Glass cloth, prepreg and printed wiring board

Abstract

To provide a glass cloth which does not produce vertical streaks even when it is subjected to a heating process after weaving. [Solution] The glass cloth of the present invention is a glass cloth constructed using glass fibers consisting of multiple glass filaments as warp and weft threads, and the difference between the maximum and minimum values ​​of the thermal shrinkage rate of the warp threads is in the range of 0.19% or less.

Description

[Technical Field]

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

[0002] Conventionally, glass cloth is produced by weaving glass fibers consisting of a plurality of glass filaments as warp and weft threads. In the weaving process, a predetermined line tension is applied to the warp threads, but the weft threads are inserted without any restraining force, which causes a problem of a wavy structure in the weft threads.

[0003] The wavy structure varies greatly when the line tension acting on the warp yarns varies across the width of the glass cloth. A prepreg manufactured using a glass cloth with a large variation in wavy structure will develop wavy buckling across the width, and a metal-clad laminate will develop anisotropy in dimensional change.

[0004] In order to solve the above problems, a glass cloth is known in which the average mass per unit length of the warp and weft yarns is set within a specific range (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-104996 Summary of the Invention [Problem to be solved by the invention]

[0006] Furthermore, according to Patent Document 1, the glass cloth can reduce fluctuations in the wavy structure of the weft yarns by ensuring that the line tension acting on the warp yarns is uniform in the width direction during the weaving process.

[0007] However, the glass cloth has a drawback in that, after weaving, when the glass cloth is subjected to a process of applying heat to the glass cloth, such as deoiling or heat drying (hereinafter sometimes referred to as a heating process), streak-like defects called vertical streaks occur.

[0008] In this application, the term "vertical streaks" refers to streaks that appear to run along the entire length of the warp yarns in the warp direction of the glass cloth. Glass cloth with such defects is likely to induce problems such as increased weave bending originating from the vertical streaks and increased likelihood of wrinkles due to waviness. Furthermore, when a prepreg is produced by applying resin to the glass cloth, and then a metal-clad laminate or a printed wiring board is manufactured, the amount of resin applied to the vertical streaks is reduced, which is likely to cause problems such as variations in the thickness and dielectric properties of the prepreg and abnormalities in the dimensional stability of the metal-clad laminate in the areas including the vertical streaks.

[0009] The present invention aims to eliminate such inconvenience and provide a glass cloth that does not develop warp streaks even when subjected to a heating process after weaving.

[0010] Another object of the present invention is to provide a prepreg and a printed wiring board containing the glass cloth of the present invention. [Means for solving the problem]

[0011] The inventors conducted research to solve the problem of warp streaks occurring in glass cloth that has undergone a heating process after weaving, and discovered that the occurrence of warp streaks after the heating process can be suppressed by setting the variation in the thermal shrinkage rate of the warp yarns in the width direction of the glass cloth to a specific range.

[0012] In order to achieve the above object, the glass cloth of the present invention is a glass cloth formed of glass fibers consisting of a plurality of glass filaments as warp and weft yarns, and is characterized in that the difference between the maximum and minimum values ​​of the thermal shrinkage rate of the warp yarns is in the range of 0.19% or less.

[0013] The heat shrinkage of the warp yarn can be measured as follows.

[0014] First, three warp threads each having a length of 1100 mm are taken from multiple positions on the glass cloth, and while fixing one end of each of the taken warp threads, a tension of 0.015 to 0.060 N is applied to prevent the warp thread from loosening and the monofilament (glass filament) from breaking. The warp threads are then cut at the center to a length of 1000 mm to obtain a warp thread sample for measurement.

[0015] Specifically, the measurement warp samples are collected by pulling out and collecting three warps, namely, a warp located 5 cm from one end of the glass cloth in the width direction and two warps adjacent to that warp, then pulling out and collecting three warps at a position 10 cm away from the initial sampling position in the same manner as the initial sampling position, and repeating this procedure of pulling out and collecting three warps at 10 cm intervals until a position 5 cm or more but less than 15 cm from the other end of the glass cloth is reached. When doing this, for example, in the case of a glass cloth having a width of 1300 mm, 39 measurement warp samples are collected.

[0016] Next, the obtained warp yarn sample for measurement is left to stand in a muffle furnace at a temperature of 625°C for 15 minutes, then taken out and cooled at room temperature (25°C) for 30 minutes.

[0017] Next, the cooled measurement warp sample is measured in 0.5 mm increments under a tension of 0.015 to 0.060 N so that the warp does not loosen and the monofilaments (glass filaments) do not break, and the length of the measurement warp sample after heating is taken as L. Then, the thermal shrinkage of the warp is calculated using the following formula (1).

[0018] Warp heat shrinkage rate (%) = (1000 - L) / 1000 × 100 (1) Next, for each position on the glass cloth where the warp yarns were taken, the average value of the thermal shrinkage of the three measurement warp yarn samples was calculated, and the difference between the maximum and minimum values ​​among the average values ​​at each position was taken as the difference between the maximum and minimum values ​​of the thermal shrinkage of the warp yarns.

[0019] According to the glass cloth of the present invention, the difference between the maximum and minimum values ​​of the thermal shrinkage rate of the warp yarns calculated from the thermal shrinkage rates of the warp yarns measured as described above is 0.19% or less, thereby making it possible to suppress the occurrence of warp streaks after the heating process.

[0020] Furthermore, in the glass cloth of the present invention, the standard deviation of the thermal shrinkage of the warp yarns is in the range of 0.073% or less, so that the generation of the warp streaks after the heating step can be suppressed.

[0021] The standard deviation of the heat shrinkage of the warp yarns is the standard deviation of the heat shrinkage of all the warp yarns sampled for the measurement of the heat shrinkage of the warp yarns.

[0022] The prepreg and printed wiring board of the present invention are characterized by containing the glass cloth of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, the embodiment of the present invention will be described in more detail.

[0024] The glass cloth of this embodiment is a glass cloth constructed using glass fibers consisting of a plurality of glass filaments as warp and weft yarns, and the difference between the maximum and minimum values ​​of the thermal shrinkage rate of the warp yarns is in the range of 0.19% or less.

[0025] Glass cloth is generally woven using glass fibers consisting of a plurality of glass filaments as warp and weft threads, but if the glass cloth is subjected to a process of applying heat to it after weaving, such as deoiling or heat drying (hereinafter sometimes referred to as a heating process), streak-like defects called warp streaks may occur. The warp streaks refer to streaks that appear to have appeared along the entire length of the warp threads in the warp direction of the glass cloth, and can be confirmed, for example, by visually observing the glass cloth from a 45-degree diagonal direction.

[0026] Although not wishing to be bound by a particular theory, it is believed that when the glass fibers shrink in the heating step, the tension acting on the glass fibers increases in accordance with the thermal shrinkage rate, and when there is a large variation in the thermal shrinkage rates of the warp yarns in the width direction of the glass cloth, there also occurs a variation in the tension acting on the warp yarns in the width direction of the glass cloth, making the warp streaks more likely to occur. Therefore, according to the glass cloth of this embodiment, by keeping the difference between the maximum and minimum values ​​of the thermal shrinkage rates of the warp yarns within the above range, the occurrence of warp streaks in the glass cloth can be suppressed.

[0027] In the glass cloth of this embodiment, the difference between the maximum and minimum values ​​of the thermal shrinkage of the warp yarns is in the range of 0.19% or less, preferably in the range of more than 0 and 0.19% or less, and more preferably in the range of 0.01 to 0.14% or less.

[0028] In addition, the glass cloth of the present embodiment preferably has a standard deviation of the heat shrinkage of the warp yarns calculated for all of the measurement warp yarn samples in the range of 0.073% or less. When the standard deviation of the heat shrinkage of the warp yarns is in the above range, the glass cloth of the present embodiment can further suppress the occurrence of the warp streaks.

[0029] In the glass cloth of this embodiment, the standard deviation of the heat shrinkage of the warp yarns is in the range of 0.073% or less, preferably in the range of more than 0 and 0.073% or less, and more preferably in the range of 0.001 to 0.060%.

[0030] In the glass cloth of this embodiment, the average heat shrinkage of the warp yarns is not particularly limited, but is, for example, in the range of 0.05 to 3.00%, preferably in the range of 0.15 to 2.30%, and more preferably in the range of 0.60 to 1.80%. The average heat shrinkage of the warp yarns is the average value of the heat shrinkage of all the warp yarns sampled for measuring the heat shrinkage of the warp yarns described above.

[0031] The thermal shrinkage of the glass cloth may be measured using the glass cloth before or after the heat treatment.

[0032] The heat shrinkage rate of the glass cloth can be adjusted, for example, by adjusting the heat shrinkage rate of the yarn used. Examples of methods for adjusting the heat shrinkage rate of the yarn used include a method of suppressing the variation in the composition ratio of raw materials within a certain range, a method of adjusting spinning conditions in the spinning process for producing the yarn, a method of taking a part of the yarn wound on a bobbin or a take-up tube or the like, measuring the heat shrinkage rate of the yarn, and selecting only the yarn having the desired heat shrinkage rate to weave the cloth, and a method of combining these methods.

[0033] The glass cloth of this embodiment can be produced, for example, as follows.

[0034] First, the glass raw materials prepared to obtain a glass composition for glass fiber having a desired composition are melted in a glass melting furnace to obtain molten glass (a melt of the glass composition for glass fiber).In the glass cloth of this embodiment, the glass composition for glass fiber is not particularly limited, and in addition to the E-glass composition which is the most general-purpose glass composition for glass fiber, it can be a high-strength, high-elasticity glass composition, a high-elasticity, easy-to-manufacture glass composition, a low-dielectric-constant, low-dielectric-loss-tangent glass composition, a low-thermal-expansion, low-dielectric-constant glass composition, a quartz glass composition, etc., but for example, it can be a composition containing SiO2 in the range of 40.0-70.0 mass%, Al2O3 in the range of 10.0-30.0 mass%, B2O3 in the range of 0.0-30.0 mass%, and MgO and CaO in total in the range of 0.0-25.0 mass% with respect to the total amount of glass fiber.

[0035] An example of the E-glass composition is a composition containing SiO2 in the range of 52.0 to 56.0 mass%, Al2O3 in the range of 12.0 to 16.0 mass%, MgO and CaO in the range of 20.0 to 25.0 mass%, and B2O3 in the range of 0 to 10.0 mass%, relative to the total amount of glass fibers.

[0036] An example of a high-strength, high-elastic modulus glass composition is a composition containing SiO2 in the range of 60.0 to 70.0 mass %, Al2O3 in the range of 20.0 to 30.0 mass %, and MgO in the range of 5.0 to 15.0 mass %, relative to the total amount of glass fibers.

[0037] An example of a high-elastic modulus, easily manufacturable glass composition is a composition containing, relative to the total amount of glass fibers, SiO2 in a range of 57.0 to 60.0 mass%, Al2O3 in a range of 17.5 to 20.0 mass%, MgO in a range of 8.5 to 12.0 mass%, CaO in a range of 10.0 to 13.0 mass%, and B2O3 in a range of 0.5 to 1.5 mass%, and wherein the total amount of SiO2, Al2O3, MgO, and CaO is 98.0 mass% or more.

[0038] An example of a low dielectric constant and low dielectric loss tangent glass composition is a composition containing SiO2 in the range of 48.0 to 75.0 mass %, B2O3 in the range of 15.00 to 30.0 mass %, and Al2O3 in the range of 0 to 18.0 mass %, relative to the total amount of glass fibers.

[0039] An example of a low thermal expansion glass composition is a composition containing, relative to the total amount of glass fibers, SiO in a range of 42.0 to 63.0 mass%, AlO in a range of 19.0 to 27.3 mass%, ZnO in a range of more than 3.00 mass% and not more than 13.00 mass%, PO in a range of 6.50 to 19.0 mass%, MgO in a range of 0.00 to 7.00 mass%, and LiO, NaO, and KO in total in a range of not more than 1.00 mass%.

[0040] Next, the molten glass is discharged from a container (bushing) made of a precious metal such as platinum, which has a nozzle plate on which several to several thousand nozzle tips are formed, and is cooled and solidified while being stretched by being wound up at high speed, thereby forming a fiber (this operation is sometimes called "spinning"), thereby forming a glass filament.

[0041] Here, the glass filaments discharged from one nozzle tip or hole and cooled and solidified usually have a perfectly circular cross-sectional shape and a diameter in the range of 3.0 to 35.0 μm, which is preferably in the range of 3.0 to 10.0 μm from the viewpoint of reducing the weight of the glass cloth.

[0042] Next, a sizing agent (sometimes referred to as a primary sizing agent) is applied to, for example, 10 to 3,000, preferably 25 to 500, and more preferably 40 to 300, glass filaments formed as described above using an applicator to bundle them together, and then the bundled glass filaments are wound onto a take-up tube to form a glass strand (glass fiber bundle). The bundled glass filaments (glass strand) wound onto the take-up tube are sometimes called a cake. Furthermore, the glass filaments are rewound onto a bobbin from the take-up tube while being twisted, and then wound onto the bobbin are sometimes called a glass yarn package.

[0043] Next, the glass cloth of this embodiment can be obtained by weaving the glass strands or glass yarns as warps and wefts. The glass strands or glass yarns can be selected as follows. First, 1100 mm of the surface layer glass strands or glass yarns are sampled from multiple cakes or glass yarn packages, and the thermal shrinkage of the sampled glass strands or glass yarns is measured in the same manner as in the measurement of the thermal shrinkage of the warp yarns described above. Then, from the measured cakes or glass yarn packages, those whose thermal shrinkage differs from the reference value by 0.10% or less are selected.

[0044] During the weaving process, a sizing agent is used for bundling the glass filaments and arranging the warp threads. Examples of the sizing agent include starch-based or PVA (polyvinyl alcohol)-based film-forming agents. The sizing agent may contain an oil or a softener.

[0045] The amount of the sizing agent attached to the glass cloth is preferably 0.1 to 5.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the glass fiber yarns. Note that the range of the amount of the sizing agent attached and the amount of the sizing agent attached when not otherwise specified represent the average amount of the sizing agent attached to the warp or weft yarns.

[0046] The weaving can be carried out by a known loom, and examples of the loom include a jet loom such as an air jet or water jet loom, a shuttle loom, a rapier loom, etc. Examples of the weaving method used by the loom include plain weave, satin weave, sash weave, twill weave, etc., with plain weave being preferred from the viewpoint of production efficiency.

[0047] Next, the glass cloth of this embodiment can be obtained by subjecting the glass cloth to a deoiling treatment, a surface treatment, or a fiber-opening treatment. In this embodiment, the deoiling treatment and the surface treatment correspond to the heating step after weaving. The order of the deoiling treatment, the surface treatment, and the fiber-opening treatment is not particularly limited, and any treatment may be performed first.

[0048] In the deoiling treatment, the glass cloth is placed in a heating furnace at an atmospheric temperature in the range of 350 to 450°C for a period of time in the range of 40 to 80 hours, whereby the sizing agent and the sizing agent adhering to the glass cloth are thermally decomposed.

[0049] The surface treatment is carried out by immersing the glass cloth in a solution of a surface treatment agent, squeezing out excess water, and then heating and drying the glass cloth at a temperature in the range of 80 to 180°C for a time in the range of 1 to 30 minutes to obtain a glass cloth.

[0050] The opening treatment is a treatment for widening the width of warp and weft yarns. Examples of the opening treatment include an opening treatment using water jet pressure while applying a tension in the range of 30 to 400 N in the warp direction of the glass cloth, an opening treatment using high-frequency vibrations with a liquid as a medium, an opening treatment using the pressure of a fluid with surface pressure, and an opening treatment using pressure with a roll. Note that the opening treatment includes a step of drying a liquid such as water used to open the glass cloth if the liquid adheres to the glass cloth.

[0051] The surface treatment agent solution used for the surface treatment may contain a silane coupling agent, a weak acid, and a surfactant.

[0052] Examples of the silane coupling agent include aminosilane, chlorosilane, epoxysilane, mercaptosilane, vinylsilane, and (meth)acrylicsilane. In this embodiment, the silane coupling agent may be used alone or in combination of two or more.

[0053] Examples of aminosilanes include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-anilinopropyltrimethoxysilane.

[0054] Examples of chlorosilane include γ-chloropropyltrimethoxysilane.

[0055] Examples of epoxy silanes include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0056] Examples of mercaptosilane include γ-mercaptotrimethoxysilane.

[0057] Examples of vinylsilanes include vinyltrimethoxysilane and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane.

[0058] Examples of (meth)acrylic silanes include γ-methacryloxypropyltrimethoxysilane.

[0059] Examples of the weak acid include acetic acid, citric acid, and propionic acid.

[0060] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. In this embodiment, the surfactants may be used alone or in combination of two or more.

[0061] The content of each component in the glass composition can be measured using an ICP optical emission spectrometer for the light element Li, and a wavelength dispersive X-ray fluorescence analyzer for the other elements. Specifically, the content of each component in the glass composition can be measured as follows.

[0062] First, glass cloth is cut to an appropriate size, placed in a platinum crucible, and melted in an electric furnace at a temperature of 1400 to 1650°C for 6 hours while stirring, to obtain a homogeneous molten glass. If organic matter is attached to the surface of the glass cloth or if glass fibers are contained in the organic matter (resin) mainly as a reinforcing material, the glass cloth is heated in a muffle furnace at 300 to 650°C for 2 to 24 hours, for example, to remove the organic matter before use.

[0063] The resulting molten glass is then poured onto a carbon plate to produce glass cullet, which is then crushed and powdered to produce glass powder. The light element Li is quantitatively analyzed using an ICP optical emission spectrometer after the glass powder is thermally decomposed with acid. The other elements are quantitatively analyzed using a wavelength-dispersive X-ray fluorescence analyzer after the glass powder is formed into a disk shape using a press. The results of these quantitative analyses are converted into oxides to calculate the content and total amount of each component, and the content (mass %) of each of the aforementioned components can be determined from these values.

[0064] The weave density of the warp and weft yarns of the glass cloth of this embodiment is, for example, in the range of 20 to 160 yarns / 25 mm, preferably in the range of 30 to 110 yarns / 25 mm, more preferably in the range of 40 to 100 yarns / 25 mm, and even more preferably in the range of 50 to 69 yarns / 25 mm.

[0065] The thickness of the glass cloth of the present embodiment is, for example, in the range of 8 to 200 μm, preferably in the range of 20 to 150 μm, more preferably in the range of 30 to 90 μm, and further preferably in the range of 35 to 80 μm.

[0066] The mass per unit area of ​​the glass cloth of this embodiment is, for example, 8 to 110 g / m 2 The range is preferably 15 to 100 g / m 2 More preferably, it is in the range of 20 to 60 g / m 2 The range is.

[0067] The weight of the warp and weft of the glass cloth of this embodiment is, for example, in the range of 0.8 to 135 g / 1000 m, and preferably in the range of 1 to 25 g / 1000 m.

[0068] The width of the glass cloth of this embodiment is, for example, in the range of 300 to 2000 mm.

[0069] The prepreg or printed wiring board of this embodiment includes the glass cloth of this embodiment and a thermoplastic resin or a thermosetting resin impregnated into the glass cloth.

[0070] In the prepreg or printed wiring board of this embodiment, the thermoplastic resin or thermosetting resin impregnated into the glass cloth of this embodiment is not particularly limited. Examples of the thermosetting resin include epoxy resin, phenol resin, unsaturated polyester resin, melamine resin, modified polyimide resin, modified polyphenylene ether resin, etc., and examples of the thermoplastic resin include polyamide resin, polyimide resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polyphenylene ether resin, modified polyphenylene ether resin, fluororesin, etc.

[0071] Next, examples of the present invention and comparative examples will be described. [Example]

[0072] Example 1 In this example, a yarn package was prepared, wound with multiple E260 yarns (fiber diameter 7.4 μm, yarn weight 19.0 g / 1000 m) consisting of multiple glass filaments with glass composition A, which contained 59 mass% SiO2, 12 mass% Al2O3, 23 mass% B2O3, and a total of 6 mass% other components, and had a low dielectric constant and low dielectric loss tangent composition with a dielectric constant of 4.0 at 10 GHz and a dielectric loss tangent of 0.0010 at 10 GHz. Next, a surface 1100 mm of the yarn from each yarn package was sampled, and the thermal shrinkage of the yarn was measured in the same manner as in the measurement of the thermal shrinkage of the warp yarns described above. Yarn packages with a thermal shrinkage of 1.01 to 1.16% were selected. Next, the selected yarns were used as warp and weft to make glass cloth equivalent to IPC4412 standard #2116 type (warp density: 59 threads / 25 mm, weft density: 57 threads / 25 mm, mass per unit area: 90.0 g / m 2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0073] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.08%, the difference between the maximum and minimum values ​​(hereinafter referred to as maximum-minimum difference) was 0.09%, and the standard deviation was 0.046%. The results are shown in Table 1.

[0074] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment. The deoiling treatment was carried out by heating at a temperature in the range of 400 to 450°C for 60 hours. Next, the glass cloth after the deoiling treatment was visually inspected from a 45-degree diagonal direction to check for the presence or absence of vertical lines. A case in which there were no vertical lines was evaluated as "Good", and a case in which there were one or more vertical lines was evaluated as "Poor". The results are shown in Table 1.

[0075] Example 2 In this example, a D520 yarn (fiber diameter 5.0 μm, yarn weight 9.5 g / 1000 m) consisting of a plurality of glass filaments having the glass composition A was used, and a yarn having a thermal shrinkage rate in the range of 1.42 to 1.47% was selected. The same procedure as in Example 1 was repeated except that a glass cloth (warp weave density: 53 threads / 25 mm, weft weave density: 53 threads / 25 mm, mass per unit area: 41.5 g / m) corresponding to the IPC4412 standard #1078 type was produced. 2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0076] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.45%, the maximum / minimum difference was 0.05%, and the standard deviation was 0.026%. The results are shown in Table 1.

[0077] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 1, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0078] Example 3 In this example, a D1040 yarn (fiber diameter 5.0 μm, yarn weight 4.8 g / 1000 m) consisting of a plurality of glass filaments having the glass composition A was used, and a yarn having a thermal shrinkage rate in the range of 1.57 to 1.68% was selected. The same procedure as in Example 1 was repeated except that a glass cloth (warp weave density: 65 threads / 25 mm, weft weave density: 67 threads / 25 mm, mass per unit area: 26.0 g / m) corresponding to the IPC4412 standard #1035 type was produced. 2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0079] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.66%, the maximum / minimum difference was 0.04%, and the standard deviation was 0.034%. The results are shown in Table 1.

[0080] Next, the obtained glass cloth was subjected to a fiber-opening treatment and a surface treatment in exactly the same manner as in Example 1, except that a deoiling treatment was carried out by heating the obtained glass cloth at a temperature in the range of 400 to 450°C for 45 hours, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0081] Example 4 In this example, a 1300 mm wide glass cloth was obtained in exactly the same manner as in Example 2, except that a D520 yarn (fiber diameter 5.0 μm, yarn weight 9.5 g / 1000 m) consisting of multiple glass filaments with glass composition B, which contains 54 mass% SiO2, 12 mass% Al2O3, 23 mass% B2O3, and a total of 11 mass% of other components, and has a low dielectric constant and low dielectric loss tangent composition with a dielectric constant of 4.5 at 10 GHz and a dielectric loss tangent of 0.0018 at 10 GHz, was used. The yarn was selected to have a thermal shrinkage rate in the range of 1.21 to 1.32%. The obtained glass cloth was visually inspected from a 45-degree diagonal direction to check for the presence or absence of vertical streaks, and no vertical streaks were observed.

[0082] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.27%, the maximum / minimum difference was 0.05%, and the standard deviation was 0.034%. The results are shown in Table 1.

[0083] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 1, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0084] Example 5 In this example, a D500 yarn (fiber diameter 5.0 μm, yarn weight 10.1 g / 1000 m) consisting of a plurality of glass filaments having glass composition C, which contains 54 mass % of SiO2, 15 mass % of Al2O3, 19 mass % of B2O3, and a total of 12 mass % of other components, and has a low dielectric constant and low dielectric loss tangent composition with a dielectric constant of 4.7 at 10 GHz and a dielectric loss tangent of 0.0025 at 10 GHz, was used, and the process was exactly the same as in Example 2, except that a yarn having a heat shrinkage rate in the range of 1.06 to 1.16% was selected. A glass cloth (warp weave density: 53 threads / 25 mm, weft weave density: 53 threads / 25 mm, mass per unit area: 43.0 g / m) corresponding to the IPC4412 standard #1078 type was used. 2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0085] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.10%, the maximum / minimum difference was 0.04%, and the standard deviation was 0.030%. The results are shown in Table 1.

[0086] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 1, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0087] Example 6 In this example, E225 yarn (fiber diameter 7.4 μm, yarn weight 22.5 g / 1000 m) consisting of a plurality of glass filaments having glass composition D, which is a high-strength, high-elastic modulus composition containing 64 mass% of SiO2, 25 mass% of Al2O3 within the range, 10 mass% of MgO, and a total of 1 mass% of other components, was used, and a glass cloth (warp weave density: 59 threads / 25 mm, weft weave density: 57 threads / 25 mm, mass per unit area: 104.5 g / m) corresponding to IPC4412 standard #2116 type was produced in exactly the same manner as in Example 1, except that yarn having a thermal shrinkage rate in the range of 0.10 to 0.20% was selected.2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0088] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 0.17%, the maximum / minimum difference was 0.02%, and the standard deviation was 0.031%. The results are shown in Table 1.

[0089] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 3, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0090] Example 7 In this example, a D900 yarn (fiber diameter 5.0 μm, yarn weight 5.6 g / 1000 m) consisting of a plurality of glass filaments having a glass composition E, which is an E-glass composition containing 55 mass% of SiO2, 15 mass% of Al2O3, 22 mass% of CaO, 5 mass% of B2O3, and a total of 3 mass% of other components, was used, and the same procedure as in Example 3 was repeated except that a yarn having a thermal shrinkage rate in the range of 0.35 to 0.45% was selected. The yarn was then subjected to a sieving process. The yarn was then sieved to obtain a glass cloth of type #1035 according to IPC4412 (warp weave density: 65 threads / 25 mm, weft weave density: 67 threads / 25 mm, mass per unit area: 29.5 g / m2). 2 ) was woven to obtain a glass cloth having a width of 1,300 mm. The obtained glass cloth was visually inspected from a 45-degree oblique direction to check for the presence or absence of vertical lines, and no vertical lines were found.

[0091] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 0.40%, the maximum / minimum difference was 0.06%, and the standard deviation was 0.035%. The results are shown in Table 1.

[0092] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 3, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0093] Comparative Example In this comparative example, a D520 yarn (fiber diameter 5.0 μm, yarn weight 9.5 g / 1000 m) consisting of a plurality of glass filaments having the glass composition A was used, and a glass cloth having a width of 1300 mm was obtained in exactly the same manner as in Example 2, except that no selection of the yarn was performed based on the thermal shrinkage rate. The obtained glass cloth was visually inspected from a 45-degree diagonal direction to check for the presence or absence of warp streaks, and no warp streaks were found.

[0094] Next, the heat shrinkage of the warp yarns of the obtained glass cloth was measured by the above-mentioned method, and the average heat shrinkage was 1.42%, the maximum / minimum difference was 0.29%, and the standard deviation was 0.100%. The results are shown in Table 1.

[0095] Next, the obtained glass cloth was subjected to a deoiling treatment, a fiber-opening treatment, and a surface treatment in exactly the same manner as in Example 2, and the glass cloth after the deoiling treatment was checked for the presence or absence of vertical streaks and evaluated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0096] [Table 1]

[0097] From Table 1, it is clear that the glass cloths of Examples 1 to 7, in which the maximum-minimum difference (difference between the maximum and minimum values) of the thermal shrinkage rates of the warp yarns is in the range of 0.19% or less, can prevent the occurrence of warp streaks after the deoiling treatment, which is a heating step. On the other hand, it is clear that the glass cloth of Comparative Example, in which the maximum-minimum difference of the thermal shrinkage rates of the warp yarns is 0.29%, which is more than 0.19%, cannot prevent the occurrence of warp streaks after the deoiling treatment.

Claims

1. A glass cloth constructed using glass fibers consisting of a plurality of glass filaments as warp and weft yarns, characterized in that the difference between the maximum and minimum values ​​of the thermal shrinkage rate of the warp yarns is 0.19% or less.

2. A glass cloth comprising glass fibers consisting of a plurality of glass filaments as warp and weft threads, characterized in that the standard deviation of the thermal shrinkage of the warp threads is 0.073% or less.

3. A prepreg comprising the glass cloth according to claim 1 or 2.

4. A printed wiring board comprising the glass cloth according to claim 1 or 2.

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