TW202413758A - Glass cloth, prepreg and printed circuit board characterized in that the low-dielectric glass clot is less loss and has uniform thickness, air permeability and resin impregnation properties - Google Patents

Abstract

The present invention provides: a low-dielectric glass cloth that is less loose and has uniform thickness, air permeability and resin impregnation properties; and a prepreg and a printed circuit board of using the glass cloth. The glass cloth of the present invention is constituted by using the glass yarns containing a plurality of glass filaments as warp yarns and weft yarns and has a thickness of 5 [mu]m to 100 [mu]m. Moreover, the length of the glass cloth in the width direction is 1000 mm or more. A difference X in warp width between an end part in the width direction and a central part in the width direction of the glass cloth is equal to or less than a standard deviation [alpha] of the warp width.

Description

Glass cloth, prepreg, and printed circuit board

The present invention relates to a glass cloth, a prepreg, and a printed circuit substrate.

With the development of information and communication society in recent years, data communication and/or signal processing are performed at high speed with large capacity. For example, the low dielectric properties of printed circuit boards used in high-end servers, high-end routers/switches, supercomputers, base stations and other communication equipment or measuring instruments have been significantly developed. Therefore, many low dielectric glass cloths have been proposed in the glass cloth constituting printed circuit boards.

For example, the low dielectric glass cloth disclosed in Patent Document 1 is compared to the commonly used E glass cloth in the past. In the glass composition, more boron oxide (B ₂ O ₃ ) is added, and the amount of other components such as silicon dioxide (SiO ₂ ) is adjusted, thereby achieving a low dielectric constant.

As a method for improving the unevenness of the performance or quality of low-dielectric glass cloth in the width direction, Patent Document 2 discloses a glass cloth with improved end relaxation of the low-dielectric glass cloth, and Patent Document 3 discloses a glass cloth with improved warping of the substrate. [Prior Technical Document] [Patent Document]

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

[The problem the invention is trying to solve]

The inventors of the present invention have studied and found that the performance or quality of the low-dielectric glass cloth made using this low-dielectric glass yarn is significantly different from that of the previously used E-glass cloth.

Compared with the previous E glass cloth, the low dielectric glass cloth tends to relax more. In particular, it relaxes more at the ends and the center in the width direction. It is speculated that the reason is that the elastic modulus of the low dielectric glass cloth is lower and the texture of the glass cloth is poor. In addition, the inventors of the present invention have made detailed observations on the low dielectric glass cloth and found that the following tendency exists: the thickness distribution in the width direction is different, and the thickness at the ends in the width direction is about 10% thicker than the thickness in the center. Furthermore, it is clear that the properties such as air permeability and resin impregnation are also different in the width direction, especially at the ends in the width direction. The uneven performance or quality of such glass cloth will also affect the characteristics or quality (resin content, heat resistance, copper foil peeling strength, dimensional stability, etc.) of the prepreg, laminate for printed circuit boards, etc. obtained by using the glass cloth.

Regarding the glass cloth disclosed in Patent Document 2, it is disclosed that the relaxation of the ends of the glass cloth is improved by suppressing the difference in the slope of the stress-strain curve in the direction parallel to the warp yarn between the ends in the width direction and the center portion to be less than 10%. However, the glass cloth disclosed in Patent Document 2 still has room for improvement in terms of the relaxation of the low-dielectric glass cloth.

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

The present invention is completed in view of the above-mentioned problems, and its purpose is to provide a low-dielectric glass cloth with less relaxation and uniform properties in thickness, air permeability, and resin impregnation, a prepreg using the glass cloth, and a printed circuit board. [Technical means for solving the problem]

The inventors of the present invention have conducted intensive research to solve the above-mentioned problem and have found that the above-mentioned problem can be solved by making the difference in the warp yarn width between the end portion and the center portion of the glass cloth within a specified range relative to the unevenness of the warp yarn width. Thus, the present invention has been completed.

That is, the present invention is as follows. [Item 1] A glass cloth having a thickness of 5 μm to 100 μm and composed of glass yarns containing a plurality of glass filaments as warp yarns and weft yarns, wherein the length of the glass cloth in the width direction is 1000 mm or more, and the difference X between the width of the warp yarns at the end portions in the width direction and the center portion in the width direction of the glass cloth is less than the standard deviation α of the width of the warp yarns. [Item 2] The glass cloth as described in Item 1, wherein the difference X between the width of the warp yarns is less than 0.7 times the standard deviation α of the width of the warp yarns. [Item 3] The glass cloth as described in Item 1 or 2, wherein the difference X between the width of the warp yarns is less than 0.5 times the standard deviation α of the width of the warp yarns. [Item 4] The glass cloth as described in any one of items 1 to 3, wherein the standard deviation α of the warp width is not more than 0.08 times the average value β of the warp width. [Item 5] The glass cloth as described in any one of items 1 to 4, wherein the standard deviation α of the warp width is not more than 0.04 times the average value β of the warp width. [Item 6] The glass cloth as described in any one of items 1 to 5, wherein the standard deviation α of the warp width is not more than 0.03 times the average value β of the warp width. [Item 7] The glass cloth as described in any one of items 1 to 6, wherein the TEX of the glass yarn is not less than 1.0 and not more than 25. [Item 8] The glass cloth as described in any one of items 1 to 7, which is composed of glass yarn having an elastic modulus of 50 GPa to 70 GPa. [Item 9] The glass cloth as described in any one of items 1 to 8, which is composed of glass yarn having an elastic modulus of 50 GPa to 63 GPa. [Item 10] The glass cloth as described in any one of items 1 to 9, wherein the sum of the boron content and the phosphorus content in the glass cloth is 5% by mass to 20% by mass. [Item 11] The glass cloth as described in any one of items 1 to 10, wherein the sum of the boron content and the phosphorus content in the glass cloth is 6.5% by mass to 20% by mass. [Item 12] A prepreg comprising the 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 product of a base resin composition impregnated in the glass cloth. [Effect of the invention]

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

Hereinafter, an embodiment of the present invention (hereinafter referred to as "this embodiment") is described in detail, but the present invention is not limited thereto and various modifications can be made within the scope not departing from the gist of the invention.

[Glass cloth] The glass cloth of this embodiment is a glass cloth composed of a plurality of glass filaments as warp yarns and weft yarns, and has 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 between the warp yarn width at the end portion in the width direction and the center portion in the width direction is less than the standard deviation of the warp yarn width.

Here, the end portion in the width direction refers to the area from 100 mm to 250 mm from the end portion in the width direction of the glass cloth having a length in the width direction of 1000 mm or more. In addition, the central portion in the width direction refers to the area from the center in the width direction to 75 mm on both sides of the glass cloth having a length in the width direction of 1000 mm or more. The difference in the warp yarn width between the end portion in the width direction and the central portion in the width direction, and the standard deviation of the warp yarn width are measured in the manner described in the following embodiments.

Compared with E glass cloth, low dielectric glass cloth is prone to sag at both ends and the middle part in the width direction. Also, there is a tendency for the thickness to be about 10% thicker near both ends in the width direction. Furthermore, there is a tendency for properties such as air permeability and resin impregnation to be different in the width direction, especially at the ends in the width direction. In order to solve the above-mentioned problems of low dielectric glass cloth, the inventors of the present invention first studied the reasons for the above-mentioned problems, and the results clearly showed that there is a big difference between the weave structure of the glass cloth at both ends in the width direction and the weave structure of the central part in the width direction.

That is, in the case of a glass cloth having a length of 1000 mm or more in the width direction, the warps are arranged horizontally in a row in the width direction in a range of 100 mm from the end portion in the width direction to 150 mm from the center (the region from 100 mm from the end portion to 250 mm from the end portion in the width direction) and are close to a straight line with almost no undulating structure. On the other hand, in the range from the end portion to 100 mm from the center and in the center portion, the warps are alternately arranged up and down relative to the horizontal and have an undulating structure. By forming such a fabric structure, it was found that when the glass cloth is conveyed in the horizontal direction, the warp yarns are stretched by gravity in the range of about 100 mm from the end to the center and in the center, and the glass cloth droops downward (the warp yarns are stretched in the range of 150 mm from the end to the center, so they do not droop due to gravity). In other words, it was found that the cause of the sag of the low-dielectric glass cloth is the uneven fabric structure in the width direction. It was also found that the sag of the low-dielectric glass cloth can be improved by correcting the strain in the width direction of the fabric structure.

In addition, it was also clarified that in the range of about 100 mm from the end to 150 mm on the central side, the warp yarns were arranged horizontally in roughly one row, and the weft yarns formed larger undulations, so the thickness became thicker. Similarly to the above, it was found that by correcting the strain in the width direction of the fabric structure, the thickness of the low-dielectric glass cloth can be made uniform in the width direction. It was further found that by correcting the strain in the width direction of the fabric structure, the air permeability, resin impregnation, and the difference in the elongation and slope in the width direction of the warp yarn in the stress-strain curve can also be improved. Furthermore, since the warp yarns and weft yarns are densely filled, the thickness of the glass cloth is also reduced.

As described above, in the glass cloth of the present embodiment, the difference X between the width of the warp yarns at the end in the width direction and the center in the width direction is less than the standard deviation α of the width of the warp yarns. More preferably, the difference X between the width of the warp yarns is less than 0.7 times the standard deviation α of the width of the warp yarns, and further preferably, the difference X between the width of the warp yarns is less than 0.5 times the standard deviation α of the width of the warp yarns. If the difference X between the width of the warp yarns at the end in the width direction and the center in the width direction is less than the standard deviation α of the width of the warp yarns, the fabric structure becomes uniform in the width direction, and the difference in the width direction of the glass cloth in terms of slack, thickness, resin impregnation, and air permeability is improved to be smaller. The smaller the difference X between the warp yarn width at the end and the center in the width direction, the better. The best is that the warp yarn width is substantially the same. Even if the warp yarn width at the end in the width direction is wider than that in the center in the width direction, as long as it is within 0.3 times the standard deviation of the warp yarn width, the difference in the width direction of the glass cloth in terms of relaxation, thickness, resin impregnation, and air permeability can be improved. Therefore, the lower limit of the difference X between the warp yarn width at the end and the center in the width direction is preferably -0.3α (0.3 times the negative standard deviation).

The inventors of the present invention have found out that the strain of the fabric structure is generated in the process of spreading the filaments of the glass yarn bundle and widening the yarn bundle width during the flattening process and the fiber opening process, and the fabric structure is formed again. The flattening process and the fiber opening process are performed by the following processes: processing using high-pressure water spray, processing using a vibration washer, or processing using high-frequency vibration using a liquid as a medium. These processes are performed while the glass cloth is conveyed in the horizontal direction while a tension is applied to the warp direction of the glass cloth. At this time, the self-weight of the glass cloth causes the force of downward hanging to act. Furthermore, these processes are performed using water, so the self-weight of the water-containing glass cloth increases, and the force of causing it to hang down in the downward direction becomes larger. In this way, in the glass cloth, the support provided by the conveying roller, the tension in the warp direction, and the downward force generated by the self-weight act in combination. As a result, the warp tension acts locally more strongly in the range from 100 mm from the end to 300 mm from the end. Therefore, in the range from 100 mm from the end to 300 mm from the end, the width of the warp does not widen, and the warp remains in a tensioned state. On the other hand, in the range of 100 mm from the end to the inside and in the center, the width of the warp widens, and the warp also undulates in the process of forming the fabric structure. In this way, it can be seen that the strain in the width direction of the fabric structure is formed.

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

It was found that the strain in the width direction of the fabric structure can be improved by using the following methods alone or in combination as appropriate. ・A method for setting the warp tension in the warp-weaving stage so that the warp yarns in the range of 100 mm from the end to 300 mm from the end are stretched weaker than those in other ranges, producing the grey cloth, and performing flattening and fiber-opening processes; ・A method for weakening the processing force in the range of 100 mm from the end and the center, and strengthening the processing force in the range of 100 mm from the end to 300 mm from the end; ・A method for weakening the tension during flattening and fiber-opening processes, so that the difference between the tension acting on the warp yarns in the range of 100 mm from the end to 300 mm from the end and the tension in other ranges during flattening and fiber-opening processes becomes smaller; ・A method to reduce the processing force of flattening and fiber opening, and to minimize the changes in the cross-sectional structure of the yarn bundle and the changes in the fabric structure.

The glass cloth of this embodiment preferably has a standard deviation α of the warp yarn width that is less than or equal to 0.08 times the average value β of the warp yarn width.

If the standard deviation α of the warp yarn width is less than 0.08 times the average value β of the warp yarn width, the fabric structure becomes more uniform in the width direction, and the difference in slack, thickness, resin impregnation, and air permeability between the end and the center of the glass cloth in the width direction is improved to be smaller, which is better.

The standard deviation α of the warp yarn width is preferably 0.04 times or less of the average value β of the warp yarn width, and more preferably 0.03 times or less of the average value β of the warp yarn width. The average value of the warp yarn width is measured in the manner described in the embodiment described below.

The smaller the standard deviation of the warp yarn width, the easier it is for the fabric structure to become uniform in the width direction, so it is better, and it is particularly preferred to be above 0, but it is not limited to this. In order to make the standard deviation of the warp yarn width within the above range, the following methods are more effective: use original yarns with less unevenness in the twist number, filament diameter, TEX, etc. of the glass yarn used in the warp yarn; make the tension or processing force of the warp weaving step and the flat fiber opening step close to uniform in the width direction; reduce the variation of the tension or processing force. In addition, as mentioned above, the method of reducing the difference in yarn width between the end and the center in the width direction is also effective.

The thickness of the glass cloth of this embodiment is 5 μm or more and 100 μm or less. If the thickness of the glass cloth of this embodiment is 100 μm or less, the printed circuit board can be made high-density and multi-layered. From the perspective of thinning or high-density printed circuit boards, the thinner the thickness, the better, but from the perspective of maintaining practical strength, the lower limit of the thickness is 5 μm. The thickness of the glass cloth of this embodiment is preferably 6 μm or more, and more preferably 8 μm or more. In addition, the thickness of the glass cloth of this embodiment is preferably 98 μm or less, and more preferably 96 μm or less. The thickness of the glass cloth of this embodiment can be measured using the method described in the embodiment.

The elastic modulus of the glass yarn constituting the glass cloth of the present embodiment is preferably 50 GPa or more, more preferably 51 GPa or more, and further preferably 52 GPa or more. If the elastic modulus is 50 GPa or more, there is a tendency as follows: the rigidity of the glass yarn is increased, it is easy to control the structural changes during the flat processing and fiber opening processing of the glass cloth, and it is easy to make a uniform fabric structure in the width direction. On the other hand, the elastic modulus of the glass yarn is preferably 70 GPa or less, more preferably 65 GPa or less, and further preferably 63 GPa or less. If the elastic modulus is below 70 GPa, the glass yarn has a moderate softness, so during the warping, weaving steps, flat processing, and fiber opening processing in the glass cloth processing, it is easy to be affected by tension or processing force, resulting in changes in the fabric structure, so it is easy to make a fabric structure that is uniform in the width direction. In addition, when the elastic modulus is below 70 GPa, the glass yarn and glass cloth are softer, so the previous glass cloth has a tendency to produce strain in the fabric structure in the width direction, and this implementation method is conducive to making a fabric structure that is uniform in the width direction. The elastic modulus of the glass yarn can be measured using the method described in the embodiment.

The dielectric constant of the glass cloth of this embodiment is preferably 5.0 or less, more preferably 4.7 or less, further preferably 4.5 or less, and particularly preferably 4.0 or less at a frequency of 1 GHz. Furthermore, in this embodiment, when the dielectric constant is mentioned, it means the dielectric constant at a frequency of 1 GHz unless otherwise specified. There is no particular limitation on the weaving structure of the glass cloth of this embodiment, for example, weaving structures such as plain weave, square weave, satin weave, and twill weave can be cited. Among them, the plain weave structure is more preferred.

The glass yarn constituting the glass cloth of the present embodiment is obtained by bundling a plurality of filaments and twisting them as needed. In this case, the glass yarn is classified as glass multifilament, and the filaments (glass filaments) contained in the glass yarn are classified as glass single filaments. The weaving density of the warp yarn and the weft yarn of the glass cloth of the present embodiment is preferably 30 to 120 filaments/25 mm, more preferably 40 to 110 filaments/25 mm, and further preferably 50 to 100 filaments/25 mm. The average diameter of the glass single filaments constituting the warp yarn and the weft yarn is preferably 2.5 to 9 μm, more preferably 3.0 to 8 μm, and further preferably 3.5 to 7.5 μm, respectively. It can be selected and used appropriately according to the target thickness of the glass cloth. The average number of glass filaments constituting the warp yarn and the weft yarn is preferably 20 to 250, more preferably 30 to 230, and even more preferably 33 to 220.

The preferred range of the ignition loss value of the glass cloth of the present embodiment is 0.25 mass % to 1.5 mass %, more preferably 0.3 mass % to 1.4 mass %, and further preferably 0.35 mass % to 1.3 mass %.

The composition of the glass cloth of the present embodiment is described below. The composition of the glass cloth has the same meaning as the composition of the glass yarn constituting the glass cloth. As the element constituting the glass cloth, at least one 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) can be cited.

The silicon (Si) content of the glass yarn is preferably 40 to 60 mass %, more preferably 45 to 55 mass %, further preferably 47.0 to 53.5 mass %, and further preferably 48.0 to 52.0 mass % when converted to SiO _2. Si is a component that forms the skeleton structure of the glass yarn. Therefore, by increasing the Si content to 40 mass % or more when converted to SiO ₂ , the strength of the glass yarn is further improved, and there is a tendency that the fracture of the glass cloth is further suppressed in subsequent steps such as the manufacturing step of the glass cloth and the manufacturing step of the prepreg using the glass cloth. In addition, by increasing the Si content to 40 mass % or more when converted to SiO ₂ , there is a tendency that the dielectric constant of the glass cloth of the present embodiment is further reduced. On the other hand, by reducing the Si content to 60% by mass or less in terms of _SiO2 , there is a tendency that the viscosity during melting is further reduced during the manufacturing process of the glass filaments, and a glass fiber with a more homogeneous glass composition is obtained. Therefore, it is not easy for the obtained glass filaments to have local areas that are prone to devitrification or areas where bubbles are difficult to remove, so it is not easy for the glass filaments to have areas with locally weak strength. As a result, the glass cloth obtained using the glass filaments is not easy to break. The Si content can be adjusted by the amount of raw materials used in the production of the glass filaments.

The _boron (B) content of the glass yarn is preferably _15-40 mass %, more preferably 17-30 mass %, or more preferably 20-40 mass %, further preferably 18-28 mass %, further preferably 19-26 mass %, further preferably 20-25 mass %, and most preferably 20.5-24.5 mass %, calculated as B 2 O 3 .

When the B content is 15% by mass or more in terms of B ₂ O ₃ , the dielectric constant tends to be further reduced. Also, when the B content is 15% by mass or more in terms of B ₂ O ₃ , the brittleness resistance of the glass cloth of the present embodiment is improved, and the glass cloth is given appropriate softness or elasticity, so that when the glass yarn contacts the weaving mechanism components such as the yarn guide and the reed, hairiness is not easily generated.

On the other hand, in order to ensure the strength of the glass yarn, the B content is preferably 40% by mass or less in terms of B ₂ O _3. When the B content is 40% by mass or less, the moisture absorption resistance is improved, and the stability of the surface characteristics of the glass yarn described later can be appropriately ensured.

In particular, when the Si content in the glass yarn is within the above range as calculated as SiO ₂ and the B content is within the above range as calculated as B ₂ O ₃ , the above effects related to Si and B can be easily exerted synergistically, which is preferred.

The B content can be adjusted by the usage (addition) of the raw materials used in the production of the glass filaments. Furthermore, when the production conditions, usage or content may change during the production process of the glass filaments, the change can be predicted in advance and the addition of raw materials can be adjusted.

The aluminum (Al) content of the glass yarn is preferably _11-18 % _by mass, more preferably 11-17.5% _by mass, and further preferably _12-17.0 % by mass. When the Al content is within the above range, the electrical properties and strength tend to be further improved. The Al content can be adjusted by the amount of raw materials used (addition amount) in the production of the glass filament.

The calcium (Ca) content of the glass yarn is preferably 5.0-10% by mass, more preferably 5.0-9.0% by mass, and further preferably 5.0-8.5% by mass, as converted to CaO. When the Ca content is 5.0% by mass or more as converted to CaO, there is a tendency that the viscosity during melting is further reduced during the manufacturing process of the glass filament, and a glass fiber with a more homogeneous glass composition is obtained. In addition, when the Ca content is 10% by mass or less as converted to CaO, there is a tendency that the dielectric constant is further increased. The Ca content can be adjusted by the amount of raw materials used (addition amount) used in the production of the glass filament.

The phosphorus (P) content of the glass yarn is preferably 8.0 mass% or less, more preferably 7.0 mass% or less, and further preferably 6.0 mass% or less, calculated as P ₂ O _5. The P content may exceed 0 mass% calculated as P ₂ O _5. When the P content exceeds 0 mass% calculated as P ₂ O ₅ , the dielectric properties of the glass cloth tend to be better. When the P content is 8.0 mass% or less, calculated as P ₂ O ₅ , the heat resistance of the glass cloth tends to be improved. The P content can be adjusted by the amount of raw materials used (addition amount) for the production of the glass filaments.

From the perspective of making it easy to reduce the dielectric constant and dielectric loss factor of the glass cloth, and from the perspective of making it easy to make a uniform fabric structure in the width direction, the sum of the boron content and the phosphorus content in the glass cloth is preferably 5% by mass or more and 20% by mass or less. The greater the sum of the boron content and the phosphorus content in the glass cloth, the smaller the dielectric constant and the dielectric loss factor of the glass cloth tend to be. By making the sum of the boron content and the phosphorus content 5% by mass or more, the dielectric constant and the dielectric loss factor are significantly reduced compared to the laminate obtained using the conventional E glass cloth, thereby improving the applicability to the large capacity and high speed of data communication or signal processing. From the perspective of making it easier to make the dielectric constant and dielectric loss factor of the glass cloth smaller, and from the perspective of making it easier to make a uniform fabric structure in the width direction, the sum of the boron content and the phosphorus content in the glass cloth is preferably 6.5 mass% or more and 20 mass% or less. The greater the sum of the boron content and the phosphorus content in the glass cloth, the smaller the dielectric constant and the dielectric loss factor of the glass cloth tend to be. By making the sum of the boron content and the phosphorus content 6.5 mass% or more, the dielectric constant and the dielectric loss factor are significantly reduced compared to the laminate obtained by using the conventional E glass cloth, thereby improving the applicability to the large capacity and high speed of data communication or signal processing. For example, compared to the dielectric constant of E glass, which is about 7, the dielectric constant tends to decrease. For example, when the sum of the boron content and the phosphorus content is 7.4 mass%, the dielectric constant is about 4.8, and when the sum of the boron content and the phosphorus content is 9.2 mass%, the dielectric constant is about 4.4.

If the sum of the boron content and the phosphorus content is 5% by mass or more, the glass cloth of the present embodiment has a moderate degree of softness, so during the warping, weaving steps, flat processing, and fiber opening processing of the glass cloth, it is easy to be affected by tension or processing force to cause the fabric structure to change, so there is a tendency to easily make a fabric structure that is uniform in the width direction. In addition, if the sum of the boron content and the phosphorus content is 6.5% by mass or more, the glass cloth of the present embodiment has a moderate degree of softness, so during the warping, weaving steps, flat processing, and fiber opening processing of the glass cloth, it is easy to be affected by tension or processing force to cause the fabric structure to change, so there is a tendency to easily make a fabric structure that is uniform in the width direction.

By making the sum of the boron content and the phosphorus content 20 mass % or less, the moisture absorption resistance and/or heat resistance of the glass cloth of this embodiment can be maintained at the same level as that of E-glass having a sum of the boron content and the phosphorus content of about 2 mass %.

The sum of the boron content and the phosphorus content in the glass cloth can be adjusted by adding the glass raw materials containing boron and phosphorus during the process of manufacturing the glass cloth. In addition, since the boron and phosphorus content in the glass will change during the step of melting the glass raw materials in the step of manufacturing the glass cloth, the addition amount can also be appropriately adjusted in combination with the change. Furthermore, the above-mentioned contents can be measured using ICP (Inductively Coupled Plasma) emission spectrometry. Specifically, the Si content and the B content can be obtained as follows: after dissolving the weighed glass cloth with sodium carbonate, dissolving it with dilute nitric acid and setting it to a specified volume, the obtained sample is measured using ICP emission spectrometry. In addition, the Fe content can be obtained by dissolving the weighed glass cloth using an alkaline dissolution method and setting the volume to a predetermined value, and measuring the obtained sample using an ICP emission spectrometry method. Furthermore, the Al content, Ca content, P content, and Mg content can be obtained by heating and decomposing the weighed glass cloth using perchloric acid, sulfuric acid, nitric acid, and hydrogen fluoride, dissolving it using dilute nitric acid and setting the volume to a predetermined value, and measuring the obtained sample using an ICP emission spectrometry method. Furthermore, as an ICP emission spectrometry analysis device, PS3520VDD II manufactured by Hitachi High-Tech Science Co., Ltd. can be used.

Here, the content of the above-mentioned elements constituting the glass cloth of the present embodiment described in this specification is the element itself if there is no description of oxide conversion, and is the weight of the above-mentioned element when the oxide conversion is recorded. In addition, when the content of the above-mentioned elements is recorded in terms of weight when the oxide conversion is required, it can also be converted based on the weight of the element itself, rather than by oxide conversion.

From the perspective of easily adjusting the thickness of the glass cloth of the present embodiment to 5 μm to 100 μm, the TEX of the glass cloth is preferably 1.0 to 25, more preferably 1.5 to 23, and further preferably 2.0 to 21. The glass cloth of the present embodiment may also be surface treated with a surface treatment agent. There is no particular limitation on the surface treatment agent, and for example, a silane coupling agent may be used, and water, an organic solvent, an acid, a dye, a pigment, a surfactant, etc. may also be used together as needed.

There are no particular limitations on the silane coupling agent, and for example, a 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 group, Y is independently an alkoxy group, n is an integer from 1 to 3, and R is independently a group selected from the group consisting of a methyl group, an ethyl group, and a phenyl group). X is preferably an organic functional group having at least three of an amino group and an unsaturated double bond group, and X is more preferably an organic functional group having at least four of an amino group and an unsaturated double bond group. The alkoxy group may be in any form, but from the viewpoint of stabilizing the glass cloth of the present embodiment, an alkoxy group having 5 or less carbon atoms is preferred. Specific examples of the silane coupling agent 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, N-β-(N-di(vinylbenzyl)aminoethyl)-N-γ-(N-vinylbenzyl)-γ-aminopropyltrimethoxysilane and its hydrochloride. Hydrochloride, N-β-(N-benzylaminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, N-β-(N-benzylaminoethyl)-γ-aminopropyltriethoxysilane and its hydrochloride, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, aminopropyltrimethoxysilane, vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane and other known monomers, or mixtures thereof. The molecular weight of the silane coupling agent is preferably 100-600, more preferably 150-500, and further preferably 200-450. Among them, it is preferred to use two or more silane coupling agents with different molecular weights. 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 becomes higher, and the reactivity with the base resin tends to be further improved.

<Method for manufacturing glass cloth> The method for manufacturing glass cloth of the present embodiment is not particularly limited, and the following method can be cited as an example: glass yarn is used for warp yarn and weft yarn, and is woven by a conventional method, and then the glass cloth is subjected to subsequent processing such as treatment with a silane coupling agent. The weaving structure of the glass cloth is not particularly limited, and examples thereof include: plain weave, square weave, satin weave, twill weave and other weaving structures. Furthermore, a mixed weaving structure using different types of glass yarns can also be used. Among them, the plain weave structure is preferred.

The manufacturing method of the glass cloth of the present embodiment is not particularly limited. For example, a method having the following steps can be appropriately exemplified: a coating step, which is to apply a treatment liquid having a silane coupling agent concentration of 0.1 to 3.0 wt% to the glass cloth so that the surface of the glass filaments is almost completely covered with the silane coupling agent; a fixing step, which is to fix the silane coupling agent on the surface of the glass filaments by heating and drying; and a fiber opening step, which is to open the glass fibers of the glass cloth.

As a solvent for dissolving or dispersing the silane coupling agent, water or an organic solvent may be used. However, from the perspective of safety and environmental protection, water is preferably used as the main solvent. As a method for obtaining a treatment solution with water as the main solvent, any of the following methods is preferred: a method of directly adding the silane coupling agent to water; a method of dissolving the silane coupling agent in a water-soluble organic solvent to prepare an organic solvent solution, and then adding the organic solvent solution to water. In order to improve the water dispersibility and stability of the treatment solution of the silane coupling agent, a surfactant may also be used in combination.

As a method of applying the treatment liquid of the silane coupling agent to the glass cloth, the following methods can be cited: (1) a method of accumulating the treatment liquid of the silane coupling agent into a bath liquid, and making the glass cloth immersed in the bath liquid and passing through the bath liquid (hereinafter referred to as the "immersion method"); (2) a method of directly applying the treatment liquid of the silane coupling agent to the glass cloth using a roll coater, a die-mouth coater, or a gravure coater. When the immersion method (1) is used for coating, it is preferred that the immersion time of the glass cloth in the treatment liquid be set to be not less than 0.5 seconds and not more than 1 minute. In addition, as a method of drying the solvent by heating after applying the treatment liquid to the glass cloth, there can be cited well-known methods such as hot air and electromagnetic waves.

The heating and drying temperature is preferably above 90°C, more preferably above 100°C, so that the silane coupling agent and the glass can react fully. In addition, in order to prevent the degradation of the organic functional groups of the silane coupling agent, the heating and drying temperature is preferably below 300°C, more preferably below 200°C.

The fiber opening method in the fiber opening step is not particularly limited, and examples thereof include a method of fiber opening the glass cloth using a water spray (high pressure water fiber opening), a vibration washer, ultrasonic water, a roller press, etc. In order to ensure that the total area of the basket holes is within a fixed range, it is preferred to perform the fiber opening step using a water spray.

When fiber opening is performed by spraying water, it is sufficient to set the water pressure appropriately. In order to adjust the total area of the basket-shaped holes in the glass cloth, the water pressure is preferably kept constant. Here, keeping the water pressure constant means reducing 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 may also be performed before and after the fiber opening step.

<Prepreg> This embodiment is also a prepreg, which is a composite of the above-mentioned glass cloth and the matrix resin composition. The matrix resin composition is impregnated in the glass cloth. The prepreg can be manufactured by a conventional method. For example, after impregnating a varnish obtained by diluting the matrix resin composition with an organic solvent into the glass cloth, the organic solvent can be volatilized in a drying furnace to produce a prepreg impregnated with the matrix resin composition.

As the resin constituting the matrix resin composition, any of a thermosetting resin and a thermoplastic resin can be used. The thermosetting resin is not particularly limited, and examples thereof include the following resins: a) epoxy resin, which is formed by reacting and curing a compound having an epoxy group with a compound having at least one of an amino group, a phenol group, an acid anhydride group, a hydrazide group, an isocyanate group, a cyanoacyl group, and a hydroxyl group that react with the epoxy group in the absence of a catalyst or with the addition of a catalyst having a reaction catalyst such as an imidazole compound, a tertiary amine compound, a urea compound, or a phosphorus compound; b) free radical polymerization type curing resin, which is formed by using a thermal decomposition type catalyst to cure the resin; c) a maleimide tris-imide resin, which is formed by reacting and curing a compound having at least one of a vinyl group, an allyl group, a methacryl group, and an acryl group using a catalyst or a photodegradable catalyst as a reaction initiator; c) a maleimide tris-imide resin, which is formed by reacting and curing a compound having a cyano group with a compound having a maleimide group; d) a thermosetting polyimide resin, which is formed by reacting and curing a maleimide compound with an amine compound; e) a benzophenone resin, which is formed by cross-linking and curing a compound having a benzophenone ring by heat polymerization.

The thermoplastic resin is not particularly limited, and examples thereof include polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, aromatic polyamide, polyetheretherketone, thermoplastic polyimide, insoluble polyimide, polyamide imide, fluororesin, etc. A thermosetting resin and a thermoplastic resin may also be used in combination.

The resin constituting the matrix resin composition in the prepreg comprising glass cloth and the matrix resin composition as one of the embodiments of the present invention is preferably a polyphenylene ether resin. Furthermore, it is preferably a polyphenylene ether resin having 1.5 to 5 functional groups containing carbon-carbon double bonds such as vinyl, allyl, methacryl, and acryl groups at the end of the main chain per molecule. Furthermore, it is preferably a polyphenylene ether resin having a number average molecular weight of 500 to 8,000. If the matrix resin is a polyphenylene ether resin, the dielectric properties are excellent, so it is preferred.

Furthermore, it is speculated that because the resin constituting the matrix resin composition has the above-mentioned functional groups and number-average molecular weight, the resin composition can easily penetrate into the interior of the glass cloth during the prepreg preparation step and the press molding step, thereby ensuring more contact points with the glass cloth, thereby having excellent dielectric properties. Even in a system where the in-plane uniformity of the glass is high and the air permeability is low, and the number of direct contact points between the resin matrix layers above and below the glass cloth is reduced, as in the present embodiment, the interface between the glass cloth and the resin composition has stronger adhesion, thereby improving heat resistance or insulation reliability.

<Printed circuit board> This embodiment is also a printed circuit board having the above-mentioned glass cloth and a cured product of a base resin composition impregnated in the above-mentioned glass cloth. In addition, the printed circuit board of this embodiment is manufactured using the above-mentioned 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 a printed circuit board, a high-quality printed circuit board with reduced signal propagation speed differences of multiple transmission lines can be provided. [Example]

The present invention is described in more detail below using examples and comparative examples. The present invention is not limited to the following examples.

[Elastic modulus] The elastic modulus of glass yarn is measured by the pulse echo superposition method using a glass block obtained by melting and cooling the glass yarn as a test piece.

[Evaluation: average value of warp yarn width in total width, standard deviation of warp yarn width] Scan the glass cloth in a direction perpendicular to the MD direction with a camera, obtain an image of the warp yarn of the total width of the glass cloth, and measure the yarn width of each warp yarn. Calculate the average value and standard deviation of the warp yarn width of the total width of the glass cloth.

[Evaluation: Warp width at the end and center] The camera was used to scan the glass cloth in a direction perpendicular to the MD direction to obtain an image of the warp of the entire width of the glass cloth, and the yarn width of each warp was measured. The average value of the warp width of the glass cloth from the position 100 mm away from the two ends in the width direction to the position 250 mm away from the ends was calculated, and the narrower value of the yarn width was taken as the warp width of the end. In addition, the average value of the warp width in the range of 75 mm to the left and right from the center in the width direction was calculated, and it was taken as the warp width of the center.

[Evaluation: Thickness average] Measure the thickness of three measuring points in the width direction of the glass cloth in accordance with JIS R3420, with the intervals between the two ends in the width direction and the intervals between each measuring point being equal. Average the thickness of the three points obtained, round off the first decimal point, and calculate the average thickness value (μm).

[Evaluation: Thickness end, center] Measure the thickness of the glass cloth 100 mm inward from both ends in the width direction according to JIS R3420. The larger value of the thickness of the two points is taken as the thickness of the end (μm).

The thickness of the glass cloth was measured in accordance with JIS R3420 with the center of the width direction of the glass cloth as the measuring point. The obtained thickness was defined as the thickness of the central portion (mm).

[Evaluation: Air permeability at the ends and center] The air permeability was measured in accordance with JIS R3420 at the points 100 mm inward from both ends of the glass cloth in the width direction. The larger value of the air permeability at the two points was taken as the air permeability at the ends (cm ³ /cm ² /s).

The air permeability was measured in accordance with JIS R3420 with the center of the width direction of the glass cloth as the measuring point. The obtained air permeability was defined as the air permeability of the central portion (cm ³ /cm ² /s).

[Evaluation: Evaluation of resin impregnation of glass cloth] Samples for impregnation measurement were collected from 100 mm inward from both ends of the glass cloth in the width direction. Also, samples for impregnation measurement were collected from the center of the glass cloth in the width direction.

At 23±2℃, bisphenol A epoxy resin was dissolved in benzyl alcohol to prepare a varnish for impregnation evaluation with a viscosity of 230±5 mPa・s. Then, a glass cloth specimen was immersed in the varnish for impregnation evaluation, and light was irradiated from the horizontal direction while an optical microscope was used to observe the impregnation of the varnish for impregnation evaluation in the glass cloth. Then, the number of pores (unimpregnated areas of the varnish for impregnation evaluation) after a specified time after the glass cloth specimen was immersed in the varnish for impregnation evaluation was counted. At this time, the field of view of the glass cloth observed by the optical microscope was set to about 6.5 mm in the warp direction and about 9 mm in the weft direction.

Regarding both ends in the width direction, the value with the larger number of pores is set as the remaining number of pores (lines) at the end.

The glass cloth of Example 1 and Comparative Example 1 counts the number of pores after 2 minutes. The glass cloth of Example 2, 2B, 2C, 2D, 2E, 2F and Comparative Example 2 counts the number of pores after 3 minutes. The glass cloth of Example 3, 4, Comparative Examples 3, 4 and Reference Example 1 counts the number of pores after 5 minutes. The glass cloth of Example 5, 6 and Comparative Examples 5 and 6 counts the number of pores after 8 minutes.

[Evaluation: Slack during fabric transport] Under a tension of 150 N, the glass cloth was unrolled from a roll-shaped glass cloth wound on a reel core, and bent 90° by a guide roller when it was transported for 2 m. The sway of the glass cloth between the unrolling and the guide roller was measured using a displacement meter (a laser displacement sensor manufactured by Keyence Corporation). The displacement meter was set at two points 100 mm inward from both ends of the glass cloth in the width direction, and at the center in the width direction. The difference between the maximum and minimum positions of the vertical position of the glass cloth measured by the displacement meter was taken as the size of the sway of the glass cloth (unit: mm).

[Evaluation: Difference in width direction (%) of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve, and difference in width direction (%) of the slope of the stress-strain curve] The elongation and slope of glass cloth when tension is applied in the warp direction are measured using the method described in 7.4 Tensile strength of JIS R3420 General test method for glass testing. In the method specified by JIS, a test piece with a width of about 30 mm and a length of about 250 mm is collected from the warp direction of the fabric, and the yarns at both ends of the test piece are loosened to a width of about 25 mm. The test piece is installed in the clamping part with a clamping interval of about 150 mm, and stretched at a tensile speed of about 200 mm/min to determine the load at the time of fracture. In this embodiment, in order to improve the measurement accuracy, the tensile test is performed under the same conditions as the method specified in the above JIS except that the tensile speed is set to about 5 mm/min. Test pieces for stress-strain curve measurement are collected from the two ends of the glass cloth in the width direction within the range of 50 mm to 200 mm inward. In addition, test pieces for stress-strain curve measurement are collected from the center of the width direction of the glass cloth. The displacement (mm) when a load of 50 N is applied to each 25 mm width of the glass cloth is calculated, and the ratio of the elongation at the end and the center in the width direction is calculated. Furthermore, for the two ends in the width direction, the larger elongation value is taken as the elongation (mm) of the end. Also, the slope (elongation (mm)/50 N) was calculated based on the elongation (mm) of the glass cloth when a load of 50 N was applied per 25 mm width, and the ratio of the slopes at the ends and the center in the width direction was calculated. Furthermore, the larger slope value of the two ends in the width direction was taken as the slope of the end.

<Comparison Example 1> The warp yarn and weft yarn are both low-dielectric glass yarn LCBC1700 (elastic modulus 61 GPa, TEX2.92) manufactured by AGY. A jet shuttleless weaving machine is used to weave glass cloth (grey cloth) with a warp yarn weaving density of 74 yarns/25 mm and a weft yarn weaving density of 74 yarns/25 mm. The obtained grey cloth is subjected to debinding water washing and fiber opening treatment by high-pressure water spraying. Then, after debinding by heating at 400°C for 24 hours, the glass cloth is immersed in a treatment liquid using a silane coupling agent as a surface treatment agent, extruded, and dried at 120°C for 1 minute. Further fiber opening processing using high-pressure water spray was carried out to obtain glass cloth with a width of 1300 mm.

<Example 1> In order to make the warp width in the range from 100 mm to 300 mm from the end in the width direction equal to that in other ranges, the tension during warping and the pressure of high-pressure water spray during fiber opening were adjusted in the width direction, and the line tension during debonding washing and fiber opening by high-pressure water spray was adjusted to be lower. In addition, a glass cloth with a width of 1300 mm was manufactured by the same method as in Comparative Example 1.

Regarding the tension during warping, the tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.2 times the pressure in other ranges. The line tension during debonding water washing and fiber opening by high-pressure water spraying was set to 0.5 times that of Comparative Example 1.

<Comparison Example 2> The warp yarn and weft yarn are both low-dielectric glass yarn LCD1020 (elastic modulus 61 GPa, TEX4.86) manufactured by AGY. A jet shuttleless weaving machine is used to weave glass cloth (grey cloth) with a warp yarn weaving density of 69 yarns/25 mm and a weft yarn weaving density of 69 yarns/25 mm. The obtained grey cloth is subjected to debinding water washing and fiber opening treatment by high-pressure water spraying. Then, after debinding by heating at 400°C for 24 hours, the glass cloth is immersed in a treatment liquid using a silane coupling agent as a surface treatment agent, extruded, and dried at 120°C for 1 minute. Further fiber opening processing using high-pressure water spray was carried out to obtain glass cloth with a width of 1300 mm.

<Example 2> In order to make the warp width in the range from 100 mm to 300 mm from the end in the width direction equal to that in other ranges, the tension during warping and the pressure of high-pressure water spray during fiber opening were adjusted in the width direction, and the line tension during debonding washing and fiber opening by high-pressure water spray was adjusted to be lower. In addition, a glass cloth with a width of 1300 mm was manufactured by the same method as in Comparative Example 2.

Regarding the tension during warping, the tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.2 times that in other ranges. The line tension during debonding water washing and fiber opening by high-pressure water spraying was set to 0.5 times that of Comparative Example 2.

<Example 2B> The tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.9 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.2 times that in other ranges. The line tension during debonding water washing and fiber opening processing by high-pressure water spraying was set to 0.5 times that of Comparative Example 2.

<Example 2C> The tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.1 times that in other ranges. The line tension during debonding water washing and fiber opening processing by high-pressure water spraying was set to 0.5 times that of Comparative Example 2.

<Example 2D> The tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.9 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.1 times that in other ranges. The line tension during debonding water washing and fiber opening processing by high-pressure water spraying was set to 0.5 times that of Comparative Example 2.

<Example 2E> The tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.9 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.1 times that in other ranges. The line tension during debonding water washing and fiber opening processing by high-pressure water spraying was set to 0.8 times that of Comparative Example 2.

<Example 2F> After the fiber opening process by high-pressure water spraying, the two ends including the ear chamber were cut off and processed to a width of 1250 mm. In addition, the same method as Example 2 was used to manufacture a glass cloth with a width of 1250 mm.

<Comparison Example 3> The warp yarn and weft yarn are both low-dielectric glass yarn LCD510 (elastic modulus 61 GPa, TEX9.73) manufactured by AGY. A jet shuttleless weaving machine is used to weave glass cloth (grey cloth) with a warp yarn weaving density of 52.5 yarns/25 mm and a weft yarn weaving density of 52.5 yarns/25 mm. The obtained grey cloth is subjected to debinding water washing and fiber opening treatment by high-pressure water spraying. Then, after debinding by heating at 400°C for 24 hours, the glass cloth is immersed in a treatment liquid using a silane coupling agent as a surface treatment agent, extruded, and dried at 120°C for 1 minute. Further fiber opening processing using high-pressure water spray was carried out to obtain glass cloth with a width of 1300 mm.

<Example 3> In order to make the warp width equal to that in the range from 100 mm from the end in the width direction to 300 mm from the end inward, the tension during warping and the pressure of high-pressure water spray during fiber opening were adjusted in the width direction, and the line tension during debonding washing and fiber opening by high-pressure water spray was adjusted to be lower. In addition, a glass cloth with a width of 1300 mm was manufactured by the same method as in Comparative Example 3.

Regarding the tension during warping, the tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.2 times that in other ranges. The line tension during debonding water washing and fiber opening by high-pressure water spraying was set to 0.5 times that of Comparative Example 3.

<Comparative Example 4> The warp yarn and weft yarn both use low dielectric glass yarn LCD520 (elastic modulus 56 GPa, TEX9.47) manufactured by AGY. In addition, the same method as in Comparative Example 3 is used to obtain a glass cloth with a width of 1300 mm.

<Example 4> The warp yarn and weft yarn are low-dielectric glass yarn LCD520 (elastic modulus 56 GPa, TEX9.47) manufactured by AGY. In addition, the same method as Example 3 is used to obtain a glass cloth with a width of 1300 mm.

<Comparison Example 5> The warp yarn and weft yarn are both low-dielectric glass yarn LCDE340 (elastic modulus 61 GPa, TEX14.59) manufactured by AGY. A jet shuttleless weaving machine is used to weave glass cloth (grey cloth) with a warp yarn weaving density of 59 yarns/25 mm and a weft yarn weaving density of 61 yarns/25 mm. The obtained grey cloth is subjected to debinding water washing and fiber opening treatment by high-pressure water spraying. Then, after debinding by heating at 400°C for 24 hours, the glass cloth is immersed in a treatment liquid using a silane coupling agent as a surface treatment agent, extruded, and dried at 120°C for 1 minute. Further fiber opening processing using high-pressure water spray was carried out to obtain glass cloth with a width of 1300 mm.

<Example 5> In order to make the warp width in the range from 100 mm to 300 mm from the end in the width direction equal to that in other ranges, the tension during warping and the pressure of high-pressure water spray during fiber opening were adjusted in the width direction, and the line tension during debonding washing and fiber opening by high-pressure water spray was adjusted to be lower. In addition, a glass cloth with a width of 1300 mm was manufactured by the same method as in Comparative Example 5.

Regarding the tension during warping, the tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from 100 mm to 300 mm from the end in the width direction was set to 1.2 times that in other ranges. The line tension during debonding water washing and fiber opening by high-pressure water spraying was set to 0.5 times that of Comparative Example 5.

<Comparative Example 6> Low dielectric glass yarn LCE255 (elastic modulus 61 GPa, TEX19.45) manufactured by AGY was used for both the warp yarn and the weft yarn. A glass cloth (grey cloth) with a weaving density of 60 yarns/25 mm for the warp yarn and 57 yarns/25 mm for the weft yarn was woven using an air jet shuttleless loom. The obtained grey cloth was subjected to debinding water washing and fiber opening treatment by high-pressure water spraying. Subsequently, after debinding by heating at 400°C for 24 hours, the glass cloth was immersed in a treatment liquid using a silane coupling agent as a surface treatment agent, extruded, and dried at 120°C for 1 minute. Further fiber opening processing using high-pressure water spray was carried out to obtain glass cloth with a width of 1300 mm.

<Example 6> In order to make the warp width in the range from 100 mm to 300 mm from the end in the width direction equal to that in other ranges, the tension during warping and the pressure of high-pressure water spray during fiber opening were adjusted in the width direction, and the line tension during debonding washing and fiber opening by high-pressure water spray was adjusted to be lower. In addition, a glass cloth with a width of 1300 mm was manufactured by the same method as in Comparative Example 6.

Regarding the tension during warping, the tension in the range from 100 mm to 300 mm from the end in the width direction was set to 0.8 times the tension in other ranges. Regarding the pressure of high-pressure water spraying, the spraying pressure in the range from the center 100 mm from the end in the width direction to 300 mm inward from the end was set to 1.2 times that of other ranges. The line tension during debonding water washing and fiber opening by high-pressure water spraying was set to 0.5 times that of Comparative Example 6.

<Reference Example 1> Except that both the warp yarn and the weft yarn use E glass yarn D450 (elastic modulus 74 GPa, TEX11.05), a glass cloth with a width of 1300 mm is obtained by the same method as in Comparative Example 3.

Compared with the glass cloth of the comparative example, the swing of the low dielectric glass cloth of the embodiment is suppressed to be smaller. In addition, compared with 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 the end and the center in the width direction. The previous E glass cloth with a higher elastic modulus shown in the reference example is manufactured by the same method as that of comparative example 3, but compared with the glass cloth of comparative examples 3 and 4, the swing is smaller, and the thickness, air permeability, resin impregnation, elongation and slope in the stress-strain curve are also the same at the end and the center in the width direction. Larger relaxation and greater swing are problems unique to low-dielectric glass cloth with a lower elastic modulus, but this problem can be solved by this implementation method.

[Table 1] Table 1 Embodiment 1 Comparison Example 1 Glass yarn Elastic modulus(GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 The composition of glass cloth Thickness(μm) Average twenty one twenty one Average value of all warp yarn widths (μm) 197 183 Average warp yarn width at the end in width direction (μm) 194 169 Average warp yarn width in the center of the width direction (μm) 200 192 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 6 twenty three Standard deviation of warp width (μm) 13.8 14.8 Characteristics of glass cloth Fabric swing (mm) 4 9 Thickness (μm) End twenty two twenty four Thickness (μm) Central twenty one twenty one Air permeability (cm ³ /cm ² /s) End 66 52 Air permeability (cm ³ /cm ² /s) Central 62 75 Impregnation (root) End 3 4 Impregnation (root) Central part 3 3 Difference in the width direction of the slope of the stress-strain curve (%) 4 7 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 4 7

[Table 2] Table 2 Embodiment 2 Example 2B Embodiment 2C Embodiment 2D Embodiment 2E Embodiment 2F Comparison 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 The composition of glass cloth Thickness(μm) Average 29 29 29 29 29 29 31 Average value of all warp yarn widths (μm) 222 222 223 222 222 222 223 Average warp yarn width at the end in width direction (μm) 219 217 217 215 211 220 190 Average warp yarn width in the center of the width direction (μm) 222 222 224 223 223 222 234 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 3 5 7 8 12 2 44 Standard deviation of warp width (μm) 6.3 8.4 12.7 12.9 13.5 6.1 18.6 Characteristics of glass cloth Fabric swing (mm) 3 5 6 7 8 3 twenty two Thickness (μm) End 29 30 30 30 31 29 35 Thickness (μm) Central 29 29 29 29 30 29 30 Air permeability (cm ³ /cm ² /s) End 27 27 27 27 27 27 17 Air permeability (cm ³ /cm ² /s) Central 28 28 29 30 30 28 30 Impregnation (root) End 2 2 2 2 2 2 4 Impregnation (root) Central part 2 2 2 2 2 2 2 Difference in the width direction of the slope of the stress-strain curve (%) 4 4 4 4 4 4 6 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 4 4 4 4 4 4 6

[table 3] table 3 Embodiment 3 Comparison Example 3 Glass yarn Elastic modulus(GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 The composition of glass cloth Thickness(μm) Average 44 49 Average value of all warp yarn widths (μm) 319 303 Average warp yarn width at the end in width direction (μm) 316 281 Average warp yarn width in the center of the width direction (μm) 322 318 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 6 37 Standard deviation of warp width (μm) 18.2 23.9 Characteristics of glass cloth Fabric swing (mm) 8 twenty one Thickness (μm) End 46 53 Thickness (μm) Central 44 48 Air permeability (cm ³ /cm ² /s) End 32 5 Air permeability (cm ³ /cm ² /s) Central 36 27 Impregnation (root) End 4 7 Impregnation (root) Central part 4 4 Difference in the width direction of the slope of the stress-strain curve (%) 3 8 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 3 8

[Table 4] Table 4 Embodiment 4 Comparison Example 4 Glass yarn Elastic modulus(GPa) 56 56 Boron content (wt%) 7.5 7.5 Phosphorus content (wt%) 1.8 1.8 The composition of glass cloth Thickness(μm) Average 45 48 Average value of all warp yarn widths (μm) 316 301 Average warp yarn width at the end in width direction (μm) 312 277 Average warp yarn width in the center of the width direction (μm) 319 320 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 7 43 Standard deviation of warp width (μm) 15.2 25.2 Characteristics of glass cloth Fabric swing (mm) 7 25 Thickness (μm) End 46 53 Thickness (μm) Central 44 47 Air permeability (cm ³ /cm ² /s) End 31 6 Air permeability (cm ³ /cm ² /s) Central 35 30 Impregnation (root) End 6 11 Impregnation (root) Central part 6 7 Difference in the width direction of the slope of the stress-strain curve (%) 3 10 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 3 4

[table 5] table 5 Embodiment 5 Comparison Example 5 Glass yarn Elastic modulus(GPa) 61 61 Boron content (wt%) 7.1 7.1 Phosphorus content (wt%) 0.04 0.04 The composition of glass cloth Thickness(μm) Average 68 80 Average value of all warp yarn widths (μm) 352 336 Average warp yarn width at the end in width direction (μm) 351 312 Average warp yarn width in the center of the width direction (μm) 352 342 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 1 30 Standard deviation of warp width (μm) 9.3 12.9 Characteristics of glass cloth Fabric swing (mm) 6 18 Thickness (μm) End 70 87 Thickness (μm) Central 67 77 Air permeability (cm ³ /cm ² /s) End 1 2 Air permeability (cm ³ /cm ² /s) Central 1 1 Impregnation (root) End 4 7 Impregnation (root) Central part 3 3 Difference in the width direction of the slope of the stress-strain curve (%) 3 5 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 3 5

[Table 6] Table 6 Embodiment 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 The composition of glass cloth Thickness(μm) Average 83 90 Average value of all warp yarn widths (μm) 395 390 Average warp yarn width at the end in width direction (μm) 395 379 Average warp yarn width in the center of the width direction (μm) 396 393 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 1 14 Standard deviation of warp width (μm) 8.9 13.5 Characteristics of glass cloth Fabric swing (mm) 5 15 Thickness (μm) End 85 95 Thickness (μm) Central 82 89 Air permeability (cm ³ /cm ² /s) End 1 4 Air permeability (cm ³ /cm ² /s) Central 1 3 Impregnation (root) End 8 11 Impregnation (root) Central part 6 6 Difference in the width direction of the slope of the stress-strain curve (%) 2 4 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied 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 The composition of glass cloth Thickness(μm) Average 45 Average value of all warp yarn widths (μm) 311 Average warp yarn width at the end in width direction (μm) 304 Average warp yarn width in the center of the width direction (μm) 313 Difference between the warp width at the center and the warp width at the end in the width direction (μm) 9 Standard deviation of warp width (μm) 15.1 Characteristics of glass cloth Fabric swing (mm) 8 Thickness (μm) End 46 Thickness (μm) Central 44 Air permeability (cm ³ /cm ² /s) End 15 Air permeability (cm ³ /cm ² /s) Central 18 Impregnation (root) End 3 Impregnation (root) Central part 3 Difference in the width direction of the slope of the stress-strain curve (%) 4 Difference in width direction of elongation in the warp direction when a load of 50 N/inch is applied in the stress-strain curve (%) 4

Claims (13)

A glass cloth having a thickness of 5 μm to 100 μm and composed of glass yarns containing a plurality of glass filaments as warp yarns and weft yarns, the length of the glass cloth in the width direction is 1000 mm or more, and the difference X between the warp yarn width at the end portion in the width direction and the center portion in the width direction of the glass cloth is less than the standard deviation α of the warp yarn width. The glass cloth of claim 1, wherein the difference X in the warp width is less than or equal to 0.7 times the standard deviation α of the warp width. The glass cloth of claim 1 or 2, wherein the difference X in the warp width is less than or equal to 0.5 times the standard deviation α of the warp width. The glass cloth as claimed in claim 1 or 2, wherein the standard deviation α of the warp yarn width is less than or equal to 0.08 times the average value β of the warp yarn width. The glass cloth of claim 1 or 2, wherein the standard deviation α of the warp yarn width is less than or equal to 0.04 times the average value β of the warp yarn width. The glass cloth as claimed in claim 1 or 2, wherein the standard deviation α of the warp yarn width is less than or equal to 0.03 times the average value β of the warp yarn width. The glass cloth as claimed in claim 1 or 2, wherein the TEX of the glass cloth is not less than 1.0 and not more than 25. The glass cloth of claim 1 or 2 is composed of glass yarn having an elastic modulus of not less than 50 GPa and not more than 70 GPa. The glass cloth of claim 1 or 2 is composed of glass yarn having an elastic modulus of not less than 50 GPa and not more than 63 GPa. The glass cloth of claim 1 or 2, wherein the sum of the boron content and the phosphorus content in the glass cloth is not less than 5 mass % and not more than 20 mass %. The glass cloth of claim 1 or 2, wherein the sum of the boron content and the phosphorus content in the glass cloth is not less than 6.5 mass % and not more than 20 mass %. A prepreg comprising the glass cloth as claimed in claim 1 or 2, and a matrix resin composition impregnated in the glass cloth. A printed circuit board comprises the glass cloth as claimed in claim 1 or 2, and a cured product of a base resin composition impregnated in the glass cloth.