Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-01-30
2002-10-22
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
Reexamination Certificate
active
06468589
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition for film formation which contains a poly (arylene ether) polymer soluble in organic solvents and excellent in heat resistance, low dielectric characteristics, and cracking resistance. The invention further relates to an insulating film formed from the composition.
DESCRIPTION OF THE RELATED ART
In the field of electronic materials, the recent progress toward a higher degree of integration, larger number of functions, and higher performances has resulted in increased circuit resistance and increased capacitance between circuits and this in turn has resulted in increases not only in power consumption but in delay time. The increase in delay time is a major factor contributing to a decrease in signal transfer speed in devices and to cross talks. Because of this, it is desired to reduce parasitic resistance or parasitic capacitance. One measure which is being taken in reducing the parasitic capacitance so as to cope with higher-speed device operation is to coat the periphery of a circuit with a low-dielectric interlayer insulating film. For use in LCDs and related products, such insulating films may be required to have transparency besides low-dielectric characteristics.
Polyimides are widely known as a heat-resistant organic material which meets those requirements. However, since polyimides contain imide groups, which are highly polar, they not only are insufficient in low-dielectric characteristics and low water absorption but have a problem that they have a color. No satisfactory polyimides have been obtained.
On the other hand, polyphenylenes are known as an organic material having high heat resistance and containing no polar groups. Since these polyphenylenes have poor solubility in organic solvents although excellent in heat resistance, soluble groups are generally incorporated into side chains. Examples of such polyphenylenes include the polymers disclosed in U.S. Pat. No. 5,214,044, WO 96/28491, and EP 629217.
These polymers basically have a poly-p-phenylene structure as the main structure. Although the structural units of the polymers are partly derived from a flexible monomer used as a comonomer, the polymers are soluble in specific organic solvents only and have a problem that solutions thereof have a high viscosity due to the stiffness of the molecules. Those polyphenylenes are by no means satisfactory in processability.
Investigations have been made on the crosslinking of a polyphenylene polymer for the purposes of impartation of solvent resistance, improvement of physical heat resistance and mechanical properties, etc., and a crosslinking reaction utilizing an acetylene bond has been known. However, this conventional technique has problems that there are limitations on polyphenylene (polyarylene) structures into which the crosslink structure can be incorporated and on reactions usable for the crosslinking, and that the processing is unsuitable for general use because a special acetylene compound should be used as a starting material and a high temperature is necessary for curing.
Furthermore, a technique for enhancing the processability and solubility of a polyarylene by incorporating ether bonds into the polymer has been investigated. However, the polymer thus obtained has insufficient heat resistance.
As described above, there have been few polymer techniques which are widely applicable simple processes for imparting curability and are effective in fully satisfying heat resistance, low-dielectric characteristics, and processability and in improving solvent resistance, physical heat resistance, and mechanical properties.
SUMMARY OF THE INVENTION
One object of the invention is to provide a composition for film formation containing a heat-curable poly(arylene ether) polymer which is excellent in heat resistance, low-dielectric characteristics, and cracking resistance and is capable of being improved in solvent resistance, physical heat resistance, and mechanical properties.
Another object of the invention is to provide an insulating film formed from the composition.
The invention provides a composition for film formation containing a polymer made up of repeating structural units which comprise units represented by the following formula (1) and have one or more alkyl groups therein (hereinafter, this polymer is often referred to as “poly(arylene ether)”):
wherein R
1
's are the same or different and each represents an alkyl group; a to d are the same or different and each is an integer of 0 to 4; and X represents a divalent organic group having one to three aromatic rings.
In formula (1), X is preferably at least one group selected from groups (A) to (L) represented by the following formulae (2):
wherein R
2
's are the same or different and each represents an alkyl group; e's are the same or different and each is an integer of 0 to 4; f's are the same or different and each is an integer of 0 to 3; and g 's are the same or different and each is an integer of 0 to 2.
Each formula (2), representing X, preferably is a group having one or more alkyl groups.
Furthermore, the poly(arylene ether) preferably contains both at least one unit wherein X is a group represented by a formula (2) having one or more alkyl groups and at least one unit wherein X is a group represented by a formula (2) having no alkyl groups.
The invention further provides an insulating film material formed from the composition for film formation.
DETAILED DESCRIPTION OF THE INVENTION
The composition for film formation of the invention contains a polymer comprising repeating structural units represented by formula (1) in an amount of generally 50% by mole or larger, preferably 70% by mole or larger. If the proportion of the units is lower than 50% by mole, the composition for film formation gives a film having poor heat resistance.
The poly(arylene ether) for use in the invention is a polymer formed by copolymerizing a compound having a fluorene framework with a compound having an aromatic ring framework so as to have repeating structural units represented by formula (1), and has one or more alkyl groups incorporated somewhere therein. These alkyl groups participate in the crosslinking of the polymer and thereby improve heat resistance and strength.
Namely, in the poly(arylene ether) for use in the invention, there are no particular limitations on the position of each alkyl group incorporated therein and the alkyl group may be present somewhere in the molecular chain. For example, the poly(arylene ether) may be one which comprises repeating structural units represented by formula (1) wherein (a+b+c+d) is 1 or larger.
In the case where X in formula (1) is represented by formulae (2), the repeating structural units may be composed of ones in which X is represented by a formula (2) wherein e to g each is 0 and ones in which X is represented by a formula (2) wherein e to g each exceeds 1. Namely, the polymer may be one in which X is represented by formulae (2) wherein the average of e to g exceeds 1.
In short, as long as one or more alkyl groups have been incorporated somewhere in the poly(arylene ether) for use in the invention, these alkyl groups participate in the crosslinking of the polymer to give an insulating film material having improved heat resistance and strength.
The poly(arylene ether) especially preferably has units represented by formula (1) wherein a+b+c+d is 1 or larger and further has units represented by formula (1) wherein a+b+c+d is 0.
Examples of the alkyl groups represented by R
1
and R
2
in formulae (1) and (2) include alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, and n-butyl.
The poly (arylene ether) to be used in the invention can be obtained, for example, by the coupling reaction of an alkali metal salt of a bisphenol compound with a dihalogenated compound.
Examples of the bisphenol compound include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene,
Nishikawa Michinori
Okada Takashi
Yamada Kinji
Cameron Erma
JSR Corporation
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