TW201404754A - Method for producing plate glass - Google Patents

Abstract

The present invention relates to a method for producing plate glass by melting glass starting materials to form a molten glass, then molding the molten glass into plate-like glass ribbons using a molding device, and gradually cooling the glass ribbons with a gradual cooling device, wherein by means of the method for producing plate glass, the plate glass is formed from the following alkali-free glass and SO2 gas is fed such that when the strain point of the alkali-free glass is Tst ( C), the time when the ambient air concentration directly underneath the bottom surface of the glass ribbons becomes 500 to 20,000 ppm is 30 seconds or greater at a temperature within a range of Tst + 70 C to Tst - 50 C. By mol% in terms of oxide, the alkali-free glass comprises 66 to 70 of SiO2, 12 to 15 of Al2O3, 0 to 1.5 of B2O3, greater than 9.5 but no greater than 13 of MgO, 4 to 9 of CaO, 0.5 to 4.5 of SrO, 0 to 1 of BaO, and 0 to 2 of ZrO2 such that MgO + CaO + SrO + BaO is 17 to 21, MgO/(MgO + CaO + SrO + BaO) is 0.40 or greater, MgO/(MgO + CaO) is 0.40 or greater, and MgO/(MgO + SrO) is 0.60 or greater, and has a stress point of 710 to 750 C, an average thermal expansion coefficient at 50 to 300 C of 30 10-7 to 43 10-7/ C, a temperature T2 at which glass viscosity becomes 102dPas of 1,710 C, and a temperature T4 at which glass viscosity becomes 104dPas of 1,320 C.

Description

Plate glass manufacturing method

The present invention relates to a method for producing a sheet glass which is preferably an alkali-free glass as a substrate glass for various displays or a substrate glass for a photomask.

Hereinafter, in this specification, when referred to the case of "alkali-free" it is meant an alkali metal oxides _{(Li 2 O, Na 2 O} , K 2 O) content of 2000 ppm by mole.

Conventionally, various substrate glass for display, particularly a metal or oxide film formed on the surface, are required to have the following characteristics.

(1) If an alkali metal oxide is contained, the alkali metal ion diffuses into the film to deteriorate the film properties, so that the content of the alkali metal oxide is required to be extremely low, specifically, the content of the alkali metal oxide is required to be 2000 moles. Below ppm.

(2) When exposed to a high temperature in the film forming step, the shrinkage (heat shrinkage) which suppresses the deformation of the glass and the structure of the glass is suppressed to a minimum, and the strain point is required to be high.

(3) It is required to have sufficient chemical durability for various chemicals used in semiconductor formation. In particular, it is durable in various chemicals (nitric acid, sulfuric acid, etc.) used in the etching of ITO (Indium Tin Oxides), a chemical containing a hydrochloric acid, a metal electrode, and a base of a photoresist stripper. .

(4) Requires internal and surface defects (bubbles, streaks, inclusions, pits, damage, etc.).

In addition to the above requirements, in recent years, the situation is as follows.

(5) The weight of the display is required, and the glass itself is also expected to be a glass having a lower density.

(6) It is required to reduce the weight of the display, and it is desirable to thin the substrate glass.

(7) In addition to the amorphous germanium (a-Si) type liquid crystal display up to now, a number of polycrystalline germanium (p-Si) type liquid crystal displays having a higher heat treatment temperature (a-Si: about 350 ° C → p-Si: 350~550°C).

(8) In order to accelerate the temperature rise and fall of the heat treatment of the liquid crystal display to improve productivity or to improve thermal shock resistance, glass having a small average thermal expansion coefficient of glass is required.

On the other hand, the drying of etching progresses, and the requirement for BHF resistance is weakened (BHF: buffered hydrofluoric acid, a mixture of hydrofluoric acid and ammonium fluoride). Based glass so far as the BHF resistance becomes good is often used a glass containing B ₂ O ₃ 6 ~ 10 mole% of the. However, B ₂ O ₃ has a tendency to lower the strain point. As an example of the alkali-free glass containing no B ₂ O ₃ or a small amount, there are the following.

Patent Document 1 discloses a SiO ₂ -Al ₂ O ₃ -SrO glass containing no B ₂ O ₃ , but the temperature required for melting is high, which causes difficulty in production.

Patent Document 2 discloses a SiO ₂ -Al ₂ O ₃ -SrO crystal glass containing no B ₂ O ₃ , but the temperature required for melting is high, which causes difficulty in production.

Patent Document 3 discloses a glass containing B ₂ O ₃ 0 to 3% by weight, but the strain point of the example is 690 ° C or lower.

Patent Document 4 discloses a glass containing B ₂ O ₃ 0 to 5 mol%, but the average thermal expansion coefficient at 50 to 300 ° C exceeds 50 × 10 ^-7 / ° C.

Patent Document 5 discloses a glass containing B ₂ O ₃ 0 to 5 mol%, but has a large thermal expansion and a large density.

In order to solve the problem of the glass described in Patent Documents 1 to 5, the alkali-free glass described in Patent Document 6 is proposed. The alkali-free glass described in Patent Document 6 has a high strain point and can be molded by a floating method, and is suitable for applications such as a substrate for a display and a substrate for a photomask.

However, as a method for producing a high-quality p-Si TFT (p-Si Thin Film Transistor), there is a solid phase crystallization method, and in order to carry out this method, it is required to further increase the strain point.

On the other hand, in terms of the glass manufacturing process, especially the requirements of melting and forming, it is required to reduce the viscosity of the glass, especially the glass viscosity becomes 10 ⁴ dPa. s temperature T ₄ .

Further, in order to prevent scratching of the glass ribbon formed into a plate shape, a method is known in which a glass ribbon after molding is blown into a slow cooling furnace to emit sulfurous acid (SO ₂ ) gas, and the glass ribbon is formed on the lower surface of the glass ribbon. A protective layer for sulfate damage prevention (see Patent Document 7).

However, in the case of an alkali-free glass, it is difficult to form a protective layer for damage prevention on the glass ribbon efficiently, and although research on equipment is carried out, there are restrictions on the configuration of the apparatus.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 62-113735

Patent Document 2: Japanese Patent Laid-Open No. 62-100450

Patent Document 3: Japanese Patent Laid-Open No. 4-325435

Patent Document 4: Japanese Patent Laid-Open No. Hei 5-232458

Patent Document 5: US Patent No. 5,326,730

Patent Document 6: Japanese Patent Laid-Open No. Hei 10-45422

Patent Document 7: Japanese Patent Laid-Open Publication No. 2009-148141

The object of the present invention is to solve the above drawbacks, and to provide a method for manufacturing a sheet glass, which has a high strain point and low viscosity, especially a glass viscosity of 10 ⁴ dPa. The temperature T _{4 of s is} low, and further, the protective layer for preventing damage of sulfate is formed on the glass ribbon formed into a plate shape efficiently, and the alkali-free glass is contained.

The present invention provides a method for producing a sheet glass, which comprises melting a glass raw material and forming a molten glass, and forming the molten glass into a sheet-shaped glass ribbon by a molding device, and then slowly cooling the glass ribbon by a slow cooling device, the plate The glass comprises the following alkali-free glass. When the strain point of the alkali-free glass is T _st (° C.), the temperature is in the range of T _st +70 ° C to T _st -50 ° C, directly below the lower surface of the glass ribbon. The SO ₂ gas is supplied so that the environmental concentration becomes 500 to 20,000 ppm for 30 seconds or longer.

The alkali-free glass has a strain point of 710 to 750 ° C, an average thermal expansion coefficient of 30×10 ^-7 to 43×10 ^-7 /° C. at 50 to 300 ° C, and a glass viscosity of 10 ² dPa. The temperature T ₂ of s is below 1710 ° C, and the glass viscosity is 10 ⁴ dPa. The temperature T ₄ of s is 1320 ° C or less, and the mole % based on the oxide is contained: SiO ₂ 66-70 mol%, Al ₂ O ₃ 12-15 mol%, B ₂ O ₃ 0-1.5 mol %, MgO more than 9.5 mole% and 13 mole% or less, CaO 4 ~ 9 mole%, SrO 0.5 ~ 4.5 mole%, BaO 0 ~ 1 mole%, ZrO ₂ 0 ~ ₂ mole%, and MgO+CaO+SrO+BaO is 17-21 mol%, MgO/(MgO+CaO+SrO+BaO) is 0.40 or more, MgO/(MgO+CaO) is 0.40 or more, and MgO/(MgO+SrO) is 0.60. the above.

Moreover, the present invention provides a method for producing a sheet glass which is obtained by melting a glass raw material and forming a molten glass, and forming the molten glass into a plate-shaped glass ribbon by a molding device, and then slowly cooling the glass ribbon by a slow cooling device. The plate glass includes the following alkali-free glass. When the strain point of the alkali-free glass is T _st (° C.), the surface of the glass ribbon is in a temperature range of T _st +70 ° C to T _st -50 ° C. The SO ₂ gas is supplied so that the environmental concentration immediately below is 500 to 20000 ppm for 30 seconds or longer.

The alkali-free glass has a strain point of 710 to 750 ° C, an average thermal expansion coefficient of 30×10 ^-7 to 43×10 ^-7 /° C. at 50 to 300 ° C, and a glass viscosity of 10 ² dPa. The temperature T ₂ of s is below 1710 ° C, and the glass viscosity is 10 ⁴ dPa. s the temperature T ₄ at 1320 ℃, the mole% based on oxides represented containing: SiO ₂ 66 ~ 70 _{mole%, Al 2 O 3 12 ~} 15 _{mole%, B 2 O 3 0 ~} 1.5 mole %, MgO 5~9.5 mol%, CaO 4~11 mol%, SrO 0.5~4.5 mol%, BaO 0~1 mol%, ZrO ₂ 0~2 mol%, and MgO+CaO+SrO+ BaO is more than 18.2% by mole and is 21% by mole or less, MgO/(MgO+CaO+SrO+BaO) is 0.25 or more, MgO/(MgO+CaO) is 0.3 or more, and MgO/(MgO+SrO) is 0.60 or more. Al ₂ O ₃ × (MgO/(MgO+CaO+SrO+BaO)) is 5.5 or more.

Further, the present invention provides a sheet glass produced by the method for producing a sheet glass of the present invention.

The method for producing a sheet glass of the present invention can form a protective layer for sulfate damage prevention on a glass ribbon efficiently and uniformly, and can also save the supply amount of sulfurous acid gas. As a result, high quality sheet glass with less damage can be obtained.

The sheet glass of the present invention is particularly suitable for a substrate for a display for high strain point applications, a substrate for a photomask, and the like.

Hereinafter, a method for producing a sheet glass of the present invention will be described.

The method for producing the sheet glass of the present invention is a glass material obtained by blending the glass composition 1 described below.

An alkali-free glass containing SiO ₂ 66-70 mol%, Al ₂ O ₃ 12-15 mol%, B ₂ O ₃ 0-1.5 mol%, and MgO exceeding 9.5 mol% and 13 mol% or less, CaO 4-9 mol%, SrO 0.5-4.5 mol%, BaO 0~1 mol%, ZrO ₂ 0-2 mol%, and MgO+CaO+ SrO+BaO is 17 to 21 mol%, MgO/(MgO+CaO+SrO+BaO) is 0.40 or more, MgO/(MgO+CaO) is 0.40 or more, and MgO/(MgO+SrO) is 0.60 or more.

Moreover, the method for producing a sheet glass of the present invention uses a glass raw material obtained by blending the glass composition 2 described below.

An alkali-free glass containing SiO ₂ 66-70 mol%, Al ₂ O ₃ 12-15 mol%, B ₂ O ₃ 0-1.5 mol%, MgO 5 ~9.5 mol%, CaO 4~11 mol%, SrO 0.5~4.5 mol%, BaO 0~1 mol%, ZrO ₂ 0~2 mol%, and MgO+CaO+SrO+BaO exceeds 18.2 mo % of ear is 21 mol% or less, MgO/(MgO+CaO+SrO+BaO) is 0.25 or more, MgO/(MgO+CaO) is 0.3 or more, and MgO/(MgO+SrO) is 0.60 or more, and Al ₂ O ₃ × (MgO / (MgO + CaO + SrO + BaO)) is 5.5 or more.

Next, the composition range of each component will be described. When SiO _{2 is} less than 66% (% by mole, unless otherwise specified, the strain point is not sufficiently increased, the coefficient of thermal expansion is increased, and the density is increased. It is preferably 66.5% or more, more preferably 67% or more. When it exceeds 70%, the meltability is lowered and the devitrification temperature is increased. It is preferably 69% or less.

Al ₂ O ₃ as glass suppress phase separation, lower coefficient of thermal expansion, increase the strain point, but less than 12% at the time does not show this effect, and, due to the increase of other ingredients to improve the expansion, the results of the thermal expansion becomes large. It is preferably 12.2% or more. When it exceeds 15%, there is a possibility that the melting property of the glass is deteriorated or the devitrification temperature is raised. It is preferably 14.5% or less, more preferably 14% or less, still more preferably 13.8% or less.

B ₂ O ₃ improves the melt reactivity of the glass and lowers the devitrification temperature, so that it can be added up to 1.5%. However, if it is too much, the strain point becomes low. Further, when the amount of B ₂ O _{3 is} too large, the efficiency of the sulfate-preventing protective layer on the glass ribbon is lowered.

Therefore, it is preferably 1.3% or less, more preferably 1% or less. Further, in consideration of the environmental load, it is preferably substantially absent.

MgO has the characteristics of not increasing the expansion in the alkaline earth and not excessively reducing the strain point, and also improving the meltability.

Here, in the glass composition 1, the MgO content is more than 9.5% and 13% or less. When it is 9.5% or less, the above effect by adding MgO is not sufficiently exhibited. However, if it exceeds 13%, the devitrification temperature rises. It is preferably 12.5% or less, more preferably 12% or less, still more preferably 11.5% or less.

On the other hand, in the glass composition 2, the MgO content is 5 to 9.5%. When the amount is less than 5%, the above effect by adding MgO is not sufficiently exhibited. It is preferably 6% or more, more preferably 7% or more. However, if it exceeds 9.5%, there is a possibility that the devitrification temperature rises. It is preferably 9.3% or less, more preferably 9% or less.

The CaO system has the characteristics that the MgO does not increase the swelling in the alkaline earth and does not excessively reduce the strain point, and also improves the meltability.

Here, in the glass composition 1, the CaO content is 4 to 9%. When the amount is less than 4%, the above effect of adding CaO is not sufficiently exhibited. However, if it exceeds 9%, the devitrification temperature rises or a large amount of phosphorus, which is an impurity in limestone (CaCO ₃ ), which is a CaO raw material, is mixed. It is preferably 7% or less, more preferably 6% or less, further preferably 5% or less.

On the other hand, in the glass composition 2, the CaO content is 4 to 11%. When the amount is less than 4%, the above effect of adding CaO is not sufficiently exhibited. It is preferably 5% or more. However, if it exceeds 11%, the devitrification temperature rises or a large amount of phosphorus, which is an impurity in limestone (CaCO ₃ ), which is a CaO raw material, is mixed. It is preferably 10% or less, more preferably 9% or less, further preferably 7% or less, and particularly preferably 6% or less.

SrO does not increase the devitrification temperature of the glass to improve the meltability, but the effect is not sufficiently exhibited when it is less than 0.5%. It is preferably 1.0% or more, and more preferably 2.0% or more. However, if it exceeds 4.5%, there is a tendency for the expansion coefficient to increase. It is more preferably 4.0% or less, further preferably 3.5% or less.

BaO is not essential, but may be contained to improve meltability. However, if it is too large, the expansion and density of the glass are excessively increased, so that it is 1% or less. It is preferably less than 1%, more preferably 0.5% or less, and further preferably substantially not contained.

ZrO ₂ may contain up to 2% in order to lower the glass melting temperature or to promote crystallization during calcination. When it exceeds 2%, the glass becomes unstable, or the relative dielectric constant ε of the glass becomes large. It is preferably 1.5% or less, more preferably 1.0% or less, still more preferably 0.5% or less, and particularly preferably substantially not contained.

In the glass composition 1, when the total amount of MgO, CaO, SrO, and BaO is less than 17%, the meltability is insufficient, and the efficiency of the sulfate-preventing protective layer on the glass ribbon is lowered. It is preferably 18% or more, and more preferably 18.5% or more. If it is more than 21%, there is a difficulty in that the coefficient of thermal expansion cannot be reduced. It is preferably 20% or less.

In the glass composition 2, when the combined amount of MgO, CaO, SrO, and BaO is 18.2% or less, the meltability is insufficient, and the efficiency of the sulfate-preventing protective layer on the glass ribbon is lowered. If it is more than 21%, there is a difficulty in that the coefficient of thermal expansion cannot be reduced. It is preferably 20% or less.

In the glass composition 1, when the combined amount of MgO, CaO, SrO, and BaO is satisfied, and the following three conditions are satisfied, the strain point can be increased without increasing the devitrification temperature, and the viscosity of the glass can be lowered, especially lowering the glass viscosity becomes 10 ⁴ dPa. s temperature T ₄ .

MgO/(MgO+CaO+SrO+BaO) is 0.4 or more, preferably 0.45 or more.

MgO/(MgO+CaO) is 0.4 or more, preferably 0.52 or more, and further preferably 0.55 or more.

MgO/(MgO+SrO) is 0.6 or more, preferably 0.7 or more.

In the glass composition 2, when the total amount of MgO, CaO, SrO, and BaO is satisfied, and the following three conditions are satisfied, the strain point can be increased without increasing the devitrification temperature, and the viscosity of the glass can be lowered, especially The glass viscosity becomes 10 ⁴ dPa. s temperature T ₄ .

MgO/(MgO+CaO+SrO+BaO) is 0.25 or more, preferably 0.3 or more, more preferably 0.4 or more, still more preferably 0.45 or more.

MgO/(MgO+CaO) is 0.3 or more, preferably 0.4 or more, more preferably 0.52 or more, still more preferably 0.55 or more.

MgO/(MgO+SrO) is 0.6 or more, preferably 0.7 or more.

In the glass composition 2, when Al ₂ O ₃ × (MgO / (MgO + CaO + SrO + BaO)) is 5.5 or more, the Young's modulus can be increased, which is preferable. It is preferably 5.75 or more, more preferably 6.0 or more, further preferably 6.25 or more, and particularly preferably 6.5 or more.

In the method for producing a sheet glass of the present invention, in order to improve the efficiency of forming a protective layer for preventing damage of sulfate on the glass ribbon, it is preferred that the glass raw material contains 600 to 2000 mols of alkali metal oxide.

In the present invention, by including the alkali metal oxide in an amount of 600 ppm or more in the glass raw material, the efficiency in forming the protective layer for damage prevention on the glass ribbon is improved. The reason is as follows.

Since the alkali-free glass does not contain an alkali metal oxide, even if a high-temperature glass ribbon is exposed to an SO ₂ gas atmosphere, a protective layer for damage prevention obtained by precipitation of an alkali metal sulfate cannot be formed. When a large amount of alkali-free glass containing a composition of an alkaline earth metal oxide is exposed to a SO ₂ gas atmosphere at a high temperature, an alkali earth metal sulfate is precipitated instead of an alkali metal sulfate, but the amount of precipitation is small, and the damage prevention is formed. The protective layer must be at a higher temperature, or longer, or exposed to a higher concentration of SO ₂ gas. However, the inventors of the present invention have found that the precipitation effect of the alkaline earth metal sulfate is increased by the addition of an alkali metal oxide in a small amount to the glass raw material, and the efficiency is improved when the protective layer for damage prevention is formed on the glass ribbon.

When the content of the alkali metal oxide is increased, the alkali metal ions diffuse into the film to deteriorate the film properties. Therefore, when used as a substrate glass for various displays, it is a problem as long as the alkali metal oxide in the glass composition is used. When the content is 2000 mol% or less, such a problem does not occur. More preferably, it is 1500 mol ppm or less, further preferably 1300 mol ppm or less, and particularly preferably 1000 mol ppm or less.

The glass raw material used in the present invention preferably contains an alkali metal oxide of 1,500 mol ppm or less, more preferably 1300 mol ppm or less, further preferably 1,000 mol ppm or less, and further preferably 700 to 900 mol ppm. More preferably, it is 700 to 800 moles ppm.

In addition, alkali metal oxides, the glass ribbon is formed to increase in the effect of preventing damage by the time efficiency of the protective layer, and the viewpoint of the balance of the cost of raw materials, it is preferably Na ₂ O, K ₂ O, more preferably Na ₂ O.

Further, in order to prevent the deterioration of the characteristics of the metal or the oxide film provided on the glass surface during the production of the panel, the glass raw material preferably contains substantially no P ₂ O ₅ . Further, in order to facilitate the reuse of the glass, the glass raw material preferably contains substantially no PbO, As ₂ O ₃ or Sb ₂ O ₃ .

In order to improve the meltability, clarity, and formability of the glass, ZnO, Fe ₂ O ₃ , SO ₃ , F, Cl, and SnO ₂ may be added to the glass raw material in an amount of 5% or less.

Since the glass compositions 1 and 2 have relatively low meltability, it is preferred to use the following materials as raw materials for the respective components.

(Source)

As the cerium source of SiO ₂ , cerium is used, and the median diameter D ₅₀ is 20 μm to 27 μm, the ratio of particles having a particle diameter of 2 μm or less is 0.3% by volume or less, and the ratio of particles having a particle diameter of 100 μm or more is 2.5 vol. When the sand is less than %, it is possible to suppress the aggregation of the sand and melt it, so that the melting of the sand is easy, and a plate glass having less bubbles, homogeneity, and flatness is obtained, which is preferable.

In addition, the term "particle diameter" in the present specification means the diameter of the approximate sphere of the cerium sand (in the present invention, the meaning of the primary particle diameter), specifically, the measurement by the laser diffraction/scattering method. The particle size in the particle size distribution of the powder.

In addition, the "median diameter D ₅₀ " in the present specification means that the volume frequency of particles larger than a certain particle diameter accounts for the volume frequency of all the powders in the particle size distribution of the powder measured by the laser diffraction method. Particle size at 50%. In other words, it means the particle size at a cumulative frequency of 50% in the particle size distribution of the powder measured by the laser diffraction method.

In the present specification, the "ratio of particles having a particle diameter of 2 μm or less" and the "ratio of particles having a particle diameter of 100 μm or more" are measured by, for example, measuring a particle size distribution by a laser diffraction/scattering method.

When the median diameter D ₅₀ of the cerium is 25 μm or less, the melting of the cerium is easier, and therefore it is more preferable.

Further, when the ratio of the particles having a particle diameter of 100 μm or more in the cerium sand is 0%, the melting of the cerium is easier, and therefore it is particularly preferable.

(alkaline earth metal source)

As the alkaline earth metal source, an alkaline earth metal compound can be used. Here, specific examples of the alkaline earth metal compound include carbonic acid salts such as MgCO ₃ , CaCO ₃ , BaCO ₃ , SrCO ₃ , (Mg, Ca)CO ₃ (dolomite), and oxidation of MgO, CaO, BaO, and SrO. a hydroxide such as Mg(OH) ₂ , Ca(OH) ₂ , Ba(OH) ₂ or Sr(OH) ₂ , but when a part or all of the alkaline earth metal source contains a hydroxide of an alkaline earth metal, the glass The amount of unmelted SiO ₂ component at the time of melting of the raw material is lowered, which is preferable. When the unmelted amount of the SiO ₂ component contained in the strontium sand is increased, the unmelted SiO ₂ enters the bubble and bubbles in the vicinity of the surface layer of the molten glass when bubbles are generated in the molten glass. Thereby, the composition ratio of SiO ₂ differs between the surface layer of the molten glass and the portion other than the surface layer, the homogeneity of the glass is lowered and the flatness is also lowered.

The content of the hydroxide of the alkaline earth metal is 100% by mass of the alkaline earth metal source (in terms of MO, wherein M is an alkaline earth metal element), preferably 15 to 100 mol% (in terms of MO), more preferably 30~ 100 mol% (in terms of MO), and further preferably 60 to 100 mol% (in terms of MO), at this time, the amount of unmelted SiO ₂ component at the time of melting the glass raw material is lowered, which is more preferable.

As the molar ratio of the hydroxide in the alkaline earth metal source increases, the amount of unmelted SiO ₂ component at the time of melting of the glass raw material decreases, so that the higher the molar ratio of the above hydroxide is, the better.

As the alkaline earth metal source, specifically, a mixture of an alkali earth metal hydroxide and a carbonate, a hydroxide of an alkaline earth metal alone, or the like can be used. As the carbonate, it is preferred to use one or more of MgCO ₃ , CaCO ₃ and (Mg, Ca)(CO ₃ ) ₂ (dolomite). And, as the alkaline earth metal hydroxide, is preferably used Mg (OH) ₂ or in the Ca ₂ (OH) at least one, and particularly preferably used Mg (OH) _2.

(boron source)

In the case where the glass compositions 1 and 2 contain B ₂ O ₃ , a boron compound can be used as the boron source of B ₂ O ₃ . Here, specific examples of the boron compound include: orthoboric acid (H ₃ BO _3), metaboric acid (HBO _2), tetraboric acid _{(H 2 B 4 O 7)} , boric anhydride (B ₂ O ₃₎ and the like. In the production of a usual alkali-free glass, orthoboric acid is used in terms of being inexpensive and easily available.

In the present invention, as the boron source, it is preferable to use a boron source in an amount of 10 to 100% by mass (in terms of B ₂ O ₃ ) in terms of 100% by mass of boron source (in terms of B ₂ O ₃ ). When the amount of the boric anhydride is 10% by mass or more, aggregation of the glass raw material is suppressed, and the effect of reducing bubbles and improving the homogeneity and flatness are obtained. The boric anhydride is more preferably 20 to 100% by mass, still more preferably 40 to 100% by mass.

As a boron compound other than boric anhydride, orthoboric acid is preferable in terms of being inexpensive and easily available.

The manufacture of the sheet glass is carried out, for example, according to the following procedure.

The raw materials of the respective components are blended so as to become the target components, and they are continuously introduced into a melting furnace, and heated to 1500 to 1800 ° C for melting. The molten glass is formed into a plate-shaped glass ribbon having a specific thickness by a molding device, and the glass ribbon is slowly cooled and then cut, whereby a plate glass can be obtained.

In the present invention, a glass ribbon formed into a plate shape by a float method is preferred.

In the present invention, sulfurous acid (SO ₂ ) gas is supplied to the glass ribbon in a slow cooling furnace so as to satisfy the conditions shown below.

When the strain point of the alkali-free glass is T _st (°C), the temperature in the temperature range from T _st +70 ° C to T _st -50 ° C is 500 to 20000 ppm below the surface under the glass ribbon. The SO ₂ gas is supplied in a manner of 30 seconds or more. If the environmental concentration is less than 500 ppm, the amount of precipitation of the alkaline earth metal sulfate becomes small. More preferably, it is 1000 ppm or more. If the environmental concentration exceeds 20,000 ppm, corrosion of the equipment becomes a problem. More preferably, it is 10000 ppm or less, More preferably, it is 5000 ppm or less. Further, if it is less than 30 seconds, the amount of precipitation of the alkaline earth metal sulfate is small. More preferably more than 1 minute.

In the present invention, it is preferably supplied to the surface of the SO ₂ gas from beneath the glass band. SO ₂ gas supplied to the surface by the self, the proportion of the heavier gas may be SO ₂ only the lower surface of the precipitated alkaline earth metal sulfates, to prevent the diffusion of the gas, the effect of improving the precipitation of alkaline earth metal sulfates.

In the present invention, it is preferred to bring the glass ribbon into contact with the SO ₂ gas in an environment where the water vapor dew point is 30 ° C or higher. If the water vapor dew point is low, there is no increase in the precipitation effect of the alkaline earth metal sulfate. More preferably, it is 40 ° C or more, and further preferably 50 ° C or more.

The glass strain point of the present invention is 710 ° C or higher, which can suppress heat shrinkage when manufacturing a panel. Further, as a method of producing the p-Si TFT, a solid phase crystallization method can be used. Further, in the production method of the present invention, since the SO ₂ gas can be supplied at a higher temperature, the formation efficiency of the protective layer for damage prevention of the sulfate containing the alkaline earth metal is preferable. The strain point is more preferably 715 ° C or higher, and further preferably 720 ° C or higher. Particularly good is 735 ° C or more. When the strain point is 735 ° C or higher, it is suitable for high strain point applications (for example, a display substrate for an organic EL (Electro-Luminescence) or a substrate for illumination, or a substrate for a display having a thickness of 100 μm or less or Lighting substrate).

In the molding of the plate glass having a thickness of 100 μm or less, the drawing speed at the time of molding tends to increase, so that the pseudo temperature of the glass rises and the tightness of the glass tends to increase. In this case, if it is a high strain point glass, the tightness can be suppressed.

However, if the strain point of the glass is too high, it is necessary to increase the temperature of the forming apparatus, and the life of the forming apparatus is lowered. Therefore, the strain point of the sheet glass of the present invention is 750 ° C or lower.

Further, the glass of the present invention preferably has a glass transition point of 760 ° C or higher, more preferably 770 ° C or higher, and still more preferably 780 ° C or higher for the same reason as the strain point.

Further, the glass of the present invention has an average thermal expansion coefficient of 30 × 10 ^-7 to 43 × 10 ^-7 / ° C at 50 to 300 ° C, and has high thermal shock resistance, which can improve productivity in manufacturing a panel. The glass of the present invention preferably has an average coefficient of thermal expansion of from 50 to 300 ° C of from 35 × 10 ^-7 to 40 × 10 ^-7 / ° C.

Further, the specific gravity of the glass of the present invention is preferably 2.65 or less, more preferably 2.64 or less, still more preferably 2.62 or less.

Further, the glass viscosity η of the present invention has a temperature T ₂ of 10 ² poise (dPa.s) of 1710 ° C or less, preferably less than 1710 ° C, more preferably 1700 ° C or less, still more preferably 1690 ° C or less. Melting is relatively easy.

Further, the glass of the present invention the viscosity η becomes ¹⁰⁴ poise temperature of T ₄ at 1320 ℃, preferably higher than 1315 deg.] C, more preferably higher than 1310 deg.] C, and further preferably higher than 1305 deg.] C, float method suitable for molding.

Further, in the case where the molding by the floating method is easy, the glass devitrification temperature of the present invention is preferably 1,350 ° C or lower. It is preferably 1340 ° C or lower, more preferably 1330 ° C or lower.

The devitrification temperature in the present specification is charged into a plate made of platinum, and the pulverized glass particles are placed in an electric furnace controlled to a certain temperature for 17 hours, and obtained on the surface and inside of the glass by optical microscopy after heat treatment. The average value of the highest temperature at which crystals are precipitated and the lowest temperature at which crystals are not precipitated.

Further, the glass of the present invention preferably has a Young's modulus of 84 GPa or more, more preferably 86 GPa or more, further preferably 88 GPa or more, and still more preferably 90 GPa or more.

Further, the glass of the present invention preferably has a photoelastic constant of 31 nm/MPa/cm or less.

The glass substrate has birefringence due to the manufacturing process of the liquid crystal display panel or the stress generated when the liquid crystal display device is used. Therefore, there is a case where the visible black display is grayed out and the contrast of the liquid crystal display is lowered. This phenomenon can be suppressed to be small by setting the photoelastic constant to 31 nm/MPa/cm or less. It is preferably 30 nm/MPa/cm or less, more preferably 29 nm/MPa/cm or less, further preferably 28.5 nm/MPa/cm or less, and particularly preferably 28 nm/MPa/cm or less.

Moreover, in consideration of the easiness of securing other physical properties, the glass of the present invention preferably has a photoelastic constant of 25 nm/MPa/cm or less.

Further, the photoelastic constant can be measured by a disk compression method.

Further, the glass of the present invention preferably has a relative dielectric constant of 5.6 or more.

The touch sensing is improved when the built-in type touch panel (the built-in touch sensor is incorporated in the liquid crystal display panel) as described in Japanese Laid-Open Patent Publication No. 2011-70092 The relative dielectric constant of the glass substrate is preferably higher from the viewpoints of sensing sensitivity, lowering driving voltage, and power saving. By setting the relative dielectric constant to 5.6 or more, the sensitivity of the touch sensor is improved. It is preferably 5.8 or more, more preferably 6.0 or more, still more preferably 6.2 or more, and particularly preferably 6.4 or more.

Further, the relative dielectric constant can be measured by the method described in JIS C-2141.

Example (Example 1, Comparative Examples 1, 2)

The raw materials of the respective components were blended so as to have the target compositions shown in Table 1, and were melted by a continuous melting furnace, and subjected to sheet forming by a floating method. The content of Na ₂ O as the content of the alkali metal oxide in the raw material used at this time, the median diameter D ₅₀ of the particle size of the cerium used in the raw material used, the ratio of the particles having a particle diameter of 2 μm or less, and The ratio of the particles having a particle diameter of 100 μm or more is shown in Table 1. Further, the molar ratio (in terms of MO) of the hydroxide material of the alkaline earth metal is also shown in Table 1.

After the obtained glass was mirror-polished, heat treatment was carried out in accordance with the heat treatment temperature, the heat treatment time, the SO ₂ gas concentration, and the water vapor dew point shown in Table 2 in an SO ₂ gas atmosphere. The sulfate precipitation state of the surface of the obtained glass was measured in the form of the surface S concentration (% by mass) obtained by the fluorescent X-ray. The strain point of the glass and the surface S concentration (% by mass) are also shown in Table 2.

[Method for Measuring Surface S Concentration Using Fluorescent X-rays]

The glass sample for the precipitation of sulfate is utilized under the conditions shown in Table 3. A 10 mm reticle measures the number of counts of S-kα rays. The S concentration is used after mirror polishing of the known glass, and is used under the conditions shown in Table 3. The number of S-kα rays was measured by a 10 mm photomask, and the correlation between the number of counts of S-kα rays and the S concentration (% by mass) was obtained. The S-kα ray count number of the sulfated glass sample was converted into the S concentration (% by mass) by using the obtained correlation. The surface S concentration is preferably 0.15% by mass or more, and more preferably 0.2% by mass or more.

(Examples 2 to 4)

The raw materials of the respective components were blended so as to have the target compositions shown in Table 4, and the platinum crucible was melted at a temperature of 1,550 ° C for 1 hour. After the melting, the mixture was discharged into a carbon plate shape, and held at a glass transition point of +30 ° C for 1 hour, and then cooled at 1 ° C / minute to carry out slow cooling. The content of Na ₂ O as the content of the alkali metal oxide in the raw material used at this time, the median diameter D ₅₀ of the particle size of the cerium used in the raw material used, the ratio of the particles having a particle diameter of 2 μm or less, and The ratio of the particles having a particle diameter of 100 μm or more is shown in Table 4 together. Further, the molar ratio (in terms of MO) of the hydroxide material of the alkaline earth metal is also shown in Table 4.

The obtained glass was cut and mirror-polished, and thereafter heat-treated in accordance with the heat treatment temperature, the heat treatment time, the SO ₂ gas concentration, and the water vapor dew point shown in Table 5 in an SO ₂ gas atmosphere. The sulfate precipitation state of the surface of the obtained glass was measured in the form of the surface S concentration (% by mass) obtained by the fluorescent X-ray. The strain point of the glass and the surface S concentration (% by mass) are also shown in Table 5.

The present invention has been described in detail with reference to the particular embodiments of the invention.

The present application is based on Japanese Patent Application No. 2012-112226, filed on Jan.

Industrial availability

The plate glass obtained by the present invention has a high strain point and is suitable for applications such as a substrate for a display and a substrate for a photomask. Moreover, it is also suitable for applications such as substrates for solar cells.

Claims (7)

A method for producing a sheet glass, which comprises melting a glass raw material and forming a molten glass, and forming the molten glass into a plate-shaped glass ribbon by a molding device, and then slowly cooling the glass ribbon by a slow cooling device, wherein the plate glass comprises In the alkali-free glass, when the strain point of the alkali-free glass is T _st (°C), the temperature is in the temperature range from T _st +70 ° C to T _st -50 ° C, and the environmental concentration directly below the lower surface of the glass ribbon. The SO ₂ gas is supplied in a manner of being 500 to 20000 ppm for 30 seconds or more; the alkali-free glass has a strain point of 710 to 750 ° C, and an average thermal expansion coefficient at 50 to 300 ° C is 30 × 10 ^-7 to 43 × 10 ^{- 7} / ° C, the glass viscosity becomes 10 ² dPa. The temperature T ₂ of s is below 1710 ° C, and the glass viscosity is 10 ⁴ dPa. The temperature T ₄ of s is 1320 ° C or less, and the mole % based on the oxide is contained: SiO ₂ 66-70 mol%, Al ₂ O ₃ 12-15 mol%, B ₂ O ₃ 0-1.5 mol %, MgO exceeds 9.5 mol% and is 13 mol% or less, CaO 4-9 mol%, SrO 0.5-4.5 mol%, BaO 0~1 mol%, ZrO ₂ 0-2 mol%, and MgO+CaO+SrO+BaO is 17-21 mol%, MgO/(MgO+CaO+SrO+BaO) is 0.40 or more, MgO/(MgO+CaO) is 0.40 or more, and MgO/(MgO+SrO) is 0.60. the above. A method for producing a sheet glass, which comprises melting a glass raw material and forming a molten glass, and forming the molten glass into a plate-shaped glass ribbon by a molding device, and then slowly cooling the glass ribbon by a slow cooling device, wherein the plate glass comprises In the alkali-free glass, when the strain point of the alkali-free glass is T _st (°C), the temperature is in the temperature range from T _st +70 ° C to T _st -50 ° C, and the environmental concentration directly below the lower surface of the glass ribbon. The SO ₂ gas is supplied in a manner of being 500 to 20000 ppm for 30 seconds or more; the alkali-free glass has a strain point of 710 to 750 ° C, and an average thermal expansion coefficient at 50 to 300 ° C is 30 × 10 ^-7 to 43 × 10 ^{- 7} / ° C, the glass viscosity becomes 10 ² dPa. The temperature T ₂ of s is below 1710 ° C, and the glass viscosity is 10 ⁴ dPa. The temperature T ₄ of s is 1320 ° C or less, and the mole % based on the oxide is contained: SiO ₂ 66-70 mol%, Al ₂ O ₃ 12-15 mol%, B ₂ O ₃ 0-1.5 mol %, MgO 5~9.5 mol%, CaO 4~11 mol%, SrO 0.5~4.5 mol%, BaO 0~1 mol%, ZrO ₂ 0~2 mol%, and MgO+CaO+SrO+ BaO is more than 18.2% by mole and is 21% by mole or less, MgO/(MgO+CaO+SrO+BaO) is 0.25 or more, MgO/(MgO+CaO) is 0.3 or more, and MgO/(MgO+SrO) is 0.60 or more. Al ₂ O ₃ × (MgO/(MgO+CaO+SrO+BaO)) is 5.5 or more. The method for producing a sheet glass according to claim 1 or 2, wherein the alkali-free glass contains an alkali metal oxide in an amount of 600 to 2000 mol ppm. The method for manufacturing a sheet glass according to any one of claims 1 to 3, wherein the forming device is It is a floating method forming device. The method for producing a sheet glass according to any one of claims 1 to 4, wherein a ratio of particles having a median diameter D ₅₀ of 20 μm to 27 μm and a particle diameter of 2 μm or less is 0.3% by volume or less as a source of SiO ₂ raw material. The ratio of the particles having a particle diameter of 100 μm or more is 2.5% by volume or less. The method for producing a sheet glass according to any one of claims 1 to 4, wherein, as an alkaline earth metal source of MgO, CaO, SrO and BaO, an alkaline earth metal source of 100 mol% is used (in terms of MO, wherein M is an alkaline earth metal element, the following In the same), the hydroxide of the alkaline earth metal is contained in an amount of 15 to 100 mol% (in terms of MO). The method for producing a sheet glass according to any one of claims 1 to 4, wherein a ratio of particles having a median diameter D ₅₀ of 20 μm to 27 μm and a particle diameter of 2 μm or less is 0.3% by volume or less as a source of SiO ₂ raw material. And the ratio of particles having a particle diameter of 100 μm or more is 2.5% by volume or less, and as an alkaline earth metal source of MgO, CaO, SrO, and BaO, an alkaline earth metal source of 100 mol% is used (in terms of MO, where M is an alkaline earth metal) The element (the same applies hereinafter) contains an alkali earth metal hydroxide of 15 to 100 mol% (in terms of MO).