JPS5940189Y2 - Plastic lens mold - Google Patents

Description

[Detailed description of the invention] The present invention is a mold for molding a plastic lens, specifically, a plastic lens consisting of an upper and lower mold for forming the surface of the plastic lens, and a gasket for forming the peripheral surface of the lens. This invention relates to a molding die manufactured using a shape mold.

As is well known, this type of conventional mold is
It is configured as shown in the figure.

Although this example shows a mold for molding a convex-concave lens in which one surface of the lens is convex and the other surface is concave, other convex lenses and concave lenses are constructed in the same manner.

That is, this mold 1 has a thick plate-like upper mold 2 made of glass material or the like having a concave surface 2a for forming the convex surface of the plastic lens, and a convex surface 3a for forming the concave surface of the plastic lens. , vinyl chloride or vinyl acetate material, which has a plate-shaped lower mold 3 made of glass material or the like, and fitting portions 4 a t 4 b in which the upper and lower molds 2 and 3 are respectively fitted from above and below and facing each other. A short cylindrical gasket 4 consisting of
It consists of

The gasket 4 has a thick inward flange 5 formed in the center, the inner circumferential surface of which serves as a side wall surface for molding the lens circumferential surface, and the upper and lower surfaces of which form the upper and lower molds. 2
, 3 form a receiving surface of the fitting portion 4at4b into which the fitting portion 4at4b is fitted.

An injection hole 6 is bored through the peripheral wall from a part of the inner peripheral surface of the inward facing flange 5, and an injection pipe 7 formed to protrude from the peripheral wall is provided on the outside of the injection hole 6. is formed integrally with.

An unpolymerized liquid plastic lens material called monomer is injected through the injection tube 7.

The upper and lower molds 2, 3 and gasket 4 thus formed are used in combination as shown in FIG. 2 when molding a plastic lens.

That is, the upper and lower mold fitting parts 4a, 4 of the gasket 4
The molds 2 and 3 are fitted from above and below into b, and are fixed by holding means (not shown), and as shown in the figure, the inner peripheral side wall surface 5a of the inward flange 5 of the gasket 4 and the upper mold 2 A gap 8 formed by the four surfaces 2a of and the convex surface 3a of the lower mold 3
is designed to serve as the casting mold part for molding the plastic lens.

Then, the monomer 10 is injected into the cavity 8 of the mold 1 assembled in this way through the monomer injection pipe 7 while exhausting the air so that no air remains inside, and then as shown in the following section. Then, the injection pipe 7 is sealed.

Next, the mold 1 filled with the monomer 10 is placed in a heating furnace (not shown) and heated at 40° C. to 90° C. for 20 hours while the temperature is gradually increased.
is polymerized to form a plastic lens in a predetermined shape.

By the way, when a plastic lens is molded using a casting mold, as the polymerization of the monomer 10 progresses, the volume of the monomer 10 decreases and shrinks (about 15%). A force is applied that draws the upper and lower molds 2°3 and the gasket 4 that are in contact with each other.

In particular, the gasket 4, which has been softened by heating, deforms as shown in FIG. 3 when the monomer 10 shrinks and the polymerization is completed.

When the gasket 4 is deformed in this way, the plastic lens 10A completed by molding has an optical axis O□ of the upper and lower uneven surfaces 10a and 10b, as shown in FIG.
t02 no longer match, and the thickness t at the center also becomes different from the predetermined thickness.

Therefore, depending on the molding means of such a gasket type, even if there is some variation in thickness like lenses for glasses, and there is some deviation in the optical axis of the vertically curved surface, it will still be within the range that can be easily adjusted by the eye. Although lenses can be molded without any practical problems, it is impossible to obtain high-precision plastic lenses used in optical equipment such as cameras and projectors.

Incidentally, as shown in FIG. 2, the monomer 10 filled in the void 8 and molded has completed its polymerization and is now in the lens 10A.
After being molded, it is released from the mold 1 by rapid cooling or impact, and its shape becomes distorted as shown in Fig. 5 due to the deformation effect described above, but its central part becomes distorted as shown in Figure 5. It is used after being trimmed as shown by the dotted line.

As described above, with the conventional gasket-type mold 1, it has not been possible to obtain high-precision plastic lenses used in optical devices such as cameras and projectors.

In view of the above points, the purpose of the present invention is to provide a gasket in the gasket type mold with a side surface forming gasket made of a high-rigidity material and a molded material made of a highly elastic material placed inside this gasket. By making the gasket double-structured with the correction gasket, the deformation of the lens to be molded is minimized, and a high-precision plastic lens that can be used as a lens for the above-mentioned optical equipment can be obtained. We provide molds.

According to the present invention, by simply adding a simple-structured gasket for compensating the shrinkage of the molded material to the conventional gasket-type mold, it can be used for optical equipment such as cameras, which was previously considered impossible. High precision plastic lenses can be easily obtained.

Hereinafter, the present invention will be explained based on the illustrated embodiments.

FIG. 6 is an exploded view of a mold for molding a plastic lens showing an embodiment of the present invention, with the right half shown in cross section.

The molding die L1 of the present invention has uneven surfaces 12a and 13a for forming the lens surface of the lens to be molded on the lower and upper surfaces, respectively, similar to the upper and lower molds 2 and 3 in FIG. 2 above.
A short cylindrical lens side surface forming gasket made of a high-rigidity material having an upper lens surface forming mold 12 and a lens surface forming lower mold 13 in which are respectively formed, and a side wall surface 16a forming the peripheral surface of the lens. 14, which is disposed within this gasket 14 and tightly covers the side wall surface 16a of the gasket 14 and the periphery of the lens molding surfaces of the upper and lower molds 12, 13.
Gasket 15 for compensating shrinkage of molded material made of highly elastic material
It is made up of.

The side surface forming gasket 14 is made of a highly rigid metal or the like, and its shape is similar to that of the gasket 4 in FIG.
is similar to y, but a plurality of ventilation holes 17 are bored in the inward flange part 16, where the inner peripheral side wall surface 16a is the side wall molding surface, to equalize the internal and external pressures communicating from the inside to the outside. The monomer injection hole 18 is different from the one shown in FIG. 2 in that the injection tube 7 formed in a protruding pipe shape in FIG. 2 is missing.

The gasket 15 for compensating shrinkage of the molded material is made of a material that is easily deformed elastically, and as shown in the figure, the upper and lower edges 15a are bent outward so that the cross-sectional shape of the edge 15a is U-shaped. A monomer injection pipe 19 extending outward is integrally formed in a part of the peripheral side wall of the ring body.

This shrinkage correction gasket 15 is disposed within the side surface forming gasket 14 during molding of a plastic lens, and constitutes a molding surface for forming the side surface. The gasket 14 is pulled away from the lens and contracted uniformly toward the center, and as described later, it not only corrects the thickness deviation of the lens to be molded and the misalignment of the optical axis between the upper and lower surfaces to a minimum, but also prevents the deformation of the gasket 14. This is to prevent the molding of plastic lenses, and this allows for high-precision plastic lens molding that could not be achieved with conventional molds of this type.

Next, the molding die 1-1 of the present invention configured as described above will be explained.
The effect of this will be explained.

First, the inward flange 16 is inserted into the side surface forming gasket 14.
The molded material shrinkage correction gasket 15 is fitted and arranged so as to sandwich the molded material.

At this time, the monomer injection tube 19 of the correction gasket 15 is fitted into the monomer injection hole 18 of the gasket 14 so as to protrude outward from its tip.

When the gasket 15 is arranged in this way, the gasket 1
The side wall surface 16a of No. 4 is closely covered by the gasket 15.

Next, as shown in FIG. 7, the upper and lower molds 12 and 13 are respectively fitted into the side surface forming gasket 14 into which the correction gasket 15 is fitted.

Then, the peripheries of the lens molding surfaces of both molds 12 and 13 are also covered by the upper and lower edges 15a of the gasket 15.

Next, the monomer 20 is injected into the gap 21 formed between the upper and lower molds 12, 13 and the correction gasket 15, that is, into the plastic lens casting mold, from the monomer injection pipe 19 while exhausting the air inside. After filling, the tip of the injection tube 19 is sealed, as shown in FIG.

Next, the mold 1 filled with the monomer 20 is heated 4P.
(not shown) and heated at 40° C. to 90° C. for 20 hours, gradually increasing the temperature to polymerize the monomer 20.

In this polymerization process, the monomer 20 that was initially liquid
As the polymerization progresses, it becomes wax-like or wax-like, and becomes solid when the polymerization is completed.

In this process, most of the contraction of the monomer 20 occurs during the process of changing from a liquid state that can freely change its shape to a somewhat viscous wax state.

Due to the shrinkage at this time, the inner peripheral edge 15 of the monomer 20, the mold 12, 13, and the gasket 15 for compensating shrinkage of the molded material
A gap will be formed between the holes 15b and 15b, but the pressure within that gap is very low.Since the inner peripheral edge 15b has high elasticity, the pressure of the atmosphere flowing through the vent hole 17 will cause
The gap is closed, and the inner circumferential edge 15b remains in close contact with the monomer 20 and is deformed as shown in FIG. 8, with the upper and lower thickness directions remaining almost immovable.

Furthermore, the monomer solidifies considerably, forming an uneven surface 12a for forming a lens surface.

Even when the plastic lens part 13a and the inner plastic lens part are bonded together, there is a slight shrinkage, but this shrinkage is caused by the gasket edge 1
When 5a contracts, it is absorbed by the deformation of the gasket inner peripheral edge 15b as described above, and the uneven surface 12a for forming the lens surface is absorbed.

Peeling between 13a and the internal plastic lens is prevented.

As a result of the above, dimensional changes in the thickness direction are extremely small, and furthermore, the molds 12 and 13 and the side surface forming gasket 14
Because of its high rigidity, there is no mold deviation, and there is almost no misalignment of the upper and lower optical axes of the cast plastic lens.

In this way, the plastic lens made of the monomer 20 that has been molded after polymerization is released by rapidly cooling or impacting the mold 11, and trimming the peripheral edge 20a for the above-mentioned correction, as in the conventional method. By cutting off the gasket 15 together with the gasket 15, it is possible to obtain a high-precision plastic lens with almost no deviation in thickness at the center or deviation in the optical axis between the upper and lower surfaces.

By using the above mold 1j, the lens diameter is 30 mm.
In the example of molding a convex-concave lens with a center thickness of 6 mm, when conventional mold 1 is used, the dimensional difference in center thickness is ±0.
．． 2 rran, the deviation of the optical axis on the upper and lower surfaces is ±0.1mm
The above problems were able to be significantly reduced to approximately ±0.03 to 0.05 mm and 0.02 to 0.05+yo++, respectively.

As explained above, according to the mold of the present invention, it is possible to obtain a high-precision lens that can be used sufficiently as a lens for optical equipment that requires high precision. Since it does not deform, it can be used permanently, and even if a new correction gasket is added, the cost of the mold can be lower than that of conventional molds.

[Brief explanation of the drawing]

Fig. 1 is an exploded side view showing an example of a conventional mold, with the right half shown in cross section; Fig. 2 is a sectional view showing the state of the mold shown in Fig. 1 during molding; Figure 3 is a sectional view showing how the mold shown in Figure 2 is deformed during molding, and Figure 4 is a cross-sectional view of the mold shown in Figure 2 above.
→L of plastic lens molded by the mold shown in the figure
FIG. 5 is a plan view showing the state of the plastic lens shown in FIG. 4 before trimming, and FIG. 6 is a cross-sectional view of the right half of the plastic lens, showing an embodiment of the present invention. An exploded side view of the mold, FIG. 7 is a sectional view showing the state of the mold shown in FIG. 6 above during molding, and FIG. 8 shows the molding process of a plastic lens molded with the mold shown in FIG. 6 above. FIG. 4 is a cross-sectional view showing a deformed state over time. L, 1... Mold, 2, 12... Upper mold for lens surface formation, 3, 13... Lower mold for lens surface formation, 4, 14
...Gasket for side surface formation, 15...Gasket for compensating shrinkage of the molded material.

Claims (1)

[Claims for Utility Model Registration] An upper mold for forming a lens surface for molding one lens surface of a plastic lens; A lower mold for forming a lens surface for molding the other lens surface of the plastic lens; , a plastic lens injection molding having a side wall surface for molding the circumferential surface of the plastic lens, and having an upper mold and a lower mold for forming the lens surface arranged to face each other, and formed by the opposing gap. A side surface forming gasket made of a highly rigid material and having an injection port for injecting a monomer of a plastic lens material into the mold, and a lens forming gasket disposed within this lens side surface forming gasket and used in both the upper and lower molds. A shrinkage correction gasket made of a highly elastic material, which tightly covers the periphery of the surface and the side wall surface of the lens side surface forming gasket, and integrates with the monomer when the monomer shrinks to compensate for the shrinkage; A mold for molding a plastic lens, characterized by comprising: