JP7812973B2 - Glass cloth, prepreg, and printed wiring board - Google Patents

Description

This disclosure relates to glass cloth, prepregs, printed wiring boards, etc.

Currently, information terminals such as smartphones are becoming more powerful, and high-speed communications, as exemplified by 5G communications, are becoming more common. Accordingly, in printed wiring boards for high-speed communications, the dielectric constant and dissipation factor of insulating materials used to reduce transmission loss are becoming significantly lower, and higher levels of insulation reliability than ever before are also being demanded.

Examples of insulating materials for printed wiring boards for high-speed communication are reported in Patent Documents 1 and 2. Specifically, Patent Documents 1 and 2 describe a method for impregnating glass cloth with a low-dielectric thermosetting resin (hereinafter collectively referred to as "matrix resin") that is crosslinked and cured by a radical reaction, such as polyphenylene ether modified at the terminals with vinyl or methacryloxy groups, and then drying the resin to obtain a prepreg. A laminate is known that is made by stacking the prepregs obtained in this manner and curing them by heating and pressurizing them. Patent Documents 1 and 2 aim to achieve a low dielectric constant and low dielectric dissipation factor for the laminate by combining the prepreg with glass cloth, which has a low dielectric constant and low dielectric dissipation factor.

Here, Patent Documents 3 and 4 report that in order to reduce the dielectric loss tangent of glass cloth, the amount of silanol groups on the glass surface is reduced by heating silica glass cloth at high temperatures. Furthermore, in order to extend the life of drills in the glass cloth drilling process, Patent Document 5 reports obtaining glass yarn by spinning glass fibers with a softening point of 1000 to 1600°C, and producing glass cloth using such glass yarn.

International Publication No. 2019/065940 International Publication No. 2019/065941 Japanese Patent Application Laid-Open No. 2021-63320 Japanese Patent Application Laid-Open No. 2021-195689 Japanese Patent Application Laid-Open No. 2023-131220

However, compared to the conventional technologies described in Patent Documents 1 to 5, there has been a strong demand for the creation of a technology that can obtain a resin substrate with a small whitening distance, on the premise that a glass cloth having excellent dielectric properties and excellent insulation reliability can be realized.
Here, the "whitening distance" that the present inventors focused on is one of the indicators that represents the degree of interfacial peeling between the glass cloth and the matrix resin. The more excellent the insulation reliability of a glass cloth, the more likely it is to provide a resin substrate with a small whitening distance.

An object of the present disclosure is to provide a glass cloth that can realize excellent dielectric properties and excellent insulation reliability, and that can also provide a resin substrate with a small whitening distance.
Another object of the present disclosure is to provide a prepreg and a printed wiring board that are realized using the glass cloth, and to provide a method for producing the glass cloth.

According to one example of the aspects of the present disclosure, it is possible to reduce the whitening distance in a resin substrate while maintaining the dielectric properties of the glass cloth.
That is, the present inventors have discovered for the first time that an example of an embodiment of the present disclosure can provide a glass cloth that has excellent dielectric properties and also has excellent insulation reliability, in that the whitening distance of the resulting resin substrate is small.
An example of an aspect of the present disclosure is as follows.

[1]
A glass cloth made by weaving glass yarn,
the glass cloth is surface-treated with a surface treatment agent,
The following formula A is calculated from the total carbon amount of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula A=peak height derived from carbonyl groups/total carbon content of the glass cloth is 10 or more,
A glass cloth having 10 or less white spots per ^square meter.
[2]
A glass cloth made by weaving glass yarn,
The glass cloth is surface-treated with a surface treatment agent,
The following formula B is calculated from the ignition loss value of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula B = peak height derived from carbonyl groups / ignition loss value of glass cloth is 11 or more,
A glass cloth having 10 or less white spots per ^square meter.
[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% by mass in terms of silicon dioxide (SiO ₂ ).
[4]
4. The glass cloth according to any one of items 1 to 3, having a dielectric loss tangent at 10 GHz of 0.002 or less.
[5]
5. The glass cloth according to any one of items 1 to 4, wherein the glass constituting the glass yarns has a bulk dielectric loss tangent of 0.002 or less at 10 GHz.
[6]
6. The glass cloth according to any one of items 1 to 5, wherein the surface treatment agent comprises a silane coupling agent.
[7]
The surface treatment agent is represented by the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
7. The glass cloth according to any one of items 1 to 6, comprising a silane coupling agent represented by the formula:
[8]
8. The glass cloth according to item 7, wherein the unsaturated carbon-carbon double bond is a bond derived from at least one of an acryloyl group and a methacryloyl group.
[9]
Item 9. The glass cloth according to any one of items 1 to 8, wherein the ignition loss value of the glass cloth is in the range of 0.01 to 0.5 mass%.
[10]
10. The glass cloth according to any one of items 1 to 9, wherein an average degree of opening calculated from the yarn width of each of the warp yarns and the weft yarns of the glass cloth is more than 40%.
[11]
Item 11. The glass cloth according to any one of items 1 to 10, wherein the total carbon content of the glass cloth is in the range of 0.01 to 0.8 mass%.
[12]
Item 12. A prepreg comprising the glass cloth according to any one of items 1 to 11 and a matrix resin.
[13]
Item 13. A printed wiring board comprising the prepreg according to item 12.
[14]
Item 14. An integrated circuit comprising the printed wiring board according to item 13.
[15]
Item 14. An electronic device comprising the printed wiring board according to item 13.
[16]
A method for manufacturing a glass cloth by weaving glass yarns,
a surface treatment step of treating the glass fiber with a surface treatment liquid containing a surface treatment agent having a molecular weight of 200 or more;
The surface treatment step includes:
a step of adding a solvent to the surface treatment agent to prepare the surface treatment liquid;
controlling the temperature of the surface treatment solution;
controlling the pH of the surface treatment solution; and filtering the surface treatment solution;
A method for producing glass cloth, comprising at least one of the steps:
[17]
The surface treatment step includes:
The method includes a step of surface-treating the deoiled glass fiber with a surface treatment agent,
The surface treatment agent has the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
Item 16. The method for producing glass cloth according to item 15, comprising the step of:
[18]
The surface treatment step includes:
controlling the temperature and pH of the surface treatment solution;
Item 18. The method for producing glass cloth according to Item 16 or 17, further comprising the step of filtering the surface treatment liquid.
[19]
Item 19. The method for producing a glass cloth according to any one of Items 16 to 18, further comprising a step of subjecting the glass yarns to an opening treatment after the surface treatment step.
[20]
20. The method for producing a glass cloth according to any one of items 16 to 19, further comprising inspecting the glass cloth for white spots.
[21]
21. A method for producing a glass cloth according to any one of items 16 to 20, comprising a step of measuring a peak height derived from a carbonyl group in the glass cloth by Fourier transform infrared spectroscopy.
[22]
A test method for glass cloth made by weaving glass yarn,
the glass cloth is surface-treated with a surface treatment agent,
The test method comprises:
a step of inspecting the glass cloth for white spots based on the height of a peak derived from a carbonyl group in the glass cloth and the total carbon content of the glass cloth or the ignition loss value of the glass cloth.

According to the present disclosure, it is possible to provide a glass cloth that can realize excellent dielectric properties and excellent insulation reliability, and further, can obtain a resin substrate with a small whitening distance.
Furthermore, according to the present disclosure, it is possible to provide a prepreg, a printed wiring board, an integrated circuit, and an electronic device that are realized using the glass cloth, and to provide a method for manufacturing the glass cloth, etc.

FIG. 4 is a diagram for explaining a calibration curve in this embodiment. 5A and 5B are diagrams for explaining white spots in the present embodiment.

The following describes an embodiment of the present disclosure (hereinafter referred to as the "present embodiment"). However, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention.

In this specification, when multiple structures represented by the same symbol exist in the same formula, unless otherwise specified, the structures may be independently selected and may be the same or different from each other. When multiple structures represented by the same symbol exist in different formulas, the structures may be independently selected and may be the same or different from each other, unless otherwise specified. In this specification, various measurements are performed based on the methods described in the Examples unless otherwise specified. In this specification, the upper or lower limit of a numerical range described in stages may be replaced by the upper or lower limit of a corresponding numerical range described in another stage, and may also be replaced by the corresponding value described in the Examples.

In this specification, 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. In the drawings, the scale, shape, and length may be exaggerated for clarity.

[Glass cloth]
The glass cloth of this embodiment is a glass cloth made by weaving glass yarns, for example, a glass cloth made by weaving glass yarns made of a plurality of glass filaments as warp and weft yarns.

In one aspect of this embodiment,
The glass cloth is surface treated with a surface treatment agent.
The carbon content of the glass cloth is calculated from the total carbon content and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy using the following formula A:
Formula A=peak height derived from carbonyl groups/total carbon content of the glass cloth is 10 or more,
The number of white spots is 10 or ^less per square meter (for example, 10.0 or less per ^square meter).

In addition, in a further aspect of this embodiment,
The glass cloth is surface treated with a surface treatment agent.
The following formula B is calculated from the ignition loss value of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula B=peak height derived from carbonyl groups/ignition loss value of glass cloth is 11 or more,
The number of white spots is 10 or ^less per square meter (for example, 10.0 or less per square ^meter ).

According to this embodiment, it is possible to provide a glass cloth that can produce a resin substrate (typically a printed wiring board) with a small whitening distance and that exhibits excellent dielectric properties and insulation reliability. The glass cloth of this embodiment is suitable as a material for producing prepregs, printed wiring boards, integrated circuits, electronic devices, etc.

[Surface treatment]
The glass cloth of this embodiment is surface-treated with a surface treatment agent.
A surface-treated glass cloth has a surface treatment agent attached to its surface. Conversely, when a surface treatment agent is attached to the surface of a glass cloth, this corresponds to "surface-treated with a surface treatment agent" in the present disclosure. Here, "the surface of the glass cloth" includes "the surface of the glass yarn that constitutes the glass cloth."
Specific examples of the surface treatment, such as a method for detecting a surface treatment agent, types of surface treatment agents, and surface treatment techniques, will be described later.

[Peak height derived from carbonyl group]
Surface treatment agents with excellent radical reactivity contain components having carbonyl groups, such as acryloyl groups and methacryloyl groups. Fourier transform infrared spectroscopy detects clear peaks at specific positions due to carbonyl groups, and therefore, can be used to evaluate the extent to which acryloyl groups, methacryloyl groups, etc. have been introduced into the glass cloth.

When using Fourier transform infrared spectroscopy, the results may vary due to factors such as the sensitivity of the light-receiving element and measurement error. In this regard, it is preferable to create a calibration curve based on glass cloth that has been surface-treated with a known surface treatment agent and has a known amount of the agent attached. Using such a calibration curve makes it easier to obtain reproducible peak heights derived from carbonyl groups.

[Total carbon content of glass cloth]
The total carbon content of the glass cloth is measured by a method for measuring the amount of carbon dioxide generated when the glass cloth is pyrolyzed, specifically, by the method described in the Examples. Since the total carbon content tends to increase as the amount of surface treatment agent attached to the glass cloth increases, the measurement method of the present disclosure makes it easy to simply evaluate the amount of surface treatment agent attached to the glass cloth.

The total carbon content of the glass cloth is preferably 0.01 to 0.8% by mass, more preferably 0.01 to 0.6% by mass, more preferably 0.01 to 0.5% by mass, even more preferably 0.01 to 0.4% by mass, and particularly preferably 0.01 to 0.3% by mass, 0.02 to 0.20%, 0.03 to 0.15, or 0.03 to 0.10% by mass. If the total carbon content is less than 0.01% by mass, the amount of surface treatment agent adhered to the glass cloth is often insufficient, which is likely to result in poor insulation. If the total carbon content of the glass cloth exceeds 0.8% by mass, the dielectric loss tangent of the glass cloth is often high, making it difficult to achieve a low dielectric loss tangent of the glass cloth.

(Relationship between peak height derived from carbonyl group and total carbon content of glass cloth)
The glass cloth of this embodiment is
The carbon content of the glass cloth is calculated from the total carbon content and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy using the following formula A:
The value of formula A=peak height derived from carbonyl groups/total carbon amount of the glass cloth is 10 or more.

A value of 10 or more in formula A means that the proportion of highly reactive components (components having carbonyl groups) in the surface treatment agent adhered to the glass cloth is high.
Here, one of the ideas of the present inventors is to focus on the "peak height derived from carbonyl groups" and the "total carbon content of the glass cloth" and to define the ratio between them (peak height derived from carbonyl groups/total carbon content of the glass cloth). Based on one of the ideas of the present inventors, a glass cloth having a high value of 10 or more in the formula A can be specified.
According to this embodiment, since the value of formula A is high, it is possible to provide a glass cloth that can give a resin substrate with a small whitening distance, and also to provide a glass cloth that exhibits excellent dielectric properties and insulation reliability.

The value of Formula A is 10 or more (e.g., 10.0 or more), preferably greater than 10 (e.g., greater than 10.0), preferably 11 or more (e.g., 11.0 or more), more preferably 12 or more (e.g., 12.0 or more), even more preferably 13 or more (e.g., 13.0 or more), even more preferably 15 (e.g., 15.0 or more), and particularly preferably 19 or more (e.g., 19.0 or more). Having a value of Formula A of 10 or more ensures adhesion between the glass cloth and the matrix resin, thereby reducing the whitening distance in the resulting resin substrate. The value of Formula A may be 60 or less (e.g., 60.0 or less).

[Ignition loss value of glass cloth]
The ignition loss value of the glass cloth is measured by a method of thermally deoiling the glass cloth (surface-treated glass cloth), specifically, by the method described in the Examples. Since the ignition loss value tends to increase as the amount of surface treatment agent attached to the glass cloth increases, the measurement method of the present disclosure makes it easy to simply evaluate the amount of surface treatment agent attached to the glass cloth.

The ignition loss value of the glass cloth is preferably 0.01 to 0.5% by mass, 0.01 to 0.4% by mass, or 0.01 to 0.3% by mass, more preferably 0.02 to 0.25% by mass, even more preferably 0.03 to 0.22% by mass, even more preferably 0.03 to 0.17% by mass, and particularly preferably 0.04 to 0.15% by mass. An ignition loss value of 0.01% by mass or greater tends to ensure good adhesion between the resin and glass cloth in the resulting prepreg. In this case, heat resistance and insulation reliability are easily ensured when a printed wiring board is produced. An ignition loss value of 0.5% by mass or less tends to avoid the presence of large amounts of surface treatment agents (or their residues) physically adhered to the glass cloth surface without forming chemical bonds with it, surface treatment agents (or their residues) that cannot be removed from the glass cloth surface by water washing, and/or modified products thereof, on the glass cloth surface. In this case, it is easy to reduce the dielectric loss tangent of the glass cloth.

(Relationship between the peak height derived from carbonyl groups and the ignition loss value of glass cloth)
The glass cloth of this embodiment is
The following formula B is calculated from the ignition loss value of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula B=peak height derived from carbonyl group/ignition loss value of glass cloth is 11 or more.

A value of 11 or more in formula B means that the proportion of highly reactive components (components having carbonyl groups) in the surface treatment agent adhered to the glass cloth is high.
Here, one of the ideas of the present inventors is to focus on the "peak height derived from carbonyl groups" and the "ignition loss value of glass cloth" and to define the ratio between them (peak height derived from carbonyl groups/ignition loss value of glass cloth). Based on one of the ideas of the present inventors, a glass cloth having a high value of 11 or more in the formula B is specified.
According to this embodiment, since the value of formula B is high, it is possible to provide a glass cloth that can give a resin substrate with a small whitening distance, and also to provide a glass cloth that exhibits excellent dielectric properties and insulation reliability.

The value of Formula B is 11 or more (e.g., 11.0 or more), preferably greater than 11 (e.g., greater than 11.0), preferably 12 or more (e.g., 12.0 or more), more preferably 13 or more (e.g., 13.0 or more), even more preferably 14 or more (e.g., 14.0 or more), and particularly preferably 15 or more (e.g., 15.0 or more). Having a value of Formula B of 11 or more ensures adhesion between the glass cloth and the matrix resin, thereby reducing the whitening distance of the resulting resin substrate. The value of Formula B may be 60 or less (e.g., 60.0 or less).

[Dielectric loss tangent]
(Dielectric loss tangent of glass cloth)
The glass cloth of this embodiment preferably has a dielectric loss tangent of 0.002 or less at 10 GHz. Such a glass cloth can provide a prepreg and a printed wiring board that can improve the dielectric properties. From the viewpoint of improving the dielectric properties, the dielectric loss tangent of the glass cloth at 10 GHz is preferably 0.0015 or less, 0.0010 or less, 0.0007 or less, 0.0006 or less, 0.0005 or less, 0.0004 or less, 0.0003 or less, or 0.0002 or less. The dielectric loss tangent of the glass cloth may be greater than 0.

(Method for measuring dielectric loss tangent)
The dielectric loss tangent at 10 GHz of the glass cloth of this embodiment is measured by a method using a split cylinder resonator (a method using a resonance method), specifically, by the method described in the Examples.
This method allows for simpler and more accurate measurement than conventional methods in which a substrate is fabricated as a measurement sample and the dielectric properties are evaluated. The reason for this, without being limited by theory, is that the resonance method is suitable for evaluation in the high frequency range, particularly for evaluation of low-loss materials.
Other than the resonance method, other methods for evaluating dielectric properties include the lumped parameter method and the reflection transmission method. However, the lumped parameter method requires the measurement sample to be sandwiched between two electrodes to form a capacitor, which can be a problem in that the operation can be complicated. Furthermore, when evaluating low-loss materials, the reflection transmission method is subject to the strong influence of the port matching characteristics, making it difficult to accurately evaluate the dielectric loss tangent of the measurement sample.
From the above, it is possible to easily and accurately measure the dielectric loss tangent of a glass cloth by using a technique that uses a resonance method, specifically, by using the technique described in the examples.

For glass cloth used in printed wiring boards, particularly for high-speed communication printed wiring boards, it is preferable that a measuring instrument for measuring the dielectric properties thereof has a predetermined measurable range. For example, for the dielectric constant (Dk) and dielectric loss tangent (Df), the measuring instrument preferably has measurable ranges of Dk = 1.1 Fm ^-1 to 50 Fm ^-1 and Df = 1.0 × 10 ^-6 to 1.0 × 10 ^-1 , respectively, more preferably Dk = 1.5 Fm ^-1 to 10 Fm ^-1 and Df = 1.0 × 10 ^-5 to 5.0 × 10 ^-1 , and even more preferably Dk = 2.0 Fm ^-1 to 5 Fm ^-1 and Df = 5.0 × 10 ^-5 to 1.0 × 10 ^-2 .

Furthermore, it is preferable that the measuring equipment for measuring dielectric properties be capable of measuring frequencies of 10 GHz or higher. Measurable frequencies of 10 GHz or higher make it easier to evaluate characteristics in frequency band regions, particularly characteristics in frequency band regions expected when the material is actually used as glass cloth for printed wiring boards for high-speed communications.

The area for measuring the dielectric properties is preferably 10 ^mm2 or more, more preferably 15 ^mm2 or more, and even more preferably 20 ^mm2 or more. This makes it easier to improve the reliability of the measurement results obtained, and therefore makes it easier to determine whether the measurement results obtained are within a predetermined reference value range.

The thickness of the measurement sample is preferably 3 μm to 300 μm, more preferably 5 μm to 200 μm, and even more preferably 7 μm to 150 μm.

(Bulk dielectric loss tangent)
In the glass cloth of this embodiment, the bulk dielectric loss tangent at 10 GHz of the glass raw materials constituting the glass cloth is measured by a method using a split cylinder resonator (a method using a resonance method), specifically, by the method described in Examples. Here, the glass raw materials may be, for example, glass threads, glass filaments, glass seeds, etc.

The bulk dielectric loss tangent at 10 GHz is preferably 0.002 or less, more preferably 0.0015 or less, even more preferably 0.001 or less, even more preferably 0.0005 or less, and particularly preferably 0.0004 or less. This makes it easier to achieve the effects of the present disclosure.

(Method for controlling dielectric loss tangent and bulk dielectric loss tangent)
The dielectric loss tangent and bulk dielectric loss tangent of the glass cloth are, for example,
A process of removing deteriorated materials and residues present on the glass surface;
can be controlled based on
Here, one embodiment of the deteriorated product and the residue, etc., is, for example, the following (i) to (ii):
(i) Degraded products of sizing agents that have physically adhered to the glass surface and are thermally oxidized. (ii) Residues of surface treatment agents that have physically adhered to the glass surface without forming a chemical bond with the surface and remain on the surface even after washing with water, or modified products thereof.

[Glass thread]
The glass yarn may be composed of a plurality of glass filaments. The glass yarn may be woven as a warp yarn and a weft yarn to produce a glass cloth.

[Average filament diameter]
The average filament diameter of the glass filaments 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, still more preferably 3.5 to 6.0 μm, and particularly preferably 3.5 to 5.0 μm.

[Placement density]
The packing density of the glass yarns (warp and weft) constituting the glass cloth is preferably 10 to 120 yarns/inch (= 10 to 120 yarns/25.4 mm), more preferably 40 to 100 yarns/inch, and even more preferably 40 to 100 yarns/inch.

[Metsuke]
The weight of the glass cloth is preferably 8 to 250 g/m ² , more preferably 8 to 100 g/m ² , still more preferably 8 to 80 g/m ² , and particularly preferably 8 to 50 g/m ² .

[Glass type]
Conventionally, glass cloth used in prepregs (laminates) is usually a glass raw material called E-glass (alkali-free glass). On the other hand, for the glass cloth of this embodiment, glass raw materials such as L-glass, NE-glass, D-glass, L2-glass, T-glass, silica glass, and quartz glass may be used. From the viewpoint of excellent dielectric properties, glass raw materials such as L-glass, L2-glass, silica glass, and quartz glass are preferably used, and among them, silica glass and quartz glass are particularly preferred. Furthermore, from the viewpoint of improving the dimensional stability of laminates containing glass cloth, glass raw materials such as S-glass, T-glass, silica glass, and quartz glass are preferably used, and among them, silica glass and quartz glass are particularly preferred.

The silicon (Si) content of the glass yarns constituting the glass cloth, calculated as silicon dioxide (SiO ₂ ), is preferably 95.0 to 100% by mass or 99.0 to 100% by mass, more preferably 99.5 to 100% by mass, and even more preferably 99.9 to 100% by mass. A particularly preferred embodiment of the SiO ₂ content of the glass yarns constituting the glass cloth is greater than 99.9% by mass. A Si content of 95.0% by mass or greater facilitates ensuring the dielectric properties of the glass cloth and the dimensional stability of the laminate. The silicon content can be determined using known measurement techniques such as atomic absorption spectrometry, inductively coupled plasma (ICP), and optical emission spectroscopy. Specifically, using an apparatus such as ICP-AES or ICP-MS, a calibration curve can be prepared from a standard sample with a known content, and the silicon content of the sample to be measured can then be determined from the prepared calibration curve.

It has been conventionally recognized that when the Si content is within the above range, the hardness of the glass is so high that a glass cloth made using the glass yarn has poor drilling processability, and that a resin substrate using a glass cloth with poor drilling processability is subjected to a strong impact during drilling, resulting in a long whitening distance of the resin substrate.
In contrast to this, according to this embodiment, a resin substrate with a small whitening distance can be obtained even though a glass cloth having a Si content within the above range is used.

[Weave structure]
Examples of weave structures for the glass cloth include plain weave, sieve weave, satin weave, and twill weave, with plain weave structures being more preferred.

[Surface treatment agent (surface treatment liquid)]
The surface treatment liquid may contain a surface treatment agent. In this embodiment, the surface treatment is performed, for example, by a method using a surface treatment liquid.

(Concentration of surface treatment agent)
The surface treatment liquid may contain a surface treatment agent and a mother liquid (e.g., an aqueous acetic acid solution). The concentration of the surface treatment agent (e.g., a silane coupling agent) in the surface treatment liquid is preferably 0.1 to 2.0 mass%, more preferably 0.2 to 1.0 mass%. By keeping the concentration of the surface treatment agent within the above range, the glass surface can be suitably surface-treated.

(Silane coupling agent)
In the present embodiment, the surface treatment agent preferably contains a silane coupling agent.
That is, the glass threads (including glass filaments) constituting the glass cloth are preferably surface-treated with a silane coupling agent.

The surface treatment agent is, for example, a compound represented by the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
It is preferable that the compound contains a silane coupling agent represented by the formula:

With regard to the above X, the unsaturated carbon-carbon double bond is preferably a bond derived from at least one of an acryloyl group and a methacryloyl group, from the viewpoint of easily improving the adhesion between the glass cloth and the matrix resin and easily reducing the whitening distance of the resin substrate. A particularly preferred embodiment of the unsaturated carbon-carbon double bond is a bond derived from a methacryloyl group.

Regarding the above Y, the alkoxy group is preferably an alkoxy group having 1 to 5 carbon atoms (1, 2, 3, 4 or 5 carbon atoms) from the viewpoint of the stability of the surface treatment on the glass cloth.

The silane coupling agent contained in the surface treatment agent may be one or more of the silane coupling agents represented by formula (1) above. For example, two or more silane coupling agents having different X values may be mixed and used.

Examples of the silane coupling agent represented by the general formula (1) include:
2-Propenoic acid, 2-methyl-, (dimethoxysilylene)bis(oxy-2,1-ethanediyl) ester,
2-Propenoic acid, 2-methyl-, 1-[(trimethoxysilyl)methyl]-1,2-ethanediyl ester,
2-Propenoic acid, 2-methyl-, 2-[(trimethoxysilyl)methyl]-1,3-propanediyl ester,
1,1′-[2-[3-(Trimethoxysilyl)propoxy]-1,3-propanediyl] bis(2-methyl-2-propenoate),
1,1'-[2-[[(2-Methyl-1-oxo-2-propen-1-yl)oxy]methyl]-2-[[3-(triethoxysilyl)propoxy]methyl]-1,3-propanediyl] bis(2-methyl-2-propenoate),
1-[2-[(2-Methyl-1-oxo-2-propen-1-yl)oxy]-1-[[(2-methyl-1-oxo-2-propen-1-yl)oxy]methyl]ethyl] 2-[3-(triethoxysilyl)propyl]butanedioate,
9,9-Diethoxy-2-[[2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethoxy]methyl]-4-oxo-3,10-dioxa-5-aza-9-siladodec-1-yl 2-methyl-2-propenoate,
1,1'-[2-[[(2-Methyl-1-oxo-2-propen-1-yl)oxy]methyl]-2-[6-(trimethoxysilyl)hexyl]-1,3-propanediyl] bis(2-methyl-2-propenoate),
Acrylic acid, [[2-[(trimethoxysilyl)methoxy]ethyl]imino]diethylene ester,
2-Propenoic acid, 1,1'-[2-(8,8-dimethoxy-3-oxo-2,9-dioxa-6-thia-8-siladec-1-yl)-2-[[(1-oxo-2-propen-1-yl)oxy]methyl]-1,3-propanediyl] ester,
1,1′-[2-Methyl-2-[[[[3-(trimethoxysilyl)propyl]amino]carbonyl]amino]-1,3-propanediyl] di-2-propenoate,
1,1'-[2-[[2-(9,9-Dimethoxy-4-oxo-3,10-dioxa-5-aza-9-silaundec-1-yl)-11,11-dimethoxy -1,6-dioxo-5,12-dioxa-2,7-diaza-11-silatridec-1-yl]amino]-2-methyl-1,3-propanediyl] di-2-propenoate,
etc.

The silane coupling agent that can be used can be appropriately adjusted depending on the dielectric loss tangent of the glass cloth before surface treatment, the matrix resin used in the resin substrate, etc. Of course, the silane coupling agent represented by the above formula (1) may be used in combination with a silane coupling agent other than that represented by the above formula (1).
On the other hand, it is preferable to use two or more silane coupling agents represented by the above formula (1) that have different molecular weights. By using two or more silane coupling agents that have different molecular weights, the density of the treatment agent on the glass surface tends to be increased, and as a result, the reactivity with the matrix resin tends to be further improved.

(molecular weight)
The molecular weight of the surface treatment agent, for example, the molecular weight of the silane coupling agent, is preferably 200 to 900, more preferably 230 to 800, still more preferably 260 to 700, and particularly preferably 300 to 600. If the molecular weight is 900 or less, dispersibility in water tends to be good, and therefore, the occurrence of white spots on the glass cloth is easily suppressed.
When two or more surface treatment agents (for example, silane coupling agents) are used, it is preferable that the weighted average value of the molecular weights of the surface treatment agents, where the weight is the mass of each surface treatment agent, is within the above range, and it is more preferable that the molecular weights of all of the multiple surface treatment agents used are within the above range.
For example, when a surface treatment agent is prepared so that silane coupling agents having molecular weights of 300 and 500 are present in amounts of 0.5 mass % and 1.0 mass %, the weighted average value is calculated by the following formula:
Weighted average value = {(300 x 0.5) / (0.5 + 1.0)} + {(500 x 1.0) / (0.5 + 1.0)} = 433
It is calculated as follows (for ease of explanation, decimal points are omitted):

[Average opening degree of glass cloth]
The average degree of opening of the glass cloth is, for example, 35% or more, and is preferably more than 40%, more preferably more than 43%, even more preferably more than 46%, more than 50%, more than 53%, more than 56%, or more than 60%, and particularly preferably more than 65%. When the average degree of opening of the glass cloth is more than 35% or 40%, it is easy to prevent air bubbles called voids from remaining in the bundle of glass yarns when a resin substrate is produced, and as a result, it is less likely to have an adverse effect on solder heat resistance, insulation reliability, etc.
The silane coupling agent represented by the formula (1) tends to have a relatively strong intermolecular force, and therefore tends to be less effective in impregnating the glass cloth with the matrix resin than silane coupling agents other than those represented by the formula (1). Therefore, in order to fully obtain the effect of improving the insulation reliability of the glass cloth surface-treated with the silane coupling agent represented by the formula (1), it is preferable that the average degree of opening is 35% or more, or exceeds 40%.

[White spots on glass cloth]
White stains (white spots) may be observed on the surface of the surface-treated glass cloth. These white spots tend to repel the matrix resin used in the preparation of the prepreg, which may result in poor appearance of the resulting prepreg and, in turn, poor solder heat resistance and insulation reliability in the resulting resin substrate.
It has been previously believed that the cause of these white spots is unknown.

In this regard, the present inventors have clarified that one of the white spots is an aggregate of a surface treatment agent (for example, a silane coupling agent) or a modified product thereof.
In particular, the present inventors have clarified that the silane coupling agent represented by the above formula (1) has a relatively large molecular weight, and therefore is relatively highly hydrophobic, and therefore tends to easily generate aggregates, and that when the solvent in the surface treatment solution contains water, the frequency of white spots occurring on the glass cloth after surface treatment tends to increase (for example, 10.0 spots/ ^m2 or more).

To suppress white spots, as described below,
Mixing the surface treatment solution by a predetermined method;
Controlling the temperature and pH of the surface treatment solution; and filtering the surface treatment solution to remove aggregates in the surface treatment solution.
Techniques such as those described above are suitable.

The frequency of white spots in the glass cloth is preferably 7.0 spots/ ^m2 or less, more preferably 4.0 spots/ ^m2 or less, even more preferably 2.0 spots/ ^m2 or less or 0.1 spots/ ^m2 or less, and particularly preferably 0.05 spots/ ^m2 or less. This makes it easy to realize a prepreg with excellent appearance. Theoretically, the frequency of white spots is greater than 0.

[Method of manufacturing glass cloth]
One aspect of this embodiment is a manufacturing method for manufacturing the glass cloth of this embodiment.
The manufacturing method of this embodiment is as follows:
a surface treatment step of treating the glass fiber with a surface treatment liquid containing a surface treatment agent having a molecular weight of 200 or more;
The surface treatment process is
a step of adding a solvent to a surface treatment agent to prepare a surface treatment liquid;
adjusting the temperature of the surface treatment solution;
adjusting the pH of the surface treatment solution; and filtering the surface treatment solution;
The method includes at least one of the steps.

Here, the manufacturing method of this embodiment may optionally include the following steps:
a step of heating the glass yarn to reduce the amount of fiber sizing agent adhering to the glass yarn (thermal deoiling step);
A step of washing the glass yarn with water (cleaning step), and/or a step of opening the glass yarn (opening step).

At least one of the surface treatment process, opening process, and cleaning process may be performed on the glass yarn before the process of weaving the glass yarn to obtain glass cloth (weaving process), or on the glass cloth after the weaving process. The order of the thermal deoiling process, surface treatment process, opening process, and cleaning process may be reversed. If the cleaning process is performed after the weaving process, the cleaning process can also serve as the opening process by using a high-pressure water spray, etc. The composition of the glass cloth usually does not change before and after opening.

[Heat deoiling process]
In this step, by heating the glass yarn, it is possible to reduce, and preferably remove, the fiber sizing agent (sizing agent), its residues, and modified products thereof that are arbitrarily attached to the glass yarn. By performing the thermal deoiling step, it is possible to form a surface treatment layer on the surface of the glass yarn (glass filament) after reducing organic substances that can increase the dielectric tangent, and therefore it is easy to produce a glass cloth with excellent dielectric properties.
As the means for thermal deoiling, known means (heating means, heating medium, heating mechanism, heating device, heating component, etc.) can be used.

One embodiment of the thermal deoiling step is, for example,
A method of heating the glass cloth at a temperature of 600 to 1600°C.
etc. are known.

In the heat treatment process, heating a glass cloth greige with a glass yarn softening point of 900°C or higher at a temperature range of 600 to 1600°C facilitates minimizing damage to the glass cloth and reducing the dielectric tangent of the glass cloth. From the perspective of optimally achieving the effects of the present disclosure, the thermal deoiling temperature is preferably 700 to 1500°C, more preferably 800 to 1400°C, even more preferably 900 to 1300°C, and particularly preferably 1000 to 1200°C. A thermal deoiling temperature of 600°C or higher facilitates effective removal of sizing agents and other substances adhering to the glass cloth greige, making it easier to produce glass cloth with excellent dielectric properties. A thermal deoiling temperature of 1600°C or lower facilitates suppressing devitrification of the glass, thereby preventing a decrease in the strength of the glass cloth.

The heating time is preferably 30 minutes or less, more preferably 15 minutes or less, even more preferably 5 minutes or less, and particularly preferably 90 seconds or less. Because the heat treatment is performed at a high temperature, a heating time of 30 minutes or less tends to minimize damage to the glass cloth, making it easier to avoid problems such as partial holes being formed in the glass cloth or the glass cloth being cut during processing. 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 perspective of effectively removing sizing agents, etc.

When thermal deoiling of glass cloth is carried out in a closed system, it is preferable to place the glass cloth in a heating furnace from the viewpoint of optimal heating by the heating means. Furthermore, from the viewpoint of efficient storage space and heating range, it is preferable to heat the glass cloth while storing it in a rolled state. Furthermore, from the viewpoint of increasing the efficiency of organic matter removal and shortening the organic matter removal time, it is preferable to heat the glass cloth while transporting it in the heating furnace. The glass cloth can be transported, for example, by a combination of an unwinding mechanism and a winding mechanism.

When thermal deoiling of glass cloth is carried out in an open system, it is preferable to heat the glass cloth while transporting it in order to ensure a sufficient heated area. The glass cloth can be transported, for example, by a combination of an unwinding mechanism and a winding mechanism.

The mode of the thermal deoiling step is not limited to the above.
As another embodiment of the thermal deoiling step, for example,
A method of heating in a vacuum or in a gas with a dew point of 15°C or less under conditions where the heating amount, expressed as a heating temperature (°C) of 100°C or more x heating time (h), is 450 (°C·h) or more (provided that the maximum heating temperature is 100 to 600°C);
etc. are also known.

(Heating means)
The heating means may be, for example, a heating furnace, an electric heater, a burner, etc., and among these, a gas single radiant tube burner or an electric heater is preferred. A plurality of different heating means may be combined.

From the perspective of efficiently removing organic matter adhering to the surface of the glass cloth, a continuous method in which the glass cloth is continuously passed through a heating furnace and heated is preferred over a batch method in which the glass cloth wound around a core is heated at a predetermined ambient temperature. A method in which the glass cloth can also be continuously washed using wash water with a low metal ion content, such as reverse osmosis (RO) water or ion-exchanged water, is even more preferable.

Furthermore, as a heating means, from the viewpoint of low running costs, the glass cloth may be heated by bringing a member (contact member) heated to a predetermined temperature into contact with the glass cloth.

The contact member is preferably capable of heating the glass cloth at high temperatures. The contact member is preferably in the form of a roll, as this allows for easier transport of the glass cloth. Specifically, the contact member is preferably a roll that uses induction heating, which can be used in high-temperature regions and has relatively little temperature variation across the width. When the glass cloth is heated by the contact member, the temperature of the contact member and the surface temperature of the glass cloth are considered to be roughly equal.

When continuously heating glass cloth, in order to remove carbonized material adhering to the roll, it is preferable that the method using the above roll be a method equipped with a mechanism for removing adhering foreign matter, such as a blade.

(Steam Application Means)
The means for applying the above to the glass cloth (steam application means) may be spraying, shower diffusion, jet nozzle, etc. Alternatively, the gas exhausted from the heating furnace can be reused as high-temperature steam.

The steam applied to the glass cloth may contain, for example, volatile solvents, water vapor, or gases other than water vapor. However, water vapor is preferred from the viewpoint of reducing toxicity to the human body and facilitating the decomposition of the sizing agent used in the glass fibers. The temperature of the high-temperature steam may be such that the surface temperature of the glass cloth is higher than 650°C. In this case, if necessary, a method may be employed that allows the supply of high-temperature steam and heated air in any ratio. The temperature of the high-temperature steam may be 400°C or higher, 450°C or higher, 550°C or higher, 600°C or higher, or 650°C or higher.

[Surface treatment process]
In the surface treatment step, the glass filaments are treated with a surface treatment solution containing a surface treatment agent having a molecular weight of 200 or more.
As a method for treating the glass filament with a surface treatment liquid (for example, a method for applying a surface treatment liquid to the glass filament),
(A) A method in which a glass cloth is transported while being immersed in a surface treatment solution stored in a bath (hereinafter referred to as the "immersion method");
(A) A method of directly applying the surface treatment liquid to the glass cloth using a roll coater, a die coater, a gravure coater, or the like;
When the immersion method is employed, the immersion time of the glass cloth in the surface treatment solution is preferably selected to be 0.5 seconds or more and 1 minute or less.

In the method of this embodiment, in the surface treatment step, the glass filaments are surface treated using a surface treatment agent having a molecular weight of 200 or more, particularly using a silane coupling agent represented by the above formula (1). The silane coupling agent used in the method of this embodiment has a larger molecular weight than general silane coupling agents, and therefore is relatively hydrophobic.
As described above, the present inventors have revealed that when the solvent in the surface treatment liquid contains water, aggregates of the surface treatment agent tend to be easily generated, and that when the solvent in the surface treatment liquid contains water, the frequency of occurrence of white spots on the glass cloth after surface treatment tends to increase.

The present inventors have found that in a surface treatment solution using a surface treatment agent having a molecular weight of 200 or more, particularly a silane coupling agent represented by the above formula (1), it is possible to form white spots on a glass cloth by taking the following measures (A) to (C):
(A) gradually adding a solvent (for example, a weakly acidic aqueous solution as a mother liquor) to the surface treatment agent;
(B) controlling the temperature and/or pH of the surface treatment solution during the surface treatment;
(C) Filtering the surface treatment solution during the surface treatment.

(A) Preparation of surface treatment liquid Since general silane coupling agents have excellent compatibility with and dispersibility in water, they are prepared by adding the silane coupling agent little by little to weakly acidic water with a pH of about 3 to 5 while stirring.
On the other hand, in the method of this embodiment, a pre-solution of the surface treatment agent can be obtained by adding a small amount of surfactant and solvent (e.g., a 60% aqueous acetic acid solution) to a diluted solution obtained by diluting the surface treatment agent with a small amount of methanol. The solvent added to the pre-solution is added to hydrolyze the alkoxide groups of the silane coupling agent, and the amount of solvent added is preferably adjusted according to the amount of hydrolysis. Then, an aqueous solution adjusted to a pH of 3 to 4 (also referred to as the "mother liquor" in this disclosure) is added little by little to the pre-solution while stirring, thereby uniformly dispersing the surface treatment agent in the aqueous solution. In this case, it is easy to suppress agglomerations in the surface treatment solution.

The surfactant composition and amount can be varied as appropriate depending on the type and amount of the surface treatment agent, and any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants may be used. Different types of surfactants may also be used in combination.

The amount of surfactant is preferably 0.2 to 10% by mass, more preferably 0.4 to 9% by mass, even more preferably 0.6 to 8% by mass, and particularly preferably 1 to 6% by mass, relative to the surface treatment agent (e.g., silane coupling agent). By using a surfactant amount that satisfies the above range, it becomes easier to uniformly disperse the silane coupling agent.

Nonionic surfactants include glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene glycols, fatty acid polyethylene glycols, fatty acid polyoxyethylene sorbitan, fatty acid alkanolamides, etc.

Anionic surfactants include fatty acid monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosinates, N-acylglutamates, dialkyl sulfosuccinates, alkane sulfonates, alpha-olefin sulfonates, linear alkylbenzene sulfonates, alkylbenzene sulfonates, naphthalene sulfonate-formaldehyde condensates, alkylnaphthalene sulfonates, N-methyl-N-acyltaurate salts, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fat and oil sulfate esters, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, etc.

Cationic surfactants include monoalkylamine salts, dialkylamine salts, trialkylamine salts, alkyltrimethylammonium chloride, alkylbenzalkonium chloride, etc.

Examples of amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, alkyl betaine, fatty acid amidopropyl betaine, alkyldiethylenetriaminoacetic acid, and alkylamine oxide.

(B) Temperature Control and/or pH Control of Surface Treatment Liquid From the viewpoint of suppressing agglomeration in the surface treatment liquid, the temperature of the surface treatment liquid is preferably controlled at 10 to 30°C, more preferably at 13 to 27°C, even more preferably at 15 to 25°C, and particularly preferably at 17 to 23°C, during the surface treatment process.

Furthermore, during the surface treatment process, impurities such as alkali metals contained in trace amounts in the glass cloth may cause the pH of the surface treatment solution to fluctuate. From the perspective of suppressing agglomerations in the surface treatment solution, it is preferable to minimize the pH fluctuation range of the surface treatment solution. During the surface treatment process, the pH of the surface treatment solution is preferably controlled to between 2.5 and 5.5, more preferably between 2.8 and 5.2, and even more preferably between 3.0 and 5.0. Examples of methods for controlling the pH within a predetermined range include bubbling carbon dioxide through the surface treatment solution.

Either the temperature control of the surface treatment liquid or the pH control of the surface treatment liquid may be performed, or both may be performed. From the perspective of effectively suppressing agglomerations in the surface treatment liquid, it is preferable to perform both the temperature control of the surface treatment liquid and the pH control of the surface treatment liquid.

Here, "temperature control of the surface treatment liquid" is a concept that includes not only an operation of increasing and/or decreasing the temperature of the surface treatment liquid, but also an operation of maintaining the temperature of the surface treatment liquid at a predetermined value, and an operation of detecting the temperature of the surface treatment liquid to confirm whether the temperature is within a predetermined range.
Furthermore, the concept of "pH control of the surface treatment solution" includes not only an operation for increasing and/or decreasing the pH of the surface treatment solution, but also an operation for maintaining the pH of the surface treatment solution at a predetermined value, and an operation for detecting the pH of the surface treatment solution to determine whether the pH is within a predetermined range.

(C) Filtration of the surface treatment liquid From the viewpoint of reliably collecting aggregates in the surface treatment liquid, it is preferable to filter the surface treatment liquid while the surface treatment process is being carried out. In this case, it is preferable to collect aggregates that may occur in the surface treatment liquid by filtration while circulating the surface treatment liquid.

To increase the efficiency of collecting agglomerates, it is preferable to use multiple stages of filtration. For example, two-stage filtration is preferable, in which agglomerates are first removed using a filter with relatively coarse mesh, and then the surface treatment liquid is filtered again using a filter with finer mesh than the primary filter. Such multiple-stage filtration makes it easier to prevent filter clogging, and as a result, makes it easier to avoid interruptions to the glass cloth production process.

(drying process)
The surface treatment process is
a step of applying a surface treatment liquid to the glass fiber and then drying the solvent contained in the surface treatment liquid (drying step);
It may further include:
The drying step makes it easy to fix the surface treatment agent to the surface of the glass yarn (surface of the glass filaments), and in particular makes it easy to fix the surface treatment agent to the surface of each individual glass yarn (surface of each individual glass filament). Examples of methods for drying the solvent include known methods such as drying by heating, specifically, methods of heating and drying by hot air, electromagnetic waves, etc.

The drying temperature is preferably 80°C or higher, more preferably 90°C or higher, from the viewpoint of ensuring sufficient reaction between the surface treatment agent and the glass. Furthermore, the drying temperature is preferably 300°C or lower, more preferably 180°C or lower, from the viewpoint of preventing deterioration of the organic functional groups contained in the surface treatment agent.

[Opening process]
The manufacturing method of this embodiment preferably includes a fiber-opening step after the surface treatment step.
Examples of the opening method in the opening step include opening the glass cloth with spray water (high-pressure water opening), a vibro washer, ultrasonic water, a mangle, or the like. By reducing the tension applied to the glass cloth during this opening process, the width of the glass yarns can be easily increased and the surface treatment agent that has not chemically bonded to the glass surface can be easily removed to some extent. In order to prevent a decrease in the tensile strength of the glass cloth due to the opening process, it is preferable to take measures such as reducing the friction of contacting members when weaving the glass yarns, optimizing the sizing agent and increasing the amount of adhesion.

In the fiber-spreading process, it is preferable to use multiple fiber-spreading methods to spread the glass fiber bundles. This makes it easier to control the average fiber-spreading degree of the glass cloth within a specified range, even if the glass cloth tends to have poor matrix resin impregnation properties.

[Cleaning process]
The washing step (finish washing step) is preferably a method capable of reducing the residue of the surface treatment agent that has not formed a chemical bond with the surface of the glass filaments, modified substances, etc., such as a method of washing the glass filaments with an organic solvent. By carrying out the washing step, even if a glass raw material with a high silicon (Si) content, such as quartz glass, is used, it becomes easy to adjust the difference between the dielectric loss tangent and the bulk dielectric loss tangent of the obtained glass cloth to fall within a predetermined range.

In the washing step, washing with a highly hydrophobic organic solvent is preferred in order to reduce the above-mentioned residues that are difficult to reduce with water, and washing with an organic solvent that has a high affinity for silane coupling agent residues having hydroxyl groups is also preferred.
Examples of the washing method include known methods such as immersion and shower spraying, and washing may be performed while heating or cooling as necessary. In order to prevent the dissolved deposits from re-adhering to the glass cloth, it is preferable to reduce the excess solvent from the washed glass cloth using a squeeze roller or the like before finish drying. Suitable organic solvents, for example, 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 cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, and ethylcyclohexane;
Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene;
Halogen-containing solvents such as chloroform, dichloromethane, and dichloroethane;
etc.

Examples of organic solvents that have a high affinity with modified surface treatment agents (e.g., 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;
etc.

Among the above, aromatic hydrocarbons, alcohols or ketones are preferred, and methanol or toluene is more preferred, from the viewpoint of easily adjusting the difference between the dielectric tangent and bulk dielectric tangent of the resulting glass cloth within a specified range.

The manufacturing method of this embodiment preferably includes a step of drying the washed glass cloth (post-washing drying step) to reduce the amount of organic solvent used after washing. From the viewpoint of facilitating the reduction of the organic solvent by drying, it is preferable that the organic solvent used for washing has a boiling point of 120°C or less. Known methods such as heat drying and air drying can be used to dry the organic solvent.

If heat drying is performed to reduce the amount of organic solvent in the post-wash drying process, hot air drying using low-pressure steam or heat transfer oil as a heat source is preferred from a safety perspective. The drying temperature is preferably above the boiling point of the washing solvent, and is preferably 180°C or lower to prevent deterioration of the silane coupling agent.

[Optional step]
The manufacturing method of this embodiment may optionally include other steps in addition to the steps described above.
Other steps include, for example, a step of processing the glass cloth into slits (slit processing step).

(Inspection process or measurement process)
In addition, other processes include:
Inspecting the glass cloth for white spots; and Measuring the peak height derived from carbonyl groups in the glass cloth using Fourier transform infrared spectroscopy;
At least one of the steps above can be mentioned.
The manufacturing method of this embodiment includes such a step, which makes it easy to realize the glass cloth of this embodiment.

[Test method]
Another aspect of this embodiment is a test method for a glass cloth made by weaving glass yarns.
The glass cloth to be tested is surface-treated with a surface treatment agent,
The above test method is
The method includes a step of inspecting the glass cloth for white spots based on the peak height derived from the carbonyl group in the glass cloth and the total carbon content of the glass cloth or the ignition loss value of the glass cloth.

In the test method of this embodiment, the glass cloth to be tested, the peak height derived from carbonyl groups, the total carbon content, the ignition loss value, and the white spots may be determined by referring to the descriptions in the "Glass Cloth" section above. The test method of this embodiment makes it possible to evaluate the properties of the glass cloth based on the white spots that the inventors focused on.

[Prepreg]
The prepreg of this embodiment contains glass cloth, a matrix resin, and an inorganic filler. The prepreg of this embodiment can be made by using the glass cloth of this embodiment as the glass cloth. This provides a prepreg with excellent properties (for example, a prepreg with few voids).

Either thermosetting resins or thermoplastic resins can be used as the matrix resin. Thermosetting resins and thermoplastic resins may be used in combination.

Examples of thermosetting resins include:
a) an epoxy resin obtained by reacting a compound having an epoxy group with a compound having at least one group reactive with the epoxy group, such as an amino group, a phenol group, an acid anhydride group, a hydrazide group, an isocyanate group, a cyanate group, or a hydroxyl group, without a catalyst or by reacting with the addition of a catalyst having a reaction catalytic ability, such as an imidazole compound, a tertiary amine compound, a urea compound, or a phosphorus compound, and then curing the resulting compound;
b) a radical polymerization type curable resin obtained by curing a compound having at least one of an allyl group, a methacryl group, and an acrylic group using a thermal decomposition type catalyst or a photodecomposition type catalyst as a reaction initiator;
c) a maleimide triazine resin obtained by reacting a compound having a cyanate group with a compound having a maleimide group and curing the reacted compound;
d) a thermosetting polyimide resin obtained by reacting and curing a maleimide compound with an amine compound;
e) a benzoxazine resin obtained by crosslinking and curing a compound having a benzoxazine ring through thermal polymerization;
Examples include:

Examples of thermoplastic resins include polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, aromatic polyamide, polyether ether ketone, thermoplastic polyimide, insoluble polyimide, polyamide imide, LCP, polyester, and fluororesin.

Since acryloyl groups or methacryloyl groups have good reactivity, it is preferable to use at least one of polyphenylene ether and modified polyphenylene ether as the matrix resin.

The prepreg may contain an inorganic filler. Examples of inorganic fillers include aluminum hydroxide, zirconium oxide, calcium carbonate, alumina, mica, aluminum carbonate, magnesium silicate, aluminum silicate, silica, talc, short glass fiber, aluminum borate, and silicon carbide. The inorganic filler may be used in combination with the thermosetting resin.

[Printed wiring board]
The printed wiring board of this embodiment includes a prepreg. In particular, the printed wiring board of this embodiment includes the prepreg of this embodiment as the prepreg. This provides a printed wiring board with excellent properties (for example, a printed wiring board with excellent insulation reliability).

[Integrated circuits and electronic devices]
The integrated circuit of this embodiment includes the printed wiring board of this embodiment. Also, the electronic device of this embodiment includes the printed wiring board of this embodiment. These provide an integrated circuit and electronic device with various excellent characteristics.

The present embodiment will be described below with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples. Regarding the examples and comparative examples, various manufacturing, measurements, evaluations, etc. were performed using the following methods.

[Thickness]
In accordance with 7.10 of JIS R 3420, a micrometer was used to gently rotate the spindle, bringing it into light contact parallel to the measurement surface, and the scale was read after the ratchet made three clicks. JIS R 3420 also specifies general test methods for long glass fibers and products such as glass cloth made from long glass fibers.

[Metsuke]
The glass cloth was cut to a predetermined size to obtain a sample. The mass of the sample was divided by the area of the sample to determine the basis weight. Here, the glass cloth was cut to a size of 10 cm x 10 cm to obtain a sample, and the mass was measured to determine the basis weight (g/ ^m2 ).

[Converted thickness]
Since the glass cloth is a discontinuous planar body made 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. The calculation formula was as follows:
Converted thickness (μm) = basis weight (g/m ² ) / glass density (g/cm ³ )
As follows.

[Dielectric loss tangent]
The dielectric loss tangent of each glass cloth was measured in accordance with IEC 62562. Specifically, glass cloth samples were sampled to the size required for measurement with each split cylinder resonator and stored in a constant temperature and humidity oven at 23°C and 50% RH for 8 hours to condition the humidity. The dielectric properties at 10 GHz were then 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. The thickness of each sample was the equivalent thickness. IEC 62562 specifies a method for measuring the dielectric properties in the microwave band of fine ceramic materials for dielectric substrates, primarily used in microwave circuits.

A 300 μm thick glass plate was prepared, having the same type and composition as each glass cloth for which the dielectric loss tangent was measured. Using the thickness obtained from the glass plate thickness measurement, the bulk dielectric loss tangent at 10 GHz was measured using the same method as for measuring the dielectric loss tangent above.

[Ignition loss value]
The ignition loss value of the glass loss was determined in accordance with JIS R3420. Specifically, the glass cloth was dried at a temperature of 110°C ± 5°C for 60 minutes. The test piece was then transferred to a desiccator and allowed to cool at room temperature for 20 minutes, after which the mass of the test piece was measured to the nearest 0.1 mg (A mg). The dried test piece was then heat-treated at a temperature of 625°C ± 20°C for 20 minutes. The test piece was then transferred to a desiccator and allowed to cool for 20 minutes, after which the mass of the test piece was measured to the nearest 0.1 mg (B mg). The ignition loss value was determined using the following formula, rounded to the fourth decimal place, and expressed to two decimal places.
Ignition loss (%) = [{A (mg) - B (mg)} / A (mg)] x 100

[Average opening degree]
The opening degree of the warp yarns of the glass cloth was calculated using the following formula:
Warp opening rate (%) = [warp width (μm) / {number of warp filaments × warp filament diameter (μm)}] × 100
It was calculated by:
The opening degree of the weft yarn of the glass cloth was calculated using the following formula:
Weft opening rate (%) = [weft width (μm) / {number of weft filaments × weft filament diameter (μm)}] × 100
It was calculated by:

Using the calculated warp opening rate (%) and weft opening rate (%), the following formula:
Average opening rate (%) = {opening rate of warp yarn (%) + open rate of weft yarn (%)} / 2
The average degree of opening was calculated by the above.

(Number of warp and weft filaments and filament diameter)
In calculating the average degree of opening, the number of filaments in the warp and weft yarns was determined by observing a cross-sectional image of the glass yarn. Specifically, a cross-sectional image of the glass yarn as the warp yarn (or the weft yarn) was obtained, and the number of filaments and the filament diameter of the warp yarn (or the weft yarn) were measured in the cross-sectional image.
Similarly, image acquisition of the glass yarn and measurement of the number of filaments were repeated, and the average values of the five measurements obtained were used as the number of filaments and filament diameter of the warp (or weft).

(Warp width and weft width)
In calculating the average degree of opening, the warp width and the weft width were determined by the following method.
First, five glass cloth test pieces each measuring 70 mm in the warp direction and 70 mm in the weft direction were cut out from the glass cloth.
Each cut specimen was observed vertically using a macroscope at 100x magnification. For each specimen, the widths of 250 warp yarns (or weft yarns) were randomly measured, and the average value of the widths of the 250 warp yarns (or weft yarns) was calculated. The average value was used as the warp width (or weft width).

[Total carbon content]
The glass cloth was cut into a square shape with a mass of about 80 mg. The cut glass cloth was heated at about 800°C for 1 minute, and the amount of carbon dioxide in the generated gas was measured by gas chromatography to determine the amount of carbon dioxide in the generated gas. In addition, the amount of carbon dioxide generated when acetanilide ( _C8H9NO ) having a predetermined mass W ( _mg ) was heated at about 800°C for 1 minute was also determined.
The amount of carbon dioxide was measured using SUMIGRAPH NC-TR22 (manufactured by Sumika Chemical Analysis Center Co., Ltd.). The molecular weight and carbon ratio of acetanilide were determined as follows:
Molecular weight of acetanilide = 135.17
Carbon percentage of acetanilide = 71.09%
was used.

The total carbon amount per mass of the glass cloth is calculated using the following formula:
Total carbon content (mass%) =
[{mass W (mg) of acetanilide × (carbon ratio of acetanilide/100)} / peak area derived from carbon dioxide generated from acetanilide] × [{peak area of carbon dioxide generated from the glass cloth / mass (mg) of the glass cloth} × 100]
It was calculated based on the following.

The glass cloth was cut from different positions, and the total carbon content was measured for each of the resulting 10 different samples, and the average value was used as the total carbon content.

[Making heat cloth]
Follow steps 1 to 3 below:
Operation 1: A glass cloth was heated at 615° C. for 1 hour to remove oil.
Operation 2: After Operation 1, the ignition loss of the glass cloth was measured.
Procedure 3: If the ignition loss value obtained in Procedure 2 exceeded 0.01% by mass, Procedure 1 was repeated (Procedures 1 and 2 were repeated until the ignition loss value obtained in Procedure 2 became 0.01% by mass or less).
By carrying out the above steps, a heat cloth from which the surface treatment agent had been removed was obtained.

[Carbonyl group peak height]
Using a glass cloth and the heat cloth obtained by the above method, the peak height derived from the carbonyl group contained in the surface treatment agent attached to the glass cloth was measured by Fourier transform infrared spectroscopy. The measuring device and measuring method are as follows.

(Measurement device: Fourier transform infrared spectrophotometer (FT-IR))
Model: Agilent Technologies Variant 670-IR
Measurement method: Transmission method Number of integration: 64 times Wavenumber resolution: 4cm ^-1
Measurement wave number: 400cm ^-1 ~ 4000cm ^-1

(Measurement method)
(1) The Variant 670-IR was calibrated and preparations were made for measurements using the transmission method.
(2) Four heat cloths were stacked to form a sample, which was then fixed in a holder and set on the sample stage in the apparatus, and the infrared spectrum of the heat cloths was measured by the transmission method.
(3) Four sheets of glass cloth were stacked to form a sample, and the infrared spectrum of the glass cloth was measured by the transmission method in the same manner as in (2) above.
(4) From the results of (2) and (3) above, the difference spectrum of the infrared spectrum was calculated.

(5) From the difference spectrum obtained in (4) above, the height of the peak derived from carbonyl groups present in the range of 1600 cm ⁻¹ to 1900 cm ⁻¹ was determined, and the peak height derived from carbonyl groups was then divided by the number of stacked glass cloths (four in this example) to determine the peak height per glass cloth.

The baseline was obtained in accordance with the baseline drawing method described in JIS K 0117:2017. Specifically, as shown in Figure 18 d) described in JIS K 0117:2017, a tangent line was drawn to two base points (in this example, the base point located to the right and left of the peak derived from the carbonyl group in (5) above), and this was treated as the baseline. The difference between the baseline and the peak top was then obtained as the height of the peak derived from the carbonyl group.

(6) The above procedures (2) to (5) were repeated using a heat cloth and a sample obtained by the method described below. This resulted in a calibration curve of the total carbon content (mass%) or ignition loss (mass%) (x-axis) of the sample and the peak height due to carbonyl groups per glass cloth (y-axis). The calibration curve passed through the origin and was approximated as a straight line.

Figure 1 shows the calibration curve L prepared in this example. Figure 1(a) shows the relationship between peak height and total carbon content, and Figure 1(b) shows the relationship between peak height and ignition loss.

(7) In the calibration curve obtained in (6) above, the y-axis value (peak height derived from carbonyl groups) when the total carbon content or ignition loss value of the sample was 0.1 mass% was defined as 1.00. The "peak height per glass cloth" obtained in (5) above was calculated using the following formula:
"Peak height per glass cloth" after relative value conversion = ("Peak height per glass cloth" before relative value conversion × 1.00) / Peak height of specimen sample (when the total carbon content or ignition loss value is 0.1 mass%)
The relative values were calculated according to the following formula: Thus, the "peak height per glass cloth" after the relative value calculation was determined.
In the formula, the "peak height per glass cloth" before conversion into a relative value is the "peak height per glass cloth" obtained in (5) above.

(8) Using the total carbon content or ignition loss value of the glass cloth treated as a sample in (3) above and the relative value-converted "peak height per glass cloth" obtained in (7) above, the following value is calculated using the following formula:
Value A = Peak height per glass cloth / Total carbon content of glass cloth (mass%)
Value B = Peak height per glass cloth / Ignition loss value of glass cloth (mass%)
were calculated respectively.

(9) The number of overlapping glass cloths was changed to five, and the operations (1) to (8) above were repeated. In this case, the number of overlapping heat cloths in (2) above was changed to five, and the number of overlapping specimen samples in (6) above was changed to five. This resulted in values A and B when the number of glass cloths was five.

(10) Furthermore, the number of overlapping glass cloths was changed to six, and the operations (1) to (8) above were repeated. In this case, the number of overlapping heat cloths in (2) above was six, and the number of overlapping specimen samples in (6) above was six. This resulted in values A and B when the number of glass cloths was six.

(11) The difference spectrum obtained when the number of glass cloths was four, the difference spectrum obtained when the number of glass cloths was five, and the difference spectrum obtained when the number of glass cloths was six were compared.
Then, the number of glass cloths that gave the difference spectrum with the least distortion in the shape of the difference spectrum was specified, and the values A and B obtained for that number of glass cloths were used as the evaluation values.

In this example, steps (1) to (11) were performed, but as long as it does not affect the measurement results, any steps that can be omitted may be omitted, and the order of steps may be reversed.

[Specimen sample]
Glass yarns (average filament diameter 5.0 μm, filament count 100, twist count 1.0Z) with a _SiO2 content of more than 99.9% by mass were used for the warp and weft. Then, using an air jet loom, a glass cloth with a weave density of 66 warp yarns/25 mm and 68 weft yarns/25 mm was obtained. The obtained glass cloth was heated at 1000°C for 20 seconds to deoil. Subsequently, the glass cloth was immersed in a surface treatment solution containing a mixture of pure water adjusted to pH 3 with acetic acid and a silane coupling agent (5-hexenyltrimethoxysilane; Z6161 (manufactured by Dow-Toray Industries, Inc.) and 3-methacryloxypropyltrimethoxysilane; Z6030 (manufactured by Dow-Toray Industries, Inc.)). After immersion, the glass cloth was removed and heated and dried at 110°C for 1 minute, thereby performing a surface treatment with the silane coupling agent.
In this way, a sample glass cloth was prepared.

The total mass percent of the silane coupling agent in the surface treatment solution was adjusted while the mass ratio of 5-hexenyltrimethoxysilane:3-methacryloxypropyltrimethoxysilane was fixed at 1.00:2.83 so that the total carbon content of the sample samples was 0.05 mass%, 0.07 mass%, 0.1 mass%, 0.12 mass%, and 0.15 mass%. Glass cloth samples were then prepared with amounts of silane coupling agent attached that were roughly close to the five points on the calibration curve.

[Glass Cloth P]
The warp and weft yarns were composed of glass yarns with a _SiO2 composition of more than 99.9% by mass. Specifically, the warp and weft yarns were glass yarns with an average filament diameter of 5.0 μm, 100 filaments, and a twist of 1.0Z. Then, using an air jet loom, 2000 m of glass cloth was woven with a plain weave structure, a warp density of 66/25 mm and a weft density of 68/25 mm, and a cloth width of 1300 mm. The bulk dielectric loss tangent at 10 GHz of the glass constituting the glass yarns was 0.00020.

[Glass Cloth Q]
The warp and weft yarns were composed of glass yarns with a _SiO2 composition of more than 99.9% by mass. Specifically, the warp and weft yarns were glass yarns with an average filament diameter of 5.0 μm, 200 filaments, and a twist of 1.0Z. Then, using an air jet loom, 2000 m of glass cloth was woven with a plain weave structure, a warp density of 54/25 mm, a weft density of 54/25 mm, and a cloth width of 1300 mm. The bulk dielectric loss tangent at 10 GHz of the glass constituting the glass yarns was 0.00020.

[Glass Cloth R]
The warp and weft yarns were composed of glass yarns with a _SiO2 composition of more than 99.9% by mass. Specifically, the warp and weft yarns were glass yarns with an average filament diameter of 4.0 μm, 50 filaments, and a twist of 1.0Z. Then, using an air jet loom, 2000 m of glass cloth was woven with a plain weave structure, a warp density of 95/25 mm and a weft density of 95/25 mm, and a cloth width of 1300 mm. The bulk dielectric loss tangent at 10 GHz of the glass constituting the glass yarns was 0.00020.

[Preparation of surface treatment solution]
The surface treatment solutions were prepared according to the following methods 1) to 5).
1) The silane coupling agent was weighed.
2) Methanol in an amount equal to the amount weighed out in 1) above was mixed with the silane coupling agent weighed out in 1) above to prepare a silane coupling agent solution.
3) The silane coupling agent solution was mixed with 0.8% by mass of polyoxyethylene alkyl ether relative to the silane coupling agent and stirred. After stirring for 1 minute, 20% by mass of acetic acid aqueous solution (concentration: 60% by mass) relative to the silane coupling agent was added to the silane coupling agent solution. This hydrolyzed the silane coupling agent.
4) A mother liquor of an aqueous acetic acid solution (pH = 3 to 4) was prepared. The silane coupling agent solution (pre-solution) obtained in 3) above was stirred for 15 minutes at room temperature of 20 to 25°C. The mother liquor was then added dropwise to the stirred silane coupling agent solution, thereby dispersing the silane coupling agent. The amount of mother liquor added (dropping rate) was set so that the entire amount of mother liquor would be added in 10 minutes.
5) After step 4), the silane coupling agent solution was stirred at room temperature of 20 to 25° C. for 2 hours to obtain a surface treatment liquid.

In one embodiment, the "solvent" in the "step of preparing a surface treatment liquid by adding a solvent to a surface treatment agent" of the present disclosure is the mother liquid. Here, an example of the mother liquid is a weakly acidic aqueous solution with a pH of 3 to 4, which is added for the purpose of dispersing the silane coupling agent after hydrolysis.
It is defined as follows.

[Examples and Comparative Examples]
Example 1
The glass cloth P was washed with ion-exchanged water and then dried. This removed alkali metal ions and the like adhering to the surface of the glass cloth. Thereafter, the glass cloth P was heated at 1000°C for 15 seconds to perform thermal deoiling (thermal deoiling step).

The silane coupling agent used was 1,1'-[2-[[(2-Methyl-1-oxo-2-propen-1-yl)oxy]methyl]-2-[6-(trimethoxysilyl)hexyl]-1,3-propanediyl] bis(2-methyl-2-propenoate) (CAS No. 1248412-07-8, Silane Coupling Agent A), and the surface treatment liquid was prepared using the above method so that the concentration of the silane coupling agent in the surface treatment liquid was 0.5% by mass.

The glass cloth, which had been heated and deoiled, was immersed in the resulting surface treatment solution. Then, excess surface treatment solution was squeezed out using an NBR rubber roll at a pressure of 0.22 MPa. The glass cloth was then heated and dried at 135°C for 1 minute, thereby adhering the silane coupling agent to the surface of the glass cloth.

In this example, temperature control (e.g., cooling) was performed to keep the temperature of the surface treatment liquid in the range of 17 to 23°C while the glass cloth was being surface treated. Furthermore, carbon dioxide was bubbled into the surface treatment liquid to keep the pH of the surface treatment liquid in the range of 3.0 to 4.0 while the glass cloth was being surface treated.

In this example, the surface treatment solution used for the surface treatment of the glass cloth was filtered using an HDCII filter (manufactured by Nippon Pall Corporation). That is, the surface treatment solution was first passed through a filter with a mesh size of 10 μm, and then passed through a filter with a mesh size of 4.5 μm. This allowed for the capture of any aggregates that may be present in the surface treatment solution. The filtered surface treatment solution was used for the surface treatment of the glass cloth.

The surface-treated glass cloth was subjected to a pressure of 5.0 kg/ ^cm² using a spray nozzle, resulting in high-pressure opening. Next, ultrasonic waves at a frequency of 25 kHz and an output of 0.60 W/ ^cm² were applied in water to further open the glass cloth while reducing excess silane coupling agent physically attached to the glass cloth. The glass cloth was then dried by heating at 130°C for 1 minute. The glass cloth was then immersed in toluene for finish washing, thereby reducing modified silane coupling agent that had not formed chemical bonds with the surface of the glass filaments. As a result of the above, 2000 m of surface-treated glass cloth was obtained.

Example 2
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that acrylic acid, [[2-[(trimethoxysilyl)methoxy]ethyl]imino]diethylene ester (CAS NO: 3390-52-1, silane coupling agent B) was used as the silane coupling agent and the concentration of silane coupling agent B was 0.8 mass%.

Example 3
As the silane coupling agent, 2-propenoic acid, 1,1'-[2-(8,8-dimethoxy-3-oxo-2,9-dioxa-6-thia-8-siladec-1-yl)-2-[[(1-oxo-2-propen-1-yl)oxy]methyl]-1,3-propanediyl] ester (CAS NO: 1801441-80-4, silane coupling agent C) was used. Except for this, a surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 2.

Example 4
As the silane coupling agent, 1,1'-[2-Methyl-2-[[[[3-(trimethoxysilyl)propyl]amino]carbonyl]amino]-1,3-propanediyl]di-2-propenoate (CAS NO: 1239892-42-2, silane coupling agent D) was used. Except for this, a surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 2.

Example 5
A surface-treated glass cloth (2000 m) was obtained in the same manner as in Example 2, except that 2-propenoic acid, 2-methyl-, 1-[(trimethoxysilyl)methyl]-1,2-ethanediyl ester (CAS NO: 143414-45-3, silane coupling agent E) was used as the silane coupling agent.

Example 6
As a silane coupling agent, 1,1'-[2-[[2-(9,9-Dimethoxy-4-oxo-3,10-dioxa-5-aza-9-silaundec-1-yl)-11,11-dimethoxy-1,6-dioxo-5,12-dioxa-2,7-diaza-11-silatridec-1-yl]amino]-2-methyl-1,3-propanediyl] di-2-propenoate (CAS NO: 1558048-41-1, silane coupling agent F) was used, except that in the same manner as in Example 2, a surface-treated glass cloth of 2000 m was obtained.

Example 7
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that glass cloth Q was used and the silane coupling agents A and B were used in a concentration of 0.4% by mass each, totaling 0.8% by mass.

(Example 8)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that Glass Cloth R was used and the concentration of Silane Coupling Agent A was set to 0.8 mass %.

Example 9
After the surface treatment, 2000 m of surface-treated glass cloth was obtained in the same manner as in Example 1, except that high-pressure spreading using a spray nozzle was not carried out.

Example 10
After the surface treatment, 2000 m of surface-treated glass cloth was obtained in the same manner as in Example 1, except that the glass cloth was spread at a high pressure of 2.5 kg/cm ² using a spray nozzle.

Example 11
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that a silane coupling agent of 0.8 mass% in total, consisting of silane coupling agent A and 3-(methacryloyloxy)propyltrimethoxysilane (CAS NO: 2530-85-0, silane coupling agent G) with a concentration of 0.4 mass% each, was used.

(Comparative Example 1)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 2, except that silane coupling agent G was used.

(Comparative Example 2)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that a surface treatment liquid was prepared by dropping a silane coupling agent solution into a mother liquid of an aqueous acetic acid solution under stirring, that the surface treatment liquid was not filtered, that the surface treatment liquid was not cooled even when the temperature of the surface treatment liquid exceeded 23°C, and that carbon dioxide bubbling was not performed even when the pH exceeded 4.0.

(Comparative Example 3)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 2, except that 3-acryloxypropyltrimethoxysilane (CAS No. 4369-14-6, silane coupling agent H) was used as the silane coupling agent.

[Frequency of white spots]
The frequency of occurrence of white spots on the surface of the glass cloth was evaluated by irradiating glass cloth of A4 size (210 mm x 297 mm) or more with a halogen lamp. When observing a sheet-like glass cloth, the halogen lamp was placed directly above the glass cloth, and the number of white spots was calculated by the following formula while changing the direction of observation of the glass cloth:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{area of glass cloth (m ² )}
The frequency of occurrence of white spots was calculated according to the following formula.
In the case of observing a glass cloth roll, a tension of 100 N/1300 mm was applied to the glass cloth on a roll-to-roll inspection table, and the number of white spots on the glass cloth was counted over a length of 2000 m while irradiating it with a halogen lamp. Then, the inspection area and the number of white spots found in the inspection were calculated using the following formula:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{width of glass cloth (m)×inspected length of glass cloth (m)}
The frequency of occurrence of white spots was calculated according to the following formula.

2A and 2B are photographs for explaining the "white spots" in this example. Fig. 2A shows a photograph of a portion without a white spot, and Fig. 2B shows a photograph of a portion with a white spot P.
In this example, a defect in which a white outline is observed upon irradiation with UV light and the area enclosed by the outline (the area including the outline) is 0.8 ^cm2 or more is defined as a "white spot." Here, the outline is, for example, circular.
The area enclosed by the contour line was calculated using known image analysis software.

[Prepreg manufacturing method]
45 parts by mass of polyphenylene ether (Noryl SA9000, manufactured by SABIC Corporation), 10 parts by mass of triallyl isocyanurate, 45 parts by mass of toluene, and 0.6 parts by mass of 1,3-di(tert-butylisopropylbenzene) were added to a stainless steel container and stirred at room temperature for 1 hour to prepare a varnish.
The glass cloths obtained in the Examples and Comparative Examples were impregnated with the prepared varnish and then dried at 115° C. for 1 minute to obtain prepregs.

[Method for manufacturing resin substrate]
The resulting prepreg was sampled to a size of 20 cm x 20 cm. Eight of the resulting samples were stacked, and 12 μm thick copper foil was placed on the top and bottom layers. The sample was then heated and pressed at 200°C and 40 kg/ ^cm² for 120 minutes to produce a resin substrate.

[Solder heat resistance]
The top and bottom copper foils were removed from the resin substrate to obtain a laminate. The resulting laminate was cut into a total of 10 pieces measuring 5 cm x 5 cm. The laminate was then heated at 133°C for 72 hours in a pressure cooker and allowed to absorb water. The absorbed laminate was then immersed in a solder bath at 288°C for 20 seconds, and each of the 10 laminate samples was visually inspected for blistering at the glass cloth/resin interface due to peeling.

Laminate samples that showed blistering due to delamination at the glass cloth/resin interface were rated as "failed," and the number of "failed" laminate samples was evaluated. The fewer the number listed in the table, the better the heat resistance of the glass cloth.

[Whitening distance]
The laminate was cut into a size of 7 cm x 4 cm, and two slits each having a length of 2 cm were made vertically and horizontally using a diamond cutter to prepare test pieces. The test pieces were prepared in accordance with the method described in JP 2020-158364 A.

The resulting test pieces were immersed in a 1 mol/L NaOH aqueous solution and heated at 60°C for 30 hours. A whitening distance test was then conducted using a digital microscope (Keyence Corporation) at 100x magnification to measure the whitening distance due to peeling between the resin and glass interface in the warp and weft directions. In the whitening distance test, the whitening distance was measured at 24 points in each of the warp and weft directions, and the average value was calculated. The whitening distance for each level was evaluated as a relative value, with the value for Comparative Example 1 set at 1.0. Reducing the whitening distance indicates improved insulation reliability in printed wiring boards. The results are shown in the table below.

The manufacturing conditions and evaluation results for the Examples and Comparative Examples are shown in the table below. Using the glass cloth of the Examples, prepregs, printed wiring boards (resin substrates), integrated circuits, and electronic devices could be manufactured using standard methods.

The examples provided glass cloth that can achieve excellent dielectric properties and excellent insulation reliability, and can also further improve the properties of resin substrates produced using the glass cloth (for example, by reducing the whitening distance of the resin substrate). On the other hand, none of the comparative examples were able to reduce the whitening distance of the resulting resin substrate, and comparative example 2 in particular was unable to achieve excellent solder heat resistance.

The present invention can be used in fields such as glass cloth, printed wiring boards (especially printed wiring boards for high-speed communication), etc.

P: White spot

Claims (20)

A glass cloth made by weaving glass yarn,
the glass cloth is surface-treated with a surface treatment agent,
The following formula A is calculated from the total carbon amount of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula A=peak height derived from carbonyl groups/total carbon content of the glass cloth is 10 or more ,
The surface treatment agent is represented by the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
A glass cloth containing a silane coupling agent represented by the formula : A glass cloth made by weaving glass yarn,
The glass cloth is surface-treated with a surface treatment agent,
The following formula B is calculated from the ignition loss value of the glass cloth and the peak height derived from the carbonyl group measured by Fourier transform infrared spectroscopy:
Formula B=peak height derived from carbonyl groups/ignition loss value of glass cloth is 11 or more ,
The surface treatment agent is represented by the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
A glass cloth containing a silane coupling agent represented by the formula : 3. The glass cloth according to claim 1, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % calculated as silicon dioxide (SiO ₂ ). The glass cloth according to claim 1 or 2, having a dielectric loss tangent at 10 GHz of 0.002 or less. The glass cloth according to claim 1 or 2, wherein the bulk dielectric loss tangent of the glass constituting the glass yarns is 0.002 or less at 10 GHz. The glass cloth according to claim 1 or 2, wherein the surface treatment agent includes a silane coupling agent. The glass cloth according to claim 1 or 2, wherein the unsaturated carbon-carbon double bond is a bond derived from at least one of an acryloyl group and a methacryloyl group. The glass cloth according to claim 1 or 2, wherein the ignition loss value of the glass cloth is in the range of 0.01 to 0.5% by mass. The glass cloth according to claim 1 or 2, wherein the average degree of opening calculated from the yarn width of each of the warp and weft yarns of the glass cloth is greater than 40%. The glass cloth according to claim 1 or 2, wherein the total carbon content of the glass cloth is in the range of 0.01 to 0.8 mass%. A prepreg containing the glass cloth according to claim 1 or 2 and a matrix resin. A printed wiring board comprising the prepreg of claim 11. An integrated circuit comprising the printed wiring board of claim 12. An electronic device comprising the printed wiring board according to claim 12. A method for manufacturing a glass cloth by weaving glass yarns,
a surface treatment step of treating the glass fiber with a surface treatment liquid containing a surface treatment agent having a molecular weight of 200 or more;
The surface treatment step includes:
a step of adding a solvent to the surface treatment agent to prepare the surface treatment liquid;
controlling the temperature of the surface treatment solution;
controlling the pH of the surface treatment solution; and filtering the surface treatment solution;
and
The surface treatment step includes:
The method includes a step of surface-treating the deoiled glass fiber with a surface treatment agent,
The surface treatment agent has the following formula (1):
X _3-n SiY _n ...(1)
(In the formula, each X is independent and may contain a different organic functional group, and is composed of a functional group having a total of two or more carbonyl groups and two or more unsaturated carbon-carbon double bonds in X; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
A method for producing glass cloth, comprising the silane coupling agent represented by the formula: The surface treatment step includes:
controlling the temperature and pH of the surface treatment solution;
The method for producing glass cloth according to claim 15, further comprising the step of filtering the surface treatment liquid. The method for manufacturing glass cloth according to claim 15 or 16, further comprising a step of opening the glass yarns after the surface treatment step. The method for producing a glass cloth according to claim 15 or 16, further comprising the step of inspecting the frequency of occurrence of white spots in the glass cloth.
The frequency of occurrence of the white spots is evaluated by irradiating a glass cloth of A4 size (210 mm x 297 mm) or larger with a halogen lamp.
In the case of observing a sheet-like glass cloth, a halogen lamp was placed directly above the glass cloth, and the number of white spots was calculated by the following formula while changing the direction of observation of the glass cloth:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{area of glass cloth (m ² )}
The frequency of occurrence of the white spots is calculated according to the following formula.
In the case of observing a glass cloth roll, a tension of 100 N/1300 mm is applied to the glass cloth on a roll-to-roll inspection table, and the number of white spots occurring on the glass cloth is counted over a length of 2000 m while irradiating the glass cloth with a halogen lamp. Then, the inspection area and the number of white spots found in the inspection are calculated using the following formula:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{width of glass cloth (m)×inspected length of glass cloth (m)}
The frequency of occurrence of the white spots is calculated according to the following formula.
However, the white spot is counted as a defect in which a white outline is observed when irradiated with UV light , and the area enclosed by the outline (the area including the outline) is 0.8 ^cm2 or more. The method for producing glass cloth according to claim 15 or 16, further comprising a step of measuring the peak height derived from carbonyl groups in the glass cloth using Fourier transform infrared spectroscopy. A test method for glass cloth made by weaving glass yarn,
the glass cloth is surface-treated with a surface treatment agent,
The test method comprises:
The test method includes a step of inspecting the frequency of occurrence of white spots on the glass cloth.
The frequency of occurrence of the white spots is evaluated by irradiating a glass cloth of A4 size (210 mm x 297 mm) or larger with a halogen lamp.
In the case of observing a sheet-like glass cloth, a halogen lamp was placed directly above the glass cloth, and the number of white spots was calculated by the following formula while changing the direction of observation of the glass cloth:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{area of glass cloth (m ² )}
The frequency of occurrence of the white spots is calculated according to the following formula.
In the case of observing a glass cloth roll, a tension of 100 N/1300 mm is applied to the glass cloth on a roll-to-roll inspection table, and the number of white spots occurring on the glass cloth is counted over a length of 2000 m while irradiating the glass cloth with a halogen lamp. Then, the inspection area and the number of white spots found in the inspection are calculated using the following formula:
Frequency of occurrence of white spots (number/m ² )=number of white spots/{width of glass cloth (m)×inspected length of glass cloth (m)}
The frequency of occurrence of the white spots is calculated according to the following formula.
However, the white spot is counted as a defect in which a white outline is observed when irradiated with UV light , and the area enclosed by the outline (the area including the outline) is 0.8 ^cm2 or more.