JP2001012860A - Continuous heating furnace for large size glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct temperature rising, insulation and the like and prevent defects in a substrate, such as strain, cracking, chipping and the like in the state where the surface temperature is controlled with precision. SOLUTION: A continuous heating furnace for a large size glass substrate comprises a plurality of heating chambers 1 each having a heating means which is capable of conducting temperature control, and a conveying means 6 for intermittently conveying an object 3 to be heated to the adjacent heating chamber. In each of the heating chambers 1, the heating means 2 and its control system are divided into some portions at least in respect of the moving direction of the object 3. Further, there are provided partition walls 4 for sectioning the inside of the heating chamber 1 so that the individual definitions correspond to the divided portions of the heating means 2, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous heating furnace for heating a large glass substrate used for, for example, a plasma display panel and the like, and more particularly, to a heating method in which the surface temperature of a large glass substrate is precisely controlled. The present invention relates to a continuous heating furnace capable of keeping heat, etc., and preventing defects such as distortion, cracking, and chipping of a substrate.

[0002]

2. Description of the Related Art In recent years, large-screen flat panel displays (hereinafter, referred to as “FPDs”), which can be used as wall-mounted televisions and multimedia displays, have been steadily put into practical use. As such a large-screen FPD, a plasma light emitting device that combines the advantages of quality, that is, a self-luminous type, a wide viewing angle, and good display quality, and the advantages of manufacturing, that is, the manufacturing process is simple and the size can be easily increased. A display panel (hereinafter, referred to as “PDP”) is listed as a leading candidate.

As shown in FIG. 4, for example, a PDP is manufactured by using a thick film method in which printing, drying, and firing steps are repeated a plurality of times on the surface of a large glass substrate called a front glass or a rear glass, by using a thick film method. , Phosphors and the like are sequentially formed, and finally the front glass and the back glass are sealed. In this case, the glass substrate is dried and fired by, for example, a plurality of heating chambers having a heating means such as a roller hearth kiln having a temperature-controllable electric heater, and a glass substrate as an object to be heated being heated to an adjacent heating chamber. Using a continuous heating furnace equipped with a conveying means such as a roller for conveying the ink, and by individually controlling the temperature of each heating chamber, in accordance with a desired temperature curve, performing a method of raising, lowering, and lowering the temperature. It is common.

When a large glass substrate such as a PDP is dried and fired, it is required that the temperature of the substrate surface be as uniform as possible. If drying and firing are performed in a state where the temperature distribution on the substrate surface is large, the substrate and the members formed on the substrate may be cracked or broken due to distortion.
Defects, such as chipping, remain in the drying and firing steps, resulting in similar defects in subsequent steps (eg, a grinding step). Defects reduce the product yield. This is because such a problem as described above occurs.

[0005] With regard to the temperature distribution on the substrate surface during drying and baking, particularly strict conditions have been required in recent years, as displays have been increasing in size to 50 to 60 inches. The temperature difference Δt between the highest temperature and the lowest temperature in each part of the surface is from room temperature to 400
Extremely strict temperature conditions are required: within 20 ° C. in the temperature rising range of 10 ° C., within 10 ° C. in the temperature rising range of 400 to 600 ° C., and within 6 ° C. after reaching the firing temperature of 600 ° C.

Therefore, in addition to the improvement of the material such as the glass substrate being made of a high strain point glass, not only the temperature of each heating chamber is individually controlled, but also the heating means and its control in one heating chamber. Attempts have been made to improve the equipment by performing more precise temperature control by dividing the system (Japanese Patent Laid-Open No. 10-82583). According to the facility, it is also possible to perform temperature control such that the degree of heating is increased only in a portion of the substrate surface where the temperature is difficult to increase (for example, the central portion of the substrate), and the maximum temperature and the minimum temperature in each portion of the substrate surface are reduced. It is said that the temperature difference Δt can be reduced.

[0007]

However, even when the above-mentioned equipment is used, each divided heating means is affected by the temperature of another adjacent heating means or another adjacent heating chamber. At present, the required precise temperature control has not been achieved. That is, even if the temperature control for each of the divided heating means is strictly performed, as shown in FIG. 5B, the heat diffuses until reaching the surface of the large glass substrate 43, which is the object to be heated, and becomes uniform. Therefore, control for adjusting the degree of heating for each portion of the surface of the large glass substrate 43 as shown in FIG. 5C cannot be performed.

The present invention has been made in view of the above-mentioned problems of the related art, and it is possible to raise and keep the temperature of a large-sized glass substrate while controlling the surface temperature of the substrate precisely. An object of the present invention is to provide a continuous heating furnace capable of preventing defects such as cracks, chips and the like.

[0009]

Means for Solving the Problems As a result of the present inventors' earnest studies on the above-mentioned problems, in addition to dividing the heating means and its control system in each heating chamber, it is necessary to cope with the divided heating means. Further, the present invention has been completed in view of solving the above-mentioned problem by structurally or substantially dividing the space in the heating chamber.

That is, according to the present invention, there are provided a plurality of heating chambers having heating means capable of controlling the temperature, and a transport means for intermittently transporting the object to be heated to an adjacent heating chamber,
By controlling the temperature of each heating chamber individually, according to a desired temperature curve, the temperature is raised, kept warm, and configured to be able to lower the temperature, a continuous heating furnace for a large glass substrate, in each of the heating chamber , Heating means and its control system, at least with respect to the traveling direction of the object to be heated, divided into several, and, corresponding to the divided heating means,
A continuous heating furnace for a large glass substrate, wherein a partition for partitioning a heating chamber is provided.

Further, according to the present invention, there are provided a plurality of heating chambers having heating means capable of controlling the temperature, and a transport means for intermittently transporting the object to be heated to an adjacent heating chamber,
By controlling the temperature of each heating chamber individually, according to a desired temperature curve, the temperature is raised, kept warm, and configured to be able to lower the temperature, a continuous heating furnace for a large glass substrate, in each of the heating chamber , The heating means and its control system are divided at least with respect to the direction of movement of the object to be heated, and the divided heating means are arranged so as to be close to the stationary position of the object to be heated. A continuous heating furnace for a large glass substrate is provided.

In the continuous heating furnace of the present invention, it is preferable that a muffle made of a material having a high infrared irradiation rate is disposed between the heating means and the moving area of the object to be heated. It is further preferable to arrange a muffle made of Si-impregnated SiC material between the moving region and the muffle region made of Si-impregnated SiC material so that the muffle made of Si-impregnated SiC material corresponds to heating means divided in the traveling direction of the object to be heated. Splitting is particularly preferred.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The continuous heating furnace for large glass substrates according to the present invention has a heating chamber and a control system thereof divided in each heating chamber, and the heating chamber is adapted to correspond to the divided heating means. Is structurally or substantially divided into a plurality of regions.

According to such a configuration, even when a large-sized glass substrate is fired, the temperature can be raised and kept in a state in which the surface temperature of the substrate is precisely controlled, and the substrate can be distorted or cracked. , Chipping and other defects can be prevented. Hereinafter, the continuous heating furnace of the present invention will be described in detail.

[0015] The continuous heating furnace according to the present invention is a tunnel-shaped heating device in which a plurality of heating chambers having heating means capable of controlling the temperature are communicated by two opening portions on an inlet side and an outlet side through which a body to be heated can pass. Furnace. In such a continuous heating furnace, an object to be heated placed on a setter or the like is sent into the furnace from the inlet side, and sequentially passed through each heating chamber whose temperature is individually controlled by an independent control system. According to a desired temperature curve, the temperature of the object to be heated can be continuously raised, kept, and lowered.

When the object to be heated is a large glass substrate as in the present invention, the transport means for transporting the object to be heated is a transport means for intermittently transporting the object to be heated to an adjacent heating chamber. is necessary. This is because the temperature distribution on the surface of the object to be heated may be increased in a transfer unit in which the object to be heated continuously moves between heating chambers having different set temperatures.

“Transmitting intermittently” means that the object to be heated is kept stationary in the n-th heating chamber for a predetermined time, and then the object to be heated is heated as soon as possible to the (n + 1) -th adjacent heating object. This is a transport method in which the operation of moving to a chamber, stopping the object to be heated again, and heating for a predetermined time is repeated. The type of the transporting means is not particularly limited as long as such a transporting method is possible. For example, a walking beam can be used, but the rollers and the conveyor may be driven intermittently.

As the heating means, it is preferable to use an electric heater whose temperature can be easily controlled, but a gas radiant tube which is advantageous in terms of operating cost may be used alone or together with the electric heater.

In the present invention, as in the past, the heating means and its control system are divided into several parts in each heating chamber, as described above. Temperature cannot be precisely controlled. Therefore, the present invention employs the following method.

(1) First Embodiment In a first embodiment of the continuous heating furnace of the present invention, in each heating chamber, a heating means and a control system for the heating means are provided at least with respect to at least the moving direction of the object to be heated. And a partition for dividing the heating chamber is provided so as to correspond to the divided heating means.

In such a continuous heating furnace, the heating chamber is structurally divided into a plurality of regions by partition walls.
It is possible to perform precise temperature control by adjusting the degree of heating for each region of the substrate surface without being affected by another adjacent heating means or another adjacent heating chamber as in (b). Become. The material of the partition is not particularly limited, but it is preferable to use a ceramic board or the like having high heat insulating properties.

The reason why the heating means and its control system (and thus the partition) are divided in the traveling direction of the object to be heated is to eliminate the influence of temperature from another adjacent heating chamber. For example, in the process of raising the temperature of the object to be heated, 1
The temperature of the heating chamber adjacent to the inlet side of the heating chamber is low, the temperature of the heating chamber adjacent to the outlet side is high, and the object to be heated is transported from the lower temperature heating chamber. Tends to have a low inlet temperature and a high outlet temperature. Therefore, in order to correct this, it is necessary to perform temperature control such that the temperature on the inlet side is high and the temperature on the outlet side is low in the heating chamber. This is the same in a second embodiment described later.

(2) Second Embodiment In a second embodiment of the continuous heating furnace according to the present invention, in each heating chamber, a heating means and a control system for the heating means are arranged at least in the moving direction of the object to be heated. The heating means is divided so as to be close to the stationary position of the object to be heated.

In the second embodiment, the diffusion of the heat of the heating means until the heat reaches the substrate surface is prevented by bringing the heating means close to the stationary position of the object to be heated. That is, according to the second embodiment, FIG.
As shown in (a), the inside of the heating chamber 41 is substantially divided into a plurality of areas, so that each area on the surface of the substrate 43 is not affected by another adjacent heating means or another adjacent heating chamber. Thus, precise temperature control can be performed by adjusting the degree of heating.

When the heating means is brought close to the stationary position of the object to be heated, the distance between the two differs depending on conditions such as the appearance of the object to be heated and the size of the control system. 1/5 or less of the length in the traveling direction, preferably 1/1
By setting it to 0 or less, the effects of the present invention can be obtained. In the second embodiment, it is not always necessary to provide a partition as in the first embodiment, but if a partition is provided, more precise temperature control can be performed.

In any of the first and second embodiments described above, it is preferable that a muffle made of a material having a high infrared irradiation rate is disposed between the heating means and the moving area of the object to be heated. This is because once the heat generated from the heating means is received by the muffle, far-infrared rays or near-infrared rays are emitted from the muffle, so that the object to be heated can be heated more quickly. In addition, the airtight separation between the heating means and the moving area of the object to be heated by the muffle has an effect of ensuring a clean degree in the moving area of the object to be heated.

Although there are various materials having a high infrared irradiation rate, in the present invention, it is preferable to arrange a muffle made of Si-impregnated SiC. This is because Si-impregnated SiC has a remarkably high infrared irradiation rate as shown in FIG.

The Si-impregnated SiC is a general term for a sintered body containing metallic Si and SiC as constituents. In the present invention, SiC powder, black smoke powder, organic binder, and the like have been disclosed by the present applicant. And, a molding raw material containing water or an organic solvent is molded, and the molded body is manufactured by a method of firing at 1350 to 2500 ° C. in a metal Si atmosphere and a reduced pressure inert gas atmosphere or vacuum. It is preferable to use a Si-SiC sintered body (Japanese Unexamined Patent Publication No. 5-270917).

Further, in the continuous heating furnace of the present invention,
It is preferable to divide the muffle made of Si-impregnated SiC so as to correspond to the heating means divided in the traveling direction of the object to be heated. Si-impregnated SiC has a thermal conductivity of 15
Since it is extremely high at about 0 W / m · K, even if the space inside the heating chamber is structurally or substantially divided into a plurality of regions as in the present invention, heat is transmitted through the muffle made of Si-impregnated SiC. It is because it is done.

Note that “corresponding to the divided heating means” means that the object to be heated is divided in the traveling direction, similarly to the heating means. In such a configuration, heat is not transmitted in the traveling direction of the object to be heated,
Heat is efficiently transmitted in a direction perpendicular to the traveling direction. Therefore, it can be particularly suitably used when using a heating means such as a gas radiant tube in which a heat source is not provided at the center of the heating chamber.

[0031]

Hereinafter, embodiments of the continuous heating furnace of the present invention will be described with reference to the drawings. However, the present invention is not limited to these examples.

(Embodiment 1) In Embodiment 1, as shown in FIG. 1, an electric heater 2 serving as a heating means is divided into four parts in a heating chamber 1 with respect to a traveling direction of a large glass substrate 3 serving as an object to be heated. This is an example in which a partition wall 4 is provided so as to correspond to this.
In the first embodiment, the upper end side of the partition 4 is a divided electric heater 2.
So that the lower end side is in contact with the muffle 5 made of Si-impregnated SiC. The distance between the electric heater 2 and the muffle 5 is 100 mm, and the distance between the muffle 5 and the large glass substrate 3 is about 200 mm. Rollers 6 that rotate in conjunction with a motor are arranged at equal intervals as the transporting means.

(Embodiment 2) In Embodiment 2, as shown in FIG. 2, a muffle 25 made of Si-impregnated SiC is divided so as to correspond to the divided electric heater 22 in the same configuration as Embodiment 1. It is. In the second embodiment, the lower end of the partition wall 24 does not abut against the muffle 25 made of Si-impregnated SiC, but is configured to penetrate the muffle 25.

(Embodiment 3) In Embodiment 3, as shown in FIG. 3, an electric heater 32 as a heating means is divided into four parts in a traveling direction of a large glass substrate 33 as an object to be heated. This is an example of approaching a stationary position. In the third embodiment, the upper end of the partition wall 34 is formed so as to divide the divided electric heater 32, and the lower end is formed so as to penetrate a muffle 35 made of Si-impregnated SiC. Electric heater 3
The distance between 2 and muffle 35 is 30 mm, and the distance between muffle 35 and large glass substrate 33 is about 50 mm. Rollers 36 that rotate in conjunction with a motor are arranged at equal intervals as the conveying means.

[0035]

As described above, according to the continuous heating furnace of the present invention, even when a large glass substrate is baked, it is possible to raise or lower the temperature while precisely controlling the surface temperature of the substrate. It is possible to prevent defects such as distortion, cracking, and chipping of the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a continuous heating furnace of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the continuous heating furnace of the present invention.

FIG. 3 is a schematic sectional view showing still another embodiment of the continuous heating furnace of the present invention.

FIG. 4 is a process chart showing a PDP manufacturing process.

FIGS. 5A, 5B, and 5C are schematic explanatory views showing the effect of the continuous heating furnace of the present invention.

FIG. 6 is a graph showing the infrared irradiation rate of Si-impregnated SiC.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating chamber, 2 ... Heating means (electric heater), 3 ... Heated body (large glass substrate), 4 ... Partition wall, 5 ... Muffle, 6 ...
Conveying means (roller), 21: heating chamber, 22: heating means (electric heater), 23: heated object (large glass substrate),
24 ... partition wall, 25 ... muffle, 26 ... transport means (roller), 31 ... heating chamber, 32 ... heating means (electric heater),
33: Heated object (large glass substrate), 34: Partition wall, 35
... Muffle, 36 ... Conveying means (roller), 41 ... Heating chamber, 42 ... Heating means (electric heater), 43 ... Heated object (large glass substrate), 46 ... Conveying means (roller).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F27D 19/00 F27D 19/00 A

Claims (5)

[Claims] 1. A heating apparatus comprising: a plurality of heating chambers having heating means capable of controlling temperature; and transport means for intermittently transporting an object to be heated to an adjacent heating chamber, wherein the temperature of each heating chamber is individually controlled. In accordance with a desired temperature curve, according to a desired temperature curve, a continuous heating furnace for a large glass substrate configured to be able to perform temperature rise, heat retention, and temperature decrease, in each of the heating chambers, a heating means and a control system thereof. , At least with respect to the traveling direction of the object to be heated, divided into several parts, and corresponding to the divided heating means,
A continuous heating furnace for large glass substrates, wherein a partition for partitioning the heating chamber is provided. 2. A heating apparatus comprising: a plurality of heating chambers having heating means capable of controlling temperature; and a transport means for intermittently transporting an object to be heated to an adjacent heating chamber, wherein the temperature of each heating chamber is individually controlled. In accordance with a desired temperature curve, according to a desired temperature curve, a continuous heating furnace for a large glass substrate configured to be able to perform temperature rise, heat retention, and temperature decrease, in each of the heating chambers, a heating means and a control system thereof. A large-sized glass substrate, wherein the large-sized glass substrate is divided into several parts at least with respect to the traveling direction of the object to be heated, and the divided heating means is arranged so as to be close to a stationary position of the object to be heated. For continuous heating furnace. 3. The continuous heating furnace for a large glass substrate according to claim 1, wherein a muffle made of a material having a high infrared irradiation rate is arranged between the heating means and the moving area of the object to be heated. 4. The continuous heating furnace for a large glass substrate according to claim 1, wherein a muffle made of Si-impregnated SiC is disposed between the heating means and the moving region of the object to be heated. 5. The continuous heating furnace for a large glass substrate according to claim 4, wherein the muffle made of Si-impregnated SiC is divided so as to correspond to the heating means divided in the traveling direction of the object to be heated.