WO2016002814A1 - ガラス基板の製造方法、ガラス基板、及びガラス基板積層体 - Google Patents
ガラス基板の製造方法、ガラス基板、及びガラス基板積層体 Download PDFInfo
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- WO2016002814A1 WO2016002814A1 PCT/JP2015/068909 JP2015068909W WO2016002814A1 WO 2016002814 A1 WO2016002814 A1 WO 2016002814A1 JP 2015068909 W JP2015068909 W JP 2015068909W WO 2016002814 A1 WO2016002814 A1 WO 2016002814A1
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- molten glass
- glass
- glass substrate
- platinum group
- temperature
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
- C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
- C03B5/225—Refining
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B7/00—Distributors for the molten glass; Means for taking-off charges of molten glass; Producing the gob, e.g. controlling the gob shape, weight or delivery tact
- C03B7/02—Forehearths, i.e. feeder channels
- C03B7/06—Means for thermal conditioning or controlling the temperature of the glass
- C03B7/07—Electric means
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Definitions
- the present invention relates to a glass substrate manufacturing method, a glass substrate, and a glass substrate laminate.
- a glass substrate is produced through a step of forming molten glass from a glass raw material, obtaining a clarification step and a homogenization step, and then forming the molten glass into a glass substrate.
- consideration should be given so that foreign substances that cause defects in the glass substrate do not enter the molten glass from any glass processing apparatus that manufactures the glass substrate. It is desirable to do.
- the wall of the member which contacts a molten glass needs to be comprised with an appropriate material according to the temperature of the molten glass which contacts the member, the quality of the required glass substrate, etc.
- the apparatus for melting, clarifying, supplying, and stirring the platinum which is a platinum group metal having high heat resistance.
- the member to contain is used (for example, patent document 1).
- the clarification step is a step in which the temperature of the molten glass is highest during the period from the melting step to the forming step, the clarification tube mainly performing the clarification step is heated to an extremely high temperature. For this reason, in the molten glass after the clarification step, a part of the aggregate obtained by aggregation of the platinum group metal volatilized from the clarification tube is easily mixed as a foreign substance.
- an object of the present invention is to provide a glass substrate manufacturing method, a glass substrate, and a glass substrate laminate that hardly cause the above problem even if foreign substances (aggregates) of a platinum group metal are mixed in the glass substrate.
- the present inventor is difficult to completely prevent foreign substances (aggregates) of the platinum group metal from being mixed into the molten glass during the manufacturing process of the glass substrate. Even when a metal foreign substance (aggregate) was mixed, the glass substrate was hardly distorted, and the form of the foreign substance that made it difficult to make irregularities on the main surface of the glass substrate was sought. As a result, the maximum length of the platinum group metal of 50 ⁇ m or less is effective in making the glass substrate difficult to be distorted, making it difficult to make irregularities on the main surface of the glass substrate, and mixing into the glass substrate.
- reducing the size of platinum group metal foreign matter (aggregates) mixed in the molten glass makes it difficult for distortion to occur on the glass substrate and makes it difficult to create irregularities on the main surface of the glass substrate.
- one embodiment of the present invention is a method for manufacturing a glass substrate.
- the manufacturing method of the said glass substrate contains the following forms.
- the manufacturing method of the glass substrate is: A melting step of melting glass raw material to produce molten glass; A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal.
- the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space is mixed into the molten glass as a foreign substance during the treatment of the molten glass.
- a molten glass processing step Among the aggregates mixed in the molten glass, the aggregates that reduce the size of the aggregate mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less is 70% or more.
- a processing step Among the aggregates mixed in the molten glass, the aggregates that reduce the size of the aggregate mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less is 70% or more.
- the manufacturing method of the glass substrate is: A melting step of melting glass raw material to produce molten glass; It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal.
- a process of processing the molten glass in a glass processing apparatus wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters.
- a molten glass processing step mixed in glass The size of the aggregates mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more.
- the manufacturing method of the glass substrate is: A melting step of melting glass raw material to produce molten glass; A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal.
- the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space is mixed into the molten glass as a foreign substance during the treatment of the molten glass.
- a molten glass processing step An agglomerate treatment step of adjusting the solubility of the agglomerates in the molten glass so that the size of the agglomerates mixed in the molten glass is reduced.
- the manufacturing method of the glass substrate is: A melting step of melting glass raw material to produce molten glass; It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal.
- a process of processing the molten glass in a glass processing apparatus wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters.
- a molten glass processing step mixed in glass Furthermore, an aggregate treatment process for controlling the amount of heat applied to the aggregate so that the amount of heat applied to the aggregate is equal to or greater than a minimum amount of heat that can reduce the size of the aggregate mixed in the molten glass.
- the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space is set to 5 ° C. or more, and the gas phase space contains oxygen.
- the agglomerate treatment step raises the temperature of the molten glass containing the agglomerates so as to be higher than the temperature of the molten glass in the region where the agglomerates are mixed into the molten glass in the molten glass treatment step,
- the temperature of the molten glass becomes the maximum temperature.
- the solubility of the agglomerate in the molten glass is made higher than the solubility in the region where the agglomerates are mixed in the molten glass in the molten glass treatment step.
- the agglomerate treatment step reduces the size of the agglomerates mixed into the molten glass by increasing the solubility of the agglomerates in the molten glass, and any one of the first to sixth aspects.
- the size of the agglomerates mixed in the molten glass is reduced by heating and controlling the molten glass so as to increase the solubility of the agglomerates in the molten glass.
- the glass processing apparatus is a clarification apparatus having a clarification tube, The molten glass flows through the clarification tube, The vapor phase space in the clarification tube is formed along the flow direction of the molten glass, and the agglomerate treatment step is performed in the clarification tube, any one of the first to seventh embodiments.
- a clarification treatment is performed to reduce the number of bubbles in the molten glass using tin oxide contained in the molten glass, the molten glass flows through the glass treatment apparatus, and the gas phase space and A temperature distribution is formed along the flow direction of the molten glass on the wall in contact, and an oxygen concentration distribution is formed along the flow direction of the molten glass in the gas phase space.
- the agglomerate processing step is performed in the glass processing apparatus, the molten glass flows through the glass processing apparatus, and among the molten glass flowing through the glass processing apparatus, in the flow direction of the molten glass in the gas phase space,
- the oxygen concentration in the gas phase space is more than 0% and 1.0% or less, and the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space is 5 ° C. or more,
- the temperature of the molten glass is controlled so that the temperature of the molten glass in the region where the aggregates are mixed in the molten glass in the molten glass treatment step is in a temperature range of 1580 ° C. to 1660 ° C.
- the concentration of the platinum group metal dissolved in the molten glass at the start of the aggregate treatment process is 0.05 to 20 ppm, according to any one of the first to fifteenth embodiments. Glass substrate manufacturing method.
- the platinum of the molten glass is within a range where [Fe 3+ ] / ([Fe 2+ ] + [Fe 3+ ]) of the glass substrate is 0.2 to 0.5.
- a melting step of melting glass raw material to produce molten glass A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal.
- the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space is mixed into the molten glass as a foreign substance during the treatment of the molten glass.
- molten glass treatment process In the molten glass treatment step, an aggregate treatment step of dissolving at least a part of the aggregate mixed in the molten glass in the molten glass, and A method for producing a glass substrate, wherein a concentration of a platinum group metal dissolved in the molten glass at the start of the agglomerate treatment step is 0.05 to 20 ppm.
- a melting process for melting glass raw materials to produce molten glass By using the glass processing apparatus, a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall in contact with the gas phase space is made of a material containing a platinum group metal.
- An agglomerate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step In the agglomerate treatment step, the agglomerates detected in the glass substrate produced by using the glass processing apparatus so that the number of defects in the agglomerate contained in the newly produced glass substrate becomes an acceptable level.
- a method for producing a glass substrate comprising adjusting the saturation solubility of the aggregate platinum group metal by adjusting the temperature of the molten glass based on the number of defects.
- a melting process for melting glass raw materials to produce molten glass By using the glass processing apparatus, a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall in contact with the gas phase space is made of a material containing a platinum group metal.
- An agglomerate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step In the agglomerate treatment step, the [Fe 3+ ] / ([Fe 2+ ] + [Fe 3+ ]) of the glass substrate is set to 0.2 to 0.2 so that the number of defects of the agglomerates contained in the glass substrate becomes an acceptable level.
- the saturation solubility of the said platinum group metal of the said molten glass is adjusted, The manufacturing method of the glass substrate characterized by the above-mentioned.
- [Fe 3+ ] / ([Fe 2+ ] + [Fe 3+ ]) regulates at least one of the content of tin oxide contained in the glass substrate and the content of oxide contained in the glass raw material. It is preferable to adjust by doing.
- Another embodiment of the present invention is a glass substrate laminate in which a plurality of glass substrates are laminated. At this time, the following 22nd form is included. (Twenty-second form) The total volume of the glass substrates in the glass substrate laminate is 0.1 m 3 or more, and among the aggregates of all platinum group metals included in the glass substrate, the maximum number of aggregates having a maximum length of 50 ⁇ m or less. A glass substrate laminate, wherein the ratio is 70% or more.
- Another embodiment of the present invention is a glass substrate, which includes the following twenty-third form. (23rd form)
- the ratio of the number of the aggregates whose maximum length is 50 micrometers or less among the aggregates of the platinum group metal which a glass substrate contains is 70% or more,
- the glass substrate characterized by the above-mentioned.
- another embodiment of the present invention is a glass substrate manufacturing apparatus.
- the said glass substrate manufacturing apparatus contains the following forms.
- (24th form) Glass substrate manufacturing equipment A melting device for melting glass raw material to produce molten glass;
- the molten glass having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal.
- An apparatus for processing glass wherein during processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass as foreign matter.
- the size of the aggregates mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more.
- a processing means for reducing the size is 70% or more.
- mode of this invention is also a glass substrate manufacturing apparatus.
- the said glass substrate manufacturing apparatus contains the following forms. (25th form) Glass substrate manufacturing equipment A melting device for melting glass raw material to produce molten glass; The molten glass having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal.
- An apparatus for processing glass wherein during processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass as foreign matter. And comprising Means for adjusting the solubility of the aggregate in the molten glass so that the size of the aggregate mixed into the molten glass is reduced.
- a method of manufacturing the glass substrate of the first to 21st forms, the glass substrate laminate of the 22nd form, the glass substrate of the 23rd form, and the glass of the 24th and 25th forms is a glass substrate which has a strain point of 650 degreeC or more.
- the glass substrate in any one form of the apparatus is a glass substrate for liquid crystal display, a glass substrate for organic EL (Electro-Luminescence) display, or a glass substrate for display using LTPS (Low Temperature Poly-silicon) thin film semiconductor. Used as
- the glass substrate manufacturing method the glass substrate, the glass substrate laminate, and the glass substrate manufacturing apparatus described above, even if a foreign substance (aggregate) of a platinum group metal is mixed in the glass substrate, the glass substrate is hardly distorted. It is possible to make it difficult to make irregularities on the main surface of the glass substrate. Thereby, the yield at the time of manufacture of a glass substrate improves.
- the glass substrate manufacturing method of this embodiment has a space in which a gas phase space surrounded by the surface of the molten glass and the wall is formed by introducing molten glass, and at least a part of the wall is made of a platinum group metal.
- a glass processing apparatus composed of a material including, for example, a liquid phase made of molten glass, and a gas phase space formed by a liquid surface and a wall of the molten glass, and at least a part of the wall surrounding the gas phase space is A molten glass is processed in a glass processing apparatus composed of a material containing a platinum group metal (a molten glass processing step).
- agglomerates of platinum group metal volatiles volatilized from the wall and existing in the gas phase space are mixed into the molten glass as foreign substances.
- a process of reducing the size of the aggregates mixed in the molten glass is performed so that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less among the aggregates mixed in the molten glass is 70% or more. (Aggregate treatment step). Or the solubility of the foreign material (aggregate) in molten glass is adjusted so that the magnitude
- the amount of heat given to the foreign matter (aggregate) is controlled so that the amount of heat given to the foreign matter (aggregate) is not less than the minimum amount of heat that can reduce the size of the foreign matter (aggregate) mixed in the molten glass.
- aggregate treatment step By reducing the size of the foreign substance (aggregate) of the platinum group metal mixed in the glass substrate, it is difficult for the glass substrate to be distorted, and it is possible to make it difficult to make irregularities on the main surface of the glass substrate. For this reason, the conventional problem is improved and the manufacturing yield of the glass substrate is improved.
- FIG. 1 is a flowchart showing an example of steps of the glass substrate manufacturing method according to the present embodiment.
- the glass substrate manufacturing method mainly includes a melting step S1, a refining step S2, a stirring step S3, a forming step S4, a slow cooling step S5, and a cutting step S6.
- FIG. 2 is a schematic diagram illustrating an example of the configuration of the glass substrate manufacturing apparatus 200 according to the present embodiment.
- the glass substrate manufacturing apparatus 200 includes a melting tank 40, a clarification tube 41, a stirring device 100, a molding device 42, and transfer tubes 43a, 43b, and 43c.
- the transfer pipe 43 a connects the melting tank 40 and the clarification pipe 41.
- the transfer pipe 43 b connects the clarification pipe 41 and the stirring device 100.
- the transfer pipe 43 c connects the stirring device 100 and the molding device 42.
- molten glass is produced by melting glass raw materials.
- the molten glass is stored in the melting tank 40 and heated to have a desired temperature.
- the molten glass contains a fining agent. From the viewpoint of reducing the environmental load, tin oxide is suitably used as a fining agent.
- the glass raw material is heated and melted at a temperature according to its composition. Thereby, in the melting tank 40, for example, a high-temperature molten glass G of 1500 ° C. to 1620 ° C. is obtained.
- the molten glass G between the electrodes may be energized and heated by passing an electric current between at least one pair of electrodes. In addition to the energization heating, a flame by the burner is supplementarily given.
- the glass raw material may be heated.
- the clarification step S2 is performed inside the transfer pipe 43a and the clarification pipe 41 through which the molten glass flows.
- the refining agent causes a reduction reaction with an increase in temperature to release oxygen. Foam contained in the molten glass absorbs the released oxygen and expands, the molten glass floats on the surface in contact with the gas phase space, breaks up and disappears. That is, the defoaming process S2A is performed. Further, the agglomeration is performed in the middle of the defoaming treatment step S2A or after the defoaming treatment step S2A, and the temperature of the molten glass is increased to reduce the size of the platinum group metal agglomerates mixed in the defoaming treatment.
- the object processing step S2B is performed. Thereafter, the temperature of the molten glass is lowered. Thereby, the reduced fining agent causes an oxidation reaction and absorbs gas components such as oxygen remaining in the molten glass. That is, the absorption process step S2C is performed.
- the molten glass G obtained in the melting tank 40 passes through the transfer pipe 43a from the melting tank 40 and flows into the clarification pipe 41.
- the clarification tube 41 has a space in which a gas phase space surrounded by the surface and wall of the molten glass G is formed by introducing the molten glass G, and at least a part of the wall is made of a material containing a platinum group metal.
- it has a liquid phase in which molten glass flows, a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal.
- the transfer pipes 43a, 43b, and 43c are platinum group metal pipes.
- the platinum group metal means a metal composed of a single platinum group element and a metal alloy composed of a platinum group element.
- the platinum group elements are six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir).
- an alloy of platinum and rhodium having a platinum content of 70% or more is preferably used.
- Platinum group metals have a high melting point and are excellent in corrosion resistance to molten glass.
- the clarification tube 41 is provided with a heating means similar to the melting tank 40. At least the transfer pipe 43a is also provided with a heating means.
- the clarification step S2 by adjusting the amount of heat given to the foreign substance (aggregate) of the platinum group metal mixed in the molten glass and the defoaming process step of defoaming the molten glass G by raising the temperature,
- the molten glass breaks or melts the foreign material (aggregate) to reduce the size of the platinum group metal foreign material (aggregate), and the molten glass cools the bubbles in the molten glass by cooling the molten glass.
- An absorption treatment process to absorb is performed.
- the amount of heat given to the foreign matter (aggregate) is reduced in order to reduce the size of the platinum group metal foreign matter (aggregate) by dividing or melting the foreign matter (aggregate) mixed in the molten glass.
- the amount of heat given to the foreign matter (aggregate) in the molten glass is controlled so that the amount of heat given to the foreign matter (aggregate) becomes equal to or greater than the minimum heat amount.
- the minimum heat quantity can be examined in advance by experiments or the like.
- the temperature of the molten glass G in the clarification tube 41 is controlled in the range of 1580 ° C. to 1730 ° C., preferably in the range of 1670 ° C. to 1730 ° C.
- the temperature of the molten glass G flowing inside the transfer pipe 43a is sequentially raised without being lowered.
- the molten glass G is preferably heated up to 1630 ° C or higher at a rate of 3 ° C / min or higher.
- the maximum temperature of the molten glass G flowing through the transfer tube 43a is 1620 ° C. to 1690 ° C., and preferably 1640 ° C. to 1670 ° C.
- the temperature of the molten glass G at the clarification tube inlet, which is a region connecting the transfer tube 43a and the clarification tube 41, is 1610 ° C.
- the temperature of the molten glass G at the clarification tube outlet which is a region connecting the clarification tube 41 and the transfer tube 43b, is 1530 ° C. to 1600 ° C., and preferably 1540 ° C. to 1580 ° C.
- the molten glass G clarified in the clarification tube 41 passes through the transfer tube 43b from the clarification tube 41 and flows into the stirring device 100.
- the molten glass G is cooled when passing through the transfer tube 43b.
- the clarified molten glass is stirred, and the components of the molten glass are homogenized. Thereby, the composition nonuniformity of the molten glass which is a cause of the striae etc. of a glass substrate is reduced.
- the homogenized molten glass is sent to the forming step S4.
- the molten glass G is stirred at a temperature lower than the temperature of the molten glass G passing through the clarification tube 41.
- the temperature of the molten glass G is 1250 ° C to 1450 ° C.
- the viscosity of the molten glass G is 500 poise to 1300 poise.
- the molten glass G is stirred and homogenized in the stirring device 100.
- the molten glass G homogenized by the stirrer 100 flows from the stirrer 100 through the transfer pipe 43 c and flows into the molding device 42.
- the molten glass G passes through the transfer tube 43c, it is cooled so as to have a viscosity suitable for forming the molten glass G.
- the molten glass G is cooled to 1100-1300 ° C.
- stirring process S3 of this embodiment is performed after clarification process S2, stirring process S3 may be performed before clarification process S2.
- the temperature of the molten glass G in the stirring step S3 may be equal to or higher than the temperature of the molten glass G in the clarification tube 41.
- the sheet glass is continuously formed from the molten glass by the overflow downdraw method or the float method.
- the molten glass G that has flowed into the molding apparatus 42 is supplied to a molded body 52 installed inside a molding furnace (not shown).
- a groove is formed on the upper surface of the molded body 52 along the longitudinal direction of the molded body 52.
- the molten glass G is supplied to the groove on the upper surface of the molded body 52.
- the molten glass G overflowing from the groove flows down along the pair of side surfaces of the molded body 52.
- a pair of molten glass G which flowed down the side surface of the molded body 52 joins at the lower end of the molded body 52, and the sheet glass GR is continuously molded.
- the sheet glass continuously formed in the forming step S4 has a desired thickness and is gradually cooled so as not to be distorted and warped.
- cutting process S6 the sheet glass annealed in slow cooling process S5 is cut
- Glass substrate laminate and glass substrate This embodiment provides a glass substrate laminate and a glass substrate formed by laminating a plurality of glass substrates.
- the glass substrate laminate of the present embodiment has a total volume of 0.1 m 3 or more, and among the aggregates of all platinum group metals contained in the glass substrate laminate, the maximum length is 50 ⁇ m or less.
- the ratio of the number of is 70% or more.
- each glass substrate of the said laminated body is suitable for the glass substrate for a display, and is especially effective in the glass substrate for display panels in which high definition is calculated
- the glass substrate of the present embodiment is characterized in that the ratio of the number of aggregates having a maximum length of 50 ⁇ m or less among the aggregates of platinum group metals included in the glass substrate is 70% or more. With the glass substrate having such a configuration, as described later, the glass substrate is less likely to be distorted, and the unevenness of the main surface of the glass substrate can be made more difficult to make.
- the ratio of the number of aggregates whose maximum length is 50 micrometers or less among the aggregates of the platinum group metal to contain is 90% or more.
- the glass substrate laminate and the glass substrate more preferably have a ratio of the number of aggregates having a maximum length of 30 ⁇ m or less among the aggregates of platinum group metal contained therein of 90% or more.
- a glass having a strain point of 600 ° C. or higher is suitable for the glass substrate manufacturing method described later.
- the strain point is more preferably 650 ° C. or higher, even more preferably 690 ° C. or higher, and particularly preferably 730 ° C. or higher.
- the glass substrate produced by the method for producing a glass substrate of the present embodiment is particularly suitable as a glass substrate for a display such as a liquid crystal display, a plasma display, and an organic EL display, and a cover glass for protecting the display.
- the display using the glass substrate for display includes a flat panel display having a flat display surface, an organic EL display and a liquid crystal display, and a curved display having a curved display surface.
- the glass substrate is a glass substrate for a high-definition display, such as a glass substrate for a liquid crystal display, a glass substrate for an organic EL (Electro-Luminescence) display, an LTPS (Low Temperature Poly-silicon) thin film semiconductor, or an IGZO (Indium, Gallium, It is preferable to use as a glass substrate for display using an oxide semiconductor such as Zinc or Oxide.
- a glass substrate for display non-alkali glass or alkali trace glass is used.
- the glass substrate for display has high viscosity at high temperatures. For example, the temperature of the molten glass having a viscosity of 10 2.5 poise is 1500 ° C. or higher.
- the alkali-free glass is a glass having a composition that does not substantially contain an alkali metal oxide (R 2 O).
- Alkali metal oxide is not practically contained means a glass having a composition in which an alkali metal oxide is not added as a glass raw material except for impurities mixed in from the raw material and the like. It is less than 1% by mass.
- Non-alkali glass suitable as a glass substrate for a display such as a glass substrate for a flat panel display (FPD) is SiO 2 50 mass% to 70 mass%, Al 2 O 3 0 mass% to 25 mass. %, B 2 O 3 0 mass% to 15 mass%, MgO 0 mass% to 10 mass%, CaO 0 mass% to 20 mass%, SrO 0 mass% to 20 mass%, BaO 0 mass% to 10 mass%. contains. Instead of BaO 0 mass% to 10 mass%, BaO 0 mass% to 20 mass% may be used.
- the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass.
- the alkali-containing glass which contains a trace amount of alkali metal oxides as a glass substrate for a display.
- the alkali-containing glass contains 0.1% by mass to 0.5% by mass of R ′ 2 O as a component, and preferably 0.2% by mass to 0.5% by mass of R ′ 2 O.
- R ′ is at least one selected from Li, Na and K
- R ′ 2 O is the total content of Li 2 O, Na 2 O and K 2 O.
- the total content of R ′ 2 O may be less than 0.1% by mass. Therefore, as the glass substrate of the present embodiment, glass having an alkali metal oxide (R ′ 2 O) content of 0 to 0.5% by mass including non-alkali glass is preferably used.
- the glass produced according to this embodiment has SnO 2 0.01 mass% to 1 mass% (preferably 0.01 mass% to 0.5 mass%), Fe 2 O 3 0 mass. % To 0.2% by mass (preferably 0.01% to 0.08% by mass) may be further contained.
- the glass produced by the present invention in consideration of environmental burden, it is preferred not to substantially contain As 2 O 3, Sb 2 O 3 , and PbO.
- tin oxide (SnO 2 ) is preferably used as a fining agent.
- the molten glass treatment process is used as a clarification process
- the molten glass treatment apparatus is described as an example of a clarification apparatus including a clarification tube 41.
- an apparatus for performing a molten glass treatment process is described below.
- the glass processing device can be, for example, a stirring device or a transfer tube for transferring molten glass.
- the treatment of the molten glass includes a treatment for homogenizing the molten glass, a treatment for transferring the molten glass, and the like in addition to the treatment for refining the molten glass.
- the agglomerate treatment step S2B has also been described with reference to an example performed in the clarification step S2, but may be performed in, for example, the stirring step S3 and a step of transferring the molten glass G using a transfer tube. Even if the aggregate treatment step S2B is performed in the clarification step S2, the aggregate treatment step S2B does not need to be performed before the absorption treatment step S2C as described above, and the absorption treatment step S2C It may be done later.
- the clarification apparatus includes a vent pipe 41a, a heating electrode 41b, and a refractory protective layer (not shown) and a refractory brick that surround the outer periphery of the clarification pipe 41.
- FIG. 3 is an external view mainly showing the clarification tube 41.
- FIG. 4 is a sectional view showing the inside of the clarification tube 41 and an example of a temperature profile of the clarification tube.
- a ventilation pipe 41a and a pair of heating electrodes 41b are attached to the clarification pipe 41.
- the clarification tube 41 has a space in which a gas phase space 41c surrounded by the surface and wall of the molten glass G is formed by introducing the molten glass G therein.
- the clarification tube 41 has a gas phase space formed by a liquid phase in which the molten glass G flows, a liquid surface of the molten glass G, and a wall.
- the gas phase space 41 c is formed along the flow direction of the molten glass G.
- At least a part of the wall surrounding the gas phase space 41c is made of a material containing a platinum group metal.
- the entire wall surrounding the gas phase space 41c is made of a material containing a platinum group metal.
- the vent pipe 41a is in the middle of the direction in which the molten glass G flows, and is provided on a wall in contact with the gas phase space 41c to communicate the gas phase space 41c with the atmosphere outside the clarification tube 41.
- the vent pipe 41a is preferably formed of a platinum group metal, like the clarification pipe 41. Since the temperature of the vent pipe 41a is likely to decrease due to the heat dissipation function, the vent pipe 41a may be provided with a heating mechanism for heating the vent pipe 41a.
- the pair of heating electrodes 41b are flange-shaped electrode plates provided at both ends of the clarification tube 41a.
- the heating electrode 41b allows a current supplied from a power source (not shown) to flow through the clarification tube 41, and the clarification tube 41 is energized and heated by this current.
- a power source not shown
- the wall of the fining tube 41 is heated so that the maximum temperature is 1670 ° C. to 1750 ° C., more preferably 1690 ° C. to 1750 ° C.
- the difference between the maximum temperature and the minimum temperature of the wall of the clarification tube 41 is 5 ° C. or more, and the gas phase space has oxygen.
- the temperature of the molten glass G is heated to a temperature at which the reduction reaction of tin oxide is promoted. Furthermore, the molten glass G is preferably heated to a temperature at which the foreign substance (aggregate) of the platinum group metal is divided or melted, for example, 1670 ° C. or higher, and more preferably 1680 ° C. or higher. More specifically, it is preferably heated to 1670 ° C. to 1730 ° C., more preferably 1680 ° C. to 1700 ° C. When the maximum temperature of the molten glass G exceeds 1730 ° C., a tube made of a platinum group metal constituting the clarification tube 41a is easily broken.
- the maximum temperature of the molten glass G can be calculated from the measured value of a thermocouple (not shown) provided in the clarification tube 41.
- the temperature of the molten glass G flowing inside the clarification tube 41 can be controlled by controlling the current flowing through the clarification tube 41.
- a pair of heating electrodes 41b are provided on the clarification tube 41, the number of heating electrodes 41b is not particularly limited.
- the amount of current of the heating electrode 41b the temperature of the wall in contact with the gas phase space 41c of the clarification tube 41 is controlled in the range of 1500 to 1750 ° C., for example.
- bubbles containing CO 2 or SO 2 contained in the molten glass G are removed by the oxidation-reduction reaction of a clarifier contained in the molten glass G, for example, tin oxide. Specifically, first, the temperature of the molten glass G is raised to reduce the fining agent, thereby generating oxygen bubbles in the molten glass G. Bubbles containing gaseous components such as CO 2 , N 2 and SO 2 contained in the molten glass G are combined with oxygen bubbles generated by the reductive reaction of the fining agent. The bubbles combined with the oxygen bubbles float on the surface of the molten glass G in contact with the gas space and release the bubbles, that is, break up and disappear. (Defoaming process).
- the temperature of the molten glass G in this defoaming treatment is 1610 ° C. to 1730 ° C., preferably 1640 ° C. to 1710 ° C.
- the platinum group metal volatilizes vigorously from the wall of the clarification tube 41. Since oxygen is released into the gas phase space by defoaming, the oxygen concentration becomes high in the portion of the gas phase space where the defoaming treatment is performed, and as a result, the volatilization of the platinum group metal becomes more active. Along with this, the concentration of the volatiles of the platinum group metal contained in the gas phase space is increased, so that aggregation of the volatiles of the platinum group metal contained in the gas phase space is likely to occur.
- the volatiles of the platinum group metal tend to aggregate at a partially cooled position on the wall, for example, the wall near the inlet of the clarification tube 41. Therefore, a part of the aggregate of platinum group metal adhering to the wall of the clarification tube 41 falls off and easily enters the molten glass G as a foreign substance. For example, after the molten glass flows into the fining tube 41, in the region where the temperature of the molten glass G is 1580 ° C. to 1660 ° C., aggregation of the volatiles of the platinum group metal contained in the gas phase space and the molten glass G of the aggregate It is easy to mix in.
- the aggregate treatment process which reduces the magnitude
- the temperature of the molten glass G containing the platinum group metal foreign matter (aggregate) is set to the region where the platinum group metal foreign matter (aggregate) is mixed into the molten glass G. It is preferable to raise the temperature of the molten glass G so as to be higher than the temperature of the molten glass at.
- a defoaming process and an aggregate processing process are performed simultaneously.
- the defoaming process and the aggregate treatment process may be performed at the same time.
- the molten glass reaches the maximum temperature in the aggregate treatment process. That is, the defoaming treatment process (molten glass treatment process) may include an aggregate treatment process.
- the agglomerate treatment step by controlling the amount of heat applied to the platinum group metal foreign matter (aggregate) mixed in the molten glass, specifically, by setting the temperature of the molten glass G to 1670 ° C. or higher, the platinum group metal It is preferable to sever and melt metal foreign matters (aggregates).
- the aggregate processing step is performed so that the ratio of the number of foreign substances having a maximum length of 50 ⁇ m or less among the foreign substances (aggregates) of the platinum group metal mixed in the molten glass G is 70% or more. As a result, the distortion generated by the glass substrate is small, and the formation of irregularities on the main surface of the glass substrate is reduced.
- the temperature of the molten glass G is maintained at 1670 ° C. or higher for 10 minutes or longer, preferably 30 minutes or longer. That is, the aggregate reduction process for reducing the size of the platinum group metal foreign matter (aggregate) is maintained at a temperature of 1670 ° C. or more for 10 minutes or longer, thereby allowing the size of the platinum group metal foreign matter (aggregate) to be maintained. Can be reduced.
- the solubility of the platinum group metal foreign matter (aggregate) mixed in the molten glass in the molten glass in the molten glass treatment step is determined based on the solubility of the platinum group metal foreign matter (aggregate) in the molten glass treatment step.
- solubility is higher than the solubility in the region mixed with the molten glass.
- the solubility of the foreign matter (aggregate) in the molten glass G is increased, the temperature of the molten glass G is increased to increase the solubility of the aggregate in the molten glass, or the temperature of the molten glass G is increased.
- the amount of foreign matters (aggregates) dissolved in the molten glass G can be increased.
- the foreign substance (aggregate) of the platinum group metal is a linear object elongated in one direction. Therefore, the maximum length of the platinum group metal aggregate (foreign matter) refers to the length of the long side of the circumscribed rectangle circumscribing the image of the foreign matter when the foreign matter (aggregate) of the platinum group metal is photographed. Before the agglomerate treatment step, the proportion of platinum group metal foreign matter (aggregate) having a maximum length of 100 ⁇ m or more exceeds 80%. Further, in the present embodiment, the platinum group metal foreign matter (aggregate) before the aggregate treatment step refers to a platinum group metal foreign matter having an aspect ratio of more than 100, which is a ratio of the maximum length to the minimum length. For example, the maximum length of the foreign substance (aggregate) of the platinum group metal is 50 ⁇ m to 300 ⁇ m, and the minimum length is 0.5 ⁇ m to 2 ⁇ m.
- the temperature of the molten glass G is lowered to oxidize the reduced fining agent.
- the oxygen of the bubble which remains in the molten glass G is absorbed by the molten glass G (absorption process).
- the remaining bubbles are reduced and disappear.
- bubbles contained in the molten glass G are removed by the oxidation-reduction reaction of the clarifying agent.
- the temperature of the molten glass G and the temperature of the wall of the clarification tube 41 are falling to 1580 degrees C or less, and the oxygen concentration contained in gaseous-phase space falls compared with degassing process S2A. Therefore, volatilization and aggregation of the platinum group metal are difficult to perform. For this reason, in the absorption treatment step S2C, the possibility that new platinum group metal aggregates become foreign matters and enter the molten glass G is much lower than in the defoaming treatment step S2A.
- a refractory protective layer is provided on the outer wall surface of the clarification tube 41.
- a refractory brick is further provided outside the refractory protective layer.
- the refractory brick is placed on a base (not shown).
- tube 41 is adjusted by adjusting the thermal radiation amount from the clarification pipe
- FIG. 4 shows an example of the temperature profile of the clarification tube 41 (the temperature profile in the X direction of the wall in contact with the gas phase space 41c of the clarification tube 41) expressed in accordance with the position of the clarification tube 41 in the X direction.
- the temperature is the maximum temperature T max between the end 41d (inlet) of the clarification tube 41 on the side where the molten glass G flows and the vent tube 41a.
- a temperature gradient in which the temperature decreases from the position P of the maximum temperature T max toward the end 41 d of the clarification tube 41 is formed.
- a temperature gradient is formed in which the temperature decreases from the position P at the maximum temperature T max toward the position in the X direction of the vent pipe 41a.
- the temperature gradient region is also formed between the position in the X direction of the ventilation pipe 41a and the end 41e (exit) of the clarification pipe 41 on the side where the molten glass G flows out. .
- the temperature difference between the maximum temperature and the minimum temperature in the temperature gradient region is more than 0 ° C. and 150 ° C. or less, more preferably more than 0 ° C. and 100 ° C. or less.
- the defoaming process starts at least in the first half of the temperature increase section that continues until the wall temperature reaches the maximum temperature Tmax , and continues at least to the maximum temperature Tmax .
- the aggregate treatment process starts, for example, when the temperature of the molten glass G is 1670 ° C. or higher.
- the end of the defoaming treatment step and the end of the agglomerate treatment step may be either, but the point that all the platinum group metal foreign matter mixed in the molten glass is the subject of the agglomerate treatment step. Therefore, the end of the agglomerate treatment process is preferably the same as or after the end of the defoaming process.
- a process of defoaming the bubbles in the molten glass G is performed.
- aggregates of platinum group metal volatiles volatilized from the walls are mixed into the molten glass G as foreign matters.
- the size of the agglomerates mixed in the molten glass G so that the ratio of the number of foreign substances (aggregates) having a maximum length of 50 ⁇ m or less among the foreign substances (aggregates) mixed in the molten glass G is 70% or more. Reduce the thickness.
- the amount of heat applied to the platinum group metal foreign matter is controlled so as to reduce the size of the mixed platinum group metal foreign matter.
- the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space in the clarification tube 41 described above is 5 ° C. or more, and the gas phase space is an atmosphere containing oxygen, that is, the platinum group metal.
- the size of the platinum group metal foreign matter contained in the molten glass can be reduced, or the ratio of the number of platinum group metal foreign matters having a maximum length of 50 ⁇ m or less is 70%. This can be done. Therefore, even if a foreign substance of a platinum group metal is mixed in the glass substrate, the glass substrate is hardly distorted, and the main surface of the glass substrate can be hardly formed.
- the temperature of the molten glass G containing the aggregate is compared with the temperature of the molten glass in the region where the foreign substance (aggregate) of the platinum group metal is mixed into the molten glass G in the molten glass treatment step. It is preferable to raise the temperature so as to increase. Thereby, the foreign material (aggregate) of the platinum group metal can be divided or melted by heat, and the size of the foreign material (aggregate) of the platinum group metal can be reliably reduced.
- the glass processing apparatus is a clarification apparatus having a clarification tube 41, the gas phase space in the clarification tube 41 is formed along the flow direction of the molten glass, and the agglomerate processing step is performed by the clarification tube 41.
- the temperature of the molten glass G in the clarification tube 41 reaches the maximum temperature until the molding step, the platinum group metal foreign matter (aggregates) can be easily divided or melted.
- a clarification treatment is performed to reduce the number of bubbles in the molten glass G using tin oxide contained in the molten glass G.
- a temperature distribution is formed along the flow direction of the glass, and an oxygen concentration distribution is formed along the flow direction of the molten glass G in the gas phase space.
- an oxygen concentration distribution that affects the volatilization of the platinum group metal, agglomerates of platinum group metal volatiles are likely to be generated, and the agglomerates are easily mixed into the molten glass as foreign substances. Even in such a case, the size of the foreign substance (aggregate) of the platinum group metal can be easily reduced, so that the glass substrate is less likely to be distorted, and the main surface of the glass substrate can be hardly made uneven. .
- the agglomerate processing step is performed in a glass processing apparatus, and among the molten glass flowing through the glass processing apparatus, the molten glass flowing in a position in the flow direction corresponding to the region where the oxygen concentration is highest in the gas phase space is included. Preferably, it is done.
- the defoaming treatment of the molten glass G is most actively performed at the maximum temperature Tmax .
- the oxygen concentration is highest in the region in the gas phase space near the maximum temperature Tmax due to the oxygen released from the bubbles.
- the agglomerate treatment step is performed on the molten glass passing through a position in the flow direction corresponding to the region in the gas phase space where the oxygen concentration is highest.
- platinum group metals are actively volatilized due to the maximum oxygen concentration, and as a result, platinum group metal aggregates are easily generated, and platinum group metal aggregates are formed as foreign substances in the molten glass. Even if it is mixed, the size of the foreign matter can be efficiently reduced.
- the oxygen concentration in the gas phase space of the clarification tube 41 is more than 0% and not more than 1.0%, and the difference between the highest temperature and the lowest temperature of the wall of the clarification tube 41 is 5 ° C. or more, 100 It is preferable to set it as below °C.
- volatilization of a platinum group metal can be suppressed and the foreign material of the platinum group metal mixed in the molten glass G can be suppressed.
- the platinum group metal foreign matter cannot be made completely zero.
- the glass substrate is less likely to be distorted, and the effects of the present embodiment that make it difficult to make irregularities on the main surface of the glass substrate become even more remarkable.
- the volatilization of the platinum group metal can be suppressed, the life of the apparatus composed of the platinum group metal such as the fining tube 41 can be improved.
- the temperature of the molten glass G is controlled to be in the temperature range of 1580 ° C. to 1660 ° C. in at least a part of the molten glass treatment step, and the temperature of the molten glass G in the aggregate treatment step is set to 1670 ° C. to 1730 ° C.
- the temperature of the molten glass G in the aggregate treatment step is set to 1670 ° C. to 1730 ° C.
- the oxygen concentration in the gas phase space of the clarification tube 41 has a distribution depending on the location, foreign substances (aggregates) of the platinum group metal are easily mixed into the molten glass G in a region where the oxygen concentration is higher than a predetermined value.
- the temperature of the molten glass G to a temperature that can reduce the size of the platinum group metal foreign matter (aggregate) even if platinum group metal foreign matter (aggregate) is mixed. Is preferably adjusted. More preferably, it is preferable to control the molten glass temperature so as to form a temperature distribution of the molten glass along the oxygen concentration distribution in the gas phase space.
- the conditions for adjusting the solubility so that the solubility is equal to or higher than the minimum solubility include the following conditions including the control of the heat amount.
- the solubility can be adjusted by controlling these conditions or by controlling these conditions in combination.
- compositions for adjusting the solubility of aggregates for example, (A) the concentration of the platinum group metal dissolved in the molten glass; (B) Temperature or temperature distribution of the molten glass (amount of heat given to the aggregate), (C) pressure in the gas phase space; (D) The oxygen activity of the molten glass.
- concentration of platinum group metal in the molten glass can be determined, for example, by sampling the molten glass in the clarification tube, crushing after cooling, and measuring using ICP quantitative analysis. If the platinum group metal concentration is too low, the solubility of the platinum group metal agglomerates will increase, but the platinum group metal will elute from the wall of the clarified tube in contact with the molten glass to the molten glass, causing the clarified tube to be damaged. It may happen. From the viewpoint of suppressing the occurrence of such disadvantages, the concentration of the platinum group metal is adjusted.
- dissolved in the molten glass at the time of the aggregate process process start in the clarification tube 41 originates mainly in the platinum group metal eluted from the wall surface which contacts molten glass, such as the clarification tube 41 and the transfer pipe 43a.
- the amount of platinum group metal eluting from the wall surface depends on the temperature of the transfer tube 43a, the temperature of the molten glass in the defoaming treatment step before the start of the agglomerate treatment step, or the temperature of the wall of the clarification tube 41 in contact with the molten glass.
- the concentration of the platinum group metal of the molten glass at the start of the aggregate treatment process can be adjusted. For example, it can be performed by adjusting the current flowing through the clarification tube 41, adjusting the current supplied to the heater arranged around the clarification tube 41, or a combination thereof.
- the solubility of the platinum group metal in the molten glass at the start of the aggregate treatment process is increased. From this point, the concentration of the platinum group metal dissolved in the molten glass at the start of the aggregate treatment process is preferably adjusted to 0.05 to 20 ppm. As a result, even when platinum group metal aggregates are mixed into the molten glass during the glass substrate manufacturing process, a glass substrate having an acceptable number of defects in the platinum group metal aggregates can be manufactured.
- the reboil bubble is a bubble containing SO 2 or CO 2 generated due to sulfur and carbon contained as impurities in the molten glass.
- SO 3 and CO 3 dissolved in the molten glass are easily reduced, so that SO 2 and CO 2 are easily generated. Since SO 2 and CO 2 are less soluble in molten glass than SO 3 and CO 3 , they tend to be bubbles.
- many reboiling bubbles are generated, they remain as bubble defects on the glass substrate, which may deteriorate the quality of the glass substrate. The bubbles remaining on the glass substrate are detected by, for example, a laser microscope or visual observation.
- the platinum group metal tends to volatilize from the wall of the clarification tube surrounding the gas phase space.
- the volatilization amount of the platinum group metal increases, the concentration of the platinum group metal in the gas phase space increases, and aggregation and mixing of the aggregate into the molten glass easily occur.
- -Melting of the clarification tube In the clarification tube 41 if the temperature of the molten glass is too high, the wall of the clarification tube 41 in contact with the molten glass may be melted. From the viewpoint of suppressing the occurrence of such disadvantages, the temperature or temperature distribution of the molten glass in the clarification tube 41 is adjusted.
- the solubility of the platinum group metal agglomerates can be increased by increasing the pressure in the gas phase space 41 c of the clarification tube 41.
- the pressure in the gas phase space means the total pressure of the gas contained in the gas phase space.
- the adjustment of the pressure in the gas phase space 41c is, for example, an amount (suction amount) in which the gas in the gas phase space 41c is sucked to the outside of the clarification tube 41 through the vent pipe 41a, the gas into the clarification tube 41, For example, it can be performed by adjusting the supply amount of the inert gas and the discharge amount of the gas released from the molten glass.
- the amount of suction is, for example, the magnitude of the pressure difference between the gas phase space 41c and the atmosphere outside the clarification tube 41 by connecting the outlet of the ventilation tube 41a of the clarification tube 41 to a suction device or by narrowing the outlet. It can be adjusted by adjusting.
- the amount of gas released from the molten glass can be adjusted, for example, by adjusting the amount of fining agent contained in the molten glass and the mixing ratio of the glass components. In addition, it can be calculated
- the method for increasing the pressure in the gas phase space 41c is as described above, such as the amount of gas supplied into the clarification tube 41, for example, the amount of inert gas supplied, or This can be done by adjusting the amount of gas released from the molten glass.
- the pressure in the gas phase space 41c is preferably adjusted in the range of 0.8 to 1.2 atm, for example.
- the solubility of the platinum group metal aggregate can be increased by increasing the oxygen activity of the molten glass.
- the oxygen activity of the molten glass means the amount of oxygen dissolved in the molten glass (excluding those present in the molten glass as bubbles).
- [Fe 3+ ] / ([Fe 2+ ] + [Fe 3+ ]) is used as an index of the oxygen activity.
- [Fe 2+ ] and [Fe 3+ ] are the activities of Fe 2+ and Fe 3+ contained in the molten glass, specifically, the mass percentage display content, which is measured using a spectrophotometric method. can do.
- the temperature of the molten glass is increased, and oxygen dissolved in the molten glass is defoamed as bubbles, so that the oxygen activity of the molten glass is lowered.
- the fining agent takes in oxygen, so that the oxygen activity increases.
- the oxygen activity of the molten glass is adjusted, for example, in the melting process by adjusting the amount of fining agent and oxide contained in the molten glass, as well as adjusting the amount of fining agent and oxide contained in the molten glass.
- the temperature of the molten glass before the start of the aggregate treatment process can be adjusted, or the oxygen-containing gas can be adjusted by bubbling the molten glass before the start of the aggregate treatment process.
- Adjustment of the oxygen activity in the molten glass may be performed together with adjustment of the temperature or temperature distribution of the molten glass.
- the adjustment of the oxygen activity in the molten glass may be performed together with the adjustment of the pressure of the gas phase space 41c.
- the oxygen activity in the molten glass is adjusted by adjusting the amount of fining agent contained in the molten glass or the oxide of the glass raw material, and in the clarification process, before the start of the aggregate treatment process.
- the temperature adjustment of the molten glass may be feedback adjusted based on the number of defects in the aggregate.
- the temperature of the molten glass to be adjusted may be the temperature at the start of the agglomerate treatment process or may be the temperature during the agglomerate treatment process.
- the defects of platinum group metal aggregates in the glass substrate are obtained by making light such as laser light incident on the surface of the glass substrate from an oblique direction and receiving the reflected light at each position of the glass substrate. It can detect by specifying the area
- the allowable level of the number of defects in the aggregate is, for example, 0.02 piece / kg or less when expressed in unit mass.
- the allowable level changes in accordance with specifications regarding distortion and irregularities on the main surface, which are required by the user of the glass substrate. For example, when the number of defects detected in the glass substrate exceeds an allowable level, the temperature of the molten glass is increased to increase the saturation solubility of the platinum group metal in the molten glass, thereby mixing into the molten glass. Promotes the dissolution of aggregates.
- the number of defects detected in the glass substrate is at an allowable level
- the number can be lowered within a range higher than the upper limit of the number of defects at the allowable level and the temperature of the molten glass corresponding to the upper limit.
- the saturation solubility of the platinum group metal can be adjusted to an appropriate range. It is possible to suppress the deterioration of the quality of the glass substrate caused by the increase in bubbles and the like.
- the glass processing apparatus is a clarification apparatus including a clarification tube
- the temperature of the molten glass can be adjusted by passing an electric current through the clarification tube and conducting heating. The amount of current can be adjusted by the magnitude of the voltage applied to the heating electrode.
- the temperature adjustment of the molten glass may be indirectly adjusted by a heater (not shown) disposed around the clarification tube in place of the electric heating or in combination with the electric heating.
- the heater is disposed, for example, inside or outside a refractory protective layer or a refractory brick.
- temperature adjustment of molten glass may be performed by adjusting the heat dissipation from a clarification pipe
- the above-mentioned index of the oxygen activity of the molten glass is used in place of or in addition to the temperature adjustment of the molten glass so that the number of defects of the agglomerates contained in the glass substrate becomes an acceptable level. It is preferable to adjust the saturation solubility of the platinum group metal by adjusting [Fe 3+ ] / ([Fe 2+ ] + [Fe 3+ ]) of the glass substrate in the range of 0.2 to 0.5.
- the ratio of the number of foreign substances (aggregates) having a maximum length of more than 50 ⁇ m among the platinum group metal foreign substances (aggregates) contained in the molten glass, the glass substrate, or the glass substrate laminate after the aggregate treatment step is 30 Decrease to less than%.
- tin oxide is preferably used as a clarifier for molten glass in order to reduce environmental impact.
- tin oxide has a clarification effect (oxidation reaction) as compared with As 2 O 3 and Sb 2 O 3.
- the temperature obtained is high.
- the temperature of the clarification tube 41 is increased as compared with the case where As 2 O 3 or Sb 2 O 3 is used as a clarifier. Need to be high.
- tin oxide is used as a fining agent, volatilization (oxidation) of the fining tube 41 is more likely to occur than before, and the problem of volatilization and aggregation of platinum group metals is likely to occur.
- the amount of platinum group metal foreign matter (aggregates) mixed in the molten glass is increased by using tin oxide as a fining agent, the size of the platinum group metal foreign matter is increased as in this embodiment. Since the thickness of the glass substrate can be reduced, the glass substrate is less likely to be distorted, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes significant. That is, the amount of foreign matters (aggregates) that cause display defects can be sufficiently reduced.
- molten glass with high viscosity has a low bubble rising speed in the refining process and is difficult to clarify. Further, even in the stirring step performed by the stirring device 100, it is difficult to uniformly stir molten glass having high viscosity. Therefore, in order to sufficiently obtain the refining effect or the homogenization of the molten glass, it is necessary to increase the temperature of the molten glass. For this reason, if the temperature of the glass processing apparatus is also increased in order to obtain a molten glass having a high temperature, volatilization of the platinum group metal becomes intense in the glass processing step, and the amount of foreign matters (aggregates) mixed into the molten glass increases. easy.
- alkali-free glass or glass containing a trace amount of alkali so as not to adversely affect the operation of the thin film transistor. Since alkali-free glass or glass containing a small amount of alkali is higher in viscosity than alkali-containing glass such as soda glass, it is difficult to clarify because the speed of foam rise is slow in the fining process. For this reason, in order to fully obtain the clarification effect, it is necessary to raise the temperature of the clarification tube 41 and to raise the temperature of the molten glass G.
- the object to be manufactured is alkali-free glass or glass containing a small amount of alkali
- volatilization (oxidation) of the clarification tube 41 is more likely to occur than alkali glass, and the problem of volatilization and aggregation of platinum group metals is likely to occur.
- the amount of foreign matter (aggregates) of platinum group metal mixed into the molten glass is increased by increasing the temperature of the clarification tube 41 in order to use alkali-free glass or glass containing a small amount of alkali. Since the size of the foreign material of the platinum group metal can be reduced as in the embodiment, the effect that the glass substrate is hardly distorted and the main surface of the glass substrate can be made difficult to make uneven is remarkable. . That is, the amount of foreign matters (aggregates) that cause display defects can be sufficiently reduced.
- the alkali-free glass or alkali trace glass described above is a glass having a high strain point.
- a glass having a high strain point has a higher viscosity than a glass having a low strain point, and therefore, the rising speed of bubbles is slow in the refining process, and it is difficult to clarify. For this reason, in order to fully obtain the clarification effect, it is necessary to raise the temperature of the clarification tube 41 and to raise the temperature of the molten glass G. That is, when producing a glass with a high strain point, the clarification tube is more likely to volatilize (oxidize) than when producing a glass with a low strain point, and the problem of volatilization and aggregation of platinum group metals is likely to occur.
- the glass substrate for display is required to have a strain point of the glass substrate of 600 ° C. or higher, more preferably 650 ° C. or higher. However, if the strain point of the glass substrate is 600 ° C. or higher, a display defect is caused.
- the glass substrate for high-definition displays is required to have a higher strain point, and the strain point is preferably 690 ° C. or higher, and more preferably 730 ° C. or higher. As described above, when the strain point is 690 ° C. or higher and 730 ° C. or higher, the above-described effect of the present embodiment becomes more remarkable. Further, the viscosity of the molten glass containing tin oxide used in the present embodiment is 10 2.5 poise at a temperature of 1500 ° C. or higher, for example, 1500 ° C. to 1700 ° C., or 1550 ° C. to 1650 ° C.
- the above-described effect of the present embodiment becomes more remarkable.
- the thickness of the glass substrate manufactured in this embodiment is 0.005 mm to 0.8 mm, preferably 0.01 mm to 0.5 mm, more preferably 0.01 mm to 0.2 mm, this embodiment The above-mentioned effect becomes more remarkable.
- foreign substances aggregates
- such a problem due to the plate thickness can be solved by the above-described effects.
- the glass substrate was produced by the manufacturing process including the aggregate processing process S2B shown in FIG. 1 (Example).
- the amount of heat given to the aggregate was controlled.
- the conditions for producing the glass substrate are as follows.
- the glass composition of the glass substrate is as follows: SiO 2 60.7 mass%, Al 2 O 3 17 mass%, B 2 O 3 11.5 mass%, MgO 2 mass%, CaO 5.6 mass%, SrO 3 mass%. SnO 2 0.2 mass%, the strain point was 660 ° C., and the plate thickness was 0.4 mm.
- the glass substrate was produced on the above-mentioned production conditions by the conventional manufacturing process which performed the absorption process S2C after the defoaming process S2A, without performing the aggregate treatment process S2B shown in FIG.
- the maximum temperature of the molten glass G in the clarification tube 41 is 1670 ° C. to 1720 ° C.
- the time for the temperature of the molten glass G to be 1670 ° C. or higher is 40 minutes. did.
- the maximum temperature of the molten glass G was set to less than 1670 ° C, and the time during which the temperature of the molten glass G was 1670 ° C or higher was set to 0 minutes.
- the number of foreign substances (aggregates) of the platinum group metal on the plurality of 0.1 m 3 glass substrates thus prepared is counted using an optical microscope, and the maximum length of the foreign substances (aggregates) of the platinum group metal is counted.
- the ratio of the number of the foreign material whose maximum length is 50 micrometers or less among the foreign materials (aggregate) of all the platinum group metals mixed in a glass substrate was calculated
- the obtained ratio is shown in Table 1 below together with the maximum temperature.
- the percentage of foreign matter in Examples 1 to 5 was 70% or more in any glass substrate, but the percentage of foreign matter in Examples 6 and 7 was 35% or less in any glass substrate.
- FIG. 5 is a graph showing the relationship between the maximum temperature of the molten glass and the ratio of foreign matter.
- the ratio of foreign matter having a maximum length of 50 ⁇ m or less rapidly increases when the maximum temperature of the molten glass is increased from 1660 ° C. to 1670 ° C. or higher, and is 70% or higher at a temperature of 1670 ° C. or higher. It became.
- the ratio of foreign matters having a maximum length of 50 ⁇ m or less was 92% or higher.
- the ratio of foreign matters having a maximum length of 50 ⁇ m or lower was 100%.
- the maximum temperature of the molten glass is set to 1670 ° C. or higher, preferably 1690 ° C. or higher, more preferably 1700 ° C. or higher, to give heat to the foreign material. It turns out that it is preferable.
- the maximum temperature of 1670 ° C. is the lower limit temperature of the maximum temperature at which the ratio of foreign matter having a maximum length of 50 ⁇ m or less is 70%, but it is essential that the maximum temperature is 1670 ° C. or more.
- adjusting the solubility of the agglomerates (foreign substances) by other methods can also realize the ratio of foreign substances having a maximum length of 50 ⁇ m or less to 70%.
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Abstract
Description
たとえば、熔融ガラスを生成した後成形工程に供給するまでの間の熔融ガラスは極めて高温状態になるため、熔融、清澄、供給、攪拌を行う装置は、耐熱性の高い白金族金属である白金を含有する部材が用いられる(例えば、特許文献1)。
このように、ガラス基板に混入する白金族金属の異物(凝集物)の量を低減することが好ましい。しかし、成形前の熔融ガラスの温度は極めて高く、特に、清澄工程を行う清澄管では、白金族金属の揮発を誘発する原因である酸素を清澄管の気相空間雰囲気から排除することはできず、白金族金属の揮発を完全になくすことはできない。また、清澄管において、白金族金属の揮発物の凝集を生じさせる原因である装置内壁面の温度差を0にすることもできず、白金族金属の揮発を完全になくすことはできない。このため、製造過程で熔融ガラス中に白金族金属の異物(凝集物)が混入することを完全に阻止することは難しい。
(第1の形態)
ガラス基板の製造方法は、
ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
前記熔融ガラスに混入した凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が70%以上になるように、前記熔融ガラスに混入した凝集物の大きさを小さくする凝集物処理工程と、を備える。
ガラス基板の製造方法は、
ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスからなる液相と、前記熔融ガラスの液面と壁から形成される気相空間とを有し、前記気相空間を囲む壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、
前記熔融ガラス処理工程で熔融ガラスに混入した凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が70%以上になるように、前記熔融ガラスに混入した凝集物の大きさを小さくする凝集物処理工程と、を備える。
ガラス基板の製造方法は、
ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
前記熔融ガラスに混入した凝集物の大きさが小さくなるように、前記熔融ガラスにおける前記凝集物の溶解度を調整する凝集物処理工程、を備える。
ガラス基板の製造方法は、
ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスからなる液相と、前記熔融ガラスの液面と壁から形成される気相空間とを有し、前記気相空間を囲む壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
さらに、前記凝集物に与える熱量が、前記熔融ガラスに混入した前記凝集物の大きさを小さくすることができる最小熱量以上となるように、前記凝集物に与える熱量を制御する凝集物処理工程、を備える。
前記ガラス基板の製造方法において、前記気相空間と接する前記壁の最高温度と最低温度との差を5℃以上にし、前記気相空間は酸素を含む、第1の形態~第4の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記凝集物処理工程は、前記凝集物を含む前記熔融ガラスの温度を、前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における熔融ガラスの温度と比べて高くなるように昇温させる、前記第1の形態~前記第5の形態のいずれか1つの形態に記載されたガラス基板の製造方法。あるいは、前記凝集物処理工程において、前記熔融ガラスの温度は最高温度となる。
前記凝集物処理工程では、前記凝集物の熔融ガラスへの溶解度を、前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における前記溶解度に比べて高くする、前記第1の形態~前記第6の形態のいずれか1つの形態に記載されたガラス基板の製造方法。あるいは、前記凝集物処理工程は、前記凝集物の熔融ガラスへの溶解度高めることで、前記熔融ガラスに混入した凝集物の大きさを小さくする、前記第1の形態~前記第6の形態のいずれか1つの形態のガラス基板の製造方法。詳細には、前記凝集物処理工程は、前記凝集物の熔融ガラスへの溶解度高めるように熔融ガラスを加熱制御することで、前記熔融ガラスに混入した凝集物の大きさを小さくする、前記第1の形態~前記第6の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記ガラス処理装置は、清澄管を有する清澄装置であり、
前記熔融ガラスは、前記清澄管を流れ、
前記清澄管内の前記気相空間は、前記熔融ガラスの流れの方向に沿って形成され、前記凝集物処理工程は、前記清澄管で行われる、前記第1の形態~前記第7の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記熔融ガラス処理工程では、前記熔融ガラスに含まれる酸化スズを用いて前記熔融ガラス中の泡数を低減する清澄処理を行い、前記熔融ガラスは、前記ガラス処理装置を流れ、前記気相空間と接する前記壁には、前記熔融ガラスの流れの方向に沿って温度分布を形成させ、前記気相空間には、前記熔融ガラスの流れの方向に沿って酸素濃度分布を形成させる、前記第1の形態~前記第8の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記凝集物処理工程は、前記ガラス処理装置で行われ、前記熔融ガラスは、前記ガラス処理装置を流れ、前記ガラス処理装置を流れる熔融ガラスのうち、前記気相空間における熔融ガラスの流れ方向において、酸素濃度が最も高くなる領域と対応する位置を流れる熔融ガラスに対して行われる、前記第1の形態~前記第9の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記気相空間中の酸素濃度を、0%超であって、1.0%以下にし、前記気相空間と接する前記壁の最高温度と最低温度の差を、5℃以上であって、100℃以下にする、前記第1の形態~前記第10の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記凝集物処理工程における前記熔融ガラスの温度を、1670℃~1730℃の温度範囲とするように熔融ガラスの温度を制御する、前記第1の形態~前記第11の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における前記熔融ガラスの温度を、1580℃~1660℃の温度範囲とするように熔融ガラスの温度を制御する、前記第1の形態~前記第12の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記熔融ガラス処理工程は、前記凝集物処理工程を含む、前記第1の形態~前記第13の形態のいずれか1つの形態に記載のガラス基板の製造方法。
前記ガラス基板は、ディスプレイ用ガラス基板である、前記第1の形態~前記第14の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
前記凝集物処理工程開始時の前記熔融ガラス中に溶けている白金族金属の濃度を、0.05~20ppmにする、前記第1の形態~前記第15の形態のいずれか1つの形態に記載のガラス基板の製造方法。
前記ガラス基板は、アルカリ金属酸化物の含有量が0~0.5質量%である、前記第1の形態~前記第17の形態のいずれか1つの形態に記載されたガラス基板の製造方法。
ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記
気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記
熔融ガラスに混入する熔融ガラス処理工程と、
前記熔融ガラス処理工程において、前記熔融ガラスに混入した凝集物の少なくとも一部を前記熔融ガラスに溶解させる凝集物処理工程と、を備え、
前記凝集物処理工程開始時の前記熔融ガラス中に溶けている白金族金属の濃度を、0.05~20ppmにする、ことを特徴とするガラス基板の製造方法。
ガラスの原料を熔解して熔融ガラスをつくる熔解工程と、
前記熔融ガラスの導入によって前記熔融ガラスの表面と壁に囲まれる気相空間が形成され、前記気相空間に接する壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置を用いて前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が前記熔融ガラスに混入する熔融ガラス処理工程と、
前記熔融ガラス処理工程で前記熔融ガラスに混入した凝集物の少なくとも一部を前記熔融ガラスに溶解させる凝集物処理工程と、を備え、
前記凝集物処理工程では、新たに作製されるガラス基板に含まれる前記凝集物の欠陥個数が許容レベルになるように、前記ガラス処理装置を用いて作製したガラス基板において検出された前記凝集物の欠陥個数に基づいて前記熔融ガラスの温度を調整することで前記凝集物白金族金属の飽和溶解度を調整することを特徴とするガラス基板の製造方法。
ここで、記凝集物処理工程では、前記凝集物の飽和溶解度を調整するために、前記熔融ガラスの温度を1660~1750℃の範囲で調整することが好ましい。
ガラスの原料を熔解して熔融ガラスをつくる熔解工程と、
前記熔融ガラスの導入によって前記熔融ガラスの表面と壁に囲まれる気相空間が形成され、前記気相空間に接する壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置を用いて前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が前記熔融ガラスに混入する熔融ガラス処理工程と、
前記熔融ガラス処理工程で前記熔融ガラスに混入した凝集物の少なくとも一部を前記熔融ガラスに溶解させる凝集物処理工程と、を備え、
前記凝集物処理工程では、ガラス基板に含まれる前記凝集物の欠陥個数が許容レベルになるように、ガラス基板の[Fe3+]/([Fe2+]+[Fe3+])を0.2~0.5の範囲で調整することにより、前記熔融ガラスの前記白金族金属の飽和溶解度を調整することを特徴とするガラス基板の製造方法。
ここで、前記[Fe3+]/([Fe2+]+[Fe3+])は、前記ガラス基板が含有する酸化錫の含有量及びガラス原料に含まれる酸化物の含有量の少なくともいずれかを調節することにより調整されることが好ましい。
(第22の形態)
前記ガラス基板積層体中のガラス基板の体積の合計は0.1m3以上であり、前記ガラス基板が含む全白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上である、ことを特徴とするガラス基板積層体。
(第23の形態)
ガラス基板が含む白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上である、ことを特徴とするガラス基板。
(第24の形態)
ガラス基板製造装置は、
ガラスの原料を熔解して熔融ガラスを生成する熔解装置と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成された、前記熔融ガラスを処理する装置であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入するガラス処理装置と、
前記熔融ガラス処理工程で熔融ガラスに混入した凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が70%以上になるように、前記熔融ガラスに混入した凝集物の大きさを小さくする処理手段と、を備える。
(第25の形態)
ガラス基板製造装置は、
ガラスの原料を熔解して熔融ガラスを生成する熔解装置と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成された、前記熔融ガラスを処理する装置であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入するガラス処理装置と、を備え、
前記熔融ガラスに混入した凝集物の大きさが小さくなるように、前記熔融ガラスにおける前記凝集物の溶解度を調整する手段、を備える。
また、前記第1の形態~前記第21の形態のガラス基板の製造方法、前記第22の形態のガラス基板積層体、前記第23の形態のガラス基板、及び前記第24、25の形態のガラス基板製造装置のいずれか1つの形態における前記ガラス基板は、650℃以上の歪点を有するガラス基板である。
このように、ガラス基板に混入する白金族金属の異物(凝集物)の大きさを小さくすることにより、ガラス基板に歪が生じ難く、ガラス基板の主表面の凹凸を作りにくくすることができる。このため、従来の問題を改善して、ガラス基板の製造歩留まりを改善する。
以降の説明では、凝集物の溶融ガラスに対する溶解度が、凝集物が熔融ガラスに溶解して大きさを小さくすることができる最小溶解度以上となるように、溶解度を調整する条件を制御する例として、凝集物に与える熱量が、熔融ガラスに混入した凝集物の大きさを小さくすることができる最小熱量以上となるように、凝集物に与える熱量を制御する例を挙げて説明する。
図1は、本実施形態に係るガラス基板製造方法の工程の一例を示すフローチャートである。ガラス基板の製造方法は、図1に示されるように、主として、熔解工程S1と、清澄工程S2と、攪拌工程S3と、成形工程S4と、徐冷工程S5と、切断工程S6とを備える。
図2は、本実施形態に係るガラス基板製造装置200の構成の一例を示す模式図である。ガラス基板製造装置200は、熔解槽40と、清澄管41と、攪拌装置100と、成形装置42と、移送管43a,43b,43cとを備える。移送管43aは、熔解槽40と清澄管41を接続する。移送管43bは、清澄管41と攪拌装置100を接続する。移送管43cは、攪拌装置100と成形装置42を接続する。
熔解槽40では、ガラス原料は、その組成等に応じた温度に加熱されて熔解される。これにより、熔解槽40では、例えば、1500℃~1620℃の高温の熔融ガラスGが得られる。なお、熔解槽40では、少なくとも1対の電極間に電流を流すことで、電極間の熔融ガラスGが通電加熱されてもよく、また、通電加熱に加えてバーナーによる火焔を補助的に与えることで、ガラス原料が加熱されてもよい。
清澄工程S2では、熔融ガラスGの清澄を十分に行なうという観点からは、移送管43aの内部を流れる熔融ガラスGの温度は、降温されることなく、順次昇温されることが好ましい。熔解工程S1の後、熔融ガラスGは1630℃以上まで3℃/分以上の速度で昇温されることが好ましい。
移送管43aを流れる熔融ガラスGの最高温度は1620℃~1690℃であり、1640℃~1670℃であることが好ましい。また、移送管43aと清澄管41を接続する領域である清澄管入口での熔融ガラスGの温度は、1610℃~1680℃であり、1630℃~1660℃であることが好ましい。さらに、清澄管41と移送管43bとを接続する領域である清澄管出口での熔融ガラスGの温度は、1530℃~1600℃であり、1540℃~1580℃であることが好ましい。
清澄管41において清澄された熔融ガラスGは、清澄管41から移送管43bを通過して攪拌装置100に流入する。熔融ガラスGは、移送管43bを通過する際に冷却される。
具体的には、攪拌装置100では、清澄管41を通過する熔融ガラスGの温度よりも低い温度で、熔融ガラスGが攪拌される。例えば、攪拌装置100において、熔融ガラスGの温度は、1250℃~1450℃である。例えば、攪拌装置100において、熔融ガラスGの粘度は、500ポアズ~1300ポアズである。熔融ガラスGは、攪拌装置100において攪拌されて均質化される。
攪拌装置100で均質化された熔融ガラスGは、攪拌装置100から移送管43cを通過して成形装置42に流入する。熔融ガラスGは、移送管43cを通過する際に、熔融ガラスGの成形に適した粘度となるように冷却される。例えば、熔融ガラスGは、1100~1300℃まで冷却される。
なお、本実施形態の攪拌工程S3は、清澄工程S2の後に行なわれるが、攪拌工程S3は、清澄工程S2の前に行われてもよい。この場合、攪拌工程S3時の熔融ガラスGの温度は、清澄管41内の熔融ガラスGの温度と同等か高くてもよい。
具体的には、成形装置42に流入した熔融ガラスGは、成形炉(図示せず)の内部に設置されている成形体52に供給される。成形体52の上面には、成形体52の長手方向に沿って溝が形成されている。熔融ガラスGは、成形体52の上面の溝に供給される。溝から溢れた熔融ガラスGは、成形体52の一対の側面を伝って下方へ流下する。成形体52の側面を流下した一対の熔融ガラスGは、成形体52の下端で合流して、シートガラスGRが連続的に成形される。
切断工程S6では、徐冷工程S5で徐冷されたシートガラスが所定の長さに切断されて、ガラスシートが得られる。ガラスシートは、さらに、所定のサイズに切断されて、ガラス基板が得られる。
本実施形態は、複数枚のガラス基板を積層して形成されたガラス基板積層体及びガラス基板を提供する。
本実施形態のガラス基板積層体は、その体積の合計は0.1m3以上であり、このガラス基板積層体が含む全白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上である、ことを特徴とする。このようなガラス基板積層体は、後述するように、ガラス基板に歪が生じ難く、ガラス基板の主表面の凹凸を作りにくくすることができる。このため、上記積層体の各ガラス基板は、ディスプレイ用ガラス基板に好適であり、特に、画面表示において高精細が求められるディスプレイパネル用ガラス基板において有効である。
また、本実施形態のガラス基板は、ガラス基板が含む白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上であることを特徴とする。このような構成のガラス基板により、後述するように、ガラス基板に歪がより生じ難く、ガラス基板の主表面の凹凸をより作りにくくすることができる。
なお、ガラス基板積層体及びガラス基板は、含有する白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が90%以上であることがより好ましい。また、ガラス基板積層体及びガラス基板は、含有する白金族金属の凝集物のうち、最大長さが30μm以下である凝集物の個数の割合が90%以上であることがより好ましい。
ガラス基板に用いるガラスは、歪点が600℃以上であるガラスが、後述するガラス基板の製造方法に適している。上記歪点は650℃以上であることがより好ましく、690℃以上であることがよりいっそう好ましく、730℃以上であることが特に好ましい。
本実施形態のガラス基板の製造方法によって製造されるガラス基板は、液晶ディスプレイ、プラズマディスプレイ、有機ELディスプレイ等のディスプレイ用ガラス基板やディスプレイを保護するカバーガラスとして、特に適している。ディスプレイ用ガラス基板を用いるディスプレイには、ディスプレイ表面がフラットなフラットパネルディスプレイの他、有機ELディスプレイ、液晶ディスプレイであって、ディスプレイ表面が湾曲した曲面ディスプレイが含まれる。ガラス基板は、高精細ディプレイ用ガラス基板として、例えば液晶ディスプレイ用ガラス基板、有機EL(Electro-Luminescence)ディスプレイ用ガラス基板、LTPS(Low Temperature Poly-silicon)薄膜半導体、あるいはIGZO(Indium,Gallium,Zinc,Oxide)等の酸化物半導体を用いたディプレイ用ガラス基板として用いることが好ましい。
ディスプレイ用ガラス基板としては、無アルカリガラス、または、アルカリ微量含有ガラスが用いられる。ディスプレイ用ガラス基板は、高温時における粘性が高い。例えば、102.5ポアズの粘性を有する熔融ガラスの温度は、1500℃以上である。なお、無アルカリガラスは、アルカリ金属酸化物(R2O)を実質的に含まない組成のガラスである。アルカリ金属酸化物を実施的に含まないとは、原料等から混入する不純物を除き、ガラス原料としてアルカリ金属酸化物を添加しない組成のガラスであり、例えば、アルカリ金属酸化物の含有量は0.1質量%未満である。
熔解槽40では、図示されない加熱手段によりガラス原料が熔解され、熔融ガラスGが生成される。ガラス原料は、所望の組成のガラスを実質的に得ることができるように調製される。ガラスの組成の一例として、フラットパネルディスプレイ(FPD)用ガラス基板等のディスプレイ用ガラス基板として好適な無アルカリガラスは、SiO2 50質量%~70質量%、Al2O3 0質量%~25質量%、B2O3 0質量%~15質量%、MgO 0質量%~10質量%、CaO 0質量%~20質量%、SrO 0質量%~20質量%、BaO 0質量%~10質量%を含有する。なお、BaO 0質量%~10質量%に代えて、BaO 0質量%~20質量%としてもよい。ここで、MgO、CaO、SrOおよびBaOの合計の含有量は、5質量%~30質量%である。
次に、本実施形態における清澄装置の清澄管41の構成について詳細に説明する。なお、清澄装置は、清澄管41の他に、通気管41a、加熱電極41b、及び、清澄管41の外周を囲む図示されない耐火物保護層及び耐火物レンガを含む。図3は、清澄管41を主に表す外観図である。図4は、清澄管41の内部を表す断面図と清澄管の温度プロファイルの一例を示す図である。
このような清澄管41の内部を流れる熔融ガラスGの温度は、清澄管41を流れる電流を制御することで制御することができる。
加熱電極41bは清澄管41に一対設けられるが、加熱電極41bの数は特に制限されない。加熱電極41bの電流量を制御することで、清澄管41の気相空間41cと接する壁の温度は、例えば1500~1750℃の範囲に制御される。
このため、脱泡処理の途中から、あるいは脱泡処理の終了後から、熔融ガラスGに混入する白金族金属の異物(凝集物)の大きさを低減させる凝集物処理工程を行う。
脱泡処理の終了後から凝集物処理工程を行う場合、白金族金属の異物(凝集物)を含む熔融ガラスGの温度を、白金族金属の異物(凝集物)が熔融ガラスGに混入する領域における熔融ガラスの温度と比べて高くなるように熔融ガラスGを昇温させることが好ましい。
また、脱泡処理工程の途中から凝集物処理工程を行う場合、脱泡処理工程と凝集物処理工程が同時に行われる。脱泡処理工程の途中から凝集物処理工程を行なう場合、脱泡処理工程と凝集物処理工程が同時に行われる場合がある。脱泡処理工程の途中から凝集物処理工程を行う場合、凝集物処理工程において熔融ガラスが最高温度となる。すなわち、脱泡処理工程(熔融ガラス処理工程)は、凝集物処理工程を含んでもよい。
また、本実施形態では、上記凝集物処理工程において、熔融ガラスに混入した白金族金属の異物(凝集物)の熔融ガラスへの溶解度を、熔融ガラス処理工程において白金族金属の異物(凝集物)が熔融ガラスに混入する領域における溶解度に比べて高くなるように溶解度を制御することも好ましい。異物(凝集物)の熔融ガラスGへの溶解度を高くする場合、熔融ガラスGの温度を上昇させることで、凝集物の熔融ガラスへの溶解度を高める、あるいは、熔融ガラスGの温度を上昇させ及び/又は処理時間を長くすることで、異物(凝集物)の熔融ガラスGへの溶解量を高めることができる。
凝集物処理工程前は、最大長さが100μm以上である白金族金属の異物(凝集物)の割合が80%を超える。また、本実施形態では、凝集物処理工程前の白金族金属の異物(凝集物)とは、最大長さの最小長さに対する比であるアスペクト比が100を超える白金族金属の異物を指す。例えば、白金族金属の異物(凝集物)の最大長さが50μm~300μm、最小長さが0.5μm~2μmである。
凝集物の溶解度を調整するための条件としては、例えば、
(a)熔融ガラスに溶けている白金族金属の濃度、
(b)熔融ガラスの温度あるいは温度分布(凝集物に与える熱量)、
(c)気相空間の圧力、
(d)熔融ガラスの酸素活量、が挙げられる。
凝集処理工程開始時の熔融ガラスに溶けている白金族金属の濃度が低いほど、白金処理工程において、熔融ガラス中の白金族金属の異物が溶解する溶解度は上昇する。熔融ガラスの白金族金属の濃度は、例えば、清澄管内の熔融ガラスをサンプリングし、冷却後粉砕してICP定量分析を用いた測定により求めることができる。
白金族金属の濃度を低くし過ぎると、白金族金属の凝集物の溶解度が大きくなる反面、熔融ガラスと接する清澄管の壁から熔融ガラスに白金族金属が溶出して、清澄管の熔損を起こす場合がある。
このようなデメリットの発生を抑える観点から、白金族金属の濃度は、調整されている。
これにより、ガラス基板の製造工程中、白金族金属の凝集物が熔融ガラスに混入しても、白金族金属の凝集物の欠陥個数を許容レベルにしたガラス基板を製造することができる。
清澄管41において、熔融ガラスに混入した白金族金属の凝集物の溶解度は、熔融ガラスの温度を高くすることで増加させることができる。熔融ガラスの温度あるいは温度分布
については、上述しているので説明を省略する。
・リボイル泡の増加
清澄管41において熔融ガラスの温度を高くし過ぎると、脱泡処理工程において過剰に脱泡されるため、熔融ガラスの酸素活量は低くなり、その結果、熔融ガラスは還元状態になる。この状態で、吸収処理工程が行われると、以下のメカニズムに従って、熔融ガラス中にリボイル泡が過剰に発生して、ガラス基板にリボイル泡の気泡が残存する場合がある。リボイル泡は、具体的には、熔融ガラスに不純物として含まれる硫黄や炭素に起因して生じたSO2あるいはCO2等を含む泡である。熔融ガラスの還元状態が時間的に長くなる場合、熔融ガラスに溶存しているSO3、CO3が容易に還元されることでSO2、CO2が生成しやすい。このSO2、CO2はSO3、CO3に比べて熔融ガラスに溶解されにくいために気泡となりやすい。このようなリボイル泡が多く発生すると、ガラス基板に泡欠陥として残り、ガラス基板の品質を低下させる場合がある。なお、ガラス基板に残存した泡は、例えば、レーザ顕微鏡または目視により検出される。
・ガラス成分の揮発量の増加
清澄管41において熔融ガラスの温度を高くし過ぎると、熔融ガラスの成分、例えばB2O3が気相空間に多く揮発する。この結果、ガラス組成が局部的に変化してガラスの熱膨張係数や粘度等のガラス特性が局所的に変わり、脈理等のスジをガラス基板に発生させる。
・白金族金属の揮発量の増加
清澄管41において、熔融ガラスの温度を高くし過ぎると、熔融ガラスに接する気相空間の温度も高くなり、さらには、熔融ガラスの脱泡処理によって気相空間に放出された酸素の量が多くなり、その結果、気相空間を囲む清澄管の壁から白金族金属が揮発しやすくなる。白金族金属の揮発量が増えると、気相空間の白金族金属の濃度が高くなり、凝集および凝集物の熔融ガラスへの混入が起きやすくなる。
・清澄管の熔損
清澄管41において、熔融ガラスの温度を高くし過ぎると、熔融ガラスに接する清澄管41の壁が熔損してしまう場合がある。
このようなデメリットの発生を抑える観点から、清澄管41における熔融ガラスの温度あるいは温度分布の調整が行われる。
白金族金属の凝集物の溶解度は、清澄管41の気相空間41cの圧力を高くすることで増加させることができる。気相空間の圧力とは、気相空間に含まれる気体の全圧を意味する。
気相空間41cの圧力の調整は、例えば、気相空間41c内の気体が通気管41aを通って清澄管41の外側に吸引される量(吸引量)や、清澄管41内へのガス、例えば不活性ガスの供給量、熔融ガラスから放出されるガスの放出量を調整することによって行うことができる。吸引量は、例えば、清澄管41の通気管41aの出口を吸引装置と接続したり、上記出口を狭める等して、気相空間41cと清澄管41の外側の大気との圧力差の大きさを調節することで調整できる。熔融ガラスから放出されるガスの放出量は、例えば、熔融ガラスに含まれる清澄剤の量、ガラス成分の配合比を調整することで調整できる。なお、気相空間41cの圧力が、清澄管41の外側の大気圧より高いまたは低いことは、例えば、通気管41aから放出されるガス量によって求めることができる。
熔融ガラス中の異物を熔融ガラスに溶かすために、気相空間41cの圧力を高くする方法は、上述したように、清澄管41内へのガスの供給量、例えば不活性ガスの供給量、あるいは熔融ガラスから放出されるガスの放出量を調整することによって行うことができる。気相空間41cの圧力は例えば0.8~1.2atmの範囲で調整されることが好ましい。
・清澄不良
気相空間41c内の圧力を高くし過ぎると、脱泡処理工程において、熔融ガラス中に発生した泡が熔融ガラスの表面から放出され難くなり、清澄不良を招く場合がある。
・白金族金属の揮発量の増加
気相空間41c内の圧力を高くし過ぎると、清澄管41の外側の大気との圧力差が大きくなって、気相空間41内の気流の流速が上昇する。このため、気相空間41c内の白金族金属の濃度が上昇せず飽和状態になり難いため、清澄管41の壁からの白金族金属の揮発量が増加する。
このようなデメリットの発生を抑える観点から、気相空間の圧力の調整が行われる。
清澄管41において、白金族金属の凝集物の溶解度は、熔融ガラスの酸素活量を上昇させることにより、増加させることができる。熔融ガラスの酸素活量とは、熔融ガラスに溶存する酸素量(気泡として熔融ガラス中に存在するものを除く)を意味する。本実施形態では、酸素活量の指標として、[Fe3+]/([Fe2+]+[Fe3+])が用いられる。ここで、[Fe2+]及び[Fe3+]は、熔融ガラスに含まれるFe2+及びFe3+の活量であり、具体的には、質量百分率表示含有量であり、分光光度法を用いて計測することができる。
例えば、清澄工程における脱泡処理工程では、熔融ガラスの温度が高くなって、熔融ガラスに溶存する酸素が気泡となって脱泡されるため、熔融ガラスの酸素活量は低下する。一方、清澄工程において、熔融ガラスの温度が低くなると、清澄剤が酸素を取り込むため、酸素活量は増大する。
熔融ガラスの酸素活量は、例えば、熔解工程において、熔融ガラスに含まれる清澄剤、酸化物の量を調整することのほか、熔融ガラスに含まれる清澄剤あるいはガラス原料の酸化物の量を調整することのほか、清澄工程において、凝集物処理工程開始前の熔融ガラスの温度を調整すること、あるいは凝集物処理工程開始前に熔融ガラス内に酸素含有ガスをバブリングすることによって調整することができる。
熔融ガラス中の酸素活量の調整は、熔融ガラスの温度あるいは温度分布の調整とともに行われてもよい。また、熔融ガラス中の酸素活量を調整は、気相空間41cの圧力の調整とともに行われてもよい。熔融ガラス中の酸素活量を調整は、上述したように、熔融ガラスに含まれる清澄剤あるいはガラス原料の酸化物の量を調整することのほか、清澄工程において、凝集物処理工程開始前の熔融ガラスの温度を調整すること、あるいは、凝集物処理工程開始前に熔融ガラス内に酸素含有ガスをバブリングすることによって調整することができる。凝集物処理工程中、酸素活量の指標である[Fe3+]/([Fe2+]+[Fe3+])を例えば0.2~0.5の範囲で調整することが好ましい。
・白金族金属の揮発量の増加
熔融ガラスの酸素活量を大きくし過ぎると、脱泡処理工程において熔融ガラスから気相空間に放出される酸素量が増加し、気相空間の酸素濃度が上昇するため、白金族金属が容易に酸化されて揮発しやすくなる。白金族金属が揮発しやすくなると、白金族金属の凝集物が生成しやすく、熔融ガラスに混入しやすくなる。
・酸素泡の熔融ガラス中の残存
熔融ガラスの酸素活量を大きくし過ぎると、吸収処理工程において、還元された清澄剤が酸素を取り込めなくなり、酸素を含んだ泡(酸素泡)が熔融ガラス中に生成され、ガラス基板において泡として残るため、ガラス基板の品質を低下させやすくなる。
このようなデメリットの発生を抑える観点から、熔融ガラスの酸素活量の調整によって白金族金属の凝集物の溶解量を大きくする際には、適宜条件パラメータ(熔融ガラスの温度等)を組み合わせて調整することが好ましい。
ガラス基板中の白金族金属の凝集物の欠陥は、ガラス基板の表面に斜め方向からレーザ光等の光を入射させ、その反射光を受光することを、ガラス基板の各位置で行ない、受光により得られた画像から白金族金属の凝集物の形状に合致する領域を特定することにより、検出することができる。凝集物の欠陥は、このように装置を用いて行う代わりに目視によって検出してもよい。この凝集物の欠陥個数の許容レベルは、単位質量で表したとき、例えば0.02個/kg以下である。上記許容レベルは、ガラス基板のユーザが求める、歪みや主表面の凹凸に関するスペックに応じて変化する。
例えば、ガラス基板において検出された欠陥個数が許容レベルを超えていた場合は、熔融ガラスの温度を高くして、熔融ガラスにおける白金族金属の飽和溶解度を高くし、これにより、熔融ガラスに混入した凝集物の溶解を促進させる。一方、ガラス基板において検出された欠陥個数が許容レベルにある場合は、許容レベルにある欠陥個数の上限値と対応する熔融ガラスの温度より高い範囲内で低くすることができる。このように熔融ガラスの温度を調整することで、白金族金属の飽和溶解度を適正な範囲に調整することができ、これにより、ガラス基板に含まれる凝集物の欠陥個数を許容レベルにしつつ、リボイル泡の増加等に起因して生じるガラス基板の品質の低下を抑制できる。
熔融ガラスの温度調整は、具体的に、ガラス処理装置が清澄管を含む清澄装置である場合は、清澄管に電流を流して通電加熱することによって行うことができる。電流量は、加熱電極に印加される電圧の大きさによって調整することができる。また、熔融ガラスの温度調整は、通電加熱に代えてまたは通電加熱と組み合わせて、清澄管の周囲に配した図示されないヒータによって間接的に調整されてもよい。ヒータは、例えば、耐火物保護層や耐火物レンガの内部または外側に配置される。また、熔融ガラスの温度調整は、耐火物保護層や耐火物レンガを用いて清澄管からの放熱量を調整することで行われてもよい。
凝集物処理工程後に熔融ガラス、ガラス基板、又はガラス基板積層体に含まれる白金族金属の異物(凝集物)のうち、最大長さが50μm超である異物(凝集物)の個数の割合は30%未満に減少する。
例えば、環境負荷低減のために、熔融ガラスの清澄剤として酸化スズが用いられることが好ましいが、酸化スズは、As2O3やSb2O3と比較して、清澄効果(酸化反応)が得られる温度が高い。このため、酸化スズを清澄剤とした用いた場合、As2O3やSb2O3を清澄剤とした用いた場合と比較して清澄管41の温度を高くして、熔融ガラスGの温度を高くする必要がある。すなわち、清澄剤として酸化スズを使用するため、従来よりも清澄管41の揮発(酸化)が生じ易くなり、白金族金属の揮発及び凝集の問題が生じ易い。このように、清澄剤として酸化スズを用いることで、白金族金属の異物(凝集物)が熔融ガラスに混入する量が増加したとしても、本実施形態のように、白金族金属の異物の大きさを低減することができるので、ガラス基板に歪が生じ難く、ガラス基板の主表面の凹凸を作りにくくすることができるといった効果が顕著になる。すなわち、表示不良を引き起こすような異物(凝集物)の量を十分に低減できる。
例えば、ディスプレイパネルに用いるガラス基板には、薄膜トランジスタが形成されるが、薄膜トランジスタの動作に悪影響を与えないように、ガラス基板には、無アルカリガラスあるいはアルカリ微量含有ガラスを用いることが好ましい。無アルカリガラスあるいはアルカリ微量含有ガラスは、ソーダガラス等のアルカリ含有ガラスと比較して、粘性が高いため、清澄工程において泡の浮上速度が遅く、清澄することが難しい。このため、清澄効果を十分に得るためには、清澄管41の温度を高くして、熔融ガラスGの温度を高くする必要がある。つまり、製造する対象が無アルカリガラスあるいはアルカリ微量含有ガラスであるため、アルカリガラスよりも清澄管41の揮発(酸化)が生じやすくなっており、白金族金属の揮発及び凝集の問題が生じ易い。このように、無アルカリガラスあるいはアルカリ微量含有ガラスを用いるために、清澄管41の温度を高くして、白金族金属の異物(凝集物)が熔融ガラスに混入する量が増加したとしても、本実施形態のように、白金族金属の異物の大きさを低減することができるので、ガラス基板に歪が生じ難く、ガラス基板の主表面の凹凸を作りにくくすることができるといった効果が顕著になる。すなわち、表示不良を引き起こすような異物(凝集物)の量を十分に低減できる。
なお、ディスプレイ用ガラス基板には、ガラス基板の歪点が600℃以上、より好ましくは650℃以上であることが求められるが、ガラス基板の歪点が600℃以上であると、表示不良を引き起こすような大きさの異物(凝集物)の量を十分に低減できる本実施形態の効果が顕著となる。また、高精細ディスプレイ用ガラス基板には、より歪点が高いことが求められ、歪点が690℃以上であることが好ましく、730℃以上であることがより好ましい。このように歪点が690℃以上、730℃以上であると、本実施形態の上述した効果がより顕著になる。
また、本実施形態で用いられる酸化スズを含む熔融ガラスの粘度は、1500℃以上の温度、例えば1500℃~1700℃、あるいは1550℃~1650℃の温度において、粘度が102.5ポアズであることが好ましい。この場合、本実施形態の上述した効果がより顕著になる。
また、本実施形態で製造されるガラス基板の板厚を0.005mm~0.8mm、好ましくは0.01mm~0.5mm、より好ましくは0.01mm~0.2mmとする場合、本実施形態の上述した効果がより顕著になる。このような板厚の薄いガラス基板を製造すると、異物(凝集物)がガラス表面にあらわれて表面凹凸を形成し易くなる。本実施形態では、このような板厚に起因する問題を上述した効果により解消することができる。
本実施形態の効果を確認するために、図1に示す凝集物処理工程S2Bを含んだ製造工程でガラス基板を作製した(実施例)。凝集物処理工程S2Bでは、凝集物に与える熱量の制御を行なった。
ガラス基板の作製条件は下記の通りである。
ガラス基板のガラスの組成は、SiO2 60.7質量%、Al2O3 17質量%、B2O3 11.5質量%、MgO 2質量%、CaO 5.6質量%、SrO 3質量%、SnO2 0.2質量%、であり、歪点は660℃であり、板厚は0.4mmであった。
また、図1に示す凝集物処理工程S2Bを行わず、脱泡処理工程S2A後、吸収処理工程S2Cを行った従来の製造工程でガラス基板を上述の作製条件で作製した。 具体的には、下記表1に示す例1~5では、清澄管41における熔融ガラスGの最高温度を1670℃~1720℃にし、熔融ガラスGの温度が1670℃以上となる時間を40分とした。一方、例6,7では、熔融ガラスGの最高温度を1670℃未満にし、熔融ガラスGの温度が1670℃以上となる時間を0分とした。
41 清澄管
41a 通気管
41b 加熱電極
41c 気相空間
42 成形装置
52 成形体
43a,43b.43c 移送管
100 攪拌装置
200 ガラス基板製造装置
Claims (19)
- ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
前記熔融ガラスに混入した凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が70%以上になるように、前記熔融ガラスに混入した凝集物の大きさを小さくする凝集物処理工程を備えることを特徴とするガラス基板の製造方法。 - ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスからなる液相と、前記熔融ガラスの液面と壁から形成される気相空間とを有し、前記気相空間を囲む壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、
前記熔融ガラス処理工程で熔融ガラスに混入した凝集物のうち、最大長さが50μm以下である凝集物の個数の割合が70%以上になるように、前記熔融ガラスに混入した凝集物の大きさを小さくする凝集物処理工程と、を備えることを特徴とするガラス基板の製造方法。 - ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスの導入により、前記熔融ガラスの表面と壁に囲まれた気相空間が形成される空間を有し、前記壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
前記熔融ガラスに混入した凝集物の大きさが小さくなるように、前記熔融ガラスにおける前記凝集物の溶解度を調整する凝集物処理工程、を備えることを特徴とするガラス基板の製造方法。 - ガラスの原料を熔解して熔融ガラスを生成する熔解工程と、
前記熔融ガラスからなる液相と、前記熔融ガラスの液面と壁から形成される気相空間とを有し、前記気相空間を囲む壁の少なくとも一部が白金族金属を含む材料で構成されたガラス処理装置において前記熔融ガラスを処理する工程であって、前記熔融ガラスの処理時、前記気相空間に存在する、前記壁から揮発した白金族金属の揮発物の凝集物が異物として前記熔融ガラスに混入する熔融ガラス処理工程と、を備え、
さらに、前記凝集物に与える熱量が、前記熔融ガラスに混入した前記凝集物の大きさを小さくすることができる最小熱量以上となるように、前記凝集物に与える熱量を制御する凝集物処理工程、を備えることを特徴とするガラス基板の製造方法。 - 前記気相空間と接する前記壁の最高温度と最低温度との差を5℃以上にし、
前記気相空間は酸素を含む、請求項1~4のいずれか1項に記載のガラス基板の製造方法。 - 前記凝集物処理工程では、前記凝集物を含む前記熔融ガラスの温度を、前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における熔融ガラスの温度と比べて高くなるように昇温させる、請求項1~5のいずれか1項に記載のガラス基板の製造方法。
- 前記凝集物処理工程では、前記凝集物の熔融ガラスへの溶解度を、前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における前記溶解度に比べて高くする、請求項1~6のいずれか1項に記載のガラス基板の製造方法。
- 前記ガラス処理装置は、清澄管を有する清澄装置であり、
前記熔融ガラスは、前記清澄管を流れ、
前記清澄管内の前記気相空間は、前記熔融ガラスの流れの方向に沿って形成され、
前記凝集物処理工程は、前記清澄管で行われる、請求項1~7のいずれか1項に記載のガラス基板の製造方法。 - 前記熔融ガラス処理工程では、前記熔融ガラスに含まれる酸化スズを用いて前記熔融ガラス中の泡数を低減する清澄処理を行い、
前記熔融ガラスは、前記ガラス処理装置を流れ、
前記気相空間と接する前記壁には、前記熔融ガラスの流れの方向に沿って温度分布を形成させ、
前記気相空間には、前記熔融ガラスの流れの方向に沿って酸素濃度分布を形成させる、請求項1~8のいずれか1項に記載のガラス基板の製造方法。 - 前記熔融ガラスは、前記ガラス処理装置を流れ、
前記凝集物処理工程は、前記ガラス処理装置で行われ、前記ガラス処理装置を流れる熔融ガラスのうち、前記気相空間における熔融ガラスの流れ方向において、酸素濃度が最も高くなる領域と対応する位置を流れる熔融ガラスに対して行われる、請求項1~9のいずれか1項に記載のガラス基板の製造方法。 - 前記気相空間中の酸素濃度を、0%超であって、1.0%以下にし、前記気相空間と接する前記壁の最高温度と最低温度の差を、5℃以上であって、150℃以下にする、請求項1~10のいずれか1項に記載のガラス基板の製造方法。
- 前記凝集物処理工程における前記熔融ガラスの温度を、1670℃~1730℃の温度範囲とするように熔融ガラスの温度を制御する、請求項1~11のいずれか1項に記載のガラス基板の製造方法。
- 前記熔融ガラス処理工程において凝集物が熔融ガラスに混入する領域における前記熔融ガラスの温度を、1580℃~1660℃の温度範囲とするように熔融ガラスの温度を制御する、請求項1~12のいずれか1項に記載のガラス基板の製造方法。
- 前記熔融ガラス処理工程は、前記凝集物処理工程を含む、請求項1~13のいずれか1項に記載のガラス基板の製造方法。
- 前記ガラス基板は、ディスプレイ用ガラス基板である、請求項1~14のいずれか1項に記載のガラス基板の製造方法。
- 前記凝集物処理工程開始時の前記熔融ガラス中に溶けている白金族金属の濃度を、0.05~20ppmにする、請求項1~15のいずれか1項に記載のガラス基板の製造方法。
- 前記凝集物処理工程では、ガラス基板の[Fe3+]/([Fe2+]+[Fe3+])が0.2~0.5となる範囲で前記熔融ガラスの前記白金族金属の飽和溶解度を調整する、請求項1~16のいずれか1項に記載のガラス基板の製造方法。
- 複数枚のガラス基板が積層されて形成されるガラス基板積層体であって、
前記ガラス基板積層体の前記ガラス基板の体積の合計は0.1m3以上であり、
前記ガラス基板積層体が含む全白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上である、ことを特徴とするガラス基板積層体。 - ガラス基板が含む白金族金属の凝集物のうち、最大長さが50μm以下である凝集物の個数の割合は、70%以上である、ことを特徴とするガラス基板。
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