Method for manufacturing glass substrate for minimizing platinum including and apparatus using same

Abstract

The present invention provides a method for manufacturing a glass substrate for minimizing platinum inclusions, the method treating molten glass by a treatment device, at least a portion of which includes a platinum group metal material, the method comprising the steps of: heating a glass material in a furnace to form molten glass; supplying a treatment device having a high temperature zone and a low temperature zone; the temperature difference of the high-temperature area is controlled to be lower than 30 DEG C, the oxygen partial pressure of the high-temperature area is reduced, and / or the oxygen partial pressure of the low-temperature area is increased; the treated molten glass is supplied to a forming device to form a glass substrate. The present invention also provides an apparatus for manufacturing a glass substrate for minimizing platinum inclusions.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for minimizing platinum inclusions in a glass manufacturing process using platinum structures. Background Art

[0002] Liquid crystal displays (LCDs) are representative flat panel display devices using a rectangular thin glass substrate. In the manufacture of the above-mentioned substrate glass, an overflow down-draw method in which molten glass overflows horizontally is widely used due to the excellent flatness and surface properties of the substrate glass. Parts or containers in the manufacturing device that come into contact with the molten glass are generally made of platinum group metals or platinum group metal alloys, or are coated with platinum group metals or platinum group metal alloys.

[0003] Platinum, as one of the platinum group elements, is a thermodynamically heat-resistant metal that does not oxidize in air even at high temperatures far above its melting point of 1,769°C, and does not oxidize even at its boiling point of 4,170°C. In addition, platinum has low chemical reactivity, low contamination to glass, low glass wettability, excellent shape processability, and can be used as a resistor in a DC heating system. Therefore, it is often used as a material for a container or a conveying path for molten glass in the manufacturing process of a glass substrate.

[0004] However, when platinum contacts molten glass at high temperatures (generally above 1600°C in the manufacture of LCD substrate glass), it reacts with oxygen physically dissolved in the molten glass and then dissolves into the molten glass in the form of an oxide. The reaction between platinum and physically dissolved oxygen in the molten glass is also related to the composition of the glass. More specifically, phosphate glass with a low melting point such as laser glass shows that platinum is oxidized at a relatively low temperature and dissolves into the molten glass.

[0005] In Technical Document 1, as shown in Formula 1, it is reported that platinum reacts with oxygen physically dissolved in molten glass, is oxidized, and is dissolved in the molten glass.

[0006]

[0007] K Pt (T) = [Pt n+ (Glass)]·[O 2- ] n / 2 / [Pt(s)]·aO2 n / 4 (2)

[0008] K' Pt (T) = K Pt (T) · [Pt(s)] / [O 2- ] n / 2 = [Pt n+ (Glass)] / aO2 n / 4(3)

[0009] log[Pt n+ (glass)] = n / 4·log aO2 + log K' Pt (4)

[0010] (s: solid, a: activity, K: equilibrium constant, O2: physically dissolved oxygen)

[0011] The solubility of platinum in glass obtained from the equilibrium constant K of equation 2 is given by equation 4 to equation 3, and the solubility of platinum increases with the increase of oxygen activity, and is proportional to n / 4 of the oxidation state (n) of platinum present in the molten glass, as shown in equation 4. Although it is known that the reaction between platinum and oxygen depends on the oxygen activity in the molten glass, as shown in equations 1 and 2, the thermodynamic free energy data of platinum is still unknown, so the temperature at which the reaction occurs can only be determined by empirical data.

[0012] Oxygen dissolved in the molten glass can be generated by the decomposition of tin dioxide and the decomposition of water and sulfate.

[0013] In another patent document 1, KR 10-1135919, it is disclosed that in the process of manufacturing a glass substrate, an electromotive force is generated due to the contact between a platinum group element or a platinum group element alloy and molten glass. Therefore, a method is provided for applying a potential from the outside to at least a part of the manufacturing process to offset the electromotive force and thus prevent the dissolution of platinum. Although relevant glass companies have developed many technologies to prevent bubbles, there are few countermeasures against the formation principle of platinum inclusions.

[0014] In fact, when the above-mentioned platinum reacts with oxygen physically dissolved in the molten glass and is oxidized and contained in the molten glass in an ion state, it is not a defect. However, due to changes in conditions such as the temperature and oxygen partial pressure of the molten glass, the dissolved platinum oxide is reduced to platinum metal and precipitates, and the platinum becomes a defect called a platinum inclusion. If the platinum inclusion exists near the surface of the glass substrate, the platinum inclusion is likely to appear in the form of a protrusion on the glass substrate. The protrusion on the surface of the glass substrate can cause the pattern to be disconnected or short-circuited during the LCD film forming process, which can cause display defects. At present, there is no clear solution for the control of platinum inclusions in the glass substrate industry.

[0015] [Patent Document]

[0016] (Patent Document 01) Korean Patent No. 10-1135919

[0017] [Technical Literature]

[0018] (Technical Literature 01) M.Yamamoto and R.Akiyama, Reports Res.Lab.Asahi Glass Co., Ltd., 56, 7 (2006) Summary of the invention

[0019] It can be seen that there are two effective ways to reduce platinum inclusion defects. The first way is to minimize the platinum dissolved in the molten glass in the ionic state by reducing the amount of oxygen physically dissolved in the molten glass in the high temperature zone, thereby inhibiting the oxidation of platinum.

[0020] The second approach is to minimize the reduction of platinum by increasing the amount of physically dissolved oxygen in the low temperature region so that platinum dissolved in the molten glass in an ionic state can remain in the ionic state without precipitating as platinum metal.

[0021] Therefore, the present invention is designed to solve the above-mentioned problems, and the above-mentioned problems are solved by the following configurations.

[0022] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

[0023] The present invention provides a method for manufacturing a glass substrate for minimizing platinum inclusions, wherein the method processes molten glass by a processing device, at least a portion of which includes a platinum group metal material, and the method comprises the following steps:

[0024] heating a glass material in a furnace to form a molten glass;

[0025] supplying the molten glass to a processing device having a high temperature zone and a low temperature zone;

[0026] The temperature change of the high temperature zone is controlled and / or a potential is applied to the high temperature zone and / or the low temperature zone.

[0027] According to the above invention, the temperature variation in the high temperature zone is less than 30°C.

[0028] According to the above invention, the potential applied in the high temperature region is positive.

[0029] According to the above invention, the potential applied in the high temperature region is a DC potential.

[0030] According to the above invention, the oxygen partial pressure in the high temperature region is reduced by the applied potential.

[0031] According to the above invention, the potential applied in the low temperature region is negative.

[0032] According to the above invention, the potential applied in the high temperature region is a DC potential.

[0033] According to the above invention, the oxygen partial pressure in the low temperature region is increased by the applied potential.

[0034] According to the above invention, the high temperature zone includes at least the refining tank, and the temperature difference between the refining tank and the platinum tube connecting the refining tank and the furnace is controlled to be less than 30°C.

[0035] According to the above invention, the temperature of the refining tank is 1620°C or higher.

[0036] According to the above invention, the low temperature zone includes at least the stirring tank.

[0037] According to the above invention, the high temperature region is above 1575°C.

[0038] According to the above invention, the low temperature region is below 1400°C.

[0039] According to the above invention, the forming apparatus forms a glass substrate by forming the glass substrate using an overflow down-draw method, a float method, or a slot down-draw method.

[0040] The present invention further provides a manufacturing apparatus for a glass substrate for minimizing platinum inclusions, comprising:

[0041] A furnace that heats glass materials to form molten glass.

[0042] a processing device having a high temperature zone and a low temperature zone, and

[0043] A forming device for forming molten glass into a glass substrate,

[0044] Wherein, the high temperature zone and / or the low temperature zone is provided with a current control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Reference will now be made to the accompanying drawings which illustrate exemplary embodiments of the invention disclosed herein. In the drawings:

[0046] Figure 1 An implementation as an apparatus for manufacturing LCD substrate glass having features of the present invention is shown and schematically described. DETAILED DESCRIPTION

[0047] Reference will now be made in detail to exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, in which the same numbers in different drawings represent the same or similar elements, unless otherwise specified. The embodiments set forth in the following description of the exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with aspects related to the present invention as described in the appended claims.

[0048] In the present invention, the terms "positive potential" and "negative potential" are relative terms, indicating that the potential applied to one end is higher than that of the other end. It does not refer to the absolute potential in electrochemistry.

[0049] Figure 1 An apparatus for manufacturing a glass substrate having features of the present invention is shown and schematically described.

[0050] like Figure 1 As shown, in the manufacturing process of the glass substrate, molten glass 9 is supplied from the furnace 1 to the forming device 8 through the processing device 7. The processing device 7 includes at least a high temperature zone and a low temperature zone. More specifically, the high temperature zone with a temperature of 1575°C or more includes the first platinum tube 3 and the refining tank 4. The low temperature zone with a temperature of 1400°C or less includes the stirring tank 5 and the second platinum tube 6.

[0051] In the high temperature zone, glass is melted in the furnace 1 by a mixture of gas combustion at the upper part and direct current heating through the furnace electrode 2. Then, the molten glass 9 is supplied to the refining tank 4 through the first platinum tube 3 to remove bubbles.

[0052] In the low temperature zone, after the refining process, the molten glass is homogenized in the stirring tank 5 by the stirrer shaft 15 to reduce the non-uniformity of the glass components. Finally, the molten glass 9 is supplied to the forming device 8 through the second platinum tube 6.

[0053] Each part of the processing device 7 can independently adjust the temperature. For example, the first platinum tube 3 and the refining tank 4 in the high temperature zone can each independently adjust its temperature.

[0054] In the forming apparatus 8 , the glass substrate can be formed using an overflow down-draw method, a float method, or a slot down-draw method.

[0055] Generally, in the manufacturing process of substrate glass, when the molten glass 9 in the furnace 1 at a temperature higher than 1600°C directly contacts the platinum (e.g., the first platinum tube 3), the platinum reacts with oxygen physically dissolved in the molten glass 9 in the high temperature region, is oxidized, and is dissolved in the molten glass 9. Thereafter, when the molten glass contacts the platinum at a temperature lower than 1400°C, the platinum is hardly dissolved in the molten glass in the low temperature region, but is reduced and precipitated as platinum inclusions.

[0056] In order to minimize platinum inclusions in the glass manufacturing process, the present invention provides two approaches. The first approach is to minimize the platinum dissolved in the molten glass in an ionic state by reducing the amount of oxygen physically dissolved in the molten glass in the high temperature zone, thereby inhibiting the oxidation of platinum. The second approach is to minimize the reduction of platinum by increasing the amount of oxygen physically dissolved in the low temperature zone, so that the platinum dissolved in the molten glass in an ionic state can remain in the ionic state without being reduced and precipitated as platinum metal.

[0057] For the first approach, the present invention provides two methods for reducing the amount of oxygen physically dissolved in the molten glass. The first method is to control the temperature change in the high temperature zone. The mechanism of the first method is provided as follows.

[0058] The oxygen solubility of molten glass depends on the temperature. That is, when the temperature decreases, the oxygen solubility increases, and when the temperature increases, the oxygen solubility decreases. This means that dissolved oxygen tends to move from a high temperature area to a low temperature area. Therefore, it is important to prevent the molten glass from being partially cooled when it is in a high temperature area.

[0059] In the present invention, the furnace 1 is higher than 1600°C, and the refining tank 4 is maintained at a high temperature of more than 1620°C to easily decompose the refining agent SnO2, thereby removing bubbles. Therefore, the molten glass 9 can be partially cooled while being conveyed through the first platinum tube 3. Therefore, in order to reduce the oxidation of platinum into the molten glass when the molten glass 9 passes through the first platinum tube 3, in the present invention, the temperature difference between the first platinum tube 3 connecting the furnace 1 and the refining tank 4 is controlled to be less than 30°C, so that the oxygen solubility near the wall of the first platinum tube 3 does not increase.

[0060] Therefore, by controlling the temperature difference in the high temperature zone to be less than 30°C, the oxygen solubility near the wall of the first platinum tube (3) can be reduced, thereby reducing the dissolution of platinum into the molten glass.

[0061] Detailed data of the embodiments and comparative examples of the first method of the first approach are shown in Table 1.

[0062] In the present invention, the defect level is evaluated by counting the number of defects in a piece of glass or the number of defects in a kilogram of glass or the number of good glasses per hour. For example, it can be evaluated by counting the number of defective parts per million glass parts.

[0063] [Table 1]

[0064]

[0065] (◎: excellent, ○: good, X: defective)

[0066] The second method is to apply a potential in the high temperature region. The mechanism of the second method is summarized as follows.

[0067] Generally, an AC current is applied to heat the molten glass. When direct current (DC) is generated in the molten glass and electrolysis occurs as shown in the following formula, excessive oxygen will be generated. Therefore, the direct current generated due to various factors such as electrochemical reactions may affect the oxygen partial pressure of the molten glass and may affect the amount of physically dissolved oxygen. For example, if a positive potential is applied to the molten glass and a negative potential is applied to platinum, the alloy reaction of water or SnO as shown in the following formula will be suppressed, and the generation of oxygen will also be suppressed.

[0068] H2O(melt)+Pt→PtxHy(alloy)+1 / 2·O2

[0069] SnO (melt) + Pt → PtxSny (alloy) + 1 / 2·O2

[0070] In the present invention, the first platinum tube current control device 12 is arranged in the high temperature zone to reduce the oxygen partial pressure. The first platinum tube current control device 12 applies a negative potential to the first platinum tube 3 through the first platinum tube current supply line 11, and electrically applies a positive potential to the furnace probe 10. The applied potential is a low voltage of less than 1 volt.

[0071] The detailed data of the embodiments and comparative examples of the second method of the first approach are shown in Table 2.

[0072] [Table 2]

[0073]

[0074] (◎: excellent, ○: good, X: defective, DC: direct current applied)

[0075] The second approach is to minimize the reduction of platinum by increasing the amount of physically dissolved oxygen in the low temperature zone, so that the platinum dissolved in the molten glass in an ionic state can be maintained in an ionic state without being reduced and precipitated as platinum metal. For the second approach, the present invention provides a method for applying an electric potential in the low temperature zone to keep the platinum dissolved in the molten glass in an ionic state. The mechanism of the method is provided as follows.

[0076] It is known that platinum is not a defect when it is oxidized in the ion state in molten glass. Therefore, platinum becomes a defect only when dissolved platinum is reduced to platinum metal and precipitates, such as in a low temperature region.

[0077] More specifically, after the refining process, the molten glass 9 containing SnO formed by the reduction of SnO2 is supplied to the stirring tank 5. As shown below, SnO can react with the residual oxygen in the molten glass 9 again and be oxidized into SnO2, wherein large bubbles become smaller and small bubbles are absorbed and dissipated.

[0078] SnO+1 / 2·O2→SnO2

[0079] Meanwhile, in the low temperature zone including the stirring tank 5, the second platinum tube 6 and the forming device 8 at a temperature below 1400°C, SnO is reduced to PtO x / 2 is the strongest component, and platinum is precipitated by the reaction shown below.

[0080] PtO x / 2 +SnO→Pt+(2+x) / 4·SnO2

[0081] Therefore, increasing the oxygen partial pressure of the molten glass in the low temperature zone can enhance the oxidation of SnO to SnO2, thereby inhibiting the oxidation of PtO x / 2 To achieve the above purpose, in the present invention, a potential is supplied between the molten glass 9 and the stirred tank 5 to increase the oxygen partial pressure of the molten glass 9. More specifically, the stirred tank current control device 16 applies a positive potential to the stirred tank current supply line 13 connected to the wall of the stirred tank 5 and a negative potential to the stirred tank probe 14. The applied potential is a low voltage of 1 volt or less.

[0082] As a result, PtO can be reduced x / 2 Reduction to platinum and precipitation of platinum.

[0083] The detailed data of the embodiment and comparative example of the method are shown in Table 3.

[0084] [Table 3]

[0085]

[0086] (◎: excellent, ○: good, X: defective, DC: direct current applied)

[0087] The above approaches and methods can be combined to minimize platinum inclusions.

[0088] [Industrial Availability]

[0089] The present invention is suitable as a method for minimizing platinum inclusion defects, which are one of the biggest defects of special glasses using platinum structures and LCD substrate glasses, and can be used to produce glasses using platinum structures, such as mobile phone cover glass and ultra-thin flat glass.

[0090] [Description of Reference Signs]

[0091] 1 furnace

[0092] 2 Furnace electrodes

[0093] 3. First platinum tube

[0094] 4 Refining Tanks

[0095] 5. Mixing tank

[0096] 6 Second platinum tube

[0097] 7 Processing device

[0098] 8 Forming device

[0099] 9 Molten Glass

[0100] 10 Furnace probe

[0101] 11 First platinum tube current supply line

[0102] 12. First platinum tube current control device

[0103] 13. Mixing tank current supply line

[0104] 14 Stirred Tank Probe

[0105] 15 Agitator shaft

[0106] 16. Stirring tank current control device

Claims

1. A method for manufacturing a glass substrate for minimizing platinum inclusions, comprising the following steps: heating a glass material in a furnace to form a molten glass; supplying the molten glass to a processing device having a high temperature zone and a low temperature zone; The temperature change of the high temperature zone is controlled and / or a potential is applied to the high temperature zone and / or the low temperature zone.

2. The method for manufacturing a glass substrate according to claim 1, wherein: The temperature variation of the high temperature zone is less than 30°C.

3. The method for manufacturing a glass substrate according to claim 1, wherein: The potential applied to the molten glass in the high temperature zone is positive.

4. The method for manufacturing a glass substrate according to claim 3, wherein: The potential applied in the high temperature region is a DC potential.

5. The method for manufacturing a glass substrate according to claim 3, wherein: The oxygen partial pressure in the high temperature region is reduced by the applied potential.

6. The method for manufacturing a glass substrate according to claim 1, wherein: The potential applied to the molten glass in the low temperature region is negative.

7. The method for manufacturing a glass substrate according to claim 6, wherein: The potential applied in the high temperature region is a DC potential.

8. The method for manufacturing a glass substrate according to claim 6, wherein: The oxygen partial pressure in the low temperature region increases due to the applied potential.

9. The method for manufacturing a glass substrate according to claim 1, wherein: The high temperature zone includes at least a refining tank, and the temperature difference between the refining tank and a platinum tube connecting the refining tank and the furnace is controlled to be less than 30°C.

10. The method for manufacturing a glass substrate according to claim 9, wherein: The temperature of the refining tank is above 1620°C.

11. The method for manufacturing a glass substrate according to claim 1, wherein: The low temperature zone at least includes a stirring tank.

12. The method for manufacturing a glass substrate according to claim 1, wherein: The high temperature zone is above 1575°C.

13. The method for manufacturing a glass substrate according to claim 1, wherein: The low temperature zone is below 1400°C.

14. The method for manufacturing a glass substrate according to claim 1, wherein: The forming apparatus forms a glass substrate by forming the glass substrate using an overflow down-draw method, a float method, or a slot down-draw method.

15. An apparatus for manufacturing a glass substrate for minimizing platinum inclusions, comprising: A furnace that heats glass materials to form molten glass. a processing device having a high temperature zone and a low temperature zone, and A forming device for forming molten glass into a glass substrate, Wherein, the high temperature zone and / or the low temperature zone is provided with a current control device.

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