JP7255604B2 - Adhesive composition, adhesive layer, laminate and image display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, an adhesive layer, a laminate and an image display device.

In recent years, flat display panels such as liquid crystal display panels (LCD) and plasma display panels (PDP) have been actively developed, and more recently, in addition to flat display panels, curved display panels and flexible display panels have also been developed. being developed.

Organic electroluminescence (organic EL) panels are generally used for such curved display panels and flexible display panels.

These display panels, including flat ones, are provided with a laminate in which a plurality of films are laminated on the surface. In addition to the optical properties and durability required for the panel, it is required that the laminate does not peel off or float even when it is bent.

As an optical film pressure-sensitive adhesive that can be used in an optical film that takes into account the bending of such a laminate, a (meth)acrylic (meth)acrylic adhesive having a specific blend of predetermined monomers and having a glass transition temperature and a weight average molecular weight within a predetermined range An optical film pressure-sensitive adhesive containing an acid ester copolymer (A) is known (see, for example, Patent Document 1).

In addition, although not considering the bending as described above, as a curable resin composition capable of suppressing display unevenness of the display device, a curable resin containing a predetermined polyfunctional oligomer and a predetermined monofunctional oligomer Compositions are known (see, for example, Patent Documents 2 and 3).

JP 2017-95654 A JP 2014-156566 A WO2016/017568

However, the pressure-sensitive adhesive for optical films described in Patent Document 1 specifically discloses a hydrocarbon-based polymer, and there is a demand for a pressure-sensitive adhesive composition with improved adhesiveness. there is

In addition, the curable resin compositions described in Patent Documents 2 and 3 are curable resin compositions that have a low elastic modulus, good flexibility, and a low cure shrinkage rate in order to prevent the display unevenness described above. However, it is intended for flat display panels and not intended for repeated bending like flexible display panels. .

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive layer having a low elastic modulus and good adhesion to a substrate such as an optical film, so that the pressure-sensitive adhesive layer can be used even when it is repeatedly bent like a flexible display panel. An object of the present invention is to provide a pressure-sensitive adhesive composition that does not cause peeling or whitening of the folded portion, and a method for producing the same.
Another object of the present invention is to provide a pressure-sensitive adhesive layer, a laminate, and an image display device using the pressure-sensitive adhesive composition.

The present inventors completed the present invention as a result of conducting studies in view of the above points. That is, the present invention is the following [1] to [ 9 ].
[1] A pressure-sensitive adhesive composition,
An oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and an acryloyloxy group, having two acryloyloxy groups in one molecule and a urethane bond in one molecule A bifunctional oligomer containing 3.90 to 6.00% by mass,
An oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and an acryloyloxy group , having one acryloyloxy group per molecule and a urethane bond per molecule A monofunctional oligomer containing 0.35 to 1.9% by mass ,
contains
The bifunctional oligomer is a reaction product of a polyoxyalkylene diol, a diisocyanate, and a hydroxyalkyl acrylate or an isocyanate alkyl acrylate,
The bifunctional oligomer has a number average molecular weight of 5,000 to 30,000,
the monofunctional oligomer is a reaction product of a polyoxyalkylene monool and an isocyanate alkyl acrylate;
The monofunctional oligomer has a number average molecular weight of 3,000 to 35,000,
Both the polyoxyalkylene chain in the bifunctional oligomer and the polyoxyalkylene chain in the monofunctional oligomer are polyoxyalkylenes in which the ratio of oxypropylene groups to all oxyalkylene groups in the polyoxyalkylene chain is 50 to 100% by mass. is a chain,
The content of the bifunctional oligomer is 20 to 80% by mass with respect to the total mass of the bifunctional oligomer and the monofunctional oligomer,
A pressure-sensitive adhesive composition, wherein the total content of the bifunctional oligomer and the monofunctional oligomer is 55 % by mass or more relative to the pressure-sensitive adhesive composition.

[ 2 ] The pressure-sensitive adhesive composition of [ 1 ], which further contains a photopolymerization initiator.
[ 3 ] A pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition of [1] or [ 2 ].

[ 4 ] The pressure-sensitive adhesive layer of [ 3 ], which has a storage modulus E′ at 25° C. of 70 to 450 kPa and a surface adhesive strength of 5 N/25 mm or more.
[ 5 ] A laminate comprising a first planar substrate and the pressure-sensitive adhesive layer of [ 3 ] or [ 4 ] disposed on the first planar substrate. .
[ 6 ] The laminate of [ 5 ], further comprising a second base material disposed on the pressure-sensitive adhesive layer.
[ 7 ] The laminate according to [ 6 ], wherein the first planar substrate is a transparent planar substrate, and the second substrate is a display device.
[ 8 ] An image display device comprising the laminate of [ 7 ].
[ 9 ] The image display device of [ 8 ], wherein the image display device is a curved display or flexible display.

ADVANTAGE OF THE INVENTION According to the adhesive composition of this invention, the adhesive composition which can form the adhesive layer which has a low elastic modulus and was excellent in the adhesiveness with respect to a base material is obtained.

According to the adhesive layer of the present invention, the elastic modulus is low, the adhesiveness to the substrate is excellent, and when the laminate is formed by laminating it on the substrate, even if the laminate is repeatedly folded, the adhesive It is possible to suppress the occurrence of peeling of the layer and whitening of the bent portion.

According to the laminate and the image display device of the present invention, since the adhesive layer having the above properties is used, it is possible to suppress the peeling of the adhesive layer and the whitening of the folded portion at the place where the adhesive layer is repeatedly bent, and the product is stable for a long period of time. It can be used as a part that constitutes a product that can exhibit its characteristics as a result.

1 is a side view of a laminate that is an embodiment of the present invention; FIG. FIG. 4 is a side view of a laminate that is another embodiment of the present invention;

In this specification, the compound represented by formula (1) is referred to as compound (1). Compounds represented by other formulas are similarly described.
As used herein, the following terms are used with the following meanings, respectively.
A "(meth)acryloyloxy group" is a generic term for an acryloyloxy group and a methacryloyloxy group.
"(Meth)acrylate" is a generic term for acrylate and methacrylate. Similarly, "(meth)acrylic acid" is a generic term for acrylic acid and methacrylic acid, and (meth)acrylamide is a generic term for acrylamide and methacrylamide.

The term "number of functional groups" means the number of (meth)acryloyloxy groups in one molecule, unless otherwise specified.
"Average functional group number" means the average number of (meth)acryloyloxy groups in one molecule per formula weight obtained based on the chemical formula or the number average molecular weight as one unit, unless otherwise specified.
"Curable component" means a compound having a (meth)acryloyloxy group.
The "index" in the reaction between the isocyanate group-containing compound and the hydroxyl group-containing compound is a value obtained by dividing the number of moles of isocyanate groups in the isocyanate group-containing compound by the number of moles of hydroxyl groups in the hydroxyl group-containing compound and multiplying the value by 100.
The hydroxyl value of the hydroxyl-containing compound is obtained by measurement according to JIS K1557 (2007 edition). The hydroxyl-equivalent molecular weight is a value calculated by applying the hydroxyl value to the formula "56100/(hydroxyl value)×(number of active hydrogens of the initiator)".

The number average molecular weight is a polystyrene-equivalent molecular weight obtained by measuring by gel permeation chromatography (GPC) using a calibration curve prepared using standard polystyrene samples with known molecular weights. The molecular weight distribution refers to a value obtained by dividing the mass average molecular weight (molecular weight in terms of polystyrene obtained by GPC like the number average molecular weight) by the number average molecular weight. If a peak of unreacted low-molecular-weight components (monomers, etc.) appears in the GPC measurement, the number-average molecular weight is obtained by excluding this peak.
Even if the number average molecular weight is specified, if there is no molecular weight distribution, the molecular weight represented by the formula weight obtained based on the chemical formula shall be substituted.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention (hereinafter referred to as "composition (X)") comprises a bifunctional oligomer (hereinafter referred to as "oligomer (A)") and a monofunctional oligomer (hereinafter referred to as "oligomer (B)"). ) as an essential ingredient. The total content of oligomer (A) and oligomer (B) is 40% by mass or more in composition (X).

[Oligomer (A)]
Oligomer (A) is an oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and a (meth)acryloyloxy group, and has two (meth)acryloyloxy groups per molecule. It is a bifunctional oligomer containing 3.90 to 6.00% by mass of urethane bonds per molecule.

The polyoxyalkylene chain in the oligomer (A) is preferably a polyoxyalkylene chain derived from a compound having a polyoxyalkylene chain such as polyoxyalkylene polyol and a hydroxyl group. The urethane bond is preferably a urethane bond formed by a reaction between an isocyanate group of an isocyanate group-containing compound such as polyisocyanate and an isocyanate group-containing (meth)acrylate and a hydroxyl group of a hydroxyl group-containing compound. Examples of the hydroxyl group-containing compound include compounds having a polyoxyalkylene chain and a hydroxyl group and hydroxyl group-containing compounds such as hydroxyl group-containing (meth)acrylates. (Meth)acryloyloxy groups are preferably (meth)acryloyloxy groups derived from (meth)acrylates such as the above isocyanate group-containing (meth)acrylates and the above hydroxyl group-containing (meth)acrylates. As the oligomer (A), a reaction product of a compound having a polyoxyalkylene chain and a hydroxyl group, a polyisocyanate, and a hydroxyl group-containing (meth)acrylate or an isocyanate group-containing (meth)acrylate is preferable.

Further, this oligomer (A) contains 3.90 to 6.00% by mass of urethane bonds in one molecule. Adhesiveness can be improved because the density|concentration (existence ratio) of a urethane bond is the said range. The concentration of urethane bonds in one molecule is preferably 3.92 to 5.70% by mass, more preferably 3.95 to 5.50% by mass.

The above concentration of urethane bonds can be calculated from the following formula, assuming that all the isocyanate groups of the isocyanate group-containing compound used in the production of the oligomer (A) form urethane bonds.
(Number of moles of isocyanate groups possessed by isocyanate group-containing compound x urethane bond molecular weight (59)/mass of oligomer (A)) x 100 (%)

Further, the number average molecular weight of the oligomer (A) is preferably 5,000 to 30,000, more preferably 10,000 to 28,000, and further preferably 15,000 to 25,000. preferable. When the number-average molecular weight of the oligomer (A) is within the above range, the viscosity of the composition (X) can be easily adjusted, and the resulting pressure-sensitive adhesive layer tends to have good adhesiveness.
When the composition (X) contains two or more oligomers (A), the number average molecular weight of each oligomer (A) is preferably within the above range.

In the production process of the oligomer (A), for example, an oligomer having one (meth)acryloyloxy group in one molecule as a by-product (hereinafter referred to as "by-product oligomer") and a product containing the oligomer (A) may be obtained.
The content of the oligomer (A) in the product is 80% by mass or more with respect to the total amount of the by-product oligomer and the oligomer (A) so that the function as the oligomer (A) can be sufficiently exhibited. preferably 85 to 100% by mass, even more preferably 90 to 100% by mass. When the product contains the oligomer (A) in the above content, the function of the oligomer (A) is fully exhibited, so the product (A) can be regarded as the oligomer (A).
When the above product can be regarded as the oligomer (A), the average functional group number obtained from the number average molecular weight and the functional group number of the mixture of the by-product oligomer and the oligomer (A) is the average functional group number of the oligomer (A). can be regarded as The average number of functional groups can be determined, for example, by NMR analysis. In this case, the average functional group number of the oligomer (A) is preferably 1.6 to 2.0, more preferably 1.7 to 2.0, and 1.8 to 1.96. is more preferred. Oligomer (A) having an average number of functional groups within the above range tends to provide a pressure-sensitive adhesive layer with good adhesiveness.

Oligomer (A) can be produced by a known method using known raw materials. For example, it can be produced using the raw materials and production method described in International Publication No. 2009/016943.
The oligomer (A) is preferably a reaction product (1) obtained by the following production method or a reaction product (2) obtained by the following production method and having an average number of functional groups within the above range. .
Reaction product (1): A polyoxyalkylene polyol and a polyisocyanate are reacted in a ratio exceeding an index of 100 to produce an isocyanate-terminated urethane prepolymer, and then groups reactive with isocyanate groups and (meth)acryloyloxy groups are a reaction product obtained by reacting the resulting isocyanate-terminated urethane prepolymer with a compound having
Reaction product (2): Polyoxyalkylene polyol and polyisocyanate are reacted at a ratio of index less than 100 to produce a hydroxyl group-terminated urethane prepolymer, and then a compound having an isocyanate group and a (meth)acryloyloxy group is obtained. A reaction product obtained by reacting the obtained hydroxyl group-terminated urethane prepolymer.

Polyoxyalkylene diol is preferable as the polyoxyalkylene polyol which is the starting material of the reaction products (1) and (2). Diisocyanate is preferable as the polyisocyanate which is the raw material of the reaction products (1) and (2). As the compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group, which is a raw material of the reaction product (1), a (meth)acrylate having a hydroxyl group or an amino group is preferable, and a hydroxyalkyl (meth) ) acrylates are more preferred. As a compound having an isocyanate group and a (meth)acryloyloxy group, which is a raw material of the reaction product (2), a (meth)acrylate having one isocyanate group is preferable, and an isocyanate alkyl (meth)acrylate is more preferable.
That is, reaction products (1) and (2) are preferably reaction products of polyoxyalkylenediol, diisocyanate, and hydroxyalkyl (meth)acrylate or isocyanatoalkyl (meth)acrylate.

As the polyoxyalkylene polyol which is the raw material of the reaction products (1) and (2), a polyoxyalkylene polyol having an average number of hydroxyl groups in one molecule of 1.6 to 2.0 is preferable, and 1.7 Polyoxyalkylene polyols with ∼2.0 are more preferred, and polyoxyalkylene polyols with 1.8 to 1.96 are even more preferred. In the present invention, these polyoxyalkylene polyols having an average number of hydroxyl groups are also referred to as polyoxyalkylene diols.
In order to obtain an oligomer (A) having a urethane bond concentration within the specific range, the hydroxyl value of the polyoxyalkylene polyol is preferably 32-112 mgKOH/g, more preferably 36-75 mgKOH/g.

A polyoxyalkylene polyol is an initiator residue and a polyoxyalkylene chain obtained by ring-opening addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group and having two or more active hydrogens. and a compound having hydroxyl groups corresponding to the number of active hydrogens in the initiator. As the initiator having two or more active hydrogens, a compound having two or more hydroxyl groups is preferable. As the alkylene oxide, an alkylene oxide having 2 to 4 carbon atoms is preferable, and specific examples include propylene oxide, ethylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and the like.
Examples of the active hydrogen-containing group of the initiator include a hydroxyl group, a carboxyl group, an amino group having a hydrogen atom bonded to a nitrogen atom, etc. A hydroxyl group is preferred, and an alcoholic hydroxyl group is more preferred. Examples of initiators having two or more active hydrogen atoms include polyhydric alcohols, polyhydric phenols, polycarboxylic acids, amine compounds having two or more hydrogen atoms bonded to nitrogen atoms, and divalent aliphatic Alcohol is preferred. The dihydric aliphatic alcohol preferably has 2 to 8 carbon atoms. Also, a polyoxyalkylene polyol having a lower molecular weight than the target polyoxyalkylene polyol can be used as the initiator.
Specific examples of initiators include polypropylene glycols such as ethylene glycol, propylene glycol and dipropylene glycol, and 1,4-butanediol.

The oxyalkylene group in the polyoxyalkylene polyol preferably consists of only an oxypropylene group or a combination of an oxypropylene group and other groups, and the oxyalkylene group other than the oxypropylene group is oxyethylene groups are preferred. The ratio of oxypropylene groups to all oxyalkylene groups in the polyoxyalkylene polyol is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. When the initiator is a polyoxyalkylene polyol having a lower molecular weight than the target polyoxyalkylene polyol, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the obtained polyoxyalkylene polyol.

Low hydroxyl value (that is, high molecular weight) polyoxyalkylene polyol is obtained by ring-opening addition polymerization of alkylene oxide having 3 or more carbon atoms (especially propylene oxide) to an initiator in the presence of a double metal cyanide complex catalyst. can be manufactured. Polyoxyalkylene polyols having a low hydroxyl value include polyoxyalkylene polyols having a hydroxyl value of 40 mgKOH/g or less.
A low hydroxyl value polyoxyalkylene polyol having an oxyethylene group is obtained by using a high hydroxyl value (preferably 50 mgKOH/g or more) polyoxyalkylene polyol having an oxyethylene group as an initiator, and in the presence of a double metal cyanide complex catalyst. , by ring-opening addition polymerization of an alkylene oxide having 3 or more carbon atoms (especially propylene oxide).
A high hydroxyl value polyoxyalkylene polyol and a high hydroxyl value polyoxyalkylene polyol as an initiator can be produced using an alkali catalyst such as KOH.

The polyoxyalkylene polyol used in the production of oligomer (A) may be a mixture of two or more polyoxyalkylene polyols. In this case, each polyoxyalkylene polyol is preferably a polyoxyalkylene polyol included in the above category, and each polyoxyalkylene polyol is preferably a polyoxyalkylene diol included in the above category.

The polyisocyanate, which is the starting material for the reaction products (1) and (2), is a compound having two or more isocyanate groups in one molecule. In order to obtain oligomers (A) which are difunctional, the polyisocyanate is preferably a diisocyanate. The polyisocyanate will be described below using diisocyanate as an example.
Polyisocyanates include non-yellowing aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified products of these diisocyanates (modified products having two isocyanate groups). Diisocyanate can also use 2 or more types together.
As the diisocyanate, aliphatic diisocyanate and alicyclic diisocyanate are preferable because they are excellent in light resistance, weather resistance and heat resistance and can maintain transparency.

Examples of non-yellowing aromatic diisocyanates include xylylene diisocyanate and tetramethylxylylene diisocyanate.
Aliphatic diisocyanates include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate and the like.
Alicyclic diisocyanates include isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate and the like.

The group that reacts with the isocyanate group and the group that reacts with the isocyanate group in the compound having a (meth)acryloyloxy group, which is the raw material of the reaction product (1), includes a hydroxyl group, an amino group having a nitrogen atom bonded to a hydrogen atom, and the like. is mentioned. The number of hydroxyl groups in the group that reacts with the isocyanate group and the number of hydrogen atoms bonded to nitrogen atoms are preferably one. As a group that reacts with an isocyanate group, a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group is preferable. As the compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group, hydroxyalkyl (meth)acrylates and hydroxycycloalkyl (meth)acrylates are preferred, and hydroxyalkyl groups having 8 or less carbon atoms in the hydroxyalkyl group ( Particular preference is given to meth)acrylates.
Specific examples of compounds having a group that reacts with an isocyanate group and a (meth)acryloyloxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4 -hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate and the like. Commercially available products include Light Ester HO-250 (N), Light Ester HOP (N), Light Ester HOA (N), Light Ester HOP-A (N), Light Ester HOB (N) (all of which are manufactured by Kyoei Chemical Co., Ltd. product name) and 4-HBA (product name of Osaka Organic Chemical Industry Co., Ltd.).

A compound having one isocyanate group is preferable as the compound having an isocyanate group and a (meth)acryloyloxy group, which is a raw material of the reaction product (2). The compound having one isocyanate group and a (meth)acryloyloxy group is preferably a (meth)acrylate having an isocyanate group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, and an isocyanate alkyl (meth)acrylate. is particularly preferred. The carbon number of the alkyl group excluding the isocyanate group of the isocyanate alkyl group is preferably 8 or less, more preferably 4 or less.
Specific examples of compounds having an isocyanate group and a (meth)acryloyloxy group include 2-isocyanatoethyl (meth)acrylate and isocyanatomethyl methacrylate. Commercially available products include Karenz-AOI and Karenz-MOI (both product names of Showa Denko KK).

As will be described later, the composition (X) of the present invention is preferably a photocurable composition. As the oligomer (A) contained in the photocurable composition (X), an oligomer (A) in which all (meth)acryloyloxy groups of the oligomer (A) are acryloyloxy groups is preferable. Such an oligomer (A) is obtained by using a raw material compound in which the raw material compound having a (meth)acryloyloxy group (hydroxyalkyl (meth)acrylate, isocyanatoalkyl (meth)acrylate, etc.) is an acryloyloxy group. be done. Similarly, the (meth)acryloyloxy group in other compounds having a (meth)acryloyloxy group contained in the photocurable composition (X) such as the oligomer (B) described below is also preferably an acryloyloxy group. .

As the reaction product (1), an isocyanate-terminated urethane prepolymer obtained by reacting a polyoxyalkylene diol and a diisocyanate at an index of more than 100 and not more than 200 is reacted with an equivalent amount of hydroxyalkyl (meth)acrylate. The resulting reaction product is preferred. The isocyanate-terminated urethane prepolymer has a higher molecular weight as the index is closer to 100, and a lower molecular weight as the index is closer to 200. Therefore, the number average molecular weight of reaction product (1) can be adjusted by adjusting the index. That is, the reaction product obtained with an index of 200 is a reaction product of 1 molecule of polyoxyalkylenediol, 2 molecules of diisocyanate and 2 molecules of hydroxyalkyl (meth)acrylate, and the lower the index, the more polyoxyalkylenediol residues. and the number of diisocyanate residues increases. In order to obtain an oligomer (A) having a number average molecular weight within the preferred range, the index is preferably 120 or less, more preferably 102-115.
The amount of hydroxyalkyl (meth)acrylate used for reacting with the isocyanate-terminated urethane prepolymer may be an amount exceeding an equimolar amount with respect to the isocyanate-terminated urethane prepolymer. The hydroxyalkyl (meth)acrylate in the reaction product (1) containing an excess of hydroxyalkyl (meth)acrylate is used as at least a part of the monomer (C) described below together with the reaction product (1) in the composition (X) can be contained in

The reaction product (2) is obtained by reacting a hydroxyl group-terminated urethane prepolymer obtained by reacting a polyoxyalkylene diol and a diisocyanate at an index of less than 100 and 50 or more with an equivalent amount of isocyanate alkyl (meth)acrylate. are preferred. The hydroxyl group-terminated urethane prepolymer has a higher molecular weight as the index is closer to 100, and a lower molecular weight as the index is closer to 50. Therefore, the number average molecular weight of reaction product (2) can be adjusted by adjusting the index. That is, the reaction product obtained with an index of 50 is a reaction product of 2 molecules of polyoxyalkylenediol, 1 molecule of diisocyanate and 2 molecules of isocyanatoalkyl (meth)acrylate, and the higher the index, the more the number of polyoxyalkylenediol residues. and the number of diisocyanate residues increases. In order to obtain an oligomer (A) having a number average molecular weight within the preferred range, the index is preferably 80 or more, more preferably 85-98.

[Monofunctional oligomer]
A monofunctional oligomer (hereinafter referred to as "oligomer (B)") is an oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and a (meth)acryloyloxy group, It is an oligomer having one meth)acryloyloxy group per molecule.
As described above, when the pressure-sensitive adhesive composition of the present invention is a UV-curable pressure-sensitive adhesive composition, the (meth)acryloyloxy group in the oligomer (B) is preferably an acryloyloxy group.

Oligomer (B) tends to reduce shrinkage during curing and tends to reduce the elastic modulus of the adhesive after curing. It is easy to suppress the occurrence of whitening when repeatedly bent. Moreover, since it has one (meth)acryloyloxy group, the stability of the adhesive after curing is superior, and bleeding out is less likely to occur.

The number of urethane bonds in one molecule of the oligomer (B) is 1 or more, which suppresses shrinkage during curing and tends to reduce the elastic modulus of the adhesive after curing, so it should be 1 or 2. is preferred, and one is more preferred.
Oligomer (B) preferably contains 0.35 to 1.9% by mass of urethane bonds in one molecule. If the concentration (existence ratio) of the urethane bond is within the above range, better adhesiveness can be obtained. The concentration of urethane bonds is more preferably 0.4 to 1.3% by mass, more preferably 0.5 to 1.2% by mass per molecule. The urethane bond concentration can be calculated in the same manner as in the oligomer (A).

The number average molecular weight of the oligomer (B) is preferably 3,000 to 35,000, more preferably 4,000 to 20,000, even more preferably 5,000 to 18,000. . If the number average molecular weight of the oligomer (B) is within this range, it is easy to adjust the viscosity of the pressure-sensitive adhesive composition. Moreover, when the number average molecular weight is 3,000 or more, the curing shrinkage of the pressure-sensitive adhesive composition tends to be low.
When the pressure-sensitive adhesive composition contains two or more oligomers (B), the number average molecular weight of each oligomer (B) is preferably within the above range.

In the production process of the oligomer (B), a by-product having a polyoxyalkylene chain other than the oligomer (B) may be produced in the product. By-products having a polyoxyalkylene chain include compounds having two (meth)acryloyloxy groups, compounds having no (meth)acryloyloxy groups, compounds having no urethane bond, and the like.
The content of the oligomer (B) in the product is preferably 80% by mass or more, more preferably 85 to 100% by mass, in order to sufficiently exhibit the function of the oligomer (B). When the product contains the oligomer (B) in the above content, the function of the oligomer (B) is fully exhibited, so the product can be regarded as the oligomer (B).

When the above product can be regarded as the oligomer (B), the average functional group number obtained from the number average molecular weight and the functional group number of the product can be regarded as the average functional group number of the oligomer (B). In this case, the product preferably has an average functional group number of 0.8 to 1.2, more preferably 0.9 to 1.1. A product within the above range tends to sufficiently exhibit the function of the oligomer (B). The average number of functional groups can be adjusted within this range by adjusting the amount of impurities contained in the raw material for producing the oligomer (B) or by adjusting the index described below. In addition, in this specification, the average functional group number can be obtained by calculation using the average functional group number of raw materials described later and an index.

Specific examples of the oligomer (B) include the following reaction product (3), reaction product (4), reaction product (5), and the like. These may be used individually by 1 type, and may use 2 or more types together.
In particular, the oligomer (B) in the pressure-sensitive adhesive composition preferably contains one or more selected from the group consisting of reaction product (3) and reaction product (4). In particular, as the oligomer (B), the content of by-products is small compared to other reaction products, and a pressure-sensitive adhesive composition having excellent flexibility and curing shrinkage is obtained. 3) is preferred.

The total content of the reaction product (3) and the reaction product (4) with respect to the oligomer (B) is preferably 50% by mass or more, more preferably 80% by mass or more, and 100% by mass. It is particularly preferred to have When the total content of the reaction product (3) and the reaction product (4) is at least the lower limit of the above range, flexibility and cure shrinkage are excellent. When the monofunctional oligomer (B) contains the reaction product (3) and the reaction product (4), the mass ratio of these is reaction product (3): reaction product (4) = 1: 0 to 1: 1 is preferred.

Reaction product (3): an equimolar reaction product of a polyoxyalkylene monool and a compound having an isocyanate group and a (meth)acryloyloxy group.
Reaction product (4): an equimolar reaction product of a polyoxyalkylene monool, a diisocyanate and a compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group.
Reaction product (5): an equimolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloyloxy group.
Compounds having an isocyanate group and a (meth)acryloyloxy group, which are raw materials for the reaction products (3) and (5), are the compounds exemplified as raw materials for the reaction product (2). The formula is also the same as the compound that is the raw material of the reaction product (2). That is, (meth)acrylates having one isocyanate group are preferred, and isocyanate alkyl (meth)acrylates are more preferred.
The diisocyanate that is the raw material of the reaction product (4) is the diisocyanate exemplified as preferable among the polyisocyanates that are the raw materials of the reaction products (1) and (2). It is the same as the diisocyanate which is the raw material of the reaction products (1) and (2).
The compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group, which is a raw material of the reaction product (4), is the compound exemplified as the raw material of the reaction product (1). Specific examples are the same as those of the compound that is the raw material of the reaction product (1). That is, (meth)acrylates having one hydroxyl group are preferred, hydroxyalkyl (meth)acrylates and hydroxycycloalkyl (meth)acrylates are more preferred, and hydroxyalkyl (meth)acrylates in which the hydroxyalkyl group has 8 or less carbon atoms are particularly preferred. preferable.

The average number of hydroxyl groups in one molecule of the polyoxyalkylene monool, which is the raw material of the reaction products (3) and (4), is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. It is more preferable to have
In order to obtain an oligomer (B) having a urethane bond concentration within the specific range, the hydroxyl value of the polyoxyalkylene monool is preferably 1.6 to 18.1 mgKOH/g, more preferably 2.8 to 14 mgKOH/g. more preferably 3.1 to 11.2 mgKOH/g.

Polyoxyalkylene monool is obtained by ring-opening addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group and having one or more active hydrogens, and an initiator residue and a polyoxyalkylene It is a compound with hydroxyl groups corresponding to the number of active hydrogens in the chain and initiator. As the alkylene oxide, an alkylene oxide having 2 to 4 carbon atoms is preferable, and specific examples include propylene oxide, ethylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and the like.
Examples of the active hydrogen-containing group of the initiator include a hydroxyl group, a carboxy group, an amino group having one hydrogen atom bonded to a nitrogen atom, and the like, and a hydroxyl group and a carboxy group are preferred. As the hydroxyl group, an alcoholic hydroxyl group is more preferable. Examples of initiators having one active hydrogen include monohydric alcohols, monohydric phenols, monohydric carboxylic acids, and amine compounds having one hydrogen atom bonded to a nitrogen atom. Preferred initiators are monohydric aliphatic alcohols and monohydric aliphatic carboxylic acids. Also, a polyoxyalkylene monool having a lower molecular weight than the target polyoxyalkylene monool can be used as an initiator.
The number of carbon atoms in the monohydric aliphatic alcohol used as the initiator is preferably 1-20, more preferably 2-8. The number of carbon atoms in the monovalent aliphatic carboxylic acid as the initiator is preferably 2 to 20, more preferably 2 to 8, including the carbon atoms of the carboxy group.

The oxyalkylene group in the polyoxyalkylene monool preferably consists of only an oxypropylene group or a combination of an oxypropylene group and a group other than the oxypropylene group. Ethylene groups are preferred. The ratio of oxypropylene groups to all oxyalkylene groups in the polyoxyalkylene monool is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. If the initiator is a polyoxyalkylene monool with a lower molecular weight than the target polyoxyalkylene monool, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the resulting polyoxyalkylene monool. shall be

A polyoxyalkylene monool with a low hydroxyl value (i.e., a high molecular weight) is subjected to ring-opening addition polymerization of an alkylene oxide having 3 or more carbon atoms (especially propylene oxide) to an initiator in the presence of a double metal cyanide complex catalyst. can be manufactured by
A low hydroxyl value polyoxyalkylene monool having an oxyethylene group uses a high hydroxyl value (preferably 50 mgKOH/g or more) polyoxyalkylene monool having an oxyethylene group as an initiator and the presence of a double metal cyanide complex catalyst. It can also be produced by ring-opening addition polymerization of an alkylene oxide having 3 or more carbon atoms (especially propylene oxide). High hydroxyl value polyoxyalkylene monools can also be produced using alkaline catalysts such as KOH.

In the production of polyoxyalkylene monool, the initiator and the alkylene oxide to be introduced into the reaction system are generally dehydrated under reduced pressure and have a low water content. Normally, the water content of the initiator in the production of polyoxyalkylene monool is preferably as small as possible, more preferably 500 mass ppm or less, and even more preferably 300 mass ppm or less. When the water content is within this range, the amount of polyoxyalkylenediol produced from water is suppressed, so that the amount of by-products produced from the polyoxyalkylenediol is finally suppressed, and the resulting poly It is easy to adjust the upper limit of the average number of hydroxyl groups of the oxyalkylene monool to 1.2 or less.
In addition, the water content in the polyoxyalkylene monool used as the raw material of the reaction products (3) and (4) is preferably as small as possible, and is preferably 300 ppm by mass or less with respect to the polyoxyalkylene monool. It is more preferably mass ppm or less, and particularly preferably 50 to 200 mass ppm. When the water content is within the above range, the formation of by-products, which are reaction products of water and the isocyanate group-containing compound, is reduced, and the stability of the reaction products (3) and (4) is improved. Furthermore, the curable composition containing the reaction products (3) and (4) tends to be less likely to change in appearance over time, and the elastic modulus of the cured product tends to be better.

The polyoxyalkylene polyol that is the raw material of the reaction product (5) is preferably the same polyoxyalkylene polyol as the polyoxyalkylene diol that is the raw material of the oligomer (A).
The average number of hydroxyl groups in one molecule of the polyoxyalkylene polyol is preferably 1.6 to 2.0, more preferably 1.8 to 1.96. That is, the polyoxyalkylene polyol that is the raw material of the reaction product (5) is preferably a polyoxyalkylene diol.
The content of oxypropylene groups with respect to all oxyalkylene groups in the polyoxyalkylene polyol is preferably 80 to 100% by mass.
In order to obtain an oligomer (B) having a urethane bond concentration within the above specific range, the hydroxyl value of the polyoxyalkylene polyol is preferably 1.6 to 18.1 mgKOH/g, more preferably 2.8 to 14 mgKOH/g. It is more preferable to have
The polyoxyalkylene polyol, which is the starting material for the reaction product (5), can be produced in the same manner as the polyoxyalkylene diol, which is the starting material for the oligomer (A).

[Reaction product (3)]
Reaction product (3) is an equimolar reaction product of a polyoxyalkylene monool and a compound having an isocyanate group and a (meth)acryloyloxy group. As the compound having an isocyanate group and a (meth)acryloyloxy group, an isocyanate alkyl (meth)acrylate is preferred.

Since polyoxyalkylene monool and isocyanate alkyl (meth)acrylate each have one group capable of urethanization reaction in one molecule, the number of urethane bonds in one molecule of the reaction product (3) is Easy to control with one. If the number of urethane bonds in one molecule of the reaction product (3) is small, the viscosity tends to be low. Therefore, it is more preferable that the oligomer (B) in the pressure-sensitive adhesive composition contains the reaction product (3), since the pressure-sensitive adhesive composition has a low viscosity and a cured product having excellent flexibility can be easily obtained.
In addition, since both polyoxyalkylene monool and isocyanate alkyl (meth)acrylate are compounds having one reactive group, by-products are unlikely to occur, and the reaction product (3) with high purity except unreacted products is obtained. easy to obtain. When an unreacted substance remains, the unreacted substance is preferably a polyoxyalkylene monool from the viewpoint of stability of the reaction product. In order to obtain a reaction product with less unreacted matter, it is preferable to react both at an index of 90 to 100, particularly preferably at an index of 100.
The average functional group number of the reaction product (3) is preferably 0.9 to 1.1. A pressure-sensitive adhesive composition containing the reaction product (3) within the above range tends to reduce shrinkage during curing, and tends to reduce the elastic modulus of the pressure-sensitive adhesive after curing.

[Reaction product (4)]
Reaction product (4) is an equimolar reaction product of a polyoxyalkylene monool, a diisocyanate and a compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group.
As the diisocyanate, the aliphatic diisocyanate and the alicyclic diisocyanate mentioned as raw materials for the reaction products (1) and (2) are preferable. As the compound having a group that reacts with an isocyanate group and a (meth)acryloyloxy group, the compounds exemplified as the starting material for the reaction product (1) are preferable, and in particular, hydroxyalkyl groups having 8 or less carbon atoms in the hydroxyalkyl group (meth) ) acrylates are particularly preferred.
As the reaction product (4), (a) a polyoxyalkylene monool and a diisocyanate are reacted at an index of 200, and then the resulting reaction product (a reaction product having an isocyanate group) is treated with a hydroxyalkyl (meth)acrylate. A reaction product obtained by reacting at an index of 100, and (b) a polyoxyalkylene monool, an equimolar hydroxyalkyl (meth)acrylate to the polyoxyalkylene monool, and the polyoxyalkylene monool and a reaction product obtained by simultaneously reacting an amount of diisocyanate with an index of 100 with respect to the sum of said hydroxyalkyl (meth)acrylates. Among these, the reaction product of (a) is more preferable because it contains less by-products.
When producing the reaction product (a), the amount of hydroxyalkyl (meth)acrylate used may be excessive, and the excess hydroxyalkyl (meth)acrylate is at least As a part, it can be included in composition (X) together with the reaction product of (a).
The average functional group number of the reaction product (4) is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. A pressure-sensitive adhesive composition containing the reaction product (4) within the above range tends to reduce shrinkage during curing, and tends to reduce the elastic modulus of the pressure-sensitive adhesive after curing.

[Reaction product (5)]
Reaction product (5) is an equimolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloyloxy group. As the polyoxyalkylene polyol, polyoxyalkylene diol is preferable, and as the compound having an isocyanate group and a (meth)acryloyloxy group, the isocyanate alkyl (meth)acrylate is preferable.
In addition, the reaction product (5) is a reaction product having a hydroxyl group, and the number of hydroxyl groups is not limited to one. Therefore, as long as the compound having an isocyanate group and a (meth)acryloyloxy group is a compound having one isocyanate group and is an equimolar reaction product, the raw material polyoxyalkylene polyol has more than two hydroxyl groups. It may be a compound.
The average functional group number of the reaction product (5) is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. The reaction product (5) within the above range tends to reduce shrinkage during curing, and tends to reduce the elastic modulus of the adhesive after curing.

The total content of oligomer (A) and oligomer (B) in composition (X) is 40% by mass or more, preferably 55% by mass or more, relative to the total amount of composition (X).
Further, the ratio of the oligomer (A) to the total amount of the oligomer (A) and the oligomer (B) in the composition (X) is preferably 20 to 80% by mass, more preferably 30 to 70% by mass. More preferably, it is 40 to 60% by mass.

Although the upper limit of the total content of oligomer (A) and oligomer (B) in composition (X) may be 100% by mass, other components may be contained. The physical properties can be further improved by incorporating other components. The content of components other than oligomer (A) and oligomer (B) is preferably 60% by mass or less, more preferably 45% by mass or less, relative to the total amount of composition (X).
Further, the total content of the oligomer (A), the oligomer (B), the monomer (C) described below, and the monomer (D) described below, which are curable components in the composition (X), is the composition (X) is preferably 65% by mass or more, more preferably 75% by mass or more, based on the total amount of

Composition (X) may further contain monomers having a (meth)acryloyloxy group other than oligomer (A) and oligomer (B), such as hydroxyl group-containing monomers and long-chain alkyl group-containing monomers. Furthermore, if necessary, a photopolymerization initiator and other components may be included.
Hereinafter, the hydroxyl group-containing monomer is referred to as "monomer (C)", and the monomer other than monomer (C), such as the long-chain alkyl group-containing monomer, is referred to as "monomer (D)".
When the composition (X) is a photocurable composition, all the (meth)acryloyloxy groups in the oligomer (A) and the oligomer (B) are acryloyloxy groups as described above, and the composition (X ) preferably contains a photoinitiator. Similarly, in the case of the photocurable composition (X) containing the following monomer (C) and monomer (D), all (meth)acryloyloxy groups contained in these compounds are preferably acryloyloxy groups.

[Monomer (C)]
Monomer C is a compound other than oligomer (A) and oligomer (B) and contains a (meth)acryloyloxy group and a hydroxyl group. The monomer (C) is preferably a compound having one (meth)acryloyloxy group and one or more hydroxyl groups, and the number of hydroxyl groups is preferably one or two.
Monomer (C) may be a compound having a polyoxyalkylene chain, in which case it is preferably a compound having no urethane bond. Moreover, the monomer (C) may be a compound having an aliphatic polyester chain obtained by ring-opening addition polymerization of a lactone.
The monomer (C) contributes to improving the adhesiveness of the cured product of the composition (X). Moreover, it contributes to the improvement of the light transmittance of the cured product of the composition (X).
Monomer (C) may be used alone or in combination of two or more.

Examples of the monomer (C) include hydroxyalkyl (meth)acrylates, dihydroxyalkyl (meth)acrylates, lactone-modified hydroxyalkyl (meth)acrylates, polyoxyalkylenediol mono(meth)acrylates, and (meth)acrylic acid-monoepoxide adducts. etc.
The number of carbon atoms in the hydroxyalkyl portion of the hydroxyalkyl (meth)acrylate is preferably 2-8, more preferably 2-6. The same applies to the number of carbon atoms in the dihydroxyalkyl portion of the dihydroxyalkyl (meth)acrylate. Specific examples of the hydroxyalkyl (meth)acrylate include those of the hydroxyalkyl (meth)acrylate mentioned as the starting material for the reaction product (1). Among these, 4-hydroxybutyl acrylate and 6-hydroxyhexyl acrylate are preferred in terms of flexibility and low volatility.
Examples of the lactone-modified hydroxyalkyl (meth)acrylate include compounds obtained by ring-opening addition of a lactone to the hydroxyalkyl (meth)acrylate exemplified as the starting material for the reaction product (1). The number of lactones to be added is preferably 1-3. Lactones include ε-caprolactone, γ-butyrolactone, γ-valerolactone and the like.
Examples of the polyoxyalkylene chain in the polyoxyalkylenediol mono(meth)acrylate include a polyoxypropylene chain, a polyoxyethylene chain, and a poly(oxypropylene/oxyethylene) chain. The number of oxyalkylene groups in the polyoxyalkylene chain is preferably 2-8, more preferably 2-6.
The (meth)acrylic acid-monoepoxide adduct is preferably a reaction product of (meth)acrylic acid and glycidyl ether or glycidyl ester, such as (meth)acrylic acid and phenylglycidyl ether.
Among these, hydroxyalkyl (meth)acrylates and (meth)acrylic acid-monoepoxide adducts are preferred because they are easily available industrially and contain few impurities.

When the composition (X) contains the monomer (C), the content thereof is preferably 1 to 20% by mass, preferably 1 to 15% by mass, relative to the total amount of the composition (X). more preferred. When the content of the monomer (C) is at least the lower limit of the above range, the effect of improving adhesion by adding the monomer (C) can be sufficiently obtained, and when the content is at most the upper limit, low curing shrinkage. It is easy to obtain good physical properties in terms of rate.

When the protective plate is an OGS (One Glass Solution) type touch panel in which a touch sensor is formed on the surface of the bonding resin layer, the bonding resin layer formed by curing the curable resin composition may cause malfunction of the touch sensor. In order to prevent this, a low dielectric constant is required. A dielectric constant of 4.5 or less is preferable because malfunction of the touch sensor can be prevented in the OGS type touch panel. If the content of the monomer (C) in the composition (X) is equal to or less than the upper limit of the above range, the dielectric constant of the bonding resin layer obtained using the composition (X) is likely to be low. easy to control.

In addition, in the synthesis of the oligomer (A) or the oligomer (B), if the (meth)acrylate used in the reaction and containing the hydroxyl group remaining as an unreacted raw material corresponds to the monomer (C), the monomer is also included in the composition. shall be included in the content of the monomer (C) in the substance (X).

[Monomer (D)]
Monomer (D) is a compound having a (meth)acryloyloxy group other than oligomer (A), oligomer (B) and monomer (C). Monomer (D) is preferably a compound having one (meth)acryloyloxy group and no urethane bond.
As the monomer (D), (meth)acrylates having a long-chain alkyl group and (meth)acrylates having an amide group are preferred. Examples of the monomer D other than these include alkyl (meth)acrylates having 7 or less carbon atoms, alkoxyalkyl (meth)acrylates, and (meth)acrylates having an aliphatic cyclic hydrocarbon group.
Two or more monomers (D) may be used in combination.

When a long-chain alkyl (meth)acrylate is contained in the composition (X), the method described later, in which the composition (X) is sealed under reduced pressure and cured in an atmosphere of higher pressure (reduced pressure sealing-pressure curing method). When forming a cured product with, air bubbles in the cured product are likely to disappear. The number of carbon atoms in the long-chain alkyl group is preferably 8-22, more preferably 8-18.
Specific examples of long-chain alkyl (meth)acrylates include lauryl (meth)acrylate, isostearyl (meth)acrylate, isodecyl (meth)acrylate, and the like. Among these, lauryl acrylate and isostearyl acrylate are preferred in terms of flexibility, low viscosity, and low crystallinity.

As the (meth)acrylate having an amide group, the hydrogen atom bonded to the nitrogen atom of the (meth)acrylamide is carbonized, such as an alkyl group, because it is easy to suppress whitening of the cured product of the composition (X) under moist heat conditions. A compound substituted with a hydrogen group or a divalent organic group is preferred. Specific examples of (meth)acrylamide derivatives include 4-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide and the like.

When the composition (X) contains the monomer (D), its content is preferably 1 to 30% by mass, more preferably 1 to 25% by mass, based on the total amount of the composition (X). When the content of the monomer (D) is at least the lower limit of the above range, the effect of addition of the monomer (D) can be sufficiently obtained. Easy to obtain physical properties.

[Photoinitiator]
Composition (X) may be a photocurable resin composition or a thermosetting resin composition. A photocurable resin composition is preferred because it can be cured at a low temperature and has a high curing speed. When the composition (X) is a photocurable resin composition, it preferably contains a photopolymerization initiator as another component. A photocurable resin composition does not require a high temperature when it is used in the production of a display device, so that the display device is less likely to be damaged by a high temperature.

Examples of photopolymerization initiators include acetophenone-based, ketal-based, benzoin or benzoin ether-based, phosphine oxide-based, benzophenone-based, thioxanthone-based, and quinone-based photopolymerization initiators. Among these, phosphine oxide-based and thioxanthone-based photopolymerization initiators are preferable, and phosphine oxide-based initiators are preferable in terms of easily suppressing coloration after the photopolymerization reaction. A photoinitiator may be used individually by 1 type, and may use 2 or more types together.
The photopolymerization initiator is not particularly limited, and commercially available products can also be used. Examples of commercially available products include IRGACURE819, IRGACURE TPO, IRGACURE 184, IRGACURE 2959, IRGACURE 1173, IRGACURE 127, IRGACURE 907, IRGACURE OXE01 and IRGACURE OXE02 manufactured by BASF.

When the composition (X) contains a photopolymerization initiator, its content is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, with respect to the total 100 parts by mass of the curable components. preferable.

[Other ingredients]
The composition (X) may contain components other than the oligomer (A), the oligomer (B), the monomer (C), the monomer (D), and the photopolymerization initiator as long as the effects of the present invention are not impaired. . Among other components, components that improve flexibility and adhesion include tackifiers such as rosin esters, terpene phenols and hydrogenated terpene phenols, plasticizers such as adipates and phthalates, polyoxyalkylene polyols, terminal and alkoxylated polyoxyalkylene polyols. In order to keep the dielectric constant low, it is better not to include compounds having hydroxyl groups as much as possible. The content of the component that improves flexibility and adhesion is preferably 48% by mass or less, more preferably 28% by mass or less, relative to the total amount of composition (X). When the content of other components is equal to or less than the upper limit of the above range, the durability is improved.
Composition (X) further contains a polymerization inhibitor, a photocuring accelerator, a chain transfer agent, a light stabilizer (ultraviolet absorber, radical scavenger, etc.), an antioxidant, a flame retardant, and an adhesion improver. (silane coupling agent, etc.), pigments, dyes, and the like may be included. Among these additives, polymerization inhibitors and light stabilizers are preferred. In particular, by including the polymerization inhibitor in an amount smaller than that of the polymerization initiator, the storage stability of the composition (X) can be improved, and the molecular weight after curing can be easily adjusted.

Examples of polymerization inhibitors include hydroquinone-based (2,5-di-tert-butylhydroquinone, etc.), catechol-based (p-tert-butylcatechol, etc.), anthraquinone-based, phenothiazine-based, and hydroxytoluene-based polymerization inhibitors. Inhibitors are included.

The ultraviolet absorber is used to prevent photodegradation of the composition (X) and improve weather resistance. agents.
As the benzotriazole-based ultraviolet absorber, for example, those described in paragraph [0076] of International Publication No. 2014/017328 can be used.

The light stabilizer is used to prevent photodegradation of the composition (X) and improve weather resistance, and examples thereof include hindered amine light stabilizers.
As the hindered amine light stabilizer, for example, those described in paragraph [0077] of WO 2014/017328 can be used.

The antioxidant is used to prevent oxidation of the composition (X) and improve weather resistance and heat resistance, and examples thereof include phenol-based and phosphorus-based antioxidants.
As the phenolic antioxidant, for example, those described in paragraph [0078] of International Publication No. 2014/017328 can be used.
As the phosphorus antioxidant, those described in paragraph [0078] of WO 2014/017328 can be used.

A product in which a plurality of antioxidants, light stabilizers, etc. are mixed can also be used. Examples include IRGASTAB PUR68 and TINUVIN B75 manufactured by BASF.

When the composition (X) contains other components, the total content of the other components is preferably 100 parts by mass or less, more preferably 40 parts by mass or less, relative to 100 parts by mass of the curable component. , 35 parts by mass or less is more preferable.

The content of the chain transfer agent in the composition (X) is preferably small, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, with respect to 100 parts by mass of the curable component, and does not contain a chain transfer agent. is particularly preferred.

The viscosity of composition (X) is a value measured using an E-type viscometer at 25°C. The viscosity of the composition (X) is preferably 0.05 to 50 Pa·s, more preferably 1 to 20 Pa·s, even more preferably 1.5 to 5 Pa·s. When the viscosity is 0.05 Pa·s or more, it is easy to achieve both the fluidity of the composition (X) and the physical properties of the cured product after curing. When the viscosity is 50 Pa·s or less, workability in forming an uncured resin layer is good. In addition, it can be suitably used in a method of sealing the composition (X) under reduced pressure and curing in a higher pressure atmosphere (reduced pressure sealing-pressure curing method), which will be described later, and effectively eliminates air bubbles in the cured product. be able to.

By containing the oligomer (A) and the oligomer (B), the composition (X) of the present invention can improve the adhesiveness while maintaining a low elastic modulus, as shown in the examples below. Therefore, peeling, whitening, etc. can be suppressed even when used on the surface of a flexible display panel or the like.

<Adhesive layer>
The pressure-sensitive adhesive layer of the present invention comprises a cured product obtained by curing the composition (X) described above.
The thickness of this adhesive layer is preferably 0.03 mm or more, more preferably 0.1 mm or more, and even more preferably 0.2 mm or more. Moreover, it is preferably 2 mm or less, more preferably 1.3 mm or less, and even more preferably 0.8 mm or less. When the thickness of the pressure-sensitive adhesive layer is within this range, the desired adhesive strength is likely to be exhibited. Moreover, it is more preferable in terms of bending resistance. In addition, this adhesive layer may be formed as a single layer, or may be formed by laminating a plurality of layers.

In this adhesive layer, the storage elastic modulus E' at 25°C is preferably 70 kPa or more, more preferably 80 kPa or more, and even more preferably 85 kPa or more. Also, the storage elastic modulus E' at 25°C is preferably 450 kPa or less, more preferably 400 kPa or less, and even more preferably 350 kPa or less. By setting the storage elastic modulus E' within the above range, the adhesive strength of the adhesive layer can be improved.

In this adhesive layer, the surface adhesive strength is preferably 5 N/25 mm or more, more preferably 6 N/25 mm or more, and even more preferably 7 N/25 mm or more. By setting the adhesive strength of the surface within the above range, it can be suitably used for a display device used in an image display device, and is particularly suitable for a flexible display device.

As this pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer obtained by curing the photocurable composition (X) by light irradiation is preferable. For light irradiation, for example, curing treatment may be performed under the conditions of UV light with an illuminance of 50 to 800 mW/cm ² and an integrated light amount of 500 to 4,000 mJ/cm ² .

<Laminate>
The laminate of the present invention is obtained by laminating the pressure-sensitive adhesive layer and the first planar substrate. For example, as shown in FIG. A laminate 11 in which layers 13 are laminated can be mentioned.
Here, the first planar substrate 12 may be any material as long as it can support the pressure-sensitive adhesive layer 13, and examples thereof include release sheets, optical films, protective plates, and the like. The first planar substrate 12 is preferably a transparent substrate.
The pressure-sensitive adhesive layer 13 may be the same as the pressure-sensitive adhesive layer described above.

Moreover, as this laminate, as shown in FIG. 2, the laminate 11 of FIG. A laminate 21 having a substrate 22 of
Here, the second substrate 22 may be any material as long as it can hold the adhesive layer 13 by sandwiching it with the first planar substrate 12, and may be the same as the first planar substrate 12, or the display A display device such as a panel and the like are included.

The laminate 11 can be produced by applying the composition (X) of the present invention to a desired thickness on the first planar substrate and curing the composition (X).
The laminate 21 is produced by applying the composition (X) of the present invention to a desired thickness on the first planar substrate, curing the composition (X), and then applying the second composition thereon. It can be manufactured by laminating two substrates. In addition, the laminate 21 is obtained by applying the composition (X) of the present invention to a desired thickness on the first planar substrate, and further laminating the second substrate thereon. It can also be produced by curing the composition (X).

When the composition (X) is sandwiched between the first planar substrate and the second substrate and then the composition (X) is cured, at least the first planar substrate and the second substrate It is preferable that one of the substrates is a transparent substrate, because curing can be performed by light irradiation through the transparent substrate during curing.

When it is preferable that no bubbles remain in the adhesive layer after curing, such as when a display device and a transparent substrate such as a protective plate are laminated and integrated, the first and second It is preferable to use a method of confining the composition (X) between substrates and curing in an atmosphere of higher pressure (reduced pressure sealing-pressure curing method).

Specifically, in a first reduced-pressure atmosphere, an uncured layer composed of the composition (X) is sandwiched between a pair of substrates, and the uncured layer is sealed with a sealing portion provided around the uncured layer. Preferably, the laminate is produced by forming a laminate precursor and curing the uncured layers under a second atmosphere that is at a higher pressure than the first reduced pressure atmosphere.
Such vacuum sealing-pressure curing methods are known and are described, for example, in paragraphs [0036] to [0042] of WO 2009/016943 and paragraphs [0080] to [0091] of WO 2011/158840. method can be used.

For example, the pressure in the first reduced-pressure atmosphere is 100 Pa or less, and the second atmosphere is preferably atmospheric pressure.
The thickness of the uncured layer of the composition (X) after curing (the pressure-sensitive adhesive layer between a pair of substrates) is, for example, preferably 0.03 to 2 mm, more preferably 0.1 to 0.8 mm. .

The seal portion may be formed using a double-sided adhesive type sealing material, as described in paragraph [0036] of WO 2009/016943, and a double-sided adhesive type seal having optical transparency. The sealing portion may be formed by applying a photocurable resin on the material. The photocurable resin of the sealing portion can be cured at the same time as curing the uncured layer of composition (X).

Or, as described in paragraph [0039] of International Publication No. 2011/158840, the composition (X) has a higher viscosity (for example, 500 to 3000 Pa s at 25 ° C.). A resin composition may be used to form the sealing portion. The seal portion may be cured at the same time as the uncured layer made of the adhesive composition (X) is cured, or semi-cured before curing the uncured layer made of the adhesive composition (X). Thereafter, the uncured layer may be cured and further cured at the same time.

In the laminate 21, it is preferable that the first planar substrate 12 is a transparent substrate having optical transparency, and the second substrate 22 is a display device. Examples of the transparent base material include a glass plate and a transparent resin plate, and the glass plate is preferable from the viewpoints of weather resistance, low birefringence, high flatness accuracy, and the like. Display devices include liquid crystal display devices, EL display devices, plasma display devices, electronic ink display devices, and the like. The display device has a structure in which a pair of base materials, at least one of which is a transparent base material, are bonded together, and the transparent base material side is arranged so as to be in contact with the pressure-sensitive adhesive layer 13 . At this time, in some display devices, an optical film such as a polarizing plate or a retardation plate may be provided on the outermost layer side of the transparent substrate that is in contact with the pressure-sensitive adhesive layer 13 . In this case, the pressure-sensitive adhesive layer 13 joins the optical film on the display device and the first substrate 12 .

For example, in manufacturing a display device having a laminate 21 in which the second substrate 22 is a display device and the first planar substrate 12 is a transparent substrate such as a protective plate, the transparent substrate and the display By using the cured product of composition (X) as the pressure-sensitive adhesive layer 13 sandwiched between the device and the display device, the stress exerted on the display device can be reduced, thereby preventing deterioration of display quality such as display unevenness. can be effectively prevented. Moreover, since the elastic modulus of the cured product is reduced and the stress exerted on the display device can be reduced, peeling between the cured product and the display device is less likely to occur.

In particular, when the display device is a liquid crystal display device and is an IPS (In-plane Switching) type or a TN (Twisted Nematic) type display device in which an optical film for improving the viewing angle is bonded to the display surface, the display Since the stress applied to the device tends to adversely affect the display quality, the effect of using the composition (X) of the present invention is great.

Furthermore, when the display device is a flexible display device, since it has resistance to repeated bending, peeling of the bent portion is less likely to occur, whitening can be suppressed, and the product life can be extended. Among others, it is particularly suitable when the display device is a foldable display that can be folded.

<Image display device>
The image display device of the present invention is an image display device comprising the above-described laminate, and is a display that is manufactured using the above-described composition (X) and displays video signals such as still images and moving images. Specifically, a laminate comprising a pressure-sensitive adhesive layer made of a cured product of the composition (X) between a first planar substrate and a second substrate, wherein the first planar substrate It comprises a laminate in which a material is a transparent substrate and a second substrate is a display device.
This image display device is electrically connected to the driving circuit board in addition to the laminate, and when driven, a voltage is applied to the electrodes of the display device from the starting circuit board side, so that an image can be displayed.

In the image display device of the present invention, particularly when the display device is a curved display or a flexible display, the effect of the pressure-sensitive adhesive layer using the composition (X) is preferably exhibited effectively.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. All parts and percentages in each example are based on mass.

[Measurement of number average molecular weight of oligomer (A) and oligomer (B)]
The number average molecular weights of oligomer (A) and oligomer (B) were measured by GPC (gel permeation chromatography) under the following conditions.
・ Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
・ Column: G7000HXL + GMHXL + GMHXL manufactured by Tosoh Corporation
・Column size: 7.8 mmφ×30 cm each, 90 cm in total
・Column temperature: 40°C
・Flow rate: 0.8 ml/min
・Injection volume: 100 μl
・ Eluent: Tetrahydrofuran ・ Detector: Differential refractometer (RI)
・Standard sample: Polystyrene

[Production Example 1-1: Production of monol (1)]
0.2 g of zinc hexacyanocobaltate-tert-butyl alcohol complex (hereinafter referred to as "DMC-TBA"), which is a double metal cyanide complex catalyst, was placed in a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube, And 59 g of n-butanol as an initiator were charged, and under a nitrogen atmosphere at 130° C., 3941 g of propylene oxide (hereinafter also referred to as “PO”) was added at a constant rate and charged over 7 hours. Thereafter, 4000 g of the product was withdrawn after confirming that the decrease in the internal pressure of the pressure-resistant reactor had stopped. The main component of the product, excluding by-products and catalyst-derived metals, etc., is polyoxylate with a hydroxyl value of 11.2 mgKOH/g (hydroxyl value equivalent molecular weight: 5000), an average number of hydroxyl groups of 1.03, and a water content of 120 mass ppm. It was propylene monool (monool (1)). The resulting product contained 8 ppm by mass of Zn and 2 ppm by mass of Co.

[Production Example 1-2: Production of monol (2)]
A pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube was charged with 0.2 g of DMC-TBA and 30 g of n-butanol as an initiator. It was put in over 7 hours while adding. Thereafter, 4000 g of the product was withdrawn after confirming that the decrease in the internal pressure of the pressure-resistant reactor had stopped. The main component of the product, excluding by-products and catalyst-derived metals, etc., is polyoxylate with a hydroxyl value of 5.6 mgKOH/g (hydroxyl value equivalent molecular weight: 10,000), an average number of hydroxyl groups of 1.08, and a water content of 143 mass ppm. It was 4000 g of propylene monool (monool (2)). The resulting product contained 8 ppm by mass of Zn and 2 ppm by mass of Co.

[Production Example 1-3: Production of diol (1)]
In a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube, 0.2 g of DMC-TBA and Exenol-720 (manufactured by AGC, polyoxypropylene diol, number of hydroxyl groups: 2, hydroxyl value equivalent molecular weight : 700) was charged, and under a nitrogen atmosphere at 130°C, 3290 g of PO was added at a constant rate over 7 hours. After that, after confirming that the decrease in the internal pressure of the pressure-resistant reactor has stopped, the product is extracted, and the hydroxyl value is 28.7 mg KOH / g (hydroxyl value conversion molecular weight: 3909), polyoxypropylene diol having an average number of hydroxyl groups of 2 (diol ( 1)) was obtained. The resulting product contained Zn in an amount of 1 mass ppm or less and Co in an amount of 1 mass ppm or less.

[Production Example 1-4: Production of diol (2)]
0.2 g of DMC-TBA and 400 g of Exenol-1020 initiator (manufactured by AGC, polyoxypropylene diol, molecular weight in terms of hydroxyl value: 1000) were placed in a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube. After preparation, a nitrogen atmosphere was established at 130° C., and 3600 g of PO was added at a constant rate over 7 hours. Thereafter, after confirming that the pressure inside the pressure-resistant reactor has stopped decreasing, the product is extracted to obtain a polyoxypropylene diol (diol (2)) having a hydroxyl value of 11.1 mgKOH/g (hydroxyl value equivalent molecular weight: 10108). rice field. The resulting product contained Zn in an amount of 1 mass ppm or less and Co in an amount of 1 mass ppm or less.

[Production Example 1-5: Production of diol (3)]
Using propylene glycol as an initiator and KOH as a catalyst, propylene oxide was reacted to produce a polyoxypropylene diol (diol (3)) having a hydroxyl value of 37.4 mgKOH/g (hydroxyl value equivalent molecular weight: 3000).

[Production Example 1-6: Production of diol (4)]
Using propylene glycol as an initiator and KOH as a catalyst, propylene oxide was reacted to produce a polyoxypropylene diol (diol (4)) having a hydroxyl value of 56.1 mgKOH/g (hydroxyl value equivalent molecular weight: 2000).

[Production Example 2-1: Production of monofunctional oligomer (B-1)]
In a reaction vessel equipped with a stirrer and a nitrogen inlet tube, 928.1 g of the monool (1) obtained in Production Example 1-1 and 2-acryloyloxyethyl isocyanate (Karenzu AOI, product name of Showa Denko Co., Ltd.) were added. 26.8 g was charged and reacted at 70° C. for 3 hours in the presence of 0.0955 g of dioctyltin distearate (DOTDS) to obtain a monofunctional oligomer (B-1).
The obtained monofunctional oligomer (B-1) had a number average molecular weight of 7,660.
The amount of 2-acryloyloxyethyl isocyanate blended with respect to monool (1) was 100 in terms of index (NCO/OH ratio).

When the obtained oligomer (B-1) was allowed to stand at 0° C. for 1 month, its appearance was observed.
After adding 0.3 parts of IRGACURE819 (BASF product name) as a photopolymerization initiator to 100 parts of the obtained oligomer (B-1) and mixing well, curing was carried out in the same manner as the storage modulus measurement described below. A product was obtained, and the storage elastic modulus E' of the cured product was measured. Table 1 shows the measurement results. The same applies to Production Examples 2-2 and 2-3 below.

[Production Example 2-2: Production of monofunctional oligomer (B-2)]
964.9 g of monol (2) obtained in Production Example 1-2 and 13.1 g of Karenz AOI were charged into a reaction vessel equipped with a stirrer and a nitrogen inlet tube, and 0.0977 g of DOTDS was added. , and 70° C. for 3 hours to obtain a monofunctional oligomer (B-2). The obtained oligomer (B-2) had a number average molecular weight of 16,000.
The blending amount of 2-acryloyloxyethyl isocyanate to monool (2) was 100 in terms of index (NCO/OH ratio).
When the obtained oligomer (B-2) was allowed to stand at 0° C. for 1 month, its appearance was observed.
[Production Example 2-3: Production of monofunctional oligomer (B-3)]
Oligomer (B-3) was obtained in the same manner as in Production Example 2-2 using the same monool as monool (2) except that the water content was 200 mass ppm. The obtained oligomer (B-3) had a number average molecular weight of 16,000.
When the resulting oligomer (B-3) was allowed to stand at 0° C. for 1 month, its appearance was observed and found to be cloudy.

[Production Example 3-1: Production of bifunctional oligomer (A-1)]
Into a reaction vessel equipped with a stirrer and a nitrogen inlet tube, 400 g of diol (1) obtained in Production Example 1-3 and 31.6 g of isophorone diisocyanate (IPDI) were charged. The mixture was reacted at 70° C. for 10 hours in the presence of .03 g to obtain an isocyanate group-terminated urethane prepolymer. The blending amount of IPDI relative to diol (1) was 142 in index. The isocyanate group content of the prepolymer was 0.145 mass %. Subsequently, 0.10 g of dibutyltin bislaurate (DBTDL), 0.11 g of 2,5-di-tert-butylhydroquinone (DtBHQ), and 1.49 g of 2-hydroxyethyl acrylate (HEA) were added to form a bifunctional An oligomer (A-1) was obtained. The obtained oligomer (A-1) had a number average molecular weight of 13,890 and a urethane bond concentration of 3.87% by mass.

Further, the urethane bond concentration of the oligomer (A-1) was calculated from the following formula, assuming that the total amount of isocyanate groups possessed by IPDI used in the production of the oligomer (A-1) formed urethane bonds. .
(Number of moles of isocyanate groups possessed by IPDI x urethane bond molecular weight (59)/mass of oligomer (A-1)) x 100 (mass%)
As the mass of the oligomer (A-1), the total mass of the charged amounts of the diol (1), IPDI, and HEA was used.

[Production Examples 3-2 to 3-6]
As shown in Table 1, diols (2) to (4) were used instead of diol (1) in Production Example 3-1, and the same procedure was performed except that the blending amounts of the raw materials were changed as described. They were reacted to obtain bifunctional oligomers (A-2), (A-3), (A-4), (A-5) and (A-6).

[Examples 1 to 8]
(Preparation of adhesive composition)
The monofunctional oligomers obtained in Production Examples 2-1 to 2-2 and the bifunctional oligomers obtained in Production Examples 3-1 to 3-6, and the following commercially available raw materials were mixed in the ratio shown in Table 2 (mass% ) using a planetary stirrer manufactured by EMC to prepare a pressure-sensitive adhesive composition. Examples 1 to 4 are working examples, and examples 5 to 8 are comparative examples.

In addition, the following commercial items were used as acrylic monomers.
LA: Lauryl acrylate (manufactured by Toho Kasei Co., Ltd.)
ACMO: 4-acryloylmorpholine (manufactured by Kojin Co., Ltd.)
Moreover, the following commercial item was used as a tackifier.
KE311: Rosin ester (product name of Arakawa Chemical Co., Ltd.: rosin ester pine crystal KE311)
Moreover, the following commercial item was used as a photoinitiator. The photopolymerization initiator was added in an amount of 0.38 parts by mass based on the total amount of the curable components.
IRGACURE819 (BASF product name)

[Characteristic test]
A film was prepared using the adhesive compositions obtained in Examples 1 to 8 above, and the static bending test, repeated bending test, and adhesive strength properties were evaluated as follows, and the storage elastic modulus E' was calculated. It was measured. These results are also shown in Table 2.

(Preparation of film for repeated bending test)
The pressure-sensitive adhesive composition of each example was applied to the silicone-treated surface of a 75 μm-thick polyethylene terephthalate (PET) film (manufactured by Mitsui Chemicals Tohcello, SP-PET-01-75BU) that had been subjected to silicone treatment (release treatment). It was applied using an automatic coater (PI1210 automatic coater manufactured by Tester Sangyo Co., Ltd.) equipped with a doctor blade so that the thickness of the subsequent adhesive layer would be 25 μm. Subsequently, using a conveyor-type UV irradiator (manufactured by ORC) in a nitrogen environment, curing was performed under the conditions of a HgXe lamp, an illumination intensity of 100 mW/cm ² and an integrated light intensity of 3,000 mJ/cm ² . The pressure-sensitive adhesive laminated film thus obtained was attached to a 50 μm thick Kapton film (manufactured by DuPont Toray Co., Ltd.) on the pressure-sensitive adhesive side, and then the silicone-treated PET was peeled off. A corona-treated PET (a PET film Lumirror S10 manufactured by Toray Industries, Inc. subjected to corona treatment) was laminated so that the corona-treated surface was in contact with the pressure-sensitive adhesive surface to prepare a film for repeated bending test.

<Static bending test>
A film prepared in the same manner as the film for the repeated bending test was used as a sample for the static bending test. Along the semicircle of a plate with a thickness of 3 mm processed into a semicircle with a diameter of 3 mm on one side, the Kapton side of the static bending test sample was brought into close contact with the inside and fixed with a tape.

After that, the film was allowed to stand for 10 days under conditions of room temperature, −20° C. and 80° C., and the appearance of the film after the test was visually evaluated according to the following criteria.
◯: No change in appearance such as whitening, blistering, peeling, floating, or cracking.
Δ: Slight peeling, bubbling, or cracking at the edge, but no practical problem.
x: Whitening and marked peeling at edges, causing practical problems.

<Repeated bending test>
Conditions are set so that the inner diameter (diameter) of the film for repeated bending test obtained above is 3 mm when the film is bent into a U-shape using a U-shaped planar bending tester (DLDM111LH manufactured by Yuasa System Equipment Co., Ltd.). Then, the bending and 180° opening were repeated 100,000 times at room temperature at a speed of 60 times per minute so that the Kapton side faced inward.

The appearance of the film after the test was visually evaluated according to the following criteria.
◯: No change in appearance such as whitening, blistering, peeling, floating, or cracking.
Δ: Slight peeling, bubbling, floating, or cracking at the edge, but no practical problem.
x: Whitening and significant peeling at the edges, causing practical problems.

(Preparation of film for adhesion measurement)
The pressure-sensitive adhesive composition of each example was applied to one side of a PET film (E5001 manufactured by Toyobo Co., Ltd.) with a thickness of 38 μm, and an automatic coating machine (with a doctor blade set so that the thickness of the adhesive layer after curing was 100 μm It was applied using a PI1210 automatic coating device manufactured by Tester Sangyo Co., Ltd.). Subsequently, using a conveyor-type UV irradiation machine (manufactured by ORC) in a nitrogen environment, curing was performed under the conditions of a HgXe lamp, illuminance of 100 mW/cm ² , and integrated light intensity of 3,000 mJ/cm ² to obtain a film for adhesion measurement. Obtained.

<Adhesive strength>
Each film for adhesive strength measurement obtained above was cut into 25 mm width×100 mm length. Subsequently, a rubber roll of 2 kg was reciprocated once so that the adhesive surface of the film was adhered to the float glass so that the film was attached to the float glass. After that, the sample was left to stand for 20 minutes in an atmosphere of 23° C./55% RH and used as a measurement sample. The adhesive strength of the adhesive layer in the measurement sample was measured.

The adhesive strength is measured by using a tensile tester with a constant temperature bath (RTG-1310 manufactured by A&D Co., Ltd.) at a peel angle of 180° at 23°C and a relative humidity of 55% RH. , and the adhesive force (N/25 mm) when peeled off was measured according to JIS Z0237 (2009) for adhesive tape and adhesive sheet testing at a peel speed of 300 mm/min.

<Measurement of storage modulus>
Using the adhesive composition obtained in each example, the adhesive layer formed by curing as described below was measured using a dynamic viscoelasticity measuring device (manufactured by Seiko Instruments Inc., EXSTAR 6100). The storage elastic modulus E' was measured in a temperature range of from 130°C to 130°C. The pressure-sensitive adhesive layer is formed by pouring the pressure-sensitive adhesive composition of each example into a silicone mold having a width of 5 mm, a length of 15 mm, and a thickness of 2 mm, using a conveyor type UV irradiation machine (manufactured by ORC) under a nitrogen environment, and applying an HgXe lamp. , an illuminance of 100 mW/cm ² and an integrated light amount of 3,000 mJ/cm ² . The obtained cured product (adhesive layer) is set in a dynamic viscoelasticity measuring device, and under the conditions of a strain of 1% in a temperature range of -80 ° C to 130 ° C in tensile mode and a heating rate of 3 ° C / min. It was measured.
As shown in Table 2, in Examples 1 to 4, the static bending test results under all temperature conditions were good, and the repeated bending test and adhesive strength were good. Example 5, which did not contain a monofunctional oligomer, gave poor results in the static bend test and the repeated bend test. In Examples 6 and 8, in which bifunctional oligomers having a small amount of urethane bonds were used, adhesive strength was inferior. In Example 7, which used a bifunctional oligomer with a large amount of urethane bonds, the results of the static bending test and repeated bending test under low temperature conditions were poor, and the adhesive strength was also poor.

The pressure-sensitive adhesive composition of the present invention has a low elastic modulus and can form a pressure-sensitive adhesive layer with excellent adhesion to substrates. When this pressure-sensitive adhesive layer is laminated on a substrate to form a laminate, even if the laminate is repeatedly folded, peeling of the pressure-sensitive adhesive layer and whitening of the folded portion can be suppressed. This laminate can be used as a component of an image display device, and is suitable for use as a component such as a flexible display panel that is repeatedly bent, and can produce a product that can exhibit its properties stably for a long period of time.
In addition, the entire contents of the specification, claims, abstract and drawings of Japanese Patent Application No. 2018-189409 filed on October 04, 2018 are cited here, and as a disclosure of the specification of the present invention, It is taken in.

DESCRIPTION OF SYMBOLS 11, 21... Laminate, 12... 1st planar base material, 13... Adhesive layer, 22... 2nd base material

Claims (9)

A pressure-sensitive adhesive composition,
An oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and an acryloyloxy group, having two acryloyloxy groups in one molecule and a urethane bond in one molecule A bifunctional oligomer containing 3.90 to 6.00% by mass,
An oligomer having a polyoxyalkylene chain, a group having a urethane bond derived from an isocyanate group-containing compound, and an acryloyloxy group , having one acryloyloxy group per molecule and a urethane bond per molecule A monofunctional oligomer containing 0.35 to 1.9% by mass ,
contains
The bifunctional oligomer is a reaction product of a polyoxyalkylene diol, a diisocyanate, and a hydroxyalkyl acrylate or an isocyanate alkyl acrylate,
The bifunctional oligomer has a number average molecular weight of 5,000 to 30,000,
the monofunctional oligomer is a reaction product of a polyoxyalkylene monool and an isocyanate alkyl acrylate;
The monofunctional oligomer has a number average molecular weight of 3,000 to 35,000,
Both the polyoxyalkylene chain in the bifunctional oligomer and the polyoxyalkylene chain in the monofunctional oligomer are polyoxyalkylenes in which the ratio of oxypropylene groups to all oxyalkylene groups in the polyoxyalkylene chain is 50 to 100% by mass. is a chain,
The content of the bifunctional oligomer is 20 to 80% by mass with respect to the total mass of the bifunctional oligomer and the monofunctional oligomer,
A pressure-sensitive adhesive composition, wherein the total content of the bifunctional oligomer and the monofunctional oligomer is 55 % by mass or more relative to the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition according to claim 1 , wherein the pressure-sensitive adhesive composition further comprises a photoinitiator. A pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition according to claim 1 or 2 . 4. The pressure-sensitive adhesive layer according to claim 3 , which has a storage elastic modulus E' at 25° C. of 70 to 450 kPa and a surface adhesive strength of 5 N/25 mm or more. a first planar substrate;
The pressure-sensitive adhesive layer according to claim 3 or 4 , which is disposed on the first planar substrate;
A laminate comprising: 6. The laminate of claim 5 , further comprising a second substrate disposed on said adhesive layer. 7. The laminate according to claim 6 , wherein said first planar substrate is a transparent planar substrate, and said second substrate is a display device. An image display device comprising the laminate according to claim 7 . 9. The image display device according to claim 8 , wherein said image display device is a curved display or a flexible display.

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