Glass cloth, prepreg and printed circuit board

Abstract

Provided are glass cloth, prepreg, and printed circuit board. The present invention aims to provide a glass cloth having excellent nap quality and stable and uniform resin impregnability for a low dielectric resin, a method for manufacturing the same, and a prepreg and printed circuit board obtained using the glass cloth. A glass cloth is provided, which is woven with glass yarn formed of a plurality of glass filaments as warp and weft, and is surface-treated with a surface treatment agent, and the number of unimpregnated sites Aα of the aforementioned glass cloth when impregnated in a benzyl alcohol solution (test solution α for impregnation evaluation) having a viscosity of 230 mPa·s and containing a bisphenol A type epoxy resin for 3 minutes is 1.50 times or less the number of unimpregnated sites Bα when the aforementioned glass cloth is impregnated in the aforementioned test solution α for impregnation evaluation for 3 minutes after a load of 10 N per 25 mm of width is applied to the warp direction.

Description

TECHNICAL FIELD

[0001] The present application relates to a glass cloth, a method for manufacturing the glass cloth, a prepreg, a printed circuit board, and the like. BACKGROUND

[0002] With the development of the information communication society in recent years, data communication and / or signal processing are increasingly performed at a large capacity and at a high speed, and the low dielectricity (low dielectric constant and low dielectric loss tangent) of printed circuit boards used in electronic devices is being significantly promoted. Therefore, as a glass cloth constituting a printed circuit board, a low dielectric glass cloth has been proposed.

[0003] For example, for the E glass cloth that has been generally used until now, a low dielectric glass cloth in which a large amount of B2O3 is blended in the glass composition is known (see Patent Literature 1). The glass cloth described in Patent Literature 1 discloses that by surface treatment with a large amount of a silane coupling agent in such a manner that the mass loss on ignition becomes in the range of 0.25 to 1.0 mass%, it is possible to suppress the hygroscopicity caused by the high content of B2O3, and it is possible to obtain practical insulation reliability.

[0004] In addition, for the resin constituting a printed circuit board, various low dielectric resins such as polyphenyl ether have been proposed. Low dielectric resins tend to have bulky functional groups, and the viscosity tends to be high, and the impregnation property into a glass cloth is sometimes poor compared to epoxy resins and the like that have been generally used until now. If the impregnation property into a glass cloth is poor, resin-unimpregnated portions (voids) are easily formed in the glass fiber bundles in the substrate, and CAF (Conductive Anodic Filaments) is easily a problem. Therefore, it is necessary to improve the CAF resistance by further improving the resin impregnation property on the glass cloth side.

[0005] In order to improve the resin impregnation property of a glass cloth, a chemical method of treating the surface of a glass fiber with a silane coupling agent or the like to improve the affinity with a resin, and a method of opening the glass fiber bundles to make it easy for a resin to penetrate are known.

[0006] As a chemical method of using a silane coupling agent or the like to improve the impregnation property, a method of using a special silane coupling agent (for example, see Patent Literature 2), a method of uniformly treating a silane coupling agent (for example, see Patent Literatures 3 and 4), and the like are known. As a method of opening the glass fiber to make it easy for a resin to penetrate, a method of using a columnar flow or a spray flow, a method based on a vibration cleaner, or a method based on high-frequency vibration using a liquid as a medium, a method of using a round bar to roll and the like (for example, Patent Literatures 5 and 6, and the like) are known.

[0007] PRIOR ART DOCUMENTS

[0008] Patent Literature

[0009] Patent Literature 1: International Publication No. 2016 / 175248

[0010] Patent Literature 2: Japanese Patent Application Laid-Open No. 09-003770

[0011] Patent Literature 3: Japanese Patent Application Laid-Open No. 2005-281889

[0012] Patent Literature 4: Japanese Patent Application Laid-Open No. 10-245766

[0013] Patent Literature 5: Japanese Patent Application Laid-Open No. 2001-348757

[0014] Patent Literature 6: Japanese Patent Application Laid-Open No. 2022-80443 SUMMARY

[0015] PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] As described above, low-dielectric glass cloth is required to have high impregnability for a low-dielectric resin such as a polyphenylene ether. However, the conventional methods described in Patent Literatures 2 to 5 each have room for improvement in impregnability. The present inventors and others have found that, in the low-dielectric glass cloth described in Patent Literature 1, there are sites where adjacent glass fibers (glass filaments) are bonded to each other, as compared with the conventional E glass cloth. It has also been found that the more the sites where adjacent glass fibers are bonded to each other exist, the worse the impregnability of the matrix resin, particularly the impregnability of a low-dielectric resin, becomes.

[0017] As a reason why the sites where a plurality of adjacent glass fibers are in contact with each other exist in the low-dielectric glass cloth, the following reasons can be presumed. For example, it can be presumed that this is a phenomenon that occurs because, as in Patent Literature 1, the low-dielectric glass cloth has a tendency to be surface-treated with a large amount of silane coupling agent in order to impart moisture absorption resistance, and thus a film based on the silane coupling agent is formed across a plurality of filaments; or because, in a state where the filament bundle is left as it is due to a protective effect of a sizing agent that is strong because the mechanical strength of the low-dielectric glass yarn is weak, the film based on the silane coupling agent is formed; or because the condensation property of the filaments to each other is made stronger due to the influence of a functional group possessed in order to improve the affinity of the silane coupling agent used in the low-dielectric glass cloth to the low-dielectric resin, and the like. In addition, it can be considered that these phenomena occur in combination, and the sites where a plurality of glass fibers are bonded to each other are generated.

[0018] Further, the present inventors have confirmed that, as a method for eliminating the adhesion of adjacent glass fibers of a low-dielectric glass cloth to each other, the known splitting method using a columnar flow or a spray flow has a certain effect. However, the low-dielectric glass cloth has a lower mechanical strength than the conventional E glass, and therefore, if splitting is performed using a columnar flow or a spray flow under the same conditions as the conventional E glass, there is a problem that fluff is easily generated. Furthermore, in order to eliminate the adhesion of the glass fibers present in a large amount in the low-dielectric glass cloth to each other and to improve the impregnation property for a low-dielectric resin, it is necessary to increase the strength of the columnar flow or the spray flow compared to the conventional glass cloth, and therefore, there is a problem that the quality of the fluff becomes even worse. Also, in the splitting processing based on the columnar flow or the spray flow, the processing force is difficult to reach the inside of the glass fiber bundle. For the reasons that it is difficult to make the spray uniformly contact the entire area of the glass cloth surface so that the spray reaches between the glass fibers and the processing force is varied due to the influence of the variation of the conveying tension of the glass cloth or the deformation of the glass cloth itself, and the like, there is a problem that the resin impregnation property of the low-dielectric glass cloth easily generates in-plane unevenness. Further, the same problems are present in other splitting methods (vibration, ultrasonic wave). The present application has been made in view of the above problems, and aims to provide a glass cloth having excellent fluff quality and a stable and uniform resin impregnation property for a low-dielectric resin, and a method for producing the same. Further, the present application aims to provide a prepreg obtained using the glass cloth and a printed circuit board.

[0019] Solution to the problem

[0020] The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have ascertained that the adhesion of glass fibers to each other with a sizing agent applied to the glass yarn or a silane coupling agent applied to the glass cloth is a major cause of the impregnation property of a low-dielectric glass cloth, and have found that, by eliminating the adhesion of the glass fibers to each other without applying an external force such as a frictional force to the glass yarn, a low-dielectric glass cloth having excellent fluff quality and a stable and uniform impregnation property for a low-dielectric resin can be obtained, thereby completing the present application. One embodiment of the present application is described below.

[0021] (1) A glass cloth which is woven with a glass yarn formed of a plurality of glass filaments as warp and weft, and which is surface-treated with a surface treatment agent,

[0022] The number of unimpregnated sites Aα when the aforementioned glass cloth is dipped in a benzyl alcohol solution (test solution α for impregnation evaluation) having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes is 1.50 times or less the number of unimpregnated sites Bα when the aforementioned glass cloth is subjected to a load of 10 N per 25 mm width in the warp direction and then dipped in the aforementioned test solution α for impregnation evaluation for 3 minutes.

[0023] (2) The glass cloth according to item 1, wherein the number of unimpregnated sites Aβ when the aforementioned glass cloth is impregnated in a benzyl alcohol solution (test solution β for impregnation evaluation) containing a bisphenol A type epoxy resin having a viscosity of 680 mPa-s for 3 minutes is 1.5 times or less of the number of unimpregnated sites Bβ when the aforementioned glass cloth is impregnated in the aforementioned test solution β for impregnation evaluation for 3 minutes after a load of 10 N per 25 mm of width is applied in the warp direction.

[0024] (3) The glass cloth according to item 1 or 2, wherein the number of unimpregnated sites Aγ when the aforementioned glass cloth is impregnated in castor oil (test solution γ for impregnation evaluation) having a viscosity of 650 mPa-s for 3 minutes is 1.5 times or less of the number of unimpregnated sites Bγ when the aforementioned glass cloth is impregnated in the aforementioned test solution γ for impregnation evaluation for 3 minutes after a load of 10 N per 25 mm of width is applied in the warp direction.

[0025] (4) The glass cloth according to any one of items 1 to 3, wherein the number of fluffs having a length of 2 mm or more is 10 pieces / m 2 or less.

[0026] (5) The glass cloth according to any one of items 1 to 4, wherein the number of fluffs having a length of 1 mm or more is 10 pieces / m 2 or less.

[0027] (6) The glass cloth according to any one of items 1 to 5, wherein the number of fluffs having a length of 0.5 mm or more is 10 pieces / m 2 or less.

[0028] (7) The glass cloth according to any one of items 1 to 6, which has a thickness of 5 to 100 μm.

[0029] (8) The glass cloth according to any one of items 1 to 7, which has an average filament diameter of 3.0 μm or more and 8 μm or less.

[0030] (9) The glass cloth according to any one of items 1 to 8, which has an average number of filaments of 80 or more.

[0031] (10) The glass cloth according to any one of items 1 to 9, wherein the glass cloth has an elastic modulus of 50 GPa or more and 70 GPa or less.

[0032] (11) The glass cloth according to item 10, wherein the elastic modulus is 50 GPa or more and 63 GPa or less.

[0033] (12) A prepreg having the glass cloth according to any one of items 1 to 11 and a matrix resin composition impregnated in the aforementioned glass cloth.

[0034] (13) A printed circuit board having the glass cloth according to any one of items 1 to 11 and a cured product of the matrix resin composition impregnated in the aforementioned glass cloth.

[0035] Effects of the Invention

[0036] According to the present application, a low-dielectric glass cloth having a stable and uniform impregnation property for a low-dielectric resin, in which variation in impregnation property at the time of prepreg coating is suppressed while maintaining excellent pile quality, can be provided, and as a result, a low-dielectric glass cloth having excellent insulation reliability can be obtained. In addition, according to the present application, a prepreg and a printed circuit board obtained using the low-dielectric glass cloth can also be provided. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present application (hereinafter referred to as "the present embodiments") will be described in detail, but the present application is not limited thereto, and various modifications can be made within the scope of the gist thereof.

[0038] [Glass Cloth]

[0039] The glass cloth of the present embodiments is woven using glass yarns formed of a plurality of glass filaments as warp and weft, and is surface-treated with a surface treatment agent, and the number of unimpregnated sites Aa when the glass cloth is impregnated in a benzyl alcohol solution (test liquid a for impregnation evaluation) having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes is 1.50 times or less the number of unimpregnated sites Ba when the aforementioned glass cloth is subjected to a load of 10 N per 25 mm of width in the warp direction and then impregnated in the same liquid (test liquid a for impregnation evaluation) for 3 minutes.

[0040] As described above, it has been clarified that a low-dielectric glass cloth is prone to generate a large amount of adhesion of adjacent glass fibers to each other with the sizing agent applied to the glass yarns or the silane coupling agent applied to the glass cloth interposed therebetween, and the adhesion of the glass fibers to each other hinders the penetration of the resin between the glass fibers, which is a cause of the generation of unimpregnated portions of the resin in the glass fiber bundle.

[0041] The adhesion of adjacent glass fibers with sizing agent or silane coupling agent interposed therebetween is broken in a very small area (in the vicinity of the junction of the glass fibers), and therefore, in the conventional opening methods such as columnar flow, spray flow, vibration cleaner, high frequency vibration using liquid as a medium, etc., it is difficult to selectively apply the opening force to the adhesion site of the adjacent glass fibers, and therefore, a large processing force needs to be applied to the entire surface of the glass cloth in order to break the adhesion of the adjacent glass fibers, and thus it is difficult to sufficiently eliminate the adhesion. Therefore, the low dielectric glass cloth is likely to have the adhesion of the adjacent fibers remaining, and has a problem of poor impregnation. In addition, in the conventional opening method, as a device for opening processing, it is difficult to uniformly generate the opening processing force on the entire surface of the glass cloth, and the opening processing force is difficult to reach the adhesion of the glass fibers present inside the glass fiber bundle, and is also likely to be affected by the variation of the handling tension of the glass cloth or the deformation of the glass cloth itself, and thus there is a problem that the adhesion of the adjacent fibers is likely to remain locally, and the resin impregnation is likely to be inhomogeneous in the plane.

[0042] The present inventors have found that, as a method for eliminating the adhesion of the glass fibers with sizing agent or silane coupling agent interposed therebetween, the adhesion can be broken by a force that moves the glass fibers constituting the warp yarns in a direction in which the glass fibers are gathered toward the center when a tensile tension of a prescribed value or more is applied to the glass cloth after the silane coupling agent treatment in the warp direction. It has also been found that, by applying a tension of a prescribed value or more to the low dielectric glass cloth after the silane coupling agent treatment in the warp direction, the adhesion of the glass fibers can be broken, the resin impregnation of the low dielectric glass cloth is improved, and by applying a tensile tension of a prescribed value or more, sufficient impregnation can be obtained.

[0043] Hereinafter, the configuration of the present embodiment will be described in more detail.

[0044] (Difference in the number of unimpregnated sites before and after a load of 10 N per 25 mm width is applied to the warp direction)

[0045] The number of unimpregnated sites Aα when the low dielectric glass cloth of the present embodiment is impregnated in a benzyl alcohol solution (test liquid α for impregnation evaluation) having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes and the number of unimpregnated sites Bα after a load of 10 N per 25 mm width is applied to the warp direction and then impregnated in a benzyl alcohol solution (test liquid α for impregnation evaluation) having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes are preferably the same, and the number of unimpregnated sites Aα is preferably 1.50 times or less, more preferably 1.40 times or less, even more preferably 1.30 times or less, further more preferably 1.20 times or less, and most preferably 1.10 times or less, the number of unimpregnated sites Bα.

[0046] If the number of non-impregnated sites Aα is 1.50 times or less than the number of non-impregnated sites Bα, stable and uniform impregnability can be obtained for low dielectric resins such as polyphenylene ether, and thus is preferred. It is presumed that this is because the number of adhesions of glass fibers to each other that hinder impregnation of the resin is suppressed to a certain amount or less. By reducing the variation in impregnability, the risk of generation of voids can be suppressed to be small, and thus a substrate with high CAF reliability can be obtained, and thus is preferred.

[0047] In addition, if the number of non-impregnated sites Aα is 1.50 times or less than the number of non-impregnated sites Bα, the variation in impregnability caused by the magnitude of the tension applied to the glass cloth at the time of prepreg coating, the variation in tension, the difference in tension in the width direction, the difference in prepreg coating equipment (for example, in the case of production using a plurality of prepreg coating machines, in the case of prepreg coating in a plurality of factories, in the case of prepreg coating using equipment with different mechanisms), and the like is small, the risk of generation of voids can be suppressed to be small, and thus a substrate with high CAF reliability can be obtained, and thus is preferred.

[0048] The lower limit value of the ratio of the number of non-impregnated sites Aα to the number of non-impregnated sites Bα is not particularly limited, and is preferably 0.80 times or more, and more preferably 0.90 times or more.

[0049] The number of non-impregnated sites Aα is the number of non-impregnated sites observed at a field angle of 32 mm x 32 mm after 3 minutes after the test piece of the glass cloth is impregnated in a benzyl alcohol solution (test liquid for impregnation evaluation α) having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin. The non-impregnated sites are counted with non-impregnated sites having a length of 160 μm or more as the target, and in the case of measuring multiple times, the average value of the number of times of measurement is taken.

[0050] The number of impregnated sites Bα is the number of non-impregnated sites observed at a field angle of 32 mm x 32 mm after 3 minutes after the glass cloth is impregnated in the same test liquid (test liquid for impregnation evaluation α) as the number of non-impregnated sites Aα after a load of 10 N per 25 mm of width is applied to the warp direction.

[0051] As a method of adjusting the value of the number of non-impregnated sites Aα to the number of non-impregnated sites Bα to the numerical range described above, it is effective to suppress the formation of a surface coating film that spans between different filaments by a surface treatment agent such as a silane coupling agent, and / or to destroy a surface coating film that spans between different filaments formed by a surface treatment agent such as a silane coupling agent.

[0052] As a method of inhibiting the formation of a surface coating film formed across different filaments due to a surface treatment agent such as a silane coupling agent, there are, for example, a method in which the amount of application of the surface treatment agent is reduced in a method in which surface treatment is performed after a sizing agent removal process, a method in which the concentration of the surface treatment agent in a treatment liquid containing the surface treatment agent is reduced, a method in which surface treatment is performed in a state in which a glass yarn is previously disassembled so that adjacent yarns of glass filaments are separated from each other by a distance, a method in which the treatment liquid containing the surface treatment agent is rapidly dried at a high temperature so that the filaments do not shrink when the treatment liquid is dried, and the like, and when it is not possible to adjust the value of the number of non-penetrated sites Aa with respect to the number of non-penetrated sites Ba using one method, it is preferable to appropriately combine them to inhibit the formation of a surface coating film across filaments.

[0053] As a method of destroying a surface coating film formed across different filaments due to a surface treatment agent such as a silane coupling agent, as described above, there is, for example, a method in which a high tension is applied to a glass cloth on which surface treatment has been performed in the warp direction (MD direction) after the sizing agent is removed. If a tension is applied to the MD direction of the glass cloth, the filaments that constitute the warp are pulled and moved toward the center of the surface perpendicular to the length direction as the warp is pulled in the length direction. At this time, the coating film based on the surface treatment agent formed across different filaments is stressed, the coating film is destroyed, and the adhesion of the filaments is torn. As a result, no mechanical force or excessive frictional force acts on the glass cloth, and thus the penetrability is improved without affecting the pile quality, and thus is preferable.

[0054] In addition, a process in which a glass cloth on which surface treatment has been performed after the sizing agent is removed is bent in the MD direction with a low radius of curvature is also effective. By applying a bending stress to the glass cloth, the coating film based on the surface treatment agent formed across different filaments is destroyed. However, depending on the radius of curvature, a frictional force acts on the glass cloth and the pile is easily generated when the glass cloth is bent, and thus attention is required. The above process can also be used depending on the balance between the pile quality and the penetrability.

[0055] Further, a method of performing shot blasting on the glass cloth subjected to surface treatment after removal of the sizing agent using particles that sublimate into gas is also effective. The particles can directly act on the surface film portion formed across different filaments, and can destroy the film using the volume expansion caused by sublimation. As the shot blasting method using particles that sublimate into gas, from the viewpoint of the effect of destroying the film, safety, and usability, dry ice shot blasting is suitable. Dry ice shot blasting is a method of spraying (blowing) dry ice particles having a particle diameter of 5 to 300 μm at a gas pressure of 0.05 to 1 MPa from a height of 5 to 1000 mm to the treated body. More preferably, it is a method of spraying dry ice particles having a particle diameter of 5 to 300 μm at a gas pressure of 0.1 to 0.5 MPa from a height of 5 to 600 mm to the treated body. By having the particle diameter, height, and gas pressure within these ranges, the film formed across different filaments can be destroyed without causing fuzzing of the glass cloth. Therefore, the wettability of the glass cloth before and after a load of 10 N per 25 mm width is applied to the warp direction becomes equivalent. This method also does not have a force acting on the glass cloth like rubbing, and therefore the wettability is improved without affecting the fuzz quality, and is thus preferred.

[0056] As for the fuzz quality of the glass cloth of the present embodiment, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 2 mm or more is preferably 10 / m 2 .

[0057] The shorter the length of the fuzz contained in the glass cloth, the more preferable it is. From this viewpoint, as the fuzz quality of the glass cloth of the present embodiment, the number of fuzz having a length of 1 mm or more is more preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 1 mm or more is more preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 1 mm or more is more preferably 10 / m 2 Hereinafter, the number of fuzz having a length of 1 mm or more is more preferably 10 / m 2 From the same viewpoint, as the fuzz quality of the glass cloth of the present embodiment, the number of fuzz having a length of 0.5 mm or more is more preferably 10 / m2 A further preferable range of the number of fluffs having a length of 0.5 mm or more is 7 / m 2 A still further preferable range is 3 / m 2 A most preferable range is 0 / m 2 .

[0058] From the viewpoint of further advancing the high viscosity of the base resin while advancing the low dielectric properties of the base resin, the number of unimpregnated sites Aβ of the glass cloth of the present embodiment when impregnated in a benzyl alcohol solution (test liquid β for impregnation evaluation) having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes is preferably 1.5 times or less than the number of unimpregnated sites Bβ when the aforementioned glass cloth is subjected to a load of 10 N per 25 mm width in the warp direction and then impregnated in the benzyl alcohol solution (test liquid β for impregnation evaluation) having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes.

[0059] The number of unimpregnated sites Aβ is more preferably 1.4 times or less, further preferably 1.3 times or less, still further preferably 1.2 times or less, and most preferably 1.1 times or less than the number of unimpregnated sites Bβ.

[0060] The lower limit value of the ratio of the number of unimpregnated sites Aβ to the number of unimpregnated sites Bβ is not particularly limited, and is preferably 0.8 or more, and more preferably 0.9 or more.

[0061] The number of unimpregnated sites Aβ is the number of unimpregnated sites observed after impregnating a test piece of the glass cloth in a benzyl alcohol solution (test liquid β for impregnation evaluation) having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin for 3 minutes, with a field angle of 32 mm x 32 mm. The unimpregnated sites are counted with a length of 160 μm or more as the target, and in the case of measuring multiple times, the average value of the number of measurements is taken. The number of unimpregnated sites Bβ is the number of unimpregnated sites observed after impregnating the glass cloth in the same test liquid (test liquid β for impregnation evaluation) as the number of unimpregnated sites Aβ after being subjected to a load of 10 N per 25 mm width in the warp direction, with a field angle of 32 mm x 32 mm after 3 minutes.

[0062] From the viewpoint of further advancing the low dielectric property of the matrix resin while also achieving stable impregnation even when the volume is large, the number of unimpregnated sites Aγ of the glass cloth of the present embodiment when impregnated in castor oil (test liquid for impregnation evaluation γ) having a viscosity of 650 mPa s for 3 minutes is preferably 1.5 times or less the number of unimpregnated sites Bγ when the aforementioned glass cloth is subjected to a load of 10 N per 25 mm width in the warp direction and then impregnated in castor oil (test liquid for impregnation evaluation γ) having a viscosity of 650 mPa s for 3 minutes. The number of unimpregnated sites Aγ is more preferably 1.4 times or less the number of unimpregnated sites Bγ, further preferably 1.3 times or less, still further preferably 1.2 times or less, and most preferably 1.1 times or less.

[0063] The lower limit of the ratio of the number of unimpregnated sites Aγ to the number of unimpregnated sites Bγ is not particularly limited, and is preferably 0.8 or more, and more preferably 0.9 or more.

[0064] The number of unimpregnated sites Aγ is the number of unimpregnated sites observed when a test piece of the glass cloth is impregnated in castor oil (test liquid for impregnation evaluation γ) having a viscosity of 650 mPa s, and observed after 3 minutes with a field angle of 32 mm x 32 mm. The unimpregnated sites are counted with a length of 160 μm or more as the target, and in the case of measuring multiple times, the average of the number of measurements is taken.

[0065] The number of unimpregnated sites Bγ is the number of unimpregnated sites observed when the glass cloth is subjected to a load of 10 N per 25 mm width in the warp direction and then impregnated in the same test liquid (test liquid for impregnation evaluation γ) as the number of unimpregnated sites Aγ, and observed after 3 minutes with a field angle of 32 mm x 32 mm.

[0066] (Composition of the Glass Cloth)

[0067] The glass yarn is obtained by bundling a plurality of filaments into a bundle and twisting as necessary. In this case, the glass yarn is classified as a glass multifilament, and the filaments (glass filaments) included in the glass yarn are classified as glass monofilaments.

[0068] The modulus of elasticity of the glass yarn is preferably 50 to 70 GPa, more preferably 50 to 63 GPa, and further preferably 53 to 63 GPa. In addition, since the modulus of elasticity of the glass cloth is the same as that of the glass yarn, the modulus of elasticity of the glass cloth is also preferably 50 GPa or more and 70 GPa or less, more preferably 50 GPa or more and 63 GPa or less, and further preferably 53 or more and 63 GPa or less.

[0069] The elastic modulus also becomes an index of the dielectric constant of the glass. In general, the elastic modulus of the glass yarn is lower than that of the conventional E glass. If the elastic modulus is below the upper limit value described above, in order to increase the strength of the glass cloth for the purpose of suppressing the generation of fluffs of the glass cloth or preventing breakage, it is necessary to apply a surface treatment agent such as a silane coupling agent in a larger amount than that of the conventional E glass. Therefore, there is a tendency that the following problems occur: the adhesion between filaments occurs due to the formation of a coating film of the surface treatment agent such as a silane coupling agent, and the impregnation property is reduced. In the present application, the coating film that spans the filaments is broken, and the impregnation property is exhibited equally with or without a tensile load. Therefore, even if the elastic modulus of the glass yarn or the glass cloth is below the upper limit value described above, stable CAF resistance can be obtained, and thus it is preferred.

[0070] In addition, by making the elastic modulus be above the lower limit value described above, the rigidity of the glass yarn is increased, and fluffs are less likely to occur in the manufacturing process, and thus it is preferred.

[0071] The average diameter of the glass filaments that constitute the warp yarns and the weft yarns is preferably independently 2.5 to 9 μm, more preferably 3.0 to 8 μm, and further preferably 3.5 to 7.5 μm. The average diameter of the glass filaments can be appropriately selected and used according to the thickness of the glass cloth that is targeted.

[0072] The average number of the glass filaments that constitute the warp yarns and the weft yarns is preferably independently 80 or more, and more preferably 180 or more.

[0073] There is a tendency that the more the average number of the glass filaments that constitute the warp yarns and the weft yarns is, the more the portions where the adjacent glass filaments adhere to each other are generated, and the more the impregnation property is reduced. In contrast, by using the present application, the adhesion between the glass filaments is eliminated, and thus stable and uniform impregnation property with respect to a low-dielectric resin is obtained, and thus it is preferred.

[0074] The insertion density of the warp yarns and the weft yarns that constitute the glass cloth is preferably 30 to 120 per 25 mm, more preferably 40 to 110 per 25 mm, and further preferably 50 to 100 per 25 mm.

[0075] 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. By making the thickness of the glass cloth be within the range described above, there is a tendency that a thin and high-strength glass cloth can be obtained.

[0076] 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 , and further preferably 8 to 50 g / m 2 , and particularly preferably 8 to 35 g / m 2 .

[0077] The preferred range of the strong thermal gravimetric value of the glass cloth is a value equal to or greater than that calculated by the following formula (i), more preferably a value equal to or greater than that calculated by the following formula (ii), and further preferably a value equal to or greater than that calculated by the following formula (iii).

[0078] 5.0 x F -1.6 ) Formula (i)

[0079] 6.0 x F -1.6 ) Formula (ii)

[0080] 6.4 x F -1.6 ) Formula (iii)

[0081] In Formulas (i) to (iii), F is the filament diameter of the glass yarn (μm).

[0082] The strong thermal gravimetric value of the glass cloth is a value obtained by adding the weight reduction amount of the glass cloth itself under heating conditions to the weight reduction amount caused by combustion to remove the silane coupling agent. If the strong thermal gravimetric value of the glass cloth is equal to or greater than the lower limit value calculated by any one of the above Formulas (i) to (iii), there is a tendency to simultaneously exhibit an increase in insulation reliability achieved by an adequate coating amount of the silane coupling agent and a tendency for the low dielectric properties of the glass cloth to become good, and thus is preferred.

[0083] Further, the preferred range of the strong thermal gravimetric value of the glass cloth is a value equal to or less than that calculated by the following formula (iv), more preferably a value equal to or less than that calculated by the following formula (v), and further preferably a value equal to or less than that calculated by the following formula (vi).

[0084] 18 x F -1.6 ) Formula (iv)

[0085] 16 x F -1.6 ) Formula (v)

[0086] 15 x F -1.6 ) Formula (vi)

[0087] In Formulas (iv) to (vi), F is the filament diameter of the glass yarn (μm).

[0088] By making the strong thermal gravimetric value of the glass cloth equal to or less than the upper limit value calculated by any one of the above Formulas (iv) to (vi), there is a tendency to simultaneously exhibit an increase in resin impregnation achieved by the coating amount of the silane coupling agent being in an appropriate range and a tendency for the low dielectric properties of the glass cloth to become good, and thus is preferred.

[0089] The strong thermal gravimetric value can be measured according to the method described in JIS R3420.

[0090] The preferable range of the amount of the silane coupling agent applied to the glass cloth is above the value calculated by the following formula (vii), more preferably above the value calculated by the following formula (viii), and further preferably above the value calculated by the following formula (ix).

[0091] 0.2 x F -0.6 ) Formula (vii)

[0092] 0.25 x F -0.6 ) Formula (viii)

[0093] 0.30 x F -0.6 ) Formula (ix)

[0094] In the formulas (vii) to (ix), F is the filament diameter of the glass yarn (μm).

[0095] If the amount of the silane coupling agent applied to the glass cloth is above the lower limit value calculated by any one of the above formulas (vii) to (ix), the amount of the silane coupling agent is sufficient, whereby sufficient reactivity with the matrix resin at the time of manufacturing the substrate can be obtained, and further, the moisture absorption resistance is improved, as a result, there is a tendency that the insulation reliability is improved, and thus it is preferable.

[0096] Further, the preferable range of the amount of the silane coupling agent applied to the glass cloth is below the value calculated by the following formula (x), more preferably below the value calculated by the following formula (xi), and further preferably below the value calculated by the following formula (xii).

[0097] 1.8 x F -1.0 ) Formula (x)

[0098] 1.6 x F -1.0 ) Formula (xi)

[0099] 1.4 x F -1.0 ) Formula (xii)

[0100] In the formulas (x) to (xii), F is the filament diameter of the glass yarn (μm).

[0101] By making the amount of the silane coupling agent applied to the glass cloth below the upper limit value calculated by any one of the above formulas (x) to (xii), the resin impregnation property to the glass cloth is more easily improved, and thus it is preferable. The weaving structure of the glass cloth is not particularly limited, and weaving structures such as plain weave, basket weave, satin weave, twill weave, and the like can be cited. Among them, the plain weave structure is preferable.

[0102] (Composition of the Glass Cloth)

[0103] The composition of the glass cloth according to the present embodiment will be described below. Note that the composition of the glass cloth has the same meaning as the composition of the glass yarn constituting the glass cloth. As the elements 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), and the like can be listed.

[0104] The silicon (Si) content of the glass yarn, calculated as Si02, 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 more further preferably 48.0 to 52.0 mass%. Si is a component that forms the skeleton structure of the glass yarn. Therefore, by making the Si content 40.0 mass% or more, there is a tendency for the strength of the glass yarn to further increase, and for the breakage of the glass cloth to be further suppressed in the post-processes such as the manufacturing process of the glass cloth and the process of manufacturing a prepreg using the glass cloth. In addition, by making the Si content 40.0 mass% or more, there is a tendency for the dielectric constant of the glass cloth to further decrease. On the other hand, by making the Si content 60.0 mass% or less, there is a tendency for the viscosity at the time of melting to further decrease in the manufacturing process of the glass filament, and for a glass fiber having a more uniform glass composition to be obtained. Therefore, the obtained glass filament is less likely to have a portion where devitrification easily occurs or a portion where it is difficult to remove air bubbles, and thus, the glass filament is less likely to have a portion where the strength is weak. As a result, the glass cloth constituted by the glass yarn obtained using such a Si content is less likely to break. The Si content can be adjusted according to the amount of the raw material used to produce the glass filament.

[0105] The boron (B) content of the glass yarn, calculated as B203, 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%, more 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%.

[0106] By making the B content 15.0 mass% or more, there is a tendency for the dielectric constant to further decrease. In addition, by making the B content 15.0 mass% or more, the glass cloth has improved brittleness resistance, and is imparted with moderate softness or ductility, and thus, there is a tendency for the glass yarn to be less likely to generate fluff when it comes into contact with the weaving members such as the yarn guide and the reed.

[0107] On the other hand, in order to maintain the strength of the glass yarn, the B content is preferably 40.0 mass% or less. In addition, by making the B content 40.0 mass% or less, the moisture absorption resistance is improved, and it is easy to appropriately maintain the stability of the surface properties of the glass yarn described later.

[0108] In particular, by making the Si content in the glass yarn be in the above range and making the B content be in the above range, the above effects related to Si and B are easily synergistically exhibited, and thus are preferred.

[0109] The B content can be adjusted by the amount (charge amount) of the raw material used for producing the glass filament. Note that in the production of the glass filament, in the case where the production conditions, the amount, or the content can vary, it is possible to estimate them in advance and adjust the charge amount of the raw material.

[0110] The aluminum (Al) content of the glass yarn, calculated as Al2O3, is preferably 11.0 to 18.0 mass%, more preferably 11.0 to 17.5 mass%, and further preferably 12 to 17.0 mass%. By making the Al content in the above range, there is a tendency that the electrical properties and the strength are further improved. The Al content can be adjusted by the amount (charge amount) of the raw material used for producing the glass filament.

[0111] The calcium (Ca) content of the glass yarn, calculated as CaO, is preferably 5.0 to 10.0 mass%, more preferably 5.0 to 9.0 mass%, and further preferably 5.0 to 8.5 mass%. By making the Ca content 5.0 mass% or more, there is a tendency that the viscosity at the time of melting during the production of the glass filament is further reduced, and a glass fiber having a more uniform glass composition is obtained. In addition, by making the Ca content 10 mass% or less, there is a tendency that the dielectric constant is further improved. The Ca content can be adjusted by the amount (charge amount) of the raw material used for producing the glass filament.

[0112] The phosphorus (P) content of the glass yarn, calculated as P2O5, is preferably 8.0 mass% or less, more preferably 7.0 mass% or less, and further preferably 6.0 mass% or less. The P content can exceed 0 mass%. By making the P content exceed 0 mass%, there is a tendency that the dielectric properties of the glass cloth become better. In addition, by making the P content 8.0 mass% or less, there is a tendency that the heat resistance of the glass cloth is improved. The P content can be adjusted by the amount (charge amount) of the raw material used for producing the glass filament.

[0113] Note that the above respective contents can be measured by ICP emission spectroscopy. Specifically, the Si content and the B content can be obtained by weighing the glass cloth, dissolving it with sodium carbonate, dissolving it with dilute nitric acid and making it to a prescribed volume, and measuring the obtained sample by ICP emission spectroscopy. In addition, the Fe content can be obtained by dissolving the weighed glass cloth by alkali dissolution and making it to a prescribed volume, and measuring the obtained sample by ICP emission spectroscopy. Further, the Al content, the Ca content, the P content, and the Mg content can be obtained by weighing the glass cloth, performing heat decomposition with perchloric acid, sulfuric acid, nitric acid, and hydrogen fluoride, dissolving it with dilute nitric acid and making it to a prescribed volume, and measuring the obtained sample by ICP emission spectroscopy. Note that, as the ICP emission spectroscopy device, a PS3520VDDII manufactured by Hitachi High-Technologies Corporation can be used.

[0114] (Surface treatment agent)

[0115] The glass cloth according to the present embodiment is surface-treated with a surface treatment agent. There is no particular limitation on the surface treatment agent, and examples include silane coupling agents, and water, organic solvents, acids, dyes, pigments, surfactants, and the like can be used as needed. There is no particular limitation on the silane coupling agent, and examples include compounds represented by the following formula (1).

[0116] X(R) 3-n SiY n …(1)

[0117] (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 or more and 3 or less, and R is each independently a group selected from the group consisting of a methyl group, an ethyl group, and a phenyl group).

[0118] 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.

[0119] As the above alkoxy group, any form can be used, and from the viewpoint of stable treatment of the glass cloth, an alkoxy group having 5 or fewer carbon atoms is preferred.

[0120] As the silane coupling agent, specifically, 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, 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, acryloyloxypropyltrimethoxysilane, and the like known single substances, or a mixture thereof can be exemplified.

[0121] The molecular weight of the silane coupling agent is preferably 100 to 600, more preferably 150 to 500, and further preferably 200 to 450. Among them, two or more kinds of silane coupling agents having different molecular weights are preferably used. By using two or more kinds of silane coupling agents having different molecular weights, the surface of the glass yarn is treated, and thus there is a tendency that the surface treatment agent density of the surface of the glass cloth becomes high, and the reactivity with the matrix resin further increases.

[0122] [Method for manufacturing glass cloth]

[0123] The method for manufacturing the glass cloth of the present embodiment is not particularly limited, and a method having, for example, a weaving step of weaving the glass yarn to obtain the glass cloth, a fiber opening step of opening the glass yarn of the glass cloth, and a degumming step of removing the sizing agent attached to the glass yarn of the glass cloth can be exemplified. In addition, as needed, the method for manufacturing the glass cloth can also have a surface treatment step based on a silane coupling agent.

[0124] The weaving method is not particularly limited as long as the weft yarn and the warp yarn are woven in a manner that a prescribed weave structure is exhibited. In addition, the fiber opening method is not particularly limited, and a method of performing fiber opening processing using, for example, a spray of water (high-pressure water fiber opening), a vibration cleaner, ultrasonic water, a mangle, or the like can be exemplified.

[0125] Further, as the degumming method, there is no particular limitation, and a method in which the sizing agent is removed by heating, for example, can be given. Note that the sizing agent is used for the purpose of protecting the glass yarn from breakage and the like in weaving and the like. As such a sizing agent, there is no particular limitation, and a starch-based binder, a polyvinyl alcohol-based binder, and the like can be given. Note that as the temperature at the time of removing the sizing agent by heating, from the viewpoint of both maintaining the breaking strength and sufficiently removing the sizing agent, 300 to 500°C is preferable, 330 to 450°C is more preferable, and 350 to 430°C is further preferable.

[0126] Further, as the method of performing the surface treatment step, a method in which a surface treatment agent containing a silane coupling agent is brought into contact with the glass cloth and dried, and the like can be given. Note that as the contact of the surface treatment agent with the glass cloth, a method in which the glass cloth is immersed in the surface treatment agent; and a method in which the surface treatment agent is applied to the glass cloth using a roll coater, a die coater, or a gravure coater, and the like can be given. As the drying method of the surface treatment agent, there is no particular limitation, and a hot air drying method or a drying method using electromagnetic waves, for example, can be given.

[0127] In the production of the glass cloth, as described above, a method in which the adhesion between the filaments in which the sizing agent or the surface treatment agent is interposed is suppressed, or a method in which the adhesion between the filaments in which the sizing agent or the surface treatment agent is interposed is destroyed can be performed. These methods can be performed individually or in combination.

[0128] [Prepreg]

[0129] The prepreg of the present embodiment has the glass cloth described above and a matrix resin composition impregnated in the glass cloth. The insulation reliability of the prepreg having the glass cloth described above is further improved, and the yield of the final product is increased. Further, since the dielectric properties and the moisture absorption resistance are excellent, the effect of being able to provide a printed circuit board in which the change in the dielectric constant due to the influence of the use environment, particularly a high-humidity environment, is small can also be exerted.

[0130] The prepreg of the present embodiment can be produced according to a conventional method. For example, it can be produced by impregnating a varnish obtained by diluting a matrix resin such as an epoxy resin with an organic solvent into the glass cloth of the present embodiment, and volatilizing the organic solvent using a drying oven to cure the thermosetting resin to a B-stage state (a semi-cured state).

[0131] As the matrix resin composition, in addition to the above-mentioned epoxy resin, a thermosetting resin such as a bismaleimide resin, a cyanate ester resin, an unsaturated polyester resin, a polyimide resin, a bismaleimide-triazine resin (BT resin), a functionalized polyphenylene ether resin, etc.; a thermoplastic resin such as a polyphenylene ether resin, a polyetherimide resin, a liquid crystal polymer (LCP) of a wholly aromatic polyester, a polybutadiene, a fluororesin, etc.; and a mixed resin thereof, etc. can be exemplified. From the viewpoint of improving the dielectric properties, heat resistance, solvent resistance, and press molding properties, as the matrix resin composition, a resin obtained by modifying a thermoplastic resin with a thermosetting resin can be used.

[0132] In addition, the matrix resin composition can contain, in the resin, an inorganic filler such as silica and aluminum hydroxide; a flame retardant such as a bromine-based, phosphorus-based, and metal hydroxide; another silane coupling agent; a heat stabilizer; an antistatic agent; an ultraviolet absorber; a pigment; a colorant; a lubricant, etc.

[0133] [Printed circuit board]

[0134] The printed circuit board of the present embodiment is provided with the above-mentioned glass cloth, and, as desired, can be provided with a cured product of the matrix resin composition impregnated into the glass cloth. The insulating reliability of the printed circuit board of the present embodiment is further improved, and the yield of the final product is increased. In addition, since the dielectric properties and the moisture absorption resistance are excellent, the effect of a small variation in the dielectric constant due to the influence of the use environment, particularly a high humidity environment, can also be exerted.

[0135] Example

[0136] Hereinafter, the present application will be described more specifically using examples and comparative examples. The present application is not at all limited to the following examples.

[0137] [Physical properties of glass cloth]

[0138] The physical properties of the glass cloth, specifically, the thickness of the glass cloth, the diameter of the filaments constituting the warp and weft yarns, the number of filaments, and the insertion density (weave density) of the warp and weft yarns were measured in accordance with JIS R3420.

[0139] [Young's modulus]

[0140] The Young's modulus of the glass yarn was measured using a glass block obtained by melting and cooling the glass yarn as a test piece, using a pulse echo overlap method.

[0141] [Coating amount of silane coupling agent]

[0142] (Drying loss A)

[0143] The glass cloth obtained in the examples and comparative examples was put into a drier at 110°C and dried for 60 minutes. After drying, the glass cloth was transferred to a desiccator and left for 20 minutes, and naturally cooled to room temperature. After natural cooling, the glass cloth was weighed in units of 0.1 mg or less.

[0144] Next, after heat treatment of the glass cloth at 600°C for 20 minutes, the glass cloth was transferred to a desiccator and left for 20 minutes, and naturally cooled to room temperature. After natural cooling, the glass cloth was weighed in units of 0.1 mg or less.

[0145] The difference (g) between the mass of the glass cloth before heat treatment at 600°C and the mass of the glass cloth after heat treatment at 600°C was divided by the mass (g) of the glass cloth used for the measurement, and the value obtained was taken as the loss on drying A (% by mass).

[0146] (Loss on drying B)

[0147] Next, using the glass cloth after the loss on drying A was determined, the loss on drying was determined by the same method as that used to determine the loss on drying A described above, and taken as the loss on drying B (%).

[0148] (Silane coupling agent coating amount)

[0149] The difference between the loss on drying B and the loss on drying A determined as described above was taken as the silane coupling agent coating amount, as shown in the following formula.

[0150] Silane coupling agent coating amount (% by mass) = Loss on drying A (% by mass) - Loss on drying B (% by mass) (Resin impregnation evaluation number of non-impregnated sites A)

[0151] From the periphery of one end in the length direction of the glass cloth, the periphery of the opposite end, and the middle portion that equally divides the length direction, a total of 5 pieces of the impregnation evaluation test sample were taken, and from each of the impregnation evaluation samples, an impregnation evaluation test piece for evaluating the number of non-impregnated sites A was prepared. Next, the glass cloth test piece was immersed in the impregnation evaluation test liquid, light from an LED lamp was irradiated from the side, and the impregnation of the impregnation evaluation varnish into the glass cloth was observed using a microscope equipped with a high-precision camera, and the number of non-impregnated sites of 160 μm or more in length after 3 minutes of immersion of the glass cloth test piece in the impregnation evaluation test liquid (non-impregnated sites of the impregnation evaluation varnish) was counted (shown in the table as "number of voids"). At this time, the field of view of the glass cloth observed using the microscope was set to about 32 mm in the warp direction and about 32 mm in the weft direction.

[0152] The average of the number of non-impregnated sites of the 5 pieces of the impregnation evaluation test piece was taken as the number of non-impregnated sites A. In addition, the standard deviation of the number of non-impregnated sites of the 5 pieces of the impregnation evaluation test piece was also determined.

[0153] The test solution for the impregnation evaluation was a solution of a bisphenol A type epoxy resin (product name "EPICLON") in benzyl alcohol having a viscosity of 230 mPa-s, a solution of a bisphenol A type epoxy resin (product name "EPICLON") in benzyl alcohol having a viscosity of 680 mPa-s, and castor oil having a viscosity of 650 mPa-s, respectively.

[0154] 〔Number of unimpregnated sites B〕

[0155] From the five impregnation evaluation test samples taken at the time of evaluation of the number of unimpregnated sites A, five impregnation evaluation test pieces B for evaluation of the number of unimpregnated sites B were prepared. Test pieces (40 mm in the weft direction x 250 mm in the warp direction) were taken from the impregnation evaluation test samples. The 50 mm at both ends in the length direction were used as holding portions, and a tensile load was applied to the sample of 40 mm in the weft direction x 150 mm in the warp direction. A tensile load of 10 N / 25 mm was applied in the warp direction in accordance with the method described in item 7.4 Tensile strength in the Glass Test General Test Method of JIS R3420. The tensile speed was set to about 5 mm / min. Next, the glass cloth test piece was dipped in the impregnation evaluation test solution used at the time of evaluation of the number of unimpregnated sites 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 light from the side with an LED lamp, and the number of unimpregnated sites having a length of 160 μm or more after 3 minutes from the dipping of the glass cloth test piece in the impregnation evaluation test solution was counted (unimpregnated sites of the impregnation evaluation varnish). At this time, the field of view of the glass cloth observed using the microscope was set to about 32 mm in the warp direction and about 32 mm in the weft direction.

[0156] The average of the number of unimpregnated sites of the five impregnation evaluation test pieces was taken as the number of unimpregnated sites B. In addition, the standard deviation of the number of unimpregnated sites of the five impregnation evaluation test pieces was also calculated.

[0157] 〔Pile evaluation〕

[0158] From the five impregnation evaluation test samples taken at the time of evaluation of the number of unimpregnated sites A, five samples for pile evaluation having a width of 1285 mm x a length of 1000 mm were prepared. The samples for pile evaluation were spread on a test plate, and visual inspection was performed, and the pile quality was evaluated in accordance with the following evaluation criteria. The piles detected in the visual inspection were observed using a microscope, and the lengths of the piles protruding from the surface of the glass cloth of 0.5 mm or more, 1 mm or more, and 2 mm or more were evaluated.

[0159] ◎: None of the five samples for pile evaluation had a pile defect.

[0160] O: 4 pieces had no fluff defects.

[0161] X: 3 or more pieces had fluff defects.

[0162] [Insulation reliability evaluation]

[0163] From the 5 pieces of the impregnation evaluation test sample taken at each site of the rolled glass cloth taken for the evaluation of the number of non-impregnated sites A, 2 pieces each of the glass cloth sample for insulation reliability evaluation (total 10 pieces) were cut. A low dielectric resin varnish containing SA9000 (manufactured by SABIC Innovative Plastics) 50 parts by weight, TAIC (manufactured by Nippon Shokubai) 25 parts by weight, Perbutyl P (manufactured by Nippon Oil and Fats) 0.4 parts by weight, thermoplastic resin SEB-SH1053 (manufactured by Asahi Kasei) 10 parts by weight, flame retardant SAYTEX 8010 (manufactured by Albemarle) 30 parts by weight, spherical silica (manufactured by Longson) 70 parts by weight, and toluene 200 parts by weight was impregnated into the glass cloth for insulation reliability evaluation, and dried at 160°C for 2 minutes to obtain a prepreg with a resin content of 60%. The prepreg was overlapped by a prescribed number of pieces, and further, a copper foil with a thickness of 12 μm was overlapped on the top and bottom, and heated and pressed at 195°C, 40 kg / cm 2 The change in resistance value was measured. At this time, the case where the resistance became less than 1 MΩ within 1000 hours after the start of the test was counted as insulation failure. The same measurement was performed for 10 pieces of the test sample, and the proportion of samples in which no insulation failure occurred among the 10 pieces was calculated.

[0164] [Comparative Example 1]

[0165] A glass yarn (filament diameter 5.1 μm, number of filaments 200, modulus of elasticity 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 for the warp and weft, and a glass cloth base fabric was obtained using an air jet loom with a warp density of 52.5 threads / 25 mm and a weft density of 52.5 threads / 25 mm.

[0166] The glass cloth was subjected to a degumming treatment by heating a glass cloth green sheet, and then, surface treatment was performed using a treatment liquid obtained by dispersing methylacryloxypropyltrimethoxysilane (Dow Corning Toray Co., Ltd.; Z6030) in water. The glass cloth after surface treatment was subjected to high-pressure water opening by spraying using a spray with a water pressure adjusted to 8.0 ± 0.1 kg / cm 2 Under conditions where the initial tension was 450 N and the final take-up tension was 150 N, the glass cloth was taken up to a take-up core tube with a diameter of 240 mm, and a glass cloth with a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m was produced. The glass cloth had a mass loss on ignition of 0.62% and a silane coupling agent coating amount of 0.21 mass%. Note that the maximum line tension during conveyance of the glass cloth after surface treatment was 150 N.

[0167] The evaluation results of the obtained glass cloth are shown in Table 1.

[0168] [Comparative Example 2]

[0169] The opening strength was increased by increasing the water pressure of the high-pressure water spray in the opening treatment to 18.0 ± 0.1 kg / cm 2 and otherwise 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 glass cloth had a mass loss on ignition of 0.56% and a silane coupling agent coating amount of 0.15 mass%. The evaluation results of the obtained glass cloth are shown in Table 1. The fluff quality evaluation of Comparative Example 2 was "X", and therefore, the insulation reliability was not evaluated.

[0170] [Example 1]

[0171] After surface treatment, the glass cloth was subjected to processing in which a tension of 500 N was applied in the MD direction, and otherwise 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 glass cloth had a mass loss on ignition of 0.61% and a silane coupling agent coating amount of 0.20 mass%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0172] [Comparative Example 2B]

[0173] After surface treatment, the glass cloth was subjected to processing in which a tension of 450 N was applied in the MD direction, and otherwise 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 glass cloth had a mass loss on ignition of 0.61% and a silane coupling agent coating amount of 0.20 mass%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0174] [Example 2A]

[0175] After the surface treatment, instead of performing high-pressure water opening, dry ice particles having a particle size of 5 to 50 μm were sprayed at a gas pressure of 0.4 MPa to perform opening processing, and otherwise, the same operation as in Comparative Example 1 was performed to produce a glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on ignition of 0.61% and a silane coupling agent coating amount of 0.20%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0176] [Example 2B]

[0177] After the surface treatment, instead of performing high-pressure water opening, a water dispersion liquid of nylon particles having a particle size of about 600 μm was sprayed at a gas pressure of 0.1 MPa to perform opening processing, and otherwise, the same operation as in Comparative Example 1 was performed to produce a glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on ignition of 0.61% and a silane coupling agent coating amount of 0.21%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0178] [Comparative Example 7]

[0179] The dispersion concentration of the silane coupling agent in water was set to 1 / 3 of that in Comparative Example 1, and otherwise, the same operation as in Comparative Example 1 was performed to produce a glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on ignition of 0.46% and a silane coupling agent coating amount of 0.07%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0180] [Comparative Example 3]

[0181] After the surface treatment, instead of performing high-pressure water opening, a water dispersion liquid of nylon particles having a particle size of about 600 μm was sprayed at a gas pressure of 0.1 MPa to perform opening processing, and otherwise, the same operation as in Comparative Example 1 was performed to produce a glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on ignition of 0.61% and a silane coupling agent coating amount of 0.21%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0182] [Comparative Example 3B]

[0183] After the surface treatment, bending processing was performed by passing over a roll having a curvature radius of 3 mm at a wrap angle of 180° for 10 times, and otherwise, the same operation as in Comparative Example 1 was performed to produce a glass cloth having a thickness of 46 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on ignition of 0.62% and a silane coupling agent coating amount of 0.21%. The evaluation results of the obtained glass cloth are shown in Table 1.

[0184] [Comparative Example 4]

[0185] A 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 a glass yarn (filament diameter: 5.1 μm, number of filaments: 200, modulus of elasticity: 56 GPa, glass composition: 49.8 mass% in terms of Si02, 16.8 mass% in terms of Al203, 3.1 mass% in terms of CaO, 0.1 mass% in terms of MgO, 23.9 mass% in terms of B203, and 4.0 mass% in terms of P205) was used, and that a surface treatment was performed using a treatment liquid obtained by dispersing methylacryloxypropyltrimethoxysilane (Dow Corning Toray Co., Ltd.; Z6030) in water. The evaluation results of the glass cloth thus obtained are shown in Table 2.

[0186] [Example 3]

[0187] A 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 4, except that a surface treatment was performed on the glass cloth after the surface treatment, by applying a tension of 500 N in the MD direction. The evaluation results of the glass cloth thus obtained are shown in Table 2.

[0188] [Comparative Example 5]

[0189] A glass cloth having a warp yarn density of 65 ends / 25 mm and a weft yarn density of 67 ends / 25 mm was obtained using an air jet loom, with a glass yarn (filament diameter: 5.1 μm, number of filaments: 100, modulus of elasticity: 61 GPa, glass composition: 51.2 mass% in terms of Si02, 14.3 mass% in terms of Al203, 8.1 mass% in terms of CaO, 0.3 mass% in terms of MgO, 23.3 mass% in terms of B203, and 0.1 mass% in terms of P205) used for both the warp yarn and the weft yarn.

[0190] A degumming treatment was performed by heating the glass cloth, and then a surface treatment was performed using a treatment liquid obtained by dispersing methylacryloxypropyltrimethoxysilane (Dow Corning Toray Co., Ltd.; Z6030) in water. The glass cloth after the surface treatment was subjected to high-pressure water opening using a spray with a water pressure adjusted to 5.0 ± 0.1 kg / cm 2 A glass cloth having a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m was produced in the same manner as in Example 1, except that the glass cloth after the surface treatment was wound onto a winding core tube having a diameter of 240 mm under conditions in which the initial tension was 450 N and the final take-up tension was 150 N. The evaluation results of the glass cloth thus obtained are shown in Table 3. Note that the maximum line tension during the handling of the glass cloth after the surface treatment was 150 N.

[0191] [Example 4]

[0192] After the surface treatment, the glass cloth was subjected to processing to apply a tension of 500 N in the MD direction, and otherwise the same operation as in Comparative Example 5 was performed to produce a glass cloth having a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on strong heating of 0.68% and a silane coupling agent coating amount of 0.23%. The evaluation results of the obtained glass cloth are shown in Table 3.

[0193] [Comparative Example 6]

[0194] A glass yarn (filament diameter: 7.1 μm, number of filaments: 200, modulus of elasticity: 61 GPa, glass composition: 51.2% by mass of Si02, 14.3% by mass of Al203, 8.1% by mass of CaO, 0.3% by mass of MgO, 23.3% by mass of B203, and 0.1% by mass of P205) was used for the warp and weft, and an air jet loom was used to obtain a glass cloth base fabric having a warp density of 60 threads / 25 mm and a weft density of 57 threads / 25 mm.

[0195] Degumming treatment was performed by heating the glass cloth base fabric, and then surface treatment was performed using a treatment liquid obtained by dispersing methacryloxypropyltrimethoxysilane (Dow Corning Toray Co., Ltd.; Z6030) in water. The glass cloth after the surface treatment was subjected to high-pressure water opening using a spray with a water pressure adjusted to 10.0 ± 0.1 kg / cm 2 The glass cloth was wound onto a winding core tube having a diameter of 240 mm under conditions in which the initial tension was 450 N and the final take-up tension was 150 N to produce a glass cloth having a thickness of 90 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on strong heating of 0.39% and a silane coupling agent coating amount of 0.16%. Note that the maximum thread tension during the handling of the glass cloth after the surface treatment was 150 N. The evaluation results of the obtained glass cloth are shown in Table 4.

[0196] [Example 5]

[0197] After the surface treatment, the glass cloth was subjected to processing to apply a tension of 500 N in the MD direction, and otherwise the same operation as in Comparative Example 6 was performed to produce a glass cloth having a thickness of 29 μm, a width of 1285 mm, and a length of 2,000 m. The glass cloth had a mass loss on strong heating of 0.39% and a silane coupling agent coating amount of 0.16%. The evaluation results of the obtained glass cloth are shown in Table 4.

[0198] [Table 1]

[0199]

[0200] [table 2]

[0201]

[0202] [table 3]

[0203]

[0204] [table 4]

[0205]

Claims

1. A glass cloth which is woven with a glass yarn formed of a plurality of glass filaments as warp and weft, and is surface-treated with a surface treatment agent, wherein the number of non-impregnated sites Aα when the glass cloth is dipped in a benzyl alcohol solution having a viscosity of 230 mPa-s and containing a bisphenol A type epoxy resin, i.e., impregnation evaluation test liquid α, for 3 minutes is 1.50 times or less of the number of non-impregnated sites Bα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction, wherein the elastic modulus of the glass cloth is 50 GPa or more and 70 GPa or less.

2. The glass cloth according to claim 1, wherein the number of non-impregnated sites Aα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes is 0.80 times or more and 1.40 times or less of the number of non-impregnated sites Bα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction.

3. The glass cloth according to claim 1, wherein the number of non-impregnated sites Aα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes is 0.80 times or more and 1.30 times or less of the number of non-impregnated sites Bα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction.

2. The glass cloth of claim 1, wherein, 4. The glass cloth according to claim 1, wherein the number of non-impregnated sites Aα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes is 0.80 times or more and 1.20 times or less of the number of non-impregnated sites Bα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction.

3. The glass cloth of claim 1, wherein, 5. The glass cloth according to claim 1, wherein the number of non-impregnated sites Aα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes is 0.90 times or more and 1.10 times or less of the number of non-impregnated sites Bα when the glass cloth is dipped in the impregnation evaluation test liquid α for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction.

4. The glass cloth of claim 1, wherein, 6. The glass cloth according to claim 1, wherein the number of non-impregnated sites Aβ when the glass cloth is dipped in a benzyl alcohol solution having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin, i.e., impregnation evaluation test liquid β, for 3 minutes is 1.5 times or less of the number of non-impregnated sites Bβ when the glass cloth is dipped in the impregnation evaluation test liquid β for 3 minutes after a load of 10 N per 25 mm width is applied to the warp direction.

5. The glass cloth of claim 1, wherein, ​ 6. The glass cloth of claim 1, wherein, ​ 7. The glass cloth of claim 1, wherein, The number of unimpregnated sites Aβ when the glass cloth is impregnated in a benzyl alcohol solution having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin, that is, an impregnation evaluation test liquid β, for 3 minutes is 0.8 times or more and 1.4 times or less of the number of unimpregnated sites Bβ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid β for 3 minutes.

8. The glass cloth of claim 1, wherein, The number of unimpregnated sites Aβ when the glass cloth is impregnated in a benzyl alcohol solution having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin, that is, an impregnation evaluation test liquid β, for 3 minutes is 0.8 times or more and 1.3 times or less of the number of unimpregnated sites Bβ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid β for 3 minutes.

9. The glass cloth of claim 1, wherein, The number of unimpregnated sites Aβ when the glass cloth is impregnated in a benzyl alcohol solution having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin, that is, an impregnation evaluation test liquid β, for 3 minutes is 0.8 times or more and 1.2 times or less of the number of unimpregnated sites Bβ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid β for 3 minutes.

10. The glass cloth of claim 1, wherein, The number of unimpregnated sites Aβ when the glass cloth is impregnated in a benzyl alcohol solution having a viscosity of 680 mPa-s and containing a bisphenol A type epoxy resin, that is, an impregnation evaluation test liquid β, for 3 minutes is 0.9 times or more and 1.1 times or less of the number of unimpregnated sites Bβ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid β for 3 minutes.

11. The glass cloth according to any one of claims 1 to 10, wherein, The number of unimpregnated sites Aγ when the glass cloth is impregnated in castor oil having a viscosity of 650 mPa-s, that is, an impregnation evaluation test liquid γ, for 3 minutes is 1.5 times or less of the number of unimpregnated sites Bγ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid γ for 3 minutes.

12. The glass cloth of claim 11, wherein, The number of unimpregnated sites Aγ when the glass cloth is impregnated in castor oil having a viscosity of 650 mPa-s, that is, an impregnation evaluation test liquid γ, for 3 minutes is 0.8 times or more and 1.4 times or less of the number of unimpregnated sites Bγ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid γ for 3 minutes.

13. The glass cloth of claim 11, wherein, The number of unimpregnated sites Aγ when the glass cloth is impregnated in castor oil having a viscosity of 650 mPa-s, that is, an impregnation evaluation test liquid γ, for 3 minutes is 0.8 times or more and 1.3 times or less of the number of unimpregnated sites Bγ when a load of 10 N per 25 mm width is applied to the warp yarn direction of the glass cloth and then the glass cloth is impregnated in the impregnation evaluation test liquid γ for 3 minutes.

14. The glass cloth of claim 11, wherein, The number of unimpregnated portions Aγ when the glass cloth is impregnated in castor oil, that is, test liquid for impregnation evaluation γ having a viscosity of 650 mPa-s for 3 minutes is 0.8 times or more and 1.2 times or less of the number of unimpregnated portions Bγ when a load of 10 N per 25 mm width is applied to the warp direction of the glass cloth and then the glass cloth is impregnated in the test liquid for impregnation evaluation γ for 3 minutes.

15. The glass cloth of claim 11, wherein, The number of unimpregnated portions Aγ when the glass cloth is impregnated in castor oil, that is, test liquid for impregnation evaluation γ having a viscosity of 650 mPa-s for 3 minutes is 0.9 times or more and 1.1 times or less of the number of unimpregnated portions Bγ when a load of 10 N per 25 mm width is applied to the warp direction of the glass cloth and then the glass cloth is impregnated in the test liquid for impregnation evaluation γ for 3 minutes.

16. The glass cloth according to any one of claims 1 to 10, wherein, The number of villi having a length of 2 mm or more is 10 / m 2 one or less.

17. The glass cloth according to any one of claims 1 to 10, wherein, The number of villi having a length of 1 mm or more is 10 / m 2 one or less.

18. The glass cloth according to any one of claims 1 to 10, wherein, The number of villi having a length of 0.5 mm or more is 10 / m 2 one or less.

19. The glass cloth according to any one of claims 1 to 10, wherein, The number of villi having a length of 0.5 mm or more is 3 / m 2 one or less.

20. The glass cloth according to any one of claims 1 to 10, having a thickness of 5 to 100 μm.

21. The glass cloth according to any one of claims 1 to 10, having an average filament diameter of 3.0 μm or more and 8 μm or less.

22. The glass cloth according to any one of claims 1 to 10, having an average filament diameter of 3.5 μm or more and 7.5 μm or less.

23. The glass cloth according to any one of claims 1 to 10, having an average number of filaments of 80 or more.

24. The glass cloth according to any one of claims 1 to 10, wherein, The elastic modulus is 50 GPa or more and 63 GPa or less.

25. The glass cloth according to any one of claims 1 to 10, wherein, The elastic modulus is 53 GPa or more and 63 GPa or less.

26. The glass cloth according to any one of claims 1 to 10, wherein, The glass cloth has a mass loss on heating value of 0.5% or more and 2.0% or less, which is calculated by the following formula (i) and the following formula (iv), 5.0 x F -1.6 ) Formula (i) 18 x F -1.6 ) Formula (iv) In formula (i), formula (vi), F is a value in μm of the filament diameter of the glass yarn.

27. The glass cloth according to any one of claims 1 to 10, wherein, The glass yarn has a boron (B) content of 15.0 to 40.0 mass% in terms of B2O3.

28. A prepreg having the glass cloth according to any one of claims 1 to 27 and a matrix resin composition impregnated in the glass cloth.

29. A printed circuit board having the glass cloth according to any one of claims 1 to 27 and a cured product of a matrix resin composition impregnated in the glass cloth.

Images