WO2021090756A1

WO2021090756A1 - Glass cloth

Info

Publication number: WO2021090756A1
Application number: PCT/JP2020/040613
Authority: WO
Inventors: 服部　剛士; 大介西中
Original assignee: ユニチカ株式会社; ユニチカグラスファイバー株式会社
Priority date: 2019-11-06
Filing date: 2020-10-29
Publication date: 2021-05-14
Also published as: JP6818278B1; JP2021075805A; TW202132435A; KR102351904B1; KR20210057051A; JPWO2021090756A1; TWI771792B

Abstract

The present invention addresses the problem of providing a low-mass glass cloth that, even when impregnated with a resin solution to produce a prepreg that contains, by mass, a low proportion of the glass cloth, can particularly effectively suppress the occurrence of pinholes and longitudinal wrinkles.　A glass cloth that has a mass of no more than 10.0 g/m². The design value Iwd for the gaps between adjacent warp threads is no more than 95 μm, and the design value Ifd for the gaps between adjacent weft threads is no more than 95 μm. The ratio (Iw/If) of the actual value (Iw) of the gaps between adjacent warp threads and the actual value (If) of the gaps between adjacent weft threads is 1.23–1.45. The basket hole area fraction is 12.0%–20.0%.

Description

Glass cloth

The present invention relates to a glass cloth.

In recent years, printed wiring boards have been required to be lighter in weight with the miniaturization of electronic devices, and the materials used are also required to have a low mass. In order to manufacture a printed wiring board, a prepreg in which a glass cloth is impregnated with a resin is used. However, as the weight of the electronic device is reduced, the prepreg is also required to have a low mass. The glass cloth contained in the prepreg is also required to have a low mass.

As a low-mass glass cloth, for example, a glass cloth satisfying the following (i) to (iv) is known (see, for example, Patent Document 1).
(I) The degree of openness represented by the following formula (1) is 70 to 90% for the warp and 95 to 120% for the weft.
Fineness (%) = {(25 × 1000) / WD-I} / (D × N) × 100 (1)
WD: Weaving density of warp or weft (book / 25 mm)
I: Gap spacing between adjacent warp threads or weft threads (μm)
D: Average filament diameter (μm) of warp or weft
N: Average number of warp or weft filaments (threads)
(Ii) Either the gap between the adjacent warp threads or the gap between the adjacent weft threads is 100 μm or less.
(Iii) The thickness measured according to JIS R 3420: 2013 7.10.1 is 14 μm or less.
(Iv) The cross mass measured according to JIS R 3420: 2103 7.2 is 11 g / m ² or less.

According to the glass cloth of Patent Document 1, while reducing the thickness to 14 μm or less, for example, when a thin prepreg having a thickness of 20 μm or less and a substrate using the prepreg are used, the occurrence of pinholes is suppressed. It is said that it can be done.

Further, as a low-mass glass cloth, glass filaments having a diameter in the range of 3.0 to 4.2 μm are composed of warp threads and weft threads in which 14 to 55 threads are focused, and the weaving density of the warp threads and weft threads is formed. Has a thickness in the range of 86 to 140 lines / 25 mm, a thickness in the range of 7.5 to 12.0 μm, and a mass in the range of 6.0 to 10.0 g per ^{1 m 2, and the thickness of the glass cloth is the warp.} It is shown as the value divided by the average value of the diameter of the glass filament and the diameter of the glass filament of the weft (glass cloth thickness / {(the diameter of the glass filament of the warp + the diameter of the glass filament of the weft) / 2}). A glass cloth having an average number of steps in the range of 2.00 or more and less than 3.00, and the degree of opening of the warp (thread width of the warp / (diameter of the glass filament constituting the warp × number of glass filaments constituting the warp). )) And the openness of the weft (the width of the weft / (the diameter of the glass filaments constituting the weft x the number of glass filaments constituting the weft))) ((the openness of the warp x the openness of the weft)) The average openness indicated by 1/2) is in the range of 1.000 to 1.300, and is indicated by the ratio of the warp yarn width to the weft yarn width (warp yarn width / weft yarn width). Glass cloths having a thread width ratio in the range of 0.720 to 0.960 are known (see, for example, Patent Document 2).

According to the glass cloth of Patent Document 2, even if the average number of stages is less than 3.00, the occurrence of pinholes can be suppressed in the prepreg using the glass cloth, and the fluffing of the glass cloth is small. It is said that the excellent appearance quality of prepreg can be maintained.

Japanese Unexamined Patent Publication No. 2017-43873 Japanese Unexamined Patent Publication No. 2018-21274

From the viewpoint of insulation reliability, a low-mass prepreg is often used as having a low mass ratio of glass cloth, for example, the ratio of the mass of the glass cloth to the total mass of the prepreg is about 10 to 40% by mass. .. However, as a result of examination by the present inventor, when the glass cloths of Patent Documents 1 and 2 are impregnated with a resin solution and cured by assuming that the mass ratio of the glass cloth is low when the glass cloth is made into a prepreg, the obtained prepreg can be produced. I learned that wrinkles (vertical wrinkles) that run in the direction of the machine may occur.

Therefore, the present invention solves the above-mentioned problems, and even when a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, pinholes are generated and the above-mentioned vertical wrinkles are generated. The main issue is to provide a glass cloth that can suppress the occurrence remarkably effectively.

When the present inventor investigated the cause of the above problem, when a low-mass glass cloth was impregnated with a resin solution so as to have a low mass ratio of the glass cloth and cured, the warp direction (glass) of the glass cloth was examined. The tension in the weft direction (glass cloth width direction) is significantly lower than the tension in the cloth length direction. Then, in the glass cloth of Patent Document 1, it was considered that the wefts tend to move slightly in the width direction of the glass cloth due to the curing shrinkage when the resin impregnated in the glass cloth is cured, and as a result, the vertical wrinkles are likely to occur. .. Specifically, in the glass cloth of Patent Document 1, the following factors (i) to (iii) are combined to cause the weft to move slightly in the width direction of the glass cloth, and the vertical wrinkles are likely to occur accordingly. Thought.
(I) The distance between the gaps between adjacent warp threads is larger than the distance between the gaps between adjacent weft threads, and the weft threads are not sufficiently gripped by the warp threads.
(Ii) Originally a thin glass cloth, the warp and weft are thin and flexible.
(Iii) When a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low and cured, the resin solution is applied so that the mass ratio of the glass cloth is relatively high. The weft is more easily moved in the width direction of the glass cloth due to curing shrinkage than when it is impregnated and cured.

Further, the present inventor has performed an excessive fiber-spreading treatment on the glass cloth of Patent Document 2, and in particular, each filament constituting the weft is bent, and vertical wrinkles are likely to occur due to this. Thought. That is, when each filament constituting the weft is bent, each filament is present in the glass cloth in a loosened state. Then, the loose filament is in a state where it can easily move in the width direction of the glass cloth, and if a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low and cured, the glass cloth is cured. It was considered that the wefts slightly moved in the width direction of the glass cloth due to the loosening of the filaments during the contraction, and the vertical wrinkles were likely to occur accordingly.

On the other hand, considering the above-mentioned mechanism of action, both suppression of pinhole generation and suppression of vertical wrinkle generation can be achieved by increasing the warp density and weft density of the glass cloth or by increasing the number of filaments in the warp and weft. It was also thought that it should be done. However, the present inventors increase the mass of the glass cloth and the mass of the prepreg when the warp density and the weft density of the glass cloth are increased or the number of filaments in the warp and the weft is increased. I learned that there is a problem of getting rid of it. Further, if the mass ratio of the glass cloth is too high in the prepreg, the glass cloth is exposed from the surface of the prepreg, and the signal layer and the exposed glass cloth are in direct contact with each other, which impairs the insulation reliability. I also learned.

Further, the present inventors have increased the warp density and the weft density of the glass cloth as the glass cloth becomes thinner, increased the number of filaments in the warp and the weft, and performed excessive fiber opening treatment. It was also found that when the gap space surrounded by the adjacent warp and weft threads becomes extremely small, the glass cloth tends to be internally distorted and vertical wrinkles are likely to occur.

Therefore, as a result of diligent studies by the present inventor in order to solve the above problems, (1) in the glass cloth, the gap design value Iwd between adjacent warp threads and the gap design value Ifd between adjacent weft threads are set to 95 μm or less. (2) In order to sufficiently grip the warp and the weft while keeping the glass cloth mass to a specific mass or less, the measured gap value (Iw) between the adjacent warp threads and the measured gap value (If) between the adjacent weft threads are used. The ratio (Iw / If) should be 1.23 or more and 1.45 or less, and (3) the area ratio of the basket hole (opening portion) formed by the adjacent warp and weft should be 12.0% or more. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg by satisfying that the content is 20.0% or less, pinholes occur and the above. It was found that the occurrence of vertical wrinkles can be suppressed remarkably effectively. The present invention has been completed by further studies based on such findings.

That is, the present invention provides the inventions of the following aspects.
Item 1. A glass cloth with a mass of 10.0 g / m ^{2 or less.}
The gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm or less, and the gap design value Ifd between adjacent weft threads represented by the following formula (2) is 95 μm or less.
The ratio (Iw / If) of the measured gap between adjacent warp threads (Iw) and the measured gap between adjacent weft threads (Iw / If) is 1.23 or more and 1.45 or less, and the following formula (3) is used. A glass cloth having a basket hole area ratio of 12.0% or more and 20.0% or less.

Item 2. The gap design value Iwd between the adjacent warp threads is 70 μm or more and 95 μm or less, and the gap design value Ifd between the adjacent weft threads is 70 μm or more and 95 μm or less, and the basket hole area ratio of the glass cloth is 12.0% or more and 18 Item 2. The glass cloth according to Item 1, which is 0.0% or less.
Item 3. A prepreg containing the glass cloth according to Item 1 or 2.
Item 4. Item 3. The prepreg according to Item 3, wherein the ratio of the mass of the glass cloth to the mass of the prepreg (mass of the glass cloth / mass of the prepreg) is 10 to 40% by mass.
Item 5. The mass is 10 g / m ² or less, the gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm or less, and the gap design value Ifd between adjacent weft threads represented by the following formula (2) is 95 μm or less. Including the process of opening the glass cloth
In the fiber opening treatment, the ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less, and the following formula is used. The basket hole area ratio shown in (3) is 12% or more and 20% or less.
Manufacturing method of glass cloth.

According to the glass cloth of the present invention, the glass cloth having a mass of 10.0 g / m ² or less has a gap design value Iwd between adjacent warp threads of 95 μm or less and a gap design value Ifd between adjacent weft threads of 95 μm. The ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less, and the basket hole area ratio. Is 12.0% or more and 20.0% or less, so that pinholes occur when a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg. And the above-mentioned vertical wrinkle generation can be suppressed remarkably effectively.

1. 1. A glass cloth having a glass cloth mass of 10 g / m ² or less, a gap design value Iwd between adjacent warp threads shown in the formula (1) of 95 μm or less, and a gap design value between adjacent weft threads shown in the formula (2). Ifd is 95 μm or less, and the ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less. Moreover, the basket hole area ratio represented by the formula (3) is 12.0% or more and 20.0% or less. Hereinafter, the glass cloth of the present invention will be described in detail.

Glass cloth of the present invention, the mass can fall within 10.0 g / m ² or less, but is preferably 9.5 g / m ² or less. The lower limit of the above mass range is not particularly limited, but for example, 5.0 g / m ² or more, 6.0 g / m ² or more is preferable, 7.0 g / m ² or more is more preferable, and 8.0 g / m or more is preferable. ² or more is more preferable, and 8.5 g / m ² or more is particularly preferable. Specifically, the mass of the glass cloth of the present invention is 5.0 g / m ² or more and 10 g / m ² or less, preferably 6.0 g / m ² or more and 10 g / m ² or less, and more preferably 7.0 g / m. ² or 9.5 g / m ² or less, more preferably include 8.5 g / m ² or more 9.5 g / m ² or less. In the present invention, the above mass is measured and calculated in accordance with "7.2 Mass of cloth and mat (mass)" of Japanese Industrial Standard JIS R 3420 2013 (general test method for glass fiber). The value.

In the glass cloth of the present invention, the gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm or less, and the gap design value Ifd between adjacent weft threads represented by the following formula (2) is 95 μm or less. The lower limit of the gap design value Iwd between the warp threads and the gap design value Ifd between the weft threads is not particularly limited, but from the viewpoint of making it easier to achieve both suppression of pinhole occurrence and suppression of vertical wrinkle occurrence. , 60 μm or more is preferable, 70 μm or more is more preferable, and 75 μm or more is further preferable. Specific examples of the gap design value Iwd between the warp threads in the glass cloth of the present invention include 60 μm or more and 95 μm or less, preferably 70 μm or more and 95 μm or less, and more preferably 75 μm or more and 95 μm or less. Further, as the gap design value Ifd between the wefts in the glass cloth of the present invention, specifically, 60 μm or more and 95 μm or less, preferably 70 μm or more and 95 μm or less, more preferably 75 μm or more and 95 μm or less can be mentioned. In particular, when both the gap design value Iwd and the gap design value Ifd are 75 μm or more, the ratio of the gap measurement value (Iw) between adjacent warp threads and the gap measurement value (If) between adjacent weft threads, which will be described later, ( It becomes easy to preferably provide the range of Iw / If) and the range of the basket hole area ratio.

The gap design value Iwd of the warp yarn and the gap design value Ifd of the weft yarn are, first, in the warp yarn and the weft yarn (glass yarn) composed of a plurality of filaments, all the filaments constituting the glass yarn have no gap in the glass yarn width direction. Virtually placed in a row. At this time, in the virtual, the width (μm) of the virtual glass yarn can be calculated by the average filament diameter × the average number of filaments (that is, Dw × Nw in the case of warp yarns and Df × Nf in the case of weft yarns). Next, since the weaving density (warp density is Ww and weft density is Wf) is the number of glass threads between 25 mm (25,000 μm) as described later, 25,000 μm is divided by the weaving density (25,000 / Ww in the case of warp threads). In the case of weft yarns, 25,000 / Wf), the sum of the width of the glass yarns and the gap spacing between the adjacent glass yarns can be calculated. Then, by subtracting the virtual glass thread width from the sum of the widths of the glass threads and the adjacent glass threads, the gap spacing between the virtual adjacent warp threads and the virtual adjacent weft threads in the above virtual are obtained. The gaps between the warp yarns can be calculated, and these are set as the gap design value Iwd between the adjacent warp yarns and the gap design value Ifd between the adjacent weft yarns, respectively.

The glass cloth cited as a specific example in Patent Document 2 is designed so that the gap design value Iwd of the warp and the gap design value Ifd of the weft exceed 100 μm, and this is subjected to excessive fiber opening treatment. It is manufactured by a method of reducing the gap. Therefore, the present inventor presents that the glass cloth of the embodiment of Patent Document 2 exists in the glass cloth in a state where each filament is loosened, and due to this, each filament constituting the weft is particularly bent. As a result, it was thought that vertical wrinkles were likely to occur. Then, the present inventor has found that the occurrence of pinholes and the occurrence of vertical wrinkles can be remarkably suppressed by setting the gap design value Iwd of the warp threads and the gap design value Ifd of the weft threads within the above-mentioned specific ranges.

In the glass cloth of the present invention, the warp density Ww and the weft density Wf (book / 25 mm) of the glass cloth are not particularly limited, but a low-mass glass cloth is made of a resin so that the mass ratio of the glass cloth is low. When impregnating the solution to form a prepreg, 90 lines / 25 mm or more and 160 lines / 25 mm or less are preferable, and 95 lines are preferable, from the viewpoint of making it easier to achieve both suppression of pinhole generation and suppression of vertical wrinkle generation. It is more preferably / 25 mm or more and 150 lines / 25 mm or less, and further preferably 100 lines / 25 mm or more and 125 lines / 25 mm or less. In the present invention, the warp density and the weft density are measured and calculated in accordance with "7.9 Density (Weaving Density)" of Japanese Industrial Standards JIS R 3420 2013 (Glass Fiber General Test Method). The value.

In the glass cloth of the present invention, the average filament diameter Dw of the filaments constituting the warp threads (glass threads) constituting the glass cloth and the average filament diameter Df of the filaments constituting the weft threads (glass threads) are not particularly limited, but are low. When a glass cloth having a mass is impregnated with a resin solution so that the mass ratio of the glass cloth is low to form a prepreg, it is easier to achieve both suppression of pinhole generation and suppression of vertical wrinkle generation. From the viewpoint of the above, 2.5 μm or more and 4.0 μm or less is preferable, and 3.0 μm or more and 3.7 μm or less is more preferable.

In the glass cloth of the present invention, the average number of filaments Nw constituting the warp threads (glass threads) constituting the glass cloth and the average number of filaments Nf of the filaments constituting the weft threads (glass threads) are such that a glass cloth having a low mass is used as the glass. When impregnating a resin solution so that the mass ratio of the cloth is low to form a prepreg, 25 or more pieces are made from the viewpoint of making it easier to achieve both suppression of pinhole generation and suppression of vertical wrinkle generation. 50 or less is preferable, 30 or more and 40 or less are more preferable, and 34 or more and 40 or less are further preferable.

In the present invention, the average filament diameters (Dw and Df) and the average number of filaments (Nw and Nf) are measured and calculated as follows.

That is, two pieces of glass cloth cut into 30 cm squares are prepared, one for observing warp threads and the other for observing weft threads, each of which is embedded in epoxy resin (trade name 3091 manufactured by Marumoto Struas Co., Ltd.). After curing, the warp and weft threads are polished to an observable degree, and the filament diameter is observed and measured at a magnification of 1000 times and the number of filaments is measured at a magnification of 500 times using a scanning electron microscope (SEM).
(1) Average filament diameter (μm) of glass thread
Thirty warp threads and weft threads are randomly selected, and the diameters (largest portion) of all filaments of the 30 glass threads are measured to calculate an average value, which is used as the average filament diameter of the warp threads and weft threads.
(2) Average number of filaments (filament)
Twenty warp threads and weft threads are randomly selected, and the total number of filaments of the 20 glass threads is measured to calculate the average value, which is used as the average filament diameter of the warp threads and the weft threads.

In the glass cloth of the present invention, the counts (texes) of the warp and weft are not particularly limited, but a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low to form a prepreg. From the viewpoint of making it easier to achieve both suppression of pinhole generation and suppression of vertical wrinkle generation, 0.5 tex or more and 1.2 tex or less are preferable, and 0.6 tex or more and 1.1 tex or less are more preferable. , 0.9 tex or more and 1.1 tex or less is more preferable. In the present invention, the warp and weft counts are values measured and calculated in accordance with the "7.1 count" of the Japanese Industrial Standards JIS R 3420 2013 (glass fiber general test method).

In the glass cloth of the present invention, the glass material constituting the warp and weft is not particularly limited, and a known glass material can be used. Specific examples of the glass material include non-alkali glass (E glass), acid-resistant alkali-containing glass (C glass), high-strength and high-elasticity glass (S glass, T glass, UT glass (Unitica glass fiber stock). (Manufactured by the company), etc.), alkali resistant glass (AR glass), low dielectric glass (NE glass, L glass, LU glass (manufactured by Unitika Glass Fiber Co., Ltd.), etc.) and the like. Among these glass materials, preferably non-alkali glass (E glass) having high versatility can be mentioned. The glass fibers constituting the glass cloth may be made of one kind of glass material, or may be a combination of two or more kinds of glass fibers made of different glass materials.

In the glass cloth of the present invention, the ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less. By setting the above ratio (Iw / If) to 1.45 or less, the weft threads can be sufficiently gripped by the warp threads, and the low-mass glass cloth is impregnated with the resin solution so that the mass ratio of the glass cloth is low. It is possible to prevent the weft from moving slightly in the width direction of the glass cloth during curing, and to sufficiently prevent the occurrence of vertical wrinkles due to this. Further, by setting the above ratio to 1.23 or more, pinholes are sufficiently generated when the low-mass glass cloth is impregnated with the resin solution and cured so that the mass ratio of the glass cloth is low. It becomes possible to suppress. When a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low to form a prepreg, it is possible to further suppress the occurrence of pinholes and the above-mentioned vertical wrinkles. From the viewpoint of facilitation, the ratio (Iw / If) is preferably 1.25 or more and 1.45 or less, more preferably 1.30 or more and 1.40 or less, and further preferably 1.34 to 1.44.

In the present invention, the measured gap value Iw between adjacent warp threads and the measured gap value If between adjacent weft threads are measured and calculated as follows. That is, first, in the glass cloth, the warp and weft threads are cut from three arbitrarily selected points to a size in which 100 consecutive gaps can be observed, and the sample is used as a sample. Next, with respect to the sample, the gap interval is observed and measured at a magnification of 150 times using a microscope. Specifically, from the normal direction of the glass cloth plane, 100 continuous gaps are observed on the same straight line in each of the cross warp direction and the weft direction. This is performed for the three arbitrarily selected locations, the gap spacing is measured at a total of 300 locations for both the warp and the weft, and the average value of the gap spacing at the 300 locations is used as the measured clearance value.

In the glass cloth of the present invention, the measured gap value Iw between adjacent warp threads is not particularly limited as long as the above ratio (Iw / If) is satisfied, and examples thereof include 70 μm and more and 120 μm or less. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, both suppression of pinhole generation and suppression of vertical wrinkle generation are further achieved. From the viewpoint, the measured value Iw of the gap between the adjacent warp threads is more preferably 80 μm or more and 110 μm or less, and further preferably 90 μm or more and 110 μm or less.

Further, in the glass cloth of the present invention, the measured gap value If between adjacent weft threads is not particularly limited as long as the above ratio (Iw / If) is satisfied, and examples thereof include 60 μm and more and 100 μm or less. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, both suppression of pinhole generation and suppression of vertical wrinkle generation are further achieved. From the viewpoint, the measured value If of the gap between adjacent weft threads is more preferably 60 μm or more and 80 μm or less, and further preferably 62 μm or more and 80 μm or less.

In the glass cloth of the present invention, the ratio (Iw / Iwd) of the measured gap value (Iw) between adjacent warp threads to the gap design value Iwd (μm) between adjacent warp threads is, for example, 1.00 or more. 30 or less can be mentioned. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, both suppression of pinhole generation and suppression of vertical wrinkle generation are further achieved. From the viewpoint, the ratio (Iw / Iwd) is preferably 1.10 or more and 1.18 or less.

Further, in the glass cloth of the present invention, the ratio (If / Ifd) of the gap measured value (If) between adjacent wefts to the gap design value Ifd (μm) between adjacent wefts is, for example, 0.70 or more. 1.00 or less can be mentioned. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, both suppression of pinhole generation and suppression of vertical wrinkle generation are further achieved. From the viewpoint, the ratio (If / Ifd) is preferably 0.80 or more and 1.00 or less.

In the glass cloth of the present invention, the basket hole area ratio represented by the following formula (3) is 12.0% or more and 20.0% or less. In the glass cloth of the present invention, by setting the basket hole area ratio to 12% or more, internal distortion is less likely to occur in the glass cloth, and the low mass glass cloth is made of a resin so that the mass ratio of the glass cloth is low. Vertical wrinkles are less likely to occur when the solution is impregnated to form a prepreg. Further, the glass cloth of the present invention has a basket hole area of 20.0% or less, so that a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low to form a prepreg. When doing so, it becomes easier to suppress the occurrence of pinholes. When a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, both suppression of pinhole generation and suppression of vertical wrinkle generation are further achieved. From the viewpoint, the baskethole area ratio is preferably 12.0% or more and 18.0% or less, and more preferably 12.0% or more and 17.0% or less.

In the glass cloth of the present invention, the basket hole area is not particularly limited as long as it satisfies the above-mentioned basket hole area ratio, but a low-mass glass cloth is made of a resin so that the mass ratio of the glass cloth is low. From the viewpoint of further suppressing the occurrence of pinholes and the above-mentioned vertical wrinkles when impregnating the solution to form a prepreg, for example, 3000 to 12000 μm ² is mentioned, and 5000 to ^{9000 μm 2} is more preferable. More preferably, 5500 to 8500 μm ^2. The basket hole area is calculated by multiplying the measured gap value Iw (μm) between adjacent warp threads and the measured gap value If (μm) between adjacent weft threads.

In the glass cloth of the present invention, the basket hole area design value is not particularly limited, but when a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg. From the viewpoint of further suppressing the occurrence of pinholes and the occurrence of vertical wrinkles, for example, 3000 to 12000 μm ² is mentioned, 5000 to ^{9000 μm 2} is more preferable, and 5500 to ^{9000 μm 2} is further preferable. .. In the present invention, the basket hole area design value is a value calculated by multiplying the above-mentioned gap design value Iwd (μm) between adjacent warp threads and the gap design value Ifd (μm) between adjacent weft threads. is there.

In the glass cloth of the present invention, the ratio of the basket hole area to the basket hole area design value (basket hole area / basket hole area design value) is not particularly limited, but a low mass glass cloth is used as the mass of the glass cloth. When impregnating the resin solution so that the ratio is low to form a prepreg, 0.8 to 1.2 is set from the viewpoint of further suppressing the occurrence of pinholes and the above-mentioned vertical wrinkles. It is mentioned, and 0.9 to 1.1 is more preferable.

The thickness of the glass cloth of the present invention is not particularly limited, but for example, 12 μm or less can be mentioned, and 11 μm or less is preferable. As the lower limit value, for example, 6 μm or more is mentioned, 7 μm or more is preferable, and 8 μm or more is more preferable. Specific examples of the thickness of the glass cloth of the present invention include 6 μm or more and 12 μm or less, preferably 7 μm or more and 11 μm or less, and more preferably 8 μm or more and 11 μm or less.

The weaving structure of the glass cloth is not particularly limited, and examples thereof include plain weave, satin weave, twill weave, diagonal weave, and ridge weave. Of these, plain weave is preferable. Further, the glass cloth of the present invention is preferably a glass cloth roll product. Examples of the length of the glass cloth roll product include 100 m or more, preferably 100 m or more and 3000 m or less.

The method for producing the glass cloth of the present invention is not particularly limited as long as a glass cloth satisfying the above-mentioned characteristics can be obtained, but a preferable example of the method for producing the glass cloth of the present invention will be described below.

A preferable example of the method for producing a glass cloth of the present invention is a method for producing a glass cloth having a mass of 10 g / m ² or less, in which the gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm. Below, while setting the gap design value Ifd between adjacent wefts represented by the following formula (2) to 95 μm or less, the gap measured value (Iw) between adjacent warp threads and the gap measured value (If) between adjacent wefts Examples thereof include a method of performing fiber opening treatment so that the ratio (Iw / If) is 1.23 or more and 1.45 or less, and the basket hole area ratio represented by the following formula (3) is 12% or more and 20% or less. ..

As described above, the weaving density of the warp and weft that make up the glass cloth, the average diameter and the number of filaments that make up the warp and the weft are adjusted, and the gap design value between the adjacent warp threads and the gap design between the adjacent weft threads are adjusted. As for the values, the ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less, and the basket hole. When a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low by performing a fiber opening treatment so that the area ratio is 12% or more and 20% or less to form a prepreg. In addition, it is possible to achieve both suppression of pinhole generation and suppression of vertical wrinkle generation.

That is, a preferred example of the method for producing a glass cloth of the present invention is a mass of 10 g / m ² or less, a gap design value Iwd between adjacent warp threads of 95 μm or less, and a gap design value Ifd between adjacent weft threads of 95 μm or less. Including the step of performing the fiber opening treatment on the glass cloth, the fiber opening treatment is the ratio (Iw) of the gap measured value (Iw) between adjacent warp threads and the gap measured value (If) between adjacent weft threads. / If) is 1.23 or more and 1.45 or less, and the basket hole area ratio is 12% or more and 20% or less.

A glass cloth having a mass of 10 g / m ² or less, a gap design value Iwd between adjacent warp threads of 95 μm or less, and a gap design value Iffd between adjacent weft threads of 95 μm or less is the weaving density of the warp threads and weft threads used. It can be obtained by weaving the warp and weft by adjusting the average diameter and the number of filaments constituting the warp and weft. As a method for weaving the glass cloth, any conventionally known method may be adopted. For example, after the warp threads are subjected to a warping step and a gluing step, a jet loom (for example, an air jet loom, a water jet loom, etc.) may be used. ), A method of driving the weft using a sulzer loom, a repeater loom, or the like.

The woven glass cloth is subjected to fiber opening treatment so that the ratio (Iw / If) is 1.23 or more and 1.45 or less and the basket hole area ratio is 12% or more and 20% or less. As a method of fiber-spreading treatment, for example, water flow processing in which water flow pressure is applied; high-frequency vibration using water (for example, degassed water, ion-exchanged water, deionized water, electrolytic cation water, electrolytic anion water, etc.) as a medium. Processing to load; pressurization processing with a roll and the like can be mentioned. A known method can be adopted as a method for adjusting the degree of opening of the warp and weft, specifically, in the warp direction (glass cloth length direction) and the weft direction (glass cloth width direction) of the glass cloth. An example is a method in which the fiber opening process is performed while adjusting by applying tension. To apply tension to the glass cloth, for example, a pinch expander, a curved rubber roller, a rotary rotating roller, a Mirabeau roller, or a tenter may be used.

From the viewpoint that the glass cloth after the fiber-spreading treatment is suitably satisfied with a range in which the above ratio (Iw / If) is 1.23 or more and 1.45 or less and the basket hole area ratio is 12% or more and 20% or less. As a method for opening the fibers, water flow processing in which the tension in the warp direction is adjusted to 18 to 22 N / m and the tension in the weft direction is adjusted to 5 to 10 N / m and the water flow pressure is set to 0.9 to 1.6 MPa. There is a way to do this.

If a substance (such as a sizing agent) that hinders the adhesion or impregnation of the resin used as a prepreg is attached to the glass cloth before the fiber-spreading treatment or the glass cloth after the fiber-spreading treatment, for example, heat cleaning. It is preferable to remove the substance by treatment or the like. Further, it is preferable that the heat-cleaned glass cloth is surface-treated with a conventionally known silane coupling agent. Such a surface treatment means may be a conventionally known means, and examples thereof include a method of impregnating a glass cloth with a silane coupling agent, a method of applying the surface treatment, and a method of spraying. The heat cleaning treatment and the surface treatment may be performed before the defibration treatment or after the defibration treatment.

2. Prepreg The prepreg of the present invention is characterized by including the above-mentioned glass cloth of the present invention. Specifically, the prepreg of the present invention is characterized by containing the glass cloth and a matrix resin composition impregnated in the glass cloth.

The ratio of the mass of the glass cloth in the prepreg of the present invention is not particularly limited. Although the glass cloth has a ^{low mass of 10.0 g / m 2} or less, it has the above-mentioned characteristics. Therefore, even if the mass ratio of the glass cloth in the prepreg is as low as 40% by mass or less, pinholes in the prepreg The occurrence and the occurrence of the vertical wrinkles can be effectively suppressed. In view of these characteristics, a preferable example of the prepreg of the present invention is that the mass ratio of the glass cloth is low. Specifically, the ratio of the mass of the glass cloth (g / m ² ) to the mass of the prepreg (total mass of the glass cloth and the matrix resin composition) (g / m ² ) (mass of the glass cloth / prepreg). The mass) is preferably 10 to 40% by mass, more preferably 20 to 30% by mass, still more preferably 22 to 30% by mass, and particularly preferably 22 to 25% by mass.

The matrix resin composition contains a thermosetting resin. The thermosetting resin is not particularly limited as long as it is a heat-curable resin, and is, for example, a phenol resin, an epoxy resin, a non-halogen epoxy resin, a cyanate resin, a maleimide resin, a bismaleimide resin, a modified bismaleimide resin, or an isocyanate. Examples thereof include resins, benzocyclobutene resins, vinyl resins, bismaleimide triazine resins, phenol resins, and thermosetting polyphenylene ether resins. The thermosetting resin may be used alone or in combination of two or more.

Further, the matrix resin composition may contain a curing agent and a curing accelerator, if necessary. The curing agent and curing accelerator may be appropriately selected according to the type of thermosetting resin to be used.

Further, it is preferable that the matrix resin composition contains an inorganic filler other than glass cloth. Examples of the inorganic filler include silicas such as natural silica, molten silica, amorphous silica, and hollow silica; boehmite; molybdenum compounds such as molybdenum oxide and zinc molybdate; alumina, talc, calcined talc, mica, and short glass fibers. Glass fillers such as spherical glass (E glass, T glass, UT glass (manufactured by Unitika Glass Fiber Co., Ltd.), S glass, D glass, NE glass, L glass, LU glass (manufactured by Unitika Glass Fiber Co., Ltd.), etc. are used as glass materials. Glass filler) and the like. These inorganic fillers may be used alone or in combination of two or more.

The average particle size (D50) of the inorganic filler is not particularly limited, but is preferably 10 nm or more from the viewpoint of providing excellent characteristics when used in a thin multilayer printed wiring board application and further improving dispersibility. 5.0 μm, more preferably 100 nm to 2.0 μm, still more preferably 100 nm to 1.0 μm. Here, the average particle size (D50) means the median diameter, and is the diameter at which the large side and the small side when the particle size distribution of the measured powder is divided into two are equal amounts. More specifically, the average particle size (D50) is the total volume integrated from the small particles when the particle size distribution of the powder dispersed in the methyl ethyl ketone is measured by a laser diffraction scattering type particle size distribution measuring device. It is a value (median diameter) when 50% of the product is reached.

The inorganic filler is preferably surface-treated with a surface-treating agent such as a silane coupling agent from the viewpoint of improving moisture resistance. The type of the surface treatment agent is not particularly limited, but for example, an aminosilane coupling agent, a vinylsilane coupling agent, an epoxysilane coupling agent, a styrylsilane coupling agent, a methacrylsilane coupling agent, a silicone oligomer coupling agent, etc. Can be mentioned. Among these, an aminosilane coupling agent is preferable. The aminosilane coupling agent is a silane having one or two amino groups and one silicon atom, preferably a silane having one amino group and one silicon atom. Examples of commercially available products of silica surface-treated with an aminosilane coupling agent include "SC-2050KNK" (average particle size 0.5 μm, manufactured by Admatex Co., Ltd.).

In the matrix resin composition, the mass ratio of the inorganic filler to the thermosetting resin is not particularly limited, but for example, the inorganic filler is 10 to 400 mass by mass with respect to 100 parts by mass of the solid content of the thermosetting resin. It is preferably parts, more preferably 20 to 100 parts by mass, and even more preferably 20 to 50 parts by mass.

The prepreg of the present invention can be produced by a known method. Specifically, as a method for producing a prepreg of the present invention, the glass cloth is impregnated with a resin solution (varnish) containing a matrix resin composition, and then, if necessary, volatile components are volatilized by drying and thermosetting. Examples thereof include a method of curing the sex resin to a B stage state (semi-cured state).

The resin solution (varnish) used in the production of the prepreg of the present invention may consist only of the matrix resin composition (nonvolatile component), but may also contain a diluting solvent (volatile component). The concentration of the non-volatile component in the resin solution (varnish) is, for example, 50 to 100% by mass.

The use of the prepreg of the present invention is not particularly limited, but it is suitable as a constituent material of a printed wiring board.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

(1) Production of glass cloth and prepreg (Example 1)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.3 μm, an average number of filaments of 35, and a twist of 0.5Z is used and woven by an air jet loom, and the warp density is 125 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 125 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 85 μm, a gap design value Ifd between adjacent weft threads of 85 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.23, and the baskethole area ratio was 19.6%.

Next, two types of varnishes for obtaining prepreg were prepared.
<Composition of varnish A>
Epoxy resin (jER5045B80 manufactured by Mitsubishi Chemical Corporation) 100 parts by mass Hardener (jER Cure DICY7 manufactured by Mitsubishi Chemical Corporation) 2.7 parts by mass (dicyandiamide)
Curing accelerator (2-ethyl-4-methylimidazole manufactured by Mitsubishi Chemical Corporation) 0.2 parts by mass Diluting solvent (dimethylformamide manufactured by Kishida Chemical Co., Ltd.) 20 parts by mass Inorganic filler (Admatex Co., Ltd. "SC-2050KNK" ”Average particle size 0.5 μm, spherical silica surface-treated with a silane coupling agent) 25 parts by mass

<Composition of varnish B>
Modified bismaleimide resin (HR3070 manufactured by Printec Co., Ltd.) 60 parts by mass Curing accelerator (2-ethyl-4-methylimidazole manufactured by Mitsubishi Chemical Co., Ltd.) 0.3 parts by mass Diluting solvent (methyl ethyl ketone manufactured by Kishida Chemical Co., Ltd.) 40 parts by mass Part Inorganic filler ("SC-2050KNK" manufactured by Admatex Co., Ltd., average particle size 0.5 μm, spherical silica surface-treated with silane coupling agent) 25 parts by mass

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish A adhered was adjusted, and the prepregrol product A was obtained by continuously winding the varnish A through a dryer so that the gel time indicating the degree of curing of the resin was about 110 seconds.

Separately, the obtained glass cloth roll product was continuously fed out in the longitudinal direction (transverse direction), and this time, the varnish B was sufficiently immersed in the varnish B to apply the varnish B to the glass cloth. Subsequently, as the proportion of glass cloth mass relative to the glass cloth varnish B was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish B adhered was adjusted, and the mixture was passed through a dryer so that the gel time was about 110 seconds and wound as it was to obtain a prepregrol product B.

(Example 2)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.1 μm, an average number of filaments of 34, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 135 /. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 135 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 80 μm, a gap design value Ifd between adjacent weft threads of 80 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.29, and the baskethole area ratio was 18.4%.

Next, as the varnish for obtaining the prepreg, varnish A and varnish B were prepared as in Example 1.

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish A adhered was adjusted, the drying conditions were adjusted so that the gel time was around 110 seconds, and the varnish A was passed through a dryer and wound as it was to obtain a prepregrol product A.

Separately, the obtained glass cloth roll product was continuously fed out in the longitudinal direction (transverse direction), and this time, the varnish B was sufficiently immersed in the varnish B to apply the varnish B to the glass cloth. Subsequently, as the proportion of glass cloth mass relative to the glass cloth varnish B was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish B adhered was adjusted, the drying conditions were adjusted so that the gel time was around 110 seconds, and the varnish was passed through a dryer and wound as it was to obtain a prepregrol product B.

(Example 3)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 115 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 115 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 88 μm, a gap design value Ifd between adjacent weft threads of 88 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.34, and the baskethole area ratio was 16.4%.

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish A adhered was adjusted, and the mixture was passed through a dryer so that the gel time was about 110 seconds and wound as it was to obtain a prepregrol product A.

(Example 4)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 105 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 94 μm, a gap design value Ifd between adjacent weft threads of 94 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.38, and the baskethole area ratio was 14.9%.

(Example 5)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 110 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 110 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.2 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 83 μm, a gap design value Ifd between adjacent weft threads of 83 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.40, and the baskethole area ratio was 12.5%.

(Example 6)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is used and woven by an air jet loom, and the warp density is 120 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 122 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 79 μm, a gap design value Ifd between adjacent weft threads of 75 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.44, and the baskethole area ratio was 13.8%.

(Example 7)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 110 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 94 μm, a gap design value Ifd between adjacent weft threads of 83 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.44, and the baskethole area ratio was 15.0%.

Further, the separately obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction), and this time, the glass cloth was sufficiently immersed in the varnish B to apply the varnish B to the glass cloth. Subsequently, as the proportion of glass cloth mass relative to the glass cloth varnish B was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 1 The amount of varnish B adhered was adjusted, and the mixture was passed through a dryer so that the gel time was about 110 seconds and wound as it was to obtain a prepregrol product B.

(Comparative Example 1)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 105 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 50 N / m in the warp direction (length direction), a tension of 20 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.2 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 94 μm, a gap design value Ifd between adjacent weft threads of 94 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.02, and the baskethole area ratio was 19.1%.

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 2 The amount of varnish A adhered was adjusted, the drying conditions were adjusted so that the gel time was around 110 seconds, and the varnish A was passed through a dryer and wound as it was to obtain a prepregrol product A.

Separately, the obtained glass cloth roll product was continuously fed out in the longitudinal direction (transverse direction), and this time, the varnish B was sufficiently immersed in the varnish B to apply the varnish B to the glass cloth. Subsequently, as the proportion of glass cloth mass relative to the glass cloth varnish B was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 2 The amount of varnish B adhered was adjusted, the drying conditions were adjusted so that the gel time was around 110 seconds, and the varnish was passed through a dryer and wound as it was to obtain a prepregrol product B.

(Comparative Example 2)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.1 μm, an average number of filaments of 32, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 148 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 148 yarns / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) JNC Corporation) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 70 μm, a gap design value Ifd between adjacent weft threads of 70 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.13, and the baskethole area ratio was 19.4%.

(Comparative Example 3)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 100 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 100 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 30 N / m in the warp direction (length direction), a tension of 20 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 106 μm, a gap design value Ifd between adjacent weft threads of 106 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.22, and the baskethole area ratio was 18.3%.

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 2 The amount of varnish A adhered was adjusted, the drying conditions were adjusted so that the gel time indicating the degree of curing of the resin was about 110 seconds, and the varnish A was passed through a dryer and wound as it was to obtain a prepregrol product A.

(Comparative Example 4)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 125 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 125 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), the tension of 20 N / m is also applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 56 μm, a gap design value Ifd between adjacent weft threads of 56 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.25, and the baskethole area ratio was 9.8%.

(Comparative Example 5)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 110 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 110 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 98 μm, a gap design value Ifd between adjacent weft threads of 98 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.29, and the baskethole area ratio was 18.9%.

(Comparative Example 6)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 38, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 110 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, the fiber was opened by water flow processing at a pressure of 0.8 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 101 μm, a gap design value Ifd between adjacent weft threads of 90 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.33, and the baskethole area ratio was 21.7%.

(Comparative Example 7)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 115 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 115 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 0.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 88 μm, a gap design value Ifd between adjacent weft threads of 88 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.34, and the basket hole area ratio was 21.5%.

(Comparative Example 8)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 105 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 0.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 94 μm, a gap design value Ifd between adjacent weft threads of 94 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.35, and the basket hole area ratio was 21.5%.

(Comparative Example 9)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is used and woven by an air jet loom, and the warp density is 130 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 130 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 50 N / m in the warp direction (length direction), a tension of 25 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 63 μm, a gap design value Ifd between adjacent weft threads of 63 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.50, and the basket hole area ratio was 8.6%.

(Comparative Example 10)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is used and woven by an air jet loom, and the warp density is 125 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 125 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 1.0 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 70 μm, a gap design value Ifd between adjacent weft threads of 70 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.53, and the basket hole area ratio was 13.3%.

(Comparative Example 11)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 110 yarns / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 110 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, while the tension of the glass cloth is set to 20 N / m in the warp direction (length direction), a tension of 10 N / m is applied in the weft direction (width direction) while grasping both ends of the glass cloth in the weft direction with a tenter. Then, a fiber opening treatment was performed by water flow processing at a pressure of 0.5 MPa to obtain a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 83 μm, a gap design value Ifd between adjacent weft threads of 83 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.58, and the basket hole area ratio was 16.8%.

The obtained glass cloth roll product was continuously fed out in the longitudinal direction (longitudinal direction) and sufficiently immersed in the varnish A to apply the varnish A to the glass cloth. Subsequently, as the ratio of the mass of glass cloth for a glass cloth varnish A was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 2 The amount of varnish A adhered was adjusted, and the mixture was passed through a dryer so that the gel time was about 110 seconds and wound as it was to obtain a prepregrol product A.

Separately, the obtained glass cloth roll product was continuously fed out in the longitudinal direction (transverse direction), and this time, the varnish B was sufficiently immersed in the varnish B to apply the varnish B to the glass cloth. Subsequently, as the proportion of glass cloth mass relative to the glass cloth varnish B was applied using a gap roll prepreg mass ^{(g / m 2) (g} / m 2) satisfies the conditions described in Table 2 The amount of varnish B adhered was adjusted, and the mixture was passed through a dryer so that the gel time was about 110 seconds and wound as it was to obtain a prepregrol product B.

(Comparative Example 12)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 40, and a twist number of 0.5Z is woven by an air jet loom, and the warp density is 105 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 105 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, the tension of the glass cloth is set to 50 N / m in the warp direction (length direction), and the fiber opening treatment is performed by water flow processing at a pressure of 1.0 MPa in a state where the tension is not applied in the weft direction (width direction). Obtained a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 94 μm, a gap design value Ifd between adjacent weft threads of 94 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.64, and the baskethole area ratio was 17.6%.

(Comparative Example 13)
As the warp and weft, the glass material is E glass, and glass yarn having an average filament diameter of 3.6 μm, an average number of filaments of 36, and a twist of 0.5Z is woven by an air jet loom, and the warp density is 115 / yarn. A glass cloth roll having a width of 130 cm in a plain weave having a width of 25 mm and a weft density of 115 threads / 25 mm was obtained. Then, the spinning sizing agent and the weaving sizing agent adhering to the obtained glass cloth were removed by heating at 400 ° C. for 30 hours. Then, a glass cloth is immersed in an aqueous solution containing 10 g / L of a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Co., Ltd.) and squeezed with a padder roll. After that, it was dried and cured at 120 ° C. for 1 minute. Then, the tension of the glass cloth is set to 50 N / m in the warp direction (length direction), and the fiber opening treatment is performed by water flow processing at a pressure of 0.5 MPa in a state where the tension is not applied in the weft direction (width direction). Obtained a glass cloth roll product. The obtained glass cloth has a gap design value Iwd between adjacent warp threads of 88 μm, a gap design value Ifd between adjacent weft threads of 88 μm, and a gap measurement value (Iw) between adjacent warp threads and a gap measurement between adjacent weft threads. The ratio to the value (If) was 1.70, and the baskethole area ratio was 17.1%.

(2) Measurement and evaluation method The measurement and evaluation of the physical properties of the glass cloth and prepregrol were carried out by the following methods.

1. 1. Average filament diameter Dw and Df (μm), average number of filaments Nw and Nf (lines)
This was performed by the method described above using a scanning electron microscope (SEM) (trade name JSM-6390A manufactured by JEOL Ltd.).

2. Count (tex)
This was done by the method described above.

3. 3. Warp density Ww and weft density Wf (book / 25 mm)
This was done by the method described above.

4. Measured gap between adjacent warp threads Iw and measured gap between adjacent weft threads If (μm)
This was done by the method described above.

5. Mass (g / m ² ) and thickness (μm) of glass cloth
The mass of the glass cloth was measured and calculated in accordance with "7.2 Mass of cloth and mat (mass)" of Japanese Industrial Standard JIS R 3420 2013 (general test method for glass fiber). The thickness of the glass cloth was measured and calculated according to Method A specified in "7.10.1 Cloth Thickness" of Japanese Industrial Standard JIS R 3420 2013 (Glass Fiber General Test Method).

6. Evaluation of Pinhole Occurrence For each of the obtained prepreg roll products A and B, three prepregs (1 set) cut into a quadrangle of 400 mm × 400 mm were collected from arbitrary three locations arranged in the width direction and parallel direction. A total of 50 sets of this were collected, and a total of 150 prepregs were prepared. The number of pinholes was visually counted for each of the 150 prepregs, and the prepreg having 4 or less pinholes per prepreg was regarded as a non-defective product, and the non-defective product rate (%) of the 150 prepregs was determined. Those with a non-defective rate of 90% or more were accepted.

7. Evaluation of vertical wrinkles Occurrence of vertical wrinkles was observed by visually inspecting each of the obtained prepregrol products A and B at a length of 1000 m at random, and the number of vertical wrinkles per 100 m in length was calculated. evaluated. The vertical wrinkles were counted to have a length of 10 cm or more.
A: The number of vertical wrinkles was 0.0 / 100 m.
B: The number of vertical wrinkles was 0.1 to 1.0 / 100 m.
C: The number of vertical wrinkles was 1.1 to 5.0 / 100 m.
D: The number of vertical wrinkles was 5.1 or more and exceeded 100 m.

(3) Results Tables 1 and 2 show the physical characteristics of Examples and Comparative Examples.

The glass cloths of Examples 1 to 7 have a mass of 10 g / m ² or less, a gap design value Iwd between adjacent warp threads of 95 μm or less, a gap design value between adjacent weft threads of 95 μm or less, and a gap between adjacent warp threads. The ratio (Iw / If) of the measured value (Iw) to the gap measured value (If) between adjacent wefts is 1.23 or more and 1.45 or less, and the basket hole area ratio is 12.0% or more and 20.0%. It met the following: In the glass cloths of Examples 1 to 7, when a low-mass glass cloth is impregnated with a resin solution so as to have a low mass ratio of the glass cloth to form a prepreg, pinholes and vertical wrinkles are remarkably suppressed. It was done. In particular, in the glass cloths of Examples 3 to 7 in which the basket hole area ratio satisfies 12.0% or more and 18.0% or less, the non-defective product rate of the pinhole occurrence evaluation is 99% or more, and the occurrence of pinholes in the prepreg is caused. It was able to be suppressed remarkably.

On the other hand, since the ratio (Iw / If) of the glass cloths of Comparative Examples 1 and 2 was less than 1.23, the low mass glass cloth was prepared as a resin solution so that the mass ratio of the glass cloth was low. The occurrence of pinholes could not be sufficiently suppressed when the glass was impregnated and cured.

The glass cloth of Comparative Example 3 has a ratio (Iw / If) of less than 1.23 and a ratio (Iw / If) of less than 1.23 under the condition that the gap design value Iwd between adjacent warp threads and the gap design value Ifd between adjacent weft threads exceed 95 μm. Since the basket hole area ratio is 12.0% or more and 20.0% or less, each filament is present in the glass cloth in a loosened state, and due to this, each filament constituting the weft is particularly eye-catching. It caused bending, which made it easy for vertical wrinkles to occur. Further, in the glass cloth of Comparative Example 3, the occurrence of pinholes in the prepreg could not be sufficiently suppressed.

The glass cloth of Comparative Example 4 has a gap design value Iwd between adjacent warp threads of 95 μm or less, a gap design value Ifd between adjacent weft threads of 95 μm or less, and a ratio (Iw / If) of 1.23 or more and 1.45 or less. However, since the baskethole area ratio is less than 12.0%, internal distortion is likely to occur in the glass cloth, and the low-mass glass cloth is made of resin so that the mass ratio of the glass cloth is low. When the solution was impregnated to form a prepreg, it was difficult to suppress the generation of vertical wrinkles. Further, the glass cloth of Comparative Example 4 had a mass exceeding ^{10 g / m 2.}

The glass cloth of Comparative Example 5 has a gap design value Iwd between adjacent warp threads and a gap design value Ifd between adjacent weft threads exceeding 95 μm, which is adjacent to the measured gap design value (Iw) between adjacent warp threads. Open so that the ratio (Iw / If) to the measured gap (If) between the wefts is 1.23 or more and 1.45 or less, and the basket hole area ratio is 12.0% or more and 20.0% or less. Since the fiber treatment was applied, each filament was present in the glass cloth in a loosened state, and as a result, each filament constituting the weft was bent, which caused vertical wrinkles. It was easy.

The glass cloth of Comparative Example 6 had a gap design value Iwd between adjacent warp threads exceeding 95 μm, and the fiber opening treatment was performed under relatively mild conditions. Therefore, the basket hole area ratio was 20.0. %, And even if the ratio (Iw / If) satisfies 1.23 or more and 1.45 or less, the low mass glass cloth is impregnated with the resin solution so that the mass ratio of the glass cloth is low. It was difficult to suppress the occurrence of pinholes when the prepreg was formed.

The glass cloths of Comparative Examples 7 and 8 have a gap design value Iwd between adjacent warp threads of 95 μm or less, a gap design value Iffd between adjacent weft threads of 95 μm or less, and a ratio (Iw / If) of 1.23 or more. Although it satisfies 45 or less, since the basket hole area ratio exceeds 20.0%, a low-mass glass cloth is impregnated with a resin solution so that the mass ratio of the glass cloth is low. It was difficult to suppress the occurrence of pinholes when using the prepreg.

Since the glass cloth of Comparative Example 9 has a ratio (Iw / If) of more than 1.45 and a basket hole area ratio of less than 12.0%, the glass cloth is liable to cause internal strain and has a low mass. When the glass cloth was impregnated with a resin solution to form a prepreg so that the mass ratio of the glass cloth was low, it was difficult to suppress the generation of vertical wrinkles.

In the glass cloths of Comparative Examples 10 to 13, the gap design value Iwd between adjacent warp threads is 95 μm or less, the gap design value between adjacent weft threads Ifd is 95 μm or less, and the basket hole area ratio is 12.0% or more and 20.0. % Or less, but the ratio (Iw / If) exceeded 1.45, so that the weft was not sufficiently gripped by the warp, and the mass ratio of the glass cloth was low. When the resin solution is impregnated and cured so as to be low, it becomes difficult to suppress the delicate movement of the weft in the width direction of the glass cloth, and due to this, the occurrence of vertical wrinkles can be sufficiently suppressed. There wasn't.

Claims

A glass cloth with a mass of 10.0 g / m 2 or less.
The gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm or less, and the gap design value Ifd between adjacent weft threads represented by the following formula (2) is 95 μm or less.
The ratio (Iw / If) of the measured gap between adjacent warp threads (Iw) and the measured gap between adjacent weft threads (Iw / If) is 1.23 or more and 1.45 or less, and the following formula (3) is used. A glass cloth having a basket hole area ratio of 12.0% or more and 20.0% or less.
The gap design value Iwd between the adjacent warp threads is 70 μm or more and 95 μm or less, and the gap design value Ifd between the adjacent weft threads is 70 μm or more and 95 μm or less, and the basket hole area ratio of the glass cloth is 12.0% or more and 18 The glass cloth according to claim 1, which is 0.0% or less.
A prepreg containing the glass cloth according to claim 1 or 2.
The prepreg according to claim 3, wherein the ratio of the mass of the glass cloth to the mass of the prepreg (mass of the glass cloth / mass of the prepreg) is 10 to 40% by mass.
The mass is 10 g / m 2 or less, the gap design value Iwd between adjacent warp threads represented by the following formula (1) is 95 μm or less, and the gap design value Ifd between adjacent weft threads represented by the following formula (2) is 95 μm or less. Including the process of opening the glass cloth
In the fiber opening treatment, the ratio (Iw / If) of the measured gap value (Iw) between adjacent warp threads and the measured gap value (If) between adjacent weft threads is 1.23 or more and 1.45 or less, and the following formula is used. The basket hole area ratio shown in (3) is 12% or more and 20% or less.
Manufacturing method of glass cloth.