JPH02102133A - Molding method of lens - Google Patents

Abstract

PURPOSE:To make possible to mold lens having excellent shape accuracy and face accuracy without molding inferiority owing to entanglment of air by keep ing processing mold consisting of upper mold and lower mold and lens raw material always in contact state and reducing molding pressure at least one time in the midst of molding. CONSTITUTION:Molding pressure is reduced or made to zero at least one time in the midst of molding with keeping processing mold consisting of upper mold and lower mold and lens raw material fed to between said molds always in contact state, thus a lens is molded. In said case, the lens raw material is molded without excess strain in molding by making viscosity of the lens raw material at beginning of the molding to below 10<11> poise, desirably 10<10> poise, and viscosity during the molding is preferably 10<9>-10<10> poise giving sufficient fluidity. Molding pressure is preferably >=2kg/mm<2>. Besides, control of dimension is facilitated by using lens raw material of columnar shape and the face accu racy of produced lens is able to be <0.1mum by making the accuracy of both end faces of the columnar lens raw material to <1mum, thus improvement of optical properties is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for press molding lenses, and more particularly to a method for molding lenses with excellent shape accuracy and surface accuracy.

2. Description of the Related Art A conventional method for press molding a lens will be explained with reference to FIGS. 2 to 5 in the case of glass.

Generally, when manufacturing glass lenses by press molding,
The lens material is cut into a predetermined size, preheated to a temperature near the glass transition point, and the preheated lens material is
The lens is supplied between upper and lower molds of an upper mold 2 and a lower mold 3, which are processed so that when the molds are closed, it has almost the same shape as the finished lens, and pressure molding is performed at a predetermined temperature.

It is desirable that the shape of the lens material 1 be as simple as possible in terms of the manufacturing process or material processing.
There is a cylindrical type made by cutting a frame material to a predetermined width as shown in the figure. However, when such a material is used for molding, the corner portion 6 of the material shown in FIG. 4 is first deformed and the upper mold 2 and lower mold 3 are fitted in the vicinity of the corner, creating a sealed space 7.

Once the sealed space is created, the sealed space remains until the molding is completed, and the machined surface of the mold is not sufficiently transferred to the material, resulting in a defective lens. A conventional method for preventing such non-transfer defects will be explained with reference to FIG.

The lower die 3 is fixed to the heath 3b via a connecting rod 3a, and the upper die 2 is attached to the piston rod 2b via a connecting rod 2a.

The material 1 is heated by the heater 8 to the forming temperature.

When the desired molding temperature is reached, the upper mold 2 is lowered by the piston 9 and comes into contact with the material. After that, the upper mold vibrates and presses up and down, and this is performed using, for example, a servo balsa 10. For example, vibration pressurization is applied to 90% of the total pressurized straw loaf, and the remaining 10% is formed by constant pressurization. When the full pressure stroke is reached, the energization is stopped, and when the temperature has fallen to the desired temperature, the mold is opened and the lens is removed after cooling.

It is disclosed that by applying vibration pressure for 90% of the total pressure stroke in the above series of molding profiles, the non-contact parts that conventionally occur can be eliminated. (For example, JP-A-60-246231).

Problems to be Solved by the Invention In conventional molding methods, the upper mold that determines the shape of the lens repeatedly comes into close contact with the lens material and separates from the mold during molding, which entrains air and creates bubbles in the softened material. There was a problem with it clumping.

Furthermore, due to the above-mentioned behavior of the upper mold, alignment with the lower mold is very difficult, and it is difficult to ensure the inclination of both sides of the molded lens. Furthermore, due to the above-mentioned behavior of the upper mold, the temperature of the upper mold becomes uneven, resulting in uneven temperature distribution of the lens material, which causes large sink marks on the molded lens.

Means for Solving the Problems In order to solve the above problems, the lens molding method of the present invention is such that a processing mold consisting of an upper mold and a lower mold and the lens material supplied therebetween are in constant contact with each other. , the molding pressure is reduced or brought to zero at least once during molding.

It is effective to start molding when the viscosity of the lens material is 10" poise or less, and reduce the molding pressure once or more when the viscosity of the lens material is 108 to 10 poise, for reasons described later.

In addition, it is desirable to mold at a molding pressure of 2 kg/M2 or more, and the lens material is cylindrical and both end surfaces have a surface roughness of 1 μm.
m or less is desirable for the reason described later.

Effects With the above configuration, the lens material can be molded in a state in which it is always in contact with the upper and lower molds, without creating a non-contact portion between the lens shape transfer surface of the mold and the lens material.

EXAMPLE Below, a lens molding method according to an embodiment of the present invention will be explained with reference to the drawings. In FIG. (It also has a body mold 4 adjusted to an arbitrary height so as to have a predetermined lens thickness, and a lens material 13 supplied to a space surrounded by the upper mold, the lower mold, and the body mold. The lens material is a cylindrical body as shown in Fig. 3, and the end surfaces are mirror-finished.This material is fed into the mold so that both end surfaces are in contact with the transfer surfaces of the upper and lower molds.No. 15 has a built-in heating source. This is a pressurizing stage, and although not shown, pressurizing force is transmitted to the pressurizing stage by, for example, a hydraulic pump or the like.Also, the pressurizing stage can be reduced to an arbitrary pressure or set to zero during molding. 16 is a molding stage with a built-in heating source, which is fixed.

A method of molding a glass material using the molding apparatus configured as described above will be explained.

The material is diameter 8mφ x length 1 (1m optical glass 5F-8
(glass transition point 420°C), this material is supplied onto the transfer surface 12a of the lower mold 12 on a fir holder, and then the upper mold 11 is inserted into the body mold 14 and brought into contact with the glass material. . After that, the heating source is energized to raise the temperature of the glass material to 5
Heat to 30°C.

When the temperature reaches 530″C, the viscosity of the glass material is 10I]
It has become poise. Next, pressure is supplied to the pressure stage and the upper die 11 begins to press the material.

The pressure at this time is preferably 2 kg/mm2 or more, but preferably 4 kg/1II112 or more is the total pressure stroke 5
When the pressure reaches 2.5 m11, the pressure supply is stopped, and the pressurizing stage 15 is raised and separated from the upper die 11 to reduce the pressure to zero. At this time, the viscosity of the glass material is 10
It is 111 poise. Also, the spaces 11b and Ila surrounded by the mold transfer surfaces 11a and 12a and the end face of the lens material, which were under positive pressure at this time, return to normal pressure. Next, after bringing the pressurizing stage 15 into close contact with the upper mold 11 again, pressurization is started, and molding is performed up to the full pressurizing stroke of 75ffII11. Thereafter, the energization is stopped, the pressure is cooled to 430° C., and the pressure is then reduced to zero. Then, when the temperature has reached room temperature, the mold is opened and the lens is removed.

In the above embodiments, the pressure was reduced to zero during molding, but depending on the size of the lens material, the pressure can be returned to normal pressure simply by reducing the pressure, so it is sufficient to simply reduce the pressure.

Effects of the Invention Since the present invention is the molding method explained above, it produces the effects as described below.

This eliminates molding defects due to air entrainment, which conventionally occurs when the molding pressure is reduced during molding, and lenses with excellent shape accuracy and surface area can be molded. Furthermore, since the upper and lower molds and the lens material are always in contact with each other during molding, the precision of the upper and lower molds can be directly transferred to the lens material. In other words, the inclination of both sides of the lens can be easily guaranteed by the mold and barrel mold. In addition, because the upper and lower molds and the lens material are in constant contact during molding, the temperature distribution is uniform, and the lens material does not deform during molding or shrink unevenly during cooling, resulting in good shape accuracy. A lens is obtained.

When the viscosity of the lens material at the start of molding is set to 10+1 poise or less, the lens material can be molded without excessive distortion during molding. Furthermore, it is preferably 1010 poise.

Furthermore, the viscosity of the lens material during molding is preferably 108 to 1010 poise, which provides sufficient fluidity as needed.

The molding pressure is preferably 2 kg/+n+a'' or more because it is necessary to sufficiently deform the lens material and to compress the space surrounded by the upper and lower molds and the lens material.

By making the lens material cylindrical, the dimensions of the material can be easily controlled. It is also easy to introduce into the manufacturing process and easy to automate. It can also contribute to process simplification.

By setting the precision of both end faces of the cylindrical lens material to 1 μm or less, the surface precision of the molded lens can be made to be 0.1 μm or less, thereby improving optical properties.

[Brief explanation of the drawing]

FIG. 11... Upper mold, lla... Mold transfer surface, llb... Space, 12... Lower mold, 1
2a... Mold transfer surface, 12b... Space, 13... Lens material, 14... Body mold, 15... Pressure Stage, I6... Molding stage. Name of agent: Patent attorney Shigetaka Awano 1 person ++ −
---e Mold 11a--Mold! ! Photo 11b-Ichito-ma 12...-Bottom model drawing

Claims (7)

[Claims] (1) A lens molding method characterized by reducing the molding pressure at least once during molding while a processing mold consisting of an upper mold and a lower mold is in constant contact with a lens material supplied therebetween. . (2) Lens molding characterized by reducing the molding pressure to zero at least once during molding, with the processing mold consisting of an upper mold and a lower mold always in contact with the lens material supplied therebetween. Method. (3) The method for molding a lens according to claim 1, wherein molding is started when the viscosity of the lens material is 10'' poise or less. (4) The method for molding a lens according to claim (3), characterized in that when the viscosity of the lens material is 10^8 to 10^1^0 poise, the compacting pressure is reduced or brought to zero at least once. (5) The method for molding a lens according to claim 1 or 2, wherein the lens material has a cylindrical shape. (6) The method for molding a lens according to claim 1, wherein both end surfaces of the cylindrical lens material have a surface roughness of 1 μm or less. (7) The method for molding a lens according to any one of claims (1) and (2), characterized in that molding is performed at a molding pressure of 2 kg/mm^2 or more.