JPH0989735A - Measurement of elasticity of primary coating layer of optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for measurement, which facilitates the formation of a test piece, and to perform the quality control of an optical fiber by the measurement of the elasticity of a primary coating layer quickly and readily on the manufacturing line. SOLUTION: One end of the strand of optical fiber is outputted and made to be a test piece 22 comprising a coated part 24 and a helical part 28. The coated part 24 of the test piece 22 is fixed to a fixing-side jig 26 of a tension tester by the force of 1-10g, and the tension test is performed. Thus, the elasticity of the primary coating layer of the optical fiber is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the elastic modulus of a primary coating layer of an optical fiber, which serves as a guide for knowing the cured state of the coating layer of the optical fiber in an optical fiber.

[0002]

2. Description of the Related Art In manufacturing an optical fiber, a primary coating layer made of a resin having a low elastic modulus is formed on a bare optical fiber for the purpose of protecting the optical fiber, and a resin having a high elastic modulus is formed on the primary coating layer. It has been practiced to form a secondary coating layer of the above to form an optical fiber strand. By the way, the ability of these coating layers to protect bare optical fibers depends on the cured state of the resin. Therefore, in order to obtain long-term reliability of the optical fiber, it is necessary to sufficiently cure the resin forming these coating layers. In particular, since the cured state of the above-mentioned primary coating layer has a great influence on the long-term reliability of the optical fiber, it is very important to grasp the cured state of the primary coating layer in the quality control of the optical fiber. . The cured state of this primary coating layer can be grasped by measuring its elastic modulus.

As a method for measuring the elastic modulus of the above-mentioned primary coating layer, the following method by an indentation test has been proposed (1994 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers Proceedings B-
816). FIG. 4 is a cross-sectional view of a test piece used in this measuring method as seen from the side surface. The optical fiber elemental wire 2 is installed in the center of the acrylic pipe 4, is filled between the optical fiber elemental wire 2 and the acrylic pipe 4, and is fixed by the cured epoxy resin 6. The above-mentioned test piece is prepared as follows. That is, the optical fiber strand 2 is placed in the center of the acrylic pipe 4, and the uncured epoxy resin is filled around the optical fiber strand 2 and cured. The both ends are cut and polished so that both end surfaces are parallel to each other to obtain a test piece.

5 and 6 are schematic diagrams showing an example of the above-mentioned measuring method. Reference numeral 8 in the figure is the above-mentioned test piece, and this test piece 8 is fixed to the jig 10 of the micro hardness tester. The center of the end face of the test piece 8 is vertically loaded from above by the indenter 12 at a constant loading speed. FIG. 6 is a cross-sectional view of an example of the state of the test piece 8 at this time as seen from the side surface. By applying a load with the indenter 14, the bare optical fiber 16 causes a displacement Z. This displacement Z depends on the elastic modulus of the primary coating layer 18 having a low elastic modulus, and the influence of the secondary coating layer 20 having a high elastic modulus can be ignored. The load amount and the displacement amount Z at this time are measured. In the figure, L indicates the length of the test piece, and Dp and Df are respectively
The outer diameter of the primary coating layer and the outer diameter of the bare optical fiber are shown.

By substituting these measured values into the following equation, the elastic modulus of the primary coating layer can be obtained. G = (1 + ν) W / πLZ · ln (D _p / D _f ) (where G: tensile elastic modulus of the optical fiber primary coating layer,
ν: Poisson's ratio, W: load amount, L: length of test piece,
Z: displacement amount of bare optical fiber, D _p : outer diameter of the primary coating layer of the bare optical fiber, D _f : outer diameter of bare optical fiber. )

[0006]

However, in the method of measuring the elastic modulus of the primary coating layer of the optical fiber described above, it is necessary to fill the acrylic resin with the epoxy resin and cure it when the test piece is prepared. In addition, since it is necessary to polish the test piece so that both end surfaces thereof are parallel to each other, it takes time to prepare the test piece and skill is required. Also, it is necessary to use a large amount of epoxy resin,
Further, when the epoxy resin is cured, heat generation and curing contraction occur, so that there has been concern about the history of heat on the optical fiber strand and the influence of compression.

The present invention has been made in view of the above circumstances, and it is easy to prepare a test piece in the measurement of the elastic modulus of the primary coating layer, which serves as a guide for knowing the cured state of the primary coating layer of the optical fiber. (EN) A measuring method is provided to enable quick and easy quality control of an optical fiber by measuring the elastic modulus of a primary coating layer on a production line. Further, by measuring the elastic modulus and the viscosity term of the primary coating layer of the optical fiber, it is possible to easily perform quality evaluation of newly developed products and the like.

[0008]

In the method of measuring the elastic modulus of the primary coating layer of an optical fiber according to claim 1 of the present invention, one end of the optical fiber element wire is exposed and the coated fiber and the bare fiber are removed. A test piece is formed by applying a force of 1 to 10 g to one jig of the tensile tester, and the bare wire part is fixed to the other jig to perform a tensile test. The measurement of the elastic modulus of the primary coating layer of the optical fiber is a means for solving the above-mentioned problems. Further, in the method for measuring the elastic modulus of the primary coating layer of an optical fiber according to claim 2, one end of the optical fiber element wire is exposed to form a test piece composed of a coated portion and a bare wire portion, and the test piece is coated. Part is fixed to one jig of a tensile tester via a buffer made of rubber-like elastic material, the bare wire part is fixed to the other jig, and a tensile test is performed to determine the primary of the optical fiber. Measuring the elastic modulus of the coating layer was used as a means for solving the above problems.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION First, an example of a method for measuring the elastic modulus of a primary coating layer of an optical fiber according to claim 1 will be described. First, the optical fiber element wire is cut into a length of about 20 to 60 mm, and one end of this optical fiber element wire is exposed while leaving a part of the coating layer, to obtain a test piece. At this time, the length of the coated portion of the test piece and the length of the bare wire portion of the test piece were 3
Adjust appropriately so that it is -10 mm and 3-15 mm. Part 1 of this test piece using a tensile tester
The elastic modulus of the next coating layer is measured.

FIG. 1 is an example of a schematic view showing a tensile tester and its measuring method. First, the covering portion 24 of the above-described test piece 22 is fixed to the fixed jig 26. Next, the end of the exposed bare wire portion 28 of the test piece 22 is fixed to the movable side jig 30 provided above the fixed side jig 26. In this state, the fixed jig 26 remains stationary and the movable jig 30 is raised at a constant speed.

FIG. 2 shows an example of a sectional view of the state of the test piece at this time as seen from the side surface. By pulling up the bare wire portion 32, the bare wire portion 32 causes a displacement δ. This displacement δ depends on the elastic modulus of the primary coating layer 34 having a low elastic modulus, and the influence of the secondary coating layer 36 having a high elastic modulus can be ignored. At this time, the load amount and the displacement amount δ are measured. In the figure, 1 indicates the length of the coating portion of the test piece. Further, r _p and r _f are the radius of the outer diameter of the primary coating layer and the radius of the outer diameter of the bare optical fiber, respectively.

Since the amount of displacement of the bare optical fiber depends on the elastic modulus of the primary coating layer, the elastic modulus of the primary coating layer of the optical fiber element wire can be obtained from the following equation. G = F / (2πlδ) · ln (r _p / r _f ) ... Formula (where G: elastic modulus of the optical fiber primary coating layer, F: load amount, δ: displacement amount, 1: test piece Length of coating, r _f :
Radius of outer diameter of bare optical fiber, r _p : Radius of outer diameter of primary coating layer. )

However, as shown in FIG. 1, the force applied to the fixed-side jig 26 for fixing the covering portion 24 is 1 to 1
Set to 0g. If it is less than 1 g, the covering portion 24 of the test piece 22
Can not be fixed sufficiently stably, and if it exceeds 10 g, the force from the side affects the measured value and an accurate measured value cannot be obtained.

When measuring the viscosity term of the primary coating layer, an arbitrary positive load is applied to the test piece 22 at an arbitrary frequency (si).
(n waves) repeatedly added. The displacement observed at that time,
The viscosity term of the primary coating layer is obtained from the time difference (phase difference) generated between the applied loads.

As described above, in the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to the first aspect, one end of the optical fiber element wire is exposed to form a test piece composed of a coated portion and a bare wire portion. Since the elastic modulus of the primary coating layer of the optical fiber can be measured by the method of subjecting this to a tensile test, the test piece can be easily prepared and the measurement operation can be carried out quickly and easily.

Next, an example of a method of measuring the elastic modulus of the primary coating layer of the optical fiber according to the second aspect will be described. In the example of the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 2, 1 of the optical fiber according to claim 1 described above is used.
The difference from the example of the method for measuring the elastic modulus of the next coating layer is that one end of the optical fiber element wire is exposed to form a test piece consisting of a coated part and a bare wire part, and when subjected to a tensile test, the coated part of this test piece Is fixed to a fixed-side jig of the tensile tester via a cushioning body made of a rubber-like elastic body.

FIG. 3 is a plan view showing an example of the covering portion 38 of the test piece, which is fixed to the fixed-side jig 42 provided in the tensile tester via the buffer 40. That is, the covering portion 38 of the test piece is bonded and fixed to the groove provided in the buffer body 40, and the buffer body 40 is fixed to the stationary jig 42. Hereinafter, the elastic modulus and the viscosity term are measured in the same manner as in the above-mentioned claim 1 and the example of measuring the elastic modulus of the primary coating layer of the optical fiber.

The force applied to the fixed-side jig 42 for fixing the above-mentioned shock absorber 40 may be 1 to 50 g. Within this range, the buffer 40 and the covering portion 38 can be fixed sufficiently stably, and an accurate measured value can be obtained. The influence of the side force on the coating portion 38 of the test piece is absorbed by the cushioning body 40,
There is no need to perform fine preparation when fixing, and the measurement operation is simple.

The depth A of the groove provided in the buffer 40 must be slightly deeper than the diameter of the coating portion 38 of the test piece,
Usually, it is set to about 260 to 450 μmm. The thickness B of the buffer 40 is 0.5 to 2 mm. If it is less than (l), the buffering effect is not sufficient, so that an accurate measured value cannot be obtained, and if it exceeds (m), the covering portion 38 cannot be sufficiently fixed.

As the rubber-like elastic body used for the cushioning body 40, acrylic elastomer, rubber or the like having an elastic modulus of 10 to 200 kg / mm ² can be used. The method of fixing the covering portion 38 of the test piece to the buffer body 40 and the fixing side jig 42 is not particularly limited. For example, the buffer 4
The covering portion 38 may be applied to the groove provided in 0, and the cushioning body 40 and the covering portion 38 may be sandwiched between the fixed-side jig 42. However, in particular, a very small amount of the instant adhesive is covered with the covering portion 38. By applying it to the side surface of and then adhering it to the buffer body 40, it is possible to adhere quickly and sufficiently.

Thus, the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 2 is the same as the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 1. Since the method is one in which one end of the strand is exposed to form a test piece composed of a covered portion and a bare wire portion, the test piece can be easily prepared. When the test piece is subjected to a tensile test, the covering portion of the test piece is fixed to a fixed jig of a tensile tester via a cushioning body made of a rubber-like elastic material.
Since the elastic modulus of the primary coating layer of the optical fiber can be measured, it is not necessary to finely adjust the force applied to the fixed jig when fixing the test piece to the fixed jig, and the measurement operation can be performed. It's easy.

Further, in the measuring method according to the first and second aspects, an ordinary tensile tester can be used. However, if a thermomechanical analyzer is used instead, a tensile tester can be used under various temperature conditions. Since the elastic modulus and the viscosity term of the primary coating layer can be measured, it is also possible to measure these temperature characteristics. Therefore, the above-described measuring method is also suitable for easily performing quality evaluation of newly developed products and the like.

[0023]

The present invention will be described below in detail with reference to examples. (Examples 1 to 5) Five kinds of urethane acrylate-based ultraviolet curable resins having different elastic moduli obtained by a tensile test in a sheet state were used as primary coating layer resins, and optical fiber strands were prepared. The elastic moduli of the primary coating layers of these optical fiber strands were measured according to the measuring method of the elastic moduli of the optical fiber coatings of claims 1 and 2.

First, a test piece of the above-mentioned optical fiber element wire was prepared as follows. The above-mentioned five types of resins for the primary coating layer were applied to bare optical fibers having an outer diameter of 125 μm, respectively, and irradiated with ultraviolet rays to be sufficiently cured to form a primary coating layer. On these primary coating layers, an uncured urethane acrylate-based UV-curing resin is applied as a resin for the secondary coating layer, and is irradiated with ultraviolet rays to be sufficiently cured to give an optical fiber element having an outer diameter of 250 μm. Created a line. One end of each of these optical fiber strands was exposed and used as a test piece.
At this time, the lengths of the coated portion and the bare wire portion of these test pieces were about 5 mm and about 10 mm, respectively.

Tensile tests were carried out using these test pieces according to the measuring method of claim 1.
That is, the thermomechanical analyzer set at 25 ° C (model name:
In TMA / SS120C manufactured by Seiko Denshi Kogyo Co., Ltd., as shown in FIG.
4 was fixed to the fixed side jig 26 by applying a force of 2 g. The end of the bare wire portion 28 of this test piece was fixed to a movable side jig 30 provided above and outside the fixed side jig 26. After holding for 3 minutes in this state, the movable side jig 30 is raised at 0.1 μm / sec while the fixed side jig 26 remains stationary,
The load amount at this time and the displacement amount of the bare optical fiber were measured. By substituting these values into the above equation, the elastic modulus of the primary coating layer was obtained.

Using the test pieces prepared in the same manner, the elastic moduli of the primary coating layers were measured according to the measuring method of claim 2. That is, as shown in FIG. 3, a very small amount of an instant adhesive was applied to the side surface of the covering portion 38 of the above-described test piece, and the covering portion 38 was adhered to the groove provided in the buffer 40. The buffer 40 is attached to the fixed jig 4
2 was fixed by applying a force of 10 g. Hereinafter, the elastic modulus of the primary coating layer of each test piece was measured in the same manner as the above method. The above-mentioned buffer 40 was created using a rubber sheet. The depth A of the groove provided in this buffer 40 is 3
The thickness B was 50 μm, and the thickness B of the buffer 40 was 1 mm.
The measurement results of the elastic moduli measured according to the measuring method according to claim 1 and claim 2 were almost the same.

(Comparative Examples 1 to 5) 1 of the above Examples 1 to 5
Sheet-shaped test pieces were prepared using the resin for the next coating layer. The elastic modulus of these sheet-shaped test pieces was measured at 25 ° C. by a normal tensile test using a thermomechanical analyzer. Comparative Examples 1 to 5 correspond to Examples 1 to 5, respectively.

FIG. 7 is a graph showing the relationship between the relative values of the measurement results of Examples 1 to 5 and the relative values of the measurement results of Comparative Examples 1 to 5. The horizontal axis of this graph shows the relative value of the elastic modulus measurement results of Comparative Examples 1 to 5, and the vertical axis shows the relative value of the elastic modulus measurement results of Examples 1 to 5. . The point a in the figure corresponds to Example 1 and Comparative Example 1. Hereinafter, similarly, points b to e correspond to Examples 2 to 5 and Comparative Examples 2 to 5, respectively. Regarding the measurement results of Examples 1 to 5, the measurement results obtained by the measurement method according to claim 1 and the measurement results obtained by the measurement method according to claim 2 have almost the same values. The relative value of the measurement result by the measuring method described in 1 is shown. From the graph of FIG. 7, it can be seen that each value has a good correlation.

(Examples 6 to 7) With respect to the test pieces prepared in the same manner as in Examples 1 to 5, the elastic moduli of the primary coating layers were measured under different temperature conditions. That is, two types of urethane acrylate-based ultraviolet curable resins having different monomer types were used as the resin for the primary coating layer to prepare test pieces. For these test pieces, -40 to
Under the temperature condition of 40 ° C., the elastic moduli of the primary coating layers were measured according to the measuring method described in claim 1 above.

FIG. 8 shows the relative values of the elastic modulus measurement results of the test pieces of Example 6 and Example 7 under each temperature condition. Curves f and g in the figure are respectively
It corresponds to Example 6 and Example 7, and shows the relative value of the measurement result under each temperature condition. FIG.
From the graph, it can be seen that even at the normal temperature, even if the optical fiber strands have almost the same value as the elastic modulus of the primary coating layer, their elastic moduli differ greatly when the temperature conditions are changed. Therefore, when evaluating a product of an optical fiber, it is necessary to measure the elastic modulus and the viscosity term of the primary coating layer of the optical fiber under various temperature conditions.

As described above, in the method of measuring the elastic modulus of the primary coating layer of the optical fiber according to the first and second aspects, almost the same measurement result was obtained by either method. Further, the relative values of these measurement results showed a good correlation with the relative values of the measurement results of the usual tensile test of the sheet-shaped test piece. Therefore, it is clear that the cured state of the primary coating layer of the optical fiber can be known from the measurement result obtained by the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 1 and claim 2. is there. Also,
At room temperature, it was found that the elastic moduli of the optical fiber strands having substantially the same value as the elastic modulus of the primary coating layer may differ greatly depending on the temperature conditions. Therefore, when evaluating optical fiber products, it is necessary to measure and study the elastic modulus and viscosity term of the primary coating layer under various temperature conditions.

[0032]

As described above, according to the first aspect of the present invention.
In the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 2, one end of the optical fiber element wire is exposed to form a test piece composed of a coated portion and a bare wire portion.
The elastic modulus of the primary coating layer of the optical fiber can be measured. Therefore, the test piece can be easily prepared, and the measurement operation can be performed quickly and easily, so that the quality control by measuring the elastic modulus of the primary coating layer of the optical fiber can be performed on the production line. Moreover, since the shape of the test piece is a method suitable for both the tensile test and the compression test, not only the elastic modulus but also the viscosity term can be measured. Furthermore, since it is possible to obtain these physical property values under various temperature conditions by using a thermomechanical analyzer in place of an ordinary tensile tester, it is possible to obtain a large amount of physical property information with a simple operation. it can. Therefore, the quality of newly developed products can be evaluated quickly and easily.

Further, in the method of measuring the elastic modulus of the primary coating layer of the optical fiber according to the second aspect, the coating portion of the test piece is placed on one side of the tensile tester through a buffer made of a rubber-like elastic body. Since it is a method of fixing the test piece to the jig, it is not necessary to finely adjust the force applied to the jig when fixing the test piece, and the measurement can be performed by a simple operation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a tensile tester and a measuring method therefor in a method of measuring the elastic modulus of a primary coating layer of an optical fiber according to claim 1.

FIG. 2 is a side sectional view showing an example of a state of the test piece when the bare wire portion of the test piece is pulled up in the method for measuring the elastic modulus of the primary coating layer of the optical fiber according to claim 1. .

FIG. 3 is a coating portion of a test piece fixed via a buffer to a fixed jig provided in a tensile tester in the method for measuring the elastic modulus of a primary coating layer of an optical fiber according to claim 2; It is a top view showing an example.

FIG. 4 is a cross-sectional view of an example of a test piece used in a measuring method in the related art as seen from a side surface.

FIG. 5 is a schematic diagram showing an example of a measuring method in the related art.

FIG. 6 is a cross-sectional view of an example of a state of the test piece when a load is vertically applied by an indenter from the center of the end surface of the test piece in a conventional measuring method, as viewed from the side.

FIG. 7 is a graph showing relative values of elastic modulus measurement results of Examples 1-5 and Comparative Examples 1-5.

FIG. 8 is a graph showing relative values of elastic modulus measurement results of Examples 6 to 7.

[Explanation of symbols]

22 ... Test piece, 24 ... Covering part, 26 ... Fixed jig, 28 ... Bare wire part, 30 ... Movable jig, 3
2 ... Bare wire part, 34 ... Primary coating layer, 36 ... 2
Next coating layer, 38 ... coating portion, 40 ... buffer body, 42
... Fixing jig, l ... Length of test piece coating, r
_p ... outer diameter radius of primary coating layer, r _f ... outer diameter radius of bare optical fiber, A ... groove depth, B ... buffer thickness

Claims (2)

[Claims] 1. A test piece consisting of a coated portion and a bare wire portion is obtained by exposing one end of an optical fiber element wire, and the coated portion of this test piece is applied to one jig of a tensile tester with a force of 1 to 10 g. A method for measuring the elastic modulus of a primary coating layer of an optical fiber, characterized by performing a tensile test by fixing the bare wire part to the other jig and fixing the same. 2. A tensile tester, wherein one end of an optical fiber element wire is exposed to form a test piece composed of a coated portion and a bare wire portion, and the coated portion of the test piece is passed through a buffer made of a rubber-like elastic body. One of the optical fibers is characterized in that it is fixed to one jig and the bare wire portion is fixed to the other jig to perform a tensile test.
Method for measuring the elastic modulus of the next coating layer.