JP6888901B2 - Adhesive Compositions, Adhesives, Adhesive Sheets and Labels - Google Patents

Description

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

In recent years, various mobile electronic devices such as smartphones and tablet terminals are provided with a display using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. It is becoming more and more popular as a touch panel.

In a display as described above, a protective panel is usually provided on the surface side of the display module. With the thinning and weight reduction of electronic devices, the protective panel has been changed from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate.

Here, a gap is provided between the protective panel and the display module 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 light reflection loss due to 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 display module is large, and the display There is a problem that the image quality is deteriorated.

Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer. However, a frame-shaped print layer may exist as a step on the display 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-following property.

In order to solve the above problems, Patent Document 1 has a shear storage elastic modulus (G') of 1.0 at 25 ° C. and 1 Hz as an adhesive layer that fills the gap between the protective panel and the display module. A pressure-sensitive adhesive layer having a gel content of × 10 ⁵ Pa or less and a gel content of 40% or more is disclosed.

JP-A-2010-97070

Patent Document 1 attempts to improve the step followability by lowering the storage elastic modulus of the pressure-sensitive adhesive layer at room temperature. However, if the storage elastic modulus at room temperature is lowered as described above, the storage elastic modulus at high temperature is lowered more than necessary, and a problem occurs under durable conditions. For example, when high temperature and high humidity conditions are applied, air bubbles are generated in the vicinity of the step, or outgas is generated from the plastic plate which is a protective panel, and blisters such as air bubbles, floating, and peeling are generated. On the other hand, if the adhesive layer is hardened in order to improve the blister resistance, the step followability is lowered.

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 composition, an adhesive, an adhesive sheet and a display body having excellent step-following property and blister resistance. ..

In order to achieve the above object, first, the present invention comprises a (meth) acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer as a monomer unit constituting the polymer, and a cyclic having a hydroxyl group as a reactive group. An adhesive composition comprising a polyrotaxane compound (B) having an oligosaccharide as a cyclic molecule, an isocyanate-based cross-linking agent (C), and a reaction accelerator (D) that promotes a urethanization reaction. Provided (Invention 1).

When the adhesive composition according to the above invention (Invention 1) is crosslinked, the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth) acrylic acid ester polymer (A), the hydroxyl group of the cyclic oligosaccharide of the polyrotaxane compound (B), and isocyanate. High three-dimensional network structure, etc., in which the isocyanate group of the system cross-linking agent (C) reacts well and a plurality of (meth) acrylic acid ester polymers (A) are mechanically bonded to each other by the polyrotaxane compound (B). It is presumed that the following structure is formed. Further, due to the urethanization reaction promoting action of the reaction accelerator (D), the higher-order structure is surely and densely formed. Due to such a high-order structure, the obtained adhesive exhibits high stress relaxation property and is excellent in step followability, and also has high cohesive force and excellent blister resistance.

In the above invention (Invention 1), the content of the polyrotaxane compound (B) in the adhesive composition is 0.5 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). As mentioned above, it is preferably 20 parts by mass or less (Invention 2).

In the above inventions (Inventions 1 and 2), the content of the reaction accelerator (D) in the adhesive composition is 0. It is preferably 01 parts by mass or more and 1.5 parts by mass or less (Invention 3).

In the above inventions (Inventions 1 to 3), the (meth) acrylic acid ester polymer (A) contains the hydroxyl group-containing monomer in an amount of 3% by mass or more and 30% by mass or less as a monomer unit constituting the polymer. It is preferable (Invention 4).

Secondly, the present invention provides a pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive compositions (Inventions 1 to 4) (Invention 5).

In the above invention (Invention 5), the gel fraction is preferably 30% or more and 90% or less (Invention 6).

Thirdly, the present invention is an adhesive sheet having an adhesive layer for adhering one display body component having a step on at least the surface to be bonded and another display body component. Provided is a pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive (inventions 5 and 6) (invention 7).

In the above invention (Invention 7), the step follow-up rate of the pressure-sensitive adhesive layer is preferably 20% or more (Invention 8).

In the above inventions (Inventions 7 and 8), the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. (Invention 9).

Fourth, in the present invention, one display body component having a step on at least the surface to be bonded, another display body component, the one display body component, and the other display body component. Provided is a display body including a pressure-sensitive adhesive layer in which the above-mentioned materials are bonded to each other, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 7 to 9). Invention 10).

The adhesive composition, adhesive, adhesive sheet and display according to the present invention are excellent in both step followability and blister resistance.

It is sectional drawing of the pressure-sensitive adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing of the laminated body which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The adhesive composition according to the present embodiment (hereinafter, may be referred to as “adhesive composition P”) is a (meth) acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer as a monomer unit constituting the polymer. ), A polyrotaxane compound (B) having a cyclic oligosaccharide having a hydroxyl group as a cyclic molecule as a cyclic molecule, an isocyanate-based cross-linking agent (C), and a reaction accelerator (D) that promotes a urethanization reaction. To do. 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 according to the present embodiment is crosslinked, the isocyanate group of the isocyanate-based crosslinking agent (C) reacts with the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth) acrylic acid ester polymer (A). , The isocyanate group of the isocyanate-based cross-linking agent (C) reacts with the hydroxyl group of the cyclic molecule of the polyrotaxane compound (B). As a result, the (meth) acrylic acid ester polymer (A) is bonded to one cyclic molecule of the polyrotaxane compound (B) by the hydroxyl group via the isocyanate-based cross-linking agent (C), and similarly, another (meth) It is presumed that the acrylic acid ester polymer (A) binds to another cyclic molecule of the polyrotaxane compound (B). 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. As a result, it is presumed that the plurality of (meth) acrylic acid ester polymers (A) form higher-order structures such as a three-dimensional network structure mechanically bonded to each other by the polyrotaxane compound (B). Due to such a high-order structure, the obtained adhesive exhibits high stress relaxation property and is excellent in step followability. For example, in the pressure-sensitive adhesive sheet obtained by using the pressure-sensitive adhesive composition P according to the present embodiment, when the pressure-sensitive adhesive sheet is attached to a display body component having a step, the pressure-sensitive adhesive layer easily follows the step, and a gap is formed in the vicinity of the step. Floating and the like are suppressed. 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, bubbles, floating, peeling and the like are suppressed in the vicinity of the step.

Further, when the adhesive composition P according to the present embodiment is crosslinked, the hydroxyl group derived from the hydroxyl group-containing monomer in the (meth) acrylic acid ester polymer (A) and the hydroxyl group due to the urethanization reaction promoting action of the reaction accelerator (D) and The hydroxyl group of the cyclic oligosaccharide of the polyrotaxane compound (B) reacts well with the isocyanate group of the isocyanate-based cross-linking agent (C), and the above-mentioned higher-order structure is surely and densely formed. As a result, the obtained adhesive has a high cohesive force while maintaining excellent stress relaxation properties, and has excellent blister resistance. For example, a display obtained by using the adhesive composition P according to the present embodiment is placed under high temperature and high humidity conditions (for example, 85 ° C., 85% RH) and outgassed from a display body component made of a plastic plate or the like. Even when the above occurs, the generation of blister such as air bubbles, floating, and peeling at the interface between the pressure-sensitive adhesive layer and the display body constituent member is suppressed.

It is not necessary that all of the obtained pressure-sensitive adhesives have the above-mentioned estimated structure, and the two (meth) acrylic acid ester polymers (A) are not mediated by the polyrotaxane compound (B), and the isocyanate-based cross-linking agent (C) is used. It may include a structure or the like that is directly bonded by.

(1) (Meta) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) in the present embodiment contains a hydroxyl 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). ) Hydroxyalkyl esters of (meth) acrylic acid such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Among them, (meth) acrylic acid 2-in the obtained (meth) acrylic acid ester polymer (A) from the viewpoint of reactivity of the hydroxyl group with the isocyanate-based cross-linking agent (C) and copolymerizability with other monomers. Hydroxyethyl or 4-hydroxybutyl (meth) acrylate is preferred. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer in an amount of 3% by mass or more, particularly preferably 5% by mass or more, as a monomer unit constituting the polymer. It is preferably contained in an amount of 10% by mass or more. When the content of the hydroxyl group-containing monomer is 3% by mass or more, the cohesive force of the obtained pressure-sensitive adhesive is improved, and thereby the blister resistance and the step followability under high temperature and high humidity conditions are further improved. Further, the (meth) acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer in an amount of 30% by mass or less, and particularly preferably 25% by mass or less, as a monomer unit constituting the polymer. Further, it is preferably contained in an amount of 20% by mass or less. When the content of the hydroxyl group-containing monomer is 30% by mass or less, it becomes easy to obtain appropriate adhesiveness, it is suppressed that the adhesive becomes too hard, and the step followability becomes more excellent.

The (meth) acrylic acid ester polymer (A) contains a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer, thereby achieving preferable adhesiveness. Can be expressed. From this point of view, the (meth) acrylic acid ester polymer (A) contains 50% 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. It is preferable that the content is 60% by mass or more, and more preferably 70% by mass or more. When the (meth) acrylic acid alkyl ester is contained in an amount of 50% by mass or more, the (meth) acrylic acid ester polymer (A) can exhibit suitable adhesiveness. Further, the (meth) acrylic acid ester polymer (A) contains 97% 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 in particular, it is preferably contained in an amount of 90% by mass or less, and more preferably 85% by mass or less. By adjusting the amount of the (meth) acrylic acid alkyl ester to 97% by mass or less, a suitable amount of other monomer components can be introduced into the (meth) acrylic acid ester polymer (A).

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) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylate Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate. Above all, from the viewpoint of further improving the adhesiveness, it is preferable that a (meth) acrylic acid ester having 1 to 8 carbon atoms in the alkyl group is contained. These may be used alone or in combination of two or more.

Further, as a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms, a monomer (hard monomer) having a glass transition temperature (Tg) exceeding 0 ° C. as a homopolymer and a glass transition temperature as a homopolymer. It is also preferable to use it in combination with a monomer (soft monomer) having (Tg) of 0 ° C. or lower. This is because the blister resistance and the step followability 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, particularly preferably 20:80 to 30:70.

Examples of the hard monomer include methyl acrylate (Tg10 ° C.), methyl methacrylate (Tg105 ° C.), isobornyl acrylate (Tg94 ° C.), isobornyl methacrylate (Tg180 ° C.), adamantyl acrylate (Tg115 ° C.), and methacrylic acid. Adamantane (Tg 141 ° C.) and the like can be mentioned. These may be used alone or in combination of two or more.

Among the above hard monomers, methyl acrylate, methyl methacrylate and isobornyl acrylate are preferable from the viewpoint of further exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesiveness and transparency. Methyl acrylate and methyl methacrylate are more preferable in consideration of adhesiveness.

Preferred examples of the soft monomer include acrylic acid alkyl esters having a linear or branched alkyl group having 2 to 12 carbon atoms. For example, 2-ethylhexyl acrylate (Tg-70 ° C.), n-butyl acrylate (Tg-54 ° C.) and the like are preferably mentioned. These may be used alone or in combination of two or more.

Further, as a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in an alkyl group, a monomer having an alicyclic structure using at least a part of the (meth) acrylic acid alkyl ester as an alkyl group (alicyclic structure). (Containing monomer) is also preferable. Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of the monomer in the polymer widens the distance between the polymers, and the obtained adhesive can be made excellent in flexibility. .. As a result, the pressure-sensitive adhesive becomes more excellent in step-following property.

The alicyclic structure carbon ring in the alicyclic structure-containing monomer may have a saturated structure or may have an unsaturated bond as a part. Further, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as two rings or three rings. From the viewpoint of making the distance between the obtained (meth) acrylic acid ester polymers (A) appropriate and imparting high stress relaxation property to the pressure-sensitive adhesive, the alicyclic structure is a polycyclic alicyclic structure. Polycyclic structure) is preferable. Further, in consideration of the compatibility between the (meth) acrylic acid ester polymer (A) and other components, the polycyclic structure is particularly preferably bicyclic to tetracyclic. Further, from the viewpoint of imparting stress relaxation property as described above, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the portion forming the ring, and when a plurality of rings exist independently) , The total number of carbon atoms) is usually preferably 5 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but from the viewpoint of compatibility as described above, it is preferably 15 or less, and particularly preferably 10 or less.

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

When the (meth) acrylic acid ester polymer (A) contains an alicyclic structure-containing monomer as a constituent monomer unit, the alicyclic structure in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group. The proportion of the contained monomer is preferably 1% by mass or more, particularly preferably 5% by mass or more, and further preferably 10% by mass or more. The proportion of the alicyclic structure-containing monomer is preferably 50% by mass or less, particularly preferably 40% by mass or less, and further preferably 30% by mass or less. When the content of the alicyclic structure-containing monomer is within the above range, the obtained adhesive has more excellent step-following property, and excellent adhesive force to the transparent conductive film and plastic is sufficiently exhibited.

Further, it is also preferable that the (meth) acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. By allowing a nitrogen atom-containing monomer to be present in the polymer as a constituent unit, a predetermined polarity is imparted to the pressure-sensitive adhesive, and the adhesive has excellent affinity for an adherend having a certain degree of polarity such as glass. Can be. Examples of the nitrogen atom-containing monomer include a monomer having an amino group, a monomer having an amide group, a monomer having a nitrogen-containing heterocycle, and the like, and among them, a monomer having a nitrogen-containing heterocycle is preferable.

Examples of the monomer having a nitrogen-containing heterocycle include N- (meth) acryloyl morpholine, N-vinyl-2-pyrrolidone, N- (meth) acryloyl pyrrolidone, N- (meth) acryloyl piperidine, and N- (meth) acryloyl. Pyrrolidine, N- (meth) acryloyl azylidine, aziridinyl ethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. Among them, N- (meth) acryloylmorpholin, which exhibits more excellent adhesive strength, is preferable, and N-acryloylmorpholin is particularly preferable.

Examples of nitrogen atom-containing monomers include (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, N-tert-butyl (meth) acrylamide, and N, N-dimethyl (meth) acrylamide. , N, N-ethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-phenyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, N-vinyl Caprolactam, monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, etc. It can also be used.
The above nitrogen atom-containing monomers may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a nitrogen atom-containing monomer in an amount of 0.5% by mass or more, and particularly preferably 1% by mass or more, as a monomer unit constituting the polymer. Further, it is preferably contained in an amount of 3% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a nitrogen atom-containing monomer in an amount of 20% by mass or less, and particularly preferably 15% by mass or less, as a monomer unit constituting the polymer. Further, it is preferably contained in an amount of 8% by mass or less. When the content of the nitrogen atom-containing monomer is within the above range, the obtained pressure-sensitive adhesive can sufficiently exert excellent adhesive strength to glass.

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. The other monomer may be a monomer containing a reactive functional group (excluding a hydroxyl group) or a monomer containing no reactive functional group.

As the monomer containing a reactive functional group, a carboxy group-containing monomer is preferably mentioned. 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. Of these, acrylic acid is preferable from the viewpoint of the influence on the reaction between the hydroxyl group derived from the hydroxyl group-containing monomer and the isocyanate-based cross-linking 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 thereof is preferably 0.5% by mass or more, particularly 1% by mass. % Or more is preferable. The content is preferably 20% by mass or less, and particularly preferably 10% by mass or less.

From the viewpoint of facilitating the control of the crosslinked structure of the obtained pressure-sensitive adhesive, it is also preferable to use only the above-mentioned hydroxyl group-containing monomer as the monomer containing a reactive functional group.

On the other hand, examples of the reactive functional group-free monomer include (meth) acrylic acid alkoxyalkyl ester such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, vinyl acetate, styrene and the like. Be done. 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 preferably 200,000 or more, particularly preferably 300,000 or more, and further preferably 400,000 or more as the lower limit value. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is at least the above, the blister resistance of the obtained pressure-sensitive adhesive becomes more excellent.

The weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 1 million or less, particularly preferably 800,000 or less, and further preferably 700,000 or less as the upper limit value. preferable. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, the step-following property of the obtained pressure-sensitive adhesive becomes more excellent. 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, the (meth) acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(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 adhesive composition P according to the present embodiment contains the polyrotaxane compound (B) having such a mechanical bond, and the (meth) acrylic acid ester polymer (A) and the polyrotaxane via the isocyanate-based cross-linking agent (C). When the compound (B) (cyclic molecule) is crosslinked, the cyclic molecule freely moves on the linear molecule in the polyrotaxane compound (B), so that the flexibility as a crosslinked product is remarkably improved. As a result, the obtained adhesive exhibits extremely high stress relaxation properties and is excellent in step followability.

The polyrotaxane compound (B) in the present embodiment has a cyclic oligosaccharide as a cyclic molecule. By using a cyclic oligosaccharide as the cyclic molecule of the polyrotaxane compound (B), an appropriate ring diameter can be selected, and thus the effect of the movement of the cyclic molecule on the linear molecule is likely to be exhibited. Further, since the cyclic oligosaccharide has a hydroxyl group as a reactive group, the reaction with the isocyanate-based cross-linking agent (C) is easy. Further, it is easy to introduce various substituents and the like, whereby the compatibility between the polyrotaxane compound (B) and other components can be adjusted by the polyrotaxane compound (B). 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 cyclic molecules of the polyrotaxane compound (B) may be mixed in the polyrotaxane compound (B) or in the adhesive composition P.

The cyclic molecule (cyclic oligosaccharide) of the polyrotaxane compound (B) has a hydroxyl group as a reactive group. This hydroxyl group may be a hydroxyl group originally possessed by the cyclic oligosaccharide (meaning the state before modification), or may be a hydroxyl group introduced into the cyclic oligosaccharide as a substituent.

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 equal to or higher than the above, the polyrotaxane compound (B) can sufficiently react with the isocyanate-based 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 stress relaxation property of the pressure-sensitive adhesive layer may not be ensured.

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, "straight line" of "linear molecule" means that it is substantially "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, particularly preferably 10,000 or more, and further preferably 20,000 or more as the lower limit value. preferable. When the lower limit of the number average molecular weight is equal to or higher than the above, the amount of movement of the cyclic molecule on the linear molecule is secured, and the stress relaxation property of the pressure-sensitive adhesive can be sufficiently obtained. The number average molecular weight of the linear molecules of the polyrotaxane compound (B) is preferably 300,000 or less as an upper limit value, particularly preferably 200,000 or less, and further preferably 100,000 or less. Is preferable. When the upper limit of the number average molecular weight is not more than the above, the solubility of the polyrotaxane compound (B) in a solvent and the compatibility with the (meth) acrylic acid ester polymer (A) are improved.

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) is a dinitrophenyl group, a cyclodextrin group, an adamantan group, a trityl group group, a fluorescein group, a pyrene group, an anthracene group, 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 is 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). It is preferably 1 part by mass or more, and further preferably 3 parts by mass or more. When the content of the polyrotaxane compound (B) is at least the above lower limit value, the stress relaxation property of the polyrotaxane compound (B), and by extension, the step followability becomes more excellent. The content of the polyrotaxane compound (B) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less as an upper limit value. When the content of the polyrotaxane compound (B) is not more than the above upper limit value, the compatibility with the (meth) acrylic acid ester polymer (A) can be well maintained, and the haze value of the obtained pressure-sensitive adhesive can be suppressed to a low level. it can.

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

The isocyanate-based cross-linking agent (C) 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. The isocyanate-based cross-linking agent (C) may be used alone or in combination of two or more.

The content of the isocyanate-based cross-linking agent (C) in the adhesive composition P is 0.05 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). It is preferable, in particular, it is preferably 0.1 part by mass or more, and further preferably 0.2 part by mass or more. When the lower limit of the content of the isocyanate-based cross-linking agent (C) is equal to or higher than the above, it is presumed that the above-mentioned higher-order structure can be formed satisfactorily. The step followability under wet conditions becomes more excellent. The content of the isocyanate-based cross-linking agent (C) is preferably 3 parts by mass or less, particularly 2 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 1 part by mass or less. When the upper limit of the content of the isocyanate-based cross-linking agent (C) is not more than the above, the degree of cross-linking can be made appropriate, and the step-following property of the obtained pressure-sensitive adhesive can be satisfactorily ensured.

(4) Reaction accelerator (D)
The reaction accelerator (D) in the present embodiment is a reaction accelerator that promotes the urethanization reaction. That is, the reaction accelerator (D) is a hydroxyl group derived from a hydroxyl group-containing monomer in the (meth) acrylic acid ester polymer (A), a hydroxyl group of a cyclic oligosaccharide of the polyrotaxane compound (B), and an isocyanate-based cross-linking agent (C). The reaction with the isocyanate group can be promoted, and the above-mentioned higher-order structure can be reliably formed. As a result, the obtained adhesive has particularly excellent blister resistance.

Examples of the reaction accelerator (D) include compounds of heavy metals such as tin, lead, mercury and bismuth (including organic metal compounds); complexes of transition metals such as titanium, iron, copper, zirconium, nickel, cobalt and manganese. In particular, acetylacetonate complexes; amine compounds; acid catalysts such as paratoluene sulfonic acid, phosphoric acid, hydrochloric acid, and ammonium chloride can be mentioned. Among these, an organotin compound and an amine compound are preferable, and an organotin compound is particularly preferable, from the viewpoint of promoting the urethanization reaction. The cross-linking accelerator (C) may be used alone or in combination of two or more.

Examples of the organic tin compound include organic tin compounds such as dimethyl tin dichloride; organic tin dilaurate, dimethyl tin di (2-ethylhexanoate), dimethyl tin diacetate, dibutyl tin dilaurate, dihexyl tin dilaurate, and dioctyl tin dilaurate. Fatty acid salts of tin compounds; thioglycolic acid ester salts of organotin compounds such as dimethyltinbis (isooctylthioglycolic acid ester) salt, dioctyltinbis (isooctylthioglycolic acid ester) salt; tin octylate, tin decanoate And the like, such as metal soap. Among the above, a fatty acid salt of an organic tin compound is preferable, and dibutyltin dilaurate is particularly preferable, from the viewpoint of promoting the urethanization reaction.

Examples of the amine compound include N, N, N', N'-tetramethylhexamethylenediamine, triethylamine, imidazole and the like. Among the above, triethylamine is preferable from the viewpoint of promoting the urethanization reaction.

The content of the reaction accelerator (D) in the adhesive composition P is preferably 0.001 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 0.003 parts by mass or more, and further preferably 0.005 parts by mass or more. When the content of the reaction accelerator (D) is at least the above lower limit value, the above-mentioned higher-order structure can be satisfactorily formed, and the blister resistance of the obtained pressure-sensitive adhesive becomes more excellent. The upper limit of the content is preferably 1.0 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less. When the content of the reaction accelerator (D) is not more than the above upper limit value, the adhesiveness of the obtained pressure-sensitive adhesive is maintained well.

(5) Reaction inhibitor The adhesive composition P preferably contains a reaction inhibitor in addition to the above components. In the adhesive composition P, depending on the type and content of the reaction accelerator (D), the urethanization reaction (crosslinking reaction) of the components (A) to (C) starts in the storage step (step before heating). However, by containing the reaction inhibitor, the storage stability (pot life) of the adhesive composition P at room temperature can be improved.

Examples of the reaction inhibitor include acetylene compounds, oxime compounds, organic nitrogen compounds, organic phosphorus compounds, and organic chlorine compounds. Among these, acetylene compounds are preferable, and acetylacetone is particularly preferable, from the viewpoint of the reaction suppressing action of the urethanization reaction. The above reaction inhibitors usually volatilize during the drying process when forming the pressure-sensitive adhesive layer. The reaction inhibitor may be used alone or in combination of two or more.

The content of the reaction inhibitor in the adhesive composition P is preferably 0.1 part by mass or more, particularly 0.2% by mass, with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably parts or more, and more preferably 0.5 parts by mass or more. The content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 3 parts by mass or less. When the content of the reaction inhibitor is within the above range, the storage stability of the adhesive composition P can be effectively improved.

(6) 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, tackifiers, and oxidations, if desired. Inhibitors, light stabilizers, softeners, fillers, refractive index adjusters and the like can be added. The polymerization solvent and the diluting solvent described later are not included in the additives constituting the adhesive composition P.

Here, when the adhesive composition P contains a silane coupling agent, the obtained adhesive has improved adhesion to a glass member or a plastic plate. As a result, the obtained pressure-sensitive adhesive becomes more excellent in blister resistance.

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

Examples of such a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 2-(. 3,4-Epoxycyclohexyl) Silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane , 3-Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, 3-Chloropropyltrimethoxysilane, 3-isocyanuppropyltriethoxysilane, or at least one of these, and alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. Examples thereof include a condensate of. These may be used individually by 1 type, and may be used in combination of 2 or more type.

When the adhesive composition P contains a silane coupling agent, the content thereof is preferably 0.01 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). In particular, it is preferably 0.05 parts by mass or more, and further preferably 0.1 parts by mass or more. The content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less.

(7) 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 (7). It can be produced by mixing B), an isocyanate-based cross-linking agent (C), and a reaction accelerator (D), and 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 a usual 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-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxyvivarate, (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 isocyanate-based cross-linking agent (C), and the reaction accelerator (D) are added to the solution of the (meth) acrylic acid ester polymer (A). ), And if desired, a diluting solvent and additives are added and mixed well to obtain a solvent-diluted tacky composition P (coating solution). 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.

[Adhesive]
The pressure-sensitive adhesive according to the present embodiment is obtained by cross-linking the pressure-sensitive 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). When this curing period is required, an adhesive is formed after the curing period has elapsed, and when the curing period is not required, after the heat treatment is completed.

By the above heat treatment (and curing), the (meth) acrylic acid ester polymer (A) and the polyrotaxane compound (B) are sufficiently crosslinked via the isocyanate-based cross-linking agent (C). The pressure-sensitive adhesive thus obtained is excellent in both step-following property and blister resistance.

The gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more as the lower limit value. When the lower limit of the gel fraction of the pressure-sensitive adhesive is equal to or higher than the above, the cohesive force of the pressure-sensitive adhesive becomes high, and the blister resistance becomes more excellent. The gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less as an upper limit value. When the upper limit of the gel fraction of the pressure-sensitive adhesive is not more than the above, the pressure-sensitive adhesive does not become too hard, and the step followability becomes more 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 has at least one display body component having a step on the surface to be bonded and an adhesive layer for bonding another display body component. The pressure-sensitive adhesive layer is made of the above-mentioned pressure-sensitive adhesive.

FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment.
As shown in FIG. 1, the 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 equal to or greater than 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 400 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 not more than the above, the 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 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 peeling 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) Step Follow-up Rate The adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment has a step-following rate (%) represented by the following formula as a lower limit of 20% or more. Is preferable, and in particular, it is preferably 25% or more, and further preferably 30% or more. The upper limit of the step follow-up rate is not particularly limited, but is usually preferably 80% or less, and particularly preferably 70% or less.
Step follow-up rate (%) = {(Height of step (μm) maintained in a buried state without bubbles, floating, peeling, etc. after a predetermined durability test) / (Thickness of adhesive layer)} × 100
The test method for the step follow-up rate is as shown in a test example described later.

As described above, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to the present embodiment is for bonding display body constituent members having a step on the surface on the side to be bonded. When the step follow-up rate of the pressure-sensitive adhesive layer is within the above range, the pressure-sensitive adhesive layer follows the step of the display body component member well, and bubbles, floats, peeling, etc. occur in the vicinity of the step even after the durability test. Is suppressed, thereby causing a loss of light reflection. The step follow-up rate in the above range can be achieved by appropriately adjusting the glass transition temperature (Tg) of the (meth) acrylic acid ester polymer (A) and the like.

(3-2) 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 5% or less, particularly preferably 3% or less, and further 1% or less. Is preferable. When the haze value of the pressure-sensitive adhesive layer 11 is 5% or less, the transparency is very high, which is suitable for optical applications (for displays). The haze value in the present specification is a value measured according to JIS K7136: 2000.

(3-3) Adhesive Strength The adhesive strength of the pressure-sensitive 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 adhesive strength of the adhesive sheet 1 is 5 N / 25 mm or more, the blister resistance 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 35 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 refers to 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 treatment is performed to adhere the adhesive sheet 1. 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. When the curing period is required, the curing period is set, and when 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 heat-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]
As shown in FIG. 2, the display body 2 according to the present embodiment has a first display body constituent member 21 (one display body constituent member) having a step on at least the surface on the side to be bonded, and a second display body constituent member 21 (one display body constituent member). A display body component 22 (another display body component) and an adhesive layer 11 located between them and for bonding the first display body component 21 and the second display body component 22 to each other. Be prepared. In the display body 2 according to the present embodiment, the first display body component 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 laminated body 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.

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 21, a display module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic)). 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 is preferable.

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 equal to or higher than the above value, it is possible to sufficiently secure concealment such as making the electrical wiring invisible to the viewer. The upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. When the upper limit value is equal to or less than the above value, 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 of the release sheets 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 printed layer of the first display body component 21. It is affixed 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 above display body 2, for example, the display body 2 is placed under high temperature and high humidity conditions (for example, 85 ° C., 85% RH) and outgassed from the first display body component 21 and / or the second display body component 22. However, since the pressure-sensitive adhesive layer 11 has excellent blister resistance, air bubbles, floats, and bubbles occur at the interface between the pressure-sensitive adhesive layer 11 and the first display body component 21 and / or the second display body component 22. The occurrence of blister such as peeling is suppressed.

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

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 or both of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1 may be omitted, and desired optical members 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 A (meth) acrylic acid ester polymer (meth) by copolymerizing 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate. A) was prepared. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, it was found to have a weight average molecular weight (Mw) of 600,000.

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 SH3400P", 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, Reaction with 5.0 parts by mass of hydroxyl value 72 mgKOH / g) and 0.25 parts by mass of trimethylol propane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Coronate L") as an isocyanate-based cross-linking agent (C). 0.005 parts by mass of dibutyltin dilaurate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) as an accelerator (D), 2.5 parts by mass of acetylacetone (manufactured by Tokyo Kasei Kogyo Co., Ltd.) as a reaction inhibitor, and 3 as a silane coupling agent. -Mixed with 0.25 parts by mass of glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name "KBM-403"), stirred well, and diluted with methyl ethyl ketone to have a solid content concentration of 35. A coating solution of a mass% adhesive composition was obtained.

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)]
2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate IBXA: isobornyl acrylate ACMO: 4-acryloylmorpholin BA: n-butyl acrylate MA: methyl acrylate
[Isocyanate-based cross-linking 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")
[Reaction accelerator (D)]
DBTDL: Dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.)
TEA: Triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

3. 3. Manufacture of Adhesive Sheet A heavy release type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") in which one side of a polyethylene terephthalate film is peeled off with a silicone-based release agent from the coating solution of the adhesive composition obtained in step 2 above. ”) Was applied to 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.

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. A first pressure-sensitive adhesive sheet having a layer (thickness: 25 μm) / light peeling type peeling sheet structure was prepared.

Further, a heavy peeling type release sheet (manufactured by Lintec Corporation, product name "SP-PET752150") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. After coating with a knife coater on the peeled surface of the above, a coating layer (thickness: 25 μm) was formed by heat treatment at 90 ° C. for 1 minute. Similarly, a light peeling type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. ) Was coated with a knife coater and then heat-treated at 90 ° C. for 1 minute to form a coating layer (thickness: 25 μm).

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, a second pressure-sensitive adhesive sheet having a structure of a heavy-release type release sheet / adhesive layer (thickness: 50 μm) / light-release type release sheet was prepared.

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 17, Comparative Examples 1 to 3]
Types and proportions of each monomer constituting the (meth) acrylic acid ester polymer (A), weight average molecular weight of the (meth) acrylic acid ester polymer (A), blending amount of the polyrotaxane compound (B), isocyanate-based cross-linking agent Example 1 except that the type and amount of (C), the type and amount of reaction accelerator (D), the amount of reaction inhibitor, and the amount of silane coupling agent are changed as shown in Table 1. The adhesive sheet was manufactured in the same manner as in the above.

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 lightly peelable 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 into polyethylene terephthalate (PET) having an easy-adhesive 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, the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then the autoclave manufactured by Kurihara Seisakusho Co., Ltd. is used. 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 Co., Ltd.). / 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] (Measurement of step follow-up rate)
On the surface of a glass plate (manufactured by NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", length 90 mm x width 50 mm x thickness 0.5 mm), UV curable ink (manufactured by Teikoku Inks, product name "POS-911 ink") ) Was screen-printed in a frame shape (outer shape: length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was any one of 5 μm, 10 μm, 15 μm, and 20 μm. 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. S: A stepped glass plate having one of 5 μm, 10 μm, 15 μm and 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 having an easy adhesive layer (Toyo Spinning Co., Ltd.). It was bonded to an easy-adhesive 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 for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under high temperature and high humidity 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 printing step is completely filled with the adhesive layer, and if bubbles, floating, peeling, etc. are observed at the interface between the printing step and the adhesive layer, the printing step is determined. It is judged that it could not follow. Here, the step followability was evaluated as the step follow rate (%) represented by the following formula. The results are shown in Table 2.
Step follow-up rate (%) = {(After the durability test, the height of the step maintained in a buried state without bubbles, floating, peeling, etc. (μm)) / (Thickness of adhesive layer: 50 μm)} × 100

[Test Example 5] (Evaluation of blister resistance)
A polyethylene terephthalate film in which the pressure-sensitive adhesive layer of the second pressure-sensitive adhesive sheet (thickness of the pressure-sensitive adhesive layer: 50 μm) obtained in Examples and Comparative Examples is provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one side. A transparent conductive film (manufactured by Oike Kogyo Co., Ltd., ITO film, thickness: 125 μm) and an acrylic plate made of polymethylmethacrylate (PMMA) (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name “Iupilon Sheet MR200”, thickness: It was sandwiched between 1 mm) and a laminated body was obtained.

The obtained laminate (sample) was autoclaved for 30 minutes under the conditions of 50 ° C. and 0.5 MPa, and then left at normal pressure at 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under high temperature and high humidity conditions of 85 ° C. and 85% RH. Then, air bubbles at the interface between the pressure-sensitive adhesive layer and the adherend were visually confirmed, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2.
◎… No bubbles ○… When the area of the sample in plan view is 100%, the ratio of the area occupied by bubbles is less than 10% △… The area occupied by bubbles when the area of the sample in plan view is 100% The ratio of air bubbles is 50% or more and less than 50% ×… When the area of the sample in a plan view is 100%, the ratio of the area occupied by bubbles is 50% or more.

As can be seen from Table 2, the adhesive sheet obtained in the examples was excellent in both step-following property and blister resistance.

The pressure-sensitive 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.

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

Claims (8)

As the monomer unit constituting the polymer, a (meth) acrylic acid ester polymer (A) containing a hydroxyl group-containing monomer and
A polyrotaxane compound (B) having a cyclic oligosaccharide having a hydroxyl group as a reactive group as a cyclic molecule, and
Isocyanate-based cross-linking agent (C) and
With the reaction accelerator (D) that promotes the urethanization reaction
Reaction inhibitors and contains <br/>,
The content of the polyrotaxane compound (B) is 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A).
The content of the reaction accelerator (D) is 0.001 part by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). An adhesive composition characterized by that. The (meth) acrylic acid ester polymer (A), as a monomer unit constituting the polymer, the hydroxyl group-containing monomer 3 wt% or more, according to claim 1, characterized in that it contains less 30 wt% Adhesive composition. A pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition according to claim 1 or 2. The pressure-sensitive adhesive according to claim 3 , wherein the gel fraction is 30% or more and 90% or less. An adhesive sheet having an adhesive layer for bonding one display body component having a step on the surface on the side to be bonded and another display body component.
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to claim 3 or 4. The pressure-sensitive adhesive sheet according to claim 5 , wherein the step-following rate of the pressure-sensitive adhesive layer is 20% or more. The adhesive sheet includes two release sheets.
The adhesive sheet according to claim 5 or 6 , wherein the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. At least one display body component having a step on the surface on the side to be bonded,
With other display body components,
A display body including the adhesive layer for adhering the one display body component and the other display body component to each other.
A display body characterized in that the pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 5 to 7.

Images