JP2002220241A - Optical element molding method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To realize perfect transfer of a fine pattern and good releasability in molding an optical element. An optical element forming method for forming an optical element having a fine pattern on its surface by pressing a glass material in a heat-softened state, wherein a pattern for forming a fine pattern is formed. The first step of pressing the glass material with the first mold 2A which has not been performed, and forming the glass material into a rough optical element shape, and the pattern for forming the fine pattern heated to a higher temperature than the glass material are performed. A second step of forming only a substantially fine pattern using the formed second mold 2B, and separating the second mold from the glass material, in a state where the second mold and the glass material are not in contact with each other. A third step of cooling the glass material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an optical element having a fine pattern on an optical functional surface with high precision by press molding.

[0002]

2. Description of the Related Art In recent years, a diffractive optical element utilizing diffraction of light, in which a fine pattern is formed on an optical functional surface of an optical element, has attracted attention. However, as a method of forming the essential fine pattern on the optical functional surface, cutting or the like can be considered, but when the optical element material is glass,
Due to its hardness, it is very difficult to form a fine pattern by cutting. In addition, mass production by continuous machining is considered to be substantially impossible due to factors such as tool consumption. Therefore, conventionally, as a technology for mass production of optical elements having an optical function surface shape which is difficult to obtain by so-called polishing such as an aspherical lens, press molding by sandwiching the optical element material in a molding die having a predetermined surface accuracy. Has proposed a molding method for producing an optical element.

[0003]

However, when a diffractive optical element is manufactured by a molding method, a fine pattern formed on a molding surface of a mold member is transferred to a glass material. Enters,
Due to shrinkage of the glass during cooling, there are many problems that the glass bites into the mold member and does not release. Conversely, a transfer failure in which the fine pattern of the mold member is not completely transferred to the glass due to too much consideration of the releasability is another problem.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize complete transfer of a fine pattern and excellent releasability in molding an optical element.

Another object of the present invention is to realize complete transfer of a fine pattern and good releasability in a one-cycle process in molding an optical element.

[0006]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a method for molding an optical element according to the present invention is a method for molding an optical element for molding an optical element having a fine pattern on its surface by pressing a glass material in a heat-softened state. A first step of pressing the glass material with a first mold on which a pattern for forming the fine pattern is not formed, and forming the glass material into a roughly optical element shape; and A second step of forming substantially only the fine pattern by a second mold on which a pattern for forming the fine pattern in a state heated to a temperature higher than that of the glass material is formed; In a state where the second mold and the glass material are not in contact with each other,
And a third step of cooling the glass material.

In the method of molding an optical element according to the present invention, the second step is performed during the step of cooling the glass material.

In the method of molding an optical element according to the present invention, the first to third steps are performed by one of the molding operations.
It is characterized in that it is performed in a cycle.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

First, an outline of the embodiment will be described.

In the present embodiment, a first step of pressing into a substantially diffractive optical element shape using a first mold set on which a fine pattern is not formed, and then forming a fine pattern heated to a temperature higher than that of a glass material Including a second step of forming only a substantially fine pattern by using the second set of molds, and a third step of cooling the mold member on which the fine pattern is formed without contact with the glass material. Features the process.

Further, the present embodiment is characterized in that the second step is performed during a cooling step, and the first to third steps are performed within one cycle.

In the present embodiment as described above, since the first step forms a rough diffracting optical element from a glass block, the processing amount in the second step of forming a fine pattern is very small. . Therefore, by lowering the temperature of the glass material and increasing the temperature of the mold member, it is possible to raise only the temperature of the surface of the glass material and perform only processing for a fine pattern. Furthermore, since the temperature of the glass material itself is low, there is no influence of its own weight deformation, and the third step of cooling without bringing the glass material and the mold member into contact realizes complete transfer of the fine pattern and good releasability. be able to.

By performing the first to third steps in one cycle, the number of steps required to obtain a diffractive optical element can be reduced, and a more inexpensive diffractive optical element can be obtained.

Hereinafter, an embodiment of the present invention will be specifically described.

This embodiment is an example of forming a concave diffractive optical element shown in FIG. 1 using heavy crown glass (SK12) as a glass material. The diffractive optical element molded in the present embodiment has a fine pattern formed on the optical function surface indicated by reference R30 in FIG. 1 in the direction shown in the enlarged view. And not all the fine patterns have the same shape, but the pitch width becomes larger and the height of the peak becomes higher as approaching the center of the optical element.
Approximately 100 to 50 μm in width of one pitch, approximately 20 in height of pitch
240 patterns of 10 to 10 μm are formed on the surface of the reference R30. The reference R indicates the R (radius of curvature) of a line connecting the peaks of the peaks of the fine pattern. In the optical element of the present embodiment, the reference R is a 30 mm spherical surface. However, depending on the shape, the reference R may have an aspherical shape. The optical function surface of the opposite R17 is also spherical in this embodiment.

FIG. 2 shows the configuration of a molding die 1 for molding a concave lens, showing a state in which the above-described first step of pressing a glass lens into a substantially diffractive optical element shape is completed. I have.

In FIG. 2, a through hole is formed in a state where the molding die 1 is vertically penetrated, and a cylindrical upper die member 2 is fitted in the upper through hole. In this state, it is slidably inserted along the vertical direction. A disk-shaped flange portion is formed at the upper end of the upper die member 2, and this flange portion comes into contact with the upper surface of the molding die 1 from above via a spacer for adjusting the thickness of the lens. Defines the press stroke of the upper die member 2. On the lower surface of the upper mold member 2, a molding surface for pressing the glass material 4 and transferring a desired shape to the surface to form an optical function surface is formed.

FIG. 3 schematically shows a molding portion of the upper mold member 2. As shown, one upper mold member 2 has four molding surfaces for molding the optical function surface of the optical element. In addition, the four molding surfaces are arranged equally at 90 degrees, the fine pattern of the diffractive optical element is not formed, and FIG.
Molded surface 2A mirror-polished to a shape for molding an ordinary spherical optical function surface having a reference R of 30 mm shown in FIG.
And two molding surfaces 2B on which a fine pattern of the diffractive optical element is also formed are alternately arranged.

On the other hand, a lower mold member 3 formed in a columnar shape like the upper mold member 2 is inserted into the lower through hole so as to be slidable vertically along the fitted state.

On the upper end surface of the lower mold member 3, a molding surface for transferring a desired shape to the lower surface of the glass material 4 to form an optical function surface is formed.

Further, as a point of this embodiment, the upper and lower mold members 2 and 3 are rotated separately from the pressing force actuator so that the upper and lower mold members 2 and 3 can rotate while being fitted to the body mold as shown in the figure. Connected to the actuator. As will be described later, after pressing the glass material between the upper and lower mold members 2 and 3, it is necessary to raise the upper mold member 2 once, rotate the upper mold member 90 by 90 degrees, and further perform pressing. A rotation actuator is provided separately.

Further, the rotation accuracy at the time of rotation is configured to be determined depending on the accuracy of the fitting portion of the body-shaped member 1. However, high accuracy is required for rotation positioning.
μm has been achieved.

Next, the thickness of the molded concave lens (glass material 4) is defined and processed by the flange portion of the upper die member 2 being in contact with the upper surface of the molding die 1, as described above. Each time, the thickness of the concave lens (4) does not change.

On the other hand, an opening is formed in the side surface of the molding die 1, through which the glass material 4 is supplied into the molding die 1 and the completion of the molding is completed. The formed concave lens (4) is taken out from the inside of the molding die 1. In this embodiment, like the upper mold member 2, the lower mold member 3 is provided with four molding surfaces for molding the optical function surface, but the molding surface actually used in one molding is the lower mold member 3. There are only two positions symmetrical with respect to the center axis by 180 degrees. Therefore, two glass materials 4 are supplied for one molding, and two optical elements are naturally obtained by one shot.

In the molding die 1, the molding die 1, the upper die member 2 and the lower die member 3 are heated while being positioned at the four corners, and the molding die 1, the upper die member 3 and the upper die member 3 are heated. A heater 5 for heating the glass material 4 via the mold member 2 and the lower mold member 3 is arranged.

The concave lens is molded by the molding process according to the present embodiment using the above-described mold structure. FIG. 4 shows a process diagram of the molding temperature and the weight.

First, the upper mold member 2 is slid upward with respect to the molding 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. Further, the molding die 1, upper mold member 2, and lower mold member 3 are heated to a temperature corresponding to predetermined molding conditions. In the present embodiment, the temperature (620 ° C.) corresponds to 10 ^9.5 dPa · s in the viscosity of the glass material 4.

Next, in this embodiment, a load of 4000 N is applied to the glass material 4 to perform pressing.
Is gradually crushed in the horizontal direction, and finally comes to a state as shown in FIG. In this state, there is no fine pattern on the upper mold member 2 above and below the glass material 4, and optical function surfaces to which the shapes of the molding surface of the R30 and the molding surface of the lower mold member 3 are transferred are formed.

Thereafter, the molded concave lens (glass material 4) is cooled.

In this cooling process, in this embodiment, in order to prevent the glass material 4 from peeling unevenly between the upper and lower mold members 2 and 3, the viscosity of the glass material 4 is set to 1
From the time it becomes equivalent to a temperature (600 ° C.) in 0 ^{10 .5} dPa · s, in a state where a load of 3200N, temperature corresponding to 10 ^13.5 dPa · s viscosity of the glass material 4 (5
Cool to 55 ° C).

When the temperature of the lower mold member 3 reaches 555 ° C., a fine pattern is formed in this embodiment. Cooling is temporarily stopped, and the upper mold member 2 is raised at the same time as the temperature is kept constant at 555 ° C., and the upper mold member 2 is rotated 90 degrees by an actuator provided for rotating the mold member. As a result, the molding surface 2B on which the fine pattern is formed becomes the molding surface 2A.
Is set on the upper part of the glass material 4 in a state where the shape is transferred. Simultaneously with the process, only the temperature of the upper mold member 2 is 620 ° C. by the heater 5 set above the body mold 1.
Heat to

Since the temperature control is controlled by the programmable temperature controller, it is easy to change the speed during the cooling. It is also easy to set the temperature independently for the upper and lower mold members.

In this embodiment, the reason why the temperature corresponding to the viscosity of the glass material 4 of 10 ^13.5 dPa · s was selected as the temperature at which the formation of the fine pattern was performed is that if the viscosity of the glass material is less than 10 dPa · s, It is too soft, and the glass material 4 adheres to the mold member 2 when the mold member 2 is raised,
This is because the possibility that the glass material 4 rotates together with the mold member 2 increases. Further, the close contact with both the upper and lower mold members 2 and 3 easily causes troubles such as breakage of the mold members. Further, after transferring the fine pattern to the glass material 4, further cooling is performed in a state where the upper mold member 2 is raised. At this time, if the viscosity of the glass material 4 is low, the shape of the optical element itself is reduced due to its own weight deformation. It will be deformed. Conversely, if the viscosity of the glass is higher than that, in the case of the fine pattern of the present embodiment, the glass material 4 becomes too hard and the fine pattern cannot be completely transferred. Therefore, in the present embodiment, judging from the viscosity of the glass material, a fine pattern was formed at a temperature (555 ° C.) corresponding to the viscosity of the glass material 4 of 10 ^13.5 dPa · s.

For forming a fine pattern, the upper mold member 2 is kept at 90 ° C. while the temperature of the lower mold member 3 is kept constant at 555 ° C.
The press is performed again on the molding surface 2B on which the fine pattern has been formed by rotating the roller. In this example, a load of 4000 N was applied again for 5 seconds. The press-in amount by the press is sufficient only for the transfer of the fine pattern.
Since the glass material 4 is heated to a high temperature of 20 ° C., only the temperature of the portion of the glass material 4 in contact with the upper mold member 2 increases, and the glass material 4 is softened on the surface.
^{Even at 13.5} dPa · s, the pattern can be sufficiently transferred to the glass material 4 with a load of 5 seconds. At the same time, contact between the glass material 4 and the upper mold member 2 for an excessively long time leads to an increase in the temperature of the glass material 4, which is not preferable. Therefore, the transfer process of the fine pattern was set to 5 seconds.

After the load for 5 seconds, the load was immediately removed, and at the same time, the upper mold member 2 was lifted to release the state of contact with the glass material 4.

With the above, the transfer process of the fine pattern is completed,
Thereafter, further cooling was performed while the upper mold member 2 was raised.

After the above steps, when the temperature dropped to a predetermined temperature, the concave lens (glass material 4) was taken out by an automatic hand or the like. In the present embodiment, the temperature of the glass material 4 at a temperature corresponding to 10 ¹⁴ dPa · s (500
By removing the concave lens at (° C.), the optical element having the fine pattern transferred thereon was successfully obtained without fusing with the mold member and without cracking the optical element itself.

In the fine pattern of the concave diffractive optical element formed as described above, the mold shape is transferred within ± 0.5 μm.
It was molded with a high precision of 0.5 or less.

Further, as a result of continuously forming the concave diffractive optical element by the method of this embodiment, it is possible to realize mold release without any problem in forming all lenses, and to achieve a fine pattern and an optical function surface accuracy on the spherical surface side. I was

(Other Embodiments) As another embodiment, a glass material was made of flint glass (F8), and the shape of the diffractive optical element to be formed was formed into a convex meniscus shape as shown in FIG. The diffractive optical element molded in this embodiment is shown in FIG.
A micropattern was formed on the optical function surface indicated by reference R23 in a direction opposite to that of the above-described embodiment shown in the enlarged view. Also, not all fine patterns have the same shape, and the pitch width becomes smaller and the height of the peak becomes smaller as approaching the center of the optical element. This also has a tendency opposite to that of the above-described embodiment. 240 patterns having a pitch of about 100 to 50 μm and a pitch of about 20 to 10 μm are formed on the surface of the reference R23.
This is the same as in the above-described embodiment. Also reference R
Is a spherical surface of R = 23 mm. The optical function surface of the opposite R14 is also spherical in this embodiment.

Since the shape of the lens to be molded is different from that of the embodiment, the molding apparatus used has different optical function surfaces of the upper mold member 2 'and the lower mold member 3' as shown in FIG. ing.

The molding surface of the upper mold member 2 'has four molding surfaces for molding the optical function surface of the optical element with respect to one upper mold member 2' as in the above-described embodiment. In addition, the four molding surfaces are equally spaced by 90 degrees, the fine pattern of the diffractive optical element is not formed, and the reference R shown in FIG.
Two molding surfaces, each of which is mirror-polished into a shape for molding a 23 mm normal spherical optical function surface shape, and two molding surfaces on which a fine pattern of a diffractive optical element is also formed, are alternately arranged.

Further, as in the above-described embodiment, in this embodiment, the lower mold member 3 'is provided with four molding surfaces for molding the optically functional surface, similarly to the upper mold member 2'. The molding surface used in one molding is 18 mm on the center axis of the lower mold member 3 '.
There are only two of the 0 degree point symmetric positions. Therefore, two glass materials 4 'are supplied for one molding, and two optical elements are naturally obtained by one shot.

Molding was performed using the above mold structure.

Since the glass material 4 'is flint glass (F8) as compared with the embodiment, the temperature is 520 ° C. and 3000N.
It is possible to sufficiently mold the optical element into a roughly optical element shape with a load of.

Next, when the temperature reaches 500 ° C., 1500
Cooling was performed to 430 ° C. under a load of N. FIG. 7 shows a process diagram of the temperature and the load in this embodiment. The temperature of the glass material 4 ′ was kept constant at 430 ° C. to form a fine pattern.

At the same time, the cooling is stopped and the temperature is kept constant at 430 ° C., and at the same time, the upper mold member 2 ′ is raised and rotated by 90 °. At the same time, only the temperature of the upper mold member 2 ′ is heated to 520 ° C.

In forming a fine pattern, 3000N
Was applied for 5 seconds. Then immediately remove the load,
At the same time, the upper mold member 2 'is raised, and the glass material 4'
Further cooling was performed in a state where the contact state with was released.

After the above steps, when the temperature dropped to a predetermined temperature, the convex meniscus lens (glass material 4 ') was taken out by an automatic hand or the like.

The fine pattern of the convex meniscus diffractive optical element formed as described above has a mold shape of ± 0.5 μm.
The spherical surface side of R14 was also formed with high accuracy within ± 0.5 Newton rings.

Further, as a result of continuously forming the convex meniscus diffractive optical element by the method of the present embodiment, mold release with no problem in molding all lenses, and fine pattern and optical function surface accuracy on the spherical surface side are realized. It was done.

[0053]

As described above, according to the present invention,
By perfect transfer of fine pattern and good releasability,
Stable mass production of optical elements becomes possible.

Further, by realizing complete transfer of a fine pattern and good releasability in a one-cycle process, stable mass production which is advantageous in terms of cost becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical element shape formed in one embodiment.

FIG. 2 is a configuration diagram of a molding die of one embodiment.

FIG. 3 is a layout view of a molding surface according to one embodiment.

FIG. 4 is a process diagram of temperature and load in one embodiment.

FIG. 5 is a schematic diagram of an optical element shape formed in another embodiment.

FIG. 6 is a configuration diagram of a molding die of another embodiment.

FIG. 7 is a process diagram of temperature and load in another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Upper mold member 3 Lower mold member 4 Glass material 5 Heating heater

Claims (3)

[Claims] An optical element forming method for forming an optical element having a fine pattern on its surface by pressing a glass material in a heat-softened state, wherein the pattern for forming the fine pattern is Pressing the glass blank with a first mold that has not been formed,
A first step of forming the glass material into a rough optical element shape, and a second step of forming a pattern for forming the fine pattern in a state of being heated to a temperature higher than the glass material.
A second step of substantially only forming the fine pattern using the mold; and separating the second mold from the glass material.
A third step of cooling the glass material in a state where the mold is not in contact with the glass material. 2. The method according to claim 1, wherein the second step is performed during a step of cooling the glass material. 3. The method according to claim 1, wherein the first to third steps are performed within one cycle of a molding operation.