Optical waveguides – Planar optical waveguide – Thin film optical waveguide
Reexamination Certificate
2001-05-16
2003-03-18
Ullah, Akm E. (Department: 2874)
Optical waveguides
Planar optical waveguide
Thin film optical waveguide
C385S129000, C385S143000, C385S145000
Reexamination Certificate
active
06535680
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing articles having a predetermined fine uneven portion on the surface of a substrate, particularly fine optical elements and information recording medium substrates.
2. Description of the Prior Art
CD-ROMs and other information recording media, and optical parts such as planar microlenses (an array of microlenses arranged on a substrate in parallel or zigzags), Fresnel lenses, diffraction grating elements and optical waveguide elements must have a predetermined fine uneven portion on the surface. The fine uneven portion on the surface serves as a pit or tracking guide in an information recording medium and as a microlens or diffraction grating for converging or diffusing light in an optical part.
(1) To form the uneven portion on the surface, there is known a process in which an ultraviolet curable resin is uniformly spread over a substrate and irradiated with ultraviolet radiation while a mold having an uneven portion is pressed against the resin to form a resin film having a surface shape which is the inversion of the surface shape of the mold on the substrate (JP-A 63-49702) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).
(2) There is also known a production process in which a hydrolysis solution prepared from a metal alcoholate is pressed against a transfer mold and cured by heat and light (JP-A 62-102445, JP-A 62-225273 and JP-A 10-142410). For example, JP-A 62-102445 discloses a so-called sol-gel production process in which a solution containing silicon alkoxide is applied to the surface of a glass substrate and heated while a mold having an uneven portion is pressed against the solution to form a gelled film having a surface shape which is the inversion of the surface shape of the mold on the surface of the substrate.
(3) WO99/39890 discloses a process for producing an article having a 1 &mgr;m to 1 mm thick single layer and an uneven surface with an unevenness of 1 to 40 &mgr;m by a sol-gel production process. That is, it teaches a process for producing an article having an uneven surface by adhering a sol-gel material containing dimethyldiethoxysilane and phenyltriethoxysilane between a substrate and a mold, arranging it into the form of a film and heating to form a gelled film having a surface shape which is the inversion of the surface shape of the mold on the surface of the substrate.
As for optical waveguide elements, there are known optical waveguide elements which are produced from organic materials such as (4) PMMA (Ryoko Yoshimura. J. of Lightwave Technology, Vol. 16, No. 6, 1998), (5) a polyimide and (6) a silicon-based polymer (Mitsuo Usui, J. of Lightwave Technology, Vol. 14, No. 10, 1996) by photolithography and etching in addition to optical waveguide elements produced from inorganic materials.
Problems to be Solved by the Invention
However, the above prior arts have the following problems to be solved. First, in the above process (1), the ultraviolet curable resin decomposes or yellows at a temperature higher than 250° C. due to its low heat resistance. Therefore, the substrate having an uneven portion of the ultraviolet curable resin cannot be applied to heat processing such as soldering and difficult to be attached to a device.
In the process (2), the gelled film (organopolysiloxane layer) has high heat resistance and can be soldered. This is a method for forming a laminate by molding organopolysiloxane layers one after another, which makes it possible to form an organopolysiloxane layer having an uneven surface and a thickness of several tens of micrometers. However, this production process is long, thereby boosting costs. Further, since the next layer is formed after an underlying layer is completely cured, undesired air is easily contained between the mold and the solution or sol with the result of low dimensional accuracy of the uneven portion.
The process (3) is capable of forming a film as thick as 1 &mgr;m to 1 mm. However, it is difficult to peel off an organopolysiloxane film from the mold due to low releasability with the mold when the mold having an uneven shape as large as 40 &mgr;m or more is to be released after it is pressed against the sol-gel material and heated. As a result, the process has such problems that part of the film remains on the mold and that there is a big dimensional error between the surface shape of the film and the surface shape of the mold.
As for optical waveguides, optical waveguide elements produced from inorganic materials have high reliability but cannot be mass-produced at a low cost. As for optical waveguide elements produced from the above organic materials (4) to (6), there are few materials which have satisfactory heat resistance and a complicated step such as photolithography or etching is needed to form a core portion for transmitting light.
The present invention has been made in view of the above problems of the prior art.
It is an object of the present invention to provide an article which can be produced at a low cost, and has excellent heat resistance and dimensional accuracy and a more uneven surface than that of the prior art, for example, an unevenness of 1 to 500 &mgr;m. It is another object of the present invention to provide an optical waveguide which has high heat resistance and small absorption at a communication wavelength of a near infrared range, and is satisfactory for reliability and a low loss at an optical communication range.
It is still another object of the present invention to provide an industrially advantageous process for producing the above article and optical waveguide of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
Means for Solving the Problems
Firstly, according to the present invention, the above objects and advantages of the present invention are attained by a process for producing an article having a predetermined surface shape, which comprises disposing a sol-gel material between a substrate and a mold in the form of a film so as to make the sol-gel material closely contact with the substrate and the mold, and heating the film to form a gelled film having a surface shape which is the inversion of the surface shape of the mold on the surface of the substrate, said sol-gel material containing at least one of (A) a silane compound represented by the following formula (1) and (B) a silane compound represented by the following formula (2), and (C) a silane compound represented by the following formula (3):
R
1
2
SiX
2
(1)
wherein R
1
is an alkyl group and X is an alkoxyl group or halogen atom,
R
2
SiY
3
(2)
wherein R
2
is an aryl group or substituted aryl group and Y is an alkoxyl group or halogen atom,
R
3
SiZ
3
(3)
wherein R
3
is a fluorine-containing alkyl group and Z is an alkoxyl group or halogen atom.
Secondly, the above objects and advantages of the present invention are attained by an article having a predetermined surface shape, which comprises a substrate and an organopolysiloxane film having a maximum thickness of 1 &mgr;m to 1 mm formed on the surface of the substrate, wherein
the organopolysiloxane film contains as essential ingredients at least one of a dialkylsiloxane represented by the following formula (4) and an arylsiloxane (or substituted arylsiloxane) represented by the following formula (5), and (6) a fluoroalkylsiloxane represented by the following formula (6):
R
4
2
SiO
2/2
(4)
wherein R
4
is an alkyl group,
R
5
SiO
3/2
(5)
wherein R
5
is an aryl group or substituted aryl group,
R
6
SiO
3/2
(6)
wherein R
6
is a fluorine-containing alkyl group.
Thirdly, the above objects and advantages of the present invention are attained by an optical waveguide element which has a 10 &mgr;m to 1 mm thick organopolysiloxane film formed on the surface of a substrate, the organopolysiloxane film being an optical waveguide which comprises a core port
Hori Masahiro
Nakamura Koichiro
Doan Jennifer
Nippon Sheet Glass Co. Ltd.
Ullah Akm E.
Wenderoth , Lind & Ponack, L.L.P.
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