JPH06264037A - Double-coated self-adhesive tape and its production - Google Patents

Abstract

PURPOSE:To obtain a self-adhesive excellent in adhesion to a low-polar surface, substrate strengths, etc., by forming a layer of an acrylic self-adhesive obtd. by thermal polymn. on both sides of a substrate formed by photopolymerizng a photopolymerizable compsn. CONSTITUTION:A self-adhesive film 1 obtd. by forming an acrylic self-adhesive layer 12 on one side of a releasable substrate 11 (e. g. a polyethylene terephthalate film) and a self-adhesive film 2 obtd. by forming an acrylic self-adhesive layer 22 on one side of a releasable substrate 21 are placed in such a manner that the self-adhesive layers 12 and 22 are facing each other. After the self-adhesive layers 12 and 22 are coated with a photopolymerizable compsn. (e.g. a urethane acrylate contg. a photopolymn. initiator), the self-adhesive films 1 and 2 are laminated in such a manner that the releasable substrates 11 and 12 are at the outside. Then, ultraviolet rays are radiated by an ultraviolet radiator 4 to the side of the substrate 11 of the self-adhesive film 1 to polymerize the photopolymerizable compsn. 3. The releasable substrate 11 is peeled from the laminate, which is then rolled up to give a roll of a double-coated self-adhesive tape 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both sides of a substrate made of a cured product of a photopolymerizable composition and a method for producing the same.

[0002]

2. Description of the Related Art Adhesive tapes are used for various joining operations by taking advantage of the one-touch adhesiveness. In recent years, in particular, the market needs for bonding structural members easily and in a short time are increasing in the fields of vehicles and building materials, and they have high adhesiveness and durability that cannot be obtained with conventional adhesives, There is a demand for the development of double-sided adhesive tape with excellent material strength. In order to satisfy the required performance of such a double-sided pressure-sensitive adhesive tape, the polymer design of both the pressure-sensitive adhesive and the base material is important, but both the pressure-sensitive adhesive layer and the base material need to be thick films to some extent.

As an adhesive used for such a purpose, an acrylic adhesive containing an acrylic polymer as a main component is excellent in performance such as light resistance, weather resistance, oil resistance and aging resistance. Considered to be suitable. The acrylic pressure-sensitive adhesive is generally produced by a method of heat-polymerizing a vinyl-based monomer containing an acrylic monomer such as an acrylic acid alkyl ester as a main component in an organic solvent, or a method of emulsion polymerization. The solvent-based pressure-sensitive adhesive obtained by the polymerization method can be mixed with various pressure-sensitive adhesive resins,
It is characterized in that it can exhibit excellent adhesive properties even on an adherend having a low-polarity surface that is difficult to adhere. However, when a double-sided pressure-sensitive adhesive tape having a thick film pressure-sensitive adhesive layer is produced by using such an acrylic solvent-based pressure-sensitive adhesive, the pressure-sensitive adhesive layer is formed by heat drying, so foaming may occur during drying or drying may occur. There was a problem that the time was long.

In recent years, by directly coating an acrylic monomer on a substrate or the like and then photopolymerizing it to form a pressure-sensitive adhesive layer,
An optical IN-SITU polymerization method for achieving solvent-free adhesives has been studied. For example, in Japanese Patent Publication No. 57-17030, an adhesive tape is directly produced by photopolymerizing a photoreactive composition. A method has been proposed.

However, if a tackifying resin is to be blended in order to obtain high adhesiveness, in the above method, it is necessary to blend the tackifying resin before photopolymerization. Since the resin causes polymerization inhibition, there is a problem that the adhesive performance such as the holding force of the obtained adhesive will be extremely reduced, and it has high adhesiveness to adherends with low polar surface where adhesion is difficult. It has been difficult to develop a photopolymerizable pressure-sensitive adhesive that develops.

As another method, for example, when a double-sided pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer of a solvent-type pressure-sensitive adhesive is formed on a base sheet obtained by photopolymerization is used for joining structures, the pressure-sensitive adhesive is generally Since the adhesiveness to the base material is poor, peeling occurs from the adhesive interface between the pressure-sensitive adhesive layer and the base material, and there is a problem that the adhesive reliability cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to exhibit high adhesiveness to an adherend having a low polar surface on which adhesion is difficult. The object is to provide a highly reliable thick film double-sided pressure-sensitive adhesive tape having a base material having structural strength and suitable for joining structures, and a method for producing the same.

[0008]

The double-sided pressure-sensitive adhesive tape of the first invention has a heat-polymerized acrylic pressure-sensitive adhesive layer formed on both sides of a substrate made of a photopolymerization product of a photopolymerizable composition. Is characterized by.

The method for producing the double-sided adhesive tape of the second invention is
Acrylic pressure-sensitive adhesive layer was formed on one side of the releasable substrate 2
After applying the photopolymerizable composition to at least one of the pressure-sensitive adhesive layers of the two sheets of pressure-sensitive adhesive film, two pressure-sensitive adhesive films are laminated so that each releasable substrate is on the outside, and the above-mentioned light is irradiated by light irradiation. It is characterized by polymerizing the polymerizable composition.

The first invention will be described in detail below. First
The substrate used in the invention is formed from a photopolymer of the photopolymerizable composition. The photopolymerizable composition, epoxy,
(Meth) such as epoxy (meth) acrylate and urethane (meth) acrylate obtained by addition-polymerizing (meth) acrylic acid to an oligomer having urethane or polyester skeleton
The main component is an acrylate oligomer or an alkyl (meth) acrylate, and a photopolymerization initiator is contained.

As the above-mentioned alkyl (meth) acrylate, at least one or more acrylate monomers 60 to 9 selected from (meth) acrylic acid alkyl esters.
It is preferably composed of 9% by weight and 40 to 1% by weight of a vinyl monomer copolymerizable with the acrylate monomer.

As the acrylate-based monomer, (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 4 to 12 carbon atoms is used. , For example, n-butyl (meth) acrylate, (meth)
2-Ethylhexyl acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate and the like can be mentioned. These acrylate-based monomers,
They can be used alone or in combination of two or more.

In order to impart a good balance of tackiness and cohesiveness to the polymer obtained from the above photopolymerizable composition, the homopolymer mainly contains an acrylic acid alkyl ester having a glass transition point of −50 ° C. or lower as a main component. As the comonomer, it is preferable to use a (meth) acrylic acid alkyl ester having a lower alkyl group or the following vinyl-based monomer.

Examples of vinyl monomers copolymerizable with the above acrylate monomers include carboxyethyl acrylate, ω-carboxypolycaprolactone monoacrylate, monohydroxyethyl succinate, 2-acryloxyethyl hexahydrophthalic acid, β -Acryloxyethyl hydrogen succinate, N-vinylpyrrolidone, acryloylmorpholine and the like.

Examples of vinyl monomers other than the above include acrylic acid, itaconic acid, acrylamide, alkylaminoethyl (meth) acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, fluorine acrylate, Silicon acrylate or the like can be used.

By co-polymerizing a monomer having a functional group which reacts with a functional group of the pressure-sensitive adhesive described later in the photopolymerizable composition, the adhesiveness between the substrate and the pressure-sensitive adhesive can be improved. Examples of the monomer having a functional group that reacts with the functional group of the pressure-sensitive adhesive include an acrylate monomer having an epoxy group, an isocyanate group, an amineimide group and the like. The amount of the monomer having a functional group is 0.5 to the total amount of the monomers used in the photopolymerizable composition.
5% by weight is preferred.

As the photopolymerization initiator used in the present invention, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Ciba Geigy, trade name "Darocur 2959"], α -Hydroxy-α, α'-dimethylacetophenone [Ciba Geigy, trade name "Darocur 1173"], acetophenone-based initiators such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; benzoin ethyl ether, benzoin isopropyl ether Examples thereof include benzoin ether-based initiators such as; ketal-based initiators such as benzyl dimethyl ketal; halogenated ketones, acyl phosphinoxides, acyl phosphonates and the like.

When the content of the photopolymerization initiator in the above-mentioned photopolymerizable composition is low, unreacted monomer is likely to remain, and not only the monomer odor remains in the obtained polymer but also the cohesive force decreases, which is high. If so, the variation in the molecular weight of the obtained polymer will be large, so 0.001 to 5 parts by weight is preferable with respect to 100 parts by weight of the monomer main component.

In order to impart heat resistance and cohesive force at high temperature to the above photopolymerizable composition, it is preferable to add a polymerizable cross-linking agent. Examples of such a polymerizable cross-linking agent 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, and the like. When the content of the polymerizable cross-linking agent increases, it becomes difficult to control the degree of cross-linking. Therefore, the content of the polymerizable cross-linking agent is preferably 5 parts by weight or less based on 100 parts by weight of the monomer main component.

If necessary, a thickener, a thixotropic agent, a bulking agent, a filler and the like may be added to the above-mentioned photopolymerizable composition as long as the photopolymerizability is not impaired. Examples of the thickener include acrylic rubber and fumed silica, and examples of the thixotropic agent include colloidal silica and polyvinylpyrrolidone. Further, examples of the extender include calcium carbonate, titanium oxide, clay, and the like, and examples of the filler include inorganic hollow bodies such as glass balloons, alumina balloons, and ceramic balloons; organic hollows such as nylon beads, acrylic beads, and silicon beads. Body: monofilaments such as polyester, rayon, nylon and the like can be mentioned.

The pressure-sensitive adhesive layer used in the first invention is formed by applying an acrylic solution-type pressure-sensitive adhesive on both surfaces of the above-mentioned base material using a conventionally known coating device and drying it, and has a thickness of 5 to 150 μm. Is preferred. The solution-type pressure-sensitive adhesive can be obtained by a conventionally known thermal polymerization method. For example, a monomer containing an acrylic ester as a main component is polymerized in an organic solvent using an azo-based or peroxide-based polymerization initiator. It is obtained by doing.

The glass transition temperature of the acrylic polymer used in the solution type pressure-sensitive adhesive is preferably equal to or higher than that of the photopolymerization product forming the substrate. In order to achieve this, among the vinyl monomers copolymerizable with the acrylate ester, those having a glass transition temperature of 30 ° C. or higher of the homopolymer may be added to the composition of the solution adhesive. .

Examples of such vinyl monomers include acrylic acid, methacrylic acid, itaconic acid, carboxyethyl acrylate, benzyl acrylate, isobornyl (meth) acrylate, N-vinylpyrrolidone,
Acryloyl morpholine etc. are mentioned. By thus increasing the glass transition temperature of the pressure-sensitive adhesive layer, a high cohesive force and a high adhesive force at the adhesive interface with the adherend are obtained, and a high loss of the photopolymerization product forming the base material layer is obtained. Due to its characteristics, it exhibits a high degree of peel resistance.

It is preferable to add a tackifying resin to the solution type pressure-sensitive adhesive. Examples of the tackifying resin include rosin-based resins, modified rosin-based resins, terpene resins,
Terpene phenol resin, aromatic modified terpene resin, C
Examples thereof include ₅ and C ₉ petroleum resins, coumarone resins, and the like, and terpene phenol resins and modified rosin esters are preferable for improving the adhesion to an adherend having a low polarity surface such as polyolefin.

Furthermore, by adding a photopolymerization initiator to the solvent-based pressure-sensitive adhesive layer, it is possible to prevent the monomer migrating to the sandwiched pressure-sensitive adhesive layer from remaining unreacted after photopolymerization. You can

Next, a method for manufacturing the double-sided pressure-sensitive adhesive tape of the second invention will be described based on an embodiment. As shown in Figure 1,
The pressure-sensitive adhesive film 2 having the pressure-sensitive adhesive layer 22 on one surface of the peelable substrate 21, and the pressure-sensitive adhesive film 1 having the pressure-sensitive adhesive layer 12 on one surface of the peelable substrate 11 are arranged so that the pressure-sensitive adhesive layers face each other, The above-mentioned photopolymerizable composition 3 is applied to both the pressure-sensitive adhesive layers 22 and 12, two pressure-sensitive adhesive films are laminated, and then ultraviolet rays are irradiated from the base material 11 side of the pressure-sensitive adhesive film 1 by the ultraviolet ray irradiation device 4, The photopolymerizable composition is polymerized, and then the peelable base material 11 of the pressure-sensitive adhesive film 1 is peeled off and wound up to obtain a wound body of the double-sided pressure-sensitive adhesive tape 5.

The releasable substrates 11 and 21 have releasability and, for example, resin sheets or films of polyethylene, polyethylene terephthalate, polypropylene, polycarbonate, acrylic resin, vinyl chloride resin or the like are preferably used. It The above-mentioned sheet or film is preferably one whose surface is treated for release.

At least one of the peelable substrates 11 and 21 is transparent in order to polymerize the photocurable composition 3 applied on the pressure-sensitive adhesive layer by irradiating the photocurable composition 3 with light from the substrate side. It must be good (at least 11 in the case of FIG. 1).

The pressure-sensitive adhesive layers 12 and 22 are formed by applying the solvent-type acrylic pressure-sensitive adhesive used in the first invention to the peelable substrates 11 and 21 by a conventionally known coating method and drying. To be done.

To cure the above photopolymerizable composition 3,
Light may be irradiated from at least one side of the peelable base materials 11 and 21.

The lamp used for light irradiation preferably has a light emission distribution at a wavelength of 400 nm or less, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a metal halide lamp, A microwave-excited mercury lamp or the like is used.

Of these, the ultra-high pressure mercury lamp emits light in the active wavelength region of the photopolymerization initiator efficiently, and has a short wavelength of light or light that reduces the viscoelastic properties of the resulting polymer by crosslinking. This is preferable because the polymerizable composition is heated and evaporated, and a large amount of long-wavelength light that causes nonuniformity of the film thickness such as foaming is not emitted. In particular, as an ultra-high pressure mercury lamp, a so-called water-cooled type in which a jacket of circulating water is provided on the lamp is remarkably effective.

The light intensity of the lamp is a factor that influences the degree of polymerization of the polymer obtained from the photopolymerizable composition, and is appropriately selected depending on the performance of the intended product. For example, when a cleavage type photopolymerization initiator having a usual acetophenone group is blended, the light intensity in the wavelength region (usually 365 to 420 nm) effective for photodecomposition of the photopolymerization initiator is 0.1 to 10.
The range of 0 mW / cm ² is preferable.

[0034]

In the double-sided pressure-sensitive adhesive tape of the first invention, the solvent-type pressure-sensitive adhesive layer is formed on both sides of the base material. Therefore, by adding a tackifying resin to the solvent-type pressure-sensitive adhesive layer, an adhesive layer having a low polarity surface can be obtained. Exhibits excellent adhesion to the body. In the method for producing a double-sided pressure-sensitive adhesive tape according to the second aspect of the invention, the thickness of the base material can be set arbitrarily, and the use of a thick film can impart adhesive fracture resistance. Further, when the photopolymerizable composition is photocured to form the base material, the photopolymerizable composition is cured in a state of being melted into the pressure-sensitive adhesive layer, so that the base material and the pressure-sensitive adhesive layer are firmly bonded. .

[0035]

EXAMPLES Next, examples and comparative examples of the present invention will be described, but the present invention is not limited to these. 1) Preparation of acrylic copolymer A In a reactor equipped with a cooling tube, 60 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of -n-butyl acrylate and 5 parts by weight of N-vinylpyrrolidone were added to 80 parts of ethyl acetate. After charging with 1 part by weight, the temperature was raised and maintained at the reflux temperature for 30 minutes, then, a solution of 0.1 parts by weight of benzoyl peroxide dissolved in 10 parts by weight of ethyl acetate was added dropwise to carry out a reaction for 7 hours. Next, benzoyl peroxide 0.
A solution prepared by dissolving 1 part by weight in 10 parts by weight of ethyl acetate was dropped and reacted for 4 hours, and then 22 parts by weight of toluene was added and cooled to obtain an acrylic copolymer solution. The solid content of this acrylic copolymer solution was 44.8% by weight, and the viscosity measured by a B-type viscometer was 14000 cps (20 ° C.).

2) Preparation of acrylic copolymer B 60 parts by weight of 2-ethylhexyl acrylate, 35 parts by weight of -n-butyl acrylate and 5 parts of N-vinylpyrrolidone 5
2-Ethylhexyl acrylate 90 in place of parts by weight
Except that 10 parts by weight of acrylic acid is used.
By the same method as for the acrylic pressure-sensitive adhesive composition A, an acrylic copolymer solution was obtained.

3) Preparation of Photopolymerizable Composition X 2-Ethylhexyl Acrylate 95 parts by weight, Acrylic Acid 5 parts by weight, Photopolymerization Initiator ("Irgacure 184" manufactured by Ciba-Geigy) 0.2 parts by weight, Hexanediol 0.05 parts by weight of diacrylate, 3 parts by weight of acrylic rubber, fumed silica (“Aerosil A20 manufactured by Nippon Aerosil Co., Ltd.
0 ") 2 parts by weight were uniformly mixed and stirred to obtain a photopolymerizable composition. The viscosity of this photopolymerizable composition measured by a B-type viscometer was 1000 cps.

4) Preparation of Photopolymerizable Composition Y Urethane-based oligomer (“Unitac 8” manufactured by Shin Nakamura Chemical Co., Ltd.)
000 ") 100 parts by weight, acrylic acid 5 parts by weight, photopolymerization initiator (" Irgacure 651 "manufactured by Ciba Geigy)
0.5 parts by weight and 30 parts by weight of polymethylmethacrylate microspheres were uniformly mixed to obtain a photopolymerizable composition.

(Examples 1 to 4) A 38 μm thick polyethylene terephthalate (PET) film having a releasable surface was prepared by mixing the acrylic pressure-sensitive adhesive composition obtained by mixing the predetermined amounts of the components shown in Table 1. It was coated on and dried to obtain an adhesive film having an adhesive layer with a thickness of 50 μm. On the pressure-sensitive adhesive layer of this pressure-sensitive adhesive film, the photopolymerizable composition having a thickness of 1
After coating so that the pressure-sensitive adhesive layer is in contact with the photopolymerizable composition, another pressure-sensitive adhesive film is laminated thereon, and the light intensity of the irradiation surface is 3 mW using an ultra-high pressure mercury lamp as a radiation source. / Cm ² [as the intensity value measured with a light intensity measuring instrument UVR-1 (manufactured by Tokyo Optical Machinery Co., Ltd.) having a maximum sensitivity at 365 nm], the height of the lamp is set, and from another adhesive film side The photopolymerizable composition was polymerized by irradiating with ultraviolet rays for 5 minutes to prepare a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer covered with a PET film.

[Evaluation of performance of double-sided pressure-sensitive adhesive tape] In order to evaluate the performance of the double-sided pressure-sensitive adhesive tape, the following three physical properties were measured, and the results are shown in Table 1. (1) 90-degree peel strength against PP (polypropylene plate) The double-sided adhesive tape was cut into a size of 10 mm in width and 150 mm in length, the PET film was peeled off, and an aluminum foil having a thickness of 100 μm was formed on one adhesive layer. A polypropylene plate having a thickness of 5 mm was attached to the other pressure-sensitive adhesive layer and pressure-bonded by reciprocating a 2 kg roller once to prepare a test piece. Peeling angle of 90 degrees and tensile speed of 50 cm for the above test pieces
The pressure-sensitive adhesive layer was peeled off from the polypropylene plate at / min, and the peel strength was measured.

(2) Peel strength at 90 ° to SP Except that a stainless steel plate (SUS304) having a thickness of 2 mm was used instead of the polypropylene plate having a thickness of 5 mm.
The 90-degree peel strength was measured in the same manner as in (1).

(3) Holding power at 80 ° C. The above-mentioned double-sided adhesive tape was cut into a width of 25 mm, and one side thereof was backed with an aluminum foil having a thickness of 100 μm.
According to IS Z1528, the holding power at 80 ° C. was measured as the time until the weight fell.

(Comparative Example 1) Without using an adhesive composition,
The photopolymerizable composition was directly coated on the PET film, another PET film was laminated thereon, and then the same photoirradiation as in Example 1 was performed to cure the photopolymerizable composition. Physical properties of the same items as in Example 1 were measured using the cured product of the photopolymerizable composition, and the results are shown in Table 1.

[0044]

[Table 1]

[0045]

The double-sided pressure-sensitive adhesive tape of the first invention is as described above, and the base material and the pressure-sensitive adhesive layer can be firmly bonded to each other. On the other hand, a strong adhesive force can be exhibited, and on the other hand, a double-sided pressure-sensitive adhesive tape having a large film thickness can be suitably used for structural bonding. The method for producing the double-sided pressure-sensitive adhesive tape of the second invention is as described above, and the thickness of the base material can be arbitrarily set. Therefore, by making the base material thick, the double-sided pressure-sensitive adhesive tape having adhesive fracture resistance. I will provide a.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method for producing a double-sided adhesive tape.

[Explanation of symbols]

 1 Adhesive Film 11 Base Material 12 Adhesive Layer 2 Adhesive Film 21 Base Material 22 Adhesive Layer 3 Photopolymerizable Composition 4 Irradiation Device

Claims (2)

[Claims] 1. A double-sided pressure-sensitive adhesive tape, comprising a heat-polymerized acrylic pressure-sensitive adhesive layer formed on both sides of a substrate comprising a photopolymerizable composition of a photopolymerizable composition. 2. A photopolymerizable composition is applied to at least one adhesive layer of two adhesive films having an acrylic adhesive layer formed on one surface of a releasable substrate, and then 2
A method for producing a double-sided pressure-sensitive adhesive tape, comprising laminating a plurality of pressure-sensitive adhesive films so that the releasable substrate is on the outside, and polymerizing the photopolymerizable composition by light irradiation.