JP6341447B2 - Method for producing silicate glass - Google Patents

Description

  The present invention relates to a method for producing a silicate glass. In particular, the present invention relates to a method for producing a silicate glass using a tin oxide powder that is easily homogeneously dispersed in a batch.

  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, aluminoborosilicate glass which is substantially free of alkali metal, so-called alkali-free glass, is used as a material for a glass substrate for LCD, and various glass compositions have been proposed so far (Patent Documents). 1-3). In recent years, the screens of personal computer monitors, televisions, and the like have become larger, and the required characteristics of bubbles and foreign matters in glass substrates have become more stringent than ever before.

  In order to industrially produce such a glass substrate, the prepared glass raw material is put into a glass melting furnace, melted and clarified, and then the molten glass is supplied to a molding apparatus, an overflow down draw method, a float A method of forming into a plate shape and cutting by a method such as a slot down draw method or the like is employed.

  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.

  In addition, LAS crystals are used as glass materials for oil stoves 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. Glass is used (see, for example, Patent Documents 4 to 6). The LAS-based crystallized glass can obtain a white or transparent appearance by changing the crystallization conditions to change the type of crystallized crystal and the crystal grain size.

  Also in this type of crystallized glass, the required characteristics of bubbles and foreign matters are becoming stricter than ever, 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, and after melting and refining, the glass melt is supplied to a molding apparatus, the float method, A method of crystallizing after forming into a plate shape and cutting by a rollout method or the like 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 supply device, 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

Carr, R.L .: Chem. Eng. 72, 2, 163 (1965)

When manufacturing alkali-free glass or LAS-based crystallized glass as described above, since it is necessary to melt at a high temperature of 1500 to 1600 ° C. or higher, arsenic oxide (As ₂ O has conventionally been used as a fining agent. 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.

  Here, the fining agent is a component that improves the foam quality of the glass, but since the amount added to the glass batch is very small, it must be uniformly dispersed in the batch in order to obtain its effect accurately. There is. In order to disperse uniformly, the particle diameter is preferably small.

  However, the finer the particles, the worse the handleability of the powder, which often becomes a problem in processes such as weighing, transporting and mixing.

  Furthermore, the finer the particles, the easier the aggregation of the primary particles, the more difficult it is to uniformly disperse in the batch, and the problem that the clarification effect cannot be fully exhibited.

  The object of the present invention is to provide a method for producing a silicate glass having excellent foam quality by using tin oxide powder which has good handleability despite being small in particle size and is easily dispersed homogeneously in a batch. To do.

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

  First, in order to obtain the effect of the fining agent accurately, it is necessary to be uniformly dispersed in the batch. In order to disperse uniformly, the particle diameter is preferably small.

  However, the finer the particles, the worse the handleability of the powder, and the agglomeration of the primary particles occurs, making it difficult to disperse uniformly in the batch, and the clarification effect cannot be fully exhibited.

Therefore, the present inventor can manufacture a silicate glass having good handleability, dispersibility, and fineness when used as a glass refining agent by regulating the median particle size D ₅₀ of each tin oxide powder. The heading and the manufacturing method of the silicate glass of this invention are proposed.

That is, the method for manufacturing silicate glass of the present invention, wherein in producing a silicate glass, the median particle diameter D ₅₀ of an oxide of tin powder in the range of less than 0.3~2.0μm as a fining agent And 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 volume-based particle size measured by a laser diffraction / scattering 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 less than 0.3 to 2.0 .mu.m, preferably used. The adjustment of the particle size may be performed by appropriately changing the production conditions of the tin oxide powder, or may be performed by adding a particle size adjusting step after obtaining the tin oxide powder. Examples of the particle size adjustment method include adjustment of reaction rate, reaction temperature, crushing conditions and the like in the production process.

In the present invention, after the median particle diameter D ₅₀ was classified tin oxide powder to be in the range of less than 0.3 to 2.0 .mu.m, preferably used. As classification methods, there are sieving classification, dry classification, wet classification and the like, and specific examples include sieving, centrifugal force, wind force, sedimentation separation, and filtration.

According to the above configuration, it is possible to median particle diameter _{D 50} obtained easily tin oxide of less than 0.3 to 2.0 .mu.m.

  Furthermore, the present inventor has found that the handleability and dispersibility of tin oxide powder are greatly related to the “fluidity” of the powder.

Therefore, as an index for evaluating the fluidity of the powder, the Carr index table described in Non-Patent Document 1 is used, and even if the particles are fine, by using tin oxide powder having appropriate powder flow characteristics, The present inventors have found that the dispersibility is good, it is difficult to cause a problem in processes such as weighing, transportation, and mixing, and the foam quality of the silicate glass can be improved.
For each measurement item in the Carr index table, “Powder Tester PT-S type” manufactured by Hosokawa Micron Corporation was used. This apparatus is generally suitably used as an apparatus for evaluating powder properties according to the Carr index table.

The tin oxide powder of the present invention preferably has a D ₆₀ / D ₁₀ of 30 or less. Here, “D ₆₀ / D ₁₀ ” is a ratio between the 60% particle size and the 10% particle size obtained from the cumulative distribution curve of particle size, and is a value serving as a guide for the particle size distribution width.

  The tin oxide powder of the present invention preferably has a loose filling bulk density in the range of 0.3 to 0.8 g / ml. Here, the “rough packing bulk density” is measured by “Powder Tester PT-S type” manufactured by Hosokawa Micron.

  The tin oxide powder of the present invention preferably has a close packed bulk density in the range of 0.8 to 1.8 g / ml. Here, the measurement of “close packing bulk density” is based on “Powder Tester PT-S type” manufactured by Hosokawa Micron.

  The tin oxide powder of the present invention preferably has a compressibility of 60% or less. The “compressibility” can be calculated by (Densely packed bulk density−Roughly packed bulk density) / Densely packed bulk density × 100 using a value measured by “Powder Tester PT-S type” manufactured by Hosokawa Micron.

  The tin oxide powder of the present invention preferably has a cohesion degree of 60% or less. The “aggregation degree” is measured by “Powder Tester PT-S type” manufactured by Hosokawa Micron.

  The tin oxide powder of the present invention preferably has an evaluation index of 20 or more in fluidity evaluation in the Carr index table. “Fluidity evaluation” is based on the evaluation method described in Non-Patent Document 1.

Here, the tin oxide powder is produced as follows, for example. First, an ingot of Sn 99.5% or more metal tin ingot is decomposed with nitric acid to produce metastannic acid (H ₂ SnO ₃ ). This is fired (H ₂ SnO ₃ → SnO ₂ + H ₂ O ↑) to obtain stannic oxide. Tin oxide powder is obtained by crushing the sintered stannic oxide sintered product (wet method).

  In addition to the above method, there is a gas phase method (dry method) as a method for producing tin oxide powder. In the gas phase method, tin oxide powder is obtained by igniting and oxidizing molten tin ingot in air.

For example, the difference in characteristics due to differences in manufacturing method, the particle distribution width, on tends to be wider in the wet method, the D ₅₀ to obtain a powder such as less than 5μm is not worth the cost. On the other hand, in the gas phase method, the particle size is relatively small and the particle size distribution width is relatively narrow as compared with the wet method.

Therefore, the tin oxide powder of the present invention is preferably produced by a gas phase method. Thus, less than the median particle diameter _{D 50} of 0.3 to 2.0 .mu.m, tends to give a good tin oxide powder flowability.

In the present invention, the silicate glass is preferably alkali-free glass or LAS-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). “LAS-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) precipitate in the glass. It refers to the 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. Specifically, since the particle size of the tin oxide powder of the present invention median particle diameter D ₅₀ is sufficiently small in a range of less than 0.3 to 2.0 .mu.m, even amount to the glass batch to a very small amount, batch It can be dispersed homogeneously inside. Furthermore, since the median particle diameter D ₅₀ is small, high reactivity fining agent during glass melting, it is possible to obtain a sufficient fining effect, and by extension can be satisfactorily bubble quality of silicate glass.

Production method of the present invention, as the tin oxide powder used as a refining agent, by median particle diameter D ₅₀ is used which is in the range of less than 0.3 to 2.0 .mu.m, easily high bubble quality glass Can be obtained.

The particle size of the tin oxide powder is a median particle diameter _{D 50} is less than 0.3~2.0μm, 0.4~1.8μm, 0.5~1.5μm, 0.6~1.2μm are preferred. If the particle size is too large, the batch reaction at the time of melting the glass is delayed, and as a result, sufficient fining performance cannot be obtained. On the other hand, if the particle size of the tin oxide powder is too small, it will be too fine and difficult to handle, or it will be easy to agglomerate. In addition, fluidity may decrease.

  Here, even when the particle size of the tin oxide powder is defined within the above range, if there are concerns about the handleability and dispersibility of the powder, the tin oxide powder may be further regulated from the following viewpoints.

  Specifically, using the Carr index table described in Non-Patent Document 1, the tin oxide powder is regulated by the index and measurement value of each evaluation item.

_D 60 _{/ D 10} of the tin oxide powder of the present invention, 30 or less, 20 or less, 10 or less, 5 or less, or 3 or less. The tin oxide powder having such characteristics has good fluidity. Here, as D ₆₀ / D ₁₀ is smaller, the particle size distribution width is narrower. Generally, when D ₅₀ is the same, the narrower the particle size distribution is, the smaller the degree of compression and the angle of repose is. It can be said that the nature is high. When the fluidity is high, problems such as blockage are unlikely to occur in processes such as weighing, transporting, and mixing, so that sufficient powder handling properties as a glass raw material can be maintained.

The bulk density of the tin oxide powder of the present invention is 0.3 to 0.8 g / ml, 0.35 to 0.75 g / ml, 0.4 to 0.7 g / ml, 0.45 to 0.6 g. / Ml is preferred. Here, the loosely packed bulk density is related to the particle size, true density, particle size distribution, particle shape, and the like. In particular, if other conditions are the same, the smaller the particle size, the smaller the loosely packed bulk density. There is. However, by adjusting the particle size distribution, etc., the median particle diameter D ₅₀ be less than 0.3 to 2.0 .mu.m, not too loose packing bulk density is small, the raw material of the volume is not too large.

  The closely packed bulk density of the tin oxide powder of the present invention is 0.8 to 1.8 g / ml, 0.85 to 1.5 g / ml, 0.88 to 1.2 g / ml, 0.88 to 1.0 g. / Ml is preferable. The tin oxide powder having such characteristics has a low compressibility and can improve the fluidity of the tin oxide powder.

  The compressibility of the tin oxide powder of the present invention is preferably 60% or less, 55% or less, 50% or less, 48% or less, 44% or less, or 45% or less. The tin oxide powder having such characteristics has good fluidity and can maintain sufficient powder handling properties as a glass raw material. Generally, the degree of compression tends to increase as the particle size decreases and the particle size distribution width increases. Moreover, when there are many gaps in the secondary particles, it is considered that the difference between the loosely packed bulk density and the densely packed bulk density becomes small and the degree of compression becomes small.

  The aggregation degree of the tin oxide powder of the present invention is preferably 60% or less, 55% or less, 50% or less, 40% or less, or 30% or less. The tin oxide powder having such characteristics hardly aggregates particles and is uniformly dispersed in the batch, so that a sufficient clarification effect is obtained and the foam quality of the glass is improved. Furthermore, since fluidity | liquidity is favorable, powder handling property sufficient as a glass raw material can be maintained. The degree of agglomeration is determined by the passage rate of the sieve with openings determined based on the results of bulk density measurement by the “Powder Tester PT-S type” manufactured by Hosokawa Micron Corporation. The rate of passing is large and the degree of aggregation is low. Further, even if the powder has agglomerated once, it is unraveled when sieving and as a result passes through the sieve, the degree of agglomeration becomes low.

  The tin oxide powder of the present invention preferably has an angle of repose of 60 ° or less, 55 ° or less, 50 ° or less, or 45 ° or less. When the angle of repose of the tin oxide powder is small, the fluidity is good and sufficient powder handling properties can be maintained as a glass raw material.

  The tin oxide powder of the present invention preferably has a spatula angle of 80 ° or less, 70 ° or less, 65 ° or less, or 60 ° or less. The spatula angle indicates the ease of discharging the powder raw material from the raw material silo. The smaller the angle, the better the fluidity and the sufficient powder handling property as a glass raw material. it can.

  The tin oxide powder of the present invention preferably has a fluidity index of 20 or more, 25 or more, 30 or more, 40 or more, or 50 or more as a fluidity index in the Carr index table. The tin oxide powder having such characteristics eliminates the need for special equipment and technology as a measure for preventing cross-linking of the raw material silo. Therefore, it can produce without raising production cost.

  The tin oxide powder of the present invention is preferably produced by a gas phase method. Since the tin oxide powder produced by the vapor phase method has a small particle size and a narrow particle size distribution width, the fluidity is good. As a result, sufficient powder handleability as a glass raw material can be maintained. In addition, since the particle size is small, it is easy to uniformly disperse in the batch, and the reactivity is high. When used as a fining agent, the foam quality of the silicate glass can be improved.

  Next, the manufacturing method of this invention is explained in full detail.

  First, a batch is prepared by measuring and 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 obtain 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 ), or the like can be 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 ), spodumene (LiAlSi ₂ O _6). ) Etc. can be used.

As the fining agent source, a powder of tin oxide (SnO ₂ ) having a median particle size D _{50 in} the range of less than 0.3 to 2.0 μm is used. Tin oxide powder before formulating the glass raw materials, by a method such as classification has median particle diameter D ₅₀ it is sufficient to adjust so that the range of less than 0.3 to 2.0 .mu.m. The preferable range of the median particle diameter D ₅₀ of the tin oxide powder and other characteristics are as described above, and the description is omitted here.

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 ) or antimony oxide (Sb ₂ O ₃ ) 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 is lowered, and the glass substrate is cracked or heat deformation or heat shrinkage is likely to occur 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 large, it increases the high temperature viscosity, it is difficult to melt and mold. 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 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, if the content of Al ₂ O ₃ is too small, the resistance to buffered hydrofluoric acid is lowered, or the liquidus temperature rises, making it difficult to form a glass substrate. A suitable range for the Al ₂ O ₃ content is 7-22%.

B ₂ O ₃ is a component that lowers the viscosity and increases the meltability. However, when it is excessively contained, the strain point is lowered, and the glass substrate is cracked or thermally deformed in the heat treatment step when manufacturing the display. Or heat shrinkage. 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 by lowering the high temperature viscosity without lowering the strain point. 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 by lowering only the high temperature viscosity without lowering the strain point. When there is too much content of CaO, while resistance to buffered hydrofluoric acid will fall, a density and a thermal expansion coefficient 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 chemical resistance and devitrification resistance. When there is too much content of SrO, a density and a thermal expansion coefficient will rise. The suitable range of SrO content is 0 to 12%.

  BaO is a component that improves chemical resistance and devitrification resistance. When there is too much content of BaO, a density and a thermal expansion coefficient 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 when mixed and contained, but the total amount RO of these components is too large. Then, the density tends to increase, and it becomes 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 resistance to buffered hydrofluoric acid and improves meltability. 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 chemical resistance, particularly acid resistance, and improves Young's modulus. When the content of ZrO ₂ is too large, the liquidus temperature increases, 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 it is preferable to prepare such a content that is 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 LAS-type 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 LAS-based 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 high. On the other hand, the high temperature viscosity if the content of SiO ₂ is too large is increased, it becomes difficult to melt and mold. 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, it increases the high temperature viscosity, it is difficult to melt and mold. 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. When the Li 2 _O content is too small, the crystallinity becomes weak, 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 increase too much. 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 there is too much ZrO ₂ , melting becomes difficult and the devitrification of the glass becomes strong. 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 3 are examples (Nos. 1, 3, 4, 6 to 9) and comparative examples (Nos. 2, 5, and 10) of the present application, and Tables 2 and 4 are those of the present application. The example of the glass composition produced by applying the method is shown.

  Sample No. 1-5 were produced as follows. First, glass raw materials were prepared so as to have the glass composition of Sample A in Table 2, and were melted in a continuous melting furnace. Moreover, the stannic oxide which has the characteristic shown in Table 1 as a clarifier was used, respectively. 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. As described later, glass 2 could not be obtained.

No. In Nos. 1, 3, and 4, since the D _{50 of the} tin oxide powder used is within the scope of the claims of the present application, it has sufficient powder handling properties as a glass raw material, and the resulting glass has good foam quality. It was.

No. 2, D ₅₀ is as small as 0.25 [mu] m, has low fluidity occurs a situation that the raw material is clogged in the conveyance, the glass could not be collected. No. No. 5 was inferior in the foam quality of the glass because tin oxide powder having a large D ₅₀ of 25 μm was used.

  Sample No. 6 to 10 were produced as follows. First, glass raw materials were prepared so as to have the glass composition of Sample J in Table 4, and were melted in a continuous melting furnace. Moreover, the stannic oxide which has the characteristic shown in Table 3 as a clarifier was used, respectively. 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 Table 3.

No. Nos. 6, 7, 8, and 9 have D _{50 of the} tin oxide powder used within the scope of claims of the present application, so that they have sufficient powder handleability as a glass raw material, and the resulting glass has good foam quality. Met.

Furthermore, no. No. 6 had a small D ₆₀ / D ₁₀ , a low degree of cohesion, and an excellent fluidity index. Therefore, it was excellent in powder handling as a glass raw material, and was excellent in the bubble quality of glass.

No. No. 10 used a tin oxide powder having a large D ₅₀ of 30 μm, so that the foam quality of the glass was inferior.

  The phenomenon obtained in the above experiment is considered to occur similarly in other materials shown in Tables 2 and 4.

  As is apparent from Tables 1 and 3, the examples No. 1, 3, 4 and no. Each of the samples 6 to 9 had a small number of bubbles of 50 / 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.

  In addition, although the example of the glass composition was shown in Table 2 and Table 4 as an Example, the glass composition produced by applying the method of this application is not restricted to these.

  On the other hand, No. which is a comparative example. Each of the samples 5 and 10 had a large number of bubbles of 300 / t or more, and the foam quality was inferior. No. Sample 2 had high cohesion, poor fluidity, clogged the plant, and could not supply stannic oxide 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 composition system, and any glass composition that uses tin oxide as a fining agent can be used.

Claims (10)

In producing a silicate glass, the median particle diameter _{D 50} of Ri range near below 0.3~2.0μm as a fining agent, 60% ratio _D 60 / D of the particle diameter _{D 60} of 10% particle size _{D 10} method for producing a silicate _{glass 10} is characterized by using the der Ru tin oxide powder 30 below. The method for producing a silicate glass according to claim 1, wherein the bulk density of the tin oxide powder is in a range of 0.3 to 0.8 g / ml. The method for producing a silicate glass according to claim 1 or 2 , wherein the close-packed bulk density of the tin oxide powder is in the range of 0.8 to 1.8 g / ml. The method for producing a silicate glass according to any one of claims 1 to 3 , wherein the tin oxide powder has a compressibility of 60% or less. The method for producing a silicate glass according to any one of claims 1 to 4 , wherein the aggregation degree of the tin oxide powder is 60% or less. The method for producing a silicate glass according to any one of claims 1 to 5 , wherein the tin oxide powder has an evaluation index of 20 or more in fluidity evaluation in the Carr index table. Tin oxide powder, method for producing a silicate glass according to any one of claims 1 to 6, characterized in that it is produced by a gas phase method. The method for producing a silicate glass according to any one of claims 1 to 7 , wherein the silicate glass is alkali-free glass or LAS-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 It was 1.5%, and substantially to prepare a glass raw material so that the silicate glass containing no alkali metal, molten, according to any one of claims 1 to 8, characterized in that molding 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 8 , wherein a glass raw material is prepared so as to be a salt glass, melted and molded, and then crystallized.