JPS59194817A - Method and apparatus for molding plastic lens - Google Patents

Abstract

PURPOSE:To obtain a high precision plastic lens by a method wherein monomer or prepolymer charged in a casting mold is prepolymerized in an atmosphere of inert gas under a reduced pressure and then polymerized and molded under pressure. CONSTITUTION:The cavity 36 of a casting mold 30 composed of a bottom force 32 with a lens molding surface 31 and a circular gasket 33 is charged with monomer or prepolymer 37 to which polymerization initiator is added, this casting mold 30 is installed in a molding container 20 and then a cover 21 is put closely on the opening of the container body 20a. Inert gas 27 is introduced from venthole 23 into the container, air is discharged from another venthole 24, they are replaced by each other, pressure is reduced in the container, the container 20 is heated by a band heater 26 to prepolymerize the prepolymer 37. Then, the inert gas 27 i introduced into the container 20 and compressed, heated to raise temperature. In this manner, the prepolymer 37 is polymerized and the shape of molding surface 31 can be transferred.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cast molding method for plastic lenses and an apparatus therefor. A casting mold having the desired lens surface shape to be molded is used once again, and while applying pressure from the side of the casting mold opposite to the lens molding surface, polymerize the monomer or sol polymer that will be the raw material for the plastic lens. By doing so, we can faithfully invert the lens surface shape of the lens molding surface of the cast mold, and provide high-precision plastic lenses that can be reused in optical equipment using the cast molding method. This is what I am trying to do.

In recent years, optical equipment lenses or eyeglass lenses made of glass have been attracting attention.

The reason for this is that plastic lenses have extremely excellent impact resistance and transparency, and are lightweight.

In addition, in recent years, glass lenses for eyeglasses such as fashion glasses have become popular, and this is also one of the factors spurring the increase in the range of applications for plastic lenses. When trying to obtain a similar lens, for example, if one were to manufacture a lens with a large diameter and sufficient breaking strength, it would be very expensive and heavy; This is because they are not suitable for use as lenses for eyeglasses, and there is an increasing demand for colored lenses to make them fashionable, such as in sunglasses, but it is not easy to tint glass lenses. In this respect, there are other reasons such as the fact that glass lenses can be colored relatively easily.

However, when molding this kind of plastic lens, do you use polycarbonate? They are manufactured by injection molding or compression molding of thermoplastic resins such as nates and polymethacrylates, or by cast molding.

In the commonly used cast molding method for plastic lenses, for example, the cast molding method described in JP-A-56-27327, optically finished surfaces ( A casting mold 1O is used, in which an upper molding mold 2 and a lower molding mold 3 having a lens molding surface 7.8 are attached via a spring flange 4, and one of the molding molds 10 is After removing the upper mold 2 and filling the cavity 5 with a plastic raw material such as a monomer, the upper mold 2 is again fitted onto the upper side of the gasket.
Both upper and lower molding molds 2 and 3 are clamped by a spring flange 4.

Thereafter, this is subjected to a treatment such as heating to harden the plastic raw material filled into the cavity 5 of the casting mold 10, thereby molding a plastic lens.

The gasket l used in this cast molding is made of a flexible material such as relatively soft synthetic resin such as rubber or elastomer, and the upper mold 2 for molding is usually made of glass.
The lower mold 3 is used in combination with the upper and lower sides of the gasket 1.

The plastic raw material such as the monomer is filled into the cavity 5 formed between the upper and lower molding molds 2 and 3, and the cavity 5 is sealed to prevent air from entering. Then, the casting mold 10 filled with the raw material is directly placed in a heating furnace or the like, and the glass raw material is polymerized and hardened. At this time, in order to reduce lens distortion and uniformly polymerize, curing often takes at least several hours, and usually more than one day and night.

Finally, remove the casting mold after cooling and take out the molded lens inside.
are often cut off, and gaskets) are not reused. On the other hand, the upper and lower molding molds 2.3 are often reused for the next casting molding.

In particular, the gasket l used in cast molding described in Japanese Patent Application Laid-open No. 56-27327 is provided with a slot z) 9(i) facing inward in the radial direction on its outer periphery.

However, when the gasket 1 softens due to the heat generated during the polymerization and curing cycle of plastic raw materials such as monomers, the upper and lower molding molds 2.3 will shrink according to the shrinkage of the plastic raw material (the shrinkage rate of CR-39 is about 13 inches). make an approach movement (therefore, 〃
The slit 1 must have sufficient elasticity so that when the plastic raw material shrinks, the upper and lower molds 2.3 can approach it in the 1/2 inch thickness direction, and the slit 1 must be able to reach the upper and lower molds 2.3 from the gasket wall 6 to 70. If the plastic raw material separates prematurely, it may cause distortion cracks or other damage to the lens, so the plastic raw material must adhere to the gasket to an appropriate extent. ), and due to the pressure applied by the clamp 4, the gasket ) falls inward in accordance with the shape of the plastic raw material after shrinkage, but normally shrinkage does not occur uniformly within the mold, and due to non-uniform shrinkage. When the polymerization and hardening are completed, it will be deformed as shown in FIG. If the gasket l is deformed in this way,
As shown in FIG. 3, the glass lens 5A completed by molding has an optical axis 0 of the upper and lower uneven surfaces 5a15b.
1102 no longer match, and the thickness of the lens 5A is 1. ．． 12 is also not symmetrical and uniform. As shown in FIG. After that, it is released from the casting mold by quenching or impact, and its shape becomes one in which the peripheral edge 5C is deformed as shown in Fig. 4 due to the above deformation effect, but the center It is used by trimming the portion as shown by the dotted line.

However, with the above-mentioned cast molding method using a thin gasket, even if there is some variation in thickness, such as in eyeglass lenses, or if there is some deviation in the optical axis of the vertically curved surface, it can be easily adjusted by eye. Lenses within this range can be molded without any practical problems, but it is impossible to obtain high-precision glass lenses such as those used in optical equipment such as cameras and grojectors.

In addition, even in eyeglass lenses, meniscus lenses with small dioptres have a small thickness deviation of Δ, but meniscus lenses with large dioptres, convex lenses, and concave lenses have large thicknesses at the center and outer diameter. So,
If the transfer reversibility with the upper F-type for molding is poor, or if pressure is forcibly applied using a spring clamp or the like, optical buds may occur inside the silastic lens.

In this way, the conventional cast molding method using a gasket-type casting mold is used to manufacture high-precision glass lenses used in eyeglass lenses that are prone to jittering, as well as optical instruments such as cameras and projectors. It is clear that it is not suitable for this purpose.

Therefore, the present invention solves the above-mentioned drawbacks of the conventional cast molding method, and makes it possible to mold high-precision plastic lenses that can be used for eyeglass lenses with strong diopters, or optical equipment such as cameras and glojectors. The purpose is to provide a molding method and an apparatus most suitable for carrying out the molding method.

The cast molding method for plastic lenses of the present invention will be specifically explained below along with examples using the illustrated cast molding apparatus.

FIG. 5 is a longitudinal sectional view of a cast molding apparatus directly used in the cast molding method of the present invention.

Now, in the figure, 20 is a molding container, and this molding container 20 is made of stainless steel. Alternatively, the container body 20a has a bottom and is made of a rigid material such as steel, and a lid 21 made of the same material is removably attached thereto.

Further, the lid body 21 has its outer edge 21a connected to the container body 2.
By tightening and fixing the tightening bolt 22 to the flange 20b protruding from the opening of the container body 2
The opening of 0a can be hermetically sealed, and the lid body 21 has two gas replacement ports 2 in the case shown in the figure.
3+ 24, and each gas replacement port 23° 24
An airtight frame 25 is removably attached to the frame. .

(The figure b'j shows a state in which one of the gas replacement ports 24 is removed and opened).

Furthermore, a band heater 26 is wrapped around the outer periphery of the container body 20a of the molding container 20, so that the container 20 can be heated.

30 is a casting mold, and this casting mold 30 has a lens molding surface 31.
It is composed of a lower mold 32 for molding integrally formed of a glass material as a casting part with
3 has a stepped portion 35 for engagement with the outer peripheral edge 34 of the lower die 32.
We have established.

When molding a plastic lens using the cast molding apparatus having the above configuration, first, a monomer containing a polymerization initiator, which is a raw material for the glass lens, is added to the cavity 36 of the casting mold 30. or prepolymer 3
After filling the required amount of 7, the cast shape 30 is placed in the molding container 20 as shown in FIG.

Moreover, the lid 21 that was removed when installing the casting mold 30 in the molding container 20 is again superimposed on the opening of the container body 20a, and this is used for fastening. By tightening with bolt 22,
The container main body 20a is sealed O. Next, an inert gas 27 such as nitrogen gas or carbon dioxide gas is gradually filled from one gas exchange port 23, and then the other gas exchange port 24 is filled with an inert gas 27 such as nitrogen gas or carbon dioxide gas.
After exhausting the air in the container 20 and no longer detecting oxygen in the exhaust gas, the other gas replacement port 24 is tightly plugged, and a decompression pump (not shown) is connected to one gas replacement port 23. The inside of the container 20 is placed under reduced pressure. Thereafter, the container 20 is heated by the band heater 26, and while the temperature is controlled, the polymerization of the monomer or prepolymer in the casting mold 30 is advanced to perform preliminary polymerization. In this prepolymerization stage, the polymerization temperature is low (35°C or less) and the polymerization time is about 8 hours. The purpose is to deaerate the deposit and deposit the raw materials to advance the volumetric contraction.

Meanwhile, the pressure reduction pump attached to the gas 1" outlet 23 is switched to pressurization rj5 pump 0, and pressure is applied inside the container 20 to place the inside of the '41 tn420 under high pressure. The gas used for one cycle at this time must be the above-mentioned inert gas f'L.

In this state, the heating temperature of the container is raised to change the conditions depending on the polymerization initiator used, but the temperature is raised to around 7 (]°C, and the monomers in the mold 30, 'gi7ζ, are used to polymerize the prepolymer. Complete the process.Then, exchange to the sword 23
After removing the pot tray attached to the pot, return the inside of the container 20 to normal pressure, take out the casting mold 30 inside the container 20, and apply after-cure to complete the first cup. In this lens molding method, the monomer or prepolymer in the cavity 36 is heated due to reaction heat at the initial stage of the reaction as the reaction is accelerated, but as the polymer is converted, Transition to contractile behavior. When this polymer shrinks, the container 2
Since the inside part 0 is under pressure, the lower die 32 is encouraged to follow the lens molding surface 31 in a volimano manner. Incidentally, the reaction associated with polymer conversion often causes a temperature difference between the periphery and the center, which appears as a time difference between solidification and shrinkage, but since the inside of the container 20 is under pressure, no amount of polymer It is possible to mold a glass lens in which the lens molding surface 31 of the lower mold 32 is faithfully inverted depending on the state of contraction.

In addition, in the conventional cast molding method using the rigid cast member 130 on both sides, uneven transfer and internal distortion occur due to the reaction mechanism described above, but as mentioned above, according to the molding method of the present invention, the lens molding surface can be faithfully formed. can be transferred and molded into a glass lens without optical distortion.

Furthermore, in a reaction system that generates heat during conversion of a monomer or prepolymer into a polymer, differences in reaction temperature occur locally in the case of lenses with uneven thickness. For this reason, the solidification of the polymer conversion block is uneven depending on the location of the lens, and to counter this uneven solidification, the two opposing sides are inverted using a casting mold having a rigid lens molding ring 31. If one side of the casting mold is separated from the molded object during the polymer conversion process, enough pressure is applied by squeezing it or using a spring crane, etc. to completely transfer the molding. Distortion remains inside the object without optically adversely affecting it. On the other hand, according to the molding method of the present invention, an inert gas 27 which itself can change its shape freely in response to volumetric contraction of the lens due to polymer conversion is used as a part to seal one surface of the lens.
By pressurizing the gas in the container 20 and pressurizing the lens, the shape of the molding surface of the casting mold 30 with M of at least one desired lens molding surface 31 is made faithful to the molded product. It is possible to obtain a molded product that is inverted and free of optical distortion.

FIG. 6 is a longitudinal sectional view showing a cast molding apparatus used in the second embodiment of the molding method of the present invention.

The cast molding apparatus shown in the figure is comprised of the lid 2. This device differs in that it is constructed by providing a glass window 28 for UV polymerization, and the other components are the same as the cast molding device shown in Figure 5, so the same numbers are given and explanations are given. Omitted.

Therefore, in order to mold a glass lens using such an apparatus, first, as in the first embodiment, a casting mold 30 filled with the necessary amount of raw materials for gelaste and cremme is placed in a container 20, and then a lid body 21 is placed inside the container 20. of? Attach to the container 20 with the seat 22,
The air in the container 20 is replaced with an inert gas 27. container 2
When there is no more oxygen in the container 20, the other gas replacement port 24 is tightly plugged, and a vacuum pump is connected to one gas replacement port 23 to place the inside of the container 20 under reduced pressure.

Prepolymerization is carried out by heating the container 20 from the strainer using a band heater 26 as a heat source and proceeding with polymerization while controlling the temperature. The preparation method for this preliminary polymerization can be carried out in the same manner as in the first practical example.Next, the pressure reduction pump attached to the gas replacement port 23 is switched to a pressure pump to apply pressure inside the container 20. The inside of the container 20 is placed under high pressure. The gas used at this time must be an inert gas as in the first embodiment. In this state, the polymer or prepolymer filled in the cavity 36 of the casting mold 30 is irradiated with an ultraviolet lamp through the glass window 12 to polymerize it. At this time, the temperature inside the container 20 is kept constant at a low 11111 I&C, and polymerization proceeds while controlling the temperature.

A glass lens can be obtained by taking out the polymer solidified in this manner from the container 20 in the same manner as in the first embodiment, and further performing after-curing to complete the polymerization. In the polymerization method in this second embodiment, the surface in contact with the inert gas is not completely smooth in the case of polymerization by heating according to the first embodiment, but by performing ultraviolet polymerization, it becomes extremely beautiful. A surface is obtained.

In the second embodiment, as in the first embodiment, the lens molding surface 31 can be faithfully reversed, and a glass lens without distortion can be molded.

The glass lens molded by the molding method of the present invention has a lens molding surface 31 of a casting mold 30 on one lens surface.
is faithfully reversed, and by performing secondary processing such as polishing or cutting on the other side, a highly accurate gelastic lens can be obtained.

Now, as is clear from the above explanation, according to the cast molding method of the present invention, monomers or prepolymers, which are raw materials for plastic lenses, are placed in an inert gas atmosphere IW, T, in a sealed container inner plate. As the lens surface shape of the casting mold is transferred to the molded product by polymerization, the desired lens surface shape can be faithfully transferred to the molded product even with the volume shrinkage that occurs when a monomer or prepolymer is converted into a polymer. In addition, the cast molding method of the present invention uses the lens body as a member to seal one side of the lens due to polymer conversion. 1# By using a gas that can change its shape freely in response to shrinkage, and by pressurizing the lens through the gas, the molded product is faithfully turned into a casting mold with the desired lens surface shape. At the same time, it is possible to mold a molded article without optical distortion.

Moreover, the plastic lens molded by the cast molding method of the present invention has one side with a high vitreous lens surface shape that could not be achieved conventionally, and the other side has the entire lens shape formed by grinding, grinding, or cutting. By the cast molding method of the present invention, it is possible to easily obtain a large quantity of a plastic lens having an aspherical surface on one surface, which is difficult to perform in post-processing.

Furthermore, in order to improve the transferability even a little, we added 1.
Compared to the conventional casting method, which takes a long time to heat the reaction to 5 temperatures, by using gas on one side, the gas can freely absorb the difference in molding shrinkage depending on the location, and the reaction takes a short time. It has the advantage of being able to advance .

Heat the appetizer under pressure in an inert gas atmosphere.
In contrast, in the case of molding by ultraviolet polymerization, the surface in contact with the inert gas can be molded with an extremely beautiful surface. This apparatus has the advantage of being able to accurately carry out the cast molding method of the present invention.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a casting mold used in the conventional cast molding method, Figure 2 is a vertical cross-sectional view showing the deformed state of the gasket in the casting mold shown in Figure 1, and Figures 3 and 4 are 1 shows a vertical cross-sectional view and a plan view showing a glass lens molded using the casting mold shown in FIG. FIG. 3 is a vertical cross-sectional view showing the first and second embodiments. 20... Container for molding, 20a... Container body, 20b
...7 lunge, 21...lid body, 22...for tightening?
route, 23.24... gas replacement port, 25... airtight frame, 26... band heater, 27... inert gas, 28... glass window, 30... casting mold, 31...
Lens molding surface, 32... Lower mold for molding, 33... Gasket, 34... Outer periphery, 35... Step part for engagement, 3
6... Cavity, 37... Raw material for plastic lenses. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Child thread δi'ilf -i'3 FKI'<+'≧1
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X+2 k Ming's name l11, Tsuno 1. f,,, Note 41v of Silens 11 and Law and Shishi 1lVt:l, i'+li + to "irusha'I"
lf'1. Takenoseki 11. To the first-generation hitter of No. 2, 2-43i, Hatagaya, Hatagaya, Shibuya-ku, Ura 11-, χ1f4!Details fJ, explanation, 1+, t
1 and Drawing 7 Contents of correction (1) 1. This type of plastic ivy lens in the 1st row of the 5th giant. (2) In the drawing, No. 331A is corrected as shown in the attached corrected drawing. 8 Attached Documents Item 1 List (1) ?+li +l-Drawing 1 83 Figure 3

Claims (1)

[Scope of Claims] (1) A monomer or a blend polymer, which is a raw material for a plastic lens filled in a casting mold, is prepolymerized under reduced pressure in an inert gas atmosphere, and then polymerized under pressure, and the A gaze molding method for glass lenses characterized by molding while transferring the lens surface shape of a cast mold. (2) After prepolymerizing the monomer or bleed polymer that is the raw material for the plastic lens filled in the casting mold under reduced pressure in an inert gas atmosphere, it is polymerized with ultraviolet light under pressure and the lens of the casting mold is formed. A cast molding method for glass and tic lenses, which is characterized by molding while completely transferring the surface shape. (:() The cast molding method for a plastic lens according to claim 1 or 2, wherein the prepolymerization is performed at a polymerization temperature of 35° C. or lower for about 8 hours. 4) A cast molding method for a plastic lens according to claim 1, wherein the polymerization is carried out by heating. (5) The inert gas atmosphere is nitrogen gas, carbon dioxide gas, or other inert gas. A cast molding method for plasti and cremme according to claim 1 or 2, characterized in that the cast molding method comprises an active gas. A lid body is provided with a plurality of gas exchange ports, which airtightly accommodates a mold made of an annular gasket that is fitted around the outer periphery of the casting part and an annular gasket that is fitted and fixed to the outer periphery of the cast part. A cast molding device for a silastic lens characterized by comprising a molding container and a heating means for heating a molding device. (7) A cast part having a required lens molding surface. a plurality of gas exchange ports and an ultraviolet polymerization method, the casting mold having a ring-shaped gasket fitted around the outer periphery of the cast part; An apparatus for cast molding of plastic lenses, characterized in that it is comprised of a molding device having an i-body provided with a glass window for molding, and a heating means for completely heating the molding container. (8) The heating means The device for molding a plastic lens according to claim 6 or claim 7, wherein the device is constituted by a band heater wrapped around the outer periphery of the container body of the molding container.