WO2013152251A1

WO2013152251A1 - Radiation-cured adhesive composition and laminate using the same

Info

Publication number: WO2013152251A1
Application number: PCT/US2013/035357
Authority: WO
Inventors: Hiroyuki Kobayashi; Jun Fujita; Takahiro Kasahara
Original assignee: 3M Innovative Properties Company
Priority date: 2012-04-05
Filing date: 2013-04-05
Publication date: 2013-10-10
Also published as: JP2013216742A; JP5989381B2

Abstract

There is provided a radiation-cured adhesive composition that is excellent in suitability for screen printing and exhibits high adhesiveness after curing. There is also provided a radiation-cured adhesive composition containing from 10 to 70 wt.% of an ethylenically unsaturated monomer not containing an aromatic ring, from 1 to 10 wt.% of a photopolymerization initiator, and from 10 to 55 wt.% of a cross linking agent; the radiation-cured adhesive composition containing from 10 to 45 wt.% of an alkyl (meth)acrylate having from 8 to 18 carbon atoms in the alkyl group as the ethylenically unsaturated monomer not containing an aromatic ring, and containing from 10 to 50 wt.% of a urethane poly(meth)acrylate having a weight average molecular weight of from 20,000 to 100,000 as the cross linking agent.

Description

RADIATION-CURED ADHESIVE COMPOSITION AND LAMINATE USING THE SAME BACKGROUND

Technical Field

[0001]

The present invention relates to a radiation-cured adhesive composition and a laminate using the same.

Background

[0002]

There are known various kinds of compositions that exhibit curability when irradiated with ultraviolet or other radiation. Adhesive tapes, adhesive sheets, and the like, are formed by applying such compositions onto substrates in a state not yet being cured by radiation and then irradiating with radiation. Examples of compositions used in such a field include those disclosed in Japanese Unexamined Patent

Application Publication No. H4- 183770, Japanese Unexamined Patent Application Publication No. 2004- 143223, Japanese Unexamined Patent Application Publication No. 2004-323796, Japanese Unexamined Patent Application Publication No. S61-209281, and Japanese Unexamined Patent Application

Publication No. HI 1-246612.

[0003]

Meanwhile, although adhesive compositions (for example, solvent-based adhesives or water- based adhesives) are applied onto substrates by roll coating, dispenser, screen-printing, or other application means, a fine pattern is not easy to apply because the contained adhesive is a polymer and is also adhesive. Accordingly, in the case when an adhesive layer having a specific shape is to be formed on a substrate, the common practice is to punch out and process the adhesive film.

[0004]

That is, a method is adopted, in which an adhesive laminated with two sheets of film is punched out and processed into a desired shape and the adhesive is affixed to an adherend after discarding the unwanted portion and after processing. However, with this method, the portions not needed for affixing come to be discarded in large quantities, and not only does this lead to discarding of adhesive, but also there is a concern of the environmental load of increased waste.

[0006]

The above-described composition, which becomes an adhesive by irradiation with radiation, is definitely superior, because a problem of production of volatile materials (organic solvents, and the like) during adhesion processing is less likely to occur compared with solvent-based adhesives, and the amount of heat, and the like, used for processing is reduced compared with water-based adhesives (emulsion- based, and the like), in which the water, having large specific heat capacity, must be volatilized.

[0007]

However, no composition is known, among such radiation-cured adhesive compositions, that is capable of fine patterning on the same level as those conventionally fabricated by die cutting and that at the same time exhibits high adhesiveness to all kinds of adherends including metal, plastic, and the like.

SUMMARY

[0008]

In a first aspect of the present invention, a radiation-cured adhesive composition can be obtained, containing from 10 to 70 wt.% of an ethylenically unsaturated monomer not containing an aromatic ring, from 1 to 10 wt.% of a photopolymerization initiator, and from 10 to 55 wt.% of a crosslinking agent; the radiation-cured adhesive composition containing from 10 to 45 wt.% of an alkyl (meth)acrylate having from 8 to 18 carbon atoms in the alkyl group as the ethylenically unsaturated monomer not containing an aromatic ring, and containing from 10 to 50 wt.% of a urethane poly(meth)acrylate having a weight average molecular weight of from 20,000 to 100,000 as the crosslinking agent.

[0009]

The radiation-cured adhesive composition of the present invention exhibits excellent adhesiveness on a wide range of adherends including stainless steel, ABS, and the like because specific components are combined in prescribed quantities. Shape processing furthermore is easy even with fine shapes because stringiness is not likely to be produced during application on an adherend by screen- printing. Also, the composition can be leveled easily after application, and therefore, for example, the adhesive layer is not likely to be formed in a swollen condition, and a desired fine shape can be obtained assuredly. Also, even if air is briefly taken in, there is a tendency for the bubbles to clear naturally, and therefore the formation of cavities in the adhesive layer and the production of roughness on the surface is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]

FIG. 1 A is a perspective view illustrating a radiation-cured adhesive composition in an uncured state that is laid on a mesh, with a squeegee and a scraper having been arranged thereon;

FIG. IB is a perspective view illustrating the radiation-cured adhesive composition being spread by the scraper on the mesh and an adherend being brought into proximity with the bottom face of the mesh;

FIG. 1 C is a perspective view illustrating the radiation-cured adhesive composition being printed on the adherend by the squeegee;

FIG. ID is a perspective view illustrating the state on completion of the printing;

FIG. IE is a perspective view illustrating the radiation-cured adhesive composition having been transferred onto the adherend; and

FIG. IF is a perspective view illustrating the adhesive having a desired shape as formed on the adherend 20.

FIG. 2A is a perspective view of the end portion of an adhesive having been drawn out from a roll-form adhesive film; and FIG. 2B is a perspective view illustrating the appearance when cut by a die cutter.

DETAILED DESCRIPTION

[0011]

Embodiments of the present disclosure are described in further detail below, but the present disclosure is not limited to just these embodiments.

[0012]

The presently disclosed radiation-cured adhesive composition contains an ethylenically unsaturated monomer not containing an aromatic ring, a polymerization inhibitor, and a crosslinking agent as necessary components, and contains an alkyl (meth)acrylate having from 8 to 18 carbon atoms in the alkyl group as the ethylenically unsaturated monomer not containing an aromatic ring, and a urethane poly(meth)acrylate having a weight average molecular weight of 20,000 to 100,000 as the crosslinking agent. In the present invention, the statement "(meth)acrylate" signifies acrylate or methacrylate, and the same applies in other cases as well.

[0013]

"Ethylenically unsaturated monomer not containing an aromatic ring" (hereinafter referred to as "component A") signifies an ethylenically unsaturated monomer in which a benzene ring, naphthalene ring, or other aromatic ring is not present in the molecule, and the ethylenically unsaturated bond contains a substituted or non-substituted vinyl bond. A content of component A is from 10 to 70 wt.% based on a total weight of the radiation-cured adhesive composition, and from 10 to 45 wt.% of an alkyl

(meth)acrylate having from 8 to 18 carbon atoms in the alkyl group (hereinafter referred to as "component Al "), based on the total weight of the radiation-cured adhesive composition, must be contained as component A. Component A 1 contributes mainly to adhesiveness after curing. Note that the number of ethylenically unsaturated groups in component A is ideally one per molecule.

[0014]

From the viewpoint of adhesiveness on metal or plastic, the content of component A is preferably from 20 to 70 wt.%, and more preferably from 30 to 60 wt.%. Also, component Al is preferably from 10 to 45 wt.%, and more preferably from 20 to 40 wt.%. The excellence of the adhesiveness is further increased by containing component A 1 to such extent. The number of carbon atoms in the alkyl group of component Al is preferably from 8 to 16, and more preferably from 8 to 12. This alkyl group may contain branches. 8 or more carbon atoms are preferable from the viewpoint of odor.

[0015]

Examples of component Al include n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth) acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, hexyldecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, and octyldecyl (meth)acrylate. 2-ethylhexyl acrylate and lauryl acrylate are particularly preferable as component Al .

[0016]

At least one kind of monomer selected from a group including an alkyl (meth)acrylate other than those having 8 to 18 carbon atoms in the alkyl group (hereinafter referred to as "component A2"), an alkoxyalkyl (meth)acrylate (hereinafter referred to as "component A3"), a (meth)acrylate containing a carboxylic acid (hereinafter referred to as "component A4"), and an ethylenically unsaturated monomer containing an amide group (hereinafter referred to as "component A5") may be contained as component A.

[0017]

Examples of component A2 include butyl (meth)acrylate, hexyl (meth)acrylate, and other alkyl (meth)acrylates having 4 to 6 carbon atoms in the alkyl group, behenyl (meth)acrylate and other alkyl (meth)acrylates having 20 to 22 carbon atoms in the alkyl group, and cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and other alicyclic (meth)acrylates. Examples of component A3 include polyalkylene glycol mono(meth)acrylate and polyalkylene glycol monoalkyl ether (meth)acrylate. The adhesive strength can often be improved by adjusting the glass transition temperature and storage modulus of the adhesive after curing by suitably using these monomers. Examples of component A4 include (meth)acrylic acid, acrylate dimers, omega-carboxy-polycaprolactone mono(meth)acrylate, and 2- (meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-

(meth)acryloyloxyethyl succinate, and other adducts of hydroxyl-containing (meth)acrylates acid anhydrides. Particularly preferable as component A4 are omega-carboxy-polycaprolactone

mono(meth)acrylate and 2-(meth)acryloyloxyethyl phthalate or 2-(meth)acryloyloxyethyl

hexahydrophthalate. The adhesive strength can be markedly improved on adherends of stainless steel, other metals, plastic, or the like, by adding these components.

[0018]

Monomers containing amide groups are ideal as component A5. The cohesive force of the adhesive is improved by adding these components, and the effect of improving the adhesive strength on adherends of stainless steel, other metals, glass, or the like, is great particularly in the case when combined with the abovementioned acid-group-containing monomers. At least one kind of monomer selected from a group including (meth)acrylamide, N-substituted (meth)acrylamide, N,N-substituted (meth)acrylamide, aminoalkyl (meth)acrylamide, N-substituted aminoalkyl (meth)acrylamide, and N,N- substituted aminoalkyl (meth)acrylamides is preferable as component A5. Specific examples include N- methylol (meth)acrylamide, N-methoxymethyl N-methylol (meth)acrylamide, N-ethoxymethyl N- methylol (meth)acrylamide, N-n-butoxymethyl N-methylol (meth)acrylamide, N-iso-butoxymethyl N- methylol (meth)acrylamide, Ν,Ν-dimethyl N-methylol (meth)acrylamide, Ν,Ν-diethyl N-methylol (meth)acrylamide, N-t-butyl N-methylol (meth)acrylamide, N-isopropyl N-methylol (meth)acrylamide, N-t-octyl N-methylol (meth)acrylamide, Ν,Ν-dimethylaminoethyl N-methylol (meth)acrylamide, N,N- dimethylaminopropyl N-methylol (meth)acrylamide, diacetone acrylamide, and other substituted acrylamides, and N-vinlypyrrolidone, N-vinylcaprolactam, and other vinyl monomers.

Dimethylaminopropyl methacrylamide (DMAPMA) is preferable among these.

[0019]

The radiation-cured adhesive composition can contain from 10 to 40 wt.% of an ethylenically unsaturated monomer containing an aromatic ring (hereinafter referred to as "B"), based on the total weight of the radiation-cured adhesive composition. Component B is an ethylenically unsaturated monomer having a benzene ring, naphthalene ring, or other aromatic ring in the molecule, and contributes mainly to cohesive force to improve adhesive strength. In the case when using component B, the boiling point of component A is preferably less than that of component B (that is, the boiling point of component B is at or above the boiling point of component A).

[0020]

A content of component B is preferably from 10 to 40 wt.%, and more preferably from 10 to 30 wt.%, from the fact that the effects above can be improved. At least one kind of monomer selected from a group including alkylene glycol mono(alkylaryl) ether mono(meth)acrylate, polyalkylene glycol mono(alkylaryl) ether mono(meth)acrylate, alkylene glycol monoaryl ether mono(meth)acrylate, and polyalkylene glycol monoaryl ether mono(meth)acrylate can be used as component B.

[0021]

An example of an alkylene glycol mono(alkylaryl) ether mono(meth)acrylate (this signifies a (meth)acrylate ester of a mono(alkylaryl) ether of alkylene glycol, and is referred to also as "oxyalkylene alkylaryl ether (meth)acrylate," "alkylaryl alcohol alkylene oxide-modified (meth)acrylate," and the like) is ethylene glycol mono(alkylphenyl) ether mono(meth)acrylate, and the number of carbon atoms in the alkyl portion of the alkylphenyl group is preferably from 1 to 12, and more preferably from 6 to 12. An example of an alkylene glycol mono(alkylaryl) ether mono(meth)acrylate is nonylphenyloxyethylene acrylate (e.g., Aronix Ml 11, Toagosei Co., Ltd.).

[0022]

An example of a polyalkylene glycol mono(alkylaryl) ether mono(meth)acrylate (this signifies a (meth) acrylate ester of a mono(alkylaryl) ether of polyalkylene glycol, and is referred to also as

"polyoxyalkylene alkylaryl ether (meth)acrylate," "alkylaryl alcohol polyalkylene oxide-modified (meth)acrylate," and the like) is polyethylene glycol mono(alkylphenyl) ether mono(meth)acrylate, and the number of carbon atoms in the alkyl portion of the alkylphenyl group is preferably from 1 to 12, and more preferably from 6 to 12. An example of a polyalkylene glycol mono(alkylaryl) ether

mono(meth)acrylate is nonylphenoxytetraethylene glycol acrylate (e.g., Aronix Ml 13, Toagosei Co., Ltd.).

[0023]

An example of an alkylene glycol monoaryl ether mono(meth)acrylate (this signifies a

(meth) acrylate ester of a monoaryl ether of alkylene glycol, and is referred to also as "oxyalkylene aryl ether (meth)acrylate," "aryl alcohol alkylene oxide-modified (meth)acrylate," and the like) is ethylene glycol monophenyl ether mono(meth)acrylate.

[0024]

An example of a polyalkylene glycol monoaryl ether mono(meth)acrylate (this signifies a

(meth)acrylate ester of a monoaryl ether of polyalkylene glycol, and is referred to also as

"polyoxyalkylene aryl ether (meth)acrylate," "aryl alcohol polyalkylene oxide -modified (meth)acrylate," and the like) is polyethylene glycol monophenyl ether mono(meth)acrylate. Examples of polyalkylene glycol monoaryl ether mono(meth)acrylates include phenoxyethoxyethyl acrylate (e.g., Aronix M101A, Toagosei Co., Ltd.) and tetraalkylene glycol monophenyl ether monoacrylate (e.g., Aronix Ml 02,

Toagosei Co., Ltd.).

[0025]

An example of an aryloxyalkyl mono(meth)acrylate is phenoxyethyl acrylate (e.g., Biscoat #192, Osaka Organic Chemical Industry). Alkylene glycol mono(alkylaryl) ether mono(meth)acrylate is preferable, and nonylphenyloxyethylene acrylate is particularly preferable, from the fact that the surface energy is lowered.

[0026]

A photopolymerization initiator (hereinafter referred to as "component C"), which is a component of the radiation-cured adhesive composition, is a substance that can bring about radical polymerization, cationic polymerization, or the like, on being irradiated with ultraviolet or other radiation, and is used for initiating a reaction with components A and B described above and a crosslinking agent to be described later. Component C is contained at from 1 to 10 wt.% based on the total weight of the radiation-cured adhesive composition. The content is preferably from 0.5 to 8 wt.%, and more preferably from 1 to 5 wt.%.

[0027]

Component C is preferably a photo-radical initiator, and specific examples include 1 -hydroxy- cyclohexyl-phenylketone, 2-hydroxy-2-methyl- 1 -phenyl- 1 -propanone, 2-hydroxy- 1 - [4-(2- hydroxyethoxy)phenyl] -2-methyl- 1 -propanone, 2-hydroxy- 1 - {4- [4-(2-hydroxy-2-methyl-propionyl)- benzyl]phenyl}-2-methyl-propane-l-one (e.g., Irgacure 127, Ciba Specialty Chemicals), and other alpha- hydroxyketones; methyl benzoylformate and other phenylglyoxylates; alpha,alpha-dimethoxy-alpha- phenylacetophenone (e.g., Irgacure 651, Ciba Specialty Chemicals) and other benzyl dimethyl ketals; 2- benzyl-2-(dimethylamino)- 1 -[4-(4-morphorinyl)phenyl]- 1 -butanone, 2-methyl- 1 -[4-(methylthio)phenyl]- 2-(4-morphorinyl)- 1 -propanone, and other alpha-aminoketones; diphenyl (2,4,6-trimethylbenzoyl)- phosphine oxide (e.g., Darocur TAF, Ciba Specialty Chemicals) and other monoacyl phosphines; bis

(2,4,6-trimethylbenzoyl) phenyl phosphine oxide (e.g., Irgacure 819, Ciba Specialty Chemicals) and other bis acyl phosphines; phosphine oxide; bis (eta5-2,4-cyclopentadiene-l-yl) bis [2,6-difluoro-3-(l-H- propyl- 1 -yl)phenyl] titanium and other metallocenes; benzoin ethyl ether, benzoin isopropyl ether, anisoin methyl ether, and other benzoin ether-based compounds; benzyl dimethyl ketal and other ketal-based compounds; 1 -phenone- 1 , 1 -propanedione-2-(o-ethoxycarbonyl)oxim and other photoactive oxim-based compounds; benzophenone, benzoyl benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and other benzophenone -based compounds; thioxanthone, 2-chloro thioxanthone, 2-methyl thioxanthone, 2,4- dimethyl thioxanthone, isopropyl thioxanthone, 2,4-dichloro thioxanthone, 2,4-diethyl thioxanthone, 2,4- diisopropyl thioxanthone, and other thioxanthone-based compounds; camphor quinone; 2-ethyl anthraquinone, 2-isopropyl anthraquinone, and the like. These compounds may be used singly or in mixtures of pluralities. A phosphorus-containing initiator is preferable from the viewpoint of speed of curing. Particularly in the case when curing in air, the combination of a phosphorus-containing initiator and 2-hydroxy- 1 - {4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl} -2-methyl-propane- 1 -one is preferable from the perspective of curability. [0028]

A crosslinking agent (hereinafter referred to as "component D"), which is a component of the radiation-cured adhesive composition, is a compound for reacting with components A and B described above to form a crosslinked structure and for adjusting the composition to a suitable viscosity. A compound having a plurality of ethylenically unsaturated bonds can be used as component D, and a poly(meth)acrylate compound is preferable as that compound. The poly(meth)acrylate compound should have from 1.1 to 6 (meth)acryloyl groups, more preferably from 1.1 to 4, and even more preferably from 1.1 to 2. A content of component D is from 10 to 55 wt.%, and preferably from 10 to 50 wt.%, based on the total weight of the radiation-cured adhesive composition.

[0029]

Component D contains from 10 to 50 wt.% of a urethane poly(meth)acrylate (hereinafter referred to as "component Dl ") having a weight average molecular weight from 20,000 to 100,000, based on the total weight of the radiation-cured adhesive composition. The content of component D 1 is preferably from 20 to 45 wt.%, and more preferably from 20 to 40 wt.%. Also, the weight average molecular weight (here, the value calculated by gel permeation chromatography (GPC) based on styrene) is more preferably from 20,000 to 90,000, and even more preferably from 35,000 to 85,000. The urethane portion of component D 1 may be a polyester urethane, a polyether urethane, or a polyester-ether urethane. The isocyanate forming the urethane may be an aliphatic isocyanate, an alicyclic isocyanate, or an aromatic isocyanate, and the number of isocyanate groups per molecule should be 2). Component Dl may also be a mixture of a multifunctional compound and a monofunctional compound. Specifically, a bifunctional compound and a monofunctional compound may be mixed to form, for example, a 1.5-functional compound.

[0030]

Examples of components D other than component Dl include 2-hydroxy-3-acryloyloxypropyl methacrylate, polyethylene glycol di(meth)acrylate, propoxylated ethoxylated bisphenol A

di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, 9,9-bis[4-(2- acryloyloxyethoxy)phenyl]fluorene, propoxylated bisphenol A di(meth)acrylate, 1 ,6-hexanediol A di(meth)acrylate, dipropylene glycol di(meth)acrylate, ethoxylated isocyanuric acid tri(meth) aery late, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and the like. The content of these components may be less than that of component Dl, and the content may be 0. That is, component D may also contain only component D 1.

[0031]

The radiation-cured adhesive composition can contain an inorganic or organic thixotropic agent (hereinafter referred to as "component E"). Examples of inorganic thixotropic agents of component E include clay (for example, bentonite) having a particle size of less than 0.1 μηι, silica, alumina, titania, zirconia, calcium carbonate, mica, smectite, and surface-treated materials thereof. Examples of organic thixotropic agents of component E include fatty acids, hydroxy fatty acids, fatty acid amines, fatty acid amides, or other aliphatic amide compounds, hydrogenated castor oil, fatty acid metal soaps, sorbitan fatty acid ester derivatives, sorbit fatty acid ester derivatives, alkylene glycol fatty acid esters, fatty acid glycerin esters, dibenzylidene sorbitol derivatives, modified acrylic polymers and copolymers, polyhydroxycarboxylic acid amines and amides, polyvinyl alcohols, and vinyl polymers (vinyl methyl ether/maleic anhydride). A typical content of component E is from 0.1 to 5 wt.% based on the total weight of the radiation-cured adhesive composition. A thixotropic agent containing inorganic

micropowder is preferable as component E.

[0032]

The radiation-cured adhesive composition preferably further contains a leveling agent (hereinafter referred to as "component F"). Examples of component F include silicone oligomers, aliphatic oils, acrylic oligomers, polyester oligomers, and liquid synthetic rubber, and BYK-Chemie Japan

DISPERBYK series, Evonik TEGO Airex series, Kusumoto Chemicals Disparlon series, Air Products

Japan Surfynol series, and other commercially available leveling agents can be used. An ideal content is from 0.01 to 10 wt.%, and more preferably from 0.05 to 2 wt.%, based on the total weight of the radiation-cured adhesive composition.

[0033]

The radiation-cured adhesive composition may further contain a tackifying resin (hereinafter referred to as "component G"). The tackifying agent of component G is not particularly limited provided that the adhesiveness of the adhesive composition of the present invention can be improved, and examples include rosin-based resins, coumarone-indene-based resins, terpene -based resins, C5-based petroleum resins, C9-based petroleum resins, styrene-based copolymers, alkylphenol resins, xylene resins, hydrated and modified resins thereof, and the like. In particular, favorable results can be obtained, from the viewpoint of compatibility with the adhesive composition, when using hydrated rosin resins, terpene resins, terpene phenol resins, and alkylphenol-modified xylene resins.

[0034]

The rosin resins used in the present dislcosure can be commercially available rosins,

hydrogenated rosins, or derivatives thereof. Examples include "Tamanol" series rosin-modified phenol resins; "Ester Gum" series, "Pensel" series, and "Super Ester" series rosin ester resins, and "Pinecrystal" rosin derivative (all manufactured by Arakawa Chemical); "Hariphenol" series rosin-modified phenol resins; "Hariester" series and "Neotall" series rosin ester resins (manufactured by Harima Chemicals), and the like. The terpene-based resins used in the present invention can be commercially available terpene resins or derivatives thereof. Examples include YS resin TO series, TR series, YS Polystar T series, 2000 series, U series, S series, N series, Mighty Ace GG series, and K series (all manufactured by Yasuhara Chemical).The xylene resins used in the present invention can be commercially available xylene resins and derivatives thereof. Nikanol (manufactured by Fudow Co., Ltd.), and the like, can be used. The softening point of component G is preferably from 60 to 150°C, and more preferably from 80 to 130°C, from the perspective of balance of properties and performance after curing. A content of component G is preferably from 10 to 30 wt.%, and more preferably from 10 to 20 wt.%, of the total quantity of the radiation-cured adhesive composition, from the perspective of the balance of properties and performance after curing.

[0035] The radiation-cured adhesive composition described above can be cured in the presence of oxygen or in the presence of an inert gas to be used as an adhesive. In the case when cured in the presence of oxygen, the curing is preferably done by UVA and/or UVB irradiation, and the intensity is ideally from 100 to 1500 mW/cm². In the case when cured in the presence of an inert gas, a

polymerization modifier is preferably included in the radiation-cured adhesive composition, and curing should be done with UV irradiation of an intensity of 20 mW/cm² or higher. The polymerization modifier is preferably a polymerization modifier by radical reaction, and specific examples include alpha- methylstyrene, alpha-methylstyrene dimers, and compounds having thiol groups. An alpha-methylstyrene dimer is particularly preferable from the perspective of odor.

[0036]

The radiation-cured adhesive composition can be obtained by mixing each component described above with the condition that light capable of bringing about a curing reaction is not introduced to the contained curing agent, and all additives that are commonly used in the field can be added in ranges that do not impede the effect of the present invention. For example, antioxidants, photostabilizers, dyes, pigments, fragrances, and the like, can be added.

[0037]

FIG. 1 is a perspective view typically illustrating states in which an adhesive having a desired shape is formed on a substrate by screen-printing using a radiation-cured adhesive composition. FIG. 1A is a perspective view illustrating a radiation-cured adhesive composition 1 in an uncured state that is laid on a mesh including a mesh body 10 for a square frame forming the letters "ab" to be screen printed and a holder 12 for holding the same, with a squeegee 14 having been arranged thereon. An adherend 20 is present at a distance from the mesh. FIG. IB is a perspective view illustrating the radiation-cured adhesive composition 1 being spread by the squeegee 14 on the mesh and the adherend 20 being brought into proximity with the bottom face of the mesh. FIG. 1 C is a perspective view illustrating the radiation- cured adhesive composition 1 being printed on the adherend 20 by wiping off with the squeegee 14 while pressing the mesh against the adherend 20. FIG. ID is a perspective view illustrating the state on completion of the printing; and FIG. IE is a perspective view illustrating the adherend 20, which has been removed from the mesh, and with the square frame and the letters "ab" having been transferred onto the adherend 20. FIG. IF is a perspective view illustrating the adhesive 2 having a desired shape as formed on the adherend 20 by irradiating the radiation-cured adhesive composition 1 with ultraviolet radiation from a UV irradiation machine 30. A laminate having a patterned adhesive composition (radiation-cured adhesive composition 2 after curing) on a substrate (adherend 20) can be obtained thereby.

[0038]

The radiation-cured adhesive composition can be shape processed easily because occurrence of stringiness during plate removal in screen-printing (stringiness in the state in FIG. IE) is not likely to occur, and there is no situation in which the adhesive layer is cured in a swollen condition, because the radiation-cured adhesive composition can be leveled easily after application. Additionally, even if air is briefly taken in, bubbles will clear naturally. The adhesive after curing exhibits excellent adhesiveness on a wide range of adherends including stainless steel, ABS, or the like. FIG. 2 illustrates the formation of an adhesive layer by conventional die cutting. FIG. 2A is a perspective view illustrating the end portion of an adhesive 50 having been drawn out from a roll- form adhesive film. FIG. 2B is a perspective view illustrating the appearance when cut by a die cutter, and the adhesive divided into adhesive 50a to be affixed to an adherend and adhesive 50b to be discarded. FIG. 2C is a perspective view illustrating the adhesive 50a for affixing having been affixed to the adherend 20. Thus, with the method by conventional die cutting, the adhesive 50b to be discarded is inevitably produced, but with the present invention, there is no such waste, and the load on the environment has been fully considered.

Following are non-limiting, exemplary embodiments and combinations of embodiments for the present disclosure:

Embodiment 1. A radiation-cured adhesive composition comprising: from 10 to 70 wt.% of an

ethylenically unsaturated monomer not containing an aromatic ring;

from 1 to 10 wt.% of a photopolymerization initiator; and

from 10 to 55 wt.% of a crosslinking agent;

the radiation-cured adhesive composition comprising from 10 to 45 wt.% of an alkyl

(meth)acrylate having from 8 to 18 carbon atoms in the alkyl group as the ethylenically unsaturated monomer not containing an aromatic ring, and from 10 to 50 wt.% of a urethane poly(meth)acrylate having a weight average molecular weight of 20,000 to 100,000 as the crosslinking agent Embodiment 2. The radiation-cured adhesive composition according to Embodiment 1, further comprising from 10 to 40 wt.% of an ethylenically unsaturated monomer containing an aromatic ring.

Embodiment 3. The radiation-cured adhesive composition according to Embodiment 1 or 2, wherein the ethylenically unsaturated monomer not containing an aromatic ring is a monomer having a boiling point at or above that of the ethylenically unsaturated monomer containing an aromatic ring.

Embodiment 4. The radiation-cured adhesive composition according to any one of Embodiments 1 to 3, wherein at least one kind of monomer selected from a group including an alkyl (meth)acrylate other than one having from 8 to 18 carbon atoms in the alkyl group, an alkoxyalkyl (meth)acrylate, a (meth)acrylate containing a carboxylic acid, and an ethylenically unsaturated monomer containing an amide group is contained as the ethylenically unsaturated monomer not containing an aromatic ring .

Embodiment 5. The radiation-cured adhesive composition according to any one of Embodiments 1 to 4, wherein the urethane poly(meth)acrylate is a mixture of a urethane di(meth)acrylate and a urethane mono(meth)acrylate, or a urethane di(meth)acrylate, and the weight average molecular weight is from 35,000 to 850,000.

Embodiment 6. The radiation-cured adhesive composition according to any one of Embodiments 2 to 5, wherein the ethylenically unsaturated monomer containing an aromatic ring is at least one kind selected from a group including alkylene glycol mono(alkylaryl) ether mono(meth)acrylate, polyalkylene glycol mono(alkylaryl) ether mono(meth)acrylate, alkylene glycol monoaryl ether mono(meth)acrylate, polyalkylene glycol monoaryl ether mono(meth)acrylate, and aryloxyalkyl mono(meth)acrylate. Embodiment 7. The radiation-cured adhesive composition according to any one of Embodiments 4 to 6, wherein the ethylenically unsaturated monomer containing an amide group is at least one kind selected from a group including (meth)acrylamide, N-substituted (meth)acrylamide, N,N-substituted

(meth)acrylamide, aminoalkyl (meth)acrylamide, N-substituted aminoalkyl (meth)acrylamide, and N,N- substituted aminoalkyl (meth)acrylamide.

Embodiment 8. The radiation-cured adhesive composition according to any one of Embodiments 1 to 7, further comprising an inorganic or organic thixotropic agent.

Embodiment 9. The radiation-cured adhesive composition according to Embodiments 1 to 8, further comprising a leveling agent.

Embodiment 10. The radiation-cured adhesive composition according to any one of Embodiments 1 to 9, wherein curing is performed by UV irradiation in the presence of oxygen. Embodiment 11. The radiation-cured adhesive composition according to any one of Embodiments 1 to 9, further comprising a polymerization modifier, and wherein curing is performed by UV irradiation at a strength of 20 mW/cm²or higher in the presence of an inert gas.

Embodiment 12. The radiation-cured adhesive composition according to any one of Embodiments 1 to 11, wherein a peeling strength on stainless steel and ABS after curing is 4 N/cm or higher.

Embodiment 13. An adhesive obtained by curing a radiation-cured adhesive according to any one of Embodiments 1 to 12. Embodiment 14. A laminate, having a layer containing an adhesive according to Embodiment 13 patterned by screen printing on a substrate.

[Examples]

[0039]

The present disclosure is described more specifically below based on working examples and comparative examples, but the present disclosure is not limited to the working examples below.

[0040]

First, the names, chemical species, manufacturers, and categories (names in the present specification) of the materials used in the examples and working examples below are summarized in Table 1. [Table 1]

Urethane

Polyester urethane

Negami Chemical poly(meth)acrylate having

KHP22M dimethacrylate (Mw46000,

Industrial Co., Ltd. weight average molecular bifunctional)

weight 20000-100000

Urethane

Polyester urethane diacrylate Negami Chemical poly(meth)acrylate having

UN7700

(Mw20000, bifunctional) Industrial Co., Ltd. weight average molecular

weight 20000-100000

Urethane

Polyester urethane diacrylate Negami Chemical poly(meth)acrylate having

UV3700

(Mw36000, bifunctional) Industrial Co., Ltd. weight average molecular

weight 20000-100000

Urethane

Polyester urethane

Negami Chemical poly(meth)acrylate having

SSFX-1 diacrylate(Mw46000,

Industrial Co., Ltd. weight average molecular bifunctional)

weight 20000-100000

Thixotropic agent

Nippon Aerosil

A200 Fumed silica containing inorganic

Co., Ltd.

micropowder

Thixotropic agent

Hydrophobic treated fumed Nippon Aerosil

R972 containing inorganic

silica Co., Ltd.

micropowder

HP100 Xylene phenol resin Fudow Co., Ltd. Tackifier

Yasuhara

T0125 Terpene resin Tackifier

Chemical Co., Ltd.

Yasuhara

TOH5 Terpene resin Tackifier

Chemical Co., Ltd.

Arakawa Chemical

A125 Rosin ester Tackifier

Industries, Ltd.

Arakawa Chemical

T125 Rosin ester Tackifier

Industries, Ltd.

Arakawa Chemical

KE311 Rosin ester Tackifier

Industries, Ltd.

HP100 Xylene phenol resin Fudow Co., Ltd. Tackifier

Goi Chemical Co.,

AMSD Alpha-methylstyrene dimer Polymerization modifier

Ltd.

Wako Pure

aMSt Alpha-methylstyrene Chemical Polymerization modifier

Industries, Ltd.

Shin-etsu

KP323 Silicone oligomers Leveling agent

Chemical Co., Ltd.

[0041]

[Working examples 1 to 3]

The compositions having the compositions listed in Table 2 below were mixed in UV-cut plastic bottles. The composition was applied by doctor blade to a thickness of 50 μηι on a silicone -treated transparent polyester film, and was cured by passing three times through a Fusion FS300 curing oven (H bulb, 15 m/minute, 200 mJ/cm²/pass) in an oxygen atmosphere. Sufficient curing was possible thereby. Curing was then further performed seven times in an oxygen atmosphere. The total dosage of irradiation was 2000 mJ/cm². The adhesive composition (pressure-sensitive adhesive) on the PET film obtained thereby was laminated with another silicone-treated PET film.

[Table 2] Embodiment Embodiment Embodiment

Trade Name

1 2 3

2EHA 10 10 10

LA 46 46 46

Acrylester HH 5 5 5

Darocur TPO 1.0 1.0 1.0

Irgacure 127 3.0 3.0 3.0

SSFX-1 39.0 39.0 39.0

R972 1.0 1.0 1.0

T0125 25.0 - -

TOH5 - 25.0 -

HP100 - - 25.0

[0042]

(Method of measurement of peeling strength)

The peeling strength (peeling adhesive strength) was measured by a method based on JIS Z 0237. The details are as follows. The adhesive sheet obtained above was cut by cutter into 25x70 mm pieces. Also, a release film was peeled from the cured surface, and the adhesive sheet was affixed to a polyester film (S-25, Unitika), which had been cut into a 30* 150 mm piece having a thickness of 25 μηι. A remaining release film was removed from the adhesive sheet, and then the adhesive sheet was affixed using a rubber roller having a weight of 2 kg to an ABS plate (manufactured by Nihon Tact Co., Ltd.) having a thickness of 2 mm, a polypropylene (PP) plate (manufactured by Nihon Tact Co., Ltd.) having a thickness of 2 mm, or a stainless steel plate (manufactured by Nihon Tact Co., Ltd.) having a thickness of 1 mm, which had been immersed in isopropyl alcohol (IPA) and wiped with a cloth. After setting aside for 20 minutes at room temperature, a tension at a peeling speed of 300 mm/minute was applied to the polyester film by tension tester (AG-IS, Shimadzu), and the 180° peeling strength of the adhesive sheet was measured.

[0043]

(Method of measurement of static shear strength)

A release film was peeled from the adhesive sheet obtained above, the adhesive sheet was affixed to a polyester film (S-25, Unitika) having a thickness of 25 μηι, and the sheet was cut by cutter into a

25 x 100 mm piece. A remaining release film was removed from the adhesive sheet, and then the adhesive sheet was affixed using a rubber roller having a weight of 2 kg to a stainless steel plate (manufactured by Nihon Tact Co., Ltd.) having a thickness of 1.0 mm, which had been washed with isopropyl alcohol (IPA) or methyl ethyl ketone (MEK), so as to cover a range of 25 mm x 25 mm of the plate. The sample was suspended together with a 500 g weight in a 70°C chamber. The time until separation and dropping (drop off) and the extent of shifting were measured after 24 hours.

[0044]

(Method of measurement of suitability for screen-printing)

The suitability for screen-printing of the radiation-cured adhesive compositions obtained in the comparative examples was evaluated using a screen printer (SERIA, HK320). A screen-printing plate was applied in a pattern on a polyester film (S-100, Unitika Ltd.) having a thickness of 100 μηι using a patterned polyester mesh plate (Tetron #120 mesh, 54 μηι line width, 55% aperture, Tokai Shoji Co., Ltd.), and the stringiness when removing from the polyester film and the leveling and bubble clearing of the printed object were observed. Those having very good stringiness, leveling, and bubble clearing were evaluated as excellent, those having good stringiness, leveling, and bubble clearing were evaluated as good, those having no stringiness but having a somewhat disorderly printed surface were evaluated as passable, and those having occurrence of stringiness during plate removal were evaluated as failed.

[0045]

The content (%) of each component and the measurement results are listed in Table 3 below. In the table, CF signifies cohesive failure, AF signifies adhesive failure, and Shocky signifies that the state of peeling is not uniform, which is a state in which high strength and low strength appear alternately. [Table 3]

[0046]

[Working examples 4 to 10]

Compositions having the compositions listed in Tables 4 and 5 below were created in the same manner as above, and the same kinds of measurements as above were performed. The content (%) of each component and the measurement results are listed in Tables 6 and 7 below.

[Table 4]

[0047] [Table 5]

[0048] [Table 6]

T0125 18.8% 0.0% 0.0% 15.9% 19.1% 0.0% 0.0%

TOH5 0.0% 18.8% 0.0% 0.0% 0.0% 19.1% 0.0%

A125 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 19.1%

HP100 0.0% 0.0% 18.8% 0.0% 0.0% 0.0% 0.0%

SUS Detachment

6.2 6.7 4.6 8.2 7.6 7.2 7.4 Strength (N/cm)

Failure Mode AF AF AF AF AF AF AF

ABS Detachment

5.1 5.1 4.4

Strength (N/cm)

Failure Mode AF AF AF - - - -

PP Detachment

4.2 3.8 3.0 6.0 6.3 3.1 3.0 strength (N/cm)

Failure Mode AF AF AF AF AF Shocky Shocky

Drop-off (min) >1440 >1440 >1440 >1440 938.0 85.0 >1440

Slippage (mm) 0 0 0 0 - - 2

Screen-printing FavorFavorFavorFavorFavorFavorFavor¬

Suitability able able able able able able able

[0049]

[Table 7]

[0050] [Working examples 18 to 23]

Compositions having the compositions listed in Table 8 below were created in the same manner as above, the same kinds of measurements as above were performed. The content (%) of each component and the measurement results are listed in Table 9 below.

[Table 8]

[0051]

[Table 9]

[0052]

[Working examples 24 to 34]

Compositions having the compositions listed in Table 10 below were created in the same manner as above; the same kinds of measurements as above were performed. The content (%) of each component and the measurement results are listed in Table 11 below. AF90/CF10 signifies an adhesive failure of 90% and a cohesive failure of 10%.

[Table 10]

[0053] [Table 11]

[0054]

[Working examples 35 to 48]

The compositions having the compositions listed in Tables 12 and 13 below were mixed in UV-cut plastic bottles. Each composition was applied by doctor blade to a thickness of 50 μηι on a silicone -treated transparent polyester film, and was cured in a UV curing oven (365 nm, UV (365) N₂purge UV irradiation device, Eye Graphics Co., Ltd.). The conditions in the curing oven were 0.5 m/s and 26 mW/cm², and the total dosage of irradiation was lOOO mJ/cm². The curing process was carried out in a nitrogen gas atmosphere (O2 concentration < 200 ppm). The adhesive composition (pressure-sensitive adhesive) on the PET film obtained thereby was laminated with another silicone-treated PET film.

[Table 12]

[0055]

[Table 13]

[0056] The content (%) of each component and the measurement results are listed in Tables 14 below.

[Table 14]

[0057]

[Table 15]

[0058]

[Comparative examples 1 to 2]

The compositions having the compositions listed in Table 16 below were mixed in UV- cut plastic bottles. Each composition was applied by doctor blade to a thickness of 50 μηι on a silicone-treated transparent polyester film, and was cured in a UV curing oven (365 nm, UV (365) N₂purge UV irradiation device, Eye Graphics Co., Ltd.). The conditions in the curing oven were 0.5 m/s and 26 mW/cm², and the total dosage of irradiation was lOOO mJ/cm². The curing process was carried out in a nitrogen gas atmosphere (O2 concentration < 200 ppm). The adhesive composition (pressure-sensitive adhesive) on the PET film obtained thereby was laminated with another silicone-treated PET film.

[Table 16]

[0059]

The suitability for screen-printing of the above adhesive compositions (pressure-sensitive adhesives) was measured in the same manner as in the working examples, at which time the suitability for screen -printing was poor in both comparative examples 1 and 2.

[0060]

1 : Radiation-cured adhesive composition, 2: Radiation-cured adhesive composition after curing, 10: Mesh body, 12: Holder, 14: Squeegee, 20: Adherend, 30: UV irradiator, 50, 50a, and 50b: adhesive.

Claims

What is Claimed is:

1. A radiation-cured adhesive composition comprising: from 10 to 70 wt.% of an

ethylenically unsaturated monomer not containing an aromatic ring;

from 1 to 10 wt.% of a photopolymerization initiator; and

from 10 to 55 wt.% of a crosslinking agent;

the radiation-cured adhesive composition comprising from 10 to 45 wt.% of an alkyl (meth)acrylate having from 8 to 18 carbon atoms in the alkyl group as the ethylenically unsaturated monomer not containing an aromatic ring, and from 10 to 50 wt.% of a urethane poly(meth)acrylate having a weight average molecular weight of 20,000 to 100,000 as the crosslinking agent

2. The radiation-cured adhesive composition according to claim 1, further comprising from 10 to 40 wt.% of an ethylenically unsaturated monomer containing an aromatic ring.

3. The radiation-cured adhesive composition according to claim 1 or 2, wherein the ethylenically unsaturated monomer not containing an aromatic ring is a monomer having a boiling point at or above that of the ethylenically unsaturated monomer containing an aromatic ring.

4. The radiation-cured adhesive composition according to any one of claims 1 to 3, wherein at least one kind of monomer selected from a group including an alkyl (meth)acrylate other than one having from 8 to 18 carbon atoms in the alkyl group, an alkoxyalkyl (meth)acrylate, a (meth)acrylate containing a carboxylic acid, and an ethylenically unsaturated monomer containing an amide group is contained as the ethylenically unsaturated monomer not containing an aromatic ring .

5. The radiation-cured adhesive composition according to any one of claims 1 to 4, wherein the urethane poly(meth)acrylate is a mixture of a urethane di(meth)acrylate and a urethane mono(meth)acrylate, or a urethane di(meth)acrylate, and the weight average molecular weight is from 35,000 to 850,000.

6. The radiation-cured adhesive composition according to any one of claims 2 to 5, wherein the ethylenically unsaturated monomer containing an aromatic ring is at least one kind selected from a group including alkylene glycol mono(alkylaryl) ether mono(meth)acrylate, polyalkylene glycol mono(alkylaryl) ether mono(meth)acrylate, alkylene glycol monoaryl ether

mono(meth)acrylate, polyalkylene glycol monoaryl ether mono(meth)acrylate, and aryloxyalkyl mono(meth)acrylate .

7. The radiation-cured adhesive composition according to any one of claims 4 to 6, wherein the ethylenically unsaturated monomer containing an amide group is at least one kind selected from a group including (meth)acrylamide, N-substituted (meth)acrylamide, N,N-substituted (meth)acrylamide, aminoalkyl (meth)acrylamide, N-substituted aminoalkyl (meth)acrylamide, and Ν,Ν-substituted aminoalkyl (meth)acrylamide.

8. The radiation-cured adhesive composition according to any one of claims 1 to 7, further comprising an inorganic or organic thixotropic agent.

9. The radiation-cured adhesive composition according to claims 1 to 8, further comprising a leveling agent.

10. The radiation-cured adhesive composition according to any one of claims 1 to 9, wherein curing is performed by UV irradiation in the presence of oxygen.

11. The radiation-cured adhesive composition according to any one of claims 1 to 9, further comprising a polymerization modifier, and wherein curing is performed by UV irradiation at a strength of 20 mW/cm²or higher in the presence of an inert gas.

12. The radiation-cured adhesive composition according to any one of claims 1 to 11, wherein a peeling strength on stainless steel and ABS after curing is 4 N/cm or higher.

13. An adhesive obtained by curing a radiation-cured adhesive according to any one of claims 1 to 12.

14. A laminate, having a layer containing an adhesive according to claim 13 patterned by screen printing on a substrate.