JPH11157853A - Method for forming optical element and forming mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for forcibly inhibiting such a tendency that the glass material in a softened state is liable to be formed into a shape having a thinner thickness than the thickness of a prescribed shape at the time of performing press forming of a glass material, and forming an optical element which secures a shape having a desired thickness and also to provide the forming mold used for this method. SOLUTION: This method comprises subjecting a glass material 4 in a softened state to press forming with a mold member 2 consisting of a combination of at least two mold elements 2-1 and 2-2, or a combination of this mold member 2 and another mold member consisting of one mold element. In the method. The press forming is performed while exerting a suction force on the glass material 4 to be subjected to press forming from the clearance between the joined surfaces of the mold elements 2-1 and 2-2 to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a mold for molding an optical element having a complicated shape, such as an aspherical lens, with high precision.

[0002]

2. Description of the Related Art In recent years, as optical devices have become smaller and lighter, aspherical lenses have been desired as glass lenses used in optical systems. As a method of manufacturing a glass lens having the above-mentioned aspherical shape, a number of methods for manufacturing an optical element having a desired accuracy by sandwiching an optical element material in a molding die having a predetermined surface accuracy and performing press molding have already been proposed. ing.

This method is disclosed in, for example, Japanese Patent Publication No. 61-322.
As disclosed in JP-A-63-63, a glass material is sandwiched in a mold having a molding surface that exactly corresponds to the final shape of a desired optical element, and the glass material has a viscosity of 10 ⁸ or more. Press molding is performed in a temperature range corresponding to 5 × 10 ¹⁰ dPa · s, and then cooling is performed so that the temperature difference between the glass material and the mold does not become at least 20 ° C. or more. Is 10 ¹² dPa
In the temperature range where the temperature is lower than s, the material is taken out from between the molds. Thus, a highly accurate optical element can be obtained.

[0004]

However, even in the method of the above-mentioned conventional example (Japanese Patent Publication No. 61-32263), for example, a large-capacity optical material using a large-capacity glass material having a total weight exceeding 15 g is used. When it is necessary to mold the element, when the temperature of the glass material reaches the softening temperature at which it can be pressed, the outer peripheral portion of the concave meniscus-shaped optical element, which normally needs a thicker wall, In the outer peripheral portion of the optical element, deformation or the like due to the weight of the glass material occurs, a required thickness is not obtained, a predetermined shape is not obtained, and a situation in which the glass material is formed into a flat thin shape is often used. Will occur.

The present invention has been made based on the above circumstances, and an object of the present invention is to forcibly prevent a glass material in a softened state at the time of press molding from deforming thinner than a predetermined shape. An object of the present invention is to provide an optical element molding method and a molding die for suppressing the optical element and obtaining an optical element having a desired thickness.

[0006]

Therefore, in the present invention,
At least two or more mold elements are combined to form one mold member, and the softened glass material is press-formed using the mold member or a combination of the mold member and one mold element. In the method for forming an optical element, the glass material to be press-formed from between the joining surfaces of the mold elements is press-formed while applying a suction force.

Further, in the present invention, when press-forming a glass material in a softened state, at least two or more mold elements are combined to constitute one mold member,
Alternatively, in a molding die of an optical element using a combination of this and a mold member composed of one mold element, the mold is provided with suction means for applying a suction force to a glass material to be press-molded from between joining surfaces of the mold elements. It is characterized by having.

In this case, suction of the glass material into the gap is prevented by setting the gap between the joining faces to be 50 μm or less at a portion communicating with the molding surface of the mold member in which the mold elements are combined. Can be. In addition, the joining surface is positioned on the molding surface along the boundary of the discontinuous surface of the molding surface of the mold member formed by combining the mold elements, so that the edge is thin. Molding of a thick concave meniscus optical element or the like can be reliably achieved in a predetermined shape. In molding an optical element such as an aspherical lens as described above, at least one of the discontinuous surfaces includes an optically functional surface transfer surface, and the boundary line is formed of a glass material. It is preferably located at a thick point.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Here, an optical element having a concave meniscus shape as shown in FIG. 1 is presented as a molding target using heavy crown glass (SK12) as a glass material. FIG. 2 shows a configuration of a molding die for molding a concave meniscus lens.

In FIG. 2, the molding die 1 has a sliding through-hole formed in the center thereof in a state penetrating it vertically, and an upper die member is provided in an upper part of the sliding through-hole. 2 is inserted slidably along the up-down direction, and the lower mold member 3 is also inserted slidably along the up-down direction at its lower part. In particular, as a part related to the present invention, the upper mold member 2 includes at least two mold elements 2-1 and 2-2.
It is composed of

The mold element 2-1 is an annular body having a molding surface portion 2A corresponding to the periphery of the optical element to be molded, and the mold element 2-2 is a central part of the optical element to be molded. Is a cylindrical body formed with a molding surface portion 2B corresponding to FIG. In particular, in this embodiment, the molding surface portion 2B has a size including the optical function surface transfer surface of the concave lens (corresponding to the required shape diameter in FIG. 1), and is non-continuous with the molding surface portion 2A. In the embodiment, the adjacent surfaces are separated by an acute angle.

A gap 6 having a size of, for example, 50 μm or less is formed between the joining surfaces of the two mold elements 2-1 and 2-2, and this is just the boundary between the molding surface portions 2A and 2B ( That is, along the boundary of the discontinuous surface). In other words, the edge (parting line) of the joining surface of both mold elements 2-1 and 2-2 in contact with the molding surface (including both molding surface portions 2A and 2B) of the upper mold member is [A ] Along the boundary line corresponding to the thick part of the optical element to be molded.

Although not shown, the mold elements 2-1,
2-2 is adapted to operate integrally by appropriate means. A disc-shaped flange is formed at the upper end of the mold element 2-1, and the flange is formed on the upper surface of the shaping die 1 via a spacer 7 for adjusting the thickness of the lens. Contact from above. Thereby, the press stroke of the upper mold member 2, that is, the mold elements 2-1 and 2-2 is defined.

On the other hand, the lower mold member 3 fitted below the sliding through-hole is, in this embodiment, a mold member in the form of a normal cylinder having one mold element. The mold member shown has a slightly concave molding surface 3 at its upper end.
A is provided, and a desired shape is transferred to the lower surface of the glass material 4. That is, by this transfer, one optical functional surface of the optical element to be molded is formed.

Further, the thickness of the molded concave meniscus lens (molded product from the glass material 4) is, as described above,
Upper mold member 2 (especially, in this embodiment, mold element 2-
The flange portion formed in 1) is defined by abutting on the upper surface of the molding die 1, so that the thickness of the concave meniscus lens does not change every time the processing is performed.

An opening 1A is formed on the side surface of the molding die 1 so as to intersect the sliding through hole.
The glass material 4 is supplied to the inside of the shaping die 1 through the opening 1 </ b> A, and the concave meniscus lens that has been shaped is taken out of the shaping die 1. Further, in this embodiment, the molding body 1, the upper mold member 2 (the mold elements 2-1 and 2-2), and the lower mold member are located in the molding body 1 at the four corners. A heater 5 for heating the glass material 4 is arranged via the molding die 1, the upper mold member 2, and the lower mold member 3 while heating the glass material 3.

In the present invention, the mold elements 2-1 and 2-
The press-forming is performed while applying a suction force to the glass material 4 to be press-formed from between the joining surfaces 2. Therefore, the gap 6
Is connected to a suction means (not shown) such as a vacuum suction mechanism (for example, a suction pump) via an appropriate path.

[0018]

(Embodiment 1) Next, the molding process of the present invention will be described with reference to Embodiment 1. First, the upper mold member 2 is slid upward with respect to the shaping die 1. In this state, the glass material 4 heated to a predetermined temperature is supplied onto the molding surface of the lower mold member 3 by an automatic hand or the like. Note that, in advance, the molding die 1 and the upper die member 2 (the die element 2-
1, 2-2) and the lower mold member 3 are heated to a temperature corresponding to predetermined molding conditions. Particularly, in this embodiment, the glass material 4 is heated to a temperature of 620 ° C. corresponding to a viscosity of 10 ^9.5 dPa · s.

Next, at the time of press molding, the upper mold member 2
, A load of 4000 N is applied to the glass material 4. As a result, the glass material 4 is gradually crushed in the horizontal direction, and finally comes to a state as shown in FIG. FIG. 3 shows an enlargement of the portion [A] in FIG. 2 at this time. When the enlargement is performed in this manner, the pattern elements 2-1 and 2-
As described above, a gap is left between 50 and 50 μm, but the gap between the two is located on the molding surface of the upper mold member 2 and the edge (parting line) of the joining surface between the two is formed. , Located along the boundary of the discontinuous surface. Especially,
In this embodiment, the boundary lines form the molding surface portions 2A and 2B at an acute angle and correspond to the thick portions of the optical element to be molded.

For example, while pressing the glass material 4 by applying a load of 4000 N, the gap 6
As described above, the suction force is applied by an appropriate suction means such as a vacuum suction device. Accordingly, since the glass material 4 is in a very low viscosity state of 10 ^9.5 dPa · s, the thick portion is drawn to the sharp boundary portion (parting line). , Because it holds, it does not flatten,
A desired optical element can be formed from the glass material 4 into a desired shape (an optical function surface or the like is transferred from the molding surfaces of the upper and lower mold members 2 and 3).

Thereafter, the formed concave meniscus lens is cooled. In this cooling process, the viscosity of the glass material 4 is set to 10 ^10.5 to prevent the glass material 4 from being unevenly peeled between the upper mold member 2 and the lower mold member 3.
From the point in time when the temperature (600 ° C.) corresponding to dPa · s is reached, the glass material 4
At a temperature corresponding to a viscosity of 10 ^13.5 dPa · s or more (53
(0 ° C.).

After the above steps, when the temperature drops to a predetermined temperature, the concave meniscus lens is taken out by an automatic hand or the like. In particular, in this embodiment, the temperature at which the viscosity of the glass material 4 corresponds to 10 ¹⁴ dPa · s (5
(00 ° C.), and the cooling rate is about 80 ° C./min.

As described above, with respect to the concave meniscus lens molded by the molding method of the present invention, the optically functional surface of the actual molded product was examined by a Fizeau interferometer. As a result, as shown in FIG. An interference fringe was projected. This indicates that the molding surface portion 2B of the upper mold member 2 (mold element 2-2) is in contact with the glass material 4. Then, as a result of measuring the dimension of the optical functional surface on which the interference fringes are reflected from the result of the Fizeau interferometer, the diameter φ: 23.42 m
m. This satisfies the required shape diameter of the optical element design dimensions shown in FIG. 1 and can secure a desired shape.

Further, as a result of actually forming a concave meniscus lens continuously by the method of the present invention, it was already confirmed that the required functional diameter φ: 23 mm was satisfied in the optical functional surfaces of all the lenses. ing.

Embodiment 2 As another embodiment, a case will be described in which the glass material is made of flint glass (F8) and the shape of the optical element to be formed is a double-sided concave shape as shown in FIG. Since the lens shape to be molded is different from that of Example 1,
The molding device used was, as shown in FIG.
(Mold elements 2-1 ', 2-2') and the molding surface shape of each optical function surface of the lower mold member 3 'are different,
This is the same as in the first embodiment.

Here, the molding was performed by the above-described mold structure. However, as compared with Example 1, the heating temperature was 520 ° C. since the glass material 4 ′ was flint glass (F8).
Also, since the shape of the glass material 4 'is concave and relatively easily deformed, the glass material 4' can be formed sufficiently with a load of 3000N. And here, too, type element 2
The glass material 4 'was press-formed while sucking from a gap 6' (parting line) generated between -1 'and 2-2'. Next, from the point in time when the temperature of the glass material 4 ′ reached 500 ° C., under a load of 1500 N
After cooling to 50 ° C., the molded optical element was taken out.

FIG. 7 shows the result of examining the optical function surface of the concave lens formed by the process of the method of the present invention with a Fizeau interferometer. Here, the surface of R = 30 mm is shown, but as a result of measuring the size of the optical function surface on which the interference fringes are reflected, the diameter φ is 15.27 mm.
This satisfies the required shape diameter of the optical element design dimensions shown in FIG. 5, and it can be seen that the desired shape can be secured. In addition, as a result of continuously forming concave lenses by the method of the present invention, it was confirmed that the required shape diameter φ: 15 mm was satisfied in the optical function surfaces of all the lenses.

As described above, according to the molding method of the present invention, and by using a molding die therefor, as shown in the above-described embodiment, a concave lens or the like, which was conventionally difficult to secure, was used. The required shape and diameter of the optical element can be sufficiently ensured. It should be noted that the present invention can be applied to various embodiments, that is, modifications or variations of the examples described in this specification without departing from the gist of the invention.

That is, for example, in the above-described embodiments and examples, the case where a concave lens and a meniscus lens are formed has been described. However, the present invention is also applicable to optical elements having other shapes, for example, a convex meniscus lens. It is possible. Further, since the gist of the present invention is to "press and mold the glass material from the gap between the joining surfaces of the mold elements", the mold member composed of the combination of the mold elements is the upper mold in the above-described embodiment. For example, the combination of the mold elements can be applied to not only the members but also the lower mold members.

[0030]

As described above, according to the present invention,
Even in an optical element having a shape in which the required shape diameter is difficult to be ensured, for example, a large-diameter optical element, it is possible to obtain an effect that sufficiently accurate shape transfer can be easily realized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an optical element according to an embodiment of the present invention.

FIG. 2 is a schematic structural view of a molding die according to the present invention.

FIG. 3 is a partially enlarged view of a portion [A] of FIG. 2;

FIG. 4 is a view showing the result of examining the optical function surface of a lens by a Fizeau interferometer, similarly obtained by using the molding method and the molding die of the present invention.

FIG. 5 is a schematic cross-sectional view of a shape of an optical element shown as another embodiment of the present invention.

FIG. 6 is a view showing a configuration of a molding die for the same.

FIG. 7 is a view showing a result obtained by examining an optically functional surface of a lens by a Fizeau interferometer, which is obtained in another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Upper mold member 2-1 Mold element (peripheral part) 2-2 Mold element (central part) 2A, 2B Molding surface part 3 Lower mold member 3A Molding surface 4 Glass material 5 Heating heater 6 Gap ( Its edge: parting line)

Claims (5)

[Claims] 1. A glass in a softened state formed by combining at least two or more mold elements to form one mold member, and using the mold member or a combination of the mold member and one mold member. A method for forming an optical element by press-forming a material, wherein the method comprises press-forming the glass material to be press-formed from between the joining surfaces of the mold elements while applying a suction force. 2. When press-forming a glass material in a softened state, at least two or more mold elements are combined to form one mold member, and the mold member or the mold member and one mold element are formed. In a molding die for an optical element using a combination of mold members, an optical element characterized by comprising suction means for applying a suction force to a glass material to be press-molded from between the joining surfaces of the mold elements. Press mold. 3. A gap between said joining surfaces is set at a point where said joining surface communicates with a molding surface of a mold member in which mold elements are combined.
3. The mold for an optical element according to claim 2, wherein the thickness is 0 μm or less. 4. The joining surface is characterized in that its edge is located on the molding surface along a boundary of a discontinuous surface in a molding surface of a mold member formed by combining mold elements. The press-molding die for an optical element according to claim 2. 5. A method according to claim 1, wherein at least one of said discontinuous surfaces includes an optically functional surface transfer surface, and said boundary line is located at a place where a thickness of a glass material is large. A press mold for the optical element according to claim 4.