U.S. patent application number 13/933378 was filed with the patent office on 2015-01-08 for optical fiber and optical cable.
The applicant listed for this patent is SUMITOMO ELECTRIC INDUSTRIES, LTD.. Invention is credited to Yuya HOMMA, Itaru SAKABE.
Application Number | 20150010279 13/933378 |
Document ID | / |
Family ID | 52112564 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150010279 |
Kind Code |
A1 |
SAKABE; Itaru ; et
al. |
January 8, 2015 |
OPTICAL FIBER AND OPTICAL CABLE
Abstract
The present invention relates to an optical fiber and an optical
cable which can be used for a long term even under environments in
which an oil content migrates into them, and the optical fiber has
a glass fiber extending along a predetermined axis, and a coating.
The coating is composed of a plurality of layers each of which is
comprised of an ultraviolet curable resin or a thermosetting resin,
and swelling rates of the respective coating layers are set so that
they increase from an outer peripheral surface of the glass fiber
to an outer peripheral surface of the cable jacket.
Inventors: |
SAKABE; Itaru;
(Yokohama-shi, JP) ; HOMMA; Yuya; (Yokohama-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO ELECTRIC INDUSTRIES, LTD. |
Osaka |
|
JP |
|
|
Family ID: |
52112564 |
Appl. No.: |
13/933378 |
Filed: |
July 2, 2013 |
Current U.S.
Class: |
385/100 ;
385/128 |
Current CPC
Class: |
G02B 6/02395 20130101;
G02B 6/443 20130101; G02B 6/4402 20130101; G02B 6/036 20130101 |
Class at
Publication: |
385/100 ;
385/128 |
International
Class: |
G02B 6/02 20060101
G02B006/02 |
Claims
1. An optical fiber comprising: a glass fiber; and a coating
surrounding the glass fiber, wherein the coating is laid on the
glass fiber along a radial direction from a central axis of the
optical fiber and comprises an inside coating layer and an outside
coating layer surrounding the inside coating layer, wherein the
inside coating layer is comprised of an ultraviolet curable resin
or thermosetting resin which has a swelling rate with a plasticizer
for polyvinyl chloride resin, wherein the outside coating layer is
comprised of an ultraviolet curable resin or thermosetting resin
which has a swelling rate with a plasticizer for polyvinyl chloride
resin, wherein the swelling rate of the inside coating layer is
smaller than the swelling rate of the outside coating layer, and
wherein the plasticizer contains at least any one of phthalate,
dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate,
dibutyl phthalate, adipate, dioctyl adipate, diisononyl adipate,
trimellitate, trioctyl trimellitate, phosphate, tricresyl
phosphate, citrate, acetyl tributyl citrate, epoxidized oil,
epoxidized soybean-oil, epoxidized linseed-oil, sebacate, and
azelate.
2. The optical fiber according to claim 1, wherein the inside
coating layer and the outside coating layer are adjacent coating
layers in contact with each other.
3-6. (canceled)
7. An optical cable comprising: the optical fiber as defined in
claim 1; and a cable jacket of resin provided around the coating of
the optical fiber.
8-9. (canceled)
10. The optical fiber according to claim 1, a crosslink density of
the inside coating layer is larger than a crosslink density of the
outside coating layer.
11. An optical cable comprising: the optical fiber as defined in
claim 10; and a cable jacket of resin provided around the coating
of the optical fiber.
12. The optical fiber according to claim 1, wherein, an elongation
break of the inside coating layer is smaller than an elongation at
break of the outside coating layer.
13. An optical cable comprising: the optical fiber as defined in
claim 12; and a cable jacket of resin provided around the coating
of the optical fiber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical fiber and an
optical cable including a glass fiber.
[0003] 2. Related Background Art
[0004] Studies have been conducted in recent years on uses of
optical fiber in very short-range areas as well, e.g., uses in
industrial robots and automobiles, and optical fiber cables
obtained by coating an optical fiber with resin have been used
under high-temperature environments in which oil or a PVC
(polyvinyl chloride) electric cable is present around them,
particularly, in the uses in industrial robots and automobiles.
[0005] For example, Japanese Patent Application Laid-Open
Publication No. 2012-223013 (Literature 1) discloses an example of
a harness in which an optical fiber cable and an electric cable are
bundled. In view of the foregoing use environments, an optical
fiber with superior resistance to ethanol is disclosed in Japanese
Patent Application Laid-Open Publication No. 2006-133669
(Literature 2) and an overcoated optical fiber easy to remove an
overcoat layer is disclosed in Japanese Patent Application
Laid-Open Publication No. 2007-199525 (Literature 3). A jacket of
the optical fiber disclosed in Literature 2 is set so that a
coating layer located inside has a larger swelling rate than a
coating layer located outside. The overcoated optical fiber
disclosed in Literature 3 is set so that a coating layer located
inside has a smaller crosslink density than a coating layer located
outside.
SUMMARY OF THE INVENTION
[0006] The Inventors conducted research on the conventional optical
cables and found the problem as described below. Namely, when the
optical cable is used under the high-temperature environment in
which oil or the PVC electric cable is present around it, a
plasticizer with a low molecular weight migrates into the optical
fiber, which caused such a trouble that the coating of the optical
fiber became cracked in long-term deterioration evaluation.
[0007] FIG. 1 is a drawing for explaining a state of the
aforementioned trouble (migration of plasticizers from PVC electric
cables into an optical fiber). FIG. 1 shows a situation
(cross-sectional view) in which an optical cable 1 and PVC electric
cables 2A, 2B are set in contact. The optical cable 1 has an
optical fiber 10 (one in which a glass fiber including a core and a
cladding is coated with resin, or, one in which a hermetic coat
layer is further provided on an outer peripheral surface of the
cladding and is coated with resin), and a cable jacket 20
surrounding the optical fiber 10. The PVC electric cable 2A has a
metal signal wire 20A and a resin layer 21A surrounding it, and the
PVC electric cable 2B has a metal signal wire 20B and a resin layer
21B surrounding it. It should be noted herein that the cable jacket
20 is not always set in contact with the optical fiber 10. The
optical cable may be one in which aramid fiber is set along and
around the periphery of the optical fiber 10 and the cable jacket
20 is laid over it.
[0008] As shown in FIG. 1, while the optical cable 1 is placed
together with the PVC electric cables 2A, 2B under the
high-temperature environment for a long term, the plasticizers in
the PVC electric cables 2A, 2B or oil migrates through the optical
cable jacket 20 into the optical fiber 10. The melting points of
the plasticizers are lower than that of the cable jacket 20 and
thus the plasticizers are more likely to migrate as the molecular
weights thereof become smaller. It is difficult to prevent the
migration, particularly, of the plasticizers having the molecular
weight of not more than 1000. A plurality of coating layers
constituting the cable jacket 20 are comprised of urethane acrylate
or epoxy acrylate and the migrating plasticizers come into spaces
between molecules of these resins. For this reason, as long as
crosslink points of molecules are firm, the cable jacket 20 itself
hardly becomes cracked even with the plasticizers migrating to
cause swelling. However, as the crosslink points start breaking
because of hydrochloric acid emanating from PVC, the cable jacket
20 becomes easier to crack due to the swelling.
[0009] The present invention has been accomplished to solve the
above problem and it is an object of the present invention to
provide an optical fiber and an optical cable with a structure for
enabling long-term use without deterioration of the coating such as
occurrence of cracking, even in environments in which the
plasticizer with a low molecular weight migrates into the optical
fiber side.
[0010] In order to solve the above problem, an optical fiber
according to an embodiment of the present invention comprises a
glass fiber extending along a central axis, and a coating
surrounding an outer peripheral surface of the glass fiber. The
coating is composed of a plurality of layers laid along a radial
direction from the central axis of the optical fiber and each of
the plurality of coating layers is comprised of an ultraviolet
curable resin or a thermosetting resin. The glass fiber comprises
at least a core functioning as a signal transmission line. A
cladding surrounding the outer periphery of the core is comprised
of glass or resin. The optical fiber may further comprise a
hermetic coat layer comprised of a low-melting-point glass
surrounding an outer peripheral surface of the cladding, in
addition to the core and the cladding.
[0011] Particularly, in a first aspect of the present embodiment,
two coating layers selected from the plurality of layers
constituting the coating are designed as to swelling rates thereof
with a plasticizer for polyvinyl chloride resin so that an inside
coating layer closer to the glass fiber has the smaller swelling
rate than an outside coating layer farther from the glass fiber
than the inside coating layer. Therefore, in cases where the
coating is composed of three or more layers, the layers are
designed as to the swelling rates thereof with the plasticizer for
polyvinyl chloride resin or the like so that the swelling rates
successively increase from the coating layer in contact with the
outer peripheral surface of the glass fiber to the coating layer
located outermost.
[0012] As a second aspect applicable to the first aspect, when the
inside coating layer and the outside coating layer are adjacent
coating layers in contact with each other, the inside coating layer
and the outside coating layer preferably satisfy the following
relation:
(d1/2).times.(1+.alpha.1).ltoreq.(d2/2-t2).times.(1+.alpha.2),
where, in a cross section of the optical fiber cable perpendicular
to the central axis, d1 represents an outer diameter of the inside
coating layer, t1 a thickness of the inside coating layer, .alpha.1
the swelling rate of the inside coating layer, d2 an outer diameter
of the outside coating layer, t2 a thickness of the outside coating
layer, and .alpha.2 the swelling rate of the outside coating
layer.
[0013] As a third aspect applicable to at least either one of the
first and second aspects, the plasticizer is preferably a
plasticizer for polyvinyl chloride. As a fourth aspect applicable
to at least either one of the first and second aspects, the
plasticizer preferably contains at least any one of phthalate,
dioctyl phthalate (DOP or DEHP), diisononyl phthalate (DINP),
diisodecyl phthalate (DIDP), dibutyl phthalate (DBP), adipate,
dioctyl adipate (DOA or DEHA), diisononyl adipate (DINA),
trimellitate, trioctyl trimellitate (TOTM), polyester, phosphate,
tricresyl phosphate (TCP), citrate, acetyl tributyl citrate (ATBC),
epoxidized oil, epoxidized soybean-oil (ESBO), epoxidized
linseed-oil (ELSO), sebacate, and azelate.
[0014] In a fifth aspect of the present embodiment, two coating
layers selected from the plurality of layers constituting the
coating are designed so that a crosslink density of an inside
coating layer closer to the glass fiber is larger than a crosslink
density of an outside coating layer farther from the glass fiber
than the inside coating layer. In the fifth aspect as well, in the
cases where the coating is composed of three or more layers, the
coating layers are designed as to the crosslink densities thereof
so that the crosslink densities successively decrease from the
coating layer in contact with the outer peripheral surface of the
glass fiber to the coating layer located outermost.
[0015] Furthermore, in a sixth aspect of the present embodiment,
two coating layers selected from the plurality of layers
constituting the coating are designed as to an elongation at break
thereof so that an inside coating layer closer to the glass fiber
has the smaller elongation at break than an outside coating layer
farther from the glass fiber than the inside coating layer. In the
sixth aspect as well, in the cases where the coating is composed of
three or more layers, the coating layers are designed as to the
elongation at break thereof so that the elongation at break
successively increase from the coating layer in contact with the
outer peripheral surface of the glass fiber to the coating layer
located outermost.
[0016] An optical cable according to an embodiment of the present
invention comprises the optical fiber according to at least any one
of the above first to sixth aspects, and a cable jacket of resin
provided around the coating of the optical fiber.
[0017] Each of embodiments according to the present invention will
become more fully understood from the detailed description given
hereinbelow and the accompanying drawings. These embodiments are
presented by way of illustration only, and thus are not to be
considered as limiting the present invention.
[0018] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, and it is
apparent that various modifications and improvements within the
scope of the invention would be obvious to those skilled in the art
from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a drawing for explaining a state of migration of
plasticizers from PVC electric cables into an optical fiber.
[0020] FIG. 2 is a drawing showing an example of a cross-sectional
structure of an optical cable according to an embodiment of the
present invention.
[0021] FIGS. 3A to 3C are drawings showing examples of various
optical fibers applicable to an optical fiber of the optical cable
according to the embodiment shown in FIG. 2.
[0022] FIG. 4 is a drawing for explaining structural parameters of
the optical fiber according to the embodiment.
[0023] FIG. 5 is a graph for explaining a magnitude relation of
swelling rates between coating layers.
[0024] FIG. 6 is a graph for explaining a magnitude relation of
crosslink densities between coating layers.
[0025] FIG. 7 is a graph for explaining a magnitude relation of
elongation at break between coating layers.
DETAILED DESCRIPTION OF EMBODIMENTS
[0026] Each of embodiments of the optical fiber and optical cable
according to the present invention will be described below in
detail with reference to the accompanying drawings. The same
elements will be denoted by the same reference signs in the
description of the drawings, without redundant description.
[0027] When an optical cable is used under the aforementioned
high-temperature environment in which oil or the PVC electric cable
is present around it, an example of cracking occurring in the
coating is assumed to be such that the oil or the plasticizer
(phthalate or the like) for PVC migrates into resin with a low
modulus of elasticity to swell each of a plurality of layers (resin
layers) constituting the coating, resulting in breakage of the
coating layer with a low elongation at break. In a configuration
wherein the coating layer located outside among the plurality of
coating layers is more likely to become swollen, the entire coating
is unlikely to crack, whereas in a configuration wherein the
coating layer located inside among the plurality of coating layers
is more likely to become swollen, the coating layer located outside
is forcibly expanded between molecules because of the swelling of
the coating layer located inside, so as to possibly result in
cracking of the entire coating. For this reason, the optical fiber
cable with a plurality of coating layers on the outer peripheral
surface of the glass fiber according to the present invention is
designed as to swelling rates with the plasticizer for PVC so that
the swelling rate of the outside coating layer located outside is
set larger than that of the inside coating layer in contact with
the glass fiber (in a configuration provided with a core and a
cladding or in a configuration further provided with a hermetic
coat layer), or, so that even if the swelling rate with the
plasticizer for PVC or the like, of the outside coating layer
located outside is smaller than that of the inside coating layer in
contact with the glass fiber, an elongation at break of the outside
coating layer is set larger than that of the inside coating layer.
A difference between the elongation at break of the inside coating
layer and the outside coating layer is made depending upon a level
of a difference between the swelling rates of the inside coating
layer and the outside coating layer, whereby, even with elongation
of the outside coating layer due to the swelling of the inside
coating layer, the elongation of the outside coating layer is kept
within the range of the elongation at break thereof. The same
effect is also achieved by such setting that the crosslink density
of the inside coating layer is set larger than that of the outside
coating layer. A difference between the crosslink densities of the
inside coating layer and the outside coating layer is made
depending upon a level of the difference between the swelling rates
of the inside coating layer and the outside coating layer. The
difference between the crosslink densities of the two layers is
made so that the inside coating layer and the outside coating layer
are swollen without occurrence of cracking of the outside coating
layer, while the swell of the inside coating layer is more
suppressed by the degree of the difference of the crosslink density
of the inside coating layer from the other, than the swell of the
outside coating layer.
[0028] A specific structure of the optical cable according to an
embodiment of the present invention will be described below. FIG. 2
is a drawing showing an example of a cross-sectional structure of
an optical cable according to an embodiment of the present
invention. FIGS. 3A to 3C are drawings showing examples of optical
fibers having various cross-sectional structures, which are
applicable to an optical fiber 100 in the optical cable 200 in FIG.
2. For example, FIG. 3A is a drawing showing an example of a
cross-sectional structure of an optical fiber 100A according to an
embodiment of the present invention, FIG. 3B a drawing showing an
example of a cross-sectional structure of an optical fiber 100B
according to an embodiment of the present invention, and FIG. 3C a
drawing showing an example of a cross-sectional structure of an
optical fiber 100C according to an embodiment of the present
invention.
[0029] As shown in FIG. 2, the optical cable 200 of the present
embodiment has the optical fiber 100 extending along the central
axis (optical axis AX) (which is the optical fiber according to the
present embodiment), and a cable jacket 210 of resin as a coating
on the optical fiber 100. The optical fiber 100 has a glass fiber
110, and a coating 150 surrounding the glass fiber 110 and
consisting of a plurality of resin layers. A variety of
cross-sectional structures as shown in FIGS. 3A to 3C are
applicable to the optical fiber 100.
[0030] The optical cable 100A shown in FIG. 3A is composed of a
glass fiber 110A extending along the central axis (optical axis
AX), and the coating 150 surrounding the glass fiber 110A. In the
optical fiber 100A, the glass fiber 110A has a core 111 functioning
as a light transmission line extending along the central axis, and
a cladding 112 surrounding the core 111. The coating 150 has an
inside coating layer 120 in contact with the glass fiber 110A, and
an outside coating layer 130 provided outside the inside coating
layer 120.
[0031] The cladding 112 can be made of a plastic material such as
urethane (meth)acrylate resin and in this case, the glass fiber is
composed of only the core, as shown in FIG. 3B. The optical fiber
100B shown in FIG. 3B has a glass fiber 110B composed of only the
core 111, the cladding 112 surrounding the glass fiber 110B and
comprised of the plastic material, and the coating 150 surrounding
the cladding 112. The structure of the coating 150 in this optical
fiber 100B may be composed of one layer, may be the same as the
coating 150 of the optical fiber 100A shown in FIG. 3A, or may be
composed of three or more coating layers.
[0032] On the other hand, the optical fiber 100C shown in FIG. 3C
is different in the structure of a glass fiber 110C from the
optical fiber 100A. Namely, the optical fiber 100C has the core 111
functioning as a light transmission line extending along the
central axis (optical axis AX), the cladding 112 surrounding the
core 111, and a hermetic coat layer 113 surrounding the cladding
112. The coating 150 of the optical fiber 100C also has the inside
coating layer 120 in contact with the hermetic coat layer 113, and
the outside coating layer 130 provided outside the inside coating
layer 120 as in the structure shown in FIG. 3A. It is a matter of
course that the coating 150 in FIG. 3C may be composed of three or
more coating layers.
[0033] FIG. 4 shows a cross-sectional front view of the optical
fibers 100A to 100C (corresponding to the optical fiber 100 of the
optical cable 200) according to the present embodiment. Namely, the
coating layer 120 (inside coating) provided on the outer periphery
of the glass fiber 110A or 110C (or the plastic cladding 112
surrounding the glass fiber 110B) has the outer diameter d1 and the
thickness t1 along the radial direction. The coating layer 130
(outside coating) provided outside the coating layer 120 has the
outer diameter d2 and the thickness t2 along the radial direction.
As the coating layers 120, 130 become swollen, stresses of both of
inward expansion and outward expansion act in the radial direction
from the optical axis AX. In each coating layer, the inward
expansion in the coating layer is released to the outward by the
swell and the inward also expands as pulled by the force. However,
when the swelling rate of the coating layer 120 located inside is
higher than that of the coating layer 130 located outside, the
coating layers 120, 130 both are subject to compressive stress. The
entire coating is likely to expand outward from a steady state, in
order to release the compressive stress. If in this state crosslink
points in each coating layer are broken because of hydrochloric
acid, ultraviolet light, heat, and so forth, the coating can crack
or break eventually.
[0034] Then, the present embodiment involves setting the swelling
rates of the coating layers 120, 130 in contact with each other as
shown in FIG. 4, among a plurality of layers constituting the
coating (which may be three or more layers), so as to satisfy the
following relation:
(d1/2).times.(1+.alpha.1).ltoreq.(d2/2-t2).times.(1+.alpha.2),
thereby to prevent the breakage of the coating in the optical
fibers 100A to 100C.
[0035] A swelling rate is measured by immersing an optical fiber as
an object in a plasticizer (liquid) and measuring volumes or
weights before and after the immersion, and is expressed as a
percentage of a ratio of the volumes or weights before and after
the immersion. The plasticizer to be used may be a plasticizer for
PVC or the like (e.g., phthalate).
[0036] FIG. 5 is a graph for explaining the magnitude relation of
swelling rates between the coating layers 120, 130. Particularly,
the present embodiment is designed as to the swelling rates with
the plasticizer for polyvinyl chloride resin so that the swelling
rate of the coating layer 120 (inside coating) is smaller than that
of the coating layer 130 (outside coating). In cases where the
coating is composed of three or more layers, the swelling rates
thereof with the plasticizer for polyvinyl chloride resin are
designed, as indicated by a dashed line in FIG. 5, so that they
successively increase from the coating layer in contact with the
outer peripheral surface of the glass fiber 110A or 110C (or the
plastic cladding 112 surrounding the glass fiber 110B) to the
coating layer located outermost in the cable jacket. Phthalate is
known as typical plasticizer for polyvinyl chloride resin.
[0037] FIG. 6 is a graph for explaining the magnitude relation of
crosslink densities between the coating layers 120, 130. The
present embodiment is designed so that the crosslink density of the
coating layer 120 (inside coating) is larger than that of the
coating layer 130 (outside coating). In the cases where the coating
150 is composed of three or more layers, the crosslink densities
thereof are designed, as indicated by a dashed line in FIG. 5, so
that they successively decrease from the coating layer in contact
with the outer peripheral surface of the glass fiber 110A or 110C
(or the plastic cladding 112 surrounding the glass fiber 110B) to
the coating layer located outermost in the cable jacket.
[0038] A crosslink density of a cured product (each coating layer
in the case of the present embodiment) is obtained from the
following equation by measurement of dynamic viscoelasticity.
.rho.=G'/.phi.RT
In this equation, G' represents the storage elastic modulus at
temperature T, .phi. the front factor (assumed to be 1), R the gas
constant, and T a temperature which is not less than Tg and at
which G' becomes approximately flat against temperature, when
measured by DMA (Dynamic Mechanical Analysis), the temperature T
being given approximately as T=Tg (glass transition
temperature)+30.degree. C. The glass transition temperature Tg is
measured by Differential Scanning Calorymetry (DSC) and Thermo
Mechanical Analysis (TMA).
[0039] Furthermore, FIG. 7 is a graph for explaining the magnitude
relation of elongation at break between the coating layers 120,
130. The present embodiment is designed as to the elongation at
break with the plasticizer for polyvinyl chloride resin so that the
elongation at break of the coating layer 120 (inside coating) is
smaller than that of the coating layer 130 (outside coating). In
the example of FIG. 7 as well, in the cases where the coating is
composed of three or more layers, the elongation at break thereof
with the plasticizer for polyvinyl chloride resin are designed so
that they successively increase from the coating layer in contact
with the outer peripheral surface of the glass fiber 110A or 110C
(or the plastic cladding 112 surrounding the glass fiber 110B) to
the coating layer located outermost.
[0040] The measurement of each elongation at break with the
plasticizer is carried out by a method conforming to AMST D882
Standard, to measure the elongation break with the plasticizer
while a film is kept in contact with the plasticizer.
[0041] (Plasticizer)
[0042] The plasticizer applicable to PVC will be described below.
Plasticizer is the general term of additive chemicals to be added
in thermoplastic synthetic resin to improve flexibility and
weatherability thereof, and it is also used for making PVC more
flexible.
[0043] In general, a thermoplastic resin has a glass transition
temperature (also called a glass transition point), and the resin
exhibits well-ordered crystallinity of molecular arrangement at
temperatures below the glass transition temperature but an
amorphous state of molecular arrangement in a temperature zone from
the glass transition temperature to a melting point. The
thermoplastic resin in the amorphous state demonstrates flexibility
and high optical transparency and thus is useful in many
applications. On the other hand, the crystalline resin is opaque
and becomes fragile against impact and external force with progress
of crystallinity at low temperatures, often demonstrating
properties deemed as disadvantages in use of the resin.
[0044] Since the melting point and glass transition point are
determined by a type of the resin and the degree of polymerization
thereof, the temperature characteristics of the resulting resin do
not always agree with those of a desired product. Addition of an
additive in the thermoplastic resin expands the temperature zone of
the amorphous state to prevent fragility from appearing even at low
temperatures and to enhance flexibility, realizing the resin with
desired temperature and physical properties. A chemical added for
this purpose is the plasticizer. The plasticizer further increases
elasticity, thereby to improve moldability as well; for example, it
becomes easier to release a molded product from a die during
injection molding.
[0045] The plasticizer comes into spaces of the resin to inhibit
the resin from being regularly oriented, whereby the resin is
maintained in the amorphous state even at temperatures below the
glass transition point. Therefore, the plasticizer having large
side chains often demonstrates useful properties. If the
plasticizer is incompatible with the objective resin, phase
separation will occur between the resin and the plasticizer;
therefore, the plasticizer needs to have a characteristic of wide
compatibility with various resins while causing no phase
separation.
[0046] Particularly, in the case of polyvinyl chloride (PVC),
products with a wide variety of properties are prepared by addition
of the plasticizer. Typical examples of the plasticizer used
include phthalates, among which DEHP and DINP have properties as
ideal general-purpose plasticizers and are manufactured in large
quantities.
[0047] (Examples of Plasticizer)
[0048] Examples of the plasticizer include phthalate, dioctyl
phthalate (DOP or DEHP), diisononyl phthalate (DINP), diisodecyl
phthalate (DIDP), dibutyl phthalate (DBP), adipate, dioctyl adipate
(DOA or DEHA), diisononyl adipate (DINA), trimellitate, trioctyl
trimellitate (TOTM), polyester, phosphate, tricresyl phosphate
(TCP), citrate, acetyl tributyl citrate (ATBC), epoxidized oil,
epoxidized soybean-oil (ESBO), epoxidized linseed-oil (ELSO),
sebacate, and azelate.
[0049] Phthalate is the general term of esters of phthalic acid
(ortho-isomer) and alcohol. Phthalates of higher alcohols typified
by bis(2-ethylhexyl)phthalate are useful as plasticizers (phthalic
acid-based plasticizers). Industrially in general, phthalic acid is
esterified by azeotropic dehydration of water and alcohol from
phthalic acid (free acid) and excess alcohol. Table 1 below
provides the abbreviation, molecular weight, melting point
(.degree. C.), boiling point (.degree. C.), and CAS number of each
of major compounds of phthalates.
TABLE-US-00001 TABLE 1 Melting Boiling point point Compound name
Abbr. Mol. wt. (.degree. C.) (.degree. C.) CAS number Dimethyl
phthalate DMP 194.19 2 282 [131-11-3] Diethyl phthalate DEP 222.24
-3 289-299 [84-66-2] Diallyl phthalate DAP 246.26 -70 165-167(*)
[131-17-9] Dibutyl phthalate DBP 278.35 -35 340 [84-74-2]
Diisobutyl phthalate DIBP -- 327 [84-69-5] Di-n-hexyl phthalate DHP
-- -- [84-75-3] Dioctyl phthalate DOP 390.56 -50 384 [117-81-7]
Bis(2-ethylhexyl)phthalate DEHP Di-n-octyl phthalate DnOP 390.56
Diisononyl phthalate DINP 418 403 [28553-12-0] [68515-48-0] Dinonyl
phthalate DNP 418 Diisodecyl phthalate DIDP 446 -50 420
[26761-40-0] Benzyl butyl phthalate BBP 312 370
Bis(butylbenzyl)phthalate BBzP (*).degree. C./5 mmHg
[0050] (Materials of Coating Layers)
[0051] Constituent materials of the coating 150 in the optical
fiber of the present embodiment will be described below. Each of
the coating layers 120, 130 is comprised of an ultraviolet (UV)
curable resin or a thermosetting resin and types and properties of
the UV curable resins applicable to each coating layer will be
described below.
[0052] The UV curable resins are roughly classified into the
radical polymerization type of acrylate and the cation
polymerization type of epoxy. The radical polymerization type
consists primarily of acrylate and has a cure shrinkage rate of 5
to 10%. The radical polymerization type is subject to curing
inhibition by oxygen, curing reaction also stops after termination
of irradiation with UV, and the curing is less accelerated by heat.
Furthermore, the radical polymerization type is characterized by
moderate thermal resistance and moderate chemical resistance, and
has a large degree of freedom of resin design. On the other hand,
the cation polymerization type consists primarily of epoxy and has
a cure shrinkage rate of 2 to 4%. The cation polymerization type is
free of the curing inhibition by oxygen, the curing reaction
continues even after termination of irradiation with UV, and the
curing is accelerated by heat. Furthermore, the cation
polymerization type is characterized by good thermal resistance and
good chemical resistance but has a small degree of freedom of resin
design.
[0053] The radical polymerization type is further classified under
epoxy acrylate, urethane acrylate, and silicone acrylate.
[0054] The cable jacket 210 can be comprised of a thermoplastic
resin, e.g., a polyolefin-based resin such as polyethylene or
polypropylene, or polyamide. The cable jacket 210 imparts
mechanical strength to the optical fiber 100 (100A-100C). The
diameter of the optical fiber 100 (100A-100C) can be in the range
of 0.25 to 0.5 mm, and the diameter of the optical cable 200 in the
range of 1 to 3 mm. The thickness of the cable jacket 210 can be in
the range of 0.3 to 1 mm. Aramid fiber functions as a tension
member of the optical cable 200 and Kevlar (registered trademark)
or the like is available.
[0055] As constructed as described above, the optical fiber and the
optical cable according to the present invention can be used for a
long term without deterioration of the coating such as cracking of
the cable jacket, even in the environments in which the oil content
such as the plasticizer with a low molecular weight migrates into
the optical fiber side.
[0056] From the above description of the present invention, it will
be obvious that the invention may be varied in many ways. Such
variations are not to be regarded as a departure from the spirit
and scope of the present invention, and all improvements as would
be obvious to those skilled in the art are intended for inclusion
within the scope of the following claims.
* * * * *