JP2015199639A - Manufacturing method for glass substrate and manufacturing apparatus for glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress platinum group metal from being oxidized to volatilize.SOLUTION: There is provided a manufacturing method for a glass substrate in which a molten glass is processed using a processing device which processes the molten glass. The manufacturing method for a glass substrate includes: supplying a molten glass into the processing device which has its inner wall made at least partially of a material including platinum group metal so that a vapor phase space is formed over the liquid level of the molten glass; making a gas which is inert to the platinum group metal flow into the vapor phase space; sucking the gas in the vapor phase space from an exhaust port connecting the vapor phase space and the space outside the processing device to each other; measuring the oxygen concentration in the gas sucked from the exhaust port; and adjusting the inflow rate of the gas which is inert to the platinum metal into the vapor phase space so that the oxygen concentration is 5.0% or less.

Description

  The present invention relates to a glass substrate manufacturing method and a glass substrate manufacturing apparatus for manufacturing a glass substrate.

  Generally, a glass substrate is produced through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above process includes a process of removing minute bubbles contained in the molten glass (hereinafter also referred to as clarification). The clarification is performed by passing a molten glass containing a clarifier in the clarifier tube body while heating the clarifier tube body, and removing bubbles in the molten glass by an oxidation-reduction reaction of the clarifier. More specifically, after raising the temperature of the molten glass that has been melted and melted, the fining agent floats and defoamed, and then the temperature is lowered to melt the relatively small bubbles that remain without being defoamed. The glass is made to absorb. That is, clarification includes a process for floating and defoaming bubbles (hereinafter also referred to as a defoaming process or a defoaming process) and a process for absorbing small bubbles into molten glass (hereinafter also referred to as an absorption process or an absorbing process).

  The inner wall of the member in contact with the high-temperature molten glass before forming needs to be made of an appropriate material according to the temperature of the molten glass in contact with the member, the required quality of the glass substrate, and the like. For example, it is known that a material constituting the above-mentioned clarification tube main body is usually a simple substance or an alloy of a platinum group metal (Patent Document 1). Platinum group metals have a high melting point and are excellent in corrosion resistance against molten glass.

JP 2010-111533 A

  When the molten glass passes through the treatment apparatus in which the platinum group metal is used for the inner wall surface, the platinum group metal volatilizes as an oxide in a portion in contact with the gas phase space (atmosphere containing oxygen) on the heated inner surface. On the other hand, the oxide of the platinum group metal is reduced at a position where the temperature locally decreases in the processing apparatus, and the reduced platinum group metal adheres to the inner wall surface. The platinum group metal adhering to the inner wall surface may drop into the molten glass during the defoaming process and enter the glass substrate as a foreign substance.

  An object of this invention is to provide the manufacturing method and manufacturing apparatus of a glass substrate which can suppress that a platinum group metal is oxidized and volatilizes, and can manufacture a high quality glass substrate.

In order to solve the above-mentioned problem, a first aspect of the present invention is a method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the liquid surface of the molten glass,
By sucking the gas in the gas phase space from an exhaust port connecting the gas phase space and the external space of the processing apparatus, an inert gas with respect to the platinum group metal flows into the gas phase space,
Measure the oxygen concentration in the gas sucked from the exhaust port,
An inflow amount of a gas inert to the platinum group metal is adjusted so that the oxygen concentration is in a range of 5.0% or less.

Here, the gas inert to the platinum group metal is a gas inert to the platinum group metal at the temperature of the gas phase space when the molten glass is processed in the processing apparatus, and the reactivity with the platinum group metal. Is a gas lower than oxygen, for example, nitrogen (N ₂ ), rare gas (eg, argon (Ar)), carbon monoxide (CO), or the like.

  It is preferable to adjust the suction pressure from the exhaust port so that the oxygen concentration falls within a range of 5.0% or less. Furthermore, it is preferable to adjust the supply amount of the inert gas with respect to the platinum group metal so that the oxygen concentration is in the range of 0.1% to 3.0%.

  It is preferable that an inert gas with respect to the platinum group metal is supplied to the gas phase space from the upstream side and the downstream side of the molten glass to the processing apparatus.

  The gas inert to the platinum group metal supplied from the upstream side of the molten glass may be made larger than the gas inert to the platinum group metal supplied from the downstream side of the molten glass. preferable.

  A gas inert to the platinum group metal is preferably preheated before flowing into the gas phase space. For example, it is preferable that a gas inert to the platinum group metal is preheated to 500 ° C. or higher before flowing into the gas phase space.

The processing device is a clarification processing device for clarifying the molten glass,
The maximum temperature of the molten glass in the clarification apparatus is preferably 1600 to 1720 ° C.

2nd aspect of this invention is a manufacturing apparatus of the glass substrate which processes molten glass using the clarification processing apparatus which clarifies molten glass,
A clarification treatment apparatus in which at least a part of the inner wall is made of a material containing a platinum group metal, a molten glass is supplied into the interior, and a gas phase space is formed above the liquid surface of the molten glass;
A gas supply device for supplying a gas other than oxygen to the gas phase space;
An exhaust port connecting the gas phase space and the external space of the clarification processing apparatus;
A suction device for allowing a gas other than oxygen to flow into the gas phase space by sucking the gas in the gas phase space from the exhaust port;
An oxygen concentration meter for measuring the oxygen concentration in the gas sucked from the exhaust port;
And a control device that adjusts the suction pressure from the exhaust port so that the oxygen concentration falls within a predetermined range according to the measurement result of the oxygen concentration meter.

  According to the present invention, by adjusting the suction pressure from the exhaust port so that the oxygen concentration in the gas sucked from the exhaust port is within a predetermined range, the oxygen concentration in the gas phase space in the processing apparatus can be set to a desired value. Can be adjusted to range. Thereby, volatilization of the platinum group metal due to an increase in the oxygen concentration in the gas phase space can be suppressed, and the deposited amount of the volatilized platinum group metal can be reduced.

It is a figure which shows the flow of the manufacturing method of a glass substrate. It is the schematic of the manufacturing apparatus of a glass substrate. It is the schematic of the clarification pipe | tube shown in FIG. It is a vertical sectional view in the longitudinal direction of the clarification tube.

The glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention will be described below.
The “processing apparatus” of the present invention includes a melting tank, a clarification pipe, a stirring tank and a molding apparatus, a transfer pipe for transferring molten glass between them, and a supply pipe for supplying glass to these apparatuses. . “Processing” in the processing apparatus includes glass melting processing, molten glass clarification processing, stirring processing, molding processing, and molten glass transfer processing and supply processing.

(Overall overview of glass substrate manufacturing method)
Drawing 1 is a figure showing an example of a process of a manufacturing method of a glass substrate of this embodiment. The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and a cutting step ( ST7) is mainly included. In addition, a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like may be included. The manufactured glass substrate is laminated in a packing process as necessary, and is transported to a supplier.

In the melting step (ST1), molten glass is made by heating the glass raw material. The molten glass can be heated by energization heating in which electricity is supplied to the molten glass to generate heat. Further, the glass raw material can be melted by auxiliary heating with a burner flame.
In addition, molten glass contains a clarifier. As a fining agent, tin oxide, arsenous acid, antimony, and the like are known, but not particularly limited. However, it is preferable to use tin oxide as a clarifying agent from the viewpoint of reducing environmental burden.

In the clarification step (ST2), when the molten glass is heated, bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated. This bubble grows by absorbing oxygen generated by the reductive reaction of the fining agent, and floats on the liquid surface of the molten glass and is released. Thereafter, in the clarification step, by reducing the temperature of the molten glass, the reducing substance obtained by the reduction reaction of the clarifier undergoes an oxidation reaction. Thereby, gas components, such as oxygen in the bubble which remain | survives in molten glass, are reabsorbed in molten glass, and a bubble lose | disappears. The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass.
In addition, the clarification process can also use the reduced pressure defoaming system which grows the bubble which exists in molten glass in a reduced pressure atmosphere, and defoams. The vacuum degassing method is effective in that no clarifier is used. However, the vacuum degassing method makes the apparatus complicated and large. For this reason, it is preferable to employ | adopt the clarification method which raises molten glass temperature using a clarifier.

In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass using a stirrer. Thereby, the composition unevenness of the glass which is a cause of striae or the like can be reduced.
In the supplying step (ST4), the stirred molten glass is supplied to the molding apparatus.

The molding step (ST5) and the slow cooling step (ST6) are performed by a molding apparatus.
In the forming step (ST5), the molten glass is formed into a sheet glass to make a flow of the sheet glass. An overflow downdraw method is used for molding.
In the slow cooling step (ST6), the sheet glass that has been formed and flowed is cooled to a desired thickness, so that internal distortion does not occur and warpage does not occur.
In the cutting step (ST7), the sheet glass after slow cooling is cut into a predetermined length to obtain a plate-like glass substrate. The cut glass substrate is further cut into a predetermined size to produce a glass substrate having a target size.

FIG. 2 is a schematic view of a glass substrate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting apparatus 100, a forming apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 101, a clarification pipe 120, a stirring tank 103, transfer pipes 104 and 105, and a glass supply pipe 106.
The melting tank 101 shown in FIG. 2 is provided with heating means such as a burner (not shown). A glass raw material to which a clarifying agent is added is charged into the melting tank, and a melting step (ST1) is performed. The molten glass melted in the melting tank 101 is supplied to the clarification tube 120 through the transfer tube 104.
In the clarification tube 120, the temperature of the molten glass MG is adjusted, and the clarification step (ST2) of the molten glass is performed using the oxidation-reduction reaction of the clarifier. The clarified molten glass is supplied to the stirring tank through the transfer pipe 105.
In the stirring vessel 103, the molten glass is stirred by the stirrer 103a and the homogenization step (ST3) is performed. The molten glass homogenized in the stirring tank 103 is supplied to the forming apparatus 200 through the glass supply pipe 106 (supply process ST4).
In the forming apparatus 200, a sheet glass is formed from molten glass by an overflow down draw method (forming step ST5) and gradually cooled (slow cooling step ST6).
In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass is formed (cutting step ST7).

(Configuration of clarification tube)
Next, the configuration of the clarification tube 120 will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic view showing the configuration of the clarification tube 120 of the embodiment, and FIG. 4 is a vertical sectional view in the longitudinal direction of the clarification tube 120.
As shown in FIGS. 3 and 4, electrodes 121 a and 121 b are provided on the outer peripheral surfaces at both ends in the length direction of the clarification tube 120, and an exhaust pipe is provided on the wall in contact with the gas phase space of the clarification tube 120. 127 is provided.

The main body of the clarification tube 120, the electrodes 121a and 121b, and the exhaust pipe 127 are made of a platinum group metal. In this specification, the “platinum group metal” means a metal composed of a platinum group element, and is used as a term including not only a metal composed of a single platinum group element but also an alloy of the platinum group element. Here, the platinum group element refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). Platinum group metals are expensive, but have a high melting point and excellent corrosion resistance against molten glass.
In the present embodiment, a case where the clarification tube 120 is made of a platinum group metal will be described as a specific example. However, a part of the clarification tube 120 may be made of a refractory or other metal. .

The electrodes 121 a and 121 b are connected to the power supply device 122. When a voltage is applied between the electrodes 121a and 121b, a current flows through the clarification tube 120 between the electrodes 121a and 121b, and the clarification tube 120 is energized and heated. By this energization heating, the maximum temperature of the main body of the clarification tube 120 is heated to, for example, 1600 ° C. to 1750 ° C., more preferably 1630 ° C. to 1750 ° C., and the maximum temperature of the molten glass supplied from the transfer tube 104 is The mixture is heated to a temperature suitable for defoaming, for example, 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C.
Further, by controlling the temperature of the molten glass by energization heating, the viscosity of the molten glass can be adjusted, and thereby the flow rate of the molten glass passing through the clarification tube 120 can be adjusted.

The electrodes 121a and 121b may be provided with a temperature measurement device (thermocouple or the like) (not shown). The temperature measuring device measures the temperature of the electrodes 121 a and 121 b and outputs the measured result to the control device 123.
The control device 123 controls the amount of current that the power supply device 122 supplies to the clarification tube 120, thereby controlling the temperature and flow rate of the molten glass passing through the clarification tube 120. The control device 123 is a computer including a CPU, a memory, and the like.

In this embodiment, the electrode 121a is provided with a purge gas supply pipe 124a for supplying a gas other than oxygen (purge gas) to the gas phase space 120a above the liquid surface of the molten glass in the clarification tube 120. May be. Similarly, the electrode 121b may be provided with a purge gas supply pipe 124b for supplying a purge gas to the gas phase space 120a above the liquid surface of the molten glass in the clarification pipe 120.
The purge gas supply pipe 124a is connected to the purge gas supply apparatus 125a, and purge gas is supplied from the purge gas supply apparatus 125a to the gas phase space 120a in the clarification pipe 120 via the purge gas supply pipe 124a from the upstream side of the molten glass. Similarly, the purge gas supply pipe 124b is connected to the purge gas supply apparatus 125b, and purge gas is supplied from the purge gas supply apparatus 125b to the gas phase space 120a in the clarification pipe 120 through the purge gas supply pipe 124b from the downstream side of the molten glass. .
By adjusting the inner diameters of the purge gas supply pipes 124a and 124b, the amount of purge gas supplied from the purge gas supply pipes 124a and 124b can be adjusted.

As the purge gas, a gas other than oxygen, in particular, a gas inert to the platinum group metal or a gas having a lower reactivity with the platinum group metal than oxygen can be used. Specifically, nitrogen (N ₂ ), a rare gas (eg, argon (Ar)), carbon monoxide (CO), or the like can be used. N ₂ gas is preferred for ease of handling. On the other hand, the purge gas dissolves in the molten glass in the clarification step or the step of lowering the glass temperature after clarification. Ar and CO are more likely to move in the glass structure than N ₂ . Therefore, even when the purge gas dissolved in the molten glass is generated as bubbles, it is easily taken into the glass again during the transfer of the molten glass, and Ar may be adopted from the viewpoint of bubble quality. In FIG. 4, nitrogen is described as an example of the purge gas.
The purge gas supply devices 125a and 125b are controlled by the control device 123, and the supply amount and supply pressure of the purge gas are adjusted.

  An exhaust pipe 127 is provided on the wall of the clarification pipe 120 in contact with the gas phase space. The exhaust pipe 127 is provided above the gas phase space 120a. The exhaust pipe 127 is preferably provided at a position between the upstream end and the downstream end in the flow direction of the molten glass in the clarification pipe 120. The exhaust pipe 127 may have a shape protruding in a chimney shape from the outer wall surface of the main body of the clarification pipe 120 toward the outside. The exhaust pipe 127 communicates the gas phase space 120a (see FIG. 4) with the external space of the clarification pipe 120.

The exhaust pipe 127 is provided with a suction device 129 for sucking the gas in the gas phase space 120a. By reducing the pressure on the exhaust pipe 127 side by the suction device 129 (for example, about 10 Pa from the atmospheric pressure), the oxygen and purge gas in the gas phase space 120a can be efficiently discharged. The suction device 129 is controlled by the control device 123. By controlling the suction pressure by the suction device 129, the oxygen concentration (oxygen partial pressure) in the gas phase space 120a can be reduced. In addition, by controlling the suction pressure, the amount of purge gas supplied from the purge gas supply devices 125a and 125b to the gas phase space 120a can be adjusted.
An oxygen concentration meter 128 is provided in the exhaust pipe 127. The oxygen concentration meter 128 measures the oxygen concentration of the gas sucked from the exhaust pipe 127 and outputs the measurement signal to the control device 123. Note that, when the purge gas is not supplied to the gas phase space 120a, the oxygen partial pressure in the gas sucked from the exhaust pipe 127 may be measured.

  In the present embodiment, oxygen released from the molten glass in the clarification tube 120 can be discharged by sucking the gas in the gas phase space 120 a from the exhaust tube 127. In addition, by supplying purge gas from the purge gas supply pipe 124a and the purge gas supply pipe 124b to the gas phase space 120a, the oxygen concentration in the gas phase space 120a can be reduced. Thereby, it can suppress that a platinum group metal is oxidized and volatilizes, and can reduce the precipitation amount of the platinum group metal by reducing the volatilized platinum group metal.

  Here, in the present embodiment, the oxygen concentration of the gas exhausted from the exhaust pipe 127 is measured by the oxygen concentration meter 128, so that the oxygen concentration falls within a certain range (for example, a range of 5.0% or less). The supply amount of the purge gas is adjusted. That is, the oxygen concentration signal measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 controls the purge gas supply devices 125a and 125b in accordance with the oxygen concentration signal to supply the purge gas supply amount and supply pressure. Adjust.

It is preferable to adjust the suction pressure from the exhaust port or the supply amount of the purge gas so that the oxygen concentration of the gas sucked from the exhaust pipe 127 is in the range of 5.0% or less. If the oxygen concentration is higher than 5.0%, volatilization of the platinum group metal is promoted, and the amount of deposited volatilized platinum group metal may be increased.
In order to further suppress the volatilization / precipitation of the platinum group, it is preferable to adjust the supply amount of the purge gas so that the oxygen concentration is in the range of 3.0% or less. Glass substrates used in the production of high-resolution displays do not allow slight defects with a thickness (diameter) of less than 1 μm, but needles with a thickness (diameter) of less than 1 μm can be obtained by setting the oxygen concentration to 3.0% or less. The generation of platinum defects can be prevented.

In addition, if purge gas is supplied so that oxygen concentration may be less than 0.1%, the temperature of the clarification pipe | tube 120 will fall with purge gas. Further, the purge gas is sprayed onto the liquid surface of the molten glass due to the increase in the supply amount and flow rate of the purge gas, and the purge gas is melted into the molten glass. Then, when the temperature of the molten glass is lowered, there is a possibility that bubbles of the purge gas that has melted are generated. For this reason, it is preferable to adjust the supply amount of the purge gas so that the oxygen concentration becomes 0.1% or more. It is particularly preferable to adjust the supply amount of the purge gas so that the oxygen concentration becomes 1% or more in order to suppress the temperature drop of the clarification tube 120 due to the purge gas and to suppress the generation of bubbles due to the dissolved purge gas.
From the above, it is preferable to adjust the supply amount of the purge gas so that the oxygen concentration is in the range of 0.1% to 3.0%, and the oxygen concentration is in the range of 1% to 3.0%. More preferably, the supply amount of the purge gas is adjusted.
In order to prevent the molten glass from cooling, it is preferable to preheat the purge gas supplied from the purge gas supply devices 125a and 125b before flowing into the gas phase space 120a. The preheating temperature of the purge gas is preferably preheated to 500 ° C. or higher, for example.

  Since the amount of oxygen released from the molten glass in the clarification tube 120 is higher on the upstream side of the molten glass than on the downstream side, the purge gas supplied from the upstream side of the molten glass is supplied from the downstream side of the molten glass. It is preferable to use more than the purge gas. That is, it is preferable that the amount of purge gas supplied from the purge gas supply pipe 124a is larger than the amount of purge gas supplied from the purge gas supply pipe 124b. By making the amount of purge gas supplied from the purge gas supply pipe 124a larger than the amount of purge gas supplied from the purge gas supply pipe 124b, oxygen released from the molten glass is more efficiently diluted with the purge gas and discharged. Can do.

  As mentioned above, although the manufacturing method of the glass substrate of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, you may make various improvement and a change. Of course. In the above description, a clarification tube has been described as an example of the processing apparatus. However, the present invention is not limited to this, and the present invention may be applied to a melting tank, a stirring tank, a molding apparatus, a transfer pipe, and a supply pipe.

  The glass substrate manufactured by the manufacturing method of this embodiment is used suitably for the glass substrate for liquid crystal displays, the glass substrate for organic EL displays, and a cover glass, for example. In addition, it can be used as a display for a portable terminal device, a cover glass for a casing, a touch panel plate, a glass substrate of a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 103 Stirring tank 104, 105 Transfer pipe 106 Glass supply pipe 120 Clarification tank 121a, 121b Electrode 122 Power supply apparatus 123 Control apparatus 124a, 124b Purge gas supply pipe 125a, 125b Purge gas supply apparatus 127 Exhaust pipe 128 Oxygen meter 129 Suction device 200 Molding device 300 Cutting device

Claims (9)

A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the liquid surface of the molten glass,
By sucking the gas in the gas phase space from an exhaust port connecting the gas phase space and the external space of the processing apparatus, an inert gas with respect to the platinum group metal flows into the gas phase space,
Measure the oxygen concentration in the gas sucked from the exhaust port,
A method for producing a glass substrate, wherein an inflow amount of a gas inert to the platinum group metal into the gas phase space is adjusted so that the oxygen concentration is in a range of 5.0% or less.   The manufacturing method of the glass substrate of Claim 1 which adjusts the suction pressure from the said exhaust port so that the said oxygen concentration may become the range of 5.0% or less.   The method for producing a glass substrate according to claim 2, wherein a supply amount of an inert gas with respect to the platinum group metal is adjusted so that the oxygen concentration is in a range of 0.1% to 3.0%. .   The method for producing a glass substrate according to claim 2 or 3, wherein an inert gas with respect to a platinum group metal is supplied to the processing apparatus from the upstream side and the downstream side of the molten glass into the gas phase space.   The gas inert to the platinum group metal supplied from the upstream side of the molten glass is made larger than the gas inert to the platinum group metal supplied from the downstream side of the molten glass. Item 5. A method for producing a glass substrate according to Item 4.   The method for producing a glass substrate according to any one of claims 1 to 5, wherein a gas inert to the platinum group metal is preheated before flowing into the gas phase space.   The method for producing a glass substrate according to claim 6, wherein a gas inert to the platinum group metal is preheated to 500 ° C. or higher before flowing into the gas phase space. The processing device is a clarification processing device for clarifying the molten glass,
The manufacturing method of the glass substrate as described in any one of Claims 1-7 whose maximum temperature of the said molten glass in the said clarification processing apparatus is 1600-1720 degreeC. A glass substrate manufacturing apparatus for processing molten glass using a clarification processing apparatus for clarifying molten glass,
A clarification treatment apparatus in which at least a part of the inner wall is made of a material containing a platinum group metal, a molten glass is supplied into the interior, and a gas phase space is formed above the liquid surface of the molten glass;
A gas supply device for supplying a gas other than oxygen to the gas phase space;
An exhaust port connecting the gas phase space and the external space of the clarification processing apparatus;
A suction device for allowing a gas other than oxygen to flow into the gas phase space by sucking the gas in the gas phase space from the exhaust port;
An oxygen concentration meter for measuring the oxygen concentration in the gas sucked from the exhaust port;
A glass substrate manufacturing apparatus, comprising: a control device that adjusts a suction pressure from the exhaust port so that the oxygen concentration falls within a predetermined range according to a measurement result of the oxygen concentration meter.

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