JPH0935338A - Mold and method variable in cavity shape and molded substrate by the mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mold and method variable in cavity shape for preventing the occurrence of defects and producing products (optical disks) having projecting parts (stack rings) of an exact shape by varying the cavity shape to prevent the occurrence of disturbance in the flow of a resin in case of injection molding and a molded substrate by the mold. SOLUTION: The cavity 10 corresponding to the shape of the optical disks is formed by closing the stationary side mold 8 and the moving side mold 9. An annular member 16 is supported freely slidably in a recessed hold 17 in the stationary side mold 8 and arranged in the position flush with a mirror finished surface 18 in an injection molding stage. The annular member 16 is withdrawn into the recessed hold 17 by a spring 14 or the pressure of the resin in a pressure holding and molding stage of an intermediate stage shifting to the pressure holding and molding stage after the completion of the injection molding stage, by which a hollow groove corresponding to the stack ring is formed. The stages are automatically executed by utilizing the automatic control of the molding machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die and a molding method for an optical disk and other injection-molded products, and a molded substrate for an optical disk, an injection-molded product, etc., and in particular, a part of a cavity shape is changed during molding. The present invention relates to a molding die and method in which the cavity shape is variable, which is suitable for producing a molded product having a shape corresponding to the changed cavity, and a molding substrate by the mold.

[0002]

2. Description of the Related Art Optical disk substrates are used as new information recording media. This substrate is molded in a mold by an injection molding method or an injection compression molding method. As shown in FIG. 7, the molded substrate 1 of the optical disc is composed of a flat disc.
Mounting seat surface portion 2 and information recording area 3 formed around it
Etc. An annular convex portion 4 (hereinafter referred to as a stack ring 4) called a stack ring is formed on the mounting seat surface portion 2. The stack ring 4 is, as shown in FIG.
This is for preventing the upper and lower molded substrates 1, 1 from contacting each other when stacking a large number of molded substrates 1 on a molded substrate storage jig 7 in which a center pole 6 is erected on a stand 5. is there.

The molded substrate storage jig 7 is necessary to save space in the optical disc manufacturing line.
Many are used. FIG. 9 shows a part of a molding die for molding the stack ring 4. The cavity 10 is formed by closing the fixed side mold 8 and the movable side mold 9. The cavity 10 corresponds to the shape of the molded substrate 1. Fixed side mold 8 has stack ring 4
The recessed groove 11 (ring groove) corresponding to is formed. Groove 1
By injecting a resin into the space of the cavity 10 forming 1 to fill the space, the molded substrate 1 having the stack ring 4 is formed.

[0004]

As shown in FIG. 9, by forming a concave groove 11 in the fixed side mold 8, a stack ring 4 matching the shape of the concave groove 11 is formed. To form the stack ring 4 shown in FIG. 7, the groove 11 shown in FIG.
Is a groove 1 having a rectangular cross section as indicated by a two-dot chain line.
It should be 1a.

However, when the concave groove 11a is formed, the thickness of the cavity 10 suddenly increases at this portion, the flow velocity of the introduced resin becomes slow, and the temperature of the resin becomes low. As a result, the flow of resin is disturbed, and as shown in FIG. 10, defects 12 such as weld due to silver streak, weld, and cold slug occur in the stack ring 4 and the information recording area 3 of the molded product. Therefore, the two-dot chain line concave groove 11a
Instead of the above, a means for reducing the above defects by adopting the concave groove 11 having the taper 13 is adopted. However, even if the shape of the concave groove 11 is used, it is not possible to completely eliminate the occurrence of the defect 12 and only the taper 13 is formed. There is a problem that the area of the stack ring 4 becomes large and the degree of freedom in design is reduced.

The present invention was devised in view of the above circumstances, and there is no disturbance in the flow of resin during molding,
A molding die having a variable cavity shape and a molding method capable of accurately forming a stack ring having a predetermined shape, capable of automatically and smoothly changing the shape of the cavity, and producing a good-quality molded substrate, and the molding method. It is an object to provide a molded substrate manufactured by a mold.

[0007]

According to a first aspect of the present invention, there is provided a molding die, wherein a part of a shape of a cavity formed between a fixed side die having a mirror plate and a movable side die having a stamper or the like is provided. A molding die that changes during a molding process, in which a resin is injected and introduced into the cavity in the part at the initial stage of molding, and is arranged flush with the other part of the cavity, and after the injection molding. In (1), a member slidably supported by the mold is arranged so as to be retracted by a predetermined amount, and a drive means for reciprocating the member is provided.

The molding die according to claim 2 is characterized in that the part corresponds to a position where a stack ring is formed in the optical disk, and the member is a ring-shaped member corresponding to the shape of the stack ring. And

In the molding die according to claim 3, the post-process corresponds to an intermediate process in which the injection molding process shifts to the pressure-holding molding process, and the driving means engages with the member. A spring or rubber elastic body, and the pressing force at the time of setting the elastic body is set to be higher than the pressure in the cavity in the initial step of injection molding and lower than the pressure in the intermediate step. And

In the molding die according to claim 4, the post-process corresponds to an intermediate process in which the injection molding process shifts to the pressure-holding molding process, and the driving means pushes the member from the outside. It is characterized in that it is a pressing means for applying a pressure and a spring balanced with this, and the operation is controlled by detecting the time when the pressing means shifts from the injection molding control to the pressure-holding molding control.

A molding die according to a fifth aspect is characterized in that a plurality of the driving means are arranged.

According to a sixth aspect of the present invention, there is provided a molding die, wherein a plurality of the driving means are arranged in the same circumference at equal intervals when the members are ring-shaped members. Characterize.

According to a seventh aspect of the present invention, there is provided a first molding method in which a resin is filled in a cavity formed between a fixed mold having a mirror plate and a movable mold having a stamper and the like to perform injection molding. And a second step of changing the shape of the cavity by retracting a part of the mold forming the cavity into the mold in the intermediate step of shifting from the injection molding step to the pressure-holding molding step, At the end of the molding step, a cavity shape variable molding method comprising a third step of restoring the retracted part, wherein the retracting and restoring of the part is elastic for engaging the part. The balance between the pressing force of the body and the pressure inside the cavity and / or the driving means that acts on the portion from the outside is performed, and these retreats and restorations are performed between the initial step of injection molding and the hold molding step. Characterized in that it is performed in synchronization with timing of completion of the molding process.

In the molded substrate according to the eighth aspect, a resin material is filled in a cavity formed between a fixed-side mold having a mirror plate and a movable-side mold having a stamper and the like in an injection molding process. Before moving to the pressure-holding molding step, part of the mold for forming the cavity is retracted into the mold to change the shape of the cavity, and the changed part is filled with resin. To do.

The molded substrate according to a ninth aspect is characterized in that the part of the molded substrate corresponds to a stack ring.

For example, a ring-shaped member, which is a member forming a groove corresponding to the shape of a stack ring, is slidably supported by the mold on a part of the fixed mold. This ring-shaped member is arranged flush with the mold surface forming the cavity during the injection molding process in which the resin is introduced into the cavity, but during the transition from the injection molding process to the pressure-holding molding process. It is drawn into the mold by the driving means to form a recess corresponding to the stack ring. The concave groove is filled with resin during the pressure-holding injection step. Upon completion of molding, the ring-shaped member returns to the original flush state. As described above, since the concave groove is not formed in the injection molding process in which a large amount of resin is introduced, the flow of resin is not disturbed. Since the molding die is formed as described above, a good quality molded substrate can be manufactured. Further, by providing a plurality of driving means, the ring-shaped member can be moved smoothly and uniformly.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are partial cross-sectional views for explaining each embodiment of a molding die and a molding method of the present invention, and FIG. 5 is a plan view showing an example of a driving means provided with a plurality of them. . In this embodiment, a ring-shaped member corresponding to the stack ring is applied as the member. Further, each drawing is a partial cross-sectional view enlarging and displaying only around the portion where the stack ring is formed.

The molding die shown in FIG. 1 uses a spring 14, which is one of elastic bodies, as the driving means. The fixed-side die 8 has a mirror plate 15 and is provided with a ring-shaped recessed hole 17 in which a ring-shaped member 16 for forming the stack ring 4 (FIG. 10) is slidably supported. The spring 14 is provided between the bottom surface of the ring-shaped recess 17 and the ring-shaped member 16. As shown in FIG. 1, the ring-shaped member 16 is arranged such that the mirror surface 18 of the fixed-side mold 8 and its lower end surface are flush with each other when the resin is not introduced into the cavity 10. In this state, the spring 14 presses the ring-shaped member 16 downward by the set pressing force, but the ring-shaped member 16 is held in the above-mentioned flush state by the protrusion preventing means (not shown). The set pressing force of the spring 14 is preferably set to 20 to 50 [kgf / cm ² ] and particularly preferably 30 to 40 [kgf / cm ² ].

On the other hand, the movable mold 9 comprises a flat surface portion 19 parallel to the mirror surface 18 of the fixed mold 8 and a stamper 20, and both molds 8 and 9 are closed (injection molding). In the state, the cavity 10 is formed between the mirror surface 18, the flat surface portion 19 and the stamper 20. In addition,
The stamper 20 is supported by a stamper side plate 21 and held by a stamper pressing claw 22.

Next, the molding method according to this embodiment will be described. When the fixed mold 8 and the movable mold 9 are closed to form the cavity 10, the resin is introduced into the cavity 10. The pressure of the introduced resin is 10 [k
gf / cm ² ] or less. Since the set pressing force of the spring 14 pressing the ring-shaped member 16 is higher than the pressure of the resin, the ring-shaped member 16 is held in a stationary state.
Therefore, a portion that changes the thickness of the cavity 10 such as the concave groove 11 is not formed in the cavity 10. As a result, the resin flows without turbulence and changes in velocity during flow,
Problems such as temperature changes do not occur.

When the injection molding process for filling the resin in the cavity 10 is completed, the holding pressure molding process is started. The pressure-holding molding process is intended to completely fill the cavity 10 by further introducing resin into a portion where the resin filling by the injection molding process is insufficient. The resin pressure in this case is usually 50 [kgf
/ Cm ² ]. Since the pressure of this resin is higher than the set pressing force of the spring 14, the ring-shaped member 16 is pushed into the ring-shaped recessed hole 17 as shown in FIG. 2, and the ring-shaped member of a size corresponding to the stack ring 4 is formed. The groove 11 is formed. Therefore, the resin in the pressure-holding molding process fills the groove 11. When the pressure-holding molding process is completed and the resin is cooled, the fixed-side mold 8 and the movable-side mold 9 are opened to manufacture the molded substrate 1 as shown in FIG. A stack ring 4 corresponding to the concave groove 11 is formed on the molded substrate 1.

As is clear from the above description, since there is no change in the thickness of the cavity 10 in the injection molding process in which a large amount of resin is introduced, the resin is smoothly introduced and the defects as in the prior art do not occur. Further, since the high-pressure resin in the pressure-holding molding step can enter the concave groove 11, the stack ring 4 having a predetermined shape can be formed.

3 and 4 show another embodiment of the present invention. In this embodiment, the content of the driving means is different from that of the above-mentioned embodiment. A ring-shaped member 16 is used as this driving means.
A pressing unit 23 that presses and moves is used. The pressing means 23 is, for example, a compressor (not shown) and the fixed mold 8
2 is a medium flow hole that is bored in the hole and communicates with the ring-shaped recess 17
4 or the like, and oil or air as a pressure medium is sent from the compressor to the concave hole 17 through the medium circulation hole 24.

The spring 14a has a spring force that balances the pressure of the medium, and urges the ring-shaped member 16 to move in the suction direction. That is, when the pressure medium is introduced into the concave hole 17, the ring-shaped member 16 moves to a position flush with the lower mirror surface 18 against the suction force of the spring 14a. When the introduction of the pressure medium is stopped, the ring-shaped member 16 is drawn into the concave hole 17 by the suction force of the spring 14a, and the concave groove 11 corresponding to the stack ring 4 is formed as in the above-described embodiment. The pressure of the pressure medium and the spring force of the spring 14a that balances with the pressure medium are lower than the pressure of the resin in the injection molding process, and are set to, for example, about 5 [kgf / cm ² ].

Next, the timing for switching the pressure medium in and out and its operation control will be described. In the molding machine, a control signal is issued when the injection molding process is switched to the pressure-holding molding process. The volume of the molten resin filled in the cavity 10 by injection contracts when it begins to solidify. Therefore, holding pressure molding is performed to supplement the volume reduction. Therefore, the ring-shaped member 1 is appropriately timed during the start of the pressure-holding molding process.
The recessed groove 11 may be formed by retracting the groove 6. For this purpose, the signal is detected, whereby the operation of the compressor of the pressing means 23 is stopped and the supply of pressure medium is stopped. As described above, since the spring 14a is biased in the direction in which the ring-shaped member 16 is pulled in, the ring-shaped member 16 is pulled into the recessed hole 17 by the spring 14a and the recessed groove 11 is formed. The above operation control is easily performed by automatic control.

FIG. 5 shows still another embodiment of the present invention, in which an air cylinder mechanism 25 is adopted as a driving means. A cylinder chamber 26 is provided behind the recessed hole in which the ring-shaped member 16 is accommodated, and a piston member 27 is slidably accommodated in the cylinder chamber 26. The passages 28 and 29 bored in the fixed-side mold 8 communicate with the cylinder chamber 26 above and below the piston member 27. Further, these passages 28 and 29 are connected to an air compressor (not shown).
The ring-shaped member 16 is moved through the piston member 27 by letting pressurized air into and out of the passages 28 and 29, and the concave groove 11 is formed as in the above-described embodiment. In addition, the operation control of the air compressor is performed based on the detection signal when the injection molding process shifts to the pressure-holding molding process.

The above-mentioned drive means may be a single drive means, but when the member is the ring-shaped member 16, it is desirable that a plurality of drive means be provided. Particularly, the one using the air cylinder mechanism 25 shown in FIG. 5 has a ring-shaped member 1 as shown in FIG.
It is desirable that a plurality of them be arranged along the circumferential direction of 6. By arranging a plurality of members, the pressure of each driving means acting on the ring-shaped member 16 can be reduced, and the ring-shaped member 16 can be moved smoothly and uniformly.

In the present invention, the driving means is not limited to that of the above-mentioned embodiment, but any means for reciprocating the ring-shaped member 16 may be used. Further, the elastic body is not limited to the springs 14 and 14a and may be rubber. The present invention can be used as it is by simply modifying a part of the mold of an existing molding machine, and can be implemented relatively inexpensively and easily.

[0029]

According to the present invention, the following remarkable effects are obtained. 1) According to the molding die of claim 1 of the present invention, during the injection molding process, the member is arranged flush with the other part of the cavity, and in the intermediate process of shifting from the injection molding process to the pressure-holding molding process. Since the member is configured to retract into the mold, the resin flow in the injection molding process is not disturbed, and the product is free from defects. 2) According to the molding die of claim 2 of the present invention, the member is equivalent to an optical fiber stack ring,
By retracting the ring-shaped member, a concave groove corresponding to the stack ring is formed, so that the stack ring having a predetermined shape can be accurately formed. 3) According to the molding die of claim 3 of the present invention, one spring of the driving means acts on the member, the pressing force of the spring is higher than the pressure of the resin in the injection molding process, and the resin in the pressure retention molding process is used. By setting the pressure to be lower than the pressure of (1), it is possible to hold the member flush with the cavity and form a concave groove, and to automatically form a convex portion (stack ring) corresponding to the concave groove. You can 4) According to the molding die of claim 4 of the present invention, as the driving means, the pressing means for applying a pressing force to the member from the outside and the spring balanced with the pressing means are adopted, and the action timing of the pressing means is set in the injection molding. Since the detection signal for detecting the transition time between the molding process and the pressure-holding molding process is used, the member can be automatically moved in and out smoothly, and the convex portion corresponding to the concave groove can be accurately formed. It 5) According to the molding die of claims 5 and 6 of the present invention, by disposing a plurality of driving means, the member such as the ring-shaped member is uniformly pressed, and the member moves smoothly. Done. 6) According to the molding method of the seventh aspect of the present invention, an accurate molded substrate can be automatically prepared by performing the steps of the first to third steps using the molding die described above. 7) According to claim 8 and claim 9 of the present invention, a high-quality molded substrate in which defects such as silver streaks and welds do not occur at the time of introducing the resin, and convex portions corresponding to stack rings are accurately formed. Can be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a molding die around a stack ring according to an embodiment of the present invention in which a spring is used as a driving unit.

FIG. 2 is a partial cross-sectional view for explaining the operation of FIG.

FIG. 3 is a partial cross-sectional view of another embodiment of the present invention in which a pressing unit that supplies a pressure medium to the ring-shaped member side and a spring that balances the pressing unit are used as the driving unit.

FIG. 4 is a partial cross-sectional view for explaining the operation of FIG.

FIG. 5 is a partial cross-sectional view of another embodiment of the present invention in which an air cylinder mechanism is adopted as driving means.

FIG. 6 is a plan view of a molding die showing an arrangement of a plurality of driving means.

FIG. 7 is a perspective view showing the shapes of an optical disc and a stack ring.

FIG. 8 is a front view showing a schematic structure of a molded substrate storage jig for explaining the function of a stack ring.

FIG. 9 is a partial cross-sectional view showing an injection mold for an optical disc having a conventional stack ring.

FIG. 10 is a plan view showing defects in a conventional optical disc.

[Explanation of symbols]

 1 Molded Substrate 2 Mounting Seat Surface 3 Information Recording Area 4 Convex Part (Stack Ring) 5 Units 6 Center Pole 7 Molded Substrate Storage Jig 8 Fixed Side Mold 9 Movable Side Mold 10 Cavity 11 Recessed Groove 12 Defect 13 Taper 14 Spring 14a Spring 15 Mirror surface plate 16 Ring-shaped member 17 Recessed hole 18 Mirror surface 19 Planar portion 20 Stamper 21 Stamper side plate 22 Stamper holding claw 23 Pressing means 24 Medium circulation hole 25 Air cylinder mechanism 26 Cylinder chamber 27 Piston member 28 Passage 29 Passage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiro Mitani 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (9)

[Claims] 1. A molding die in which a part of the shape of a cavity formed between a fixed-side mold having a mirror plate and a movable-side mold having a stamper or the like changes during a molding step, wherein the part is formed. Is placed flush with other parts of the cavity at the beginning of molding when resin is injected into the cavity, and is slidably supported by the mold so as to be retracted by a predetermined amount in the post-process of injection molding. And a driving means for reciprocating the member are provided, and a molding die having a variable cavity shape. 2. The cavity shape according to claim 1, wherein the part corresponds to a position where a stack ring is formed on the optical disk, and the member is a ring-shaped member corresponding to the shape of the stack ring. Variable mold. 3. The post-process corresponds to an intermediate process for shifting from the injection molding process to the pressure-holding molding process, and the drive means is a spring or a rubber elastic body engaging with the member, 3. The pressing force at the time of setting the elastic body is set to be higher than the pressure inside the cavity in the initial step of injection molding and lower than the pressure in the intermediate step. Mold with variable cavity shape. 4. The post-process corresponds to an intermediate process in which the injection-molding process shifts to the pressure-holding molding process, and the driving unit applies a pressing force to the member from the outside, and the pressing unit. 2. A balanced spring, which is operated and controlled by detecting the time when the pressing means shifts from the injection molding control to the pressure-holding molding control.
Molds with variable cavity shapes. 5. The molding die according to claim 1, wherein a plurality of the driving means are arranged. 6. The cavity shape according to claim 5, wherein a plurality of the driving means are arranged at equal intervals in the same circumference when the members are ring-shaped members. Variable mold. 7. A first procedure in which a cavity is formed between a fixed-side mold having a mirror plate and a movable-side mold having a stamper and the like is filled with resin to perform injection molding, and a process from the injection molding step is performed. In the intermediate process that shifts to the pressure molding process,
A second step of changing a shape of the cavity by retracting a part of the die forming the cavity into the die;
A cavity forming variable molding method comprising a third step of restoring the retracted portion at the end of the pressure-holding molding step, wherein the retracting and restoring of the portion engages with the portion. The balance between the pressing force of the elastic body and the pressure in the cavity and / or the driving means that acts on the part from the outside, and the retreating and restoring of these parts are performed.
A molding method with variable cavity shape, which is performed between an initial step of injection molding and a pressure-holding molding step and in synchronism with a timing of ending the pressure-holding molding step. 8. A resin material is filled in a cavity formed between a fixed-side mold having a mirror surface plate and a movable-side mold having a stamper or the like in the injection molding process, and the subsequent pressure-holding molding process is performed. A molded substrate, which is formed by previously retracting a part of a mold for forming the cavity into the mold to change the shape of the cavity and filling the changed part with a resin. 9. The molded substrate according to claim 8, wherein the part of the molded substrate corresponds to a stack ring.