JP2006113103A - Colored optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colored optical fiber that suppresses generation of blisters when immersed in water particularly in warm water for a long period and that has no increase in optical transmission loss. <P>SOLUTION: The colored optical fiber 10 has a plurality of covering layers 12, 13 formed on a bare optical fiber 11, and a pigmented layer 14 formed on the outermost layer, wherein the pigmented layer 14 is formed of resin having an elution rate of ≤3% in water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a colored optical fiber used for an optical fiber cable.

  An example of the optical fiber cable is shown in FIG. 5 or FIG.

  As shown in FIG. 5A, the optical fiber cable 50 has a slot 53 formed in a rod 52 having a tension member 51 at the center, and a plurality of tape fibers 54 are accommodated in the slot 53. As shown in FIG. 5B, the tape fiber 54 is obtained by integrating a plurality of optical fiber strands 55 (four in the drawing) with a tape material 56. A sheath 57 or a protective tape is provided outside the slot 53 in which the tape fiber 54 is accommodated.

  Further, as shown in FIG. 6, the optical fiber cable 60 includes a plurality of optical fiber strands 55 embedded in a thermoplastic resin layer 61 and surrounded by a reinforcing layer, a waterproof layer, a protective sheath, etc. (not shown). It has been made.

  As shown in FIG.5 (c), the optical fiber strand 55 used for the optical fiber cables 50 and 60 plays the role of the buffer layer with respect to a side pressure etc. on the outer side of the optical fiber bare wire 11 formed with the glass-type material. A primary coating layer (primary layer) 12 is coated, and a secondary coating layer (secondary layer) 13 for preventing external damage and the like is coated on the outside. Further, the optical fiber 55 is provided with a colored layer 58 outside the secondary coating layer 13 for identification. The colored layer 58 is mainly made of an ultraviolet curable resin to which a colorant is added.

  In an environment where the optical fiber cable 50 has been exposed to water for a long time, water or the like may enter the optical fiber cable 50. Water (water vapor) passes through the coating layers 12 and 13 of the optical fiber strand (colored optical fiber) 55, and between the bare fiber 11 and the primary coating layer 12, or between the primary coating layer 12 and the secondary coating layer 13. In some cases, each layer such as a gap is partially peeled off, and water accumulates in the peeled portion to cause partial blistering (blister).

  Such deformation of the coating layers 12 and 13 applies a lateral pressure to the bare fiber 11 to cause non-uniform microbending in the longitudinal direction, which causes an increase in optical transmission loss. Regarding such a problem, an optical fiber (for example, refer to Patent Document 1) in which blisters generated between the bare optical fiber 11 and the primary coating layer 12 are suppressed, and blisters between the secondary coating layer 13 and the colored layer 58 are suppressed. There is an optical fiber that can be used (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 9-5587 JP 11-31723 A

  However, the occurrence of blisters is not limited to each layer, but occurs in each layer, particularly in the primary coating layer 12. The adhesion between the bare optical fiber 11 and the primary coating layer 12 and the secondary coating layer 13 It cannot be prevented only by increasing the adhesion between the colored layers 58. In particular, the colored optical fiber has a problem that blisters are generated in the primary coating layer 12 and the optical transmission loss is increased.

  Here, the transmission loss of the conventional colored optical fiber will be briefly described.

  FIG. 3 shows a colored optical fiber (colored layer B in the figure) using a polyester urethane acrylate-based ultraviolet curable resin as an ultraviolet curable resin for forming the colored layer 58 of the colored optical fiber 55 in FIG. It is a measurement result of the time change of the transmission loss when the colored optical fiber (colored layer C in the figure) using an ultraviolet curable resin is immersed in warm water of 60 ° C., respectively.

  The transmission loss of the colored optical fiber in which the colored layer B is formed gradually increases from the start of immersion, and increases approximately 0.3 dB / km after 30 days of immersion. Further, in the colored optical fiber in which the colored layer C is formed, the transmission loss is larger than that in the colored optical fiber in which the colored layer B is formed, and the maximum is increased by 0.6 dB / km or more.

  Therefore, an object of the present invention is to provide a colored optical fiber that solves the above-mentioned problems and suppresses the generation of blisters even when immersed in water, particularly in warm water for a long period of time, thereby suppressing an increase in optical transmission loss. is there.

  In order to achieve the above object, according to the first aspect of the present invention, in the colored optical fiber in which a plurality of coating layers are provided on the bare optical fiber and the colored layer is formed on the outermost layer, the elution rate into water is 3% or less. A colored optical fiber in which a colored layer is formed of the above resin.

  The invention according to claim 2 is the colored optical fiber according to claim 1, wherein the dissolution rate is determined by the change in weight with respect to the initial weight after the colored layer is immersed in warm water of normal temperature water, preferably 60 ° C. for 30 days.

  The invention of claim 3 is the colored optical fiber according to claim 1 or 2, wherein the colored layer is formed of a polyether urethane acrylate-based ultraviolet curable resin having a gel fraction of 95% or more.

  According to the present invention, an excellent effect is exhibited in that an increase in optical transmission loss can be suppressed even when immersed in water for a long time.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing a preferred embodiment of a colored optical fiber according to the present invention.

  In the colored optical fiber 10 according to the present embodiment, a primary coating layer 12 is formed around the bare optical fiber 11 and a secondary coating layer 13 is formed around the primary coating layer 12.

  The bare optical fiber 11 is made of a glass-based material whose main component is quartz.

  For the primary coating layer 12 and the secondary coating layer 13, urethane (meth) acrylate-based, epoxy (meth) acrylate-based, polyester (meth) acrylate-based, and silicon (meth) acrylate-based ultraviolet curable resin compositions are used. A material having a Young's modulus of 0.5 to 10 MPa is mainly used for the primary coating layer 12, and a material having a Young's modulus of 50 to 200 MPa is used for the secondary coating layer 13.

  A colored layer 14 that is a feature of the present embodiment is formed around the secondary coating layer 13. The colored layer 14 is a layer provided as the outermost layer of the optical fiber in order to color the optical fiber, and is formed of an ultraviolet curable resin composition to which a colorant such as a pigment is added. In addition to the pigment, a photocuring initiator, a stabilizer, a plasticizer, a dye, and the like are added to the ultraviolet curable resin composition.

  An ultraviolet curable resin composition will not be specifically limited if the elution rate to water is 3% or less. Here, the dissolution rate represents the change in weight with respect to the initial weight after being immersed in normal temperature water or 60 ° C. warm water for 30 days.

  The reason for setting the elution rate of the colored layer 14 in water to 3% or less is that when the elution rate is higher than 3%, the internal stress due to the volume shrinkage of the colored layer 14 increases, so the primary coating layer 12 and the secondary coating layer. This is because even if non-uniform stress acts on 13 and the respective layers are in close contact with each other, blisters are easily generated in the coating layer, particularly in the primary coating layer 12.

  In addition, the temperature of water is set to 60 ° C., usually, it is sufficient that the elution rate (absorption rate) into water at room temperature is low, but as the temperature increases, the volume change (volume shrinkage) due to elution increases. Considering the use under high temperature, the elution rate was lowered under more severe conditions.

  In particular, since the colored layer 14 is colored, it is more likely to hinder the transmission of ultraviolet light compared to the primary coating layer 12 or the secondary coating layer 13 that is not colored, so that the resin is cured between the surface and the inside of the colored layer 14. There is a difference in the degree, and the degree of curing tends to decrease toward the inside. For this reason, volume shrinkage due to elution from the inside is likely to occur, and the stress caused by the volume shrinkage is transmitted to the primary and secondary coating layers 12 and 13 to cause microbending. If a microbend is present in an optical fiber, light transmission loss is likely to increase.

  As a cause of elution of the colored layer 14 in water, non-crosslinked components such as the above-mentioned photocuring initiator, stabilizer, plasticizer, pigment and dye are eluted. Further, after curing by ultraviolet rays, unreacted monomers remaining in the resin are also eluted. The higher the hydrophilicity of these non-crosslinked components and unreacted monomers, the greater the degree of elution into water.

  Furthermore, if the ultraviolet curable resin itself has low water resistance (high hydrophilicity), the resin itself is easily hydrolyzed by contact with water. The smaller the amount of non-crosslinked components and unreacted monomers remaining in the cured ultraviolet curable resin, the lower the elution rate. That is, the higher the degree of cure of the resin, the lower the elution rate.

  An index representing the degree of cure is a gel fraction. The measurement of the gel fraction of the ultraviolet curable resin is performed by a Soxhlet extraction method. The extraction conditions were methyl ethyl ketone as the solvent used, 110 ° C. as the solvent temperature, and 12 hours as the extraction time. The gel fraction is expressed by the following formula.

Gel fraction (%) = (resin weight after extraction / resin weight before extraction) × 100
In order to reduce the elution rate of the colored layer 14 to 3% or less, the gel fraction of the ultraviolet curable resin forming the colored layer 14 is preferably 95% or more.

  In the present embodiment, a polyether urethane acrylate-based ultraviolet curable resin is used as the ultraviolet curable resin having a gel fraction of 95% or more. The gel fraction of the polyether urethane acrylate UV curable resin is 95 to 97%.

  The gel fraction of the polyester urethane acrylate resin used for the colored layer 58 of the conventional colored optical fiber 50 was 93 to 94%, and that of the polyester acrylate resin was 90 to 92%.

  Further, the higher the water resistance (non-hydrophilicity) of the ultraviolet curable resin, the lower the elution rate. When the water resistance of the resin is compared, the water resistance of the polyether urethane acrylate resin is the highest, followed by the polyester urethane acrylate resin and the polyester acrylate resin in this order. Therefore, it is most preferable to use a polyether urethane acrylate resin having a gel fraction of 95% or more for the ultraviolet curable resin of the colored layer 14.

  Furthermore, the elution rate of the colored layer may be further reduced by adding non-hydrophilic non-crosslinking components such as photocuring initiators, stabilizers, plasticizers, pigments and dyes to the ultraviolet curable resin. .

  Table 1 shows the results of measuring the dissolution rate after immersing a sheet obtained by curing an ultraviolet curable resin (colored UV material) used for the colored layer 14 of the colored optical fiber 10 of the present embodiment in 60 ° C. warm water. It shows in comparison with the measurement result of the dissolution rate of the colored UV material used for the optical fiber.

In Table 1, colored UV material A is obtained by adding 4% by weight of a red colorant to a polyether urethane acrylate ultraviolet curable resin composition, and colored UV material B is red on a polyester urethane acrylate ultraviolet curable resin. The colored UV material C is obtained by adding 4% by weight of a red colorant to a polyester acrylate UV curable resin. The sheet used for the measurement is prepared by adjusting the thickness of the three kinds of colored UV materials so that the thickness after UV curing is 50 ± 5 μm, and curing them in a nitrogen atmosphere at an irradiation dose of 1000 mJ / cm ² .

  As shown in Table 1, in the colored UV material B, although it was 3% after 5 days of immersion, there was a change in weight due to elution of 5% after 30 days of immersion. In the colored UV material C, the elution rate is already 5% after 5 days of immersion. On the other hand, in the colored UV material A used in the present embodiment, the elution rate is kept as low as 2% even after 30 days of immersion.

  FIG. 3 is a measurement result of the amount of change in transmission loss when the colored optical fiber 10 of the present embodiment is immersed in warm water at 60 ° C. (colored layer A in the figure), and shows a conventional colored optical fiber (colored in the figure). This is a comparison with the measurement results of layers B and C).

  Colored optical fibers made using colored UV materials with different elution rates after immersion in 60 ° C warm water are bundled with a length of 1000 m and a diameter of 300 mm, respectively, and immersed in warm water at 60 ° C to change the transmission loss. Measurements were taken every 5 days.

  The primary coating layer 12 and the secondary coating layer 13 used in the colored optical fiber 10 are formed of a urethane acrylate ultraviolet curable resin composition, and the optical fiber bare wire 11 and the coating layers 12 and 13 other than the colored layer 14 are 3 The same species was formed. Moreover, the coating layers 12 and 13 used the coating material from which the pulling force of the coating layers 12 and 13 becomes 500-1000 g / cm for the bare optical fiber 11 of the colored optical fiber 10. The pulling force is a value obtained by measuring the maximum load required to pull out the bare optical fiber 11 from the length 1 cm of the coating layer 12. The colored layer B is formed using the colored UV material B, and the colored layer C is formed using the colored UV material C.

  As shown in FIG. 3, in the colored optical fiber formed with the colored layers B and C in which the weight loss when immersed in warm water at 60 ° C., that is, the elution rate is 3% or more, the transmission loss in warm water is increased. In contrast, in the colored optical fiber 10 according to the present embodiment in which the elution rate is 3% or less, almost no increase in transmission loss occurs. Furthermore, even if the colored optical fiber 10 is immersed for 30 days, an increase in transmission loss is hardly observed.

  FIG. 4 is a measurement result of a change in transmission loss of the colored optical fiber 10 in the tape fiber when immersed in warm water at 60 ° C. As shown in FIG. 2, the tape fiber 20 is a combination of the colored optical fiber 10, the colored optical fiber 55 b provided with the colored layer B, the colored optical fiber 55 c provided with the colored layer C, and one dummy fiber 21. A four-fiber tape fiber fixed with a tape material 22.

  As shown in FIG. 4, in the colored optical fibers 55 of the colored layers B and C, an increase in transmission loss occurs as in the case where the colored optical fibers are directly immersed (see FIG. 5). In contrast, in the colored optical fiber 10 in which the colored layer 14 (colored layer A) having an elution rate of 3% or less is formed, an increase in transmission loss hardly occurs.

  As described above, the colored optical fiber is formed by forming the colored layer 14 in the outermost layer of the primary and secondary coating layers 12 and 13 formed around the bare optical fiber 11 so that the elution rate into water is 3%. Increase in optical transmission loss can be suppressed. In particular, it is possible to suppress an increase in transmission loss in 60 ° C. warm water having a high elution rate due to immersion in water.

It is sectional drawing which shows the colored optical fiber of this Embodiment. It is sectional drawing of the tape fiber formed connecting the colored optical fiber of FIG. 1, and the conventional colored optical fiber. It is a graph which shows the change of the transmission loss when a colored optical fiber is immersed in 60 degreeC warm water. It is a graph which shows the change of the transmission loss when the tape fiber of FIG. 2 is immersed in 60 degreeC warm water. (A) is sectional drawing which shows an optical fiber cable, (b) is sectional drawing which shows the detail of the tape fiber of (a), (c) shows the detail of the colored optical fiber of (b). It is sectional drawing shown. It is sectional drawing which shows a thermoplastic resin embedding type optical fiber cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Colored optical fiber 11 Optical fiber bare wire 12 Primary coating layer 13 Secondary coating layer 14 Colored layer

Claims (3)

  A colored optical fiber in which a plurality of coating layers are provided on an optical fiber bare wire, and a colored layer is formed on the outermost layer thereof. fiber.   The colored optical fiber according to claim 1, wherein the elution rate is determined by a change in weight with respect to an initial weight after the colored layer is immersed in warm water at room temperature, preferably 60 ° C for 30 days. The colored optical fiber according to claim 1 or 2, wherein the colored layer is formed of a polyether urethane acrylate ultraviolet curable resin having a gel fraction of 95% or more.

Images