JP3766882B2 - Release film for ceramic sheet production - Google Patents

Description

【００１３】
また、シリコーン樹脂の硬化は緩やかに進行する為、硬化時間、温度をあげるか、シリコーン樹脂の厚みを薄くし架橋密度をあげる方法がある。以上のような方法で硬化が進行し分子量が増大することにより、強固な三次元網状構造の膜とし、シリコーン樹脂面の硬い離型フィルムを完成させた。
【００１４】
（シリコーン樹脂塗膜の塗設）
本発明においては、ポリエステルフィルムの少なくとも片面に、前記に示す付加反応系、縮合反応系、紫外線硬化系のいずれかの塗液を塗布し、加熱乾燥、熱硬化または紫外線硬化することにより離型性塗膜を塗設するが、塗布法としては公知の任意の塗工法が適用でき、例えばグラビアコート法やリバースコート法などのロールコート法、マイヤーバーなどのバーコート法、スプレーコート法、エアーナイフコート法等の従来から知られている方法が利用出来る。
溶液の塗布量は走行しているフィルム１ｍ² 当たり２〜２０ｇ，特に２〜１０ｇが好ましい。塗布量がこの範囲にあると乾燥が容易に行なえ、かつ塗布ムラが生じ難いので好ましい。また、シリコーン樹脂のポリエステルへの密着性を上げる為に、ポリエステル表面にコロナ処理をしても良いし、アンカーコートしてもよい。
【００１５】
（乾燥及び硬化）
シリコーン樹脂層の乾燥及び硬化は同時に行うことが出来、条件としては１２０℃以上で２０秒程度が好ましい。乾燥温度が１２０℃以下、及び乾燥時間が２０秒以下ではシリコーン樹脂の硬化が不完全であり、重剥離化（目標剥離力に達しない）やシリコーン樹脂層の背面転写（裏移り）の原因となり性能上、不安が残る。硬化シリコーン樹脂の層の乾燥量は特に限定されないが、０．０５〜２０g/ｍ² の範囲が好ましい。シリコーン樹脂層があまり薄いと剥離性能が低下し、本来の剥離性能が出なくなる。また、あまり厚いと硬化に時間がかかり生産上不都合が生じる。
【００１６】
（ダイナミック硬さ）
本発明の離型フィルムでは、離形層の面の硬さ（ダイナミック硬さ）が、セラミックグリーンシートの剥離性能に大きく影響することを見いだした。剥離性能を良くするには、ダイナミック硬さを８．０ｇｆ／μｍ² 以上にすることが必要であり、好ましくは１５ｇｆ／μｍ² 以上で、特に好ましくは２０ｇｆ／μｍ² 以上である。硬さが８ｇｆ／μｍ² 未満の場合はシリコーン樹脂層のひずみによる影響を受け、剥離性能が悪くなる傾向にある。特に薄膜のセラミックシート剥離時には、セラミックの破れや剥離不良が多く発生し、収率が下がるなどの問題が発生する。ダイナミック硬さを制御する手段は〔００１１〕，〔００１２〕に記載した。
【００１７】
実施例
次に実施例により本発明を説明する。
本発明に用いる測定・評価方法を以下に示す。
１）常態剥離評価
ポリエステルフィルムの離型層面にポリエステル粘着テープ（ニットー３１Ｂ）を貼合わせ、５Kgの圧着ローラーで圧着し室温で２０時間放置後、離型層と粘着テープとの剥離力を引張り試験機（剥離角度９０°）にて測定し、下記評価にて判定した。
Ａ・・・・・・１２g/50mm巾以下。
Ｂ・・・・・・１３g/50mm巾以上。
剥離力の好ましい範囲は、１２g/50mm巾以下であり、剥離力が１３g/50mm巾以上であると、離型性能が悪くなるため好ましくない。
【００１８】
２）耐溶剤性評価
学振式摩擦ケンロウ度試験機にて、ガーゼにトルエンをしみ込ませ２００ｇ／ｍ² の荷重を加え、１００回往復作動後にラビング面の剥離力を測定し、下記式にて判定した。
ラビング面剥離力／常態剥離力＝耐溶剤性
Ａ・・・・２．０以下。
Ｂ・・・・２．１〜５．０。
Ｃ・・・・５．１以上。
耐溶剤性指数の好ましい範囲は、５．０以下であり、特に２．０以下が好ましい。耐溶剤性が悪いと、上記値は大きくなり、５．０以上ではセラミックスラリーなどの溶剤分が塗工させた場合、離型性能が低下する恐れがあるため好ましくない。
【００１９】
３）ダイナミック硬さ
島津ダイナミック超微小硬度計（ＤＵＨ−２０１−２０２）を用いて、荷重２ｇｆの三角すいを試料（サンプリングフィルムのシリコーン樹脂面）に押しつけ、２秒保持した後のダイナミック硬さを下記式より求めた。
ＤＨ＝α（Ｐ／Ｄ ² ）
Ｐ（ｇｆ）：試験荷重
Ｄ（μｍ）：圧子の試料への侵入量
α：３７．８３８ 圧子形状による定数（１１５°三角すい）
【００２０】
４）セラミック剥離評価
溶剤、セラミック原料、結合剤、可塑剤などを混合し、ペースト状にした後、ボールミルにて分散し、セラミックスラリーを得た。次に、ポリエステルフィルムの離型面側にアプリケーターにて、上記セラミックスラリーを厚み３０μでコートし、１２０℃×１分で乾燥し、セラミックグリーンシートを得た。次に、セラミックグリーンシートを５ｃｍ巾にカットし、ピール法にて剥離を行い剥離力を確認した。
Ａ・・・・・２．０g/５０mm巾以下。
Ｂ・・・・・２．１〜３．０g/５０mm巾。
Ｃ・・・・・３．１〜５．０g/５０mm巾。
Ｄ・・・・・５．１g/５０mm巾以上。
Ａ、Ｂの場合には、セラミックが破れることなく剥離したが、Ｃは剥離時セラミックに一部破れが生じ、Ｄは剥離時完全に破れてしまった。
【００２１】
実施例１
架橋密度の高いタイプである付加反応硬化型レジンＫＳ−８３０（信越化学（株）製）を溶剤希釈し、シリコーンレジン１００重量％に対し、１重量％の白金触媒を添加し、３％濃度のシリコーン塗工液を作成した。次にポリエステルフィルムにワイヤーバーにて、シリコーン塗工液を塗布し、１６０℃×３０秒で乾燥、硬化させ、離型フィルム（乾燥固形分０．０５g/ｍ² ）を得た。この離型フィルムの特性を表１に示す。
【００２２】
実施例２
シリコーン塗工液を乾燥固形分量０．１５g/ｍ² で塗工した以外は、実施例１と同じ条件で、離型フィルムを得た。この離型フィルムの特性を表１に示す。
【００２３】
比較例１
シリコーン塗工液を乾燥固形分量０．５g/ｍ² で塗工した以外は、実施例１と同じ条件で、離型フィルムを得た。この離型フィルムの特性を表１に示す。
【００２４】
比較例２
乾燥条件を１００℃×３０秒に変更した以外は、実施例１と同様にして、離型フィルムを作成した。この離型フィルムの特性を表１に示す。
【００２５】
実施例３、比較例３
一般に付加重合反応型シリコーンの中でも、粘着剤評価で軽剥離とされるＴＰＲ６７２１（東芝シリコーン（株）製）シリコーンレジンを使用し、乾燥固形分量を０．１５及び０．５g/ｍ² に変更した、それ以外は実施例１と同様に離型フィルムを得た。
【００２６】
【表１】

【００２７】
【発明の効果】
ポリエステルフィルムの少なくとも片面に、シリコーン樹脂を塗布して得た離型フィルムにおいて、離型面のダイナミック硬さが８．０gf／μｍ² 以上であれば、セラミック剥離において、剥離不良がなく、軽剥離化が可能でありセラミックシート等の成形用キャリアーフィルム（特に薄膜用セラミック）に使用できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film release sheet, and more particularly to a release film suitable for production of a ceramic green sheet having a release performance that is lightly peeled and stable.
[0002]
[Prior art]
Polyester films made of polyethylene terephthalate or polyethylene naphthalate are widely used as materials for release films and the like. As a method for producing a release film, it is produced by applying an addition reaction type or condensation reaction type silicone resin, and is widely used as a mount for adhesive labels, adhesive tapes and the like. It is known that there are various types of silicones for light, medium and heavy peeling, and different peeling levels are required depending on the application and purpose of use. In recent years, with the general use of release films for the production of ceramic sheets, there has been a demand for release films that are lighter than before with the thinning of ceramics. However, what is considered to be light in the evaluation of pressure-sensitive adhesives such as conventional labels is not necessarily light in thin layer ceramics, and a light release film in thin layer ceramics is required.
[0003]
The green ceramic sheet (green sheet) is obtained by applying a slurry in which ceramic powder and a binder are dispersed in a solvent on a carrier film, and then passing through a drying furnace to remove the solvent by heating. Then, it is cut into a certain size, and the ceramic is peeled off from the release film and used as a component such as a ceramic capacitor. However, when the ceramic is peeled from the release film, if the peeling force is heavy, a peeling failure occurs, and the productivity is lowered. This is because ceramics have become thinner (especially the peeling becomes heavier as the ceramic becomes thinner) with the increase in capacity and size of ceramic capacitors in recent years. Yes.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to provide a release film having a release layer surface that eliminates the disadvantages of the prior art and has a release layer surface that can be peeled off with an appropriate force without a peeling failure, especially when the thin ceramic layer is peeled off. To do.
[0005]
[Means for Solving the Problems]
The present invention is a release film in which a silicone release layer obtained by curing a curable silicone resin is provided on at least one surface of a polyester film, and the release film has a weight after drying of the release layer of 0.05. a ~0.15g / m ^2, and a release film ceramic sheet production, wherein the dynamic hardness of the surface of the release layer is 8.0 (gf / μm ²⁾ or more.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
(Polyester film)
Polyester films made of polyethylene terephthalate or polyethylene naphthalate are widely used as release film materials. In the present invention, a polyester film is used as the base film of the release film. In particular, a biaxially stretched polyester film is preferred for reasons such as excellent mechanical strength. The polyester constituting the polyester film is preferably a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component. For example, polyethylene terephthalate, polyethylene-2-6 naphthalate, polymethylene terephthalate, etc. It can be illustrated.
[0007]
In order to improve the handleability and slipperiness of the film, organic and inorganic fine particles can be blended with the polyester. In particular, it is preferable to contain fine particles having an average particle diameter of 0.01 to 10 μm in a proportion of 0.005 to 5% by weight. The polyester film in the present invention can be produced by a conventionally known method. For example, it is possible to obtain an unstretched film by melting the polyester with an extruder, extruding it into a film, and cooling it with a rotary cooling drum, and by uniaxially stretching the unstretched film in the longitudinal direction or the transverse direction. A uniaxially stretched film can be obtained.
[0008]
The biaxially stretched film is obtained by a method of sequentially biaxially stretching a uniaxially stretched film in the longitudinal direction or the transverse direction in the transverse direction or the longitudinal direction, or a method of simultaneously biaxially stretching an unstretched film in the longitudinal direction and the transverse direction. be able to. The stretching temperature is preferably equal to or higher than the secondary transition point (Tg) of the polyester. Moreover, in the case of a biaxially stretched film, it is preferable to make it a draw ratio of 1 to 8 times, particularly 2 to 6 times in each direction.
As a thickness of a polyester film, it is preferable that it is 2-300 micrometers, for example, and it is especially preferable that it is 10-125 micrometers.
[0009]
(Silicone resin layer)
The silicone resin layer of the present invention can be molded, for example, by applying a coating liquid containing a curable silicone resin to the surface of a polyester film, and drying and curing.
As the curable silicone resin, any reaction system such as an addition reaction system, a condensation reaction system, or an ultraviolet ray or electron beam curing system can be used. Examples of the addition reaction type silicone resin include those in which a polydimethylsiloxane having a vinyl group introduced at the terminal thereof is reacted with a hydrodienesiloxane using a platinum catalyst to form a three-dimensional crosslinked structure. As a silicone resin of a condensation reaction system, for example, a polydimethylsiloxane having a terminal —OH group and a polydimethylsiloxane having a —H group at the terminal are subjected to a condensation reaction using an organic tin catalyst to form a three-dimensional crosslinked structure. Can be mentioned.
[0010]
Examples of UV curable silicone resins include those that use the same radical reaction as ordinary silicone rubber crosslinks as the most basic types, those that introduce photopolymerization by introducing unsaturated groups, and those that decompose onium salts with UV light. Examples include those that generate a strong acid and then cleave the epoxy group to crosslink, and those that crosslink by the addition reaction of thiol to vinylsiloxane. Electron beams have stronger energy than ultraviolet rays, and a crosslinking reaction by radicals occurs without using an initiator as in the case of ultraviolet curing.
[0011]
In order to increase the hardness of the silicone resin surface, it is necessary to increase the crosslinking density. Among them, a strong release film can be formed by increasing the vinyl group content. This is because the hardness of the silicone resin surface is increased by arranging vinyl groups in the side chain, but in general, a silicone resin shown in Chemical Formula 1 can be used to obtain a thin film resin layer.
[0012]
[Chemical 1]

[0013]
Further, since the curing of the silicone resin proceeds slowly, there are methods of increasing the curing time and temperature, or decreasing the thickness of the silicone resin and increasing the crosslinking density. As the curing progressed and the molecular weight increased by the above method, a strong three-dimensional network structure film was formed, and a release film having a hard silicone resin surface was completed.
[0014]
(Coating of silicone resin coating)
In the present invention, at least one surface of the polyester film is coated with any one of the above-described addition reaction system, condensation reaction system, and ultraviolet curable coating solution, and is heat-dried, heat-cured, or UV-cured to release the mold. Although a coating film is applied, any known coating method can be applied as a coating method, for example, a roll coating method such as a gravure coating method or a reverse coating method, a bar coating method such as a Mayer bar, a spray coating method, an air knife Conventionally known methods such as a coating method can be used.
The coating amount of the solution is preferably ^{2 to 20} g, particularly ^{2 to} 10 g, per 1 m ² of the running film. A coating amount in this range is preferable because drying can be easily performed and coating unevenness is unlikely to occur. Further, in order to improve the adhesion of the silicone resin to the polyester, the polyester surface may be subjected to corona treatment or may be anchor-coated.
[0015]
(Drying and curing)
The silicone resin layer can be dried and cured at the same time, and the conditions are preferably 120 ° C. or higher and about 20 seconds. If the drying temperature is 120 ° C or less and the drying time is 20 seconds or less, the silicone resin is incompletely cured, causing heavy release (not reaching the target release force) and back transfer (setback) of the silicone resin layer. Anxiety remains in performance. Drying of the layer of cured silicone resin is not particularly limited, the range of 0.05 to 20 g / m ² is preferred. If the silicone resin layer is too thin, the peeling performance is lowered and the original peeling performance is not obtained. On the other hand, if it is too thick, it takes a long time to cure, resulting in inconvenience in production.
[0016]
(Dynamic hardness)
In the release film of the present invention, it was found that the hardness (dynamic hardness) of the surface of the release layer greatly affects the peeling performance of the ceramic green sheet. To improve the release performance, it is necessary to the dynamic hardness in 8.0gf / μm ² or more, preferably at 15 gf / [mu] m ² or more, particularly preferably 20 gf / [mu] m ² or more. When the hardness is less than 8 gf / μm ² , it is affected by the strain of the silicone resin layer, and the peeling performance tends to deteriorate. In particular, when the thin ceramic sheet is peeled off, there are many problems such as breakage of the ceramic and poor peeling, resulting in a decrease in yield. Means for controlling the dynamic hardness are described in [0011] and [0012].
[0017]
EXAMPLES Next, the present invention will be described with reference to examples.
The measurement / evaluation method used in the present invention is shown below.
1) Evaluation of normal release A polyester adhesive tape (Nitto 31B) is bonded to the release layer surface of the polyester film, and after pressing with a 5 kg pressure roller and left at room temperature for 20 hours, the release force between the release layer and the adhesive tape is subjected to a tensile test. It measured with the machine (peeling angle 90 degrees), and determined by the following evaluation.
A: 12g / 50mm width or less.
B ... 13g / 50mm width or more.
The preferable range of the peeling force is 12 g / 50 mm width or less, and if the peeling force is 13 g / 50 mm width or more, the release performance is deteriorated.
[0018]
2) Solvent resistance evaluation Using a Gakuken-type frictional Kenro tester, impregnate toluene with gauze, apply a load of 200 g / m ² , measure the peel force on the rubbing surface after 100 reciprocations, and use the following formula: Judged.
Rubbing surface peel strength / normal peel strength = solvent resistance A... 2.0 or less.
B ... 2.1-5.0.
C ... 5.1 or more.
A preferable range of the solvent resistance index is 5.0 or less, and particularly preferably 2.0 or less. If the solvent resistance is poor, the above value becomes large, and if it is 5.0 or more, when a solvent such as ceramic slurry is applied, there is a possibility that the mold release performance may be deteriorated.
[0019]
3) Dynamic hardness Using a Shimadzu dynamic ultra-micro hardness tester (DUH-201-202), the triangular hardness of 2 gf was pressed against the sample (silicone resin surface of the sampling film) and the dynamic hardness after holding for 2 seconds. Was obtained from the following formula .
DH = α (P / D ² )
P (gf): test load D (μm): penetration amount of indenter into sample α: 37.838 constant according to indenter shape (115 ° triangular cone)
[0020]
4) Ceramic peeling evaluation A solvent, a ceramic raw material, a binder, a plasticizer, and the like were mixed to form a paste, and then dispersed in a ball mill to obtain a ceramic slurry. Next, the ceramic slurry was coated with a thickness of 30 μm on the release surface side of the polyester film with an applicator and dried at 120 ° C. for 1 minute to obtain a ceramic green sheet. Next, the ceramic green sheet was cut into a width of 5 cm and peeled by a peel method to confirm the peeling force.
A: 2.0g / 50mm width or less.
B: 2.1-3.0 g / 50 mm width.
C: 3.1-5.0 g / 50 mm width.
D: 5.1g / 50mm width or more.
In the case of A and B, the ceramic was peeled without being broken, but C was partially broken at the time of peeling, and D was completely broken at the time of peeling.
[0021]
Example 1
Addition reaction curing type resin KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a type having a high crosslinking density, is diluted with a solvent, and 1% by weight of a platinum catalyst is added to 100% by weight of silicone resin. A silicone coating solution was prepared. Next, a silicone coating liquid was applied to the polyester film with a wire bar, and dried and cured at 160 ° C. for 30 seconds to obtain a release film (dry solid content 0.05 g / m ² ). The properties of this release film are shown in Table 1.
[0022]
Example 2
A release film was obtained under the same conditions as in Example 1 except that the silicone coating solution was applied at a dry solid content of 0.15 g / m ² . The properties of this release film are shown in Table 1.
[0023]
Comparative Example 1
A release film was obtained under the same conditions as in Example 1 except that the silicone coating solution was applied at a dry solid content of 0.5 g / m ² . The properties of this release film are shown in Table 1.
[0024]
Comparative Example 2
A release film was prepared in the same manner as in Example 1 except that the drying conditions were changed to 100 ° C. × 30 seconds. The properties of this release film are shown in Table 1.
[0025]
Example 3 and Comparative Example 3
Generally, among the addition polymerization reaction type silicones, TPR6721 (made by Toshiba Silicone Co., Ltd.) silicone resin, which is lightly peeled by adhesive evaluation, was used, and the dry solid content was changed to 0.15 and 0.5 g / m ² . Otherwise, a release film was obtained in the same manner as in Example 1.
[0026]
[Table 1]

[0027]
【The invention's effect】
In a release film obtained by applying a silicone resin to at least one surface of a polyester film, if the release surface has a dynamic hardness of 8.0 gf / μm ² or more, there is no peeling failure in the ceramic peeling, and a light peeling. And can be used for a carrier film for molding such as a ceramic sheet (especially a ceramic for a thin film).

Claims (1)

A release film in which a silicone release layer obtained by curing a curable silicone resin is provided on at least one side of a polyester film, and the release film has a weight after drying of the release layer of 0.05 to 0.15 g. / m is ² and the dynamic hardness of the surface of the release layer is 8.0 (gf / μm ²⁾ or the release film ceramic sheet production, characterized in that.