JPS6121928A - Forming of platy glass - Google Patents

Abstract

PURPOSE:To obtain a product having only small fluctuation of thickness in the width direction even from a thermally unstable and easily divitrifiable glass in the process for producing platy glass by flowing molten glass out of a slit by arranging so as to store the molten glass temporarily in an expanded part at the top end of an orifice pipe. CONSTITUTION:An expanded part 2 connected to the top end of an orifice pipe 1 expands toward the width direction, and the thickness of the expanded part 2 is thicker than the thickness of the orifice at the part of the pipe of the orifice, and a slit 3 opening toward the width direction is formed to the center of the bottom surface of the expanded part 2. The molten glass passes 4 through the orifice pipe 1 and accumulates temporarily in the expanded part 2, which is discharged on to a die 5 after the temp. becomes sufficiently uniform, and cooled well and discharged. Since the temp. distribution in the width direction of the molten glass 4 is made uniform by this method in the expanded part 2, forming of platy glass having wide range of quality from thermally stable glass to thermally unstable and easily divitrifiable glass is possible, therefore, products with high accuracy is obtd. easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a high-precision plate glass such as a photomask, and particularly to a method for forming a plate glass with little variation in thickness in the width direction.

Prior Art 1 Photomasks used in the manufacture of semiconductor integrated circuits, etc., require a high level of flatness and dimensional accuracy in order to form circuit patterns in microns on the surface. It is desirable to obtain a molded product with a high degree of strength. Glass that is thermally unstable and prone to devitrification has a high liquidus temperature, so it must be formed by pouring out the glass in a very low viscosity state. It is very difficult to make plate glass for photo-i-masks by molding or the like. Therefore, in recent years, a method has been adopted in which the liquid flows out from a slit at the tip of an orifice tube into a flat metal mold.

[Problems to be Solved by the Invention] Compared to forming methods such as the above-mentioned float method, the method of obtaining sheet glass by flowing molten glass through a slit can produce various types of glass ranging from low viscosity glass to high viscosity glass. Since it is possible to mold glass, it can be said to be a highly versatile molding method. However, with the glass that has been used until now, it is difficult to make the temperature distribution uniform in the width direction of the molten glass flowing out from the slit, and the thickness of the formed sheet glass varies in the width direction. There was a problem that occurred. That is, as shown in FIGS. 5 and 6, the molten glass flowing into the orifice tube 11 is guided to the enlarged part 12 and spread in the width direction, and then flows out from the slit 13 at the lower end of the enlarged part 12. Although it spreads out in the width direction from the tip of the orifice tube, its thickness gradually decreases toward the bottom end, so the flow inside the enlarged part 12 is insufficient and the temperature distribution in the width direction becomes uniform. was there.

[Step 1 to Solve the Problems] The present invention can be formed into a plate shape from thermally stable glass to unstable and easily devitrified glass, and has little variation in thickness in the width direction. The purpose is to form sheet glass.

In order to achieve the above object, the present invention has found that it is necessary to make the temperature distribution in the width direction uniform by increasing the thickness of the enlarged portion at the tip of the orifice tube. Therefore, in the present invention, when molten glass flows out from a slit-shaped outlet to form a plate glass, the Iζ molten glass flowing to the tip of the orifice tube is spread out in a wide shape in the width direction, and from the diameter of the A-refice tube. After the molten glass is introduced into an enlarged part with a large thickness to make the temperature distribution in the width direction uniform, it is made to flow out into a mold l: from a slit-shaped outlet opened at the lower surface of the enlarged part.

[Example] The present invention will be described in detail based on the following drawings.

Figure 1 is a front view of the orifice of the present invention, Figure 2 is a side view,
FIG. 3 is a sectional view.

As shown in Fig. 1, the enlarged part 2 connected to the tip of the orifice pipe 1 is widened in the width direction, and the thickness is increased toward the diameter of the orifice pipe. Sulins 1 to 3 opening in the width direction are formed. The molten glass 4 passes through the orifice tube 1 and accumulates in the enlarged portion 2 for a while, and after the temperature becomes sufficiently uniform, it flows out onto the mold 5 as shown in FIG. The glass 4 poured onto the mold 5 is bent from vertical to horizontal, sufficiently cooled on the mold 5, drawn out by rollers 6, and continuously annealed in a lehr (not shown).

The ratio of the thickness B of the enlarged part to the orifice tube diameter is usually 1.8.
or more is preferable.

For example, when molding low expansion glass (LE30 aluminum/silica II salt glass) for IC photomasks, 1250
Molten glass at ~1350°C is made uniform in the slit width direction within the enlarged section with a B/A ratio of 2.0, and a sheet glass is formed at a drawing speed of 10 o/sec.

[Effects of the Invention] As described above, in the present invention, the molten glass is temporarily held in the enlarged part where the thickness of the tip of the orifice tube is sufficiently increased, the humidity distribution in the width direction is made uniform, and the glass flows out through the slit. It is possible to form a plate at temperatures above the liquidus temperature, and it can be applied to glass that is thermally unstable and prone to devitrification, and has the effect of facilitating the formation of seminal plate glass.

[Brief explanation of the drawing]

Fig. 1 is a front view of the orifice used in the present invention, Fig. 2 is a side view, Fig. 3 is a cross-sectional view, Fig. 4 is a lIj plane view when manufacturing sheet glass, and Fig. 5 is a front view of a conventional orifice. Figure, 6th
The figure is also a side view showing a part longitudinally.

Claims (1)

[Claims] 1 In a method of forming plate glass by flowing molten glass from a slit-shaped outlet, the molten glass flowing at the tip of an orifice tube is guided to an enlarged part that spreads out in the width direction and has a thickness larger than the orifice tube diameter. A method for forming sheet glass, which comprises making the temperature distribution of the molten glass uniform in the width direction, and then flowing the molten glass onto a mold through a slit-shaped outlet opened at the lower surface of the enlarged glass.