Adhesive composition, adhesive sheet, laminate, and display including the laminate

Abstract

The invention provides an adhesive composition which has adhesive force, heat resistance, wet heat whitening resistance, gas escape resistance, light resistance, low dielectric constant and metal corrosion resistance even under the condition that materials of biological origin are used, an adhesive sheet using the adhesive composition, a laminated body and a display. The problem is solved by an adhesive composition containing: an acrylic polymer (A) which is a copolymer of a monomer mixture containing specific amounts of (a1) a (meth) acrylate monomer having an alicyclic structure (excluding (a3)), (a2) a (meth) acrylate monomer having an alicyclic structure (a3), and (a3) a curing agent (B); (a2) an alkyl (meth) acrylate monomer having a C8-18 linear alkyl group; and (a3) a (meth) acrylate monomer having a carboxyl group and / or a (meth) acrylate monomer having a hydroxyl group.

Description

Technical Field

[0001] The present disclosure relates to an adhesive composition, an adhesive sheet, a laminate, and a display including the laminate. Background Art

[0002] An adhesive sheet having an adhesive layer formed of an adhesive is used in a wide range of fields such as label use or medical use because of its ease of operation. Among them, adhesives for uses assumed to be used for a long time, such as marking films, window films, automotive components, and optical displays, ideally have durability such as heat resistance, hygrothermal resistance, weather resistance, and light resistance. Accordingly, in recent years, research has been actively conducted to improve the durability of adhesives.

[0003] In addition, various optical displays such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs) are widely used as display devices. In addition, optical displays are also used as input devices such as touchscreens. A cover panel is provided for the purpose of protecting the surface of the touchscreen. Usually, the members constituting these optical displays are bonded via an adhesive layer.

[0004] As described above, in adhesives for optical displays assumed to be used for a long time, high durability such as not floating or peeling from the adherend (peel resistance) in an environment of high temperature and high humidity, the adhesive layer itself not turning white (hygrothermal whitening resistance), and the adhesive layer itself not turning yellow (yellowing resistance) is required. In addition, in adhesives for fixing cover panels containing transparent plastic raw materials such as polycarbonate (PC) and polymethyl methacrylate (PMMA), in addition to the above durability, appearance defects caused by gases generated from the transparent plastic (outgassing resistance) are also required. Furthermore, if the dielectric constant of the adhesive used around an electrostatic capacitance type touchscreen is high, there is a tendency for malfunction to easily occur when touching the display, so an adhesive capable of forming an adhesive layer with a low dielectric constant is required. Furthermore, in addition to this, it is also assumed to be used in transparent electrodes, so a property of not corroding such metal materials is also required.

[0005] In terms of durability, high durability is required in displays, especially in in-vehicle applications. In particular, due to the revolutionary progress of information technologies such as the fifth-generation mobile communication (5G), Internet of Things (IoT), and artificial intelligence (AI) in recent years, the electrification of automobiles and the development of vehicles equipped with out-of-vehicle displays are underway. Along with this, heat resistance at higher temperatures such as 120 °C (previously around 85 °C to 105 °C) is required, and the required performance has become more stringent. Therefore, developing an adhesive that fully meets the heat resistance at higher temperatures and the moisture-heat whitening resistance or outgassing resistance that has been continuously required previously has become a major issue.

[0006] To date, a great deal of research has been conducted to meet the durability requirements of adhesives for optical displays. In the adhesive described in Patent Document 1, an acrylic adhesive obtained by copolymerizing a hydroxyl group-containing acrylate and a nitrogen-containing acrylate is used to impart moisture-heat whitening resistance and outgassing resistance, but the heat resistance or light resistance at 120 °C may sometimes be insufficient.

[0007] In addition, in the adhesive described in Patent Document 2, an acrylic adhesive obtained by copolymerizing an acrylic alkyl ester having 4 to 8 carbon atoms as a monomer and N-(2-hydroxyethyl)acrylamide is used to suppress display unevenness. However, in this adhesive, the heat resistance, moisture-heat whitening resistance, outgassing resistance, and adhesiveness at 120 °C may sometimes be insufficient.

[0008] In addition to the improvement of required performance, in the industrial field using adhesive sheets, the depletion of petroleum resources or the emission of carbon dioxide caused by the combustion of petroleum-derived products is also regarded as a problem. Therefore, starting from the packaging material field, in various industries such as the optical field and the semiconductor field, attempts have been made to save petroleum resources by using bio-derived materials instead of petroleum-derived materials.

[0009] In an adhesive mainly composed of an acrylic polymer, as a method of increasing the ratio of bio-derived materials, a method of copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer obtained by esterifying a linear alkyl alcohol produced by a living organism with (meth)acrylic acid to obtain an acrylic polymer can be cited. Bio-derived linear alcohols are currently relatively inexpensive and are in stable supply, so they can be used industrially. Patent Document 3 discloses an adhesive obtained by copolymerizing a monomer mixture containing a biomass-derived acrylate having an alkyl group with 12 to 24 carbon atoms, but the conditions of the heat retention test are low temperature and short time, and even through this test, the heat resistance may sometimes be insufficient.

[0010] [Prior Art Documents]

[0011] [Patent Document]

[0012] Patent Document 1: Japanese Patent Laid-Open No. 2017-106000

[0013] Patent Document 2: Japanese Patent Laid-Open No. 2007-264092

[0014] Patent Document 3: Japanese Patent Laid-Open No. 2020-105308 Summary of the Invention

[0015] Problems to be Solved by the Invention

[0016] The problem to be solved by the present disclosure is to provide an adhesive composition that has adhesiveness, heat resistance, moisture heat whitening resistance, outgassing resistance, light resistance, low dielectric constant, and metal corrosion resistance even when using bio-derived materials, an adhesive sheet, a laminate, and a display using such an adhesive composition.

[0017] Technical Means for Solving the Problems

[0018] The inventors of the present invention made repeated intensive studies and found that the above problems can be solved in the following form, thus completing the present disclosure.

[0019] That is, the present disclosure relates to an adhesive composition comprising an acrylic polymer (A) and a curing agent (B), wherein the acrylic polymer (A) is a copolymer of a monomer mixture containing the following (a1), (a2), and (a3).

[0020] In 100% by mass of the monomer mixture, 2.5% by mass to 20% by mass of (a1), 30% by mass to 80% by mass of (a2), and 0.1% by mass to 20% by mass of (a3) are contained.

[0021] (a1) A (meth)acrylate monomer having an alicyclic structure (excluding (a3));

[0022] (a2) A (meth)acrylate alkyl ester monomer having a linear alkyl group with 8 to 18 carbon atoms;

[0023] (a3) A (meth)acrylate monomer having a carboxyl group and / or a (meth)acrylate monomer having a hydroxyl group.

[0024] In addition, the present disclosure relates to the adhesive composition, characterized in that (a3) contains a (meth)acrylate monomer having a hydroxyl group.

[0025] In addition, the present disclosure relates to the adhesive composition, characterized in that the monomer mixture further comprises an (alkyl) acrylate monomer (a4) having an alkyl group with 1 to 4 carbon atoms.

[0026] In addition, the present disclosure relates to the adhesive composition, characterized in that it further comprises a silane coupling agent (C).

[0027] In addition, the present disclosure relates to the adhesive composition, characterized in that the curing agent (B) comprises an isocyanate-based curing agent or a block thereof.

[0028] In addition, the present disclosure relates to an adhesive sheet comprising an adhesive layer containing the adhesive composition.

[0029] In addition, the present disclosure relates to a laminate, characterized in that it comprises the adhesive sheet and a light-transmissive substrate.

[0030] In addition, the present disclosure relates to a display device comprising the laminate, a polarizing plate, and an optical element.

[0031] Effects of the Invention

[0032] According to the present disclosure, there is provided an adhesive composition having adhesiveness, heat resistance, resistance to moisture and heat whitening, outgassing resistance, light resistance, low dielectric constant, and metal corrosion resistance even when using bio-derived materials, an adhesive sheet, a laminate, and a display device using the adhesive composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic cross-sectional view partially showing an example of the laminate of the present embodiment.

[0034] Figure 2 is a schematic cross-sectional view partially showing an example of the use of the laminate of the present embodiment as a display device.

[0035] Figure 3 is a schematic cross-sectional view of a dielectric constant measurement sample. DETAILED DESCRIPTION

[0036] Hereinafter, the adhesive composition (also referred to as the present adhesive composition), the adhesive sheet, the laminate, and the display device of the present disclosure will be described, but are not limited thereto.

[0037] In addition, in the present specification, (meth)acrylate means acrylate and methacrylate, and refers to either or both of acrylate and methacrylate. The monomers in the monomers (a1) to (a4) described later refer to monomers having an ethylenically unsaturated group.

[0038] ​​​In this specification, monomers (a1) to (a4) may sometimes be abbreviated as (a1) to (a4), respectively.

[0039] In addition, in this specification, a numerical range defined by "~" is set to include the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0040] In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerically described range. In addition, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may also be replaced with the value shown in the examples.

[0041] In addition, a "film" or a "sheet" is regarded as an object that is not distinguished by thickness. In other words, the "sheet" in this specification is regarded as including a film-like object with a small thickness, and the "film" in this specification is regarded as including a sheet-like object with a thickness.

[0042] Furthermore, the adherend refers to the object (the other party) to which the adhesive layer of the pressure-sensitive adhesive sheet is attached.

[0043] As long as there is no special note for the various components appearing in this specification, each component can be used independently alone, or two or more components can be used in combination.

[0044] 《Pressure-Sensitive Adhesive Composition》

[0045] The pressure-sensitive adhesive composition of the present disclosure contains an acrylic polymer (A) and a curing agent (B).

[0046] <Acrylic Polymer (A)>

[0047] The acrylic polymer (A) is a copolymer of a monomer mixture containing the monomers (a1), (a2), and (a3) described below. In addition, the acrylic polymer (A) contains (in total) 2.5% by mass to 20% by mass of (a1), (in total) 30% by mass to 80% by mass of (a2), and (in total) 0.1% by mass to 20% by mass of (a3) in 100% by mass of the monomer mixture. When two or more monomer components (a1) to (a3) are used, the content ratio of these monomers refers to the total content ratio of the monomer components used. For example, when a (meth)acrylate monomer having a carboxyl group and a (meth)acrylate monomer having a hydroxyl group are used in combination as the monomer (a3), their total content ratio is the content ratio of (a3).

[0048] [Monomer (a1)]

[0049] (a1) is a (meth)acrylate monomer having an alicyclic structure. Herein, in the present specification, a (meth)acrylate monomer having a carboxyl group or a hydroxyl group is regarded as monomer (a3) even if it has an alicyclic structure.

[0050] As the alicyclic structure, a cycloalkane structure, a cycloolefin structure, and an alicyclic ether structure can be mentioned. However, from the viewpoint of yellowing resistance, a cycloalkane structure or an alicyclic ether structure having no unsaturated bond in the ring is preferable.

[0051] Examples of monomer (a1) include isobornyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (5-ethyl-1,3-dioxan-5-yl)methyl (meth)acrylate, etc. Among them, from the viewpoints of outgassing resistance and increasing the ratio of bio-derived materials, as (a1), isobornyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate which can be produced from an alcohol obtainable as a biomass raw material are further preferably used.

[0052] The (total) content of (a1) is 2.5% by mass to 20% by mass, preferably 5% by mass to 15% by mass, and further preferably 7% by mass to 13% by mass in 100% by mass of the monomer mixture. When the content of (a1) is less than 2.5% by mass, the cohesion of the adhesive layer decreases, and the adhesive strength, heat resistance, and light resistance are insufficient. When the content of (a1) exceeds 20% by mass, the viscosity of the adhesive layer decreases, and the adhesive strength, heat resistance, and light resistance are insufficient.

[0053] [Monomer (a2)]

[0054] (a2) is a (meth)acrylate alkyl ester monomer having a linear alkyl group with 8 to 18 carbon atoms. Since such a (meth)acrylate alkyl ester monomer with this number of carbon atoms can be obtained from bio-derived materials, the ratio of bio-derived materials can be increased by using them. In addition, by containing this monomer, the polarity of the entire adhesive layer can be reduced, and thus the dielectric constant can be decreased. Further, since the alkyl group is linear, it can be partially crystallized in the adhesive layer, thereby improving the heat resistance.

[0055] Examples of monomer (a2) include n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, etc.

[0056] The (total) content rate of (a2) is 30% by mass to 80% by mass, preferably 30% by mass to 78% by mass, more preferably 40% by mass to 70% by mass, further preferably 42% by mass to 68% by mass, still further preferably 45% by mass to 68% by mass, and most preferably 50% by mass to 60% by mass in 100% by mass of the monomer mixture. When the content rate of (a2) is less than 30% by mass, sufficient bio-derived materials cannot be used for the adhesive and the adhesive layer. In addition, since the dielectric constant becomes high, it cannot be used for electronic devices having a high-frequency signal transmission function. When the content rate of (a2) exceeds 80% by mass, the cohesion of the adhesive layer decreases, and the adhesive strength, heat resistance, and light resistance are insufficient.

[0057] In 100% by mass of (a2), the content rate of the (meth)acrylate monomer having a linear alkyl group with 8 to 14 carbon atoms is preferably 70% by mass or more. By setting such a ratio, it is easy to obtain higher adhesive strength.

[0058] In 100% by mass of (a2), the ratio of acrylate to methacrylate is preferably 50:50 to 100:0, more preferably 60:40 to 100:0, further preferably 70:30 to 100:0, still further preferably 80:20 to 100:0, and most preferably 90:10 to 100:0. By setting such a ratio, it is easy to obtain higher adhesive strength.

[0059] [Monomer (a3)]

[0060] (a3) is a (meth)acrylate monomer having a carboxyl group and / or a (meth)acrylate monomer having a hydroxyl group. In other words, (a3) is either or both of a (meth)acrylate monomer having a carboxyl group and a (meth)acrylate monomer having a hydroxyl group. In addition, as (a3), it is preferably to use a (meth)acrylate monomer having a carboxyl group and a (meth)acrylate monomer having a hydroxyl group in combination. By using them in combination in the adhesive composition, it is easy to impart excellent heat resistance, light resistance, and metal corrosion resistance.

[0061] The (total) content rate of (a3) is 0.1% by mass to 20% by mass, preferably 0.1% by mass to 15% by mass, further preferably 0.5% by mass to 10% by mass, and most preferably 1% by mass to 5% by mass in 100% by mass of the monomer mixture. By setting the content rate of (a3) to 0.1% by mass or more, the resistance to damp heat can be ensured. By setting it to 20% by mass or less, outgassing can be reduced, and the dielectric constant can be lowered.

[0062] As the (meth)acrylate monomer having a carboxyl group, there is no limitation as long as it is a monomer having a carboxyl group in the molecule. Specific examples of such a monomer include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleate, itaconic acid, citraconic acid, fumaric acid, etc. Among these, from the viewpoint of adhesiveness, (meth)acrylic acid is preferred.

[0063] Regarding the content rate of the (meth)acrylate monomer having a carboxyl group, in 100% by mass of the monomer mixture, it is preferably more than 0% by mass and 5% by mass or less, more preferably 0.1% by mass to 4% by mass, still more preferably 0.2% by mass to 2% by mass, and most preferably 0.4% by mass to 1% by mass. By setting it within the above range, in a structure where the adhesive layer is in contact with a metal such as a transparent conductive layer, metal corrosion can be reduced, and the dielectric constant can be lowered.

[0064] As the (meth)acrylate monomer having a hydroxyl group, there is no limitation as long as it is a monomer having a hydroxyl group in the molecule. Specific examples of such a monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.

[0065] Among these, from the viewpoints of adhesiveness and heat and humidity resistance, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0066] Regarding the content rate of the (meth)acrylate monomer having a hydroxyl group, in 100% by mass of the monomer mixture, it is preferably 0.1% by mass to 20% by mass, more preferably 0.1% by mass to 15% by mass, still more preferably 0.5% by mass to 10% by mass, even more preferably 1% by mass to 5% by mass, and most preferably 2% by mass to 4% by mass. By setting it at 0.1% by mass or more, heat and humidity resistance can be easily ensured, and by setting it at 20% by mass or less, outgassing can be easily reduced, and the dielectric constant can be easily lowered.

[0067] [Monomer (a4)]

[0068] The monomer mixture as a raw material of the acrylic polymer (A) preferably further contains a (meth)acrylic acid alkyl ester monomer (a4) having an alkyl group with 1 to 4 carbon atoms. Here, the monomer (a4) may be contained, for example, at 0.1% by mass or more in 100% by mass of the monomer mixture, and may be contained at 1% by mass or more. By containing (a4), it is easy to balance adhesiveness, heat resistance, and heat and humidity resistance.

[0069] Examples of the monomer (a4) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and the like.

[0070] Among these, from the viewpoint of ease of molecular weight adjustment, as (a4), an acrylic acid alkyl ester monomer is preferably used.

[0071] The preferred (total) content of (a4) is 10% by mass to 42% by mass in 100% by mass of the monomer mixture, and more preferably 20% by mass to 40% by mass. By setting it to 10% by mass or more, it is easier to balance adhesion, heat resistance, and humidity heat resistance, and by setting it to 42% by mass or less, the dielectric constant can be further reduced. In addition, from the viewpoint of ensuring viscosity, in 100% by mass of (a4), the ratio of acrylate to methacrylate is preferably 80:20 to 100:0, and more preferably 90:10 to 100:0.

[0072] [Other Monomers]

[0073] In the monomer mixture as a raw material of the acrylic polymer (A), other monomers other than the above (a1) to (a4) may be contained as optional components. Examples of other monomers include (meth)acrylic acid alkyl ester monomers having a branched alkyl group, nitrogen-containing (meth)acrylates such as acrylamide, alkoxy-based (meth)acrylates such as methoxyethyl acrylate, vinyl-based monomers such as vinyl acetate and styrene, and monomers having a glycidyl group such as glycidyl (meth)acrylate.

[0074] The (total) content of other monomers is preferably 35% by mass or less, more preferably 25% by mass or less, further preferably 15% by mass or less, and most preferably 5% by mass or less in 100% by mass of the monomer mixture.

[0075] [Manufacture of Acrylic Polymer (A)]

[0076] The acrylic polymer (A) can be manufactured by polymerizing the monomer mixture.

[0077] The polymerization can be a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., but solution polymerization is preferred. Solvents used in solution polymerization are preferably, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, etc. The polymerization temperature is preferably a boiling point reaction at 60°C to 120°C. In addition, the polymerization time is preferably about 5 hours to 12 hours.

[0078] The polymerization initiator used in the polymerization is preferably a radical polymerization initiator. Radical polymerization initiators are usually peroxides and azo compounds.

[0079] Examples of peroxides include: dialkyl peroxides such as di-tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, α,α'-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-bis(tert-butylperoxy)hex-3-yne;

[0080] peroxy esters such as tert-butyl peroxybenzoate, tert-butyl peroxyacetate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane;

[0081] peroxyesters such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide;

[0082] peroxyketals such as 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate;

[0083] hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide;

[0084] diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide;

[0085] peroxydicarbonates such as bis(tert-butylcyclohexyl) peroxydicarbonate, etc.

[0086] Examples of azo compounds include: 2,2'-azobisisobutyronitrile (abbreviation: AIBN (2,2'-azobisisobutyronitrile)), 2,2'-azobis(2-methylbutyronitrile) and other 2,2'-azobisbutyronitriles;

[0087] 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile) and other 2,2'-azobisvaleronitriles;

[0088] 2,2'-azobis(2-hydroxymethylpropionitrile) and other 2,2'-azobispropionitriles;

[0089] 1,1'-azobis(cyclohexane-1-carbonitrile) and other 1,1'-azobis-1-alkanenitriles, etc.

[0090] With respect to 100 parts by mass of the monomer mixture, the polymerization initiator is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass.

[0091] (Weight-average molecular weight (Mw))

[0092] The weight-average molecular weight of the acrylic polymer (A) is preferably 500,000 to 1,500,000, more preferably 600,000 to 1,200,000. By setting the weight-average molecular weight within the above range, the peel resistance, gas resistance, and light resistance in a high-temperature and high-humidity environment are further improved. In addition, the weight-average molecular weight is a value in terms of polystyrene conversion measured by gel permeation chromatography (GPC).

[0093] <Hardener (B)>

[0094] The pressure-sensitive adhesive composition of the present disclosure contains a hardener (B). As the hardener (B) formulated in the present pressure-sensitive adhesive composition, a hardener that forms a bond by reacting with the carboxyl group and hydroxyl group of the monomer (a3) by heat or the like is preferred. By formulating the hardener (B), the cohesion of the pressure-sensitive adhesive layer is improved, and the adhesive strength, heat resistance, and light resistance are improved.

[0095] As the hardener (B), one or more can be appropriately selected from known crosslinking agents such as isocyanate-based hardeners, epoxy-based hardeners, oxazoline-based hardeners, aziridine-based hardeners, carbodiimide-based hardeners, metal chelate-based hardeners, and melamine-based hardeners, considering the reactivity with the functional groups of the polymer in the pressure-sensitive adhesive composition. However, from the viewpoints of adhesive strength, heat resistance, and light resistance, the hardener (B) preferably contains an isocyanate-based hardener or a blocked body thereof.

[0096] The isocyanate-based hardener is an isocyanate having two or more isocyanate groups or a blocked body thereof. As the isocyanate, for example, aromatic (poly)isocyanates, aliphatic (poly)isocyanates, araliphatic (poly)isocyanates, alicyclic (poly)isocyanates, and their biuret bodies, nurate bodies, and adduct bodies are preferred. From the viewpoint of yellowing resistance, aliphatic isocyanates, alicyclic isocyanates, and their biuret bodies, nurate bodies, and adduct bodies are further preferred.

[0097] Aliphatic isocyanates include, for example: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (alias: HMDI (hexamethylene diisocyanate)), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc.

[0098] Cycloaliphatic isocyanates include, for example: 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (alias: IPDI (isophorone diisocyanate), isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, etc.

[0099] Aromatic isocyanates include, for example: 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, benzidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4”-triphenylmethane triisocyanate, etc.

[0100] Aromatic aliphatic isocyanates include, for example: ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, etc.

[0101] The biuret body is a self-condensate with a biuret bond formed by self-condensation of isocyanate monomers. Examples of the biuret body include: the biuret body of hexamethylene diisocyanate.

[0102] The isocyanurate body is a trimer of isocyanate monomers. Examples include: the trimer of hexamethylene diisocyanate, the trimer of isophorone diisocyanate, the trimer of toluene diisocyanate, etc.

[0103] The adduct is a polyfunctional isocyanate compound formed by the reaction of an isocyanate monomer with a polyfunctional low-molecular-weight compound containing active hydrogen. Examples of the adduct include compounds formed by reacting trimethylolpropane with hexamethylene diisocyanate, compounds formed by reacting trimethylolpropane with toluene diisocyanate, compounds formed by reacting trimethylolpropane with xylylene diisocyanate, compounds formed by reacting trimethylolpropane with isophorone diisocyanate, compounds formed by reacting 1,6-hexanediol with hexamethylene diisocyanate, etc.

[0104] From the viewpoint of forming a sufficient crosslinked structure, the isocyanate compound is preferably a trifunctional isocyanate compound. The isocyanate compound is more preferably an adduct and an allophanate formed as reaction products of an isocyanate monomer with a trifunctional low-molecular-weight compound containing active hydrogen. The isocyanate compound is preferably a trimethylolpropane adduct of hexamethylene diisocyanate, an allophanate of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, an allophanate of toluene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, an allophanate of isophorone diisocyanate, and more preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate.

[0105] Examples of the epoxy-based hardener (epoxy compound) include glycerol diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidylaminophenylmethane, etc.

[0106] Examples of the aziridine-based hardener (aziridine compound) include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), tri-2,4,6-(1-aziridinyl)-1,3,5-triazine, 4,4'-bis(ethyleneimino carbonylamino)diphenylmethane, etc.

[0107] The carbodiimide-based hardener (carbodiimide compound) is preferably a high-molecular-weight polycarbodiimide formed by subjecting a diisocyanate compound to a decarbonation condensation reaction in the presence of a carbodiimidization catalyst. Commercially available products of the high-molecular-weight polycarbodiimide are preferably the CARBODILITE series of Nisshinbo Co., Ltd. Among them, CARBODILITE V-03, 07, 09 (all are trade names) are excellent in compatibility with organic solvents, and thus are preferred.

[0108] Metal chelate hardeners are, for example, preferably coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with acetylacetone or ethyl acetoacetate. Examples of metal chelate hardeners include aluminum diisopropoxide ethylacetoacetate, aluminum acetylacetonate, aluminum monoacetylacetonate bisethylacetoacetate, and aluminum diisopropoxide alkylacetoacetate.

[0109] Oxazoline hardeners are substances having two or more oxazoline groups in the molecule and can be low-molecular compounds or polymers. Examples of low-molecular oxazoline hardeners include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2'-bis(2-oxazoline), 2,2'-methylenebis(2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-trimethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-ethylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-(1,3-phenylenebis(2-oxazoline), bis(2-oxazolinylcyclohexane) sulfide, and bis(2-oxazolinylnorbornane) sulfide. Examples of polymeric oxazoline hardeners include polymers having addition-polymerizable oxazoline as an essential component in their constituent components. Examples of the addition-polymerizable oxazoline include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0110] Examples of melamine hardeners include fully alkylated melamine resins, hydroxymethyl melamine resins, and imino melamine resins having imino groups in part as representative melamine hardeners.

[0111] Per 100 parts by mass of the acrylic polymer (A) in the adhesive composition, the curing agent (B) is preferably contained in an amount of 0.02 to 4 parts by mass, more preferably 0.04 to 1 part by mass. When the content is 0.02 parts by mass or more, the cohesive force is further improved. When the content is 4 parts by mass or less, it is easy to balance the cohesive force and flexibility, and thus it is easy to obtain sufficient adhesive strength, heat resistance, and light resistance.

[0112] <Silane Coupling Agent (C)>

[0113] This adhesive composition preferably contains a silane coupling agent (C). By containing the silane coupling agent (C), the adhesive strength, heat resistance, resistance to wet heat whitening, and light resistance can be further improved. Per 100 parts by mass of the acrylic polymer (A), the silane coupling agent (C) is preferably contained in an amount of 0.05 to 0.2 parts by mass. By setting it to 0.05 to 0.2 parts by mass, it is easy to impart excellent heat resistance, gas resistance, and light resistance.

[0114] Examples of the silane coupling agent (C) include: alkoxysilane compounds having (meth)acryloyloxy groups, alkoxysilane compounds having vinyl groups, alkoxysilane compounds having amino groups, alkoxysilane compounds having mercapto groups, or alkoxysilane compounds having epoxy groups, etc.

[0115] As commercially available products, specifically, for example, KBM-403 (3-glycidoxypropyltrimethoxysilane), KBE-403 (3-glycidoxypropyltriethoxysilane), KBM-303 (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) (the above are trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), BYK-325N (polyether-modified polymethylalkylsiloxane) (trade name, manufactured by BYK-Chemie Japan Co., Ltd.), etc.

[0116] In this adhesive composition, as long as it is within the range that can solve the problems, various resins, the chlorinated polyolefins described later, oils, softeners, dyes, pigments, antioxidants, and ultraviolet absorbers can be contained as optional components.

[0117] Examples of the chlorinated polyolefins include: chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic acid-modified chlorinated polypropylene, chlorinated polyethylene, chlorinated ethylene-vinyl acetate copolymer, etc. Here, from the viewpoints of good compatibility with acrylic polymers, etc. and effectively reducing polarity, chlorinated polypropylene or chlorinated ethylene-vinyl acetate copolymer is preferred.

[0118] As commercially available products, specifically, for example, Supercron 390S (chlorinated polypropylene, chlorine content 36%) and Supercron BX (ethylene-vinyl acetate (EVA), chlorine content 18%) (the above are trade names, manufactured by Nippon Paper Industries Co., Ltd.) can be cited.

[0119] 《Adhesive Sheet》

[0120] The adhesive sheet of the present disclosure (also referred to as this adhesive sheet) includes an adhesive layer, and the adhesive layer contains the adhesive composition of the present disclosure.

[0121] This adhesive sheet has either a structure in which release films are formed on both sides of the adhesive layer or a structure in which a release film is formed on one side of the adhesive layer and a light-transmissive substrate is included on the other side of the adhesive, and this adhesive layer is an adhesive layer formed from this adhesive composition.

[0122] <Release Film>

[0123] As the release film, there is no particular limitation, and a transparent plastic substrate can be suitably used. As raw materials for the transparent plastic substrate, for example, polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose, polysulfone, polyarylate, polycycloolefin and other plastic materials can be cited. In addition, the plastic materials can be used alone or in combination of two or more.

[0124] As the release film, among the transparent plastic substrates as described above, a transparent plastic substrate with excellent heat resistance can be suitably used, that is, a transparent plastic substrate that suppresses or prevents deformation under harsh conditions such as high temperature and high temperature and high humidity. As the transparent plastic substrate, a PET film or a PET sheet is particularly suitable.

[0125] <Light-Transmissive Substrate>

[0126] As the light-transmissive substrate, a transparent plastic substrate is used. As raw materials for such a light-transmissive substrate, for example, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate (PC), polycycloolefin, polyimide, polyphenylene ether, polysulfone, polyethersulfone, polystyrene, polypropylene and other plastic materials can be cited. Particularly preferably, a PET film or PC, and more preferably PC in terms of durability.

[0127] In addition, the plastic materials can be used alone or in combination of two or more.

[0128] In addition, the light-transmissive substrate can also be subjected to suitable surface treatments such as physical treatments like corona discharge treatment and plasma treatment, and chemical treatments like primer treatment.

[0129] This adhesive sheet has excellent adhesiveness, heat resistance, resistance to moisture and heat whitening, resistance to outgassing, light resistance, low dielectric constant, and metal corrosion resistance. Therefore, it is suitable as an adhesive for forming optical display components such as display devices like LCDs or OLEDs or input devices like touchscreens, or for bonding these components to each other. There is no particular limitation on the optical component, and examples include: PET films, polarizing plates, retardation plates, elliptical polarizing plates, optical compensation films, brightness enhancement films, infrared / electromagnetic wave blocking films, antireflection films for the front surface, surface protection films, films having an indium tin oxide (ITO) layer, films having a zinc oxide (ZnO) layer, films obtained by coating or printing metal nanoparticles, films obtained by coating or printing a dispersion containing carbon nanotubes, films obtained by coating or printing a dispersion containing graphene, films obtained by coating or printing a dispersion containing a conductive polymer, metal plates formed of stainless steel (SUS), etc., metal meshes, and those obtained by laminating them.

[0130] The thickness of the transparent plastic substrate is not particularly limited. For example, it is preferably 10 μm to 200 μm, more preferably 25 μm to 150 μm.

[0131] When applying the adhesive composition, an appropriate liquid medium can also be added to adjust the viscosity. Specifically, for example, hydrocarbon solvents such as toluene, xylene, hexane, and heptane; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; halogenated hydrocarbon solvents such as dichloromethane and chloroform; ether solvents such as diethyl ether, methoxytoluene, and dioxane; or other hydrocarbon solvents, etc. However, water or alcohol may cause hindrance to the reaction between the acrylic polymer (A) and the isocyanate-based curing agent (B), so it needs to be used with caution.

[0132] The coating method is not particularly limited, and various coating methods such as Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, and spin coater can be cited. In addition, the drying and hardening method is not particularly limited, and methods using hot air drying, infrared rays, reduced pressure method, or active energy rays can be cited. However, from the viewpoint of gas resistance, as the drying and hardening method, hot air or steam heating at 60°C to 180°C is preferred.

[0133] The thickness of the adhesive layer is preferably 2 μm to 1000 μm, and more preferably 5 μm to 500 μm. In addition, the adhesive layer can be a single layer or any form of lamination of two or more layers.

[0134] 《Laminate》

[0135] The laminate includes a light-transmissive substrate and an adhesive layer, and the adhesive layer is formed using the adhesive sheet of the present disclosure. Specifically, for example, the release film can be peeled off from the present adhesive sheet, and the adhesive layer can be attached to the light-transmissive substrate to form a laminate.

[0136] The laminate of the present disclosure has, for example, a structure of light-transmissive substrate / adhesive layer / polarizing plate. In this case, it preferably includes a light-transmissive substrate, an adhesive layer, and a polarizing plate in this order. Thereby, a laminate with excellent transparency can be produced.

[0137] Figure 1 An example of a schematic cross-sectional view partially showing the laminate of the present disclosure is shown. In Figure 1 , reference numeral 3 is a light-transmissive substrate (cover plate), reference numeral 1 is an adhesive layer, and reference numeral 4 is a polarizing plate.

[0138] In Figure 1 In the laminate shown, the light-transmissive substrate (cover plate) 3 is attached to the polarizing plate 4 with the adhesive layer 1 interposed therebetween.

[0139] <Manufacture of laminate for display>

[0140] The manufacturing method of the laminate of the present disclosure can be, for example, to form a laminate by peeling off the release films from an adhesive sheet having release films on both sides of the adhesive layer and attaching the adhesive layer to adherends such as a light-transmissive flexible substrate or a polarizing plate respectively. Alternatively, after directly forming an adhesive layer on a light-transmissive flexible substrate, a laminate can be formed by attaching the adhesive layer included in the adherend or another adhesive sheet to the adhesive layer.

[0141] "Display"

[0142] The display preferably includes the laminate of the present disclosure, a polarizing plate, and an optical element. Thus, the display of the present disclosure is excellent in bendability and visibility.

[0143] The optical element is not particularly limited, and examples thereof include a liquid crystal element, an organic electroluminescence (EL) element, and the like.

[0144] Figure 2 An example of a schematic cross-sectional view of a display partially showing a usage example of the present adhesive sheet is shown. In Figure 2 wherein, reference numeral 3 is a light-transmissive substrate (cover glass), reference numeral 2 is a release film, reference numeral 1 is a first adhesive layer, reference numeral 4 is a polarizing plate, reference numeral 5 is a second adhesive layer, reference numeral 6 is a barrier layer such as silicon nitride, reference numeral 7 is an organic EL layer, reference numeral 8 is a support such as polyimide, and reference numeral 9 is an organic EL unit. In addition, the structure of the display of the present disclosure is not limited to Figure 2 .

[0145] In Figure 2 the display shown, the light-transmissive substrate (cover glass) 1 is attached to the polarizing plate 4 with the adhesive layer of the present disclosure (first adhesive layer 1) interposed therebetween, and further attached to the organic EL unit 9 with a polarizing plate adhesive layer (second adhesive layer 5) interposed therebetween. Thus, the present adhesive sheet can be used in the following form: the transparent adhesive layer formed from the adhesive composition is attached to the light-transmissive substrate (cover glass) 3 and the polarizing plate 4, and then the laminate is attached to the organic EL unit 9 with a polarizing plate adhesive layer interposed therebetween.

[0146] For example, in Figure 2 the present adhesive layer can be used for either the first adhesive layer 1 or the second adhesive layer 5.

[0147] Generally, when comparing the first adhesive layer 1 and the second adhesive layer 5, the required quality for the adhesive layer is higher for the first adhesive layer 1. That is, since the adhesive composition of the present disclosure has good adhesion and bonding properties to the substrate, it is preferably used for the first adhesive layer 1. At this time, the adhesive used to form the second adhesive layer 5 can be the adhesive composition of the present disclosure or a conventionally known adhesive.

[0148] As for the use of the display, there is no particular limitation. However, typical examples include organic EL smartphones, organic EL tablets, organic EL smartwatches, etc., represented by organic EL TVs.

[0149] Examples

[0150] Hereinafter, the present disclosure will be further specifically described by way of examples. However, the present disclosure is not limited to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass". In addition, the blending amounts in the tables are parts by mass, and those other than the solvents are converted values of non-volatile components. In addition, the blank in the blending amount of each component in the table indicates that the component is not blended.

[0151] In addition, the method for measuring the weight average molecular weight of the acrylic polymer (A) is as follows.

[0152] <Measurement of weight average molecular weight (Mw)>

[0153] The weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC). As the apparatus, a GPC apparatus manufactured by Shimadzu Corporation is used: a liquid chromatography (LC)-GPC system "Prominence". In addition, for the column, those manufactured by Tosoh Corporation: TSKgel α-M are used, and two are connected in series. N,N-Dimethylformamide (DMF) is used as the washing liquid, and the measurement is carried out at 40°C. The determination of Mw is carried out by conversion using polystyrene with a known Mw as a standard substance.

[0154] The materials used in the examples and comparative examples are listed below.

[0155] <Hardener (B)>

[0156] [Isocyanate-based hardener]

[0157] B-1: (Trade name "NP-1200", manufactured by Mitsui Chemicals, Inc., biuret of hexamethylene diisocyanate)

[0158] B-2: (Trade name "D-172N", manufactured by Mitsui Chemicals, Inc., allophanate of hexamethylene diisocyanate)

[0159] B-3: (Trade name "D-160N", manufactured by Mitsui Chemicals, Inc., trimethylolpropane-modified product of hexamethylene diisocyanate)

[0160] B-4: (Trade name "Desmodur 2565", manufactured by Covestro, urethane body of isophorone diisocyanate)

[0161] B-5: (Trade name "Coronate L", manufactured by Tosoh, trimethylolpropane-modified toluene diisocyanate body)

[0162] [Other hardeners]

[0163] B-6: Zirconium tetraacetylacetonate: (Trade name "ORGATIX ZC-700", manufactured by Matsumoto Fine Chemical)

[0164] B-7: N,N,N',N'-tetraglycidyl-m-xylenediamine (TETRAD-X)

[0165] <Silane coupling agent (C)>

[0166] KBM-303: (Trade name, [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0167] KBE-303: (Trade name, 3-glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0168] <Manufacturing examples of acrylic polymers>

[0169] (Acrylic polymer (A-1))

[0170] Using a reaction apparatus including a blender, a reflux cooling pipe, a nitrogen inlet pipe, a thermometer, and a dropping funnel, 11 parts of isobornyl acrylate (IBXA) as monomer (a1), 56.5 parts of octyl acrylate (OA) as monomer (a2), 2 parts of 2-hydroxyethyl acrylate (HEA) as monomer (a3), 0.5 parts of acrylic acid (AA), and 30 parts of methyl acrylate (MA) as monomer (a4), each in a half amount, were charged into the reaction tank. 0.2 parts of azobisisobutyronitrile as an initiator and 60 parts of ethyl acetate as a solvent were added. It took about 2 hours to dropwise add a solution prepared by mixing the remaining half amount of the monomer mixture, 60 parts of ethyl acetate, and 0.2 parts of azobisisobutyronitrile from the dropping funnel. Under a nitrogen atmosphere, polymerization was carried out at about 80 °C for 6 hours. After the reaction was completed, cooling was performed and dilution was carried out using ethyl acetate to obtain an acrylic polymer solution with a non-volatile content of 30%. Here, the obtained acrylic polymer was designated as (A-1). In addition, the weight average molecular weight (Mw) of the obtained acrylic polymer is shown in Table 1.

[0171] (Acrylic polymers (A-2 to A-57, A'-1 to A'-10))

[0172] The composition and blending amount (parts by mass) described in Tables 1 to 5 were changed. Except for this, acrylic polymers (A-2 to A-57, A'-1 to A'-10) were synthesized using the same method as the production of acrylic polymer (A-1). In addition, the weight average molecular weight of the obtained acrylic polymers is shown in Tables 1 to 5.

[0173] [Table 1]

[0174] Table 1

[0175]

[0176] [Table 2]

[0177] Table 2

[0178]

[0179] [Table 3]

[0180] Table 3

[0181]

[0182] [Table 4]

[0183] Table 4

[0184]

[0185] [Table 5]

[0186] Table 5

[0187]

[0188] In addition, the abbreviations are as follows.

[0189] IBXA: Isobornyl acrylate

[0190] THFA: Tetrahydrofurfuryl acrylate

[0191] TMCHA: 3,3,5-Trimethylcyclohexyl acrylate

[0192] CHA: Cyclohexyl acrylate

[0193] IBXMA: Isobornyl methacrylate

[0194] CTFA: (5-Ethyl-1,3-dioxan-5-yl)methyl acrylate

[0195] BZA: Benzyl acrylate

[0196] PEA: Phenoxyethyl acrylate

[0197] OA: n-Octyl acrylate (alkyl has 8 carbon atoms)

[0198] OMA: n-Octyl methacrylate (alkyl has 8 carbon atoms)

[0199] DA: n-Decyl acrylate (alkyl has 10 carbon atoms)

[0200] DMA: n-Decyl methacrylate (alkyl has 10 carbon atoms)

[0201] DDA: n-Dodecyl acrylate (alkyl has 12 carbon atoms)

[0202] DDMA: n-Dodecyl methacrylate (alkyl has 12 carbon atoms)

[0203] TrDA: n-Tridecyl acrylate (alkyl has 13 carbon atoms)

[0204] TrDMA: n-Tridecyl methacrylate (alkyl has 13 carbon atoms)

[0205] TeDA: n-Tetradecyl acrylate (alkyl has 14 carbon atoms)

[0206] TeDMA: n-Tetradecyl methacrylate (alkyl has 14 carbon atoms)

[0207] HDA: n-Hexadecyl acrylate (the alkyl group has 16 carbon atoms)

[0208] HDMA: n-Hexadecyl methacrylate (the alkyl group has 16 carbon atoms)

[0209] ODA: n-Octadecyl acrylate (the alkyl group has 18 carbon atoms)

[0210] ODMA: n-Octadecyl methacrylate (the alkyl group has 18 carbon atoms)

[0211] 2EHA: 2-Ethylhexyl acrylate

[0212] iDA: Isodecyl acrylate

[0213] iDMA: Isodecyl methacrylate

[0214] HEA: Hydroxyethyl

[0215] 4HBA: 4-Hydroxy-n-butyl

[0216] AA: Acrylic acid

[0217] MAA: Methacrylic acid

[0218] MA: Methyl acrylate

[0219] EMA: Ethyl methacrylate

[0220] BA: n-Butyl acrylate

[0221] <Example 1>

[0222] With respect to 100 parts of the acrylic polymer (A-1), 0.4 part of "NP-1200" (trade name, manufactured by Mitsui Chemicals, Inc., biuret of hexamethylene diisocyanate) as the isocyanate-based curing agent (B) and 0.1 part of KBE-403 (trade name, 3-glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) as the silane coupling agent (C) were blended to obtain an adhesive composition.

[0223] Using a beveled wheel coater, the obtained adhesive composition was coated on a release liner (trade name SP-PET-O1-BU: manufactured by Mitsui Chemicals Tohcello, Inc.) with a thickness of 38 μm as a release sheet so that the dried thickness became 100 μm, and dried at 110°C for 3 minutes. Then, a release liner (trade name SP-PET-O3-B3: manufactured by Mitsui Chemicals Tohcello, Inc.) with a thickness of 75 μm as a release sheet was laminated on the adhesive layer, and aged at 23°C for seven days in this state to obtain an adhesive sheet.

[0224] <Examples 2 to 69, Comparative Examples 1 to 11>

[0225] As shown in Tables 6 to 8, the types and blending amounts of the acrylic polymer, hardener, and silane coupling agent were changed, and adhesive compositions and adhesive sheets were obtained in the same manner as in Example 1, respectively, except for this.

[0226] [Table 6]

[0227] Table 6

[0228]

[0229] [Table 7]

[0230] Table 7

[0231]

[0232] [Table 8]

[0233] Table 8

[0234]

[0235] "Physical Property Values and Evaluation of Adhesive Composition and Adhesive Sheet"

[0236] The adhesiveness, heat resistance (peeling, yellowing), moisture and heat resistance whitening resistance, outgassing resistance, light resistance (peeling, yellowing), metal corrosion resistance of the obtained adhesive composition and adhesive sheet were evaluated and the dielectric constant was measured by the following methods. The results are shown in Tables 9 to 11.

[0237] <Adhesiveness>

[0238] The 38-μm release liner of the obtained adhesive sheet was peeled off, the adhesive layer was laminated on a PET film (manufactured by Toyobo Co., Ltd., trade name: Cosmoshine A-4360, thickness 100 μm) as a base material, cut into a size of width 25 mm × length 100 mm, and a test adhesive sheet was produced. The other 75-μm release liner of the test adhesive sheet was peeled off, and in an environment of 23°C - relative humidity 50% (50% RH (Relative Humidity)), the adhesive layer was attached to a glass plate, and then, in accordance with Japanese Industrial Standards (JIS) Z-0237, crimping was performed using a roll. After 24 hours from the crimping, the peel strength (peel angle 180°, peel speed 300 mm / minute; unit N / 25 mm width) was measured using a tensile tester (Tensilon: manufactured by Orientec Co., Ltd.).

[0239] [Evaluation Criteria]

[0240] A+: The peel strength is 25 N / 25 mm or more. Excellent.

[0241] A: The peel strength is 21 N / 25 mm or more and less than 25 N / 25 mm. Good.

[0242] B: The peel strength is 18 N / 25 mm or more and less than 21 N / 25 mm. Slightly good.

[0243] C: The peel strength is 15 N / 25 mm or more and less than 18 N / 25 mm. Practicable.

[0244] D: The peel strength is less than 15 N / 25 mm. Not practicable.

[0245] <Heat Resistance (Peel)>

[0246] Peel off the 38-μm release liner of the adhesive sheet obtained. In an environment of 23°C - 50% RH, use a laminator to bond the adhesive layer to a 0.5-mm-thick polycarbonate (PC) plate (product name: Iupilon NF2000, manufactured by Mitsubishi Gas Chemical Company). Subsequently, peel off another 75-μm release liner of the adhesive sheet and bond it to a glass plate using the same laminator. Apply a pressure of 0.5 MPa to it in an environment of 50°C and hold for 20 minutes to fabricate a test piece laminated in the order of PC plate / adhesive layer / glass plate, and place it in an environment of 120°C for 1000 hours. After cooling it in 23°C - 50% RH for 24 hours, evaluate the degree of peeling of the test piece by visual inspection.

[0247] [Evaluation Criteria]

[0248] A+: The peeled area is less than 5% of the whole. Excellent.

[0249] A: The peeled area is 5% or more and less than 15% of the whole. Good.

[0250] B: The peeled area is 15% or more and less than 30% of the whole. Slightly good.

[0251] C: The peeled area is 30% or more and less than 50% of the whole. Practicable.

[0252] D: The peeled area is 50% or more of the whole. Not practicable.

[0253] <Heat Resistance (Yellowing)>

[0254] Peel off the 38 μm release liner of the obtained adhesive sheet. In an environment of 23°C - 50% RH, use a laminator to bond the adhesive layer to a glass plate. Subsequently, peel off another 75 μm release liner of the adhesive sheet and bond it to the glass plate using the same laminator. Apply a pressure of 0.5 MPa to it in an environment of 50°C and hold for 20 minutes to fabricate a test piece laminated in the order of glass plate / adhesive layer / glass plate. Place it in an environment of 120°C for 1000 hours. After cooling it for 1 hour at 23°C - 50% RH, measure the b value and calculate the difference Δb from the b value before the heat resistance test. In addition, the b value is measured using a spectrocolorimeter SE6000 manufactured by Nippon Denshoku Industries Co., Ltd. under the conditions of D65 light source and 2° viewing angle.

[0255] [Evaluation Criteria]

[0256] A+: Δb is less than 0.8. Excellent.

[0257] A: Δb is 0.8 or more and less than 1.3. Good.

[0258] B: Δb is 1.3 or more and less than 2.0. Slightly good.

[0259] C: Δb is 2.0 or more and less than 3.0. Practically usable.

[0260] D: Δb is 3.0 or more. Not practically usable.

[0261] <Damp Heat Whitening Resistance (Glass Structure)>

[0262] Peel off the 38 μm release liner of the obtained adhesive sheet. In an environment of 23°C - 50% RH, use a laminator to bond the adhesive layer to a glass plate. Subsequently, peel off another 75 μm release liner of the adhesive sheet and bond it to the glass plate using the same laminator. Apply a pressure of 0.5 MPa to it in an environment of 50°C and hold for 20 minutes to fabricate a test piece laminated in the order of glass plate / adhesive layer / glass plate. Place it in an environment of 85°C - 85% RH for 1000 hours. After cooling it for 1 hour at 23°C - 50% RH, measure the haze. In addition, the haze is measured using a turbidimeter NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd.

[0263] [Evaluation Criteria]

[0264] A+: Haze is less than 1.0. Excellent.

[0265] A: Haze is 1.0 or more and less than 2.0. Good.

[0266] B: Haze is 2.0 or more and less than 3.5. Slightly good.

[0267] C: The HAZE is 3.5 or more and less than 5.0. It is practical.

[0268] D: The HAZE is 5.0 or more. It is not practical.

[0269] <Humidity and Heat Resistance Whitening Resistance (PC Structure)>

[0270] Peel off the 38μm release liner of the obtained adhesive sheet, attach the adhesive layer to a PET film (manufactured by Toyobo Co., Ltd., product name: A-4300, thickness 100μm), cut it into a size of width 40mm × length 60mm to produce a test adhesive sheet. Subsequently, peel off another 75μm release liner of the test adhesive sheet and attach it to a polycarbonate (PC) plate with a thickness of 0.5mm (product name: Iupilon NF2000, manufactured by Mitsubishi Gas Chemical Company). Apply a pressure of 0.5MPa to it in an environment of 50°C and hold for 20 minutes to produce a test piece laminated in the order of PET film / adhesive layer / PC plate, and place it in an environment of 85°C - 85%RH for 240 hours. After cooling it in an environment of 23°C - 50%RH for 1 hour, measure the HAZE. In addition, the HAZE is measured using a turbidimeter NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd.

[0271] [Evaluation Criteria]

[0272] A+: The HAZE is less than 1.5. Excellent.

[0273] A: The HAZE is 1.5 or more and less than 2.5. Good.

[0274] B: The HAZE is 2.5 or more and less than 4.0. Slightly good.

[0275] C: The HAZE is 4.0 or more and less than 5.5. It is practical.

[0276] D: The HAZE is 5.5 or more. It is not practical.

[0277] <Outgassing Resistance>

[0278] After producing a test piece according to the same process as the evaluation of humidity and heat resistance whitening resistance (PC structure), place it in an environment of 85°C - 85%RH for 72 hours. Then, after placing it in an environment of 23°C - 50%RH for 1 hour, visually observe the appearance of the test piece.

[0279] [Evaluation Criteria]

[0280] A+: No bubbles or floating. Excellent.

[0281] A: There are extremely few bubbles or lifting of the adhesive layer (if it is bubbles, there are more than one and less than five; if it is lifting, the lifted area is less than 3% of the whole). Good.

[0282] B: There are a small number of bubbles or lifting of the adhesive layer (if it is bubbles, there are more than five and less than fifteen; if it is lifting, the lifted area is 3% or more and less than 5% of the whole). Slightly good.

[0283] C: There are bubbles or lifting of the adhesive layer (if it is bubbles, there are more than fifteen and less than thirty; if it is lifting, the lifted area is 5% or more and less than 10% of the whole). Practicable.

[0284] D: There are many bubbles or lifting of the adhesive layer (if it is bubbles, there are more than thirty; if it is lifting, the lifted area is 10% or more of the whole). Not practicable.

[0285] <Light resistance (peeling)>

[0286] Relative to 100 parts of the surface protection coating agent (manufactured by Toyo Ink Co., Ltd., trade name: YL454UR, acrylic varnish), 10 parts of D-172N as a hardener is mixed and the coating liquid is prepared, and it is coated on a polycarbonate (PC) plate with a thickness of 0.5 mm (trade name: Iupilon NF2000: manufactured by Mitsubishi Gas Chemical Co., Inc.) using a bar coater. Thereafter, it is aged at 40 °C for 72 hours to produce a PC plate with a surface protection layer. Except for using the PC plate with the said surface protection layer instead of Iupilon NF2000, after producing a test piece according to the same process as the evaluation of heat resistance (peeling), a xenon weather resistance tester manufactured by Q-Lab Corporation is used to irradiate light for 500 hours under the conditions of a black panel temperature of 83 °C and an illuminance of 60 W / m2. After cooling it at 23 °C - 50% RH for 24 hours, the peeling degree of the test piece is evaluated visually.

[0287] [Evaluation criteria]

[0288] A+: The peeled area is less than 5% of the whole. Excellent.

[0289] A: The peeled area is 5% or more and less than 15% of the whole. Good.

[0290] B: The peeled area is 15% or more and less than 25% of the whole. Slightly good.

[0291] C: The peeled area is 25% or more and less than 50% of the whole. Practicable.

[0292] D: The peeled area is 50% or more of the whole. Not practicable.

[0293] <Light resistance (yellowing)>

[0294] After preparing test pieces according to the same procedure as the evaluation of heat resistance (yellowing), use a xenon weather resistance tester manufactured by Q-Lab Corporation, and irradiate with light for 1000 hours under the conditions of a black panel temperature of 63 °C and an illuminance of 85 W / m 2 . After cooling it for 1 hour at 23 °C - 50% RH, measure the b value and calculate the difference Δb from the b value before the light resistance test. In addition, the b value is measured using a spectrocolorimeter SE6000 (trade name) manufactured by Nippon Denshoku Industries Co., Ltd. under the conditions of a D65 light source and a viewing angle of 2°.

[0295] [Evaluation Criteria]

[0296] A+: Δb is less than 1.0. Excellent.

[0297] A: Δb is 1.0 or more and less than 2.0. Good.

[0298] B: Δb is 2.0 or more and less than 3.5. Slightly good.

[0299] C: Δb is 3.5 or more and less than 5.0. Practicable.

[0300] D: Δb is 5.0 or more. Not practicable.

[0301] <Metal Corrosion Resistance>

[0302] Peel off the 38 μm release liner of the obtained adhesive sheet, laminate the adhesive layer on a PET film (manufactured by Toyobo Co., Ltd., trade name: A-4300, thickness 100 μm), cut it into a size of width 40 mm × length 60 mm to prepare a test adhesive sheet. Subsequently, peel off another 75 μm release liner of the test adhesive sheet, and in an environment of 23 °C - 50% RH, use a laminator to paste the exposed adhesive layer on the transparent conductive film of a PET film with a width of 40 mm × length of 160 mm formed with ITO to obtain a laminate, and measure its resistance value using a resistance meter (loresta) GP (model MCP-T600, manufactured by Mitsubishi Chemical Corporation).

[0303] Subsequently, place the laminate in an environment of 85 °C - 90% RH for 1000 hours, and then measure the resistance value again. Evaluate the corrosion resistance of the transparent conductive film by calculating the change rate of the resistance value before and after the placement.

[0304] [Evaluation Criteria]

[0305] A+: The change rate of the resistance value is less than 120%. Excellent.

[0306] A: The change rate of the resistance value is 120% or more and less than 130%. Good.

[0307] B: The change rate of the resistance value is 130% or more and less than 140%. Slightly good.

[0308] C: The change rate of the resistance value is 140% or more and less than 150%. Practically applicable.

[0309] D: The change rate of the resistance value is 150% or more. Not practically applicable.

[0310] <Dielectric constant>

[0311] According to Figure 3 Describe the method for measuring the dielectric constant. Prepare the obtained adhesive sheet into a size of 100 mm in width × 100 mm in length to make a test adhesive sheet. Peel off the 38-μm release liner of the test adhesive sheet, and attach the exposed adhesive layer 4 to the aluminum vapor deposition layer 3C formed on the glass plate 6. Subsequently, peel off another 75-μm release liner of the test adhesive sheet, and form an aluminum vapor deposition layer 3A and an aluminum vapor deposition layer 3B on the surface of the exposed adhesive layer 4 that does not contact the aluminum vapor deposition layer 3C, thereby obtaining a dielectric constant measurement sample 1. Then, connect the connection terminal (measurement terminal 2A) of the measuring device 7 to the measurement terminal joint portion 5 of the dielectric constant measurement sample 1, and connect the connection terminal (measurement terminal 2B) to the aluminum vapor deposition layer 3A. Then, measure the dielectric constant under the following conditions. In addition, the evaluation criteria are as follows.

[0312] Measuring device: 1260 impedance meter manufactured by SOLARTRON, UK

[0313] Amplifier: 1296-type dielectric constant measurement interface manufactured by SOLARTRON, UK

[0314] Electrode structure: Aluminum vapor deposition layer with a diameter of 21 mm and a thickness of 40 nm

[0315] Opposing electrode: Aluminum vapor deposition layer with a diameter of 21 mm and a thickness of 40 nm

[0316] Alternating current: 100 mV

[0317] Terminal: Pin probe

[0318] Frequency: 100 kHz

[0319] Measurement environment: 23°C - 50% RH

[0320] Specimen thickness: 25 μm

[0321] [Evaluation criteria]

[0322] A+: The dielectric constant is 3.0 or less. Excellent.

[0323] A: The dielectric constant exceeds 3.0 and is 3.1 or less. Good. B: The dielectric constant exceeds 3.1 and is 3.3 or less. Slightly good. C: The dielectric constant exceeds 3.3 and is 3.5 or less. Practically applicable. D: The dielectric constant exceeds 3.5. Not practically applicable.

[0324] [Table 9]

[0325] Table 9

[0326]

[0327] [Table 10]

[0328] Table 10

[0329]

[0330] [Table 11]

[0331] Table 11

[0332]

[0333] As shown in Table 9 and Table 10, the results show that the adhesive composition of the present disclosure is excellent in adhesive strength, heat resistance, moisture and heat whitening resistance, outgassing resistance, light resistance, low dielectric property, and metal corrosion resistance. On the other hand, as shown in Table 11, the adhesive compositions of the comparative examples do not satisfy all of the adhesive strength, heat resistance, moisture and heat whitening resistance, outgassing resistance, light resistance, low dielectric property, and metal corrosion resistance.

[0334] Based on these results, it can be said that the adhesive composition of the present disclosure is suitably used for bonding optical members.

[0335] This application claims priority based on Japanese Patent Application No. 2022-209352 filed on December 27, 2022, and incorporates the entire contents disclosed therein into this application.

[0336] Explanation of reference numerals

[0337] The following explanation Figure 1 、 Figure 2 of the symbols.

[0338] 1: First adhesive layer

[0339] 2: Release film

[0340] 3: Transparent substrate (cover plate)

[0341] 4: Polarizing plate

[0342] 5: Second adhesive layer

[0343] 6: Barrier layer

[0344] 7: Organic EL layer

[0345] 8: Support

[0346] 9: Organic EL unit

[0347] The following explains Figure 3 the symbols.

[0348] 1: Dielectric constant measurement sample

[0349] 2A: Measurement terminal

[0350] 2B: Measurement terminal

[0351] 3A: Aluminum evaporation coating

[0352] 3B: Aluminum evaporation coating

[0353] 3C: Aluminum evaporation coating

[0354] 4: Adhesive layer

[0355] 5: Measurement terminal joint part

[0356] 6: Glass plate

[0357] 7: Measuring device

Claims

1. An adhesive composition comprising an acrylic polymer (A) and a hardener (B), wherein the adhesive composition is characterized in that the acrylic polymer (A) is a copolymer of a monomer mixture containing the following (a1), (a2) and (a3), the monomer mixture contains 2.5% to 20% by mass of (a1), 30% to 80% by mass of (a2), and 0.1% to 20% by mass of (a3) in 100% by mass, (a1) (Meth)acrylate monomer having an alicyclic structure (wherein, (excluding (a3)); (a2) is an alkyl (meth)acrylate monomer having a linear alkyl group with 8 to 18 carbon atoms; (a3) is a (meth)acrylate monomer having a carboxyl group and / or a (meth)acrylate monomer having a hydroxyl group.

2. The pressure-sensitive adhesive composition according to claim 1, wherein (a3) contains a (meth)acrylate monomer having a hydroxyl group.

3. The adhesive composition according to claim 1, characterized in that, The monomer mixture further contains (a4) an alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms.

4. The adhesive composition according to claim 1, wherein It further contains a silane coupling agent (C).

5. The adhesive composition according to claim 1, characterized in that, The hardener (B) contains an isocyanate-based hardener or a blocked body thereof.

6. An adhesive sheet comprising an adhesive layer containing the adhesive composition according to any one of claims 1 to 5.

7. A laminate, characterized in that, It includes the adhesive sheet according to claim 6, and a light-transmissive substrate.

8. A display including the laminate according to claim 7, a polarizing plate, and an optical element.

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