JPH073212A - Photopolymerizable composition and adhesive tape or sheet - Google Patents

Abstract

PURPOSE:To stably obtain an adhesive sheet having sufficient adhesiveness even to inorganic materials, etc., giving high bond strength by using a new photopolymerizable composition. CONSTITUTION:The objective photopolymerizable composition comprising (A) 30-98 pts.wt. of an acrylate monomer selected from (meth)acrylic 1-12C alkyl esters, (B) 2-70 pts.wt. of a vinyl monomer copolymerizable with the component A, (C) 0.5-70 pts.wt. of a second acrylate monomer selected from esters of epoxy group-contg. alcohols and (meth)acrylic acid and (D) 0.01-5 pts.wt. of a photopolymerization initiator. The other objective adhesive tape or sheet obtained from this composition, bearing tack agent layer containing epoxy groups in an unreacted state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylate-based photopolymerizable composition and an adhesive tape and sheet obtained by using the composition. More specifically, a high bonding strength to a structure or the like is obtained. The present invention relates to an adhesive tape and a sheet that can be easily joined.

[0002]

2. Description of the Related Art A so-called adhesive tape or sheet (hereinafter, referred to as "in the present specification") having a simple adhesive work of an adhesive tape and a high bonding strength equivalent to that of an adhesive.
A bonding material called simply “adhesive sheet” is required particularly in the adhesive work field where solvent-free working environment and shortening of working time are required.

As an adhesive sheet applicable in such a field of use, for example, in Japanese Patent Publication No. 57-17030, it is obtained by irradiating with light a reactive composition containing an acrylic monomer as a main component after coating and film formation. , High-thickness adhesive sheets have been proposed.

This adhesive sheet exhibits a peel resistance equivalent to that of an adhesive which cannot be obtained by a conventional adhesive tape by increasing the thickness of the adhesive sheet, and the composite of fine spheres or the like allows the inside of the adhesive sheet to be peeled. It is considered that the bias of the stress acting on the surface is dispersed to reduce the peeling force acting on the interface so as to develop a high degree of bonding strength.

[0005]

However, in this adhesive sheet, the bonding with the adherend interface is mainly due to the so-called adhesive and the Van der Waals force or hydrogen bond between the adherend interface. Is not due to a chemical bond as in the bonding between the adherend and the adherend interface. Therefore, when the adherend is an inorganic material such as tile, cement, asbestos, roof tile, etc., it is difficult to obtain sufficient bonding strength because the surface smoothness of these materials is low.

[0006] Due to such circumstances, the adhesive sheet has limited usable applications, despite its excellent workability.

As a measure to solve this problem, it is considered that a functional group having reactivity with the adherend is introduced into the pressure-sensitive adhesive to mold and produce the adhesive sheet. However, such a reactive functional group generally has a problem that the reaction is likely to proceed even during the molding of the adhesive sheet, so that the molding is difficult and the adhesive performance of the obtained adhesive sheet is not stable.

The object of the present invention against the above-mentioned problems is
Providing a novel photopolymerizable composition, and using the composition, an adhesive sheet which has sufficient adhesiveness to an inorganic material and the like and has a high bonding strength and which can be stably produced. To provide.

The present inventors have achieved the above object by blending an acrylate-based monomer having an epoxy group in a photopolymerizable composition.

[0010]

That is, according to the present invention, (a) the alkyl group has 1 to 12 carbon atoms (meth).
30 to 98 parts by weight of at least one acrylate-based monomer selected from the group consisting of alkyl acrylates, and (b) a vinyl compound-based monomer having an unsaturated double bond copolymerizable with the acrylate-based monomer (a) 2 to
70 parts by weight, and (c) at least one acrylate-based monomer selected from the group consisting of an ester of an epoxy group-containing alcohol and (meth) acrylic acid 0.5 to 70
A photopolymerizable composition is provided, which comprises 0.01 to 5 parts by weight of (d) a photopolymerization initiator.

Further, according to the present invention, there is provided an adhesive sheet having a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, which is obtained from the above photopolymerizable composition.

Further, according to the present invention, there is provided an adhesive sheet in which an acrylic pressure-sensitive adhesive layer containing a functional group reactive with an epoxy group is laminated on at least one surface of the pressure-sensitive adhesive layer.

The components constituting the photopolymerizable composition according to the present invention and the photopolymerization method of the composition will be described below.

(Acrylate-based Monomer (a)) The acrylate-based monomer (a) is the monomer main component of the composition of the present invention, and is used in the production of known photopolymerized acrylic viscoelastic products.

As the acrylate monomer, an alkyl acrylate or methacrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, preferably 4 to 12 carbon atoms is used. Specific examples of these acrylate-based monomers include n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate.

These monomers may be used alone or in combination of two or more. From the viewpoint of balance between tackiness and cohesiveness, usually, a homopolymer has a glass transition temperature of −50 ° C. or lower as an acrylic acid alkyl ester as a main component, and as a comonomer, a lower alkyl group (meth)
It is preferable to use an acrylic ester or the following vinyl-based monomer (b).

(Vinyl type monomer (b)) Other vinyl compound type monomer copolymerizable with acrylate type monomer
(b) is the following epoxy group-containing acrylate-based monomer
Those which are non-reactive with the epoxy group of (c) are preferable,
For example, acrylonitrile, methacrylonitrile, N-
Examples thereof include vinylpyrrolidone, acryloylmorpholine, isobornyl acrylate and the like.

Of these vinyl monomers, N-vinylpyrrolidone and isobornyl acrylate are particularly preferable.

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

(Epoxy group-containing acrylate-based monomer
(c)) Epoxy group-containing acrylate-based monomers (c) include glycidyl (meth) acrylate, alicyclic epoxy (meth) acrylate (Cyclomer, trade name, manufactured by Daicel Chemical Industries, Ltd.) and the like. The acrylate-based monomer containing an alicyclic epoxy group has a low glass transition temperature of the obtained copolymer even when blended in a high ratio,
A highly tacky adhesive is obtained.

(Photopolymerization initiator (d)) As the monofunctional photopolymerization initiator, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Darocur 2959: manufactured by Ciba Geigy] is used. 1-hydroxycyclohexyl phenyl ketone [IRGACURE 184:
Ciba-Geigy], α-hydroxy-α, α-dimethylacetophenone [Darocur 1173: Ciba-Geigy]; acetophenone initiators such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; benzoin ethyl ether, benzoin isopropyl Benzoin ether-based initiators such as ethers; ketal-based initiators such as benzyl dimethyl ketal; and halogenated ketones, acylphosphinoxides, acylphosphonates and the like.

The mixing ratio of these components is 30 to 98 parts by weight of the acrylate-based monomer (a), 2 to 70 parts by weight of the vinyl compound-based monomer (b), and 0.5 to 70 of the epoxy group-containing acrylate-based monomer (c). And 0.01 to 5 parts by weight of the photopolymerization initiator (d), preferably 60 to 95 parts by weight of the acrylate-based monomer (a), 5 to 40 parts by weight of the vinyl compound-based monomer (b), and epoxy. It is 5 to 20 parts by weight of the group-containing acrylate-based monomer (c) and 0.1 to 5 parts by weight of the photopolymerization initiator (d).

(Crosslinking Agent) In the photopolymerizable composition of the present invention, in order to increase heat resistance and cohesive force at high temperature, a polyfunctional vinyl compound is contained as a crosslinking agent together with the above photopolymerization initiator. be able to.

Examples of such crosslinking agents include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth). Acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, other epoxy acrylate,
Examples thereof include polyester acrylate and urethane acrylate.

The cross-linking agent is generally added in an amount of 5 parts by weight or less based on 100 parts by weight of the total of the monomer components (a) to (c). The incorporation of the cross-linking agent causes cross-linking between polymer molecules in the photopolymerization reaction, improves the heat resistance of the pressure-sensitive adhesive, increases the cohesive force at high temperature, and improves the holding power at high temperature.

(Tackifier) It is preferable to add a tackifier to the photopolymerizable composition according to the present invention.

Examples of tackifiers used in the present invention include rosin resins, modified rosin resins, terpene resins, terpene phenol resins, aromatic modified terpene resins, C ₅ and C ₉ petroleum resins and coumarone resins.

In the present invention, a tackifier having a functional group reactive with an epoxy group such as a carboxyl group is not preferable, and an alicyclic hydrocarbon type tackifier is preferable. An example of this is Alcon (trade name, manufactured by Arakawa Chemical Co., Ltd.).

(Other Additives) The photopolymerizable composition according to the present invention may be mixed with commonly used additives such as a thickener, a thixotropic agent, a filler and a filler.

As the thickener, acrylic rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber and the like are used.

It is also possible to irradiate the photopolymerizable composition with light to partially polymerize the composition to increase the viscosity.

In the present invention, since the epoxy group is also grafted to the partial polymer, the partial polymer and the monomer are
It also has the property that it is co-crosslinked by heating and can further improve heat resistance.

As the thixotropic agent, colloidal silica, polyvinylpyrrolidone, etc. are used.

As the extender, calcium carbonate, titanium oxide, clay or the like is used.

As the filler, inorganic hollow bodies such as glass balun, alumina balun, ceramic baln, etc .; organic spherical bodies such as nylon beads, acrylic beads, silicone beads; organic hollow bodies such as vinylidene chloride, acrylic balun; polyester, rayon. Single fibers such as nylon, glass, etc. are used.

Particularly for glass fiber, the epoxy group forms a chemical bond with the surface of the fiber, so that a strong reinforcing effect can be exhibited.

(Photopolymerization process conditions) As a lamp used for light irradiation, a lamp having an emission distribution at a light wavelength of 400 nm or less is used, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, and a chemical lamp. , Black light lamps, microwave excited mercury lamps, metal halide lamps, etc. are used. Among these, the chemical lamp efficiently emits light in the active wavelength region of the initiator, and since light absorption of the composition components other than the initiator is small, light is transmitted to the inside to manufacture a high-thickness film product. Is preferred.

The intensity of light irradiation of the photopolymerizable composition by the lamp is a factor that influences the degree of polymerization of the polymer obtained, and is appropriately controlled depending on the performance of the target product. When a cleavage type initiator having a normal acetophenone group is blended,
The light intensity in the wavelength region effective for photodecomposition of the initiator (light with a wavelength of 365 to 420 nm is generally used, although it varies depending on the initiator) is preferably 0.1 to 100 mW / cm ² .

The photopolymerization in the present invention is inhibited by oxygen in the air or oxygen dissolved in the photopolymerizable composition. Therefore, the light irradiation must be carried out by using a method capable of eliminating the reaction inhibition of oxygen. As one of the methods, a photopolymerizable composition is covered with a film made of polyethylene terephthalate or Teflon to cut off contact with oxygen,
There is a method of irradiating the composition with light through this film. Further, the composition may be irradiated with light through a light transmissive window in an inert atmosphere in which oxygen is replaced by an inert gas such as nitrogen gas or carbon dioxide gas. In the latter method, in order to sufficiently complete the polymerization of the photopolymerizable composition until the conversion becomes 99.7% or more, the oxygen concentration in this irradiation atmosphere needs to be 5000 ppm or less.
The molecular weight of the polymer product obtained by light irradiation of the composition decreases with increasing atmospheric oxygen concentration. Atmospheric oxygen concentration is 1000 pp in order to obtain a molecular weight similar to that of the product of polymerization in a completely inert atmosphere.
Must be less than or equal to m Further, the extremely thin surface layer portion of the photopolymerizable composition is more susceptible to reaction inhibition by oxygen than the inside of the polymer, and the cohesive force is reduced. In order for this surface layer portion to have the same degree of cohesiveness as the inside, the atmospheric oxygen concentration is 300
It is desirable to be less than ppm.

When the light irradiation is performed in the inert zone, a constant amount of inert gas is always introduced into this zone in order to keep the atmospheric oxygen concentration at a low level. Due to this introduced gas, an air flow is generated on the surface of the photopolymerizable composition, and the monomer is evaporated. The air velocity required to suppress this evaporation level to a low level is preferably 1 m / sec or less, more preferably 0.1 m / sec, relative to the composition moved together with the support in this zone. It is less than sec. If the airflow velocity is set to about 0.1 m / sec, evaporation by the airflow can be substantially suppressed.

The photopolymerization reaction is carried out at a low temperature, for example, -5 to 30 ° C, preferably -5 to 10 ° C in order to avoid the reaction between epoxy groups. The cause of the temperature rise is
Radiant heat from the lamp and polymerization heat of the monomer. Therefore, the photopolymerization reaction is carried out at a low temperature by using a light cut filter to suppress the lamp radiation heat, and by positively removing the heat of polymerization by bringing the polymer into contact with a cooling back plate during light irradiation. be able to.

By the above method, the adhesive sheet of the present invention having a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state can be obtained.

The adhesive sheet of the present invention has strong contact adhesiveness with a general adhesive sheet having a functional group such as a carboxyl group reactive with an epoxy group. Therefore, by using the adhesive sheet of the present invention and a general adhesive sheet for two adherends, an adhesive system for highly joining two adherends having different surface energies, which has been difficult to join in the past, is used. Can be realized. Examples of the functional group having reactivity with an epoxy group include a carboxyl group, a hydroxyl group, a phenol group, and various amino groups. The pressure-sensitive adhesive containing these functional groups can be easily obtained by copolymerizing an acrylic acid ester and a vinyl monomer having these functional groups.

[0044]

The adhesive sheet according to the present invention has a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, and since the epoxy group exists at the sheet interface, it reacts particularly with an epoxy group such as an inorganic material or a metal. It is possible to form a chemical bond with the interface of the adherend having properties.

[0045]

EXAMPLES Next, in order to specifically describe the present invention,
Examples showing one example of the present invention and some comparative examples showing comparison therewith are given, and the performance test results of the respective viscoelastic products obtained are shown.

[Example 1] 900 g of 2-ethylhexyl acrylate and 100 g of Cyclomer A200,
Photopolymerization initiator Irgacure 184 (manufactured by Ciba Geigy,
0.3 g of the product (trade name) was stirred and mixed in a separable flask until uniform, and then nitrogen gas was purged to remove dissolved oxygen. When this composition was irradiated with ultraviolet rays from a black light lamp, the temperature of the composition increased and the viscosity increased at the same time. When the temperature of the composition increased by 5 ° C., the ultraviolet irradiation was stopped. The conversion ratio of the resulting partially photopolymerized thickening composition was 4.5.
%, The viscosity was 1400 cps.

Further, 0.5 g of hexanediol diacrylate was added to this thickening composition, and the mixture was applied to a PET film having a peelable surface and a thickness of 38 μm so as to have a thickness of 1 mm. Then, the composition coated surface,
The same PET film was covered so that the peelable surface was in contact with the coated surface. A chemical lamp is used as a source of ultraviolet rays, and the lamp intensity of the irradiation surface is ² mW / cm ² (365
The lamp height is set so as to be a light intensity measuring instrument UVR-1 (manufactured by Tokyo Optical Machinery Co., Ltd.) having a maximum sensitivity in nm, and the composition is coated with a PET film. It was irradiated with ultraviolet rays for 5 minutes. The residual monomer in the sample at that time was 0.1% by weight, and the gel fraction was 80%.

The width 2 of the adhesive sheet thus obtained
A 0 mm sample was attached to a cement board (standard) with an adhesive area of 20 mm x 20 mm using an aluminum foil with a thickness of 300 μm as a backing material, and a load of 2 k
It was pressure-treated with a rubber roller of g. When the obtained adhesive piece was pulled in the shearing direction at a peeling speed of 50 mm / min, the maximum shearing force was 6.5 kgf / cm ² .

[Comparative Example 1] 900 g of 2-ethylhexyl acrylate, 100 g of acrylic acid, and a photopolymerization initiator Irgacure 184 (trade name, manufactured by Ciba-Geigy).
3 g was stirred and mixed in a separable flask until uniform, and then nitrogen gas was purged to remove dissolved oxygen. When this composition was irradiated with ultraviolet rays from a black light lamp, the temperature of the composition increased and the viscosity increased at the same time. When the temperature of the composition increased by 5 ° C., the ultraviolet irradiation was stopped. The resulting partially photopolymerized thickening composition had a conversion of 2.5% and a viscosity of 4
It was 00 cps.

Further, 0.5 g of hexanediol diacrylate was added to this thickening composition, and an adhesive sheet was obtained in the same manner as in Example 1, and the shearing force was measured. The shear force was 1.6 kgf / cm ² .

Example 2 1) Production of acrylic copolymer In a reactor equipped with a cooling pipe, 60 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid and 80 parts by weight of ethyl acetate. Prepare the department,
The temperature was raised and kept at the reflux temperature for 30 minutes. Then, a solution prepared by dissolving 0.1 part by weight of benzoyl peroxide in 10 parts by weight of ethyl acetate was added dropwise and reacted for 7 hours.

Thereafter, a solution of 0.1 part by weight of benzoyl peroxide dissolved in 10 parts by weight of ethyl acetate was further added dropwise and the reaction was carried out for 4 hours.

Then, 22 parts by weight of toluene was added thereto and cooled to obtain an acrylic copolymer solution.

This acrylic copolymer solution had a solid content of 4
The viscosity was 4.8% and the viscosity was 1400 cps (20 ° C.).

2) Production of surface adhesive layer Further, 100 g of this acrylic copolymer solution was mixed with
Rosin ester resin ¹⁾20g and isocyanate as a curing agent
Anate compound²⁾1 g was added and mixed. This adhesive
The composition is PET having a peelable surface and a thickness of 38 μm.
It was coated on a film and the organic solvent was removed by drying. Formed
The pressure-sensitive adhesive layer thus formed had a thickness of 50 μm.

Note 1) Superester A-115 (softening point 115 ° C.) (Arakawa Chemical Co., Tackfire, trade name) Note 2) Coronate L55E (solid content 55%) (Nippon Polyurethane Co., polyisocyanate compound, Trade name) 3) Production of laminated adhesive sheet The above adhesive layers were laminated on both sides of the adhesive layer of the adhesive sheet obtained in Example 1, and then cured at room temperature for 1 week.

When the adhesive strength of this laminated adhesive sheet to polypropylene was measured, the peeling strength at a peeling angle of 90 degrees and a peeling speed of 50 mm / min was 8.5 kgf (when the width was 20 mm).

In order to measure the shear cohesive force at a high temperature, an aluminum foil having a thickness of 300 μm was used as a backing material for the sheet, and the sheet was attached to a stainless steel plate with a width of 20 mm and a length of 20 mm. , 1k in the shear direction
When a fall time at an ambient temperature of 80 ° C. was measured under a load of g, the weight did not fall even after 100 hours.

Comparative Example 2 A laminated adhesive sheet was prepared in the same manner as in Example 2 except that the adhesive sheet obtained in Comparative Example 1 was used.

Regarding the adhesiveness to polypropylene of this laminated adhesive tape, the peeling force was 7.8 kgf, but when the high temperature shear holding force at 80 ° C. was measured, the weight dropped in 2 hours. The peeling mode was destroyed at the interface between the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive layer laminated on the surface layer.

Example 3 The adhesive sheet obtained in Example 1 was attached to a cement plate, while the adhesive sheet obtained in Comparative Example 1 was attached to a stainless plate.

Two types of test pieces to which the adhesive sheets were respectively attached were attached and left at 40 ° C. for 1 week.

The tensile shearing force of the obtained test piece was 25.1.
It was kgf / cm ² .

[Comparative Example 3] The adhesive sheet obtained in Comparative Example 1 was attached to a cement plate and a stainless plate.

When the shearing force was measured in the same manner as in Example 3, it was 10.3 kgf / cm ² , and the film was broken at the adhesive interface of the adhesive sheet.

[0066]

According to the adhesive sheet of the present invention, a high degree of bonding strength can be obtained even for adherends having poor surface smoothness such as cement, tiles and asbestos plates that are difficult to bond. The attaching process can be significantly shortened and simplified.

Further, according to the adhesive sheet of the present invention, the cohesive force of the adhesive sheet can be improved by further performing the heating operation after pasting, and the bonding strength can be further increased.

According to the method for producing an adhesive sheet of the present invention,
Since photopolymerization occurs at a low temperature, the epoxy groups can be present in the sheet in an unreacted active state, the manufacturing process is stable, and the adhesive sheet has high stability over time.

An acrylic pressure-sensitive adhesive layer may be laminated on the adhesive sheet of the present invention. In this laminated adhesive sheet, an epoxy group and a functional group present in the pressure-sensitive adhesive layer,
Since a strong chemical bond is formed, a strong anchoring force can be realized between the adhesive sheet layer and the surface pressure-sensitive adhesive layer, and as a result,
The cohesive force of the laminated adhesive sheet is improved.

Further, the adhesive sheet of the present invention has strong contact adhesiveness with a general adhesive sheet having a functional group such as a carboxyl group which is reactive with an epoxy group. Therefore, by using the adhesive sheet of the present invention and a general adhesive sheet, it is possible to realize an adhesive system for highly bonding two adherends having different surface energies, which has been difficult to bond conventionally.

Claims (3)

[Claims] 1. (a) 30 to 98 parts by weight of at least one acrylate-based monomer selected from the group consisting of (meth) acrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms, and (b) Selected from the group consisting of 2 to 70 parts by weight of a vinyl compound-based monomer having an unsaturated double bond copolymerizable with the acrylate-based monomer (a), and (c) an ester of an epoxy group-containing alcohol and (meth) acrylic acid. A photopolymerizable composition containing 0.5 to 70 parts by weight of at least one acrylate-based monomer and 0.01 to 5 parts by weight of (d) a photopolymerization initiator. 2. An adhesive tape or sheet having a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, which is obtained from the photopolymerizable composition according to claim 1. 3. An adhesive tape or sheet in which an acrylic pressure-sensitive adhesive layer containing a functional group having reactivity with an epoxy group is laminated on at least one side of the pressure-sensitive adhesive layer according to claim 2.