JPH03284913A - Manufacture of plastic lens and apparatus therefor - Google Patents

Abstract

PURPOSE:To improve the productivity and accuracy of a lens by injecting a liquid plastic raw material, which is hardened by heat, into a lens forming cavity defined by a pair of molds, and hardening it into a predetermined lens shape while heating and pressing the raw material by the molds. CONSTITUTION:A lens molding cavity is defined by molds 2a, 2b and sealed by a packing 3. Into the molding cavity 6, a liquid resin raw martial monomer 1 is injected that is added by a polymerization initiator. By raising the tempera ture of molds 2a, 2b, the liquid resin raw material monomer starts reacting and, by the spring force of pressing springs 4, the molds 2a, 2b are urged in the proximity direction so that the liquid resin raw material monomer 1 is pressed therein. By heating, the liquid resin raw material monomer 2 comes into polymerization so as to be hardened and contracted, however, it is in a state of being pressed by the springs and the package 3 is subjected to deforma tion, whereby the molding cavity 6 is configured into a predetermined lens shape by following the hardening an contraction of the liquid resin raw material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a plastic lens by a cast polymerization method and an apparatus therefor.

[Prior art] Plastic lenses have advantages over glass lenses, such as being lightweight and being low cost, and have come to be widely used not only as lenses for eyeglasses but also as lenses for optical equipment. It has become to.

Various thermoplastic resins and thermosetting resins are used as materials for plastic lenses, and various manufacturing methods have been proposed.

Polycarbonate is a thermoplastic resin.

Polystyrene, polymethyl methacrylate, etc. are known, and injection molding, compression molding, etc. are known as methods for producing them. Further, as thermosetting resins, glycol dimethacrylate resin, diethylene glycol dimethacrylate 1J resin, diethylene glycol bisallyl carbonate resin, etc. are known, and a casting method is known as a representative method for producing them.

[Problems to be Solved by the Invention] Both the injection molding method and the compression molding method described above are methods in which thermoplastic resin is filled in a mold under high pressure in a molten state. The method must be designed in anticipation of volumetric shrinkage when the temperature and pressure are returned to normal temperature, and it cannot be said to be an appropriate method for manufacturing lenses for optical instruments that particularly require optical precision. In addition, lenses molded using the above method leave residual strain inside the lens due to the significant difference in cooling rate between the inside and outside of the lens (the part that comes into contact with the mold), as well as mechanical strength and optical There will also be a negative impact on the physical properties of the patient.

On the other hand, the conventional casting method is a method in which a thermosetting monomer liquid is injected into a mold consisting of a two-plate glass mold and a synthetic resin gasket, and then heated and cured. This method can be said to be effective for mass production of relatively uniform and thin lenses such as spectacle lenses. However, there is a problem in terms of productivity as the assembly of the mold and gasket must be done manually. Another disadvantage is that shape distortion occurs due to volumetric shrinkage during polymerization, and the resulting lens may differ considerably in shape from the desired shape.In particular, it may not be able to meet the high precision required for lenses for optical equipment. have.

The present invention was made under these circumstances, and
The purpose is to provide a method and apparatus for manufacturing plastic lenses with excellent productivity and precision.

[Means for Solving the Problems] The present invention has achieved the above object by injecting a liquid plastic raw material that hardens by heating into a lens molding space formed by a pair of molds, and This is a method for manufacturing plastic lenses, the gist of which is to harden raw materials into a predetermined lens shape while heating and pressurizing them.

Further, as an apparatus for carrying out the above method, a pair of lens molding molds are arranged facing each other so as to be sealed from the outside and provide a predetermined lens molding space, and the lens molding molds are An apparatus is provided which is configured to be able to pressurize a liquid plastic raw material filled in a molding space to a predetermined lens shape while heating it.

[Operations and Examples] The inventors have found that lenses with relatively less distortion can be obtained by the casting method compared to other methods, and that molding while applying pressure provides a more accurate shape. While paying attention to the fact that this was obtained, we conducted repeated studies from various angles in order to improve the conventional casting method. As a result, a liquid plastic raw material that hardens when heated is injected into a lens molding space that is formed into a predetermined lens shape by a pair of molds, and the raw material is hardened while being heated and pressurized by the molds to achieve the desired optical precision. The inventors have discovered that a plastic lens having the following characteristics can be obtained, and have completed the method of the present invention. It has also been found that productivity can be improved by employing the above-described configuration as an apparatus for carrying out such a method.

According to the present invention, since polymerization and curing are performed while heating and pressurizing, there is no need to take into account deformation due to thermal expansion of the mold or polymerization contraction of raw materials, and a plastic lens having a shape faithful to the mold shape can be obtained.

The mold temperature in the present invention may be any temperature necessary to thermally polymerize the thermosetting liquid plastic raw material.
The temperature is preferably about 20 to 150°C, more preferably about 30 to 100°C, but it goes without saying that the temperature should be selected in consideration of the materials used. In addition, the mold used in the present invention must have good heat conductivity because it is necessary to remove the polymerization heat during the polymerization of the plastic raw materials and to remove the heat before releasing the mold after heating and curing. It's good. With such a mold, heating and heat removal can be performed efficiently,
Lenses with low optical distortion can be molded in a short time.

FIG. 1 is a schematic explanatory diagram showing one embodiment of the manufacturing apparatus according to the present invention, in which 1 is a liquid resin raw material monomer that hardens by heating, and 2a and 2b are molds.

3 is a packing, 4 is a pressure spring, 5 is a positioning pin, and 6 is a lens molding space. Although FIG. 1 shows the case of manufacturing a concave lens consisting of a flat surface and a concave surface, the lens shape is not limited to that shown in the figure.
It is also possible to manufacture a convex lens consisting of , or a lens combining a concave surface and a convex surface, and the shapes of the molds 2a and 2b may be determined accordingly.

A lens molding space 6 (hereinafter simply referred to as molding space) is formed by the molds 2a and 2b, and the molding space 6 is sealed with a packing 3. The molds 2a and 2b also include a pin 5 and an insertion hole 5 into which the pin is fitted.
It is positioned at the proper position by a. A liquid resin raw material stamp 1 to which a polymerization initiator has been added is injected into the molding space 6 (FIG. 1). By raising the temperature of the molds 2a and 2b, the liquid resin raw material stamp 1 starts to react, and the mold 2 is heated by the spring force of the pressure spring 4.
A and 2b are machined in the proximal direction, and the liquid resin raw material stamp 1 is pressurized. Due to the heating, the liquid resin raw material monomer 1 polymerizes and hardens and shrinks, but due to the fact that it is pressurized by the spring 4 and the seal 3 deforms, the liquid resin raw material seal knob 1 hardens and shrinks. Following this, the molding space 6 assumes a predetermined lens shape (see FIG. 2). It is preferable that the injection amount of the raw material 1 is set in advance in an appropriate range through learning, taking into account the amount of curing shrinkage and the like.

When the curing molding is completed, the molds are gradually cooled by heat radiation, and then the molds 2a and 2b are opened in the direction of separation to take out the hardened plastic.Then, the thin pars around the lens portion are removed, leaving only the lens portion. The presence of the above-mentioned paris makes it easy to take out the hardened plastic from the molds 2a and 2b, and also functions to prevent foreign matter from seeping out from the gasket 3 from reaching the lens portion. .

Although FIGS. 1 and 2 above show an apparatus for manufacturing one lens, for example, as shown in FIG. 3, there is a configuration for manufacturing two lenses, or a configuration for manufacturing three or more lenses. It is also possible to adopt such a configuration. In an apparatus for manufacturing a large number of lenses, for example, as shown in FIG. 4, a product sheet 9 is obtained in which a large number of lens parts 7 share a peripheral edge part 8.

In the device structure of the present invention, since the lens molding space 6 is sealed from the outside, the device can be installed freely; for example, as shown in FIGS. 1 and 2, the lens portion can be oriented vertically. Alternatively, the lens portion may be oriented laterally as shown in FIG.

The heating means during molding is not particularly limited, but for example, the molds 2a and 2b may be immersed in a hot bath,
Are the molds 2a and 2b equipped with jackets?
A heat medium (for example, hot water) may be circulated by digging a groove inside the tank.

On the other hand, the pressurizing means is not particularly limited, and a pressurizing spring 4 as shown in FIGS. 1 to 3 may be used.
When the molds 2a and 2b become large (for example, when a large number of molds are manufactured at the same time), pressure may be applied using hydraulic pressure.

The finished lens is then subjected to additional treatments such as polishing and coating, if necessary. In addition, when manufacturing lenses of various standards, it is possible to cope with this by replacing only the lens-shaped portion of the mold with a core instead of replacing the entire mold.

[Effects of the Invention] As described above, according to the present invention, a plastic lens with excellent productivity and accuracy can be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic explanatory diagrams showing one embodiment of the apparatus of the present invention, Figure 3 is a schematic explanatory diagram showing another embodiment of the apparatus of the present invention, and Figure 4 is for manufacturing a large number of lenses at once. It is a top view of the product sheet body 9 obtained when doing. 1... Liquid resin raw material stamps 2a, 2b... Mold 3... Packing 4...
・Pressure spring 5...Positioning pin 6...
Space for lens molding

Claims (2)

[Claims] (1) Liquid plastic raw materials that harden by heating,
A method for manufacturing a plastic lens, which comprises injecting the raw material into a lens molding space formed by a pair of molds, and hardening the raw material into a predetermined lens shape while heating and pressurizing the raw material with the molds. (2) A pair of lens molding molds are arranged facing each other so as to be sealed from the outside and provide a predetermined lens molding space, and the lens molding molds are made of liquid plastic filled in the molding space. A plastic lens manufacturing device characterized by being configured to be able to heat raw materials and pressurize them into a predetermined lens shape.