JPH03228837A - Production of optical glass parts - Google Patents

Abstract

PURPOSE:To efficiently produce optical parts having satisfactory surface accuracy by continuously pressing glass held between a pair of die members for molding without closing the peripheries of the members until the glass attains to a temp. below the strain point and forming a body with a protruding by part. CONSTITUTION:Right and left die members are set at a prescribed interval, a pair of shears 6 is kept open and molten glass 4 is dropped from a nozzle 2 into the space between the members. At the time when the lower end of the dropped molten glass 4 reaches a position under the space between the members, the members are moved forward and a body 30 with a lug part 32 is formed with the members and a grooving ring. During this time, pressing is continued until the glass attains to a temp. below the strain point and then the shears 6 are closed to shear the molten glass. Optical glass parts are obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a glass optical component, and in particular, an optical component is obtained by pressing glass in a molten state with mold members from both sides while flowing down. Regarding the method.

[Prior Art and Problems to be Solved by the Invention] Methods for obtaining optical components from glass materials by press molding include the so-called reheat press method and the direct press method.

In the above-mentioned reheat press method, a glass blank having a shape similar to that of the final molded product is first formed, then the blank is placed in a molding device, heated and pressurized, and then formed by the mold members of the molding device. Obtain a final molded product that corresponds to the shape of the cavity.

In the above-mentioned direct press method, molten glass is introduced into a mold device and pressurized to directly obtain a final molded product corresponding to the shape of a cavity formed by a mold member of the mold device.

By the way, since it is preferable that the glass blank used in the reheat pressing method has a certain degree of shape accuracy and surface accuracy, the glass blank may be ground and polished to obtain a blank with a predetermined accuracy. However, since this requires time and effort for grinding and polishing, the above-mentioned direct press method is sometimes used to manufacture the above-mentioned glass blank.

As a direct press method, for example, Japanese Patent Application Laid-Open No. 63-2
As described in Japanese Patent Publication No. 48727 and Japanese Unexamined Patent Publication No. 1-133948, while the molten glass is flowing down from a nozzle, a pair of mold members for forming the glass are horizontally opposed from both sides of the molten glass. There is a method in which a molded product of a predetermined shape is obtained by sandwiching the glass and cooling and hardening the glass in the cavity thus formed. In this method, a ring-shaped cutting member is placed around the outer periphery of the optical surface molding surface of one mold member, and is moved forward at the same time as or after the mold member advances to cut and remove the protruding glass. An optical component having a desired shape is formed. According to this method, an optical component can be obtained without leaving cutting marks of flowing molten glass on the optical surface, which is preferable.

However, in the above method, when glass is cut with a ring-shaped cutting member, dust is generated due to contact between the cutting member and the other mold member, and the dust is transferred to the molding surface of the mold member after the molded product is released. It may adhere to the glass surface that becomes the optical surface during the next pressing, deteriorating the optical properties of the molded product.

Furthermore, as described above, since the ring-shaped cutting member comes into contact with the other mold member, its lifespan is short, requiring frequent replacement, which hinders improvement in manufacturing efficiency.

In addition, with the above method, shrinkage (sink marks) may occur in the glass during pressing.
(There was a problem that the surface precision of the obtained optical component was considerably lower than the molding surface precision of the mold member.

Therefore, in view of the prior art as described above, the present invention aims to provide a method for manufacturing glass optical components that can obtain optical components with good optical properties including surface precision and improve manufacturing efficiency. That is.

[Means for Solving the Problems] According to the present invention, the above object is achieved by pressing the flowing molten glass from both sides with a pair of mold members for molding so as to correspond to the molding surfaces of the mold members. In the method for manufacturing an optical component having a surface, pressing is continued without closing the periphery between the pair of mold members until the glass reaches a temperature equal to or lower than its strain point, and the flowing molten glass is poured into the pressed material. A glass optical component characterized in that a glass molded product is obtained by cutting the glass molded product above the portion where the mold member is formed, and having an ear protruding outward from the optical component main body formed between the mold members. A method of manufacturing is provided.

In the present invention, a groove forming ring is provided around at least one molding surface of the mold member for forming, the groove forming ring forms a groove in the molten glass during the pressing, and the groove forming ring forms the mold member. The thickness of the molded glass optical component is adjusted by varying the amount of protrusion from the surface. There is a state.

In the present invention, there is a mode in which the above-mentioned ears of the optical component obtained by the above-mentioned method are removed.

In the present invention, there is a mode in which one surface of the main body of the optical component obtained by the above method is further processed into a desired shape and precision, and an optical component having a desired thickness is formed.

According to the present invention, the above method provides a glass optical component having at least one aspherical surface.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing the steps of an embodiment of the method for manufacturing a glass optical component according to the present invention.

In the figure, 2 is a molten glass outflow nozzle connected to a glass melting device (not shown), and 4 is molten glass that is continuously made to flow down from the nozzle. Reference numeral 6 denotes a shear (cutting blade) located directly below the nozzle 4 for cutting the flowing molten glass 4 at appropriate timing.

Reference numerals 12 and 12' designate a pair of mold members disposed on both sides of the flowing molten glass, and in this embodiment, they are used to mold a convex meniscus lens. 12a, 12a'
indicates a molding surface for forming the optical surface, and the molding surface is finished to a mirror surface. These mold members are rotationally symmetrical and are coaxially arranged with their molding surfaces facing each other. A pair of mold sets includes the mold members 12 and 12°.

For the mold member 12.12', the molding surface of the Ni-based super super heat-resistant alloy base material is polished to a surface roughness RmaxO of 01 μm and a desired shape accuracy, and a nitride ceramic coating layer is applied to the surface to a thickness of about 0.8 μm. A thickly coated material can be used.

Other mold base materials include MO-based heat-resistant alloy, Fe-based heat-resistant alloy, stainless steel heat-resistant alloy, MOLTa, carbon,
and carbon composite materials, etc. can be used. The coating layer is used to supplement the hot strength of the base material, and the BN%T
In addition to nitrides such as iN and AIN, carbides such as Tic, SiC, and TaC, C (diamond), and others can be used. These can be applied using various film formation techniques. The coating layer does not need to be a single layer (an intermediate layer may be provided to improve adhesion strength and heat resistance.Also, in the case of a coating layer formed by CVD method, the coating layer itself In order to make the surface of (
Processing such as ultra-precision grinding and polishing can be performed. Furthermore,
If the hot strength of the base material is large (if the shape accuracy can be maintained even after press forming is performed a sufficient number of times, use soft materials such as platinum, platinum-based alloys, Ni, and their alloys as the coating layer). I can do it.

In the mold set on the left, the mold member 12 for molding is fixed to a support member 14, and the support member is attached to member 1.
It is attached to 6. Further, a groove forming ring 18 is attached around the mold member 12. The tip of the ring has a shape of 1''. The ring 18 is fixed to the SSi 20 with bolts in the above-mentioned attachment 1, and a spacer ring 20 is interposed during the fixing.

The amount of protrusion of the blades of the ring 18 from the mold member molding surface 12a is set depending on the thickness of the spacer ring. In addition, when the nuclear force is not projected from the mold member molding surface 12a (projection amount 0)
There are also cases where the groove forming ring is not installed.

Incidentally, a heater 22 and a thermocouple 24 for temperature measurement are built inside the mold member 12.

Although not shown, the mounting member 16 is supported by a base (not shown) so as to be movable back and forth in the direction AB. The reciprocating movement is performed by a drive means (not shown).

Although the mold set on the left side has been described above, the mold set on the right side is also substantially the same except for the shape of the mold member molding surface 12a.
Corresponding members are marked with a “°”. However, although not shown, in the right mold set, the most advanced stop position in the B direction is set by a stopper (not shown). By making the position of the stopper variable and adjusting the position, the above-mentioned stopping position can be appropriately set.

Hereinafter, the manufacturing process will be explained according to the drawings.

First, as shown in FIG. 1(a), the left and right mold sets are opened at a predetermined interval, and while the shear 6 is kept open, the molten glass 4 is injected from the nozzle 2 between the mold members 12 and 12'.
flow down. Then, as shown in FIG. 1(a), a sensor (not shown) detects that the lower end of the molten glass 4 has reached below between the mold members.

Next, based on the detection signal, the right side type set is advanced in the direction B until it comes into contact with the stopper.

The left mold set is advanced in the A direction with a very slight delay in response to the forward movement. As a result, Fig. 1(b)
As shown in Figure 1, molten glass is pressed into a cavity formed by a pair of mold members 12.12° and a groove forming ring 18.18'. At this time, as shown in FIG. 1(b), the tips of the groove forming rings 18 and 18' are not in contact with each other but are separated by a gap, so that both the left and right sides of the pressed molten glass A groove is formed around the surface corresponding to the mold member molding surfaces 12a, 12a'. Then, a glass optical component main body portion 30 is formed inside the groove.

Next, as shown in FIG. 1(C), close the shear 6,
Cut the molten glass 4. As a result, an ear portion 32 protruding outside the groove is formed around the glass optical component main body portion 30.

Then, pressing is continued until the glass temperature falls below the strain point. During this time, the left mold set continues to apply press pressure to the glass without being stopped by a stopper or the like.

Thereafter, as shown in FIG. 1(d), the left and right mold sets are opened, and the shear 6 is opened to take out the molded product. A take-out robot (not shown) is used for the take-out.

FIG. 2 is a front view showing the molded product obtained in the above process, and FIG. 3 is a schematic partial cross-sectional view thereof.

1 In these figures, 30 is the optical component body;
Reference numeral 2 indicates an ear portion protruding from the outside, and reference numeral 34 and 36 indicate grooves formed on both sides between the main body portion 30 and the ear portion 32. As shown in Fig. 3, the cross-sectional shape of the groove is wedge-shaped, and the inner side on the left side forms an angle θ1, the outer side forms an angle θ2, and the right side makes an angle θ1 with respect to the direction parallel to the optical axis of the lens. The inner side forms an angle θ1° and the outer side forms an angle θ2°.

These angles are, for example, θ1=30°, θ2=156
θ1°=45', θ2°=15°.

In addition, in the above process, the mold member 12, 12' is connected to the thermocouple 2.
PI to the fixed point temperature based on the temperature measurement result at 4,24°
D is controlled. The fixed point temperature can be changed as appropriate.

The molded product formed as described above can be used as is by being assembled into a lens barrel, or the ear portion 32 can be removed and used.

Since the grooves 34 and 36 are formed, this removal can be easily performed mechanically by generating tensile stress at a desired location. That is, for example, it can be removed by applying force with your fingers and breaking it, or it can be removed by impact from falling from a slight height, or it can be removed by using a special jig to support the main body part 30 while holding the ear. It is also possible to apply force to the portion 32 and remove it.

FIG. 4 is a partial schematic sectional view showing the optical component main body 30 from which the ears 32 have been removed.

As shown in the figure, the optical component main body 30 has a slope 35.37, which is a part of the groove 34, 36, and a fractured surface 40 when the ear is removed, on its outer circumference. The fracture surface is formed at a desired position because the fracture occurs stably from the bottom of the groove 34 to the bottom of the groove 36 when the ear is removed.

Note that the slopes 35 and 37 are just above the optical component main body 3.
It functions as a chamfered portion on both sides of 0.

In the above-described press, the left die set is not stopped by a stopper, etc., so press pressure can be applied evenly to the glass until the glass hardens and the final shape of the molded product is determined, thereby preventing sink marks on at least one side. The precision of the molding surface of the mold member can be sufficiently transferred to the molded product without causing any problems. Note that the right-side type set can be supported with a sufficiently large force at the stop position so as not to retreat against the oppression of the left-side type set.

The thickness of the molded product is determined by the viscosity of the supplied molten glass, the temperature of the mold member, the press pressure, and other molding conditions.
By adjusting these appropriately, a molded product with a desired thickness can be obtained. The viscosity of the supplied molten glass can be adjusted, for example, in the range of 106 to 10" poise. The temperature of the mold member is initially set, for example, in the range from the transition point to the strain point of the glass, and then changed as necessary. The above press pressure may be, for example, 1 to 500 kg/
It can be adjusted within a range of "cm".

The thickness of the molded product is determined by the thickness of the groove forming ring 18.
It can also be adjusted by changing the amount of protrusion from the 18° molding surfaces 12a, 12a'; the greater the amount of protrusion, the thicker the molded product will be.

FIG. 5 is a sectional view showing a modification of the above embodiment of the method for manufacturing a glass optical component according to the present invention. This figure corresponds to the above-mentioned FIG. 1(b), and the same members as in the same figure are given the same reference numerals.

This modification differs from the embodiment shown in FIG. 1 only in that no groove forming ring is provided around the right mold member 12°, and the outer diameter of the mold member 12° is larger.

Also shown in FIG. 5 is a stopper 50 for setting the most advanced stop position in the B direction of the right mold set.

Next, the results of specifically manufacturing a glass optical component using the method described above are shown below.

Closure 11 Skin 1: Using a device as shown in Fig. 1 above, but removing the groove forming ring 18.18°, the outer diameter was 16.0 mmφ, the maximum effective beam aperture was 14.8 mmφ, the edge thickness was 1.33 mm,
A double spherical concave meniscus lens with a wall thickness difference of 0.55mm,
It was manufactured as follows.

The diameters of the mold members 12 and 12° were both 16.0 mmφ.

Heavy flint glass with a transition point temperature of 455°C and a strain point temperature of 378°C was heated to a viscosity of 10 through a platinum nozzle 2 with an inner diameter of 15 mmφ.
It was stabilized at 61 poise and allowed to flow down.

The press conditions were as follows: initial mold member temperature was 360°C, heating was stopped 2 seconds after the start of pressing, and press pressure was 50 kg/cm.
'', the press time was 9 seconds, the mold was released, and this press cycle was performed continuously.

(As a result, 600 molded products were obtained. Both surfaces of the main body of the molded optical component had no surface defects (optical surfaces with good appearance, and the variation in surface accuracy was within 3 Newtons on the convex surface. The dovetail concavity was within 1°5 Newtons.The variation in thickness was ±0.09 mm.This is sufficiently usable as an optical lens.

The molded product obtained in this example can be made into an optical lens of a normal shape by performing centering processing if desired.

] l Skin λ: Using a device as shown in Fig. 5 above, the outer diameter is 21.0.
mmφ, maximum beam effective aperture 20.0mmφ, edge thickness 1.
A double-spherical convex meniscus lens with a diameter of 78 mm and a wall thickness difference of 1.42 mm was manufactured as follows.

The diameter of the mold member 12 was 21.0 mmφ, the diameter of the mold member 12 was 26.0 mmφ, and the protrusion amount of the tip of the groove forming ring 18 was 1.20 mm.

Heavy flint glass with a transition point temperature of 430°C and a strain point temperature of 373°C is heated to a viscosity of 10 through a platinum nozzle 2 with an inner diameter of 15 mmφ.
It was stabilized at 47 bores and allowed to flow down.

The press conditions were as follows: initial mold member temperature was 380°C, 3.5 seconds after the start of pressing, it was increased to 330°C, and press pressure was 40K.
g/cm”, press time was 14 seconds,
It was then released from the mold.

The concave surface of the main body 30 of the thus obtained molded optical component had no surface defects (it was an optical surface with a good appearance, and its surface accuracy was sufficiently high at about 1 newton). Only a few sink marks were observed.Therefore, this optical component can be used well as a surface reflector by forming a reflective film on the concave surface.In addition, the convex surface can be processed to have even better surface precision. It can also be used as an optical lens.

Next, the amount of protrusion of the tip of the groove-forming ring 18 was varied, and changes in the thickness of the molded product were measured. Incidentally, molding was performed 100 times for the same amount of protrusion. The results are shown in FIG.

As can be seen from FIG. 6, the thickness of the molded glass optical component can be adjusted by changing the amount of protrusion of the groove forming ring 18 from the molding member molding surface 12a.

28.8mm diameter; using a device such as that shown in Figure 1 above,
mmφ, maximum beam effective aperture 27.0mmφ, edge thickness 2.
A double-spherical convex meniscus lens with a diameter of 18 mm and a wall thickness difference of 0.89 mm was manufactured as follows.

The diameter of the mold member 12 is 28.8 mmφ, and the protrusion amount of the tip of the groove forming ring 18.18” is 0.45 mm.
mm.

Heavy crown glass having a transition point temperature of 659° C. and a strain point temperature of 602° C. was stabilized at a viscosity of 1037 bores and allowed to flow down from a platinum nozzle 2 having an opening of 25 mm×5 mm.

The pressing conditions were a mold member temperature of 550°C, a pressing pressure of 113 kg/cm'', and a pressing time of 8 seconds.
It was then released from the mold.

0 Both surfaces of the main body portion 300 of the thus obtained molded optical component had optical surfaces with no surface defects and good appearance, and the surface accuracy was within 3 Newtons. Furthermore, the edge thickness of the molded optical component was within ±0.05 mm with respect to the target value of 2.18 mm.

In the three examples described above, the press time was set after measuring and confirming that the glass temperature became equal to or lower than the strain point after the press time had elapsed.

In the above embodiments, both surfaces of the molded optical component are spherical, but it goes without saying that one or both surfaces can be aspheric.

[Effects of the Invention] As explained above, according to the present invention, pressing is continued without closing the periphery between the pair of mold members until the temperature reaches the strain point of the glass or lower. By obtaining a glass molded product with ears that protrude outward from the optical component body formed between the parts, there is no generation of dust during pressing, which prevents dust from adhering to the molding surface of the mold part. Optical components with good optical characteristics can be obtained without deteriorating accuracy. In addition, press pressure can be applied evenly to the glass until the glass hardens and the final shape of the molded product is determined, and this allows the molded product to be molded with sufficient precision on the molding surface without causing sink marks on at least one side. It is possible to easily obtain an optical component with a desired shape and precision.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing the steps of an embodiment of the method for manufacturing a glass optical component according to the present invention. FIG. 2 is a front view of the molded product, and FIG. 3 is a schematic partial cross-sectional view thereof. FIG. 4 is a partial schematic sectional view showing the main body of the optical component with the ears removed. FIG. 5 is a sectional view showing a modification of the method for manufacturing a glass optical component according to the present invention. FIG. 6 is a graph showing the results of measuring changes in the thickness of a molded product obtained by varying the amount of protrusion of the tip of the groove forming ring. 2: Nozzle, 4: Molten glass, 6: Shear 12.12°: Molding mold member, 12a, 12a: Molding surface, 18.18°: Groove forming ring, 22.22": Heater, 24.24°: Thermocouple, 30: Optical component main body, 32: Ear portion, 34, 36: Groove, 35. 37: Chamfered portion, 40: Fractured surface.

Claims (5)

[Claims] (1) In a method of manufacturing an optical component having a surface corresponding to the molding surface of the mold member by pressing flowing molten glass from both sides with a pair of mold members, the glass is heated to a temperature below its strain point. Continue pressing without closing the periphery between the pair of mold members until the molten glass is pressed, and cut the flowing molten glass above the pressed part,
A method for manufacturing a glass optical component, the method comprising obtaining a glass molded product having an outer protruding ear attached to an optical component main body formed between the mold members. (2) A groove-forming ring is provided around at least one molding surface of the mold member for forming, the groove-forming ring forms a groove in the molten glass during the pressing, and the groove-forming ring forms a groove in the molten glass from the molding surface of the mold member. 2. The method for manufacturing a glass optical component according to claim 1, wherein the thickness of the molded glass optical component is adjusted by changing the amount of protrusion of the molded glass optical component. (3) A method for manufacturing a glass optical component, which comprises removing the ears of the optical component obtained by the method according to claim 1. (4) A method for manufacturing a glass optical component, which further processes one surface of the main body of the optical component obtained by the method according to claim 1 into a desired shape and precision, and forms an optical component with a desired thickness. (5) A glass optical component obtained by the method according to any one of claims 1 to 4, wherein at least one surface is an aspherical surface.