Glass cloth and glass yarn

Abstract

The main objective is to provide a glass cloth and a glass yarn that contribute to achieving both suppression of fluffing and suppression of voids. [Solution] The glass cloth is composed of warp yarns and weft yarns formed by bundling a plurality of glass filaments, and the tensile strength of the glass cloth in the warp direction is 20 to 85 (N / 25mm), and the warp yarns have a yarn width variation coefficient Ftcv of 0.040 to 0.070. It is preferable that the average yarn width Ftw of the warp yarns is 100 to 200 μm.

Description

[Technical field]

[0001] The present invention relates to a glass cloth and a glass yarn used in the production of the glass cloth. [Background technology]

[0002] In recent years, with the miniaturization of electronic devices, printed wiring boards are required to be lightweight, and the materials used are also required to be low in mass. Prepregs, which are glass cloths impregnated with resin, are used to manufacture printed wiring boards, and the glass cloths are also required to be low in mass.

[0003] Furthermore, with the trend toward larger capacity and faster speeds in communications, materials constituting printed wiring boards are required to have low dielectric properties, and in some cases, glass cloth is also required to have low dielectric properties.

[0004] Furthermore, there is a demand for glass yarns constituting the above-mentioned low-mass glass cloth or glass cloth having the above-mentioned low dielectric properties to have a low thread count and low dielectric properties, and the quality of the glass yarns has a significant effect on the performance of the glass cloth.

[0005] The woven fabric is made of warp and weft yarns each having 14 to 55 glass filaments with a diameter in the range of 3.0 to 4.2 μm, and the weaving density of the warp and weft yarns is in the range of 86 to 140 yarns / 25 mm, the thickness is in the range of 7.5 to 12.0 μm, and the length per m is 100 mm. 2a mass in the range of 6.0 to 10.0 g per unit area, and an average number of steps, expressed as a value obtained by dividing the thickness of the glass cloth by the average value of the diameter of the warp glass filaments and the diameter of the weft glass filaments (thickness of the glass cloth / {(diameter of the warp glass filaments+diameter of the weft glass filaments) / 2}), is in the range of 2.00 or more and less than 3.00, and the degree of opening of the warp yarns (width of the warp yarns / (diameter of the glass filaments constituting the warp yarns×diameter of the glass filaments constituting the warp yarns) is 2.00 or more and less than 3.00. There is known a glass cloth having an average degree of opening, which is expressed as the geometric mean ((warp opening degree×weft opening degree) / 2) of the opening degree of the weft (weft width / (diameter of glass filaments constituting the weft×number of glass filaments constituting the weft)) in the range of 1.000 to 1.300, and a width ratio, which is expressed as the ratio of the warp width to the weft width (warp width / weft width), in the range of 0.720 to 0.960 (see, for example, Patent Document 1). According to this document, it is said that there is provided a glass cloth which can suppress the occurrence of pinholes in a prepreg using the glass cloth even if the average number of steps is less than 3.00, and which can maintain the excellent appearance quality of the prepreg by reducing the fuzzing of the glass cloth.

[0006] In addition, there is a method for producing a glass cloth by weaving glass yarns consisting of a plurality of glass filaments as warp yarns and weft yarns, wherein the density of the glass yarns that become the weft yarns is 2.2 g / cm 3 More than 2.5g / cm 3 A method for producing a glass cloth is known in which the glass yarn to be the weft has a yarn width distribution coefficient indicating the yarn width variation of the glass yarn to be the weft, which is 0.003 to 0.013, and / or the glass yarn to be the weft has a yarn width distribution variation coefficient A indicating the yarn width distribution variation of the glass yarn to be the weft, which is 0.0002 to 0.0015 (see, for example, Patent Document 2). This document states that it is possible to provide a method for producing a low dielectric glass cloth having uniform quality, and a glass yarn suitable for producing a low dielectric glass cloth. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-21274 A [Patent Document 2] JP 2020-105683 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned glass cloth made of glass yarns having a low count or low dielectric properties tends to have low mechanical strength, such as tensile strength in the warp direction. In addition, glass cloth is generally subjected to a fiber-opening treatment using a water flow or the like, and if the above-mentioned glass cloth having a low tensile strength is subjected to a fiber-opening treatment under the same conditions as, for example, a glass cloth made of a general-purpose E-glass yarn not having a low count, there is a risk of fluff being generated in the glass cloth.

[0009] On the other hand, if the above-mentioned glass cloth having a relatively low tensile strength in the warp direction is subjected to a spreading treatment under milder conditions than those for a glass cloth made of, for example, a general-purpose E-glass yarn that has not been made low-count, there will be some parts that are not sufficiently spread, and when the glass cloth is made into a prepreg or printed wiring board, resin impregnation into these parts will be insufficient, which may result in the generation of voids.

[0010] As described above, in a glass cloth made of glass yarns having a low count or low dielectric properties, there is a trade-off between suppressing the generation of fuzz and suppressing the generation of voids, and it is difficult to say that the above-mentioned conventional techniques sufficiently achieve both of these.

[0011] Therefore, a main object of the present invention is to provide a glass cloth and a glass yarn which solve the above problems and contribute to simultaneously suppressing the generation of fluff and the generation of voids. [Means for solving the problem]

[0012] As a result of investigations conducted by the present inventors to solve the above problems, they discovered that the generation of fuzz and voids is largely caused by the warp yarns of the glass cloth, and that in order to solve these problems, it is important to reduce unevenness in the yarn width of the warp yarns.

[0013] Specifically, in glass cloth production, the warp yarns have a higher tension than the weft yarns, and therefore are difficult to open. In addition, since the warp yarns have a relatively high tension, the yarns are more likely to be damaged during the process and fluff is more likely to occur. As described above, glass cloth made of glass yarns having a low count or low dielectric properties is inferior in mechanical strength, such as tensile strength in the warp direction, and needs to be opened under relatively mild conditions, which makes it more difficult to open and more likely to produce fluff.

[0014] The inventors further investigated the causes of fuzz and voids and found that in areas where the warp width is wider, the yarn bundles are poorer and fuzz is more likely to occur, and in areas where the warp width is narrower, the yarn bundles too much, making it difficult to open the yarns, and voids are more likely to occur in these areas.

[0015] Therefore, the present inventors have further studied and found that a glass cloth having a warp yarn width variation coefficient Ftcv of 0.040 to 0.070 can contribute to both suppressing the generation of fuzz and suppressing the generation of voids. The present inventors have also found that the glass cloth can be obtained by setting the standard deviation of the twist number of the glass yarn used as the warp yarn within a specific range, and by providing the glass yarn with a spinning bundling agent containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45%, and by using the glass yarn and setting the contact length with the roll within a specific range in the beaming process to equalize the warp tension, and by setting the warp tension within a specific range in the weaving process. The present invention was completed through further studies based on these findings.

[0016] That is, the present invention provides the following aspects. Item 1. A glass cloth composed of warp yarns and weft yarns each formed by bundling a plurality of glass filaments, the glass cloth having a tensile strength in the warp direction of 20 to 85 (N / 25 mm) and a yarn width variation coefficient Ftcv of the warp yarns of 0.040 to 0.070. Item 2. The glass cloth according to item 1, wherein the average warp width Ftw is 100 to 200 μm. Item 3. A prepreg comprising the glass cloth according to item 1 or 2 and a thermosetting resin impregnated in the glass cloth. Item 4. A glass yarn formed by bundling a plurality of glass filaments, wherein a coating containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45% is formed on the surface of the glass filaments, and the standard deviation of the number of twists of the glass yarn is 0.05 to 0.15 (twists / 25 mm). Item 5. A method for producing a glass cloth according to item 1 or 2, comprising the steps of: preparing the glass yarn according to claim 4 as the warp yarn; beaming the warp yarn so that the contact length between the warp yarn and a roll other than a winding roll and a take-up roll is 0.60 to 1.27 m / roll; and weaving the warp yarn at a tension T (cN) that satisfies the following formula (I): Formula (I) 5.0×10 -3 ≦T(cN) / (π×(D / 2) 2 ×N)≦12.0×10 -3 In formula (I), D is the average diameter (μm) of the glass filaments, and N is the number of the glass filaments. Effect of the Invention

[0017] The glass cloth of the present invention is a glass cloth constituted by warp yarns and weft yarns each formed by bundling a plurality of glass filaments, and has a tensile strength in the warp direction of the glass cloth of 20 to 85 (N / 25 mm) and a yarn width variation coefficient Ftcv of the warp yarns of 0.040 to 0.070, which contributes to achieving both suppression of the generation of fuzz and suppression of the generation of voids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The glass cloth of the present invention is a glass cloth constituted by warp yarns and weft yarns each formed by bundling a plurality of glass filaments, and has a tensile strength of 20 to 85 (N / 25 mm) and a yarn width variation coefficient Ftcv of the warp yarns of 0.040 to 0.070. The glass cloth of the present invention will be described in detail below.

[0019] [Glass material] In the glass cloth of the present invention, the glass material constituting the glass filaments is not particularly limited, and examples thereof include E glass, T glass, S glass, UT glass, D glass, NE glass, L glass, LU glass, C glass, AR glass, and the like, which are trade names of products manufactured by Unitika Ltd.

[0020] From the viewpoint of versatility, it is preferable to use glass filaments having an E-glass composition, which is a composition containing, relative to the total amount of the glass filaments, SiO2 in the range of 52-56 mass%, B2O3 in the range of 5-10 mass%, Al2O3 in the range of 12-16 mass%, CaO and MgO in the range of 20-25 mass% in total, and Li2O, K2O and Na2O in the range of 0-1 mass% in total.

[0021] From the viewpoint of further increasing the strength of the prepreg and the printed wiring board, the glass filaments are preferably made of a glass material having a composition containing, with respect to the total amount of the glass filaments, 60 to 66 mass % of SiO2, 20 to 26 mass % of Al2O3, and 10 to 15 mass % of MgO.

[0022] From the viewpoint of reducing the dielectric constant and dielectric loss tangent of the prepreg and the printed wiring board, the glass filaments are preferably made of a glass material containing SiO2 in the range of 45 to 60 mass%, B2O3 in the range of 15 to 35 mass%, and Al2O3 in the range of 10 to 20 mass%, relative to the total amount of the glass filaments, and more preferably made of a glass material containing SiO2 in the range of 45 to 55 mass%, B2O3 in the range of 20 to 35 mass%, and Al2O3 in the range of 10 to 20 mass%, relative to the total amount of the glass filaments.

[0023] In the present invention, the glass composition is measured by ICP optical emission spectroscopy. Specifically, the Si content and B content are obtained by melting a weighed glass cloth sample with sodium carbonate, dissolving it in dilute nitric acid to a constant volume, and measuring the obtained sample by ICP optical emission spectroscopy. The Fe content is obtained by dissolving a weighed glass cloth sample by an alkali dissolution method to a constant volume, and measuring the obtained sample by ICP optical emission spectroscopy. Furthermore, the Al content, Ca content, and Mg content are obtained by thermally decomposing a weighed glass cloth sample with sulfuric acid, nitric acid, and hydrogen fluoride, dissolving it in dilute nitric acid to a constant volume, and measuring the obtained sample by ICP optical emission spectroscopy. The ICP optical emission spectroscopy device can be an iCAP6300Duo manufactured by Thermo Fisher Scientific.

[0024] [Glass cloth] The glass cloth of the present invention is composed of warp yarns and weft yarns each formed by bundling a plurality of glass filaments. The warp yarns have a yarn width variation coefficient Ftcv of 0.040 to 0.070. This contributes to achieving both suppression of fuzz generation and suppression of void generation in a glass cloth having a relatively low tensile strength of 20 to 85 (N / 25 mm) as described below. The warp width variation coefficient Ftcv is more preferably 0.045 to 0.051.

[0025] The warp width variation coefficient Ftcv is obtained by the following method. That is, a glass cloth is cut to 20 cm x 20 cm, and observed in a planar direction with an optical microscope or the like. 25 warp threads are randomly selected, and the width of each of the 25 threads is measured at a point 1 cm from the end. Measurements are then repeated 18 times every 1 cm from that point, for a total of 19 points to measure the width of the thread. Next, the arithmetic mean and standard deviation of the yarn width values ​​at the 19 points are calculated, and the variation coefficient (= the standard deviation / the arithmetic mean) of the 19 points is calculated. This is performed for the 25 threads, and the arithmetic mean of the variation coefficients calculated for each of the 25 threads is taken as the warp width variation coefficient Ftcv.

[0026] In the glass cloth of the present invention, the average warp width (Ftw) is not particularly limited, but from the viewpoint of making the glass cloth thinner while simultaneously suppressing the generation of fuzz and the generation of voids, it is preferably 100 to 200 μm, and more preferably 100 to 150 μm. Here, the average warp width (Ftw) is determined by calculating the arithmetic mean of the yarn width values ​​at 19 positions measured when determining the above-mentioned warp width variation coefficient Ftcv, performing this for 25 yarns, and further arithmetically averaging the arithmetic mean values ​​of the yarn widths determined for each of the 25 yarns, to obtain the average warp width (Ftw).

[0027] It is technically common knowledge that glass cloth is manufactured under conditions in which the warp threads are subjected to greater tension than the weft threads. Therefore, the weft threads of the glass cloth are manufactured in a relatively tension-free state, and therefore have a larger thread width than the warp threads when viewed in the planar direction of the glass cloth. Therefore, in the present invention, when the average thread width of the weft threads is determined by the same method as the above-mentioned average thread width (Ftw) of the warp threads, the warp threads can also be defined as the glass threads of the warp threads and the weft threads that have a smaller average thread width when viewed in the planar direction.

[0028] In the glass cloth of the present invention, the warp width standard deviation (Ftσ) is not particularly limited, but from the viewpoint of making the glass cloth thinner while simultaneously suppressing the generation of fuzz and the generation of voids, it is preferably 1.0 to 20.0 μm, more preferably 3.0 to 18.0 μm, even more preferably 3.0 to 15.0 μm, particularly preferably 3.0 to 10 μm, and even more preferably 4.0 to 10.0 μm. Here, the warp width standard deviation (Ftσ) is calculated by calculating the standard deviation from the yarn widths of a total of 19 points and the arithmetic mean value of the 19 points measured when calculating the warp width variation coefficient Ftcv described above, and this is performed for 25 yarns, and the value obtained by arithmetically averaging the standard deviations calculated for each of the 25 yarns is defined as the warp width standard deviation (Ftσ).

[0029] The glass cloth of the present invention has a tensile strength in the warp direction of 20 to 85 (N / 25mm). As described above, the glass cloth of the present invention has a warp yarn width variation coefficient Ftcv of 0.040 to 0.070, and therefore, in the glass cloth having the tensile strength, it is possible to contribute to suppressing the generation of fluff and the generation of voids at the same time. Here, the tensile strength in the warp direction is measured in accordance with JIS R 3420:2013 7.4.2 using a constant-speed extension tensile tester (manufactured by Intesco Co., Ltd.), with a test piece length of 25 cm, a test piece width (width before the yarn is loosened from both ends) of 30 mm, a grip interval of 15 cm, a test piece width (width after the yarn is loosened from both ends) of 25 mm, and a constant-speed tensile speed of 200 mm / min, and the breaking strength is measured five times in the warp direction of the glass cloth, and the arithmetic mean value of the measured values ​​is taken as the tensile strength (N / 25mm) of the glass cloth.

[0030] The average diameter of the glass filaments in the warp and weft constituting the glass cloth of the present invention is not particularly limited, but from the viewpoint of making the thickness of the glass cloth thinner, it is, for example, 2 to 7 μm, preferably 2.5 to 5.5 μm, more preferably 3 to 5 μm, further preferably 3.2 to 4.5 μm, and particularly preferably 3.2 to 4.2 μm. In addition, the number of glass filaments constituting the warp and weft in the glass cloth of the present invention is not particularly limited, but from the viewpoint of making the thickness of the glass cloth thinner, it is, for example, 20 to 200, preferably 20 to 100, and more preferably 20 to 55. Here, the average diameter and number of glass filaments are measured and calculated as follows. That is, the obtained glass cloth was cut into two pieces of 30 cm square, one for observing the warp threads and the other for observing the weft threads, and each was embedded in an epoxy-based cold embedding resin (manufactured by Struers K.K., product name: Epoxy Resin Specfix-40), hardened, and polished to the extent that the warp and weft threads could be observed. Using an SEM (manufactured by JEOL Ltd., product name: JSM-6390A), the average diameter was observed and measured at a magnification of 2000x and the number of threads at a magnification of 500x. (1) Average diameter of glass filaments (μm) Thirty warp threads and 30 weft threads are randomly selected, and the diameters (largest parts) of all the glass filaments in the 30 warp threads and weft threads are measured and the arithmetic mean value is calculated to be the average diameter of the glass filaments in the warp and weft threads. (2) Number of pieces Thirty warp threads and 30 weft threads are randomly selected, and the total number of filaments in the 30 warp threads and weft threads is measured and the arithmetic mean value is calculated to be the number of glass filaments in the warp and weft threads.

[0031] In the glass cloth of the present invention, the count of the warp and weft yarns is not particularly limited, but from the viewpoint of making the thickness of the glass cloth thinner, for example, 0.5 to 12 tex is preferable, 0.5 to 5 tex is more preferable, 0.5 to 3 tex is more preferable, 0.5 to 2 tex is further preferable, and 0.5 to 1.5 tex is particularly preferable. In the present invention, the count of the glass yarn is a value measured and calculated according to the specification of "7.1 Count" of the Japanese Industrial Standard JIS R 3420 2013 (General Test Method for Glass Fibers).

[0032] In the glass cloth of the present invention, the weaving density of the warp and weft is not particularly limited, but may be, for example, 80 yarns / 25 mm or more and 160 yarns / 25 mm or less, and preferably 85 yarns / 25 mm or more and 130 yarns / 25 mm or less. Here, in the present invention, the warp density and weft density are values ​​measured and calculated according to the specification in "7.9 Density (weaving density)" of the Japanese Industrial Standard JIS R 3420 2013 (General test method for glass fibers).

[0033] The weave of the glass cloth of the present invention is not particularly limited, and examples thereof include plain weave, satin weave, twill weave, basket weave, rib weave, etc. Among these, plain weave is preferred.

[0034] The thickness of the glass cloth of the present invention is not particularly limited, but may be, for example, 20 μm or less, preferably 15 μm or less. The lower limit may be, for example, 5 μm or more, preferably 6 μm or more, and more preferably 7 μm or more. The thickness of the glass cloth of the present invention may be specifically 5 μm or more and 20 μm or less, preferably 6 μm or more and 15 μm or less, more preferably 7 μm or more and 15 μm or less. Here, the thickness of the glass cloth is measured using an outside micrometer with a minimum display value of 0.001 mm in accordance with JIS R3420:2013 7.10.1.

[0035] The mass of the glass cloth of the present invention is not particularly limited, but is, for example, 20 g / m 2The following are listed: 15g / m 2 The lower limit is preferably 5 g / m or less. 2 The above are listed, and 6g / m 2 More than 7g / m is preferable. 2 More preferably, the mass of the glass cloth of the present invention is 5 g / m 2 More than 20g / m 2 Less than 6g / m 2 More than 15g / m 2 Less than 7g / m, more preferably 2 More than 15g / m 2 Here, the mass of the glass cloth is measured in accordance with JIS R 3420:2013 7.2.

[0036] [Glass yarn] Next, the glass yarn of the present invention will be described.

[0037] The glass yarn of the present invention is a glass yarn formed by bundling a plurality of glass filaments, a coating containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45% is formed on the surface of the glass filaments, and the standard deviation of the number of twists of the glass yarn is 0.05 to 0.15 (turns / 25 mm).By weaving using such a glass yarn as a raw warp thread, it becomes possible to efficiently produce the glass cloth of the present invention described above.

[0038] As described above, in inventing the glass cloth of the present invention, the inventors found that in the conventional technology, in the portion where the warp width is widened, the bundle property is poor and fuzz is more likely to occur, and in the portion where the warp width is narrowed, the bundle is too tightly bundled and opening becomes difficult, and voids are more likely to occur in said portion. Then, after studying the cause of the mixture of such portions where the warp width is widened and portions where the warp width is narrowed in the conventional technology, the inventors found that the glass yarn used in the conventional technology has large twist unevenness, and that this causes the mixture of portions where the warp width is widened and portions where the warp width is narrowed.

[0039] As a result of investigations into reducing the above-mentioned twist unevenness, it was found that by producing a glass yarn using a spinning bundling agent that contains non-crosslinked soybean starch and crosslinked rice starch with an amylose content of 35 to 45% as a spinning bundling agent for bundling the glass yarn, the standard deviation of the number of twists, which is an index of twist unevenness of the glass yarn, can be made to be 0.05 to 0.15 (turns / 25 mm).

[0040] Here, the mechanism by which the standard deviation of the number of twists, which is an index of uneven twisting of glass yarn, is set to 0.05 to 0.15 (turns / 25 mm) by producing glass yarn using a spinning bundling agent containing non-crosslinked soybean starch and crosslinked rice starch with an amylose content of 35 to 45% is not necessarily clear, but can be considered as follows.

[0041] That is, the glass yarn is produced through a spinning process and a twisting process as described below. (1-1) Spinning process Glass raw materials are melted in a glass melting furnace and drawn out from a nozzle as multiple glass filaments, and a spinning bundling agent is applied to the multiple glass filaments to bundle them into a glass strand. A collet equipped with a cylindrical winding tube is then rotated to wind the glass strand onto the winding tube, forming a cake (a cylindrically wound mass of thread formed by winding up the strand immediately after it is fiberized from the bushing in the spinning process). (1-2) Yarn twisting process Glass strands are pulled out from the cake, twisted in a ring twister to form glass yarn, and wound onto a take-up bobbin to form glass yarn.

[0042] Here, the principle of the ring twisting machine is that the yarn passes through a traveler that moves along the edge of the ring and is wound onto a take-up bobbin attached to a spindle. At this time, the traveler rotates along the edge of the ring due to the rotation of the spindle and the tension of the yarn, and twists the yarn. The rotation speed of the traveler is smaller than the rotation speed of the spindle, and the yarn is twisted by the difference in the rotation speed and wound onto the take-up bobbin. After investigation, the inventors of the present invention have found that the reason for the high standard deviation of the twist number in the conventional technology is that the friction between the traveler of the ring twisting machine and the glass yarn is likely to be uneven in the twisting process during the production of glass yarn, which causes the above-mentioned standard deviation to be high.

[0043] Here, the present inventors aimed to reduce the friction between the traveler of a ring twisting machine and the glass yarn passing through the traveler in order to reduce the unevenness of the friction between the traveler and the glass yarn in the twisting process during the production of glass yarn, and focused on starch, which is a film-forming component of a spinning sizing agent applied to the glass filaments in the spinning process.

[0044] It is known that starch used as a film-forming component of a spinning bundling agent for glass yarn is generally corn, potato, tapioca starch, or the like. These starches are resistant to retrogradation (gelation of gelatinized starch when cooled). On the other hand, soybean starch is more prone to retrogradation than corn, potato, or tapioca starch. When starch retrogrades, the starch molecules transition to a denser aggregate state. The present inventors have deliberately utilized this retrogradation to form a starch film between glass filaments, and have attempted to bundle the glass filaments more uniformly by shrinking the film through the retrogradation of the starch film. They have speculated that the uniformity of the bundling of the glass yarn can be increased and the friction between the traveler and the glass yarn passing through the traveler can be reduced by using non-crosslinked soybean starch, which has high film-forming ability among soybean starches and has an amylose content of 35 to 45%.

[0045] The present inventors further speculated that by using cross-linked rice starch in addition to the non-cross-linked soybean starch having an amylose content of 35 to 45% as starch, the friction between the traveler and the glass yarn passing through the traveler can be further reduced. That is, rice starch has a smaller starch particle size than other starches such as corn starch. The inventors speculated that by using cross-linked rice starch in combination with the non-cross-linked soybean starch, the rice starch having a small particle size is allowed to remain on the glass filaments without forming a film, and the non-cross-linked soybean starch film causes less interference with uniform bundling, thereby further reducing the friction of the glass yarn like a ball bearing.

[0046] In fact, when glass yarn was produced using a spinning bundling agent containing non-crosslinked soybean starch and crosslinked rice starch with an amylose content of 35-45%, the ring running of the traveler was stabilized, and the standard deviation of the twist number, which is an index of uneven twisting of the glass yarn, was able to be reduced to 0.05-0.15 (turns / 25 mm).

[0047] As described above, the glass yarn of the present invention contains non-crosslinked soybean starch with an amylose content of 35 to 45% in the film formed on the surface of the glass filament. Here, the amylose content of starch is determined by amperometric titration of the iodine affinity measurement method (Starch Science Handbook, pages 177 to 179, supervised by Jiro Nikuni, first published in 1977, Asakura Publishing). The starch used for the measurement is dissolved in dimethyl sulfoxide (hereinafter referred to as DMSO), impurities are removed by centrifugation, and the starch in the DMSO solution after centrifugation is reprecipitated with ethanol and powdered by drying under reduced pressure. In addition, an automatic potentiometric titrator (model AT-118, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) can be used for the titration.

[0048] Examples of raw materials for soybean starch include peas, lentils, broad beans, etc., with peas being preferred.

[0049] As described above, the glass yarn of the present invention contains crosslinked rice starch in the coating formed on the surface of the glass filaments. The crosslinking agent used to crosslink the rice starch may be a known agent, such as epichlorohydrin, dialdehyde, sodium trimetaphosphate, diepoxide, cyanuric chloride, formalin, etc., with epichlorohydrin being preferred.

[0050] The preferred glass material constituting the glass filaments of the glass yarn of the present invention, the average diameter, number and count of the glass filaments are as described above in the description of the glass cloth of the present invention. Regarding the difference in the measurement method, in the glass yarn of the present invention, the average diameter of the glass filaments is measured and calculated according to the method specified in the B method (cross-sectional method) of "7.6 Single fiber diameter" of "General test method for glass fibers" of JIS R 3420 2013. In addition, the number of glass filaments of the glass yarn is measured in the measurement of the average diameter of the glass filaments.

[0051] The cross-sectional area of ​​the glass yarn is 250 to 1000 μm 2 is preferable, and more preferably 300 to 800 μm 2 , particularly preferably 325 to 700 μm 2 In order to reduce the mass of the glass cloth and further suppress the generation of fluff, the thickness is set to 600 to 700 μm. 2 The cross-sectional area of ​​the glass yarn is calculated by the following formula (II). Formula (II) Glass yarn cross-sectional area (μm 2 )=π×(average diameter of glass filaments in glass yarn (μm) / 2) 2 × Number of glass filaments in glass yarn

[0052] The glass yarn of the present invention has a standard deviation of the number of twists of 0.05 to 0.15 (turns / 25 mm). As described above, when a glass yarn is produced using a spinning bundling agent containing non-crosslinked soybean starch and crosslinked rice starch with an amylose content of 35 to 45%, the ring running of the traveler is stabilized, and the standard deviation of the number of twists, which is an index of unevenness in the twist of the glass yarn, can be set to 0.05 to 0.15 (turns / 25 mm). By weaving the glass yarn as a raw warp thread, the glass cloth of the present invention described above can be efficiently produced.

[0053] The number of twists of the glass yarn of the present invention is not particularly limited, but from the viewpoint of producing a thinner glass cloth while controlling the yarn width within a certain range, it is preferably 0.4 to 1.10 turns / 25 mm, and more preferably 0.45 to 1.05 turns / 25 mm.

[0054] The standard deviation of the twist number of the glass yarn is determined by measuring the twist number per 25 mm at 10 measurement points in accordance with JIS R 3420:2013 7.5. The twist number of the glass yarn is determined by measuring the arithmetic mean value of 10 measurement points in accordance with JIS R 3420:2013 7.5.

[0055] The glass yarn of the present invention preferably has an average yarn width of 40 to 100 μm, more preferably 40 to 85 μm, measured while applying a tension T (cN) satisfying the following formula (III). Formula (III)...5.0×10 -3 ≦T(cN) / (π×(D / 2) 2 ×N)≦12.0×10 -3 In formula (III), D is the average diameter (μm) of the glass filaments, and N is the number of the glass filaments.

[0056] Moreover, the glass yarn of the present invention preferably has a yarn width variation coefficient of 0.02 to 0.05, measured while applying a tension T (cN) satisfying the above formula (III).

[0057] The average value and variation coefficient of the yarn width of the glass yarn measured while applying a tension T (cN) satisfying the above formula (III) are obtained by measuring the yarn width every 0.50 mm while applying the tension T (cN) to the glass yarn at a speed of 50 m / min and a measuring length of 50 m using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as a measuring instrument, and the average of the obtained values ​​is regarded as the average value of the yarn width. The variation coefficient of the yarn width is calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0058] The tensile strength of the glass yarn of the present invention is preferably 0.2 to 1.7 N, more preferably 0.3 to 1.7 N, further preferably 0.8 to 1.7 N, and particularly preferably 1.3 to 1.7 N, from the viewpoint of further suppressing the generation of fluff while reducing the mass of the glass cloth. The tensile strength is the tensile strength (N) measured in accordance with JIS R 3420:2013 7.4.3 using an autograph (AGS-100S) manufactured by Shimadzu Corporation, using a circular clamp with a radius of 13 mm, at a test speed of 250 mm / min and a grip interval of 250 mm.

[0059] [Glass cloth manufacturing method] The method for producing the glass cloth of the present invention is not particularly limited as long as it is possible to obtain a glass cloth composed of warp yarns and weft yarns formed by bundling a plurality of glass filaments, the glass cloth having a tensile strength in the warp direction of 20 to 85 (N / 25 mm) and the warp yarn width variation coefficient Ftcv of 0.040 to 0.070. One suitable example of the method for producing a glass cloth includes the steps of: preparing the glass yarn of the present invention as a warp yarn; beaming the warp yarn with a contact length between the warp yarn and a roll other than an unwinding roll and a winding roll of 0.60 to 1.27 m / yarn; and weaving the warp yarn with a tension T (cN) that satisfies the following formula (I). Formula (I) 5.0×10 -3 ≦T(cN) / (π×(D / 2) 2 ×N)≦12.0×10 -3 In formula (I), D is the average diameter (μm) of the glass filaments, and N is the number of the glass filaments.

[0060] The method for producing the glass cloth of the present invention will be described in detail below.

[0061] (1) Warp preparation process The above-mentioned glass yarn of the present invention is prepared as the warp yarn. The glass yarn is made by bundling a plurality of glass filaments, and a coating containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45% is formed on the surface of the glass filament, and the standard deviation of the number of twists of the glass yarn is 0.05 to 0.15 (turns / 25 mm). By using the glass yarn as the warp yarn, a glass cloth having a warp yarn width variation coefficient Ftcv of 0.040 to 0.070 can be efficiently obtained.

[0062] (2) Beaming process The glass yarn prepared in the warp preparation step is used as the warp yarn, and after warping and sizing, beaming is performed. Beaming is a process for preparing a warp beam so that it can be set on a loom. Usually, yarns are paid out from a number of sized beams obtained in the sizing step, and these are combined to form a single warp beam, so that it can be set on a loom. In the glass cloth manufacturing method of the present invention, it has been found that by performing beaming with a contact length per warp yarn between the warp yarn and a roll other than the unwinding roll (usually the roll on which the sizing beam is set) and the take-up roll being 0.60 to 1.27 m, it is possible to keep the tension per warp yarn within a certain range and efficiently suppress the variation in the warp yarn width. The contact length is preferably 0.70 to 1.15 m per warp yarn.

[0063] In the beaming process, the material of the rolls other than the unwinding roll and the winding roll is not particularly limited, but examples thereof include metals such as stainless steel and aluminum alloys, rubber, and resins, and metal rolls are preferably metal rolls that have been surface-treated such as hard chrome plating. The diameter of the rolls other than the unwinding roll and the winding roll is, for example, about 100 to 500 mm. The number of rolls other than the unwinding roll and the winding roll is not particularly limited, but examples thereof include 3 to 5 rolls.

[0064] The warp speed in the beaming step is not particularly limited, but may be, for example, 5 to 100 m / min, more preferably 10 to 60 m / min, and particularly preferably 15 to 50 m / min.

[0065] The method for producing a glass cloth of the present invention includes a weaving step in which the tension of the warp yarns is set to a tension T (cN) that satisfies the following formula (I). Formula (I) 5.0 × 10 -3 ×π×(D / 2) 2 ×N}≦T(cN) / (π×(D / 2) 2 ×N)≦12.0×10 -3 In formula (I), D is the average diameter (μm) of the glass filaments, and N is the number of the glass filaments.

[0066] By weaving under the above conditions, the glass cloth of the present invention having a yarn width variation coefficient Ftcv of 0.040 to 0.070 can be efficiently produced.

[0067] The warp tension in the loom can be monitored by a load cell installed just after the unwinding, and can be adjusted by increasing or decreasing the unwinding tension of the loom beam.

[0068] In the method for producing a glass cloth according to the present invention, after the weaving step, an opening treatment and / or a heat cleaning treatment can be carried out as necessary. Examples of the method for opening the glass cloth include an opening treatment by the pressure of a water flow, an opening treatment by high-frequency vibration using water (e.g., degassed water, ion-exchanged water, deionized water, electrolytic cation water, electrolytic anion water, etc.) as a medium, and a processing treatment by pressurization using a roll. Such an opening treatment may be carried out simultaneously with weaving or after weaving. In addition, the opening treatment may be carried out before or after a heat cleaning treatment described later or simultaneously with the heat cleaning treatment, or may be carried out simultaneously with or after a surface treatment described later. In addition, a known method can be adopted as a method for adjusting the opening degree of the warp and weft yarns, and examples thereof include a method of adjusting the warp tension, a method of adjusting and applying the tension balance between the warp and weft directions by using a pinch expander, a curved rubber roller, a rotating roller, a Mirabeau roller, or a tenter in the weft direction, and a method of combining these methods.

[0069] When a substance that inhibits the adhesion and impregnation of the matrix resin when the woven glass cloth is made into a prepreg or a printed wiring board, such as a spinning binder, is attached to the woven glass cloth, it is preferable to remove the substance by, for example, a heat cleaning treatment. The temperature condition of the heat cleaning treatment is preferably 350° C. or higher, more preferably 350 to 500° C., and even more preferably 380 to 450° C. The time of the heat cleaning treatment may be appropriately set according to the temperature conditions employed. For example, when the glass cloth is made into a roll product (a product in which the glass cloth is wound around a core), and the roll product is subjected to the heat cleaning treatment as it is, the time may be 20 to 60 hours, preferably 24 to 48 hours, and even more preferably 24 to 36 hours.

[0070] [Prepreg] Next, the prepreg of the present invention will be described. The prepreg of the present invention contains the glass cloth of the present invention and a thermosetting resin that is impregnated in the glass cloth.

[0071] The thermosetting resin is not particularly limited as long as it is a resin that is cured by heat, and examples thereof include phenol resin, epoxy resin, non-halogen epoxy resin, cyanate resin, maleimide resin, bismaleimide resin, modified bismaleimide resin, isocyanate resin, benzocyclobutene resin, vinyl resin, bismaleimide triazine resin, phenol resin, thermosetting polyphenylene ether resin, etc. The thermosetting resin may be used alone or in combination of two or more kinds.

[0072] The prepreg of the present invention may also contain an inorganic filler, such as silicas such as natural silica, fused silica, amorphous silica, and hollow silica, boehmite, molybdenum compounds such as molybdenum oxide and zinc molybdate, and glass fillers such as alumina, talc, calcined talc, mica, short glass fibers, and spherical glass (glass fillers using E glass, T glass, UT glass, S glass, D glass, NE glass, L glass, LU glass, or the like as a glass material).

[0073] The glass cloth and prepreg of the present invention can be suitably used for printed wiring boards. EXAMPLES

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] 1. Glass yarn manufacturing example (1) Spinning bundling agent The following materials were prepared as the raw materials for the spinning sizing agent: ·Cross-linked rice starch ·Non-crosslinked bean starch (amylose content: 40%, raw material: pea) · Non-crosslinked high amylose corn starch (amylose content 70%) · Oils and fats (raw materials: animal oils, vegetable oils, emulsifiers) Resin (a mixture of isocyanate-modified polyether polymer and modified epoxy resin) Fabric softener (alkylamide derivatives) Antistatic agents (N,N,N,N-tetraalkyl quaternary ammonium salts) Preservatives Defoamer

[0076] The above raw materials were mixed with a predetermined amount of pure water as an aqueous solvent so that the composition ratio of the non-volatile components was as shown in Table 1, to obtain sizing agents of Blend A and Blend B. The concentration of the non-volatile components in each spinning sizing agent was 6.00% by mass. The units of the values ​​in Table 1 are parts by mass.

[0077] [Table 1]

[0078] (2) Glass yarn manufacturing example <Production Example 1> The spinning sizing agent of blend A was applied by an applicator to a plurality of glass filaments (containing SiO2 in the range of 45-60 mass%, B2O3 in the range of 15-35 mass%, and Al2O3 in the range of 10-20 mass% relative to the total amount of the glass filaments) spun out of a spinning furnace, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0079] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2 When tension is applied that satisfies the following: T(cN) / (π×(D / 2)=9.0 (*D is the average diameter (μm) of the glass filaments, and N is the number (pieces) of the glass filaments), the average yarn width is 58.3 μm, the coefficient of variation is 0.04, and the tension T is T(cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D x N) = 4.3 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 60.7 μm, and the coefficient of variation was 0.04. Note that, the average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, measuring the yarn width every 0.50 mm using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument, setting the measurement length to 50 m, and taking the average of the obtained values ​​as the average yarn width, and also calculating the coefficient of variation of the yarn width by dividing the standard deviation of the obtained yarn width by the average value.

[0080] <Production Example 2> The spinning sizing agent of blend A was applied by an applicator to a plurality of glass filaments (containing SiO2 in the range of 45-60 mass%, B2O3 in the range of 15-35 mass%, and Al2O3 in the range of 10-20 mass% relative to the total amount of the glass filaments) spun out of a spinning furnace, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0081] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D x N) = 9.2 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 49.8 μm, and the coefficient of variation was 0.03. The average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, setting the measurement length to 50 m, and using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was regarded as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0082] <Production Example 3> The spinning sizing agent of blend A was applied to a plurality of glass filaments (containing SiO2 in the range of 60-66 mass%, Al2O3 in the range of 20-26 mass%, and MgO in the range of 10-15 mass% with respect to the total amount of glass filaments) spun out of a spinning furnace using an applicator, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0083] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D × N) = 8.6 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 45.1 μm, and the coefficient of variation was 0.03. The average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, setting the measurement length to 50 m, and using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was determined as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0084] <Production Example 4> The spinning sizing agent of blend A was applied to a plurality of glass filaments (E glass composition) spun out of a spinning furnace using an applicator, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound around a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0085] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2 When tension is applied that satisfies the following formula: T(cN) / (π×(D / 2)=9.6 (*D is the average diameter of the glass filaments (μm), and N is the number of the glass filaments (number)), the average yarn width is 42.4 μm, the coefficient of variation is 0.03, and the tension T is T(cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D × N) = 25.0 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 39.5 μm, and the coefficient of variation was 0.03. The average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, setting the measurement length to 50 m, and using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was regarded as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0086] <Production Example 5> The spinning sizing agent of blend A was applied to a plurality of glass filaments (containing SiO2 in the range of 60-66 mass%, Al2O3 in the range of 20-26 mass%, and MgO in the range of 10-15 mass% with respect to the total amount of glass filaments) spun out of a spinning furnace using an applicator, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0087] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D × N) = 9.8 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 39.2 μm, and the coefficient of variation was 0.03. The average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, setting the measurement length to 50 m, and using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was regarded as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0088] <Comparative Manufacturing Example 1> The spinning sizing agent of Blend B was applied by an applicator to a plurality of glass filaments (containing SiO2 in the range of 45-60 mass%, B2O3 in the range of 15-35 mass%, and Al2O3 in the range of 10-20 mass% relative to the total amount of the glass filaments) spun out of a spinning furnace, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was wound around a bobbin while being unwound and twisted to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0089] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D x N) = 9.3 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 50.1 μm, and the coefficient of variation was 0.06. The average yarn width and the coefficient of variation were determined by applying the above tension T (cN) to the glass yarn at a speed of 50 m / min, setting the measurement length to 50 m, and using an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was regarded as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0090] <Comparative Manufacturing Example 2> The spinning sizing agent of Blend B was applied to a plurality of glass filaments (containing SiO2 in the range of 60-66 mass%, Al2O3 in the range of 20-26 mass%, and MgO in the range of 10-15 mass% relative to the total amount of glass filaments) spun out of a spinning furnace using an applicator, and the glass filaments were bundled into one bundle (strand). Next, this strand was wound up on a tube without twisting to obtain a cake. Next, the obtained cake was dried. The dried cake was set in a ring twisting machine, and the strand was unwound and twisted while being wound around a bobbin to obtain a glass yarn. The physical properties of the obtained glass yarn are shown in Table 2.

[0091] The average value and the coefficient of variation of the yarn width of the obtained glass yarn were measured while applying a tension T (cN). The tension T was T (cN) / (π×(D / 2) 2When a tension was applied satisfying the following equation: D × N) = 8.6 (*D is the average diameter (μm) of the glass filaments, and N is the number of glass filaments (number of pieces)), the average yarn width was 44.1 μm, and the coefficient of variation was 0.06. Note that, to determine the average yarn width and the coefficient of variation, the glass yarn was subjected to the above tension T (cN) at a speed of 50 m / min, a measurement length of 50 m, and an ultra-high speed, high precision dimension measuring instrument LS-9006 manufactured by Keyence Corporation was used as the measuring instrument to measure the yarn width every 0.50 mm. The average of the obtained values ​​was regarded as the average yarn width, and the coefficient of variation of the yarn width was calculated by dividing the standard deviation of the obtained yarn width by the average value.

[0092] [Table 2]

[0093] As shown in Table 2, the glass yarns of Production Examples 1 to 5 are glass yarns formed by bundling a plurality of glass filaments, and a coating containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45% is formed on the surface of the glass filament, so that the ring running of the traveler is stable in the twisting process, and the standard deviation of the twist number of the glass yarn is 0.05 to 0.15 (turns / 25 mm). On the other hand, the glass yarns of Comparative Production Examples 1 and 2 do not have a coating containing non-crosslinked soybean starch and crosslinked rice starch having an amylose content of 35 to 45% formed on the surface of the glass filament, so that the ring running of the traveler is unstable in the twisting process, and the standard deviation of the twist number of the glass yarn exceeds 0.15 (turns / 25 mm).

[0094] 2. Example of glass cloth <Example 1> (1) Preparation of glass yarn The glass yarns produced in Production Example 1 were prepared as warp and weft yarns.

[0095] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0096] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.0×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0097] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 1. The physical properties of the obtained glass cloth are shown in Table 3.

[0098] <Example 2> (1) Preparation of glass yarn The glass yarns produced in Production Example 2 were prepared as warp and weft yarns.

[0099] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0100] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.2×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0101] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 2. The physical properties of the obtained glass cloth are shown in Table 3.

[0102] <Example 3> (1) Preparation of glass yarn The glass yarns produced in Production Example 3 were prepared as warp and weft yarns.

[0103] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0104] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=8.6×10 ―3(*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0105] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 3. The physical properties of the obtained glass cloth are shown in Table 3.

[0106] <Example 4> (1) Preparation of glass yarn The glass yarns produced in Production Example 4 were prepared as warp and weft yarns.

[0107] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0108] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.6×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0109] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 4. The physical properties of the obtained glass cloth are shown in Table 3.

[0110] <Example 5> (1) Preparation of glass yarn The glass yarns produced in Production Example 5 were prepared as warp and weft yarns.

[0111] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0112] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.8×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0113] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 5. The physical properties of the obtained glass cloth are shown in Table 3.

[0114] <Example 6> (1) Preparation of glass yarn The glass yarns produced in Production Example 2 were prepared as warp and weft yarns.

[0115] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and five rolls with a diameter of 160 mm were used, the contact length between the warp yarns and the five rolls was 1.15 m per warp yarn, and the warp speed was 20 m / min.

[0116] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.2×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0117] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Example 6. The physical properties of the obtained glass cloth are shown in Table 3.

[0118] <Comparative Example 1> (1) Preparation of glass yarn The glass yarns produced in Comparative Production Example 1 were prepared as warp and weft yarns.

[0119] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0120] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.3×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0121] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spray, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 1. The physical properties of the obtained glass cloth are shown in Table 4.

[0122] <Comparative Example 2> (1) Preparation of glass yarn The glass yarns produced in Comparative Production Example 2 were prepared as warp and weft yarns.

[0123] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0124] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=8.6×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0125] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 2. The physical properties of the obtained glass cloth are shown in Table 4.

[0126] <Comparative Example 3> (1) Preparation of glass yarn The glass yarns produced in Production Example 1 were prepared as warp and weft yarns.

[0127] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0128] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=4.3×10 ―3(*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0129] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spray, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 3. The physical properties of the obtained glass cloth are shown in Table 4.

[0130] <Comparative Example 4> (1) Preparation of glass yarn The glass yarns produced in Production Example 4 were prepared as warp and weft yarns.

[0131] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarns and the four rolls was 0.90 m per warp yarn, and the warp speed was 20 m / min.

[0132] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=25.0×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0133] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 4. The physical properties of the obtained glass cloth are shown in Table 4.

[0134] <Comparative Example 5> (1) Preparation of glass yarn The glass yarns produced in Production Example 3 were prepared as warp and weft yarns.

[0135] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel, and six rolls with a diameter of 160 mm were used. The contact length between the warp yarns and the six rolls was 1.31 m per warp yarn, and the warp speed was 20 m / min.

[0136] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=9.0×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0137] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 5. The physical properties of the obtained glass cloth are shown in Table 4.

[0138] <Comparative Example 6> (1) Preparation of glass yarn The glass yarns produced in Production Example 3 were prepared as warp and weft yarns.

[0139] (2) Preparation of the warp beam The prepared warp yarns were warped, sized, and beamed to prepare a warp beam. In the beaming process, the rolls other than the unwinding roll and the take-up roll were made of stainless steel and had a diameter of 160 mm. The contact length between the warp yarn and the two rolls was 0.55 m per warp yarn, and the warp speed was 20 m / min.

[0140] (3) Weaving An air jet loom was used, the above prepared warp beam was set on the loom, and the above prepared glass yarn was used as the weft. The warp tension T (cN) was calculated as T (cN) / (π×(D / 2) 2 ×N)=8.6×10 ―3 (*D is the average diameter (μm) of the glass filaments, and N is the number (number) of the glass filaments.) Plain weaving was performed so as to satisfy these conditions. During weaving, the tension of the warp threads was measured by a load cell.

[0141] (4) Other processing, etc. The woven fabric was subjected to a heat cleaning treatment by heating at an atmospheric temperature of 400° C. for 30 hours, a fiber opening treatment by high-pressure spraying, and a surface treatment by a silane coupling agent to obtain a glass cloth of Comparative Example 6. The physical properties of the obtained glass cloth are shown in Table 4.

[0142] 3. Measurement methods for physical properties (1) Glass yarn count (tex) Using the glass yarn prepared in the manufacturing example, measurements and calculations were performed according to the provisions of "7.1 Yarn count" of the Japanese Industrial Standard JIS R 3420 2013 (General test method for glass fibers).

[0143] (2) Average diameter (μm) and number (of filaments) of glass filaments in glass yarn Using the glass yarn prepared in the manufacturing example, the average diameter of the glass filaments was measured and calculated according to the method specified in "7.6 Single fiber diameter" B method (cross section method) of "General test method for glass fibers" in JIS R 3420 2013. In addition, the number of glass filaments in the glass yarn was measured in the measurement of the average diameter of the glass filaments.

[0144] (3) Cross-sectional area of ​​glass yarn (μm 2 ) The value was calculated from the average diameter of the filaments of the glass yarn and the number of glass filaments according to formula (II). Formula (II) Glass yarn cross-sectional area (μm 2 )=π×(average diameter of glass filaments in glass yarn (μm) / 2) 2 × Number of glass filaments in glass yarn

[0145] (4) Number of twists of glass yarn (twists / 25 mm) and standard deviation of the number of twists (twists / 25 mm) Using the glass yarn prepared in the manufacturing example, the standard deviation of the twist number of the glass yarn was determined by measuring the twist number per 25 mm at 10 measurement points in accordance with JIS R 3420:2013 7.5. The twist number of the glass yarn was determined by measuring the arithmetic mean value of 10 measurement points in accordance with JIS R 3420:2013 7.5.

[0146] (5) Tensile strength of glass yarn (N) Using the glass yarn prepared in the manufacturing example, measurements were taken in accordance with JIS R 3420:2013 7.4.3 using an autograph (AGS-100S) manufactured by Shimadzu Corporation, using a circular clamp with a radius of 13 mm, at a test speed of 250 mm / min and a gripping distance of 250 mm.

[0147] (6) Count (tex) of warp and weft threads in glass cloth The glass cloths obtained in the examples and comparative examples were used, and measurements and calculations were carried out in accordance with the provisions of "7.1 Thread count" of the Japanese Industrial Standard JIS R 3420 2013 (general testing method for glass fibers).

[0148] (7) The average diameter (μm) and number (of filaments) of the glass filaments in the warp and weft that make up the glass cloth The glass cloth obtained in the Examples and Comparative Examples was cut into two pieces of 30 cm square, one for observing the warp threads and the other for observing the weft threads. Each was embedded in an epoxy-based cold embedding resin (manufactured by Struers K.K., product name: Epoxy Resin Specfix-40), hardened, and polished to the extent that the warp and weft threads could be observed. Using an SEM (manufactured by JEOL Ltd., product name: JSM-6390A), the average diameter was observed and measured at a magnification of 2000x and the number of threads was observed and measured at a magnification of 500x. (i) Average diameter of the glass filaments (μm) Thirty warp threads and 30 weft threads were randomly selected, and the diameters (largest parts) of all the glass filaments in the 30 warp threads and weft threads were measured and the arithmetic mean value was calculated to obtain the average diameter of the glass filaments in the warp and weft threads. (ii) Number of pieces Thirty warp threads and 30 weft threads were randomly selected, and the total number of filaments in the 30 warp threads and weft threads was measured and the arithmetic mean value was calculated to determine the number of glass filaments in the warp and weft threads.

[0149] (8) Weave density of glass cloth (strands / 25 mm) The glass cloths obtained in the Examples and Comparative Examples were measured and calculated in accordance with the provisions of "7.9 Density (weaving density)" of the Japanese Industrial Standard JIS R 3420 2013 (general testing method for glass fibers).

[0150] (9) Coefficient of variation of warp width Ftcv, average width Ftw (μm), standard deviation of width Ftσ (μm) The glass cloths obtained in the Examples and Comparative Examples were cut to 20 cm x 20 cm, and observed in a planar direction using an optical microscope or the like. 25 warp yarns were randomly selected, and the yarn width was measured at a point 1 cm from the end for each of the 25 yarns. Measurements were then repeated 18 times every 1 cm from that point, for a total of 19 yarn widths. The arithmetic mean and standard deviation of the yarn width values ​​at the 19 points were then calculated, and the coefficient of variation (= the standard deviation / the arithmetic mean) for the 19 points was calculated. This was performed for the 25 yarns, and the arithmetic mean of the coefficients of variation calculated for each of the 25 yarns was designated as the warp width variation coefficient Ftcv.

[0151] (10) Average warp width Ftw (μm) The arithmetic mean of the yarn width values ​​at 19 points measured when calculating the warp yarn width variation coefficient Ftcv was calculated, and this was performed for the 25 yarns. The arithmetic mean of the yarn widths calculated for each of the 25 yarns was further arithmetically averaged to obtain the average warp yarn width (Ftw).

[0152] (11) Standard deviation of warp width Ftσ(μm) The standard deviation was calculated from the yarn width of a total of 19 locations measured when calculating the warp yarn width variation coefficient Ftcv described above, and the arithmetic mean value of the 19 locations. This was performed for the 25 yarns, and the value obtained by arithmetically averaging the standard deviations calculated for each of the 25 yarns was designated as the warp yarn width standard deviation (Ftσ).

[0153] (12) Tensile strength of glass cloth in the warp and weft directions (N / 25mm) For the glass cloths obtained in the Examples and Comparative Examples, a constant-speed extension-type tensile tester (manufactured by Intesco Co., Ltd.) was used in accordance with JIS R 3420:2013 7.4.2, with the test specimen length set to 25 cm, the test specimen width (width before the yarns are unraveled from both ends) to 30 mm, the gripping distance set to 15 cm, the test specimen width (width after the yarns are unraveled from both ends) to 25 mm, and the constant tensile speed set to 200 mm / min. The breaking strength was measured five times in the warp and weft directions of the glass cloth, and the arithmetic mean of the measured values ​​was regarded as the tensile strength (N / 25 mm) of the glass cloth.

[0154] (13) Thickness of glass cloth (μm) The glass cloths obtained in the examples and comparative examples were measured using an outside micrometer with a minimum display value of 0.001 mm in accordance with JIS R3420:2013 7.10.1.

[0155] (14) Mass of glass cloth (g / m 2 ) The glass cloths obtained in the examples and comparative examples were measured in accordance with JIS R 3420:2013 7.2.

[0156] (15) Evaluation of void generation in glass cloth First, the following varnish was prepared. [Varnish composition] Epoxy resin (Mitsubishi Chemical Corporation jER5045 or 1001B80) 100 parts by weight Hardener (Mitsubishi Chemical Corporation jER Cure DICY7) 3.2 parts by weight (Dicyandiamide) Curing accelerator (Dimethylbenzylamine, manufactured by Tokyo Chemical Industry Co., Ltd.) 0.18 parts by mass Dilution solvent (dimethylformamide manufactured by Kishida Chemical Co., Ltd.) 30 parts by weight

[0157] For the glass cloth obtained in the Examples and Comparative Examples, the glass cloth was cut to 10 cm x 10 cm and placed on a glass plate covered with a polyester film, and about 1 mL of the above varnish adjusted to a temperature of 20°C was gently poured on top of it, and the impregnation behavior of the glass cloth after 60 seconds was observed and photographed using a stereomicroscope under transmitted light, and the frequency and maximum length of voids observed in the warp strands constituting the glass cloth were measured to evaluate the impregnation ability according to the following criteria. In this Example, a grade of ○ or higher was considered to be acceptable. <Evaluation criteria> Voids completely disappear and are not observed... ◎ There are a few remaining voids, but the maximum length of each is 50μm or less. Residual voids with a maximum length of 50 μm or more were observed in several places, but no residual voids with a maximum length of 100 μm or more were observed. Many residual voids with a maximum length of 100 μm or more are found... ×

[0158] (16) Evaluation of glass cloth fluff For the glass cloths obtained in the Examples and Comparative Examples, a 500 mm x 1000 mm area was irradiated with light from a right angle using a glass cloth appearance inspection machine, the surface of the glass cloth was visually inspected, and the number of fuzzing (number of fuzzing) was counted. The number of fuzzing was evaluated as "◎" when it was 5 or less, "○" when it was 6 to 11, "△" when it was 12 to 19, and "×" when it was 20 or more. ○ or more (i.e., 11 or less) was considered to be pass. The fuzzing is a portion where the glass filament is cut and the glass filament protrudes from the warp (weft) yarn, and is observed as a portion where light is strongly reflected.

[0159] [Table 3]

[0160] [Table 4]

[0161] As can be seen from Table 3, the glass cloths of Examples 1 to 6 were glass cloths constituted by warp yarns and weft yarns formed by bundling a plurality of glass filaments, and had a tensile strength in the warp direction of the glass cloth of 20 to 85 (N / 25 mm) and a yarn width variation coefficient Ftcv of the warp yarns of 0.040 to 0.070, and therefore could contribute to achieving both suppression of the generation of fuzz and suppression of the generation of voids.

[0162] In particular, in Examples 1 and 3, the tensile strength of the warp yarns was 1.3 N or more, and thus the generation of fluff was further suppressed.

[0163] On the other hand, in the glass cloths of Comparative Examples 1 and 2, a glass yarn having no coating containing non-crosslinked soybean starch and crosslinked rice starch with an amylose content of 35 to 45% on the surface of the glass filaments was used as the raw glass yarn for the warp, and therefore the warp yarn width variation coefficient Ftcv exceeded 0.070, and it was not possible to simultaneously suppress the generation of fuzz and the generation of voids.

[0164] In the glass cloth of Comparative Example 3, the tension of the warp yarns, T (cN), is T (cN) / (π×(D / 2) 2 ×N) is 5.0×10 -3 As a result of weaving with a tension of less than 0.070, the warp width variation coefficient Ftcv exceeded 0.070, and the generation of fuzz could not be suppressed.

[0165] In the glass cloth of Comparative Example 4, the tension of the warp yarns, T (cN), is T (cN) / (π×(D / 2) 2 ×N) is 12.0×10 -3 As a result of weaving with a tension exceeding 0.038, the warp width variation coefficient Ftcv was less than 0.040, making it impossible to simultaneously suppress the generation of fuzz and the generation of voids.

[0166] In the glass cloth of Comparative Example 5, the beaming process was performed under conditions in which the contact length with rolls other than the unwinding roll and the take-up roll exceeded 1.27 m / roll, resulting in a warp width variation coefficient Ftcv of more than 0.070, and it was not possible to simultaneously suppress the generation of fuzz and the generation of voids.

[0167] In the glass cloth of Comparative Example 6, the beaming process was performed under conditions in which the contact length with rolls other than the unwinding roll and the take-up roll was less than 0.60 m per roll, and as a result, the warp width variation coefficient Ftcv of the glass cloth exceeded 0.070, making it impossible to simultaneously suppress the generation of fuzz and the generation of voids.

Claims

1. A glass cloth composed of warp yarns and weft yarns each formed by bundling a plurality of glass filaments, The tensile strength of the glass cloth in the warp direction is 20 to 85 (N / 25 mm), The warp yarn width variation coefficient Ftcv is 0.040 to 0.070, The warp yarn width standard deviation (Ftσ) is 3.0 to 10 μm.

2. 2. The glass cloth according to claim 1, wherein the warp yarns have a yarn width standard deviation (Ftσ) of 3.0 to 8.0 μm.

3. The glass cloth according to claim 1 or 2, wherein the average warp width Ftw is 100 to 200 μm.

4. A prepreg comprising the glass cloth according to any one of claims 1 to 3 and a thermosetting resin impregnated in the glass cloth.

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