Glass cloth, prepreg, and printed wiring board

Abstract

The present invention provides a glass cloth. The object is to make the glass cloth capable of inhibiting the case where impregnation time of resin with respect to glass precursor filament for warp becomes uneven. In the case where the glass cloth is made into a prepreg, excellent adhesion between the glass cloth and the resin can be achieved without deteriorating the manufacturing efficiency of the prepreg. The glass cloth of the present invention has a warp and a weft, and is formed of a glass precursor filament 1 composed of a plurality of glass filaments 2. The number of adhesion dispersals represented by the following formula (1) is in the range of 0.027 to 0.077. max -B min |B max is the number of adhesions representing the maximum value when the number of adhesions in each of the following regions is measured, B min is the number of adhesions representing the minimum value, and N is the number of glass filaments included in the glass precursor filament for warp. The above-mentioned each region refers to the case where the glass precursor filament for warp is divided into three regions of a left region, a center region, and a right region, and these regions become regions of equal width in the filament width direction of the glass precursor filament for warp.

Description

Technical Field

[0001] This invention relates to glass cloth, prepreg, and printed wiring boards. Background Technology

[0002] In the past, in order to prevent the glass filaments used for the warp of glass cloth from being damaged during weaving due to contact with the reed or heald frame, a protective agent for the warp filaments was coated on them (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

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

[0006] The problem that the invention aims to solve

[0007] However, glass cloth woven using warp glass filaments coated with the aforementioned warp protectant has a localized problem: the time it takes for the resin to completely impregnate the warp glass filaments (hereinafter, sometimes referred to as the impregnation time) becomes uneven. When manufacturing prepreg by impregnating glass cloth containing warp glass filaments with uneven impregnation times with resin, if the impregnation time of the glass cloth is set to coincide with the portion of the warp glass filaments in the glass cloth containing the shorter impregnation time, the adhesion between the longer impregnation time portion of the warp glass filaments and the resin will decrease. This localized decrease in the adhesion between the glass cloth and the resin is one reason for a reduction in the overall insulation reliability of the prepreg containing the glass cloth. On the other hand, if the impregnation time of the glass cloth is set to coincide with the portion of the warp glass filaments containing the longer impregnation time, the time required for prepreg manufacturing increases, resulting in decreased manufacturing efficiency.

[0008] The purpose of this invention is to eliminate the above-mentioned undesirable conditions and to provide a glass cloth that can suppress the uneven impregnation time of the resin relative to the glass filaments for warp.

[0009] Methods for solving problems

[0010] The inventors investigated the reasons for the following phenomenon: in glass cloth woven using glass filaments coated with the aforementioned warp protectant, uneven impregnation time of the resin on the glass filaments occurred locally. As a result, the inventors discovered that, due to the dry state, regions called adhesions formed among the multiple glass filaments constituting the glass filaments in the glass filaments coated with the aforementioned warp protectant. While the distribution of the number of adhesions in the glass filaments was weakly affected by the silane coupling agent coated on the surface of the glass cloth, a weak correlation still existed between the adhesions and the insulation reliability of the prepreg containing the glass cloth woven using the glass filaments. The adhesions refer to regions formed by the seamless contact of 3-4 glass filaments constituting the warp filaments on their outer peripheral surfaces, and regions that are completely enclosed by the outer peripheral surfaces of the 3-4 glass filaments in a cross-section perpendicular to the length direction of the glass filaments.

[0011] It should be noted that gapless sealing means the following: in two contacting glass filaments, the shortest distance between the outer peripheral surfaces of one glass filament and the outer peripheral surfaces of the other glass filament is less than 0.3 μm.

[0012] Through further repeated studies, the inventors discovered that by controlling the number of adhesive dispersions in the glass cloth within a specific range, it is possible to suppress the uneven impregnation time of the resin on the warp glass filaments of the glass cloth.

[0013] Therefore, in order to achieve the above objectives, the glass cloth of the present invention is a glass cloth having glass filaments composed of multiple glass filaments as warp and weft, characterized in that the adhesion dispersion number shown in the following formula (1) is in the range of 0.027 to 0.077.

[0014] |B max -B min | / N…(1)

[0015] (where B) max B represents the maximum adhesion quantity measured in the following regions. min N is the minimum number of adhesions, and N is the number of glass filaments contained in the warp glass filament. The aforementioned regions refer to the three regions that divide the warp glass filament into the left region, the central region, and the right region. These regions are of equal width in the filament width direction of the warp glass filament.

[0016] According to the glass cloth of the present invention, by making the adhesion dispersion number within the above-mentioned range, when resin is impregnated into the glass cloth, it is possible to suppress the situation where the resin impregnation time relative to the warp glass filament becomes uneven throughout the glass cloth. Therefore, when it is made into a prepreg, excellent adhesion between the glass cloth and the resin can be achieved without the prepreg manufacturing efficiency deteriorating.

[0017] The ability to suppress uneven impregnation time of resin relative to the glass filament for warp yarns means that the unevenness of the impregnation time of resin relative to the glass filament for warp yarns, as determined by the method described later, is less than 1.0 minute.

[0018] In the glass cloth of the present invention, when the adhesion dispersion number exceeds 0.077, the impregnation time of the resin relative to the warp glass filaments becomes locally uneven. When it is made into a prepreg, the manufacturing efficiency of the prepreg deteriorates or it is impossible to achieve excellent adhesion between the glass cloth and the resin. In addition, in the glass cloth of the present invention, when the adhesion dispersion number is less than 0.027, the glass filaments tend to stick together, and it is impossible to suppress the occurrence of fluff and breakage during weaving.

[0019] Furthermore, the prepreg and printed wiring board of the present invention are characterized in that they contain the glass cloth of the present invention.

[0020] Brief description of the attached diagram

[0021] Figure 1 This is a copy of an electron microscope photograph showing the cross-section of the glass filaments used in the glass cloth of the present invention.

[0022] Figure 2 This is an explanatory diagram of the method for determining the amount of adhesion. Detailed Implementation

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

[0024] In a glass cloth having glass filaments composed of multiple glass filaments as warp and weft, the adhesion dispersion number of the glass cloth in this embodiment, as shown by the following formula (1), is in the range of 0.027 to 0.077.

[0025] |B max -B min | / N…(1)

[0026] (where B) max B represents the maximum adhesion quantity measured in the following regions. minN is the minimum number of adhesions, and N is the number of glass filaments contained in the warp glass filament. The aforementioned regions refer to the three regions that divide the warp glass filament into the left region, the central region, and the right region. These regions are of equal width in the filament width direction of the warp glass filament.

[0027] According to the glass cloth of this embodiment, by keeping the adhesion dispersion number within the above-mentioned range, when resin is impregnated in the glass cloth, it is possible to suppress the situation where the impregnation time of the resin relative to the warp glass filament becomes uneven throughout the glass cloth. Therefore, when it is made into a prepreg, excellent adhesion between the glass cloth and the resin can be achieved without the manufacturing efficiency of the prepreg deteriorating.

[0028] In the glass cloth of this embodiment, the adhesion dispersion number is preferably in the range of 0.045 to 0.070, and more preferably in the range of 0.055 to 0.064.

[0029] The glass cloth of this embodiment can be manufactured, for example, by the following methods.

[0030] First, molten glass (the melt of the glass composition for glass fibers) is produced by melting glass raw materials, which are formulated to have the desired composition, in a glass melting furnace.

[0031] In the glass cloth of this embodiment, the glass composition for 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 and 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 as follows: containing 52.0 to 56.0% by mass of SiO2, 12.0 to 16.0% by mass of Al2O3, a total of 20.0 to 25.0% by mass of MgO and CaO, and 5.0 to 10.0% by mass of B2O3 relative to the total amount of glass fibers.

[0033] The aforementioned high-strength, high-elasticity modulus glass composition comprises, relative to the total amount of glass fibers, 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. Preferably, the aforementioned high-strength, high-elasticity modulus glass composition comprises, relative to the total amount of glass fibers, 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 aforementioned high elastic modulus easy-to-manufacture glass composition is as follows: containing 57.0 to 60.0% by mass of SiO2, 17.5 to 20.0% by mass of Al2O3, 8.5 to 12.0% by mass of MgO, 10.0 to 13.0% by mass of CaO, and 0.5 to 1.5% by mass of B2O3 relative to the total amount of glass fibers, and the total amount of SiO2, Al2O3, MgO and CaO is 98.0% by mass or more.

[0035] The aforementioned low dielectric constant and low dielectric loss tangent glass composition is as follows: relative to the total amount of glass fibers, it contains 48.0–62.0% by mass of SiO2, 17.0–26.0% by mass of B2O3, 9.0–18.0% by mass of Al2O3, 0.1–9.0% by mass of CaO, 0–6.0% by mass of MgO, a total of 0.05–0.5% by mass of Na2O, K2O, and Li2O, 0–5.0% by mass of TiO2, 0–6.0% by mass of SrO, a total of 0–3.0% by mass of F2 and Cl2, and 0–6.0% by mass of P2O5.

[0036] The content of each component in the glass composition described above can be determined using an ICP-based spectral analyzer to determine Li, a light element, and a wavelength dispersive X-ray fluorescence analyzer to determine other elements. Specifically, the content of each component in the glass composition can be determined using the following methods.

[0037] First, the glass cloth is cut into appropriate sizes and placed in a platinum crucible. It is then kept at 1400–1650°C in an electric furnace for 6 hours while being stirred until it melts, thus obtaining homogeneous molten glass. If organic matter adheres to the surface of the glass cloth, or if the organic matter (resin) mainly contains glass fiber as a reinforcing material, it can be heated in a muffle furnace at 300–650°C for approximately 2–24 hours to remove the organic matter before use.

[0038] Next, the molten glass was poured onto a carbon plate to create glass shavings, which were then pulverized and powdered to form glass powder. The glass powder was then heated and decomposed with acid, and Li, as a light element, was quantitatively analyzed using an ICP-based spectrophotometer. After the glass powder was shaped into a disc shape using a press, other elements were quantitatively analyzed using a wavelength dispersive X-ray fluorescence spectrometer. These quantitative analysis results were converted into oxides, and the content and total amount of each component were calculated. Based on these values, the content (mass%) of each component could be determined.

[0039] Next, the molten glass is ejected from a container (sleeve) having a nozzle plate with several to thousands of nozzle heads, and is stretched and cooled at high speed to solidify into fibers (sometimes referred to as "spinning"), thereby forming glass filaments. The sleeve is made of precious metals such as platinum.

[0040] The glass filaments that are ejected from a single nozzle or orifice, cooled, and solidified typically have a perfectly circular cross-sectional shape and a diameter ranging from 3.0 to 10.0 μm.

[0041] The elastic modulus of the glass fibers constituting the above-mentioned glass filaments is not particularly limited, but is, for example, in the range of 40 to 120 GPa, preferably in the range of 71 to 110 GPa. Conventionally, since there is a tendency for the resin to be impregnated for a longer time than the warp glass filaments, from the viewpoint that the present invention can more significantly reduce the unevenness of 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, but is, for example, in the range of 1.5 to 6.0 GPa, preferably in the range of 3.5 to 5.2 GPa.

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

[0043] Next, a bundling agent (sometimes called a primary sizing agent) is applied to the 20 to 300 glass filaments formed in the above manner using a coater and they are bundled together and wound into a collet to form glass filaments (glass fiber bundles).

[0044] In the aforementioned glass filaments, if the fiber diameter of the glass filaments exceeds 10 μm or the number of glass filaments exceeds 300, there is a tendency that the glass cloth obtained by weaving the glass filaments cannot achieve sufficient lightweighting. Furthermore, in the aforementioned glass filaments, if the fiber diameter of the glass filaments is less than 3 μm, manufacturing efficiency decreases in order to prevent fuzzing and breakage; if the number of glass filaments is less than 20, it is difficult to suppress pinhole formation when making the glass cloth obtained by weaving the glass filaments into a prepreg.

[0045] In the aforementioned glass precursor fiber, the fiber diameter of the glass filament 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 aforementioned glass precursor fiber, the number of glass filaments is preferably in the range of 20 to 300, more preferably in the range of 120 to 250.

[0046] Next, the formed glass filaments are used as warp and weft glass filaments, and a warp protectant (sometimes referred to as a secondary sizing agent relative to the primary sizing agent) is applied to the warp glass filaments. Examples of warp protectants include sizing agents whose film-forming agent is starch-based or PVA (polyvinyl alcohol)-based. The warp protectant may contain lubricants, emulsifiers, softeners, preservatives, antistatic agents, organic solvents, etc. Examples of warp protectants include substances 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 protectant; however, this embodiment is not limited to this.

[0047] The amount of protective agent applied to the warp yarns in the glass cloth is preferably 0.1 to 3.0 parts by weight relative to 100 parts by weight of the glass precursor, more preferably 0.5 to 1.5 parts by weight.

[0048] The application of the warp protectant to the glass filament for warping can be performed as follows: while adjusting the tension of the glass filament, it is passed through a treatment tank containing a treatment liquid containing the warp protectant; then, the linear speed is adjusted to achieve a specified drying strength index, for example, passing it through a dryer with an ambient temperature in the range of 100 to 250°C for a time period 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 passage time is preferably in the range of 0.1 to 0.35 minutes. The drying strength index is expressed as the product of the drying time (minutes) and the ambient temperature of the dryer (°C), for example, taking a value in the range of 25.0 to 35.0.

[0049] In the aforementioned warp-fiber glass filaments, by coating with the aforementioned warp-fiber protective agent and handling them while adjusting the tension, the arrangement of the glass filaments within the warp-fiber filaments can be eased. Then, drying promotes the coating of the warp-fiber protective agent, thereby fixing the arrangement of the filaments and locally forming the aforementioned adhesion. The tension applied to the warp-fiber filaments is preferably in the range of 70 to 120 N.

[0050] The aforementioned adhesion refers to the area in a cross section perpendicular to the length direction of the glass filament that is surrounded by the outer circumference of 3 to 4 glass filaments and is closed without gaps.

[0051] In the aforementioned warp glass filaments, a higher drying strength index promotes drying. This results in better coating of the warp protective agent on the outer edge of the filaments, and fixation of the filament shape before the arrangement of the glass filaments within the filaments eases. Consequently, the number of adhesions in the central portion increases, as does the number of adhesion dispersions. Conversely, when the drying strength index is low, the drying of the warp protective agent becomes insufficient, causing the warp glass filaments to adhere to each other. When the warp filaments are peeled apart during weaving, this can lead to fuzzing and breakage.

[0052] It should be noted that the glass filaments used for the weft yarns are only coated with the aforementioned bundling agent, and are not coated with the aforementioned protective agent for the warp yarns at all.

[0053] Next, the aforementioned warp yarns are woven using glass precursor yarns as warp yarns, and the aforementioned weft yarns are woven using glass precursor yarns as weft yarns, thereby obtaining a first glass cloth, which is one embodiment of the glass cloth of this embodiment. The weaving can be performed using a loom that is known in itself. Examples of such looms include: jet looms or water jet looms, shuttle looms, rapier looms, etc. Furthermore, examples of weaving methods using such looms include plain weave, satin weave, square plain weave, twill weave, etc., and from the viewpoint of manufacturing efficiency, plain weave is preferred.

[0054] Next, by performing degreasing, surface treatment, or fiber opening treatment on the first glass cloth, a second glass cloth, which is one embodiment of the glass cloth of this embodiment, can be obtained. The order of the above-mentioned degreasing, surface treatment, or fiber opening treatment is not particularly limited, and any of the treatments can be performed first.

[0055] In the above degreasing process, the first glass cloth is placed in a heating furnace with an ambient temperature in the range of 350 to 400°C for a period of 40 to 80 hours, thereby thermally decomposing the bundling agent and the warp protectant attached to the first glass cloth.

[0056] The above surface treatment can be carried out in the following manner: the first glass cloth is immersed in the surface treatment agent solution, the excess water is squeezed out, and then it is heated and dried in the temperature range of 80 to 180°C for 1 to 30 minutes.

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

[0058] Examples of silane coupling agents include: aminosilanes, chlorosilanes, epoxysilanes, mercaptosilanes, vinylsilanes, and (meth)acrylate silanes. In this embodiment, the above-mentioned silane coupling agents can be used alone or in combination of two or more of them.

[0059] Examples of aminosilanes include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-anilinepropyltrimethoxysilane.

[0060] Examples of chlorosilanes include γ-chloropropyltrimethoxysilane.

[0061] Examples of epoxy silanes include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-epoxypropoxypropyltrimethoxysilane.

[0062] Examples of mercaptosilanes include γ-mercaptotrimethoxysilane.

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

[0064] Examples of (meth)acrylic silanes include γ-methacryloyloxypropyltrimethoxysilane.

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

[0066] As an example of the above-mentioned fiber opening process, the following processes can be described: while applying a tension of 30 to 200 N to the warp yarns of the first glass cloth, fiber opening is performed using water flow pressure, high-frequency vibration based on liquid as a medium, pressure of a fluid with surface pressure, or pressure application using rollers, thereby expanding the width of the warp and weft yarns.

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

[0068] Furthermore, in the first or second glass cloth, which is one of the embodiments of the glass cloth in this embodiment, the average number of layers, defined by (filament diameter) × (number of filaments) / (filament width), is, for example, in the range of 0.6 to 4.5, and preferably in the range of 2.5 to 4.0, and more preferably in the range of 3.0 to 3.8. When the average number of layers of the first or second glass cloth is less than 0.6, there is a tendency for the number of adhesive dispersions to be too small; when the average number of layers exceeds 4.5, there is a tendency for the impregnation time of the resin relative to the first or second glass cloth to increase.

[0069] The aforementioned adhesion quantity can be determined as follows: First, cut 100mm x 100mm pieces of glass cloth centered at three points: a point 200mm inward from one end of the glass cloth in the width direction, a point 200mm inward from the other end, and a point at the center of the glass cloth in the width direction. It should be noted that if the width of the glass cloth is less than 800mm, a glass cloth width of 1000mm can be used as a reference, and the distance from the aforementioned ends and the size of the glass cloth pieces can be changed proportionally to that width to cut the glass cloth pieces.

[0070] Next, the cut glass cloth sheet is embedded in epoxy resin and the epoxy resin is cured. The cured epoxy resin is then ground until a cross-section perpendicular to the length direction of the warp filament can be observed, thus preparing a test piece for determining the adhesion dispersion number. At this point, a glass filament for the warp filament located 5 mm from one end of the test piece is selected, and the ground surface of the test piece is observed using a scanning electron microscope at 1600x magnification.

[0071] The aforementioned adhesion is maintained even after the first glass cloth, woven as described above, undergoes the degreasing, surface treatment, or fiber-opening treatment. Therefore, either the first glass cloth or the second glass cloth can be used to determine the amount of adhesion.

[0072] Next, the determination of the adhesion quantity using the second glass cloth will be explained.

[0073] Figure 1 This is a copy of an electron microscope photograph showing a portion of the ground surface of the aforementioned test piece, representing the cross-section of the aforementioned second glass cloth. Symbol 1 indicates the glass filament for the warp, and symbol 3 indicates the glass filament for the weft. The glass filament 1 for the warp is composed of a bundle of multiple glass filaments 2.

[0074] Next, as Figure 2 As shown, the warp filament 1 of width L is divided into three regions along its width direction: a left region 1a, a central region 1b, and a right region 1c. The widths L1, L2, and L3 of each region are made identical (L1 = L2 = L3, L1 + L2 + L3 = L). The number of adhesions in each region 1a, 1b, and 1c is measured. The maximum value among the adhesions in the three regions 1a, 1b, and 1c is set as B. max Let the minimum value be B. min When the number of glass filaments 2 contained in the glass precursor 1 used for warping is set to N, |B max -B min | / N is set as the adhesion dispersion number of the glass filament used for the warp.

[0075] The above measurements were performed on five adjacent warp glass fibers from each glass cloth sheet cut from the above three points. The adhesion and dispersion number of a total of 15 warp glass fibers was measured, and the average value was taken as the adhesion and dispersion number of the glass cloth. The standard deviation of the adhesion and dispersion number of the 15 warp glass fibers was taken as the standard deviation of the adhesion and dispersion number of the glass cloth.

[0076] In the first or second glass cloth, which is one of the embodiments of the glass cloth in this embodiment, the standard deviation of the adhesion 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 thermosetting resin impregnated in the first glass cloth or the second glass cloth.

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

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

[0080] [Example 1]

[0081] First, a glass fiber was fabricated by bundling 196 glass filaments with a circular cross-section and a diameter of 7.0 μm, which consisted of the glass composition shown in Table 1 (high-strength, high-elasticity modulus glass composition, containing 65.00% by mass of SiO2, 25.00% by mass of Al2O3, 9.50% by mass of MgO, 0.05% by mass of CaO, 0.30% by mass of Fe2O3, 0.05% by mass of ZrO2, a total of 0.10% by mass of Li2O, Na2O and K2O, 0.00% by mass of B2O3, 0.00% by mass of TiO2 and 0.00% by mass of F2).

[0082] Next, a warp protectant treatment solution is prepared, comprising 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.

[0083] Next, the glass filaments formed in the above manner are used as warp glass filaments and weft glass filaments, and the aforementioned warp protective agent is coated onto the warp glass filaments. The operation of coating the warp glass filaments with the aforementioned warp protective agent can be performed by passing the warp glass filaments through a treatment tank containing the aforementioned warp protective agent treatment solution, and then adjusting the linear speed to a drying strength index of 31.5, and passing them through a dryer with an ambient temperature range of 100 to 150°C.

[0084] It should be noted that the glass filaments used for the weft yarns are only coated with the aforementioned bundling agent, and are not coated with the aforementioned protective agent for the warp yarns at all.

[0085] Next, the above-mentioned warp yarns are made of glass filaments, and the above-mentioned weft yarns are made of glass filaments. The yarns are woven using an air-jet loom. The weaving density of the warp yarns is set to 65 threads / 25mm, and the weft yarns are set to 62 threads / 25mm, to obtain the first glass cloth with a plain weave structure.

[0086] Next, the first glass cloth is subjected to degreasing, surface treatment, and fiber-opening treatment to obtain a second glass cloth, which is the glass cloth of this embodiment. In the degreasing treatment, the first glass cloth is placed in a heating furnace at an ambient temperature of 350–400°C for 60 hours to decompose the bundling agent and warp protectant attached to the first glass cloth. The surface treatment is performed by coating the first glass cloth with a silane coupling agent and curing the silane coupling agent while continuously passing it through a heating furnace at 130°C. The fiber-opening treatment is performed by applying a tension of 50N to the warp fibers of the first glass cloth and opening the fibers using a water flow pressure set to 3.0 MPa. In the fiber-opening treatment, the tension value detected by a tension detector is fed back to the guide rollers conveying the first glass cloth, and the tension is adjusted by changing the position of the guide rollers.

[0087] It should be noted that the tension applied to the warp fibers of the glass cloth in processes other than fiber opening is in the range of 70 to 120 N.

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

[0089] For the second glass cloth obtained in this embodiment, the adhesion dispersion number was determined by the following method, the standard deviation of the adhesion dispersion number was calculated, and the glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were determined. On the other hand, the impregnation time of the resin relative to the second glass cloth was determined. The results are shown in Table 1.

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

[0091] First, cut 100mm x 100mm pieces of glass cloth at three points: one 200mm inside one end of the second glass cloth in the width direction, another 200mm inside the other end, and the center point in the width direction. Next, embed the cut glass cloth pieces in epoxy resin and allow the epoxy resin to cure. Grind the cured epoxy resin until a cross-section perpendicular to the length direction of the warp yarn is observable, thus creating a test piece for determining the adhesion dispersion number. Select a glass filament for the warp yarn located 5mm from one end of the test piece, and observe the ground surface of the test piece using a scanning electron microscope to determine the adhesion quantity.

[0092] The above-mentioned adhesion quantity was determined by the following method: the warp with width L was divided into three regions, namely left region 1a, central region 1b, and right region 1c, by glass filament 1 in such a way that the widths L1, L2, and L3 of each region were the same (L1=L2=L3, L1+L2+L3=L). Each region 1a, 1b, and 1c was observed at a magnification of 1600 using a scanning electron microscope.

[0093] Furthermore, let B be the maximum value among the adhesion counts in the three regions 1a, 1b, and 1c mentioned above. max Let the minimum value be B. min When the number of glass filaments 2 contained in the glass precursor 1 for warping is set to N, |B max -B min | / N is set as the adhesion dispersion number of the glass filament used for the warp.

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

[0095] In addition, the standard deviation of the adhesion dispersion number of the above 15 warp filaments using glass filaments is used as the standard deviation of the adhesion dispersion number of the second glass cloth.

[0096] [Glass fiber strength]

[0097] First, a glass raw material with a glass composition identical to that of the glass fibers in the examples or comparative examples was heated in a muffle furnace at 1400–1650°C for 0.5–24 hours, and the resulting molten glass was poured onto a carbon plate to form glass shavings. Next, the obtained glass shavings were fed into a small cylindrical platinum sleeve with a circular nozzle at the bottom of the container. The sleeve was heated to a specified temperature so that the viscosity of the fed glass shavings was 1000 ± 150 poise, causing the glass shavings to melt and obtain molten glass. The molten glass ejected from the nozzle of the platinum sleeve was wound at a specified speed using a winding machine, resulting in glass fibers with a diameter of 13 ± 2 μm. The fibers were stretched and cooled to solidify, yielding glass filaments with a perfectly circular cross-sectional shape. A single glass filament (monofilament) was collected between the nozzle of the platinum sleeve and the winding machine, and the filament in a state where deterioration caused by contact and friction was minimized was collected as a sample for tensile strength evaluation. Next, the obtained glass filament is aligned with the line connecting the center points of the short sides of the backing paper, which has two clamping parts and two supporting parts (described later), in the long side direction and bonded together to form a monofilament test piece. Next, the diameter of the obtained glass filament is measured using a scanning electron microscope (Hitachi, Ltd., trade name: S-3400), and the cross-sectional area of ​​the glass filament is calculated based on the obtained diameter. Next, the two clamping parts of the backing paper are placed on the upper and lower clamps of a tensile testing machine (A&D Corporation, trade name: STB-1225S benchtop material testing machine), with the clamping distance between the upper and lower clamps set at 25 mm. The two supporting parts of the backing paper are removed, leaving only the glass filament connecting the clamping parts, and a tensile test is performed at a crosshead speed of 5 mm / min. Next, the tensile strength is calculated by dividing the maximum load value at which the glass filament breaks by the cross-sectional area of ​​the glass filament. Excluding the aforementioned monofilament test pieces that experienced incomplete breakage such as fraying or breakage during the measurement, the average value of the aforementioned tensile strength for n=30 was calculated, and the glass fiber strength was determined accordingly.

[0098] It should be noted that the aforementioned backing paper has a short side of 25mm and a long side of 50mm. In addition, there is a cut-off portion with a short side of 15mm and a long side of 25mm in the center of its interior, so that the short side and long side of the backing paper are parallel to the short side and long side of the cut-off portion, respectively. A clamping portion is provided between the short side of the cut-off portion and the short side of the backing paper, which is mounted on the fixture of a tensile testing machine. Furthermore, a support portion is provided between the long side of the cut-off portion and the long side of the backing paper, which connects to and supports the two clamping portions.

[0099] [Glass fiber elastic modulus]

[0100] First, a tensile test was conducted on the glass filament in exactly the same manner as the method for determining the strength of the glass fiber described above. Next, the stresses corresponding to the strains ε1 = 0.0005 and ε2 = 0.0025 between the two points were designated as σ1 and σ2, respectively. The tensile modulus of elasticity was calculated by dividing the difference in stress (σ2 - σ1) by the difference in strain (ε2 - ε1). After removing any monofilament test pieces that had experienced fraying during the test, the average tensile modulus of elasticity for n = 15 was calculated, thereby determining the elastic modulus of the glass fiber.

[0101] [Immersion time of resin]

[0102] First, cut out 60mm × 40mm pieces of glass cloth centered at three points: one 200mm inside one end of the second glass cloth in the width direction, another 200mm inside the other end, and the center in the width direction, to prepare impregnation evaluation test pieces.

[0103] Next, the impregnation evaluation test piece was immersed in benzyl alcohol, and the time from immersion to complete saturation of the test piece was measured in both the warp and weft directions. For each measurement point, five test pieces were used, and the average value was calculated for each measurement point.

[0104] Furthermore, the difference between the maximum and minimum immersion times of the warp and weft yarns at each measurement point is defined as the non-uniformity of immersion time.

[0105] The refractive index of benzyl alcohol is similar to that of glass filaments. Therefore, when the above-mentioned impregnation evaluation test piece is impregnated with benzyl alcohol, the impregnated part appears transparent because the benzyl alcohol permeates between the glass filaments of the original glass fiber. The unimpregnated part appears opaque because it has a refractive index difference with the air present between the glass filaments. Therefore, it is easy to visually identify whether impregnation has been completed.

[0106] [Example 2]

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

[0108] Next, the glass filaments formed in the above manner were used as warp and weft glass filaments. Except that the weaving density of the warp and weft filaments was set to 95 threads / 25mm, the first glass cloth with a plain weave was made in the same manner as in Example 1.

[0109] Next, except that the water pressure in the fiber opening process is set to 1.0 MPa, the first glass cloth is subjected to degreasing, surface treatment and fiber opening in the same manner as in Example 1 to obtain the second glass cloth as the glass cloth of this embodiment.

[0110] The second glass cloth in this embodiment has warp yarns with a width of 120 μm and an average number of layers of 1.4, and weft yarns with a width of 185 μm and an average number of layers of 0.9, and a thickness of 13 μm. The results are shown in Table 1.

[0111] Next, except for using the second glass cloth obtained in this embodiment, the adhesion dispersion number was measured in the same manner as in Example 1, the standard deviation of the adhesion dispersion number was calculated, and the glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were measured. On the other hand, the impregnation time of the resin relative to the second glass cloth was measured. The results are shown in Table 1.

[0112] [Comparative Example 1]

[0113] In this comparative example, except that the linear speed was adjusted so that the drying strength index during the operation of coating the warp protective agent on the warp glass filament was 40.9, the second glass cloth used as the glass cloth of this comparative example was prepared in exactly the same manner as in Example 1.

[0114] The second glass cloth of this comparative example has warp yarns with a width of 374 μm and an average number of layers of 3.7, and weft yarns with a width of 360 μm and an average number of layers of 3.8, and a thickness of 96 μm. The results are shown in Table 1.

[0115] Next, except for using the second glass cloth obtained in this comparative example, the adhesion dispersion number was measured in the same manner as in Example 1, the standard deviation of the adhesion dispersion number was calculated, the glass fiber elastic modulus and glass fiber strength of the glass fibers constituting the second glass cloth were measured, and the impregnation time of the resin relative to the second glass cloth was measured. The results are shown in Table 1.

[0116] [Table 1]

[0117]

[0118] As shown in Table 1, according to the glass cloths of Examples 1 and 2, by keeping the adhesion dispersion number in the range of 0.027 to 0.077, the unevenness of the resin impregnation time relative to the warp glass filaments is less than 1.0 minute, thus suppressing the unevenness 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 filaments at the ends of the glass cloth is the same as in Example 1, and the unevenness of the weft impregnation time is less than 1.0 minute, but the adhesion dispersion number is 0.094, which is greater than 0.077. Therefore, the unevenness of the resin impregnation time relative to the warp glass filaments is 1.5 minutes, which is greater than the unevenness of the glass cloths of Examples 1 and 2, indicating that the impregnation time becomes uneven.

Claims

1. A glass cloth having warp threads and weft threads formed of glass strands composed of a plurality of glass filaments, the glass cloth being characterized in that the number of adhesion dispersals represented by the following formula (1) is in the range of 0.027 to 0.077, |B max -B min | / N … (1) wherein B max is the number of adhesions, B min is the number of adhesions, N is the number of glass filaments contained in the warp glass precursor, and the regions refer to three regions of a left region, a center region, and a right region into which the warp glass precursor is divided, the regions being regions of equal width in the width direction of the warp glass precursor, the adhesion refers to a region enclosed without a gap by the outer peripheral surfaces of 3 to 4 glass filaments in a cross section perpendicular to the length direction of the glass strands, the region enclosed without a gap refers to a region in which the shortest distance between the outer peripheral surface of one glass filament and the outer peripheral surface of another glass filament among two glass filaments in contact is less than 0.3 μm, the method for measuring the number of adhesions is as follows: a glass cloth sheet is embedded in an epoxy resin and the epoxy resin is cured, the cured epoxy resin is ground to a degree that enables observation of a cross section perpendicular to the length direction of the warp threads to produce a test piece for measuring the number of adhesion dispersals, a glass strand of a warp thread located 5 mm from one end of the test piece is selected, and the ground surface of the test piece is observed at a magnification of 1600 times using a scanning electron microscope.

2. A prepreg, characterized by, A glass cloth comprising the glass cloth according to claim 1.

3. A printed wiring board, characterized by, A glass cloth comprising the glass cloth according to claim 1. A glass cloth comprising the glass cloth according to claim 1.

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