JP7473865B2 - Silicone release polyester film - Google Patents

Description

The present invention relates to a silicone release polyester film, and more specifically to a silicone release polyester film that has light release properties and wettability suitable for molding thin ceramic green sheets used in the manufacture of multilayer ceramic capacitors, and can prevent tears and pinholes in the ceramic green sheets.

In the manufacture of multilayer ceramic capacitors, release films are used as carrier films for molding ceramic green sheets (also called ceramic sheets or green sheets). In particular, polyester films are used as the base material for release films, in terms of dimensional stability and heat resistance. In recent years, as multilayer ceramic capacitors have become smaller and larger in capacity, the thickness of ceramic green sheets has also become thinner and thinner, and as a result, the thickness of the sheets after drying is in the range of 1 μm or less. Therefore, two points are required for carrier films: easy peelability and pinhole resistance. Regarding the former, easy peelability is required because the rigidity of the ceramic green sheets decreases due to thinning, and the peeling force of conventional release films causes tears when peeling the green sheets. Regarding the latter, slight repelling defects during the application of ceramic slurry can penetrate the sheet to generate pinholes, significantly worsening the yield of multilayer ceramic capacitors, so the wettability and coating uniformity of the release layer of the release film are required. In addition, the use of emulsion-type release agents using water-based solvents is required from the standpoint of environmental consideration and safety.

Regarding these issues, Patent Document 1 proposes adding a component made of a silicone resin having a trifunctional unit siloxane or tetrafunctional unit siloxane structure, but does not provide a specific silicone resin content, and there is no mention of emulsion-type release agents.

Japanese Patent Application Laid-Open No. 9-1527

The present invention has been made in view of the above-mentioned background art, and its object is to provide a silicone release polyester film that can be suitably used as a carrier film in the manufacture of multilayer ceramic capacitors, and that has both easy peelability and good wettability, which is particularly suitable for molding thin ceramic green sheets.

As a result of extensive research, the inventors discovered that under certain conditions, it is possible to achieve both light release and good wettability even when using emulsion-type silicone, and thus completed the present invention.

That is, the present invention employs the following configuration to achieve the above object.
1. A silicone release polyester film for molding ceramic green sheets, comprising, on at least one side of a polyester film, an aqueous dispersion of one or more types of silicone A containing an alkenyl group and/or a Q unit represented by SiO _4/2 , and an aqueous dispersion of silicone B having a hydrogen atom directly bonded to a Si atom represented by a Si-H group, and having a coating layer formed using a release coating composition containing a crosslinking reaction inhibitor, a platinum catalyst, and a nonionic emulsifier, wherein the content of Si atoms bonded to alkenyl groups is in the range of 0.05 mol % to 20 mol % relative to the total Si atoms in the silicone A, and the content of Si atoms contained in the Q unit is in the range of 0.05 mol % to 60 mol %.
2. The silicone release polyester film for molding ceramic green sheets according to item 1, wherein the coating layer has a surface free energy of 10 mN/m or more and 40 mN/m or less.
3. The silicone release polyester film for molding ceramic green sheets according to item 1 or 2, wherein the polyester film has a surface layer that does not contain particles, and the coating layer is formed on the surface layer.

The silicone release polyester film of the present invention has a small peeling force against thin ceramic green sheets when manufacturing multilayer ceramic capacitors, and furthermore, repelling defects during ceramic slurry coating are suppressed, so pinholes in the ceramic green sheets can be reduced. This in turn reduces the defective rate of thin multilayer ceramic capacitors.

The following describes an embodiment of the present invention.

[Release Coating Composition]
The silicone release polyester film of the present invention is a silicone release polyester film for molding ceramic green sheets, which comprises _, on at least one side of a polyester film, an aqueous dispersion of one or more types of silicone A containing an alkenyl group and/or a Q unit represented by SiO 4/2, and an aqueous dispersion of silicone B having a hydrogen atom directly bonded to a Si atom represented by a Si-H group, and which has a coating layer formed using a release coating composition containing a crosslinking reaction inhibitor, a platinum catalyst, and a nonionic emulsifier, in which, relative to all Si atoms in the silicone A, the Si atoms bonded to alkenyl groups are in the range of 0.05 mol % to 20 mol %, and the Si atoms of the Q units are in the range of 0.05 to 60 mol %.
Each component will be described in detail below.

(Silicone A containing alkenyl groups and/or Q units represented by SiO _4/2 )
In the present invention, the silicone A containing alkenyl groups and/or Q units represented by SiO _4/2 (hereinafter simply referred to as Q units) is exemplified by organopolysiloxanes having the following general formula (I).
R1 _a R2 _b SiO _{(4-a-b) / 2} ... (I)
(In formula (I), R1 is an alkenyl group having 2 to 8 carbon atoms, R2 is a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, a is an integer of 0 to 3, b is an integer of 0 to 3, and a+b≦3 is satisfied.)

Examples of alkenyl groups having 2 to 8 carbon atoms represented by R1 include vinyl groups, allyl groups, butenyl groups, pentenyl groups, and hexenyl groups, with vinyl groups being particularly preferred. Examples of alkyl groups represented by R2 include methyl groups, ethyl groups, propyl groups, and butyl groups, while examples of aryl groups include phenyl groups and tolyl groups. In particular, it is preferred in terms of light peelability that 50 mol % or more of the substituents of R2 are methyl groups.

The content of Si atoms bonded to alkenyl groups is in the range of 0.05 to 20 mol%, preferably 0.1 to 17 mol%, and more preferably 0.2 to 15 mol%, of all Si atoms in the silicone containing alkenyl groups and/or Q units contained in the release coating composition. If the content of Si atoms bonded to alkenyl groups is less than the lower limit, the curing speed of the composition decreases, making it difficult to efficiently form a cured silicone coating during film formation, which will be described later. If the proportion of Si atoms bonded to alkenyl groups exceeds the upper limit, excessive wettability is imparted, resulting in strong adhesion to the green sheet, which ultimately causes heavy peeling.

In addition, the silicone containing alkenyl groups and/or Q units must contain Q units. However, when multiple types of silicone containing alkenyl groups and/or Q units are included, it is sufficient that any of them contains Q units. By including Q units in the silicone-based release layer, the coating hardness of the silicone-based release layer increases, and the viscosity loss when peeling off the green sheet can be suppressed, leading to light peeling. In addition, when silicone containing Q units is included in the alkenyl group-containing silicone, wettability is improved, so pinhole defects during green sheet coating can be suppressed. The content of Si atoms included in Q units is 0.05 to 60 mol%, preferably 0.1 to 55 mol%, and more preferably 1.0 to 50 mol%, based on the total Si atoms in the silicone containing alkenyl groups and/or Q units. If the content of Si atoms included in Q units is less than 0.05 mol%, sufficient coating hardness cannot be achieved, and light peeling cannot be achieved. If the content exceeds 60 mol%, excessive wettability is imparted, and strong adhesion to the green sheet occurs, resulting in heavy peeling.

The silicone containing alkenyl groups and/or Q units of the present invention can be produced by known methods. The silicone containing alkenyl groups and/or Q units of the present invention is contained in the composition in the form of an aqueous dispersion.

(Silicones having hydrogen atoms directly bonded to Si atoms represented by Si-H groups)
An example of the silicone in the present invention having a hydrogen atom directly bonded to a Si atom represented by a Si—H group (hereinafter sometimes referred to as a Si—H group-containing silicone) is an organohydrogenpolysiloxane having a structure represented by the following general formula (II):
_{R3cHdSiO ( 4-cd)/2} ... (II)
(In formula (II), R3 is a monovalent saturated hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group, c is an integer of 0 to 2, d is an integer of 1 to 3, and c+d≦3.)

Examples of alkyl groups represented by R3 include methyl groups, ethyl groups, propyl groups, and butyl groups, and examples of aryl groups include phenyl groups and tolyl groups. In particular, it is preferable for 50 mol % or more of the substituents of R3 to be methyl groups in terms of light peelability.

From the viewpoint of curing properties, it is preferable that the Si-H group-containing silicone has at least three hydrogen atoms bonded to Si atoms, and preferably five or more hydrogen atoms bonded to Si atoms in one molecule of the silicone.

The Si-H group-containing silicone can be produced by a known method. The Si-H group-containing silicone of the present invention is contained in the composition in the form of an aqueous dispersion. The content of the Si-H group-containing silicone is preferably 1 to 60 parts by weight, more preferably 2 _to 50 parts by weight, and more preferably 3 to 40 parts by weight, when the total content of the silicone containing an alkenyl group and/or a Q unit represented by SiO 4/2 and the Si-H group-containing silicone is taken as 100 parts by weight. If the content is less than 1 part by weight, the curing reaction is unlikely to proceed, and sufficient coating hardness may not be obtained, and if the content exceeds 60 parts by weight, Si-H may precipitate excessively on the surface and adhere strongly to the green sheet, resulting in heavy peeling.

(Aqueous Solvent)
In the present invention, water is preferably used as the aqueous solvent for forming each of the above-mentioned aqueous dispersions. By using an aqueous solvent, it is possible to form a silicone release layer without using explosion-proof equipment and recovery equipment that are required for organic solvents during the film formation process.

(Nonionic emulsifier)
Each aqueous dispersion is prepared using a nonionic emulsifier to increase the stability and shear resistance of the aqueous dispersion. After extensive research, the inventors found that the emulsifier must be a nonionic emulsifier in order to prevent the aqueous dispersions from flocculating and not affect the silicone curing reaction. Cationic emulsifiers affect the silicone curing reaction, and are localized in the coating film, for example, bleed out to the surface, affecting the releasability and causing heavy peeling. Although the details are unclear, when a cationic emulsifier is used, the silicone aqueous dispersions tend to flocculate.

The nonionic emulsifier preferably has an HLB value in the range of 6 to 18, and examples thereof include at least one selected from alkylene oxide adducts such as alkylene oxide adducts of higher alcohols or higher fatty acids, esters of alkylene oxide adducts of higher fatty acids and alcohols, alkylene oxide adducts of alkanolamides, alkylene oxide adducts of sorbitan esters, and alkylene oxide adducts of higher fatty acid glycerides. Here, the HLB value is a value calculated by Griffin's formula.

Examples of alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide. One or more of these may be used. When more than one is used, the addition may be in the form of block or random, but the HLB value is preferably in the range of 8 to 18, and more preferably in the range of 10 to 15. Among these nonionic emulsifiers, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, etc. are preferred. If a nonionic emulsifier with an HLB value outside this range is used as an emulsifier for a silicone water dispersion, the emulsification dispersion power and the stability of the water dispersion may decrease. The nonionic emulsifier is preferably used in the range of 0.1 to 20% by weight, more preferably in the range of 0.2 to 15% by weight, and even more preferably in the range of 0.5 to 10% by weight, based on the total solid content. If the amount is less than this range, emulsification tends to be poor, and if the amount is more than this range, heavy peeling may occur.

(Platinum-based catalyst)
In the release coating composition constituting the coating layer of the present invention, it is necessary to use a platinum-based catalyst in order to cause an addition reaction between one or more types of silicone containing an alkenyl group and/or a Q unit and a Si—H group-containing silicone.

Known platinum catalysts can be used, such as platinum chloride and chloroplatinic acid. Taking into account dispersibility in silicone, the platinum catalyst may be 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum(0) complex (Karstedt catalyst), which can be dispersed simultaneously with the silicone being emulsified to ensure uniform dispersion.

The amount of platinum catalyst is preferably in the range of 10 to 800 ppm by weight of platinum element per 100 parts by weight of one or more silicone water dispersions containing alkenyl groups and/or Q units and Si-H group-containing silicone water dispersion. By setting the weight in such a range, silicone can be sufficiently cured. In addition, the generation of silicone aggregates can be suppressed, and a release polyester film with excellent surface properties can be obtained. If the weight ratio of platinum element exceeds the upper limit, the addition reaction between alkenyl groups and Si-H groups is accelerated, tending to generate silicone aggregates. From this viewpoint, the amount of platinum catalyst is more preferably 600 ppm or less, even more preferably 500 ppm or less, particularly preferably 200 ppm or less, very preferably 120 ppm or less, and most preferably 100 ppm or less. Also, if the weight ratio of platinum element is below the lower limit, the addition reaction does not proceed, tending to cause poor curing of silicone. From this perspective, the amount of platinum catalyst is more preferably 15 ppm or more, even more preferably 20 ppm or more, particularly preferably 25 ppm or more, and most preferably 80 ppm or more.

(Crosslinking reaction inhibitor)
In the present invention, it is necessary that the release coating composition contains a crosslinking reaction inhibitor in order to suppress the activity of the platinum-based catalyst at room temperature. The content of the crosslinking reaction inhibitor is preferably 5 to 1000 ppm, more preferably 10 to 700 ppm, and even more preferably 20 to 500 ppm, based on the weight of the coating solution used to form the coating layer.

If the content of the crosslinking reaction inhibitor is below the lower limit, the pot life will be reduced and silicone aggregates will tend to be more likely to occur due to the silicone addition curing reaction proceeding at room temperature. If the content of the crosslinking reaction inhibitor exceeds the above range, the addition curing reaction will tend to proceed less smoothly, silicone will tend to migrate to the mating material after it is peeled off, and the amount of reaction inhibitor that volatilizes during heat treatment will increase, which may lead to contamination of the inside of the oven.

(Other ingredients)
To the release coating composition of the present invention, an adhesion imparting agent, a colorant, an ultraviolet absorbing agent, particles, etc. may be further added within the range not impairing the object of the present invention.

[Base film]
As the polyester film constituting the silicone release polyester film of the present invention, known polyester films can be used, and known polyesters such as polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate), polyethylene naphthalenedicarboxylate, etc. Of these, polyethylene terephthalate is particularly preferred because it has a good balance between mechanical properties and moldability.

Each of the polyesters exemplified above may be a homopolymer, a copolymer containing one of these polyesters as the main component, or a blend. Here, the "main component" is 80 mol% or more based on the number of moles of the repeating structural unit of the polyester. The proportion of the main component is preferably 85 mol% or more, and more preferably 90 mol% or more. The copolymerization component or blend component is 20 mol% or less, preferably 15 mol% or less, and more preferably 10 mol% or less, based on the number of moles of the repeating structural unit of the polyester.

The polyester film may contain lubricant particles, colorants, antistatic agents, and antioxidants within the scope of the present invention. When surface flatness is required, it is preferable that the film does not substantially contain lubricant particles.

Polyesters are produced by known methods, such as an esterification reaction or transesterification reaction to obtain a polyester with a low degree of polymerization, followed by the use of a polymerization catalyst to increase the degree of polymerization.

Polyester films can also be obtained by known methods, and either a sequential stretching method or a simultaneous biaxial stretching method can be used. For example, polyester can be extruded in a molten state from the die of an extruder into a sheet, the resulting sheet is cooled and solidified to form an unstretched polyester film, and the unstretched polyester film obtained is stretched in the film-forming direction and the width direction. When the polyester film has a laminated structure, for example, a polyester for layer A and a polyester for layer B are prepared, laminated in a molten state, and co-extruded from a die into a sheet, and then film-formed according to the above-mentioned method.

In addition, it is preferable that the polyester film in the present invention does not contain particles. When the polyester film has a laminated structure, in addition to the structure in which all layers do not contain particles, it is preferable that at least one surface layer of the laminated polyester film (preferably the surface layer on the side where the coating layer is formed) does not contain particles. With such a structure, both surface smoothness and slipperiness can be achieved. In the present invention, not containing particles specifically refers to a particle content of 0.5% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less, even more preferably 0.01% by weight or less, and particularly preferably 0.005% by weight or less, based on the weight of the polyester film. In addition, when at least one surface layer of the laminated polyester film does not contain particles, it refers to a particle content of 0.5% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less, even more preferably 0.01% by weight or less, and particularly preferably 0.005% by weight or less, based on the weight of the layer. If particles are contained in the polyester film, the surface protrusions of the polyester film formed by the particles may transfer to the green sheet in a dented shape or cause the green sheet to penetrate.

[Coating layer]
In the present invention, a coating layer is formed on at least one surface of a substrate film using the release coating composition of the present invention. The coating layer of the present invention is formed by applying the release coating composition onto the substrate film and then drying the composition. The coating layer is preferably formed during a film forming process.

In the present invention, the coating layer thickness after drying is preferably 10 to 100 nm. If the coating layer thickness is less than the lower limit, the release characteristics may be insufficient, and if it exceeds the upper limit, the peel strength tends to increase and it becomes difficult to apply the coating liquid because it is necessary to make the coating liquid more concentrated or to increase the amount of coating. The thickness is more preferably 20 to 80 nm, and even more preferably 30 to 70 nm.

When applying a release coating composition onto a substrate film, an aqueous coating liquid containing the composition is prepared, and the solids concentration of the aqueous coating liquid is preferably 20% by weight or less, more preferably 1 to 10% by weight, based on the weight of the coating liquid. If the solids concentration in the aqueous coating liquid is below the lower limit, the coating ability onto the substrate film may be insufficient. If the solids concentration exceeds the upper limit, the stability of the coating liquid and the appearance of the coating layer may deteriorate. Water is preferably used as the aqueous solvent for adjusting the solids concentration.

The aqueous coating solution can be applied to the base film at any stage, but it is preferable to apply it during the polyester film manufacturing process, and more preferably to the polyester film before the orientation crystallization is completed.

Here, the polyester film before the crystal orientation is completed includes unstretched film, uniaxially oriented film obtained by aligning unstretched film in either the longitudinal direction (hereinafter, the direction of continuous film production, the longitudinal direction, or the MD direction) or the transverse direction (hereinafter, the direction perpendicular to the longitudinal direction, the width direction, or the TD direction), and further, film oriented by low-magnification stretching in both the longitudinal and transverse directions (biaxially oriented film before the film is finally re-stretched in the longitudinal or transverse direction to complete the orientation crystallization). Among them, so-called in-line coating is preferred, in which an aqueous coating solution of the above composition is applied to an unstretched film or a uniaxially oriented film, and the film is then stretched longitudinally and/or transversely and heat-set. The coating layer may be dried by a stretching process or heat-setting process after coating, and a drying process may be added as necessary. In addition, when the composition is cured using a catalyst to obtain a cured coating, the composition can be cured by a stretching process or heat-setting process, and a curing process may be added as necessary.

When applying the aqueous coating solution to a polyester film, it is preferable to subject the film surface to a physical treatment such as corona surface treatment, flame treatment, or plasma treatment as a preliminary treatment to improve coatability, or to use the above-mentioned emulsifier together with the composition as a wetting agent.

As a coating method, any known coating method can be applied. For example, roll coating, gravure coating, roll brushing, spray coating, air knife coating, impregnation, curtain coating, etc. can be used alone or in combination.

[Characteristics of release polyester film]
In the present invention, the peel strength of the ceramic sheet as measured by the test method described below is preferably less than 8 g/25 mm. More preferably, it is less than 5 g/25 mm. With such a peel strength, the ceramic sheet can be easily peeled off after it is formed without being torn.

In addition, in the present invention, the surface free energy of the release layer in the test method described below is preferably in the range of 10 mN/m to 40 mN/m, more preferably 12 mN/m to 38 mN/m, even more preferably 14 mN/m to 36 mN/m, and particularly preferably 15 mN/m to 35 mN/m. If the surface free energy of the release layer exceeds the above range, the adhesive force may increase and the release may become heavy. If it is below the above range, repelling defects may occur when the ceramic slurry is applied, which may cause pinhole defects.

[Application]
The silicone release polyester film of the present invention is used as a release polyester film used as a carrier film for molding a thin ceramic green sheet used in manufacturing a multilayer ceramic capacitor. When used for such purposes, since it has excellent light peelability, a thin green sheet having a thickness of 1 μm or less after drying is prepared on the release polyester film, and when the release polyester film is peeled off, the thin green sheet does not break, and since it has good wettability, it is possible to reduce pinholes in the ceramic green sheet and reduce the defective rate of thin multilayer ceramic capacitors.

The present invention will be further explained below with reference to examples. Various physical properties were evaluated by the following methods.

1. Evaluation of release polyester film (1) Coating uniformity of release layer A release polyester film was cut into A4 size, and the coating layer surface was visually observed using a fluorescent lamp and a halogen light to compare the number of aggregated coating defects, and the evaluation was performed according to the following criteria.
◎: No coating defects ○: 1-2 coating defects △: 3-5 coating defects ×: 6 or more coating defects

(2) Ceramic Sheet Removability 100 parts by weight of barium titanate (BaTiO ₃ ), 7 parts by weight of polyvinyl butyral, and 3 parts by mass of dioctyl phthalate were added to a mixed solvent of toluene:ethanol = 1:1 (volume ratio), and dispersed by a ball mill to prepare a slurry. This slurry was uniformly applied to the coating layer of a release polyester film so that the thickness after drying was 2 μm, and then dried to form a ceramic sheet. The release polyester film on which the ceramic sheet was formed was cut into 25 mm x 150 mm, and an adhesive tape (manufactured by Nitto Denko Corporation, product name "31B tape") was attached to the ceramic sheet side to prepare a test piece. This test piece was conditioned for 24 hours under conditions of 23 ° C and 50% humidity, and then the ceramic sheet was peeled off using a tensile tester at a peel angle of 180 ° and a peel speed of 300 mm / min, and the peel strength was measured. The peel strength of the ceramic sheet was judged to be superior or inferior based on the following index.
⊚: peel strength is less than 5 g/25 mm. ◯: peel strength is 5 g/25 mm or more and less than 8 g/25 mm. Δ: peel strength is 8 g/25 mm or more and 12 g/25 mm or less. ×: peel strength exceeds 12 g/25 mm or the ceramic sheet breaks.

(3) Surface free energy of release layer For samples that had been conditioned for 24 hours under conditions of 23 ° C. and 50% RH, a contact angle meter (DMo-501 manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the static contact angle when water was dropped and left to stand for 30 seconds. Similarly, the static contact angles of ethylene glycol and methylene iodide were measured, and the following simultaneous equations regarding the surface tension components of the release layer were established using the surface tension components of each liquid below (measured liquids of water, ethylene glycol, and methylene iodide are 1, 2, and 3, respectively, γLD is the dispersion force component of the liquid, γLP is the polar force component of the liquid, γLH is the hydrogen bond component of the liquid, γL is the total value of each surface tension component in the liquid, γSD is the dispersion force component of the release layer, γSP is the polar force component of the release layer, and γSH is the hydrogen bond component of the release layer. θ also represents the contact angle.).
(γSD·γLD1) ^1/2 + (γSP·γLP1) ^1/2 + (γSH·γLH1) ^1/2 = γL1 (1 + cos θ1)/2
(γSD·γLD2) ^1/2 + (γSP·γLP2) ^1/2 + (γSH·γLH2) ^1/2 = γL2 (1 + cos θ2)/2
(γSD·γLD3) ^1/2 + (γSP·γLP3) ^1/2 + (γSH·γLH3) ^1/2 = γL3 (1 + cos θ3)/2
The γLD, γLP, γLH, and γL of water, ethylene glycol, and methylene iodide are as shown in Table 1.

Next, the surface free energy γS of the release layer surface was calculated from the values of γSD, γSP and γSH obtained above using the following formula.
γS = γSD + γSP + γSH

[Examples 1 to 15, Comparative Examples 1 to 7]
Polyethylene terephthalate ([η]=0.64 dl/g, Tg=78°C) containing 0.1% by weight of calcium carbonate particles having an average particle size of 0.7 μm as the A layer and polyethylene terephthalate ([η]=0.64 dl/g, Tg=78°C) not containing particles as the B layer were laminated in a molten state to form a two-layer structure of A layer/B layer, extruded from the die of an extruder, cooled by a cooling drum in a conventional manner to obtain an unstretched film, and then stretched 3.6 times in the machine direction at 80°C, after which a coating solution having the composition shown in Tables 4 and 5 was uniformly applied to the B layer surface of the film by a roll coater. The coating solution used was one that had been prepared within 24 hours.

The coated film was then dried at 115°C, stretched 4.0 times in the transverse direction at 145°C, and further heat-set at 230°C for approximately 10 seconds to obtain a release polyester film (total thickness 25 μm, layer A thickness 22 μm, layer B thickness 3 μm) having the coating layers shown in Tables 4 and 5, which was then evaluated. The evaluation results are shown in Tables 4 and 5.

The ingredients in Tables 4 and 5 were prepared as follows:

<Water Dispersion of Silicone A Containing Alkenyl Group and/or Q Unit Represented by SiO4 _/2 >
Production Example 1 (Water Dispersion of Silicone Containing Alkenyl Group and Q Unit Represented by SiO _4/2 , Silicones A-1 to A-13)
Using an emulsifier capable of stirring the entire inside of the container (manufactured by NP Labs, device name "Ultra Planetary Mixer"), raw materials consisting of 98% by weight of silicone containing alkenyl groups and Q units represented by SiO _4/2 , and 2% by weight of polyoxyethylene lauryl ether (manufactured by Kao Corporation, product name "Emulgen 109P") as a surfactant were mechanically emulsified in an aqueous medium to obtain a silicone water dispersion with a solid content of 20% by weight. In addition, the emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification. In addition, the composition of silicone containing alkenyl groups and Q units represented by SiO _4/2 is represented by formula (I), where R1 is a vinyl group and R2 is a methyl group, and only one vinyl group is bonded to the silicon to which the vinyl group is directly bonded, and the content of the silicon atoms bonded to the alkenyl groups and the silicon atoms contained in the Q units relative to the total Si atoms in silicone A was adjusted to the amount listed in Table 2. In addition, the number average molecular weight was adjusted to be 25,000 in all cases.

Production Example 2 (Water Dispersions of Silicone Containing No Alkenyl Group and Containing Q Units Represented by SiO _4/2 , A-14 to A-18)
This silicone was prepared in the same manner as Silicone A-1, except that a silicone not containing an alkenyl group but containing a Q unit represented by SiO _4/2 was used instead of a silicone containing an alkenyl group and a Q unit represented by SiO _4/2 . The content of silicon atoms contained in the Q unit relative to the total Si atoms in Silicone A was adjusted to the amount shown in Table 3.

Production Example 3 (Water Dispersion of Silicone Containing Alkenyl Groups and Not Containing Q Units Represented by SiO _4/2 , A-19)
This silicone was prepared in the same manner as Silicone A-1, except that instead of a silicone containing an alkenyl group and a Q unit represented by SiO _4/2 , a silicone containing an alkenyl group and not containing a Q unit represented by SiO _4/2 was used. The content of Si atoms bonded to alkenyl groups relative to the total Si atoms in Silicone A was adjusted to 10 mol %.

<Aqueous Dispersion of Si—H Group-Containing Silicone B>
Using an emulsifier capable of stirring the entire inside of a container (manufactured by NP Labs, device name "Ultra Planetary Mixer"), raw materials consisting of 98% by weight of Si-H group-containing silicone and 2% by weight of polyoxyethylene lauryl ether (manufactured by Kao Corporation, product name "Emulgen 109P") as a surfactant were mechanically emulsified in an aqueous medium to obtain an aqueous dispersion of Si-H group-containing silicone with a solid content of 10% by weight. The emulsion particle size was adjusted by adjusting the stirring speed and stirring time during emulsification. The composition of the Si-H group-containing silicone was adjusted so that in formula (II), R3 was a methyl group, only one hydrogen group was bonded to the silicon to which a hydrogen group was directly bonded, no hydrogen atom was bonded to the terminal silicon atom, the number of repetitions of the unit having a silicon atom to which a hydrogen group was directly bonded was 30, and the number average molecular weight was 4500.
Platinum-based catalyst: A platinum-based catalyst emulsion (manufactured by Shin-Etsu Chemical Co., Ltd., product name "CATPM-10A") was used.
Crosslinking reaction inhibitor: 1-ethynylcyclohexanol (Lancaster) was used without purification.

<Coating Solution>
As a release coating composition, 0.02 parts by weight of a platinum-based catalyst per 100 parts by weight of a silicone water dispersion containing an alkenyl group and/or a Q unit, a Si—H group-containing silicone water dispersion, a silicone water dispersion containing an alkenyl group and/or a Q unit, and a Si—H group-containing silicone water dispersion, and 150 ppm of a crosslinking reaction inhibitor per weight of the coating solution used to form a coating layer were mixed, and the solids concentration of the coating solution was diluted with water to obtain a target coating layer thickness, to prepare a coating solution.

The silicone release polyester film of the present invention has a small peeling force against thin ceramic green sheets during the production of multilayer ceramic capacitors, and furthermore suppresses repelling defects during ceramic slurry coating, making it possible to reduce pinholes in ceramic green sheets, and thereby reducing the defective rate of thin multilayer ceramic capacitors, making it extremely valuable industrially.

Claims (4)

A silicone release polyester film for molding a ceramic green sheet, comprising a polyester film and a coating layer formed on at _least one side thereof using a release coating composition which contains an aqueous dispersion of one or more types of silicone A containing an alkenyl group and a Q unit represented by SiO4/2, and an aqueous dispersion of silicone B having a hydrogen atom directly bonded to a Si atom represented by a Si-H group, and which also contains a crosslinking reaction inhibitor, a platinum-based catalyst, and a nonionic emulsifier;
the content of Si atoms bonded to alkenyl groups is in the range of 0.2 to 15 mol % relative to all Si atoms in silicone A, the content of Si atoms contained in Q units is in the range of 10 to 50 mol %, and the surface free energy of the coating layer is 10 mN/m or more and 40 mN/m or less;
A silicone release polyester film for molding ceramic green sheets, wherein when the content of Si atoms contained in Q units relative to all Si atoms in silicone A exceeds 20.30 mol %, the blending amount of silicone B exceeds 25.8 parts by weight. 2. The silicone release polyester film for molding ceramic green sheets according to claim 1, wherein the surface free energy of the coating layer is from 10 mN/m to 23 mN/m . The silicone release polyester film for molding ceramic green sheets according to claim 1, wherein the polyester film has a surface layer, the particle content is 0.5% by weight or less based on the weight of the polyester film, and a coating layer is formed on the surface layer. The silicone release polyester film for molding ceramic green sheets according to claim 1 or 3, wherein the coating layer has a thickness of 10 to 100 nm after drying.