JP2001343553A - Antireflection resin-composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition capable of giving sufficient strength to practical use and realizing an antireflection film easily removable at the time of replacement and to provide an optical connector using this composition. SOLUTION: The resin composition is for forming the antireflection film on the joining face of a ferrule, in an optical connector that has the ferrule for holding optical fibers and that connects by abutting the end faces of the optical fibers. The adhesive strength to the ferrule in hardening is set in the range of 0.1 to 10 kg/cm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for forming an anti-reflection film on a joint surface of a ferrule of an optical connector.

[0002]

2. Description of the Related Art Generally, when a pair of optical fibers are connected to each other, an optical connector method in which the end faces of the optical fibers are detachably adhered to each other, and the end faces of the optical fibers are permanently connected by heat fusion. There is a fusion method.

In the case of using the optical connector method, if a minute gap is formed between the end faces of the optical fiber, a difference in the refractive index between the air interposed in the gap and the core of the optical fiber causes a difference.
Part of the optical signal transmitted through the core of one optical fiber undergoes interfacial reflection, which is one of the causes of an increase in connection loss due to the optical connector.

As countermeasures against this, a) a method in which a matching liquid having a refractive index substantially equal to the refractive index of the core portion is interposed between the end faces of the optical fiber, and b) a method disclosed in, for example, Japanese Patent Publication No. 2-3481. As described above, a method has been proposed in which a soft resin film having a refractive index substantially equal to that of a core portion of an optical fiber is adhered to a connection end surface of a ferrule in an optical connector using an adhesive. When a soft resin is interposed, a minute gap existing between the end faces of the optical fiber is filled by elastic deformation of the resin, so that connection loss can be greatly reduced.

[0005]

However, when a matching liquid is interposed or a resin film is stuck with an adhesive, it is difficult to remove the resin film when replacing it due to deterioration or the like. For example, when the matching liquid is removed, wiping with a rag or the like is not sufficient because the viscosity of the liquid is relatively high. It is necessary to immerse the liquid in an organic solvent or the like to sufficiently dissolve the liquid. Also, when trying to peel off the resin film stuck with the adhesive, the adhesive strength of the adhesive is large, and the strength of the resin film is relatively small, so it is difficult to peel it off. The adhesive needs to be dissolved.

An object of the present invention is to provide an anti-reflection resin composition capable of providing a sufficient practical strength and realizing an anti-reflection film which can be easily removed at the time of replacement, and an optical connector using the same. is there.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided an optical connector having a ferrule for holding an optical fiber and joining the end faces of the optical fiber by abutting each other. a resin composition, adhesive strength to the ferrule during curing is a resin composition in the range of ^{0.1kg / cm 2 ~10kg / cm 2} .

According to the present invention, if the adhesive strength to the ferrule at the time of curing is small, peeling is likely to occur at the time of attaching and detaching the optical connector, while if too large, it becomes difficult to remove at the time of replacement. Therefore, the adhesive strength is set to 0.1 kg / cm ^2-
By setting the pressure in the range of 10 kg / cm ² , sufficient practical strength can be obtained, and removal at the time of replacement becomes easy.

Further, the present invention is characterized in that the resin composition contains a curable resin and a wax, and that the adhesive strength during curing can be adjusted according to the mixing ratio of the wax.

According to the present invention, since the adhesive strength at the time of curing can be adjusted according to the compounding ratio of the wax, a resin composition having a desired adhesive strength can be easily realized.

Various resins can be used as the anti-reflection film. However, when a plastic resin is used, it is difficult to adjust the film refractive index to match the refractive index of the core of the optical fiber. Resistance to various chemicals decreases. Therefore, it is preferable to use a curable resin which is easy to adjust the refractive index and has excellent chemical resistance.

In the present invention, the curable resin is at least one of an epoxy resin, a silicone resin, an acrylic resin, and a urethane resin, and the wax is a higher fatty acid such as stearic acid or montanic acid or a derivative thereof. It is characterized by.

According to the present invention, the above resin has a relatively high refractive index, facilitates matching with an optical fiber, and has excellent chemical resistance. Therefore, the resin is suitable as an antireflection film for an optical fiber. is there.

Further, the wax has a good affinity with the resin, can adjust the adhesive strength of the resin in a wide range, and has little deterioration over time.

The present invention is also characterized in that the refractive index at the time of curing is substantially equal to the refractive index of the core of the optical fiber.

According to the present invention, since the refractive index at the time of curing is substantially equal to the refractive index of the core portion of the optical fiber, the reflection at the interface between the film and the optical fiber is reduced. Can be prevented.

Further, the present invention is characterized in that the viscosity before curing at a temperature of 23 ° C. is 1 Pa · S to 20 Pa · S.

According to the present invention, when forming an anti-reflection film on a ferrule, a method of applying a liquid resin to the ferrule and curing the resin is effective from the viewpoint of easy operation. At this time, if the viscosity is low, the resin is likely to flow, and may adhere to an extra place. On the other hand, when the viscosity is high, stringing or the like occurs, and it is difficult to make the film thickness uniform. Therefore, by setting the viscosity before curing in the range of 1 Pa · S to 20 Pa · S, workability is improved and a uniform light reflection preventing film can be easily formed.

The thickness of the anti-reflection film is preferably 5 to 20 μm, because if it is thin, it is easily broken at the time of connection of the optical connector, and if it is thick, loss due to light leakage from the connection occurs.

Further, the present invention is characterized in that the curable resin is an ultraviolet curable resin. According to the present invention, the curing time is generally shorter for the ultraviolet-curable resin than for the thermosetting resin, so that the working efficiency can be improved.

Further, the present invention is an optical connector having an anti-reflection film formed of the above resin composition.

According to the present invention, by forming the above-described anti-reflection film on the end face of the optical fiber, the interface reflection on the end face is reduced, and an optical connector with less connection loss can be realized. Further, removal and replacement of the light antireflection film are facilitated, and workability is improved.

[0023]

FIG. 1 is a perspective view showing an example of an optical connector to which a resin composition according to the present invention can be applied. FIG. 2 is a partial cross-sectional view showing the tip structure of the ferrule 18. FIG. 3 is an exploded perspective view showing a connection state between the optical connectors. Here, an MT type optical connector having a four-core structure holding four optical fibers 17 will be described as an example.
The present invention can be applied to an optical connector having a single core to three or five or more cores.

As shown in FIG. 1, the optical connector comprises a ferrule 18 for holding four optical fibers 17, a housing 12 for slidably holding the ferrule 18, and a detachable housing for slidably holding the housing 12. It is composed of an operation tube 13 and the like.

When the optical connectors are connected to each other, as shown in FIG. 3, when the operator grips the detachable operation tube 13 and inserts the housing 12 into the adapter 11, the housing 12 is detachably attached to the adapter 11. Is done.

A receiving frame (not shown) is integrally connected to the rear end of the housing 12, and the receiving frame and the holding frame 14 superimposed on the receiving frame are formed by a metal plate having a groove-shaped cross section. It is integrated with the surrounding rubber boots 15. The distal end of the optical cable 16 is gripped by the receiving frame and the holding frame 14, and the tension member (not shown) pulled out from the distal end of the optical cable 16 is held between the receiving frame and the holding frame 14. .

The multi-core optical fiber 17 extending from the end of the optical cable 16 in an exposed state is connected to a ferrule 18 slidably fitted between the housing 12 and the receiving frame, and these connection end faces are connected. The ferrule 18 faces the connection end face 19.

A spring force is applied to the ferrule 18 so as to project from the front end surface of the housing 12. A pair of positioning holes 21 are formed in the connection end face 19 of the ferrule 18 so as to be tightly fitted to a pair of positioning pins 20 whose tips project from the connection end face 19 of the other ferrule 18. , These positioning holes 21
When the positioning pins 20 are fitted to the optical fibers 17, the alignment of the pair of optical fibers 17 is accurately performed.

The arrangement state of the optical fibers 17 facing the connection end face 19 of the ferrule 18 is, as shown in FIGS. 1 and 2, a state in which the positioning pins 20 are arranged at predetermined intervals in the arrangement direction, that is, in FIG. It has become. An antireflection film 22 is formed on the connection end face 19 of the ferrule 18 so as to cover the tip end face of the optical fiber 17.

As shown in FIG. 3, when the distal ends of the housings 12 of the pair of optical connectors are respectively inserted into the adapter 11, the pair of positioning pins 20 projecting from the connection end face 19 of the ferrule 18 of the other optical connector. The distal end is fitted into a pair of positioning holes 21 opened in the connection end face 19 of the ferrule 18 of one of the optical connectors, and the relative positions thereof are accurately matched. When the housing 12 is inserted into the adapter 11 to a proper position, the connection end face 19 of the ferrule 18 of one optical connector and the connection end face 19 of the ferrule 18 of the other optical connector exert spring forces acting on these ferrules 18. End faces of the ferrules 18 of the pair of optical connectors.
9 are brought into close contact with each other with the elastic deformation of the antireflection film 22, so that the end faces of the optical fibers 17 face exactly.

The antireflection film 22 is made of an ultraviolet-curable epoxy resin mixed with stearic acid having a refractive index substantially equal to the core of the optical fiber.

For example, 0.1 part of anthracene and 0.1 part of benzenesulfonic acid are added to 100 parts of a mixture of bisphenol S type epoxy resin and bisphenol F type epoxy resin at a ratio of 1: 1. The anti-reflection film 22 is formed by dropping a few microliters of the epoxy resin onto the connection end face 19 of the ferrule 18 and then irradiating ultraviolet rays for about 10 seconds to cure the epoxy resin.

When a liquid resin is applied to the ferrule and cured, the viscosity before curing is preferably set in the range of 1 Pa · S to 20 Pa · S, so that workability is improved and a uniform light reflection preventing film is formed. It can be easily formed.

The thickness of the antireflection film 22 is set to fall within the range of 5 μm to 20 μm.

The adhesive strength of the anti-reflection film 22 to the ferrule 18 is adjusted by adjusting the number of stearic acid to the epoxy resin, and is 0.1 kg / cm ^{2 to} 10 kg / cm ² .
It is set to be within the range of cm ² . The method of measuring the adhesive strength is as follows: an antireflection film having a width of 10 mm, a thickness of 0.1 mm and a length of 5 cm is formed on a flat plate of 50 × 100 × 2 mm having the same surface roughness Rmax = 1 μm or less and made of the same material as the ferrule 18 A film of the same material as in Example 1 was formed, and the peel strength in the 90 ° direction was measured. The viscosity of the resin composition was measured according to JIS K7117.

Here, by changing the amount of stearic acid added to the epoxy resin as shown in (Table 1), the adhesive strength of the antireflection film 22 to the ferrule 18 was variously changed as shown in (Table 2) below. Was prepared, the coupling loss, the return loss, whether or not the film could be removed using an air gun with an air pressure of 5 kg / cm ² , and whether the antireflection film 22 was peeled off after being attached to and detached from the adapter 1000 times. The occurrence situation was evaluated.

[0037]

[Table 1]

[0038]

[Table 2]

As is apparent from these results, when the antireflection films of the present invention of Sample Nos. 1 to 4 were used, the average coupling loss was 0.4 dB or less and the return loss was 40%.
It showed good characteristics of more than dB. Further, the film could be easily removed using an air gun, and the antireflection film 22 did not peel off even after the optical connector was attached and detached 1000 times.

In the above description, an example in which an epoxy resin is used as the curable resin has been described.
Acrylic resin, urethane resin, etc. can be used.

Although an example in which stearic acid is used as the wax has been described, montanic acid or the like can be used.

[0042]

As described above, according to the present invention, the adhesive strength to the ferrule at the time of curing is 0.1 kg.
By setting the ratio in the range of / cm ^{2 to} 10 kg / cm ² , sufficient practical strength can be obtained and removal at the time of replacement becomes easy.

Further, since the adhesive strength at the time of curing can be adjusted in accordance with the mixing ratio of the wax, a resin composition having a desired adhesive strength can be easily realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an optical connector to which a resin composition according to the present invention can be applied.

FIG. 2 is a partial cross-sectional view showing a tip structure of a ferrule 18.

FIG. 3 is an exploded perspective view showing a connection state between optical connectors.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Adapter 12 Housing 13 Detachable operation cylinder 14 Holding frame 15 Rubber boot 16 Optical cable 17 Optical fiber 18 Ferrule 19 Connection end face 20 Positioning pin 21 Positioning hole 22 Anti-reflection film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsukasa Sakuraba 580-32 Takuji, Nagaura-shi, Sodegaura-shi, Chiba F-term (reference) 2H036 JA02 QA13 QA41 QA53 2K009 AA02 CC24 CC33 CC42 DD01 FF03 4J002 BG001 CD001 CK021 CP031 EF056 FD026

Claims (7)

[Claims] 1. An optical connector having a ferrule for holding an optical fiber and joined by abutting end faces of the optical fiber, wherein the resin composition is for forming an anti-reflection film on a joint surface of the ferrule. When the adhesive strength to the ferrule at the time of curing is 0.1
kg / cm ² resin composition ranges from to 10 kg / cm ^2. 2. The resin composition according to claim 1, wherein the resin composition contains a curable resin and a wax, and the adhesive strength at the time of curing can be adjusted according to the mixing ratio of the wax. 3. The curable resin is at least one of an epoxy resin, a silicone resin, an acrylic resin, and a urethane resin.
3. The resin composition according to claim 2, wherein the wax is a higher fatty acid or a derivative thereof. 4. The resin composition according to claim 1, wherein the refractive index at the time of curing is substantially equal to the refractive index of the core of the optical fiber. 5. The viscosity before curing at a temperature of 23 ° C. is 1
The resin composition according to claim 1, wherein the pressure is from Pa · S to 20Pa · S. 6. The resin composition according to claim 5, wherein the curable resin is an ultraviolet curable resin. 7. An optical connector comprising an antireflection film formed of the resin composition according to claim 1. Description: