JP2003137607A - Washing method for glass processed article and manufacturing method for optical fiber using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a washing method for a glass processed article by which a matter to be washed can be highly purely washed without damaging the surface thereof and to provide a manufacturing method for glass fiber by which the reduction of the characteristics of glass fiber caused by washing stages for a glass preform and a glass bar which are to be semiproducts of optical fiber can be suppressed. SOLUTION: The glass processed article is supersonically washed using a supersonic wave having 80-1,000 kHz frequency. Washing liquid containing a quaternary ammonium hydroxide is favorably used. Defective products can be suppressed and yield can be enhanced in the manufacturing stage for the optical fiber by applying this washing method to the washing of the glass base material and the glass bar for the optical fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a glass processed material, such as a glass base material for optical fiber, which requires a high degree of cleanliness, and more particularly, a glass processed material in which scratches caused by cleaning are suppressed. Regarding the cleaning method.

[0002]

2. Description of the Related Art In the fields of optical communication and optical measurement, optical fibers are widely used as signal light transmission paths. In this type of optical fiber, generally, a fiber preform is prepared by first providing a clad part to be the clad of the optical fiber around the core part to be the core of the optical fiber, and further to prepare this fiber preform. It is manufactured by heating and drawing to a predetermined wire diameter.

The fiber base material is manufactured by various methods. Among them, there is a method in which a glass rod serving as a core portion is inserted into a glass tube serving as a clad portion and further heated and drawn to be integrated. In addition, as a method of manufacturing a fiber preform for a polarization-maintaining optical fiber, two or four holes are punched in a predetermined portion of a clad portion, a rod-shaped stress applying member is inserted into each hole, and heating is further performed. There is a method of stretching and integrating.

In the manufacturing process of an optical fiber in which a glass rod is inserted into the hollow portion of the hollow cylindrical glass preform as described above and heated and integrated to produce a fiber preform, the glass preform and the glass rod are The surface should be highly smooth and clean before inserting the glass rod into the hollow of the glass preform. Therefore, the surface of the glass base material or the like is smoothed by a multi-step process such as grinding stone grinding, loose abrasive grain grinding, and finish polishing. Further, grindstone components, loose abrasive grains, rust preventive oil, cutting oil, processing wastes and the like generated in the processing step are removed by cleaning the glass processed material with various cleaning agents. .

In the cleaning process of such a glass processed product, ultrasonic cleaning using ultrasonic waves having a frequency of several to several tens of kHz is often used. In this ultrasonic cleaning, when the glass processed product is immersed in a cleaning tank filled with a cleaning liquid, and further ultrasonic vibration is applied to the cleaning liquid,
By vibrating particles such as water molecules in the cleaning liquid at high speed, water is rapidly vaporized to generate bubbles, and the bubbles are rapidly condensed and disappeared repeatedly. It becomes a state. This is called cavitation (cavitation phenomenon), and contaminants are decomposed by this phenomenon and easily dispersed in the cleaning liquid, so that cleaning can be effectively performed.

[0006]

However, when such ultrasonic cleaning is performed, defects such as scratches, cracks, and chips are generated on the surface of the glass due to the impact of the above-mentioned cavitation, or the scratches are generated. It may expand. Then, such scratches cause bubbles to be generated in the process of manufacturing the optical fiber. Then, the optical fiber may be easily broken at the time of drawing, the optical characteristics of the optical fiber may be varied or defective, and the yield may be reduced.

Therefore, an object of the present invention is to develop a method for cleaning a glass work which can be cleaned extremely cleanly without damaging the surface of the glass work which is the object to be cleaned, and also An object of the present invention is to provide a method of manufacturing an optical fiber, which can suppress deterioration of characteristics of the optical fiber due to a cleaning process of a glass base material and a glass rod which are semi-finished products of the optical fiber.

[0008]

The above problems can be solved by ultrasonically cleaning the glass workpiece with ultrasonic waves having a frequency of 80 kHz to 1000 kHz. At this time, it is preferable to use a cleaning liquid containing quaternary ammonium hydroxide. By applying this cleaning method to cleaning the glass base material for optical fiber and the glass rod, it is possible to suppress the generation of defective products in the manufacturing process of the optical fiber and improve the yield.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on the embodiments. The glass processed product in the glass processed product cleaning method of the present invention refers to a glass processed product processed by any known processing method, but the glass processed product cleaning method of the present invention is, in particular, grindstone grinding, loosening. Grinding, finishing grinding, etc. are processed, and grindstone components such as diamond powder generated in the working process, metal components such as iron and copper transferred from the fixtures, silicon carbide, free abrasive grains such as cerium oxide, etc. It is suitable for those to which submicron-order fine contaminants consisting of are attached.

In the present embodiment, the glass workpiece is ultrasonically cleaned using ultrasonic waves having a frequency of 80 kHz to 1000 kHz (1 MHz). The reason for using the ultrasonic wave in the high frequency band as compared with the conventional one is as follows.

As described above, cavitation occurs when ultrasonic waves of several to several tens of kHz are used. However, when the frequency of ultrasonic waves is set higher than this, it is known that the lower limit of the sound pressure in liquid that may cause cavitation becomes large, and therefore cavitation becomes difficult to occur. Also, when the frequency of ultrasonic waves increases,
Since the acceleration of vibration of particles such as water molecules due to ultrasonic waves increases in proportion to the square of the frequency, a strong detergency based on the vibration of the particles can be obtained. In the present embodiment, in order to obtain a high cleaning effect, the output of ultrasonic waves is
It is preferable to set it in the range of 100 to 1200 W.

As the cleaning liquid in the present embodiment, a liquid containing a known suitable cleaning agent can be used, but a liquid containing quaternary ammonium hydroxide is particularly preferable. The surface of the glass workpiece is thinly etched with quaternary ammonium hydroxide. Therefore, the contaminants are peeled off from the surface of the glass processed material and removed regardless of the type or property.

Quaternary ammonium hydroxide is an alkali that is as strong as inorganic hydroxides such as sodium hydroxide, but does not contain metal ions or halogen ions.
Residual component ions do not change the composition and properties of the glass. Therefore, for example, even if the cleaning method according to the present embodiment is applied to the glass base material for an optical fiber, there is no risk of deteriorating the characteristics of the final product, the optical fiber.

As the quaternary ammonium hydroxide,
It is preferable that even if it remains on the surface of the glass, it is easily decomposed and vaporized by heating to be removed. Examples of the quaternary ammonium hydroxide include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, diethyldimethylammonium hydroxide, triethylmethylammonium hydroxide, tetraethylammonium hydroxide and the like. Of these, tetramethylammonium hydroxide (hereinafter referred to as TMAH) is particularly preferable because it decomposes into methanol and trimethylamine by heating and is easily vaporized.

The quaternary ammonium hydroxide is used after being dissolved in a solvent such as water or a lower alcohol or a mixed solvent of a plurality of kinds of the above solvents. The concentration of the quaternary ammonium hydroxide in this cleaning liquid is 2 to 30% by weight,
In particular, it is preferably 5 to 20% by weight. If the concentration is less than 2% by weight, the detergency is weak, and if it exceeds 30% by weight, the alkali is too strong, which may damage the glass and impair the smoothness of the surface.

In the case where the object to be cleaned is highly contaminated, the cleaning liquid may optionally contain 0.01 to 1% of a known surfactant in order to enhance the cleaning power. However, the surfactant does not contain an alkali metal.

In the present embodiment, the temperature of the cleaning liquid is preferably in the range of 20 to 80 ° C, particularly preferably 20 to 60 ° C. If the temperature is lower than 20 ° C., the cleaning effect is not sufficient, and if it is higher than 80 ° C., there is a problem of deterioration of the cleaning agent or deterioration of working environment due to generation of steam. The washing time is preferably in the range of 3 to 180 minutes, more preferably in the range of 3 to 120 minutes. If the washing time is shorter than 3 minutes, the washing effect is not sufficient, and if it is longer than 180 minutes, the washing effect is not further improved and the productivity is deteriorated.

The treatment after cleaning can be performed, for example, by appropriately rinsing the object to be cleaned with pure water and then drying, as is conventionally done. However, since the quaternary ammonium hydroxide used as the cleaning agent in the present embodiment has the property of being decomposed and vaporized by heating as described above, even if the rinsing is insufficient, the residual cleaning agent causes There is no risk of the glass being deteriorated.

Next, an embodiment of the method for producing an optical fiber according to the present invention will be described with reference to specific examples. [Embodiment 1] An example of a procedure for manufacturing a single-mode optical fiber. First, a quartz glass rod is punched, and then the inner surface of this hole is polished to manufacture a quartz glass tube to be a clad. Next, the quartz glass tube is cleaned on both the inner surface and the outer surface by the method for cleaning a glass workpiece of the present invention. Next, a core rod prepared by a known method such as the VAD method is inserted into the hole of the quartz glass tube and heated and integrated to form a fiber preform. Further, a single mode optical fiber is obtained by drawing this fiber preform.

[Embodiment 2] This is an example of a procedure for manufacturing a polarization maintaining optical fiber. First, two holes are punched in a clad portion of a glass base material on which a core and a clad are formed, at predetermined symmetrical positions with respect to the core. Then, the inner surface of this hole is polished. Next, the perforated glass base material is washed by the method for washing a glass processed material of the present invention. Further, the glass rod that serves as the stress applying portion is ground to have a predetermined outer diameter to form a stress applying member. Next, this stress imparting member is washed by the method for washing a glass processed product of the present invention. Next, the stress applying member is inserted into the hole of the perforated glass base material and heated and integrated to form a fiber base material. Furthermore, a polarization-maintaining optical fiber is obtained by drawing this fiber preform.

However, the embodiment of the optical fiber manufacturing method of the present invention is not necessarily limited to the above-mentioned specific example. In the method of manufacturing an optical fiber that is usually carried out, cleaning the glass base material, which is a semi-finished product of the optical fiber,
By performing the method for cleaning a glass work of the present invention, an optical fiber having high cleanliness and no deterioration in characteristics can be manufactured.

The present invention will be described below with reference to test examples.
The present invention is not limited thereby. [Test Example 1] Further, a glass rod made of glass for stress application part was roughly ground using a # 80 grindstone, and then finely ground using a # 800 grindstone. further,
After performing centerless grinding with a # 1500 grindstone, final polishing was performed using a polishing liquid containing a cerium oxide having an average particle size of 1.7 μm or less and a brush to obtain a stress imparting member.

Further, a quartz glass rod having a diameter of 20 mm and a length of 500 mm is first perforated at a predetermined position with a # 170 tool, and then # 400, # 800, # 20 in that order.
The inner surface of the hole was ground using the grindstones of No. 00 and # 4500. Further, final polishing is performed using a polishing liquid containing a cerium oxide having an average particle diameter of 1.7 μm or less and a brush,
A glass base material was obtained.

The stress-applying member and the glass base material thus obtained were immersed in TMAH having a concentration of 10% by weight, and ultrasonic waves of various frequencies shown in Table 1 were used to obtain a temperature of 2%.
Ultrasonic cleaning was performed at 5 ° C for 10 minutes. The output of ultrasonic waves was 300W. After washing, each was rinsed three times with pure water and then dried by blowing clean air.

Evaluation of each cleaning agent was carried out by observing the object to be cleaned under a laser microscope (× 1000) and inspecting for the presence of residual contaminants and for the occurrence and progress of scratches. The test results are shown in Table 1 for the stress applying member.
Table 2 shows the glass base material.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from Table 1, when the ultrasonic frequencies were 28 kHz and 38 kHz, it was confirmed that contaminants remained and scratches were generated. On the other hand, when the frequency of ultrasonic waves was 100, 200, 950, and 1000 kHz, residual contaminants and the generation of scratches were not detected, and the surface was extremely clean and smooth.

[Test Example 2] The stress applying member and the glass base material were cleaned in the same manner as in Test Example 1 except that the cleaning temperature was 70 ° C. Use a laser microscope (× 10
00) to observe the presence or absence of residual contaminants and the occurrence and progress of scratches. The results of the test are shown in Table 3 for the stress applying member and in Table 4 for the glass base material.

[0030]

[Table 3]

[0031]

[Table 4]

As is clear from Tables 3 and 4, when the ultrasonic frequencies were 28 kHz and 38 kHz, it was confirmed that contaminants remained and scratches were generated. For it,
Ultrasonic frequency is 100, 200, 950, 1000k
At Hz, no residual contaminants or scratches were detected and the surface was very clean and smooth.

[Test Example 3] Similar to the test example 1 described above, a stress applying member and a glass base material perforated at predetermined positions were manufactured, and these were immersed in TMAH having a concentration of 10% by weight. Then, ultrasonic cleaning with a frequency of 100 kHz and an output of 300 W was performed at a temperature of 25 ° C. for 10 minutes. After rinsing and drying with pure water three times, the stress applying member was inserted into the hole of the glass base material, integrated with heating, and then spun to a predetermined thickness to manufacture a polarization maintaining optical fiber. 10k
No disconnection occurred when the m wire was drawn. When the polarization-maintaining optical fiber thus obtained was inspected, the number of bubbles generated was 2-3 cells / 10 km. No abnormalities were observed in the characteristics of this polarization maintaining optical fiber.

[Test Example 4] Similar to Test Example 1 described above, a stress applying member and a glass base material perforated at predetermined positions were manufactured, and the stress applying member was washed without washing them. Was inserted into the hole of the glass base material, heated and integrated, and then spun into a predetermined thickness to manufacture a polarization-maintaining optical fiber. When the wire was drawn for 10 km, the wire was broken 10 times / 10 km. When the obtained polarization-maintaining optical fiber was inspected, the number of bubbles generated was 50 cells / 10 km.

[0035]

As described above, according to the method for cleaning a glass processed product of the present invention, the glass processed product that has been subjected to processing such as polishing can be effectively and efficiently cleaned, and scratches in the cleaning process can be prevented. Occurrence and expansion are prevented. At this time, a higher cleaning effect can be obtained by using quaternary ammonium hydroxide used as a cleaning agent. Since this quaternary ammonium hydroxide is easily decomposed and vaporized by heating, even if the rinsing is insufficient, it does not adversely affect the obtained product.

The method for producing an optical fiber according to the present invention utilizes the above-described method for cleaning a glass workpiece. According to this method, the productivity of the step of cleaning a glass base material which is a semi-finished product of an optical fiber is improved. And the reliability is significantly improved. Therefore, when an optical fiber is manufactured from this glass base material, defects such as bubbles are hardly generated in the obtained optical fiber, and the yield is improved.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takafumi Kashima             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office F-term (reference) 4G021 BA01 BA02 BA03                 4G059 AA11 AB01 AB03

Claims (3)

[Claims] 1. A method for cleaning a glass workpiece, which comprises ultrasonic cleaning using ultrasonic waves having a frequency of 80 to 1000 kHz. 2. The method for cleaning a glass processed product according to claim 1, wherein the glass processed product is immersed in a cleaning liquid containing quaternary ammonium hydroxide and ultrasonically cleaned. 3. An optical fiber for producing an optical fiber by inserting a glass rod into a hollow portion of a hollow cylindrical glass preform, heating and integrating the fiber preform, and drawing the fiber preform to produce an optical fiber. In the method, one or both of the glass base material and the glass rod is used,
A method for manufacturing an optical fiber, comprising: cleaning the glass processed material according to claim 4.