JP2001064040A - Coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent strength of an optical fiber from being deteriorated in a deteriorative environment under no stress by forming plural coated layers consisting of an ultraviolet ray-curing resin around a glass fiber based on quartz glass and specifying the pH and the turbidity of the resin of at least the lowermost layer of the coated layers. SOLUTION: The coated optical fiber 4 is obtained by forming two or more coated layers, first and second layers 2, 3, consisting of the ultraviolet ray-curing resin around the glass fiber 1 based on quartz glass. The ultraviolet ray-curing resin of at least the first coated layer 2 is made to have 8.0 or lower pH and 0.2 or higher turbidity. The pH and turbidity are adjusted, for example in the case of urethane-acrylate resin, by the selection of material kinds of the component materials and by adjusting the mixing amount of alkaline materials such as amine additives and other materials having polar groups. When the resin of the layer 2 has such pH and turbidity, the fiber 1 in high temperature water under no stress is prevented from being deteriorated and has around 90% or higher breaking strength holding rate. When the resin of the second coated layer 3 has also the similar pH and turbidity, the breaking strength holding rate can be made into almost 100%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated optical fiber in which a coating layer made of at least two ultraviolet-curable resins is provided on a glass fiber mainly composed of quartz glass.

[0002]

2. Description of the Related Art In a coated optical fiber in which a coating layer made of a UV-curable resin is provided on a glass fiber mainly composed of quartz glass, the coating optical fiber is made neutral or acidic. Can suppress the decrease in glass fiber strength during long-term use, see JP-A-6-250053; Am. Ceram. So
c. , 71 [3] 177-83 (1988) (M. JO
HN MATTHEWSON, etc.) "Environme
ntal Effects on the Stati
c Fatique of Silica Optic
al Fiber "and the like.

[0003]

The inventors of the present invention have confirmed by experiments that even if the UV-curable resin for the coating layer has a neutral pH, the coated light produced by the UV-curable resin can be used. Fibers do not necessarily have properties related to glass strength in a degraded environment under stress (Zero Street).
ss Aging characteristics: hereinafter referred to as "ZSA characteristics")
Was not always good. Thus, the present inventors have conducted various studies on the UV-curable resin for the coating layer, and found that the ZSA characteristics of the coated optical fiber can be improved by setting the turbidity of the resin together with the pH of the UV-curable resin. Was found.

[0004]

The coated optical fiber according to the present invention is a coated optical fiber comprising a glass fiber and two or more coating layers made of an ultraviolet curable resin provided on a glass fiber. The UV-curable resin or the UV-curable resin of the first coating layer and the second coating layer has a pH of 8.0 or less and a turbidity of 0.2 or more. The coating layer immediately above the glass fiber is referred to as a first coating layer, and the coating layer thereon is referred to as a second coating layer.

[0005] As described above, p of the ultraviolet curable resin of the coating layer is
By defining H and turbidity in a certain range, a coated optical fiber in which the breaking strength of the glass fiber does not decrease even in a degraded environment under no stress, as is clear from the experimental results shown in the following Examples, That is, a coated optical fiber having good ZSA characteristics can be obtained.

The pH of the UV-curable resin of the coating layer is
Is determined by the following method. First, 1 g of the resin liquid is collected from the resin liquid immediately before application in the production of the coating layer, and 200 ml of ether is added thereto, and the mixture is stirred and completely dissolved. And
This solution is used as a pH meter (P manufactured by Electrochemical Instruments Co., Ltd.).
H20).

[0007] The turbidity of the ultraviolet curable resin of the coating layer is determined by the following method. FIG. 2 is a cross-sectional view illustrating a method of measuring the turbidity of a resin, where 5 is a quartz glass cell,
Reference numeral 6 denotes a resin-dissolved solution, 7 denotes eyes, and 8 denotes newsprint.
First, 10 g of the resin liquid is collected from the resin liquid immediately before application in the production of the coating layer, and 200 ml of methanol or ethanol is added thereto and stirred to completely dissolve the resin liquid. 5 g of dilute hydrochloric acid having a concentration of 0.01 mol / liter is added to the solution, and the mixture is stirred to be uniform. Next, the solution 6 was placed in a quartz glass cell 5 (a quartz glass container provided with two quartz glass plates having a thickness of t = 1 mm in parallel and an inner space having a thickness of a = 8 mm provided therebetween). , The thickness of the entire container b = 10 mm), and a plurality of the cells 5 are stacked.
Then, the number of cells 5 of the limit at which the characters of the newspaper 8 placed on the opposite side can be visually read is checked.

When the number of cells 5 is N, the reading is readable, and when the number of cells 5 is N + 1, the reading is unreadable. The turbidity of the liquid is (1-N / 10). Turbidity is set to 0 for N = 10 or more. When one cell is not visible, turbidity is 1
When 10 cells can be seen, the turbidity is 0. The turbidity of pure water is 0 because the cells filled with pure water can be seen even when 10 cells are stacked. Also, a turbidity of 0.2 means
If there are eight cells, you can read the text of the newspaper through it,
If the number of cells is nine, it means that the liquid in the quartz cell is turbid to the extent that the characters on the newspaper cannot be read.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view showing an example of a coated optical fiber, wherein 1 is a glass fiber comprising a core / cladding mainly composed of quartz glass, and 2 is a relatively soft ultraviolet curing type. The first coating layer 3 made of a resin or the like is a second coating layer made of a relatively hard UV-curable resin or the like, and 4 is a coated optical fiber. The reason why the first coating layer 2 is made of a relatively soft UV-curable resin and the second coating layer 3 is made of a relatively hard UV-curable resin is that the glass fiber 1 is formed by microbending based on environmental temperature change or the like. This is to protect them from the like.

The coated optical fiber 4 is formed by heating and melting an optical fiber glass preform and drawing the glass fiber.
And apply UV curable resin in two layers on it,
It is obtained by irradiating it with ultraviolet light to cure the resin. Examples of the coated optical fiber provided with three or more coating layers include those in which a coating layer made of an ultraviolet curable resin is further provided on the second coating layer.
There are various types of coated optical fibers, such as those in which a plurality of coating layers are arranged in parallel and a collective coating layer made of an ultraviolet curable resin is provided to cover them collectively.

In the coated optical fiber of the present invention, at least the first coating layer 2 or the first and second coating layers 2 and 3
UV curable resin having a pH of 8.0 or less and a turbidity of 0.1.
Select from two or more. In addition, such a resin, when the ultraviolet-curable resin is a urethane acrylate-based resin, selection of the constituent material type of the urethane acrylate,
It can be obtained by reducing the amount of alkaline raw materials such as amine-based additives and the content of other polar groups excluding alkali, such as ester and urethane groups.

By making the pH of the resin of the first coating layer 2 at least 8.0 and the turbidity at least 0.2, the ZSA characteristic of the coated optical fiber 4 is improved,
It is possible to maintain the breaking strength retention of the glass fiber in a high-temperature water or high-temperature and high-humidity degradation-free accelerated deterioration test at 90% or more. Further, at least the first coating layer 2
By setting the pH of the resin of the second coating layer 3 to 8.0 or less and the turbidity to 0.2 or more, the finished coated optical fiber 4 has further improved ZSA characteristics, It is possible to maintain the breaking strength retention of the glass fiber in the deterioration promotion test under no stress in the glass at almost 100%.

[0013]

EXAMPLE The urethane acrylate of the urethane acrylate-based UV-curable resin was changed in various kinds of constituent materials to add an alkaline material such as an amine-based additive, and other polar groups excluding alkali such as an ester / urethane group. Fourteen kinds of UV-curable resins were prepared by changing the content in various ways, and prepared as materials for the coating layer. Then, from the above-mentioned ultraviolet curable resin, a relatively soft resin, that is, a resin having an elastic modulus in a range of 0.05 to 0.2 kg / mm ^{2 is used} as a resin for the first coating layer, and a relatively hard resin, that is, an elastic modulus is used. 2
A resin in the range of 5 to 150 kg / mm ² is selected as a resin for the second coating layer, applied to a glass fiber made of quartz glass having an outer diameter of 125 μm, and cured by irradiating ultraviolet rays. 200 μm first coating layer and outer diameter 24
Seven types of coated optical fibers having a second coating layer of 5 μm were obtained.

Tables 1 and 2 show the measured values of the pH and turbidity of the ultraviolet-curable resin used for the seven types of coated optical fibers, and the values of the seven types of coated optical fibers in high-temperature water, high-temperature and high-humidity, respectively. It is a table | surface which shows the breaking strength retention of the glass fiber in the deterioration test in an atmosphere, Table 1 shows that pH of the resin used for at least 1st coating layer is 8.0 or less,
Those having a turbidity of 0.2 or more are shown as Examples 1 to 4 of the present invention, and Table 2 shows those whose pH or turbidity is not within the range as Comparative Examples 1 to 3.

[0015]

[Table 1]

[0016]

[Table 2]

The breaking strength retention of the glass fiber in a deterioration test in high-temperature water or high-temperature, high-humidity atmosphere was determined as follows. A coated optical fiber in which two coating layers are provided on a glass fiber and cut into 2 m lengths.
A set of books is 3 for Examples 1-4 and Comparative Examples 1-3.
One set is prepared and left in a high-temperature water at 85 ° C. for 30 days so that no stress such as bending is applied to the coated optical fiber, and the other set is a high temperature at 85 ° C. and a relative humidity of 85%. Each set was left for 30 days in a high-humidity atmosphere and was not placed in such a degraded environment.

The breaking strength of each coated optical fiber was measured by using an autograph tester (manufactured by Shimadzu Corporation) to perform a tensile test at a tensile speed of 25 mm / min and a mark interval of 500 mm. In the tensile test, the coated optical fiber is pulled with the coating layer provided. However, since the coating layer has an extremely large breaking elongation as compared with the glass fiber, the breaking strength in the tensile test shows the breaking strength of the glass fiber itself. In addition, those placed in the degraded environment and those not placed in the degraded environment are distinguished from each other, and the respective breaking strengths are respectively displayed on a Weibull distribution map, and 50% of each value is placed in the degraded environment or not placed in the degraded environment. And the breaking strength retention was determined from those ratios.

As can be seen from Examples 1 to 3 in Table 1, the UV-curable resin of the first coating layer and the second coating layer having a pH of 8.0 or less and a turbidity of 0.2 or more were treated at high temperatures. The glass fiber has a breaking strength retention of 98% to 105% even in a degraded environment in water or high temperature and high humidity, and hardly changes. In Example 4 of Table 1, the resin of the first coating layer was a resin having a pH of 8.0 or less and a turbidity of 0.2 or more, but the resin of the second coating layer had a turbidity of 0. Not more than 2. Therefore, the breaking strength retention rate of the glass fiber when placed in a degraded environment in high-temperature water or high-temperature and high-humidity slightly decreases to 90% to 95%, but is lower than that of a comparative example described later. The breaking strength retention is improved.

Comparative Examples 1 to 3 in Table 2 show the results of experiments in which the pH of the UV-curable resin for the first coating layer is not less than 8.0 or the turbidity is not more than 0.2, When placed in a degraded environment in high-temperature water and high-temperature and high-humidity environments, the breaking strength retention of all glass fibers is 90% or less.

From the above experimental results, since the UV-curable resin of the first coating layer is in contact with the glass fiber, the influence on the glass fiber is high, and the pH of the resin is 8.0.
Hereinafter, it is understood that when the turbidity is 0.2 or more, a decrease in the breaking strength of the glass fiber when placed in a degraded environment in high temperature water or high temperature and high humidity under no stress can be suppressed. Also,
The pH of the resin in the coating layer is in the neutral or acidic range,
And by selecting a low transparency of the resin solution, the hydrophilicity of the coating layer is reduced, the content of the polar group of the resin is reduced, the hydrolysis with hot water deterioration and the decrease in crosslink density are less likely to occur, It is presumed that the penetration of water into the interface between the coating layer and the glass fiber is reduced, and as a result, the breaking strength of the glass fiber in the degraded environment is maintained.

[0022]

According to the coated optical fiber of the present invention, the ultraviolet curable resin of at least the first coating layer on the glass fiber is p-type.
Since it is composed of a resin having a H of 8.0 or less and a turbidity of 0.2 or more, even if it is left in a high-temperature water or a high-temperature and high-humidity atmosphere under no stress for a long time, a decrease in the breaking strength of the glass fiber is hardly observed. I can't. Therefore, the strength of the glass fiber can be guaranteed for a long time. In addition, if the second coating layer in addition to the first coating layer is made of an ultraviolet curable resin having a pH of 8.0 or less and a turbidity of 0.2 or more, the coated light having good ZSA characteristics and reliability over a long period of time. Fiber can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a coated optical fiber.

FIG. 2 is a cross-sectional view illustrating a method for measuring the turbidity of an ultraviolet curable resin.

[Explanation of symbols]

 1: glass fiber 2: first coating layer 3: second coating layer 4: coated optical fiber 5: cell made of quartz glass 6: solution in which resin is dissolved 7: eyes 8: newspaper

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoyuki Hattori 1-chome, Taya-cho, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works F-term (reference) 2H050 BA32 BB07Q BB07S BB14S BB14S BB14S BB33Q BB33S BC03 BD03 BD05 4G060 AA01 AA03 AC02 AC04 AC14 AD43 CB09 CB22 CB35 4J011 QB24 SA82 SA90 UA01 WA03

Claims (2)

[Claims] 1. A coated optical fiber comprising a glass fiber and two or more ultraviolet-curable resin coating layers provided thereon, wherein at least the ultraviolet-curable resin of the first coating layer has a pH of 8.0 or less and a turbidity of at least one. Coated optical fiber characterized by being 0.2 or more. 2. A coated optical fiber comprising a glass fiber and two or more ultraviolet-curable resin coating layers provided thereon, wherein the ultraviolet-curable resin of the first coating layer and the ultraviolet-curable resin of the second coating layer are both PH 8.0 or less, turbidity 0.2
A coated optical fiber as described above.