JPH0215235A - Heat treating method for glass substrate - Google Patents

Abstract

PURPOSE:To shorten a heat treatment time by operating the cooling device for the center part of a substrate so as to cool the center part first, heating compensating device so as to heat the peripheral part of the substrate more, or the both so as to cool the center part of the substrate faster than the outer peripheral part at the time of lowering the temperature. CONSTITUTION:When an air shower is used for the cooling device as to a continuous heat treating method wherein the substrate is conveyed by a belt conveyor, the high- temperature glass substrate 3 after a heat treatment is sent intermittently by the belt conveyor 2 as shown by an arrow A while stopping below the cooling device 5 having a nozzle 51 arranged so as to blow cooling air 5 to the center part of the substrate 3. Further, when this method is applied to the heating compensating device such as a heater plate used for the initial-stage part of a cooling zone, the substrate which is heated at high temperature is heated by a heater so as to prevent the substrate from being quenched and the substrate is mounted on the plate held at temperature a little bit lower than the heat treatment temperature to lower the temperature as a 1st stage. The heater 81 is arranged roughly at the center part of the device 8 and closely at the peripheral part, and heating compensation is made weak at the center part to lower the temperature of the center part faster than that of the peripheral part.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for heat treatment of glass substrates used in the manufacturing process of flat display panels such as liquid crystal display panels and plasma display panels, the cooling time is increased by increasing the temperature drop rate during the cooling process. The purpose of this is to provide a method for heat treatment of glass substrates that does not cause damage such as cracking even when shortened, and in a continuous flow heat treatment process in which a plate-shaped glass substrate is heated to y temperature and the temperature is lowered after heat treatment.
When the temperature is lowered, the central part of the substrate is cooled faster than the outer periphery by either or both of a cooling means that cools the central part of the substrate first or a heating compensation means that strongly heats the peripheral part of the substrate.

[Industrial application field]

The present invention relates to a method for heat treating a glass 7A plate used in the manufacturing process of flat display panels such as liquid crystal display panels and plasma display panels.

Flat display panels are widely used in various display devices because of their thinness and light weight, and recently, the screen size has been increasing in particular.

These display panels usually consist of a pair of glass substrates with drive electrodes formed on their inner surfaces, facing each other with a tiny gap between them.During the manufacturing process, the glass substrates go through various firing processes, so processing is difficult. Improvements in firing methods are required to reduce time and improve quality.

[Conventional technology]

During the manufacturing process of flat display panels such as liquid crystal display panels, various films such as transparent drive electrodes and insulating layers are formed on the surface of the glass substrate. For bonding substrates, etc., heat treatment is repeated many times at a low temperature below the strain point temperature of the glass substrate.

These heat treatments are carried out in a continuous flow heat treatment furnace that has good mass productivity.

Figure 2 shows a conceptual diagram of a continuous flow heat treatment furnace.

Figure (a) is a belt-conhair type with a large number of heaters 11, 12, 13. ... are arranged linearly to form a heating zone A and a cooling zone B. While the glass substrate 3 placed on the belt conveyor 2 passes through the inside of the heat treatment furnace 1, the temperature is raised to a predetermined temperature. It is then held for a predetermined period of time and slowly cooled. Also, (b
) is a plate-type heat treatment furnace, in which multiple stages, such as a heater plate 41 heated by a heater and a cooling plate 42 cooled by cooling water or air, are arranged and maintained at a predetermined temperature to separate heating zones A and cooling zones. A zone B is configured in which the glass substrate 3 is intermittently transported to the next stage using a shuttle bar or the like, and is heated, held, and cooled while passing through the furnace.

In a conventional heat treatment furnace, the temperature of the multiple stages of heating units and cooling plates that make up cooling zone B gradually decreases toward the exit of the furnace, but the temperature inside each stage is - It was heated or cooled to

[Problem to be solved by the invention]

In the conventional heat treatment method described above, in order to prevent the glass substrate from cracking during cooling, the cooling rate must be slowed down, and the length of the cooling zone must be increased, making the furnace larger and more expensive, as well as increasing the processing time. The problem was that it took a long time.

For example, heat treatment after applying a liquid crystal molecular alignment film made of a resin material to a 30 cm square glass substrate for a liquid crystal display panel requires heating at 250°C and then slowly cooling it for 5 minutes or more. Therefore, the length of the cooling zone is required to be 10 m or more, and it is necessary to perform continuous heat treatment using a large furnace.

The reason why the glass substrate is easily broken during cooling is considered to be as follows.

In other words, these heat treatments are performed at a temperature below the glass transition point that does not cause deformation of the glass, so throughout the heat treatment process the glass substrate behaves as a substantially rigid body with no internal material flow; Even if strain occurs locally, the stress will not be alleviated. In conventional cooling methods, the periphery of the substrate has better heat dissipation, so it is cooled first and tends to shrink. However, the center part radiates heat more easily than the periphery and remains at high temperature, resulting in a large volume due to thermal expansion.

Therefore, the peripheral portion of the substrate cannot be completely contracted, and tensile stress is generated due to elongation strain.

However, glass inherently has material properties such that it is strong against compressive stress but has low strength against tensile stress. In addition, localized weak points occur inside the glass substrate due to minute microcracks and residual stress during cutting of the outer shape and polishing of the surface.

Therefore, when the temperature distribution becomes unbalanced during the cooling process and tensile stress is generated in the peripheral area, the local weak point cannot withstand the stress and breaks. In order to avoid this, it is thought that it is necessary to cool down the temperature distribution over a sufficient period of time while minimizing the imbalance.

The present invention was created in order to solve the problems of the prior art, focusing on the above-mentioned results.In the heat treatment process in which glass substrates are heated at high temperatures, the cooling rate is increased during the cooling process to increase the cooling time. An object of the present invention is to provide a method for heat treatment of a glass substrate that does not cause damage such as cracking even if the heat treatment method is short.

[Means to solve the problem]

The above problem is caused by the continuous flow type heat treatment process in which the temperature of a plate-shaped glass substrate is raised and then lowered after the heat treatment. This problem is solved by the glass substrate heat treatment method of the present invention, which is characterized in that the central part of the substrate is cooled faster than the outer peripheral part by one or both of the heating compensation means.

[Effect]

The periphery of the glass substrate is always at a higher temperature than the center when it is cooled to room temperature, so the center shrinks more than the periphery and is brought to room temperature with compressive stress applied to the periphery. . Therefore, rapid cooling can be performed without applying tensile stress to the surrounding area during the cooling process, so the number of cooling stages can be reduced, reducing the cooling time and downsizing the firing furnace.

〔Example〕

The present invention will be described in detail in Section 4-J below.

FIG. 1 is a conceptual diagram showing the cooling process in the heat treatment method of the present invention.

FIG. 1 (Part 1) is an embodiment in which the present invention is applied to continuous heat treatment in which a substrate is transferred by a heat converter.

In the figure (a), an air shower is used as a cooling means, and the high temperature glass substrate 3 after heat treatment is cooled by cooling air 52
The air is stopped under the cooling means 5 having a nozzle 51 disposed so as to blow the air into the center of the substrate 3, and is then intermittently sent in the direction indicated by the arrow by the Hell I Conhair 2.

In the figure (b), the two sides of the substrate are brought close to the cooling plate as the cooling means 6, and the cooling plate 63 is used as the cooling means 6 for the substrate.
The cooling vibro 1 is provided in a spiral shape in the center thereof without passing through a cooling medium 62 such as cooling air or water, and the temperature thereof is lower than that of the peripheral portion.

The heated glass substrate 3 placed on the held conditioner 2 after being heated is intermittently transferred in the direction indicated by the arrow while stopping under the cooling plate 63 . -1- In both examples, the center part of the glass substrate 3 is exposed to a lower temperature than the peripheral part while the glass substrate 3 is stopped at the cooling means 6 during the process of being intermittently transferred by the held container, so it is cooled first. be done.

FIG. 1 (Part 2) is an embodiment applied to plate-mounted continuous heat treatment.

Figure (c) shows a cooling plate mounted type, which cools the glass substrate 3, which is hot after heat treatment, and the cooling plate, etc., which has cooling pipes 71 embedded in a high density in the center, making it cooler than the surrounding area. A certain amount of time on means 7! 32 and cooled down, it is sent to the next stage at a lower temperature by a transfer means such as a shuttle bar (not shown), and is similarly cooled to a lower temperature.

(d) of the figure is a case where it is applied to a heating compensation means such as a heater plate used in the first stage of the cooling zone.
This plate is often placed before the cooling means mentioned above in a), (b), and (c), and is heated with a heater and kept at a temperature slightly lower than the heat treatment temperature to avoid rapid cooling of the heated substrate. A substrate is first placed on top and the temperature is lowered in the first stage.

In this case, the heater (electrothermal heating 'f/A) 8 is placed sparsely in the center of the heating compensation means 8 such as a heater plate, and densely in the periphery.
1 and weakens the heating compensation in the central part, the central part of the heating compensation means 8 is kept at a lower temperature than the peripheral part, and the central part of the substrate 3 to be placed is lower than the peripheral part. The temperature is lowered first.

By appropriately arranging the cooling means and heating compensation means described above in the cooling zone of the continuous heat treatment furnace, the heat-treated high-temperature glass substrate can be cooled while maintaining its central part at a lower temperature than the peripheral part. No tensile stress is applied to the periphery of the substrate.

Therefore, it is possible to reduce the number of stages in the cooling zone of the furnace to achieve rapid cooling, and it is possible to reduce the equipment cost by downsizing the furnace and to improve the throughput of the heat treatment process by shortening the cooling time.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to shorten the heat treatment time of glass substrates and downsize the heat treatment furnace in the manufacturing process of flat display panels such as liquid crystal display panels, and the practical effects thereof are remarkable.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an embodiment of the present invention, and FIG. 2 is a conceptual diagram of a continuous flow heat treatment furnace. In the figure: 1, IL - one continuous flow heat treatment furnace, 2 - belt conhair, 3 - glass substrate, 5, 6.7 - cooling means,
8-Heating compensation means.

Claims (1)

[Claims] Cooling means (5, 6, 7) that cools the central part of the substrate first when the temperature is lowered in a continuous flow heat treatment process in which the temperature of the plate-shaped glass substrate (3) is raised and then lowered after the heat treatment.
Or a heating compensation means (8) that strongly heats the peripheral area of the substrate.
A method for heat treatment of a glass substrate, characterized by cooling the central part of the substrate faster than the outer peripheral part by one or both of the following.