JPH08157781A - Preparation of pressure-sensitive adhesive material - Google Patents

Abstract

PURPOSE: To improve the adhesion to flat and rough surfaces by coating a supporting substrate with a photopolymerizable compsn. and applying ultraviolet light to the coated substrate through a particular sheet permeable to ultraviolet light. CONSTITUTION: A photopolymerizable compsn. in an amount of 100 pts.wt. comprising 50 to 98wt.% alkyl (meth)acrylate and 50 to 2wt.% vinyl monomer having a polar group is mixed with 0.01 to 1.0 pt.wt. crosslinking agent and 0.1 to 5 pts.wt. photopolymerization initiator to prepare a photopolymerizable compsn. A supporting substrate, such as paper, cloth plastic film, or metal foil, is coated with the photopolymerizable compsn., and the coated substrate is covered with an ultraviolet-permeable sheet having at least two portions different from each other in ultraviolet transmission. Ultraviolet light is applied to the coating through the sheet under conditions of a light wavelength of not more than 400nm and a light irradiation intensity of 0.1 to 100W/cm<2> until the conversion for polymerization reaches not less than 99.7%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is suitable for applications requiring a balance of both adhesive strength and cohesive strength, including adhesion to an adherend having a rough surface such as concrete and calcium silicate plate. , A method for producing an adhesive member obtained by photopolymerization.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesive tapes have been used in a wide variety of applications, but it is a fundamental important matter to balance the adhesive force and the cohesive force as the adhesive property. As one of the means for solving the above-mentioned problems, an adhesive member has been reported in which the degree of cross-linking is partially different by UV-curing the UV-curable pressure-sensitive adhesive layer (JP-A-2-
No. 75679).

[0003]

However, in the above-mentioned pressure-sensitive adhesive member, the means for imparting a partial difference in irradiation intensity due to a pattern mask or the like is adopted when the pressure-sensitive adhesive polymer is subjected to the ultraviolet crosslinking treatment. , There were the following problems.

That is, the production efficiency is poor because the two steps of "formation of pressure-sensitive adhesive layer" and "crosslinking treatment by ultraviolet rays" are required, and at the crosslinking treatment stage, polymerization of the adhesive polymer has already been completed. Therefore, it was impossible to control the molecular weight of the polymer, which greatly contributes to the adhesive properties.

That is, there is a problem that the balance range is small because the only factor controlling the difference between the portion having a high adhesive force and the portion having a high cohesive force is the degree of crosslinking of the polymer.

The present invention has been made in view of the above-mentioned problems, and the degree of polymerization is made different at the stage of polymerizing a photopolymerizable monomer by irradiating with an ultraviolet ray, and a simpler process is performed in a wider range than before. It is to provide a method for producing an adhesive member having a balance between the “adhesive strength” and the “cohesive strength”.

[0007]

The supporting base material used in the present invention includes known materials such as paper, cloth, plastic film, foam, and metal foil. Those having an anchoring property with the pressure-sensitive adhesive layer formed on the substrate are preferable, and those having a peeling property are preferable in the case of producing a double-sided pressure-sensitive adhesive tape.

Examples of the photopolymerizable composition used in the present invention include those obtained by adding a crosslinking agent and a photopolymerization initiator to a photopolymerizable monomer containing an alkyl (meth) acrylate as a main component. The alkyl (meth) acrylate has an alkyl group with 1 to 12 carbon atoms, preferably 4 to
12, specifically n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth)
Acrylate, isononyl (meth) acrylate, lauryl acrylate, etc. are mentioned, and these can be used in combination of 2 or more types.

The above-mentioned alkyl (meth) acrylate is 50 to 98% by weight with respect to the total amount of the photopolymerizable monomer, since the shearing force of the obtained pressure-sensitive adhesive member decreases when the amount increases and the adhesive force decreases when the amount decreases. More preferably 70
~ 95% by weight.

In addition to the above alkyl (meth) acrylate, a vinyl monomer having a polar group may be added to the photopolymerizable monomer. Specifically, (meth) acrylic acid, maleic acid, fumaric acid, A vinyl monomer having a carboxyl group such as itaconic acid or an anhydride thereof, (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) )
Acrylate, nitrogen-containing vinyl monomers such as dimethylaminopropyl acrylamide, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl acrylate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, caprolactone-modified (meth) acrylate And a vinyl monomer having a hydroxyl group.

The amount of the vinyl monomer having a polar group is 2 to 50% by weight based on the total amount of the photopolymerizable monomer because the adhesive force of the obtained pressure-sensitive adhesive member decreases and the shearing force decreases when the amount decreases. , And more preferably 5 to 3
0% by weight.

The cross-linking agent used in the present invention is for cross-linking the acrylic copolymers, and specifically, hexanediol (meth) acrylate and (poly).
Ethylene glycol diol di (meth) acrylate,
(Poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate,
Examples thereof include pentaerythritol tri (meth) acrylate, trimethylpropane trimethacrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate and the like.

If the amount of the above-mentioned monomer added is increased, the crosslinking density will be high and the peeling force will be difficult to obtain, and if it is small, the crosslinking density will be low and the cohesive force will be difficult to be obtained.
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.

Examples of the photopolymerization initiator used in the present invention include ketones 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: manufactured by Ciba Geigy] Methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone [Irgacure 651: manufactured by Ciba Geigy], 2-
Acetophenone-based compounds such as hydroxy-2-cyclohexylacetophenone [Irgacure 184: manufactured by Ciba-Geigy], ketal-based compounds such as benzyldimethyl ketal,
Others, halogenated ketones, acylphosphinoxides,
An acyl phosphonate etc. are mentioned.

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.

In the photopolymerizable composition of the present invention, a tackifying resin may be added 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 polymerizing the above photopolymerizable composition,
Since the polymerization rate may decrease or the molecular weight may decrease, in such a case, for example, a chain transfer agent such as n-dodecyl mercaptan (dodecane thiol) or t-dodecyl mercaptan is used as a photopolymerizable monomer. You may add in 0.01-0.1 weight part with respect to 100 weight part.

Further, in addition to the above, the photopolymerizable composition of the present invention includes inorganic hollow fine particles such as glass balloons, shirasu balloons and fly ash balloons, polymethylmethacrylate, acrylonitrile-vinylidene chloride copolymer, polystyrene. Further, organic hollow particles made of phenol resin or the like, organic particles such as polyethylene, polypropylene, ethyl polyacrylate and polyurethane may be added.

The method for producing a pressure-sensitive adhesive member according to the present invention comprises applying the above-mentioned photopolymerizable composition onto the above-mentioned supporting substrate, and applying ultraviolet rays through an ultraviolet-transparent sheet having at least two portions having different ultraviolet transmittances. Irradiate.

The above-mentioned sheet is a film which transmits ultraviolet rays and which is printed in a pattern such as a circular shape, a mosaic shape, or a stripe shape in which the color and the density for absorbing the ultraviolet rays at a desired ratio are applied. By irradiating the photopolymerizable composition with ultraviolet rays, it is possible to control a desired portion of the pressure-sensitive adhesive to a desired molecular weight.

Examples of the material for the sheet include polyester films and polyolefin films. Among them, polyethylene terephthalate film (hereinafter abbreviated as "PET film") is preferable in view of transparency and toughness.

As a method for coating the above-mentioned photopolymerizable composition on a supporting substrate, a coating machine such as knife coater, comma coater, roll coater, reverse roll coater, dam coater, fan ten coater, kiss coater and the like can be mentioned. .

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, PET subjected to surface release treatment after coating a photopolymerizable composition on a supporting substrate.
A method of covering with a film or a Teflon film and irradiating the photopolymerizable composition with ultraviolet rays through the film, a method of irradiating ultraviolet rays in an inert zone in which oxygen is replaced by an inert gas such as nitrogen gas or carbon dioxide gas, etc. Can be mentioned. In the latter method, the oxygen concentration in the irradiation atmosphere is preferably 5000 ppm or less, and more preferably 300 ppm or less, in order to sufficiently complete the polymerization conversion rate of the photopolymerizable composition to 99.7% or more. is there.

The thickness of the pressure-sensitive adhesive member of the present invention is not particularly limited, but from the viewpoint of ease of use, it is preferably 10 to 100 μm in the case of a single-sided pressure-sensitive adhesive tape and 0. The range of 1-5 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), elastomer such as triblock rubber, polymethylmethacrylate (PMMA), Examples thereof include a method of adding a thermoplastic resin such as polystyrene (Pst), and fine particles such as hydrophilic silica and hydrophobic silica. It is also possible to increase the viscosity by preliminarily partially polymerizing a part of the photopolymerizable composition without adding the above additives.

[0028]

According to the method of the present invention, the molecular weight of the polymer becomes low in the portion where the intensity of UV irradiation transmitted through the sheet is high, and inevitably the degree of crosslinking also becomes low in correlation with the molecular weight. Further, the polymer molecular weight becomes high in the portion where the ultraviolet ray transmittance is suppressed by the sheet, and the degree of crosslinking also becomes high in correlation with the molecular weight. Therefore, both the low molecular weight and low cross-linking part and the high molecular weight and high cross-linking part are mixed in the pressure-sensitive adhesive layer, and the range of the balance of "adhesive force" and "cohesive force" is controlled only by controlling the degree of cross-linking. It is possible to control over.

[0029]

EXAMPLES Examples of the present invention will be described below.
In the following, "parts" means "parts by weight". (Example 1) 90 parts of 2-ethylhexyl acrylate,
Acrylic acid 10 parts, 2,2-dimethyl-2-phenylacetophenone (Irgacure 651 "trade name" manufactured by Ciba Geigy) 0.1 part, hexanediol diacrylate 0.03 part, and hydrophilic silica (Aerosil # 200).
"Brand name" manufactured by Nippon Aerosil Co., Ltd.) was uniformly mixed to obtain a photopolymerizable composition.

The above photopolymerizable composition was treated with P
It is coated on ET film to a thickness of about 1 mm, and it is printed in orange with a 5 mm square mosaic pattern so that it is in contact with the coated surface (about 1 mW of 30 mW of ultraviolet light).
And a PET cover film having a releasability, which is transparent to the glass.

Then, using a chemical lamp, the PE
An adhesive member was obtained by irradiating the T cover film with an irradiation intensity of 30 mW / cm ² for 10 minutes.

(Example 2) 90 parts of 2-ethylhexyl acrylate, 10 parts of acrylic acid, 2,2-dimethyl-2
-A photopolymerizable composition comprising 0.1 part of phenylacetophenone (Irgacure 651 "trade name" manufactured by Ciba Geigy) and 0.03 part of hexanediol diacrylate;
Prepolymerization (partially thickened product) was performed by irradiation with ultraviolet rays until the viscosity reached about 2000 cps.

The above-mentioned partially thickened product is treated with PET having peeling property.
It is coated on the film to a thickness of about 50 μm, and it is printed in orange with a 5 mm square mosaic pattern (approx. 1 mW of 30 mW of ultraviolet light) so that it touches the coated surface.
And a PET cover film having a releasability, which is transparent to the glass.

Then, using a chemical lamp, the PE
An adhesive member was obtained by irradiating the T cover film with an irradiation intensity of 30 mW / cm ² for 10 minutes.

Comparative Example 1 A photopolymerizable composition similar to that of Example 1 was applied on a PET film having releasability so as to have a thickness of about 1 mm, and the releasability was applied so as to contact the coated surface. The transparent PET cover film having the above was laminated.

Then, using a chemical lamp, the PE
Irradiation intensity of 1 mW / cm ² from above the T cover film
It was irradiated for 0 minutes to obtain an adhesive member.

Comparative Example 2 90% by weight of 2-ethylhexyl acrylate and 10% by weight of acrylic acid,
0.1 part of 2,2-dimethyl-2-phenylacetophenone (Irgacure 651 "trade name" manufactured by Ciba-Geigy) and 100 parts of hexanediol diacrylate based on 100 parts of the acrylic polymer having a weight average molecular weight of 400,000.
An acrylic adhesive solution was obtained by adding 3 parts and 200 parts of ethyl acetate.

The above-mentioned acrylic pressure-sensitive adhesive solution was applied onto a PET film having releasability and dried to form a pressure-sensitive adhesive layer having a thickness of 50 μm, and then the pressure-sensitive adhesive layer had an area occupied by holes having a diameter of 1 mm of 55. % Through the mask material having 1%
The ultraviolet ray of 10 was irradiated for 10 minutes to obtain an adhesive member.

[Evaluation of Adhesiveness on Rough Surface] (1. Evaluation of Initial Adhesion Strength) Each of the pressure-sensitive adhesive members obtained above was cut into 20 mm × 150 mm and one surface thereof was subjected to 23 ° C. and 65% relative humidity. Width 25 mm x 200 mm, thickness 5
a 100 mm long concrete mortar board (manufactured by Nippon Test Panel Co., Ltd.) with a thickness of 50 mm on the other surface.
A μm SUS304 sheet was attached as a backing material, a 2 kg roller was reciprocated twice, and a peeling test in a 90 ° direction was immediately performed by a tensile tester at a tensile speed of 300 mm / min.

(2. Evaluation of Initial Tensile Strength) Each pressure-sensitive adhesive member obtained above was cut into 20 mm × 20 mm, and 23
At 65 ° C and 65% relative humidity, sandwiched between two concrete mortar boards (made by Nippon Test Panel Co., Ltd.) having a width of 55 mm x 50 mm and a thickness of 5 mm, and sandwiched between them.
After pressing with a load of 5 kg for 15 minutes, a tensile strength test was performed at a pulling speed of 50 mm / min.

(3. Evaluation of holding power) Each of the pressure-sensitive adhesive members obtained above was cut into 20 mm × 20 mm, and the temperature was set to 65 ° C. at 23 ° C.
2% of concrete mortar board (made by Nippon Test Panel) with a width of 55 mm x 50 mm and a thickness of 5 mm under% relative humidity
Affixed in a sandwich form between the sheets, with a load of 5 kg, 15
After crimping for one minute, one concrete mortar in the shearing direction was measured at 40 ° C. and 65% relative humidity for a time (hr) required for dropping when a load of 1 kg was applied.

[Evaluation of Plane Adhesive Strength] (4. Evaluation of Adhesive Strength) Each of the pressure-sensitive adhesive members obtained above was subjected to JI.
An adhesive strength test was conducted according to S-Z-1528.

(5. Evaluation of Tack) At 20 ° C. and 65% relative humidity, the stainless steel balls having different inclinations were formed on the adhesive surface of each of the adhesive members obtained above with a slope angle of 30 ° at an approach distance of 10 cm. The ball with the largest diameter that rolled and stopped at 10 cm on the adhesive surface was examined. The ball No. is shown in Table 1 showing the result, and its diameter is calculated by the following formula. Diameter (inch) = Ball No./36

(6. Evaluation of Holding Power) Each adhesive member obtained above was attached to a Bakelite plate with an adhesive area of 10 mm width × 20 mm length, and a load of 500 g was applied to the free end of the test piece. Suspend weight, 40 ℃ and 80
The time (minutes) required for the test piece to fall due to cohesive failure was measured in a thermostat at 0 ° C.

[Evaluation of Physical Properties] (Evaluation of Molecular Weight) The surface layer portions on the front and back surfaces of each pressure-sensitive adhesive member obtained above are scraped off, and the weight average molecular weight of each of the front and back surfaces is measured by gel permeation chromatography (GPC). Was measured.

(Evaluation of Gel Fraction) Similarly, the surface layer portions 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 results of the above measurement evaluations are shown in Table 1.

[0047]

[Table 1]

[0048]

According to the production method of the present invention, a low molecular weight / low crosslinked portion and a high molecular weight / highly crosslinked portion coexist in the adhesive layer. Therefore, the low molecular weight / low crosslinked portion improves the wettability to the adherend, that is, the adhesiveness,
The highly crosslinked portion has a high cohesive force and improves performance such as holding power.

As shown in Table 1, it is possible to cope with an adherend having a rough surface such as a concrete mortar plate by increasing the thickness of the adhesive layer. Further, if the surface is smooth, it can be applied with a normal thickness, the initial adhesive performance is improved as compared with the pressure-sensitive adhesive layer prepared by the conventional method, and the cohesive force is the same as the conventional one.

As described above, according to the manufacturing method of the present invention,
It becomes possible to obtain a balance between the “adhesive force” and the “holding force” at a higher level than in the conventional technique and in a simple process. Since such an adhesive member can realize not only an adhesive force on a flat surface but also a high adhesiveness on a rough surface, it is suitably used for a structural adhesive tape such as a building material.

Claims (1)

[Claims] 1. A photopolymerizable composition is applied onto a supporting substrate, and the photopolymerizable composition is irradiated with ultraviolet rays through an ultraviolet ray transmissive sheet having at least two portions having different ultraviolet ray transmittances. A method of manufacturing an adhesive member, comprising: