CN113165351A

CN113165351A - Adhesive composition, adhesive sheet, and laminate

Info

Publication number: CN113165351A
Application number: CN201980082073.0A
Authority: CN
Inventors: 山口贵迪; 山本真之
Original assignee: Oji Holdings Corp
Current assignee: Oji Holdings Corp
Priority date: 2018-12-11
Filing date: 2019-12-11
Publication date: 2021-07-23
Also published as: KR20210092281A; TW202031830A; WO2020122111A1; JP2020094114A

Abstract

Provided is an adhesive composition which can improve metal corrosion resistance, ultraviolet absorption, adhesive force, holding power, level difference filling performance and foreign matter filling performance. An adhesive composition; an adhesive sheet; a laminate, the adhesive composition comprising: a copolymer of a non-crosslinkable monomer and a crosslinkable monomer having a functional group, a crosslinking agent, and an ultraviolet absorber, wherein the non-crosslinkable monomer constituting the copolymer comprises a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer and a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer, the crosslinkable monomer constituting the copolymer comprises a crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group, and an amino group, and the crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group, and an amino group is contained in the copolymer in a mass ratio of 20 to 60% by mass, the mass ratio of the unit derived from the monomer having an acid group is less than 0.5 mass%, and the ultraviolet absorber is liquid or oily at 23 ℃.

Description

Adhesive composition, adhesive sheet, and laminate

Technical Field

The invention relates to an adhesive composition, an adhesive sheet and a laminate.

Background

In recent years, display devices such as Liquid Crystal Displays (LCDs) and devices in which a display device and an input device are combined, such as touch panels, have been widely used in various fields. Among them, the capacitive touch panel is rapidly spread due to its functionality, and is particularly used in a mobile phone, a smart phone, and the like. Pressure-sensitive adhesive sheets are used for bonding optical members in the production of mobile phones, smart phones, and the like.

As an adhesive composition constituting an adhesive sheet, an adhesive composition containing a polymer and a crosslinking agent is known (see patent documents 1 to 4).

Patent document 1 describes an optical adhesive containing an acrylic polymer and an ultraviolet absorber having a maximum absorption wavelength at a wavelength of 350nm or more, wherein the ultraviolet absorber contains at least one compound that is oily or liquid at 23 ℃ and is 3 to 8 parts by mass per 100 parts by mass of the solid content of the adhesive.

Patent document 2 describes an acrylic adhesive composition containing an acrylic resin (a) and an ultraviolet absorber (B) having a maximum absorption wavelength of 345nm or more, wherein the acrylic resin (a) is an acrylic resin substantially free of an acidic group, and the content of the ultraviolet absorber (B) is 3 to 9 parts by mass with respect to 100 parts by mass of the acrylic resin (a).

Patent document 3 describes an optical foil-shaped adhesive having a light transmittance at a wavelength of 350nm of 10% or less, which is obtained by crosslinking an adhesive composition containing: a hydroxyl group-containing adhesive component, a crosslinking agent capable of reacting with a hydroxyl group, and an ultraviolet absorber having no hydroxyl group.

Patent document 4 describes a laminate comprising an adhesive composition derived from a precursor comprising: about 60 to about 95 parts by mass of an alkyl acrylate having 1 to 14 carbon atoms in the alkyl group, 0 to about 5 parts by mass of a polar monomer capable of copolymerization, and about 5 to 50 parts by mass of a hydroxyl group-containing monomer having an OH equivalent of less than 400.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2012-014043

Patent document 2: japanese laid-open patent publication No. 2014-196377

Patent document 3: japanese laid-open patent publication No. 2012-207055

Patent document 4: japanese Kohyo publication No. 2012-504512

Disclosure of Invention

Problems to be solved by the invention

Since mobile phones, smart phones, and the like are exposed to sunlight when used outdoors, ultraviolet absorbability is sometimes required for pressure-sensitive adhesive layers and pressure-sensitive adhesive sheets formed from pressure-sensitive adhesive compositions in order to prevent deterioration of members in mobile phones and smart phone products.

In the production of mobile phones, smart phones, and the like, an adhesive layer or an adhesive sheet may be bonded to an ITO (Indium Tin Oxide) electrode or a metal mesh electrode, and in such a case, the ITO electrode or the metal mesh electrode may be corroded by an acid contained in the adhesive layer or the adhesive sheet. Since the ITO electrode and the metal mesh electrode are members having irregularities, bubbles may be generated in the irregularities when the adhesive layer and the adhesive sheet are used by being bonded to the ITO electrode and the metal mesh electrode. From the above, when an adhesive layer or an adhesive sheet is used by bonding an ITO electrode or a metal mesh electrode, metal corrosion resistance and level difference filling property are required. When a mobile phone, a smartphone, or the like is used for a long time in a high-temperature and high-humidity environment, it is also required that the pressure-sensitive adhesive sheet and the adherend have no bubble and have a good level difference filling property (i.e., have good durability).

Further, when the dissimilar materials are bonded, external dust, foreign matter, or the like may be caught. Therefore, foreign matter embeddability is required in which bubbles are not generated even when the dust and the foreign matter are sandwiched.

Further, adhesive compositions used for adhesive sheets for cell phones, smart phones, and the like are required to have these properties and also to have adhesive force and holding power.

The present inventors have studied the adhesive composition described in the examples of patent document 1, and as a result, have found that the copolymer has poor metal corrosion resistance due to the large amount of units having an acidic group.

The present inventors have studied the pressure-sensitive adhesive composition described in the examples of patent document 2 and found that the ultraviolet absorber easily suppresses crosslinking of the copolymer as the main component and has poor holding power.

The present inventors have studied the pressure-sensitive adhesive composition described in the examples of patent document 3, and as a result, have found that since ultraviolet absorbability is exhibited by blending a large amount of an ultraviolet absorber which is solid (not liquid or oil) at 23 ℃ and has no hydroxyl group, at least one of foreign matter embeddability and adhesive force (balance between both) is poor. In addition, adhesive compositions containing a large amount of an ultraviolet absorber that is solid at 23 ℃ may suffer from whitening and defects due to the compatibility (recrystallization) of the ultraviolet absorber.

On the other hand, patent document 4 does not describe an ultraviolet absorber.

Accordingly, an object of the present invention is to provide an adhesive composition that can improve metal corrosion resistance, ultraviolet absorption, adhesion, holding power, level difference filling ability, and foreign matter filling ability.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that an adhesive layer having excellent metal corrosion resistance, ultraviolet absorbability, adhesion, holding power, level difference filling property, and foreign matter filling property can be formed by obtaining an adhesive composition containing: a copolymer having a structural unit derived from a monomer having a glass transition temperature in a specific range when forming a homopolymer, and having a mass ratio of a unit having any of a hydroxyl group, an amide group, or an amino group to a unit having an acidic group in a specific range; a crosslinking agent; and an ultraviolet absorber which is liquid or oily at 23 ℃.

Specifically, the present invention and the configuration of the preferred embodiment of the present invention are as follows.

[1] An adhesive composition comprising: a copolymer of a non-crosslinkable monomer and a crosslinkable monomer having a functional group, a crosslinking agent and an ultraviolet absorber,

the copolymer contains, as units constituting the non-crosslinkable monomer, a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower in the formation of a homopolymer and a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher in the formation of a homopolymer,

the copolymer contains, as a unit constituting the crosslinkable monomer, a unit derived from a crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group and an amino group,

the mass ratio of the units derived from the crosslinkable monomer having any one of a hydroxyl group, an amide group and an amino group as the functional group in the copolymer is 20 to 60% by mass,

the mass ratio of the unit derived from the monomer having an acidic group in the units constituting the copolymer is less than 0.5% by mass,

the UV absorber is liquid or oily at 23 deg.C.

[2] The adhesive composition according to [1], wherein the mass ratio of the unit derived from the monomer having a glass transition temperature of-60 ℃ or lower to the unit derived from the monomer having a glass transition temperature of-15 ℃ or higher among the units constituting the non-crosslinkable monomer in the copolymer is 1: 1-5: 1.

[3] the adhesive composition according to [1], wherein the mass ratio of the unit derived from the monomer having a glass transition temperature of-60 ℃ or lower to the unit derived from the monomer having a glass transition temperature of-15 ℃ or higher among the units constituting the non-crosslinkable monomer in the copolymer is 3: 1-5: 1.

[4] the adhesive composition according to any one of [1] to [3], wherein the copolymer contains a unit derived from an acrylate ester as a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower,

the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher contains a unit derived from a methacrylate ester,

the acrylate and methacrylate ester structures are the same.

[5] The adhesive composition according to any one of [1] to [4], wherein the copolymer contains a unit derived from 2-ethylhexyl acrylate as a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower,

the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher contains a unit derived from 2-ethylhexyl methacrylate.

[6] The adhesive composition according to any one of [1] to [5], wherein the crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group and an amino group is 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate.

[7] The adhesive composition according to any one of [1] to [6], wherein the crosslinking agent is one or more selected from a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound.

[8] The adhesive composition according to any one of [1] to [7], wherein the ultraviolet absorber is a compound having a hydroxyl group.

[9] The adhesive composition according to any one of [1] to [8], wherein the ultraviolet absorber is contained in an amount of 0.1 to 8 parts by mass per 100 parts by mass of the copolymer.

[10] An adhesive sheet having an adhesive layer,

the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [9 ].

[11] The adhesive sheet according to [10], wherein the 90 ° peel force of the adhesive layer is 10N or more.

[12] The adhesive sheet according to [10] or [11], which comprises a 1 st release sheet on one surface of the adhesive layer,

the other surface of the adhesive layer is provided with a 2 nd release sheet,

the peel force of the 1 st peel sheet is different from that of the 2 nd peel sheet.

[13] A laminate having an adherend on at least one surface of the pressure-sensitive adhesive sheet according to [10] or [11 ].

[14] The laminate according to [13], wherein the metal or the metal oxide is provided on a surface of any layer of the laminate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided an adhesive composition capable of forming an adhesive layer having excellent metal corrosion resistance, ultraviolet absorbability, adhesion, holding power, level difference filling properties, and foreign matter filling properties.

Drawings

Fig. 1 is a cross-sectional view showing an example of the structure of the pressure-sensitive adhesive sheet of the present invention.

Fig. 2 is a cross-sectional view showing an example of the structure of the laminate of the present invention.

Detailed Description

The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment and a specific example, but the present invention is not limited to such an embodiment. In the present specification, the numerical range expressed by the term "to" is meant to include ranges in which the numerical values before and after the term "to" are the lower limit value and the upper limit value.

In addition, "(meth) acrylic acid" is a generic name of acrylic acid and methacrylic acid.

[ adhesive composition ]

The adhesive composition of the present invention comprises: a copolymer of a non-crosslinkable monomer and a crosslinkable monomer having a functional group, a crosslinking agent, and an ultraviolet absorber.

The copolymer contains, as units constituting the non-crosslinkable monomer, a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower in the case of forming a homopolymer and a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher in the case of forming a homopolymer,

the UV absorber is liquid or oily at 23 deg.C.

According to the above configuration, the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer having excellent metal corrosion resistance, ultraviolet absorbability, adhesive strength, holding power, level difference filling ability, and foreign matter filling ability.

Specifically, the metal corrosion resistance of the adhesive layer can be improved by controlling the mass ratio of the units derived from the monomer having an acidic group in the units constituting the copolymer to a very small range.

By controlling the mass ratio of the unit derived from the crosslinkable monomer having any of a hydroxyl group, an amide group, or an amino group as a functional group in the unit constituting the copolymer to a certain extent in a large range, the probability of crosslinking between the crosslinking agent and the copolymer can be increased, and the holding power of the pressure-sensitive adhesive layer can be improved even when an ultraviolet absorber which is liquid or oily at 23 ℃. The crosslinkable monomer having any of a hydroxyl group, an amide group, or an amino group as a functional group serves as a reaction site when a crosslinking agent is used, and thus the adhesive force and the holding force can be controlled by crosslinking.

By using a copolymer having a monomer with a high glass transition temperature and a monomer with a low glass transition temperature in combination with an ultraviolet absorber which is liquid or oily at 23 ℃, it is possible to improve both (balance of both) the adhesive strength and the level difference filling property or the foreign matter filling property in the adhesive layer in addition to the ultraviolet absorber.

Further, the adhesive composition of the present invention can form an adhesive layer having excellent impact resistance. The impact resistance of the pressure-sensitive adhesive layer can be effectively improved by adjusting the composition of the copolymer or the like so that the 90 ° peel force of the pressure-sensitive adhesive layer becomes 10N or more.

Preferred embodiments of the adhesive composition of the present invention will be described below.

< copolymer >

The copolymer of a non-crosslinkable monomer and a crosslinkable monomer having a functional group used in the present invention contains, as units of the non-crosslinkable monomer constituting the copolymer, units derived from a monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer and units derived from a monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer, and contains, as units of the crosslinkable monomer constituting the copolymer, units derived from a crosslinkable monomer having a functional group of any of a hydroxyl group, an amide group, or an amino group. The mass ratio of the units derived from the crosslinkable monomer having any one of a hydroxyl group, an amide group and an amino group as the functional group in the copolymer is 20 to 60% by mass, and the mass ratio of the units derived from the monomer having an acidic group in the units constituting the copolymer is less than 0.5% by mass.

In the present invention, the copolymer is preferably an acrylic copolymer, and more preferably a crosslinkable acrylic copolymer. The copolymer is not limited as long as it contains the above-mentioned structural unit under predetermined conditions, and a known copolymer may be used.

(units constituting non-crosslinkable monomers)

Units derived from monomers having a glass transition temperature below-60 ℃ -

The copolymer contains, as a unit of a non-crosslinkable monomer constituting the copolymer, a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer. That is, the copolymer contains a unit derived from a non-crosslinkable monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer.

Examples of the non-crosslinkable monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer include 2-ethylhexyl acrylate (2EHA) and 2- (2-ethoxyethoxy) ethyl acrylate. Among them, the non-crosslinkable monomer having a glass transition temperature of-60 ℃ or lower in the formation of a homopolymer is preferably 2-ethylhexyl acrylate (2 EHA). These may be used in combination of two or more kinds as necessary.

In the non-crosslinkable monomer units, the mass ratio of the unit derived from a monomer having a glass transition temperature of-60 ℃ or lower to the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher is preferably 1: 1-5: 1, more preferably 2: 1-5: 1. further, from the viewpoint of improving the filling property of foreign matter, the mass ratio of the unit derived from the monomer having a glass transition temperature of-60 ℃ or lower to the unit derived from the monomer having a glass transition temperature of-15 ℃ or higher is particularly preferably 3: 1-5: 1.

units derived from monomers having a glass transition temperature above-15 ℃ -

The copolymer contains, as a unit of a non-crosslinkable monomer constituting the copolymer, a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer. That is, the copolymer contains a unit derived from a non-crosslinkable monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer.

Examples of the non-crosslinkable monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer include Methyl Acrylate (MA), Methyl Methacrylate (MMA), Ethyl Methacrylate (EMA), cyclohexyl acrylate (CHA), isobornyl acrylate (IBXA), tert-butyl acrylate (TBA), benzyl acrylate (BZA), and 2-ethylhexyl methacrylate (2 EHMA). Among them, the non-crosslinkable monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer is preferably Methyl Acrylate (MA) or 2-ethylhexyl methacrylate (2EHMA), and more preferably 2-ethylhexyl methacrylate (2 EHMA). These may be used in combination of two or more kinds as required.

Combination of units

The copolymer is preferably: the unit derived from a monomer having a glass transition temperature of-60 ℃ or lower in the formation of a homopolymer is an acrylate-derived unit, and the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher in the formation of a homopolymer is a methacrylate-derived unit. And it is preferable that the ester structure of the acrylate is the same as that of the methacrylate. Here, the same ester structure means: the moiety constituting the side chain containing an ester bond (in this case, the side chain means a moiety which becomes a side chain when forming a polymer) has the same structure. As the acrylic ester and the methacrylic ester having the same ester structure, for example, a combination of 2-ethylhexyl acrylate (2EHA) and 2-ethylhexyl methacrylate (2EHMA) is exemplified.

The unit derived from a monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer is more preferably a unit derived from a monomer having a glass transition temperature of-65 ℃ or lower when forming a homopolymer, and the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer is particularly preferably a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher and 0 ℃ or lower when forming a homopolymer. Among them, it is preferable that the unit derived from a monomer having a glass transition temperature of-60 ℃ or lower is 2-ethylhexyl acrylate (2EHA) and the unit derived from a monomer having a glass transition temperature of-15 ℃ or higher is 2-ethylhexyl methacrylate (2 EHMA). By adopting the above-mentioned structure for the copolymer, an adhesive layer excellent in metal corrosion resistance, ultraviolet absorption, adhesive force, holding power, level difference filling property and foreign matter filling property can be formed from the adhesive composition of the present invention, and the impact resistance of the adhesive layer can be improved.

Units derived from monomers having a glass transition temperature of more than-60 ℃ and less than-15-

In the copolymer, the units derived from a monomer having a glass transition temperature of more than-60 ℃ and less than-15 ℃ in the formation of a homopolymer may be included as the units of the non-crosslinkable monomer constituting the copolymer.

Examples of the non-crosslinkable monomer having a glass transition temperature of more than-60 ℃ and less than-15 ℃ in the case of forming a homopolymer include n-Butyl Acrylate (BA), Ethyl Acrylate (EA), isobutyl acrylate (IBA), isooctyl acrylate (IOA), isononyl acrylate (INAA), isostearyl acrylate (ISTA), phenoxyethyl acrylate (PHEA), Lauryl Acrylate (LA), and methoxyethyl acrylate (2 MEA). These may be used in combination of two or more kinds as required.

Among the non-crosslinkable monomer units constituting the copolymer, the mass ratio of the units derived from the monomer having a glass transition temperature of more than-60 ℃ and less than-15 ℃ in the formation of a homopolymer is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and particularly preferably 0 to 3% by mass.

Here, the glass transition temperature in the present specification means: the glass transition temperature at which the monomers form a homopolymer. As specific glass transition temperatures, literature values may be used, and the following values may also be used: a value obtained by forming a homopolymer having a weight average molecular weight of 1 ten thousand or more from each monomer and measuring the glass transition temperature of the homopolymer by DSC (differential scanning calorimeter).

(units derived from a crosslinkable monomer)

In the present invention, the unit of the crosslinkable monomer constituting the copolymer includes a unit derived from a crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group, and an amino group. That is, the copolymer contains a unit derived from a crosslinkable monomer having any one of a hydroxyl group, an amide group, or an amino group.

The functional group may be any of a hydroxyl group, an amide group, or an amino group, and preferably the functional group is a hydroxyl group.

In the present invention, the mass ratio of the unit derived from the crosslinkable monomer having any one of a hydroxyl group, an amide group and an amino group as a functional group in the copolymer is 20 to 60% by mass, preferably 20 to 50% by mass, and particularly preferably 20 to 40% by mass.

Units derived from monomers having hydroxyl groups-

When the crosslinkable monomer is a monomer having a hydroxyl group, examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and polyethylene glycol (meth) acrylate. These may be used in combination of two or more kinds as required.

The crosslinkable monomer having a functional group of any of a hydroxyl group, an amide group and an amino group is preferably a crosslinkable monomer having a functional group of a hydroxyl group, and among them, 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is more preferable.

The mass ratio of the units derived from the monomer having a hydroxyl group in the copolymer is preferably 20 to 60 mass%, more preferably 20 to 50 mass%, and particularly preferably 20 to 40 mass%. When the mass ratio of the unit derived from the monomer having a hydroxyl group in the copolymer is 60 mass% or less, the coating suitability of the pressure-sensitive adhesive composition can be improved, and the adhesive strength of the pressure-sensitive adhesive layer can be improved.

Units derived from monomers having amide or amino groups-

When the crosslinkable monomer has a unit derived from a monomer having an amide group or an amino group, examples of the unit derived from a monomer having an amide group or an amino group include amino group-containing (meth) acrylates such as (meth) acrylamide, N-methylaminoethyl acrylate, and N-tert-butylaminoethyl acrylate.

Among the units constituting the copolymer, the units derived from the monomer having an amide group or an amino group are units derived from a monomer having a crosslinkable functional group, and therefore can be used in a range of 20 to 60 mass%, and the monomer having a crosslinkable functional group preferably contains a monomer having a hydroxyl group. Therefore, the actual mass ratio is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, particularly preferably 0 to 5 mass%, and even more preferably 0 mass%.

The copolymer may contain, as a unit derived from the crosslinkable monomer, a unit derived from a monomer having a functional group other than a hydroxyl group, an amide group, or an amino group. Examples of the monomer having another functional group include epoxy group-containing monomers such as glycidyl (meth) acrylate.

(units derived from monomers having acidic groups)

Examples of the monomer having an acidic group include carboxyl group-containing monomers such as (meth) acrylic acid, maleic anhydride, itaconic acid, fumaric acid, and fumaric anhydride.

Among the units constituting the copolymer, the mass ratio of the unit derived from the monomer having an acidic group is less than 0.5 mass%, preferably less than 0.1 mass%, more preferably less than 0.01 mass%, and particularly preferably 0 mass%.

The monomer having an acidic group may be a crosslinkable monomer.

(physical Properties of copolymer)

The weight average molecular weight of the copolymer is preferably 10 to 200 ten thousand, more preferably 20 to 100 ten thousand, and particularly preferably 30 to 80 ten thousand. When the weight average molecular weight is within the above range, sufficient filling ability of foreign matter can be ensured. The weight average molecular weight of the copolymer is a value before crosslinking with the crosslinking agent. The weight average molecular weight is a value determined based on polystyrene standards by Gel Permeation Chromatography (GPC) measurement.

As the copolymer, commercially available products may be used, and copolymers synthesized by a known method may be used. When a copolymer synthesized by a known method is used as the copolymer, for example, a solution polymerization method can be applied. Examples of the solution polymerization method include an ion polymerization method and a radical polymerization method. Examples of the solvent used in this case include tetrahydrofuran, chloroform, ethyl acetate, toluene, hexane, acetone, and methyl ethyl ketone. Examples of the method other than the solution polymerization method include a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method.

The glass transition temperature (Tg) of the copolymer is preferably-70 ℃ or higher and 0 ℃ or lower, more preferably-65 ℃ or higher and-5 ℃ or lower, and still more preferably-60 ℃ or higher and-10 ℃ or lower. When the glass transition temperature (Tg) of the copolymer is in the above range, the cohesive force when the adhesive composition is formed into an adhesive layer can be further increased. This provides an adhesive layer having excellent durability and excellent adhesion.

< crosslinking agent >

The crosslinking agent is preferably one which reacts with the copolymer by heating.

The crosslinking agent is suitably selected from known crosslinking agents, for example, isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, butylated melamine compounds, and the like, considering reactivity with the functional group of the copolymer. In the present invention, since the copolymer contains any of a hydroxyl group, an amide group, or an amino group, an isocyanate compound or an epoxy compound is preferably used from the viewpoint of ease of crosslinking.

In the present invention, the crosslinking agent is preferably one or two or more selected from the group consisting of a bifunctional or higher epoxy compound and a bifunctional or higher isocyanate compound, and more preferably a bifunctional or higher isocyanate compound.

Examples of the isocyanate compound include toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, tetraglycidyl xylylenediamine, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

As the crosslinking agent, commercially available products can be used. Examples of commercially available products include xylene diisocyanate compounds (Takenate D-110N, manufactured by Mitsui chemical Co., Ltd.), xylene diisocyanate-based crosslinking agents (TD-75, manufactured by Sukai chemical Co., Ltd.), and polyisocyanate-based crosslinking agents (Nippon Polyurethane Industry Co., Ltd., CORONATE L-55E).

(content of crosslinking agent)

One kind of the crosslinking agent may be used alone, or two or more kinds may be used in combination. The content of the crosslinking agent in the pressure-sensitive adhesive composition is not particularly limited, and may be appropriately selected depending on the desired adhesive properties and the like. For example, the amount is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and particularly preferably 0.05 to 0.8 parts by mass, based on 100 parts by mass of the copolymer.

< ultraviolet absorber >

The adhesive composition of the present invention comprises an ultraviolet absorber that is liquid or oily at 23 ℃.

The ultraviolet absorber is liquid or oily at 23 ℃ and means that: even if there is no diluent solvent and only the ultraviolet absorber, the resin composition has fluidity at 23 ℃.

The ultraviolet absorber is preferably an ultraviolet absorber having a maximum absorption wavelength at a wavelength of 340nm or more.

In the present invention, the ultraviolet absorber is preferably a compound having a hydroxyl group, from the viewpoint that the ultraviolet absorbability can be improved even if the content of the ultraviolet absorber is small.

Examples of the skeleton of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds.

The ultraviolet absorber is preferably a compound represented by the following general formula (1) or (2). Further, as the ultraviolet absorber, a mixture of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) is preferably used.

In the general formula (1) above,

r1: a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or a cyano group

R2: hydrogen atom or C1-C8 alkyl group

R3: an alkyl system.

In the general formula (2), in the formula,

r1, R2, R3: at least 1 or more of the groups are hydroxyl groups, alkyl group-based structures, or halogen atoms.

Among them, from the viewpoint of improving compatibility, it is preferable to introduce an alkyl group having a large molecular weight into the aromatic ring of the basic skeleton.

The reason why the compound represented by the general formula (1) or (2) is preferable is, for example: when chlorine as an electrophilic group is bonded to an aromatic ring forming a triazole ring side and when phenol ring side is dimerized by methylene, the maximum absorption wavelength of ultraviolet rays shifts to the long wavelength side and absorption in the near ultraviolet region becomes strong.

As the ultraviolet absorber, commercially available ones can be used. Examples of commercially available products include compounds represented by general formula (1) such as Tinuvin 384-2 and Tinuvin 109 manufactured by BASF corporation, and compounds represented by general formula (2) such as Tinuvin 477 manufactured by BASF corporation.

(content of ultraviolet absorber)

The invention also has the following features: the amount of the ultraviolet absorber blended in the adhesive composition can be increased. When a large amount of an ultraviolet absorber is added to a pressure-sensitive adhesive composition in the past, it is sometimes difficult to achieve high blending such as precipitation of the ultraviolet absorber. On the other hand, when the composition of the pressure-sensitive adhesive composition and the type of the ultraviolet absorber are adjusted to increase the amount of the ultraviolet absorber to be blended, there are cases where both the metal corrosiveness and the adhesive property cannot be satisfied. Therefore, in the present invention, by setting the composition of the pressure-sensitive adhesive composition to a predetermined composition, it is possible to achieve high incorporation of the ultraviolet absorber and to achieve compatibility of various performances such as metal corrosivity, adhesion, holding power, level difference filling property, and foreign matter filling property.

The content of the ultraviolet absorber is not particularly limited and varies depending on the thickness of the pressure-sensitive adhesive layer, and for example, when the pressure-sensitive adhesive layer is 100 μm (about ± 50 μm), the ultraviolet absorber is preferably contained in an amount of 0.1 to 8 parts by mass, more preferably 0.5 to 6 parts by mass, and particularly preferably 1 to 4 parts by mass, based on 100 parts by mass of the copolymer.

By setting the content of the ultraviolet absorber to be not less than the lower limit of the above range, the ultraviolet absorbability can be improved. By setting the content of the ultraviolet absorber to the upper limit of the above range or less, compatibility, adhesion, and holding power can be improved.

In addition, two or more types of ultraviolet absorbers may be used in combination, and in the case of the ultraviolet absorber, the content ratio in this case may be arbitrarily selected within the above-mentioned blending amount.

< solvent >

The adhesive composition may further contain a solvent. The solvent is used for improving the coating suitability of the adhesive composition.

Examples of such solvents include: hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, diacetone alcohol and the like; ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate, and the like; polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate, and derivatives thereof.

One solvent may be used alone, or two or more solvents may be used in combination. The content of the solvent in the adhesive composition is not particularly limited, and may be 25 parts by mass or more and 500 parts by mass or less, and may be 30 parts by mass or more and 400 parts by mass or less, with respect to 100 parts by mass of the copolymer.

The content of the solvent may be 10 mass% or more and 90 mass% or less, and may be 20 mass% or more and 80 mass% or less, based on the total mass of the adhesive composition.

In the state where the binder composition contains a solvent, the solid content concentration is preferably 20 to 60% by mass, and more preferably 30 to 50% by mass.

< additives which can be used in combination >

As the additive used in combination with the crosslinking agent and the ultraviolet absorber, a light stabilizer represented by a hindered amine compound is preferable from the viewpoint of reducing the transmittance of ultraviolet light.

The mechanism of action of the light stabilizer is different from that of the above-mentioned ultraviolet absorber, and the radical-supplementing effect is presumed to be a main stabilizing effect mainly centering on 3 kinds of HALS oxides.

In addition, in order to allow the ultraviolet absorber to more effectively withstand long-term use, it is preferable to contain an antioxidant represented by a hindered phenol compound. It is presumed that the deterioration of the ultraviolet absorber is caused by radicals generated from residues of the polymerization initiator used in the polymerization of the copolymer, and it is considered that the deterioration of the ultraviolet absorber can be suppressed by capturing the generated radicals with the antioxidant.

Likewise, antioxidants are generally divided into primary antioxidants known as radical chain terminators and secondary antioxidants that function as peroxide decomposers. Examples of the primary antioxidant include hindered phenol antioxidants, amine antioxidants, and lactone antioxidants. Further, as the secondary antioxidant, a phosphorus-based antioxidant and a sulfur-based antioxidant can be cited.

These antioxidants may be used alone or in combination of two or more.

The content of the additive used in combination is preferably 0.03 to 1.5 parts by mass, and more preferably 0.05 to 1.0 part by mass, per 100 parts by mass of the copolymer.

When the content is not less than the lower limit, the ultraviolet absorptivity can be reliably maintained even when the composition is used under a high-temperature, low-temperature, and hot-humid environment for a long time, and when the content is not more than the upper limit, the transmittance at 380nm can be further prevented from increasing and the adhesive strength from decreasing.

The adhesive composition may contain, in addition to the above-mentioned additives, other additives such as a tackifier, a silane coupling agent, and a metal corrosion inhibitor, as required.

Examples of the tackifier include rosin-based resins, terpene-phenol-based resins, coumarol-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum resins.

Examples of the silane coupling agent include mercaptoalkoxysilane compounds (e.g., mercapto-substituted alkoxy oligomers), and the like.

The metal corrosion inhibitor is preferably of a type which prevents corrosion by forming a complex with a metal to form a film on the surface of the metal, and particularly preferably a benzotriazole-based metal corrosion inhibitor.

[ adhesive sheet ]

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition of the present invention.

The adhesive sheet of the present invention has an adhesive layer. The adhesive sheet may be a single-layer adhesive sheet composed of only an adhesive layer. The pressure-sensitive adhesive sheet of the present invention may be a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet.

As the single-sided pressure-sensitive adhesive sheet, a multilayer sheet in which a pressure-sensitive adhesive layer is laminated on a support is exemplified. Further, another layer may be provided between the support and the adhesive layer.

Examples of double-sided pressure-sensitive adhesive sheets include single-layer pressure-sensitive adhesive sheets each including a pressure-sensitive adhesive layer, multilayer pressure-sensitive adhesive sheets each including a plurality of pressure-sensitive adhesive layers stacked together, multilayer pressure-sensitive adhesive sheets each including another pressure-sensitive adhesive layer stacked between a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer, and multilayer pressure-sensitive adhesive sheets each including a support stacked between a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer. When the double-sided pressure-sensitive adhesive sheet has a support, a transparent support is preferably used as the support. Such a double-sided pressure-sensitive adhesive sheet is excellent in transparency as a whole, and therefore can be suitably used for bonding optical members to each other.

The pressure-sensitive adhesive sheet of the present invention is preferably of the above-mentioned carrier-free type, and is preferably a single-layer pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer or a multilayer pressure-sensitive adhesive sheet obtained by laminating a plurality of pressure-sensitive adhesive layers, and particularly preferably a single-layer double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer.

When the psa sheet of the present invention has a support, examples of the support include plastic films such as polystyrene, styrene-acrylic copolymers, acrylic resins, polyethylene terephthalate, polycarbonate, polyether ether ketone, and triacetylcellulose; and optical films such as antireflection films, transparent conductive films such as ITO vapor deposition films and metal mesh films, and electromagnetic wave shielding films.

The surface of the adhesive layer is preferably covered with a release sheet. That is, the pressure-sensitive adhesive sheet may be a release sheet-attached pressure-sensitive adhesive sheet.

Fig. 1 is a cross-sectional view showing an example of the structure of a pressure-sensitive adhesive sheet with a release sheet. The pressure-sensitive adhesive sheet 11 shown in fig. 1 has release sheets (12a, 12 b). The pressure-sensitive adhesive sheet 11 of fig. 1 is a carrier-free single-layer pressure-sensitive adhesive sheet and is a double-sided pressure-sensitive adhesive sheet.

Examples of the release sheet include: a releasable laminate sheet having a release sheet substrate and a release agent layer provided on one surface of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate.

Paper or a polymer film can be used as the release sheet substrate in the releasable laminate sheet. Examples of the release agent constituting the release agent layer include general-purpose addition or condensation type silicone release agents and long chain alkyl group-containing compounds. In particular, an addition silicone release agent having high reactivity is preferably used.

Specific examples of the silicone-based release agent include: BY24-4527, SD-7220 and the like available from Toray Dow Corning Silicone Co; KS-3600, KS-774 and X62-2600, all of which are available from shin Etsu chemical Co. In addition, thePreferably, the silicone-based release agent contains SiO₂Unit and (CH)₃)₃SiO_1/2Unit or CH₂＝CH(CH₃)SiO_1/2A unit of an organosilicon compound, i.e. a silicone resin. Specific examples of the silicone resin include: BY24-843, SD-7292, SHR-1404 and the like, which are manufactured BY Toray Dow Corning Silicone Co; KS-3800 and X92-183, each of which is available from shin Etsu chemical Co.

In the present invention, it is preferable that the first release sheet is provided on one surface of the pressure-sensitive adhesive layer, the second release sheet is provided on the other surface of the pressure-sensitive adhesive layer, and the release forces of the first release sheet and the second release sheet are different from each other. In the example of fig. 1, the release sheets 12 are preferably different in releasability between the release sheet 12a and the release sheet 12b in order to facilitate peeling. That is, if the peelability from one side is different from the peelability from the other side, it is easy to peel only the release sheet 12 having high peelability first. In this case, the peelability of the release sheet 12a and the release sheet 12b may be adjusted according to the bonding method and the bonding procedure.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably in the range of usually 10 μm or more and 500 μm or less, more preferably 20 μm or more and 450 μm or less, further preferably 30 μm or more and 450 μm or less, further preferably 40 μm or more and 400 μm or less, further more preferably 40 μm or more and 350 μm or less, and particularly preferably 40 μm or more and 300 μm or less. When the thickness of the pressure-sensitive adhesive layer is within the above range, the level difference following property can be sufficiently ensured, and the durability can be further improved. In addition, by setting the thickness of the adhesive layer within the above range, the double-sided adhesive sheet can be more easily manufactured. When the thickness of the pressure-sensitive adhesive layer is small, the ultraviolet absorber is preferably added in an amount close to the upper limit.

In the present invention, the spectral transmittance of the pressure-sensitive adhesive sheet for light having a wavelength of 380nm is preferably controlled to 5% or less, regardless of the thickness of the pressure-sensitive adhesive sheet. It is known from experience that generally, when the ultraviolet transmittance at 380nm is 8% or less, no problem occurs for a long period of time in flat panel displays such as mobile phones and smart phones, but when the ultraviolet absorber used in the present invention is blended in the above range, the thickness of the pressure-sensitive adhesive layer is 5% or less within the thickness range of the above preferable range.

The adhesive strength of the adhesive layer is preferably 1N/25mm or more, more preferably 5N/25mm or more, and particularly preferably more than 8N/25 mm.

The adhesive force of the pressure-sensitive adhesive layer to an adherend is a value obtained by peeling each adherend at 180 ° and measuring the adhesive force based on JIS Z0237.

The 90 ° peel force of the pressure-sensitive adhesive layer is preferably 10N or more, and more preferably 11N or more. The upper limit of the 90 ° peel force of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 50N or less because the pressure-sensitive adhesive layer can be easily peeled off even when it is stuck to an undesired place. When the 90 ° peel force of the adhesive layer is in the above range, the impact resistance of the adhesive layer can be more effectively improved.

The 90 ° peel force of the adhesive layer can be measured by the following method.

First, a transparent PET film (Cosmoshine A4300100 μm manufactured by Toyo Boseki) was laminated on one surface of the pressure-sensitive adhesive sheet. After the pressure-sensitive adhesive sheet having a transparent PET film as a substrate was cut into 25mm × 60mm, the separator on the other side of the pressure-sensitive adhesive sheet was peeled off, pressed against a glass plate with a 2kg load roll, and left to stand at room temperature for 24 hours. Thereafter, 90 ° peel was performed as described in 10.4.6 of JIS Z0237, and the 90 ° peel force was measured based on the method for measuring the adhesive force.

(method for producing adhesive sheet)

The method for producing the pressure-sensitive adhesive sheet is not particularly limited.

The adhesive sheet of the present invention may be composed of an adhesive layer and other layers, and preferably is composed of only an adhesive layer. Examples of the other layer include an adhesive layer, a support, and a release sheet formed from an adhesive composition other than the above. Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymers, acrylic resins, polyethylene terephthalate, polycarbonate, polyether ether ketone, and cellulose triacetate; optical films such as antireflection films and electromagnetic wave shielding films; and the like.

The adhesive sheet preferably includes: a step of applying an adhesive composition to a release sheet to form a coating film; and a step of forming a cured product of the coating film by heating.

Hereinafter, a typical case of the step of applying the adhesive composition to the release sheet to form a coating film and the step of heating the coating film to form a cured product will be described.

The application of the adhesive composition for forming the adhesive sheet can be performed using a known application apparatus. Examples of the coating device include a knife coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a mini gravure coater, a bar knife coater, a lip coater, a die coater, and a curtain coater.

The coating film can be heated by a known heating device such as a heating furnace or an infrared lamp. The copolymer and the crosslinking agent react with each other by heating the coating film to form a cured product (adhesive sheet). After the application and after the removal of the solvent, the pressure-sensitive adhesive sheet may be subjected to a curing treatment in which the pressure-sensitive adhesive sheet is allowed to stand at a certain temperature for a certain period of time in order to cure the pressure-sensitive adhesive composition. The aging treatment can be carried out, for example, by leaving at 23 ℃ for 7 days.

(method of Using adhesive sheet)

In the method for using the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of an adherend.

[ laminate ]

The laminate of the present invention is a laminate having an adherend on at least one surface of the pressure-sensitive adhesive sheet of the present invention.

The adherend may have a metal or a metal oxide on the surface. In addition, the surface of any layer in the laminate may have a metal or a metal oxide.

In the laminate of the present invention, the adherend may have a level difference portion. The adherend is preferably an optical member constituting an image display device having a liquid crystal module or an optical member constituting a touch panel. The laminate is preferably obtained through a step of bringing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet into contact with the surface of the adherend.

Fig. 2 is a cross-sectional view showing an example of the structure of a laminate 20 in which an adhesive sheet 21 of the present invention is bonded to an adherend 22 and an adherend 24. As shown in fig. 2, the adherends 22 and 24 have a level difference portion (which may be any one side of 27a, 27b, 27c, 27d, or 27a and 27b, or 27c and 27 d). In fig. 2, the adherend 22 has level difference portions (27a, 27b), and the adherend 24 has level difference portions (27c, 27 d). The height difference portions (27a, 27b, 27c, 27d) are generally 5 μm or more and 60 μm or less thick. Therefore, the adhesive sheet 21 of the present invention is preferably capable of being bonded to a member having a step portion, and preferably capable of following the irregularities of the step portion.

The adherend is preferably an optical member. The optical member includes components of optical products such as touch panels and image display devices.

Examples of the constituent members of the touch panel include: an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on a surface of a glass plate, a transparent conductive film in which a conductive polymer is coated on a transparent resin film, a hard coat film, a fingerprint resistant film, and the like. The adhesive sheet of the present invention is preferably used for a sensor of a laminated touch panel, and more preferably used for a sensor of a laminated touch panel using a stylus. From this viewpoint, as the adherend of the pressure-sensitive adhesive sheet of the invention, an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on the surface of a glass plate, and a transparent conductive film in which a conductive polymer is coated on a transparent resin film are preferable.

Examples of the constituent members of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used for a liquid crystal display device.

Examples of the material used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetylcellulose, polyimide, cellulose acylate, and the like.

The pressure-sensitive adhesive sheet of the present invention can be used for bonding 2 adherends when it is a double-sided pressure-sensitive adhesive sheet. In this case, the adhesive sheet of the present invention can be used for bonding ITO thin films to each other, bonding ITO thin films to ITO glass, bonding ITO thin films to liquid crystal panels, bonding cover glass to ITO thin films, and bonding cover glass to decorative films in touch panels.

(method of producing laminate)

The present invention also relates to a method for producing the laminate. The method for producing a laminate preferably includes a step of bringing the pressure-sensitive adhesive sheet into contact with the surface of an adherend.

Examples

The features of the present invention will be described in more detail below with reference to examples and comparative examples. The materials, amounts, ratios, processing contents, processing steps and the like shown in the following examples may be appropriately changed within the limits not departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited to the specific examples shown below.

[ example 1]

< preparation of adhesive composition >

2-ethylhexyl acrylate (2 EHA; Tg about-70 ℃) as a non-crosslinking monomer having a Tg of not more than-60 ℃ is compounded so as to be 50 mass%, Methyl Acrylate (MA) as a non-crosslinking monomer having a Tg of not less than-15 ℃ is compounded so as to be 15 mass%, and 2-hydroxyethyl acrylate (2HEA) as a hydroxyl group-containing monomer is compounded so as to be 35 mass%, and 2, 2' -azobis (2, 4-dimethylvaleronitrile) as a radical polymerization initiator is dissolved in the solution. The solution was heated to 60 ℃ to cause random copolymerization to obtain a copolymer (A). The weight average molecular weight of the copolymer (A) is 40 to 50 ten thousand. The mass ratio of the non-crosslinking monomer having a Tg of not more than-60 ℃ to the non-crosslinking monomer having a Tg of not less than-15 ℃ is about 3.3: 1.

the number average molecular weight or the weight average molecular weight is a value determined based on polystyrene standards, measured by Gel Permeation Chromatography (GPC).

The measurement conditions of Gel Permeation Chromatography (GPC) are as follows.

Solvent: tetrahydrofuran (THF)

A chromatographic column: shodex KF801, KF803L, KF800L, KF800D (used in connection with Showa Denko K.K.)

Temperature of the column: 40 deg.C

Sample concentration: 0.5% by mass

A detector: RI-2031plus (manufactured by JASCO)

A pump: RI-2080plus (JASCO system)

Flow rate (flow velocity): 0.8 ml/min

Injection amount: 10 μ l

Standard curve: a calibration curve was obtained using 10 samples each having Mw of 1320 to 2500000, which was obtained from standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko K.K.).

To 100 parts by mass of the solid content of the copolymer (A) obtained above, 0.12 parts by mass of a xylene diisocyanate compound (Takenate D-110N, manufactured by Mitsui chemical Co., Ltd.) as a crosslinking agent, 2 parts by mass of an ultraviolet absorber (Tinuvin 477 manufactured by BASF) and 0.56 parts by mass of another ultraviolet absorber (Tinuvin 384-2 manufactured by BASF) were added, and ethyl acetate was added so that the solid content concentration became 40% by mass to obtain an adhesive composition.

Tinuvin 477 manufactured by BASF corporation and used as an ultraviolet absorber is a triazine compound containing a hydroxyl group, and Tinuvin 384-2 is a benzotriazole compound containing a hydroxyl group, and is in an oily state at 23 ℃.

< production of adhesive sheet >

The adhesive composition thus prepared was applied in an amount of 150 μm/m after drying²The surface of a polyethylene terephthalate film (No. 1 release sheet) (Oji F-Tex Co., Ltd.; 38RL-07(2) manufactured by Ltd.) having a thickness of 38 μm and a release agent layer treated with a silicone-based release agent was uniformly coated with an applicator. Thereafter, the sheet was dried in an air circulation oven at 100 ℃ for 3 minutes to form an adhesive layer on the surface of the 1 st release sheet. Then, a 2 nd release sheet (38 RL-07(L) manufactured by Ltd., Oji F-Tex Co., Ltd.) having a thickness of 38 μm was bonded to the surface of the pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive sheet having a structure in which the pressure-sensitive adhesive layer was subjected to a difference in peel forceThe pair of release sheets sandwiching the 1 st release sheet, the adhesive layer, and the 2 nd release sheet. The pressure-sensitive adhesive sheet was subjected to aging treatment by leaving it at 23 ℃ and a relative humidity of 50% for 7 days.

< production of laminate (1) >

The ultraviolet curable ink was screen-printed in a frame shape (90 mm in length × 50mm in width, 5mm in width) on the surface of a glass plate (90 mm in length × 50mm in width × 0.5mm in thickness) so as to have a coating thickness of 5 μm, thereby obtaining a printed glass having a height difference portion of 5 μm.

The obtained adhesive sheet was cut into a shape of 90mm in length × 50mm in width, and the 1 st release sheet was peeled off and laminated using a laminator (YOUBON co., ltd., IKO-650EMT) so that the adhesive layer covered the entire printing surface of the frame shape of the printing height difference glass. Thereafter, the 2 nd release sheet was peeled off, and a glass plate (90 mm in length. times.50 mm in width. times.0.5 mm in thickness) was laminated on the exposed adhesive layer surface by the laminator, and autoclave treatment (40 ℃, 0.5MPa, 30 minutes) was performed to obtain a laminate (1).

< production of laminate (2) >

The pressure-sensitive adhesive sheet thus obtained was cut into a 50mm longitudinal by 25mm transverse shape, and the No. 1 release sheet was peeled off to bond a transparent PET film (brand name: Cosmoshine A4300, manufactured by Toyo Co., Ltd.) having a thickness of 100 μm.

As an adherend, an adherend was prepared by cutting a polarizing plate (manufactured by stratechno co., ltd., SKN-18243T) into pieces having the same size as one surface of a glass plate (90 mm in length × 50mm in width × 0.5mm in thickness), and dispersing glass beads having a center particle diameter of 30 μm of about 0.05mg on the surface of the polarizing plate.

The 2 nd release sheet of the laminate integrated with the transparent PET film was peeled off, and the laminate was bonded to the surface of the adherend, which was the polarizing plate and on which the glass beads were dispersed, with a laminator. Then, autoclave treatment (40 ℃, 0.5MPa, 30 minutes) was carried out to obtain a laminate (2).

Examples 2 and 3 and comparative example 4

An adhesive composition, an adhesive sheet, and a laminate were obtained in the same manner as in example 1 except that a copolymer synthesized by changing the mass ratio of non-crosslinkable monomers used for synthesizing the copolymer according to the following table 1 was used instead of the copolymer (a) synthesized in example 1.

[ example 4]

2, 2' -azobis (2, 4-dimethylvaleronitrile) as a radical polymerization initiator was dissolved in a solution by compounding 2-ethylhexyl acrylate (2 EHA; Tg about-70 ℃) as a non-crosslinking monomer having a Tg of not more than-60 ℃ in an amount of 50 mass%, 2-ethylhexyl methacrylate (2 EHMA; Tg about-10 ℃) as a non-crosslinking monomer having a Tg of not less than-15 ℃ in an amount of 15 mass%, and 2-hydroxyethyl acrylate (2HEA) as a hydroxyl group-containing monomer in an amount of 35 mass%. The solution was heated to 60 ℃ to cause random copolymerization to obtain a copolymer (E). The weight average molecular weight of the copolymer (E) is from 40 to 50 ten thousand. The mass ratio of the non-crosslinking monomer having a Tg of not more than-60 ℃ to the non-crosslinking monomer having a Tg of not less than-15 ℃ is about 3.3: 1.

to 100 parts by mass of the solid content of the copolymer (E) obtained above, 0.12 parts by mass of a xylene diisocyanate compound (Takenate D-110N, manufactured by Mitsui chemical Co., Ltd.) as a crosslinking agent, 2 parts by mass of an ultraviolet absorber (Tinuvin 477 manufactured by BASF) and 0.56 parts by mass of another ultraviolet absorber (Tinuvin 384-2 manufactured by BASF) were added, and ethyl acetate was added so that the solid content concentration became 40% by mass to obtain an adhesive composition.

[ examples 5 and 6]

An adhesive composition, an adhesive sheet, and a laminate were obtained in the same manner as in example 4 except that a copolymer synthesized by changing the mass ratio of non-crosslinkable monomers used for synthesizing the copolymer was used instead of the copolymer E synthesized in example 4 as described in table 1 below.

[ example 7]

Referring to example 1 of japanese patent application laid-open No. 2017-171777, the adhesive composition of example 7 was prepared by the following method.

2, 2' -azobis (2, 4-dimethylvaleronitrile) as a radical polymerization initiator was dissolved in a solution by compounding 2-ethylhexyl acrylate (2 EHA; Tg about-70 ℃) as a non-crosslinkable monomer having a Tg of not more than-60 ℃ in an amount of 60 mass%, methyl methacrylate (MMA; Tg about 105 ℃) as a non-crosslinkable monomer having a Tg of not less than-15 ℃ in an amount of 20 mass%, and 2-hydroxyethyl acrylate (2HEA) as a hydroxyl group-containing monomer in an amount of 20 mass%. The solution was heated to 60 ℃ to cause random copolymerization to obtain a copolymer (F). The weight average molecular weight of the copolymer (F) was 60 ten thousand. The mass ratio of the non-crosslinking monomer having a Tg of not more than-60 ℃ to the non-crosslinking monomer having a Tg of not less than-15 ℃ is about 3: 1.

to 100 parts by mass of the solid content of the copolymer (F) obtained above, 0.4 parts by mass of trimethylolpropane-modified tolylene diisocyanate (product name "BHS 8515" manufactured by TOYOCHEM Co., Ltd.), 2 parts by mass of an ultraviolet absorber (Tinuvin 477 manufactured by BASF Co., Ltd.), and 0.56 parts by mass of another ultraviolet absorber (Tinuvin 384-2 manufactured by BASF Co., Ltd.) were added, and ethyl acetate was added so that the solid content concentration became 30% by mass to obtain an adhesive composition.

Comparative example 1

Referring to example 1 of japanese patent laid-open No. 2012-014043, the adhesive composition of comparative example 1 was prepared by the following method.

An adhesive composition, an adhesive sheet, and a laminate were obtained in the same manner as in example 1 except that a copolymer (B) synthesized by changing the mass ratio of monomers used for synthesizing the copolymer as described in table 1 below was used instead of the copolymer a synthesized in example 1 and an ultraviolet absorber was used as described in table 1 below.

A copolymer (B) was obtained in the same manner as in example 1 except that in comparative example 1, n-butyl acrylate (BA; Tg of about-55 ℃ C.) as a non-crosslinkable monomer was blended so as to be 65% by mass, MA was 35% by mass, and Acrylic Acid (AA) as a crosslinkable monomer, which is an acid group-containing monomer, was blended so as to be 2% by mass.

In comparative example 1, 2 parts by mass of Tinuvin 144 manufactured by BASF and 4 parts by mass of Tinuvin 109 manufactured by BASF were used as ultraviolet absorbers. Tinuvin 144 manufactured by BASF corporation used as an ultraviolet absorber was pale yellow powder, and Tinuvin 109 was oily at 23 ℃.

Comparative example 2

Referring to example 1 of japanese patent laid-open publication No. 2014-196377, an adhesive composition of comparative example 2 was prepared by the following method.

An adhesive composition, an adhesive sheet, and a laminate were obtained in the same manner as in example 1 except that a copolymer (C) synthesized by changing the mass ratio of monomers used for synthesizing the copolymer as described in table 1 below was used instead of the copolymer a synthesized in example 1, and "CORONATE L-55E" manufactured by japan polyurethane corporation was used as a crosslinking agent and an ultraviolet absorber was used as described in table 1 below.

In comparative example 2, a copolymer (C) was obtained in the same manner as in example 1, except that BA, MA and 2HEA were used, and blending was performed so that BA was 39 mass%, MA was 60 mass% and 2HEA was 1 mass%, and 2,2 '-azobisisobutyronitrile was used as a radical polymerization initiator instead of 2, 2' -azobis (2, 4-dimethylvaleronitrile). The weight average molecular weight of the copolymer (C) was 65 ten thousand.

In comparative example 2,4 parts by mass of Tinuvin 477 manufactured by BASF corporation was used as the ultraviolet absorber.

Comparative example 3

Referring to example 1 of japanese patent laid-open publication No. 2012-207055, the adhesive composition of comparative example 3 was prepared by the following method.

An adhesive composition, an adhesive sheet and a laminate were obtained in the same manner as in example 1 except that a copolymer (D) synthesized by changing the mass ratio of monomers used for synthesizing the copolymer as described in table 1 below was used in place of the copolymer a synthesized in example 1, and 3.75 parts by mass of a xylene diisocyanate-based crosslinking agent (TD-75, manufactured by seiko chemical corporation) was used as the crosslinking agent and an ultraviolet absorber was used as described in table 1 below.

In comparative example 3, a copolymer (D) was obtained in the same manner as in example 1, except that 2- (dimethylamino) ethyl acrylate (DMAEA; Tg of about-60 ℃), BA, MA and 2HEA were used and compounded so that DMAEA, BA, MA and 2HEA were 0.5 mass%, 66.5 mass%, 30 mass% and 3 mass%. The weight average molecular weight of the copolymer (D) was 75 ten thousand.

In comparative example 3, 4 parts by mass of an ultraviolet absorber containing ethyl 2-cyano-3, 3-diphenylacrylate (SEESORB 501 manufactured by ZYPRO INC., Ltd.; containing no hydroxyl group) was used as the ultraviolet absorber. SEESORB 501 manufactured by zyro inc.

[ evaluation ]

< resistance to Metal Corrosion >

The pressure-sensitive adhesive sheet was cut into 5 mm. times.12 mm, and a release sheet on the peeled side was bonded to a transparent PET film (trade name: Cosmoshine A4300, manufactured by Toyo Co.) having a thickness of 100 μm to obtain a pressure-sensitive adhesive sheet having a transparent film as a substrate. Subsequently, the other release sheet was peeled off, and the pressure-sensitive adhesive layer side was bonded to a copper plate, followed by storage in an atmosphere of 85 ℃ and 85% relative humidity for 240 hours. Thereafter, the surface of the copper foil was visually observed from the transparent PET film side, and the presence or absence of corrosion on the surface of the copper foil was confirmed, and evaluated according to the following evaluation criteria.

(evaluation criteria)

O: no corrosion was observed.

X: corrosion was observed.

< ultraviolet absorptivity >

An adhesive sheet comprising a transparent PET film as a substrate was cut into pieces of 50mm X50 mm, and a light-peeling separator was peeled off, followed by bonding to glass (product name: S9112, manufactured by Songlanzi Kogyo Co., Ltd.). Subsequently, the glass/pressure-sensitive adhesive layer was formed by peeling off the heavy-release separator, and then the spectral transmittance at a wavelength of 380nm was measured using an ultraviolet-visible near-infrared spectrophotometer (model: UV-3100PC, manufactured by Shimadzu corporation).

Evaluation was carried out according to the following evaluation criteria.

(evaluation criteria)

O: the transmittance is less than 8%.

X: the transmittance is 8% or more.

< compatibility (recrystallization) >)

The pressure-sensitive adhesive sheet having a transparent PET film as a substrate was cut into 50 mm. times.50 mm, treated at-40 ℃ for 250 hours, and visually inspected for appearance whether or not the ultraviolet absorber was recrystallized. Those in which the ultraviolet absorber was not recrystallized were evaluated as "good", and those in which the ultraviolet absorber was recrystallized and was present locally were evaluated as "poor".

< adhesion >

After the pressure-sensitive adhesive sheet having a transparent PET film as a base material was cut into a size of 25mm × 60mm, the separator was peeled off and pressed with a roll at a load of 2kg against a glass plate, and the plate was left to stand at room temperature for 24 hours. Thereafter, 180-degree peel was performed at a tensile rate of 300 mm/min by using a tensile tester (model: AUTOGRAPH AGS-J, manufactured by Shimadzu corporation) according to JIS Z0237, and the peel strength at this time was measured and used as the adhesive force.

The adhesive strength was evaluated as "excellent" for those with adhesive strengths exceeding 8N/25mm, as "good" for those with adhesive strengths of 5 to 8N/25mm, as "delta" for those with adhesive strengths of 1N/25mm or more and less than 5N/25mm, and as "x" for those with adhesive strengths less than 1N/25 mm.

< holding force >

For the adhesive sheet, the holding power was measured based on JIS Z0237 by the following procedure.

The pressure-sensitive adhesive sheet produced as described above was peeled off from the light release separator, and a PET film (Cosmoshine a 4300100 μm manufactured by toyobo) was bonded to the exposed pressure-sensitive adhesive, and then cut into a size of 25mm × 50mm, and the pressure-sensitive adhesive layer exposed by peeling off the heavy release sheet was bonded so that the contact surface with the surface of the SUS plate became 25mm × 25 mm. Thereafter, a 1kg weight was attached to the adhesive sheet protruding from the SUS plate, and the plate was left to stand at 40 ℃ for 24 hours in a dry environment. After removal, the offset distance between the adhesive sheet and the SUS plate interface was measured.

Evaluation was carried out according to the following evaluation criteria.

(evaluation criteria)

O: the offset distance is less than 5 mm.

X: the offset distance is 5mm or more or the weight is dropped.

Peeling force < 90 DEG >

After the pressure-sensitive adhesive sheet having a transparent PET film as a base material was cut into a size of 25mm × 60mm, the separator was peeled off and pressed with a roll at a load of 2kg against a glass plate, and the plate was left to stand at room temperature for 24 hours. Thereafter, the 90 ° peel force was measured based on the method for measuring 90 ° peel adhesion described in 10.4.6 of JIS Z0237.

< level difference landfill and foreign matter landfill >

(original)

The height difference portion of the laminate (1) and the glass bead-dispersed portion of the laminate (2) were observed with a microscope (magnification: 25 times), and the height difference filling property and foreign matter filling property of the adhesive sheet were evaluated according to the following criteria.

Very good: the height difference portion and the periphery of the glass beads did not generate bubbles having a diameter of 50 μm or more at all.

O: the height difference portion and the periphery of the glass beads generate less than 5 bubbles having a diameter of 50 μm or more and less than 150 μm.

X: 6 or more bubbles having a diameter of 50 μm or more and less than 150 μm or bubbles having a diameter of 150 μm or more are generated in the height difference portion and/or the periphery of the glass beads.

(durable)

The height difference portion of the laminate (1) and the laminate (2) were treated at 85 ℃ and 85% relative humidity for 24 hours, and the treated height difference portion and the glass bead-dispersed portion were observed with a microscope (magnification: 25 times), and the height difference filling property and foreign matter filling property of the adhesive sheet were evaluated according to the following criteria.

Very good: no new bubbles having a diameter of 50 μm or more were generated from the level difference portion and the periphery of the glass beads.

O: less than 5 new bubbles having a diameter of 50 μm or more and less than 150 μm are generated from the level difference portion and the periphery of the glass beads.

X: 6 or more new bubbles having a diameter of 50 μm or more and less than 150 μm or new bubbles having a diameter of 150 μm or more are generated from the height difference portion and/or the periphery of the glass beads.

< impact resistance >

The laminate (1) was dropped from a position having a height of 1.0m so that the surface of the laminate (1) was at 90 ° to the ground, and evaluated by the following criteria.

O: less than 5 new bubbles having a diameter of 50 μm or more and less than 150 μm are generated from the periphery of the step portion of the laminate.

And (delta): at least 6 new bubbles having a diameter of 50 μm or more and less than 150 μm or at least 1 new bubble having a diameter of 150 μm or more and less than 5 new bubbles are generated around the step portion of the laminate.

X: 5 or more new bubbles having a diameter of 150 μm or more are generated or completely peeled off around the step portion of the laminate.

[ Table 1]

As is clear from Table 1 above, the pressure-sensitive adhesive compositions obtained in examples 1 to 7 were excellent in metal corrosion resistance, ultraviolet absorbability, adhesive strength, holding power, level difference filling property, foreign matter filling property and impact resistance. In particular, examples 3 to 6 exhibited excellent level difference filling properties and impact resistance.

In comparative example 1 in which a copolymer containing a large mass ratio of a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower, a unit derived from a crosslinkable monomer having any one of a hydroxyl group, an amide group and an amino group, and a unit derived from a monomer having an acidic group was used, the obtained adhesive sheet was inferior in metal corrosion resistance, and also inferior in level difference filling properties and foreign matter filling properties.

In comparative example 2 in which the copolymer containing no unit derived from a monomer having a glass transition temperature of-60 ℃ or lower and no unit derived from a crosslinkable monomer having a functional group of any of a hydroxyl group, an amide group and an amino group in a mass ratio of less than the lower limit value defined in the present invention was used, the obtained adhesive sheet was inferior in holding power, and also inferior in level difference filling property, foreign matter filling property (durability) and impact resistance.

In comparative example 3 in which a copolymer containing no unit derived from a monomer having a glass transition temperature of-60 ℃ or lower and no unit derived from a crosslinkable monomer having a functional group of any of a hydroxyl group, an amide group and an amino group in a mass ratio of less than the lower limit value defined in the present invention was used and an ultraviolet absorber which is not liquid or oily at 23 ℃ was used, the obtained pressure-sensitive adhesive sheet was poor in adhesive force, and also poor in level difference filling property and foreign matter filling property. In comparative example 3, the compatibility was also poor.

Comparative example 4, which uses a copolymer containing no units derived from a monomer having a glass transition temperature of-60 ℃ or lower, gives a pressure-sensitive adhesive sheet having poor level difference filling properties and poor foreign matter filling properties.

Description of the reference numerals

1 pressure-sensitive adhesive sheet with Release sheet

11 adhesive sheet (adhesive layer)

12a, 12b release sheet

20 laminated body

21 adhesive sheet (adhesive layer)

22 adherend

24 adherend

27a, 27b, 27c, 27d height difference part

Claims

1. An adhesive composition comprising: a copolymer of a non-crosslinkable monomer and a crosslinkable monomer having a functional group, a crosslinking agent and an ultraviolet absorber,

the copolymer comprises, as units constituting the non-crosslinkable monomer, a unit derived from a monomer having a glass transition temperature of-60 ℃ or lower when forming a homopolymer and a unit derived from a monomer having a glass transition temperature of-15 ℃ or higher when forming a homopolymer,

the mass ratio of the units derived from the crosslinkable monomer having any one of a hydroxyl group, an amide group and an amino group as a functional group in the copolymer is 20 to 60% by mass,

the UV absorber is liquid or oily at 23 ℃.

2. The adhesive composition according to claim 1, wherein, among the units constituting the non-crosslinkable monomer of the copolymer, the mass ratio of the unit derived from a monomer having a glass transition temperature of-60 ℃ or less to the unit derived from a monomer having a glass transition temperature of-15 ℃ or more is 1: 1-5: 1.

3. the adhesive composition according to claim 1, wherein the mass ratio of the unit derived from the monomer having a glass transition temperature of-60 ℃ or lower to the unit derived from the monomer having a glass transition temperature of-15 ℃ or higher in the units constituting the non-crosslinkable monomer of the copolymer is 3: 1-5: 1.

4. the adhesive composition according to any one of claims 1 to 3, wherein the copolymer contains, as the unit derived from a monomer having a glass transition temperature of-60 ℃ or lower, an acrylate-derived unit,

the acrylate and the methacrylate have the same ester structure.

5. The adhesive composition according to any one of claims 1 to 4, wherein the copolymer contains, as the unit derived from a monomer having a glass transition temperature of-60 ℃ or lower, a unit derived from 2-ethylhexyl acrylate,

6. The adhesive composition according to any one of claims 1 to 5, wherein the crosslinkable monomer having a functional group of any one of a hydroxyl group, an amide group and an amino group is 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate.

7. The adhesive composition according to any one of claims 1 to 6, wherein the crosslinking agent is one or more selected from difunctional or higher epoxy compounds and difunctional or higher isocyanate compounds.

8. The adhesive composition according to any one of claims 1 to 7, wherein the ultraviolet absorber is a compound having a hydroxyl group.

9. The adhesive composition according to any one of claims 1 to 8, wherein the ultraviolet absorber is contained in an amount of 0.1 to 8 parts by mass based on 100 parts by mass of the copolymer.

10. An adhesive sheet having an adhesive layer,

the adhesive layer is a cured product of the adhesive composition according to any one of claims 1 to 9.

11. The adhesive sheet according to claim 10, wherein the 90 ° peel force of the adhesive layer is 10N or more.

12. The adhesive sheet according to claim 10 or 11, which is provided with a 1 st release sheet on one surface of the adhesive layer,

the other surface of the adhesive layer is provided with a No. 2 release sheet,

the 1 st release sheet and the 2 nd release sheet have different release forces.

13. A laminate having an adherend on at least one surface of the adhesive sheet according to claim 10 or 11.

14. The laminate according to claim 13, wherein a metal or a metal oxide is provided on a surface of any layer of the laminate.