RADIATION FOR RELEASE FILM FOR DIELECTRIC CERAMIC-FORMING MATERIAL.

AND RELEASE FILM FOR DIELECTRIC CERAMIC-FORMING MATERIAL USING THE

SAME

Technical Field

[0001] The present invention relates to use of an acryloxy-functional silicone composition cured by irradiation with ultraviolet radiation or other high-energy radiation in a release layer of a release film for dielectric ceramic-forming material, and to a release film for dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet, having the release layer. The present invention also relates to a method of production of a dielectric ceramic-forming material, particularly a ceramic green sheet, using the aforementioned release film.

Background Technology

[0002] There is hitherto known a method of manufacturing laminated ceramic products, particularly laminated ceramic electronic components, including laminated ceramic capacitors, laminated inductors, and multilayer ceramic substrates, in which laminated ceramic products, particularly laminated ceramic electronic components, are manufactured by mixing a ceramic raw material before firing, with a binder, solvent, and the like, as needed, and forming into a paste-form mixture, to serve as a dielectric ceramic-forming material, applying this mixture onto a plastic carrier film and drying, and fabricating a dielectric ceramic-forming material, for example, a sheet referred to as a "ceramic green sheet"; and furthermore printing a paste-form internal electrode material on top of the ceramic green sheet and forming internal electrodes, laminating a plurality of ceramic green sheets while aligning the electrode patterns among themselves, then crimping to unify the sheets, and furthermore firing the result.

[0003] These dielectric ceramic-forming materials, particularly ceramic green sheets, can be fabricated, for example, by applying a ceramic slurry containing barium titanate, titanium oxide, or other ceramic raw material, and a dispersing medium, and the like, onto a release film, and furthermore drying the result. The ceramic green sheet, obtained by applying the ceramic slurry on the release film, referred to also as a "carrier film," and drying, is released from the release film in a subsequent step before the step of firing the ceramic at the latest. A commonly used release film, for example, is a release film that is conferred with releasability from a ceramic green sheet by using polysiloxane or other silicone-based compound on the surface of a base film of polyethylene terephthalate, or the like (Patent Documents 1 to 8). This release film requires release characteristics such that the thin ceramic green sheet moulded on the release film can be released from the release film without being broken.

[0004] Miniaturization and multi-layering of laminated ceramic capacitors and multilayer ceramic substrates are furthermore progressing in recent years accompanying

miniaturization and performance enhancement of electronic devices, and formation of ceramic green sheets into thin films is progressing in tandem.

[0005] The present inventors have already proposed, as a material for conferring to a base material film releasability to be usable also as a carrier film for a ceramic green sheet, and as a curable organopolysiloxane composition that is easy to handle, can be used to form a cured film on a base material surface, and can confer to the base material surface a favourable releasability from pressure-sensitive adhesive materials and a smooth slipperiness of the cured film, a curable organopolysiloxane composition containing: (A) 100 parts by weight of one or more kinds of organopolysiloxane having a viscosity at 25°C of 20 to 500 mPa s, and having a content of C4 to C12 higher alkenyl groups in a range of 1.0 to 5.0% by mass; (B) 0.5 to 15 parts by weight of an organopolysiloxane having a viscosity at 25°C of 1 ,000,000 mPa-s or higher, and having a content of C2 to C12 higher alkenyl groups in a range of 0.005 to 0.100% by mass; (C) an organo-hydrogenated polysiloxane having 2 or more silicon-bonded hydrogen atoms (Si-H) per molecule in a quantity such that the molar ratio of SiH groups in ingredient (C) per alkenyl groups in ingredients (A) and (B) is 0.5 to 5; and (D) a catalytic quantity of a platinum-based catalyst (Japanese Unexamined Patent Application Publication No. 201 1-26582). Meanwhile, the present applicant proposed, in Japanese Unexamined Patent Application Publication No. 2004-269589, an acryloxy-functional silicone composition curable by high-energy radiation, in a technical field different from release agents and expecting a technical effect different from releasability or formation of ceramic green sheets (specifically, to obtain a cured film excellent in storage stability and excellent in abrasion resistance, transparency, water repellency, and close adhesiveness after curing). The present applicant also proposed, in paragraph 0024 of document in question, use of a protective film, or the like, based on performance thereof as a common coating agent. However, the document neither describes nor suggests the use of such composition in a release agent for use on a material having adhesiveness and fluidity, and particularly in a release film used in production of ceramic green sheets and other dielectric ceramic-forming materials, nor does the document disclose a technical effect such as to provide a specific motivation.

Prior Art Documents

1. Japanese Unexamined Patent Application Publication No. 2002-01 1710

2. Japanese Unexamined Patent Application Publication No. 2004-182836 3. Japanese Unexamined Patent Application Publication No. 2004-216613

4. Japanese Unexamined Patent Application Publication No. 2008-254207

5. Japanese Unexamined Patent Application Publication No. 2009-034947

6. Japanese Unexamined Patent Application Publication No. 2009-215428

7. Japanese Unexamined Patent Application Publication No. 2009-227976

8. Japanese Unexamined Patent Application Publication No. 2009-227977

9. Japanese Unexamined Patent Application Publication No. 201 1-026582

10. Japanese Unexamined Patent Application Publication No. 2004-269589 (Patent

4646497)

Summary of the Invention

Problems to Be Solved by the Invention

[0006] In the case when fabricating a thin-film-form ceramic green sheet for the purpose of miniaturization and/or multi-layering of a laminated ceramic capacitor or a multilayer ceramic substrate as described above, when the thickness after drying of a ceramic slurry applied onto a base material film was 3 pm or smaller, there were problems that so-called "end contraction," in which the ends of the portion applied with ceramic slurry contract when the ceramic slurry is applied and dried and the thickness of the ends of the applied portion becomes thicker than the interior portion, the formation of pin holes, and/or uneven application tended to occur. Also, when releasing the moulded ceramic green sheet from the base material film, that is, from the release film, there were problems that breakage of the sheet or other unfavourable situations tended to occur due to a decrease of strength of the ceramic green sheet by having a thin film thickness.

[0007] Furthermore, in electronic materials and electronic components produced using ceramic green sheets, the kinds of inorganic ceramic materials, binder resins, dispersing agents, organic solvents, and the like, used differ in accordance with their use, and therefore the applicability of the ceramic slurry to the release film changes in accordance with the kind of ceramic slurry applied to the release film. Accordingly, there is still a demand at present for a release film that combines favourable applicability to the ceramic slurry and favourable releasability from the obtained ceramic green sheet regardless of the kind of ceramic slurry used.

[0008] Meanwhile, the curable organopolysiloxane composition disclosed by the present inventors in Japanese Unexamined Patent Application Publication No. 2011-026582 as a material for conferring releasability to a base material film surface as described above is a curable organopolysiloxane composition that is substantially of a solvent-less type, that is, does not contain a solvent, and is useful as a material for use in surface protection sheets for displays, and the like, but there was a feature that this was unsuitable for use as-is as a material for a release film for a ceramic green sheet

[0009] The present invention was created in consideration of such realities, and an object thereof is to provide a release film for forming a ceramic green sheet, being a film for forming a ceramic green sheet, that is, being a so-called "carrier film," having excellent applicability of a ceramic slurry onto the surface thereof, and having excellent releasability of the ceramic green sheet formed on its surface, as well as to provide a release agent composition suitable for producing that film.

Means for Solving the Problems

[0010] The present inventors completed the present invention, having discovered that when a release film is obtained by coating a sheet-form base material, for example, a base material film, with the acryloxy-functional silicone composition curable by high-energy radiation noted below, as a release agent composition for modifying surface characteristics of the base material film for use in a release film for forming a ceramic green sheet, and by curing the composition, the release film exhibits excellent characteristics as a release film for a dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet. That is, the release agent composition of the present invention, for the release film for dielectric ceramic-forming material of the present invention, that is, for the release film for forming a ceramic green sheet, contains the following ingredients (A) through (E): (A) at least one kind of multifunctional acrylate;

(B) at least one kind of siloxane compound selected from (B1 ) and (B2) below:

(B1 ) an amine-modified organopolysiloxane (where a molar quantity of amine groups in ingredient (B1) is a quantity less than a molar quantity of acrylate-functional groups in ingredient (A)); and

(B2) a Michael addition reaction product of an amine-modified organopolysiloxane with at least one kind of multifunctional acrylate;

(C) a fatty unsaturated group-containing organoalkoxysilane;

(D) colloidal silica as optionally selected; and

(E) an organic solvent for rendering the present composition into liquid form as optionally selected; and comprises an acryloxy-functional silicone composition curable by high-energy radiation selected from ultraviolet radiation, electron beam radiation, and gamma radiation. In particular, an alcohol-containing organic solvent can be contained and is preferred from the view of dispersibility and handling characteristics of the ingredients.

[0011] The above composition furthermore preferably contains 1 to 30 parts by weight ingredient (B1 ), 1 to 30 parts by weight ingredient (C), 0 to 100 parts by weight ingredient (D), and 10 to 1000 parts by weight ingredient (E), per 100 parts by weight of the above ingredient (A).

[0012] The composition also preferably contains 1 to 100 parts by weight ingredient (B2), 1 to 30 parts by weight ingredient (C), 0 to 100 parts by weight ingredient (D), and 10 to 1000 parts by weight ingredient (E), per 100 parts by weight of the above ingredient (A).

Ingredient (B2) is a reaction product of the above ingredient (A) and the aforementioned unreacted ingredient (B1 ), and each ingredient (B) may be used singly or in combination.

[0013] Any of the above compositions also can further contain (G) water for hydrolysis of the above ingredient (C).

[0014] When the above acryloxy-functional silicone composition curable by high-energy radiation contains (G) water, the water is preferably 1 to 50 parts by weight per 100 parts by weight ingredient (C).

[0015] In each of the above compositions, the weight of ingredient (B) is preferably less than or equal to 1/5 of the weight of ingredient (A).

[0016] In each of the above compositions, ingredient (A) is preferably a pentafunctional or higher acrylate.

[0017] Each of the above compositions may further contain (F) at least one kind of photopolymerization initiator.

[0018] The present invention furthermore provides a release film for dielectric

ceramic-forming material, including a cured layer obtained by curing the release agent composition for dielectric ceramic-forming material comprising any of the above compositions, and a sheet-form base material. The release film is ideal, in particular, as a release film for forming a ceramic green sheet.

[0019] The above cured layer may be a cured layer obtained by applying the release agent composition comprising any of the above acryloxy-functional silicone compositions curable by high-energy radiation at a quantity of 0.01 to 0.5 g/m ² on a sheet-form base material, and furthermore curing the applied composition by irradiation with high-energy radiation selected from ultraviolet radiation, electron beam radiation, and gamma radiation.

[0020] The above sheet-form base material is preferably a plastic film.

[0021] The present invention furthermore provides a method of production of a dielectric ceramic-forming material, particularly a ceramic green sheet. This method uses the above-described release film for forming a ceramic green sheet of the present invention, and includes a step of applying a ceramic slurry onto a layer of the silicone composition cured on the film and drying the applied ceramic slurry.

Effects of the Invention

[0022] A release film for dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet, obtained using the release agent composition comprising an acryloxy-functional silicone composition curable by high-energy radiation of the present invention, is excellent in applicability of a ceramic slurry to the film. Specifically, when a ceramic slurry is applied and dried on the surface of a cured layer obtained by curing the release agent composition of the present invention, the occurrence of so-called "end contraction," in which the ends of the applied ceramic slurry contract and the thickness of the ends becomes thicker than the interior, can be suppressed. Also, the release film for dielectric ceramic-forming material, particularly the release film for forming a ceramic green sheet, according to the present invention is excellent in releasability of the dielectric ceramic-forming material, particularly the ceramic green sheet, formed thereon, and the ceramic green sheet can be released with low releasing force from the release agent layer of the film, that is, the carrier film.

Preferred Embodiment of the Invention

[0023] As described above, the present invention relates to a release film for dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet, that is excellent in releasability of the dielectric ceramic-forming material, particularly of the ceramic green sheet, from the release film, and is excellent in applicability of the ceramic slurry onto the film. The present invention relates also to an acryloxy-functional silicone composition curable by high-energy radiation that is suitable for producing the release sheet. Each ingredient constituting the acryloxy-functional silicone composition curable by high-energy radiation used in the present invention, and the release film produced using the curable silicone composition of the present invention, are described in detail below.

Ingredient (A)

[0024] Ingredient (A) is an ingredient for conferring curability by high-energy radiation to the curable silicone composition of the present invention, and a bifunctional or higher acrylate can be used. Specific examples of ingredient (A) include: 1 ,6-hexanediol diacrylate, 1 ,4-butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, 1 ,4-butanediol dimethacrylate, poly(butanediol) diacrylate, tetraethylene glycol

dimethacrylate, 1 ,3-butylene glycol diacrylate, triethylene glycol diacrylate, triisopropylene glycol diacrylate, polyethylene glycol diacrylate, bisphenol A dimethacrylate, and other bifunctional acrylate monomers; trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol monohydroxy triacrylate, trimethylpropane triethoxy triacrylate, and other trifunctional acrylate monomers; pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and other tetrafunctional acrylate monomers; and dipentaerythritol hexaacrylate, dipentaerythritol (monohydroxy) pentaacrylate, and other pentafunctional or higher acrylate monomers. Oligomers of multifunctional acrylates also can be used, and specific examples include bisphenol A epoxy diacrylate, hexafunctional aromatic urethane acrylate [trademark: Ebecryl 220], aliphatic urethane diacrylate

[trademark: Ebecryl 230], and tetrafunctional polyester acrylate [trademark: Ebecryl 80]. One kind of these multifunctional acrylates may be used singly, or two or more kinds may be used in combination. In particular, pentafunctional or higher acrylates are preferably contained as ingredient (A), and the content thereof is preferably 30 wt% or higher, more preferably 50 wt% or higher, and further preferably 80 wt% or higher, of ingredient (A).

Ingredient (B)

[0025] Ingredient (B) is an ingredient for conferring water repellency and lubricity to the cured film obtained from the curable silicone composition of the present invention, and is at least one kind of siloxane compound selected from (B1 ) and (B2) below:

(B1 ) an amine-modified organopolysiloxane (where a molar quantity of amine groups in ingredient (B1 ) is a quantity less than a molar quantity of acry!ate-functional groups in ingredient (A)); and

(B2) a Michael addition reaction product of an amine-modified organopolysiloxane with at least one kind of multifunctional acrylate.

[0026] An example of ingredient (B1 ) is an organopolysiloxane fluid having amine-functional organic groups on the molecular chain terminal or on a portion of a side chain. Examples of amine-functional organic groups include 2-aminoethyl group, 3-aminopropyl group, 3-(2-aminoethyl)aminopropyl group, and 6-aminohexyl group. Examples of groups bonded to silicon atoms other than multifunctional organic groups include: methyl group, ethyl group, propyl group, and other alkyl groups; phenyl group and other aryl groups; methoxy group, ethoxy group, propoxy group, and other alkoxy groups; and hydroxyl group. Methyl group in particular is preferable among these. The molecular structure of the organopolysiloxane is preferably linear form or partially branched linear form. The degree of polymerization of siloxane of the organopolysiloxane is preferably in a range of 2 to 1000, more preferably in a range of 2 to 500, and particularly preferably in a range of 2 to 300. An organopolysiloxane having primary amine groups expressed by the following formula is given as a preferred ingredient as such ingredient (B). "Me" in the average molecular formula below is a methyl group.

Chemical formula 1 N H ₂ C ₃ H ₆ -M e ₂ S i O (M Θ ₂ S i O) ₁₀ S i M Θ ₂ -C ₃ H ₆ N H ₂

Me M e Me

I I I

N H ₂ C ₂ H ₄ NH C ₃ H ₆ -S i O (S i O) ₆ S i -C ₃ H ₆ NH C ₂ H ₄ N H.

I I I

Me M e Me

M e ₃ S i O (Me ₂ S i O) ₅₀ (M e S i O) ₆ S i Me ₃

I

C ₃ H ₆ N H ₂

Me ₃ S i O (Me ₂ S i O) ₈₀ (M e S i O) ₁₀ S i Me ₃

C ₃ H ₆ N H C ₂ H ₄ N H ₂

[0027] The quantity mixed of ingredient (B1) in the curable silicone composition used in the present invention is a quantity such that the total molar quantity of amine groups in ingredient (B1) is less than the molar quantity of acrylate-functional groups in ingredient (A). The weight of ingredient (B1) is preferably less than or equal to 1/5 of the weight of ingredient (A) because a cured film having favourable characteristics is obtained.

Ingredient (B2)

[0028] Ingredient (B2) is a Michael addition reaction product of an amine-modified organopolysiloxane with at least one kind of multifunctional acrylate, and is equivalent to a reaction product obtained by reaction of the amine groups in ingredient (B1) with the acrylate-functional groups in the above ingredient (A). Because such ingredient (B2) is finally formed in the process of the curing reaction eve when ingredient (B1) is used, ingredient (B2) reacted in advance can be mixed in the curable silicone composition according to the present invention instead of the aforementioned ingredient (B1) or together with the aforementioned ingredient (B2).

Ingredient fC)

[0029] Ingredient (C) is an ingredient that can crosslink with ingredient (A) and improve the degree of crosslinking of the cured material and improve the close adhesiveness between the cured layer and the base material, and additionally can treat the surface of the colloidal silica of ingredient (D) as an optional ingredient and improve the affinity with ingredient (A) or ingredient (B), and can confer favourable storage stability to the composition of the present invention. Examples of groups having fatty unsaturated bonds include:

3-(methacryloxy)propyl group, 3-(acryloxy)propyl group, and other acrylic group-containing organic groups; and vinyl group, allyl group, and other alkenyl groups. Examples of alkoxy groups include methoxy group, ethoxy group, propoxy group, and butoxy group. Examples of such ingredient (C) include 3-(methacryloxy)propyltrimethoxysilane,

3-(methacryloxy)propyltriethoxysilane, 3-(methacryloxy)propylmethyldimethoxysilane, 3-(acryloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,

methylviny!dimethoxysilane, and allyltriethoxysilane.

Ingredient (D)

[0030] Ingredient (D) is an optional ingredient, and may be used or not used as needed.

Ingredient (D) is an ingredient for curing to a high degree the cured film formed from the curable silicone composition of the present invention and improving abrasion resistance thereof. Examples of such ingredient (D) include water-dispersible colloidal silica, alcohol-dispersible colloidal silica, and organic solvent-dispersible colloidal silica. The mean particle size of the colloidal silica is normally in a range of several nm to several tens of nm.

The releasable cured film of the present invention does not necessarily require hardness or abrasion resistance, considering the use, but ingredient (D) can be contained and is preferred from the view of releasability and strength of the release layer. The quantity of ingredient (D) when used is preferably 1 to 100 parts by weight per 100 parts by weight of the above ingredient (A).

Ingredient (E)

[0031] Ingredient (E) is an optional ingredient, and may be used or not used as needed. Ingredient (E) is an organic solvent for rendering the present composition into liquid form. Ingredient (E) is preferably an alcohol-containing organic solvent in order to uniformly disperse the aforementioned ingredients (A) to (C) as well as ingredient (D) as optionally selected and to be applicable to a sheet-form base material. Examples of alcohols in ingredient (E) include methanol, ethanol, isopropyl alcohol, butanol, isobutyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and triethylene glycol monomethyl ether, but the alcohol is not limited to these. Examples of organic solvents other than alcohol include: acetone, methyl ethyl ketone, methyl isobutyl ketone, and other ketones; toluene, xylene, and other aromatic hydrocarbons; hexane, octane, heptane, and other aliphatic

hydrocarbons; chloroform, methylene chloride, trichloroethylene, carbon tetrachloride, and other organic chlorine-based solvents; and ethyl acetate, butyl acetate, isobutyl acetate, and other aliphatic carboxylic esters. Ingredient (E) may be an alcohol singly or a mixture of an alcohol with another solvent. Two or more kinds of alcohols and other solvents also may be used in combination. The content ratio of alcohol is preferably in a range of 10 to 90 wt%, more preferably 30 to 70 wt%, of the total quantity of solvent.

Mixture ratios of each ingredient

[0032] The quantity mixed of each ingredient is not particularly limited, but ingredients (B1 ) and (C) each are preferably in a range of 1 to 30 parts by weight, more preferably 1 to 20 parts by weight, per 100 parts by weight ingredient (A). Ingredient (D) is an optional ingredient, and is preferably in a range of 0 to 100 parts by weight, more preferably 1 to 80 parts by weight, per 100 parts by weight ingredient (A). Ingredient (E) is an optional ingredient, and is preferably in a range of 10 to 1000 parts by weight, more preferably in a range of 10 to 500 parts by weight, per 100 parts by weight ingredient (A), in order to obtain a favourably applicable composition when ingredient (E) is used. When ingredient (B2) is used instead of ingredient (B1) or together with ingredient (B1), ingredient (B2) is preferably in a range of 1 to 100 parts by weight, more preferably in a range of 1 to 50 [parts by] weight, per 100 parts by weight ingredient (A).

Ingredient (F)

[0033] Ingredient (F) is preferably added to the curable composition of the present invention when curing the composition by irradiation with high-energy radiation, for example, ultraviolet radiation. Specific examples of ingredient (F) include

2-methyl-{4-(methylthio)phenyl}-2-morpholino-1-propane [trade name: Irgacure 907;

manufactured by Ciba-Geigy Japan Ltd.] and 1-hydroxycyclohexylphenylketone [trade name: Irgacure 184; manufactured by Ciba-Geigy Japan Ltd.]. In addition to these, benzophenone, acetophenone, benzoin or various kinds of benzoin derivatives, and well-known photopolymerization initiators can be used as ingredient (F). One kind of such photopolymerization initiators may be used singly, or mixtures of two or more kinds may be used. The quantity mixed of ingredient (F) into the curable silicone composition of the present invention is not particularly limited, but is preferably in a range of 1 to 30 parts by weight, more preferably in a range of 1 to 20 parts by weight, per 100 parts by weight ingredient (A).

Ingredient (G)

[0034] Ingredient (G) is water, and is an optional ingredient used for hydrolysis of ingredient (C). The quantity mixed of ingredient (G) when used is preferably in a range of 1 to 50 parts by weight, more preferably in a range of 5 to 30 parts by weight, per 100 parts by weight ingredient (C). Ingredient (C) normally reacts with silanol groups on the surface of the colloidal silica being ingredient (D) and is furthermore hydrolyzed by ingredient (G). Therefore, the quantity mixed of ingredient (G) may be less than the quantity capable of completely hydrolyzing ingredient (C).

Other optional ingredients

[0035] Ingredients other than those mentioned above may be admixed into the composition of the present invention within a range that does not impede the object of the present invention. For example, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and other tetraalkoxysilanes; methyltrimethoxysilane, methyltriethoxysilane,

methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane,

ethyltriisopropoxysilane, and other aklylalkoxysilanes are given as examples of those other ingredients.

[0036] Pressure-sensitive adhesives; ultraviolet absorbers; all kinds of pigments, dyes, and other colourings; aluminum paste, talc, glass frit, metal powder, and additionally butylated hydroxytoluene (BHT), phenothiazine (PTZ), and other inhibitors of self-polymerization of acrylates, and the like, furthermore can be admixed as needed into the composition of the present invention.

[0037] Various kinds of additives for modifying surface characteristics of the cured silicon may be further added, in addition to the above-described ingredients, to the

high-energy-curable acryloxy-functional silicone composition used in the present invention. For example, an antistatic agent can be added to the curable silicone composition of the present invention.

[0038] Well-known ionic or nonionic antistatic agents can be used without particular limitation, and examples include a method of adding a silicone oil having a hydrophilic group as a main ingredient (Japanese Unexamined Patent Application Publication No.

S52-103499), a method of adding a sulfonate (Japanese Examined Patent Application Publication No. H3-59096), a method of adding a fluorine-containing silicone oil (Japanese Unexamined Patent Application Publication Nos. H1-83085, H1-83086, and H1-121390), a method of adding a surfactant-containing silicone oil (Japanese Unexamined Patent Application Publication No. H1-294099), and a method of adding a conductive powder (Japanese Unexamined Patent Application Publication Nos. H2-69763, H3-292108, and H4-86765). In particular, an antistatic agent being a lithium salt or a polyether-modified polysiloxane is ideally used because it is compatible with the curable organopolysiloxane composition of the present invention. These ionic antistatic agents, polyether-modified polysiloxanes, and the like, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2009-30028, Japanese Unexamined Patent Application Publication No. 2012-157978, or Japanese Unexamined Patent Application Publication No. 201 1-178828, can be used without limitation. In addition to use of the aforementioned antistatic agents as an additive from the viewpoint of static prevention, the base material may be treated with an antistatic agent selected from surfactant-based, silicone-based, organic boron-based, conductive polymer-based, metal oxide-based, vapor-deposited metal-based, and the like.

Method of preparing the curable silicone composition used in the present invention

[0039] The method of production of the composition of the present invention is not particularly limited, but a homogeneous mixture is obtained by simply stirring the constituent ingredients. At this time, ingredients (A) and (B1) may be reacted first, and the other ingredients may be mixed thereafter. The addition reaction product of ingredients (A) and (B1 ) corresponds to the above ingredient (B2). Because the molar quantity of amine groups in ingredient (B1 ) is less than the molar quantity of acrylate-functional groups in ingredient (A), the mixture comes to contain a Michael addition reaction product (B2) of ingredient (B1 ) with ingredient (A), as well as unreacted ingredient (A), after the reaction between ingredients (A) and (B1 ). A specific example of a method of preparation of the curable silicone composition of the present invention is to mix ingredients (A) and (B) in ingredient (E) for one minute to 20 hours in a range from room temperature to a reflux temperature of the solvent and bring about a reaction, then add ingredients (C) and (D) and further add ingredient (G) as needed, and mix for one minute to 20 hours in a range from room temperature to the reflux temperature of the solvent. Another method is to mix ingredients (A) and (B) in ingredient (E) in a range from room temperature to the reflux temperature of the solvent and bring about a reaction, then add a mixture of ingredient (G) in a mixture of ingredients (C) and (D), or a mixture of ingredients (C), (D), and (G), and mix for one minute to 20 hours in a range from room temperature to the reflux temperature of the solvent. Ingredient (F) may be admixed after cooling.

[0040] The curable acryloxy-functional silicone composition according to the present invention is cured in a very short time by irradiation with high-energy radiation after application to various kinds of base materials and drying. Here, "high-energy radiation" is light radiation having a short wavelength and great irradiation energy to promote a chemical reaction, being selected from ultraviolet radiation, electron beam radiation, and gamma radiation, and ultraviolet radiation is preferably used industrially. A cured thin-film layer is formed in a very short time when ultraviolet radiation is used. The exposure rate of ultraviolet radiation is at least 2 mJ/cm ² , preferably 10 to 2000 mJ/cm ² . Ingredient (F) may be mixed when electron beam radiation or gamma (y) radiation is used as the high-energy radiation. The composition of the present invention is dried at normal temperature, but may be heated in the case of drying faster.

[0041] The above acryloxy-functional silicone composition curable by high-energy radiation is excellent in storage stability, and can form a highly hard thin-film layer that is excellent in abrasion resistance, transparency, water repellency, close adhesiveness, weather resistance, and/or ultraviolet radiation resistance after curing. Advantages of further suppression of exudation of oil from the cured film and excellent stability over time of the cured film are provided by reacting ingredients (A) and (B) in advance. In the present invention, the above curable acryloxy-functional silicone composition is applied onto a base material, particularly a sheet-form base material, and a layer of cured silicone film is formed on the base material by irradiating with high-energy radiation, specifically ultraviolet radiation, electron beam radiation, or gamma radiation. The thin-film layer thus formed has characteristics of favourable applicability of a ceramic slurry on the layer, and of ease of release of a dielectric ceramic-forming material obtained after drying of the slurry, from the layer. The curable silicone composition of the present invention therefore is suitable for use as a release agent composition for a release film for dielectric ceramic-forming material, particularly, a release film for forming a ceramic green sheet.

Application method and base material

[0042] The method used to apply the curable acryloxy-functional silicone composition onto a sheet-form base material can be any optional method, and examples include dip coating method, curtain coating method, gravure coating method, bar coating method, spray coating method, spin coating method, knife coating method, roll coating method, die coating method, and other well-known coating methods.

[0043] The thickness of the layer of the cured silicone composition when the curable acryloxy-functional silicone composition is applied onto a sheet-form base material and cured is not particularly limited, but it preferably 0.01 to 3 μιτι, more preferably 0.03 to 1 μιη. When the thickness of the layer of cured silicone composition on the sheet-form base material is less than 0.01 μηη, the layer might not exhibit sufficient function as a release agent layer when it is used as a release film for forming a ceramic green sheet. Meanwhile, when the thickness of the layer of cured silicone composition on the sheet-form base material is greater than 3 Mm, blocking might occur when the obtained release film for dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet is taken up into a roll form.

[0044] The base material on which the composition of the present invention is applicable is not particularly limited. Examples of materials of base materials include: polyethylene, polypropylene, polymethylpentene, and other polyolefin-based resins; polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, copolymers thereof, and other polyester-based resins; polyoxymethylene and other polyamide-based resins; polystyrene, poly(meth)acrylic ester, polyacrylonitrile, polyvinyl acetate, polycarbonate, cellophane, polyimide, polyetherimide, polyphenylenesulfone, polysulfone, polyether ketone, ionimer resins, fluorine resins, and other thermoplastic resins; and melamine resin, polyurethane resin, epoxy resin, phenol resin, unsaturated polyester resin, alkyd resin, urea resin, silicone resin, and other heat-curable resins. The shape of the base material is not particularly limited, but a sheet-form base material is commonly used in order to produce a release film to form a ceramic green sheet. A thermoplastic plastic film, in particular, is preferable as the base material. The thickness of the base material is not particularly limited, but is normally in a range of 5 to 100 pm when in sheet form. The film may be constituted by a single layer or by multiple layers of two or more layers including the same kind or different kinds of plastic. The sheet-form base material used in the present invention is preferably a plastic film, particularly a polyester film, and especially a polyethylene terephthalate film. A biaxially stretched polyethylene terephthalate film is especially preferably used as the sheet-form base material. A polyethylene terephthalate film tends not to collect dust, or the like, during processing, use, and the like. Accordingly, poor application of ceramic slurry on the sheet-form base material, which is caused by dust, or the like, can be advantageously prevented. Treating the polyethylene terephthalate film for static prevention and using this as a sheet-form base material also is advantageous for prevention of the occurrence of poor application of ceramic slurry on the sheet-form base material, or the like.

[0045] The thickness of the sheet-form base material is commonly 10 to 300 pm, preferably 15 to 200 pm, and particularly preferably 20 to 125 pm.

[0046] Surface treatment by oxidation method, roughening method, or the like, or primer treatment can be applied on one side or both sides of the sheet-form base material as desired in order to improve the close adhesiveness between the silicone composition applied and cured on the sheet-form base material and the surface of the sheet-form base material. Examples of oxidation methods include corona discharge treatment, plasma discharge treatment, chromium oxide treatment (wet type), flame treatment, hot blast treatment, ozone treatment, and irradiation with ultraviolet radiation. Examples of roughening methods include sand blasting method and thermal spraying treatment method. Another example of a surface treatment method is well-known anchor treatment using urethane resin. A surface treatment method suitable for the kind of sheet-form base material can be selected, but the corona discharge treatment method is given as a preferred method due to the extent of the desired effect obtained by surface treatment of the sheet-form base material and the convenience of operation.

[0047] Another layer, in addition to the above-described static prevention layer, furthermore may be provided as optionally selected on the surface of the sheet-form base material on the side opposite the one having the layer of cured silicone composition, or between the sheet-form base material and the layer of silicone composition.

[0048] A sheet-form article including a sheet-form base material and a cured layer obtained by applying and curing the acryloxy-functional silicone composition curable by high-energy radiation of the present invention is highly suitable for use as a release film for dielectric ceramic-forming material, particularly a release film for forming a ceramic green sheet. A ceramic green sheet can be fabricated by a method including a step of applying a ceramic slurry on the release film for forming a ceramic green sheet of the present invention, that is, on the side of the cured silicone composition, and drying the slurry. More specifically, a ceramic green sheet is formed by applying a ceramic slurry on the surface of the layer of cured silicone composition formed on the release film for forming a ceramic green sheet, by an optional application method, for example, slot die application method or doctor blade method, and furthermore drying. At this time, when a release film for forming a ceramic green sheet having a release layer formed using the curable silicone composition of the present invention is used, the occurrence of so-called "end contraction," in which the ends of the applied ceramic slurry contract and the thickness of the ends becomes thicker than the interior portion, is suppressed. In addition, the occurrence of pin holes on the surface applied with ceramic slurry and the occurrence of uneven application of ceramic slurry also are suppressed. Also, because the surface including the cured silicone composition has favourable releasability when the release film for forming a ceramic green sheet of the present invention is used, even when a thin-film ceramic green sheet having low strength is formed thereon, there is no occurrence of cracking, breakage, or other unfavourable situation in the ceramic green sheet, and the ceramic green sheet can be release with low releasing force from the layer of cured silicone there under. Thus, the release film for forming a ceramic green sheet of the present invention has excellent applicability to a ceramic slurry and excellent releasability from a ceramic green sheet formed thereafter.

[0049] The present invention is described more specifically below based on examples. In the description of the example below, "Me" represents a methyl group, and "Vi" represents a vinyl group.

Example

[0050] 8.56 g of toluene, 8.53 g of isobutanol, 21.3 g of a mixture of dipentaerythritol hexaacrylate (60 wt%) and dipentaerythritol (monohydroxy)pentaacrylate (40 wt%) (quantity of acrylate-functional groups: 0.22 moles), and 0.01 g of dibutylhydroxytoluene were put into a flask and stirred. 0.457 g of an amine-modified dimethylpolysiloxane fluid expressed by the average molecular formula: NH ₂ C ₃ H ₆ -Me2SiO(Me ₂ SiO) ₉ SiMe ₂ -C ₃ H ₆ NH2 (quantity of amine groups: 0.0006 moles) was next added, the mixture was heated to 50°C and stirred for one hour, and a reaction mixture was thus obtained. 5.3 g of

3-methacryloxypropyltrimethoxysilane, 53.3 g of a dispersion of colloidal silica in IPA (concentration 30 wt%, mean particle size of colloidal silica 13 nm), and 0.53 g of water were next added to this in sequence, and the mixture was further stirred for one hour. The mixture was cooled to room temperature, 2.25 g of a photopolymerization initiator [trade name: Irgacure 184; manufactured by Ciba-Geigy Japan Ltd.] and 4.0 mg of phenothiazine were then added, and a composition I was thus prepared. This composition I was applied onto a PET film having a thickness of 38 microns so that the quantity applied after drying was 0.15 g/m ² , the material was dried for 30 seconds in a hot blast circulation-type oven heated to 120°C, then cured by 600 mJ/cm ² UV irradiation, and an application film I having a silicone film cured on the PET film was thus obtained. A binder resin solution I for ceramic slurry containing 3.0 parts of separately prepared polyvinyl butyrate resin (BM-1 , manufactured by Sekisui Chemical Co., Ltd.), 55.0 parts of toluene, 33.0 parts of methanol, and 9.0 parts of n-butanol was applied onto the application film I by wire bar so that the film thickness after drying was 1.6 to 2.0 microns, the material was dried for 90 seconds in a hot blast circulation-type oven heated to 105°C, and a cured film I of ceramic slurry binder resin was thus obtained. Upon visual observation of the surface of the film, the cured film I was applied uniformly, and no shedding of the binder resin solution was observed even at the ends of the film.

Comparative example

[0051] A solvent-type silicone release agent composition, containing 19.0 parts of polydimethylsiloxane having both ends of the molecular chain closed by trimethylsiloxy groups and having a hexenyl group on a side chain, 9.0 parts of polydimethylsiloxane having both ends of the molecular chain closed by trimethylsiloxy groups and having a vinyl group on a side chain, 2.1 parts of dimethyl-hydrogen polysiloxane having both ends of the molecular chain closed by trimethylsiloxy groups and having a viscosity of 25 mPa-s (25°C), as a quantity such that the SiH/Vi ratio in the total composition was 1.5, 67 parts of toluene and 1.0 parts of 3-methyl-1-butine-ol, 2.0 parts of platinum-based hydrosilylation reaction catalyst (product name: SRX212; manufactured by Dow Corning Toray Co., Ltd.), 450 parts of toluene, and 450 parts of hexane, was used instead of composition I in the above example. The composition was applied onto a PET film having a thickness of 38 microns so that the quantity applied after drying was 0.15 g/m ² , the material was dried for 30 seconds in a hot blast circulation-type oven heated to 120°C, then cured by 600 mJ/cm ² UV irradiation, whereby an application film II having a silicone film cored on the PET film was obtained. The above binder resin solution I for ceramic slurry was applied onto the application film II and dried, and a cured film II of ceramic slurry binder resin was thus obtained. Upon visual observation of the surface of the film, the cure film II was not applied uniformly, and irregularity of the binder resin solution was confirmed particularly at the ends of the coating film.

[0052] The acryloxy-functional silicone composition curable by high-energy radiation used in the present invention contains the above ingredients (A) to (C) as necessary ingredients, and may contain ingredients (D) and (E) as optionally selected ingredients, and is excellent in storage stability. This composition can form a highly hard cured film that is excellent in abrasion resistance, transparency, water repellency, and close adhesiveness to the base material. The cured film is excellent in applicability to a ceramic slurry, and is markedly excellent in releasability of a dielectric ceramic-forming material, more specifically, a ceramic green sheet, obtained by drying. A film obtained by applying this curable silicone composition onto a sheet-form base material and curing exhibits uniform applicability of a ceramic slurry onto the cured silicone composition, and is suitable for use in a release film for dielectric ceramic-forming material, and particularly a release film for forming a ceramic green sheet.