JP3737873B2 - Lens injection compression molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens injection compression molding method for obtaining a lens (mainly a spectacle lens) by injection compression molding of a thermoplastic resin. Specifically, the present invention relates to a lens injection compression molding method capable of molding a lens with high accuracy and high quality.
[0002]
[Prior art]
An injection compression molding method is known as a method for molding a spectacle lens from a thermoplastic resin. For example, Japanese Patent Laid-Open No. 55-27300 (corresponding US Pat. No. 4,364,878) discloses a mold opening means for forming a mold space having a capacity larger than the capacity of a thermoplastic resin to be injected, and an amount necessary for a finished lens. A method for forming a lens in combination with a means for measuring and injecting a thermoplastic resin equal to the above, that is, a quantitative precision measuring means that does not inject irregular surplus resin is disclosed. There has been proposed a molding method for eliminating the weld line of the molten resin inside.
[0003]
[Problems to be solved by the invention]
However, the technique disclosed in Japanese Patent Laid-Open No. 55-27300 relates to a single lens molding method that does not have gates and runners communicating between lens cavities, and thus can be applied as it is when molding a plurality of lenses simultaneously. I can't do it. For example, when molding using a plurality of cavities, it is important to control the distribution of thermoplastic lens resin to the cavities and their fluidity, pressure, mold temperature, etc. This is not applicable because there is no disclosure.
[0004]
Further, according to the above publication, a lens having a large center thickness with a center thickness of 3 mm is relatively difficult for a spectacle lens to generate a weld line that can maintain the fluidity of the resin in the mold. Only the method of the case is illustrated, and the practical application range is confirmed only in the technically easy manufacturing area. In addition, these manufacturing areas are practically a narrow range of production frequency as a spectacle lens. The publication also mentions how to mold lenses with power differences such as intensity lenses and weak lenses, and molding of special lens shapes such as single focus aspheric surfaces, progressive surfaces, and astigmatic lenses. The problem in carrying out these moldings was still unresolved. For example, a minus lens is prone to a middle bending phenomenon (a phenomenon in which the center of the lens is bent after lens molding), which is considered to be caused by the shape characteristic that the peripheral wall thickness is large and the center wall thickness is small. Although there is a problem that it is difficult to reproduce the lens curvature, the technique disclosed in the publication cannot cope with this point. In addition, a major problem remains with respect to measures for preventing the weld line of the weak minus lens having a thin central thickness.
[0005]
The present invention has been made to solve such a problem, and an object of the present invention is to provide an injection compression molding method of an optical lens particularly suitable for manufacturing a lens having a specific thickness difference or shape.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a lens molding cavity constituted by at least a pair of cavity forming members for forming an uneven lens surface, a runner communicating with the lens molding cavity via a gate portion, and a sprue communicating with the runner. A lens injection compression molding method for molding a lens using a mold having a mold structure having the above-mentioned mold, and a required amount of thermoplastic resin for the mold structure having the lens molding cavity, runner, and sprue A measuring step for measuring the mold, a mold preparing step for closing the mold, leaving a compression allowance in the lens molding cavity, and setting the volume of the mold structure to a predetermined size, and the measuring step. An injection step of injecting a measured thermoplastic resin to the mold structure through a nozzle passage, and the thermoplastic resin A compression step for compressing the compression allowance after completion of injection or immediately before completion of injection, and a mold temperature adjustment step for controlling the mold temperature during these steps to solidify the thermoplastic resin in the mold component. In the injection process, in the section from the start of the injection of the thermoplastic resin until the molten resin reaches the lens molding cavity, the injection speed is controlled so as to become the set speed, and the injection speed is temporarily set in the gate portion. In the section from when the molten resin reaches the lens molding cavity until the injection filling is completed, The injection speed is controlled by changing the minus-weakness lens and minus-strength lens so that the minus-strength lens is slower than the minus-weakness lens. In the mold temperature adjusting step, the lens extraction temperature of the lens convex surface molding cavity forming member is controlled to be lower than the lens extraction temperature of the lens concave surface molding cavity forming member.
[0007]
According to a second aspect of the present invention, in the first aspect, the mold structure has a handle portion communicating with the runner and the sprue.
[0009]
The invention according to claim 3 is the lens according to claim 1 or 2, wherein the lens is a spectacle lens. It is characterized by that.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an injection compression molding apparatus for carrying out an injection compression molding method for a lens (meniscus eyeglass lens) according to this embodiment. The material of the spectacle lens formed here is a thermoplastic resin such as PMMA (polymethyl methacrylate) or PC (polycarbonate).
[0011]
The injection compression molding apparatus includes a mold clamping device 60 having an injection mold 50, a plasticizing device 70 for plasticizing a raw material resin, and the injection molding by measuring the molten resin plasticized by the plasticizing device 70. The injection device 80 is configured to inject and fill the mold 50 and a mold temperature adjusting device 51 that controls the temperature of the injection mold 50 to a preset temperature.
[0012]
The mold clamping device 60 includes a fixed die plate 61, a cylinder fixing plate 64 fixed to the fixed die plate 61 via a plurality of tie bars 62 and mounted with a mold clamping cylinder 63, and ascending / descending along the tie bar 62. The movable die plate 66 is provided freely and connected to the piston rod 65 of the clamping cylinder 63. The injection mold 50 is attached between the fixed die plate 61 and the movable die plate 66.
[0013]
The plasticizing device 70 is constituted by a plasticizing cylinder 74 that plasticizes a raw material resin introduced from a hopper 71 with a heater 73 while feeding it with a screw 72. The screw 72 is rotated by a hydraulic motor 75.
[0014]
The injection device 80 includes an injection cylinder 82 having a plunger 81 therein and a hydraulic cylinder 83 that slides (moves up and down) the plunger 81 of the injection cylinder 82. A nozzle 85 is attached to the tip (upper end) of the injection cylinder 82. A band heater (not shown) is wound around the upper peripheral position of the injection cylinder 82.
[0015]
A position sensor 87 and a speed sensor 88 for detecting the position P and the speed degree V of the piston 86 of the hydraulic cylinder 83 (or the plunger 81 of the injection cylinder 82) are provided below the hydraulic cylinder 83. The control device 90 sends a control signal to the drive control circuit 84 based on the signals P and V from the position sensor 87 and speed sensor 88 to control the injection cylinder 82.
[0016]
The mold temperature control device 51 includes a temperature control fluid supply device 52 that supplies a temperature control fluid (heating fluid and cooling fluid) to the injection mold 50, and each part of the mold 50 from the temperature control fluid supply device 52. And a control device 53 that commands the temperature control fluid supply device 52 to control the temperature of the temperature control fluid supplied to the temperature control fluid. The control device 53 stores a plurality of types of mold temperature control curves according to the type of lens to be molded in advance. When any one of the mold temperature control curves is specified, the specified mold temperature is stored. According to the control curve
The temperature of the temperature control fluid supplied from the temperature control fluid supply device 52 to each part of the mold 50 (insert guide members 5, 9, the upper mold insert 11, the lower mold insert 12, etc. described later) is controlled. Yes.
[0017]
2 is a cross-sectional view of the injection mold 50, and FIG. 3 is a cross-sectional view taken along arrow III-III in FIG. As shown in FIG. 2, the injection mold 50 includes an upper mold (movable mold) 1 and a lower mold (fixed mold) 2 that are divided vertically in a parting line PL. Two eyeglass lens molding cavities 3 and a runner 49 connecting the two lens molding cavities 3 are formed. A sprue 48 formed by the sprue bush 47 is formed at a right angle with respect to the runner 49, and a handle 46 (see FIG. 4) is formed at a right angle with respect to these. Here, a mold structure 45 having two eyeglass lens molding cavities 3, a runner 49, a sprue 48, and a handle 46 is formed.
[0018]
The mold body 4 of the upper mold 1 includes an insert guide member 5 and mold plates 6 and 7. The mold body 8 of the lower mold 2 includes an insert guide member 9 and a template 10. Inserts 11 and 12 forming the cavity 3 are accommodated in the insert guide members 5 and 9 so as to be slidable in a direction perpendicular to the parting line PL. Although not shown, the insert guide members 5 and 9 and the inserts 11 and 12 are formed with a temperature control fluid circulation groove for circulating the temperature control fluid supplied from the temperature control fluid supply device 52. Has been.
[0019]
The mold body 8 of the lower mold 1 is fixed to a mold attachment member 15 fixed on the fixed die plate 61. The mold body 4 of the upper mold 1 is connected to a mold mounting member 16 composed of an upper member 16A and a lower member 16B by a bolt 17 shown in FIG. 3, and between the mold body 4 and the mold mounting member 16. The disc spring 17A inserted in the outer periphery of the bolt 17 is interposed. The mold attachment member 16 is fixed to the movable die plate 66 so that a downward mold clamping force acts on the mold clamping cylinder 63.
[0020]
A gap S is provided between the mold body 4 and the mold mounting member 16, and the mold body 4 and the mold mounting member 16 are vertically moved by the gap S while being guided by the guide pins 18. It opens and closes. Further, a dimension opening cylinder (not shown) is disposed below the mold mounting member 15, and the mold mounting member 16 is pushed up against the mold clamping force of the mold clamping cylinder 63 by the dimension opening cylinder, so that a gap is formed. S is formed.
[0021]
The mold mounting member 16 is provided with a downward hydraulic cylinder 19 that can move up and down. The piston rod 21 connected to the piston 20 of the hydraulic cylinder 19 passes through the back insert 22 fixed to the surface of the cylinder 9 and includes a T-shaped clamp member 23 at the tip thereof. The T-shaped clamp member 23 is detachably engaged with a T-shaped groove 24 formed on the upper end surface of the insert 11.
[0022]
The mold attachment member 15 is provided with an upward hydraulic cylinder 26. A piston rod 28 connected to the piston 27 of the hydraulic cylinder 26 passes through the mold mounting member 15 and includes a T-shaped clamp member 29 at the tip thereof. The T-shaped clamp member 29 is detachably engaged with a T-U groove 30 formed on the lower end surface of the insert 12.
[0023]
A pressure receiving member 32 is fixed to the upper end of the hydraulic cylinder 19. When the pressure receiving member 32 is pushed down by the eject rod 34 inserted from the hole 33 formed in the mold attaching member 16, the hydraulic cylinder 19, the back insert 22 and the insert 11 are also pushed down, so that the lens molded in the cavity 3 is formed. The upper mold 1 and the lower mold 2 are protruded when divided.
[0024]
At the center of the upper mold 4 and the mold mounting member 16, an eject pin 35 is arranged to be movable up and down. A pressure receiving member 36 is fixed to the upper end of the eject pin 35. When the pressure receiving member 38 is pushed down by the eject rod 38 inserted from the hole 37 formed in the mold attaching member 16, the eject pin 35 is pushed down.
[0025]
On the pressure receiving member 32, the spring force of the spring 40 wound around the outer periphery of the eject return pin 39 acts upward. Although not shown in the drawing, the spring force of a spring wound around the outer periphery of the eject return pin is acting upward on the pressure receiving member 36 as well. Accordingly, when the eject rods 34 and 38 are lifted, the pressure receiving members 32 and 36 are also lifted to return to the initial positions.
[0026]
FIG. 4 shows the nozzle shut mechanism 90. The nozzle shut mechanism 90 includes a nozzle shut pin 91 as a blocking member. The nozzle shut pin 91 is fitted on the side wall of the sprue bush 47 so as to be able to advance and retreat in a direction substantially perpendicular to the center line of the sprue bush 47, and its rear end is connected to the piston rod 94 of the hydraulic cylinder 93 via the connection piece 92. Has been. The hydraulic cylinder 93 is fixed to the mold attachment member 15 via a cylinder attachment plate 95. Then, in a state where the nozzle 85 is in pressure contact with the sprue bush 47, the nozzle shut pin 91 slides to close the tip opening of the nozzle 85, thereby preventing the back flow of the resin. At this time, as shown in FIGS. 5 and 6, the front end surface 91A and the front end portion side surface 91B of the nozzle shut bin 91 are not in contact with the inner wall of the sprue bush 47 (sprue 48).
[0027]
Next, a procedure during molding will be described.
First, the inserts 11 and 12 are exchanged according to the type of lens to be molded. In exchanging the inserts 11 and 12, the upper mold 1 including the mold attachment member 16 is raised and the mold is divided from the lower mold 2. Further, the piston rod 21 of the hydraulic cylinder 19 is lowered, the piston rod 28 of the hydraulic cylinder 26 is raised, and the T-shaped clamp members 23 and 29 attached to the tips of the piston rods 21 and 28 are inserted into the insert guide member 5, Project from 6.
[0028]
The inserts 11 and 12 newly mounted on the mold bodies 4 and 8 of the upper mold 1 and the lower mold 2 are horizontally transferred while being held by a robot arm (not shown), and the T-shaped grooves 24 and 30 of the inserts 11 and 12 are moved. The T-clamp members 23 and 29 are engaged. Thereafter, the piston rod 27 of the hydraulic cylinder 26 is raised to raise the insert 11, and the piston rod 28 of the hydraulic cylinder 26 is lowered to lower the insert 12. Thereby, the inserts 11 and 12 are fitted to the insert guide members 5 and 6.
[0029]
Thus, in the case of molding a plus lens, the insert is replaced with an insert having a cavity 3 whose center thickness is thicker than that of the peripheral portion. In the case of molding of a minus lens, a cavity whose center thickness is thinner than that of the peripheral portion. Replace with an insert with 3.
[0030]
Now, the molding of the lens is performed according to the procedure shown in FIG.
First, the molten resin plasticized by the plasticizing device 70 is introduced into the injection cylinder 82 of the injection device 80 and weighed (metering step). Here, a necessary amount of molten resin is weighed in the mold structure 45 having the two lens forming cavities 3, the runner 49, the sprue 48, and the handle portion 46.
[0031]
Next, the mold 50 is closed, and the volume of the mold structure 45 is set to a predetermined size while leaving a compression allowance in the lens molding cavity 3 (mold preparation step). That is, the upper mold 1 is lowered by the mold clamping cylinder 63, the mold plate 6 of the upper mold 1 is in contact with the mold plate 10 of the lower mold 2, and the disk spring 17A is closed so as not to be compressed (FIGS. 2 and 2). The mold is closed to the state shown in 3). In this state, the gap S is set to the maximum opening amount (about 15 mm).
[0032]
Next, an opening amount (compression allowance) is set. At this time, an opening amount S of 0.8 mm or less is set in the molding of the plus lens. In molding of the minus lens, an opening amount S larger than 0.8 mm is set. That is, the compression allowance at the time of molding the minus lens is set larger than the compression allowance at the time of forming the plus lens.
[0033]
Next, the mold 50 is heated up to a set temperature (heat up process). For this, the temperature-controlled fluid is supplied from the temperature-controlled fluid supply device 52 to each part of the mold 50 (insert guides 5, 9, the upper mold insert 11, the lower mold insert 12, etc.), and the mold 50 Heat up to the set temperature. After that, the nozzle 85 is opened. That is, the nozzle shut pin 91 is retracted from the sprue 48.
[0034]
Next, an injection process in which the molten resin measured in the measurement process is injected into the mold structure 45 through the passage of the nozzle 85 and the passage tip of the nozzle 85 is closed will be described with reference to FIGS. .
[0035]
First, molten resin is injected and filled. For this purpose, the molten resin plasticized by the plasticizing device 70 is measured and injected by the injection cylinder 82 of the injection device 80 and filled into the cavity 3 through the nozzle 85, the sprue 48, the runner 49 and the gate portion 46.
[0036]
At this time, the control device 90 performs control so that the speed V (injection speed) of the plunger 81 of the injection cylinder 82 approximates the speed shown in FIG.
8A, when forming a minus lens having a lens power of −4.00 D, a center thickness of 1.4 mm, and an edge thickness of 7.9 mm, (B) shows a lens power of −2.00 D, When molding a minus lens with a center thickness of 1.4 mm and an edge thickness of 4.8 mm, (C) is a plus lens with a lens power of +2.00 D, a center thickness of 4.2 mm, and an edge thickness of 1.0 mm. (D) shows a case where a semi-finished lens having a convex base cup of 3.00, a center thickness of 5.4 mm, and an edge thickness of 5.8 mm is formed, respectively.
[0037]
In the case of (A), the injection speed V is the first set speed V1A in the section (the section from S0 to S1 shown in FIG. 9) from the start of injection filling of the molten resin until the molten resin reaches before the gate portion 46. In the section from the front of the gate portion 46 to the inside of the cavity 3 (the section from S1 to S2 shown in FIG. 8), the molten resin is melted so that the injection speed V becomes the second set speed V2A. Control is performed so that the injection speed V becomes the third set speed V3A in the section from the time when the resin reaches the cavity 3 until the completion of injection filling (the section from S2 to S3 shown in FIG. 9). Similarly, in the cases of (B), (C), and (D), the injection speed V is set to the first set speeds V1B, V1C, and V1D in the sections S0 to S1, and the injection speed is set in the sections S1 to S2. V is controlled to the second set speeds V2B, V2C, and V2D, and the injection speed V is controlled to be the third set speeds V3B, V3C, and V3D in the sections S2 to S3.
[0038]
In FIG. 8, P0 is the position of the plunger 81 at the start of injection and injection of the molten resin, P1 is the position of the plunger 81 when the molten resin reaches the front of the gate portion 46, and P2 is the molten resin in the cavity 3. The position of the plunger 81 when reached, P3 indicates the position of the plunger 81 when injection filling is completed. These are detected by the position sensor 87. These positions P0, P1, P2, and P3 are obtained in advance by calculation or experiment according to the lens shape.
[0039]
Specifically, control is performed according to the flowchart shown in FIG.
First, after commanding the first set speed V1 to the drive control circuit 84, the actual injection speed V1 is compared while comparing the speed data (actual injection speed V) from the speed sensor 88 with the first set speed V1. Is given to the drive control circuit 84 so that the speed becomes the first set speed V1. At the same time, it is checked whether or not the position data P from the position sensor 87 has reached P1, and closed control is performed so that the actual injection speed V becomes the first set speed V1 until the position data P reaches P1. . Accordingly, the molten resin can be accurately filled up to the position P1 where the molten resin reaches before the gate portion 46.
[0040]
After the position data P reaches P1, that is, after the molten resin reaches before the gate portion 46, the second set speed V2 is commanded to the drive control circuit 84. Here, while comparing the speed data from the speed sensor 88 (actual injection speed V) with the second set speed V2, an acceleration or deceleration command is issued so that the actual injection speed V becomes the second set speed V2. This is given to the drive control circuit 84. At the same time, it is checked whether or not the position data P from the position sensor 87 has reached P2, and closed control is performed so that the actual injection speed V becomes the second set speed V2 until the position data P reaches P2. . As a result, the molten resin can be slowly filled from the position P1 where the molten resin reaches before the gate portion 46 to the position P2 where the molten resin reaches into the cavity 3.
[0041]
After the position data P reaches P2, that is, after the molten resin reaches the cavity 3, it is determined whether the plus lens is molded or the minus lens is molded. In the case of molding a plus lens, after the third set speed V3 is instructed to the drive control circuit 84, the actual injection speed V is compared with the third set speed V3 while comparing the actual injection speed V with the third set speed V3. 3. An acceleration or deceleration command is given to the drive control circuit 84 so that the set speed V3 is obtained. At the same time, it is checked whether or not the position data P from the position sensor 87 has reached P3, and closed control is performed so that the actual injection speed V becomes the third set speed V3 until the position data P reaches P3. When the position data P reaches P3, the operation is stopped. Thereby, in the case of molding a plus lens, the molten resin can be filled while ensuring a sufficient injection speed. At this time, since the thickness of the central portion 15 of the cavity 3 (the central portion of the lens) is large, the molten resin that has reached the cavity 3 passes through the central portion of the cavity 3 (the central portion of the lens) and reaches the peripheral portion. Weld marks can be suppressed.
[0042]
In the case of molding of a minus lens, after commanding the third set speed V3 to the drive control circuit 84 (open control), it is checked whether or not the position data P from the position sensor 87 has reached P3. Stop when the position data P reaches P3. In other words, in the case of molding of a minus lens, an opening amount S larger than 0.8 mm is set, and the injection resistance in the mold is small, so that a sufficient injection speed is ensured even if the above-described open control is used. However, the change in the injection speed can be reduced. Accordingly, it is difficult for an injection history to appear as a change in injection speed on the surface of the molded product. Moreover, since the thickness of the central portion of the cavity 3 is set to be large by setting a large opening amount, the molten resin that has reached the cavity 3 passes through the central portion of the cavity 3 without being diverted, and the peripheral portion. To reach. For this reason, weld marks can be suppressed and a high-quality lens can be obtained.
[0043]
Next, in the case of molding a plus lens, after the injection filling of the molten resin is completed, the nozzle is closed and subsequently pressurized (compressed). The operation of the closing mechanism is well known in the applicant's Japanese Utility Model Publication No. 7-27140, Japanese Patent Publication No. 5-44893, Japanese Patent Publication No. 5-30608, etc., and will not be described in detail here.
[0044]
On the other hand, in the case of molding a minus lens, pressurization (compression) is started before completion of injection filling of the molten resin. Specifically, when about 90 to 95% of the molten resin to be injected is injected, pressurization is started by the mold clamping cylinder 63. Finally, the nozzle 85 is closed.
[0045]
As described above, the actual injection speed is compared with the first and second preset speeds V1 and V2 set in advance in the sections S0 to S2 from the start of the injection filling of the molten resin until the molten resin reaches the cavity 3. However, since the injection speed V is controlled so that the actual injection speed V becomes the first and second set speeds V1 and V2, that is, the closed control is adopted, the molten resin enters the cavity 3. The molten resin can be filled accurately up to the position where it reaches.
[0046]
In this closed control, in the sections S0 to S1 from the start of the injection filling of the molten resin until the molten resin reaches before the gate portion 46, the injection speed V is set to the first set speed V1 and the gate section (sections S1 to S2). ), Since the injection speed V is once lowered to the second set speed V2, it is possible to prevent a rapid intrusion of the molten resin into the cavity 3. Thereby, in the cavity 3, air entrainment can be reduced as much as possible, and smooth filling without greatly changing the behavior of the molten resin can be compensated.
[0047]
Further, at the time of molding the minus lens, the injection speed V is commanded to the preset third set speed V3 in the sections S2 to S3 from when the molten resin reaches the cavity 3 until the injection filling is completed. That is, since open control is employed, the speed change of the molten resin in the cavity 3 can be reduced. Therefore, the phenomenon that the filling history appears on the surface of the molded product can be reduced. In particular, when molding a minus lens, the dimension opening amount S is set to be large and the injection resistance is small. Therefore, even when the open control is adopted, the change in the injection speed is reduced while ensuring a sufficient injection speed. be able to. Therefore, the phenomenon that the filling history appears on the surface of the molded product can be reduced.
[0048]
At this time, as in FIGS. 8A and 8B, the injection speed of the injection cylinder is controlled by changing between the minus weak lens and the minus strength lens, and the minus strength lens is slower. Therefore, even when molding a negative strength lens in which the difference between the center thickness and the edge thickness is larger than that of the minus weak lens, the speed change of the molten resin in the lens molding cavity 3 can be reduced. .
[0049]
Further, at the time of molding the minus lens, since the compression of the opening amount S is started before the injection of the molten resin is completed, the capacity of the cavity 3 is reduced before the injection filling of the molten resin is completed. Accordingly, at the time when the injection filling of the molten resin is completed, a large unfilled portion is hardly left in the cavity 3, and thus generation of a flow mark can be prevented. That is, when the opening amount S is set to be large, the flow of the molten resin is stopped while leaving a large unfilled portion in the cavity 3 when the injection filling of the molten resin is completed. There is a problem that the flow mark is likely to be generated on the critical line, but the occurrence of the flow mark can be prevented by using the present embodiment.
[0050]
Further, during the plus lens molding, the actual injection speed is compared while comparing the actual injection speed V with the preset third set speed V3 in the section from when the molten resin reaches the cavity 3 until the completion of injection filling. Since the injection speed V is controlled so that V becomes the third set speed V3, that is, closed control is adopted, a sufficient injection speed can be secured. By the way, in plus lens molding, since the gate opening amount S is small and the gate structure is narrowed down to prevent the gate sink, the injection resistance is very large. It is expected that a high injection speed cannot be obtained and a high-quality molded product cannot be obtained.
[0051]
In the molding of a minus lens, the flow resistance is increased at the cavity center due to the shape characteristic that the center of the lens is thinner than the peripheral edge. For this reason, the molten resin injected into the cavity is difficult to flow in the central portion of the cavity, and is diverted and goes around from the peripheral portion, so that a weld mark is likely to occur. Therefore, it is necessary to pay sufficient attention to the injection history. In this point, in this example, the compression allowance at the time of molding the minus lens is set to be larger than the compression allowance at the time of molding the plus lens, so even when the minus lens is molded, the molten resin that has reached the cavity is not diverted. It flows into the peripheral portion through the central portion, and as a result, the generation of weld marks can be suppressed.
[0052]
Next, while the molten resin is being compressed and compressed, the mold 50 is reheated and then cooled (reheating and cooling step). That is, the temperature of the upper mold insert 11 and the lower mold insert 12 is raised by supplying the heating fluid from the temperature adjusting fluid supply device 52, and then the thermoplastic resin is solidified while decreasing the temperature by supplying the cooling fluid.
[0053]
For example, as shown in FIGS. 11A to 11D, the temperature of the upper mold insert 11 and the lower mold insert 12 is once raised and then lowered. In FIG. 11, when (A) forms a minus lens with a lens power of -2.00, a center thickness of 1.4 mm, and a peripheral edge thickness of 4.8 mm, (B) shows a lens power of -4. .00, when forming a negative lens with a center thickness of 1.4 mm and a peripheral portion thickness of 7.9 mm, (C) is a lens power of +2.00, a central portion thickness of 4.2 mm, and a peripheral portion When molding a positive lens with a thickness of 1.0 mm, (D) shows a semi-finished lens with a convex base cup of 3.00 D, a center thickness of 5.4 mm, and a peripheral edge thickness of 5.8 mm. The lens one side is a finished surface and the other lens one side is finished by post-processing.
[0054]
At this time, as shown in FIGS. 11 (A), 11 (B), 11 (D), in particular, (A), (B), the lower mold insert 12 (lens convex surface forming cavity) when taking out the molded product from the mold 50 The temperature of the forming member is lower than that of the upper mold insert 11 (lens concave surface forming cavity forming member). When such a temperature difference is provided between the lower mold insert 12 and the upper mold insert 11, the lens convex surface of the molded product when taken out from the mold 50 has a lower temperature than the lens concave surface. The solidification of the molded product taken out from the mold 50 can be prevented from occurring at an early stage. In other words, if the lens to be molded is a lens with a difference in thickness between the central part and the peripheral part, and the thickness of the peripheral part is larger than the thickness of the central part, the lens concave surface side from the central part with a small thickness However, the occurrence of the bending phenomenon can be prevented by providing the temperature difference as described above. This is because the lens molding surface shapes of the upper mold insert 11 (lens concave surface molding cavity forming member) and the lower mold insert 12 (lens convex surface molding cavity forming member) are accurately transferred to the molten resin. Means you can get
[0055]
When the molding is performed in this manner and then ejected, a molded product 101 shown in FIG. 12 is obtained. The molded product 101 is molded by the spectacle lens 102 molded by the two lens molding cavities 3, the connecting portion 103 molded by the runner 49 and connecting the two spectacle lenses 102, and the sprue 48. And a rod-like portion 104 extending perpendicularly from the central portion of the connecting portion 103 in the thickness direction of the lens 102, and a handle 105 formed by the handle portion 46 and extending perpendicularly to the connecting portion 103 and the rod-like portion 104. Has been.
[0056]
After the ejection, the lens 102 of the molded product 101 is immersed in the wear-resistant hard coat liquid in a state where the handle 105 is held by the knob member 133 of the immersion working tool 130 shown in FIG. Next, after being immersed for a certain time, the lens 102 and the connecting portion 103 are separated by a cutter device, whereby two lenses 102 coated with a coating film with a hard coat liquid are obtained from one molded article 101. Raru.
[0057]
Therefore, according to the present embodiment, after a required amount of molten resin is measured in the mold structure 45 having the plurality of lens molding cavities 3, the runners 49, and the sprues 48, the molten resin is passed through the passage in the nozzle 85. The resin is then injected into the mold structure 45, where the nozzle shut pin 91 closes the end of the passage of the nozzle 85 and the molten resin in the mold structure 45 is compressed after completion of injection of the molten resin or immediately before completion of injection. Since the molded product is taken out after cooling, that is, since the measured amount of resin corresponds to the amount taken out as a molded product, a lens with high shape accuracy can be molded.
[0058]
Further, in the injection process, the molten resin in the mold structure 45 is pressurized and cooled to be taken out as a molded product in a state where the passage end of the nozzle 85 is closed by the nozzle shut pin 91. Since the part taken out as a product and the part remaining in the nozzle 85 are blocked by the nozzle shut pin 91 in a state where the edge is completely cut off, the resin remaining in the nozzle 85 is molded as a foreign object in the next molding. It is not mixed into the product. Therefore, a high quality lens can be molded.
[0059]
Further, in the reheating and cooling step, while the molten resin is being compressed and compressed, the upper mold insert 11 and the lower mold insert 12 are reheated by supplying heated fluid from the temperature control fluid supply device and then cooled. Therefore, the thermoplastic resin injected and filled in the lens molding cavity 3 is once heated in a pressurized state, thereby improving the homogeneity and fluidity of the resin, and cooled and solidified from this state. Therefore, the homogeneity of the molded product and the transferability with the upper mold insert 11 and the lower mold insert 12 can be further improved. Therefore, also from this point, it is possible to mold a lens with high quality and high shape accuracy.
[0060]
In the reheating and cooling step, the temperature of the lower mold insert 12 (lens convex surface molding cavity forming member) when the molded product is taken out from the mold 50 is set to the temperature of the upper mold insert 11 (lens concave surface molding cavity forming member). Since the lens convex surface of the molded product when it is taken out from the mold 50 has a lower temperature than the lens concave surface, the lens convex surface is solidified earlier than the lens concave surface and the molded product taken out from the mold 50 is removed. Occurrence of the middle break phenomenon can be prevented. In other words, if the lens to be molded is a lens having a difference in thickness between the central portion and the peripheral portion, and the thickness of the peripheral portion is larger than the thickness of the central portion, the lens concave surface from the central portion having a small thickness. Although a side-folding phenomenon that easily bends to the side is likely to occur, the occurrence of the center-breaking phenomenon can be prevented by providing a temperature difference as described above. This is because the lens mold surface shape of the upper mold insert 11 (lens concave surface molding cavity forming member) and the lower mold insert 12 (lens convex surface molding cavity forming member) is accurately transferred to the molten resin. It means you can get.
[0061]
Further, since the mold structure 45 includes two lens forming cavities 3, a plurality of lenses 102 can be formed simultaneously. Further, since the mold component 45 includes the handle portion 46, the molded product 101 having the handle 105 can be formed. Therefore, when the lens 102 portion of the molded article 101 is crushed with the wear-resistant hard coat liquid or the like, it can be crushed with the handle 105, so that the dip treatment can be facilitated.
[0062]
Further, in the injection process, the nozzle shut pin 91 protrudes to a position immediately before the tip of the nozzle shut pin 47 contacts the inside of the sprue bush 47 so as to close the passage tip of the nozzle 85, and the tip surface 91A and the side surface 91B of the nozzle shut pin 91 are closed. And the inner wall of the sprue bush 47, a molded sprue portion is not lost during mold release, and foreign matter can be reliably prevented.
[0063]
In the above-described embodiment, the case where the mold 50 having the two spectacle lens molding cavities 3 is used is shown. However, one lens molding cavity or three or more lens molding cavities are used. You may make it shape | mold using the metal mold | die which has a cavity.
[0064]
Further, in the above embodiment, closed control is adopted in the sections S0 to S2 from the start of the injection filling of the molten resin to the arrival of the molten resin in the cavity 3, but the molten resin is supplied to the gate portion 46 from the start of the injection filling of the molten resin. Closed control is adopted in the sections S0 to S1 until reaching the position before, and open control is adopted in the sections S1 to S2 (section of the gate section 46) until the molten resin reaches the cavity 3 from before the gate section 46. It may be. In this way, sudden infiltration of the molten resin into the cavity can be prevented, so that air can be prevented from being trapped in the cavity as much as possible, and smooth filling without greatly changing the behavior of the molten resin can be compensated. it can.
[0065]
Moreover, in the said embodiment, a mold structure is shown.
Although 45 includes the handle portion 46, the handle portion 46 may be omitted.
[0066]
Moreover, in the said embodiment, although the compression allowance at the time of shaping | molding was set with the opening amount formed between the type | mold main body 4 and the type | mold attachment member 16, you may use another metal mold | die. For example, a mold having a structure in which a cavity core that protrudes into the cavity 3 is provided, a compression margin is set from the position of the cavity core, and then the cavity core is protruded into the cavity 3 to be compressed is used. Good.
[0067]
Further, in the above embodiment, at the time of molding the minus lens, the compression of the opening amount S is started when the molten resin is injected about 90 to 95%, but the percentage at this time is also the volume of the cavity 3, the resin It may be arbitrarily determined according to the type of lens and the characteristics of the lens.
[0068]
In the above embodiment, the speed sensor 88 is provided in addition to the position sensor 87. However, without providing the speed sensor 88, the relationship between the position data from the position sensor 87 and the time selected from the position data. From this, the speed may be obtained by calculation.
[0069]
In the above embodiment, the opening amount is set to 0.8 mm or less in the case of a plus lens and larger than 0.8 mm in the case of a minus lens, but these numerical values depend on the characteristics of the lens. Can be determined arbitrarily.
[0070]
Further, the molding apparatus is not limited to the one in the present embodiment, and a horizontal apparatus may be used. Of course, the mold, its temperature adjustment mechanism, injection cylinder, and the like can be similarly implemented using other mechanisms.
[0071]
Moreover, although the said embodiment demonstrated the injection compression molding of the spectacle lens, it is not necessarily restricted to a spectacle lens, This invention is applicable to other lenses generally.
[0072]
【The invention's effect】
As described above, according to the present invention, a lens having excellent optical performance and having a power difference such as the strength and weakness of a meniscus lens, and a unique lens shape such as a single focus aspherical surface, a progressive surface, and an astigmatic lens. Therefore, it is possible to reliably prevent the bending phenomenon that occurs when the minus lens is molded.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an injection compression molding apparatus for carrying out a method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an injection mold in the apparatus.
3 is a cross-sectional view taken along arrow III-III in FIG.
4 is a cross-sectional view taken along the line IV-IV in FIG. 2;
FIG. 5 is an enlarged view of a main part of FIG.
6 is a view taken along arrow VI-VI in FIG. 5;
FIG. 7 is a flowchart showing a lens molding procedure in the embodiment of the present invention.
FIG. 8 is a view showing a relationship between an injection speed and a position in the same embodiment.
FIG. 9 is a view showing a molded product obtained in the embodiment.
FIG. 10 is a flowchart of control in an injection process of the embodiment.
FIG. 11 is a diagram showing a temperature control curve in the reheating / cooling step of the same embodiment;
FIG. 12 is a perspective view showing a molded product obtained in the embodiment.
FIG. 13 is a view showing a state of coating treatment of a molded product obtained in the same embodiment.
[Explanation of symbols]
3 Cavity for molding eyeglass lenses
11 Upper mold insert (cavity forming member for lens concave molding)
12 Lower mold insert (cavity forming member for lens convex surface molding)
45 Mold structure
46 Handle part
48 sprue
49 Lanna
50 Mold for injection molding
85 nozzles
90 Nozzle shut mechanism
82 Injection cylinder
V Actual injection speed
V1 1st set speed
V2 Second set speed
V3 Third set speed
P0 Injection filling start position
P1 The position where the molten resin has reached the gate
P2 Position where the molten resin reaches the cavity
P3 Injection filling completion position

Claims (3)

A lens forming cavity including at least a pair of cavity forming members for forming an uneven lens surface, a runner communicating with the lens forming cavity via a gate portion, and a mold structure having a sprue communicating with the runner A lens injection compression molding method for molding a lens using a mold,
A metering step of metering a required amount of thermoplastic resin for the mold structure having the lens molding cavity, runner, and sprue;
A mold preparing step of closing the mold and setting the volume of the mold structure to a predetermined size while leaving a compression allowance in the lens molding cavity;
An injection step of injecting the thermoplastic resin measured in the measurement step to the mold component through a nozzle passage;
A compression step of compressing the compression allowance after completion of injection of the thermoplastic resin or immediately before completion of injection;
A mold temperature adjustment step for controlling the mold temperature during these steps to solidify the thermoplastic resin in the mold structure, and
In the injection process, in the section from the start of the injection of the thermoplastic resin until the molten resin reaches the lens molding cavity, the injection speed is controlled to be a set speed, and the injection speed is once set at the gate portion. To the speed of
Furthermore, in the interval from when the molten resin reaches the lens molding cavity until the completion of injection filling, the injection speed is controlled by changing the minus weak lens and the minus strength lens, and the minus strength lens is the minus weak lens. Try to be slower,
In the mold temperature adjusting step, the lens extraction temperature of the lens convex surface molding cavity forming member is controlled to be lower than the lens extraction temperature of the lens concave surface molding cavity forming member. .   2. The lens injection compression molding method according to claim 1, wherein the mold structure has a handle portion communicating with the runner and the sprue. The lens injection molding method according to claim 1 , wherein the lens is a spectacle lens.

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