TWI873822B - Glass cloth, prepreg, and printed circuit board - Google Patents

Abstract

The purpose of the present invention is to provide a glass cloth having excellent raising quality and stable and uniform resin impregnation with a low dielectric resin, a manufacturing method thereof, and a prepreg and a printed circuit board using the glass cloth. The present invention provides a glass cloth, which is woven with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns, and surface-treated with a surface treatment agent. When the glass cloth is immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa·s (impregnation evaluation test solution α) for 3 minutes, the number of unimpregnated parts Aα is less than 1.50 times the number of unimpregnated parts Bα when the glass cloth is immersed in the impregnation evaluation test solution α for 3 minutes after a load of 10 N is applied to each width of 25 mm in the warp direction.

Description

Glass cloth, prepreg, and printed circuit board

The present invention relates to a glass cloth, a method for manufacturing the glass cloth, a prepreg, a printed circuit board, etc.

In recent years, with the development of information and communication society, data communication and/or signal processing are performed with large capacity and high speed, and the printed circuit boards used in electronic equipment have significantly lowered dielectric constant (lower dielectric constant and lower dielectric loss factor). Therefore, low dielectric glass cloth has been proposed as a glass cloth constituting the printed circuit board.

For example, a low dielectric glass cloth is known in which a large amount of B ₂ O ₃ is added to the glass composition of the previously commonly used E glass cloth (see Patent Document 1). The glass cloth described in Patent Document 1 discloses that by using a large amount of silane coupling agent for surface treatment so that the ignition loss value is in the range of 0.25 mass % to 1.0 mass %, the moisture absorption caused by the large amount of B ₂ O ₃ can be suppressed, and practical insulation reliability can be obtained.

In addition, low-dielectric resins such as polyphenylene ether are also proposed in the resins constituting printed circuit boards. Low-dielectric resins tend to have large functional groups and high viscosity, and have poorer impregnation in glass cloth than the epoxy resins commonly used before. If the impregnation in glass cloth is poor, parts (gaps) that are not impregnated with resin are likely to appear in the glass fiber yarns in the substrate, and CAF (Conductive Anodic Filaments) is likely to become a problem. Therefore, it is necessary to further improve the resin impregnation on the glass cloth side to improve CAF resistance.

In order to improve the resin impregnation of glass cloth, the following methods are known: a chemical method, which is to treat the surface of glass fiber by silane coupling agent to improve the affinity with resin; and a fiber opening method, which is to open the glass fiber yarn to facilitate the resin impregnation.

As a chemical method for improving impregnation by using a silane coupling agent, there are known methods of using a special silane coupling agent (for example, see Patent Document 2), a method of uniformly treating a silane coupling agent (for example, see Patent Documents 3 and 4), etc. As a method of opening the glass fiber to facilitate the infiltration of the resin, there are known methods of using a columnar flow or a spray flow, a method of using a vibration washer, or a method of using high-frequency vibration using a liquid as a medium, a method of rolling by a round rod, etc. (for example, Patent Documents 5 and 6, etc.). [Prior Technical Documents] [Patent Documents]

[Patent Document 1] International Publication No. 2016/175248 [Patent Document 2] Japanese Patent Publication No. 09-003770 [Patent Document 3] Japanese Patent Publication No. 2005-281889 [Patent Document 4] Japanese Patent Publication No. 10-245766 [Patent Document 5] Japanese Patent Publication No. 2001-348757 [Patent Document 6] Japanese Patent Publication No. 2022-80443

As mentioned above, low dielectric glass cloth is required to have high impregnation property for low dielectric resin such as polyphenylene ether. However, in the previous methods described in patent documents 2 to 5, there is still room for improvement in terms of impregnation property.

The inventors of the present invention have found through research that the low dielectric glass cloth described in Patent Document 1 has a portion where adjacent glass fibers (glass filaments) are connected to each other compared to the previous E glass cloth. It is also known that the more portions where adjacent glass fibers are connected to each other, the worse the impregnation of the base resin, especially the impregnation of the low dielectric resin.

The following speculation is made as to why there are many places where adjacent glass fibers are connected to each other in the low-dielectric glass cloth. For example, the low dielectric glass cloth in Patent Document 1 is presumed to be caused by the following circumstances: in order to impart moisture absorption resistance, there is a trend of surface treatment with a large amount of silane coupling agent, thereby forming a coating formed by the silane coupling agent spanning multiple single filaments; or a strong protective slurry is applied to the low dielectric glass yarn to make up for the insufficient mechanical strength of the low dielectric glass yarn so that the bundle of the single filaments remains intact and a coating formed by the silane coupling agent is formed; or because of the influence of the functional group of the silane coupling agent used in the low dielectric glass cloth to improve the affinity with the low dielectric resin, the condensation between the single filaments becomes stronger. Furthermore, it is also believed that the combined effect of these phenomena produces more areas where the glass fibers are connected to each other.

Furthermore, the inventors of the present invention have confirmed through research that the previously known fiber opening method using a columnar flow or a spray flow has a certain effect as a method for eliminating the adhesion between adjacent glass fibers of low-dielectric glass cloth. However, compared with the previous E-glass, the mechanical strength of low-dielectric glass cloth is lower. Therefore, if the fiber opening using a columnar flow or a spray flow is performed under the same conditions as the previous E-glass, there is a problem that fuzzing is easily generated. Furthermore, in order to eliminate the adhesion between the glass fibers existing in the low-dielectric glass cloth and improve the impregnation with the low-dielectric resin, the strength of the columnar flow or the spray flow needs to be increased compared with the previous glass cloth, resulting in the problem that the fuzzing quality is gradually deteriorating. In addition, the processing force of the fiber opening process using columnar flow or spray flow is difficult to reach the inside of the glass fiber yarn bundle. In view of the fact that it is not easy to spray the spray evenly on the entire glass cloth surface in a way that the spray can reach the space between the glass fibers, and the processing force will also change due to changes in the conveying tension of the glass cloth or the deformation of the glass cloth itself such as relaxation, etc., there is also a problem that the resin impregnation is easy to be uneven in the surface in low-dielectric glass cloth. In addition, other fiber opening methods (vibration, ultrasonic) also have the same problem.

The present invention is made in view of the above problems, and its purpose is to provide a glass cloth with excellent nap quality and stable and uniform resin impregnation with low dielectric resin, and a manufacturing method thereof. In addition, the present invention also aims to provide a prepreg and a printed circuit board using the glass cloth.

The inventors of the present invention have conducted intensive research to solve the above-mentioned problems, and have found that the adhesion of glass fibers mediated by the slurry applied to the glass yarn or the silane coupling agent applied to the glass cloth is the main reason for inhibiting the impregnation of the low-dielectric glass cloth. By eliminating the adhesion of the glass fibers and not applying external forces such as friction to the glass yarn, a low-dielectric glass cloth with excellent fuzzing quality and stable and uniform impregnation with the low-dielectric resin can be obtained, thereby completing the present invention. One aspect of the present invention is recorded below.

(1) A glass cloth, which is woven with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns and surface-treated with a surface treatment agent, wherein the glass cloth is immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa.s (impregnation evaluation test solution α) for 3 minutes, and the number of unimpregnated parts Aα is less than 1.50 times the number of unimpregnated parts Bα when the glass cloth is immersed in the impregnation evaluation test solution α for 3 minutes after a load of 10 N is applied to each width of 25 mm in the warp direction.

(2) Glass cloth as described in item 1, wherein the number of unimpregnated parts Aβ of the glass cloth when immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 680mPa.s (impregnation evaluation test solution β) for 3 minutes is less than 1.5 times the number of unimpregnated parts Bβ of the glass cloth when a load of 10N is applied to each width of 25mm in the warp direction and the glass cloth is immersed in the impregnation evaluation test solution β for 3 minutes.

(3) Glass cloth as described in item 1 or 2, wherein the number of unimpregnated parts Aγ of the glass cloth when immersed in castor oil (containing the impregnation evaluation test solution γ) with a viscosity of 650mPa.s for 3 minutes is less than 1.5 times the number of unimpregnated parts Bγ of the glass cloth when a load of 10N is applied to each 25mm width in the warp direction and then the glass cloth is immersed in the impregnation evaluation test solution γ for 3 minutes.

(4) Glass cloth as described in any of items 1 to 3, wherein the number of raised fibers with a length of 2 mm or more is not more than 10 fibers/ ^m2 .

(5) Glass cloth as described in any one of items 1 to 4, wherein the number of raised fibers with a length of 1 mm or more is not more than 10 fibers/ ^m2 .

(6) Glass cloth as described in any one of items 1 to 5, wherein the number of raised fibers with a length of 0.5 mm or more is not more than 10 fibers/ ^m2 .

(7) Glass cloth as described in any of items 1 to 6, with a thickness of 5 to 100 μm.

(8) Glass cloth as described in any of items 1 to 7, wherein the average filament diameter is not less than 3.0 μm and not more than 8 μm.

(9) Glass cloth as described in any of items 1 to 8, wherein the average number of filaments is 80 or more.

(10) Glass cloth as described in any one of items 1 to 9, wherein the elastic coefficient of the glass cloth is not less than 50 GPa and not more than 70 GPa.

(11) Glass cloth as described in item 10, wherein the elastic coefficient is not less than 50 GPa and not more than 63 GPa.

(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.

(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.

According to the present invention, it is possible to provide a low-dielectric glass cloth that maintains excellent fuzzing quality, has a degree of suppressing the variation of impregnation during prepreg coating, and has stable and uniform impregnation of low-dielectric resin, resulting in a low-dielectric glass cloth with excellent insulation reliability. In addition, according to the present invention, it is also possible to provide a prepreg and a printed circuit board using the low-dielectric glass cloth.

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 implemented within the scope of the gist thereof.

[Glass cloth] The glass cloth of this embodiment is woven with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns, and the surface is treated with a surface treatment agent. The number of unimpregnated parts Aα when immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa·s (impregnation evaluation test solution α) for 3 minutes is 1.50 times or less of the number of unimpregnated parts Bα when the glass cloth is immersed in the same liquid (impregnation evaluation test solution α) for 3 minutes after applying a load of 10 N per 25 mm width in the warp direction.

As described above, it is found that low dielectric glass cloth is more likely to cause the adjacent glass fibers to adhere to each other through the slurry applied to the glass cloth or the silane coupling agent applied to the glass cloth, and the adhesion between the glass fibers hinders the resin from penetrating between the glass fibers, resulting in a portion of the glass fiber yarn that is not impregnated with the resin.

The adjacent glass fibers mediated by the sizing agent or silane coupling agent are bonded in a very small area (near the contact points of the glass fibers). Therefore, in the previous fiber opening methods such as columnar flow, spray flow, vibration cleaning device, and high-frequency vibration with liquid as the medium, it is difficult to selectively act the fiber opening force on the bonding parts of the glass fibers. Therefore, it is necessary to apply a larger processing force to the entire surface of the glass cloth to peel off the bonding between the adjacent glass fibers. Even so, it is difficult to fully eliminate the bonding. Therefore, low-dielectric glass cloth has the problem that the bonding between adjacent fibers is easy to remain and the impregnation is poor.

In addition, the previous fiber opening method also has the problem of local residual adhesion between adjacent fibers and uneven resin impregnation due to the following reasons: it is difficult for the fiber opening force to be evenly generated on the entire surface of the glass cloth due to the mechanism of the device used in the fiber opening process; the fiber opening force is not easy to reach the adhesion between the glass fibers inside the glass fiber bundle; it is also easily affected by changes in the conveying tension of the glass cloth or deformation such as relaxation of the glass cloth itself.

The inventors of the present invention have found that, as a method for eliminating the bonding between glass fibers interposed with a sizing agent or a silane coupling agent, when a tensile force greater than a certain value is applied to the glass cloth treated with a silane coupling agent in the warp direction, the glass fibers constituting the warp are bonded and peeled off due to the force acting in the direction in which the glass fibers constituting the warp converge toward the center. In addition, the inventors have found that by applying a tensile force greater than a certain value in the warp direction to the low-dielectric glass cloth treated with a silane coupling agent, the bonding between the glass fibers is peeled off, and the resin impregnation of the low-dielectric glass cloth is improved. By applying a tensile force greater than a certain value, sufficient impregnation can be obtained.

The following describes the structure of this embodiment in more detail.

(Difference in the number of unimpregnated sites before and after applying a load of 10 N per 25 mm width in the warp direction) The low-dielectric glass cloth of this embodiment is preferably such that the number of unimpregnated sites Aα when immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa·s (impregnation evaluation test solution α) for 3 minutes is equivalent to the number of unimpregnated sites Bα when immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa·s (impregnation evaluation test solution α) for 3 minutes after applying a load of 10 N per 25 mm width in the warp direction, and the number of unimpregnated sites Aα is less than 1.50 times the number of unimpregnated sites Bα. The number of non-impregnated sites Aα is preferably 1.40 times or less, more preferably 1.30 times or less, further preferably 1.20 times or less, and most preferably 1.10 times or less of the number of non-impregnated sites Bα.

If the number of unimpregnated sites Aα is less than 1.50 times the number of unimpregnated sites Bα, stable and uniform impregnation of low dielectric resins such as polyphenylene ether can be obtained, which is preferred. The reason for this is presumably that the number of glass fibers that are connected to each other, which hinders resin impregnation, is suppressed to a certain amount or less. By reducing the variation in impregnation, the risk of void generation can be suppressed to a smaller extent, so a substrate with higher CAF reliability can be obtained, which is preferred.

Furthermore, if the number of non-impregnated portions Aα is less than or equal to 1.50 times the number of non-impregnated portions Bα, the variation in impregnation caused by the magnitude of the tension acting on the glass cloth during prepreg coating, the variation in the tension, the difference in the width direction of the tension, the difference in the prepreg coating equipment (for example, when production is performed by a plurality of prepreg coating machines, when prepreg coating is performed in a plurality of factories, when prepreg coating is performed by equipment with different mechanisms), etc. is smaller, and the risk of void generation can be suppressed to a smaller extent, so a substrate with higher CAF reliability can be obtained, which is better.

The lower limit of the ratio of the number of non-impregnated sites Aα to the number of non-impregnated sites Bα is not particularly limited, but is preferably 0.80 times or more, and more preferably 0.90 times or more.

The number of non-impregnated areas Aα is the number of non-impregnated areas observed within a viewing angle of 32 mm × 32 mm after the glass cloth specimen is immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230 mPa·s (impregnation evaluation test solution α) for 3 minutes. The non-impregnated areas are counted based on the non-impregnated areas with a length of more than 160 μm. In the case of multiple measurements, the average value of the measured times is used.

The impregnation position number Bα is the number of unimpregnated positions observed within a viewing angle of 32 mm × 32 mm after applying a load of 10 N to the glass cloth in the warp direction for every 25 mm width and then immersing it in a test solution (test solution α for impregnation evaluation) that is the same as the impregnation position number Aα for 3 minutes.

As a method for adjusting the value of the number of non-impregnated parts Aα relative to the number of non-impregnated parts Bα to within the numerical range described above, the following method is effective: a method for inhibiting the formation of a surface coating between different single filaments caused by a surface treatment agent such as a silane coupling agent, and/or a method for destroying the surface coating between different single filaments formed by a surface treatment agent such as a silane coupling agent.

As a method for suppressing the formation of a surface film between different filaments caused by a surface treatment agent such as a silane coupling agent, the following methods can be cited: a method of reducing the amount of the surface treatment agent applied in the method of performing the surface treatment after the sizing agent removal step; a method of reducing the concentration of the surface treatment agent in the treatment solution containing the surface treatment agent; a method of creating a distance between adjacent yarns of the glass filaments to prevent the glass filaments from being formed; A method of first unwinding the glass yarn and performing surface treatment in this state; and a method of rapidly drying at a high temperature so that the single yarn does not condense when drying a treatment solution containing a surface treatment agent; and, when it is impossible to adjust the value of the number of non-impregnated parts Aα relative to the number of non-impregnated parts Bα by one method, it is better to appropriately combine the above methods to suppress the formation of a surface coating across the long yarns.

As a method for destroying the surface coating formed by the surface treatment agent such as silane coupling agent and spanning between different single yarns, as mentioned above, there can be cited a method of applying a high tension in the warp direction (MD direction) to the glass cloth that has been surface treated after the sizing agent is removed. If tension is applied in the MD direction of the glass cloth, as the warp yarn is stretched in the length direction, the single yarns constituting the warp yarn are stretched and moved toward the center of the plane perpendicular to the length direction. At this time, the coating formed by the surface treatment agent spanning between different single yarns is subjected to stress, the coating is destroyed, and the connection between the single yarns is peeled off. Thus, mechanical force or excessive friction will not act on the glass cloth, so it will not affect the quality of the fuzzing, thereby improving the impregnation, which is better.

In addition, it is also effective to bend the glass cloth that has been surface treated after the sizing agent is removed in the MD direction with a low curvature radius. By applying bending stress to the glass cloth, the coating formed by the surface treatment agent across different single filaments is destroyed. However, depending on the curvature radius, when the glass cloth is bent, friction will act on the glass cloth, which is easy to cause fuzzing, so you need to pay attention. Depending on the balance between the fuzzing quality and the impregnation, the above processing can sometimes be used.

In addition, the method of using particles that sublimate into gas to blast glass cloth that has been surface treated after the sizing agent is removed is also effective. The particles can directly act on the surface coating formed by different filaments, and the coating can be destroyed by the volume expansion caused by sublimation. As a blasting method using particles that sublimate into gas, dry ice blasting is suitable from the perspective of the effect of destroying the coating, safety, and excellent usability. Dry ice blasting is a method of spraying (blowing) dry ice particles with a particle size of 5 to 300 μm at a height of 5 to 1000 m at a pressure of 0.05 to 1 MPa on the treated body. A more preferred method is to spray dry ice particles with a particle size of 5 to 300 μm at a height of 5 to 600 mm at an air pressure of 0.1 to 0.5 MPa to the treated body. By keeping the particle size, height or air pressure within these ranges, the glass cloth will not be fluffed and the film formed between different filaments will not be damaged. Therefore, the impregnation of the glass cloth before and after applying a load of 10 N per 25 mm width in the warp direction is the same. This method also does not apply forces such as rubbing the glass cloth, so it will not affect the fluffing quality, thereby improving the impregnation, so it is better.

The fluff quality of the glass cloth of this embodiment is preferably that the number of fluffs with a length of 2 mm or more is 10 pieces/ ^m2 or less. When the number of fluffs with a length of 2 mm or more is 10 pieces/ ^m2 or less, the insulation of the printed circuit board containing the glass cloth as a component is reliable and excellent, so it is better. The fluff quality of the glass cloth can be inspected by visual inspection using a halogen lamp or LED (light emitting diode) light. In addition, the length of the fluff can be measured by observing the fluff detected by visual inspection using a microscope or the like. The number of fluffs with a length of 2 mm or more is more preferably 7 pieces/ ^m2 or less, further preferably 5 pieces/ ^m2 or less, particularly preferably 3 pieces/ ^m2 or less, and most preferably 0 pieces/ ^m2 .

The shorter the length of the fluff contained in the glass cloth, the better. From this point of view, as the fluff quality of the glass cloth of this embodiment, it is more preferable that the number of fluffs with a length of 1 mm or more is 10 pieces/ ^m2 or less. The further preferable range of the number of fluffs with a length of 1 mm or more is 7 pieces/ ^m2 or less, the further preferable range is 3 pieces/ ^m2 or less, and the best is 0 pieces/ ^m2 . From the same point of view, as the fluff quality of the glass cloth of this embodiment, it is more preferable that the number of fluffs with a length of 0.5 mm or more is 10 pieces/ ^m2 or less. The further preferable range of the number of fluffs with a length of 0.5 mm or more is 7 pieces/ ^m2 or less, the further preferable range is 3 pieces/ ^m2 or less, and the best is 0 pieces/ ^m2 .

With respect to the glass cloth of the present embodiment, from the viewpoint of obtaining stable impregnation even when the viscosity is further increased in order to promote the low dielectric constant of the base resin, the number of unimpregnated portions Aβ when immersed in a benzyl alcohol solution containing a bisphenol A type epoxy resin with a viscosity of 680 mPa·s (impregnation evaluation test solution β) for 3 minutes is preferably 1.5 times or less the number of unimpregnated portions Bβ when the glass cloth is immersed in a benzyl alcohol solution containing a bisphenol A type epoxy resin with a viscosity of 680 mPa·s (impregnation evaluation test solution β) for 3 minutes after a load of 10 N is applied to the glass cloth per 25 mm of width in the warp direction.

The number of non-impregnated sites Aβ is more preferably 1.4 times or less, further preferably 1.3 times or less, further preferably 1.2 times or less, and most preferably 1.1 times or less of the number of non-impregnated sites Bβ.

The lower limit of the ratio of the number of non-impregnated sites Aβ to the number of non-impregnated sites Bβ is not particularly limited, but is preferably 0.8 or more, and more preferably 0.9 or more.

The number of non-impregnated areas Aβ is the number of non-impregnated areas observed within a viewing angle of 32 mm × 32 mm after the glass cloth specimen is immersed in a benzyl alcohol solution containing bisphenol A epoxy resin with a viscosity of 680 mPa·s (impregnation evaluation test solution β) for 3 minutes. The non-impregnated areas are counted based on the non-impregnated areas with a length of more than 160 μm. In the case of multiple measurements, the average value of the measured times is used.

The impregnation position number Bβ is the number of unimpregnated positions observed within a viewing angle of 32 mm × 32 mm after applying a load of 10 N to the glass cloth for every 25 mm width in the warp direction and immersing it in the same test solution (impregnation evaluation test solution β) as the impregnation position number Aβ for 3 minutes.

From the perspective of obtaining stable impregnation even when the expansion is further promoted in order to promote the low dielectric constant of the base resin, the glass cloth of the present embodiment is preferably such that the number of unimpregnated portions Aγ when immersed in castor oil (impregnation evaluation test solution γ) with a viscosity of 650 mPa·s for 3 minutes is less than 1.5 times the number of unimpregnated portions Bγ when the glass cloth is immersed in castor oil (impregnation evaluation test solution γ) with a viscosity of 650 mPa·s for 3 minutes after a load of 10 N is applied to the glass cloth per 25 mm of width in the warp direction.

The number Aγ of non-impregnated portions is more preferably 1.4 times or less, further preferably 1.3 times or less, further preferably 1.2 times or less, and most preferably 1.1 times or less of the number Bγ of non-impregnated portions.

The lower limit of the ratio of the number of non-impregnated sites Aγ to the number of non-impregnated sites Bγ is not particularly limited, but is preferably 0.8 or more, and more preferably 0.9 or more.

The number of non-impregnated areas Aγ is the number of non-impregnated areas observed within a viewing angle of 32 mm × 32 mm after the glass cloth specimen is immersed in castor oil (impregnation evaluation test solution γ) with a viscosity of 650 mPa·s for 3 minutes. The non-impregnated areas are counted based on the non-impregnated areas with a length of more than 160 μm. In the case of multiple measurements, the average value of the measured times is used.

The impregnation position number Bγ is the number of unimpregnated positions observed within a viewing angle of 32 mm × 32 mm after applying a load of 10 N to the glass cloth for every 25 mm width in the warp direction and immersing it in a test solution (impregnation evaluation test solution γ) that is the same as the impregnation position number Aγ for 3 minutes.

(Constitution of glass cloth) Glass yarn is obtained by bundling multiple filaments and twisting them as needed. In this case, the glass yarn is classified as multiple glass filaments, and the filaments (glass filaments) contained in the glass yarn are classified as single glass filaments.

The elastic coefficient of glass yarn is preferably 50-70 GPa, more preferably 50-63 GPa, and further preferably 53-63 GPa. In addition, the elastic coefficient of glass cloth is equivalent to that of glass yarn, so the elastic coefficient of glass cloth is also preferably 50 GPa to 70 GPa, more preferably 50 GPa to 63 GPa, and further preferably 53 GPa to 63 GPa.

The elastic coefficient is also an indicator of the dielectric constant of glass. Usually, the elastic coefficient of glass yarn is lower than that of previous E glass. If it is below the upper limit, in order to improve the strength of glass cloth to suppress the fuzzing of glass cloth or prevent cracking, it is necessary to apply more surface treatment agents such as silane coupling agents than previous E glass. Therefore, it is easy to cause the problem of adhesion between single filaments and reduced impregnation due to the formation of the coating of surface treatment agents such as silane coupling agents. In the present invention, the coating of the span and single filaments is destroyed to achieve the same impregnation without being affected by the presence or absence of tensile load. Even if the elastic coefficient of glass yarn or glass cloth is below the upper limit, stable CAF resistance can be obtained, so it is better.

In addition, by having an elastic modulus above the above lower limit, the rigidity of the glass yarn is increased, and it is less likely to cause fuzzing during the manufacturing process, which is better.

The average diameter of the single glass 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. The average diameter of the single glass filament can be appropriately selected according to the target thickness of the glass cloth.

The average number of single glass filaments constituting the warp yarn and the weft yarn is preferably 80 or more, and more preferably 180 or more, respectively.

The greater the average number of single glass filaments constituting the warp and weft yarns, the more likely it is that adjacent glass filaments will be in contact with each other, and the tendency is that the impregnation property will be worse. In contrast, according to the present invention, by eliminating the contact between the glass filaments, stable and uniform impregnation with the low dielectric resin can be obtained, which is better.

The weaving density of the warp yarns and weft yarns constituting the glass cloth is preferably 30 to 120 yarns/25 mm, more preferably 40 to 110 yarns/25 mm, and further preferably 50 to 100 yarns/25 mm.

The thickness of the glass cloth is preferably 5 to 100 μm, more preferably 6 to 90 μm, and further preferably 7 to 80 μm. When the thickness of the glass cloth is within the above range, there is a tendency to obtain a thin glass cloth with relatively high strength.

The cloth weight (weight per unit area) of the glass cloth is preferably 8 to 250 g/m ² , more preferably 8 to 100 g/m ² , further preferably 8 to 50 g/m ² , and particularly preferably 8 to 35 g/m ² .

The preferred range of the ignition loss value of the glass cloth is the value obtained by the following formula (i) or more, the more preferred range is the value obtained by the following formula (ii) or more, and the further preferred range is the value obtained by the following formula (iii) or more. 5.0×F( ^-1.6 )…Formula (i) 6.0×F( ^-1.6 )…Formula (ii) 6.4×F( ^-1.6 )…Formula (iii) In formulas (i) to (iii), F is the filament diameter of the glass cloth (μm).

The ignition weight loss of the glass cloth is the sum of the weight loss of the glass cloth itself under heating conditions and the weight loss caused by the combustion and removal of the silane coupling agent. If the ignition weight loss of the glass cloth is greater than the lower limit value obtained according to any one of the above formulas (i) to (iii), there is a tendency that the insulation reliability is improved due to the sufficient coating amount of the silane coupling agent and the low dielectric properties of the glass cloth are improved, so it is better.

The preferred range of the ignition loss value of the glass cloth is the value obtained by the following formula (iv) or less, the more preferred range is the value obtained by the following formula (v) or less, and the further preferred range is the value obtained by the following formula (vi) or less. 18×F( ^-1.6 )…Formula (iv) 16×F( ^-1.6 )…Formula (v) 15×F( ^-1.6 )…Formula (vi) In formulas (iv) to (vi), F is the filament diameter of the glass cloth (μm).

When the burning weight loss value of the glass cloth is below the upper limit value obtained according to any one of the above formulas (iv) to (vi), there is a tendency that the resin permeability is improved due to the coating amount of the silane coupling agent being within an appropriate range, and the low dielectric properties of the glass cloth become good, so it is preferred.

The loss on ignition value can be measured according to the method described in JISR3420.

The preferred range of the coating amount of the silane coupling agent on the glass cloth is the value obtained by the following formula (vii) or more, the more preferred range is the value obtained by the following formula (viii) or more, and the further preferred range is the value obtained by the following formula (ix) or more. 0.2×F( ^-0.6 )…Formula (vii) 0.25×F( ^-0.6 )…Formula (viii) 0.30×F( ^-0.6 )…Formula (ix) In formulas (vii) to (ix), F is the filament diameter of the glass cloth (μm).

If the coating amount of the silane coupling agent on the glass cloth is greater than or equal to the lower limit value obtained according to any one of the above formulas (vii) to (ix), the coating amount of the silane coupling agent is sufficient, thereby obtaining sufficient reactivity with the base resin during the manufacture of the substrate, and further improving the moisture absorption resistance. As a result, there is a tendency for the insulation reliability to be improved, which is preferred.

Furthermore, the preferred range of the coating amount of the silane coupling agent on the glass cloth is the value obtained by the following formula (x) or less, the more preferred range is the value obtained by the following formula (xi) or less, and the further preferred range is the value obtained by the following formula (xii) or less. 1.8×F( ^-1.0 )…Formula (x) 1.6×F( ^-1.0 )…Formula (xi) 1.4×F( ^-1.0 )…Formula (xii) In formulas (x) to (xii), F is the filament diameter of the glass cloth (μm).

When the coating amount of the silane coupling agent on the glass cloth is below the upper limit value obtained according to any one of the above formulas (x) to (xii), the resin impregnation of the glass cloth is easily further improved, which is preferred.

The weave structure of the glass cloth is not particularly limited, and examples thereof include plain weave, square weave, satin weave, twill weave, etc. Among them, the plain weave structure is preferred.

(Composition of glass cloth) 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. Examples of elements constituting the glass cloth include: 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).

The silicon (Si) content of the glass yarn is preferably 40.0 to 60.0 mass%, more preferably 45.0 to 55.0 mass%, further preferably 47.0 to 53.5 mass%, and further preferably 48.0 to 52.0 mass% in terms of _SiO2 . Si is a component that forms the skeleton structure of the glass yarn. Therefore, by having an Si content of 40.0 mass% or more, the strength of the glass yarn is further improved, and in subsequent steps such as the manufacturing step of the glass cloth and the manufacturing step of the prepreg using the glass cloth, there is a tendency that the fracture of the glass cloth is further suppressed. In addition, by having an Si content of 40.0 mass% or more, there is a tendency that the dielectric constant of the glass cloth is further reduced. On the other hand, when the Si content is 60.0 mass % or less, 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 can be obtained. Therefore, it is not easy to produce a local portion that is easy to lose transparency or a portion where it is difficult for local bubbles to be discharged in the obtained glass filament, and therefore it is not easy to produce a local portion with weak strength in the glass filament. As a result, the glass cloth including the glass yarn obtained using such Si content is not easy to break. The Si content can be adjusted according to the amount of raw materials used to make the glass filament.

The boron (B) content of the glass yarn, calculated as B ₂ O ₃ , is preferably 15.0 to 40.0 mass %, more preferably 17.0 to 30.0 mass %, or 20.0 to 40.0 mass %, further preferably 18.0 to 28.0 mass %, further preferably 19.0 to 26.0 mass %, particularly preferably 20.0 to 25.0 mass %, and most preferably 20.5 to 24.5 mass %.

When the B content is 15.0 mass % or more, the dielectric constant tends to further decrease. Also, when the B content is 15.0 mass % or more, the brittleness resistance of the glass cloth is improved, and the glass cloth is given appropriate softness or elasticity, so when the glass cloth contacts the yarn guide and the weaving mechanism such as the reed, there is a tendency that it is not easy to cause fuzz.

On the other hand, in order to ensure the strength of the glass yarn, it is preferred that the B content is 40.0 mass % or less. Also, by making the B content 40.0 mass % or less, the moisture absorption resistance is improved, and it is easy to properly maintain the stability of the surface characteristics of the glass yarn described below.

In particular, when the Si content in the glass yarn is within the above range and the B content is within the above range, the above effects related to Si and B are easy to work together, so it is better.

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

The aluminum (Al) content of the glass yarn is preferably 11.0-18.0 mass%, more preferably 11.0-17.5 mass%, and further preferably 12-17.0 mass%, calculated as Al ₂ O _3. When the Al content is within the above range, there is a trend that the electrical properties and strength are further improved. The Al content can be adjusted by the amount of raw materials used (addition amount) used in the production of glass filaments.

The calcium (Ca) content of the glass yarn is preferably 5.0-10.0 mass%, more preferably 5.0-9.0 mass%, and further preferably 5.0-8.5 mass% when converted to CaO. When the Ca content is 5.0 mass% or more, the viscosity of the glass yarn during the manufacturing process is further reduced during melting, and a glass fiber with a more homogeneous glass composition can be obtained. In addition, when the Ca content is 10 mass% or less, there is a trend 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 yarn.

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 be more than 0 mass%. When the P content is more than 0 mass%, there is a tendency that the dielectric properties of the glass cloth become better. Also, when the P content is less than 8.0 mass%, there is a tendency that the heat resistance of the glass cloth is improved. The P content can be adjusted by the amount of raw materials used (addition amount) used in the production of the glass filament.

Furthermore, the above contents can be measured by ICP (inductively coupled plasma) emission spectrometry. Specifically, the Si content and the B content can be obtained by dissolving the weighed glass cloth with sodium carbonate, dissolving it with dilute nitric acid to obtain a specified volume, and measuring the obtained sample by ICP emission spectrometry. In addition, the Fe content can be obtained by dissolving the weighed glass cloth with an alkaline dissolution method to obtain a specified volume, and measuring the obtained sample by ICP emission spectrometry. Furthermore, the Al content, Ca content, P content and Mg content can be obtained by heating and decomposing the weighed glass cloth with perchloric acid, sulfuric acid, nitric acid and hydrogen fluoride, dissolving it with dilute nitric acid to obtain a predetermined volume, and measuring the obtained sample by ICP emission spectrometry. Furthermore, as an ICP emission spectrometry device, PS3520 VDD II manufactured by Hitachi High-Tech Science can be used.

(Surface treatment agent) The glass cloth of the present embodiment is surface treated with a surface treatment agent. The surface treatment agent is not particularly limited, and examples thereof include silane coupling agents, which can be used together with water, organic solvents, acids, dyes, pigments, surfactants, etc. as needed. The silane coupling agent is not particularly limited, and examples thereof include compounds represented by the following formula (1). 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 each independently an alkoxy group, n is an integer of 1 to 3, and R is each independently a group selected from the group consisting of methyl, ethyl and phenyl groups)

In formula (1), X is preferably an organic functional group having 3 or more groups selected from an amino group and an unsaturated double bond group, and X is more preferably an organic functional group having 4 or more groups selected from an amino group and an unsaturated double bond group.

The alkoxy group may be in any form, but an alkoxy group having 5 or less carbon atoms is preferred from the viewpoint of stabilizing the glass cloth.

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. Its 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, methacryloyloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane and other known monomers, or mixtures thereof.

The molecular weight of the silane coupling agent is preferably 100 to 600, more preferably 150 to 500, and further preferably 200 to 450. It is preferred to use two or more silane coupling agents with different molecular weights. By treating the surface of the glass cloth with two or more silane coupling agents with different molecular weights, the surface treatment agent density on the surface of the glass cloth becomes higher, and there is a tendency that the reactivity with the base resin is further improved.

[Glass cloth manufacturing method] The glass cloth manufacturing method of the present embodiment is not particularly limited. For example, a method having the following steps can be cited: a weaving step, which is to weave glass yarns to obtain glass cloth; a fiber opening step, which is to open the glass yarns of the glass cloth; a debinding step, which is to remove the slurry attached to the glass yarns of the glass cloth. In addition, if necessary, the glass cloth manufacturing method may also have a surface treatment step using a silane coupling agent.

The weaving method is not particularly limited as long as the weft yarns and the warp yarns are woven in a manner that forms a predetermined fabric structure. Also, the fiber opening method is not particularly limited, and examples thereof include: fiber opening processing methods such as spraying water (high-pressure water fiber opening), a vibration washer, ultrasonic water, and a roller press.

Furthermore, there is no particular limitation on the de-pasting method, and for example, a method of removing the sizing agent by heating can be cited. Furthermore, the sizing agent is used in the weaving step, etc., to protect the glass yarn from breaking. Such sizing agents are not particularly limited, and for example, starch-based adhesives, polyvinyl alcohol-based adhesives, etc. can be cited. Furthermore, as for the temperature when the sizing agent is removed by heating, from the viewpoint of maintaining the fracture strength while fully removing the sizing agent, it is preferably 300 to 500°C, more preferably 330 to 450°C, and further preferably 350 to 430°C.

In addition, as a method for performing the surface treatment step, a method of bringing a surface treatment agent including a silane coupling agent into contact with a glass cloth and then drying the surface treatment agent can be cited. Furthermore, the contact of the surface treatment agent with the glass cloth can be cited as follows: a method of immersing the glass cloth in the surface treatment agent, and a method of applying the surface treatment agent to the glass cloth using a roll coater, a die coater, or a gravure coater. The method of drying the surface treatment agent is not particularly limited, and for example, hot air drying or a drying method using electromagnetic waves can be cited.

In the production of glass cloth, as described above, a method of suppressing the bonding between the single filaments mediated by the sizing agent or the surface treatment agent, or a method of destroying the bonding between the single filaments mediated by the sizing agent or the surface treatment agent can be performed. These methods can be performed individually or in combination.

[Prepreg] The prepreg of this embodiment has: the above-mentioned glass cloth, and a base resin composition impregnated in the glass cloth. The insulation reliability of the prepreg having the above-mentioned glass cloth is further improved, and the yield of the final product is higher. In addition, due to the excellent dielectric properties and excellent moisture absorption resistance, it can also provide a printed circuit board that is less affected by the use environment, especially the dielectric constant changes less in a high humidity environment.

The prepreg of this embodiment can be manufactured according to conventional practice. For example, it can be manufactured by impregnating the glass cloth of this embodiment with a varnish made by diluting a base resin such as epoxy resin with an organic solvent, and then using a drying furnace to volatilize the organic solvent and harden the thermosetting resin to the B-stage state (semi-hardened state).

As the matrix resin composition, in addition to the above-mentioned epoxy resin, there can also be cited: thermosetting resins such as dimaleimide resins, cyanate resins, unsaturated polyester resins, polyimide resins, dimaleimide-tris resins (BT resins), and functionalized polyphenylene ether resins; thermoplastic resins such as polyphenylene ether resins, polyetherimide resins, liquid crystal polymers (LCP) of wholly aromatic polyesters, polybutadiene, and fluororesins; and mixed resins thereof. From the viewpoint of improving dielectric properties, heat resistance, solvent resistance, and press moldability, a resin obtained by modifying a thermoplastic resin with a thermosetting resin may be used as the base resin composition.

In addition, the base resin composition may contain inorganic fillers such as silicon dioxide and aluminum hydroxide; flame retardants such as bromine, phosphorus, and metal hydroxide; other silane coupling agents; thermal stabilizers; antistatic agents; ultraviolet absorbers; pigments; colorants; lubricants, etc. in the resin.

[Printed Circuit Board] The printed circuit board of this embodiment has the above-mentioned glass cloth, and, if necessary, can also have a cured product of a base resin composition impregnated in the glass cloth. The insulation reliability of the printed circuit board of this embodiment is further improved, and the yield of the final product is higher. In addition, due to the excellent dielectric properties and excellent moisture absorption resistance, it can also be less affected by the use environment, especially the change of the dielectric constant in a high humidity environment. [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.

[Physical properties of glass cloth] The physical properties of glass cloth, specifically, the thickness of glass cloth, the diameter of the filaments constituting the warp and weft yarns, the number of filaments, and the weaving density (weaving density) of the warp and weft yarns are measured in accordance with JIS R3420.

[Elastic coefficient] The elastic coefficient 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.

[Amount of silane coupling agent applied] (Drying loss A) The glass cloth obtained in the embodiment and the comparative example was placed in a dryer at 110°C and dried for 60 minutes. After drying, the glass cloth was moved to the dryer, left for 20 minutes, and cooled to room temperature. After cooling, the glass cloth was weighed in units of 0.1 mg or less. Next, the glass cloth was heated at 600°C for 20 minutes, moved to the dryer, left for 20 minutes, and cooled to room temperature. After cooling, the glass cloth was weighed in units of 0.1 mg or less. The difference (g) between the mass of the glass cloth before and after the heat treatment at 600°C is divided by the mass (g) of the glass cloth used for measurement, and the value obtained is set as the drying loss A (mass %). (Drying loss B) Next, using the glass cloth for which the drying loss A has been obtained, the drying loss is obtained by the same method as the above method for obtaining the drying loss A, and it is set as the drying loss B (%). (Silane coupling agent coating amount) As shown in the following formula, the difference between the above-obtained drying loss B and the drying loss A is set as the silane coupling agent coating amount. Silane coupling agent coating amount (mass %) = drying loss A (mass %) - drying loss B (mass %)

[Resin impregnation evaluation, number of unimpregnated areas A] A total of 5 test samples for impregnation evaluation were collected from the periphery of one end in the longitudinal direction of the long glass cloth, the periphery of the end on the opposite side, and the middle part of the longitudinal quarter. The impregnation evaluation test pieces for evaluating the number of unimpregnated areas A were prepared from each impregnation evaluation sample.

Next, the glass cloth specimen was immersed in the impregnation evaluation test solution, and the light of the LED lamp was irradiated from the side, while a microscope equipped with a high-precision camera was used to observe the impregnation of the impregnation evaluation varnish in the glass cloth. The number of unimpregnated parts with a length of more than 160 μm (unimpregnated parts of the impregnation evaluation varnish) was counted after the glass cloth specimen was immersed in the impregnation evaluation test solution for 3 minutes (indicated as "number of gaps" in the table). At this time, the field of view of the glass cloth observed by the microscope was set to about 32 mm in the warp direction and about 32 mm in the weft direction.

The average value of the number of non-impregnated sites of the five test pieces for evaluating impregnation properties was defined as the number of non-impregnated sites A. Furthermore, the standard deviation of the number of non-impregnated sites of the five test pieces for evaluating impregnation properties was also determined.

The test solutions used for the impregnation evaluation were: a benzyl alcohol solution of bisphenol A epoxy resin (product name "EPICLON") adjusted to a viscosity of 230 mPa·s, a benzyl alcohol solution of bisphenol A epoxy resin (product name "EPICLON") adjusted to a viscosity of 680 mPa·s, and castor oil adjusted to a viscosity of 650 mPa·s.

[Resin impregnation evaluation, number of non-impregnated parts B] From the total of 5 test samples for impregnation evaluation taken when evaluating the number of non-impregnated parts A, make the test piece B for impregnation evaluation for the number of non-impregnated parts B. Take a test piece (40 mm in the weft direction × 250 mm in the warp direction) from the test sample for impregnation evaluation. Set the two ends of 50 mm in the length direction as the clamping part, and apply a tensile load to the sample of 40 mm in the weft direction × 150 mm in the warp direction. Apply a tensile load of 10 N/25 mm in the warp direction according to the method described in the general test method for glass testing of JIS R3420, 7.4 tensile strength. Set the tensile speed to about 5 mm/min.

Next, the glass cloth specimen was immersed in the impregnation evaluation test solution used when evaluating the number of non-impregnated locations A, and the impregnation of the impregnation evaluation varnish into the glass cloth was observed using a microscope equipped with a high-precision camera while irradiating the light of an LED lamp from the side. The number of non-impregnated locations (non-impregnated locations of the impregnation evaluation varnish) with a length of more than 160 μm after the glass cloth specimen was immersed in the impregnation evaluation test solution for 3 minutes was counted. At this time, the field of view of the glass cloth observed by the microscope was set to about 32 mm in the warp direction and about 32 mm in the weft direction.

The average value of the number of non-impregnated sites of the five test pieces for evaluating impregnation properties was defined as the number of non-impregnated sites B. Furthermore, the standard deviation of the number of non-impregnated sites of the five test pieces for evaluating impregnation properties was also determined.

[Fuzz evaluation] Take 5 test samples for impregnation evaluation from each part of the roll glass cloth taken when evaluating the number of unimpregnated parts A, and prepare 5 samples for fuzz evaluation with a width direction of 1285 mm and a length direction of 1000 mm from the 5 test samples for impregnation evaluation. Spread the samples for fuzz evaluation on the test cloth board and conduct a visual inspection. Evaluate the fuzz quality according to the following evaluation criteria. The fuzz detected by visual inspection is observed under a microscope, and the length of fuzz that is 0.5 mm or more, 1 mm or more, and 2 mm or more above the surface of the glass cloth is evaluated. ◎: None of the 5 samples for fuzz evaluation have fuzz defects. ○: 4 samples have no fuzz defects. ×: 3 or more samples have fuzz defects.

[Insulation reliability evaluation] Take 5 test samples for impregnation evaluation from each part of the roll of glass cloth taken when evaluating the number of unimpregnated parts A, and cut 2 glass cloth samples for insulation reliability evaluation from each of the 5 test samples for impregnation evaluation (a total of 10 pieces). Glass cloth for insulation reliability evaluation was impregnated with a low dielectric resin varnish containing 50 parts by weight of SA9000 (manufactured by Sabic Innovative Plastics), 25 parts by weight of TAIC (manufactured by Nippon Chemical Co., Ltd.), 0.4 parts by weight of PERBUTYL P (manufactured by NOF Corporation), 10 parts by weight of thermoplastic resin SEB-SH1053 (manufactured by Asahi Kasei Co., Ltd.), 30 parts by weight of flame retardant SAYTEX8010 (manufactured by Albemarle Corporation), 70 parts by weight of spherical silica (manufactured by Ronson Corporation), and 200 parts by weight of toluene, and dried at 160°C for 2 minutes to obtain a prepreg with a resin content of 60%. The prepreg is stacked in the specified number of pieces, and then a copper foil with a thickness of 12 μm is stacked on top and bottom. It is heated and pressed at 195°C and 40 kg/ ^cm2 for 60 minutes to obtain a substrate with a thickness of about 0.4 mm. A circuit pattern with through holes with a spacing of 0.15 mm is made on the copper foil on both sides of the obtained substrate to obtain a test substrate for insulation reliability evaluation. In an atmosphere of temperature 95°C and humidity 95%RH, a voltage of 10 V is applied to the obtained sample to measure the change in resistance value. At this time, the situation where the resistance does not reach 1 MΩ within 1000 hours after the start of the test is considered to be poor insulation and counted. Perform the same test on 10 samples and calculate the percentage of samples that do not have insulation failure.

[Comparative Example 1] Glass yarn (filament diameter 5.1 μm, filament number 200, elastic modulus 61 GPa, glass composition: 51.2 mass% in terms of _SiO2 , _14.3 mass% in terms of _Al2O3 , 8.1 mass% in terms of CaO, 0.3 mass% in terms of MgO, 23.3 mass% in terms of _B2O3 , 0.1 mass% in terms of _P2O5 ) was used as warp yarn _and weft yarn, and _a glass cloth grey fabric with a warp yarn weaving density of 52.5 yarns/25 mm and a weft yarn weaving density of 52.5 yarns/25 mm was obtained in an air jet chamber.

The glass cloth was debonded by heating the raw cloth, and then the surface was treated with a treatment solution consisting of methacryloyloxypropyl trimethoxysilane (manufactured by Toray Dow Corning Co., Ltd.; Z6030) dispersed in water as a silane coupling agent. The surface treated glass cloth was subjected to high-pressure water fiber opening using a spray with a water pressure adjusted to 8.0±0.1 kg/ ^cm2 . The glass cloth was rolled up to a roll core with a diameter of 240 mm under an initial tension of 450 N and a final roll tension of 150 N to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss of the glass cloth was 0.62% by mass, and the coating amount of the silane coupling agent was 0.21% by mass. Furthermore, the maximum linear tension of the surface-treated glass cloth during transportation was 150 N. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 2] A glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m was produced in the same manner as in Comparative Example 1 except that the water pressure of the high-pressure water spray during the fiber opening process was increased to 18.0±0.1 kg/cm ² to improve the fiber opening strength. The ignition loss value of the glass cloth was 0.56 mass%, and the amount of silane coupling agent applied was 0.15 mass%. The evaluation results of the obtained glass cloth are shown in Table 1. Since the fuzzing quality of Comparative Example 2 was evaluated as "×", the insulation reliability was not evaluated.

[Example 1] After surface treatment, a tensile force of 500 N was applied to the glass cloth in the MD direction. In the same manner as in Comparative Example 1, a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m was produced. The ignition loss value of the glass cloth was 0.61% by mass, and the amount of silane coupling agent applied was 0.20% by mass. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 2B] After the surface treatment, a tensile force of 450 N was applied to the glass cloth in the MD direction. The same operation as in Comparative Example 1 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.61% by mass, and the amount of silane coupling agent applied was 0.20% by mass. The evaluation results of the obtained glass cloth are shown in Table 1.

[Example 2A] After surface treatment, dry ice particles with a particle size of 5 to 50 μm were sprayed at an air pressure of 0.4 MPa to perform fiber opening instead of high-pressure water fiber opening. In addition, the same operation as in Comparative Example 1 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.61% by mass, and the amount of silane coupling agent applied was 0.20% by mass. The evaluation results of the obtained glass cloth are shown in Table 1.

[Example 2B] After surface treatment, dry ice particles with a particle size of about 300 μm were sprayed at an air pressure of 0.15 MPa to perform fiber opening processing instead of high-pressure water fiber opening. In addition, the same operation as in Comparative Example 1 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.61 mass%, and the amount of silane coupling agent applied was 0.20 mass%. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 7] Except that the dispersion concentration of the silane coupling agent in water was set to 1/3 of that in Comparative Example 1, the same operation as in Comparative Example 1 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.46 mass%, and the amount of silane coupling agent applied was 0.07 mass%. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 3] After the surface treatment, a water dispersion of nylon particles with a particle size of about 600 μm was sprayed at an air pressure of 0.1 MPa to perform fiber opening instead of high-pressure water fiber opening. The same operation as in Comparative Example 1 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.61% by mass, and the amount of silane coupling agent applied was 0.21% by mass. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 3B] After the surface treatment, the glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m was produced in the same manner as in Comparative Example 1 except that the glass cloth was bent 10 times at an angle of 180° by a roller with a curvature radius of 3 mm. The ignition loss value of the glass cloth was 0.62% by mass, and the amount of silane coupling agent applied was 0.21% by mass. The evaluation results of the obtained glass cloth are shown in Table 1.

[Comparative Example 4] Glass yarn (filament diameter 5.1 μm, number of filaments 200, modulus of elasticity 56 GPa, glass composition: 49.8 mass% in terms of _SiO2 , _16.8 mass% in terms of _Al2O3 , 3.1 mass% in terms of CaO, 0.1 mass% in terms of MgO, 23.9 mass% in terms of _B2O3 , 4.0 mass% in terms of _P2O5 ) was used. Except for this, the same operation as in Comparative Example 1 was performed to prepare a glass cloth _having a thickness of 46 μm, _a width of 1285 mm, and a length of 2,000 m. The ignition loss of the glass cloth was 0.92 mass%, and the amount of silane coupling agent applied was 0.21 mass%. The evaluation results of the obtained glass cloth are shown in Table 2.

[Example 3] After surface treatment, a tensile force of 500 N was applied to the glass cloth in the MD direction. In addition, the same operation as in Comparative Example 4 was performed to produce a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.93% by mass, and the amount of silane coupling agent applied was 0.21% by mass. The evaluation results of the obtained glass cloth are shown in Table 2.

[Comparative Example 5] Glass yarn (filament diameter 5.1 μm, filament number 100, elastic modulus 61 GPa, glass composition: 51.2 mass% in terms of _SiO2 , _14.3 mass% in terms of _Al2O3 , 8.1 mass% in terms of CaO, 0.3 mass% in terms of MgO, 23.3 mass% in terms of _B2O3 , and 0.1 mass% in terms of _P2O5 ) was used as warp yarn _and weft yarn, and _a glass cloth grey fabric with a warp yarn weaving density of 65 yarns/25 mm and a weft yarn weaving density of 67 yarns/25 mm was obtained by using an air jet chamber.

The glass cloth was debonded by heating, and then surface treated with a treatment solution consisting of methacryloyloxypropyl trimethoxysilane (Z6030, manufactured by Toray Dow Corning Co., Ltd.) dispersed in water as a silane coupling agent. The surface treated glass cloth was subjected to high-pressure water fiber opening by spraying at a water pressure of 5.0±0.1 kg/cm ^2. The glass cloth was rolled up to a roll core with a diameter of 240 mm under an initial tension of 450 N and a final winding tension of 150 N to produce a glass cloth with a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss of the glass cloth was 0.68% by mass, and the coating amount of the silane coupling agent was 0.23% by mass. Furthermore, the maximum linear tension of the surface-treated glass cloth during transportation was 150 N. The evaluation results of the obtained glass cloth are shown in Table 3.

[Example 4] After surface treatment, a tensile force of 500 N was applied to the glass cloth in the MD direction. In addition, the same operation as in Comparative Example 5 was performed to produce a glass cloth with a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.68% by mass, and the amount of silane coupling agent applied was 0.23% by mass. The evaluation results of the obtained glass cloth are shown in Table 3.

[Comparative Example 6] Glass yarn (filament diameter 7.1 μm, filament number 200, elastic modulus 61 GPa, glass composition: 51.2 mass% in terms of _SiO2 , _14.3 mass% in terms of _Al2O3 , 8.1 mass% in terms of CaO, 0.3 mass% in terms of MgO, 23.3 mass% in terms of _B2O3 , and 0.1 mass% in terms of _P2O5 ) was used as warp yarn _and weft yarn, and _a glass cloth grey fabric with a warp yarn weaving density of 60 yarns/25 mm and a weft yarn weaving density of 57 yarns/25 mm was obtained by using an air jet chamber.

The glass cloth was debonded by heating, and then surface treated with a treatment solution consisting of methacryloyloxypropyl trimethoxysilane (Z6030, manufactured by Toray Dow Corning Co., Ltd.) dispersed in water as a silane coupling agent. The surface treated glass cloth was subjected to high-pressure water fiber opening by spraying at a water pressure of 10.0±0.1 kg/cm ^2. The glass cloth was rolled up to a roll core with a diameter of 240 mm under an initial tension of 450 N and a final winding tension of 150 N to produce a glass cloth with a thickness of 90 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss of the glass cloth was 0.39% by mass, and the coating amount of the silane coupling agent was 0.16% by mass. Furthermore, the maximum linear tension of the surface-treated glass cloth during transportation was 150 N. The evaluation results of the obtained glass cloth are shown in Table 4.

[Example 5] After surface treatment, a tensile force of 500 N was applied to the glass cloth in the MD direction. In addition, the same operation as in Comparative Example 6 was performed to produce a glass cloth with a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m. The ignition loss value of the glass cloth was 0.39% by mass, and the amount of silane coupling agent applied was 0.16% by mass. The evaluation results of the obtained glass cloth are shown in Table 4.

[Table 1] Table 1 Comparison Example 1 Comparison Example 2 Embodiment 1 Comparative Example 2B Example 2A Example 2B Comparison Example 7 Comparative Example 3B Comparison Example 3 Evaluation of impregnation of glass cloth Resin varnish with a viscosity of 230 mPa·s Number of gaps average value 22.0 15.0 9.2 12.9 1.8 1.8 12.8 16.0 17.4 Standard Deviation 8.7 4.2 1.3 3.1 0.8 0.8 4.0 4.8 4.6 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 7.6 8.6 8.2 8.3 1.6 1.6 8.4 8.7 9.6 Standard Deviation 1.7 1.9 1.3 1.5 0.5 0.5 1.5 1.6 1.7 Void ratio before and after tensile load application 2.89 1.74 1.12 1.55 1.13 1.13 1.52 1.84 1.81 Resin varnish with a viscosity of 680 mPa·s Number of gaps average value 135.8 102.6 51.6 82.3 3.8 3.8 78.0 115.3 124.8 Standard Deviation 40.1 16.5 6.5 10.9 0.8 0.8 8.2 16.9 26.0 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 49.6 50.6 49.2 50.2 3.6 3.6 51.8 52.0 51.0 Standard Deviation 7.1 6.5 6.3 7.0 0.5 0.5 4.8 6.8 6.7 Void ratio before and after tensile load application 2.74 2.03 1.05 1.64 1.06 1.06 1.51 2.22 2.45 castor oil Number of gaps average value 646.6 466.8 218.0 378.2 6.4 6.4 290.0 483.2 537.0 Standard Deviation 119.9 61.6 14.0 29.9 1.6 1.6 16.8 63.0 57.2 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 252.8 208.0 195.4 201.0 6.6 6.6 192.4 209.7 192.6 Standard Deviation 35.8 33.3 17.6 24.9 2.1 2.1 28.1 32.1 20.7 Void ratio before and after tensile load application 2.56 2.24 1.12 1.88 0.97 0.97 1.51 2.30 2.79 Evaluation of raising quality (2 mm and above) ○ × ○ ○ ◎ ◎ ○ × ○ Evaluation of raising quality (above 1 mm) ○ × ○ ○ ◎ ◎ ○ × ○ Evaluation of raising quality (0.5 mm and above) ○ × ○ ○ ○ ○ × × ○ Insulation reliability evaluation (%) 50 No rating 100 70 100 100 0 No rating 60

[Table 2] Table 2 Comparison Example 4 Embodiment 3 Evaluation of impregnation of glass cloth Resin varnish with a viscosity of 230 mPa·s Number of gaps average value 82.2 10.6 Standard Deviation 13.6 1.5 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 9.0 10.2 Standard Deviation 1.6 0.7 Void ratio before and after tensile load application 9.13 1.04 Resin varnish with a viscosity of 680 mPa·s Number of gaps average value 412.2 52.2 Standard Deviation 35.7 6.2 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 53.8 51.4 Standard Deviation 6.4 4.9 Void ratio before and after tensile load application 7.66 1.02 castor oil Number of gaps average value 917.4 214.2 Standard Deviation 78.4 16.3 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 236.6 215.0 Standard Deviation 39.2 14.2 Void ratio before and after tensile load application 3.88 1.00 Evaluation of raising quality (2 mm and above) ○ ○ Evaluation of raising quality (above 1 mm) ○ ○ Evaluation of raising quality (0.5 mm and above) ○ ○ Insulation reliability evaluation (%) 40 100

[Table 3] Table 3 Comparison Example 5 Embodiment 4 Evaluation of impregnation of glass cloth Resin varnish with a viscosity of 230 mPa·s Number of gaps average value 4.8 2.6 Standard Deviation 3.3 1.1 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 2.0 2.4 Standard Deviation 0.7 0.5 Void ratio before and after tensile load application 2.40 1.08 Resin varnish with a viscosity of 680 mPa·s Number of gaps average value 58.4 31.0 Standard Deviation 19.4 3.8 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 33.0 31.0 Standard Deviation 2.3 3.7 Void ratio before and after tensile load application 1.77 1.00 castor oil Number of gaps average value 293.8 118.4 Standard Deviation 75.0 10.8 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 158.4 122.8 Standard Deviation 20.4 15.1 Void ratio before and after tensile load application 1.85 0.96 Evaluation of raising quality (2 mm and above) ○ ○ Evaluation of raising quality (above 1 mm) ○ ○ Evaluation of raising quality (0.5 mm and above) ○ ○ Insulation reliability evaluation (%) 50 100

[Table 4] Table 4 Comparative Example 6 Embodiment 5 Evaluation of impregnation of glass cloth Resin varnish with a viscosity of 230 mPa·s Number of gaps average value 235.0 108.2 Standard Deviation 85.2 8.0 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 103.2 100.8 Standard Deviation 18.8 4.3 Void ratio before and after tensile load application 2.28 1.07 Resin varnish with a viscosity of 680 mPa·s Number of gaps average value 461.0 124.8 Standard Deviation 147.5 15.5 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 120.4 119.8 Standard Deviation 12.4 12.3 Void ratio before and after tensile load application 3.83 1.04 castor oil Number of gaps average value 765.6 434.2 Standard Deviation 120.5 23.3 Number of gaps after applying a load of 10 N per 25 mm width in the warp direction average value 410.4 410.2 Standard Deviation 39.4 25.7 Void ratio before and after tensile load application 1.87 1.06 Evaluation of raising quality (2 mm and above) ○ ○ Evaluation of raising quality (above 1 mm) ○ ○ Evaluation of raising quality (0.5 mm and above) ○ ○ Insulation reliability evaluation (%) 40 100

Claims (13)

A glass cloth is woven with glass yarns containing a plurality of glass filaments as warp yarns and weft yarns, and the surface is treated with a surface treatment agent. When the glass cloth is immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 230mPa.s (impregnation evaluation test solution α) for 3 minutes, the number of unimpregnated parts Aα is less than 1.50 times the number of unimpregnated parts Bα when the glass cloth is immersed in the impregnation evaluation test solution α for 3 minutes after a load of 10N is applied to each width of 25mm in the warp direction. For example, the glass cloth in claim 1, the number of unimpregnated parts Aβ of the glass cloth when immersed in a benzyl alcohol solution containing bisphenol A type epoxy resin with a viscosity of 680mPa.s (impregnation evaluation test solution β) for 3 minutes is 1.5 times or less of the number of unimpregnated parts Bβ of the glass cloth when immersed in the impregnation evaluation test solution β for 3 minutes after applying a load of 10N per 25mm width in the warp direction. For the glass cloth in claim 1 or 2, the number of unimpregnated parts Aγ of the glass cloth when immersed in castor oil (containing the impregnation evaluation test solution γ) with a viscosity of 650mPa.s for 3 minutes is less than 1.5 times the number of unimpregnated parts Bγ of the glass cloth when a load of 10N is applied to each width of 25mm in the warp direction and the glass cloth is immersed in the impregnation evaluation test solution γ for 3 minutes. For glass cloth as claimed in claim 1 or 2, the number of fuzz of the cloth with a length of 2 mm or more shall be less than 10 pieces/ ^m2 . For glass cloth as claimed in claim 1 or 2, the number of fuzz of the cloth with a length of 1 mm or more shall be less than 10 pieces/ ^m2 . For glass cloth as claimed in claim 1 or 2, the number of fuzz of the cloth with a length of 0.5 mm or more shall be less than 10 pieces/ ^m2 . For glass cloth in request 1 or 2, the thickness is 5~100μm. For glass cloth as claimed in claim 1 or 2, the average filament diameter is between 3.0 μm and 8 μm. For glass cloth in claim 1 or 2, the average number of filaments is more than 80. For example, the glass cloth of claim 1 or 2, wherein the elastic coefficient of the glass cloth is greater than 50 GPa and less than 70 GPa. For example, the glass cloth in claim 10, wherein the elastic coefficient is greater than 50 GPa and less than 63 GPa. 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 cured product of a base resin composition impregnated in the glass cloth.