JP2004188621A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin laminated polyester film which satisfies productivity at the time of production and workability at the time of processing and imparts high-degree functionality. <P>SOLUTION: This thin laminated polyester film has a laminated structure and is characterized in that the thickness thereof due to a weight method is 3.0-8.0 μm and the arithmetic average roughness (Ra) of at least one surface thereof is not more than 0.050 μm. The number of coarse projections on one surface of the laminated polyester film is 200/cm<SP>2</SP>or less and at least one layer thereof preferably contains at least one kind of an oxidation inhibitor. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２８】
【化２】

【００２９】
【化３】

【００３０】
【化４】

【００３１】
【化５】

【００３２】
【化６】

【００３３】
【化７】

【００３４】
【化８】

【００３５】
【化９】

【００３６】
次に、溶融シートを、回転冷却ドラム上でガラス転移温度以下の温度になるように急冷固化し、実質的に非晶状態の未配向シートを得る。この場合、シートの平面性を向上させるため、シートと回転冷却ドラムとの密着性を高めることが好ましく、本発明においては、静電印加密着法および／または液体塗布密着法が好ましく採用される。
本発明においては、このようにして得られたシートを二軸方向に延伸してフィルム化する。二軸延伸条件について具体的に述べると、前記未延伸シートをまず第一軸方向に延伸する。延伸温度範囲は通常７０〜１５０℃、延伸倍率は通常２．５〜６倍の範囲とし、延伸は一段階または二段階以上で行うことができる。次に第二軸方向、すなわち第一軸方向と直交する方向に一軸配向フィルムを一旦ガラス転移点以下に冷却するか、または冷却することなく、例えば８０〜１５０℃の温度範囲に予熱して、さらにほぼ同温度の下で２．５〜５倍、好ましくは３．０〜４．５倍に延伸を行い、二軸に配向したフィルムを得る。
【００３７】
なお、第一軸方向の延伸を２段階以上で行うことは、良好な厚さ均一性を達成できるので好ましい。また、横延伸した後、さらに長手方向に再延伸する方法も可能であるが、いずれにしても長手方向の総合延伸倍率を３．５倍以上とすることが好適である。
かくして得られたフィルムを、３０％以内の伸長、制限収縮、または定長下で１秒〜５分間熱処理する。この際、熱処理工程内または熱処理後に長手方向または横方向、あるいは両方向に再延伸を行ってもよい。
【００３８】
【実施例】
以下、実施例を挙げてさらに本発明を詳細に説明するが、本発明は、その要旨を越えない限り、以下の実施例によって限定されるものではない。なお、実施例中の評価方法は下記のとおりである。実施例および比較例中、「部」とあるのは「重量部」を示し、「％」とあるのは「重量％」を示し、「ｐｐｍ」とあるのは「重量ｐｐｍ」を示す。
【００３９】
（１）ポリマーの極限粘度 ［η］ （ｄｌ／ｇ）
ポリマー１ｇをフェノール／テトラクロロエタン＝５０／５０（重量比）の混合溶媒１００ｍｌに溶解し、３０℃で測定した。
【００４０】
（２）添加粒子の平均粒径（ｄ５０）（μｍ）
島津製作所製遠心沈降式粒度分布測定装置（ＳＡ−ＣＰ３型）で測定した等価球形分布において大粒子側から積算した積算体積分率５０％の粒径を平均粒径（ｄ５０）とした。
【００４１】
（３）析出粒子の平均粒径（ｄ５０）（μｍ）
析出粒子を含むポリエステルフィルムをプレパラートに挟み込んで溶融、冷却した後、顕微鏡にて観察し、その画像を画像処理装置（ライカ社製「Ｑｕａｎｔｉｍｅｔ５００＋」）で処理することにより測定し、その等価球形分布において大粒子側から積算した積算体積分率５０％の粒径を平均粒径（ｄ５０）とした。
【００４２】
（４）析出粒子量の測定
ポリエステル１００ｇにｏ―クロルフェノール１．０リットルを加え１２０℃で３時間加熱後、超遠心分離機（日立工機製商品「５５Ｐ―７２」）を用いて４０分間遠心分離を行い、得られた粒子を１００℃で真空乾燥する。走査型差動熱量計にて上記の粒子を処理し、ポリマーに相当する溶融ピークが認められる場合は、当該粒子にｏ―クロルフェノールを加えて加熱冷却後、再び遠心分離操作を行う。そして、溶融ピークが認められなくなった粒子を析出粒子とする。遠心分離操作は、通常２回で足りる。
【００４３】
（５）トータルの重量法厚み（総重量法厚み）（μｍ）
まず、フィルム試験片の密度（ρ；（ｇ／ｃｍ^３ ））をＪＩＳ Ｋ７１１２に規定するＤ法（密度勾配管法）により測定し、次に、１００±０．５ｃｍ^２ に切り取った試験片を天秤に乗せ、フィルム質量（ｍ；（ｇ））を０．０００１ｇまで正しく測定した後、以下の式により算出した。かかる測定を５回繰り返し、得られたｔの値の中央値を総重量法厚み ｄ（μｍ）とした。
ｔ＝１００ｍ／ρ
【００４４】
（６）算術平均粗さ Ｒａ（μｍ）
試験片を切り出し、以下の方法で両面についてＲａを測定・算出し、各々の、算術平均粗さとした。すなわち、小坂研究所株式会社製「ＳＥ３５００」を用い、先端半径５μｍ、荷重３０ｍｇの触針を用い、評価長さ２．５ｍｍについて測定した。算術平均粗さ（Ｒａ）は、ＪＩＳ Ｂ ０６０１−１９９４に従った。すなわち、粗さ曲線からその平均線の方向に基準長さＬだけ抜き取り、この抜き取り部分の平均線の方向にｘ軸を、縦倍率の方向にｙ軸を取り、粗さ曲線をｙ＝ｆ（ｘ）で表したときに、次の式によって求められる値をマイクロメートル（μｍ）で表したものをいう。なお、縦倍率＝２００，０００倍、カットオフ値＝０．０８ｍｍとし、ひとつの面につき、粗さ曲線を１０本測定し、おのおののＲａの１０点平均を取った。
Ｒａ＝（１／Ｌ）∫_０ ^Ｌ｜ｆ（ｘ）｜ｄｘ
【００４５】
（７）平滑面側の粗大突起数 ｆ（個／ｃｍ^２）
下記巻き歩留まり評価法で作製したロールの巻き芯近傍より、切り取った試験片について、その算術平均粗さの低い方の面に厚さ４５０Åのアルミニウムを蒸着し、日本光学工業社製二光束干渉顕微鏡を用いて測定した。測定波長０．５４μｍで５次以上の干渉縞を示すものを５次以上の粗大突起として５ｃｍ^２にわたりカウントし、単位面積当たり（１ｃｍ^２当たり）に換算した。５次の高さとは測定波長の１／２の５倍＝１．３５μｍに相当し、５次以上の粗大突起とは１．３５μｍ以上の高さを持つことを意味する。
【００４６】
（８）蒸着フィルムのくもり度（外観）
下記巻き歩留まり評価法で作製したロールの巻き芯近傍より、切り取った試験片について、その算術平均粗さの低い方の面に厚さ４５０Åのアルミニウムを蒸着し、目視にて、以下の基準で判定した。
◎：外観上、くもりが認識できず、優秀
○：外観上、くもりが認識できるが、実用上問題ないレベルであり良好
×：外観上、くもりがひどく、使用に耐えず不良
【００４７】
（９）巻き歩留まり
フィルム製膜後、マスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、ロール状に２５０ｍ／分の速度で、平滑面側が外面になるように巻き取り、全長にわたり、しわなく卷けるものを合格とし、その合格率について以下の基準で判定した。
◎：９５％以上であり優秀
○：８０％以上９５％未満であり良好
×：８０％未満。不良
【００４８】
実施例１
（粗面側原料）
ジメチルテレフタレート１００部、エチレングリコール７０部および酢酸カルシウム一水塩０．１１部を反応器にとり、加熱昇温するとともにメタノールを留去してエステル交換反応を行い、反応開始から４時間を要して２３０℃まで昇温し、実質的にエステル交換反応を終了した。次にこの反応混合物にトリエチルホスファイト０．１２４部とトリエチルホスフェート０．５４部とをエチレングリコールに均一に溶解させた液を添加し、次いで三酸化アンチモン０．０４部を添加したのち１０分間を要して２３６℃に達せしめた。この時点から系内の圧力を徐々に減じ、三酸化アンチモン添加後８０分で系内の温度を２６５℃、圧力を３００ｍｍＨｇとし、以後も徐々に昇温減圧し最終的に２８５℃、１ｍｍＨｇ以下とした。４時間後、系内を常圧に戻しポリマーを吐出しチップ化し、極限粘度０．６６のポリエステル（ａ）を得た。このポリエステル（ａ）には均一で微細な析出粒子が多数認められ、その平均粒径は１．４０μｍであった。記載の方法に従ってその析出粒子量を測定したところポリエステルに対して０．４０重量％であった。
【００４９】
一方、ジメチルテレフタレート１００部、エチレングリコール６０部および酢酸カルシウム１水塩０．０９部を反応器にとり、加熱昇温するとともにメタノールを留去してエステル交換反応を行い、反応開始から４時間を要して２３０℃まで昇温し、実質的にエステル交換反応を終了した。さらにリン酸０．０６部、三酸化アンチモン０．０４部を加え、徐々に反応系を減圧とし、温度を高めて重縮合反応を４時間行い、極限粘度０．６６の希釈用ポリエステル（ｂ）を得た。
ポリエステル（ａ）とポリエステル（ｂ）を混合し、平均粒径１．４０μｍの析出粒子を０．１２％含有する原料とした。
【００５０】
（平滑面側原料）
テレフタル酸８６部、エチレングリコール７０部を反応器にとり、約２５０℃で０．５ｋｇ／ｍｍ^２ の加圧下、４時間エステル化反応を行った。次いで、三酸化アンチモン０．０１５部、平均粒径０．８０μｍの炭酸カルシウム粒子、平均粒径０．３５μｍの架橋高分子粒子およびリン酸０．０１部を添加した。温度を２５０℃から２８５℃まで徐々に昇温するとともに、圧力を常圧から徐々に減じ０．５ｍｍＨｇとした。４時間後重縮合反応を停止し、極限粘度０．６６のポリエステル（ｃ）を得た。このポリエステル（ｃ）には、０．０６重量％の炭酸カルシウム粒子および０．３０重量％の架橋高分子粒子が含有されていた。
【００５１】
（製膜・スリット）
粗面側原料および平滑面側原料を常法により乾燥して別々の押出機に供給し、２９０℃で溶融してシート状に押出し、静電印加密着法を用いて冷却ロール上で急冷し、無定形シートとした。この際、平滑面側原料の押出機はベント型二軸押出機とし、該押出機中で酸化防止剤としてペンタエリスリチル−テトラキス［３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート］を平滑面の層のポリエステルに対し、５００ｐｐｍとなるように定量フィーダーを用いて添加した。なお、ベント口は減圧とし、水分等の揮発物を除去した。なお、粗面側の押出量と平滑面側の押出量を４対５に制御し、冷却ロール面には平滑面が接触するように押し出した。得られたシートを、ロール延伸法を用いて縦方向に８４℃で２．９倍延伸した後、さらに７０℃で１．３倍延伸した。得られた一軸延伸フィルムをテンターに導いて、横方向に１１０℃で４．０倍延伸し、２３０℃で熱処理を行い、フィルムのトータルの重量法厚み４．５０μｍの二軸延伸ポリエステルフィルムを得た。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
【００５２】
実施例２
（粗面側原料）
ポリエステル（ｃ）に、炭酸カルシウム粒子、架橋高分子粒子の替わりに、平均粒径２．４０μｍのシリカ粒子を添加する以外はまったく同様にして極限粘度０．６６のポリエステル（ｄ）を得た。このポリエステル（ｄ）には、１．００重量％のシリカ粒子が含有されていた。粒子を添加しないこと以外はポリエステル（ｄ）と同様にして、極限粘度０．６６の希釈用ポリエステル（ｅ）を得た。ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．０８重量％含有する原料を得た。
【００５３】
（平滑面側原料）
ポリエステル（ｃ）において炭酸カルシウム粒子、架橋高分子粒子の替わりに平均粒径０．７０μｍの炭酸カルシウム粒子添加する以外はまったく同様にして極限粘度０．６６のポリエステル（ｆ）を得た。このポリエステル（ｆ）には、０．５０重量％の炭酸カルシウム粒子が含有されていた。
【００５４】
（製膜・スリット）
実施例１と同様にして、フィルムのトータルの重量法厚み４．５０μｍの二軸延伸ポリエステルフィルムを得た。この際、平滑面側原料の押出機はベント型二軸押出機とし、該押出機中で酸化防止剤としてペンタエリスリチル−テトラキス［３−（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニル）プロピオネート］を平滑面の層のポリエステルに対し、５００ｐｐｍとなるように定量フィーダーを用いて添加した。なお、ベント口は減圧とし、水分等の揮発物を除去した。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
【００５５】
実施例３
（粗面側原料）
ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．１８重量％含有する原料を得た。
（平滑面側原料）
ポリエステル（ａ）とポリエステル（ｂ）を混合し、平均粒径１．４０μｍの析出粒子を０．１２％含有する原料を得た。
（製膜・スリット）
粗面側の押出量と平滑面側の押出量を４対４に制御する以外は実施例１と同様にして、フィルムのトータルの重量法厚み４．００μｍの二軸延伸ポリエステルフィルムを得た。なお、何れの層の押出機中においても、酸化防止剤は添加しなかった。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
【００５６】
実施例４
（粗面側原料）
ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．４０重量％含有する原料を得た。
（平滑面側原料）
ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．１０重量％含有する原料を得た。
（製膜・スリット）
粗面側の押出量と平滑面側の押出量を６対５に制御する以外は実施例１と同様にして、フィルムのトータルの重量法厚み５．５０μｍの二軸延伸ポリエステルフィルムを得た。なお、何れの層の押出機中においても、酸化防止剤は添加しなかった。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
【００５７】
比較例１
（粗面側原料・平滑面側原料）
何れにも、ポリエステル（ｆ）を用いた。
（製膜・スリット）
粗面側の押出量と平滑面側の押出量を１対１に制御する以外は実施例１と同様にして、フィルムのトータルの重量法厚み５．５０μｍの実質上、単層の二軸延伸ポリエステルフィルムを得た。なお、何れの層の押出機中においても、酸化防止剤は添加しなかった。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
【００５８】
比較例２
（粗面側原料）
ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．７０重量％含有する原料を得た。
（平滑面側原料）
ポリエステル（ｄ）とポリエステル（ｅ）とを混合し、シリカ粒子を０．３０重量％含有する原料を得た。
（製膜・スリット）
実施例１と同様にして、フィルムのトータルの重量法厚み４．５０μｍの二軸延伸ポリエステルフィルムを得た。なお、何れの層の押出機中においても、酸化防止剤は添加しなかった。このマスターロールから５００ｍｍ幅にトリミングしながら、内径６インチの巻き芯にトータル長３５０００ｍ、２５０ｍ／分の速度で、ロール状に巻き取り、ロール状フィルムとした。
実施例１〜４および比較例１〜２について得られた結果をまとめて下記表１および２に示す。
【００５９】
【表１】

【００６０】
【表２】

【００６１】
【発明の効果】
本発明のフィルムは、優れた表面特性および特定の表裏差を有するため、薄膜であり、かつ、表面が平滑であるにも関わらず、生産時および加工時の作業性を満足し、かつ、高度な機能性を与えることができ、その工業的価値は高い。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laminated polyester film. More specifically, the present invention relates to a laminated polyester film that is thin and satisfies workability during production and processing and has high functionality despite having a smooth surface. is there.
[0002]
[Prior art]
The biaxially oriented polyester film has various properties such as mechanical properties, heat resistance, electrical properties, and chemical resistance in a highly balanced manner and is excellent in terms of cost performance. Widely used as industrial material for industrial use. Not only for these uses but also for miniaturization of electrical equipment and information equipment, the demand for a polyester film which is thinner than before is rapidly increasing. In addition to thinning, it is important that the smoothness is not impaired in various applications.
For example, the surface should be flat so as not to impair the magnetic recording output as typified by a magnetic recording medium, etc. ) Is required to have a flat surface.
[0003]
However, according to the conventional formulation, when the thickness is small and the surface is smooth, when the film surfaces are in contact with each other when the film is wound into a roll at the time of film production, the film is smooth and hard to slip, thereby causing wrinkles. This causes a decrease in winding yield and significantly impairs productivity. In addition, defects (such as uneven coating at the time of coating on the surface) are caused in the subsequent processing step.
Thus, it is extremely difficult to have a trade-off between reducing the film thickness and maintaining the smoothness of the surface, and satisfying both at the same time.
[0004]
[Patent Document 1] JP-A-7-227949
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a thin-film polyester film that satisfies the productivity at the time of production and the workability at the time of processing, and can provide high functionality.
[0006]
[Means for Solving the Problems]
The present inventor has conducted intensive studies in view of the above problems, and as a result, has found that having a specific laminated structure can easily solve the above problems, and has completed the present invention.
[0007]
That is, the gist of the present invention is characterized in that the film thickness by a gravimetric method is 3.0 to 8.0 μm, the arithmetic average roughness (Ra) of at least one surface is 0.050 μm or less, and the film has a laminated structure. To be present in the polyester film.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The polyester constituting the film of the present invention refers to a polyester in which 80% or more of the repeating units have an ethylene terephthalate unit or an ethylene-2,6-naphthalate unit. Such polyesters are usually subjected to a polycondensation reaction via a transesterification reaction using (1) a lower alkyl ester of an aromatic dicarboxylic acid and glycol as main starting materials, or (2) a reaction between an aromatic dicarboxylic acid and glycol. Is obtained by performing a polycondensation reaction via an esterification reaction using as a main starting material. In order to carry out these reactions, a method of adding a metal compound as a catalyst is usually used. For example, compounds such as Ca, Mg, Mn, and Li are generally used as transesterification catalysts, and compounds such as Sb, Ti, Ge, Sn, and Co are generally used as polycondensation reaction catalysts. Further, the polyester of the present invention may contain another third component without departing from the scope of the present invention.
[0009]
As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid and the like) ) Etc. can be used. As the glycol component, in addition to ethylene glycol, for example, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like can be used.
[0010]
The intrinsic viscosity of the polyester used in the present invention is usually 0.45 or more, preferably 0.50 to 1.0, and more preferably 0.52 to 0.80. If the intrinsic viscosity is less than 0.45, there may be a problem that productivity during film production is reduced and mechanical strength of the film is reduced. On the other hand, from the viewpoint of melt extrusion stability of the polymer, the intrinsic viscosity preferably does not exceed 1.0.
[0011]
The polyester film of the present invention needs to have a total thickness measured by a gravimetric method of 3.0 μm to 8.0 μm, and preferably 4.0 μm to 6.0 μm. When the film thickness exceeds 8.0 μm, the capacity as a final product becomes large, which is inappropriate. When the thickness of the film is less than 3.0 μm, it is difficult to design the surface roughness of the front and back surfaces within the range intended by the present patent by forming a laminated structure.
In the present invention, as described later, a surface having a lower arithmetic average roughness (Ra) on the film surface is defined as a smooth surface, and the other surface is defined as a roughened surface.
[0012]
The polyester film of the present invention must have an arithmetic average roughness (Ra) of the smoother film surface of 0.050 μm or less, and preferably 0.030 μm or less, for the purpose of improving the functionality as a final product. And more preferably 0.020 μm or less. The arithmetic average roughness (Ra) will be described in detail in Examples. If the arithmetic average roughness of both surfaces exceeds 0.050 μm, the functionality of the final product is inferior and is unsuitable.
The greatest feature of the present invention resides in adopting a laminated structure having a layer constituting the above-mentioned smooth surface and at least another layer.
[0013]
That is, the opposite surface of the smooth surface is to provide an appropriate rough surface in consideration of the suitability for processing during and after production. This roughened surface can be achieved by including the above-mentioned particles in the layer, but it is preferable that the weight-average thickness of the final roughened layer be 2.0 μm or less. It is preferable from the viewpoints of forming a projection and cost.
The laminated structure referred to in the present invention is obtained by stretching and heat-treating an unstretched film extruded by a so-called co-extrusion method in which all layers are co-melt extruded from a die of an extruder. Hereinafter, a co-extruded two-layer film will be described as a laminated structure, but is not limited to a co-extruded two-layer film and may have a structure of three or more layers as long as the gist of the present invention is not exceeded. Hereinafter, an example of lamination by the co-extrusion method will be described.
[0014]
First, the polyester raw material constituting each layer is supplied to an extruder for coextrusion lamination. That is, they are laminated using a multi-manifold or a feed block, and extruded from a slit die as a laminated molten sheet. At that time, the thickness of each layer can be set by adjusting the flow rate of the polymer using a fixed-quantity feeder such as a gear pump installed on the melt line.
Examples of the particles used in the present invention include calcium carbonate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, inorganic particles such as molybdenum sulfide, crosslinked polymer particles, Examples thereof include organic particles such as calcium oxalate and precipitated particles formed during the polymerization of polyester, and are preferably precipitated particles containing calcium carbonate, silica, and calcium and phosphorus.
[0015]
This is because calcium carbonate is preferable because the particle size distribution is sharpened, coarse particles (particles significantly larger than the average particle size) are easily cut, and slip and abrasion resistance are easily obtained after forming a film. Another reason is that silica is preferably available at a relatively low price compared to other particles. In addition, for precipitated particles containing calcium and phosphorus, there is no need to add particles again, it is inexpensive, the deformation of the particles during stretching during film formation is small, the projection height can be maintained, and good winding It is preferable that the properties can be exhibited.
[0016]
In addition, it is of course possible to employ a plurality of types of particles represented above in order to achieve the effects of the present invention for each of the roughened surface and the smooth surface. Particularly, in order to further improve the slipperiness of the film surface and the winding workability, in addition to the above-described particles, small particles having an average particle diameter of 0.50 μm or less are used in combination without impairing the gist of the present invention. You can also. Preferred as small particles are silica, crosslinked polymer particles, calcium carbonate and precipitated particles formed during polymerization of polyester.
[0017]
In producing the polyester containing the added particles, the particles may be added during the polyester synthesis reaction or may be added directly to the polyester. In the case of adding during the synthesis reaction, a method of adding the slurry as a slurry in which particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, a method of adding and mixing to the polyester as a dried particle or as a slurry dispersed in water or an organic solvent having a boiling point of 200 ° C. or lower using a twin-screw kneading extruder is preferable. . The particles to be added may be subjected to a process such as pulverization, dispersion, classification, and filtration as needed.
[0018]
As a method of adjusting the content of particles, a master material containing particles at a high concentration is prepared in the above-described manner, and at the time of forming a film, the material is diluted with a material that does not substantially contain particles. The method of adjusting is effective.
Further, as an additive other than the above-mentioned projection forming agent, as necessary, an antistatic agent, a stabilizer, a lubricant, a cross-linking agent, an anti-blocking agent, an antioxidant, a coloring agent, a light-blocking agent, an ultraviolet absorber, etc. May be contained within a range that does not deteriorate the capacitor characteristics.
[0019]
In the present invention, the difference in arithmetic average roughness (Ra) between both surfaces is preferably 0.030 μm or less, and more preferably 0.020 μm or less. That is, it is possible to prevent the so-called show-through phenomenon, that is, the roughness on the rough surface side from being transferred to the smooth surface when the pressure is applied between the layers and the interlayer is pressed, thereby preventing the effect from being reduced.
In order to suppress the roughness on the rough surface side, the arithmetic average roughness is kept low, and, as the particles exhibiting the winding characteristics, among the above-mentioned particles, the precipitated particles containing calcium and phosphorus are formed during film formation. It is most preferable because the deformation of the particles during stretching is small, the height of the protrusions can be maintained, and good winding characteristics are exhibited.
[0020]
Further, in the present invention, the number of coarse protrusions on the smooth surface measured by the method described later is 200 / cm.²The following is preferred. That is, not only the average roughness such as the arithmetic average roughness (Ra) is kept low, but also the number of coarse projections is kept low, so that the appearance is typified by an appearance represented by a vapor-deposited film. The phenomenon can be suppressed more effectively. To achieve such a large number of projections, it is effective to add a so-called antioxidant. The antioxidant may be added at the time of polymerization of the polyester raw material, or may be added in an extrusion step at the time of film formation as described later.
[0021]
In the film of the present invention, a layer for imparting adhesiveness can be provided on the above-mentioned smooth side layer in order to enhance the adhesiveness with a layer in contact with the film according to various end uses. In order to impart this adhesiveness, a polymer (binder polymer) comprising at least one selected from the group consisting of an aqueous polyester polymer and an aqueous acrylic polymer is particularly useful.
In addition, urea-based, melamine-based, guanamine-based, and acrylamide-based methylolated or alkylolated crosslinkable polymers for improving the adhesion resistance (blocking resistance), water resistance, solvent resistance, and mechanical strength of the coating layer. -Based, polyamide-based compounds, epoxy-based compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, zircoaluminate-based coupling agents, peroxides, heat and photoreactive vinyl compounds Or a photosensitive resin.
[0022]
Further, for the purpose of improving the sticking property and the slipperiness, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black, as inorganic fine particles in the coating layer. Molybdenum sulfide, antimony oxide sol, or the like, as organic fine particles, may contain polystyrene, polyethylene, polyamide, polyester, polyacrylate, epoxy resin, silicone resin, fluororesin, or the like.
Further, if necessary, it may contain an antifoaming agent, a coating improver, a thickener, an antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like. .
[0023]
As a method of applying the above-mentioned coating solution to a polyester film, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, and other coating apparatuses described in “Coating System”, written by Yuji Harasaki, Maki Shoten, 1979 Can be used. The coating layer may be provided in the film manufacturing process, or may be applied after the film is manufactured. In particular, from the viewpoint of uniformity of coating thickness and production efficiency, a method of coating in a film manufacturing process is preferable.
[0024]
As a method of applying in a film manufacturing process, a method of applying a coating solution to a polyester unstretched film, sequentially or simultaneously biaxially stretching, applying to a uniaxially stretched polyester film, and further perpendicularly to a further uniaxial stretching direction Or a method in which the film is applied to a biaxially stretched polyester film and further stretched in the transverse and / or longitudinal directions.
The thickness of the coating layer is usually in the range of 0.005 to 1.0 μm, preferably in the range of 0.01 to 0.5 μm. When the thickness of the coating layer exceeds 1.0 μm, the electrical characteristics may be deteriorated. On the other hand, when the thickness of the coating layer is less than 0.005 μm, there is a tendency that coating unevenness and coating slippage tend to occur.
[0025]
Next, the method for producing the film of the present invention will be specifically described.
First, a polyester raw material is supplied to an extruder for coextrusion lamination. That is, they are laminated using a multi-manifold or a feed block, and extruded from a slit die as a laminated molten sheet. At that time, the thickness of each layer can be set by adjusting the flow rate of the polymer using a fixed-quantity feeder such as a gear pump installed on the melt line.
In the present invention, when the antioxidant is added in the extrusion step, the antioxidant may be added as a powder or as a slurry dispersed in an appropriate solvent. In the case of dispersing and adding in a solvent, water or an organic solvent having a boiling point of 200 ° C. or less is preferable as the solvent, and ethylene glycol is particularly preferable as the organic solvent. In this case, the extruder is preferably a twin-screw extruder, and the twin-screw extruder has one or more vent ports, and it is preferable that at least one of the vent ports is depressurized. That is, it is preferable to remove the solvent in the extrusion step.
[0026]
The addition of the antioxidant is performed at any stage until the polymer has passed through the twin-screw extruder. Examples of the method of adding the antioxidant include (1) a method in which particles are previously sprayed on a raw material polyester, and (2) a raw material polyester chip is provided with an addition port in a twin-screw extruder, and is melted or partially melted. A method of adding particles to the polyester in the state is mentioned. In particular, the method (2) is preferably employed.
The amount of the antioxidant added in the twin-screw extruder is usually in the range of 10 to 3000 ppm, preferably 50 to 1500 ppm, more preferably 100 to 1000 ppm, based on the polyester constituting the layer. If the added amount is 10 ppm or less, the effect of preventing oxidation may not be sufficiently exerted. If the added amount is 3000 ppm or more, unreacted antioxidant may remain in the film, and the quality of the film may be deteriorated.
The antioxidant used in the present invention may be a phosphorus-based antioxidant or a phenol-based antioxidant, but a phenol-based antioxidant is preferably used. Examples of the phenolic antioxidants include the following antioxidants.
[0027]
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[0028]
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[0029]
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[0030]
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[0031]
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[0032]
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[0033]
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[0034]
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[0035]
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[0036]
Next, the molten sheet is quenched and solidified on a rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature, to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.
In the present invention, the sheet thus obtained is biaxially stretched to form a film. To describe the biaxial stretching conditions specifically, the unstretched sheet is first stretched in the first axial direction. The stretching temperature range is usually from 70 to 150 ° C., the stretching ratio is usually from 2.5 to 6 times, and the stretching can be performed in one step or two or more steps. Next, the second axis direction, that is, once cooling the uniaxially oriented film below the glass transition point in the direction orthogonal to the first axis direction, or without cooling, for example, preheated to a temperature range of 80 to 150 ° C. Further, the film is stretched 2.5 to 5 times, preferably 3.0 to 4.5 times at substantially the same temperature to obtain a biaxially oriented film.
[0037]
In addition, it is preferable to perform stretching in the first axial direction in two or more steps because good thickness uniformity can be achieved. In addition, a method of further stretching in the longitudinal direction after the transverse stretching is possible, but in any case, it is preferable that the total stretching ratio in the longitudinal direction is 3.5 times or more.
The film thus obtained is heat-treated under elongation, limited shrinkage, or constant length within 30% for 1 second to 5 minutes. At this time, re-stretching may be performed in the longitudinal direction, the lateral direction, or both directions during or after the heat treatment step.
[0038]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “parts” indicates “parts by weight”, “%” indicates “% by weight”, and “ppm” indicates “ppm by weight”.
[0039]
(1) Intrinsic viscosity of polymer [η] (dl / g)
1 g of the polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C.
[0040]
(2) Average particle size of added particles (d50) (μm)
In the equivalent spherical distribution measured by a centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type) manufactured by Shimadzu Corporation, the particle size with an integrated volume fraction of 50% integrated from the large particle side was defined as the average particle size (d50).
[0041]
(3) Average particle size of precipitated particles (d50) (μm)
After the polyester film containing the precipitated particles is sandwiched between the preparations, melted and cooled, observed with a microscope, the image is measured by processing with an image processing device (“Quantimet 500+” manufactured by Leica), and its equivalent spherical distribution is measured. The particle diameter at an integrated volume fraction of 50% integrated from the large particle side was defined as the average particle diameter (d50).
[0042]
(4) Measurement of the amount of precipitated particles
After adding 1.0 liter of o-chlorophenol to 100 g of polyester and heating at 120 ° C. for 3 hours, centrifugation was performed for 40 minutes using an ultracentrifuge (“55P-72” manufactured by Hitachi Koki) to obtain particles. Is vacuum dried at 100 ° C. The above particles are treated with a scanning differential calorimeter, and if a melting peak corresponding to the polymer is observed, o-chlorophenol is added to the particles, heated and cooled, and then centrifuged again. Then, particles in which the melting peak is no longer recognized are regarded as precipitated particles. The centrifugation operation is usually performed twice.
[0043]
(5) Total gravimetric thickness (total gravimetric thickness) (μm)
First, the density of the film specimen (ρ; (g / cm³  )) Was measured by the method D (density gradient tube method) defined in JIS K7112, and then 100 ± 0.5 cm²  Was placed on a balance, the film mass (m; (g)) was correctly measured to 0.0001 g, and then calculated by the following equation. This measurement was repeated five times, and the median of the obtained values of t was defined as the total weight d (μm).
t = 100m / ρ
[0044]
(6) Arithmetic mean roughness Ra (μm)
A test piece was cut out, and Ra was measured and calculated for both surfaces by the following method, and each was defined as an arithmetic average roughness. That is, using an SE3500 manufactured by Kosaka Laboratory Co., Ltd., a 2.5 mm evaluation length was measured using a stylus having a tip radius of 5 μm and a load of 30 mg. Arithmetic mean roughness (Ra) was in accordance with JIS B 0601-1994. That is, the roughness curve is extracted by the reference length L in the direction of the average line, the x-axis is taken in the direction of the average line of the extracted portion, the y-axis is taken in the direction of the vertical magnification, and the roughness curve is represented by y = f ( When expressed in x), the value obtained by the following equation is expressed in micrometers (μm). The longitudinal magnification was set to 200,000 times, the cut-off value was set to 0.08 mm, and ten roughness curves were measured for one surface, and the average of 10 points of Ra was obtained.
Ra = (1 / L) ∫₀ ^L| F (x) | dx
[0045]
(7) Number of coarse protrusions on the smooth surface side f (pieces / cm²)
From the vicinity of the core of the roll produced by the winding yield evaluation method described below, a test piece cut out was vapor-deposited with aluminum having a thickness of 450 mm on the surface having a lower arithmetic average roughness, and a two-beam interference microscope manufactured by Nippon Kogaku Kogyo Co., Ltd. It measured using. Those exhibiting fifth or higher order interference fringes at a measurement wavelength of 0.54 μm are 5 cm or larger coarse projections of 5 cm²Over a unit area (1 cm²Per). The fifth-order height corresponds to five times の the measurement wavelength = 1.35 μm, and the fifth-order or larger coarse projection means having a height of 1.35 μm or more.
[0046]
(8) Cloudiness of vapor deposited film (appearance)
From the vicinity of the roll core produced by the roll yield evaluation method described below, a test piece cut out was coated with aluminum having a thickness of 450 mm on the surface having the lower arithmetic average roughness, and visually judged according to the following criteria. did.
◎: Excellent cloudiness not recognized in appearance
：: Cloudiness can be visually recognized, but there is no problem in practical use and good.
×: The appearance is so cloudy that it is unusable and defective
[0047]
(9) Roll yield
After film formation, while trimming to a width of 500 mm from the master roll, the total length is 35,000 m, and the roll is wound at a speed of 250 m / min on a 6-inch inner diameter winding core so that the smooth surface side becomes the outer surface. Those that were wound without wrinkling were accepted, and the acceptance rate was judged according to the following criteria.
◎: 95% or more and excellent
：: 80% or more and less than 95%, good
X: Less than 80%. Bad
[0048]
Example 1
(Rough surface material)
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol and 0.11 part of calcium acetate monohydrate were placed in a reactor, heated and heated, and methanol was distilled off to perform a transesterification reaction. It took 4 hours from the start of the reaction. The temperature was raised to 230 ° C., and the transesterification reaction was substantially completed. Next, a solution in which 0.124 part of triethyl phosphite and 0.54 part of triethyl phosphate are uniformly dissolved in ethylene glycol is added to the reaction mixture, and 0.04 part of antimony trioxide is added. In short, the temperature reached 236 ° C. From this point, the pressure in the system was gradually reduced, and the temperature in the system was raised to 265 ° C. and the pressure to 300 mmHg 80 minutes after the addition of antimony trioxide. Thereafter, the temperature was gradually raised and reduced to 285 ° C. and 1 mmHg or less. did. After 4 hours, the inside of the system was returned to normal pressure and the polymer was discharged to form chips, thereby obtaining a polyester (a) having an intrinsic viscosity of 0.66. A large number of uniform and fine precipitated particles were observed in the polyester (a), and the average particle size was 1.40 μm. When the amount of the precipitated particles was measured according to the method described, it was 0.40% by weight based on the polyester.
[0049]
On the other hand, 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of calcium acetate monohydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction, requiring 4 hours from the start of the reaction. Then, the temperature was raised to 230 ° C., and the transesterification reaction was substantially completed. Further, 0.06 part of phosphoric acid and 0.04 part of antimony trioxide were added, the reaction system was gradually reduced in pressure, the temperature was raised, and the polycondensation reaction was carried out for 4 hours to obtain a diluting polyester (b) having an intrinsic viscosity of 0.66. Got.
Polyester (a) and polyester (b) were mixed to obtain a raw material containing 0.12% of precipitated particles having an average particle size of 1.40 μm.
[0050]
(Smooth surface side material)
In a reactor, 86 parts of terephthalic acid and 70 parts of ethylene glycol are placed, and at about 250 ° C., 0.5 kg / mm²  The esterification reaction was carried out for 4 hours under pressure. Next, 0.015 parts of antimony trioxide, calcium carbonate particles having an average particle size of 0.80 μm, crosslinked polymer particles having an average particle size of 0.35 μm, and 0.01 part of phosphoric acid were added. The temperature was gradually raised from 250 ° C. to 285 ° C., and the pressure was gradually reduced from normal pressure to 0.5 mmHg. After 4 hours, the polycondensation reaction was stopped to obtain a polyester (c) having an intrinsic viscosity of 0.66. This polyester (c) contained 0.06% by weight of calcium carbonate particles and 0.30% by weight of crosslinked polymer particles.
[0051]
(Film forming / slit)
The raw material on the rough side and the raw material on the smooth side are dried in a conventional manner, supplied to separate extruders, melted at 290 ° C., extruded into a sheet, and quenched on a cooling roll using an electrostatic contact method, An amorphous sheet was used. At this time, the extruder for the raw material on the smooth surface side is a vented twin-screw extruder, and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxy) is used as an antioxidant in the extruder. Phenyl) propionate] was added to the smooth-surface layer polyester using a quantitative feeder so as to be 500 ppm. The vent port was depressurized to remove volatiles such as water. In addition, the extrusion amount on the rough surface side and the extrusion amount on the smooth surface side were controlled to 4 to 5, and the cooling roll surface was extruded so that the smooth surface was in contact therewith. The obtained sheet was stretched 2.9 times in the longitudinal direction at 84 ° C. using a roll stretching method, and further stretched 1.3 times at 70 ° C. The obtained uniaxially stretched film is guided to a tenter, stretched 4.0 times in the transverse direction at 110 ° C., and heat-treated at 230 ° C. to obtain a biaxially stretched polyester film having a total gravimetric thickness of 4.50 μm of the film. Was. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
[0052]
Example 2
(Rough surface material)
Polyester (d) having an intrinsic viscosity of 0.66 was obtained in exactly the same manner except that silica particles having an average particle size of 2.40 μm were added to polyester (c) instead of calcium carbonate particles and crosslinked polymer particles. This polyester (d) contained 1.00% by weight of silica particles. A polyester for dilution (e) having an intrinsic viscosity of 0.66 was obtained in the same manner as the polyester (d) except that no particles were added. Polyester (d) and polyester (e) were mixed to obtain a raw material containing 0.08% by weight of silica particles.
[0053]
(Smooth surface side material)
Polyester (f) having an intrinsic viscosity of 0.66 was obtained in exactly the same manner as polyester (c) except that calcium carbonate particles having an average particle size of 0.70 μm were added instead of calcium carbonate particles and crosslinked polymer particles. This polyester (f) contained 0.50% by weight of calcium carbonate particles.
[0054]
(Film forming / slit)
In the same manner as in Example 1, a biaxially oriented polyester film having a total gravimetric thickness of the film of 4.50 μm was obtained. At this time, the extruder for the raw material on the smooth surface side is a vented twin-screw extruder, and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxy) is used as an antioxidant in the extruder. Phenyl) propionate] was added to the smooth-surface layer polyester using a quantitative feeder so as to be 500 ppm. The vent port was depressurized to remove volatiles such as water. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
[0055]
Example 3
(Rough surface material)
Polyester (d) and polyester (e) were mixed to obtain a raw material containing 0.18% by weight of silica particles.
(Smooth surface side material)
Polyester (a) and polyester (b) were mixed to obtain a raw material containing 0.12% of precipitated particles having an average particle size of 1.40 μm.
(Film forming / slit)
A biaxially stretched polyester film having a total gravimetric thickness of 4.00 μm was obtained in the same manner as in Example 1 except that the extrusion amount on the rough side and the extrusion amount on the smooth side were controlled at 4: 4. No antioxidant was added in any of the extruders. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
[0056]
Example 4
(Rough surface material)
Polyester (d) and polyester (e) were mixed to obtain a raw material containing 0.40% by weight of silica particles.
(Smooth surface side material)
Polyester (d) and polyester (e) were mixed to obtain a raw material containing 0.10% by weight of silica particles.
(Film forming / slit)
A biaxially oriented polyester film having a total gravimetric thickness of 5.50 μm was obtained in the same manner as in Example 1 except that the extrusion amount on the rough side and the extrusion amount on the smooth side were controlled at 6: 5. No antioxidant was added in any of the extruders. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
[0057]
Comparative Example 1
(Rough surface material / Smooth surface material)
In each case, polyester (f) was used.
(Film forming / slit)
Except for controlling the amount of extrusion on the rough surface side and the amount of extrusion on the smooth surface side in a one-to-one manner, substantially the same monolayer biaxial stretching with a total gravimetric thickness of 5.50 μm was performed in the same manner as in Example 1. A polyester film was obtained. No antioxidant was added in any of the extruders. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
[0058]
Comparative Example 2
(Rough surface material)
The polyester (d) and the polyester (e) were mixed to obtain a raw material containing 0.70% by weight of silica particles.
(Smooth surface side material)
The polyester (d) and the polyester (e) were mixed to obtain a raw material containing 0.30% by weight of silica particles.
(Film forming / slit)
In the same manner as in Example 1, a biaxially oriented polyester film having a total gravimetric thickness of the film of 4.50 μm was obtained. No antioxidant was added in any of the extruders. While trimming from this master roll to a width of 500 mm, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a roll core having an inner diameter of 6 inches to obtain a roll film.
The results obtained for Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Tables 1 and 2 below.
[0059]
[Table 1]

[0060]
[Table 2]

[0061]
【The invention's effect】
The film of the present invention has excellent surface properties and a specific difference between front and back, so that it is a thin film and satisfies workability during production and processing, despite having a smooth surface, and Functionality, and its industrial value is high.

Claims (3)

A polyester film having a laminated structure having a film thickness by a weight method of 3.0 to 8.0 μm, an arithmetic average roughness (Ra) of at least one side of 0.050 μm or less, and a laminated structure. The polyester film according to claim 1, wherein the number of coarse protrusions on one film surface is 200 / cm ² or less. 3. The polyester film according to claim 1, wherein at least one layer contains at least one antioxidant.