JPH10297941A - Annealing of plate glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a plate glass having a flat surface suitable for an electronic apparatus substrate without causing a flaw on the surface, by spraying an aqueous solution suspending inorganic powder for polishing, having specific particle diameters on the surface of a plate glass, laminating plural sheets of the sprayed plate glass, placing the sheets on a fixed plate and annealing. SOLUTION: Inorganic powder for polishing such as cerium oxide or alundum, having 0.01-1 μm average particle diameter is mixed with water to prepare a suspension. Then the suspension is successively sprayed on the surfaces of plural sheets of the plate glass by a spray gun and the sprayed plural sheets are laminated on a fixed plate. The fixed plate is introduced into a heat-treating furnace. Water is evaporated and a state in which the inorganic powder is uniformly scattered into gaps between the sheets of the plate glass is reached. The glass plate is softened and deformed along the flat face of the fixed plate by heating the glass plate to improve flatness. Neither fusing between the sheets of the plate glass during annealing in the heat-treating furnace nor occurrence of scratching flaw on the surface of the plate glass by position displacement during transportation is caused by the interposition of the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for gradually cooling a glass plate used in electronic equipment.

[0002]

2. Description of the Related Art In recent years, with the development of the electronic equipment industry, various electronic equipments, especially liquid crystal, electroluminescence,
As a display device such as a plasma display, or a glass for a substrate such as an image sensor or a porcelain disk, a glass plate having a thickness of about 0.03 to 1.5 mm has been widely used.

[0003] In order to manufacture this type of glass sheet, first, glass is formed into a sheet shape and cut into predetermined dimensions. Thereafter, the glass sheet is put into a heat treatment furnace, and heated for a certain period of time at a temperature equal to or higher than the strain point of the glass to remove the distortion of the glass and then taken out of the heat treatment furnace, and then to reduce irregularities on the surface of the glass sheet. After polishing, a method of washing is adopted.

[0004] If the flatness of this type of glass plate is poor, the exposure distance will not be as designed, or there will be a difference in the distance between two glass plates used in a display device such as a liquid crystal display, which impairs the display performance. It causes a variety of problems, from essential problems to the incompatibility of being incompatible with mechanical operations in automated manufacturing processes, and in some applications tens of μm
It is required to have a degree of flat surface.

However, glass sheets manufactured by known industrial molding methods do not have satisfactory flatness. Therefore, when the glass sheet is gradually cooled, it is placed on a surface plate having excellent flatness. A method is adopted in which the glass plate is placed on a transfer conveyer in a heat treatment furnace in a state where the glass plate is placed, and the glass plate is moved at a predetermined speed to gradually cool the glass plate.

The platen used at this time is made of alumina ceramics or low expansion crystallized glass having excellent heat resistance, and is gradually cooled while a glass plate is placed thereon.
The surface of the glass plate is softened and deformed, and a flat surface along the surface of the platen is obtained.

[0007]

By the way, in order to improve the productivity of the glass plate for the above-mentioned use, a plurality of glass plates are laminated on a platen, or a plurality of platens and glass plates are alternately laminated. Attempts have been made to slowly cool in a hot state.

However, when a plurality of glass plates are laminated on a surface plate, the glass plates are likely to be fused to each other or to be rubbed against each other when moving on a conveyor, so that scratches are easily formed on the surface of the glass plates.

Incidentally, in the case of a glass plate used in electronic equipment, the scratch on the surface is not only a problem that the transparency is impaired in appearance, but also the thin film electric circuit formed thereon is damaged due to the scratch, as designed. It is not possible to obtain the desired electrical performance, or it may be a fatal cause of disconnection.Especially, in the case of fine thin-film electrical circuits, even a scratch with a length of only a few μm is a problem. Become. Also, such scratches can be removed by polishing the glass surface,
Polishing cost is not preferable because it greatly increases the price of the glass plate.

When a plurality of platens and glass plates are alternately laminated, the contact area between the surface of the glass plate and the platen made of a heat-resistant material becomes large, and the heat capacity required for gradually cooling the glass plate is reduced. Since the temperature rises significantly and the transfer speed in the heat treatment furnace must be considerably reduced, productivity is rather lowered.

The present invention has been made in view of the above circumstances, and even if the glass plates are gradually cooled in a state in which a plurality of glass plates are laminated on a surface plate, the glass plates are fused together or the surface is damaged. It is an object of the present invention to provide a method capable of performing slow cooling without generating odor.

[0012]

The method for gradually cooling a glass sheet according to the present invention is directed to a method for gradually cooling a glass sheet in which a plurality of glass sheets are laminated on a surface plate having excellent flatness. A large number of inorganic powders for polishing are interposed between the glass plates.

The method for gradually cooling glass plates of the present invention is characterized in that an aqueous solution in which an inorganic powder for polishing is suspended is sprayed on the surface of each glass plate and then laminated.

Further, in the method for gradually cooling a glass plate according to the present invention, the particle size of the polishing inorganic powder is 0.01 to 1 μm.

[0015]

According to the method of the present invention, a large number of inorganic powders for polishing are interposed as spacers in the gap between a plurality of laminated glass plates, and the glass plates do not come into contact with each other. Even when cooled, there is no fusing or scratching of the glass plate due to fusing.

Further, since the polishing inorganic powder is extremely fine, when each glass plate is heated, it softens and deforms along the flat surface of the platen, and the flatness is improved.

Further, when the glass sheets laminated on the surface plate are slightly displaced during the transfer in the heat treatment furnace, the inorganic powder rotates and the friction coefficient between the glass sheet and the inorganic powder is small. In addition, the surface of the glass plate is hardly scratched.

In addition, since a slight air layer is formed in the gap between the glass plates, the cooling can be performed slowly without significantly increasing the heat capacity.

Further, in the present invention, since the inorganic powder for polishing is used as the spacer, even if the inorganic powder adhered to the surface of the glass plate remains at the time of polishing, the polishing can be performed without any trouble. .

In other words, when an inorganic powder that cannot be used as an abrasive is interposed in the gap between the glass plates, if the inorganic powder remains during polishing, the glass plate becomes incompatible with these inorganic powders. Since they are forcibly rubbed against each other and are rather damaged, it is necessary to completely remove the inorganic powder before polishing.

It is also conceivable to prevent the fusion and rubbing of the glass plates by interposing paper or glass paper in the gap between the plurality of glass plates. The work of placing and removing is complicated, and it is also difficult to automate the work of stacking and picking up glass plates one by one.

Further, in the present invention, as a method of interposing a large number of polishing inorganic powders in the gaps between the glass plates, an aqueous solution in which the polishing inorganic powders are suspended is sprayed on the surface of each glass plate and then laminated. This method is preferable because the inorganic powder for polishing can be uniformly spread on the surface of the glass plate.

Next, in the present invention, a method for interposing a large number of polishing inorganic powders in a gap between a plurality of glass plates will be described with reference to an example.

First, a polishing inorganic powder such as cerium oxide or alundum, which is generally used as an abrasive, is prepared, mixed with water, and a suspension is prepared. Next, the suspension was sprayed onto a plurality of glass plate surfaces sequentially with a spray gun,
These are laminated on a surface plate. This is put into the heat treatment furnace,
When heated, the moisture evaporates, leaving only a large number of inorganic powders in a state of being uniformly dispersed in the gaps between the glass plates. The inorganic powder may be interposed not only in the gap between the glass plates but also in the gap between the surface plate and the glass plate.

The heat treatment furnace for gradually cooling the glass is set at a temperature from around the strain point to near the softening point of the glass.
Usually, borosilicate glass used as a glass plate for electronic equipment has a strain point of about 500 to 550 ° C and a softening point of about 750.
８００800 ° C., and the strain point of the alkali-free glass is about 630
７750 ° C., softening point about 840-950 ° C.

Further, in the present invention, when the inorganic powder for polishing used is too small, there is a risk that the glass plate may partially come into contact with the inorganic powder, and when it is too large, the effect of reducing the warpage of the glass plate is reduced. And it becomes difficult to spray uniformly with a spray gun, so that the average particle size is preferably regulated to 0.01 to 1 μm.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for gradually cooling a glass plate of the present invention will be described in detail with reference to embodiments.

First, three glass plates (thickness 0.7 mm), which were formed by cutting molten glass and cut into predetermined dimensions, and a rectangular platen (thickness 3 mm) slightly larger than the glass plates were prepared. As the glass plate, a non-alkali glass plate for liquid crystal (OA-2 manufactured by Nippon Electric Glass Co., Ltd.) is used. As the glass platen, a low expansion crystallized glass plate having excellent flatness (Nippon Electric Glass Co., Ltd.) (Manufactured by: Neoceram N-0)
It was used.

An aqueous solution in which cerium oxide having an average particle size of 0.3 μm is suspended in water is prepared, and this aqueous solution is sprayed with a spray gun equipped with a needle nozzle (nozzle length 100 mm, inner diameter 0.7 mm).
mm) on the surface of each glass plate.

Next, as shown in FIG.
Two glass plates 11 were stacked and put into a heat treatment furnace. The platen on which the three glass plates are placed is transported in the heat treatment furnace by a conveyor made of heat-resistant steel mesh, heated to a temperature near the annealing point, which is higher than the strain point of the glass, and held for a certain time. After the strain was removed by the heat treatment, it was taken out of the heat treatment furnace.

As shown in FIG. 2, a large number of polishing inorganic powders 12 are interposed in the gaps between the glass plates 11 thus obtained, and the glass plates 11 are not fused to each other.
It could be easily separated. Also, one for each glass plate 11
When the surface was observed by irradiating 0000 lux of halogen light, the scratches on each surface were equivalent to the level after molding, and no scratches caused by rubbing of the glass plate 11 during slow cooling were observed. . Further, when the warp of each glass plate 11 was examined using a stylus-type warp measuring device, it was found that the glass plate 11 had a good flat surface within 50 μm.

Thereafter, these glass plates 11 were passed through a polishing step using cerium oxide as an abrasive and a cleaning step, and finished to a surface roughness Rmax of about 20 angstroms.

In the above embodiment, an example is shown in which a heat treatment furnace provided with a conveyor is used. However, the method of the present invention can be applied to a batch type heat treatment furnace.

[0034]

As described above, according to the method for gradually cooling glass plates of the present invention, even when a plurality of glass plates are laminated on a surface plate and cooled slowly, the glass plates are fused or rubbed. The resulting glass plate without any scratches on the surface has a small warpage, and thus is suitable as a glass plate used in various electronic devices.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which three glass plates are laminated on a surface plate of the present invention.

FIG. 2 is a partially enlarged sectional view showing a gap portion of the glass plate of FIG.

[Explanation of symbols]

 10 Surface plate 11 Glass plate 12 Inorganic powder for polishing

Claims (3)

[Claims] In a method for gradually cooling glass plates, wherein a plurality of glass plates are laminated on a surface plate having excellent flatness, a large number of inorganic powders for polishing are provided in gaps between the glass plates. A method of gradually cooling a glass plate. 2. The slow cooling method for a glass plate according to claim 1, wherein an aqueous solution in which an inorganic powder for polishing is suspended is sprayed on the surface of each glass plate and then laminated. 3. The polishing inorganic powder has a particle size of 0.01-1.
3. The method for slowly cooling a glass sheet according to claim 1, wherein the diameter is μm.