Adhesive composition and bonded body

Abstract

Disclosed is an adhesive composition comprising a (meth)acrylate compound, an epoxy compound, and a photoinitiator. When the adhesive composition is formed into a shape having a length of 20 mm, a width of 20 mm, and a thickness of 500 μm and cured by irradiation with ultraviolet light, the obtained cured object has a transmittance of infrared light with 1,310-nm wavelength of 70% or greater.

Description

Adhesive composition and adhesive

[0001] This disclosure relates to adhesive compositions and adhesives.

[0002] As an adhesive composition, a composition containing a (meth)acrylate compound, an epoxy compound, and a photoacid generator is known (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2018-141137

[0004] The primary objective of this disclosure is to provide an adhesive composition containing a (meth)acrylate compound, an epoxy compound, and a photoinitiator that can produce a cured product with sufficient adhesive strength.

[0005] The present inventors conducted diligent research to solve the above problems and discovered that when cured by irradiation with ultraviolet light, the adhesive composition that has a high transmittance to infrared rays of a specific wavelength tends to exhibit superior adhesive strength. This led to the completion of the present invention.

[0006] This disclosure includes the following [1] to

[14] : [1] An adhesive composition comprising a (meth)acrylate compound, an epoxy compound, and a photoinitiator, wherein when the adhesive composition is molded to a length of 20 mm × width of 20 mm × thickness of 500 μm and cured by irradiation with ultraviolet light, the resulting cured product has a transmittance of 70% or more to infrared light with a wavelength of 1310 nm. [2] The adhesive composition according to [1], wherein the (meth)acrylate compound comprises a (meth)acrylate having a fluorine-containing organic group. [3] The adhesive composition according to [1], wherein the (meth)acrylate compound does not comprise a (meth)acrylate having a fluorine-containing organic group. [4] The adhesive composition according to any one of [1] to [3], wherein the (meth)acrylate compound comprises a (meth)acrylate having a hydroxyl group. [5] The adhesive composition according to any one of [1] to [4], wherein the (meth)acrylate compound comprises a (meth)acrylate having an alkoxy group. [6] The adhesive composition according to any one of [1] to [5], further comprising a (meth)acrylic resin. [7] The adhesive composition according to [6], wherein the (meth)acrylic resin has structural units derived from (meth)acrylate having a cyclic ether group. [8] The adhesive composition according to [7], wherein the (meth)acrylate having a cyclic ether group comprises a (meth)acrylate having an alicyclic epoxy group. [9] The adhesive composition according to [7], wherein the (meth)acrylic resin further comprises structural units derived from a (meth)acrylate having a fluorine-containing organic group.

[10] The adhesive composition according to any one of [1] to [9], wherein the epoxy compound comprises an aliphatic epoxy compound.

[11] The adhesive composition according to

[10] , wherein the epoxy compound further comprises an alicyclic epoxy compound.

[12] The adhesive composition according to any one of [1] to

[11] , further comprising a coupling agent.

[13] The irradiation of ultraviolet light is illuminance 30 mW / cm ２The adhesive composition according to any one of [1] to

[12] , which is carried out under the condition of a time of 30 seconds.

[14] An adhesive comprising a first adherend, a second adherend, and an adhesive portion that adheres the first adherend and the second adherend to each other, wherein the adhesive portion contains a cured product of the adhesive composition according to any one of [1] to

[13] .

[0007] This disclosure provides an adhesive composition containing a (meth)acrylate compound, an epoxy compound, and a photoinitiator that can produce a cured product with sufficient adhesive strength. Some forms of the adhesive composition tend to have a sufficient curing rate and a sufficiently low refractive index. This disclosure also provides an adhesive using such an adhesive composition.

[0008] The embodiments of this disclosure are described below. However, this disclosure is not limited to the embodiments described below.

[0009] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of one stage of the numerical range may be replaced with the upper or lower limit of another stage of the numerical range. Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. Furthermore, the upper and lower limits described individually can be combined in any way. In the notation "A to B" for a numerical range, the numbers A and B at both ends are included in the numerical range as the lower and upper limits, respectively. In this specification, for example, the description "10 or more" means "10" and "numbers greater than 10," and the same applies when the numbers are different. Also, for example, the description "10 or less" means "10" and "numbers less than 10," and the same applies when the numbers are different.

[0010] In this specification, (meth)acrylate compounds mean compounds having one or more (meth)acryloyl groups, and (meth)acrylic resins mean (co)polymers having structural units derived from (meth)acrylate compounds. (Meth)acrylate compounds may be compounds that do not have epoxy groups and oxetanyl groups. (Meth)acryloyl groups mean acryloyl groups or the corresponding methacryloyl groups. The same applies to other similar expressions such as (meth)acrylate. Furthermore, "A or B" means that either A or B may be included, or both may be included.

[0011] In this specification, a cyclic ether group means a monovalent group containing either an oxirane ring (epoxy ring) or an oxetane ring. Examples of such cyclic ether groups include epoxy groups (oxiranyl groups), oxetanyl groups, glycidyl groups, glycidyl ether groups, (3-ethyloxetan-3-yl)methyl groups, epoxycyclohexyl groups, and the like. Similarly, an epoxy group means a monovalent group containing an oxirane ring (epoxy ring), and an oxetanyl group means a monovalent group containing an oxetane ring.

[0012] The materials exemplified below may be used individually or in combination of two or more, unless otherwise specified. The amount or content of each component refers to the total amount of any multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component exist in the composition.

[0013] [Adhesive Composition] The adhesive composition of one embodiment contains a (meth)acrylate compound (hereinafter sometimes referred to as "component (A)"), an epoxy compound (hereinafter sometimes referred to as "component (B)"), and a photoinitiator (hereinafter sometimes referred to as "component (C)"). The adhesive composition may further contain, for example, a (meth)acrylic resin (hereinafter sometimes referred to as "component (D)"), an oxetane compound (hereinafter sometimes referred to as "component (E)"), a coupling agent (hereinafter sometimes referred to as "component (F)"), etc. The adhesive composition may be an adhesive composition that exhibits photocurability.

[0014] According to the inventors' studies, it has been found that when cured by irradiation with ultraviolet light, the adhesive composition tends to exhibit superior adhesive strength if it has a high transmittance to infrared rays of a specific wavelength. The transmittance of the cured adhesive composition to infrared rays at a wavelength of 1310 nm (hereinafter sometimes simply referred to as "infrared transmittance") is 70% or more, and may be 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 96% or more, or 98% or more. The upper limit of the infrared transmittance of the cured adhesive composition may be, for example, 100% or less, 99.9% or less, or 99.5% or less.

[0015] The adhesive composition of this embodiment is adjusted so that the transmittance of the cured product at a wavelength of 1310 nm is 70% or more. Examples of methods for achieving such high transmittance include the following (1) and (2). However, the methods are not limited to these.

[0016] (1) Reduce the content of structures having an absorption band around 1310 nm (e.g., aromatic rings) as components in the adhesive composition. For example, it is effective to mainly use an aliphatic epoxy compound or an alicyclic epoxy compound as component (B).

[0017] (2) To suppress light scattering (clouding) due to phase separation of the cured product. For example, to improve the compatibility between component (A) and component (B), it is effective to incorporate a (meth)acrylate compound having a polar group (e.g., a hydroxyl group, an alkoxy group, etc.).

[0018] In particular, when using fluorine-containing (meth)acrylates, it is preferable to avoid using those having an aromatic ring as component (B) (for example, bisphenol-type epoxy resins) from the viewpoint of compatibility. This is because the combination of fluorine atoms and aromatic rings tends to induce phase separation during curing, which can cause light scattering (clouding).

[0019] In this specification, the infrared transmittance of a cured adhesive composition can be determined by measuring a sample using a spectrophotometer. A sample can be prepared by the following procedure. First, a 500 μm thick spacer film is placed on a glass plate (substrate) so that its dimensions are 20 mm in length, 20 mm in width, and 500 μm in thickness, and the adhesive composition is applied to the glass plate and molded. Next, the molded adhesive composition is irradiated with ultraviolet light using an ultraviolet light irradiation device (wavelength: 365 nm), and 600 seconds after the ultraviolet light irradiation is finished, the spacer film is peeled off and used as the sample. The ultraviolet light irradiation can be set to conditions that allow the molded adhesive composition to cure sufficiently, for example, an illuminance of 30 mW / cm². ２ And for a time of 30 seconds, i.e., an integrated light intensity of 900 mJ / cm². ２ The process may be carried out under the following conditions. Furthermore, a glass plate is used as the base material. The ultraviolet light may be, for example, light with a wavelength of 10 to 400 nm.

[0020] Next, an embodiment of each component constituting the adhesive composition will be described. By using such components, it tends to be easier to adjust the infrared transmittance of the cured product of the adhesive composition to a predetermined range.

[0021] Component (A): (meth)acrylate compound Component (A) is not particularly limited as long as it is a compound having one or more (meth)acryloyl groups. In one embodiment, Component (A) may include a (meth)acrylate having a fluorine-containing organic group (hereinafter sometimes referred to as "Component (A1)"). In one embodiment, Component (A) may not include Component (A1). In one embodiment, Component (A) may include a (meth)acrylate having a hydroxyl group (hereinafter sometimes referred to as "Component (A2)"). In one embodiment, Component (A) may include a (meth)acrylate having an alkoxy group (hereinafter sometimes referred to as "Component (A3)".

[0022] The inclusion of component (A1) in component (A) makes it possible to lower the refractive index in the cured product of the adhesive composition. Component (A1) may be, for example, a (meth)acrylate having a fluoroalkyl group. Examples of (meth)acrylates having a fluoroalkyl group include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl (meth)acrylate, perfluoroethylmethyl (meth)acrylate, perfluoropropylmethyl (meth)acrylate, perfluorobutylmethyl (meth)acrylate, perfluoropentylmethyl (meth)acrylate, perfluorohexylmethyl (meth)acrylate, perfluoroheptylmethyl (meth)acrylate, perfluorooctylmethyl (meth)acrylate, perfluorononylmethyl (meth)acrylate, perfluorodecylmethyl (meth)acrylate, perfluoroundecylmethyl (meth)acrylate, perfluorododecylmethyl (meth)acrylate, and perfluorotridecyl Examples include methyl (meth)acrylate, perfluorotetradecyl methyl (meth)acrylate, 2-(trifluoromethyl)ethyl (meth)acrylate, 2-(perfluoroethyl)ethyl (meth)acrylate, 2-(perfluoropropyl)ethyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 2-(perfluoropentyl)ethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluoroheptyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorononyl)ethyl (meth)acrylate, 2-(perfluorotridecyl)ethyl (meth)acrylate, 2-(perfluorotetradecyl)ethyl (meth)acrylate, and 1H,1H,5H-octafluoropentyl (meth)acrylate.

[0023] (A1) In a (meth)acrylate having a fluoroalkyl group as component, the number of carbon atoms of the fluoroalkyl group may be, for example, 1 to 20, 2 or more, 3 or more, 4 or more, or 6 or more, or 18 or less, 16 or less, 14 or less, or 12 or less, from the viewpoint of lowering the refractive index of the cured product.

[0024] (A1) In a (meth)acrylate having a fluoroalkyl group as a component, the proportion of fluorine atoms in the fluoroalkyl group is calculated based on the total amount of hydrogen and fluorine atoms directly bonded to the carbon atoms constituting the fluoroalkyl group. For example, in the trifluoromethyl group of trifluoromethyl (meth)acrylate, there are 3 fluorine atoms and 0 hydrogen atoms, so the proportion of fluorine atoms is 100%. For example, in the 2,2,2-trifluoroethyl group of 2,2,2-trifluoroethyl (meth)acrylate, there are 3 fluorine atoms and 2 hydrogen atoms, so the proportion of fluorine atoms is 60%. From the viewpoint of lowering the refractive index of the cured product, the proportion of fluorine atoms may be, for example, 100% or less, 90% or less, or 80% or less, and may be 30% or more, 40% or more, or 50% or more.

[0025] The inclusion of component (A2) in component (A) can further improve the curability and adhesion of the adhesive composition. Component (A2) has excellent compatibility with component (B), and can therefore suppress phase separation during curing of the adhesive composition and enhance the transparency of the cured product (preventing a decrease in transmittance due to light scattering). Component (A2) may be, for example, a (meth)acrylate having a hydroxyalkyl group. Examples of (meth)acrylates having a hydroxyalkyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0026] By including component (A3) in component (A), the compatibility with component (B) can be further improved, and the transmittance of the cured adhesive composition can be further improved. Because component (A3) has excellent compatibility with component (B), it can suppress phase separation during curing of the adhesive composition and play a role in increasing the transparency of the cured product (preventing a decrease in transmittance due to light scattering). Component (A3) may be, for example, a (meth)acrylate having an alkoxyalkyl group. Examples of component (A3) include 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate.

[0027] Component (A) may contain other (meth)acrylates (hereinafter sometimes referred to as "component (A4)") to the extent that they do not impair the effects of the present disclosure. Examples of component (A4) include monofunctional (meth)acrylates having one (meth)acryloyl group other than components (A1), (A2), and (A3), and polyfunctional (meth)acrylates having two or more (meth)acryloyl groups other than components (A1), (A2), and (A3).

[0028] Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates having alkyl groups such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate; alkenyl (meth)acrylates having alkenyl groups such as 3-butenyl (meth)acrylate; (meth)acrylates having aromatic groups such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate. Examples include (meth)acrylates having alicyclic groups such as acrylate and dicyclopentanyl (meth)acrylate; (meth)acrylates having heterocyclic groups such as 4-(meth)acryloylmorpholine; alkoxy polyalkylene glycol (meth)acrylates such as methoxyethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, methoxyhexaethylene glycol (meth)acrylate, and methoxyoctaethylene glycol (meth)acrylate; polyalkylene glycol mono(meth)acrylates such as tetraethylene glycol mono(meth)acrylate, hexaethylene glycol mono(meth)acrylate, and octapropylene glycol mono(meth)acrylate; and (meth)acrylates having a siloxane skeleton.

[0029] Examples of polyfunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated polypropylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. Aliphatic (meth)acrylates such as acrylates, glycerin di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethoxylated 2-methyl-1,3-propanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate; ethoxylated bisphenol A type di(meth)acrylate, propoxylated bisphenol A type di(meth)acrylate, ethoxylated Examples include aromatic (meth)acrylates such as propoxylated bisphenol A type di(meth)acrylate, ethoxylated bisphenol F type di(meth)acrylate, propoxylated bisphenol F type di(meth)acrylate, ethoxylated propoxylated bisphenol F type di(meth)acrylate, ethoxylated fluorene type di(meth)acrylate, propoxylated fluorene type di(meth)acrylate, and ethoxylated propoxylated fluorene type di(meth)acrylate.

[0030] When the (A) component contains the (A1) component, the content of the (A1) component may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of the (A) component, from the viewpoint of reducing the refractive index of the cured product, and may be 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less.

[0031] When the (A) component contains the (A1) component, the content of the (A2) component may be 0.1% by mass or more, 1% by mass or more, 2% by mass or more, or 3% by mass or more, based on the total amount of the (A) component, from the viewpoints of the curability and adhesion of the adhesive composition, and may be 15% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less.

[0032] When the (A) component contains the (A1) component, the content of the (A3) component may be 0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 35% by mass or more, based on the total amount of the (A) component, from the viewpoint of compatibility with the (B) component, and may be 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less.

[0033] When the (A) component contains the (A1) component, the content of the (A4) component may be 0 to 90% by mass, 0 to 75% by mass, 0 to 60% by mass, 0 to 45% by mass, 0 to 30% by mass, or 0 to 15% by mass, based on the total amount of the (A) component.

[0034] When the (A) component contains the (A1) component, the total content of the (A3) component and the (A4) component may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of the (A) component, and may be 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0035] When the (A) component contains the (A1) component, the content of the (A) component (the total of the (A1) component, the (A2) component, the (A3) component, and the (A4) component) may be 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of the adhesive composition, and may be 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less.

[0036] In the case where component (A) does not contain component (A1), the content of component (A2) may be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more, based on the total amount of component (A), and may be 20% by mass or less, 15% by mass or less, 10% by mass or less, or 8% by mass or less, from the viewpoint of the curability and adhesion of the adhesive composition.

[0037] If component (A) is in a form that does not contain component (A1), the content of component (A3) may be 0 to 90% by mass, 0 to 75% by mass, 0 to 60% by mass, 0 to 45% by mass, 0 to 30% by mass, or 0 to 15% by mass, based on the total amount of component (A), from the viewpoint of compatibility with component (B).

[0038] If component (A) is in a form that does not contain component (A1), the content of component (A4) may be 10% by mass or more, 25% by mass or more, 40% by mass or more, 55% by mass or more, 70% by mass or more, 85% by mass or more, or 90% by mass or more, based on the total amount of component (A), and may be 99% by mass or less, 98% by mass or less, or 97% by mass or less.

[0039] If component (A) is in a form that does not contain component (A1), the total content of component (A3) and component (A4) may be 70% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, and may be 99% by mass or less, 98% by mass or less, or 97% by mass or less, based on the total amount of component (A).

[0040] In the case where component (A) does not contain component (A1), the content of component (A) (the sum of components (A2), (A3), and (A4)) may be 10% by mass or more, 25% by mass or more, 40% by mass or more, or 45% by mass or more, and may be 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less, based on the total amount of the adhesive composition.

[0041] Component (B): Epoxy compound Component (B) is a compound having one or more epoxy groups. Component (B) may be a compound that does not have a (meth)acryloyl group and an oxetanyl group. Component (B) may be a compound having two or more epoxy groups. Component (B) may contain an aliphatic epoxy compound (hereinafter sometimes referred to as "component (B1)"). Component (B1) is an epoxy compound having a chain-like aliphatic skeleton in its molecule. Component (B1) may be an epoxy compound that does not contain either an aromatic ring or an alicyclic structure in its molecule. Component (B) may contain an alicyclic epoxy compound (hereinafter sometimes referred to as "component (B2)"). Component (B2) is a compound having an alicyclic epoxy group. Component (B2) may be an epoxy compound that does not contain an aromatic ring in its molecule. Component (B) may contain both component (B1) and component (B2).

[0042] The inclusion of component (B1) in component (B) tends to improve the compatibility and crosslinkability of the adhesive composition. Component (B1) may be, for example, an aliphatic diglycidyl ether having at least one aliphatic group (linking group) selected from the group consisting of alkylene groups, oxyalkylene groups, and cycloalkylene groups. Alternatively, component (B1) may be an epoxy compound that does not have an aromatic ring.

[0043] Examples of aliphatic diglycidyl ethers include diglycidyl ethers having alkylene groups such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether; diglycidyl ethers having oxyalkylene groups such as diethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether; and diglycidyl ethers having cycloalkylene groups such as 1,4-cyclohexanedimethanol diglycidyl ether and diglycidyl-1,2-cyclohexanedicarboxylate.

[0044] If component (A) is a form containing component (A1), the content of component (B1) may be 0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total amount of component (B), and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0045] If component (A) is in a form that does not contain component (A1), the content of component (B1) may be 0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total amount of component (B), and may be 100% by mass or less, 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 65% by mass or less.

[0046] Component (B2) is a compound having an alicyclic structure and one or more epoxy groups within its molecule. Component (B2) can be broadly classified into, for example, a first alicyclic epoxy compound having an epoxy group (e.g., an epoxycyclohexyl group) formed together with two carbon atoms constituting the alicyclic ring, and a second alicyclic epoxy compound in which an epoxy group such as a glycidyl group is bonded to the alicyclic structure, based on its structure. In this disclosure, either the first alicyclic epoxy compound or the second alicyclic epoxy compound may be used alone, or both may be used in combination. Component (B2) may contain the first alicyclic epoxy compound from the viewpoint of heat resistance and crosslinkability of the adhesive composition, and may contain the second alicyclic epoxy compound from the viewpoint of surface hardness of the adhesive composition.

[0047] Examples of commercially available first alicyclic epoxy compounds include Celoxide 8010, Celoxide 2021P, and Celoxide 2081 (trade names, all manufactured by Daicel Corporation). The first alicyclic epoxy compound may also be an epoxy compound that does not have an aromatic ring.

[0048] Examples of commercially available second alicyclic epoxy compounds include EHPE3150 (1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, manufactured by Daicel Corporation) and Epolite 4000 (hydrogenated bisphenol A diglycidyl ether, manufactured by Kyoeisha Chemical Co., Ltd.). The second alicyclic epoxy compound may also be an epoxy compound that does not have an aromatic ring.

[0049] If component (A) is a form containing component (A1), the content of component (B2) may be 0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of component (B), and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0050] If component (A) is in a form that does not contain component (A1), the content of component (B2) may be 0% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 35% by mass or more, based on the total amount of component (B), and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0051] Component (B) may include, in addition to components (B1) and (B2), other epoxy compounds (hereinafter sometimes referred to as "component (B3)"), to the extent that they do not impair the effects of the present disclosure. Examples of other epoxy compounds include epoxy compounds having aromatic rings.

[0052] Examples of component (B3) include diglycidyl phthalate, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, and biphenyl aralkyl type epoxy resin.

[0053] The content of component (B3) may be 0 to 30% by mass, 0 to 20% by mass, 0 to 10% by mass, or 0 to 5% by mass, based on the total amount of component (B). The content of component (B3) (epoxy compounds having aromatic rings, etc.) may be 0% by mass, based on the total amount of component (B), from the viewpoint of further increasing the infrared transmittance of the cured product.

[0054] If component (A) is a form containing component (A1), the content of component (B) (the sum of components (B1), (B2), and (B3)) may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less, based on the total amount of the adhesive composition.

[0055] If component (A) is in a form that does not contain component (A1), the content of component (B) (the sum of components (B1), (B2), and (B3)) may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total amount of the adhesive composition.

[0056] (C) Component: Photoinitiator Component (C) is a component that initiates polymerization upon irradiation with light, and can also be called a photopolymerization initiator. Examples of (C) components include photoacid generators, photoradical generators, and photobase generators.

[0057] Component (C) may, for example, include a photoacid generator. The photoacid generator is a component that generates an acid that initiates polymerization upon irradiation with light. The photoacid generator may be a component that generates an acid that initiates polymerization upon irradiation with light (ultraviolet light) containing wavelengths in the range of 10 to 400 nm. The photoacid generator may also be a component that generates radicals that initiate radical polymerization upon irradiation with light. The photoacid generator may be a component that generates radicals and acid upon irradiation with light, and may be a component that generates radicals and acid upon irradiation with ultraviolet light.

[0058] Examples of the photoacid generator include onium salts such as sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, iodonium salts, and anilinium salts. Examples of the anion of the onium salt include, for example, BF ４ － , BR ４ － (where R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups), PF ６ － , SbF ６ － , AsF ６ － , SO ４ R － (where R represents an alkyl group), and the like.

[0059] Examples of commercially available photoacid generators include, for example, CPI-100P, CPI-110P, CPI-101A, CPI-200K, CPI-210S (all manufactured by San-Apro Ltd.), UVI-6990, UVI-6992, UVI-6976 (all manufactured by Dow Chemical Japan Ltd.), SP-150, SP-152, SP-170, SP-172, SP-300 (all manufactured by ADEKA Corporation), and the like.

[0060] The content of the photoacid generator may be, for example, 0.1 part by mass or more, 0.5 part by mass or more, or 1 part by mass or more, and may be 15 parts by mass or less, 8 parts by mass or less, or 6 parts by mass or less with respect to 100 parts by mass of the total amount of component (B) and component (D) described below.

[0061] Component (C) may contain, for example, a photo-base generator. A photo-base generator is a component that generates a base that initiates polymerization upon irradiation with light. The photo-base generator may be a component that generates a base that initiates polymerization upon irradiation with light (ultraviolet light) having a wavelength within the range of 10 to 400 nm. The photo-base generator may also be a component that generates a radical that initiates radical polymerization upon irradiation with light. The photo-base generator may be a component that generates radicals and bases upon irradiation with light, and may be a component that generates radicals and bases upon irradiation with ultraviolet light.

[0062] Examples of photobase generators include the WPBG series from Fujifilm Wako Pure Chemical Industries, Ltd. Commercially available photobase generators include WPBG-027, WPBG-140, and WPBG-165.

[0063] The amount of the photobase generator may be, for example, 0.1 parts by mass or more, 0.5 parts by mass or more, or 1 part by mass or more, and 15 parts by mass or less, 8 parts by mass or less, or 6 parts by mass or less, based on 100 parts by mass of the total amount of component (B) and component (D) described below.

[0064] Component (C) may, for example, include a photoradical generator. The photoradical generator may be used in combination with a photoacid generator or a photobase generator.

[0065] A photoradical generator is a component that generates radicals that initiate polymerization upon irradiation with light. The photoradical generator may be a component that generates radicals upon irradiation with light (ultraviolet light) containing wavelengths within the range of 10 to 400 nm. The photoradical generator may primarily act on component (A).

[0066] Photoradical generators generate free radicals in response to light. In other words, photoradical generators are compounds that generate radicals by applying external light energy. Photoradical generators may be compounds having structures such as oxime ester structures, bisimidazole structures, acridine structures, α-aminoalkylphenone structures, aminobenzophenone structures, N-phenylglycine structures, acylphosphine oxide structures, benzyldimethylketal structures, and α-hydroxyalkylphenone structures. For example, photoradical generators may be compounds having structures selected from the group consisting of oxime ester structures, α-aminoalkylphenone structures, and acylphosphine oxide structures, and may also be compounds having an acylphosphine oxide structure.

[0067] Specific examples of compounds having an oxime ester structure include 1-phenyl-1,2-butanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-o-benzoyloxime, 1,3-diphenylpropanetrione-2-(o-ethoxycarbonyl)oxime, and 1-phenyl-3-ethoxypropanetrione-2-(o-benzoyl)oxime.

[0068] Specific examples of compounds having an α-aminoalkylphenone structure include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1.

[0069] Specific examples of compounds having an acylphosphine oxide structure include bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

[0070] The amount of photoradical generator may be 0.1 to 15 parts by mass, 0.5 to 10 parts by mass, or 1 to 8 parts by mass per 100 parts by mass of the total amount of component (A).

[0071] Component (D): (meth)acrylic resin. Component (D) is a (co)polymer having structural units derived from at least a (meth)acrylate compound. Component (D) may also have structural units derived from (meth)acrylate having a cyclic ether group. A (meth)acrylic resin having such structural units can act as a component (crosslinking agent) for crosslinking cyclic ether groups such as component (B).

[0072] The (meth)acrylate having a cyclic ether group may be, for example, at least one selected from the group consisting of (meth)acrylates having an epoxy group and (meth)acrylates having an oxetanyl group. Examples of (meth)acrylates having an epoxy group include (meth)acrylates having alicyclic epoxy groups such as 3,4-epoxycyclohexylmethyl(meth)acrylate, and (meth)acrylates having epoxy groups other than alicyclic epoxy groups such as glycidyl(meth)acrylate. Examples of (meth)acrylates having an oxetanyl group include (3-ethyloxetan-3-yl)methyl(meth)acrylate. The (meth)acrylate having a cyclic ether group may also include (meth)acrylates having alicyclic epoxy groups, for example, from the viewpoint of adhesive strength.

[0073] The content of structural units derived from (meth)acrylate having a cyclic ether group may be 1 to 90 mol%, 1 to 80 mol%, 1 to 70 mol%, or 1 to 60 mol%, based on the total structural units of component (D), from the viewpoint of crosslinking with component (B), etc.

[0074] Component (D) may have structural units derived from a (meth)acrylate having a fluorine-containing organic group, from the viewpoint of adhesive strength, infrared transmittance, and refractive index.

[0075] The (meth)acrylate having a fluorine-containing organic group may be, for example, a (meth)acrylate having a fluoroalkyl group. Examples of (meth)acrylates having a fluoroalkyl group include those exemplified in component (A1).

[0076] In a (meth)acrylate having a fluoroalkyl group, the number of carbon atoms of the fluoroalkyl group may be, for example, 1 to 10, 2 or more, 8 or less, 6 or less, 4 or less, or 3 or less, from the viewpoint of compatibility with component (A) or its polymer.

[0077] In a (meth)acrylate having a fluoroalkyl group, the proportion of fluorine atoms in the fluoroalkyl group may be, for example, 100% or less, 80% or less, or 70% or less, and may be 30% or more, 40% or more, or 50% or more, from the viewpoint of compatibility with component (A) or its polymer.

[0078] The content of structural units derived from (meth)acrylate having a fluorine-containing organic group may be 10 to 99 mol%, 20 to 99 mol%, 30 to 99 mol%, or 40 to 99 mol%, based on the total structural units of the (meth)acrylic resin, from the viewpoint of compatibility with component (A) or its polymer.

[0079] The (meth)acrylic resin may have structural units other than those derived from (meth)acrylate having a cyclic ether group and structural units derived from (meth)acrylate having a fluorine-containing organic group, to the extent that they do not impair the effects of the present invention. Examples of compounds that provide other structural units include, for example, alkyl (meth)acrylates having alkyl groups, (meth)acrylates having aromatic groups, (meth)acrylates having alicyclic groups, (meth)acrylates having heterocyclic groups containing nitrogen and / or oxygen atoms, monofunctional (meth)acrylates having one (meth)acryloyl group such as alkoxy polyalkylene glycol (meth)acrylates, polyalkylene glycol mono(meth)acrylates, and (meth)acrylates having a siloxane skeleton; polyfunctional (meth)acrylates having two or more (meth)acryloyl groups such as aliphatic poly(meth)acrylates and aromatic poly(meth)acrylates; and compounds having radical polymerizable groups other than (meth)acryloyl groups such as styrene, 4-methylstyrene, vinylpyridine, vinylpyrrolidone, vinyl acetate, cyclohexylmaleimide, and phenylmaleimide.

[0080] The content of other structural units may be 0 to 40 mol%, 0 to 30 mol%, 0 to 20 mol%, or 0 to 10 mol%, based on the total structural units of the (meth)acrylic resin.

[0081] Component (D) may be a form that does not have structural units derived from a (meth)acrylate having a fluorine-containing organic group.

[0082] In the case where component (D) does not have structural units derived from (meth)acrylate having a fluorine-containing organic group, the content of structural units derived from (meth)acrylate having a cyclic ether group may be 1 to 90 mol%, 1 to 70 mol%, 1 to 50 mol%, or 1 to 30 mol%, based on the total structural units of component (D).

[0083] In the case where component (D) does not have structural units derived from (meth)acrylate having a fluorine-containing organic group, the content of other structural units may be 10 to 99 mol%, 30 to 99 mol%, 50 to 99 mol%, or 70 to 99 mol%, based on the total structural units of component (D).

[0084] The weight-average molecular weight (Mw) of the (meth)acrylic resin may be, for example, 1,000 to 200,000, 3,000 or more, 5,000 or more, or 10,000 or more, and may be 150,000 or less, 100,000 or less, 60,000 or less, or 50,000 or less. The weight-average molecular weight (Mw) is a polystyrene-converted value using a calibration curve with standard polystyrene by gel permeation chromatography (GPC). The weight-average molecular weight (Mw) can be measured, for example, by the method described in the examples.

[0085] (Meth)acrylic resins can be obtained, for example, by radical polymerization using a solution polymerization method. More specifically, they can be obtained by polymerizing monomers containing a (meth)acrylate having a cyclic ether group and a (meth)acrylate having a fluorine-containing organic group in a solvent.

[0086] The solvent can be any organic solvent commonly used in the field of radical polymerization. The solvent may be one that has a cyclic ether group (epoxy group or oxetanyl group) and does not have a radical polymerizable group. By using such a solvent, the (D) component can be incorporated into a curable resin such as a compound having a cyclic ether group (epoxy resin) as a solution after the polymerization reaction, without having to perform an isolation operation of the (D) component (removal and substitution of the solvent), and subjected to a curing reaction. Examples of solvents include those commonly used in the field of epoxy resin diluents, and epoxy resins that are liquid at 25°C. From the viewpoint of being usable as component (B1), the solvent may be, for example, an aliphatic diglycidyl ether. Examples of aliphatic diglycidyl ethers include those exemplified in component (B1).

[0087] In this specification, a radical polymerizable group means a group having a carbon-carbon double bond. Examples of radical polymerizable groups include (meth)acryloyl groups, vinyl groups, allyl groups, styryl groups, alkenyl groups, alkenylene groups, and maleimide groups.

[0088] The amount of solvent used can be appropriately determined depending on the type of monomer, reaction conditions, and the solid content concentration of the (meth)acrylic resin solution.

[0089] When polymerizing monomers, thermal radical generators, additives, etc., may be added as needed.

[0090] Examples of thermal radical generators include organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-amyl peroxy-2-ethylhexanoate, and t-butyl peroxy-2-ethylhexanoate; and azo compounds such as 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl-2,2'-azobis(2-methylpropionate).

[0091] The amount of thermal radical generator added can be set appropriately according to the type of monomer, reaction conditions, etc., and is not particularly limited, but may be 100 to 200,000 ppm by mass, 100 to 100,000 ppm by mass, 1,000 to 100,000 ppm by mass, 1,000 to 50,000 ppm by mass, 3,000 to 30,000 ppm by mass, or 10,000 to 80,000 ppm by mass, based on the total amount of monomer.

[0092] Examples of additives include chain transfer agents, antioxidants, light stabilizers, weather stabilizers, UV absorbers, and radical scavengers. The amount of additives added is not particularly limited, but may be 0.001 to 2% by mass or 0.005 to 1% by mass based on the total amount of monomers.

[0093] The polymerization temperature may be 40 to 120°C, 50 to 100°C, or 60 to 90°C. The polymerization time may be 0.1 to 24 hours, 0.5 to 20 hours, or 1 to 12 hours.

[0094] If component (A) is a form containing component (A1), the content of component (D) may be 0% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total amount of the adhesive composition, and may be 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less.

[0095] If component (A) is in a form that does not contain component (A1), the content of component (D) may be 0% by mass or more, 1% by mass or more, 3% by mass or more, or 5% by mass or more, based on the total amount of the adhesive composition, and may be 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less.

[0096] (E) Component: Oxetane compound. Component (E) is a compound having one or more oxetanyl groups. Component (E) may be a compound that does not have (meth)acryloyl groups or epoxy groups. Component (E) may be a compound having two or more oxetanyl groups. Further inclusion of component (E) in the adhesive composition tends to further enable lower refractive index in the cured product of the adhesive composition.

[0097] Examples of commercially available products of component (E) include Aronoxetane® OXT-101, OXT-211, OXT-213, OXT-212, OXT-121, and OXT-221 (trade names, all manufactured by Toagosei Co., Ltd.).

[0098] The content of component (E) may be 1% by mass or more, 3% by mass or more, or 5% by mass or more, and may be 30% by mass or less, 20% by mass or less, or 10% by mass or less, based on the total amount of the adhesive composition.

[0099] Component (F): Coupling agent Component (F) may be, for example, a silane coupling agent. The silane coupling agent may be, for example, a compound having a hydrolyzable silyl group and a functional group that can react with either a (meth)acrylate compound or an epoxy compound. The hydrolyzable silyl group is, for example, a group having a silicon atom and 1 to 3 alkoxy groups bonded to the silicon atom. The number of carbon atoms in the alkoxy group bonded to the silicon atom may be, for example, 1 to 4. Examples of functional groups include amino groups such as primary amino groups and secondary amino groups, epoxy groups, mercapto groups, (meth)acryloyl groups, isocyanate groups, etc. The functional group may be an isocyanate group because the effects of this disclosure are more easily obtained. That is, component (F) may contain a silane coupling agent having an isocyanate group. In this specification, compounds having a hydrolyzable silyl group and a (meth)acryloyl group, as well as compounds having a hydrolyzable silyl group and an epoxy group, are classified as silane coupling agents.

[0100] Examples of commercially available silane coupling agents include KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KBM-4803, KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, KBM-5803, KBM-602, KBM-603, KBM-903, KBE-903, KBE-9103P, KBM-573, KBM-575, KBM-802, KBM-803, and KBE-9007N (product names, all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0101] The silane coupling agent content may be 0.1% by mass or more, 0.2% by mass or more, or 0.5% by mass or more, based on the total amount of the adhesive composition, and may be 10% by mass or less, 8% by mass or less, 5% by mass or less, 3% by mass or less, or 2% by mass or less.

[0102] The adhesive composition may contain other components. Examples of other components include antioxidants and photosensitizers.

[0103] Examples of antioxidants include quinone derivatives such as benzoquinone and hydroquinone, phenol derivatives (hindered phenol derivatives) such as 4-methoxyphenol and 4-t-butylcatechol, aminooxyl derivatives such as 2,2,6,6-tetramethylpiperidine-1-oxyl and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and hindered amine derivatives such as tetramethylpiperidyl methacrylate.

[0104] The antioxidant content may be 0.1 to 10% by mass, based on the total amount of the adhesive composition.

[0105] Examples of photosensitizers include benzoflavin, anthracene, pyrene, thioxanthone, benzophenone, anthraquinone, camphorquinone, coumarin dyes, and oxazole compounds.

[0106] The amount of photosensitizer may be 0.01 to 10% by mass, or 0.01 to 1% by mass, based on the total amount of the adhesive composition.

[0107] The refractive index of the adhesive composition at room temperature (25°C) may be, for example, 1.470 or less, 1.468 or less, 1.466 or less, 1.464 or less, 1.462 or less, 1.460 or less, 1.458 or less, 1.456 or less, 1.454 or less, 1.452 or less, 1.450 or less, 1.448 or less, 1.446 or less, 1.444 or less, 1.442 or less, 1.440 or less, 1.438 or less, 1.436 or less, 1.434 or less, 1.432 or less, or 1.430 or less. The refractive index may be, for example, 1.350 or more, 1.380 or more, or 1.400 or more. In this specification, the refractive index can be determined by measuring it using a refractometer at a wavelength of 589 nm.

[0108] The adhesive composition can be prepared by mixing (or kneading) components (A), (B), and (C), as well as components (D), (E), (F), and other components. Mixing can be carried out using a combination of conventional agitators, rotary mixers, and other dispersers as appropriate. In addition, degassing treatment by vacuum degassing or the like may be applied as appropriate during mixing.

[0109] The adhesive composition can form an adhesive layer (adhesive portion) with excellent adhesion to various substrates. The adhesive portion can be obtained by placing the adhesive composition in a predetermined position to form an adhesive portion precursor, and then irradiating the placed adhesive portion precursor with light. Light irradiation may be performed while heating. The adhesive portion contains a cured product of the adhesive composition. Light irradiation may be performed directly on the adhesive composition or through a transparent resin, glass, or the like.

[0110] The light used for illumination may be light containing wavelengths in the range of 150 to 750 nm or light containing wavelengths in the range of 254 to 405 nm, and may also be ultraviolet light.

[0111] Examples of light sources for illumination include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, metal halide lamps, and LED light sources.

[0112] The irradiation time, illuminance, and total light intensity can be set as appropriate. The irradiation time may be, for example, 60 seconds or less, 40 seconds or less, or 30 seconds or less, or 1 second or more. The illuminance of the irradiation is 400 mW / cm². ２ Below, 250mW / cm ２ The following, or 150 mW / cm² ２ The following may be true: 10 mW / cm² ２ The above is sufficient. The integrated light intensity of the light irradiation is 6000 mJ / cm². ２ Below, 4500mJ / cm ２ The following, or 2500 mJ / cm² ２ The following may be true: 100 mJ / cm² ２ That's all.

[0113] The atmosphere for light irradiation is not particularly limited, but may be, for example, an air atmosphere or an inert gas atmosphere such as nitrogen or argon.

[0114] When light irradiation is performed while heating, the heating conditions may be, for example, 60 to 150°C.

[0115] After irradiating the bonding precursor with light, the bonding precursor may be further subjected to heat treatment. The heat treatment can be carried out, for example, under conditions of a heating temperature of 60 to 180°C and a holding time of 5 to 60 minutes.

[0116] [Adhesive] An adhesive according to one embodiment comprises a first adherend, a second adherend, and an adhesive portion that adheres the first adherend and the second adherend to each other. The adhesive portion contains a cured product of the adhesive composition described above.

[0117] Examples of the first and second adherends include organic materials such as polyolefin resin, polyamide resin, ABS (acrylonitrile butadiene styrene) resin, PC (polycarbonate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, acrylic resin, and transparent resin; inorganic materials such as steel, stainless steel, individual metals (aluminum, copper, nickel, chromium, etc.) or alloys of these metals, glass, and silicon wafers; wood; and rubber. Furthermore, composite materials of the above-mentioned plastics and inorganic materials can also be used as the first and second adherends. Either the first or second adherend may be a transparent resin or glass from the viewpoint of light irradiation.

[0118] The thicknesses of the first adherend and the second adherend may be, for example, 0.1 to 2.0 mm, 0.1 to 1.0 mm, or 0.1 to 0.5 mm.

[0119] The adhesive can be obtained, for example, by a method that includes the steps of: applying an adhesive composition onto a first adherend to form an adhesive precursor containing the adhesive composition; placing a second adherend on the adhesive precursor to create a laminate; and irradiating the adhesive precursor of the laminate with light to form an adhesive portion containing a cured product of the adhesive composition.

[0120] The adhesive composition can be applied using a knife coater, roll coater, applicator, comma coater, die coater, dispenser, etc.

[0121] The light irradiation conditions for the adhesive precursor of the laminate (wavelength of light, light source, irradiation time, illuminance, integrated light amount, etc.) may be the same as the light irradiation conditions described above (wavelength of light, light source, irradiation time, illuminance, integrated light amount, etc.).

[0122] Light irradiation of the adhesive precursor of the laminate may be performed while heating. The heating conditions (heating temperature, etc.) may be the same as those described above.

[0123] After irradiating the adhesive surface precursor of the laminate with light, the adhesive surface precursor may be further subjected to heat treatment. The heat treatment conditions (heating temperature, holding time, etc.) may be the same as those described above.

[0124] The thickness of the adhesive portion containing the cured product of the adhesive composition may be, for example, 0.01 to 1.0 mm, 0.01 to 0.5 mm, or 0.01 to 0.2 mm.

[0125] The adhesive composition of this embodiment has high infrared transmittance of the cured product and excellent adhesive strength, making it suitable for use as an adhesive (adhesive for optical devices) in optical devices such as optical fibers used in communications, sensing, medical applications, etc.

[0126] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0127] [Synthesis of (meth)acrylic resin] The following raw materials were prepared: ・(meth)acrylate compounds M-3F: Trifluoroethyl methacrylate (Light Ester M-3F, manufactured by Kyoeisha Chemical Co., Ltd.) TTA-15: 3,4-Epoxycyclohexylmethyl methacrylate (manufactured by Sun Chemical Co., Ltd.) BA: Butyl acrylate (manufactured by Toagosei Co., Ltd.) BMA: Butyl methacrylate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) MMA: Methyl methacrylate (Acryester M, manufactured by Mitsubishi Chemical Corporation) GMA: Glycidyl methacrylate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) ・Thermal radical generator V-601: Dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm Wako Pure Chemical Corporation) ・Solvent NPG(D): Neopentyl glycol diglycidyl ether (Epogose® NPG(D)) (manufactured by Yokkaichi Gosei Co., Ltd.) HD(D): 1,6-Hexanediol diglycidyl ether (EpoGose® HD(D)) (manufactured by Yokkaichi Synthetic Co., Ltd.) BisF: Bisphenol F type epoxy resin (EPICLON® 830, manufactured by DIC Corporation, liquid at 25°C)

[0128] <Production Example 1> Mixture (a-1) was prepared by mixing 84.06 g of M-3F and 98.12 g of TTA-15 (molar ratio of M-3F / TTA-15 = 50% / 50%) with 10.17 g of V-601 and 23.72 g of NPG(D). Separately, solution (b-1) was prepared by dissolving 1.82 g of V-601 in 7.29 g of NPG(D).

[0129] 163.2 g of NPG(D) was placed in a flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube. The mixture was stirred under a nitrogen atmosphere while gas substitution was performed, and the temperature was raised to 85°C. Next, mixture (a-1) was added dropwise to the flask over 2 hours. After the dropwise addition was complete, the mixture was stirred at 85°C for 20 minutes, then solution (b-1) was added, and the mixture was stirred for a further 7 hours. Then, while continuing to stir, the mixture was cooled to room temperature (25°C) to obtain a solution containing (meth)acrylic resin D-1 of Production Example 1. The solid content concentration was 50% by mass. Note that the solid content of the solution containing (meth)acrylic resin refers to the components of the solution other than the solvent.

[0130] <Production Example 2> Mixture (a-2) was prepared by mixing 144.38 g of M-3F and 42.13 g of TTA-15 (molar ratio of M-3F / TTA-15 = 80% / 20%) with 5.78 g of V-601 and 24.11 g of NPG(D). Separately, solution (b-2) was prepared by dissolving 1.87 g of V-601 in 7.46 g of NPG(D).

[0131] 162.44 g of NPG(D) was placed in a flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube. The mixture was stirred under a nitrogen atmosphere while gas substitution was performed, and the temperature was raised to 85°C. Next, mixture (a-2) was added dropwise to the flask over 2 hours. After the dropwise addition was complete, the mixture was stirred at 85°C for 20 minutes, then solution (b-2) was added, and the mixture was stirred for a further 7 hours. Then, while continuing to stir, the mixture was cooled to room temperature (25°C) to obtain a solution containing (meth)acrylic resin D-2 of Production Example 2. The solid content concentration was 50% by mass.

[0132] <Production Example 3> A solution containing (meth)acrylic resin D-3 of Production Example 3 was obtained by the same procedure as in Production Example 2, except that the solvent was changed from NPG(D) to HD(D). The solid content concentration was 50% by mass.

[0133] <Production Example 4> Mixture (a-4) was prepared by mixing 182.17 g of M-3F (molar ratio of M-3F / TTA-15 = 100% / 0%), 10.17 g of V-601, and 23.72 g of NPG(D). A solution containing the (meth)acrylic resin D-4 of Production Example 4 was obtained by following the same procedure as in Production Example 1, except that mixture (a-1) was replaced with mixture (a-4). The solid content concentration was 50% by mass.

[0134] <Production Example 5> Mixture (a-5) was prepared by mixing 95.41 g of BA, 82.81 g of MMA, and 11.76 g of GMA (molar ratio of BA / MMA / GMA = 45% / 50% / 5%) with 2.28 g of V-601 and 24.42 g of BisF. Separately, solution (b-5) was prepared by dissolving 1.87 g of V-601 in 7.46 g of BisF. A solution containing the (meth)acrylic resin D-5 of Production Example 5 was obtained by following the same procedure as in Production Example 2, except that mixture (a-2) was changed to mixture (a-5) and solution (b-2) was changed to solution (b-5). The solid content concentration was 50% by mass.

[0135] <Production Example 6> Mixture (a-6) was prepared by mixing 18.67 g of BMA, 112.62 g of MMA, and 7.50 g of GMA (molar ratio of BMA / MMA / GMA = 10% / 86% / 4%) with 2.28 g of V-601 and 24.42 g of HD(D). Separately, solution (b-6) was prepared by dissolving 1.87 g of V-601 in 7.46 g of HD(D). A solution containing the (meth)acrylic resin D-6 of Production Example 6 was obtained by following the same procedure as in Production Example 5, except that mixture (a-5) was changed to mixture (a-6), solution (b-5) was changed to solution (b-6), the solvent was changed from BisF to HD(D), and the amount of HD(D) to be placed in the flask was changed to 182.5 g. The solid content concentration was 40% by mass.

[0136] <Production Example 7> Mixture (a-7) was prepared by mixing 19.98 g of BMA, 108.77 g of MMA, and 10.03 g of TTA-15 (molar ratio of BMA / MMA / TTA-15 = 11% / 85% / 4%) with 2.28 g of V-601 and 24.42 g of NPG(D). Separately, solution (b-7) was prepared by dissolving 1.87 g of V-601 in 7.46 g of NPG(D). The solution containing the (meth)acrylic resin D-7 of Production Example 7 was obtained by following the same procedure as in Production Example 6, except that mixture (a-6) was changed to mixture (a-7), solution (b-6) was changed to solution (b-7), the solvent was changed from HD(D) to NPG(D), and the amount of NPG(D) to be charged into the flask was changed to 182.5 g. The solid content concentration was 40% by mass.

[0137] [Evaluation of (meth)acrylic resin] (Measurement of viscosity (25°C)) The viscosity of the solution containing (meth)acrylic resin at 25°C was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: VISCOMETER-TV22, applicable cone-plate rotor: 3° × R17.65) with a sample volume of 0.5 to 1.0 mL, at a rotation speed of 10 rpm. The results are shown in Table 1.

[0138] (Measurement of weight-average molecular weight (Mw)) For Mw measurement, a solution containing (meth)acrylic resin was dissolved in tetrahydrofuran (THF) to prepare a 0.2 mass% THF solution. Mw was measured by gel permeation chromatography (GPC) and derived by conversion using a calibration curve for standard polystyrene. The GPC conditions are shown below. The results are shown in Table 1. Measuring device: SHOWDEX® GPC-101 (manufactured by RESONAC Corporation) Detector: Differential refractometer SHOWDEX RI-71S (manufactured by RESONAC Corporation) Column: SHOWDEX LF-804 + LF-804 (manufactured by RESONAC Corporation) Column temperature: 40°C Eluent: Tetrahydrofuran (THF) Flow rate: 1 mL / min

[0139]

[0140] [Preparation of Adhesive Compositions] <Examples 1-25 and Comparative Examples 1-4> The adhesive compositions of Examples 1-25 and Comparative Examples 1-4, each containing the respective components, were prepared by mixing the amounts (unit: parts by mass) of each component shown in Tables 2, 3, and 4 using a rotary mixer (5 min / 1500 rpm).

[0141] Details of each ingredient are as follows: (A) Component: (meth)acrylate compound ・(A1) Component V-13F: 1H,1H,2H,2H-tridecafluorooctyl acrylate (2-(perfluorohexyl)ethyl acrylate) (manufactured by Osaka Organic Chemical Industry Co., Ltd.) M-3F: Trifluoroethyl methacrylate (light ester M-3F, manufactured by Kyoeisha Chemical Co., Ltd.) ・(A2) Component 4-HBA: 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・(A3) Component 2-MTA: 2-methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・(A4) Component A-9300S: Tris(2-acryloxyethyl) isocyanurate (trifunctional, isocyanuric acid EO modified triacrylate, manufactured by Shin Nakamura Chemical Industry Co., Ltd.) #200: Cyclic trimethylolpropane formal acrylate (viscoat #200, manufactured by Osaka Organic Chemical Industry Co., Ltd.) #295: Trimethylolpropane triacrylate (trifunctional, Viscoat #295, manufactured by Osaka Organic Chemical Industry Co., Ltd.) NOAA: n-octyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) SR420NS: 3,3,5-trimethylcyclohexyl acrylate (manufactured by Arkema) (B) component: epoxy compound (B1) component NPG(D): neopentyl glycol diglycidyl ether (Epogose® NPG(D)) (manufactured by Yokkaichi Synthetic Co., Ltd.) HD(D): 1,6-hexanediol diglycidyl ether (Epogose® HD(D)) (manufactured by Yokkaichi Synthetic Co., Ltd.) (B2) component 2021P: 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (Celoxide® 2021P, manufactured by Daicel Corporation) EHPE3150: 1,2-bis(hydroxymethyl)-1-butanol2-Epoxy-4-(2-oxyranyl)cyclohexane adduct (manufactured by Daicel Corporation) ・(B3) Component BisF: Bisphenol F type epoxy resin (EPICLON® 830, manufactured by DIC Corporation, liquid at 25°C) (C) Component: Photoinitiator CPI-110P: Sulfonium salt (photoacid generator, manufactured by Sunapro Co., Ltd.) CPI-210S: Sulfonium salt (photoacid generator, manufactured by Sunapro Co., Ltd.) (D) Component: (meth)acrylic resin D-1 from Production Example 1 D-2 from Production Example 2 D-3 from Production Example 3 D-4 from Production Example 4 D-5 from Production Example 5 D-6 from Production Example 6 D-7 from Production Example 7 (E) Component: Oxetane compound OXT-221: 3-ethyl-3-{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (Aronoxetane® OXT-221, manufactured by Toagosei Co., Ltd.) OXT-121: 1,4-bis{[(3-ethyloxetan-3-yl)methoxy]methyl}benzene (Aronoxetane® OXT-121, manufactured by Toagosei Co., Ltd.) (F) Component: Coupling agent KBE-9007N: 3-isocyanate propyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0142] In each example and comparative example, the (meth)acrylic resins D-1 to D-7 of Production Examples 1 to 7 were formulated using a solution containing the (meth)acrylic resin obtained above. The amounts of component (D) shown in Tables 2 to 4 represent the parts by mass of (meth)acrylic resin (solids) contained in the solution, and the parts by mass of the solvent (epoxy compound) contained in the solution are listed together in the column for component (B).

[0143] [Evaluation of Adhesive Compositions] (Measurement of Refractive Index) The refractive index of the adhesive composition at room temperature (25°C) was measured using an Abbemat 300 (Anton Paar, wavelength: 589 nm) with the sample volume adjusted to 0.1–0.2 mL. The results are shown in Tables 2, 3, and 4.

[0144] (Measurement of Infrared Transmittance) The infrared transmittance of the cured adhesive composition was measured using a spectrophotometer (Agilent Technologies, product name: Cary 7000) to measure the transmittance at a wavelength of 1310 nm. The measurement sample was prepared by the following procedure. First, a 500 μm thick spacer film was placed on a glass plate (substrate) with dimensions of 20 mm in length, 20 mm in width, and 500 μm in thickness, and the adhesive composition was applied to the glass plate and molded. Next, an LED lamp (Ushio Inc., wavelength: 365 nm) was used to irradiate the molded adhesive composition with an irradiance of 30 mW / cm². ２ And for a time of 30 seconds, i.e., an integrated light intensity of 900 mJ / cm². ２ Under these conditions, ultraviolet light was irradiated, and 600 seconds after the ultraviolet light irradiation ended, the spacer film was peeled off and used as the measurement sample. Glass was used as the base material for the baseline. The results are shown in Tables 2, 3, and 4.

[0145] (Measurement of Shear Strength) The adhesive strength was evaluated by measuring the following shear strength. A 50 μm thick spacer film was placed on a glass slide so that its dimensions were 5 mm in length, 5 mm in width, and 50 μm in thickness, and the adhesive composition was applied to the glass slide. A glass chip measuring 7 mm in length, 7 mm in width, and 1.0 mm in thickness was placed on top of the applied adhesive composition, and an illuminance of 30 mW / cm was measured using an LED lamp (manufactured by Ushio Inc., wavelength: 365 nm). ２ And for a time of 30 seconds, i.e., an integrated light intensity of 900 mJ / cm². ２ The adhesive composition was irradiated with ultraviolet light under the specified conditions. Shear strength was measured using a bond tester (Nordson, product name: DAGE4000) at a shear rate of 180 mm / min, with the sample being measured 270 seconds after the end of ultraviolet light irradiation. The results are shown in Tables 2, 3, and 4.

[0146]

[0147]

[0148]

[0149] As shown in Tables 2, 3, and 4, when photocured under specific conditions, the adhesive compositions of Examples 1 to 25, which had high transmittance to infrared rays of a specific wavelength, exhibited good shear strength, whereas the adhesive compositions of Comparative Examples 1 to 4, which did not meet such conditions, had insufficient shear strength. Furthermore, it was found that the adhesive compositions of Examples 1 to 25 had a sufficient curing speed and a sufficiently low refractive index. From these results, it was confirmed that the adhesive composition of this disclosure, which contains a (meth)acrylate compound, an epoxy compound, and a photoinitiator, can provide a cured product with sufficient adhesive strength.

Claims

1. An adhesive composition comprising a (meth)acrylate compound, an epoxy compound, and a photoinitiator, wherein when the adhesive composition is molded to a length of 20 mm × width of 20 mm × thickness of 500 μm and cured by irradiation with ultraviolet light, the resulting cured product has a transmittance of 70% or more to infrared light with a wavelength of 1310 nm.

2. The adhesive composition according to claim 1, wherein the (meth)acrylate compound comprises a (meth)acrylate having a fluorine-containing organic group.

3. The adhesive composition according to claim 1, wherein the (meth)acrylate compound does not contain a (meth)acrylate having a fluorine-containing organic group.

4. The adhesive composition according to claim 1, wherein the (meth)acrylate compound comprises a (meth)acrylate having a hydroxyl group.

5. The adhesive composition according to claim 1, wherein the (meth)acrylate compound comprises a (meth)acrylate having an alkoxy group.

6. The adhesive composition according to claim 1, further comprising (meth)acrylic resin.

7. The adhesive composition according to claim 6, wherein the (meth)acrylic resin has structural units derived from (meth)acrylate having a cyclic ether group.

8. The adhesive composition according to claim 7, wherein the (meth)acrylate having a cyclic ether group comprises a (meth)acrylate having an alicyclic epoxy group.

9. The adhesive composition according to claim 7, wherein the (meth)acrylic resin further comprises structural units derived from (meth)acrylate having a fluorine-containing organic group.

10. The adhesive composition according to claim 1, wherein the epoxy compound comprises an aliphatic epoxy compound.

11. The adhesive composition according to claim 10, wherein the epoxy compound further comprises an alicyclic epoxy compound.

12. The adhesive composition according to claim 1, further comprising a coupling agent.

13. The irradiation of ultraviolet light results in an illuminance of 30 mW / cm². ２ The adhesive composition according to claim 1, which is carried out under the condition of a time of 30 seconds.

14. An adhesive comprising a first adherend, a second adherend, and an adhesive portion for adhering the first adherend and the second adherend to each other, wherein the adhesive portion contains a cured product of the adhesive composition according to any one of claims 1 to 13.

Images