like is not a necessary condition when obtaining the coating solution, and the diluting solvent may not be added as long as the adhesive composition P has a coatable viscosity or the like. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as it is as a diluting solvent.

(3) Production of Adhesive The adhesive according to the present embodiment is obtained by cross-linking the adhesive composition P. Crosslinking of the adhesive composition P can usually be carried out by heat treatment. In addition, this heat treatment can also serve as a drying treatment when volatilizing the diluting solvent or the like from the coating film of the adhesive composition P applied to the desired object.

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

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

By the above heat treatment (and curing), at least the polyrotaxane compound (B) and, in some cases, the (meth) acrylic acid ester polymer (A) are also crosslinked via the cross-linking agent (C). The pressure-sensitive adhesive thus obtained is excellent in both light diffusivity and step-following property.

(4) Physical Properties of Adhesive The gel fraction of the adhesive according to the present embodiment is 20% or more, preferably 30% or more, and particularly preferably 40% or more as the lower limit value. When the lower limit of the gel fraction of the pressure-sensitive adhesive is the above, the cohesive force of the pressure-sensitive adhesive becomes high, and the step followability under high temperature and high humidity conditions becomes excellent. The gel fraction of the pressure-sensitive adhesive according to the present embodiment is 99% or less, preferably 95% or less, particularly preferably 90% or less, and further 80% or less as an upper limit value. Is preferable. When the upper limit value of the gel fraction of the pressure-sensitive adhesive is the above, the pressure-sensitive adhesive does not become too hard, and the initial step followability becomes excellent. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in a test example described later.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to the present embodiment is, at least, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive, and preferably a pressure-sensitive adhesive sheet obtained by laminating a release sheet on one or both sides of the pressure-sensitive adhesive layer. ..

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 adhesive sheet 1 according to the embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. , 12b and the pressure-sensitive adhesive layer 11 sandwiched between the two. The peeling surface of the release sheet in the present specification means a surface of the release sheet that has peelability, and includes both a surface that has been peeled and a surface that exhibits peelability without peeling. ..

(1) Adhesive Layer The adhesive layer 11 is composed of the above-mentioned pressure-sensitive adhesive, that is, is composed of a pressure-sensitive adhesive formed by cross-linking the pressure-sensitive adhesive composition P.

The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) in the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 10 μm or more, more preferably 25 μm or more, and particularly 50 μm as the lower limit value. The above is preferable. When the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, it is easy to exert a desired adhesive force, and it is possible to secure sufficient step-following property with respect to a normal step of the display body constituent member.

The thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less, more preferably 500 μm or less, and particularly preferably 300 μm or less as the upper limit value. When the upper limit of the thickness of the pressure-sensitive adhesive layer 11 is the above, the workability becomes good. 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 when the pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (the pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not always necessary.

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, polyethylene naphthalate film, and polybutylene. Telephthalate 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 film, polyimide film, fluorine A resin film or the like is used. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surfaces (particularly the surfaces in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b are 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. Of the release sheets 12a and 12b, it is preferable that one release sheet is 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) Haze Value The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 30% or more, particularly 35% or more, as a lower limit value. It is preferable, and more preferably 40% or more. When the lower limit of the haze value is the above, the pressure-sensitive adhesive layer 11 has excellent light diffusivity. In the present embodiment, the high haze value as described above can be achieved by forming the pressure-sensitive adhesive layer 11 from the pressure-sensitive adhesive formed by cross-linking the above-mentioned pressure-sensitive adhesive composition P.

The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 90% or less, particularly preferably 85% or less, and further 80% or less as an upper limit value. Is preferable. When the upper limit of the haze value is the above, the desired transparency can be ensured, and the image of the liquid crystal module can be displayed with good image quality on the obtained display body (display). The haze value in the present specification is a value measured according to JIS K7136: 2000.

(3-2) Adhesive Strength The adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 5 N / 25 mm or more as a lower limit value, particularly preferably 10 N / 25 mm or more, and further. It is preferably 15 N / 25 mm or more. When the lower limit of the adhesive force is the above, the step followability under high temperature and high humidity conditions becomes more excellent. The adhesive strength of the pressure-sensitive 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 20 N / 25 mm or less as an upper limit value. Is particularly preferable. When the adhesive strength of the adhesive sheet 1 is 50 N / 25 mm or less, good reworkability can be obtained, and if a bonding error occurs, an expensive display body component can be reused.

Here, the adhesive strength in the present specification basically means the adhesive strength measured by the 180-degree peeling method according to JIS Z0237: 2009, but the measurement sample is 25 mm wide and 100 mm long, and the measurement sample is used. It is attached to an adherend, pressurized at 0.5 MPa and 50 ° C. for 20 minutes, left at normal pressure, 23 ° C. and 50% RH for 24 hours, and then measured at a peeling speed of 300 mm / min. It shall be.

(4) Production of Adhesive Sheet As an example of production of the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b) and heat-treated to adhere. After the sex composition P is thermally crosslinked to form a coating layer, the peeling surface of the other release sheet 12b (or 12a) is superposed on the coating layer. If a curing period is required, the curing period is set, and if the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another production example of the pressure-sensitive adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a, heat-treated to thermally crosslink the adhesive composition P, and then applied. A layer is formed to obtain a release sheet 12a with a coating layer. Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, heat-treated to heat-crosslink the adhesive composition P to form a coating layer, and the coating layer is attached. To obtain the release sheet 12b of. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded so that both coating layers are in contact with each other. When the curing period is required, the curing period is set, and when the curing period is not required, the laminated coating layer becomes the pressure-sensitive adhesive layer 11. As a result, the adhesive sheet 1 is obtained. According to this production example, stable production is possible even when the pressure-sensitive adhesive layer 11 is thick.

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 and the like can be used.

[Display body]
FIG. 2 shows an example of a display body obtained by using the adhesive sheet 1 according to the present embodiment. The display body 2 according to the present embodiment includes a first display body component 21 (one display body component) having a step on at least the surface to be bonded, and a second display body component 22 (others). The display body constituent member (1) and the pressure-sensitive adhesive layer 11 located between them and adhering the first display body constituent member 21 and the second display body constituent member 22 to each other are provided. In the display body 2 according to the present embodiment, the first display body constituent 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. ..

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

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

The first display body constituent member 21 is preferably a protective panel made of a glass plate, a plastic plate, or the like, or a laminate containing them. In this case, the print layer 3 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the first display body constituent member 21.

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

The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate. 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, antiglare layer, etc.) may be provided on one side or both sides of the glass plate or the plastic plate, or an optical member. May be laminated. Further, the transparent conductive film and the metal layer may be patterned.

The second display body component 22 is an optical member to be attached to the first display body component member 21, a display body module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic)). It is preferably an EL) module or the like), an optical member as a part of the display body module, or a laminated body including the display body module.

Examples of the optical member include a shatterproof film, a polarizing plate (polarizing film), a polarizer, a retardation plate (phase difference film), a viewing angle compensation film, a brightness improving film, a contrast improving film, a liquid crystal polymer film, and a diffusion film. , Semi-transmissive reflective film, transparent conductive film and the like. Examples of the shatterproof film include a hard coat film in which a hard coat layer is formed on one side of the base film.

The material constituting the printing layer 3 is not particularly limited, and a known material for printing is used. The thickness of the print layer 3, that is, the lower limit of 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. preferable. When the lower limit value is the above, it is possible to sufficiently secure concealment such as making the electrical wiring invisible from the viewer side. 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. By setting the upper limit value as described above, it is possible to prevent deterioration of the step followability of the pressure-sensitive 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 pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is separated from the printing layer of the first display body component 21. It is bonded to the surface on the side where 3 exists. At this time, since the pressure-sensitive adhesive layer 11 is excellent in step-following property, it is possible to prevent gaps and floating from occurring in the vicinity of the step due to the printing layer 3.

After that, the other release sheet 12b is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 and the second display body constituent member 22 are bonded together. Further, as another example, the bonding order of the first display body constituent member 21 and the second display body constituent member 22 may be changed.

In the display body 2, since the pressure-sensitive adhesive layer 11 is excellent in light diffusivity, the brightness is made uniform, and the occurrence of glare, moire, liquid crystal unevenness, and the like is suppressed.

Further, in the display body 2, since the pressure-sensitive adhesive layer 11 is excellent in step followability under high temperature and high humidity conditions, the display body 2 is placed under high temperature and high humidity conditions (for example, 85 ° C., 85% RH). Even if it is scratched, the occurrence of air bubbles, floating, peeling, etc. in the vicinity of the step is suppressed.

The position of use of the adhesive sheet 1 (adhesive layer 11) according to the present embodiment on the display body is not limited to the above example. For example, the adhesive sheet 1 according to the present embodiment may be used to bond display body constituent members having no step as described above. Specifically, the adhesive sheet 1 according to the present embodiment is also suitably used for bonding the liquid crystal cell and the backlight. Since the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is excellent in light diffusivity, the obtained display body has a uniform brightness by the pressure-sensitive adhesive layer 11. Further, due to the excellent flexibility of the adhesive layer 11, it can flexibly cope with the expansion and contraction of the optical member due to the temperature difference, and highly durable adhesion is expected.

The embodiments described above are described for facilitating the 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, either one or both of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted, and a desired optical member may be laminated in place of the release sheets 12a and / or 12b. Further, the first display body constituent member 21 may have a step other than the print layer 3. Further, not only the first display body constituent member 21 but also the second display body constituent member 22 may have a step on the adhesive layer 11 side.

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

[Example 1]
1. 1. Preparation of (meth) acrylic acid ester polymer Solution weight of 47.5 parts by mass of n-butyl acrylate, 47 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of acrylic acid and 0.5 parts by mass of 2-hydroxyethyl acrylate. A (meth) acrylic acid ester polymer (A) was prepared by legally copolymerizing. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, the weight average molecular weight (Mw) was 700,000.

2. 2. Preparation of Adhesive Composition 100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1 and a polyrotaxane compound (B) (Advanced Soft Materials Co., Ltd.) , Product name "SELM Superpolymer SH3407P", Linear molecule: Polyethylene glycol, Cyclic molecule: α-cyclodextrin having hydroxypropyl group and caprolactone chain, Block group: Adamantane group, Weight average molecular weight (Mw) 700,000, A hydroxyl value of 72 mgKOH / g) (5.0 parts by mass) and a trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Coronate L") (2.0 parts by mass) as a cross-linking agent (C) were mixed. A coating solution of the tacky composition was obtained by thoroughly stirring and diluting with methyl ethyl ketone.

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). Details of the abbreviations and the like shown in Table 1 are as follows.
[(Meta) Acrylic Acid Ester Polymer (A)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: HEA acrylate: 2-hydroxyethyl acrylate IBXA: isobornyl acrylate
[Crosslinking agent (C)]
TDI: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L")
XDI: Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")
Epoxy: N, N, N', N'-tetraglycidyl-m-xylylenediamine (manufactured by Soken Chemical Co., Ltd., product name "E-AX")
[Fine particles]
Fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, trade name "Tospearl 145", average particle size: 4.5 μm, refractive index: 1.42)

Table 1 shows the ratio of the number of moles of the hydroxyl group (2-hydroxyethyl acrylate) of the (meth) acrylic acid ester polymer (A) to the number of moles of the reactive group (isocyanate group) of the cross-linking agent (C). Described.

3. 3. Manufacture of Adhesive Sheet (1) Manufacture of First Adhesive Sheet (Thickness of Adhesive Layer: 25 μm) Apply the coating solution of the adhesive composition obtained in the above step 2 to one side of the polyethylene terephthalate film with a silicone-based release agent. The heavy peeling type peeling sheet (manufactured by Lintec Corporation, product name "SP-PET752150") peeled by the above was coated with a knife coater on the peeled surface. Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a coating layer.

Next, the coating layer on the heavy-release type release sheet obtained above and the light-release type release sheet obtained by peeling one side of the polyethylene terephthalate film with a silicone-based release agent (manufactured by Lintec, product name "SP-PET382120"). The light peeling type peeling sheet / adhesive was attached so that the peeling surface of the light peeling type peeling sheet was in contact with the coating layer, and cured under the conditions of 23 ° C. and 50% RH for 7 days. An adhesive sheet having a layer / light release type release sheet structure was produced. The thickness of the pressure-sensitive adhesive layer in this pressure-sensitive adhesive sheet was 25 μm. The adhesive sheet is referred to as a first adhesive sheet.

(2) Production of Second Adhesive Sheet (Thickness of Adhesive Layer: 50 μm) The coating solution of the adhesive composition obtained in the above step 2 was peeled off on one side of a polyethylene terephthalate film with a silicone-based release agent. A heavy peeling type peeling sheet (manufactured by Lintec Corporation, product name "SP-PET752150") was coated on the peeled surface with a knife coater. Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a coating layer. Similarly, the obtained coating solution of the adhesive composition was applied to the peeled surface of a light peeling type release sheet (manufactured by Lintec Corporation, product name "PET382120") in which one side of a polyethylene terephthalate film was peeled with a silicone-based release agent. After coating with a knife coater so that the thickness after drying was 25 μm, a coating layer was formed by heat treatment at 90 ° C. for 1 minute.

Next, the heavy-release type release sheet with the coating layer obtained above and the light-release type release sheet with the coating layer obtained above are bonded together so that both coating layers are in contact with each other, and the temperature is 23 ° C. By curing for 7 days under the condition of 50% RH, an adhesive sheet having a structure of a heavy release type release sheet / an adhesive layer / a light release type release sheet was prepared. The thickness of the pressure-sensitive adhesive layer in this pressure-sensitive adhesive sheet was 50 μm. The adhesive sheet is called a second adhesive sheet.

The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring device (manufactured by Teclock Co., Ltd., product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 21, Comparative Examples 1 to 7]
The type and proportion 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 blending amount of the polyrotaxane compound (B), and the cross-linking agent ( The first and second pressure-sensitive adhesive sheets were produced in the same manner as in Example 1 except that the type and blending amount of C) were changed as shown in Table 1.

In the adhesive composition of Comparative Example 6, fine particles (fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic; manufactured by Momentive Performance Materials Japan, Inc., trade name “Tospearl 145”, The average particle size: 4.5 μm and the refractive index: 1.42) were blended in 7.0 parts by mass.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
-GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard volume HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
・ Measurement solvent: tetrahydrofuran ・ Measurement temperature: 40 ° C

[Test Example 1] (Measurement of gel fraction)
The first pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples was cut into a size of 80 mm × 80 mm, and the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200). , 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. The mass at this time is M1.

Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Then, the adhesive was taken out, air-dried for 24 hours in an environment of 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. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Measurement of haze value)
Regarding the adhesive layer of the first adhesive sheet (adhesive layer thickness: 25 μm) obtained in Examples and Comparative Examples, a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name) according to JIS K7136: 2000. The haze value (%) was measured using "NDH-2000"). The results are shown in Table 2.

[Test Example 3] (Measurement of adhesive strength)
The light release type release sheet was peeled off from the first pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 25 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was separated from the exposed pressure-sensitive adhesive layer by polyethylene terephthalate (PET) having an easy-adhesion layer. ) A film (manufactured by Toyo Boseki Co., Ltd., product name "PET A4300", thickness: 100 μm) was bonded to an easy-adhesive layer to obtain a laminate of a 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 above sample, and the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) and then placed in an autoclave manufactured by Kurihara Seisakusho. The pressure was increased at 0.5 MPa and 50 ° C. for 20 minutes. Then, after leaving it for 24 hours under the conditions of 23 ° C. and 50% RH, the adhesive strength (N) was set to a peeling speed of 300 mm / min and a peeling angle of 180 degrees using a tensile tester (Tencilon manufactured by Orientec). / 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 4] (Evaluation of step followability)
On the surface of a glass plate (manufactured by NSG Precision, product name "Corning Glass Eagle XG", length 90 mm x width 50 mm x thickness 0.5 mm), UV curable ink (manufactured by Teikoku Ink Co., Ltd., product name "POS-911 ink") ) Was screen-printed in a frame shape (outer shape: length 90 mm × width 50 mm, width 5 mm). Next, the printed ultraviolet curable ink is cured by irradiating with ultraviolet rays (80 W / cm ² , ² metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min), and a step (height of the step) due to printing is cured. A stepped glass plate having (5 μm, 10 μm, 15 μm, 20 μm) was produced.

The light release type release sheet is peeled off from the second adhesive sheet (thickness of the adhesive layer: 50 μm) obtained in Examples and Comparative Examples, and the exposed adhesive layer is a polyethylene terephthalate film (Toyobo) having an easy adhesive layer. It was bonded to an easy-adhesion layer manufactured by the company, product name "PET A4300", thickness: 100 μm). Next, the heavy-release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (manufactured by Fujipla, product name "LPD3214"), the laminate was laminated on each stepped glass plate so that the adhesive layer covered the entire surface of the frame-shaped print, and this was used as an evaluation sample. did.

The obtained evaluation sample was autoclaved under the conditions of 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under moist heat conditions of 85 ° C. and 85% RH (durability test), and then the step followability was evaluated. The step followability is judged by whether or not the print step is completely filled by the adhesive layer, and if gaps or bubbles are observed at the interface between the print step and the adhesive layer, the print step can be followed. It is judged that there was no such thing. Here, the step followability was evaluated as the step follow rate (%) according to the following criteria. The results are shown in Table 2.

Step follow-up rate (%) = {(height of printed step filled without gaps or bubbles (μm)) / (thickness of adhesive layer: 50 μm)} × 100
⊚: Step follow rate 40%
◯: Step follow rate 30%
Δ: Step follow rate 20%
×: Step follow rate 10% or less

As can be seen from Table 2, the adhesive sheet obtained in the examples had a high haze value and was also excellent in step followability.

The adhesive sheet of the present invention can be suitably used, for example, for bonding a protective panel having a step and a desired display body constituent member, or for bonding a liquid crystal cell and a backlight.

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Display body 21 ... First display body component 22 ... Second display body component 3 ... Printing layer

Claims (4)

An adhesive sheet including a release sheet and an adhesive layer provided so as to be in contact with the release surface of the release sheet.
The pressure-sensitive adhesive layer
The (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 300,000 or more and less than 1.5 million
Polyrotaxane compound (B) and
It is composed of a pressure-sensitive adhesive obtained by cross-linking a pressure-sensitive adhesive composition containing a cross-linking agent (C) .
When the (meth) acrylic acid ester polymer (A) contains at least one of a hydroxyl group-containing monomer and a carboxy group-containing monomer as a monomer unit constituting the polymer, and the hydroxyl group-containing monomer is contained. , the hydroxyl group-containing monomers contain at a content of less than 20% by weight, when it contains the carboxyl group-containing monomer, the carboxyl group-containing monomer containing at a content of less than 15 wt%,
The polyrotaxane compound (B) has a cyclic molecule containing a reactive group and has a cyclic molecule.
Gel fraction of the pressure-sensitive adhesive is more than 20% state, and are 99% or less,
A pressure-sensitive adhesive sheet, wherein the haze value of the pressure-sensitive adhesive layer is 30% or more and 90% or less . The content of the polyrotaxane compound (B) in the adhesive composition is 1 part 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). The adhesive sheet according to claim 1. The (meth) acrylic acid ester polymer (A) contains 30% by mass or more and 99% by mass of a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. The adhesive sheet according to claim 1 or 2, which comprises the following. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the cross-linking agent (C) is an isocyanate-based cross-linking agent.

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