Glass cloth, prepreg, and printed wiring board

Abstract

The invention provides glass cloth. The present invention addresses the problem of making it possible to suppress uneven impregnation time of resin with respect to glass filaments for warp yarns. When the glass cloth is made into a prepreg, excellent adhesion between the glass cloth and a resin can be achieved without deteriorating the production efficiency of the prepreg. The glass cloth according to the present invention is provided with warp yarns and weft yarns, is formed from a glass strand (1) comprising a plurality of glass filaments (2), and has an adhesion dispersion number represented by formula (1) within the range of 0.027-0.077. Bmax-Bmin / N... (1) (where Bmax represents the maximum number of adhesions when the number of adhesions is measured in each of the regions, Bmin represents the minimum number of adhesions, N represents the number of glass filaments included in the glass filament for warp, and each of the regions is divided into a left region, a center region, and a right region, and N represents the number of glass filaments included in the glass filament for warp. These regions are equal in width in the yarn width direction of the glass precursor for warp yarns. )

Description

Technical Field

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

[0002] Conventionally, a warp protective agent has been applied to glass raw yarns used for glass cloth warps to prevent them from being damaged by contact with a reed or a heald frame during weaving (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 7-102483 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, the glass cloth woven from the warp glass strands coated with the warp protective agent has the following problem locally: the time until the resin completely permeates the warp glass strands (hereinafter sometimes referred to as the impregnation time) becomes uneven. When the resin is impregnated into the glass cloth containing the warp glass strands with uneven impregnation time to produce a prepreg, if the time for the glass cloth to be impregnated with the resin is set to coincide with the glass strands with a short impregnation time contained in the warp glass strands in the glass cloth, the adhesion between the glass strands with a long impregnation time and the resin will be reduced. When the adhesion between the glass cloth and the resin is locally reduced, it will form a reason for the reduction in the insulation reliability of the prepreg as a whole containing the glass cloth. On the other hand, if the time for the glass cloth to be impregnated with the resin is set to coincide with the glass strands with a long impregnation time of the warp glass strands, the time required for the prepreg production will be longer, and the manufacturing efficiency will deteriorate.

[0008] An object of the present invention is to solve the above-mentioned problem and provide a glass cloth capable of suppressing unevenness in the impregnation time of the warp glass yarn with the resin.

[0009] Means for solving problems

[0010] The present inventors investigated the causes of the phenomenon in which the impregnation time of the warp glass strands with the resin is locally uneven in glass cloth woven from warp glass strands coated with the aforementioned warp protective agent. The present inventors discovered that, due to the dry state, regions known as "blocking" occur within the multiple glass filaments constituting the warp glass strands coated with the aforementioned warp protective agent. While the distribution of the number of these blocks within the warp glass strands is minimally affected by the silane coupling agent applied to the surface of the glass strands, there is a weak correlation between the distribution of the number of these blocks and the insulation reliability of the prepreg comprising the glass cloth woven from the warp glass strands. These blocks are formed by the three to four glass filaments that form the warp glass strands being in close contact with each other on their outer circumferential surfaces, and are thus enclosed by the outer circumferential surfaces of the three to four glass filaments in a cross-section perpendicular to the longitudinal direction of the warp glass strands.

[0011] Note that, "closed without gaps" means that, among two contacting glass filaments, the shortest distance between the outer peripheral surface of one glass filament and the outer peripheral surface of the other glass filament is less than 0.3 μm.

[0012] The present inventors have further studied the blocking and found that by controlling the blocking distribution number in the glass cloth within a specific range, it is possible to suppress uneven impregnation time of the warp glass yarns of the glass cloth with the resin.

[0013] Therefore, in order to achieve the above object, the glass cloth of the present invention is a glass cloth comprising glass strands composed of a plurality of glass filaments as warp and weft yarns, characterized in that the adhesion dispersion number represented by the following formula (1) is within the range of 0.027 to 0.077.

[0014] |B max -B min | / N…(1)

[0015] (Among them, B max The maximum value of the number of adhesions when the number of adhesions in each of the following areas is measured is shown in FIG. min is the minimum number of adhesions, N is the number of glass filaments contained in the glass strands for warp yarns, and the above-mentioned regions refer to the three regions of the left region, the center region, and the right region in which the glass strands for warp yarns are divided, and these regions become regions of uniform width in the yarn width direction of the glass strands for warp yarns).

[0016] According to the glass cloth of the present invention, by setting the adhesion dispersion number within the above-mentioned range, when the glass cloth is impregnated with a resin, it is possible to suppress the situation where the impregnation time of the resin with respect to the glass strands for the warp yarns becomes uneven over the entire range of the glass cloth. Therefore, when the glass cloth is made into a prepreg, it is possible to achieve excellent adhesion between the glass cloth and the resin without deteriorating the manufacturing efficiency of the prepreg.

[0017] The fact that the time for impregnation of the warp glass yarn with the resin can be suppressed from becoming uneven means that the unevenness of the time for impregnation of the warp glass yarn with the resin measured by the method described below is 1.0 minute or less.

[0018] In the glass cloth of the present invention, if the adhesion dispersion number exceeds 0.077, the impregnation time of the warp glass strands with the resin becomes locally uneven, resulting in reduced prepreg production efficiency and failure to achieve excellent adhesion between the glass cloth and the resin. Furthermore, in the glass cloth of the present invention, if the adhesion dispersion number is less than 0.027, the glass strands are prone to sticking to each other, making it impossible to prevent fuzz and breakage during weaving.

[0019] Furthermore, the prepreg and printed wiring board of the present invention are characterized by comprising the glass cloth of the present invention.

[0020] Brief description of the accompanying drawings

[0021] Figure 1 This is a reproduction of an electron microscope photograph showing a cross section of a glass strand for warp yarns used in the glass cloth of the present invention.

[0022] Figure 2 This is an explanatory diagram of the method for measuring the number of adhesions. DETAILED DESCRIPTION

[0023] Next, embodiments of the present invention will be described in further detail with reference to the accompanying drawings.

[0024] In the glass cloth including glass strands composed of a plurality of glass filaments as warp and weft yarns, the glass cloth of the present embodiment has a blocking dispersion number represented by the following formula (1) within a range of 0.027 to 0.077.

[0025] |B max -B min | / N…(1)

[0026] (Among them, B max The maximum value of the number of adhesions when the number of adhesions in each of the following areas is measured is shown in FIG. minis the minimum number of adhesions, N is the number of glass filaments contained in the glass strands for warp yarns, and the above-mentioned regions refer to the three regions of the left region, the center region, and the right region in which the glass strands for warp yarns are divided, and these regions become regions of uniform width in the yarn width direction of the glass strands for warp yarns).

[0027] According to the glass cloth of this embodiment, by making the adhesion dispersion number within the above-mentioned range, when the resin is impregnated into the glass cloth, it is possible to suppress the situation where the impregnation time of the resin with respect to the glass raw yarn for the warp yarn becomes uneven throughout the entire range of the glass cloth. Therefore, when the glass cloth is made into a prepreg, it is possible to achieve excellent adhesion between the glass cloth and the resin without deteriorating the manufacturing efficiency of the prepreg.

[0028] In the glass cloth of the present embodiment, the blocking dispersion number is preferably within a range of 0.045 to 0.070, and more preferably within a range of 0.055 to 0.064.

[0029] The glass cloth of this embodiment can be produced as follows, for example.

[0030] First, glass raw materials of a glass composition for glass fibers prepared to have a desired composition are melted in a glass melting furnace to prepare molten glass (a melt of the glass composition for glass fibers).

[0031] In the glass cloth of this embodiment, the glass composition of the above-mentioned glass fiber is not particularly limited. For example, the most common E glass composition, high strength and high elastic modulus glass composition, high elastic modulus easy-to-manufacture glass composition and low dielectric constant and low dielectric loss tangent glass composition can be cited.

[0032] The above-mentioned E glass composition is the following composition: relative to the total amount of glass fiber, it contains SiO2 in the range of 52.0~56.0 mass%, Al2O3 in the range of 12.0~16.0 mass%, MgO and CaO in the range of 20.0~25.0 mass%, and B2O3 in the range of 5.0~10.0 mass%.

[0033] The high-strength, high-elastic modulus glass composition is a composition containing, relative to the total amount of glass fiber, 60.0-70.0% by mass of SiO2, 20.0-30.0% by mass of Al2O3, 5.0-15.0% by mass of MgO, 0-1.5% by mass of Fe2O3, and a total of 0-0.2% by mass of Na2O, K2O, and Li2O. The high-strength, high-elastic modulus glass composition is preferably a composition containing 0.15-1.50% by mass of Fe2O3, 0.01-0.10% by mass of ZrO2, and a total of 0.02-0.20% by mass of Na2O, K2O, and Li2O.

[0034] The above-mentioned high elastic modulus and easy-to-manufacture glass composition is the following composition: relative to the total amount of glass fiber, it contains SiO2 in the range of 57.0 to 60.0 mass%, Al2O3 in the range of 17.5 to 20.0 mass%, MgO in the range of 8.5 to 12.0 mass%, CaO in the range of 10.0 to 13.0 mass% and B2O3 in the range of 0.5 to 1.5 mass%, and the total amount of SiO2, Al2O3, MgO and CaO is more than 98.0 mass%.

[0035] The above-mentioned low dielectric constant and low dielectric loss tangent glass composition is the following composition: relative to the total amount of glass fiber, it contains SiO2 in the range of 48.0 to 62.0 mass%, B2O3 in the range of 17.0 to 26.0 mass%, Al2O3 in the range of 9.0 to 18.0 mass%, CaO in the range of 0.1 to 9.0 mass%, MgO in the range of 0 to 6.0 mass%, Na2O, K2O and Li2O in the range of 0.05 to 0.5 mass%, TiO2 in the range of 0 to 5.0 mass%, SrO in the range of 0 to 6.0 mass%, F2 and Cl2 in the range of 0 to 3.0 mass%, and P2O5 in the range of 0 to 6.0 mass%.

[0036] The content of each component of the glass composition can be measured using an ICP emission spectrometer to measure Li as a light element, and a wavelength dispersive X-ray fluorescence analyzer to measure other elements. Specifically, the content of each component of the glass composition can be measured as follows.

[0037] First, the glass cloth is cut into appropriate sizes, placed in a platinum crucible, and held in an electric furnace at 1400-1650°C for 6 hours while being stirred and melted to produce a homogeneous molten glass. If organic matter adheres to the surface of the glass cloth, or if the organic matter (resin) primarily contains glass fibers as a reinforcing material, the glass cloth is heated in a muffle furnace at 300-650°C for approximately 2-24 hours to remove the organic matter before use.

[0038] Next, the resulting molten glass is poured onto a carbon plate to produce glass chips, which are then crushed and powdered to form glass powder. The glass powder is then decomposed by heating with acid, and then quantitatively analyzed for Li, a light element, using an ICP emission spectrometer. After the glass powder is formed into a disc shape using a press, other elements are quantitatively analyzed using a wavelength-dispersive X-ray fluorescence analyzer. These quantitative analysis results are converted into oxides, and the content and total amount of each component are calculated. Based on these values, the content (mass %) of each component can be determined.

[0039] Next, the molten glass is ejected from a container (sleeve) equipped with a nozzle plate with several to several thousand nozzle tips, and is taken up at high speed while being stretched and cooled, solidifying into a fibrous shape (this operation is sometimes referred to as "spinning"), thereby forming glass filaments. The sleeve is formed of a noble metal such as platinum, for example.

[0040] Among them, the glass filaments ejected from a single nozzle head or hole, cooled, and solidified generally have a true circular cross-sectional shape and a diameter in the range of 3.0 to 10.0 μm.

[0041] The elastic modulus of the glass fibers constituting the above-mentioned glass filaments is not particularly limited, and is, for example, in the range of 40 to 120 GPa, preferably in the range of 71 to 110 GPa. In the past, due to the tendency for the impregnation time of the resin relative to the glass strands for the warp yarns to be longer, from the perspective of utilizing the present invention to more significantly reduce the unevenness of the impregnation time, the elastic modulus is more preferably in the range of 80 to 100 GPa. Furthermore, the strength of the glass fibers constituting the above-mentioned glass filaments is not particularly limited, and is, for example, in the range of 1.5 to 6.0 GPa, and preferably in the range of 3.5 to 5.2 GPa.

[0042] The elastic modulus and strength of the glass fibers constituting the glass filaments can be measured by the methods described in the examples below.

[0043] Next, a sizing agent (sometimes referred to as a primary sizing agent) is applied to the 20 to 300 glass filaments formed in the above manner using an applicator to bundle them, and the bundle is wound on a collet to form glass strands (glass fiber bundles).

[0044] If the fiber diameter of the glass filaments exceeds 10 μm or the number of glass filaments exceeds 300, the glass cloth obtained by weaving the glass filaments may not be sufficiently lightweight. Furthermore, if the fiber diameter of the glass filaments is less than 3 μm, production efficiency is reduced to prevent fuzz and breakage. If the number of glass filaments is less than 20, it may be difficult to prevent the formation of pinholes when the glass cloth obtained by weaving the glass filaments is made into a prepreg.

[0045] In the glass strands, the fiber diameter of the glass filaments is preferably in the range of 3.0 to 10.0 μm, more preferably in the range of 4.8 to 9.0 μm, and even more preferably in the range of 6.0 to 8.0 μm. Furthermore, in the glass strands, the number of the glass filaments is preferably in the range of 20 to 300, and more preferably in the range of 120 to 250.

[0046] Next, the formed glass strands are used as glass strands for warps and glass strands for wefts, and a warp protective agent (sometimes referred to as a secondary sizing agent relative to the above-mentioned primary sizing agent) is coated on the warp glass strands. Examples of the above-mentioned warp protective agent include sizing agents whose coating forming agent components are starch-based or PVA (polyvinyl alcohol)-based. The above-mentioned warp protective agent may contain a lubricant, an emulsifier, a softener, a preservative, an antistatic agent, an organic solvent, and the like. Examples of the above-mentioned warp protective agent include a substance containing 5.0% by mass of polyvinyl alcohol (PVA), 1.0% by mass of starch, 0.5% by mass of paraffin wax, and 93.5% by mass of water relative to the total amount of the warp protective agent, but the present embodiment is not limited thereto.

[0047] The amount of the warp yarn protective agent deposited in the glass cloth is preferably 0.1 to 3.0 parts by mass, more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of the glass strands.

[0048] The operation of coating the warp protective agent on the warp glass strands can be performed in the following manner: while adjusting the tension of the warp glass strands, the strands are passed through a treatment tank containing a treatment liquid containing the warp protective agent, and then the line speed is adjusted to achieve a specified drying strength index, for example, passing through a dryer with an ambient temperature in the range of 100 to 250°C for a time range of 0.1 to 1.0 minutes. The ambient temperature of the dryer is preferably in the range of 100 to 150°C, and the time of the passage is preferably in the range of 0.1 to 0.35 minutes. The drying strength index is represented by the product of the drying time (minutes) and the ambient temperature of the dryer (°C), for example, a value in the range of 25.0 to 35.0.

[0049] By applying the warp protective agent to the warp glass strands and conveying them while adjusting the tension, the arrangement of the glass filaments within the warp strands can be relaxed. Drying then promotes the formation of a film of the warp protective agent, thereby fixing the arrangement of the filaments and locally forming the aforementioned adhesions. The tension applied to the warp strands is preferably in the range of 70 to 120 N.

[0050] The above-mentioned adhesion refers to a region which is surrounded by the outer peripheral surfaces of three to four glass filaments and is sealed without any gaps in a cross section perpendicular to the longitudinal direction of the glass filaments.

[0051] In the aforementioned warp glass strands, a higher drying strength index promotes drying of the warp glass strands. This results in faster coating of the warp protective agent on the outer edges of the warp glass strands, allowing the strand shape to stabilize before the glass filaments within the strands are properly aligned. This increases the number of stickings in the central portion and the number of sticking dispersions. On the other hand, a lower drying strength index results in insufficient drying of the warp protective agent, causing the warp glass strands to adhere to one another. This can lead to fuzz and breakage when the warp strands are separated during weaving.

[0052] It should be noted that the glass strands for weft are only coated with the sizing agent, and are not coated with the protective agent for warp.

[0053] Next, the warp glass strands are used as warp yarns, and the weft glass strands are used as weft yarns to produce a first glass cloth, which is one embodiment of the glass cloth of this embodiment. The weaving can be performed using a known loom. Examples of such looms include jet looms such as air jet looms and water jet looms, shuttle looms, and rapier looms. Examples of weaving methods using such looms include plain weave, satin weave, basket weave, and twill weave. From the perspective of manufacturing efficiency, plain weave is preferred.

[0054] Next, the first glass cloth is subjected to a deoiling treatment, a surface treatment, or a fiber opening treatment to obtain a second glass cloth, which is one embodiment of the glass cloth of this embodiment. The order of the deoiling treatment, the surface treatment, or the fiber opening treatment is not particularly limited; any of the treatments can be performed first.

[0055] In the deoiling treatment, the first glass cloth is placed in a heating furnace at an ambient temperature of 350 to 400° C. for 40 to 80 hours to thermally decompose the sizing agent and the warp yarn protective agent attached to the first glass cloth.

[0056] The surface treatment can be performed by immersing the first glass cloth in a surface treatment agent solution, squeezing out excess water, and then heating and drying the glass cloth at a temperature of 80 to 180° C. for 1 to 30 minutes.

[0057] As the surface treatment agent solution, a solution containing a silane coupling agent, a weak acid (eg, acetic acid, citric acid, propionic acid, etc.), and a surfactant can be used.

[0058] Examples of the silane coupling agent include aminosilane, chlorosilane, epoxysilane, mercaptosilane, vinylsilane, and (meth)acrylic silane. In this embodiment, the silane coupling agent may be used alone or in combination of two or more.

[0059] Examples of the aminosilane include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-N′-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-anilinopropyltrimethoxysilane.

[0060] Examples of the chlorosilane include γ-chloropropyltrimethoxysilane and the like.

[0061] Examples of epoxysilane include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0062] Examples of the mercaptosilane include γ-mercaptotrimethoxysilane and the like.

[0063] Examples of the vinylsilane include vinyltrimethoxysilane and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane.

[0064] Examples of the (meth)acrylic silane include γ-methacryloxypropyltrimethoxysilane.

[0065] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. In this embodiment, the surfactants described above may be used alone or in combination of two or more.

[0066] Examples of the above-mentioned fiber-opening treatment include the following treatments: while applying a tension in the range of 30 to 200 N to the warp yarns of the above-mentioned first glass cloth, fiber-opening using water flow pressure, fiber-opening based on high-frequency vibration using a liquid as a medium, fiber-opening based on pressure of a fluid having surface pressure, fiber-opening using roller pressure, etc., thereby expanding the yarn width of the warp yarns and the weft yarns.

[0067] In the first glass cloth or the second glass cloth, which is one embodiment of the glass cloth of this embodiment, the warp or weft weave density is, for example, in the range of 20 to 160 threads / 25 mm, and preferably in the range of 50 to 80 threads / 25 mm. Furthermore, in the first glass cloth or the second glass cloth, the warp or weft width is, for example, in the range of 80 to 600 μm, and preferably in the range of 250 to 450 μm, and more preferably in the range of 300 to 400 μm. Furthermore, the thickness of the first glass cloth or the second glass cloth is, for example, in the range of 8 to 200 μm, and preferably in the range of 70 to 170 μm, and more preferably in the range of 91 to 140 μm. Furthermore, the width of the first glass cloth or the second glass cloth is, for example, in the range of 800 to 2000 mm.

[0068] In the first glass cloth or the second glass cloth, which is one embodiment of the glass cloth of this embodiment, the average number of layers defined by (filament diameter) x (number of filaments) / (filament width) is, for example, in the range of 0.6 to 4.5, preferably in the range of 2.5 to 4.0, and more preferably in the range of 3.0 to 3.8. If the average number of layers of the first glass cloth or the second glass cloth is less than 0.6, the number of sticking dispersions tends to be too small. If the average number of layers exceeds 4.5, the time required for the resin to be impregnated into the first glass cloth or the second glass cloth tends to be prolonged.

[0069] The amount of sticking can be measured as follows. First, cut out a 100 mm x 100 mm glass cloth piece centered at three points: a point 200 mm inward from one end in the width direction of the glass cloth, a point 200 mm inward from the other end, and a point in the center of the width direction of the glass cloth. If the glass cloth width is less than 800 mm, the glass cloth piece can be cut out by adjusting the distance from the ends and the size of the glass cloth piece in proportion to the width, using a glass cloth width of 1000 mm as a reference.

[0070] Next, the cut glass cloth pieces were embedded in epoxy resin, cured, and polished to a point where a cross-section perpendicular to the longitudinal direction of the warp yarn could be observed, thereby forming test pieces for measuring the adhesion dispersion number. At this point, a warp glass strand located 5 mm from one end of the test piece was selected, and the polished surface of the test piece was observed using a scanning electron microscope at a magnification of 1600x.

[0071] The above-mentioned sticking is also maintained after the above-mentioned deoiling treatment, surface treatment or fiber opening treatment is performed on the above-mentioned woven first glass cloth. Therefore, the above-mentioned sticking amount can be measured using the first glass cloth or the second glass cloth.

[0072] Next, a description will be given of the case where the second glass cloth is used to measure the number of stickings.

[0073] Figure 1 This is a reproduction of an electron micrograph of a portion of the polished surface of the test piece, showing a cross section of the second glass cloth. Reference numeral 1 represents a warp glass strand, and reference numeral 3 represents a weft glass strand. The warp glass strand 1 is formed by bundling a plurality of glass filaments 2.

[0074] Then, if Figure 2 As shown, the warp glass strand 1 having a strand width L is divided into three regions, namely, a left region 1a, a center region 1b, and a right region 1c, in the width direction of the strand cross section so that the widths L1, L2, and L3 of the regions are the same (L1=L2=L3, L1+L2+L3=L), and the number of stickings in each region 1a, 1b, and 1c is measured. The maximum value of the number of stickings in the three regions 1a, 1b, and 1c is set as B. max , the minimum value is set to B min , when the number of glass filaments 2 contained in the warp glass yarn 1 is N, | B max -B min | / N is set as the adhesion dispersion number of the glass yarn for the warp.

[0075] The above measurement is performed on 5 adjacent warp glass strands in each glass cloth piece cut out from the above three points, and the adhesion dispersion number of a total of 15 warp glass strands is measured. The average value is taken as the adhesion dispersion number of the glass cloth, and the standard deviation of the adhesion dispersion number of the 15 warp glass strands is taken as the standard deviation of the adhesion dispersion number of the glass cloth.

[0076] In the first glass cloth or the second glass cloth as one embodiment of the glass cloth of the present embodiment, the standard deviation of the blocking dispersion number is preferably in the range of 0.006 to 0.070, and more preferably in the range of 0.016 to 0.022.

[0077] The prepreg or printed wiring board of this embodiment includes the first glass cloth or the second glass cloth, and a thermoplastic resin or a thermosetting resin impregnated into the first glass cloth or the second glass cloth.

[0078] In the prepreg or printed wiring board of this embodiment, the resin impregnated into the first or second glass cloth is not particularly limited. Examples of thermosetting resins include epoxy resins, phenolic resins, unsaturated polyester resins, melamine resins, modified polyimide resins, thermosetting polyphenylene ether resins, and thermosetting modified polyphenylene ether resins. Examples of thermoplastic resins include polyamide resins, polyimide resins, polybutylene terephthalate resins, polyethylene terephthalate resins, polyphenylene sulfide resins, thermoplastic polyphenylene ether resins, thermoplastic modified polyphenylene ether resins, and fluororesins.

[0079] Next, examples of the present invention and comparative examples are shown.

[0080] [Example 1]

[0081] First, a glass raw yarn was prepared, which was composed of 196 glass filaments with a perfect circular cross-sectional shape and a filament diameter of 7.0 μm, and was composed of a glass composition shown in Table 1 (high-strength and high-elastic modulus glass composition, containing 65.00 mass% SiO2, 25.00 mass% Al2O3, 9.50 mass% MgO, 0.05 mass% CaO, 0.30 mass% Fe2O3, 0.05 mass% ZrO2, a total of 0.10 mass% Li2O, Na2O and K2O, 0.00 mass% B2O3, 0.00 mass% TiO2, and 0.00 mass% F2, relative to the total amount of glass fiber).

[0082] Next, a warp yarn protecting agent treatment liquid containing 5.0 mass % of polyvinyl alcohol (PVA), 1.0 mass % of starch, 0.5 mass % of paraffin wax, and 93.5 mass % of water was prepared based on the total amount.

[0083] Next, the glass strands formed in the above manner are used as warp glass strands and weft glass strands, and the warp protective agent is applied to the warp glass strands. The application of the warp protective agent to the warp glass strands can be performed by passing the warp glass strands through a treatment tank containing a treatment solution containing the warp protective agent, and then passing the warp glass strands through a dryer at an ambient temperature within a range of 100 to 150° C. while adjusting the linear speed to achieve a dryness index of 31.5.

[0084] It should be noted that the glass strands for weft are only coated with the sizing agent, and are not coated with the protective agent for warp.

[0085] Next, the warp glass strands were used as warp yarns, and the weft glass strands were used as weft yarns, and were woven using an air jet loom. The warp yarns had a weaving density of 65 yarns / 25 mm, and the weft yarns had a weaving density of 62 yarns / 25 mm, to produce a first glass cloth with a plain weave.

[0086] Next, the first glass cloth was subjected to deoiling, surface treatment, and fiber-opening to obtain the second glass cloth, which serves as the glass cloth of this embodiment. During the deoiling process, the first glass cloth was placed in a heating furnace at an ambient temperature of 350-400°C for 60 hours to thermally decompose the sizing agent and warp yarn protective agent attached to the first glass cloth. Furthermore, the surface treatment was performed by applying a silane coupling agent to the first glass cloth and curing the silane coupling agent while continuously passing the cloth through a heating furnace at 130°C. Furthermore, the fiber-opening process was performed by applying a tension of 50N to the warp yarns of the first glass cloth and opening them using a water flow pressure set to 3.0 MPa. During the fiber-opening process, the tension detected by a tension detector was fed back to the guide rollers conveying the first glass cloth, and the tension was adjusted by changing the position of the guide rollers.

[0087] In addition, the tension applied to the warp yarns of the glass cloth in the steps other than the fiber-opening treatment is in the range of 70 to 120N.

[0088] Through the above treatment, the second glass cloth had a warp yarn width of 372 μm and an average number of 3.7 layers, a weft yarn width of 365 μm and an average number of 3.8 layers, and a thickness of 96 μm. The results are shown in Table 1.

[0089] The second glass cloth obtained in this example was measured for blocking dispersion using the following method to determine the standard deviation of the blocking dispersion. The glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were also measured. Furthermore, the time it took for the second glass cloth to be impregnated with resin was measured. The results are shown in Table 1.

[0090] 〔Adhesion dispersion number and its standard deviation〕

[0091] First, 100 mm x 100 mm glass cloth pieces were cut out of the second glass cloth at three points: 200 mm inward from one end in the width direction, 200 mm inward from the other end, and at the center of the width direction. Next, the cut glass cloth pieces were embedded in epoxy resin and cured. The cured epoxy resin was polished to a point where a cross-section perpendicular to the longitudinal direction of the warp yarns could be observed. This formed a test piece for measuring the number of stickings. Warp glass yarns were selected at a position 5 mm from one end of the test piece, and the polished surface of the test piece was observed using a scanning electron microscope to measure the number of stickings.

[0092] The above-mentioned adhesion amount is measured in the following manner: the warp glass yarn 1 with a yarn width L is divided into three regions, namely the left region 1a, the center region 1b, and the right region 1c, in such a manner that the widths L1, L2, and L3 of each region are the same (L1=L2=L3, L1+L2+L3=L), and each region 1a, 1b, and 1c is observed at a magnification of 1600 times using a scanning electron microscope.

[0093] Then, the maximum value of the number of adhesions in the three regions 1a, 1b, and 1c is set as B. max , the minimum value is set to B min , when the number of glass filaments 2 contained in the glass yarn 1 for warp yarn is N, |B max -B min | / N is set as the adhesion dispersion number of the glass yarn for the warp.

[0094] The measurement was performed on five adjacent warp glass strands in each glass cloth piece cut out from the three points. The blocking dispersion number of a total of 15 warp glass strands was measured, and the average value was taken as the blocking dispersion number of the second glass cloth.

[0095] Furthermore, the standard deviation of the sticking dispersion number of the 15 warp glass yarns was used as the standard deviation of the sticking dispersion number of the second glass cloth.

[0096] 〔Glass fiber strength〕

[0097] First, a glass raw material having the same glass composition as the glass fiber of the embodiment or comparative example is heated in a muffle furnace at 1400-1650°C for 0.5-24 hours, and the resulting molten glass is poured onto a carbon plate to produce glass chips. Next, the resulting glass chips are placed into a small cylindrical platinum sleeve with a circular nozzle at the bottom of the container. The sleeve is heated to a specified temperature so that the viscosity of the glass chips reaches 1000±150 poise, melting the glass chips and obtaining molten glass. The molten glass ejected from the nozzle of the platinum sleeve is wound at a specified speed using a winder to obtain a glass fiber diameter of 13±2μm. The glass fiber is then cooled and solidified while being stretched to obtain a glass filament having a perfectly circular cross-section. A single glass filament (monofilament) is collected between the nozzle of the platinum sleeve and the winder, and the glass filament in a state where degradation due to contact and friction is minimized is collected as a sample for tensile strength evaluation. Next, the resulting glass filaments were aligned with a line connecting the center points of the short sides of a backing paper (described later) with two clamps and two support portions, and bonded together to form a single-filament test piece. The diameter of the resulting glass filaments was then measured using a scanning electron microscope (S-3400, manufactured by Hitachi, Ltd.), and the cross-sectional area of ​​the glass filaments was calculated based on the obtained diameter. Next, the two clamps in the backing paper were placed on the upper and lower clamps of a tensile testing machine (STB-1225S, manufactured by A&D Co., Ltd.), with a clamp spacing of 25 mm. After removing the two support portions from the backing paper, leaving only the glass filaments connected to the clamps, a tensile test was performed at a crosshead speed of 5 mm / minute. The tensile strength was then calculated by dividing the maximum load at break by the cross-sectional area of ​​the glass filaments. The glass fiber strength was measured by calculating the average value of the tensile strength of n=30, excluding the single-filament test pieces that had incomplete breakage such as yarn breakage or yarn breakage during the measurement.

[0098] It should be noted that the above-mentioned backing paper has a short side of 25 mm and a long side of 50 mm, and furthermore, a cutout portion having a short side of 15 mm and a long side of 25 mm is provided in the center thereof, so that the short side and long side of the backing paper are respectively parallel to the short side and long side of the cutout portion, and a clamping portion provided on the fixture of the tensile testing machine is provided between the short side of the cutout portion and the short side of the backing paper, and further, a supporting portion connecting and supporting the two clamping portions is provided between the long side of the cutout portion and the long side of the backing paper.

[0099] 〔Glass fiber elastic modulus〕

[0100] First, a tensile test of glass filaments was conducted in exactly the same manner as the glass fiber strength measurement method described above. Next, the stresses corresponding to strains ε1 = 0.0005 and ε2 = 0.0025 between two points were designated σ1 and σ2, respectively. The tensile modulus was calculated by dividing the stress difference (σ2 - σ1) by the strain difference (ε2 - ε1). Excluding single-filament test pieces that experienced yarn debonding during the measurement, the average tensile modulus values ​​for n = 15 samples were calculated to determine the glass fiber modulus.

[0101] 〔Resin impregnation time〕

[0102] First, at three points of the second glass cloth, namely, a point 200 mm inward from one end in the width direction, a point 200 mm inward from the other end, and a point in the center in the width direction, glass cloth pieces of 60 mm × 40 mm were cut out centered on each point to prepare test pieces for evaluating impregnation.

[0103] Next, the impregnation test piece was impregnated with benzyl alcohol. The time it took for the benzyl alcohol to completely permeate the test piece was measured in both the warp and weft directions. Five test pieces were used for each measurement point, and the average value was calculated for each measurement point.

[0104] Then, the difference between the maximum value and the minimum value of the impregnation time of the warp and weft at each measurement point was defined as the unevenness of the impregnation time.

[0105] The refractive index of the benzyl alcohol is similar to that of the glass filaments. Therefore, when the impregnation evaluation test piece is impregnated with benzyl alcohol, the impregnated portion appears transparent because the benzyl alcohol penetrates between the glass filaments of the glass strands. However, the unimpregnated portion appears opaque due to a refractive index difference with the air present between the glass filaments. Therefore, it is easy to visually determine whether the impregnation has been completed.

[0106] [Example 2]

[0107] In this embodiment, a glass composition for glass fiber is made into a glass raw yarn consisting of 41 glass filaments having a filament diameter of 4.0 μm and a glass composition shown in Table 1 (E glass composition, containing 54.60 mass% SiO2, 14.10 mass% Al2O3, 1.20 mass% MgO, 22.40 mass% CaO, 0.20 mass% Fe2O3, 0.00 mass% ZrO2, a total of 0.50 mass% Li2O, Na2O and K2O, 6.10 mass% B2O3, 0.30 mass% TiO2, and 0.60 mass% F2, relative to the total amount of glass fiber).

[0108] Next, the glass strands formed as above were used as warp and weft glass strands, and a plain weave first glass cloth was produced in exactly the same manner as in Example 1 except that the weaving density of the warp and weft yarns was set at 95 strands / 25 mm.

[0109] Next, the first glass cloth was subjected to deoiling, surface treatment, and fiber-opening treatment in the same manner as in Example 1, except that the water pressure in the fiber-opening treatment was set to 1.0 MPa, thereby obtaining a second glass cloth as the glass cloth of this example.

[0110] The second glass cloth of this example had a warp yarn with a yarn width of 120 μm and an average number of layers of 1.4, and a weft yarn with a yarn width of 185 μm and an average number of layers of 0.9, and had a thickness of 13 μm.

[0111] Next, the blocking dispersion number was measured in exactly the same manner as in Example 1, except that the second glass cloth obtained in this example was used. The standard deviation of the blocking dispersion number was determined, the glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were measured, and the time for impregnation of the second glass cloth with resin was measured. The results are shown in Table 1.

[0112] [Comparative Example 1]

[0113] In this comparative example, a second glass cloth as the glass cloth of this comparative example was produced in exactly the same manner as in Example 1 except that the line speed was adjusted so that the dry strength index in the operation of coating the warp protective agent on the warp glass yarns was 40.9.

[0114] The second glass cloth of this comparative example had a warp yarn with a yarn width of 374 μm and an average number of layers of 3.7 and a weft yarn with a yarn width of 360 μm and an average number of layers of 3.8, and had a thickness of 96 μm.

[0115] Next, the blocking dispersion number was measured in exactly the same manner as in Example 1, except that the second glass cloth obtained in this comparative example was used. The standard deviation of the blocking dispersion number was determined. The glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were measured. Furthermore, the time for impregnation of the second glass cloth with the resin was measured. The results are shown in Table 1.

[0116] [Table 1]

[0117]

[0118] As shown in Table 1, the glass cloths of Examples 1 and 2 have a dispersion of adhesion values ​​within the range of 0.027 to 0.077, which allows the nonuniformity of the impregnation time of the resin with respect to the warp glass strands to be less than 1.0 minute, thus preventing the nonuniformity of the impregnation time. On the other hand, in the glass cloth of Comparative Example 1, the impregnation time of the warp and weft glass strands at the ends of the glass cloth is the same as that of Example 1, and the nonuniformity of the weft impregnation time is less than 1.0 minute. However, the dispersion of adhesion values ​​is 0.094, exceeding 0.077. Therefore, the nonuniformity of the impregnation time of the resin with respect to the warp glass strands is 1.5 minutes, which is greater than the nonuniformity of the glass cloths of Examples 1 and 2, indicating that the impregnation time is nonuniform.

Claims

1. A glass cloth comprising warp and weft yarns, wherein the warp and weft yarns are formed from glass strands consisting of a plurality of glass filaments, wherein the glass cloth has an adhesion dispersion number represented by the following formula (1) within a range of 0.027 to 0.

077. |B max -B min | / N…(1) in, B max The maximum value of the number of adhesions when the number of adhesions in each of the following areas is measured is shown in FIG. min is the minimum adhesion number, N is the number of glass filaments contained in the warp glass strand, and the above-mentioned regions refer to the three regions of the left region, the center region, and the right region in which the warp glass strand is divided, and these regions become regions of uniform width in the yarn width direction of the warp glass strand.

2. A prepreg, characterized in that The invention comprises the glass cloth according to claim 1.

3. A printed wiring board, characterized in that The invention comprises the glass cloth according to claim 1.

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