U.S. patent application number 15/770294 was filed with the patent office on 2019-11-07 for production method for gi optical waveguide.
This patent application is currently assigned to NISSAN CHEMICAL INDUSTRIES, LTD.. The applicant listed for this patent is NISSAN CHEMICAL INDUSTRIES, LTD.. Invention is credited to Takaaki ISHIGURE, Takehiro NAGASAWA, Kentaro OHMORI, Yuki SAITO, Kazuki YASUHARA, Sho YOSHIDA.
Application Number | 20190338095 15/770294 |
Document ID | / |
Family ID | 58557062 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190338095 |
Kind Code |
A1 |
ISHIGURE; Takaaki ; et
al. |
November 7, 2019 |
PRODUCTION METHOD FOR GI OPTICAL WAVEGUIDE
Abstract
A production method for an optical waveguide including: a first
step of inserting a needle-like portion at a tip end of an ejection
unit into uncured cladding; a second step of moving the needle-like
portion in the uncured cladding while ejecting an uncured material
from the needle-like portion to form an uncured core surrounded and
covered with the uncured cladding; a third step of removing the
needle-like portion from the uncured cladding; and a fourth step of
curing the uncured cladding and core, wherein the uncured cladding
is composed of a composition including a reactive silicone compound
composed of a polycondensate of a diarylsilicic acid compound of
Formula [1] ##STR00001## and an alkoxy silicon compound of Formula
[2] Ar.sup.3--Si(OR.sup.1).sub.aR.sup.2.sub.3-a [2], and a
di(meth)acrylate compound of Formula [3] ##STR00002## and the
uncured core is composed of a composition including a reactive
silicone compound and an aromatic vinyl compound of Formula [4]
##STR00003##
Inventors: |
ISHIGURE; Takaaki;
(Mitaka-shi, JP) ; YOSHIDA; Sho; (Adachi-ku,
JP) ; SAITO; Yuki; (Funabashi-shi, JP) ;
YASUHARA; Kazuki; (Yokohama-shi, JP) ; NAGASAWA;
Takehiro; (Funabashi-shi, JP) ; OHMORI; Kentaro;
(Funabashi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NISSAN CHEMICAL INDUSTRIES, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
NISSAN CHEMICAL INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
58557062 |
Appl. No.: |
15/770294 |
Filed: |
October 21, 2016 |
PCT Filed: |
October 21, 2016 |
PCT NO: |
PCT/JP2016/081320 |
371 Date: |
April 23, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 230/08 20130101;
G02B 2006/12095 20130101; B29D 11/00663 20130101; G02B 6/138
20130101; B29L 2011/0075 20130101; B29D 11/00673 20130101; C08J
2483/07 20130101; B29K 2083/00 20130101; G02B 6/13 20130101; C08F
290/14 20130101; C08J 2383/07 20130101; G02B 6/12 20130101; C08J
7/042 20130101 |
International
Class: |
C08J 7/04 20060101
C08J007/04; G02B 6/13 20060101 G02B006/13; B29D 11/00 20060101
B29D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2015 |
JP |
2015-207586 |
Claims
1. A production method for an optical waveguide, the production
method comprising: a first step of inserting a needle-like portion
at a tip end of an ejection unit into uncured cladding; a second
step of moving the needle-like portion in the uncured cladding
while ejecting an uncured material from the needle-like portion to
form an uncured core surrounded and covered with the uncured
cladding; a third step of removing the needle-like portion from the
uncured cladding; and a fourth step of curing the uncured cladding
and the uncured core, wherein the uncured cladding is composed of a
composition including 100 parts by mass of a reactive silicone
compound (a) composed of a polycondensate of a diarylsilicic acid
compound A of Formula [1] and an alkoxy silicon compound B of
Formula [2], or a polycondensate of the diarylsilicic acid compound
A, the alkoxy silicon compound B, and another polycondensable
compound, and 1 part by mass to 200 parts by mass of a
di(meth)acrylate compound (b) of Formula [3], and the uncured core
is composed of a composition including 100 parts by mass of a
reactive silicone compound (x) composed of a polycondensate of a
diarylsilicic acid compound A of Formula [1] and an alkoxy silicon
compound B of Formula [2], or a polycondensate of the diarylsilicic
acid compound A, the alkoxy silicon compound B, and another
polycondensable compound, and 1 part by mass to 100 parts by mass
of an aromatic vinyl compound (y) of Formula [4]: ##STR00011##
(wherein Ar.sup.1 and Ar.sup.2 are independently a phenyl group
optionally substituted with a C.sub.1-6 alkyl group, a naphthyl
group optionally substituted with a C.sub.1-6 alkyl group, or a
biphenyl group optionally substituted with a C.sub.1-6 alkyl
group), Ar.sup.3--Si(OR').sub.aR.sup.2.sub.3-a [2] (wherein
Ar.sup.3 is a phenyl group having at least one group having a
polymerizable double bond, a naphthyl group having at least one
group having a polymerizable double bond, or a biphenyl group
having at least one group having a polymerizable double bond,
R.sup.1 is independently methyl group or ethyl group, R.sup.2 is
methyl group, ethyl group, or vinylphenyl group, and a is 2 or 3),
##STR00012## (wherein R.sup.3 and R.sup.4 are independently a
hydrogen atom or methyl group, R.sup.5 is a hydrogen atom, methyl
group, or ethyl group, L.sup.1 and L.sup.2 are independently a
C.sub.2-6 alkylene group, and m and n are 0 or a positive integer,
wherein m+n is 0 to 20), ##STR00013## (wherein R.sup.6 is a
hydrogen atom or methyl group, L.sup.3 is a single bond, a hydrogen
atom, an oxygen atom, a C.sub.1-20 q-valent aliphatic hydrocarbon
residue optionally substituted with a phenyl group, or a C.sub.1-20
q-valent aliphatic hydrocarbon residue optionally including an
ether bond, Ar.sup.4 is a p+1-valent aromatic hydrocarbon residue,
p is independently 1 or 2, and q is an integer of 1 to 3 (wherein q
is 1 when L.sup.3 is a hydrogen atom, and q is 2 when L.sup.3 is a
single bond or an oxygen atom)).
2. The production method for an optical waveguide according to
claim 1, wherein between the third step and the fourth step, the
first step, the second step, and the third step are repeatedly
performed as a sequential process to form a plurality of uncured
cores surrounded and covered with the uncured cladding.
Description
TECHNICAL FIELD
[0001] The present invention relates to a production method for a
GI optical waveguide, and more specifically to a production method
for a GI optical waveguide using a polymerizable composition
composed of a certain reactive silicone compound and a
di(meth)acrylate compound as optical waveguide-forming
materials.
BACKGROUND ART
[0002] With recent development of cloud computing and increase of
smartphone users, communication traffic is ever-increasing. This
requires an enormous amount of electricity in data servers where
transmitted information data is gathered. Moreover, their
processing capacity is reaching the limit. There is an urgent need
for development of technologies for improving such problems. One of
the actively studied technologies is opto-electronic circuit boards
(also called opto-electronic hybrid boards) which change part of
electrical interconnects in a server board to optical
interconnects, and this technology enables data processing at high
density and at high speed.
[0003] The opto-electronic circuit board requires an optical
waveguide as an optical transmission path as well as a
photoelectric transducer converting an electrical signal into an
optical signal. Techniques including vertical cavity surface
emitting layers (VCSEL) and silicon photonics are known as light
sources for the photoelectric transducer. Especially, silicon
photonics developed from an application of semiconductor processes,
such as CMOS and MEMS, has become a mainstream. The wavelengths of
light transmitted have changed from 850 nm for VCSEL to the long
wavelength range, such as the wavelength of 1,310 nm and the
wavelength of 1,550 nm, for silicon photonics.
[0004] To incorporate electrical interconnects, a solder reflowing
process up to about 300.degree. C. is required, and the optical
waveguide should have heat resistance to the process.
[0005] There is a need for optical waveguides that have a low
transmission loss in the above-noted long wavelength range and have
heat resistance to 300.degree. C. or higher, and preferably
350.degree. C. or higher. A vinyl-based silicone compound is
disclosed as a material that can form such optical waveguides
(Patent Document 1).
[0006] Optical waveguides are classified in accordance with their
structure mainly into two types: step-index (SI) and graded-index
(GI) structures. The SI structure has been employed in conventional
optical waveguides in view of its processability. In the SI
structure, a core and cladding define an interface between
refractive indices, and reflection at the interface allows light to
propagate. On the other hand, in the GI structure, the refractive
index is highest at the core center and gradually decreases
outward. This structure allows light to be guided and propagate
only in the vicinity of the core center. The GI structure is free
from crosstalk even with cores with narrow pitches and is thought
to be an ideal optical waveguide shape.
[0007] Known materials used in few reports on GI optical waveguides
include certain norbornene resins and epoxy compounds (Patent
Document 2). Light is applied to a coating film of this resin to
induce mass diffusion of the photolyte and the photocurable epoxy
compound, thereby producing a refractive index gradient.
PRIOR ART DOCUMENTS
Patent Documents
[0008] Patent Document 1: Japanese Patent Application Publication
No. 2014-510159 (JP 2014-510159 A)
[0009] Patent Document 2: Japanese Patent Application Publication
No. 2012-198488 (JP 2012-198488 A)
[0010] Patent Document 3: International Publication WO2013/002013
Pamphlet
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0011] GI optical waveguides described above are difficult to
produce. For example, an injection process called the Mosquito
method or the like has been proposed, in which a siloxane resin
composition is used as a photocurable resin for forming core and
cladding, and a photocurable resin serving as a core is drawn as
interconnects in a photocurable resin serving as cladding, using a
dispenser (Patent Document 3). However, reported examples are
few.
[0012] On the other hand, in the GI optical waveguides proposed so
far, for example, the materials specifically proposed in Patent
Document 2 and Patent Document 3 above include hydrocarbon or epoxy
group having absorption in the long wavelength band and lead to a
problem of high propagation loss in a long wavelength range, which
is the recent mainstream. Patent Document 1 merely discloses an SI
optical waveguide including the air for a cladding layer and does
not discuss an application to GI optical waveguides.
[0013] As described above, there has been no report on a production
method for a GI optical waveguide having heat resistance to
300.degree. C. or higher, preferably 350.degree. C. or higher and
with low propagation loss even in the long wavelength range, and it
has been necessary to develop such a production method.
Means for Solving the Problem
[0014] The inventors of the present invention have conducted
elaborate studies in order to achieve the object above and have
found a production method, in which a polymerizable composition
including a reactive silicone compound having a certain structure
in combination with a di(meth)acrylate compound or an aromatic
vinyl compound having a certain structure is used as a cladding
material or a core material of an optical waveguide, and a GI
optical waveguide having high heat resistance and low light
propagation loss in the long wavelength range can be produced with
a high degree of flexibility in layout design of cores and through
a simple process. This finding has led to completion of the present
invention.
[0015] As a first aspect, the present invention relates to a
production method for an optical waveguide, comprising:
[0016] a first step of inserting a needle-like portion at a tip end
of an ejection unit into uncured cladding;
[0017] a second step of moving the needle-like portion in the
uncured cladding while ejecting an uncured material from the
needle-like portion to form an uncured core surrounded and covered
with the uncured cladding;
[0018] a third step of removing the needle-like portion from the
uncured cladding; and
[0019] a fourth step of curing the uncured cladding and the uncured
core, in which
[0020] the uncured cladding is composed of a composition including
100 parts by mass of a reactive silicone compound (a) composed of a
polycondensate of a diarylsilicic acid compound A of Formula [1]
and an alkoxy silicon compound B of Formula [2], or a
polycondensate of the diarylsilicic acid compound A, the alkoxy
silicon compound B, and another polycondensable compound, and 1
part by mass to 200 parts by mass of a di(meth)acrylate compound
(b) of Formula [3], and
[0021] the uncured core is composed of a composition including 100
parts by mass of a reactive silicone compound (x) composed of a
polycondensate of a diarylsilicic acid compound A of Formula [1]
and an alkoxy silicon compound B of Formula [2], or a
polycondensate of the diarylsilicic acid compound A, the alkoxy
silicon compound B, and another polycondensable compound, and 0.1
part by mass to 100 parts by mass of an aromatic vinyl compound (y)
of Formula [4]:
##STR00004##
[0022] (wherein Ar.sup.1 and Ar.sup.2 are independently a phenyl
group optionally substituted with a C.sub.1-6 alkyl group, a
naphthyl group optionally substituted with a C.sub.1-6 alkyl group,
or a biphenyl group optionally substituted with a C.sub.1-6 alkyl
group),
Ar.sup.3--Si(OR.sup.1).sub.aR.sup.2.sub.3-a [2]
[0023] (wherein Ar.sup.3 is a phenyl group having at least one
group having a polymerizable double bond, a naphthyl group having
at least one group having a polymerizable double bond, or a
biphenyl group having at least one group having a polymerizable
double bond, R.sup.1 is independently methyl group or ethyl group,
R.sup.2 is methyl group, ethyl group, or vinylphenyl group, and a
is 2 or 3),
##STR00005##
[0024] (wherein R.sup.3 and R.sup.4 are independently a hydrogen
atom or methyl group, R.sup.5 is a hydrogen atom, methyl group, or
ethyl group, L.sup.1 and L.sup.2 are independently a C.sub.2-6
alkylene group, and m and n are 0 or a positive integer, wherein
m+n is 0 to 20),
##STR00006##
[0025] (wherein R.sup.6 is a hydrogen atom or methyl group, L.sup.3
is a single bond, a hydrogen atom, an oxygen atom, a C.sub.1-20
q-valent aliphatic hydrocarbon residue optionally substituted with
a phenyl group, or a C.sub.1-20 q-valent aliphatic hydrocarbon
residue optionally including an ether bond, Ar.sup.4 is a
p+1-valent aromatic hydrocarbon residue, p is independently 1 or 2,
and q is an integer of 1 to 3 (wherein q is 1 when L.sup.3 is a
hydrogen atom, and q is 2 when L is a single bond or an oxygen
atom)).
[0026] As a second aspect, in the production method for an optical
waveguide according to the first aspect, between the third step and
the fourth step, the first step, the second step, and the third
step are repeatedly performed as a sequential process to form a
plurality of uncured cores surrounded and covered with the uncured
cladding.
Effects of the Invention
[0027] The production method for an optical waveguide according to
the present invention can produce a GI optical waveguide having
excellent optical characteristics such as a high refractive index
and low light propagation loss even in the long wavelength region
including 1,550 nm, and having high heat resistance against a
solder reflowing process required in the production process for
opto-electronic circuit boards.
[0028] The optical waveguide-forming composition in the present
invention can produce a GI optical waveguide, which is said to be
difficult to produce, by a simple technique and can produce not
only a multimode optical waveguide but also a single-mode GI
optical waveguide.
[0029] In this way, the present invention enables production of a
GI optical waveguide that has high heat resistance and extremely
high transparency (low propagation loss) in the long wavelength
range and is workable for use on an opto-electronic circuit
board.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a first diagram illustrating a production process
for an optical waveguide.
[0031] FIG. 2 is a second diagram illustrating a production process
for an optical waveguide.
[0032] FIG. 3 is a third diagram illustrating a production process
for an optical waveguide.
[0033] FIG. 4 is a fourth diagram illustrating a production process
for an optical waveguide.
[0034] FIG. 5 is a fifth diagram illustrating a production process
for an optical waveguide.
[0035] FIG. 6 is a plan view illustrating an optical waveguide
(first embodiment) fabricated according to the present
invention.
[0036] FIG. 7 is a sectional view taken along line A-A in FIG.
6.
[0037] FIG. 8 is a sectional view taken along line B-B in FIG.
6.
[0038] FIG. 9 is a plan view illustrating an optical waveguide in
another embodiment (second embodiment) fabricated according to the
present invention.
[0039] FIG. 10 is a sectional view taken along line E-E in FIG.
9.
[0040] FIG. 11 is a sectional view taken along line F-F in FIG.
9.
[0041] FIG. 12 is a plan view illustrating an optical waveguide in
another embodiment (third embodiment) fabricated according to the
present invention.
[0042] FIG. 13 is a sectional view taken along line G-G in FIG.
12.
[0043] FIG. 14 is a sectional view taken along line H-H in FIG.
12.
[0044] FIG. 15 is a diagram illustrating the .sup.1H NMR spectrum
of a reactive silicone compound (SC1) obtained in Production
Example 1.
[0045] FIG. 16 is a diagram illustrating the .sup.1H NMR spectrum
of a reactive silicone compound (SC2) obtained in Production
Example 2.
[0046] FIG. 17 is a sectional photograph illustrating the
observation result (transmission mode) of an optical waveguide
fabricated in Example 1 with a digital microscope.
[0047] FIG. 18 is a sectional photograph illustrating the
observation result of an emission near field pattern of the optical
waveguide fabricated in Example 1.
[0048] FIG. 19 is a sectional photograph illustrating the
observation result (transmission mode) of an optical waveguide
fabricated in Comparative Example 1 with a digital microscope.
[0049] FIG. 20 is a sectional photograph illustrating the
observation result (transmission mode) of an optical waveguide
fabricated in Example 2 with a digital microscope.
[0050] FIG. 21 is a sectional photograph illustrating the
observation result (transmission mode) of an optical waveguide
fabricated in Example 3 with a digital microscope.
MODES FOR CARRYING OUT THE INVENTION
[0051] <<Production Method for Optical Waveguide>>
[0052] A production method for an optical waveguide according to
the present invention includes a first step of inserting a
needle-like portion at a tip end of an ejection unit into uncured
cladding, a second step of moving the needle-like portion in the
uncured cladding while ejecting an uncured material from the
needle-like portion to form an uncured core surrounded and covered
with the uncured cladding, a third step of removing the needle-like
portion from the uncured cladding, and a fourth step of curing the
uncured cladding and the uncured core.
[0053] In the production method in the present invention, between
the third step and the fourth step, the first step, the second
step, and the third step may be repeatedly performed as a
sequential process to form a plurality of uncured cores surrounded
and covered with the uncured cladding, and thereafter the fourth
step of curing the uncured cladding and the uncured core may be
performed.
[0054] In the production method for an optical waveguide according
to the present invention, as will be described later, the uncured
cladding is composed of a composition (which hereinafter may be
referred to as a cladding-forming composition) including 100 parts
by mass of a reactive silicone compound (a) composed of a
polycondensate of a diarylsilicic acid compound A of Formula [1]
and an alkoxy silicon compound B of Formula [2], or a
polycondensate of the diarylsilicic acid compound A, the alkoxy
silicon compound B, and another polycondensable compound, and 1
part by mass to 200 parts by mass of a di(meth)acrylate compound
(b) of Formula [3]. The uncured core is composed of a composition
(which hereinafter may be referred to as a core-forming
composition) including 100 parts by mass of a reactive silicone
compound (x) composed of a polycondensate of a diarylsilicic acid
compound A of Formula [1] and an alkoxy silicon compound B of
Formula [2], or a polycondensate of the diarylsilicic acid compound
A, the alkoxy silicon compound B, and another polycondensable
compound, and 0.1 part by mass to 100 parts by mass of an aromatic
vinyl compound (y) of Formula [4].
[0055] An example of the actual process for producing an optical
waveguide according to the present invention is described in
detail.
[0056] FIG. 1 to FIG. 5 are diagrams illustrating part of the
production process for an optical waveguide. This production
process may be referred to as an injection process.
[0057] First of all, in the step illustrated in FIG. 1, a support
91 is prepared. The support 91 is a member including a bottom plate
92 having a substantially rectangular shape in a two-dimensional
view and an outer frame 93 removably disposed on the periphery of
the bottom plate 92. The outer frame 93 has an opening 93a having a
substantially frame-like shape in a two-dimensional view. For
example, resins (for example, acrylic resins), glass, silicon,
ceramics, or metals can be used as the material of the bottom plate
92 and the outer frame 93. It is noted that the bottom plate 92 and
the outer frame 93 may not be formed of the same material. It is
preferable that the upper surface of the bottom plate 92 has high
flatness.
[0058] Next, in the step illustrated in FIG. 2, a predetermined
material is applied on the upper surface of the bottom plate 92
exposed within the outer frame 93 of the support 91 and uniformly
spread to fabricate uncured cladding 19A with a substantially
constant layer thickness. The uncured cladding 19A can be
fabricated by applying a cladding-forming composition as described
later using, for example, an applicator (for example, dispenser) or
a printing device or by filling (injecting) the composition from
the opening 93a. The material (cladding-forming composition) of the
uncured cladding 19A may contain, for example, a raw material that
absorbs light, such as carbon black.
[0059] The viscosity of the uncured cladding 19A may be, for
example, about 3,800 mPas. The thickness of the uncured cladding
19A can be determined as desired in accordance with, for example,
the diameter of cores 11 to 14 as described later and the
production conditions and is preferably about a few mm, and more
preferably about 50 .mu.m to 1,000 .mu.m.
[0060] Next, in the step illustrated in FIG. 3, an applicator (not
illustrated) having an ejection unit 94 (including an ejection body
95 and a needle-like portion 96) is prepared, and the prepared
applicator (not illustrated) is operated to partially insert the
needle-like portion 96 at the tip end of the ejection unit 94 into
the uncured cladding 19A (first step). The height H.sub.1 from the
upper surface of the bottom plate 92 of the support 91 to the tip
end of the needle-like portion 96 can be selected as appropriate
and is set to, for example, about 100 .mu.m to 1,000 .mu.m (when
the layer thickness of the uncured cladding 19A is about a few
mm).
[0061] The applicator (not illustrated) includes a CPU and a memory
and has a function programmed to accurately move the ejection unit
94 relative to the uncured cladding 19A in the X direction, the Y
direction, and the Z direction at a predetermined moving speed. The
needle-like portion 96 is shaped like, for example, a ring in
section, and the applicator (not illustrated) has a function of
ejecting a predetermined material from the inside of the ring of
the needle-like portion 96 at a predetermined ejection pressure.
The inner diameter of the ring of the needle-like portion 96 can be
selected as appropriate and is set to, for example, about 100 .mu.m
to 200 .mu.m. The sectional shape of the needle-like portion 96 may
not be a ring and may be a square. The applicator (not illustrated)
may include, for example, a tabletop application robot and a
dispenser.
[0062] Next, in the step illustrated in FIG. 4, the applicator (not
illustrated) is operated to move the needle-like portion 96 in the
uncured cladding 19A while ejecting a core-forming composition as
described later as a material forming an uncured core, from the
needle-like portion 96 inserted in the uncured cladding 19A to form
an uncured core 11A (second step). In FIG. 4, (A) is a plan view,
and (B) is a sectional view taken along line C-C in (A). It is
noted that (A) does not illustrate the ejection unit 94. The
needle-like portion 96 can be moved in a direction selected
appropriately and, here, is moved only in the X direction, by way
of example. The moving speed of the needle-like portion 96 can be
selected as appropriate and is set to, for example, about 5 mm/s to
30 mm/s. The ejection pressure of the needle-like portion 96 can be
selected as appropriate and is set to, for example, about 10 kPa to
1,000 kPa.
[0063] The viscosity of the uncured core 11A may be, for example,
about 80,800 mPas.
[0064] The moving speed of the ejection unit 94, the ejection
pressure of the needle-like portion 96, and the inner diameter of
the ring of the needle-like portion 96 are adjusted in accordance
with the properties (for example, viscosity) of the material
forming the uncured core 11A (core-forming composition) and the
material forming the uncured cladding 19A (cladding-forming
composition) to form a core 11, for example, having a circular
sectional shape and having a refractive index higher toward the
center and lower toward the periphery after curing described later.
When the sectional shape of the uncured core 11A is circular, the
diameter may be, for example, about 5 .mu.m to 200 .mu.m.
[0065] Furthermore, a core 11 having a partially different diameter
may be formed by changing the moving speed of the ejection unit 94
and the ejection pressure of the needle-like portion 96 while
ejecting the core-forming composition under instructions of a
program (spot size conversion).
[0066] The uncured core 11A shaped in a circle (sectional shape)
having a diameter smaller than the inner diameter of the ring of
the needle-like portion 96 can be fabricated by adjusting the
moving speed of the ejection unit 94 and the ejection pressure of
the needle-like portion 96, depending on the properties (for
example, viscosity) of the material (core-forming composition) of
the uncured core 11A and the material (cladding-forming
composition) of the uncured cladding 19A.
[0067] This is achieved as follows. The respective viscosities of
the materials are adjusted so that a more viscous material of the
uncured core 11A is ejected from the needle-like portion 96. Then,
the friction force is increased between the inside surface of the
ring of the needle-like portion and the material. As a result, the
material is ejected less from the vicinity of the inside surface of
the ring, whereas the material is ejected more in the vicinity of
the center of the ring where friction with the inside surface of
the ring is not produced.
[0068] In the step illustrated in FIG. 4 by way of example, the
support 91 having the uncured cladding 19A formed therein is fixed,
and the needle-like portion 96 is moved in the uncured cladding 19A
to form the uncured core 11A. The present invention, however, is
not limited to such a manner. For example, the needle-like portion
96 may be fixed while the support 91 having the uncured cladding
19A formed therein may be moved to form the uncured core 11A.
[0069] Next, in the step illustrated in FIG. 5, the ejection unit
94 is moved in the Z direction from the state illustrated in FIG.
4, and the needle-like portion 96 is removed from the uncured
cladding 19A (third step). Subsequently, uncured cores 12A, 13A,
and 14A may be formed in parallel with the uncured core 11A by
repeating the step in FIG. 3 of inserting the needle-like portion
96 into the uncured cladding 19A, the step in FIG. 4 of forming the
uncured core 11A, and the step in FIG. 5 of removing the
needle-like portion 96 from the uncured cladding 19A. Although the
core-forming composition is used as the material of the uncured
cores 12A, 13A, and 14A in the same manner as in the uncured core
11A, any other materials for cores as described later may be used
together. The pitch between adjacent cores can be set to, for
example, about 20 .mu.m to 300 .mu.m.
[0070] As previously mentioned above, the uncured cladding 19A has
an adequate flowability (viscosity). Therefore, when the
needle-like portion 96 is removed from the uncured cladding 19A, no
mark of removal is left, so that after the uncured cores are
formed, no interface is formed between the uncured cladding 19A and
the uncured cores 11A, 12A, 13A, and 14A. In FIG. 5, (A) is a plan
view, and (B) is a sectional view taken along line D-D in (A). It
is noted that (A) does not illustrate the ejection unit 94.
[0071] After the step illustrated in FIG. 5 (not illustrated), the
uncured cores 11A, 12A, 13A, and 14A as well as the uncured
cladding 19A are cured by a predetermined method described later,
that is, by applying light (for example, ultraviolet rays) or by
heating (fourth step). When a material that is not completely cured
only with radiation of light is used, heating may be additionally
performed after applying light.
[0072] In the case of the photocuring, examples of actinic light
used for light radiation include ultraviolet rays, electron beams,
and X-rays. Examples of the light source used for ultraviolet
radiation include sunlight, chemical lamps, low-pressure mercury
lamps, high-pressure mercury lamps, metal halide lamps, xenon
lamps, and UV-LEDs. After light radiation, post baking is
performed, if necessary. Specifically, heating is performed using a
hot plate, an oven, or the like, typically at 50.degree. C. to
300.degree. C. for 1 minute to 120 minutes to complete curing
(polymerization).
[0073] In the case of the thermal curing, the heating conditions
may be selected typically from, but not limited to, the ranges of
50.degree. C. to 300.degree. C. and 1 minute to 120 minutes.
Examples of the heating means include, but not limited to, a hot
plate and an oven.
[0074] Through the curing process, the uncured cores 11A, 12A, 13A,
and 14A, as well as the uncured cladding 19A are polymerized and
cured to form cores 11,12, 13, and 14 as well as cladding 19 (see
FIG. 6 to FIG. 8 described later, optical waveguide 10). The cores
11 to 14 are formed continuously and integrally without an
interface in the cores 11 to 14, and the cladding 19 is formed
integrally without an interface in the cladding 19.
[0075] Although the support 91 is prepared in producing an optical
waveguide in the present embodiment, the support 91 is not always
necessary. For example, the uncured cladding 19A may be fabricated
in a concave shape formed in an integrated circuit or a printed
circuit board, or a groove or a slit in the board may be fabricated
as an alternative to the support.
[0076] Although the ejection unit 94 is a single system in the
example illustrated in the present embodiment, the present
invention is not limited to such an embodiment, and the
core-forming composition may be ejected simultaneously from a
plurality of ejection units 94 to simultaneously form a plurality
of uncured cores (for example 11A to 14A).
[0077] An example of the optical waveguide fabricated by the
production method as described above is illustrated in FIG. 6 to
FIG. 8 (first embodiment).
[0078] FIG. 6 is a plan view illustrating an optical waveguide 10
in a first embodiment according to the present invention. FIG. 7 is
a sectional view taken along line A-A in FIG. 6. FIG. 8 is a
sectional view taken along line B-B in FIG. 6.
[0079] The optical waveguide 10 illustrated in FIG. 6 to FIG. 8 is
an optical waveguide having a graded-index (GI)-type refractive
index gradient, in which cores 11 to 14 of four channels are
juxtaposed in the cladding 19. In FIG. 6 to FIG. 8, the cladding 19
is shaped in a cube or a cuboid, by way of example. The direction
parallel to a side of the bottom surface of the cube or the cuboid
is the X direction, the direction vertical to the X direction in
the bottom surface of the cube or the cuboid is the Y direction,
and the direction vertical to the X direction and the Y direction
(the height direction of the cube or the cuboid) is the Z direction
(the same applies in the subsequent drawings).
[0080] In the optical waveguide 10, the cladding 19 is formed of a
cured product of the cladding-forming composition, and the cores 11
to 14 are formed of a cured product of the core-forming
composition.
[0081] The cores 11 to 14 each are a part through which light
propagates and are formed of, for example, the core-forming
composition, that is, formed of a cured product of the core-forming
composition. All of the cores 11 to 14 may be formed of the same
material or they may be formed of different materials. For example,
a material other than the core-forming composition may be selected
as appropriate from materials composed mostly of acrylic resins,
epoxy resins, polyimide resins, polyolefin resins, and
polynorbornene resins.
[0082] As will be described later, the cores 11 to 14 each have a
higher refractive index toward the center and have a lower
refractive index toward the periphery. The refractive index of the
center of each of the cores 11 to 14 may be, for example, about
1.52 to 1.62.
[0083] The cores 11 to 14 are each formed continuously and
integrally without an interface in the cores 11 to 14. As used
herein, the interface refers to the boundary surface formed between
two layers when the two layers are in contact with each other (the
same applies to the cladding described later). The sectional shape
of each of the cores 11 to 14 may be, for example, circular. When
the cross-sectional shape of each of the cores 11 to 14 is
circular, the diameter of each core is, for example, about 5 .mu.m
to 200 .mu.m. In the cores 11 to 14, the pitch between adjacent
cores is, for example, about 20 .mu.m to 300 .mu.m. In each of the
cores 11 to 14, the height from the bottom surface of the cladding
19 is substantially constant. That is, the cores 11 to 14 are each
formed substantially parallel to the XY plane.
[0084] In the subject application, the word "circle" means an
approximate circle and does not mean a strictly perfect circle.
Therefore, the circle may be deviated from a perfect circle without
substantially impairing a predetermined effect of the GI optical
waveguide.
[0085] The cladding 19 is formed to cover the periphery of the
cores 11 to 14. In the optical waveguide in the present invention,
the cladding 19 is formed of the cladding-forming composition, and
more specifically, formed of a cured product of the
cladding-forming composition. The cladding-forming composition may
contain, for example, a raw material that absorbs light, such as
carbon black. The raw material that absorbs light, such as carbon
black, is dispersed in the cladding 19 to reduce crosstalk between
the adjacent cores. This is particularly advantageous for cores
with narrow pitches.
[0086] It is noted that the cladding 19 is formed of a material
having a refractive index lower than that of the center of the
cores 11 to 14. The refractive index of the cladding 19 may be, for
example, about 1.51 to 1.60. The sectional shape of the cladding 19
may be, for example, rectangular. The thickness of the cladding 19
may be determined as desired, depending on the diameters of the
cores 11 to 14, the production conditions, and the like, and is
preferably about a few mm, and more preferably about 50 .mu.m to
1,000 .mu.m. As is clear from the description above of the
production process for the optical waveguide 10, the cladding 19 is
formed integrally, and there exists no interface in the cladding
19.
[0087] Another example of the optical waveguide fabricated by the
production method described above is illustrated in FIG. 9 to FIG.
11 (second embodiment).
[0088] In this example, a slope-type optical waveguide with cores
partially inclined is illustrated. FIG. 9 is a plan view
illustrating an optical waveguide 20 according to a second
embodiment. FIG. 10 is a sectional view taken along line E-E in
FIG. 9. FIG. 11 is a sectional view taken along line F-F in FIG.
9.
[0089] In FIG. 9 to FIG. 11, the optical waveguide 20 is a GI
optical waveguide in which cores 21 to 24 of four channels are
juxtaposed in cladding 29. The materials, the sectional shapes,
functions, and the like of the cores 21 to 24 and the cladding 29
are similar to those of the cores 11 to 14 and the cladding 19 in
the foregoing first embodiment and will not be further
elaborated.
[0090] In the optical waveguide 10, the entire cores 11 to 14 are
each formed linearly in one direction (a direction substantially
parallel to the X direction). In the optical waveguide 20, the
cores 21 to 24 are each formed to include an inclined portion
(slope portion). That is, the cores 21 to 24 each include a bending
portion and are not formed linearly in one direction. The bending
portion may be curved (may be bent like a bow).
[0091] More specifically, the core 21 of the optical waveguide 20
includes a portion 21a formed linearly in a direction substantially
parallel to the X direction, a bending portion 21b, a portion 21c
(slope portion) formed linearly in a direction inclined in the Z
direction relative to the X direction, a bending portion 21d, and a
portion 21e formed linearly in a direction substantially parallel
to the X direction.
[0092] The portions 21a, 21c, and 21e lie on straight lines
different from each other. The portion 21a and the portion 21e are
on different levels with different distances from the bottom
surface of the cladding 29. It is noted that these portions are
obtained by dividing the core 21 into a plurality of portions for
the sake of convenience, and the core 21 is formed continuously and
integrally without an interface in the core 21. The cores 22 to 24
have a shape similar to the shape of the core 21.
[0093] To produce a slope-type optical waveguide, for example, in
the step illustrated in FIG. 4 (second step), the applicator (not
illustrated) may be programmed such that the needle-like portion 96
moves while changing the vertical distance from the bottom surface
of the uncured cladding. That is, the slope portion (portion 21c)
can be formed by programming the applicator (not illustrated) such
that the needle-like portion 96 moves in the X direction and also
moves in the Z direction. The moving speed in the X direction and
the moving speed in the Z direction can be set as appropriate,
considering the inclined angle of the slope portion (portion 21c)
as intended.
[0094] A core including a portion inclined in the Y direction
relative to the XZ plane may be formed by moving the needle-like
portion 96 while changing the horizontal distance from the side
surface of the uncured cladding. Furthermore, a core including a
portion inclined in the Z direction relative to the XY plane and
inclined in the Y direction relative to the XZ plane may be formed
by moving the needle-like portion 96 while changing the vertical
distance from the bottom surface of the uncured cladding and
changing the horizontal distance from the side surface. In short,
cores of various shapes can be formed in a simple process by
controlling the applicator (not illustrated) such that the
needle-like portion 96 ejects a predetermined material while the
needle-like portion 96 moves in a desired direction.
[0095] In the second embodiment, the example in which the portions
21a, 21c, and 21e are formed linearly has been illustrated.
Alternatively, the portions 21a, 21c, and 21e may be formed in a
curved shape (including a coil shape, a spiral shape, and a helix
shape. The same shall apply hereinafter). Even when the portions
21a, 21c, and 21e are curved, light propagates in the same manner
as when they are linear. Alternatively, both the linear portion and
the curved portion may be present. For example, the portion 21a is
formed linearly, and the portions 21c and 21e may be formed in a
curved shape. The portions 21a, 21c, and 21e may lie on the same
plane or may lie on planes different from each other.
[0096] In this way, the second embodiment achieves similar effects
as in the first embodiment. More specifically, a slope-type optical
waveguide is formed, which includes a core parallel to a
predetermined surface of the cladding and/or a core inclined
relative to a predetermined surface of the cladding in single
cladding formed integrally without an interface.
[0097] Another example of the optical waveguide fabricated by the
production method described above is further illustrated in FIG. 12
to FIG. 14 (third embodiment).
[0098] The present example illustrates a three-dimensional
intersection-type optical waveguide in which cores
three-dimensionally intersect with each other. FIG. 12 is a plan
view illustrating an optical waveguide according to a third
embodiment. FIG. 13 is a sectional view taken along line G-G in
FIG. 12. FIG. 14 is a sectional view taken along line H-H in FIG.
12.
[0099] In FIG. 12 to FIG. 14, an optical waveguide 30 is a GI
optical waveguide including cores 31 to 38 of eight channels formed
in cladding 39. The materials, sectional shapes, functions, and the
like of the cores 31 to 38 and the cladding 39 are similar to those
of the cores 11 to 14 and the cladding 19 in the foregoing first
embodiment and will not be further elaborated.
[0100] In the optical waveguide 30, the entire cores 31 to 34 are
each formed linearly in one direction (a direction substantially
parallel to the Y direction). On the other hand, the cores 35 to 38
are each formed to include an inclined portion (slope portion).
That is, the cores 35 to 38 each include a bending portion and are
not formed linearly in one direction. The bending portion may be
curved (may be bent like a bow).
[0101] More specifically, the core 35 of the optical waveguide 30
includes a portion 35a formed linearly in a direction substantially
parallel to the X direction, a bending portion 35b, a portion 35c
(slope portion) formed linearly in a direction inclined (rising) in
the Z direction relative to the X direction, a bending portion 35d,
a portion 35e formed linearly in a direction substantially parallel
to the X direction, a bending portion 35f, a portion 35g (slope
portion) formed linearly in a direction inclined (declining) in the
Z direction relative to the X direction, a bending portion 35h, and
a portion 35i formed linearly in a direction substantially parallel
to the X direction.
[0102] The portions 35a, 35c, 35e, and 35g lie on straight lines
different from each other, whereas the portions 35a and 35i lie on
the same straight line. However, the portions 35a and 35i may not
necessarily be formed on the same straight line. The portions 35a
and 35i and the portion 35e are on different levels with different
distances from the bottom surface of the cladding 39. It is noted
that these portions are obtained by dividing the core 35 into a
plurality of portions for the sake of convenience, and the core 35
is formed continuously and integrally without an interface in the
core 35. The cores 36 to 38 have a shape similar to the shape of
the core 35. The cores 35 to 38 three-dimensionally intersect with
the cores 31 to 34.
[0103] To produce the three-dimensional intersection-type optical
waveguide, for example, the production method in the first
embodiment and the production method in the second embodiment may
be combined. It should be noted that the cores 31 to 34 should be
fabricated first, and that the cores 35 to 38 should be thereafter
fabricated. In the same manner as in the second embodiment, cores
of various shapes can be formed in a simple process by controlling
the applicator (not illustrated) such that the needle-like portion
96 ejects a predetermined material while the needle-like portion 96
moves in a desired direction. In the same manner as in the second
embodiment, the portions 35a, 35c, 35e, 35g, and 35i may be formed
in a curved shape, or both a linear portion and a curved portion
may be present. The portions 35a, 35c, 35e, 35g, and 35i may lie on
the same plane or may lie on planes different from each other.
[0104] In this way, in the third embodiment, a three-dimensional
intersection-type optical waveguide is formed, in which the cores
three-dimensionally intersect with each other in single cladding
formed integrally without an interface as in the first
embodiment.
[0105] <Cladding-Forming Composition>
[0106] The cladding-forming composition is a composition including
100 parts by mass of a reactive silicone compound (a) composed of a
polycondensate of a diarylsilicic acid compound A of Formula [1]
with an alkoxy silicon compound B of Formula [2], or a
polycondensate of the diarylsilicic acid compound A and the alkoxy
silicon compound B with another polycondensable compound, and 1
part by mass to 200 parts by mass of a di(meth)acrylate compound
(b) of Formula [3].
[0107] More preferably, 1 part by mass to 100 parts by mass of the
component (b) is blended with respect to 100 parts of the component
(a).
[0108] <(a) Reactive Silicone Compound>
[0109] The reactive silicone compound (a) included in the
cladding-forming composition is a polycondensate of the
diarylsilicic acid compound A having a certain structure with the
alkoxy silicon compound B having a certain structure, or a
polycondensate of the diarylsilicic acid compound A and the alkoxy
silicon compound B with another polycondensable compound. The
polycondensate is obtained by polycondensation of the compound A
with the compound B and, if desired, another polymerizable compound
in the presence of an acid or a base.
[0110] <Polycondensable Compound>
[0111] [Diarylsilicic Acid Compound A]
[0112] The diarylsilicic acid compound A is a compound of Formula
[1] below.
##STR00007##
[0113] In Formula [1] above, Ar.sup.1 and Ar.sup.2 are
independently a phenyl group optionally substituted with a
C.sub.1-6 alkyl group, a naphthyl group optionally substituted with
a C.sub.1-6 alkyl group, or a biphenyl group optionally substituted
with a C.sub.1-6 alkyl group.
[0114] Examples of the phenyl group optionally substituted with a
C.sub.1-6 alkyl group, represented by Ar.sup.1 and Ar.sup.2,
include phenyl group, o-tolyl group, m-tolyl group, p-tolyl group,
4-ethylphenyl group, 4-isopropylphenyl group, 4-tert-butylphenyl
group, 3,5-dimethylphenyl group, 3,5-diethylphenyl group,
3,5-diisopropylphenyl group, and 2,4,6-trimethylphenyl group.
[0115] Examples of the naphthyl group optionally substituted with a
C.sub.1-6 alkyl group, represented by Ar.sup.1 and Ar.sup.2,
include 1-naphthyl group, 2-naphthyl group, 4-methylnaphthalen-1-yl
group, and 6-methylnaphthalen-2-yl group.
[0116] Examples of the biphenyl group optionally substituted with a
C.sub.1-6 alkyl group, represented by Ar.sup.1 and Ar.sup.2,
include [1,1'-biphenyl]-2-yl group, [1,1'-biphenyl]-3-yl group, and
[1,1'-biphenyl]-4-yl group.
[0117] Specific examples of the compound of Formula [1] above
include, but not limited to, diphenylsilanediol,
di-p-tolylsilanediol, bis(4-ethylphenyl)silanediol,
bis(4-isopropylphenyl)silanediol, dinaphthylsilanediol, and
bis([1,1'-biphenyl]-4-yl)silanediol.
[0118] [Alkoxy Silicon Compound B]
[0119] The alkoxy silicon compound B is a compound of Formula [2]
below.
Ar.sup.3--Si(OR.sup.1).sub.aR.sup.2.sub.3-a [2]
[0120] In Formula [2] above, Ar.sup.3 is a phenyl group having at
least one group having a polymerizable double bond, a naphthyl
group having at least one group having a polymerizable double bond,
or a biphenyl group having at least one group having a
polymerizable double bond, R.sup.1 is independently methyl group or
ethyl group, R.sup.2 is methyl group, ethyl group, or vinylphenyl
group, and a is 2 or 3.
[0121] Examples of the phenyl group having at least one group
having a polymerizable double bond, represented by Ar.sup.3,
include 2-vinylphenyl group, 3-vinylphenyl group, 4-vinylphenyl
group, 4-vinyloxyphenyl group, 4-allylphenyl group,
4-allyloxyphenyl group, and 4-isopropenylphenyl group.
[0122] Examples of the naphthyl group having at least one group
having a polymerizable double bond, represented by Ar.sup.3,
include 4-vinylnaphthalen-1-yl group, 5-vinylnaphthalen-1-yl group,
6-vinylnaphthalen-2-yl group, 4-allylnaphthalen-1-yl group,
5-allylnaphthalen-1-yl group, 6-allylnaphthalen-2-yl group,
4-allyloxynaphthalen-1-yl group, 5-allyloxynaphthalen-1-yl group,
8-allyloxynaphthalen-1-yl group, 5-vinyloxynaphthalen-1-yl group,
and 5-isopropenylnaphthalen-1-yl group.
[0123] Examples of the biphenyl group having at least one group
having a polymerizable double bond, represented by Ar.sup.3,
include 4'-vinyl-[1,1'-biphenyl]-2-yl group,
4'-vinyl-[1,1'-biphenyl]-3-yl group, 4'-vinyl-[1,1'-biphenyl]-4-yl
group, 4'-vinyloxy-[1,1'-biphenyl]-4-yl group,
4'-allyl-[1,1'-biphenyl]-4-yl group,
4'-allyloxy-[1,1'-biphenyl]-4-yl group, and
4'-isopropenyl-[1,1'-biphenyl]-4-yl group.
[0124] Specific examples of the compound of Formula [2] include,
but not limited to, trimethoxy(4-vinylphenyl)silane,
triethoxy(4-vinylphenyl)silane,
(4-isopropenylphenyl)trimethoxysilane,
dimethoxy(methyl)(4-vinylphenyl)silane,
dimethoxybis(4-vinylphenyl)silane,
trimethoxy(4-vinyl-1-naphthyl)silane,
trimethoxy(5-vinyl-1-naphthyl)silane,
trimethoxy(6-vinyl-2-naphthyl)silane, and
trimethoxy(4'-vinyl-[1,1'-biphenyl]-4-yl)silane.
[0125] [Another Polycondensable Compound]
[0126] The reactive silicone compound (a) included in the
cladding-forming composition may include another polycondensable
compound, in addition to the diarylsilicic acid compound A and the
alkoxy silicon compound B.
[0127] Another polycondensable compound may be any compound that is
polymerizable with the compound A and the compound B, such as
hydrolytic silane compounds, other than the compound A and the
compound B.
[0128] Examples of another polycondensable compound include
tetramethoxysilane, tetraethoxysilane, trimethoxy(methyl)silane,
trimethoxy(vinyl)silane,
3-(meth)acryloyloxypropyl(trimethoxy)silane,
trimethoxy(phenyl)silane, trimethoxy(l-naphthyl)silane,
dimethoxy(dimethyl)silane, dimethoxy(diphenyl)silane,
dimethoxy(methyl)(vinyl)silane,
3-(meth)acryloyloxypropyl(dimethoxy)(methyl)silane, and
dimethoxy(methyl)(phenyl)silane.
[0129] [Preferable Examples of Reactive Silicone Compound]
[0130] It is preferable that the reactive silicone compound (a) is
composed of a polycondensate of the diarylsilicic acid compound A
with the alkoxy silicon compound B (a polycondensate not including
another polymerizable compound). In particular, a polycondensate of
diphenylsilanediol as the diarylsilicic acid compound A with a
compound of Formula [2a] below as the alkoxy silicon compound B is
preferred.
##STR00008##
[0131] In Formula [2a] above, R.sup.1 is the same as defined
above.
[0132] [Blending Ratio of Diarylsilicic Acid Compound A and Alkoxy
Silicon Compound B]
[0133] The blending molar ratio in a polycondensation reaction of
the diarylsilicic acid compound A of Formula [1] and the alkoxy
silicon compound B of Formula [2] for use in the reactive silicone
compound is not limited to a particular value, but preferably, for
the purpose of preventing block-copolymerization, the diarylsilicic
acid compound A:alkoxy silicon compound B is in a range of 2:1 to
1:2. More preferably, the blending ratio is in a range of 1.1:0.9
to 0.9:1.1.
[0134] When another polycondensable compound is contained as a
polycondensable compound, in addition to the compound A and the
compound B, the blending ratio is not limited to a particular
value, but, in general, another polycondensable compound is blended
preferably in 50 mol % or less with respect to the alkoxy silicon
compound B.
[0135] Compounds can be appropriately selected as necessary and
used as the diarylsilicic acid compound A and the alkoxy silicon
compound B, and different kinds of compounds may be used in
combination. Also in this case, the molar ratio of the total amount
of the diarylsilicic acid compound A and the total amount of the
alkoxy silicon compound B falls within the range above.
[0136] [Acid or Basic Catalyst]
[0137] A polycondensation reaction of the diarylsilicic acid
compound A of Formula [1] with the alkoxy silicon compound B of
Formula [2] (and, if desired, another polycondensable compound) is
preferably performed in the presence of an acid or basic
catalyst.
[0138] The catalyst for use in the polycondensation reaction may be
appropriately selected as necessary and used out of any kind as
long as it is dissolved or uniformly dispersed in a solvent
described later.
[0139] Examples of the catalyst that can be used include acid
compounds, such as B(OR).sub.3, Al(OR).sub.3, Ti(OR).sub.4, and
Zr(OR).sub.4; and basic compounds, such as alkali metal hydroxides,
alkaline-earth metal hydroxides, ammonium salts, and amines; and
fluoride salts, such as NH.sub.4F and NR.sub.4F. Here, R is at
least one group selected from the group consisting of a hydrogen
atom, a linear alkyl group having a carbon atom number of 1 to 12,
a branched alkyl group having a carbon atom number of 3 to 12, and
a cyclic alkyl group having a carbon atom number of 3 to 12.
[0140] Examples of the acid compounds include boric acid,
trimethoxyboron, triethoxyboron, tri-n-propoxyboron,
triisopropoxyboron, tri-n-butoxyboron, triisobutoxyboron,
tri-sec-butoxyboron, tri-tert-butoxyboron, trimethoxyaluminum,
triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum,
tri-n-butoxyaluminum, triisobutoxyaluminum, tri-sec-butoxyaluminum,
tri-tert-butoxyaluminum, tetramethoxytitanium, tetraethoxytitanium,
tetra-n-propoxytitanium, tetraisopropoxytitanium (titanium
tetraisopropoxide), tetra-n-butoxytitanium, tetraisobutoxytitanium,
tetra-sec-butoxytitanium, tetra-tert-butoxytitanium,
tetramethoxyzirconium, tetraethoxyzirconium,
tetra-n-propoxyzirconium, tetraisopropoxyzirconium,
tetra-n-butoxyzirconium, tetraisobutoxyzirconium,
tetra-sec-butoxyzirconium, and tetra-tert-butoxyzirconium.
[0141] Examples of the basic compounds include sodium hydroxide,
potassium hydroxide, magnesium hydroxide, calcium hydroxide,
strontium hydroxide, barium hydroxide, ammonium hydroxide,
tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and
triethylamine.
[0142] Examples of the fluoride salts include ammonium fluoride,
tetramethylammonium fluoride, and tetrabutylammonium fluoride.
[0143] Among these catalysts, preferably used are one or more
selected from the group consisting of tetraisopropoxytitanium
(titanium tetraisopropoxide), magnesium hydroxide, calcium
hydroxide, strontium hydroxide, and barium hydroxide.
[0144] The amount of the catalyst used is 0.01% by mass to 10% by
mass, and preferably 0.1% by mass to 5% by mass with respect to the
total mass of the diarylsilicic acid compound and the alkoxy
silicon compound. When the amount of the catalyst used is 0.01% by
mass or more, the reaction proceeds better. Considering cost
efficiency, the use in the amount of 10% by mass or less is
sufficient.
[0145] [Polycondensation Reaction]
[0146] One feature of the reactive silicone compound is the
structure of the alkoxy silicon compound. The reactive group
(polymerizable double bond) included in the alkoxy silicon compound
used in the present invention is easily polymerized radically and
ionically (anionically, cationically) and exhibits high heat
resistance after polymerization (after curing).
[0147] When such an alkoxy silicon compound and the diarylsilicic
acid compound are polycondensed into a silicone compound with high
heat resistance, it is necessary to terminate the reaction at an
adequate degree of polymerization in order to keep the product in a
liquid state. The alkoxy silicon compound used in the present
invention does not actively hydrolyze and therefore is
characterized in that a polycondensation reaction with the
diarylsilicic acid compound is moderate and that the degree of
polymerization is easily controlled.
[0148] A polycondensation reaction of the alkoxy silicon compound
and the diarylsilicic acid compound by dealcoholation can be
performed in the absence of a solvent but can be performed using a
solvent that is inert against the alkoxy silicon compound, such as
toluene, as described later, as a reaction solvent. The absence of
a solvent is advantageous in that alcohol that is a reaction
by-product is easily distilled off. On the other hand, the use of a
reaction solvent is advantageous in that the reaction system is
easily homogenized, and that a polycondensation reaction proceeds
more stably.
[0149] The synthesis reaction of the reactive silicone compound may
be performed in the absence of a solvent as previously mentioned,
or a solvent may be used in order to homogenize the reaction system
more. Any solvent may be used as long as it does not react with the
diarylsilicic acid compound or the alkoxy silicon compound and
dissolves the condensate thereof.
[0150] Examples of such a reaction solvent include ketones, such as
acetone and methyl ethyl ketone (MEK); ethers, such as
tetrahydrofuran (THF) and 1,4-dioxane; aromatic hydrocarbons, such
as benzene, toluene, and xylene; glycols, such as ethylene glycol,
propylene glycol, and hexylene glycol; glycol ethers, such as ethyl
cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol,
diethyl cellosolve, and diethyl carbitol; and amides, such as
N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF). These
solvents may be used singly or in combination of two or more. Among
them, toluene is preferred.
[0151] The reactive silicone compound (a) contained in the
cladding-forming composition is obtained by performing
dealcoholation condensation of the diarylsilicic acid compound A of
Formula [1] and the alkoxy silicon compound B of Formula [2] (and,
if desired, another polycondensable compound) in the presence of an
acid or basic catalyst. It is desirable that the reaction is
performed in an inert gas atmosphere, such as nitrogen gas, in
order to prevent mixing of moisture. The reaction temperature is
20.degree. C. to 150.degree. C., and more preferably 30.degree. C.
to 120.degree. C.
[0152] The reaction time is not limited as long as it is equal to
or longer than the time required for termination of molecular
weight increase of the polycondensate and for stabilization of the
molecular weight distribution. More specifically, the reaction time
is a few hours to a few days.
[0153] After the polycondensation reaction is finished, the
resulting reactive silicone compound is collected by any methods,
such as filtration and solvent distillation, and, if necessary, a
purification process is performed as appropriate.
[0154] In the reactive silicone compound composed of the
polycondensate obtained through such a reaction, the weight average
molecular weight Mw measured by gel permeation chromatography (GPC)
in terms of polystyrene is 500 to 10,000, and the degree of
distribution Mw (weight average molecular weight)/Mn (number
average molecular weight) is 1.0 to 10.
[0155] <Di(meth)acrylate Compound (b)>
[0156] The di(meth)acrylate compound (b) included in the
cladding-forming composition is a dioxane compound of Formula [3]
below. In this description, (meth)acrylate refers to both acrylate
and methacrylate.
##STR00009##
[0157] In Formula [3] above, R.sup.3 and R.sup.4 are independently
a hydrogen atom or methyl group, R.sup.5 is a hydrogen atom, methyl
group, or ethyl group, L.sup.1 and L.sup.2 are independently a
C.sub.2-6 alkylene group, and m and n are 0 or a positive integer,
wherein m+n is 0 to 20.
[0158] Examples of the C.sub.2-6 alkylene group represented by
L.sup.1 and L.sup.2 include ethylene group, trimethylene group,
methylethylene group, tetramethylene group, 1-methyltrimethylene
group, 2-methyltrimethylene group, 1,1-dimethylethylene group,
pentamethylene group, 1-methyltetramethylene group,
2-methyltetramethylene group, 1,1-dimethyltrimethylene group,
1,2-dimethyltrimethylene group, 2,2-dimethyltrimethylene group,
1-ethyltrimethylene group, hexamethylene group,
1-methylpentamethylene group, 2-methylpentamethylene group,
3-methylpentamethylene group, 1,1-dimethyltetramethylene group,
1,2-dimethyltetramethylene group, 2,2-dimethyltetramethylene group,
1-ethyltetramethylene group, 1,1,2-trimethyltrimethylene group,
1,2,2-trimethyltrimethylene group, 1-ethyl-1-methyltrimethylene
group, and 1-ethyl-2-methyltrimethylene group.
[0159] In the compound of Formula [3], m and n are such that
preferably m+n is 0 to 10, and that more preferably m+n is 0 to
5.
[0160] Specific examples of the compound of Formula [3] include,
but not limited to,
2-(5-hydroxymethyl-1,3-dioxan-2-yl)-2-methylpropan-1-ol
di(meth)acrylate,
2-(5-methyl-5-hydroxymethyl-1,3-dioxan-2-yl)-2-methylpropan-1-ol
di(meth)acrylate,
2-(5-ethyl-5-hydroxymethyl-1,3-dioxan-2-yl)-2-methylpropan-1-ol
di(meth)acrylate, ethylene oxide-modified
2-(5-ethyl-5-hydroxymethyl-1,3-dioxan-2-yl)-2-methylpropan-1-ol
di(meth)acrylate, and propylene oxide-modified
2-(5-ethyl-5-hydroxymethyl-1,3-dioxan-2-yl)-2-methylpropan-1-ol
di(meth)acrylate.
[0161] Among commercially available products, for example, NK Ester
A-DOG [manufactured by Shin-Nakamura Chemical CO., Ltd] can be
suitably used.
[0162] The di(meth)acrylate compound (b) included in the
cladding-forming composition may contain at least one selected from
the group consisting of the dioxane compounds above singly, or in
combination of two or more.
[0163] The optical waveguide-forming composition in the present
invention may include an aromatic vinyl compound (y) described
later.
[0164] <Core-Forming Composition>
[0165] The core-forming composition is a composition including 100
parts by mass of a reactive silicone compound (x) composed of a
polycondensate of a diarylsilicic acid compound A of Formula [1]
and an alkoxy silicon compound B of Formula [2], or a
polycondensate of the diarylsilicic acid compound A, the alkoxy
silicon compound B, and another polycondensable compound, and 0.1
part by mass to 100 parts by mass of an aromatic vinyl compound (y)
of Formula [4].
[0166] More preferably, 0.1 part by mass to 25 parts by mass of the
component (y) is blended with respect to 100 parts of the component
(x).
[0167] <Reactive Silicone Compound (x)>
[0168] The <reactive silicone compound (a)> in the
cladding-forming composition described above can be used as the
component (x) included in the core-forming composition. In the
component (a) and the component (x), the same compound or different
compounds may be used.
[0169] <Aromatic Vinyl Compound (y)>
[0170] The aromatic vinyl compound (y) is a compound of Formula
[4].
##STR00010##
[0171] In Formula [4], R.sup.6 is a hydrogen atom or methyl group,
L.sup.3 is a single bond, a hydrogen atom, an oxygen atom, a
C.sub.1-20 q-valent aliphatic hydrocarbon residue optionally
substituted with a phenyl group, or a C.sub.1-20 q-valent aliphatic
hydrocarbon residue optionally including an ether bond, Ar.sup.4 is
a p+1-valent aromatic hydrocarbon residue, p is independently 1 or
2, and q is an integer of 1 to 3 (wherein q is 1 when L.sup.3 is a
hydrogen atom, and q is 2 when L.sup.3 is a single bond or an
oxygen atom).
[0172] Examples of a C.sub.1-20 q-valent aliphatic hydrocarbon in
the C.sub.1-20 q-valent aliphatic hydrocarbon residue optionally
substituted with a phenyl group or the C.sub.1-20 q-valent
aliphatic hydrocarbon residue optionally including an ether bond,
represented by L.sup.3, include linear alkanes, such as methane,
ethane, propane, n-butane, n-pentane, n-hexane, n-heptane,
n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane,
n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane,
n-octadecane, n-nonadecane, and n-eicosane; branched alkanes, such
as 2-methylpropane and 2,2-dimethylpropane; and cyclic alkanes,
such as cyclopentane and cyclohexane. Examples of the C.sub.1-20
q-valent aliphatic hydrocarbon residue include an alkyl group, an
alkanediyl group, and an alkanetriyl group obtained by removing 1
to 3 hydrogen atoms from the alkanes above.
[0173] Examples of such L.sup.3 include methyl group, ethyl group,
n-propyl group, isopropyl group, n-butyl group, n-hexyl group,
cyclohexyl group, benzyl group, phenethyl group, methoxymethyl
group, ethoxymethyl group, 2-methoxyethyl group, methylene group,
ethylene group, trimethylene group, 1-methylethylene group,
propane-2,2-diyl group, tetramethylene group, pentamethylene group,
2,2-dimethyltrimethylene group, hexamethylene group,
3-methylpentamethylene group, cyclohexane-1,4-diyl group,
diethylene glycol residue (--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2--),
triethylene glycol residue
(--(CH.sub.2CH.sub.2O).sub.2CH.sub.2CH.sub.2--), dipropylene glycol
residue (--CH(CH.sub.3)CH.sub.2OCH(CH.sub.3)CH.sub.2--),
oxytetramethyleneoxy group, propane-1,1,1-triyl group,
propane-1,1,3-triyl group, butane-1,2,4-triyl group, and
cyclohexane-1,3,5-triyl group.
[0174] Examples of the p+1-valent aromatic hydrocarbon residue,
represented by Ar.sup.4, include groups obtained by removing p+1
hydrogen atoms from an aromatic hydrocarbon ring, such as benzene
and naphthalene.
[0175] Among the compounds of Formula [4], a compound in which
L.sup.3 is a hydrogen atom, q is 1, and p is 2 is preferred.
[0176] Specific examples of the compound of Formula [4] include
styrene, 1-phenethyl-4-vinylbenzene, 1-vinylnaphthalene,
2-vinylnaphthalene, divinylbenzene, diisopropenylbenzene,
divinylnaphthalene, 4,4'-divinylbiphenyl, bis(4-vinylphenyl) ether,
1-vinyl-2-(4-vinylphenoxy)benzene, 2,2-bis(4-vinylphenyl)propane,
and 1,1,1-tris(4-vinylphenoxy)propane.
[0177] Among them, styrene, 1-vinylnaphthalene, divinylbenzene, and
2,2-bis(4-vinylphenyl)propane are preferred, and divinylbenzene is
more preferred.
[0178] In the core-forming composition used in the present
invention, the aromatic vinyl compound (y) may be used singly, or
two or more may be used in combination.
[0179] <Polymerization Initiator>
[0180] The cladding-forming composition can yield a cured product
by allowing the polymerizable double bonds included in the reactive
silicone compound (a) and the di(meth)acrylate compound (b) to
react in the presence of a polymerization initiator by light
radiation or heating.
[0181] Similarly, the core-forming composition can yield a cured
product by allowing the polymerizable double bonds included in the
reactive silicone compound (x) and the polymerizable double bonds
included in the aromatic vinyl compound (y) to react in the
presence of a polymerization initiator by light radiation or
heating.
[0182] Either of a thermal polymerization initiator or a
photopolymerization initiator can be used as the polymerization
initiator.
[0183] Examples of the thermal polymerization initiator include
azos and organic peroxides.
[0184] Examples of commercially available azo thermal
polymerization initiators include V-30, V-40, V-59, V-60, V-65, and
V-70 [all of which are manufactured by Wako Pure Chemical
Industries, Ltd.].
[0185] Examples of commercially available organic peroxide thermal
polymerization initiators include, but not limited to, Perkadox
(registered trademark) CH, Perkadox BC-FF, Perkadox 14, Perkadox
16, Trigonox (registered trademark) 22, Trigonox 23, Trigonox 121,
Kayaester (registered trademark) P, Kayaester O, and Kayabutyl
(registered trademark) B [all of which are manufactured by Kayaku
Akzo Corporation], and PERHEXA (registered trademark) HC, PERCUMYL
(registered trademark) H, PEROCTA (registered trademark) O,
PERHEXYL (registered trademark) O, PERHEXYL Z, PERBUTYL (registered
trademark) O, and PERBUTYL Z [all of which are manufactured by NOF
CORPORATION].
[0186] Examples of the photopolymerization initiator include
alkylphenones, benzophenones, acylphosphine oxides, Michler's
benzoylbenzoates, oxime esters, tetramethylthiuram monosulfides,
and thioxanthones.
[0187] In particular, a photocleavage-type photo-radical
polymerization initiator is preferred. Examples of the
photocleavage-type photo-radical polymerization initiator include
those described in "SAISHIN UV KOUKA GIJUTSU (Latest UV Curing
Technology)" (p. 159, issuer: Kazuhiro Takausu, published by
TECHNICAL INFORMATION INSTITUTE CO., LTD, 1991).
[0188] Examples of commercially available photo-radical
polymerization initiators include IRGACURE (registered trademark)
127, IRGACURE 184, IRGACURE 369, IRGACURE 651, IRGACURE 500,
IRGACURE 819, IRGACURE 907, IRGACURE 784, IRGACURE 2959, IRGACURE
CGI1700, IRGACURE CGI1750, IRGACURE CGI1850, IRGACURE CG24-61,
IRGACURE TPO, Darocur (registered trademark) 1116, and Darocur 1173
[all of which are manufactured by BASF Japan Ltd.], and ESACURE
KIP150, ESACURE KIP65LT, ESACURE KIP100F, ESACURE KT37, ESACURE
KT55, ESACURE KT046, and ESACURE KIP75 [all of which are
manufactured by Lamberti].
[0189] When a polymerization initiator is added, the polymerization
initiator may be used singly, or two or more may be used in
combination. The amount added is 0.1 part by mass to 20 parts by
mass, and further preferably 0.3 part by mass to 10 parts by mass
with respect to 100 parts by mass of the reactive silicone compound
(a) or 100 parts by mass of the reactive silicone compound (x).
[0190] <(c) Sulfur Compound>
[0191] The cladding-forming composition as well as the core-forming
composition may include, as a component (c), at least one sulfur
compound selected from the group consisting of thiol compounds and
disulfide compounds, in addition to the component (a) and the
component (b) [or the component (x) and the component (y)].
[0192] [Thiol Compound]
[0193] In the component (c) used in the present invention, examples
of the thiol compounds include mercaptocarboxylic acid esters, such
as methyl mercaptoacetate, methyl 3-mercaptopropionate,
4-methoxybutyl 3-mercaptopropionate, 2-ethylhexyl
3-mercaptopropionate, n-octyl 3-mercaptopropionate, stearyl
3-mercaptopropionate, 1,4-bis(3-mercaptopropionyloxy)butane,
1,4-bis(3-mercaptobutyryloxy)butane, trimethylolethane
tris(3-mercaptopropionate), trimethylolethane
tris(3-mercaptobutyrate), trimethylolpropane
tris(3-mercaptopropionate), trimethylolpropane
tris(3-mercaptobutyrate), pentaerythritol
tetrakis(3-mercaptopropionate), pentaerythritol
tetrakis(3-mercaptobutyrate), dipentaerythritol
hexakis(3-mercaptopropionate), dipentaerythritol
hexakis(3-mercaptobutyrate), tris(2-(3-mercaptopropionyloxy)ethyl)
isocyanurate, and tris(2-(3-mercaptobutyryloxy)ethyl) isocyanurate;
mercaptoalkanes, such as ethyl mercaptan, 1,2-dimercaptoethane,
1,3-dimercaptopropane, tert-butyl mercaptan, n-dodecanethiol, and
tert-dodecanethiol; mercapto alcohols, such as 2-mercaptoethanol
and 4-mercapto-1-butanol; aromatic ring-containing mercaptans, such
as thiophenol, benzylthiol, m-toluenethiol, p-toluenethiol,
2-naphthalenethiol, 2-pyridylthiol, 2-mercaptobenzimidazole, and
2-mercaptobenzothiazole; and silane-containing thiols, such as
(.gamma.-mercaptopropyl)trimethoxysilane and
triethoxy(.gamma.-mercaptopropyl)silane. Among them,
mercaptoalkanes are preferred, and n-dodecanethiol is more
preferred.
[0194] [Disulfide Compound]
[0195] In the component (c) used in the present invention, examples
of the disulfide compounds include alkyl disulfides, such as
diethyl disulfide, dipropyl disulfide, diisopropyl disulfide,
dibutyl disulfide, di-tert-butyl disulfide, dipentyl disulfide,
diisopentyl disulfide, dihexyl disulfide, dicyclohexyl disulfide,
didecyl disulfide, di-tert-dodecyl disulfide, bis(2-hydroxyethyl)
disulfide, and bis(2,2-diethoxyethyl) disulfide; aromatic
ring-containing disulfides, such as diphenyl disulfide, ditolyl
disulfide, dibenzyl disulfide, 2,2'-dipyridyl disulfide,
2,2'-dibenzimidazolyl disulfide, and 2,2'-dibenzothiazolyl
disulfide; and thiuram disulfides, such as tetramethylthiuram
disulfide, tetraethylthiuram disulfide, tetrabutylthiuram
disulfide, and dipentamethylenethiuram disulfide. Among them, alkyl
disulfides are preferred, and didecyl disulfide is more
preferred.
[0196] When the component (c) is blended, the component (c) is
included preferably in the amount of 0.01 part by mass to 5 parts
by mass, and more preferably 0.1 part by mass to 1 part by mass,
with respect to 100 parts by mass of the component (a) or 100 parts
by mass of the component (x).
[0197] In the present invention, as the component (c), a thiol
compound may be used singly or two or more thereof may be used in
combination, a disulfide compound may be used singly or two or more
thereof may be used in combination, or one or more thiol compounds
and one or more disulfide compounds may be used in combination.
When different kinds of compounds are used as the component (c),
the total amount of the different kinds of compounds blended is
within the range of the amount described above.
[0198] <Silane Coupling Agent (d)>
[0199] The cladding-forming composition as well as the core-forming
composition may include a silane coupling agent as a component (d),
in addition to the component (a) and the component (b) [or the
component (x) and the component (y)].
[0200] Examples of the silane coupling agent include vinyl silane
coupling agents, such as trimethoxy(vinyl)silane,
triethoxy(vinyl)silane, trimethoxy(4-vinylphenyl)silane, and
triethoxy(4-vinylphenyl)silane; (meth)acrylic silane coupling
agents, such as 3-(meth)acryloyloxypropyltrimethoxysilane,
triethoxy(3-(meth)acryloyloxypropyl)silane,
3-(meth)acryloyloxypropyl(dimethoxy)(methyl)silane, and
diethoxy(3-(meth)acryloyloxypropyl)(methyl)silane; epoxy silane
coupling agents, such as 3-glycidyloxypropyltrimethoxysilane,
triethoxy(3-glycidyloxypropyl)silane,
3-glycidyloxypropyl(dimethoxy)(methyl)silane,
diethoxy(3-glycidyloxypropyl)(methyl)silane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; amine silane coupling
agents, such as 3-aminopropyltrimethoxysilane,
3-aminopropyltriethoxysilane,
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-aminopropyltriethoxysilane,
N-(2-aminoethyl)-3-aminopropyl(dimethoxy)(methyl)silane,
N-(2-aminoethyl)-3-aminopropyl(diethoxy)(methyl)silane,
N-(1-methylpentylidene)-3-trimethoxysilylpropylamine,
3-triethoxysilyl-N-(1-methylpentylidene)propylamine,
N-(1,3-dimethylbutylidene)-3-trimethoxysilylpropylamine,
N-(1,3-dimethylbutylidene)-3-triethoxysilylpropylamine,
N-phenyl-3-aminopropyltrimethoxysilane, and
N-phenyl-3-aminopropyltriethoxysilane; ureido silane coupling
agents, such as 3-ureidopropyltrimethoxysilane and
triethoxy(3-ureidopropyl)silane; mercapto silane coupling agents,
such as 3-mercaptopropyltrimethoxysilane,
triethoxy(3-mercaptopropyl)silane,
(3-mercaptopropyl)(dimethoxy)(methyl)silane, and
diethoxy(3-mercaptopropyl)(methyl)silane; sulfide silane coupling
agents, such as bis(3-trimethoxysilylpropyl) tetrasulfide and
bis(3-triethoxysilylpropyl) tetrasulfide; and isocyanate silane
coupling agents, such as 3-isocyanatopropyltrimethoxysilane and
triethoxy(3-isocyanatopropyl)silane.
[0201] Among them, 3-(meth)acryloyloxypropyltrimethoxysilane,
triethoxy(3-(meth)acryloyloxypropyl)silane,
3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,
N-phenyl-3-aminopropyltrimethoxysilane,
N-phenyl-3-aminopropyltriethoxysilane,
3-mercaptopropyltrimethoxysilane, and
triethoxy(3-mercaptopropyl)silane are preferred.
[0202] When the silane coupling agent (d) is blended, the silane
coupling agent may be used singly, or two or more kinds may be used
in combination. The amount blended is 0.1 part by mass to 20 parts
by mass, and further preferably 0.1 part by mass to 5 parts by mass
with respect to 100 parts by mass of the component (a) or 100 parts
by mass of the component (x).
[0203] <Other Components Optionally Blended>
[0204] The cladding-forming composition as well as the core-forming
composition may additionally include a cross-linking agent, a
surfactant, a leveling agent, an antioxidant, an photostabilizer,
and the like, as appropriate without affecting the performance of
the cladding material or the core material of the optical
waveguide.
[0205] <Preparation Process of Cladding-Forming Composition and
Core-Forming Composition>
[0206] The process for the cladding-forming composition as well as
the core-forming composition is not limited to a particular
process. For example, the component (a) and the component (b) [or
the component (x) and the component (y)], and, if necessary, the
component (c), the component (d), and other additives, such as a
polymerization initiator are mixed to prepare a homogeneous
solution, or a commonly used solvent may be used in addition to
those components.
[0207] When a solvent is used, the proportion of a solid content in
the cladding-forming composition or the core-forming composition is
not limited as long as the components are uniformly dissolved in
the solvent. For example, the solid content is 1% by mass to 50% by
mass, or 1% by mass to 30% by mass, or 1% by mass to 25% by mass.
Here, the solid content is the content obtained by removing the
solvent component from all the components of the cladding-forming
composition or the core-forming composition.
[0208] The solution of the cladding-forming composition or the
core-forming composition is preferably used after being filtered
using a filter having a pore size of 0.05 .mu.m to 5 .mu.m.
[0209] It is preferable that the cladding-forming composition as
well as the core-forming composition in the present invention has a
viscosity with excellent processability in formation of an optical
waveguide by the production method in the present invention.
[0210] For example, it is preferable that the viscosity of the
cladding-forming composition is 500 to 20,000 mPas at 25.degree.
C., and the viscosity of the core-forming composition is 1,000 to
100,000 mPas at 25.degree. C.
EXAMPLES
[0211] Although the present invention will be described more
specifically below with examples, the present invention is not
limited to the following examples.
[0212] In the examples, the apparatuses and the conditions for
preparation of samples and analysis of physical properties are as
follows.
[0213] (1) Stirring and Defoaming Machine
[0214] Apparatus: planetary centrifugal mixer Awatori Rentaro
(registered trademark) ARE-310 manufactured by THINKY
CORPORATION
[0215] (2) UV Exposure
[0216] Apparatus: batch process UV radiation apparatus
(high-pressure mercury lamp 2 kW.times.1 lamp) manufactured by EYE
GRAPHICS CO., LTD.
[0217] (3) .sup.1H NMR
[0218] Apparatus: AVANCE III HD manufactured by Burker
[0219] Measurement frequency: 500 MHz
[0220] Measurement solvent: CDCl.sub.3
[0221] Reference substance: tetramethylsilane (0.00 ppm)
[0222] (4) Gel Permeation Chromatography (GPC)
[0223] Apparatus: Prominence (registered trademark) GPC system
manufactured by
[0224] Shimadzu Corporation
[0225] Column: Shodex (registered trademark) GPC KF-804L and GPC
KF-803L manufactured by SHOWA DENKO K.K.
[0226] Column temperature: 40.degree. C.
[0227] Solvent: tetrahydrofuran
[0228] Detector: RI
[0229] Calibration curve: standard polystyrene
[0230] (5) Viscosity
[0231] Apparatus: MCR rheometer MCR302 manufactured by Anton Paar
Measuring system: cone plate (diameter 25 mm, angle 2 degrees)
[0232] Temperature: 25.degree. C.
[0233] Number of revolutions: 1 rpm
[0234] Wait time: 5 minutes
[0235] (6) Refractive Index
[0236] Apparatus: Model 2010/M prism coupler manufactured by
Metricon Corporation
[0237] (7) 5% Weight Loss Temperature (Td.sub.5%)
[0238] Apparatus: TG/DTA 2000SA manufactured by Bruker AXS K.K.
[0239] Measuring condition: under nitrogen atmosphere
[0240] Temperature increase rate: 10.degree. C./min (25.degree. C.
to 450.degree. C.)
[0241] (8) Digital Microscope
[0242] Apparatus: VHX-500F manufactured by KEYENCE CORPORATION
[0243] (9) Near Field Pattern
[0244] Light source: LED light source LDS1007 manufactured by
Precise Gauges Co., Ltd.
[0245] Incident probe: SI-type quartz multimode fiber AFS50/125Y
manufactured by Fiberguide Industries Limited (core diameter 50
.mu.m, length 1 m, FC connectors on both ends (flat polish))
[0246] Beam profiler: BeamStar FX50 manufactured by Ophir Optronics
Solutions Ltd.
[0247] (10) Propagation Loss
[0248] Light source: white light source AQ-4303B manufactured by
Ando Electric Co., Ltd.
[0249] Incident probe: GI-type multimode fiber manufactured by
Furukawa Electric Co., Ltd. (core diameter 25 .mu.m, length 1 m, FC
connectors on both ends (flat polish))
[0250] Emission probe: SI-type quartz multimode fiber AFS105/125Y
manufactured by Fiberguide Industries Limited (core diameter 105
.mu.m, length 2 m, FC connectors on both ends (flat polish))
[0251] Detector: Optical spectrum analyzer AQ-6315B manufactured by
Ando Electric Co., Ltd.
[0252] Abbreviations represent the following meaning.
[0253] DPSD: diphenylsilanediol [manufactured by Tokyo Chemical
Industry Co., Ltd.]
[0254] STMS: trimethoxy(4-vinylphenyl)silane [manufactured by
Shin-Etsu Chemical Co., Ltd.]
[0255] BPE: ethoxylated bisphenol A diacrylate (10 mol of ethoxy
group added) [NK Ester A-BPE-10 manufactured by Shin-Nakamura
Chemical CO., Ltd]
[0256] DOG: dioxane glycol diacrylate [NK Ester A-DOG manufactured
by Shin-Nakamura Chemical CO., Ltd]
[0257] TEG: tetraethylene glycol diacrylate [NK Ester A-200
manufactured by Shin-Nakamura Chemical Co., Ltd.]
[0258] DVB: divinylbenzene [DVB-810 manufactured by NIPPON STEEL
& SUMIKIN CHEMICAL CO., LTD., purity 81%]
[0259] I127:
2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpro-
pan-1-one [IRGACURE (registered trademark) 127 manufactured by BASF
Japan Ltd.]
[0260] TPO: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide
[IRGACURE (registered trademark) TPO manufactured by BASF Japan
Ltd.]
[0261] W712: epoxy siloxane resin [FX-W712 manufactured by ADEKA
CORPORATION]
[0262] W713: epoxy siloxane resin [FX-W713 manufactured by ADEKA
CORPORATION]
Production Example 1
[0263] Production of Reactive Silicone Compound (SC1)
[0264] In a 200-mL eggplant flask with a condenser and a Dean-Stark
apparatus, 43.3 g (0.20 mol) of DPSD, 44.9 g (0.20 mol) of STMS,
and 35 g of toluene were charged, and the air in the flask was
purged with nitrogen using a nitrogen balloon. After this reaction
mixture was heated to 50.degree. C., 38 mg (0.2 mmol) of barium
hydroxide monohydrate [manufactured by Aldrich] was added and
stirred at 50.degree. C. for one hour. After heating to 85.degree.
C., dealcoholation condensation was performed by stirring the
mixture for five hours while removing byproduct methanol out of the
system. The reaction mixture was cooled to room temperature (about
23.degree. C.), and an insoluble matter was removed using a
membrane filter having a pore size of 0.2 .mu.m. Toluene was
distilled off under a reduced pressure at 50.degree. C. from this
reaction mixture using a rotary evaporator to yield 74.9 g of a
colorless transparent oily product that is a reactive silicone
compound (SC1).
[0265] The .sup.1H NMR spectrum of the resultant reactive silicone
compound is illustrated in FIG. 15. The weight average molecular
weight Mw measured by GPC in terms of polystyrene is 1,570, and the
degree of distribution: Mw (weight average molecular weight)/Mn
(number average molecular weight) is 1.2.
Production Example 2
[0266] Production of Reactive Silicone Compound (SC2)
[0267] In a 1-L eggplant flask with a condenser, 177 g (0.80 mol)
of DPSD, 179 g (0.80 mol) of STMS, and 141 g of toluene were
charged, and the air in the flask was purged with nitrogen using a
nitrogen balloon. After this reaction mixture was heated to
50.degree. C., 0.303 g (1.6 mmol) of barium hydroxide monohydrate
[manufactured by Aldrich] was added and further stirred at
50.degree. C. for two days to perform dealcoholation condensation.
The reaction mixture was cooled to room temperature (about
23.degree. C.), and an insoluble matter was removed using a
membrane filter having a pore size of 0.2 Toluene and byproduct
methanol were distilled off under a reduced pressure at 50.degree.
C. from this reaction mixture using a rotary evaporator to yield
305 g of a colorless transparent oily product that is a reactive
silicone compound.
[0268] The .sup.1H NMR spectrum of the resultant reactive silicone
compound is illustrated in FIG. 16. The weight average molecular
weight Mw measured by GPC in terms of polystyrene is 1,270, and the
degree of distribution Mw/Mn is 1.2.
Production Example 3
[0269] Preparation of Polymerizable Composition 1
[0270] Seventy-five parts by mass of SC1 produced in Production
Example 1 as the reactive silicone compound (a), 25 parts by mass
of DOG as the di(meth)acrylate compound (b), and 1 part by mass of
1127 and 1 part by mass of TPO as polymerization initiators were
stirred and mixed at 50.degree. C. for three hours. The mixture was
further stirred and defoamed for two minutes to prepare a
polymerizable composition 1.
[0271] The viscosity of the resultant composition at 25.degree. C.
was 3,800 mPas.
Production Example 4
[0272] Preparation of Polymerizable Composition 2
[0273] A polymerizable composition 2 was prepared by performing the
same operation as in Production Example 3 except that the
composition was changed as described in Table 1. In Table 1, "part"
represents "part(s) by mass".
[0274] The viscosity of the resultant composition at 25.degree. C.
was 9,000 mPas.
[0275] [Comparative Production Examples 1 and 2]
[0276] Preparation of Polymerizable Compositions 3 and 4
[0277] Polymerizable compositions 3 and 4 were prepared by
performing the same operation as in Production Example 3 except
that the composition was changed as described in Table 1.
[0278] [Evaluation of Refractive Index of Cured Product]
[0279] Each polymerizable composition was put on a silicon wafer,
with 50 .mu.m-thick Kapton (registered trademark) tape affixed as a
spacer, and sandwiched with a glass substrate subjected to release
treatment in advance. The sandwiched polymerizable composition was
exposed to UV at 20 mW/cm.sup.2 for 60 seconds. After the glass
substrate holding the polymerizable composition was removed, the
composition was heated on a hot plate at 150.degree. C. for 20
minutes to fabricate a cured product.
[0280] The refractive index of the resultant cured product was
measured. The result is also listed in Table 1.
[0281] [Evaluation of Heat Resistance of Cured Product]
[0282] Each polymerizable composition was sandwiched together with
a 200 .mu.m-thick silicone rubber spacer between two glass
substrates subjected to release treatment in advance. The
sandwiched polymerizable composition was exposed to UV at 20
mW/cm.sup.2 for 60 seconds, and the cured product was removed from
the glass substrates to fabricate a cured product.
[0283] The 5% weight loss temperature (Td.sub.5%) of the resultant
cured product was measured to evaluate the heat resistance. The
result is also listed in Table 1.
TABLE-US-00001 TABLE 1 Production Polymerizable SC1
Di(metyh)acrylate I127 TPO Refractive index Td.sub.5% Example
composition [parts] [part] [part] [part] 833 nm 1,305 nm 1,551 nm
[.degree. C.] Production Polymerizable 75 DOG 25 1 1 1.558 1.550
1.549 351 Example 3 Composition 1 Production Polymerizable 87.5 DOG
12.5 1 1 1.567 1.559 1.558 -- Example 4 Composition 2 Comparative
Polymerizable 80 TEG 20 1 1 1.564 1.556 1.554 327 Production
Composition 3 Example 1 Comparative Polymerizable 67 BPE 33 1 1
1.565 1.557 1.556 315 Production Composition 4 Example 2
[0284] As listed in Table 1, it has been confirmed that when a
polymerizable composition is prepared such that the refractive
index of its cured product is substantially equal, blending the
di(meth)acrylate compound of Formula [3] yields a cured product
that has a high Td.sub.5%, that is, high heat resistance, compared
with other (meth)acrylate compounds.
[Production Example 5] Preparation of Polymerizable Composition
5
[0285] Ninety-nine point four (99.4) parts by mass of SC2 produced
in Production Example 2 as the reactive silicone compound (x), 0.6
part by mass of DVB as the aromatic vinyl compound (y), and 1 part
by mass of TPO as a polymerization initiator were stirred and mixed
at 50.degree. C. for three hours. The mixture was further stirred
and defoamed for two minutes to prepare a polymerizable composition
5.
[0286] The viscosity of the resultant composition at 25.degree. C.
was 80,800 mPas. The refractive index of the cured product prepared
in the same manner as in the foregoing [Evaluation of Refractive
Index of Cured Product] was 1.586 (833 nm), 1.577 (1,305 nm), and
1.575 (1,551 nm).
[Example 1] Fabrication of GI Optical Waveguide
[0287] An optical waveguide including cores of 12 channels formed
in cladding was fabricated under the conditions described in Table
2. The specifics are described below (see FIG. 1 to FIG. 5).
[0288] On a glass plate (FIG. 1: bottom plate 92) with a length of
3 cm, a width of 15 cm, and a thickness of 3 mm, a 500 .mu.m-thick
silicone rubber sheet (FIG. 1: outer frame 93) having an opening
(FIG. 1: opening 93a) with a length of 1 cm and a width of 10 cm at
the center was affixed, and the polymerizable composition 1 was
filled as a cladding material in the opening. In so doing, the
cladding material was filled at an angle of 45 degrees in the
horizontal direction and left for 30 minutes so that the cladding
material was uniformly filled in the opening. Uncured cladding
(FIG. 2: uncured cladding 19A) was thus obtained.
[0289] The glass plate filled with this cladding material was
attached to the work table of a tabletop application robot
[SHOTmini SL 200DS manufactured by Musashi Engineering, Inc.]. In a
5-mL UV block syringe [PSY-5E manufactured by Musashi Engineering,
Inc.] (FIG. 3: ejection unit 94), the polymerizable composition 5
was filled as a core material and defoamed. A metal needle
[SN-32G-LF manufactured by Musashi Engineering, Inc.] having an
inner diameter of 100 .mu.m (FIG. 3: needle-like portion 96) was
connected to the syringe ejection portion (FIG. 3: ejection body
95) and then attached to the tabletop application robot.
[0290] Subsequently, the position of the ejection portion was
adjusted such that the height from the upper surface of the glass
substrate to the tip end of the metal needle (FIG. 3: H.sub.1) was
300 Thereafter, the ejection pressure of a dispenser [ML-808FXcom
manufactured by Musashi Engineering, Inc.] was set to 600 kPa, and
the drawing operation speed of the tabletop application robot (the
moving speed of the ejection unit) was set to 4 mm/sec. The
ejection program of the tabletop application robot was operated,
and the polymerizable composition 5 serving as a core material was
ejected into the polymerizable composition 1 serving as a cladding
material such that the length of the optical waveguide was 8.5 cm
at a position where the height from the upper surface of the glass
substrate to the tip end of the metal needle was 300 .mu.m. An
uncured core (FIG. 4: uncured core 11A) was thus formed. This
operation was repeated with 300 .mu.m pitches of uncured cores to
form uncured cores of 12 channels (see FIG. 5. FIG. 5 illustrates
formation of up to 4 channels of uncured cores). Immediately after
the drawing of the uncured core of the twelfth channel was
finished, the UV-LED (wavelength at 365 nm) installed in the
tabletop application robot swept three times with an illumination
of 10 mW/cm.sup.2 (detected at 365 nm) and a rate of 1 mm/sec, to
cure the uncured cores and the uncured cladding, yielding cores and
cladding. Through this operation, the cores of 12 channels can be
varied in the wait time before exposure from drawing to curing. The
wait time for the core of the twelfth channel was 0 second, and the
wait time for the core of the first channel was 261 seconds. The
difference in wait time between adjacent cores was 23.7
seconds.
[0291] Subsequently, after the silicone rubber sheet was removed
from the glass substrate using a razor, heating was performed with
an oven at 150.degree. C. for 20 minutes. The section of the
optical waveguide was exposed using a razor, and the end surfaces
were polished with sandpaper for optical fibers to obtain a 5
cm-long GI optical waveguide.
[0292] The fabricated optical waveguide was set vertically in a
digital microscope and illuminated with light from a white light
source below, and the optical waveguide was observed in a
transmission mode. The result is illustrated in FIG. 17 [FIG. 17(a)
is an overall core cross-sectional view of 12 channels, FIG. 17(b)
is an enlarged core cross-sectional view of the twelfth channel
(wait time 0 second) and the eleventh channel (wait time 24
seconds), FIG. 17(c) is an enlarged core cross-sectional view of
the seventh channel (wait time 119 seconds) and the sixth channel
(wait time 143 seconds), and FIG. 17(d) is an enlarged core
cross-sectional view of the second channel (wait time 238 seconds)
and the first channel (wait time 261 seconds).
[0293] All of the cores are shaped in a perfect circle having a
diameter of about 50 and it has been confirmed that they each have
a suitable size for a multimode optical waveguide.
[0294] Next, the emission near field pattern (NFP) of the
fabricated optical waveguide was observed. The result is
illustrated in FIG. 18 [FIG. 18(b) is an enlarged core
cross-sectional view of the twelfth channel (wait time 0 second)
and the eleventh channel (wait time 24 seconds), FIG. 18(c) is an
enlarged core cross-sectional view of the seventh channel (wait
time 119 seconds) and the sixth channel (wait time 143 seconds),
and FIG. 18(d) is an enlarged core cross-sectional view of the
second channel (wait time 238 seconds) and the first channel (wait
time 261 seconds). The center of each image exhibits a darker color
as the intensity of incident light beams is higher. As a result, it
has been confirmed that when the wait time is set to 119 seconds or
longer, light concentrates on the core center and that a GI optical
waveguide is formed.
Comparative Example 1
[0295] Fabrication of GI Optical Waveguide
[0296] An optical waveguide including a core of one channel formed
in cladding was fabricated by performing the same operation as in
Example 1 except that the conditions were changed to those
described in Table 2.
[0297] The fabricated optical waveguide was observed with a digital
microscope in the same manner as in Example 1. The result is
illustrated in FIG. 19. All of the cores are shaped in a perfect
circle having a diameter of about 50 .mu.m, and it has been
confirmed that they have a suitable size for a multimode optical
waveguide.
[0298] [Propagation Loss]
[0299] The propagation loss of the first channel of the optical
waveguide fabricated in Example 1 and the optical waveguide
fabricated in Comparative Example 1 was measured. In the
measurement, the cut-back method was used, in which insertion loss
was measured at a plurality of optical waveguide lengths, the x
axis represents the optical waveguide length, the y axis represents
the insertion loss, and the inclination indicates propagation loss.
The propagation loss at each of the wavelengths 850 nm, 1,310 nm,
and 1,550 nm of the optical communication wavelength range are
summarized in Table 3.
TABLE-US-00002 TABLE 2 Ejection Moving Metal Example/ pressure
speed of needle Metal Pitch Comparative Cladding of core ejection
inner needle between Example Core material material material unit
diameter height channels Example 1 Polymerizable Polymerizable 600
kPa 4 mm/sec 100 .mu.m 300 .mu.m 300 .mu.m Composition 5
Composition 1 Comparative W712 W713 250 kPa 8 mm/sec 190 .mu.m 300
.mu.m -- Example 1
TABLE-US-00003 TABLE 3 Example/ Comparative Propagation loss
[dB/cm] Example 850 nm 1,310 nm 1,550 nm Example 1 0.08 0.25 0.56
Comparative 0.03 0.34 1.25 Example 1
[0300] As listed in Table 3, it has been confirmed that the optical
waveguide obtained by the production method in the present
invention has an extremely low propagation loss in the optical
communication wavelength band of long wavelengths, such as 1,310 nm
and 1,550 nm. On the other hand, in the optical waveguide
(Comparative Example 1) formed from the epoxy siloxane resin,
increase of propagation loss was observed at the wavelengths longer
than 1,310 nm, and it has been found that the characteristics for
optical waveguides are not satisfied.
Example 2
[0301] Fabrication of GI Optical Waveguide
[0302] An optical waveguide including cores of 10 channels formed
in cladding was fabricated by performing the same operation as in
Example 1 except that the conditions were changed to those
described in Table 4. The wait time for the core of the tenth
channel was 0 second, the wait time for the core of the first
channel was 61.1 seconds, and the difference in wait time between
adjacent cores was 6.79 seconds.
[0303] The fabricated optical waveguide was observed with a digital
microscope in the same manner as in Example 1. The result is
illustrated in FIG. 20 [FIG. 20(a) is a core cross-sectional view,
FIG. 20(b) is an enlarged core cross-sectional view of the tenth
channel (wait time 0 second) and the ninth channel (wait time 6.79
seconds), FIG. 20(c) is an enlarged core cross-sectional view of
the sixth channel (wait time 27.1 seconds) and the fifth channel
(wait time 33.9 seconds), and FIG. 20(d) is an enlarged core
cross-sectional view of the second channel (wait time 54.3 seconds)
and the first channel (wait time 61.1 seconds).
[0304] All of the cores are shaped in a perfect circle having a
diameter of about 10 .mu.m, and it has been confirmed that they
have a suitable size for a single-mode optical waveguide.
TABLE-US-00004 TABLE 4 Core Moving Metal Example/ material speed of
needle Metal Pitch Comparative Cladding ejection ejection inner
needle between Example Core material material pressure unit
diameter height channels Example 2 Polymerizable Polymerizable 50
kPa 15 mm/sec 100 .mu.m 300 .mu.m 250 .mu.m Composition 5
composition 2
Production Example 6
[0305] Preparation of Polymerizable Composition 6
[0306] Ninety-two parts by mass of SC1 produced in Production
Example 1 as the reactive silicone compound (a), 4 parts by mass of
DOG as the di(meth)acrylate compound (b), 4 parts by mass of DVB as
the aromatic vinyl compound (y), and 1 part by mass of 1127 and 1
part by mass of TPO as polymerization initiators were stirred and
mixed at 50.degree. C. for 3 hours. The mixture was further stirred
and defoamed for two minutes to prepare a polymerizable composition
6.
[0307] The viscosity of the resultant composition at 25.degree. C.
was 3,400 mPas. The refractive index of the cured product
fabricated in the same manner as in the foregoing [Evaluation of
Refractive Index of Cured Product] was 1.578 (833 nm), 1.568 (1,305
nm), and 1.567 (1,551 nm).
Example 3
[0308] Fabrication of GI Optical Waveguide
[0309] An optical waveguide including cores of four
channels.times.two levels formed in cladding was fabricated by
performing the same operation as in Example 1 except that the
conditions were changed to those described in Table 5. The cores on
the upper level of two levels were formed above the lower level
after the cores of four channels on the lower level were
formed.
[0310] The fabricated optical waveguide was observed with a digital
microscope in the same manner as in Example 3. The result is
illustrated in FIG. 21.
[0311] All of the cores are shaped in a perfect circle having a
diameter of about 10 .mu.m, and it has been confirmed that they
have a suitable size for a single-mode optical waveguide.
TABLE-US-00005 TABLE 5 Core Moving Metal Example/ material speed of
needle Metal Pitch Comparative Cladding ejection ejection inner
needle between Example Core material material pressure unit
diameter height channels Example 3 Polymerizable Polymerizable 500
kPa 40 mm/sec 10 .mu.m Upper 125 .mu.m composition 5 Composition 6
level: 400 .mu.m Lower level: 270 .mu.m
[0312] As described above, the production method for an optical
waveguide according to the present invention can fabricate not only
a multimode optical waveguide but also a single-mode GI optical
waveguide with an extremely small diameter, and the optical
waveguide has high heat resistance to 350.degree. C. or higher and
extremely high transparency (low propagation loss) in the long
wavelength range. The resultant optical waveguide is workable for
use on an opto-electronic circuit board.
DESCRIPTION OF THE REFERENCE NUMERALS
[0313] 10, 20, 30 optical waveguide [0314] 11,12, 13, 14, 21 (21a
to 21e), 22, 23, 24 31, 32, 33, 34, 35 (35a to 35i), 36, 37, 38
core [0315] 11A, 12A, 13A, 14A uncured core [0316] 19 29 39
cladding [0317] 19A uncured cladding [0318] 91 support [0319] 92
bottom plate [0320] 93 outer frame [0321] 94 ejection unit [0322]
95 ejection body [0323] 96 needle-like portion [0324] H.sub.1
height
* * * * *