Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-03-25
2003-11-04
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S076000, C521S134000, C521S138000
Reexamination Certificate
active
06642282
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a porous para-oriented aromatic polyamide film, a prepreg made of this film, and a base substrate for printed circuit board.
2. Description of the Related Art
Recently, in electronic apparatus field, there has been an increasing requirement for high speed signal processing and digitization for high performance. A laminated film using a para-aromatic polyamide (hereinafter, sometimes referred to as para-aramid) film has characteristics of light weight and low linear thermal expansion coefficient, and the use of the laminated film has been developed in this field.
However, this film has low toughness and handling thereof for a circuit board is difficult. There has been known a method of enhancing toughness of para-aramid film by adding a binder composed of a heat-resistant resin. For example, JP-A-10-338762 discloses a porous para-oriented aromatic polyamide film containing short fiber and/or pulp composed of a heat-resistant resin, for example aramid.
However, the tear propagation resistance of the conventional film, which is the index of toughness, is still small, and a film having large tear propagation resistance has been required.
An object of the present invention is to provide a porous para-oriented aromatic polyamide film having a large tear propagation resistance while maintaining the characteristics of para-aramid such as light weight and low linear thermal expansion coefficient. The present invention also provides a method of producing this film, a prepreg obtained by impregnating this film with a thermoplastic resin and/or a thermosetting resin (hereinafter, sometimes simply referred to as resin), and a base substrate for printed circuit board using such a prepreg.
The present inventors have intensively studied to solve the above problems, and resultantly found that a porous para-oriented aromatic polyamide film containing fine particles composed of a heat-resistant resin in a specific amount and having a specific linear thermal expansion coefficient, has a large tear propagation resistance while maintaining the characteristics of a para-aramid such as light weight and low linear thermal expansion coefficient, leading to completion of the present invention.
SUMMARY OF THE INVENTION
Namely, the present invention relates to [1] a porous para-oriented aromatic polyamide film containing fine particles composed of a heat-resistant resin in an amount of 10 to 400 parts by weight based on 100 parts by weight of the para-oriented aromatic polyamide and having a linear thermal expansion coefficient at 200 to 300° C. of from −50×10
−6
/° C. to +50×10
−6
/° C.
Also, the present invention relates to [2] a method of producing the porous para-oriented aromatic polyamide film of [1] wherein the method comprises the following steps (a) to (c):
(a) a step of forming a film-like material from a solution containing 0.1 to 10% by weight of a para-oriented aromatic polyamide having an inherent viscosity of 1.0 to 2.8 dl/g, 1 to 10% by weight of a chloride of an alkali metal or alkaline earth metal, and 10 to 400 parts by weight of fine particles composed of a heat-resistant resin based on 100 parts by weight of said polyamide, in a polar amide solvent or a polar urea solvent,
(b) a step of depositing a para-oriented aromatic polyamide from the film-like material obtained in step (a), and
(c) a step of immersing the film-like material having a deposited para-oriented aromatic polyamide obtained in step (b) in an aqueous solution or an alcoholic solution, eluting the solvent and the chloride of an alkali metal or alkaline earth metal, then, drying to obtain a porous para-oriented aromatic polyamide film.
The present invention also relates to [3] a prepreg obtained by impregnating the porous para-oriented aromatic polyamide film of [1] with a thermoplastic resin and/or a thermosetting resin.
Further, the present invention relates to [4] a base substrate for printed circuit board obtained by using the prepreg of [3].
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the para-oriented aromatic polyamide is obtained by polycondensation of a para-oriented aromatic diamine with a para-oriented aromatic dicarboxylic dihalide, and substantially composed of repeating units in which amide bonds are connected at the para-position of the aromatic ring or the equivalently oriented position of the aromatic ring (for example, the orientation position extending coaxially or in parallel to the oppsoite direction such as 4,4′-biphenylene, 1,5-naphthalene, and 2,6-naphthalene).
Specifically exemplified are para-aramids of para-oriented or the equivalently oriented structure such as poly(paraphenyleneterephthalamide), poly(parabenzamide), poly(4,4′-benzanilideterephthalamide), poly(paraphenylene-4,4′-biphenylenedicarboxylic amide), poly(paraphenylene-2,6-naphthalenedicarboxylic amide), poly(2-chloro-paraphenyleneterephthalamide) or a coplymer of paraphenylenediamine/2,6-dichloroparaphenylenediamine/terephthalic acid dichloride, and the like. Further, a para-aramid having a phenolic hydroxyl group as a terminal functional group can also be used.
The para-aramid having a phenolic hydroxyl group as an terminal functional group means a terminal hydroxyl group-containing para-oriented aromatic polyamide in which part or all of the terminal functional groups are hydroxyl groups. Such a terminal hydroxyl group-containing para-oriented aromatic polyamide is typically a para-oriented aromatic polyamide having part or all of the molecular chain end bound to an aromatic compound having hydroxyl groups.
The average particle size of fine particles composed of a heat-resistant resin used in the film of the present invention is usually 500 &mgr;m or less, and from the standpoint of uniformity of the film, preferably 200 &mgr;m or less, further preferably 150 &mgr;m or less, particularly preferably 120 &mgr;m or less. Here, the average particle size of the fine particles can be measured by a laser scattering method.
The aspect ratio of fine particles composed of a heat-resistant resin used in the film of the present invention is usually less than 50.
The heat-resistant resin used for the film of the present invention is a resin which is not melted at a temperature of less than 230° C., preferably less than 250° C.
Specific examples of the heat-resistant resin of the present invention include aromatic polyamides such as the above mentioned para-aramid typically represented by poly(paraphenyleneterephthalamide), polyparabenzamide and the like; aromatic polyesters such as polyparabenzoate, polyparaphenylene terephthalate, polyethylene terephthalate and the like; aromatic heterocyclic polymers such as polyparaphenylenebenzobisthiazole, polyparaphenylenebisoxazole; and the like. Of them, aromatic polyamides are preferable, and particularly, poly(paraphenyleneterephthalamide) can be suitably used due to excellent affinity with a porous film.
In the film of the present invention, the amount of the above-mentioned fine particles is from 10 to 400 parts by weight, preferably from 30 to 250 parts by weight, more preferably from 50 to 150 parts by weight based on 100 parts by weight of a para-oriented aromatic polyamide. Out of the above-mentioned range, the tear propagation resistance of the film is insufficient. When over the upper limit, the viscosity of a solution containing the para-oriented aromatic polyamide and fine particles increases too much, causing a difficulty in forming a film-like material from the solution.
The film of the present invention is usually made of fibrils of para-aramid, and has a form of non-woven fabric, microscopically. Namely, the porous para-oriented aromatic film usually has a structure in which fibrils having a diameter of 1 &mgr;m or less composed of a para-aramid are in the form of network or non-woven fabric and laminated in the form of layer.
The film of the present invention
Shinohara Yasuo
Takahashi Tsutomu
Foelak Morton
Sumitomo Chemical Company Limited
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