JP7399743B2 - adhesive composition - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition that exhibits slight tackiness under normal conditions and exhibits high adhesive strength after being irradiated with ultraviolet rays.

In the manufacturing process of electronic components, optical components, etc., a protective film is used to temporarily protect the component, and a method is used in which the protective film is peeled off and removed after the protection step. Since protective films are required to be easily peelable after use, photo-curable adhesives have been used in recent years. Such pressure-sensitive adhesives have strong adhesive strength before being photocured, and therefore have excellent protective performance, and by reducing the adhesive strength through photocuring, they improve releasability.

On the other hand, since such adhesives have a strong adhesive force from the initial state, they are not suitable for rework work in which if the adhesive is misaligned when it is bonded to a member, it must be peeled off and then bonded again.
Patent Document 1 discloses an adhesive whose one purpose is to prevent damage to glass, and which can be applied and peeled multiple times for alignment. However, since the adhesive strength remains the same between bonding and holding, there was a risk that the adhesive strength would be insufficient during holding.

Japanese Patent Application Publication No. 2011-178929

An object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits slight tackiness under normal conditions and exhibits high tackiness after irradiation with ultraviolet rays.

In order to solve the above-mentioned problem, the invention according to claim 1 provides the following features: (a) an acrylic copolymer, (b) a curing agent, (c) an ultraviolet polymerization initiator, and (d) a monofunctional (meth) having a cyclic structure. A (meth)acrylic monomer containing an acrylic monomer and (e) a fluorine-based leveling agent , wherein the monomer constituting the above (a) has a substituent having 4 or more carbon atoms including n-butyl acrylate. 80 to 98% by weight of the monomer and 0.05 to 5% by weight of the acidic group-containing (meth)acrylic monomer or/and 1 to 10% by weight of the hydroxyl group-containing (meth)acrylic monomer, and the above (d) Provided is an adhesive composition characterized in that the compound contains a structure having a hydroxyl group and/or a polycyclic structure .

The invention according to claim 2 provides that the (d) monofunctional (meth)acrylic monomer having a cyclic structure is contained in 10 to 80 parts by weight based on 100 parts by weight of the (a) acrylic copolymer. A pressure-sensitive adhesive composition according to claim 1 is provided.

The invention according to claim 3 provides the adhesive composition according to claim 1 or 2, wherein the acrylic copolymer (a) has a weight average molecular weight of 100,000 to 2,000,000 .

The adhesive composition of the present invention exhibits low adhesion under normal conditions, can be easily reapplied, and has excellent reworkability, and exhibits high adhesive strength after irradiation with ultraviolet rays, so it can be used to temporarily protect electronic component materials during storage or transportation. Particularly suitable for carrier tapes.

The adhesive composition of the present invention comprises (a) an acrylic copolymer, (b) a curing agent, (c) an ultraviolet polymerization initiator, (d) a monofunctional (meth)acrylic monomer, and (e ) Contains a fluorine leveling agent. Note that (meth)acrylic in the present invention includes acrylic and methacryl, and (meth)acrylic monomer refers to a monomer having a (meth)acrylic acid ester structure.

The acrylic copolymer (a) used in the present invention is obtained by polymerizing (meth)acrylic monomers and monomers copolymerizable with these monomers. Examples of the alkyl group-containing (meth)acrylic monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec- Butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2- Ethylhexyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl ( meth)acrylate, heptadecyl(meth)acrylate, stearyl(meth)acrylate, behenyl(meth)acrylate, isodecyl(meth)acrylate, isomystyryl(meth)acrylate, isostearyl(meth)acrylate, propylheptyl(meth)acrylate, isoundecyl( Examples include meth)acrylate, isododecyl(meth)acrylate, isotridecyl(meth)acrylate, isopentadecyl(meth)acrylate, isohexadecyl(meth)acrylate, isoheptadecyl(meth)acrylate, etc. singly or in combination of two or more. can be used. Among these, (meth)acrylic monomers having an alkyl group having 4 or more carbon atoms are preferable because they have a low glass transition temperature and have a low glass transition temperature in order to bring out adhesive properties, and specifically, n-butyl acrylate (hereinafter referred to as BA), It is preferable to select 2-ethylhexyl acrylate (hereinafter referred to as 2EHA), isostearyl acrylate (hereinafter referred to as ISTA), and the like.

The blending ratio of the (meth)acrylic monomer having an alkyl group having 4 or more carbon atoms in (a) is preferably 80 to 98% by weight, more preferably 90 to 95% by weight. When the content is 80% by weight or more, excessive crosslinking reaction can be suppressed and sufficient reworkability can be ensured before UV irradiation, and when the content is 98% by weight or less, sufficient adhesive strength can be ensured.

Further, (a) contains a (meth)acrylic monomer containing a functional group, so that it can undergo a crosslinking reaction with a curing agent to obtain appropriate adhesive strength before UV irradiation, and can improve reworkability. Examples of functional groups include acidic groups and hydroxyl groups; examples of acidic group-containing (meth)acrylic monomers include acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, and hydroxyl group-containing (meth)acrylic monomers. Examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate. Examples include acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and the like. Among these, acrylic acid (hereinafter referred to as AA) is preferred as the acidic group-containing (meth)acrylic monomer because it has good copolymerizability with other (meth)acrylic monomers, and hydroxyl group-containing (meth)acrylic As monomers, 2-hydroxyethyl acrylate (hereinafter referred to as 2HEA) and 2-hydroxyethyl methacrylate (hereinafter referred to as 2HEMA) are preferred from the viewpoint of copolymerizability with (meth)acrylic monomers.

The blending ratio of the acidic group-containing (meth)acrylic monomer in (a) is preferably 0.05 to 5% by weight, more preferably 0.08 to 4% by weight. By setting the content to 0.05% by weight or more, sufficient adhesiveness required for rework can be ensured, and by setting the content to 5% by weight or less, sufficient removability can be ensured. The blending ratio of the hydroxyl group-containing (meth)acrylic monomer is preferably 1 to 10% by weight, more preferably 3 to 8% by weight. By setting the content to 3% by weight or more, sufficient adhesiveness required for rework can be ensured, and by setting the content to 8% by weight or less, sufficient removability can be ensured.

Various other monomers can also be used for the above (a). For example, amide group-containing (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, (meth)acryloylmorpholine, N-vinylpyrrolidone, diacetone (meth)acrylamide, etc. Examples include acrylic monomers, glycidyl group-containing (meth)acrylic monomers such as glycidyl (meth)acrylate, and vinyl monomers such as styrene, acrylonitrile, and vinyl acetate.

For the above (a), these monomers can be polymerized by known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. Preferably, the preparation is carried out by solution polymerization.

The solvents used in the solution polymerization in (a) include methyl acetate, ethyl acetate, butyl acetate, benzene, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, n-hexane, isopropyl alcohol, n-butanol, and propylene glycol. Examples include organic solvents such as monomethyl ether, propylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, and propylene carbonate. However, there is no problem in using solvents other than these, and two or more types of solvents may be used in combination.

It is preferable to use a thermally decomposable polymerization initiator as the polymerization initiator (a). 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl- 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'- Azobis[N-(2-propenyl)-2-methoxypropionamide], 1-[(1-cyano-1-methylethyl)azo]formamide, 2,2'-azobis(N-butyl-2-methylpropionamide) ), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), [1,1'-azobis(1-acetoxy-1-phenylethane)], lauroyl peroxide, octa Noyl peroxide, benzoyl peroxide, ethyl methyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, cumyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t -Butyl peroxy-2-ethylhexanoate, dicumyl peroxide, isobutyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, t-butyl peroxybenzoate, 2,5-dimethyl-2 , 5-di(t-butylperoxy)hexane, di(2-ethylhexyl)peroxydicarbonate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 3,3, Organic oxide compounds such as 5-trimethylcyclohexanoyl peroxide can be used. Further, the peroxide compound can be redox-polymerized by using a reducing agent such as N,N-dimethyltoluidine or N,N-diethyltoluidine.

The amount of the polymerization initiator (a) may be 0.05 to 3 parts by weight per 100 parts by weight of the monomer. If the amount of the polymerization initiator used increases, the molecular weight of the obtained copolymer tends to decrease, and if the amount of the polymerization initiator used decreases, the molecular weight of the obtained copolymer tends to increase.

The weight average molecular weight (hereinafter Mw) of the polymer (a) copolymerized as described above is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,000,000, and particularly preferably 250,000 to 600,000. By setting it to 100,000 or more, sufficient durability as an adhesive layer can be ensured, and by setting it to 2,000,000 or less, sufficient compatibility with a curing agent, a photoinitiator, etc. can be ensured. Note that Mw can be calculated by measuring the molecular weight in terms of standard polystyrene by gel permeation chromatography using a column using a styrene divinylbenzene-based packing material and using a tetrahydrofuran eluent.

The curing agent (b) used in the present invention is used to impart slight tackiness to the pressure-sensitive adhesive composition before UV irradiation by reacting with the functional group (a). Specific examples include polyvalent isocyanate compounds, polyvalent epoxy compounds, and metal chelate compounds.

Examples of the polyvalent isocyanate (b) include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and adduct types thereof. Examples include isocyanurate type and biuret type. Examples of metal chelate compounds include aluminum chelate, zirconium chelate, and titanium chelate.

The amount of (b) added to 100 parts by weight of (a) is preferably 0.1 to 8 parts by weight, more preferably 0.5 to 5 parts by weight. By setting it within this range, the crosslinking reaction with the functional group in (a) will proceed, the adhesiveness before ultraviolet irradiation will be appropriate, and an adhesive layer with excellent reworkability can be formed.

Examples of the ultraviolet polymerization initiator (c) used in the present invention include benzyl ketal, α-hydroxyacetophenone, acylphosphine oxide, benzophenone, thioxanthone, benzoin ether, α-ketol, and aromatic sulfonyl. Examples include chloride type and photoactive oxime type.

As the above (c), for example, 2,2-dimethoxy-1,2-diphenylethan-1-one is used as a benzyl ketal type, 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4 -(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is 2-methyl-1-(4-methylthiophenyl)-2-morpho as α-aminoacetophenone. There are acylphosphine oxides such as 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2.4.6-trimethylbenzoyl)-phenylphosphine oxide, and linopropan-1-one is used alone. Alternatively, two or more types can be used in combination. Among these, it is preferable to include an acylphosphine oxide type which has excellent internal curability, and commercially available products include Omnirad TPO (trade name: manufactured by IGM).

The amount of the ultraviolet curing component (c) relative to 100 parts by weight is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight.

(d) The monofunctional (meth)acrylic monomer having a cyclic structure used in the present invention can advance the polymerization reaction by UV irradiation and improve the adhesive force of the adhesive layer, and also has a cyclic structure. It is possible to maintain a high elastic modulus even at high temperatures. The cyclic structure referred to herein may be any of alicyclic, aromatic, and heterocyclic compounds, and may be monocyclic or polycyclic. In the case of a polyfunctional (meth)acrylic monomer, even after UV irradiation, it does not exhibit sufficient peel strength compared to a monofunctional (meth)acrylic monomer, and is therefore unsuitable for blending alone.

Examples of (d) include dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, adamantanyl (meth)acrylate, 1,4 -Alicyclic (meth)acrylic monomers such as cyclohexanediol acrylate and cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl acrylate, methylphenoxyethyl acrylate, ethoxylated o-phenylphenol acrylate, 2-hydroxy Aromatic (meth)acrylic monomers such as -3-phenoxypropyl acrylate, tetrahydrofurfuryl (meth)acrylate, pentamethylpiperidinyl (meth)acrylate, tetramethylpiperidinyl (meth)acrylate, acryloylmorpholine, etc. These heterocyclic compounds can be used alone or in combination of two or more kinds. Among these, structures having a hydroxyl group and/or polycyclic structures are preferred because they are less likely to volatilize in the solvent drying step after applying the adhesive composition, such as 2-hydroxy-3- Examples include phenoxypropyl acrylate and ethoxylated o-phenylphenol acrylate.

The amount of (d) added to 100 parts by weight of (a) is preferably 10 to 80 parts by weight, more preferably 15 to 70 parts by weight, and particularly preferably 20 to 60 parts by weight. By setting it within this range, sufficient adhesive force can be ensured after ultraviolet irradiation. The amount of (d) added to the total solid content is preferably 10 to 50% by weight, more preferably 15 to 40% by weight.

The fluorine-based leveling agent (e) used in the present invention is blended as an additive to reduce adhesive strength before UV irradiation. Although the mechanism of reducing adhesive strength is not clear, it not only simply improves the leveling properties of the coated surface, but also suppresses the crosslinking reaction between (a) and (b) due to the synergistic effect with (d). This is expected to suppress the increase in peel strength. As a commercially available product, there is the Megafac F series (trade name: manufactured by DIC Corporation).

The amount of (e) added to 100 parts by weight of (a) is preferably 0.05 to 3.0 parts by weight, more preferably 0.1 to 1.0 parts by weight. By setting it within this range, the adhesive force before ultraviolet irradiation can be suppressed due to the synergistic effect with (d). The amount of (e) to be blended is preferably 0.05 to 2.0 parts by weight, preferably 0.1 to 1.0 parts by weight, based on 100 parts by weight of the above (a) and (d).

The adhesive composition of the present invention has a peel strength of 30 gf/25 mm or less at a peeling speed of 300 mm/min when glass and a 75 μm thick PET film are bonded together with a film thickness of 13 μm, and a peel strength of 30 gf/25 mm or less at a peeling speed of 300 mm after irradiation with ultraviolet rays. It is preferable that the peel strength in /min is 500 gf/25 mm or more. Due to these properties, when used as an adhesive for carrier tapes, it can be bonded to electronic component materials in a slightly adhesive state, and then be irradiated with ultraviolet rays to obtain physical properties that result in strong adhesive properties. .

The adhesive composition of the present invention may further contain various additives such as ultraviolet absorbers, near-infrared absorbers, antioxidants, preservatives, antifungal agents, tackifying resins, plasticizers, antifoaming agents, and wettability regulators. It may also contain an agent.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but these are intended to be specific examples and are not particularly limited to these. Note that all parts are parts by weight.

Preparation of Acrylic Copolymer A 55 parts of BA as monomers, 38.9 parts of 2EHA, 0.1 part of AA, 6 parts by weight of 2HEA, 0.1 part of azobisdimethylvaleronitrile as a polymerization initiator, A monomer mixture was prepared by dissolving 27 parts of ethyl acetate as a solvent. 50 parts of ethyl acetate was added as a solvent to a separable flask equipped with a stirrer and a reflux condenser, the temperature was raised to 75°C, and nitrogen gas was introduced for 30 minutes or more to remove oxygen in the polymerization system. Next, the monomer mixture was added dropwise over a period of 3 hours while maintaining the temperature at 75±1°C, and the reaction was allowed to continue for 2 hours while maintaining the temperature at 75±1°C. Thereafter, the reaction temperature was raised to 78°C and maintained at 78±2°C for 2 hours to complete the polymerization reaction. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to adjust the solid content concentration to 40% to obtain a solution of acrylic copolymer A as a pale yellow transparent viscous liquid. Mw was 480,000.

Preparation of acrylic copolymers B and C Acrylic copolymers B and C were prepared by changing the monomer ratio of the above acrylic copolymer A to the values listed in Table 1.

Examples 1 to 5
Acrylic copolymers A to C are used as (a), Coronate HA (trade name: manufactured by Tosoh Corporation, polyvalent isocyanate) and Nacem aluminum (trade name: manufactured by Nippon Kagaku Sangyo Co., Ltd., acetylacetone aluminum complex) and TETRAD-X (product name: Mitsubishi Gas Chemical Co., Ltd., polyfunctional epoxy resin), (c) Omnirad TPO (iGM), (d) FA-610 (product name: Hitachi Chemical Co., Ltd., 1) , 4-cyclohexanediol acrylate) and NK ester 702A (product name: Shin Nakamura Chemical Co., Ltd., 2-hydroxy-3-phenoxypropyl acrylate) and NK ester A-LEN-10 (product name: Shin Nakamura Chemical Co., Ltd., ethoxy The adhesive compositions of Examples 1 to 5 were prepared by adding and mixing Megafac F559 (trade name: manufactured by DIC Corporation) as (e).

Comparative examples 1 to 6
In addition to the materials used in the examples, acrylic monomers such as ISTA (isostearyl acrylate), Plaxel FA2D (trade name: unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone), and 1.9-NDA (1.9 nonanedi acrylate) as a leveling agent, Polyflow No. By mixing 77 (trade name: manufactured by Kyoeisha Chemical Co., Ltd., acrylic type) and Polyflow KL-401 (trade name: manufactured by Kyoeisha Chemical Co., Ltd., silicone type) in the formulation shown in Table 2, the adhesives of Comparative Examples 1 to 6 were prepared. A composition was prepared.

Evaluation method Each adhesive composition was applied onto a 75 μm thick PET film so that the dry thickness was 13 μm, and after heating and drying at 100°C for 2 minutes, a release film (silicone-treated PET film) was formed. A pressure-sensitive adhesive sheet was obtained by laminating the sheets together and leaving the sheet in an atmosphere of 23° C. and 50% RH for 7 days.

Peel strength (before UV irradiation): Create a film piece with a width of 25 mm and a length of 100 mm from the adhesive sheet, peel off the release film, and stick it on glass using a laminator at 23 ° C and 50% RH atmosphere. , 23° C., and a relative humidity of 50% RH for one day to prepare a test piece. Thereafter, it was pulled in a 180° direction at a pulling speed of 300 mm/min, and its center value was taken as the measured value, and 30 gf/25 mm or less was rated ○, and more than 30 gf/25 mm was rated x.

Peel strength (after UV irradiation): After preparing a test piece in the same manner, the PET film surface of the test piece was irradiated with ultraviolet light using an LED lamp (irradiation intensity: 100 mW/cm ² , irradiation amount: 1000 mJ/cm ² ). Thereafter, it was pulled in a 180° direction at a pulling speed of 300 mm/min, and its center value was taken as the measured value. 500 gf/25 mm or more was rated as ○, and less than 500 gf/25 mm was rated as x.

Storage modulus: Each adhesive composition is applied onto a release film (silicone-treated PET film) so that the thickness after drying is 100 μm, and after drying by heating at 95°C for 10 minutes, the release film is (Silicone-treated PET film) was laminated together, and this sheet was left in an atmosphere of 23° C. and 50% RH for 7 days to obtain an adhesive sheet for elastic modulus measurement. A part of this adhesive sheet was irradiated with ultraviolet light using a high-pressure mercury lamp (irradiation intensity 150 mW/cm2, irradiation amount 2000 mJ/cm2), and the storage modulus was measured before and after the ultraviolet irradiation using a DMA (DMS6100 model) manufactured by Hitachi High-Tech Science. The measurements were performed at a frequency of 1 Hz, a temperature of 160° C., and a sample thickness of 400 μm. A storage modulus of 1×10 ⁴ or more was rated as ○, and a storage modulus of less than 1×10 ⁴ was rated as ×.

Each of the pressure-sensitive adhesive compositions of Examples had slight tackiness before irradiation with ultraviolet rays, and the adhesive strength significantly improved after irradiation with ultraviolet rays. Moreover, the elastic modulus was also good.

On the other hand, in (d), Comparative Example 1 in which a chain monomer was blended had a low elastic modulus, and Comparative Example 2 in which an acyclic monomer was blended and Comparative Example 3 in which a bifunctional monomer was blended had a low elastic modulus after UV irradiation. The peel strength of Comparative Examples 4 and 5, which contained leveling agents other than fluorine-based, and Comparative Example 6, which contained no leveling agent, had strong adhesive strength before UV irradiation, and both were not suitable for the present invention. there were.

Claims (3)

Contains (a) an acrylic copolymer, (b) a curing agent, (c) an ultraviolet polymerization initiator, (d) a monofunctional (meth)acrylic monomer having a cyclic structure, and (e) a fluorine-based leveling agent. , the monomer constituting the above (a) contains 80 to 98% by weight of a (meth)acrylic monomer having a substituent having 4 or more carbon atoms including n-butyl acrylate, and an acidic group-containing (meth)acrylic monomer. Contains 0.05 to 5% by weight of a monomer or/and 1 to 10% by weight of a hydroxyl group-containing (meth)acrylic monomer, and (d) contains a structure having a hydroxyl group and/or a polycyclic structure. Characteristic adhesive composition. 2. The method according to claim 1 , wherein the (d) monofunctional (meth)acrylic monomer having a cyclic structure is contained in 10 to 80 parts by weight based on 100 parts by weight of the (a) acrylic copolymer. Adhesive composition. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the weight average molecular weight of the acrylic copolymer (a) is 100,000 to 2,000,000 .