JPS62170920A - Optical fiber covered with ultraviolet cured resin - Google Patents

Abstract

PURPOSE:To reduce transmission loss of light at low temp. of optical fiber by forming primary and secondary clad with a cured product of resin cured by ultraviolet rays. CONSTITUTION:The optical fiber 1 comprises quartz glass optical fiber. The ultraviolet cured resin to be used for the formation of the primary clad 2 is one having Young's modulus being 10-100kg/cm<2> at 25 deg.C and 100-20,000kg/cm<2> at -30 deg.C contg. urethane acrylate oligomer having at least one polyester polyol unit. The ultraviolet cured resin to be used for the formation of the secondary clad 3 has 1,000-20,000kg/cm<2> Young's modulus at 25 deg.C. The optical fiber to be clad with the resin may be single fiber type or tape type. By this constitution, the light transmission loss at low temp. is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber coated with an ultraviolet curing resin. More specifically, the present invention relates to a silica glass optical fiber coated with resin and having excellent low-temperature properties.

[Prior Art] A silica glass optical fiber is provided with a multilayer resin coating to protect the optical fiber from external impact. These resin coatings usually consist of a primary coating J3 provided directly above the optical fiber and a secondary coating provided outside it.In other words, a buffer layer is provided between the primary coating and the secondary coating. Sometimes it's even pulled.

Optical fibers are used in various environments and are improved to have the characteristics required in each environment. For example, when used at low 2H (below -io°C), such as in extremely cold regions, optical transmission loss increases. This phenomenon is thought to be due to microbending occurring in the optical fiber due to shrinkage of the resin coating.
A soft resin having a Young's modulus of 1 to 100 Nf/m at room temperature and whose Young's modulus hardly changes even at low temperatures (about -30° C.) is used as the primary coating.

[The problems that the invention attempts to solve, however,
Even if a resin having a small Young's modulus even at low temperatures is used as the primary coating material, the optical fiber's optical transmission loss at low temperatures still increases.

The present inventors have found that even if the resin has a specific Young's modulus, even if the Young's modulus increases at low temperatures, it will not cause a significant increase in optical transmission loss as described above, and will hardly change the Young's modulus. We have discovered the surprising fact that the increase in loss at low temperatures is smaller than those without, and have completed the present invention.

[Means for Solving the Problems] The present invention provides ultraviolet I! of ultraviolet curing resin. A silica glass optical fiber in which the primary coating and the secondary coating are formed of a cured product, and the primary coating is made of an ultraviolet cured product.
It has a Young's modulus of 10 to 100 Ny/d and 100 to 20.000 Kg/cd at 5°C and -30°C, respectively, and the UV-cured product of the secondary coating has a modulus of 1.0 at 25°C.
It relates to an ultraviolet curing resin coated optical fiber having a Young's modulus of 9/d between 00 and 20.000.

[Operations and Examples] A major feature of the resin-coated optical fiber of the present invention is that a resin whose Young's modulus increases at low temperatures, which was conventionally thought to increase optical transmission loss at low temperatures, is used for the primary coating. The resin for secondary coating is 1,000 to 20,00
A conventionally used ultraviolet curing resin having a Young's modulus of about OKfl/ai can be used.

The reason why the increase in optical transmission loss is reduced when an ultraviolet curable resin with a specific temperature dependence of Young's modulus is used as the primary coating is not yet clear, but as shown in the examples to be described, excellent You can get the effect.

The structure and module of the optical fiber to which the present invention is directed does not matter, as long as it is a silica glass optical fiber.

As mentioned above, the UV-curable resin used for forming the primary coating, which is an important feature of the present invention, has an ultraviolet cured product of 10 to 100 Kg/ad, preferably 30 to 80 Kg/cjA1, at 25°C. is 65
It has a Young's modulus of ~80 to 9/ctd, and the Young's modulus increases at a low temperature of -30°C to 100 to 20, OOO
Ng/cd, preferably 500-5.000kg/
ci, particularly preferably 1.000 to 3.000Kg
/ CD. Those having a Young's modulus NU dependence in this range surprisingly have better optical transmission characteristics at low temperatures than conventional ones. Ultraviolet light for primary coating formation [[
! Examples of the curing resin include UV curable resins such as urethane acrylate, polybutadiene acrylate, silicone acrylate, polyester acrylate, epoxy acrylate, and polyether acrylate. Among these, urethane acrylate resins are preferred, and those containing urethane acrylate oligomers containing at least one polyester polyol unit are particularly preferred. For example, the polyol component is polytetramethylene glycol (PTMG).
It is also preferable to use a polyester polyol of adipic acid and 1,6-hexanediol, in which the isocyanate component is isophorone diisocyanate (IPDI) and the acrylate component is 2-hydroxyethyl acrylate (HEA).

The cured product of the ultraviolet curable resin used for forming the secondary coating has a molecular weight of 1,000 to 20.00089 at 25°C.
Conventional secondary coating resins can be used as long as they have a Young's modulus of /cd, and specific examples include urethane acrylate, epoxy acrylate,
Examples include UV-curable resins of polyester acrylate type or a mixture thereof.

In the present invention, a buffer layer may be provided between the primary coating and the secondary coating. As the resin used to form the buffer layer, ultraviolet curable resins such as urethane acrylate, silicone acrylate, polybutadiene acrylate, polyether acrylate, and polyester acrylate are preferably used, and the Young's modulus of the cured product is 10 to 1,000 Kg/cd at 25°C, preferably 10
~100Kg/cd is suitable.

The thickness of the primary coating, buffer layer, and secondary coating varies depending on the optical fiber core structure, etc., but each has a thickness of 10 to 20 mm.
It is usually selected in the ranges of 0 ρ, 0 to 300 p, and 10 to SOO.

Each of these ultraviolet curable resins is made into a varnish by adding and blending an appropriate reaction diluent, photopolymerization initiator, pigment, etc. to each resin. Examples of reaction diluents include HEA, phenoxyethyl acrylate, IPDI, phenyldiethylene glycol acrylate, phenyltriethylene glycol acrylate, lauryl acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, triethene glycol diacrylate. ), neopentyl glycol diacrylate, tetraethylene glycol diacrylate, N-vinylpyrrolidone, 2-ethylhexyl acrylate, etc., and photopolymerization initiators include, for example, 1-hydroxycyclohexylphenyl ketone, benzyl dimethyl ketal. , benzophenone, jetoxyacetophenone, 2-hydroxy-2-
Examples include, but are not limited to, methyl-1-phenylpropen-1-one, isobutylbenzoin ether, isopropylbenzoin ether, and hydroxycyclohexylphenyl ketone.

Various methods are used to form the primary coating. For example, an optical fiber made by melting and drawing a quartz glass optical fiber base material is passed through a varnish for the primary coating, and then cured by irradiation with ultraviolet rays. Similarly, there is a method of applying and curing a varnish for a buffer layer and a method of applying and curing a varnish for a secondary coating. Coating conditions and curing conditions may be appropriately selected depending on the type of resin used, coating thickness, line speed, etc.

The resin-coated optical fiber of the present invention may be applied to a 1g linear optical fiber as shown in FIG. 1, or a tape-type optical fiber as shown in FIG.

In FIG. 1, (1) is an optical fiber, a first optical fiber (2) is provided directly above it, and a secondary coating (3) is provided via a buffer (4). The tape-type optical fiber shown in Figure 2 has one
Happi coat fi! (2) If necessary, a buffer layer (not shown) and then two optical fibers (3) are bundled together. (61 is provided.) As the coating agent for the tape IW4 (6), for example, an ultraviolet curable resin such as urethane acrylate, polyester acrylate, or epoxy acrylate, or a mixture thereof is used.

Next, the resin-coated optical fiber of the present invention will be explained based on Examples, but the present invention is not limited to these Examples.

Example 1 Urethane acrylate-based ultraviolet curable resin (manufactured by Dainippon Ink & Chemicals) consisting of a polyol component (PTHG + polyester polyol of adipic acid and 1,6-hexanediol), an isoanate component (IPDI), and an acrylate component (IIεA) Grandic FG70G)
was used as the primary coating material, and PTH was used as the secondary coating material.
Urethane acrylate consisting of G, tolylene diisocyanate (TDI) and HEA, and bisphenol A.
A mixture of epoxy acrylate consisting of epichlorohydrin and acrylic acid (Japan Synthetic Rubber (t[, Desolite 950Y100) was used.

A Gl-type quartz glass optical fiber base material prepared by the VAD method was drawn at a drawing speed of 30 m/min, and passed through a pot containing the primary coating varnish at the same speed as the obtained optical fiber (diameter 12 hm). The next coating material varnish was applied and then cured through an ultraviolet irradiation device with an effective length of 50α (effective irradiation time: 1 second) to form a primary coating with a thickness of 90 mm.

Subsequently, a secondary coating varnish was applied and ultraviolet rays were irradiated (effective irradiation time: 1 second) to form a secondary >1L fa having a thickness of 300ρ, thereby producing a resin-coated optical fiber of the present invention.

The A Young's modulus of each coating layer was as shown below.

Primary coating: 75 to 97 dl at 25℃ 2,200 to 9/l:d at -30℃ Secondary coat: 5.0OOK at 25℃! F/C
8,400 Ky/cd at -30°C Young's modulus is measured by molding the varnish used into a film with a thickness of about 150", curing it by sufficiently irradiating it with ultraviolet rays, and making a film with a width of 1
5. A tanzak-shaped sample was prepared, and this sample was subjected to a tensile test at a tensile rate of 11 m/min, and the tensile modulus at an elongation of 2.5% was taken as Young's modulus.

The resulting resin-coated optical fibers were bundled into a bundle of about 30 cm, placed in a thermostatic oven, and measured for transmission loss at a wavelength of 1.30 Jl. The transmission loss at 25°C was 0.
50dB/km, transmission loss at -30℃ is 0.5
5dB/ka+, and its transmission loss increase is 0.0.
It was suppressed to 5dB/+a.

Comparative Example 1 Urethane acrylate consisting of PTHG, IPDI, and 11[A] (Grandic FC70 g manufactured by Dainippon Ink & Chemicals, 25°C and -30°C) was used as the primary coating material.
An optical fiber coated with an ultraviolet curable resin was prepared in the same manner as in Example 1 except that Young's modulus at 38 Kf/7) was used, and the transmission loss was measured in the same manner as in Example 1. .50dB/1v1-3.0 at 30℃
There was +a t' in dB/ (loss increase amount: 2.5d
B/km).

Comparative Example 2 As the primary coating material, urethane acrylate-based ultraviolet & II resin (Desolite 950x065.25°C manufactured by Dead Co., Ltd.) was used as the primary coating material.
An optical fiber coated with an ultraviolet curing resin was prepared in the same manner as in Example 1, except that the Young's modulus at -30°C was 25, 9/- and 30.000 Kg/cd, respectively. When the transmission loss was measured, it was 0.50dB/km at 25℃ and 20.5d at 30℃.
B/kn+ (loss increase m: 20, OdB/km
).

Example 2 Ethylene glycol adipate and TOI as primary coating
and IEA. Urethane acrylate (0GEI manufactured by Mitsubishi Yuka Fine@, Young's modulus at 25°C and -30°C is 22 to 9/ctA and 13, respectively)
An optical fiber coated with an ultraviolet curable resin was prepared in the same manner as in Example 1 except that 0.00 * g/m ) was used, and the transmission loss was measured in the same manner as in Example 1.
．． 50dB/km, -30℃-(-0, f35dB
/kill (loss increaseffl: 0.15
dB/km).

Example 3 A resin-coated optical fiber strand having primary and secondary coatings was produced using the same resin as in Example 1, except that the thickness of the primary coating was 200Al111 and the thickness of the secondary coating was 300 items. .

Five of these optical fiber cables are lined up and made into Desolite 950Y.
100 and cured by irradiating with ultraviolet rays to form a tape-type optical fiber core (0.45 am x 1.
6m> was produced.

When the transmission loss of the obtained tape-shaped core wire was measured in the same manner as in Example 1, it was 0.50 dB/lv at 25°C, and the loss did not change even when the temperature was lowered to -30°C.

[Effects of the Invention] According to the present invention, a resin-faced optical fiber with excellent optical transmission characteristics is provided, which breaks the conventional wisdom that unless the Young's modulus is low even at low temperatures, the optical transmission loss will be large at low temperatures. can do.

4. Brief description of aspects Fig. 1 is a schematic cross-sectional view of an embodiment of the resin-coated optical fiber of the single wire type of the present invention, and Fig. 2 is a schematic cross-sectional view of an embodiment of the tape-type resin-coated optical fiber of the present invention. It is.

(Main symbols on drawings) (1): Optical fiber (21: Primary coating (31: Secondary coating 71 Figure Figure 72

Claims (1)

[Scope of Claims] 1. A silica glass optical fiber having a primary coating and a secondary coating formed of an ultraviolet cured product of an ultraviolet curable resin, wherein the ultraviolet cured product of the primary coating is heated at 25°C and -30°C.
10-100 kg/cm^2 and 100 respectively at °C
It has a Young's modulus of ~20,000 kg/cm^2, and the UV-cured material of the secondary coating has a Young's modulus of 1,000~20 at 25°C.
An ultraviolet curing resin coated optical fiber with a Young's modulus of 000 kg/cm^2. 2. The optical fiber according to claim 1, wherein the ultraviolet curable resin for primary coating contains a urethane acrylate oligomer containing at least one polyester polyol unit. 3. The optical fiber according to claim 1 or 2, which is a single-wire optical fiber. 4. The optical fiber according to claim 1 or 2, which is a tape-type optical fiber.