Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2001-06-19
2002-06-25
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyester
C428S041500, C428S041800, C428S480000, C428S483000, C428S520000
Reexamination Certificate
active
06410157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a casting film for producing a ceramic green sheet. More particularly, it is concerned with a casting film which is used in the production process of a ceramic green sheet in producing ceramic electronic part items, and which has excellent wettability of ceramic slurry and moderate releasability for the ceramic green sheet.
2. Description of the Related Arts
A ceramic electronic part item such as a capacitor, a laminated inductor element, a piezoelectric-part, a thermistor and a varister is produced by a method comprising the steps of forming a green sheet by coating a casting film with ceramic slurry which is well suited to the above-mentioned electronic part items, which is used in high dielectric-constant, magnetism and the like, and which is composed of ceramic powders, organic binders, plasticizers, solvents (an organic solvent or water) and the like (Step {circle around (1)}); equipping the resultant green sheet with an electrode made of palladium, silver, nickel or the like by means of screen printing (Step {circle around (2)}); then peeling off the green sheet from the casting film and laminating the green sheets in multi-layer (Step {circle around (3)}); forming ceramic green chips through steps of pressing and cutting (Step {circle around (4)}); baking the chips thus obtained (Step {circle around (5)}); and equipping the baked chips with terminal electrodes made of silver, silver palladium, nickel, copper or the like (Step {circle around (6)}). In addition thereto, there has recently been proposed a new production process in which the above-mentioned Steps {circle around (1)} and {circle around (2)} are repeated plural times, followed by the Step {circle around (3)} {refer to Japanese Patent Application Laid-Open No. 130150/1996 (Heisei-8)}.
As a casting film used in the production process of ceramic electronic part items, a polyester film coated with a silicone based releasing agent has hitherto been frequently employed.
Further, there is proposed a carrier film which is used for casting green sheets, and in which a releasing layer is composed of an alkyd resin, melamine resin and dimethylpolysiloxane {refer to Japanese Patent Application Laid-Open No. 137218/1995 (Heisei-7)}.
In addition, there is proposed a releasable base film which is used for producing ceramic sheets, and in which a releasing layer is composed of an amino base copolymer resin {refer to Japanese Utility Model Publication No. 38884/1993 (Heisei-5)}.
Accompanying miniaturization, weight-saving and improved performance of ceramic electronic parts in recent years, a thin-filmed green sheet is in rapid progress, and is required to have a film thickness of 10 &mgr;m or smaller for aqueous ceramic green sheets and a film thickness of 4 &mgr;m or smaller for solvent base ceramic green sheets. However, it has been difficult for any of conventional casting films to satisfy at the same time, both the requirements including wettability such that enables uniform coating to be formed even for small coating thickness without causing repelling in the case of applying ceramic slurry, and also moderate releasability from a green sheet such that, in the case of a method in which the above-mentioned Steps {circle around (1)} and {circle around (2)} are repeated plural times so as to constitute a multi-layer coating, enables favorable multi-layer coating to be carried out without causing excessive releasability and without causing relieving and/or peeling off of the firstly formed green sheet from the casting film when ceramic slurry is repeatedly applied on and after the second time.
SUMMARY OF THE INVENTION
In such circumstances, an object of the present invention is to provide a casting film which is used in the production of a ceramic green sheet to be employed in a ceramic electronic part items, and which is imparted with excellent wettability of ceramic slurry and moderate releasability for the ceramic green sheet, while occurrence of repelling is suppressed at the time of ceramic slurry coating.
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 which is used for producing a ceramic green sheet and which is imparted with the foregoing requisite performances, it has been found that a casting film which is adapted to the objects of the invention is obtainable by using, as a releasing agent which constitutes a releasing layer, a cured resin from a stearic acid-modified alkyd resin and/or a stearic acid-modified acrylic resin and an amino resin. The present invention has been accomplished on the basis of such 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 releasing layer formed on at least either side thereof, wherein said releasing layer comprises a cured resin from (A) a stearic acid-modified alkyd resin and/or a stearic acid-modified acrylic resin and a (B) amino resin;
(2) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the stearic acid-modified alkyd resin has a stearyl group content of 40 to 60% by weight, and/or stearic acid-modified acrylic resin has a stearyl group content of 20 to 40% by weight;
(3) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the (B) amino resin is at least one member selected from the group consisting of melamine resin, urea resin and urea-melamine resin each being etherified by a lower alcohol;
(4) the casting film for producing a ceramic green sheet as set forth in any of the preceding items (1), (2) and (3), wherein the content of the component (B) is 5 to 40% by weight based on the total sum of the solid content of the components(A) and (B);
(5) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the substrate film comprises polyethylene terephthalate;
(6) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the component (A) is composed of the mixture of the stearic acid-modified alkyd resin and the stearic acid-modified acrylic resin; and
(7) the casting film for producing a ceramic green sheet as set forth in the preceding item (1), wherein the cured resin is formed in the presence of an acid catalyst.
DESCRIPTION OF PREFERRED EMBODIMENT
The casting film for producing a ceramic green sheet (hereinafter referred simply to as “casting film”) according to the present invention comprises a substrate film and a releasing layer formed on at least either side thereof. The releasing agent constituting the releasing layer comprises a cured resin from (A) a stearic acid-modified alkyd resin and/or a stearic acid-modified acrylic resin and a (B) amino resin, and may further be incorporated as desired, with a release modifier, an adhesion improver and the like.
The alkyd resin and acrylic resin as the component (A) are each modified with stearic acid, whereas any of alkyd resin and acrylic resin that are not modified therewith fails to assure favorable releasing performance for the green sheet and attain the objects of the present invention.
The degree of modification in the above-mentioned resins is not specifically limited, but it is suitable to select said degree so that the stearic acid-modified alkyd resin has a stearyl group content of about 40 to 60% by weight, and the stearic acid-modified acrylic resin has a stearyl group content of about 20 to 40% by weight from the viewpoint of the balance between favorable wettability of ceramic slurry and the releasability of green sheets.
As the above-mentioned alkyd resin and acrylic resin, there are usable the alkyd resin and acrylic resin that have hitherto been customarily used as a resin co
Nakamura Toru
Shibano Tomishi
Chen Vivian
Lintec Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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