JP2504997B2 - Optical element molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for molding an optical element such as a lens, a prism or a filter by press-molding a glass material softened by heating.

[Prior Art] Conventionally, a glass material is heated and softened without processing such as an optical element such as a lens, a prism, and a filter, and the glass material is highly accurately corresponding to a shape of a desired optical element. Press molding is performed by the formed molding die. Then, in the molding method of such an optical element, a method of carrying the glass material or a lens after molding while holding it in a ring-shaped barrel mold is known, for example, JP-A-60-118641. The method is described.

FIG. 8 shows a method of molding an optical element using a conventional ring-shaped barrel die, FIG. 8a is a sectional explanatory view showing a state before press molding, and FIG. 8b is a state at the time of press molding. It is sectional explanatory drawing which shows.

In the figure, 1 is a glass material that has been softened by heating, and this glass material 1 is held in a ring-shaped body 2 and has a pair of upper and lower molds on which molding surfaces 3a, 4a corresponding to desired lenses are formed.
It is transferred between 3 and 4 by a conveying means (not shown) (see FIG. 6a), and then the lens 6 having desired molding surfaces 6a and 6b is press-molded by the upper and lower molds 3 and 4 (see FIG. 6b). ).

Next, the molded lens 6 is transferred from the molds 3 and 4 while being held by the ring-shaped barrel mold 2, and the molded lens 6 is recovered from the barrel mold 2 through the slow cooling process.

[Problems to be Solved by the Invention] However, in the above method, the ring-shaped barrel mold 2 is formed by the difference in the coefficient of thermal expansion between the lens 6 and the ring-shaped barrel mold 2 during slow cooling of the molded lens 6 after press molding. In some cases, the lens 6 held in the barrel mold 2 is compressed, and it becomes impossible to remove the lens 6 from the barrel mold 2. Further, there is a problem that the lens 6 is deformed, resulting in defective reversal of the molding surfaces 3a, 4a of the molds 3, 4 to the lens 6, and further, the lens 6 is broken. . This problem can be solved by using a material having a coefficient of thermal expansion smaller than that of glass material such as cemented carbide or SiC, Mo of the material of the ring-shaped body 6, but the material is very expensive. In addition, there is a problem that processing is difficult.

Therefore, the present invention has been made in view of the above problems,
An object of the present invention is to provide a molding method of an optical component using a ring-shaped barrel mold that can be used as a transfer member and can be reliably recovered after cooling the lens after press molding without reducing the use value of the molded lens. is there.

[Means and Actions for Solving Problems] The present invention provides a method of molding an optical element in which a glass material is heated and softened and then pressure-molded by a molding die. Hold and press-molded by the molding die, and then cool the molded lens while holding it in the barrel mold to prevent variation in the thickness of the optical element due to the excess glass material at the time of press molding, It is possible to absorb and weaken the compressive force applied to the molded lens caused by the difference in the coefficient of thermal expansion between the molded lens and the barrel mold during the cooling process.

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

(First Embodiment) FIGS. 1 to 3 show a molding apparatus for carrying out a first embodiment of a method for molding an optical element according to the present invention, and FIG. 1 shows press molding of a glass material. FIG. 2 is a cross-sectional front view of the barrel die for holding and transferring the glass material and the molded lens, and FIG. 3 is a plan view of the barrel die held by the holding arms.

In the figure, 10 is a press-molding die for an optical element 13 including a pair of dies of an upper die 11 and a lower die 12. The upper mold 11 and the lower mold 12 of the mold 10 have molding surfaces 11a and 12a corresponding to desired optical elements 13, respectively, and are arranged coaxially (coaxially) to face each other, and drive devices not shown respectively. Direction to move toward and away from the vehicle (up and down direction in the figure)
It can move on the same axis.

Reference numeral 15 is a ring-shaped body used to hold and transfer the glass material and the molded lens, and is made of a heat-resistant alloy such as SUS420J ₂ having high heat resistance, and a thin plate having a thickness of 0.6 mm is formed by pressing.

The ring-shaped barrel die 15 has an inner peripheral portion 17 for accommodating a glass material or the like in which an inner peripheral surface 17a having a diameter slightly larger than the outer diameter of the molded lens 13 is formed in a substantially central portion of the inner surface portion 16. A holding portion 1 for the glass material and the molded lens 13 in which a step portion 18a having a diameter smaller than the diameter of the inner peripheral portion 17 is formed on the peripheral side of the lower end portion of the inner peripheral surface 17a.
Formed 8.

On the other hand, a tapered portion 19 is formed on the peripheral side of the upper end portion of the inner peripheral surface 17a so as to widen outward and to facilitate the supply guide of the glass material.

Further, four slit portions 21 each having a width of about 0.5 mm are formed in the inner surface portion 17 and the tapered portion 19 from the inner surface portion 16 to the outer peripheral portion 20 at the time of pressing the glass material and gradually cooling the molded lens 13. The body mold 15 is elastically deformable. The number of the slit portions 21 is not limited to the above number, and can be appropriately selected and formed depending on the material and thickness of the body mold 15.

On the other hand, a sandwiching portion 23 having a diameter smaller than that of the outer peripheral portion 20 is formed in a lower portion of the outer peripheral portion 20 of the body mold 15, that is, a portion corresponding to a lower portion of the inner peripheral portion 17.

Reference numeral 30 designates the body die 15 held by the holding portion 23, and the body die 15 is heated by a heating furnace (not shown) and the molding die 10
A body-shaped holding arm for transferring between the upper die 11 and the lower die 12 or to an annealing furnace (not shown). The body-shaped holding arm 30 is divided at a position which becomes the center of the body die 15 when the body die 15 is clamped. This pair of body shape holding members 31 and 32
1, 32 are respectively connected to a driving device (not shown), and are arranged to face each other so as to be movable in the left-right direction in the figure, so that the body mold 15 can be sandwiched and transferred from the left and right.

The barrel mold 15 can be formed by coating the surface with TiN in order to further improve the heat resistance.

When the optical element 15 is molded by applying the molding method of the first embodiment of the present invention using the molding apparatus having the above-described configuration, the barrel die 15 is used as the barrel die holding members 31, 32 of the barrel die holding arm 30. And the glass material that has been heated and softened to a temperature at which the viscosity is in the vicinity of 10 ⁶ to 10 ⁸ poise is held in the body mold 15 by the body mold holding arm 30. Transferred between the upper mold 11 and the lower mold 12 of the 10. This upper model
The lower mold 11 and the lower mold 12 are heated and held near the transition temperature of the glass material, and the glass material held in the barrel mold 15 is pressed and molded by the upper and lower molds 11 and 12 at a pressure of about 100 kg / cm ² for 15 seconds. . At this time, the excess glass material at the time of pressing due to the variation in the volume of the glass material is the slitting portion 21 formed in the body mold 15.
As a result, the body material is easily elastically deformed, and this elastic deformation absorbs it, preventing variation in the thickness of the molded lens 13.

After completion of the press molding, the barrel mold 15 holding the molded lens 13 is
Transferred to a slow cooling furnace (not shown) by the body-shaped holding arm 30,
The holding by the body-shaped holding arm 30 is released. The maximum temperature of the annealing furnace is set to a temperature lower than the glass transition temperature of the glass material. At this time, the compressive force to the molded lens 13 caused by the contraction of the body mold 15 due to the difference in the thermal expansion coefficient between the body mold 15 and the molded lens 13 is absorbed by the elastic deformation of the body mold 15 and gradually cooled. Is performed.

After that, the molded lens 13 gradually cooled in the annealing furnace is
A take-out jig 36 provided with a taper portion 35 fitted to the taper portion 19 formed in 15 is press-fitted from above the body mold 15 and taken out.
The molded lens 13 can be obtained (see FIG. 4).

According to the molding method of the optical element according to the present embodiment, the body for holding the glass material and the molded lens is made of a thin plate material, and the slit portion 21 is provided to be elastically deformable. The surplus glass material due to the variation in the capacity of the material can be absorbed by the elastic deformation of the barrel mold, and the thickness of the molded lens can be kept constant. Further, when the molded lens is gradually cooled, the compression force to the molded lens of the barrel die caused by the difference in the shrinkage amount due to the difference in thermal expansion coefficient between the barrel die and the molded lens held in the barrel die is Since it is absorbed and weakened by being elastically deformed, damage to the molded lens can be prevented, and the molded lens can be easily and reliably taken out from the barrel mold.

(Second Embodiment) FIG. 5 is a cross-sectional front view at the time of press molding of a glass material in a molding apparatus for carrying out a second embodiment of the optical element molding method according to the present invention.

In the molding apparatus of this embodiment, only the shape of the ring-shaped body mold 40 for holding and transferring the glass material and the molded lens is different from that of the first embodiment, and other configurations are the same, so the same members are designated by the same reference numerals. Is attached and its description is omitted.

The body mold 40 of this embodiment has an inner peripheral portion for accommodating glass materials and the like.
The inner peripheral surface 17a of the upper part 17 of the holding part 18 rises upward from the step part 18a.
11, The lower mold 12 is configured by expanding an inclined surface having an angle of 10 degrees with respect to the axis of the lower mold 12 upward and outward. Other holding unit
18, Since the structure of the sandwiching part 23 and the structure made of a thin plate heat-resistant alloy are the same as those in the first embodiment, the same parts are designated by the same reference numerals and the description thereof will be omitted.

The optical element 13 can be molded in the same manner as in the first embodiment by using the molding device having the above structure. Then, the surplus glass material due to the variation in the capacity of the glass material at the time of press molding the glass material by the upper mold 11 and the lower mold 12,
The gap 41 formed between the inner peripheral surface 17a and the glass material can absorb the variation, and the variation in the wall thickness of the molded lens 13 can be prevented.
Further, the compressive force to the molded lens 13 due to the contraction of the inner peripheral portion 17 of the barrel mold 40 caused by the difference in the coefficient of thermal expansion between the barrel mold 40 and the molded lens 13 in the step of gradually cooling the molded lens 13 is the inner peripheral portion 17.
Since it is formed by an inclined surface, it is dispersed and weakened in the thrust direction (optical axis direction), and since the barrel die 40 is made of a thin plate-like member, the member easily elastically deforms, and this elastic deformation causes compression. The molded lens is gradually cooled while absorbing the force. Therefore, also in the molding method of this embodiment, the optical element can be molded while exhibiting the same operation and effect as those of the first embodiment.

(Third Embodiment) FIGS. 6 and 7 show a molding apparatus for carrying out a third embodiment of the method for molding an optical element according to the present invention, and FIG. 6 is a pressure molding of a glass material. FIG. 7 is a cross-sectional front view of the time, and FIG. 7 is a plan view of a state in which a holding die holds a barrel die for holding and transferring a glass material and a molded lens.

In the molding apparatus of the present embodiment, only the shape of the ring-shaped body mold 50 for holding and transferring the glass material and the molded lens is different from the first and second embodiments, and the other configurations are the same, so the same member is not included. The same numbers are assigned and the description thereof is omitted.

The body mold 50 of this embodiment has an inner peripheral portion for storing glass materials and the like.
The entire inner peripheral surface 17a of 17 is formed in a wave shape having a constant period having irregularities in the radial direction (radial direction), and at the convex portion of this wave shape, the lens material and the molded lens 13 are formed. The outside is inscribed, and the concave portion is the void portion 41. Others, holding part 18, clamping part 2
The configuration of 3 and the configuration of a thin plate heat-resistant alloy are
Since it is similar to the embodiment, the same parts are designated by the same reference numerals and the description thereof is omitted.

The optical device 13 can be molded by using the molding apparatus having the above-described configuration, as in the first embodiment. And
The excess glass material due to the variation in the volume of the glass material when the glass material is pressed by the upper mold 11 and the lower mold 12 has a void portion 41.
Can be absorbed, and variation in the thickness of the molded lens 13 can be prevented. Further, the barrel die 50 caused by the difference in coefficient of thermal expansion between the barrel die 50 and the molded lens 13 in the step of gradually cooling the molded lens 13.
The compressive force on the molded lens 13 due to the contraction of the inner peripheral portion 17 of the inner peripheral portion 17 does not act on the entire outer periphery of the molded lens 13 because the contact between the inner peripheral portion 17 and the molded lens 13 is point contact due to the convex portion
Since the thin plate member of the barrel die 50 is easily elastically deformed by the point contact, the elastic deformation allows the molded lens to be gradually cooled while absorbing the compressive force. Therefore, also in the molding method of this embodiment, it is possible to mold the optical element while exhibiting the same actions and effects as those of the above embodiment.

[Effects of the Invention] As described above, according to the present invention, since a thin plate-shaped and elastically deformable cylinder die is used for holding, pressing, and transferring the glass material and the molded lens, the barrel mold is used in the cooling process. Since it is possible to absorb and weaken the compression force of the molded lens caused by the difference in the coefficient of thermal expansion between the molded lens and the molded lens, the molded lens can be collected easily and surely without damage.

In addition, as the material of the barrel type, it is expensive such as SiC, Mo, carbide,
There is no need to use a difficult-to-process material, and thin plate-shaped members can be mass-produced by press working, so that it is economical to obtain a barrel mold at low cost.

As a result, a good lens can be molded at low cost.

[Brief description of drawings]

1 to 3 show a molding apparatus used for carrying out the method of the first embodiment of the present invention. FIG. 1 is a cross-sectional view at the time of press molding of a glass material, and FIG. 2 is the same method. FIG. 3 is a plan view of the barrel die clamped by a holding arm, FIG. 4 is an explanatory view of a method for collecting a molded lens, and FIG. 6 is a cross-sectional view of the glass material at the time of press molding by the molding apparatus used for carrying out the method of Example 2,
FIGS. 7 to 7 show a molding apparatus used for carrying out the method of the third embodiment of the present invention. FIG. 6 is a cross-sectional view of a glass material during press molding, and FIG. 7 is a holding arm. FIG. 8A and FIG. 8B are plan views of the body in the sandwiched state, and are explanatory views of the conventional technique. 10 …… Molding mold 11 …… Upper mold 12 …… Lower mold 13 …… Molding lens (glass material) 15,40,50 …… Ring-shaped body mold 16 …… Inner surface part 17 …… Inner peripheral part 17a… … Inner surface 18 …… Holding part 18a …… Step part 21 …… Slitting part 23 …… Clamping part 30 …… Body type holding arm 41 …… Gap

Claims (1)

(57) [Claims] 1. A method of molding an optical element, comprising heating and softening a glass material and then press-molding with a molding die, wherein the glass material is held in an elastically deformable barrel mold and press-molded with the molding die. And then, cooling the molded lens while holding the molded lens in the barrel mold.