JP4279103B2 - Optical fiber - Google Patents

Description

  The present invention relates to an optical fiber that has improved reliability, particularly fatigue resistance, of the optical fiber.

The optical fiber is coated on a quartz optical fiber bare wire having an outer diameter of 125 μm with a primary coating layer made of an ultraviolet curable resin (UV resin) having a relatively low Young's modulus of about 1 to 10 MPa, a silicone resin, In general, a secondary coating layer made of an ultraviolet curable resin (UV resin) having a relatively high Young's modulus of about 100 to 1000 MPa and having an outer diameter of 250 μm is used on the primary coating layer. The secondary coating layer has the effect of protecting the optical fiber from friction and external force by increasing the Young's modulus, and the primary coating layer has the effect of reducing external side pressure and the like by reducing the Young's modulus. At present, UV resin is often used as a coating material from the viewpoint of manufacturability.
The use form of the optical fiber is assembled in the state of a single core, or in the state where a plurality of optical fibers are arranged in parallel, the periphery thereof is coated with an ultraviolet curable UV resin to form a tape core, In most cases, a plurality of tape cores are assembled and used as optical cables. This optical cable is used by being laid in an aerial, a cave, a pipe or the like. In an installed optical cable, a tensile force is always applied depending on the installed state, and part of this tensile force also acts on the optical fiber that constitutes the optical cable, and a small load is continuously applied to the optical fiber for a long period of time. It may take over. If such a relatively small load is continuously applied to the optical fiber, a phenomenon may occur in which the optical fiber is suddenly broken at a certain point in time or is broken only by applying a slightly large tensile force. There is. This problem is caused by the fatigue characteristics of the optical fiber, and in order to avoid this problem, the optical fiber needs to have sufficient fatigue characteristics.
The fatigue characteristics of the optical fiber are closely related to the characteristics of the resin coating the bare optical fiber, particularly the resin constituting the primary coating layer 2. It is necessary to select and use an appropriate resin for 2.

  Usually, a silane coupling agent is added to the primary coating layer in order to provide adhesion between the bare optical fiber and the primary coating layer. A silane coupling agent chemically combines an organic functional group having affinity or reactivity with an organic resin and a hydrolyzable alkoxy group having affinity or reactivity with an inorganic material such as a quartz optical fiber bare wire. Is a silane compound bonded to. The UV resin is coated during drawing, is immediately cured by receiving UV irradiation, and is wound on a bobbin. Since UV resin hardens rapidly by UV irradiation, the silane coupling agent present near the fiber bare wire / primary coating layer interface reacts with the primary coating material on the organic functional group side and the fiber bare wire on the alkoxy group side. Thus, it has the effect of improving the adhesion between the bare fiber and the primary coating layer interface. The higher the concentration of the silane coupling agent in the interface between the bare fiber and the primary coating layer, the higher the adhesion.

As silane coupling agents, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyl Methyldimethoxysilane, vinyltriethoxysilane, and the like are commercially available, of which γ-mercaptopropyltrimethoxysilane is most commonly used.
Other than this, as the silane coupling agent, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glucidoxypropyltrimethoxysilane, γ-glucidoxypropylmethyldiethoxysilane, γ-glucidoxy Examples of propyltriethoxysilane and the like are shown, and these are said to be effective in suppressing the optical fiber breaking strength under high temperature and high humidity. (For example, refer to Patent Document 1).
However, among these silane coupling agents, for example, γ-mercaptopropyltrimethoxysilane acts as a chain transfer agent itself, but reacts with the unsaturated double bond in the constituent material in the uncured resin. Problems such as adversely affecting the stability of the resin such as the Young's modulus during curing being higher than the original value along with the storage time of the resin, and further the storage time when the silane coupling agent is deactivated in the resin At the same time, it has been found that there are not a few phenomena in which the adhesion properties of the resin to glass deteriorate.

By the way, a glass optical fiber made of quartz generally has a transmission loss that is considered to be caused by absorption of hydrogen gas when hydrogen gas is present. Therefore, the ultraviolet curable resin used as the coating material is also required to have excellent long-term reliability without generation of hydrogen gas due to degradation and decomposition. An amine compound has an excellent effect in suppressing hydrogen generation from a resin (for example, Patent Document 2), and is generally used at present. Examples of the amine compound include a primary monoamine represented by R ₁ —NH ₂ , a primary diamine represented by NH ₂ —R ₂ —NH ₂ , and a secondary amine represented by R ₃ R ₄ —NH, R ₅ R ₆ A tertiary amine represented by R ₇ —N can be mentioned. The primary monoamine is an aliphatic alkylamine in which R ₁ is an alkyl group such as ethyl or propyl, for example, ethylamine or propylamine, and R ₁ is an aromatic amine such as a benzene ring, such as aniline or aminobenzophenone. Primary diamines are aliphatic amines in which R ₂ is an alkyl group, such as ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,6-hexamethylene diamine, and R ₂ is from a benzene ring or the like. Examples of the aromatic amine include toluene diamine, xylene diamine, and metaphenylene diamine. Examples of secondary amines include dibutylamine, dipropylamine, 2-ethylhexylamine, N-methylaniline, N-methylbenzylamine and the like. Tertiary amines include tributylamine, trioctylamine, N, N-dimethylaniline and the like. All of these have the effect of effectively suppressing hydrogen generation.
JP 2000-86936 A JP 63-27503 A

However, it has been found that when an amine compound is added to a resin, the following problems occur in γ-mercaptopropyltrimethoxysilane which is the most commonly used silane coupling agent. In other words, the external line curable resin is composed of an oligomer, a monomer, a photoinitiator, and an additive such as an anti-aging agent and a silane coupling agent, but γ-mercaptopropyltrimethoxysilane is a basic amine compound. By addition, the mercapto group reacts with the acrylic double bond at the end of the oligomer or monomer in advance to eliminate the mercapto group, so that the silane coupling agent itself already exists in a polymer state in the resin before curing. Because it is a polymer, it is difficult to move to the interface between the bare fiber and the primary coating layer during curing, and the concentration of the silane coupling agent on the glass surface is reduced. It has been found that good fatigue properties cannot be obtained.
In addition, although amine compounds are effective in suppressing hydrogen generation, they often show basicity and have been found to affect the breaking strength and fatigue resistance of optical fiber bare wires themselves.
Examples of the influence of the pH of the resin on the fatigue resistance of the fiber include those in which the pH of the uncured resin of the coating layer is 8.0 or less as in JP-A-2001-064040, or JP-A-2003-004993. What is characterized by what the pH of the resin after hardening of the coating layer in direct contact with the bare optical fiber is 4.5 or less is known.
However, as described above, the present inventors also show that fatigue resistance does not increase even when the pH of the resin is 8.0 or less or the pH of the resin directly in contact with the bare optical fiber is 4.5 or less. It became clear by examination.

  An object of the present invention is to solve the above problems and provide an optical fiber having good fatigue resistance.

As a means for solving the above problems, the present invention provides:
An optical fiber element comprising a primary coating layer and a secondary coating layer made of an ultraviolet curable resin on a bare optical fiber, wherein the resin composition forming the primary coating layer contains a silane coupling agent. It contains 0.01 to 5% by mass and contains a non-basic additive that exists alone after UV curing , and the organic functional group of the silane coupling agent is selected from at least one selected from an acrylic group and a methacryl group Do Ri, said additive as a phosphorus-based antioxidant 6- [3- (3-t- butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra -t- butyldibenz The present invention provides an optical fiber that contains [d, f] [1,3,2] dioxaphosphine .
Also, ultraviolet curing resin constituting the secondary coating layer comprises additives present after alone UV curing, it said additive is characterized in that a non-basic.

  The optical fiber of the present invention has good fatigue resistance and excellent reliability. Therefore, the optical fiber of the present invention exhibits high reliability without disconnection even when tension is continuously applied for a long period of time when used in a cable.

The present invention is described in further detail below.
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 a bare optical fiber according to the present invention. In the figure, an optical fiber 1 is composed of a primary coating layer 3 coated on the outer peripheral surface of a bare optical fiber 2 and a secondary coating layer 4 coated on the outer periphery of the primary coating layer 3. .

(Primary coating layer)
Specific examples of the primary coating material for forming the primary coating layer in the present invention include a resin composition containing a UV curable resin such as a urethane acrylate type or an epoxy resin type having a double bond at the terminal, a so-called oligomer. Is mentioned. In addition, a reactive monomer having a double bond at the terminal (hereinafter also referred to as a reactive diluent monomer) and a photopolymerization initiator may be used as a diluent.
However, since the pH of the resin varies depending on the amount of polar groups such as esters and urethane groups, a resin material appropriately selected from the types of urethane acrylate components, monomers, and photoinitiators is used.
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.
A silane coupling agent is added to these resins, and an anti-aging agent, a chain transfer agent, a light stabilizer, a polymerization inhibitor, a sensitizer, and other additives are added as necessary.
The additive does not undergo a crosslinking reaction with the resin at the time of the crosslinking reaction by ultraviolet irradiation, and remains alone after curing, and the amount of the additive used is in the range of 0.005 to 3%. If the amount added is small, there is no effect, and if it is too large, problems such as bleeding and discoloration easily occur.
The primary coating material is preferably applied to the outer peripheral surface of the bare optical fiber, cured by ultraviolet rays, and coated so as to have an outer diameter of 180 μm to 200 μm. 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.

The silane coupling agent contained in the primary coating material has a role of improving the adhesion between the bare optical fiber and the coating resin. A silane coupling agent chemically combines an organic functional group having affinity or reactivity with an organic resin and a hydrolyzable alkoxy group having affinity or reactivity with an inorganic material such as a quartz optical fiber bare wire. Is a silane compound bonded to.
In the present invention, the amount of the silane coupling agent contained in the primary coating material is 0.01 to 5% by mass, and preferably 0.1 to 1% by mass. This is because if the amount of the silane coupling agent is too small, the adhesion between the bare optical fiber and the primary coating layer is deteriorated and the fatigue resistance is deteriorated, and if too large, the curability is deteriorated.
The silane coupling agent used in the present invention has at least one of an acrylic group and a methacryl group as an organic functional group. There may be at least one organic functional group in one molecule. The silane coupling agent whose organic functional group is an acryl group or a methacryl group does not react with other components in the uncured resin and exists in a so-called low molecular weight stable state as it is. Since it exists in a low molecular state, it can be considered that it can move to the bare fiber / primary coating layer interface during curing by UV irradiation. In addition, these are acrylic and methacrylic groups in which the organic functional group has a double bond, and since they have the same structure as the terminal of the oligomer or monomer, the curing speed of the resin itself is not impaired. Preferred silane coupling agents include 3-acryloxypropyltrimethoxysilane (trade name KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.), γ-methacryloxypropyltrimethoxysilane (trade name KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), γ-methacryloxypropyltriethoxysilane (trade name KBE-503, manufactured by Shin-Etsu Chemical Co., Ltd.) may be mentioned, among which 3-acryloxypropyltrimethoxysilane is particularly preferable.
By the way, the pH of the ultraviolet curable resin varies greatly before and after the resin is cured, and the pH value is lowered by curing. This is because acids such as carboxylic acid are generated as a by-product during the curing reaction of the urethane acrylate resin.
The ultraviolet curable resin is used as a coating layer for the bare optical fiber in a cured state. Therefore, the pH of the resin in the cured state has a greater influence on the fiber than the pH of the uncured resin.
Furthermore, as a result of intensive studies, the present inventors have found that the additive that exists alone after curing does not have a crosslinking reaction with the resin during the crosslinking reaction by ultraviolet irradiation, and greatly increases the pH. .
That is, the present inventors have found that the additive added to the ultraviolet curable resin composition used in the present invention is preferably non-basic.
For example, conventionally used amine compounds for suppressing hydrogen generation are basic, and the addition amount is very small compared to the main component, but the effect of raising the pH of the resin is very large. Increase the value by about 1.
Basic additives having the effect of greatly increasing the pH even in such a small amount include primary monoamines such as ethylamine, propylamine, aniline, aminobenzophenone, ethylenediamine, 1,2-diaminopropane, Examples include amine compounds such as primary diamines such as 1,4-diaminobutane, 1,6-hexamethylenediamine, toluenediamine, xylenediamine, and metaphenylenediamine.
On the other hand, non-basic hindered phenol additives such as thiodiethylene-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) pyropionate] (trade name: Irganox 1035, ciba Specialty Chemicals, Inc.) was found to be effective in preventing long-term deterioration, suppressing hydrogen generation, and sufficiently functioning as an alternative to amine-based additives.
In the present specification, the term “non-basic” means that the pH value does not increase even when added (likely, the increase in pH value by adding less than 0.5) as in the above-mentioned amine compounds. It means that.
In the present invention, pH is measured by the following method.
An uncured resin is applied on a glass plate to a thickness of 0.2 mm, and cured under an air dose of 500 mJ / cm ² (using a metal halide lamp). From the obtained cured sheet, a mass of 2.0 g is precisely weighed, then placed in a glass container such as a volumetric flask, further sealed with 20 ml of pure water adjusted to pH 7.0 in advance, and heated at 80 ° C. for 18 hours. . After cooling the container to room temperature, the water is transferred to another container and the pH is measured with a pH meter.
In order to confirm the influence on the pH of the most important additive in the present invention, the pH before and after the addition of each additive is measured, and the difference obtained by subtracting the pH value before the addition from the pH value after the addition is the pH increase amount. It was.
Furthermore, the present inventors have found the following matters. That is, in the present invention, it is preferable that the additive is non-basic, but the uncured resin is stored for a long period of time compared with the case where basic additives represented by some amine-based additives are added. In this case, it has been found that a problem that the fatigue characteristics deteriorate is newly generated.
This is because the alkoxy group in the silane coupling agent reacts with a small amount of moisture in the resin to form a silanol group, and further, the silanol groups react with each other to deactivate the alkoxy group, resulting in adhesion between the resin and the glass. Therefore, it is considered that the dynamic fatigue characteristics are lowered.
Urethane acrylate oligomers and monomers constituting the ultraviolet curable resin contain impurities such as catalyst residues necessary for the synthesis. In general, such impurities are removed during purification, but depending on the degree of purification, there are many traces that remain, and such catalyst residues are caused by the alkoxy groups of the silane coupling agent and trace moisture in the resin. It has been found to promote and deactivate the reaction. This phenomenon can be improved by adding a basic additive such as an amine compound.
That is, as described above, it is preferable that the additive is non-basic, but when a basic additive such as some amine-based additives is not added, the glass adhesion of the resin as well as the storage time of the resin. This reduces the force and also causes the problem of reducing dynamic fatigue properties.
As a result of intensive studies to solve such problems, specific antioxidants have the effect of maintaining dynamic fatigue properties that decrease with the storage time of the resin, which is the above problem, without increasing the pH of the resin. Newly found that.
As the antioxidant, it is generally known that there are sulfur, phenol, phosphorus and amine types.
The antioxidant used in the present invention is not particularly limited as long as it does not increase the pH of the resin even if added in a trace amount. Among the above antioxidants, phosphorus antioxidants, particularly 6 -[3- (3-t-Butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphepin (Sumitomo It has been newly found that Sumilizer GP manufactured by Chemical Co., Ltd. is effective in suppressing a decrease in adhesion during long-term storage. The addition amount of the present antioxidant is preferably 0.05 to 3%, particularly preferably 0.5 to 2.0%.

(Secondary coating layer)
As the secondary coating layer material for forming the secondary coating layer in the present invention, a resin composition comprising an ultraviolet curable resin such as a polyether urethane acrylate resin or epoxy acrylate resin having a double bond at the terminal Is mentioned. In addition, a reactive reactive monomer having a double bond at the terminal and a photopolymerization initiator may also be used. Examples thereof include the resin compositions described in Japanese Patent Nos. 2021130, 2135130, 2525177, and 2601699. These are preferably contained in the secondary coating material in an amount of 35 to 100% by mass.
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. These additives do not undergo a crosslinking reaction with the resin at the time of the crosslinking reaction by ultraviolet irradiation, and exist alone after curing, and their addition amounts are used in the range of 0.005 to 3%. . If the amount added is small, there is no effect, and if it is too large, problems such as bleeding and discoloration easily occur.
Since the additive in the secondary coating layer is present alone in the resin, there is a concern that it may move to the primary coating layer, increase the pH of the primary coating layer resin, and reduce the fatigue resistance of the optical fiber. . Therefore, the additive added to the ultraviolet curable resin composition used in the present invention is preferably non-basic.
For example, a conventionally used amine compound for suppressing hydrogen generation is a small amount compared to the main component, but the effect of raising the pH of the resin is very large, and the pH value is increased by about 1. Let
Additives that have the effect of greatly increasing the pH even in such a small amount include primary monoamines such as ethylamine, propylamine, aniline, aminobenzophenone, ethylenediamine, 1,2-diaminopropane, 1,4 Examples include amine compounds such as primary diamines such as diaminobutane, 1,6-hexamethylenediamine, toluenediamine, xylenediamine, and metaphenylenediamine.
On the other hand, non-basic hindered phenol additives such as thiodiethylene-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) pyropionate] (trade name: Irganox 1035, ciba Specialty Chemicals, Inc.) was found to be effective in preventing long-term deterioration, suppressing hydrogen generation, and sufficiently functioning as an alternative to amine-based additives.
The term “non-basic” means that the pH does not increase even when added (specifically, the increase in pH value due to the addition is less than 0.5) as in the above-described amine compound.
Therefore, it is preferable to use an additive having an increase in pH value by addition of less than 0.5, more preferably an additive of less than 0.3.
The secondary coating material is preferably applied to the outer peripheral surface of the primary coating material, cured by ultraviolet rays, and coated with an outer diameter of 240 to 250 μm. In the present invention, the secondary coating layer may be composed of multiple layers. The Young's modulus during curing is preferably from 100 to 1000 MPa, particularly preferably from 500 to 800 MPa. If the Young's modulus is too low, the lateral pressure characteristics cannot be secured, and if it is too high, the rigidity becomes too high and bending loss occurs, and workability is poor.

For the bare optical fiber in the present invention, a glass fiber composed of a core and a clad can be used, and although not particularly limited, for example, a silica-based glass fiber can be used. The bare optical fiber can be manufactured according to the method described in, for example, Tech. Dig. Fiber Communication 1994 Tul 1 PJLemaire 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.

  Furthermore, the present inventors preferably coat with a resin having a small contact angle change before and after coating, which will be described below, because the fatigue resistance of the optical fiber is improved. Conversely, the resin is coated with a resin with a large contact angle change. Then, it was found that the fatigue resistance decreases, and in particular, the concentration of the silane coupling agent on the surface of the bare optical fiber in the optical fiber has a great influence on the fatigue resistance. It has been found that the fatigue resistance of the optical fiber is improved.

The contact angle change amount before and after coating will be described.
When the resin is coated on the glass plate and cured and then peeled off, a part of the resin remains on the glass plate surface. When the contact angle of pure water with respect to the glass plate is measured in this state, the wettability with pure water is lowered due to the influence of the remaining resin and the contact angle is increased as compared with before coating. However, when a large amount of silane coupling agent is present at the interface, many Si atoms of alkoxy groups remain, so that the wettability with pure water does not deteriorate so much and the change in contact angle before and after coating is small.
That is, if the measured value of the contact angle change before and after coating is small, a large amount of silane coupling agent is present at the interface.

The method for measuring the contact angle is as follows.
After measuring the contact angle of pure water (or ion-exchanged water) against an unused soda glass plate (manufactured by Suzuki Optics: main components SiO ₂ , CaO, Na ₂ O) with a clean surface wiped with alcohol, etc. again the surface coated with the primary coating material to clean wipe glass plate and irradiated with ultraviolet rays of 100 mJ / cm ² under a nitrogen atmosphere, to create a thickness 200μm sheet. Then, after standing at room temperature for 7 days, the cured sheet is peeled off from the blue plate glass. The contact angle of pure water (or ion exchange water) to the glass surface after peeling off is measured, and the difference from the contact angle before coating of the coating material is taken. This difference is defined as the contact angle change amount before and after coating.
The resin composition for forming the primary coating layer in the present invention preferably has a contact change amount of 30 ° or less before and after the coating. More preferably, it is 5 to 25 °. In order to obtain such a contact angle change amount, for example, it is preferable that the type and content of the silane coupling agent are as described above, or that moisture is present to some extent in the atmosphere.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
After melt spinning a single-mode optical fiber bare wire with an outer diameter of 125 μm, and providing a primary coating layer made of urethane acrylate type UV curable resin of each Example, Comparative Example and Reference Example whose characteristics after curing are shown in Table 1, Subsequently, a secondary coating layer made of a urethane acrylate type ultraviolet 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 materials of the examples, comparative examples, and reference examples . In Examples, the ratio Comparative Examples and the structure of the resin for primary coating layer of the reference example, the type and amount of the silane coupling agent as shown in Table 1, and changing the combination of additives, other configurations All were the same. The same material was used for the secondary coating layer except for the additives.
In addition, three types of A, B, and C were prepared as combinations of additives for the primary coating layer and the secondary coating layer. That is, A is obtained by adding a conventional basic additive (ethylenediamine). B is a non-basic additive (thiodiethylene-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) pyropionate] (trade name: Irganox1035, ciba Specialty Chemicals) , Inc.))). C is a 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10- as a phosphorus antioxidant in addition to the non-basic additive of B. Tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphepine [ 6- [3- (3-t-Butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4, 8,10-tetra-t-butyldibenz [d, f] [1,3,2 ] dioxaphosphepin ] (Sumilizer GP manufactured by Sumitomo Chemical Co., Ltd. ) is further added.

For the primary coating layer, the contact angle measurement test was performed as described above, and the change in the contact angle before and after coating the primary coating layer on the glass plate was measured.
The Young's modulus of both the primary coating layer and the secondary coating layer is about 200 μm thick, cured at an irradiation dose of 1.0 J / cm ² under air (using a metal halide lamp), and cut out to a width of 6 mm from the prepared sheet. As a sample, the sample was pulled at 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.
Moreover, the fatigue resistance of the manufactured optical fiber strand sample was tested by the dynamic fatigue coefficient n.
This dynamic fatigue coefficient n was measured using a tensile tester according to the test method defined in TIA / EIA-455-76: Method for measuring Dynamic Fatigue of Optical Fibers by Tension. In the present invention, those having a dynamic fatigue coefficient n of 20 or more were judged as having good fatigue resistance.
As for n value, both fiber drawn using primary resin untreated and fiber drawn using heat-aged resin with primary resin previously heated at 60 ° C for 7 days for 1 week are measured. did.
The results are shown in Table 1 below.

According to the results in Table 1 above, the optical fiber strand samples (Comparative Examples 1 and 2) in which the organic functional group of the silane coupling agent contained in the primary coating material is a mercapto group have a n value of less than 20 and resistance to resistance. Inferior to fatigue properties. Further, the optical fiber strand sample of Comparative Example 3 in which the amount of the silane coupling agent contained in the primary coating material is too small is inferior in fatigue resistance, and in the comparative example 4 in which the amount of silane coupling agent is too large, the primary coating material has poor curability. Could not be completed and an optical fiber could not be produced.
In contrast, the organic functional group of the silane coupling agent is an acrylic group or a methacryl group, and the amount of the silane coupling agent is 0.01 to 5% by mass (Example 1). ~ 3 ) all have good fatigue resistance. In addition, it turns out that it has favorable fatigue resistance as the variation | change_quantity of a contact angle is 30 degrees or less.
Moreover, in Example 1 and 2 , the favorable result was obtained even if it uses resin after aging by adding a specific antioxidant. Furthermore, in Example 3 , in addition to the addition of the antioxidant, the secondary material additive was also made non-basic, so that even better fatigue resistance was obtained.

It is sectional drawing which shows an example of the optical fiber strand of this invention.

Explanation of symbols

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

Claims (2)

An optical fiber element comprising a primary coating layer and a secondary coating layer made of an ultraviolet curable resin on a bare optical fiber, wherein the resin composition forming the primary coating layer contains a silane coupling agent. It contains 0.01 to 5% by mass and contains a non-basic additive that exists alone after UV curing , and the organic functional group of the silane coupling agent is selected from at least one selected from an acrylic group and a methacryl group Do Ri, said additive as a phosphorus-based antioxidant 6- [3- (3-t- butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra -t- butyldibenz An optical fiber , comprising [d, f] [1,3,2] dioxaphosphine . The secondary coating layer ultraviolet curable resin constituting the comprises additives present after alone UV curing, optical fiber according to claim 1, wherein said additive is non-basic .

Images