JP6629557B2 - Glass substrate manufacturing equipment - Google Patents

Description

The present invention relates to a forming apparatus made of glass substrate comprising a surface treatment device for one roughened main surface of the thin glass.

  In manufacturing a flat panel display using a liquid crystal display panel, a plasma display panel, an organic EL display panel, or the like used as a display panel, a higher definition thin film pattern is formed on a thin glass substrate.

  A display panel used for such a flat panel display is manufactured by putting a glass substrate into a manufacturing line, and then carrying out processing steps such as transport, film formation, photolithography, etching, doping, and wiring. In each processing step, the panel including the glass substrate is placed in an environment that is easily charged due to various factors. For example, when a glass substrate is put into a production line, the interleaf is peeled and removed from a plurality of glass substrates laminated with the interleaf interposed therebetween, and the glass substrates are taken out one by one. At this time, the glass substrate is easily charged when the slip sheet is removed. When a semiconductor manufacturing apparatus is used for film formation or the like, a glass substrate is mounted on a mounting table to perform film formation. At this time, the glass substrate is likely to be charged by airflow, contact charging, or peeling charging.

  Such charging causes various problems. For example, when a TFT (Thin Film Transistor) and a wiring pattern are formed on a glass substrate, foreign matter such as dust or dirt adheres to the glass substrate or the wiring pattern due to electrification, and the wiring pattern is damaged or peeled off or accumulated. Discharge of the accumulated electric charges may cause the destruction of the TFT or the like. Further, the glass substrate may be stuck to the mounting table due to charging, and the glass substrate may be broken when the glass substrate is peeled off from the mounting table. Therefore, it is preferable that the glass substrate is not charged as much as possible.

  In particular, the surface of the thin glass formed by the fusion method or the down-draw method is much smoother than that of the thin glass formed by the float method, so that a problem of charging is likely to occur. For this reason, it is preferable that the main surface of the thin glass substrate obtained by the fusion method or the downdraw method is subjected to some treatment for preventing electrification. As a general method, one of the main surfaces of the thin glass substrate is roughened by a chemical method, and charging of the thin glass substrate can be prevented by appropriate roughening. In addition, there is known a method for removing electricity from a charged glass substrate using an ionizer (Patent Document 1). There is also known an exposure apparatus that reduces the amount of static electricity charged on a processing substrate generated in a process of placing, adhering, and removing a processing substrate on which a photosensitive layer and the like are formed on a stage (Patent Document 2).

JP 2009-64950 A JP 2007-322630 A

  In a thin glass substrate for a flat panel display, of the main surface, a main surface on a side where a TFT and a wiring pattern are not formed (hereinafter, referred to as a first surface) is roughened by a chemical treatment or the like to prevent electrification. I do. The main surface on which the TFT and the wiring pattern are formed (hereinafter, referred to as a second surface) is not processed, and dirt and foreign matter must be removed.

  According to the surface treatment method using an etching solution, while it is possible to continuously roughen a plurality of glass substrates, it is not easy to increase the processing speed while keeping the degree of surface roughness within a certain range. . This is because the etching rate of the etchant decreases as the continuous processing proceeds.

  2. Description of the Related Art Conventionally, when performing continuous processing using an etchant, the etchant is completely replaced when the performance of the etchant drops to a certain level without controlling the etching rate. If the frequency of the total replacement of the etching liquid increases, the downtime of the production line increases, the production efficiency decreases, and the cost of waste liquid treatment also increases.

  If the concentration of the etching component in the etching solution is increased, the etching rate can be maintained for a certain period even if the etching solution is repeatedly used in a continuous process, and the timing of the total replacement of the etching solution in the etching bath is required. Can be extended. However, when the concentration of the etching component is increased, the etching performance is rather lowered due to the amount of sludge generated in the etching solution, and the problem of waste liquid treatment is further increased.

  Therefore, the present invention provides a surface treatment step of roughening a glass substrate by continuous treatment, even if an etchant is used repeatedly, without decreasing the etching rate, maintaining the etching rate for a long time, and improving the quality. Provided are a method for manufacturing a glass substrate including a surface treatment step and an apparatus for manufacturing the same, which can efficiently manufacture high-thin glass sheets.

One embodiment of the present invention is a method for manufacturing a glass substrate for a display, comprising a surface treatment step of continuously roughening a first surface of a glass substrate,
In the surface treatment step, the etchant circulates between an etchant tank that adjusts and stores an etchant containing hydrofluoric acid and an etch tank that is supplied with the etchant and roughens the etchant. Circulating the etching solution while replenishing the etching solution tank with hydrofluoric acid so that the etching rate in the bath is maintained, and roughening the first surface of the glass substrate in the etching bath; A method for manufacturing a glass substrate.

  In the etching tank for performing the surface roughening, it is preferable that the rate of decrease in the etching rate (under the condition of processing 400 wafers at 25 ° C.) is set to 10% to 30%.

  It is preferable that the etching solution volume A of the etching solution tank is larger than the etching solution volume B of the etching bath, and the volume A has a capacity of twice or more the volume B.

  Preferably, the circulation of the etching solution is controlled based on the measurement of the etching rate in the etching bath.

  The etching solution preferably has an etching rate at 25 ° C. of 0.1 μm / min or more.

  The manufacturing of the glass substrate for a display according to any one of claims 1 to 3, wherein the etching solution contains at least 0.3 to 10% by mass of hydrofluoric acid and 0.3 to 10% by mass of phosphoric acid. Method.

  The etching solution preferably contains at least 0.3 to 10% by mass of hydrofluoric acid, 0.3 to 10% by mass of phosphoric acid, and 0.3 to 15% by mass of hydrochloric acid.

  The arithmetic mean roughness Ra of the first surface after the surface treatment step is preferably 0.40 nm or more.

One embodiment of the present invention is an apparatus for manufacturing a glass substrate for a display including a surface treatment apparatus,
The surface treatment apparatus, an etching tank for roughening the first surface of the main surface of the glass substrate,
An etchant tank for adjusting and storing the etchant;
A pipe connecting an etching solution inlet port of the etching tank with a supply port of the etching solution tank, and connecting an etching solution outlet of the etching bath with a recovery port of the etching solution tank. An etchant circulation mechanism having a pipe,
A hydrofluoric acid tank that supplies hydrofluoric acid to the etching solution tank as needed,
With
The etching solution volume A of the etching solution tank is twice or more the etching solution volume B of the etching bath.

  The etching solution volume A of the etching solution tank is set such that the rate of decrease in the etching rate (under the conditions of processing 400 wafers at 25 ° C.) of the etching tank for roughening can be controlled to 10% to 30%. It is preferable that the volume A is larger than the volume B of the etching solution in the tank, and the volume A is five times or more the volume B.

  According to the glass substrate manufacturing method and the glass substrate manufacturing apparatus described above, in the surface treatment step of roughening the glass substrate by continuous processing, even if the etching solution is repeatedly used, a decrease in the etching rate in the etching tank is suppressed. However, the first surface of the thin glass sheet can be roughened while maintaining the etching rate for a long time. This provides a method of manufacturing a glass substrate including a surface treatment step and a manufacturing apparatus thereof, which can efficiently manufacture high-quality thin glass.

It is a flowchart which shows the outline | summary of an example of the manufacturing process of the glass substrate of this embodiment. It is a schematic diagram explaining an example of the glass substrate surface treatment apparatus used in the surface treatment process of this embodiment. It is a schematic top view of the roughening roller of the glass substrate surface treatment apparatus of this embodiment. FIG. 4 is a diagram illustrating the roughening of the glass substrate by the roughening roller illustrated in FIG. 3.

  Hereinafter, the glass substrate manufacturing method and the glass substrate surface treatment apparatus of the present embodiment will be described. FIG. 1 is a flowchart showing an outline of a manufacturing process of the glass substrate 100. FIG. 1 shows an outline of steps from a state where a glass substrate is melted to a state where it is shipped to a customer or the like.

(1) Manufacturing Method of Glass Substrate Hereinafter, a manufacturing apparatus of a glass substrate and a manufacturing method of a glass substrate of the present invention will be described.
Although the glass substrate manufactured in the present embodiment is not particularly limited, for example, each of a vertical dimension and a horizontal dimension is, for example, 500 mm to 3500 mm, 1500 mm to 3500 mm, 1800 to 3500 mm, 2000 mm to 3500 mm, and 2000 mm to 3500 mm. Preferably, there is.
The thickness of the glass substrate is, for example, 0.1 to 1.1 (mm), more preferably an extremely thin rectangular plate having a thickness of 0.75 mm or less, for example, 0.55 mm or less, and more preferably 0.5 mm or less. A thickness of 45 mm or less is more preferred. The lower limit of the thickness of the glass substrate is preferably 0.15 mm or more, more preferably 0.25 mm or more.

First, the molten glass is formed into a sheet glass which is a band-shaped glass having a predetermined thickness by a known method such as a fusion method or a float method (Step S1).
Next, the formed sheet glass is sampled on a glass substrate which is a raw plate having a predetermined length (step S2). The glass substrate obtained by sampling may be guided to a heat treatment step and transported while being pinched and held by the transport mechanism, and then the transported glass substrate may be subjected to heat treatment.

  The glass substrate after the step S2 or the heat treatment is conveyed to a cutting step, and cut into a product size to obtain a glass substrate (step S3). The obtained glass substrate is subjected to edge processing including grinding, polishing and corner cutting of the edge (step S4). The glass substrate is cleaned in order to remove fine foreign matter and dirt on the glass surface of the glass substrate after the end face processing (Step S5).

  The surface treatment S6 (the surface roughening step Pr1 and the rinsing step Pr2) of the present embodiment is performed after the cleaning step S5 immediately after the end face processing. Details of the surface treatment step of the present embodiment will be described later.

  After the surface treatment step S6, the second post-cleaning step S7 is performed, after which the cleaned glass substrate is subjected to an optical inspection for scratches, dust, dirt and scratches including optical defects (step S8). The glass substrate having a quality conforming to the inspection is loaded on a pallet and packed as a laminated body alternately laminated with paper protecting the glass substrate (step S9). The packaged glass substrates are shipped to the supplier.

As such a glass substrate, a glass substrate having the following glass composition is exemplified. That is, the raw materials of the molten glass are prepared so as to produce a glass substrate having the following glass composition.
55 to 80 mol% of SiO ₂ ,
Al ₂ O ₃ 8~20 mol%,
B ₂ O ₃ 0 to 12 mol%,
RO 0 to 17 mol% (RO is the total amount of MgO, CaO, SrO and BaO).

SiO ₂ is preferably from 60 to 75 mol%, more preferably from 63 to 72 mol%, from the viewpoint of reducing the heat shrinkage.
Of the RO, it is preferable that MgO is 0 to 10 mol%, CaO is 0 to 15 mol%, SrO is 0 to 10%, and BaO is 0 to 10%.

It contains at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and RO, and the molar ratio is ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO). The glass may be five or more. Further, it is preferable that at least one of MgO, CaO, SrO, and BaO is contained, and the molar ratio (BaO + SrO) / RO is 0.1 or more.

The total of twice the content of B ₂ O ₃ expressed in mol% and the content of RO expressed in mol% is preferably 30 mol% or less, more preferably 10 to 30 mol%.
The content of the alkali metal oxide in the glass substrate having the above glass composition may be 0 mol% or more and 0.4 mol% or less.
In addition, a metal oxide (tin oxide, iron oxide) whose valence varies in the glass is contained in a total of 0.05 to 1.5 mol%, and As ₂ O ₃ , Sb ₂ O ₃ and PbO are substantially contained. The absence is not mandatory and optional.

  The glass substrate manufactured in the present embodiment is a glass substrate for a flat panel display or a glass substrate for a curved panel display, and is suitable as, for example, a glass substrate for a liquid crystal display or a glass substrate for an organic EL display. Furthermore, the glass substrate manufactured in the present embodiment is particularly suitable as a glass substrate for a low-temperature polysilicon (LTPS), an indium-gallium-zinc-oxide (IGZO), or a TFT display used for a high-definition display.

  As a method of forming a sheet glass from the molten glass in the present embodiment, a float method, a fusion method, or the like is used. In the present embodiment, a glass substrate manufacturing method including off-line heat treatment of the glass substrate is performed by a fusion method (overdown method). The draw method) is suitable for the fusion method because it is difficult to lengthen the slow cooling device on the production line. The heat shrinkage of the glass substrate of this embodiment is 50 ppm or less, preferably 40 ppm or less, more preferably 30 ppm or less, and even more preferably 20 ppm or less. The range of the heat shrinkage of the glass substrate before the heat shrinkage is reduced is preferably 10 ppm to 40 ppm.

(2) Surface treatment step S6
(2-1) Surface Treatment Method and Surface Treatment Apparatus The surface treatment step of the present embodiment will be described in detail. The surface treatment step of the present embodiment includes a roughening step (Pr1) in which one surface (first surface) of the main surface of the glass substrate is treated with an etchant, and an etching of the roughened first surface. A rinsing step (Pr2) of washing the liquid with washing water and again washing again, and washing the second surface that has not been roughened with pure water. Details of the surface treatment S5 will be described later.

  In the surface treatment step S6, only one surface of the main surface of the glass substrate is subjected to a roughening treatment. The main surface to be subjected to the surface roughening treatment is the main surface opposite to the surface on which the TFT and the wiring pattern are formed, and the other main surface is not subjected to the surface treatment (roughening).

  By performing the surface roughening treatment, it is possible to prevent various problems due to charging as described below. For example, when a TFT (Thin Film Transistor) and a wiring pattern are formed on a glass substrate, foreign matter such as dust or dirt adheres to the glass substrate or the wiring pattern due to electrification, and the wiring pattern is damaged or peeled off or accumulated. There is a problem that the breakdown of the TFT is caused by the discharge of the accumulated electric charge. Further, the glass substrate may be stuck to the mounting table due to charging, and the glass substrate may be broken when the glass substrate is peeled off from the mounting table. In order to prevent these problems caused by charging, it is preferable that one surface of the main surface of the glass substrate is roughened as much as possible to prevent charging, and in particular, by a fusion method or an overflow down draw method. The formed glass sheet is preferably subjected to a surface roughening treatment.

  FIG. 2 is a schematic diagram illustrating an example of the glass substrate surface treatment apparatus 1 that performs the surface treatment step S6. The apparatus shown in FIG. 2 employs a method in which a glass substrate is transported in a horizontal state over an etching roller to roughen the glass substrate. A method of roughening one surface of the main surface of the glass substrate while conveying the glass substrate obliquely or vertically may be employed.

  FIG. 3 is a schematic top view of an etching roller used in the glass substrate surface treatment apparatus 1. FIG. 4 is a diagram illustrating roughening of a glass substrate by an etching roller.

The surface treatment step of the present embodiment will be described with reference to FIG. 2, but the glass substrate surface treatment apparatus 1 (FIGS. 2 to 4) is an example, and the surface treatment step S <b> 6 is other than the glass substrate surface treatment apparatus 1. It can be performed using the device having the configuration described above.
The glass substrate surface treatment apparatus 1 roughens one main surface while transporting the glass substrate in a transport direction (specifically, a direction indicated by an arrow A1 in FIGS. 2 to 4). Here, the glass substrate surface treatment apparatus 1 roughens the first surface 100a (see FIG. 2), which is one main surface of the glass substrate 100, to make the first surface 100a have a predetermined surface roughness. ing. Here, the first surface 100a is a surface on which a thin-film TFT element or a wiring pattern is not formed in a manufacturing process of the display device.

<Apparatus Configuration of Roughening Step Pr1>
As shown in FIGS. 2 to 4, the glass substrate surface treatment apparatus 1 mainly includes a plurality of etching rollers 12, a plurality of squeezing rollers 14, and a plurality of etching liquids in a surface roughening step (Pr1) for performing surface treatment. An etching tank 11 for storing the gas, an etching solution tank 16, and an etching solution circulation mechanism are provided.

  The surface roughening step (Pr1) may be further provided with a temperature control unit that is surrounded by the housing 2 and manages the temperature of the space in the housing. In the surface roughening step, the etching solution in the etching tank 11 is vaporized and stays in the air in the housing, so that the air in the housing is appropriately ventilated and is derived from the etching solution contained in the discharged air in the housing. It is preferable to provide a recovery mechanism for recovering the chemical substance.

A. Embodiment 1 FIG. Surface treatment equipment including etchant circulation mechanism (Fig. 2)
The surface treatment device in the present embodiment is at least
An etching bath 11 for roughening the first surface of the main surface of the glass substrate;
An etching solution tank 16 for adjusting and storing the etching solution;
A pipe 15a for connecting an etching solution inlet port of the etching bath with a supply port of the etching solution tank, an etching solution outlet of the etching bath, and a recovery port of the etching solution tank are connected. An etching solution circulation mechanism 16A having a pipe 15b;
A hydrofluoric acid tank for supplying hydrofluoric acid to the etching solution tank as needed;
Is provided.
Further, it is preferable that the etching solution tank is twice as large as the etching tank.
Further, the etching solution volume A of the etching solution tank is set so that the reduction rate of the etching rate (under the condition of processing 400 wafers at 25 ° C.) of the etching tank for performing the surface roughening can be controlled to 10% to 30%. Preferably, the capacity A is larger than the capacity B of the etching solution in the etching tank, and the capacity A has a capacity five times or more the capacity B.
In the surface roughening step (Pr1) of the present embodiment, an etching solution tank 16 for adjusting and storing the etching solution is provided, and the etching solution is supplied to the etching bath 11 and circulated by the etching solution tank 16. Further, the etching solution is adjusted while replenishing the etching solution tank 16 with hydrofluoric acid so as to maintain the etching rate in the surface roughening treatment, and the adjusted etching solution is circulated to the etching bath 11 for use. A pipe is provided between the etching tank 11 and the etching liquid tank so that the etching liquid MS can circulate.

  A plurality of tanks for supplying a constituent material for adjusting the etchant (acid component of the etchant) are connected to the etchant tank 16. For example, at least a hydrofluoric acid tank for supplying hydrofluoric acid and a phosphoric acid tank for supplying phosphoric acid are connected to the etchant tank 16, and constituent materials of the etchant are supplied from these tanks. The etchant is adjusted. The installation of the plurality of tanks for supplying the constituent material (acid component) of the etching solution is determined according to the type of the constituent material. For example, when the etching solution further contains hydrochloric acid, a hydrochloric acid tank is further connected to the etching solution tank 16.

(Replenishment of hydrofluoric acid HF)
Hydrofluoric acid is replenished in an etching solution tank 16 for supplying an etching solution to the etching bath 11 so that the etching rate in the etching bath 11 does not decrease. Since the hydrofluoric acid HF is consumed during the etching process, the hydrofluoric acid HF can be additionally replenished to the etching solution tank 16 to such an extent as to compensate for this consumption. The etchant MS replenished with hydrofluoric acid HF is supplied to the etching bath 11 and circulated, whereby a decrease in the etching rate in the etching bath 11 can be suppressed. The timing of replenishing hydrofluoric acid HF is not particularly limited. Further, replenishment of the hydrofluoric acid HF to the etching solution tank 16 may be performed based on the measurement of the etching rate in the etching tank 11 and / or the etching solution tank 16.

  The etching tank 11 stores an etching liquid MS as a processing fluid for processing the surface of the glass substrate 100. In the present embodiment, an etchant that essentially contains hydrofluoric acid and phosphoric acid, or an etchant that further contains hydrochloric acid in addition to hydrofluoric acid and phosphoric acid (the details will be described later) . By etching with the etchant MS, the first surface 100a of the glass substrate 100 can obtain a shape having a desired surface roughness, for example, a desired arithmetic average roughness Ra. The arithmetic average roughness Ra is preferably 0.3 nm or more, and more preferably, the arithmetic average roughness Ra is 0.45 nm or more. The upper limit value of the arithmetic average roughness Ra is preferably 0.6 nm or less, more preferably 0.5 nm or less, from the viewpoint of preventing roughness of the glass substrate.

  The etching tank 11 is a substantially rectangular parallelepiped container whose upper part is opened. The etching solution 11 is stored in the etching tank 11 so as to substantially fill the container. The etching tanks 11 are arranged at predetermined intervals along the direction in which the glass substrate 100 is transported. In the form of FIG. 2, three are arranged. In FIG. 2 of the present embodiment, three etching tanks 11 are arranged, but the number of arrangement may be one, two, or four or more. The number of arrangements is appropriately set based on the number of productions, an etching solution and an etching rate, a transport speed, and the like.

In each etching tank 11, one etching roller 12 is disposed so as to be immersed in the etching liquid MS. In the etching liquid tank 16, each etching tank 11 is connected to the etching liquid tank 16 by pipings 15a and 15b. The etching solution in the etching solution tank 16 supplies hydrofluoric acid (HF), phosphoric acid (H ₃ PO ₄₎ , and optional hydrochloric acid (HCl), which are essential components of the etchant MS, a hydrofluoric acid tank 11b and a phosphoric acid tank 11c. , And a hydrochloric acid tank 11d via flow control valves 11e, 11f, and 11g.

  The etching solution tank 16 is designed so that the capacity for storing the etching solution is larger than that of the etching bath 11. The capacity [capacity A] of the amount of etching solution in the etching solution tank 16 is set to be at least twice as large as the capacity [capacity B] of the amount of etching solution in the etching tank 11. As long as the installation environment allows, the larger the capacity A is, the better the capacity B is. The size of the capacity A with respect to the capacity B is set at least 2 to 15 times, and more preferably 5 to 10 times. As described above, by setting the capacity A larger than the capacity B, the effect of maintaining the etchin rate becomes higher.

  The etching roller 12 functions as a rotating body that absorbs (holds) the etching liquid MS and is driven and rotated by a driving motor (not shown). As the etching roller 12 is rotated by the drive motor, the glass substrate 100 that comes into contact with the etching roller 12 is transported in a direction in which the plurality of etching rollers 12 are arranged (that is, a transport direction). That is, the etching roller 12 also has a function of transporting the glass substrate 100. A plurality of the etching rollers 12 are arranged at predetermined intervals along the transport direction of the glass substrate 100. The plurality of roughening rollers 12 all rotate in the same direction.

  The etching roller 12 is fixed in a state in which a part (specifically, a lower part) is immersed in the etching liquid MS stored in one etching tank 11. The length in the vertical direction of the portion of the etching roller 12 that is immersed in the etching solution MS is appropriately set.

The etching roller 12 has a core member 12a and a roller member 12b that covers the core member 12a.
The core member 12a includes a shaft core made of SUS or the like and a columnar member made of a vinyl chloride-based material. The core member 12a may be a carbon shaft. The core member 12a has a diameter of, for example, 15 to 20 mm. The core member 12 a is a rotation shaft of the roughening roller 12.

  The roller member 12b is a cylindrical member whose outer diameter is larger than that of the core member 12a and whose central portion is opened. The roller member 12b is made of a foamed resin that easily absorbs liquid, that is, a sponge. The sponge of the roller member 12b is made of PVA, PU, or the like. The inner surface of the roller member 12b contacts the outer surface of the core member 12a. The diameter of the roller member 12b is appropriately set.

  Here, the etching roller 12 (the roller member 12b) absorbs the etching liquid MS by being immersed in the etching liquid MS. Then, a part of the etching liquid MS absorbed by the roller member 12b is supplied and adheres to the first surface 100a of the glass substrate 100 which comes into contact with the etching roller 12 (the roller member 12b) which absorbs and holds the etching liquid MS.

  The squeezing roller 14 has a function of adjusting the amount of the etching liquid MS held by the etching roller 12 by being pressed against the etching roller 12. The squeeze roller 14 is made of a material having higher rigidity than the roller member 12b, for example, a material such as vinyl chloride or carbon. The squeezing roller 14 is a round bar having a columnar shape. The shape of the squeeze roller 14 is not limited to a round bar. As shown in FIG. 3, the squeezing roller 14 is arranged on the upstream side in the transport direction of the glass substrate 100 with respect to the core member 12 a which is the rotation axis of the etching roller 12.

  The squeezing roller 14 rotates following the rotation of the etching roller 12. Therefore, it rotates in the opposite direction to the etching roller 12. Here, it is not necessary to separately use a motor or the like for rotating the squeezing roller 14, so that the cost can be suppressed.

  As shown in FIG. 4, the squeezing roller 14 is supported by a support member 17 so that the vertical position and the horizontal position with respect to the etching roller 12 can be adjusted. That is, the contact position of the squeeze roller 14 with the etching roller 12 is adjustable. Thereby, the contact pressure of the squeezing roller 14 with the etching roller 12 can be adjusted.

  Further, the etching roller 12 has a mechanism capable of adjusting a relative position with respect to the glass substrate 100. That is, the rotation axis of the etching roller 12 can be moved closer to or away from the glass substrate 100 side. Further, the etching tank 11 is provided with a mechanism capable of adjusting the liquid level of the etching liquid MS. Thereby, the amount of the etching liquid MS that the etching roller 12 attaches to the glass substrate 100 can be adjusted.

  The transport roller 18 includes a rotating shaft and a plurality of rollers. The roller is a cylindrical member fixed to a rotating shaft and to which an O-ring is attached. When the transport roller 18 is rotated by a drive motor (not shown), the glass substrate 100 supported in contact with the upper portion of the transport roller 18 is transported into the housing 2 that performs the roughening process Pr1. A plurality of transport rollers 18 are arranged at predetermined intervals along the transport direction of the glass substrate 100. The transport rollers 18 all rotate in the same direction.

<Roughening process>
In the surface treatment method according to the present embodiment, the etching solution is supplied between the etching solution tank 16 for adjusting and storing the etching solution containing hydrofluoric acid and the etching bath 11 for supplying the etching solution and roughening the surface. The etching solution stored in the etching solution tank is replenished with hydrofluoric acid so as to circulate and maintain the etching rate in the etching bath, and the first surface of the glass substrate is roughened in the etching bath 11. Is done.

B. Embodiment 2. FIG. Surface treatment method to maintain the etching rate The surface treatment step in the method for manufacturing a glass substrate for a display of the present embodiment,
An etchant tank for adjusting and storing an etchant containing hydrofluoric acid,
The etchant is circulated between the etchant and the roughening surface of the etching bath, so that the etchant circulates and the etching rate in the etching bath is maintained, while replenishing the etchant tank with hydrofluoric acid. The etching solution is circulated to roughen the first surface of the glass substrate in the etching bath.
Furthermore, it is preferable that the rate of decrease in the etching rate of the etching bath (under the condition of processing 400 wafers at 25 ° C.) is set to 10% to 30%.
Furthermore, it is preferable that the etching solution volume A of the etching solution tank is larger than the etching solution volume B of the etching bath, and the volume A has a capacity of twice or more the volume B.
Furthermore, it is preferable that the circulation of the etching liquid is controlled based on the measurement of the etching rate in the etching bath.
Further, it is preferable that the etching solution has an etching rate at 25 ° C. of 0.1 μm / min or more.

  The glass substrate 100 that has been subjected to the cleaning process S6 after the end face processing while being transported in a predetermined direction (transport direction) in a horizontal state is transported by the transport rollers 18 while maintaining the state, and the glass substrate surface treatment apparatus 1 into the housing 2.

  The lower surface of the tip of glass substrate 100 in housing 2 contacts etching roller 12 and is supported by etching roller 12. Since the etching roller 12 (roller member 12b) is immersed in the etching liquid MS, it absorbs the etching liquid MS, and the upper surface of the etching roller 12 (roller member 12b) absorbing the etching liquid MS has a surface. When the first surface 100a to be roughened comes into contact with the glass substrate 100, the glass substrate 100 is transported in the transport direction by the rotational driving of the etching roller 12. At this time, since the etching roller 12 (the roller member 12b) has absorbed the etching liquid MS, the first surface 100a of the glass substrate 100 that is in contact with the etching roller 12 (the roller member 12b) has the etching roller 12 (the roller member 12b). The etching liquid MS adheres via 12b). In this way, the etching liquid MS adheres to the first surface 100a while the glass substrate 100 is being conveyed by the etching roller 12, whereby the first surface 100a of the glass substrate is roughened.

  Since the contact time between the etching roller 12 and the glass substrate 100 during the period from when the etchant MS adheres to the first surface 100a to the rinsing step Pr2 is the etching period, the desired etching is performed during this etching period. The rotation speed (transport speed) of the etching roller 12 that roughens the surface while transporting the glass substrate 100 can be adjusted so that the amount is achieved. For example, the contact time between the etching roller 12 and the glass substrate 100 is increased by slowing down the rotation speed of the etching roller and increasing the transport time of the glass substrate 100 transported on the etching roller 12. The degree and shape of the etching of 100a can be adjusted.

(Control of etching rate)
In this embodiment, for example, the rate of decrease in the etching rate is set to be small based on the composition of the etching MS described later. According to the present invention, the etching liquid MS contains at least 0.3% or more of phosphoric acid together with hydrofluoric acid, whereby the rate of decrease in the etching rate of the etching liquid can be significantly reduced. As described above, by setting the etching solution MS to include hydrofluoric acid and phosphoric acid, the etching rate can be maintained and controlled. For example, when it is necessary to increase the transport speed (processing speed) in the surface treatment step, the etching rate can be set to a high level (specifying conditions such as concentration and temperature) and the rate can be maintained.

Further, improving the performance of the etchant leads to an effect of maintaining an etching rate in long-time continuous processing. For example, by suppressing the generation of sludge, the maintenance of the etching rate can be further continued. According to the present invention, if the etchant MS is a mixture of two types of hydrofluoric acid and phosphoric acid, the amount of sludge generated can be suppressed, so that the etchant MS contains hydrofluoric acid and phosphoric acid. By being set, the etching rate can be controlled. Furthermore, according to the present invention, since the etchant contains HCl hydrochloride, a sludge generation suppressing effect can be further obtained. In addition to the hydrofluoric acid and phosphoric acid, the etchant MS further contains HCl hydrochloride, The amount of sludge generated is suppressed, leading to control of the etching rate.
As described above, the etching rate can be controlled so as to be maintained for a long time (the rate of decrease in the etching rate is reduced). By maintaining the etching rate for a long period of time (decreasing the rate of decrease in the etching rate), the processing speed can be stabilized in the surface treatment step, and the production can be leveled.
The etching rate is, for example, preferably 0.1 μm / min or more, more preferably 0.2 μ / min or more, still more preferably 0.3 μm / min or more, and particularly preferably 0.5 μm / min or more.

(Control of etching rate decrease rate)
By using an etching solution containing (a) two kinds of combinations of hydrofluoric acid and phosphoric acid, and (b) three kinds of combinations of hydrofluoric acid, phosphoric acid and phosphoric acid with respect to the components contained in the etching solution MS, The etching reduction rate can be controlled to be small. In other words, the etching rate can be maintained at a high level. For example, when a combination of three kinds of (b) hydrofluoric acid, phosphoric acid and phosphoric acid is used, the rate of decrease in the etching rate is about 5% to 30% under the condition of 100 treatments at 25 ° C. And the etching rate is maintained at about 75-90%). Therefore, the rate of decrease in the etching rate can be controlled, and long-term continuous processing can be realized.

(Replenishment of hydrofluoric acid HF)
Further, hydrofluoric acid is replenished in an etching solution tank 16 for supplying an etching solution to the etching bath 11 so that the etching rate in the etching bath 11 does not decrease. Since the hydrofluoric acid HF is consumed during the etching process, the hydrofluoric acid HF can be additionally replenished to the etching solution tank 16 to such an extent as to compensate for this consumption. The etchant MS replenished with hydrofluoric acid HF is supplied to the etching bath 11 and circulated, whereby a decrease in the etching rate in the etching bath 11 can be suppressed. The timing of replenishing hydrofluoric acid HF is not particularly limited. Further, replenishment of the hydrofluoric acid HF to the etching solution tank 16 may be performed based on the measurement of the etching rate in the etching tank 11 and / or the etching solution tank 16.

(Determining the transport speed)
Furthermore, the range of the required processing speed (transport speed) of the surface treatment step and the range of the etching rate can be specified so as to match the tact time of the preceding step.
The tact time (target operation time) can be set, for example, with the processing speed of the step immediately before the surface treatment step (first cleaning step S6) as a target. By setting the time so as to correspond to the tact time of the immediately preceding process, synchronization with the immediately preceding process can be achieved, and it is not necessary to set up an intermediate stock, and the production efficiency can be further improved.
(Circulation of etchant volume)
The etching liquid MS is adjusted and stored in the etching liquid tank in advance. The amount of the etching solution [liquid amount A] stored in the etching solution tank 16 is preferably 2 to 15 times the amount of the etching solution [liquid amount B] maintained in the etching tank 11, and is preferably 3 to 5 times. It is more preferably 8 times, more preferably 4 to 9 times, and particularly preferably 5 to 10 times. The amount of liquid A is larger than the amount of liquid B at such a large capacity, and the etching liquid is circulated so that the etching rate during the surface roughening treatment is maintained substantially constant for a long time. Can be.
The circulation of the etching liquid MS can be controlled based on the measurement of the etching rate in the etching tank 11 and / or the etching liquid tank 16. For example, when a decrease in the etching rate is recognized, the circulation can be controlled so as to further increase the circulation of hydrofluoric acid HF replenished in the etching solution tank.

<Apparatus configuration of rinsing step Pr2>
In the rinsing step (Pr2), a plurality of transport rollers 18, a distilled water nozzle 25 for applying distilled water to the surface of the glass substrate that is not roughened, a cleaning nozzle 24 for cleaning the roughened glass substrate surface, A nozzle 26 for sufficiently washing away the etching solution to be removed and an arc cutter for removing the liquid adhering to both surfaces of the glass substrate from the surface of the glass substrate so as to remain in the housing.

  The rinsing step (Pr2) is a space surrounded by the housing 4, and the temperature management of the space in the housing may or may not be performed. A slit through which the glass substrate 100 can pass is provided in a part of the housing wall where the roughening step (Pr1) and the rinsing step (Pr2) are in contact.

  The cleaning nozzle 24 is provided along the transport path of the glass substrate 100 so as to wash away the etching liquid MS attached to the first surface 100a of the glass substrate 100, and jets cleaning water toward the first surface 100a. The cleaning water used for the cleaning nozzle 24 does not necessarily have to be pure water (distilled water). In the cleaning water tank 24a, water after cleaning once used for cleaning can be stored, circulated for cleaning the first surface 100a of the glass substrate 100, and reused.

  The distilled water nozzle 25 is provided along the transport path of the glass substrate 100 from the main surface opposite to the first surface 100a to clean the main surface of the glass substrate 100 opposite to the first surface 100a. Water is spouted toward the main surface opposite to the first surface 100a.

  The nozzle 26 jets cleaning water toward the first surface 100a in order to sufficiently wash away the etchant remaining on the first surface 100a of the glass substrate 100. The nozzle 26 is provided on the first surface 100a side of the glass substrate 100 along the transport path of the glass substrate 100. In addition, the same pure water as that jetted from the distilled water nozzle 25 or the same wash water as jetted from the cleaning nozzle 24 may be used as the wash water jetted from the nozzle 26.

  After cleaning the first surface a and the opposite surface of the glass substrate 100, the liquid is blown off from the surface of the glass substrate by an air cutter, and the housing 4 is transported by the transport roller 18 to perform the second cleaning process of the next process. It is carried out of the.

<Rinse process>
After the surface roughening process (Pr1), the glass substrate 100 moves in the transport direction during the surface roughening process. Therefore, when the etching liquid MS is attached to a part of the first surface 100a, the tip of the glass substrate 100 The portion contacts the transport roller 18 in the housing 4. The glass substrate 100 proceeds to the rinsing step Pr2 by the transport rollers 18.

  In the rinsing step Pr2, first, the first surface 100a is washed with the cleaning water spouting from the cleaning nozzle 24, and the etching liquid MS is almost washed off. Thereafter, the water spouting from the first surface 100a further from the nozzle 26 (reused water) Wash). At this time, the main surface of the glass substrate 100 opposite to the first surface 100a is washed with pure water ejected from the distilled water nozzle 25. Thereafter, air is blown toward the first surface 100a and the main surface opposite to the first surface 100a by an air cutter to blow off the liquid. Thus, the rinsing step Pr2 is completed, and the sheet is carried out by the transport roller 18 in order to perform the second cleaning step S8.

(2-2) Etching solution The etching solution MS in the present invention is an aqueous solution containing at least hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ in pure water (the concentrations described below also represent mass%). .
The concentration of phosphoric acid H ₃ PO ₄ in the etching solution MS is 0.3% (mass%) to 10%. If the concentration of phosphoric acid H ₃ PO ₄ exceeds 10%, it is not preferable from the viewpoint of wastewater recovery. The concentration of the phosphoric acid H ₃ PO ₄ in the etching solution MS is preferably 0.3% to 8%, more preferably 0.5% to 8%, and still more preferably 1% from the viewpoint of the effect of suppressing a decrease in the etching rate. ~ 6%. When the etching solution MS contains 1% or more of hydrofluoric acid and phosphoric acid H ₃ PO ₄ , the hydrofluoric acid, a mixed acid of hydrofluoric acid and hydrochloric acid (the same concentration as phosphoric acid), and Compared with sulfuric acid (same concentration as phosphoric acid), under the same temperature condition, a decrease in the etching rate can be greatly suppressed. That is, the mixed acid of hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ can reduce the etching rate. High suppression effect. In the etching solution MS, the concentration of hydrofluoric acid in a mixed acid containing hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ is preferably 0.3% to 10%, more preferably 0.3% to 8%, and 0%. 0.3% to 6% is more preferred, and 0.3% to 5% is even more preferred. If the concentration of hydrofluoric acid exceeds 5%, the burden on the environment, such as the problem of drainage recovery, increases, so that it is preferably 5% or less. In the present embodiment, the hydrofluoric acid concentration of the etching solution MS can be kept low, so that the environmental load is small and the cost of treating the waste liquid of hydrofluoric acid can be suppressed.

The fact that the etching solution MS containing hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ is excellent in the effect of suppressing the decrease in the etching rate indicates that the etching solution MS containing 5% hydrofluoric acid HF is repeatedly used for 14 hours. The reduction in the etching rate is 45%, and the reduction in the etching rate after repeatedly using the etching solution MS of a mixed acid of 5% hydrofluoric acid HF and 5% hydrochloric acid HCl for 14 hours is 44%, The decrease in the etching rate after repeatedly using the etching solution MS of a mixed acid of 5% hydrofluoric acid HF and 5% phosphoric acid H ₃ PO ₄ for 14 hours is 15%. Thus, the decrease in the etching rate of the glass substrate 100 in the etching solution MS containing hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ is extremely small. These etching rates are all measured under the same temperature conditions.

When the etching solution MS contains 1% or more of hydrofluoric acid and phosphoric acid H ₃ PO ₄ , the hydrofluoric acid, hydrofluoric acid and sulfuric acid (the same concentration as phosphoric acid) are used under the same hydrofluoric acid concentration. In addition, the amount of generated sludge can be suppressed low, and the mixed acid of hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ also has an effect of suppressing the amount of generated sludge.
It is assumed that the etching solution MS containing hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ is excellent in the effect of suppressing the amount of generated sludge, for example, in the case of the etching solution MS having a sludge generation amount of 5% hydrofluoric acid HF. As compared with the above, the etching solution MS of the mixed acid of 5% hydrofluoric acid HF and 5% phosphoric acid H ₃ PO ₄ is 20 to 30% less. Thus, the mixed acid of hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ is also excellent in the effect of suppressing the amount of sludge.

For etchant MS containing hydrofluoric acid HF and phosphoric acid _H 3 PO _4, hydrofluoric acid HF and the concentration ratio of the phosphoric acid _H 3 PO _4: The (hydrofluoric acid), about 1: 1 to 30: is 1 , Preferably 1: 1 to 10: 1. The etching solution MS of the present embodiment is a mixed acid containing hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ as essential components. By using hydrofluoric acid and phosphoric acid as essential components, the etching solution MS has an effect of suppressing a decrease in etching rate and has a rough effect. It has two simultaneous effects of suppressing the amount of sludge generated by the surface etching treatment.

  A solution containing sodium fluoride and phosphoric acid, which has been conventionally known as an etching solution, is not suitable as an etching solution in a continuous roughening treatment because the etching rate itself is low.

The etching solution MS may be used in combination with the above combination (two kinds of mixed acids with hydrofluoric acid and phosphoric acid, or three kinds of mixed acids with hydrofluoric acid and phosphoric acid and hydrochloric acid), if necessary, such as sulfuric acid H ₂ SO ₄ and nitric acid HNO _3. May be combined.

In the present embodiment, the etching solution MS may further include hydrochloric acid HCl in addition to hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ . In the case of three kinds of mixed acids in which hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ are combined with hydrochloric acid HCl, generation of sludge can be further suppressed. Therefore, the etching solution MS of the present embodiment preferably further contains HCl hydrochloride together with hydrofluoric acid HF and phosphoric acid H ₃ PO ₄ , and in this case, the effect of suppressing the amount of sludge can be further enhanced.
In etchant MS, when combining hydrochloric acid HCl in hydrofluoric acid HF and phosphoric acid _H 3 PO _4, the concentration of hydrochloric acid HCl is 0.3% to 15% by weight, preferably hydrochloric HC0.3 wt% to 10 wt% is there. In this case, in the etching solution MS, hydrofluoric acid HF is 0.3% to 10% by mass, phosphoric acid H ₃ PO ₄ is 0.3% to 10% by mass, and hydrochloric acid HCl is 0.3% to 15% by mass. It is. When hydrochloric acid is used for the etching solution MS, the concentration ratio between hydrofluoric acid HF and hydrochloric acid HCl (hydrofluoric acid: hydrochloric acid) is approximately 1:10 to 5: 1.

(Roughening treatment temperature)
The etching rate differs depending on the temperature of the etching solution MS. The temperature of the etching solution MS is appropriately determined so as to obtain a predetermined etching rate. During the surface roughening process, it is preferable to keep the temperature of the etching solution MS constant so that the etching rate becomes constant. In this embodiment, the temperature of the etching MS is controlled between 20 ° C. and 30 ° C. Since the processing environment deteriorates when the etchant is vaporized, it is preferable that the temperature of the etchant MS does not exceed 40 ° C. If the temperature of the etching MS is lower than 20 ° C., it becomes difficult to obtain a predetermined etching rate.

(Processing time for surface roughening)
The processing time of the surface roughening determines the surface roughness (arithmetic average roughness Ra) obtained by the surface roughening, and is used in the transfer speed of the surface roughening and the surface roughening based on the tact time of the previous process. It is set together with the number of etching rollers to be used, the composition of the etching solution MS used for the surface roughening treatment, and the etching rate.
The surface roughness obtained by the roughening is preferably 0.30 nm or more, and more preferably the arithmetic average roughness Ra is 0.45 nm or more. The upper limit of the arithmetic average roughness Ra is preferably 0.60 nm or less, more preferably 0.50 nm or less.

<Glass composition>
As the glass composition to which the present embodiment is applied, for example, the following can be cited (in mass%).
SiO ₂ : 50 to 70% (preferably 57 to 64%), Al ₂ O ₃ : 5 to 25% (preferably 12 to 18%), B ₂ O ₃ : 0 to 15% (preferably 6%) -13%), and may optionally further contain the composition shown below. As optional components, MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 3 to 7%), SrO: 0 to 20% (preferably, 0.5 to 8%, more preferably 3~7%), BaO: 0~10% ( preferably 0-3%, more preferably _{0~1%), ZrO 2: 0~10} % ( preferably , 0 to 4%, more preferably 0 to 1%). Further, it is more preferable that R ′ ₂ O: more than 0.10% and not more than 2.0% (where R ′ is at least one selected from Li, Na and K).
_{Alternatively,} SiO 2: _{50~70% (preferably, 55~65%), B 2 O} 3: 0~10% ( _{preferably, 0~5%, 1.3~5%),} Al 2 O 3: 10 to 25% (preferably 16 to 22%), MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 2 to 10%, 2 to 6%) %), SrO: 0 to 20% (preferably 0 to 4%, 0.4 to 3%), BaO: 0 to 15% (preferably 4 to 11%), RO: 5 to 20% (preferably) (8 to 20%, 14 to 19%) (R is at least one selected from Mg, Ca, Sr and Ba). Further, it is more preferable that R ′ ₂ O contains more than 0.10% and not more than 2.0% (where R ′ is at least one selected from Li, Na and K).
<Young's modulus>
The Young's modulus of the glass plate to which the present embodiment is applied is, for example, preferably 72 (Gpa) or more, more preferably 75 (Gpa) or more, and still more preferably 77 (Gpa) or more.
<Strain point>
The strain rate of the glass substrate to which the present embodiment is applied is, for example, preferably 650 ° C. or higher, more preferably 680 ° C. or higher, even more preferably 700 ° C. or higher and 720 ° C. or higher.

Using the above-described glass substrate surface treatment apparatus 1 (FIG. 2), a thin glass sheet having a thickness of 0.5 mm was roughened.
As for the etchant MS, an etchant (etchant MS1) containing 3% hydrofluoric acid HF, 9% hydrochloric acid HCl, and 1% phosphoric acid H3PO4, 5% hydrofluoric acid HF, 9% hydrochloric acid HCl, and The surface roughening treatment was performed under the condition of 25 ° C. using each of these two kinds of etching solutions (etching solution MS2) containing 2% phosphoric acid H3PO4.
The first surface 100a of the glass substrate subjected to the surface roughening treatment has a surface roughness capable of suppressing the charging of the surface of the glass substrate and a surface roughness that does not impair the strength of the glass substrate 100. Ra (JIS B0601-2001) was 0.42 to 0.48 nm.
Further, in the surface roughening process, continuous processing could be performed for 24 hours without causing a line stop due to the amount of sludge generated and suppressing a decrease in the etching rate.
Further, according to the surface treatment apparatus 1 of the present invention, not only the stabilization of the processing speed by maintaining the etching rate, but also the etching rate can be known and maintained for a long time, so that the production efficiency can be significantly increased. . As a result, the production of the surface treatment process was leveled, and the intermediate stock was significantly reduced.

As described above, the surface treatment apparatus provided with the etchant circulation mechanism of the present invention, or, in the surface treatment method of the present invention, an etchant tank for adjusting and storing an etchant containing hydrofluoric acid; The etching solution is circulated between the supplied etching bath and the etching bath, and the etching solution is replenished with hydrofluoric acid so that the etching rate in the etching bath is maintained. According to the surface treatment method of circulating and roughening the first surface of the glass substrate in the etching bath,
Even if an etchant containing hydrofluoric acid is used repeatedly in continuous processing, the etch rate in the etching bath is maintained for a long time while suppressing the decrease in the etch rate, and the amount of sludge contained in the etchant is suppressed. Therefore, the quality of the surface roughening treatment can be efficiently achieved. Thus, a glass substrate useful for a high-definition display can be provided by an economically excellent method.

  As described above, the glass substrate manufacturing apparatus and the glass substrate manufacturing method of the present invention have been described in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications may be made without departing from the gist of the present invention. May be.

DESCRIPTION OF SYMBOLS 1 Glass substrate surface treatment apparatus 2, 4 Housing 11 Etching tank 16 Etching liquid tank 11b Hydrofluoric acid tank 11c Phosphoric acid tank 11d Hydrochloric acid tank 11e, 11f, 11g Flow control valve 12a Core member 12b Roller member 14 Contact member 15 Pipe 18 Transport roller 24 Cleaning water nozzle 24a Cleaning tank 1
25 Distilled water nozzle 25a Distilled water tank 26 Cleaning water nozzle 26a Cleaning tank 2
100 glass substrate 100a first surface

Claims (2)

A glass substrate manufacturing equipment for a display comprising a surface treatment apparatus,
The surface treatment apparatus, an etching tank for roughening the first surface of the main surface of the glass substrate,
An etchant tank for adjusting and storing the etchant;
A pipe connecting an etching solution inlet port of the etching tank with a supply port of the etching solution tank, and connecting an etching solution outlet of the etching bath with a recovery port of the etching solution tank. An etchant circulation mechanism having a pipe,
A hydrofluoric acid tank that supplies hydrofluoric acid to the etching solution tank as needed,
With
The apparatus for manufacturing a glass substrate for a display, wherein the etching solution tank is twice as large as the etching tank. The etching solution volume A of the etching solution tank is set such that the rate of decrease in the etching rate of the etching bath (under the conditions of processing 400 wafers at 25 ° C.) can be controlled to 5% to 30%. greater than B, the capacitor a has a more than five times the capacity of the capacitor B, a glass substrate manufacturing apparatus for a display according to claim 1.

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