Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-04-11
2001-11-13
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, C528S172000, C528S173000, C528S174000, C528S176000, C528S183000, C528S188000, C528S220000, C528S229000, C528S350000, C528S351000, C524S600000, C524S602000, C524S606000, C427S256000, C427S372200, C264S235000, C264S236000, C264S338000
Reexamination Certificate
active
06316589
ABSTRACT:
CLAIM OF PRIORITY
This invention makes reference to, incorporates the same herein, and claims all benefits accruing under 35U.S.C.§119 from an application for POLYIMIDE FOR OPTICAL COMMUNICATION earlier filed in the Korean Industrial Property Office on the of Apr. 14, 1999 is and there duly assigned Ser. No. 99-13153.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyimide for optical communications, and more particularly, to a polyimide for use in manufacturing optical waveguides, which shows low optical absorption loss at wavelengths for optical communications, and has easily controllable refractive index, good solubility in organic solvent and superior processibility.
2. Description of the Related Art
Rapid advances in information industries have increased the demand for optical materials for use in manufacturing main optical devices associated with future generation high-speed and large-amount information communications business, such as optical power dividers, optical wavelength dividers and the like. At the early stage of research into optical materials, inorganic compounds such as lithium niobate (LiNbO
3
) were used as an optical material. However, inorganic compounds such as this inherently have difficulties in preparation and further processing, and thus are not suitable for mass production. For this reason, attention has shifted from inorganic compounds as optical materials to organic optical materials, in particular, polymers, which are more attractive in terms of the cost, processibility and mass production, and this has boosted research into organic optical materials.
However, common polymers absorb light in the near infrared wavelength range of 1,000 to 1,700 nm due to overtone of harmonics by stretching and deformation vibrations of carbon and hydrogen (C—H) bonds. In order to reduce the optical absorption loss, a method for substituting hydrogen of the carbon and hydrogen bonds by fluorine (F) or deuterium (D) has been considered.
However, C—D bonds formed by the substitution of hydrogen by deuterium causes light absorption at a wavelength of 1550 nm, and thus this substitution technique is not appropriate for optical communications materials that utilize light in the near infrared wavelength range of 1,000 to 1,700 nm. Meanwhile, the substitution of hydrogen by fluorine has been verified as yielding an optical material capable of minimizing the optical absorption loss at a wavelength of 1000 to 1700 nm.
Polyimide has been widely known as a semiconductor protective buffering material due to its thermal and mechanical stabilities. Recently, the fluorine substitution technique has been adapted to polyimide having good physical properties to produce low-optical loss optical communications materials.
Optical waveguides consist of a core layer as a light waveguide, and a cladding layer surrounding the core layer, wherein the core layer must have a higher refractive index than the cladding layer. When a fluorine-substituted polyimide is used in the manufacture of optical waveguides, a fluorine-containing monomer and a non-fluorine-containing monomer must be copolymerized in an appropriate mixing ratio to adjust the fluorine content in the resultant polymer, such that the requirement associated with the refractive index of the core and cladding layers is met.
The fluorine content of a polyimide is generally proportional to a decease in refractive index. Accordingly, as the hydrogen of carbon-hydrogen bonds in a polyimide is substituted by fluorine, the refractive index of the polyimide decreases. Thus, use of such a fluorine-substituted polyimide as a material for a core layer narrows the selection range of materials for the cladding layer thereof. Also, in a case where the same polymer is used for both core and cladding layers, the fluorine content of the polymer must be reduced for core layer having a higher refractive index than the cladding layer, which causes optical absorption loss due to the increased carbon-hydrogen bonds. Also, a higher fluorine content in polymer decreases its surface tension, so that use of the fluorinated polyimide as a material for core and cladding layers degrades their adhesion strength and coating properties.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved polyimide composition for use in optical communication.
It is a further object of the invention to provide a polyimide which avoids increasing optical absorption associated with increasing refractive index.
It is a yet further object of the invention to provide a polyimide with improved adhesion strength and coating properties.
It is a still further object of the invention to provide a polyimide with superior heat resistance.
The above objective of the present invention is achieved by a polyimide for optical communications, expressed by the formula (1)
where R
1
and R
2
are independently selected from the group consisting of CF
3
, CCl
3
, unsubstituted aromatic ring group and halogenerated aromatic ring group; R
3
and R
4
are independently selected from the group consisting of Cl, F, I, Br, CF
3
, CCl
3
, unsubstituted aromatic ring group and halogenated aromatic ring group; and n is an integer from 1 to 39.
For R
1
, R
2
, R
3
and R
4
of the formula (1), the unsubstituted aromatic ring group may include phenyl group, naphthyl group and biphenyl group, and the halogenated aromatic ring group may include 4-chlorophenyl group, 4-fluorophenyl group, 4-trifluoromethylphenyl group and 4-trichloromethylphenyl group. Aromatic carbon-hydrogen (C—H) bonds within the unsubstituted or halogenated aromatic ring group show less optical absorption loss compared to aliphatic carbon-hydrogen bonds, and thus the polyimide having the formula (1) is useful as an optical material for optical communications.
In one embodiment, R
1
, R
2
, R
3
and R
4
of the formula (1) are the same as CF
3
, which results in the compound having the formula (E) hereinbelow. In another embodiment, R
1
and R
2
of the formula (1) are the same as CF
3
, and R
3
and R
4
are the same as Cl, which results in the compound having the formula (F) hereinbelow.
In the formulas (E) and (F), e and f are each independently integers from 1 to 39.
Preferably, the polyimides having the formulas (E) and (F) have a refractive index of 1.5179 to 1.5714 in a transverse electric (TE) mode and of 1.5076 to 1.5590 in a transverse magnetic (TM)c mode at a wavelength of 1,550 nm.
In another embodiment, the present invention provides a polyimide for optical communications, expressed by the formula (2):
where Z may be
R
3
and R
4
are independently selected from the group consisting of Cl, F, I, Br, CF
3
, CCl
3
, unsubstituted aromatic ring group and halogenated aromatic ring group; R
1
and R
2
are independently selected from the group consisting of CF
3
, CCl
3
, unsubstituted aromatic ring group and halogenerated aromatic ring group; x represents a mole fraction in the range of 0<x<1.
As for R
1
, R
2
, R
3
and R
4
of the formula (2) hereinabove, the unsubstituted aromatic ring group may include phenyl group, naphthyl group and biphenyl group, and the halogenated aromatic ring group may include 4-chlorophenyl group, 4-fluorophenyl group, 4-trifluoromethylphenyl group and 4-trichloromethylphenyl group.
In one embodiment, Z of the formula (2) is
and R
3
and R
4
are Cl, which results in the compound having the formula (G) hereinbelow. In another embodiment, Z of the formula (2) is the same as
and R
3
and R
4
are the same as Cl, which results in the compound having the formula (M) hereinbelow.
In the formulas (G) and (M), g
1
and g
2
are independently an integer from 1 to 39, and m
1
and m
2
are independently an integer from 1 to 39.
Preferably, the polyimide having the formula (G) has a refractive index of 1.5176 to 1.5714 in a TE mode and of 1.5076 to 1.5590 in a TM mode at a wavelength of 1,550 nm. The polyimide having the formula (M) may have a refractive index of 1.6021 to 1.7213 in a transverse magnetic mode and
Han Kwan-Soo
Rhee Tae-hyung
You Kyung-Hee
Bushnell , Esq. Robert E.
Hampton-Hightower P.
Samsung Electronics Co,. Ltd
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