JP7795015B2 - Glass cloth, prepreg, printed wiring board, and surface treatment liquid - Google Patents

Description

This disclosure relates to glass cloth, prepregs, printed wiring boards, surface treatment solutions, 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, the insulating materials used in printed wiring boards for high-speed communications are becoming significantly lower in dielectric constant and dielectric dissipation factor to reduce transmission loss, and higher levels of insulation reliability 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 whose ends are modified 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. Patent Documents 1 and 2 aim to obtain a laminate with a low dielectric constant and low dielectric dissipation factor using glass cloth with a low dielectric constant and low dielectric dissipation factor.

Patent Documents 3 and 4 describe a method for reducing the dielectric loss tangent of glass cloth by heating the silica glass cloth at high temperatures to reduce the amount of silanol groups on the glass surface. Patent Document 5 describes a method for reducing the silanol groups present on the glass cloth surface through surface treatment, thereby reducing the dielectric loss tangent of the glass cloth. Patent Document 6 describes a method for packaging quartz glass cloth to prevent the dielectric loss tangent of the quartz glass cloth from increasing over time.

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. 2020-194888 Patent No. 7375902

One of the objects of the present disclosure is to provide a glass cloth that has excellent dielectric properties and can suppress an increase in dielectric loss tangent over time. Another object is to provide a method for producing the glass cloth and a surface treatment liquid for use with the glass cloth. Finally, another object of the present disclosure is to provide prepregs, printed wiring boards, and the like that use the glass cloth.

Examples of embodiments of the present invention are listed in the following items [1] to [38].
[1]
A glass cloth configured with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns,
The glass cloth has a surface treatment agent on its surface,
The surface treatment agent is represented by the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The glass cloth contains a silane coupling agent having a molecular structure in which a value determined by the following formula is 15.0 or less.
[2]
2. The glass cloth according to item ¹ , wherein the number of white spots is 10 or less 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 mass % in terms of silicon dioxide (SiO ₂ ).
[4]
The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
4. The glass cloth according to any one of items 1 to 3, comprising a silane coupling agent represented by the formula:
[5]
Item 5. The glass cloth according to item 4, wherein X in the general formula (1) contains at least one group selected from the group consisting of an epoxy group, an amino group, an aromatic vinyl group, an acryloyl group, and a methacryloyl group.
[6]
Item 6. The glass cloth according to any one of items 1 to 5, wherein the dielectric loss tangent of the glass cloth at 10 GHz is 0.002 or less.
[7]
7. The glass cloth according to any one of items 1 to 6, wherein the ignition loss value is in the range of 0.01 to 0.3% by mass.
[8]
8. The glass cloth according to any one of items 1 to 7, wherein the value determined by the above formula (A) is 14.4 or less.
[9]
9. The glass cloth according to any one of items 1 to 8, wherein the value determined by the above formula (A) is 13.8 or less.
[10]
10. The glass cloth according to any one of items 1 to 9, wherein the value determined by the above formula (A) is 13.5 or less.
[11]
11. The glass cloth according to any one of items 1 to 10, wherein the number of white spots is 4 or less per ^square meter.
[12]
Item 12. The glass cloth according to any one of items 1 to 11, wherein the number of white spots is 2 or less ^per square meter.
[13]
Item 13. The glass cloth according to any one of items 1 to 12, wherein the number of white spots is 0.1 or less per square ^meter .
[14]
Item 14. The glass cloth according to any one of items 1 to 13, wherein the number of white spots is 0.05 or less per square ^meter .
[15]
Item 15. The glass cloth according to any one of items 1 to 14, wherein the molecular weight of the silane coupling agent is in the range of 250 to 1000.
[16]
Item 16. The glass cloth according to any one of items 1 to 15, wherein the molecular weight of the silane coupling agent is in the range of 300 to 750.
[17]
Item 17. The glass cloth according to any one of items 1 to 16, wherein the molecular weight of the silane coupling agent is in the range of 350 to 700.
[18]
Item 18. The glass cloth according to any one of items 1 to 17, which is for a printed wiring board.
[19]
Item 19. A prepreg comprising the glass cloth according to any one of items 1 to 18, a matrix resin, and an inorganic filler.
[20]
20. A printed wiring board comprising the prepreg according to item 19.
[21]
21. An integrated circuit comprising the printed wiring board according to item 20.
[22]
21. An electronic device comprising the printed wiring board according to item 20.
[23]
A method for producing glass cloth, the method comprising:
a step of weaving glass yarns containing a plurality of glass filaments as warp yarns and weft yarns to obtain a glass cloth;
The method includes a step of degreasing the glass cloth and then surface-treating the glass cloth with a surface treatment liquid containing a surface treatment agent,
The surface treatment agent has the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The present invention relates to a method for producing glass cloth, the method comprising: providing a silane coupling agent having a molecular structure in which a value determined by the above formula (1) is 15.0 or less.
[24]
The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
Item 24. The method for producing glass cloth according to Item 23, comprising:
[25]
Item 25. The method for producing glass cloth according to Item 23 or 24, wherein the surface treatment liquid is prepared by adding an acidic aqueous solution to a hydrolysis solution of the silane coupling agent.
[26]
The surface treatment step includes:
controlling the temperature and pH of the surface treatment solution;
and filtering the surface treatment liquid.
[27]
Item 27. The method for producing a glass cloth according to any one of Items 23 to 26, further comprising a step of subjecting the glass cloth to an opening treatment after the surface treatment step.
[28]
28. The method for producing a glass cloth according to any one of items 23 to 27, further comprising inspecting for white spots after the surface treatment step.
[29]
A surface treatment liquid containing a surface treatment agent containing a silane coupling agent,
The silane coupling agent is represented by the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The surface treatment solution has a molecular structure in which the value determined by the following formula is 15.0 or less.
[30]
the surface treatment liquid contains a silane coupling agent in an amount of 0.20 to 1.2 mass % based on the total mass of the surface treatment liquid;
the pH of the surface treatment solution is in the range of 2.5 to 5.5;
Item 30. The surface treatment liquid according to item 29, wherein the surface treatment liquid contains a surfactant in a range of 0.5 to 5.0 mass% based on the total mass of the silane coupling agent.
[31]
The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
Item 31. The surface treatment solution according to Item 29 or 30, comprising:
[32]
32. The surface treatment solution according to any one of items 29 to 31, wherein the value obtained by the above formula (A) is 14.4 or less.
[33]
33. The surface treatment solution according to any one of items 29 to 32, wherein the value obtained by the above formula (A) is 13.8 or less.
[34]
34. The surface treatment solution according to any one of items 29 to 33, wherein the value obtained by the above formula (A) is 13.5 or less.
[35]
35. The surface treatment solution according to any one of items 29 to 34, wherein the pH of the surface treatment solution is in the range of 3.0 to 5.0.
[36]
36. The surface treatment solution according to any one of items 29 to 35, wherein the pH of the surface treatment solution is in the range of 3.0 to 4.0.
[37]
37. The surface treatment liquid according to any one of items 29 to 36, wherein the surface treatment liquid contains a surfactant in a range of 1.0 to 4.5 mass% based on the total mass of the silane coupling agent.
[38]
38. The surface treatment liquid according to any one of items 29 to 37, wherein the surface treatment liquid contains a surfactant in a range of 1.5 to 4.0 mass% based on the total mass of the silane coupling agent.

The present disclosure provides a glass cloth that has excellent dielectric properties and can suppress an increase in dielectric loss tangent over time. It also provides a method for manufacturing the glass cloth and a surface treatment solution for use with the glass cloth. The present disclosure also provides prepregs, printed wiring boards, and the like that use the glass cloth.

FIG. 1 is a diagram for explaining a white spot.

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

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 "step" includes not only independent steps but also steps that cannot be clearly distinguished from other steps, as long as the function of the step is achieved. In the drawings, the scale, shape, and length may be exaggerated for clarity.

Glass cloth
The glass cloth of the present disclosure is a glass cloth woven from glass yarns, for example, a glass cloth configured with glass yarns containing a plurality of glass filaments as warp and weft yarns. The surface of the glass cloth has a surface treatment agent, and the silane coupling agent contained in the surface treatment agent has a molecular structure such that the value calculated by the following formula (A) is 15.0 or less:
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)

According to the present disclosure, it is possible to provide a glass cloth that has excellent dielectric properties and can suppress an increase in the dielectric loss tangent over time. The glass cloth of the present disclosure is suitable as a constituent material for producing prepregs, printed wiring boards, integrated circuits, electronic devices, and the like. Preferably, the dielectric loss tangent of the glass cloth can be further reduced compared to the conventional techniques described in Patent Documents 1 to 6. Furthermore, it is also preferable that the increase in the dielectric loss tangent of the glass cloth over time can be suppressed without using the method of packaging the quartz glass cloth in a predetermined manner, as described in Patent Document 6.

After extensive research, the present inventors focused on glass cloth that has been surface-treated after being heated and deoiled at high temperatures. The present inventors discovered for the first time that glass cloth that has been surface-treated with a silane coupling agent having a molecular structure in which the value calculated from the above formula (A) is 15.0 or less after being heated and deoiled at high temperatures has a low dielectric tangent, and that it is possible to suppress the increase in the dielectric tangent of the glass cloth over time. While not limited by theory, the reason for this is thought to be that the silane coupling agent coats the glass fiber surface, making it less likely to adsorb moisture present in the storage environment. Therefore, for example, it is possible to suppress the increase in the dielectric tangent of the glass cloth over time, even without special packaging. The technical significance of each parameter will be discussed later.

Silane coupling agents are generally applied to glass cloth as a mixture with a solvent, and in this case, it is preferable to use water as the solvent from the perspective of reducing the environmental impact. However, it has been found that silane coupling agents whose value calculated from formula (A) is 15.0 or less are highly hydrophobic and have extremely poor dispersibility and/or compatibility in water, making them prone to the formation of "white spots" caused by the surface treatment agent on the glass cloth surface. Since white spots can impair the adhesion at the interface between the glass cloth and the resin, it is preferable to provide glass cloth that suppresses white spots while also having a dielectric loss tangent that is lower than that of bulk glass.

According to a preferred aspect of the present disclosure, even surface treatment agents that have poor dispersibility and/or compatibility in water, i.e., highly hydrophobic surface treatment agents (e.g., highly hydrophobic silane coupling agents), can be stably dispersed in water to suppress white spots. In this case, it becomes easier to provide glass cloth with an even lower dielectric tangent, and it also becomes easier to further suppress the increase in the dielectric tangent of the glass cloth over time without the need for special packaging. It also becomes easier to provide glass cloth that can be used to provide resin substrates with excellent solder heat resistance.

[Dielectric loss tangent]
(Dielectric loss tangent of glass cloth)
The glass cloth of the present disclosure preferably has a dielectric loss tangent of 0.0020 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 of glass cloth)
The dielectric loss tangent at 10 GHz of the glass cloth of the present disclosure is measured by a method using a split cylinder resonator (a method using a resonance method), specifically, the method described in the Examples. This method allows for simpler and more accurate measurement than conventional measurement 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 evaluating low-loss materials. Known methods for evaluating dielectric properties other than the resonance method 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 cumbersome operation. Furthermore, the reflection transmission method has the disadvantage that, when evaluating low-loss materials, the port matching characteristics are strongly affected, making it difficult to accurately evaluate the dielectric loss tangent of the measurement sample. Based on the above, the dielectric loss tangent of glass cloth can be easily and accurately measured by a method using a resonance method, specifically, the method 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 to 50 and Df = 1.0 × 10 ^-6 to 1.0 × 10 ^-1 , respectively, more preferably Dk = 1.5 to 10 and Df = 1.0 × 10 ^-5 to 5.0 × 10 ^-1 , and even more preferably Dk = 2.0 to 5 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 bands, particularly those 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 the present disclosure, 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 even easier to achieve excellent dielectric properties.

[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 μm to 9.0 μm, more preferably 2.5 μm to 7.5 μm, even more preferably 3.5 μm to 7.0 μm, still more preferably 3.5 μm to 6.0 μm, and particularly preferably 3.5 μm 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 45 to 90 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 made of a glass raw material called E-glass (alkali-free glass). On the other hand, for the glass cloth of the present disclosure, 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 mass %, or 99.0 to 100 mass %, more preferably 99.5 to 100 mass %, and even more preferably 99.9 to 100 mass %. The SiO ₂ content of the glass yarns constituting the glass cloth is particularly preferably more than 99.9 mass %. When the Si content is 95.0 mass % or more, it is easy to ensure the dielectric properties of the glass cloth and the dimensional stability of the laminate.

[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]
The glass cloth has a surface treatment agent on its surface. The surface treatment is carried out, for example, by a method using a surface treatment liquid containing the surface treatment agent. Details will be described later.

It has traditionally been recognized that using common surface treatment agents (e.g., common silane coupling agents) increases the dielectric tangent of the glass cloth and that the dielectric tangent of the glass cloth increases over time. As a result of research into this issue, the present inventors have discovered that treating the glass surface with a highly hydrophobic surface treatment agent (e.g., a highly hydrophobic silane coupling agent) can reduce the increase in the dielectric tangent of the glass cloth due to the surface treatment, and also makes it difficult for moisture present in the storage environment to be adsorbed onto the glass surface. As a result, it is easier to suppress the increase in the dielectric tangent of the glass cloth over time, even without special moisture-proof packaging.

In this disclosure, a "strongly hydrophobic surface treatment agent (strongly hydrophobic silane coupling agent)" refers to an agent in which, when an aqueous solution prepared by mixing a 0.3% by mass aqueous solution of acetic acid with a surface treatment agent (silane coupling agent) at a concentration of 0.8% by mass is stirred at room temperature of 25°C for 3 hours, the surface treatment agent (silane coupling agent) is not uniformly dispersed as an emulsion in the aqueous solution or is not dissolved. A state in which the surface treatment agent (silane coupling agent) is not uniformly dispersed as an emulsion or is not dissolved means, for example, a state in which the surface treatment agent (silane coupling agent) is separated in the aqueous solution as oil droplets and an oil film.

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

The glass cloth according to the present disclosure is surface-treated with a silane coupling agent whose value calculated by the following formula (A) is 15.0 or less: 1.10 x MaxEStateIndex + 14.6 x MaxPartialCharge - 0.0917 x SPS + 2.47 x HallKierAlpha... (A)

MaxEStateIndex, MaxPartialCharge, SPS, and HallKierAlpha contained in formula (A) can be calculated using the method described in the Examples. Specifically, they can be calculated using open source software called "RDKit."

The MaxEStateIndex used in formula (A) is a value that indicates the electronic properties of an atom, calculated based on the atomic charge, bond order, etc. It is generally believed that the higher the MaxEStateIndex value of an atom, the greater the molecular polarity and hydrogen bonding ability. Furthermore, MaxPartialCharge represents the molecular partial charge; the larger the value, the greater the intramolecular dipole moment, making it more likely to polarize. To achieve excellent dielectric properties and to suppress the increase in the dielectric loss tangent over time, lower values of MaxEStateIndex and MaxPartialCharge are preferred. This is because the more strongly polarized a glass cloth coated with a silane coupling agent is, the more it adsorbs moisture from the air, making it more difficult to suppress the increase in the dielectric loss tangent of the glass cloth over time without special packaging.

The SPS used in formula (A) is an empirical scoring system for expressing the spatial complexity of a compound in a uniform manner on a highly granular scale for ranking and comparing molecules, with higher values indicating less steric hindrance. Hall-Kier Alpha is a topological index that represents the steric hindrance of a molecule, with higher values indicating greater steric hindrance. These results suggest that the more sterically hindrance a silane coupling agent used to treat the glass cloth surface, the more likely it is to adsorb moisture from the air. This is because the more sterically hindrance a silane coupling agent is used, the more difficult it is to uniformly chemically modify the glass surface, making the silane coupling agent layer more sparse. This makes it more susceptible to adsorption of moisture from the air, and the dielectric loss tangent of the glass cloth is more likely to increase over time.

From the viewpoint of easily achieving excellent dielectric properties and suppressing the increase in dielectric loss tangent over time, the value calculated from formula (A) is preferably 14.9 or less, more preferably 14.8 or less, even more preferably 14.7 or less, even more preferably 14.6 or less, and particularly preferably 14.4 or less, 14.2 or less, 14.0 or less, or 13.8 or less. The lower limit of the value calculated from formula (A) is not particularly limited, but may be greater than 0, 1 or more, 5 or more, or 10 or more.

The surface treatment agent is, for example, a compound represented by the following formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
When the surface treatment agent contains the silane coupling agent, it becomes easier to suppress an increase in the dielectric loss tangent of the glass cloth over time.

From the viewpoint of easily improving adhesion to resins, X in formula (1) is preferably an organic functional group having at least one group selected from the group consisting of an epoxy group, an amino group, an aromatic vinyl group, an acryloyl group, and a methacryloyl group. Furthermore, the organic functional groups are preferably each independently at least one selected from the group consisting of an aromatic group, an aliphatic group that may be saturated or unsaturated, may be linear or branched, may or may not have a cyclic structure, and may or may not have a heteroatom, and combinations thereof. The total number of carbon atoms in X may preferably be 3 to 20, 5 to 18, 6 to 16, or 7 to 14.

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 3,6-diethenyl-1-(trimethoxysilyl)naphthalene represented by the following formula:
[4-[2-(trimethoxysilyl)ethyl]phenyl]methyl 2-propenoate represented by the following formula:
4-(trimethoxysilyl)phenyl 2-propenoate represented by the following formula:
N-ethenyl-N-(2-oxiranylmethoxy)-3-(trimethoxysilyl)-1-propanamine represented by the following formula:
1-ethenyl-4-[3-(trimethoxysilyl)propoxy]benzene represented by the following formula:
4-[2-(trimethoxysilyl)ethyl]benzenamine represented by the following formula:
[bicyclo[2.2.1]hept-5-en-2-yl]triethoxysilane represented by the following formula:
4-[[4-[3-(trimethoxysilyl)propoxy]phenyl]sulfonyl]phenyl 2-methyl-2-propenoate, represented by the following formula:
6-[[[3-(trimethoxysilyl)propyl]amino]carbonyl]-2-naphthalenyl 2-methyl-2-propenoate, represented by the following formula:
2-Propenoic acid, 2-methyl-,2-[(trimethoxysilyl)methyl]-1,3-propanediyl ester represented by the following formula:
Diethoxy(methyl)[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane represented by the following formula:
Ethoxy(dimethyl)[3-(oxiran-2-ylmethoxy)propyl]silane represented by the following formula:
[2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyl](trimethoxy)silane represented by the following formula:
N-2-propen-1-yl-N-[3-(trimethoxysilyl)propyl]-2-oxiranemethanamine represented by the following formula:
N1-ethenyl-N1-(phenylmethyl)-N2-[3-(trimethoxysilyl)propyl]-1,2-ethanediamine represented by the following formula:
1-[trans-4-[4-(3-methylbutyl)phenyl]cyclohexyl]-2-(trimethoxysilyl)ethyl 2-methyl-2-propenoate, represented by the following formula:
etc.

The silane coupling agents that can be used can be adjusted appropriately depending on factors such as the matrix resin used in the resin substrate. Of course, a silane coupling agent for which the value calculated from formula (A) above is 15.0 or less may be used in combination with a silane coupling agent other than a silane coupling agent for which the value calculated from formula (A) above is 15.0 or less. On the other hand, it is preferable to use two or more silane coupling agents with different molecular weights that have a value calculated from formula (A) above of 15.0 or less. Using two or more silane coupling agents with different molecular weights tends to increase the density of the treatment agent on the glass surface, which tends to further improve reactivity with the matrix resin.

(Molecular weight of silane coupling agent)
The molecular weight of the surface treatment agent, for example, the molecular weight of the silane coupling agent, is preferably 250 to 1000, more preferably 270 to 800, even more preferably 300 to 750, and particularly preferably 350 to 700. When two or more surface treatment agents (e.g., silane coupling agents) are used, it is preferable that the weighted average value of the molecular weights, weighted by 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 surface treatment agents used are within the above range. For example, when the surface treatment agent is prepared so that silane coupling agents with molecular weights of 300 and 500 are present at 0.5% by mass and 1.0% by mass, respectively, the weighted average value can be calculated as follows:
Weighted average value = 300 x 0.5 ÷ (0.5 + 1.0) + 500 x 1.0 ÷ (0.5 + 1.0)
=433

[Average opening degree of glass cloth]
The average openness of the glass cloth is preferably 35% or more or greater than 36%, more preferably greater than 38%, and even more preferably greater than 40%, 45%, 50%, 52%, or 55%, with greater than 57% being particularly preferred. When the average openness of the glass cloth is 35% or more, it is easy to prevent air bubbles called voids from remaining in the glass yarn bundle when a resin substrate is produced, which makes it less likely to adversely affect solder heat resistance and insulation reliability. Note that the silane coupling agent represented by the above formula (1) tends to have relatively strong intermolecular forces, so that the impregnation of the matrix resin in the glass cloth is more likely to be inferior to silane coupling agents other than those represented by the above formula (1). Therefore, for glass cloth surface-treated with the silane coupling agent represented by the above formula (1), it is preferable that the average openness be 35% or more or greater than 36%, in order to fully obtain the effect of improving its insulation reliability. The upper limit of the average openness is 85%. If an average degree of opening is to be increased to 85% or more, it is necessary to subject the glass cloth to a strong opening treatment, which is likely to cause a deterioration in the fluff quality of the glass cloth.

[Ignition loss value of glass cloth]
From the viewpoint of easily reducing the dielectric loss tangent of the glass cloth, the ignition loss value of the glass cloth is preferably 0.01 to 0.3 mass% or 0.02 to 0.27 mass%, more preferably 0.03 to 0.24 mass%, even more preferably 0.03 to 0.20 mass%, and particularly preferably 0.03 to 0.17 mass%. When the ignition loss value is 0.01 mass% or more, adhesion between the resin and the glass cloth in the resulting prepreg is easily ensured. In this case, heat resistance and insulation reliability are easily ensured when a printed wiring board is produced. When the ignition loss value of the glass cloth is 0.3 mass% or less, it is easy to avoid a situation in which a surface treatment agent (or its residue) that is physically adhered to the glass cloth surface without forming a chemical bond with the glass cloth, a surface treatment agent (or its residue) that cannot be removed from the glass cloth surface by water washing, and/or modified products thereof are present in large amounts on the glass cloth surface. In this case, it is easy to achieve a low dielectric loss tangent of the glass cloth.

[White spots on glass cloth]
White spots may be observed on the surface of surface-treated glass cloth. These white spots tend to repel the matrix resin used in producing the prepreg, which may result in poor appearance of the resulting prepreg. The cause of these white spots has not been known until now.

In this regard, the present inventors have clarified that one of the above white spots is an aggregate or a modified product thereof of a highly hydrophobic surface treatment agent (e.g., a highly hydrophobic silane coupling agent). In particular, the present inventors have clarified that a silane coupling agent having a value of 15.0 or less obtained from the above formula (A) is relatively 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 on the glass cloth after surface treatment tends to increase (e.g., more than 10.0 spots/ ^m2 ).

As described below, suitable methods for suppressing white spots include preparing the surface treatment solution using a specific 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.

The frequency of white spots in the glass cloth is preferably 10.0 spots/ ^m2 or less, more preferably 7.0 spots/ ^m2 or less, even more preferably 4.0 spots/ ^m2 or less, still 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.

<Glass cloth manufacturing method>
The present disclosure also provides a manufacturing method for manufacturing the glass cloth of the present disclosure. The manufacturing method of the present disclosure includes a weaving step of weaving glass yarns containing a plurality of glass filaments as warp and weft yarns to obtain a glass cloth, and a surface treatment step of deoiling the glass yarns and then surface-treating the glass yarns with a surface treatment solution containing a surface treatment agent. The surface treatment agent is the surface treatment agent of the present disclosure. It is preferable that the dielectric loss tangent at 10 GHz of the glass cloth after the surface treatment is lower than the dielectric loss tangent at 10 GHz of the glass cloth before the surface treatment.

wherein the surface treatment step may optionally further include one or more of 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).

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, but the thermal deoiling process should be performed before the surface treatment process. When 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 process, by heating the glass yarn, it is possible to reduce, and preferably remove, the fiber sizing agent (sizing agent), its residue, and modified products thereof, which are optionally attached to the glass yarn. By performing the thermal deoiling process, it is possible to form a surface treatment layer on the surface of the glass yarn (glass filament) after reducing organic substances that may increase the dielectric tangent, making it easy to produce glass cloth with excellent dielectric properties. As a means for thermal deoiling, known means (heating means, heating medium, heating mechanism, heating device, heating component, etc.) can be used.

One known example of a thermal deoiling process is a method in which the glass cloth is heated to a temperature of 600 to 1600°C.

In the heat treatment process, glass cloth greige fabric, whose glass yarns have a softening point of 900°C or higher, is heated in the temperature range of 600 to 1600°C, which makes it easy to minimize damage to the glass cloth and reduce the dielectric loss tangent of the glass cloth. From the perspective of suppressing the increase in the dielectric loss tangent of the glass cloth over time, it is preferable to sufficiently dehydrate and condense the silanol groups present on the glass surface to an extent that does not adversely affect the subsequent surface treatment process. Reducing the number of silanol groups on the glass surface to a certain amount or less makes it possible to suppress the adsorption of moisture from the air, which results in excellent dielectric properties and makes it easy to suppress the increase in the dielectric loss tangent over time.

From the viewpoint of achieving excellent dielectric properties and suppressing the increase in dielectric loss tangent over time, 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 makes it easy to effectively remove sizing agents and other substances adhering to the glass cloth green fabric, making it easy to produce glass cloth with excellent dielectric properties. A thermal deoiling temperature of 1600°C or lower makes it easy to suppress devitrification of the glass, and as a result, makes it easy to prevent a decrease in the strength of the glass cloth.

The heating time is preferably 1 hour or less or 30 minutes or less, more preferably 15 minutes or less, and even more preferably 5 minutes or less. Heating the glass cloth at a high temperature for a sufficient time tends to induce a dehydration condensation reaction of the silanol groups on the glass surface. From the perspective of effectively removing sizing agents, etc., the heating time may be, for example, 1 second or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more.

When thermal deoiling of glass cloth is performed 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 heated while passing through a heating furnace 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 washing water with a low metal ion content, such as reverse osmosis (RO) water or ion-exchanged water, is even more preferable.

When the sodium ions adhering to the glass cloth exceed a predetermined amount, thermal deoiling of the glass cloth at 700°C or higher may result in a decrease in the tensile strength of the glass cloth due to devitrification of the quartz glass. In order to prevent this, washing the glass cloth with water containing 20 ppm or less sodium ions before thermal deoiling can easily reduce the amount of sodium ions on the glass surface. In this case, devitrification of the quartz glass can be easily prevented even when thermal deoiling is performed at 700°C or higher. Maintaining the strength of the glass cloth after thermal deoiling helps prevent wrinkles and/or scratches on the glass cloth during the surface treatment process.

To obtain excellent dielectric properties and effectively suppress the increase in dielectric tangent over time, the sodium ion content of the water used for washing may be 18 ppm or less, 15 ppm or less, 12 ppm or less, 10 ppm or less, or 7 ppm or less. A sodium ion content of 0 ppm is preferred, but it may exceed 0.

The means for cleaning glass cloth to a sodium ion content of 20 ppm or less may be any known cleaning method, as long as it is capable of removing sodium ions from the glass surface. Possible methods include ultrasonic methods (e.g., methods using an ultrasonic vibrator), spraying (e.g., spraying using a high-pressure spray), and water vapor spraying. From the perspective of inexpensive processing, a preferred method involves immersing the glass cloth in a water tank containing cleaning water (water with a sodium ion content of 20 ppm or less), removing excess cleaning water with a squeeze roller or the like, and then drying the glass cloth. In this case, the immersion time may be, for example, 2 seconds or more, 5 seconds or more, 10 seconds or more, 15 seconds or more, or 120 seconds or less, 90 seconds or less, 60 seconds or less, or 45 seconds or less.

Water with a sodium ion content of 20 ppm or less can be produced by any known production method. Examples include filtration using an RO membrane and deionization using an ion exchange resin. "Water with a sodium ion content of 20 ppm or less" may contain other liquid components (liquids other than water, etc.) as long as the effects of the present invention are not impaired.

From the viewpoint of facilitating the dehydration condensation reaction of the silanol groups on the glass surface, it is preferable to make the surrounding environment as moisture-free as possible during the period from thermal deoiling to lowering the temperature of the glass cloth surface to 100°C or less, that is, to reduce the surrounding moisture during thermal deoiling. Examples of methods for reducing the surrounding moisture during thermal deoiling include:
A method of introducing dry air into a heating furnace, a method of creating a vacuum inside the furnace, a method of introducing an inert gas such as nitrogen into the furnace,
When the thermal deoiling treatment is carried out while the glass cloth is being conveyed, it is preferable to introduce an inert gas such as nitrogen into the furnace.

[Surface treatment process]
In this process, the glass fiber is surface-treated using a surface treatment solution containing a predetermined surface treatment agent, particularly a predetermined silane coupling agent (in one embodiment, a silane coupling agent advantageous in terms of reducing the dielectric tangent of the glass cloth). The silane coupling agent used in the method of the present disclosure is more hydrophobic than general silane coupling agents. As described above, the present inventors have discovered that when the solvent in the surface treatment solution contains water, aggregates of the surface treatment agent tend to occur more easily, 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.

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.

(Surface treatment liquid)
The surface treatment solution of the present disclosure is a surface treatment solution containing a surface treatment agent, and can be used for surface treatment of glass cloth. The surface treatment agent has a molecular structure in which the value calculated from the following formula (A) is 15.0 or less.
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)

The surface treatment agent contained in the surface treatment liquid preferably contains a silane coupling agent represented by the above formula (1). In the surface treatment process, the glass yarn is preferably treated using a surface treatment liquid containing a surface treatment agent with a molecular weight of 200 or more. Other details about the surface treatment agent are as explained above in the "Glass Cloth" section.

The present inventors have found that in a given surface treatment solution, it is possible to suppress white spots on glass cloth by, for example, one or more of the following methods (A) to (C):
(A) preparing a surface treatment liquid by adding an acidic aqueous solution to a hydrolyzed solution of a surface treatment agent;
(B) controlling the temperature and/or pH of the surface treatment solution, and/or (C) filtering the surface treatment solution.

(A) Preparation of Surface Treatment Solution Because typical silane coupling agents have excellent compatibility with and dispersibility in water, they are prepared by gradually adding a hydrolysis solution of the silane coupling agent (also referred to as a "pre-solution" in this disclosure) to weakly acidic water with a pH of approximately 3 to 5 while stirring. On the other hand, in the method disclosed herein, it is preferable to prepare the surface treatment solution by adding an acidic aqueous solution to the silane coupling agent. More preferably, a pre-solution containing the surface treatment agent is prepared, and the acidic aqueous solution is added to the resulting pre-solution. More specifically, a hydrolysis solution of the surface treatment agent (pre-solution) can be obtained by adding a surfactant and a small amount of solvent (e.g., a 60% aqueous acetic acid solution) for hydrolyzing the silane coupling agent to a diluted solution obtained by diluting the surface treatment agent with a small amount of methanol. The solvent in the pre-solution is added to hydrolyze the alkoxide groups of the silane coupling agent, and the amount of solvent added is preferably adjusted depending on the amount of hydrolysis. The acidic aqueous solution (also referred to as "mother liquor" in the present disclosure) is then added little by little to the pre-solution while stirring, thereby enabling the surface treatment agent to be uniformly dispersed in the aqueous solution. In this case, it is easy to suppress agglomerations in the surface treatment solution. The acidic aqueous solution used as the mother liquor is preferably a weak acid aqueous solution, for example, a weak acid aqueous solution adjusted to a pH of 2.5 to 5.5, 3.0 to 5.0, 3.0 to 4.5, or 3.0 to 4.0. Examples of weak acids include carboxylic acids having the general formula RCOOH, where R is an alkyl group having 1 to 10 carbon atoms, which may be substituted or unsubstituted, linear or branched. Preferred weak acids include formic acid, acetic acid, and propionic acid.

The "small amount of solvent for hydrolyzing the silane coupling agent" may be the acidic aqueous solution used as the mother liquor. Alternatively, a solvent for hydrolyzing the silane coupling agent (e.g., a 60% aqueous acetic acid solution) may be used as the mother liquor.

(Concentration of silane coupling agent)
In the present disclosure, the concentration of the silane coupling agent in the surface treatment agent is preferably in the range of 0.20 to 1.2 mass%. It is more preferably in the range of 0.25 to 1.1 mass%, even more preferably 0.30 to 1.0 mass%, even more preferably 0.33 to 0.9 mass%, and particularly preferably 0.35 to 0.7 mass%. If the concentration of the silane coupling agent is 1.2 mass% or less, the amount of silane coupling agent attached to the glass cloth surface decreases, resulting in a lower dielectric loss tangent of the glass cloth. If the concentration of the silane coupling agent is 0.2 mass% or more, the amount of silane coupling agent attached to the glass cloth surface increases, improving adhesion to the matrix resin, thereby contributing to improved performance such as heat resistance of the laminate.

The surfactant composition and amount can be changed appropriately 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.

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, and fatty acid alkanolamides.

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-acyltaurates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fat and oil sulfate esters, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkyl phenyl ether phosphates.

Examples of cationic surfactants include monoalkylamine salts, dialkylamine salts, trialkylamine salts, alkyltrimethylammonium chloride, and alkylbenzalkonium chloride.

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

(Concentration of surfactant)
In the present disclosure, the concentration of the surfactant in the surface treatment solution is preferably in the range of 0.5 to 5.0% by mass relative to the silane coupling agent. It is more preferably 1.0 to 4.5% by mass, even more preferably 1.5 to 4.0% by mass, even more preferably 1.8 to 3.7% by mass, and particularly preferably 2.0 to 3.5% by mass. When the surfactant concentration is 5.0% by mass or less relative to the silane coupling agent, the amount of surfactant remaining on the glass cloth surface is reduced, improving the CAF resistance of the laminate. When the surfactant concentration is 0.5% by mass or more relative to the silane coupling agent, the water dispersibility of the silane coupling agent is improved, making it easier to control the frequency of white spots to 10 spots/ ^m² .

(B) Temperature control and/or pH control of the surface treatment solution From the viewpoint of suppressing aggregation in the surface treatment solution, it is preferable to have a step of controlling the temperature of the surface treatment solution during the surface treatment. The temperature range is preferably controlled to 10 to 30°C, more preferably 13 to 27°C, even more preferably 15 to 25°C, and particularly preferably 17 to 23°C.

Furthermore, during surface treatment, 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 agglomeration in the surface treatment solution, it is preferable to include a step of controlling the pH of the surface treatment solution. During surface treatment processing, the pH of the surface treatment solution is preferably controlled to 2.5 to 5.5, more preferably 2.8 to 5.2, and even more preferably 3.0 to 5.0, 3.0 to 4.5, or 3.0 to 4.0. Examples of methods for controlling the pH within a predetermined range include bubbling carbon dioxide through the surface treatment solution.

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

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

From the perspective of increasing the efficiency of collecting agglomerates, it is preferable to perform filtration in multiple stages. 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 multi-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 step may further include a step (drying step) of drying the solvent contained in the surface treatment solution after applying the surface treatment solution to the glass fiber. The drying step makes it easy to fix the surface treatment agent to the surface of the glass fiber (the surface of the glass filaments), and in particular, makes it easy to fix the surface treatment agent to the surface of each individual glass fiber (the 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 the present disclosure preferably includes a fiber-opening step after the surface treatment step. Examples of the fiber-opening method in the fiber-opening step include a method of 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 fiber-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 fiber-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.

[Cleaning process]
The 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, etc. 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 process, washing with a highly hydrophobic organic solvent is preferred 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 containing hydroxyl groups is also preferred. Examples of washing methods include known methods such as immersion and shower spraying, and washing may be performed while heating or cooling as necessary. To prevent dissolved substances from reattaching to the glass cloth, it is preferable to use a squeeze roller or the like to reduce excess solvent from the washed glass cloth before 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 cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, and ethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene; and halogen-containing solvents such as chloroform, dichloromethane, and dichloroethane.

Organic solvents that have a high affinity for 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 is more preferred, from the viewpoint of making it easier to adjust the difference between the dielectric loss tangent and bulk dielectric loss tangent of the resulting glass cloth to within a specified range.

The manufacturing method of the present disclosure preferably includes a step of drying the washed glass cloth (post-washing drying step) in order to reduce the amount of organic solvent used after washing. From the viewpoint of facilitating the reduction of the organic solvent through 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 the present disclosure may optionally include other steps in addition to the steps described above. Examples of other steps include a step of processing the glass cloth into slits (slit processing step).

(Inspection process or measurement process)
Further, as another step, a step of inspecting the glass cloth for white spots can be mentioned. By including such a step, the manufacturing method of the present disclosure can easily realize the glass cloth of the present disclosure.

Prepreg
The prepreg of the present disclosure contains a glass cloth, a matrix resin, and an inorganic filler. The glass cloth of the present disclosure can be used as the glass cloth in the prepreg of the present disclosure. This provides a prepreg with excellent properties (for example, a prepreg with few voids).

Both thermosetting and thermoplastic resins can be used as the matrix resin. Thermosetting 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, followed by curing;
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.

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 fibers, 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 the present disclosure includes a prepreg. In particular, the printed wiring board of the present disclosure can be formed by using the prepreg of the present disclosure 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 the present disclosure includes the printed wiring board of the present disclosure. Furthermore, the electronic device of the present disclosure includes the printed wiring board of the present disclosure. These provide an integrated circuit and an electronic device with various excellent characteristics. Examples of the electronic device include information terminals such as smartphones, and the integrated circuit can be used to improve the performance of the electronic device and to achieve high-speed communications, such as those typified by 5G communications.

The present disclosure will be explained below using examples and comparative examples. However, the present disclosure is not limited to the following examples. For the examples and comparative examples, various manufacturing, measurements, evaluations, etc. were performed using the following methods.

<<Measurement and Evaluation Methods>>
[Calculation of Formula A]
The formula (A) of the silane coupling agent was determined by the following procedure.
(1) The MaxEStateIndex, MaxPartialCharge, SPS, and HallKierAlpha included in formula (A) were calculated using open source software called RDKit. The version of RDKit used was 2023.09.4.
(2) In the silane coupling agent represented by the following structure, the alkoxy group or halogen group (-Y) was converted to a hydroxy group (-OH) to prepare a silanol structure, namely, a silane coupling agent X _4-n -Si(OH) _n .
Silane coupling agent: X _4-n -Si—Y _n
Each X is independently an organic functional group, n is an integer of 1 to 3, and each Y is independently an alkoxy group or a halogen group.
(3) The silane coupling agent converted into the silanol structure prepared in the operation (2) was converted into a chemical structure in SMILES notation (simplified molecular input line entry system), which is a string of alphanumeric characters and symbols in ASCII code.
(4) For the structure in SMILES notation created in operation (3), a MOL object was created by the MolFromSmiles method of the rdkit.Chem.rdmolfiles module in the RDKit.
(5) The descriptor MaxEStateIndex was calculated for the MOL object created in operation (4) by the MaxEStateIndex method of the rdkit.Chem.EState.EState module in the RDKit.
(6) The descriptor MaxPartialCharge was calculated for the MOL object created in operation (4) by the MaxPartialCharge method of the rdkit.Chem.Descriptors module in the RDKit.
(7) The descriptor SPS was calculated for the MOL object created in operation (4) using the SPS method of the rdkit.Chem.SpatialScore module in the RDKit.
(8) The descriptor HallKierAlpha was calculated for the MOL object created in operation (4) using the HallKierAlpha method of the rdkit.Chem.GraphDescriptors module in the RDKit.

(Linear sum of MaxEStateIndex, MaxPartialCharge, SPS, HallKierAlpha)
Using the values of MaxEStateIndex, MaxPartialCharge, SPS, and HallKierAlpha obtained by the above operation, the linear sum of the values of these descriptors was calculated according to the following formula.
1.10 × MaxEStateIndex + 14.6 × MaxPartialCharge − 0.0917 × SPS + 2.47 × HallKierAlpha

[Thickness]
The thickness of the glass cloth was measured using a micrometer in accordance with 7.10 of JIS R 3420. The spindle was gently rotated to lightly contact the surface parallel to the surface to be measured, and the scale was read after the ratchet made three clicks. JIS R 3420 specifies general test methods for long glass fibers and products such as glass cloth made of 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/m ² ).

[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 (EM Lab) and an impedance analyzer (Agilent Technologies). Measurements were performed five times for each sample, and the average was calculated. The dielectric loss tangent of the glass cloth was calculated using the equivalent thickness of each sample. The bulk dielectric loss tangent of the glass was determined using a split cylinder from the thickness of a glass plate with the same composition as the glass cloth. IEC 62562 specifies a method for measuring the dielectric properties of fine ceramic materials for dielectric substrates, primarily used in microwave circuits, in the microwave band.

[Increase in dielectric loss tangent over time]
The moisture present in the storage environment can increase the dielectric loss tangent of the glass cloth. Using a thermo-hygrostat, the glass cloth was stored for one week in a high-temperature, high-humidity environment (40°C, relative humidity 90%), and the increase in the dielectric loss tangent before and after storage (dielectric loss tangent after storage - dielectric loss tangent before storage) was determined.
(conditions)
Storage conditions: 40°C x 90% RH
Storage period: 1 week Dielectric loss tangent: Measurement method described above in [Dielectric loss tangent]

[Ignition loss value]
The ignition loss value of the glass cloth 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 the third decimal place.
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)
In calculating the average degree of opening, the number of filaments in each of 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 in the warp yarn (or the weft yarn) was measured in the cross-sectional image. Similarly, the image acquisition of the glass yarn and the measurement of the number of filaments were repeated, and the average value of the five measurements obtained was used as the number of filaments in the warp yarn (or the weft yarn).

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

<Glass cloth manufacturing example>
[Glass Cloth P]
The warp and weft yarns were composed of glass yarns with a _SiO2 content 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 count 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 of the glass constituting the glass yarns used was 0.00020 at 10 GHz.

[Glass Cloth Q]
The warp and weft yarns were composed of glass yarns with a _SiO2 content 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 content 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 count 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 example of surface treatment solution>
Preparation Method I: Addition of Mother Liquor to Silane Coupling Agent Pre-Solution
The surface treatment liquid was prepared by the following methods 1) to 6).
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 and 0.8% by mass of polyoxyethylene alkyl ether based on the mass of the silane coupling agent weighed in 1) above were mixed and stirred for 1 minute.
4) To the silane coupling agent solution stirred in 3) above, an aqueous solution of acetic acid with a concentration of 60% by mass was added so that the concentration was 20% by mass based on the mass of the silane coupling agent weighed in 1) above. This gave a pre-solution (hydrolyzed solution) containing hydrolyzed silane coupling agent.
5) A mother liquor of an aqueous acetic acid solution (pH = 3-4) was prepared. The pre-solution of the silane coupling agent obtained in 4) above was stirred for 15 minutes at room temperature of 20-25°C. The mother liquor was added to the stirring pre-solution of the silane coupling agent, thereby dispersing the silane coupling agent. The amount and rate of addition of the mother liquor were set so that the addition of the entire amount of the mother liquor was completed in 10 minutes.
6) After step 5), the silane coupling agent solution was stirred at room temperature of 20 to 25° C. for 2 hours to obtain a surface treatment liquid.

[Preparation Method II: Addition of Silane Coupling Agent Pre-Solution to Mother Liquor]
The surface treatment liquid was prepared by the following methods 1) to 6).
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 and 0.8% by mass of polyoxyethylene alkyl ether based on the mass of the silane coupling agent weighed in 1) above were mixed and stirred for 1 minute.
4) To the silane coupling agent solution stirred in 3) above, an aqueous solution of acetic acid with a concentration of 60% by mass was added so that the concentration was 20% by mass based on the mass of the silane coupling agent weighed in 1) above, thereby obtaining a pre-solution (hydrolyzed solution) containing hydrolyzed silane coupling agent.
5) A mother solution of acetic acid (pH = 3-4) was prepared. The pre-solution of the silane coupling agent obtained in 4) above was stirred for 15 minutes at room temperature of 20-25°C. At this time, the stirred pre-solution of the silane coupling agent was added to the mother solution, thereby dispersing the silane coupling agent. The amount and rate of addition of the pre-solution were set so that the addition of the entire amount of the pre-solution was completed in 10 minutes.
6) After step 5), the silane coupling agent solution was stirred at room temperature of 20 to 25° C. for 2 hours to obtain a surface treatment liquid.

Examples and Comparative Examples
[Example of glass cloth manufacturing]
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 was heated and deoiled for 30 seconds in a furnace adjusted to a set temperature of 700°C while being conveyed (thermal deoiling step).

A surface treatment liquid was prepared by the above-described Preparation Method I using 3,6-diethenyl-1-(trimethoxysilyl)naphthalene (CAS NO: 2230040-75-0, molecular weight = 300.42, silane coupling agent A) represented by the following formula as a silane coupling agent so that the concentration of the silane coupling agent in the surface treatment liquid was 0.35 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 0.3 MPa. The glass cloth was then heated and dried at 130°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 maintain the temperature of the surface treatment solution in the range of 17 to 23°C while the glass cloth was being surface treated. Also, carbon dioxide was bubbled into the surface treatment solution to maintain the pH of the surface treatment solution 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). Specifically, 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 3.5 kg/ ^cm2 using a spray nozzle, thereby high-pressure opening. Next, ultrasonic waves with a frequency of 25 kHz and an output of 0.40 W/ ^cm2 were applied in water, further opening 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. As a result of the above, 2000 m of surface-treated glass cloth was obtained.

Example 2
A glass cloth of 2000 m was obtained in the same manner as in Example 1, except that [4-[2-(trimethoxysilyl)ethyl]phenyl]methyl 2-propenoate (CAS NO: 141813-20-9, molecular weight = 310.42, silane coupling agent B) represented by the following formula was used as the silane coupling agent.

Example 3
A glass cloth of 2000 m was obtained in the same manner as in Example 1, except that 4-(trimethoxysilyl)phenyl 2-propenoate (CAS NO: 220369-00-6, molecular weight = 268.34, silane coupling agent C) represented by the following formula was used as the silane coupling agent.

Example 4
A glass cloth of 2000 m was obtained in the same manner as in Example 1, except that N-ethenyl-N-(2-oxiranylmethoxy)-3-(trimethoxysilyl)-1-propanamine (CAS NO: 142177-48-8, molecular weight = 277.39, silane coupling agent D) represented by the following formula was used as the silane coupling agent.

Example 5
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that 1-ethenyl-4-[3-(trimethoxysilyl)propoxy]benzene (CAS NO: 149738-31-8, molecular weight = 282.41, silane coupling agent E) represented by the following formula was used as the silane coupling agent.

Example 6
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that 4-[2-(trimethoxysilyl)ethyl]benzeneamine (CAS NO: 56926-97-7, molecular weight = 241.36, silane coupling agent F) represented by the following formula was used as the silane coupling agent.

Example 7
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that [bicyclo[2.2.1]hept-5-en-2-yl]triethoxysilane (CAS NO: 18401-43-9, molecular weight = 256.41, silane coupling agent G) represented by the following formula was used as the silane coupling agent.

(Example 8)
A 2000 m glass cloth was obtained in the same manner as in Example 1, except that the glass cloth Q was used instead of the glass cloth P and the concentration of the silane coupling agent in the surface treatment liquid was changed to 0.25 mass %.

Example 9
A 2000 m glass cloth was obtained in the same manner as in Example 1, except that the glass cloth R was used instead of the glass cloth P and the concentration of the silane coupling agent in the surface treatment liquid was set to 0.25 mass %.

Example 10
A glass cloth of 2000 m was obtained in the same manner as in Example 1, except that the surface treatment was carried out without filtering the surface treatment solution.

Example 11
A glass cloth of 2000 m was obtained in the same manner as in Example 1, except that the surface treatment solution was not cooled even when the temperature of the surface treatment solution exceeded 23°C, and that carbon dioxide bubbling was not performed even when the pH exceeded 4.0.

Example 12
A 2000 m glass cloth was obtained in the same manner as in Example 1, except that the concentration of the silane coupling agent in the surface treatment liquid was set to 0.75 mass %.

Example 13
A 2000 m glass cloth was obtained in the same manner as in Example 1, except that the concentration of the silane coupling agent in the surface treatment liquid was 1.1 mass %.

(Comparative Example 1)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that 3-(trimethoxysilyl)propyl methacrylate (CAS NO: 2530-85-0, molecular weight = 248.35, silane coupling agent H) was used as the silane coupling agent.

(Comparative Example 2)
A surface-treated glass cloth of 2000 m was obtained in the same manner as in Example 1, except that 5-hexenyl trimethoxysilane (CAS NO: 58751-56-7, molecular weight = 204.34, silane coupling agent I) was used as the silane coupling agent.

Example 14
2000 m of glass cloth was obtained in the same manner as in Example 1, except that the surface treatment liquid was prepared by the above-mentioned preparation method II, the surface treatment of the glass cloth was carried out without filtering the surface treatment liquid, the surface treatment liquid was not cooled even when the temperature of the surface treatment liquid exceeded 23°C, and carbon dioxide bubbling was not carried out even when the pH exceeded 4.0.

[Frequency of white spots]
On a roll-to-roll inspection table, a tension of 100 N/1300 mm was applied to the glass cloth and a halogen lamp was irradiated, while the number of white spots occurring on the glass cloth was counted over a length of 2000 m. Then, from the inspection area and the number of white spots found by the inspection, the following formula was used:
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.

FIG. 1 is a photograph for explaining the "white spot" in the present disclosure. Of these, FIG. 1(a) shows a photograph of a portion without a white spot, and FIG. 1(b) shows a photograph of a portion with a white spot P. In the present disclosure, a "white spot" is defined as 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. Here, the outline is, for example, circular. The area enclosed by the outline was calculated using known image analysis software.

[Prepreg Production Example 1]
In Production Example 1, polyphenylene ether resin was used as a raw material. Specifically, 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. This produced a varnish. The glass cloths obtained in Examples 1 to 3, 5, 7, 8 to 14, and Comparative Examples 1 and 2 were impregnated with the varnish, and then dried at 130°C for 1 minute to obtain prepregs.

[Prepreg Production Example 2]
In Production Example 2, an epoxy resin was used as a raw material. Specifically, a varnish was prepared by blending 80 parts by mass of low-brominated bisphenol A epoxy resin, 20 parts by mass of cresol novolac epoxy resin, 2 parts by mass of dicyandiamide, 0.2 parts by mass of 2-ethyl-4-methylimidazole, and 100 parts by mass of 2-methoxyethanol. The glass cloth obtained in Examples 4 and 6 was impregnated with the prepared varnish and then dried at 130°C for 7 minutes to obtain a prepreg.

[Production Example of Polyphenylene Ether 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.

[Example of manufacturing epoxy 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 195°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 pieces were then heated in a pressure cooker at 133°C for 24 hours 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 such "failed" laminate samples was recorded. The fewer the number of glass cloths listed in the table, the more excellent the heat resistance.

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.

Examples 1 to 14 provided glass cloths that were capable of achieving excellent dielectric properties, suppressing the increase in dielectric loss tangent over time, and achieving excellent solder heat resistance for resin substrates made using the glass cloths. On the other hand, Comparative Examples 1 and 2 were unable to suppress the increase in dielectric loss tangent over time.

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

P: White spot

Claims (37)

A glass cloth configured with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns,
the glass cloth has a surface treatment agent on its surface;
The surface treatment agent is represented by the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The silane coupling agent has a molecular structure in which the value determined by
The ignition loss value of the glass cloth is in the range of 0.01 to 0.3 mass%,
The glass cloth has a basis weight of 8 to 250 g/m2 ^. 2. The glass cloth according to claim ¹ , wherein the number of white spots is 10 or less per square meter. 3. The glass cloth according to claim 1, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % in terms of silicon dioxide (SiO ₂ ). The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
The glass cloth according to claim 1 or 2, which contains a silane coupling agent represented by the formula: The glass cloth according to claim 4, wherein X in the general formula (1) includes at least one group selected from the group consisting of an epoxy group, an amino group, an aromatic vinyl group, an acryloyl group, and a methacryloyl group. The glass cloth according to claim 1 or 2, wherein the dielectric loss tangent of the glass cloth at 10 GHz is 0.002 or less. The glass cloth according to claim 1 or 2, wherein the value calculated by formula (A) is 14.4 or less. The glass cloth according to claim 1 or 2, wherein the value calculated by formula (A) is 13.8 or less. The glass cloth according to claim 1 or 2, wherein the value calculated by formula (A) is 13.5 or less. 3. The glass cloth according to claim 1, wherein the number of white spots is 4 or less per square ^meter . 3. The glass cloth according to claim 1, wherein the number of white spots is 2 or less per ^square meter. 3. The glass cloth according to claim 1, wherein the number of white spots is 0.1 or less per square ^meter . 3. The glass cloth according to claim 1, wherein the number of white spots is 0.05 or less per square ^meter . The glass cloth according to claim 1 or 2, wherein the molecular weight of the silane coupling agent is in the range of 250 to 1,000. The glass cloth according to claim 1 or 2, wherein the molecular weight of the silane coupling agent is in the range of 300 to 750. The glass cloth according to claim 1 or 2, wherein the molecular weight of the silane coupling agent is in the range of 350 to 700. The glass cloth according to claim 1 or 2 is for use in printed wiring boards. A prepreg containing the glass cloth according to claim 1 or 2, a matrix resin, and an inorganic filler. A printed wiring board comprising the prepreg of claim 18 . 20. An integrated circuit comprising the printed wiring board of claim 19 . An electronic device comprising the printed wiring board according to claim 19 . 1. A method for producing glass cloth, the method comprising:
a step of weaving glass yarns containing a plurality of glass filaments as warp yarns and weft yarns to obtain a glass cloth;
The method includes a step of degreasing the glass cloth and then surface-treating the glass cloth with a surface treatment liquid containing a surface treatment agent,
The surface treatment agent is represented by the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The silane coupling agent has a molecular structure in which the value obtained by
The ignition loss value of the glass cloth is in the range of 0.01 to 0.3 mass%,
The method for producing a glass cloth, wherein the glass cloth has a basis weight of 8 to 250 g/m2 ^. The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
The method for producing glass cloth according to claim 22 , comprising: The method for producing glass cloth according to claim 22 or 23 , wherein the surface treatment liquid is prepared by adding an acidic aqueous solution to a hydrolysis solution of the silane coupling agent. The surface treatment step includes:
controlling the temperature and pH of the surface treatment solution;
The method for producing glass cloth according to claim 22 or 23 , further comprising filtering the surface treatment liquid. The method for producing a glass cloth according to claim 22 or 23, further comprising a step of subjecting the glass cloth to an opening treatment after the surface treatment step. The method for producing glass cloth according to claim 22 or 23 , further comprising the step of inspecting for white spots after the surface treatment step. A surface treatment liquid for glass cloth containing a surface treatment agent containing a silane coupling agent,
The silane coupling agent is represented by the following formula (A):
1.10×MaxEStateIndex+14.6×MaxPartialCharge−0.0917×SPS+2.47×HallKierAlpha...(A)
The surface treatment solution has a molecular structure in which the value determined by the following formula is 15.0 or less. the surface treatment liquid contains the silane coupling agent in an amount of 0.20 to 1.2 mass % based on the total mass of the surface treatment liquid;
the pH of the surface treatment liquid is in the range of 2.5 to 5.5;
The surface treatment liquid according to claim 28 , wherein the surface treatment liquid contains a surfactant in an amount of 0.5 to 5.0 mass % based on the total mass of the silane coupling agent. The silane coupling agent is represented by the following general formula (1):
X _4-n -Si-Y _n ...(1)
(In formula (1), each X is independently an organic functional group having at least one selected from an epoxy group, an amino group, and an unsaturated double bond group having radical reactivity; each Y is independently an alkoxy group; and n is an integer of 1 or more and 3 or less.)
The surface treatment solution according to claim 28 or 29, comprising: 30. The surface treatment solution according to claim 28 or 29 , wherein the value obtained from the formula (A) is 14.4 or less. 30. The surface treatment solution according to claim 28 , wherein the value obtained from the formula (A) is 13.8 or less. 30. The surface treatment solution according to claim 28 or 29 , wherein the value obtained from the formula (A) is 13.5 or less. 30. The surface treatment liquid according to claim 28 , wherein the pH of the surface treatment liquid is in the range of 3.0 to 5.0. 30. The surface treatment liquid according to claim 28 , wherein the pH of the surface treatment liquid is in the range of 3.0 to 4.0. 30. The surface treatment liquid according to claim 28 , wherein the surface treatment liquid contains a surfactant in an amount of 1.0 to 4.5 mass % based on the total mass of the silane coupling agent. 30. The surface treatment liquid according to claim 28 , wherein the surface treatment liquid contains a surfactant in an amount of 1.5 to 4.0 mass % based on the total mass of the silane coupling agent.