JP2018127560A - Adhesive and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive and an adhesive sheet excellent in both light diffusibility and step followability.SOLUTION: The adhesive is obtained by crosslinking an adhesive composition containing a (meth)acrylate polymer (A) having a weight-average molecular weight of 300,000 or more and less than 1,500,000, a polyrotaxane compound (B), and a crosslinking agent (C). The (meth)acrylate 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. When the (meth)acrylate polymer (A) contains the hydroxyl group-containing monomer, the content of the hydroxyl group-containing monomer is less than 20 mass%. When the (meth)acrylate polymer (A) contains the carboxy group-containing monomer, the content of the carboxy groups is less than 15 mass%. The polyrotaxane compound (B) has a cyclic molecule containing a reactive group. The gel fraction of the adhesive is 20% or more and 95% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet, and particularly relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that are suitable for bonding display member constituting members.

  In recent years, liquid crystal panels are often used as display bodies (displays). In such a liquid crystal panel, a light diffusing member for diffusing light from the light source is required to make the luminance of the backlight uniform. In recent liquid crystal panels, high-definition image quality is required, so that problems such as glare, moire, and liquid crystal unevenness are likely to occur. From the viewpoint of solving such a problem with the pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer having light diffusibility has attracted attention.

  As such a light diffusable pressure-sensitive adhesive layer, for example, Patent Document 1 has (A) (a) (meth) acrylic acid ester copolymer, (b) a polymerizable unsaturated group in the side chain ( An adhesive resin component obtained by curing a mixture for forming an adhesive resin containing a (meth) acrylic acid ester 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 elastic modulus (G ′) at 23 ° C. of 2 MPa or more and 20 MPa or less is disclosed.

  Patent Document 2 discloses that a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing monomer as a functional group-containing monomer copolymerizable with at least one alkyl (meth) acrylate monomer having an alkyl group with C1 to C14 carbon atoms. 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 crosslinking agent, and silicon-based particles (fine particles) The light diffusion adhesive layer formed from the thing 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 radically polymerizable monomer, specifically, a modified (meth) acrylate copolymer (B) obtained by blending and polymerizing a monomer having an aromatic group such as a styrene monomer, benzyl acrylate, or phenoxyethyl acrylate; And a light-diffusing pressure-sensitive adhesive layer obtained by crosslinking a light-diffusing pressure-sensitive adhesive composition containing a crosslinking agent.

Japanese Patent No. 5149533 Japanese Patent Laying-Open No. 2015-86297 JP 2010-159333 A

  Incidentally, the liquid crystal panel usually includes a liquid crystal module and a protection 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 hit the display module even when the protective panel is deformed by an external force.

  However, the presence of the air gap, that is, the air layer as described above, causes a large light reflection loss due to the refractive index difference between the protective panel and the air layer, and the refractive index difference between the air layer and the liquid crystal module. There is a problem that decreases.

  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 printed 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, thereby causing light reflection loss. For this reason, the pressure-sensitive adhesive layer is required to have a step following ability.

  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. As described above, it is not suitable for applications where step following ability is required. Similarly to the pressure-sensitive adhesive layer disclosed in Patent Document 1, the pressure-sensitive adhesive layer disclosed in Patent Document 2 becomes hard due to the inclusion of fine particles. It is difficult to satisfy.

  In addition, as in Patent Documents 1 and 2, when the pressure sensitive adhesive contains fine particles, it is necessary to use a dedicated pipe or a dedicated kettle when manufacturing the pressure sensitive adhesive, and to other products that do not contain fine particles. There is also a risk of contamination. Furthermore, the operation | work which disperse | distributes microparticles | fine-particles in an adhesive is also needed, and it causes the raise of not only the raw material cost of microparticles | fine-particles but a manufacturing cost.

  On the other hand, the pressure-sensitive adhesive layer that does not use the fine particles of Patent Document 3 is preferable in that the above problem does not occur. However, since the pressure-sensitive adhesive layer becomes hard due to the modified (meth) acrylate copolymer (B) obtained by polymerizing the monomer having an aromatic group, the pressure-sensitive adhesive layer is also inferior in the step following property.

  This invention is made | formed in view of the above actual conditions, and it aims at providing the adhesive and adhesive sheet which are excellent in both light diffusibility and level | step difference followable | trackability.

  In order to achieve the above object, first, the present invention provides a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 300,000 or more and less than 1,500,000, a polyrotaxane compound (B), and a crosslinking agent. (C) is a pressure-sensitive adhesive formed by crosslinking a pressure-sensitive adhesive composition, and the (meth) acrylic acid ester polymer (A) is a hydroxyl group-containing monomer and a monomer unit constituting the polymer. When containing at least one carboxy group-containing monomer and containing the hydroxyl group-containing monomer, the hydroxyl group-containing monomer is contained at 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, and the polyrotaxane compound (B) has a cyclic molecule containing a reactive group. Fraction is 20% or more, to provide a pressure-sensitive adhesive, characterized in that at most 99% (Invention 1).

  In the said invention (invention 1), the reactive agent of a crosslinking agent (C) and the reactive group of the cyclic molecule which a polyrotaxane compound (B) reacts give a crosslinking agent adduct. Since this cross-linking agent adduct has low compatibility with the (meth) acrylic acid ester polymer (A), the haze value of the pressure-sensitive adhesive obtained is increased, whereby the pressure-sensitive adhesive is excellent in light diffusibility. It becomes. Moreover, the said crosslinking agent adduct reacts also with the hydroxyl group or carboxy group of (meth) acrylic acid ester polymer (A) after that, and forms a crosslinked structure. The pressure-sensitive adhesive having such a crosslinked structure is excellent in flexibility by allowing each cyclic molecule of the polyrotaxane compound (B) to freely move on the linear molecule, and thus the resulting pressure-sensitive adhesive has excellent step following ability. It will be.

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

  In the said invention (invention 1 and 2), the said (meth) acrylic ester polymer (A) is a (meth) acrylic acid whose carbon number of an alkyl group is 1-20 as a monomer unit which comprises the said polymer. The alkyl ester is preferably contained in an amount of 30% by mass to 99% by mass (Invention 3).

  In the said invention (invention 1-3), it is preferable that the said crosslinking agent (C) is an isocyanate type crosslinking agent (invention 4).

  It is preferable that the adhesive which concerns on the said invention (invention 1-4) 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. The pressure-sensitive adhesive sheet is characterized in that the layer is composed of the pressure-sensitive adhesive (Invention 1 to 4) (Invention 5).

  In the said invention (invention 5), it is preferable that the haze value of the said adhesive layer is 30% or more and 90% or less (invention 6).

  The pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention are excellent in both light diffusibility and level difference followability.

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 this 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 crosslinking agent (C). It is a pressure-sensitive adhesive obtained by crosslinking a pressure-sensitive adhesive composition (hereinafter sometimes referred to as “pressure-sensitive adhesive composition P”). 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, When the hydroxyl group-containing monomer is contained at a content of less than 20% by mass and the carboxy group-containing monomer is contained, the carboxy group is contained at a content of less than 15% by mass. The polyrotaxane compound (B) has a cyclic molecule containing a reactive group. And the gel fraction of the said adhesive is 20% or more and 99% or less. In the present specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  When the adhesive composition P is cross-linked, the reactive group of the cross-linking agent (C) reacts with the reactive group of the cyclic molecule that the polyrotaxane compound (B) has. 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 crosslinking agent (C) added to the above-mentioned crosslinking agent adduct is then a hydroxyl group derived from a hydroxyl group-containing monomer or a carboxy group derived from a carboxy group-containing monomer of the (meth) acrylic acid ester polymer (A). React with each other to form a crosslinked structure. Since the content of the hydroxyl group-containing monomer and the carboxy group-containing monomer is relatively small, the (meth) acrylic acid ester polymer (A) is a reactive group of the crosslinking agent (C) without interposing the polyrotaxane compound (B). It is presumed that the cross-linking agent adduct of the polyrotaxane compound (B) is preferentially formed rather than reacting directly with it, thereby increasing the haze value of the resulting pressure-sensitive adhesive.

  Here, the polyrotaxane compound (B) has a mechanical bond between a cyclic molecule and a 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) through 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) is bonded to another cyclic molecule of the polyrotaxane compound (B). As a result, a structure (crosslinked structure) is formed in which a plurality of (meth) acrylic acid ester polymers (A) are crosslinked via the polyrotaxane compound (B) having the mechanical bond. The pressure-sensitive adhesive according to the present embodiment can be softly designed by not requiring fine particles, and includes the above-described cross-linking structure, so that it has excellent stress relaxation properties and excellent step following properties.

  In addition, it is not necessary that all of the obtained pressure-sensitive adhesives have the above structure, and the two (meth) acrylic acid ester polymers (A) are directly bonded by the crosslinking agent (C) without using the polyrotaxane compound (B). The structure etc. which are made may be included.

  As described above, the pressure-sensitive adhesive according to the present embodiment having the above composition and gel fraction has a high haze value and can be designed softly, and thus is excellent in both light diffusibility and step following ability. Specifically, the adhesive according to this embodiment can achieve a haze value of 30% or more. In addition, the adhesive layer made of the adhesive according to the present embodiment is easy to follow the step when pasted to a display member having a step, and the occurrence of gaps, floats, etc. near the step is suppressed. . Furthermore, even when the film is placed in a high temperature and high humidity condition, for example, 85 ° C. and 85% RH for 72 hours in this state, the occurrence of bubbles, floating, peeling, etc. in the vicinity of the step is suppressed.

  In addition, according to the pressure-sensitive adhesive according to the present embodiment, a high haze value can be obtained without using fine particles, so there is no need to use a dedicated pipe or a dedicated pot, and no other fine particles are contained. There is no risk of product contamination. Furthermore, since fine particles as raw materials are not required to disperse the fine particles 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, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, among them, reactivity with the crosslinking agent (C) and other monomers From the viewpoint of copolymerization, 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is preferred. 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, its content is less than 20% by mass, preferably 18% by mass or less. Especially preferably, it is 15 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 cyclic molecule included in the reactive group of the crosslinking agent (C) and the polyrotaxane compound (B). This hinders an increase in haze value due to the addition agent of the polyrotaxane compound (B). Furthermore, the content of the hydroxyl group-containing monomer is more preferably 10% by mass or less, and preferably 4% by mass or less from the viewpoint of obtaining a higher haze value while favorably maintaining the step following property of the obtained adhesive. More preferably, the content is 2% by mass or less.

  Further, when the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, the content is preferably 0.1% by mass or more, particularly The content 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-described crosslinked structure is formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive has excellent cohesive strength while maintaining stress relaxation properties.

  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 adhesive, the crosslinking agent (C) Acrylic acid is preferable from the viewpoints of reactivity with the monomer, the influence on the reaction between the hydroxyl group derived from the hydroxyl group-containing monomer and the crosslinking agent (C), and the 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 is less than 15% by mass and 10% by mass or less. It is preferable that it is 5 mass% or less especially. When the content of the carboxy group-containing monomer is 15% by mass or more, the carboxy group of the carboxy group-containing monomer includes the reactive group of the crosslinking agent (C) and the reactive group of the cyclic molecule that the polyrotaxane compound (B) has. This hinders the above reaction and inhibits the haze value from increasing due to the formation of the cross-linking agent adduct of the polyrotaxane compound (B).

  Further, when the (meth) acrylic acid ester polymer (A) contains a carboxy group-containing monomer as a monomer unit constituting the polymer, the content 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-described crosslinked structure is formed in the pressure-sensitive adhesive, and the pressure-sensitive adhesive has excellent cohesive strength while maintaining stress relaxation properties.

  The (meth) acrylic acid ester polymer (A) preferably contains a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms as the monomer unit constituting the polymer. Preferred adhesiveness can be expressed. The alkyl group may be linear or branched, or may have a cyclic structure.

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

  Among these, the (meth) acrylic acid ester polymer (A) preferably contains a (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. . By including a (meth) acrylic acid alkyl ester having a large number of carbon atoms as a constituent monomer unit in this way, the hydrophobicity of the (meth) acrylic acid ester polymer (A) is increased, and a polyrotaxane compound (B) is added with a crosslinking agent. The compatibility with the product is further lowered, and the haze value of the obtained pressure-sensitive adhesive is further improved.

  Among (meth) acrylic acid alkyl esters having 5 to 20 carbon atoms in the alkyl group, in particular, a monomer (hard monomer) having a glass transition temperature (Tg) exceeding 0 ° C. as a homopolymer and a glass transition as a homopolymer It is preferable to use in combination with a monomer (soft monomer) having a temperature (Tg) of 0 ° C. or lower. This is because the step following property under high temperature and high humidity conditions can be further improved by improving the cohesive force with the hard monomer while ensuring the adhesiveness and flexibility with the soft monomer. 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 said hard monomer, the (meth) acrylic-acid alkylester which has an alicyclic structure in a molecule | numerator is preferable, and the (meth) acrylic-acid alkylester which has a some alicyclic structure is mentioned more preferably. Examples include isobornyl acrylate (Tg 94 ° C.), isobornyl methacrylate (Tg 180 ° C.), adamantyl acrylate (Tg 115 ° C.), adamantyl methacrylate (Tg 141 ° C.), and the like. Among the above 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.

  Preferred examples of the soft monomer include (meth) acrylic acid alkyl esters having a linear or branched alkyl group. Specifically, 2-ethylhexyl acrylate (Tg-70 ° C.) is particularly preferable. That is, as a combination of a hard monomer and a 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 (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms as the monomer unit constituting the polymer. In particular, the content is preferably 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 tackiness. Moreover, (meth) acrylic acid ester polymer (A) contains 99 mass% or less of (meth) acrylic acid alkyl ester whose carbon number of an alkyl group is 1-20 as a monomer unit which comprises the said polymer. In particular, it is preferable to contain 98% by mass or less, more preferably 96% by mass or less. By setting 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).

  The (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group preferably contains (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group. When a (meth) acrylic acid alkyl ester having 5 to 20 carbon atoms in the alkyl group is included, the alkyl group in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group has 5 carbon atoms. The content ratio of (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. Thereby, said haze value improvement effect is exhibited well with adhesiveness. On the other hand, the content is preferably 100% by mass or less, particularly preferably 95% by mass or less, and more preferably 70% by mass or less. When the said content rate shall be 95 mass% or less, the (meth) acrylic-acid alkylester which has a C1-C4 alkyl group can be contained. Thereby, hardness can be given to (meth) acrylic acid ester polymer (A), or hydrophobic fine adjustment can be performed. 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 make it.

  The (meth) acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. The other monomer is preferably a monomer that does not contain a reactive functional group so as not to inhibit the action of the hydroxyl group-containing monomer and the carboxy group-containing monomer. Examples of such a monomer that does not contain a reactive functional group 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 (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 300,000 or more and less than 1,500,000. When the weight average molecular weight is 1,500,000 or more, the resulting pressure-sensitive adhesive becomes hard, and the step following ability decreases. On the other hand, if the weight average molecular weight is less than 300,000, the cohesive force of the resulting pressure-sensitive adhesive is lowered, and the step following property under high temperature and high humidity conditions is lowered.

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

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

  The content of the (meth) acrylic acid ester polymer (A) in the pressure-sensitive adhesive composition P according to this embodiment is preferably 60% by mass or more, particularly 70% by mass or more, as the lower limit. Is more preferable, and 80% by mass or more is preferable. When the lower limit value of the content of the (meth) acrylic acid ester polymer (A) is as described above, the pressure-sensitive adhesive of the obtained pressure-sensitive adhesive is 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 more preferably 95% by mass or less, as an upper limit. Preferably there is. When the upper limit of the content of the (meth) acrylic acid ester polymer (A) is the above, the haze value of the pressure-sensitive adhesive obtained by securing the content of the polyrotaxane compound (B) and the crosslinking agent (C) Can be improved effectively.

(1-2) Polyrotaxane compound (B)
The polyrotaxane compound (B) is a compound in which a linear molecule penetrates through openings of at least two cyclic molecules and has a blocking group 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 blocking group. That is, the linear molecule and the cyclic molecule maintain their forms not by chemical bonds such as covalent bonds but by so-called mechanical bonds.

  The polyrotaxane compound (B) in the present embodiment has a cyclic molecule containing a reactive group. When the pressure-sensitive 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), and (meth) acrylic acid. A cross-linking agent adduct having low compatibility with the ester polymer (A) is formed. The haze value of the pressure-sensitive adhesive obtained is increased by the cross-linking agent adduct. Moreover, the said crosslinking agent addition product bridge | crosslinks the (meth) acrylic acid ester polymer (A) which has a hydroxyl group or a carboxy group. The cross-linking agent adduct provided for the cross-linking is a cross-linking 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 a high stress relaxation property while having a sufficient cohesive force, and has excellent step following ability.

  The reactive group of the cyclic molecule of the polyrotaxane compound (B) is not particularly limited as long as it can react with the reactive group of the crosslinking 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 a state where it is not modified. In addition, by using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (B), it becomes possible to select an appropriate ring diameter, thereby producing an effect due to the movement of the cyclic molecule on the linear molecule. Cheap. Furthermore, introduction of various substituents and the like is easy, and thereby the physical properties of the obtained pressure-sensitive adhesive can be adjusted. Furthermore, if it is cyclic oligosaccharide, there also exists an advantage that acquisition is easy. In the present specification, “cyclic” of “cyclic molecule” or “cyclic oligosaccharide” means substantially “cyclic”. In other words, the cyclic molecule may not be completely closed as long as it can move on the linear molecule, and may have a helical structure, for example.

  Preferred cyclic oligosaccharides include cyclodextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and among them, 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 that the cyclic oligosaccharide has as a reactive group may be a hydroxyl group that the cyclic oligosaccharide originally has (refers to a state before modification), or a hydroxyl group that is introduced into the cyclic oligosaccharide as a substituent. May be.

  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. When the lower limit of the hydroxyl value is the above, the polyrotaxane compound (B) can sufficiently react with the crosslinking agent (C). In addition, 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 particularly preferably 100 mgKOH / g or less. 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 as the whole polyrotaxane compound (B) can be exhibited. As a result, there is a possibility that sufficient flexibility cannot be secured in the obtained pressure-sensitive adhesive.

  The linear molecule of the polyrotaxane compound (B) is a molecule or substance that is included in a cyclic molecule and can be integrated by mechanical bonds rather than chemical bonds such as covalent bonds, and is linear If it is, it will not be specifically limited. In the present specification, “linear” of “linear molecule” means substantially “linear”. 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 molecule of the polyrotaxane compound (B) is preferably 3,000 or more as a lower limit, particularly preferably 10,000 or more, and more 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 resulting from the polyrotaxane compound (B) is sufficiently obtained. The number average molecular weight of the linear molecule of the polyrotaxane compound (B) is preferably 300,000 or less, particularly preferably 200,000 or less, more preferably 100,000 or less, as an upper limit. It is preferable. When the upper limit of the number average molecular weight is as described 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 the cyclic molecule is a group that can maintain a skewered form with a linear molecule. Examples of such groups include bulky groups and ionic groups.

  Specifically, the blocking group of the polyrotaxane compound (B) may be a dinitrophenyl group, a cyclodextrin, an adamantane group, a trityl group, a fluorescein, a pyrene, an anthracene, or the like, or a number average molecular weight of 1,000. A polymer main chain or side chain of ˜1,000,000 is preferred, and two or more of these blocking groups may be mixed in the polyrotaxane compound (B) or 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 this embodiment is 1 part 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 2 parts by mass or more, more preferably 5 parts by mass or more. When the lower limit value of the content of the polyrotaxane compound (B) is the above, the haze value of the obtained pressure-sensitive adhesive can be improved satisfactorily. Moreover, it is preferable that content of a polyrotaxane compound (B) is 30 mass parts or less as an upper limit, It is more preferable that it is 25 mass parts or less, It is especially preferable that it is 20 mass parts or less. When the upper limit value of the content of the polyrotaxane compound (B) is as described above, the adhesive force of the obtained adhesive can be made sufficient.

(1-3) Crosslinking agent (C)
The crosslinking agent (C) has a reactive group. This reactive group should just react with the reactive group which the cyclic molecule of the hydroxyl group or carboxy group which (meth) acrylic acid ester polymer (A) has, and the polyrotaxane compound (B) has. Such a crosslinking agent (C) forms a crosslinking agent adduct with the polyrotaxane compound (B). And the said crosslinking agent adduct bridge | crosslinks (meth) acrylic acid ester polymer (A).

  As a reactive group which a crosslinking agent (C) has, an isocyanate group, an epoxy group, an amino group, a vinyl sulfone group, an organic metal etc. are mentioned, for example. Examples of the crosslinking agent (C) having such a reactive group include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, vinylsulfone crosslinking agents, and organic titanium / zirconium compounds. Among these, an isocyanate type crosslinking agent having high reactivity with a hydroxyl group is preferable. According to the isocyanate-based crosslinking agent, it is possible to sufficiently add the crosslinking agent to the polyrotaxane compound (B) having a hydroxyl group as a reactive group, thereby effectively increasing the haze value of the obtained pressure-sensitive adhesive. it can. In addition, a crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, etc. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanate, 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) does not contain a hydroxyl group-containing monomer as a monomer unit constituting the polymer, but contains a carboxy group-containing monomer, as a crosslinking agent (C), It is also preferable to use an epoxy-based crosslinking agent having high reactivity with a carboxy group.

  Examples of the epoxy-based crosslinking agent include 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether. 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine and the like. Of these, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine is preferred from the viewpoint of reactivity with a carboxy group.

  The content of the crosslinking agent (C) in the adhesive composition P is preferably 0.5 parts by mass or more as a lower limit 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 value of the content of the crosslinking agent (C) is the above, the above-mentioned crosslinking agent adduct of the polyrotaxane compound (B) can be satisfactorily formed, and the haze value of the resulting pressure-sensitive adhesive is effectively improved. Can be made. Moreover, it is preferable that content of a crosslinking agent (C) is 30 mass parts or less as an upper limit with respect to 100 mass parts of (meth) acrylic acid ester polymer (A), and is especially 25 mass parts or less. It is preferable that it is 20 parts by mass or less. When the upper limit value of the content of the cross-linking agent (C) is the above, it is possible to make the degree of cross-linking moderate, and to ensure good level difference followability of the obtained pressure-sensitive adhesive. Furthermore, from the viewpoint of making the step following property more excellent, the upper limit value of the crosslinking agent (C) is more preferably 14 parts by mass or less, and particularly preferably 6 parts by mass or less.

  Further, when the crosslinking agent (C) is an isocyanate crosslinking agent, the hydroxyl group of the (meth) acrylic acid ester polymer (A) is too much relative to the reactive group (isocyanate group) of the crosslinking agent (C). The probability that the crosslinking agent (C) is consumed in the crosslinking reaction with the (meth) acrylic acid ester polymer (A) increases, and the probability of forming a crosslinking agent adduct with the polyrotaxane compound (B) decreases. On the other hand, if the hydroxyl group of the (meth) acrylic acid ester polymer (A) is too small relative to the reactive group of the cross-linking agent (C), the cross-linking structure of the resulting pressure-sensitive adhesive becomes too dense, and the step following ability is high. May be insufficient. From such a viewpoint, the ratio of the number of moles of the hydroxyl group of the (meth) acrylate polymer (A) to the number of moles of the reactive group of the crosslinking agent (C) is preferably 5 or less, and preferably 3 or less. Is more preferable, it is especially preferable that it is 1 or less, and it is still more preferable that it is 0.5 or less. Further, the molar ratio 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 For the adhesive composition P, if necessary, various additives usually used for acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, and tackifiers. Antioxidants, light stabilizers, softeners, refractive index adjusters, rust inhibitors and the like can be added. In addition, the below-mentioned polymerization solvent and dilution solvent shall not be contained in the additive which comprises the adhesive composition P.

  On the other hand, it is preferable that the adhesive composition P does not contain fillers such as fine particles. According to the pressure-sensitive adhesive according to this 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. Furthermore, since the filler as a raw material and the operation | work which disperse | distributes a filler in an adhesive become unnecessary, cost reduction can be aimed at.

(2) Manufacture of adhesive composition The adhesive composition P manufactured the (meth) acrylic acid ester polymer (A), the obtained (meth) acrylic acid ester polymer (A), the polyrotaxane compound ( While mixing B) and a crosslinking agent (C), it can manufacture by adding an additive if desired.

  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. Two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 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 organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  When the (meth) acrylic acid ester polymer (A) is obtained, the polyrotaxane compound (B), the cross-linking agent (C), and a diluting solvent and an optional addition are added to the solution of the (meth) acrylic acid ester polymer (A). An adhesive composition P (coating solution) diluted with a solvent is obtained by adding the agent and mixing thoroughly. When any of the above components is used in a solid state or when precipitation occurs when mixed with other components in an undiluted state, the component is used alone as a dilution solvent. It may be dissolved or diluted and then mixed with other components.

  Examples of the dilution 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, 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 / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may be 10-60 mass%. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as a dilution solvent.

(3) Production of pressure-sensitive adhesive The pressure-sensitive adhesive according to this embodiment is obtained by crosslinking the pressure-sensitive adhesive composition P. The crosslinking of the pressure-sensitive adhesive composition P can be usually performed by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing a dilution solvent etc. from the coating film of the adhesive composition P apply | coated to the desired target object.

  The heating temperature of the heat treatment is preferably 50 to 150 ° C, and particularly preferably 70 to 120 ° C. The heating time is preferably 10 seconds to 10 minutes, 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). When this curing period is necessary, after the curing period has elapsed, and when the curing period is unnecessary, an adhesive is formed after the heat treatment.

  By the heat treatment (and curing), at least the polyrotaxane compound (B) and, in some cases, the (meth) acrylate polymer (A) are also cross-linked through the cross-linking agent (C). The pressure-sensitive adhesive obtained in this manner is excellent in both light diffusibility and step following ability.

(4) Physical properties of the pressure-sensitive adhesive The gel fraction of the pressure-sensitive adhesive according to this embodiment is 20% or more as a lower limit, preferably 30% or more, and particularly preferably 40% or more. When the lower limit of the gel fraction of the pressure-sensitive adhesive is as described above, the cohesive force of the pressure-sensitive adhesive is increased, and the step following property under high-temperature and high-humidity conditions is excellent. Further, the gel fraction of the pressure-sensitive adhesive according to the present embodiment is 99% or less as an upper limit, preferably 95% or less, particularly preferably 90% or less, and more preferably 80% or less. It is preferable. When the upper limit value of the gel fraction of the pressure-sensitive adhesive is as described above, the pressure-sensitive adhesive does not become too hard, and the initial level-step following property is excellent. Here, the measuring method of the gel fraction of an adhesive is as showing to the test example mentioned later.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to this embodiment is a pressure-sensitive adhesive sheet having at least 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. .

The specific structure as an example of the adhesive sheet which concerns on this embodiment is shown in FIG.
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to an embodiment includes two release sheets 12a and 12b and the two release sheets 12a so as to be in contact with the release surfaces of the two release sheets 12a and 12b. , 12b and an adhesive layer 11 sandwiched between the two layers. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

(1) Adhesive layer The adhesive layer 11 is comprised from the adhesive mentioned above, ie, it is comprised from the adhesive formed by bridge | crosslinking the adhesive composition P. As shown in FIG.

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

  The thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less as an upper limit, more preferably 500 μm or less, and particularly preferably 300 μm or less. When the upper limit value of the thickness of the pressure-sensitive adhesive layer 11 is the above, workability is 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 pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to this 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, polyethylene naphthalate film, and 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 film, polyimide film, fluorine A resin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  It is preferable that the peeling surface (especially the surface in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b is subjected to a peeling treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Of the release sheets 12a and 12b, one release sheet is preferably a heavy release release sheet having a high release force, and the other release sheet is preferably a light release release sheet having a low release force.

  Although there is no restriction | limiting in particular about the thickness of release sheet 12a, 12b, Usually, it is about 20-150 micrometers.

(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 this embodiment is preferably 30% or more, and particularly preferably 35% or more, as a lower limit. It is preferably 40% or more. When the lower limit of the haze value is as described above, the pressure-sensitive adhesive layer 11 is excellent in light diffusibility. In this embodiment, the high haze value as described above can be achieved by forming the pressure-sensitive adhesive layer 11 from a pressure-sensitive adhesive obtained by crosslinking the above-described pressure-sensitive adhesive composition P.

  In addition, 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 more preferably 80% or less as an upper limit value. It is preferable. When the upper limit value of the haze value is as described above, 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 this specification is a value measured according to JIS K7136: 2000.

(3-2) Adhesive strength The adhesive strength of the pressure-sensitive adhesive sheet 1 according to the present embodiment with respect to soda lime glass is preferably 5 N / 25 mm or more as a lower limit, and particularly preferably 10 N / 25 mm or more. It is preferable that it is 15N / 25mm or more. When the lower limit value of the adhesive strength is as described above, the step following property under a high temperature and high humidity condition becomes more excellent. Moreover, it is preferable that the adhesive force with respect to soda-lime glass of the adhesive sheet 1 which concerns on this embodiment is 50 N / 25mm or less as an upper limit, It is more preferable that it is 40 N / 25mm or less, It is 20 N / 25mm or less Is particularly preferred. When the adhesive strength of the pressure-sensitive adhesive sheet 1 is 50 N / 25 mm or less, good reworkability is obtained, and when a bonding error occurs, an expensive display member can be reused.

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

(4) Production of pressure-sensitive adhesive sheet As a production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and heat treatment is performed for adhesion. After heat-crosslinking property composition P and forming a coating layer, the peeling surface of the other peeling sheet 12b (or 12a) is piled up on the coating layer. When a curing period is required, a curing period is set, and when the curing period is unnecessary, the coating layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

  As another production example of the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one release sheet 12a, heat-treated to thermally cross-link the pressure-sensitive adhesive composition P, and then applied. A layer is formed to obtain a release sheet 12a with a coating layer. Moreover, the coating liquid of the said adhesive composition P is apply | coated to the peeling surface of the other peeling sheet 12b, heat processing is performed, the adhesive composition P is heat-crosslinked, a coating layer is formed, and a coating layer is attached. The release sheet 12b is obtained. And the peeling sheet 12a with an application layer and the peeling sheet 12b with an application layer are bonded together so that both application layers may mutually contact. When the curing period is necessary, the curing period is set, and when the curing period is unnecessary, the above-mentioned laminated application layer becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the said adhesive sheet 1 is obtained. According to this production example, even when the pressure-sensitive adhesive layer 11 is thick, it can be stably produced.

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

[Display]
An example of the display body obtained using the adhesive sheet 1 according to the present embodiment is shown in FIG. The display body 2 according to the present embodiment includes a first display body constituent member 21 (one display body constituent member) and a second display body constituent member 22 (others) having a step on at least a surface to be bonded. Display body constituent member) and an adhesive layer 11 which is located between them and bonds the first display body constituent member 21 and the second display body constituent member 22 to each other. In the display body 2 according to the present embodiment, the first display body constituting member 21 has a step on the surface on the pressure-sensitive 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. Moreover, as the display body 2, the member which comprises those some may be sufficient.

  It is preferable that the 1st display body structural member 21 is a protection panel which consists of a laminated body etc. other than a glass plate, a plastic plate, etc. In this case, the printing layer 3 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side in the first display member constituting member 21.

  The glass plate is not particularly limited. For example, chemically tempered glass, alkali-free glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate Glass etc. are mentioned. Although the thickness of a glass plate is not specifically limited, Usually, it is 0.1-5 mm, Preferably it is 0.2-2 mm.

  The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate. Although the thickness of a plastic board is not specifically limited, Usually, it is 0.2-5 mm, Preferably it is 0.4-3 mm.

  Various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, antiglare layer, etc.) may be provided on one or both surfaces of the glass plate or plastic plate, or an optical member. May be laminated. Moreover, the transparent conductive film and the metal layer may be patterned.

  The second display member constituting member 22 includes an optical member to be attached to the first display member constituting member 21, a display member module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic) EL) module, etc.), an optical member as a part of the display module, or a laminate including the display module.

  Examples of the optical member include a scattering prevention film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, and a diffusion film. , Transflective film, transparent conductive film, and the like. Examples of the scattering prevention film include a hard coat film in which a hard coat layer is formed on one side of a base film.

  The material which comprises the printing layer 3 is not specifically limited, The well-known material for printing is used. The lower limit of the thickness of the printing 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. preferable. When the lower limit is as described above, it is possible to sufficiently ensure concealment properties such as making the electrical wiring invisible from the viewer side. The upper limit value is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and further preferably 20 μm or less. When the upper limit value is as described above, it is possible to prevent deterioration in the step following property of the pressure-sensitive adhesive layer 11 with respect to the printing layer 3.

  In order to manufacture the said display body 2, as an example, one peeling sheet 12a of the adhesive sheet 1 is peeled, and the adhesive layer 11 which the adhesive sheet 1 exposed is used as the printing layer of the 1st display body structural member 21. It is bonded to the surface on the side where 3 is present. At this time, since the pressure-sensitive adhesive layer 11 is excellent in level difference followability, it is possible to suppress the occurrence of gaps and floating in the vicinity of the level difference due to the printing layer 3.

  Then, the other peeling sheet 12b is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1 and the second display member constituting member 22 are bonded together. As another example, the bonding order of the first display member constituting member 21 and the second display member constituting member 22 may be switched.

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

  Furthermore, 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. and 85% RH). Even in the case of being opened, the occurrence of bubbles, floating, peeling, etc. in the vicinity of the step is suppressed.

  In addition, the use position in the display body of the adhesive sheet 1 (adhesive layer 11) which concerns on this embodiment is not limited to said example. For example, the pressure-sensitive adhesive sheet 1 according to the present embodiment may be used for bonding display body constituent members having no steps as described above. Specifically, the pressure-sensitive adhesive sheet 1 according to this embodiment is also suitably used for bonding a liquid crystal cell and a backlight. Since the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is excellent in light diffusibility, the brightness of the obtained display body is made uniform by the pressure-sensitive adhesive layer 11. In addition, the excellent flexibility of the pressure-sensitive adhesive layer 11 can flexibly cope with the expansion and contraction of the optical member due to the temperature difference, and high durability is expected.

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

  For example, one or both of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12a and / or 12b. Further, the first display member constituting member 21 may have a step other than the printed layer 3. Furthermore, not only the 1st display body structural member 21, but the 2nd display body structural member 22 may also have a level | step difference in the adhesive layer 11 side.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 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 The (meth) acrylic acid ester polymer (A) was prepared by copolymerization using a legal method. 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. Preparation of Adhesive Composition 100 parts by mass of the (meth) acrylic acid ester polymer (A) obtained in Step 1 above (converted to a solid content; the same applies hereinafter) and a polyrotaxane compound (B) (Advanced Soft Materials, Inc.) Manufactured, product name “Celum 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 mg KOH / g) 5.0 parts by mass and 2.0 parts by mass of trimethylolpropane-modified tolylene diisocyanate (product name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) as a crosslinking agent (C) are mixed. Adhesive composition by stirring well and diluting with methyl ethyl ketone To obtain a coating solution.

Here, Table 1 shows each formulation (solid content converted value) of the adhesive composition when the (meth) acrylic acid ester polymer (A) is 100 parts by mass (solid content converted value). Details of the abbreviations and the like described in Table 1 are as follows.
[(Meth) acrylic acid ester polymer (A)]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: acrylic acid HEA: 2-hydroxyethyl acrylate IBXA: isobornyl acrylate
[Crosslinking agent (C)]
TDI: Trimethylolpropane-modified tolylene diisocyanate (product name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.)
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 (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) acrylate polymer (A) to the number of moles of the reactive group (isocyanate group) of the crosslinking agent (C). Described.

3. Production of pressure-sensitive adhesive sheet (1) Production of first pressure-sensitive adhesive sheet (thickness of pressure-sensitive adhesive layer: 25 μm) The coating solution of the pressure-sensitive adhesive composition obtained in the above step 2 was applied to one side of the polyethylene terephthalate film with a silicone release agent. The release treatment surface of the heavy release type release sheet (product name: “SP-PET752150”, manufactured by Lintec Corporation) that had been subjected to the release treatment was applied with a knife coater. And the application layer was heat-processed at 90 degreeC for 1 minute (s), and the application layer was formed.

  Next, a light release type release sheet (product name “SP-PET382120”, manufactured by Lintec Corporation) in which the coating layer on the heavy release type release sheet obtained above and one side of the polyethylene terephthalate film were release-treated with a silicone-based release agent Are bonded so that the release-treated surface of the light release-type release sheet is in contact with the coating layer, and is cured for 7 days under the conditions of 23 ° C. and 50% RH. A pressure-sensitive adhesive sheet composed of a layer / light release type release sheet was prepared. The thickness of the pressure-sensitive adhesive layer in this pressure-sensitive adhesive sheet was 25 μm. The pressure-sensitive adhesive sheet is referred to as a first pressure-sensitive adhesive sheet.

(2) Production of second pressure-sensitive adhesive sheet (thickness of pressure-sensitive adhesive layer: 50 μm) One side of the polyethylene terephthalate film was peeled off with a silicone-based release agent from the adhesive composition coating solution obtained in Step 2 above. It applied with the knife coater to the peeling process surface of the heavy peeling type peeling sheet (the product name "SP-PET752150" by Lintec Corporation). And the application layer was heat-processed at 90 degreeC for 1 minute (s), and the application layer was formed. Similarly, the coating solution of the obtained adhesive composition was applied to the release-treated surface of a light release-type release sheet (product name “PET382120” manufactured by Lintec Corporation) in which one side of a polyethylene terephthalate film was release-treated with a silicone-based release agent. After coating with a knife coater so that the thickness after drying was 25 μm, the coating layer was formed by heat treatment at 90 ° C. for 1 minute.

  Subsequently, 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 were bonded so that both coating layers were in contact with each other. By curing for 7 days under the condition of 50% RH, a pressure-sensitive adhesive sheet having a structure of heavy release type release sheet / adhesive layer / light release type release sheet was produced. The thickness of the pressure-sensitive adhesive layer in this pressure-sensitive adhesive sheet was 50 μm. This pressure-sensitive adhesive sheet is referred to as a second pressure-sensitive adhesive sheet.

  In addition, the thickness of the said adhesive layer is the value measured using the constant pressure thickness measuring device (The product name "PG-02" by the Teclock company) based on JISK7130.

[Examples 2 to 21, Comparative Examples 1 to 7]
Kind 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 blending amount of the polyrotaxane compound (B), and a crosslinking agent ( Except changing the kind and compounding quantity of C) as shown in Table 1, it carried out similarly to Example 1, and manufactured the 1st and 2nd adhesive sheet.

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

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
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 of the pressure-sensitive adhesive alone was calculated by weighing the mass with a precision balance and 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. Thereafter, the pressure-sensitive 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 pressure sensitive 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)
About the adhesive layer of the 1st adhesive sheet (thickness of an adhesive layer: 25 micrometers) obtained by the Example and the comparative example, according to JISK7136: 2000, a haze meter (Nippon Denshoku Industries Co., Ltd. make, product name) 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 release sheet was peeled from the first pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer thickness: 25 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was replaced with polyethylene terephthalate (PET ) The film (Toyobo Co., Ltd., product name “PET A4300”, thickness: 100 μm) was bonded to an easy adhesion layer to obtain a laminate of release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

  In an environment of 23 ° C. and 50% RH, the heavy release type release sheet is peeled off from the above sample, and the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). And pressurized at 0.5 MPa and 50 ° C. for 20 minutes. Then, after being allowed to stand for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (Orientec, Tensilon), the adhesive strength (N / 25 mm). Conditions other than those described here were measured according to JIS Z 0237: 2009. The results are shown in Table 2.

[Test Example 4] (Evaluation of step following ability)
On the surface of a glass plate (manufactured by NSG Precision, product name “Corning Glass Eagle XG”, length 90 mm × width 50 mm × thickness 0.5 mm), UV curable ink (product name “POS-911 Black”, manufactured by Teikoku Ink Co., Ltd.) ) Was screen-printed in a frame shape (outer shape: 90 mm long × 50 mm wide, 5 mm wide). Next, irradiation with ultraviolet rays (80 W / cm ² , ^two metal halide lamps, lamp height of 15 cm, belt speed of 10 to 15 m / min) is performed to cure the printed ultraviolet curable ink, and a level difference due to printing (level difference) Stepped glass plates having 5 μm, 10 μm, 15 μm, and 20 μm) were produced.

  The lightly peelable release sheet was peeled off from the second pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 50 μm) obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was replaced with a polyethylene terephthalate film (Toyobo Co., Ltd.) having an easy-adhesive layer. The product was bonded to an easy-adhesion layer having a 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 (product name “LPD3214”, manufactured by Fuji Plastics Co., Ltd.), the laminate is laminated on each stepped glass plate so that the adhesive layer covers the entire frame-like print, and this is used as an evaluation sample. did.

  The obtained sample for evaluation was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then allowed to stand at normal pressure, 23 ° C. and 50% RH for 24 hours. Next, the film was stored for 72 hours under a wet heat condition of 85 ° C. and 85% RH (endurance test), and then the step following property was evaluated. Step followability is determined by whether or not the printing step is completely filled with the adhesive layer.If gaps or bubbles are observed at the interface between the printing step and the adhesive layer, it can follow the printing step. It is judged that there was not. Here, the step following property was evaluated as a step following rate (%) according to the following criteria. The results are shown in Table 2.

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

  As can be seen from Table 2, the pressure-sensitive adhesive sheets obtained in the examples had high haze values and excellent level difference followability.

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

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Display body 21 ... 1st display body structural member 22 ... 2nd display body structural member 3 ... Print layer

Claims (6)

(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);
A pressure-sensitive adhesive obtained by crosslinking a pressure-sensitive adhesive composition containing a crosslinking 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 contains the hydroxyl group-containing monomer , When the hydroxyl group-containing monomer is contained at a content of less than 20% by mass, and when the carboxy group-containing monomer is contained, the carboxy group is contained at a content of less than 15% by mass,
The polyrotaxane compound (B) has a cyclic molecule containing a reactive group,
The pressure-sensitive adhesive has a gel fraction of 20% or more and 99% or less.   Content in the said adhesive composition of the said polyrotaxane compound (B) is 1 mass part or more and 30 mass parts or less with respect to 100 mass parts of said (meth) acrylic acid ester polymers (A). The pressure-sensitive adhesive according to claim 1.   The (meth) acrylic acid ester polymer (A) is 30% by mass to 99% by mass of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms as the monomer unit constituting the polymer. The pressure-sensitive adhesive according to claim 1 or 2, which is contained below.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the crosslinking agent (C) is an isocyanate-based crosslinking agent. Two release sheets,
An adhesive sheet comprising an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets,
The said adhesive layer consists of an adhesive as described in any one of Claims 1-4, The adhesive sheet characterized by the above-mentioned.   The pressure-sensitive adhesive sheet according to claim 5, wherein the pressure-sensitive adhesive layer has a haze value of 30% or more and 90% or less.

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