JP7610796B2 - Method for manufacturing glass articles - Google Patents

Description

The present invention relates to a method for manufacturing glass articles.

A glass melting furnace produces molten glass by heating glass raw materials supplied into the furnace using heating devices such as burners and electrodes. The produced molten glass is discharged from the glass melting furnace and formed into a glass article by a forming device or the like.

When changing the type (glass composition) of a glass article, a process of changing the base material of the molten glass is carried out. Known methods for the base material changing process include the base material removal method and the extrusion method (see, for example, Patent Document 1). For example, in the extrusion method, a first type of molten glass that has been produced in a glass melting furnace is pushed downstream by a second type of molten glass that is produced later, and then the production of a glass article using the second type of molten glass is started.

JP 2017-65933 A

When the base material changing process is performed using the extrusion method, as disclosed in Patent Document 1, it is common to directly switch the type of glass raw material supplied to the glass melting furnace from the first type to the second type. In other words, it is common to supply the second type of glass raw material as the glass raw material from the beginning of the base material changing process.

However, if the second type of glass raw material is supplied from the beginning of the glass change process, the properties of the molten glass in the glass melting furnace will change suddenly, which can lead to the following problems:

First, the quality of the molten glass supplied from the glass melting furnace to the molding device may deteriorate, leading to a risk of deterioration in the quality of the glass articles produced during and after the base material changing process.

Secondly, the flow rate of molten glass supplied from the glass melting furnace to the molding device cannot be properly controlled, which may result in a failure to stably manufacture glass articles during and after the base material changing process.

The objective of the present invention is to stably produce high-quality glass articles, both during and after the substrate replacement process.

As a result of intensive research, the inventors have discovered that when the density and/or viscosity of the molten glass properties change significantly, the above-mentioned problems, such as a decrease in the quality of the glass article and instability in the manufacture of the glass article, are more likely to occur. Therefore, the inventors propose the present invention based on this discovery in order to solve the above-mentioned problems.

(1) That is, the present invention is a method for manufacturing a glass article, which includes a base material changing process for changing the type of molten glass from a first type to a second type while supplying glass raw materials to generate molten glass in a glass melting furnace, and the base material changing process includes an intermediate material supplying process for supplying an intermediate material between the first type and the second type as glass raw materials, and the intermediate material supplying process is characterized in that a plurality of intermediate materials having different glass compositions are supplied in sequence so that at least one of the characteristics of the density and viscosity of the molten glass gradually approaches the characteristics of the second type.

In this way, in the base material changing process, the properties including density and/or viscosity of the molten glass produced in the glass melting furnace gradually approach the properties including density and/or viscosity of the second variety. In other words, in the base material changing process, it is possible to reliably prevent the properties including density and/or viscosity of the molten glass produced in the glass melting furnace from suddenly changing. This makes it possible to stably manufacture high-quality glass articles both during and after the base material changing process.

(2) In the above configuration (1), the base material changing process preferably includes a characteristic evaluation process for evaluating the characteristics of the molten glass, and a glass composition adjustment process for adjusting the glass composition of the subsequent intermediate material based on the results of the characteristic evaluation process.

In this way, the glass composition of the intermediate material can be more precisely adjusted, which makes it possible to more reliably prevent abrupt changes in the properties, including the density and/or viscosity, of the molten glass produced in the glass melting furnace.

(3) In the above configuration (2), it is preferable that the characteristic evaluation process includes an analysis process for analyzing the glass composition of the molten glass.

In this way, the properties of the molten glass (e.g., viscosity) whose relationship with the glass composition of the molten glass can be known or predicted in advance can be easily determined from the analyzed glass composition. This is particularly advantageous when it is difficult to measure the properties directly or when it takes a long time to measure the properties.

(4) In any one of the above configurations (1) to (3), it is preferable that the characteristic includes a density of the molten glass, and in the intermediate material supplying step, the intermediate material is supplied so that a change in density of the molten glass is 0.05 [g/cm ³ ] or less per 24 hours.

This makes it possible to more reliably prevent problems caused by changes in the density of the molten glass produced in the glass melting furnace.

(5) In any one of the above configurations (1) to (4), it is preferable that the characteristic includes a viscosity of the molten glass, and in the intermediate material supplying step, the intermediate material is supplied so that a temperature change at a viscosity of 10 ⁴ dPa·s of the molten glass is 15° C. or less per 24 hours.

This makes it possible to more reliably prevent problems caused by changes in the viscosity of the molten glass produced in the glass melting furnace.

According to the present invention, high-quality glass articles can be stably produced even during and after the substrate replacement process.

FIG. 2 is a side view showing a manufacturing apparatus used in the glass article manufacturing method according to the first embodiment. FIG. 2 is a cross-sectional view showing the periphery of a glass melting furnace of the manufacturing apparatus of FIG. FIG. 2 is a flow diagram of a melting step included in the method for manufacturing a glass article according to the first embodiment. FIG. 11 is a flow diagram of a melting step included in a method for producing a glass article according to a second embodiment. 1 is a graph showing a transition of substrate replacement (density change) in a substrate replacement step according to Comparative Example 1 of the present invention. 1 is a graph showing a transition of substrate replacement (density change) in a substrate replacement step according to Example 1 of the present invention. 13 is a graph showing a transition of base material change (change in viscosity) in a base material change step according to Comparative Example 2 of the present invention. 11 is a graph showing a transition of base material change (change in viscosity) in a base material change step according to Example 2 of the present invention.

The manufacturing method of a glass article according to an embodiment of the present invention will be described below with reference to the drawings. Note that in each embodiment, corresponding components are given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments can be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

First Embodiment
As shown in FIG. 1, the manufacturing apparatus used in the method for manufacturing a glass article according to the first embodiment includes, in order from the upstream side, a glass melting furnace 1, a transfer flow path 2, and a forming device 3.

The glass melting furnace 1 is used to carry out a melting process to produce molten glass Gm. The molten glass Gm produced in the glass melting furnace 1 is discharged from an outlet 1a on the downstream side of the glass melting furnace 1 and supplied to a subsequent process. In this embodiment, the molten glass Gm is, for example, alkali-free glass, soda glass, soda lime glass, borosilicate glass, aluminosilicate glass, alkali-containing glass, etc.

The transfer flow path 2 is used to carry out the transfer process of transferring the molten glass Gm from the glass melting furnace 1 to the forming device 3, and is electrically heated as necessary. The transfer flow path 2 includes a fining chamber 4, a homogenization chamber (stirring chamber) 5, a pot 6, and transfer pipes 7 to 10 that connect these respective parts. The transfer pipe 7 is connected to the outlet 1a on the downstream side of the glass melting furnace 1. Here, the terms "chamber" and "pot" such as the fining chamber 4 include those having a tank-like structure and those having a tubular structure.

The fining chamber 4 is used to carry out the fining process in which the molten glass Gm supplied from the glass melting furnace 1 is clarified (removed bubbles) by the action of fining agents, etc.

The homogenization chamber 5 is for carrying out the homogenization process in which the clarified molten glass Gm is stirred and homogenized by the stirring blades 5a. The homogenization chamber 5 may be a series of multiple homogenization chambers. In this case, it is preferable to connect the upper end of one of two adjacent homogenization chambers to the lower end of the other by a transfer pipe.

Pot 6 is used to carry out a condition adjustment process in which the flow rate, viscosity, etc. of the molten glass Gm are adjusted to a state suitable for molding. Pot 6 may be omitted.

The transfer pipes 7 to 10 are cylindrical pipes made of, for example, platinum or a platinum alloy, and transfer the molten glass Gm laterally (approximately horizontally). In this embodiment, the transfer pipe 7 located at the most upstream part of the transfer flow path 2 is inclined so that the downstream end is located higher than the upstream end.

The flanges (not shown) at the ends of the transfer pipes 7 to 10 are joined to mating members by welding or the like. For example, the upstream end of the transfer pipe 7 located at the most upstream portion is joined to the outlet 1a located downstream of the glass melting furnace 1, and the downstream end of the transfer pipe 10 located at the most downstream portion is joined to the forming device 3.

The forming device 3 is for carrying out a forming process in which the molten glass Gm is formed into a desired shape. In this embodiment, the forming device 3 is a forming body that continuously forms a glass ribbon G from the molten glass Gm by the overflow downdraw method.

The forming device 3 may also be one that performs other downdraw methods such as the slot downdraw method or the float method. In order to obtain a smooth surface, it is preferable to use the overflow downdraw method as the forming method.

In the case of the overflow downdraw method, the molten glass Gm supplied to the forming device 3 overflows from a groove formed at the top of the forming device (forming body) 3, flows along both sides of the forming device 3 that have a wedge-shaped cross section, and joins at the bottom end, thereby continuously forming a plate-shaped glass ribbon G. The formed glass ribbon G is gradually cooled and then cut to a predetermined size, and a glass plate is manufactured as a glass product. The glass plate formed by the overflow downdraw method has a forming joining surface inside.

The glass plate produced has a thickness of, for example, 0.01 to 10 mm (preferably 0.1 to 3 mm) and is used as a substrate or protective cover for panel displays such as liquid crystal displays and organic electroluminescence displays, organic electroluminescence lighting, solar cells, etc.

As shown in FIG. 2, the glass melting furnace 1 melts glass raw material Gr (which may include cullet) by heating, including electrical heating, to continuously produce molten glass Gm. The molten glass Gm produced in the glass melting furnace 1 flows into the transfer pipe 7 from the outlet 1a of the glass melting furnace 1.

The glass melting furnace 1 defines a melting space within the furnace by walls made of refractory materials. Examples of refractory materials include electrocast zirconia bricks, electrocast alumina bricks, electrocast alumina-zirconia bricks, electrocast AZS (Al-Zr-Si) bricks, and dense fired bricks.

The bottom wall 1b of the glass melting furnace 1 is provided with a number of rod-shaped electrodes 11 immersed in the molten glass Gm. These electrodes 11 electrically heat the molten glass Gm. In this embodiment, in the melting process for continuously producing the molten glass Gm, the glass raw material Gr is continuously melted only by electrically heating the electrodes 11, so-called full electric melting is performed. Full electric melting has the advantages of a small environmental load due to exhaust gases, a low moisture content in the produced glass sheets, and improved thermal dimensional stability.

The heating method in the glass melting furnace 1 is not limited to the so-called full electric melting method in which the glass raw material Gr is continuously melted only by electrical heating of the electrodes 11, but may be, for example, a method in which heating is performed only by combustion of gas fuel (burner) from above the liquid surface of the molten glass Gm, or a method in which heating is performed by combining electrical heating and combustion of gas fuel.

The electrode 11 is not limited to being rod-shaped, but may be plate-shaped or block-shaped, or a combination of these. The electrode 11 is not limited to being arranged on the bottom wall 1b, but may be arranged on the side wall, or may be arranged on both the bottom wall 1b and the side wall.

A raw material feed device 12 for feeding glass raw material Gr is provided at the upstream feed port 1c of the glass melting furnace 1. The raw material feed device 12 is not particularly limited and may be, for example, a pusher or a vibration feeder, but in this embodiment, it is a screw feeder.

The glass melting furnace 1 is provided with a flue 13 as a gas exhaust passage for discharging gas from within the furnace to the outside. A fan 13a is provided within the flue 13 for sending the gas to the outside.

In this embodiment, the melting space of the glass melting furnace 1 is a single melter consisting of a single melting space, and the transport flow path 2 is a single feeder consisting of a single flow path.

Next, we will explain the manufacturing method of the glass article according to the first embodiment.

This manufacturing method includes a melting process, a transporting process, and a molding process. Of these, the transporting process includes a clarifying process, a homogenizing process, and a conditioning process.

As shown in FIG. 3, in the melting process, when it becomes necessary to change (or improve) the type of molten glass Gm produced in the glass melting furnace 1, a base material changing process S2 is performed.

When the base material changing step S2 is performed, the melting step includes a first step (step before base material changing) S1 in which a first type of glass raw material Gr is supplied by the raw material input device 12 to generate a first type of molten glass Gm in the glass melting furnace 1, a base material changing step S2 in which the type of molten glass Gm is changed from the first type to the second type while supplying glass raw material Gr by the raw material input device 12 to generate molten glass Gm in the glass melting furnace 1, and a second step (step after base material changing) S3 in which a second type of glass raw material Gr is supplied by the raw material input device 12 to generate a second type of molten glass Gm in the glass melting furnace 1, in this order. In this embodiment, the glass sheets manufactured from the molten glass Gm generated in the first step S1, base material changing step S2, and second step S3, respectively, are treated as products if they satisfy a predetermined quality.

In the base material changing step S2, the type of molten glass is changed from a first type to a second type having a glass composition different from that of the first type. The base material changing step S2 is a step of changing the base material using a so-called extrusion method. In detail, the base material changing step S2 includes a final material supplying step B for supplying a final material the same as the second type as a glass raw material, and intermediate material supplying steps A ₁ to A n for supplying intermediate materials between the first type and the second type as glass raw materials before the final material supplying step B. In the intermediate material supplying steps A ₁ to A _n , a plurality of intermediate materials having different glass compositions are sequentially supplied so that the density of the molten glass Gm _in the glass melting furnace 1 gradually approaches the density of the second type.

Here, the intermediate material means a material having a glass composition between the glass compositions of the first and second varieties. In other words, the content of each component of the glass composition of the intermediate material is included in a numerical range having one of the contents of each component of the glass composition of the first and second varieties as a lower limit and the other as an upper limit, among the contents of each component of the glass composition of the first and second varieties. In this embodiment, the intermediate material has a density (D ₁ to D _n ) between the density of the first and second varieties.

In this embodiment, if intermediate material supplying steps A ₁ to A _n are performed a total of n times, and the content of an arbitrary component (referred to as a specific component) in the glass composition of the first variety is P1 and the content of the specific component in the glass composition of the second variety is P2, the content difference of the specific component (P2-P1) is divided by n+1 for each intermediate material and the final material. That is, in the kth intermediate material of the kth intermediate material supplying step A _k (k is an integer from 1 to n), the content of the characteristic component is set so as to satisfy the following relational expression:
P1+k・(P2-P1)/(n+1)...(1)

As a result, the glass composition and density (D ₁ to D _n ) of the first to n-th intermediate materials supplied in each of the intermediate material supplying steps A ₁ to A _n are gradually brought closer to the glass composition and density of the second variety from the glass composition and density of the first variety. That is, in this embodiment, for all components whose content differs between the glass composition of the first variety and the glass composition of the second variety, the k-th intermediate material in the k-th intermediate material supplying step A _k is closer to the glass composition of the second variety than the k-1st intermediate material in the k-1st intermediate material supplying step A _k-1 immediately before. At the same time, the density D _k of the k-th intermediate material in the _k -th intermediate material supplying step A k is closer to the density of the second variety than the density D _k-1 of the k-1st intermediate material in the _{k-1st intermediate material supplying step A k-1} immediately before. Note that, as can be seen from the above formula (1), for components whose content is the same in the glass composition of the first variety and the glass composition of the second variety, the content of the component in the intermediate material is not changed.

Specifically, the first and second varieties have different contents of _SiO2 ( _SiO2 for the first variety: 50 mass%, _SiO2 for the second variety: 65 mass%) and _P2O5 ( _P2O5 for the _{first variety} : 8 mass%, _P2O5 for the second variety: 2 mass% ₎ , and two intermediate material supplying processes _A1 and _A2 are performed. In this case, the _SiO2 content of the first intermediate material in the first intermediate material supplying process _A1 is 55 mass%, the SiO2 content of the intermediate material in the second intermediate material supplying process _A2 is 60 mass%, and _{the SiO2} content of the final material in the final material supplying process B is 65 mass%, the same as the second variety. In addition, the P ₂ O ₅ content of the intermediate material in the first intermediate material supplying process _A1 is 6 mass%, the P ₂ O ₅ content of the intermediate material in the second intermediate material supplying process _A2 is 4 mass%, and the P ₂ O ₅ content of the final material in the final material supplying process B is 2 mass%, the same as the second variety.

In this way, in the base material changing process S2, the glass composition of the molten glass Gm produced in the glass melting furnace 1 gradually approaches the glass composition of the second variety from the glass composition of the first variety. At the same time, the density of the molten glass Gm produced in the glass melting furnace 1 gradually approaches the density of the second variety from the density of the first variety. This makes it possible to prevent the density of the molten glass Gm produced in the glass melting furnace 1 from changing suddenly. Therefore, even during and after the base material changing process S2, high-quality glass sheets (glass articles) can be stably manufactured.

In this embodiment, all components whose contents differ between the first and second glass compositions are linearly changed using formula (1), but the present invention is not limited to this embodiment. For example, only components that have a large effect on density change (e.g., SrO and BaO) may be linearly changed using formula (1), and the remaining components may be kept approximately constant at the same content as the second glass composition. In addition, if the relationship between the content and the density does not have a linear correlation, other relational expressions (e.g., a relational expression using an exponential function) may be used.

In the intermediate material supplying steps A ₁ to A _n , the density change of the molten glass Gm is preferably 0.05 [g/cm ³ ] or less per 24 hours, and more preferably 0.03 [g/cm ³ ] or less per 24 hours. The density change of the molten glass Gm can be controlled by the glass composition of the intermediate material (the glass composition difference (or density difference) between the kth intermediate material and the k-1th intermediate material) and the supply amount, etc. The density of the molten glass Gm can be measured, for example, using molten glass collected from the vicinity of the discharge port 1a of the glass melting furnace 1. Alternatively, it can be measured using molten glass collected from a drain provided in the fining chamber 4, the homogenization chamber 5, etc. Alternatively, it can be measured using a glass plate cut out from the glass ribbon G.

The period (time) for performing each of the intermediate material supplying steps A ₁ to A _n (or each of the intermediate material supplying steps A ₁ to A _n and the final material supplying step B) may be the same or different. Similarly, the amount of change in density of the molten glass Gm in each of the intermediate material supplying steps A ₁ to A _n (or each of the intermediate material supplying steps A ₁ to A _n and the final material supplying step B) may be the same or different.

Here, in the case where the intermediate material supplying steps A ₁ to A _n are not performed in the base material changing step S2 and the second type of glass raw material Gr is supplied from the beginning of the base material changing step, if there is a large density difference between the first type and the second type, the following problems may occur due to the density difference.

First, due to the density difference between the first and second varieties, the first and second varieties may not be mixed uniformly in the glass melting furnace 1. If the molten glass Gm is supplied to the forming device 3 in this state, defects such as streaks may occur in the glass sheet (glass article). The occurrence of such defects leads to a deterioration in the quality of the glass sheet.

Secondly, due to the density difference between the first and second varieties, a stagnant layer of the molten glass Gm of the first variety may be formed in the surface or bottom layer of the molten glass Gm in the glass melting furnace 1. The molten glass Gm of the first variety in the stagnant layer may flow out during and after the substrate replacement process. The molten glass Gm in the stagnant layer is likely to be altered to become a different type of glass due to the volatilization of some components or the inclusion of foreign matter. As a result, if the molten glass Gm of the first variety in the stagnant layer is mixed with the molten glass Gm of the second variety during and after the substrate replacement process, defects such as bubbles may occur in the glass sheet. The occurrence of such defects leads to a deterioration in the quality of the glass sheet.

Thirdly, when the molten glass Gm of the first variety in the stagnant layer formed in the glass melting furnace 1 flows into the forming device 3, the flow rate of the molten glass Gm may suddenly change, which may cause the production of glass sheets to become unstable.

In contrast, if the intermediate material supply steps A ₁ to A _n are performed in the base material changing step S2 according to the present embodiment, the molten glass Gm in the glass melting furnace 1 can be prevented from abruptly changing in density, and therefore the occurrence of these problems can be reliably suppressed.

Second Embodiment
As shown in Fig. 4, the manufacturing method of a glass article according to the second embodiment of the present invention is different from the first embodiment in the intermediate material supplying steps _X1 to _Xn in the base material changing step T2. In the intermediate material supplying steps _X1 to _Xn , attention is paid to the viscosity change, not the density change, as the characteristic change of the molten glass Gm in the glass melting furnace 1.

The base material changing step T2 according to the present embodiment includes intermediate material supplying steps X ₁ to X _n for supplying intermediate materials between the first and second varieties as the glass raw material Gr. In the intermediate material supplying steps X ₁ to X _n , a plurality of intermediate materials having different glass compositions are sequentially supplied so that the viscosity of the molten glass Gm in the glass melting furnace 1 gradually approaches the viscosity of the second variety.

Here, the intermediate material means a material having a glass composition between the glass composition of the first type and the glass composition of the second type. Furthermore, in this embodiment, the intermediate material has a viscosity (V ₁ to V _n ) between the viscosity of the first type and the viscosity of the second type.

In this embodiment, if a total of n intermediate material supply steps _X1 to _Xn are performed, and the content of an arbitrary component (referred to as a specific component) in the glass composition of the first type is Q1 and the content of the specific component in the glass composition of the second type is Q2, the content difference of the specific component (Q2-Q1) is divided by n+1 for each intermediate material and the final material. That is, in the kth intermediate material of the _kth intermediate material supply step Xk (k is an integer from 1 to n), the content of the characteristic component is set to satisfy the following relational expression:
Q1+k・(Q2-Q1)/(n+1)...(2)

As a result, the glass composition and viscosity (V ₁ to V _n ) of the first to n-th intermediate materials supplied in each of the intermediate material supplying steps X ₁ to X _n are gradually brought closer to the glass composition and viscosity of the second product type from the glass composition and viscosity of the first product type. In other words, in this embodiment, for all components whose content differs between the glass composition of the first product type and the glass composition of the second product type, the k-th intermediate material in the k-th intermediate material supplying step X _{k is brought closer to the glass composition of the second product type than the k-1st intermediate material in the k-1st intermediate material supplying step X k -} 1 immediately before. At the same time, the viscosity V _k of the k-th intermediate material in the k-th intermediate material supplying step X _k is brought closer to the viscosity of the second product type than the viscosity V _k-1 of the k-1st intermediate material in the k-1st intermediate material supplying step X k- ₁ immediately before. As can be seen from the above formula (2), for components whose content is the same in the glass composition of the first product type and the glass composition of the second product type, the content of the component in the intermediate material is not changed.

In this way, in the base material changing process T2, the glass composition of the molten glass Gm produced in the glass melting furnace 1 gradually approaches the glass composition of the second variety from the glass composition of the first variety. At the same time, the viscosity of the molten glass Gm produced in the glass melting furnace 1 gradually approaches the viscosity of the second variety from the viscosity of the first variety. This makes it possible to prevent the viscosity of the molten glass Gm produced in the glass melting furnace 1 from changing suddenly. Therefore, even during and after the base material changing process T2, high-quality glass sheets (glass articles) can be stably manufactured.

In this embodiment, all components whose contents differ between the first and second glass compositions are linearly changed using the above formula (2), but the present invention is not limited to this embodiment. For example, only components that have a large effect on viscosity change (e.g., MgO and CaO) may be linearly changed using the above formula (2), and the remaining components may be kept approximately constant at the same content as the second glass composition. In addition, if the relationship between the content and the viscosity does not have a linear correlation, other relational expressions (e.g., a relational expression using an exponential function) may be used.

In the intermediate material supplying steps X ₁ to X _n , the temperature change of the molten glass Gm at a viscosity of 10 ⁴ dPa·s is preferably 15° C. or less per 24 hours, more preferably 5° C. or less per 24 hours. The viscosity change of the molten glass Gm can be controlled by the glass composition of the intermediate material (the glass composition difference (or viscosity difference) between the kth intermediate material and the k-1th intermediate material), the supply amount of the intermediate material, and the like. The viscosity of the molten glass Gm can be measured, for example, using molten glass collected from the vicinity of the outlet 1a of the glass melting furnace 1. Alternatively, it can be measured using molten glass collected from a drain provided in the fining chamber 4, the homogenization chamber 5, or the like. Alternatively, it can be measured using a glass plate cut out from the glass ribbon G.

The period (time) for performing each of the intermediate material supplying steps X ₁ to X _n (or each of the intermediate material supplying steps X ₁ to X _n and the final material supplying step Y) may be the same or different. Similarly, the amount of change in viscosity of the molten glass Gm in each of the intermediate material supplying steps X ₁ to X _n (or each of the intermediate material supplying steps X ₁ to X _n and the final material supplying step Y) may be the same or different.

Here, in the case where the intermediate material supplying steps X ₁ to X _n are not performed in the base material changing step T2 and the second type of glass raw material Gr is supplied from the beginning of the base material changing step T2, if there is a large viscosity difference between the first type and the second type, the following problems may occur due to the viscosity difference.

Firstly, due to a sudden change in viscosity of the molten glass Gm in the glass melting furnace 1, the flow rate of the molten glass Gm in the forming device 3 cannot be properly controlled, and it may become impossible to stably manufacture glass sheets. In the worst case, the flow rate of the molten glass Gm in the forming device 3 may go out of control, making it impossible to manufacture glass sheets at all.

Secondly, the sudden change in viscosity of the molten glass Gm in the glass melting furnace 1 makes it impossible to properly control the flow rate of the molten glass Gm in the forming device 3, making it difficult to control the size of the glass sheet produced, such as its thickness and width. Such size defects lead to a deterioration in the quality of the glass sheet.

Thirdly, a sudden change in the viscosity of the molten glass Gm in the glass melting furnace 1 can cause the glass sheet to have a defective size, which can lead to unexpected contact between the glass sheet and the manufacturing equipment. Such contact can damage the manufacturing equipment and can also lead to a deterioration in the quality of the glass sheet.

In contrast, if the intermediate material supply steps X ₁ to X _n are performed in the base material changing step T2 according to the present embodiment, the molten glass Gm in the glass melting furnace 1 can be prevented from suddenly changing in viscosity, so that the occurrence of these problems can be reliably suppressed.

Third Embodiment
Although not shown in the drawings, the method for manufacturing a glass article according to the third embodiment of the present invention differs from the first and second embodiments in the intermediate material supply step of the base material changing step.

The intermediate material supply process according to the third embodiment includes a characteristic evaluation process for evaluating characteristics including the density and/or viscosity of the molten glass Gm, and a glass composition adjustment process for adjusting the glass composition of the subsequent intermediate material based on the results of the characteristic evaluation process. As described in the first and second embodiments, when the intermediate material supply process is composed of multiple intermediate material processes, it is sufficient that at least one intermediate material supply process includes a characteristic evaluation process and a glass composition adjustment process, but it is preferable that all intermediate material processes include a characteristic evaluation process and a glass composition adjustment process.

The evaluation object in the characteristic evaluation process is not limited to the molten glass Gm in the glass melting furnace 1, but may be, for example, a glass plate manufactured from the molten glass Gm, as long as the characteristics of the molten glass Gm can be evaluated.

In the glass composition adjustment process, the glass composition of the intermediate material is adjusted so that the target characteristics of the molten glass Gm are achieved in each intermediate material supply process. Specifically, for example, the glass composition of the intermediate material determined by the above formula (1) or formula (2) is changed depending on the difference between the target characteristics of the molten glass Gm and the characteristics obtained in the characteristic evaluation process.

In this way, the glass composition of the intermediate material can be adjusted more precisely, so that the characteristics of the molten glass Gm produced in the glass melting furnace 1 can be more reliably prevented from changing suddenly.

The characteristic evaluation process preferably includes an analysis process for analyzing the glass composition of the molten glass. For example, X-ray fluorescence analysis can be used as a method for analyzing the glass composition.

In this way, the characteristics (e.g., viscosity) of the molten glass Gm whose relationship with the glass composition of the molten glass Gm can be known or predicted in advance can be easily determined from the analyzed glass composition. This is therefore advantageous in cases where it is difficult to measure the characteristics directly or where it takes a long time to measure the characteristics.

The above describes the manufacturing method of a glass article according to an embodiment of the present invention, but the embodiment of the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

In the above embodiment, a case has been exemplified in which, in the intermediate material supplying process, multiple intermediate materials with different glass compositions are supplied in sequence so that the density or viscosity of the molten glass gradually approaches the corresponding characteristic (density or viscosity) of the second variety, but this is not limited thereto. In the intermediate material supplying process, multiple intermediate materials with different glass compositions may be supplied in sequence so that the density and viscosity of the molten glass gradually approaches the density and viscosity of the second variety.

In the above embodiment, the glass article is a glass plate, but the glass article is preferably a glass substrate for a display. That is, in glass substrates for displays, it is required to reduce the thermal shrinkage of the glass substrate during display manufacturing in order to suppress pixel pitch deviation. Thermal shrinkage of the glass substrate can be suppressed by increasing the low-temperature viscous characteristic temperature, which is represented by the strain point or glass transition point. However, when the glass composition is improved in order to increase the low-temperature viscous characteristic temperature, the density and viscosity tend to change significantly. Therefore, when the glass composition is improved in order to increase the low-temperature viscous characteristic temperature, it is preferable to carry out a base material replacement process including an intermediate material supply process according to the present invention.

In the above embodiment, the glass melting furnace is described as a single melter in which one melting space is formed within the furnace, but the glass melting furnace may be a multi-melter in which multiple melting spaces are connected together within the furnace.

In the above embodiment, a single feeder was described in which one transport flow path extending toward one molding device was connected to a glass melting furnace, but a multi-feeder may also be used in which multiple transport flow paths extending toward multiple molding devices are connected to a glass melting furnace.

In the above embodiment, the glass article is described as a glass plate, but is not limited thereto. The glass article formed by the forming device may be, for example, a glass roll in which a glass film is wound into a roll, an optical glass part, a glass tube, a glass block, glass fiber, etc., and may be of any shape.

5 and 6 are graphs illustrating the state of transition of the substrate in the substrate changing process according to Example 1 and Comparative Example 1 of the present invention. The density in these figures was measured using a glass plate cut out from the glass ribbon G. In addition, the density in these figures is shown as a relative value with the density of the first type before substrate changing as the reference (zero). In Example 1 and Comparative Example 1, the first type before substrate changing and the second type after substrate changing are both alkali-free glass, and the difference between the density of the second type after substrate changing and the density of the first type before substrate changing is about 0.120 g/cm ³ .

As shown in FIG. 5, the melting process according to Comparative Example 1 includes, in this order, a first step S11 in which a first type of glass raw material is supplied to produce a first type of molten glass in a glass melting furnace, a base material changing step S12 in which the type of molten glass in the glass melting furnace is changed from the first type to the second type, and a second step S13 in which a second type of glass raw material is supplied to produce a second type of molten glass in the glass melting furnace. In the base material changing step S12 according to Comparative Example 1, the second type of glass raw material is supplied from the beginning. In this way, the density of the molten glass in the glass melting furnace approaches the density of the second type from the density of the first type abruptly, so that the density change of the molten glass in the glass melting furnace becomes too large. In this case, due to the density change of the molten glass, the quality of the glass plate (glass article) produced during or after the base material changing step S12 may be reduced, or the glass plate may not be stably produced.

In contrast, as shown in Fig. 6, the melting process according to Example 1 includes a first step S1 of supplying a first type of glass raw material to produce a first type of molten glass in a glass melting furnace, a raw material changing step S2 of changing the type of molten glass from the first type to the second type, and a second step (step after raw material changing) S3 of supplying a second type of glass raw material to produce a second type of molten glass in a glass melting furnace, in this order. The raw material changing step S2 according to Example 1 includes a final material supplying step B of supplying a second type of glass raw material (final material), and intermediate material supplying steps A ₁ to A ₆ of supplying an intermediate material between the first type and the second type before step B. In detail, in Example 1, in order to divide the density from the first type to the second type into seven, six intermediate material supplying steps A ₁ to A ₆ and one final material supplying step B are performed. In other words, six intermediate materials with different glass compositions are supplied in order as glass raw materials, and then the final material same as the second type is supplied. Then, the intermediate materials of each intermediate material supplying process A1 to _A6 are set so that the material replacement rate with respect to the target is 1/7 in the first intermediate material supplying process _A1 , 2/7 in the second intermediate material supplying process A2, ..., 6/7 in the sixth intermediate material supplying process _A6 , and 7/7 in the final material supplying process B. Specifically, the content of each component of the glass composition of the intermediate materials of each intermediate material supplying process _A1 to _A6 is set to satisfy the above formula (1). In this way, as shown in FIG. ₆ , the density of the molten glass in the glass melting _furnace approaches the density of the second variety in stages from the density of the first variety, so that the density of the molten glass in the melting furnace can be prevented from changing suddenly. As a result, a high-quality glass plate (glass article) can be stably manufactured during and after the base material replacement process.

Here, in the base material changing step S12 of Comparative Example 1, the density change of the molten glass is a maximum of about 0.115 [g/cm ³ ] per 24 hours. In contrast, in the base material changing step S2 including the intermediate material supply steps A ₁ to A ₆ of Example 1, the density change of the molten glass is suppressed to about 0.03 [g/cm ³ ] per 24 hours.

7 and 8 are graphs illustrating the state of transition of the substrate in the substrate changing process according to Example 2 and Comparative Example 2 of the present invention. The viscosities in these figures were measured using glass plates cut out from the glass ribbon G. In addition, the viscosities in these figures are shown as relative values with the viscosity of the first type before substrate changing as the reference (zero). In Example 2 and Comparative Example 2, the first type before substrate changing and the second type after substrate changing are both alkali-free glasses, and the difference between the temperature at which the viscosity of the first type before substrate changing is 10 ⁴ dPa·s and the temperature at which the viscosity of the second type after substrate changing is 10 ⁴ dPa·s is about 75°C.

As shown in FIG. 7, the melting process according to Comparative Example 2 includes, in this order, a first process T11 in which a first type of glass raw material is supplied to produce a first type of molten glass in a glass melting furnace, a base material changing process T12 in which the type of molten glass in the glass melting furnace is changed from the first type to the second type, and a second process T13 in which a second type of glass raw material is supplied to produce a second type of molten glass in the glass melting furnace. In the base material changing process T12 according to Comparative Example 2, the second type of glass raw material is supplied from the beginning. In this way, the viscosity of the molten glass in the glass melting furnace approaches the viscosity of the second type from the viscosity of the first type abruptly, so that the viscosity change of the molten glass in the glass melting furnace becomes too large. In this case, due to the viscosity change of the molten glass, the quality of the glass plate (glass article) produced during or after the base material changing process T12 may be reduced, or the glass plate may not be stably produced. There is also a risk of damage to the production equipment.

In contrast, as shown in Fig. 8, the melting process according to Example 2 includes a first step T1 of supplying a first type of glass raw material to produce a first type of molten glass in a glass melting furnace, a raw material changing step T2 of changing the type of molten glass from the first type to the second type, and a second step T3 of supplying a second type of glass raw material to produce a second type of molten glass in a glass melting furnace, in this order. The raw material changing step T2 according to Example 2 includes a final material supplying step Y of supplying a second type of glass raw material (final material), and intermediate material supplying steps _X1 to _X6 of supplying an intermediate material between the first type and the second type before the step Y. In detail, in Example 2, in order to divide the temperature from the viscosity of the first type to the viscosity of the second type of ¹⁰⁴ dPa·s into seven, six intermediate material supplying steps _X1 to _X6 and ^one final material supplying step Y are performed. In other words, six types of intermediate materials with different glass compositions are supplied in order as glass raw materials, and then the final material same as the second type is supplied. Then, the intermediate materials of each intermediate material supplying process X1 to _X6 are set so that the first intermediate material supplying process _X1 has a material replacement rate of 1/7 relative to the target, the second intermediate material supplying process X2 has a material replacement rate of 2/7 relative to the target, ..., the _sixth intermediate material supplying process _X6 has a material replacement rate of 6/7 relative to the target, and the final material supplying process _Y has a material replacement rate of 7/7 relative to the target. Specifically, the content of each component of the glass composition of the intermediate materials of each intermediate material supplying process _X1 to _X6 is set to satisfy the above formula (2). In this way, the viscosity of the molten glass generated in the glass melting furnace can be prevented from changing suddenly because the viscosity of the first type approaches the viscosity of the second type in stages. As a result, even during and after the base material replacement process, high-quality glass sheets (glass articles) can be stably manufactured while suppressing damage to the manufacturing equipment.

Here, in the base material changing step T12 of Comparative Example 2, the temperature change of the molten glass Gm with a viscosity of 10 ⁴ dPa·s is about 50 [°C] per 24 hours at maximum. In contrast, in the base material changing step T2 including the intermediate material supply steps _X1 to _X6 of Example 2, the temperature change of the molten glass with a viscosity of 10 ⁴ dPa·s is suppressed to about 10 [°C] per 24 hours.

Reference Signs List 1 Glass melting furnace 2 Transport flow path 3 Forming device 4 Refining chamber 5 Homogenization chamber 6 Pot 7 Transport pipe 10 Transport pipe 11 Electrode 12 Raw material input device 13 Flue 13a Fan G Glass ribbon Gm Molten glass Gr Glass raw material

Claims (5)

A method for producing a glass article, comprising a base material changing step of changing a type of the molten glass from a first type to a second type while supplying glass raw materials to generate molten glass in a glass melting furnace,
The glass raw material changing step includes an intermediate material supplying step of supplying an intermediate material between the first variety and the second variety as the glass raw material,
The method for manufacturing a glass article, characterized in that in the intermediate material supplying step, a plurality of intermediate materials having different glass compositions are supplied in sequence so that at least one of the density and viscosity characteristics of the molten glass gradually approaches the characteristics of the second variety. The method for manufacturing a glass article according to claim 1, wherein the base material changing process includes a characteristic evaluation process for evaluating the characteristics of the molten glass, and a glass composition adjustment process for adjusting the glass composition of the subsequent intermediate material based on the results of the characteristic evaluation process. The method for manufacturing a glass article according to claim 2, wherein the characteristic evaluation process includes an analysis process for analyzing the glass composition of the molten glass. the property includes a density of the molten glass;
The method for manufacturing a glass article according to any one of claims 1 to 3, wherein in the intermediate material supplying step, the intermediate material is supplied so that a change in density of the molten glass is 0.05 [g/cm ³ ] or less per 24 hours. the characteristics include the viscosity of the molten glass;
The method for manufacturing a glass article according to any one of claims 1 to 4, wherein in the intermediate material supplying step, the intermediate material is supplied so that a temperature change at a viscosity of 10 ⁴ dPa·s of the molten glass is 15°C or less per 24 hours.

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