JPS6291432A - Production of porous quartz glass base material - Google Patents

Abstract

PURPOSE:To enable production of the titled base material having a regulated shape and a large diameter by changing the flow rate of hydrogen supplied to a burner, the flow rate of silicon compd. and the angle of the burner for a starting member with the passage of time. CONSTITUTION:In a method synthesizing a porous quartz glass base material by accumulating a fine grain of silica which is produced by hydrolyzing a silicon compd. in the inside of oxyhydrogen flame on a rotating member, the shape of a produced porous quartz glass base material 11 is regulated by changing the flow rate of hydrogen supplied to a burner 5 for synthesis, the flow rate of silicon compd. and the angle of the burner 5 for the starting member 10 with the passage of time. An irregular shape part such as a recess is not formed in a bottom of the base material and the following base material can be produced with excellent reproducibility wherein the shape is regulated in the bottom, an outside peripheral part and the other part as a whole and the diameter is large.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a large diameter porous glass base material using a gas phase reaction method.

[Prior Art] Conventionally, as one of the methods for manufacturing synthetic quartz glass, a porous quartz glass base material is formed by a gas phase reaction method (also referred to as a gas phase reaction synthesis reaction method), and this material is then The method used is heating and vitrification. That is, a starting member (hereinafter referred to as "starting member" or "seed rod") made of six shells, etc., which rotates from a burner with a silicon compound such as silicon tetrachloride, hydrogen, and a raw gas of unrefined gas suspended vertically. The silicon compound such as silicon tetrachloride is hydrolyzed in a hydrogen-resistant flame, and the generated silica fine particles are attached to the lower end of the seed rod Φ111
It is dried to form a porous quartz glass matrix. Then, this porous hexapod glass I4 material is placed in a heating furnace, heated with a heater, and vitrified by sintering the base material. -1- The porous quartz glass base material formed by the force distribution method has a substantially cylindrical shape.

[Point to be solved by the invention 1 When using the quartz glass produced starting from the above-mentioned gas phase reaction method as a plate material for a photomask, for example,
The quartz glass material is required to be quite large, and when it is manufactured from a porous quartz glass base material (hereinafter simply referred to as base material) using the gas phase reaction synthesis reaction method, the base material is A diameter of 28 to 30 cmφ and a length of less than 10 cm are also required. When synthesizing such a large material, it is necessary to use a large burner and to stick silica particles in a strong flame in order to increase the strength of the j+I material. However, in the conventionally adopted method, that is, starting from a seed rod and blowing an oxyhydrogen flame containing silica fine particles at the bottom of the I' and 7 materials in the middle of formation, porous quartz glass is formed. Burner position, hydrogen flow - Y
If you try to synthesize a large one under fixed conditions, the strong flame will cause the central part to become depressed as shown in Figure 2 (a), or as shown in Figure 2 (b). This resulted in an angular shape, which changed the flow of glass particles near the L1 material, and finally the shape of the outer periphery of the base material was disturbed, making stable synthesis impossible.

[Means for Solving the Problems] The present invention solves the above problems and proposes a method for stably manufacturing a large I-diameter long material. In a method for synthesizing a porous quartz glass LζI material by hydrolyzing a compound in an oxyhydrogen flame and depositing the generated silica fine particles on a rotating starting member, the flow of hydrogen supplied to the synthesis burner 1. , silicon compound flow Jl
), and a method for producing porous silica glass particles, characterized in that the shape of the material II to be formed is adjusted by changing the angle of the burner with respect to the starting part over time.

In the present invention, while rotating and pulling up a vertically suspended seed rod, trichlorosilane, 41! Silica fine particles produced by hydrolyzing silicon compounds of silicon silicide and silicon tetrabromide in an oxyhydrogen flame are deposited on the seed rod 7, and the position of a determined portion of the deposition surface is detected. , 1 S( of the detection site)
Porous quartz glass Lz to keep the height from the mold surface constant
In the method for manufacturing large-diameter and long I+J materials, which controls the drawing speed of I materials, 8-
Gradually tilt the angle of the blade from the vertical upper blade, and
This is a method for producing porous quartz glass particles in which the flow rate of hydrogen is gradually increased. For example, a protrusion on the bottom of the base material, which will be described later, is suitable as the part on the stacking surface of the one-size material for detecting the above-mentioned position.

Here, the burner angle refers to the angle between the central axis of the multi-tube burner and the vertical line, and when the multi-tube burner is oriented vertically, the burner angle is 0°.

According to a preferred form IE of the invention, the growth surface is 1 mJ
The shape of the bottom of the material is shown in Figures 1 (b) and (C). A protrusion with a height of 8 to 15 mm is always formed in the center, and the end of the flame containing silica is the protrusion 20. The burner angle and the flow rate of hydrogen and silicon compound are gradually changed within a range that covers the radial direction of the base metal without exceeding the tip of the burner. In this way, the flame flow containing silica is rectified by the protrusion 20 at the bottom of the porous quartz glass base material and rises along the outer periphery of the base material, so that a uniform base material 11 with a uniform shape is formed. be done.

If you try to synthesize a large-diameter base material with the burner angle, silicon compound, and hydrogen ratios fixed from the beginning, the flame will be trapped in the bottom of the rat material as the diameter of the base material grows, as shown in Figure 2 ( As shown in a), the temperature near the center becomes concentrated and the center becomes depressed, or as shown in Fig. 2(b).
This results in an angular shape as shown in the figure.

In the present invention, the burner 5 is tilted outward while gradually increasing the flow rate of the raw material waste in accordance with the growth of the diameter of the porous glass TNI material, so that the shape and temperature distribution of the silica adhesion surface are always kept constant. No sag or disturbance of the bottom shape.

[Example] Using the apparatus shown in FIG.
layer, 7th layer, 9th layer, 3rd layer, 6th layer, 8th layer, 1st layer
Nitrogen gas is applied as a seal gas to the 0th layer, 4th layer, 5th layer, 1st layer.
Oxygen gas was introduced into one layer, and a burner 5 was installed at a position 80 mm away from the tip of a vertically suspended quartz seed rod 10 with a diameter of 75 mm, and while the seed rod 10 was rotated, the fl upper material formation reaction was carried out. started.

After the start, while changing the flow rate of silicon tetrachloride, the flow rate of hydrogen, and the angle of the burner under the conditions shown in Table 1, the position of the protrusion 20 on the bottom of the base material was kept constant.
1 upward, and the base material 11 is grown in the radial and axial directions of the base material 11. When the diameter of the base material 11 reaches 30 cmφ, the flow rate of silicon tetrachloride, hydrogen, and the angle of the burner are adjusted. The base material was fixed, and the protrusion 20 at the bottom of the base material was controlled to maintain a constant position while being pulled and grown to a diameter of 30cm over about 28 hours.
A porous glass preform having a length of 100 cm and a length of 100 cm was formed.

Approximately 60 minutes after the start of the base material synthesis reaction, a protrusion 20 with a height of approximately 8 mm was formed at the bottom of the porous glass base material, and as the diameter of the base material increased, this protrusion 20 gradually grew, but eventually The height was held constant at 12 mm. The silica-containing flame flow was rectified and spread uniformly over the radial direction of the cylindrical base material 11 on the side where the burner was tilted, thereby making it possible to synthesize a well-shaped base material.

In order to maintain the position of the protrusion 20 on the bottom of the base material, that is, the height from the reference plane, at an appropriate constant value, a horizontally running laser beam 14 was used in this embodiment. The laser beam 14 runs horizontally at a height from the reference plane where the position of the protrusion 20 is to be maintained by a device not shown, and when the protrusion 2o crosses the laser beam 14, the base material 11 is rotated. It was linked with a base material 1-device (not shown) so that the base material could be pulled upward.

Table 1 Changes in burner angle, H2 flow rate, and 5iC14 flow rate = □□■ [Effects of the invention] As explained above, according to the present invention, irregularly shaped portions such as recesses are formed at the bottom of the base material. This makes it possible to manufacture a large-diameter base material with a well-shaped bottom, outer periphery, and other parts. Furthermore, the shape reproducibility is also excellent.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the present invention, in which (a) is a starting time, (b) is a steady state, and (c) is an explanatory diagram of a protrusion on the bottom of the base material. FIGS. 2(a) and 2(b) are explanatory diagrams showing examples of base material shapes obtained by methods other than the present invention. FIG. 3 is an explanatory diagram showing an example of an apparatus for obtaining a porous quartz glass base material. 1...H2 gas cylinder 2...02 gas cylinder 3.4...Flow rate controller 5...Multiple Pipe burner 6...5iGIa storage tank 7...5iGI4 supply pump 8...
・・・・・・5iG14 Vaporizer 9・・・・・・Reactor 10・・・・・・Seed cup 11・・・・・・Porous glass ffJ material 12・・・・
......NaOH storage tank 13...HCI absorption tower 14...Laser beam 20 for base material position detection
・・・・・・Protrusion grass on the bottom of the base material 1 Figure <o,,) (b)
(C)X 2 Figure (α) ()))

Claims (1)

[Claims] (1) In a method of synthesizing a porous quartz glass base material by depositing silica fine particles produced by hydrolyzing a silicon compound in an oxygen flame on a rotating starting member, the flow rate of hydrogen supplied to a synthesis burner, A method for producing a porous quartz glass base material, which comprises adjusting the shape of the base material by changing the flow rate of a silicon compound and the angle of a synthesis burner relative to a starting member over time.