JPS58151223A - Manufacturing method and mold of optical disk substrate - Google Patents

Abstract

PURPOSE:To enable to mass-produce readily an optical disk substrate which enables to write arbitrarily and has large mechanical strength and high accuracy, by attaching a stamper to the molding surface of a core in a specified condition in order to mold the optical disk substrate. CONSTITUTION:When an optical disk substrate which has a plurarity of minute groove tracks (b) for recording on the back face of a disk composed of transparent synthetic resin is injection molded, a stamper 6 is attached detachably to one core 4 of a pair of cores 3, 4 shaping a cavity 5, the outer edge of the stamper 6 is lightly held with a holding ring 11, a space 14 which allows thermal expansion of the stamper 6 is made inside the holding ring 11, the holding ring 11 is sustained at its entire periphery uniformly by a ring fixing member 12 of high mechanical strength which is hardly defomred by external force while a ring fixing member 12 is fixed to a die plate 2 with a bolt 202. MOlten resin is injected in a cavity 5 at a stroke from its middle point to its outside in circular form.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an optical disk substrate for file memory and a molding die.

In addition to read-only optical discs that utilize lasers, optical discs on which arbitrary data can be written are also known.

The purpose of the present invention is to provide a device that can be arbitrarily written with high precision, high mechanical strength, no optical problems, can be easily mass-produced, and can be obtained at low cost. That is.

As the original disc, a large number of trunks of minute grooves are arranged on the back side of a circular substrate made of transparent synthetic resin, and a thin layer of a recording medium that can be perforated with a powerful laser is provided on the back side. Furthermore, a reflective film is provided on the outside as required, and the substrate is appropriately molded using a special mold equipped with a stamper or a glass plate in place of the stamper. I have achieved the 9 targets mentioned above.

The illustrated embodiment will be explained below.

FIG. 1 is a plan view of the original disk according to the present invention, which is a circular substrate A made of transparent synthetic resin with a through hole a in the center.
On the back side of the trunk, a large number of recording micro-groove trunks b... are arranged in parallel in a centric circle, and one starting reference micro-groove line c'lz is provided in the radial direction.

It is injection molded as described below to a thickness of 1 to 1, 5 m.
The micro-grooves are formed in a circular disk of 500 m in width, and have a width of 1 μm and a depth of 0.1 μm, and a pitch between trunks of 2 μm and a width of 0.1 μm.

In addition, on the back surface of the substrate A, that is, on the side of the minute grooves, a thin layer Bk of a recording medium that can be perforated with a powerful laser (writing device) is provided as shown in the enlarged view of FIG. A reflective film C is provided on the surface.

As the thin layer B of the recording medium, for example, Terrell is used,
It is melted and applied and solidified to form a thickness of 0.01 to 0.1 μm. As the reflective film C, for example, aluminum is vacuum-deposited and formed to a thickness of about 0.1 to 0.2 nm.

The original disc made in this way is for single-sided use.While rotating this original disc, from the front side, the thin layer BiC% of the recording medium in the minute groove trunk b...
The laser source of the writing device is irradiated to drill through holes E at appropriate intervals as shown in the enlarged views of Figures 2 and 3, and all of the required information is encoded and recorded using these holes. . Also,
When reproducing this, while rotating the original disk in the same way, the minute groove tracks B... are irradiated with a reading source from the front side, and the reflected light is used to open the through hole E. ... is detected and reproduced as an electrical signal for recording.

During this writing and reproducing, a predetermined minute groove trunk is automatically selected using a trunk thermometer, that is, a reading laser and detection of reflected light, and the start position is set at the starting reference minute groove line C. The selection is based on the detection of.

Next, FIGS. 5 and 6 show a mold of an injection molding machine for molding the substrate A' and its surroundings.

In Figures 5 and 6, % 1 is a fixed die plate;
2 is the moving die plate; 3 is the fixed side core; 4 is the moving die plate) 201, 2
This is the movable core fixed at 01.

The fixed side core 3 and the movable side core 4 form a disc-shaped cavity 5 to be formed on the substrate A' on their abutting surfaces.
The movable core has 6 stampers (electroformed thin plates) attached to its capacity.

The stamper 6 excavates all the necessary minute grooves to obtain the above-mentioned minute groove trunk b... and minute groove line ck by laser digging means on a glass plate whose surface has been polished flat, and then electroforms it on the mounting surface. A nickel disk having a thickness of 0.2 to 1 am was produced by depositing nickel on the substrate and peeling it off.

Further, the stamper 6 has a circular through hole 61' in the center.
The cylindrical stamper is fastened through the through hole by passing the member 7't through the stamper.The stamper is fastened by screwing the member into the center of the movable core 4 and removably fixing it to the core. There is.

For tightening the stamper, the member 7 is provided with a narrow edge 71 on the outer edge of the outer end, and this is used as the edge of the through hole 61 of the stamper 6. Further, the corners of the protruding edge 71 are rounded, and the inner and outer end surfaces thereof are sloped and recessed.

For tightening the stamper, a bush 8 and an extrusion pin 9 inserted into the bushing 8 are provided in the member 7, and the tip of the extrusion pin is slightly protruded to form a small groove 91 around the core. An air passage lOt for sending air into the cavity 5 is formed between the bushing 7 and the bushing 8, and is connected to the entire air supply means, and the rear end of the push-out pin 9 is mechanically connected to the air cylinder.

The outer ring of the moving core 4 is formed to have almost the same dimensions as the outer ring of the stamper 6, and a stamper holding ring 11 is loosely fitted around the outer circumference of the moving side core. A ring fixing member 12' is fitted on the outer periphery of I-1 and is supported by fixing the ring fixing member to the movable die plate 2 with bolts 202, 202.

The stamper holding ring 11 is provided with an inward flange 112' at one end of a relatively short metal tube 111 and an outward flange 113k at the other end. Stamper 6 at 112
The outer edge of the stamper 6 is held down, and a space 141 is provided inside to allow outward thermal expansion of the stamper 6.
is pressed by the ring fixing member 12.

The ring fixing member 12 has approximately the same thickness as the movable core 4 and a sufficiently large outer ring, and has bolts 202 and 202.
In order to avoid deformation during tightening, the stamper holding ring is tightened with a uniform torque over the entire circumference.

A protrusion 301t is provided around the cavity 5 of the stationary core 3.
- The protrusion is located on the inner side of the outer edge of the stamper 6, so that an air vent gap of about 0.01 wyx can be created between the stamper and the stamper.

The fixed side core 3 is equipped with a sprue-bushing 15 penetrating through the center, and the sprue bushing is abutted against the injection cylinder 16', and the sprue 1''I is inserted between the sprue bushing and its periphery and the stamper holding ring 11. A series of launches 18 are formed, and the runners are circular and communicate with the outer donut-shaped cavity 5 via a narrowed channel.

In the figure, % 302 and 402 are cooling water passages. 19
is a guide bin.

With the above configuration, when the cores 3 and 4 are clamped and transparent heated molten resin is injected from the injection cylinder 16,
The molten resin is sprue 17% ranch 18? It flows into the cavity 5 via Il-.

At this time, since the runner 18 opens into the cavity 5 in a circular manner, the molten resin is evenly and uniformly fed into the cavity 5, and the flow path between the launch 18 and the cavity 5 is narrow. As a result, the molten resin is sent to the end at high speed, and the air inside the cavity is released to the outside through a small gap around the cavity.

In addition, when tightening the stamper, since the corners of the protruding edge 71 of the member 7 are rounded, the molten resin is sufficiently rotated directly under the protruding edge 71, and as the molten resin flows in, it is applied to the stamper 6 from the center side to the outside. The air on the back side of the stamper 6 is also released to the outside, and the molten resin injected by the stamper 6 into the core 4 is transferred to a transparent material such as acrylic, polycarbonate, polystyrene, vinyl chloride, etc. The injection time is within 5 seconds, and the injection pressure is 1000 ~
3000 to 97m and a melting temperature of 150 to 300'O are suitable.

Incidentally, in this case, the stamper 6 has a different thermal expansion from the core 4 and extends outward during injection. At this time, the outer edge bulges into the space 14 in the stamper retainer ring 11 while slipping occurs between the core 4 and the stamper retainer ring 11, causing inconveniences such as bending of the stamper 6. Don't let it happen.

The stamper 6 is replaced after forming several dozen pieces.

After injection is completed, the injected molten resin is cooled and solidified, and the mold is opened. At this time, the molded product remains on the movable core 4 because the extrusion pin 9 has the small groove 91. Therefore, if air is supplied from the air passage 10 and the extrusion pin 9' is made to protrude with an air cylinder, the molded product and the stamper 6 will be smoothly separated from each other, causing problems such as deformation and damage to the phase gauge. Cut out the sprue 17 and runner 18i without cutting out the pattern. The stamper is tightened in a circular manner slightly outside the protruding edge 71 of the member 7, and the resulting circular hole in the product is used as a hole for mounting on the turntable.

The substrate A formed in this manner has a high transfer efficiency with the stamper 6, and the fine groove tracks b... and the fine groove lines C can be obtained with high accuracy, and there is no warping or bending. I-2
00μm or less, and the mechanical strength can be made uniform at various locations.
Adverse optical effects such as birefringence can be prevented, and problems caused by changes over time can be sufficiently prevented.

In the above embodiment, the stamper was made of electroformed nickel, but it may also be made of a glass plate. In this case, since the thermal expansion is smaller than that of the core 4, the core 4 is pulled inward.

Furthermore, although the above embodiments have been described exclusively with respect to file memory disks, the present invention can also be applied to video and audio disks.

It is possible to obtain a large original disk without problems such as optical birefringence, it can be easily mass-produced, it can be produced at low cost, and it is possible to eliminate distortion of the substrate and annealing of the sheet. Therefore, problems caused by changes over time can be avoided.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention. FIG. 1 is a plan view of the original disk, FIG. 2 is an enlarged plan view of the same part, FIG. 3 is an enlarged cross-sectional view of the same part, and FIG. 4 is a case where both sides are used. FIG. 5 is an enlarged vertical sectional view showing a molding die and its surroundings in an injection molding machine for the original disk substrate, and FIG. 6 is a plan view of the essential parts thereof. A...Substrate B...Thin layer of recording medium C...
Reflective film D...Science sensor E...Through hole 1...Fixed die plate 2...
Moving die plate 3... Fixed side core 4... Moving side core 5... Cavity 6... Stamper
7... Stamper tightening is done by member 8... Bush 9...
・Ejection pin 10...Air passage 11...Stamper holding ring 12...Ring fixing member 14...Space 16
...Injection cylinder 17 thread sprue 18...Lunch patent applicant Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] (1) A stamper is arranged on the molding surface of the core to form a capity, and the stamper is removably fixed to the central T-core, and is lightly pressed by a stamper holding ring on the entire outer edge. The entire circumference of the stamper holding ring is uniformly supported by a ring fixing member having a mechanical strength that is difficult to deform due to external force, and the ring fixing member is bolted to the die plate. The cavity is molded by injecting transparent heated molten resin in a circular shape from one point in the center outwards, and at this time, the pressure of the resin is used to exhaust all the air from the back of the stamper while bringing it into close contact with the entire core of the stamper, and then injecting it. After the resin solidifies, air is blown out at the center of the stamper to separate the molded product from the stamper 2
Method 3 for manufacturing a substrate for an optical disk having a characteristic of t% of t%, ■) A stamper metal is disposed on the formed surface of the core to form a cavity, the center of which is removably fixed to the core, and the outer edge of the stamper is fixed to the core in a removable manner. Lightly press the stamper with a presser ring, the stamper presser ring has a space inside to allow thermal expansion of the stamper, and the stamper presser ring is held uniformly around the entire circumference by a ring fixing member that has mechanical strength that prevents it from being easily deformed by external force. The ring fixing member is bolted to the die plate, a sprue is provided in the center of the stamper, a circular launch is provided in series with the sprue, and a narrow flow path is formed from the runner to the capity. A mold for forming optical disc substrates.