Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-10-17
2004-09-28
Hightower, P. Hampton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S353000, C428S473500, C428S457000, C428S458000, C264S290200, C264S291000, C264S292000, C264S299000
Reexamination Certificate
active
06797801
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyimide film having highly improved mechanical properties and a production process thereof.
BACKGROUND ART
A wholly aromatic polyimide has been widely used in industry due to its excellent heat resistance and mechanical properties. Particularly, its film occupies an important position as a substrate for a thin-layer electronic part including an electronic packaging application. In recent years, a thinner polyimide film is desired in response to a strong demand for smaller electronic parts. However, it is an essential requirement from viewpoints of actual use and handling of the film that the film have high rigidity along with a decrease in thickness. Although the wholly aromatic polyimide film has a rigid structure, it cannot be necessarily said that the film has a truly high Young's modulus as compared with, for example, a wholly aromatic polyamide film. It is a current situation that a Young's modulus of a commercially available polyimide film having the highest Young's modulus is merely as high as 9 GPa.
As a method of achieving a high Young's modulus in the wholly aromatic polyimide film, (1) application of a chemical structure which is rigid and has high linearity to a molecular skeleton constituting a polyimide and (2) orientation of molecules of the polyimide by a physical technique are considered. As the chemical structure of (1), a raw material to attain the chemical structure has been studied by use of various combinations of pyromellitic acid or 3,3′,4,4′-biphenyltetracarboxylic acid as an acid component and paraphenylenediamine, benzidine or nucleus substituted compounds thereof as an amine component. Of the studied raw materials, polyparaphenylenepyromellitimide is the most promising raw material as a raw material for a film having a high Young's modulus since it has the highest theoretical elastic modulus (refer to Tashiro et al., Journal of Society of Textiles, Vol. 43, p. 78 (1987)) and its raw materials are inexpensive. However, despite its potential, a conventional polyparaphenylenepyromellitimide film is extremely brittle, and a polyparaphenylenepyromellitimide film which is balanced and has a high Young's modulus is not yet attained.
As a method for overcoming the situation, a method of chemically cyclizing a polyamide acid solution obtained by a reaction between paraphenylenediamine and pyromellitic anhydride is proposed in JP-A 1-282219. However, a Young's modulus of a polyparaphenylenepyromellitimide film obtained by the method is merely as high as 8.5 GPa.
JP-A 6-172529 discloses that a film having a Young's modulus of 20.1 GPa is obtained by flow-casting a dope produced by adding a large amount of acetic anhydride to a polyamide acid solution obtained by a reaction between nucleus-substituted paraphenylenediamine and pyromellitic anhydride, drying the cast dope at low temperatures under a reduced pressure and heat-treating the resulting dope. However, this method is an industrially unrealistic technique since it requires dry treatment at low temperatures over a few hours. Further, it is also disclosed that a film which can be obtained when the technique is applied to polyparaphenylenepyromellitimide is only a film which is so brittle that it cannot undergo even mechanical measurements. Therefore, the effect of the technique is limited. Thus, a technique for attaining a film having a high Young's modulus which can be widely used in aromatic polyimides which are rigid is not completed. In particular, a polyparaphenylenepyromellitimide film having a high Young's modulus and practical toughness is not known.
Meanwhile, as a method for orienting a polyimide by stretching, a method in which a polyamic acid solution which is a precursor of polyparaphenylenepyromellitimide is formed into a film, dried, monoaxially stretched in a solvent and formed into an imide is disclosed in Polymer Articles, Vol. 56, No. 5, pp. 282 to 290. Further, a method in which a precursor polyamic ester having an ester group of a long chain (having 10 to 18 carbon atoms) introduced into a polymer chain is wet-spun, oriented by stretching and formed into an imide by heating is proposed in Polymer Preprint Japan, Vol. 41, No. 9 (1992) 3752. However, both of the publications set forth nothing about a biaxially stretched film which is balanced in a plane.
Therefore, a polyparaphenylenepyromellitimide film with a high Young's modulus which is balanced in a plane is not yet known.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a polyimide film having mechanical properties, particularly a Young's modulus, improved by a high degree of orientation which could not be achieved by the prior art.
Another object of the present invention is to provide a polyparaphenylenepyromellitimide film having a high Young's modulus.
Another object of the present invention is to provide a process for producing the above film of the present invention.
Other objects and advantages of the present invention will be apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are achieved by a polyimide film which comprises a polyimide consisting essentially of a diamine component and a tetracarboxylic acid component, the diamine component comprising a p-phenylenediamine component whose amount is more than 80 mol % to 100 mol % and an aromatic diamine component other than p-phenylenediamine whose amount is 0 mol % to less than 20 mol % and the tetracarboxylic acid component comprising pyromellitic acid whose amount is more than 80 mol % and an aromatic tetracarboxylic acid component other than pyromellitic acid whose amount is 0 mol % to less than 20 mol %, and which has two directions each having a Young's modulus of higher than 10 GPa and perpendicular to each other in a film plane.
According to the present invention, secondly, the above objects and advantages of the present invention are achieved by a process (hereinafter may be referred to as “first production process”) for producing a polyimide film which comprises the steps of:
(1) preparing a solution of polyamic acid in a solvent, the polyamic acid consisting essentially of a diamine component and a tetracarboxylic acid component, the diamine component comprising a p-phenylenediamine component whose amount is more than 80 mol % to 100 mol % and an aromatic diamine component other than p-phenylenediamine whose amount is 0 mol % to less than 20 mol % and the tetracarboxylic acid component comprising pyromellitic acid whose amount is more than 80 mol % and an aromatic tetracarboxylic acid component other than pyromellitic acid whose amount is 0 mol % to less than 20 mol %, the solvent comprising at least one solvent selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and 1,3-dimethylimidazolidinone,
(2) immersing a film obtained by flow casting the solution prepared in the above (1) on a substrate into an isoimidating solution produced by dissolving dicyclohexylcarbodiimide in at least one solvent selected from the above solvents, with the film being attached to the substrate, so as to form a gelled film in which at least a portion of the polyamic acid has been converted into a polyisoimide,
(3) separating the obtained gelled film from the substrate, rinsing the film as required, and then biaxially stretching the film, and
(4) subjecting the resulting film to heat treatment, as required, after rinsing the obtained biaxially stretched film to remove the solvent therefrom, so as to form a biaxially oriented polyimide film.
Further, according to the present invention, thirdly, the above objects and advantages of the present invention are achieved by a process (hereinafter may be referred to as “second production process”) for producing a polyimide film which comprises the steps of:
(1) preparing a solution of polyamic acid in a solvent, the polyamic acid consisting of a
Honda Susumu
Nakamura Tsutomu
Nishio Rei
Sadanobu Jiro
Hampton Hightower P.
Teijin Limited
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