TWI904470B - Glass cloth, prepreg, and printed circuit board - Google Patents

Abstract

This invention provides a low-dielectric glass cloth with low slack and uniform properties in terms of thickness, air permeability, and resin impregnation, as well as a prepreg using the glass cloth and a printed circuit board. The glass cloth of this invention is constructed by using glass yarn comprising a plurality of glass filaments as warp and weft yarns, with a thickness of 5 μm to 100 μm, and the length of the glass cloth in the width direction is 1000 mm or more, and the difference X between the warp width at the ends and the center of the glass cloth in the width direction is less than or equal to the standard deviation α of the warp width.

Description

Glass cloth, prepreg, and printed circuit board

This invention relates to a glass cloth, a prepreg, and a printed circuit board.

With the development of the information and communication society in recent years, data communication and/or signal processing are carried out at high capacity and high speed. For example, the printed circuit boards used in communication equipment or measuring instruments such as high-end servers or high-end routers/switches, supercomputers, and base stations have seen significant development in low dielectric properties. Therefore, more low dielectric glass cloths are being proposed for the glass cloths that make up printed circuit boards.

For example, the low dielectric glass cloth disclosed in Patent Document 1 _, compared with the previously commonly used E glass cloth, contains more boron oxide ( _B2O3 ) in its glass composition, while adjusting the amount of other components such as silicon dioxide ( _SiO2 ) to achieve a low dielectric constant.

As a method to improve the performance or quality of low-dielectric glass cloth by addressing width-direction unevenness, Patent 2 discloses a glass cloth whose end-to-end looseness is improved, and Patent 3 discloses a glass cloth that improves substrate warping. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2010-508226 [Patent Document 2] International Publication No. 2021/124913 [Patent Document 3] Japanese Patent Application Publication No. 2017-132651

[The problem that the invention aims to solve]

Through research, the inventors have found that the low-dielectric glass cloth made using this type of low-dielectric glass yarn has significantly different performance or quality compared to the previously used E-glass cloth.

The low-dielectric glass cloth tends to be more loose compared to the previous E-glass cloth. This looseness is particularly pronounced at the ends and center of the cloth in the width direction. This is presumably due to the lower elastic modulus and poorer texture of the low-dielectric glass cloth. Furthermore, the inventors conducted detailed observations of the low-dielectric glass cloth and confirmed the following tendency: the thickness distribution differs in the width direction, with the thickness at the ends being approximately 10% greater than that at the center. Moreover, it was determined that properties such as air permeability and resin impregnation also differ in the width direction, especially at the ends. Inconsistencies in the performance or quality of this type of glass cloth can also affect the characteristics or quality of prepregs, laminates for printed circuit boards, etc. obtained by using this glass cloth (resin content, heat resistance, copper foil peel strength, dimensional stability, etc.).

Regarding the glass cloth disclosed in Patent 2, it is disclosed that the looseness at the ends of the glass cloth is improved by suppressing the difference in the slope of the stress-strain curves in the width direction between the ends and the center in the direction parallel to the warp yarns to less than 10%. However, there is still room for improvement in the looseness of the glass cloth disclosed in Patent 2 regarding low-dielectric glass cloth.

Regarding the glass cloth disclosed in Patent Document 3, the following low-dielectric glass cloth is disclosed, which improves substrate warping by suppressing the difference in the width direction of the elongation of the stress-strain curve in the warp direction to less than 10%. However, substrate warping is also closely related to the elongation in the weft direction. Glass cloth usually has the characteristic that the weft yarns elongate more than the warp yarns. Therefore, controlling only the elongation of the warp yarns cannot improve substrate warping, and there is still room for improvement in terms of glass cloth looseness.

This invention addresses the aforementioned problems and aims to provide a low-dielectric glass cloth with low looseness and uniform properties in terms of thickness, air permeability, and resin impregnation, a prepreg using this glass cloth, and a printed circuit board. [Technical Means for Solving the Problems]

In order to solve the above-mentioned problem, the inventors conducted intensive research and found that the problem could be solved by ensuring that the difference in warp width between the ends and the center of the glass cloth was within a specified range relative to the unevenness of the warp width; thus, the invention was completed.

That is, the present invention is as follows: [Item 1] A glass cloth, comprising glass yarn including a plurality of glass filaments as warp and weft yarns, having a thickness of 5 μm to 100 μm, the length of the glass cloth in the width direction is 1000 mm or more, and the difference X between the warp widths at the ends and the center of the glass cloth in the width direction is less than or equal to the standard deviation α of the warp width. [Item 2] The glass cloth as described in Item 1, wherein the difference X between the warp widths is less than or equal to 0.7 times the standard deviation α of the warp width. [Item 3] The glass cloth as described in Item 1 or 2, wherein the difference X between the warp widths is less than or equal to 0.5 times the standard deviation α of the warp width. [Item 4] The glass cloth described in any of Items 1 to 3, wherein the standard deviation α of the warp width is less than or equal to 0.08 times the average warp width β. [Item 5] The glass cloth described in any of Items 1 to 4, wherein the standard deviation α of the warp width is less than or equal to 0.04 times the average warp width β. [Item 6] The glass cloth described in any of Items 1 to 5, wherein the standard deviation α of the warp width is less than or equal to 0.03 times the average warp width β. [Item 7] The glass cloth described in any of Items 1 to 6, wherein the TEX of the glass yarn is 1.0 or higher and less than 25. [Item 8] The glass cloth described in any of items 1 to 7 is composed of glass yarn with an elastic modulus of 50 GPa to 70 GPa. [Item 9] The glass cloth described in any of items 1 to 8 is composed of glass yarn with an elastic modulus of 50 GPa to 63 GPa. [Item 10] The glass cloth described in any of items 1 to 9, wherein the sum of the boron content and phosphorus content in the glass cloth is 5% by mass to 20% by mass. [Item 11] The glass cloth described in any of items 1 to 10, wherein the sum of the boron content and phosphorus content in the glass cloth is 6.5% by mass to 20% by mass. [Item 12] A prepreg comprising a glass cloth as described in any one of items 1 to 11, and a matrix resin composition impregnated in the glass cloth. [Item 13] A printed circuit board comprising a glass cloth as described in any one of items 1 to 11, and a cured form comprising a matrix resin composition impregnated in the glass cloth. [Effects of the Invention]

According to the present invention, a low-dielectric glass cloth with less looseness and uniform properties such as thickness, air permeability, and resin impregnation can be provided.

The following describes in detail the embodiments of the present invention (hereinafter referred to as "the embodiments"), but the present invention is not limited thereto and various changes can be made without departing from its spirit.

[Glass Cloth] The glass cloth of this embodiment is constructed by using glass yarn comprising a plurality of glass filaments as warp and weft yarns, with a thickness of 5 μm to 100 μm. The width of the glass cloth is 1000 mm or more, and the difference in warp width between the ends and the center of the width direction is below the standard deviation of the warp width.

Here, the "end portion" in the width direction refers to the area of a glass cloth with a width length of 1000 mm or more, ranging from 100 mm to 250 mm from its widest point in the width direction. The "center portion" in the width direction refers to the area of a glass cloth with a width length of 1000 mm or more, extending 75 mm from the center to both ends in the width direction. The difference in warp width between the end portion and the center portion in the width direction, and the standard deviation of the warp width, are measured in accordance with the method described in the embodiments below.

Compared to E-type glass cloth, low-dielectric glass cloth is prone to loosening at both ends and in the middle of the width direction. Furthermore, it tends to be about 10% thicker near the ends in the width direction. Additionally, properties such as air permeability and resin impregnation also tend to differ in the width direction, especially at the ends. To address these problems with low-dielectric glass cloth, the inventors first investigated the causes of these problems, and the results clearly showed that the fabric structure of the glass cloth differs significantly between the ends and the middle portion in the width direction.

That is, in the case of glass cloth with a length of 1000 mm or more in the width direction, the warp yarns are arranged in a roughly straight line horizontally in the width direction within a range of 100 mm from the outermost part of the cloth to 150 mm from the center (the area from 100 mm from the outermost part to 250 mm from the outermost part of the cloth), with almost no undulation. On the other hand, in the range of 100 mm from the outermost part to the center and in the center, the warp yarns are arranged vertically and horizontally, with an undulating structure. Because of this fabric structure, it is clear that when the glass cloth is transported horizontally, the warp yarns stretch due to gravity in a range of approximately 100 mm from the outermost edge to the center, and in the central portion, causing the glass cloth to sag downwards (within a range of 150 mm from the outermost edge to the center, the warp yarns are taut, and therefore it does not sag due to gravity). That is, it is clear that the slackness of the low-dielectric glass cloth is caused by the uneven fabric structure in the width direction. Furthermore, it was found that by modifying the width-direction strain of the aforementioned fabric structure, the slackness of the low-dielectric glass cloth can be improved.

Furthermore, it was clarified that within a range of approximately 150 mm from the center to the outermost point (about 100 mm from the very end), the warp yarns are arranged horizontally in roughly one row, while the weft yarns create greater undulations, thus increasing the thickness. Similarly, it was found that by modifying the width-direction strain of the fabric structure, the thickness of the low-dielectric glass cloth can be made more uniform in the width direction. It was further found that modifying the width-direction strain of the fabric structure can also improve air permeability, resin impregnation, and the width-direction differences in the elongation and slope of the warp yarns in the stress-strain curve. Furthermore, due to the dense filling of the warp and weft yarns, the thickness of the glass cloth is also reduced.

As described above, in the glass cloth of this embodiment, the difference X between the warp width at the ends and the center in the width direction is less than or equal to the standard deviation α of the warp width. More preferably, the difference X is less than or equal to 0.7 times the standard deviation α, and even more preferably, it is less than or equal to 0.5 times the standard deviation α. If the difference X between the warp width at the ends and the center in the width direction is less than or equal to the standard deviation α, the fabric structure becomes more uniform in the width direction, and the differences in width direction regarding the looseness, thickness, resin impregnation, and air permeability of the glass cloth are reduced. The smaller the difference X between the warp width at the width-direction ends and the width-direction center, the better; ideally, the warp widths should be substantially the same. Even if the warp width at the width-direction ends is wider than that at the width-direction center, as long as it is within 0.3 times the standard deviation of the warp width, it can still improve the width-direction differences in the looseness, thickness, resin impregnation, and air permeability of the glass cloth. Therefore, the lower limit of the difference X between the warp width at the width-direction ends and the width-direction center is preferably -0.3α (0.3 times the negative standard deviation).

Based on the mechanism described below, the inventors have determined that the strain in the fabric structure occurs during flattening and splitting processes, where the filaments of the glass fiber bundle are spread out, widening the bundle width and simultaneously reforming the fabric structure. Flattening and splitting are performed using processes such as high-pressure water spraying, vibrating cleaning, or high-frequency vibration with a liquid as the medium. These processes are carried out while tension is applied to the warp direction of the glass fiber cloth and it is horizontally transported. During this process, the cloth's own weight causes a downward force. Furthermore, since these processes utilize water, the weight of the water-containing glass fiber cloth increases, thus increasing the downward force. Thus, within the glass cloth, the support provided by the conveyor rollers, the tension in the warp direction, and the downward force generated by its own weight all work in combination. As a result, the warp tension is locally stronger in the range from 100 mm to 300 mm from the end. Consequently, the warp width does not widen in this range, maintaining tension. On the other hand, the warp width widens in the range 100 mm inward from the end and in the center, creating undulations in the warp during the fabric structure formation. This demonstrates the strain in the width direction that forms the fabric structure.

Based on the above understanding of the mechanism of action of the fabric structure strain in the width direction, during the degreasing and washing of glass cloth (grey cloth) and the fiber opening treatment by high-pressure water spray, and the fiber opening treatment by high-pressure water spray after silane coupling agent treatment, the width direction distribution of the high-pressure water spray pressure, the processing force of degreasing and washing and high-pressure water, and the tension acting on the MD (Machine direction) are adjusted by means of the following method, in a manner that the width of the warp yarns in the range from 100 mm away from the end of the width direction to 300 mm away from the end is increased in the same way as other ranges.

It was found that by using the following methods individually or in appropriate combinations, the dimensional flexibility of the fabric structure can be improved. • A method for setting warp yarn tension during the warping and weaving stages so that the tension of the warp yarns in the range from 100 mm to 300 mm from the end is weaker than in other ranges, producing greige fabric, and then performing flattening and splitting processes; • A method for reducing the processing force in the range 100 mm from the end and the central part, and increasing the processing force in the range from 100 mm to 300 mm from the end; • A method for reducing the tension during flattening and splitting processes, so that the difference in tension between the warp yarns in the range from 100 mm to 300 mm from the end and other ranges is smaller during flattening and splitting processes; • A method to reduce the processing forces during flattening and splitting processes, thereby minimizing changes in the cross-sectional structure of the yarn and the fabric structure.

In this embodiment, the glass cloth preferably has a standard deviation α of warp width that is less than 0.08 times the average value β of warp width.

If the standard deviation α of the warp width is less than 0.08 times the average value β of the warp width, the fabric structure is more likely to become uniform in the width direction, and the difference in looseness, thickness, resin impregnation and air permeability between the ends and the center of the glass cloth in the width direction is smaller, so it is better.

The standard deviation α of the warp width is preferably less than 0.04 times the average warp width β, and more preferably less than 0.03 times the average warp width β. The average warp width is measured in accordance with the method described in the embodiments below.

The smaller the standard deviation of the warp width, the easier it is for the fabric structure to become uniform in the width direction, so it is preferable, and particularly preferably 0 or more, but is not limited thereto. In order to keep the standard deviation of the warp width within the above range, the following methods are more effective: use original yarns with smaller variations in the twist number, filament diameter, TEX, etc. of the glass yarn used in the warp yarn; make the tension or processing force in the warp weaving step and flat fiber spreading step nearly uniform in the width direction; reduce the variation in tension or processing force. Furthermore, as mentioned above, it is also effective to reduce the yarn width difference between the width direction end portion and the center portion.

The thickness of the glass cloth in this embodiment is 5 μm to 100 μm. If the thickness of the glass cloth in this embodiment is 100 μm or less, the printed circuit board can be made denser and more multilayered. From the viewpoint of making the printed circuit board thinner or denser, the thinner the thickness, the better; however, from the viewpoint of maintaining practical strength, the lower limit of the thickness is 5 μm. The thickness of the glass cloth in this embodiment is preferably 6 μm or more, more preferably 8 μm or more. Furthermore, the thickness of the glass cloth in this embodiment is preferably 98 μm or less, more preferably 96 μm or less. The thickness of the glass cloth in this embodiment can be measured using the method described in the embodiments.

The elastic modulus of the glass yarn in the glass cloth constituting this embodiment is preferably 50 GPa or higher, more preferably 51 GPa or higher, and even more preferably 52 GPa or higher. If the elastic modulus is 50 GPa or higher, the following advantages are observed: increased stiffness of the glass yarn, easier control of structural changes during flattening and fiber opening processes in glass cloth manufacturing, and easier fabrication with a uniform fabric structure in the width direction. On the other hand, the elastic modulus of the glass yarn is preferably 70 GPa or lower, more preferably 65 GPa or lower, and even more preferably 63 GPa or lower. If the elastic modulus is below 70 GPa, the glass yarn possesses moderate softness. Therefore, during the warping, weaving, flattening, and opening processes in glass cloth manufacturing, the fabric structure is easily affected by tension or processing forces, leading to changes in the fabric structure. This results in a tendency to easily produce a fabric structure with uniformity in the width direction. Furthermore, when the elastic modulus is below 70 GPa, both glass yarn and glass cloth are relatively soft. Therefore, previous glass cloths tended to exhibit fabric structure strain in the width direction. This embodiment facilitates the production of a fabric structure with uniformity in the width direction. The elastic modulus of the glass yarn can be measured using the method described in the embodiments.

The dielectric constant of the glass cloth in this embodiment is preferably 5.0 or less, more preferably 4.7 or less, further preferably 4.5 or less, and especially preferably 4.0 or less, at a frequency of 1 GHz. Furthermore, in this embodiment, unless otherwise specified, the dielectric constant refers to the dielectric constant at a frequency of 1 GHz. Regarding the weaving structure of the glass cloth in this embodiment, there are no particular limitations. Examples include plain weave, square plain weave, satin weave, and twill weave. A plain weave structure is preferred.

The glass yarn constituting the glass cloth of this embodiment is obtained by gathering a plurality of filament bundles and twisting them as necessary. In this case, the glass yarn is classified as glass multifilament, and the filament (glass filament) contained in the glass yarn is classified as glass monofilament. The weaving density of the warp yarns and weft yarns constituting the glass cloth of this embodiment is preferably 30 to 120 yarns/25 mm, more preferably 40 to 110 yarns/25 mm, and even more preferably 50 to 100 yarns/25 mm. The average diameter of the glass monofilaments constituting the warp yarn and the weft yarn is independently preferably 2.5 to 9 μm, more preferably 3.0 to 8 μm, and further preferably 3.5 to 7.5 μm. The appropriate type of glass cloth can be selected based on the desired thickness. The average number of glass monofilaments constituting the warp and weft yarns is preferably 20 to 250, more preferably 30 to 230, and even more preferably 33 to 220.

The preferred range of the loss on ignition value of the glass cloth in this embodiment is 0.25% to 1.5% by mass, more preferably 0.3% to 1.4% by mass, and even more preferably 0.35% to 1.3% by mass.

The composition of the glass cloth of this embodiment will be explained below. Furthermore, the composition of the glass cloth has the same meaning as the composition of the glass yarn constituting the glass cloth. As elements constituting the glass cloth, at least one can be selected from the group consisting of silicon (Si), boron (B), aluminum (Al), calcium (Ca), magnesium (Mg), phosphorus (P), sodium (Na), potassium (K), titanium (Ti), zinc (Zn), iron (Fe), and fluorine (F).

The silicon (Si) content of the glass yarn, converted from _SiO2 , is preferably 40-60% by mass, more preferably 45-55% by mass, further preferably 47.0-53.5% by mass, and even more preferably 48.0-52.0% by mass. Si is a component that forms the skeletal structure of the glass yarn. Therefore, by having a Si content of 40% by mass or more, converted from _SiO2 , the strength of the glass yarn is further improved, and there is a tendency for the glass cloth to break further in subsequent steps such as the manufacturing process of the glass cloth and the manufacturing process of the prepreg using the glass cloth. Furthermore, by having a Si content of 40% by mass or more, converted from _SiO2 , there is a tendency for the dielectric constant of the glass cloth of this embodiment to be further reduced. On the other hand, by using a Si content of 60% by mass (converted to _SiO2) or less, there is a tendency for the viscosity during the molten phase to decrease further during the glass filament manufacturing process, resulting in glass fibers with a more homogeneous glass composition. Therefore, the resulting glass filaments are less prone to localized devitrification or areas where bubbles are difficult to remove, thus reducing the likelihood of locally weak areas. Consequently, glass cloths made from these glass filaments are less prone to breakage. The Si content can be adjusted by varying the amount of raw materials used in the production of the glass filaments.

The boron (B) content of the glass yarn, converted to _{B₂O₃ ,} is preferably 15–40% by mass, more preferably 17–30% by mass, or preferably 20–40% by mass, further preferably 18–28% by mass, further preferably 19–26% by mass, further preferably 20–25% by mass, and most preferably 20.5–24.5% by mass.

With a B content of 15% or more (equivalent to _B₂O₃ by mass ₎ , the dielectric constant tends to decrease further. Furthermore, with a B content of 15% or more (equivalent to _B₂O₃ by mass ₎ , the brittleness resistance of the glass cloth in this embodiment is improved. Additionally, by imparting appropriate softness or elasticity to the glass cloth, it tends to reduce the generation of fuzz when the glass yarn comes into contact with weaving mechanisms such as yarn guides and reeds.

On the other hand, to ensure the strength of the glass yarn, the B content, converted from _B₂O₃ , is preferably below 40% by _mass . By keeping the B content below 40% by mass, the moisture resistance is improved, and the stability of the glass yarn surface properties described later can be easily and appropriately ensured.

In particular, since the Si content in the glass yarn _{, when converted to SiO2, is within the above-mentioned range, and the B content, when converted to B2O3 , is} within the above-mentioned range, it is easier to synergistically exert the aforementioned effects related to Si and B, and therefore it is better.

The B content can be adjusted by adjusting the amount of raw materials used in the production of glass filaments. Furthermore, if the production conditions, usage, or content may change during the glass filament production process, such changes can be predicted in advance, and the amount of raw materials added can be adjusted accordingly.

The aluminum (Al) content of glass fiber, converted to _{Al₂O₃ ,} is preferably 11–18% by mass, more preferably 11–17.5% by mass, and even more preferably 12–17.0% by mass. By keeping the Al content within this range (converted to _{Al₂O₃ )} , there is a tendency for improved electrical properties and strength. The Al content can be adjusted by adjusting the amount of raw materials used (added amount) in the production of the glass filament.

The calcium (Ca) content of glass fiber, converted to CaO, is preferably 5.0–10% by mass, more preferably 5.0–9.0% by mass, and even more preferably 5.0–8.5% by mass. A Ca content of 5.0% by mass or higher tends to result in a lower viscosity during the molten phase of the glass filament, leading to a more homogeneous glass fiber composition. Furthermore, a Ca content of 10% by mass or less tends to result in a higher dielectric constant. The Ca content can be adjusted by the amount of raw materials used (added) in the production of the glass filament.

The phosphorus (P) content of glass cloth _, converted from _{P₂O₅ ,} is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 6.0% by mass or less. The P content, converted from _P₂O₅ , can exceed 0% by mass. When the P content, converted from _{P₂O₅ ,} exceeds 0% by mass, the dielectric properties of the glass cloth tend to improve. Furthermore, when the P content, converted from _{P₂O₅ ,} is 8.0% by mass or less, the heat resistance of the glass cloth tends to improve. The P content can be adjusted by the amount of raw materials used (added amount) in the production of glass filaments.

From the perspective of easily reducing the dielectric constant and dielectric loss factor of glass cloth, and from the perspective of easily forming a fabric structure with uniformity in the width direction, the sum of the boron and phosphorus content in the glass cloth is preferably 5% by mass to 20% by mass. A higher sum of boron and phosphorus content in the glass cloth tends to result in a lower dielectric constant and dielectric loss factor. By using a sum of boron and phosphorus content of 5% by mass or more, compared with laminates obtained using conventional E-glass cloth, the dielectric constant and dielectric loss factor are significantly reduced, thus improving its applicability to high-capacity and high-speed data communication or signal processing. From the perspective of easily reducing the dielectric constant and dielectric loss factor of the glass cloth, and from the perspective of more easily fabricating a uniform fabric structure in the width direction, the sum of the boron and phosphorus content in the glass cloth is preferably 6.5% by mass to 20% by mass. The higher the sum of the boron and phosphorus content in the glass cloth, the lower the dielectric constant and dielectric loss factor of the glass cloth tend to be. By using a sum of boron and phosphorus content of 6.5% by mass or higher, compared with laminates obtained using conventional E-glass cloth, the dielectric constant and dielectric loss factor are significantly reduced, thus improving the applicability for high-capacity and high-speed data communication or signal processing. For example, compared to E-glass, which has a dielectric constant of around 7, there is a tendency for the dielectric constant to decrease. For instance, when the sum of boron and phosphorus content is 7.4% by mass, the dielectric constant is approximately 4.8; and when the sum of boron and phosphorus content is 9.2% by mass, the dielectric constant is approximately 4.4.

If the sum of boron and phosphorus content is 5% by mass or more, the glass cloth of this embodiment possesses moderate softness. Therefore, during the warping, weaving, flattening, and fiber opening processes, the fabric structure is easily affected by tension or processing forces, leading to changes in the fabric structure. This results in a tendency to easily produce a fabric structure with uniformity in the width direction. Furthermore, if the sum of boron and phosphorus content is 6.5% by mass or more, the glass cloth of this embodiment possesses moderate softness. Therefore, during the warping, weaving, flattening, and fiber opening processes, the fabric structure is easily affected by tension or processing forces, leading to changes in the fabric structure. This also results in a tendency to easily produce a fabric structure with uniformity in the width direction.

By ensuring that the sum of boron and phosphorus content is less than 20% by mass, the moisture resistance and/or heat resistance of the glass cloth of this embodiment can be maintained at the same level as that of E glass with a sum of boron and phosphorus content of about 2% by mass.

The sum of boron and phosphorus content in the glass cloth can be adjusted during the glass yarn manufacturing process by increasing the amount of boron and phosphorus-containing glass raw materials added. Furthermore, since the boron and phosphorus content in the glass changes during the melting of the glass raw materials in the glass yarn manufacturing process, this change can also be considered to appropriately adjust the addition amount. Moreover, the above contents can be determined using ICP (Inductively Coupled Plasma) emission spectrometry. Specifically, the Si and B contents can be obtained as follows: after dissolving the weighed glass cloth in sodium carbonate, dissolve it again in dilute nitric acid at a predetermined capacity, and then measure the obtained sample using ICP emission spectrometry. Furthermore, the Fe content can be obtained by dissolving the weighed glass cloth using an alkaline dissolution method, setting the volume to a specified value, and then measuring the obtained sample using ICP emission spectrometry. Furthermore, the Al, Ca, P, and Mg contents can be obtained by heating and decomposing the weighed glass cloth using perchloric acid, sulfuric acid, nitric acid, and hydrogen fluoride, then dissolving it using dilute nitric acid, setting the volume to a specified value, and then measuring the obtained sample using ICP emission spectrometry. Moreover, the Hitachi High-Tech Science PS3520VDD II can be used as the ICP emission spectrometry instrument.

Hereinafter, regarding the content of the aforementioned elements in the glass cloth constituting this embodiment as described in this specification, if no oxide conversion is specified, the content refers to the element itself; if an oxide conversion is specified, the content refers to the weight of the aforementioned element expressed in oxide form. Furthermore, when it is necessary to record the content of the aforementioned elements in oxide form, the conversion can be performed based on the weight of the element itself, rather than using oxide conversion.

From the viewpoint of easily adjusting the thickness of the glass cloth of this embodiment to 5 μm to 100 μm, the TEX of the glass yarn is preferably 1.0 to 25, more preferably 1.5 to 23, and even more preferably 2.0 to 21. The glass cloth of this embodiment can also be surface-treated with a surface treatment agent. There are no particular limitations on the surface treatment agent; for example, silane coupling agents can be used, and water, organic solvents, acids, dyes, pigments, surfactants, etc., can also be used as needed.

There are no particular limitations on the silane coupling agent, and for example, the compound represented by formula (1) can be cited. X(R) _3-n SiY _n …(1) (In formula (1), X is an organic functional group having at least one of an amino group and an unsaturated double bond, Y is an alkoxy group independently, n is an integer of 1 to 3, and R is a group selected from the group consisting of methyl, ethyl, and phenyl). X is preferably an organic functional group having at least three of an amino group and an unsaturated double bond, and X is more preferably an organic functional group having at least four of an amino group and an unsaturated double bond. As the above-mentioned alkoxy group, any form can be used, but from the viewpoint of stabilizing the glass cloth of this embodiment, an alkoxy group with 5 or fewer carbon atoms is preferred. Examples of silane coupling agents include: N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropylmethyldimethoxysilane and its hydrochloride, N-β-(N-di(vinylbenzyl)aminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, and N-β-(N-di(vinylbenzyl)aminoethyl)-N-γ-(N-vinylbenzyl)-γ-aminopropyltrimethoxysilane and its hydrochloride. The silane coupling agent comprises, but is not limited to, known monomers such as hydrochlorides, N-β-(N-benzylaminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochlorides, N-β-(N-benzylaminoethyl)-γ-aminopropyltriethoxysilane and its hydrochlorides, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, aminopropyltrimethoxysilane, vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, etc., or mixtures thereof. The molecular weight of the silane coupling agent is preferably 100–600, more preferably 150–500, and even more preferably 200–450. Preferably, two or more silane coupling agents with different molecular weights are used. By using two or more silane coupling agents with different molecular weights to treat the surface of the glass cloth, the density of the surface treatment agent on the surface of the glass cloth increases, and the reactivity with the matrix resin is further enhanced.

<Manufacturing Method of Glass Cloth> The manufacturing method of the glass cloth according to this embodiment is not particularly limited. Examples include: using glass yarn as warp and weft yarns, weaving using conventional methods, and then subjecting the glass cloth fabric to subsequent processing such as treatment with a silane coupling agent. The weaving structure of the glass cloth is not particularly limited; examples include plain weave, square plain weave, satin weave, and twill weave. Furthermore, a mixed weave structure using different types of glass yarn is also possible. A plain weave structure is preferred.

The manufacturing method of the glass cloth in this embodiment is not particularly limited. For example, a method with the following steps can be appropriately exemplified: a coating step, in which a treatment liquid with a concentration of 0.1 to 3.0 wt% of silane coupling agent is applied to the glass cloth so that the surface of the glass filament is almost completely covered by the silane coupling agent; a fixing step, in which the silane coupling agent is fixed to the surface of the glass filament by heating and drying; and a fiber-opening step, in which the glass yarn of the glass cloth is opened.

As a solvent for dissolving or dispersing the silane coupling agent, either water or an organic solvent can be used, but from the perspective of safety and environmental protection, water is preferred as the primary solvent. As a method for obtaining a treatment solution with water as the primary solvent, one of the following methods is preferred: directly adding the silane coupling agent to water; or dissolving the silane coupling agent in a water-soluble organic solvent to prepare an organic solvent solution, and then adding that organic solvent solution to water. To improve the water dispersibility and stability of the silane coupling agent in the treatment solution, a surfactant may also be used.

Methods for applying a silane coupling agent treatment solution to glass cloth include the following: (a) accumulating the silane coupling agent treatment solution into a bath, immersing the glass cloth in the bath, and passing it through the bath (hereinafter referred to as the "immersion method"); (b) directly applying the silane coupling agent treatment solution to the glass cloth using a roller coating machine, a die coating machine, or a gravure coating machine. When using the immersion method described in (a) above, it is preferable to set the immersion time of the glass cloth in the treatment solution to be more than 0.5 seconds and less than 1 minute. Furthermore, as a method for drying the solvent by heating it after applying the treatment liquid to the glass cloth, examples include known methods such as hot air and electromagnetic waves.

The heating and drying temperature is preferably above 90°C, and more preferably above 100°C, to ensure that the silane coupling agent reacts fully with the glass. Furthermore, in order to prevent the deterioration of the organic functional groups of the silane coupling agent, the heating and drying temperature is preferably below 300°C, and more preferably below 200°C.

There are no particular limitations on the fiber-opening method used as a fiber-opening step. For example, methods such as using water spray (high-pressure water opening), vibration cleaner, ultrasonic water, and roller press can be used to open fiberglass cloth. In order to ensure that the total area of the basket holes is within a fixed range, it is preferable to use water spray for the fiber-opening step.

When using water spray for fiber opening, simply set the water pressure appropriately. To adjust the total area of the basket-like holes in the fiberglass cloth, it is best to keep the water pressure constant. Keeping the water pressure constant here means minimizing the difference between the maximum and minimum values of the spray water pressure set for fiber opening and the actual water pressure. A heating and drying step can also be included before or after the fiber opening process.

<Prepreg> This embodiment is also a prepreg, which is a composite of the aforementioned glass cloth and a matrix resin composition. The matrix resin composition is impregnated in the glass cloth. The prepreg can be manufactured using conventional methods. For example, a prepreg impregnated with the matrix resin composition can be produced by impregnating the glass cloth with a varnish prepared by diluting the matrix resin composition with an organic solvent, followed by evaporating the organic solvent in a drying oven.

As a resin constituting the matrix resin composition, either thermosetting resin or thermoplastic resin can be used. There is no particular limitation on thermosetting resins; examples include the following: a) epoxy resins, which are formed by reacting and curing an epoxy-containing compound with at least one of the following groups (amine, phenol, anhydride, acetic acid, isocyanate, cyanido, and hydroxyl groups) that react with epoxy groups, either without a catalyst or with a catalyst possessing reaction catalytic ability (such as imidazole, tertiary amine, urea, or phosphorus compounds); b) free radical polymerization type curing resins, which are formed using a thermally decomposable catalyst... The following are examples of resins: a) a compound having at least one of vinyl, allyl, methacryl, and acrylonitrile groups, which is formed by reacting a compound having a cyano group with a compound having a maleimide group and then curing it; d) a thermosetting polyimide resin, which is formed by reacting a maleimide compound with an amine compound and then curing it; e) a benzo[a] ...

Furthermore, as a thermoplastic resin, there are no particular limitations; examples include: polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polyurethane, polyetherurethane, polyarylate, aromatic polyamide, polyetheretherketone, thermoplastic polyimide, insoluble polyimide, polyamide-imide, fluororesins, etc. Additionally, thermosetting resins and thermoplastic resins can be used together.

The resin constituting the prepreg comprising glass cloth and a matrix resin composition as one embodiment of this invention is preferably a polyphenylene ether resin. More preferably, it is a polyphenylene ether resin having 1.5 to 5 carbon-carbon double-bonded functional groups such as vinyl, allyl, methacryl, and acrylonitrile per molecule at the main chain terminal. Furthermore, it is more preferably a polyphenylene ether resin with a number average molecular weight of 500 to 8,000. If the matrix resin is a polyphenylene ether resin, its dielectric properties are excellent, and therefore preferred.

Furthermore, it is hypothesized that because the resin constituting the matrix resin composition has the aforementioned functional groups and number average molecular weight, the resin composition can easily penetrate into the interior of the glass cloth during the prepreg manufacturing and press molding steps, ensuring a greater number of bonding points with the glass cloth. Therefore, it exhibits excellent dielectric properties. Even in a system where the in-plane uniformity of the glass is higher and the air permeability is lower, as in this embodiment, resulting in a reduced number of direct bonding points between the upper and lower resin matrix layers of the glass cloth, the interface between the glass cloth and the resin composition still exhibits stronger adhesion, thereby improving heat resistance or insulation reliability.

<Printed Circuit Board> This embodiment is also a printed circuit board, comprising the aforementioned glass cloth and a cured matrix resin composition impregnated in the glass cloth. Furthermore, the printed circuit board of this embodiment is manufactured using the aforementioned prepreg. That is, the printed circuit board of this embodiment is a printed circuit board formed by molding the prepreg of this embodiment. By using the prepreg of this embodiment to manufacture the printed circuit board, a high-quality printed circuit board with reduced signal propagation speed differences among multiple transmission lines can be provided. [Example]

The present invention will now be described in more detail using embodiments and comparative examples. The present invention is not limited to the following embodiments.

[Elastic Modulus] The elastic modulus of glass yarn is determined using a glass block obtained by melting and cooling glass yarn as a sample, employing the pulse-echo superposition method.

[Evaluation: Average warp width and standard deviation of warp width across all widths] Scan the glass cloth with the camera perpendicular to the MD direction to acquire images of the warp yarns across all widths of the glass cloth. Measure the width of each warp yarn. Calculate the average and standard deviation of the warp width across all widths of the glass cloth.

[Evaluation: Warp Width at Ends and Center] Scan the glass cloth with the camera in a direction perpendicular to the MD direction to obtain an image of the warp yarns across the entire width of the glass cloth. Measure the width of each warp yarn. Calculate the average warp yarn width within a range from 100 mm from each end of the glass cloth in the width direction to 250 mm from the ends. Use the narrower value as the warp yarn width at the ends. Also, calculate the average warp yarn width within a range of 75 mm to the left and right of the center in the width direction; use this as the warp yarn width at the center.

[Evaluation: Thickness Average Value] The thickness of three measurement points along the width direction was measured according to JIS R3420, with equal intervals between the two ends of the glass cloth and between each measurement point. The thicknesses of the three points were averaged, and the average thickness (μm) was calculated by rounding to the nearest whole number.

[Evaluation: Thickness - Ends, Center] Measure the thickness of the glass cloth according to JIS R3420, using 100 mm points inward from both ends along the width direction. The larger of the two measured thicknesses is taken as the end thickness (μm).

Furthermore, the center of the fiberglass cloth along its width is used as the measuring point, and the thickness is measured according to JIS R3420. The obtained thickness is taken as the thickness (mm) of the central portion.

[Evaluation: Air permeability at both ends and center] The air permeability was measured according to JIS R3420 at 100 mm inward from both ends of the fiberglass cloth in the width direction. The larger of the two air permeability values was taken as the air permeability at the end (cm ³ /cm ² /s).

Furthermore, the air permeability was measured according to JIS R3420, with the center of the fiberglass cloth along its width as the measuring point. The obtained air permeability was taken as the air permeability of the central part (cm ³ /cm ² /s).

[Evaluation: Resin Impregnation Evaluation of Glass Cloth] Impregnation test samples were collected from both ends of the glass cloth in the width direction, 100 mm inwards. Also, an impregnation test sample was collected from the center of the glass cloth in the width direction.

Bisphenol A type epoxy resin was dissolved in benzyl alcohol at 23±2℃ to prepare a varnish for impregnation evaluation with a viscosity of 230±5 mPa·s. Then, glass cloth samples were immersed in the varnish, and the impregnation of the varnish in the glass cloth was observed using an optical microscope while being illuminated from the side. Next, the number of pores (unimpregnated areas) of the glass cloth samples after immersion in the varnish for a specified time was counted. During this observation using an optical microscope, the field of view was set to approximately 6.5 mm in the warp direction and approximately 9 mm in the weft direction.

Regarding the two ends in the width direction, the value with more pores is set as the remaining number of pores (strips) at the end.

The glass cloth used in Examples 1 and Comparative Example 1 was counted after 2 minutes. The glass cloth used in Examples 2B, 2C, 2D, 2E, 2F, and Comparative Example 2 was counted after 3 minutes. The glass cloth used in Examples 3 and 4, Comparative Examples 3 and 4, and Reference Example 1 was counted after 5 minutes. The glass cloth used in Examples 5 and 6, and Comparative Examples 5 and 6 was counted after 8 minutes.

[Evaluation: Slack During Fabric Transport] Under a tension of 150 N, a cylindrical glass cloth wound from a core was transported for 2 m, then bent 90° using guide rollers. The oscillation of the glass cloth between the wound end and the guide rollers was measured using a displacement meter (a laser displacement sensor manufactured by Keyence). The displacement meter was set at two points 100 mm inward from each end of the glass cloth in the width direction, and at the center in the width direction. The difference between the maximum and minimum vertical positions of the glass cloth measured by the displacement meter was taken as the magnitude of the oscillation of the glass cloth (unit: mm).

[Evaluation: Width-direction difference (%) of warp elongation and width-direction difference (%) of the slope of the stress-strain curve when a load of 50 N/inch is applied] The elongation and slope of the glass cloth under tension in the warp direction were determined using the method described in section 7.4, Tensile Strength, of JIS R3420 General Test Method for Glass. In the JIS-specified method, a specimen with a width of approximately 30 mm and a length of approximately 250 mm is collected from the warp direction of the fabric. The yarns at both ends of the specimen are loosened, leaving a width of approximately 25 mm. The specimen is then mounted in a clamping device with a clamping interval of approximately 150 mm and stretched at a tensile speed of approximately 200 mm/min to determine the load at break. In this embodiment, to improve measurement accuracy, the tensile test is performed under the same conditions as the JIS-specified method, except that the tensile speed is set to approximately 5 mm/min. Stress-strain curve determination specimens are collected from both ends of the glass cloth in the width direction within a range of 50 mm to 200 mm inwards. Furthermore, stress-strain curves were measured on a specimen taken from the center of the fiberglass cloth along its width. The displacement (mm) of the fiberglass cloth under a 50 N load per 25 mm width was determined, and the ratio of elongation at the ends to that at the center along the width was calculated. Furthermore, for both ends along the width, the larger elongation was taken as the elongation (mm) at the end. Also, based on the elongation (mm) of the fiberglass cloth under a 50 N load per 25 mm width, the slope (elongation (mm)/50 N) was calculated, and the ratio of the slope at the ends to that at the center along the width was calculated. Furthermore, for both ends along the width, the larger slope was taken as the slope at the end.

<Comparative Example 1> Both warp and weft yarns were made of AGY Corporation's low-dielectric glass yarn LCBC1700 (elastic modulus 61 GPa, TEX 2.92). A glass cloth (grey fabric) with a warp yarn inlay density of 74 threads/25 mm and a weft yarn inlay density of 74 threads/25 mm was woven using an air-jet shuttleless loom. The obtained grey fabric was subjected to desizing and washing, and then splitting treatment using high-pressure water spray. Next, after degreasing by heat treatment at 400℃ for 24 hours, the glass cloth was immersed in a treatment solution using a silane coupling agent as a surface treatment agent, extruded, and then dried at 120℃ for 1 minute. Further fiber-opening processing using high-pressure water spraying was then performed to obtain glass cloth with a width of 1300 mm.

<Example 1> The warp width in the range from 100 mm to 300 mm from the end in the width direction is made the same as in other ranges. The tension during warping and the pressure of the high-pressure water spray during opening are adjusted in the width direction. The tension during desizing and washing, and during opening via high-pressure water spray, is also adjusted to be lower. Otherwise, a glass cloth with a width of 1300 mm is manufactured using the same method as in Comparative Example 1.

Regarding the tension during warping, the tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.2 times the pressure in other ranges. The tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 1.

<Comparative Example 2> Both warp and weft yarns were made of AGY Corporation's low-dielectric glass yarn LCD1020 (elastic modulus 61 GPa, TEX 4.86). A glass cloth (bare fabric) with a warp yarn density of 69 threads/25 mm and a weft yarn density of 69 threads/25 mm was woven using an air-jet shuttleless loom. The obtained bare fabric was subjected to desizing washing and high-pressure water spraying for fiber opening. Subsequently, after desizing by heat treatment at 400°C for 24 hours, the glass cloth was immersed in a treatment solution using a silane coupling agent as a surface treatment agent, extruded, and then dried at 120°C for 1 minute. Further, a fiber-opening process using high-pressure water spray was implemented to obtain fiberglass cloth with a width of 1300 mm.

<Example 2> The warp width in the range from 100 mm to 300 mm from the end in the width direction is made the same as in other ranges. The tension during warping and the pressure of the high-pressure water spray during opening are adjusted in the width direction. The tension during desizing and washing, and during opening via high-pressure water spray, is also adjusted to be lower. Otherwise, a glass cloth with a width of 1300 mm is manufactured using the same method as in Comparative Example 2.

Regarding the tension during warping, the tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.2 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 2.

<Example 2B> The tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.9 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.2 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 2.

<Example 2C> The tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.1 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 2.

<Example 2D> The tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.9 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.1 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 2.

<Example 2E> The tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.9 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.1 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.8 times that of Comparative Example 2.

<Example 2F> After the fiber-opening process using high-pressure water spray in this embodiment, both ends, including the ear chambers, are cut off to a width of 1250 mm. Otherwise, a glass cloth with a width of 1250 mm is manufactured using the same method as in Example 2.

<Comparative Example 3> Both warp and weft yarns were made of AGY Corporation's low-dielectric glass yarn LCD510 (elastic modulus 61 GPa, TEX 9.73). A glass cloth (grey fabric) with a warp yarn inlay density of 52.5 threads/25 mm and a weft yarn inlay density of 52.5 threads/25 mm was woven using an air-jet shuttleless loom. The obtained grey fabric was subjected to desizing and washing, and then splitting treatment using high-pressure water spray. Next, after degreasing by heat treatment at 400℃ for 24 hours, the glass cloth was immersed in a treatment solution using a silane coupling agent as a surface treatment agent, extruded, and then dried at 120℃ for 1 minute. Further fiber-opening processing using high-pressure water spraying was then performed to obtain glass cloth with a width of 1300 mm.

<Example 3> The warp width is made equal in the width direction by adjusting the warp tension during warping and the pressure of the high-pressure water spray during opening, in a range from 100 mm from the end in the width direction to 300 mm inward from the end. The tension during desizing and washing, and during opening via high-pressure water spray, is also adjusted to be lower. Otherwise, a glass cloth with a width of 1300 mm is manufactured using the same method as in Comparative Example 3.

Regarding the tension during warping, the tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.2 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 3.

<Comparative Example 4> Both the warp and weft yarns used were AGY Corporation's low-dielectric glass yarn LCD520 (elastic modulus 56 GPa, TEX 9.47). Otherwise, a glass cloth with a width of 1300 mm was obtained using the same method as in Comparative Example 3.

<Example 4> Both the warp and weft yarns are made of LCD520 low-dielectric glass yarn (elastic modulus 56 GPa, TEX 9.47) manufactured by AGY Corporation. Otherwise, a glass cloth with a width of 1300 mm is obtained using the same method as in Example 3.

<Comparative Example 5> Both warp and weft yarns were made of low-dielectric glass yarn LCDE340 (elastic modulus 61 GPa, TEX 14.59) manufactured by AGY Corporation. A glass cloth (grey fabric) with a warp yarn inlay density of 59 ends/25 mm and a weft yarn inlay density of 61 ends/25 mm was woven using an air-jet shuttleless loom. The obtained grey fabric was subjected to desizing and washing, and then splitting treatment using high-pressure water spray. Next, after degreasing by heat treatment at 400℃ for 24 hours, the glass cloth was immersed in a treatment solution using a silane coupling agent as a surface treatment agent, extruded, and then dried at 120℃ for 1 minute. Further fiber-opening processing using high-pressure water spraying was then performed to obtain glass cloth with a width of 1300 mm.

<Example 5> The warp width in the range from 100 mm to 300 mm from the end in the width direction is made the same as in other ranges. The tension during warping and the pressure of the high-pressure water spray during opening are adjusted in the width direction. The tension during desizing and washing, and during opening via high-pressure water spray, is also adjusted to be lower. Otherwise, a glass cloth with a width of 1300 mm is manufactured using the same method as in Comparative Example 5.

Regarding the tension during warping, the tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of 100 mm to 300 mm from the end in the width direction is set to 1.2 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 5.

<Comparative Example 6> Both warp and weft yarns were made of low-dielectric glass yarn LCE255 (elastic modulus 61 GPa, TEX 19.45) manufactured by AGY Corporation. A glass cloth (grey fabric) with a warp yarn inlay density of 60 ends/25 mm and a weft yarn inlay density of 57 ends/25 mm was woven using an air-jet shuttleless loom. The obtained grey fabric was subjected to desizing and washing, and then splitting treatment using high-pressure water spray. Next, after degreasing by heat treatment at 400℃ for 24 hours, the glass cloth was immersed in a treatment solution using a silane coupling agent as a surface treatment agent, extruded, and then dried at 120℃ for 1 minute. Further fiber-opening processing using high-pressure water spraying was then performed to obtain glass cloth with a width of 1300 mm.

<Example 6> The warp width in the range from 100 mm to 300 mm from the end in the width direction is made the same as in other ranges. The tension during warping and the pressure of the high-pressure water spray during opening are adjusted in the width direction. The tension during desizing and washing, and during opening via high-pressure water spray, is also adjusted to be lower. Otherwise, a glass cloth with a width of 1300 mm is manufactured using the same method as in Comparative Example 6.

Regarding the tension during warping, the tension within the range of 100 mm to 300 mm from the end in the width direction is set to 0.8 times the tension in other ranges. Regarding the pressure of the high-pressure water spray, the spray pressure within the range of the center point 100 mm from the end in the width direction to 300 mm inward from the end is set to 1.2 times the pressure in other ranges. The linear tension during desizing and washing, and during the opening process using high-pressure water spray, is set to 0.5 times that of Comparative Example 6.

<Reference Example 1> Except for the warp and weft yarns, both were made of E-glass yarn D450 (elastic modulus 74 GPa, TEX 11.05), a glass cloth with a width of 1300 mm was obtained using the same method as in Comparative Example 3.

Compared to the glass cloth of the comparative example, the low-dielectric glass cloth of the embodiment exhibits less swaying. Furthermore, compared to the glass cloth of the comparative example, the glass cloth of the embodiment has the same thickness, air permeability, resin impregnation, elongation, and slope in the stress-strain curve at both ends and the center in the width direction. The previous E-glass cloth with a higher elastic modulus shown in the reference example, although manufactured using the same method as in Comparative Example 3, exhibits less swaying compared to the glass cloths of Comparative Examples 3 and 4. Its thickness, air permeability, resin impregnation, elongation, and slope in the stress-strain curve are also the same at both ends and the center in the width direction. Large slack and significant oscillation are characteristic problems of low-dielectric glass cloths with low elastic modulus, but this embodiment can solve these problems.

[Table 1] Table 1 Implementation Example 1 Comparative example 1 Glass yarn Elastic modulus (GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 Composition of glass cloth Average thickness (μm) twenty one twenty one Average of all warp yarn widths (μm) 197 183 Average warp width at the ends in the width direction (μm) 194 169 Average warp width (μm) at the center of the width direction 200 192 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 6 twenty three Standard deviation of warp yarn width (μm) 13.8 14.8 Properties of glass cloth Cloth movement (mm) 4 9 Thickness (μm) end twenty two twenty four Thickness (μm) Central part twenty one twenty one Air permeability ( ^cm³ / ^cm² /s) at the end 66 52 Breathability ( ^cm³ / ^cm² /s) Central section 62 75 Impregnated (root) tip 3 4 Infiltrative (root) central part 3 3 Difference in the slope of the stress-strain curve in the width direction (%) 4 7 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 4 7

[Table 2] Table 2 Implementation Example 2 Implementation Example 2B Implementation Example 2C Implementation Example 2D Implementation Example 2E Implementation Example 2F Comparative example 2 Glass yarn Elastic modulus (GPa) 61 61 61 61 61 61 61 Boron content (wt%) 7.1 7.1 7.1 7.1 7.1 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 0.04 0.04 0.04 0.04 0.04 Composition of glass cloth Average thickness (μm) 29 29 29 29 29 29 31 Average of all warp yarn widths (μm) 222 222 223 222 222 222 223 Average warp width at the ends in the width direction (μm) 219 217 217 215 211 220 190 Average warp width (μm) at the center of the width direction 222 222 224 223 223 222 234 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 3 5 7 8 12 2 44 Standard deviation of warp yarn width (μm) 6.3 8.4 12.7 12.9 13.5 6.1 18.6 Properties of glass cloth Cloth movement (mm) 3 5 6 7 8 3 twenty two Thickness (μm) end 29 30 30 30 31 29 35 Thickness (μm) Central part 29 29 29 29 30 29 30 Air permeability ( ^cm³ / ^cm² /s) at the end 27 27 27 27 27 27 17 Breathability ( ^cm³ / ^cm² /s) Central section 28 28 29 30 30 28 30 Impregnated (root) tip 2 2 2 2 2 2 4 Infiltrative (root) central part 2 2 2 2 2 2 2 Difference in the slope of the stress-strain curve in the width direction (%) 4 4 4 4 4 4 6 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 4 4 4 4 4 4 6

[Table 3] Table 3 Implementation Example 3 Comparative example 3 Glass yarn Elastic modulus (GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 Composition of glass cloth Average thickness (μm) 44 49 Average of all warp yarn widths (μm) 319 303 Average warp width at the ends in the width direction (μm) 316 281 Average warp width (μm) at the center of the width direction 322 318 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 6 37 Standard deviation of warp yarn width (μm) 18.2 23.9 Properties of glass cloth Cloth movement (mm) 8 twenty one Thickness (μm) end 46 53 Thickness (μm) Central part 44 48 Air permeability ( ^cm³ / ^cm² /s) at the end 32 5 Breathability ( ^cm³ / ^cm² /s) Central section 36 27 Impregnated (root) tip 4 7 Infiltrative (root) central part 4 4 Difference in the slope of the stress-strain curve in the width direction (%) 3 8 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 3 8

[Table 4] Table 4 Implementation Example 4 Comparative example 4 Glass yarn Elastic modulus (GPa) 56 56 Boron content (wt%) 7.5 7.5 Phosphorus content (wt%) 1.8 1.8 Composition of glass cloth Average thickness (μm) 45 48 Average of all warp yarn widths (μm) 316 301 Average warp width at the ends in the width direction (μm) 312 277 Average warp width (μm) at the center of the width direction 319 320 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 7 43 Standard deviation of warp yarn width (μm) 15.2 25.2 Properties of glass cloth Cloth movement (mm) 7 25 Thickness (μm) end 46 53 Thickness (μm) Central part 44 47 Air permeability ( ^cm³ / ^cm² /s) at the end 31 6 Breathability ( ^cm³ / ^cm² /s) Central section 35 30 Impregnated (root) tip 6 11 Infiltrative (root) central part 6 7 Difference in the slope of the stress-strain curve in the width direction (%) 3 10 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 3 4

[Table 5] Table 5 Implementation Example 5 Comparative example 5 Glass yarn Elastic modulus (GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 Composition of glass cloth Average thickness (μm) 68 80 Average of all warp yarn widths (μm) 352 336 Average warp width at the ends in the width direction (μm) 351 312 Average warp width (μm) at the center of the width direction 352 342 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 1 30 Standard deviation of warp yarn width (μm) 9.3 12.9 Properties of glass cloth Cloth movement (mm) 6 18 Thickness (μm) end 70 87 Thickness (μm) Central part 67 77 Air permeability ( ^cm³ / ^cm² /s) at the end 1 2 Breathability ( ^cm³ / ^cm² /s) Central section 1 1 Impregnated (root) tip 4 7 Infiltrative (root) central part 3 3 Difference in the slope of the stress-strain curve in the width direction (%) 3 5 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 3 5

[Table 6] Table 6 Implementation Example 6 Comparative example 6 Glass yarn Elastic modulus (GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 Composition of glass cloth Average thickness (μm) 83 90 Average of all warp yarn widths (μm) 395 390 Average warp width at the ends in the width direction (μm) 395 379 Average warp width (μm) at the center of the width direction 396 393 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 1 14 Standard deviation of warp yarn width (μm) 8.9 13.5 Properties of glass cloth Cloth movement (mm) 5 15 Thickness (μm) end 85 95 Thickness (μm) Central part 82 89 Air permeability ( ^cm³ / ^cm² /s) at the end 1 4 Breathability ( ^cm³ / ^cm² /s) Central section 1 3 Impregnated (root) tip 8 11 Infiltrative (root) central part 6 6 Difference in the slope of the stress-strain curve in the width direction (%) 2 4 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 2 4

[Table 7] Table 7 Reference Example 1 Glass yarn Elastic modulus (GPa) 74 Boron content (wt%) 1.9 Phosphorus content (wt%) 0.03 Composition of glass cloth Average thickness (μm) 45 Average warp yarn width (μm) of all widths 311 Average warp width at the ends in the width direction (μm) 304 Average warp width (μm) at the center of the width direction 313 The difference (μm) between the warp width at the center and the warp width at the ends in the width direction. 9 Standard deviation of warp yarn width (μm) 15.1 Properties of glass cloth Cloth movement (mm) 8 Thickness (μm) end 46 Thickness (μm) Central part 44 Air permeability ( ^cm³ / ^cm² /s) at the end 15 Breathability ( ^cm³ / ^cm² /s) Central section 18 Impregnated (root) tip 3 Infiltrative (root) central part 3 Difference in the width of the slope of the stress-strain curve in the direction of (%) 4 Width-direction difference (%) of warp elongation under a 50 N/inch load in the stress-strain curve. 4

Claims (13)

A type of glass cloth, which is made of glass yarn containing a plurality of glass filaments as warp and weft yarns, having a thickness of 5 μm to 100 μm, wherein the length of the glass cloth in the width direction is 1000 mm or more, and the difference X between the warp width at the ends and the center of the width direction of the glass cloth is less than or equal to the standard deviation α of the warp width of the glass cloth in the entire width measurement. For example, in the glass cloth of Request 1, the difference X in the warp width is less than 0.7 times the standard deviation α of the warp width of the total width of the glass cloth. For example, in the glass cloth of request item 1 or 2, the difference X of the warp width is less than 0.5 times the standard deviation α of the warp width of the total width of the glass cloth. For example, in the glass cloth of request item 1 or 2, the standard deviation α of the warp width of all width measurements of the glass cloth is less than 0.08 times the average value β of the warp width of all width measurements of the glass cloth. For example, in the glass cloth of request item 1 or 2, the standard deviation α of the warp width of all width measurements of the glass cloth is less than 0.04 times the average value β of the warp width of all width measurements of the glass cloth. For example, in the glass cloth of request item 1 or 2, the standard deviation α of the warp width of all width measurements of the glass cloth is less than 0.03 times the average value β of the warp width of all width measurements of the glass cloth. For example, the glass cloth in request item 1 or 2, wherein the TEX of the glass yarn is 1.0 or higher and 25 or lower. The glass cloth in Request 1 or 2 is composed of glass yarn with an elastic modulus of 50 GPa or more and 70 GPa or less. The glass cloth in Request 1 or 2 is composed of glass yarn with an elastic modulus of 50 GPa or more and 63 GPa or less. For example, the glass cloth in request item 1 or 2, wherein the sum of the boron content and phosphorus content in the glass cloth is more than 5% by mass and less than 20% by mass. For example, the glass cloth in request item 1 or 2, wherein the sum of the boron content and phosphorus content in the glass cloth is more than 6.5% by mass and less than 20% by mass. A prepreg having a glass cloth as claimed in claim 1 or 2, and a matrix resin composition impregnated in the glass cloth. A printed circuit board having a glass cloth as claimed in claim 1 or 2, and a hardened matrix resin composition impregnated in the glass cloth.