Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-09-07
2004-06-15
Moore, Margaret G. (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C428S480000, C428S447000, C522S099000, C524S357000, C524S358000, C524S359000, C528S015000, C528S031000, C528S032000, C427S515000
Reexamination Certificate
active
06749898
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a casting film for producing a ceramic green sheet and a process for producing the casting film. More particularly, it is concerned with a casting film which is used in producing a ceramic green sheet to be employed in a ceramic capacitor, a laminated inductor element and the like; is equipped with a cured layer of a silicone composition formed thereon having favorable adhesiveness to a substrate film; is excellent in both coatability of ceramic slurry and releasability of the ceramic green sheet; and has high flatness never can be realized by any of conventional film. Furthermore, the present invention is concerned with a process for efficiently producing the above-mentioned casting film.
BACKGROUND ART
Accompanying the market demand in recent years towards miniaturization and weight-saving of electronic equipment in general, the part items constituting the electronic equipment are required to be thin-filmed and lightweight.
For instance, it has come to be possible to miniaturize the electronic part items such as capacitors and laminated inductor elements that have heretofore been part items with leads through practical application of the technology which forms monolithic structure equipped with an internal conductor by simultaneously firing a laminate composed of a ceramic layer and an electro-conductive layer each having a prescribed pattern configuration. Nevertheless still further miniaturization is required.
In general, a ceramic capacitor is produced by the steps of firstly preparing a slurry by mixing ceramic powders having high dielectric constant of a compound, etc. which has perovskite crystalline structure such as barium titanate with a binder or an organic solvent; coating a casting film such as polyethylene terephthalate film with the resultant slurry; drying the coating to prepare ceramic green sheets; then forming an electrode pattern on the ceramic green sheets through screen printing or the like by the use of an electroconductive paste; thereafter releasing the ceramic green sheets from the casting film; then laminating a large number of the printed ceramic green sheets in a prescribed order; press sticking the laminate under heating; cutting the same into chips of desirable shape; and subjecting the chips to firing treatment to proceed with sintering.
On the one hand, in general, a laminated inductor element is produced by at first preparing ceramic green sheets on a casting film in the same manner as the foregoing by the use of magnetic ceramic powders such as ferrite; then forming a coil pattern on the ceramic green sheets through screen printing or the like by the use of an electroconductive paste; releasing the ceramic green sheets from the casting film; and then preparing a laminated inductor element in the shape of chips in the same manner as the foregoing.
The ceramic capacitor and laminated inductor element in the shape of chips thus obtained are required to be still further miniaturized in response to the demand for miniaturization as mentioned above. Accompanying such demand, the thickness of the aforesaid ceramic green sheet being presently in the range of 5 to 20&mgr;m is required to be further small.
As the ceramic green sheet is thinned to such an extent, a conventional casting film is no longer capable of coping with the need, whereby it is indispensable to realize a casting film which is excellent in both coatability of ceramic slurry and releasability of the ceramic green sheet, is free from thermal shrinkage or wrinkle and has extremely high flatness.
There has heretofore been generally employed as a castings film, a polyethylene terephthalate film (PET film) subjected to releasing treatment with a releasing agent composed of a heat curing addition reaction type silicone. However, in order to assure a stable cured film, the releasing agent composed of a heat curable addition reaction type silicone is obliged to be crosslinked at a high temperature of usually 140° C. or higher with the result that the thermal shrinkage of the PET film is inevitably caused in the releasing treatment step. The thermal shrinkage or wrinkle, when being found in the PET film, brings about the problem of making it impossible to form a homogeneous thin film sheet at the time of film forming from ceramic slurry.
Under such circumstances, an attempt is made to carry out processing treatment with a heat curable addition reaction type silicone resin by retarding processing rate at a low temperature (110 to 130° C.) in order to suppress thermal shrinkage or wrinkle to the utmost. However, such attempt brings about the problems of not only poor productivity, but also insufficiency in curing, stability for adhesion of the silicone to the PET film, coatability of ceramic slurry and the like.
There is known, as a releasing agent composed of silicone capable of curing at a low temperature, a releasing agent composed of single ultraviolet ray curable (without heating; the same applies hereinafter) silicone having a functional group such as an epoxy group, acrylic group, mercapto group or the like. Nevertheless such a releasing agent is problematic in that uniform silicone-coated surface is difficult to obtain and besides, the ceramic green sheet is poor in releasability and stability.
DISCLOSURE OF THE INVENTION
In such circumstances, an object of the present invention is to provide a casting film which is used in producing a ceramic green sheet to be employed in a ceramic capacitor, a laminated inductor element and the like; is equipped with a cured layer of silicone composition having favorable adhesiveness to a substrate film; is excellent in coatability of ceramic slurry and releasability of the ceramic green sheet; and has high flatness never can be realized by any of conventional film, and besides a process for efficiently producing the aforesaid casting film.
Other objects of the present invention will be obvious from the text of this specification hereinafter disclosed.
As a result of intensive extensive research and investigation accumulated by the present inventors in order to develop a casting film for producing a ceramic green sheet imparted with the foregoing excellent functions, it has been found that by coating a substrate film in a specific thickness with an addition reaction type silicone composition containing a photosensitizer as a releasing agent, then heat-treating the resultant coating and thereafter curing it by inline ultraviolet ray irradiation, there is formed a cured layer of a silicone composition excellent in adhesiveness to a substrate film, and that the film equipped with the foregoing cured layer is adapted to the objects of the invention as a casting film. The present invention has been accomplished by the above-mentioned findings and information.
That is to say, the present invention provides:
(1) a casting film which is used for producing a ceramic green sheet and which comprises a substrate film and a cured layer coated thereon of an addition reaction type silicone composition containing a photosensitizer, characterized in that said cured layer is formed by heat treating a layer of a photosensitizer-containing addition reaction type silicone composition in a coating amount expressed in terms of solid content in the range of 0.01 to 0.2 g/m
2
at a temperature in the range of 40 to 120° C., followed by a treatment with ultraviolet ray irradiation.
(2) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the substrate film comprises polyethylene terephthalate.
(3) the casting film for producing a ceramic green sheet as set forth in the preceding item (1) or (2), wherein the addition reaction type silicone composition comprises polydimethylsiloxane having a vinyl group as a functional group.
(4) the casting film for producing a ceramic green sheet as set forth in the preceding item (1) or (2), wherein the addition reaction type silicone composition comprises polydimethylsiloxane having a hexenyl group as a functional group.
(5) the casting film fo
Nakamura Toru
Shibano Tomishi
Lintec Corporation
Moore Margaret G.
Zimmer Marc S
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