Polyimide for optical communications, method of preparing...

Details Polyimide for optical communications, method of preparing... Polyimide for optical communications, method of preparing...

1999-11-17

2001-10-16

Hampton-Hightower, P. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

C528S125000, C528S126000, C528S128000, C528S170000, C528S171000, C528S172000, C528S173000, C528S174000, C528S175000, C528S176000, C528S179000, C528S183000, C528S185000, C528S188000, C528S220000, C528S229000, C528S350000, C528S352000, C427S162000, C427S256000, C427S258000, C427S362000, C427S372200, C264S299000, C264S330000, C264S331110, C264S331160

Reexamination Certificate

active

06303743

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my applications POLYIMIDE FOR OPTICAL COMMUNICATIONS, METHOD OF PREPARING THE SAME, AND METHOD OF FORMING MULTIPLE POLYIMIDE FILM USING THE POLYIMIDE filed with the Korean Industrial Property Office on Nov. 18, 1998 and there duly assigned Serial No. 49506/1998, and POLYIMIDE FOR OPTICAL COMMUNICATIONS, METHOD OF PREPARING THE SAME, AND METHOD OF FORMING MULTIPLE POLYIMIDE FILM USING THE POLYIMIDE filed with the Korean Industrial Property Office on Oct. 18, 1999 and there duly assigned Serial No. 45048/1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyimides as optical polymers for use in manufacturing optical communication devices for optical communications, and to methods of preparing polyimides, and methods of forming multiple polyimide film layers.
2. Description of the Related Art
An ideal optical material for use in manufacturing optical communication devices has low optical loss at a wavelength of 1300-1500 nm for optical communications. Optical loss in this wavelength range is caused by overtones of harmonics due to stretching and deformation vibrations of carbon and hydrogen bonds (C—H) in alkyl, phenyl and other similar functional groups. Thus, using a common polymer as a material for optical waveguides that utilize light in this near infrared wavelength range is not desirable due to a large optical transmission loss. In order to reduce optical transmission loss, the light absorption wavelength of the polymer should be shifted from a near infrared light wavelength region to a longer or shorter wavelength region. To this end, a method for substituting hydrogen of the carbon and hydrogen (C—H) bond by fluorine (F) has been suggested.
Also, an optical material for use in manufacturing an optical communications device such as an opto-electronic integrated circuit (OEIC), an opto-electrical mixed wiring board (OEMWB), a hybrid integration device or a plastic optical fiber requires thermal stability during a manufacturing process. Because the thermal resistance of the optical material is very important, glass transition temperature, thermal decomposition temperature, thermal expansion coefficient and birefringence of the optical material should be carefully considered.
Polyimide is widely known as a polymer having good thermal resistance. Because polyimide has a resistance to heat at a high temperature, for example, approximately 400° C., great efforts are being made to utilize polyimide as a material for optical communications.
However, in general, polyimides have many C—H bonds in the molecules, so that optical absorption loss is large at the near infrared region. To avoid this problem, a polyimide whose hydrogen of C—H bond is partially or completely substituted for fluorine (F) has been reported.
However, as the F content in the polyimide increases, solubility of the polyimide in the organic solvent which is commonly used in the formation of a polyimide film, also increases. Thus, in the case of forming multiple polyimide films, a lower polyimide film is partially solubilized in the organic solvent used to form an upper polyimide film, causing cracks to occur in the lower polyimide film. Such cracks cause optical scattering loss, thereby increasing optical loss. Also, polyimide films has a large birefringence, so that there is a problem in that optical waveguiding characteristics vary in accordance with the degree of polarization during optical waveguiding.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved polyimide for use in optical waveguides.
A further object of the invention is to provide an improved method of making polyimides for optical waveguides.
A yet further object is to provide an improved method of forming polyimide films layer in optical waveguides.
A still further object is to provide a polyimide which has a lower solubility in the organic solvents used to form upper film layers.
Another object is to provide a polyimide which has a lower tendency to crack in multiple films.
Still another object is to provide a polyimide which has a lower birefringence.
Yet another object is to provide a polyimide with low light loss in the near infrared region.
Yet another object is to provide a polyimide with low light loss due to scattering.
According to an aspect of the present invention, there is provided a polyimide for optical communications, expressed by the formula (1):
X, X
2
, X
3
, A
1
, A
2
, B
1
, B
2
, B
3
, D
1
, D
2
, E
1
, E
2
, Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, Y
6
, Y
7
, and Y
8
, are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, halogenated alkyl group, aryl group and halogenated aryl group; Z is a simple chemical bond or selected from the group consisting of —O—, —CO—, —SO
2
—, —S—, —(T)
m
—, —(OT)
m
— and —(OTO)
m
—wherein T is alkylene or arylene group substituted by at least one of halogen atom and halogenated alkyl group, and m is an integer from 1 to 10; and n is an integer from 1 to 39.
Preferably, A
1
and A
2
are independently fluorine atom or fluorinated alkyl group; Y
1
, Y
2
,Y
3
, Y
4
, Y
5
, Y
6
, Y
7
, and Y
8
are independently selected from the group consisting of fluorine atom, fluorinated alkyl group and fluorinated aryl group; Q is a single bond or selected from the group consisting of —C(CF
3
)
2
—, —O—, —CO— and —SO
2
—; and D
1
, D
2
, E
1
, and E
2
, are all hydrogen. Also, the polyimide may be selected from the compounds expressed as follows:
According to another aspect of the present invention, there is provide a method of preparing a polyimide for optical communications, the polyimide expressed by the formula (1), the method comprising the steps of: (a1) polymerizing an acid anhydride (A) and a diamine compound (B), which are shown in the following reaction scheme, in a mole ratio of 0.7:1 to 0.98:1; (a2) adding a substituted maleic anhydride (C) to the reaction mixture of the step (a1) to synthesize a polyamic acid (D); and (a3) imidizing the polyamic acid (D), wherein the reaction scheme is given by
X, X
2
, X
3
, A
1
, A
2
, B
1
, B
2
, B
3
, D
1
, D
2
, E
1
, E
2
, Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, Y
6
, Y
7
, and Y
8
, are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, halogenated alkyl group, aryl group and halogenated aryl group; Z is a simple chemical bond or selected from the group consisting of —O—, —CO—, —SO
2
—, —S—, —(T)
m
—, —(OT)
m
— and —(OTO)
m
—wherein T is alkylene or arylene group substituted by at least one of halogen atom and halogenated alkyl group, and m is an integer from 1 to 10; and n is an integer from 1 to 39.
Preferably, the acid anhydride (A) and diamine (B) are mixed in a mole ratio of 0.7:1 to 0.98:1, and more preferably, 0.9:1 to 0.95:1.
In another embodiment, the present invention provides a method of preparing a polyimide for optical communications, the polyimide expressed by the formula (1), the method comprising the steps of: (b1) adding a substituted maleic anhydride (C), which is shown in the following reaction scheme, to a mixture of an acid anhydride (A) and a diamine compound (B) in a mole ratio of 0.1: 1-0.98:1, and polymerizing the mixture to synthesize a polyamic acid (D); and (b2) imidizing the polyamic acid (D), wherein the reaction scheme is given by
X, X
2
, X
3
, A
1
, A
2
, B
1
, B
2
, B
3
, D
1
, D
2
, E
1
, E
2
, Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, Y
6
, Y
7
, and Y
8
, are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, halogenated alkyl group, aryl group and halogenated aryl group; Z is a simple chemical bond or selected from the group consisting of —O—, —CO—, —SO
2
—, —S—, —(T)
m
—, —(OT)
m
— and —(OTO)
m
—wherein T is alkylene or arylene group substituted by at least one of halogen atom and halogenated alkyl group, and m is an integer from 1 to 10; and n is an integer from 1 to 39.
Preferably, in the

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