JP6587844B2 - Display glass plate manufacturing method and display glass plate manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing a glass plate for display, and an apparatus for manufacturing a glass plate for display.

  In recent years, in the field of displays, higher definition of pixels has been advanced in order to improve image quality. With the progress of this high definition, it is desired that the glass substrate used for the display has high dimensional accuracy. For example, a glass substrate having a low thermal shrinkage rate is preferable so that the dimensions of the glass substrate are not easily changed even when the glass substrate is heat-treated at a high temperature during the manufacturing process of the display.

  In general, the thermal shrinkage rate of a glass substrate decreases as the strain point of the glass increases. Moreover, it is known that the thermal shrinkage rate of a glass substrate will become so small that the slow cooling rate in the manufacturing process of the glass plate from which a glass substrate is cut out becomes small. However, if the slow cooling rate is reduced, it is necessary to lengthen the slow cooling furnace for performing the slow cooling step of the glass plate, but it is difficult to lengthen the slow cooling device on the production line.

  Therefore, the heat shrinkage rate is further lowered by performing heat treatment on a plurality of glass plates produced on the production line over time. As a technique related to off-line heat treatment, for example, it is known that a plurality of glass plates are erected so that the main surface faces the traveling direction, and heat treatment is performed while being transported in a heat treatment furnace with a space between each other (patent document) 1). It is also known that when heat treatment is performed in a heat treatment furnace, heat treatment is performed by blowing hot air from the upper end side of the standing glass plate to the gap between the glass plates.

International Publication No. 2014/022632 Pamphlet

  However, in the method in which hot air is blown into the gap between the glass plates, the hot air comes into contact with the glass plates and heat is taken away by the glass plates, so that the temperature on the leeward side of the hot air is lower than that on the upwind side. Therefore, a temperature difference arises between the upper end part and lower end part of a glass plate. When such a temperature difference is continued during the heat treatment, a difference in thermal history occurs in the plane of the glass plate, and strain is generated due to tensile stress and compressive stress. As a result, the thermal shrinkage rate varies within the plane of the glass plate. A plurality of glass substrates cut out from a glass plate having a variation in thermal shrinkage rate may have different thermal shrinkage rates from each other, or may still vary in thermal shrinkage within each plane. In particular, a glass substrate used for a liquid crystal display is increased in size with the recent increase in size of the liquid crystal display, and a temperature difference is likely to occur in a wide plane in a heat treatment process, and a thermal contraction rate is likely to vary.

  Then, an object of this invention is to provide the manufacturing method of the glass plate for a display which can manufacture the glass plate for a display in which the variation in the thermal contraction rate was reduced, and the glass plate manufacturing apparatus for a display.

The present invention provides the following (1) to ( 5 ).
(1) a heat treatment step for heat-treating the molded glass plate;
A conveyance step of conveying a plurality of suspended glass plates on a conveyance path at intervals from each other while the heat treatment step is performed ,
In the heat treatment step, a heated gas is blown into a gap between the plurality of glass plates, and the glass plate is heated by a heat source disposed on the downstream side in the direction in which the gas is blown with respect to the glass plate. And
The temperature T _{1 of the} gas in the transport path that has flowed in by blowing and the temperature T _{2 of the} gas that has flowed out of the transport path are measured so that the difference between the temperature T ₁ and the temperature T ₂ is reduced. A method for producing a glass plate for a display, wherein the temperature of the heat source is controlled .

(2) In the heat treatment step, using the heat source, the glass plate is heated so that a temperature difference in the main surface of the glass plate is reduced. .

( 3 ) In the heat treatment step, the gas is blown from above the glass plate,
The said heat source is a manufacturing method of the glass plate for a display as described in said (1) or the said ( 2) arrange | positioned below the said glass plate.

( 4 ) In the heat treatment step, any one of (1) to ( 3 ), wherein the glass plate is heated using the heat source so that a temperature difference within a main surface of the glass plate is within 20 ° C. The manufacturing method of the glass plate for displays as described in a term.

( 5 ) a heat treatment apparatus for performing heat treatment on the molded glass plate;
A transport unit that transports a plurality of suspended glass plates on a transport path at intervals from each other while the heat treatment is performed ;
The heat treatment device blows a heated gas in a gap between the plurality of glass plates, and heats the glass plate by a heat source disposed on the downstream side in the direction in which the gas is blown with respect to the glass plate. And
The temperature T _{1 of the} gas in the transport path that has flowed in by blowing and the temperature T _{2 of the} gas that has flowed out of the transport path are measured so that the difference between the temperature T ₁ and the temperature T ₂ is reduced. A glass plate manufacturing apparatus for a display, wherein the temperature of the heat source is controlled .

  According to the above-described method for manufacturing a glass plate for display, etc., a glass plate for display with reduced variation in thermal shrinkage can be manufactured.

It is a figure which shows an example of the process of the manufacturing method of the glass plate of this embodiment. It is a figure explaining the internal structure of the heat treatment furnace used at the heat treatment process of this embodiment. It is a figure explaining the heat treatment process of this embodiment. It is a figure which shows the glass plate hold | gripped by the clamp at the heat processing process of this embodiment seeing from a side. It is an external view which shows an example of the heat source of this embodiment.

Hereinafter, the manufacturing method of the glass plate for a display of this embodiment and the glass plate manufacturing apparatus for a display are demonstrated.
The manufacturing method of the glass plate for a display of this embodiment is equipped with the heat processing process which heat-processes with respect to the shape | molded glass plate. In the heat treatment step, the heated gas (hot air) is blown into the gaps between the plurality of glass plates arranged at intervals, and the downstream side (leeward side) in the direction in which the gas is blown to the glass plate. The glass plate is heated by a heat source arranged in In this method, since the glass plate is heated by a heat source from the leeward side while heating the glass plate using hot air, the temperature difference in the plane of the glass plate is reduced, and the difference in thermal history in the plane of the glass plate is reduced. Is suppressed from occurring. For this reason, the variation in the thermal contraction rate in the surface of the glass plate is reduced. Such a glass plate is suitable as a glass plate for a display.

(Outline explanation of the method of manufacturing the glass plate)
Drawing 1 is a figure showing an example of a process of a manufacturing method of a glass plate of this embodiment.
The glass plate manufacturing method includes a forming step (S1), a slow cooling step (S2), a plate-drawing step (S3), a heat treatment step (S4), a cutting step (S5), and an end face processing step (S6). And a cleaning process (S7), an inspection process (S8), and a packing process (S9).

In the forming step (S1), the molten glass is formed into a sheet glass. As the molding method, a known method such as a fusion method (overflow down draw method) or a float method is used. Of these, the fusion method is suitable for the method of this embodiment in which offline annealing is performed because it is difficult to lengthen the slow cooling device included in the production line.
In the slow cooling step (S2), cooling is performed in a slow cooling device so as not to cause internal distortion and warpage of the sheet glass that is formed and conveyed.
In the plate-drawing step (S3), the slowly cooled sheet glass is cut into predetermined lengths to obtain a plurality of glass plates. The glass plate is preferably sampled in a rectangular shape, and the size is not particularly limited. For example, the vertical length and the horizontal length are 500 mm to 3500 mm, respectively. The plate | board thickness of a glass plate is 0.1-1.1 mm, for example.
In the heat treatment step (S4), the glass plate is heat treated in a heat treatment furnace described later. In the heat treatment furnace, while the heat treatment step (S4) is performed, a conveyance step for conveying the glass plate is also performed.
In the cutting step (S5), the heat-treated glass plate is cut into a predetermined size to obtain a plurality of glass substrates. The glass substrate is preferably cut into a rectangular shape, and the size is not particularly limited. For example, the vertical length and the horizontal length are 500 mm to 3500 mm, respectively.
In the end face processing step (S6), end face processing including end face grinding, polishing and corner cutting is performed on the glass substrate.
In the cleaning step (S7), the glass substrate is cleaned.
In the inspection step (S8), the cleaned glass substrate is optically inspected for scratches, dust and dirt on the surface, or internal defects such as bubbles and foreign matters.
In the packing step (S9), the glass substrate that conforms to the desired quality is packed as a result of the inspection. The packed glass substrate is shipped to a supplier.

(Glass plate manufacturing equipment)
The display glass plate manufacturing apparatus of the present embodiment includes a forming device, a slow cooling device, and a cutting device as devices for performing the steps of the forming step (S1) to the plate-drawing step (S3) described above. Among these, a shaping | molding apparatus has a molded object for shape | molding molten glass, when shaping | molding by the overflow downdraw method is performed. The glass plate manufacturing apparatus further includes a heat treatment unit (heat treatment apparatus) for performing a heat treatment process and a conveyance unit (conveyance apparatus) for performing a conveyance process, which will be described later.

(Glass plate)
The glass plate manufactured by this embodiment is a glass plate for a display used for a display, for example, a glass plate for flat panel displays (FPD) and a glass plate for curved displays. Moreover, the glass plate manufactured by this embodiment uses the glass plate for oxide semiconductor displays which used oxide semiconductors, such as IGZO (indium, gallium, zinc, oxygen), and LTPS (low-temperature polysilicon) semiconductor, for example. LTPS display glass plate. Moreover, the glass plate manufactured by this embodiment is a glass plate for liquid crystal displays, a glass plate for organic EL displays, for example.

The glass plate produced in the present embodiment preferably has a heat shrinkage rate of 10 ppm or less from the viewpoint of being used for a display, the heat shrinkage rate is more preferably 6 ppm or less, and more preferably 3 ppm or less. Preferably, it is 2 ppm or less. By setting the thermal contraction rate of the glass plate to 2 ppm or less, the variation of the thermal contraction in the surface of the glass plate can be set to 2 ppm or less. In the present specification, when the variation in the thermal shrinkage rate is reduced, it means that the thermal shrinkage rates measured at a plurality of positions in the plane of the glass plate are all 2 ppm or less.
The strain point of the glass plate is preferably 600 ° C. to 760 ° C. in order to obtain a high-definition glass plate for display. For example, the strain point is 661 ° C.
The thermal shrinkage rate of the glass substrate before reducing the thermal shrinkage rate by the heat treatment of the present embodiment is 80 ppm or less, more preferably 40 ppm to 60 ppm, when heat treatment is performed at 500 ° C. for 10 minutes.

As such a glass plate, the glass plate of the following glass compositions is illustrated. That is, in the method of this embodiment, the raw material of molten glass is prepared so that the glass plate of the following glass compositions is manufactured.
SiO ₂ 55~80 mol%,
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 60 to 75 mol%, and more preferably 63 to 72 mol%, from the viewpoint of reducing the heat shrinkage rate.
Among RO, it is preferable that MgO is 0-10 mol%, CaO is 0-15 mol%, SrO is 0-10%, and BaO is 0-10%.

Further, at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO are included, and the molar ratio ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) is 4. The glass which is 5 or more may be sufficient. In addition, it is preferable that at least one of MgO, CaO, SrO, and BaO is included, and the molar ratio (BaO + SrO) / RO is 0.1 or more.

The total content of 2-fold and mol% of RO for the content of mol% of B ₂ O ₃ is 30 mol% or less, it is preferred that preferably 10 to 30 mol%.
Moreover, 0 mol% or more and 0.4 mol% or less may be sufficient as the content rate of the alkali metal oxide in the glass substrate of the said glass composition.
Further, it contains 0.05 to 1.5 mol% of metal oxides (tin oxide and iron oxide) whose valence fluctuates in the glass, and substantially contains As ₂ O ₃ , Sb ₂ O ₃ and PbO. It is not essential but optional.

(Configuration of heat treatment furnace)
The heat treatment step (S4) of this embodiment is performed using the heat treatment furnace shown in FIG. FIG. 2 is a diagram for explaining the internal structure of the heat treatment furnace 1. The transfer process is also performed using the heat treatment furnace 1.
The heat treatment furnace 1 includes an inlet 3 that is opened so that the glass plate G is carried in, an outlet 5 that is opened so that the glass plate G that has passed through the furnace 1 is carried out, and the inlet 3 and the outlet 5 that are in the furnace 1. And a conveyance path 7 extending so as to be connected inside. The conveyance direction of the glass plate G is a direction from left to right in FIG. In FIG. 2, the portion of the heat treatment furnace 1 between the inlet 3 and the outlet 5 is omitted for convenience.

The glass plate G is transported upstream of the heat treatment furnace 1 with the main surface facing up and down, and the main surface is adsorbed and supported by the suction mechanism (not shown) at the inlet 3 while the main surface is transported in the transport direction. Standing to face.
The glass plate G is laid down (turned down) at the outlet 5 so that the main surface faces in the vertical direction while the main surface is adsorbed and supported by another suction mechanism (not shown). The laid glass plate G is transported on the downstream side of the heat treatment furnace 1 with the main surface facing up and down.

  The transport path 7 has three sections divided into three in the transport direction, and the glass plate G is transported through the three sections, so that the glass plate G is heated, kept, and cooled. Each heat treatment is performed in order. FIG. 2 shows a part of each of the temperature raising section 7a and the temperature lowering section 7c, and FIG. 3 to be referred to later shows a part of the keep section 7b. The three sections 7a to 7c are different in heat treatment conditions such as temperature and time during which the glass sheet G is conveyed, but the apparatus configuration is the same. Measuring means for measuring the temperature of the glass plate G is provided in the conveying path 7 at predetermined intervals in the conveying direction. Specifically, the measuring means measures the temperatures of the windward end (upper end) and the leeward end (lower end) of the glass sheet G, respectively. For example, a thermocouple thermometer is used as the measuring means.

  The heat treatment furnace 1 includes a transport unit that transports a plurality of glass plates G on the transport path 7 and a heat treatment unit that performs heat treatment on the transported glass plates G.

(A) Conveying unit The conveying unit is for carrying out a conveying process, and is provided with two chain belts (conveying belts) 21 (Fig. 3) that are stretched over both ends of the conveying direction above the glass plate G to be conveyed. Reference), a plurality of bars 23 that move in the transport direction together with the chain belt 21, and a plurality of clamps 25 attached to the bars 23.

For example, the chain belt 21 is spanned by a plurality of rollers at both ends in the transport direction, and is driven as shown in FIG. For convenience, FIG. 2 shows only some of the plurality of rollers on the upstream side in the transport direction. As shown in FIG. 3, one chain belt 21 is provided so as to correspond to both ends in the width direction of the glass plate G to be conveyed, and is driven by a drive mechanism (not shown) during the heat treatment step (S4). The FIG. 3 is a diagram for explaining the heat treatment process of the present embodiment. In FIG. 3, a portion of the chain belt 21 that moves in the conveyance direction is shown, and a portion that moves in the direction opposite to the conveyance direction is omitted. Further, in FIG. 3, for convenience of explanation, the illustration of the clamp 25 is omitted, and the bar 23 and the glass plate G are shown in a state of being spaced apart from each other.
Belts 27 constituting the bottom of the heat treatment furnace 1 are suspended at both ends in the transport direction at positions facing the chain belt 21 with the glass plate G being transported in between. The belt 27 is not driven during the heat treatment step (S4), but can be driven by operating an operating device (not shown) if necessary. As the belt 27, for example, a mesh belt is used in which openings that penetrate in the thickness direction are arranged in the surface direction. By using the mesh belt, the hot air of the downflow blown in the heat treatment process can pass through the mesh belt and flow downward, and the downward flow of the hot air can be stabilized. Furthermore, when a belt that does not have an opening that penetrates in the thickness direction is used, there is a risk that dust on the belt will rise by hot air colliding with the belt and adhere to the glass plate G being transported. When a belt is used, there is no possibility of dust collecting on the belt surface, so that it is possible to suppress the occurrence of inconvenience due to such dust. Note that the bottom portion of the heat treatment furnace 1 may be configured with a plate-like member that is not driven instead of the belt 27.

The bar 23 is a plate-like member made of, for example, metal. In the transport step (S4), both ends of the bar 23 are placed on the portion of the chain belt 21 that moves in the transport direction, and the bar 23 moves in the transport direction so as to follow the chain belt 21. A clamp 25 is attached to the bar 23, and the glass plate G is suspended from the bar 23 when the glass plate G is held by the clamp 25 by the holding mechanism 4 at the inlet 3 of the heat treatment furnace 1. FIG. 4 shows the bar 23 and the clamp 25 in more detail. FIG. 4 is a view showing the glass plate G held by the clamp 25 as viewed from the side. In order to convey the glass plate G at a predetermined interval (pitch) in the conveyance path 7, one bar 23 suspending the glass sheet G is provided by the load mechanism 8 disposed at the upstream end of the conveyance path 7. One by one, they are placed on the chain belt 21 at intervals. As a result, the glass plate G is conveyed (vertically suspended) while being hung from the chain belt 21 via the bar 23. The narrower the interval between the glass plates G, the higher the productivity, but the heat of the hot air is easily taken away by the glass plates G. In the manufacturing method of this embodiment, since the dispersion | variation in the thermal contraction rate in the surface of the glass plate G can be reduced as mentioned later, it is suitable also when the space | interval of the glass plates G is narrow. The distance between the glass plates G is preferably 20 to 200 mm, more preferably 50 to 150 mm, from the viewpoint of productivity and prevention of contact between the glass plates. In FIG. 2 and FIG. 4, for the convenience of explanation, the intervals between the plurality of glass plates G are shown close together.
The bar 23 from which the glass plate G is suspended is removed from the chain belt 21 by the unload mechanism 9 disposed at the downstream end of the conveyance path 7, and the glass plate is removed by the extraction mechanism 6 at the outlet 5 of the heat treatment furnace 1. G is extracted from the clamp 25.

  The clamp 25 is a member that holds the upper end of the glass plate G. The clamp 25 is not particularly limited. For example, a spring clamp that sandwiches both main surfaces of the glass plate G by a spring force can be employed. Although the number of the clamps 25 attached to one bar 23 may be one, in order to make the attitude | position of the glass plate G in conveyance more stable, it is preferable that it is two or more. When two or more clamps 25 are attached to the bar 23, the clamp 25 is preferably configured to be slidable in the width direction with respect to the bar 23. The bar 23 made of a metal material has a higher coefficient of thermal expansion than the glass plate G and easily extends in the width direction. For this reason, when the clamp 25 moves in the width direction with respect to the bar 23, it is possible to prevent the upper end portion of the glass plate G from being bent or deformed even if the bar 23 is thermally expanded.

(B) Heat treatment unit The heat treatment unit is for performing the heat treatment step (S4), and includes a plurality of fan-equipped heaters 31 arranged in the conveyance direction above and below the glass plate G to be conveyed. And a plurality of heaters 33. The heater 31 with the fan and the heater 33 are controlled by a control device (not shown) so that a temperature profile designed in advance is formed on the glass plate G to be conveyed.

  The fan-equipped heater 31 is an integrated device in which the heater and the fan are arranged adjacent to each other so that the gas heated by the heater is blown by the fan. Arranged. As the heater of the heater 31 with a fan, for example, a burner heater or an electric heater is used. During the heat treatment step (S4), the fan is driven to blow the air heated by the heater downward as shown in FIG. In FIG. 3, the direction in which the hot air flows is indicated by a thick arrow. Even when dust is floating in the atmosphere in the heat treatment furnace 1, large dust (for example, dust having a maximum length of several μm or more) is carried to the bottom of the furnace 1 by the hot air of such downflow. And accumulate. In addition, small dust (for example, a maximum length of less than 0.5 μm) is removed by a filter. For this reason, it can suppress that dust continues floating in the atmosphere and adheres to the surface of the glass plate G. Since the filter is exposed to hot air, a filter having heat resistance is preferable. For example, the filter is disposed below a belt 27 described later and above the heater 31 with a fan. Further, the downflow hot air is preferable in that an air flow circulating in the heat treatment furnace 1 can be formed. The hot air flows downward between the glass plates G, then flows along the bottom of the heat treatment furnace 1 to a side wall (not shown) of the heat treatment furnace 1, rises along the side wall, and further flows along the ceiling of the heat treatment furnace 1. Thus, it circulates around the conveyance path 7.

The blowing of hot air is not limited to the mode described above, and may be performed in the mode described below.
For example, you may blow hot air using the following hot air generator (not shown) arrange | positioned on the outer side of the furnace wall of the heat processing furnace 1. FIG. This hot air generator is an apparatus for supplying hot air into the furnace 1 from a blower opening (not shown) provided in the furnace wall. Specifically, the hot air generator is a device including a heater and a fan for blowing the gas heated by the heater, and the heater may be disposed on the downstream side of the fan. It may be arranged on the downstream side. When using a hot air generator, the hot air supplied into the furnace 1 is placed at a position (for example, the bottom of the furnace 1) different from the position (for example, the ceiling of the furnace 1) of the furnace wall of the heat treatment furnace 1. An exhaust port (not shown) for discharging outside the furnace 1 is provided. The position at which the air outlet and the exhaust port are provided is adjusted so that the glass plate G conveyed in the furnace 1 is arranged in the middle of the flow of hot air. Thus, in the aspect which blows hot air, the hot air discharged | emitted out of the furnace 1 from the exhaust port may be returned to a hot air generator, and it may circulate in the furnace 1 and the outside of the furnace 1, and is circulating. It may be released into the atmosphere as it is.
For example, you may blow hot air using the following hot air generator (not shown) arrange | positioned in the heat processing furnace 1 or the outer side of the furnace wall. This hot air generating device uses a hot air generating device having a heating element having a shape extending in one direction and a cylindrical member surrounding the heating element with a gap between the heating element and the heating element. You may blow. For example, the heating element may have a shape such that the gas flows spirally in the axial direction in the gap between the heating element and the cylindrical member. In this hot air generator, the gas sucked from one end of the cylindrical member to the inside of the cylindrical member is heated by contact with the heating element while passing through the cylindrical member, and becomes hot air. It is discharged from the other end.
In these embodiments, the hot air may flow through the gaps between the glass plates G in the lateral direction instead of flowing in the vertical direction.

  The heater 33 (heat source) is not particularly limited as long as it can heat the glass plate G. For example, a burner heater, an electromagnetic wave heater, a heat conduction heater, or a hot air heater is used. The heater 33 is preferably disposed at a position adjacent to a portion where the temperature of the glass plate G is lowest when the heat treatment step (S4) is performed using only hot air. By arranging the heater 33 at such a position, it is possible to effectively suppress the variation in the thermal contraction rate due to the occurrence of a temperature difference in the surface of the glass plate G. Specifically, the heater 33 is preferably arranged at a position facing the heater 31 with the fan through the glass plate G, that is, on the leeward side of the hot air. For example, a plurality of heaters 33 are arranged below the portion of the belt 27 that moves in the transport direction with an interval in the transport direction. The heater 33 is preferably configured so that the flow of hot air is not hindered. Such a heater 33 has, for example, a shape having a gap between the heating elements in the planar direction, like the heater 33 shown in FIG. The heater 33 shown in FIG. 5 is a heating element formed so as to have a substantially M shape in a plan view, and has a gap between the heating elements in the planar direction. FIG. 5 is an external view showing an example of the heater 33. In FIG. 5, the hot air passes in the vertical direction. The heater 33 shown in FIG. 5 is connected to a power source (not shown) at both ends of the heating element, and generates heat when a current flows through the heating element. For example, the downflow hot air blown from the fan-equipped heater 31 flows through the gap between the heating elements to flow further downstream without being interrupted by the heater 33, and the hot air circulates as described above. Can do.

In the fan-equipped heater 31 and the heater 33, it is preferable that the length of the heat generating region in the horizontal direction (the depth direction in FIG. 2) is longer than the width direction length of the glass plate G to be conveyed. Further, the interval between the fan-equipped heaters 31 adjacent to each other in the transport direction is adjusted so that the temperature of the hot air does not vary across the transport direction. Further, the interval between the heaters 33 adjacent to each other in the transport direction is adjusted so that the radiant heat of the heater 33 transmitted to the glass plate G is not uneven in the transport direction.
The heater 33 may have a shape extending along the transport direction as shown in FIG. 3, instead of the one shown in FIG. FIG. 3 shows a part of such a conveyance region of the heater 33. As such a heater 33, for example, a metal plate-shaped member extending in the transport direction is provided with a heating wire extending in the transport direction, or such a plate member is energized in the transport direction. And those that generate heat. The heater shown in FIG. 3 may be applied to the heater 31 with the fan.

(Heat treatment process)
The heat treatment step (S4) is performed using the heat treatment furnace 1 described above. In the heat treatment step, heat treatment is performed on the formed glass plate G in a range where the temperature of the glass plate G is preferably 400 to 600 ° C, more preferably 450 to 550 ° C. Specifically, in the heat treatment furnace 1, hot air is blown into gaps between a plurality of glass plates G that are spaced apart from each other, and downstream in the direction in which hot air is blown to the glass plate G. The glass plate G is heated by the radiant heat radiated from the heater 33 arranged on the side (leeward side). While the heat treatment step (S4) is performed, in the heat treatment furnace 1, a conveyance step of conveying the glass sheets G at intervals may be performed in parallel. In the transport process, the glass plate G is suspended from the chain belt 21 so that the main surface of the glass plate G faces the transport direction, and is transported vertically.

The heat treatment in the above temperature range is performed in the keep section. The temperature range of 400 to 600 ° C. is a range including the temperature when a semiconductor layer composed of LTPS (low temperature polysilicon) and IGZO (indium, gallium, zinc, oxygen) is formed on a glass substrate. It is only necessary to reduce the variation in the thermal shrinkage rate in the surface of the glass plate in the temperature range.
In the heat treatment in the keep section, specifically, the temperature of the glass plate G is preferably maintained at a predetermined temperature (keep temperature) within a range of 400 to 600 ° C., more specifically, This is performed by maintaining the temperature of the glass plate G so that the in-plane temperature difference is within the range of the keep temperature. The keep temperature is determined so as to reduce the variation in the thermal shrinkage rate in the plane of the glass plate G. The difference between the upper limit value and the lower limit value of the keep temperature range is preferably within 20 ° C., more preferably no difference. For example, the keep temperature is in the range of 450 to 550 ° C. where the difference between the upper limit value and the lower limit value is 20 ° C. or less, more preferably 480 to 530 where the difference between the upper limit value and the lower limit value is 20 ° C. or less. It is in the range of ° C. Moreover, the time (keep time) for performing the heat treatment in the keep section is adjusted in consideration of the reduction of the heat shrinkage rate, and is, for example, 60 minutes or more.

As an example of a method of setting the difference between the upper limit value and the lower limit value of the range of the keep temperature within 20 ° C., the hot air temperature T ₁ when hot air flows into the transfer path 7 of the heat treatment furnace ₁ and the heat treatment from the transfer path 7. It is possible to measure the hot air temperature T ₂ when flowing to the bottom of the furnace 1 and to heat the heater 33 so as to suppress a temperature difference between the hot air temperature T ₁ and the hot air temperature T _2. . For example, when the hot air temperature T ₁ is 520 ° C. and the hot air temperature T ₂ is 490 ° C. as a result of the measurement, the set temperature (for example, 520 ° C. to 530 ° C.) of the heater 33 is set to a temperature higher than the hot air temperature T _2. Then, the difference between the upper limit value and the lower limit value can be set within 20 ° C. by controlling the temperature of the heater 33 so that the hot air temperature T ₂ approaches 520 ° C.

In the heat treatment step (S4), in addition to the heat treatment in the keep section described above, a heat treatment having a temperature lower than the keep temperature may be performed. The heat treatment below the keep temperature is performed in the temperature increase interval and the temperature decrease interval.
In the temperature raising section, specifically, the glass plate G is heated to the keep temperature. The temperature of the glass plate G at the start of temperature rise is not particularly limited, and is, for example, room temperature. The heating rate is preferably substantially constant throughout the section, and is, for example, 6.7 to 60 ° C./min. The temperature raising time is adjusted in consideration of reduction of the heat shrinkage rate, and is, for example, 10 minutes or more.
In the temperature lowering section, specifically, the temperature of the glass plate G is decreased from the keep temperature to a temperature (for example, 400 ° C.) within the range of strain point −100 ° C. to strain point −300 ° C. The temperature decreasing rate is preferably substantially constant throughout the section, and is, for example, 0.8 to 2.5 ° C./min. The temperature lowering time is adjusted in consideration of reduction of the heat shrinkage rate, and is, for example, 60 minutes or more.

  By performing the heat treatment step (S4), a temperature profile designed in advance is reproduced in each glass plate. The temperature profile indicates the temperature change of the glass plate G with the elapsed time of the heat treatment step, and is designed in advance from the viewpoint of reducing the variation in the thermal shrinkage rate in the surface of the glass plate G. The temperature profile is not particularly limited. For example, the temperature of the glass sheet G is maintained at the highest and constant temperature during the time corresponding to the keep interval, and increases from room temperature to the keep temperature during the time corresponding to the temperature increase interval. In the time corresponding to the temperature drop period, the temperature is gradually lowered from the keep temperature, and has a substantially trapezoidal shape when the temperature is the vertical axis and the elapsed time of the heat treatment process is the horizontal axis. . The temperature lowering time is preferably longer than the temperature rising time.

The temperature of the fan-equipped heater 31 and the heater 33 is set so that the temperature profile is reproduced.
The heat treatment step (S4) can be performed, for example, by changing the temperature of the hot air without changing the air volume of the hot air between the temperature raising, keeping, and temperature lowering sections. The temperature of the hot air can be changed by adjusting the heater temperature of the heater 31 with a fan.

  The hot air is preferably blown from the end of the glass plate G toward the center in the plane. Thereby, heat can be transmitted to a wider region of the main surface of the glass plate G, and the in-plane temperature difference of the glass plate G can be effectively reduced. For this reason, the glass plate G is transported in a horizontally long direction so that the horizontal dimension (direction perpendicular to the direction in which the hot air flows) is shorter than the vertical dimension (the direction in which the hot air flows) with respect to the direction in which the hot air flows. It is preferred that By carrying in this way, compared with the case where the glass plate G of the same dimension is carried vertically, the length by which the heat of the hot air is taken away by the glass plate G is shortened, and the windward side portion and the leeward side of the glass plate G are reduced. It is possible to reduce the temperature difference that occurs between the side portions.

  In the heat treatment step, the interval between the glass plates G adjacent to each other in the conveyance direction is adjusted in consideration of productivity and the conveyance speed of the glass plate G. In FIG. 3, the space | interval of the glass plate G is shown with a bidirectional arrow. Moreover, the conveyance speed of the glass plate G is adjusted from a viewpoint which conveys the glass plate G with the stable attitude | position. The conveyance speed may be the same between the sections or may be different.

  In the manufacturing method of the glass plate of this embodiment, a plurality of glass plates G are spaced apart from each other, and hot air is blown into the gaps between the adjacent glass plates G to perform uniform heat treatment on each glass plate. Thus, variation in the thermal shrinkage rate between the glass plates G is suppressed. And, in each of the glass plates G, in the heat treatment step, the radiant heat of the heater 33 disposed on the leeward side of the hot air is transmitted, so even if the temperature on the leeward side of the hot air is lower than the windward side, Generation | occurrence | production of the temperature difference in the surface of the glass plate G is suppressed. For this reason, it is suppressed that the difference of a thermal history arises in the surface of the glass plate G, and internal distortion generate | occur | produces, and the variation in the thermal contraction rate in the surface of each glass plate G is suppressed. Moreover, the glass plate manufactured by the manufacturing method of the glass plate of this embodiment is a semiconductor layer comprised from LTPS and IGZO, when heat processing is performed in the range from which the temperature of the glass plate G will be 400-600 degreeC. As the glass plate for display, the heat shrinkage rate when the material is formed on the main surface is small, and even if the size is relatively large, the heat shrinkage rate is suppressed in the surface. Is suitable.

  In the heat treatment step, hot air is blown from one side of the glass plate in the side direction (the depth direction in FIG. 2) instead of being blown in the vertical direction of the glass plate, and to the other side of the side direction. You may heat-process by heating a glass plate using the arrange | positioned heat source. Further, in the heat treatment step, the glass plate may not be transported, and the heat treatment performed in each of the temperature rise, keep, and temperature drop intervals by changing the temperature of the heater 31 with the fan and the heater 33 at a fixed position, for example. In each of the three different positions, heat treatment is performed in any section, the glass plate is moved between the three different positions, and another heat treatment is performed to raise the temperature, You may perform each heat processing of a keep and temperature fall. Further, the glass plate may be gripped not only on the windward end of the hot air but also on the leeward side in the heat treatment step. In this case, it is preferable that a passage of hot air is secured on the leeward side so that the hot air can pass from the windward side through the center in the plane of the glass plate to the leeward side.

(Experimental example)
SiO ₂ 67.0 mol%, Al ₂ O ₃ 10.6 mol%, B ₂ O ₃ 11.0 mol%, RO 11.4 mol% (RO is MgO, CaO) prepared by using the overflow downdraw method. A sheet glass having a thickness of 0.5 mm having a glass composition of (total amount of SrO and BaO) is sampled on a plurality of rectangular glass plates having a size of 2270 mm × 2000 mm, and in the heat treatment furnace 1 described above, The heat treatment process was performed on the plurality of glass plates under the following conditions (Example 1).
Temperature rise interval: from room temperature to 500 ° C to 520 ° C over 30 minutes Keep interval: hold for 120 minutes at 500 ° C to 520 ° C Temperature drop interval: 60 from 500 ° C to 520 ° C to 120 ° C Temperature drop over minutes Pitch between glass plates: 100mm

  Moreover, the heat processing process was performed similarly to the Example except the point which did not heat with the heater 33 using the glass plate sampled from the same sheet glass which sampled the glass plate of Example 1 (comparative example). ). In the comparative example, the in-plane temperature difference of the glass plate in the keep section exceeded 30 ° C.

(Measurement of heat shrinkage)
Nine glass substrates were cut out from each of the glass plates of the examples and comparative examples subjected to the heat treatment step, and the thermal shrinkage rate of each glass substrate was measured in the following manner.
A scribing line is put on both ends of the long side of the glass substrate and cut in half at the center of the short side to obtain two glass samples. One of the glass samples is heat-treated (temperature rising rate is 100 ° C./min, left at 500 ° C. for 30 minutes). Measure the length of the other glass sample without heat treatment. Further, the heat-treated glass sample and the untreated glass sample are put together to measure the deviation amount of the marking line with a laser microscope or the like, and the difference in the length of the glass sample is obtained to obtain the thermal contraction amount of the sample. . Using the difference, which is the amount of heat shrinkage, and the length of the glass sample before the heat treatment, the heat shrinkage rate is obtained by the following equation. Let the thermal shrinkage rate of this glass sample be the thermal shrinkage rate of a glass substrate.
Thermal contraction rate (ppm) = (difference) / (length of glass sample before heat treatment) × 10 ⁶
As a result of the measurement, the thermal shrinkage rate of the glass substrate of the example was all within 3 ppm, whereas the thermal shrinkage rate of the glass substrate of the comparative example was in the range of 4 to 10 ppm. It was confirmed that the in-plane variation was reduced.

(Example 2)
A glass substrate having a size of 300 mm × 300 mm was cut out from a glass plate having the same composition and thickness as in Example 1, and the heat treatment step was performed in the heat treatment furnace 1 described above under the following conditions 1 and 2 (implementation) Example 2). By reducing the size of the glass substrate to 300 mm × 300 mm, the temperature difference between the upper part and the lower part of the glass substrate caused by the heat treatment by downflow was suppressed, and the glass substrate was heat-treated so that the in-plane temperature of the glass substrate became uniform. By this heat treatment, the variation of the thermal shrinkage rate in the surface of the glass substrate was made zero. The thermal contraction rate of the glass substrate obtained by the heat treatment of each of the conditions 1 and 2 was determined, and the variation in the thermal contraction rate caused by the heat treatment temperature difference of 20 ° C. between the condition 1 and the condition 2 was determined.
Condition 1
Temperature rise interval: Temperature rise from room temperature to 500 ° C over 30 minutes Keep interval: Hold at temperature of 500 ° C for 90 minutes Temperature drop interval: Temperature fall from 500 ° C to 400 ° C over 90 minutes Pitch between glass substrates: 100mm
Condition 2
Temperature rise interval: Temperature rise from room temperature to 520 ° C over 30 minutes Keep interval: Hold at 520 ° C for 90 minutes Temperature drop interval: Temperature fall from 520 ° C to 400 ° C over 90 minutes Pitch between glass substrates: 100 mm

  The thermal shrinkage rate of the glass substrate under condition 1 was -0.1 ppm, and the thermal shrinkage rate of the glass substrate under condition 2 was 1.9 ppm. Since the temperature difference of the keep temperature between the condition 1 and the condition 2 is 20 ° C., the variation in the thermal shrinkage rate of the glass substrate with the temperature difference of the heat treatment being 20 ° C. is 2 ppm (= 1.9 ppm − (− 0.1 ppm)) ). For this reason, it was confirmed that the difference in heat treatment temperature should be 20 ° C. or less in order to make the variation of the thermal shrinkage rate in the plane of the glass plate 2 ppm or less.

  As mentioned above, although the manufacturing method of the glass plate for displays and the glass plate manufacturing apparatus for displays of this invention were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, various improvement is carried out. Of course, you may make changes.

1 Heat treatment furnace 3 Inlet 5 Outlet 7 Conveying path 21 Chain belt (conveying belt)
23 Bar 25 Clamp 27 Belt 31 Fan heater 33 Heater G Glass plate

Claims (5)

A heat treatment step for heat-treating the molded glass plate ;
A conveyance step of conveying a plurality of suspended glass plates on a conveyance path at intervals from each other while the heat treatment step is performed ,
In the heat treatment step, a heated gas is blown into a gap between the plurality of glass plates, and the glass plate is heated by a heat source disposed on the downstream side in the direction in which the gas is blown with respect to the glass plate. And
The temperature T _{1 of the} gas in the transport path that has flowed in by blowing and the temperature T _{2 of the} gas that has flowed out of the transport path are measured so that the difference between the temperature T ₁ and the temperature T ₂ is reduced. A method for producing a glass plate for a display, wherein the temperature of the heat source is controlled .   The method for manufacturing a glass plate for a display according to claim 1, wherein in the heat treatment step, the glass plate is heated using the heat source so that a temperature difference in a main surface of the glass plate is reduced. In the heat treatment step, the gas is blown from above the glass plate,
The said heat source is a manufacturing method of the glass plate for a display of Claim 1 or 2 arrange | positioned below the said glass plate. In the heat treatment step, by using the heat source, the temperature difference in the main surface of the glass plate is heated to the glass plate so as to be within 20 ° C., for a display according to any one of claims 1 3 Manufacturing method of glass plate. A heat treatment apparatus for heat-treating the molded glass plate ;
A transport unit that transports a plurality of suspended glass plates on a transport path at intervals from each other while the heat treatment is performed ;
The heat treatment device blows a heated gas in a gap between the plurality of glass plates, and heats the glass plate by a heat source disposed on the downstream side in the direction in which the gas is blown with respect to the glass plate. And
The temperature T _{1 of the} gas in the transport path that has flowed in by blowing and the temperature T _{2 of the} gas that has flowed out of the transport path are measured so that the difference between the temperature T ₁ and the temperature T ₂ is reduced. A glass plate manufacturing apparatus for a display, wherein the temperature of the heat source is controlled .

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