JPH05140510A - Photopolymerizable adhesive composition, pressure-sensitive adhesive using the same and bonding sheets using the adhesive - Google Patents

Abstract

PURPOSE:To obtain the subject composition, composed of a monomeric mixture consisting essentially of an alkyl (meth)acrylate, silicone rubber grains and a photopolymerization initiator, capable of providing a pressure-sensitive adhesive excellent in bonding characteristics and low-temperature impact resistance by carrying out the photopolymerization. CONSTITUTION:The objective photopolymerizable adhesive composition consists essentially of (A) 100 pts.wt. monomeric mixture composed of (A1) 70-99wt.% main monomer, mainly comprising an alkyl (meth)acrylate having a 1-14C alkyl group and optionally containing <=30wt.% various vinyl monomers (e.g. styrene) and (A2) 30-1wt.% polar group-containing copolymerizable monomer [e.g. (meth) acrylic acid], (B) 2-60 pts.wt., preferably 5-35 pts.wt. silicone rubber grains having 1-100mum grain diameter and (C) 0.01-5 pts.wt., preferably 0.01-2 pts.wt. photopolymerization initiator (e.g. benzoin methyl ether). A pressure-sensitive adhesive is obtained by photopolymerizing this composition and imparting the pressure-sensitive adhesiveness and cohesive force thereto. Furthermore, bonding sheets having at least one layer of the adhesive are provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photopolymerizable adhesive composition containing an alkyl (meth) acrylate monomer and the like, and pressure-sensitive adhesiveness and cohesive force by photopolymerizing this adhesive composition. The present invention relates to a pressure-sensitive adhesive provided with a pressure-sensitive adhesive, and an adhesive sheet in which the pressure-sensitive adhesive is provided on one surface or both surfaces of a base material to form a sheet or tape.

[0002]

2. Description of the Related Art An acrylic (meth) acrylate monomer as a main component, which is obtained by copolymerizing a monomer mixture in which a polar group-containing monomer such as acrylic acid is added, is obtained. Pressure sensitive adhesives are already known.

In the production of acrylic pressure-sensitive adhesives,
A large amount of solvent effective for polymerization of acrylic polymers is often used, but recently, due to the safety and environmental restrictions of this large amount of solvent, emulsion polymerization and photopolymerization by ultraviolet irradiation have been widely used. is there. In particular, the photopolymerized pressure-sensitive adhesive has the effect of improving safety and the environment because it does not use any solvent in its manufacturing process.

Apart from this viewpoint of safety and environmental improvement, the range of use of pressure-sensitive adhesives has expanded in recent years, and household electric appliances and the like, which have been used only indoors until now, are now used outdoors. As a result, they are often subjected to the impact of being carried around, and are often stored near the outdoors. For this reason, the required properties also tend to be advanced, and in particular, the temperature range used is widened, and it is necessary to improve the adhesive properties at lower and higher temperatures than ever before. Adhesive properties at normal temperatures of ° C are also naturally required.

In response to this requirement, it is known that the glass transition temperature of the acrylic polymer is lowered to improve the adhesive property at low temperature, but in this case, the cohesive force at normal temperature is lowered. There is a tendency and it is not preferable.

JP-A-57-47308 discloses that 100 parts by weight of an alkyl (meth) acrylate monomer, 50 to 250 parts by weight of a substantially saturated tackifying resin polymer and the above-mentioned monomer are used. A photopolymerizable pressure-sensitive adhesive containing 4 to 150 parts by weight of an amorphous elastomer block copolymer dissolved in the above is shown. However, since the amount of the tackifying resin polymer used is very large, there is a problem that the glass transition temperature of the polymer is remarkably increased and the impact resistance at low temperature is lowered.

Japanese Unexamined Patent Publication Nos. 2-45580 and 2-
Japanese Patent No. 47182 discloses a pressure-sensitive adhesive obtained by adding a hydrocarbon elastomer having a glass transition temperature lower than that of an acrylic polymer to an acrylic polymer. However, although the use of the above-mentioned hydrocarbon elastomer gives good results in impact resistance at low temperature, it causes problems in aging resistance, heat resistance, and adhesive properties at high temperature, and is required as the usage range is expanded. It is not always possible to satisfy the high level of adhesive properties.

Japanese Unexamined Patent Publication (Kokai) No. 63-72532 discloses a pressure-sensitive adhesive-coated sheet material containing elastic non-adhesive hollow thermoplastic polymer spheres, which has adhesive properties at low temperatures. Not enough. Japanese Unexamined Patent Publication (Kokai) No. 1-284572 discloses an ionizing radiation-curable pressure-sensitive adhesive containing an organic resin fine powder, but it is not satisfactory in terms of adhesive strength and impact resistance at low temperatures. ..

[0009]

In view of the above-mentioned conventional circumstances, the present invention provides a photopolymerization type acrylic pressure-sensitive adhesive having excellent adhesive properties from low temperature to high temperature, and
The purpose is to obtain a material that has excellent impact resistance at low temperatures.

[0010]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that when the silicone rubber particles are added to the adhesive composition to be photopolymerized, it is In addition to having good adhesive properties up to high temperatures,
The inventors have found that a pressure-sensitive adhesive having excellent impact resistance at low temperatures can be obtained, and have completed the present invention.

That is, the present invention provides the following three components a to c: a) a main monomer containing an alkyl (meth) acrylate monomer whose alkyl group has an average of 1 to 14 carbon atoms as a main component. 100 to 100 parts by weight of a monomer mixture consisting of 70 to 99% by weight of a copolymer and 30 to 1% by weight of a polar group-containing copolymerizable monomer b) Silicon rubber particles 2 to 60 parts by weight c) Photopolymerization initiator The present invention relates to a photopolymerizable adhesive composition containing 0.01 to 5 parts by weight as an essential component.

The present invention also provides an acrylic pressure-sensitive adhesive having pressure-sensitive adhesiveness and cohesive force obtained by photopolymerizing the above-mentioned photopolymerizable adhesive composition by irradiation with light such as ultraviolet rays. The present invention relates to an adhesive sheet in which the pressure-sensitive adhesive is provided on one surface or both surfaces of a base material so as to have a sheet shape or a tape shape.

[0013]

The monomer mixture as the component a in the present invention comprises a main monomer mainly comprising an alkyl (meth) acrylate monomer and a polar group-containing copolymerizable monomer. It is composed of a mixture with the body, and the former main monomer includes, in addition to the alkyl (meth) acrylate monomer as the main component, general acrylic pressure-sensitive adhesives such as vinyl acetate and styrene. Various vinyl-based monomers known as modifying monomers for agents are usually used in the main monomer in an amount of 30% by weight or less.

Examples of the alkyl (meth) acrylate monomer include, for example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate. Acryl
Any of those having an alkyl group having a carbon number of 1 to 14 such as bisphenol and isononyl (meth) acrylate can be used.

The polar group-containing copolymerizable monomer includes
Unsaturated acids such as (meth) acrylic acid, itaconic acid and 2-acrylamidopropanesulfonic acid, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate Is used.

The proportion of the main monomer containing an alkyl (meth) acrylate monomer as the main component and the polar group-containing copolymerizable monomer is 70 to 99% by weight in the former case and the latter in the latter case. Should be 30 to 1% by weight, particularly preferably 90 to 98% by weight for the former and 10 to 2% by weight for the latter. Outside of these ranges, favorable results cannot be obtained in terms of adhesive properties.

The silicone rubber particles as the component b in the present invention are, for example, those obtained by polycondensation of silanol by hydrolysis of dimethyldichlorosilane, and those obtained by substituting a part of dimethylsiloxane units with vinyl groups or methyl. It is obtained by copolymerizing phenyl siloxane and has a glass transition temperature of -100.
It is about -120 ° C. Examples of commercially available products include Trefil E-500 and Trefil E-501 manufactured by Toray Dow Corning Silicone Co., Ltd.

The silicone rubber particles can have various particle shapes, but are preferably spherical. The average particle size should be smaller than the thickness of the layer when a pressure-sensitive adhesive layer containing the particles is provided on one or both sides of a substrate to produce adhesive sheets. It is preferable to set the thickness in a range of 1 to 100 μm.

The use of such silicone rubber particles makes it possible to obtain a pressure-sensitive adhesive which has excellent adhesive strength and impact resistance at low temperatures, and which is satisfactory in terms of cohesive strength. The amount of the silicone rubber particles used is usually 2 to 60 parts by weight, preferably 5 to 35 parts by weight, per 100 parts by weight of the component a. If the amount is less than 2 parts by weight, the above-mentioned effects cannot be obtained, and if the amount is more than 60 parts by weight, the adhesive properties at normal temperature are impaired.

Examples of the c component photopolymerization initiator in the present invention include benzoin ether such as benzoin methyl ether and benzoin isopropyl ether, and substituted benzoin ether such as anisolemethyl ether, 2.2-
Diethoxyacetophenone, 2,2-dimethoxy-2-
Substituted acetophenones such as phenylacetophenones, 2
-Substituted alpha-ketols such as methyl-2-hydroxypropionenone, aromatic sulfonyl chlorides such as 2-naphthalene sulphonyl chloride, 1-phenyl-1. 1-propanedione-2- (o- Photoactive oximes such as ethoxycarbonyl) -oxime are used.

The amount of such a photopolymerization initiator to be used is usually 0.01 to 5 parts by weight, preferably 0.01 to 2 parts by weight, per 100 parts by weight of the component a.
If the amount is less than 0.01 parts by weight, the polymerization rate will decrease. If the amount is more than 5 parts by weight, the polymerization rate will increase, but the molecular weight will decrease and the cohesive force will be insufficient.

The photopolymerizable adhesive composition of the present invention comprises, in addition to the above-mentioned three components a to c, a polyfunctional acrylate if necessary.
A monomer may be added. Examples of this monomer include trimethylol propane triacrylate, pentaerythritol tetraacrylate, 1.2-ethylene glycol diacrylate, 1.6-hexanediol diacrylate, 1. A bifunctional or higher-functional polyvalent alkyl acrylate monomer such as 12-dodecanediol diacrylate is used.

The amount of such a polyfunctional acrylate monomer used varies somewhat depending on the number of functional groups, etc., but is generally 0.1 to 3 parts by weight per 100 parts by weight of the component a. Parts, preferably 0.2 to 2 parts by weight. When the polyfunctional acrylate monomer is used in such a range, good cohesive force is maintained due to the crosslinking effect of the above monomer.

The photopolymerizable adhesive composition of the present invention has the above a.
To c are essential components and, if necessary, a polyfunctional acrylate monomer, but in view of handling the monomer mixture of the component a, this is a part of the photopolymerization initiator of the component c. Can be used for pre-polymerization to some extent.

In addition to the above-mentioned components, various optional additives such as plasticizers, softeners, fillers, pigments, dyes, tackifying resins, etc., which have been publicly known, are added to the photopolymerizable adhesive composition. The agent can be appropriately blended within a range that does not impair the photopolymerizability.

In the present invention, such a photopolymerizable adhesive composition is directly coated on an adherend or once coated on a release paper, and then 400 to 2000 mj / cm ²
By irradiating a certain amount of ultraviolet rays and photopolymerizing, a pressure-sensitive acrylic pressure-sensitive adhesive having pressure-sensitive adhesive property can be obtained.

Further, instead of coating on an adherend or a release paper, various base materials such as a synthetic resin film such as a polyester film and a fiber base material are used, and the base material is coated on one side or both sides. By subjecting this to photopolymerization in the same manner as described above, it is possible to obtain an adhesive sheet in the form of a sheet, a tape or the like.

Further, in obtaining such an adhesive sheet, the pressure-sensitive adhesive layer may have a multi-layer structure, and at least one of them may be a layer obtained by photopolymerizing the adhesive composition of the present invention. Further, in the pressure-sensitive adhesive layer having a single-layer structure, only a part thereof may be formed by a layer obtained by photopolymerizing the adhesive composition of the present invention.

The photopolymerized acrylic pressure-sensitive adhesive thus obtained is characterized in that it has good adhesive properties from low temperature to high temperature and is excellent in impact resistance at low temperature. The reason for this is not necessarily clear, but the silicone rubber particles are photopolymerized in a uniformly dispersed state to have a pressure-sensitive adhesive property, which is a pressure-sensitive adhesive that has been tackified. This is probably because the adhesive properties and impact resistance-improving action based on the above are sufficiently exhibited.

On the other hand, for example, an acrylic polymer is obtained by solution polymerization using a monomer mixture corresponding to the component a of the present invention, and the silicone rubber particles are uniformly dispersed in the polymer solution to give a feeling. When a pressure-sensitive adhesive solution is prepared and applied and dried to form a pressure-sensitive adhesive layer,
Perhaps because the uniform dispersion of the silicone rubber particles is impaired during drying, the adhesive properties from low temperature to high temperature tend to be slightly lower than those of the present invention, and the impact resistance at low temperature is almost the same. Without improvement, the object of the present invention cannot be achieved.

[0031]

As described above, according to the present invention, a monomer mixture containing an alkyl (meth) acrylate monomer as a main component contains a specific amount of silicone rubber particles together with a photopolymerization initiator. Since it is photopolymerized, it has good adhesive properties from low temperature to high temperature, and it has excellent impact resistance at low temperature.
You can get the kind.

[0032]

EXAMPLES Next, examples of the present invention will be described to more specifically describe. In the following, "parts" means "parts by weight". The characteristics of the adhesive tape were evaluated by the following methods.

<Adhesive strength> According to JIS Z-1522,
Using a stainless steel plate as an adherend, the adhesive force (g / 20 mm width) at each temperature was measured.

<Creapability deviation distance> Stainless steel plate with a BA finish on the surface (30 mm x 120 mm x 3.0 mm)
Using the above, a sample for evaluation (width 10 mm) was attached to one end of this stainless steel plate in the longitudinal direction so that the adhesion area was 20 mm × 10 mm, and the sample was left for 30 minutes, then at 40 ° C.
It heat-processed at the temperature of 20 minutes. Next, the stainless steel plate was set vertically so that the side where the sample was stuck was on the bottom, and a load of 500 g was applied to the other end of the sample. The shift distance of the sample was measured by a creep tester.

<Low temperature impact resistance> Polyvinyl chloride plate (15
mm × 150 mm × 3.0 mm), the evaluation sample is pressure-bonded with a 5 kg roller, and this is a coated steel plate (100 mm × 300 mm)
(mm × 2.0 mm), the sample for evaluation was placed on the inner side by pressure bonding with a 5 kg roller to give a test piece. The test piece was stored at 23 ± 1 ° C for 24 hours, and further stored at -30 ° C for 2 hours.
After leaving it for more than an hour, an impact tester (a test piece capable of applying an impact from a 90 degree angle to JIS G-319
(Equal helix angle steel specified in 2) is attached to the test piece mounting frame with the polyvinyl chloride plate inside and is given 50 shocks from an angle of 90 degrees (π / 2 · rad). It was examined whether the above polyvinyl chloride plate dropped from the test piece.

Example 1 90 parts of 2-ethylhexyl acrylate, acrylic acid 1
0 part, 0.05 parts of 2,2-dimethoxy-2-phenylacetophenone (photopolymerization initiator) were charged into a 4-neck flask and exposed to ultraviolet rays under a nitrogen atmosphere to partially photopolymerize. By this, a coatable syrup (viscosity 30 poise) was obtained.

To 100 parts of this partially polymerized syrup, 0.2 part of trimethylolpropane triacrylate, 0.2 part of additional photopolymerization initiator, spherical silicone rubber particles having an average particle size of 3 μm [ Toray Dow Corning Silicone KK-made TREFIL E-500] 15 parts were uniformly mixed to prepare a photopolymerizable adhesive composition.

This adhesive composition was applied to the above-mentioned release-treated surface of a polyethylene terephthalate film having a thickness of 25 μm which had been subjected to a low-adhesion release treatment, and further, a polyethylene having a thickness of 25 μm was applied thereon. After coating with terephthalate film as the base material, it is exposed to ultraviolet rays at 1500 mj / cm ²
By irradiation and photopolymerization, an adhesive tape having an adhesive layer thickness of 400 μm was obtained.

Example 2 As the silicone rubber particles, 15 parts of spherical silicone rubber particles having an average particle size of 10 μm [Trefyl E-501 manufactured by Toray Dow Corning Silicone Co., Ltd.] were used. In the same manner as in Example 1, a photopolymerizable adhesive composition was prepared, and an adhesive tape was produced in the same manner as in Example 1 using this composition.

Example 3 90 parts of isodecyl acrylate, 10 parts of acrylic acid, 2
-Hydroxyethyl acrylate 2 parts, 2.2-dimethoxy-2-phenylacetophenone (photopolymerization initiator)
0.1 part was placed in a four-necked flask and exposed to ultraviolet rays in a nitrogen atmosphere to partially photopolymerize to obtain a coatable syrup (viscosity 50 poise).
A photopolymerizable adhesive composition was prepared in the same manner as in Example 1 except that this syrup was used, and an adhesive tape was prepared in the same manner as in Example 1 using this composition.

Example 4 90 parts of 2-ethylhexyl acrylate, acrylic acid 1
0 part, 2.2'-azobisisobutyronitrile 0.4
Parts, 250 parts of ethyl acetate are charged into a four-necked flask,
Polymerization was carried out at 60 ° C. for 10 hours in a nitrogen atmosphere to obtain a polymer solution. To this polymer solution, for 100 parts of polymer,
A pressure sensitive adhesive solution was prepared by adding 2 parts of a trifunctional isocyanate compound.

Next, this adhesive solution was applied to a polyethylene terephthalate film having a thickness of 25 μm and subjected to a low-adhesion peeling treatment so that the thickness after drying would be 25 μm, and the temperature was 40 ° C. After drying for 5 minutes at 100 ° C., it was dried for 5 minutes. This was adhered to both sides of the adhesive tape obtained in Example 3 with a laminator, and then heated at 100 ° C. for 2 hours.
Then, an adhesive tape having a three-layer structure was obtained.

Comparative Example 1 A photopolymerizable adhesive composition was prepared in the same manner as in Example 1 except that no silicone rubber particles were used. Adhesion was performed in the same manner as in Example 1 using this composition. A tape was made.

Comparative Example 2 Same as Example 1 except that 2 parts of elastic non-adhesive hollow thermoplastic polymer spheres [Expansel 551DE manufactured by Nippon Fluorite Co., Ltd.] were used in place of the silicone rubber particles. Then, a photopolymerizable adhesive composition was prepared, and an adhesive tape was prepared in the same manner as in Example 1 using this composition.

Comparative Example 3 The same procedure as in Example 1 was repeated except that 15 parts of crosslinked polystyrene spherical microbeads [Fair Impal PB3011E manufactured by Sumitomo Chemical Co., Ltd.] was used in place of the silicone rubber particles. A polymerizable adhesive composition was prepared, and an adhesive tape was produced in the same manner as in Example 1 using this composition.

Reference Example 1 2-Ethylhexyl acrylate 90 parts, acrylic acid 1
0 part, 2.2'-azobisisobutyronitrile 0.4
Parts, 250 parts of ethyl acetate are charged into a four-necked flask,
Polymerization was carried out at 60 ° C. for 10 hours in a nitrogen atmosphere to obtain a polymer solution. To this polymer solution, for 100 parts of polymer,
Spherical silicone rubber particles with an average particle size of 3 μm [Toray
Trefoil E- manufactured by Dow Corning Silicone Co., Ltd.
500] 15 parts of 2 parts of trifunctional isocyanate compound was added to prepare a pressure sensitive adhesive solution.

Next, this adhesive solution was added to a thickness of 25 μm.
m of polyethylene terephthalate film so that the thickness after drying was 400 μm, dried at 40 ° C. for 5 minutes and then at 100 ° C. for 5 minutes to obtain an adhesive tape.

The adhesive properties of the adhesive tapes of Examples 1 to 4, Comparative Examples 1 to 3 and Reference Example 1 were examined, and the results are shown in Table 1 below.

[0049]

[Table 1]

From the results of Table 1 above, Example 1 of the present invention
It can be seen that the adhesive tapes Nos. 4 to 4 have excellent adhesive properties from low temperature to high temperature and excellent impact resistance at low temperature, as compared with the adhesive tapes of Comparative Example and Reference Example.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takao Yoshikawa 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (5)

[Claims] 1. The following a to c three components; a) A main monomer 70 to 99 containing an alkyl (meth) acrylate monomer whose alkyl group has an average of 1 to 14 carbon atoms as a main component. 100 parts by weight of a monomer mixture composed of 30% by weight of a polar group-containing copolymerizable monomer b) 2 to 60 parts by weight of silicone rubber particles c) 0.01 to 0.01 of a photopolymerization initiator A photopolymerizable adhesive composition comprising 5 parts by weight as an essential component. 2. A pressure-sensitive adhesive obtained by photopolymerizing the photopolymerizable adhesive composition according to claim 1 to impart pressure-sensitive adhesiveness and cohesive force. 3. An adhesive sheet comprising a substrate and a layer of the pressure-sensitive adhesive according to claim 2 provided on one side or both sides of the substrate. 4. The adhesive sheet according to claim 3, wherein the silicone rubber particles contained in the pressure-sensitive adhesive layer have an average particle size smaller than the thickness of the layer. 5. An adhesive sheet in which the pressure-sensitive adhesive layer has a multi-layer structure, at least one layer of which is formed of the pressure-sensitive adhesive layer according to claim 2.