阅读说明：本技术 玻璃基板的制造方法 (Method for manufacturing glass substrate ) 是由 林昌宏 藤井未侑 于 2020-05-22 设计创作，主要内容包括：本发明提供一种能够避免设备的短寿命化并减少热处理时的尺寸变化的玻璃基板的制造方法。该方法的特征在于：将玻璃原料熔融、成型,制造应变点为690～750℃的玻璃基板,在成型时的冷却过程中,将(退火点+150℃)至(退火点－200℃)的温度范围内的平均冷却速度设为100～400℃/分钟,从而得到以500℃进行1小时的热处理时的热收缩率为15ppm以下的玻璃基板。(The invention provides a method for manufacturing a glass substrate, which can avoid the short service life of equipment and reduce the dimensional change during heat treatment. The method is characterized in that: a glass substrate having a strain point of 690-750 ℃ is produced by melting and molding a glass raw material, and the average cooling rate in the temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) is set to 100-400 ℃/min in the cooling process at the time of molding, whereby a glass substrate having a heat shrinkage rate of 15ppm or less at the time of heat treatment at 500 ℃ for 1 hour is obtained.)

1. A method for manufacturing a glass substrate, characterized in that:

a glass substrate having a strain point of 690-750 ℃ is produced by melting and molding a glass raw material, and the average cooling rate in the temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) is set to 100-400 ℃/min in the cooling process at the time of molding, whereby a glass substrate having a heat shrinkage rate of 15ppm or less at the time of heat treatment at 500 ℃ for 1 hour is obtained.

2. The method for manufacturing a glass substrate according to claim 1, wherein:

and (4) forming by using an overflow downward drawing method.

3. The method for manufacturing a glass substrate according to claim 1 or 2, wherein:

a glass substrate having a plate width of 3m or more was obtained.

4. The method for manufacturing a glass substrate according to any one of claims 1 to 3, wherein:

the following glass substrate was obtained,

the glass composition of the glass substrate contains SiO in mol%₂ 60～75％、Al₂O₃10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％。

5. The method for manufacturing a glass substrate according to any one of claims 1 to 4, wherein:

after the glass substrate was molded, the glass substrate was divided to obtain 2 or more glass substrates having a G6 size (1.5m × 1.8 m).

6. A method for manufacturing a glass substrate, characterized in that:

glass raw materials are melted and molded to produce a glass substrate,

the glass substrate has a strain point of 690-750 ℃, a thermal shrinkage rate of 15ppm or less when subjected to a heat treatment at 500 ℃ for 1 hour, and contains SiO in mol% as a glass composition₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％，

In this production method, a glass substrate is molded and then divided to obtain 2 or more glass substrates having a G6 size (1.5m × 1.8 m).

7. A method for manufacturing a glass substrate, characterized in that:

glass raw materials are melted and formed by drawing down to manufacture a glass substrate,

the glass substrate has a strain point of 690-750 ℃, and contains SiO in mol% as a glass composition of the glass substrate₂60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％，

In the manufacturing method, an average cooling rate in a temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) is set to 100-400 ℃/min in a cooling process during molding, so that a glass substrate with a heat shrinkage rate of 15ppm or less and a plate width of 3m or more when heat treatment is performed at 500 ℃ for 1 hour is obtained, and then the glass substrate is divided in a width direction, so that 2 or more glass substrates with a G6 size (1.5m × 1.8m) are obtained.

8. A glass substrate, characterized in that:

a strain point of 690 to 750 ℃, a thermal shrinkage rate of 15ppm or less when heat-treated at 500 ℃ for 1 hour, and a glass composition containing SiO in mol%₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％。

Technical Field

The invention relates to a method for manufacturing a glass substrate, in particular to a method for manufacturing a glass substrate suitable for an organic EL (OLED) display screen and a liquid crystal display screen, and also relates to a method for manufacturing a glass substrate suitable for an oxide TFT and a low-temperature p-Si/TFT (LTPS) driven display screen.

Background

Currently, glass substrates are widely used as substrates for flat panel displays such as liquid crystal displays, hard disks, filters, sensors, and the like. In recent years, in addition to conventional liquid crystal display panels, OLED display panels have been actively developed for the reasons of self-luminescence, high color reproducibility, high viewing angle, high-speed response, high image quality, and the like, and some of them have been put into practical use.

In addition, since liquid crystal displays and OLED displays of mobile devices such as smartphones are required to have a small area and display a large amount of information, super high quality images are required. High speed response is also required in order to display animation.

In such applications, OLED displays or liquid crystal displays driven by LTPS are suitable. The OLED display panel emits light by causing current to flow in OLED elements constituting pixels. Therefore, a low-resistance, high-electron-mobility material can be used as the driving TFT element. As such a material, an oxide TFT represented by IGZO (indium, gallium, zinc oxide) has attracted attention in addition to the LTPS described above. Oxide TFTs are low resistance, high mobility, and can be formed at relatively low temperatures. In addition, oxide TFTs have been attracting attention as a powerful TFT forming material because they have excellent uniformity of TFT characteristics when elements are formed on a large-area glass substrate, and have been partially put into practical use.

A glass substrate used for a high-quality display panel is required to have various characteristics. The following characteristics (1) and (2) are particularly required.

(1) When the alkali content in the glass is large, alkali ions diffuse into the semiconductor material to be formed during the heat treatment, and the film characteristics deteriorate. Therefore, the content of the alkali component (particularly, Li component and Na component) is small or substantially not contained.

(2) In the steps of film formation, dehydrogenation, crystallization of a semiconductor layer, annealing, and the like, a glass substrate is heat-treated at several hundred degrees centigrade. As a problem occurring at the time of heat treatment, image shift due to thermal shrinkage of the glass substrate or the like can be cited. The higher the image quality of the display panel, the higher the heat treatment temperature, but the allowable range of image shift becomes smaller. Therefore, the glass substrate is required to have a small dimensional change during heat treatment. The main factors of dimensional change during heat treatment are mainly thermal shrinkage, film stress after film formation, and the like. Therefore, in order to reduce the dimensional change during heat treatment, a high strain point is required.

From the viewpoint of producing a glass substrate, the following characteristics (3) to (5) are also required for the glass substrate.

(3) The molding temperature is low for the purpose of extending the life of the molding equipment.

(4) The composition has excellent meltability to prevent melting defects such as bubbles, lumps, and striae.

(5) The devitrification resistance is excellent in order to avoid mixing of devitrification crystals into the glass substrate.

Disclosure of Invention

Technical problem to be solved by the invention

As one of the studies for reducing the heat shrinkage rate, as described above, it is possible to set the strain point high. However, if the strain point is too high, the melting temperature and the molding temperature become high, and therefore, the life of the melting equipment and the molding equipment becomes short.

The present invention has been made in view of the above circumstances, and a technical problem to be solved by the present invention is to: provided is a method for manufacturing a glass substrate, wherein dimensional changes during heat treatment can be reduced while avoiding shortening of the life of equipment.

Technical solution for solving technical problem

As a result of intensive studies, the inventors of the present invention have found that the strain point of a glass substrate and the cooling rate at the time of molding are controlled to be within predetermined ranges, whereby the load on manufacturing equipment can be reduced and the thermal shrinkage rate can be reduced to a desired value, thereby providing a glass substrate having a high thermal shrinkage rateThe invention is disclosed. That is, the method for manufacturing a glass substrate of the present invention is characterized in that: a glass substrate having a strain point of 690-750 ℃ is produced by melting and molding a glass raw material, and the average cooling rate in the temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) is set to 100-400 ℃/min in the cooling process at the time of molding, whereby a glass substrate having a heat shrinkage rate of 15ppm or less at the time of heat treatment at 500 ℃ for 1 hour is obtained. Here, "strain point" and "annealing point" refer to values measured by the method according to ASTM C336. "Heat shrinkage at 500 ℃ for 1 hour of heat treatment" was measured by the following method. First, as shown in FIG. 1(a), a long sample G of 160 mm. times.30 mm was prepared as a measurement sample. A mark M was formed at a position 20 to 40mm from the end edge of the long sample G using #1000 water-resistant polishing paper at each of the longitudinal ends thereof. Then, as shown in fig. 1(b), the long sample G on which the mark M is formed is divided into 2 pieces in a direction perpendicular to the mark M, and sample pieces Ga and Gb are prepared. Then, only one sample Gb was heated from room temperature to 500 ℃ at 5 ℃/min, and held at 500 ℃ for 1 hour, and then subjected to heat treatment to be cooled at 5 ℃/min. After the heat treatment, as shown in fig. 1(c), the dislocation amounts (Δ L) of the marks M of the 2 sample pieces Ga and Gb are read by a laser microscope in a state where the sample piece Ga which has not been heat-treated and the sample piece Gb which has been heat-treated are arranged in parallel with each other₁、△L₂) The thermal shrinkage was calculated by the following equation. Here, l0mm in the following formula is the distance between the initial markers M. The "average cooling rate" is a rate obtained by calculating a time for passing through the central portion of the glass in the sheet width direction for a region (annealing point +150 ℃) within a temperature range from (annealing point +150 ℃) to (annealing point-200 ℃), and dividing a temperature difference (350 ℃) in the annealing region by a time required for the passage.

Thermal shrinkage (ppm) [ { Δ L [ ]₁(μm)+ΔL₂(μm)}×10³]/l0(mm)

The method for producing a glass substrate of the present invention is preferably a method for forming a glass substrate by overflow downdraw.

In the method for producing a glass substrate of the present invention, a glass substrate having a plate width of 3m or more is preferably obtained.

The method for producing a glass substrate of the present invention preferably yields a glass substrate having: the glass composition of the glass substrate contains SiO in mol%₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％。

In the method for producing a glass substrate of the present invention, it is preferable that the glass substrate is molded and then divided to obtain 2 or more glass substrates having a G6 size (1.5m × 1.8 m).

The method for manufacturing a glass substrate of the present invention is characterized in that: melting and molding a glass raw material to produce a glass substrate comprising: the glass substrate has a strain point of 690-750 ℃, a thermal shrinkage rate of 15ppm or less when subjected to a heat treatment at 500 ℃ for 1 hour, and contains SiO in mol% as a glass composition₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂0 to 1 percent; in this production method, a glass substrate is molded and then divided to obtain 2 or more glass substrates having a G6 size (1.5m × 1.8 m).

The method for manufacturing a glass substrate of the present invention is characterized in that: melting and down-drawing a glass material to produce a glass substrate having a strain point of 690 to 750 ℃ and containing SiO in mol% as a glass composition of the glass substrate₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂0 to 1%, and the manufacturing method comprises setting an average cooling rate in a temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) to 100 to 400 ℃/min in a cooling process during molding to obtain a glass substrate having a heat shrinkage rate of 15ppm or less and a sheet width of 3m or more when subjected to a heat treatment at 500 ℃ for 1 hour, and then dividing the glass substrate in the width direction to obtain 2 or more glass substrates having a G6 size (1.5m × 1.8 m).

The glass substrate of the present invention is characterized in that: a strain point of 690 to 750 ℃, a thermal shrinkage rate of 15ppm or less when heat-treated at 500 ℃ for 1 hour, and a glass composition containing SiO in mol%₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O 0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO 0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂ 0～1％。

Effects of the invention

The present invention can provide a method for manufacturing a glass substrate, which can reduce dimensional changes during heat treatment while avoiding shortening of the life of equipment.

Drawings

Fig. 1 is an explanatory view for explaining a method of measuring the heat shrinkage rate.

Detailed Description

The thermal shrinkage of a glass substrate is mainly influenced by the strain point of the glass substrate and the cooling rate during molding. Therefore, in the present invention, by adjusting the strain point of the glass substrate to 690 to 750 ℃ and the average cooling rate in the temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) in the cooling process at the time of molding to 100 to 400 ℃/min, a glass substrate having a heat shrinkage rate of 15ppm or less at the time of heat treatment at 500 ℃ for 1 hour can be obtained.

First, the characteristics and composition of the glass substrate will be described.

The heat shrinkage ratio when heat treatment is performed at 500 ℃ for 1 hour is preferably 15ppm or less, 14.5ppm or less, 14ppm or less, 13.5ppm or less, 13ppm or less, 12.5ppm or less, and particularly 12ppm or less. Thus, even if the LTPS is subjected to heat treatment in the manufacturing process, defects such as image shift are less likely to occur. In addition, when the thermal shrinkage is too low, the production efficiency of the glass substrate tends to be low. Therefore, the thermal shrinkage is preferably 1ppm or more, 2ppm or more, 3ppm or more, 4ppm or more, particularly 5ppm or more.

The higher the strain point, the lower the thermal shrinkage rate. The strain point is preferably 690 ℃ or higher, 695 ℃ or higher, 700 ℃ or higher, 702 ℃ or higher, 704 ℃ or higher, 705 ℃ or higher, 706 ℃ or higher, 707 ℃ or higher, 708 ℃ or higher, 709 ℃ or higher, and particularly 710 ℃ or higher. On the other hand, when the strain point is too high, the melting temperature or the molding temperature is increased, so that the production efficiency of the glass substrate tends to be lowered, and the load on the molding equipment tends to be increased. Therefore, the strain point is preferably 750 ℃ or lower, 748 ℃ or lower, 746 ℃ or lower, 744 ℃ or lower, 742 ℃ or lower, 740 ℃ or lower, 738 ℃ or lower, 736 ℃ or lower, 735 ℃ or lower, 734 ℃ or lower, 733 ℃ or lower, 732 ℃ or lower, 731 ℃ or lower, and particularly 730 ℃ or lower. The most preferable range of the strain point is 710 to 730 ℃.

10^4.5The lower the temperature at dPa · s, the lower the load applied to the molding equipment can be. 10^4.5The temperature at dPa · s is preferably 1300 ℃ or lower, 1295 ℃ or lower, 1290 ℃ or lower, 1285 ℃ or lower, 1280 ℃ or lower, 1275 ℃ or lower, particularly 1270 ℃ or lower. On the other hand, 10^4.5If the temperature at dPa · s is too low, the strain point cannot be set high. Thus, 10^4.5The temperature at dPa · s is preferably 1150 ℃ or more, 1170 ℃ or more, 1180 ℃ or more, 1185 ℃ or more, 1190 ℃ or more, 1195 ℃ or more, 1200 ℃ or more, 1205 ℃ or more, 1210 ℃ or more, 1215 ℃ or more, particularly 1220 ℃ or more.

In addition to the above characteristics, the glass substrate preferably has the following characteristics.

Resistance to devitrification is important when the sheet is formed by an overflow down-draw method or the like. In the glass composition, it is considered to containSiO₂、Al₂O₃、B₂O₃And alkaline earth metal oxide (RO), the liquidus temperature is preferably 1300 ℃ or lower, 1280 ℃ or lower, 1270 ℃ or lower, 1250 ℃ or lower, 1240 ℃ or lower, 1230 ℃ or lower, 1220 ℃ or lower, 1210 ℃ or lower, particularly 1200 ℃ or lower. Further, the liquid phase viscosity is preferably 10^4.810 dPas or more^4.910 dPas or more^5.010 dPas or more^5.110 dPas or more^5.2dPas or more, particularly 10^5.3dPas or more. The "liquidus temperature" is a temperature at which devitrification crystals (foreign crystals) are observed in glass by placing glass powder which has passed through a standard sieve of 30 mesh (500 μm) and remained in 50 mesh (300 μm) in a platinum boat, holding the boat in a temperature gradient furnace set at 1100 to 1350 ℃ for 24 hours, and then taking out the platinum boat. The "liquidus viscosity" is a value obtained by measuring the viscosity of a glass at a liquidus temperature by the platinum ball pulling method.

The higher the Young's modulus, the more difficult the glass substrate is to deform. The Young's modulus is preferably 78GPa or more, 78.5GPa or more, 79GPa or more, 79.5GPa or more, 80GPa or more, 80.5GPa or more, 81GPa or more, 81.5GPa or more, 82GPa or more, 82.5GPa or more, particularly 83GPa or more. On the other hand, a composition having a high young's modulus tends to have poor chemical resistance. Therefore, the Young's modulus is preferably 120GPa or less, 110GPa or less, 100GPa or less, 95GPa or less, 90GPa or less, particularly 88GPa or less. Here, the "young's modulus" refers to a value measured by a dynamic elastic modulus measurement method (resonance method) according to JIS R1602.

The preferred upper limit range of the thermal expansion coefficient is 45X 10^－742X 10 ℃ C. or lower^－741X 10 ℃ C below^－7Lower than/° C, in particular 40X 10^－7Lower limit of 35X 10 when measured at temperatures of 35 ℃ or lower^－736X 10 ℃ C. or higher^－7Over/° C, in particular 37X 10^－7Above/° c. When the thermal expansion coefficient is out of the above range, the thermal expansion coefficient of the film is not matched with that of various films (e.g., a-Si and p-Si), and defects such as film peeling and dimensional change during heat treatment are likely to occur. Wherein "The "coefficient of thermal expansion" is an average coefficient of thermal expansion measured at a temperature of 30 to 380 ℃, and can be measured, for example, by an dilatometer.

The etching depth when immersed in a 10 mass% HF aqueous solution at room temperature for 30 minutes is preferably 20 μm or more, 22 μm or more, 25 μm or more, 27 μm or more, 28 μm or more, 29 to 50 μm, and particularly 30 to 40 μm. When the etching depth is too small, the glass substrate is not easily thinned in the thinning step. The etching depth is an index of the etching rate. That is, when the etching depth is large, the etching speed becomes fast; when the etching depth is small, the etching rate becomes slow.

The beta-OH value is preferably 0.50/mm or less, 0.45/mm or less, 0.40/mm or less, 0.35/mm or less, 0.30/mm or less, 0.25/mm or less, 0.20/mm or less, 0.15/mm or less, particularly 0.10/mm or less. When the beta-OH value is reduced, the strain point can be increased. Examples of the method for reducing the β -OH value include the following methods. (1) The raw material with low water content is selected. (2) Adding components (Cl, SO) for reducing water content in the glass₃Etc.). (3) The moisture content in the furnace atmosphere is reduced. (4) N in molten glass₂Bubbling. (5) A small melting furnace is used. (6) The flow rate of the molten glass is increased. (7) An electric melting method is adopted. The "β -OH value" is a value obtained by measuring the transmittance of the glass by FT-IR and using the following formula.

beta-OH value ═ (1/X) log (T)₁/T₂)

X: the thickness (mm) of the glass plate;

T₁: control wavelength 3846cm^－1Transmittance (%) of time;

T₂: hydroxyl absorption wavelength of 3600cm^－1Near minimum transmittance (%).

The glass substrate of the present invention preferably contains SiO in mol% as the glass composition of the glass substrate₂ 60～75％、Al₂O₃ 10～15％、B₂O₃ 0～5％、Li₂O 0～0.1％、Na₂O0～0.1％、K₂O 0～1％、MgO 0～8％、CaO 0～10％、SrO 0～10％、BaO0～10％、ZnO 0～10％、P₂O₅ 0～10％、SnO₂0 to 1 percent. The reasons for limiting the content ranges of the respective components as described above are shown below. In the description of the content range of each component, the expression "% means mol%.

SiO₂If the content of (b) is too small, the chemical resistance, particularly the acid resistance, tends to be low, and the strain point tends to be low. On the other hand, SiO₂When the content of (A) is too large, the etching rate of hydrofluoric acid or a mixed solution of hydrofluoric acid tends to be low, the high-temperature viscosity tends to be high, the meltability tends to be low, and SiO₂Crystals, particularly cristobalite, precipitate, and the viscosity of the liquid phase tends to decrease. Thus, SiO₂The preferred upper limit content is 75%, 74%, 73%, 72%, 71%, 70%, in particular 69%, and the preferred lower limit content is 60%, 61%, 62%, 62.5%, 63%, 63.5%, 64%, 64.5%, 65%, 65.5%, 66%, 66.5%, in particular 67%. The most preferable content range is 67 to 69%.

Al₂O₃When the content of (b) is too small, the strain point is lowered, the heat shrinkage amount is increased, the Young's modulus is lowered, and the glass substrate is easily bent. On the other hand, Al₂O₃When the content of (b) is too large, the BHF (buffered hydrofluoric acid) resistance is lowered, the glass surface is likely to be clouded, and the crack resistance is likely to be lowered. In addition, SiO precipitates in the glass₂－Al₂O₃The liquid phase viscosity of crystalline mullite, in particular, mullite is liable to decrease. Al (Al)₂O₃The preferred upper limit content is 15%, 14.5%, 14%, 13.5%, particularly 13%, and the preferred lower limit content is 10%, 10.5%, 11%, 11.5%, particularly 12%. The most preferable content range is 12 to 13%.

B₂O₃The flux is a component that acts to reduce viscosity and improve meltability. Or a component that improves the BHF resistance, crack resistance, and lowers the liquidus temperature. On the other hand, B₂O₃When the content of (b) is too large, the strain point, heat resistance and acid resistance are liable to be lowered, and particularly the strain point is liable to be lowered. Glass also tends to phase separate. B is₂O₃The preferred upper limit content is 5%, 4.5%, particularly 4%, and the preferred lower limit content is 0%, 1%, 1.5%, 2%, 2.5%, 3%, particularly more than 3%. The most preferable content range is more than 3% and 4% or less.

Li₂O、Na₂O deteriorates characteristics of various films and semiconductor elements formed on a glass substrate, and therefore, it is preferable to reduce the content to 0.1% (preferably 0.06%, 0.05%, 0.02%, and particularly 0.01%) respectively. K₂O and Li₂O、Na₂The deterioration of the characteristics of various films and semiconductor elements formed on the glass substrate is slight compared to O. In addition, the small amount of the additive has the effects of improving solubility and eliminating static electricity. Thus, K₂O is preferably reduced to 1% (desirably 0.5%, 0.4%, particularly 0.3%).

MgO is a component that reduces the high-temperature viscosity without lowering the strain point and improves the meltability. MgO has the most effect of reducing the density of RO (R is at least one selected from the group consisting of Mg, Ca, Sr, Ba and Zn), but when it is introduced excessively, SiO₂Crystals, particularly cristobalite, precipitate, and the liquid phase viscosity tends to decrease. Further, MgO is also a component which easily reacts with BHF to form a product. The reaction product is fixed to the element on the surface of the glass substrate or adheres to the glass substrate, and may contaminate the element and the glass substrate. Further, Fe₂O₃And the like, and the transmittance of the glass substrate may be lowered by mixing the impurities into the glass from the MgO-introduced raw material such as dolomite. Therefore, the preferable upper limit content of MgO is 8%, 7.5%, 7%, 6.5%, and particularly 6%, and the preferable lower limit content is 0%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, and particularly 4.5%. The most preferable content range is 4.5 to 6%.

CaO is a component that lowers the high-temperature viscosity without lowering the strain point and remarkably improves the meltability, similarly to MgO. However, when the content of CaO is too large, SiO₂－Al₂O₃RO crystals, particularly anorthite, are easily precipitated, the viscosity of the liquid phase is easily lowered, the BHF resistance is lowered, and the reaction product is fixed to the element on the glass surface or attached to the glass substrate, and the element and the glass may be caused to adhere to each otherThe substrate is clouded. Accordingly, the preferable upper limit content of CaO is 10%, 9.5%, 9%, 8.5%, 8%, 7.5%, particularly 7%, and the preferable lower limit content is 0%, 1%, 2%, 3%, 3.5%, 4%, 4.5%, particularly 5%. The most preferable content range is 5 to 7%.

SrO is a component for improving chemical resistance and resistance to devitrification, but if the ratio of SrO is too high in all ROs, the meltability tends to decrease, and the density and thermal expansion coefficient tend to increase. Therefore, the content of SrO is preferably 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, particularly 0 to 5%.

BaO is a component for improving chemical resistance and devitrification resistance, but when the content thereof is too large, the density tends to increase. In addition, SiO₂－Al₂O₃－B₂O₃RO glass is generally not easily melted, and from the viewpoint of supplying a high-quality glass substrate at low cost and in large quantities, it is important to improve the meltability and reduce the fraction defective due to bubbles, foreign matter, and the like. However, BaO has a poor effect of improving meltability in RO. Accordingly, the preferred upper limit content of BaO is 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, particularly 3.5%, and the preferred lower limit content is 0%, 0.1%, 0.2%, 0.3%, 0.4%, particularly 0.5%.

ZnO is a component for improving meltability and BHF resistance, but when the content is too large, glass is likely to devitrify, the strain point is lowered, and heat resistance is not easily secured. Therefore, the content of ZnO is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to 2%, particularly 0 to 1%.

P₂O₅Is to reduce SiO₂－Al₂O₃CaO-based crystal (in particular, anorthite) and SiO₂－Al₂O₃Is the liquidus temperature component of the crystal (particularly mullite). However, introduction of a large amount of P₂O₅When the phase is separated, the phase of the glass is easily separated. Thus, P₂O₅The content of (B) is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.1%.

SnO₂With fining agent as a means of reducing bubbles in the glassThe function of (c). On the other hand, SnO₂When the content of (A) is too large, SnO is liable to be generated in the glass₂Devitrification crystallization of (1). SnO₂The upper limit content is preferably 1%, 0.5%, 0.4%, particularly 0.3%, and the lower limit content is preferably 0%, 0.01%, 0.03%, particularly 0.05%. The most preferable range is 0.05 to 0.3%.

In addition to the above components, other components may be introduced. The amount of incorporation is preferably 5% or less, 3% or less, particularly 1% or less, in total.

ZrO₂Is a component for improving chemical durability, ZrSiO is easily generated when the amount of the introduced component is increased₄The crystallization of (4). ZrO (ZrO)₂The preferable upper limit content of (b) is 1%, 0.5%, 0.3%, 0.2%, particularly 0.1%, and from the viewpoint of chemical durability, it is preferable to introduce 0.001% or more. The most preferable range of the content is 0.001% to 0.1%. In addition, ZrO₂The raw material may be introduced, or the raw material may be introduced by elution from a refractory.

TiO₂A component that reduces high-temperature viscosity and improves meltability, or a component that improves chemical durability, but when introduced excessively, the ultraviolet transmittance is liable to decrease. TiO 2₂The content of (b) is preferably 3% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, 0.03% or less, particularly 0.01% or less. In which a very small amount of TiO is introduced₂(e.g., 0.0001% or more), the effect of suppressing coloring by ultraviolet rays can be obtained. The most preferable range is 0.0001 to 0.01%.

As₂O₃、Sb₂O₃Is a component that functions as a clarifying agent, but is also an environmentally-friendly chemical substance, and is desirably not used as much as possible. As₂O₃、Sb₂O₃The content of (b) is preferably less than 0.3%, less than 0.1%, less than 0.09%, less than 0.05%, less than 0.03%, less than 0.01%, less than 0.005%, in particular less than 0.003%, respectively.

Iron is a component mixed from the raw material as an impurity, and when the content of iron is too large, the ultraviolet transmittance may decrease. When the ultraviolet transmittance is lowered, in the production of TFTThere is a possibility that defects may occur in the photolithography process, the alignment process of liquid crystals using ultraviolet rays, and the laser lift-off process in the plastic OLED manufacturing process. Therefore, the preferable lower limit content of iron is converted to Fe₂O₃0.0001%, 0.0005%, 0.001%, particularly 0.0015%, and the preferable upper limit content is in terms of Fe₂O₃0.01%, 0.009%, 0.008%, 0.007%, especially 0.006%. The most preferable range of the content is 0.0015% to 0.006%.

Cr₂O₃Cr as an impurity is a component mixed from the raw material₂O₃If the content of (d) is too large, light is not easily transmitted when light enters from the end face of the glass substrate and the foreign object inspection is performed in the glass substrate by scattered light, and thus a problem may occur in the foreign object inspection. In particular, when the substrate size is 730mm × 920mm or more, such a problem is likely to occur. In addition, when the glass substrate has a small thickness (for example, 0.5mm or less, 0.4mm or less, particularly 0.3mm or less), the light incident from the end face of the glass substrate is reduced, and therefore Cr is restricted₂O₃The significance of the content (c) becomes large. Cr (chromium) component₂O₃The upper limit content is preferably 0.001%, 0.0008%, 0.0006%, 0.0005%, particularly 0.0003%, and the lower limit content is preferably 0.00001%. The most preferable range is 0.00001 to 0.0003%.

SO₃SO as an impurity is a component mixed in from the raw material₃When the content of (b) is too large, bubbles called reboiling may be generated during melting or molding, and defects may be generated in the glass. SO (SO)₃The upper limit content is preferably 0.005%, 0.003%, 0.002%, particularly 0.001%, and the lower limit content is preferably 0.0001%. The most preferable range is 0.0001% to 0.001%.

Next, a method for manufacturing a glass substrate will be described.

The glass raw material adjusted to obtain the glass substrate having the above composition and characteristics is supplied to a glass melting apparatus and melted at a temperature of about 1500 to 1650 ℃. Melting as used herein includes various steps such as clarification and stirring. In the melting step, the glass raw material is preferably electrically melted. The "electric melting" is a melting method in which electricity is applied to glass and the glass is heated and melted by joule heat generated thereby.

Next, the molten glass is supplied to a forming apparatus and formed into a plate shape by a down-draw method. As the down-drawing method, an overflow down-drawing method is preferably employed. The overflow down-draw method is a method of forming glass into a plate by overflowing molten glass from both sides of a channel-shaped refractory having a wedge-shaped cross section, and drawing the molten glass downward while merging the overflowed molten glass at the lower end of the channel-shaped refractory. In the overflow down-draw method, the surface to be the surface of the glass substrate is molded in a free surface state without being in contact with the groove-like refractory. Therefore, a glass substrate having a good surface quality can be produced at low cost without polishing, and the glass can be easily made larger and thinner. The structure and material of the groove-shaped refractory used in the overflow down-draw method are not particularly limited as long as the desired dimensional and surface accuracy can be achieved. Further, the method of applying the force is not particularly limited when the downward stretching is performed. For example, a method of rotating a heat-resistant roller having a sufficiently large width in contact with glass to perform drawing may be employed, or a method of rotating a plurality of heat-resistant rollers in pairs in contact with only the vicinity of the end faces of glass to perform drawing may be employed. In addition to the overflow down-draw method, for example, a slit down-draw method or the like may be used.

The sheet width of the plate-shaped glass is not particularly limited, and is preferably 2m or more, 2.2m or more, 2.4m or more, 2.6m or more, 2.8m or more, and particularly 3m or more, in order to obtain a plurality of glass substrates in the width direction (i.e., the direction orthogonal to the sheet drawing direction) in the dividing step described later. On the other hand, if the sheet width of the sheet glass is too large, the molding apparatus becomes too large, and the life of the molding apparatus tends to be short. Therefore, the plate width of the plate-like glass is preferably 4m or less, 3.5m or less, particularly 3.2m or less.

Subsequently, the plate-like glass is supplied to an annealing furnace and cooled. The cooling rate is directly related to the thermal shrinkage rate of the glass substrate obtained, and therefore strict control is required. Specifically, in order to reduce the thermal shrinkage rate of the glass substrate, the average cooling rate in the temperature range from (annealing point +150 ℃) to (annealing point-200 ℃) is preferably 400 ℃/min or less, 390 ℃/min or less, 380 ℃/min or less, 370 ℃/min or less, 360 ℃/min or less, and 350 ℃/min or less. On the other hand, if the average cooling rate is too low, the production efficiency tends to decrease. Therefore, the average cooling rate in the temperature range from (annealing point +150 ℃ C.) to (annealing point-200 ℃ C.) is preferably 100 ℃/min or more, 150 ℃/min or more, 200 ℃/min or more, particularly 250 ℃/min or more. The cooling rate may be adjusted by adjusting the power supply of the heater in the glass conveying direction. Specifically, a plurality of heaters capable of being individually adjusted are provided in the glass conveying direction, and the output of each heater may be adjusted. In order to reduce the in-plane variation in the thermal shrinkage rate of the glass substrate, it is preferable to control the temperature so that the variation in the cooling rate in the width direction of the glass substrate is reduced. Specifically, a plurality of individually adjustable heaters may be provided in the plate width direction, and the output of each heater may be adjusted. From the viewpoint of reducing the heat shrinkage rate, the annealing furnace is preferably longer, and specifically, the length is preferably 2m or more, 3m or more, 4m or more, 5m or more, 6m or more, 7m or more, 8m or more, 9m or more, and particularly 10m or more. On the other hand, when the annealing furnace is lengthened, the glass melting apparatus or the forming furnace must be installed at a high position, and there is a possibility that the facility design is restricted. In addition, the glass hanging down from the molding apparatus becomes too heavy to hold. Specifically, the length of the annealing furnace is preferably 30m or less, 25m or less, 22m or less, 20m or less, 18m or less, 16m or less, and particularly 15m or less.

The plate-shaped glass thus formed was cut into a predetermined length to obtain a glass substrate (mother glass substrate). Then, the obtained glass substrate is divided in the width direction, whereby a plurality of glass substrates can be obtained. For example, a glass substrate (3m × 1.8m glass substrate) produced by cutting a plate-shaped glass having a plate width of 3m by a length of 1.8m can obtain 2G 6-sized (1.5m × 1.8m) glass substrates, and similarly, a glass substrate 2.6m × 1.1m can obtain 2G 5-sized (1.2m × 1.0m to 1.3m × 1.1m) glass substrates. Similarly, a glass substrate of 2.19m × 0.92m can provide 3 glass substrates of G4.5 size (0.73m × 0.92 m). By molding the glass substrate having a large sheet width and dividing the glass substrate into a plurality of glass substrates in this manner, the production efficiency can be improved. Therefore, even if the average cooling rate is lowered in order to reduce the thermal shrinkage rate of the glass substrate as described above, the production efficiency can be maintained. After the glass substrate is cut, various chemical processing, mechanical processing, and the like may be performed as necessary.

The thickness of the glass substrate is not particularly limited, but is preferably 0.5mm or less, 0.4mm or less, 0.35mm or less, and particularly 0.3mm or less in order to facilitate weight reduction of the device. On the other hand, when the thickness is too small, the glass substrate is easily bent. Therefore, the thickness of the glass substrate is preferably 0.001mm or more, particularly 0.005mm or more. The thickness of the sheet can be adjusted by the flow rate, the sheet drawing speed, and the like in the glass production.

Example 1

The present invention will be described in detail below based on examples. The following examples are only illustrative. The present invention is not limited to the following examples.

Table 1 shows examples of the present invention (samples A to C, F to H) and comparative example (sample D, E, I).

[ Table 1]

First, silica sand, alumina, anhydrous boric acid, calcium carbonate, strontium nitrate, barium nitrate, tin dioxide, strontium chloride, and barium chloride were mixed and then blended as shown in the composition of table 1.

Next, the glass raw material is supplied to an electric melting furnace not using a burner for combustion, and melted, and then the molten glass is clarified and homogenized in a clarifying tank and a regulating tank, and the viscosity is regulated to a viscosity suitable for molding.

Then, the molten glass was supplied to an overflow downdraw forming apparatus, formed into a plate shape, and then used as a watch1, and cutting the glass substrate to obtain a glass substrate having a thickness of 0.5mm, a width of 3m and a length of 1.8 m. Thereafter, the glass substrate was divided to obtain 2 glass substrates of G6 size (1.5 m. times.1.8 m) having a thickness of 0.5 mm. The molten glass flowing out of the melting furnace is supplied to the forming apparatus while being in contact with platinum or a platinum alloy. Each of the obtained samples was evaluated for β -OH value, density, thermal expansion coefficient, Young's modulus, strain point, annealing point, and 10^4.5Temperature at dPa · s, liquid phase viscosity, and heat shrinkage.

The β -OH value is a value calculated according to the above description.

The density is a value measured by a known archimedes method.

The thermal expansion coefficient is an average thermal expansion coefficient measured by an dilatometer in a temperature range of 30 to 380 ℃.

The young's modulus is a value measured by a dynamic elastic modulus measurement method (resonance method) based on JIS R1602.

The strain point and the annealing point are values measured by a method according to ASTM C336.

High temperature viscosity 10^4.5The temperature at dPa · s is a value measured by a platinum ball pulling method.

The liquidus viscosity is a value obtained by measuring the viscosity of glass at a liquidus temperature by the platinum ball pulling method.

The heat shrinkage is a value measured by the above-mentioned method.

The samples A to C, F to H had a strain point of 750 ℃ or lower and a cooling rate as low as 400 ℃ per minute or lower, and therefore had a thermal shrinkage of 15ppm or lower. Further, since the strain points of the samples A to C, F to H were 750 ℃ or lower, the load on the molding equipment was considered to be low. On the other hand, sample D, E, I had a strain point of 750 ℃ or lower, but the cooling rate was as high as 460 ℃ C/min or higher, and therefore the thermal shrinkage was as high as 16ppm or higher.

Example 2

Table 2 shows examples (samples 1 to 8) and comparative example (sample 9) of the present invention.

[ Table 2]

Samples 1 to 8 shown in Table 2 were prepared and evaluated in the same manner as in example 1.

The samples 1 to 8 had a strain point of 750 ℃ or less and a cooling rate as low as 400 ℃ per minute or less, and therefore had a thermal shrinkage of 14ppm or less. Further, samples 1 to 8 had a strain point of 750 ℃ or lower, and thus the load on the molding equipment was considered to be low. On the other hand, sample 9 has a strain point as low as less than 690 ℃ and therefore a thermal shrinkage as high as 20 ppm.