JP2024086540A - Glass cloth and manufacturing method thereof - Google Patents

Abstract

[Problem] To provide a glass cloth having excellent dielectric properties, little breakage of ground-entangled yarns during high-temperature heat treatment, and excellent mass productivity, and a manufacturing method thereof. [Solution] A glass cloth is provided that is configured with glass yarns containing a plurality of filaments as warp yarns and weft yarns. The glass cloth has ground-entangled yarns woven into its ear portions. The glass yarns and the ground-entangled yarns have softening points of 900°C or higher. A manufacturing method for the glass cloth is also provided, which includes a step of heat treating the glass cloth in the range of 600°C to 1600°C. [Selected Figures] None

Description

This disclosure relates to glass cloth and its manufacturing method.

Currently, the performance of information terminals such as smartphones is improving, and high-speed communication, as typified by 5G communication, is advancing. Against this background, there is a demand not only for the improvement in heat resistance that has been conventionally required, but also for further improvement in the dielectric properties of the insulating material (e.g., lowering the dielectric tangent), particularly for printed wiring boards for high-speed communication. Similarly, there is a demand for improved dielectric properties for prepregs used as insulating materials for printed wiring boards, and for the glass yarns and glass cloth contained in the prepregs.

Patent documents 1 and 2 describe constructing insulating materials using prepregs in which low dielectric resin (hereinafter referred to as "matrix resin") is impregnated into glass cloth in order to reduce the dielectric constant of insulating materials. Patent documents 1 and 2 describe that polyphenylene ether modified at the terminals with vinyl groups or methacryloxy groups is advantageous in terms of low dielectric properties and heat resistance, and that this modified polyphenylene ether is used as a matrix resin.

Patent Documents 3 and 4 describe constructing a prepreg using silica glass cloth made of glass yarns with a silicon dioxide (SiO ₂ ) content of 96.0 to 100.0 mass % in order to improve the dielectric properties of the prepreg. Patent Documents 3 and 4 disclose a method of heating the glass cloth at 450° C. to 1650° C. for 1 minute to 72 hours in order to reduce the dielectric tangent of the silica glass cloth. By performing heat treatment at a high temperature, the amount of silanol groups contained in the silica glass is reduced, making it possible to reduce the dielectric tangent of the glass cloth.

Incidentally, as described in Patent Document 5, a common weaving method is to weave a ground-entangled yarn into the endmost yarn of the glass cloth in order to prevent the yarns at the ears of the glass cloth from fraying.

International Publication No. 2019/065940 International Publication No. 2019/065941 JP 2021-63320 A JP 2021-195689 A Japanese Patent Application Laid-Open No. 59-15566

However, conventional glass cloths require further study in terms of improving their dielectric properties. For example, Patent Documents 1 and 2 do not take into consideration the use of low dielectric glass as described in Patent Documents 3 and 4.

As described in Patent Documents 3 and 4, the method of performing heat treatment at high temperatures of 450°C to 1650°C to reduce the dielectric tangent of glass cloth has the problem that if the softening point of the glass yarns that make up the glass cloth is low, the glass yarns may be broken by the heat treatment.

In addition, when a conventional glass cloth having ground-entangled yarns at the selvage portions as described in Patent Document 5 is used as the green fabric, the ground-entangled yarns are cut by the high-temperature heat treatment described above, which causes the ground yarns of the glass cloth to fray and wrap around rolls during the process, or causes the resulting glass cloth to have a poor appearance.

Therefore, the present disclosure aims to provide a glass cloth that has excellent dielectric properties, is less susceptible to breakage of ground-entangled yarns during high-temperature heat treatment, and is excellent for mass production, as well as a method for manufacturing the same.

Some aspects of the present disclosure are illustrated below.
[1]
A glass cloth formed of warp and weft yarns each including a glass yarn containing a plurality of filaments,
The glass cloth has ground-entangled yarns at its ears,
The glass cloth, wherein the softening points of the glass yarns and the ground-entangled yarns are 900° C. or higher.
[2]
2. The glass cloth according to item 1, wherein the softening point of the ground entangled yarn is 1000° C. or higher.
[3]
3. The glass cloth according to item 1 or 2, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % calculated as silicon dioxide (SiO ₂ ).
[4]
4. The glass cloth according to any one of items 1 to 3, wherein a ratio (B2/B1) of a count B1 of the glass yarn to a count B2 of the ground intertwining yarn is 1.0 or less.
[5]
5. The glass cloth according to any one of items 1 to 4, wherein a ratio (B2/B1) of a count B1 of the glass yarn to a count B2 of the ground intertwining yarn is 0.9 or less.
[6]
Item 6. The glass cloth according to any one of items 1 to 5, having a thickness in the range of 5 to 200 μm.
[7]
7. The glass cloth according to any one of items 1 to 6, wherein the glass cloth is a grey glass cloth in which the warp and weft yarns are surface-treated with a sizing agent containing, as a main component, at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin.
[8]
8. The glass cloth according to any one of items 1 to 7, wherein the glass cloth is a green glass cloth having an ignition loss value of 0.07% by mass or more and 5.0% by mass or less.
[9]
Item 9. The glass cloth according to any one of items 1 to 8, wherein the glass cloth is a green glass cloth having an ignition loss value of 0.07% by mass or more and less than 2.0% by mass.
[10]
10. The glass cloth according to any one of items 1 to 9, wherein FD2/FD1, which is a ratio of a filament diameter FD1 of the glass yarn to a filament diameter FD2 of the ground intertwining yarn, is 1.0 or less.
[11]
11. The glass cloth according to any one of items 1 to 10, wherein FD2/FD1, which is a ratio of a filament diameter FD1 of the glass yarn to a filament diameter FD2 of the ground intertwining yarn, is 0.95 or less.
[12]
Item 12. The glass cloth according to any one of items 1 to 11, wherein the ground-entangled yarn is a glass cloth greige that has been surface-treated with a sizing agent containing, as a main component, at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin, and the amount of the sizing agent attached to the ground-entangled yarn is in the range of 0.1 to 10.0 mass %.
[13]
Item 13. The glass cloth according to any one of items 1 to 12, wherein the bulk dielectric tangent of the glass of the glass yarn at 10 GHz is in the range of 0.002 or less.
[14]
Item 14. The glass cloth according to any one of items 1 to 13, wherein the glass cloth has a dielectric tangent at 10 GHz in the range of 0.002 or less.
[15]
Item 15. The glass cloth according to any one of items 1 to 14, wherein the glass cloth is surface-treated with a surface treatment agent containing a silane coupling agent.
[16]
A method for producing a glass cloth, comprising the steps of:
A process of preparing a glass cloth green machine in which glass yarns containing a plurality of filaments are used as warp yarns and weft yarns, which have ground-entangled yarns at the ears, and in which the softening points of the glass yarns and the ground-entangled yarns are 900° C. or higher;
A method for producing glass cloth, comprising a step of heat-treating the glass cloth green machine at a temperature in the range of 600 ° C. to 1600 ° C.
[17]
Item 17. The method for producing a glass cloth according to item 16, wherein the softening points of the glass yarns and the ground intertwining yarns are 1000° C. or higher.
[18]
Item 18. The method for producing a glass cloth according to item 16 or 17, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % calculated as silicon dioxide (SiO ₂ ).
[19]
Item 19. The method for producing a glass cloth according to any one of items 16 to 18, wherein the heat treatment time is 10 minutes or less.
[20]
20. The method for producing a glass cloth according to any one of items 16 to 19, wherein the heat treatment is performed by a roll-to-roll method.
[21]
21. The method for producing a glass cloth according to any one of items 16 to 20, further comprising a washing step prior to the heat treatment.

This disclosure makes it possible to provide a glass cloth that has excellent dielectric properties, is less susceptible to breakage of ground-entangled yarns during high-temperature heat treatment, and is excellent for mass production, as well as a method for manufacturing the same.

The following describes the embodiments of the present disclosure, but the present disclosure is not limited thereto, and various modifications are possible without departing from the gist of the disclosure. In this disclosure, a numerical range described using "~" indicates a numerical range that includes the numerical values before and after "~" as the lower and upper limits. In this disclosure, the upper or lower limit described in a certain numerical range can be replaced with the upper or lower limit of another numerical range. Furthermore, in this disclosure, the upper or lower limit described in a certain numerical range can also be replaced with a value shown in the examples. And, in this disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the function of the process is achieved.

[Glass cloth]
〔overall structure〕
The glass cloth of the present disclosure is composed of glass yarns including a plurality of filaments as warp yarns and weft yarns. Hereinafter, the glass yarns constituting the warp yarns and weft yarns are also referred to as "ground yarns". The above glass cloth has ground-entangled yarns at its ears. The softening points of the above glass yarns and ground-entangled yarns are 900°C or higher. In the present disclosure, unless otherwise specified, "glass cloth" includes all of glass cloths before heat treatment, glass cloths obtained after heat treatment, and glass cloths obtained after surface treatment. In the present disclosure, glass cloths before heat treatment are also referred to as "glass cloth greige".

Although not limited by theory, by using a glass yarn having a high softening point as the ground-entangled thread constituting the glass cloth, the ground-entangled thread hardly breaks even when the glass cloth is subjected to high-temperature heat treatment, and the glass cloth can be stably processed. More specifically, by using a glass yarn having a softening point of 900°C or more for the ground-entangled thread, the ground-entangled thread hardly breaks even when the glass cloth is subjected to high-temperature heat treatment at 600°C to 1600°C, and fraying of the glass thread can be suppressed in the manufacturing and processing process of the glass cloth. In addition, since the softening point of the glass thread is 900°C or more, even when the glass cloth is subjected to high-temperature heat treatment at 600°C to 1600°C, the glass thread is rarely broken, and the glass cloth can be stably processed. As a result, foreign matter on the surface of the glass cloth can be removed more than before, and the dielectric loss tangent of the obtained glass cloth can be reduced. Therefore, according to the above configuration, it is possible to provide a glass cloth having excellent dielectric properties (for example, a low dielectric loss tangent), and having excellent mass productivity with little breakage of the ground-entangled thread during high-temperature heat treatment.

In this disclosure, the "ears" of the glass cloth refer to the portions near both ends of the glass cloth, including a total of about 20 ground entanglement threads and warp threads located at both ends of the width of the glass cloth. Fraying of the ears refers to the phenomenon in which the ground entanglement threads break, causing the warp threads near the ground entanglement threads to come loose.

The glass cloth can have a woven structure using glass yarns as warp and weft threads. The glass yarns are, for example, composed of multiple glass filaments. Examples of the weaving structure of the glass cloth include plain weave, sash weave, satin weave, and twill weave. Of these, the plain weave structure is preferred.

The weaving density (weaving density) of the warp and weft threads that make up the glass cloth is preferably 10 to 120 threads/inch (= 10 to 120 threads/25 mm), and more preferably 40 to 100 threads/inch. If the weaving density is within the above range, it becomes easier to obtain glass cloth with excellent appearance quality. The weaving densities of the warp and weft threads may be the same or different.

The thickness of the glass cloth is preferably in the range of 5 to 200 μm, more preferably in the range of 10 to 100 μm, even more preferably in the range of 11 to 80 μm, and particularly preferably in the range of 13 to 60 μm. If the thickness of the glass cloth is within the above range, it becomes easier to obtain a glass cloth with a high quality appearance and an excellent dielectric tangent.

The dielectric loss tangent of the glass cloth at 10 GHz is preferably 0.002 or less, more preferably 0.0015 or less, even more preferably 0.001 or less, and particularly preferably 0.0005 or less. If the dielectric loss tangent of the glass cloth is within the above range, it is easy to obtain a glass cloth with an excellent dielectric loss tangent.

[Glass thread]
The glass yarn (ground yarn) used for the warp and weft yarns constituting the glass cloth has a softening point of 900° C. or higher. By using glass yarns having a softening point of 900° C. or higher for the warp and weft yarns of the glass cloth, it is possible to reduce the dielectric tangent of the obtained glass cloth, as described above. Since the glass cloth is subjected to a heat deoiling treatment at a temperature of 600° C. to 1600° C., the softening point of the glass yarn is preferably 1000° C. or higher, more preferably 1050° C. or higher, even more preferably 1100° C. or higher, and particularly preferably 1200° C. or higher. The softening point of the glass yarn is preferably higher than the temperature at which the heat deoiling treatment is performed.

The composition of the glass yarn preferably has a silicon (Si) content in the glass yarn in the range of 95.0 to 100 mass% calculated as silicon dioxide ( _SiO2 ). By using such glass yarn, the dielectric properties of the obtained glass cloth can be improved. From the viewpoint of improving the dielectric properties of the obtained glass cloth, the Si content is preferably in the range of 99.0 to 100 mass%, more preferably in the range of 99.5 to 100 mass%, and even more preferably in the range of 99.9 to 100 mass%.

In order to provide a glass cloth with excellent dielectric properties, the bulk dielectric tangent of the glass yarn used at 10 GHz is preferably 0.002 or less, more preferably 0.0015 or less, even more preferably 0.001 or less, and particularly preferably 0.0005 or less.

The average filament diameter of the glass filaments constituting the glass yarn is preferably 2.5 to 9.0 μm, more preferably 2.5 to 7.5 μm, even more preferably 3.5 to 7.0 μm, even more preferably 3.5 to 6.0 μm, and particularly preferably 3.5 to 5.0 μm. If the filament diameter is 2.5 μm or more, the filament breaking strength is high, so that the resulting glass cloth is less likely to generate fluff. Furthermore, if the filament diameter is 9.0 μm or less, the mass of the glass cloth is not too large, making it easy to transport or process. Furthermore, if the average filament diameter of the glass filaments is within the above range, the glass cloth has excellent handleability and is more likely to provide good appearance quality.

The glass yarns in the glass cloth greige are preferably surface-treated with a sizing agent. A sizing agent containing at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin as a main component is preferably used because it is easy to heat-deoil, inexpensive to obtain, and relatively easy to handle. By surface-treating the glass yarns with a sizing agent, fuzzing during spinning and warping of the glass yarns can be suppressed.

[Ground-tie thread]
The ground entanglement yarn of the glass cloth has a softening point of 900° C. or more. The ground entanglement yarn may be woven into the ears of the glass cloth. The manner in which the ground entanglement yarn is woven is not limited, but from the viewpoint of making the glass yarn less likely to fray, for example, the entanglement structure can be formed with a plurality of ground entanglement yarns, preferably 2 to 10, more preferably 2 to 4, and even more preferably 2, on the outer side of the ground yarns (warp yarns) located at both ends in the width direction of the glass cloth. One or more leno weave entanglement structures may be formed with a pair of ground entanglement yarns. The ground entanglement yarn can be entangled at the start and end of weaving the glass cloth during weaving so that the glass yarns of the woven warp yarns do not fray. In general, it is possible to weave the ground entanglement yarn into the glass cloth using a leno device provided on a loom. Here, the "entangled structure" refers to any structure in which the yarns are entangled as long as the woven yarns do not fray, but when the glass cloth has a plain weave structure, it is preferable to entangle the yarns to form a plain weave structure similar to that of the warp yarns. By using a ground-entangled yarn having a softening point of 900°C or more, the ground-entangled yarn can be broken even when the heat deoiling treatment is performed at a temperature range of 600°C to 1600°C. If the ground-entangled yarn is broken, the selvage of the glass cloth will come undone, causing the yarn to wind around a roller or the like during processing of the glass cloth, or causing a defective appearance of the obtained glass cloth. In order to process the glass cloth while maintaining improved quality and high productivity, the softening point of the ground-entangled yarn is preferably 1000°C or more, more preferably 1050°C or more, even more preferably 1100°C or more, and particularly preferably 1200°C or more. The softening point of the ground-entangled yarn is preferably higher than the temperature at which the heat deoiling treatment is performed.

The composition of the ground-entangled yarn is not particularly limited to inorganic fibers, organic fibers, etc., as long as the softening point is 900°C or higher, but glass yarn is preferably used from the viewpoint of preventing foreign matter from being mixed into the ground yarn of the glass cloth. High heat-resistant glass yarns such as T glass, S glass, quartz glass, and silica glass are known as glass yarns with a softening point of 900°C or higher. Among them, silica yarn and quartz yarn are particularly preferred as the ground-entangled yarn because they have a high softening point. When the ground-entangled yarn is a glass yarn, its Si content is preferably in the range of 95.0 to 100 mass%, preferably 99.0 to 100 mass%, more preferably 99.5 to 100 mass%, and even more preferably 99.9 to 100 mass%, calculated as _SiO2 .

In order to prevent the ground-entangled yarn from breaking during weaving, it is preferable that the ground-entangled yarn of the glass cloth greige is surface-treated with a sizing agent. It is preferable to use a sizing agent containing at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin as a main component, because it is easy to heat-deoil, inexpensive to obtain, and relatively easy to handle. From the viewpoint of preventing the ground-entangled yarn from breaking, the amount of sizing agent attached to the ground-entangled yarn is preferably in the range of 0.1 to 10.0 mass%, more preferably in the range of 0.2 to 9.0 mass%, even more preferably in the range of 0.3 to 8.0 mass%, and particularly preferably in the range of 0.35 to 7.5 mass%. If the amount of sizing agent attached is 0.1 mass% or more, the ground-entangled yarn is less likely to break on the loom. If the amount of sizing agent attached is 10.0 mass% or less, the amount of sizing agent residue attached to the glass cloth after heat-deoiling can be reduced, and the dielectric loss tangent of the obtained glass cloth can be reduced.

The count (tex) of the ground entanglement yarn is preferably the same as or finer than the ground yarn, and more preferably finer than the ground yarn. Since the entanglement structure is preferably composed of multiple ground entanglement yarns, by using a yarn thinner than the ground yarn as the ground entanglement yarn, the ears of the glass cloth do not become thick, and it is possible to prevent the end portions from becoming thicker when the glass cloth is wound into a roll. Specifically, the ratio (B2/B1) of the count B1 of the glass yarn used in the warp and weft yarns to the count B2 of the ground entanglement yarns is preferably 1.0 or less, more preferably less than 1.0, even more preferably 0.9 or less, even more preferably 0.8 or less, and particularly preferably 0.7 or less. The count B1 of the glass yarn means the average count of the warp yarn and the weft yarn.

From the viewpoint that the ground entanglement yarn is preferably a thinner yarn than the ground yarn, the ratio of the filament diameter FD1 of the glass yarn used as the warp and weft yarn to the filament diameter FD2 of the ground entanglement yarn, FD2/FD1, is preferably 1.0 or less, more preferably less than 1.0, even more preferably 0.95 or less, and particularly preferably 0.9 or less. When the filament diameter ratio is 1.0 or less, it is possible to suppress the occurrence of thickening of the ears when the glass cloth is wound into a roll. The filament diameter FD1 of the glass yarn means the average value of the filament diameter of the warp yarn and the filament diameter of the weft yarn.

[Method of manufacturing glass cloth]
The method for producing a glass cloth according to the present disclosure includes a step of preparing a glass cloth (a glass cloth green machine) and a step of heat-treating the glass cloth (a glass cloth green machine) in the range of 600° C. to 1600° C. Here, the glass cloth (a glass cloth green machine) is a glass cloth that is configured with glass yarns containing a plurality of filaments as warp yarns and weft yarns as described above, has ground-entangled yarns at its ears, and has a softening point of 900° C. or higher for the glass yarns and the ground-entangled yarns. After the heat treatment step, the method for producing a glass cloth may further include, optionally, a step of surface-treating the glass cloth surface, a step of reducing a silane coupling agent, and a step of opening the glass cloth.

[Process for preparing glass cloth fabric]
The process of preparing the glass cloth machine may include warping and weaving the glass yarn. This allows, for example, the manufacture of a glass cloth machine that is a woven fabric with a plain weave structure. The glass yarn used in the glass cloth machine is preferably surface-treated with a sizing agent mainly composed of starch, polyvinyl alcohol, or the like in order to suppress fluffing during spinning and warping of the glass yarn. The sizing agent treatment may be performed simultaneously with the spinning and warping process of the glass yarn. In addition, it is preferable that the ground-entangled yarn is also sized to suppress yarn breakage during weaving. The ground-entangled yarn may be sizing-treated simultaneously with the warp warping process.

The glass cloth fabric is woven by weaving the weft yarn into the warp yarn obtained in the warping process. The ground-entangled yarn is woven into the selvage of the glass cloth fabric during the weaving process to form a ground-entangled structure.

The ignition loss value of the glass cloth green machine, that is, the ignition loss value of the glass cloth green machine before thermal deoiling, is preferably 0.07% by mass or more and 5.0% by mass or less, more preferably 0.07% by mass or more and 3.0% by mass or less, more preferably 0.07% by mass or more and 2.0% by mass or less, even more preferably 0.07% by mass or more and less than 2.0% by mass, even more preferably 0.10% by mass or more and less than 1.8% by mass, and particularly preferably 0.1% by mass or more and less than 1.5% by mass. If the ignition loss value is 5.0% by mass or less, the amount of sizing agent on the surface of the glass cloth green machine is not too much, and the amount of sizing agent residue adhering to the glass cloth after thermal deoiling can be reduced. As a result, the dielectric tangent of the obtained glass cloth can be reduced. If the ignition loss value is 0.07% by mass or more, the effect of improving convergence as a sizing agent is sufficient, and fluff and scratches are less likely to occur during the glass cloth green machine and its processing.

[Heat treatment process of glass cloth raw material]
The heat treatment process of the glass cloth green machine includes a process of heat treating the glass cloth green machine in the range of 600°C to 1600°C. The heat treatment process can remove sizing agents (glues) and their modified products that are arbitrarily attached to the surface of the glass cloth green machine. In the present disclosure, the heat treatment process is also referred to as a "heat deoiling" process. In the heat treatment process of the glass cloth green machine, the glass cloth green machine, in which the softening points of the glass yarn and the ground entangled yarn are 900°C or higher, is heat deoiled in the temperature range of 600°C to 1600°C, thereby reducing the dielectric tangent of the glass cloth while suppressing damage to the glass cloth. From the viewpoint of obtaining the effects of the present disclosure, the temperature of the heat deoiling is preferably in the range of 700°C to 1500°C, more preferably in the range of 800°C to 1400°C, even more preferably in the range of 900°C to 1300°C, and particularly preferably in the range of 1000°C to 1200°C. When the heat deoiling temperature is 600° C. or higher, the residue of the sizing agent adhering to the glass cloth green fabric can be effectively removed, and the dielectric tangent of the obtained glass cloth can be effectively reduced. On the other hand, when the heat deoiling temperature is 1600° C. or lower, the devitrification phenomenon of the glass can be suppressed, and the decrease in the strength of the glass cloth can be prevented.

The heating time can be selected appropriately, and is preferably 10 minutes or less, more preferably 5 minutes or less, even more preferably 2 minutes or less, and particularly preferably 90 seconds or less. Since the heat treatment is performed at a high temperature, if the heating time is 10 minutes or less, damage to the glass cloth is reduced, and problems such as partial holes being made in the glass cloth or the glass cloth being cut during processing are less likely to occur. The lower limit of the heating time may be, for example, 1 second or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, from the viewpoint of effectively removing adhesive residues, etc.

It is preferable to include a step of washing the sizing agent attached to the surface of the glass cloth before subjecting the glass cloth to the thermal deoiling treatment. By removing the sizing agent to a certain extent before the thermal deoiling treatment, it is possible to reduce damage to the glass cloth caused by the thermal deoiling treatment. The solvent used for washing is not particularly limited, but washing with water, reverse osmosis (RO) water, ion-exchanged water, distilled water, etc. is preferable from the viewpoint of safety and cost. From the viewpoint of removing excess metal ions attached to the glass cloth surface, it is particularly preferable that the solvent used for washing is water with high purity such as ion-exchanged water or distilled water. The method of washing the glass cloth is not particularly limited, but for example, a method using ultrasonic waves (e.g., a method using an ultrasonic vibrator), spraying (e.g., spraying with a high-pressure spray), spraying with water vapor, etc. can be considered. From the viewpoint of inexpensive processing, a method of immersing the glass cloth in a tank containing a cleaning solution, removing excess cleaning solution with a squeeze roller, etc., and then drying the glass cloth is preferable. In this case, the immersion time may be, for example, 2 seconds or more, 5 seconds or more, 10 seconds or more, 15 seconds or more, or 120 seconds or less, 90 seconds or less, 60 seconds or less, or 45 seconds or less.

The means for heating the glass cloth machine can be any known heating method, heating medium, heating mechanism, heating device, and heating component, so long as the heating is performed so that the deoiling temperature is in the range of 600°C to 1600°C. Examples of the heating means include (1) heating the glass cloth machine in a heating furnace, (2) contacting the glass cloth machine with a heating section, and (3) applying high-temperature steam to the glass cloth machine. By heating the glass cloth machine so that the deoiling temperature is 600°C or higher, organic matter adhering to the surface of the glass cloth machine can be efficiently removed and the time required for removing the organic matter can be shortened. The glass cloth machine can be heated sequentially or continuously in a closed or open system, or in a combination of a closed system and an open system.

In the case of a closed system, it is preferable to place the glass cloth fabric in a heating furnace from the viewpoint of suitable heating by the heating means, and/or it is preferable to heat the glass cloth fabric while storing it in a rolled state from the viewpoint of storage space and heating range. It is also preferable to heat the glass cloth fabric while transporting it in the heating furnace from the viewpoint of increasing the efficiency of organic matter removal and shortening the time required for organic matter removal.

In the case of an open system, it is preferable to heat the glass cloth fabric while transporting it, from the viewpoint of the heated area. The glass cloth fabric can be transported, for example, by an unwinding mechanism and a winding mechanism, for example, a roll-to-roll system.

〔heating furnace〕
The heating means for the heating furnace is not limited to a specific means and may be various means such as an electric heater or a burner as long as it can heat the material so that the thermal deoiling temperature is 600° C. to 1600° C. In addition, a combination of multiple means may be used for heating, but it is preferable to use a gas-type single radiant tube burner or an electric heater.

From the viewpoint of heating efficiency, it is preferable that the heating furnace is provided with a means for discharging the gas generated in the heating furnace and/or an air circulation means. The gas discharge means may be, for example, a nozzle, a gas pipe, a small hole, a gas vent valve, etc. The air circulation means may be, for example, a fan, an air conditioning system, etc.

In order to efficiently remove organic matter adhering to the surface of the glass cloth fabric, a continuous method is preferred, in which the glass cloth fabric can be heated while being continuously passed through a heating furnace, rather than a batch method in which the glass fiber fabric is wound around a core and the glass cloth fabric is heated at a specified atmospheric temperature. Furthermore, a method in which the glass cloth fabric can be continuously washed with reverse osmosis (RO) water is the most preferable.

[Contact member for heating glass cloth fabric]
The above-mentioned heating furnace may be used as a method for heating the glass cloth green machine, but from the viewpoint of low running costs, the glass cloth green machine may be heated by contacting a member heated to a predetermined temperature with the glass cloth green machine.

There are no particular limitations on the shape of the contact member as long as it can heat the glass cloth green machine so that the heating and de-oiling temperature is in the range of 600°C to 1600°C, but a roll shape is preferred for ease of transporting the glass cloth green machine. As a member capable of heating the glass cloth green machine in a roll shape, a roll that heats by induction heating is preferred, as it can be used in high temperature ranges and has relatively little temperature variation in the width direction. When the glass cloth green machine is heated by the contact member, it is considered that the temperature of the contact member and the surface temperature of the glass cloth green machine are roughly the same.

In order to remove carbonized material that adheres to the heating roll as the glass cloth greige is continuously heated, it is preferable that the above heating roll method is a method equipped with a mechanism for removing the adhered foreign matter, such as a blade.

[Means for applying high-temperature steam to glass cloth fabric (steam application means)]
The steam applied to the glass cloth greige may contain, for example, a volatile solvent, water vapor, a gas other than water vapor, etc., but water vapor is preferred from the viewpoint of toxicity to the human body and the viewpoint of facilitating the decomposition of the sizing agent used in the glass fiber. The temperature of the high-temperature steam may be a method that can supply high-temperature steam and heated air at any ratio, if necessary, so that the surface temperature of the glass cloth greige is in the range of 600 ° C to 1600 ° C. The temperature of the high-temperature steam is 500 ° C or higher, preferably 600 ° C or higher, more preferably 700 ° C or higher, even more preferably 800 ° C or higher, and particularly preferably 900 ° C or higher. The steam application means is not limited, but may be spray, shower diffusion, jet nozzle, etc. Alternatively, the gas discharged from the heating furnace may be reused as high-temperature steam.

[Glass cloth fabric heating and de-oiling equipment]
As described above, the thermal deoiling device for the glass cloth green machine can heat the glass cloth green machine so that the thermal deoiling temperature is in the range of 600 ° C. to 1600 ° C. More specifically, the thermal deoiling device for the glass cloth green machine preferably includes a heating furnace that has an unwinding mechanism and a winding mechanism and is capable of performing a process of heating the glass cloth green machine so that the thermal deoiling temperature is in the range of 600 ° C. to 1600 ° C. while transporting the glass cloth green machine.

The unwinding mechanism and winding mechanism may be, for example, at least one pair of rolls, a roll-to-roll system, etc. The heating furnace, air circulation means, contact member, and steam application means are as described in the heat treatment process for the glass cloth greige above.

From the viewpoint of production efficiency, it is preferable to include a cleaning device for washing off the sizing agent from the glass cloth raw material immediately before the heating furnace.

[Glass cloth surface treatment process]
The method for producing a glass cloth may further include a step of subjecting the glass cloth surface to a surface treatment after subjecting the glass cloth green machine to a heat deoiling treatment. The surface treatment agent is not particularly limited, but it is preferable to use a silane coupling agent because it is inexpensive.

The process of applying the surface treatment agent includes, for example, a coating process in which the surface treatment agent is applied to the surface of the glass using a treatment liquid containing the surface treatment agent, and a fixing process in which the surface treatment agent is fixed to the surface of the glass by heating and drying. This makes it easier to perform a suitable surface treatment on the glass cloth.

Methods for applying the treatment liquid to the glass in the coating process include (a) immersing or passing the glass in the treatment liquid stored in a bath (hereinafter referred to as the "immersion method"), and (b) applying the treatment liquid to the glass using a roll coater, die coater, gravure coater, or the like. When using the immersion method, it is preferable to select a time for immersing the glass in the treatment liquid of 0.5 seconds or more and 1 minute or less. Furthermore, when using the immersion method, the glass can be passed through the treatment liquid at a conveying speed of 10 to 50 m/min while applying a predetermined tension (e.g., 100 to 250 N) to the glass. Furthermore, after the treatment liquid is applied to the glass, the solvent contained in the treatment liquid can be heated and dried using methods such as hot air or electromagnetic waves.

The concentration of the surface treatment agent in the treatment solution is preferably 0.1 to 0.5% by mass, more preferably 0.1 to 0.45% by mass, and even more preferably 0.1 to 0.4% by mass. This makes it easier to perform surface treatment on the glass more effectively.

In the fixing step, the heating and drying temperature is preferably 80°C or higher, more preferably 90°C or higher, so that the reaction between the surface treatment agent and the glass is sufficiently carried out. In addition, the heating and drying temperature is preferably 300°C or lower, more preferably 180°C or lower, to prevent deterioration of the organic functional groups of the surface treatment agent.

[Surface treatment agent reduction process]
The method for producing glass cloth may further include a step of reducing the surface treatment agent after the surface treatment step of the glass cloth. The step of reducing the surface treatment agent may include, for example, a cleaning step of cleaning the surface treatment agent that has not formed a chemical bond with the glass surface, and a drying step of heating and drying the glass after cleaning. The step of reducing the surface treatment agent may further include a finish cleaning step of reducing unnecessary components that have not been cleaned and have not formed a chemical bond with the glass surface after the drying step. The finish cleaning step makes it easier to control the amount of adhesion of the surface treatment agent. The step of reducing the surface treatment agent may further include, for example, a finish drying step after the finish cleaning step.

In the finish cleaning step, unnecessary components that are not completely washed off with water in the cleaning step and do not form chemical bonds with the glass surface can be reduced. In this finish cleaning step, for example, an organic solvent can be used as the cleaning liquid. By having the finish cleaning step, even when low dielectric glass is used, the difference between the dielectric tangent and bulk dielectric tangent of the resulting glass cloth can be reduced. As the organic solvent here, a highly hydrophobic organic solvent is preferable, and an organic solvent that has a high affinity with the residue and modified product of a surface treatment agent having a hydroxyl group, such as a silane coupling agent, is also preferable. The cleaning method can be an immersion method, a shower spray, or the like, and may be heated or cooled as necessary. In order to prevent the glass dissolved in the cleaning liquid from reattaching, it is preferable to reduce excess solvent from the glass after cleaning using a squeeze roller or the like.

The organic solvents that can be used as the cleaning liquid in the finish cleaning process include, for example, the following solvents, which can be used alone or in combination. Examples of highly hydrophobic organic solvents include saturated chain aliphatic hydrocarbons such as n-pentane, i-pentane, n-hexane, i-hexane, n-heptane, i-heptane, n-octane, i-octane, 2,2,4-trimethylpentane (isooctane), n-nonane, i-nonane, n-decane, i-decane, and 2,2,4,6,6-pentamethylheptane (isododecane); saturated cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, and ethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene; and halogen-containing solvents such as chloroform, dichloromethane, and dichloroethane.

Examples of organic solvents that have a high affinity with surface treatment agents, such as residues or modified products of silane coupling agents, include alcohols such as methanol, ethanol, and butanol; ketones such as acetone and methyl ethyl ketone; ethers such as methyl ethyl ether and diethyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; dimethyl sulfoxide; and the like. Among these, aromatic hydrocarbons, alcohols, and ketones are preferred, and methanol is more preferred, from the viewpoint of easily and efficiently reducing the surface treatment agents physically attached to the glass. Therefore, it is preferable to use a cleaning solution in which methanol is the main component (50% by mass or more, or 60% by mass or more of methanol relative to 100% by mass of the cleaning solution) as the cleaning solution in the finish cleaning step.

In the finish drying step, the cleaning liquid used in the finish washing step can be reduced. In order to easily reduce the amount of cleaning liquid by drying, it is preferable that the cleaning liquid used in the finish washing step has a boiling point of 120°C or less. For drying, a method of heat drying or air drying can be used. When an organic solvent is used as the cleaning liquid, it is preferable to perform heat drying by hot air drying using low pressure steam or heat transfer oil as a heat source from a safety standpoint. The drying temperature is preferably equal to or higher than the boiling point of the cleaning liquid, and is preferably equal to or lower than 180°C from the standpoint of suppressing deterioration of the silane coupling agent.

[Glass cloth spreading process]
The method for producing a glass cloth may further include a step of opening the glass cloth. As a method for opening the glass cloth in the opening step, for example, a method of opening the glass cloth with spray water (high pressure water opening), a vibro washer, ultrasonic water, a mangle, or the like can be adopted. By lowering the tension applied to the glass cloth during this opening process, the air permeability tends to be reduced. In order to suppress a decrease in the tensile strength of the glass cloth due to the opening process, it is preferable to take measures such as reducing friction with contact members when weaving the glass yarn, optimizing the bundling agent and increasing the amount of adhesion.

Each step in the above-mentioned glass cloth manufacturing method does not necessarily have to be performed separately, and multiple steps can be combined into one step. For example, if the cleaning step is performed after the weaving step, the cleaning step can also serve as the fiber-spreading step by using a high-pressure water spray or the like. In most cases, the composition of the glass cloth does not usually change before and after fiber-spreading. In addition, the glass cloth manufacturing method can have any step other than the above-mentioned steps. For example, a slitting step can be performed after the fiber-spreading step. If possible, the order of the above-mentioned steps can be reversed.

The manufacturing method for glass cloth described above makes it easy to apply a surface treatment agent to the surface of each glass filament that makes up the glass thread after effectively reducing unnecessary components that are thought to increase the dielectric tangent.

Embodiments of the present disclosure will be described with reference to examples and comparative examples. However, the present disclosure is not limited to the following examples and comparative examples.

[Method of measuring thickness of glass cloth]
The thickness of the glass cloth was measured according to JIS R 3420, 7.10. Specifically, a micrometer was used to gently rotate the spindle and lightly contact the measurement surface of the sample in parallel. Then, the scale was read after the ratchet made three noises. JIS R 3420, 7.10 specifies the general test method for cloth products such as glass cloth.

[Method for measuring ignition loss value]
The ignition loss value of the glass loss before the heat deoiling treatment was determined in accordance with JIS R 3420. The ignition loss value of the glass cloth was determined by sampling so as not to include the ground-entangled yarns.

[Method for measuring the amount of sizing agent attached to ground-entangled yarn]
The ground-entangled yarn was heated at about 800°C for 1 minute, and the amount of carbon dioxide in the gas generated was measured by gas chromatography to determine the amount of carbon dioxide in the gas generated. The total carbon amount ( _% ) per mass of the ground-entangled yarn contained in the ground-entangled yarn was determined by comparing the amount of carbon dioxide generated when a predetermined amount of acetanilide (C 8 H ₉ NO ) was similarly heated at about 800°C for 1 minute in advance. A SUMIGRAPH NC-90A (manufactured by Sumika Chemical Analysis Center) was used for the measurement.
Molecular weight of acetanilide=135.17
Carbon content of acetanilide = 71.09%
That is, the total carbon content of the ground-entangled yarn was calculated based on the following formula.
Total carbon amount of the ground-entangled yarn = [{mass of acetanilide x (carbon ratio of acetanilide / 100)} / peak area derived from carbon dioxide generated from acetanilide] x {(peak area of carbon dioxide generated from the ground-entangled yarn / mass of the ground-entangled yarn) x 100}
The total carbon amount of the obtained ground-entangled yarn was calculated as the amount of sizing agent attached.

[Method for measuring the softening point of glass yarn]
The softening point of the glass yarn in the present disclosure was measured in accordance with JIS R3103-1 using glass yarn. Also, the glass cullet having the same composition as the glass yarn was measured according to the method described below. That is, the glass cullet was remelted in a platinum crucible, and the range of 1000 poise to 2000 poise was measured using a high-temperature rotational viscometer (manufactured by Shibaura Systems Co., Ltd.), and the temperature at which the viscosity log η = 7.65 was calculated by extrapolation to obtain the softening point. The softening points of the glass yarn and the glass cullet were measured, and the higher temperature value was taken as the softening point of the glass yarn.

[Method of measuring basis weight (fabric weight)]
The basis weight of the glass cloth was obtained by cutting the glass cloth to a predetermined size and dividing the weight by the sample area. In this embodiment and comparative example, the glass cloth was cut to a size of ¹⁰ cm2 and the weight was measured to obtain the basis weight of each glass cloth.

[Converted thickness]
Since the glass cloth is a discontinuous planar body consisting of air and glass, the converted thickness required for measurement by the resonance method was calculated by dividing the basis weight of each glass cloth by the density of the glass.
Converted thickness (μm)=weight per unit area (g/m ² )÷density (g/cm ³ )

[Method of measuring dielectric tangent]
The dielectric loss tangent of each glass cloth was measured in accordance with IEC 62562. Specifically, the glass cloth samples sampled to a size required for measurement with each split cylinder resonator were stored in a thermostatic oven at 23°C and 50% RH for 8 hours or more to adjust the humidity. Thereafter, the dielectric properties at 10 GHz were measured using a split cylinder resonator (manufactured by EM Lab) and an impedance analyzer (manufactured by Agilent Technologies). The measurement was performed five times for each sample, and the average value was calculated. In addition, the thickness of each sample was measured using the above-mentioned converted thickness. Similarly, a glass plate having a thickness of 300 μm or less and having the same type and composition as each glass cloth raw material was prepared, and the bulk dielectric loss tangent at 10 GHz was also measured. IEC 62562 specifies a method for measuring the dielectric properties in the microwave band of fine ceramic materials for dielectric substrates used mainly in microwave circuits, and can be used to measure the bulk dielectric loss tangent of the glass of the glass yarn. More specifically, the glass plates sampled to the size required for measurement with each split cylinder resonator were stored in a thermo-hygrostatic oven at 23°C and 50% RH for 8 hours or more to adjust the humidity. Then, the dielectric properties at 10 GHz were measured using a split cylinder resonator (manufactured by EM Lab) and an impedance analyzer (manufactured by Agilent Technologies). The measurement was performed five times for each sample, and the average value was calculated. In addition, the thickness of each sample was measured using the thickness value obtained from the thickness measurement of the glass plate.

[Manufacture of glass cloth fabric]
6 kg of partially saponified polyvinyl alcohol was dispersed in 70 kg of water, heated to 90°C, stirred and held for 10 minutes, and then cooled to 65°C (liquid A). In a separate container, 500 g of paraffin emulsion (solid content 30% by weight) (liquid B), 100 g of formalin (liquid C), and 300 gr of octyltrimethylammonium ethosulfate (liquid D) were prepared. After liquids B, C, and D were added to liquid A in order, water was added to bring the total weight to 100 kg, and the mixture was kept at 60°C. The paste was applied to warped glass yarn using a paste applicator (manufactured by SUCKER), dried, divided, wound on a weaving beam, and woven by a high-speed air jet loom to obtain a green glass cloth. In addition, the ground intertwining yarns were woven using a leno device installed on a loom so that two ground intertwining yarns were woven outside the ground yarns (warp yarns) located at both ends of the glass cloth in the width direction so as to form an intertwining structure.

[Sizing agent treatment of ground-entangled yarn]
A ground-entangled yarn in which starch is used as a sizing agent was used. When the amount of sizing agent attached was insufficient, an additional sizing treatment was performed using the above-mentioned paste. The ground-entangled yarn was dipped in the paste, the excess paste was squeezed out with a squeeze roller, and the yarn was heated at 130°C for 10 seconds and dried, and then wound on a bobbin, whereby an additional sizing treatment was performed. Here, the amount of sizing agent attached to the ground-entangled yarn could be adjusted to any amount by adjusting the squeezing pressure of the squeeze roller.

[Surface treatment of glass cloth]
A treatment liquid was prepared by dispersing 0.12% by mass of 3-methacryloxypropyltrimethoxysilane; Z6030 (manufactured by Dow Toray Co., Ltd.) in pure water adjusted to pH = 3 with acetic acid. A glass cloth that had been subjected to a thermal deoiling treatment at a line speed of 30 m / min was immersed in the treatment liquid (surface treatment agent coating process), and after squeezing, it was heated and dried at 130 ° C for 35 seconds to fix the silane coupling agent (fixing process). The dried glass cloth was irradiated with ultrasonic waves of a frequency of 25 kHz and an output of 0.85 W / cm ² in water to reduce the excess silane coupling agent physically attached to the glass cloth (cleaning process). Then, the glass cloth was dried at 130 ° C for 1 minute (drying process) to perform surface treatment. Then, the glass cloth was immersed in methanol for finish cleaning, and modified products of the silane coupling agent that did not form chemical bonds with the surface of the glass filaments were removed (finish cleaning process). After the finish cleaning, the glass cloth was dried at 110° C. for 1 minute to obtain glass cloth from which the physically adhered modified product of the silane coupling agent had been removed.

Example 1
A green machine was manufactured using warp yarns, weft yarns and ground-entangled yarns (amount of sizing agent attached = 1.5% by mass) composed of glass fibers having a softening point of 1700 ° C. Specifically, a silica glass yarn having an average filament diameter of 5.0 μm, 100 filaments and 1.0Z twist was used as the warp yarn, and a silica glass yarn having an average filament diameter of 5.0 μm, 100 filaments and 1.0Z twist was used as the weft yarn. A silica glass yarn having an average filament diameter of 4.5 μm, 100 filaments and 1.0Z twist was used as the ground-entangled yarn. Then, a glass cloth was woven using an air jet loom with a weaving density of 66 warp yarns/25 mm and 68 weft yarns/25 mm. The sizing agent attached to the glass surface was washed while conveying the obtained cloth at a line speed at which it was immersed in a water tank containing RO water for 20 seconds (pre-deoiling washing process). Thereafter, the glass cloth was heated at 1000°C for 30 seconds in a heating furnace installed on the same line by a roll-to-roll method to deoil the glass cloth (thermal deoiling process). Both ends of the wound glass cloth after thermal deoiling were checked to check for breakage of the ground entanglement yarn, fraying of the ground yarn at the edge, and the winding shape of the roll. As a result of surface treatment of the glass cloth after thermal deoiling, no winding around the roll due to fraying of the edge was confirmed, and the glass cloth had good appearance quality.

(Examples 2 and 3)
The glass cloths were subjected to the thermal deoiling treatment and surface treatment under the same conditions as in Example 1, except that ground-entangled yarns with different softening points and amounts of sizing agent attached were used, the ignition loss values of the glass cloths, and the thermal deoiling conditions were different, as shown in Table 1. No fraying of the edge portions of the glass cloths caused winding around rolls or the like during the surface treatment was observed, and all of the glass cloths had good appearance quality.

Example 4
A green machine was manufactured using warp yarns, weft yarns and ground-entangled yarns (amount of sizing agent attached = 2.5% by mass) composed of glass fibers having a softening point of 1700 ° C. Specifically, a silica glass yarn having an average filament diameter of 5.0 μm, 200 filaments and 1.0Z twist was used as the warp yarn, and a silica glass yarn having an average filament diameter of 5.0 μm, 200 filaments and 1.0Z twist was used as the weft yarn. A silica glass yarn having an average filament diameter of 4.5 μm, 100 filaments and 1.0Z twist was used as the ground-entangled yarn. Then, a glass cloth was woven using an air jet loom with a weaving density of 54 warp yarns/25 mm and 54 weft yarns/25 mm. The sizing agent attached to the glass surface was washed while conveying the obtained cloth in a water tank containing RO water at a line speed at which it was immersed for 15 seconds (pre-deoiling washing process). Thereafter, the glass cloth was heated at 1200°C for 20 seconds in a heating furnace installed on the same line by a roll-to-roll method to deoil the glass cloth (thermal deoiling process). Both ends of the wound glass cloth after thermal deoiling were checked to check for breakage of the ground entanglement yarn, fraying of the ground yarn at the edge, and the winding shape of the roll. As a result of surface treatment of the glass cloth after thermal deoiling, no winding around the roll due to fraying of the edge was confirmed, and the glass cloth had good appearance quality.

Example 5
The glass cloth was subjected to the thermal deoiling treatment and surface treatment under the same conditions as in Example 4, except that ground-entangled yarns with different softening points and amounts of sizing agent attached were used, the ignition loss value of the glass cloth, and the thermal deoiling conditions were different, as shown in Table 1. The glass cloth also had good appearance quality, with no fraying of the edge portions during the surface treatment causing winding around rolls, etc.

Example 6
A green machine was manufactured using warp yarns, weft yarns and ground-entangled yarns (amount of sizing agent attached = 5.0% by mass) composed of glass fibers having a softening point of 1700 ° C. Specifically, a silica glass yarn having an average filament diameter of 4.0 μm, 50 filaments and 1.0Z twist was used as the warp yarn, and a silica glass yarn having an average filament diameter of 4.0 μm, 50 filaments and 1.0Z twist was used as the weft yarn. A silica glass yarn having an average filament diameter of 4.0 μm, 50 filaments and 1.0Z twist was used as the ground-entangled yarn. Then, a glass cloth was woven using an air jet loom with a weaving density of 95 warp yarns/25 mm and 95 weft yarns/25 mm. The sizing agent attached to the glass surface was washed while conveying the obtained cloth at a line speed at which it was immersed in a water tank containing RO water for 20 seconds (pre-deoiling washing process). Thereafter, the glass cloth was heated at 1000°C for 30 seconds in a heating furnace installed on the same line by a roll-to-roll method to deoil the glass cloth (thermal deoiling process). Both ends of the wound glass cloth after thermal deoiling were checked to check for breakage of the ground entanglement yarn, fraying of the ground yarn at the edge, and the winding shape of the roll. As a result of surface treatment of the glass cloth after thermal deoiling, no winding around the roll due to fraying of the edge was confirmed, and the glass cloth had good appearance quality.

(Example 7)
A green machine was manufactured using warp yarns, weft yarns and ground-entangled yarns (amount of sizing agent attached = 5.0% by mass) composed of glass fibers having a softening point of 1700 ° C. Specifically, a silica glass yarn having an average filament diameter of 3.6 μm, 38 filaments and 1.0Z twist was used as the warp yarn, and a silica glass yarn having an average filament diameter of 3.6 μm, 38 filaments and 1.0Z twist was used as the weft yarn. A silica glass yarn having an average filament diameter of 3.6 μm, 38 filaments and 1.0Z twist was used as the ground-entangled yarn. Then, using an air jet loom, a glass cloth was woven with a weaving density of 105 warp yarns/25 mm and 110 weft yarns/25 mm. The sizing agent attached to the glass surface was washed while conveying the obtained cloth at a line speed at which it was immersed in a water tank containing RO water for 20 seconds (pre-deoiling washing process). Thereafter, the glass cloth was heated at 1000°C for 30 seconds in a heating furnace installed on the same line by a roll-to-roll method to deoil the glass cloth (thermal deoiling process). Both ends of the wound glass cloth after thermal deoiling were checked to check for breakage of the ground entanglement yarn, fraying of the ground yarn at the edge, and the winding shape of the roll. As a result of surface treatment of the glass cloth after thermal deoiling, no winding around the roll due to fraying of the edge was confirmed, and the glass cloth had good appearance quality.

(Example 8)
As shown in Table 1, except for the difference in the ground-entangled yarn, the glass cloth was subjected to a heat deoiling treatment and a surface treatment under the same conditions as in Example 1. No fraying of the edge portions caused winding around a roll or the like during the surface treatment was observed, but because a ground-entangled yarn thicker than the ground yarn was used, the end of the roll was raised, and winding wrinkles of a degree that was not practical were generated.

(Comparative Example 1)
As shown in Table 1, the glass cloth was subjected to a heat deoiling treatment and a surface treatment under the same conditions as in Example 1, except that a ground-entangled yarn having a softening point of 840° C. was used. During the surface treatment, fraying of the edge portions was confirmed, causing winding around a roll or the like, and poor appearance such as severe winding wrinkles or winding creases was observed.

(Comparative Example 2)
As shown in Table 1, the glass cloth was subjected to a heat deoiling treatment and a surface treatment under the same conditions as in Example 4, except that a ground-entangled yarn having a softening point of 840° C. was used. During the surface treatment, fraying of the edge portions was confirmed, causing winding around a roll or the like, and poor appearance such as severe winding wrinkles and scratches was observed.

[Checking for breakage of ground-tangling wire]
When the glass cloths of the above-mentioned Examples and Comparative Examples were subjected to surface treatment, the glass cloths were observed over a longitudinal length of 2000 m for the presence or absence of breakage of the ground-entangled yarns at both ends.
A: The total number of cut points of the ground-entangled yarns at both ends is less than 5. B: The total number of cut points of the ground-entangled yarns at both ends is 5 or more.

[Checking for fraying of the edges]
After the surface treatment of the glass cloth of the above-mentioned Examples and Comparative Examples was performed, 2000 m of the glass cloth was wound up around a core tube such as an FRP or a paper tube. The presence or absence of fraying at the edge portions was confirmed by observing both ends of the obtained product roll.
A: The glass thread is not wrapped around the transport members such as rolls in the surface treatment process. B: The ears on both ends of the product are frayed, and the glass thread is wrapped around the transport members such as rolls in the surface treatment process.

[About the roll shape]
The glass cloths of the above-mentioned Examples and Comparative Examples were visually inspected for wrinkles on the glass cloth for every 1 m of the product while irradiating a halogen lamp under tension of 100 N/1300 mm on a roll-to-roll inspection table. The number of defective products per 2000 m of product was counted, with the number of product parts with wrinkle-induced appearance defects occurring at one or more locations per 1 m of product being regarded as defective, and the number of product parts with no appearance defects occurring at one location per 1 m of product being regarded as non-defective. From the inspection results, the glass cloths of the Examples and Comparative Examples were graded according to the following index. Evaluation D was judged as a failed product.
A: The total length of the product with wrinkles is less than 101 m (= the defective quantity rate is less than 5%)
B: The total length of the product with wrinkles is 101m or more and less than 200m (= the defective quantity rate is 5% or more and less than 10%)
C: The total length of the product with wrinkles is between 200m and 300m (= the defective quantity rate is between 10% and 15%)
D: The total length of the product with wrinkles is 300m or more (= the defective quantity rate is 15% or more)

The manufacturing conditions and evaluation results for the examples and comparative examples are shown in the table below.

Claims (21)

A glass cloth formed of warp and weft yarns each including a glass yarn containing a plurality of filaments,
The glass cloth has ground-entangled yarns at its ears,
The glass cloth, wherein the softening points of the glass yarns and the ground-entangled yarns are 900° C. or higher. The glass cloth according to claim 1, wherein the softening point of the ground entanglement yarn is 1000°C or higher. 3. The glass cloth according to claim 1, wherein the glass yarns have a silicon (Si) content of 95.0 to 100 mass % calculated as silicon dioxide (SiO ₂ ). The glass cloth according to claim 1 or 2, in which the ratio (B2/B1) of the count B1 of the glass yarn to the count B2 of the ground entanglement yarn is 1.0 or less. The glass cloth according to claim 1 or 2, in which the ratio (B2/B1) of the count B1 of the glass yarn to the count B2 of the ground entanglement yarn is 0.9 or less. The glass cloth according to claim 1 or 2, having a thickness in the range of 5 to 200 μm. The glass cloth according to claim 1 or 2, wherein the warp and weft yarns of the glass cloth are surface-treated with a sizing agent containing at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin as a main component. The glass cloth according to claim 1 or 2, wherein the glass cloth is a grey glass cloth having an ignition loss value of 0.07% by mass or more and 5.0% by mass or less. The glass cloth according to claim 1 or 2, wherein the glass cloth is a grey glass cloth having an ignition loss value of 0.07% by mass or more and less than 2.0% by mass. The glass cloth according to claim 1 or 2, in which the ratio FD2/FD1 of the filament diameter FD1 of the glass yarn to the filament diameter FD2 of the ground entanglement yarn is 1.0 or less. The glass cloth according to claim 1 or 2, in which the ratio FD2/FD1 of the filament diameter FD1 of the glass yarn to the filament diameter FD2 of the ground entangled yarn is 0.95 or less. The glass cloth according to claim 1 or 2, wherein the ground-entangled yarn is a glass cloth greige whose surface has been treated with a sizing agent containing, as a main component, at least one selected from the group consisting of starch, polyvinyl alcohol, polyurethane resin, epoxy resin, and acrylic resin, and the amount of sizing agent attached to the ground-entangled yarn is in the range of 0.1 to 10.0 mass %. The glass cloth according to claim 1 or 2, wherein the bulk dielectric tangent of the glass of the glass yarn at 10 GHz is in the range of 0.002 or less. The glass cloth according to claim 1 or 2, wherein the dielectric tangent of the glass cloth at 10 GHz is in the range of 0.002 or less. The glass cloth according to claim 1 or 2, wherein the glass cloth is surface-treated with a surface treatment agent containing a silane coupling agent. A method for producing a glass cloth, comprising the steps of:
A process of preparing a glass cloth green machine in which glass yarns containing a plurality of filaments are used as warp yarns and weft yarns, the glass yarns have ground-entangled yarns at the ears, and the softening points of the glass yarns and the ground-entangled yarns are 900° C. or higher;
A method for producing glass cloth, comprising a step of heat-treating the glass cloth green machine at a temperature in the range of 600 ° C. to 1600 ° C. The method for manufacturing glass cloth according to claim 16, wherein the softening points of the glass yarn and the ground yarn are 1000°C or higher. The method for producing a glass cloth according to claim 16 or 17, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % calculated as silicon dioxide (SiO ₂ ). The method for producing glass cloth according to claim 16 or 17, wherein the heat treatment time is 10 minutes or less. The method for manufacturing glass cloth according to claim 19, wherein the heat treatment is performed by a roll-to-roll method. The method for producing glass cloth according to claim 16 or 17, further comprising a cleaning step prior to the heat treatment.