Glass filament manufacturing method

Abstract

To provide a manufacturing method of an ultrafine glass filament containing less hydroxy group content and low dielectric loss.SOLUTION: A manufacturing method of a glass filament with a hydroxy group (Si-OH) content of 300 ppm or under and diameter of 1-20 μm includes irradiating a raw yarn having a raw yarn diameter of 100-2000 μm and involving 70 mass% or over of SiO2 with a laser beam having a wavelength of 0.7-100 μm, followed by heating and drawing the raw yarn to obtain the glass filament.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing glass filaments, and more specifically to a method for producing ultrafine glass filaments with a low hydroxyl group content. [Background technology]

[0002] In recent years, the spread of fifth-generation mobile communication systems (5G) and the development and production of IoT devices have led to demand for high-performance printed wiring boards that can handle faster information processing and higher communication frequencies. As a result, glass cloth for printed wiring boards is required to have low dielectric loss, which can further reduce signal degradation. Compared to ordinary glass fibers, glass fibers with a high SiO2 content are known to have superior dielectric properties. In particular, highly pure quartz glass fibers made of SiO2 have very low dielectric constants and dielectric loss tangents, resulting in very low dielectric loss, and are expected to be used more widely as glass cloth for printed circuit boards.

[0003] It has been reported that silica glass filaments can be produced by heating a silica glass rod to nearly 2000°C and stretching it (Patent Document 1). In this production method, an ultrafine silica glass rod is heated and stretched using an oxyhydrogen flame burner, but the water produced by the oxyhydrogen flame increases the number of hydroxyl groups, which causes a problem of increased dielectric loss in the resulting silica glass filaments. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-28240 [Patent Document 2] Japanese Patent Publication No. 58-55349 [Patent Document 3] U.S. Patent Application No. 3,981,705 [Patent Document 4] Patent No. 4748513 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing ultrafine glass filaments having a low hydroxyl group content and low dielectric loss. [Means for solving the problem]

[0006] As a result of extensive research to achieve the above object, the inventors have discovered that by applying a heating and drawing technique using laser light irradiation to glass yarn with a high SiO content, an increase in hydroxyl groups during the drawing process can be prevented and ultra-fine glass filaments with low dielectric loss can be obtained, thereby completing the present invention. Incidentally, laser light irradiation of optical glass fibers is a long-known technique. For example, Patent Document 2 discloses that laser light is irradiated onto joints, and Patent Document 3 discloses that laser light irradiation enables precise diameter control of glass fibers for optical waveguides. However, these techniques do not involve laser light irradiation for heating and drawing glass filaments in the production of glass filaments. Furthermore, Patent Document 4 discloses a technology for producing ultrafine fibers by irradiating organic resins with laser light, but this is an application to organic substances and does not disclose the use of laser light irradiation for heating and drawing glass filaments produced from inorganic substances.

[0007] That is, the present invention provides: 1. A method for producing glass filaments, comprising irradiating a raw yarn containing 70% by mass or more of SiO2 and having a diameter of 100 to 2000 μm with a laser beam having a wavelength of 0.7 to 100 μm, and then heating and stretching the raw yarn, thereby obtaining glass filaments having a hydroxyl group (Si-OH) content of 300 ppm or less and a diameter of 1 to 20 μm. 2. The method for producing glass filaments according to claim 1, wherein the laser source of the laser light is selected from carbon dioxide, YAG, Nd / glass, Nd / vanadate, diode, fiber, disk, HeCd, copper vapor laser, iodine laser, argon laser, krypton laser and chemical laser; 3. The method for producing a glass filament according to 1 or 2, wherein the raw yarn is made of silica glass containing 99% by mass or more of SiO2. 4. The method for producing glass filaments according to 3, wherein the raw yarn is irradiated with a carbon dioxide laser, heated to a temperature of 1700°C or higher, and then drawn. 5. The method for producing glass filaments according to 3 or 4, wherein the raw yarn is irradiated with a carbon dioxide laser, heated, and stretched by 1000 times or more to obtain glass filaments having a diameter of 3 to 10 μm. to provide. [Effects of the Invention]

[0008] In the method for producing glass filaments of the present invention, heating and drawing are performed by irradiating with laser light. Therefore, even in the case of glass types with a high SiO content, which increase hydroxyl groups and deteriorate dielectric loss characteristics when heated and drawn using conventional oxyhydrogen flames, the increase in hydroxyl groups during the drawing process can be prevented, and glass filaments with fewer hydroxyl groups and less dielectric loss can be obtained. Furthermore, the production method of the present invention is superior in productivity and economy compared to a production method in which all steps are carried out by heating in an electric furnace, and in addition, since the thermal history during drawing is small, the amount of distortion on the surface of the glass filaments is small, and the decrease in strength of the obtained glass filaments can be suppressed. Glass filaments containing 70% or more by mass of SiO2 obtained by the manufacturing method of the present invention have excellent dielectric properties, and in particular, glass filaments made of high-purity quartz glass with an SiO2 content of 99% or more by mass have even better heat resistance, weather resistance, thermal shock resistance, chemical stability, low thermal expansion coefficient, electrical properties, etc. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a schematic side view showing an example of a glass filament drawing apparatus used in the glass filament production method of the present invention. [Figure 2] 2 is a schematic side view showing an irradiation / heating means provided in the glass filament drawing device of FIG. 1 for irradiating laser light to heat the raw yarn. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be specifically described below. The method for producing glass filaments according to the present invention involves irradiating a raw yarn containing 70% by mass or more of SiO2 and having a diameter of 100 to 2000 μm with laser light having a wavelength of 0.7 to 100 μm, and then heating and stretching the raw yarn, thereby obtaining glass filaments having a hydroxyl group (Si—OH) content of 300 ppm or less and a diameter of 1 to 20 μm.

[0011] [1] Raw glass The raw glass constituting the yarn used in the manufacturing method of the glass filament of the present invention is a glass containing 70% by mass or more of SiO2 and having excellent low dielectric loss, and examples thereof include D glass having an SiO2 content of 72 wt% and containing B2O3 and other metal oxides, quartz glass having an SiO2 content of 90% by mass or more, and high-purity quartz glass having an SiO2 content of 99% by mass or more. Generally, dielectric loss improves with an increase in SiO2 content, so the raw glass used in the present invention is preferably silica glass with an SiO2 content of 90 mass% or more, and more preferably high-purity silica glass with an SiO2 content of 99 mass% or more.

[0012] [2] Raw yarn The raw yarn used in the manufacturing method of the present invention has a diameter of 100 to 2000 μm. This raw yarn can be obtained, for example, by heating an ingot made of the raw glass described above and having an average diameter of 100 mm in an electric furnace to 1700 to 2300° C. and drawing it. There are no particular restrictions on the shape of the raw yarn used in the present invention, and examples include glass ingots with a maximum diameter of 2 mm, monofilaments, multifilaments, and the like. The diameter of the raw yarn can be measured using a vernier caliper (CD-20, manufactured by Mitutoyo Corporation) as will be described later in the Examples.

[0013] [3] Laser source In the manufacturing method of the present invention, a laser beam is used as a light source for absorption into the raw yarn and thermal softening. Laser beams are suitable for the manufacturing method of the present invention because they have high parallelism, are easy to focus and form a parallel beam, and can produce a large output. The laser source is not limited as long as it has a wavelength of 0.7 to 100 μm, and for example, a laser source selected from carbon dioxide, YAG, Nd / glass, Nd / vanadate, diode, fiber, disk, HeCd, copper vapor laser, iodine laser, argon laser, krypton laser, and chemical laser can be used. Among these, a carbon dioxide gas laser with a wavelength of 10.6 μm, and a Nd-doped YAG laser or YVO laser with a wavelength of 1.06 μm are particularly preferred, with a carbon dioxide gas laser being more preferred because it can heat glass with high output in a short time.

[0014] [4] Glass filament manufacturing conditions In the production method of the present invention, the raw yarn described above is heated by irradiating it with laser light having a wavelength of 0.7 to 100 μm while applying tension to soften it, and then stretched. In this case, the amount of energy of the laser light absorbed by the yarn cannot be generally determined because it depends on the wavelength of the laser light, the diameter, density, heat capacity, yarn feed speed, yarn speed, and laser light absorption rate of the yarn. However, an amount of energy that heats the yarn to a temperature of 1700°C or higher, preferably 1800°C or higher, and more preferably 1900°C or higher, is suitable. The laser light absorptance of the raw yarn is preferably 0.6 or more, more preferably 0.9 or more, from the viewpoint of heating efficiency. If the absorptance is less than 0.6, the raw yarn may not be heated sufficiently, resulting in high drawing tension and making the yarn more susceptible to breakage. The draw ratio is not particularly limited as long as glass filaments having the desired average diameter can be obtained, but it is preferably 1000 times or more, more preferably 1050 times or more.

[0015] [5] Glass filament drawing device There are no particular limitations on the glass filament drawing apparatus used in the production method of the present invention, and for example, as shown in FIG. 1 , an apparatus can be used which basically comprises a supply means 10 capable of continuously supplying a raw yarn 1 at a constant speed v, a winding means 11 for winding the filament at a speed V faster than the speed v, and an irradiation / heating means 13 between these supply means 10, 11 for irradiating the running raw yarn 1 with a laser beam to heat it in order to soften and draw it.

[0016] In the irradiation and heating means 13, as shown in FIG. 2, the laser beam 15 is focused by a lens 16. In this case, the focal point of the laser beam 15 is located to the left of the yarn 1 in FIG. 2, but it may be located to the right. By shifting the running position of the yarn 1 from the focal point of the laser beam 15 in this way, the irradiation area of ​​the laser beam 15 can be made wider. In addition, an air-cooled or water-cooled shielding plate 20 is provided further to the right of the yarn 1 in FIG. 2, and this shielding plate 20 absorbs the laser beam 15 that is not absorbed by the yarn 1. Suitable materials for the shielding plate 20 include heat-resistant materials such as brick, and metals with roughened surfaces coated with heat-resistant paint.

[0017] In addition to the above-mentioned basic configuration, the glass filament drawing apparatus may also be equipped, as necessary, with, for example, a yarn preheating means that is installed upstream of the irradiating / heating means and that preheats the yarn to eliminate any tendency for the yarn to wind; a guide means that is slightly larger than the diameter of the yarn and that passes through and supplies the yarn so that the yarn is accurately supplied to the laser irradiation spot; an oil treatment means that is installed downstream of the irradiating / heating means and that focuses the filaments to make them easier to handle when a multifilament yarn is used; a heat retention means that is installed downstream of the irradiating / heating means and that keeps the thinned filaments warm to prevent fiber breakage; a protective means (cover) that protects the thinned fibers from the influence of external disturbances; and in particular, it is preferable to flow air or the like within the protective means in order to reduce the influence of air resistance during winding, and it is more preferable to flow air in the direction of the yarn flow.

[0018] [6] Glass filament The glass filaments obtained by the manufacturing method of the present invention described above have a hydroxyl group content of 300 ppm or less, preferably 200 ppm or less, and more preferably 150 ppm or less. The diameter of the resulting glass filaments can be set to 1 to 20 μm depending on the drawing conditions described above, but is preferably 3 to 10 μm, more preferably 3 to 7 μm. The filament diameter can be measured using a scanning microscope (model: DS130-S) manufactured by Topcon Corporation, as described in the Examples below. The filament diameter can also be calculated from the law of conservation of mass (volume) by dividing the original yarn diameter by the draw ratio. [Example]

[0019] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following, the diameter of the raw yarn and the diameter of the glass filament were measured as follows. The diameter of the raw yarn was measured using a vernier caliper (manufactured by Mitutoyo Corporation, CD-20). The filament diameter after drawing was measured using a scanning microscope (model: DS130-S) manufactured by Topcon Corp. It was confirmed that there was consistency between the original yarn diameter and the filament diameter calculated from the drawing ratio, and the converted values ​​are shown in the examples. The hydroxyl group content of the glass filaments was measured by diffuse reflectance IR.

[0020] [Example 1] A 230 μm diameter raw yarn made from a quartz glass ingot containing 99.9% SiO2 by mass was irradiated with a carbon dioxide laser with a laser diameter of 3.5 mm, a wavelength of 10.6 μm, and an output of 22.2 W to heat it up to a surface temperature of 2208°C, and then stretched 1080 times at a raw yarn feed rate of 0.074 m / min and a filament take-up rate of 80.0 m / min to obtain a glass filament with a diameter of 7 μm. The laser light absorptivity of the raw yarn was 0.9, and the hydroxyl group content of the resulting filament was 110 ppm.

[0021] [Example 2] The same raw yarn as in Example 1 was irradiated with a carbon dioxide laser having a laser diameter of 3.5 mm, a wavelength of 10.6 μm, and an output of 20 W to heat it up to a surface temperature of 2090°C, and then drawn 3300 times at a raw yarn feed rate of 0.074 m / min and a filament take-up rate of 224 m / min to obtain a glass filament having a diameter of 4 μm. The hydroxyl group content of the obtained filament was 135 ppm.

[0022] [Comparative Example 1] The same raw yarn as in Example 1 was heated to a surface temperature of 2010°C using an oxyhydrogen flame burner made of a mixed gas of oxygen and hydrogen, and then stretched 540 times to obtain glass filaments with an average diameter of 10 µm. The hydroxyl group content of these filaments was 450 ppm. [Explanation of symbols]

[0023] 1. Raw yarn 10 Supply means 11 Winding means 13 Irradiation / heating means 15 Laser light 16 lenses 20 shielding panels

Claims

1. SiO 2 a method for producing glass filaments, the method comprising: irradiating a raw yarn having a diameter of 100 to 2000 μm with a laser beam having a wavelength of 0.7 to 100 μm; and heating and stretching the raw yarn, thereby obtaining glass filaments having a hydroxyl group (Si—OH) content of 300 ppm or less and a diameter of 1 to 20 μm, a step of continuously supplying the raw yarn at a constant speed by a supplying means, irradiating the supplied raw yarn with the laser light to heat it, and then winding and drawing the heated raw yarn by a winding means which winds it at a speed faster than the constant speed.

2. 2. The method for producing glass filaments according to claim 1, wherein the laser source of the laser light is selected from the group consisting of carbon dioxide gas-based, YAG-based, Nd / glass, Nd / vanadate, diode, fiber, disk, HeCd, copper vapor laser, iodine laser, argon laser, krypton laser and chemical laser.

3. The raw yarn is made of SiO 2 3. The method for producing glass filaments according to claim 1, wherein the glass filaments are made of quartz glass containing 99% by mass or more of the above.

4. 4. The method for producing glass filaments according to claim 3, wherein the raw yarn is irradiated with a carbon dioxide laser, heated to a temperature of 1700° C. or higher, and drawn.

5. 5. The method for producing glass filaments according to claim 4, wherein the raw yarn is irradiated with a carbon dioxide laser, heated, and stretched by a factor of 1000 or more to obtain glass filaments having a diameter of 3 to 10 μm.

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