JP2003165958A - Uv-curable acrylic pressure-sensitive adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a UV-curable acrylic pressure-sensitive adhesive composition having a high degree of polymerization after UV-curing even in a short period of curing time by incorporating a specified rosin based tackifying resin thereinto, an acrylic pressure-sensitive adhesive using the UV-curable acrylic pressure- sensitive adhesive composition, and to provide a pressure-sensitive self-adhesive tape or a pressure-sensitive self-adhesive sheet using the pressure-sensitive adhesive. <P>SOLUTION: In the UV-curable acrylic pressure-sensitive adhesive composition comprising 50-95 mass% at least one monomer selected from the group consisting of an alkyl acrylate and an alkyl methacrylate and 5-30 mass% rosin based tackifying resin, a specified compound whose content in the pressure- sensitive adhesive composition is not greater than a specified amount is used. Thus, the UV-curable acrylic pressure-sensitive adhesive composition having a high degree of polymerization after UV-curing and a high adhesive power can be obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a UV-curable acrylic pressure-sensitive adhesive composition which can be used for a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet, and an acrylic pressure-sensitive adhesive obtained by UV polymerization of the composition.

[0002]

2. Description of the Related Art Due to its convenience, adhesives are currently used for bonding a variety of adherends, including many adhesive products such as labels, sheets and tapes. As the applications of pressure-sensitive adhesives have expanded, the performance required for pressure-sensitive adhesives has become more widespread. As such required performance, adhesion to polyolefins such as polypropylene and polyethylene is emphasized due to diversification of base materials and adherends.

In order to improve the adhesion of the acrylic pressure-sensitive adhesive to the polyolefin, it is common to add a tackifying resin. As the tackifying resin, a rosin-based tackifying resin is preferably used because it has a great effect of improving the adhesiveness to polyolefin.

Generally, an acrylic pressure-sensitive adhesive composition containing a tackifying resin is a monomer containing an acrylic acid ester and / or a methacrylic acid ester (hereinafter abbreviated as (meth) acrylic acid ester) as a main component. It is prepared by a so-called post-addition method in which a tackifying resin is added after polymerizing. For example, it is produced by radically polymerizing a monomer in an organic solvent and then compounding a tackifying resin. According to this method, the tackifying resin is added after the polymerization, so that it does not affect the polymerization process.

On the other hand, after adjusting the viscosity of a monomer containing a (meth) acrylic ester as a main component to a coatable viscosity, it is coated on a UV light transmissive substrate such as a polyethylene terephthalate (PET) film, and then UV. A method of forming an adhesive layer on a substrate by irradiating it with light to produce an adhesive tape and an adhesive sheet is described in US Pat. No. 4,181,752. According to this method, the tackifying resin must be compounded before the polymerization, and therefore the influence on the polymerization process must be examined.

In general, the rosin-based tackifying resin which is preferably used as the tackifying resin inhibits the polymerization because the aliphatic double bond existing in the molecular skeleton acts as a chain transfer / terminating agent for the radical polymerization reaction. Therefore, it is not possible to form a pressure-sensitive adhesive layer having sufficient cohesive strength and adhesive performance. As a means for solving such a problem, JP-A-2-18485 discloses a rosin-based tackifying resin in which an aliphatic double bond is reduced by hydrogenation, and JP-A-5-255417 discloses a disproportionation.
The rosin-based tackifying resin in which the aliphatic double bond has been reduced by (dehydrogenation), when blended with a monomer containing a (meth) acrylic acid ester as a main component, is less susceptible to polymerization inhibition and has an improved adhesive force. It is described that an excellent pressure-sensitive adhesive layer can be formed. Further, JP-A-2000-327708, a rosin substance containing tetrahydroabietic acid 40% or more and / or ester compound derived from the rosin substance (hereinafter,
It is disclosed that the use of the compound C) makes it possible to obtain an acrylic polymer without being hindered by polymerization.

However, when manufactured with a curing time of several minutes,
Despite the use of the rosin-based tackifying resin described in the above findings, the polymerization rate of the obtained acrylic pressure-sensitive adhesive does not increase sufficiently, and a long curing time is required to obtain sufficient adhesive performance. Met. For this reason, there are cases where the adhesive tapes and adhesive sheets, which require a short curing time, are not satisfactory for use in adhesive products.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a UV-curable acrylic pressure-sensitive adhesive composition having a high degree of polymerization after UV curing even in a short curing time by incorporating a specific rosin-based tackifying resin. The purpose is to provide. Further, it is an object to provide an acrylic pressure-sensitive adhesive using the UV-curable acrylic pressure-sensitive adhesive composition, and a pressure-sensitive adhesive tape or pressure-sensitive sheet using the pressure-sensitive adhesive.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates 50 to 95
In the UV-curable pressure-sensitive adhesive composition containing a mass% and a rosin-based tackifying resin, the content of the specific compound in the pressure-sensitive adhesive composition by using a specific amount or less, found that the above problems can be solved The present invention has been completed.

That is, the present invention is a UV-curable resin containing 50 to 95% by mass of at least one monomer selected from the group consisting of alkyl acrylate and alkyl methacrylate and 5 to 30% by mass of a rosin-based tackifying resin. Type acrylic pressure-sensitive adhesive composition, the formula (I) contained in the rosin-based tackifying resin

[0011]

[Chemical 3]

The content of the compound having a partial skeleton represented by (hereinafter abbreviated as compound A) in the pressure-sensitive adhesive composition is
The UV-curable acrylic pressure-sensitive adhesive composition is 0.01% by mass or less. Furthermore, formula (II-1) contained in the rosin-based tackifying resin, formula (II-2) or formula (II-3),

[0013]

[Chemical 4]

A UV-curable acrylic pressure-sensitive adhesive composition in which the content of the compound having a partial skeleton represented by (hereinafter abbreviated as compound B) in the pressure-sensitive adhesive composition is 3.0% by mass or less. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The UV-curable acrylic pressure-sensitive adhesive composition of the present invention is suitable for an acrylic pressure-sensitive adhesive and a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet using the same.

<(Meth) acrylic acid alkyl ester> The acrylic acid alkyl ester and methacrylic acid alkyl ester used in the acrylic polymer composition of the present invention are acrylic acid and / or methacrylic acid (hereinafter referred to as (meth)).
Abbreviated as acrylic acid. ) And the number of carbon atoms is 1 to 12, preferably 4 to 1
It is an ester compound with an alkyl which is 2. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, etc. Can be mentioned. These monomers are used alone or in admixture of two or more.

<Other Monomers> In order to adjust the adhesive properties and the like, vinyl monomers which are copolymerizable with (meth) acrylic acid alkyl ester, such as acrylic acid, methacrylic acid, glycidyl (meth) acrylate, (meth ) Acrylic acid
2-hydroxyethyl, N-methylol (meth) acrylamide, N-vinyl-2-pyrrolidone, acrylamide, maleic anhydride, vinyl acetate, styrene and other conventionally known copolymerizable vinyl group-containing monomers are used in combination. You may.

<Rosin-based tackifying resin> The rosin-based tackifying resin used in the present invention is 50 to 95% by mass of at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates and rosin. UV-curable acrylic pressure-sensitive adhesive composition containing 5 to 30% by mass of a tackifying resin, wherein the compound in the pressure-sensitive adhesive composition is
The content of A is 0.01% by mass or less. Further, a rosin-based tackifying resin having a compound B content of 3.0% by mass or less of the pressure-sensitive adhesive composition is used. As such a rosin-based tackifying resin, a commercially available hydrogenated rosin-based derivative or dehydrogenated rosin derivative can be used.

<Compound A> The rosin-based tackifying resin used in the present invention is a rosin-based tackifying resin so that the content of the compound A in the UV-curable acrylic pressure-sensitive adhesive composition is 0.01% by mass or less. use. In particular, the rosin-based tackifying resin used in the present invention preferably contains substantially no compound A. When the content of the compound A exceeds 0.01% by mass, the polymerization of the acrylic polymer is hindered, and it becomes difficult to obtain a high polymerization rate in a short time. Also, in order to obtain a high polymerization rate, a large amount of polymerization initiator and a long time are required. When the polymerization rate is low, it is impossible to obtain a sufficient adhesive force required for the adhesive composition.

By achieving a high polymerization rate, an acrylic polymer having a high weight average molecular weight can be obtained. The weight average molecular weight is preferably 200,000 to 1,500,000, more preferably 400,000 to 1,000,000 in terms of polystyrene.

The method for producing the rosin-based tackifying resin is not particularly limited as long as it is a rosin-based tackifying resin that allows the content of the compound A in the UV-curable acrylic adhesive composition to be 0.01% by mass or less. For example, conventionally known methods such as hydrogenation treatment and dehydrogenation treatment may be used, and a low content rate can be obtained by using these treatments twice or more or in combination.

The content of the compound A in the rosin-based tackifying resin is preferably 0.1% by mass or less, 0.03% by mass or less, and more preferably substantially no content. It is also preferable that the components other than the rosin-based tackifying resin in the UV-curable acrylic pressure-sensitive adhesive composition do not substantially contain the compound A.

Examples of the compound A include abietic acid and abietic acid esters such as methyl abietic acid, ethyl abietic acid, 2-ethylhexyl abietic acid, esters of abietic acid and diethylene glycol, esters of abietic acid and glycerin, and abietic acid. Examples thereof include esters with pentaerythritol, but are not limited thereto.

<Compound B> Furthermore, the rosin-based tackifying resin used in the present invention is preferably one in which the content of the compound B in the UV-curable acrylic pressure-sensitive adhesive composition is 3.0% by mass or less. It is preferable that the content is at most% by mass, and further, substantially no content is included. It is also preferable that the components other than the rosin-based tackifying resin in the UV-curable acrylic pressure-sensitive adhesive composition do not substantially contain the compound B.

The method for producing the rosin-based tackifying resin is not particularly limited as long as it is a rosin-based tackifying resin in which the content of the compound B in the UV-curable acrylic adhesive composition can be 3.0% by mass or less. For example, conventionally known methods such as hydrogenation treatment and dehydrogenation treatment may be used, and a low content rate can be obtained by using these treatments twice or more or in combination. The content of the compound B in the rosin-based tackifying resin is preferably 10.0% by mass or less, 7.0% by mass or less, and more preferably substantially no content.

As the compound B, dihydroabietic acid, dihydroabietic acid ester, for example, methyl dihydroabietic acid, ethyl dihydroabietic acid,
Examples include, but are not limited to, 2-ethylhexyl dihydroabietic acid, esters of dihydroabietic acid and glycerin, esters of dihydroabietic acid and pentaerythritol, and the like.

When the rosin-based tackifying resin used in the present invention is a rosin ester compound, it can be obtained by hydrotreating or dehydrogenating the raw material rosin before or after esterification.

As the raw material rosin, gum rosin,
Wood rosin, tall oil rosin, polymerized rosin and the aforementioned gum rosin, wood rosin, tall oil rosin, polymerized rosin and the like maleic acid, maleic anhydride, fumaric acid, (meth)
Examples thereof include unsaturated acid-modified rosin modified with an unsaturated acid such as acrylic acid.

<Measurement Method of Content> The content of the compound A and the compound B in the UV-curable acrylic pressure-sensitive adhesive composition is determined by hydrolyzing the compound A and the compound B in the rosin-based tackifying resin to obtain abietic acid. Or dihydroabietic acid, or after further methyl esterification of the acid with diazomethane, it was measured by gas chromatography analysis according to ASTM D3008-82, and based on the results, the compounding ratio of the adhesive composition was determined. Calculated from

<Crosslinking Agent> When it is desired to improve the heat resistance and cohesiveness of the acrylic pressure-sensitive adhesive using the UV-curable acrylic pressure-sensitive adhesive composition of the present invention, or the pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet using the same. A compound having two or more copolymerizable vinyl groups in one molecule may be blended in the UV-curable acrylic pressure-sensitive adhesive composition. When the UV-curable pressure-sensitive adhesive composition contains a monomer having a hydroxyl group, a carboxyl group, or the like, a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin, an epoxy resin, a carbodiimide compound, etc. A heat activated cross-linking agent may be used.

<Photopolymerization Initiator> In the present invention, a photopolymerization initiator is used in order to cure the pressure-sensitive adhesive composition by irradiation with UV light. As the photoinitiator, conventionally known ones such as acetophenone-based, benzoin ether-based, ketal-based, acylphosphine oxide-based, benzophenone-based, benzoin-based, halogenated ketone-based, acylphosphonate-based can be used. Further, JP-A-2-160802, JP-A-2-235908, JP-A-4-239508, JP-A-7-
The photopolymerization initiator described in 62010, which has two or more cleavage points in one molecule, may be used.

<Other additives> If necessary, various additives such as tackifying resins other than the rosin-based tackifier resins used in the present invention, antioxidants, ultraviolet absorbers, fillers, pigments, etc., within a range that does not impair the performance. You may add a thickener and the like.

The UV-curable acrylic pressure-sensitive adhesive composition of the present invention is preferably thickened in advance in order to ensure coating suitability. As the thickening method, a method in which a thickener soluble in the monomer used in the composition is added, or a part of the monomer component may be preliminarily polymerized. In that case, the ratio of the thickening component is 40% of the total of the UV curable acrylic pressure-sensitive adhesive composition.
It is not more than mass%, preferably 5 to 25 mass%. The viscosity after thickening is 1 to 30 Pa · s, preferably 4 to 20 Pa · s.

<Adhesive Tape and Adhesive Sheet> U of the Present Invention
The acrylic pressure-sensitive adhesive using the V-curable acrylic pressure-sensitive adhesive composition is used as a pressure-sensitive adhesive tape or pressure-sensitive adhesive sheet. The thickness of the adhesive layer is not particularly limited, but preferably
10 μm to 3 mm.

<Support> As the support, non-woven fabric, cloth such as chemical fiber, paper such as Japanese paper, kraft paper, Kurupack paper, crepe paper, polyester film, polyethylene film, polypropylene film, polyvinyl chloride resin, etc. Films, plastic films such as polystyrene films, metal foils such as copper foil, aluminum foil, and iron foil, foams such as urethane foam, polyethylene foam, and acrylic foam, etc. are generally used as the base material for adhesive tapes. All substrates can be used.

Processing of the pressure-sensitive adhesive composition into a tape or sheet is usually carried out by a flow operation such as roll-to-roll, so that sufficient curing in a short time is required. From this point of view, the UV curing time required is within 15 minutes. It is preferably within 10 minutes.

When UV curing is carried out after coating or impregnating a UV-curable acrylic pressure-sensitive adhesive composition on a substrate or release paper, oxygen in the air inhibits the curing, and means for preventing this must be implemented. I have to. For example, after coating a UV-curable acrylic pressure-sensitive adhesive composition, a method of covering it with a film having high UV light transmission such as a polyethylene terephthalate film to block oxygen, or a method such as nitrogen, carbon dioxide, or helium gas is used. There is a method of curing using an active gas in an atmosphere having an oxygen concentration of 0.1% by mass or less, preferably 0.03% by mass or less.

The UV-curable acrylic pressure-sensitive adhesive composition of the present invention is cured by UV light. As a source of UV light,
There are fluorescent chemical lamps, black lights, low pressure, high pressure, ultra high pressure mercury lamps, metal halide lamps, and sun rays. Irradiation intensity of UV light may be constant throughout, or the physical properties after curing can be finely adjusted by changing the intensity during curing.

[0039]

[Examples] Specific examples will be described below. Unless otherwise specified, "part" means "part by mass" and "%" means "mass".
% ".

Example 1 <Preparation of Acrylic Syrup> 90 parts of 2-ethylhexyl acrylate and 10 parts of acrylic acid were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a fluorescent chemical lamp and a nitrogen gas inlet. 0.3 part of Darocur 1173 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added as a photopolymerization initiator, and UV light was irradiated in a nitrogen atmosphere until the polymerization rate reached 7% to prepare an acrylic syrup.

<Preparation of UV-curable acrylic pressure-sensitive adhesive composition 1> To 100 parts of the above acrylic syrup, 10 parts of rosin-based tackifying resin pine crystal KE-656 (manufactured by Arakawa Chemical Co., Ltd .; content of compound A) 0.1% or less, compound B content 9.8
%), Polypropylene glycol diacrylate (Shin Nakamura Chemical Co., Ltd .: APG700) 0.3 part, additional photoinitiator Lucillin
0.1 part of TPO (manufactured by BASF) was added and stirred uniformly. Air bubbles mixed during stirring and mixing are removed by a defoaming operation, and UV curable acrylic pressure-sensitive adhesive composition 1 (2-ethylhexyl acrylate: 75.8%, rosin-based tackifying resin: 9.1%, compound A
Content rate of 0.01% or less, content rate of compound B: 0.89%) were prepared.

<Preparation of Adhesive Sheet 1> The surface of the UV curable acrylic adhesive composition 1 is treated with a release agent to give a thickness of 75.
It is coated on a polyethylene terephthalate (PET) film of μm so that the thickness after curing is 0.05 mm, and the thickness is then applied.
After coating with 38μm PET film, fluorescent chemical lamp
(Toshiba Lightec, wavelength 300-400 nm) was used to irradiate the ultraviolet ray having an irradiation intensity of 0.64 mW / cm ^{2 on} the PET film surface for 8 minutes to obtain an adhesive sheet 1.

[Examples 2 and 3, Comparative Examples 1 to 3] Example 1
A UV-curable acrylic pressure-sensitive adhesive composition was prepared in the same manner as the UV-curable acrylic pressure-sensitive adhesive composition 1, except that the rosin-based pressure-sensitive adhesive shown in Table 1 was used instead of the rosin-based pressure-sensitive adhesive resin. Then, an adhesive sheet was obtained using the same procedure as the adhesive sheet 1.

The pressure-sensitive adhesive sheets prepared from the UV-curable acrylic pressure-sensitive adhesive compositions prepared in Examples and Comparative Examples were tested by the following method, and the results are shown in Table 1.

(1) Polymerization rate Approximately 1 g of the pressure-sensitive adhesive sheet was allowed to stand in a hot air dryer at 100 ° C. for 1 hour and then calculated by the following formula.

[0046]

[Equation 1]

In the formula, A is (mass of pressure-sensitive adhesive sheet before drying-mass of base material), and Y is a ratio of monomer components in the UV-curable acrylic pressure-sensitive adhesive composition.

[0048]

[Equation 2]

The polymerization rate thus determined is preferably 96% or more, more preferably 98% or more.

(2) Adhesive strength A pressure-sensitive adhesive sheet cut into a width of 20 mm was attached to a polypropylene plate at 23 ° C., and a reciprocating pressure of 2 kg roller was applied. 1 at 23 ° C
After standing for a time, it was pulled in the direction of 180 ° at a speed of 300 mm / min to measure the adhesive force (N / 20 mm).

<Effect of the Invention> As is clear from the results of Examples 1 to 3, according to the present invention, the polymerization rate after UV curing is high,
A UV-curable acrylic pressure-sensitive adhesive composition having high adhesive strength can be obtained. Comparative Example 1, according to the description of JP 2000-327708, tetrahydroabietic acid is a rosin-based tackifying resin that is an ester compound derived from a rosin substance containing 40% or more (foral 85, tetrahydroabietic acid content: 44.8%) was used, but since the content of compound B in the UV-curable acrylic pressure-sensitive adhesive composition exceeds 3.0%, the polymerization rate is low at 92%, and the obtained pressure-sensitive adhesive sheet has sufficient adhesive strength. Did not have.

In Comparative Example 2, the disproportionated rosin ester (super ester A-10 was used, as described in JP-A-5255417.
In Comparative Example 3, hydrogenated rosin ester (Stevelite ester 10) was used in Comparative Example 3 according to JP-A No. 2-18485, and both of them were compound A and / or UV-curable acrylic pressure-sensitive adhesive composition. Alternatively, since the content of the compound B exceeds the range of the present invention, the polymerization rate is low.

[0053]

[Table 1]

-: Cannot be measured because the adhesive layer was not formed. SS: Discontinuous peeling KE-656, KE-311, KE-100, A-100: Arakawa Chemical's rosin-based tackifying resin Foral 85, steberite ester 10: Eastman Chemical's rosin-based tackifying resin

[0055]

EFFECT OF THE INVENTION A UV-curable pressure-sensitive adhesive containing 50 to 95% by mass of a monomer selected from the group consisting of alkyl acrylate and alkyl methacrylate of the present invention and a rosin-based tackifying resin. In the composition, when the content of the specific compound in the pressure-sensitive adhesive composition is a specific amount or less, UV can be used even for a short curing time.
It was possible to obtain a UV-curable acrylic pressure-sensitive adhesive composition having a high polymerization rate after curing and high adhesive strength.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihiro Yamada             4-2-3-502 Kamikizaki, Saitama City, Saitama Prefecture F-term (reference) 4J040 BA202 FA131 JB07 KA26

Claims (4)

[Claims] 1. A UV-curable acrylic resin containing 50 to 95% by mass of at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates and 5 to 30% by mass of a rosin tackifying resin. In the pressure-sensitive adhesive composition, the formula contained in the rosin-based tackifying resin
(I) [Chemical formula 1] The UV content of the compound having a partial skeleton represented by 0.01 mass% or less in the pressure-sensitive adhesive composition
Curable acrylic pressure-sensitive adhesive composition. 2. The formula contained in the rosin-based tackifying resin.
(II-1), Formula (II-2) or Formula (II-3), 2. The UV-curable acrylic pressure-sensitive adhesive composition according to claim 1, wherein the content of the compound having a partial skeleton represented by in the pressure-sensitive adhesive composition is 3.0% by mass or less. 3. An acrylic pressure-sensitive adhesive comprising the UV-curable acrylic pressure-sensitive adhesive composition according to claim 1 or 2. 4. A pressure-sensitive adhesive tape or sheet using the acrylic pressure-sensitive adhesive according to claim 3.