JP2003292327A - Method for producing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an optical element such as a centrationless lens, a lens barrel unified mold lens, or the like, using a direct press method while transferring faithfully its outer circumferential shape. <P>SOLUTION: An upper mold 1 which is positional above a lower mold 2 and has an outer circumference regulating part 13 and the lower mold 2 are relatively moved to get closer to each other after fused glass is dropped on a curved and recessed part 21 formed on the upper surface of the lower mold 2. The optical element is produced by the press molding of glass while the outer circumference of the glass is regulated with the outer circumference regulating part 13. Preferably, a lens barrel 4 is set on the upper mold 1 and used as the outer circumference regulating part in order to produce the lens barrel unified optical element efficiently. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element, and more particularly to a method for manufacturing an optical element by a direct pressing method.

[0002]

2. Description of the Related Art In recent years, with the development of optical technology, the shape of optical elements has become more complicated than before. In particular, aspherical lenses are indispensable for connecting lenses for optical communication, input / output elements of optical fibers, objective lenses for optical pickups, etc., but due to their complicated shape, they have been processed directly by ultra-precision processing machines. Or it was manufactured by injection molding of plastic.

However, recently, the demand for molded articles made of a glass material has rapidly increased. This is because the glass material has a small thermal expansion coefficient, is easy to position, has a high refractive index, has a high shape accuracy of the molding surface, and has excellent thermal stability.

Therefore, many methods for inexpensively mass-producing glass optical elements by press molding have been studied. As one of the methods for producing an optical element by press molding, a preform preprocessed into a desired optical element shape is reheated to be in a softened state, and pressure-molded between molds,
There is a so-called "reheating press method". This manufacturing method is
It is widely used because there are a wide variety of glass materials that can be used and there is no restriction on the size of the optical element that can be molded, but the process time for each of the softening process, molding process, and cooling process is from a few minutes. There is a problem that the manufacturing cost becomes high because it is extremely long, which is ten minutes or more.

On the other hand, as another method of manufacturing an optical element by press molding, a molten glass material is held by a lower mold or a supporting member and directly pressed between the molds without reheating. The so-called "direct press method" has been proposed (for example, Japanese Patent Publication No. 4-327).
72 publication). In this direct press method, the molten glass is dropped on the mold and then pressed with another mold, so the time from dropping the glass to molding and removal is extremely short, from tens of seconds to a few seconds, and productivity is extremely low. Very expensive.

[0006]

By the way, in recent years, in order to facilitate the joining of a lens to an optical element such as a laser diode or a photodiode, or an optical pickup unit, it is necessary to preliminarily set the outer circumference of the lens in a centered shape. Demand for molded lenses (lens-less lenses) and lenses integrally molded with a lens barrel (lens-barrel-integrated lens) is increasing. Conventionally, these molded lenses have been produced by the reheating press method, but this method has the problem of increasing the production cost as described above. Attempts have been made to manufacture by the pressing method.

However, in the direct press method, as in the reheating method, a lower mold having a bottomed round hole or a lower mold having a lens barrel attached (the round hole / the peripheral wall of the lens barrel is an outer peripheral regulating portion). ) Is used to press the glass by lowering the upper mold from the upper side of the lower mold, the round bottomed hole or the bottomed round glass may be spread at the moment when the molten glass is dropped on the lens barrel. The bottom surface of the hole or the lens barrel and the outer peripheral surface are first cooled and solidified, so that the shape of the outer peripheral surface cannot be faithfully transferred, resulting in a distorted lens shape.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an optical element such as a centering-less lens or a lens barrel integrally molded lens on the outer periphery by using a direct press method. It is an object of the present invention to provide a method capable of manufacturing while faithfully transferring the surface shape.

Another object of the present invention is to provide a method capable of efficiently manufacturing a minute optical element by a direct pressing method.

[0010]

According to the first aspect of the invention, after the molten glass is dropped into the curved concave portion formed on the upper surface of the lower mold, the molten glass is positioned above the lower mold opposite to the concave mold. Then, by relatively moving the upper mold having an outer peripheral restriction portion and the lower mold so that they approach each other, press-molding the glass while restricting the outer periphery of the glass by the outer peripheral restriction portion. An optical element manufacturing method is provided, which comprises manufacturing an optical element.

Here, in order to efficiently manufacture the optical element integrated with the lens barrel, it is preferable to attach the lens barrel to the upper mold and use this as the outer peripheral regulating portion.

According to the second invention, after the molten glass is dropped into the curved concave portion formed on the upper surface of the lower mold,
While relatively moving the upper mold and the lower mold located above the lower mold facing each other so that they approach each other,
An outer peripheral regulating member divided into two or more is moved so as to sandwich the lower mold from the side, and the upper mold and the outer peripheral regulating member are brought into contact with the glass substantially at the same time to perform press molding to form an optical element. A method for manufacturing an optical element, which comprises manufacturing the optical element, is provided.

Further, in order to manufacture a minute glass optical element in the above manufacturing method, a dropping amount adjusting member having a through hole is provided in the dropping path of the molten glass, and the glass drop is made to collide with and pass through the through hole. It is desirable to make the glass droplets smaller.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION One of the major features common to the manufacturing methods according to the inventions of the present application is that a curved concave portion is formed on the upper surface of a lower mold, and glass is dripped there. With this configuration, the glass gob moves so as to reduce the variation in the dropping position due to the effects of the glass viscosity and the surface tension, and the shape accuracy is improved. At the same time, as a result of this configuration, it is possible to obtain a glass soul with a small (thick) outer diameter, and as a result, it is possible to suppress rapid cooling of the glass, and it is possible to perform precise surface transfer during the pressing process.

Another major feature common to the manufacturing methods according to the inventions of the present application is that the outer periphery is regulated by bringing the outer periphery regulating portion or the outer periphery regulating member into contact with the glass after the glass is dropped on the lower mold. is there. With this configuration, rapid cooling of the glass can be avoided and precise surface transfer can be performed. Further, during the pressing process, the glass is gradually spread from the top of the glass toward the periphery by the upper mold, so that a good outer peripheral surface can be transferred and the centering process is unnecessary.

The manufacturing method according to each invention of the present application will be described below in order. First, FIG. 1 is a process diagram showing an example of the manufacturing method according to the first invention. First, glass melted in a crucible (not shown) is dropped from the lower end of the nozzle N into a curved concave portion 21 formed on the upper surface of the lower mold 2 (FIG. 11A). At this time, a dropping amount adjusting member 3 having a tapered through hole 31 that expands upward is provided in the middle of the dropping path of the molten glass, and the glass drop is made to collide with and pass through the through hole 31. To make the glass droplets smaller. The size of the glass drop dropped on the lower mold 2, that is, the amount of the glass drop can be adjusted by the size of the through hole 31. On the other hand, the glass drop dropped on the lower mold 2 moves to the center position of the curved concave portion 21 due to the effect of its viscosity and surface tension.
Therefore, variations in the dropping position are reduced. Further, thick glass drops are formed, and rapid cooling of the glass drops is suppressed.

The dropping distance of the glass droplet may be appropriately determined from the size of the glass droplet, the viscosity of the glass, the temperature, etc., but is preferably about 200 to 1000 mm. The material of the mold can be selected from conventionally known materials, but the lower mold in direct contact with the molten glass preferably has a thermal conductivity of 40 W / mK or more in order to release heat. The temperature of both the upper mold and the lower mold is controlled near the Tg of the glass by a heating means (not shown). Further, the glass used in the present invention is not particularly limited, and conventionally known glass, for example, optical glass such as heavy flint glass, lanthanum glass, and borosilicate crown glass can be used.

Next, the upper die 1 having the outer peripheral regulating portion 13 is lowered from above the lower die 2 facing the lower die 2 (FIG. 2 (b)). Here, the outer peripheral regulation portion 13 is a peripheral wall of a bottomed hole formed in the upper mold 1. Therefore, if such a bottomed hole is bored in the upper mold 1, the outer peripheral regulating portion is formed at the same time.
Since the bottom surface of the hole is a transfer surface, high surface accuracy is required, but in general, drilling processing cannot provide sufficient surface accuracy.
Therefore, the upper mold 1 is composed of a member 11 having a convex portion and a member 12 having a hole that fits into the convex portion, and after the tip surface of the convex portion 111 is mirror-finished, It is preferable to fit the groove-shaped portion 111 into the hole 121 of the other member 12 so that a part of the hole remains so as to be combined.
Further, both members 11 and 12 may be made of different materials, but the same material is desirable because gaps and stress are generated between the members when the coefficients of thermal expansion are different.

Then, the upper die 1 is lowered while the outer periphery of the glass is regulated by the outer periphery regulating portion 13 to press-mold the glass (FIG. 2 (c)). At this time, the glass is gradually spread from the apex toward the periphery by the bottom surface of the hole of the upper mold 1. As a result, a good outer peripheral surface is transferred. As the molding conditions for press molding, conventionally known conditions can be adopted here. Although the bottom surface of the hole of the upper mold 1 is a flat surface in this drawing, the shape is not limited to this, and various shapes can be adopted according to the shape of the optical element to be manufactured. For example, as shown in FIG. 2, if a curved concave portion is formed on the bottom surface of the hole of the upper mold 1, an optical element having spherical lenses on both sides can be formed (FIG. 2A), and the curved projection portion on the bottom surface. By forming (1), an optical element in which one surface is spherically convex and the other surface is spherically concave can be formed ((b) in the figure). It should be noted that when forming a curved concave portion on the bottom surface of the hole of the upper mold, the curvature of the curved concave portion is made larger than the curvature of the glass droplet. Figure 3
When the curvature of the curved concave portion is smaller than the curvature of the glass drop, as shown in Fig. 3, the periphery of the glass drop apex first comes into contact with the upper mold, so that there is a gap between the glass drop apex and the upper mold. Occurs, and the gas is trapped there, and good transfer cannot be performed.

When the press molding is completed, the upper mold 1 is raised to take out the glass molded product from the mold (see FIG. 1).
(D)). Then, again, the molten glass is dropped onto the lower mold 2 and the above steps are repeated. According to such a manufacturing method, the heating / cooling time of the mold as in the reheating method is unnecessary, so that the manufacturing time can be shortened to about 1/10 to 1/20 of that of the reheating method.

Another embodiment of the manufacturing method according to the first invention will be described below. FIG. 4 is a process diagram showing an example of this manufacturing method. The difference from the manufacturing method shown in FIG. 1 is that the lens barrel 4 is attached to the upper mold 1 and is used as an outer circumference restricting portion. Hereinafter, this manufacturing method will be described focusing on the points different from the manufacturing method shown in FIG. Glass is dropped from the lower end of the nozzle N into the curved concave portion 21 formed on the upper surface of the lower mold 2 (FIG. 4A). Next, the upper die 1 is lowered from above the lower die 2 facing the upper die 1 (FIG. 2B). Here upper mold 1
Is composed of a member 11 having a convex portion 111 and a member 12 having a hole 121 fitted into the convex portion 111. The enlarged diameter portion 122 is provided at the lower end of the hole 121.
Is formed, and the lens barrel 4 is attached to the enlarged diameter portion 122. The inner peripheral surface of the hole 121 and the inner peripheral surface of the lens barrel 4 need to be flush with each other.

Next, the glass is press-molded while the outer circumference of the glass is regulated by the lens barrel 4 attached to the upper mold 1 (FIG. 2 (c)). Then, the upper mold 1 is raised to take out the press-formed product from the mold. At this time, the glass and the lens barrel are strongly adhered to each other due to the cooling and solidification of the glass, and the optical element is taken out as an integral lens barrel.

Next, the manufacturing method according to the second invention will be described. FIG. 5 is a process diagram showing an example of the manufacturing method according to the present invention. Description of the same parts as those of the manufacturing method shown in FIG. 1 will be omitted, and different parts will be mainly described. First, a big difference from the manufacturing method shown in FIG. 1 is that when the dropped glass is press-molded, the manufacturing method of FIG. In the manufacturing method, the upper die 1 and the outer periphery regulating members 5, 5'are separated, and the outer periphery regulating member is further divided into two, and the upper die 1 is lowered and at the same time the outer periphery regulating members 5, 5'are divided.
Is to perform press molding by moving the lower mold 2 so as to sandwich the lower mold 2 from the side. Here, it is important that the upper mold 1 and the outer peripheral regulating members 5 and 5'contact the glass at substantially the same time. When there is a time lag in contact between the upper mold 1 and the outer periphery restricting members 5, 5 ′ with the glass, cooling is performed from the glass portion where one of the upper mold 1 and the outer periphery restricting members 5, 5 ′ comes into contact first. This is because when the other members come into contact with each other and the glass solidifies, good transfer cannot be performed. Therefore, “substantially simultaneously” includes not only “simultaneously” but also a contact time difference in a range where good transfer is possible. In this figure, the outer circumference regulating members 5 and 5'are divided into two, but the present invention is not limited to this, and it is of course possible to divide into two or more.

[0024]

Example 1 A lanthanum borate-based glass having a glass transition temperature of 650 ° C. and a viscosity of 10 dPa · s at a temperature of 1,100 were used in a nitrogen atmosphere throughout the apparatus using the manufacturing apparatus shown in FIG.
200 mg was dripped from the lower end of the nozzle at ℃. Then, the glass droplet is made to collide with and pass through a through hole having a diameter of 1.3 mm formed in a metal plate (a dropping amount adjusting member) provided in the dropping path.
After forming micro drops of mg, radius of curvature 0.9 mm, spherical surface diameter 1.2 formed on the lower mold set at a temperature of 650 ° C.
It was dripped in a spherical concave portion of mm. Next, a centerless lens was produced by press molding with an upper die (650 ° C.) having an outer diameter regulating portion. As shown in FIG. 6A, the manufactured lens had good transfer shapes on the molding surface and the outer peripheral side surface.

Example 2 Microdroplets of glass were prepared under the same production conditions as in Example 1,
It was dropped into a spherical concave portion having a radius of curvature of 0.7 mm and a spherical portion diameter of 1.0 mm formed in the lower mold set to a temperature of 650 ° C. Next, a lens barrel-integrated lens was produced by press molding with an upper mold (650 ° C.) to which a lens barrel was attached. As shown in FIG. 6B, the lens barrel-integrated lens produced had good transfer shapes on the molding surface and the outer peripheral side surface.

Example 3 Phosphoric acid glass having a glass transition temperature of 490 ° C. had a viscosity of 3
1 from the lower end of the nozzle at a temperature of 1,000 ° C, which is dPa · s
80 mg was added dropwise. Then, the glass drops are heated to a temperature of 450.
Curvature radius 6.0m formed on the lower mold set at ℃
m, spherical portion received in a spherical concave portion having a diameter of 7.0 mm. Next, a centerless lens was produced by press molding with an upper die (450 ° C.) having an outer diameter regulating portion. The transfer shapes of the molding surface and the outer peripheral side surface of the manufactured lens were good.

Comparative Example 1 Using the manufacturing apparatus shown in FIG. 7, microdroplets were prepared under the same conditions as in Example 1, and were placed on the lower mold 2 having the outer diameter restricting portion 22 set to a temperature of 650 ° C. Dropped. Next, the upper die 1 (6
A lens aiming at the same shape as the centering-less lens of Example 1 was manufactured by press molding at 50 ° C.), but as shown in FIG. 8, the transferability of the molding surface of the manufactured lens was good. The transfer shape on the outer peripheral side surface was distorted.

Comparative Example 2 After forming microdroplets under the same conditions as in Example 3, the temperature was changed to 4
It was dropped onto a lower mold having an outer diameter regulating portion set to 50 ° C. Next, a lens aiming at the same shape as the centering-less lens of Example 3 was manufactured by performing press molding with an upper mold (450 ° C.), but the transferability of the molding surface of the manufactured lens was good. However, the transfer shape on the outer peripheral side surface was distorted.

[0029]

According to the manufacturing method of the present invention, a curved concave portion is formed on the upper surface of the lower mold, and glass is dropped on the concave portion. Therefore, variation in dropping position is reduced by the action of glass viscosity and surface tension. As the glass lump moves, the shape accuracy is improved. Further, with such a structure, it is possible to obtain a thick glass body having a small outer diameter, so that rapid cooling of the glass can be suppressed and precise surface transfer can be performed during the pressing process.

Further, in the manufacturing method according to the present invention, after the glass is dropped on the lower die, the outer periphery regulating portion or the outer periphery regulating member is brought into contact with the glass to regulate the outer periphery, so that rapid cooling of the glass can be avoided. Precise surface transfer is possible, and in the pressing step, the upper die gradually spreads from the top of the glass toward the periphery, so that good outer peripheral surface transfer is possible and the centering step is unnecessary.

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of a manufacturing method according to a first invention.

FIG. 2 is a diagram showing another shape of an optical element that can be manufactured.

FIG. 3 is a diagram showing the relationship between the curvature of the bottom surface of the hole of the upper mold and the curvature of the glass droplet.

FIG. 4 is a process drawing showing another example of the manufacturing method according to the first invention.

FIG. 5 is a process drawing showing an example of the manufacturing method according to the second invention.

6 is a sectional view of the optical lens obtained in Examples 1 and 2. FIG.

FIG. 7 is a process drawing showing the manufacturing method of comparative example 1.

8 is a cross-sectional view of the optical lens obtained in Comparative Example 1. FIG.

[Explanation of symbols]

1 Upper mold 2 Lower mold 3 Dropping amount adjusting member 4 lens barrel 5,5 'Perimeter control member 13,22 Perimeter control section 21 recess 31 through hole

Claims (4)

[Claims] 1. An upper mold having an outer peripheral restricting portion located above and facing the lower mold after dropping molten glass into a curved concave portion formed on the upper surface of the lower mold. An optical element, characterized in that an optical element is manufactured by press-molding the glass while relatively moving the lower mold so that the both approaches and controlling the outer circumference of the glass by the outer circumference restricting portion. Manufacturing method. 2. The method of manufacturing an optical element according to claim 1, wherein a lens barrel attached to an upper mold is used as the outer peripheral regulation portion to manufacture a lens barrel-integrated optical element. 3. After the molten glass is dripped into the curved concave portion formed on the upper surface of the lower mold, both of the upper mold and the lower mold located above the lower mold facing each other. While relatively moving so as to approach each other, the outer peripheral regulating member divided into two or more is moved so as to sandwich the lower mold from the side, and the upper mold and the outer peripheral regulating member are substantially simultaneously moved to the glass. A method for manufacturing an optical element, which comprises contacting with a substrate and press-molding to manufacture the optical element. 4. A minute glass optical element is manufactured by providing a dropping amount adjusting member having a through hole in a dropping path of molten glass and making the glass droplet collide with and pass through the through hole to miniaturize the glass droplet. 4. The method for manufacturing an optical element according to any one of 3 to 3.