JP2016183085A - Manufacturing method of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-quality glass substrate having a target composition capable of suppressing damage to a manufacturing apparatus.SOLUTION: A manufacturing method of a glass substrate includes a melting step ST1 for producing molten glass by melting a glass-making feedstock, an agitation step ST3 for agitating the molten glass, and a shaping step ST5 for shaping the agitated molten glass into a glass sheet. Manufacturing a glass substrate is initiated with molten glass having a composition of high devitrification viscosity or low devitrification temperature and then transferred to molten glass having a composition of low devitrification viscosity or high devitrification temperature. The composition of the molten glass is analyzed after the agitation step ST3, and manufacturing conditions in the shaping step ST5 are adjusted based on the analysis result.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a glass substrate used in a flat panel display such as a liquid crystal display or a plasma display.

  As a glass substrate used for a flat panel display (hereinafter referred to as “FPD”) such as a liquid crystal display or a plasma display, a thin glass plate having a thickness of, for example, 0.5 to 0.7 mm is used. For example, the FPD glass substrate has a size of 300 × 400 mm in the first generation, but has a size of 2850 × 3050 mm in the tenth generation.

  In order to manufacture a glass substrate for FPD having a large size with such a thin plate, an overflow down draw method or a float method is preferably used. For example, Patent Document 1 discloses a glass substrate manufacturing method using an overflow downdraw method. That is, in patent document 1, the glass substrate is manufactured by pinching the sheet glass overflowed from the molded body with a conveyance roller (pulling roller) and gradually cooling it in the process of pulling it downward.

International Publication No. 2012/132425

  By the way, in such a glass substrate for FPD, in order to suppress the problem of pixel pitch shift, for example, it is strongly demanded to reduce thermal shrinkage of the glass substrate during display manufacturing. The thermal contraction of the glass substrate can be suppressed by increasing the low temperature viscosity characteristic temperature represented by the strain point or the glass transition point. However, if the glass composition is improved by paying attention only to increasing the strain point or the like of the glass, the liquidus temperature of the glass tends to increase, and there arises a problem that the devitrification resistance tends to deteriorate. A glass composition having a high strain point tends to have a high devitrification temperature. This problem of devitrification becomes prominent when the overflow down draw method, which requires molding with a relatively high viscosity, is used as the molding method.

  In order to prevent such glass devitrification during molding by the overflow downdraw method, for example, the temperature of the molten glass during molding may be kept sufficiently higher than the liquidus temperature.

  From the above point of view, for example, when manufacturing a glass having a high temperature and high viscosity and a low liquid phase viscosity, starting from the beginning with a glass composition having a high temperature and high viscosity, the load on the manufacturing apparatus is increased. The damage to the platinum device used for the above and the molded body of the molding device is increased.

  With the recent increase in definition of FPD, quality requirements for FPD glass substrates have become increasingly severe, and stricter control of manufacturing conditions during the production of glass substrates has become more necessary than ever.

  Therefore, the present invention is a glass substrate capable of producing a high-quality glass substrate having a target composition by suppressing damage to an apparatus for producing a glass substrate, occurrence of devitrification of the produced glass substrate, and the like. An object is to provide a manufacturing method.

  As a result of intensive studies to solve the conventional problems, the present inventor has come up with an invention having the following configuration.

(Invention of Configuration 1)
A method for producing a glass substrate, comprising: a melting step of melting a glass raw material to form molten glass; a stirring step of stirring the molten glass; and a molding step of forming the stirred molten glass into a sheet shape. Production is started from a composition having a high or low devitrification temperature, a glass substrate is produced by changing to a composition having a low devitrification viscosity or a high devitrification temperature over time, and after the stirring step in the middle A composition analysis of a molten glass is performed, and the manufacturing conditions of the forming step are adjusted based on the result, and the manufacturing method of the glass substrate is characterized by the following.

(Invention of Configuration 2)
The glass substrate manufacturing method according to the invention of Configuration 1, wherein a rate of change of composition is estimated based on a result of composition analysis of the molten glass, and a temperature condition of the forming step is adjusted.

(Invention of Configuration 3)
The method for producing a glass substrate according to the invention of Configuration 1 or 2, wherein composition analysis of the molten glass is performed by fluorescent X-ray analysis.

(Invention of Configuration 4)
The method for producing a glass substrate according to any one of Structures 1 to 3, wherein the forming step is performed using an overflow downdraw method.

  According to the present invention, the above configuration can suppress damage to the apparatus for manufacturing the glass substrate, occurrence of devitrification of the manufactured glass substrate, and the like, and can manufacture a high-quality glass substrate having a target composition. It is.

It is a figure which shows an example of the flow of the manufacturing method of the glass substrate of this embodiment. It is a figure which shows typically an example of the apparatus which performs the melt | dissolution process thru | or cutting process in this embodiment. It is a schematic side view of a shaping | molding apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
(Overall overview of glass substrate manufacturing method)
An example of the outline of the manufacturing process of the glass substrate in which the overflow downdraw method is adopted can be shown in FIG. 1, for example.
FIG. 1 is a diagram illustrating an example of a flow of a glass substrate manufacturing method according to the present embodiment.

  In this glass substrate manufacturing process, a melting process (ST1), a clarification process (ST2), a stirring (homogenization) process (ST3), a supply process (ST4), a molding process (ST5), and a cooling (gradual) A cold) step (ST6) and a cutting step (ST7), and the downdraw method is employed in the molding step (ST5) and the cooling (slow cooling) step (ST6). In the molding step, for example, As shown in FIG. 3, it is molded by an apparatus including a wedge-shaped molded body 210.

  FIG. 2 is a diagram schematically showing an example of an apparatus for performing the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting apparatus 100, a molding apparatus 200, and a cutting apparatus 300. The dissolution apparatus 100 includes a dissolution tank 101, a clarification tank 102, a stirring tank 103, a first pipe 104, a second pipe 105, and a third pipe 106. Details of the molding apparatus 200 will be described later.

  In the melting step (ST1), molten glass MG is obtained by melting the glass raw material supplied in the melting tank 101 by energization heating using a flame and / or an electrode. Molten glass MG is supplied from the melting tank 101 to the clarification tank 102 through the first pipe 104.

In the clarification step (ST2), the molten glass MG supplied to the clarification tank 102 is heated, so that bubbles containing gas components such as O ₂ , CO ₂ or SO ₂ contained in the molten glass MG are produced. , Which grows by absorbing O ₂ generated by the reduction reaction of a clarifying agent such as SnO ₂ , floats on the liquid surface of the molten glass MG, and is released into the air above the fining tank 102 and into an atmosphere containing nitrogen gas, etc. To be removed. Next, the internal pressure of the gas component in the foam is lowered due to the temperature drop of the molten glass MG, and the reduced fining agent (for example, SnO) undergoes an oxidation reaction due to the temperature drop of the molten glass MG, whereby the molten glass The gas component such as O ₂ in the foam remaining in the MG is reabsorbed to eliminate the foam.
Molten glass MG defoamed in the clarification step is supplied from the clarification tank 102 to the stirring tank 103 through the second pipe 105.

  In the stirring (homogenization) step (ST3), the molten glass MG defoamed in the clarification step is supplied, and the molten glass MG in the stirring vessel 103 is stirred using a stirring means (for example, a stirrer 103a shown in the figure). By stirring, the glass components are homogenized.

  In the supply step (ST4), the homogenized molten glass MG is supplied from the stirring vessel 103 to the molding apparatus 200 through the third pipe 106. An example of the molding apparatus 200 is shown in FIG. FIG. 3 is a schematic side view of the molding apparatus.

  In FIG. 3, the molding apparatus 200 includes a molding furnace 240 and a slow cooling furnace 250. In the molding apparatus 200, the molding step (ST5) and the cooling (slow cooling) step (ST6) are sequentially performed.

  In the forming step (ST5), the molten glass MG is formed into a sheet glass SG to make a flow of the sheet glass SG. In this embodiment, the overflow down draw method using the molded body 210 is used. In this case, the flow direction of the sheet glass SG is vertically downward.

  More specifically, as shown in FIGS. 2 and 3, the formed body 210 forms molten glass MG flowing from the melting device 100 through the third pipe 106 into a sheet glass SG. Thereby, the flow of the sheet glass SG in the vertically lower direction is created in the forming apparatus 200. The molded body 210 is a long and narrow structure made of firebrick or the like, and has a wedge-shaped cross section as shown in FIG. A supply groove 212 serving as a flow path for guiding the molten glass MG is provided in the upper part of the molded body 210. The supply groove 212 is connected to the third pipe 106 at a supply port provided in the molded body 210, and the molten glass MG flowing through the third pipe 106 flows along the supply groove 212. The depth of the supply groove 212 is shallower toward the downstream side of the flow of the molten glass MG, so that the molten glass MG overflows vertically downward from the supply groove 212.

  Also, platinum guide members (not shown) are provided on both side walls and / or the lower end of the molded body 210. The platinum guide member is provided for managing the glass width, but functions as a heat dissipation member for glass. For this reason, by providing a structure in which the amount of heat is applied to the both side walls and the lower end of the molded body 210 by an internal heater or the like, adhesion of the crystalline substance to the platinum guide member is suppressed.

The molten glass MG overflowing from the supply groove 212 flows down along the side walls on both sides of the molded body 210. The molten glass MG that has flowed through the side walls merges at the lower end 213 (shown in FIG. 3) of the molded body 210 to form one sheet glass SG. The sheet glass SG flows vertically downward, which is the flow direction of the sheet glass SG shown in FIG. The temperature of the sheet glass SG immediately below the lower end 213 of the molding 210 is a temperature (e.g. 1000 to 1250 ° C.) corresponding to a viscosity of example 10 ^4.3 ~10 ⁶ poise. Moreover, 1150 degreeC-1250 degreeC may be sufficient.

An atmosphere partition member 220 is provided near the lower portion of the lower end 213 of the molded body 210. The atmosphere partition member 220 is a pair of plate-like heat insulating members provided so as to sandwich the sheet glass SG from both sides in the thickness direction.
The atmosphere partition member 220 made of this heat insulating member is provided to partition the molding furnace 240 that is the upper space in which the molded body 210 is accommodated from the lower space. The thermal resistance between the upper space and the lower space of the atmosphere partition member 220 made of this heat insulating member is desirably 0.2 m ² · K / W or more at the atmospheric temperature of the upper space. The viscosity of both end portions of the molten glass when the molten glass passes through the lowermost end portion of the molded body 210 is, for example, 10 ^4.3 to 10 ⁶ poise. In addition, the edge part of sheet glass means the range within 150 mm from the edge of the width direction of sheet glass.

In order to increase the thermal resistance, it is necessary to increase the thickness of the atmosphere partition member 220, for example, but an excessive thickness is not preferable because it affects the glass forming quality. Therefore, it is preferable that the thermal resistance of the atmosphere partition member 220 is 0.4 to ² m ² · K / W.
As the heat insulating member, for example, a ceramic fiber board having a high alumina content is used.

A cooling roller (conveying roller having a function as a cooling roller) 230 is provided below the atmosphere partition member 220. As shown in FIG. 3, the cooling roller 230 is provided on both sides in the thickness direction of the sheet glass SG so as to sandwich the sheet glass SG from both sides in the thickness direction. In addition, it is preferable to cool the cooling roller 230 until the temperature of the width direction both ends of the sheet glass SG falls to the temperature (for example, 900 degrees C or less) corresponded to the viscosity of about 10 < ⁹ > .0 poise or more.

  In addition, a plurality of conveyance rollers including further conveyance rollers 250a to 250d and a temperature adjusting device (not shown) are provided in a region below the cooling roller 230 along the flow direction of the sheet glass SG. Each conveyance roller is provided on each of both sides in the thickness direction of the sheet glass SG, and holds both ends of the sheet glass SG as a pair. That is, a pair of roller conveying means is configured.

  In this region, heater units (not shown), which are heat sources, are provided on both sides in the thickness direction of the sheet glass SG as the temperature adjusting device. The heater unit is provided along the width direction of the sheet glass so that the temperature profile in the width direction of the sheet glass SG can be appropriately controlled.

  As described above, in the cooling (slow cooling) step (ST6), the sheet glass SG that has been formed and flows has a desired thickness in the process of being sandwiched and conveyed by the cooling roller 230 and the conveying rollers 250a to 250d. Then, cooling (slow cooling) is performed so as not to cause warping and internal distortion caused by cooling.

In the said cutting process (ST7), in the cutting device 300, the sheet glass SG supplied from the shaping | molding apparatus 200 is cut | disconnected by predetermined length, and a plate-shaped glass plate is obtained.
The glass plate cut into a plate shape is further cut into a predetermined size to produce a glass substrate with a target size. After this, the end surface of the glass substrate is ground and polished, and the glass substrate is cleaned. Further, after checking for defects such as bubbles and striae, the glass substrate that has passed the inspection is packed as a final product. The

  The glass substrate produced in the present embodiment is suitably used for, for example, a liquid crystal display glass substrate, an organic EL display glass substrate, and the like. In addition, the glass substrate can also be used as a display for a portable terminal device, a cover glass for a housing, a touch panel plate, a glass substrate for a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for liquid crystal display. Among them, it can be suitably used for products that require high-temperature treatment in the panel manufacturing process, such as LTPS (low-temperature polysilicon) / TFT and oxide semiconductor / TFT, which are particularly required to have a low thermal shrinkage rate.

Moreover, the length of the width direction and the vertical direction of the glass substrate manufactured in this embodiment is 500 mm-3500 mm, for example, it is preferable that it is 1000 mm-3500 mm, and it is more preferable that it is 2000 mm-3500 mm.
Moreover, the thickness of the glass substrate manufactured in this embodiment is 0.01 mm-1.0 mm, for example. Preferably, it is 0.1 mm-0.7 mm.

(Composition of glass substrate)
As a glass composition of the glass substrate of the above-mentioned use, they are aluminosilicate glass and boroaluminosilicate glass, Furthermore, they are alkali free glass and fine alkali glass, For example, the following can be mentioned preferably. In addition, the content rate display of the composition shown below is mol%.
_{SiO 2 55~75%, Al 2 O} 3 5~20%, B 2 O 3 0~15%, RO 5~20% ( wherein, R is Mg, Ca, among Sr and Ba, contained in the glass substrate All elements), R ′ ₂ O 0 to 0.4% (where R ′ is all elements contained in the glass substrate among Li, Na and K).
650 degreeC or more may be sufficient as the strain point of the molten glass used by this invention, and it is more preferable that it is 680 degreeC or more.
Further, for example, the liquid phase viscosity of the glass substrate is 10 ^4.3 poise to 10 ^6.7 poise.
Of course, in the present invention, the glass composition of the glass substrate is not limited.

Next, features of the configuration of the glass substrate manufacturing method according to the present invention will be described.
The manufacturing method of the glass substrate which concerns on this invention is the sheet | seat form of the melting process which melt | dissolves a glass raw material to make molten glass, the stirring process which stirs molten glass, and the stirred molten glass as it exists in the invention of the said structure 1. A method for producing a glass substrate having a molding step of molding, starting from a composition having a high devitrification viscosity or a low devitrification temperature, and a composition having a low devitrification viscosity or a high devitrification temperature over time A glass substrate is manufactured by changing the composition of the molten glass after passing through the stirring step in the middle, and the manufacturing conditions of the molding step are adjusted based on the result. .

  Conventionally, when a glass substrate having a target composition is manufactured using, for example, an overflow down draw method, a glass raw material corresponding to the target composition is prepared and put into a manufacturing apparatus to manufacture a sheet-like glass. Then, a method of analyzing the composition of the glass at any stage in the middle and adjusting the composition of the glass raw material to be introduced based on the result to bring it close to the target composition is usually carried out.

  However, as described above, for example, when manufacturing a high-temperature and high-viscosity glass substrate, a glass raw material corresponding to the target high-temperature and high-viscosity glass composition is prepared from the beginning according to the conventional method, and is introduced into a manufacturing apparatus. Then, when the production is started, the load on the production apparatus becomes high, and in particular, the damage to the platinum apparatus used in the clarification tank or the like and the molded body of the molding apparatus becomes large. Moreover, the occurrence of devitrification may not be suppressed. Therefore, it becomes difficult to continue producing glass substrates with stable quality over the long term.

As a result of intensive studies to solve such problems of the prior art, the present inventors have found that the following manufacturing method is optimal.
That is, at first, it is different from the target glass composition of high temperature and high viscosity, but it has a high devitrification viscosity (low devitrification temperature) that is easy to melt and mold, especially considering the devitrification of glass. Production starts from By gradually changing the raw material charged from there, the composition is changed over time to a composition having a low devitrification viscosity (high devitrification temperature), and a glass substrate having the above-mentioned composition is produced. Thus, the occurrence of devitrification can be suppressed, and the load and damage to the manufacturing apparatus can be suppressed. Therefore, it is possible to manufacture a high-quality glass substrate that is stable over the long term.

For example, if glass crystal substances adhere to platinum guide members provided on both side walls and the lower end of the molded body 210, the glass ribbon is cracked and cut. It also affects the thickness and flatness of the glass being produced. In order to remove the glass crystals adhering to the platinum guide member, it is necessary to remove the glass crystals by raising the temperature of the molten glass flowing through the molded body 210. Further, creep deformation of the molded body 210, volatilization of the platinum member, and other deformation and wear of the platinum member occur.
Therefore, it is necessary to manage the temperature according to the composition so that glass crystals are not generated.

In the present invention, the heat resistance of the atmosphere partition member 220 is, for example, 0.4 to ² m ² · K / W, thereby suppressing the movement of heat from the upper space of the molding furnace to the lower space, and the glass liquid phase. It corresponds to the molding of glass with high viscosity.

  In addition, if there is concern about the devitrification of the glass and the viscosity of the molten glass is lowered beyond the range of sheet glass forming conditions, the glass viscosity deviates from that suitable for the structure of the molded body 210, making it difficult to manage the sheet glass thickness and width. Become. If it does so, the thickness deviation and fluctuation | variation of sheet glass will arise, a molten glass will contact the atmosphere partition member 220, a wear will arise in a partition member, As a result, the surface quality of a glass substrate is affected.

  In the present invention, the glass substrate is produced as described above. However, it is important to perform composition analysis of the molten glass after an intermediate stirring step and adjust the production conditions of the forming step based on the result. It is. Not only changes in raw materials to be introduced over time, but also by feeding back the glass composition in the middle of molding to the manufacturing conditions of the molding process, damage to the manufacturing equipment can be more effectively suppressed, and Formation can be suppressed.

  As a more specific embodiment of the present invention, the molten glass after the stirring step is collected and subjected to composition analysis, and the rate of change of the composition is estimated based on the result of the composition analysis of the molten glass, and the estimated composition It is preferable to adjust the manufacturing conditions of the molding process, for example, the temperature conditions of the molded body, in accordance with the rate of change of. In particular, when changing to a glass composition with high temperature and high viscosity, the glass composition in the middle of molding is fed back to the temperature conditions of the molding process because the ease of devitrification and the devitrification temperature differ depending on the fluctuation of the composition. It is preferable to suppress the damage to the manufacturing apparatus, the occurrence of devitrification, the formation of a heterogeneous substrate, and the like.

  In the present invention, the reason why the composition analysis of the molten glass after the stirring process is performed is that the molten glass before the stirring process is not homogenized, and therefore an accurate composition analysis cannot be performed. It is.

  Moreover, you may acquire a sample in multiple places, if it is a molten glass after passing through the stirring process. It is possible to obtain a more accurate composition analysis result without variation. Moreover, you may analyze the glass immediately after shape | molded in the sheet form with the molded object.

  Moreover, in the manufacturing flow of FIG. 1, although the stirring process is implemented after a clarification process, when implementing an agitation process also before a clarification process, you may acquire a sample by a clarification process.

  In the present invention, the composition analysis of the molten glass can be performed by, for example, X-ray fluorescence analysis (XRF). Of course, it is not necessary to be limited to this analysis method, and for example, an inductively coupled plasma (ICP) analysis method or the like can be applied.

Further, the present invention is suitable for manufacturing a glass substrate by the overflow downdraw method as described in the above embodiment.
As described above, when the overflow down draw method, which requires molding with a relatively high viscosity, is used as the molding method, the problem of devitrification tends to occur. And when trying to manufacture high-temperature and high-viscosity glass, for example, using such an overflow down-draw molding method, starting from the beginning with a high-temperature and high-viscosity glass composition, the load on the manufacturing equipment increases. This causes a problem that damage to the manufacturing apparatus increases.

  Therefore, in the production of a glass substrate by such an over-down draw method, it is possible to suppress damage to the apparatus for producing the glass substrate, occurrence of devitrification of the produced glass substrate, etc. The effect of the method for producing a glass substrate of the present invention capable of producing a substrate becomes remarkable.

  As described above, in the method for producing a glass substrate of the present invention, the production starts from a composition having a high devitrification viscosity or a low devitrification temperature, and a composition having a low devitrification viscosity or a high devitrification temperature over time. The glass substrate is manufactured by changing to, the composition analysis of the molten glass is performed after the intermediate stirring step, and the manufacturing conditions of the forming step are adjusted based on the result, so the glass substrate is manufactured. It is possible to suppress damage to the apparatus to be performed and occurrence of devitrification of the glass substrate to be manufactured. For example, it is possible to stably manufacture a high-quality glass substrate having a high temperature and high viscosity composition for a long period of time.

Hereinafter, the present invention will be described more specifically with reference to examples.
The glass substrate was manufactured using the manufacturing apparatus of embodiment shown by FIG.2 and FIG.3 mentioned above.
Here, the composition of the target glass substrate was the following composition.
SiO ₂ 70.5 mol%, Al ₂ O ₃ 10.9 mol%, B ₂ O ₃ 7.4 mol%, RO (MgO, CaO, SrO and BaO in total amount) 10.9 mol%.

The above composition is a composition having a low devitrification viscosity (high devitrification temperature), but first of all, especially considering the devitrification of glass, it has a high devitrification viscosity that is easy to melt and mold (devitrification temperature). The glass substrate was manufactured by changing the raw material to be charged from there to the above-mentioned glass composition over time. In this example, composition analysis of the molten glass after an intermediate stirring step was performed by fluorescent X-ray analysis. And the glass substrate was manufactured, estimating the rate of change of a composition based on the result of the composition analysis of the molten glass, and adjusting the temperature conditions in a formation process.
The strain point of the glass substrate produced at this time was 700 ° C.

In the same manner as above, 1000 glass substrates were manufactured. As a result of performing composition analysis by fluorescent X-ray analysis for each of the manufactured glass substrates, the target composition was obtained for any of the glass substrates, and there was no occurrence of devitrification. Furthermore, after the glass substrate was manufactured, no damage to the manufacturing apparatus occurred.
From this, the effect of the manufacturing method of the glass substrate by this invention is clear.

  The embodiment and specific example of the present invention have been described above. However, the present invention is not limited to the above embodiment and example, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you may do it.

DESCRIPTION OF SYMBOLS 100 Melting | dissolving apparatus 101 Dissolution tank 102 Clarification tank 103 Agitation tank 104 1st piping 105 2nd piping 106 3rd piping 200 Molding apparatus 210 Molding body 212 Supply groove 213 Lower end part 220 Atmosphere partition member 230 Cooling roller 240 Molding furnace 250 Slow cooling furnace 250a ~ 250d Conveying roller 300 Cutting device

Claims (4)

A method for producing a glass substrate, comprising: a melting step for melting glass raw material to form molten glass; a stirring step for stirring molten glass; and a molding step for forming the stirred molten glass into a sheet shape,
Start manufacturing from a composition with high devitrification viscosity or low devitrification temperature, and manufacture a glass substrate by changing to a composition with low devitrification viscosity or high devitrification temperature over time,
A method for producing a glass substrate, comprising performing composition analysis of the molten glass after passing through the stirring step in the middle, and adjusting the production conditions of the forming step based on the result.   The method for producing a glass substrate according to claim 1, wherein a rate of change of the composition is estimated based on a result of composition analysis of the molten glass, and a temperature condition of the forming step is adjusted.   The method for producing a glass substrate according to claim 1 or 2, wherein composition analysis of the molten glass is performed by fluorescent X-ray analysis.   The method for producing a glass substrate according to claim 1, wherein the forming step is performed using an overflow downdraw method.

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