JP3387635B2 - Optical element manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical element such as a concave lens or a concave meniscus lens.

[0002]

2. Description of the Related Art In recent years, a molding die member having a molding surface having a predetermined surface accuracy heats an element for molding an optical element, for example, a glass preform preformed to a certain shape and surface accuracy. To develop an optical element with high-precision optical functional surface that does not require post-processing such as conventional grinding and polishing, by developing a manufacturing method that press-molds under the condition to make a final optical element molded product. Is now possible.

Generally, in such a method of manufacturing an optical element by press molding, a molding upper mold member and a molding lower mold member are slidably opposed to each other in a molding body mold member, respectively. A glass material to be molded is introduced into the cavity formed by the mold member, the lower mold member and the body member, and the atmosphere is a non-oxidizing atmosphere such as a nitrogen atmosphere to prevent the mold member from being oxidized to a moldable temperature. The mold member is heated, the mold is closed, and pressed for an appropriate time to transfer the molding surface of the mold member to the surface of the glass material to be molded, and the mold member temperature is sufficiently higher than the glass transition temperature of the glass material to be molded. It is cooled to a very low temperature, the press pressure is removed, and finally the molding die is opened to take out the optical element molded product.

Before being introduced into the mold member, the glass material to be molded is preheated to an appropriate temperature, or
It is also possible to heat the mold to a moldable temperature and then introduce it into the mold member. Further, a continuous working method in which the glass material to be molded is conveyed together with the mold member, and heating, pressing and cooling are carried out at respective predetermined places, has been adopted, and it has become possible to speed up the molding of the optical element.

Further, it is also practiced that a glass in a molten state is discharged from an outflow tank and directly received by a molding die to press-mold an optical element. In addition, a manufacturing method in which a preform of an optical element is press-molded by this method is also adopted.

The method of manufacturing an optical element as described above is widely disclosed in a considerable number of patent publications.
However, most of them relate to the molding of a convex lens, and regarding the concave lens, they are slightly described in JP-A-59-116.
137, JP-A-59-121124, JP-A-59-121126, and JP-A-59-12362.
No. 9 and JP-A-60-118642 are only disclosed as one of the embodiments.

Each of the optical lenses disclosed in these publications has a simple concave lens shape or is formed by leaving an escape portion for excess glass outside the optically effective diameter. Further, the shape of the preform also has a great influence on the difficulty of molding the optical element, but considering the productivity of the optical element which is the final molded product, the preform for the concave lens from the molten glass is used. No technical disclosure about the manufacturing method is found anywhere.

[0008]

Generally, a problem in molding a concave lens is that the shape transferability during press molding is poor. The cause is that in the process of press molding, the glass material to be molded easily escapes in the outer diameter direction, so that the molding surface of the mold member does not come into contact with the glass, and as a result, the desired molding surface of the molded product is desired. The transfer up to the transfer area cannot be obtained.

There are two possible means for solving the above problem. The first is to restrict the spreading of the glass material to be molded in the outer diameter direction during press molding, and secondly,
The shape of the preform used should be as close as possible to the desired optical element.

As a first means, the outer peripheral portion of the glass material to be molded in the molding process is suppressed by the inner peripheral surface of the body surrounding the upper and lower mold members, and the lens outer diameter as a molding result is regulated. There is a method to secure the transfer pressure to the molding surface at the outer peripheral portion of the glass material to be molded, but in this case, the glass is formed in the gap formed between the sliding parts of the upper and lower mold members and the body mold. When the optical element (lens) that enters and is molded is taken out from the molding die, a part of it may be chipped, and the debris generated by this may damage the molding surface and shorten the life of the die. is there.

Although the concave lens is not symmetrical, a method for improving the shape accuracy by pressing the side surface of the molded product during press molding in order to improve transferability is disclosed in JP-A-60-
The methods described in JP-A-171235 and JP-A-63-176319 are known.

[0012] In any of these, the side surface pressing member is mechanically pressed against the outer diameter portion of the glass material to be molded by the pressure of the cylinder to regulate the spread of the glass in the outer peripheral direction. However, also in this case, as described above, the glass enters the gap between the side pressure member and the upper and lower mold members,
There are inconveniences such as the glass breaking. Also,
In order to prevent fusion and reaction between the side surface pressing member and the glass, there is a problem that the material of the side surface pressing member is limited and the device becomes mechanically complicated.

As a second means, in consideration of the fact that the shape of the preform has a great influence on the shape accuracy of the final molded product, the shape of the preform is approximated to the shape of the final molded product as much as possible. However, in this case, in consideration of the stability when the preform is placed on the mold member during the final molding, it is preferable that the preform has a concave shape on at least one side. Therefore, when receiving the molten glass that has flowed out of the outflow tank and making a preform, it is possible to pre-press the received glass with another mold member. Tended to escape in the radial direction. On the other hand, similarly to the first means, it is effective to regulate the side surface of the glass material in the molding process. However, since the temperature of the glass is high, the mechanical regulation is to break or melt the glass. Problems such as wearing are more likely to occur.

As described above, in an optical element molded product such as a concave lens or a concave meniscus lens, in order to improve shape transferability, the contact pressure of the glass material to be molded is applied to a desired transfer region on the molding surface of the mold member. Although it is important to secure these issues, it is also necessary to solve the above problems.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has the problems of cracking and fusing of glass material caused by mechanically restricting the deformation of glass by utilizing the pressure of gas. It is an object of the present invention to provide a method for manufacturing an optical element that is avoidable and that can ensure the necessary transferability of the optical functional surface.

[0016]

Therefore, in the present invention,
A method of manufacturing an optical element by press-molding a glass material that has been softened by heating between molding die members having opposing molding surfaces, which is present in the outer peripheral portion of the glass material to be molded in the process of press molding. injecting a gas to the free surface, with the pressure, characterized in that abut against the transfer area of the molding surface of at least the mold member, the the glass molding material.

In this case, the gas is at least 1 k
It is desirable to inject at a pressure of g / cm ² or more. Further, the gas is, with respect to the transfer area of the molding surface of the mold member,
When the glass material to be molded is brought into contact with the glass material, the glass material may be sprayed so as to concentrate on a portion of the glass material which is easily spread.
The glass material to be molded is a preform, and when molding the optical element in the process of press molding, it is better that the above gas is composed of an inert gas. It is a molten glass flowing out from, when molding the molten glass received in the mold member into a preform of the required optical element, the gas is at least at the surface of the glass or the molding mold member at the press molding temperature. On the other hand, it is preferable to be composed of a gas such as an inert gas or the atmosphere that does not substantially change chemically.

[0018]

【Example】

(First Embodiment) FIG. 1 shows an embodiment of the present invention, in which reference numeral 101 is an optical element molded product molded from a glass material to be molded (described later), and 102 is an upper mold member. Reference numeral 103 is a lower mold member, 104 is a donut-shaped tubular injection member for gas having an injection port in the inner peripheral portion, and 105 is a heater for heating the gas inside the injection member. FIG. 2 shows the injection member 104 in a plan view, and the reference numeral 106 shown therein is a gas inlet.

FIG. 3 schematically shows a conventional molding state, in which the optical element molded product 107 in a molding completed state according to the conventional method is not transferred to a desired transfer area. It is shown.

On the other hand, in the molding method according to the present invention, as shown in FIG. 4, the glass material 109 to be molded placed on the molding lower die member 103 is preheated by the heater 1
It is heated to the required temperature at 08. Here, as the glass material of the optical element, SK12 (nd = 1.58428:
The above glass material 109 (glass preform) was prepared in advance by using (νd = 59.6: Tg = 497 ° C.:At=526° C.). Then, as an optical element, the radius of curvature R ₁ = R ₂ = 30 mm, the center thickness = 1 mm, the outer diameter = φ1
A 5 mm biconcave lens is molded. On molding this
The molding surface of the lower mold member has an outer diameter of φ20 and a radius of curvature R ₁ ≡R
_{2 It} has a convex shape of 30 mm.

As shown in FIG. 4, the temperature of the mold member is set to 526.
The glass material 109, which is held on the molding surface of the lower mold member while being kept at ℃, is heated to 630 ° C. by the heater 108.
It was heated to a temperature (corresponding to a glass viscosity of 10 ⁷ dPaS). Next, the heater 108 was retracted outward from between the mold members, and then the upper mold member was lowered to perform press molding. Simultaneously with the start of molding of the glass, a high temperature N ₂ gas is injected from the injection port of the injection member 104, and as shown in FIG. 1, the injection pressure pushes the outer peripheral portion of the glass material to be formed, and at least the mold member 102 is pressed. The outer peripheral portion was spread and brought into contact with a desired transfer area on the molding surface of each of Nos.

The injection pressure of N ₂ at this time is 1 kg.
/ Cm ² or more, preferably 1 kg / cm ^{2 to} 5 kg / c
The temperature is set to m ² , and the temperature is detected by a sensor provided at the injection port, but is set to, for example, 600 ° C. (this is slightly lower than the temperature of the glass material to be molded).
The reason for setting the injection pressure is that if it is less than 1 kg, sufficient deformation is not given, and if it exceeds 5 kg, the deformation speed is too fast to control.

After completion of the press molding, cooling was carried out until the temperature dropped to Tg, and then the press pressure was released to take out an optical element molded product. As a result, the molded product is transferred from the molding surface of the mold member up to the outer diameter = φ16, which exceeds the optically effective diameter, on both surfaces. By centering this on the diameter = φ15, the desired biconcave lens can be obtained. Was obtained. (Comparative Example 1) In Example 1, a glass material to be molded (with the same material as the present invention, conditions such as molding temperature) was press-molded by the conventional molding method shown in FIG. 3 without using the manufacturing method of the present invention. The case where it did is given as a comparative example. Here, in the optical element molded product 107 taken out from between the mold members, the desired transfer region of the molding surface of the mold member is not completely transferred on the outer peripheral portion thereof, and both the concave surfaces have a substantial transfer outer diameter = φ1
2, the desired diameter = φ15 could not be obtained. (Embodiment 2) FIG. 5 shows a second embodiment of the present invention. In the figure, reference numeral 201 is an optical element molded product molded from a glass material to be molded, and 202 is an upper mold member. , 20
Reference numeral 3 denotes a lower mold member, 204 denotes a donut-shaped tubular gas injection member, and 205 denotes a heater for heating the internal gas. On the other hand, FIG. 6 shows a state of press molding in the conventional molding method, in which reference numeral 206 indicates
The resulting optical element molded product is the conventional one.

In the manufacturing method of the present invention, as shown in FIG. 7, the glass material 208 to be molded placed on the lower mold member is
Like the first embodiment, it is preheated by the heater 207. Then, the heater 207 was retracted outward from between the mold members, and then the upper mold member was lowered to perform press molding. Simultaneously with the start of molding of the glass, a high temperature N ₂ gas is injected from the injection port of the injection member 204, and as shown in FIG. 5, the injection pressure pushes the outer peripheral portion of the glass material to be formed and at least the mold member 202. The outer peripheral portion was spread and brought into contact with a desired transfer region on the molding surface of.

As a result, the obtained optical element molded product 209
As shown in FIG. 8, R ₁ = 10 (concave), R ₂ = 70
mm (convex), outer diameter = 21 mm, diameter of R ₁ surface = 19 m
m is a concave meniscus lens having a center thickness of 2 mm. Incidentally, as the glass material to be molded of the optical element in this case,
LaK12 (nd = 1.67790: νd = 55.3:
Tg = 554 ° C .: At = 596 ° C.) is used, and this is preliminarily used for the glass preform 20 as shown in FIG.
8 is preformed. Also, this mold member 20
At the time of press molding with No. 2, 203, as shown in FIG. 7, the temperature of the mold member was maintained at 554 ° C., and the glass material 208 placed on the lower mold member was heated by the heater 207 to 680 ° C. (10 ^6.5 dPaS). Equivalent).

The subsequent steps are as described above. In this embodiment, the mold member 203 is attached to the outer periphery of the glass material to be molded in the process of molding the optical element molded product.
The N ₂ gas was injected in a concentrated manner in a portion close to the R ₂ surface. This is because, in the shape having a large R difference as in this embodiment, the glass easily spreads along the molding surface on the side with a large R, so that the transfer region on the molding surface on the side with a small R is This is because it is necessary to prevent the spread of the glass from being sufficiently expected and the transferability from being deteriorated.

Then, after the press molding is completed and the glass temperature becomes uniform, the press pressure is released, the optical element molded product is taken out, and then the molded product 201 is centered to obtain a desired product. An outer diameter lens 209 was obtained. (Comparative Example 2) FIG. 6 shows a state in which press molding was carried out by the conventional manufacturing method without using the manufacturing method of the present invention in Example 2. Here, in the process of molding, the outer peripheral portion of the glass material to be molded flows unevenly toward the side with a large R, and as a result, the molded product 206 taken out does not sufficiently transfer the transfer area of the molding surface of the mold member, _{Since 1} = φ14 and R ₂ = φ24, the transferability on the R ₁ surface side was not satisfied, and the desired lens could not be obtained. (Embodiment 3) FIGS. 9 to 11 show a third embodiment of the present invention, in which reference numeral 301 denotes a molten glass directly from an outflow tank (not shown) through an outflow nozzle 303. 304 is a glass lump when it is received by the lower mold member 302.
Is a preform formed by lowering the upper mold member 305, and 307 is a preform whose outer peripheral portion is spread to a desired transfer region by the gas injection from the gas injection member 306.

Here, the same SK12 as in the first embodiment is used as the glass material to be molded of the optical element. Further, the temperature of the lower mold member is maintained at 500 ° C., and the temperature of the molten glass 301 at the moment of dropping onto the lower mold member is 900 ° C.
Met.

Here, the lower mold member 30 is immediately thereafter.
2 is moved to the pressing position, where it is pressed and deformed by the upper mold member 305 to be deformed to the shape of the initial preform 304. Further, high-temperature air (atmosphere component) is jetted from the jetting member 306 and applied to the outer periphery of the preform, and a concave surface as shown in the preform 307 is formed there, and the transfer area of the molding surface of the upper and lower mold members is formed. On the other hand, the outer peripheral portion of the preform 304 was spread to obtain a preform exhibiting sufficient transferability.

Preform 30 thus obtained
No. 7 has a different transfer area on the upper and lower surfaces as compared with the preform 304 (see FIG. 10) prepared by a molding method that does not inject gas, and has a sufficient optical function effective diameter in the final optical element molded product. It can be secured. (Embodiment 4) FIG. 12 is a view showing a fourth embodiment of the present invention, in which reference numeral 408 denotes a pair of right and left straight tubular injection members 306 provided corresponding to the outer peripheral portion of the glass material. Is another gas injection pipe, and 409 is a preform made of molten glass dropped on the lower mold member.
For example, in FIG. 9, after the molten glass 301 is dropped, immediately before the lower mold member 302 is moved to the required press molding position for main molding, the lower mold member 302 is moved to below the injection pipe 408, and high temperature air from here is moved. By the gas pressure, the surface of the molten glass 301 is made concave, and the air pressure from the injection member 306 deforms the outer peripheral surface of the glass to be molded to form a preform (for the concave meniscus lens) 409. To get.

The preform 409 has a smoother surface than that of the above-mentioned preform 307 because its concave surface is not in contact with the upper mold, and as a preform,
It was more preferable.

The gas used for molding the final molded product in the present invention is N ₂ gas as the inert gas, but other gas such as argon gas can be used. Further, in the case of preform, at the press molding temperature, if at least the chemical change is not substantially given to the surface of the glass or the molding die member, a gas of the same component as the atmosphere,
That is, air can be adopted as the jet gas.

[0033]

As described in detail above, the present invention is a method for producing an optical element by press-molding a glass material that has been softened by heating between molding die members having opposing molding surfaces.
A is, in the course of press molding, by injecting the gas to the free surface present on the outer periphery of the glass molding material,
In the pressure, to the transfer area of the molding surface of at least the mold member, since the abutting said the glass molding material in molding an optical element, such as a concave lens and a concave meniscus lens, in molded state, the target Peripheral part of molded glass material
The free surface present in, without mechanical contact, is changed into a desired shape, with respect to the required transfer area of the molding surface of the mold, sufficient spreadability, play a contact, the desired optical function effective diameter The secured optical element can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a molding method (when molding is completed) according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a mold member omitted in FIG.

FIG. 3 is a diagram showing a conventional example as a comparison with the first embodiment.

FIG. 4 is a diagram showing a molding method (before molding) according to the first embodiment.

FIG. 5 is a diagram showing a molding system (when molding is completed) according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a conventional example as a comparison with the second embodiment.

FIG. 7 is a diagram showing a molding method (before molding) according to a second embodiment.

FIG. 8 is a diagram showing the shape of a concave meniscus lens formed in a second example.

FIG. 9 is a view showing a molding method (when glass is flowing out) according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a molding method (during upper die pressing) according to a third embodiment.

FIG. 11: Molding method according to the third embodiment (when molding is completed)
FIG.

FIG. 12 is a diagram showing a fourth embodiment of the present invention.

[Explanation of symbols] 101 molded products 102 Upper mold member 103 Lower mold member 104 Gas injection member 105 heater 106 gas inlet 107 Conventional molded product 108 heater 109 glass material 201 molded products 202 Upper mold member 203 Lower mold member 204 Gas injection pipe 205 heater 206 Conventional molded product 207 heater 208 glass material 209 Optical element 301 Preform (glass lump) 302 Lower mold member 303 Outflow nozzle 304 preform 305 Upper mold member 306 Gas injection member 307 preform 408 Gas injection tube 409 preform

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Nakagawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-4-367525 (JP, A) JP-A-2 -133326 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C03B 11/00 C03B 11/08

Claims (3)

(57) [Claims] 1. An optical element produced by press-molding a heat-softened glass material between molding die members having opposing molding surfaces.
A method of manufacturing a child , in the process of press molding, injecting gas to the free surface existing on the outer peripheral portion of the glass material to be molded, and at that pressure, at least to the transfer area of the molding surface of the mold member. Te, method of manufacturing an optical element, characterized in that is brought into contact with the the glass molding material. Wherein said gas in the course of the press forming, according to claim 1, characterized in that said injected to concentrate on the most spread easily portion of the glass molding material
Of manufacturing optical element of. Wherein the the glass molding material is a preform, serial in the course of the press forming, the gas to claim 1, characterized in that it is constituted by an inert gas
Method for manufacturing mounted optical element.