JP2023178209A - Quartz glass cloth heating method and low dielectric quartz glass cloth manufacturing method - Google Patents

Abstract

To provide a quartz glass cloth heating method capable of suppressing dielectric loss tangent at a low level and a manufacturing method capable of manufacturing a low dielectric quartz glass cloth without special post processing after heat treatment.SOLUTION: In the quartz glass cloth heating method, a quartz glass cloth containing SiO2 of 95 mass% or more is put in a heating furnace and the quartz glass cloth is heated under conditions where maximum heating temperature is 100 to 600°C and heating amount expressed by heating temperature (°C) of 100°C or more×heating time (h) is 450 (°C h) in vacuum or gas having dew point of 15°C or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of heating a quartz glass cloth that can lower the dielectric loss tangent, and a method of manufacturing a low dielectric quartz glass cloth.

BACKGROUND ART Currently, as information terminals such as smartphones become more sophisticated and communicate at higher speeds, the printed wiring boards used are becoming denser, thinner, and have lower dielectric and dielectric loss tangents. The insulating material for this printed wiring board is a laminate made by laminating prepreg obtained by impregnating glass cloth with thermosetting resin such as epoxy resin (hereinafter referred to as "matrix resin") and curing it under heat and pressure. is widely used. Signal transmission loss in the board is described by Edward A. Wolff formula: Transmission loss ∝√ε×tanδ It is known that materials with smaller dielectric constant (ε) and dielectric loss tangent (tanδ) are improved as shown by It is known that the contribution of the dielectric loss tangent is large. Therefore, glass cloth is required to have a low dielectric loss tangent, and glass cloths with improved dielectric properties such as D glass, NE glass, L glass, and Q glass have been proposed (Patent Documents 1 to 4). However, from the viewpoint of achieving sufficient transmission speed performance in future 5G communication applications, etc., there is still a need for improvement in these low dielectric property glass cloths that are excellent in low dielectric constant and low dielectric loss tangent.

Japanese Patent Application Publication No. 5-170483 Japanese Patent Application Publication No. 2009-263569 Japanese Patent Application Publication No. 2009-19150 Japanese Patent Application Publication No. 2006-282401 Japanese Patent Application Publication No. 2021-195689

Silica glass is a glass containing 95% by mass or more of SiO ₂ and has very excellent electrical properties. However, due to its high purity, silica glass tends to produce SiOH groups, and even if the quartz glass has exactly the same composition, the dielectric loss tangent varies greatly depending on the amount of SiOH groups contained in the quartz glass. In Patent Document 5, quartz glass is treated at high temperature. However, there was a problem in that the glass surface was distorted by high-temperature heating, the strength was lowered, and etching treatment had to be performed for 24 hours or more after heating to remove the distortion.

The present invention has been made in view of the above circumstances, and includes a heating method for quartz glass cloth that can lower the dielectric loss tangent, a method for manufacturing quartz glass cloth that can produce a low dielectric quartz glass cloth without special post-treatment after heat treatment, and a method for manufacturing quartz glass cloth. The purpose is to provide a method.

Silica glass contains more than 95% by mass of SiO ₂ , and the Si-OH groups on its surface are highly active. Especially in high-temperature atmospheres, it absorbs moisture through hydrogen bonds and cleaves the Si-O-Si bonds, further forming Si-OH groups. It is thought that a group is generated (SiO ₂ +H ₂ O⇔Si-OH). The Si--OH groups generated here deteriorate the dielectric loss tangent of the glass cloth. In the mass production of glass cloth, a gas furnace is generally used to heat the glass cloth, and since the heat source is combustion of city gas, etc., a large amount of carbon dioxide and water are produced as products. As a result, it was found that by using a heating furnace that generates moisture as a heating mechanism, the equilibrium of the above reaction can be tilted in the direction in which Si--OH groups are produced. The present inventors placed a quartz glass cloth in a heating furnace, and heated the furnace inside a vacuum or in a gas with a dew point of 15°C or less at a temperature of 100 to 600°C, and a temperature of 100 to 600°C (°C) x heating time (h). ) By heating under conditions such that the heating amount expressed by It was discovered that by including this heating step, a low dielectric quartz glass cloth with a dielectric loss tangent of 0.0015 or less at 40 GHz could be obtained, which led to the creation of the present invention. be.

Therefore, the present invention provides a method for heating a quartz glass cloth and a method for manufacturing a low dielectric quartz glass cloth as described below.
1. A quartz glass cloth containing 95% by mass or more of SiO ₂ is placed in a heating furnace, and the maximum heating temperature is 100 to 600°C, and the heating temperature (°C) x heating time is 100°C or higher, in vacuum or in a gas with a dew point of 15°C or lower. The method for heating the quartz glass cloth described above, wherein heating is performed under conditions such that the amount of heating expressed by (h) is 450 (° C./h) or more.
2. 3. The method for heating a quartz glass cloth according to 1 or 2, wherein the gas is selected from air and an inert gas and has a dew point of 15° C. or lower.
3. 4. The method for heating a quartz glass cloth according to any one of 1 to 3, wherein dry gas having a dew point of 0° C. or lower is introduced into the furnace.
4. 4. The method for heating a quartz glass cloth according to 3, wherein dry gas having a dew point of 0° C. or lower is introduced into the furnace at least one of the following steps: before heating, during temperature increase, during temperature maintenance, and during temperature decrease.
5. 4. The method for heating a quartz glass cloth according to 4, wherein dry gas having a dew point of 0° C. or lower is introduced into the furnace during cooling.
6. A method for producing a low dielectric quartz glass cloth having a dielectric loss tangent of 0.0015 or less at 40 GHz, which includes the heating method according to any one of 1 to 5 as a step.

It is possible to provide a heating method for quartz glass cloth that can lower the dielectric loss tangent, and a manufacturing method that can manufacture a low dielectric quartz glass cloth without special post-treatment after heat treatment.

It is a figure showing the calculation method of the amount of heating of the present invention.

The present invention will be explained in detail below.
[Quartz glass cloth]
The quartz glass cloth of the present invention has a SiO ₂ composition of 95% by mass or more, and preferably 99.9% by mass or more from the viewpoint of electrical properties such as dielectric loss tangent and physical properties such as thermal expansion. Examples of methods for manufacturing quartz glass cloth include the following methods.

A quartz thread with a diameter of 200±100 μm can be obtained by melting quartz glass with a diameter of 50 to 500 mm at 1,700 to 2,300° C. and winding the thread-like product. If the melting temperature is within this range, stable stretching is possible.

Since quartz thread has very low strength, it is preferable to coat it with a coating agent before winding it up. The coating agent is preferably an acrylate resin that is UV curable and has excellent curability. The thickness of the coating film is preferably 5 μm or more since a sufficient reinforcing effect can be obtained. The quartz filament can be obtained by redrawing the quartz thread to a diameter of 2 to 15 μm at 1700 to 2,300° C. in a mixed flame of oxygen and hydrogen.

A quartz strand can be manufactured by bundling 20 to 400 quartz filaments, and a sizing agent is used to bundle the strands. The sizing agent has starch as its main raw material, and may contain a softener or a lubricant to provide functionality, and the sizing agent composition is generally called a sizing agent. The quartz yarn is obtained by twisting the strands prepared above. The frequency of twisting is preferably 0.1 to 5.0 twists per 25 mm.

Quartz glass cloth is obtained by weaving quartz yarn. The quartz glass cloth of the present invention is not particularly limited, but one having a basis weight of 10 to 100 g/m ² is preferably used. The weaving method is not particularly limited, but examples include weaving methods using an air jet loom, water jet loom, rapier loom, shuttle loom, and the like. When weaving is carried out using an air jet loom or the like, PVA or starch can be attached as a secondary sizing agent in order to obtain further lubricity.

The above-mentioned sizing agent remains attached to the surface of the quartz glass cloth after weaving, and the remaining sizing agent deteriorates the dielectric properties. Furthermore, the silane coupling agent treatment on the quartz glass cloth becomes insufficient, resulting in poor adhesion with the resin. Therefore, a deoiling step may be used after weaving to remove the attached sizing agent. The deoiling process includes a method of washing with water or an organic solvent, and a method called a process of burning and removing organic substances, and heat treatment is generally used because it can more reliably remove oil. This process can be carried out using a flow type or batch type heating furnace, but since the flow type burns off the sizing agent at once at high temperatures, there are problems such as a decrease in the strength of the glass cloth and unburned sizing agent. A batch method is common, in which organic matter is slowly burned and removed at 300-400°C.

The quartz glass cloth used in the present invention may have a sizing agent attached thereto, or may have the sizing agent removed in advance by washing with water or heat cleaning. Further, the quartz glass cloth used in the present invention may be a quartz glass cloth that has been opened or an unopened quartz glass cloth. When the heating method of the present invention is a heat cleaning method (sizing agent removal), dry air is preferably used as the dry gas. Depending on the components of the sizing agent, some may easily become colored if burned all at once at a high temperature, so the heating method of the present invention may be used as a heat cleaning method after pre-baking instead of at a constant temperature. In that case, there are no particular limitations on the preliminary firing, and the temperature and the like are not particularly limited, and may be 100° C. or lower. Further, when using a quartz glass cloth from which the sizing agent has been removed before the present invention, a vacuum drying oven, an electric oven, etc., an inert gas, etc. can also be used.

The glass cloth after oil removal can be used as it is, but it can also be made into a silane-treated quartz glass cloth that has been treated with silane. The silane treatment will be described later.

[How to heat quartz glass cloth]
The heating method of the present invention is performed under the conditions that the maximum heating temperature is 100 to 600°C and the amount of heating expressed as heating temperature (°C) of 100°C or more x heating time (h) is 450 (°C/h) or more. It's something to heat.
(heating furnace)
The heating furnace used for heating can be one that can heat to 100 to 600°C and can create a vacuum or a dry gas atmosphere with a dew point of 15°C or less in the furnace. There are no particular limitations, and examples of heating furnaces include gas furnaces, electric furnaces, muffle furnaces, laser heating, and the like.

Among these, it is preferable to use a heating furnace having a heat generating mechanism such that the amount of water generated per unit calorific value (1,000 kcal) is 0.12 L or less. As long as it has such a heat generating mechanism, it is not particularly limited, and examples thereof include an electric furnace, a muffle furnace, a laser heating, and the like, which include a heating furnace having a heat generating mechanism capable of the above. In particular, since electric furnaces do not involve combustion, the amount of water in the gas can be 0.12 L or less, less than 0.10 L.

It is preferable that the heating furnace has a device for feeding dry gas into the furnace. This equipment includes a mechanism that generates dry gas such as a compressor or air dryer, piping that connects the inside of the furnace to the mechanism that generates dry gas that fills or introduces dry gas, and an exhaust mechanism that exhausts air from inside the furnace. Examples include things that are done.

(Heating atmosphere)
In the present invention, the quartz glass cloth is heated in vacuum or in a gas having a dew point of 15° C. or lower. As the gas, inert gases such as air, nitrogen, and argon are preferred. If the inside of the furnace is to be evacuated, a vacuum heating and firing furnace such as the vacuum heating and firing furnace VASTA manufactured by Shimadzu Corporation is used.

The method of filling the inside of the furnace with a gas with a dew point of 15°C or less is not particularly limited as long as the inside of the furnace is in a gas with a dew point of 15°C or less, but it is possible to fill the inside of the furnace with dry gas with a dew point of 15°C or less before heating. Alternatively, a method of introducing dry gas having a dew point of 15° C. or lower into the furnace may be mentioned. The introduction may be performed before heating, during temperature rise, during temperature maintenance, or during temperature fall, and a plurality of these may be selected and introduced. Among these, it is preferable to introduce a dry gas having a dew point of 15° C. or lower, preferably 0° C. or lower, into the furnace, and it is preferable to introduce the dry gas into the furnace during cooling. Examples of the drying gas include drying gases having a dew point of 15° C. or lower and selected from air, nitrogen, and inert gases such as argon. Among these, dry air is preferred in terms of production efficiency. Examples of devices that generate the dry air include a compressor, an air dryer, and the like. Note that the dew point in the present invention refers to the atmospheric pressure dew point. The dew point of the dry gas to be filled or introduced is preferably 15°C or lower (moisture content; 12.8 g/m ³ ), more preferably 0°C (water content: 4.85 g/m ³ ) or lower, and -20°C. The temperature is more preferably below (moisture content; 1.07 g/m ³ ), particularly preferably below -60°C (moisture content: 0.0193 g/m ³ ). In the heating step in gas, the lower the dew point, the more the equilibrium of the SiO ₂ +H ₂ O⇔Si-OH reaction tilts to the left, lowering the dielectric loss tangent of the quartz glass cloth.

The drying gas that is previously filled and introduced into the furnace before heating has a dew point of 15° C. or lower, preferably 0° C. or lower, and more preferably -20° C. or lower from the viewpoint of production efficiency and economic efficiency.
The dew point of the drying gas introduced into the heating furnace is preferably 15°C or less, and in order to further reduce the dielectric loss tangent of the quartz glass cloth, the dewpoint of the drying gas in the heating process from temperature rise to temperature drop is preferably 0°C or less, - The temperature is more preferably 20°C, and even more preferably -60°C or lower.

The amount of drying gas to be introduced is not particularly limited, but it should be 0.5 to 20 times the volume of the drying oven per hour, as long as the dew point inside the oven can be sufficiently lowered and the temperature inside the oven can be kept constant. is preferred.

(Heating temperature)
The reaction of SiO ₂ +H ₂ O⇔Si-OH is activated at temperatures above 100°C, and as the temperature rises, the equilibrium shifts to the left and the Si-OH groups combine again to form a Si-O-Si bond. That is, the lower the dew point and the higher the heating temperature, the fewer Si--OH groups and the lower the dielectric loss tangent of the quartz glass cloth. Therefore, the maximum heating temperature of the quartz glass cloth in the present invention is 100 to 600°C, preferably 300 to 550°C, and more preferably 350 to 450°C. If the temperature is below 100° C., the activation energy for the reaction between Si—OH groups is insufficient as described above, so the amount of Si—OH groups does not decrease and the dielectric loss tangent does not decrease. Additionally, if the sizing agent is still attached to the quartz glass cloth, there is insufficient energy to burn the sizing agent, so the sizing agent will remain even if the heating time is extended, and the dielectric loss tangent due to the residual sizing agent will decrease. Deterioration or defects may occur during the silane coupling treatment in the post-process.

On the other hand, if heating is performed at a maximum heating temperature of over 600° C., some of the filaments of the quartz glass cloth will stick to each other and lose flexibility. In addition, expansion and contraction due to thermal expansion becomes large, and the filaments in the glass cloth rub against each other, resulting in microcracks, which cause defects such as a significant decrease in strength and flexibility. For this reason, during the silane treatment process or when resin is applied to produce prepreg, the glass cloth may break or wrinkle due to bending or lack of flexibility.

(Amount of heating)
The amount of heating expressed as temperature (°C) x heating time (h) of 100 to 600°C in dry gas is 450 (°C·h) or more. FIG. 1 shows a method for calculating this amount of heating. The shaded area is the amount of heating, which is not affected by heating, holding, and cooling. If the amount of heat is less than 450 (℃・h), there is not enough time to tilt the equilibrium reaction of SiO ₂ + H ₂ O ⇔ Si-OH to the left, and the dielectric loss tangent of the quartz glass cloth does not decrease completely, making it unsuitable. . There is no particular limitation as long as the heating amount is 450 (℃・h) or more, but from the point of view of production efficiency, 450 to 50,000 (℃・h) is preferable, and 3,000 to 50,000 (℃・h) is preferable. More preferred.

Heating may be divided into several steps during temperature increase, temperature maintenance, and temperature reduction, and temperature may be maintained at a plurality of temperatures. Further, as long as the above heating amount can be satisfied, there is no need for holding time. There are no particular limitations on the temperature increase and temperature decrease rates, but from the viewpoint of productivity, it is preferably 10° C./h or more, and from the viewpoint of preventing blackening of the sizing agent and the strength of the quartz glass cloth, it is preferably less than 200° C./h.

In particular, in an atmosphere of 100 to 300°C, although the activation energy is exceeded, the equilibrium of SiO ₂ + H ₂ O ⇔ Si-OH tends to tilt to the right because it is a low temperature region, and the Si-O-Si bond is most likely to be cleaved. In particular, it is necessary to keep the dew point low. The drying gas may be introduced at any timing during temperature rise, temperature fall, or temperature maintenance. In order to keep the dew point in the furnace low, it is preferable to continue introducing dry gas into the furnace during the entire heating at 100 to 600° C. during heating, holding, and cooling. In particular, introducing dry gas into the furnace while the temperature is decreasing from the maximum heating temperature to 100° C. is effective in improving the dielectric loss tangent.

According to the heating method of the present invention, the dielectric loss tangent of the silica glass cloth containing 95% by mass or more of SiO ₂ can be lowered. The dielectric loss tangent of the quartz glass cloth after the heating step is preferably 0.0015 or less, more preferably 0.0012 or less at 40 GHz. Further, the dielectric loss tangent at 10 GHz is preferably 0.0010 or less, more preferably 0.0008 or less. The method for measuring the dielectric loss tangent is based on the resonance method, and specifically, it is based on the description of the examples described later. Further, the change ratio of the dielectric loss tangent at 10 GHz and 40 GHz before and after the heating step is preferably 0.1 to 0.9, more preferably 0.1 to 0.7. Note that the change ratio of the dielectric loss tangent at 10 GHz and 40 GHz is based on the description of Examples described later.

[Production method of low dielectric quartz glass cloth]
The method for producing a low dielectric quartz glass cloth of the present invention includes the heating step described above, and the preferred components, ranges, etc. are also the same. By including the heating step of the present invention, it is possible to manufacture a low dielectric quartz glass cloth without any special post-treatment after the heat treatment.

[Low dielectric quartz glass cloth]
The dielectric loss tangent of the quartz glass cloth obtained by the manufacturing method including the heating step of the present invention is preferably 0.0015 or less, more preferably 0.0012 or less at 40 GHz. Further, the dielectric loss tangent at 10 GHz is preferably 0.0010 or less, more preferably 0.0008 or less.

In the method for manufacturing a low dielectric quartz glass cloth, the heating step of the present invention may be a heat cleaning step for removing the sizing agent, or may be a separate step from the heat cleaning step. Furthermore, the above-mentioned silane treatment may be performed. When the silane treatment step is further included, it is preferable to include the silane treatment step after the heating step in order to more effectively exhibit the effects of the silane treatment step.

[Silan treatment process]
The silane treatment liquid used to treat glass cloth is not particularly limited, but from the viewpoint of productivity and environmental impact, an aqueous solution in which a silane coupling agent is dispersed in an amount of 0.05 to 1% by mass is suitable. A pH adjuster can be added to the silane coupling agent to form an aqueous solution. The pH adjuster is not particularly limited, but adjustment using acetic acid or ammonia is preferred depending on the silane coupling agent used. The silane treatment is not particularly limited, and the glass cloth to be silane treated may be immersed in the above aqueous solution. The temperature and time are appropriately selected from 50 to 200°C and 30 seconds to 1 hour.

Silane coupling agents include trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trimethoxysilane, and triethoxysilane. Silane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenylmethylvinylethoxysilane, naphthyltrimethoxysilane, naphthyltriethoxysilane, 1,4-bis(methoxydimethylsilyl)benzene, Tetramethoxysilane, tetraethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, vinyltrimethoxysilane, vinyltriethoxy Silane, p-styryltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, Sidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxysilane Roxypropyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3 -Aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-phenyl-3-aminopropyl Trimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane and its hydrochloride, N-(vinylbenzyl)-2-aminoethyl-3-aminopropylmethyldimethoxysilane and its hydrochloric acid salt, 3-isocyanatepropyltriethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyl Examples include alkoxysilane compounds such as dimethoxysilane and bis(trisethoxysilylpropyl)tetrasulfide, which may be used alone or in combination of two or more. Among these, 3-aminopropyltrimethoxysilane, N-(2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, etc.) are preferable. It is not limited to these, and one type can be used alone or two or more types can be used in combination.

In the present invention, by including the above-mentioned heating step, a low dielectric quartz glass cloth can be obtained in the same manner even after the silane coupling treatment. That is, the dielectric loss tangent of the silane coupling-treated silica glass cloth after the heating step of the present invention is preferably 0.0015 or less, more preferably 0.0012 or less at 40 GHz. Further, the dielectric loss tangent at 10 GHz is preferably 0.0010 or less, more preferably 0.0008 or less.

Further, glass cloth is generally subjected to fiber opening treatment, for example, before desizing treatment or during silane treatment, in order to increase resin impregnation in a subsequent process. The opening treatment method is not particularly limited, but examples include opening treatment methods using ultrasonic waves, methods using high-pressure columnar water level flow, and methods using a gas-liquid mixed mist with an adjusted air-water volume ratio. It can be used appropriately depending on the type of cross. Regardless of whether the fibers are opened or not, the effect of lowering the dielectric loss tangent by the heating method of the present invention can be obtained.

[Prepreg]
The low dielectric quartz glass cloth obtained by the manufacturing method of the present invention can be made into a prepreg by using resin, filler, etc. By using the low dielectric quartz glass cloth of the present invention, it can be made into prepreg without any problem.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples below.
[Preparation example of quartz glass cloth (SQ1 to SQ3)]
A quartz glass ingot containing 99.9% by mass or more of SiO ₂ was heated and stretched to produce a quartz glass fiber consisting of a silica glass filament with a diameter of 5.3 μm. The above-mentioned quartz glass fiber sizing agent (3.0% by mass of starch, 0.5% by mass of beef tallow, 0.1% by mass of emulsifier, balance water) is applied to the quartz glass fibers using an applicator, and then the quartz glass fibers are bundled by a concentrator. Then, it was wound up to produce a quartz glass strand having 200 quartz glass filaments. The wound quartz glass strand was twisted at 24 T/m to produce a quartz glass yarn.
After applying an aqueous solution consisting of 1.5% by mass of polyvinyl alcohol (PVA) and 1.5% by mass of starch as a secondary sizing agent to the obtained quartz glass yarn, an IPC standard 1078 quartz glass cloth was applied using an air jet loom. was manufactured and subjected to fiber opening treatment using an air/water mixed mist (SQ1).

In the same manner, 100 filaments each having a diameter of 4.0 μm were bundled and woven to produce IPC standard 1027 quartz glass cloth (SQ2). 200 filaments with a diameter of 7.3 μm were bundled and woven to produce IPC standard 2116 quartz glass cloth (SQ3).
Note that approximately 2% by mass of sizing agent is attached to the silica glass cloths SQ1 to SQ3 obtained above.

[When heat treating quartz glass with sizing agent attached]
[Example 1]
A 1078 quartz glass cloth (SQ1) was heated to 400°C at a rate of 100°C/h using an electric furnace B80 x 85 x 200-3Z12-10 manufactured by Nems, held for 24 hours, and then cooled at a rate of 30°C/h. During the heat treatment, dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP is pumped into the electric furnace in an amount 5 times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall. I did it.

[Example 2]
Examples except that heat treatment is carried out by feeding dry air with a dew point of -70°C made with Super Heatless Dryer SHD3025 manufactured by CKD Co., Ltd. from temperature rise to temperature fall in an amount of 5 times the volume of the electric furnace per hour. SQ1 was heat-treated in the same manner as in Example 1.

[Example 3]
Examples except that heat treatment is performed by feeding dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP in an amount of 5 times the volume of the electric furnace per hour only when the temperature drops. SQ1 was heat-treated in the same manner as in Example 1.
Since the dew point of the outside air was 20°C, the amount of heating when the dew point was 15°C or lower was as follows only when the temperature dropped.
((400-100)×(400-100)/30)÷2=1,500℃・h

[Example 4]
Only when the temperature was maintained, heat treatment was performed by feeding dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP in an amount of 5 times the volume of the electric furnace per hour. SQ1 was heat treated in the same manner as in Example 1. Since the dew point of the outside air was 20°C, the amount of heating when the dew point was 15°C or lower was as follows only during holding.
400×24=9,600℃・h

[Example 5]
The heat treatment was carried out only when the temperature was raised by sending dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP in an amount of 5 times the volume of the electric furnace per hour. SQ1 was heat treated in the same manner as in Example 1.
Since the dew point of the outside air was 20°C, the amount of heating when the dew point was 15°C or lower was as follows only when the temperature was raised.
((400-100)×(400-100)/100)÷2=450℃・h.

[Example 6]
SQ1 was heated to 600° C. at 100° C./h using an electric furnace B80×85×200-3Z12-10 manufactured by Nems, held for 10 hours, and then cooled at 30° C./h. During the heat treatment, dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP is pumped into the electric furnace in an amount 5 times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall. I did it.

[Example 7]
Heat treatment was performed in the same manner as in Example 1, except that 1078 quartz glass cloth (SQ1) was replaced with 1027 quartz glass cloth (SQ2).

[Example 8]
Heat treatment was performed in the same manner as in Example 1, except that 1078 quartz glass cloth (SQ1) was changed to 2116 quartz glass cloth (SQ3).

[When heat-treating quartz glass after removing sizing agent]
The SQ1 glass cloth was heat-cleaned at 400° C. for 72 hours in a gas furnace 7 m ³ fiber superior kiln manufactured by Mino Ceramics Co., Ltd., and the sizing agent was removed to obtain a heat-cleaned glass fiber SQ1'. The dielectric loss tangent of SQ1' at 10 GHz was 0.0017, and the dielectric loss tangent at 40 GHz was 0.0023.

[Example 9]
SQ1' was heat treated in the same manner as in Example 1.

[Example 10]
SQ1' was heated to 150° C. at 100° C./h using an electric furnace B80×85×200-3Z12-10 manufactured by Nems, held for 24 hours, and then cooled at 30° C./h. During the heat treatment, dry air with a dew point of -20°C made using HITATHI's inverter package oil-free Bebicon POD-15VNP is pumped into the electric furnace in an amount 5 times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall. I did it.

[Example 11]
SQ1' was heated to 400°C at a rate of 100°C/h in a vacuum from temperature rise to temperature drop using a vacuum heating and firing furnace VASTA manufactured by Shimadzu Corporation instead of the electric furnace of Example 1, and after being held for 12 hours, it was heated to 30°C. The temperature decreased at /h.

[Example 12]
In Example 11, heat treatment was carried out by replacing the inside of the furnace with nitrogen gas (dew point -70°C) manufactured by Tomoe Co., Ltd. from temperature rise to temperature fall instead of vacuum.

[Comparative example 1]
As in Example 8, SQ1 was heat-treated using an electric furnace B80×85×200-3Z12-10 manufactured by Nems. At that time, since the dew point of the outside air was 20°C, the dew point inside the furnace was 20°C from the time of temperature rise to the time of temperature fall.

[Comparative example 2]
SQ1 was heated to 700°C at a rate of 100°C/h using an electric furnace B80x85x200-3Z12-10 manufactured by Nems, and after being held for 24 hours, the temperature was lowered at a rate of 30°C/h. At that time, heat treatment was carried out by feeding dry air with a dew point of -20°C in an amount of five times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall.

[Comparative example 3]
SQ1' was heated to 80° C. at a rate of 100° C./h using an electric furnace B80×85×200-3Z12-10 manufactured by Nems, and after being held for 24 hours, the temperature was lowered at a rate of 30° C./h. At that time, heat treatment was carried out by feeding dry air with a dew point of -20°C in an amount of five times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall.

[Comparative example 4]
An electric furnace B80 x 85 x 200-3Z12-10 manufactured by Nems was heated to 400°C, and SQ1' was placed in the furnace at 400°C and held for 1 hour, then taken out without waiting for the temperature to fall. At that time, dry air with a dew point of -20°C was fed in at an amount five times the volume of the electric furnace per hour from the time of temperature rise to the time of temperature fall.

1. Measurement of Dew Point The dew point was measured using a dew point monitor MG-40 manufactured by Orion.

The glass cloth obtained above after the heating process was evaluated by the following method. The results are listed in the table.
2. Measurement of dielectric loss tangent The dielectric loss tangent of the glass cloth at 10 GHz and 40 GHz was measured using a cavity resonator manufactured by ET (TE011 mode). The thickness of the glass cloth is measured using the theoretical film thickness, and the theoretical film thickness of the glass cloth is: Theoretical film thickness t (μm) = Area weight (g/m ² )/Specific gravity (g/cm ³ )
Calculated from.

3. Degree of reduction in dielectric loss tangent Calculated magnification of dielectric loss tangent before and after heat treatment (when glass cloth with sizing agent attached is used for heat treatment)
Wash SQ1 to SQ3 with alkaline electrolyzed water S-2665 manufactured by Suzuki Yushi Kogyo Co., Ltd. at 60°C for 2 hours, remove the adhering sizing agent, and then dry the glass cloth at 100°C for 30 minutes to obtain sizing agent-washed glass cloth SQ. ~The dielectric loss tangent of SQ3'' is the dielectric loss tangent before heat treatment, and the dielectric loss tangent of SQ1'' at 10 GHz is 0.0008, and the dielectric loss tangent at 40 GHz is 0.0012.
The dielectric loss tangent of SQ2” at 10GHz is 0.0009, and the dielectric loss tangent at 40GHz is 0.0013.
The dielectric loss tangent of SQ3” at 10GHz is 0.0007, and the dielectric loss tangent at 40GHz is 0.0010.
Met.
Dielectric loss tangent ratio = SQ1~3/SQ1”~SQ3” after heat treatment
<When SQ1' to SQ3' after sizing agent removal corresponds to before heat treatment>
Dielectric loss tangent ratio = SQ1'~3'/SQ1'~SQ3' after heat treatment

4. Silane coupling processability and prepreg formation After the heating process, the glass cloth is immersed in an aqueous solution in which 0.2% by mass of KBM-503 (3-methacryloxypropyltrimethoxysilane, trade name manufactured by Shin-Etsu Chemical Co., Ltd.) is dispersed. Then, silane treatment was performed by drying at 110°C for 10 minutes. The obtained silane-treated cloth was immersed in a 55% by mass toluene solution of SLK-3000 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) and dried at 110° C. for 10 minutes to form a prepreg. Those that were able to be silane-treated and made into prepreg without any problems were rated as "○", and those that were broken or wrinkled due to bending or lack of flexibility of the glass cloth were rated as "x".

5. The dielectric loss tangent at 10 GHz and 40 GHz after the silane coupling treatment was measured in the same manner as above.

Claims (6)

A quartz glass cloth containing 95% by mass or more of SiO ₂ is placed in a heating furnace, and the maximum heating temperature is 100 to 600°C, and the heating temperature (°C) x heating time is 100°C or higher, in vacuum or in a gas with a dew point of 15°C or lower. The method for heating the quartz glass cloth described above, wherein heating is performed under conditions such that the amount of heating expressed by (h) is 450 (° C./h) or more. 2. The method for heating a quartz glass cloth according to claim 1, wherein the gas is selected from air and an inert gas and has a dew point of 15° C. or less. 2. The method for heating quartz glass cloth according to claim 1, wherein dry gas having a dew point of 0° C. or lower is introduced into the furnace. 4. The method for heating quartz glass cloth according to claim 3, wherein dry gas having a dew point of 0° C. or less is introduced into the furnace at least one of the following steps: before heating, during temperature increase, during temperature maintenance, and during temperature decrease. 5. The method for heating quartz glass cloth according to claim 4, wherein dry gas having a dew point of 0° C. or lower is introduced into the furnace during cooling. A method for producing a low dielectric quartz glass cloth having a dielectric loss tangent of 0.0015 or less at 40 GHz, which comprises the heating method according to any one of claims 1 to 5 as a step.

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