JP3911653B2 - Release film for manufacturing ceramic green sheets - Google Patents

Description

（ただし式中、Ｒ１は、メチル基および／またはフェニル基、Ｖｉはビニル基を示す。）
本発明において、シリコーン系樹脂被膜の形成する際の塗布方法は特に限定されないが、通常、ベンゼン、トルエン、キシレン等の芳香族炭化水素、シクロヘキサン、ｎ−ヘキサン、ｎ−ヘプタン等の脂肪族炭化水素、パークロロエチレン等のハロゲン化炭化水素、酢酸エチル、メチルビニルケトン等の有機溶媒にシリコーン系樹脂を４〜１８重量％の濃度で溶解した塗剤を用い、ダイレクトグラビアコーター、マイクログラビアコーター、リバースグラビアコーター、ダイレクトキスコーター、リバースキスコーター、コンマコーター、ダイコーター、バー・ロッドタイプの塗布装置等によって塗布することによって得られる。この中でも、マイクログラビアコーター、ダイレクトキスコーター、リバースキスコーターを用いるとシリコーン系樹脂皮膜の厚みの均一性が良好となり塗布ムラの発生が少ないので好ましい。
【００２１】
本発明において、離型用被膜のないポリエステルフィルム背面の臨界表面張力Ａ（単位：ｄｙｎｅ／ｃｍ）が下記（１）式を満足することが必要である。好ましくは、下記（２）式を満足することが望ましい。
【００２２】
４６ ≦ Ａ ≦ ７０ ‥‥ （１）
５０ ≦ Ａ ≦ ６０ ‥‥ （２）
該臨界表面張力が４６ｄｙｎｅ／ｃｍ未満であるとオリゴマーの析出抑制効果がほとんど見られなくなり好ましくなく、また、７０ｄｙｎｅ／ｃｍを越えるとセラミックグリーンシートを形成後、ロール状に巻いた後の離型用被膜面と該背面でブロッキングが発生し易くなるため好ましくない。ここで、セラミックグリーンシート製造工程における加熱処理で離型フィルムの離型面の背面側にオリゴマーが析出すると、該セラミックグリーンシートを積層後、焼成する工程でセラミックコンデンサ内部にボイドが発生し易くなり、かつ、積層型セラミックコンデンサを作製後に通電した際にショート等の初期不良が発生し易くなるため耐電圧不良率が大幅に上昇し好ましくない。
【００２３】
本発明における上記特定範囲の臨界表面張力は、プラスチックフィルムをスパークギャップ方式や半導体方式のコロナ放電処理装置等を用いて処理することで得られるが、もとより、本発明は、これらの方式・装置に限定されるものではない。
【００２４】
また、この際の臨界表面張力Ａは、プラスチックフィルムに対するコロナ処理装置の出力ならびに処理速度を調整することによって所望の値にすることができる。
【００２５】
また、本発明におけるコロナ放電処理とは、空気中、窒素雰囲気中、二酸化炭素雰囲気中で電極とフィルム表面および誘電体ロールの間に一定の電圧をかけ発光放電させる処理のことをいう。同処理を行うことによりポリエステルフィルム、特には、ポリエチレンテレフタレートフィルムを１５０℃以上に加熱処理した時のオリゴマー発生が著しく抑制される。
【００２６】
本発明におけるオリゴマーとは、ポリエステルフィルムを構成するポリマーに微量含有される分子量１５００以下の低分子量のポリマーをいう、特に、ポリエチレンテレフタレートの場合は、３量体を主成分とする環状オリゴエステル（環状オリゴマー）として１．５〜４重量％程度含有し、１００℃あるいは１５０℃の温度で３０分間位加熱するとポリエチレンテレフタレートフィルム内を拡散し該フィルム表面に六角形状の結晶として析出する。
【００２７】
また、該離型フィルムを１５０℃の温度で３分間加熱処理後、ポリエステルフィルム面側を４００倍の顕微鏡にて１０視野観察した際（面積０．５ｍｍ²）に、円相当径で２μｍφ以上のオリゴマー析出物が５０個未満、好ましくは２０個以下であるとオリゴマーの析出抑制効果が良好であるといえる。
【００２８】
【実施例】
本発明を実施例にて具体的に説明するが、本発明はそれらに限定されるものではない。
【００２９】
なお、離型フィルムの特性評価は下記の方法にて行った。
【００３０】
（１）オリゴマー析出性
離型フィルムを１５０℃の温度で３分間あるいは１０分間加熱後、離型面の背面側にアルミニウムを蒸着し、４００倍の微分干渉顕微鏡にて１０視野（面積０．５ｍｍ²）観察し、熱処理前の離型面の背面側と比較で増加の見られた析出物の円相当径で２μｍφ以上のものの個数をカウントし、オリゴマー析出性を評価する。この際、前記オリゴマー個数が１００個以上のものを「××」、５０〜１００個のものを「×」、５０個未満を「△」、２０個未満を「○」、１０個未満を「◎」とした。「△」以上であれば、オリゴマー析出性が良好であるといえる。
【００３１】
（２）離型性
離型フィルムとポリエステル粘着フィルム（日東電工製３１Ｂテープ：５０ｍｍ幅）を５ｋｇのローラーで圧着させながら貼り合わせ、２０℃で２０時間放置した後の１８０゜剥離強度をテンシロンで測定する。ここで、剥離力が３０ｇ以下であれば良好であるといえる。
【００３２】
（３）セラミックスシートのブロッキング性
離型フィルムの離型層上に下記組成のセラミックスラリーをドクターブレード法にて塗布し、乾燥固化させた後、離型フィルムとセラミックグリーンシートを貼り合わせた状態で１０シート重ね、２０ｇ／ｃｍ²の荷重下で４０℃、２週間放置した。この後、該セラミックグリーンシートを剥離し厚さ１５μｍのセラミックグリーンシートを得た。この際のセラミックグリーンシートを光学顕微鏡で観察し、ピンホールが多数見られたものを「×」、ピンホールが少し見られたものを「△」、ピンホールが全く見られないないものを「○」とした。
【００３３】
「セラミックスラリーの組成」
アルミナ ５３ 重量部
酸化バリウム ８ 重量部
酸化ケイ素 ３６ 重量部
ポリビニルブチラール ３０ 重量部
ジクロルエタン ８０ 重量部
（４）セラミックスシート積層・焼成後のブリスター発生性（ボイド発生性）離型フィルムの離型層上に前記組成のセラミックスラリーをドクターブレード法にて塗布し、乾燥固化させた後、離型フィルムとセラミックグリーンシートを貼り合わせた状態で１０シート重ね、２０ｇ／ｃｍ²の荷重下で４０℃、２週間放置した。この後、該セラミックグリーンシートを剥離し厚さ１５μｍのセラミックグリーンシートを得た。これを５枚重ね合わせ８００ｋｇ／ｃｍ２でプレス後、１０００℃の電気炉中にて１時間加熱した。この際に積層セラミックシートの表面にブリスター（隆起）が多数見られたものを「×」、ブリスターが少し見られたものを「△」、ブリスターが僅かに見られるものを「○」、ブリスターが全く見られないないものを「◎」とした。
【００３４】
（５）臨界表面張力
基材フィルムの場合は、ＪＩＳ−Ｋ−６７６８に基づき市販の濡れ張力試験液にて測定した。また、液状塗剤は、濡れ張力の判明している合成樹脂板に該塗剤を塗布しハジキ度合いから臨界表面張力を求めた。
【００３５】
［実施例１］
厚み５０μｍの２軸延伸ポリエステルフィルム「東レ( 株) 社製“ルミラーＳ２８」の片面にコロナ放電処理を行い、臨界表面張力５６ｄｙｎｅ／ｃｍとした。
【００３６】
さらに、該処理面の背面に離熱硬化性シリコーン系樹脂塗剤として下記組成Ｂをグラビアロール（＃２００、斜線タイプ）を用い塗工し、１２０℃のオーブンにて１５秒乾燥、熱硬化させ離型フィルムを得た。該離型フィルムの離型面の背面側の臨界表面張力は５１ｄｙｎｅ／ｃｍであった。
【００３７】
結果を表１に示したが離型性、オリゴマー析出性ともに良好である。
【００３８】
「熱硬化性シリコーン系樹脂塗剤・組成Ｂ」
１）信越化学（株）製ＫＳ８４７Ｈ １０重量部
２）信越化学 (株) 製ＰＬ−５０Ｔ ０．１０重量部
３）トルエン １００重量部
［実施例２］
離型フィルム製造後の離型面の背面側の臨界表面張力を６０ｄｙｎｅ／ｃｍとする以外は、［実施例１］と同様の方法にて離型フィルムを得た。
【００３９】
結果を表１に示したが離型性、オリゴマー析出性、セラミックグリーンシートのブロッキング性のすべてが良好である。
【００４０】
［実施例３］
離型フィルム製造後の離型面の背面側の臨界表面張力を７０ｄｙｎｅ／ｃｍとする以外は、［実施例１］と同様の方法にて離型フィルムを得た。
【００４１】
結果を表１に示したが離型性、オリゴマー析出性、セラミックグリーンシートのブロッキング性のすべてが良好である。しかしながら、実用上問題がないもののシリコーンコート面に塗工ムラが見られた。
【００４２】
［比較例１］
コロナ放電処理を実施しない以外は、［実施例１］と同様の方法にて離型フィルムを得た。この場合の離型フィルム製造後の離型面の背面側の臨界表面張力は４２ｄｙｎｅ／ｃｍであった。
【００４３】
結果を表１に示したが離型性、オリゴマー析出性に劣っており、セラミックスシート積層・焼成後のブリスター発生性（ボイド発生性）も劣っていた。
【００４４】
［比較例２］
離型フィルム製造後の離型面の背面側の臨界表面張力を４５ｄｙｎｅ／ｃｍとする以外は、［実施例１］と同様の方法にて離型フィルムを得た。
【００４５】
結果を表１に示したが離型性、オリゴマー析出性に劣っており、セラミックスシート積層・焼成後のブリスター発生性（ボイド発生性）も劣っていた。
【００４６】
【表１】

【００４７】
【発明の効果】
以上説明したように、本発明の離型フィルムを使用すれば、ポリエステルフィルム中から析出するオリゴマー凝集物の付着が極めて少ないセラミックグリーンシートを製造用することができる。これにより、該セラミックグリーンシートを積層後、焼成する工程でセラミックコンデンサ内部にブリスター（ボイド）が発生し難くなるため積層型セラミックコンデンサの耐電圧不良率が大幅に改善される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a release film used in the production of ceramic green sheets.
[0002]
[Prior art]
In recent years, a release film in which a heat or ultraviolet curable silicone film is provided as a release layer on a polyester film is generally used as a carrier film for a process when manufacturing a ceramic green sheet for a multilayer ceramic capacitor or the like. ing. As such a release film having a silicone film, JP-A-60-141553, JP-A-3-231812, JP-B-4-59207, JP-B-6-2393 are known. ing.
[0003]
The ceramic green sheet is composed of an aqueous or organic solvent in which ceramic powder such as barium titanate or alumina is dispersed, a polymer binder such as polymethyl methacrylate, polyvinyl acetal, polyvinyl butyral, or polyvinyl alcohol, a plasticizer, and a dispersant. The added material is mixed and dispersed by a high-speed mixer or ball mill, and the resulting ceramic slurry is applied to a release film by a doctor blade method to a thickness of several hundreds of μm to several tens of μm, which is dried and wound up. Is generally manufactured.
[0004]
In recent years, in order to realize a small-sized and high-capacitance multilayer ceramic chip capacitor, it has been demanded that the thickness of one layer of the ceramic layer be made thinner and multilayered, and for this purpose, a very thin layer of 20 μm or less is required. The ceramic green sheet is released from the release film with high accuracy and without defects, and by using a release film having a smoother surface, the surface of the ceramic green sheet after release is smoothed. It is necessary to stabilize the capacity of the multilayer multilayer ceramic capacitor and reduce the withstand voltage failure rate by improving the sheet stacking adhesion.
[0005]
That is, the thickness uniformity of the polyester film used for the release film, the surface smoothness and the uniformity of the release force on the release surface are important. However, after applying the ceramic slurry layer to the release film with a die coater or the like, a step of drying in an oven at a temperature of 80 to 120 ° C, or an electrode such as a metal paste on the ceramic green sheet after the drying step In the process of printing and drying, there is a problem that oligomers are deposited on the back side of the release film, and a part of the oligomer is dropped and adheres to the ceramic green sheet. If such an oligomer adheres to the ceramic green sheet, voids are likely to be generated in the ceramic capacitor during the firing process after the ceramic green sheet is laminated, so the withstand voltage failure rate of the multilayer ceramic capacitor significantly increases. It is not preferable.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described problems and to provide a release film for producing a ceramic green sheet, which can efficiently produce a ceramic green sheet, in particular, a thin ceramic green sheet of 20 μm or less.
[0007]
[Means for Solving the Problems]
The object of the present invention has been industrially advantageously achieved by the present invention having the following constitution.
[0008]
[1] The polyester film has a release coating on one side, and the critical surface tension A (unit: dyne / cm) on the back of the polyester film without the release coating satisfies the following formula (1): A release film for producing ceramic green sheets.
[0009]
46 ≦ A ≦ 70 (1)
[2] The release film for producing a ceramic green sheet according to the above [1], wherein the critical surface tension A satisfies the following formula (2).
[0010]
50 ≦ A ≦ 60 (2)
[3] At least the polyester film is selected from a polyethylene terephthalate film, a polyethylene-2,6-naphthalate film, and a polyethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate film. The release film for producing a ceramic green sheet according to the above [1] or [2], wherein the release film is one type.
[0011]
[4] The release film for producing a ceramic green sheet according to any one of [1] to [3], wherein the release film is a silicone resin film.
[0012]
[5] The release film for producing a ceramic green sheet according to any one of the above [1] to [4], wherein the back surface of the polyester film having no release coating is subjected to corona discharge treatment.
[0013]
A feature of the present invention is that the critical surface tension of the back surface of the polyester film on which the release film layer for the polyester film is not provided is in a specific range so that the oligomer is not substantially precipitated. This reduces oligomer adhesion to the ceramic green sheet, and in particular, reduces the void generation inside the ceramic capacitor during the firing process after laminating a thin ceramic green sheet of 20 μm or less. The voltage failure rate could be greatly improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0015]
Examples of the polyester film of the present invention include polyethylene terephthalate film, polyethylene-2,6-naphthalate film, and polyethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate film. . Among these, a biaxially stretched polyethylene terephthalate film having an excellent balance of cost, mechanical strength, and dimensional stability is preferable. These polyester films may be produced by a conventional method, and the thickness thereof is particularly preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene-2,6-naphthalate film, and a biaxially stretched polyethylene. In the case of -α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate film, the mechanical properties, dimensional stability, heat resistance, price are in the range of 15 to 350 μm, preferably 20 to 100 μm. It is desirable from the point of view.
[0016]
The surface smoothness of such a polyester film has a centerline surface roughness (Ra) of 0.01 to 0.03 μm, preferably 0.01 to 0.025 with a cutoff value of 0.25 mm in order to clarify the characteristics of the present invention. A range of 0.02 μm is desirable.
[0017]
The release film in the present invention is a film made of a resin capable of relatively easily peeling a ceramic green sheet such as a silicone resin, an acrylic silicone resin, a fluorine resin, or a melamine resin. In particular, among the silicone resin coatings, a silicone resin coating containing a polyorganosiloxane having the structure of the following formula (1) as a main component is preferable in order to clarify the purpose and effect of the present invention.
[0018]
The silicone resin film forms a crosslinked structure of silicone by the addition reaction of polyorganosiloxane represented by the following formula (1) and organohydrogenpolysiloxane in the presence of a platinum catalyst represented by chloroplatinic acid. Is generally obtained.
[0019]
At this time, drying and curing (thermal curing, ultraviolet curing, etc.) of the silicone-based resin film can be performed individually or simultaneously. When it is performed simultaneously, it depends on the heat resistance (thermal dimensional stability) of the plastic film, but it is preferably heated at a temperature range of 80 ° C. to 200 ° C., preferably 120 ° C. to 180 ° C. for 15 seconds or longer. The film thickness of the silicone-based film is 0.05 to 0.5 μm, preferably 0.1 to 0.3 μm, after drying.
[0020]
[Chemical 1]

(In the formula, R1 represents a methyl group and / or a phenyl group, and Vi represents a vinyl group.)
In the present invention, the coating method for forming the silicone-based resin coating is not particularly limited, but usually, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as cyclohexane, n-hexane and n-heptane. , Direct gravure coater, micro gravure coater, reverse using a coating material in which silicone resin is dissolved in an organic solvent such as halogenated hydrocarbons such as perchloroethylene, ethyl acetate, methyl vinyl ketone, etc. It can be obtained by coating with a gravure coater, direct kiss coater, reverse kiss coater, comma coater, die coater, bar / rod type coating apparatus or the like. Among these, a micro gravure coater, a direct kiss coater, and a reverse kiss coater are preferable because the uniformity of the thickness of the silicone resin film is good and the occurrence of coating unevenness is small.
[0021]
In the present invention, it is necessary that the critical surface tension A (unit: dyne / cm) on the back of the polyester film without the release coating satisfies the following formula (1). It is preferable that the following expression (2) is satisfied.
[0022]
46 ≦ A ≦ 70 (1)
50 ≦ A ≦ 60 (2)
When the critical surface tension is less than 46 dyne / cm, the effect of suppressing oligomer precipitation is hardly observed, and it is not preferable. When the critical surface tension exceeds 70 dyne / cm, the ceramic green sheet is formed and then released into a roll. This is not preferable because blocking tends to occur between the coating surface and the back surface. Here, if the oligomer is deposited on the back side of the release surface of the release film by the heat treatment in the ceramic green sheet manufacturing process, voids are likely to be generated inside the ceramic capacitor in the process of laminating and firing the ceramic green sheet. In addition, an initial failure such as a short circuit is likely to occur when energized after the production of the multilayer ceramic capacitor, which is not preferable because the withstand voltage failure rate significantly increases.
[0023]
The critical surface tension in the above specific range in the present invention can be obtained by processing a plastic film using a spark gap type or semiconductor type corona discharge treatment apparatus, etc. It is not limited.
[0024]
Further, the critical surface tension A at this time can be set to a desired value by adjusting the output of the corona treatment apparatus for the plastic film and the treatment speed.
[0025]
The corona discharge treatment in the present invention refers to a treatment in which light emission discharge is performed by applying a certain voltage between an electrode, a film surface and a dielectric roll in air, nitrogen atmosphere, or carbon dioxide atmosphere. By performing the same treatment, the generation of oligomers is remarkably suppressed when a polyester film, in particular, a polyethylene terephthalate film is heated to 150 ° C. or higher.
[0026]
The oligomer in the present invention refers to a low molecular weight polymer having a molecular weight of 1500 or less contained in the polymer constituting the polyester film. In particular, in the case of polyethylene terephthalate, a cyclic oligoester (cyclic) mainly composed of a trimer. Oligomer) is contained in an amount of about 1.5 to 4% by weight, and when heated for about 30 minutes at a temperature of 100 ° C. or 150 ° C., it diffuses in the polyethylene terephthalate film and precipitates as hexagonal crystals on the film surface.
[0027]
Further, after the release film was heat-treated at a temperature of 150 ° C. for 3 minutes, when the polyester film surface side was observed with 10 fields of view with a 400 × microscope (area 0.5 mm ² ), the equivalent circle diameter was 2 μmφ or more. When the number of oligomer precipitates is less than 50, preferably 20 or less, it can be said that the oligomer precipitation suppressing effect is good.
[0028]
【Example】
The present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[0029]
In addition, the characteristic evaluation of the release film was performed by the following method.
[0030]
(1) After heating the oligomer precipitating release film at a temperature of 150 ° C. for 3 minutes or 10 minutes, aluminum was deposited on the back side of the release surface, and 10 fields of view (area 0.5 mm) with a 400 times differential interference microscope. ² ) Observe and count the number of precipitates with an equivalent circle diameter of 2 μmφ or more, which are increased compared to the back side of the release surface before the heat treatment, and evaluate oligomer precipitation. In this case, the number of oligomers of 100 or more is “XX”, 50 to 100 is “×”, less than 50 is “△”, less than 20 is “◯”, and less than 10 is “ ◎ ”. If it is “Δ” or more, it can be said that the oligomer precipitation is good.
[0031]
(2) Releasable release film and polyester adhesive film (31B tape made by Nitto Denko: 50mm width) were bonded together while being pressed with a 5kg roller, and the 180 ° peel strength after standing at 20 ° C for 20 hours was measured with Tensilon. taking measurement. Here, it can be said that it is good if the peeling force is 30 g or less.
[0032]
(3) A ceramic slurry having the following composition is applied onto the release layer of the blocking release film of the ceramic sheet by the doctor blade method, dried and solidified, and then the release film and the ceramic green sheet are bonded together. 10 sheets were stacked and left at 40 ° C. for 2 weeks under a load of 20 g / cm ² . Thereafter, the ceramic green sheet was peeled off to obtain a ceramic green sheet having a thickness of 15 μm. At this time, the ceramic green sheet was observed with an optical microscope. “X” indicates that many pinholes were observed, “△” indicates that a few pinholes were observed, and “No” indicates that no pinholes were observed. ○ ”.
[0033]
"Composition of ceramic slurry"
Alumina 53 parts by weight Barium oxide 8 parts by weight Silicon oxide 36 parts by weight Polyvinyl butyral 30 parts by weight Dichloroethane 80 parts by weight (4) Blister generation (void generation) after ceramic sheet lamination / firing on the release layer of the release film After applying the ceramic slurry having the above composition by the doctor blade method and drying and solidifying, 10 sheets are stacked in a state where the release film and the ceramic green sheet are bonded to each other, and the load is 20 g / cm ² at 40 ° C. for 2 weeks. I left it alone. Thereafter, the ceramic green sheet was peeled off to obtain a ceramic green sheet having a thickness of 15 μm. Five of these were stacked and pressed at 800 kg / cm 2, and then heated in an electric furnace at 1000 ° C. for 1 hour. At this time, “×” indicates that a large number of blisters are seen on the surface of the multilayer ceramic sheet, “△” indicates that a few blisters are observed, “○” indicates that a few blisters are observed, Those that could not be seen at all were marked with “◎”.
[0034]
(5) In the case of a critical surface tension substrate film, it was measured with a commercially available wetting tension test solution based on JIS-K-6768. Further, the liquid coating material was applied to a synthetic resin plate whose wetting tension was known, and the critical surface tension was determined from the degree of repellency.
[0035]
[Example 1]
One side of a 50 μm thick biaxially stretched polyester film “Lumirror S28” manufactured by Toray Industries, Inc. was subjected to corona discharge treatment to a critical surface tension of 56 dyne / cm.
[0036]
Furthermore, the following composition B was applied to the back surface of the treated surface as a heat release curable silicone resin coating using a gravure roll (# 200, hatched type), dried in an oven at 120 ° C. for 15 seconds, and thermally cured. A release film was obtained. The critical surface tension on the back side of the release surface of the release film was 51 dyne / cm.
[0037]
The results are shown in Table 1, and both release properties and oligomer precipitation are good.
[0038]
"Thermosetting silicone resin coating composition B"
1) KS847H 10 parts by weight manufactured by Shin-Etsu Chemical Co., Ltd. 2) 0.10 parts by weight PL-50T manufactured by Shin-Etsu Chemical Co., Ltd. 3) 100 parts by weight of toluene [Example 2]
A release film was obtained in the same manner as in [Example 1] except that the critical surface tension on the back side of the release surface after the release film was manufactured was 60 dyne / cm.
[0039]
The results are shown in Table 1. All of the mold release property, oligomer precipitation property, and ceramic green sheet blocking property are good.
[0040]
[Example 3]
A release film was obtained in the same manner as in [Example 1], except that the critical surface tension on the back side of the release surface after the release film was manufactured was 70 dyne / cm.
[0041]
The results are shown in Table 1. All of the mold release property, oligomer precipitation property, and ceramic green sheet blocking property are good. However, although there was no practical problem, uneven coating was observed on the silicone coat surface.
[0042]
[Comparative Example 1]
A release film was obtained in the same manner as in [Example 1] except that the corona discharge treatment was not performed. In this case, the critical surface tension on the back side of the release surface after the release film was produced was 42 dyne / cm.
[0043]
Although the result was shown in Table 1, it was inferior in mold release property and oligomer precipitation property, and also blister generation property (void generation property) after ceramic sheet lamination | stacking and baking was also inferior.
[0044]
[Comparative Example 2]
A release film was obtained in the same manner as in [Example 1] except that the critical surface tension on the back side of the release surface after production of the release film was 45 dyne / cm.
[0045]
Although the result was shown in Table 1, it was inferior in mold release property and oligomer precipitation property, and also blister generation property (void generation property) after ceramic sheet lamination | stacking and baking was also inferior.
[0046]
[Table 1]

[0047]
【The invention's effect】
As described above, when the release film of the present invention is used, a ceramic green sheet with very little adhesion of oligomer aggregates precipitated from the polyester film can be produced. As a result, blisters (voids) are less likely to be generated inside the ceramic capacitor in the step of firing after laminating the ceramic green sheets, so that the withstand voltage failure rate of the multilayer ceramic capacitor is greatly improved.

Claims (5)

The polyester film has a release coating on one side, and the critical surface tension A (unit: dyne / cm) on the back of the polyester film without the release coating satisfies the following formula (1): Release film for manufacturing ceramic green sheets.
46 ≦ A ≦ 70 (1) The release film for producing a ceramic green sheet according to claim 1, wherein the critical surface tension A satisfies the following formula (2).
50 ≦ A ≦ 60 (2)   The polyester film is at least one selected from a polyethylene terephthalate film, a polyethylene-2,6-naphthalate film, and a polyethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate film. The release film for producing a ceramic green sheet according to claim 1 or 2, wherein the release film is provided.   The release film for producing a ceramic green sheet according to any one of claims 1 to 3, wherein the release film is a silicone resin film. The release film for producing a ceramic green sheet according to any one of claims 1 to 4, wherein the back surface of the polyester film having no release coating is subjected to corona discharge treatment.