JP2006281614A - Method and device for injecting plastic raw material and plastic lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence of foam due to the shock caused at the time of injection of a plastic raw material. <P>SOLUTION: A casting mold 8 is arranged so that its injection port 85 becomes an upper side to insert a plastic raw material injection nozzle 7 in the injection port and the plastic raw material ejected from the nozzle is injected in the casting mold while dripped therein using gravity. At the time of injection of the plastic raw material, the casting mold is inclined by a necessary angle with respect to a vertical direction so that the plastic raw material dripped in the casting mold is dripped on the optical surface of either one of a pair of the molds within the casting mold. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic raw material injecting method, a plastic raw material injecting apparatus, and a plastic lens that are used when molding spectacle lenses and other plastic lenses.

    For example, a plastic lens used as a spectacle lens or the like is generally manufactured by molding using a plastic lens molding mold. In this molding, a thermosetting monomer or the like as a raw material is injected into a plastic lens molding mold, and the raw material in the mold is heated and polymerized to be cured. Injecting the raw material into the molding mold, the plastic raw material is transported from the raw material tank for storing the plastic raw material to the molding mold through the raw material transport channel, and an injection nozzle provided at the tip of the raw material transport path is used for the molding mold. Injection is performed by inserting it into the inlet and dropping it into the mold mainly using gravity (see Patent Document 1 and Patent Document 2).

By the way, when the raw material is dropped into the mold, if the liquid raw material collides with the bottom surface or the liquid surface of the mold, the surrounding air may be taken in to form bubbles. For this reason, the injection port is formed close to the eyeball side lens surface forming mold (hereinafter sometimes referred to as “eyeball side mold”), and the convex portion of the optical surface of the eyeball side mold is located inside the mold. Attempts have been made to prevent the liquid from entraining bubbles by dripping the protruding surface so that the raw material is transmitted using the protrusion (see Patent Document 3).
JP2002-18866 JP2004-142429 JP 10-264178 A

  However, if the injection port is formed close to the eyeball side mold side, when the nozzle is inserted into the injection port, the tip of the nozzle may come into contact with the optical surface of the mold and may be damaged. For this reason, it is necessary to bring the injection port close to the object-side lens surface forming mold (hereinafter sometimes referred to as “object-side mold”) by a necessary distance so as not to damage.

  However, in that case, if the distance between the optical surfaces of the eyeball side mold and the object side mold is large, the raw material cannot be filled along the side surface inside the mold, and bubbles are generated by injection. Inconvenience occurs.

  The present invention has been made under such a background, and a plastic raw material injection method and a plastic raw material injection method capable of reducing the generation of bubbles due to impact during injection by a very simple method. It is another object of the present invention to provide a plastic lens manufactured by using these apparatuses or methods.

As means for solving the above-mentioned problem, the first means is:
A plastic raw material injection method for injecting a plastic raw material into a plastic lens molding mold,
As the molding mold, a pair of glass molding dies each having a lens forming optical surface are arranged so that the lens forming optical surfaces face each other at a predetermined interval, and portions other than the portions surrounded by these glass molding dies Among them, using a molding mold that closes except the part that becomes the injection port,
The molding mold is placed with its injection port facing upward, a plastic raw material injection nozzle is inserted into this injection port, and the plastic raw material ejected from this nozzle is dropped into the molding mold using gravity. Like injecting,
In the injection, the plastic raw material dropped into the molding die is dropped onto the lens surface forming optical surface of one of the pair of molding dies in the molding die. A plastic raw material pouring method characterized in that a molding mold is inclined at a necessary angle with respect to a vertical direction.
The second means is
The molding mold is provided with an inlet at a position close to the molding die disposed opposite to the molding die having an optical surface to which the raw material is dropped from the pair of molding dies. The plastic raw material injection method according to the first means is characterized in that there is.
The third means is
The plastic mold injecting method according to the first or second means, wherein the molding mold is one in which the pair of glass molding dies are housed and disposed inside a cylindrical gasket.

The fourth means is
A plastic raw material injection device for injecting a plastic raw material into a plastic lens molding mold,
The molding mold has a pair of glass molding dies each having a lens forming optical surface arranged so that the lens forming optical surfaces face each other at a predetermined interval, and a portion other than a portion surrounded by the glass molding dies. Among them, it is a molding mold that closes except the part that becomes the injection port,
A positioning device for arranging the molding mold so that its injection port is on top;
An injection nozzle that is inserted into this injection port to inject plastic raw material into the mold, and is dropped into the mold using gravity and injected;
In the injection, the plastic raw material dropped into the molding die is dropped onto the lens surface forming optical surface of one of the pair of molding dies in the molding die. An apparatus for injecting a plastic material, characterized in that it has a tilting device for tilting a molding mold by a necessary angle with respect to a vertical direction.
The fifth means is
A plastic lens formed into a lens shape by injecting a plastic raw material into a molding mold, and the plastic raw material injection method according to any of the first to third means is used during the molding step. It is a plastic lens characterized by being manufactured.
The sixth means is
A plastic lens formed into a lens shape by injecting a plastic raw material into a molding mold, and manufactured using the plastic raw material injection apparatus according to the fourth means in the molding step. It is a plastic lens characterized by being.

    According to the above-described means, the raw material is injected into the eyeball during the raw material injection even when the distance between the optical surfaces of the eyeball side mold and the object side mold is large by dropping the mold at a predetermined amount. It can be dropped on the optical surface of the side mold. Thereby, generation | occurrence | production of the bubble by the impact at the time of injection | pouring can be reduced.

  FIG. 1 is a block diagram showing an overall configuration of a plastic raw material injecting apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a raw material conveyance path and a control connection state of the plastic raw material injecting apparatus shown in FIG. 1 is a partial perspective view of the plastic raw material injection apparatus shown in FIG. 1, FIG. 4 is a view showing a roller pump, FIG. 5 is a view showing an injection nozzle, FIG. A is a plan view, and FIG. FIG. 6 is a diagram showing a plastic lens molding mold, FIG. 7 is a flowchart showing a plastic lens manufacturing process, FIG. 8 is an explanatory diagram showing an injection state of a plastic raw material, and FIGS. 9 and 10 show an injection state of the plastic raw material. FIG. 11 is an explanatory diagram of the generation of bubbles during the injection of the plastic raw material. Hereinafter, the best mode for carrying out the present invention will be described with reference to these drawings, but the present invention is not limited thereto.

  The plastic raw material injection apparatus shown in FIG. 1 is an apparatus that makes it possible to inject plastic raw materials from a raw material tank into a number of molding molds simultaneously. In FIG. 1, the code | symbol 1 is a raw material tank which stores the prepared plastic raw material. The raw material tank 1 is configured so that the internal pressure can be appropriately pressurized by the pressurizing device 2. Further, the raw material tank 1 is connected to a pipe body 101 that constitutes a raw material transfer flow path, and this pipe body 101 is connected to a first branch portion 102 and branched into a plurality of branch pipes 103, 103,. The Each branch pipe 103 is connected to each of a plurality of second branch pipe sections 104, and the first filter 3 is interposed in the middle thereof.

    The second branch pipe section 104 is branched into a plurality of branch pipes 105, and the roller pump 4 is connected to the end of each branch pipe 105. The roller pump 4 is connected to the second filter 6 through an open / close valve 5. A connection pipe 107 is connected to the outlet of the second filter 6, and the injection nozzle 7 is connected to the tip of the connection pipe 107. A plastic material is injected from the injection nozzle 7 into the plastic lens mold 8. As shown in FIG. 2, the pressurizing device 2, the roller pump 4, and the opening / closing valve 5 are appropriately controlled by a control circuit 9. Further, as shown in a partial perspective view in FIG. 3, the roller pump 4, the on-off valve 5, the second filter 6, and the injection nozzle 7 are mounted on the base 1000 via various mounting members and necessary drive mechanisms. Attached to and fixed.

  The molding mold 8 is transferred by a transfer device 803 (see FIG. 9) or the like and can be positioned by positioning and fixing devices 801 and 802. The injection nozzle 7 has a horizontal movement device 701 and a vertical drive device. The vertical position and the horizontal position can be moved by 702, and the inclination angle can be adjusted by the inclination adjustment mechanism 703.

(Raw material tank)
The raw material tank 1 is a closed tank provided with a stirring device and a cooling device. As the stirring device, a known device that rotates a magnetic rod with an external magnetic field can be used. Moreover, as a cooling device, what surrounds the circumference | surroundings with a jacket and cools the jacket with cooling water can be used. The internal pressure can be arbitrarily changed by the pressurizing device 2. In the present embodiment, the pressure is set to be larger than the atmospheric pressure, and the pressure in the plastic raw material transfer channel is set to a positive pressure with respect to the atmospheric pressure, thereby obtaining a specific effect. However, depending on the type of raw material and other conditions, it may not be necessary to pressurize.

(Raw material transfer channel)
The conveyance passages such as the pipe body 101, the plurality of branch pipes 103, the plurality of branch pipes 105, and the connection pipe 107 are formed of a tubular elastic body. The tubular elastic body is selected in consideration of the characteristics of the plastic raw material, chemical resistance, elastic function, economy, and simplified piping. In this embodiment, a general-purpose silicon tube is used. The inner diameter of the silicon tube is 6 mm, the outer diameter is 8 mm, and the thickness for forming the tubular portion of the silicon tube is 1 mm. The inner diameter, outer diameter, thickness, and the like are selected according to the plastic raw material, but preferable ranges are 4 to 8 mm for the inner diameter, 6 to 14 mm for the outer diameter, and 1 to 3 mm for the thickness. Other materials include polyolefin tubes, nylon tubes, urethane tubes, fluorine tubes, rubber tubes, and the like.

(First and second filters)
The first filter 3 is mainly intended for filtering impurities and foreign matters in plastic raw materials containing small particles. Therefore, as the first filter 3, a filter having a large filtration area and a high filtration function capable of removing impurities having a predetermined size is used. On the other hand, the second filter 6 provided at the tip of the valve 5 is provided with a coarse filter having lower filtration performance, less clogging, and less pressure loss than the first filter. That is, the filter arrangement in this embodiment is an arrangement opposite to the common sense arrangement. This is the first proposal by the inventor of the present invention. Impurities and foreign matters contained in the plastic raw material itself are sufficiently removed by the first filter having a high filtering performance, and the second filter is not an impurity contained in the raw material itself. In addition to removing the relatively large foreign matter that may occur in the roller pump or the like, the roller pump has a role of suppressing the pulsation of the roller pump. As a result, foreign matter is not included, and pulsation is extremely small, enabling extremely stable injection.

    Here, in general, the filter is disposed for the purpose of removing impurities in the raw material and preventing foreign matters from being mixed into the molded product. The filter is generally arranged immediately after a supply tank that is a raw material supply unit or before an injection nozzle that is a discharge unit. In that case, the filter is selected according to the size of the impurity to be removed. However, the filter that removes small particles is clogged with impurities, and the filtration function tends to deteriorate. For this reason, it is common to avoid clogging by installing two or more types of filters in series, removing large particles with the first filter, and sequentially filtering small particles. In that sense, the filter arrangement of the present embodiment is opposite to the common sense arrangement.

    Furthermore, to explain, the second filter 6 arranged on the injection nozzle side has two purposes. One reason is to filter and remove dust generated inside the piping generated by opening and closing the roller pump 4 and the valve 5. The dust generated from these is larger than the fine foreign substances originally contained in the raw material. The second is to eliminate the pulsation caused by the roller pump and maintain a stable flow rate. That is, the second filter 6 is disposed for both the filtration function and the purpose of suppressing the pulsation of the pump. Here, if the second filter 6 is given priority to the filtration function in the same manner as the first filter 3, the control accuracy of the injection amount is lowered. When the filtration function of the second filter 6 is high, the liquid feeding from the pump is held until a certain pressure is reached, and is discharged when the certain pressure is exceeded. Therefore, when a filter having a high filtering function is interposed between the pump and the injection nozzle, the injection is not started immediately after the pump starts feeding the liquid, and the injection is not completed even when the pump is stopped. Furthermore, a filter with a high filtration function is easily clogged, and the pressure loss changes greatly, and the time difference between the pump operation time and the actual injection time cannot be qualitatively understood. Since this time difference lowers the control accuracy of the injection amount, the flow rate cannot be controlled by the roller pump.

    Thus, in the present embodiment, with regard to the filtration, the first filter 3 having a high filtration performance is sufficiently performed, and the second filter 6 is mainly intended to suppress pulsation, and the filtration performance is a secondary purpose. did. And the 2nd filter 6 arrange | positions the coarse filter which has low filtration performance, is hard to clog, and has little pressure loss. In the present embodiment, in the injection apparatus configured to inject simultaneously into 12 molding molds, the first filter 3 for filtering the spilled resin system has a filtration function of 0.1 to 10 microns and a pressure loss of 5 to 5 100 KPa (at 10 L / min) is used as the second filter 6 with a filtration function of 1 to 25 microns and a pressure loss of 0.1 to 5 KPa (at 10 L / min).

    In the case of a plastic raw material different from the above, for example, in a polythiourethane system, the first filter 3 has a filtration function of 1 to 10 microns and a pressure loss of 5 to 50 KPa (at 10 L / min) as the second filter 6. Has a filtration function of 3 to 25 microns and a pressure loss of 0.1 to 2 KPa (at 10 L / min).

(Roller pump)
The roller pump 4 conveys a conveyed product in the tubular elastic body by moving the roller and crushing a position while crushing a part of the tubular elastic body with a rotating roller. In other words, the pump gives a flow in a certain direction to the raw material by squeezing the elastic pump tube while rotating the roller. In general, the roller pump 4 sucks the raw material to be sent next by the negative pressure when the elastic tube closed by the roller restores its shape to the original shape. FIG. 4 is a sectional view of the roller pump 4 according to the embodiment. The roller pump 4 is respectively connected to six roller shafts 44a that are spanned and fixed at equal intervals around the outer peripheral end portions of the two disc bodies 40, 40 provided to face each other with a gap therebetween. Six rollers 44 are rotatably supported, and these disk bodies 40 and 40 fixed integrally are rotatably supported by a shaft 41. Further, the cover member 43 having a substantially semi-cylindrical shape is arranged and fixed so as to wrap the three rollers arranged on the lower side among the six rollers 44, and the three rollers 44 and the cover member 43 are A tubular elastic body 42 is interposed therebetween.

    The raw material is conveyed by the roller pump 4 as follows. First, the plastic raw material supplied from the raw material tank 1 is filled into the tubular elastic body 43, and the entire roller pump rotates around the central shaft 41 in the filled state. With this rotation, the rollers 44 supported by the two disc bodies 40 press and seal a part of the tubular elastic body 42. When the roller pump further rotates, the roller 44 also seals a part of the tubular elastic body 42, and forms a space for holding the raw material in the tubular elastic body between the roller 44 and the adjacent roller 44. The roller 44 moves while maintaining this space, whereby the raw material is conveyed. Since the space sealed between the rollers 44 is always a constant amount, the conveyance amount of the raw material can be controlled according to the number of rotations of the roller pump 4. That is, in the roller pump 4, a plurality of rollers 44 arranged at regular intervals move while pressure-bonding the tubular elastic body 42 to send out a predetermined amount.

(Open / close valve)
The on-off valve 5 is disposed before the plastic material passes through the second filter 6. The on-off valve 5 is for starting and stopping the injection of the plastic raw material. The on-off valve structure of the valve 5 promotes solidification of the plastic raw material and may become a source of impurities, but the solid matter generated by the on-off valve 5 is removed by the second filter 6 and molded together with the raw material. It is not injected into the mold.

(Injection nozzle)
5A is a plan view of the injection nozzle 7, and FIG. 5B is a cross-sectional view taken along the line aa of FIG. 5A. As shown in the figure, the injection nozzle 7 covers a nozzle main body 71 made of metal and a large part of the nozzle main body 71, and also covers an area protruding from the tip portion 712 of the nozzle main body 71 by a predetermined distance. The resin covering 72 is made up of. The nozzle main body 71 has a hollow structure in which a base end portion 711 is formed in a circular tube shape and is flattened in a stepwise manner toward the tip end portion 712. That is, the region 713 following the base end portion 711 is flattened slightly abruptly, and the next region 714 is flattened gently.

    The outer thickness of the opening of the tip 712 of the nozzle body 71 is 1.1 mm, the inner thickness of the opening is 0.5 mm, and the width is about 9 mm. In addition, the preferable dimension range of the opening part outside thickness of the front-end | tip part 712 is 0.5-5 mm, the preferable dimension range of the opening part inside thickness is 0.3-4.6 mm, and the preferable dimension range of a width | variety is about 2-25 mm. The injection nozzle 7 of the present embodiment is wider than the conventional circular injection tube type, and ensures a large sectional area of the opening of the injection nozzle. Therefore, a sufficient flow rate and injection rate can be ensured.

    Further, the resin coating 72 covers almost the entire nozzle body 71 except for a part of the base end portion 711 of the nozzle body 71, and has a tubular shape in which the inside is hollow and both ends are openings. It has a flat shape in close contact with the metal so that it has a similar shape to the injection nozzle. Further, the resin coating 72 protrudes further in the distal direction than the distal end 712 of the nozzle body 71. Further, the protruding portion of the resin coating has a hollow shape that extends the flat tubular shape of the tip portion 712 of the nozzle body 71, and the tip portion is open. The protruding portion of the resin coating has a predetermined length depending on the molding mold to be inserted, but in the case of the present application, it is, for example, about 3 to 7 mm. The outer thickness of the resin tip is 0.6 to 0.9 mm, the inner thickness of the resin tip is 0 to 0.6, and the width is 9.6 mm. It should be noted that the tip of the resin coating 72 is always closed in a standby state where the raw material is not fed, and the opposite resin is separated only when the raw material passes through the inside, and the tube shape may have a cross-sectional area inside. it can. If it does in this way, the role of an automatic on-off valve can also serve as a tip part.

    The resin used as the material of the resin coating 72 is made of a material that does not easily damage the optical surface of the molding mold. For example, a fluorine resin, a polyolefin resin, a synthetic rubber, and the like are suitable, and a tetrafluoroethylene-6fluoropropylene copolymer resin is suitable. The tetrafluoroethylene-6fluoropropylene copolymer resin is characterized by causing thermal seeding at a shrinkage temperature of 120 ° C. In the present embodiment, a resin coating is formed on the metal nozzle body 71 by utilizing this heat shrinkage property.

    In the method of manufacturing the resin coating according to the present embodiment, the metal nozzle main body 71 is formed from a tubular tetrafluoroethylene-6fluoropropylene copolymer resin having both ends open and cut to a predetermined length. Cover the tip of the. In a state where the tubular heat-denatured resin is placed on the metal nozzle body 71, heat treatment is performed at 120 ° C. or higher in an electric furnace. The heat-shrinkable resin shrinks to the shape of the metal nozzle body 71 and adheres and stabilizes to the metal nozzle body 71. Moreover, when a thin plate is inserted into the opening of the metal nozzle body 71 and heat treatment is performed, the opposing surfaces of the protruding tip portions of the resin coating 72 can be processed into a closed state. Further, the tubular thermal tetrafluoroethylene-6fluoropropylene copolymer resin is characterized by excellent solvent resistance and high flexibility.

    Depending on the type of spectacle lens, the distance between the molds is extremely small, and the injection port of the mold may have a gap of about 1 mm. The injection into the mold is generally performed by an injection tube such as an injection needle, and metal is suitable for manufacturing an injection tube having an outer thickness and an outer diameter of about 1 mm. However, the glass mold is easily damaged when the metal comes into contact with the glass that is the mold. Scratches are also transferred to the molded product from the mold. Furthermore, in accordance with the generation of scratches, glass fragments are mixed into the molding mold, and the glass fragments float at an arbitrary position of the molded product and are recognized as foreign matters. In order to avoid these problems, a soft resin injection nozzle other than metal is suitable. However, it is difficult to manufacture a resin injection tube having a hollow structure with an outer diameter of about 1 mm, and the cost increases. Furthermore, it is more difficult to manufacture a resin injection tube having a hollow structure that is thin and has a width that is about 10 times the thickness of the injection nozzle of the present application.

(Plastic lens molding mold)
FIG. 6 is a sectional view showing a plastic lens molding mold. As shown in the figure, this plastic lens molding mold 8 is a mold for molding a plastic spectacle lens by a manufacturing method called a casting method, and a molding die 81 (hereinafter referred to as an optical surface on the object side). (Also referred to as an upper mold), a mold 82 (hereinafter also referred to as a lower mold) that forms an optical surface on the eyeball side, and a gasket 83. The upper mold 81 and the lower mold 82 are collectively referred to as a lens matrix.

  The gasket 83 is formed in a cylindrical shape with an elastic resin, and holds the upper mold 81 and the lower mold 82 on the inner peripheral surface with a predetermined distance therebetween in a liquid-tight manner. A molding mold (hereinafter also referred to as a cavity) 84 is configured by being surrounded by the upper mold 81, the lower mold 82 and the gasket 83. The gasket 83 is integrally provided with an injection portion 85 for injecting the raw material of the optical lens into the cavity 84. The height of the gasket 83 is set to a dimension that can secure the thickness of the peripheral edge of the optical lens that is a molded product.

  The upper mold 81 and the lower mold 82 are made of glass or the like. The molded lens mainly targeted by the present embodiment has a meniscus shape. The upper mold 81 is formed in a concave shape so as to form a curved surface (convex surface) of the optical lens. The lower mold 82 is formed in a convex shape so as to form a curved surface (concave surface) of the optical lens. In these upper mold 81 and lower mold 82, as shown in FIG. 6, the surface that forms the lens curved surface of the optical lens is referred to as a use surface 86, and the surface that does not form the lens curved surface is a non-use surface 87. Called. A part of the gasket 84 is provided with an injection port 85 for injecting material. The inlet is sufficiently large with respect to an injection nozzle 7 described later. Further, a receiving port 85a having a hopper-like taper structure for guiding the injection nozzle 7 to the injection port 85 is provided so that the injection nozzle 7 is reliably inserted into the injection port 85.

(Manufacture of plastic lenses)
Next, a procedure for manufacturing a plastic lens for spectacles using the above-described plastic lens raw material injection device will be described with reference to FIGS. First, a raw material for the plastic lens is prepared. In this embodiment, the raw material is a thermosetting resin, which is prepared by adding a catalyst and an ultraviolet absorber to the resin, and filtered through a filter. The blending is first performed in the raw material tank 1 which is a sealed tank equipped with a stirring device and a cooling device. The raw material tank 1 is cooled by passing cold water of 5 ° C. through the jacket of the raw material tank 1.

    Next, 4.000 kg of 1,3-diisocyanatomethyl-cyclohexane cooled to 5 ° C. is weighed, and 2- (2′-hydroxy-5′-t-octylphenyl) benzotriazole (Cypro Chemical) is used as an ultraviolet absorber. 19.0 g of Seesorb 709), 29.0 g of butoxyethyl acid phosphate (JP-506H, Johoku Chemical Co., Ltd.) as a release agent, and 81.0 g of dimethyltin dichloride as a polymerization catalyst are added and stirred for 20 minutes. By this stirring, each additive is dissolved in 1,3-diisocyanatomethyl-cyclohexane to form a uniform solution.

    Next, 4.557 kg of 1,3-diisocyanate methyl-cyclohexane is added. To this, 4.764 kg of pentaerythritol tetrakis- (2-mercaptoacetate) and 4.679 kg of 2,5-dimercaptomethyl-1,4-dithiane cooled to 5 ° C. were added, respectively, and the tank was sealed and stirred for 10 minutes. . Stirring is once stopped, the raw material tank 1 is connected to a vacuum pump, and vacuum degassing is started. Stirring was started while confirming the foaming state of the internal monomer composition, and when the stirring speed was gradually increased, the degree of vacuum was stable at 40 Pa. This is maintained for 30 minutes, vacuum degassing is performed, and then the pressure is returned to normal pressure to finish the monomer composition preparation step.

    Thereafter, the inside of the raw material tank 1 is immediately pressurized with 0.3 kgf of dry nitrogen by the pressurizer 2. The raw material tank 1 that has been blended is maintained in a state where the internal pressure is about 0.5 to 1.0 kg / Cm and the temperature is about 5 ° C. to 10 ° C., for example. In addition to the above, the plastic lens produced in the present embodiment and its raw material include, for example, a copolymer of methyl methacrylate and one or more other monomers, diethylene glycol bisallyl carbonate and one or more other Copolymers with monomers, polycarbonates, polystyrenes, polythiourethanes, spilled resins using ene-thiol reaction, vinyl polymers containing sulfur, and the like are not limited thereto.

  Next, the upper mold 81 and the lower mold 82 are assembled to the gasket 83 to assemble the plastic lens molding mold 8. Next, the plastic raw material prepared as described above is injected into the cavity 84 of the mold 8. This injection process is as shown in FIGS. First, the mold 8 is conveyed to a predetermined position of the injection device by the transfer device 803 (FIG. 8a). Then, the mold 8 is held between the positioning portions 801 and 802 and held at the injection position (FIG. 8b). Further, the injection nozzle 7 and the liquid level sensor 7a are lowered and stopped at a predetermined position of the mold 8 (FIG. 8c).

    The injection receiving port 85a has a hopper-like taper structure, and the injection nozzle 7 is accurately guided to the injection port 85. When the valve 5 is opened, the roller pump 4 is rotated and the injection device injects at a predetermined speed. On the other hand, depending on the type of the mold 8, the mold 8 and the injection device are tilted for injection (FIG. 8 d). When the liquid level reaches the injection port and is detected by the liquid level sensor 7a, the roller pump 4 is stopped and the injection is terminated. When the injection device is tilted, it returns to the original vertical posture, the injection nozzle 7 and the liquid level sensor 7a are slightly raised to the vicinity of the center of the injection port receiving port 85a, and an appropriate amount of additional injection to the injection port receiving port 85a is performed (FIG. 8e). ).

    The additional injection is for preventing air suction due to shrinkage of the material itself during the raw material polymerization process. For this purpose, in addition to the filled material inside the mold 8, the material is filled into the inlet 85 a outside the mold 8. When the additional injection is completed, the injection nozzle 7 and the liquid level sensor 7a rise and return to the standby position (FIG. 8f). When the injection is completed, the positioning devices 801 and 802 holding the mold 8 are opened and transferred to the next process by the transfer device 803. At the same time, the empty mold 8 is transferred to the state shown in FIG. 8a. Thereafter, the injection is continuously performed by automatically repeating FIGS. 8a to 8f.

  Here, in the above-described injection step, the case where the injection is performed while the molding mold 8 and the injection device are inclined will be described with reference to FIG. The foam 800 in the mold 8 is first generated when the raw material comes into contact with the mold or gasket. Second, air is left behind as the liquid level rises. Third, when the raw material is injected from above, the raw material falls on the liquid surface and is generated due to a turbulent flow like a waterfall (see FIG. 9A). As an effective method for suppressing the generation of bubbles, there is a method of reducing the injection speed as a known technique, but this causes a decrease in productivity and causes an increase in cost.

    Therefore, in the present embodiment, the above problem is solved by tilting the holding posture of the molding mold 8 at the time of pouring. That is, with respect to a shape in which the distance between the glass molds is small, it can be injected along the lower mold even in a standing state, but in the case of a semi-finished lens as shown in FIG. When injection is performed while the mold interval is large and vertical, the raw material strikes the liquid surface and bubbles are generated (see FIG. 9A). Therefore, the generation of bubbles is suppressed by injecting the raw material along the surface of the eyeball side mold 82 by inclining the posture of the mold 8 (see FIG. 9B).

    Further, as shown in FIG. 9, a molding mold having a large interval between the glass molding dies is deformed into a shape in which the central portion of the gasket side surface is dented. This is because the outer diameter of the glass mold is larger than the inner diameter of the gasket in order for the gasket to improve hermeticity with the glass mold. When injected in the state shown in FIG. 9A, the liquid level rises horizontally, so that air remains at the uppermost eyeball-side mold end 810 (circled portion). Therefore, as shown in FIG. 9B, when the injection port 85 is formed so as to be located in the very vicinity of the molding die 81 on the object side, and the molding die 8 is inclined, The highest position in the cavity 84 is set. As a result, all the air in the mold 8 is discharged from the inlet 85 installed at the uppermost position before the injection is completed, and does not remain in the mold 8.

    Further, the direction of inclination of the mold 8 is opposite to that shown in FIG. 9A, and the raw material may be dropped on the surface of the object-side mold 81 as shown in FIG. Good. In this case, the injection port 85 is formed so as to be located in the very vicinity of the mold 82 on the eyeball side, and the injection port 85 is located at the uppermost position in the cavity 84 when the molding mold 8 is tilted. To be. Also by this, all of the air in the mold 8 is discharged from the injection port 85 installed at the uppermost position before the injection is completed, and does not remain in the mold 8.

    The inclination angle was set to about 30 degrees from the vertical direction. This inclination angle satisfies the condition of dropping on the optical surface for forming the lens surface of one of the pair of molds in the mold, and the shape of the mold 8 of the present embodiment. In some cases, the conditions are defined so that the raw material does not leak when the injection is completed. Therefore, if the shape of the molding mold 8 is different, the inclination angle is also changed to a predetermined size. Further, the shape of the mold to be injected with an inclination is not particularly limited, but an inclination may be suitable depending on the material or shape. In particular, in the case of a shape in which the inlet and its vertical direction are open, it is effective to incline the mold.

    For example, it is not necessary to incline a part of the molded lens for the plus lens and the minus lens that are finished products. However, lenses with a general transmission refractive power of less than -2.00D and lenses with thick center thickness such as semi-finished products are effective in suppressing the generation of bubbles while increasing the injection speed by inclining. It is.

(About foam size control)
When the injection is completed, it is desirable that the entire mold is filled with the lens material. However, even when the injection is completed, a very small amount of air bubbles remains, and if this minute bubble is about 1 mm, it adheres to the mold near the mold due to its own surface tension and the viscosity of the raw materials. It cannot be removed easily. In the polymerization step after the injection, the mold is sealed and the polymerization is performed. If bubbles remain inside the molding mold, they remain in the molded product after polymerization. Furthermore, the bubbles move during the polymerization and are fixed at important positions on the lens optical surface, which may cause optical defects.

    The present inventor has tried various methods that do not generate residual bubbles, for example, by reducing the injection speed, but cannot completely remove the residual bubbles. Therefore, as a result of trial and error, it was found that if the residual foam was increased, removal from the inlet was easy. This is considered to be because a sufficiently large bubble has a higher buoyancy than the surface tension and can easily move upward. Furthermore, the inventor has found that as a method of increasing the residual bubbles, the control is performed by the insertion amount of the injection nozzle into the molding mold and the pulling speed of the injection nozzle.

    Conventionally, the injection nozzle has not been inserted so much into the mold for reasons such as damaging the optical surface inside the molding mold, or even when it is inserted into the mold, the amount of insertion has been very small. FIG. 11 shows an event in which residual bubbles are formed after injection into the mold 8. FIG. 11A shows a state in which the injection nozzle 7 is inserted into the molding mold 8 by a distance d to perform injection. In the figure, the tip of the injection nozzle 7 is inserted into the mold about a distance d = 5 mm. FIG. 11 (b) shows a state where the injection is completed.

    Residual bubbles 820 of 0.5 to 4 mm are generated in the vicinity of the injection nozzle 7. The size of the residual foam is controlled by the amount of insertion at the tip of the injection nozzle. In the present application, the insertion amount d at the tip of the injection nozzle is set to about 3 to 7 mm, and the residual bubbles are controlled to about 2 to 4 mm. Bubbles of this size float with their own buoyancy and can be easily removed from the inlet after injection. Therefore, in the present embodiment, the injection is performed while increasing the amount of insertion of the injection nozzle 7 into the mold 8. After the injection, when the injection nozzle 7 is pulled out, the bubbles rise by their own buoyancy and the removal of the bubbles is completed. Further, even when the bubbles are not naturally removed, the bubbles can be discharged from the injection port if a light impact is applied to the mold. The speed at which the injection nozzle is pulled out is 1 to 10 mm / sec, but 5 mm / sec is preferred.

    When pouring and defoaming are completed, the mixture is cured by heating in an electric furnace (not shown). Since the plastic lens is molded by completing the polymerization of the raw material in the molding mold 8, the plastic lens is released from the molding mold 8 to obtain a product. After releasing the optical lens, a heat treatment called annealing is performed to remove distortion inside the lens caused by polymerization. Thereafter, visual inspection and projection inspection are performed on the optical lens as intermediate inspection. At this stage, the optical lens is divided into a finished product and a semi-finished product (semi-finished product), and the second product is polished on the second surface according to the prescription. The finished product is then subjected to a dyeing process for obtaining a color product, a reinforcing coating process for strengthening against scratches, and an antireflection coating process for antireflection, and a final inspection is performed. The finished product becomes a product after this final inspection.

  The embodiment described above has the following advantages. That is, first, by simultaneously injecting a large number of molding molds 8 from the raw material tank 1, it is possible to improve productivity and quality. In other words, the compounded raw material starts to be polymerized from the moment it is compounded, and if a raw material that has been used for a long time after compounding is used, the injection will be hindered due to a change in viscosity, and at the same time the optical performance of the resulting lens will deteriorate. (Hereinafter also referred to as partial polymerization non-uniformity). For this reason, it is desirable to use the prepared raw materials as soon as possible. However, if the capacity of the storage tank is small, the blending must be repeated frequently, resulting in low productivity. Therefore, in this application, a raw material is supplied to the several injection | pouring apparatus from the raw material supply tank prepared in large quantities. In addition, each injection device simultaneously injects raw materials with a plurality of injection shafts to perform a large amount of injection in a short time, improving productivity and maintaining quality at the same time.

  Moreover, the following advantages are obtained by injecting the raw material tank using a roller pump while pressurizing the raw material tank. That is, as a method for delivering raw materials from the raw material supply tank, a pressure feeding means using compressed air (gas) is generally used. However, in this method, particularly when the injection shaft of the injection device has a multi-axis configuration, the resistance inside the pipe, which is different for each injection shaft, and clogging of the filter arranged on each device / shaft occur. And the dispersion | distribution generate | occur | produces in the delivery amount for every injection | pouring axis | shaft, and it becomes difficult to make the flow volume of each axis | shaft constant. Moreover, even if injection is started at the same time for multiple axes, such as when an error is caused in the capacity of the molding mold, particularly when different items are injected for each injection axis, the injection cannot be completed at the same time. For example, when supplying to 12 shafts with a tank pressure of 0.1 Mpa, due to the variation in the injection speed due to the above-mentioned reasons, the injection into the molding mold is completed in order, not simultaneously, and the valves of each shaft are sequentially closed. Since the pressure in the supply tank is constant, the flow rate of the remaining injection shaft increases, and it becomes impossible to inject at an appropriate flow rate. Then, since the injection speed increases, bubbles are easily generated during the injection.

    That is, the raw material delivered from the supply tank by the pressure in the tank may be ejected in a large amount instantaneously when the other injection shaft shaft stops injection, the pressure concentrates on the remaining injection shaft. The raw material discharged in a large amount may collide with the liquid surface inside the molding mold and involve bubbles. Therefore, the present application performs independent flow rate control for each injection shaft, and as a method thereof, performs flow rate control by a roller pump. Therefore, according to the present invention, it is possible to supply the raw material stably without being influenced by the pressure change from the supply side.

    In general, when the raw material comes into contact with the drive portion, a part of the liquid raw material is solidified and generates dust. Furthermore, regular cleaning is necessary because the pump and the raw material are in contact. Cleaning requires an organic solvent and a washing machine, which is expensive and reduces workability. However, roller pumps are different in structure from other pumps and rarely generate dust because the raw materials do not come into direct contact with the pump drive. In addition, the tubular elastic body that is only in contact with the raw material is inexpensive, can be replaced, and does not need to be cleaned.

    Furthermore, the plastic raw material is deaerated in advance in order to suppress the generation of bubbles during polymerization and curing, but when the plastic lens raw material is pressurized with compressed air for a long time, the air melts into the raw material, Bubbles may be generated during polymerization and curing, which may cause a decrease in yield. When a long time has passed, it is necessary to perform deaeration again. Therefore, when there is a raw material supply means using a metering pump, the necessity of liquid feeding by pressurization cannot be considered. Therefore, the necessity of selecting the combination of the roller pump and the pressurization as the optimum means cannot be considered by conventional common sense.

    In this embodiment, a combination of pressurization of the roller pump and the raw material tank is performed. In the present embodiment, the first problem is dealt with by dividing a raw material from the same raw material tank, performing a plurality of injections in parallel, and performing a large amount of injection in a short time. Secondly, liquid feeding by a roller pump is the main, and pressurization is set to the minimum pressure necessary for restoring the shape of the tubular elastic body, thereby reducing the amount of gas per unit time into the raw material. In this embodiment, a roller pump is used to obtain a specific effect. However, depending on the type of raw material, a constant effect may be obtained even if a metering pump or other pump is used instead of the roller pump. May be obtained.

  The present invention can be used as a technique for mass-producing and manufacturing plastic lenses for eyeglasses and other plastic lens products.

It is a block diagram which shows the whole structure of the plastic lens raw material injection | pouring apparatus concerning embodiment of this invention. It is explanatory drawing of the raw material conveyance path | route and control connection state of the plastic lens raw material injection | pouring apparatus shown by FIG. It is a fragmentary perspective view of the plastic lens raw material injection | pouring apparatus shown by FIG. It is a figure which shows a roller pump. It is a figure which shows the injection | pouring nozzle, Comprising: FIG. A is a top view, FIG. B is the aa sectional view. It is a figure which shows a plastic lens shaping | molding die. It is a flowchart figure which shows the manufacturing process of a plastic lens. It is explanatory drawing which shows the injection | pouring state of a plastic raw material. It is explanatory drawing which shows the injection | pouring state of a plastic raw material. It is explanatory drawing which shows the injection | pouring state of a plastic raw material. It is explanatory drawing of the bubble generation state at the time of injection | pouring of a plastic raw material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material tank 2 Pressurization apparatus 3 1st filter 4 Roller pump 5 On-off valve 6 2nd filter 7 Injection nozzle 8 Plastic lens molding mold

Claims (6)

A plastic raw material injection method for injecting a plastic raw material into a plastic lens molding mold,
As the molding mold, a pair of glass molding dies each having a lens forming optical surface are arranged so that the lens forming optical surfaces face each other at a predetermined interval, and portions other than the portions surrounded by these glass molding dies Among them, using a molding mold that closes except the part that becomes the injection port,
The molding mold is placed with its injection port facing upward, a plastic raw material injection nozzle is inserted into this injection port, and the plastic raw material ejected from this nozzle is dropped into the molding mold using gravity. Like injecting,
In the injection, the plastic raw material dropped into the molding die is dropped onto the lens surface forming optical surface of one of the pair of molding dies in the molding die. A plastic raw material pouring method characterized in that a molding mold is inclined by a necessary angle with respect to a vertical direction.     The molding mold is provided with an inlet at a position close to the molding die disposed opposite to the molding die having an optical surface to which the raw material is dropped from the pair of molding dies. The plastic raw material injection method according to claim 1, wherein:     3. The plastic raw material injecting method according to claim 1, wherein the molding mold is one in which the pair of glass molding dies are accommodated in a cylindrical gasket. A plastic raw material injection device for injecting a plastic raw material into a plastic lens molding mold,
The molding mold has a pair of glass molding dies each having a lens forming optical surface arranged so that the lens forming optical surfaces face each other at a predetermined interval, and a portion other than a portion surrounded by the glass molding dies. Among them, it is a molding mold that closes except the part that becomes the injection port,
A positioning device for arranging the molding mold so that its injection port is on top;
An injection nozzle that is inserted into this injection port to inject plastic raw material into the mold, and is dropped into the mold using gravity and injected;
In the injection, the plastic raw material dropped into the molding die is dropped onto the lens surface forming optical surface of one of the pair of molding dies in the molding die. An apparatus for injecting plastic raw material, characterized in that it has a tilting device for tilting a molding mold by a required angle with respect to the vertical direction.   A plastic lens formed into a lens shape by injecting a plastic raw material into a molding mold and manufactured by using the plastic raw material injection method according to any one of claims 1 to 3 during the molding step. A plastic lens characterized by being a thing.   A plastic lens formed into a lens shape by injecting a plastic raw material into a molding mold and formed by using the plastic raw material injection device according to claim 4 during the molding step. A plastic lens characterized by being.

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