JPH10182171A - Formation of optical glass element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an optical glass element, enabling to product the optical glass element excellent in surface accuracy and not having air reservoirs and air bubbles on the surface by removing fine glass pieces from the surface of a glass gob having specific surface roughness and subsequently heating the glass gob in a support member until the surface portions of the glass gob reach a specific viscosity. SOLUTION: The surface roughness Rmax of a glass gob is controlled to 0.1-5μm. Fine cut or ground glass pieces on the surface of the glass gob are removed. The fine glass pieces are preferably removed by immersing the glass gob in a cleaning solution containing a synthetic detergent and subsequently subjecting the glass gob to a ultrasonic cleaning treatment. The cleaned glass gob is set to a concave support member provided with a non-spherical transfer surface having a desired surface accuracy and a desired curvature, inserted into an electric oven, heated with a heater up to a temperature at which the viscosity of the surface portions of the glass gob becomes 10<6> -10<3> poises, and subsequently maintained for a constant time. The whole body of the glass gob as well as its surface portions can be thereby thermally uniformly deformed to control the glass molded product to the desired surface accuracy and the desired shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an optical glass element such as an optical lens or prism having a spherical surface or an aspherical surface, a lens array, and more specifically, to an optical glass element having a mirror surface by heating a glass block. It relates to a method of forming.

[0002]

2. Description of the Related Art As a conventional method for forming an optical glass element having a spherical surface or an aspherical surface, a press molding method in which a glass mold having a mirror surface is press-molded is a typical method. In this press molding method, a glass lump is previously processed into a predetermined shape to form a preform having a certain degree of surface accuracy, and the preform is reheated and molded with a metal mold to give a desired surface accuracy. The "reheating method" is generally used, and mass production is possible even for glass lenses requiring high precision, such as optical lenses.

However, according to this reheating method, the surface of the preform is made almost mirror-finished, that is, the surface roughness is set to Rmax0.
It is necessary to finish the surface to an extent of not more than 02 μm to eliminate unevenness on the surface, and if the finish is insufficient, it was trapped between the uneven portion of the preform surface and the mold during press molding. The air causes air pockets or crater-shaped recesses on the surface of the optical glass element, and a desired mirror surface cannot be obtained.

When a preform is actually processed from a glass material, irregularities having a depth of about several microns with a pv value (peak to valley value) such as grinding streaks or grinding flaws are generated on the surface thereof. Finishing methods such as polishing after slicing from a glass rod are widely performed. In such a method, when the lens becomes large in diameter, the processing amount of the preform increases by that much, so the lens cost increases. If the required accuracy of the lens increases, the preform must also be processed with high precision in advance, and the yield will decrease.

Therefore, in Japanese Patent Application Laid-Open No. 7-329203, a glass material having an Rmax of about 0.04 μm is heated by heating (fire polishing) the glass material in a temperature range of 10 ¹⁰ to 10 ⁵ poise.
A method of processing down to μm has been proposed. However, in this method, the glass material is heated in a relatively low temperature range of 10 ¹⁰ to 10 ⁵ poise, and the softening deformation due to this heating extends only to the very surface of the glass material. The resulting Rmax
Even if a surface having a surface roughness of 0.1 μm or more is subjected to this heating, a desired surface accuracy cannot be obtained. Therefore, it is necessary to preliminarily process the glass material to a surface roughness Rmax of about 0.04 μm by polishing or the like, and as a result, there is a problem that the lens cost is increased.

On the other hand, in Japanese Patent Application Laid-Open No. Hei 8-169721, a cubic glass material is held by a holding member, heated to a predetermined temperature and softened, and the corners are rounded by surface tension, and the surface roughness is reduced. A method of reducing the height to Rmax 0.04 μm or less is disclosed. In this method, as is apparent from the fact that the SF14 glass material is heated to 800 to 850 ° C. in the embodiment, the glass surface becomes a mirror surface relatively easily because it is heated at a high temperature. Processing is unnecessary, but during this heat treatment, the viscosity near the center of the glass material is considered to be 10 ³ poise or less, so it is very difficult to control the glass material to a desired shape. .

[0007] Further, the glass material is used, for example, after being obtained by cutting or grinding from a glass rod, the fine glass fragments generated by these processes are usually completely removed by subsequent polishing. Are disclosed in Japanese Patent Application Laid-Open Nos. 7-329203 and 8-169.
In the method disclosed in Japanese Patent Application Laid-Open No. 721-721, the glass is subjected to a heat deformation treatment without polishing, so that the fine glass pieces bite into the unevenness of the glass processing surface or remain attached by electrostatic attraction, that is, the fine glass pieces and the glass Heat deformation processing will be performed with the cavity formed between the material and the surface,
The optical glass element in which the air in the cavity becomes fine bubbles and remains near the surface is manufactured. Furthermore, even if this optical glass element is molded as a preform, there is a problem that air remains on the molding surface or fine bubbles remain near the surface, and the appearance quality of the obtained optical glass element is significantly impaired.

[0008]

SUMMARY OF THE INVENTION According to the present invention, no air accumulation or bubbles are generated on the surface without a preliminary processing such as polishing of a glass material, and the shape of the glass material can be easily controlled. It is an object of the present invention to provide an efficient and economical method for manufacturing an optical glass element having excellent surface accuracy.

[0009]

According to the present invention, a surface roughness Rm is provided.
After removing small glass fragments on the surface from a glass block having an ax of 0.1 to 5 μm, the glass block is placed in a supporting member until the viscosity near the surface of the glass block becomes 10 ⁶ to 10 ³ poise. And a method for forming an optical glass element, characterized by heating the substrate.

[0010] The present invention is characterized in that prior to the heat deformation treatment, the minute glass pieces on the surface of the glass block are removed, whereby a cavity is formed between the minute glass pieces and the surface of the glass material. Since it is avoided, the formation of air pockets and bubbles on the surface of the optical glass element and in the vicinity thereof can be prevented even by the subsequent heat deformation treatment and press molding.

Further, another aspect of the present invention is characterized in that the viscosity near the surface of the glass lump is set to 10 ⁶ to 10 ³ poise in the heat deformation treatment, whereby the softening deformation of the glass lump is mainly exerted. In addition, it is possible to easily make the glass surface mirror-like, to eliminate the need for preliminary processing prior to the heat deformation treatment, and to prevent the shape from being uncontrollable due to excessive softening.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the constitution of the present invention, the method for forming an optical glass element of the present invention comprises at least a surface roughness Rma.
supporting the glass gobs of x is 0.1 to 5 [mu] m, up to the step of removing the fine pieces of glass on its surface, and the glass gob, the viscosity near the surface of the glass gob is 10 ⁶ to 10 ³ poise member And heating the inside. For example, it is manufactured by a series of manufacturing steps as shown in FIG. Hereinafter, FIG.
This will be described with reference to FIG.

The glass block 1 used in the present invention has a surface roughness Rmax of 0.1 to 5 μm, preferably 0.1 to 3 μm.
μm, which does not mean that glass blocks less than Rmax less than 0.1 μm cannot be used, meaning that finishing to less than 0.1 μm is not required. If Rmax is less than 0.1 μm, the processing takes too much time, resulting in poor efficiency and economy. On the other hand, Rmax is 5 μm
Is exceeded, the irregularities on the surface of the glass ingot are not completely eliminated by the subsequent heat deformation treatment. To eliminate this, it is necessary to further raise the surface temperature of the glass ingot, which makes it difficult to control the glass shape.

The glass block may be made of any glass material having the above-mentioned surface roughness.
It is obtained by cutting and grinding a glass rod made of 70 glass, SF14 glass, and heat resistant glass to a desired thickness. Usually, the surface roughness Rm of the cut surface and other surfaces in this case
ax is 3 μm or less.

In the present invention, first, fine glass fragments on the surface of the glass lump generated by cutting and grinding the glass lump are removed. The removal method is not particularly limited as long as it can completely remove the small glass pieces remaining on the surface of the glass lump without substantially altering the surface of the glass lump, and for example, a method using a cleaning solution containing a synthetic detergent and the like can be used. No. Specifically, the cleaning liquid is preferably a cleaning liquid generally used for cleaning a completed optical element with an ultrasonic cleaning machine, for example, a sun wash LPW
-1 (manufactured by Lion Corporation) and Fine Cleaner A (manufactured by Furuuchi Chemical Co., Ltd.). These cleaning solutions remove dirt such as machine oil and dust by the surface active effect, and also slightly dissolve the surface where the glass surface comes into contact with the small glass piece, and combine with the cavitation effect by ultrasonic waves to remove the small glass piece. It is considered that this promotes separation from the surface.

On the other hand, with a diluting solution such as hydrofluoric acid, hydrochloric acid, acetic acid or the like used for chemical etching or an etching solution such as an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, fine glass fragments are removed more effectively. However, it is preferable because the erosion of the glass becomes remarkable, and the liquid locally penetrates into the inside of the glass through grooves such as cutter marks and grinding scratches remaining on the cutting surface, so that the internal quality of the glass becomes non-uniform, which is preferable. Absent.

In the step of removing the minute glass pieces, the glass block to which the glass pieces are adhered is immersed in a cleaning solution for 20 to 1 minute.
Preferably, ultrasonic cleaning is performed at 00 Hz for 5 to 20 minutes. By rubbing with a physical means such as a brush in the cleaning liquid, fine glass fragments can be removed, but this is not preferable because it adversely affects the surface of the glass block.

Before the glass block is washed with the washing liquid, it is preferable to wash the glass lump with tap water for the purpose of roughly removing grinding debris. After the washing with the washing liquid, washing with pure water, washing with tap water, and so on are performed. Preferably, it is subjected to drying. If a foreign substance such as a cleaning liquid adheres to the surface of the glass lump, the surface of the glass lump to be used in the next step is undesirably stained or burned on the surface of the glass lump in the next step of the heat deformation treatment and cannot be obtained. This is because it is necessary to keep it clean.

The glass block from which the fine glass pieces have been removed in this manner is subjected to a heat deformation treatment. Specifically, as shown in FIG. 1, the glass block 1 is placed on a concave support member 4 having an aspherical transfer surface 3 having a desired surface accuracy and a desired curvature, and these are inserted into an electric furnace 5. The viscosity around the surface of the glass block (10 to 20% depth from the surface) is 10 ⁶ to 10 ³
Poise, preferably heated by a heater to a temperature of 10 ⁵ to 10 ⁴ poise for 5 to 30 minutes, preferably 5 to
Hold for 20 minutes.

Since the viscosity in the vicinity of the surface is set within the above specified range, it is possible to provide a desired surface accuracy by applying thermal deformation to the entire glass lump without remaining on the surface of the glass lump. It is also possible to control the shape. If it is lower than 10 ³ poise, the whole glass block is fluidized, and it is difficult to control its shape. 1 on the other hand
0 ⁶ higher thermal deformation can not be obtained the desired surface accuracy for that does not lead to reforming a small portion to remain a surface shape of the surface. The heating temperature differs depending on the glass material, for example, about 890 to 1030 ° C. for glass B270,
In the case of glass SF14, about 750-840 ° C. is appropriate.

In the present specification, the support member is capable of holding a glass lump without deterioration or deformation even at the heating temperature in the heat deformation treatment of the present invention, and the holding surface has a desired surface accuracy. That is, the surface roughness Rma
A member which is precisely processed to x 0.02 to 0.1 μm, preferably 0.03 to 0.1 μm is intended, and includes a lower mold in press molding. In FIG. 1, a concave aspherical support member is used. However, in order to obtain a desired preform shape, for example, a concavo-convex shape, a biconvex shape, a biconcave shape, a plano-convex shape, etc. May be used. Further, it may be spherical or aspherical.

When the preform 6 is taken out of the support member 4 after the heating, the shape of the transfer surface 3 is accurately transferred to the contact surface 7 which has been in contact with the support member 4 on the preform 6. Thus, the surface roughness Rmax ensures the surface roughness of the transfer surface 3. The contact surface 7 is the transfer surface 3
Of curvature. On the other hand, a gentle free surface 8 is formed on the opposite surface by thermal deformation, and the surface roughness Rma
x is 0.01-0.05 μm, preferably 0.02-0.0 μm.
3 μm is secured. The curvature of the free surface 8 is
In other words, the curvature of the free surface can be adjusted by adjusting the curvature.

Further, the above-mentioned air pockets and bubbles hardly exist on both sides of the obtained preform. For this reason, if the shape precision of the desired optical glass element is low, the obtained preform can be used as it is as the optical glass element. Therefore, in the present invention, it is possible to efficiently and economically obtain an optical glass element having excellent appearance quality and surface accuracy without press molding without preliminary processing such as polishing.

Next, the preform is further subjected to a press molding step in order to precisely control the shape. When the supporting member in the heating deformation step is a lower mold in press molding, it is apparent that the preform can be subjected to the press molding step only by transporting the preform placed on the lower mold after the heating deformation processing. If the member is not a lower mold, the preform is transferred while being placed on the support member after the heat deformation treatment and then transferred between the dies, or the preform on the support member is transferred to the lower mold first. It needs to be mounted and transported and subjected to a press forming process. In any case, it is necessary to convey the obtained preform to a press molding machine. However, since the necessity of the transfer step depends on whether or not the support member is a lower mold in the press molding, a press member is used as the support member. It is preferable to use a lower mold. This is because a series of manufacturing steps of the optical glass element can be simplified, and the optical glass element can be obtained more efficiently.

The press molding is performed by a conventionally used press molding machine. For example, before the obtained preform is almost cooled, the preform is transferred between a mold having a desired surface accuracy as described above. Install and apply pressure to the mold to transfer the surface accuracy and shape of the mold surface.

More specifically, when press-molding the concavo-convex preform 6 shown in FIG. 1, an optical glass element can be produced by a reheat press method using, for example, a press-forming apparatus shown in FIG. An upper mold 14 (material: SiC) having a mold surface precision mirror-finished to a convex spherical surface and a holding mold 16A for holding the same, and a lower mold 15 (material: SiC) having a mold surface precisely machined to a concave aspheric surface. SiC) and a holding mold 16B (material: carbon) for holding the same. The holding die 16A moves downward integrally with the upper die 14 by the push rod 17, and engages with the holding die 16B integrated with the lower die 15. The above mold structure is a transparent quartz tube 18
Heated by a heating light source 19 installed on the outer peripheral portion of
The temperature is measured and controlled by the thermocouple 20 buried in the holding mold 16B.

The above-described preform 6 is placed in the upper and lower molds (14,
15), the upper and lower molds (14, 15) are heated to a temperature 50 to 100 ° C. higher than the transition point of the preform by a heating light source 19 under a nitrogen atmosphere, and the push rod 17 is Then, the upper mold 14 and the holding mold 16A for holding the upper mold 14 are pressed and molded by applying a load (pressure: 20 kg).
/ cm ² , pressurization time: 30 seconds). Next, the pressure of the push rod 17 is removed, and the press-molded product, that is, the optical glass element is allowed to cool while being surrounded in the mold (14, 15, 16A, 16B), and then the optical glass element is taken out. The surface of the mold is accurately transferred to the surface of the optical glass element, and the accuracy of the shape is further improved as compared with the preform.

The surface accuracy of the mold is about the same as the surface accuracy of the transfer surface of the support member (excluding the case of a mold).
Or higher. This is because, as a result, the surface accuracy of the mold is given to the surface of the optical glass element, so that even if the surface accuracy of the preform is high, it is meaningless if the surface accuracy of the mold is low. That is, 0.01 to 0.05 μ in terms of surface roughness
m, 0.01 to 0.03 μm is preferred. Regarding the shape of the mold, it is preferable that the radius of curvature of the mold is larger than the radius of curvature of the support member in order to prevent air from being trapped during molding. The heating temperature in press molding is not particularly limited as long as the preform surface has a desired mirror surface due to the previous heating deformation treatment, so long as the preform shape can be finely adjusted. Specifically, it is desirable to set the viscosity near the surface of the preform to 10 ⁶ to 10 ⁹ poise, preferably 10 ⁷ to 10 ⁸ poise.

In the press molding as described above, since fine glass fragments do not adhere to the surface of the preform as in the prior art, it is possible to prevent air accumulation or bubbles from being generated on the surface of the optical glass element after molding. Strict shape control is possible. Further, it is not necessary to go through a preparatory processing step such as polishing which requires time and cost, and as a result, it is efficient and economical. The present invention is described in more detail by the following examples.

[0030]

EXAMPLE 1 Example 1 will be described with reference to FIG. The rod material of the white plate glass B270 was cut into a substantially disk shape to form a glass lump 1 having a diameter of 40 mm and a thickness of 10 mm. When the surface roughness of the cut surface of the glass lump and other surfaces was measured with a commercially available surface roughness meter (Surfcom; manufactured by Tokyo Seimitsu Co., Ltd.), the cut surface was Rmax.
3 μm, and the other surface was Rmax 1 μm. In addition, when the cut surface was observed at a magnification of 1000 with a scanning electron microscope, as shown in FIG. 4, fine glass fragments generated when the glass lump was cut remained, and cutter marks and scratches were continuous. It was observed as unevenness.

This glass lump 1 was supplied to a washing / drying apparatus 2. This device 2 is used for cleaning with tap water-cleaning with detergent-
This is a device that continuously performs washing with pure water, washing with tap water, and drying. Sunwash LPW-1 is used as a detergent.
(Manufactured by Lion Corporation). In addition, in this apparatus, the glass lump is immersed in each tank as it is, and then lifted to remove the small glass fragments remaining on the surface.
It was immersed in a detergent at 0 ° C. for 5 minutes, and dried at 80 ° C. for 10 minutes. When the surface roughness of the cut surface and other surfaces of the glass block coming out of this apparatus was measured, the cut surface was Rm
ax 2.9 μm, and the other surface was Rmax 1 μm.
Further, when the cut surface was observed at a magnification of 1000 with a scanning electron microscope, as shown in FIG. 5, the surface roughness and surface condition showed almost no change, and continuous irregularities were observed as before the treatment. However, the fine glass fragments were almost completely removed.

Next, the glass block 1 from which the fine glass pieces have been removed is placed on a support member 4 as shown in FIG.
It was inserted into an electric furnace 5 and subjected to a heating deformation treatment. Support member 4
Is the surface roughness Rmax 0.03 μm, the approximate radius of curvature R = 45
It is an aspherical concave type provided with a transfer surface 3 having a depth of 11 mm at a central portion of 11 mm. In the electric furnace 5, the glass B270, which is the material of the glass lump, was maintained at about 1000 ° C. (accurately, 1000 ° C.) at which the polish becomes 10 ⁴ poise for 7 minutes.

After the heating is completed, the preform 6 is taken out from the support member 4 and left to cool, and the surface roughness of the contact surface 7 which has been in contact with the support member 4 is measured by a stylus type surface roughness meter (Surfcom;
Rmax about 0.0 measured by Tokyo Seimitsu Co., Ltd.)
3, which indicates that the shape of the transfer surface 3 having a curvature radius R = 45 mm has a convex aspherical surface to which the transfer is accurately performed. On the other side, the radius of curvature R =
A gentle free surface 8 of 60 mm was formed, and the surface roughness Rmax was about 0.03 μm. Further, when the contact surface 7 and the free surface 8 were observed with a differential interference microscope at a magnification of 50 times, as shown in FIG. 6, almost no irregularities such as cutting streaks and processing scratches were observed, and air accumulation and bubbles were also observed. No observations were made. From the above, the effective diameter is 40 mm, the core thickness is 15 mm, and one surface has an approximate radius of curvature of R = 45 mm.
An aspherical preform was obtained, and the other surface was a spherical surface having an approximate radius of curvature of R = 60 mm. This preform can be sufficiently used as an optical glass element whose shape accuracy may be low.

Example 2 A disk-shaped glass lump having a diameter of 35 mm and a thickness of 15 mm was used, and a surface roughness Rmax of 0.0 was used as a supporting member.
A preform was obtained in the same manner as in Example 1, except that a flat mold having a transfer surface of 3 μm was used. Further, a support member that cannot be used as a lower mold in press molding was used. This preform has an effective diameter of 30 mm and a core thickness of 13 mm, and one surface has an approximate radius of curvature of R = 50.
The aspheric surface of mm and the other surface were a plano-convex preform which was flat.

The obtained preform was conveyed and subjected to press molding. Specifically, immediately after the heat deformation treatment, FIG.
As shown in (1), the preform 11 is conveyed and transferred between the upper mold 14 'and the lower mold 15' of the press molding machine while being placed on the support member 41, and the mold is applied at a pressure of 20 kg / cm ^{2 for} 120 seconds. After being pressed and allowed to cool, it was taken out. FIG. 3 is a conceptual diagram showing the upper mold and the lower mold in the press molding machine shown in FIG. 2, and the press molding machine used in the present embodiment uses the upper mold as the upper mold. It is the same as the press molding machine shown in FIG. 2 except that it is replaced with 14 ′ and the lower mold 15 ′, and the operation method is also the same. The upper mold 14 ′ has a surface roughness Rmax of 0.03 μm, an approximate radius of curvature R = 50 mm,
It is an aspheric concave type with a transfer surface with a center depth of 11 mm,
The lower mold 15 ′ is a flat mold having a transfer surface with a surface roughness Rmax of 0.03 μm.

The surface roughness of the pressure-molded product taken out, that is, the surface in contact with the upper mold of the optical glass element 12 was measured by a stylus type surface roughness meter (Surfcom; Tokyo Seimitsu Co., Ltd.). Rmax is about 0.03, radius of curvature R = 50 m
It was clarified that the transfer surface shape of m had a convex aspherical surface transferred accurately. A flat surface having a surface roughness Rmax of about 0.03 μm was transferred to the opposite surface.
Further, when these curved surfaces and flat surfaces were observed at a magnification of 50 times with a differential interference microscope, as shown in FIG. 7, almost no irregularities such as cutting streaks and processing scratches were observed, and no air accumulation or bubbles were observed at all. Was. From the above, the shape is accurately controlled, the effective diameter is 30 mm, the core thickness is 12 mm,
A plano-convex optical glass element was obtained in which one surface was a convex aspheric surface having an approximate radius of curvature of R = 50 mm and the other surface was a flat surface.

COMPARATIVE EXAMPLE 1 A glass lump was prepared in the same manner as in Example 1, except that the glass lump was not subjected to the washing / drying apparatus, but the conventional ultrasonic cleaning with pure water was performed for 5 minutes. Obtained. When the surface roughness of the cut surface and other surfaces of this glass block was measured, the cut surface was Rmax 2.9 μm, and the other surfaces were Rm.
ax 1.2 μm. Further, when the cut surface was observed at a magnification of 1000 with a scanning electron microscope, as shown in FIG. 8, countless fine glass pieces were adhered.

Further, the glass lump was subjected to a conventional hand wiping cleaning process for cleaning the lens, but almost no fine glass fragments were removed.

Thereafter, the glass lump was subjected to a heating deformation step again in the same manner as in Example 1 to obtain a preform. The surface roughness of the preform in contact with the lower mold and the surface opposite to the lower mold were measured by a stylus type surface roughness meter (Surfcom; manufactured by Tokyo Seimitsu Co., Ltd.), and Rmax was about 0.04 μm. The surface roughness was almost the same as the optical glass element surfaces of Examples 1 and 2. However, when both surfaces were observed at a magnification of 50 times with a differential interference microscope, as shown in FIG. And the like were observed in almost the entire visual field, and the appearance quality was remarkably inferior.

[0040]

According to the method of the present invention, it is possible to easily provide an optical glass element having excellent surface accuracy without air accumulation or bubbles on the surface without performing a preliminary processing such as polishing of a glass material. Became. In addition, this method can easily control the shape of the glass material, and can be said to be efficient and economical.

[Brief description of the drawings]

FIG. 1 shows an example of a schematic diagram illustrating a process until a preform is obtained in a process of manufacturing an optical glass element according to the present invention.

FIG. 2 shows an example of a schematic configuration diagram of a press molding machine used in the present invention.

FIG. 3 is an example of a schematic view showing a step of press-molding a preform in a manufacturing process of an optical glass element according to the present invention.

FIG. 4 is a SEM photograph showing a cut surface of a glass lump before removing fine glass pieces in Example 1.

FIG. 5 is a SEM photograph showing a cut surface of a glass lump after removing fine glass pieces in Example 1.

FIG. 6 shows a differential interference micrograph of the preform surface obtained in Example 1.

FIG. 7 shows a differential interference micrograph of the surface of the optical glass element obtained in Example 2.

FIG. 8 is an SEM photograph showing a cut surface of the glass lump after cleaning the glass lump by the conventional cleaning method in Comparative Example 1.

9 shows a differential interference micrograph of the preform surface obtained in Comparative Example 1. FIG.

[Explanation of symbols]

1: glass block, 2: washing / drying device, 3: transfer surface, 4:
Supporting member, 5: electric furnace, 6: preform, 7: contact surface, 8: free surface, 11: preform, 12: optical glass element, 14: convex upper mold, 14 ': concave upper mold, 15: Recessed lower mold, 15 ': Flat lower mold, 16A: Holding mold, 16B:
Holding type, 17: push rod, 18: transparent quartz tube, 19: heating light source, 20: thermocouple, 41: support member

Claims (4)

[Claims] 1. After removing fine glass fragments on the surface of a glass lump having a surface roughness Rmax of 0.1 to 5 μm, the glass lump has a viscosity of 10 ⁶ near the surface of the glass lump.
A method for forming an optical glass element, wherein heating is performed in a support member until the pressure becomes 10 to ³ poise. 2. After removing fine glass fragments on the surface of a glass lump having a surface roughness Rmax of 0.1 to 5 μm, the glass lump has a viscosity of 10 ⁶ near the surface of the glass lump.
A method for forming an optical glass element, comprising heating in a lower mold of press molding until the pressure becomes 10 to ³ poise, and further press-molding the lower mold and an upper mold disposed opposite to the lower mold. 3. When the supporting member cannot be used as a lower die for press molding, the surface roughness Rmax is 0.1 to 1.0.
After removing fine glass fragments on the surface from a 5 μm glass lump, the glass lump is heated in a support member until the viscosity near the surface of the glass lump becomes 10 ⁶ to 10 ³ poise. A method for forming an optical glass element, comprising: moving a lump of glass between press-molding dies; 4. The surface roughness Rm of the obtained optical glass element
The method for forming an optical glass element according to claim 1, wherein ax is 0.05 μm or less.