TW202028404A - Pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, laminate, and image display device - Google Patents

Abstract

Provided is a pressure-sensitive adhesive composition which gives pressure-sensitive adhesive layers having a low modulus and has excellent pressure-sensitive adhesiveness to substrates such as optical films. The pressure-sensitive adhesive composition comprises: a bifunctional oligomer which includes a polyoxyalkylene chain and urethane-bond-containing groups derived from an isocyanate-group-containing compound and has two (meth)acryloyloxy groups in the molecule, and which has a urethane bond content in the molecule of 3.90-6.00 mass%; and a monofunctional oligomer which includes a polyoxyalkylene chain and urethane-bond-containing groups derived from an isocyanate-group-containing compound and has one (meth)acryloyloxy group in the molecule. The pressure-sensitive adhesive composition has a total content of the bifunctional oligomer and the monofunctional oligomer of 40 mass% or higher.

Description

Adhesive composition, adhesive layer, laminated body and image display device

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

Background of the invention In recent years, liquid crystal display panels (LCD) or plasma display panels (PDP) have been actively developed for flat display panels, and recently, in addition to flat display panels, curved display panels or flexible display panels have also been developed.

Such curved display panels or flexible display panels generally use organic electroluminescence (organic EL) panels.

Including flat display panels, these display panels will be provided with a laminate on the surface of which a multilayer film is laminated. For the laminate used in the above-mentioned flexible display panel, in addition to the optical requirements required by the conventional flat display panel The characteristics and durability are also required to prevent peeling or floating even if the laminate is flexed.

As an adhesive for an optical film that can be used for an optical film that allows for the deflection of the laminate, an adhesive for an optical film containing a (meth)acrylate copolymer (A) is known. The ester copolymer (A) is specifically blended with a predetermined monomer, and the glass transition temperature and the weight average molecular weight are within a predetermined range (for example, refer to Patent Document 1).

In addition, as a curable resin composition that can suppress display unevenness of a display device although the above-mentioned deflection is not taken into consideration, there is known a curable resin composition containing a predetermined polyfunctional oligomer and a predetermined monofunctional oligomer ( For example, refer to Patent Documents 2 to 3).

Prior art literature Patent literature Patent Document 1: Japanese Patent Laid-Open No. 2017-95654 Patent Document 2: Japanese Patent Laid-Open No. 2014-156566 Patent Document 3: International Publication No. 2016/017568

Summary of the invention Problems to be solved by the invention However, the adhesive for an optical film described in Patent Document 1 specifically discloses a hydrocarbon-based polymer, and an adhesive composition with improved adhesiveness is sought.

In addition, the curable resin compositions described in Patent Documents 2 and 3 are curable resin compositions with low modulus of elasticity, good flexibility, and low curing shrinkage in order to prevent the above-mentioned display unevenness, but these are The flat display panel is used as a preset object, and it is not preset to repeatedly bend like a flexible display panel. Therefore, it is expected that its adhesion will be insufficient for this type of use.

The purpose of the present invention is to provide an adhesive composition and a manufacturing method thereof for the above-mentioned problems. The adhesive composition has a low elastic modulus of the adhesive layer and has good adhesion to substrates such as optical films. When the flexible display panel is repeatedly flexed, the adhesive layer will not peel off or the bent part will be whitened. In addition, the object of the present invention is to provide an adhesive layer, a laminate, and an image display device using the adhesive composition.

Means to solve the problem The inventors of the present invention conducted studies in view of the above viewpoints, and as a result, completed the present invention. That is, the present invention is the following [1] to [16]. [1] An adhesive composition characterized by containing: A bifunctional oligomer, an oligomer having a polyoxyalkylene chain, a group derived from a urethane bond of an isocyanate group-containing compound, and a (meth)acryloxy group, and in one molecule It has 2 (meth)acryloxy groups and contains 3.90~6.00% by mass of urethane bonds in 1 molecule; and Monofunctional oligomer is an oligomer having a polyoxyalkylene chain, a group derived from a urethane bond of an isocyanate group-containing compound, and a (meth)acryloxy group, and has an oligomer in 1 molecule 1 (meth)acryloyloxy group; The total content of the bifunctional oligomer and the monofunctional oligomer is 40% by mass or more with respect to the adhesive composition.

[2] The adhesive composition according to [1], wherein the content ratio of the bifunctional oligomer is 20 to 80% by mass relative to the total mass of the bifunctional oligomer and the monofunctional oligomer. [3] The adhesive composition according to [1] or [2], wherein the aforementioned bifunctional oligomer is polyoxyalkylene glycol, diisocyanate and hydroxyalkyl (meth)acrylate or isocyanate alkyl ( The reaction product of meth)acrylate. [4] The adhesive composition of any one of [1] to [3], wherein the number average molecular weight of the aforementioned bifunctional oligomer is 5,000 to 30,000. [5] The adhesive composition according to any one of [1] to [4], wherein the aforementioned monofunctional oligomer is a reaction product of a polyoxyalkylene unit alcohol and an isocyanate alkyl (meth)acrylate.

[6] The adhesive composition of any one of [1] to [5], wherein the number average molecular weight of the aforementioned monofunctional oligomer is 3,000 to 35,000. [7] The adhesive composition of any one of [1] to [6], wherein the polyoxyalkylene chain in the bifunctional oligomer and the polyoxyalkylene chain in the monofunctional oligomer All chains are polyoxyalkylene chains in which the ratio of the oxyalkylene groups to the total oxyalkylene groups in the polyoxyalkylene chain is 50-100% by mass. [8] The adhesive composition according to any one of [1] to [7], wherein the (meth)acryloxy group possessed by the aforementioned bifunctional oligomer and the (meth)acryloxy group possessed by the aforementioned monofunctional oligomer ( The meth)acryloxy groups are all acryloxy groups. [9] The adhesive composition according to [8], which further contains a photopolymerization initiator. [10] An adhesive layer characterized in that it is composed of a hardened material of the adhesive composition as described in any one of [1] to [9].

[11] For the adhesive layer of [10], its storage elastic modulus E'at 25°C is 70~450kPa, and the surface adhesion is above 5N/25mm. [12] A layered product characterized by having a first planar substrate and an adhesive layer such as [10] or [11] arranged on the first planar substrate. [13] The layered body of [12], which further has a second base material disposed on the adhesive layer. [14] The laminate according to [13], wherein the first planar substrate is a transparent planar substrate, and the second substrate is a display device. [15] An image display device characterized by comprising the laminated body as described in [14] above. [16] The image display device of [15], wherein the image display device is a curved display or a flexible display.

Invention effect According to the adhesive composition of the present invention, an adhesive composition can be obtained that can form an adhesive layer with a low elastic modulus and excellent adhesion to a substrate.

According to the adhesive layer of the present invention, the modulus of elasticity is low and the adhesion to the substrate is excellent. When the laminate is formed on the substrate, even if the laminate is repeatedly bent, the generation of adhesive can be suppressed When the layer is peeled off or the bent part is whitened.

According to the laminated body and the image display device of the present invention, the adhesive layer having the above-mentioned characteristics is used. Therefore, the peeling of the adhesive layer or the whitening of the bent part can be suppressed at the repeated bending position, and the structure can be made stable for a long time. Parts of products with characteristics.

The form used to implement the invention In this specification, the compound represented by formula (1) is referred to as compound (1). Compounds represented by other chemical formulas are also represented in the same way. In this specification, the following terms are used with the following definitions. "(Meth) acryloxy group" is the general term for acryloxy group and methacryloxy group. "(Meth)acrylate" is the general term for acrylate and methacrylate. Similarly, "(meth)acrylic acid" is the general term for acrylic acid and methacrylic acid, and (meth)acrylamide is the general term for acrylamide and methacrylamide.

The "number of functional groups" means the number of (meth)acryloxy groups in one molecule, unless otherwise specified. "Average number of functional groups" means the number of average (meth)acryloxy groups in 1 molecule per formula weight or number average molecular weight obtained according to the chemical formula, unless otherwise specified. The "curable component" means a compound having a (meth)acryloxy group. Regarding the "index" in the reaction between an isocyanate group-containing compound and a hydroxyl-containing compound, the value obtained by dividing the molar number of the isocyanate group of the isocyanate group-containing compound by the molar number of the hydroxyl group of the hydroxyl-containing compound multiplied by 100 times . The hydroxyl value of the hydroxyl-containing compound can be obtained by measurement based on JIS K1557 (2007 edition). In addition, the hydroxyl-converted molecular weight is a value calculated by applying the hydroxyl value to the formula "56100/(hydroxyl value)×(active hydrogen number of initiator)".

The number average molecular weight is a polystyrene conversion molecular weight obtained by gel permeation chromatography (GPC) measurement using a calibration curve made with a standard polystyrene sample of known molecular weight. Molecular weight distribution refers to the value obtained by dividing the mass average molecular weight (same as the number average molecular weight, the polystyrene conversion molecular weight obtained by GPC) by the number average molecular weight. When a peak of unreacted low molecular weight components (monomers, etc.) appears in the GPC measurement, the peak is excluded to calculate the number average molecular weight. Even if the number average molecular weight has been specified, if there is no molecular weight distribution, the molecular weight expressed by the formula weight obtained from the chemical formula is used instead.

>Adhesive composition> The adhesive composition of the present invention (hereinafter referred to as "composition (X)" contains a bifunctional oligomer (hereinafter referred to as "oligomer (A)") and a monofunctional oligomer (hereinafter referred to as "oligomer (B) )”) as an essential component. In addition, the total content of the oligomer (A) and the oligomer (B) is 40% by mass or more in the composition (X).

[Oligomer (A)] The oligomer (A) is a bifunctional oligomer, which is an oligomer with a polyoxyalkylene chain, a urethane bond derived from an isocyanate group-containing compound, and a (meth)acryloxy group And, it has two (meth)acryloxy groups in one molecule and contains 3.90 to 6.00% by mass of urethane bonds in one molecule.

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

In addition, the oligomer (A) contains 3.90 to 6.00% by mass of urethane bonds in one molecule. When the concentration (existence ratio) of the urethane bond is within the above range, the adhesion can be improved. The concentration of the urethane bond in one molecule is preferably 3.92-5.70% by mass, and more preferably 3.95-5.50% by mass.

As for the concentration of the above-mentioned urethane bond, it can be regarded that the total amount of the isocyanate group of the isocyanate group-containing compound used in the production of the oligomer (A) forms the urethane bond, and is calculated by the following calculation formula. (The number of moles of isocyanate groups of the isocyanate group-containing compound × the molecular weight of the urethane bond (59)/the mass of the oligomer (A)) × 100 (%)

In addition, the number average molecular weight of the oligomer (A) is preferably 5,000 to 30,000, preferably 10,000 to 28,000, and more preferably 15,000 to 25,000. If 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 adhesiveness of the resulting adhesive layer can be easily improved. 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 step of oligomer (A), for example, by-products, oligomers having one (meth)acryloxy group contained in one molecule (hereinafter referred to as "by-product oligomers") are sometimes obtained. Polymer ") and oligomer (A). The content of the oligomer (A) in the above product is preferably 80% by mass or more relative to the total amount of the by-product oligomer and the oligomer (A) in order to fully function as the oligomer (A), and 85-100% by mass is preferable, and 90-100% by mass is more preferable. When the product contains the oligomer (A) in the above content, the function of the oligomer (A) can be fully exerted, so the product (A) can be regarded as the oligomer (A). When the above product can be regarded as the oligomer (A), the average number of functional groups calculated from the number average molecular weight and the number of functional groups of the mixture of the by-product oligomer and the oligomer (A) can be regarded as the oligomer (A) ) The average number of functional groups. The average number of functional groups can be determined by NMR analysis, for example. The average number of functional groups of the oligomer (A) at this time is preferably 1.6 to 2.0, preferably 1.7 to 2.0, and more preferably 1.8 to 1.96. The adhesive layer of the oligomer (A) whose average number of functional groups is within the above range tends to have better adhesiveness.

The oligomer (A) can be produced by a known method using known raw materials. For example, it can be manufactured using the raw materials and manufacturing methods 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 an oligomer having an average number of functional groups within the aforementioned range. Reaction product (1): The polyoxyalkylene polyol and the polyisocyanate are reacted at a ratio exceeding 100 to produce an isocyanate-terminated urethane polymer, and then the isocyanate-terminated urethane polymer is made to have a group that can react with the isocyanate group and (former The reaction product obtained by reacting the obtained isocyanate-terminated urethane polymer with an acryloxy compound. Reaction product (2): make polyoxyalkylene polyol and polyisocyanate react at a ratio of less than index 100 to produce hydroxyl-terminated urethane polymer, and then make it have isocyanate groups and (meth)acrylic acid groups The compound is the reaction product obtained by reacting the obtained hydroxyl-terminated urethane polymer.

The polyoxyalkylene polyol used as the raw material of the reaction products (1) and (2) is preferably polyoxyalkylene glycol. The polyisocyanate used as the raw material of the reaction products (1) and (2) is preferably a diisocyanate. As the raw material of the reaction product (1), the compound having a group capable of reacting with an isocyanate group and a (meth)acryloyloxy group is preferably a (meth)acrylate having a hydroxyl group or an amino group, and preferably has 1 Hydroxyalkyl (meth)acrylates having one hydroxyl group are preferred. The compound having an isocyanate group and a (meth)acryloxy group as the raw material of the reaction product (2) is preferably a (meth)acrylate having one isocyanate group, and an isocyanate alkyl (meth)acrylate Better. That is, the reaction products (1) and (2) are preferably the reaction products of polyoxyalkylene glycol, diisocyanate and hydroxyalkyl (meth)acrylate or isocyanate alkyl (meth)acrylate.

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

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

The oxyalkylene group in the polyoxyalkylene polyol is preferably composed of only oxypropylene group or a combination of oxypropylene group and other groups, and the oxyalkylene group other than oxypropylene group is preferably oxygen Ethylene. The ratio of the oxyalkylene group to the total oxyalkylene group in the polyoxyalkylene polyol is preferably 50-100% by mass, and more preferably 80-100% by mass. In addition, when the initiator is a polyoxyalkylene polyol with a lower molecular weight than the target polyoxyalkylene polyol, the oxyalkylene group in the initiator can be regarded as the oxygen extension in the obtained polyoxyalkylene polyol. alkyl.

Low hydroxyl value (that is, high molecular weight) polyoxyalkylene polyols can cause alkylene oxides (especially propylene oxide) with carbon number 3 or more to react with the initiator in the presence of a complex metal cyanide complex catalyst. Manufactured by ring-opening addition polymerization. The low hydroxyl value polyoxyalkylene polyol may include a polyoxyalkylene polyol having a hydroxyl value of 40 mgKOH/g or less. Polyoxyalkylene polyols with low hydroxyl value of oxyethylene can have high hydroxyl value of oxyethylene (50mgKOH/g or more is preferred) polyoxyalkylene polyols as initiators in complex metal cyanide In the presence of a complex catalyst, an alkylene oxide with a carbon number of 3 or more (especially propylene oxide) is prepared by ring-opening addition polymerization. The high hydroxy value polyoxyalkylene polyol or the high hydroxy value polyoxyalkylene polyol used as an initiator can be manufactured using an alkali catalyst such as KOH.

The polyoxyalkylene polyol used to manufacture the oligomer (A) may also be a mixture of two or more polyoxyalkylene polyols. At this time, each polyoxyalkylene polyol is preferably a polyoxyalkylene polyol contained in the above category, and each polyoxyalkylene polyol is a polyoxyalkylene polyol contained in the above category. Polyols are better.

The polyisocyanate as the raw material of the reaction products (1) and (2) is a compound having two or more isocyanate groups in one molecule. In order to obtain the bifunctional oligomer (A), the polyisocyanate is preferably a diisocyanate. Hereinafter, a diisocyanate is used as an example to describe polyisocyanate. Examples of the polyisocyanate include non-yellowing aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified products of these diisocyanates (modified products having two isocyanate groups). Two or more kinds of diisocyanates may be used in combination. The diisocyanate is preferably an aliphatic diisocyanate and an alicyclic diisocyanate from the viewpoint of excellent light resistance, weather resistance, and heat resistance and maintaining transparency.

Examples of the non-yellowing aromatic diisocyanate include diisocyanate and tetramethyl diisocyanate. Examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate, and the like.

The raw material of the reaction product (1) is a group that can react with an isocyanate group and a group that can react with an isocyanate group in a compound having a (meth)acryloyloxy group, such as a hydroxyl group and a group bonded with a hydrogen atom Amino groups of nitrogen atoms, etc. The number of hydroxyl groups in the group that can react with the isocyanate group or the number of hydrogen atoms bonded to the nitrogen atom is preferably one. The group capable of reacting with the isocyanate group is preferably a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group. The compound having a group capable of reacting with an isocyanate group and a (meth)acryloyloxy group is preferably a hydroxyalkyl (meth)acrylate and a hydroxycycloalkyl (meth)acrylate, and the carbon of the hydroxyalkyl group Hydroxyalkyl (meth)acrylates having a number of 8 or less are particularly preferred. Specific examples of compounds having a group capable of reacting with an isocyanate group and a (meth)acryloyloxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (meth) Base) 2-hydroxybutyl acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, etc. Commercial products can include: Lightester HO-250(N), Lightester HOP(N), Lightester HOA(N), Lightester HOP-A(N), Lightester HOB(N) (all are the product names of Gongrong Chemical Company), 4-HBA (product name of Osaka Organic Chemical Industry Co., Ltd.).

The compound having an isocyanate group and a (meth)acryloxy group as the raw material of the reaction product (2) is preferably a compound having one isocyanate group. The compound having an 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, isocyanate alkyl (methyl) Acrylic is particularly preferred. The carbon number of the alkyl group excluding the isocyanate group of the isocyanate alkyl group is preferably 8 or less, and preferably 4 or less. Specific examples of the compound having an isocyanate group and a (meth)acryloyloxy group include 2-isocyanate ethyl (meth)acrylate, isocyanate methacrylate, and the like. Commercially available products include Karenz-AOI and Karenz-MOI (both are product names of Showa Denko).

As described later, the composition (X) of the present invention is preferably a photocurable composition. The oligomer (A) contained in the photocurable composition (X) is an oligomer (A) in which all (meth)acryloxy groups of the oligomer (A) are acryloxy groups good. The oligomer (A) can be made into acrylic acid by using a raw material compound having the aforementioned (meth)acryloyloxy group (hydroxyalkyl (meth)acrylate, isocyanate alkyl (meth)acrylate, etc.) The raw material compound of the oxy group is obtained. Similarly, the (meth)acryloyloxy group in other compounds having a (meth)acryloyloxy group contained in the light-curable composition (X) such as the oligomer (B) described later is also preferably an acrylicooxy group. base.

The aforementioned reaction product (1) is preferably a reaction product obtained by equivalently reacting a hydroxyalkyl (meth)acrylate with an isocyanate-terminated urethane prepolymer, and the isocyanate-terminated urethane prepolymer is It is obtained by reacting polyoxyalkylene glycol and diisocyanate with an index exceeding 100 and 200 or less. The more the isocyanate-terminated urethane prepolymer is obtained by the reaction at an index close to 100, the higher the molecular weight; the more the isocyanate-terminated urethane prepolymer is obtained by the reaction at an index close to 200, the lower the molecular weight. Therefore, the number average molecular weight of the 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 polyoxyalkylene glycol, 2 molecules of diisocyanate, and 2 molecules of hydroxyalkyl (meth)acrylate. The lower the index, the lower the index of polyoxyalkylene glycol. The number of alcohol residues and diisocyanate residues will increase. In order to obtain the oligomer (A) of the number average molecular weight in the aforementioned ideal range, the index is preferably 120 or less, and preferably 102 to 115. In addition, the amount of hydroxyalkyl (meth)acrylate used for reacting the isocyanate-terminated urethane prepolymer can also be greater than equal moles relative to the isocyanate-terminated urethane prepolymer. the amount. The hydroxyalkyl (meth)acrylate in the reaction product (1) containing an excessive amount of hydroxyalkyl (meth)acrylate can be included in the composition (X) as the monomer described later together with the reaction product (1) At least part of (C).

The aforementioned reaction product (2) is preferably a reaction product obtained by equivalently reacting isocyanate alkyl (meth)acrylate to a hydroxyl-terminated urethane prepolymer, and the hydroxyl-terminated urethane prepolymer is Polyoxyalkylene glycol and diisocyanate are obtained by reacting at an index of less than 100 and above 50. The more the hydroxyl-terminated urethane prepolymer is obtained by the reaction under the condition that the index is close to 100, the higher the molecular weight; the more the reaction is obtained under the condition of the index close to 50, the lower the molecular weight is. Therefore, the number average molecular weight of the 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 polyoxyalkylene glycol, 1 molecule of diisocyanate, and 2 molecules of isocyanate alkyl (meth)acrylate. The higher the index, the higher the number of polyoxyalkylene glycols. The number of alcohol residues and diisocyanate residues will increase. In order to obtain the oligomer (A) of the number average molecular weight in the aforementioned ideal range, the index is preferably 80 or more, and preferably 85-98.

[Monofunctional oligomer] Monofunctional oligomer (hereinafter referred to as "oligomer (B)") has a polyoxyalkylene chain, a group with a urethane bond derived from an isocyanate group-containing compound, and (meth)acrylic acid An oligomer having one (meth)acryloyloxy group in one molecule. As mentioned above, when the adhesive composition of the present invention is an ultraviolet curable adhesive composition, the (meth)acryloxy group in the oligomer (B) is preferably an acrylicoxy group.

The oligomer (B) is easy to reduce the shrinkage during curing, and it is easy to reduce the elastic modulus of the adhesive after curing. Therefore, when used as an adhesive in a laminated body such as a display device, the adhesive layer is not easy to peel off from the substrate. Suppresses whitening during repeated bending. Moreover, it has one (meth)acryloxy group, so the stability of the adhesive after curing is better, and it is not easy to overflow.

The number of urethane bonds in one molecule of the oligomer (B) is more than one, which is easy to inhibit shrinkage during curing and reduce the elastic modulus of the adhesive after curing. Therefore, it is preferably one or two, and one Better. The oligomer (B) preferably contains 0.35 to 1.9% by mass of urethane bonds per molecule. As long as the concentration (existence ratio) of the urethane bond is within the above range, better adhesiveness can be obtained. The concentration of the urethane bond in one molecule is preferably 0.4 to 1.3% by mass, and more preferably 0.5 to 1.2% by mass. In addition, the concentration of the aforementioned urethane bond 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, preferably 4,000 to 20,000, and 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 adhesive composition. In addition, if the number average molecular weight is above 3,000, the curing shrinkage rate of the adhesive composition is likely to decrease. When two or more types of oligomers (B) are contained in the adhesive composition, the number average molecular weight of each oligomer (B) is preferably within the above range.

In the production step of the oligomer (B), a by-product having a polyoxyalkylene chain other than the oligomer (B) may be produced in the product. Examples of by-products having a polyoxyalkylene chain include compounds having two (meth)acryloxy groups, compounds without (meth)acryloxy groups, and compounds without urethane bonds. In order for the content of the oligomer (B) in the product to fully exert its function as the oligomer (B), it is preferably 80% by mass or more, and more preferably 85-100% by mass. When the product contains the oligomer (B) in the above content, the function of the oligomer (B) can be fully exerted, so the product can be regarded as the oligomer (B).

When the above product can be regarded as the oligomer (B), the average number of functional groups obtained from the number average molecular weight of the product and the number of functional groups can be regarded as the average number of functional groups of the oligomer (B). At this time, the average number of functional groups in the product is preferably 0.8 to 1.2, and preferably 0.9 to 1.1. Products within the above range are easy to fully exert the function of oligomer (B). The above-mentioned average number of functional groups can be adjusted within this range by adjusting the amount of impurities contained in the raw material for the production of the oligomer (B) or adjusting the index described below. In addition, in this specification, the average number of functional groups can be calculated using the average number of functional groups and the index of the raw materials described later.

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 adhesive composition preferably contains one or more selected from the group consisting of the reaction product (3) and the reaction product (4). Especially for the oligomer (B), compared with other reaction products, the content of by-products is small, and an adhesive composition with excellent flexibility and curing shrinkage can be obtained. Therefore, the reaction product (3) is preferred.

The total content of the reaction product (3) and the reaction product (4) relative to the oligomer (B) is preferably 50% by mass or more, preferably 80% by mass or more, and particularly preferably 100% by mass. If the total content of the reaction product (3) and the reaction product (4) is more than the lower limit of the above range, flexibility and curing shrinkage are better. When the monofunctional oligomer (B) contains the reaction product (3) and the reaction product (4), the mass ratio of these should be reaction product (3): reaction product (4)=1:0~1:1.

Reaction product (3): an isomolar reaction product of a polyoxyalkylene unit alcohol and a compound having an isocyanate group and a (meth)acryloxy group. Reaction product (4): isomolar reaction products of polyoxyalkylene unit alcohols, diisocyanates, and compounds having isocyanate groups and (meth)acryloxy groups. Reaction product (5): an isomolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloxy group. The compounds having isocyanate groups and (meth)acryloxy groups as the raw materials of the reaction products (3) and (5) are the compounds listed as the raw materials of the reaction product (2). The ideal compounds and specific examples thereof are also the same The raw material compounds of the aforementioned reaction product (2) are the same. That is, it is preferably a (meth)acrylate having one isocyanate group, and more preferably an isocyanate alkyl (meth)acrylate. The diisocyanate of the raw material of the reaction product (4) is the diisocyanate listed as ideal among the polyisocyanates of the raw material of the reaction product (1) and (2). The ideal compound and its specific examples are also the same as the aforementioned reaction product (1). The diisocyanate of the raw materials of) and (2) are the same. The raw material of the reaction product (4), the compound having a group capable of reacting with an isocyanate group and a (meth)acryloyloxy group is the compound listed as the raw material of the reaction product (1), the ideal compound and its specific examples It is also the same as the compound of the raw material of the aforementioned reaction product (1). That is, it is preferably a (meth)acrylate having one hydroxy group, and a hydroxyalkyl (meth)acrylate and a hydroxycycloalkyl (meth)acrylate are preferred, and the hydroxyalkyl group has a carbon number of 8 or less Hydroxyalkyl (meth)acrylate is particularly preferred.

The average number of hydroxyl groups in one molecule of the polyoxyalkylene unit alcohol of the raw materials of the reaction products (3) and (4) is preferably 0.8 to 1.2, preferably 0.9 to 1.1. In order to obtain the oligomer (B) with the urethane bond concentration within the aforementioned specific range, the hydroxyl value of the polyoxyalkylene unit alcohol is preferably 1.6~18.1mgKOH/g, preferably 2.8~14mgKOH/g, 3.1~ 11.2mgKOH/g is particularly preferred.

The polyoxyalkylene unit alcohol is obtained by ring-opening addition polymerization of an alkylene oxide to an initiator having an active hydrogen-containing group and an active hydrogen number of one or more, and has an initiator residue and a polyoxyalkylene The chain and the compound of the hydroxyl group corresponding to the active hydrogen number of the initiator. The alkylene oxide is preferably an alkylene oxide having a molar number of 2 to 4, 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 possessed by the initiator include a hydroxyl group, a carboxyl group, an amino group having one hydrogen atom bonded to a nitrogen atom, and the like, and a hydroxyl group and a carboxyl group are preferred. As the hydroxyl group, an alcoholic hydroxyl group is preferred. Examples of initiators having one active hydrogen include monohydric alcohols, monohydric phenols, monocarboxylic acids, and amine compounds having one hydrogen atom bonded to a nitrogen atom. The initiators are preferably mono-aliphatic alcohols and mono-aliphatic carboxylic acids. In addition, a polyoxyalkylene unit alcohol having a lower molecular weight than the target polyoxyalkylene unit alcohol can be used as an initiator. The carbon number of the initiator monobasic aliphatic alcohol is preferably 1-20, preferably 2-8. The carbon number of the monovalent aliphatic carboxylic acid of the initiator includes the carbon atom of the carboxyl group, and is preferably 2-20, preferably 2-8.

The oxyalkylene group in the polyoxyalkylene unit alcohol is preferably composed only of oxypropylene group or a combination of oxypropylene group and other groups, and the oxyalkylene group other than oxypropylene group is preferably oxygen Ethylene. The ratio of the oxyalkylene group in the polyoxyalkylene unit alcohol to the total oxyalkylene group is preferably 50-100% by mass, preferably 80-100% by mass. In addition, when the initiator is a polyoxyalkylene unit alcohol with a lower molecular weight than the target polyoxyalkylene unit alcohol, the oxyalkylene group in the initiator can be regarded as the oxygen extension in the obtained polyoxyalkylene unit alcohol. alkyl.

Low hydroxyl value (that is, high molecular weight) polyoxyalkylene unit alcohols can cause alkylene oxides (especially propylene oxide) with carbon number 3 or more to react to the initiator in the presence of a composite metal cyanide complex catalyst. Manufactured by ring-opening addition polymerization. The polyoxyalkylene unit alcohol with low hydroxyl value of oxyethylene group can also have the high hydroxyl value of oxyethylene group (50mgKOH/g or more is preferred) polyoxyalkylene unit alcohol as the initiator, in the composite metal cyanide In the presence of a compound complex catalyst, an alkylene oxide with a carbon number of 3 or more (especially propylene oxide) is prepared by ring-opening addition polymerization. The high hydroxyl value polyoxyalkylene unit alcohol can also be produced using alkali catalysts such as KOH.

In the production of polyoxyalkylene unit alcohol, the initiator or alkylene oxide that can be put into the reaction system is usually the one with less water after the water is removed by degassing under reduced pressure. Generally, the lower the moisture content of the initiator when producing the polyoxyalkylene unit alcohol, the better, and it is preferably 500 ppm by mass or less, and more preferably 300 ppm by mass or less. If the moisture content is within this range, the amount of polyoxyalkylene glycol produced from water can be suppressed, so that the amount of by-products ultimately derived from the polyoxyalkylene glycol can be suppressed, and the obtained The upper limit of the average number of hydroxyl groups of the polyoxyalkylene unit alcohol is adjusted to 1.2 or less. In addition, the polyoxyalkylene unit alcohol used as the raw material of the reaction products (3) and (4) should have as little water as possible, and the content of the polyoxyalkylene unit alcohol is preferably 300 mass ppm or less, 250 mass ppm ppm or less is preferable, and 50 to 200 mass ppm is particularly preferable. If the moisture content is within the above range, the by-products of the reaction product of moisture and the isocyanate group-containing compound are less generated, and the stability of the reaction products (3) and (4) can be improved. In addition, the change in appearance of the curable composition containing the reaction products (3) and (4) over time can be easily suppressed, and the elastic modulus of the cured product can easily become better.

The polyoxyalkylene polyol as the raw material of the reaction product (5) is preferably the same polyoxyalkylene polyol as the polyoxyalkylene glycol as the raw material of the aforementioned oligomer (A). The average number of hydroxyl groups in one molecule of the polyoxyalkylene polyol is preferably 1.6 to 2.0, preferably 1.8 to 1.96. That is, the polyoxyalkylene polyol which is the raw material of the reaction product (5) is preferably polyoxyalkylene glycol. The content of the oxyalkylene group in the polyoxyalkylene polyol relative to the total oxyalkylene group is preferably 80-100% by mass. In order to obtain the oligomer (B) with the urethane bond concentration within the aforementioned specific range, the hydroxyl value of the polyoxyalkylene polyol is preferably 1.6 to 18.1 mgKOH/g, and preferably 2.8 to 14 mgKOH/g. The polyoxyalkylene polyol used as the raw material of the reaction product (5) can be produced in the same manner as the polyoxyalkylene glycol used as the raw material of the aforementioned oligomer (A).

[Reaction product (3)] The reaction product (3) is an isomolar reaction product of a polyoxyalkylene unit alcohol and a compound having an isocyanate group and a (meth)acryloxy group. The compound having an isocyanate group and a (meth)acryloxy group is preferably an isocyanate alkyl (meth)acrylate.

Polyoxyalkylene unit alcohol and isocyanate alkyl (meth)acrylate each have a feasible urethane reaction group in one molecule, so it is easy to convert the reaction product (3) in one molecule of urethane The number of ester bonds is controlled to one. If the number of urethane bonds in one molecule of the reaction product (3) is small, the viscosity is likely to decrease. Therefore, it is preferable that the oligomer (B) in the adhesive composition contains the reaction product (3) from the viewpoint that the adhesive composition has a low viscosity and can easily obtain a cured product with excellent flexibility. Moreover, both polyoxyalkylene unit alcohols and isocyanate alkyl (meth)acrylates are compounds with one reactive group, so by-products are not easily generated, except for unreacted substances, and highly pure reaction products can be easily obtained ( 3). When the unreacted material remains, from the viewpoint of the stability of the reaction product, the unreacted material is preferably a polyoxyalkylene unit alcohol. In order to obtain a reaction product with less unreacted substances, it is preferable to react the two at an index of 90-100, and it is particularly preferable to react with an index of 100. The average number of functional groups of the reaction product (3) is preferably 0.9-1.1. The adhesive composition containing the reaction product (3) within the above range can easily reduce the shrinkage during curing and easily reduce the elastic modulus of the adhesive after curing.

[Reaction product (4)] The reaction product (4) is an isomolar reaction product of a polyoxyalkylene unit alcohol, a diisocyanate, and a compound having a group capable of reacting with an isocyanate group and a (meth)acryloxy group. The diisocyanate is preferably aliphatic diisocyanate and alicyclic diisocyanate listed as the raw material of the aforementioned reaction products (1) and (2). The compound having a group capable of reacting with an isocyanate group and a (meth)acryloyloxy group is preferably the compound exemplified as the raw material of the reaction product (1), especially the hydroxyalkyl group having a carbon number of 8 or less (form Base) hydroxyalkyl acrylate is particularly preferred. The reaction product (4) may include: (a) the polyoxyalkylene unit alcohol and the diisocyanate are reacted with an index of 200, and then the resulting reaction product (the reaction product having an isocyanate group) is reacted with (meth)acrylic acid hydroxy A reaction product obtained by reacting an alkyl ester with an index of 100; and (b) making the polyoxyalkylene unit alcohol an equal molar (meth)acrylic acid hydroxyalkyl group relative to the polyoxyalkylene unit alcohol A reaction product obtained by simultaneously reacting an ester and a diisocyanate having an index of 100 for the total of the polyoxyalkylene unit alcohol and the hydroxyalkyl (meth)acrylate. Among them, the reaction product of (a) is preferred from the viewpoint of fewer by-products. In addition, when the reaction product of (a) is produced, the amount of hydroxyalkyl (meth)acrylate used may be an excess amount, and an excessive amount of hydroxyalkyl (meth)acrylate can be used as at least the monomer (C) described later Part of the reaction product of (a) is contained in the composition (X). The average number of functional groups of the reaction product (4) is preferably 0.8 to 1.2, and preferably 0.9 to 1.1. The adhesive composition containing the reaction product (4) within the above range can easily reduce the shrinkage during curing and easily reduce the elastic modulus of the adhesive after curing.

[Reaction product (5)] The reaction product (5) is an isomolar reaction product of a polyoxyalkylene polyol and a compound having an isocyanate group and a (meth)acryloxy group. The polyoxyalkylene polyol is preferably a polyoxyalkylene glycol, and the compound having an isocyanate group and a (meth)acryloxy group is preferably the aforementioned isocyanate alkyl (meth)acrylate. In addition, the reaction product (5) is a reaction product having a hydroxyl group, and the number of the hydroxyl group 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 isomolar reaction product, the polyoxyalkylene polyol can also be a raw material having more than 2 hydroxyl groups. compound of. The average number of functional groups of the reaction product (5) is preferably 0.8 to 1.2, and preferably 0.9 to 1.1. The reaction product (5) within the above range can easily reduce the shrinkage during curing and easily reduce the elastic modulus of the adhesive after curing.

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

The upper limit of the total content of the oligomer (A) and the oligomer (B) in the composition (X) may be 100% by mass, or may contain other components. By containing other ingredients, the physical properties can be further improved. The content of components other than the oligomer (A) and the oligomer (B) is preferably 60% by mass or less, and more preferably 45% by mass or less relative to the total amount of the composition (X). In addition, with respect to the total amount of the composition (X), the oligomer (A), the oligomer (B), the monomer (C) and the monomer (C) which are the curable components in the composition (X) The total content of D) is preferably 65% by mass or more, and more preferably 75% by mass or more.

The composition (X) may further include oligomers (A) such as hydroxyl-containing monomers and long-chain alkyl-containing monomers, and monomers having (meth)acryloxy groups other than the oligomers (B). It can also contain a photopolymerization initiator or other ingredients according to the needs. Hereinafter, the hydroxyl-containing monomer is referred to as "monomer (C)", and monomers other than the monomer (C), such as a long-chain alkyl-containing monomer, are referred to as "monomer (D)". When the composition (X) is a photocurable composition, the (meth)acryloxy groups in the aforementioned oligomer (A) and oligomer (B) are all acryloxy groups, and the composition (X) ) It is more preferable to include a photopolymerization initiator. Similarly, when the composition (X) is a photocurable composition (X) containing the following monomer (C) or monomer (D), the (meth)acryloxy group contained in these compounds is preferably All are acryloxy groups.

[Single (C)] Monomer C is a compound containing a (meth)acryloxy group and a hydroxyl group other than the oligomer (A) and the oligomer (B). The monomer (C) is preferably a compound having one (meth)acryloxy group and one or more hydroxyl groups, and the number of hydroxyl groups is preferably one or two. The monomer (C) may also be a compound having a polyoxyalkylene chain, and at that time, it is preferably a compound without a urethane bond. In addition, the monomer (C) may be a compound having an aliphatic polyester chain obtained by ring-opening addition polymerization of lactone. The monomer (C) contributes to improving the adhesion of the cured product of the composition (X). It also helps increase the light transmittance of the hardened product of the composition (X). A monomer (C) may be used individually by 1 type, and may use 2 or more types together.

Monomer (C) may include hydroxyalkyl (meth)acrylate, dihydroxyalkyl (meth)acrylate, lactone-modified hydroxyalkyl (meth)acrylate, polyoxyalkylene glycol monomer (Meth)acrylate, (meth)acrylic acid-monoepoxide adduct, etc. The carbon number of the hydroxyalkyl part of the hydroxyalkyl (meth)acrylate is preferably 2-8, preferably 2-6. The carbon number of the dihydroxyalkyl part of the dihydroxyalkyl (meth)acrylate is also the same. Specific examples of the hydroxyalkyl (meth)acrylate include the specific examples of the hydroxyalkyl (meth)acrylate exemplified as the raw material of the aforementioned reaction product (1). Among them, from the viewpoint of flexibility and low volatility, 4-hydroxybutyl acrylate and 6-hydroxyhexyl acrylate are preferred. Examples of the lactone-modified hydroxyalkyl (meth)acrylate include compounds obtained by ring-opening addition of lactones to the hydroxyalkyl (meth)acrylates listed as the raw material of the reaction product (1). The addition number of lactone is preferably 1~3. Examples of lactones include ε-caprolactone, γ-butyrolactone, and γ-valerolactone. The polyoxyalkylene chain in the polyoxyalkylene glycol mono(meth)acrylate can include polyoxypropylene chain, polyoxyethylene chain, poly(oxyethylene-oxyethylene) Chain etc. The number of oxyalkylenes in the polyoxyalkylene chain is preferably 2-8, preferably 2-6. The (meth)acrylic acid-monoepoxide adduct is preferably the reaction product of (meth)acrylic acid and glycidyl ether or glycidyl ester, such as (meth)acrylic acid and phenylglycidyl Ether etc. Among these, the hydroxyalkyl (meth)acrylate and the (meth)acrylic acid-monoepoxide adduct are preferable from the viewpoint of easy availability in the industry and less impurities.

When the composition (X) contains the monomer (C), its content is preferably 1-20% by mass relative to the total amount of the composition (X), preferably 1-15% by mass. If the content of the monomer (C) is above the lower limit of the above range, it is easy to fully obtain the effect of improving the adhesion that can be obtained by adding the monomer (C); if it is below the upper limit, it is based on the low From the viewpoint of curing shrinkage, good physical properties are easily obtained.

In the case of an OGS (One Glass Solution) type touch panel in which the touch sensor is formed on the side of the protective plate and the bonding resin layer, the bonding resin formed by curing the curable resin composition In order to prevent the touch sensor from malfunctioning, the layer requires a low dielectric constant. If the relative dielectric constant is 4.5 or less, it can prevent the misoperation of the touch sensor in the OGS type touch panel, so it is suitable. If the content of the monomer (C) in the composition (X) is below the upper limit of the above-mentioned range, the bonding resin layer obtained by using it is likely to have a low dielectric constant, and therefore it is easy to control the relative dielectric constant to Below 4.5.

In addition, in the synthesis of the aforementioned oligomer (A) or oligomer (B), when the hydroxyl-containing (meth)acrylate remaining as an unreacted raw material used in the reaction corresponds to the monomer (C), the single The body is also included in the content of monomer (C) in composition (X).

[Single (D)] The monomer (D) is a compound having a (meth)acryloxy group other than the oligomer (A), the oligomer (B), and the monomer (C). The monomer (D) is preferably a compound having one (meth)acryloxy group and no urethane bond. The monomer (D) is preferably a (meth)acrylate having a long-chain alkyl group or a (meth)acrylate having an amide group. 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. The monomer (D) may be used in combination of two or more kinds.

If the composition (X) contains the long-chain alkyl (meth)acrylate, the air bubbles in the cured product will easily disappear when the cured product is formed by the vacuum sealing-pressurization hardening method described later, and the vacuum sealing- The pressure-increasing hardening method is a method in which the composition (X) is sealed under reduced pressure and hardened in a higher pressure gas environment. The carbon number of the long-chain alkyl group is preferably 8-22, and preferably 8-18. Specific examples of the long-chain alkyl (meth)acrylate include lauryl (meth)acrylate, isostearyl (meth)acrylate, isodecyl (meth)acrylate, and the like. Among these, lauryl acrylate and isostearyl acrylate are preferred from the viewpoints of flexibility, low viscosity, and low crystallinity.

For (meth)acrylic acid esters with amide groups, the hardened substance of the composition (X) can be easily inhibited from whitening under humid and hot conditions, so it is preferably nitrogen bonded to (meth)acrylamide A compound in which the hydrogen atom of the atom has been substituted with a hydrocarbon group such as an alkyl group or a divalent organic group. Specific examples of (meth)acrylamide derivatives include 4-(meth)acrylamide mopholin, 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 1-30% by mass relative to the total amount of the composition (X), preferably 1-25% by mass. If the content of the monomer (D) is above the lower limit of the above range, the effect of adding the monomer (D) will be easily obtained; if it is below the upper limit, it is easy to obtain good results from the viewpoint of low curing shrinkage. The physical properties.

[Photopolymerization initiator] The composition (X) may be a photocurable resin composition or a thermosetting resin composition. From the viewpoint that it can be cured at a low temperature and has a fast curing speed, it is preferably a photocurable resin composition. When the composition (X) is a photocurable resin composition, it is preferable to contain a photopolymerization initiator as another component. If it is a photocurable resin composition, for example, high temperature is not required when manufacturing a display device, so there is little doubt that high temperature will damage the display device.

系、醌系等光聚合引發劑。該等中，又以膦氧化物系、9-氧硫𠮿

系的光聚合引發劑為佳，基於光聚合反應後容易抑制著色的觀點，則以膦氧化物系為佳。光聚合引發劑可單獨使用1種，亦可將2種以上併用。 光聚合引發劑並無特別限定，亦可使用市售物。市售物可舉如BASF公司製IRGACURE819、IRGACURE TPO、IRGACURE 184、IRGACURE 2959、IRGACURE 1173、IRGACURE 127、IRGACURE 907、IRGACURE OXE01、IRGACURE OXE02。Examples of photopolymerization initiators include acetophenone series, ketal series, benzoin or benzoin ether series, phosphine oxide series, diphenylketone series, and 9-oxysulfur 𠮿

Photopolymerization initiators such as quinones Among them, phosphine oxide series, 9-oxysulfur 𠮿

A type of photopolymerization initiator is preferable, and a phosphine oxide type is preferable from the viewpoint that coloration is easily suppressed 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 a commercially available product can also be used. Examples of commercially available products include IRGACURE 819, 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, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the curable components in total.

[Other ingredients] The composition (X) may include the above-mentioned oligomer (A), oligomer (B), monomer (C), monomer (D) and photopolymerization initiator within a range that does not impair the effects of the present invention. ingredient. Among other ingredients, which can improve the softness or adhesion, include: rosin ester, terpene phenol, hydrogenated terpene phenol and other tackifiers, adipate, phthalate and other plasticizers, polyoxygen Alkylene polyols, polyoxyalkylene polyols with alkoxylated ends, etc. In the case where the dielectric constant is to be kept low, it is advisable to avoid compounds with hydroxyl groups as much as possible. The content of the component that can improve flexibility or adhesion is preferably 48% by mass or less, preferably 28% by mass or less, relative to the total amount of the composition (X). If the content of other components is below the upper limit of the above range, it is preferable from the viewpoint of durability. The composition (X) may further include polymerization inhibitors, light hardening accelerators, chain transfer agents, light stabilizers (ultraviolet absorbers, radical scavengers, etc.), antioxidants, flame retardants, and adhesion promoters (silicone Coupling agent, etc.), pigments, dyes, etc. Among these additives, polymerization inhibitors and light stabilizers are preferred. In particular, by containing a smaller amount of polymerization inhibitor than the polymerization initiator, the storage stability of the composition (X) can be improved, and the molecular weight after curing can be easily adjusted.

系、羥甲苯系之聚合抑制劑。Examples of polymerization inhibitors include: hydroquinone series (2,5-di-tertiary butyl hydroquinone, etc.), catechol series (p-tertiary butyl catechol, etc.), anthraquinone series, phenanthrene

It is a polymerization inhibitor of hydroxytoluene series.

系、二苯基酮系、苯甲酸酯系等紫外線吸收劑。 苯并三唑系紫外線吸收劑例如可使用國際公開第2014/017328號段落[0076]中所記載之物。UV absorbers are used in order to prevent the light deterioration of the composition (X) and improve the weather resistance, such as benzotriazole series, three

UV absorbers such as benzene series, benzophenone series, and benzoate series. As the benzotriazole-based ultraviolet absorber, for example, what is described in paragraph [0076] of International Publication No. 2014/017328 can be used.

The light stabilizer is used in order to prevent the light deterioration of the composition (X) and improve the weather resistance. For example, hindered amine light stabilizers can be mentioned. As the hindered amine-based light stabilizer, for example, what is described in paragraph [0077] of International Publication No. 2014/017328 can be used.

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

Also, products mixed with various antioxidants and light stabilizers can also be used. For example, IRGASTAB PUR68, TINUVIN B75 manufactured by BASF Corporation, etc. are mentioned.

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

In the composition (X), the content of the chain transfer agent is as small as possible, and it is preferably 3 parts by mass or less with respect to 100 parts by mass of the curable component, preferably 2 parts by mass or less, and it is particularly preferable that the chain transfer agent is not contained.

The viscosity of the composition (X) is the value measured with an E-type viscometer at 25°C. The viscosity of the composition (X) is preferably 0.05-50 Pa·s, preferably 1-20 Pa·s, and more preferably 1.5-5 Pa·s. If the viscosity is 0.05 Pa·s or more, it is easy to balance the fluidity of the composition (X) and the physical properties of the cured product after curing. If it is 50 Pa·s or less, workability when forming an uncured resin layer is good. It is also suitable for the method of sealing the composition (X) under reduced pressure and hardening it in a higher pressure gas environment (decompression sealing-pressure-increasing hardening method) described later, which can make the air bubbles in the hardened material good To disappear.

By including the oligomer (A) and the oligomer (B), the composition (X) of the present invention can maintain the elastic modulus low while improving the adhesiveness as shown in the following examples. Therefore, even if it is used on the surface of a flexible display panel, etc., peeling or whitening can still be suppressed.

>Adhesive layer> The adhesive layer of the present invention is composed of a cured product obtained by curing the composition (X) described above. The thickness of the adhesive layer is preferably 0.03 mm or more, preferably 0.1 mm or more, and more preferably 0.2 mm or more. In addition, 2 mm or less is preferable, 1.3 mm or less is preferable, and 0.8 mm or less is more preferable. If the thickness of the adhesive layer is within this range, the desired adhesive force can be easily exerted. And it is ideal based on the viewpoint of flexibility. In addition, the adhesive layer may be formed in a single layer, or may be formed by stacking multiple layers.

For the adhesive layer, the storage elastic modulus E'at 25° C. is preferably 70 kPa or more, preferably 80 kPa or more, and more preferably 85 kPa or more. And the storage elastic modulus E'at 25°C is preferably 450kPa or less, 400kPa or less is preferred, and 350kPa or less is more preferred. By making the storage elastic modulus E'within the above range, the adhesive force of the adhesive layer can be made good.

In addition, the adhesive force on the surface of the adhesive layer is preferably 5N/25mm or more, preferably 6N/25mm or more, and more preferably 7N/25mm or more. By making the surface adhesive force within the above-mentioned range, it is suitable for display devices used in image display devices, especially for flexible display devices.

The adhesive layer is preferably an adhesive layer that is cured by irradiating the photocurable composition (X) with light. For example, the light irradiation may be cured by setting UV light to an illuminance of 50 to 800 mW/cm ² and a cumulative light amount of 500 to 4,000 mJ/cm ² .

>Laminated body> In the laminated system of the present invention, the adhesive layer and the first planar base material are laminated. As shown in FIG. 1, a laminate 11 in which the adhesive layer 13 is laminated on the first planar base 12 can be exemplified. Here, the first planar substrate 12 may be any one that can support the adhesive layer 13, and examples thereof include a release sheet, an optical film, and a protective plate. Furthermore, the first planar substrate 12 is preferably a transparent substrate. In addition, the adhesive layer 13 and the above-mentioned adhesive layer may be the same.

In addition, the laminated body can be exemplified as shown in FIG. 2. The laminated body 11 in FIG. 1 further has a laminated body 21 of a second base material 22, and the second base material 22 is sandwiched opposite to the first surface material 12 The adhesive layer 13 is set. Here, the second substrate 22 may be one that can sandwich and hold the adhesive layer 13 with the first planar substrate 12, and it may be the same as the first planar substrate 12 or displays such as a display panel. Devices, etc.

The layered body 11 can be produced by applying the composition (X) of the present invention to a desired thickness on the first planar base material and curing the composition (X). The layered body 21 can be manufactured by coating the composition (X) of the present invention to a desired thickness on the first planar substrate and curing the composition (X), and then laminating the second substrate thereon. In addition, the layered body 21 may be formed by coating the composition (X) of the present invention to a desired thickness on the first planar substrate and further layering the second substrate thereon to make the composition (X) Hardened to manufacture.

When the composition (X) is to be cured after sandwiching the composition (X) between the first planar substrate and the second substrate, if at least one of the first planar substrate and the second substrate is The transparent substrate can be cured by light irradiation through the transparent substrate when it is cured, so it is suitable.

When the display device is laminated and integrated with a transparent substrate such as a protective plate, etc., when no bubbles remain in the cured adhesive layer, it is advisable to seal the composition (X) on the first substrate under reduced pressure. A method of hardening between the base material and the second substrate in a higher-pressure gas environment (decompression sealing-boosting hardening method).

Specifically, it is preferable to manufacture a laminate by the following method: in a first reduced-pressure gas environment, an uncured layer composed of the composition (X) is sandwiched between a pair of base materials and placed around the uncured layer After the sealing part is sealed to form a layered precursor, the uncured layer is hardened in a second gas atmosphere that is higher than the first reduced pressure gas atmosphere. The reduced-pressure sealing-pressure-increasing hardening method is a well-known method. For example, paragraphs [0036] ~ paragraphs [0042] of International Publication No. 2009/016943 and paragraphs [0080] ~ [0091] of International Publication No. 2011/158840 can be used. The recorded technique.

For example, it can be suitably performed under the conditions that the pressure in the first pressure reducer body environment is 100 Pa or less, and the second gas environment is an atmospheric gas environment. The thickness of the hardened layer (adhesive layer between a pair of base materials) of the unhardened layer composed of the composition (X) is preferably 0.03 to 2 mm, and preferably 0.1 to 0.8 mm.

The sealing portion can be formed using a double-sided adhesive type sealing material as described in paragraph [0036] of International Publication No. 2009/016943, or a light-curing resin can be further coated on a light-transmitting double-sided adhesive type sealing material. Form a sealing part. The photocurable resin of the sealing part can harden the uncured layer composed of the composition (X) at the same time.

Alternatively, as described in the paragraph [0039] of International Publication No. 2011/158840, a light-curable sealant with a higher viscosity than the composition (X) (for example, 500 to 3000 Pa·s at 25°C) may be used The resin composition forms the sealing part. The sealing portion can be hardened while hardening the unhardened layer composed of the adhesive composition (X), or can be half-hardened before hardening the uncured layer composed of the adhesive composition (X) After curing, the uncured layer is cured and further cured.

In the laminate 21, it is preferable that the first planar substrate 12 is a transparent substrate with light-transmitting properties, and the second substrate 22 is a display device. The transparent surface material may be a glass plate or a transparent resin plate. From the viewpoints of weather resistance, low birefringence, and high plane accuracy, a glass plate is preferable. Display devices include: liquid crystal display devices, EL display devices, plasma display devices, electronic ink-type display devices, etc. The display device has a structure in which at least one of the transparent substrates is attached to the substrate, and is configured such that the side of the transparent substrate is in contact with the adhesive layer 13. At this time, in some display devices, an optical film such as a polarizing plate and a phase difference plate may be provided on the outermost layer side of the transparent substrate that is in contact with the adhesive layer 13. In this case, the adhesive layer 13 will be in a state of joining the optical film on the display device and the first substrate 12.

For example, when 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 display device is sandwiched by the transparent substrate. The adhesive layer 13 between the material and the display device is a hardened substance of the composition (X), which can reduce the stress applied to the display device, thereby effectively preventing display unevenness and damage to the display quality. Moreover, the elastic modulus of the hardened object can be reduced, so that the stress applied to the display device can be reduced, so that the hardened object does not easily peel off from the display device.

Especially when the above-mentioned display device is a liquid crystal display device, even an IPS (In-plane Switching, in-plane switching) display device, or a TN (Twisted Nematic) type with an optical film that improves the viewing angle on the display surface In the case of a display device, the stress applied to the display device is likely to have an adverse effect on the display quality, so the effect obtained by using the composition (X) of the present invention is great.

In addition, when the above-mentioned display device is a flexible display device, it is resistant to repeated bending, so the bending part is less likely to peel off, and the occurrence of whitening can be suppressed, thereby extending the product life. Among them, it is especially suitable for the case where the above-mentioned display device is a foldable display.

>Video display device> The image display device of the present invention is an image display device provided with the above-mentioned laminate, and is a display manufactured using the above-mentioned composition (X) and capable of displaying image signals such as still images or moving images. Specifically, it is composed of a laminated body provided with an adhesive layer composed of a cured product of the composition (X) between the first planar substrate and the second substrate, and the first planar substrate The substrate is a transparent substrate, and the second substrate is a display device. In addition to the above-mentioned laminate, the image display device is also electrically connected to a drive circuit board. During driving, a voltage can be applied to the electrodes of the display device from the side of the drive circuit board to display images.

In the image display device of the present invention, especially when the display device is a curved display or a flexible display, the effect of using the adhesive layer of the composition (X) can be effectively exerted, so it is suitable. Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. As for the parts and% in each case, all are quality standards.

[Determine the number average molecular weight of oligomers (A) and oligomers (B)] The number average molecular weight of oligomer (A) and oligomer (B) was measured by GPC (gel permeation chromatography) under the following conditions. ・Analysis device: HLC-8120GPC manufactured by Tosoh Corporation ・Pipe string: manufactured by Tosoh Corporation, G7000HXL+GMHXL+GMHXL ・Column size: each 7.8mmφ×30cm, total 90cm ・Column temperature: 40℃ . Flow rate: 0.8ml/min ・Injection volume: 100μl ・Eluent: Tetrahydrofuran ・Detector: Differential Refractometer (RI) ・Standard sample: Polystyrene

[Production Example 1-1: Production of unit alcohol (1)] Feed the zinc hexacyanocobaltate-tertiary butyl alcohol complex compound (hereinafter referred to as "DMC-TBA") as a composite metal cyanide complex catalyst into a pressure-resistant reactor equipped with a stirrer and a nitrogen introduction tube 0.2 g and 59 g of n-butanol as an initiator, 3941 g of propylene oxide (hereinafter also referred to as "PO") was added and poured in while taking 7 hours at a constant rate under a nitrogen atmosphere set at 130°C. Then, after confirming that the internal pressure in the pressure-resistant reactor had stopped falling, 4000 g of the product was taken out. The main component except by-products in the product or metals derived from catalysts is a polyoxypropylene unit with a hydroxyl value of 11.2 mgKOH/g (hydroxyl value converted molecular weight: 5000), an average hydroxyl number of 1.03, and a water content of 120 mass ppm. Alcohol (monoalcohol (1)). The obtained product contains 8 mass ppm of Zn and 2 mass ppm of Co.

[Production Example 1-2: Production of unit alcohol (2)] Feed 0.2g of DMC-TBA and 30g of n-butanol as initiator into a pressure-resistant reactor equipped with a stirrer and a nitrogen introduction tube. Under a nitrogen environment set to 130°C, it takes 7 hours to add and add Put in PO 3970g. Then, after confirming that the internal pressure in the pressure-resistant reactor had stopped falling, 4000 g of the product was taken out. The main component except by-products in the product or metals derived from catalysts is a polyoxypropylene unit with a hydroxyl value of 5.6 mgKOH/g (hydroxyl value converted molecular weight: 10000), an average number of hydroxyl groups of 1.08, and a moisture content of 143 mass ppm Alcohol (monoalcohol (2)) 4000g. The obtained product contains 8 mass ppm of Zn and 2 mass ppm of Co.

[Production Example 1-3: Production of Glycol (1)] Into a pressure-resistant reactor equipped with a stirrer and a nitrogen introduction tube, 0.2g of DMC-TBA and initiator EXCENOL-720 (manufactured by AGC, polyoxypropylene glycol, hydroxyl number: 2, hydroxyl value converted molecular weight: 700) 700g are fed , In a nitrogen environment set to 130°C, 3290g of PO was added and poured in while taking 7 hours at a constant speed. Then, after confirming that the internal pressure of the pressure-resistant reactor had stopped falling, the product was taken out to obtain a polyoxypropylene glycol (diol (1)) with a hydroxyl value of 28.7 mgKOH/g (hydroxyl value converted molecular weight: 3909) and an average hydroxyl number of 2 . The obtained product contains less than 1 mass ppm of Zn and less than 1 mass ppm of Co.

[Production Example 1-4: Production of Glycol (2)] Into a pressure-resistant reactor equipped with a stirrer and a nitrogen introduction tube, 0.2 g of DMC-TBA and initiator EXCENOL-1020 (manufactured by AGC, polyoxypropylene glycol, hydroxyl value converted molecular weight: 1000) 400 g are fed, and set at 130°C Under a nitrogen environment, add and put in PO 3600g while taking 7 hours at a constant speed. Then, after confirming that the internal pressure of the pressure-resistant reactor stopped falling, the product was taken out to obtain a polyoxypropylene glycol (diol (2)) having a hydroxyl value of 11.1 mgKOH/g (hydroxyl value converted molecular weight: 10108). The obtained product contains less than 1 mass ppm of Zn and less than 1 mass ppm of Co.

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

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

[Production Example 2-1: Production of monofunctional oligomer (B-1)] Into a reaction vessel equipped with a stirrer and a nitrogen introduction tube were fed 928.1 g of the unit alcohol (1) obtained in Production Example 1-1 and 26.8 g of 2-propylene oxyethyl isocyanate (Karenz AOI, product name of Showa Denko), In the presence of 0.0955 g of dioctyl tin distearate (DOTDS), it was reacted at 70°C for 3 hours to obtain a monofunctional oligomer (B-1). The number average molecular weight of the obtained monofunctional oligomer (B-1) was 7,660. The blending amount of 2-propylene oxyethyl isocyanate with respect to the unit alcohol (1) was calculated as 100 as an index (NCO/OH ratio).

The appearance of the obtained oligomer (B-1) was observed after being allowed to stand at 0°C for 1 month. The appearance of the oligomer (B-1) was not changed from the state before being left standing, and it was transparent. After adding 0.3 part of IRGACURE819 (product name of BASF Corporation) as a photopolymerization initiator to 100 parts of the obtained oligomer (B-1) and uniformly mixing, the cured product was obtained and measured in the same manner as the storage elastic modulus described below. The storage elastic modulus E'of the hardened material. The measurement results are listed in Table 1. The same applies to the following manufacturing example 2-2 and manufacturing example 2-3.

[Production Example 2-2: Production of monofunctional oligomer (B-2)] The unit alcohol (2) 964.9g and Karenz AOI 13.1g obtained in Production Example 1-2 were fed into a reaction vessel equipped with a stirrer and a nitrogen introduction tube, and reacted at 70°C in the presence of 0.0977g of DOTDS 3 The monofunctional oligomer (B-2) was obtained after hours. The number average molecular weight of the obtained oligomer (B-2) was 16,000. The blending amount of 2-propylene oxyethyl isocyanate with respect to the unit alcohol (2) was calculated as 100 as an index (NCO/OH ratio). The appearance of the obtained oligomer (B-2) was observed after being allowed to stand at 0°C for 1 month. The appearance of the oligomer (B-2) was not changed from the state before being left standing, and it was transparent. [Production Example 2-3: Production of monofunctional oligomer (B-3)] Except that the water content was 200 ppm by mass, the same monoalcohol as the monoalcohol (2) was used, and the oligomer (B-3) was obtained in the same manner as in Production Example 2-2. The number average molecular weight of the obtained oligomer (B-3) was 16,000. After the obtained oligomer (B-3) was allowed to stand at 0°C for 1 month, its appearance was observed, and it became cloudy.

[Production Example 3-1: Production of bifunctional oligomer (A-1)] Into a reaction vessel equipped with a stirrer and a nitrogen introduction tube were fed 400 g of the diol (1) obtained in Production Example 1-3 and 31.6 g of isophorone diisocyanate (IPDI), and 0.03 bismuth 2-ethylhexanoate In the presence of g, the reaction was carried out at 70°C for 10 hours to obtain an isocyanate group-terminated urethane prepolymer. The blending amount of IPDI relative to the glycol (1) was 142 as an index. The isocyanate group content of the prepolymer was 0.145% by mass. Next, 0.10 g of dibutyl tin dilaurate (DBTDL), 0.11 g of 2,5-di-tertiary butyl hydroquinone (DtBHQ), and 1.49 g of 2-hydroxyethyl acrylate (HEA) were added to obtain a bifunctional oligomer物(A-1). The number average molecular weight of the obtained oligomer (A-1) was 13,890, and the urethane bond concentration was 3.87% by mass.

In addition, the urethane bond concentration of the oligomer (A-1) is regarded as the total amount of isocyanate groups possessed by the IPDI used to produce the oligomer (A-1) to form urethane bonds, and Calculated by the following calculation formula. (Mole number of isocyanate group possessed by IPDI×Molecular weight of urethane bond (59)/mass of oligomer (A-1))×100 (mass%) In addition, the mass of the oligomer (A-1) is the total mass of the feed amount of the glycol (1), IPDI and HEA.

[Manufacturing Examples 3-2~3-6] As shown in Table 1, use diols (2) to (4) instead of diol (1) of Production Example 3-1 and change the blending amount of the raw materials as shown in the description. The same operation was made to react to obtain bifunctional oligomers (A-2), (A-3), (A-4), (A-5), and (A-6).

[Table 1]

[Example 1~8] (Preparation of adhesive composition) The monofunctional oligomers obtained in manufacturing examples 2-1 to 2-2 and the bifunctional oligomers obtained in manufacturing examples 3-1 to 3-6 were combined with the following commercially available raw materials using a planetary mixer manufactured by EMC Corporation. The blending ratio (mass%) shown in 2 is mixed to produce an adhesive composition. Examples 1 to 4 are examples, and examples 5 to 8 are comparative examples.

In addition, the following commercially available products were used for the acrylic single system. LA: Lauryl Acrylate (manufactured by Dongfang Chemical Co., Ltd.) ACMO: 4-Propylene Glyphosate (manufactured by Xingren) And the following commercially available products were used as tackifiers. KE311: Rosin ester (Arakawa Chemical Company product name: PINECRYSTAL KE311) In addition, the following commercially available products were used as the photopolymerization initiator. The photopolymerization initiator was added by 0.38 parts by mass to the total amount of the curable components. IRGACURE819 (BASF company product name)

[Table 2]

[Characteristic test] The adhesive composition obtained in the above Examples 1 to 8 was used to make a film, and the static bending test, repeated bending test, and adhesion characteristics were evaluated as follows, and the storage elastic modulus E'was measured. These results are combined in Table 2.

(Making the film for repeated bending test) Using an automatic coating machine (PI1210 automatic coating device manufactured by TESTER SANGYO CO,. LTD.) with a doctor blade, the adhesive composition of each example is adjusted to the thickness of the adhesive layer after curing Coated to 25μm on a 75μm-thick polyethylene terephthalate (PET) film (manufactured by Mitsui Chemicals Tohcello Inc., SP-PET-01-75BU) with a silicone treatment (peeling treatment) The surface is treated with silicone. Next, using a conveyor-type UV irradiation machine (manufactured by ORC) in a nitrogen environment, it was cured under the conditions of a HgXe lamp, an illuminance of 100 mW/cm ² , and a cumulative light quantity of 3,000 mJ/cm ² . The resulting adhesive laminate film was bonded to the adhesive surface side of KAPTON film (manufactured by DU PONT-TORAY CO., LTD.) with a thickness of 50 μm, and then the silicone-treated PET was peeled off, and then corona-treated PET with a thickness of 50 μm (for TORAY Industries, Inc. PET film Lumirror S10 has been corona-treated and the corona-treated surface is in contact with the adhesive surface, and bonded to the exposed adhesive surface to produce a film for repeated bending tests.

>Static bending test> A film made in the same way as the film for the repeated bending test was used as the sample for the static bending test. Processed along one side into a semicircle with a diameter of 3mm and a semicircle of a plate with a thickness of 3mm, the KAPTON side of the above-mentioned static bending test sample was made the inside, and it was adhered and fixed with tape.

Then, it was allowed to stand for 10 days under the conditions of room temperature, -20°C, and 80°C, and the appearance of the film after the test was evaluated visually according to the following criteria. ○: There is no change in appearance such as whitening, foaming, peeling, floating, and cracks. △: Peeling, foaming, or cracks are slightly at the end, but it is not a problem in practice. ×: Whitening or significant peeling at the end, which is problematic in practice.

>Repetitive bending test> The conditions are set as follows: the film for repeated bending test obtained above is bent into a U-shape with a U-shaped surface bending tester (DLDM111LH manufactured by Yuasa System Co., Ltd.) with an inner diameter (diameter) of 3 mm and placed in the chamber. Under warm temperature, it is repeated to bend and open 180° with the KAPTON side as the inner side at a speed of 60 times per minute and perform 100,000 repetitions.

The appearance of the film after the test was evaluated visually on the following basis. ○: There is no change in appearance such as whitening, foaming, peeling, floating, and cracks. △: There are some peeling, foaming, floating or cracks on the end, but it is not a problem in practice. ×: Whitening or significant peeling at the end, which is problematic in practice.

(Making the film for adhesive force measurement) Using an automatic coating machine (PI1210 automatic coating device manufactured by TESTER SANGYO CO,. LTD.) with a doctor blade, the adhesive composition of each example was adjusted to the thickness of the adhesive layer after curing It was applied to one side of a PET film (E5001 manufactured by Toyobo Co., Ltd.) with a thickness of 38 μm so as to be 100 μm. Next, using a conveyor belt UV irradiation machine (manufactured by ORC) in a nitrogen environment, it was cured under the conditions of an HgXe lamp, an illuminance of 100 mW/cm ² , and a cumulative light quantity of 3,000 mJ/cm ² to obtain a film for adhesive force measurement.

>Adhesion> The films for measuring the adhesive force obtained above were cut into 25 mm wide x 100 mm long. Next, a rubber roller of 2 kg was reciprocated and bonded so that the adhesive surface of the film was adhered to the float glass. Then, let it stand for 20 minutes in a 23°C/55%RH gas environment to make a measurement sample. Measure the adhesive force of the adhesive layer in the test sample.

Adhesive force is measured by using a tensile testing machine (RTG-1310 manufactured by A&D Company, Limited) attached to a thermostatic bath to measure the adhesive layer in the sample at a peeling angle of 180° at 23°C and a relative humidity of 55%RH. The peeling speed is 300mm/min. According to the test method of adhesive tape and adhesive sheet of JIS Z0237 (2009), the value obtained by measuring the adhesive force (N/25mm) during peeling.

>Measure the storage elastic modulus> For the adhesive layer formed by using the adhesive composition obtained in each example and hardening as described later, the dynamic viscoelasticity measuring device (manufactured by Seiko Instruments Inc., EXSTAR 6100) was used to measure -80°C or higher And the storage elastic modulus E'in the temperature range below 130°C. The above-mentioned adhesive layer is made by pouring the adhesive composition of each example into a polysilicon mold with a width of 5 mm × a length of 15 mm × a thickness of 2 mm, using a conveyor-type UV irradiation machine (manufactured by ORC) in a nitrogen environment, and using a HgXe lamp , The illuminance is 100mW/cm ² , and the accumulated light quantity is 3,000mJ/cm ² by curing it to form. The obtained hardened product (adhesive layer) is installed in a dynamic viscoelasticity measuring device, and it is carried out in a temperature range of -80°C or more and 130°C in a tensile mode under the conditions of a strain of 1% and a heating rate of 3°C/min Determination. As shown in Table 2, in Examples 1 to 4, the results of the static bending test under all temperature conditions are good, and the repeated bending test and adhesion are good. Example 5 does not contain monofunctional oligomers, and the results of static bending test and repeated bending test are not good. Examples 6 and 8 use difunctional oligomers with a small amount of urethane bonds, and the adhesion is not good. Example 7 uses a bifunctional oligomer with a large amount of urethane bonds, but the results of the static bending test and the repeated bending test under low temperature conditions are not good, and the adhesion is also poor.

Industrial availability The adhesive composition of the present invention can form an adhesive layer with low elastic modulus and excellent adhesion to the substrate. When the adhesive layer is formed on a substrate to form a layered body, even if the layered body is repeatedly bent, peeling of the adhesive layer or whitening of the bent portion can be suppressed. The laminate can be used as a part of an image display device, and is suitable for use in parts such as a flexible display panel that can be repeatedly bendable, and can produce products that can stably exhibit characteristics for a long time. In addition, the entire contents of the specification, scope of patent application, abstract, and drawings of Japanese Patent Application No. 2018-189409 filed on October 04, 2018 are cited here and incorporated as the disclosure of the specification of the present invention.

11, 21: layered body 12: The first surface substrate 13: Adhesive layer 22: The second substrate

Fig. 1 is a side view of a laminate according to an embodiment of the present invention. Fig. 2 is a side view of a laminate of another embodiment of the present invention.

Claims (16)

An adhesive composition, characterized in that it contains: A bifunctional oligomer, an oligomer having a polyoxyalkylene chain, a group derived from a urethane bond of an isocyanate group-containing compound, and a (meth)acryloxy group, and in one molecule It has 2 (meth)acryloxy groups and contains 3.90~6.00% by mass of urethane bonds in 1 molecule; and Monofunctional oligomer is an oligomer having a polyoxyalkylene chain, a group derived from a urethane bond of an isocyanate group-containing compound, and a (meth)acryloxy group, and has an oligomer in 1 molecule 1 (meth)acryloyloxy group; The total content of the bifunctional oligomer and the monofunctional oligomer is 40% by mass or more with respect to the adhesive composition. The adhesive composition of claim 1, wherein the content ratio of the bifunctional oligomer is 20 to 80% by mass relative to the total mass of the bifunctional oligomer and the monofunctional oligomer. The adhesive composition of claim 1 or 2, wherein the aforementioned bifunctional oligomer is polyoxyalkylene glycol, diisocyanate and hydroxyalkyl (meth)acrylate or isocyanate alkyl (meth)acrylate The reaction product. The adhesive composition according to any one of claims 1 to 3, wherein the number average molecular weight of the aforementioned bifunctional oligomer is 5,000 to 30,000. The adhesive composition according to any one of claims 1 to 4, wherein the aforementioned monofunctional oligomer is a reaction product of a polyoxyalkylene unit alcohol and an isocyanate alkyl (meth)acrylate. The adhesive composition according to any one of claims 1 to 5, wherein the number average molecular weight of the aforementioned monofunctional oligomer is 3,000-35,000. The adhesive composition of any one of claims 1 to 6, wherein the polyoxyalkylene chain in the aforementioned bifunctional oligomer and the polyoxyalkylene chain in the aforementioned monofunctional oligomer are both: poly The ratio of the oxyalkylene group to the total oxyalkylene group in the oxyalkylene chain is a polyoxyalkylene chain of 50-100% by mass. The adhesive composition according to any one of claims 1 to 7, wherein the (meth)acryloyloxy group of the bifunctional oligomer and the (meth)acryloyloxy group of the monofunctional oligomer The oxy groups are all propylene oxy groups. As in the adhesive composition of claim 8, the adhesive composition further contains a photopolymerization initiator. An adhesive layer, characterized in that it is composed of a hardened material of the adhesive composition according to any one of claims 1 to 9. Such as the adhesive layer of claim 10, its storage elastic modulus E'at 25°C is 70~450kPa, and the surface adhesion is 5N/25mm or more. A laminated body characterized by having a first planar substrate and an adhesive layer such as claim 10 or 11 arranged on the first planar substrate. Such as the laminated body of claim 12, which further has a second substrate disposed on the aforementioned adhesive layer. The laminate according to claim 13, wherein the first planar substrate is a transparent planar substrate, and the second substrate is a display device. An image display device characterized by having a laminate as claimed in claim 14. Such as the image display device of claim 15, the aforementioned image display device is a curved display or a flexible display.

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