Non-alkali glass

Abstract

To provide a low-thermal-shrinkage non-alkali glass, the glass being less prone to problems due to BHF, having high productivity, and a low thermal shrinkage.SOLUTION: Provided is a non-alkali glass having a strain point of 690°C or higher and 738°C or lower, an average thermal expansion coefficient of 30×10-7 to 45×10-7 / °C at 50 to 350°C, a Young's modulus of 77-86 GPa, containing SiO2, Al2O3, B2O3, MgO, CaO and SrO, with SiO2, Al2O3, B2O3, MgO and CaO being specific contents, the total amount of the MgO+CaO+SrO+BaO being 18.0% or less, CaO / (MgO+CaO+SrO+BaO) being 0.22 or more and 0.59 or less, SrO / (MgO+CaO+SrO+BaO) being 0.06 or more and 0.52 or less, Na2O / B2O3 being 0.001 or more and 0.3 or less, and the content of alkali metal oxide being 1000 mass ppm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an alkali-free glass that is suitable as a substrate glass for various displays and a substrate glass for photomasks, substantially contains no alkali metal oxide, and can be formed by float molding. Hereinafter, in this specification, when referring to "alkali-free", it means that the content of alkali metal oxides (Li2O, Na2O, K2O) is 1000 mass ppm or less.

Background Art

[0002] Conventionally, for substrate glasses for various displays, particularly those on which metal or oxide thin films are formed on the surface, the following characteristics have been required. (1) When containing alkali metal oxides, alkali metal ions diffuse into the thin film and deteriorate the film characteristics. Therefore, the content of alkali metal oxides is extremely low. Specifically, the content of alkali metal oxides is 1000 mass ppm or less. (2) Little deformation, particularly little thermal shrinkage, of the glass substrate due to heating in the thin film forming process. That is, the thermal shrinkage rate is small.

[0003] (3) Having sufficient chemical durability against various chemicals used for semiconductor formation. Particularly, for buffered hydrofluoric acid (BHF: a mixture of hydrofluoric acid and ammonium fluoride) for etching SiO x and SiN x , a chemical solution containing hydrochloric acid used for etching ITO, various acids (nitric acid, sulfuric acid, etc.) used for etching metal electrodes, and being durable against the alkali in the resist stripper. (4) Having no defects (bubbles, veins, inclusions, pits, scratches, etc.) inside and on the surface.

[0004] In addition to the above requirements, in recent years, the following situations exist. (5) Weight reduction of the display is required, and glass with a small density is desired for the glass itself. (6) Weight reduction of the display is required, and thinning of the substrate glass is desired.

[0005] (7) In addition to the conventional amorphous silicon (a-Si) type liquid crystal displays, polycrystalline silicon (p-Si) type liquid crystal displays with slightly higher heat treatment temperatures have come to be produced (a-Si: about 350°C → p-Si: 350 - 550°C). (8) In order to increase productivity and improve thermal shock resistance by increasing the heating and cooling rates of the heat treatment for liquid crystal display production, glass with a small average thermal expansion coefficient of glass is required.

[0006] On the other hand, the dry etching has advanced, and the requirement for BHF resistance has weakened. For the conventional glass, in order to improve the BHF resistance, glass containing 6 - 10 mol% of B2O3 has been widely used. However, B2O3 tends to lower the strain point. Examples of alkali-free glass that does not contain B2O3 or has a low content are as follows.

[0007] Patent Document 1 discloses glass containing 0 - 3 wt% of B2O3, but the strain point of the examples is 690°C or lower.

[0008] Patent Document 2 discloses glass containing 0 - 5 mol% of B2O3, but the average thermal expansion coefficient at 50 - 350°C exceeds 50×10 -7 / °C.

[0009] In order to solve the problems of the glass described in Patent Documents 1 and 2, alkali-free glass described in Patent Document 3 has been proposed. The alkali-free glass described in Patent Document 3 has a high strain point, can be formed by the float method, and is considered suitable for applications such as display substrates and photomask substrates.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

[0011] In recent years, in high-definition small displays such as mobile terminals like smartphones, a method using laser annealing has been adopted as a method for manufacturing high-quality p-Si TFTs. However, for the improvement of commercial value, further higher definition is desired, and for this reason, glass with an even smaller thermal shrinkage rate is required. On the other hand, due to requirements in the glass manufacturing process, particularly in float forming, it is required to lower the temperature T4 at which the viscosity of the glass, particularly the glass viscosity, becomes 10 4 dPa·s and the devitrification temperature, and further not to raise the strain point excessively.

[0012] As described above, alkali-free glass used as various display substrate glasses and photomask substrate glasses is required to have a smaller thermal shrinkage rate. For this purpose, it is effective to change the main component composition of the glass to increase the strain point or to reduce the cooling rate of the glass. However, as a result, when the thermal shrinkage rate in heat treatment at 600°C for 80 minutes reaches a level below 50 ppm, the influence of various impurities in the glass cannot be ignored.

[0013] In particular, the alkali components (R2O: R is an alkali metal element such as Li, Na, K, etc.) inevitably mixed in from the raw materials move rapidly in the glass structure, so they have a great influence on the thermal shrinkage rate. Especially in the glass containing B2O3 component, the alkali components affect the coordination number of boron, resulting in a change in the glass structure. Therefore, the content ratio of the alkali component to the B2O3 component (R2O / B2O3 ratio) is an important parameter. However, in the conventional alkali-free glass, the R2O / B2O3 ratio has not been regarded as important, and since the B2O3 content is high, even if the content is, for example, 0.1 wt% (1000 ppm), which is considered preferable as the upper limit of the alkali-free glass, the R2O / B2O3 is as low as about 0.02 or less.

[0014] When the amount of B2O3 decreases to obtain a low thermal shrinkage glass, in order to reduce this ratio, it is necessary to further reduce the amount of alkali components. To extremely reduce the alkali components, extremely high-purity raw materials can be used, but using such high-purity raw materials will increase the cost, which is not preferable. On the other hand, since the alkali components act as a flux to improve the initial solubility, if the amount is reduced too much, there is a risk of causing a decrease in defective quality.

[0015] In addition, since the alkali components are impurities, they are difficult to manage. Therefore, when fluctuations occur, there is a high possibility that the thermal shrinkage rate will vary between lots. On the other hand, due to the high definition of displays in recent years, the variation between lots is a great concern because it may increase the defective rate in the panel manufacturing process.

[0016] An object of the present invention is to solve the above problems and provide an alkali-free glass that has a low thermal shrinkage rate, is less likely to cause problems due to BHF, has good productivity, and has a low thermal shrinkage rate.

Means for Solving the Problems

[0017] The present invention has a strain point of 680 °C or more and less than 738 °C, and an average thermal expansion coefficient at 50 to 350 °C is 30×10 -7 ~45×10-7 in °C, the devitrification viscosity η is logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO2: 57 - 63% Al2O3: 18 - 23% B2O3: 0.2 - 5.5% MgO: 1 - 8.5% CaO: 3 - 12% SrO: 0 - 10% BaO: 1.3 - 5% MgO + CaO + SrO + BaO: 13 - 23% containing, and containing Na2O at 600 mass ppm or less, the mass ratio of Na2O to B2O3 (Na2O / B2O3) is 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) is 0.15 or more, CaO / (MgO + CaO + SrO + BaO) is 0.60 or less, SrO / (MgO + CaO + SrO + BaO) is 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) is 0.50 or less, to provide an alkali-free glass. Also, the present invention has a strain point of 680°C or more, an average thermal expansion coefficient at 50 - 350°C of more than 35×10 -7 / °C and 45×10 -7 / °C or less, the devitrification viscosity η is logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO2: 57 - 63% Al2O3: 18 - 23% B2O3: 0.2 - 5.5% MgO: 1 - 8.5% CaO: 3 - 12% SrO: 0 - 10% BaO: 1.3 - 5% MgO + CaO + SrO + BaO: 13 - 23% To provide an alkali-free glass that contains [substance], contains Na₂O at 600 mass ppm or less, has a mass ratio of Na₂O to B₂O₃ (Na₂O / B₂O₃) of 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) of 0.15 or more, CaO / (MgO + CaO + SrO + BaO) of 0.60 or less, SrO / (MgO + CaO + SrO + BaO) of 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) of 0.50 or less. Further, the present invention provides an alkali-free glass having a strain point of 680 °C or higher, an average thermal expansion coefficient at 50 to 350 °C of 30×10 -7 ~45×10 -7 / °C, a devitrification viscosity η of logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO₂: 57~63% Al₂O₃: 18~23% B₂O₃: 0.2~5.5% MgO: 1~8.5% CaO: 3~12% SrO: 0~6.5% BaO: 1.3~5% MgO + CaO + SrO + BaO: 13~23% To provide an alkali-free glass that contains [substance], contains Na₂O at 600 mass ppm or less, has a mass ratio of Na₂O to B₂O₃ (Na₂O / B₂O₃) of 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) of 0.15 or more, CaO / (MgO + CaO + SrO + BaO) of 0.60 or less, SrO / (MgO + CaO + SrO + BaO) of 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) of 0.50 or less. Further, the present invention provides an alkali-free glass having a strain point of 680 °C or higher and less than 738 °C, an average thermal expansion coefficient at 50 to 350 °C of 30×10 -7 ~45×10 -7 / °C, a devitrification viscosity η of logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO₂: 57~63% Al₂O₃: 18~23% B₂O₃: 0.2~5.5% MgO: 1 to 8.5% CaO: 3 to 12% SrO: 0 to 10% BaO: 0 to 5% MgO + CaO + SrO + BaO: 13% or more and less than 17% containing, and containing 600 mass ppm or less of Na2O, the mass ratio of Na2O to B2O3 (Na2O / B2O3) being 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) being 0.15 or more, CaO / (MgO + CaO + SrO + BaO) being 0.60 or less, SrO / (MgO + CaO + SrO + BaO) being 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) being 0.50 or less, to provide an alkali-free glass. Further, the present invention has a strain point of 680°C or higher, an average thermal expansion coefficient at 50 to 350°C of more than 35×10 -7 / °C and 45×10 -7 / °C or less, a devitrification viscosity η of logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO2: 57 to 63% Al2O3: 18 to 23% B2O3: 0.2 to 5.5% MgO: 1 to 8.5% CaO: 3 to 12% SrO: 0 to 10% BaO: 0 to 5% MgO + CaO + SrO + BaO: 13% or more and less than 17% containing, and containing 600 mass ppm or less of Na2O, the mass ratio of Na2O to B2O3 (Na2O / B2O3) being 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) being 0.15 or more, CaO / (MgO + CaO + SrO + BaO) being 0.60 or less, SrO / (MgO + CaO + SrO + BaO) being 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) being 0.50 or less, to provide an alkali-free glass. Further, the present invention has a strain point of 680°C or higher, an average thermal expansion coefficient at 50 to 350°C of 30×10 -7 to 45×10 -7is in °C, the devitrification viscosity η is logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO2: 57 - 63% Al2O3: 18 - 23% B2O3: 0.2 - 5.5% MgO: 1 - 8.5% CaO: 3 - 12% SrO: 0 - 6.5% BaO: 0 - 5% MgO + CaO + SrO + BaO: 13% or more and less than 17% contains, and contains Na2O at 600 mass ppm or less, the mass ratio of Na2O to B2O3 (Na2O / B2O3) is 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) is 0.15 or more, CaO / (MgO + CaO + SrO + BaO) is 0.60 or less, SrO / (MgO + CaO + SrO + BaO) is 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) is 0.50 or less, and provides an alkali-free glass. Further, the present invention has a strain point of 680°C or more and 718°C or less, and an average thermal expansion coefficient at 50 - 350°C of 30×10 -7 ~45×10 -7 / °C, the devitrification viscosity η is logη = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO2: 57 - 63% Al2O3: 18 - 23% B2O3: 0.2 - 5.5% MgO: 1 - 8.5% CaO: 3 - 12% SrO: 0 - 6% BaO: 0 - 5% MgO + CaO + SrO + BaO: 13 - 23% Containing it and containing Na₂O at 600 mass ppm or less, with the mass ratio of Na₂O to B₂O₃ (Na₂O / B₂O₃) being 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) being 0.15 or more, CaO / (MgO + CaO + SrO + BaO) being 0.28 or more and 0.60 or less, SrO / (MgO + CaO + SrO + BaO) being 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) being 0.50 or less, an alkali-free glass is provided. Further, the present invention has a strain point of 680 °C or more and 718 °C or less, and an average thermal expansion coefficient at 50 to 350 °C of 35 × 10 -7 / °C exceeding 45 × 10 -7 / °C or less, a devitrification viscosity η of log η = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO₂: 57 - 63% Al₂O₃: 18 - 23% B₂O₃: 0.2 - 5.5% MgO: 1 - 8.5% CaO: 3 - 12% SrO: 0 - 6% BaO: 0 - 5% MgO + CaO + SrO + BaO: 13 - 23% Containing it and containing Na₂O at 600 mass ppm or less, with the mass ratio of Na₂O to B₂O₃ (Na₂O / B₂O₃) being 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) being 0.15 or more, CaO / (MgO + CaO + SrO + BaO) being 0.28 or more and 0.60 or less, SrO / (MgO + CaO + SrO + BaO) being 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) being 0.50 or less, an alkali-free glass is provided. Further, the present invention has a strain point of 680 °C or more and 718 °C or less, and an average thermal expansion coefficient at 50 to 350 °C of 30 × 10 -7 ~45 × 10 -7 / °C, a devitrification viscosity η of log η = 3.5 [dPa·s] or more, and in terms of mass% based on oxides, SiO₂: 57 - 63% Al₂O₃: 18 - 23% B₂O₃: 0.2 - 5.5% MgO: 1 to 8.5% CaO: 3 to 12% SrO: 0 to 6% BaO: 0 to 5% MgO + CaO + SrO + BaO: 13 to 23% containing, and containing Na2O at 600 mass ppm or less, the mass ratio of Na2O to B2O3 (Na2O / B2O3) being 0.001 or more and 0.3 or less, MgO / (MgO + CaO + SrO + BaO) being 0.15 or more, CaO / (MgO + CaO + SrO + BaO) being 0.28 or more and 0.60 or less, SrO / (MgO + CaO + SrO + BaO) being 0.70 or less, and BaO / (MgO + CaO + SrO + BaO) being 0.50 or less, to provide an alkali-free glass.

Advantages of the Invention

[0018] The alkali-free glass of the present invention is suitable for display substrates, photomask substrates, etc. for applications where a particularly small thermal shrinkage rate is required, and is also a glass that is easy to float-form. The alkali-free glass of the present invention can also be used as a glass substrate for magnetic disks. Moreover, since there is little variation in the thermal shrinkage rate due to the content of Na2O, which accounts for most of the alkali metal oxides inevitably mixed in the raw materials, the possibility of variation in the thermal shrinkage rate between lots is suppressed. Thereby, it is described that the defective rate in the panel manufacturing process is reduced.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, the composition ranges of the respective components will be described. If SiO2 is less than 54% (mass%, the same hereinafter unless otherwise specified), the strain point does not rise sufficiently, the thermal expansion coefficient increases, and the density increases, so it is 54% or more. When float forming is adopted as the forming method for using the alkali-free glass of the present invention as a display substrate or a photomask substrate, 57% or more is preferable. On the other hand, when fusion forming is adopted as the forming method, 58% or more is preferable.

[0021] If SiO2 exceeds 66%, the solubility decreases, the glass viscosity at the temperature T2 when it becomes 10 2 dPa·s and the temperature T4 when it becomes 10 4 dPa·s increase, and the devitrification temperature increases, so it is 66% or less. When float forming is adopted as the forming method, 63% or less is preferable. On the other hand, when fusion forming is adopted as the forming method, 65% or less is preferable.

[0022] Al2O3 suppresses the phase separation of the glass, lowers the thermal expansion coefficient, and raises the strain point. However, if it is less than 10%, this effect does not appear, and components that increase other expansions will be increased, resulting in a large thermal expansion, so it is 10% or more. When float forming is adopted as the forming method, 18% or more is preferable. On the other hand, when fusion forming is adopted as the forming method, 14% or more is preferable.

[0023] If Al2O3 exceeds 27%, the solubility of the glass may deteriorate or the devitrification temperature may increase, so it is 27% or less. When float forming is adopted as the forming method, 23% or less is preferable. On the other hand, when fusion forming is adopted as the forming method, 22% or less is preferable.

[0024] B2O3 improves the melting reactivity of the glass, lowers the devitrification temperature, and improves the BHF resistance. However, if it is less than 0.2%, this effect is not fully manifested. Also, the strain point becomes excessively high, making it difficult to form into a plate, or it is likely to cause haze problems after treatment with BHF. Therefore, it is 0.2% or more. 0.3% or more is preferable, 0.5% or more is more preferable, 1% or more is further preferable, and 1.5% or more is particularly preferable. However, if it exceeds 5.5%, the strain point becomes low and the Young's modulus becomes small. Therefore, it is 5.5% or less. 4.5% or less is preferable, 4% or less is more preferable, 3.5% or less is further preferable, and 3% or less is even more preferable.

[0025] MgO is not essential, but among alkaline earths, it has the characteristic of increasing the Young's modulus while not increasing the expansion and maintaining a low density. Therefore, it can be contained to improve solubility. However, if it is too much, the devitrification temperature will increase. Therefore, it is 10% or less. When the float forming method is adopted as the forming method, 1% or more is preferable. When the float forming method is adopted as the forming method, 8.5% or less is preferable. On the other hand, when the fusion forming method is adopted as the forming method, 6% or less is preferable.

[0026] CaO is not essential, but it has the characteristic of increasing the Young's modulus while not increasing the expansion and maintaining a low density among alkaline earths after MgO, and it also has the characteristic of improving solubility. Therefore, it can be contained. However, if it is too much, the devitrification temperature may increase, or there is a risk of a large amount of phosphorus, which is an impurity in limestone (CaCO3), the CaO raw material, being mixed in. Therefore, it is 15% or less. 12% or less is preferable. In order to exhibit the above characteristics, 3% or more is preferable.

[0027] SrO is not essential, but it can be contained to improve solubility without increasing the devitrification temperature of the glass. However, if it is too much, there is a risk of increasing the expansion coefficient. Therefore, it is 15% or less. 10% or less is preferable, 6.5% or less is more preferable, 6% or less is further preferable, and 5.5% or less is even more preferable.

[0028] BaO is not essential but can be included to improve solubility. However, if it is too much, it will excessively increase the expansion and density of the glass, so it should be 15% or less. When adopting the float forming method as the forming method, 5% or less is preferable, 3% or less is more preferable, and 1% or less is even more preferable. On the other hand, when adopting the fusion forming method as the forming method, 10% or less is preferable, 8% or less is more preferable, 6% or less is even more preferable, and 4% or less is even more preferable. In any case, it is more preferable not to contain it substantially. Not containing it substantially means not containing it except for inevitable impurities. In the present invention, not containing BaO substantially means, for example, 0.15% or less.

[0029] If the total amount of MgO, CaO, SrO, and BaO is less than 8%, the photoelastic constant becomes large and the solubility tends to decrease, so it is 8% or more. Since it is preferable to contain a large amount of the total amount of MgO, CaO, SrO, and BaO for the purpose of reducing the photoelastic constant, it is more preferably 10% or more, even more preferably 13% or more, and particularly preferably 16% or more. If it is more than 25%, the average thermal expansion coefficient cannot be lowered and the strain point may become low, so it is 25% or less. Preferably it is 22% or less, and even more preferably 20% or less.

[0030] When adopting the float forming method as the forming method, by satisfying that the total amount of MgO, CaO, SrO, and BaO satisfies the above, more preferably satisfies 13 - 23%, and satisfies the following conditions, the Young's modulus and specific elastic modulus can be increased without increasing the devitrification temperature, and furthermore, the viscosity of the glass, particularly T4, can be lowered. MgO / (MgO + CaO + SrO + BaO) is 0.15 or more, preferably 0.20 or more, more preferably 0.25 or more. CaO / (MgO + CaO + SrO + BaO) is 0.60 or less, preferably 0.55 or less, more preferably 0.50 or less. SrO / (MgO + CaO + SrO + BaO) is 0.70 or less, preferably 0.60 or less, more preferably 0.50 or less. BaO / (MgO + CaO + SrO + BaO) is 0.50 or less, preferably 0.45 or less, more preferably 0.40 or less.

[0031] When fusion forming is adopted as the forming method, the total amount of MgO, CaO, SrO, and BaO preferably satisfies the above conditions, more preferably satisfies 8 - 22%, and preferably satisfies the following conditions. MgO / (MgO + CaO + SrO + BaO) is 0.25 or less, preferably 0.20 or less, more preferably 0.15 or less. CaO / (MgO + CaO + SrO + BaO) is 0.20 or more, preferably 0.30 or more, more preferably 0.40 or more. SrO / (MgO + CaO + SrO + BaO) is 0.50 or less, preferably 0.45 or less, more preferably 0.40 or less. BaO / (MgO + CaO + SrO + BaO) is 0.70 or less, preferably 0.50 or less, more preferably 0.40 or less.

[0032] In addition, in order to facilitate the recycling of the glass of the present invention, it is preferable that the glass does not substantially contain PbO, As2O3, and Sb2O3.

[0033] For the same reason, it is preferable that the P2O5 content is not substantially contained. The content of impurities mixed in is preferably 80 mass ppm or less, more preferably 70 mass ppm or less, still more preferably 60 mass ppm or less, and particularly preferably 50 mass ppm or less.

[0034] In the glass of the present invention, alkali metal oxides are inevitably contained from raw material impurities, etc., and the inclusion of a very small amount of alkali metal oxides is allowed to improve solubility. However, when the content of alkali metal oxides is too high, the movement of alkali ions into the TFT element becomes significant, resulting in unstable transistor characteristics or loss of reliability. Therefore, it is necessary to keep the content within an appropriate range.

[0035] Since Na2O accounts for the majority of the alkali metal oxides inevitably mixed in the raw materials, in the present invention, attention is paid to the content of Na2O. The glass of the present invention has a Na2O content of 600 mass ppm or less, preferably less than 600 mass ppm, more preferably 500 mass ppm or less, still more preferably 400 mass ppm or less, and still more preferably 300 mass ppm or less. Particularly preferably, it is 200 ppm or less, and most preferably 150 ppm or less.

[0036] However, when the raw materials inevitably contain a significant amount of components other than Na2O (for example, K2O) as alkali metal oxides (for example, when these components are contained at 100 mass ppm or more), the total content of alkali metal oxides including components other than Na2O is preferably 700 mass ppm or less, more preferably less than 700 mass ppm, still more preferably 600 mass ppm or less, still more preferably 500 mass ppm or less, and still more preferably 400 mass ppm or less. Particularly preferably, it is 300 ppm or less, and most preferably 200 ppm or less.

[0037] On the other hand, since the alkali metal oxides in the glass act as a flux to improve the initial solubility, if the content of the alkali metal oxides is too low, it may cause a deterioration in the defective quality of the produced glass. The glass of the present invention preferably has a Na2O content of 50 mass ppm or more, more preferably 100 mass ppm or more.

[0038] The glass of the present invention contains a predetermined amount of B2O3 to enhance the BHF resistance. However, the inventors of the present application have found that in such glass, by optimizing the ratio of Na2O, which accounts for the majority of the alkali metal oxides inevitably mixed in the raw materials, and B2O3, it is possible to achieve both the solubility and low thermal shrinkage of the glass. This can be considered as follows.

[0039] The thermal shrinkage phenomenon is related to the glass transition temperature (T g) This is due to the structural relaxation occurring in the vicinity. Glass containing B2O3 has a structure that easily changes its bonding at T g or higher, so the structural change due to the fictive temperature is large, and therefore, thermal shrinkage is likely to occur. When a small amount of alkali ions is added to such glass, the alkali ions are likely to change boron to a four-coordinate state. Also, since alkali ions have a large diffusion coefficient, they are more likely to move compared to alkaline earth ions. Therefore, when the alkali ions are in excess relative to the amount of boron, the rate of structural change increases, and as a result, the thermal shrinkage becomes larger. When the mass ratio (Na2O / B2O3) of Na2O, which occupies most of the alkali metal oxide, and B2O3 exceeds 0.3, this effect becomes significant, and the thermal shrinkage rate becomes unnecessarily large.

[0040] For the above reasons, regarding Na2O / B2O3, it is 0.3 or less, preferably 0.2 or less, more preferably 0.12 or less, even more preferably 0.08 or less, even more preferably 0.06 or less, and still more preferably 0.04 or less. If Na2O / B2O3 is too small, the initial solubility may decrease and the quality may deteriorate, so it is 0.001 or more. Preferably it is 0.002 or more, more preferably 0.003 or more, and particularly preferably 0.005 or more.

[0041] The alkali-free glass of the present invention has a B2O3 content within a predetermined amount. When the B2O3 content is within a predetermined range, the variation in the thermal shrinkage rate due to Na2O / B2O3 is small. Since Na2O is inevitably mixed in from the raw materials, it is difficult to strictly control the Na2O content. The alkali-free glass of the present invention has little variation in the thermal shrinkage rate due to Na2O / B2O3, so the variation in the thermal shrinkage rate due to the content of Na2O inevitably mixed in from the raw materials is small. Therefore, the possibility of variation in the thermal shrinkage rate between lots is suppressed.

[0042] Furthermore, in the present invention, the inventors have found that the less B2O3 there is, the easier it is for alkali ions to diffuse from the glass surface to the counterpart member side such as a TFT. That is, the inventors have found that by reducing the content of alkali ions relative to the content of B2O3, the diffusion of alkali ions into the TFT element can be suppressed and the characteristics of the TFT element can be improved. In order to sufficiently obtain this effect, Na2O / B2O3 is preferably less than 0.06, more preferably 0.05 or less, still more preferably 0.04 or less, even more preferably 0.02 or less, particularly preferably 0.01 or less, and most preferably 0.008 or less.

[0043] In addition to the above components, the alkali-free glass of the present invention can contain ZnO, Fe2O3, SO3, F, Cl, and SnO2 in a total amount of preferably 2% or less, more preferably 1% or less, still more preferably 0.5% or less, and most preferably 0.1% or less in order to improve the solubility, fining property, and formability (float formability) of the glass. It is more preferable that ZrO2 and ZnO are substantially not contained.

[0044] The alkali-free glass of the present invention has a strain point of 680°C or higher. Since the alkali-free glass of the present invention has a strain point of 680°C or higher, thermal shrinkage during panel manufacturing can be suppressed. In addition, a method by laser annealing can be applied as a method for manufacturing a p-Si TFT. More preferably, it is 685°C or higher, and still more preferably 690°C or higher.

[0045] Since the alkali-free glass of the present invention has a strain point of 680°C or higher, it is suitable for high strain point applications (for example, display substrates or lighting substrates made of thin plates with a thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.1 mm or less). In the forming of these thin plate glasses, since the drawing speed during forming tends to increase, the virtual temperature of the glass rises and the thermal shrinkage rate of the glass tends to increase. In this case, if it is the high strain point glass of the present invention, the thermal shrinkage rate can be suppressed.

[0046] On the one hand, the alkali-free glass of the present invention preferably has a strain point of 780°C or lower. If the strain point of the alkali-free glass is too high, it is necessary to increase the temperature of the forming device accordingly, and the life of the forming device tends to decrease. Therefore, the alkali-free glass of the present invention more preferably has a strain point of 750°C or lower, even more preferably 740°C or lower, and particularly preferably 730°C or lower.

[0047] Also, for the same reason as the strain point, the glass transition point of the alkali-free glass of the present invention is preferably 730°C or higher, more preferably 740°C or higher, and even more preferably 750°C or higher. Also, it is preferably 840°C or lower, more preferably 820°C or lower, and particularly preferably 800°C or lower.

[0048] Also, the alkali-free glass of the present invention has an average thermal expansion coefficient at 50 to 350°C of 30×10 -7 ~45×10 -7 / °C, has high thermal shock resistance, and can improve productivity during panel production. In the alkali-free glass of the present invention, the average thermal expansion coefficient at 50 to 350°C is preferably 35×10 -7 / °C or more. The average thermal expansion coefficient at 50 to 350°C is preferably 43×10 -7 / °C or less, more preferably 41×10 -7 / °C or less, and even more preferably 40×10 -7 / °C or less.

[0049] Furthermore, the alkali-free glass of the present invention preferably has a specific gravity of 2.70 or lower, more preferably 2.65 or lower, and even more preferably 2.60 or lower.

[0050] Also, for the alkali-free glass of the present invention, the temperature T2 at which the viscosity becomes 10 2 dPa·s is 1800°C or lower, preferably 1750°C or lower, more preferably 1700°C or lower, even more preferably 1680°C or lower, and particularly preferably 1670°C or lower, so melting is relatively easy.

[0051] Furthermore, the alkali-free glass of the present invention has a viscosity of 10 4The temperature T4 at which the glass becomes 104 dPa·s is 1350 °C or lower, preferably 1325 °C or lower, more preferably 1300 °C or lower, still more preferably less than 1300 °C, 1295 °C or lower, or 1290 °C or lower, which is preferable for float forming.

[0052] Further, for the alkali-free glass of the present invention, the devitrification temperature is preferably 1300 °C or lower because it facilitates forming by the float method. More preferably, it is less than 1300 °C, still more preferably 1290 °C or lower, and most preferably 1280 °C or lower. Further, the difference (T4 - devitrification temperature) between the temperature T4 (the temperature at which the glass viscosity becomes 104 dPa·s, unit: °C), which is a measure of float formability and fusion formability, and the devitrification temperature is preferably -20 °C or higher, more preferably -10 °C or higher, still more preferably 0 °C or higher, even more preferably 10 °C or higher, particularly preferably 20 °C or higher, and most preferably 30 °C or higher. 4 In this specification, the devitrification temperature is the average value of the highest temperature at which crystals precipitate on the surface and inside of the glass and the lowest temperature at which no crystals precipitate, obtained by putting glass particles pulverized in a platinum dish into an electric furnace controlled at a constant temperature and performing heat treatment for 17 hours, followed by observation with an optical microscope after the heat treatment.

[0053]

[0054] Further, when the float forming method is employed for the alkali-free glass of the present invention, the devitrification viscosity η [dPa·s] is preferably such that logη = 3.5 or higher. The devitrification viscosity η in this specification is the viscosity value at the devitrification temperature. On the other hand, when the fusion forming method is employed, the devitrification viscosity η is preferably such that logη = 4.5 [dPa·s] or higher.

[0055] Further, for the alkali-free glass of the present invention, the Young's modulus is preferably 78 GPa or higher, more preferably 79 GPa or higher, 80 GPa or higher, still more preferably 81 GPa or higher, and even more preferably 82 GPa or higher.

[0056] ​Further, the alkali-free glass of the present invention preferably has a photoelastic constant of 31 nm / MPa / cm or less. Due to the birefringence of the glass substrate caused by the stress generated during the manufacturing process of the liquid crystal display panel or during the use of the liquid crystal display device, the black display may turn gray, and the phenomenon of reduced contrast of the liquid crystal display may be observed. By setting the photoelastic constant to 31 nm / MPa / cm or less, this phenomenon can be suppressed to a small extent. Preferably it is 30 nm / MPa / cm or less, more preferably 29 nm / MPa / cm or less, still more preferably 28.5 nm / MPa / cm or less, and particularly preferably 28 nm / MPa / cm or less.

[0057] Also, considering the ease of ensuring other physical properties, the photoelastic constant of the alkali-free glass of the present invention is preferably 21 nm / MPa / cm or more, more preferably 23 nm / MPa / cm or more, and still more preferably 25 nm / MPa / cm or more. The photoelastic constant can be measured at a measurement wavelength of 546 nm by the disk compression method.

[0058] The alkali-free glass of the present invention can be manufactured, for example, by the following method. The raw materials of each component usually used are formulated to become the target components, and this is continuously charged into a melting furnace and heated to 1500 to 1800 °C to be melted. This molten glass is formed into a predetermined plate thickness by the float method or the fusion method, and after slow cooling, it is cut to obtain sheet glass. Since the glass of the present invention has relatively low solubility, it is preferable to use the following as the raw materials of each component.

[0059] Further, the alkali-free glass of the present invention preferably has a small shrinkage amount during heat treatment. In the manufacture of liquid crystal panels, the heat treatment processes are different on the array side and the color filter side. Therefore, especially in high-definition panels, when the thermal shrinkage rate of the glass is large, there is a problem that dots are displaced during fitting.

[0060] Note that the heat shrinkage rate can be measured by the following procedure. After holding the sample at a temperature of the glass transition point + 100°C for 10 minutes, it is cooled to room temperature at 40°C per minute. Here, the total length L1 of the sample is measured. Then, it is heated to 600°C at 100°C / hour, held at 600°C for 80 minutes, cooled to room temperature at 100°C / hour, and the total length L2 of the sample is measured again.

[0061] Here, the heat shrinkage rate C (ppm) can be obtained by the following formula. C = (L1 - L2) / L1 × 10 6

[0062] In the above evaluation method, the heat shrinkage rate is preferably 90 ppm or less, more preferably 80 ppm or less, still more preferably 70 ppm or less, even more preferably 60 ppm or less, and particularly preferably 50 ppm or less.

[0063] The alkali-free glass of the present invention can incorporate a manufacturing method for improving the low heat shrinkage rate property. Specifically, for example, the equivalent cooling rate is set to 400°C / min or less. Here, the definition and evaluation method of the equivalent cooling rate are as follows.

[0064] The glass processed into a rectangular parallelepiped of 10 mm × 10 mm × 1 mm is held at Tg + 120°C for 5 minutes using an infrared heating type electric furnace, and then the glass is cooled to room temperature (25°C). At this time, a plurality of glass samples are prepared in the range of a cooling rate from 1°C / min to 1000°C / min. Using KPR2000 manufactured by Shimadzu Device Co., Ltd., the refractive index n of the d-line (wavelength 587.6 nm) of these samples d is measured by the V-block method. The obtained n d is plotted against the logarithm of the cooling rate to obtain a calibration curve of n d with respect to the cooling rate. Next, the n of the glass actually manufactured through processes such as melting, forming, and cooling in the actual production line d is measured by the above measurement method. The corresponding cooling rate (referred to as the equivalent cooling rate in the present invention) corresponding to the obtained n d is obtained from the calibration curve.

[0065] The alkali-free glass of the present invention can further improve the transistor characteristics and reliability of TFTs formed on a glass substrate. In the present invention, the characteristics of TFTs formed on a glass substrate can be evaluated by the following procedure.

[0066] (Method for manufacturing TFT) Taking as an example the manufacturing method of a bottom-gate structure and top-contact type TFT10 shown in FIG. 2, an explanation will be given. First, a gate electrode 12 is formed on one main surface of a glass substrate 11. After film formation, if necessary, patterning is performed into a predetermined shape by photolithography and etching methods or a lift-off method or the like. Thereby, the gate electrode 12 is formed. The gate electrode 12 preferably has high conductivity, and for example, metals such as Al and Mo can be used.

[0067] After the formation of the gate electrode 12, a gate insulating layer 13 is formed on the gate electrode 12 and on the exposed surface of the glass substrate 11. After film formation, if necessary, patterning is performed into a predetermined shape by photolithography and etching methods or a lift-off method or the like. Thereby, the gate insulating layer 13 is formed. The gate insulating layer 13 preferably has high insulation properties, and for example, SiO2, SiNx, etc. can be used.

[0068] After the formation of the gate insulating layer 13, an active layer 14 made of a semiconductor film is formed on the gate insulating layer 13 and at a position facing the gate electrode 12. For the active layer 14, amorphous silicon, polysilicon, or an oxide semiconductor such as In-Ga-Zn-O can be used.

[0069] After film formation, if necessary, patterning is performed into a predetermined shape by photolithography and etching methods or a lift-off method or the like. Thereafter, a heat treatment may be appropriately performed to adjust the electrical resistivity or the like. After the formation of the active layer 14, source electrodes 15 and drain electrodes 16 are formed on the active layer 14 and on the exposed surface of the gate insulating layer 13. The source electrodes 15 and drain electrodes 16 preferably have high conductivity, and for example, metals such as Al and Mo can be used.

[0070] After film formation, if necessary, patterning is performed into a predetermined shape by photolithography and etching methods or a lift-off method or the like. Thereby, the source electrodes 15 and drain electrodes 16 are formed. The gate electrode 12, the gate insulating layer 13, the active layer 14, the source electrodes 15 and the drain electrodes 16 are formed by a wet method or a dry method. Examples of the wet method include a coating method, and examples of the dry method include a sputtering method.

[0071] (Method for Evaluating TFT Characteristics) For the TFT on the glass substrate fabricated by the above method, in the present invention, the characteristics of the TFT can be evaluated by performing current-voltage measurement using a semiconductor parameter analyzer. When current-voltage measurement is performed by a semiconductor parameter analyzer, the threshold voltage V th of the TFT is obtained. On the other hand, after applying a bias voltage Vgs between the gate electrode and the source and drain electrodes for a predetermined time and then performing current-voltage measurement again, a shift of the threshold voltage V th is observed. By evaluating the magnitude of this threshold voltage shift amount ΔV th , the characteristics of the TFT can be evaluated. That is, it can be said that the smaller the ΔV th , the higher the characteristics of the TFT. In the present invention, high TFT characteristics include the meaning of high reliability of the TFT.

[0072] Note that when a characteristic test is performed, regardless of the influence from the glass substrate, to some extent V thA shift is observed. The cause is considered to be the injection and trapping of electrons from the semiconductor layer into the gate insulating film, and the increase in the local potential in the semiconductor film. This is a positive shift, i.e., when a positive bias voltage is applied to the gate electrode with respect to the source and drain electrodes, a positive V th shift, and a negative shift is observed when a negative bias is applied. th As for the mechanism in which the glass substrate causes a V

[0073] shift, it is considered that when a voltage is applied between the gate electrode and the source and drain electrodes, alkali metals such as Na diffuse from the glass substrate into the TFT layer and localize between the source and the drain, changing the depletion layer width of the TFT. th When performing the characteristic test, the test can also be performed with the TFT heated to a predetermined temperature. In this case, since the diffusion rate of the alkali metal increases, the characteristic test under higher load conditions can be performed.

[0074]

[0075] The threshold voltage V th in the present invention uses the rising voltage V on as follows. That is, in the current-voltage measurement of the TFT, the gate voltage V ds when the current I ds0 between the source and drain exceeds a specific value I gs is defined as V on . I ds0 can be arbitrarily selected according to the convenience of measuring the W / L ratio (the ratio of the channel width to the channel length) and V on . In the present invention, the rising voltage V ds0 when I -9 = 1×10 on is defined as the threshold voltage V th . Also, V th is not limited to this method, and for example, it may be obtained using the √I ds -V gs method or the like.

Example

[0076] ​In the following, Examples 1 to 3, 9, 11, 13, 15, 17, 19, 21, 23 to 32 are examples, and Comparative Examples 4 to 8, 10, 12, 14, 16, 18, 20, 22 are comparative examples. The raw materials of each component were formulated to achieve the target composition and melted at a temperature of 1550 to 1650 °C using a platinum crucible. During melting, a platinum stirrer was used for stirring to homogenize the glass. Subsequently, the molten glass was poured into a mold heated to 800 °C, and the glass was cooled at 40 °C / min from a temperature 100 °C higher than Tg to room temperature to obtain a plate-shaped glass.

[0077] Tables 1 to 4 show the glass composition (unit: mass %), the physical property values described above, and the thermal shrinkage rate measured by the procedure described above.

[0078]

Table 1

[0079]

Table 2

[0080]

Table 3

[0081]

Table 4

[0082] As is clear from Tables 1 to 4, in Examples 5 to 8 where the B2O3 content exceeded 5.5% and in Examples 4, 10, 12, 14, 16, 18, 20, 22, 23 to 32 where the Na2O content exceeded 600 ppm, the thermal shrinkage rate was greater than 90 ppm. Also, the thermal shrinkage rate increased according to Na2O / B2O3. On the other hand, in Examples 1 to 3, 9, 11, 13, 15, 17, 19, 21 where the B2O3 content was 0.2 to 5.5%, the Na2O content was 600 ppm or less, and Na2O / B2O3 was 0.001 or more and 0.3 or less, the thermal shrinkage rate increased according to Na2O / B2O3, but all were 90 ppm or less.

[0083] Figure 1 is a graph showing the relationship between Na2O / B2O3 and the thermal shrinkage rate. However, the thermal shrinkage rate C is the value obtained by extrapolating the regression line obtained by the least squares method to 0 as C0, and shows (C / C0) obtained by dividing the thermal shrinkage rate of each glass by C0. This plot shows the variation in the thermal shrinkage rate due to Na2O / B2O3. As shown in Figure 1, for Examples 1 to 4 where the B2O3 content was 0.2 to 5.5%, the slope of the straight line showing the variation in the thermal shrinkage rate was about 1 / 2 with respect to Examples 5 to 8 where the B2O3 content exceeded 5.5% (however, Example 4 is a comparative example in terms of the fact that Na2O exceeded 600 ppm). Therefore, in the alkali-free glass of the present invention, the variation in the thermal shrinkage rate due to the content of Na2O, which accounts for most of the alkali metal oxides inevitably mixed in from the raw materials, is reduced, and the thermal shrinkage rate is also reduced.

[0084] Figures 3, 4, and 5 show the results of performing TFT characteristic tests on Examples 1, 9, and 6. As the glass substrate, a plate-shaped glass produced by the above procedure was processed into a 40 mm square with a thickness of 0.5 mm. The TFT was fabricated by the above method. For the gate electrode, Mo with a film thickness of 100 nm was used, for the gate insulating film, SiO2 with a film thickness of 200 nm was used, for the semiconductor layer, In-Ga-Zn-O with a film thickness of 35 nm was used, and for the source and drain electrodes, Mo with a film thickness of 100 nm was used.

[0085] A source and drain electrode width, i.e., channel width, of 300 μm and a source-drain electrode spacing, i.e., channel length, of 50 μm were formed. The characteristics of the TFT were evaluated by the above method. For the semiconductor parameter analyzer, B1500A manufactured by Keysight Technologies was used. Current-voltage measurements were performed at atmospheric pressure, in an air atmosphere, at 70 °C, and in a light-shielded environment, with the voltage V ds between the source and drain being 10 V and the gate voltage V gs being changed from -10 V to 20 V, and the drain current I ds was observed. Also, after applying a positive bias voltage V gs of 10 V to the gate electrode with respect to the source and drain electrodes for 0 s, 3000 s, and 7000 s, current-voltage measurements were performed, and the presence or absence of a shift in the threshold voltage V th was observed.

[0086] As is clear from Figure 3, in Example 1 where Na2O / B2O3 is 0.001 or more and less than 0.06, the shift amount of V th is small, and V th shifts in the positive direction with respect to the application of a positive bias voltage, indicating that the TFT has high characteristics.

[0087] On the other hand, from Figure 4, for Example 9 where Na2O / B2O3 is 0.06 or more, V th shifts in the negative direction, and it is considered that alkali ions diffuse into the TFT during the characteristic test, affecting the TFT side more easily compared to Figure 3.

[0088] Also, as is clear from Figure 5, in Example 6, although the Na2O is the same as in Example 9, since Na2O / B2O3 is 0.001 or more and less than 0.06, the TFT has high characteristics. From this, in order to improve the characteristics of the TFT fabricated on the glass substrate, it is effective to reduce not only Na2O but also Na2O / B2O3 especially when B2O3 is 5.5% or less.

[0089] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese Patent Application (Japanese Patent Application No. 2014-216174) filed on October 23, 2014, the entire contents of which are incorporated herein by reference.

Claims

【Claim 1】 The deviation point is 680 °C or higher, and the average coefficient of thermal expansion at 50 to 350 °C is 30×10 －７ ~45×10 －７ / °C, and in terms of mass% based on oxides, SiO ２ : 54 to 66% Al ２ O ３ : 10 to 27% B ２ O ３ : 0.2 to 5.5% MgO: 0 to 10% CaO: 0 to 15% SrO: 0 to 15% BaO: 0 to 15% MgO + CaO + SrO + BaO: 8 to 25% containing Na ２ containing 600 mass ppm or less of Na ２ O and B ２ O ３ and the mass ratio of (Na ２ O / B ２ O ３ ) is 0.001 or more and 0.3 or less, an alkali-free glass.

Images