JP2007079603A - Method of manufacturing glass optical fiber strand for fiber grating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a highly reliable glass optical fiber strand for a fiber grating having excellent adhesiveness of a coating and favorable removing property of the coating. <P>SOLUTION: The optical fiber strand (1) has a primary coating layer (3) and a secondary coating layer (4) applied on a glass optical fiber bare wire (2). The glass optical fiber bare wire is coated with the primary coating layer (3) made of a resin composition containing a silane coupling agent of 0.05 to 5 mass% and having adhesion strength with glass of 5 to 20 N/m and tensile strength ≥0.5 MPa at an elongation percentage of 50% so that a coating of an intermediate part of the optical fiber strand is removed during writing of the grating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical fiber for a fiber grating, which is used for writing a grating by removing an intermediate coating portion. More specifically, the present invention has high reliability and improved coating removal performance. The present invention relates to a method of manufacturing a glass optical fiber for a fiber grating.

  An optical fiber grating is one in which a predetermined region of the glass part of an optical fiber is irradiated with light of a predetermined wavelength from the side to change the refractive index of the core or a predetermined region of the core and the cladding, and travels in the optical fiber. It reflects the light portion of a specific wavelength in the light to be transmitted. With the progress of optical fiber communication technology in recent years, the complexity of networks and the multiplexing of signal wavelengths have progressed, and the importance of optical circuit elements has increased as the system configuration has become more sophisticated. A fiber-type element as one of the general configurations of optical circuit elements has advantages such as small size and low insertion loss, and easy connection with optical fibers. Demand is growing as an important and effective fiber type element. The predetermined wavelength used for grating writing is generally in the ultraviolet region of 240 to 270 μm, and writing is performed by irradiation with an argon laser or a carbon dioxide gas laser.

In general, a glass optical fiber is coated immediately after spinning in order to prevent deterioration of the strength of the optical fiber during manufacture. In general, there are 0.9 mm diameter strands coated with silicon / nylon and 0.25 mm diameter strands coated with UV curable urethane acrylate resin. For this reason, 0.25 mm diameter strands coated with an ultraviolet curable resin are the mainstream. A coating layer of 0.25 mm diameter wire coated with an ultraviolet curable resin generally comprises two layers, a primary coating layer 3 and a secondary coating layer 4 as shown in FIG. 1, and the primary coating layer is influenced by external force. A soft resin having a Young's modulus of 1 to 10 MPa is used so as not to be transmitted to the glass portion, and a hard resin having a Young's modulus of 100 to 1000 MPa is used for the secondary coating layer for protection.
In addition, the coating layer of the 0.25 mm diameter wire covered with the ultraviolet curable resin is further made from the same urethane acrylate resin having a thickness of about 5 μm on the outer periphery of the secondary coating layer 4 in order to make the identification easier. It often has a colored layer. Although the colored layer is thin, a hard resin having a Young's modulus of 1000 MPa or more is usually used, including the meaning of protecting the fiber strand.

The application in which glass optical fiber is most frequently used is an optical fiber cable. In the cable application, since it is laid in various environments, it is essential that the adhesion of the coating resin, particularly the primary coating layer, to the glass is large. This is because a transmission loss occurs when peeling occurs at the interface between the glass fiber and the primary coating layer, or when the cable sheath is damaged and water enters, the adhesion between the glass fiber and the primary coating layer is reduced. This is to prevent problems such as water entering the interface and causing separation to increase transmission loss.
Under such circumstances, the interface adhesion between the optical fiber primary coating layer and the glass fiber is large, and generally speaking, at the sheet evaluation level, a material having an interface adhesion with the glass of 30 N / m or more is generally used. It has been.

  When producing the optical fiber grating, as shown in FIG. 2, the intermediate portion of the coating layer of the optical fiber (primary coating layer 3 and secondary coating layer 4 and, in the case of a dyed wire, a colored layer) is removed to remove glass. Part 2 needs to be exposed. This is because when writing is performed by irradiating a laser in a coated state, writing may not be possible because the transmittance of the resin in a predetermined wavelength region is very low, and in addition, the resin may burn and deteriorate. It is because it has. In recent years, a resin that can be written by irradiation from the top of the coating has been developed. However, in this case, only the condition that the output level of the laser itself is lowered and the irradiation is performed for a longer time can be taken. In addition, with a resin having a relatively high transmittance such as silicone, it is not possible to maintain excellent productivity such as coating at the time of glass spinning at a high linear velocity, as in the case of a UV curable resin coating material. There is a problem. After all, the method of writing the grating after removing the UV curable resin coating material once coated is the most efficient.

  However, such a method has a problem that the surface of the optical fiber is damaged when the coating is removed, resulting in a decrease in mechanical strength and a decrease in reliability. As described above, the resin of the coating layer is made of an ultraviolet curable crosslinked resin and cannot be easily removed. Therefore, as a method for removing the coating on the intermediate part, a part of the coating is removed with a razor blade or the like so that it is not directly applied to the glass part, and then the organic solvent is immersed and swollen and peeled off. Has been done. In this method, the adhesion of the primary coating material to the glass is greatly affected. In other words, if the adhesion of the primary coating material to the glass is large, the coating material will not peel off even if the coating material swells, and the coating material cannot be removed. This damages the surface of the glass portion and reduces the breaking strength of the fiber. Therefore, from the viewpoint of removing the covering material, it is important that the adhesion with the glass is small.

Furthermore, in recent years, high reliability has been required for optical fiber strands used in optical components such as fiber gratings. That is, a fiber having high screening characteristics has been demanded. The screening level of the optical fiber used for the optical fiber cable or the like is 0.5 to 1%, and even this level is a level that can sufficiently withstand the long-term installation environment. The same screening level fiber is used for optical components. However, in recent years, higher reliability with a screening level of 2% or higher has been demanded.
In order to maintain the reliability of the fiber, the screening is an operation in which a portion corresponding to a predetermined elongation of the fiber is rewound and a portion having a low breaking strength of the fiber is cut in advance. This predetermined elongation is called a screening level. Therefore, the higher the value, the greater the tension, and the higher the reliability.
The fiber breakage during screening occurs mainly due to the glass part, but it is also affected by the following.

  In general, when the adhesion between the glass portion and the primary coating layer is small, the higher the screening level, the easier the peeling at the glass portion / primary coating interface occurs, the glass portion is damaged, and the breaking strength decreases. That is, problems such as a reduction in screening characteristics and a decrease in breaking strength even after passing screening occur. On the other hand, if the adhesion between the glass portion and the primary coating layer is high, the screening characteristics are good, but the peeling characteristics are poor, making it unsuitable for optical parts such as fiber gratings.

  In view of the above circumstances, the present invention has an object to provide a method for manufacturing an optical fiber for a fiber grating that ensures a good peeling property of a coating layer, and further has a high screening level and excellent reliability. To do.

In removing the optical fiber intermediate coating, the ease of removal of the coating material and the optical fiber breaking strength after removal depend on the adhesion between the optical fiber glass part and the primary coating, and the smaller the adhesion, the more the coating is removed. As a result of the study by the present inventors, it was found that the ratio at which the breaking strength is easy to decrease is small. However, if the adhesion between the glass and the primary coating material is small, the higher the screening level, the easier the separation occurs at the glass part / primary coating layer interface, which damages the glass part during screening and degrades mechanical properties. Arise.
As a result of intensive studies, the present inventors have developed an optical fiber using a primary coating layer comprising a resin composition containing a specific amount of a silane coupling agent and having a specific range of adhesion to glass. And found that a good screening level can be secured.
Furthermore, as a result of intensive studies, it has been clarified that a good coating removability can be secured when the tensile strength at a certain elongation rate of the primary coating layer is a specific level or more.
In addition, the present inventors can ensure a high screening level when the glass transition temperature of the secondary coating material is lower than a specific temperature, and further, when the glass transition temperature of the outer colored coating material is a specific temperature or lower. It became clear as a result of earnest examination.

Based on these findings, the inventors have made the present invention.
That is, the present invention
(1) A method of manufacturing an optical fiber in which a primary coating layer and a secondary coating layer are provided on a glass optical fiber bare wire, wherein the coating of an intermediate portion of the optical fiber strand is performed when writing a grating. As the primary coating layer, the primary coating layer contains 0.05 to 5% by mass of a silane coupling agent, the adhesion with glass is 5 to 20 N / m, and the tensile strength at an elongation of 50% is A method of manufacturing an optical fiber for a fiber grating, comprising coating a bare glass optical fiber with a resin composition of 0.5 MPa or more,
(2) Production of an optical fiber for a fiber grating according to (1), wherein a resin composition having a glass transition temperature of less than 110 ° C. is coated on the primary coating layer as the secondary coating layer. Method,
(3) The optical fiber is a colored optical fiber in which a colored layer is further provided on the outer periphery of the secondary coating layer, and a resin composition having a glass transition temperature of 100 ° C. or lower is used as the colored layer. The method for producing an optical fiber for a fiber grating according to (1) or (2), wherein the outer periphery of the secondary coating layer is coated, and
(4) As the secondary coating layer, coating the primary coating layer with a resin composition containing an ultraviolet curable resin mainly composed of a polyether-based urethane (meth) acrylate having a double bond at the terminal. The manufacturing method of the optical fiber for fiber grating according to any one of (1) to (3),
Is to provide.

The glass optical fiber manufactured by the method of the present invention is excellent in reliability because of its high screening level, and there is almost no reduction in the breaking strength in the intermediate coating removal for writing the grating on the optical fiber. Excellent in properties. In particular, a fiber strand having a secondary coating layer or a colored layer made of a resin composition having a specific glass transition temperature is excellent in screening characteristics and can further increase the pull-out force.
Therefore, according to the optical fiber manufactured by the method of the present invention, an excellent grating-formed optical fiber with high reliability can be obtained.

A preferred embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a cross-sectional view showing an example of the configuration of an optical fiber manufactured by the method of the present invention. In the figure, an optical fiber 1 includes an optical fiber bare wire 2, a primary coating layer 3 coated on the outer periphery of the optical fiber bare wire 2, and a secondary coating layer 4 further coated thereon. ing. In addition, although not shown, in the case of a colored optical fiber, it is further composed of a colored layer on the outer periphery of the secondary coating layer. These are described in detail below.

(Bare optical fiber)
The bare optical fiber in the present invention refers to a glass fiber composed of a core and a clad, and examples thereof include a silica-based glass fiber. In the present invention, an ordinary SM (single mode) fiber can be used. In particular, a bare optical fiber in which hydrogen is dissolved in a glass fiber is advantageous because it is advantageous for writing a grating. The bare optical fiber used preferably has an outer diameter of 90 to 150 μm, and more preferably a normal 125 μm. For example, Tech. Dig. Fiber Communication 1994 Tul 1 p. J. Lemaire et. It can be produced according to the method described in al et al.
In this specification, the bare optical fiber is also referred to as a glass fiber, an optical fiber glass part, or simply a glass part.

(Primary coating layer)
The primary coating material for forming the primary coating layer is composed of an ultraviolet curable resin mainly composed of a polyether-based urethane (meth) acrylate having a double bond at the terminal, but is not particularly limited thereto. In addition, a reactive monomer having a double bond at the terminal (hereinafter sometimes referred to as a reactive diluent monomer) and a photopolymerization initiator may also be used as a diluent. Additives such as anti-aging agents, chain transfer agents, light stabilizers, silane coupling agents, polymerization inhibitors and sensitizers are added as necessary. Examples thereof include resin compositions described in Japanese Patent No. 1535199, Japanese Patent No. 2018841, Japanese Patent No. 2784339, Japanese Patent No. 2893135, and the like. These are preferably contained in the primary coating material in an amount of 40% by mass or more and less than 99.95% by mass.

The Young's modulus of the primary coating layer used in the present invention can be adjusted by changing the molecular weight of the polyether moiety in the resin composition or by selecting the type of reactive dilution monomer in the resin composition. For example, the Young's modulus can be reduced by increasing the molecular weight of the polyether moiety or by using a linear monofunctional reactive diluent monomer having a large linear molecular weight.
The primary coating material is applied to the bare optical fiber and cured by ultraviolet irradiation or the like, and is preferably coated to have an outer diameter of 180 μm to 200 μm to form a primary coating layer. In the present invention, the primary coating layer may be composed of multiple layers. The Young's modulus during curing is preferably 0.8 MPa to 10 MPa, and particularly preferably 1 MPa to 3 MPa. If the Young's modulus is too small, the coating layer is likely to be deformed by side pressure or the like, and if it is too large, loss increases due to the side pressure.

Although the primary coating material used for this invention contains 0.05-5 mass% of silane coupling agents, Preferably it is 0.1-3 mass%, More preferably, it contains 0.2-1 mass%. If it is less than 0.05% by mass, peeling tends to occur at the glass / primary coating layer interface in the screening test, and if it exceeds 5% by mass, the curability becomes poor. The silane coupling agent is not particularly limited. For example, an organic functional group such as γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, A type of silane coupling agent having both groups can be used, preferably γ-mercaptopropyltrimethoxysilane.
The silane coupling agent has an effect of enhancing the adhesion to glass, but the adhesion to glass can be controlled by the type of the reactive monomer as well as that. When a reactive monomer having a high Tg when a homopolymer is formed is blended, the viscoelasticity of the resin changes and the glass adhesion increases. By selecting such a reactive monomer having a high Tg of homopolymer (hereinafter referred to as an adhesive monomer) and changing its blending amount, it is possible to control the glass adhesive force.

Examples of the adhesion monomer include cyclohexyl methacrylate, dicyclopentenyloxyethyl acrylate, isobornyl acrylate, isobornyl methacrylate, tetrahydrofurfuryl acrylate, N-vinylpyrrolidone and the like. In addition to the glass adhesion, the reactive monomer can be added to adjust the resin viscosity. In addition to the adhesion monomer as mentioned above, a reactive monomer having a low homopolymer Tg is also included. In addition, there is no problem in blending a plurality of types. Examples of the reactive monomer having a low Tg of homopolymer include 2-ethylhexyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, tridecyl methacrylate and the like.
Thus, by adjusting the addition amount of the adhesive monomer, for example, a primary coating layer having a glass adhesive force as shown in Table 1 described later can be provided.

The intermediate peeling method is performed as follows.
Cut surfaces are inserted in the circumferential direction of the fiber using commercially available fiber strippers (Micro-Strip, KLEN TOOLS, Inc .: the inner diameter of the blade is 152 μm) at both ends of the coating removal section of the optical fiber. Next, the coating is inclined up and down in the longitudinal direction in the coating removal section by making an inclination of 50 degrees with respect to the longitudinal direction of the optical fiber and running between the two blades installed up and down at a distance of 155 μm. The glass part is exposed. Thereafter, the coating removal section is immersed in acetone subjected to ultrasonic waves. Finally, the covering resin not cut at the removal end is completely taken out with tweezers. The reason why the interval of 155 μm is maintained is to prevent the blade from directly contacting the glass.
By setting the inclination of the upper and lower blades to 50 degrees with respect to the fiber intermediate coating layer, the portion where the tip of the blade hits does not simply cut the resin, but the action of hooking and pulling the resin with the blade occurs. At the same time, the resin is cut. At this time, if the adhesion force at the glass / primary coating layer interface is small, the action of pulling the resin works, so that the coating layer is peeled off from the interface and the glass is exposed and the resin is cut and removed. . When the glass is exposed, acetone easily penetrates into the glass / primary coating layer interface, and the intermediate coating layer can be easily and completely removed.

In the present invention, the adhesion of the primary covering material to the glass is 5 to 20 N / m, preferably 5 to 18 N / m, and more preferably 8 to 15 N / m. If the adhesion of the primary coating material to the glass is less than 5 N / m, peeling tends to occur at the interface between the glass portion and the primary coating layer, making it difficult to ensure reliability. If it is higher than 20 N / m, the resin is cut without being peeled off from the glass and the glass is not exposed. If it is going to be exposed, it is necessary to narrow the gap between the blades, so that the glass is easily damaged and the breaking strength is reduced. .
In addition, the measuring method of glass adhesive force is as follows.
A primary coating material is applied onto an unused soda glass plate (manufactured by Suzuki Optical Co., Ltd .: main components SiO ₂ , CaO, Na ₂ O) whose surface has been wiped clean with alcohol or the like, and 100 mJ / cm ² in a nitrogen atmosphere. A sheet having a thickness of 200 μm is prepared. In that state, a 10 mm wide cut was made, the end was peeled from the glass, and the peel force (N / m) measured by a 90 ° peel test was taken as the glass adhesion force.

Furthermore, the action of pulling the resin with the blade is greatly affected by the elastic properties of the primary coating layer. When the elastic properties of the primary coating layer are small when the pulling action works, that is, when the tensile strength at an elongation rate of 50% is 0.5 MPa or less, the primary coating layer is cut before peeling from the glass, As a result, a part of the coating layer remains on the glass surface and the glass is not exposed.
The larger the elastic modulus of the primary coating layer, the more effective. However, a material having a tensile strength exceeding 1 MPa when stretched by 50% has a large Young's modulus, and as a result, the lateral pressure characteristics are lowered. From this point, it is preferable that the tensile strength at 50% elongation is 1 MPa or less.

(Secondary coating layer)
The secondary coating material forming the secondary coating layer is composed of an ultraviolet curable resin mainly composed of a polyether-based urethane (meth) acrylate having a double bond at the terminal, but is not particularly limited thereto. . In addition, a reactive dilution monomer having a double bond at the terminal and a photopolymerization initiator may also be used. Various additives such as a chain transfer agent, an antioxidant, a light stabilizer, a plasticizer, a polymerization inhibitor, a sensitizer, and a lubricant are added as necessary. Examples thereof include resin compositions described in Japanese Patent No. 2021130, Japanese Patent No. 2135130, Japanese Patent No. 2525177, Japanese Patent No. 2601699, and the like. These are preferably contained in the secondary coating material in an amount of 35 to 100% by mass.
As the secondary coating material, a resin composition having a glass transition temperature of less than 110 ° C. is preferably used, and a resin composition having a temperature of 100 ° C. or less is more preferably used. However, if the glass transition temperature is too low, the glass transition temperature is likely to be influenced by the environmental temperature, particularly the high temperature side. In the present invention, the glass transition temperature is more preferably 70 to 105 ° C, particularly preferably 80 to 100 ° C.

In the present invention, when the glass transition temperature of the secondary coating material is in the above range, the higher screening level can be secured for the following reason.
As the optical fiber coating material, a urethane acrylate ultraviolet curable resin having an unsaturated double bond is generally used, and the unsaturated double bond portion is polymerized and cross-linked by ultraviolet irradiation. The polymerization reaction is an exothermic reaction and cures while expanding due to the relationship of the linear thermal expansion coefficient of the resin. It is said that the fiber temperature usually rises above 100 ° C. due to the exothermic reaction. When the curing by the polymerization reaction is completed, conversely, due to the relationship of the coefficient of linear thermal expansion, it shrinks by cooling to room temperature.
Usually, as the primary coating material, one having a Young's modulus of 1 to 10 MPa and a glass transition temperature of about 0 ° C. is generally used. On the other hand, as the secondary covering material, one having a Young's modulus of about 100 to 1000 MPa and a glass transition temperature of 110 ° C. or higher is generally used.
In addition, as the colored covering material, one having a Young's modulus of usually 1000 MPa or more and a glass transition temperature exceeding 100 ° C. is generally used.
Since the resin state changes with the glass transition temperature as a boundary, the linear thermal expansion coefficient also changes. That is, if it is lower than the glass transition temperature, the linear thermal expansion coefficient becomes smaller, and if it is higher than the glass transition temperature, the linear thermal expansion coefficient becomes larger.

For this reason, the primary coating material and the secondary coating material are cured while linearly expanding due to the polymerization exothermic reaction, but in the subsequent cooling to room temperature, the primary coating layer has a uniform glass transition temperature of about 0 ° C. Although the secondary coating material has a high glass transition temperature, it follows the shrinkage of the primary coating material at a temperature higher than the glass transition temperature, but follows the shrinkage of the primary coating material at a temperature lower than the glass transition temperature. However, when it cools to room temperature, it will be fixed in the state expanded more than the primary coating | covering material. That is, it is considered that the primary coating material is subjected to stress that is pulled outward by the secondary coating material.
However, if a secondary coating material having a low glass transition temperature is used, that is, if the glass transition temperature is less than 110 ° C., the shrinkage of the secondary coating material increases, and the stress that causes the secondary coating material to pull the primary coating material outward. Accordingly, the tightening force corresponding to the adhesion of the glass part / primary coating layer interface is increased, and it is considered that the screening characteristics are further improved.

The glass transition temperature and Young's modulus of the secondary coating material can be adjusted to various values by changing the type and blending amount of the oligomer and reactive dilution monomer in the composition. That is, for the oligomer, the glass transition temperature and Young's modulus can be increased by reducing the molecular weight or increasing the rigidity of the urethane portion. In the case of secondary coating materials, the glass transition temperature and Young's modulus are adjusted by adding a multifunctional monomer to the reactive diluent monomer and adjusting the amount, or by selecting a monomer having a high Tg of the homopolymer. can do.
The secondary coating material is applied from above the primary coating layer and cured by ultraviolet irradiation or the like, and is preferably coated to have an outer diameter of 240 to 250 μm to form a secondary coating layer. In the present invention, the secondary coating layer may be composed of multiple layers. The Young's modulus during curing is preferably 100 to 1000 MPa, and particularly preferably 500 to 800 MPa. If the Young's modulus is too small, the lateral pressure characteristics cannot be secured, and if it is too large, the rigidity is too high and bending loss occurs, and workability is poor.

(Colored layer)
By the way, in the colored optical fiber strand in which the outer periphery of the secondary coating layer is further coated with a colored layer, when a resin composition having a glass transition temperature of 100 ° C. or lower is used as the colored coating material, the strand not provided with the colored layer As a result of examination, it became clear that the screening characteristics based on the adhesion strength were further improved.
The colored coating material forming the colored layer is made of an ultraviolet curable resin such as urethane acrylate resin or epoxy acrylate resin, but is not limited thereto. In addition, the reactive dilution monomer and photoinitiator which have a double bond at the terminal may be used similarly to the primary coating material, the secondary coating material, and the like. As necessary, various additives such as a chain transfer agent and an antioxidant are added. The colored layer is preferably coated on the outer periphery of the secondary coating layer with a thickness of about 3 to 10 μm.
As the colored coating material, the Young's modulus at the time of curing is preferably 1000 to 1500 MPa, and the glass transition temperature is preferably 100 ° C. or less. However, if the glass transition temperature is too low, it is likely to be affected by the environmental temperature, particularly the high temperature side, as described above. In the present invention, the glass transition temperature of the colored coating material is more preferably 85 to 95 ° C. When a colored coating material having a low glass transition temperature is used, that is, when the glass transition temperature is 100 ° C. or lower, the colored layer shrinks greatly, and the stress that the secondary coating material pulls the primary coating material outward is reduced. Accordingly, it is considered that the tightening force corresponding to the adhesion force at the glass / primary coating layer interface increases.

The effect of the glass transition temperature of the colored coating material on the adhesion characteristics of the coating layer as the optical fiber can be confirmed by the pull-out force of the optical fiber. That is, the pull-out force increases when the glass transition temperature of the colored coating material is 100 ° C. or lower, and the coating layer peeling during screening of the optical fiber can be suppressed.
In addition, in this invention, although mentioned as an effect of a colored layer, as long as it can coat | cover the outer periphery of a secondary coating layer similarly to a colored layer even if there is no coloring, it will not specifically limit to a colored layer. .

The optical fiber produced by the method of the present invention preferably has a pull-out force of 6N or more, more preferably 6 to 15N, and particularly preferably 7 to 12N. If the pull-out force is too large, the peel cannot be made clean, and the resin remains on the glass. If the pull-out force is too small, peeling occurs at the glass / primary coating layer interface in the screening test.
The method for measuring the pull-out force is as follows.
The coating portion is removed leaving the coating length of 1 cm from the end of the optical fiber, and the glass portion is exposed. Next, the outer periphery of the covering material is fixed to an auxiliary jig with an adhesive or the like, the glass portion is pulled at a constant speed, and the tension at that time is measured.
The pull-out force can be adjusted preferably by adjusting the glass adhesion force of the primary coating layer (primary layer) and the glass transition temperature of the secondary coating layer (secondary layer). Increasing the pull-out force is effective in further improving the coating adhesion characteristics of the optical fiber. As shown in FIG. 3, in Examples 1 to 5 and Comparative Example 1 having a large pull-out force, it is understood that peeling of the coating layer during screening of the optical fiber is suppressed, and the adhesion is improved.

As described above, since the optical fiber manufactured by the method of the present invention has excellent coating adhesion (peeling resistance) and coating removal performance (peeling property), it is a fiber-type element, particularly an optical fiber grating. Suitable for use.
The optical fiber grating has a wavelength in the ultraviolet region of 240 to 270 μm, for example, on the bare optical fiber exposed by removing the primary and secondary coating layers or further colored layers from the optical fiber produced by the method of the present invention. A grating is formed by irradiating with an argon laser or a carbon dioxide gas laser, and if necessary, it is then coated again with a secondary coating material or a UV curable resin having a Young's modulus similar to that of the secondary coating material. Can be manufactured.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
Examples 1-5
After melt spinning a single-mode optical fiber bare wire having an outer diameter of 125 μm, a primary coating layer made of urethane acrylate type ultraviolet curable resin of each example and comparative example having the characteristics after curing as shown in Table 1 was provided. Subsequently, a secondary coating layer made of a urethane acrylate type UV curable resin was provided to manufacture an optical fiber having an outer diameter of 250 μm. Table 1 shows the structures and characteristics of the coating layers of Examples 1 to 5 and Comparative Examples 1 and 2.
In addition, the resin for primary coating layers used for each Example and the comparative example changed the component structure and the amount of silane coupling agents so that it might become the glass adhesive force shown in Table 1, respectively, and selected material. .
The secondary coating layer resin used for the secondary coating layer is an ultraviolet curable resin made of urethane acrylate, and is selected from resins having different glass transition temperatures. The Young's modulus of both the primary coating layer and the secondary coating layer is about 200 μm thick, cured with an irradiation amount of 1.0 J / cm ² under air (using a metal halide lamp), and from the prepared sheet to a width of 6 mm. The sample was cut out and pulled at a speed of 1 mm / min with a tensile tester, and the elastic modulus was calculated from the tensile strength at 2.5% elongation to obtain the Young's modulus.

The test method of the prototype fiber sample is as follows.
(1) Pull-out force The pull-out force was measured by the method described above.
(2) Screening characteristics evaluation 1% or 2% screening was repeated up to 5 times, and the appearance after screening was observed. As for the appearance criteria after repeated screening, no change was observed before and after screening, ○ was broken during screening, or there were changes such as peeling of the covering material, scratches, etc. after screening.
(3) Breaking strength after peeling of the intermediate portion The peeling of the intermediate portion was performed as follows.
As described above, using a commercially available fiber stripper (Micro-Strip, KLENTOOLS, inc .: blade inner diameter is 152 μm), incision is made in the fiber circumferential direction at both ends of the coating removal section of the optical fiber. . Subsequently, the optical fiber is inclined by 50 degrees with respect to the longitudinal direction of the fiber, and is further run between two blades installed at intervals of 155 μm above and below. At this time, the optical fiber bare wire (glass part) is exposed by removing the coating in the longitudinal direction in the coating removal section so that the fiber is at the center of the distance between the two blades and the blade is not directly applied to the glass part. Let Thereafter, the coating removal zone is immersed in ultrasonically applied acetone. Finally, the covering resin that is not cut at the removal end is taken off with tweezers.
The breaking strength of the bare optical fiber (intermediate coating removal portion 5 in FIG. 2) in the coating removal section thus obtained was measured, and the fiber breaking strength after peeling the intermediate portion was determined.

  The test results are shown in Table 1, FIG. 3 and FIG.

Since the optical fiber strand sample of Comparative Example 1 had too high glass adhesion, strength degradation was observed in the breaking strength measurement after intermediate peeling as shown in FIG. Further, since the optical fiber strand sample of Comparative Example 2 does not contain a silane coupling agent and has low glass adhesion, the glass / primary layer interface after repeated screening of 1% strain shown in Table 1 and FIG. Peeling occurred.
On the other hand, in the optical fiber strand samples (Examples 1 and 2) manufactured by the method of the present invention, good results were obtained for both the 1% repeated screening test and the peeling performance.
Furthermore, in Examples 3 to 5, as shown in Table 1, FIG. 3, and FIG. 4, by setting the Tg of the secondary coating layer to less than 110 ° C., any of the 2% strain repeated screening test and the peeling performance Good results were also obtained.
As described above, in the optical fiber manufactured by the method of the present invention, it is shown that good characteristics can be obtained by setting the glass adhesion force of the primary coating material within the range specified by the present invention. It was done.
In addition, as shown in FIG. 3, when the test result of the pullout force and the result of the appearance after repeated screening were combined, it was recognized that the screening characteristics were good when the value of the pullout force was large.

Examples 6-7
Next, regarding the invention according to claim 3, the presence or absence of a colored layer and the pull-out force depending on the glass transition temperature of the colored coating resin used therefor were examined. Similar to Examples 1-5 above, a single-mode optical fiber bare wire having an outer diameter of 125 μm, a primary coating layer made of a urethane acrylate type UV curable resin having characteristics after curing as shown in Table 2, and a urethane acrylate type An optical fiber having an outer diameter of 250 μm was manufactured by providing a secondary coating layer made of an ultraviolet curable resin. The structures and characteristics of the coating layers of Examples 6 to 7 and Comparative Examples 3 to 4 are as shown in Table 2.
The resin for the primary coating layer and the resin for the secondary coating layer used in each example and comparative example were all the same as shown in Table 2 without changing the component configuration and the amount of the silane coupling agent. .
Further, for the outer colored layer, a resin having a different glass transition temperature is selected as a urethane acrylate type ultraviolet curable resin in each of the examples and comparative examples, and the thickness is 5 μm.
The Young's modulus was calculated in the same manner as described in the above example. Moreover, the measurement of the pull-out force of the colored optical fiber wire of each Example and Comparative Example is as described above.

  The test results are shown in Table 2. In the table, the criterion is ○ when the increase rate of the pull-out force due to the provision of the colored layer is 15% or more, and x when it is less than 15%.

  As shown in Table 2, in Examples 6 and 7, the pull-out force increased greatly even when the glass adhesion of the primary coating layer was the same. That is, it was recognized that the adhesion between the glass and the coating layer was greatly improved. On the other hand, in Comparative Examples 3 and 4 of the invention according to claim 5, the increase in pull-out force was small, and it was recognized that the colored layer was a resin composition having a glass transition temperature of 100 ° C. or less, and that there was clearly a significant difference.

It is sectional drawing which shows an example of a structure of an optical fiber strand. It is a perspective view which shows an example of the peeling state of the coating layer intermediate part of the optical fiber strand for optical fiber gratings. It is a graph which shows the result of the pullout force of the optical fiber strand sample produced in the Example. It is a graph which shows the result of the breaking strength after intermediate | middle peeling of the optical fiber strand sample produced in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber strand 2 Optical fiber bare wire 3 Primary coating layer 4 Secondary coating layer 5 Middle part coating removal part

Claims (4)

  A method of manufacturing an optical fiber in which a primary coating layer and a secondary coating layer are provided on a bare glass optical fiber, wherein an intermediate coating of the optical fiber is removed when writing a grating Thus, as the primary coating layer, the silane coupling agent is contained in an amount of 0.05 to 5% by mass, the adhesion with the glass is 5 to 20 N / m, and the tensile strength at an elongation of 50% is 0.5 MPa. A method for producing an optical fiber for a fiber grating, comprising coating a bare glass optical fiber with the resin composition as described above.   The method for producing an optical fiber for a fiber grating according to claim 1, wherein a resin composition having a glass transition temperature of less than 110 ° C is coated on the primary coating layer as the secondary coating layer.   An optical fiber is a colored optical fiber in which a colored layer is further provided on the outer periphery of a secondary coating layer, and a resin composition having a glass transition temperature of 100 ° C. or lower is used as the colored layer. 3. The method of manufacturing an optical fiber for a fiber grating according to claim 1, wherein the outer periphery of the coating layer is coated.   The secondary coating layer is characterized in that a resin composition containing an ultraviolet curable resin mainly composed of a polyether urethane (meth) acrylate having a double bond at the terminal is coated on the primary coating layer. The manufacturing method of the optical fiber for fiber gratings of any one of Claims 1-3 to do.

Images