JP3053693B2 - Method and apparatus for manufacturing double-sided tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a double-sided tape having a high thickness using a photoreactive composition.

[0002]

2. Description of the Related Art Generally, an acrylic pressure-sensitive adhesive is mainly composed of an acrylic polymer, so that it has light resistance, weather resistance,
Acrylic adhesive tapes with excellent oil resistance, etc.
It is widely used because it has excellent adhesive properties such as adhesive strength and cohesive strength, and aging resistance such as heat resistance and weather resistance.

[0003] For example, a typical method for producing an acrylic pressure-sensitive adhesive tape as a viscoelastic product is as follows. First, a vinyl-based monomer having an acrylate-based monomer such as an alkyl acrylate or an acrylic methacrylate as a main component is used. It has been manufactured by solution polymerization with an organic solvent to form a pressure-sensitive adhesive solution, or emulsion polymerization with an aqueous system to form an emulsion, which is coated or impregnated on a substrate, and dried by heating.

However, when an adhesive solution is used in the above production method, a large amount of energy is required to dry the adhesive solution coated or impregnated on a substrate at a high temperature, and air pollution by a solvent is required. Large-scale recovery equipment is required to prevent the Moreover, since the solvent is easily flammable, a sufficient safety device is required for maintaining safety. Especially recently, there is a problem that some solvents are inevitably released to the atmosphere from the viewpoint of environmental protection at the global level.
This approach is being phased out.

[0005] On the other hand, when an emulsion is used, more energy is required to evaporate water than when a solvent is used, and in terms of performance, water resistance is reduced due to an emulsifier mixed during polymerization. Furthermore, since a water-soluble monomer cannot be used, the type of the monomer is limited, and there is a disadvantage that the ability to respond to various needs required for the pressure-sensitive adhesive tape is weak.

Therefore, a method has been proposed in which the solvent of the photoreactive composition is eliminated by photopolymerizing the monomer of the photoreactive composition. For example, JP-A-58-125776
In the publication, a UV-permeable cover such as a polyethylene terephthalate film is put on the surface of the monomer of the photoreactive composition, and photopolymerization is performed in a state where reaction inhibition by oxygen is eliminated. A method for producing a double-sided tape with force is described.

[0007]

However, in the case of the above-mentioned conventional production method by photopolymerization, it is possible to prevent the reaction inhibition by the atmosphere or dissolved oxygen during the photopolymerization, but the following disadvantages arise. It will be. That is, a photoreactive composition is coated on a substrate that moves in the horizontal direction, a UV-transmissive film is coated thereon, and when UV light is irradiated from the surface of the film, the film is transported between rolls. This film is bent by the weight of the reaction solution,
There is a disadvantage that an adhesive having a uniform film thickness cannot be obtained. In order to prevent this bending, it is conceivable to increase the tension of the base material. In this case, the tension causes vertical wrinkles in the base material, and the product is also excellent in surface smoothness and uniform in film thickness. Is not obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and apparatus for producing a double-sided tape having a uniform thickness excellent in surface smoothness and having a high cohesive force. And

[0009]

According to the present invention, there is provided a method for producing a pressure-sensitive adhesive tape, comprising the steps of: providing a substrate having a releasable surface; The photoreactive composition is supplied to the gap to form a photoreactive composition layer, and the photoreactive composition layer is vertically conveyed from the upper side to the lower side. The reactive composition layer is irradiated with light, and the photoreactive composition layer is polymerized to form an adhesive layer.

Further, as shown in FIG. 1, a manufacturing apparatus 1 for a double-sided tape 6 of the present invention comprises a base material 2 having a releasable surface.
And the ultraviolet-transmissive film 3 are kept at an appropriate distance, and the photoreactive composition 4 is supplied to the gap by the application roll 11 to form the photoreactive composition layer 40, which is conveyed. At the same time, the photoreactive composition layer 40 is irradiated with light 5 via the ultraviolet-transmissive film 3 during the transport process, and the photoreactive composition layer 40 is photopolymerized to form an adhesive layer. A manufacturing apparatus 1 comprising: a substrate 2 on which a photoreactive composition layer 40 is formed;
Transport roll 1 for transporting the paper vertically from above to below
0 is provided.

[0011] Among the photoreactive compositions used in the present invention,
The monomer main component is used for the synthesis of a known photopolymerizable acrylic pressure-sensitive adhesive, and is specifically selected from the group consisting of alkyl acrylates and alkyl methacrylates having an alkyl group having 1 to 14 carbon atoms. At least one acrylate monomer 60 to 10
0% by weight and 0 to 40% by weight of a vinyl monomer copolymerizable with the acrylate monomer.

As the acrylate-based monomer, an alkyl acrylate or alkyl methacrylate having an alkyl group of 1 to 14, preferably 4 to 12 carbon atoms is used.
-Butyl, 2-ethylhexyl (meth) acrylate,
Examples thereof include isooctyl (meth) acrylate and isononyl (meth) acrylate.

These are used alone or in combination of two or more. In general, the glass transition temperature of the homopolymer is -50 due to the balance between tackiness and cohesiveness.
It is preferable to use an alkyl acrylate at a temperature of not more than ° C as a main component, and to use a (meth) acrylic ester of a lower alkyl group or a vinyl monomer described below as a comonomer.

The vinyl monomer copolymerizable with the acrylate monomer has a polar group such as carboxy or a medium-polar functional group, thereby increasing the interfacial adhesive force as a pressure-sensitive adhesive and adversely affecting the adhesiveness. It is preferable that the composition does not contain an excess of the polyfunctional unsaturated compound component and has low evaporation. Those having high evaporation properties are not preferable because they cause a composition difference between the surface layer portion and the inside during photopolymerization and cause deterioration in performance.

[0015] Those satisfying such required quality include carboxyethyl acrylate, ω-carboxy-polycaprolactone-monoacrylate, monohydroxyethyl succinate, and 2-acryloxyethylhexahydrophthalic acid. Of the polar monomers mentioned above, carboxyethyl acrylate is particularly preferred because it not only satisfies the above required performance but also has high polymerizability. Other suitable monomers include acrylic acid, itaconic acid, vinylpyrrolidone, acryloylmorpholine, acrylamide, alkylaminoethyl (meth) acrylate, and the like.

Further, in order to impart viscosity and improve interfacial adhesion by introducing a medium polarity into the polymer,
For example, vinyl monomers such as isobornyl acrylate, tetrahydrofurfuryl acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, fluorine acrylate, and silicon acrylate can be used. However, the amount of the vinyl monomer to be added must be in the range of 2 to 20 parts by weight based on 100 parts by weight of the vinyl monomer. The addition of more than this has a favorable effect on the adhesive strength, but increases the glass transition temperature of the pressure-sensitive adhesive and reduces the low-temperature tackiness.

Among the photoreactive compositions used in the present invention,
As the photopolymerization initiator, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl)
Ketone [Darocure 2959: manufactured by Merck]; α-hydroxy-α, α'-dimethyl-acetophenone [Darocure 1173: manufactured by Merck]; acetophenones such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; benzoin Ethyl ether,
Benzoin ethers such as benzoin isopropyl ether; ketals such as benzyl dimethyl ketal;
In addition, halogenated ketone, acyl phosphinoxide,
Monofunctional photopolymerization initiators such as acylphosphonates can be mentioned.

The preferable addition amount for the compounding is about 0.1 to 5 parts by weight based on 100 parts by weight of the monomer component. When the lamp intensity during light irradiation is constant, the molecular weight of the obtained polymer is inversely proportional to the square root of the amount of the initiator to be added. In other words, the molecular weight of the target adhesive polymer can be controlled by the amount of the initiator.

The photoreactive composition of the present invention preferably contains a polyfunctional vinyl compound as a crosslinking agent together with the above photopolymerization initiator in order to impart heat resistance and cohesive strength at high temperatures. .

Examples of such a 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. Acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, other epoxy acrylates,
Examples include polyester acrylate and urethane acrylate.

In general, when the crosslinking agent is contained in an amount of 5 parts by weight or less based on 100 parts by weight of the monomer component, a cross-linking occurs between the polymer molecules in the course of the photopolymerization reaction, and the heat resistance of the adhesive product is reduced. The performance is improved. When the viscoelastic product is a double-sided tape, the cohesive strength at high temperatures increases, and the holding power at high temperatures improves.

The peel resistance of the double-sided tape to an adherend having a curved surface mainly depends on the degree of crosslinking of the pressure-sensitive adhesive, and this performance is exhibited when the gel fraction is 70% or less.

The peeling resistance against a load in the shearing direction in a high temperature region becomes high when the gel fraction of the pressure-sensitive adhesive is 50% or more.

Therefore, in general, the amount of the crosslinking agent added is blended and designed so as to achieve this level of gel fraction.

Of course, for certain applications, the level of gel fraction to be designed may be different from the above case.

In the present invention, a tackifying resin called tackifier may be added to the photopolymerizable composition.

[0027] as used herein is a rosin resin, modified rosin resin, terpene resin, terpene phenol resin, aromatic modified terpene resins, C ₅ and C ₉ petroleum resin, coumarone resin.

In the present invention, commonly used additives such as a thickener, a thixotropic agent, a bulking agent and a filler may be added to the photopolymerizable composition.

Examples of the extender include calcium carbonate, titanium oxide and clay.

Examples of the filler include inorganic hollow bodies such as glass balun, alumina balun, and ceramic balun; organic spherical bodies such as nylon beads, acrylic beads, and silicon beads; organic hollow bodies such as vinylidene balun and acrylic balun; polyester and rayon And monofilaments such as nylon.

Next, a method for producing a double-sided tape using the photoreactive composition will be described.

First, as shown in FIG.
In the meantime, the base material 2 and the ultraviolet-transmissive film 3 having a releasable surface are supplied, and the base material 2 and the ultraviolet-transmissive film 3 are opposed to each other so that there is an appropriate distance between them. I do.

Next, the photoreactive composition 4 is supplied to the gap formed in a valley by the coating roll 11 provided above the transport roll 10, and the gap between the base material 2 and the ultraviolet transparent film 3 is supplied. The photoreactive composition 4 is infiltrated into the substrate and is conveyed from above to below by the conveyance rolls 10 while forming the photoreactive composition layer 40.

At this time, the thickness of the photoreactive composition layer 40 is
By appropriately setting the gap between the base material 2 and the ultraviolet light transmitting film 3, a high film thickness in the range of 400 μm to 3000 μm can be obtained. However, when the photoreactive composition 4 has a low viscosity, the reaction solution of the photoreactive composition layer 40 may hang down from two opposing substrates 2 and the side of the ultraviolet-transmissive film 3. . In this case,
At the same time as supplying the photoreactive composition 4, the photoreactive composition 4
By feeding the spacer 7 to both sides of the substrate 2 at the same speed as the speed at which the substrate 2 and the ultraviolet-transmissive film 3 are conveyed, the leakage of the photoreactive composition 4 can be prevented.

To prevent this leakage, the photoreactive composition 4
Is preferably 200 cps or more.

[0036] It can also be prevented by appropriately adding a thickener or a thixotropic agent to the photoreactive composition 4. As this thickener, fumed silica or acrylic rubber is used.

Then, the photoreactive composition layer 40 is irradiated with light 5 from the outside of the ultraviolet transmissive film 3 through the ultraviolet transmissive film 3, and the photoreactive composition layer 40 is photopolymerized and adhered. Form an agent layer.

After the polymerization, the ultraviolet-permeable film 3 on the surface of the pressure-sensitive adhesive layer is peeled off, and the pressure-sensitive adhesive layer, the substrate 2 and the spacer 7 after peeling are wound up to form a double-sided tape 6.

In the case where the spacer 7 is used, particularly, as in the present embodiment, the spacer 7 is used as the adhesive layer and the base material 2.
It is not necessary to wind up, peel off from the adhesive layer,
It is also possible to wind up only the pressure-sensitive adhesive layer and the base material 2 to obtain a product.

The double-sided tape 6 thus obtained is a single-sided release type double-sided tape 6 in which the base material 2 is a release liner. Alternatively, a double-sided release type double-sided tape 6 in which the base material 2 and the ultraviolet-transmissive film 3 serve as a release liner can be used.

Further, in this embodiment, the non-support type double-sided tape 6 in which the supporting base material is not contained in the pressure-sensitive adhesive layer is used.
However, when forming the photoreactive composition layer 40, a support type double-sided tape 6 can also be manufactured by inserting an ultraviolet-transparent support base material that does not hinder photopolymerization.

The type of lamp used for the light irradiation 5 is one that emits a light wavelength in the same region as the absorption wavelength of the photoinitiator. Examples thereof include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and the like. Ultra-high pressure mercury lamp, chemical lamp,
Black light lamp, microwave excitation mercury lamp,
A metal halide lamp or the like is used. Among them, ultra-high pressure mercury lamps efficiently emit light in the active wavelength region of the initiator, and emit light having a short wavelength that reduces the viscoelastic properties of the obtained polymer by crosslinking, or to evaporate the reaction composition by heating. This is preferable because it does not emit much long-wavelength light.

For the reaction efficiency, it is preferable to use a lamp having light having a wavelength in the active wavelength region of the photoinitiator to be used. However, in this respect, the chemical lamp emits light having a wavelength in the active wavelength region of the photoinitiator. It is effective.

The intensity of irradiation of the reactive composition by the above-mentioned lamp is a factor which affects the degree of polymerization of the obtained polymer and is appropriately controlled for each performance of the target product. Is preferably 0.1 to 100 mW / cm ² .

It is necessary to appropriately adjust the molecular weight depending on the performance of the pressure-sensitive adhesive to be obtained. The adjustment can be controlled by the light intensity of the irradiated surface and by the amount of the initiator to be added.

In order to exhibit peel resistance against a particularly static load such as a structural tape, the weight average molecular weight is preferably from 2,000,000 to 3,000,000. Can be achieved by employing a system to which a chain transfer agent is added.

[0047]

According to the method for producing a double-sided tape of the present invention, a substrate having a releasable surface and an ultraviolet-permeable film are placed at an appropriate distance from each other, and the photoreactive composition is supplied to the gap. To form a photoreactive composition layer and transport it vertically from above to below, so that the deflection due to the weight of the photoreactive composition does not add to the base material or the ultraviolet-transmissive film. .

Further, according to the method for producing a double-sided tape of the present invention, there is provided a transporting means for vertically transporting the substrate on which the photoreactive composition layer is formed and the ultraviolet ray transmitting film from above to below. Therefore, the photoreactive composition layer can be formed and transported in the gap between the base material and the ultraviolet-transmissive film without adding bending due to the weight of the photoreactive composition.

[0049]

EXAMPLES Examples according to the present invention and comparative examples to which the present invention is compared are shown below to clarify the reasons why the present invention is superior.

[0050]

Example 1 (1) Preparation of Photoreactive Composition 95 g of 2-ethylhexyl acrylate, 5 of acrylic acid
g, Irgacure 184 (trade name, manufactured by Ciba-GayGy)
0.2 g and acrylic rubber 3 g were mixed and stirred. further,
2 g of fumed silica was added to the photoreactive composition, and the mixture was stirred at a high speed with a homogenizer for 30 minutes. Dissolved bubbles were removed under reduced pressure.

The viscosity measured with a B-type viscometer is 1000 cp
s. (2) Production of double-sided tape The pressure-sensitive adhesive tape 6 was produced from the photoreactive composition 4 using the production apparatus 1 for the adhesive tape 6 shown in FIG. However, release paper was used as the base material 2, and a release-treated polyethylene terephthalate film (PET film) having a thickness of 38 μm was used as the ultraviolet-permeable film 3.
The gap between the coating rolls 11 and between the transport rolls 10 was set to be 1000 μm. The distance from the supply of the photoreactive composition 4 to the winding of the double-sided tape 6 was 3 m, and the photoreactive composition layer 40 sandwiched between the release paper and the PET film was interposed through the PET film. Then, ultraviolet irradiation 5 was performed using a chemical lamp as a light source. The light intensity on the irradiation surface was ² mW / cm ² . (3) Performance evaluation The pressure-sensitive adhesive layer of the double-sided tape 6 was adhered to a stainless steel plate, backed with a PET film, and the 180 ° peeling force was measured.
/ 25 mm width.

The surface of the obtained tape was smooth, there was no dripping from the side, and no peeling impact occurred.

[0053]

Comparative Example 1 A double-sided tape was manufactured in the same manner as in Example 1 except that the transport by the transport roll was performed in the horizontal direction.

When the tension was increased during transport, vertical wrinkles were found on the release paper as the base material, and vertical wrinkles were found on the surface of the obtained adhesive tape.

When the tension was gradually lowered, the release paper no longer had vertical wrinkles. However, the release paper was bent between the transport rolls, and the tape polymerized at that portion had a variable tape width and a uniform film thickness. Was not.

When the obtained tape was bonded to a stainless steel plate, the tapered portion of the tape was bonded to the plate, but the valley portion could not be bonded.

The peeling force was measured using a PET film as a backing, and peeling impact occurred on the non-adhesive surface, and the film was peeled off with almost no resistance.

[0058]

As described above, according to the production method of the present invention, since the bending of the photoreactive composition due to its own weight is not added to the substrate or the ultraviolet ray transmitting film, the thickness of the film due to the bending is reduced. It is possible to manufacture a double-sided tape which prevents change and has a uniform thickness and excellent smoothness. In addition, since there is no bending, a good double-faced tape without vertical wrinkles can be manufactured without increasing the tension of the base material.

Further, according to the production apparatus of the present invention, the photoreactive composition layer is formed in the gap between the base material and the ultraviolet ray transmissive film without being bent by the weight of the photoreactive composition, and is conveyed. Therefore, a change in the film thickness due to the bending can be prevented, and a double-sided tape having a uniform thickness and excellent smoothness can be manufactured. Also, since there is no such bending,
A good double-sided tape without vertical wrinkles can be manufactured without increasing the tension of the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of a double-sided tape manufacturing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 10 Conveying roll (conveying means) 2 Substrate 3 UV transparent film 4 Photoreactive composition 40 Photoreactive composition layer 5 Light irradiation 6 Double-sided tape

Claims (2)

(57) [Claims] Claims: 1. A substrate having a releasable surface and a UV-transmissive film are placed at an appropriate distance from each other, and a photoreactive composition is supplied to the gap to form a photoreactive composition layer. And transport it vertically from above to below, and in the transport process, irradiate the photoreactive composition layer with light through an ultraviolet-transmissive film to polymerize the photoreactive composition layer. A method for producing a double-sided tape, comprising forming an adhesive layer. 2. A photoreactive composition is supplied to a gap between a substrate having a releasable surface and an ultraviolet-transmissive film at an appropriate distance, and the photoreactive composition layer is supplied to the gap. Forming and transporting this, so as to irradiate the photoreactive composition layer with light through an ultraviolet ray permeable film in the transporting process, and polymerize the photoreactive composition layer to form an adhesive layer. An apparatus for manufacturing a double-sided tape, comprising: a conveying means for vertically conveying the substrate and the ultraviolet-permeable film on which the photoreactive composition layer is formed, from above to below. Double-sided tape manufacturing equipment.