JPS6295510A - Coated optical fiber - Google Patents

Abstract

PURPOSE:To decrease work strains by selecting a curable resin from spiroortho- esters, spiroortho-carbonates and bicycloortho-esters. CONSTITUTION:The curable resin for an optical fiber to be coated with the curable resin which exhibits non-shrinkability when cured is selected from the spiroortho-esters, spiroortho-carbonates and bicycloortho-esters. The curable resin which exhibits the non-shrinkability when cured refers to the resin which is a liquid compsn. prior to curing is the insoluble three-dimensional network solid compsn. after curing and does not exhibit volumetric shrinkage at all or makes slight volumetric shrinkage or expansion by curing. The rate of the volumetric shrinkage of the referred resin is preferably <=1%. The above- mentioned spiroortho-esters, bicycloortho-esters and spiroorth-carbonates can be cured under heating by a cationic polymerization catalyst such as Lewis acid and can be cured under heating by using a curing agent such as polybasic acid and the acid anhydride thereof, polycarboxylic acid resin, or phenolic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to optical fibers for optical transmission, and particularly to coated optical fibers.

Conventional optical transmission glass fibers have their surfaces coated with curable resins such as silicone resins, epoxy resins, and various UV-curable resins that have UV-active groups such as acrylic groups in their molecules. There is. In addition, a reinforcing layer of thermoplastic resin such as polyamide resin or fluororesin may be further coated.

However, these curable resins are known to shrink during curing, and there is concern that distortion, internal stress, etc. caused by this shrinkage may adversely affect the performance of the optical fiber.

In particular, this problem may be inevitable when a curable resin having a high rigidity is used as a secondary coating. In addition, the thermoplastic resin used to coat optical fibers is a crystalline polymer and tends to produce processing distortion. If this distortion remains, there is a possibility that the performance of the optical fiber will be impaired. Although it is possible to provide a small amount of coated optical fiber to some extent by coating these resins under appropriate manufacturing conditions, this requires strict control of manufacturing conditions.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional techniques and provide a coated optical fiber that has low processing distortion and is easy to manufacture.

[Summary of the Invention] The present invention provides an optical fiber coated with a curable resin that exhibits non-shrinkage properties upon curing, wherein the curable resin is made of spiro-orthoesters, spiro-orthocarbonates, and bicycloorthoesters. It is characterized by being selected.

Here, a curable resin that exhibits non-shrinkage properties when cured is a liquid composition before curing, which becomes an insoluble three-dimensional network solid composition after curing, and which has a volumetric composition after curing. It shows no shrinkage or only a slight volumetric shrinkage or expansion. The volume shrinkage rate permissible in the present invention is not particularly limited, but is preferably 1% or less. Note that even if the composition is solid at room temperature before curing, it becomes liquid upon heating or the like, and this is considered to be a liquid composition. That is, materials that are liquid at the time of coating fall within the scope of the present invention. In addition, various types of molecularly designed curable resins that exhibit non-shrinkage properties during curing can be considered, and those that utilize ring-opening polymerization during curing are applicable. Specifically, compositions consisting of spiro-orthoesters, dicycloorthoesters, and spiro-orthocarbonates are applicable.

Spiroorthoesters are synthesized, for example, from epoxy compounds and lactones as follows. Incidentally, this compound undergoes ring opening during polymerization as shown in the following formula.

→R Polymerization of unsaturated spiro-orthoesters, for example, by reaction of epichlorohydrin and lactones, CHz=C00゛. ′ is required. This compound reacts with maleic anhydride and maleimides to form an alternating copolymer. In addition, when a radical copolymer with acrylonitrile, methyl methacrylate, etc. is prepared and treated with a cationic catalyst, the spiro-orthoester group undergoes ring-opening crosslinking and a non-shrinkable cured product is obtained.

Bicycloorthoesters are obtained from orthoesters and triols, which are easily obtained by reacting nitriles and alcohols.

RC(OR″)3 + (HOCHz)3 CR-
-CH./Bicycloorthoesters or urethanes, bifunctional monomers, vinyl monomers, acrylates, and methacrylates having a bicycloester groove structure also undergo ring-opening procedures to give cured products exhibiting non-shrinkage properties.

Spiro-orthocarbonates undergo ring-opening polymerization with cationic catalysts to give polyether carbonates, which rather expand in volume during polymerization.

Spiro-orthocarbonates These spiro-orthoesters, bicyclo-orthoesters, and spiro-orthocarbonates can be cured by heat using a cationic polymerization catalyst such as a Lewis acid, polybasic acids and their acid anhydrides, polycarphone-stabilized resins, and phenols. It can be cured by heating using a curing agent such as a resin. Furthermore, those having an acrylic group or a methacrylic group introduced into the molecule can be cured by electron beams or by ultraviolet irradiation in the presence of a well-known photosensitizer.

Note that the cured product of the present invention may be directly coated on the glass fiber, or in some cases, it may be coated after being coated with a silicone resin or the like which has relatively little shrinkage during curing.

Further, the composition of the present invention may be used alone or in combination of two or more. Additives such as adhesives, reactive adhesives, etc. within the range that does not cause shrinkage during curing.
Colorants, antioxidants, flexibility agents, reaction modifiers, etc. may be mixed.

Furthermore, an organic solvent may be used to lower the viscosity.

Since the composition of the present invention serves as 190% of the reinforcing layer, it does not require the normally used thermoplastic resin, but a protective layer such as a thermoplastic resin or fiber reinforced plastic is provided on the outside of the coated optical fiber of the present invention. You can also do that.

[Example] Example 1 72 parts by weight of dodecynylsuccinic anhydride was mixed with 100 parts by weight of spiro-orthoester resin (EXP-101 manufactured by Toagosei Chemical Co., Ltd.) made by 1% bisphenol A glycidyl ether type epoxy resin and ε-caprolactone. The composition was coated on a multimode quartz glass fiber drawn to an outer diameter of 125 μm at a drawing speed of 60 TrL/min, and baked and hardened in a heating furnace maintained at 400'C to obtain an outer diameter of 2
A coated optical fiber of 00 μm was manufactured.

The curing shrinkage rate of the coated optical fiber thus obtained was 0.3%, the optical fiber strain was as low as 0.02%, and the transmission loss of the coated optical fiber was as low as that of a normal coated fiber. It was the same or lower than the value of .

Example 2 A silicone resin containing a phenyl group was applied to a multi-mode quartz glass fiber that had been previously drawn to an outer diameter of 125 μm at a drawing speed of 60 m/min to an outer diameter of 200!1T.
The composition of Example 1 was immediately coated with the composition of Example 1 so as to have an outer diameter of 400 μm, and baked and cured in a heating furnace maintained at 450'C to obtain a coated optical fiber. was manufactured. The curing shrinkage rate of the coated optical fiber thus obtained was 0.4%, the optical fiber strain was extremely small at 0.03%, and the transmission loss of the coated optical fiber was as low as that of a normal coated fiber. It was about the same.

Example 3 Glycidyl ether type epoxy to 1-ethyl-4-hydroxymethyl-2,6,7-drioxabidiclo[2,2,2]octane and bisphenol obtained by the reaction of pentaerythritol and trimethyl orthopropionate A kneaded product prepared by adding a Lewis acid catalyst to the difunctional bicycloorthoester produced by the reaction of the resin, EXP-151 manufactured by Toagosei Chemical Co., Ltd., was drawn at a drawing speed of 60 m/min to an outer diameter of 12 mm.
A multimode quartz glass fiber drawn to 5 μm was coated and baked and hardened in a heating furnace maintained at 400°C to produce a coated optical fiber with an outer diameter of 200 μm. The curing shrinkage rate of the coating is 0.1%, the optical fiber strain is 0.01%, which is comparatively small, and the transmission loss of the coated optical fiber is the same as that of ordinary coated optical fiber. Ta.

Example 4 Multi-mode quartz was drawn to an outer diameter of 125 μm at a drawing speed of 60 m/m r n using a composition in which a bicycloorthoester compound having an acrylic group at the end was added with 5 parts of a photosensitizer benzophenone. It was coated on a glass fiber and cured by passing through an ultraviolet curing device (120 W/cm) to produce a coated optical fiber with a coated outer diameter of 200 μm. The curing shrinkage rate of the coating is 0.2%, and the optical fiber strain is 0.
．． The transmission loss of the coated optical fiber was as small as 0.02%, and was equivalent to that of a normal coated optical fiber.

The method for measuring the curing shrinkage rate of the coating of the coated optical fiber and the strain on the circumferential optical fiber in the above examples will be described below.

(1) Curing Shrinkage Rate The specific gravity of the composition before curing is dl, and the specific gravity of the cured coating peeled from the coated optical fiber is dl. The curing shrinkage rate was calculated using the following formula.

(2) Optical fiber distortion Using the measuring device shown in Figure 1, detect the phase difference θ at a modulation frequency of 12 MHz for an optical fiber with a length of 100 m, and find the change in phase difference Δθ = θ1-02 before and after the measurement. , the optical fiber strain was calculated from this Δθ. In the figure, 1 is a light source, 2 is a fiber to be measured, 3 is an O/E converter,
4 is an amplifier, 5 is a vector portometer, 6 is a synthesized standard signal generator, and ψ1 and ψ2 are the phases of the sine wave signal.

[Effects of the Invention j] As explained above, the coated optical fiber of the present invention uses a non-shrinkable curable resin as a coating, and since it does not shrink during curing, almost no processing strain remains. Therefore, the adverse effect of microbending on transmission characteristics can be reduced.

Furthermore, since the coating can be easily applied to glass fibers in the same manner as conventional curable resins, no new equipment is required, and conventional equipment can be used to manufacture coated optical fibers. It can produce excellent industrial effects.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a measuring device used for measuring optical fiber strain according to the present invention. 1... Light source, 2... Fiber to be measured, 3... O/
E converter, 4... amplifier, 5... vector voltmeter, 6... synthesized standard signal generator.

Claims (1)

[Claims] (1) In an optical fiber coated with a curable resin that exhibits non-shrinkage properties when cured, the curable resin is selected from spiro-orthoesters, spiro-orthocarbonates, and bicyclo-orthoesters. A coated optical fiber characterized by: