JP4104420B2 - Laminated polyester film - Google Patents

Description

【００８７】
Ｚ_jkは測定方法（２４６．６μｍ）、それと直行する方法（１８７．５μｍ）をそれぞれｍ分割、ｎ分割したときの各方向のｊ番目、ｋ番目の位置における２次元粗さチャート上の高さである。
【００８８】
（６）ヤング率
フィルムを試料巾１０ｍｍ、長さ１５ｃｍに切り、チャック間１００ｍｍ、引張速度１０ｍｍ／分、チャート速度５００ｍｍ／分の条件下で万能引張試験装置（東洋ボールドウィン製、商品名：テンシロン）にて引っ張る。得られた荷重―伸び曲線の立ち上がり部の接線よりヤング率を計算する。
【００８９】
（７）層Ｂ中の不活性粒子
試料フィルム小片を走査型電子顕微鏡用試料台に固定し、日本電子（株）製スパッターリング装置（ＪＦＣ−１１００型イオンエッチング装置）を用いてフィルム表面に下記条件にてイオンエッチング処理を施す。条件は、ベルジャー内に試料を設置し、約１０^-3Ｔｏｒｒの真空状態まで真空度を上げ、電圧０.２５ｋＶ、電流１２.５ｍＡにて約１０分間イオンエッチングを実施する。更に同装置にて、フィルム表面に金スパッターを施し、走査型電子顕微鏡にて５,０００〜１０,０００倍で観察し、日本レギュレーター（株）製ルーゼックス５００にて各不活性粒粒子の等価球径分布を求める。得られら等価球形分布から、粒径が１００ｎｍを超える不活性粒子を抜き出し、その重量積算５０％の点から、粒径１００ｎｍを超える不活性粒子の平均粒径を算出する。
【００９０】
（８）磁気テープの製造及び特性評価
積層ポリエチレンテレフタレートフィルムの第一の層側の表面に、真空蒸着によりコバルト−酸素薄膜を１１０ｎｍの厚みで形成し、次にコバルト−酸素薄膜層上に、スパッタリング法によりダイヤモンド状カーボンを１０ｎｍの厚みで形成させ、更に含フッ素カルボン酸系潤滑剤を順次設ける。続いて、コバルト−酸素薄膜を形成したのとは反対側の表面に、カーボンブラック、ポリウレタン、シリコーンからなるバックコート層を厚みが５００ｎｍとなるように設け、スリッターにより幅８ｍｍ及び６．３５ｍｍにスリットし、市販のリールに巻き取り、磁気テープを作成した。市販のＨｉ８方式８ｍｍビデオテープレコーダーを用いてビデオＳ／Ｎ比を、市販のカメラ一体型デジタルビデオテープレコーダーを用いてドロップアウト（ＤＯ）個数を求める。
【００９１】
ＤＯ個数の測定は、作成した６．３５ｍｍテープを市販のカメラ一体型デジタルビデオテープレコーダーで録画後、１分間の再生をして画面に現れたブロック状のモザイクの個数をカウントすることによって行う。
【００９２】
Ｃ／Ｎは、市販のＨｉ８用ＶＴＲ（ＳＯＮＹ株式会社製、ＥＶ−ＢＳ３０００）を用いて、７ＭＨｚ±１ＭＨｚのＣ／Ｎの測定を行った。このＣ／Ｎを市販のＨｉ８用ビデオテープ（ＳＯＮＹ株式会社製、蒸着型テープ Ｅ６−１２０ＨＭＥ４）と比較して、＋３ｄＢ以上のフィルムを優、＋１〜＋３ｄＢのフィルムを良、＋１ｄＢ未満を不良として、評価した。
【００９３】
高温恒湿下の走行耐久性は４０℃、８０％ＲＨで記録再生を７００回繰り返した後のＣ／Ｎを測定し、初期値からのずれで判定する。
○：初期値に対して＋０．０ｄＢ以上
△：初期値に対して−１．０ｄＢ以上〜＋０．０ｄＢ未満
×：初期値に対して−１．０ｄＢ未満
【００９４】
［実施例１］
ジメチルテレフタレート１００部とエチレングリコール７０部の混合物に、エステル交換触媒として酢酸マンガン・4水塩０．０２５部を添加し、内温を１５０℃から徐々に上げながらエステル交換反応を行った。エステル交換反応が９５％となった時点で、安定剤として亜リン酸を０．０１部添加し、充分撹拌した後、エチレングリコール２．５部中で無水トリメリット酸０．８部とテトラブチルチタネート０．６５部を反応せしめた液（チタン含有率は１１重量％）０．０１４部を添加して充分撹拌した後、次いで反応生成物を重合反応器に移し、高温真空下（最終内温２９５℃）にて重縮合を行い、固有粘度０．６０のポリエステルA用のポリエチレンテレフタレート（樹脂A１）を得た。
【００９５】
さらに、上記と同様の方法で、エステル交換反応を行い、エステル交換反応が９５％となった時点で、安定剤として亜リン酸を０．０１部添加し、充分撹拌した後、三酸化アンチモン０．０３部添加した。系内に混入した水を充分留出させた後、滑剤（不活性粒子Ｂ）として、平均粒径３００ｎｍのシリコーン粒子および平均粒径１００ｎｍのθ型アルミナを、樹脂中にそれぞれ０．０５％および０．２％添加して充分撹拌した後、次いで反応生成物を重合反応器に移し、高温真空下（最終内温２９５℃）にて重縮合を行い、固有粘度０．７０のポリエチレンテレフタレートを得た。この際、本ポリマー中のアンチモン残存量は２５０ｐｐｍであった。
【００９６】
得られたポリエチレンテレフタレート９９．７％に、炭素数が８個以上の脂肪族モノカルボン酸および多価アルコールからなる（部分ケン化）エステルワックスとしてソルビタントリステアレート（融点５５℃）の粉末０．１５％をまぶし、ベント付き二軸ルーダーにて練り込み、固有粘度０．６９のポリエステル層Ｂ用のポリエチレンテレフタレート（樹脂Ｂ１）を得た。
【００９７】
得られた樹脂Ａ１、樹脂Ｂ１を、それぞれ１７０℃で３時間乾燥後、２台の押し出し機に供給し、溶融温度２８０〜３００℃にて溶融し、平均目開き１１μｍの鋼線フィルターで高精度ろ過したのち、マルチマニホールド型共押出しダイを用いて、ポリエステル層Ａの片面にポリエステル層Ｂを積層させ、急冷して厚さ８９μｍの未延伸積層ポリエステルフィルムを得た。
【００９８】
得られた未延伸フィルムを予熱し、さらに低速・高速のロール間でフィルム温度１００℃にて３．３倍に延伸し、急冷して縦延伸フィルムを得た。次いで縦延伸フィルムのＡ層側に下記に示す組成（固形分換算）の水性塗液（全固形分濃度１．０％）をキスコート法により塗布した。
【００９９】

続いてステンターに供給し、１１０℃にて横方向に４．２倍に延伸した。得られた二軸延伸フィルムを、２２０℃の熱風で４秒間熱固定し、全厚み６．４μｍで、ポリエステル層Ｂの厚み１．０μｍの積層二軸配向ポリエステルフィルムを得た。なお、該積層二軸配向ポリエステルフィルムをロール状に巻き取る際の接圧は、窪みの形成を抑制するために、５００〜９００Ｎになるように調整した。また、このフィルムのポリエステル層Ａ、Ｂの厚みについては、２台の押し出し機の吐出量により調整した。このフィルムの皮膜層Ｃ側の表面から測定した表面粗さＷＲａは、１．７ｎｍ、このフィルムのヤング率は縦方向５０００Ｎ／ｍｍ²、横方向７０００Ｎ／ｍｍ²であった。この積層フィルムのその他の特性（表面欠点など）、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１００】
［実施例２，３］
ポリエステル層Ｂに含有させる不活性粒子Ｂの種類、平均粒径、添加量を表１に示すとおり変更した（樹脂Ｂ２）以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性、およびそのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１０１】
［実施例４］
ポリエステル層Ａおよびポリエステル層Ｂにおけるジメチルテレフタレートの代わりに２，６−ナフタレンジカルボン酸ジメチルを同モル量使用した以外は、実施例１と同様にしてポリエステル層Ａ、Ｂ用のポリエチレン−２，６−ナフタレート（ＰＥＮ）（樹脂Ａ３、Ｂ３）を得た。固有粘度は樹脂Ａ３は０．６０、樹脂Ｂ３は０．６７であった。
【０１０２】
この樹脂Ａ３、Ｂ４を、それぞれ１７０℃で６時間乾燥後、実施例１と同様にして、各層厚みを調整し、厚さ８９μｍの未延伸積層ポリエステルフィルムを得た。
【０１０３】
得られた未延伸フィルムを予熱し、さらに低速・高速のロール間でフィルム温度１３５℃にて３．６倍に延伸し、急冷して縦延伸フィルムを得た。次いで縦延伸フィルムのＡ層側に、不活性粒子Ｃをコアシェルフィラー（コア；架橋ポリスチレン、シェル；ポリメチルメタクリレート）（平均粒径；３０ｎｍ、体積形状係数０．４５）ジェイエスアール株式会社製、「SX 8721」に変更した以外は実施例１と同じ組成の水性塗液（全固形分濃度１．０％）を実施例１と同様に塗布した。
【０１０４】
続いてステンターに供給し、１５５℃にて横方向に５．７倍に延伸した。得られた二軸延伸フィルムを、２００℃の熱風で４秒間熱固定し、全厚み４．４μｍ、ポリエステル層Ｂの厚み０．６μｍの積層二軸配向ポリエステルフィルムを得た。このフィルムのポリエステル層Ａ、Ｂの厚みについては、２台の押し出し機の吐出量により調整した。このフィルムの塗膜層Ｃ側の表面から測定した表面粗さＷＲａは、１．２ｎｍ、このフィルムのヤング率は縦方向５５００Ｎ／ｍｍ²、横方向１０，５００Ｎ／ｍｍ²であった。この積層フィルムのその他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１０５】
［実施例５］
不活性粒子を表１に示した通り、変更する以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムは、フイルム表面の平坦性が損なわれてしまい、磁気テープにした際、十分な電磁変換特性を得ることができなかった。その他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１０６】
［比較例１〜３］
不活性粒子を表１に示した通り、変更し、かつロール状に巻き取る際の接圧を１０００〜１２００Ｎになるように調整した以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムは、フイルム表面の平坦性が損なわれてしまい、磁気テープにした際、十分な電磁変換特性を得ることができなかった。その他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１０７】
【表１】

【０１０８】
表１から明らかなように、本発明による積層ポリエステルフィルムは、片面が非常に平坦で、巻取り性が極めて良好であり、優れた電磁変換特性を示し、一方、本発明の要件を満たさないものは、これらの特性を同時に満足できない。
【０１０９】
【発明の効果】
本発明の積層ポリエステルフイルムは、巻き取り性に必要とされる十分な表面粗さを一方の面に具備させつつも、他方の磁性層を形成する側の面に生じるドロップアウトや電磁変換特性の低下を著しく惹起する最大高さ１５nｍ以上の突起と連続している最大深さ１０ｎｍ以上の窪みを高々１５０００個／ｍｍ²以下としたことから、高密度磁気記録媒体のベースフィルムとして用いると、得られる磁気記録媒体に、ドロップアウトが少なく、電磁変換特性に優れ、しかも走行耐久性に優れるという特性を同時に具備させることができ、その工業的価値は極めて高い。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated polyester film. More specifically, the surface of the magnetic recording medium has excellent electromagnetic conversion characteristics and running durability and a small dropout when the base film of the magnetic recording medium is used. The present invention relates to a laminated polyester film and a magnetic recording medium using the same for a base film.
[0002]
[Prior art]
In recent years, the progress of high-density magnetic recording media has been remarkable, for example, a metal thin film type magnetic recording medium in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum deposition or sputtering or a plating method, Development and commercialization of thin-layer coating type magnetic recording media in which acicular magnetic powder such as metal powder or iron oxide powder is applied to 2 μm or less are underway. As the former example, for example, a Co vapor deposition tape (Japanese Patent Laid-Open No. 54-147010) and a perpendicular magnetic recording medium made of a Co—Cr alloy (Japanese Patent Laid-Open No. 52-134706) are known. Further, as the latter example, for example, high-density magnetic recording using an ultrathin layer coating type magnetic recording medium (Electrotechnical Society Technical Report MR94-78 (1995-02)) is known. Furthermore, it is also known to use a polyethylene-2,6-naphthalate film, which can be made thinner than a polyethylene terephthalate film, as a base film of the magnetic recording medium in order to achieve high-density recording of the obtained magnetic recording medium.
[0003]
Conventional coating type magnetic recording media (magnetic recording media in which magnetic powder is mixed with an organic polymer binder and coated on a nonmagnetic support) have a magnetic layer thickness of about 2 μm or more, so that the recording wavelength In addition, only a long and low recording density was obtained. Therefore, it has been studied to improve the recording density by reducing the thickness of the magnetic layer, and a ferromagnetic metal thin film formed by thin film forming means such as vacuum deposition, sputtering or ion plating is used as the magnetic layer ( The thickness of the magnetic layer is 0.2 μm or less), or a magnetic layer thinner than the conventional coating type by providing a nonmagnetic underlayer when applying the magnetic layer (the thickness of the magnetic layer) Is about 0.13 μm).
[0004]
By the way, in a high-density magnetic recording medium in which the recording density is increased by thinning the magnetic layer in this way, the surface state of the nonmagnetic support (base film) tends to have a great influence on the surface properties of the magnetic layer. In a thin-film magnetic recording medium, the surface state of the nonmagnetic support is directly expressed as irregularities on the surface of the magnetic layer (magnetic recording layer), which causes noise in recording / reproducing signals. Therefore, it is desirable that the surface of the nonmagnetic support is as flat as possible, and that there is no foreign matter due to the catalyst.
[0005]
On the other hand, the surface of the nonmagnetic support (base film) is as rough as possible from the viewpoint of handling such as film formation of the nonmagnetic support (base film), transport in the film forming process, scratching, winding and unwinding. It is desirable. This is because if the film surface is too flat, the slipping property between the film and the film deteriorates, blocking phenomenon occurs, and the shape (roll formation) when wound on a roll deteriorates, resulting in a decrease in product yield. This increases the manufacturing cost of the product.
[0006]
As described above, the surface of the nonmagnetic support is required to be flat from the viewpoint of electromagnetic conversion characteristics, and is required to be rough from the viewpoint of handling properties and film manufacturing costs.
[0007]
Further, the metal thin film type magnetic recording medium has a traveling property on the surface of the metal thin film as a serious problem when actually used. In a coating type magnetic recording medium in which a conventional magnetic powder is mixed in an organic polymer binder and applied to a base film, a lubricant can be dispersed in the binder to improve the runnability of the magnetic layer surface. It was. However, the metal thin film type magnetic recording medium cannot take such a measure, and has a drawback such as inferior running property, particularly running property under high temperature and high humidity conditions.
[0008]
Therefore, in order to produce an excellent quality high density magnetic recording medium, it is necessary for the handling of the film and the traveling property of the magnetic recording medium while having the above-mentioned contradictory properties, that is, the flatness required for electromagnetic conversion characteristics and the like. It is necessary to give a rough surface to the surface.
[0009]
As specific methods for this purpose, (1) a method of applying a specific coating agent on the film surface to form a discontinuous film (Japanese Patent Publication No. 3-80410, Japanese Patent Application Laid-Open No. 60-180839, No. 60-180838, JP-A-60-180837, JP-A 56-16937, JP-A 58-68223, etc.), (2) A continuous film having fine irregularities on the film surface (3) A method of making the front and back surfaces different by a technique such as a co-extrusion method (JP-A-2-214657, JP-B-7) No.-80282), (1) or a method using a combination of (2) and (3) (Japanese Patent Laid-Open No. 3-73409) has been proposed.
[0010]
However, the above-mentioned method of coating and forming a discontinuous film or a continuous film having fine irregularities can solve problems such as film-to-film sliding and blocking, but it can be used to form a base film, transport it in the film forming process, From the viewpoint of product yield and product cost, there is a problem in application to a base film for a high-density and large-capacity magnetic recording medium in terms of handling such as sticking, winding and unwinding. The conventional coextrusion technique or the method of combining the coextrusion technique with a discontinuous film or a continuous film also has the same problem. Further, in the case of a metal thin film type magnetic recording medium, the problem of running property under high temperature and high humidity conditions still remains.
[0011]
In response to these problems, a polyester film composed of a three-layer laminate having a flat surface property and a running property can be obtained by specifying protrusions and depressions on at least one surface and specifying the individual ratio of both. This is proposed in Japanese Patent Laid-Open No. 11-77932. However, the film proposed in the publication requires at least three layers and cannot be achieved by two layers, and the electromagnetic conversion characteristics of the obtained magnetic recording medium even when the individual ratio of protrusions and depressions is in a specific range. In some cases, there was a shortage and dropouts occurred frequently, and further improvements were desired.
[0012]
Therefore, at present, a laminated polyester film having few surface defects, excellent winding properties, and excellent electromagnetic conversion characteristics and running properties when used as a metal thin film type magnetic recording medium has not yet been provided.
[0013]
[Patent Document 1]
JP 54-147010 A
[Patent Document 2]
JP-A-52-134706
[Patent Document 3]
Japanese Patent Publication No. 3-80410
[Patent Document 4]
JP 60-180839 A
[Patent Document 5]
JP 60-180838 A
[Patent Document 6]
JP-A-60-180837
[Patent Document 7]
JP-A-56-16937
[Patent Document 8]
JP 58-68223 A
[Patent Document 9]
Japanese Patent Application Laid-Open No. 5-194472
[Patent Document 10]
Japanese Patent Laid-Open No. 5-210833
[Patent Document 11]
JP-A-2-214657
[Patent Document 12]
Japanese Patent Publication No. 7-80282
[Patent Document 13]
JP-A-3-73409
[Patent Document 14]
JP-A-11-77932
[0014]
[Problems to be solved by the invention]
An object of the present invention is to eliminate such disadvantages of the prior art, have few surface defects, have excellent winding properties, and have excellent runnability and electromagnetic conversion characteristics when used as a metal thin film magnetic recording medium, and a laminated polyester film thereof An object of the present invention is to provide a magnetic recording medium used for a base film, particularly a ferromagnetic metal thin film type magnetic recording medium.
[0015]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the film described in the above-mentioned Japanese Patent Application Laid-Open No. 11-77932 contains inert particles on the flat surface side and has poor flatness. Was a problem. Thus, although examination was made simply to remove the inert particles from the flat surface side, sufficient electromagnetic conversion characteristics could not be obtained. Therefore, when further research is carried out, when inert particles are removed, defects of protrusions and depressions appear, which causes a situation where the electromagnetic conversion characteristics corresponding to the defects cannot be obtained even though the surface is flat. The present invention has been found.
[0016]
Thus, an object of the present invention is, according to the present invention, to comprise a polyester layer A substantially free of inert particles and a polyester layer B containing inert particles laminated on one surface thereof. The surface of the layer B has a center plane average roughness (WRaB) of 3 nm or more and 20 nm or less, and the surface of the polyester layer A is a depression having a maximum depth of 10 nm or more continuous with a protrusion having a maximum height of 15 nm or more. At most 15000 pieces / mm ² This is achieved by a laminated polyester film having the following simultaneously.
[0017]
Further, according to the present invention, as a preferred embodiment of the present invention, the surface of the polyester layer A has 10,000 depressions / mm of a maximum depth of 10 nm or more that are not continuous with protrusions of a maximum height of 15 nm or more. ² A laminated polyester film having at least one of the following: a depression having a maximum depth of 10 nm or more on the surface of the polyester layer A has a maximum major axis of 2 μm or less and a maximum minor axis of 1.5 nm or less. Provided.
[0018]
Furthermore, according to the present invention, as a preferred embodiment of the present invention, the inert particles B contained in the polyester layer B are crosslinked silicone resin, crosslinked acrylic resin, crosslinked polyester, crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide. , At least one particle selected from the group consisting of kaolin and clay, and polyester layer B is an ester wax (which may be partially saponified) consisting of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. .), The coating layer C is laminated on the surface of the polyester layer A, and the coating layer C contains inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6. The polyester which comprises 0.5 to 30 weight% and the polyester layer A or layer B is polyethylene terephthalate The polyester constituting the polyester layer A or B is polyethylene-2,6-naphthalate, the average particle size of the inert particles B contained in the polyester layer B, and the thickness of the polyester layer A Satisfying the specific formula, the inert particle B has an average particle size (d _B ) Is 50 nm or more and 1000 nm or less, and the content is 0.01 wt% or more and 1.0 wt% or less when the weight of the polyester layer B is used as a reference, the center plane average roughness of the polyester layer A side surface (WRa _A ) Is 0.5 nm or more and 10 nm or less, the polyester layer A has a thickness of 0.8 μm or more, and the polyester layer B has an average particle diameter (d _B ), And the total thickness of the polyester layer A and the layer B is 2 μm or more and 7 μm or less, or is used for a base film of a digital recording magnetic recording medium. A laminated polyester film is also provided.
[0019]
Another object of the present invention is that according to the present invention, the laminated polyester film of the present invention, the magnetic layer provided on the surface of the laminated polyester film on the polyester layer A side, and the polyester layer B side of the laminated polyester film are provided. The magnetic recording medium is characterized by comprising a back coat layer provided on the surface of the magnetic recording medium, and in particular, the magnetic recording medium is preferably a ferromagnetic metal thin film layer.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The laminated polyester film of the present invention has a polyester layer A (hereinafter sometimes simply referred to as layer A) and a polyester layer B (hereinafter sometimes simply referred to as layer B) laminated on one surface thereof. It is a laminated film.
[0021]
Examples of the polyesters A and B forming the polyester layer A and the layer B include aliphatic polyesters and aromatic polyesters, and aromatic polyesters are particularly preferable. Polyesters A and B may be the same type or different types.
[0022]
Examples of the aromatic polyester include polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalate (polyethylene-2,6-naphthalenedicarboxylate). Etc. can be illustrated. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable.
[0023]
These polyesters may be homopolyesters or copolyesters. In the case of a copolyester, for example, as a copolymerization component of polyethylene terephthalate or polyethylene-2,6-naphthalate, diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, 1,4-cyclohexanedi Other diol components such as methanol and p-xylylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalate), 2,6-naphthalenedicarboxylic acid ( However, in the case of polyethylene terephthalate), other dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, oxycarboxylic acid components such as p-oxyethoxybenzoic acid, and the like. The amount of these copolymer components is preferably 20 mol% or less, more preferably 10 mol% or less, as long as the effects of the present invention are not impaired.
[0024]
Furthermore, trifunctional or more polyfunctional compounds such as trimellitic acid, pyromellitic acid and pentaerythritol can be copolymerized. In this case, the copolymer is preferably copolymerized in an amount that is substantially linear, for example, 2 mol% or less.
[0025]
The copolymer component in the case of polyester other than polyethylene terephthalate and polyethylene-2,6-naphthalate may be considered in the same manner as described above.
[0026]
Furthermore, additives such as pigments, dyes, antioxidants, antistatic agents, light stabilizers, and light-shielding agents (for example, carbon black, titanium oxide, etc.) are required for the above polyester as long as the effects of the present invention are not impaired. It can be contained according to.
[0027]
In the laminated polyester film of the present invention, the polyester layer A and the layer B are preferably made of the same polyester, but may be made of different polyesters. For example, a laminated film in which both layer A and layer B are made of polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable, but layer A (or layer B) is polyethylene terephthalate, and layer B (or layer A) is polyethylene-2, A laminated film made of 6-naphthalate may be used.
[0028]
The polyester A forming the polyester layer A can be produced by a conventionally known method. For example, polyethylene terephthalate can be produced by a method in which terephthalic acid and ethylene glycol are esterified, or dimethyl terephthalate and ethylene glycol are transesterified, and then the reaction product is polycondensed.
[0029]
The polyester obtained by the above method (melt polymerization) can be made into a polymer having a higher degree of polymerization by a solid phase polymerization method (solid phase polymerization) as necessary.
[0030]
In the above polymerization, a known catalyst can be used, and the transesterification catalyst in the melt polymerization is preferably manganese, calcium, magnesium, titanium oxide, chloride, carbonate, carboxylate, etc., particularly acetate. That is, preferable examples include manganese acetate, calcium acetate, magnesium acetate, and titanium acetate.
[0031]
In addition, examples of the polycondensation catalyst include antimony compounds, titanium compounds, and germanium compounds.
[0032]
Preferred examples of the antimony compound include antimony trioxide, antimony pentoxide, and antimony acetate.
[0033]
Preferred examples of the titanium compound include organic titanium compounds, such as those described in JP-A-5-298670. More specifically, titanium alcoholate, organic acid salt, reaction product of tetraalkyl titanate and aromatic polyvalent carboxylic acid or anhydride, etc. can be exemplified, and preferred examples include titanium tetrabutoxide, titanium isopropoxide, titanium oxalate. , Titanium acetate, titanium benzoate, trimellitic acid titanium, a reaction product of tetrabutyl titanate and trimellitic anhydride, and the like.
[0034]
Examples of the germanium compound include those described in Japanese Patent No. 2792068. More specifically, (a) amorphous germanium oxide, (b) crystalline germanium, (c) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal, an alkaline earth metal or a compound thereof, and (d) Examples thereof include a solution of germanium oxide in a solution prepared by dissolving germanium oxide in water, adding glycol thereto and distilling off water. However, when a germanium compound is employed as a polycondensation catalyst, if the amount is large, the amount of by-product DEG during polyester synthesis increases and the thermal stability of the polyester layer A described above is reduced, so it is contained in polyester A. The germanium element (Ge) is preferably 10 ppm or less. More preferably, it is 5 ppm or less. And in order not to reduce thermal stability, it is especially preferable that the polyester A does not contain a germanium element (Ge) substantially.
[0035]
Moreover, in order to maintain thermal stability, it is preferable that the polyester A contains a phosphorus compound that is conventionally added in the polyester production process. The phosphorus compound is not particularly limited, but preferred examples include orthophosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, and tri-n-butyl phosphate.
[0036]
Further, the polyester layer A in the present invention needs to contain substantially no inactive particles. If particles are substantially contained, dropout and electromagnetic conversion characteristics are impaired. Note that the phrase “substantially containing no inert particles” as used herein means that no catalyst residue is actively precipitated or inert particles are not added. Specifically, the particle size is 0.05. The content of inactive particles of μm or more is preferably at most 0.001% by weight based on the weight of the layer A.
[0037]
Polyester B can be produced by the method described for polyester A, and those described for polyester A can be suitably used.
[0038]
By the way, the polyester layer B in this invention needs to contain particle | grains in order to provide winding property. The average particle diameter (dB) of the inert particles B is 50 to 1,000 nm, preferably 100 to 800 nm, more preferably 150 to 700 nm, and particularly preferably 200 to 600 nm. The content of the inert particles B is 0.001 to 1% by weight, preferably 0.005 to 0.8% by weight, more preferably 0.01 to 0.6% by weight, based on the polyester layer B. Particularly preferred is 0.01 to 0.2% by weight.
[0039]
Examples of the inert particles B include (1) heat-resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, crosslinked polyester, etc. Particles), (2) metal oxides (eg, aluminum oxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide, zirconium oxide, etc.), (3) metal carbonates (eg, magnesium carbonate, Calcium carbonate, etc.), (4) metal sulfates (eg, calcium sulfate, barium sulfate, etc.), (5) carbon (eg, carbon black, graphite, diamond, etc.), and (6) clay minerals (eg, kaolin, No such as clay, bentonite etc) Fine particles comprising compounds. Among these, at least one kind of particle selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, a crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide, kaolin and clay is preferable. There is no problem in further adding the above particles within a range that does not adversely affect the film properties.
[0040]
The polyester layer B in the present invention preferably further contains 0.001 to 1% by weight of an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. Here, the ester wax includes not only ester wax but also partially saponified ester wax.
[0041]
The aliphatic monocarboxylic acid has 8 or more carbon atoms, preferably 8 to 34 carbon atoms. When the number of carbon atoms is less than 8, the obtained (partially saponified) ester wax has insufficient heat resistance, and the (partially saponified) ester wax can be easily obtained under heating conditions when dispersed in polyester. It is inappropriate because it breaks down.
[0042]
Examples of aliphatic monocarboxylic acids having 8 or more carbon atoms include pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, Examples thereof include pehenic acid, lignoceric acid, serotic acid, montanic acid, melissic acid, hentriacontanoic acid, petroceric acid, oleic acid, erucic acid, linoleic acid, and mixtures containing these.
[0043]
The alcohol component of the (partially saponified) ester wax is a polyhydric alcohol having two or more hydroxyl groups. Furthermore, it is preferable that it is a polyhydric alcohol which has 3 or more of hydroxyl groups from a heat resistant viewpoint. When monoalcohol is used, the heat resistance of the produced (partially saponified) ester wax is insufficient.
[0044]
Examples of the polyhydric alcohol having two hydroxyl groups include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,7-heptanediol. 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol and the like are preferable. Preferable examples of the polyhydric alcohol having 3 or more hydroxyl groups include glycerin, erythritol, trait, pentaerythlit, arabit, xylit, tarit, sorbit, mannitol and the like.
[0045]
Examples of the ester wax obtained from the aliphatic monocarboxylic acid and the polyhydric alcohol include monoesters, diesters, triesters and the like, depending on the number of hydroxyl groups of the polyhydric alcohol. Among these, from the viewpoint of heat resistance, a diester is preferable to a monoester, and a triester is preferable to a diester. Specific examples of preferred ester waxes include sorbitan tristearate, pentaerythritol triphenate, glycerin tripalmitate, polyoxyethylene distearate and the like.
[0046]
The partially saponified ester wax composed of the aliphatic monocarboxylic acid and the polyhydric alcohol is obtained by partially esterifying the polyhydric alcohol with an aliphatic monocarboxylic acid having 8 or more carbon atoms, It is obtained by saponification. Specific examples include wax E, wax OP, wax O, wax OM, and wax FL (all trade names manufactured by Hoechst Co., Ltd.) obtained by saponifying montanic acid diol ester with calcium hydroxide. Such (partially saponified) ester wax may be used alone or in combination of two or more.
[0047]
The amount of the (partially saponified) ester wax added to the layer B is 0.001 to 1% by weight, further 0.003 to 0.5% by weight, still more 0.005 to 0.5% by weight, particularly 0. The range is preferably from 0.01 to 0.3% by weight. When the addition amount of the (partially saponified) ester wax is less than the lower limit, the film winding property is likely to be insufficiently improved, and the blocking improving effect tends to be poor. On the other hand, if the added amount exceeds the upper limit, a large amount of the wax component is transferred by bleed-out to the opposite surface that comes into contact with the film when it is rolled up on the roll in the film production process, for example, adhesion between the metal vapor deposition layer and the base film This causes harmful effects such as obstructing.
[0048]
By the way, the greatest characteristic of the laminated polyester film of the present invention is that the maximum height of the polyester layer A is 15 nm on the surface of the polyester layer A that is not laminated with the polyester layer B (hereinafter sometimes simply referred to as the surface of the polyester layer A). At most 15000 cavities / mm that are continuous with the above protrusions and have a maximum depth of 10 nm or more (hereinafter sometimes referred to as uneven defects). ² It is in the following. The preferred frequency of irregularities is 12000 / mm ² Below, particularly preferably 10,000 pieces / mm ² It is as follows. In order to suppress the irregularity defect within a predetermined range, when the film is wound in a roll shape, it is carried out under the condition that the interlayer air does not increase, and among the inert particles contained in the layer B, This is achieved by appropriately combining the ratio of organic particles and further improving the crystallinity of the layer A.
[0049]
Such surface defects are detected in a film in which the layer A containing substantially no particles and the layer B containing inert particles are laminated and contained in the layer B in a state of being wound as a roll. After the inactive particles contacted with the surface of the layer A, the shape is transferred and recessed in a state where it is pressed with a strong pressure, and further, the displacement between the film layers due to the passage of a minute amount of air between the layers causes stress on the base. A mechanism of forming protrusions continuously in the above-described depressions by applying is considered. When the depth of the recess is 10 nm or more, and the protrusion continuous to the recess is also 15 nm or more, the flatness of the surface is significantly impaired, and the total number is 15000 / mm. ² It is the present invention that it has been found that sufficient electromagnetic conversion characteristics cannot be obtained when the value exceeds.
[0050]
Further, among the defects on the surface of the polyester layer A, those consisting only of depressions having a maximum depth of 10 nm or more that are not continuous with protrusions having a maximum height of 15 nm or more (hereinafter sometimes referred to as depression defects) are 10,000. Piece / mm ² The following is preferable. Furthermore, the preferable frequency of the dent defect is 8000 / mm. ² Or less, particularly preferably 5000 / mm ² It is as follows. This dent defect is a defect that did not reach the formation of a continuous projection in the dent that should have occurred by the mechanism described above, and is a state in which only the dent exists on the surface. However, if the frequency of the depression alone exceeds the upper limit, the electromagnetic conversion characteristics may be affected.
[0051]
Further, the depression having a maximum depth of 10 nm or more on the surface of the polyester layer A that is not laminated with the polyester layer B has a maximum major axis of 2 μm or less and a maximum minor axis of 1.5 nm or less. preferable. Further, the maximum major axis of a recess having a maximum depth of 10 nm or more is 1.5 μm or less, and the maximum minor axis is 1 μm or less. If either the maximum major axis or the maximum minor axis of the recess having the maximum depth of 10 nm or more exceeds the upper limit, the electromagnetic conversion characteristics may be affected.
[0052]
In order to bring the above-described irregularity defect and depression defect into the above range, it is preferable that the average particle diameter of the inert particles contained in the layer B and the thickness of the layer A satisfy a specific relationship. Specifically, the layer B contains one kind of inert particles or two or more kinds of inert particles having different kinds and particle sizes. If the number of the inert particles is one, the average particle size is determined. If the number of the inert particles is two or more, the average particle size of the inert particles having the largest average particle size is defined as d. _B (Μm) and the thickness of layer A is t _A (Μm), d _B / T _A Is preferably 0.01 or more and 0.5 or less. Further preferred d _B / T _A Is 0.03 or more and 0.3 or less.
[0053]
In the present invention, the surface on the layer A side has a surface roughness of center surface average roughness (WRa). _A ) In the range of 0.5 nm to 10 nm, preferably 0.5 nm to 5 nm. When the surface roughness exceeds the upper limit, electromagnetic conversion characteristics and the like are likely to be deteriorated. On the other hand, if the surface roughness is less than the lower limit, the blocking resistance of the film may deteriorate.
[0054]
In the present invention, the layer B contains inert particles as described above. Therefore, the surface on the layer B side naturally has a center surface average roughness (WRa) that is rougher than the surface on the layer A side. The surface of the laminated polyester film on the layer B side is center surface average roughness (WRa). _B ) Is 3 nm to 20 nm, preferably 3 nm to 15 nm, and more preferably 5 nm to 10 nm. Surface roughness on the layer B side (WRa _B ) Exceeds the upper limit, the flatness of the surface on the layer A side is disturbed, and the electromagnetic conversion characteristics of the obtained magnetic recording medium are deteriorated. On the other hand, the WRa _B However, if it is less than the lower limit, the blocking property of the film in transportation or the like, the running property when used as a tape, and the like are lowered. WRa _B Is WRa _A In the following, due to its flatness, handling properties such as transport, scratching, winding and unwinding in the film forming process of the base film are deteriorated, and the shape (roll formation) when wound on a roll is deteriorated. Deteriorating productivity, reducing product yield, and increasing product manufacturing costs.
[0055]
In order to give the above-mentioned surface roughness to the surface on the layer B side, and to suppress the surface defects in which the above-described depressions and protrusions are continuously formed on the surface on the layer A side, the layer B contains Average particle size of the inert particles (d _B ) Is preferably 0.1 μm or more and 1 μm or less, more preferably 0.2 μm or more and 0.8 μm or less, and particularly preferably 0.2 μm or more and 0.6 μm or less.
[0056]
In the present invention, the total thickness of the laminated polyester film is usually 2 μm or more and 20 μm or less, preferably 2.5 μm or more and 10 μm or less, more preferably 3 μm or more and 7 μm or less. The layer thickness configuration of the layer A forming the flat surface and the layer B forming the running surface is such that the average particle diameter d of the inert particles added to the layer B is such that the surface defects do not occur on the surface of the layer A. _B And the thickness of the layer A are preferably configured to satisfy the aforementioned relationship. Further, the thickness of the layer A is preferably 0.8 μm or more, and the thickness of the layer B is the average particle diameter d. _B It is preferable that it is 1/2 times or more (μm).
[0057]
In addition, the laminated polyester film of the present invention has a coating layer C on the surface on which the magnetic layer is provided, that is, on the surface of the polyester layer A that is not in contact with the polyester layer B, in order to improve various properties when used as a magnetic tape. It is preferable to provide it.
[0058]
The coating layer C preferably contains 0.5 to 30% by weight of inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6.
[0059]
Preferred examples of the resin forming the film layer C include water-based polyester resins, water-based acrylic resins, water-based polyurethane resins, and the like, and water-based polyester resins are particularly preferable.
[0060]
As this aqueous polyester resin, the acid component is, for example, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecane. From one or more polycarboxylic acids such as dicarboxylic acid, succinic acid, sodium 5-sulfoisophthalate, potassium 2-sulfoterephthalate, trimellitic acid, trimesic acid, trimellitic acid monopotassium salt, p-hydroxybenzoic acid For example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylolpropane, and bisphenol A. Echile Mainly comprising a polyester resin from one or more polyhydroxy compounds such as oxide adducts are preferably used. Also, a graft polymer or block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or a specific physical configuration (IPN (interpenetrating polymer network) type, core-shell type, etc.) in the form of microscopic particles of two types of polymers It may be an acrylic-modified polyester resin formed. As this aqueous polyester resin, a type that dissolves, emulsifies and finely disperses in water can be freely used, but a type that emulsifies and finely disperses in water is preferable. Moreover, since these impart hydrophilicity, for example, a sulfonate group, a carboxylate group, or a polyether unit may be introduced into the molecule.
[0061]
The inert particles C contained in the coating layer C are not particularly limited, but those having a relatively low specific gravity that are difficult to settle in the coating liquid are preferable. For example, particles comprising organic particles such as crosslinked silicone resin, acrylic resin, polystyrene, melamine-formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic polyester, silicon dioxide (silica), calcium carbonate, etc. Preferably mentioned. Of these, crosslinked silicone resin particles, acrylic resin particles, silica particles, and core-shell type organic particles (core: crosslinked polystyrene, shell: polymethyl methacrylate particles, etc.) are particularly preferred.
[0062]
The average particle diameter (dC) of the inert particles C is 10 to 50 nm, preferably 12 to 45 nm, and more preferably 15 to 40 nm. If the average particle size is less than 10 nm, the slipperiness of the film may be poor. On the other hand, if it exceeds 50 nm, the electromagnetic conversion characteristics of the magnetic recording medium may be poor.
[0063]
As for the shape of the inert particles C, the volume shape factor (f) described later is usually 0.1 to π / 6, preferably 0.2 to π / 6, and more preferably 0.4 to π / 6. .
[0064]
The shape of the particles having a volume shape factor (f) of π / 6 is a sphere (true sphere). That is, those having a volume shape factor (f) of 0.4 to π / 6 substantially include spheres, true spheres, and elliptical spheres such as rugby balls, and are preferable as the inert particles C. Particles having a volume shape factor (f) of less than 0.1, such as flaky particles, are not preferred because running durability is reduced.
[0065]
The content of the inert particles C is 0.5 to 30% by weight, preferably 2 to 20% by weight, and more preferably 3 to 10% by weight with respect to the coating layer C (solid content of the coating liquid). If the content is less than 0.5% by weight, the slipperiness of the film may be poor. On the other hand, if it exceeds 30% by weight, the electromagnetic conversion characteristics of the magnetic recording medium may be poor. Is not preferable.
[0066]
The total thickness of the laminated polyester film in the present invention is 2 μm or more and less than 8 μm, preferably 2.5 to 7.5 μm. The thickness structure of the polyester layer A and the polyester layer B is preferably such that the thickness of the B layer is 1/50 to 1/2 of the total thickness of the laminated film, more preferably 1/30 to 1/3, particularly preferably 1/20. ~ 1/4. The thickness of the coating layer C is usually 1 to 100 nm, preferably 2 to 50 nm, more preferably 3 to 10 nm, and particularly preferably 3 to 8 nm.
[0067]
The laminated polyester film in the present invention can be produced according to methods conventionally known or accumulated in the industry. Among them, the laminated structure of the polyester layer A and the polyester layer B is preferably manufactured by a coextrusion method, and the coating layer C is preferably laminated by a coating method.
[0068]
For example, in the case of a biaxially oriented polyester film, in the extrusion die or before the die (generally, the former is called a multi-manifold method and the latter is called a feed block method), the inert particles B (if necessary, the above-mentioned ester wax is also used. ) And polyester B finely dispersed and contained, and polyester A to which inert particles are not substantially added or precipitated are further highly accurately filtered, and then laminated and composited in a molten state. A laminated structure having the above preferred thickness ratio is formed, and then coextruded from the die at a melting point (Tm) to (Tm + 70) ° C. at a temperature of a film, and then rapidly cooled and solidified with a cooling roll of 40 to 90 ° C., and an unstretched laminated film Get. Thereafter, the unstretched laminated film is uniaxially (longitudinal or transverse) uniaxially (longitudinal or transverse) at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester), 2.5 to The film is stretched at a magnification of 8.0 times, preferably at a magnification of 3.0 to 7.5 times, and then in a direction perpendicular to the stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching is transverse The film is stretched at a temperature of (Tg) to (Tg + 70) ° C. at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps, 3 steps, 4 steps, or multi-stage stretching. The total draw ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.
[0069]
Further, the biaxially oriented film is imparted with excellent dimensional stability by heat-set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180 to 250 ° C. in the case of a polyethylene terephthalate film. The At that time, the heat setting time is preferably 1 to 60 seconds.
[0070]
In the production of the laminated polyester film, additives other than the above-mentioned inert particles, for example, a stabilizer, a colorant, a specific resistance adjusting agent for a molten polymer, and the like can be added to the polyesters A and B as required.
[0071]
The film layer C is preferably laminated on the polyester layer A in the present invention by a method of applying an aqueous coating liquid.
[0072]
The coating is preferably performed on the surface of the polyester layer A before the final stretching treatment, and after coating, the film is preferably stretched at least in a uniaxial direction. The film is dried before or during the stretching. Among them, the coating is preferably performed on an unstretched laminated film or a longitudinal (uniaxial) stretched laminated film, particularly a longitudinal (uniaxial) stretched laminated film. Although it does not specifically limit as a coating method, For example, a roll coat method, a die coat method, etc. are mentioned.
[0073]
The solid concentration of the coating liquid, particularly the aqueous coating liquid, is preferably 0.2 to 8% by weight, more preferably 0.3 to 6% by weight, and particularly preferably 0.5 to 4% by weight. In addition, other components such as other surfactants, stabilizers, dispersants, ultraviolet absorbers, thickeners and the like can be added to the aqueous coating liquid as long as the effects of the present invention are not hindered.
[0074]
In the present invention, in order to improve various performances including head touch as a magnetic recording medium, running durability, and at the same time to achieve a thin film, the Young's modulus of the laminated film is set in the vertical and horizontal directions, respectively. Usually 4500 N / mm ² Above and 6000 N / mm ² Or more, preferably 4800 N / mm ² Above and 6800 N / mm ² Or more, more preferably 5500 N / mm ² Above and 8000 N / mm ² Above, particularly preferably 5500 N / mm ² Above and 10,000 N / mm ² That's it.
[0075]
The degree of crystallinity of the polyester layers A and B is desirably 30 to 50% when the polyester is polyethylene terephthalate and 28 to 38% when the polyester is polyethylene-2,6-naphthalate. If both are below the lower limit, the thermal shrinkage rate is increased, while if the upper limit is exceeded, the abrasion resistance of the film is deteriorated, and white powder is liable to be produced when sliding with the roll or guide pin surface.
[0076]
According to the present invention, the laminated polyester film in which the polyester layer B is laminated on one side of the polyester layer A, and the laminated polyester film in which the film layer C is laminated on the surface of the polyester layer A that is not in contact with the polyester layer B. A magnetic recording medium having each of the above as a base film is also provided.
[0077]
An embodiment for producing a magnetic recording medium from the laminated polyester film of the present invention is as follows.
[0078]
The laminated polyester film of the present invention is mainly composed of iron, cobalt, chromium or the like on the surface of the polyester layer A, preferably the coating layer C, that is, the surface on the flat surface side, by a method such as vacuum deposition, sputtering, or ion plating. A ferromagnetic metal thin film layer made of an alloy or oxide as a component is formed, and a protective layer such as diamond-like carbon (DLC) or a fluorine carboxylic acid-based lubricant layer is formed on the surface as required for the purpose or application. Providing sequentially, and further providing a known backcoat layer on the surface of the layer B side, it has excellent electromagnetic conversion characteristics such as output in the short wavelength region, S / N, C / N, etc., and high dropout and low error rate It can be set as the vapor deposition type magnetic recording medium for density recording. This vapor deposition type magnetic recording medium is extremely useful as an analog signal recording Hi8, digital signal recording digital video cassette recorder (DVC), data 8 mm, mammoth, and AIT tape medium.
[0079]
In addition, the laminated polyester film of the present invention is made of iron chloride or acicular fine magnetic powder mainly composed of iron such as vinyl chloride, vinyl chloride / vinyl acetate copolymer on the surface on the layer A side, that is, the flat surface side surface. By coating the binder uniformly so that the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm, and further providing a backcoat layer on the surface of the layer B by a known method, particularly in the short wavelength region. Output, S / N, C / N and other electromagnetic conversion characteristics are excellent, and a metal-coated magnetic recording medium for high density recording with low dropout and error rate can be obtained. Further, if necessary, a nonmagnetic layer containing fine titanium oxide particles or the like as an underlayer of the metal powder-containing magnetic layer is dispersed and coated in the same organic binder as the magnetic layer on the surface on the layer A side. You can also. This metal-coated magnetic recording medium is a tape medium for analog signal recording 8 mm video, Hi8, β cam SP, W-VHS, data 8 mm, DDSIV, digital β cam, D2, D3, SX, LTO, DLT, etc. As extremely useful.
[0080]
【Example】
Hereinafter, the present invention will be specifically described by way of examples. Each characteristic in the present invention is measured or evaluated by the following method. In the examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
(1) Surface defects (dents and protrusions continuous with them)
Using a J Scanner of Atomic Force Microscope Nano Scope III AFM manufactured by Digital Instruments, scanning range is 30 μm ² And count the number of areas with dents. Further, in the case where there are projections that are continuous with the respective depths of these depressions, the heights of the respective projections are obtained by analyzing in the direction perpendicular to the surface (cross section). Whether or not the depression and the protrusion are continuous is analyzed by using the AFM in the vertical direction (cross section) with respect to the surface of the depression and the protrusion, and the base line on the side not facing the depression and the protrusion is determined. When the distance between the point α at which the connection intersects the depression and the point β at which the connection intersects the depression is 1 nm or less, the depression and the protrusion are substantially continuous.
Further, the depression is enlarged and its major axis and minor axis are obtained. In addition, for the major axis, five measured values were taken from the larger one, and the average value was taken. In addition, for the minor axis, five measured values were taken from the larger one, and the average value thereof was taken.
[0081]
Short hand: single bond silicon sensor
Scanning mode: Tapping mode
Number of pixels: 256 x 256 data points
Scanning speed: 2.0Hz
Measurement environment: room temperature, air
[0082]
(2) Average particle diameter 1 (average particle diameter: 0.06 μm or more)
Measurement is performed using a CP-50 type centrifuggle particle size analyzer (Shimadzu Seisakusho). The particle size “equivalent sphere diameter” corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is used as the average particle size. (See Book “Particle Size Measurement Technology” published by Nikkan Kogyo Shimbun, 1975, pages 242-247).
[0083]
(3) Average particle diameter 2 (average particle diameter: less than 0.06 μm)
Particles having an average particle size of less than 0.06 μm that form small protrusions are measured using a light scattering method. That is, the “equivalent sphere diameter” of the particle at the point of 50% by weight of the total particle determined by NICOM MODEL 270 SUBMICRON PARTICLE SIZER manufactured by Nicomp Instruments Inc. is displayed.
[0084]
(4) Layer thickness
The total thickness of the film is measured at 10 points randomly with a micrometer, and the average value is used. The layer thickness is obtained by measuring the layer thickness on the thin side by the method described below, and subtracting the layer thickness on the thick side from the layer thickness on the side thinner than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), the concentration ratio of the element due to the highest concentration of particles in the film in the range from the surface layer to the depth of 5000 nm and the carbon element of the polyester (M ⁺ / C ⁺ ) Is the particle concentration, and analysis in the thickness direction is performed from the surface to a depth of 5000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, the particle concentration may once increase to a stable value 1 and then increase or decrease to reach a stable value 2, or may decrease monotonously. Based on this distribution curve, in the former case, the depth gives a particle concentration of (stable value 1 + stable value 2) / 2, and in the latter case, the depth at which the particle concentration is ½ of the stable value 1. (This depth is deeper than the depth that gives a stable value of 1), which is the layer thickness of the layer.
The measurement conditions are as follows.
(1) Measuring device
Secondary ion mass spectrometer (SIMS): 6300 manufactured by PERKIN ELMER
(2) Measurement conditions Primary ion species: O2 +
Primary ion acceleration voltage: 12 kV
Primary ion current: 200 nA
Raster area: 400 μm
Analysis area: 30% gate
Measuring vacuum: 6.0 × 10 ^-9 Torr
E-GUNN: 0.5kV-3.0A
In the case where the most contained particles in the range of 5000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure with SIMS, so FT-IR (Fourier transform infrared spectroscopy) while etching from the surface, Depending on the particle, a concentration distribution curve similar to the above is measured by XPS (X-ray high electron spectroscopy) or the like to determine the layer thickness.
[0085]
(5) Center plane average roughness (WRa)
Using a non-contact type three-dimensional surface roughness meter (manufactured by WYKO: NT-2000), measurement magnification is 25 times, measurement area is 246.6 μm × 187.5 μm (= 0.0462 mm) ² ), And the center plane average roughness WRa is obtained from the following formula using surface analysis software built in the roughness meter.
[0086]
[Expression 2]

[0087]
Z _jk Is the height on the two-dimensional roughness chart at the j-th and k-th positions in each direction when the measurement method (246.6 μm) and the direct method (187.5 μm) are divided into m and n, respectively. .
[0088]
(6) Young's modulus
The film is cut into a sample width of 10 mm and a length of 15 cm, and is pulled with a universal tensile tester (manufactured by Toyo Baldwin, trade name: Tensilon) under the conditions of 100 mm between chucks, 10 mm / min tensile speed, and 500 mm / min chart speed. The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.
[0089]
(7) Inactive particles in layer B
The sample film piece is fixed on a sample stage for a scanning electron microscope, and an ion etching process is performed on the film surface under the following conditions using a sputtering apparatus (JFC-1100 type ion etching apparatus) manufactured by JEOL. The condition is that a sample is placed in a bell jar and about 10 ^-3 The degree of vacuum is raised to the Torr vacuum state, and ion etching is performed at a voltage of 0.25 kV and a current of 12.5 mA for about 10 minutes. Further, using the same apparatus, the film surface was sputtered with gold, observed with a scanning electron microscope at a magnification of 5,000 to 10,000 times, and an equivalent sphere of each inert particle with a Luzex 500 manufactured by Japan Regulator Co., Ltd. Find the diameter distribution. From the obtained equivalent spherical distribution, inert particles having a particle size exceeding 100 nm are extracted, and the average particle size of the inert particles exceeding 100 nm is calculated from the point of 50% by weight.
[0090]
(8) Manufacture and evaluation of magnetic tape
A cobalt-oxygen thin film is formed with a thickness of 110 nm by vacuum deposition on the surface of the first layer side of the laminated polyethylene terephthalate film, and then diamond-like carbon is formed with a thickness of 10 nm on the cobalt-oxygen thin film layer by sputtering. Then, a fluorine-containing carboxylic acid-based lubricant is sequentially provided. Subsequently, a back coat layer made of carbon black, polyurethane and silicone is provided on the surface opposite to the surface on which the cobalt-oxygen thin film is formed so as to have a thickness of 500 nm, and slitted to a width of 8 mm and 6.35 mm by a slitter. Then, it was wound up on a commercially available reel to produce a magnetic tape. A commercially available Hi8 8 mm video tape recorder is used to determine the video S / N ratio, and a commercially available camera-integrated digital video tape recorder is used to determine the number of dropouts (DO).
[0091]
The number of DOs is measured by recording the produced 6.35 mm tape with a commercially available camera-integrated digital video tape recorder, playing it for 1 minute, and counting the number of block mosaics that appear on the screen.
[0092]
C / N measured C / N of 7 MHz ± 1 MHz using a commercially available VTR for Hi8 (manufactured by Sony Corporation, EV-BS3000). Compare this C / N with a commercially available video tape for Hi8 (manufactured by Sony Corporation, vapor deposition type tape E6-120HME4), a film of +3 dB or more is excellent, a film of +1 to +3 dB is good, and a film less than +1 dB is bad, evaluated.
[0093]
The running durability under high temperature and humidity is determined by measuring the C / N after repeating recording and reproduction 700 times at 40 ° C. and 80% RH and deviating from the initial value.
○: +0.0 dB or more with respect to the initial value
Δ: From −1.0 dB to less than +0.0 dB with respect to the initial value
X: Less than -1.0 dB with respect to the initial value
[0094]
[Example 1]
To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.025 part of manganese acetate tetrahydrate was added as a transesterification catalyst, and the ester exchange reaction was carried out while gradually raising the internal temperature from 150 ° C. When the transesterification reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, 0.8 part of trimellitic anhydride and tetrabutyl in 2.5 parts of ethylene glycol After adding 0.014 part of a solution obtained by reacting 0.65 part of titanate (titanium content: 11% by weight) and stirring sufficiently, the reaction product was transferred to a polymerization reactor and subjected to high temperature vacuum (final internal temperature). Polycondensation was performed at 295 ° C. to obtain polyethylene terephthalate (resin A1) for polyester A having an intrinsic viscosity of 0.60.
[0095]
Further, a transesterification reaction was carried out in the same manner as described above. When the transesterification reaction reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, antimony trioxide was added. 0.03 part was added. After sufficiently distilling water mixed in the system, silicone particles having an average particle diameter of 300 nm and θ-type alumina having an average particle diameter of 100 nm were added as 0.05% and After adding 0.2% and stirring sufficiently, the reaction product is then transferred to a polymerization reactor and subjected to polycondensation under high temperature vacuum (final internal temperature 295 ° C.) to obtain polyethylene terephthalate having an intrinsic viscosity of 0.70. It was. At this time, the remaining amount of antimony in this polymer was 250 ppm.
[0096]
A powder of sorbitan tristearate (melting point 55 ° C.) as an ester wax (partially saponified) composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol was added to 99.7% of the obtained polyethylene terephthalate. 15% was coated and kneaded with a vented biaxial ruder to obtain polyethylene terephthalate (resin B1) for polyester layer B having an intrinsic viscosity of 0.69.
[0097]
The obtained resin A1 and resin B1 were each dried at 170 ° C. for 3 hours, then supplied to two extruders, melted at a melting temperature of 280 to 300 ° C., and highly accurate with a steel wire filter having an average opening of 11 μm. After filtration, the polyester layer B was laminated on one side of the polyester layer A using a multi-manifold type coextrusion die and quenched to obtain an unstretched laminated polyester film having a thickness of 89 μm.
[0098]
The obtained unstretched film was preheated, stretched 3.3 times at a film temperature of 100 ° C. between low-speed and high-speed rolls, and rapidly cooled to obtain a longitudinally stretched film. Next, an aqueous coating solution (total solid concentration: 1.0%) having the following composition (in terms of solid content) was applied to the A layer side of the longitudinally stretched film by a kiss coating method.
[0099]

Then, it supplied to the stenter and extended | stretched 4.2 times in the horizontal direction at 110 degreeC. The obtained biaxially stretched film was heat-fixed with hot air of 220 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a total thickness of 6.4 μm and a polyester layer B thickness of 1.0 μm. In addition, the contact pressure at the time of winding this laminated biaxially oriented polyester film in a roll shape was adjusted to 500 to 900 N in order to suppress the formation of the dent. Moreover, about the thickness of the polyester layers A and B of this film, it adjusted with the discharge amount of two extruders. The surface roughness WRa measured from the surface on the film layer C side of this film is 1.7 nm, and the Young's modulus of this film is 5000 N / mm in the longitudinal direction. ² , Horizontal direction 7000N / mm ² Met. Table 1 shows other characteristics of the laminated film (surface defects, etc.) and characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using the film.
[0100]
[Examples 2 and 3]
A laminated polyester film was obtained in the same manner as in Example 1 except that the type, average particle diameter, and addition amount of the inert particles B contained in the polyester layer B were changed as shown in Table 1 (resin B2). Table 1 shows the characteristics of the obtained film and the characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using the film.
[0101]
[Example 4]
Polyethylene-2,6- for polyester layers A and B in the same manner as in Example 1 except that the same molar amount of dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate in polyester layer A and polyester layer B. Naphthalate (PEN) (resins A3 and B3) was obtained. Intrinsic viscosities were 0.60 for resin A3 and 0.67 for resin B3.
[0102]
After the resins A3 and B4 were dried at 170 ° C. for 6 hours, respectively, the thickness of each layer was adjusted in the same manner as in Example 1 to obtain an unstretched laminated polyester film having a thickness of 89 μm.
[0103]
The obtained unstretched film was preheated, stretched 3.6 times at a film temperature of 135 ° C. between low-speed and high-speed rolls, and rapidly cooled to obtain a longitudinally stretched film. Next, on the A layer side of the longitudinally stretched film, the inert particles C are core-shell filler (core: crosslinked polystyrene, shell: polymethyl methacrylate) (average particle size: 30 nm, volume shape factor 0.45) manufactured by JSR Corporation, “ An aqueous coating liquid having the same composition as in Example 1 (total solid content concentration: 1.0%) was applied in the same manner as in Example 1 except that it was changed to “SX 8721”.
[0104]
Then, it supplied to the stenter and extended | stretched 5.7 times in the horizontal direction at 155 degreeC. The obtained biaxially stretched film was heat-fixed with hot air at 200 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a total thickness of 4.4 μm and a polyester layer B thickness of 0.6 μm. The thicknesses of the polyester layers A and B of this film were adjusted by the discharge amounts of two extruders. The surface roughness WRa measured from the surface on the coating layer C side of this film is 1.2 nm, and the Young's modulus of this film is 5500 N / mm in the longitudinal direction. ² , Lateral direction 10,500 N / mm ² Met. Table 1 shows the other characteristics of the laminated film and the characteristics of the ferromagnetic thin film deposition type magnetic tape using the film.
[0105]
[Example 5]
A laminated polyester film was obtained in the same manner as in Example 1 except that the inert particles were changed as shown in Table 1. In the obtained film, the flatness of the film surface was impaired, and when it was made into a magnetic tape, sufficient electromagnetic conversion characteristics could not be obtained. Table 1 shows other characteristics and characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using this film.
[0106]
[Comparative Examples 1-3]
A laminated polyester film was obtained in the same manner as in Example 1 except that the inert particles were changed as shown in Table 1 and the contact pressure at the time of winding in a roll shape was adjusted to 1000 to 1200 N. In the obtained film, the flatness of the film surface was impaired, and when it was made into a magnetic tape, sufficient electromagnetic conversion characteristics could not be obtained. Table 1 shows other characteristics and characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using this film.
[0107]
[Table 1]

[0108]
As can be seen from Table 1, the laminated polyester film according to the present invention has a very flat one side, extremely good winding properties and excellent electromagnetic characteristics, while not satisfying the requirements of the present invention. Cannot satisfy these characteristics at the same time.
[0109]
【The invention's effect】
The laminated polyester film of the present invention has sufficient surface roughness required for windability on one side, while having dropout and electromagnetic conversion characteristics that occur on the other side of the magnetic layer. No more than 15000 pits with a maximum depth of 10 nm or more that are continuous with protrusions with a maximum height of 15 nm or more that cause a significant drop. ² Because of the following, when used as a base film of a high-density magnetic recording medium, the resulting magnetic recording medium can simultaneously have the characteristics of low dropout, excellent electromagnetic conversion characteristics, and excellent running durability. And its industrial value is extremely high.

Claims (16)

It consists of a polyester layer A containing substantially no inert particles and a polyester layer B containing inert particles B laminated on one surface thereof, and the surface of the polyester layer B has a center surface average roughness ( WRaB) is 3 nm or more and 20 nm or less, and the surface of the polyester layer A has a maximum depth of 10 nm or more continuous with protrusions having a maximum height of 15 nm or more and 15000 pieces / mm ² or less at most. A laminated polyester film characterized by being simultaneously provided. ^2. The laminated polyester film according to claim 1, wherein the surface of the polyester layer A has at most 10,000 dents / mm ² or less of recesses having a maximum depth of 10 nm or less that are not continuous with protrusions having a maximum height of 15 nm or more. 2. The laminated polyester film according to claim 1, wherein the depression having a maximum depth of 10 nm or more on the surface of the polyester layer A has a maximum major axis of 2 μm or less and a maximum minor axis of 1.5 μm or less. 2. The inert particle B is at least one particle selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, a crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide, kaolin, and clay. Laminated polyester film. The laminated polyester film according to claim 1, wherein the polyester layer B contains an ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. The laminated polyester film according to claim 1, wherein a film layer C is laminated on the surface of the polyester layer A. The coating layer C contains 0.5 to 30% by weight of inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6, based on the weight of the coating layer C. The laminated polyester film according to claim 6. The laminated polyester film according to any one of claims 1 to 7, wherein the polyester constituting the polyester layer A or the layer B is polyethylene terephthalate. The laminated polyester film according to any one of claims 1 to 7, wherein the polyester constituting the polyester layer A or the layer B is polyethylene-2,6-naphthalate. The laminated polyester film according to claim 1, wherein the average particle diameter of the inert particles B and the thickness of the polyester layer A satisfy the following formula (1).
[Expression 1]
0.01 ≦ d _B / t _A ≦ 0.5
(Wherein, in the formula, t _A is the thickness of layer A (μm), d _B is the average particle diameter of the inert particles contained in the layer B ([mu] m).) The inert particles B have an average particle diameter (d _B ) of 50 nm or more and 1000 nm or less and are contained in a range of 0.01 wt% or more and 1.0 wt% or less based on the weight of the layer B. The laminated polyester film described. Polyester layer A-side surface of the laminated polyester film has a center plane average roughness (WRa _A) is 0.5nm or more 10nm or less claim 1 laminated polyester film according. The polyester layer A has a thickness of 0.8 μm or more, the polyester layer B has a thickness of 0.5 times or more of the average particle diameter (d _B ) of the inert particles B, and the polyester layer A and the layer B The laminated polyester film according to claim 1, wherein the total thickness is 2 µm or more and 7 µm or less. The laminated polyester film according to any one of claims 1 to 13, which is used for a base film of a digital recording magnetic recording medium. The laminated polyester film according to claim 1, a magnetic layer provided on the polyester layer A side surface of the laminated polyester film, and a polyester layer B side surface of the laminated polyester film. A magnetic recording medium comprising a backcoat layer. The magnetic recording medium according to claim 15, wherein the magnetic layer is a ferromagnetic metal thin film layer.