JP2862453B2 - Double-sided pressure-sensitive adhesive tape and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thick 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 utilizing the characteristics of one-touch adhesiveness. Particularly in recent years, market needs for bonding structural members easily and in a short time have been increasing in the field of vehicles and construction materials, and they have high adhesiveness and durability that cannot be obtained with conventional pressure-sensitive adhesives. There is a demand for the development of a double-sided adhesive tape having excellent material strength. In order to satisfy the required performance of such a double-sided pressure-sensitive adhesive tape, it is important to design the polymer of both the pressure-sensitive adhesive and the substrate, but it is necessary that both the pressure-sensitive adhesive layer and the substrate have a certain thickness.

As an adhesive used for such a purpose, an acrylic adhesive containing an acrylic polymer as a main component is excellent in light resistance, weather resistance, oil resistance, aging resistance and the like. It is considered suitable. The acrylic pressure-sensitive adhesive is generally manufactured by a method of thermally polymerizing a vinyl-based monomer containing an acrylic monomer such as an alkyl acrylate as a main component in an organic solvent, or a method of emulsion polymerization. Solvent-type pressure-sensitive adhesive obtained by the polymerization method, because various pressure-sensitive resins can be blended,
There is a feature that excellent adhesive properties can be exhibited even on an adherend having a low-polarity surface where adhesion is difficult. However, when manufacturing a double-sided pressure-sensitive adhesive tape having a thick-film pressure-sensitive adhesive layer with such an acrylic solvent-type pressure-sensitive adhesive, since the pressure-sensitive adhesive layer is formed by thermal drying, foaming occurs during drying, or drying occurs. There was a problem that time was long.

In recent years, by applying an acrylic monomer directly to a substrate or the like and then photopolymerizing to form a pressure-sensitive adhesive layer,
A photo-in-situ polymerization method for removing the solvent from the pressure-sensitive adhesive has been studied. For example, Japanese Patent Publication No. 57-17030 discloses a method for directly producing a pressure-sensitive adhesive tape by photopolymerizing a photoreactive composition. A method has been proposed.

However, in order to mix a tackifying resin in order to obtain high adhesion, the above-mentioned method requires that the tackifying resin be compounded before photopolymerization. Since the resin causes polymerization inhibition, there is a problem that the adhesive performance such as the holding power of the obtained adhesive is extremely reduced, and the adhesiveness to the adherend having a low-polarity surface, which is difficult to adhere, is high. It has been difficult to develop a photopolymerizable pressure-sensitive adhesive exhibiting the following.

Further , Japanese Patent Application Laid-Open No. 63-118392 discloses
Consists of photopolymerized acrylic polymer pressure-sensitive adhesive
From non-stick acrylic polymer material photopolymerized with outer layer
Pressure-sensitive adhesive tape having an intermediate layer and its manufacturing method
Is being planned. However, the method obtained by thermal polymerization
Non-adhesive photopolymerized with outer layer consisting of a cryl-based adhesive layer
Pressure-sensitive adhesive with an intermediate layer made of acrylic polymer
Tapes and their production are not known.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to exhibit high adhesion to an adherend having a low-polarity surface which is difficult to adhere. It is another object of the present invention to provide a highly reliable thick-film double-sided pressure-sensitive adhesive tape having a substrate having structural strength and suitable for bonding a structure, and a method for producing the same.

[0008]

Means for Solving the Problems The double-sided pressure-sensitive adhesive tape of the first invention contains a tackifier resin on both sides of a base material made of a photopolymerizable composition of a photopolymerizable composition and has an acrylic resin obtained by thermal polymerization. </ RTI> is characterized in that a cellulose-based pressure-sensitive adhesive layer is formed.

The method for producing a double-sided pressure-sensitive adhesive tape according to the second invention comprises:
Contains a tackifying resin on one side of the releasable substrate and is thermally polymerized.
After applying the photopolymerizable composition to at least one of the pressure-sensitive adhesive layers of the two pressure-sensitive adhesive films on which the obtained acrylic pressure-sensitive adhesive layer is formed, each of the two pressure-sensitive adhesive films is used as a peelable substrate. It is characterized in that the photopolymerizable composition is laminated so as to be on the outside, and the photopolymerizable composition is polymerized by light irradiation.

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

The alkyl (meth) acrylate is preferably at least one or more acrylate monomers 60 to 9 selected from alkyl (meth) acrylates.
It is preferable to use 9% by weight and 40 to 1% by weight of a vinyl monomer copolymerizable with the acrylate monomer.

As the acrylate monomer, an alkyl (meth) acrylate 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 monomers, respectively,
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, a homopolymer generally contains an alkyl acrylate having a glass transition point of -50 ° C. or lower as a main component. As the comonomer, it is preferable to use an alkyl (meth) acrylate of a lower alkyl group or the following vinyl monomers.

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

Other vinyl monomers such as 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.

The adhesion between the substrate and the pressure-sensitive adhesive can be improved by copolymerizing a monomer having a functional group which reacts with the functional group of the pressure-sensitive adhesive described later in the photopolymerizable composition. 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 amine imide group, and the like. The amount of the monomer having the functional group is from 0.5 to the total amount of the monomers used in the photopolymerizable composition.
5% by weight is preferred.

Examples of the photopolymerization initiator used in the present invention include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [trade name “Darocur 2959”, manufactured by Ciba-Geigy), α Acetophenone-based initiators such as -hydroxy-α, α'-dimethylacetophenone [trade name “Darocur 1173” manufactured by Ciba Geigy), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone; benzoin ethyl ether, benzoin isopropyl ether Benzoin ether-based initiators, such as benzyl dimethyl ketal; halogenated ketones, acylphosphinoxides, acylphosphonates, and the like.

In the above photopolymerizable composition, when the content of the photopolymerization initiator is too small, unreacted monomer tends to remain, and not only a monomer odor remains in the obtained polymer, but also the cohesive strength is reduced, and Since the dispersion of the molecular weight of the obtained polymer becomes large, the amount is preferably 0.001 to 5 parts by weight based on 100 parts by weight of the monomer main component.

In order to impart heat resistance, cohesive strength at high temperature, and the like to the photopolymerizable composition, it is preferable to include a polymerizable crosslinking agent. Examples of such a polymerizable crosslinking agent include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. Pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like. The content of such a polymerizable crosslinking agent is preferably 5 parts by weight or less based on 100 parts by weight of the monomer main component, because the control of the degree of crosslinking becomes difficult as the content increases.

If necessary, a thickener, a thixotropic agent, a bulking agent, a filler, and the like may be added to the 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. Examples of the bulking agent include calcium carbonate, titanium oxide, and clay, and examples of the filler include inorganic hollow bodies such as glass balloons, alumina balloons, and ceramic balloons; and organic hollow bodies such as nylon beads, acrylic beads, and silicon beads. Body: monofilaments such as polyester, rayon, and nylon.

The pressure-sensitive adhesive layer used in the first invention is formed by applying and drying an acrylic solution-type pressure-sensitive adhesive on both sides of the base material by a conventionally known coating device, and has a thickness of 5 to 150 μm. Is preferred. The solution-type pressure-sensitive adhesive is obtained by a conventionally known thermal polymerization method.For example, a monomer mainly containing an acrylate ester is used in an organic solvent, using an azo-based or peroxide-based polymerization initiator.
Obtained by thermal polymerization .

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 photopolymer forming the base material. In order to realize this, among the vinyl monomers copolymerizable with the acrylate in the composition of the solution-type pressure-sensitive adhesive, those having a glass transition temperature of the homopolymer of 30 ° C. or higher may be blended. .

Examples of such vinyl monomers include acrylic acid, methacrylic acid, itaconic acid, carboxyethyl acrylate, benzyl acrylate, isobornyl (meth) acrylate, N-vinylpyrrolidone,
Acryloylmorpholine and the like can be 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 bonding interface with the adherend can be obtained, and a high loss of the photopolymer that forms the base layer is obtained. Due to its properties, it exhibits a high degree of peel resistance.

[0024] A tackifying resin is added to the solution-type pressure-sensitive adhesive.
Be added. Examples of the tackifying resin include a rosin resin, a modified rosin resin, a terpene resin, a terpene phenol resin, an aromatic modified terpene resin, C5 and C9.
Examples thereof include terpene phenol resins and modified rosin esters as those which improve adhesion to adherends having a low polarity surface such as polyolefin.

Further, by adding a photopolymerization initiator to the solution-type pressure-sensitive adhesive, it is possible to prevent the migrated monomers from remaining in the sandwiched pressure-sensitive adhesive layer without being reacted even after the photopolymerization. it can.

Next, a method for manufacturing a double-sided pressure-sensitive adhesive tape of the second invention will be described based on one embodiment. As shown in FIG.
The solution-type pressure-sensitive adhesive layer 2 as described above is formed on one surface of the peelable substrate 21.
Adhesive film 2 having a peelable base material 2
The pressure-sensitive adhesive film 1 having the solution-type pressure-sensitive adhesive layer 12 as described above is disposed so that the pressure-sensitive adhesive layers face each other, and the photopolymerizable composition 3 as described above is applied to both the pressure-sensitive adhesive layers 22 and 12. Then, after laminating two pressure-sensitive adhesive films, ultraviolet rays are irradiated from the substrate 11 side of the pressure-sensitive adhesive film 1 by the ultraviolet irradiation device 4 to polymerize the photopolymerizable composition, and then the peelable substrate of the pressure-sensitive adhesive film 1 The wound body of the double-sided pressure-sensitive adhesive tape 5 is obtained by winding while peeling 11.

The releasable substrates 11 and 21 have releasability. For example, resin sheets or films of polyethylene, polyethylene terephthalate, polypropylene, polycarbonate, acrylic resin, vinyl chloride resin and the like are preferably used. You. It is preferable that the above-mentioned sheet or film has been subjected to a surface release treatment.

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

The solution type pressure-sensitive adhesive layers 12 and 22 are
Acrylic solution type pressure-sensitive adhesive solution used in the invention ,
It is formed by applying to the releasable substrates 11 and 21 by a conventionally known application method and drying.

To cure the photopolymerizable composition 3,
Light irradiation may be performed from at least one of the peelable substrates 11 and 21.

As the lamp used for light irradiation, those having a light emission distribution at a wavelength of 400 nm or less are preferable. A microwave excitation mercury lamp or the like is used.

Of these, the ultra-high pressure mercury lamp efficiently emits light in the active wavelength region of the photopolymerization initiator, and has short wavelength 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 does not emit much long-wavelength light that causes nonuniform film thickness such as foaming. In particular, as an ultra-high pressure mercury lamp, a so-called water-cooled type in which a circulating water jacket is provided on the lamp has a remarkable effect.

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

[0034]

The double-sided pressure-sensitive adhesive tape of the first invention is a photopolymerizable composition.
Contains tackifying resin on both sides of base material made of photopolymer
Since the acrylic pressure-sensitive adhesive layer obtained by thermal polymerization is formed, excellent tackiness to an adherend having a low-polarity surface is exhibited by adding a tackifier resin . The acrylic pressure-sensitive adhesive layer obtained by thermal polymerization
Can be mixed with the tackifier resin without any problem
You. In the method for producing a double-sided pressure-sensitive adhesive tape according to the second invention, the thickness of the base material can be arbitrarily set, and a thick film can provide an adhesive breakage resistance. Also,
When the photopolymerizable composition is photocured to form a substrate, the photopolymerizable composition is cured while being melted into the pressure-sensitive adhesive layer, so that the substrate and the pressure-sensitive adhesive layer are strongly bonded.

[0035]

EXAMPLES Next, examples of the present invention and comparative examples will be described, but the present invention is not limited to these examples. 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 the mixture was charged together with the parts by weight and the temperature was raised and maintained at the reflux temperature for 30 minutes, the mixture was reacted for 7 hours while dropwise adding a solution of 0.1 parts by weight of benzoyl peroxide in 10 parts by weight of ethyl acetate. Next, the benzoyl peroxide was added to 0.1.
A solution prepared by dissolving 1 part by weight of ethyl acetate in 10 parts by weight of ethyl acetate was added dropwise and reacted for 4 hours. 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 with 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 N-vinylpyrrolidone 5
Instead of parts by weight, 2-ethylhexyl acrylate 90
Parts by weight, except that 10 parts by weight of acrylic acid were used.
An acrylic copolymer solution was obtained in the same manner as in the acrylic pressure-sensitive adhesive composition A.

3) Preparation of photopolymerizable composition X 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, 0.2 parts by weight of a photopolymerization initiator ("Irgacure 184" manufactured by Ciba Geigy), 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 with a B-type viscometer was 1000 cps.

4) Preparation of Photopolymerizable Composition Y A urethane 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 poly (methyl methacrylate) microspheres were uniformly mixed to obtain a photopolymerizable composition.

( Examples 1 and 2 and Reference Examples 1 and 2 ) An acrylic pressure-sensitive adhesive composition obtained by mixing predetermined amounts of components shown in Table 1 was used to form a 38 μm-thick polyethylene having a peelable surface. It was coated on a terephthalate (PET) film and dried to obtain an adhesive film having an adhesive layer having a thickness of 50 μm. On the adhesive layer of this adhesive film,
After coating the photopolymerizable composition to a thickness of 1 mm,
After laminating another pressure-sensitive adhesive film such that the pressure-sensitive adhesive layer is in contact with the photopolymerizable composition, the light intensity of the irradiated surface is 3 mW / cm2 [light having a maximum sensitivity at 365 nm using an ultrahigh pressure mercury lamp as a radiation source. The height of the lamp is set so that the intensity is measured by an intensity meter UVR-1 (manufactured by Tokyo Optical Machinery Co., Ltd.), and ultraviolet light is irradiated from another adhesive film side for 5 minutes to perform photopolymerization. Polymerizing the composition,
A double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer covered with a PET film was produced.

[Performance evaluation 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) Peeling strength against PP (polypropylene plate) 90 degrees The above double-sided pressure-sensitive adhesive tape was cut into a size of 10 mm in width and 150 mm in length, and the PET film was peeled off. A 5 mm thick polypropylene plate was adhered to the other pressure-sensitive adhesive layer and pressure-bonded by reciprocating a 2 kg roller once to produce a test piece. For the above test piece, 90 degree peel angle, tensile speed 50 cm
The pressure-sensitive adhesive layer was peeled from the polypropylene plate at a rate of / min, and the peel strength was measured.

(2) SP (stainless steel plate) 90 ° peel strength 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 double-sided pressure-sensitive 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 force at 80 ° C. was measured as the time until the weight dropped.

(Comparative Example 1) A photopolymerizable composition was directly applied on a PET film without using an acrylic pressure-sensitive adhesive composition, and another PE was applied thereon.
After laminating the T film, light irradiation was performed in the same manner as in Example 1 to cure the photopolymerizable composition. Using the cured product of the photopolymerizable composition, physical properties of the same items as in Example 1 were measured, and the results are shown in Table 1.

[0044]

[Table 1]

[0045]

The double-sided pressure-sensitive adhesive tape according to the first aspect of the present invention is as described above. The substrate and the pressure-sensitive adhesive layer can be firmly bonded to each other.
In addition, by incorporating a tackifying resin, it is possible to develop a strong adhesive force to a low-polarity surface, and on the other hand, by using a double-sided pressure-sensitive adhesive tape having a large film thickness, it can be suitably used for structural bonding. . The method for producing a double-sided pressure-sensitive adhesive tape according to the second invention is as described above, and the thickness of the substrate can be arbitrarily set. I will provide a.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for producing a double-sided pressure-sensitive adhesive tape.

[Description of Signs] 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)

(57) [Claims] An acrylic pressure-sensitive adhesive layer containing a tackifier resin and obtained by thermal polymerization is formed on both surfaces of a substrate made of a photopolymerizable composition of a photopolymerizable composition. A double-sided adhesive tape characterized by the following. 2. The method according to claim 1, wherein the releasable base material contains a tackifier resin on one side.
After applying the photopolymerizable composition to at least one of the two pressure-sensitive adhesive films on which the acrylic pressure-sensitive adhesive layer obtained by thermal polymerization is formed, the two pressure-sensitive adhesive films are peeled off. A method for producing a double-sided pressure-sensitive adhesive tape, comprising laminating a substrate so that the substrate is on the outside, and polymerizing the photopolymerizable composition by light irradiation.