JP2006052109A - Method of manufacturing glass molding, glass base material for press molding, optical device and glass substrate, respectively - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optically homogeneous solid glass molding from molten glass and a method of manufacturing a glass base material for press-molding, an optical device and a glass substrate, respectively. <P>SOLUTION: The method of manufacturing the glass molding is a method for molding into solid glass by using a mold having a through-hole, continuously pouring the molten glass flow to an inlet of the through-hole and continuously taking out from an outlet. The mold is arranged so that the inlet of the though-hole is positioned higher than the outlet. The surface temperature of the molten glass flow poured into the mold is controlled to be lower than that of the core part. The molten glass flow is poured into the mold while prompting the cooling of the surface. The cooling of the surface of the molten glass is prompted by bringing the molten glass poured into the through-hole into contact with the inner peripheral surface of the through-hole. The temperature of the molten glass collected in a vessel is controlled to be higher than the temperature of a lower end of a pipe through which the molten glass flows out (the difference of the temperature is 20-120°C). The methods of manufacturing the glass base material for press molding, the optical device and the glass substrate are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming solid glass such as rod-like glass and plate-like glass from molten glass, a method for producing a glass material for press molding using the method, and heating and softening the material for press molding. The present invention relates to a method for manufacturing an optical element that is press-molded. Furthermore, this invention relates to the method of processing the said glass molded object and manufacturing a glass substrate.

  As a method for forming a rod-shaped or plate-shaped glass, a method is known in which molten glass is continuously cast into a mold and the molded glass is drawn out from one opening. For example, in Japanese Patent Application Laid-Open No. 52-6719 (Patent Document 1) and Japanese Patent Application Laid-Open No. 52-6720 (Patent Document 2), a mold is arranged so that a flow path of cast glass is horizontal. A method is disclosed in which molten glass is poured into the glass, glass formed from one opening is drawn out, and optical glass is continuously formed.

  However, when the rod-shaped or plate-shaped glass is formed by the methods disclosed in Patent Documents 1 and 2 according to the study by the present inventors, inhomogeneity occurs in the glass, resulting in a defect called striae. It turned out to be. In the methods disclosed in Patent Documents 1 and 2, the molten glass is poured from a molten glass outlet pipe disposed above at a substantially right angle with respect to a horizontally disposed mold. Therefore, the cast glass is formed into a glass rod or a glass plate after being bent at a substantially right angle in the mold. At the corner of the mold where the molten glass stream is bent at a right angle, the molten glass flowing outside the corner takes a longer path than the molten glass flowing inside the corner. Therefore, in the glass rod obtained by this method, the glasses that have passed through different paths in the mold are located on the same vertical section with respect to the flow direction. In this way, it is considered that the glasses that have passed through different paths in the process of being cooled and molded in the mold are located on the same cross section, which causes inhomogeneities in the glass. In general glass, such inhomogeneity is not a problem, but in optical glass, such inhomogeneity becomes a defect called striae. The above problem is particularly remarkable when the viscosity of the molten glass to be cast is low.

On the other hand, Japanese Patent Application Laid-Open No. 60-251136 (Patent Document 3) discloses a method of forming a rod-shaped glass by pulling a molten glass cast into a pipe-shaped mold vertically or at an angle of 45 °. Yes. This method is suitable for forming a molten glass having a glass viscosity of about 10 ² to 10 ³ Pa · s.
JP 52-6719 A JP 52-6720 A JP 60-251136 A

Incidentally, in recent years, optical glass having a higher refractive index has been demanded. In addition, there is an increasing demand for glass having a low-temperature softening property that enables low-temperature press molding (for example, precision press molding). Such a new type of glass has a lower viscosity at the time of molding than the conventional glass. If a low viscosity glass is poured into a mold or the like to be molded, striations occur in the molded glass and it is difficult to obtain a highly homogeneous glass. If the problem caused by the low viscosity of the glass, such as striae, is to be solved by lowering the glass outflow temperature and increasing the viscosity, a new problem of glass devitrification occurs. As described above, in the field of manufacturing glass that requires high quality such as optical glass, how to manufacture glass having high homogeneity with high productivity is a major issue. Yes.
Considering the technique described in Patent Document 3 from this point of view, the technique is very excellent. However, if the technique is applied as it is to the molding of the glass which is becoming mainstream, the problem of striae occurs. It is difficult to eliminate completely.

  The present invention has been made to solve the above problems, and provides a method for producing an optically homogeneous solid glass molded body from molten glass, in particular, low-viscosity molten glass, and the glass molding. Providing a method for producing a glass material for press molding for use in press molding from a body, and providing a method for producing an optical element that is press-molded using the glass material for press molding, the glass molded body Another object of the present invention is to provide a method for producing an optical element that is processed into an optical element through a glass block, and a method for producing a high-quality glass substrate from the glass molded body.

Means for achieving the above object are as follows.
[Claim 1] A glass molded body that uses a mold having a through hole, continuously flows a molten glass flow into the inlet of the through hole, and continuously draws it from the outlet of the through hole to form a solid glass. In the manufacturing method,
The mold is arranged so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, wherein a surface temperature of a molten glass flow poured into the mold is set lower than a temperature at a central portion.
[Claim 2] Using a mold having a through-hole, the molten glass accumulated in the container flows out from the lower end of a pipe connected to the container and continuously flows into the entrance of the through-hole. In the method of manufacturing a glass molded body that is continuously drawn out from the outlet and formed into a solid glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
While making the temperature of the molten glass in the said container higher than the temperature of the lower end of a pipe, the temperature difference of the molten glass in the said container and the lower end of a pipe is made into the range of 20-120 degreeC, It is characterized by the above-mentioned. A method for producing a glass molded body.
[Claim 3] A glass molded body that uses a mold having a through hole, continuously flows a molten glass flow into the inlet of the through hole, and continuously draws it from the outlet of the through hole to form a solid glass. In the manufacturing method,
The mold is arranged so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, comprising pouring into the mold while promoting cooling of the surface of the molten glass flow.
[Claim 4] A glass molded body that uses a mold having a through-hole, continuously flows a molten glass flow into the inlet of the through-hole, and continuously draws out from the outlet of the through-hole to form a solid glass. In the manufacturing method,
Place the mold so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, comprising bringing molten glass poured into the through hole into contact with an inner peripheral surface of the through hole to promote cooling of the surface of the molten glass.
[5] The method for producing a glass molded body according to any one of [1] to [4], wherein the molten glass flow has a viscosity of less than 10 ² dPa · s.
[6] The method for producing a glass molded body according to any one of [1] to [5], wherein the molten glass flow has a viscosity of 0.5 dPa · s or more.
[7] The molten glass poured into the through hole is brought into contact with the inner peripheral surface of the through hole to form the outer peripheral surface of the glass molded body. A method for producing a glass molded body.
[8] The method for producing a glass molded body according to [7], wherein the glass molded body is used by removing the outer peripheral surface.
[9] The method for producing a glass molded body according to any one of [1] to [8], wherein the through hole has a linear connection between the inlet and the outlet.
[10] The method for producing a glass molded body according to [9], wherein the mold is disposed so that a central axis of the through-hole is vertical or inclined.
[11] The method for producing a glass molded body according to any one of [1] to [10], wherein rod-shaped or flat glass is molded.
[12] A method for producing a glass material for press molding, comprising a step of dividing a glass molded product produced by the method according to any one of [1] to [11].
[Claim 13] In the method of manufacturing an optical element having a step of heating and press molding a glass material,
A method for producing an optical element, comprising using a glass material for press molding produced by the method according to claim 12.
[14] The method for producing an optical element according to [13], wherein the press-molded product produced by the press molding is ground and / or polished.
[15] An optical element for producing an optical element by dividing the glass molded body produced by the method according to any one of [1] to [11] to produce a glass block, and processing the glass block Manufacturing method.
[16] A method for producing a glass substrate, comprising a step of slicing a glass molded product produced by the method according to any one of [1] to [11] into a sheet glass.

  According to the present invention, it is possible to produce an optically homogeneous solid glass molded body from a low-viscosity molten glass. Further, it is possible to produce a homogeneous glass material for press molding for use in press molding from the glass molded body, and by pressing using the glass material for press molding, or glass from the glass molded body. By processing the optical element through a block, a high-quality optical element free from defects such as striae can be manufactured with high productivity. Furthermore, a high-quality glass substrate free from defects such as striae can be produced by processing the glass molded body with high productivity.

Hereinafter, the present invention will be described in more detail.

[Method for producing glass molded body]
The method for producing a glass molded body of the present invention comprises the first to fourth aspects, and in any of the aspects, a molten glass flow is continuously poured into the inlet of the through hole using a mold having a through hole, It is a manufacturing method of the glass forming body which draws continuously from the exit of a through-hole, and shape | molds it into solid glass.

The cause of striae that occurs when a molten glass flow, particularly a molten glass flow made of low-viscosity glass, is poured into a mold to form a glass molded body is presumed as follows.
(1) The surface of the molten glass stream is slightly altered by being exposed to the atmosphere while the molten glass stream flows out of the pipe and is poured into the mold. In addition, the molten glass that has been wetted and changed in quality on the outer periphery of the pipe may be taken into the molten glass flow surface again to generate a modified layer on the molten glass flow surface.
(2) When the molten glass flow is poured into the mold, the glass spreads in the mold, so that the altered layer localized on the surface also spreads inside the glass.
(3) The portion where the altered layer spreads is observed as a striae because a difference in refractive index occurs between the portion where the altered layer is spread and a homogeneous portion.

Therefore, the inventors of the present invention do not completely eliminate the striae during the production of the glass molded body, but if the portion where the striae exists is limited to the vicinity of the outer peripheral surface of the glass molded body, By removing the vicinity, it was considered that a homogeneous glass molded body free from striae could be obtained, and the method for producing the glass molded body of the first to fourth aspects was completed.
Hereinafter, each aspect will be described.

(First aspect)
The method for producing a glass molded body according to the first aspect uses a mold having a through hole, continuously flows a molten glass flow into the inlet of the through hole, and continuously pulls out the molten glass from the outlet of the through hole. In the method for producing a glass molded body to be molded into glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
It is a manufacturing method of the glass forming body characterized by making the surface temperature of the molten glass flow poured into the mold lower than the temperature of the central part.

  In this embodiment, the surface temperature of the molten glass flow poured into the mold is set lower than the temperature at the center. Thereby, the flow velocity near the surface of the molten glass flow becomes smaller than the internal flow velocity. By providing such a flow rate difference, it is possible to prevent a portion including a heterogeneous glass (modified glass) near the surface of the molten glass flow flowing out from the pipe from entering the glass. As a result, the glass near the surface of the molten glass flow flows in the mold in contact with the mold, and the glass in the center of the molten glass flow flows along the center of the mold through hole. Even if it is altered, the altered glass can be limited to the vicinity of the surface of the glass molded body, and a glass molded body having no striae inside can be produced with high productivity. As a method for making the surface temperature of the molten glass flow poured into the mold lower than the temperature at the center, the methods of the second and third aspects described later can be used.

  In this embodiment, the surface temperature of the molten glass stream poured into the mold can be regarded as the same as the temperature at the lower end of the outflow pipe. The temperature at the lower end of the outflow pipe can be measured with a thermocouple. The temperature at the center of the molten glass flow can be measured by inserting a thermocouple into the molten glass. The temperature difference between the surface temperature of the molten glass flow measured in this way and the temperature at the center is preferably 20 to 120 ° C, more preferably 20 to 60 ° C, and further preferably 30 to 50 ° C. is there. Moreover, it is preferable that the surface temperature of the molten glass flow poured into a casting_mold | template is the range of (liquid phase temperature +10 degreeC)-(liquid phase temperature +100 degreeC). The temperature of the center part of the molten glass flow can be set within the above-mentioned preferable temperature difference range.

(Second aspect)
The method for producing a glass molded body according to the second aspect uses a mold having a through hole, and flows the molten glass accumulated in the container out of the lower end of a pipe connected to the container and continues to the entrance of the through hole. In the method for producing a glass molded body that is poured into the glass and continuously drawn out from the outlet of the through hole and formed into a solid glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
While making the temperature of the molten glass in the said container higher than the temperature of the lower end of a pipe, the temperature difference of the molten glass in the said container and the lower end of a pipe is made into the range of 20-120 degreeC, It is characterized by the above-mentioned. It is a manufacturing method of a glass molded object.

  In this aspect, the molten glass accumulated in the container flows out from the lower end of the pipe connected to the container and flows into the entrance of the through hole, and the temperature of the molten glass in the container is made higher than the temperature of the lower end of the pipe, The difference between the temperature of the molten glass in the container and the temperature of the lower end of the pipe is set to 20 to 120 ° C, preferably 20 to 60 ° C, more preferably 30 to 50 ° C. Since the molten glass in the container is homogenized by stirring, for example, the temperature is substantially constant. However, when flowing through the pipe, the temperature is lowered because heat is taken away by the pipe. At that time, the glass flowing near the inner wall of the pipe is easier to cool than the glass flowing in the center of the pipe, so by controlling the temperature of the pipe, the temperature difference between the surface of the molten glass flowing out from the pipe and the center is changed. be able to. Thereby, like the above-mentioned 1st aspect, the surface temperature of the molten glass flow poured into a casting_mold | template can be made lower than the temperature of center part. The surface temperature of the molten glass flow poured into the mold in the second aspect, the temperature at the center, and the temperature difference between them are as described in the first aspect. In this aspect, by making the temperature difference between the molten glass in the container and the lower end of the pipe larger than a predetermined value, the flow velocity near the surface of the flowing molten glass flow is made smaller than the internal flow velocity. Can do. As a result, the glass near the surface of the molten glass flow can flow in the mold in contact with the mold, and the glass in the center of the molten glass flow can flow along the central portion of the mold through hole. As a result, even if the molten glass flow surface is altered, the altered glass can be limited to the vicinity of the surface of the glass molded body, and a glass molded body having no striae inside can be produced with high productivity. it can.

  Since the temperature of the molten glass in the container can be regarded as substantially the same as the temperature outside the container, in this embodiment, the temperature measured by providing a thermocouple on the outside of the container is the temperature of the molten glass in the container. Can be considered. The temperature at the lower end of the pipe can be measured by providing a thermocouple at the lower end of the pipe. Both the container and the pipe are preferably made of platinum or a platinum alloy so that heat conduction is good. The temperature of the molten glass in the container is preferably 1230 ° C to 1430 ° C, and the temperature at the lower end of the pipe is preferably 1210 to 1310 ° C.

  As a method of controlling the difference between the temperature of the molten glass in the container and the temperature of the lower end of the pipe, (1) a method of keeping the temperature of the molten glass in the container constant and controlling the temperature of the lower end of the pipe, (2) the lower end of the pipe There is a method for controlling the temperature of the molten glass in the container and (3) a method for controlling the temperature of the molten glass in the container and the temperature of the lower end of the pipe. In general, the method (1) is more preferable.

  When controlling the temperature at the lower end of the pipe, the temperature at the lower end of the pipe may be directly monitored, and the amount of heating of the pipe may be controlled based on the monitoring result (for example, a monitor signal). Monitoring may be performed, and the heating amount of the pipe may be controlled based on a monitoring result (for example, a monitor signal). The pipe is heated by applying an electric current to the pipe to generate heat, a heating method by placing a heating element around the pipe, and a high-frequency coil around the pipe to generate a high-frequency electromagnetic field and heat it. And a combination of these methods, and the input control for heating can be controlled based on the monitor signal.

(Third aspect)
The method for producing a glass molded body according to the third aspect uses a mold having a through-hole, continuously flows a molten glass flow into the inlet of the through-hole, and continuously draws it out from the outlet of the through-hole. In the method for producing a glass molded body to be molded into glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
It is a method for producing a glass molded body, wherein the casting is performed into the mold while promoting the cooling of the surface of the molten glass flow.

  In this aspect, by promoting the cooling of the surface of the molten glass flow, a difference in flow velocity between the surface of the molten glass flow poured into the mold and the inside is made, and the inside is homogeneous as in the first and second aspects. A glass molded body can be produced with high productivity. Here, “promoting the cooling of the surface” means a method of controlling the temperature of the atmosphere to which the molten glass flow surface is exposed, a method of blowing a gas on the molten glass flow surface, or a combination of the above methods, This refers to increasing the temperature difference from the ambient temperature near the glass surface.

  A specific example of the method for promoting the cooling of the molten glass flow surface is shown in FIG. FIG. 1 (a) shows a method of lowering the ambient temperature by installing a cover that surrounds between the pipe outlet and the inlet of the mold through-hole, and flowing a temperature-controlled atmospheric gas into the cover. In this case, it is desirable to be careful not to blow cooling gas to the lower end of the pipe so as not to prevent stable glass outflow. FIG.1 (b) shows the method of accelerating | stimulating cooling of a molten glass flow surface by spraying cooling gas on a molten glass flow surface. In this case as well, the above points should be noted. For this purpose, it is desirable to blow the cooling gas from above or obliquely above the molten glass flow surface, and it is desirable to keep the gas flow rate and temperature constant. The atmospheric temperature and the gas flow rate / temperature can be set as appropriate. For example, the surface temperature of the molten glass flow can be monitored and adjusted as appropriate. The ambient temperature can be, for example, 100 to 500 ° C., the temperature of the cooling gas can be, for example, 20 to 300 ° C., and the gas flow rate can be, for example, 10 to 100 l / min.

  Various gases can be used as the atmospheric gas and the cooling gas, but it is desirable to use a dry gas. Examples of the gas include air, inert gas (for example, nitrogen, argon, or a mixture of the above gases), and the like. By accelerating the cooling of the molten glass flow surface, a difference in flow velocity between the surface of the molten glass flow and the inside can be formed, and further, there is an effect of reducing surface alteration by lowering the temperature of the glass surface. As described above, by promoting the cooling of the molten glass flow, the surface temperature of the molten glass flow poured into the mold can be made lower than the temperature at the center as in the first aspect. The surface temperature of the molten glass flow poured into the mold in the third aspect, the temperature at the center, and the temperature difference between them are as described in the first aspect.

(Fourth aspect)
A method for producing a glass molded body according to a fourth aspect uses a mold having a through hole, continuously flows a molten glass flow into the inlet of the through hole, and continuously draws it out from the outlet of the through hole. In the method for producing a glass molded body to be molded into glass,
Place the mold so that the entrance of the through hole is higher than the exit,
It is a method for producing a glass molded body characterized in that the molten glass poured into the through hole is brought into contact with the inner peripheral surface of the through hole to promote the cooling of the surface of the molten glass.
Here, the “through-hole inner peripheral surface” is an inner wall of the through-hole, and is a surface surrounding the movement path of the cast glass.

  In this aspect, when the molten glass flow is poured into the mold and spreads in the through-hole, the molten glass thus poured is brought into contact with the inner peripheral surface of the through-hole to promote cooling of the cast glass surface. Similarly to each aspect of the above, the temperature difference between the surface and the inside can be made to change the flow velocity of both to prevent striae inside the glass. In this embodiment, the area of the entrance of the through hole is made smaller than the cross-sectional area when the glass molded body is cut perpendicular to the pulling direction when the glass molded body is pulled out from the through hole, and the shape gradually widens from the entrance to the exit. It is preferable to use a mold having through holes. In this way, by reducing the entrance area of the through hole, the surface of the molten glass flow comes into contact with the mold quickly and cooling of the surface is promoted, and the above-described effects can be obtained. In order to enhance the cooling promotion effect, it is preferable to make the through-hole entrance small as long as the molten glass flow is not hindered.

  In order to create a state in which the glass near the surface of the molten glass flow flows along the inner peripheral surface of the through-hole, the inner diameter of the through-hole increases from the through-hole entrance to a predetermined portion and from the through-hole entrance to the inside of the through-hole. Alternatively, it is desirable to gradually increase the cross-sectional area (the cross-sectional area of the cross section perpendicular to the traveling direction of the glass). However, if the viscosity of the surface of the glass cooled by the mold rises excessively, the filling of the glass into the through holes becomes insufficient, and it may be difficult to obtain a glass molded body having a desired shape. Therefore, it is desirable to fully consider the above points when determining the shape near the entrance of the through hole.

  In the method for producing a glass molded body according to the fourth aspect, the surface of the molten glass poured into the through hole is not cooled excessively so that the glass filling becomes insufficient, or the surface of the molten glass poured into the through hole It is preferable to control the temperature of the mold with a heater or the like so that the fusion between the glass and the mold does not occur due to the excessively high temperature.

(Common points of the first to fourth aspects)
Next, common points of the above embodiments will be described.
The manufacturing method of the glass forming body of this invention can be used suitably especially in order to manufacture a glass forming body without striae from low viscosity glass. The viscosity of the molten glass stream flowing out from the outflow pipe is preferably less than 10 ² dPa · s. From the viewpoint of ease of molding, the viscosity of the molten glass flow is preferably 0.5 dPa · s or more. According to the present invention, an excellent striae-preventing effect can be obtained in the molding of a molten glass having a low viscosity as described above. The viscosity is more preferably in the range of ² dPa · s to less than 10 ² dPa · s, and still more preferably in the range of ^{2 to} 90 dPa · s.

  In order not to allow striae to enter the glass molded body from any direction, it is desirable to form the outer peripheral surface of the glass molded body by bringing the molten glass poured into the through hole into contact with the inner peripheral surface of the through hole. Here, the “outer peripheral surface of the glass molded body” means the surface of the glass molded body extending along the direction when the glass molded body is pulled out from the through-hole exit. The molding as described above can be performed by filling the inside of the through-hole with molten glass up to the vicinity of the entrance and bringing the molten glass into contact with the inner peripheral surface of the through-hole that is submerged below the glass liquid surface. Such molding is effective not only to prevent striae from entering in any direction inside the glass molded body, but also to alter the glass by minimizing the area exposed to the molten glass atmosphere in the mold. This is also an effective method for preventing the problem. By removing the outer peripheral surface of the glass molded body thus formed, a homogeneous glass molded body free from striae can be obtained.

  Furthermore, a mold having a through hole in which the inlet and the outlet are linearly connected is used so that the glass near the surface of the molten glass flow stably flows along the inner peripheral surface of the mold through hole. It is preferable. Thereby, it is possible to prevent an excessive force from being applied to the glass when pulling out the glass molded body, and it is possible to prevent breakage of the glass. Furthermore, by using such a mold, there is no significant difference between the length of the movement path of the glass flowing along the central axis of the through hole and the length of the movement path of the glass flowing along the inner peripheral surface of the through hole. It is possible to effectively prevent the occurrence of reason.

  In such a mold in which the inlet and outlet of the through hole are in linear communication, the central axis of the through hole is a straight line, and the inclination of the through hole can be defined by the angle θ formed by the horizontal plane and the central axis of the through hole. it can. The angle θ can be determined in consideration of the viscosity of the molten glass flowing out, the shape and dimensions of the target glass molded body, and the like. By increasing θ (closer to 90 °), the length of the movement path of the molten glass in the through hole is made to be constant regardless of the distance from the central axis, and the glass flow is parallel to the central axis. Can be approached. Making the glass flow in the through hole in this way is desirable from the viewpoint of reducing striae. From such a viewpoint, a preferable range of θ is 45 ° to 90 °, a more preferable range is 60 ° to 90 °, and a particularly preferable θ is 90 °.

  FIG. 2 shows an example of a method for producing a glass molded body of the present invention, and is a schematic view of a state in which molten glass is poured into a mold and formed into a rod-like glass from the side. The mold part is shown in a vertical section so that the inside can be seen. In FIG. 2, the through hole is provided so that the entrance and the exit communicate linearly, and is fixed so that the central axis thereof faces the vertical direction (θ = 90 °).

Hereinafter, based on FIG. 2, an example of the manufacturing method of the glass forming body of this invention is demonstrated.
A molten glass stream is continuously poured from the opening on the high position side of the through hole, that is, the inlet 13 of the through hole. Here, it is preferable that the mold 11 is arranged so that the inlet 13 is located directly below the outflow pipe 12 that flows down the molten glass flow, and the molten glass flow is poured into the center of the molten glass liquid level surface in the through hole. . By doing in this way, the length of the movement path | route of the glass in a casting_mold | template can be arrange | equalized uniformly, and it can prevent effectively that a striae enters the inside of a glass forming body.

  A molten glass container (not shown) in which molten, clarified and homogenized molten glass is accumulated is arranged on the upper part of the outflow pipe 12, and from there, the molten glass is preferably passed through the outflow pipe 12. It is made to flow down continuously at a flow rate of. The molten glass flow that has flowed down is poured into the through hole from the inlet 13, and as shown in FIG. 2, the glass flows out from the outflow pipe 12 in a straight line without interruption. Fill the molten glass.

  The molten glass poured into the through hole comes into contact with the inner peripheral surface of the through hole, and cools while moving vertically downward along the central axis direction of the through hole. Glass that has been deprived of heat by the mold and has increased viscosity is drawn from the through-hole outlet 14, which is an opening on the lower side of the mold through-hole, and formed into a rod-shaped glass (hereinafter also referred to as “glass rod”). Can do. Until the glass rod is pulled out from the outlet 14, the viscosity of the molten glass, the inflow amount, and the drawing speed are adjusted, and the molten glass is moved in the through hole in a state of being in contact with the inner peripheral surface of the through hole without any gap. It is desirable to form the outer peripheral surface of the glass molded body in contact with the inner peripheral surface of the hole. By forming so that there is no gap between the inner peripheral surface of the through hole and the molten glass, the area where the glass in the high temperature state is exposed to the outside air can be minimized. Thereby, since the volatilization of the volatile component in the glass can be reduced, it is possible to prevent deterioration of the portion in contact with the outside air, and it is also possible to prevent striae caused by volatilization.

In the present invention, it is desirable to keep both the speed at which the molten glass flow flows out from the outflow pipe (that is, the speed at which the molten glass flow flows into the mold) and the speed at which the glass molded body is drawn out from the through hole outlet. Moreover, it is preferable to control the said inflow rate and the drawing-out speed | rate of a glass molded object so that a molten glass liquid level may be maintained in predetermined | prescribed height in a through-hole. By creating such a state, the flow of the molten glass in the mold becomes stable, and the striae can be more reliably limited to the glass surface.
Moreover, if the drawing speed from the glass mold is too high or the inflow speed of the molten glass is too low, a gap is formed between the inner peripheral surface of the through hole and the glass, and the outer diameter of the glass molded body is not stable. On the other hand, when the drawing speed is slow or the inflow speed is too high, the molten glass overflows from the mold or the shape of the glass molded body becomes defective. If the amount of molten glass poured into the mold and the drawing speed of the glass are controlled so that the molten glass liquid level is maintained at a predetermined height in the through hole, the distance between the inner peripheral surface of the through hole and the molten glass is reduced. Alternatively, the molding can be performed so that there is no gap between the glass and the glass. Thereby, the area where the glass in the high temperature state is exposed to the outside air can be minimized, and the volatilization of the volatile components in the glass can be reduced. It is also possible to prevent striae caused by volatilization.

  The flow rate and the glass drawing speed vary depending on the shape and size of the glass molded body and the type of glass used, but the striae of the molded glass is inspected, and the depth of the layer where striae is 0.5 mm. The conditions are preferably set so as to be as follows. The depth of the surface layer having striae can be measured by using a method such as visual inspection after facing polishing, a striae inspection apparatus including a point light source and a lens system, and a schlieren inspection apparatus. In this way, it is desirable that conditions suitable for the production of the target glass molded body are obtained in advance by test molding, and mass production of the glass molded body is performed by applying these conditions. In the case of promoting the cooling of the molten glass flow surface by controlling the atmospheric gas or blowing the cooling gas, various conditions such as the atmospheric temperature, the temperature of the cooling gas, the flow rate of the cooling gas, etc. are also suitable in advance by test molding. It is desirable to obtain the conditions.

  In the method shown in FIG. 2, in order to keep the molten glass liquid level in the through-hole constant as described above, the inflow speed of the molten glass flowing out from the outflow pipe 12 is kept constant, and the liquid level monitoring device 17 may be used to monitor the molten glass liquid level in the mold through hole and feed back the monitoring result of the liquid level or the liquid level change to the drawing speed of the glass molded body. The liquid level can be monitored by, for example, a thermometer or a laser sensor.

  The material of the mold used in the present invention is preferably a heat-resistant metal such as carbon, casting, or nickel. If temperature control is not performed, the temperature at the inlet side of the through hole becomes higher than the temperature at the outlet side during molding. Therefore, if the mold through hole is formed with a constant inner diameter at room temperature, the through hole is formed during molding because of thermal expansion. The inner diameter will not be constant. In the present invention, it is preferable to determine the processing shape of the through hole in consideration of thermal expansion so that the inner diameter of the through hole is increased from the through hole entrance to the outlet, and the inner diameter of the through hole becomes constant during molding. As described above, in the fourth aspect, when the through hole entrance area is reduced, it is preferable to determine the processed shape of the through hole in consideration of thermal expansion.

In this invention, it is preferable to perform the process of producing a glass forming body from molten glass in an inert atmosphere from a viewpoint of preventing deterioration of a casting_mold | template.
The mold may be composed of a single article, or may be an assembly of a plurality of members. When a mold is constituted by a plurality of members, a plurality of members may be brought into close contact with each other to form a through hole, a through hole of one member may be provided, or each of the plurality of members may be provided. A through hole may be provided, and each member may be closely attached so that each through hole is connected to one.

The temperature of the mold is determined in consideration of the following points: (1) the glass does not melt, (2) no glass breakage called canister, (3) the molten glass spreads in the mold through-holes without any gaps. It is preferable to do. The mold may be provided with a heater or a cooler as necessary for temperature control. Moreover, it is preferable that the temperature of the glass forming body surface in a through-hole exit is a temperature below a glass yield point. If the temperature of the surface of the glass molded body at the outlet of the through hole is a temperature below the glass yield point, the glass molded body can be prevented from being deformed when being drawn out from the mold. In addition, since the glass can be deformed by an external force at a temperature equal to or higher than the yield point, as described later, when the glass drawn from the through-hole outlet is bent in a direction in which a post-process can be easily performed, the outlet The temperature of the glass surface at is preferably a temperature above the yield point. When the temperature is too high, the temperature of the surface of the glass molded body at the outlet is cooled by cooling the mold by air cooling or by providing a water-cooled plate. It can be adjusted by heating.

  The mold temperature can be 20-50 ° C. lower than the glass transition temperature in the vicinity of the through-hole entrance, and 0-30 ° C. lower than the glass transition temperature in the vicinity of the through-hole exit. In the intermediate portion, the temperature is near the temperature near the entrance and above the temperature near the exit.

  From the viewpoint of preventing glass fusion, cracking, spreading, bending, and the like, the ratio between the inner diameter and the length of the through hole is preferably in the range of 1/50 to 1/1. More preferably, it is in the range of 1/20 to 1/5. The inner diameter of the through hole should be determined in consideration of the outer diameter of the glass molded body to be obtained, and can be set to, for example, 10 to 100 mm. At that time, the length of the through hole is preferably in the range of 100 to 500 mm. Here, the “length of the through hole” means a length along the central axis from the center of the surface including the through hole entrance to the center of the surface including the exit, as shown in FIG. 3. The “inner diameter of the through hole” refers to the diameter of the portion where the inner diameter is constant during molding.

  The glass can be pulled out from the outlet of the through hole by using the gravity direction component of gravity acting on the molten glass in the through hole and the glass molded body drawn from the outlet. Depending on various conditions such as the magnitude of the frictional force acting between the glass and the inner peripheral surface of the through hole, the volume in the through hole, the specific gravity of the glass, the angle θ between the through hole and the horizontal plane, When the pulling speed becomes excessive due to the above, it is preferable to pull out while controlling the glass so that the pulling speed becomes appropriate while supporting the glass. When the pulling speed is too low only by the pulling direction component of the gravity, it is preferable to pull the glass while applying a force in the pulling direction to control the pulling speed to be appropriate. The glass may be supported at its lower end or by sandwiching a side surface (a surface formed by transferring the inner peripheral surface of the through hole). Note that the gravity pull-out direction component increases as θ approaches 90 °. When supporting the glass across the side surface of the drawn glass molded body or applying a pulling force, a method of rotating the driving roller by sandwiching the side surface of the solidified glass coming out from the outlet of the through hole with a driving roller is used. be able to.

  In the present invention, if necessary, the conveyance path of the glass molded body drawn from the through hole is changed before annealing, so that the glass molded body drawn from the through hole can be easily subjected to subsequent processes such as annealing. It may be bent. In addition, in order to prevent damage or distortion from occurring before changing the conveyance path of the glass molded body, the glass molded body drawn out from the outlet is heated again so that the surface temperature is equal to or higher than the glass yield point. And may be softened. However, excessive heating deteriorates the shape of the glass molded body or alters the side surface of the glass molded body. Therefore, when heating is performed, the heating temperature should be determined in consideration of this point. Heating can be performed, for example, by providing a heater near the driven roller disposed near the outlet of the through hole.

  In order to change the transfer path of the glass molded body drawn out from the through-hole outlet, for example, the driven roller is arranged in the vicinity of the outlet as described above, and the drive roller is arranged in a direction in which the transfer path is changed as viewed from the driven roller. . In such an apparatus, the force for pulling out the glass molded body can be obtained by the rotation of the drive roller. By passing the glass molded body between the driven roller and between the drive rollers, the glass molded body is moved in a desired direction. Can be bent. In order to stably pull out the glass molded body, it is preferable that the positions of the driven roller and the driving roller are fixed. The number of driven rollers and driving rollers is not particularly limited as long as the glass molded body can be pulled out and bent in a desired direction. The glass molded body drawn out from the outlet of the through hole is subjected to a subsequent process through a driven roller and a driving roller.

  Examples of the post-process to be performed on the glass molded body drawn out from the through-hole outlet include an annealing process, a process of cutting to a predetermined length, a packing process, and the like, and a homogeneous glass molded body after the post-process such as annealing. Can be obtained. The glass after the annealing step can be cut into a glass molded body having an appropriate length, or can be cut into a glass block having a desired size for use as a glass material for press molding.

  As for the shape of the glass molded object shape | molded using the method of this invention, it is desirable that the shape of the cross section perpendicular | vertical with respect to the drawing-out direction of the said molded object is congruent or substantially congruent along the said drawing-out direction. In addition, the method of the present invention is suitable for molding a glass molded body having a longer length along the pull-out direction than the outer diameter of the glass molded body (the diameter of the molded body in the cross section). From such a viewpoint, examples of the preferable shape of the glass molded body include a rod shape, for example, a cylinder, an elliptical column, a rectangular column, and a plate shape. In order to obtain a homogeneous glass molded body having a desired cross-sectional shape, a cross-sectional shape perpendicular to the direction in which the glass molded body is pulled out from the mold (when the glass molded body has a central axis, this corresponds to a cross-sectional shape perpendicular to the central axis). The mold is preferably designed so that the cross-sectional shape perpendicular to the central axis of the mold through hole matches.

  When the ratio of the major axis to the minor axis (major axis / minor axis) of the cross section of the glass molded body is close to 1, even if the angle θ between the central axis of the through hole and the horizontal plane is relatively small, the pulse from the inside of the glass molded body. However, if θ is decreased as the ratio increases, it becomes difficult to remove striae from the inside of the molded body. Therefore, it is desirable to increase θ when the plate-shaped glass molded body is formed. Therefore, it is desirable to increase θ. When forming a rod-shaped glass molded body, the ratio is close to 1 or 1, so that θ can be reduced. Good. In order to improve the striae elimination effect regardless of the shape, it is preferable to make θ close to 90 ° or 90 ° as described above. Further, in order to obtain the striae elimination effect most effectively regardless of the shape, it is desirable that the shape of the glass molded body is a cylinder, and then it is desirable that the ratio (major axis / minor axis) is a prism close to 1.

As described above, according to the present invention, even if striae occur during molding, the region where the striae exist can be limited to the vicinity of the outer peripheral surface of the glass molded body. An optically homogeneous glass molded body that does not contain any reason can be obtained.
Depending on the type of glass, molding conditions, shape and dimensions of the glass molded body, but removing the surface layer from the outer peripheral surface to at least 0.5 mm, an optically homogeneous glass molded body can be obtained, In molding, it is desirable to determine the dimension of the mold through hole in consideration of the thickness of the surface layer.

Using the method of the present invention, a solid glass cylinder made of optical fiber cladding glass is formed, a hole corresponding to the cylinder axis is made into a hollow glass, and then an optical fiber core is placed in the hole. Glass fiber preforms can also be made by fitting glass cylinders made of glass. It is also possible to make a glass fiber preform by fitting a glass column for glass formed by the method of the present invention into a glass column for cladding with a hole in the center. The above two methods can be combined. Such a preform can be drawn to produce an optical fiber.
It is also possible to arrange a cylindrical shaft made of a heat-resistant material on the central axis of the mold through-hole, and pour molten glass into a hollow glass molded body having a hole on the central axis. The method of the present invention should be applied to obtain a solid columnar (non-hollow) glass because the flow of the molten glass poured in may disturb the flow of the molten glass.

In the present invention, glass as a raw material for obtaining a glass molded body is not particularly limited except that the viscosity at the time of outflow is in the above range, but glass molding made of optical glass that requires optically high homogeneity. It is desirable to apply the method of the present invention to the production of a body. Such glasses include B ₂ O ₃ and rare earth oxide-containing glasses, SiO ₂ and TiO ₂ containing glasses, P ₂ O ₅ and Nb ₂ O ₅ containing glasses, P ₂ O ₅ and RO (R is Ba and / or Or, optical glass such as Zn) -containing glass and fluorophosphate glass can be exemplified.

Examples of the glass containing B ₂ O ₃ and rare earth oxide include glass containing B ₂ O ₃ and La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O _{3 and the} like. Specifically, the following glass can be illustrated.
(1) represented by _{mass%, B 2 O 3 2~50%,} SiO 2 0~30%, La 2 O 3 10~60%, Gd 2 O 3 0~20%, Y 2 O 3 0~20% Yb ₂ O ₃ 0-10%, Ta ₂ O ₅ 0-20%, WO ₃ 0-20%, Li ₂ O 0-15%, Na ₂ O 0-10%, K ₂ O 0-10%, GeO ₂ 0-10%, Bi ₂ O ₃ 0-20%, TiO ₂ 0-30%, ZnO 0-30%, ZrO ₂ 0-15%, Nb ₂ O ₅ 0-35%, BaO 0-35% SrO 0-15%, CaO 0-15%, MgO 0-15%, Al ₂ O ₃ 0-10%, Sb ₂ O ₃ 0-2%, SnO ₂ 0-1% glass;
(2) by _{mol%, B 2 O 3 20~60%,} SiO 2 0~10%, La 2 O 3 5~22%, Gd 2 O 3 0~20%, Y 2 O 3 0~10% Yb ₂ O ₃ 0-10%, Ta ₂ O ₅ 0-10%, WO ₃ 0-8%, Li ₂ O 0-10%, Na ₂ O 0-5%, K ₂ O 0-5%, GeO ₂ 0-10%, Bi ₂ O ₃ 0-8%, TiO ₂ 0-8%, ZnO 0-30%, ZrO ₂ 0-7%, Nb ₂ O ₅ 0-8%, BaO 0-10% , SrO 0~10%, CaO 0~10% , 0~10% MgO, Al 2 O 3 0~10%, Sb 2 O 3 0~1%, SnO2 0~1% glass containing.

Among the B ₂ O ₃ and rare earth oxide-containing glasses, glass having a refractive index (nd) of 1.85 or more and an Abbe number (νd) of 20 to 45 has a low viscosity especially when flowing out. The application of the method of the invention is even more effective. Further, the glass having low viscosity at the time of outflow has a small amount of B ₂ O ₃ and SiO ₂ which are glass network forming components, and has relatively low glass stability. Such glass has a total content of B ₂ O ₃ and SiO ₂ of 25% by mass or less, particularly less than 20% by mass. The method of the present invention is particularly suitable for molding such glass. Can be used.

Further, the glass contains B ₂ O ₃ which is volatile. The striae, particularly striae near the surface, are also generated by the volatilization of glass components from the surface of high-temperature glass. Therefore, in the present invention, volatilization of easily volatile components can be minimized by bringing the surface of the molten glass poured into the through hole into contact with the atmosphere only with the liquid level. In particular, according to the fourth aspect, volatilization of easily volatile components can be more effectively suppressed by reducing the opening at the entrance of the through hole.

Since the alkali metal oxide has the property of being easily volatilized like B ₂ O ₃ , the method of the present invention is applied to a glass containing one or more of Li ₂ O, Na ₂ O and K ₂ O. It is also preferable to apply to.

The SiO ₂ and TiO ₂ containing glass, represented by _{mass%, SiO 2 18~40%, TiO 2} 20~40%, BaO 9~23%, Nb 2 O 5 7~20%, Li 2 O 0~5 %, Na ₂ O 5-20%, K ₂ O 0-10%, CaO 0-5%, SrO 0-5%, ZrO ₂ 0-6%, Ta ₂ O ₅ 0-5%, WO ₃ 0 A glass containing 5% and 0 to 1% of Sb ₂ O ₃ can be exemplified.

Examples of the P ₂ O ₅ and Nb ₂ O ₅ -containing glass include the following glasses.
(1) represented by _{mass%, P 2 O 5 10~47%,} Nb 2 O 5 20~65%, TiO 2 0~20%, SiO 2 0~5%, B 2 O 3 0~12%, Li ₂ O 0-10%, Na ₂ O 0-25%, K ₂ O 0-15%, MgO 0-10%, CaO 0-10%, SrO 0-10%, BaO 0-30%, ZnO 0 10%, Bi ₂ O ₃ 0-25%, WO ₃ 0-25%, Ta ₂ O ₅ 0-20%, ZrO ₂ 0-5%, Al ₂ O ₃ 0-7%, La ₂ O ₃ + Y ₂ Glass containing O ₃ + Gd ₂ O ₃ 0-10%, GeO ₂ 0-5%, Sb ₂ O ₃ 0-1%;
(2) by _{mol%, P 2 O 5 10~45%,} Nb 2 O 5 3~35%, TiO 2 0~20%, WO 3 0~40%, Bi 2 O 3 0~20%, SiO _{2 0~15%, B 2 O 3} 0~30%, Al 2 O 3 0~15%, Li 2 O 2~35%, Na 2 O 0~35%, K 2 O 0~30%, ZnO 0 ~25%, 0~20% MgO, CaO 0~20%, SrO 0~20%, BaO 0~25%, ZrO 2 0~5%, La 2 O 3 0~10%, Gd 2 O 3 0~ Glass containing 10%, Y ₂ O ₃ 0-10%, Yb ₂ O ₃ 0-10%, Ta ₂ O ₅ 0-10%, Sb ₂ O ₃ 0-1%.
In particular, a glass having an optical constant having a refractive index (nd) of 1.7 or more and an Abbe number (νd) of 35 or less (particularly a refractive index (nd) of 1.75 to 2 and an Abbe number (νd) of 17 to 30). It is preferable to apply the invention.

Examples of the glass containing P ₂ O ₅ and RO (R is Ba and / or Zn) include an optical constant having an Abbe number (νd) of 55 or more (particularly an Abbe number (νd) of 55 to 80). Can do. Among such ones, as the P ₂ O ₅ and BaO-containing glass can be exemplified the following glass.
(1) by _{mol%, P 2 O 5 20~65%,} BaO 1~50%, Li 2 O 0~30%, Na 2 O 0~20%, K 2 O 0~15%, ZnO 0~ 20%, B ₂ O ₃ 0-25%, Al ₂ O ₃ 0-10%, Gd ₂ O ₃ 0-10%, MgO 0-20%, CaO 0-20%, SrO 0-20%, Bi ₂ Glass containing O ₃ 0-10%, Sb ₂ O ₃ 0-1%;
(2) by _{mol%, P 2 O 5 20~65%,} 0.1~20% ZnO, Li 2 O 0~30%, Na 2 O 0~20%, K 2 O 0~15%, B ₂ O ₃ 0-25%, Al ₂ O ₃ 0-10%, Gd ₂ O ₃ 0-10%, MgO 0-20%, CaO 0-20%, SrO 0-20%, BaO 0-50%, Glass containing Bi ₂ O ₃ 0-10%, Sb ₂ O ₃ 0-1%.

Furthermore, as glass containing P ₂ O ₅ , BaO and ZnO, P ₂ O ₅ 20 to 65%, BaO 1 to 50%, ZnO 0.1 to 20%, Li ₂ O 0 30%, Na ₂ O 0-20%, K ₂ O 0-15%, B ₂ O ₃ 0-25%, Al ₂ O ₃ 0-10%, Gd ₂ O ₃ 0-10%, MgO 0-20 %, CaO 0-20%, SrO 0-20%, Bi ₂ O ₃ 0-10%, Sb ₂ O ₃ 0-1%.

Examples of the fluorophosphate glass include low-dispersion glass having an Abbe number (νd) of 65 or more. More specifically, examples include those containing Al, Ca, Sr as cation components and F, O as essential components as anion components. For example, in terms of mol%, Al (PO ₃ ) ₃ 0-20%, Ba (PO ₃ ) ₂ 0-30%, Mg (PO ₃ ) ₂ 0-30%, Ca (PO ₃ ) ₂ 0-30% Sr (PO ₃ ) ₂ 0-30%, Zn (PO ₃ ) ₂ 0-30%, NaPO ₃ 0-15%, AlF ₃ 2-45%, ZrF ₄ 0-10%, YF ₃ 0-15% YbF ₃ 0-15%, GdF ₃ 0-15%, BiF ₃ 0-15%, LaF ₃ 0-10%, MgF ₂ 0-20%, CaF ₂ 2-45%, SrF ₂ 2-45%, ZnF ₂ 0-20%, BaF ₂ 0-30%, LiF 0-10%, NaF 0-15%, KF 0-15%, Li ₂ O 0-5%, Na ₂ O 0-5%, K ₂ Exemplify glass containing O 0-5%, MgO 0-5%, CaO 0-5%, SrO 0-5%, BaO 0-5%, ZnO 0-5%. It can be.

[Method of manufacturing glass material for press molding]
Next, the manufacturing method of the glass material for press molding of this invention is demonstrated.
The manufacturing method of the glass material for press molding of this invention is a manufacturing method of the glass raw material for press molding including the process of dividing | segmenting the glass molded object manufactured with the manufacturing method of the glass molded object of the above-mentioned this invention.
According to the method for producing a glass molded body of the first to fourth aspects described above, even if the obtained glass molded body has optical non-uniform portions such as striae, the striae is glass molded. It is limited to the surface layer of the body (for example, within 0.5 mm from the surface). Therefore, even in a glass material for press molding produced by dividing the glass molded body, optically nonuniform portions such as striae are limited to the surface layer of the glass material (for example, within 0.5 mm from the surface). The In addition, when producing an optical element by polishing and / or grinding the surface of a press-molded product obtained by press-molding such a glass material, the optically non-uniform surface layer is removed by the above-described processing. Thus, an optically uniform optical element can be obtained without the step of removing the surface layer on the glass material surface.

  In the dividing step, the glass molded body whose strain is reduced by annealing is cut or cleaved to divide the glass molded body into a plurality of glass blocks. When the glass molded body has a shape having a central axis such as a columnar shape, it is desirable to divide the glass molded body perpendicularly to the central axis. The columnar glass block thus divided is limited to the surface layer on the side surface of the columnar block (for example, within 0.5 mm from the surface) even if striae exist. If this surface layer is press-molded so as not to enter the optical functional surface of the optical element (the surface for refracting, reflecting, or diffracting the light beam to be controlled), the surface layer on the side surface of the block is pulsed. Even if reason exists, the performance of the optical element is not deteriorated. The press molding can be realized by pressurizing the surface formed by dividing the glass molded body (the bottom surface facing the columnar block) with a press mold.

  In addition, since the striae may be localized near the outer peripheral surface of the glass molded body as described above, a step of removing the surface of the glass molded body is added to the manufacturing process of the glass material for press molding. May be. In addition, the thickness of the surface layer removed by the said process is as above-mentioned.

When cutting a glass molded body, it can cut | disconnect using a wire, a grindstone, etc., and can obtain a glass block. Moreover, when cleaving, it is preferable to apply stress to the glass molded body to break the glass molded body at a desired position.
In order to produce a glass material for press molding from a glass molded body, it preferably crosses the central axis of the glass molded body as described above, or crosses the drawing direction of the glass molded body, preferably with respect to the central axis or the drawing direction. It is desirable to divide in a vertical plane.

  In the present invention, it is preferable to determine the outer diameter of the rod-shaped glass molded body and the width and thickness of the plate-shaped glass molded body in consideration of the shape and dimensions of the press-molding glass material to be obtained. The width for dividing the glass molded body (corresponding to the interval between the divided surfaces when divided at a plurality of positions) can be appropriately set according to the thickness of the press-formed product to be obtained and the optical element. . The obtained glass block can be heated and softened as it is, and then press-molded to obtain a press-molded product. In that case, it is desirable to press the surface formed by dividing as described above with a press mold. Further, a glass block subjected to grinding or polishing can be heated and softened, and then press-molded to obtain a press-molded product. In the present invention, a glass article that can be press-molded when heated and softened in this way is referred to as a “press-molding glass material”.

[Method of manufacturing optical element]
Next, the manufacturing method of the optical element of this invention is demonstrated.
According to a first aspect of the optical element manufacturing method of the present invention, in the optical element manufacturing method including a step of heating and press-molding a glass material, the press-molding glass material produced by the method is used. It is a manufacturing method of the optical element which makes.
The press molding can be performed by a known method. A molded product produced by press molding can be used as an optical element as it is, or an optical element can be produced by grinding and / or polishing the press molded product produced by press molding.

  When producing an axially symmetric optical element such as a lens by press molding, it is preferable to mold a cylindrical glass molded body and cut it perpendicularly to the central axis of the glass molded body. In other cases, it is preferable to determine the shape of a glass material for press molding suitable for press molding from the shape of a desired optical element, and to mold a glass molded body having such a shape that the material can be easily produced. The weight of the glass material for press molding obtained by dividing the glass molded body can be made equal to the weight of the optical element to be obtained. Alternatively, it is possible to obtain a press-molding glass material having a weight of a target press-molded product by performing machining after the division.

  When an optical element is manufactured by precision press molding in which the optical functional surface of the optical element is formed by press molding, it is desirable to finish the surface of the glass material for press molding smoothly by polishing or the like. Further, when press molding is performed in an oxidizing atmosphere, the release film (for example, made of carbon) may be deteriorated. Therefore, the press molding is preferably performed in a non-oxidizing atmosphere.

  When precision press molding is performed, the obtained press-molded product is cooled slowly, and then, as it is, various lenses such as aspherical lenses, spherical lenses, microlenses, lens arrays, prisms, polygon mirrors, diffraction gratings, filters, etc. It can be used as various optical elements. If necessary, the surface around the optical functional surface may be machined to finish the optical element.

  Or, press-molding glass material is heated and softened in the atmosphere and then press-molded to form a press-molded product, and the press-molded product is ground and polished to produce optical elements such as various lenses and prisms. You can also.

  According to a second aspect of the method for producing an optical element of the present invention, the glass molded body produced by the method for producing a glass molded body according to the first to fourth aspects of the present invention is divided to produce a glass block, An optical element is manufactured by processing a glass block. In this case, it is preferable to mold a rod-like glass molded body having an outer diameter equal to the outer diameter of the optical element to be obtained or an outer diameter obtained by adding a machining allowance to the outer diameter. The width of the glass block can be the thickness of the optical element or the thickness of the optical element plus a processing allowance. Optical elements such as lenses and prisms can be produced by further grinding and polishing the glass block produced by dividing the glass molded body in this way.

[Glass substrate manufacturing method]
Next, the manufacturing method of the glass substrate of this invention is demonstrated.
The method for producing a glass substrate of the present invention includes a step of slicing a glass molded body produced by the method for producing a glass molded body of the first to fourth aspects of the present invention to form a sheet glass. . In order to produce a glass molded body used in the method for producing a glass substrate of the present invention, a mold whose sectional shape perpendicular to the central axis of the straight through hole is approximated to the planar shape of the glass substrate is used. Thus, it is preferable to form a glass molded body. That is, in order to obtain a disk-shaped substrate, a cylindrical glass molded body having an outer diameter equal to the diameter of the disk or having an outer diameter obtained by adding a margin described later to the above-mentioned diameter is obtained to obtain a square substrate. It is preferable to produce a prismatic glass molding. And it is preferable to slice the said molded object on the plane perpendicular | vertical with respect to the drawing-out direction of a glass molded object. In the case of a columnar shaped body, it can be sliced perpendicular to the central axis. Prior to slicing, it is desirable to anneal the glass compact to reduce strain in order to prevent breakage of the glass. The surface of the plate glass thus produced can be polished to finish into a glass substrate.

  According to the present invention, an optically homogeneous glass substrate can be produced with high productivity. The glass substrate thus produced is suitable for an optical filter, a cover glass for a solid-state imaging device, and the like. In addition, the glass substrate said here shall also contain the flat glass in which the film | membrane etc. are not formed on the board | substrate.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
The temperature of the lower end of the molten glass (glass viscosity: 1.1 dPa · s, center temperature: 1280 ° C) in a well-clarified and homogenized melting vessel (made of platinum alloy) is controlled to 1250 ° C. The upper part continuously flows down from the platinum alloy outflow pipe connected to the melting vessel at a constant outflow rate (37.8 ml / min), and straight into the carbon mold placed at the position shown in FIG. Poured into the center of the entrance of the through hole. As described above, the surface temperature of the molten glass stream flowing out from the pipe can be regarded as the same as the temperature at the lower end of the outflow pipe. In addition, the temperature of the molten glass in the melting vessel was also controlled to keep the above set value. Since the temperature difference between the temperature of the glass in the melting vessel and the lower end of the outflow pipe was set to 30 ° C., the surface temperature of the molten glass flow flowing out from the pipe (1250 ° C.) when the molten glass in the vessel passes through the pipe. Was lower than the temperature at the center (1280 ° C.). Here, the inner diameter of the mold through-hole was φ20 mm, and the angle θ formed by the central axis of the through-hole and the horizontal plane was 90 °. The length of the mold through-hole was set to 100 mm, and a band heater (not shown) was wound around the mold and heated so that good molding was possible. The glass molded body is pulled out from the outlet of the through-hole using the weight of the glass, and the lower end of the glass molded body is supported by a support base so that the pulling speed is constant. Is equivalent to 12.0 cm / min. In addition, you may control the descent | fall speed of a support stand so that the height (liquid level) of the molten glass liquid level in a casting_mold | template through-hole may become fixed. In such control, the liquid level of the molten glass is monitored using a liquid level gauge such as a laser liquid level gauge, and the descending speed of the support base is increased or decreased based on the monitor signal output from the liquid level gauge. Can be done. For example, when the liquid level is higher than a preset reference liquid level, the descending speed of the support base is increased. Conversely, when the liquid level is lower than the reference liquid level, the descending speed of the support base is decreased. By such control, the liquid level can be controlled to be kept constant.

In this way, a glass rod (cylindrical glass) having a diameter of 20 mm was drawn vertically downward from the mold through-hole exit at a constant speed. When the length of the glass rod drawn out from the mold reached 500 mm, the glass rod was cut from the direction perpendicular to the drawing direction (horizontal direction) and annealed to remove strain.
In this embodiment, since the surface temperature of the molten glass flow poured into the mold through-hole entrance is controlled to be lower than the temperature at the center, the molten glass flow surface portion flows along the inner peripheral surface of the mold through-hole. I was able to make.
In this way, B ₂ O ₃ and La ₂ O ₃ the refractive index of the content (nd) is 1.883, a glass rod Abbe number ([nu] d) is made of optical glass of 40.8 (liquidus temperature 1200 ° C.) Produced. The obtained solid columnar glass rod was homogeneous and transparent, and when observed visually after face-to-face polishing, no striae entering the inside from the surface were recognized.

  Similarly, a fluorophosphate optical glass (liquid phase temperature 645 ° C.) having a refractive index (nd) of 1.497 and an Abbe number (νd) of 81.6, a refractive index (nd) of 1.457, an Abbe number (νd) ) Was made of 90.3 fluorophosphate optical glass (liquid phase temperature 680 ° C.), and a uniform and transparent solid columnar glass rod having no defects such as striae could be formed.

(Example 2)
Dry air maintained at 50 ° C. was sprayed on the surface of the molten glass stream that flowed out in the same manner as in Example 1 to promote cooling of the surface of the molten glass stream. Others were the same as in Example 1. The solid columnar glass rod obtained in this way was homogeneous and transparent, and when visually observed after facing polishing, no striae entering the inside from the surface were observed.

  Similarly, a fluorophosphate optical glass having a refractive index (nd) of 1.497 and an Abbe number (νd) of 81.6 and a refractive index (nd) of 1.457 and an Abbe number (νd) used in Example 1. ) Was made of 90.3 fluorophosphate optical glass, and a uniform and transparent solid columnar glass rod with no defects such as striae inside could be formed.

(Example 3)
Cover the area including the space between the lower end of the outflow pipe and the mold through-hole and the lower end of the pipe and the through-hole with a cover, flow dry air of 30 ° C. through the cover to lower the ambient temperature in the cover, The cooling of the flowing molten glass flow surface was promoted. Others were the same as in Example 1. The solid columnar glass rod obtained in this way was homogeneous and transparent, and when visually observed after facing polishing, no striae entering the inside from the surface were observed.

  Similarly, a fluorophosphate optical glass having a refractive index (nd) of 1.497 and an Abbe number (νd) of 81.6 used in Examples 1 and 2 and a refractive index (nd) of 1.457 and an Abbe number. It was made of a fluorophosphate optical glass having a (νd) of 90.3, and a homogeneous and transparent solid columnar glass rod having no defects such as striae could be formed.

Example 4
The mold of Example 1 has an opening diameter at the entrance of the through-hole of 10 mm, which is smaller than the inner diameter of the through-hole, and the cross-section of the through-hole along the central axis expands into a taper shape, and the penetration of Example 1 After reaching the inner diameter of the hole, replace it with one that is almost constant, and form a cylindrical glass rod so that the molten glass liquid level that is poured is in contact with the inner peripheral surface of the through hole formed in the tapered shape did. Since the surface of the molten glass poured into the through hole is deprived of heat by the tapered inner peripheral surface, the cooling is promoted and the molten glass surface descends along the inner peripheral surface of the through hole. Others were the same as in Example 1. The solid columnar glass rod obtained in this way was homogeneous and transparent, and when visually observed after facing polishing, no striae entering the inside from the surface were observed.
In addition, it was also possible to produce a high-quality glass molded body by combining Example 1 and Example 4, Example 2 and Example 4, Example 3 and Example 4.
Similarly, a fluorophosphate optical glass having a refractive index (nd) of 1.497 and an Abbe number (νd) of 81.6 or a fluorin having a refractive index (nd) of 1.457 and an Abbe number (νd) of 90.3. A homogeneous and transparent solid columnar glass rod made of acid optical glass with no defects such as striae inside was able to be formed.

(Example 5)
A glass rod made of B ₂ O ₃ and La ₂ O ₃ -containing optical glass molded in Examples 1, 2, 3, and 4 was cut in a direction perpendicular to the central axis to form a cylindrical block having a thickness of 10 mm. Further, the cylindrical block was ground or polished to produce an axisymmetric shaped glass material for press molding. No defects such as striae were observed in the press-molding glass material thus produced.
Further, the obtained cylindrical block can be ground and polished without press molding to produce an optical element such as a lens. In the optical element thus obtained, no defects such as striae were observed.

  Furthermore, optical elements such as press-molding glass materials and lenses using the glass rods made of the two types of fluorophosphate optical glasses molded in Examples 1, 2, 3, and 4, in which defects such as striae are not recognized. Could also be made.

Incidentally, divided in a direction perpendicular to the central axis of the glass rod made of molded B ₂ O ₃ and content _of La ₂ O ₃ optical glass or two fluorophosphate optical glass in Example 1, 2, 3, 4 The obtained cylindrical block can be used as it is or by grinding a divided cross section to obtain a glass material for press molding or a glass material for precision press molding. In that case, it is desirable to form the glass material by pressing the opposing cross sections of the glass material with a press mold. In press molding or precision press molding, the molding surface of the press mold is transferred to glass to form an optical functional surface such as a lens surface, so that the cross section of the glass material becomes the optical functional surface of the optical element. And since the side surface of the glass material is the outside of the optical function surface of the optical element (the part surrounding the optical function surface), the striae is not possible with the glass material of this embodiment in which the striae are localized near the side surface of the glass material. A high-quality optical element can be produced without entering the optical functional surface or inside of the optical element.

(Example 6)
The glass material for press molding having a smooth surface produced in Example 5 is heated, softened, precision press-molded using a press mold in a mixed gas atmosphere in which hydrogen is mixed with nitrogen, and annealed to obtain an aspheric lens. Got. The obtained lens was good without defects such as striae. In this example, an aspherical lens was prepared using the B ₂ O ₃ and La ₂ O ₃ -containing optical glass and the two types of fluorophosphate optical glass.

(Example 7)
The glass material for press molding produced in Example 5 was heated and softened, press-molded using a press mold in the atmosphere, and annealed to obtain a spherical lens. The lens produced in Example 6 was good without defects such as striae. In this example, a spherical lens was produced using the B ₂ O ₃ and La ₂ O ₃ -containing optical glass and the two types of fluorophosphate optical glass.

(Example 8)
The mold used in Example 1 was replaced with a mold whose vertical cross section with respect to the central axis of the through-hole was rectangular (vertical 10 mm, horizontal 100 mm), and the angle θ between the through-hole central axis and the horizontal plane was set to 90 °, and the high position A carbon mold was placed so that the opening on the side (through hole entrance) was directly under the outflow pipe made of platinum alloy. In this example, the temperature (1280 ° C.) of the molten glass in the platinum alloy melting vessel is controlled to be constant as in Example 1, and the temperature at the lower end of the outflow pipe connected to the melting vessel (1250 ° C.) is also set. Control was made to be constant. In this way, the temperature of the molten glass flow surface flowing out of the pipe was controlled to be lower than the temperature at the center. As in the case of Example 1, the square columnar glass molded body was pulled out using its own weight. As in Example 1, the drawing speed was such that the lower end of the molded body was supported by a support base, and the descending speed of the support base (corresponding to the drawing speed of the glass molded body) was constant at 3.8 cm / min. The control of the molten glass liquid level in the mold and the control of the drawing speed of the glass molded body were performed in the same manner as in Example 1.

Thus, the same prismatic glass rod made of optical glass having the same refractive index (nd) of 1.883 and Abbe number (νd) of 40.8 containing B ₂ O ₃ and La ₂ O ₃ as in Example 1. Was made. A portion of 0.3 mm or more from the surface of the obtained solid columnar glass rod was homogeneous and transparent, and no defects such as striae were observed.

  Similarly, a fluorophosphate optical glass having a refractive index (nd) of 1.497 and an Abbe number (νd) of 81.6 or a fluorin having a refractive index (nd) of 1.457 and an Abbe number (νd) of 90.3. It was made of acid optical glass, and it was possible to form a homogeneous and transparent square columnar glass rod with no defects such as striae inside.

Example 9
Dry air maintained at 30 ° C. was sprayed onto the surface of the molten glass stream that flowed out in the same manner as in Example 2 to promote cooling of the surface of the molten glass stream. Others were the same as in Example 8. The portion of 0.3 mm or more from the surface of the solid columnar glass rod thus obtained was homogeneous and transparent, and no defects such as striae were observed. Incidentally, the glass rod made of the B ₂ O ₃ and content _of La ₂ O ₃ optical glass, to prepare three types although each composed of the two kinds of fluorophosphate optical glass.

(Example 10)
Cover the area including the space between the lower end of the outflow pipe and the mold through-hole and the lower end of the pipe and the through-hole with a cover, and lower the atmospheric temperature in the cover by flowing dry air of 30 ° C. through the cover, The cooling of the flowing molten glass flow surface was promoted. Others were the same as in Example 8. The portion of 0.3 mm or more from the surface of the solid columnar glass rod thus obtained was homogeneous and transparent, and no defects such as striae were observed.
Incidentally, the glass rod made of the B ₂ O ₃ and content _of La ₂ O ₃ optical glass, to prepare three types although each composed of the two kinds of fluorophosphate optical glass.

(Example 11)
In the mold of Example 8, the inner diameter in one direction of the through hole entrance is 10 mm, the inner diameter in the direction perpendicular to the direction is 10 mm, which is smaller than the inner diameter of the through hole, and the cross section of the through hole along the central axis goes inside. In accordance with the above, it is changed to a taper shape and replaced with a substantially constant one after reaching the inner diameter of the through hole of Example 1, and the poured molten glass liquid level comes into contact with the inner peripheral surface of the through hole formed in the taper shape. A cylindrical glass rod was formed so as to be positioned. Since the surface of the molten glass poured into the through hole is deprived of heat by the tapered inner peripheral surface, the cooling is promoted and the molten glass surface descends along the inner peripheral surface of the through hole. Others were the same as in Example 8. The portion of 0.3 mm or more from the surface of the solid columnar glass rod thus obtained was homogeneous and transparent, and no defects such as striae were observed.
Incidentally, the glass rod made of the B ₂ O ₃ and content _of La ₂ O ₃ optical glass, to prepare three types although each composed of the two kinds of fluorophosphate optical glass.
In addition, a high quality glass molded object can also be manufactured combining the said Example 8 and Example 11, Example 9 and Example 11, Example 10 and Example 11. FIG.

(Example 12)
The glass rods molded in Examples 8, 9, 10, and 11 were cut in a direction perpendicular to the central axis to form a square prism block having a thickness of 100 mm. Furthermore, the square column block was ground or polished to produce an axially symmetric glass material for press molding. No defects such as striae were observed in the press-molding glass material thus produced.
Further, an optical element such as a lens can be produced by grinding and polishing the obtained rectangular column block without press molding. In the optical element thus obtained, no defects such as striae were observed.

(Example 13)
The glass material for press molding having a smooth surface produced in Example 12 is heated, softened, precision press-molded using a press mold in a mixed gas atmosphere in which hydrogen is mixed with nitrogen, and annealed to obtain an aspheric lens. Got. The obtained lens was good without defects such as striae.

(Example 14)
The glass material for press molding produced in Example 12 was heated and softened, and press-molded using a press mold in the atmosphere, and annealed to obtain a spherical lens. The lens produced in Example 12 was good without defects such as striae.

(Example 15)
The molten glass from which the copper-containing fluorophosphate glass was obtained was sufficiently clarified, homogenized and accumulated in a platinum alloy melting vessel, and the temperature of the molten glass in the vessel was controlled to 700 ° C. A carbon which is connected to the vessel and continuously flows down at a constant outflow rate (54.5 ml / min) from an outflow pipe provided with a molten glass outlet at the lower end, and is disposed at the position shown in FIG. Poured into the center of the entrance of the through-hole provided straight in the mold made of metal. The temperature at the lower end of the outflow pipe was controlled at 585 ° C., and the temperature difference between the glass temperature in the melting vessel and the lower end of the outflow pipe was set at 115 ° C. When the molten glass in the container passes through the pipe in such a state, the surface temperature of the molten glass flowing out of the pipe can be made lower than the center temperature. Here, the inner diameter of the mold through-hole was φ20 mm, and the angle θ formed by the central axis of the through-hole and the horizontal plane was 90 °. The length of the mold through-hole was set to 100 mm, and a band heater (not shown) was wound around the mold and heated so that good molding was possible. The glass molded body is pulled out from the outlet of the through-hole using the weight of the glass, and the lower end of the glass molded body is supported by a support base so that the pulling speed is constant. Is equivalent to 17.3 cm / min. In addition, you may control the descent | fall speed of a support stand so that the height (liquid level) of the molten glass liquid level in a casting_mold | template through-hole may become fixed. In such control, the liquid level of the molten glass is monitored using a liquid level gauge such as a laser level gauge, and the descending speed of the support base is increased or decreased based on the monitor signal output from the liquid level gauge. Can be done. For example, when the liquid level is higher than a preset reference liquid level, the descending speed of the support base is increased. Conversely, when the liquid level is lower than the reference liquid level, the descending speed of the support base is decreased. By such control, the liquid level can be controlled to be kept constant.
In this way, a glass rod (cylindrical glass) having a diameter of 20 mm was drawn vertically downward from the mold through-hole exit at a constant speed. When the length of the glass rod drawn out from the mold reached 500 mm, the glass rod was cut from the direction perpendicular to the drawing direction (horizontal direction) and annealed to remove strain.
In this embodiment, since the surface temperature of the molten glass flow poured into the mold through hole entrance is controlled to be lower than the temperature of the central portion, the molten glass flow surface portion extends along the inner peripheral surface of the mold through hole. I was able to create a flowing state.
In this embodiment, the cooling of the molten glass flow surface may be promoted as in Examples 2, 3, and 4.

  The glass rod made of the columnar copper-containing fluorophosphate glass thus obtained was sliced in a direction perpendicular to the central axis to produce a disk-shaped glass. Next, the surface formed by slicing was ground and polished to obtain a glass substrate having a near infrared absorption function. Since the glass substrate produced in this way is made of optically homogeneous glass, it is suitable as a color correction filter for a semiconductor imaging device such as a CCD or CMOS sensor. In addition, you may provide an optical multilayer film on the surface of a glass substrate as needed.

  According to the present invention, a glass molded body having no striae or very few can be produced with high productivity. The manufacturing method of the present invention is to manufacture and store a glass molded body made of various optical glasses, and make a glass material for press molding by machining such as cutting into a predetermined dimension according to demand, or the glass By pressing the material and manufacturing the optical element, it is possible to respond flexibly and quickly to demand.

A specific example of a method for promoting cooling of the molten glass flow surface will be described. An example of the manufacturing method of the glass forming body of this invention is shown. It is explanatory drawing of the length of a through-hole.

Claims (16)

In a method for producing a glass molded body, using a mold having a through hole, continuously flowing a molten glass flow into the inlet of the through hole, and continuously drawing out from the outlet of the through hole to form a solid glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, wherein a surface temperature of a molten glass flow poured into the mold is set lower than a temperature at a central portion. Using a mold having a through-hole, the molten glass accumulated in the container flows out from the lower end of the pipe connected to the container and continuously flows into the inlet of the through-hole, and continuously from the outlet of the through-hole. In the method for producing a glass molded body that is drawn out and formed into a solid glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
While making the temperature of the molten glass in the said container higher than the temperature of the lower end of a pipe, the temperature difference of the molten glass in the said container and the lower end of a pipe is made into the range of 20-120 degreeC, It is characterized by the above-mentioned. A method for producing a glass molded body. In a method for producing a glass molded body, using a mold having a through hole, continuously flowing a molten glass flow into the inlet of the through hole, and continuously drawing out from the outlet of the through hole to form a solid glass,
The mold is arranged so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, comprising pouring into the mold while promoting cooling of the surface of the molten glass flow. In a method for producing a glass molded body, using a mold having a through hole, continuously flowing a molten glass flow into the inlet of the through hole, and continuously drawing out from the outlet of the through hole to form a solid glass,
Place the mold so that the entrance of the through hole is higher than the exit,
A method for producing a glass molded body, comprising bringing molten glass poured into the through hole into contact with an inner peripheral surface of the through hole to promote cooling of the surface of the molten glass. The method for producing a glass molded body according to any one of claims 1 to 4, wherein a viscosity of the molten glass flow is less than 10 ² dPa · s. The method for producing a glass molded body according to any one of claims 1 to 5, wherein a viscosity of the molten glass flow is 0.5 dPa · s or more. The molten glass poured into the through-hole is brought into contact with the inner peripheral surface of the through-hole to form the outer peripheral surface of the glass molded body. Method. The method for producing a glass molded body according to claim 7, wherein the glass molded body is used by removing the outer peripheral surface. The said through-hole is a manufacturing method of the glass molded object of any one of Claims 1-8 in which the said entrance and exit are connecting linearly. The manufacturing method of the glass molded object of Claim 9 which arrange | positions the said casting_mold | template so that the center axis | shaft of the said through-hole may be in the state where it was vertical or inclined. The manufacturing method of the glass molded object of any one of Claims 1-10 which shape | mold a rod-shaped or flat glass. The manufacturing method of the glass raw material for press molding including the process of dividing | segmenting the glass forming body manufactured by the method of any one of Claims 1-11. In the method of manufacturing an optical element having a step of heating and pressing a glass material,
A method for producing an optical element, comprising using a glass material for press molding produced by the method according to claim 12. The method for manufacturing an optical element according to claim 13, wherein a press-molded product produced by the press molding is ground and / or polished. The manufacturing method of the optical element which divides | segments the glass molded object manufactured by the method of any one of Claims 1-11, produces a glass block, processes the said glass block, and produces an optical element. The manufacturing method of the glass substrate characterized by including the process of slicing the glass forming body manufactured by the method of any one of Claims 1-11, and making it into plate glass.

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