JP2013208800A - Optical lens molding mold and manufacturing method of plastic lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic lens molding metal mold which reduces cooling time by improving cooling efficiency and increases production efficiency without causing a variation in temperature even if molding a product of a radius-curved shape such as a lens, and a manufacturing method of the plastic lens using such an optical lens molding mold.SOLUTION: A groove for forming a passage for making temperature-adjusting water circulate is formed so that a distance between the bottom of the groove and a lens molding face becomes constant by making passage forming members 11c, 12c conform to a radius-curved face of a lens molding face, and the passage is formed between the joined passage molding members 11c, 12c and bases 11d, 12d.

Description

  The present invention relates to an optical lens molding die in which a flow path for circulating water for temperature adjustment is formed, and a method for producing a plastic lens using the optical lens molding die.

  Conventionally, some plastic lenses for spectacles are manufactured by an injection molding method using a thermoplastic resin such as a polycarbonate resin or a methacrylic resin, and a plastic having a complicated optical surface shape like a progressive power lens. Even with a lens, high-precision molding is possible by transferring the cavity shape of the mold.

In such an injection molding method, the molten resin filled in the cavity shortens the time required for cooling until it sufficiently solidifies for its removal, thereby improving productivity. It is effective to set the temperature of the mold when the molten resin is injected and filled as low as possible.
However, although the cooling time can be shortened by lowering the set temperature of the mold, on the other hand, appearance defects such as jetting and flow marks are likely to occur. Since such appearance defects are often improved by increasing the set temperature of the mold, it is necessary to control the mold temperature so that it is as low as possible without causing these appearance defects. There was a limit to shortening the cooling time.

  For this reason, instead of lowering the set temperature of the mold, a method of performing the cooling process at a position different from the position where the filling process is performed, a method of increasing the heat exchange efficiency and shortening the cooling time, etc. have been proposed. (See Patent Documents 1 to 3).

JP-A-9-39023 Japanese Utility Model Publication No. 5-26327 JP-A-6-8250

  However, these methods have the following problems.

For example, in Patent Document 1, another mold 13b that has moved to a lower position of the injection unit 16 while the mold 13a filled with the molten resin is moved from the lower position of the injection unit 16 and cooled. There is disclosed a slide molding apparatus that efficiently manufactures an injection-molded product without causing the injection unit 16 to be filled with a molten resin.
However, in Patent Document 1, an injection molded product is efficiently manufactured by simultaneously performing a cooling process and a filling process using two molds 13a and 13b. There are problems such as complicated structure.

Further, in Patent Document 2, a mold member (first metal member and second metal member) that forms a cavity (recess for molding) is a beryllium copper alloy (thermal conductivity: 83.7 W / m · K). By using a material with a high thermal conductivity such as the above, the thermal conductivity is more than three times that of general steel, SDK61 (thermal conductivity: 26.1 W / m · K), and from resin to mold The heat transfer can be performed efficiently, and the cooling time can be shortened.
However, the linear expansion coefficient of the beryllium copper alloy is 17.8 × 10 ^−6, which is larger than that of SKD61 (linear expansion coefficient: 13.3 × 10 ⁻⁶ ) which is a general steel material. When the temperature is raised or lowered in combination with this steel material, problems such as malfunction and breakage occur due to differences in expansion.

In Patent Document 3, the groove shape of the cooling water disposed in the mold is improved to a multiple spiral groove to improve the heat exchange efficiency of the mold and keep the temperature distribution uniform.
However, Patent Document 3 relates to an optical disk molding die, and is intended for molding a flat optical disk, and does not assume that a lens having a curvature shape such as a lens is molded. The depth is constant depending on the location. For this reason, when the optical disc molding die of Patent Document 3 is applied to a lens die having a curvature as it is, the distance between the groove through which the cooling water circulates and the surface of the molded product will be different. Problems such as unevenness occur.

  The present invention has been made in view of the above-described circumstances, and even when a lens having a curvature shape such as a lens is molded, the cooling efficiency is improved without causing temperature unevenness and cooling. An object of the present invention is to provide a plastic lens molding die capable of shortening the time required for increasing the production efficiency and a method for producing a plastic lens using such an optical lens molding die.

  An optical lens molding die according to the present invention is an optical lens molding die in which a flow channel for circulating water for temperature control is formed inside, a flow channel forming member located on the lens molding surface side, A mold body comprising a base joined to the flow path forming member and forming the flow path between the flow path forming member and a groove forming the flow path is provided on the flow path forming member. In addition, in accordance with the curvature shape of the lens molding surface, the distance between the groove bottom and the lens molding surface is made constant so as to be engraved on the joint surface with the base.

  The plastic lens manufacturing method according to the present invention is a method for manufacturing a plastic lens using the optical lens molding die as described above.

  According to the present invention, even when a lens having a curvature shape such as a lens is molded, the cooling efficiency is improved without causing temperature unevenness on the molding surface, and the time required for cooling is shortened so that the production efficiency is improved. Can be increased.

It is explanatory drawing which shows an example of an injection molding apparatus. It is sectional drawing which shows the outline of the shaping | molding die with which the injection molding apparatus shown in FIG. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is a principal part expanded sectional view which expands and shows the circumference | surroundings of the cavity in FIG. It is explanatory drawing which shows an example of arrangement | positioning of the flow path which circulates the water for temperature control. It is explanatory drawing which shows another example of arrangement | positioning of the flow path which circulates the water for temperature control. It is a flowchart which shows each step in embodiment of the manufacturing method of the plastic lens which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Injection molding equipment]
FIG. 1 is an explanatory view showing an example of an injection molding apparatus for molding a plastic lens using the optical lens molding die according to the present embodiment.

  The injection molding apparatus shown in FIG. 1 includes a mold 50 having a movable mold 1 and a fixed mold 2 as a pair of split molds divided by a parting line PL, and opening / closing and mold clamping of the mold 50 by a toggle link mechanism 65. A mold clamping device 60, and an injection device 80 that melts, kneads, and measures the raw material resin introduced from the hopper 81 and injects it from the nozzle 85.

[Injection device]
An injection apparatus 80 provided in the injection molding apparatus shown in FIG. 1 has a heating cylinder 82 having a nozzle 85 formed at the tip. Inside the heating cylinder 82, a screw whose rotation and forward / backward movement are controlled by the drive unit 84 is disposed.

  Further, a hopper 81 for feeding pellet-shaped raw material resin into the heating cylinder 82 is connected to the proximal end side of the heating cylinder 82. The raw material resin charged into the heating cylinder 82 from the hopper 81 is melted and kneaded by shearing heat and heating from the heater provided in the heating cylinder 82 while being sheared and pulverized by a screw rotating in the heating cylinder 82. Is sent to a cylinder front chamber formed between the front end of the nozzle and the nozzle 85 and weighed. Thereafter, a predetermined amount of raw material resin that is adjusted to a viscosity suitable for injection molding and in a molten state is injected from the nozzle 85. .

[Clamping device]
In the injection pressure molding apparatus shown in FIG. 1, the mold clamping device 60 has a plurality of tie bars 63 installed between a fixed die plate 61 and a rear plate 62 erected on a gantry 66 at a predetermined interval, and a movable die plate. 64 is configured to be moved by being guided by the tie bar 63. A molding die 50 is attached between the fixed die plate 61 and the movable die plate 64, and a toggle link mechanism 65 is attached between the rear plate 62 and the movable die plate 64.
As a result, when the toggle link mechanism 65 is driven, the movable die plate 64 is guided by the tie bar 63 to advance and retreat, and accordingly, the mold 50 is opened and closed and the mold is clamped.

  Here, the toggle link mechanism 65 is configured so that the screwed crosshead 73 moves along the ball screw 72 as the ball screw 72 connected to a motor (not shown) rotates. When the cross head 73 moves to the movable die plate 64 side, the toggle links 71A and 71B extend linearly by the connecting links 74A and 74B, and the movable die plate 64 moves so as to approach the fixed die plate 61 (advance). To do. On the contrary, when the cross head 73 moves to the rear plate 62 side, the toggle links 71A and 71B are bent inward by the connecting links 74A and 74B so that the movable die plate 64 is separated from the fixed die plate 61. Move (retreat).

[Molding mold]
FIG. 2 is a cross-sectional view showing a cross section of the molding die 50 shown in FIG. 1 cut along a plane perpendicular to the paper surface passing through the central axis, and shows an initial state in which the die is closed. 3 is a cross-sectional view taken along the line AA in FIG. 2, FIG. 4 is a cross-sectional view taken along the line BB in FIG. 2, and FIG. 5 is an enlarged cross-sectional view of the main part showing the periphery of the cavity 3 in FIG. FIG.

  In the examples shown in these drawings, a pair of split molds, a mold 50 and a movable mold 1 and a fixed mold 2 are sandwiched between two movable cavities 3 for molding a plastic lens of a predetermined shape and a gate G. Thus, a runner 49 as a resin flow path connected to each cavity 3 is formed. A sprue bush 47 that forms a sprue 48 connected to the runner 49 at a right angle is attached to the template 10 of the fixed mold 2.

The mold body 4 of the movable mold 1 has two insert guide members 5 and mold plates 6 and 7 for holding them. Inside the insert guide member 5, an insert die 11 as an optical lens molding die is accommodated so as to be slidable in a direction perpendicular to the parting line PL.
The mold body 8 of the fixed mold 2 includes two insert guide members 9 and a template 10, and the insert guide member 9 is held by the template 10 and the mold attachment member 15. Inside the insert guide member 9, an insert mold 12 as an optical lens molding die is accommodated so as to be slidable in a direction perpendicular to the parting line PL.

  A molding die 50 having such a movable die 1 and a fixed die 2 includes an insert die 11 on the movable die 1 side and an insert die 12 on the fixed die 2 side between the movable die 1 and the fixed die 2. A cavity 3 including a molding surface formed in each is formed. The cavity 3 is formed corresponding to the shape of the plastic lens to be molded, and the molding surfaces of the insert molds 11 and 12 forming the cavity 3 are formed on the glass bases 11a and 12a.

  More specifically, in the insert mold 11 on the movable mold 1 side, the molding surface corresponding to one optical surface (the concave surface in the illustrated example) of the plastic lens to be molded has a glass base material 11a. The insert mold 11 is formed by joining the glass substrate 11a to the mold body 11b. Similarly, in the insert mold 12 on the fixed mold 2 side, a molding surface corresponding to the other optical surface of the plastic lens to be molded (in the example shown, the surface on the convex surface side) is formed on the glass substrate 12a. The insert mold 12 is formed by joining the glass substrate 12a to the mold body 12b (see FIG. 5).

  As the glass substrates 11a and 12a, for example, an amorphous glass material such as a crown, flint, barium, phosphate, fluorine-containing, or fluorophosphate can be used. Among these, an amorphous glass material having a thermal conductivity of 0.4 to 1.3 W / m · K is appropriately selected and used. Due to its heat insulation effect, the mold temperature is set low and cooling is performed. This is preferable for shortening the time.

Further, such an amorphous glass material is easily suitable for forming a molding surface that requires high precision because the surface can be easily mirror-finished by cutting or polishing.
That is, in order to form a molding surface directly on an insert mold made of steel through a polishing process, a high-level technique and a laborious process are required, but a molding surface for molding an optical surface of a lens was formed. By forming the insert molds 11 and 12 by joining the glass base materials 11a and 12a to the mold main bodies 11b and 12b, the formation of the molding surface can be facilitated and the number of manufacturing steps can be reduced. Thereby, it becomes possible to manufacture the insert molds 11 and 12 at low cost.

  The glass substrates 11a and 12a are preferably formed with a thickness of 3 to 4 mm so as to sufficiently withstand the injection pressure and holding pressure during injection molding in consideration of molding conditions. Surface treatment can be performed with tempered glass or DLC (diamond-like carbon) for the purpose of preventing damage during handling as well as during injection molding.

  In order to join the glass base materials 11a and 12a to the mold bodies 11b and 12b, a thermosetting resin having a low coefficient of linear expansion and excellent stability in a high temperature environment can be used as an adhesive. And what is necessary is just to join both by apply | coating with a brush etc. to the joining surface of type | mold main bodies 11b and 12b. As such a thermosetting resin, a sulfur-containing thermosetting resin obtained by reacting a thermosetting monomer containing sulfur is preferable. The sulfur-containing thermosetting resin has a low coefficient of linear expansion, is excellent in stability even in a high temperature environment, and is excellent in adhesiveness (adhesion) with a glass substrate. Furthermore, in the state of the monomer before curing, the surface tension is low and it is possible to make it adhere to the adhesion target surface in the form of a liquid film, so that it is formed between the glass base materials 11a, 12a and the mold bodies 11b, 12b. The adhesive layer can be a very thin layer.

  The sulfur-containing thermosetting resin is preferably at least one resin selected from thiourethane resins and epithio resins. Here, the thiourethane resin refers to a resin obtained by reacting a polyisocyanate compound and a polythiol compound, and the epithio resin is obtained by reacting a lens raw material monomer having a compound having an epithio group as an essential component. Refers to the resin that is produced. It is particularly preferable to use a thiourethane resin as the sulfur-containing thermosetting resin because it is extremely excellent in adhesion to a glass substrate and is economical. Examples of commercially available thiourethane resins include MR series manufactured by Mitsui Chemicals, Inc., trade names “MR-6”, “MR-7”, “MR-8”, “MR-10”, and “MR-20”. “MR-1746” or the like is preferably used.

  The mold bodies 11b and 12b can be formed using a steel material such as maraging steel or beryllium copper alloy, but a steel material having a higher thermal diffusivity than the glass material used for the glass base materials 11a and 12a is used. Is preferred.

In the present embodiment, the insert molds 11 and 12 are provided with a flow path C for circulating temperature adjusting water supplied from a mold temperature controller (not shown).
That is, the mold main bodies 11b and 12b are formed by joining the bases 11d and 12d and the flow path forming members 11c and 12c at a joint surface perpendicular to the axial direction, and the flow path forming member 11c, which is located on the lens molding surface side. In 12c, a groove for forming a flow path is formed on the joint surface with the bases 11d and 12d. Thereby, the flow path C is formed between the flow path forming members 11c and 12c and the bases 11d and 12d.
On the bases 11d and 12d, an annular groove CG is formed on the joint surface with the flow path forming members 11c and 12c so as to surround the flow path forming groove, and an O-ring OR is fitted into the annular groove. Thus, the flow path forming members 11c and 12c and the bases 11d and 12d are joined in a liquid-tight manner. As the O-ring OR, fluorine rubber having high heat resistance (for example, JIS B 2401 type 4 D) is preferable.

  In the present embodiment, the flow path C provided in the insert molds 11 and 12 is, for example, as shown in FIG. 6, the temperature adjustment water flowing in from the inlet IN passes around the outer periphery after passing through the center. In addition, as shown in FIG. 7, the temperature control water flowing in from the inlet IN advances to the outer periphery in a spiral shape as shown in FIG. It can be arranged to flow out from. The arrangement of the channel C is not limited to these as long as the entire molding surface can be uniformly cooled.

  As a parameter that greatly affects the quality and productivity of plastic lens injection molding, there is a mold temperature. In order to control the mold temperature and maintain a constant temperature, water for temperature adjustment supplied from the mold temperature control device can be circulated in the insert molds 11 and 12. The water heated to a constant temperature by the heater in the mold temperature control device is sent by a pump, goes around the flow path C provided in the insert molds 11 and 12, and then returns to the temperature controller. It is sent to the channel again after being adjusted. The temperature adjusting water circulating in the insert molds 11 and 12 plays a role of increasing the temperature of the insert molds 11 and 12 as the heat is transferred from the wall of the flow path C. On the other hand, the heat of the molten resin injected and filled into the cavity at the time of injection molding is transferred from the wall of the flow path C to the water for temperature control through the insert molds 11 and 12, and also has a role of cooling the resin. At the same time.

Then, in the channel C arranged as described above, the water for temperature adjustment flowing in from the inlet IN flows out of the outlet OUT after making a round of the channel C, but this series of flow is intermittently performed. Heat exchange is performed between the temperature adjusting water flowing in the flow path C and the insert molds 11 and 12.
In order to efficiently perform the heat exchange at this time, the surface area of the flow path C may be increased, but the depth of the flow path C formed by the flow path forming grooves formed in the flow path forming members 11c and 12c is increased. When the distance is constant, the distance L between the bottom of the channel C and the molding surface varies depending on the location. Then, when molding a lens with a curved shape such as a lens, the amount of heat transferred can vary depending on the location, resulting in temperature unevenness on the molding surface, and this difference in temperature affects the lens quality. End up.

Therefore, in the present embodiment, when the flow path forming grooves are engraved in the flow path forming members 11c and 12c, the molding surface is formed so that the distance L between the groove bottom and the molding surface is constant. The groove depth is appropriately adjusted according to the curvature shape. Thereby, the molding surface can be cooled more uniformly.
Therefore, according to the present embodiment, even when a lens having a curvature shape such as a lens is molded, the molding surface is not uneven in temperature, and the cooling efficiency is improved and the time required for cooling is shortened. Production efficiency.

  In the mold 50 configured as described above, the mold body 4 of the movable mold 1 is fixed to the movable die plate 64 via the mold mounting member 16, and the mold body 8 of the fixed mold 2 is mounted to the mold. It is fixed to the fixed die plate 61 via the member 15. As a result, the mold 50 is attached between the fixed die plate 61 and the movable die plate 64 of the mold clamping device 60.

  Further, the mold mounting member 16 on the movable mold 1 side is provided with a hydraulic cylinder 19 corresponding to each of the insert molds 11, and the piston rod 21 connected to the piston 20 is connected to one end side of the hydraulic cylinder 19. It penetrates through the back insert 22 fixed to. A T-shaped clamp member 23 provided at the tip of each piston rod 21 is formed in a T-shaped groove 24 formed on the back surface of the insert mold 11 (the surface opposite to the surface on which the molding surface is formed). Engageable and detachable.

  Thus, with the mold 50 opened, the piston rods 21 of the respective hydraulic cylinders 19 are advanced, and the T-shaped clamp members 23 provided at the tips of the piston rods 21 are protruded from the insert guide members 5. Thus, the insert mold 11 can be exchanged according to the plastic lens to be molded. When the piston rod 21 of each hydraulic cylinder 19 is retracted, the insert mold 11 attached to the T-shaped clamp member 23 is housed inside the insert guide member 5.

  Similarly, a hydraulic cylinder 26 is provided in the mold mounting member 15 on the fixed mold 2 side so as to correspond to each of the insert molds 12, and a piston rod 28 connected to the piston 27 is provided in the mold mounting member 15. It penetrates. A T-shaped clamp member 29 provided at the tip of each piston rod 28 is formed in a T-shaped groove 30 formed on the back surface of the insert mold 12 (the surface opposite to the surface on which the molding surface is formed). Engageable and detachable.

  Thus, with the mold 50 opened, the piston rod 28 of each hydraulic cylinder 26 is advanced, and the T-shaped clamp member 29 provided at the tip of each piston rod 28 is projected from the insert guide member 9. Thus, the insert mold 12 can be exchanged according to the plastic lens to be molded. When the piston rod 28 of each hydraulic cylinder 26 is retracted, the insert mold 12 attached to the T-shaped clamp member 29 is housed inside the insert guide member 9.

  When the mold body 4 of the movable mold 1 is fixed to the movable die plate 64, the mold body 4 is bolted to the mold mounting member 16 composed of the first member 16A and the second member 16B, as shown in FIG. 17 is attached. At this time, a plurality of disc springs 17 </ b> A inserted on the outer periphery of the bolt 17 are interposed between the mold body 4 of the movable mold 1 and the mold mounting member 16, and the mold body 4 and the mold of the movable mold 1 are interposed. A gap S is formed between the mounting member 16 and the mounting member 16.

The gap S is generated when the movable die plate 64 further advances after the molding die 50 is closed, and the die mounting member 16 guided by the guide pins 18 is pressed against the elastic force of the disc spring 17A. It is designed to be closed. Accordingly, in the illustrated example, each hydraulic cylinder 19 provided on the mold mounting member 16 presses the insert mold 11 via the back insert 22. Thereby, the volume of the cavity 3 at the time of mold clamping is made variable, and the molten resin injected and filled in the cavity 3 can be pressurized and compressed by the insert mold 11.
The guide pin 18 protrudes toward the fixed mold 2 so as to guide the opening / closing operation of the mold 50 and is inserted through an insertion hole formed in the fixed mold 2.

A pressure receiving member 32 is attached to the other end side of the hydraulic cylinder 19 provided on the die attaching member 16 on the movable die 1 side. When the eject rod 34 inserted from the hole 33 formed in the mold attachment member 16 presses the pressure receiving member 32, the hydraulic cylinder 19, the back insert 22 and the insert mold 11 are also pressed and molded in the cavity 3. The lens is pushed out.
At the same time, an eject pin 35 is disposed at the center of the mold attachment member 16 so as to be movable back and forth in parallel with the opening / closing direction of the mold 50. When the pressure receiving member 36 attached to the eject pin 35 is pressed by the eject rod 38 inserted from the hole 37 formed in the mold attaching member 16, the eject pin 35 is pushed out.
Therefore, when the mold is opened, the ejected rods 34 and 38 are advanced to take out the molded product.

  As shown in FIG. 4, the spring force of the spring 42 wound around the outer periphery of the eject return pin 41 acts on the pressure receiving member 36 in the left direction in the figure. Although not particularly shown, the pressure receiving member 32 has the same structure so that a leftward spring force acts in the drawing. Thus, when the eject rods 34 and 38 are retracted, the pressure receiving members 32 and 36 are also retracted and returned to the standby position.

  Moreover, the shaping | molding die 50 has the nozzle shut mechanism 90 which obstruct | occludes the nozzle 85 of the injection apparatus 80, as shown in FIG. The nozzle shut mechanism 90 has a nozzle shut pin 91 as a blocking member protruding into the sprue 48 formed by the sprue bush 47. The nozzle shut pin 91 is connected to a piston rod 94 of a hydraulic cylinder 93 via a connecting piece 92, and the hydraulic cylinder 93 is fixed to the mold mounting member 15 by a cylinder mounting plate 95. As a result, when the hydraulic cylinder 93 is driven in a state where the nozzle 85 is in pressure contact with the sprue bush 47, the nozzle shut pin 91 projects into the sprue 48 and closes the nozzle 85, thereby preventing back flow of the resin. Yes.

[Plastic lens manufacturing method]
In order to manufacture a plastic lens using the injection molding apparatus as described above, for example, the steps (ST1 to ST10) shown in the flowchart of FIG. 8 can be sequentially performed.

  In ST1, a resin pressurizing condition is set. This is for adjusting the clamping force according to the characteristics of the plastic lens to be molded (lens shape, lens power, etc.) in advance in order to apply an appropriate pressure to the resin in the cavity 3 in advance. is there.

In ST2, weighing is performed. In the injection device 80, the pellet-shaped raw resin charged from the hopper 81 is melted and kneaded by shearing heat and heating from the heater provided in the heating cylinder 82 while being sheared and pulverized by a screw rotating in the heating cylinder 82. While being sent, it is sent to the cylinder front chamber formed between the tip of the screw and the nozzle 85 and weighed. Here, an amount of molten resin necessary for filling the cavity 3, the runner 49, and the sprue 48 is measured.
As the raw material resin, a thermoplastic resin such as a polycarbonate resin or an acrylic resin generally used for molding this type of plastic lens can be used.

  In ST3, the mold is closed at the parting line PL. Specifically, when the toggle link mechanism 65 is driven to advance the cross head 73, the toggle links 71A and 71B extend, and the movable die plate 64 advances toward the fixed die plate 61. 50 molds are closed. At this time, a gap S is maintained in a state where the disc spring 17A interposed between the mold body 4 of the movable mold 1 and the mold mounting member 16 is not compressed, and the fixed mold 2 and the movable mold 1 are separated by the parting line PL. Close the mold. In this state, the gap S is set to the maximum opening amount.

  In ST4, the cavity volume is set. In ST3, the crosshead 73 is further advanced to a preset position (cavity volume setting position) from the state in which the movable mold 1 and the fixed mold 2 are brought into close contact with each other by the parting line PL. As a result, the toggle links 71A and 71B are extended, and the movable die plate 64 is moved toward the fixed die plate 61 and moved to the cavity expansion position. The cavity enlargement amount is determined by setting the crosshead position. As a result, the gap S of the mold 50 is reduced leaving the cavity enlargement. At this time, the volume (thickness) of the cavity 3 is larger than the lens volume (thickness) to be molded, that is, the thickness of the extracted molded product. Further, since the disc spring 17A is compressed, some clamping force is generated as the reaction force.

  In ST5, injection is performed. The molten resin weighed in ST2 is injected into the mold 50 through the passage of the injection nozzle 85. That is, the molten resin introduced into the heating cylinder 82 of the injection device 80 and weighed is injected. Then, molten resin is injected from a nozzle 85 formed at the tip of the heating cylinder 82 and filled into the cavity 3 through the sprue 48, the runner 49, and the gate G. When the molten resin is filled into the cavity 3, the injection speed is controlled to be constant.

  In ST6, the resin is sealed in the mold. After injecting a predetermined amount of resin at T5, the cross head 73 is further advanced immediately before the injection filling of the molten resin is completed. Then, after the injection filling is completed, the nozzle shut pin 91 is protruded into the sprue 48 by the nozzle shut mechanism 90 and the nozzle 85 is closed. Thereby, the filled molten resin is enclosed in the mold 50 in a compressed and pressurized state.

  In ST7, resin pressurization is performed. In ST6, the crosshead 73 starts to advance, and when the crosshead 73 advances to the origin (zero position) and stops, the toggle links 71A and 71B extend, so that the molten resin contained in the mold 51 is compressed. Pressed.

  In ST8, cooling is performed. For this purpose, the temperature of each part (insert, insert guide member, etc.) of the mold 50 is adjusted for temperature by a mold temperature control device so that the temperature is set to the Tg point or less according to the lens characteristics to be molded. Perform water temperature control. When the molten resin contained in the mold 50 is cooled while being compressed and pressurized, the raw material resin injected and filled in the cavity 3 is solidified as the cooling progresses in the compressed state. By contracting, a plastic lens having a predetermined volume is molded.

  In ST9, a release operation is performed. In the mold release operation, the crosshead 73 of the toggle link mechanism 65 is moved backward toward the rear plate 62 to open the mold 50.

  In ST10, a molded product ejecting operation is performed. When the cross head 73 is retracted to the end, the distance between the movable die plate 64 and the fixed die plate 61 is maximized, and the mold 50 is divided and opened by the parting line PL. When opening the mold, the eject rods 34 and 38 are advanced to take out the molded plastic lens.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

[Example 1]
In the injection molding apparatus shown in FIG. 1, a flow path C for circulating water for temperature adjustment is shown in FIG. 6 in both the insert mold 11 on the movable mold 1 side and the insert mold 12 on the fixed mold 2 side. Formed in the arrangement.
At that time, in the flow path forming members 11c and 12c, a groove for forming the flow path C is engraved in accordance with the curvature shape of the lens molding surface so that the distance between the groove bottom and the lens molding surface is 7 mm. did.
With such an injection molding device, using polycarbonate as the raw material resin, the time from the start of filling of the resin into the cavity until the cooled and solidified lens is taken as the reference value, and the reference value In this case, a plastic lens having a lens central portion thickness of 10 mm, a lens peripheral portion thickness of 12 mm, and a diameter of 77 mm was formed.
The power was measured at the center and the peripheral edge of the molded plastic lens, and the transferability was evaluated based on whether or not the tolerance was within the target power (D: -3.3). Those that are within tolerance are indicated by “◯”, those that are not within tolerance are indicated by “x”, and the results are shown in Table 1.

[Example 2]
In the injection molding apparatus shown in FIG. 1, the same plastic lens was molded under the same molding conditions as in Example 1 except that the arrangement of the flow paths was as shown in FIG.
As in Example 1, Table 1 shows the results of evaluating the transferability by measuring the power at the central part and the peripheral part of the molded plastic lens.

[Comparative example]
In the injection molding apparatus shown in FIG. 1, a flow path is not arranged inside the insert mold, and an annular flow path is provided on the back surfaces of both the movable mold side insert mold and the fixed mold side insert mold. A similar plastic lens was molded under the same molding conditions as in Example 1 except that was placed.
As in Example 1, Table 1 shows the results of evaluating the transferability by measuring the power at the central part and the peripheral part of the molded plastic lens.

  As shown in these results, when the cooling time is the reference value, good transferability is obtained in any of Examples 1 and 2 and the comparative example. In the comparative example, when the transfer time is 60 seconds earlier than the reference value, the transferability of the peripheral portion is deteriorated, but in Examples 1 and 2, good transferability is obtained in both the central portion and the peripheral portion. Yes. Therefore, according to this embodiment, even when a lens having a curvature shape such as a lens is molded, the cooling efficiency is improved without causing temperature unevenness on the molding surface, and the time required for cooling is increased. It was confirmed that the production efficiency could be improved by shortening the length.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. Nor.

  For example, in the above-described embodiment, the molding surfaces corresponding to the optical surfaces of the plastic lenses to be molded are formed on the glass base materials 11a and 12a, and this is joined to the mold bodies 11b and 12b to insert molds 11 and 12. However, the present invention is not limited to this. If necessary, the glass bases 11a and 12a may be omitted, and the molding surfaces may be directly formed on the mold bodies 11b and 12b.

  In addition, as a method of manufacturing a plastic lens for spectacles, a lens is molded in a state of a semi-finished product that is thicker than the finished dimensions, and this semi-finished product called a semi-finished lens is finally processed by post-processing. A method of finishing in a shape, for example, a plurality of types of semi-finished lenses, which are molded as different optical surface shapes on the convex side and formed with a common concave surface on the concave side, are prepared according to the user's prescription from these There is known a method of manufacturing by selecting an appropriate lens, and cutting and polishing the concave side so as to satisfy the prescription to finish the final shape.

  When such a semi-finished lens is manufactured by an injection molding method, at least one of a pair of split molds forming a cavity (a mold that molds a surface that is not cut or polished by post-processing) The optical lens molding die according to the invention may be applied.

  The present invention is used as a technique for shortening the cooling time and shortening the molding cycle time by increasing the cooling efficiency by circulating the water for temperature adjustment inside the mold when manufacturing the plastic lens by the injection molding method. it can.

11,12 Insert mold (mold for optical lens molding)
11a, 12a Glass base material 11b, 12b Type body 11c, 12c Channel forming member 11d, 12d Base C Channel

Claims (3)

An optical lens molding die in which a flow path for circulating water for temperature control is formed inside,
A mold body comprising a flow path forming member located on the lens molding surface side and a base that is joined to the flow path forming member and forms the flow path between the flow path forming member;
The flow path forming member has a groove that forms the flow path with the base so that the distance between the groove bottom and the lens molding surface is constant according to the curvature shape of the lens molding surface. An optical lens molding die characterized by being engraved on the joint surface.   The optical lens molding die according to claim 1, wherein a glass substrate on which the lens molding surface is formed is bonded to the die body.   A method for producing a plastic lens, comprising producing a plastic lens using the optical lens molding die according to claim 1.

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