Glass cloth, prepreg, and printed circuit board

Abstract

The present disclosure aims to provide a glass cloth, prepreg, and printed circuit board that can improve the offset of a printed circuit board and have excellent productivity and resin impregnation. According to the present disclosure, a glass cloth is provided that is composed of glass filaments formed by a plurality of glass filaments as warp and weft. The thickness of the glass cloth is in the range of 26 to 36 μm, and the warp width and weft width are in the range of 211 to 300 μm and 326 to 400 μm, respectively; or the thickness is in the range of 42 to 58 μm, and the warp width and weft width are in the range of 267 to 385 μm and 425 to 550 μm, respectively. Furthermore, the coefficient of variation of the dielectric constant at 10 GHz measured using a split post resonator of the glass cloth is 8.0% or less.

Description

Technical Field

[0001] This disclosure relates to glass cloth, prepreg, and printed circuit boards. Background Technology

[0002] Currently, with the increasing performance of information terminals such as smartphones and the high-speed communication represented by 5G, the dielectric constant and dielectric loss tangent of the insulating materials used in high-speed communication printed circuit boards are significantly reduced to lower transmission loss.

[0003] Currently, the high performance of information terminals such as smartphones and the continuous development of high-speed communications, represented by 5G, are driving this trend. Against this backdrop, there are increasing demands for improved heat resistance and insulation reliability in printed circuit boards (PCBs) used for high-speed communication. Furthermore, with the increasing miniaturization of PCB wiring patterns, there is a strong desire to improve the delay (skew) of propagating signals caused by differences in the distribution of the PCB's matrix resin and glass cloth.

[0004] Various efforts have been made to improve offset, and Patent Document 1 discloses a prepreg effective in reducing offset. Furthermore, as a further example of offset improvement, Patent Document 2 reports improving printed circuit board offset by processing glass cloth while simultaneously untwisting the twist of the glass yarn (glass filament). Patent Document 3 describes improving offset by dispersing hexagonal boron nitride in a matrix resin.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2013 / 140812

[0008] Patent Document 2: International Publication No. 2023 / 238763

[0009] Patent Document 3: Japanese Patent Application Publication No. 2017-170748 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, in Patent Documents 1-3, there is still room for further improvement in the misalignment of the glass cloth. Furthermore, for example, in Patent Document 2, the untwisting of the glass yarn easily generates fuzz on the glass cloth, which can reduce the productivity of the prepreg. Therefore, from the viewpoint of suppressing voids in the prepreg, a glass cloth with high resin impregnation is required. Therefore, the object of this disclosure is to provide a glass cloth that can improve the misalignment of printed circuit boards and has excellent productivity and resin impregnation.

[0012] Solution for solving the problem

[0013] The following illustrates a portion of the manner of this disclosure. [1]

[0015] A type of glass cloth, which is made of glass fibers formed by multiple long glass filaments as warp and weft threads.

[0016] The thickness of the glass cloth is in the range of 26–36 μm.

[0017] The warp and weft widths of the glass cloth range from 211 to 300 μm and 326 to 400 μm, respectively.

[0018] The coefficient of variation of the dielectric constant of the glass cloth measured at 10 GHz using a split cylindrical resonator is less than 8.0%. [2]

[0020] A type of glass cloth is made of glass filaments formed from multiple long glass filaments as warp and weft yarns. The thickness of the glass cloth is in the range of 42 to 58 μm, and the width of the warp yarns and the width of the weft yarns are in the ranges of 267 to 385 μm and 425 to 550 μm, respectively. The coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%. [3]

[0022] A type of glass cloth is made of glass filaments formed from multiple long glass filaments as warp and weft yarns. The thickness of the glass cloth is in the range of 13 to 19 μm, and the width of the warp yarns and the width of the weft yarns are in the range of 125 to 135 μm and 200 to 240 μm, respectively. The coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%. [4]

[0024] A type of glass cloth is made of glass filaments formed from multiple long glass filaments as warp and weft yarns. The thickness of the glass cloth is in the range of 17 to 25 μm, and the width of the warp yarns and the width of the weft yarns are in the range of 178 to 198 μm and 310 to 342 μm, respectively. The coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%. [5]

[0026] A type of glass cloth is made of glass filaments formed from multiple long glass filaments as warp and weft yarns. The thickness of the glass cloth is in the range of 20 to 30 μm, and the width of the warp yarns and the width of the weft yarns are in the range of 176 to 232 μm and 329 to 353 μm, respectively. The coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%. [6]

[0028] The glass cloth according to any one of items 1 to 5, wherein the dielectric constant is in the range of 3.8 to 4.5. [7]

[0030] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 45 to 55% by mass of SiO2; 17 to 27% by mass of B2O3; 11 to 21% by mass of Al2O3; a total of 2.7 to 5.7% by mass of CaO and MgO; and a total of 0 to 0.15% by mass of Li2O, K2O, and Na2O. [8]

[0032] According to the glass cloth described in Project 7, the glass fibers, based on their total mass, contain, in oxide terms: 0.15 to 0.45% by mass of TiO2; 2.5 to 7.5% by mass of P2O5; and 0 to 0.02% by mass of SrO. [9]

[0034] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 48 to 58% by mass of SiO2; 18 to 28% by mass of B2O3; 8 to 18% by mass of Al2O3; a total of 3.4 to 6.4% by mass of CaO and MgO; and a total of 0 to 0.15% by mass of Li2O, K2O, and Na2O.

[10]

[0036] According to the glass cloth described in Project 9, the glass fibers, based on their total mass, contain, in oxide terms, 0.9 to 2.9% TiO2; 0 to 0.03% P2O5; and 0 to 3% SrO.

[11]

[0038] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 48 to 58% by mass of SiO2; 17 to 27% by mass of B2O3; 11 to 21% by mass of Al2O3; a total of 3.5 to 6.5% by mass of CaO and MgO; and a total of 0 to 0.1% by mass of Li2O, K2O, and Na2O.

[12]

[0040] According to the glass cloth of Project 11, the glass fibers contain, based on their total mass and in oxide equivalents, the following: 0 to 0.3% by mass of TiO2; 0 to 4.2% by mass of P2O5; and 0 to 1% by mass of SrO.

[13]

[0042] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 47 to 57% by mass of SiO2; 22 to 32% by mass of B2O3; 8 to 18% by mass of Al2O3; a total of 1.4 to 4.4% by mass of CaO and MgO; and a total of 0.1 to 1.0% by mass of Li2O, K2O, and Na2O.

[14]

[0044] According to the glass cloth described in Item 13, the glass fibers, based on their total mass, contain, in oxide terms, the following: 0 to 1% by mass of TiO2; 0 to 0.2% by mass of P2O5; and 0 to 0.3% by mass of SrO.

[15]

[0046] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 47 to 57% by mass of SiO2; 18 to 28% by mass of B2O3; 9 to 19% by mass of Al2O3; a total of 3.4 to 6.4% by mass of CaO and MgO; and a total of 0 to 0.3% by mass of Li2O, K2O, and Na2O.

[16]

[0048] According to the glass cloth of Project 15, the glass fibers contain, based on their total mass and in oxide equivalents, 0.01 to 0.3% TiO2; 0 to 0.2% P2O5; and 0 to 0.3% SrO.

[17]

[0050] The glass cloth according to any one of items 1 to 6, wherein the glass fibers, based on their total mass and converted to oxides, contain: 47 to 57% by mass of SiO2; 20 to 30% by mass of B2O3; 8 to 18% by mass of Al2O3; a total of 3.0 to 7.0% by mass of CaO and MgO; and a total of 0 to 0.3% by mass of Li2O, K2O, and Na2O.

[18]

[0052] According to the glass cloth of Project 17, the glass fibers contain, based on their total mass and in oxide equivalents: 1.0 to 5.0% by mass of TiO2; 0 to 0.1% by mass of P2O5; and 0 to 0.2% by mass of SrO.

[19]

[0054] According to the glass cloth described in Project 6, the dielectric constant is in the range of 4.0 to 4.3.

[20]

[0056] The glass cloth according to any one of items 1 to 6, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 0.0025. [twenty one]

[0058] The glass cloth according to any one of items 1 to 6, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 0.0023. [twenty two]

[0060] The glass cloth according to any one of items 1 to 6, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 0.0020°. [twenty three]

[0062] The glass cloth according to any one of items 1 to 6, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 0.0010 to 0.0018. [twenty four]

[0064] The glass cloth according to any one of items 1 to 6, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 0.0018 to 0.0020.

[25]

[0066] The glass cloth according to any one of items 1 to 6, wherein the coefficient of variation of the dielectric constant is less than 6.0%.

[26]

[0068] The glass cloth according to any one of items 1 to 6, wherein the coefficient of variation of the dielectric constant is less than 4.0%.

[27]

[0070] The glass cloth according to any one of items 1 to 6, wherein the coefficient of variation of the dielectric constant is less than 2.0%.

[28]

[0072] According to the glass cloth described in Project 1, the warp width and weft width of the glass cloth are in the range of 213-290μm and 335-390μm, respectively.

[29]

[0074] According to the glass cloth described in Project 1, the warp width and weft width of the glass cloth are in the range of 215-275μm and 345-380μm, respectively.

[30]

[0076] According to the glass cloth described in Project 1, the warp width and weft width of the glass cloth are in the range of 218-260μm and 350-375μm, respectively.

[31]

[0078] According to the glass cloth described in Project 1, the standard deviations of the warp width and weft width of the glass cloth are respectively within the range of less than 16 μm and less than 34 μm.

[32]

[0080] According to the glass cloth described in Project 2, the warp width and weft width of the glass cloth are in the range of 270-370μm and 440-540μm, respectively.

[33]

[0082] According to the glass cloth described in Project 2, the warp width and weft width of the glass cloth are in the range of 275-360μm and 450-530μm, respectively.

[34]

[0084] According to the glass cloth described in Project 2, the warp width and weft width of the glass cloth are in the range of 285-350μm and 460-500μm, respectively.

[35]

[0086] According to the glass cloth described in Project 2, the standard deviations of the warp width and weft width of the glass cloth are less than 26 μm and less than 39 μm, respectively.

[36]

[0088] According to the glass cloth described in Project 3, the warp width and weft width of the glass cloth are in the range of 126-134 μm and 204-236 μm, respectively.

[37]

[0090] According to the glass cloth described in Project 3, the warp width and weft width of the glass cloth are in the range of 127-133 μm and 208-232 μm, respectively.

[38]

[0092] According to the glass cloth described in Project 3, the standard deviations of the warp width and weft width of the glass cloth are respectively within the range of less than 15 μm and less than 24 μm.

[39]

[0094] According to the glass cloth described in Project 4, the warp width and weft width of the glass cloth are in the range of 180-196μm and 313-339μm, respectively.

[40]

[0096] According to the glass cloth described in Project 4, the warp width and weft width of the glass cloth are in the range of 182-194μm and 316-336μm, respectively.

[41]

[0098] According to the glass cloth described in Project 4, the standard deviations of the warp width and weft width of the glass cloth are respectively below 20 μm and below 40 μm.

[42]

[0100] According to the glass cloth described in Project 5, the warp width and weft width of the glass cloth are in the range of 183-225μm and 332-350μm, respectively.

[43]

[0102] According to the glass cloth described in Project 5, the warp width and weft width of the glass cloth are in the range of 190-218 μm and 335-347 μm, respectively.

[44]

[0104] According to the glass cloth described in Project 5, the standard deviations of the warp width and weft width of the glass cloth are respectively within the range of less than 20 μm and less than 43 μm.

[45]

[0106] The glass cloth according to any one of items 1 to 44, wherein the coefficient of variation of the TEX of the glass filament is less than 4.0%.

[46]

[0108] The glass cloth according to any one of items 1 to 44, wherein the coefficient of variation of the TEX of the glass filament is less than 3.0%.

[47]

[0110] A prepreg comprising glass cloth and matrix resin as described in any one of items 1 to 46.

[48]

[0112] A printed circuit board comprising the prepreg described in item 47.

[49]

[0114] An integrated circuit comprising the printed circuit board described in item 48.

[50]

[0116] An electronic device comprising the printed circuit board described in item 48.

[0117] The effects of the invention

[0118] According to this disclosure, a glass cloth that can improve the offset of printed circuit boards and has excellent productivity and resin impregnation can be provided. Detailed Implementation

[0119] The following describes examples of embodiments of this disclosure, but this disclosure is not limited thereto, and various modifications can be made without departing from its spirit. In this disclosure, the numerical range recorded using "~" indicates a range of values ​​including the values ​​before and after "~" as lower and upper limits. Furthermore, in this disclosure, within a range of numerical values ​​recorded in stages, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges recorded in stages. Moreover, in this disclosure, the upper or lower limit value recorded in a certain numerical range can also be replaced with the value shown in the embodiment. Furthermore, in this disclosure, the term "process" not only includes independent processes, but also includes processes as long as their function is achieved, even when it is difficult to clearly distinguish them from other processes.

[0120] Glass cloth

[0121] The glass cloth disclosed herein is a glass cloth constructed by using glass filaments formed from multiple long glass filaments as warp and weft yarns. Examples of the weaving structures of the glass cloth include plain weave, basket weave, satin weave, and twill weave. Among these, a plain weave structure is preferred.

[0122] [Dielectric loss tangent and dielectric constant of glass cloth]

[0123] The dielectric loss tangent (Df) of the glass cloth at 10 GHz, measured using a split cylindrical resonator, is preferably 0.0025 or less. By keeping the dielectric loss tangent of the glass cloth within this range, the transmission loss of the printed circuit board can be reduced, making high-speed signal communication easier. From the viewpoint of easily achieving the effect of reducing transmission loss, the dielectric loss tangent of the glass cloth is further preferably 0.0023 or less, more preferably 0.0021 or less, particularly preferably 0.0020 or less, and may also be 0.0019 or less or 0.0018 or less. The lower limit of the dielectric loss tangent is not particularly limited, but is preferably 0.0010 or more, more preferably in the range of 0.0010 to 0.0018. In addition, from the viewpoint of easily balancing high glass fiber yield, fluff quality, and reduced dielectric loss tangent during glass cloth production, the dielectric loss tangent of the glass cloth is preferably in the range of 0.0017 to 0.0020, more preferably in the range of 0.0018 to 0.0020. From the viewpoint of easily reducing the difference in dielectric constant between the glass cloth and the matrix resin and easily improving the offset performance, the dielectric constant (Dk) of the glass cloth is preferably in the range of 3.8 to 4.5, and more preferably in the range of 4.0 to 4.3. It should be noted that the dielectric loss tangent and dielectric constant of the glass cloth were measured using the method described in the examples.

[0124] [Glass cloth type P]

[0125] In the glass cloth disclosed herein, the thickness of the glass cloth is in the range of 26 to 36 μm, the warp width and weft width of the glass cloth are in the range of 211 to 300 μm and 326 to 400 μm respectively (also referred to as "cloth type P" in this disclosure), and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 8.0% or less.

[0126] The glass cloth (cloth type P) disclosed herein, by having the above-described structure, provides a glass cloth with excellent offset characteristics, as well as excellent productivity and resin impregnation. The reasoning is not limited to theory, but is speculative as follows: A printed circuit board has copper foil patterns for receiving and transmitting signals on the surface of a laminate composed of a matrix resin and glass cloth. In the surface of the glass cloth, a difference in signal velocity (generally referred to as "offset") occurs between the matrix resin portion and the glass fiber portion, primarily due to the discontinuous state arising from the mixing of voids filling the matrix resin with glass fiber portions, and the difference in dielectric constant between the glass cloth and the matrix resin. Therefore, to improve the offset using the glass cloth, it is effective to increase the fiber width of the glass cloth to make the surface of the glass cloth more uniform. Increasing the fiber width of the glass cloth also contributes to improving resin impregnation. It should be noted that the printed circuit board is made of prepreg, which is obtained by impregnating a resin composition into glass cloth and then allowing it to semi-cure. By using glass cloth with high resin impregnation, it is less likely to generate voids (commonly referred to as voids) in the prepreg and the printed circuit board, thus improving insulation reliability. In addition, excellent resin impregnation also helps to improve the heat resistance of printed circuit boards, etc. Here, in order to increase the fiber width of the glass cloth, the method of splitting the glass cloth can usually be cited. However, if the glass cloth is split to increase the fiber width, the surface of the glass cloth will become fuzzy, resulting in a decrease in productivity. That is, the offset and the improvement of resin impregnation are inversely related to productivity (flocking quality). Therefore, the inventors conducted in-depth research and found that by designing the thickness of the glass cloth, as well as the warp and weft fiber widths, within an appropriate range, the fiber width can be fully split even without strengthening the splitting process of the glass cloth. That is, when the warp and weft widths of the glass cloth are in the range of 211–300 μm and 326–400 μm, respectively, by making the thickness of the glass cloth 26 μm or more, it is not necessary to excessively increase the width of the glass cloth fibers, nor is it necessary to strengthen the fiber-opening process of the glass cloth. Therefore, the pile quality of the glass cloth can be improved, and productivity can be increased. On the other hand, by making the thickness of the glass cloth 36 μm or less, the fiber width is sufficiently opened, improving offset and resin impregnation. Furthermore, since very fine patterns are formed on printed circuit boards using low-dielectric glass cloth, it is required to improve the offset characteristics of the glass cloth to a level higher than that currently. Therefore, the inventors conducted research and found that by setting the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, measured using a split cylindrical resonator, to 8.0% or less while keeping the thickness, warp width, and weft width of the glass cloth within the above-mentioned ranges, the offset characteristics of the printed circuit board can be significantly improved. The reason is that it was previously thought that the offset characteristics were caused by the difference in dielectric constant between the glass cloth and the matrix resin. However, the inventors have discovered that during the heating and degreasing process of the glass cloth, elements such as boron, which are easily volatilized by heating, change within the glass cloth surface. As a result, the dielectric constant within the glass cloth surface deviates significantly, which also affects the offset characteristics.Therefore, the inventors conceived of reducing not only the difference in offset properties between the glass cloth and the matrix resin, but also the difference in offset properties between the glass cloths themselves, by suppressing the deviation of the dielectric constant within the glass cloth's surface. Furthermore, in-depth research was conducted, and the results, as described later, show that by processing the glass cloth to make its surface composition more uniform, the deviation of the dielectric constant within the glass cloth's surface is reduced, leading to a significant improvement in the offset properties of the printed circuit board. Through these methods, a glass cloth that highly balances productivity, offset characteristics, and resin impregnation can be obtained.

[0127] The thickness of the glass cloth (cloth type P) is in the range of 26–36 μm, preferably in the range of 27–35 μm, more preferably in the range of 28–34 μm, even more preferably in the range of 29–33 μm, and particularly preferably in the range of 30–32 μm. When the thickness of the glass cloth is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0128] The warp and weft widths of the glass cloth (cloth type P) are in the ranges of 211–300 μm and 326–400 μm, respectively; preferably, they are in the ranges of 213–290 μm and 335–390 μm, respectively; more preferably, they are in the ranges of 215–275 μm and 345–380 μm, respectively; and particularly preferably, they are in the ranges of 218–260 μm and 350–375 μm, respectively. Alternatively, the warp and weft widths of the glass cloth (cloth type P) can be in the ranges of 211–280 μm and 326–400 μm, 215–270 μm and 335–390 μm, 220–260 μm and 345–380 μm, respectively, or 225–250 μm and 350–375 μm, respectively. If the warp and weft widths of the glass cloth are within the above range, a glass cloth that better balances productivity and offset characteristics can be obtained.

[0129] The standard deviations of the warp and weft widths of the glass cloth (cloth type P) are preferably 16 μm or less and 34 μm or less, respectively. If the standard deviations of the filament widths are within these ranges, it is easier to improve the offset characteristics of the glass cloth. From the viewpoint of more easily achieving improved offset characteristics, the standard deviations of the warp and weft widths of the glass cloth are more preferably 15 μm or less and 33 μm or less, further preferably 14 μm or less and 32 μm or less, and particularly preferably 13 μm or less and 31 μm or less. For example, the standard deviation of the filament width can be reduced by performing a fiber-opening treatment to widen the filament width of the glass cloth. Preferably, after surface treatment with a silane coupling agent, fiber-opening treatment is performed using high-pressure spraying or the like; more preferably, the glass cloth is treated with ultrasound in water after a heat degreasing treatment to eliminate adhesion between the glass filaments. The lower limits of the standard deviations of the warp and weft widths are not limited; for example, they can be 5 μm or more and 10 μm or more, respectively.

[0130] The coefficient of variation of the dielectric constant of the glass cloth (cloth type P) measured at 10 GHz using a split cylindrical resonator is in the range of 8.0% or less. The inventors conducted research and found that, as described later, by controlling the amount of Na and Mg ions attached to the surface of the glass cloth and adjusting the heating degreasing conditions, it is possible to suppress variations in the composition of the glass fibers, thereby achieving a coefficient of variation of the dielectric constant of the glass cloth of 8.0% or less. From the viewpoint of easily obtaining improved offset characteristics, the coefficient of variation of the dielectric constant of the glass cloth is preferably in the range of 6.0% or less, more preferably in the range of 4.0% or less, and particularly preferably in the range of 2.0% or less. The lower limit of the coefficient of variation of the dielectric constant is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0131] The preferred warp and weft yarn drive density of the glass cloth (cloth type P) is 55–75 yarns / 25 mm, more preferably 57–73 yarns / 25 mm, even more preferably 59–71 yarns / 25 mm, and particularly preferably 61–73 yarns / 25 mm. If the drive density is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained. The warp and weft yarn drive densities can be the same or different.

[0132] [Glass cloth type Q]

[0133] Another aspect of the glass cloth disclosed herein is that the thickness of the glass cloth is in the range of 42 to 58 μm, the width of the warp yarns and the width of the weft yarns are in the range of 267 to 385 μm and 425 to 550 μm respectively (also referred to as "cloth type Q" in this disclosure), and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 8.0% or less.

[0134] The glass cloth (cloth type Q) disclosed herein, by having the above-described structure, provides a glass cloth with excellent offset characteristics, as well as excellent productivity and resin impregnation. The reasons for this are the same as those for cloth type P described above, except that the thickness of the glass cloth and the appropriate range of warp and weft widths differ.

[0135] The thickness of the glass cloth (cloth type Q) is in the range of 42–58 μm, preferably in the range of 43–57 μm, more preferably in the range of 44–56 μm, even more preferably in the range of 45–55 μm, and particularly preferably in the range of 46–53 μm. When the thickness of the glass cloth is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0136] The warp and weft widths of the glass cloth (cloth type Q) are in the ranges of 267–385 μm and 425–550 μm, respectively; preferably, they are in the ranges of 270–370 μm and 440–540 μm, respectively; more preferably, they are in the ranges of 275–360 μm and 450–530 μm, respectively; and particularly preferably, they are in the ranges of 285–350 μm and 460–500 μm, respectively. Alternatively, the warp and weft widths of the glass cloth (cloth type Q) can be in the ranges of 290–320 μm and 460–500 μm, respectively. If the warp and weft widths of the glass cloth are within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0137] The standard deviations of the warp and weft yarn widths of the glass cloth (cloth type Q) are preferably in the range of 26 μm or less and 39 μm or less, respectively. If the standard deviations of the yarn widths are within these ranges, it is easier to improve the offset characteristics of the glass cloth. From the viewpoint of more easily achieving improved offset characteristics, the standard deviations of the warp and weft yarn widths of the glass cloth are more preferably in the range of 25 μm or less and 38 μm or less, further preferably in the range of 24 μm or less and 37 μm or less, and particularly preferably in the range of 23 μm or less and 36 μm or less. The adjustment of the standard deviation of the yarn width is the same as that of cloth type P. The lower limits of the standard deviations of the warp and weft yarn widths are not limited; for example, they can be 10 μm or more and 20 μm or more, respectively.

[0138] The coefficient of variation of the dielectric constant of the glass cloth (cloth type Q) measured at 10 GHz using a split cylindrical resonator is in the range of 8.0% or less. The inventors conducted research and found that, as described later, by controlling the amount of Na and Mg ions attached to the surface of the glass cloth and adjusting the heating degreasing conditions, it is possible to suppress compositional variations in the glass fibers, thereby achieving a coefficient of variation of the dielectric constant of the glass cloth of 8.0% or less. From the viewpoint of easily obtaining improved offset characteristics, the coefficient of variation of the dielectric constant of the glass cloth is preferably in the range of 6.0% or less, more preferably in the range of 4.0% or less, and particularly preferably in the range of 2.0% or less. The lower limit of the coefficient of variation of the dielectric constant is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0139] The preferred warp and weft yarn drive density of the glass cloth (cloth type Q) is 43–63 yarns / 25 mm, more preferably 45–61 yarns / 25 mm, even more preferably 47–59 yarns / 25 mm, and particularly preferably 49–57 yarns / 25 mm. If the drive density is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained. The warp and weft yarn drive densities can be the same or different.

[0140] [Glass cloth type R]

[0141] In the glass cloth disclosed herein, the thickness of the glass cloth is in the range of 13 to 19 μm, the warp width and weft width of the glass cloth are in the range of 125 to 135 μm and 200 to 240 μm respectively (also referred to as "cloth type R" in this disclosure), and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 8.0% or less.

[0142] The glass cloth (cloth type R) disclosed herein, by having the above-described structure, provides a glass cloth with excellent offset characteristics, as well as excellent productivity and resin impregnation. The reasoning is not limited to theory, but is speculative as follows: A printed circuit board has copper foil patterns for receiving and transmitting signals on the surface of a laminate composed of a matrix resin and glass cloth. In the surface of the glass cloth, a difference in signal velocity (generally referred to as "offset") occurs between the matrix resin portion and the glass fiber portion, mainly due to the discontinuous state existing in the mixture of voids filling the matrix resin and glass fiber portions, and the difference in dielectric constant between the glass cloth and the matrix resin. Therefore, to improve the offset using the glass cloth, it is effective to increase the fiber width of the glass cloth to make the surface of the glass cloth more uniform. Increasing the fiber width of the glass cloth also improves resin impregnation. It should be noted that the printed circuit board is made of prepreg, which is obtained by impregnating a resin composition into glass cloth and then allowing it to semi-cure. By using glass cloth with high resin impregnation, it is less likely to generate voids (commonly referred to as voids) in the prepreg and the printed circuit board, thus improving insulation reliability. In addition, excellent resin impregnation also helps to improve the heat resistance of printed circuit boards, etc. Here, in order to increase the fiber width of the glass cloth, the method of splitting the glass cloth can usually be cited. However, if the glass cloth is split to increase the fiber width, the surface of the glass cloth will become fuzzy, resulting in a decrease in productivity. That is, the offset and the improvement of resin impregnation are inversely related to productivity (flocking quality). Therefore, the inventors conducted in-depth research and found that by designing the thickness of the glass cloth, as well as the warp and weft fiber widths, within an appropriate range, the fiber width can be fully split even without strengthening the splitting process of the glass cloth. That is, when the warp and weft widths of the glass cloth are in the range of 125–135 μm and 200–240 μm, respectively, by making the thickness of the glass cloth 13 μm or more, it is not necessary to excessively increase the width of the glass cloth fibers, nor is it necessary to strengthen the fiber-opening process of the glass cloth. Therefore, the pile quality of the glass cloth can be improved, and productivity can be increased. On the other hand, by making the thickness of the glass cloth 19 μm or less, the fiber width is sufficiently opened, improving offset and resin impregnation. Furthermore, since very fine patterns are formed on printed circuit boards using low-dielectric glass cloth, it is required to improve the offset characteristics of the glass cloth to a level higher than that currently. Therefore, the inventors conducted research and found that by setting the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, measured using a split cylindrical resonator, to 8.0% or less while keeping the thickness, warp width, and weft width of the glass cloth within the above-mentioned ranges, the offset characteristics of the printed circuit board can be significantly improved. The reason is that it was previously thought that the offset characteristics were caused by the difference in dielectric constant between the glass cloth and the matrix resin. However, the inventors have discovered that during the heating and degreasing process of the glass cloth, elements such as boron, which are easily volatilized by heating, change within the glass cloth surface. As a result, the dielectric constant within the glass cloth surface deviates significantly, which also affects the offset characteristics.Therefore, the inventors conceived of reducing not only the difference in offset properties between the glass cloth and the matrix resin, but also the difference in offset properties between the glass cloths themselves, by suppressing the deviation of the dielectric constant within the glass cloth's surface. Furthermore, in-depth research was conducted, and the results, as described later, show that by processing the glass cloth to make its surface composition more uniform, the deviation of the dielectric constant within the glass cloth's surface is reduced, leading to a significant improvement in the offset properties of the printed circuit board. Through these methods, a glass cloth that highly balances productivity, offset characteristics, and resin impregnation can be obtained.

[0143] The thickness of the glass cloth (cloth type R) is in the range of 13 to 19 μm, preferably in the range of 14 to 18 μm, and particularly preferably in the range of 15 to 17 μm. When the thickness of the glass cloth is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0144] The warp and weft widths of the glass cloth (cloth type R) are in the range of 125–135 μm and 200–240 μm, respectively; preferably, they are in the range of 126–134 μm and 204–236 μm, respectively; more preferably, they are in the range of 127–133 μm and 208–232 μm, respectively; and particularly preferably, they are in the range of 128–132 μm and 209–230 μm, respectively. If the warp and weft widths of the glass cloth are within the above ranges, a glass cloth that better balances productivity and offset characteristics can be obtained.

[0145] The standard deviations of the warp and weft widths of the glass cloth (cloth type R) are preferably 15 μm or less and 24 μm or less, respectively. If the standard deviations of the filament widths are within these ranges, it is easier to improve the offset characteristics of the glass cloth. From the viewpoint of more easily achieving improved offset characteristics, the standard deviations of the warp and weft widths of the glass cloth are more preferably 14 μm or less and 23 μm or less, even more preferably 13 μm or less and 22 μm or less, and particularly preferably 12 μm or less and 21 μm or less. For example, the standard deviation of the filament width can be reduced by performing a fiber-opening treatment to widen the filament width of the glass cloth. Preferably, after surface treatment with a silane coupling agent, fiber-opening treatment is performed using high-pressure spraying or the like; more preferably, the glass cloth is treated with ultrasound in water after a heat degreasing treatment to eliminate adhesion between the glass filaments. The lower limits of the standard deviations of the warp and weft widths are not limited; for example, they can be 2 μm or more and 5 μm or more, respectively.

[0146] The coefficient of variation of the dielectric constant of the glass cloth (cloth type R), measured using a split cylindrical resonator at 10 GHz, is in the range of 8.0% or less. The inventors conducted research and found that, as described later, by controlling the amount of Na and Mg ions attached to the surface of the glass cloth and adjusting the heating degreasing conditions, compositional variations in the glass fibers can be suppressed, resulting in a dielectric constant coefficient of variation of the glass cloth of 8.0% or less. From the viewpoint of easily obtaining improved offset characteristics, the dielectric constant coefficient of variation of the glass cloth is preferably in the range of 6.0% or less, more preferably in the range of 4.0% or less, and particularly preferably in the range of 2.0% or less. The lower limit of the dielectric constant coefficient of variation is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0147] The preferred warp and weft yarn penetration density of the glass cloth (cloth type R) is 88–98 yarns / 25 mm, more preferably 89–97 yarns / 25 mm, even more preferably 90–96 yarns / 25 mm, and particularly preferably 91–95 yarns / 25 mm. If the penetration density is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained. The warp and weft yarn penetration densities can be the same or different.

[0148] [Glass cloth type S]

[0149] In the glass cloth disclosed herein, the thickness of the glass cloth is in the range of 17 to 25 μm, the warp width and weft width of the glass cloth are in the range of 178 to 198 μm and 310 to 342 μm, respectively (also referred to as "cloth type S" in this disclosure), and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 8.0% or less.

[0150] The glass cloth (cloth type S) disclosed herein, by having the above-described structure, provides a glass cloth with excellent offset characteristics, as well as excellent productivity and resin impregnation. The reasoning is not limited to theory, but is speculative as follows: A printed circuit board has copper foil patterns for receiving and transmitting signals on the surface of a laminate composed of a matrix resin and glass cloth. In the surface of the glass cloth, a difference in signal velocity (generally referred to as "offset") occurs between the matrix resin portion and the glass fiber portion, mainly due to the discontinuous state existing in the mixture of voids filling the matrix resin and glass fiber portions, and the difference in dielectric constant between the glass cloth and the matrix resin. Therefore, to improve the offset using the glass cloth, it is effective to increase the fiber width of the glass cloth to make the surface of the glass cloth more uniform. Increasing the fiber width of the glass cloth also improves resin impregnation. It should be noted that the printed circuit board is made of prepreg, which is obtained by impregnating a resin composition into glass cloth and then allowing it to semi-cure. By using glass cloth with high resin impregnation, it is less likely to generate voids (commonly referred to as voids) in the prepreg and the printed circuit board, thus improving insulation reliability. In addition, excellent resin impregnation also helps to improve the heat resistance of printed circuit boards, etc. Here, in order to increase the fiber width of the glass cloth, the method of splitting the glass cloth can usually be cited. However, if the glass cloth is split to increase the fiber width, the surface of the glass cloth will become fuzzy, resulting in a decrease in productivity. That is, the offset and the improvement of resin impregnation are inversely related to productivity (flocking quality). Therefore, the inventors conducted in-depth research and found that by designing the thickness of the glass cloth, as well as the warp and weft fiber widths, within an appropriate range, the fiber width can be fully split even without strengthening the splitting process of the glass cloth. That is, when the warp and weft widths of the glass cloth are in the range of 178–198 μm and 310–342 μm, respectively, by making the thickness of the glass cloth 17 μm or more, it is not necessary to excessively increase the width of the glass cloth fibers, nor is it necessary to strengthen the fiber-opening process of the glass cloth. Therefore, the pile quality of the glass cloth can be improved, and productivity can be increased. On the other hand, by making the thickness of the glass cloth 25 μm or less, the fiber width is sufficiently opened, improving offset and resin impregnation. Furthermore, since very fine patterns are formed on printed circuit boards using low-dielectric glass cloth, it is required to improve the offset characteristics of the glass cloth to a level higher than that currently. Therefore, the inventors conducted research and found that by setting the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, measured using a split cylindrical resonator, to 8.0% or less while keeping the thickness, warp width, and weft width of the glass cloth within the above-mentioned ranges, the offset characteristics of the printed circuit board can be significantly improved. The reason is that it was previously thought that the offset characteristics were caused by the difference in dielectric constant between the glass cloth and the matrix resin. However, the inventors have discovered that during the heating and degreasing process of the glass cloth, elements such as boron, which are easily volatilized by heating, change within the glass cloth surface. As a result, the dielectric constant within the glass cloth surface deviates significantly, which also affects the offset characteristics.Therefore, the inventors conceived of reducing not only the difference in offset properties between the glass cloth and the matrix resin, but also the difference in offset properties between the glass cloths themselves, by suppressing the deviation of the dielectric constant within the glass cloth's surface. Furthermore, in-depth research was conducted, and the results, as described later, show that by processing the glass cloth to make its surface composition more uniform, the deviation of the dielectric constant within the glass cloth's surface is reduced, leading to a significant improvement in the offset properties of the printed circuit board. Through these methods, a glass cloth that highly balances productivity, offset characteristics, and resin impregnation can be obtained.

[0151] The thickness of the glass cloth (cloth type S) is in the range of 17 to 25 μm, preferably in the range of 18 to 24 μm, more preferably in the range of 19 to 23 μm, and particularly preferably in the range of 20 to 22 μm. When the thickness of the glass cloth is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0152] The warp and weft widths of the glass cloth (cloth type S) are in the range of 178–198 μm and 310–342 μm, respectively; preferably, they are in the range of 180–196 μm and 313–339 μm, respectively; more preferably, they are in the range of 182–194 μm and 316–336 μm, respectively; and particularly preferably, they are in the range of 184–192 μm and 320–333 μm, respectively. If the warp and weft widths of the glass cloth are within the above ranges, a glass cloth that better balances productivity and offset characteristics can be obtained.

[0153] The standard deviations of the warp and weft widths of the glass cloth (cloth type S) are preferably 20 μm or less and 40 μm or less, respectively. If the standard deviations of the filament widths are within the above ranges, it is easier to improve the offset characteristics of the glass cloth. From the viewpoint of more easily achieving improved offset characteristics, the standard deviations of the warp and weft widths of the glass cloth are more preferably 19 μm or less and 39 μm or less, further preferably 18 μm or less and 38 μm or less, and particularly preferably 17 μm or less and 37 μm or less. For example, the standard deviation of the filament width can be reduced by performing a fiber-opening treatment to widen the filament width of the glass cloth. Preferably, after surface treatment with a silane coupling agent, fiber-opening treatment is performed using high-pressure spraying or the like, and more preferably, the glass cloth is treated with ultrasound in water after a heat degreasing treatment to eliminate adhesion between the glass filaments. The lower limits of the standard deviations of the warp and weft widths are not limited; for example, they can be 5 μm or more and 10 μm or more, respectively.

[0154] The coefficient of variation of the dielectric constant of the glass cloth (cloth type S), measured using a split cylindrical resonator at 10 GHz, is in the range of 8.0% or less. The inventors conducted research and found that, as described later, by controlling the amount of Na and Mg ions attached to the surface of the glass cloth and adjusting the conditions of heating and degreasing, it is possible to suppress variations in the composition of the glass fibers, thereby achieving a coefficient of variation of the dielectric constant of the glass cloth of 8.0% or less. From the viewpoint of easily obtaining improved offset characteristics, the coefficient of variation of the dielectric constant of the glass cloth is preferably in the range of 6.0% or less, more preferably in the range of 4.0% or less, and particularly preferably in the range of 2.0% or less. The lower limit of the coefficient of variation of the dielectric constant is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0155] The preferred warp and weft yarn penetration density of the glass cloth (cloth type S) is 65-80 yarns / 25mm, more preferably 67-79 yarns / 25mm, even more preferably 68-78 yarns / 25mm, and particularly preferably 69-77 yarns / 25mm. If the penetration density is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained. The warp and weft yarn penetration densities can be the same or different.

[0156] [Glass cloth type T]

[0157] In the glass cloth disclosed herein, the thickness of the glass cloth is in the range of 20 to 25 μm, the warp width and weft width of the glass cloth are in the range of 176 to 232 μm and 239 to 353 μm respectively (also referred to as "cloth type T" in this disclosure), and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is in the range of 8.0% or less.

[0158] The glass cloth (cloth type T) disclosed herein, by having the above-described structure, provides a glass cloth with excellent offset characteristics, as well as excellent productivity and resin impregnation. The reasoning is not limited to theory, but is speculative as follows: A printed circuit board has copper foil patterns for receiving and transmitting signals on the surface of a laminate composed of a matrix resin and glass cloth. In the surface of the glass cloth, a difference in signal velocity (generally referred to as "offset") occurs between the matrix resin portion and the glass filament portion, mainly due to the discontinuous state existing in the mixture of voids filling the matrix resin and glass filament portions, and the difference in dielectric constant between the glass cloth and the matrix resin. Therefore, to improve the offset using the glass cloth, it is effective to increase the filament width of the glass cloth to make the surface of the glass cloth more uniform. Increasing the filament width of the glass cloth also improves resin impregnation. It should be noted that the printed circuit board is made of prepreg, which is obtained by impregnating a resin composition into glass cloth and then allowing it to semi-cure. By using glass cloth with high resin impregnation, it is less likely to generate voids (commonly referred to as voids) in the prepreg and the printed circuit board, thus improving insulation reliability. In addition, excellent resin impregnation also helps to improve the heat resistance of printed circuit boards, etc. Here, in order to increase the fiber width of the glass cloth, the method of splitting the glass cloth can usually be cited. However, if the glass cloth is split to increase the fiber width, the surface of the glass cloth will become fuzzy, resulting in a decrease in productivity. That is, the offset and the improvement of resin impregnation are inversely related to productivity (flocking quality). Therefore, the inventors conducted in-depth research and found that by designing the thickness of the glass cloth, as well as the warp and weft fiber widths, within an appropriate range, the fiber width can be fully split even without strengthening the splitting process of the glass cloth. That is, when the warp and weft widths of the glass cloth are in the range of 176–232 μm and 329–353 μm, respectively, by making the thickness of the glass cloth 20 μm or more, it is not necessary to excessively increase the width of the glass cloth fibers, nor is it necessary to strengthen the fiber-opening process of the glass cloth. Therefore, the pile quality of the glass cloth can be improved, and productivity can be increased. On the other hand, by making the thickness of the glass cloth 30 μm or less, the fiber width is sufficiently opened, improving offset and resin impregnation. Furthermore, since very fine patterns are formed on printed circuit boards using low-dielectric glass cloth, it is required to improve the offset characteristics of the glass cloth to a level higher than that currently. Therefore, the inventors conducted research and found that by setting the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, measured using a split cylindrical resonator, to 8.0% or less while keeping the thickness, warp width, and weft width of the glass cloth within the above-mentioned ranges, the offset characteristics of the printed circuit board can be significantly improved. The reason is that it was previously thought that the offset characteristics were caused by the difference in dielectric constant between the glass cloth and the matrix resin. However, the inventors have discovered that during the heating and degreasing process of the glass cloth, elements such as boron, which are easily volatilized by heating, change within the glass cloth surface. As a result, the dielectric constant within the glass cloth surface deviates significantly, which also affects the offset characteristics.Therefore, the inventors conceived of reducing not only the difference in offset properties between the glass cloth and the matrix resin, but also the difference in offset properties between the glass cloths themselves, by suppressing the deviation of the dielectric constant within the glass cloth's surface. Furthermore, in-depth research was conducted, and the results, as described later, show that by processing the glass cloth to make its surface composition more uniform, the deviation of the dielectric constant within the glass cloth's surface is reduced, leading to a significant improvement in the offset properties of the printed circuit board. Through these methods, a glass cloth that highly balances productivity, offset characteristics, and resin impregnation can be obtained.

[0159] The thickness of the glass cloth (cloth type T) is in the range of 20–30 μm, preferably in the range of 21–29 μm, more preferably in the range of 22–28 μm, even more preferably in the range of 23–27 μm, and particularly preferably in the range of 24–26 μm. When the thickness of the glass cloth is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained.

[0160] The warp and weft widths of the glass cloth (cloth type T) are in the range of 176–232 μm and 329–353 μm, respectively; preferably, they are in the range of 183–225 μm and 332–350 μm, respectively; more preferably, they are in the range of 190–218 μm and 335–347 μm, respectively; and particularly preferably, they are in the range of 197–211 μm and 338–344 μm, respectively. If the warp and weft widths of the glass cloth are within the above ranges, a glass cloth that better balances productivity and offset characteristics can be obtained.

[0161] The standard deviations of the warp and weft widths of the glass cloth (cloth type T) are preferably 20 μm or less and 43 μm or less, respectively. If the standard deviations of the filament widths are within the above ranges, it is easier to improve the offset characteristics of the glass cloth. From the viewpoint of more easily achieving improved offset characteristics, the standard deviations of the warp and weft widths of the glass cloth are more preferably 19 μm or less and 42 μm or less, further preferably 18 μm or less and 41 μm or less, and particularly preferably 17 μm or less and 40 μm or less. For example, the standard deviation of the filament width can be reduced by performing a fiber-opening treatment to widen the filament width of the glass cloth. Preferably, after surface treatment with a silane coupling agent, fiber-opening treatment is performed using high-pressure spraying or the like, and more preferably, the glass cloth is treated with ultrasound in water after a heat degreasing treatment to eliminate adhesion between the glass filaments. The lower limits of the standard deviations of the warp and weft widths are not limited; for example, they can be 5 μm or more and 10 μm or more, respectively.

[0162] The coefficient of variation of the dielectric constant of the glass cloth (cloth type T) measured at 10 GHz using a split cylindrical resonator is in the range of 8.0% or less. The inventors conducted research and found that, as described later, by controlling the amount of Na and Mg ions attached to the surface of the glass cloth and adjusting the heating degreasing conditions, it is possible to suppress variations in the composition of the glass fibers, thereby achieving a coefficient of variation of the dielectric constant of the glass cloth of 8.0% or less. From the viewpoint of easily obtaining improved offset characteristics, the coefficient of variation of the dielectric constant of the glass cloth is preferably in the range of 6.0% or less, more preferably in the range of 4.0% or less, and particularly preferably in the range of 2.0% or less. The lower limit of the coefficient of variation of the dielectric constant is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0163] The preferred warp and weft yarn penetration density of the glass cloth (cloth type T) is 60-80 yarns / 25mm, more preferably 61-79 yarns / 25mm, even more preferably 62-78 yarns / 25mm, and particularly preferably 63-77 yarns / 25mm. If the penetration density is within the above range, a glass cloth that better balances productivity, offset characteristics, and resin impregnation can be obtained. The warp and weft yarn penetration densities can be the same or different.

[0164] [Glass fiber]

[0165] The average diameter of the glass filaments constituting the glass fiber is preferably 2.5–9.0 μm, more preferably 2.5–7.5 μm, even more preferably 3.5–7.0 μm, and still more preferably 3.5–6.5 μm, particularly preferably 3.5–6.0 μm. If the filament diameter is within the above range, the breaking strength of the filaments is higher, and therefore the resulting glass cloth is less prone to fuzzing.

[0166] The coefficient of variation of the filament diameter is preferably 10.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less. If the coefficient of variation of the glass fiber filament diameter is 10.0% or less, the variation in the TEX of the glass fiber is smaller, thus suppressing deviations in the dielectric constant of the glass cloth. As a result, the offset characteristics of the printed circuit board are improved. The coefficient of variation of the TEX of the glass fiber is preferably 4.0% or less, more preferably 3.0% or less. If the coefficient of variation of the TEX of the glass fiber is 4.0% or less, deviations in the dielectric constant of the glass cloth can be effectively suppressed, resulting in further improvement in the offset characteristics of the printed circuit board. The coefficient of variation of the TEX of the glass fiber can be reduced by increasing the replacement frequency of the nozzle (bushing) during glass fiber spinning. The lower limit of the coefficient of variation of TEX is not limited and can exceed 0%, for example, it can be 1.0% or more.

[0167] [Glass Type A]

[0168] As one of the components of the glass fiber (glass type A), based on the total mass of the glass fiber and converted to oxides, it preferably contains 45-55% by mass of SiO2, 17-27% by mass of B2O3, 11-21% by mass of Al2O3, a total of 2.7-5.7% by mass of CaO and MgO, and a total of 0-0.15% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 46-54% by mass, further preferably in the range of 47-53% by mass, and particularly preferably in the range of 48-52% by mass. B2O3 is more preferably in the range of 18-26% by mass, further preferably in the range of 19-25% by mass, and particularly preferably in the range of 20-24% by mass. The content of Al2O3 is more preferably in the range of 12-20% by mass, more preferably in the range of 13-19% by mass, and particularly preferably in the range of 14-18% by mass. The total content of CaO and MgO is more preferably in the range of 3.0-5.4% by mass, more preferably in the range of 3.3-5.1% by mass, and particularly preferably in the range of 3.6-4.8% by mass. Alternatively, the total content of CaO and MgO can be in the range of 1.5-4.5% by mass, 2.0-4.0% by mass, 2.5-3.5% by mass, or 2.7-3.3% by mass. The total content of Li2O, K2O, and Na2O is more preferably in the range of 0.01-0.13% by mass, more preferably in the range of 0.02-0.11% by mass, and particularly preferably in the range of 0.03-0.09% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0169] From the viewpoint of improving the productivity of glass fiber (glass type A), the glass fiber, based on its total mass, preferably contains 0.15 to 0.45% by mass of TiO2, 2.5 to 7.5% by mass of P2O5, and 0 to 0.02% by mass of SrO, calculated in oxide terms. From the viewpoint of easily obtaining superior productivity, TiO2 is more preferably in the range of 0.17 to 0.43% by mass, further preferably in the range of 0.20 to 40% by mass, and particularly preferably in the range of 0.25 to 0.35% by mass. P2O5 is more preferably in the range of 3.0 to 7.0% by mass, further preferably in the range of 3.5 to 6.5% by mass, and particularly preferably in the range of 4.0 to 6.0% by mass. SrO is more preferably in the range of 0.0005 to 0.015% by mass, further preferably in the range of 0.001 to 0.010% by mass, and particularly preferably in the range of 0.0015 to 0.005% by mass. It should be noted that the contents described above, as described in the examples, can be determined by ICP emission spectroscopy.

[0170] [Glass Type B]

[0171] As one of the components of the glass fiber (glass type B), based on the total mass of the glass fiber and converted to oxides, it preferably contains 48-58% by mass of SiO2, 18-28% by mass of B2O3, 8-18% by mass of Al2O3, a total of 3.4-6.4% by mass of CaO and MgO, and a total of 0-0.15% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 49-57% by mass, further preferably in the range of 50-56% by mass, and particularly preferably in the range of 51-55% by mass. B2O3 is more preferably in the range of 19-27% by mass, further preferably in the range of 20-26% by mass, and particularly preferably in the range of 21-25% by mass. The content of Al2O3 is more preferably in the range of 9–17% by mass, further preferably in the range of 10–16% by mass, and particularly preferably in the range of 11–15% by mass. The total content of CaO and MgO is more preferably in the range of 3.6–6.2% by mass, further preferably in the range of 3.8–6.0% by mass, and particularly preferably in the range of 4.0–5.8% by mass. The total content of Li2O, K2O, and Na2O is more preferably in the range of 0.01–0.13% by mass, further preferably in the range of 0.03–0.11% by mass, and particularly preferably in the range of 0.05–0.09% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0172] From the viewpoint of improving the resistance of glass fibers (glass type B) to descaling (making it less likely for the glass to dissolve into the descaling solution), the glass fibers, based on their total mass and calculated in terms of oxides, preferably contain 0.9–2.9% by mass of TiO2, 0–0.03% by mass of P2O5, and 0–3% by mass of SrO. From the viewpoint of easily obtaining better productivity, TiO2 is more preferably in the range of 1.1–2.7% by mass, further preferably in the range of 1.3–2.5% by mass, and particularly preferably in the range of 1.5–2.3% by mass. P2O5 is more preferably in the range of 0.001–0.025% by mass, further preferably in the range of 0.002–0.023% by mass, and particularly preferably in the range of 0.003–0.020% by mass. SrO is more preferably in the range of 0.2–2.5% by mass, further preferably in the range of 0.2–2.0% by mass, and particularly preferably in the range of 0.4–1.5% by mass. It should be noted that the contents described above, as described in the examples, can be determined by ICP emission spectroscopy.

[0173] [Glass Type C]

[0174] As one of the components of the glass fiber (glass type C), based on the total mass of the glass fiber and converted to oxides, it preferably contains 48-58% by mass of SiO2, 17-27% by mass of B2O3, 11-21% by mass of Al2O3, a total of 3.5-6.5% by mass of CaO and MgO, and a total of 0-0.1% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 49-57% by mass, further preferably in the range of 50-56% by mass, and particularly preferably in the range of 51-55% by mass. B2O3 is more preferably in the range of 18-26% by mass, further preferably in the range of 19-25% by mass, and particularly preferably in the range of 20-24% by mass. The content of Al2O3 is more preferably in the range of 12-20% by mass, further preferably in the range of 13-19% by mass, and particularly preferably in the range of 14-18% by mass. The total content of CaO and MgO is more preferably in the range of 3.7-6.3% by mass, further preferably in the range of 4.0-6.0% by mass, and particularly preferably in the range of 4.5-5.5% by mass. The total content of Li2O, K2O, and Na2O is more preferably in the range of 0.005-0.09% by mass, further preferably in the range of 0.01-0.08% by mass, and particularly preferably in the range of 0.02-0.07% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0175] From the viewpoint of improving the productivity of glass fiber (glass type C), the glass fiber, based on its total mass, preferably contains 0-0.3% by mass of TiO2, 0-4.2% by mass of P2O5, and 0-1% by mass of SrO, calculated in oxide terms. From the viewpoint of easily obtaining superior productivity, TiO2 is more preferably in the range of 0.005-0.25% by mass, further preferably in the range of 0.01-0.20% by mass, and particularly preferably in the range of 0.013-0.15% by mass. P2O5 is more preferably in the range of 1.0-4.0% by mass, further preferably in the range of 1.3-3.7% by mass, and particularly preferably in the range of 1.6-3.4% by mass. SrO is more preferably in the range of 0.05-0.9% by mass, further preferably in the range of 0.1-0.8% by mass, and particularly preferably in the range of 0.14-0.7% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0176] [Glass Type D]

[0177] As one of the components of the glass fiber (glass type D), based on the total mass of the glass fiber and converted to oxides, it preferably contains 47-57% by mass of SiO2, 22-32% by mass of B2O3, 8-18% by mass of Al2O3, a total of 1.4-4.4% by mass of CaO and MgO, and a total of 0.1-1.0% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 48-56% by mass, further preferably in the range of 49-55% by mass, and particularly preferably in the range of 50-54% by mass. B2O3 is more preferably in the range of 23-31% by mass, further preferably in the range of 24-30% by mass, and particularly preferably in the range of 25-29% by mass. The content of Al2O3 is more preferably in the range of 9–17% by mass, further preferably in the range of 10–16% by mass, and particularly preferably in the range of 11–15% by mass. The total content of CaO and MgO is more preferably in the range of 1.6–4.2% by mass, further preferably in the range of 1.8–4.0% by mass, and particularly preferably in the range of 2.0–3.8% by mass. The total content of Li2O, K2O, and Na2O is more preferably in the range of 0.12–0.9% by mass, further preferably in the range of 0.14–0.7% by mass, and particularly preferably in the range of 0.16–0.5% by mass. Alternatively, the total content of Li2O, K2O, and Na2O can be in the range of 0.1–0.5% by mass, 0.12–0.48% by mass, 0.14–0.46% by mass, or 0.16–0.44% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0178] From the viewpoint that bubbles are unlikely to enter the interior of the glass fiber (glass type D), the glass fiber, based on its total mass and converted to oxides, preferably contains 0-1% by mass of TiO2, 0-0.2% by mass of P2O5, and 0-0.3% by mass of SrO. From the viewpoint that it is easier to produce uniform glass fiber without allowing bubbles to enter, TiO2 is further preferably in the range of 0.1-0.9% by mass, even more preferably in the range of 0.2-0.8% by mass, and particularly preferably in the range of 0.3-0.7% by mass. P2O5 is more preferably in the range of 0.003-0.18% by mass, further preferably in the range of 0.006-0.16% by mass, and particularly preferably in the range of 0.008-0.14% by mass. SrO is more preferably in the range of 0.001-0.25% by mass, further preferably in the range of 0.01-0.20% by mass, and particularly preferably in the range of 0.02-0.15% by mass. It should be noted that the contents described above, as described in the examples, can be determined by ICP emission spectroscopy.

[0179] [Glass Type E]

[0180] As one of the components (glass type E) of the glass fiber in this embodiment, based on the total mass of the glass fiber and converted to oxides, it preferably contains 47-57% by mass of SiO2, 18-28% by mass of B2O3, 9-19% by mass of Al2O3, 3.4-6.4% by mass of CaO and MgO, and 0-0.3% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 48-56% by mass, further preferably in the range of 49-55% by mass, and particularly preferably in the range of 50-54% by mass. B2O3 is more preferably in the range of 19-27% by mass, further preferably in the range of 20-26% by mass, and particularly preferably in the range of 21-25% by mass. Alternatively, B2O3 can be in the range of 19–29% by mass, 20–28% by mass, 21–27% by mass, or 22–26% by mass. Al2O3 is more preferably in the range of 10–18% by mass, further preferably in the range of 11–17% by mass, and particularly preferably in the range of 12–16% by mass. Alternatively, Al2O3 can be in the range of 7–17% by mass, 8–16% by mass, 9–16% by mass, or 10–15% by mass. The combined value of CaO and MgO is more preferably in the range of 3.6–6.2% by mass, further preferably in the range of 3.8–6.0% by mass, and particularly preferably in the range of 4.1–5.7% by mass. The combined value of Li2O, K2O, and Na2O is more preferably in the range of 0.01–0.25% by mass, further preferably in the range of 0.02–0.20% by mass, and particularly preferably in the range of 0.03–0.15% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0181] From the viewpoint of making it difficult for bubbles to enter the interior of the glass fiber (glass type E) and improving the fluff quality of the glass fiber, the glass fiber, based on its total mass and calculated in terms of oxides, preferably contains 0.01 to 0.3% by mass of TiO2, 0 to 0.2% by mass of P2O5, and 0 to 0.3% by mass of SrO. From the viewpoint of not only making it easier to produce uniform glass fiber without the entry of bubbles, but also making it easier to control the fluff quality to a stable level, TiO2 is more preferably in the range of 0.02 to 0.25% by mass, further preferably in the range of 0.03 to 0.2% by mass, and particularly preferably in the range of 0.04 to 0.15% by mass. P2O5 is more preferably in the range of 0.001 to 0.15% by mass, further preferably in the range of 0.0015 to 0.12% by mass, and particularly preferably in the range of 0.002 to 0.08% by mass. The SrO content is more preferably in the range of 0.0001 to 0.25% by mass, more preferably in the range of 0.0005 to 0.20% by mass, and particularly preferably in the range of 0.001 to 0.10% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0182] [Glass Type F]

[0183] As one of the components (glass type F) of the glass fiber in this embodiment, based on the total mass of the glass fiber and converted to oxides, it preferably contains 47-57% by mass of SiO2, 20-30% by mass of B2O3, 8-18% by mass of Al2O3, a total of 3.0-7.0% by mass of CaO and MgO, and a total of 0-0.3% by mass of Li2O, K2O, and Na2O. By making the glass composition within the above range, it is easy to provide a glass cloth exhibiting a low dielectric constant and a low dielectric loss tangent. From the viewpoint of easily obtaining a glass cloth with an even lower dielectric loss tangent, SiO2 is more preferably in the range of 48-56% by mass, further preferably in the range of 49-55% by mass, and particularly preferably in the range of 50-54% by mass. B2O3 is more preferably in the range of 21-29% by mass, further preferably in the range of 22-28% by mass, and particularly preferably in the range of 23-27% by mass. The content of Al2O3 is more preferably in the range of 9–17% by mass, further preferably in the range of 10–16% by mass, and particularly preferably in the range of 11–15% by mass. The total content of CaO and MgO is more preferably in the range of 3.2–6.8% by mass, further preferably in the range of 3.4–6.6% by mass, and particularly preferably in the range of 3.6–6.4% by mass. The total content of Li2O, K2O, and Na2O is more preferably in the range of 0.001–0.25% by mass, further preferably in the range of 0.002–0.2% by mass, and particularly preferably in the range of 0.003–0.1% by mass. It should be noted that the above contents, as described in the examples, can be determined by ICP emission spectroscopy.

[0184] From the viewpoint of ensuring good spinning stability by preventing bubbles from entering the interior of the glass fiber (glass type E) and enabling uniform glass melting, the glass fiber, based on its total mass and converted to oxides, preferably contains 1.0 to 5.0% by mass of TiO2, 0 to 0.1% by mass of P2O5, and 0 to 0.2% by mass of SrO. From the viewpoint of easily producing uniform glass fiber without the entry of bubbles and easily obtaining glass fiber with excellent spinning stability, TiO2 is more preferably in the range of 1.2 to 4.8% by mass, further preferably in the range of 1.5 to 4.5% by mass, and particularly preferably in the range of 1.8 to 4.2% by mass. P2O5 is more preferably in the range of 0 to 0.08% by mass, further preferably in the range of 0 to 0.05% by mass, and particularly preferably in the range of 0 to 0.03% by mass. SrO is more preferably in the range of 0 to 0.01% by mass, further preferably in the range of 0 to 0.005% by mass, and particularly preferably in the range of 0 to 0.001% by mass. It should be noted that the contents described above, as described in the examples, can be determined by ICP emission spectroscopy.

[0185] [Na ion content and Mg ion content]

[0186] The amounts of Na ions and Mg ions attached to the surface of the glass cloth before heat degreasing are preferably in the ranges of 0–50 ppm and 0–30 ppm, respectively. The inventors conducted research and determined that when the glass cloth is subjected to heat degreasing treatment at a high temperature of 300–400°C, the Na ions and Mg ions attached to the glass surface are absorbed into the glass interior. It was determined that because the Na ions and Mg ions are absorbed into the glass interior, the original glass composition is modified, thus changing the dielectric constant and dielectric loss tangent of the glass. Therefore, by controlling the Na ions and Mg ions attached to the surface of the glass cloth before heat degreasing within a certain range, the difference in dielectric constant between the length and width directions of the glass cloth can be suppressed, resulting in a glass cloth with excellent offset characteristics. From the viewpoint of easily obtaining improved offset characteristics, the amount of Na ions attached to the surface of the glass cloth is preferably 40 ppm or less, more preferably 30 ppm or less, further preferably 20 ppm or less, and particularly preferably 10 ppm or less. In addition, the amount of Mg ions adhering to the surface of the glass cloth is preferably 25 ppm or less, more preferably 20 ppm or less, even more preferably 15 ppm or less, and particularly preferably 10 ppm or less.

[0187] The amount of Na and Mg ions adhering to the surface of the glass cloth can be controlled by the glass cloth manufacturing method described later. Specifically, it can be controlled by the cleaning of the glass cloth, the ion content of the solvent used in the cleaning, and the amount of sizing agent adhering. The amount of Na and Mg ions was determined by the method described in the examples.

[0188] [Sizing agent]

[0189] The glass cloth before heat degreasing can be surface-treated with a sizing agent. That is, the glass fibers can be surface-treated with a sizing agent. From the viewpoint of improving the bundled properties of the glass fibers, reducing fuzz, and improving weavability, the sizing agent preferably contains at least one main component selected from the group consisting of starch, PVA resin, polyurethane resin, epoxy resin, and acrylic resin. From the viewpoint of suppressing fuzz in the glass cloth, the sizing agent more preferably contains starch and / or PVA resin as the main component. Here, "main component" refers to the component that accounts for the largest percentage by mass in the sizing agent, such as a component accounting for 50% or more by mass, 65% or more by mass, 80% or more by mass, or 95% or more by mass.

[0190] Manufacturing Method of Fiberglass Cloth

[0191] The method for manufacturing glass cloth disclosed herein includes a step of weaving glass filaments, formed from multiple glass filaments, as warp and weft yarns to obtain glass cloth (weaving step). Preferably, the method includes, before the weaving step, a step of checking whether the coefficient of variation (TEX) of the glass filaments used is 4.0% or less (TEX inspection step). Preferably, the method further includes, before, during, or after the weaving step, a step of opening the glass filaments before heat degreasing (preheat degreasing opening step); a step of cleaning the glass filaments before heat degreasing with a solvent (preheat degreasing cleaning step); and a subsequent step of heat degreasing the glass filaments (heat degreasing step). This not only suppresses the influence of TEX variations in the glass cloth, but also suppresses the deviation of the dielectric loss tangent of the glass cloth by suppressing variations in the glass composition caused by the heat degreasing step. The method for manufacturing glass cloth disclosed herein may further include a step of washing and splitting cleaned and heated degreased glass fibers while conveying them in a liquid irradiated with ultrasonic waves at a speed of 50 m / min or less (washing and splitting step). This allows for easy adjustment of the warp and weft widths of the glass cloth, as well as their standard deviations, to the aforementioned preferred ranges, thereby providing a glass cloth with excellent resin impregnation properties and improved heat resistance of printed circuit boards, etc.

[0192] The aforementioned glass processing method (fiber opening process before heating and degreasing, cleaning process before heating and degreasing, heating and degreasing, and cleaning and fiber opening process) can be applied to glass fibers before weaving, or it can also be applied to woven glass cloth. In other words, the process of weaving glass fibers to obtain glass cloth can be set before, during, or after the glass processing method. The method may also include a surface treatment process and a fiber opening process after the heating and degreasing process. Hereinafter, an example will be given, which includes the TEX inspection process, the fiber opening process before heating and degreasing, the cleaning process before heating and degreasing, the heating and degreasing process, the cleaning and fiber opening process, the surface treatment process, and the fiber opening process after surface treatment. However, the glass cloth manufacturing method disclosed herein is not limited to this.

[0193] [TEX Inspection Procedure for Glass Fibers]

[0194] The glass fibers used in the glass cloth disclosed herein have all their TEX measured, and preferably only glass fibers with a coefficient of variation of 4.0% or less are used. It should be noted that the TEX of the glass fibers is measured using the method described in JIS 3420 7.1. If the deviation of the TEX value of the glass fibers is small, the deviation of the dielectric constant and dielectric loss tangent within the printed circuit board surface can be further reduced, thus further improving the offset characteristics.

[0195] [Fiber opening process before heating and degreasing]

[0196] The glass cloth disclosed herein is preferably subjected to fiber-opening treatment before heat degreasing. By performing fiber-opening treatment on the glass cloth before heat degreasing, the filament width can be efficiently increased without the formation of lint on the surface of the glass cloth. The fiber-opening method is not particularly limited, and methods such as using water spray (high-pressure water fiber opening), vibrating washing machine, ultrasonic water, and liquid rolling mill can be cited. From the viewpoint that it is easy to wash off the sizing agent adhering to the surface of the glass filaments while performing fiber opening treatment, the fiber opening methods using water spray (high-pressure water fiber opening) and vibrating washing machine are preferred.

[0197] [Cleaning process before heating and degreasing]

[0198] The pre-heat degreasing cleaning process includes a step of reducing the amount of sizing agent by cleaning the glass cloth before heat degreasing with a solvent. This reduces adhesion caused by the sizing agent on the glass filaments and by combustion residue of the sizing agent during heat degreasing, thereby improving the resin impregnation of the resulting glass cloth. From the viewpoint of cleaning efficiency, water is preferably used as the cleaning solvent in this process, and the temperature is preferably 50°C or higher. By using water at 50°C or higher, the amount of sizing agent required to protect the glass filaments up to the heat degreasing process can be retained, while the remaining sizing agent is cleaned. The water temperature is preferably 50°C or higher and less than 100°C. The lower limit of the water temperature is more preferably 55°C or higher, further preferably 60°C or higher, and even more preferably 65°C or higher. The upper limit of the water temperature that can be combined with these lower limits is more preferably 95°C or lower, and further preferably 90°C or lower. The cleaning method for the glass cloth blank is not particularly limited; for example, ultrasonic methods (e.g., methods using an ultrasonic vibrator), spray-based spraying (e.g., high-pressure spraying), steam spraying, etc., can be considered. From the viewpoint of enabling inexpensive processing, a preferred method is to immerse the glass cloth blank in a tank containing a cleaning solution, remove excess cleaning solution using a squeeze roller or similar device, and then dry the glass cloth blank. In this case, the immersion time can be, for example, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, and 120 seconds or less, 90 seconds or less, 60 seconds or less, or 45 seconds or less.

[0199] To easily control the coefficient of variation of the dielectric constant of the glass cloth to below 8.0%, the cleaning water used in the pre-heating degreasing cleaning process is preferably low in impurities, such as RO water, ion-exchange water, or distilled water. Specifically, the Na ion content of the cleaning water is preferably below 20 ppm, more preferably below 15 ppm, further preferably below 12 ppm, even more preferably below 10 ppm, particularly preferably below 7 ppm, and most preferably below 1.5 ppm. If the Na ion content of the cleaning solution is below 20 ppm, it is easier to reduce the amount of Na ions adhering to the surface of the glass cloth. In addition, the Mg ion content is preferably below 18 ppm, more preferably below 12 ppm, further preferably below 8 ppm, even more preferably below 6 ppm, particularly preferably below 3 ppm, and most preferably below 1 ppm. If the Mg ion content of the cleaning solution is below 18 ppm, it is easier to reduce the amount of Mg ions adhering to the surface of the glass cloth. The inventors have clarified that by reducing the amount of Na and Mg ions, during the heat degreasing treatment of glass cloth, it is possible to suppress the ion exchange reaction between Na and Mg ions adhering to the surface of the glass fibers and the glass composition. As a result, the deviations in the dielectric constant and dielectric loss tangent of the glass cloth are further reduced. Therefore, by washing the glass cloth with cleaning water containing Na and Mg ions within the aforementioned range, the offset characteristics can be further improved.

[0200] [Heating and degreasing process]

[0201] In the heat degreasing process, any known heating method, heating medium, heating mechanism, heating device, and heating components can be used as long as the heat degreasing temperature can be appropriately controlled. However, from a productivity point of view, it is generally known that glass cloth is processed in multiple rolls in an intermittent oven while wound around a metal core tube (intermittent oven method). In this intermittent oven method, the surface side of the glass cloth roll is easily heated, while the inner layer is difficult to heat, resulting in different thermal histories on the surface and inner layers. Regarding this, the inventors aimed to suppress the deviation of the dielectric constant within the glass cloth surface by reducing the previously neglected difference in thermal histories between the surface and inner layers. Furthermore, the inventors conducted in-depth research and found that performing heat degreasing treatment multiple times is effective in making the thermal histories of the glass cloth roll as uniform as possible. Specifically, by rewinding the glass cloth that has undergone heat degreasing treatment to another metal core tube, and reversing the inner and outer layers of the glass cloth, the same heat degreasing treatment is performed again, thereby enabling heat degreasing treatment that homogenizes the thermal process in both the width and length directions of the glass cloth.

[0202] To reduce the deviation in the dielectric constant of the glass cloth, the temperature for the heating degreasing treatment is preferably 330–450°C, more preferably 340–440°C, even more preferably 350–430°C, and particularly preferably 360–420°C. Furthermore, to thoroughly remove the sizing agent adhering to the surface of the glass cloth, the heating time is preferably 24–72 hours, more preferably 30–60 hours, and even more preferably 40–55 hours. By reducing the number of times the glass cloth is unwound and the heating degreasing treatment is performed, the deviation in the dielectric constant of the glass cloth can be suppressed, and the pile quality of the glass cloth can be well maintained. Therefore, to balance the deviation in dielectric constant and the pile quality, it is particularly preferable to perform one unwound treatment and two heating degreasing treatments.

[0203] [Cleaning and fiber opening process]

[0204] The preferred method for the cleaning and fiber-opening process is to irradiate the glass cloth in a liquid with ultrasonic waves after the heating and degreasing process and before the surface treatment process, thereby primarily cleaning out the combustion residue from the heating and degreasing process and performing fiber opening (ultrasonic cleaning). Preferably, the process involves handling the glass cloth in a liquid irradiated with ultrasonic waves by an ultrasonic oscillator, using a roll-to-roll conveying method.

[0205] As a liquid used for ultrasonic cleaning, either water or organic solvents can be used, but from the perspective of safety and environmental protection, a water-based liquid is preferred. Surfactants and pH adjusters can also be added to the liquid used for cleaning to improve cleaning efficiency.

[0206] There are no particular restrictions on the temperature of the liquid used in ultrasonic cleaning, but from the viewpoint of improving cleaning effectiveness, a temperature of 5°C or higher is preferred. Furthermore, from a safety perspective, the temperature of the cleaning liquid is preferably below 60°C.

[0207] By immersing the glass cloth in a liquid irradiated with ultrasonic waves, it can be cleaned by irradiating the glass cloth with ultrasonic waves in the liquid. The linear tension acting on the warp threads during the cleaning process is preferably 30N to 500N / 1m.

[0208] Ultrasonic cleaning can utilize ultrasonic waves with frequencies of 20 kHz or higher and 200 kHz or lower. The preferred ultrasonic frequency is 20 kHz or higher and 50 kHz or lower, more preferably 20 kHz or higher and 30 kHz or lower. Using ultrasonic waves with frequencies of 20 kHz or higher and 200 kHz or lower allows for cleaning without significant drawbacks such as the weft of the glass cloth, and is therefore preferred.

[0209] Ultrasonic cleaning can preferably use 0.07W / cm. 2 Above and 3.60W / cm2 The following are ultrasonic waves with output power. A more preferred range for ultrasonic output power is 0.14 W / cm². 2 Above and 2.16W / cm 2 The further preferred range is 0.21 W / cm. 2 Above and 1.44W / cm 2 The ultrasonic output power is as follows: 0.07W / cm² 2 At the above levels, it can perform cleaning effectively, with an ultrasonic output power of 3.60 W / cm². 2 The following method allows for uniform cleaning without the occurrence of weft or other defects, making it the preferred choice.

[0210] The conveying speed of the glass cloth in ultrasonic cleaning is preferably 50 m / min or less, more preferably 40 m / min or less, and particularly preferably 30 m / min or less. If the conveying speed of the glass cloth is 50 m / min or less, the glass cloth or its intermediates can be cleaned and split effectively. Furthermore, this speed is preferred because it can suppress lint and yarn misalignment caused by damage during conveying.

[0211] In liquids used for ultrasonic cleaning, dissolved air, primarily composed of nitrogen and oxygen, is typically present. However, the dissolved oxygen content (by weight) is preferably 1 ppm to 20 ppm, more preferably 3 ppm to 17 ppm, and even more preferably 4 ppm to 14 ppm. By managing the dissolved oxygen content, the amount of dissolved gas can be indirectly controlled, thereby controlling the degree to which the dissolved gas attenuates the ultrasonic waves. A dissolved oxygen content of 1 ppm or higher allows for uniform fiber opening, and is therefore preferred. A dissolved oxygen content of 20 ppm or lower provides good cleaning properties to fibrous fabrics, and is therefore preferred. A uniform and good fiber opening effect can be obtained within the dissolved oxygen content range of 1 ppm to 20 ppm, and is therefore preferred.

[0212] [Surface treatment process]

[0213] The surface treatment process involves attaching a surface treatment agent, such as a silane coupling agent, to a glass cloth. For example, it may include at least one of the following steps: a covering step that attaches the surface treatment agent to the glass surface, and a fixing step that fixes the surface treatment agent to the glass surface by heating and drying. This allows for easy and appropriate surface treatment of the glass.

[0214] Methods for applying surface treatment agents include coating the glass cloth with a treatment solution containing the surface treatment agent or immersing the glass cloth in the treatment solution. Methods for applying the treatment solution to the glass during the covering process include (a) immersing the glass in or passing it through a treatment solution stored in a tank (hereinafter referred to as the "immersion method"), and (b) applying the treatment solution to the glass using a roller coater, die coater, or gravure coater. When using the immersion method, it is preferable to select an immersion time of 0.5 seconds or more and 1 minute or less in the treatment solution. Furthermore, when using the immersion method, the glass can be passed through the treatment solution at a conveying speed of 10 to 50 m / min while being subjected to a specified tension (e.g., 100 to 250 N). Additionally, after applying the treatment solution to the glass, the solvent contained in the treatment solution can be heated and dried using methods such as hot air or electromagnetic waves.

[0215] The concentration of the surface treatment agent contained in the treatment solution is preferably 0.1 to 1.0% by mass, more preferably 0.1 to 0.8% by mass, and even more preferably 0.1 to 0.5% by mass. This makes it easier and more appropriate to perform surface treatment on the glass.

[0216] In the fixed process, in order to fully allow the surface treatment agent, such as a silane coupling agent, to react with the glass, the heating and drying temperature is preferably 80°C or higher, more preferably 90°C or higher. Furthermore, in order to prevent the deterioration of the organic groups present in the surface treatment agent, such as the silane coupling agent, the heating and drying temperature is preferably 300°C or lower, more preferably 180°C or lower.

[0217] [Finite opening process after surface treatment]

[0218] As a process for opening bonded glass filaments using a surface treatment agent, methods such as spray water (high-pressure water opening), vibrating washing machine, ultrasonic water, or mangle can be used to open the glass cloth. During this opening process, by reducing the tension applied to the glass cloth, there is a tendency to further increase the filament width. It should be noted that, in order to suppress the generation of fuzz in the glass cloth caused by the opening process, it is preferable to implement measures such as low friction between the glass filaments and contact parts during weaving, as well as optimization and high adhesion of the surface treatment agent.

[0219] The processes described above do not necessarily need to be performed in separate processes; multiple processes can be combined into one. The composition of the glass cloth usually remains unchanged before and after fiber opening. Furthermore, the manufacturing method of glass cloth can include any processes other than those described above. For example, a slit-forming process can be performed after the fiber opening process. Additionally, the order of the above processes can be reversed if possible.

[0220] Prepreg

[0221] The prepreg disclosed herein contains the glass cloth of this disclosure and a matrix resin. Therefore, it is possible to provide a prepreg capable of improving the offset characteristics, etc., of printed circuit boards. Examples of matrix resins include thermosetting resins, thermoplastic resins, and combinations thereof.

[0222] Examples of thermosetting resins include: (a) epoxy resins, which are formed by reacting a compound having an epoxy group with a compound having at least one of an amino group, phenolic group, acid anhydride group, hydrazide group, isocyanate group, cyanate group, and hydroxyl group that reacts with the epoxy group under catalyst-free conditions, or by adding a catalyst with reaction catalytic ability such as an imidazole compound, tertiary amine compound, urea compound, or phosphorus compound; and (b) free radical polymerization type curing resins, which are formed using a thermally decomposable catalyst. (c) A compound having at least one of allyl, methacrylate, and acrylic groups, which is cured by using a photocatalyst as a reaction initiator; (d) A maleimide triazine resin which is formed by reacting a compound having a cyanate group with a compound having a maleimide group and then curing it; (e) A thermosetting polyimide resin which is formed by reacting a maleimide compound with an amine compound and then curing it; (f) A benzoxazine resin which is formed by crosslinking and curing a compound having a benzoxazine ring through heating polymerization; etc.

[0223] Examples of thermoplastic resins include polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, aromatic polyamide, polyetheretherketone, thermoplastic polyimide, insoluble polyimide, polyamide-imide, LCP, polyester, cycloolefin polymers, and fluoropolymers.

[0224] The prepreg may further contain inorganic fillers. 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 fillers are thermosetting resins. Thermoplastic resins and both can be used in combination.

[0225] Printed Circuit Boards

[0226] The printed circuit board disclosed herein incorporates the prepreg of this disclosure. This provides a printed circuit board with excellent offset characteristics, etc.

[0227] Integrated Circuits and Electronic Devices

[0228] The integrated circuit disclosed herein includes the printed circuit board of this disclosure. Additionally, the electronic device disclosed herein includes the printed circuit board of this disclosure. Thus, an integrated circuit and an electronic device with excellent offset characteristics are provided. Examples of electronic devices include information terminals such as smartphones, and the integrated circuit can be used to increase the performance of electronic devices and to enable high-speed communication, exemplified by 5G communication.

[0229] [Example]

[0230] Next, embodiments and comparative examples of this disclosure will be described. This disclosure is not limited in any way by the following embodiments and comparative examples. Various evaluation methods will be described below.

[0231] Determination Method

[0232] [Methods for measuring the thickness of glass cloth]

[0233] According to JISR 3420 7.10, which specifies the general test methods for products such as glass fibers and glass cloth using glass fibers, a micrometer is used to quietly rotate the mandrel and gently contact it parallel to the test surface, and the scale is read after the ratchet clicks three times.

[0234] [Method for determining the weight per unit area (weight of glass cloth)]

[0235] The weight per unit area of ​​the fabric is determined by cutting the fabric to a specified size and dividing its weight by the sample area. In this embodiment, the glass cloth is cut into 10cm pieces. 2 The dimensions and weight of each glass cloth are determined, and the weight per unit area of ​​each glass cloth is calculated accordingly.

[0236] [Number of warp and weft filaments and diameter of each filament (μm)]

[0237] The number of warp and weft filaments and their diameters are determined by observing cross-sectional images of the glass fiber. Specifically, a cross-sectional image of the glass fiber used as a warp (or weft) is obtained, and the number of warp (or weft) filaments and their diameters are measured within this image. Similarly, the acquisition of images and the measurement of filament counts are repeated, and the average of the five measurements is taken as the number of warp (or weft) filaments and their diameters.

[0238] [Converted Thickness]

[0239] Glass cloth is a discontinuous planar body formed by air and glass. Therefore, the equivalent thickness required for measurement by the resonance method can be calculated by dividing the weight per unit area of ​​each piece of glass cloth by the bulk density of the glass.

[0240] Conversion thickness (μm) = Weight per unit area (g / m²) 2 ) ÷ Bulk density of glass (g / cm³)3 )

[0241] [Methods for determining the dielectric constant and dielectric loss tangent of glass cloth]

[0242] According to JIS R1641 / IEC 62562, which specifies the method for measuring the dielectric properties of fine ceramic materials used in microwave circuits in the microwave band, the dielectric loss tangent of each glass cloth was measured. Specifically, glass cloth samples, taken according to the dimensions required for measurement using each resonator, were conditioned in a constant temperature and humidity oven at 23°C and 50% RH for at least 8 hours. Measurements were then performed using a split cylindrical resonator (manufactured by EM Labs) and an impedance analyzer (manufactured by Agilent Technologies). A total of 27 sampling points were taken, each at 3 points in the width direction, corresponding to 5%, 10%, 20%, 30%, 50%, 70%, 80%, 90%, and 95% of the length from the surface of the glass cloth roll, relative to the total length of the roll. Based on the results of these 27 measurements, the average value and coefficient of variation of the dielectric constant and dielectric loss tangent at 10 GHz were calculated. Furthermore, the thickness of each sample was measured using the aforementioned converted thickness.

[0243] Coefficient of variation (%) = Standard deviation ÷ Mean × 100

[0244] [Warp width and weft width]

[0245] The warp and weft widths of the glass cloth were determined using the following method. First, five samples of glass cloth, each 100 mm in the warp direction and 100 mm in the weft direction, were cut from the glass cloth. The cut samples were then observed vertically at 100x magnification using a microscope. For each sample, the width of 250 warp (or weft) yarns was randomly measured, and the average and standard deviation of the obtained 250 warp (or weft) yarn widths were calculated. This average value was then used as the warp (or weft) width.

[0246] [Determination of Na ion, Mg ion, and SO4 ion content in cleaning solution]

[0247] The amounts of Na, Mg, and SO4 ions in the cleaning solution used to clean glass cloth before heating and degreasing were determined by ion chromatography.

[0248] <Preprocessing conditions>

[0249] The sample was adjusted by diluting it appropriately with distilled water.

[0250] <Cation Ion Chromatography Conditions>

[0251] Device: Tosoh, IC-2010

[0252] Separation column: Tosoh, TSKgel-Super IC-Cation / P (4.6mm × 150mm)

[0253] Separation solution: 2.5 mM HNO3 + 0.5 mM L-histidine

[0254] Flow rate: 1.0 mL / min

[0255] Testing: Conductivity

[0256] Column temperature: 40℃

[0257] Injection volume: 30μL

[0258] <Anion Chromatography Conditions>

[0259] Device: Tosoh, IC-2010

[0260] Separation column: Tosoh, TSKgel-Super IC-AZ (4.6mm × 150mm)

[0261] Eluent: 6.3mM NaHCO3 + 1.7mM Na2CO3

[0262] Flow rate: 0.8 mL / min

[0263] Testing: Conductivity

[0264] Column temperature: 40℃

[0265] Injection volume: 30μL

[0266] [Determination of Na ion, Mg ion, and SO4 ion content on the surface of glass cloth before heating and degreasing]

[0267] The amounts of Na, Mg, and SO4 ions on the surface of glass cloth (the raw cloth) before heating and degreasing were determined using ion chromatography.

[0268] <Preprocessing conditions>

[0269] Cut a piece of glass cloth into 18cm x 7cm lengths and place it in a cleaning bottle (manufactured by Wakayama CIC Research Institute, product name: Clean Pack Good Boy 100ml (SCC: already cleaned with ultrapure water), AS ONE model: 7-2214-01). Next, immerse it in 10ml of distilled water at room temperature and then irradiate with ultrasound for 30 minutes. Then, let it stand overnight at room temperature (20°C–25°C, e.g., 23°C) and centrifuge (12000 rpm x 15 minutes). The supernatant, from which foreign matter originating from the glass cloth has been removed, is then used as a sample. The supernatant obtained without adding glass cloth during the same procedure is used as a blank. It should be noted that the amounts of Na ions, Mg ions, and SO4 ions (ppm) adhering to the surface of the glass cloth are calculated using the following formulas.

[0270] The amount of each ion adhering to the surface of the glass cloth (ppm) = (the amount of each ion in the supernatant with glass cloth added (μg / ml) - the amount of each ion in the blank supernatant (μg / ml)) × 10 (ml) / the mass of the glass cloth (g)

[0271] <Cation Ion Chromatography Conditions>

[0272] Device: Tosoh, IC-2010

[0273] Separation column: Tosoh, TSKgel-Super IC-Cation / P (4.6mm × 150mm)

[0274] Elution buffer: 2.5 mM HNO3 + 0.5 mM L-histidine

[0275] Flow rate: 1.0 mL / min

[0276] Testing: Conductivity

[0277] Column temperature: 40℃

[0278] Injection volume: 30μL

[0279] <Anion Chromatography Conditions>

[0280] Device: Tosoh, IC-2010

[0281] Separation column: Tosoh, TSKgel-Super IC-AZ (4.6mm × 150mm)

[0282] Eluent: 6.3mM NaHCO3 + 1.7mM Na2CO3

[0283] Flow rate: 0.8 mL / min

[0284] Testing: Conductivity

[0285] Column temperature: 40 °C

[0286] Injection volume: 30 μL

[0287] [Content of each element contained in glass fiber]

[0288] The content of each element constituting the glass fiber is determined by the absolute calibration curve method using an ICP mass spectrometer.

[0289] [Content of SiO2, B2O3, and Al2O3 (mass%)]

[0290] In order to reduce impurities (such as sizing agents, etc.) adhering to the glass cloth, glass fiber, or their raw materials, the preparation of the determination solution was carried out by the following method. That is, the glass fiber (sample) was weighed, then hydrolyzed with sodium hydroxide and dissolved with dilute nitric acid to prepare the determination solution.

[0291] For the obtained determination solution, the content of silicon was measured using an ICP emission spectrometer (PS3520VDDII manufactured by Hitachi High-Tech Science Corporation), and then converted into an oxide value to determine the content of SiO2, B2O3, and Al2O3 contained in the sample.

[0292] [Content of CaO, MgO, Li2O, K2O, Na2O, TiO2, P2O5, SrO (mass%)]

[0293] The weighed glass cloth or glass fiber (sample) was decomposed by heating with sulfuric acid, nitric acid, and hydrofluoric acid, and then dissolved by heating with dilute nitric acid to prepare the determination solution. For the obtained determination solution, the content of each element in the sample was determined by ICP emission spectrometry and converted into an oxide value (ICP emission spectrometer PS3250VDDII manufactured by Hitachi High-Tech Science, atomic absorption spectrometer ZA3300 manufactured by Hitachi High-Tech Science).

[0294] [TEX of glass fiber]

[0295] The TEX of the glass fiber was measured in accordance with R 3420:2013. The average value and standard deviation were obtained from 15 TEX measurement operations.

[0296] <<Manufacturing example of glass cloth>>

[0297] [Manufacture of cloth type P]

[0298] Glass fiber cloth P was obtained by weaving glass fibers using an air-jet loom with a weaving density of 65 warp threads / 25mm and 67 weft threads / 25mm. It should be noted that the weaving was performed with a glass fiber cloth width of 1300mm. Glass fibers with an average filament diameter of 5.0μm, 100 filaments, and a twist count of 1.0Z were used as both warp and weft threads.

[0299] [Manufacturing of Cloth Type Q]

[0300] Glass fiber cloth P was obtained by weaving glass fibers using an air-jet loom with a weaving density of 53 warp threads / 25mm and 53 weft threads / 25mm. It should be noted that the weaving was performed with a glass fiber cloth width of 1300mm. Glass fibers with an average filament diameter of 5.0μm, 200 filaments, and a twist count of 1.0Z were used as both warp and weft threads.

[0301] [Manufacturing of Cloth Type R]

[0302] Glass fiber cloth R is obtained by weaving glass fibers using an air-jet loom with a weaving density of 94 warp threads / 25mm and 94 weft threads / 25mm. It should be noted that the weaving is performed with a glass fiber cloth width of 1300mm. Glass fibers with an average filament diameter of 4.0μm, 50 filaments, and a twist count of 1.0Z are used as both warp and weft threads.

[0303] [Manufacturing of Cloth Type S]

[0304] Glass fiber cloth S is obtained by weaving glass fibers using an air-jet loom with a weaving density of 74 warp threads / 25mm and 74 weft threads / 25mm. It should be noted that the weaving is performed with a glass fiber cloth width of 1300mm. Glass fibers with an average filament diameter of 4.0μm, 100 filaments, and a twist count of 1.0Z are used as both warp and weft threads.

[0305] [Manufacturing of Cloth Type T-Shirts]

[0306] Glass fiber cloth T was obtained by weaving glass fibers using an air-jet loom with a weaving density of 69 warp threads / 25mm and 72 weft threads / 25mm. It should be noted that the weaving was performed with a glass fiber cloth width of 1300mm. Glass fibers with an average filament diameter of 4.5μm, 100 filaments, and a twist count of 1.0Z were used as both warp and weft threads.

[0307] [Ion content in the cleaning solution]

[0308] The amounts of Na and Mg ions in cleaning solution 1 are shown in the table below.

[0309] Na ion concentration = 1.6 ppm

[0310] Mg ion concentration = 0.0 ppm

[0311] Examples and Comparative Examples

[0312] (Example 1)

[0313] For glass cloth type P made from glass fibers A1 with a coefficient of variation of less than 2.5% in TEX testing, the process was carried out using high-pressure spraying (pressure = 3.0 kg / cm²). 2 The glass cloth undergoes a fiber-opening process using a vibrating washing machine (multi-blade rotor speed = 400 rpm) to remove the sizing agent adhering to the glass fiber surface through washing and to open the warp and weft fibers (fiber-opening process before heat degreasing). Then, while being conveyed at a linear speed (conveyor speed = 20 m / min) to immerse the cloth in a tank of accumulated washing water 1 for 20 seconds, the ions adhering to the glass surface are cleaned. The water adhering to the glass cloth is then removed by heating it at 110°C for 10 seconds using a dryer on the same line (cleaning process before heat degreasing). 2000 m of the resulting glass cloth is then rolled back into a metal core tube and subjected to heat degreasing treatment at 370°C for 30 hours. After the first degreasing treatment, the glass cloth is rolled back into the metal core tube again and subjected to heat degreasing treatment at 370°C for another 30 hours, thereby completely removing the sizing agent from the glass fiber surface (heat degreasing process). Next, while the glass cloth was being propelled through the water at a conveying tension of 200N and a linear speed of 30m / min, it was simultaneously irradiated with a frequency of 25GHz and an output power of 0.72W / cm². 2 Ultrasonic cleaning was used to remove residue (cleaning and fiber opening process). Next, a treatment solution was prepared by dispersing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (Z6030, manufactured by Dow Toray) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution, squeezed out, and then heated and dried at 130°C for 60 seconds to fix the silane coupling agent (surface treatment process). The dried fabric was then sprayed with 3.0 kg / cm² water. 2 The fiber is opened under high pressure (fiber opening process after surface treatment), and then dried at 130°C for 1 minute to obtain glass cloth.

[0314] (Examples 2-13, Comparative Examples 1-9)

[0315] Except for the changes to the items listed in the table below, the glass cloth is obtained using the same method as in Example 1.

[0316] (Example 14)

[0317] The fiber opening process before heating and degreasing is carried out using high-pressure spraying (pressure = 4.0 kg / cm²). 2The fiber opening process involves a vibrating washing machine (multi-blade rotor speed = 500 rpm), where the conveying tension is set to 100 N during the cleaning and fiber opening process, and a spray is used at 3.5 kg / cm² during the fiber opening process after surface treatment. 2 High-pressure fiber opening is performed under pressure, and otherwise glass cloth is obtained using the same method as in Example 1.

[0318] (Example 15)

[0319] For glass cloth type Q made from glass fibers A2 with a coefficient of variation of less than 1.7% in TEX testing, the process was carried out using high-pressure spraying (pressure = 4.0 kg / cm²). 2 The glass cloth undergoes a fiber-opening process using a vibrating washing machine (multi-blade rotor speed = 500 rpm) to remove the sizing agent adhering to the glass fiber surface through washing and to open the warp and weft fibers (fiber-opening process before heat degreasing). Then, while being conveyed at a linear speed (conveyor speed = 20 m / min) to immerse the cloth in a tank of accumulated washing water 1 for 20 seconds, the ions adhering to the glass surface are cleaned. The water adhering to the glass cloth is then removed by heating it at 110°C for 10 seconds using a dryer on the same line (cleaning process before heat degreasing). 2000 m of the resulting glass cloth is then rolled back into a metal core tube and subjected to heat degreasing treatment at 370°C for 30 hours. After the first degreasing treatment, the glass cloth is rolled back into the metal core tube again and subjected to heat degreasing treatment at 370°C for another 30 hours, thereby completely removing the sizing agent from the glass fiber surface (heat degreasing process). Next, while the glass cloth was being propelled through the water at a conveying tension of 200N and a linear speed of 30m / min, it was simultaneously irradiated with a frequency of 25GHz and an output power of 0.95W / cm². 2 Ultrasonic cleaning was used to remove residue (cleaning and fiber opening process). Next, a treatment solution was prepared by dispersing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (Z6030, manufactured by Dow Toray) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution, squeezed out, and then heated and dried at 130°C for 60 seconds to fix the silane coupling agent (surface treatment process). The dried fabric was then sprayed with 4.5 kg / cm² water. 2 The fiber is opened under high pressure (fiber opening process after surface treatment), and then dried at 130°C for 1 minute to obtain glass cloth.

[0320] (Examples 16-27, Comparative Examples 10-18)

[0321] Except for the changes to the items listed in the table below, the glass cloth is obtained by the same method as in Example 15.

[0322] (Example 28)

[0323] The fiber opening process before heating and degreasing is carried out using high-pressure spraying (pressure = 4.3 kg / cm²). 2 The fiber opening process involves a vibrating washing machine (multi-blade rotor speed = 500 rpm), where the conveying tension is set to 130 N during the cleaning and fiber opening process, and a spray is used at 3.8 kg / cm² during the fiber opening process after surface treatment. 2 High-pressure fiber opening is performed under pressure, and otherwise glass cloth is obtained using the same method as in Example 15.

[0324] (Example 29)

[0325] For glass cloth type R made from glass fiber A13 with a coefficient of variation of less than 1.6% in TEX testing, the process was carried out by high-pressure spraying (pressure = 2.0 kg / cm²). 2 The glass cloth undergoes a fiber-opening process using a vibrating washing machine (multi-blade rotor speed = 450 rpm) to remove the sizing agent adhering to the glass fiber surface through washing and to open the warp and weft fibers (fiber-opening process before heat degreasing). Then, while being conveyed at a linear speed (conveyor speed = 20 m / min) to immerse the cloth in a tank of accumulated washing water 1 for 20 seconds, the ions adhering to the glass surface are cleaned. The water adhering to the glass cloth is then removed by heating it at 110°C for 10 seconds using a dryer on the same line (cleaning process before heat degreasing). 2000 m of the resulting glass cloth is then rolled back into a metal core tube and subjected to heat degreasing treatment at 370°C for 30 hours. After the first degreasing treatment, the glass cloth is rolled back into the metal core tube again and subjected to heat degreasing treatment at 370°C for another 30 hours, thereby completely removing the sizing agent from the glass fiber surface (heat degreasing process). Next, while the glass cloth was being propelled through the water at a conveying tension of 200N and a linear speed of 30m / min, it was simultaneously irradiated with a frequency of 25GHz and an output power of 0.55W / cm². 2 Ultrasonic cleaning was used to remove residue (cleaning and fiber opening process). Next, a treatment solution was prepared by dispersing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (Z6030, manufactured by Dow Toray) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution, squeezed out, and then heated and dried at 130°C for 60 seconds to fix the silane coupling agent (surface treatment process). The dried fabric was then sprayed with 3.0 kg / cm² water. 2 The fiber is opened under high pressure (fiber opening process after surface treatment), and then dried at 130°C for 1 minute to obtain glass cloth.

[0326] (Examples 30-41, Comparative Examples 19-27)

[0327] Except for the changes to the items listed in the table below, the glass cloth is obtained using the same method as in Example 29.

[0328] (Example 42)

[0329] The fiber opening process before heating and degreasing involves high-pressure spraying (pressure = 3.5 kg / cm²). 2 The fiber opening process involves a vibrating washing machine (multi-blade rotor speed = 500 rpm), where the conveying tension is set to 100 N during the cleaning and fiber opening process, and a spray at 3.0 kg / cm² is used during the fiber opening process after surface treatment. 2 High-pressure fiber opening is performed under pressure, and otherwise glass cloth is obtained using the same method as in Example 29.

[0330] (Example 43)

[0331] For glass cloth type S made from glass fibers A14 with a coefficient of variation of less than 1.5% in TEX testing, the process was carried out using high-pressure spraying (pressure = 3.0 kg / cm²). 2 The glass cloth undergoes a fiber-opening process using a vibrating washing machine (multi-blade rotor speed = 450 rpm) to remove the sizing agent adhering to the glass fiber surface through washing and to open the warp and weft fibers (fiber-opening process before heat degreasing). Then, while being conveyed at a linear speed (conveyor speed = 20 m / min) to immerse the cloth in a tank of accumulated washing water 1 for 20 seconds, the ions adhering to the glass surface are cleaned. The water adhering to the glass cloth is then removed by heating it at 110°C for 10 seconds using a dryer on the same line (cleaning process before heat degreasing). 2000 m of the resulting glass cloth is then rolled back into a metal core tube and subjected to heat degreasing treatment at 370°C for 30 hours. After the first degreasing treatment, the glass cloth is rolled back into the metal core tube again and subjected to heat degreasing treatment at 370°C for another 30 hours, thereby completely removing the sizing agent from the glass fiber surface (heat degreasing process). Next, while the glass cloth was being propelled through the water at a conveying tension of 200N and a linear speed of 30m / min, it was simultaneously irradiated with a frequency of 25GHz and an output power of 0.60W / cm². 2 Ultrasonic cleaning was used to remove residue (cleaning and fiber opening process). Next, a treatment solution was prepared by dispersing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (Z6030, manufactured by Dow Toray) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution, squeezed out, and then heated and dried at 130°C for 60 seconds to fix the silane coupling agent (surface treatment process). The dried fabric was then sprayed with 3.0 kg / cm² water. 2 The fiber is opened under high pressure (fiber opening process after surface treatment), and then dried at 130°C for 1 minute to obtain glass cloth.

[0332] (Examples 44-55, Comparative Examples 28-36)

[0333] Except for the changes to the items listed in the table below, the glass cloth is obtained by the same method as in Example 43.

[0334] (Example 56)

[0335] The fiber opening process before heating and degreasing is carried out using high-pressure spraying (pressure = 4.0 kg / cm²). 2 The fiber opening process involves a vibrating washing machine (multi-blade rotor speed = 500 rpm), where the conveying tension is set to 100 N during the cleaning and fiber opening process, and a spray at 3.0 kg / cm² is used during the fiber opening process after surface treatment. 2 High-pressure fiber opening is performed under pressure, and otherwise glass cloth is obtained using the same method as in Example 43.

[0336] (Example 57)

[0337] For glass cloth type T made from glass fiber A15 with a coefficient of variation of less than 1.3% in TEX testing, the process was carried out by high-pressure spraying (pressure = 3.5 kg / cm²). 2 The glass cloth undergoes a fiber-opening process using a vibrating washing machine (multi-blade rotor speed = 480 rpm) to remove the sizing agent adhering to the glass fiber surface through washing and to open the warp and weft fibers (fiber-opening process before heat degreasing). Then, while being conveyed at a linear speed (conveyor speed = 20 m / min) to immerse the cloth in a tank of accumulated washing water 1 for 20 seconds, the ions adhering to the glass surface are cleaned. The water adhering to the glass cloth is then removed by heating it at 110°C for 10 seconds using a dryer on the same line (cleaning process before heat degreasing). 2000 m of the resulting glass cloth is then rolled back into a metal core tube and subjected to heat degreasing treatment at 370°C for 30 hours. After the first degreasing treatment, the glass cloth is rolled back into the metal core tube again and subjected to heat degreasing treatment at 370°C for another 30 hours, thereby completely removing the sizing agent from the glass fiber surface (heat degreasing process). Next, while the glass cloth was being propelled through the water at a conveying tension of 200N and a linear speed of 30m / min, it was simultaneously irradiated with a frequency of 25GHz and an output power of 0.60W / cm². 2Ultrasonic cleaning was used to remove residue (cleaning and fiber opening process). Next, a treatment solution was prepared by dispersing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (Z6030, manufactured by Dow Toray) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution, squeezed out, and then heated and dried at 130°C for 60 seconds to fix the silane coupling agent (surface treatment process). The dried fabric was then sprayed with 3.0 kg / cm² water. 2 The fiber is opened under high pressure (fiber opening process after surface treatment), and then dried at 130°C for 1 minute to obtain glass cloth.

[0338] (Examples 58-69, Comparative Examples 37-45)

[0339] Except for the changes to the items listed in the table below, the glass cloth is obtained by the same method as in Example 57.

[0340] (Example 70)

[0341] The fiber opening process before heating and degreasing is carried out using high-pressure spraying (pressure = 4.0 kg / cm²). 2 The fiber opening process involves a vibrating washing machine (multi-blade rotor speed = 520 rpm), where the conveying tension is set to 100 N during the cleaning and fiber opening process, and a spray at 3.0 kg / cm² is used during the fiber opening process after surface treatment. 2 High-pressure fiber opening is performed under pressure, and otherwise glass cloth is obtained using the same method as in Example 57.

[0342] Evaluation Methods

[0343] [Evaluation methods for downy fibers]

[0344] Apply a tension of 100 N / 1000 mm to the glass cloth on a roll-to-roll inspection table, and visually determine the tension per 1 m while illuminating it with a halogen lamp. 2 The number of protrusions larger than 0.8 mm. The surface and inner layers of the obtained roll-shaped glass cloth were evaluated separately, and the average number of fibers was evaluated according to the following criteria.

[0345] A: 3 or fewer fibers

[0346] B: 4 or more but less than 8 fibers

[0347] C: 9 or more but less than 10 fibers

[0348] D: 11 or more fibers

[0349] [Evaluation Methods for Resin Impregnation]

[0350] Take samples of the glass cloth in sizes of 50mm x 50mm or larger. Ensure the sampling is performed in a manner that prevents bending or contact with the measurement area. The sampled glass cloth is then impregnated with castor oil (manufactured by Hayashi Chun-Yaku Kogyo Co., Ltd., model: 03001535, static viscosity at 24°C = 560 mPa·s × g / cm³) at a liquid temperature of 24°C. 3 The number of voids at specified times was counted for evaluation. A high-precision camera (frame size: 5120×5120 pixels) was set up perpendicular to the glass cloth, and LED lights (CCS Power Flash Bar type illumination, manufactured by CCS Corporation) were used as the light source, shining from both sides with the glass cloth sandwiched between it, at a position 15 cm from the side. Then, at a viewing angle of 32 mm × 32 mm, the number of voids larger than 160 μm existing between the glass filaments was counted, and the average of three measurements was taken as the void count. Voids correspond to the unimpregnated matrix resin portion. Therefore, a low void count in the glass cloth indicates excellent impregnation of the matrix resin.

[0351] The resin impregnation performance was evaluated according to the following criteria. It should be noted that the time from immersing the glass cloth test piece in the impregnation varnish to counting the number of unimpregnated areas was defined as 5 minutes.

[0352] A: Number of un-permeable areas is less than 30

[0353] B: Number of unimpregnated areas: 31 to 45

[0354] C: Number of unimpregnated areas 45 or more

[0355] [How to manufacture laminated boards]

[0356] In the examples and comparative examples, 45 parts by weight of polyphenylene ether (manufactured by SABIC Corporation, Noryl (trade name) SA9000), 10 parts by weight of triallyl isocyanurate, 45 parts by weight of toluene, and 0.6 parts by weight of 1,3-di(tert-butylisopropylbenzene) were added to a stainless steel container and stirred at room temperature for 1 hour to prepare a varnish. The glass cloth was then impregnated with the prepared varnish and dried at 115°C for 1 minute to obtain a prepreg. Ten sheets of the obtained prepreg were stacked together, and copper foil (manufactured by Furukawa Electric Industries, Ltd., model: F2-WS, 12μm) was further stacked on top and bottom, and then dried at 200°C and 40 kg / cm². 2 The plates are heated and pressurized for 120 minutes to obtain laminated plates.

[0357] [Methods for evaluating the heat resistance of laminated boards]

[0358] After removing the copper foil from the laminate obtained as described above through etching, the laminate was heated and dehydrated at 133°C for 50 hours in a pressure cooker. Then, the dehydrated laminate was immersed in a solder bath at 288°C for 20 seconds, and visual inspection was performed to check for any 0.03cm peeling caused by the interface between the glass cloth and the resin. 2 The above-mentioned bulges (protrusions) were observed. Six tests were conducted using each layer of laminate. The evaluation of heat resistance is as follows. It should be noted that a greater tendency for fewer bulges in the laminate indicates better heat resistance.

[0359] A: The bulge of the laminated board is less than 2 pieces.

[0360] B: The bulges of the laminated plates are 3 to 4 pieces.

[0361] C: The number of bulges in the laminated board is 5 or more.

[0362] [Evaluation methods for offset characteristics]

[0363] Etching was performed only on one side of the copper foil of the laminate obtained by the above method to fabricate 15 microstrip lines with a circuit length of 10 cm. The transmission speed of the 15 copper foil lines (impedance = 100Ω, wiring angle = 0 degrees) was measured from 10 GHz to 24 GHz, and the ratio of the maximum value to the minimum value was used as the offset characteristic of the glass cloth.

[0364] Offset characteristic = maximum value ÷ minimum value

[0365] [Table 1-1]

[0366] Table 1-1

[0367]

[0368] [Table 1-2] Table 1-2

[0369]

[0370] [Table 1-3] Table 1-3

[0371]

[0372] [Table 2-1] Table 2-1

[0373]

[0374] [Table 2-2] Table 2-2

[0375]

[0376] [Table 2-3] Table 2-3

[0377]

[0378] [Table 3] Table 3

[0379]

[0380] [Table 4] Table 4

[0381]

[0382] [Table 5] Table 5

[0383]

[0384] [Table 6] Table 6

[0385]

[0386] [Table 7] Table 7

[0387]

[0388] [Table 8] Table 8

[0389]

[0390] [Table 9] Table 9

[0391]

[0392] [Table 10] Table 10

[0393]

[0394] [Table 11] Table 11

[0395]

[0396] [Table 12] Table 12

[0397]

[0398] [Table 13] Table 13

[0399]

[0400] [Table 14] Table 14

[0401]

[0402] [Table 15] Table 15

[0403]

[0404] [Table 16] Table 16

[0405]

[0406] [Table 17]

[0407] Table 17

[0408]

[0409] Industrial availability

[0410] The glass cloth disclosed herein can be used in printed circuit boards, particularly printed circuit boards for high-speed communication. Furthermore, the printed circuit boards disclosed herein can be used in integrated circuits and high-speed communication applications in electronic devices such as smartphones.

Claims

1. A type of glass cloth, which is composed of glass fibers formed from multiple long glass filaments as warp and weft fibers. The thickness of the glass cloth is in the range of 26–36 μm. The warp and weft widths of the glass cloth range from 211 to 300 μm and 326 to 400 μm, respectively. The coefficient of variation of the dielectric constant of the glass cloth measured at 10 GHz using a split cylindrical resonator is less than 8.0%.

2. A glass cloth, comprising glass filaments formed from multiple glass filaments as warp and weft yarns, wherein the thickness of the glass cloth is in the range of 42–58 μm, the warp width and weft width of the glass cloth are in the range of 267–385 μm and 425–550 μm respectively, and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%.

3. A glass cloth, which is composed of glass filaments formed from multiple glass filaments as warp and weft yarns, wherein the thickness of the glass cloth is in the range of 13 to 19 μm, the width of the warp yarns and the width of the weft yarns are in the range of 125 to 135 μm and 200 to 240 μm, respectively, and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%.

4. A glass cloth, which is composed of glass filaments formed from multiple glass filaments as warp and weft yarns, wherein the thickness of the glass cloth is in the range of 17 to 25 μm, the warp width and weft width of the glass cloth are in the range of 178 to 198 μm and 310 to 342 μm, respectively, and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%.

5. A glass cloth comprising glass filaments formed from multiple glass filaments as warp and weft yarns, wherein the thickness of the glass cloth is in the range of 20–30 μm, the warp width and weft width of the glass cloth are in the range of 176–232 μm and 329–353 μm respectively, and the coefficient of variation of the dielectric constant of the glass cloth at 10 GHz, as measured using a split cylindrical resonator, is less than 8.0%.

6. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric constant is in the range of 3.8 to 4.

5.

7. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 45–55% by mass of SiO2; 17–27% by mass of B2O3; 11–21% by mass of Al2O3; a total of 2.7–5.7% by mass of CaO and MgO; and a total of 0–0.15% by mass of Li2O, K2O, and Na2O.

8. The glass cloth according to claim 7, wherein, The glass fiber contains, based on its total mass, 0.15 to 0.45% TiO2 by mass, calculated in oxide form. P2O5 in the range of 2.5 to 7.5% by mass; and SrO in the range of 0 to 0.02% by mass.

9. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 48–58% by mass of SiO2; 18–28% by mass of B2O3; 8–18% by mass of Al2O3; a total of 3.4–6.4% by mass of CaO and MgO; and a total of 0–0.15% by mass of Li2O, K2O, and Na2O.

10. The glass cloth according to claim 9, wherein, The glass fiber, based on its total mass, contains, in oxide terms, 0.9–2.9% TiO2, 0–0.03% P2O5, and 0–3% SrO.

11. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 48–58% by mass of SiO2; 17–27% by mass of B2O3; 11–21% by mass of Al2O3; a total of 3.5–6.5% by mass of CaO and MgO; and a total of 0–0.1% by mass of Li2O, K2O, and Na2O.

12. The glass cloth according to claim 11, wherein, The glass fiber, based on its total mass, comprises, in oxide terms, 0–0.3% TiO2, 0–4.2% P2O5, and 0–1% SrO.

13. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 47–57% by mass of SiO2; 22–32% by mass of B2O3; 8–18% by mass of Al2O3; a total of 1.4–4.4% by mass of CaO and MgO; and a total of 0.1–1.0% by mass of Li2O, K2O, and Na2O.

14. The glass cloth according to claim 13, wherein, The glass fiber, based on its total mass, contains, in oxide terms, 0–1% TiO2, 0–0.2% P2O5, and 0–0.3% SrO.

15. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 47–57% by mass of SiO2; 18–28% by mass of B2O3; 9–19% by mass of Al2O3; a total of 3.4–6.4% by mass of CaO and MgO; and a total of 0–0.3% by mass of Li2O, K2O, and Na2O.

16. The glass cloth according to claim 15, wherein, The glass fiber, based on its total mass, contains, in oxide terms, 0.01 to 0.3% TiO2, 0 to 0.2% P2O5, and 0 to 0.3% SrO.

17. The glass cloth according to any one of claims 1 to 5, wherein, The glass fiber, based on its total mass and converted to oxides, contains: 47–57% by mass of SiO2; 20–30% by mass of B2O3; 8–18% by mass of Al2O3; a total of 3.0–7.0% by mass of CaO and MgO; and a total of 0–0.3% by mass of Li2O, K2O, and Na2O.

18. The glass cloth according to claim 17, wherein, The glass fiber, based on its total mass, comprises, in oxide terms, 1.0–5.0% TiO2, 0–0.1% P2O5, and 0–0.2% SrO.

19. The glass cloth according to claim 6, wherein, The dielectric constant is in the range of 4.0 to 4.

3.

20. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric loss tangent of the glass cloth measured at 10 GHz using a split cylindrical resonator is below 0.0025.

21. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric loss tangent of the glass cloth measured at 10 GHz using a split cylindrical resonator is below 0.0023.

22. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric loss tangent of the glass cloth measured at 10 GHz using a split cylindrical resonator is below 0.0020°.

23. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric loss tangent of the glass cloth measured at 10 GHz using a split cylindrical resonator is in the range of 0.0010 to 0.0018.

24. The glass cloth according to any one of claims 1 to 5, wherein, The dielectric loss tangent of the glass cloth measured at 10 GHz using a split cylindrical resonator is in the range of 0.0018 to 0.0020.

25. The glass cloth according to any one of claims 1 to 5, wherein, The coefficient of variation of the dielectric constant is less than 6.0%.

26. The glass cloth according to any one of claims 1 to 5, wherein, The coefficient of variation of the dielectric constant is less than 4.0%.

27. The glass cloth according to any one of claims 1 to 5, wherein, The coefficient of variation of the dielectric constant is less than 2.0%.

28. The glass cloth according to claim 1, wherein, The warp and weft widths of the glass cloth are in the range of 213–290 μm and 335–390 μm, respectively.

29. The glass cloth according to claim 1, wherein, The warp and weft widths of the glass cloth are in the range of 215–275 μm and 345–380 μm, respectively.

30. The glass cloth according to claim 1, wherein, The warp and weft widths of the glass cloth are in the range of 218–260 μm and 350–375 μm, respectively.

31. The glass cloth according to claim 1, wherein, The standard deviations of the warp and weft widths of the glass cloth are below 16 μm and below 34 μm, respectively.

32. The glass cloth according to claim 2, wherein, The warp and weft widths of the glass cloth are in the range of 270–370 μm and 440–540 μm, respectively.

33. The glass cloth according to claim 2, wherein, The warp and weft widths of the glass cloth range from 275 to 360 μm and 450 to 530 μm, respectively.

34. The glass cloth according to claim 2, wherein, The warp and weft widths of the glass cloth are in the range of 285–350 μm and 460–500 μm, respectively.

35. The glass cloth according to claim 2, wherein, The standard deviations of the warp and weft widths of the glass cloth are below 26 μm and 39 μm, respectively.

36. The glass cloth according to claim 3, wherein, The warp and weft widths of the glass cloth are in the range of 126–134 μm and 204–236 μm, respectively.

37. The glass cloth according to claim 3, wherein, The warp and weft widths of the glass cloth are in the range of 127–133 μm and 208–232 μm, respectively.

38. The glass cloth according to claim 3, wherein, The standard deviations of the warp and weft widths of the glass cloth are below 15 μm and below 24 μm, respectively.

39. The glass cloth according to claim 4, wherein, The warp and weft widths of the glass cloth range from 180 to 196 μm and 313 to 339 μm, respectively.

40. The glass cloth according to claim 4, wherein, The warp and weft widths of the glass cloth range from 182 to 194 μm and 316 to 336 μm, respectively.

41. The glass cloth according to claim 4, wherein, The standard deviations of the warp and weft widths of the glass cloth are below 20 μm and below 40 μm, respectively.

42. The glass cloth according to claim 5, wherein, The warp and weft widths of the glass cloth range from 183 to 225 μm and 332 to 350 μm, respectively.

43. The glass cloth according to claim 5, wherein, The warp and weft widths of the glass cloth range from 190 to 218 μm and 335 to 347 μm, respectively.

44. The glass cloth according to claim 5, wherein, The standard deviations of the warp and weft widths of the glass cloth are below 20 μm and below 43 μm, respectively.

45. The glass cloth according to any one of claims 1 to 5, wherein, The coefficient of variation of the TEX of the glass fiber is less than 4.0%.

46. ​​The glass cloth according to any one of claims 1 to 5, wherein, The coefficient of variation of the TEX of the glass filament is less than 3.0%.

47. A prepreg comprising glass cloth and matrix resin as described in any one of claims 1 to 5.

48. A printed circuit board comprising the prepreg of claim 47.

49. An integrated circuit comprising the printed circuit board of claim 48.

50. An electronic device comprising the printed circuit board of claim 48.

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