Glass cloth, prepreg, printed wiring board, etc.

Abstract

The present disclosure relates to a glass cloth having a glass yarn as a warp yarn and a weft yarn. The number of twists of the weft yarn is 0.40-1.80 times / 25 mm or -1.80-0.40 times / 25 mm, an absolute value difference in the number of twists of the warp yarn and the weft yarn is 0.01-0.70 times / 25 mm, and the amount of bowed filling of the weft yarn is at most 35 mm.

Description

Glass cloth, prepreg, printed wiring boards, etc.

[0001] The present invention relates to a glass cloth, a prepreg, a printed wiring board, and the like.

[0002] Currently, the performance of information terminals such as smartphones is improving, and high-speed communications, typified by 5G communications, are advancing. Accordingly, printed wiring boards for high-speed communications are being required to have lower dielectric constants and lower dielectric loss tangents for the insulating materials used to reduce transmission loss, as well as higher levels of insulation reliability than ever before.

[0003] Known insulating materials for printed wiring boards for high-speed communication include, for example, prepregs and laminates using resin compositions containing terminal-modified polyphenylene ether, etc. Specifically, a prepreg obtained by impregnating a glass cloth with a low-dielectric thermosetting resin containing terminal-modified polyphenylene ether, etc. (hereinafter collectively referred to as "matrix resin") and drying the prepreg, and a laminate obtained using the prepreg are known (Patent Documents 1 and 2).

[0004] Here, Patent Document 3 describes the production of a quartz glass cloth from a glass yarn made of 20 to 400 quartz glass filaments having an average filament diameter of 3 to 20 μm and a standard deviation of diameter of 0.15 or less. Regarding the quartz glass cloth, Patent Document 3 reports that even greater smoothness (surface smoothness of the glass cloth) can be obtained by reducing the number of twists of the glass yarns constituting the glass cloth or by using non-twisted yarns.

[0005] International Publication No. 2019 / 065940 International Publication No. 2019 / 065941 Japanese Patent Application Laid-Open No. 2016-11484

[0006] However, Patent Document 3 leaves room for improvement in terms of ensuring the quality of the appearance of the glass cloth. In particular, when a glass cloth is produced using glass yarns with a small number of twists or no twist, as in Patent Document 3, the concentration of the glass yarns is likely to be poor, and therefore the amount of weft bending of the glass cloth is likely to be excessive. In this case, the glass cloth is likely to meander during transport, and as a result, the glass cloth is likely to wrinkle, making it difficult to ensure the quality of the appearance of the glass cloth.

[0007] Therefore, an object of the present invention is to provide a glass cloth that has excellent smoothness and can ensure excellent appearance quality even when glass yarns (weft yarns) with a small twist number are used. Another object of the present invention is to provide a prepreg obtained using the glass cloth, and to provide a printed wiring board, an integrated circuit, and an electronic device obtained using the prepreg.

[0008] One aspect of the present invention is as follows. [1] A glass cloth having glass yarns as warp and weft yarns, wherein the number of twists of the weft yarn is 0.40 to 1.80 turns / 25 mm or -1.80 to -0.40 turns / 25 mm, the absolute value difference in the number of twists of the warp and weft yarns is 0.01 to 0.70 turns / 25 mm, and the amount of weft bending is 35 mm or less. [2] The glass cloth according to item 1, wherein the silicon (Si) content in the glass yarns is 95.0 to 100 mass% in terms of silicon dioxide (SiO2). [3] The glass cloth according to item 1 or 2, wherein the silicon (Si) content in the glass yarns is 99.0 to 100 mass% in terms of silicon dioxide (SiO2). [4] The glass cloth according to any one of items 1 to 3, wherein the number of twists of the warp yarns is 0.40 to 1.80 times / 25 mm or -1.80 to -0.40 times / 25 mm. [5] The glass cloth according to any one of items 1 to 4, wherein the glass yarns are treated with a surface treatment agent containing a silane coupling agent. [6] The surface treatment agent is a compound represented by the following formula (1): X(R) 3-n SiY n...(1) (wherein X is an organic functional group having at least one of an amino group and an unsaturated double bond group having radical reactivity, each Y is independently an alkoxy group, n is an integer of 1 to 3, and each R is independently a group selected from the group consisting of functional groups composed of hydrocarbon groups having 1 to 10 carbon atoms). [7] The glass cloth according to item 6, wherein X in the formula is an organic functional group that does not form a salt with an ionic compound. [8] The glass cloth according to item 6 or 7, wherein X in the formula does not contain an amine or an ammonium cation. [9] The glass cloth according to any one of items 6 to 8, wherein X in the formula is an organic functional group having at least one methacryloxy group and at least one acryloxy group.

[10] The glass cloth according to any one of items 6 to 9, wherein R in the formula is a group selected from the group consisting of a methyl group, an ethyl group, and a phenyl group.

[11] The glass cloth according to any one of items 1 to 10, wherein the TEX of the warp and weft yarns is 0.5 to 40 g / 1000 m.

[12] The glass cloth according to any one of items 1 to 11, wherein the bulk dielectric loss tangent at 10 GHz of the glass constituting the glass yarns is in the range of 0.001 or less.

[13] The glass cloth according to any one of items 1 to 12, which is for a printed wiring board.

[14] A prepreg containing the glass cloth according to any one of items 1 to 12, a thermosetting resin, and an inorganic filler.

[15] A printed wiring board comprising the prepreg according to item 14.

[16] An integrated circuit comprising the printed wiring board according to item 15.

[17] An electronic device comprising the printed wiring board according to item 15.

[0009] The present invention aims to provide a glass cloth that has excellent smoothness and can ensure excellent appearance quality even when glass yarns with a small number of twists are used. The present invention also provides a prepreg obtained by using the glass cloth, and a printed wiring board, an integrated circuit, and an electronic device obtained by using the prepreg.

[0010] The present invention is not limited to the present embodiment, but can be practiced in various modifications within the scope of the present invention.

[0011] In this specification, the upper or lower limit of a numerical range described in stages may be replaced with the upper or lower limit of a corresponding numerical range described in another stage, and may also be replaced with the corresponding value described in the Examples. Furthermore, in this specification, the term "step" is included not only in cases where the step is an independent step, but also in cases where the step cannot be clearly distinguished from other steps, as long as the function of the step is achieved. Furthermore, in this specification, various productions, measurements, etc. are performed based on the methods described in the Examples, unless otherwise specified.

[0012] [Embodiment 1] <Glass Cloth> This embodiment is a glass cloth having glass yarns as warp and weft, wherein the twist number of the weft is 0.40 to 1.80 turns / 25 mm or -1.80 to -0.40 turns / 25 mm, the absolute value difference between the twist numbers of the warp and weft is 0.01 to 0.70 turns / 25 mm, and the amount of weft bending is 25 mm or less. This glass cloth can provide a glass cloth that has excellent smoothness and can ensure excellent appearance quality even when glass yarns with a low twist number are used.

[0013] The glass cloth may be produced in a long shape having a longitudinal direction (in one embodiment, the MD direction) and a transverse direction (in one embodiment, the TD direction). In one embodiment, the warp yarns are held under tension on a loom, and the weft yarns are woven so that they pass above and below the warp yarns, thereby forming a glass cloth having a plain weave structure. According to this embodiment, a glass yarn having a low twist number is used as the weft yarn woven with the warp yarns. Using a weft yarn having a low twist number is advantageous from the viewpoint of suppressing thickness unevenness (thickness variation coefficient) in the obtained glass cloth, that is, from the viewpoint of realizing a glass cloth with high smoothness. In this regard, the inventors have focused on actively ensuring the absolute value difference in the twist number between the warp yarn and the weft yarn. In this embodiment, by actively ensuring the absolute value difference in the twist number between the warp yarn and the weft yarn while using a glass yarn (weft yarn) having a low twist number, it is possible to control the amount of weft bending within a small range, and in this case, it is possible to suppress meandering of the glass cloth during production, transportation, etc. of the glass cloth.

[0014] In the present embodiment, meandering of the glass cloth can be suppressed during production or transportation of the glass cloth, and therefore, wrinkles are less likely to occur in the glass cloth, and as a result, appearance quality can be easily ensured. That is, the present embodiment provides a glass cloth whose appearance quality is less likely to deteriorate with various processes such as handling, storage, and transportation, in other words, a glass cloth whose appearance quality is less likely to deteriorate with time.

[0015] The glass cloth of this embodiment is suitable as a component of the base material of a printed wiring board. By using the glass cloth of this embodiment, a highly reliable printed wiring board can be easily realized.

[0016] Twist Number of Glass Yarns In this embodiment, the twist number of the weft yarn is 0.40 to 1.80 turns / 25 mm or -1.80 to -0.40 turns / 25 mm. If the twist number of the weft yarn is 0.40 turns / 25 mm or more or -0.40 turns / 25 mm or less, a sufficient twist number of the weft yarn can be ensured, thereby suppressing yarn breakage during the warping process and preventing fluffing of the glass cloth. If the twist number of the weft yarn is 1.80 turns / 25 mm or less or -1.80 turns / 25 mm or more, thickness unevenness of the resulting glass cloth can be suppressed, and in this case, variation in dimensional change in the warp and weft directions when a printed wiring board is produced can be suppressed. Furthermore, according to this embodiment, even when using such a weft yarn with a low twist number, a glass cloth can be provided that has excellent smoothness and ensures excellent appearance quality.

[0017] In this embodiment, it is preferable that the twist number of not only the weft yarns but also the warp yarns is 0.40 to 1.80 turns / 25 mm or −1.80 to −0.40 turns / 25 mm, which makes it easier to achieve the effects of this embodiment.

[0018] The twist of the glass yarn is classified as either the z-direction or the s-direction depending on the direction of the twist. In this embodiment, the twist in the z-direction is defined as "positive" and the twist in the s-direction as "negative." For example, in this specification, a "1.00z twist number" is expressed as a twist number of 1.00, and a "1.00s twist number" is expressed as a twist number of -1.00.

[0019] The twist number of the glass yarn can be adjusted, for example, in the process of twisting the glass yarn (twisting process). In one embodiment, bundling the glass filaments makes it easier to increase the twist number of the glass yarn. Increasing the twist number of the glass yarn makes it easier to suppress the generation of fluff due to breakage of the glass filaments and to suppress yarn breakage during the warping process of the glass cloth. On the other hand, the twist of the glass yarn tends to hinder the glass yarn from expanding in width and tends to cause thickness unevenness of the glass cloth at the twisted portion. Therefore, finding an appropriate twist number and using glass yarn adjusted to such twist number is advantageous in producing a high-quality glass cloth.

[0020] The number of twists of the weft yarn is preferably 0.40 to 1.50 turns / 25 mm or -1.50 to -0.40 turns / 25 mm, more preferably 0.50 to 1.30 turns / 25 mm or -1.30 to -0.50 turns / 25 mm, even more preferably 0.50 to 1.10 turns / 25 mm or -1.10 to -0.50 turns / 25 mm, still more preferably 0.60 to 1.00 turns / 25 mm or -1.00 to -0.60 turns / 25 mm, and particularly preferably 0.60 to 0.90 turns / 25 mm or -0.90 to -0.60 turns / 25 mm. The number of twists of the warp yarns is preferably 0.50 to 1.70 turns / 25 mm or -1.70 to -0.50 turns / 25 mm, more preferably 0.60 to 1.60 turns / 25 mm or -1.60 to -0.60 turns / 25 mm, even more preferably 0.60 to 1.40 turns / 25 mm or -1.40 to -0.60 turns / 25 mm, still more preferably 0.70 to 1.30 turns / 25 mm or -1.30 to -0.70 turns / 25 mm, and particularly preferably 0.80 to 1.10 turns / 25 mm or -1.10 to -0.80 turns / 25 mm. From the viewpoint of excellent productivity of the glass cloth, it is preferable that the number of twists of the weft yarns is smaller than the number of twists of the warp yarns.

[0021] Absolute Value Difference in the Number of Twists of Warp and Weft Yarns In the present embodiment, the absolute value difference in the number of twists of warp and weft yarns is 0.01 to 0.70 turns / 25 mm. If the absolute value difference is 0.01 turns / 25 mm or more, thickness unevenness of the glass cloth can be suppressed, in which case the smoothness of the glass cloth can be improved and the glass yarns can be easily opened during the production of the glass cloth. On the other hand, if the absolute value difference is 0.7 turns / 25 mm or less, even when a weft yarn with a small number of twists is used, it is easy to suppress the generation of fluff in the obtained glass cloth. From the same viewpoint, the absolute value difference in the number of twists between the warp and weft yarns is preferably 0.05 turns / 25 mm or more, more preferably 0.08 turns / 25 mm or more, even more preferably 0.10 turns / 25 mm or more, even more preferably 0.13 turns / 25 mm or more, even more preferably 0.15 turns / 25 mm or more, even more preferably 0.08 turns / 25 mm or more, even more preferably 0.20 turns / 25 mm or more, and most preferably 0.30 turns / 25 mm or more. Also, it is preferably 0.65 turns / 25 mm or less, more preferably 0.60 turns / 25 mm or less, even more preferably 0.0.55 turns / 25 mm, even more preferably 0.13 to 0.52 turns / 25 mm, even more preferably 0.50 turns / 25 mm or less, and particularly preferably 0.45 turns / 25 mm.

[0022] Constructing a glass cloth using a weft yarn with a large twist number is one useful means for suppressing the generation of fuzz in the glass cloth, but in this case, excellent smoothness of the glass cloth cannot be achieved. Here, the present inventors have focused on actively ensuring the absolute difference in the twist number between the warp yarn and the weft yarn of the glass cloth. The greater the absolute difference in the twist number between the warp yarn and the weft yarn of the glass cloth, the greater the amount of weft bending. If the amount of weft bending is large, the glass cloth is likely to meander during transportation in the process of processing the obtained glass cloth into a prepreg, and as a result, the prepreg yield is likely to decrease. In response to this, the present inventors have discovered that in the warp warping process, tapered control of the yarn tension is performed, in which the yarn tension at the center of the yarn is used as a reference and the yarn tension is increased toward both ends.

[0023] In this embodiment, by controlling the taper of the yarn tension in a preferred manner, it is easy to reduce the amount of weft bending even if the absolute difference in the number of twists between the warp and weft yarns is large. In this case, it is easy to simultaneously suppress the generation of fluff and reduce thickness unevenness in the glass cloth, and it is also easy to suppress meandering of the glass cloth during transportation and improve the yield of prepreg.

[0024] The absolute value difference between the twist numbers of the warp and weft yarns is derived, for example, by calculating the difference between the absolute value of the twist number of the warp yarn and the absolute value of the twist number of the weft yarn and then determining the absolute value of that difference.

[0025] Amount of weft bending In this embodiment, the amount of weft bending is 35 mm or less. If the amount of weft bending is 35 mm or less, meandering of the glass cloth can be prevented during transport of the glass cloth. In this case, wrinkles are less likely to occur in the glass cloth, and in the resulting prepreg. From the same viewpoint, the amount of weft bending is preferably 30 mm or less, more preferably 25 mm or less, more preferably 20 mm or less, even more preferably 18 mm or less, and particularly preferably 16 mm or less, and 14 mm or less. The amount of weft bending may be 0 mm or more.

[0026] As described above, by controlling the taper of the yarn tension in a preferred manner, it is easy to reduce the amount of weft bending even if the absolute difference between the twist numbers of the warp and weft yarns is increased. In other words, it is possible to appropriately control the amount of weft bending by adjusting the twist numbers of the warp and weft yarns and the conditions for controlling the taper of the yarn tension.

[0027] Average Filament Diameter of Glass Yarn The average filament diameter of the glass filaments is preferably 2.5 to 9.0 μm, more preferably 2.5 to 7.5 μm, even more preferably 3.5 to 7.0 μm, still more preferably 3.5 to 6.0 μm, and particularly preferably 3.5 to 5.0 μm.

[0028] TEX of Glass Yarn The TEX of the glass yarn is preferably 0.5 to 40 g / 1000 m, more preferably 0.8 to 35 g / 1000 m, even more preferably 1.0 to 30 g / 1000 m, even more preferably 1.5 to 25 g / 1000 m, and particularly preferably 2.0 to 20 g / 1000 m. If the TEX is 0.5 g / 1000 m or more, breakage of the glass yarn and cutting of the glass cloth during the glass cloth manufacturing process are easily prevented. If the TEX is 40 g / 1000 m or less, it is easy to avoid the glass cloth from becoming too thick, and it is easy to obtain the effects of ensuring the absolute value difference in the twist numbers of the warp and weft yarns (for example, the effect of reducing thickness unevenness of the glass cloth).

[0029] Weave Density The weave density of the warp and weft threads is preferably 10 to 120 threads / 25 mm, more preferably 40 to 100 threads / 25 mm, and even more preferably 40 to 100 threads / 25 mm.

[0030] The thickness of the glass cloth is preferably 5 to 150 μm, more preferably 10 to 120 μm, even more preferably 15 to 100 μm, even more preferably 20 to 90 μm, and particularly preferably 30 to 70 μm. When the thickness of the glass cloth is within the above range, it becomes easier to obtain the effect of ensuring the absolute value difference in the number of twists of the warp and weft yarns (for example, the effect of reducing unevenness in the thickness of the glass cloth).

[0031] Coefficient of variation of thickness of glass cloth The coefficient of variation of thickness of the glass cloth is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, even more preferably 5% or less, and particularly preferably 3% or less. In one aspect, "glass cloth having excellent smoothness" means "glass cloth having a coefficient of variation of thickness of 10% or less." By using the glass cloth having a coefficient of variation of thickness within the above range, it is easy to realize a prepreg having excellent dimensional stability, and ultimately a printed wiring board having excellent dimensional stability. Weave structure Examples of the weave structure of the glass cloth include plain weave, sieve weave, satin weave, and twill weave. Among these, the plain weave structure is preferred as the weave structure of the glass cloth.

[0032] Glass Type Examples of glass types constituting the glass yarn include glass called E glass (alkali-free glass). Examples of glass types constituting the glass yarn include, for example, L glass, NE glass, D glass, L2 glass, T glass, silica glass, and quartz glass. From the viewpoint of achieving excellent dielectric properties, preferred examples of glass types constituting the glass yarn include L glass, L2 glass, silica glass, and quartz glass, with silica glass and quartz glass being more preferred. From the viewpoint of improving the dimensional stability of the resulting prepreg, preferred examples of glass types constituting the glass yarn include S glass, T glass, silica glass, and quartz glass, with silica glass and quartz glass being more preferred.

[0033] In glass cloth (silica glass cloth) made of silica glass and glass cloth (quartz glass cloth) made of quartz glass, the Si content of the glass yarns, calculated as SiO2, is preferably 95.0 to 100 mass%, more preferably 99.0 to 100 mass%, even more preferably 99.5 to 100 mass%, even more preferably 99.7 to 100 mass%, and particularly preferably 99.9 to 100 mass%. Glass yarns with an Si content of 95.0 mass% or more are prone to cause thickness unevenness in the glass cloth at the twisted portions of the glass yarns due to the high hardness of the glass itself. Therefore, when glass with an Si content of 95.0 mass% or more is used, it is easy to benefit from the effect of ensuring an absolute difference in the number of twists between the warp and weft yarns (e.g., the effect of reducing thickness unevenness in the glass cloth).

[0034] Bulk Dielectric Loss Tangent of Glass In the glass cloth of this embodiment, the bulk dielectric loss tangent at 10 GHz of the glass raw materials constituting the glass cloth is measured by a method using a split cylinder resonator (a method using a resonance method), specifically, by the method described in Examples. Here, the glass raw materials may be, for example, glass threads, glass filaments, glass seeds, etc.

[0035] The bulk dielectric loss tangent at 10 GHz is preferably 0.001 or less, more preferably 0.0008 or less, even more preferably 0.0006 or less, even more preferably 0.0004 or less, and particularly preferably 0.0003 or less, which makes it easier to achieve the effects of the present disclosure.

[0036] Silane Coupling Agent The glass yarns (including glass filaments) constituting the glass cloth are preferably surface-treated with a silane coupling agent. In one embodiment, the surface treatment agent for the glass yarns contains a silane coupling agent. Examples of the silane coupling agent include those represented by the following formula (1): X(R) 3-n SiY n ...(1) {wherein X is an organic functional group having at least one of an amino group and an unsaturated double bond group having radical reactivity, such as a carbon-carbon double bond having radical reactivity, each Y is independently an alkoxy group, n is an integer of 1 to 3, and R is a group selected from the group consisting of hydrocarbon groups having 1 to 10 carbon atoms.} In the above formula (1), R is preferably a group selected from the group consisting of a methyl group, an ethyl group, and a phenyl group.

[0037] In this embodiment, from the viewpoint of easily obtaining a glass cloth having excellent dielectric properties, X in formula (1) is preferably an organic functional group that does not form a salt with an ionic compound. Furthermore, from the viewpoint of excellent reactivity with the matrix resin, X in formula (1) is more preferably an organic functional group having one or more methacryloxy groups or acryloxy groups. Furthermore, from the viewpoint of good reactivity with the radically reactive matrix resin, X in formula (1) is preferably an amine such as a primary amine, a secondary amine, or a tertiary amine, and preferably does not contain an ammonium cation such as a quaternary ammonium cation.

[0038] Regarding Y in the above formula (1), the alkoxy group is preferably an alkoxy group having 1 to 5 carbon atoms (1, 2, 3, 4 or 5 carbon atoms) from the viewpoint of easily achieving stable treatment of the glass cloth.

[0039] As a surface treatment agent, the silane coupling agent represented by formula (1) may be used alone or in combination with two or more silane coupling agents having different X's in formula (1). Examples of the silane coupling agent represented by formula (1) include simple substances such as vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 5-hexenyltrimethoxysilane, as well as mixtures of these simple substances.

[0040] The molecular weight of the silane coupling agent is preferably 100 to 600, more preferably 150 to 500, and even more preferably 200 to 450. It is particularly preferable to use two or more silane coupling agents with different molecular weights. Treating the glass fiber surface with two or more silane coupling agents with different molecular weights tends to increase the density of the treatment agent on the glass surface, which in turn tends to further improve reactivity with the matrix resin.

[0041] From the viewpoint of not inhibiting reactivity with resin, the silane coupling agent is preferably nonionic. Among nonionic silane coupling agents, silane coupling agents having at least one group selected from the group consisting of vinyl groups, methacryloxy groups, and acryloxy groups are preferred, and silane coupling agents having at least one methacryloxy group or acryloxy group are particularly preferred. By not inhibiting reactivity with resin, the heat resistance and reliability of printed wiring boards can be improved.

[0042] In one embodiment, X in formula (1) is an organic functional group having at least one of the unsaturated double bond group and an amino group. Therefore, not only an embodiment in which X has both the unsaturated double bond group and the amino group, but also an embodiment in which X has the unsaturated double bond group but not the amino group, and an embodiment in which X does not have the unsaturated double bond group but has the amino group are all included in the scope of formula (1). However, X in formula (1) is preferably the unsaturated double bond group, and preferably does not contain an amino group.

[0043] <Method for manufacturing glass cloth> One aspect of this embodiment is a method for manufacturing the glass cloth. This method includes, for example, the following steps: a step of warping warp yarns to obtain a section beam of warp yarns (warping step), and a step of weaving a glass cloth using the section beam (weaving step), wherein the warping step performs taper control in which the yarn tension at the center of the yarn is used as a reference and is increased toward both ends.

[0044] The method for producing a glass cloth may include, after the warping step, a step of combining the obtained section beams to produce one loom beam (beaming step). This makes it possible to weave a glass cloth using the loom beam obtained in the beaming step, and in this case, it is easy to produce a glass cloth excellent in various properties.

[0045] The method for producing a glass cloth may further include a step of thermally deoiling the woven glass cloth (thermal deoiling step), which makes it easy to suitably reduce the dielectric loss tangent of the glass cloth.

[0046] The method for producing glass cloth may include a step of applying a treatment liquid containing a silane coupling agent to the glass cloth (coating step), and a step of drying the treatment liquid and fixing the silane coupling agent to the surface of the glass filaments (drying step), which facilitates the surface treatment of the glass cloth.

[0047] The method for producing a glass cloth may further include a step of cleaning the silane coupling agent (in one embodiment, the silane coupling agent that has not formed a chemical bond with the surface of the glass filaments) and performing an opening treatment on the glass filaments (opening step), which makes it easier to open the glass cloth in a suitable manner.

[0048] The covering step, drying step, and fiber-opening step may be performed on the glass yarn before the weaving step in which the glass yarn is woven to obtain a glass cloth, or on the glass cloth after the weaving step. The order of the thermal deoiling step, covering step, drying step, and fiber-opening step may be appropriately reversed or repeated. When the cleaning step is performed after the weaving step, the cleaning step may also serve as the fiber-opening step by using a high-pressure water spray or the like. The composition of the glass cloth usually does not change before and after fiber-opening.

[0049] Warping process In the warping process, the warp yarns are warped to obtain a warp beam. The warping process may include, for example, a process of aligning multiple warp yarns to a desired weave density and width, and a process of performing a sizing treatment on the warp yarns. In the sizing treatment, a sizing agent mainly composed of starch and / or polyvinyl alcohol (PVA) can be attached to the surface of the glass yarn to suppress the generation of fluff in the glass yarn and to prevent water absorption.

[0050] Here, in the warping process, taper control is performed in which the yarn tension at the center of the yarn is used as a reference and is increased as the yarn approaches both ends. Even when a glass yarn with a low twist count is used as the weft, such taper control is advantageous in suppressing the amount of weft bending. For example, in taper control, when warping 800 warp yarns, the yarn tension at the 400th and 401st yarns, which are in the center, is set to 5 g, and the yarn tension at the 1st and 800th yarns, which are at both ends, is set to 8 g. The yarn tensions at the 2nd to 399th yarns and the 402nd to 799th yarns are controlled so that the yarn tensions continuously increase as the yarn approaches both ends. The yarn tension (taper control amount) that is increased as the yarn approaches both ends is calculated according to the following formula: Taper control amount: (8 g - 5 g) ÷ 399 warps ≒ 0.0075 g / warp. In the example of this specification, the yarn tensions of the 341st and 460th yarns are 5 g + 0.0075 g × 59 ≒ 5.4 g. For ease of explanation, the figures are rounded to one decimal place.

[0051] The number of warp threads selected for the center portion is one when the total number of warp threads is odd, and two when the total number of warp threads is even. As in the above example, when the total number of warp threads is even, the same thread tension is set for the two warp threads selected for the center portion.

[0052] Beaming Process In the beaming process, the section beams obtained in the warping process are combined to produce a single loom beam (warp beam). The beaming process makes it easy to produce a loom beam that can be set on a loom based on the section beams obtained in the warping process. The number of warp threads in the loom beam and the number of bundles of the section beams to be beamed are appropriately adjusted according to the weave density and width of the warp threads of the glass cloth. In one embodiment, the number of warp threads in the section beam is about 800, and the number of bundles of the section beams to be beamed is about 4.

[0053] In one embodiment, when four section beams obtained in the warping step are combined to produce one loom beam, warp yarns are provided sequentially from each section beam. For example, if four section beams (A) to (D) are used and the first warp yarn of loom beam (A) is referred to as "(A)-1," warp yarns are provided sequentially from each section beam so as to be (A)-1, (B)-1, (C)-1, (D)-1, (A)-2, (B)-2, (C)-2, (D)-2, (A)-3, .... This makes it easier to obtain the effect of taper control performed in the warping step. That is, it is easier to control the yarn tension of the glass cloth to be suitably higher at both ends than at the center, and in this case, it is easier to control the amount of weft bending to be small even when a weft yarn with a low twist is used.

[0054] In the weaving process, a glass cloth is woven using a beam, preferably a loom beam produced in the beaming process. Here, glass yarns having different twist numbers are used as the warp and weft yarns, respectively, to ensure an absolute difference in the twist numbers of the warp and weft yarns. From the viewpoint of excellent productivity of the glass cloth, it is preferable that the twist number of the weft yarns is smaller than the twist number of the warp yarns.

[0055] In the thermal deoiling step, the woven glass cloth is heated to deoil it. When a sizing treatment is performed on the warp yarns in the warping step, the sizing agent applied to the warp yarns is suitably removed in this thermal deoiling step. However, the thermal deoiling step may be performed regardless of whether or not a sizing treatment is performed.

[0056] As a means for thermal deoiling, known heating methods, heating media, heating mechanisms, heating devices, and heating components can be used. Specific examples of thermal deoiling include a method of thermal deoiling the glass cloth at a temperature of 600 to 1600°C, and a method of heating in a vacuum or in a gas with a dew point of 15°C or less under conditions where the maximum heating temperature is 100 to 600°C and the heating amount, expressed as heating temperature (°C) of 100°C or more x heating time (h), is 450 (°C·h) or more.

[0057] When the thermal deoiling treatment is carried out in a closed system, it is preferable to place the glass cloth in a heating furnace from the viewpoint of efficient heating by a heating means, and it is also preferable to heat the glass cloth while storing it in a rolled state from the viewpoint of saving storage space. Furthermore, it is also preferable to heat the glass cloth while conveying it in the heating furnace from the viewpoint of increasing the efficiency of removing organic substances and shortening the time required for removing organic substances.

[0058] When the thermal deoiling treatment is performed in a closed system, it is preferable to heat the glass cloth while transporting it, from the viewpoint of ensuring a heated area. The transportation of the glass cloth can be carried out, for example, by combining a mechanism for unwinding the rolled glass cloth (unwinding mechanism) with a mechanism for winding the unwound glass cloth (winding mechanism).

[0059] The thermal deoiling step preferably includes a step of heat-treating the glass cloth in the range of 600 to 1600°C (heat treatment step). In the heat treatment step, a glass cloth greige having a glass yarn softening point of 900°C or higher is heat-deoiled in the temperature range of 600 to 1600°C, thereby reducing the dielectric loss tangent of the glass cloth while suppressing damage to the glass cloth. When the thermal deoiling temperature is 600°C or higher, the dielectric loss tangent of the resulting glass cloth is easily reduced. When the thermal deoiling temperature is 1600°C or lower, the devitrification phenomenon of the glass is easily suppressed, and therefore, a decrease in the strength of the glass cloth is easily prevented. From the same viewpoint, the thermal deoiling temperature is more preferably 700 to 1500°C, even more preferably 800 to 1400°C, even more preferably 900 to 1300°C, and particularly preferably 1000 to 1200°C.

[0060] In the thermal deoiling step, the heating time is preferably 10 minutes or less, more preferably 5 minutes or less, even more preferably 2 minutes or less, and particularly preferably 90 seconds or less. If the heating time is 10 minutes or less, damage to the glass cloth is reduced, making it easier to avoid situations such as partial holes being formed in the glass cloth during processing or the glass cloth being cut. The heating time may be, for example, 1 second or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more.

[0061] (Heating furnace) The heating furnace used as the heating means in the thermal deoiling step may be any furnace that satisfies the above-mentioned conditions for thermal deoiling, and examples thereof include an electric heater and a burner. A plurality of heating furnaces may also be used in combination. A gas single radiant tube burner or an electric heater is preferably used as the heating furnace.

[0062] From the viewpoint of efficiently removing organic substances adhering to the surface of the glass cloth, a continuous system capable of heating the glass cloth while continuously passing it through a heating furnace is preferred over a batch system in which a glass fiber fabric is wound around a core and the glass cloth is heated at a predetermined atmospheric temperature. Furthermore, a system capable of continuously washing the glass cloth with washing water having a low metal ion content, such as reverse osmosis (RO) water or ion-exchanged water, is also preferred.

[0063] (Contact Member for Heating Glass Cloth) The above-mentioned heating furnace may be used as a method for heating the glass cloth. However, from the viewpoint of easily realizing low running costs, the glass cloth may be heated by bringing a member (contact member) heated to a predetermined temperature into contact with the glass cloth.

[0064] As the contact member, a roll is preferred from the viewpoint of facilitating conveyance of the glass cloth. As this type of roll, a roll that can be used in a high-temperature range and that heats by an induction heating method is preferred, as it has relatively little temperature variation in the width direction. When the glass cloth is heated by the contact member, it is expected that the temperature of the contact member and the surface temperature of the glass cloth are approximately equal.

[0065] When continuously heating the glass cloth, it is preferable to employ a system equipped with a mechanism for removing foreign matter (e.g., carbides) adhering to the roll, such as a blade.

[0066] (Means for applying high-temperature steam to glass cloth) As a method for heating the glass cloth, high-temperature steam may be applied to the glass cloth. The steam applied to the glass cloth may contain, for example, a volatile solvent, water vapor, etc., and may also contain gases other than water vapor. Among these, water vapor is preferred as the steam applied to the glass cloth from the viewpoint of suppressing toxicity to the human body and facilitating decomposition of the sizing agent used in the glass fiber. The temperature of the high-temperature steam may be a method in which high-temperature steam and heated air are supplied in any ratio, if necessary, so that the surface temperature of the glass cloth is higher than 650°C. The temperature of the high-temperature steam is 400°C or higher, preferably 450°C or higher, more preferably 550°C or higher, even more preferably 600°C or higher, and particularly preferably 650°C or higher. Means for applying steam may include spraying, shower diffusion, jet nozzle, etc. Gas discharged from the heating furnace may be reused as high-temperature steam.

[0067] When the sodium ions adhering to the surface of a glass cloth exceed a predetermined amount, thermal deoiling of the glass cloth at 700°C or higher tends to significantly reduce the tensile strength of the glass cloth due to devitrification of the quartz glass. To prevent devitrification, the glass cloth is preferably washed with water containing 20 ppm or less sodium ions before thermal deoiling. This makes it easy to reduce the amount of sodium ions on the glass surface, and in this case, even when thermal deoiling is performed at 700°C or higher, it is easy to prevent devitrification of the quartz glass. Maintaining the strength of the glass cloth after thermal deoiling makes it easy to prevent wrinkles and / or scratches during the process of treating the glass cloth with a surface treatment agent.

[0068] From the viewpoint of optimally achieving the effects of this embodiment, the sodium ion content in the water used for washing is preferably 18 ppm or less, more preferably 15 ppm or less, even more preferably 12 ppm or less, even more preferably 10 ppm or less, and particularly preferably 7 ppm or less. If the sodium ion content exceeds 20 ppm, it becomes difficult to suppress the devitrification phenomenon of the quartz glass when thermal deoiling is performed at 700°C or higher, and in this case, a decrease in the tensile strength of the glass cloth is likely to occur. The sodium ion content may be 0 ppm or may exceed 0 ppm.

[0069] Examples of means for cleaning the glass cloth include a method using ultrasonic waves (specifically, a method using an ultrasonic vibrator), a method using a spray (specifically, a method using a high-pressure spray), and a method of spraying water vapor. From the viewpoint of inexpensive and easy cleaning, a preferred method is to immerse the glass cloth in a water tank containing cleaning water (water having a sodium ion content of 20 ppm or less), remove excess cleaning water with a squeeze roller or the like, and then dry the glass cloth. In this case, the immersion time may be, for example, 2 seconds or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more, or 120 seconds or less, 90 seconds or less, 60 seconds or less, or 45 seconds or less.

[0070] Water having a sodium ion content of 20 ppm or less may be produced, for example, by filtration using an RO membrane, deionization using an ion exchange resin, etc. "Water having a sodium ion content of 20 ppm or less" may contain other liquid components (liquids other than water, etc.) within a range that does not impair the effects of this embodiment.

[0071] Coating Process The coating process is a process of applying a treatment liquid containing a silane coupling agent to a glass cloth. Methods for applying the treatment liquid to a glass cloth include, for example, (a) a method in which the glass cloth is immersed in and / or passed through a treatment liquid stored in a bath (hereinafter referred to as the "immersion method"), and (b) a method in which the treatment liquid is directly applied to the glass cloth using a roll coater, die coater, gravure coater, or the like. When the immersion method is used, the immersion time of the glass cloth in the treatment liquid is preferably set to 0.5 seconds or more and 1 minute or less. The treatment liquid in the coating process has a silane coupling agent concentration of, for example, 0.01 to 1.5 wt %.

[0072] In the drying step, the treatment liquid is dried and the silane coupling agent is fixed to the surface of the glass filaments. Methods for drying, preferably drying by heating, include, for example, hot air and electromagnetic waves.

[0073] The drying temperature is preferably 80° C. or higher, more preferably 90° C. or higher, so that the reaction between the silane coupling agent and the glass is sufficiently carried out, and is preferably 300° C. or lower, more preferably 180° C. or lower, from the viewpoint of preventing deterioration of the organic functional group of the silane coupling agent.

[0074] Spreading Process In the spreading process, the silane coupling agent (in one embodiment, the silane coupling agent that has not formed a chemical bond with the surface of the glass filaments) is washed away, and the glass yarns are spread. Examples of spreading methods include methods in which the glass cloth is spread using spray water (high-pressure water spreading), a vibro washer, ultrasonic water, a mangle, or the like. By reducing the tension applied to the glass cloth during the spreading process, it becomes easier to widen the width of the glass yarns and to remove to some extent the silane coupling agent that has not chemically bonded to the glass surface. In order to prevent a decrease in the tensile strength of the glass cloth due to the spreading process, it is preferable to take measures such as reducing the friction of contact members when weaving the glass yarns and increasing the amount of attached sizing agent.

[0075] <Prepreg> Another aspect of the present embodiment is a prepreg, which contains at least the glass cloth and a matrix resin impregnated into the glass cloth.

[0076] As the matrix resin, either a thermosetting resin or a thermoplastic resin can be used.

[0077] Examples of thermosetting resins include: a) epoxy resins obtained by reacting and curing a compound having an epoxy group with a compound having at least one of an amino group, a phenol group, an acid anhydride group, a hydrazide group, an isocyanate group, a cyanate group, and a hydroxyl group that reacts with the epoxy group, either without a catalyst or with the addition of a catalyst having reaction catalytic ability, such as an imidazole compound, a tertiary amine compound, a urea compound, or a phosphorus compound; b) radical polymerization curable resins obtained by curing a compound having at least one of an allyl group, a methacryl group, and an acrylic group, using a thermal decomposition catalyst or a photodecomposition catalyst as a reaction initiator; c) maleimide triazine resins obtained by reacting and curing a compound having a cyanate group with a compound having a maleimide group; d) thermosetting polyimide resins obtained by reacting and curing a maleimide compound with an amine compound; and e) benzoxazine resins obtained by crosslinking and curing a compound having a benzoxazine ring by thermal polymerization.

[0078] Examples of thermoplastic resins include polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, aromatic polyamide, polyether ether ketone, thermoplastic polyimide, insoluble polyimide, polyamideimide, and fluororesin.

[0079] In this embodiment, a thermosetting resin and a thermoplastic resin may be used in combination. The prepreg may contain an inorganic filler as desired. The inorganic filler is preferably used in combination with the thermosetting resin. Examples of inorganic fillers include aluminum hydroxide, zirconium oxide, calcium carbonate, alumina, mica, aluminum carbonate, magnesium silicate, aluminum silicate, silica, talc, short glass fiber, aluminum borate, and silicon carbide.

[0080] <Printed Wiring Board> Another aspect of this embodiment is a printed wiring board. Such a printed wiring board contains the prepreg. This makes it possible to provide a printed wiring board with excellent insulation reliability. <Integrated Circuit and Electronic Device> Another aspect of this embodiment is an integrated circuit and an electronic device. Such an integrated circuit and an electronic device contain the printed wiring board. This makes it possible to provide an integrated circuit and an electronic device with excellent properties.

[0081] The present embodiment will be further described with reference to examples and comparative examples. The present embodiment is not limited to the examples. The values ​​of various parameters described in this specification were measured by the methods described in the examples section.

[0082] [Measurement and Evaluation] <Glass Cloth Thickness and Standard Deviation of Thickness> In accordance with 7.10 of JIS R 3420, a micrometer was used, and the spindle was gently rotated while being lightly brought into parallel contact with the measurement surface, and the scale was read when the ratchet made three sounds. The read value was regarded as the thickness of the glass cloth. JIS R 3420 specifies general test methods for long glass fibers and products such as glass cloth using long glass fibers.

[0083] The thickness of the glass cloth was measured 50 times while changing the measurement position, and the coefficient of variation (%) of the thickness of the glass cloth was calculated from the average value and standard deviation according to the following formula: Coefficient of variation (%) = {(standard deviation of thickness) / (average thickness value)} × 100.

[0084] <Weft Curvature Amount> Measurement was carried out in accordance with JIS L1096 to obtain the weft curvature amount (mm). Specifically, the following procedures (1) to (3) were performed: (1) One weft thread in a glass cloth stretched between a pair of rolls was visually observed. (2) The TD tangent line between the roll and the cloth was used as a reference line, and the amount of displacement from the reference line was measured. (3) The difference between the maximum and minimum values ​​of the measured displacement amount was calculated, and this procedure was repeated five times to calculate the average of these differences. The average value obtained based on the above was treated as the "weft curvature amount."

[0085] <TEX of Glass Yarn> Measurement was carried out in accordance with JIS R3911 to obtain the TEX (g / 1000 m) of the glass yarn. Note that the value described as "TEX" in the table below is a value measured on the glass yarn that is the raw material of the glass cloth, but this value can also be treated as a value measured on the glass yarns (warp and weft) extracted from the glass cloth obtained using the glass yarn.

[0086] <Glass Yarn Twist Number and Its Absolute Value Difference> Measurements were made in accordance with JIS R3420 to obtain the twist number (turns / 25 mm) of the glass yarn. When measuring the twist number, the glass yarn was pulled out from the glass cloth, and the measurement was made on the glass yarn so that the twist number of the glass yarn in the glass cloth could be accurately measured. Regarding the obtained values, the twist in the z direction was treated as positive, and the twist in the s direction was treated as negative. For example, a 1.00z twist (1.00 (turns / 25 mm) twist in the z direction) was treated as +1.00, and a 1.00s twist (1.00 (turns / 25 mm) twist in the s direction) was treated as -1.00. Then, the absolute value difference (turns / 25 mm) between the twist numbers of the warp and weft yarns was calculated using the following formula: Absolute Value Difference in Twist Number = |Warp Twist Number - Weft Twist Number|

[0087] <Bulk Dielectric Loss Tangent of Glass> A 300 μm thick glass plate of the same type and composition as the glass cloth was prepared. The thickness of the glass plate was measured, and the bulk dielectric loss tangent of the glass at 10 GHz was measured using the thickness obtained. Specifically, in accordance with IEC 62562, the glass plate was sampled to a size required for measurement using a split cylinder resonator. The sample was then stored in a constant temperature and humidity oven at 23°C and 50% RH for 8 hours to condition the humidity. The dielectric properties at 10 GHz were then measured using a split cylinder resonator (EM Lab) and an impedance analyzer (Agilent Technologies). Each sample was measured five times, and the average value was calculated. IEC 62562 specifies a method for measuring the dielectric properties of fine ceramic materials for dielectric substrates, primarily used in microwave circuits, in the microwave band.

[0088] <Fluff Quality> The glass cloths obtained in the examples and comparative examples were subjected to a roll-to-roll inspection table, and while applying a tension of 100 N / 1000 mm and irradiating with a halogen lamp, the number of fluffs, particularly the number of fluffs with protrusions of 1 mm or more, was visually counted. ２ The number of fluffs per m was treated as the fluff frequency, and fluff quality was evaluated using this based on the following criteria: (Measurement criteria) Fluff quality A: The fluff frequency is 15 fluffs / m ２ Fluff quality B: Fluff frequency is 16 to 30 pieces / m ２ Fluff quality C: Fluff frequency is 31 pieces / m ２ That's all.

[0089] Looking at the relationship between "weft twist number" and "fluff quality" in the table below, good fluff quality was observed in the examples in which the weft twist number was relatively large, while fluff quality was rated C in Comparative Example 3, which had the smallest weft twist number. Regarding "weft twist number" and "fluff quality," it can be inferred that the glass cloth with a smaller weft twist number tends to have poorer fluff quality. The glass cloth of the examples in which good fluff quality was observed is expected to improve the reliability of printed wiring boards obtained using this glass cloth (for example, suppression of insulation defects).

[0090] Examples and Comparative Examples Example 1 Glass yarns with a SiO2 content of more than 99.9% by mass (glass bulk dielectric loss tangent @ 10 GHz = 0.0002) were used as warp and weft yarns. In the warp warping process, 857 glass yarns (filament diameter = 5.0 μm, number of filaments = 100) with a 5.0 TEX and a twist of +1.00 were arranged and processed into a section beam. The tension during warp warping was set to 8.0 g / fiber for the first and 857th warps, and 5.0 g / fiber for the 429th warp. For the 2nd to 428th warps and the 430th to 856th warps, tapered control was performed by increasing the yarn tension by 0.007 g each toward both ends, based on the 429th warp (the yarn located in the middle of the 857 warps). The yarn tension was controlled by rounding off the value to the nearest tenth. A total of four section beams were produced under the above conditions.

[0091] The obtained section beams were arranged in order, and a loom beam with a total of 3,428 warp threads was produced. Using the obtained loom beam, a glass cloth having a weave density of 65.0 warp threads / 25 mm and 66.9 weft threads / 25 mm and a width of 1,310 mm was woven in an air jet loom. A 5.0 TEX glass yarn was used as the weft, and the twist number of the glass yarn and the weaving conditions were adjusted so that the twist number of the weft thread of the glass cloth was +0.65. The obtained glass cloth greige was washed with ion-exchanged water, then dried, and subjected to a heat deoiling treatment at 800°C for 50 seconds.

[0092] Subsequently, the glass cloth after the thermal deoiling treatment was immersed in a treatment liquid. The treatment liquid was prepared by dispersing 0.2% of 3-methacryloxypropyltrimethoxysilane (Z6030, manufactured by Dow-Toray Industries, Inc.), a silane coupling agent, in pure water adjusted to pH = 3 with acetic acid. The glass cloth from which the treatment liquid had been squeezed out was heated and dried at 110 °C for 1 minute. The dried glass cloth was then immersed in water at a frequency of 25 kHz and an output of 0.50 W / cm. ２ After the fiber was opened by irradiation with ultrasonic waves of 100 Hz, it was dried at 110° C. for 1 minute, thereby obtaining a surface-treated glass cloth.

[0093] In the table below, the yarn tension (g / thread) at the center (the 429th thread, located in the center of 857 threads) in the warp yarn adjustment process is represented as "center"; the yarn tension (g / thread) at each end (the 1st and 857th threads, located at both ends of 857 threads) is represented as "both ends"; and the amount of increase in yarn tension (g / thread) in taper control, which increases the yarn tension as it approaches from the center to both ends, is represented as "taper amount".

[0094] Examples 2, 3, 4, 9, and 10 Glass cloths were obtained in the same manner as in Example 1, except that the values ​​and controls were changed as shown in the table.

[0095] Example 5: Glass yarns with a SiO2 content exceeding 99.9% by mass (glass bulk dielectric loss tangent at 10 GHz = 0.0002) were used as the warp and weft yarns. In the warp warping process, 689 glass yarns (filament diameter = 5.0 μm, number of filaments = 200) with a 9.8 TEX and +1.00 twist were arranged and processed into a section beam. The warp tension during warp warping was set to 8.0 g / fiber for the first and 689th yarns, and 5.0 g / fiber for the 345th yarn. For the 2nd to 344th yarns and the 346th to 688th yarns, tapered control was performed, increasing the yarn tension by 0.009 g each toward both ends, based on the 345th yarn (the yarn located in the middle of the 689 yarns). The yarn tension was controlled by rounding to the nearest tenth decimal point. A total of four section beams were fabricated under the above conditions.

[0096] The obtained section beams were arranged in order, and a loom beam with a total of 2,756 warp threads was produced. Using the obtained loom beam, a glass cloth having a weave density of 52.6 warp threads / 25 mm and 52.6 weft threads / 25 mm and a width of 1,310 mm was woven in an air jet loom. At this time, 9.8 TEX glass yarn was used as the weft, and the twist number of the glass yarn and the weaving conditions were adjusted so that the twist number of the weft thread of the glass cloth was +0.50. The obtained glass cloth greige was washed with ion-exchanged water, then dried, and subjected to a heat deoiling treatment at 800°C for 50 seconds.

[0097] Thereafter, the same procedure as in Example 1 was carried out to obtain a glass cloth (surface-treated glass cloth).

[0098] Example 6 to Example 8 Glass cloths were obtained in the same manner as in Example 5, except that the values ​​and controls were changed as shown in the table.

[0099] Comparative Examples 1 to 3 Glass cloths were obtained in the same manner as in Example 1, except that the values ​​and controls were changed as shown in the table.

[0100] <Method for Producing Prepreg> 45 parts by mass of polyphenylene ether (Noryl SA9000, manufactured by SABIC Corporation), 10 parts by mass of triallyl isocyanurate, 45 parts by mass of toluene, and 0.6 parts by mass of 1,3-di(tert-butylisopropylbenzene) were mixed in a stainless steel container and stirred at room temperature for 1 hour to produce a varnish.

[0101] The glass cloths obtained in the Examples and Comparative Examples were rolled. The glass cloths were drawn from the resulting rolls at a line speed of 2 m / min. At this time, a tension of 100 N was applied to the glass cloth during drawing. The drawn glass cloth was immersed in the above-mentioned varnish while being conveyed, and then passed through a slit whose gap was adjusted so that the resin content was 68% by mass, thereby removing excess varnish. Next, drying was performed under conditions of a drying temperature of 130°C and a drying time of 1 minute 30 seconds. As a result, prepregs were obtained (Examples and Comparative Examples).

[0102] <Meandering Amount of Glass Cloth During Prepreg Production> In accordance with the conditions during prepreg production, the glass cloth was pulled out from the roll at a line speed of 2 m / min while applying a tension of 100 N to the glass cloth, and the amount of meandering of the glass cloth was measured.

[0103] Here, the following conditions were taken into consideration in the method for measuring the meandering amount. (1) A detector was placed at a distance of about 10 cm from the roll, and the glass cloth was unwound in the MD direction so that one end of the glass cloth passed through the detector. (2) The glass cloth was unwound over about 500 m, and during this time, the detector detected the amount of deviation in the width direction (TD) relative to a predetermined reference value. Here, the amount of deviation of the cloth toward the outside was treated as a "positive deviation amount," and the amount of deviation of the cloth toward the inside was treated as a "negative deviation amount," and each deviation amount was detected. (3) The sum of the maximum value of the detected "positive deviation amount" and the maximum value of the detected "negative deviation amount" was calculated as the "amount of meandering."

[0104] <Prepreg Yield> Samples of 400 mm x 400 mm were cut out from the obtained prepreg. After sampling, samples that were visually inspected to be free of wrinkles and fluff were deemed "good products," and the number of such samples was counted to determine the prepreg yield based on the following formula: Prepreg Yield (%) = {(Number of Good Samples) / (Number of Samples)} x 100.

[0105] The manufacturing conditions and evaluation results of the examples and comparative examples are shown in the table below. Looking at the relationship between "meandering amount" and "yield" in the table below, it was confirmed that the greater the "meandering amount" of the glass cloth, the lower the "yield." This is presumably because the greater the "meandering amount" of the glass cloth, the more likely wrinkles are to occur in the prepreg, and therefore the more likely the "yield" is to decrease.

[0106]

Claims

1. A glass cloth having glass yarns as warp and weft, wherein the twist number of the weft is 0.40 to 1.80 turns / 25 mm or -1.80 to -0.40 turns / 25 mm, the absolute value difference between the twist numbers of the warp and weft is 0.01 to 0.70 turns / 25 mm, and the amount of weft bending is 35 mm or less.

2. The glass cloth according to claim 1, wherein the silicon (Si) content in the glass yarn is 95.0 to 100 mass % calculated as silicon dioxide (SiO2).

3. The glass cloth according to claim 1 or 2, wherein the silicon (Si) content in the glass yarn is 99.0 to 100 mass % calculated as silicon dioxide (SiO2).

4. The glass cloth according to claim 1 or 2, wherein the number of twists of the warp yarns is 0.40 to 1.80 times / 25 mm or -1.80 to -0.40 times / 25 mm.

5. The glass cloth according to claim 1 or 2, wherein the glass yarn is treated with a surface treatment agent containing a silane coupling agent.

6. The surface treatment agent is represented by the following formula (1): X(R) 3-n SiY n 7. The glass cloth according to claim 5, comprising the silane coupling agent represented by the formula: (1) (wherein X is an organic functional group having at least one of an amino group and an unsaturated double bond group having radical reactivity, each Y is independently an alkoxy group, n is an integer of 1 or more and 3 or less, and each R is independently a group selected from the group consisting of functional groups composed of a hydrocarbon group having 1 to 10 carbon atoms).

7. The glass cloth according to claim 6, wherein X in the formula is an organic functional group which does not form a salt with an ionic compound.

8. The glass cloth according to claim 6, wherein X in said formula does not include an amine or an ammonium cation.

9. The glass cloth according to claim 6, wherein X in the formula is an organic functional group having at least one of a methacryloxy group and an acryloxy group.

10. The glass cloth according to claim 6, wherein R in said formula is a group selected from the group consisting of a methyl group, an ethyl group, and a phenyl group.

11. The glass cloth according to claim 1 or 2, wherein the TEX of the warp and weft is 0.5 to 40 g / 1000 m.

12. The glass cloth according to claim 1 or 2, wherein the bulk dielectric tangent of the glass constituting the glass yarns is in the range of 0.001 or less at 10 GHz.

13. The glass cloth according to claim 1 or 2, which is for use in printed wiring boards.

14. A prepreg comprising the glass cloth according to claim 1 or 2, a thermosetting resin, and an inorganic filler.

15. A printed wiring board comprising the prepreg of claim 14.

16. An integrated circuit comprising the printed wiring board of claim 15.

17. An electronic device comprising the printed wiring board according to claim 15.

Images