JPH0635566B2 - Adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition suitable for a re-peelable pressure-sensitive adhesive tape, and more specifically, an excellent pressure-sensitive adhesive that imparts re-peelability by irradiation with ultraviolet rays. It relates to a composition.

(Prior art) With the recent miniaturization of electric equipment and rationalization and labor saving of manufacturing processes, electronic parts such as resistors and capacitors are fixed to an adhesive tape in a predetermined order, and the electronic parts are automatically inserted. The number of methods to supply machines and sequencers is increasing rapidly.

Conventionally, as the adhesive of the adhesive tape used for these,
Acrylics and rubbers are known. Generally, an acrylic adhesive is obtained by copolymerizing a monomer having a low glass transition temperature such as butyl acrylate or 2-ethylhexyl acrylate with a monomer having a high glass transition temperature such as vinyl acetate or methyl methacrylate, and further adding acrylic acid or hydroxyethyl. A cross-linking monomer such as methacrylate is added to balance the adhesive strength. On the other hand, in the case of a rubber-based pressure-sensitive adhesive, physical properties are balanced by compounding various tackifiers with a rubber component such as natural rubber or synthetic rubber.

However, since the adhesive strength of these adhesives becomes extremely high in a short time, when it is necessary to remove the electronic component from the tape again, the adhesive is transferred to the surface of the adherend, and on the contrary, easy removability is achieved. However, there was a serious drawback in that the adhesive strength was not initially obtained.

As a method of imparting such contradictory performance, a method of adding a polyfunctional photosensitive monomer represented by trimethylolpropane triacrylate to the pressure-sensitive adhesive component, and subjecting the pressure-sensitive adhesive to cross-linking and curing by irradiation with ultraviolet rays and peeling (Japanese Patent Publication No. 58-50164) is known. However, in the case of this method, the photosensitive monomer is limited to a tetrafunctional or less functional monomer, and there is a problem that a sufficient effect cannot be obtained in terms of initial adhesive strength and removability.

(Problems to be Solved by the Invention) Then, as a result of intensive research to solve the above-mentioned drawbacks found in the prior art, the present inventors have replaced the conventionally awarded trimethylolpropane triacrylate with a valence of 5 or more. Of polyhydric alcohol and (meth) acrylic acid ester,
Use of a photosensitive monomer having 5 or more double bonds derived from (meth) acrylic acid improves the initial strength,
Moreover, it was found that re-peeling was extremely easy and the adhesive did not transfer to the surface of the adherend, and the present invention was completed based on this finding.

(Means for Solving Problems) Thus, according to the present invention, a double bond derived from (meth) acrylic acid is used as an adhesive component with an ester of a polyhydric alcohol having a valence of 5 or more and (meth) acrylic acid. A pressure-sensitive adhesive composition comprising a photosensitive monomer having 5 or more, silicone di (meth) acrylate and a sensitizer is provided. The pressure-sensitive adhesive component used in the present invention is not particularly limited as long as it is used in such a technical field, for example, in addition to an acrylic pressure-sensitive adhesive, natural rubber, SBR,
Examples thereof include rubber-based pressure-sensitive adhesives based on synthetic rubber such as styrene-butadiene block copolymers and styrene-isoprene block copolymers. These pressure-sensitive adhesive components may optionally contain a tackifier such as rosin, terpene resin and hydrocarbon resin, and the pressure-sensitive adhesive preferably has an initial adhesive force of 500 g / inch or more. .

The photosensitive monomer used as the second essential component is 5
It is an ester of a polyhydric alcohol having a valence of at least one and acrylic acid or methacrylic acid, and contains five or more double bonds derived from (meth) acrylic acid. Specific examples of such a photosensitive monomer include dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate obtained from a condensate of a tetravalent alcohol, pentavalent alcohol and a condensate thereof. Pentit penta (meth) acrylate, dipentit penta (meth) acrylate, dipentit hexa (meth) acrylate, dipentit hepta (meth)
Hexite penta (meth) acrylate obtained from acrylate, hexavalent alcohol and its condensate, hexite hexa (meth) acrylate, dihexite penta (meth) acrylate, dihexite hexa (meth)
Acrylate, dihexite hepta (meth) acrylate, hepta (meth) acrylate obtained from a condensate of trihydric alcohol and tetrahydric alcohol, trihydric alcohol and 5
Examples thereof include hepta (meth) acrylate and hexa (meth) acrylate obtained from a condensate of a polyhydric alcohol. These can be used as a mixture of two or more, if necessary.

Conventionally, a double bond that can be polymerized into a molecule with acrylic acid or methacrylic acid ester as a photosensitive monomer is used.
It is known to use one containing 4 to 4, for example, 1,4-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, trimethylolpropane triacrylate, etc. (Japanese Patent Publication No. 58-50164).
When a photosensitive monomer having a functionality of 5 or more is used in accordance with the present invention, much better performance is exhibited in terms of reduction in initial adhesive strength and adhesive strength after ultraviolet irradiation.

However, as long as the effects of the present invention are not substantially impaired, tetrafunctional or less photosensitive monomers such as 1,4-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, and neopentel glycol diacrylate are used. , (Poly) ethylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetraacrylate and the like can be appropriately used in combination, and the upper limit thereof is usually 30% by weight or less.

Further, in addition to the photosensitive monomer used in the present invention, the initial adhesive strength can be improved by using a silicone di (meth) acrylate obtained by esterifying the silanol groups at both ends of the organosiloxane polymer with (meth) acrylic acid. It is possible to sufficiently reduce the adhesive force after ultraviolet irradiation without significantly reducing The blending amount of the silicone di (meth) acrylate may be within a range that does not substantially hinder the initial adhesive force, and is 2 parts by weight or less, preferably 0.1 to 1 part by weight, per 100 parts by weight of the pressure-sensitive adhesive component. .

The photosensitizer used as the fourth essential component is, for example, diacetyl, benzyl, benzophenone, benzoin, benzyldimethylketal, ω-bromoacetophenone,
Examples thereof include organic carbonyl compounds such as chloroacetone, benzoquinone, anthraquinone, benzoin propyl ether and benzoin ethyl ether.

In the present invention, these essential components are used in appropriate proportions, but the blending ratio is usually 1 to 100 parts by weight of the photosensitive monomer and 0.01 to 100 parts by weight of the photosensitizer per 100 parts by weight of the adhesive component. 10 parts by weight, and more preferably 2 to 30 parts by weight of the photosensitive monomer and 0.02 to 5 parts by weight of the photosensitizer per 100 parts by weight of the adhesive component. At this time, if the amount of the photosensitive monomer is small, the adhesive force after the irradiation with ultraviolet rays is difficult to decrease, and if the amount is large, on the contrary, the initial adhesive force is decreased and economically poor.

The pressure-sensitive adhesive composition of the present invention can be obtained by uniformly mixing the above components according to a conventional method. At this time, if necessary, a plasticizer, a filler and the like can be appropriately mixed.

The pressure-sensitive adhesive composition thus obtained is applied to a film substrate as a solid so as to have a thickness of 5 to 20 μm to obtain a pressure-sensitive adhesive tape, and an initial adhesive force is caused to appear by heating or the like, if necessary. When re-peeling is required, use a high pressure mercury lamp, etc.
Irradiation with ultraviolet rays having a wavelength of 0 to 4000 Å for 5 seconds or longer, preferably 30 seconds or longer causes the photosensitive groups to react and cause polymerization,
A polymerizing reaction such as cross-linking occurs, the pressure-sensitive adhesive is solidified, the adhesive strength is reduced, and transfer is extremely unlikely to occur, and a preferable removability is obtained.

(Effects of the Invention) Thus, according to the present invention, the adhesive strength during use is excellent, and after being put into use, it is excellent in removability as compared with the prior art by irradiating with ultraviolet rays, and non-transferred to an adherend. It is possible to obtain a pressure-sensitive adhesive composition having excellent adherence.

The pressure-sensitive adhesive composition of the present invention is extremely useful as a pressure-sensitive adhesive for carrier tapes of electronic parts, etc., and transports and processes metal plates such as stainless steel plates and aluminum plates and coated metal plates or decorative plates, glass plates, etc. It is also useful as a temporary surface protection to prevent scratches.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. The parts in the examples are based on weight unless otherwise specified.

Example 1 A pressure-sensitive adhesive composition was produced by uniformly mixing the components shown in Table 1, and a polyethylene film having a thickness of 60 μ was coated with a coating amount of 1 after heating.
It was applied to 0 μm and heated at 100 ° C. for 2 minutes to obtain an adhesive tape. The adhesive tape was attached to a stainless BA plate at room temperature, left for 1 week, and then the initial adhesive strength was measured. Furthermore, from the surface of the film of this stainless steel plate, an ultraviolet ray of 1 is emitted from an ozoneless high pressure mercury lamp of 80 w / cm from a distance of 10 cm.
After irradiation for 0 sec, the adhesive force was measured.

From Table 1, in the present invention, when a photosensitive monomer having 5 or more functional groups and silicone di (meth) acrylate are used in combination, the adhesive strength after irradiation with ultraviolet rays is significantly reduced without lowering the initial adhesive strength. I understand. On the other hand, when a photosensitive monomer having a functionality of 4 or less is blended in place of a photosensitive monomer having a functionality of 5 or more (Comparative Example 3), the initial adhesive force is low and the adhesive force after irradiation with ultraviolet rays is less likely to decrease. In addition, it was found that when the silicone di (meth) acrylate was not blended (Comparative Example 4), the decrease in the adhesive force after the irradiation with ultraviolet rays was small.

Claims (1)

[Claims] 1. A photosensitive monomer which is an ester of a polyhydric alcohol having a valence of 5 or more and (meth) acrylic acid as an adhesive component, and which has at least 5 double bonds derived from (meth) acrylic acid.
A pressure-sensitive adhesive composition comprising a silicone di (meth) acrylate and a photosensitizer.