Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-02-04
2003-05-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S535000
Reexamination Certificate
active
06566439
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to lowly-adhesive coating materials used upon formation of a releasing liner for adhesive materials, upon treatment of the backside of a single-sided tape, upon oil- and dirt-preventing treatment of electronic parts, etc. and, more particularly, it relates to lowly-adhesive coating materials for precision electronic instruments which are required to contain no silicone.
2. Related Art of the Invention
Usually, adhesive tapes are composed of a substrate and an adhesive layer provided thereon, and are traded in a rolled state and used while being rewound. In such an adhesive tape, a releasing liner for adhesive materials is allowed to temporarily adhere to the adhesive surface of the adhesive tape, in order to prevent the surface carrying an adhesive from strongly adhering to the backside carrying no adhesive agent and then make easy the rewinding upon use.
As the releasing liner for adhesive materials, there has been used in general a coat of polydimethylsiloxane. This is because 1) a force (releasing force) necessary for releasing the adhered releasing liner from the adhesive surface is small; 2) its stability against aging is good; and 3) its production cost is relatively low.
Recently, however, problems due to a silicone pollution have been highlighted in precision electronic instruments and there is a tendency that releasing liners of a silicone type are not preferred. Thus, it is believed that, if and when polydimethylsiloxane causes a pollution in the instruments via some routes, polydimethylsiloxane is decomposed by electric energy which is generated during the operation of the electronic instruments to form solid particles of silicon dioxide, and the resulting particles are precipitated in fine spaces in a driving system of the electronic instruments, whereby operation of the driving system is disturbed and scratches are generated. Particularly, in the case of the instruments equipped with a hard disk as recording mediums, they are very sensitive to this problem because of high airtightness, of a short distance between the recording head and the disk due to high density and also of a rotation of the disk in a high speed. Accordingly, there has been a demand for the non-use of silicone not only for the materials of the parts which directly constitute the electronic instruments but also for the indirect materials which contact with the electronic parts, in order to prevent transfer pollution of silicone from the materials used. There has been a demand for the non-use of silicone for a releasing liner for adhesive materials as well.
With regard to a releasing agent which forms a releasing liner for adhesive materials of a non-silicone type, agents of a non-fluorine-type and of a fluorine-type are available and, with respect to the agent of a non-fluorine-type, that of an alkyl pendant type and of a condensed wax type (refer to “
Nenchaku Handobukku
” (Handbook of Adhesion), pages 163-171) have been known. All of them have a releasing force in a medium degree of around 2 to 10 N/dm as compared with the pressure-sensitive adhesive agent of an acrylic type having a strong cohesive force and are difficult to give a light releasing force which is preferred in the market, i.e., 0.2 to 2 N/dm.
On the other hand, a fluorine-containing acrylic polymer has been known as a releasing agent of a fluorine-type. The fluorine-containing acrylic polymer gives a releasing force of 2 to 4 N/dm if well-designed, but that is still heavy as compared with the releasing force which has been demanded in the market. There is another inconvenience that the fluorine-containing acrylic polymer has a strong tendency of a stick-slip upon releasing.
As to a releasing agent of a fluorine-type, that which is mainly composed of a perfluoropolyether has been known (see Japanese Patent Application Laid-open No. 3-258863, Claims). Although such a releasing agent gives a sufficiently light releasing property, that agent is disadvantageous in view of cost since a perfluoropolyether is very expensive. In addition, in a production process of a releasing liner for adhesive materials from this releasing agent, the releasing agent is applied on a substrate and the resulting coat is hardened to form the releasing liner, where during the hardening stage it is necessary to conduct a UV irradiation in an inert gas. Accordingly this process is very troublesome as compared with the common solvent coating method. Moreover, adhesion between the substrate and the releasing liner is insufficient. With regard to a method for improving the adhesion therebetween, there is a proposal that a primer mainly comprising a special acrylic monomer which is copolymerizable with a perfluoropolyether is previously coated on the substrate (Japanese Patent Application Laid-open No. 3-40754 and U.S. Pat. Nos. 4,567,073 and 4,614,667). However according to this proposal, the production process for a releasing liner for adhesive materials becomes more troublesome, resulting in a high cost.
SUMMARY OF THE INVENTION
Against the problems in the above-mentioned prior art, objects of the present invention is that a coat of a non-silicone type can be easily formed only by applying a coating solution to a substrate followed by drying; that, although the coat shows a sufficient adhesion to the substrate, it shows a releasing property of at least medium degree or, preferably, a releasing property of as light as not more than 2 N/dm to the adhesive layer of pressure-sensitive adhesive agent of an acrylic type having a strong adhesive property; that the stability of a releasing force against aging is made good; and that the adhesive layer which has been stuck to the coat and then released therefrom is made to possess the same adhesive force as before.
The present inventor has found that a coating material prepared by compounding a specific fluorine-containing acrylic polymer with a fluorine-type oil in a specific ratio has features that a coat prepared from the coating material shows a little releasing force to an adhesive layer whereby a tendency of stick-slip upon releasing is reduced and that it has a good stability against aging and a good re-adhesion of the adhesive layer after sticking to the coat as well, and have accomplished the present invention.
Thus, the present invention provides a lowly-adhesive coating material which comprises 99 to 33% by weight of a fluorine-containing acrylic polymer prepared from a monomer composition mainly comprising acrylate or methacrylate having a C
6-16
perfluoroalkyl group and 1 to 67% by weight of a fluorine-type oil.
The present invention also provides a releasing liner for an adhesive material which comprises a substrate and a coat of the lowly-adhesive coating material of the present invention provided on one or both surfaces of the substrate, and it further provides an adhesive tape which comprises a substrate, an adhesive layer provided on one surface of the substrate, and a coat of the lowly-adhesive coating material of the present invention provided on the other surface of the substrate.
In the lowly-adhesive coating material of the present invention, the fluorine-containing acrylic polymer shows an appropriate compatibility to the fluorine-type oil because of a good balance between the common point in view of the constituting element that the fluorine-containing acrylic polymer and the fluorine-type oil both are of a fluorine-type and the different point in view of the structure that the polymer is an acrylic type while the fluorine-type oil is usually an ether or of a vinyl type. As a result, it does not happen that the fluorine-containing acrylic polymer and the fluorine-type oil do not form a uniform coat due to too poor compatibility therebetween to cause a clear phase separation therebetween and also that they rather form a completely united coat due to too good compatibility therebetween. The lowly-adhesive coating material of the present invention has a property that the fluorine-containing acrylic polym
Bissett Melanie
Oliff & Berridg,e PLC
Seidleck James J.
Sony Chemicals Corporation
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