JPH08151555A - Production of acrylic adhesive double-coated tape. - Google Patents

Abstract

PURPOSE: To simply obtain an acrylic adhesive double-coated tape having different stickiness properties on each side. CONSTITUTION: This tape is obtained by coating a releasing sheet with a composition consisting of (A) 100 pts.wt. of photopolymerizable monomer mixture of alkyl (meth)acrylates and vinyl monomers having a polar group, (B) 0.01-1 pts.wt. of monomer having at least two reactive double bonds, (C) 0.01-5 pts.wt. of photopolymerization initiator and (D) 0.05-1 pts.wt. of titanium oxide of 0.001-1μm average particle size, and photopolymering with ultraviolet rays on the coated side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic double-sided pressure-sensitive adhesive tape obtained by photopolymerization, which has different adhesive properties on the front and back surfaces.

[0002]

2. Description of the Related Art Conventionally, double-sided pressure-sensitive adhesive tapes have been used for a wide range of purposes, but generally, the adhesive properties on the front and back sides are the same. However, it is necessary to create different adhesive properties on the front and back sides when the type and surface condition of the adherend that corresponds to the front and back sides greatly differ from the application, and when the removability on only one side is improved. There is.

As a method of obtaining a double-sided pressure-sensitive adhesive tape which requires such a difference between the front and back sides, for example, laminating different kinds of pressure-sensitive adhesives on both sides of a base material or changing the thickness of the pressure-sensitive adhesives. Although considered, the above method is preferable because it has different manufacturing steps because different pressure-sensitive adhesives are laminated on both sides of the base material and causes interlaminar failure between the base material layer and the pressure-sensitive adhesive layer. Not a method.

Therefore, as a means for solving the above problems,
A method for producing a double-sided pressure-sensitive adhesive tape having a front-back difference by applying a photocrosslinking solvent to one surface of a pressure-sensitive adhesive sheet made of an acrylic monomer and irradiating with light has been reported (Japanese Patent Publication No. 4-50351).

[0005]

In the above manufacturing method, since there is no possibility of interlayer breakage between the base material layer and the pressure-sensitive adhesive layer because there is no base material, one-sided surface after the acrylic pressure-sensitive adhesive sheet is once prepared. Since a photo-crosslinkable solvent must be applied to the above, the number of manufacturing steps has not been improved yet.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a double-sided pressure-sensitive adhesive tape which has different adhesive properties on the front and back surfaces, does not include a base material, and can be manufactured in one step in the number of manufacturing steps. A manufacturing method is provided.

[0007]

The photopolymerizable monomer (a) used in the present invention comprises an alkyl (meth) acrylate and a vinyl monomer having a polar group.

The above alkyl (meth) acrylate has an alkyl group having 1 to 12 carbon atoms, preferably 4 to 1 carbon atoms.
2, specifically, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylate, lauryl acrylate and the like. These can be used in combination of two or more.

The above-mentioned alkyl (meth) acrylate is 50 to 98% by weight based on the total amount of the photopolymerizable monomer, since the shearing force of the pressure-sensitive adhesive sheet obtained is decreased when the amount is increased and the peeling force is decreased when the amount is decreased. , And more preferably 70 to 95% by weight.

The above-mentioned vinyl monomer having a polar group is a monomer copolymerizable with the above-mentioned alkyl (meth) acrylate, specifically, a carboxyl group such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid. Having a vinyl monomer or an anhydride thereof, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl Nitrogen-containing vinyl monomers such as acrylamide, 2-hydroxyethyl (meth) acrylate, 4
-Hydroxybutyl acrylate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth)
Examples thereof include vinyl monomers having a hydroxyl group such as acrylate and caprolactone-modified (meth) acrylate.

The amount of the above-mentioned vinyl monomer having a polar group is 2 to 50% by weight based on the total amount of the photopolymerizable monomer because the peeling force of the obtained pressure-sensitive adhesive sheet decreases and the shearing force decreases when it decreases. , And more preferably 5
It is 30% by weight.

The monomer (b) having two or more reactive double bonds used in the present invention is for crosslinking acrylic copolymers, and specifically, hexanediol (meth) acrylate. , (Poly) ethylene glycol diol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylpropane trimethacrylate, allyl (meth) Examples thereof include acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate and urethane acrylate.

If the amount of the above-mentioned monomer added is too large, the crosslink density becomes high and it becomes difficult to obtain the peeling force. If it becomes too small, the crosslink density becomes low and it becomes difficult to obtain the cohesive force.
0.01 to 100 parts by weight of the photopolymerizable monomer
It is 1.0 part by weight, preferably 0.02 to 0.8 part by weight.

The photopolymerization initiator (c) used in the present invention is, for example, a ketone system such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Darocur 2959: manufactured by Ciba Geigy]. , Α-
Hydroxy-α, α'-dimethyl-acetophenone [Darocur 1173: Ciba Geigy] methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone [Irgacure 651: Ciba Geigy], 2
Examples thereof include acetophenone-based compounds such as -hydroxy-2-cyclohexylacetophenone [IRGACURE 184: manufactured by Ciba-Geigy], ketal-based compounds such as benzyldimethyl ketal, halogenated ketones, acylphosphinoxides, and acylphosphonates.

If the amount of the above-mentioned photopolymerization initiator added is too large, the amount of radicals generated becomes too large, and a low-molecular weight copolymer is likely to be produced. If it is too small, the polymerization reaction is difficult to proceed. The amount is 0.1 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the monomer.

The titanium oxide fine particles (d) used in the present invention have a high ultraviolet reflectance, and are compounded in the photopolymerizable composition to utilize the ultraviolet shielding effect, so that the photopolymerizable composition is subjected to photopolymerization. It is possible to control the molecular weight and make a difference in the molecular weight between the front surface and the back surface.

If the average particle size of the titanium oxide fine particles is large, voids are apt to be generated in the tape when stress is applied to the obtained double-sided pressure-sensitive adhesive tape, and the cohesive force is lowered. As a result, the same disadvantages as described above tend to occur, so that the average particle size is 0.0
It is 1 to 1 μm.

When the addition amount of the above titanium oxide fine particles is small, the ultraviolet ray shielding effect is lowered and the difference in molecular weight between the front and back sides (difference in adhesive properties) becomes small, and when the addition amount is large, it becomes difficult for ultraviolet rays to pass therethrough, and thus polymerization is unsuccessful. Since the amount is sufficient and it becomes difficult to obtain an adhesive tape, the amount is 0.05 to 1 part by weight relative to 100 parts by weight of the photopolymerizable monomer.

The photopolymerizable composition of the present invention may be added with a tackifying resin in addition to the above-mentioned composition, for example, rosin resin, modified rosin resin, terpene resin, terpene phenol resin, C5 and C9. A petroleum-based resin, a coumarone resin, and hydrogenated products thereof can be used alone or in combination.
However, when the photopolymerizable composition is polymerized, the polymerization rate may decrease or the molecular weight may decrease. In such a case, for example, n-dodecyl mercaptan (dodecanethiol), t -A chain transfer agent such as dodecyl mercaptan is added to 100 parts by weight of the photopolymerizable monomer,
It may be added within the range of 0.01 to 0.1 part by weight.

In the method for producing an acrylic double-sided pressure-sensitive adhesive tape of the present invention, the above-mentioned photopolymerizable composition is applied onto a release sheet, and ultraviolet rays are irradiated from the applied surface.

Examples of the method for applying the photopolymerizable composition onto the release sheet include coating machines such as knife coater, comma coater, roll coater, reverse roll coater, dam coater, fan ten coater and kiss coater.

The release sheet usable in the present invention includes:
It is not particularly limited as long as it is a support having releasability, and one having a release treatment applied to one side of a paper or resin film can be used, but particularly, thickness accuracy and mechanical strength are high,
In addition, a polyethylene terephthalate film (hereinafter abbreviated as PET film) that has been subjected to a peeling treatment is preferable because it is inexpensive.

As the lamps for irradiating the ultraviolet rays, those having an emission distribution with a light wavelength of 400 nm or less are used, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp,
Among them are high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps. Among them, chemical lamps efficiently emit light in the active wavelength region of photoinitiators It is preferable because it allows light to pass therethrough and facilitates the production of thick film products. The light irradiation intensity is 0.1 to 100 m.
The range of W / cm ² is preferable.

In the photopolymerization in the present invention, the reaction is easily inhibited by oxygen in the air and oxygen dissolved in the photopolymerizable composition. Therefore, it is preferable to provide a means capable of removing the inhibition of oxygen.

As the above-mentioned means, for example, a method in which after coating the photopolymerizable composition, it is covered with a PET film or Teflon film subjected to surface release treatment, and the photopolymerizable composition is irradiated with ultraviolet rays through the film, Examples include a method of irradiating with ultraviolet light in an inert zone in which oxygen is replaced by an inert gas such as nitrogen gas or carbon dioxide gas. In the latter method, the polymerization conversion rate of the photopolymerizable composition is 99.7.
In order to fully complete the oxygen content in the irradiation atmosphere, the oxygen concentration in the irradiation atmosphere is preferably 5000 ppm or less, more preferably 300 ppm.

The coated surface in the present invention is usually the surface side coated with the above-mentioned photopolymerizable composition, but it may be the surface of the release sheet as long as the release sheet is transparent to ultraviolet rays. Even in this case, it means that the irradiation surface is from one side.

The thickness of the double-sided adhesive tape of the present invention is as follows:
From the viewpoint of ease of use, the range of 50 μm to 5 mm is preferable. When the thickness is 100 μm or less, the photopolymerizable composition can be applied even when the viscosity is 1000 cps and the thixotropic index value (hereinafter, abbreviated as TI value) is about 1.5. Especially, it is preferable that the viscosity is higher or the TI value is higher in order to secure the thickness.

As means for increasing the viscosity of the photopolymerizable composition, acrylic rubber, nitrile rubber, diblock such as styrene-isoprene-styrene block (SIS), or 1 elastomer such as triblock rubber, polymethylmethacrylate ( PMMA), polystyrene (Pst)
Examples of the method include adding and dissolving a thermoplastic resin such as.

The viscosity can also be increased by preliminarily partially polymerizing a part of the photopolymerizable composition without adding the above additives. In this case, the photopolymerizable composition has two or more reactive double bonds. It is preferable to carry out before the addition of the monomer (b) so as not to generate the microgel, because streaks, spots and the like are less likely to occur during coating.

[0030]

In the photopolymerizable composition of the present invention, the specific particle size and the specific amount of titanium oxide fine particles are added. Therefore, when ultraviolet rays are irradiated from one side, the ultraviolet intensity is not completely shielded by the light scattering of the fine particles. It gradually decreases. Therefore, the photopolymerizable composition is applied on a release sheet, and the irradiation side is irradiated with ultraviolet rays to have a high molecular weight, and the opposite side (adhesion side with the release sheet) is A double-sided adhesive tape having a low molecular weight and having different adhesive properties on the front side and the back side can be obtained.

[0031]

Embodiments of the present invention will be described below.
In the following, "parts" means "parts by weight". (Examples 1 and 2, Comparative Examples 1 to 3) In accordance with the composition table of Table 1, 2-ethylhexyl acrylate, acrylic acid,
N-vinylpyrrolidone, n-dodecanethiol, 2,2
-Dimethyl-2-phenylacetophenone (Irgacure 651 "trade name" manufactured by Ciba Geigy) and titanium oxide fine particles (average particle size 0.001 to 0.1 µm, MT
-500HD "trade name" (manufactured by TAYCA) was placed in a separable flask and stirred until uniformly dispersed, and then nitrogen gas was purged to remove dissolved oxygen.

Next, when the composition was irradiated with ultraviolet rays using a black 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 light irradiation was stopped (this composition is referred to as a partial photopolymerization thickening composition). The partial photopolymerization thickening composition had a conversion of 3.7% and a viscosity of 2200 cps.

0.2 part of hexanediol diacrylate was added to the obtained partial photopolymerization thickening composition, and the thickness at the end of the polymerization was about 1 on a PET film which had been subjected to a release treatment.
It was coated so as to have a thickness of mm and further covered with the same PET film so as to be in contact with the coated surface.

Then, using a chemical lamp, the irradiation intensity was 2 mW / from above the PET film surface used for the cover.
Irradiation was carried out at 8 cm ² for 8 minutes to obtain an acrylic double-sided adhesive tape.

(Evaluation of Adhesive Strength) Each of the double-sided adhesive tapes obtained above was cut into a width of 20 mm, and one side was backed with a stainless plate having a thickness of 1 mm to prepare a sample, and a PET film was formed on the remaining surface of the double-sided adhesive tape. At 23 ° C., a 2 kg roller was reciprocated two times to perform pressure bonding, and after 15 minutes, a peeling test was conducted by a peeling tester at 23 ° C. at a pulling speed of 300 mm / min.

(Evaluation of molecular weight) The surface layers of the front and back surfaces of the double-sided pressure-sensitive adhesive tape obtained above were scraped off, and the weight average molecular weight of each of the front and back surfaces was measured by the gel permeation chromatography (GPC) method.

(Evaluation of Gel Fraction) Similarly, the surface layers on the front and back surfaces were evaluated by the weight ratio (% by weight) of the original weight (each solid weight) to the insoluble matter after being immersed in ethyl acetate. The above measurement results are shown in Table 1.

[0038]

[Table 1]

[0039]

According to the production method of the present invention, the photopolymerizable composition containing an acrylic monomer as a main component is mixed with fine particles of titanium oxide, and ultraviolet rays are radiated from the coated surface so that the adhesive properties of the front and back surfaces are improved. Different baseless (non-support type) acrylic double-sided adhesive tape can be obtained in one step.

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Claims (1)

[Claims] 1. (a) 50 to 98% by weight of an alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms,
And 100 parts by weight of a photopolymerizable monomer composed of 2 to 50% by weight of a vinyl monomer having a polar group, (b) 0.01 to 1.0 part by weight of a monomer having two or more reactive double bonds (c) initiation of photopolymerization 0.01 to 5 parts by weight of the agent, and (d) titanium oxide fine particles 0.05 having an average particle diameter of 0.01 to 1 μm 0.05
A method for producing an acrylic double-sided pressure-sensitive adhesive tape, which comprises applying 1 part by weight of a photopolymerizable composition onto a release sheet, and irradiating ultraviolet rays from the coated surface.