JPH0635140B2 - Disk-shaped recording medium molding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a disk-shaped recording medium (hereinafter referred to as a disk) such as a video disk or an audio disk, and more particularly to a method for molding a disk center hole by a gate cut method. .

[0002]

2. Description of the Related Art A disk molding die of this type is disclosed in Japanese Patent Laid-Open No.
-52613 and 54-156062, a cutting pin is provided on the movable side of the mold so that it can move forward and backward, and a sprue bush with clearance is provided on the fixed side by nozzle touch so that it can move forward and backward. The gate portion at the center of the disk-shaped cavity was formed between the pin and the sprue bush.

Regarding injection molding of a disk, the sprue bush is advanced to the gate portion side by the nozzle touch force, the molten resin is filled into the cavity through the gate portion, and the sprue bush is pressed by the nozzle touch force for the resin pressure. It was After the molten resin is cooled and solidified, the cut pin is moved forward to transmit the forward force to the sprue bush through the resin product portion solidified in the gate gap, and the nozzle is retracted at this forward timing, with respect to the cavity cross section. The center hole was sheared by changing the position of the gate gap.

[0004]

However, according to Japanese Patent Laid-Open No. 58-52613, the gate cutting is not performed until the molten resin solidifies on the information track surface and the gate portion is sealed. During cooling, as in Japanese Patent Laid-Open No. 54-156062, the sprue bush retracts after the gap in the gate is compressed as the cut pin moves, causing a stress gradient to the product around the gate. , A disk having birefringence of approximately the same value cannot be molded.
As a result, the molding cycle was lengthened because a waiting period was required until the product was solidified. Normally, one cycle took about 20 to 30 seconds.

Further, it is unavoidable that the tip end surface of the cut pin is dulled and rounded by repeated cutting after solidification of the product. Due to the sag, the disk center hole is
The cross section is formed in the direction of the center of rotation or in the direction away from the center of rotation, and the concentricity is reduced. With continued use, the above-mentioned accuracy was further reduced. At present, even if there is a defective product despite the decrease in concentricity, the cut pin is used as it is, and when there are a large number of defective products, replacement is performed for the first time.

As a result of repeated studies by the present inventors in view of the above circumstances, the following findings were obtained. When the gate was cut in the solidified state of the product, chips, which were fine particles of the product, were found to be generated from the cut portion, and the chips were mixed into the information track surface, which was a major cause of an erroneous signal. It has been known that fine particles left in the previous molding cycle are mixed into the information track surface to cause a difference in birefringence, but it has been confirmed that the most probable cause is chips. The amount of chips is further increased by the sagging of the cutting pin, which further deteriorates the accuracy.

In order to prevent the generation of the above chips, it has been found that shearing may be performed in the semi-solidified state of the product in the gate portion. Here, the semi-solidified state is a state in which at least the molten resin is cooled and shaped below the softening point,
A state in which the product has a viscosity that does not generate chips due to product cutting. In this case as well, it was necessary to prevent stress from being generated during cutting.

Further, it was possible to elucidate the cause of the sagging of the tip of the cut pin when cutting at the gate portion. That is,
A linear resin pressure was generated against the advancing and retracting sprue bush structure, but this resin pressure was countered by a strong nozzle touch force. Since the nozzle touch force was dispersed by the spherical surface of the bush, the sprue bush had to be distorted. It was found that if the Nord's touch force can be kept low, the distortion of the sprue bush can be eliminated and the galling of the cut pin can be avoided.

However, the present invention was further developed based on the above-mentioned findings, and it is possible to further improve the accuracy of a gate-cut type disc product for a long period of time and to enable high cycle molding. It is the main purpose.

[0010]

A feature of the method for molding a disk-shaped recording medium according to the present invention is that a pressure oil working chamber is provided on the fixed side of a mold to face a large-diameter stepped portion of a sprue bush and to fill it. At the timing when the resin pressure is generated, the pressure oil that opposes the resin pressure is applied to the action chamber of the sprue bush, and the cut pin and the sprue bush are independently moved forward and backward in synchronization with the semi-solidified state of the product at the gate. Therefore, the relative movement of the gate portion can be obtained with the same gate volume.

[0011]

The nozzle is in contact with the spherical surface of the bush, and a gate gap is formed between the cut pin and the tip of the sprue bush. When the molten resin is filled in the nozzle sprue gate, resin pressure is generated in the gate portion. Pressure oil is applied to the working chamber at the timing of generation of the resin pressure, and linear pressure is applied to the tip end surface of the sprue bush to counteract the linear resin pressure.

When cooling is started after filling and at least the vicinity of the gate portion is in a semi-solidified state, pressure oil is caused to act on the working chamber at such timing. As a result, the sprue bush is brought into a no-load or negative pressure state, so that the sprue bush side can be moved with a slight force. If the cut pin is advanced at this timing, the tip surface of the sprue bush retracts with the same gate volume corresponding to this advance force, and punching in a semi-solidified state is performed.

[0013]

EXAMPLE FIG. 1 shows an embodiment of a method for molding a disc-shaped recording medium according to the present invention. FIG. 1 is a perspective view showing a cross section of a main part of a mold used in the molding method, and FIG. FIG. 3 is a perspective view of a cut pin, FIG. 3 is a cross-sectional view of a main part of the mold, FIG. 4 is a cross-sectional view of the main part showing a gate cut state, and FIG. 5 is a cross-sectional view of a main part showing a cut portion in a protruding state.

Therefore, the mold has a fixed mold plate 1 and a movable mold plate 2
A cavity 3 having a disk molding space is formed from the above, a sprue bush 4 is attached to the cylinder structure on the fixed side, and a cut pin 5 is attached to face the movable side. To describe in detail from the fixed side, the cylinder is composed of the head side and the barrel side of the fixed receiving plate 11 and the holes 13 of the fixed mounting plate 12, and the bottom side of the bush cylinder 41. A pressure oil working chamber 14 is formed in the remaining space where 42 is fitted in the hole 13.

The sprue bush 4 is composed of a large diameter portion 43 mounted in the cylinder space and a small diameter portion 44 extending from the large diameter portion 43. The large diameter portion 43 is formed by a step portion 46 having a diameter larger than that of the spherical surface portion 45, and a sealing material 48 is provided in a groove 47 on the outer peripheral surface thereof. The step portion 46 faces the working chamber 14 and receives the pressure oil from the flow path 15. As the seal material 48, a wear resistant wear ring or the like is used. In the figure, 49 is a sprue hole, 141 ... are sealing materials between respective members, and 142 is a bolt for fixing the bush cylinder 41.
Further, the small-diameter portion 44 of the sprue bush 4 is inserted into the hole 16 of the fixed receiving plate 11 so as to be able to move forward and backward, and the tip end surface 143 thereof is always projected to coincide with the core surface of the cavity 3. Incidentally, reference numeral 17 is a passage for the refrigerant of the fixed mold plate 1.

Next, the movable side will be described. The cavity 3
A sprue ejector pin 6 and a cut pin 5 located at the center of the, and ejector pin 7, a cylindrical member 21 and a stamper inner peripheral pressing member 8 which form a clamping area of the product and are fitted and inserted into the outer circumference of the cut pin 5, respectively. It comprises a stamper 31 and an outer peripheral pressing member 9 which constitute the information track surface area.

The cut pin 5 is composed of an elongated small diameter portion 51 and a large diameter portion 52, and the large diameter portion 52 is a cut pin cylinder.
Small-diameter portions 51 are fitted inside the ejector pins 7 inside the ejector pins 7, respectively, and the rear ends thereof are fixed to ejector plates (not shown). The small-diameter portion 51 has the same cross-section as the small-diameter portion 44 of the sprue bush 4 and is arranged to face each other so as to be movable back and forth. The first gate 32 is constituted by. Inside the cut pin 5, the slack well 55, a small hole 56, and a communication hole 57 having a diameter larger than the small hole 56 are arranged from the tip side.
And a cylinder hole 58 having a larger diameter, and each hole 56, 57, 58
A sprue ejector pin 6 is inserted in the so that it can move forward and backward. The end face 59 of the large diameter portion 52 faces the working chamber 151 defined by the cut pin cylinder 53. Reference numeral 152 is a flow passage provided in the cut pin cylinder 53 and communicating with the working chamber 151, 153 is a refrigerant flow passage provided in the large diameter portion 52,
4 ... is a sealing material.

[0018] The sprue ejector pin 6, a pin 61 for pin-like protrusion, the flat portion 62 of the wing-like, made of a piston 63 of large diameter, the respective 61, 62 and 63 of the cutting pin 5 holes
It is inserted in 56,57,58. The flat portion 62 has a communication hole 57.
The blade part 64 so that it is vertically blocked along its length.
And a reduced taper portion 65 is formed at the tip portion of the blade portion 64. The taper portion 65 forms a communication passage with the inner wall of the communication hole 57. As a result, the passages that are blocked above and below the communication hole 57 communicate with the refrigerant passages 153, 153, and a circuit is constructed in which the passages are connected to the tapered portion 65 and supplied. This circuit works regardless of whether the sprue ejector pin 6 moves back or forth. Further, the piston 63 is locked at its rear end and normally follows the cut pin 5, but can move independently by receiving the pressure medium in the cylinder hole 58. In the figure, 66 is a sealing material.

The ejector pin 7 is a large-diameter piston.
It has a tubular shape composed of 71 and a body portion 72, and the piston 71 is fitted in the cut pin cylinder 53 and the body portion 72 is fitted in the cylindrical member 21 so as to be able to move forward and backward. The cylindrical member 21 is a cut pin cylinder 53
It is fixedly attached to and positioned. The ejector pin 7 is provided with V-shaped grooves 73, 74 on the inner peripheral surface of the rear half and the outer peripheral surface of the front half on the piston side, and the grooves 73, 744 are connected to each other by through holes 75, ... The groove 74 in the first half portion is terminated slightly apart from the tip end surface. In the figure, 76 and 77 are pistons
The working chambers before and after 71 and 78 are sealing materials. The ejector pin 7 functions to eject air at the same time as being ejected by air pressure.

Further, the stamper inner peripheral pressing member 8 is movably moved by operating means from the outside of the mold, and the claw 82 of the tip 81 thereof presses the stamper 31 so that the tip 81 projects annularly from the movable die surface. To form the second gate 33. The tip 83 is provided with a tapered surface 83 that reduces the cross section of the cavity. The second gate 33 is wider than the first gate 32 when the gate 32 is the first gate. The pressure sensor 18 is attached to the inside of the second gate 33.

Next, the cavity area will be described. The mold surface of the information track surface is mirror-finished. The outer peripheral pressing member 9 of the stamper is the outer peripheral pressing claw 91 of the stamper 31.
And a peripheral surface 92 which is vertically raised from the claw 91, and a guide surface 93 which is inclined from the peripheral surface 92 toward the outer peripheral direction. The cavity 3 is constructed by fitting the mold surface end of the fixed mold plate 1 to the peripheral surface 92.

Only the operation unique to the present invention based on the above configuration will be described. When the cavity 3 is filled with the molten resin, the molten resin causes the first gate 32 to generate shear heat, so that the molten resin flows radially in a state where it easily flows, and the second gate 33 absorbs the stress while the stamper 31 of the information track surface is absorbed. To be filled along.

Since a high resin pressure is generated in the first gate 32, pressure oil is applied to the working chamber 14 at the timing of this generation. As a result, it is possible to apply a linear hydraulic pressure from the breaking portion 46 to the linear resin pressure by suppressing the nozzle touch force, and to apply a linear pressure to the tip surface 143 so as to face each other. Becomes

A holding pressure is applied after the filling. The holding pressure mainly acts inside the clamping area. That is, the second gate 33 prevents the holding pressure that causes residual stress from spreading to the information track surface. Whether or not cooling of the molten resin starts from the outer peripheral portion of the cavity 3 has not been sufficiently clarified, but it is sufficient that at least the first gate 32 and the clamping region around it have a semi-solidified state.

When the gate is cut, the pressure oil is removed from the working chamber 14 so that the tip surface 14 of the sprue bush 4 can be cut.
No. 3 is no load or negative pressure. The above state can be arbitrarily set by adjusting the pressure oil drainage. That is, The sprue bush side can be moved with a slight force. If the cut pin 5 is advanced at this timing, the tip surface 14 of the sprue bush 4 will remain with the same gate volume corresponding to this forward force.
3 retreats. As a result, the first gate 32 is cut without applying a compressive force. When cutting, the sprue ejector pin 6 moves at the same time as the cutting pin 5.

As the mold is opened after cutting, the sprue ejector pin 6 advances, so that the remaining product of the slack well 31 is projected.

FIG. 6 is a cross-sectional view of essential parts showing a mold applied to another molding method. In the figure, the same reference numerals as those in FIGS.

Thus, the cylinder is composed of a bush cylinder 144 on the barrel side and the bottom side, and a return working chamber 149 is formed between the tip end surface 145 of the large diameter portion 43 and the thick bush cylinder cover 146. To be done. In the figure, reference numeral 148 is a flow path provided in the bush cylinder cover 146.

When molding is performed using this mold structure, the working chamber
Since the gate cutting can be performed by supplying the pressure oil to 14 and moving the sprue bush 4 forward, it is suitable for forming a large-sized disc. Moreover, since the pressure oil can be applied to the action chamber 147, it can be synchronized with the movement of the cut pin 5 and the sprue ejector pin 7.

In each of the above-mentioned embodiments, the semi-solidified state can be implemented in such a manner that the semi-solidified state is such a degree that it does not generate chips during cutting and is in a melting degree. Further, when the present invention is carried out, the present invention is not restricted to the above-mentioned mold structures and does not prevent its application to other mold structures.

[0031]

As described above, the present invention has the following effects.

It was possible to eliminate one cause of the sagging of the tip of the cutting pin, which is the cause of generation of chips. That is, the cylinder structure of the sprue bush can suppress the nozzle touch force dispersed by the spherical surface portion of the bush against the linear resin pressure, so that the strain of the sprue bush can be avoided and it occurs when the gate is cut. This is because problems such as galling of the cut pin could be resolved. Further, the cutting in the semi-solidified state does not require a large shearing force, and tip sagging hardly occurs.

As a means for ensuring the same gate volume, a cylinder structure is used in which a large-diameter step portion of the sprue bush moves forward and backward by providing a working chamber for pressure oil on the fixed side, so that relative movement can be performed accurately. It was possible to eliminate the effect of compressive force on the gate part during cutting. Therefore, it is possible to prevent the generation of chips and the stress ripple on the information track surface, and it is possible to perform high cycle punching in a semi-solidified state.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a method of molding a disk recording medium according to the present invention, and a sectional view of a main part of a mold used in this molding method.

FIG. 2 is a perspective view of a cut pin of the mold.

FIG. 3 is a cross-sectional view of a main part of the mold.

FIG. 4 is a cross-sectional view of essential parts showing a gate cut state.

FIG. 5 is a cross-sectional view of essential parts showing a punched state of a cut portion.

FIG. 6 is a cross-sectional view showing a mold applied to another molding method.

[Explanation of symbols]

 1 Fixed mold plate 2 Movable mold plate 3 Cavity 4 Sprue bush 5 Cut pin 6 Sprue ejector pin 7 Ejector pin 32 (First) gate 33 (Second) gate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B29L 17:00 4F (72) Inventor Isao Kobayashi 5-7-15 Higashi-Kojiya, Ota-ku, Tokyo Stock company Within Technoplus (56) Reference JP-A-58-188636 (JP, A) JP-A-54-156062 (JP, A)

Claims (1)

[Claims] 1. A cut pin and a nozzle-touched sprue bush are provided on a movable side and a fixed side of a die, and a gate section is formed in the center of a disk-shaped cavity so as to be movable back and forth between these. In the method of molding a disk-shaped recording medium in which the center hole of the gate portion is formed with respect to the cavity by the relative movement of the cut pin and the sprue bush, a pressure oil working chamber is provided on the fixed side of the mold to increase the diameter of the sprue bush. The stepped part is exposed, and pressure oil that opposes the resin pressure is applied to the working chamber of the sprue bush at the timing of resin pressure generation during filling, and the cut pin and sprue bush are synchronized in the semi-solid state of the product at the gate part. A method for molding a disk-shaped recording medium, characterized in that the gate portion can be moved relative to each other by moving back and forth independently while maintaining the same gate volume.