JP2005077509A - Method for treating end surface of plastic optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for processing an end surface of a plastic optical fiber that suppresses a connection loss low only through a simple treatment and also suppresses an increase of the connection loss even if a connector is repeatedly attached and detached. <P>SOLUTION: In the method for processing an end surface of a plastic optical fiber, in which the end surface of the plastic optical fiber inserted and fixed in a ferrule is coated with polymer composition liquid to form a coating by setting the polymer composition, it is characterized in that the hardness of the coating material is harder than H in terms of a pencil scratch value prescribed in JIS-K-5400 and an increase in connection loss is ≤1 dB in 500-time attachment/detachment test prescribed in JIS-C-5961. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for treating an end face of a plastic optical fiber, and more particularly to an end face treating method for forming a coating film of a hard polymer on an end face of a plastic optical fiber.

  In recent years, with the advancement of information communication, the adoption of optical fibers as communication media is rapidly spreading. This is because the use of optical fibers has penetrated not only to conventional trunk lines but also to user terminals. In order to use the optical fiber at the user end, a method using a connector is simple and preferable. Specifically, a connector is used for connecting optical fibers and connecting an optical fiber and a device. Further, as an optical fiber, a plastic optical fiber having a relatively large diameter and having high flexibility and being easy to handle as a result has recently been widely used.

  However, optical fiber connection using this connector has problems of reducing connection loss and ensuring reliability. Here, securing reliability means that the value of connection loss does not increase as much as possible when the connector is repeatedly attached and detached. These problems are particularly important in a plastic optical fiber in which the end face of the optical fiber is relatively soft and the connection loss is likely to increase due to damage to the end face. Among the above-mentioned problems, a technique using a silicone gel pad has been proposed for reducing connection loss (see Patent Document 1).

JP-A-10-111429

  However, even if the technique described in Patent Document 1 is used, it is difficult to ensure reliability, and connection loss sometimes increases when the connector is repeatedly attached and detached. This increase in connection loss was often observed particularly when a plastic optical fiber was used as the optical fiber. Moreover, it was necessary to process the silicone gel pad in advance, and workability was not always high.

  Therefore, the present invention provides a plastic optical fiber end face processing method in which the connection loss is suppressed to a low level only by simple processing, and the increase in the connection loss is suppressed even when the connector is repeatedly attached and detached. The purpose is to do.

  The present invention is an end face treatment method in which a polymer composition liquid is applied to an end face of a plastic optical fiber inserted through and fixed to a ferrule, and the polymer composition is cured to form a coating film. The hardness of the film material is higher than H by the pencil scratch value specified in JIS-K-5400, and the increase in connection loss is 1 dB or less in the 500 times attachment / detachment test specified in JIS-C-5961. A method for treating an end face of a plastic optical fiber is provided. According to the end face processing method of the present invention, the connection loss is suppressed to a low level by only simple processing, and an increase in connection loss is suppressed even when the connector is repeatedly attached and detached. Moreover, if the coating film to be formed is sufficiently hard, even if foreign matter is present on the surface of the coating film, the influence thereof is small, and it is particularly difficult to be damaged. Moreover, it is preferable that the curing of the polymer composition is a crosslinking type curing because the durability of the coating film is high.

  Moreover, it is preferable that the polymer is polysilazane because a good coating film is easily formed. Furthermore, it is preferable that the plastic optical fiber has an acrylic resin as a constituent element in combination with the coating film.

  According to the end face processing method of the present invention, the connection loss is suppressed to a low level by only simple processing, and an increase in connection loss is suppressed even when the connector is repeatedly attached and detached.

  In the present invention, the plastic optical fiber is inserted and fixed to the ferrule. Here, the ferrule is used as one member of a connector (optical connector) for holding and fixing an optical fiber. As the ferrule, various materials such as metal, ceramics, glass, and resin are used. Examples of this metal include stainless steel, metallic nickel, nickel alloy and the like. Examples of ceramics include zirconia. Examples of the glass include crystallized glass. Examples of the resin include polyphenylene sulfide resin and liquid crystal resin. Among these materials, those made of resin are preferable because they are easy to process, have high molding accuracy, and are inexpensive.

  Examples of the plastic of the plastic optical fiber in the present invention include resins such as acrylic resins and fluororesins. As the resin used for the light guide portion of the plastic optical fiber, a resin in which fluorine atoms or deuterium atoms are introduced to reduce C—H bonds to reduce transmission loss in the near-infrared region from visible light is preferable. Specific examples of the resin used for the light guide unit include acrylic resins obtained by polymerizing monomers such as deuterated methyl methacrylate (MMA-d8) and trifluorodeuterated methyl methacrylate (MMA-d5F3). And fluororesins obtained by polymerizing monomers such as perfluororesin, perfluoro (butenyl vinyl ether) and perfluoro (dimethyldioxole). Examples of the resin used for the sheath (coating) portion include acrylic resins, styrene resins, ABS resins, EVA resins, nylon resins, and modified PPO resins.

  In the present invention, as the optical fiber made of plastic, an optical fiber having an acrylic resin as a constituent element is preferable because of good adhesion to a coating film described later. Here, having as a component means that the resin is used for the light guide part and / or the sheath (coating) part of the optical fiber. Specifically, examples of the plastic optical fiber include an optical fiber made of acrylic resin for the light guide portion and the sheath portion, an optical fiber made of fluororesin for the light guide portion and made of acrylic resin for the light guide portion, etc. It can be illustrated. In particular, the light guide part made of fluororesin and the sheath part made of acrylic resin have low transmission loss and excellent adhesion to the coating film, resulting in increased connection loss even after repeated attachment and detachment. It is preferable because it is difficult to do.

  The polymer composition liquid in the present invention is a liquid containing a polymer to be described later. This polymer composition liquid may be a liquid diluted with a solvent or a liquid not containing a solvent, but since a low viscosity is preferable from the viewpoint of workability, it is a liquid diluted with a solvent. Preferably there is. However, when a solvent is used, the polymer may be dissolved or dispersed in the solvent. Examples of the solvent include aromatic hydrocarbon solvents, alcohol solvents, ketone solvents, ester solvents, fluorine-containing solvents, and the like. However, examples of the aromatic hydrocarbon solvent include toluene and xylene. Examples of alcohol solvents include methanol, ethanol, isopropyl alcohol, n-butanol, and isobutanol. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of ester solvents include ethyl acetate, propyl acetate, butyl acetate, and isobutyl acetate. Examples of the fluorine-containing solvent include 1,3-dichloro-1,1,2,2,3-pentafluoropropane. Although the said solvent may be used individually by 1 type or may be used in mixture of 2 or more types, it is preferable to select what can melt | dissolve the polymer mentioned later arbitrarily by a homogeneous composition. When a solvent is used, it is preferable to select a solvent having a relatively high boiling point from the viewpoint that a uniform and smooth coating film can be easily formed. Specifically, the boiling point is preferably in the range of 80 to 150 ° C. .

  The polymer in the present invention is preferably transparent, less scattered, and has a predetermined hardness, and is preferably an inorganic polymer. Here, the polymer may be a reactive polymer or a non-reactive polymer, but is preferably a reactive polymer from the viewpoint of durability of the coating film. Here, the reactive polymer is composed of a polymer obtained by mixing two or more raw materials such as a combination of a main agent and a curing agent, or a one-component curable composition that is cured by ultraviolet light or moisture. This refers to a polymer, and means a polymer obtained by crosslinking type curing. Examples of the polymer include silica polymers, urethane resins, silicone resins, epoxy resins, (non-urethane) acrylic resins, and the like. Of these, examples of the silica-based polymer include polysilazane. Among these polymers, a silica-based polymer is preferable in that the connection loss is low and the durability of the coating film is good.

  Further, in the polymer composition liquid, if necessary, as additives (auxiliaries), stabilizers such as antioxidants and thermal polymerization inhibitors; leveling agents, antifoaming agents, thickeners, antisettling agents, Surfactants such as pigment dispersants, antistatic agents and antifogging agents; light absorbers such as near infrared absorbers and ultraviolet absorbers may be appropriately blended. In particular, when a lubricant such as silicone oil is blended, the obtained coating film is preferably protected. Specifically, the coating film can be prevented from peeling off from the end face of the optical fiber when the connector is replaced for a long time after long-term connection.

  Specific examples of the polymer composition liquid described above are preferably polysilazane xylene solutions and the like from the viewpoint of workability in forming a coating film. 5-100 mass% is preferable and, as for the solid content concentration of this polymer composition liquid, 5-30 mass% is more preferable. However, the solid content concentration of 100% by mass means a case where no solvent is used. The viscosity of the polymer composition liquid at 20 ° C. is preferably 1 to 10,000 mPa · s, and more preferably 1 to 100 mPa · s.

  In the present invention, the polymer composition liquid is applied to an end face of a plastic optical fiber, and the polymer composition is cured to form a coating film.

  As this coating method, a known coating method is employed. Specific examples include dip coating, flow coating, spray coating, bar coating, gravure roll coating, roll coating, blade coating, air knife coating, spin coating, and flow coating. The Among these, the preparation of a special tool is unnecessary, and the dip coating method or the spray coating method is preferable because of high workability.

  As the curing method, a curing method using heat and / or light is employed. Here, the curing includes so-called drying in which heat is applied to evaporate the solvent. However, in the present invention, the curing of the polymer is preferably a crosslinking type curing rather than a simple drying. That is, it is preferable to employ the reactive polymer described above and cure it with heat and / or light because the durability of the coating film is increased.

  When a thermosetting resin (reactive polymer) is used, the resin is cured by heating to a predetermined curing temperature. As a heat source at the time of curing by heat, a hot-air circulating oven, a halogen lamp, an infrared lamp, or the like can be used. Moreover, it is preferable to employ | adopt the hardening by an ultraviolet-ray for hardening by light. In this case, a xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a tungsten lamp, or the like can be used as the ultraviolet ray source.

  In the present invention, the polymer composition solution is applied as described above, and the polymer composition is cured to obtain a coating film. Here, the hardness of the coating material is a pencil scratch value defined in JIS-K-5400, is harder than H, preferably harder than 3H, and particularly preferably harder than 5H. However, the hardness of the coating material is a hardness based only on the polymer excluding the influence of the substrate. When the coating film to be formed is hard, even if a foreign substance is present on the surface of the coating film, the influence is small, and it is particularly difficult to be damaged. Here, the foreign matters are those having a size of about several μm to several tens of μm, and are mainly dust in the atmosphere. Even when these foreign substances are present on the surface of the coating film, the end face of the optical fiber itself is protected by the hard coating film. In addition, since the coating film is hard, the coating film itself is less likely to be scratched and has high scratch resistance.

  Specific examples of the end face processing method in the present invention will be described below. Insert and fix the plastic optical fiber through the ferrule, and assemble the connector. A plastic optical fiber is cut at the end face of the ferrule. The cut end face may not be polished, but it is preferable to perform the polishing. The end face of the optical fiber may be flush with the end face of the ferrule, and the end face of the optical fiber may protrude slightly. The end face is preferably polished by wet or dry using abrasive paper having two or three stages of roughness. A polymer composition liquid is applied to this end face. For example, a 10% by mass xylene solution of polysilazane is applied by a dip coating method.

  Prior to the application of the polymer composition liquid, the ferrule alone or both the ferrule and the optical fiber may be further pretreated. Specifically, the adhesion between the coating film and the ferrule can be further strengthened by applying a primer. Further, before applying the polymer composition liquid, another coating film (hereinafter referred to as a lower coating film) made of a softer material than the coating film obtained by curing the polymer composition may be provided. This lower coating film is preferably obtained by applying a polymer composition that provides a soft coating film and curing it. Specific examples of the polymer include urethane resins and silicone resins.

  After applying the polymer composition liquid, the polymer is cured by heating and / or light irradiation. The thickness of the coating film obtained by curing is preferably 0.2 to 50 μm. The application may be repeated only once or several times. When applying the polymer composition liquid, it is preferable that a coating film is not formed on a portion other than the end face of the ferrule, that is, the side face. This is because the coating film adheres to the side surface of the ferrule with high molding accuracy and does not adversely affect the insertion. Specifically, methods such as masking the side surfaces or wiping off the liquid immediately after applying the polymer composition liquid can be mentioned. By the above operation, a plastic optical fiber having an end face protected with a coating film is obtained.

  In the present invention, the following method was employed for performance evaluation. The connection loss is measured by a method based on the insertion loss evaluation method defined in 6.1 of JIS-C-5961. Further, the increase in connection loss due to attachment / detachment is measured by a method based on the evaluation method of repetitive operation (the repetitive number is 500) defined in 7.3 of JIS-C-5961.

  The details of the present invention will be described below by way of specific examples. As the plastic optical fiber, a refractive index distribution type plastic optical fiber (trade name: Lucina, manufactured by Asahi Glass Co., Ltd.) whose light guide part is made of fluororesin and whose sheath part is made of acrylic resin was used. A ferrule made of liquid crystal resin was used, and an SC connector was used as a connector. The connector was assembled, the end face of the optical fiber was cut, and the end face of the optical fiber was polished wet using three types of polishing paper of 9 μm, 1 μm, and 0.3 μm. When the end face of the optical fiber was observed using a microscope, it was a smooth end face. A connector having an optical fiber subjected to the above pretreatment on its end face was prepared and tested.

  Moreover, as a polymer composition liquid, the polymer composition liquid was prepared so that polysilazane N-V110 made from Clariant was diluted with xylene so that the solid concentration would be 10% by mass. In addition, when this polymer composition liquid was applied on a polyester (PET) film and cured to prepare a test piece on which a 10 cm × 10 cm × 0.6 μm coating film was formed, and the pencil scratch value was measured, 2H Met.

  The connection loss was evaluated as follows. The light source was AQ4215 (085) LED UNIT manufactured by Ando Electric Co., AQ2730OPM UNIT manufactured by Ando Electric Co., Ltd., and MODE SCRAMBLER MZ106C manufactured by Anritsu Co., Ltd. was used as the exciter. The insertion loss as connection loss was measured according to Method 4 (insertion method B) described in 6.1 of JIS-C-5961.

(Comparative Example 1)
The attachment / detachment test was performed without applying the polymer composition liquid to the connector having the pretreated optical fiber. The connection loss before the detachment test was 0.5 dB, the connection loss after the test was 1.5 dB, and the connection loss increased by 1.0 dB.

(Example 1)
The polymer composition liquid was applied once to the end face of the ferrule of the connector having the pretreated optical fiber (the end face of the optical fiber was also treated) by the dip coating method. After standing at room temperature for 1 hour (room temperature drying), the polymer was cured for 24 hours in a humid heat oven with a humidity (RH) of 95% and a temperature of 60 ° C. to form a coating film. The connection loss before the detachment test was 0.2 dB, the connection loss after the test was 0.3 dB, and the connection loss increased by 0.1 dB.

The present invention is applied to the end face processing method of the plastic optical fiber, and the connection loss is suppressed to a low level only by simple processing, and the increase in the connection loss is suppressed even when the connector is repeatedly attached and detached, This processing method is suitable for a connector that is frequently attached and detached.

Claims (4)

  An end face treatment method for forming a coating film by applying a polymer composition liquid to an end face of a plastic optical fiber inserted and fixed in a ferrule, and curing the polymer composition. Characterized in that it is harder than H with a pencil scratch value specified in JIS-K-5400, and an increase in connection loss is 1 dB or less in a 500 times attachment / detachment test specified in JIS-C-5961. An end face processing method of an optical fiber.   The method for treating an end face of a plastic optical fiber according to claim 1, wherein the curing of the polymer composition is a crosslinking type curing.   The method for treating an end face of a plastic optical fiber according to claim 1 or 2, wherein the polymer is polysilazane. 4. The method of treating an end face of a plastic optical fiber according to claim 1, wherein the plastic optical fiber has an acrylic resin as a constituent element.