Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1997-12-30
1999-10-19
Hampton-Hightower, P.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528172, 528173, 528185, 528220, 528229, 528310, 528322, 528332, 528353, 4284735, 4284745, 428900, C08G 7300, B32B 2700
Patent
active
059690801
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a film made of an aromatic polyamide and/or aromatic polyimide. In more detail, it relates to a film made of an aromatic polyamide and/or aromatic polyimide free from curling and excellent in flatness.
BACKGROUND ARTS
It is conventionally proposed to use films made of an aromatic polyamide and/or aromatic polyimide as base films for magnetic recording media, flexible printed boards, heat sensitive transfer films, etc. since they are excellent in mechanical properties and heat resistance. The base films used in these applications are required to have a flat surface free from curling and wrinkles since the yield in processing and the functions as products are adversely affected.
It is proposed to use them as base films for magnetic recording media such as video tapes and data memory tapes which are densified especially in recent years. In these applications, the films are exposed to high temperatures when the magnetic layer is dried after coating or vapor-deposited, and they are curled or wrinkled to be poor in flatness. So, the tapes produced from them are wound in awkward styles or touch the head imperfectly, not allowing sufficient electromagnetic conversion characteristics to be obtained disadvantageously.
DISCLOSURE OF THE INVENTION
The present invention provides a film which is not degraded in film flatness by the curling caused during film production or even by the curling, etc. caused in severe conditions during film processing or use.
The object of the present invention can be achieved by a film made of an aromatic polyamide and/or aromatic polyimide, characterized by satisfying the following relation: Raman spectrum in the section direction of the film, Pmin is the minimum value and Pavr is the average value.
BEST MODE FOR CARRYING OUT THE INVENTION
The aromatic polyamide used in the present invention contains the repeating units expressed by the formula (I) and/or (II) preferably in an amount of not less than 50 mol %, more preferably not less than 70 mol %. ##STR1## General formula (I) ##STR2## wherein Ar.sub.1, Ar.sub.2 and Ar.sub.3 represent, for example, ##STR3## wherein X and Y represent --O--, --CH.sub.2 --, --CO--, --SO.sub.2 --, --S--, --C(CH.sub.3)2-- or the like, although Ar.sub.1, Ar.sub.2 and Ar.sub.3 are not restricted to those described above. Furthermore, those with some of hydrogen atoms on these aromatic rings substituted by halogen groups such as chlorine, fluorine or bromine (particularly chlorine), nitro groups, alkyl groups such as methyl groups, ethyl groups and propyl groups (particularly methyl groups), alkoxy groups such as ethoxy groups, methoxy groups, propoxy groups and isopropoxy groups are also included, and furthermore, those in which the hydrogen atoms in the amide bonds constituting the polymer are substituted by other groups are also included.
In view of properties, a polymer in which the above aromatic rings connected at the para position account for 50% or more of all the aromatic rings is preferable since a film with good thermal dimensional stability and high elastic modulus can be obtained, and more preferable is 75% or more. Furthermore, it is more preferable for a smaller moisture absorption that aromatic rings with some of hydrogen atoms on them substituted by halogen groups (particularly chlorine) account for 30% or more of all the aromatic rings. More preferable is 50% or more, and further more preferable is 70% or more.
The aromatic polyamide which may be used in the present invention contains the repeating unit represented by the above-described formula (I) and/or formula (E) in an amount of not less than 50 mol %. The remaining less than 50 mol % may be the repeating units other than aromatic amide units by the way of copolymering and/or polymer-blending.
The aromatic polyimide used in the present invention contains one or more aromatic rings and imido rings in the repeating units, and preferably contains the repeating units expressed by the formula (III) and/or (IV) preferably in an amount of
REFERENCES:
patent: 4910068 (1990-03-01), Takagi et al.
patent: 5324475 (1994-06-01), Okahashi et al.
patent: 5460890 (1995-10-01), Okahashi et al.
patent: 5686166 (1997-11-01), Tsukuda et al.
Ieki Toshiya
Tsukuda Akimitsu
Tsuzuki Toshihiro
Hampton-Hightower P.
Miller Austin R.
Toray Industries Inc.
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