Glass composition, glass fiber, glass cloth, and method for manufacturing glass fiber

Abstract

To provide a novel glass composition that has a low permittivity and is suitable for mass production.SOLUTION: A glass composition for glass fiber is provided that satisfies, in wt.%, for example, SiO2+B2O3≥81, (SiO2+B2O3+Al2O3) / (SiO2+B2O3)≥1.13. The permittivity at a frequency of 1 GHz is 4.4 or less, the dielectric loss tangent at a frequency of 1 GHz is 0.007 or less, the temperature T2 at which the viscosity is 102 dPas is 1700°C or less, and the temperature T3 at which the viscosity is 103 dPas is 1365°C or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a glass composition, glass fibers composed of the composition, and glass cloth. Furthermore, this invention relates to a method for producing glass fibers. [Background technology]

[0002] One type of printed circuit board found in electronic devices is made of resin, glass, etc. The substrate is composed of fibers, inorganic fillers, and, if necessary, further materials such as curing agents and modifiers. Also, there is the printed wiring board (printed wiring board) before electronic components are mounted. Some printed circuit boards (printed circuit boards) have a similar configuration to the above-mentioned boards. Hereinafter, in this specification, both printed circuit boards and printed wiring boards will be referred to collectively as "printed circuit boards (printed board)". This document describes the functions of glass fibers in printed circuit boards (PCBs), including their role as insulators, heat-resistant materials, and reinforcing materials. Glass fibers are included in PCBs, for example, as glass cloth woven from glass yarn (multiple glass fibers joined together). Glass cloth is also typically used in PCBs as a prepreg impregnated with resin. In recent years, PCBs have become thinner to meet the demands for miniaturization of electronic devices and for higher-performance PCB mounting. Thinner PCBs require glass fibers with smaller diameters. Furthermore, due to the rapidly increasing demand for high-speed transmission of large amounts of data, there is a growing need for glass fibers with lower dielectric constants in PCBs.

[0003] Glass is sometimes used as an inorganic filler in printed circuit boards. A typical example is flake glass. When glass molded bodies such as flake glass are used as inorganic fillers in printed circuit boards, the molded bodies are required to have properties similar to those of glass fibers used in printed circuit boards, such as a low dielectric constant.

[0004] Glass fibers composed of low dielectric constant glass compositions are disclosed in Patent Documents 1 to 5. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 62-226839 [Patent Document 2] Special Publication No. 2010-508226 [Patent Document 3] Japanese Patent Publication No. 2009-286686 [Patent Document 4] International Publication No. 2017 / 187471 [Patent Document 5] International Publication No. 2018 / 216637 [Overview of the project] [Problems that the invention aims to solve]

[0006] Glass compositions are required to have a low dielectric constant and a characteristic temperature suitable for mass production. An important characteristic temperature for glass compositions in the mass production of glass fibers is the spinning temperature T3, i.e., a viscosity of 10. 3 The temperature at which dPas occurs is one example. Temperature T2 T2.5, and even the devitrification temperature TL, are indicators used to determine whether a glass composition is suitable for mass production of glass fibers. However, glass compositions with low dielectric constants do not easily allow for adjustment of their characteristic temperature.

[0007] In view of the above, the present invention aims to provide a novel glass composition with a low dielectric constant and suitable for mass production. [Means for solving the problem]

[0008] The present invention Expressed as a percentage by weight, 40 ≤ SiO2 ≤ 60 25 ≤ B2O3 ≤ 45 5 ≤ Al2O3 ≤ 15 0 < R2O ≤ 5 0 < RO < 15 including SiO2 + B2O3 ≥ 80, and / or SiO2 + B2O3 ≥ 78 and 0 < RO < 10 To provide a glass composition in which the above holds. In this specification, R2O is at least one oxide selected from Li2O, Na2O, and K2O, and RO is at least one oxide selected from MgO, CaO, and SrO.

[0009] From another aspect, the present invention expressed in weight percentage 40 ≤ SiO2 ≤ 60 25 ≤ B2O3 ≤ 45 0 < Al2O3 ≤ 18 0 < R2O ≤ 5 0 ≤ RO ≤ 12 including i) SiO2 + B2O3 ≥ 80, and SiO2 + B2O3 + Al2O3 ≤ 99.9, and ii) SiO2 + B2O3 ≥ 78, SiO2 + B2O3 + Al2O3 ≤ 99.9, and 0 < RO < 10 To provide a glass composition in which at least one of the above holds.

[0010] From another aspect, the present invention expressed in weight percentage 40 ≤ SiO2 ≤ 60 25 ≤ B2O3 ≤ 45<​​​​​​​​​​​​​​​​​​​ The dielectric loss tangent at a frequency of 1 GHz is 0.007 or less. viscosity 10 2 The temperature T2 at which dPas occurs is 1700℃ or less. The present invention provides a glass composition.

[0012] This invention, from another perspective Expressed as a percentage by weight, 40 ≤ SiO2 ≤ 49.95 25 ≤ B2O3 ≤ 40 10 ≤ Al2O3 ≤ 20 0.1 ≤ R²O ≤ 2 1 ≤ RO ≤ 10 Includes, SiO2 + B2O3 ≥ 70, and SiO2 + B2O3 + Al2O3 ≤ 97 The present invention provides a glass composition that satisfies the following conditions.

[0013] This invention, from another perspective Expressed as a percentage by weight, 40 ≤ SiO2 ≤ 49.95 25 ≤ B2O3 ≤ 29.9 10 ≤ Al2O3 ≤ 20 0.1 ≤ R²O ≤ 1 2 ≤ RO ≤ 8 Includes, SiO2 + B2O3 ≥ 70, and SiO2 + B2O3 + Al2O3 ≤ 97 The present invention provides a glass composition that satisfies the following conditions.

[0014] This invention, from another perspective Expressed as a percentage by weight, 40 ≤ SiO2 ≤ 49.95 31 ≤ B2O3 ≤ 40 8 ≤ Al2O3 ≤ 18 0.1 ≤ R²O ≤ 1 1 ≤ RO ≤ 10 Includes, SiO2 + B2O3 ≥ 77, and SiO2 + B2O3 + Al2O3 ≤ 97 The present invention provides a glass composition that satisfies the following conditions.

[0015] This invention also has another aspect to it. The present invention provides glass fibers composed of a glass composition.

[0016] This invention also has another aspect to it. The present invention provides a glass cloth composed of glass fibers.

[0017] This invention also has another aspect to it. The present invention provides a prepreg containing glass cloth.

[0018] This invention also has another aspect to it. The present invention provides a printed circuit board containing glass cloth.

[0019] This invention also has another aspect to it. The present invention provides a method for producing glass fibers, which includes a step of melting a glass composition at a temperature of 1400°C or higher to obtain glass fibers having an average fiber diameter of 1 to 6 μm. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a glass composition with a lower dielectric constant and a characteristic temperature suitable for mass production. [Modes for carrying out the invention]

[0021] In the following, all "%" indications for the content of each component represent weight percent. "Substantially absent" means a content of less than 0.1% by weight, preferably less than 0.07% by weight, and more preferably less than 0.05% by weight. In this wording, "substantially" means that impurities that are inevitably mixed in from industrial raw materials are permitted up to the above limits. The content, characteristics, and other preferred ranges of each component can be determined by arbitrarily combining the upper and lower limits described individually below.

[0022] In the following, the characteristic temperature of the glass composition is when the viscosity is 10 n The temperature at which dPas occurs is Tn This is expressed as (for example, T2.5 means that the viscosity of the glass composition is 10 2.5 Temperature at which dPas is reached (This means...). Strictly speaking, dielectric constant refers to relative permittivity, but in this specification, it is simply referred to as dielectric constant in accordance with convention. Dielectric constant and dielectric loss tangent are values ​​at room temperature (25°C). The following description is provided not to limit the present invention, but to illustrate preferred embodiments.

[0023] [Composition components] (SiO2) SiO2 is a component that forms the network structure of glass. SiO2 has the effect of lowering the dielectric constant of the glass composition. If the SiO2 content is too low, the dielectric constant of the glass composition will not be sufficiently low. It cannot be made lower. If the SiO2 content is too high, the viscosity during melting will be too high. This makes it difficult to obtain a homogeneous glass composition. When the homogeneity of the glass composition decreases, fiber breakage is induced during spinning of glass fibers, especially glass fibers with a small fiber diameter. The SiO2 content is 40% or more, 45% or more, 46% or more, and even 48% or more, especially 49%. Preferably, it should be 50% or more, and in some cases 50.5% or more, 51% or more, 52% or more, or 53% or more. The SiO2 content should be 60% or less, and less than 58%. Preferably 56% or less, even less than 55%, and especially 54.5% or less, and in some cases 54% or less, 53% or less, 52% or less, or 51% or less. An example of a suitable range is 40% to less than 58%, and even further, 40% to less than 55%. Additionally, the SiO2 content can be 40% to 49.95%.

[0024] (B2O3) B2O3 is a component that forms the network structure of glass. B2O3 lowers the dielectric constant of the glass composition, reduces the viscosity of the glass composition when melted, improves degassing (bubble release), and suppresses the incorporation of bubbles into the formed glass fibers. On the other hand, B2O3 is easily volatile when the glass composition melts, and if its content is excessive, it may become difficult to obtain sufficient homogeneity in the glass composition, the suppression of bubble incorporation into the formed glass fibers may be insufficient, or B2O3 volatilized from the glass may adhere to the tip of the bushing used in spinning, causing so-called yarn breakage. The B2O3 content is preferably 25% or more, 27% or more, 29% or more, 30% or more, and even more than 30%, and in some cases it may be 30.5% or more, and even 31% or more, 32% or more, 33% or more, or 34% or more. The B2O3 content is preferably 45% or less, 43% or less, 41% or less, and even 39% or less, and in some cases may be 38% or less, even 36% or less, 35% or less, 34% or less, or 32% or less. An example of a preferred range for the B2O3 content is over 30% and up to 45%. In addition, the B2O3 content can be 25% to 40%, 25% to 29.9%, or 31% to 40%.

[0025] (SiO2+B2O3), (SiO2+B2O3+Al2O3) To obtain a glass composition with a sufficiently low dielectric constant, the SiO2 content and the B2O3 content are important. If you adjust the total (SiO2 + B2O3) to 77% or more, 78% or more, and even 80% or more Good. (SiO2+B2O3) is preferable if it is 81% or higher, 82% or higher, or even 83% or higher. In some cases, it may be 84% or more, or even 85% or more. (SiO2+B2O 3) may be 90% or less, or even 87.5% or less. This is because if the value of (SiO2 + B2O3) is too high, it promotes the tendency for the glass composition to separate into phases. Also, (SiO2 The SiO2 content, B2O3 content, and The total content of Al2O3 (SiO2 + B2O3 + Al2O3) allows for the inclusion of other components. Therefore, 99.9% or less is preferable. (SiO2 + B2O3 + Al2O3) is 98% or less. It may be 97% or less, less than 97%, or even 96% or less. (SiO2 + B2O3) A preferred example of a combination with (SiO2+B2O3+Al2O3) is when (SiO2+B2O3) is 82% or more and (SiO2+B2O3+Al2O3) is 98% or less. Alternatively, (SiO2+B2O3+Al2O3) can be 90% to 98% or 90% to 97%.

[0026] The ratio of (SiO2 + B2O3 + Al2O3) to (SiO2 + B2O3), i.e., (SiO2 + B2O3 + Al2O3) / (SiO2 + B2O3), is preferably 1.05 or higher, and may be 1.12 or higher, 1.13 or higher, 1.15 or higher, or even 1.20 or higher. As this ratio increases, defects such as fuzzing of the glass fibers are suppressed. This effect becomes particularly pronounced in the fifth combination of SiO2 and B2O3 content, which will be described later.

[0027] (Preferred combination of SiO2 and B2O3) To obtain a glass composition with a lower dielectric constant and easier melting, the content of SiO2 and B2O3 is required. There are preferred combinations of concentrations. The first combination is when the SiO2 content is 4 The first combination has a B2O3 content of 8-51%, preferably 49-51%, more preferably 50-51%, and a B2O3 content of 33-35%, preferably 34-35%. The second combination has an SiO2 content of 50-53%, preferably 51-52%, and a B2O3 content The combination is 32-35%, preferably 32-34%. The third combination has an SiO2 content of 52-54%, preferably 52.5-54%, and a B2O3 content of 3 The combination is 1-34%, preferably 32-34%. The fourth combination has an SiO2 content of 52-55%, preferably 53-55%, and a B2O3 content of 30-3%. This combination has a 2% probability.

[0028] The fifth combination has an SiO2 content of 47-52%, preferably 48-51%, Preferably, the content is 48.5-50.5%, particularly preferably 48.95-49.95%, and the B2O3 content is 25-30%, preferably 26-29.5%, more preferably 26-29%. In the fifth combination, the sum of the MgO content and CaO content (MgO + CaO) is 3.5% or more, more preferably 4% or more, and preferably 8% or less. In the sixth combination, the SiO2 content is 48-53%, preferably 49% The content is approximately 52%, more preferably 49-51.5%, and in some cases 49-51% or 48.95-49.95%, with a B2O3 content of 28-35%, preferably 30-33%, and in some cases 30.5-32.5%. In the sixth combination, (MgO+CaO) is 1% or more and less than 3.5%, preferably 1-3%, more preferably 1-2.5%, and in some cases 1.5-2.5%.

[0029] (Al2O3) Al2O3 is a component that forms the network structure of glass. Al2O3 has the effect of increasing the chemical durability of the glass composition. On the other hand, Al2O3 makes the glass composition more susceptible to devitrification during spinning. The Al2O3 content is preferably 5% or more, 7.5% or more, 8% or more, 9% or more, and even 10% or more, and may be 10.5% or more, 12% or more, or 13% or more in some cases. The Al2O3 content is preferably 20% or less, 18% or less, 17% or less, and even 15% or less, and may be 14% or less, even 13% or less, or 12.5% ​​or less in some cases. An example of an Al2O3 content suitable when it is desirable to reliably control the devitrification temperature TL to a range lower than the temperature T3 is 12.3% or less. Al2O3 is generally It is understood to be a component that increases the viscosity of the glass composition during melting. However, SiO2 + B2O3 In glass compositions with high values, Al2O3 can specifically reduce viscosity during melting.

[0030] Examples of preferred ranges for the Al2O3 content are 8-12.5%, particularly 10-12.5%. When adopting the first to fourth combinations of SiO2 and B2O3 content described above, These ranges are particularly suitable.

[0031] Another example of a preferred range for the Al2O3 content is 13-17%. When adopting the fifth combination of B2O3 content, an Al2O3 content of 13-17% is particularly suitable. Another example of a preferred range for Al2O3 content is 12-15%. When adopting the sixth combination of SiO2 and B2O3 content, the Al2O3 content A prevalence rate of 12-15% is particularly suitable.

[0032] Alkali metal oxides are well known as components that reduce viscosity during melting, but increasing the content of alkali metal oxides simultaneously increases the dielectric constant. In contrast, in the preferred glass composition according to the present invention, Al2O3 has the effect of specifically reducing viscosity during melting, but with only a slight side effect of increasing the dielectric constant.

[0033] (MgO) MgO is an optional component that reduces the viscosity of the glass composition during melting, suppresses the incorporation of bubbles into the glass fibers, and improves the homogeneity of the glass composition. The MgO content may be 0.1% or more, 0.2% or more, even 0.5% or more, 0.6% or more, and in some cases 0.8% or more, and even 1% or more. The MgO content is preferably less than 10%, 8% or less, 7% or less, and 5% or less, and in some cases 3% or less, even 2% or less, and especially 1.6% or less. In order to maintain an appropriate ratio with the CaO content, the MgO content may be preferably 1.7% or less, 1.5% or less, even 1.2% or less, and 1% or less. However, depending on the content of other components, the optimal MgO content may be 2% or more, for example 2-8%, even 2-5%, or 3-5%. It should be noted that MgO has a significant effect in lowering the devitrification temperature, while being less effective than alkali metal oxides R2O. To avoid increasing the dielectric constant, it is preferable to add it preferentially over R2O, or in other words, to have a higher content than R2O.

[0034] A preferred range for the MgO content is 0.5–2%. (Content of SiO2 and B2O3) When adopting the first to fourth combinations of ratios, an MgO content of 0.5-2%, and more specifically 0.5-1.6%, is suitable. When used, an MgO content of 0.5-2%, and more preferably 1-2%, is suitable. Another example of a preferred range for MgO content is 0.1-1%. SiO2 and B2O3 content When adopting the sixth combination, an MgO content of 0.1-1%, and more specifically, between 0.1% and less than 1%, is particularly suitable.

[0035] (CaO) CaO is an optional component that improves the solubility of glass raw materials and reduces the viscosity of the glass composition during melting. The effect of CaO is greater than that of MgO. The CaO content may be 0.1% or more, 0.5% or more, even 1% or more, and in some cases 1.5% or more, and even 2% or more. Preferably, the CaO content is less than 10%, 7% or less, or 5% or less, and in some cases 4% or less, 3.5% or less, 3% or less, and even 2.5% or less. It should be noted that CaO has a greater effect on increasing the dielectric constant of the glass composition compared to MgO and ZnO. For the same reasons as MgO, CaO is also more effective than alkali metal oxide R2O. It is preferable to add it preferentially, in other words, in such a high proportion as R2O.

[0036] Examples of preferred CaO content ranges include 2-5%, and even more specifically, 2-3.5%. SiO2 When adopting combinations 1 to 5 of the B2O3 content, a CaO content of 2 to 5% is particularly suitable, 2 to 3.5% is more suitable for combinations 1 to 4, and 2.5 to 5% is more suitable for combination 5. Another example of a preferred range for CaO content is 0.5 to 2%. When adopting a sixth combination of SiO2 and B2O3 content, CaO A content of 0.5-2% is particularly suitable.

[0037] A particularly preferred combination of MgO and CaO content is 1-2% MgO and 2-5% CaO. This combination is especially suitable when adopting the fifth combination of SiO2 and B2O3 content.

[0038] (SrO) SrO is an optional component that improves the solubility of glass raw materials and reduces the viscosity of the glass composition during melting. However, since SrO increases the dielectric constant of the glass composition compared to MgO and CaO, it is desirable to limit its content. The SrO content is preferably 1% or less, 0.5% or less, and even 0.1% or less. SrO may be substantially absent.

[0039] When adopting the 1st to 5th combinations of SiO2 and B2O3 content, the SrO content A ratio of 0.1% or less is particularly suitable. In this case, SrO may not be present at all. However, SrO may be added to a concentration of 0.1-5%, and even 1-3.5%. When adopting the sixth combination of SiO2 and B2O3 concentrations. For this, a SrO content of 0.1 to 5%, and more specifically 1 to 3.5%, is suitable. In particular, in the sixth combination, contrary to the common technical knowledge of those skilled in the art, it has been found that SrO can effectively reduce dielectric loss, or in other words, reduce dielectric loss tangent. In the sixth combination, the ratio of SrO content to CaO content, SrO / CaO, may exceed 1. In this case, the ratio of CaO content to MgO content, CaO / MgO, may also exceed 1.

[0040] (RO) The RO content, i.e., the combined content of MgO, CaO, and SrO, is preferably less than 15%, 12% or less, 10% or less, less than 10%, 9.5% or less, 8% or less, and even less than 7%, particularly less than 6%, and in some cases it may be 5% or less, and even 4% or less. If the RO content is too high, the dielectric constant may not decrease sufficiently. Each component constituting RO is an arbitrary component individually, but it is preferable that at least one of them is included, i.e., the sum of their contents exceeds 0%. The RO content is preferably 1% or more, 1.5% or more, 2% or more, and even more than 2.5%, and in some cases it may be 3% or more, and even more than 3.5%.

[0041] A preferred range for RO content is 2-7%, particularly 2-4%.

[0042] (MgO / RO) The MgO / RO ratio, that is, the ratio of MgO content to RO content, is preferably less than 0.8, more preferably less than 0.7, and in some cases may be 0.5 or less, or 0.4 or less. When the MgO / RO ratio is high, the glass composition tends to separate into phases more significantly, which can impair the homogeneity of the glass composition. In addition, the presence of phases with different physical properties may make spinning difficult. On the other hand, in order to suppress the dielectric constant of the glass composition, the MgO / RO ratio is preferably 0.1 or higher, more preferably 0.14 or higher, and in some cases may be 0.19 or higher. The MgO / RO ratio is preferably 0.1 to 0.5.

[0043] (MgO / (MgO+CaO)) The ratio of MgO content to the sum of MgO and CaO content, MgO / (MgO+CaO), may also be within a range that can be arbitrarily combined from the upper and lower limits for MgO / RO mentioned above. MgO / (MgO+CaO) is preferably 0.1 to 0.5, and particularly 0.1 to 0.4.

[0044] (Li2O) Li2O, even in small amounts, reduces the viscosity of the glass composition during melting, thus reducing the glass. This optional component has the effect of suppressing the incorporation of bubbles into the fibers and also suppressing devitrification. Furthermore, the addition of an appropriate amount of Li2O significantly suppresses the tendency of the glass composition to separate into phases. However, Li2O increases the dielectric constant of the glass composition, although its effect is relatively weaker than that of other R2O materials. Li2O content is preferably 1.5% or less, 1% or less, or 0.5% or less. Furthermore, in some cases, it may be 0.4% or less, 0.3% or less, or even 0.2% or less. The Li2O content should be 0.01% or more, 0.03% or more, or even 0.05% or more. Preferred. Examples of preferred ranges for the Li2O content are 0.01 to 0.5%, and even more preferably 0.0 The percentages range from 5% to 0.4%.

[0045] (Na2O) Even a small amount of Na2O can lower the viscosity of the glass composition during melting. It is an optional component that has the effect of suppressing the incorporation of foam into the fibers and also has the effect of suppressing devitrification. From this perspective, the Na2O content should be 0.01% or more, 0.05% or more, and further The amount may be 0.1% or more. However, the addition of Na2O increases the dielectric constant of the glass composition. It is necessary to keep it within a limited range to prevent it from rising further. The Na2O content should be 1.5% or less. Preferably, the content is 1% or less, 0.5% or less, and even 0.4% or less, and in some cases, 0.2% or less, even 0.15% or less, and especially 0.1% or less, 0.05% or less, or 0.01% or less. An example of a preferred range for the Na2O content is 0.01 to 0.4%.

[0046] (K2O) Even a small amount of K2O added can lower the viscosity of the glass composition during melting, thus reducing the glass fibers. It is an optional component that has the effect of suppressing the incorporation of bubbles into the fibers and also suppressing devitrification. However, K2O has a greater effect of increasing the dielectric constant of the glass composition. The K2O content is preferably 1% or less, 0.5% or less, or 0.2% or less, and in some cases it may be 0.1% or less, 0.05% or less, or 0.01% or less. K2O is substantially absent. That's fine.

[0047] (R2O) The combined content of R2O, Li2O, Na2O, and K2O is preferably 5% or less, 4% or less, 3% or less, 2% or less, and even 1.5% or less, and in some cases may be 1% or less, and even 0.6% or less, and 0.5% or less. Each component constituting R2O is individually... Although optional components, it is preferable that at least one of them is included, i.e., that the total content exceeds 0%. The content of R2O is 0.03% or more, 0.05% or more, Furthermore, a concentration of 0.1% or more is preferred, particularly 0.15% or more, and 0.2% or more.

[0048] Furthermore, when the Li2O content is greater than the Na2O content, the tendency for the glass composition to undergo phase separation may be more effectively suppressed.

[0049] If the Li2O content is 0.25% or more, and even 0.3% or more, the characteristic temperature will be higher. It may be possible to adjust it to a favorable range. In particular, the first combination of SiO2 and B2O3 content. If this is adopted, the Li2O content must be 0.25% or more, and moreover, 0.3% or more. It is preferable to add it in such a way. In this case, the Na2O content should be 0.05% or more. It may be added in such a way that the i2O content is less than the total i2O content.

[0050] (T-Fe2O3) T-Fe2O3 is an optional component that improves the solubility of glass raw materials through its heat-absorbing properties and also improves the homogeneity of the glass composition during melting. Due to the homogeneity-improving effect of T-Fe2O3, even when the fiber diameter of the formed glass fibers is small, the occurrence of fiber breakage during spinning is suppressed, and spinning operability is improved. The T-Fe2O3 content is preferably 0.01% or more, 0.02% or more, 0.05% or more, and more preferably 0.10% or more. The effect of improving solubility is particularly noticeable when the T-Fe2O3 content is 0.01% or more, while the effect of improving homogeneity is particularly noticeable when it is 0.02% or more. For purposes such as suppressing excessive heat-absorbing properties by T-Fe2O3, the T-Fe2O3 content is preferably 0.5% or less, 0.3% or less, and more preferably 0.25% or less, and may be 0.20% or less in some cases. In this specification, following convention, the total amount of iron oxide in the glass composition is defined as Fe2 such as FeO. The value of iron oxides other than O3 converted to Fe2O3 is displayed as the T-Fe2O3 content. Therefore, at least a portion of the T-Fe2O3 may be present as FeO. Examples of preferred ranges for the T-Fe2O3 content are 0.01–0.5%, and more specifically, 0.1–0.3%.

[0051] (ZnO) ZnO is an optional component that improves the solubility of glass raw materials and reduces the viscosity of the glass composition during melting. However, ZnO increases the dielectric constant of the glass composition. The ZnO content is preferably 3.5% or less, 2% or less, 1% or less, and even 0.5% or less. ZnO may be substantially absent.

[0052] (Other ingredients) Other components that the glass composition may contain include P2O5, BaO, PbO, and TiO2. Examples include ZrO2, La2O3, Y2O3, MoO3, WO3, Nb2O5, Cr2O3, SnO2, CeO2, As2O3, Sb2O3, and SO3. Other components that the glass composition may contain are, for example, noble metal elements such as Pt, Rh, and Os, and halogen elements such as F and Cl. The permissible content of each of these components is preferably less than 2%, more preferably less than 1%, and particularly less than 0.5%, and in total preferably less than 5%, more preferably less than 3%, particularly less than 2%, and especially less than 1%. However, the glass composition may not substantially contain any of the above other components. TiO2 is added in trace amounts for reasons described later. It is acceptable, but it is not necessary for it to be substantially included. The same applies to ZrO2. Also, BaO and It is preferable that PbO is substantially absent. It is also preferable that P2O5 is substantially absent. This is because BaO and PbO have a significant effect in increasing the dielectric constant of the glass composition, and P2O5 induces phase separation. Other than the components listed above from SiO2 to ZnO. The components do not need to be substantially present. However, even in this case, the glass composition contains components effective in promoting clarification during melting, preferably SO3, F, and Cl, in amounts of less than 2% each. It's okay to do so.

[0053] The addition of a small amount of TiO2, contrary to the common technical knowledge of those skilled in the art, alters the dielectric constant and induction properties of the glass composition. It was found that the electrotangent may decrease. From this perspective, the TiO2 content is It may be greater than 0% and less than or equal to 1%. In particular, the sixth combination of SiO2 and B2O3 content. If this method is adopted, TiO2 may be added in an amount greater than 0% but less than or equal to 1%.

[0054] (Examples of preferred compositions) In a preferred embodiment, the glass composition of the present invention comprises the following components: 40 ≤ SiO2 < 58 25 ≤ B2O3 ≤ 40 7.5 ≤ Al2O3 ≤ 18 0 <R2O≦4 0 ≤ Li2O ≤ 1.5 0 ≤ Na2O ≤ 1.5 0 ≤ K2O ≤ 1 1 ≤ RO < 10 0 ≤ MgO < 10 0 ≤ CaO < 10 0 ≤ SrO ≤ 5 0 ≤ T - Fe2O3 ≤ 0.5

[0055] In one form containing the above components, the following conditions may hold: 7.5 ≤ Al2O3 ≤ 15 and 0 ≤ SrO ≤ 1.

[0056] At the end of the above 0 ≤ ZnO ≤ 3.5 A glass composition to which this is added is also a preferred alternative.

[0057] These forms of glass compositions preferably further satisfy 40 ≤ SiO2 < 55. Furthermore, the condition SiO2 + B2O3 ≥ 80 may also be satisfied, and preferably SiO2 + B2O3 + Al2 It may also satisfy O3 ≤ 99.9. MgO / RO < 0.8 is also a form of galaxy as described above. This is another condition that the composition may satisfy.

[0058] [Characteristics] (dielectric constant) In a preferred embodiment, the dielectric constant of the glass composition according to the present invention at a measurement frequency of 1 GHz is 4.65 or less, 4.4 or less, 4.35 or less, 4.30 or less, 4.25 or less, and moreover, 4.20 or less, and in some cases, 4.18 or less. The dielectric constant at a measurement frequency of 5 GHz is 4.63 or less, 4.4 or less, 4.31 or less, 4.27 or less, 4.22 or less, and moreover, 4.17 or less, and in some cases, 4.15 or less. The dielectric constant at a measurement frequency of 10 GHz is 4.55 or less, 4.4 or less, 4.22 or less, 4.18 or less, 4.14 or less, and moreover, 4.08 or less, and in some cases, 4.06 or less.

[0059] (Dielectric loss tangent: tanδ) In one preferred embodiment, the dielectric loss tangent of the glass composition according to the present invention at a measurement frequency of 1 GHz is 0.007 or less, 0.005 or less, 0.004 or less, and more preferably 0.003 or less, and in some cases 0.002 or less. The dielectric loss tangent at a measurement frequency of 1 GHz may be 0.001 or less, less than 0.001, 0.0009 or less, 0.0008 or less, and more preferably 0.0007 or less. The dielectric loss tangent at a measurement frequency of 5 GHz is 0.007 or less, 0.005 or less, 0.004 or less, and more preferably 0.003 or less, and in some cases 0.002 or less. The dielectric loss tangent at a measurement frequency of 10 GHz is 0.007 or less, 0.006 or less, 0.005 or less, 0.004 or less, and more preferably 0.003 or less, and in some cases 0.002 or less.

[0060] (characteristic temperature) In a preferred embodiment, the T2 of the glass composition according to the present invention is 1700°C or lower, 1650°C or lower, 1640°C or lower, 1620°C or lower, and moreover, 1610°C or lower, and in some cases less than 1600°C, 1550°C or lower, moreover, 1520°C or lower, and particularly 1510°C or lower. T2 is a temperature that serves as a guideline for the melting temperature of the glass molten liquid. An excessively high T2 requires extremely high temperatures to melt the glass molten liquid, which increases energy costs and the cost of equipment that can withstand high temperatures. High. At the same temperature, glass with a lower T2 has a lower viscosity melt, which is effective for clarifying and homogenizing the glass melt. On the other hand, when melting at the same viscosity, glass with a lower T2 can be melted at a lower temperature, making it suitable for mass production. T2.5 is preferably 1590°C or lower, 1550°C or lower, and more preferably 1500°C or lower, and in some cases 1450°C or lower, and more preferably 1400°C or lower. T3 is preferably 1450°C or lower, 1420°C or lower, 1400°C or lower, and more preferably 1365°C or lower, particularly 1360°C or lower, and in some cases 1330°C or lower, and more preferably 1300°C or lower. T3 is a temperature that serves as a guideline for the spinning temperature of glass fibers. An excessively high T3 can result in a large amount of B2O3 volatilizing from the glass at the bushing tip, which can adhere to the tip and increase the risk of so-called thread breakage.

[0061] In one preferred embodiment, T3 of the glass composition according to the present invention is higher than the devitrification temperature TL. In another more preferred embodiment, T3 is 10°C or more, even 50°C or more, and in some cases 100°C or more, higher than TL. In one preferred embodiment, T2.5 of the glass composition according to the present invention is 50°C or more higher than the devitrification temperature TL. In another more preferred embodiment, T2.5 is 100°C or more higher than TL. T3 and T2.5, which are sufficiently higher than TL, contribute greatly to the stable production of glass fibers.

[0062] The fifth combination of SiO2 and B2O3 content is particularly suitable for achieving a preferred characteristic temperature. The preferred characteristic temperature is, for example, T2 below 1520°C, particularly below 1510°C, and also T3 above TL at 1300°C or below. SiO2 and B2O3 content In the first combination, the glass composition also has a Li2O content of 0.25% or more. It is suitable for achieving the desirable characteristic temperature described above.

[0063] [Application] The uses of the glass composition according to the present invention are not limited. Examples of uses include glass fibers and glass molded articles. An example of a glass molded article is flake glass. That is, the glass composition of the present invention may be a glass composition for glass fibers, a glass composition for glass molded articles, or a glass composition for flake glass.

[0064] The glass composition according to the present invention is a glass composition that can further suppress the occurrence of devitrification and the inclusion of bubbles in the glass fibers even when the fiber diameter of the glass fibers to be formed is small. Here, "glass fibers with a small fiber diameter" means, for example, glass fibers with an average fiber diameter of 1 to 6 μm. In other words, the glass composition according to the present invention can be a glass composition for small fiber diameter glass fibers, and more specifically, a glass composition for glass fibers with an average fiber diameter of 1 to 6 μm. Furthermore, as described above, the effects of the present invention become more pronounced when glass fibers manufactured from the glass composition according to the present invention are used in printed circuit boards. From this viewpoint, the glass composition according to the present invention can be a glass composition for glass fibers used in printed circuit boards (printed wiring boards, printed circuit boards).

[0065] Similarly, the glass composition according to the present invention is a glass composition that can further suppress the occurrence of devitrification and the inclusion of bubbles in the glass molded article, such as flake-shaped glass, even when the thickness of the formed glass molded article is small. Here, "small thickness" means, for example, 0.1 to 2.0 μm. Furthermore, as described above, the effects of the present invention become more pronounced when a glass molded article manufactured from the glass composition of the present invention (a glass molded article composed of the glass composition according to the present invention) is used as a printed circuit board. From this viewpoint, the glass composition according to the present invention can be a glass composition for glass molded articles used in printed circuit boards.

[0066] Focusing on its use in printed circuit boards, the glass composition according to the present invention can be a glass composition for printed circuit boards.

[0067] [Glass fiber] The glass fibers according to the present invention are composed of the glass composition according to the present invention. The specific composition of the glass fibers is not particularly limited, and as long as they are composed of the glass composition according to the present invention, they can have the same composition as conventional glass fibers. However, as described above, since the glass composition according to the present invention is a low dielectric constant glass composition and is a composition that can further suppress the occurrence of devitrification and the inclusion of bubbles in the glass fibers even when the fiber diameter of the formed glass fibers is small, the glass fibers according to the present invention may be glass fibers with a small fiber diameter. Furthermore, such low dielectric constant glass fibers with a small fiber diameter are one form of the glass fibers according to the present invention.

[0068] The average fiber diameter of the glass fibers may be, for example, 1 to 10 μm, more specifically 6 to 10 μm, or 1 to 6 μm. The average fiber diameter may be 3 μm or more, and may be 10 μm or less, 5.1 μm or less, 4.6 μm or less, or even 4.3 μm or less. A glass composition having a characteristic temperature suitable for mass production is suitable for stable production as fine glass fibers. In one preferred embodiment, the average fiber diameter is even finer, for example 3.9 μm or less, or even 3.5 μm or less. The glass fibers are, for example, glass filaments.

[0069] A preferred application for the glass fibers according to the present invention is printed circuit boards. Glass fibers with low dielectric constant and small fiber diameter are suitable for use in printed circuit boards. However, the applications are not limited to printed circuit boards.

[0070] Glass fibers can be used to make glass yarn. The glass yarn may contain glass fibers other than those according to the present invention, but it may also consist only of glass fibers according to the present invention, specifically glass filaments. This glass yarn suppresses defects such as breakage and fuzzing of the glass fibers, resulting in high productivity.

[0071] The number of glass fibers (filaments) in glass yarn is, for example, 30 to 400. When used in printed circuit boards, the number of filaments should be, for example, 30 to 120, 30 to 70, or even 30 to 60. An appropriate number of filaments is advantageous for easier and more reliable formation of glass cloth and for achieving thinner printed circuit boards. However, the composition and applications of glass yarn are not limited to these examples.

[0072] Glass yarn containing glass fibers may have a count of, for example, 0.7-6 tex, 0.9-5 tex, 1-4 tex, 1-3 tex, or even 10-70 tex. An appropriate count is advantageous for more easily and reliably forming thin glass cloth and for reducing the thickness of printed circuit boards.

[0073] The glass yarn may have a strength of 0.4 N / tex or higher, more specifically 0.6 N / tex or higher, and particularly 0.7 N / tex or higher.

[0074] The glass fibers according to the present invention can be manufactured by applying known methods. For example, when manufacturing glass fibers with an average fiber diameter of about 1 to 6 μm, the following method can be used. That is, the glass composition according to the present invention is placed in a glass melting furnace, melted to form molten glass, and then the molten glass is drawn out from a number of spinning nozzles provided at the bottom of a heat-resistant bushing in a spinning furnace and formed into a thread-like shape. This makes it possible to manufacture glass fibers composed of the glass composition according to the present invention. The glass fibers may be glass filaments. The melting temperature in the melting furnace is, for example, 1300 to 1700°C, preferably 1400 to 1700°C, and more preferably 1500 to 1700°C. In these cases, even when the fiber diameter of the glass fibers to be formed is small, the occurrence of minute devitrification and the inclusion of bubbles in the glass fibers can be further suppressed, and excessively high spinning tension can be prevented, resulting in glass The properties (e.g., strength) and quality of the fibers can be reliably ensured.

[0075] To produce glass fibers with a small fiber diameter, methods such as increasing the extraction speed of molten glass from the spinning furnace or lowering the temperature of the spinning nozzle can be considered. However, the former method may not allow sufficient time to promote degassing of the molten glass within the spinning furnace. This can lead to yarn breakage during spinning due to the inclusion of bubbles, and a decrease in fiber strength. In addition, the tension generated in the fiber during spinning (spinning tension) increases with increasing spinning speed, and this can also be a factor in yarn breakage during spinning, a decrease in fiber strength, and a decrease in fiber quality. Normally, a winding rotating device called a collet is used to wind glass fibers, but if the spinning tension increases excessively, yarn kinks caused by indentations between the fingers occur in the wound glass fibers, which leads to a decrease in the quality of the glass fibers. A collet is a device equipped with multiple fingers on the outer circumference of the collet body that move outward in diameter when it rotates and sink into the collet body when it stops. A decline in the quality of glass fibers can lead to, for example, poor appearance and / or poor fiber opening in glass cloth. On the other hand, the latter method requires lowering the melting temperature in the melting furnace, which brings the melting temperature closer to the devitrification temperature of the glass composition. This can increase the viscosity of the molten glass, making it impossible to perform sufficient degassing. The increased viscosity also leads to increased spinning tension, which can cause the aforementioned problems.

[0076] By using the glass composition according to the present invention and melting it within the above-mentioned temperature range, the above-mentioned problems can be mitigated. Improved glass fiber quality also results in better appearance and / or fiber-opening properties of the glass cloth using these glass fibers.

[0077] A glass strand can be formed by applying a sizing agent to the surface of glass fibers formed by spinning and bundling multiple glass fibers, for example, 10 to 120 glass fibers together. This strand contains the glass fibers according to the present invention. The strand can be wound onto a tube on a collet that rotates at high speed (for example, a paper tube) to form a cake, and then the strand can be unwound from the outer layer of the cake, air-dried while being twisted, and then wound back onto a bobbin or the like and twisted to form glass yarn.

[0078] [Glass cloth] The glass cloth according to the present invention is composed of glass fibers according to the present invention. The glass cloth according to the present invention may also have the above-mentioned properties such as a low dielectric constant possessed by the glass composition according to the present invention. The weave structure of the glass cloth according to the present invention may be, for example, plain weave, satin weave, twill weave, diagonal weave, or rib weave, and is preferably plain weave. However, the weave structure is not limited to these examples. The glass yarn may also contain glass fibers other than the glass fibers according to the present invention, but may also be composed only of the glass fibers according to the present invention, specifically glass filament. The glass cloth according to the present invention has suppressed defects such as breakage and fuzzing of the glass fibers and has high productivity.

[0079] In one preferred embodiment, the thickness of the glass cloth is preferably 200 μm or less, more preferably 7 to 150 μm, even more preferably 7 to 30 μm, and particularly preferably 8 to 15 μm, as expressed by the thickness measured in accordance with item 7.10.1 of JIS R3420:2013. This preferred embodiment of glass cloth is suitable for thinning printed circuit boards.

[0080] In one preferred embodiment, the mass of the glass cloth is expressed as the cloth mass measured in accordance with item 7.2 of JIS R3420:2013, preferably 250 g / m². 2 More preferably, 150 g / m² 2 More preferably 50 g / m 2 , especially preferred 15g / m 2 The following is the case. This preferred form of glass cloth is thinned print Suitable for use on circuit boards.

[0081] In a preferred embodiment, the number of glass fibers per unit length (25 mm) of the glass cloth (weaving density) is, for both the warp and weft, for example, preferably 40 to 130 per 25 mm in length, more preferably 60 to 120, and even more preferably 90 to 120. The glass cloth of this preferred form is suitable for reducing its thickness, increasing the entanglement points of the warp and weft, making it difficult for the glass cloth to warp, and suppressing the occurrence of pinholes when impregnated with resin.

[0082] In a preferred embodiment, the air permeability of the glass cloth is, for example, 400 cm 3 / (cm 2 ·sec) or less, preferably 300 cm 3 / (cm 2 ·sec) or less, more preferably 250 cm 3 / (cm 2 ·sec) or less. The glass cloth of this preferred form is suitable for reducing its thickness and suppressing the occurrence of the above-mentioned pinholes. In order to open the fibers so that the glass cloth has the air permeability of the above degree, it is advisable to apply the above-mentioned melting temperature, that is, 1400 °C or higher, preferably 1400 to 1650 °C, to the glass composition according to the present invention or the glass raw material prepared so as to obtain the glass composition according to the present invention to obtain glass fibers. The glass cloth according to the present invention can be manufactured by a known method using the glass fiber according to the present invention. An example of the manufacturing method is a method in which a warping process and a sizing process are performed on a glass yarn, and then this is used as the warp and the weft of the glass yarn is beaten in. For beating in the weft, various weaving machines, for example, a jet loom, a Sulzer loom, a rapier loom can be used. Specific examples of a jet loom include an air jet loom and a water jet loom. However, the weaving machine for manufacturing the glass cloth is not limited to these.

[0083] The glass cloth according to the present invention can be manufactured by a known method using the glass fiber according to the present invention. An example of the manufacturing method is a method in which a warping process and a sizing process are performed on a glass yarn, and then this is used as the warp and the weft of the glass yarn is beaten in. For beating in the weft, various weaving machines, for example, a jet loom, a Sulzer loom, a rapier loom can be used. Specific examples of a jet loom include an air jet loom and a water jet loom. However, the weaving machine for manufacturing the glass cloth is not limited to these.

[0084] The glass cloth according to the present invention may be subjected to a fiber-opening treatment. Fiber-opening treatment is advantageous for thinning the glass cloth. The specific method of fiber-opening treatment is not particularly limited, and for example, fiber-opening by pressure of a water flow, fiber-opening by high-frequency vibration using water or the like as a medium, and fiber-opening by pressurization using a roll or the like can be applied. The water used as the medium for fiber-opening can be degassed water, ion-exchanged water, deionized water, electrolyzed cationized water, electrolyzed anionized water, etc. The fiber-opening treatment may be performed simultaneously with the weaving of the glass cloth or after weaving. Furthermore, the fiber-opening treatment may be performed simultaneously with various treatments such as heat cleaning and surface treatment, or after various treatments.

[0085] If substances such as sizing agents are attached to the woven glass cloth, a further treatment to remove such substances, such as heat cleaning, may be performed. Glass cloth that has undergone this removal treatment will have excellent impregnation properties and adhesion to the matrix resin when used in printed circuit boards. After the removal treatment, or separately from the removal treatment, the woven glass cloth may be surface-treated with a silane coupling agent or the like. Surface treatment can be carried out by known means, specifically by impregnating the glass cloth with the silane coupling agent, applying it, spraying it, etc.

[0086] The glass cloth according to the present invention is suitable for printed circuit boards. When used in printed circuit boards, its characteristics such as low dielectric constant and the ability to be composed of glass fibers with small fiber diameter can be effectively utilized. However, its applications are not limited to printed circuit boards.

[0087] [Prepreg] The prepreg according to the present invention may be composed of the glass cloth according to the present invention. The prepreg according to the present invention may also have the above-mentioned properties such as the low dielectric constant of the glass composition according to the present invention. The method for manufacturing the prepreg according to the present invention is not particularly limited, and any conventionally known manufacturing method may be employed. The resin impregnated into the prepreg according to the present invention is not particularly limited as long as it is a synthetic resin that can be compounded with the glass cloth according to the present invention, for example, a thermosetting resin, a thermoplastic resin Examples include resins and composite resins thereof. It is desirable to use a resin having a low dielectric constant that matches the glass cloth according to the present invention, which has a low dielectric constant.

[0088] [Printed circuit board] The printed circuit board according to the present invention may be constructed from the glass cloth according to the present invention. The printed circuit board according to the present invention may also have the above-mentioned properties, such as the low dielectric constant of the glass composition according to the present invention. The method for manufacturing the substrate of the present invention is not particularly limited, and any conventionally known manufacturing method may be employed. For example, a method in which a prepreg containing a resin impregnated in glass cloth is manufactured and then cured can be used. [Examples]

[0089] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples.

[0090] Glass raw materials were weighed to achieve the compositions shown in Tables 1-6 (component content is in weight %), and mixed to a homogeneous state to prepare glass raw material mixed batches. Next, the prepared mixed batches were placed in a platinum-rhodium crucible and heated in an indirectly heated electric furnace set to 1600°C in an atmospheric environment for more than 3 hours to produce molten glass. Then, the obtained molten glass was poured into a refractory mold and cast, and the resulting molded body was slowly cooled to room temperature in an annealing furnace to obtain glass composition samples for evaluation.

[0091] For the glass samples prepared in this manner, the dielectric constant and dielectric loss tangent were evaluated at characteristic temperatures T2, T2.5, and T3, devitrification temperature TL, and frequencies of 1 GHz, 5 GHz, and 10 GHz. The evaluation method is as follows.

[0092] (characteristic temperature) The viscosity was measured using the platinum ball pulling method, and the viscosity was 10 2 dPa·s, 10 2.5 dPa·s, 10 3 The temperatures at which dPa·s is obtained were defined as T2, T2.5, and T3, respectively.

[0093] (devitrification temperature) The sample glass was crushed, passed through a sieve with a mesh size of 2.83 mm, and the particles remaining on a sieve with a mesh size of 1.00 mm were sieved off. These particles were washed to remove any fine powder adhering to them, dried, and prepared as a sample for devitrification temperature measurement. 25 g of the sample for devitrification temperature measurement was placed in a platinum boat (a rectangular, lidless platinum container) so that the thickness was approximately uniform, and held in a temperature gradient furnace for 2 hours. After being removed from the furnace, the highest temperature at which devitrification was observed inside the glass was defined as the devitrification temperature.

[0094] (Dielectric constant and dielectric loss tangent) The dielectric constant and dielectric loss tangent at each frequency were measured using a dielectric constant measuring device based on the cavity resonator perturbation method. The measurement temperature was 25°C, and the dimensions of the measurement sample were a rectangular prism with a base of 1.5 cm on each side and a length of 10 cm.

[0095] The glass compositions of Examples 1-44 and 48-99 had a dielectric constant of 4.65 or less at a measurement frequency of 1 GHz, a T2 of 1700°C or less, and a T3 of 1450°C or less. Some of these glass compositions had a dielectric constant of 4.4 or less at a measurement frequency of 1 GHz, and the glass compositions of Examples 1-43, 48-81, 83-84, and 93-99 had a dielectric constant of 4.36 or less at a measurement frequency of 1 GHz. The glass compositions of Examples 1-41, 48-81, 83-84, and 94-99 had a dielectric constant of 4.35 or less at a measurement frequency of 1 GHz. In addition, the glass compositions of Examples 5-6, 66-67, and 83-92 had a T2 of 1520°C or less and a T3 of 1300°C or less, which were higher than TL. The glass compositions of Examples 66-67 and 83-92 have a B2O3 content of 35% or less, and in some cases 30% or less, and T2 The temperature was 1520°C or lower, and T3 was 1300°C or lower, which was higher than TL. The glass compositions of Example 2 and Examples 93-99 had a dielectric loss tangent of less than 0.001 at a frequency of 1 GHz. The glass compositions of Examples 93-99 had a dielectric loss tangent of less than 0.001 at a frequency of 1 GHz, and T2 was less than 1600°C. The glass compositions of Examples 45-47 were comparative examples, with Example 45 having a T2 exceeding 1700°C, and Examples 46-47 having a dielectric constant of more than 4.7 at a measurement frequency of 1 GHz.

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] [Table 5]

[0101] [Table 6]

Claims

1. Expressed as a percentage by weight, 45≦SiO 2 <58 25≦B 2 O 3 ≦40 7.5≦Al 2 O 3 ≦18 0<R 2 O≦4 0≦Li 2 O≦1.5 0≦Na 2 O≦1.5 0≦K 2 O≦1 4.0 ≤ RO < 10 0 ≤ MgO < 10 0 ≤ CaO < 10 0 ≤ SrO ≤ 5 0.01≦T-Fe 2 O 3 ≦0.5 0 ≤ ZnO ≤ 1 Includes, SiO 2 +B 2 O 3 ≥ 80, and The condition 0.1 ≤ MgO / (MgO + CaO) ≤ 0.4 holds true. TiO 2 A glass composition for glass fibers that is substantially free of [the specified substance]. However, R 2 O is Li 2 O, Na 2 O and K 2 O is at least one oxide selected from O, RO is at least one oxide selected from MgO, CaO and SrO, and T-Fe 2 O 3 Fe 2 O 3 This is the total iron oxide in the glass composition, converted to an equivalent value.

2. Expressed as a percentage by weight, 45≦SiO 2 <58 30<B 2 O 3 ≦40 7.5≦Al 2 O 3 ≦18 0<R 2 O≦4 0≦Li 2 O≦1.5 0≦Na 2 O≦1.5 0≦K 2 O≦1 1 ≤ RO < 10 0 ≤ MgO < 10 0 ≤ CaO < 10 0 ≤ SrO ≤ 5 0≦T-Fe 2 O 3 ≦0.5 0 ≤ ZnO ≤ 1 Includes, SiO 2 +B 2 O 3 ≥ 80, and The condition 0.1 ≤ MgO / (MgO + CaO) ≤ 0.4 holds true. TiO 2 A glass composition for glass fibers that is substantially free of [the specified substance]. However, R 2 O is Li 2 O, Na 2 O and K 2 O is at least one oxide selected from O, RO is at least one oxide selected from MgO, CaO and SrO, and T-Fe 2 O 3 Fe 2 O 3 This is the total iron oxide in the glass composition, converted to an equivalent value.

3. Expressed as a percentage by weight, 45≦SiO 2 ≦49.95 25≦B 2 O 3 ≦40 7.5≦Al 2 O 3 ≦18 0<R 2 O≦4 0≦Li 2 O≦1.5 0≦Na 2 O≦1.5 0≦K 2 O≦1 1 ≤ RO < 10 0 ≤ MgO < 10 0 ≤ CaO < 10 0 ≤ SrO ≤ 5 0≦T-Fe 2 O 3 ≦0.5 0 ≤ ZnO ≤ 1 Includes, SiO 2 +B 2 O 3 ≥ 80, and The condition 0.1 ≤ MgO / (MgO + CaO) ≤ 0.4 holds true. TiO 2 A glass composition for glass fibers that is substantially free of [the specified substance]. However, R 2 O is Li 2 O, Na 2 O and K 2 O is at least one oxide selected from O, RO is at least one oxide selected from MgO, CaO and SrO, and T-Fe 2 O 3 Fe 2 O 3 This is the total iron oxide in the glass composition, converted to an equivalent value.

4. Glass fibers comprising the glass composition according to any one of claims 1 to 3.

5. A glass cloth made of glass fibers as described in claim 4.

6. A prepreg comprising the glass cloth described in claim 5.

7. A printed circuit board comprising the glass cloth described in claim 5.

8. A method for producing glass fibers, comprising the step of melting a glass composition according to any one of claims 1 to 3 at a temperature of 1400°C or higher, to obtain glass fibers having an average fiber diameter of 1 to 6 μm.

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