Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1997-02-18
1998-12-29
Yoon, Tae
Stock material or miscellaneous articles
Composite
Of inorganic material
428143, 428149, 428458, 4284744, 428694SL, 428900, B32B 2734
Patent
active
058539077
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an aromatic polyamide film having a slippery smooth surface and good mechanical properties, and a method for producing the same. As the aromatic polyamide film according to the present invention is excellent in electrical insulation, resistance to heat, resistance to chemicals and resistance to climate, and also has particularly high elastic modulus, slipperiness and surface smoothness, it is suitable to be used as a base film of a recording medium such as a video tape, audio tape or computer tape and as a substrate on which a deposition layer is formed by a sputtering method.
BACKGROUND ART
An aromatic polyamide (hereinafter referred to as an aramid) is a polymeric material which has recently been highlighted because of its good crystallinity and high melting point as well as its excellent resistance to heat and high mechanical strength due to the rigid molecular structure thereof. Also the aramid is better in mechanical properties such as rigidity or mechanical strength compared with other polymers, and is thought to be very suitable for forming a film having a smaller thickness, and therefore it is expected to be used as a material for a magnetic tape, photographic film, printer ink sheet, solar cell base film, substrate film for a flexible printed circuit, electrical insulation film or capacitor film.
In this regard, for enhancing the production of the aramid film and the application thereof to the above uses, it is necessary to improve the slipperiness. That is, if the film lacks slipperiness, the winding, unwinding, coating or slitting operation become troublesome, which may cause wrinkles or scratches on the film surface or generate static to attract dust. There have been various proposals for providing projections on the film surface to improve the slipperiness. For example, Japanese Examined Patent Publication (Kokoku) No. 53-23860 describes that a soluble or fluidized sol (such as colloidal silica) is added to a polymer solution, which is positively separated and then agglomerated during the film formation process to improve the slipperiness. Although the slipperiness can be improved to some extent according to this method, the resultant film has too rough a surface to be used as a magnetic tape or the like.
Japanese Examined Patent Publication (Kokoku) No. 5-36849 and Japanese Unexamined Patent Publication (Kokai) No. 2-133434 disclose a film having a number of micro-projections on the surface thereof formed from added micro-particles. However, according to the study made by the present inventors, the slipperiness is not compatible with the surface smoothness in this film. That is, although a base film for a magnetic recording medium having micro-projections of a predetermined size is disclosed in Japanese Kokoku No. 5-36849, there is only one description regarding projections having a height exceeding 50 nm, as a comparative example, in that the electromagnetic transducing characteristic is lowered if a relatively large number of projections having a height in a range from 90 to 180 nm exists. However, there is none regarding larger projections having a substantial influence upon the electromagnetic transducing characteristic. In fact, according to the study made by the present inventors, a particular range of numbers of projections having a height exceeding 50 nm should be defined for establishing the compatibility of the electromagnetic transducing characteristic with the slipperiness. Nevertheless, there is no technology for controlling the number of projections to a predetermined range in the method for producing a film disclosed in Kokoku 5-36849. Therefore, it has been found that a satisfactory base film for high density recording is not obtainable by this known method.
An aramid film having a relatively large number of projections with a relatively large height in a range from 0.06 to 0.25 nm is disclosed in Japanese Kokai 2-133434. However, there is also no description therein regarding larger projections of a height of 0.27 .mu.m or
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Nakatani Masayuki
Yamada Takashi
Asahi Kasei Kogyo Kabushiki Kaisha
Yoon Tae
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