JP3826060B2 - Glass body forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a molten glass flow flowing out from a molten glass outlet is received on a receiving mold installed at a position close to the molten glass outlet, and after obtaining a desired weight of molten glass, The present invention relates to a method for forming a glass body by cutting to obtain a glass body. In particular, the present invention relates to a method for molding a glass body used as a molding material for a molding optical element.
[0002]
[Prior art]
As a method for obtaining a glass body, which is a material for manufacturing a glass optical element, from a molten glass, a method for obtaining a desired amount of a glass body by cutting a relatively high viscosity (low temperature) molten glass stream with a shear (scissors) has long been known. It has been. In this method, the viscosity of the glass is about 10 ⁵ dPa · s and the glass temperature is about 700 ° C. Also, when this glass body is press-molded to obtain a molded glass body, when molding is performed at a mold temperature of about 450 ° C., the molding surface of the obtained molded glass body is As a result, a relatively smooth molding surface with small undulation was obtained. However, when the glass is cut with a shear, fine bubbles called shear marks are generated at the cutting position, and it has been necessary to remove the portion.
[0003]
On the other hand, in recent years, a technique for producing a molding material for obtaining a molded glass element by cutting a molten glass flow without generating the above-mentioned shear mark has been developed. That is, it is a technique for cutting molten glass by a flow caused by the surface tension of the molten glass in a state where the viscosity of the molten glass at the time of cutting is lower (high temperature). Specifically, a constriction is formed in the molten glass flow, the constriction is developed by surface tension, and the glass flow is naturally cut. As a known technique relating to such natural cutting of a glass flow, there is a technique disclosed in Japanese Patent Publication No. 51-24525.
[0004]
On the other hand, as a known technique for obtaining a large glass body, one disclosed in Japanese Patent Publication No. 57-57415 is known. Here, the outflow suppression member which suppresses the outflow of a molten glass is provided in the molten glass outflow port.
[0005]
[Problems to be solved by the invention]
However, the glass body obtained by natural cutting in this way generates large undulations on the contact surface with the mold. The cause of this undulation is that the glass temperature becomes high in the natural cutting state, the temperature difference from the mold increases, and a large temperature difference is formed in the glass at the contact surface with the mold. It is considered.
[0006]
Further, the conventional molding optical element is mainly an aspherical lens having a rotational axis symmetry shape, but recently, the development to a prismatic reflection optical element is also progressing. The shape of the molding material for molding an aspherical lens having an axisymmetric shape could be a spherical shape or a substantially spherical shape, but the shape of a molding material for a prismatic reflective optical element approximates that of a molding optical element. Need to be.
[0007]
Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a glass molded body that is a molding material for a deformed optical element such as a prism in a state where there is no large undulation on the surface. .
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, the glass body forming method according to the present invention is such that after the molten glass is supplied to the first mold, the second mold is covered with the first mold. A method of forming a glass body by sandwiching the molten glass between the first mold and the second mold, and approximates a space formed by a receiving surface that receives the molten glass of the first mold on an outer peripheral portion. A glass flow outlet in which a wall portion having the shape is arranged is brought close to the receiving surface of the first mold, and the molten glass flows down to the receiving surface; the glass outlet and the first mold A cutting step in which at least one of the first and second molds is moved away from each other and the molten glass is naturally cut, and the first mold is covered with the second mold, and the melt supplied to the first mold Glass is sandwiched between the first mold and the second mold. It is characterized by comprising a shaping step of shaping the scan body.
[0009]
Moreover, in the glass body forming method according to the present invention, in the flow-down step, the glass outlet is moved until the distance between the lower end of the wall portion and the receiving surface of the first mold becomes 3 mm or less. It is characterized by approaching the surface.
[0010]
The glass body forming method according to the present invention is characterized by further comprising a precision forming step of further precisely forming the glass body obtained in the forming step.
[0011]
In the glass body molding method according to the present invention, the glass body has a shape approximate to the precision molded body molded in the precision molding step.
[0012]
In the glass body molding method according to the present invention, the precision molded body is an optical element.
[0013]
In the glass body molding method according to the present invention, the precision molded body has three or more optical functional surfaces.
[0014]
In the glass body molding method according to the present invention, the optically functional surface of the precision molded body has a free-form surface.
[0015]
In the glass body forming method according to the present invention, the molten glass is supplied to the first mold, and then the second mold is covered with the first mold, and the molten glass is combined with the first mold and the first mold. A method of forming a glass body by sandwiching between two molds, having a shape approximating a space formed by a receiving surface that receives the molten glass of the first mold, and a function of suppressing outflow of the molten glass A flow-out step of bringing a glass outlet having the outflow restraining member disposed therein closer to the receiving surface of the first mold and causing the molten glass to flow down to the receiving surface; and at least the glass outlet and the first mold One of them is moved in a direction away from each other and the molten glass is naturally cut, and the molten glass supplied to the first mold is covered with the second mold on the first mold. Sandwiched between the first mold and the second mold It is characterized by comprising a shaping step of shaping the glass body Nde.
[0016]
Further, in the glass body forming method according to the present invention, in the flow-down step, the glass outflow port until the distance from the receiving surface of the first mold at the lower end of the outflow suppression member becomes 5 mm or less. It is characterized by approaching the receiving surface.
[0017]
The glass body forming method according to the present invention is characterized by further comprising a precision forming step of further precisely forming the glass body obtained in the forming step.
[0018]
In the glass body molding method according to the present invention, the glass body has a shape approximate to the precision molded body molded in the precision molding step.
[0019]
In the glass body molding method according to the present invention, the precision molded body is an optical element.
[0020]
In the glass body molding method according to the present invention, the precision molded body has three or more optical functional surfaces.
[0021]
In the glass body molding method according to the present invention, the optically functional surface of the precision molded body has a free-form surface.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
[0023]
(First embodiment)
The first embodiment is an embodiment in which an outflow suppression member that suppresses outflow of molten glass is not provided at the molten glass outflow port.
[0024]
FIG. 1 is a view for explaining the shape of a molten glass outlet in the first embodiment. In FIG. 1, (a) is a front view of the molten glass outlet, (b) is a side view, and (c) is a bottom view.
[0025]
In FIG. 1, 1 is a molten-glass outflow path, 2 is an outer peripheral board which comprises the outer peripheral part of a molten-glass outflow port. As shown in FIG.1 (c), the planar shape of the molten glass outflow port in this embodiment is a rectangle. As shown to Fig.1 (a), the height of the lower surface of the outer periphery board 2 is changing with the position of the left-right direction. Moreover, as shown in FIG.1 (b), a molten glass outflow part is a shape open | released below except the outer peripheral board 2 of the outer peripheral part.
[0026]
Moreover, FIG. 2 is a figure explaining the process of obtaining the shaping | molding glass body in 1st Embodiment. In FIG. 2, 3 is a receiving mold, 4 is a glass body, and 5 is an upper mold.
[0027]
As shown in FIG. 2, the shape of the receiving surface of the receiving mold 3 and the shape of the side surface of the outer peripheral plate of the molten glass outlet are approximate shapes.
[0028]
The height of the gap formed between the outer peripheral plate 2 and the receiving mold 3 is increased at the outer peripheral portion of the molten glass outlet when the receiving mold 3 is raised to the desired amount in order to receive the desired amount of the molten glass in the receiving mold 3. The lower surface shape of the outer peripheral plate 2 is designed so as to be within a desired range (specifically, 3 mm or less), and the highest rising position of the receiving die 3 is set.
[0029]
When molten glass flows out through the molten glass outflow path 1 and molten glass starts to accumulate on the receiving mold 3, the receiving mold 3 is lowered at a slow speed, and when the desired amount of molten glass is obtained, the receiving mold 3 is further lowered by a predetermined distance to generate a constriction in the molten glass flow, and the constriction is developed by the surface tension of the molten glass to naturally cut the molten glass.
[0030]
In this way, a molten glass body 4 is obtained on the receiving mold 3.
[0031]
The lower surface (contact surface with the receiving mold) of the glass body 4 thus obtained was smooth. According to this embodiment, even if the glass body was obtained from the molten glass under the condition that the molten glass can be naturally cut, no large undulation was generated on the contact surface with the mold.
[0032]
The following two actions can be considered in this embodiment.
[0033]
First, since the gap formed between the outlet and the receiving mold 3 is small, the heat from the hot outlet is transferred to the receiving mold 3 and the molten glass received by the receiving mold, and the temperature of the lower surface of the glass body Is kept at a relatively high temperature, and as a result, it is considered that large undulation did not occur at the contact surface with the mold. Further, since the gap formed between the outlet and the receiving mold 3 is small, the head pressure of the molten glass acts on the molten glass in that portion, and as a result, no large undulation is generated on the contact surface with the mold. It is also considered.
[0034]
The molten glass body 4 thus obtained in the receiving mold 3 is immediately molded with the upper mold 5 to obtain a molded glass body. Further, this molded glass body is press-molded with a precision mold to obtain a molded optical element. At this time, since the shapes of the molded glass body and the molded optical element are close to each other, the press amount is small and the heating time is short.
[0035]
In the embodiment described above, the receiving mold is lowered and the molten glass is naturally cut. However, the glass outlet side may be raised, or the glass outlet side may be raised at the same time. The mold may be lowered.
[0036]
(Second Embodiment)
The second embodiment is an embodiment in which an outflow suppression member that suppresses outflow of molten glass is provided at the molten glass outlet.
[0037]
FIG. 3 is a cross-sectional view for explaining the shape of the molten glass outlet in the second embodiment.
[0038]
In FIG. 3, 1 is a molten glass outflow path, and 6 is an outflow suppressing member provided at the molten glass outflow port for suppressing outflow of molten glass. The lower surface of the outflow suppression member 6 has a polyhedral shape.
[0039]
Moreover, FIG. 4 is a figure explaining the process of obtaining a molded glass body in 2nd Embodiment. In FIG. 4, 3 is a receiving mold, 4 is a glass body, 5 is an upper mold, and 7 is molten glass that has flowed out to the lower surface of the outflow suppressing member.
[0040]
As shown in FIG. 4, the shape of the receiving surface of the receiving mold 3 and the shape of the lower surface of the outflow suppressing member 6 at the molten glass outlet are approximate shapes.
[0041]
The height of the gap formed between the outlet and the receiving die on the lower surface of the outflow suppressing member 6 of the molten glass outlet when the receiving die 3 is raised to the desired amount in the receiving glass 3 However, the shape of the lower surface of the outflow suppression member 6 is designed so as to be within a desired range (specifically, 5 mm or less), and the highest rising position of the receiving die 3 is set.
[0042]
Subsequently, as in the first embodiment, the molten glass is naturally cut to obtain a molten glass body 4 on the receiving mold 3.
[0043]
The lower surface (contact surface with the receiving mold) of the glass body 4 thus obtained was smooth. According to this embodiment, even if the glass body was obtained from the molten glass under the condition that the molten glass can be naturally cut, no large undulation was generated on the contact surface with the mold.
[0044]
The operation in this embodiment is considered to be the same as in the first embodiment.
[0045]
The molten glass body 4 thus obtained in the receiving mold 3 is immediately molded with the upper mold 5 to obtain a molded glass body. Further, this molded glass body is press-molded with a precision mold to obtain a molded optical element. At this time, since the shapes of the molded glass body and the molded optical element are close to each other, the press amount is small and the heating time is short.
[0046]
【Example】
(Example 1 to Example 4)
In Examples 1 to 4, specific examples of the first embodiment will be described.
[0047]
In Examples 1 to 4, the finally obtained molded optical element is a reflective optical element having five reflective surfaces, an incident surface, and an output surface. The optical surface of the molded optical element has a free-form surface shape. This optical element has a length of 35 mm and an average thickness of 8 mm. As the glass material, phosphoric acid-based low softening glass was used. An alloy of gold and nickel was used as the material for the receiving mold 3 and the upper mold 5. On the receiving surface of the receiving mold 3, three optical surface equivalent surfaces are formed, and these optical surface equivalent surfaces are formed into free-form surfaces. Further, four optical surface equivalent surfaces are formed on the molding surface of the upper mold 5. The receiving mold 3 is always heated to 400 ° C., and the upper mold 5 is constantly heated to 350 ° C.
[0048]
The glass is melted at 1000 ° C. in a platinum crucible (not shown) and flows out through a platinum outflow pipe (not shown). The temperature of the outflow pipe is 1000 ° C., and 1000 ° C. molten glass flows out in the form of droplets from the molten glass outlet. The head height of the molten glass (the difference between the liquid surface height of the molten glass in the platinum crucible and the outlet height) is 500 mm.
[0049]
The receiving die 3 is connected to an NC (numerical control) driving device (not shown) and can move to a predetermined position at a predetermined speed.
[0050]
In Examples 1 to 4, the molten glass is formed between the outer peripheral plate 2 and the receiving mold 3 at the outer peripheral portion of the molten glass outlet when the receiving mold 3 is moved up to receive the molten glass. Four examples were examined in which the minimum clearance height was 3 mm (Example 1), 2 mm (Example 2), 1 mm (Example 3), and 0.5 mm (Example 4). Further, two comparative examples having a gap height of 4 mm (Comparative Example 1) and 5 mm (Comparative Example 2) were examined. The result is shown in FIG.
[0051]
10 g of molten glass was received in the receiving mold 3, and the molten glass flow was naturally cut to obtain a molten glass body 4, which was immediately press-molded with the upper mold 5 to obtain a molded glass body. FIG. 5 shows the amount of undulation (P-V value) on the lower surface of this molded glass body.
[0052]
The molded glass body thus obtained was press-molded with a precision mold (not shown) to obtain a molded optical element (not shown). The precision mold is manufactured by press molding using glass as a raw material, and a noble metal release film is formed on the molding surface of the glass precision mold. A molded glass body was sandwiched between the pair of upper and lower precision molds, heated to a molding temperature of 420 ° C., and press molded with a press force of 3000 N to obtain a molded optical element. At this time, since the shapes of the molded glass body and the molded optical element are approximate, the pressing amount may be 0.5 mm, and the heating time is sufficient for 2 minutes.
[0053]
FIG. 5 shows the results of the appearance evaluation of the molding surfaces of the molding optical elements in Examples 1 to 4 and Comparative Examples 1 and 2.
[0054]
As a result, when the minimum gap between the outlet and the receiving mold is 3 mm or less, the amount of undulation on the lower surface of the molded glass body is small, and the appearance of the molded surface of the molded optical element obtained by precision molding is good. I found out.
[0055]
A reflection layer of silver was provided on the reflection surface of the molded optical element thus obtained, and an antireflection film was provided on the incident / exit surface to obtain a reflection optical element.
[0056]
(Examples 5 to 8)
In Examples 5 to 8, specific examples of the second embodiment will be described.
[0057]
In Examples 5 to 8, the finally obtained molded optical element is a pentaprism. This optical element has a length of 35 mm and a height of 30 mm. As the glass material, SF optical glass was used. Brass was used as the material for the receiving mold 3 and the upper mold 5, and nickel plating and gold plating were applied thereon. The receiving mold 3 is always heated to 470 ° C., and the upper mold 5 is always heated to 400 ° C.
[0058]
The glass is melted at 1100 ° C. in a platinum crucible (not shown) and flows out through a platinum outlet pipe (not shown). The temperature of the outflow pipe (not shown) is 1100 ° C., and 1100 ° C. molten glass flows out in the form of droplets from the molten glass outlet. The head height of this molten glass (the difference between the liquid surface height of the molten glass in the platinum crucible and the outlet height) is 1000 mm.
[0059]
The receiving die 3 is connected to an NC (numerical control) driving device (not shown) and can move to a predetermined position at a predetermined speed.
[0060]
In Example 5 to Example 8, at the time when the receiving mold 3 is moved up to receive the molten glass by the receiving mold 3, the lower surface of the outflow suppressing member 6 and the lower surface of the outflow suppressing member 6 at the molten glass outlet Four examples in which the minimum gap height formed between the receiving molds 3 was 5 mm (Example 5), 4 mm (Example 6), 2 mm (Example 7), and 1 mm (Example 8) were examined. . Further, two comparative examples having a gap height of 6 mm (Comparative Example 3) and 7 mm (Comparative Example 4) were examined. The result is shown in FIG.
[0061]
50 g of molten glass was received in the receiving mold 3, and the molten glass flow was naturally cut to obtain a molten glass body 4, which was immediately press-molded with the upper mold 5 to obtain a molded glass body. FIG. 6 shows the amount of undulation (P-V value) on the lower surface of this molded glass body.
[0062]
The molded glass body thus obtained was press-molded with a precision mold (not shown) to obtain a molded optical element (not shown). The precision mold is made of a cemented carbide, and after the molding surface is polished, a carbon-based release film is formed. A molded glass body was sandwiched between the pair of upper and lower precision molds, heated to a molding temperature of 570 ° C., and press molded with a pressing force of 5000 N to obtain a molded optical element. At this time, since the shapes of the molded glass body and the molded optical element approximated each other, the press amount may be 1 mm, and the heating time is sufficient for 3 minutes.
[0063]
The results of the appearance evaluation of the molding surface of the molding optical element for Examples 5 to 8, Comparative Example 3, and Comparative Example 4 are shown in FIG.
[0064]
As a result, when the minimum gap between the outlet and the receiving mold is 5 mm or less, the amount of undulation on the lower surface of the molded glass body is small, and the appearance of the molded surface of the molded optical element obtained by precision molding is also good. I found out.
[0065]
A reflection layer of silver was provided on the reflection surface of the molded optical element thus obtained, and an antireflection film was provided on the incident / exit surface to obtain a reflection optical element.
[0066]
As described above, according to the first and second embodiments described above, a molding material for obtaining a deformed optical element such as a reflective optical element by molding can be manufactured at low cost. The manufacturing cost can be reduced.
[0067]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a glass molded body, which is a material for molding a deformed optical element such as a prism, without a large undulation on the surface.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a structure of a molten glass outlet in a first embodiment.
FIG. 2 is a diagram for explaining a manufacturing process of a glass molded body in the first embodiment.
FIG. 3 is a diagram for explaining a structure of a molten glass outlet in a second embodiment.
FIG. 4 is a diagram for explaining a manufacturing process of a glass molded body in the second embodiment.
5 is a view showing molding results of Examples 1 to 4 and Comparative Examples 1 and 2. FIG.
6 is a diagram showing the molding results of Examples 5 to 8, Comparative Example 3, and Comparative Example 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Molten glass outflow path 2 Outer peripheral board 3 Receiving type | mold 4 Glass body 5 Upper mold | type 6 Outflow suppression member 7 Molten glass

Claims (14)

After the molten glass is supplied to the first mold, a glass body is formed by covering the first mold with a second mold and sandwiching the molten glass between the first mold and the second mold. A method,
A glass outlet having a wall portion having a shape approximating a space formed by a receiving surface that receives the molten glass of the first mold on the outer peripheral portion is brought close to the receiving surface of the first mold, and the molten glass is A flow-down process of flowing down to the receiving surface;
A cutting step of naturally cutting the molten glass by moving at least one of the glass outlet and the first mold in a direction away from each other;
Forming the glass body by covering the first mold with the second mold and sandwiching the molten glass supplied to the first mold between the first mold and the second mold; A method for forming a glass body.   In the flow-down step, the glass outlet is made to approach the receiving surface until the distance from the receiving surface of the first mold at the lower end of the wall portion is 3 mm or less. The molding method of the glass body of description.   The glass body forming method according to claim 1, further comprising a precision forming step of further precisely forming the glass body obtained in the forming step.   The method for molding a glass body according to claim 3, wherein the glass body has a shape approximate to the precision molded body molded in the precision molding step.   The method for molding a glass body according to claim 3, wherein the precision molded body is an optical element.   6. The method for molding a glass body according to claim 5, wherein the precision molded body has three or more optical functional surfaces.   6. The glass body molding method according to claim 5, wherein the optically functional surface of the precision molded body has a free-form surface. After the molten glass is supplied to the first mold, a glass body is formed by covering the first mold with a second mold and sandwiching the molten glass between the first mold and the second mold. A method,
A glass outlet having a shape approximating a space formed by a receiving surface for receiving the molten glass of the first mold and having an outflow suppressing member having a function of suppressing the outflow of the molten glass is provided as the first mold. A flow-down process of bringing the molten glass down to the receiving surface;
A cutting step of naturally cutting the molten glass by moving at least one of the glass outlet and the first mold in a direction away from each other;
Forming the glass body by covering the first mold with the second mold and sandwiching the molten glass supplied to the first mold between the first mold and the second mold; A method for forming a glass body.   The said flow-down process makes the said glass outflow port approach the said receiving surface until the distance from the receiving surface of the said 1st type | mold of the lower end of the said outflow suppression member becomes 5 mm or less. A method for forming a glass body according to 1.   The glass body forming method according to claim 8, further comprising a precision forming step of further precisely forming the glass body obtained in the forming step.   The method for molding a glass body according to claim 10, wherein the glass body has a shape approximate to the precision molded body molded in the precision molding step.   The method for molding a glass body according to claim 10, wherein the precision molded body is an optical element.   The method for molding a glass body according to claim 12, wherein the precision molded body has three or more optical functional surfaces.   The method for molding a glass body according to claim 12, wherein the optically functional surface of the precision molded body has a free-form surface.

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