JPS59150728A - Forming of optical element - Google Patents

Abstract

PURPOSE:To continuously manufacture an optical element by a method wherein a unit including an optical element material arranged between upper and lower dies of a forming die is transferred in a continuous furnace to pass a heating section and then a pressurizing section using a pushing rod. CONSTITUTION:Units W each including an optical element forming material 6 such as optical glass arranged between an upper die 5 having the first functional surface of an optical element and a lower die 4 having the second functional surface thereof, are transferred in a continuous furnace 1 in turn to pass a heating section 1a where each unit is heated up to such temperatures as capable of forming. Next, the unit is moved to a forming section 16 where the unit W1 is stopped using a unit detection sensor and a pressurization cylinder interlocked with the sensor is operated, so that a pushing rod 2 is descended to push the upper die against the lower die, thereby forming an optical element 7. Subsequently, the unit is sent to a cooling section 1c.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure molding method for an optical element, and more particularly to a molding method that can continuously pressure mold an optical element that can be used as a product without post-processing.

Many optical elements such as lenses, prisms, and filters are
Conventionally, optical elements have been formed by a method that mainly involves polishing a material for forming optical elements such as glass.

However, this polishing process requires a considerable amount of time and skill, and in particular, forming an aspherical lens by polishing requires an even more advanced polishing technique, and the processing time is also longer. It was difficult to manufacture in large quantities.

Therefore, a method of molding an optical element such as a lens by simply inserting and arranging a material for molding an optical element into a pair of molds and applying pressure is attracting attention.

Conventionally, there are two general methods for processing and molding optical elements: a reheat press method and a direct press method.

The reheat press method involves measuring out the required amount of a glass material, such as a glass material, that has been melted and solidified in advance, heating it to a predetermined temperature to soften it, and then putting it into a mold for molding. This is a method of molding optical elements by applying pressure. On the other hand, in the direct press method, the required amount of the glass material in a molten state is directly pressed into a lower mold for molding placed on a rotating table, without going through the process of melting and solidifying the glass material in advance as in the reheat press method. In this method, an optical element is molded by pressing an upper mold, which is held by a pressurizing cylinder, against a lower mold.

These methods require more than a certain amount of pressurizing time in order to obtain a molded product with predetermined quality, precision, etc., or the conditions of the upper mold and lower mold during pressure molding are Even after molding and shaping, the entire mold must be maintained and gradually cooled down to a temperature at which the molded optical element can be taken out. It takes a considerable amount of time and productivity is low, and in order to improve productivity, a large number of molds and a large number of pressurizing cylinders are required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method that enables continuous and highly productive molding of optical elements having predetermined quality and precision.

``The above object is achieved by the following method of the present invention.

That is, in the pressure molding method for an optical element of the present invention, in the heating section of a continuous furnace having a heating section, a molding section, and a cooling section, a top layer having a surface forming the first functional surface of the optical element is A mold having a mold and a lower mold having a surface forming a second functional surface of the optical element, a molding mold having a material for molding an optical element disposed between these molds is moved, and the material is molded. a step of heating the material to a moldable temperature in the molding section, pressurizing the material heated to a moldable state by the upper mold and a lower mold, molding the optical element; The method includes a step of cooling the molded optical element by moving the mold within the cooling section while maintaining the state of the mold at the time.

Hereinafter, the method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing essential parts of an example of an optical element continuous pressure molding apparatus used in the method of the present invention. FIG. 2 is a schematic cross-sectional view for explaining the operation of the forming section in the apparatus of FIG. 1.

In the figure, reference numeral 1 denotes a continuous furnace having a predetermined temperature gradient, and its main parts include a heating section 1a, a forming section 1b, and a cooling section IC. 2 is a pressure rod, which is connected or integrated with a pressure cylinder (not shown) during pressurization. Note that the shape of the pressure*tS2 or the installation positions of the pressure rod 2 and the pressure cylinder are not limited to those shown in this example, and other shapes and installation positions that can efficiently and accurately apply pressure during molding may be used. can be selected. W is a molding mold having an upper mold 5 and a lower mold 4, and a material 6 for molding an optical element is placed between these molds. Of course, the unit w after pressure molding has the molded optical element 7. This unit W is continuously or intermittently conveyed in the direction of the arrow within the continuous furnace 1 at a predetermined speed. 8 is a spacer for maintaining a constant distance between units. Incidentally, each unit can also be sequentially carried into the continuous furnace 1 without arranging this spacer 8 between each unit. Whether or not this spacer 8 is used is determined by the form of the mold used, the transportation method, etc.

Inside the continuous furnace (±), it is desirable that the atmosphere be replaced by an inert gas or reducing gas to prevent deterioration due to oxidation of the mold.

Using such an apparatus, optical elements can be continuously molded according to the method of the present invention in the following manner.

First, an optical element molding material 6 is inserted into a lower mold 4 of a mold, and an upper mold 5 is placed at a predetermined position to assemble a set of units w. Similarly, a desired number of units W are assembled.

Next, these units W are sequentially carried into the continuous furnace I,
The material is continuously or intermittently conveyed through the heating section la toward the forming section 1b at a predetermined speed. While the unit W moves within the heating section la, the optical element molding material 6 placed within the unit W is heated to a moldable temperature by the heater 3 provided at an appropriate position in the heating section 1a.

The operation of any unit W1 among the plurality of units W will be explained below.

As shown in FIG. 2, the unit W1 heated to a moldable temperature is sent to the molding section 1b, and when the unit Wr reaches a predetermined position in the molding section 1b, it is placed at an appropriate position in the molding section 1b. The installed unit detection sensor (not shown) is activated, and the unit W1 is stopped. Then, a pressurizing cylinder (not shown) linked to the detection sensor is activated.
The pressure rod 2 descends, and after a predetermined time and pressure, the upper mold 5
is pressed against the lower die 4. At this time, the optical element molding material 6 in the unit Wr is molded into an optical element 7 having a predetermined shape. When the unit W1 is pressurized, the optical element molding material 6, which is placed inside the container of the unit W2 carried in following the unit W1, is heated to a temperature at which it can be molded and then sent. After the pressure molding is completed, the unit Wl is sent to the cooling section 1c, and then the unit W2 is moved under the pressure rod 2 and pressurized, and then sent to the cooling section 1c at f. Thereafter, the units W carried into the continuous furnace 1 one after another are sequentially processed in the same manner, and the optical element molding material 6 placed in the unit W is continuously molded into the optical element 7.

The unit Wl sent to the cooling part IC is transported through the cooling part lc, taking into account the shape, quality and precision required for the optical element to be molded, the properties of the material, the type of inert gas, etc. Then, it is cooled down to a predetermined temperature by an appropriate cooling means (not shown) over the required number of hours. At this time, the state of the upper die 5 and lower die 4 of the unit W1 is as follows:
It is maintained in the state it was in when it was pressurized. During cooling, generally in order to obtain a high-quality, high-precision product, it is preferable that the molded optical element be cooled gradually over as long as possible while being held in the mold.

This is to prevent distortion or cranking from occurring in the molded optical element due to partially uneven shrinkage during rapid cooling or temperature differences between the surface layer and the inner layer.゛.

The cooled unit W + is taken out of the continuous furnace I by appropriate means (not shown), and the pressure-molded optical element 7 is taken out from the unit Wl. Thereafter, the pressure-molded optical elements 7 are continuously taken out from the unit W in the same manner.

In addition, when carrying the unit W into and out of the continuous furnace 1, an unloading means (not shown) is used that does not disturb the inert gas or reducing gas atmosphere and temperature distribution in the continuous furnace 1. . Further, the same applies to the transfer of units, and units within the continuous furnace l.

The operating conditions of the device, such as the conveyance speed of the units W in the continuous furnace 1, the interval between each unit W, and the number of pressurization times per unit time by the pressure rod 2, are determined based on the material required for molding the target optical element. It is determined based on the heating time of the unit W, the cooling time of the unit W after molding, the productivity, etc. For example, when each unit W is transported through the continuous furnace l at a constant interval and speed, if the interval between each unit W is made shorter, the transport distance of each unit W during the pressurizing operation by the pressurizing rod 2 becomes shorter. , the residence time of each unit w in the heating section 1a and the cooling section 1c becomes longer.

The conveyance speed of the unit W in the continuous furnace 1 can be controlled uniformly throughout the continuous furnace 1, or individually in each of the heating section 1a, forming section 1b, and cooling section 1c.

On the other hand, the surface condition of the surfaces 4a and 5a of the upper and lower molds forming the functional surfaces of the optical element of the molding mold constituting the unit W is such that the optical element 7 molded by these surfaces is a desired university element product. If the optical element is finished so that it can be used as a product, the optical element that has been pressure-formed and carried out of the continuous furnace 1 can be used as a product without any post-processing.

In the method of the present invention described above, one line is formed within the continuous furnace 1, but a plurality of lines may be provided in parallel within the same continuous furnace. Furthermore, the shape of the mold forming the unit W can be various depending on the shape of the optical element to be molded. In the example of the present invention shown in FIGS. 1 and 2, a plurality of units W of the same type were carried into the 91i continuous furnace 1, but they formed the functional surface of the optical element of the mold. It is also possible to import a plurality of units W having molds with different surface shapes. Furthermore, it is also possible to use a plurality of units W having different forms and shapes in one mold.

According to the method of the present invention as described above, a predetermined number of molds are carried into a continuous furnace one after another and transferred to a molding section through a heating section, and between a linear upper mold and a lower mold. A set of units consisting of the arranged optical element molding material is sequentially pressurized by a pressure rod, and the material in the mold can be continuously molded into an optical element of a predetermined shape. It has become possible to manufacture elements with higher productivity than the conventional pressure molding method.

Moreover, the state of the unit after pressure molding, that is, the molded optical element is sandwiched between the upper mold and the lower mold, and the unit is conveyed through the cooling section while being pressed by the upper mold and is gradually cooled. It is possible to suppress the occurrence of distortion, cracks, etc. in the optical element.

Further, according to the method of the present invention, an optical element having a predetermined shape and precision as a product can be molded without post-processing.

On the other hand, in the conventional pressure molding method, the mold was built into the molding device, whereas in the device used in the method of the present invention, the mold and the pressure mechanism are separated. and
Mold replacement and maintenance inspection have become extremely easy.

Hereinafter, the method of the present invention will be explained in more detail according to Examples.

Example Upper mold 5 and lower mold 4 made of molybdenum of the mold shown in FIG.
Optical glass 5F14 polished into a disk shape was placed between them as the optical element molding material 6, and a large number of units were assembled. Note that the surface 5 forming the functional surface of the optical element of the upper mold 5
a is outer diameter 25III+, radius of curvature 20.5 n+m
Newton ring, power in surface accuracy and shape
Mirror finishing was performed to within 3 grains, irregularity within 1 grain, and center line average surface roughness within 0.02 grains. The surface 4a forming the functional surface of the lower mold 4 has an outer diameter of 1
The mold was mirror-finished to a size of 6 ml11, a radius of curvature of 5.5.5 mm, and the surface accuracy was the same as that of the upper mold 5.

These units were sequentially introduced into the continuous furnace 1 shown in Fig. 1 with an interval of 200 mm between each unit. While the unit is being transferred through the heating section la, the glass material 6 placed in the mold is heated to a predetermined temperature of 570.degree.

The residence time of one unit in the heating section la was 15 minutes.

When the unit reaches a predetermined position in the molding section 1b, a unit detection sensor (not shown) installed at an appropriate position in the molding section 1b is activated, and the conveyance of the unit is stopped.

Then, a pressurizing cylinder (not shown) linked to the detection sensor is activated, and the pressurizing rod 2 is lowered to produce a load of 10 kg for 5 minutes.
The upper mold 5 was pressed against the lower mold 4 with a pressure of /cm 2 to mold a lens 7 corresponding to the shape and surface precision of the upper mold 5 and the lower mold 4.

The unit is sent to the cooling section IC while maintaining its pressure-molded state, and is slowly cooled. The residence time of one unit in the cooling section 1c was 15 minutes.

Finally, the units were transported one after another from inside the continuous furnace 1, and the lenses 7 were taken out from inside the units.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing essential parts of an example of an optical element molding apparatus used in the method of the present invention, and FIG. 2 is a schematic diagram for explaining the operation of the molding section in the apparatus of FIG. 1. FIG. 1 - continuous furnace la; heating section 1b; forming section 1c; cooling section 2; pressure rod 3; heater 4; lower mold 4a; surface forming functional surface 5; upper 5
5a; Surface forming a functional surface 6; Optical element molding material 7; Molded optical elements W, Wl, W2; Unit

Claims (2)

[Claims] (1) In the heating section of a continuous furnace having a heating section, a molding section, and a cooling section, an upper mold having a surface forming a first functional surface of the optical element and a second functional surface of the optical element are provided. a lower mold having a surface forming a functional surface of the mold, and moving a molding mold between which a material for molding an optical element is disposed, and heating the material to a temperature at which it can be molded; , the process of pressurizing the material heated to a moldable state in the molding section by the upper mold and the lower mold to mold the optical element, and the state of the mold when pressurized. A method for pressure molding an optical element, comprising the step of cooling the molded optical element by moving the mold within the cooling section while maintaining the mold. (2) The surface condition of the surfaces forming the first and second functional surfaces of the optical element of the upper mold and the lower mold is molded by these surfaces! 2. The pressure molding method for an optical element according to claim 1, wherein the optical element is finished so that it can be used as a product.