JP2013063870A - Method for producing silicate glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing silicate glass having excellent foam quality by using tin oxide.SOLUTION: When silicate glass is produced, tin oxide powder whose median particle size Dis in the range of 2-50 μm is used as a refining agent. As the silicate glass, alkali-free glass or lithium aluminosilicate-based crystallized glass can be named for example.

Description

  The present invention relates to a method for producing a silicate glass. In particular, it relates to a method for producing a silicate glass using tin oxide powder as a fining agent.

  Electronic devices such as thin-film transistor active matrix liquid crystal displays (TFT-AMLCD) are thin and have low power consumption, so they are used in various applications such as car navigation, digital camera viewfinders, personal computer monitors, and televisions. Yes.

In general, an aluminoborosilicate glass that does not substantially contain an alkali metal, so-called alkali-free glass, is used as a material for an LCD glass substrate, and various glass compositions have been proposed so far. (See Patent Documents 1 to 3)
By the way, in recent years, the screens of personal computer monitors, televisions, and the like have become larger, and the specifications of bubbles and foreign matters in glass substrates have become stricter than before.

  In order to industrially produce such a glass substrate, the prepared glass raw material is put into a glass melting furnace, and after melting and refining, the glass melt is supplied to a molding apparatus, an overflow downdraw method, A method of forming and cutting into a plate shape by a method such as a float method, a slot down draw method, or a roll out method is adopted.

  In particular, when producing a large alkali-free glass substrate inexpensively and in large quantities, an overflow down-draw method in which a glass melt is supplied and molded on a bowl-shaped refractory molded body, and molten tin A float method is often used in which a glass melt is supplied onto a bath and molded.

  Lithium aluminosilicate is also used as a glass material for oil stove and wood stove front windows, heat-resistant cooking containers, setters for firing electronic parts, shelf plates for microwave ovens, top plates for electromagnetic cookers, fire doors, color filter image sensor substrates, etc. Salt-based crystallized glass is used. (For example, refer to Patent Documents 4 to 6) Lithium aluminosilicate-based crystallized glass can have a white or transparent appearance by changing the crystallization conditions and changing the type and crystal grain size of the precipitated crystals.

  Also in this type of crystallized glass, the specifications of bubbles and foreign matters are becoming more strict than before, especially for electronic component applications.

  In order to industrially produce such a crystallized glass plate, the prepared glass raw material is put into a glass melting furnace, melted and refined, and then the glass melt is supplied to a molding apparatus, followed by slot down draw. A method of crystallization after forming into a plate shape and cutting by a method such as a method, an overflow downdraw method, a float method, or a rollout method is employed. Moreover, when manufacturing a crystallized glass product having a container shape, a method of crystallizing a gob, which is a molten glass lump supplied from a feeder, is adopted.

Japanese Patent No. 2990379 JP 2002-29775 A JP 2009-167090 A JP-A-11-228480 Japanese Patent Laid-Open No. 11-228181 JP 2006-1828 A JP 2006-306690 A

When manufacturing alkali-free glass or lithium aluminosilicate-based crystallized glass as described above, it is necessary to melt at a high temperature of 1500 to 1600 ° C. or higher, so that arsenic oxide (As ₂ O ₃ ) has been used. However, since arsenic oxide is highly toxic and harmful to the environment, its use is avoided. Instead, tin oxide (SnO ₂ ) has been widely used (for example, Patent Document 7). Tin oxide, like arsenic oxide, is in the high temperature range of 1500-1600 ° C.
2SnO ₂ → 2SnO + O ₂ ↑
To release oxygen gas (O ₂ ). When the released oxygen gas diffuses into the bubbles in the glass, the bubbles expand and promote to rise, and the bubbles are removed.

  However, when tin oxide is used, it may be impossible to obtain a glass having a sufficiently high foam quality.

  An object of the present invention is to provide a method for easily producing a silicate glass excellent in foam quality using tin oxide.

  As a result of verifying the above problems, the present inventor has obtained the following knowledge.

The tin oxide powder used for the glass fining agent is produced as follows. First, an ingot of Sn 99.5% or more metal tin ingot is dissolved and pulverized, and this is decomposed with nitric acid to produce metastannic acid. This is baked to produce SnO ₂ fumes having a particle diameter of 1 mm or less and sintered. Thereafter, the sintered product is crushed to obtain a tin oxide powder.

  However, it has been found that if there is a problem in the above sintering process, the particle size of the resulting tin oxide powder becomes inappropriate, which causes the clarity to deteriorate. The present invention has been made based on this finding.

That is, the method for producing a silicate glass according to the present invention is characterized in that tin oxide powder having a median particle diameter D50 in the range of 2 to ₅₀ μm is used as a fining agent in producing the silicate glass. Here, the "silicate glass", glass mainly containing SiO _2, and more specifically means a glass containing SiO ₂ more than 50 wt%. “Tin oxide” refers to stannic oxide (SnO ₂ ), but does not exclude stannous oxide (SnO). The median particle size D ₅₀ means a particle size measured by a laser diffraction particle size distribution meter.

In the present invention, after the median particle diameter D ₅₀ was adjusted particle size of the tin oxide powder to be in the range of 2 to 50 [mu] m, preferably used.

In the present invention, it is preferable to use the tin oxide powder after it is classified so that the median particle size D ₅₀ is in the range of 2 to ₅₀ μm.

According to the above configuration, it is possible to median particle diameter D ₅₀ obtained easily oxidized tin 2 to 50 [mu] m.

In the present invention, the silicate glass is preferably alkali-free glass or lithium aluminosilicate-based crystallized glass. Here, “non-alkali glass” means a glass that does not substantially contain an alkali metal component, and more specifically, the content of alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O). It refers to glass having a total amount of 1000 ppm or less (0.1 mass% or less). “Lithium aluminosilicate-based crystallized glass” contains Li ₂ O, SiO ₂ and Al ₂ O ₃ as essential components, and crystals (particularly β-spodumene and / or β-quartz solid solution) are contained in the glass. It refers to the precipitated glass.

  According to the said structure, this invention will be applied to the glass which needs high temperature melting, and can enjoy the effect of this invention exactly.

In the present invention, in mass percent on the oxide _{basis, SiO 2 50~80%, Al 2} O 3 5~25%, B 2 O 3 0.1~20%, 0~15% MgO, CaO 3~15 %, SrO 0-15%, BaO 0-15%, RO (RO represents the total amount of MgO, CaO, SrO and BaO) 0-25%, ZnO 0-10%, ZrO ₂ 0-10%, It is preferable to prepare, melt, and mold a glass raw material so as to be a silicate glass containing 0.01 to 1.5% of SnO ₂ and substantially not containing an alkali metal. Here, “substantially no alkali metal” means that the total content of alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O) is 5000 ppm or less (0.5 mass% or less). It means that there is.

  According to the above configuration, in addition to LCD, glass suitable for flat panel display devices such as organic electroluminescence display (OLED), plasma display panel (PDP), field emission display (FED), substrates of various electronic components, etc. It is possible to obtain.

In the present invention, in mass percent on the oxide _{basis, SiO 2 50~80%, Al 2} O 3 12~30%, Li 2 O 1~6%, 0~5% MgO, 0~10% ZnO, BaO _{0~8%, Na 2 O 0~5%} , K 2 O 0~10%, TiO 2 0~8%, ZrO 2 0~7%, P 2 O 5 0~10%, SnO 2 0.01~ It is preferable to crystallize the glass raw material so that the silicate glass containing 2% is prepared, melted and molded.

  According to the above configuration, it can be used for glass materials such as oil stove and wood stove front windows, heat-resistant cooking containers, electronic component baking setters, microwave oven shelf plates, top plates for electromagnetic cookers, fire doors, and color filter image sensor substrates. It is possible to obtain a suitable low expansion crystallized glass.

  According to the method of the present invention, tin oxide powder having an appropriate particle size can be used as a fining agent. Therefore, it is possible to effectively solve the problem that the particle size is too coarse and the batch reaction at the time of melting the glass is delayed, and as a result, sufficient clarification performance cannot be obtained. Therefore, it is suitable as a method for producing a glass substrate or the like used for a flat panel display device or an electronic component requiring high foam quality.

  Further, according to the method of the present invention, there is no problem that the particle size of tin oxide is too fine to be handled easily.

In the production method of the present invention, a glass having a high foam quality can be easily obtained by using a tin oxide powder used as a fining agent having a median particle diameter D50 in the range of 2 to ₅₀ μm.

  Hereinafter, the production method of the present invention will be described in detail.

  First, a batch is prepared by mixing glass raw materials to be a silica source, an alumina source, a boric acid source, an alkaline earth metal source, an alkali metal source, a fining agent source, etc. so as to have a target glass composition. Moreover, you may use glass cullet as a glass raw material as needed. Glass cullet is glass waste discharged in the process of manufacturing glass. Each raw material and glass composition will be described later.

  Next, the prepared batch is charged from the glass raw material charging port of the melting kiln and melted and vitrified. The batch is charged into the melting furnace continuously, but may be intermittent. Moreover, the melting temperature of the batch in a melting furnace is about 1500-1600 degreeC. In this way, the glass raw material is melted to obtain molten glass.

  Next, the molten glass is supplied to a molding apparatus, and the glass is molded and cut so as to have a predetermined thickness, surface quality, and shape. As a method for forming glass into a plate shape, a known overflow downdraw method, float method, or other plate glass forming method can be used. In order to produce a large glass substrate in large quantities, an overflow down draw method or a float method may be employed. When it is desired to omit the polishing step, an overflow down draw method may be employed. Moreover, what is necessary is just to use a well-known press method etc. when shape | molding glass into a container shape.

  Furthermore, if necessary, it can be crystallized by heat treatment, or post-processing such as surface polishing, end face processing, and painting can be performed.

  The glass article thus produced is used for various applications.

  Then, the glass raw material used in this invention is demonstrated.

Silica sand (SiO ₂ ) can be used as the silica source.

As the alumina source, alumina (Al ₂ O ₃ ), aluminum hydroxide (Al (OH) ₃ ), or the like can be used.

As the boric acid source, boric acid (H ₃ BO ₃ ) and boric anhydride (B ₂ O ₃ ) can be used.

Alkaline earth metal sources include calcium carbonate (CaCO ₃ ), magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂ ), barium carbonate (BaCO ₃ ), barium nitrate (Ba (NO ₃ ) ₂ ), Strontium carbonate (SrCO ₃ ), strontium nitrate (Sr (NO ₃ ) ₂ ) and the like are used.

Examples of the alkali metal source include lithium carbonate (Li ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), spodomen (LiAlSi ₂ O _6). ) Etc. can be used.

As the fining agent source, a tin oxide (SnO ₂ ) powder having a median particle size D ₅₀ in the range of ₂ to ₅₀ μm is used. The tin oxide powder may be adjusted so that the median particle diameter D50 is in the range of 2 to ₅₀ μm by a method such as classification before preparing the glass raw material. When the median particle diameter D ₅₀ of the tin oxide powder is smaller than 2 μm, aggregation between the particles occurs, and clogging in the preparation plant is likely to occur. If the median particle diameter D ₅₀ of the tin oxide powder is larger than ₅₀ μm, the dissolution reaction of the tin oxide powder into the glass melt is delayed, and the clarification of the melt does not proceed. As a result, oxygen gas cannot be sufficiently released at an appropriate time of glass melting, bubbles are likely to remain in the glass product, and it becomes difficult to obtain a product excellent in foam quality. Also in the glass product, easily causing a so undissolved lumps of SnO ₂ crystal appears. Preferred ranges of median particle diameter _{D 50} of the tin oxide powder is 5～45Myuemu.

Further, in order to complement the fining power, a chloride such as barium chloride (BaCl ₂ ) or other fining agents may be used in combination. For environmental reasons, the use of arsenic oxide (As ₂ O ₃ , As ₂ O ₅ ) or antimony oxide (Sb ₂ O ₃ , Sb ₂ O ₅ ) should be avoided.

In addition to the above, various glass raw materials can be used depending on the glass composition. For example, zinc oxide (ZnO) or the like as a zinc source, zircon (ZrSiO ₄ ) or the like as a zirconia source, titanium oxide (TiO ₂ ) or the like as a titanium source, and sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ) as a phosphoric acid source , Aluminum metaphosphate (Al (PO ₃ ) ₃ ), magnesium phosphate (MgP ₂ O ₇ ) and the like can be used.

  Next, the target glass composition is illustrated.

For example, when used as a glass substrate for LCD, it is required to be excellent in electrical characteristics, heat resistance, durability and the like. As suitable glass satisfying such requirements, SiO ₂ 50 to 80%, Al ₂ O ₃ 5 to 25%, B ₂ O ₃ 0.1 to 20%, MgO 0 to 15 in terms of mass% based on oxide. %, CaO 3-15%, SrO 0-15%, BaO 0-15%, RO (RO represents the total amount of MgO, CaO, SrO and BaO) 0-25%, ZnO 0-10%, ZrO An alkali-free glass containing _{20 to} 10%, SnO ₂ 0.01 to 1.5% and substantially not containing an alkali metal can be exemplified. The glass having the above composition can be suitably used as a substrate for flat panel display devices such as OLED, PDP, and FED, various electronic components, or a cover glass thereof, in addition to the LCD substrate.

  The reason why the composition range of the alkali-free glass is limited as described above will be described below. In the following description, “%” means “mass%” unless otherwise specified.

If the content of SiO ₂ is too small, the strain point of the glass is lowered, and the glass substrate is cracked or heat deformation or heat shrinkage easily occurs in the heat treatment process when manufacturing the display device. In addition, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the thermal expansion coefficient of the surrounding materials, and the thermal shock resistance is likely to decrease. Furthermore, acid resistance also deteriorates. On the other hand, if the content of SiO ₂ is too much, the high temperature viscosity of the glass becomes high, it becomes difficult to melt and mold the glass. In addition, the thermal expansion coefficient becomes too small, making it difficult to match the thermal expansion coefficient of the surrounding material. A suitable range for the SiO ₂ content is 52-70%.

When the content of Al ₂ O ₃ is too large, the strain point of the glass is lowered, the heat treatment step in manufacturing the display, or cracked glass substrate, thermal deformation or thermal shrinkage may become likely to occur. On the other hand, when the content of Al ₂ O ₃ is too small, or decreased resistance to buffered hydrofluoric acid for glass, the liquidus temperature of the glass and becomes difficult to mold the glass substrate increases. A suitable range for the Al ₂ O ₃ content is 7-22%.

B ₂ O ₃ is a component that lowers the viscosity of the glass and increases the melting property of the glass. Cracks and heat deformation and shrinkage are likely to occur. On the other hand, when the content of B ₂ O ₃ is too small, it becomes difficult to obtain an effect as a flux. A preferred range of the content of B ₂ O ₃ is 3-20%.

  MgO is a component that improves the meltability of the glass by lowering the high temperature viscosity without lowering the strain point of the glass. When there is too much content of MgO, it exists in the tendency for the devitrification bumps of cristobalite and enstatite to occur easily. Further, the resistance to buffered hydrofluoric acid is lowered, the glass substrate is eroded in the photoetching process, the reaction product adheres to the surface of the glass substrate, and the glass substrate tends to become cloudy. The suitable range of MgO content is 0 to 10%.

  CaO improves the meltability of the glass by reducing only the high temperature viscosity without reducing the strain point of the glass. When there is too much content of CaO, while resistance to buffered hydrofluoric acid will fall, the density and thermal expansion coefficient of glass will rise. When there is too little content of CaO, high temperature viscosity will rise and meltability will deteriorate easily. A preferred range for the CaO content is 3-12%.

  SrO is a component that improves the chemical resistance and devitrification resistance of glass. When there is too much content of SrO, the density and thermal expansion coefficient of glass will rise. The suitable range of SrO content is 0 to 12%.

  BaO is a component that improves the chemical resistance and devitrification resistance of glass. When there is too much content of BaO, the density and thermal expansion coefficient of glass will rise. A suitable range for the BaO content is 0-12%.

  Alkaline earth metal oxides (MgO, CaO, SrO and BaO) can improve the meltability and devitrification resistance of glass when mixed and contained. If the amount is too large, the density of the glass tends to increase, making it difficult to reduce the weight of the glass substrate. On the other hand, if the total amount RO of these components is too small, the meltability deteriorates and the devitrification property tends to deteriorate. The preferred range of RO is 3-22%.

  ZnO is a component that improves the buffered hydrofluoric acid resistance of glass and improves the meltability of glass. When there is too much content of ZnO, it will become easy to devitrify glass, or a strain point will fall. The suitable range of ZnO content is 0 to 5%.

ZrO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance, and improves the Young's modulus. When the content of ZrO ₂ is too large, the liquidus temperature of the glass rises, devitrification stones of zircon is readily released. A suitable range of the ZrO ₂ content is 0 to 2%.

SnO ₂ is a component that acts as a fining agent. When the content of SnO ₂ is too large it tends to occur devitrification. To exhibit sufficient clarifying effect when the content of SnO ₂ is too small becomes difficult. The preferred range for SnO ₂ is 0.01-1%.

As ₂ O ₃ and Sb ₂ O ₃ are preferably substantially not contained for environmental reasons. Here, "substantially free of _As 2 _{O 3} and _Sb 2 _{O 3"} refers to the content of _As 2 _{O 3} and _Sb 2 _{O 3} in the glass composition, respectively 0.1% (1000 ppm) or less It means that.

Fe ₂ O ₃ is a component that affects the transmittance of glass. Fe ₂ O ₃ is a component mixed as an impurity during the process or from the raw material, but the content is preferably adjusted to be 0.001 to 0.03%. When the content of Fe ₂ O ₃ is too large, the transmittance of the glass substrate tends to decrease. On the other hand, if the content of Fe ₂ O ₃ is attempted to be less than 0.001%, the raw material cost and the manufacturing cost increase.

It is preferable that the alkali metal oxide (Li ₂ O, Na ₂ O, K ₂ O) is not substantially contained. “Containing substantially no alkali metal oxide” means that the content is suppressed to 0.5% or less. When the total content of the alkali metal oxide exceeds 0.5%, the alkali metal is diffused into the TFT semiconductor material on which the TFT is formed on the substrate, and the film characteristics are reduced. to degrade.

In addition to the above, various components can be added as long as the glass properties are not impaired. For example, Y ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ , TiO ₂ or the like may be added.

Moreover, when used for the top plate of an electromagnetic cooker or a gas cooker, electrical characteristics, heat resistance, durability, etc. are required. As suitable glass satisfying such requirements, SiO ₂ 50-80%, Al ₂ O ₃ 12-30%, Li ₂ O 1-6%, MgO 0-5%, ZnO in terms of mass% based on oxides. _{0~10%, BaO 0~8%, Na} 2 O 0~5%, K 2 O 0~10%, TiO 2 0~8%, ZrO 2 0~7%, P 2 O 5 0~10%, it can be exemplified lithium aluminosilicate-based crystallized glass containing SnO ₂ 0.01 to 2%. In addition to the top plate for cooking, this crystallized glass has front windows such as petroleum stoves and wood stoves, heat-resistant cooking containers, setters for firing electronic components, shelf boards for microwave ovens, fire doors, color filter image sensor substrates, etc. The glass material can be used suitably.

  The reason why the composition range of the exemplified lithium aluminosilicate crystallized glass is limited as described above will be described below. In the following description, “%” means “mass%” unless otherwise specified.

SiO ₂ forms a glass skeleton and is a main constituent of crystallized crystals. When the content of SiO ₂ is too small thermal expansion coefficient becomes too large. On the other hand, if the content of SiO ₂ is too much high temperature viscosity of the glass becomes high, it becomes difficult to melt and mold the glass. A suitable range for the SiO ₂ content is 52-77%.

Al ₂ O ₃ forms a glass skeleton and is a constituent of crystallized crystals. Al ₂ When the content of O ₃ is too small chemical durability is deteriorated, and the glass tends to be devitrified. On the other hand, when the content of Al ₂ O ₃ is too large, the high temperature viscosity of the glass becomes high, it becomes difficult to melt and mold the glass. A suitable range of the Al ₂ O ₃ content is 13 to 28%.

Li ₂ O is a crystal constituent, has a large effect on crystallinity, and functions to lower the viscosity of the glass. When the Li 2 _O content is too small, the crystallinity of glass becomes weak and the thermal expansion coefficient becomes too large. Further, in the case of transparent crystallized glass, the crystalline substance tends to become cloudy, and in the case of white crystallized glass, the whiteness tends to decrease. On the other hand, if the content of Li ₂ O is too large, the crystallinity becomes too strong, the glass becomes devitrified, or the metastable β-quartz solid solution cannot be obtained, and the crystal becomes cloudy, resulting in transparent crystallization. It becomes impossible to obtain glass. A preferred range of the content of Li ₂ O is from 1.2 to 5.5%.

  When there is too much content of MgO, crystallinity will become strong and the amount of precipitated crystals will become too strong. A preferred range for MgO is 0-4.5%.

  When there is too much content of ZnO, crystallinity will become strong and the amount of precipitated crystals will become too strong. A preferred range for ZnO is 0-8%.

  The total amount of MgO and ZnO is preferably 0 to 10%, particularly preferably 0 to 8%. If the total amount of these components is too large, the crystallized product tends to be strongly colored.

  When there is too much content of BaO, precipitation of a crystal | crystallization will be inhibited, and since sufficient crystal amount cannot be obtained, a thermal expansion coefficient will become large too much. Furthermore, when obtaining transparent crystallized glass, the crystallized product tends to become cloudy. The preferred range of BaO is 0.3-7%.

Na 2 _O is not sufficient amount of crystals is obtained and the content is too much weakened crystallinity, and the thermal expansion coefficient becomes too large. A preferred range of Na ₂ O is 0-4%.

K 2 _O without sufficient amount of crystals is obtained and the content is too much weakened crystallinity, and the thermal expansion coefficient becomes too large. Furthermore, when obtaining transparent crystallized glass, the crystallized product tends to become cloudy. A preferred range of K ₂ O is 0-8%.

The Na ₂ O and _K the total amount of ₂ O is preferably 0 to 12%. If the total amount of these components is too large, the thermal expansion coefficient tends to increase. Moreover, when obtaining transparent crystallized glass, a crystal substance becomes easy to become cloudy.

TiO ₂ is a nucleating agent during crystallization. When the content of TiO ₂ is too large, impurity coloring becomes remarkable. A suitable range for the content of TiO ₂ is 0.3-7%.

ZrO _{2 is} also a nucleating agent during crystallization. When ZrO ₂ is too large with glass melting becomes difficult, devitrification of the glass increases. The preferred range of ZrO ₂ is 0.5-6%.

The total amount of TiO ₂ and ZrO ₂ is preferably 0.5% or more. If the total amount of these components is too small, crystal precipitation becomes insufficient, making it difficult to obtain desired characteristics.

P ₂ O ₅ is a component that promotes phase separation and promotes crystal precipitation. When there is too much content, the viscosity of a glass matrix will fall. Suitable range of P ₂ O ₅ is 0-5%.

SnO ₂ acts as a fining agent and also has a function as a nucleating agent, and forms a ZrO ₂ —TiO ₂ —SnO ₂ based crystal nucleus. Refining effect when the SnO ₂ content is too low is not sufficient, crystallinity is decreased. On the other hand, when the content of SnO ₂ is too large, coloring due to Fe ions becomes remarkable, which is not preferable. Moreover, it becomes difficult to melt the glass or it becomes easy to devitrify. Suitable range of SnO ₂ content is 0.01 to 1.8%.

Also the Cl to aid in fining SnO ₂ may be contained 0-2%. However, when the content of Cl is too large, chemical durability is deteriorated, which is not preferable. The preferred range of Cl is 0-1%.

In addition to the above, various components can be added as long as the glass properties are not impaired. For example, Y ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ or the like may be added. Further, as a colorant, for example, V ₂ O ₅ can be contained up to 1.5%.

As ₂ O ₃ and Sb ₂ O ₃ are preferably substantially not contained for environmental reasons. Here, "substantially free of _As 2 _{O 3} and _Sb 2 _{O 3"} refers to the content of _As 2 _{O 3} and _Sb 2 _{O 3} in the glass composition, respectively 0.1% (1000 ppm) or less It means that.

  Hereinafter, the present invention will be described based on examples.

  Tables 1 and 2 show examples (Nos. 1 to 3 and 6 to 8) and comparative examples (Nos. 4 and 5 and 9) of the present invention, respectively.

  Sample No. 1-5 were produced as follows. First, glass raw materials were prepared so as to have the glass composition in Table 1, and were melted in a continuous melting furnace. In addition, stannic oxide having the particle size shown in the table was used as a fining agent. Then, it shape | molded by the overflow method so that thickness might be set to 0.7 mm, and it was set as sample glass by cut | disconnecting to the size of 1.8m x 1.5m.

  Sample No. 6 to 9 were produced as follows. First, glass raw materials were prepared so as to have the glass glass composition shown in Table 2, and were melted in a continuous melting furnace. In addition, stannic oxide having the particle size shown in the table was used as a fining agent. Then, it shape | molded by the rollout method so that thickness might be set to 5 mm, and cut | disconnected to the size of 1 m x 1 m. Thereafter, it was crystallized by heat treatment at 800 ° C. for 2 hours to obtain a sample glass. The obtained sample glasses were all transparent, and as a result of X-ray diffraction, β-quartz solid solution was precipitated.

  The foam quality was evaluated for each sample thus prepared. The results are shown in each table.

  As is clear from Tables 1 and 2, No. in the examples. 1-3 and No.1. Each of the samples 6 to 8 had a small number of bubbles of 40 / t or less, and could be used without any problem as a glass substrate used for a flat panel display device or an electronic component.

  On the other hand, No. which is a comparative example. Each of the samples 4 and 9 had a large number of bubbles of 300 / t or more, and the foam quality was inferior. No. In the sample No. 5, since the stannic oxide was fine, the preparation plant was clogged, and stannic oxide could not be supplied to the glass batch.

  The foam quality was evaluated by detecting bubbles on the sample surface with an optical device and converting the counted number per 1 t (ton) of glass.

  The production method of the present invention is not limited to the above-described applications, and can be applied to the production of various glass products such as solar cell substrate applications, flat lamps, and other electronic component applications. Moreover, the glass composition to which this method is applied is not limited to the above-described composition system, and any glass composition that uses tin oxide as a fining agent can be used.

Claims (6)

In producing a silicate glass, the production method of the silicate glass to median particle diameter D ₅₀ is characterized by using a tin oxide powder in the range of 2~50μm as a fining agent. The method for producing a silicate glass according to claim 1, wherein the particle size of the tin oxide powder is adjusted so that the median particle size D50 is in a range of 2 to ₅₀ µm, and then used. The method for producing a silicate glass according to claim 1 or 2, wherein the tin oxide powder is used after being classified so that the median particle diameter D50 is in a range of 2 to ₅₀ µm.   The method for producing a silicate glass according to any one of claims 1 to 3, wherein the silicate glass is an alkali-free glass or a lithium aluminosilicate-based crystallized glass. % By mass on the oxide _{basis, SiO 2 50~80%, Al 2} O 3 5~25%, B 2 O 3 0.1~20%, 0~15% MgO, CaO 3~15%, SrO 0~ 15%, BaO 0-15%, RO (RO represents the total amount of MgO, CaO, SrO and BaO) 0-25%, ZnO 0-10%, ZrO ₂ 0-10%, SnO ₂ 0.01 The glass raw material is prepared so as to be silicate glass that is substantially 1.5% and does not contain an alkali metal, and is melted and molded. Manufacturing method of silicate glass. % By mass on the oxide _{basis, SiO 2 50~80%, Al 2} O 3 12~30%, Li 2 O 1~6%, 0~5% MgO, 0~10% ZnO, BaO 0~8%, Silic acid containing Na ₂ O 0-5%, K ₂ O 0-10%, TiO ₂ 0-8%, ZrO ₂ 0-7%, P ₂ O ₅ 0-10%, SnO ₂ 0.01-2% The method for producing a silicate glass according to any one of claims 1 to 4, wherein a glass raw material is prepared so as to be a salt glass, melted, molded, and then crystallized.