JPH01503A - Method for manufacturing flexible optical waveguide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) This invention uses a transparent rubber-like elastic body with a high refractive index.

A) Regarding a method for manufacturing a flexible optical waveguide using a rubber-like elastic material with a low refractive index as a cladding, in particular, it is possible to effectively prevent scattering loss of light rays and others at the boundary between the core and the cladding. This sufficiently improves optical transmission characteristics.

(Prior Art) A conventionally known manufacturing method for this type of flexible optical waveguide is disclosed in, for example, Japanese Unexamined Patent Publication No. 61-259202.

In this manufacturing method, liquid polymers for forming a core and a cladding are made to flow down from a concentric nozzle with the liquid polymer for forming the core as an inner layer and the liquid polymer for forming a cladding as an outer layer, and during this flow, they are Both liquid polymers are simultaneously vulcanized by irradiation with radiation or ultraviolet rays, or by heating. According to this method, a long elastomeric optical fiber having at least the core with rubber-like elastic properties is produced.

(Problem to be Solved by the Invention) However, in such conventional technology, the liquid polymer for forming the core and the liquid polymer for forming the cladding are co-extruded from concentric nozzles, and both of these polymers are Since they are liquids, there is a problem that they mix with each other during flowing down, making the interface between the core and cladding unclear, and the flowing speed of both liquid polymers is affected by the gravity acting on them. To prevent this, both liquid polymers were rapidly vulcanized at high temperatures to prevent the problem that precise control of the final diameter is virtually impossible as the effect is faster than the extrusion rate. In some cases, thermal deterioration occurs in the core and cladding, and non-uniform vulcanization of the core occurs due to a large temperature difference between the inner and outer parts in the radial direction.
There was a problem in that it was not possible to manufacture optical fibers with excellent transparency. − Also, here, if the viscosity of both polymers to be coextruded is increased, the interface between the two polymers will have a
In addition to unevenness in the circumferential direction due to the surface roughness of each nozzle, unevenness in the longitudinal direction occurs due to changes in the extrusion speed. , since it brings about radiation waves into the cladding and also brings about mode conversion, there is a problem that a coupling phenomenon between modes occurs due to scattering loss and mode conversion, resulting in an increase in optical transmission loss.

The present invention advantageously solves the problems of the prior art by sufficiently preventing intermingling of the core and cladding materials, allowing for control of the final diameter, and reducing the heat dissipation of the core and cladding. In addition to preventing deterioration, it also provides excellent transparency of the core, and further improves the interface between the core material and the cladding material, or more precisely, the interface between the coating material and the cladding material located outside the core material. The present invention provides a method for manufacturing an optical waveguide that can sufficiently improve optical transmission characteristics by making the cladding sufficiently smooth to effectively prevent the generation of radiation waves in the cladding and mode conversion. be.

(Means for Solving the Problems) The method for manufacturing a flexible optical waveguide of the present invention includes extruding a transparent core material from a nozzle, and applying a method to A liquid, low-viscosity transparent coating material is applied by an appropriate method such as dipping, spraying, or smearing, and then the transparent core material and the transparent coating material, or only the transparent coating material, are vulcanized by heating. Also, a liquid cladding material is applied to the peripheral surface of the transparent coating material in the same manner as described above, and this cladding material is
It consists of vulcanization by irradiation with ultraviolet rays, radiation, or electron beams, or by heating.

Here, the transparent core material can also be constructed by mixing a transparent base material with transparency particles having a refractive index substantially equal to the refractive index of the transparent base material.

(Function) According to this method, only the core material is extruded from the nozzle, and since the core material is vulcanized and hardened before applying the cladding material, there is a possibility that it will mix with the cladding material. This is not the case at all, and because of the early vulcanization of the core material, elongation of the core material due to its own weight is effectively prevented, making it extremely easy to control the core diameter.

Also, by starting the vulcanization of the core material early enough, it can be done slowly and at relatively low temperatures, which prevents thermal degradation of the core and also allows its radial Sufficiently homogeneous vulcanization can be carried out over the entire area. Note that similar low-temperature vulcanization can also be performed on the cladding material, and thereby thermal deterioration of the cladding can also be sufficiently prevented.

Here, when the transparent core material is constructed by mixing transparent particles having a refractive index substantially equal to the refractive index of the transparent base material to increase the viscosity of the transparent core material, , the change in the core diameter due to the effect of its own weight will be more effectively prevented, and the diameter of the core material can be made more uniform over its entire length under high productivity, and the core Diameter control can be made easier.

In addition, here, after extruding the transparent core material from the nozzle, a low-viscosity transparent coating material is applied to the circumferential surface of the transparent core material, thereby eliminating irregularities in the circumferential direction and length direction that occur on the circumferential surface of the transparent core material. , can be almost completely compensated for by a transparent coating material, and the transparent coating material can be applied immediately after its application to the core material.
By vulcanizing it together with the core material or alone, it is possible to prevent the low-viscosity transparent coating material from flowing down or dripping, and to make the outer peripheral surface sufficiently smooth. Reliable adhesion to the core material can be achieved.

Therefore, according to this, it is preferable to use a transparent coating material having a refractive index equal to that of the transparent core material to almost completely compensate for the irregularities on the circumferential surface of the core material, and to make the adhesion surface of the cladding material an optically smooth surface. It can be done.

Furthermore, by applying the cladding material to the circumferential surface of the transparent coating material by coating, it is possible to reliably prevent the occurrence of unevenness of the cladding material, especially on the inner circumferential surface. The interface with the transparent coating material can also be a smooth surface depending on the smoothness of the peripheral surface of the transparent coating material.

Therefore, in the flexible optical waveguide manufactured by this method, the interface between the transparent coating material and the cladding material is sufficiently clear and smooth, so that light radiation, mode conversion, etc. on that surface are prevented. This can be effectively prevented, and the optical transmission characteristics can be sufficiently improved.

(Example) The present invention will be explained below based on illustrated examples.

FIG. 1 is a route map illustrating an embodiment of the present invention.

In the figure, reference numeral 1 denotes an extrusion device, which functions to extrude transparent core material 3 from a nozzle 4, here downward, based on the rotational movement of a screw 2.

Note that the extrusion direction of the transparent core material 3 can also be upward or lateral, diagonally upward or downward.

Here, the transparent core material 3 extruded from the nozzle 4 is
In order to maintain the core material 3 in a predetermined size and shape, it is preferable that the core material 3 has a viscosity that does not cause flow, deformation, etc. until it is vulcanized.
When expressed in terms of plasticity, it is preferable that the Williams plasticity is 50 to 1000.

Further, examples of such transparent core material 3 include chloroprene rubber, butadiene rubber, isoprene rubber, silicone rubber,
Synthetic rubbers such as acrylic rubber, urethane rubber, ethylene propylene rubber, ethylene propylene terpolymer, and epichlorohydrin rubber can be used.

By the way, the transparent core material 3 mentioned here has a transparent base material,
It can also be configured by mixing transparent fine particles having a refractive index substantially equal to the refractive index, in which case,
As the material for the transparent base material, any one can be selected from the various materials for the transparent core material mentioned above, and as the weighing material for the transparent fine particles, the refractive index of the material and the refractive index of the transparent base material can be selected. A material having a difference of preferably 0.01 or less,
For example, a material selected from inorganic materials such as glass, silica, and quartz powder, and organic materials such as silicone polymers, acrylic polymers, polystyrene, and silicone rubber can be used. Among these, when using dry silica, the particle size is extremely small relative to the wavelength of light, and the amount of impurities is extremely small, so it is possible to produce a transparent core material 3 with excellent optical properties. Yes, in addition,
By mixing a small amount, the flow characteristics of the transparent core material 3 can be increased (
It can be changed. Further, it is preferable to subject such transparent fine particles to silicone treatment or other appropriate surface treatment in order to improve their dispersion within the transparent base material. In addition, these transparent fine particles can be mixed into the transparent base material in the form of a powder or in the form of a paste.In particular, when mixing in the form of a powder, it is recommended to Processing aids such as silazane can also be added.

Here, it goes without saying that the blending ratio of the transparent base material and the transparent fine particles can be appropriately selected in relation to the required viscosity of the transparent core material 3, but it is preferable that the transparent core material 3 In the extrusion step, a blending ratio is selected such that the viscosity exhibits optimal flow characteristics, which is expressed as plasticity, and has a William plasticity of 50 to 1000. For this purpose, when dry silica is used as the transparent fine particles, the dry silica is preferably 2 to 50 parts, more preferably 10 parts by weight, per 100 parts by weight of the transparent base material.
Mix in ~30 parts.

Then, under the combination ratio specified in this way,
The transparent fine particles can be mixed into the transparent base material by using any one of a mill, a roll, a Banbury mixer, etc., or by using two or more of them in combination.

By the way, as a transparent base material, the phenyl group content is 5 to 4.
0% and a viscosity of 1 million to 50 million cP, and as the transparent fine particles, silicone polymer fine particles having the same refractive index as the transparent base material were selected, and the blending ratio of the transparent base material and the transparent fine particles was adjusted. 10: 10-1
When the ratio was 0:3, it was possible to extrude a transparent core material 3 with excellent transparency and dispersibility of transparency particles, and also with extremely excellent dimensional stability.

Next, the transparent core material 3 extruded from the nozzle 4 as described above is passed through the coating tank 5 to make the liquid, low-viscosity transparent coating material 6 stored in the coating tank 5 transparent. By applying the core material 3 and subsequently passing it through a heating furnace 7, the transparent core material 3 and the transparent coating material 6 are vulcanized at relatively low temperatures and with sufficient radial homogeneity.

Therefore, here, the unevenness formed by the nozzle 4 is formed on the circumferential surface of the transparent core material 3 by the coating material 6.
The outer surface of the coating material 6 can be made optically sufficiently smooth by rapid vulcanization.

Here, the difference between the refractive index of the liquid, low-viscosity transparent coating material 6 and the refractive index of the transparent core material 3 is 0.
01 or less, and more preferably, it is a material of the same quality as the transparent core material 3 and has a lower degree of polymerization than that.

Examples of such coating material 6 include synthetic rubbers such as chloroprene rubber, butadiene rubber, isoprene rubber, urethane rubber, silicone rubber, acrylic rubber, ethylene propylene rubber, ethylene propylene terpolymer, and epichlorohydrin rubber, with a viscosity of 1 to 200 P. Liquid rubber can be selected.

Here, from among the above-mentioned materials, the transparent core material 3 has a phenyl group content of 5 to 35
% of dimethyldiphenylpolysiloxane or phenylmethylpolysiloxane with William plasticity of 50~
1000, the low-viscosity transparent coating material 6 is a liquid silicone rubber made of dimethyldiphenylpolysiloxane or phenylmethylpolysiloxane with a viscosity of 1 to 200P, with a phenyl group content of By selecting the same material as the core material 3, a vulcanized structure 8 of the core material 3 and the coating material 6, which had the same refractive index and excellent transparency and heat resistance, was obtained.

In addition to this, when the vulcanization mechanism of the silicone rubber as the transparent core material 3 is an addition type, the amount of vulcanization catalyst can be reduced to a very small amount, and the amount of reaction by-products can also be reduced to a very small amount. Therefore, the transparency of the structure 8 is significantly improved.

These are based on a transparent base material made of silicone rubber made of dimethyldiphenylsiloxane or phenylmethylpolysiloxane with a phenyl group content of 5 to 40%, and a transparent base material made of silicone polymer fine particles with a refractive index equal to that of the transparent base material. The same is true when the transparent core material 3 is mixed with fine particles, and the transparent coating material 6 is a liquid silicone rubber made of phenylmethylpolysiloxane with a viscosity of 1 to 200 P, and the transparent base material has a phenyl group content. By selecting materials equal to , the core material 3 and the coating material 6 have excellent adhesion, have the same refractive index, and have excellent transparency and heat resistance.
A vulcanized structure 8 was obtained.

As mentioned above, the application of the transparent coating material 6 to the transparent core material 3 can be performed not only before the transparent core material 3 is vulcanized as shown in the figure, but also after its vulcanization. In order to improve the adhesive strength between the core material 3 and the coating material 6, it is preferable to use the illustrated method. In addition, as the vulcanization means here, an electric furnace,
In addition to heating furnaces such as heating steam furnaces, hot liquid furnaces, and hot blast furnaces, ultraviolet ray, radiation, or electron beam irradiation devices can also be used.

After that, the thus formed vulcanized structure 8 of the core material 3 and the coating material 6 is passed through a coating tank 10 that stores the cladding material 9, so that the vulcanized structure 8 formed in this manner is A cladding material 9 is applied to the circumferential surface of the coating material 6, and then it is heated in a heating furnace 1.
1, the cladding material 9 is vulcanized, and as a result, a transparent rubber-like elastic body with a high refractive index, in other words, a rubber-like material with a low refractive index is formed with the vulcanized structure 8 as a core. A flexible optical waveguide 12 whose cladding is an elastic body is provided.

Here, the manufactured flexible optical waveguide 12 is wound onto a winding drum 14 via a pulley 13.

According to this, the cladding material 9 is applied to the optically sufficiently smooth outer surface of the coating material 6 in a state that corresponds exactly to it and is cured, so that in the optical waveguide here, the cladding material 9 is cured. Optical transmission loss caused by unevenness on the interface between the finished structure 8 and the cladding material 9 can be effectively prevented.

Here, the cladding material 9 that forms the cladding by vulcanization includes liquid silicone rubber, liquid fluororubber,
Among liquid rubbers such as liquid butadiene rubber and liquid ethylene propylene rubber, those having a lower refractive index than the structure 8 can be selected and used. When type dimethylsiloxane is used, the vulcanization time can be shortened and the coating speed can be increased.In this case, the vulcanized structure 8, especially its transparent coating material 6, can also be made of silicone rubber. In some cases, the adhesive strength between the structure 8 and the cladding material 9 increases, resulting in an optical waveguide with excellent mechanical strength.

Further, here, if the structure 8 is completely vulcanized when applying the rad material 9 as described above,
- For boat fishing, it is difficult to vulcanize and bond vulcanized rubber and unvulcanized rubber, so depending on their materials, it may not be possible to vulcanize and bond the two sufficiently. When an adhesive is interposed, the adhesive layer deteriorates the optical properties of the optical waveguide, so the length and temperature of the heating furnace 7 and the core are adjusted so that the structure 8 is in a semi-vulcanized state. Preferably, the extrusion speed of the material 3 is determined and the cladding material 9 is applied onto the semi-vulcanized structure.

Although the present invention has been described above based on the illustrated examples, a primary coat material, a buffer coat material, a cover material, etc. are provided on the outside of the cladding material 9 for the purpose of protecting and buffering against mechanical shock, removing stray light, etc. Coating is also possible.

Below, a main light transmission test of the flexible optical waveguide manufactured by the method of the present invention will be explained.

[Examination example summer]

Addition reaction type phenylmethyl silicone raw rubber (phenyl foundation content 25% 1 polymerization degree approximately 5000) as core material
) was extruded from a 1.8 φ nozzle at a speed of 5 m/win, and a coating material made of addition reaction type phenylmethyl silicone rubber (25% phenyl radical content, 30P viscosity) was applied thereto, and then a long A vulcanized structure of core material and coating material is obtained by vulcanizing it in a 1.0 m heating furnace (temperature 200° C.), and the structure is then coated with addition-reacted dimethyl silicone rubber. Apply a cladding material consisting of (viscosity 30P),
Thereafter, a flexible optical waveguide was manufactured by vulcanizing it in a heating furnace with a length of 1.2 m and a temperature of 200°C.

The diameter of the optical waveguide thus obtained was 2.2φ, and its white light transmittance was 90% per 1 m.

[Test example ■]

As a transparent base material, addition reaction type phenylmethyl silicone rubber (phenyl group content 12%, viscosity 10 million cP)
At the same time, dry silica with the same refractive index as the transparent base material was selected as the transparency particle, and 20 parts of the dry silica (particle size 5I11μ) was uniformly mixed with phenylmethyl silicone rubber using a mill and a roll. The transparent core material obtained by dispersing the
Addition reaction type fermethyl silicone rubber (phenyl group content 12%, viscosity 100
After applying a transparent coating material consisting of 0 cP),
A vulcanized structure of core material and coating material is obtained by vulcanizing it in a 1.0 m long furnace (temperature 300'C), and then the structure is treated with addition-reacted dimethyl A cladding material made of silicone rubber (viscosity 3000cP) is applied, and then the length is 1-
A flexible optical waveguide was manufactured by vulcanization in a heating furnace at an Om % temperature of 200°C.

The diameter of the optical waveguide thus obtained is approximately 1.2 m.
m, and its white transmittance was 55% per 1 m.

(Effects of the Invention) Therefore, according to the present invention, by extruding only the core material from the nozzle and vulcanizing the core material before applying the cladding material, mixing of the core material and the cladding material is prevented. By vulcanizing the core material early before or after applying the coating material, it is possible to reliably prevent the elongation of the core material due to the influence of gravity, and to make the interface between the two sufficiently clear. It is possible to effectively prevent thermal deterioration of the core and achieve the desired core dimensions by slowly vulcanizing the core material at a relatively low temperature. can significantly increase the transparency of

And here also, the application of the transparent coating material can completely compensate for the circumferential and longitudinal irregularities of the transparent core material extruded from the nozzle, and the early vulcanization of the coating material can completely compensate for the circumferential and longitudinal irregularities of the transparent core material extruded from the nozzle. The outer peripheral surface, in other words, the surface to which the cladding material is attached, can be made sufficiently smooth, and by applying the cladding material to the peripheral surface of the coating material, it is possible to prevent unevenness from occurring on the inner peripheral surface of the cladding material. The interface between it and the coating material is
Since the smooth surface can be formed to correspond to the outer peripheral surface of the coating material, optical transmission loss caused by unevenness of the boundary surface can be extremely effectively eliminated.

Moreover, when the transparent core material is constructed by incorporating transparency particles having a refractive index substantially equal to the refractive index of the transparent base material to improve the flow characteristics of the transparent core material, To more effectively prevent the core material extruded from the nozzle from elongating under the influence of gravity, so that the core diameter can be made sufficiently uniform over its entire length and can be controlled with higher precision. Can be done.

[Brief explanation of drawings]

FIG. 1 is a route map illustrating an embodiment of the present invention. 1... Extrusion device 3... Transparent core material 4.
... Nozzle 6 ... Transparent coating material 7.11 ... Heating furnace 8 ... Vulcanized structure 9 ... Clad material Engineering 2 ... Flexible optical waveguide patent applicant Bridgestone Corporation

Claims (1)

[Claims] 1. When manufacturing a flexible optical waveguide having a core made of a transparent rubber-like elastic material with a high refractive index and a cladding made of a rubber-like elastic material with a low refractive index, the transparent core material is passed through a nozzle. a step of extruding, a step of applying a liquid low viscosity transparent coating material to the extruded transparent core material, and a step of vulcanizing each of the core material and the coating material;
A method for manufacturing a flexible optical waveguide that combines the steps of applying a liquid cladding material to the peripheral surface of a transparent coating material and vulcanizing the cladding material. 2. Manufacturing the flexible optical waveguide according to claim 1, wherein the transparent core material is formed by mixing transparent fine particles having a refractive index substantially equal to the refractive index of the transparent base material into a transparent base material. Method.