JP2004292274A - Manufacturing method of glass plate, manufacturing method of base material for press molding, and manufacturing method of optical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a glass plate to stably supply a glass plate having a constant thickness, a manufacturing method of a base material for press molding made of glass, and a manufacturing method of an optical part. <P>SOLUTION: This glass plate is continuously manufactured by continuously introducing a melt glass flow into a mold and forms into a plate in the mold and the molded glass plate is drawn out of the mold. In this method, the variation of the thickness is reduced by changing the drawing speed of the glass plate based on the change of the height of the molten glass surface introduced in the die. This glass plate is processed into the glass base material for press molding of a desired weight, or the glass base material for press molding is heated and softened and this optical glass part is manufactured via press molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming glass, in which glass flowing out of an outflow pipe is continuously poured into a groove-shaped fixed mold, and molded glass is drawn from one end of the mold. Further, a method of cutting a glass plate obtained by such a method and manufacturing a material for press molding and a method of press-forming the material for press molding and manufacturing an optical component such as a lens from the obtained molded product About.
[0002]
[Prior art]
Patent Document 1 (Japanese Patent Publication No. 45-19987) discloses a method of continuously forming glass that flows out of an outflow pipe into a groove-shaped fixed mold and draws the formed glass from one end of the mold. Known methods are known. At this time, the speed of the stepless transmission of the drive motor of the belt conveyor that conveys the glass and the frequency of the inverter are manually adjusted as needed so that the glass thickness becomes the target thickness with respect to the width of the glass to be formed. It has been adjusted by changing in. Also, in the method described in Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2002-265229), which enables continuous molding of a glass plate having a uniform thickness, the glass cast in a mold is continuously formed. The speed of the moving means is adjusted so that the liquid level of the molten glass around the cooling plate continuously striking the upper surface of the glass becomes an appropriate height.
[0003]
[Patent Document 1] Japanese Patent Publication No. 45-19987 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-265229
[Problems to be solved by the invention]
After being melted in the melting furnace, the flow rate of the molten glass that continuously flows down from the outflow pipe may fluctuate by several percent for various reasons at the current general level of melting technology, even if it tries to maintain a constant value. Inevitable. The main causes of this fluctuation are pressure drop due to lowering of the liquid level in the intermittent melting furnace, fluctuations in the ambient temperature including ambient temperature, etc. Fluctuations, temperature fluctuations in the furnace before and after the input of raw materials, fluctuations in the liquid level, and fluctuations in the outside air temperature over time. In the case where the flow rate is reduced and the glass withdrawing speed is too high, in the method described in Patent Literature 2, the cooling plate does not come into contact with the glass, and thus does not perform its function at all. In this case, the product naturally goes out of the thickness standard. Conversely, when the flow rate is increased and the glass withdrawing speed is too slow, the method described in Patent Literature 1 only deviates from the thickness standard of the product, but the method described in Patent Literature 2 uses the side wall of the cooling plate and the mold. The glass protrudes from the gap, and product defects such as "can" and "break" occur.
[0005]
Even if it does not lead to out-of-specification products or product defects, inconsistency between the glass flow rate and the drawing speed leads to instability of the glass cross-sectional area at an arbitrary cross section. It appears as a change in the magnitude of R on the side upper surface. This variation leads to a variation in the weight of both side portions when the glass plate is cut at an equal width, and thus causes a reduction in the yield of the subsequent process of “making a target weight press-forming material”.
[0006]
Even if there is no fluctuation in the flow rate of the molten glass flowing down from the outflow pipe, the glass drawing speed is manually adjusted using the thickness of the molded glass at a certain moment and the liquid level of the molten glass around the cooling plate as a judgment material. It is almost impossible to "match" the glass flow over a long period of time. (Because the speed of the glass drawer does not change at all)
[0007]
The present invention has been made in order to solve the above problems, and a method of manufacturing a glass plate for stably supplying a glass plate having a certain thickness, a method of manufacturing a glass press molding material, and an optical device. An object of the present invention is to provide a method for manufacturing a component.
[0008]
[Means for Solving the Problems]
The present invention provides the following means.
(1) A method of continuously casting a molten glass flow into a mold, forming a plate in the mold, drawing out the formed plate glass out of the mold, and continuously manufacturing a glass plate,
A method for manufacturing a glass sheet, comprising: changing a drawing speed of a sheet glass based on a change in a height of a surface of a molten glass cast in a mold to reduce a change in thickness of the glass sheet.
(2) The cooling plate is repeatedly pressed on the upper surface of the softened glass at a position where the molten glass flow is cast and a position on the glass drawing direction side of the position where the height of the surface is measured. 3. The method for producing a glass plate according to item 1.
(3) The method for producing a glass sheet according to (1) or (2), wherein the casting of the molten glass flow is performed while replenishing and melting the glass raw material.
(4) The sheet glass is drawn out of the mold by using a horizontally arranged mold and a glass sheet transfer device, and the sheet glass is transferred in the horizontal direction by the transfer device, and the sheet glass is drawn out. The method for manufacturing a glass sheet according to any one of (1) to (3), wherein the speed is controlled by a driving speed of the transport device.
(5) A method for producing a press-forming material, comprising processing a glass plate produced by the method according to any one of (1) to (4) into a glass material for press-forming having a desired weight.
(6) In a method of manufacturing an optical component for heating and softening a material for press molding to produce an optical component made of glass through press molding, the material for press molding produced by the method described in (5) is used. A method for producing an optical component, comprising:
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the invention will be described. The following embodiment is an example of the present invention.
[0010]
The present invention is a method for continuously producing a glass sheet by continuously casting a molten glass flow into a mold, shaping the sheet glass in the mold, drawing out the formed sheet glass out of the mold. The casting of the molten glass flow into the continuous mold is performed, for example, by pouring the molten glass continuously flowing down from the outflow pipe into the mold. The mold used is, for example, a pair of opposing "sidewalls" that regulate the width of the glass plate to a required width, and between the two side walls, to block the flow of glass to the opposite side in the glass drawing direction. And a "bottom" for forming one of two opposing main surfaces of the glass plate.
[0011]
The molten glass cast into the mold is formed into a plate shape in the mold, and the plate glass is drawn out of the mold. Concretely, from the opposite side of the "weir plate" of the mold, the required plate is formed by cooling and forming while pulling out the sheet glass in the horizontal direction using a conveying means such as a belt conveyor arranged horizontally with the mold. A thick glass plate is continuously formed.
[0012]
In the present invention, the variation in the thickness of the glass sheet is reduced by changing the drawing speed of the sheet glass based on the change in the height of the surface of the molten glass cast in the mold. The change in the height of the surface of the molten glass is measured around the outflow pipe of the molten glass, specifically, in the temperature range where the glass has just flowed down and is still in a sufficiently viscous flow in the direction in which the glass is slightly drawn from the outflow pipe. You. Specifically, it is appropriate to measure the change in surface height at a position where the viscosity of the molten glass is less than 10 ⁴ dPa · S. This is because if the viscosity is too high, it is difficult to keep the glass surface horizontal, and it becomes difficult to select a position for detecting an appropriate height of the molten glass surface.
[0013]
The change in the height of the surface of the molten glass can be measured, for example, continuously or intermittently by a non-contact type or contact type sensor. However, it is preferable to use a non-contact type sensor, for example, a laser displacement meter, from the viewpoint that the height of the surface of the molten glass in a high temperature state can be measured with high measurement accuracy even if the distance is increased.
[0014]
As a result of the measurement of the change in the height of the surface of the molten glass, the drawing speed of the sheet glass is changed so that the height of the surface becomes a set value having a required allowable width. In the present invention, the drawing speed of the sheet glass is automatically or constantly fed back to the sheet glass drawing device automatically or intermittently with the measurement result of the change in surface height, thereby changing the drawing speed of the drawing device. . In the present invention, as described above, by adjusting the driving speed of the sheet-like glass drawer-conveying device by automatic control at any time, fluctuations in the thickness of the glass sheet can be reduced, and a constant thickness within a permissible range. A glass plate can be manufactured. At the position where the change in surface height is measured, the upper surface of the molten glass is a free surface.
[0015]
In the present invention, the drawing of the sheet glass out of the mold is performed by using a horizontally arranged mold and a glass sheet conveying apparatus, and conveying the sheet glass in the horizontal direction with the conveying apparatus, and the sheet glass is removed. It is preferable that the drawing speed is controlled by the driving speed of the transport device. As a driving source of the glass sheet pulling and conveying device, for example, a servo motor, an inverter motor, or the like can be used. The height (liquid level) change information of the molten glass surface is introduced as an external signal, and the set sheet thickness is set. Speed control is performed to obtain a glass plate.
[0016]
According to the method of the present invention, even if the flow rate of the outflow glass fluctuates, the fluctuation of the cross-sectional area in an arbitrary cross section of the formed glass can be suppressed small, which can greatly contribute to the improvement of the yield in the post-process.
[0017]
Next, the above embodiment will be described in more detail with reference to FIG. 1 showing an example of a manufacturing apparatus for carrying out the manufacturing method of the present invention.
In a continuous glass forming method in which the molten glass 12 flowing out of the outflow pipe 11 is continuously poured into the groove-shaped fixed mold 13 and the formed glass is drawn out from the right side of the mold, the molten glass 12 flows down in a slightly advancing direction from the outflow pipe. A non-contact type sensor 21 or 22 continuously or intermittently detects a change in the liquid level of the molten glass having a free surface in a temperature range where the liquid still flows sufficiently viscously. By adjusting the speed of the drive motor 15 of the glass drawer / transporter 14 by automatic control at any time so that the target value has a required allowable width, even if the flow rate of the outflow glass fluctuates, It is possible to obtain a glass sheet material having a very small variation in cross-sectional area. In addition to the above control, it is preferable to control the temperature of the outflow pipe so that the casting speed of the molten glass is constant.
[0018]
A feature of the present invention resides in that the drawing speed of the glass is automatically controlled based on the height of the glass liquid level in a non-solidified molten state, not on the thickness of the glass at the solidified place. With this control, the change (adjustment) result of the drawing speed is reflected on the thickness of the glass at the forming position with almost no time delay. Therefore, the amount of defective products (non-standard products) can be reduced. On the other hand, even if the drawing speed is controlled based on the thickness information of the location after the solidification, the thickness is changed up to the portion where the thickness is already determined by losing fluidity and upstream of the position where the thickness is measured. I can't. Therefore, if the thickness of the part is out of the standard, the part becomes a loss.
[0019]
The upper surface of the cast molten glass is leveled by the action of low glass viscosity and gravity. By fixing the mold horizontally, the bottom surface of the mold and the top surface of the molten glass become parallel. The drawing speed of the glass is controlled so that the distance between the bottom of the mold and the top of the molten glass is always constant. For example, as the casting speed of the molten glass increases, the liquid level of the molten glass in the mold rises. In that case, the thickness of the glass plate can be prevented from increasing by increasing the drawing speed of the glass and returning the liquid level to the set value. Conversely, when the casting speed of the molten glass decreases, the liquid level of the molten glass in the mold falls. In that case, the thickness of the glass plate can be prevented from being reduced by reducing the drawing speed of the glass and returning the liquid level to the set value.
[0020]
The sensor 21 is an example of a method of detecting reflected light from the liquid surface from above the glass with a laser displacement meter, and the sensor 22 is an example of a method of detecting transmitted light from the lateral direction of the glass liquid surface. You are not bound.
The transfer device is arranged such that a glass plate formed in an annealing furnace (not shown) is transferred. The glass plate is gradually cooled in the annealing furnace to remove the distortion.
[0021]
In addition, on the upper side of the portion where the glass is softened, which is located on the glass drawing direction side of the casting position of the molten glass flow and the position where the liquid level of the molten glass is measured, cooling is performed repeatedly so as not to hinder the drawing of the glass. It is preferable that the plate 33 is pressed to adjust the shape of the glass plate. By doing so, a glass plate having a more uniform thickness can be produced. Further, since the liquid level of the molten glass is controlled to be constant even when the cooling plate is pressed, the above-described defects such as cans and cracks can be prevented.
The pressing of the cooling plate is preferably performed over the entire width of the drawn glass.
[0022]
INDUSTRIAL APPLICABILITY The present invention is suitable for a case in which a molten glass stream is cast while replenishing and melting glass materials. In the so-called continuous melting method in which the molten glass flow is cast while replenishing and melting the glass material, the casting speed of the molten glass tends to fluctuate due to the refilling of the glass material. Conventionally, the fluctuation of the casting speed fluctuates the thickness of the glass sheet.According to the present invention, it is possible to form a glass sheet having a constant thickness even when the glass sheet is formed while replenishing the glass raw material. Can be. Needless to say, the present invention can be applied to a system in which a required amount of molten glass is melted and then cast. In either case, it is desired that the molten glass to be cast into the mold be refined and homogenized. In the case where optical components such as lenses, prisms, filters, and optical substrates are made from a molded glass plate, it is preferable to use optical glass.
[0023]
The present invention includes a method for producing a press-forming material, which comprises processing the glass plate produced by the above method into a glass material for press-forming having a desired weight. The glass plate manufactured by the above-described method is cut longitudinally and laterally after removing distortion by annealing, and is processed into a glass piece called a cut piece. Then, a mechanical processing such as barrel polishing can be performed to obtain a press-formed glass material having a required weight.
[0024]
Furthermore, the present invention relates to a method for producing an optical component, which comprises heating and softening a material for press molding and producing an optical component made of glass through press molding, wherein the press molding material produced by the above method is used as the material for press molding. And a method for producing an optical component characterized by using a material for use.
When producing an optical component from a material for press molding, the material for press molding is heated and softened, and press-molded using a press mold. Known conditions and methods for the heat softening of the material for press molding, press molding dies, and conditions and methods for press molding can be used as they are. The press-formed product after the press-forming is gradually cooled, and the gradually cooled press-formed product can be subjected to grinding and polishing as required, thereby completing optical components such as lenses, prisms, filters, and optical substrates.
An optical thin film such as an anti-reflection film may be formed on the surface of the obtained optical component, if necessary.
[0025]
【Example】
Next, the present invention will be specifically described with reference to examples.
The optical glass at 1050 ° C. flowing out of the outlet pipe at a flow rate of 100 ml / min is cast into a 150 mm wide groove-shaped mold maintained at 550 ° C., and the height of the liquid level at the center in the width direction 50 mm rearward from the outlet pipe Is detected from the lateral side of the liquid level by a transmission type laser displacement meter, and the drive motor (inverter motor) of the glass pulling and conveying device is feedback controlled so that the liquid level is maintained at 12 mm ± 0.3 mm from the bottom of the mold. Then, when the cross-sectional area of the obtained glass plate was measured 10 times every 10 minutes at the same place on the transfer device, the fluctuation range was within 5%. In this embodiment, as shown in FIG. 1, a cooling plate is repeatedly pressed against the upper surface of the cast glass so as not to hinder the drawing of the glass. No defects such as cans and cracks due to pressing by the cooling plate were observed.
[0026]
With the conventional method of drawing out the drive speed of the drawer-conveying device at a constant speed, it was extremely difficult to keep the variation of the glass cross-sectional area within 10%.
While being conveyed by the conveying device, the formed glass sheet is gradually cooled by passing through an annealing furnace, and the glass sheet is cut into a required length.
[0027]
When this glass plate is used as a material for press molding, the glass plate is cut in a dice shape by a cutting machine to produce a plurality of cut pieces having a substantially constant weight. According to the present embodiment, since the thickness of the glass plate is constant, the weight of the cut pieces can be made uniform by performing the above-mentioned cutting at equal intervals.
These cut pieces are barrel-polished to round corners, and the weight of the material for press molding is used as a material for press molding.
[0028]
Next, after a powdery release agent was uniformly applied to the surface of the material, the material was heated and softened, and press-molded using a press mold including an upper and lower mold. The lens-shaped press-formed product thus obtained was gradually cooled in an annealing furnace to remove distortion, and then ground and polished to produce a lens.
[0029]
【The invention's effect】
As described above, according to the present invention, a method for manufacturing a glass sheet for stably supplying a glass sheet having a constant thickness, a method for manufacturing a glass press molding material, and a method for manufacturing an optical component are provided. can do.
[Brief description of the drawings]
FIG. 1 is an example of a manufacturing apparatus for performing a manufacturing method of the present invention.

Claims (6)

A method of continuously casting a molten glass flow into a mold, forming a plate in the mold, drawing the formed plate glass out of the mold, and continuously manufacturing a glass plate,
A method for manufacturing a glass sheet, comprising: changing a drawing speed of a sheet glass based on a change in a height of a surface of a molten glass cast in a mold to reduce a change in thickness of the glass sheet. 2. The cooling plate according to claim 1, wherein the cooling plate is repeatedly pressed against the upper surface of the softened glass at a position where the molten glass flow is cast and a position which is on a glass drawing direction side of a position where the height of the surface is measured. Manufacturing method of glass plate. 3. The method for producing a glass sheet according to claim 1, wherein the casting of the molten glass flow is performed while replenishing and melting the glass raw material. The drawing of the sheet glass out of the mold is performed by horizontally transferring the sheet glass with the transfer device using a horizontally arranged mold and a glass sheet transfer device, and the drawing speed of the sheet glass is The method for manufacturing a glass sheet according to claim 1, wherein the control is performed by a driving speed of the transport device. A method for producing a press-forming material, comprising processing a glass sheet produced by the method according to any one of claims 1 to 4 into a glass material for press-forming having a desired weight. A method for manufacturing an optical component, wherein the material for press molding is heated and softened to produce an optical component made of glass via press molding, wherein the material for press molding produced by the method according to claim 5 is used. Manufacturing method of an optical component.

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