JPH05337899A - Punching device for stamper and the like - Google Patents

Abstract

PURPOSE:To obviate the finish machining for deburring by specifying a clearance between an upper cutting edge and a lower cutting edge and the surface roughness-hardness of the respective cutting edges, and applying specified surface treatment to the respective cutting edges forming a cutting edge for punching a stamper used to form a disk like recording medium. CONSTITUTION:In a cutting device provided with a cutting edge for punching the center part and outer peripheral part of a stamper used for the transfer formation of a disk like recording medium such as a compact disk or a laser disk, the cutting edge is formed of an upper edge 1 and a lower edge 2, and a radial clearance between these upper and lower edges 1, 2 is set to be 8% or less of the wall thickness of a workpiece 3. The surface roughness Rmax of the respective cutting edges 1, 2 is set to be 0.1s or less, and the surface hardness of the respective cutting edges 1, 2 is set to be HV500 or more. In addition, the tips R of the respective cutting edges 1, 2 are set to be 0.05mm or less, and surface treatment by titanium nitride or ion nitriding is applied to the respective cutting edges 1, 2 in order to reduce the coefficient of friction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in punching devices such as stampers used for transfer molding of compact discs and laser discs.

[0002]

2. Description of the Related Art Electroforming of a conventional stamper used when molding a disc-shaped recording medium as a digital information recording medium such as a compact disc (CD), a laser disc (LD) or an analog information recording medium such as an LP record. As a processing method, for example, there is a method performed in steps (1) to (5) in FIG. That is, first, step (1) shows a glass substrate 1 that has been circularly cut to a required size and subjected to flat polishing, and in step (2), 1,000 to 2, corresponding to the signal groove depth on this glass substrate 1. The photoresist 2 is applied to the thickness of 000Å by spin coating, and in step (3), the glass substrate 1 adsorbed and fixed on a rotating jig (turntable) not shown is rotated and irradiated with laser light to be exposed. From the step (4) to obtain a pre-format pattern with fine irregularities according to the recorded information by developing from
Then, a conductive film 3 of 500 to 1,000 liters is formed on the preformat pattern by sputtering or the like, and then Ni electroforming is performed using the conductive film 3 as a cathode to form about 0.2 to 0.3 m / m. The Ni electroformed plate 4 is formed.
In step (5), the glass substrate 1 is peeled off to remove the resist 2
Are removed and washed to form the master 4. A mother is prepared by peeling the Ni layer obtained by subjecting the master 4 to the release coating treatment and then performing the Ni electroforming, and further subjecting the mother to the release coating treatment and then performing the Ni electroforming. A stamper (sun) having a wall thickness of about 0.2 to 0.4 m / m is obtained by applying the stamper, and the recording medium made of plastic is molded by injection molding using this stamper. The stamper using the mother is completed by punching with a punching device for punching the central hole and shaping the outer peripheral shape.

Generally, in press punching of a metal plate, it is considered that the quality is good if the height of the burr formed in the punching portion by the cutting edge is about 0.1 mm or less, but in the above stamper, it is 5 μm. Even if it is a burr of a degree,
Since the optical properties (birefringence) and mechanical properties (tilt mRad) of the finally obtained plastic molded product are highly likely to be seriously affected, the occurrence rate of burr and the burr height are reduced to the utmost limit. Is strictly required. Also, the presence of burrs on the stamper causes non-uniform peeling behavior when peeling between the mold, the plastic resin, and the stamper in injection molding using the stamper, resulting in flow pits in the final product. It is known to cause re-collision pits (ghosts).

From this point of view, the deburring work of the edge part of the stamper is manually added after the above-mentioned press removing step. During this finishing work, metal chips are mixed into the recording surface, and the stamper is bent and deformed. The risk of causing defects such as damage and increase in defect rate increases. FIG. 6 is an enlarged view showing a state of punching with a conventional cutting blade, and shows a clearance CL1 between the upper blade 1 and the lower blade 2 for cutting the center hole or the outer peripheral portion of the work (stamper) 3. Since the work thickness is set to be 9% or more, a part of the punched portion is plastically fractured to form the burr portion 4. Next, FIG. 7 shows a state where punching is performed with the clearance set to 8% or less of the work thickness. In this case, a region to be shaving (shearing while rubbing) is formed in the center of the shear fracture part. to be born. In this state, the surface pressure becomes extremely high, which causes damage to the blade and a tendency to cause the adhesion phenomenon of nickel composing the stamper. Further, plastic deformation sagging portions are formed in the upper and lower portions of the shaving area.

The accuracy of the center hole diameter of the optical disk is defined as + tolerance by setting the clearance within the range of +5 to +15 μm with respect to the target hole diameter. On the other hand, the holding ring used for holding the inner diameter of the stamper in the injection molding die is set to have a tolerance of −15 to −25 μm. As described above, when the inner diameter pressing ring manufactured within the tolerance is inserted and pressed into the center hole of the stamper manufactured within the tolerance, the eccentricity of up to 40 μm may occur. However, there is a risk of narrowing the margin of the track deflection specification value (60 μm or less) in the medium.

Next, FIG. 8 shows a state in which the punch 7 punches the center hole of the stamper 3 with the stamper 3 sandwiched between the die 5 and the knockout plate 6. In this conventional method, the knockout plate is used. Since the stamper and the stamper are in surface contact with each other and the contact area is large, the foreign matter 8 easily enters between the spring-biased knockout plate 6 and the stamper 3, and when punching in this state, the stamper 3 An indentation will be formed on the surface.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and eliminates the need for finishing work for deburring after punching, and the eccentricity of the media is determined by the respective tolerances of the stamper and the pressing ring. It is an object of the present invention to provide a punching device such as a stamper that can eliminate the problems caused by the above.

[0008]

To achieve the above object, the first invention of the present application is a punching device provided with a cutting blade for punching out a central portion and an outer peripheral portion of a stamper for molding a disk recording medium. The clearance between the upper and lower blades constituting the blade is set to 8% or less of the wall thickness of the stamper, and at the same time, the surface roughness Rmax of the upper and lower blades is set to 0.1 s or less, and the surface hardness of each blade is further set. Is Hv 500 or more, and each blade is surface-treated by titanium nitride (TiN) or ion nitriding treatment in order to reduce the friction coefficient.

According to a second aspect of the present invention, when punching the center of the stamper with a punch, a ring-shaped protrusion having a wedge-shaped cross section is formed on the periphery of the center hole of the knockout plate that holds the center of the stamper with the die. An annular indentation is formed in the center of the stamper by press-contacting the ridges, and a retaining ring-shaped ridge provided on the pressing ring for pressing the stamper during injection molding is fitted into the indentation of the stamper. The feature is that it is fixed.

A third aspect of the present invention is characterized in that the width of the annular projection of the knockout plate is 0.5 mm or less, the tip R is 0.05 mm or less, and the height is 1/4 or less of the stamper thickness. And

According to a fourth aspect of the present invention, the position of the tip of the upper blade for cutting the outer peripheral portion of the stamper having a wall thickness of t is the tip of the punch for cutting the center of the stamper. By arranging it by a height h (1 / 2t <h <t) above the position, the cutting of the central part is started during the cutting of the outer peripheral part, and the amplified cutting during the cutting of the outer peripheral part by the cutting blade. The feature is that the cutting force by the punch is amplified by using energy.

The present invention will be described in detail below with reference to the accompanying drawings. 1 (a) and 1 (b) are views showing a punched state of a center hole or an outer peripheral portion of a stamper according to a preferred embodiment of the present invention. As in the case of FIG. 7, the upper blade 1 and the lower blade 2 are shown. The radial clearance between and is set to 8% or less of the wall thickness of the work 3, the surface roughness Rmax of each cutting edge 1 and 2 is set to 0.1 s or less, and the surface hardness of each cutting edge is set to Hv500.
The tip R of each cutting edge is set to 0.05 mm or less, and each cutting edge is surface-treated by titanium nitride (TiN) or ion nitriding treatment to reduce the friction coefficient.

Repeated punching experiments using the punching device provided with these conditions show that the life can be extended to the extent that 200 or more works can be punched without forming shaving as in the case of FIG. It has been found. Furthermore, when punching the center hole and the outer peripheral portion of the stamper at the same time by the conventional punching device, so that the cutting start timing of the central hole punching blade and the cutting edge for the outer peripheral punching are completely matched, The upper blades are fixed to the pressing means of the cutting device with the positions of the upper blades set to the same level. For this reason, in order to perform high-speed punching, it was necessary to increase the speed by using a press device equipped with an accumulator or the like, but in the present invention, as shown in FIG. By setting each cutting start position by the cutting blades (punches, dies) 12 and 13 for punching out the central hole 3a to be less than the thickness t of the work 3 and within a range of 1/2 or more, in other words, In the illustrated example, the position of the tip of the upper blade 10 for cutting the outer peripheral portion is higher than the position of the tip of the punch 12 for cutting the central portion by a height h.
By arranging the lower part by (1 / 2t <h <t), the cutting of the central portion is started during or immediately before the cutting of the outer peripheral portion. In addition, 14 in FIG. 2 is a knockout plate.

According to the embodiment shown in FIG. 2, since the punching completion timing of the central hole 3a is slightly behind the punching completion timing of the outer peripheral portion, amplification is performed during the cutting of the outer peripheral portion by the cutting edge 10 or immediately before the end. The cutting force by the punch 12 can be amplified by using the cutting energy. Therefore, even if the force normally required for punching the central portion by the punch is 2 tons, according to the present embodiment,
It is possible to obtain the applied pressure of ton. As a result, it is possible to perform high-speed punching without increasing the output of the pressurizing means of the cutting device by only slightly shifting the fixed position of each cutting edge for cutting the outer periphery and the central portion. As a result, it is possible to prevent plastic deformation during punching of the central hole and obtain highly accurate roundness.

Next, FIGS. 3 (a) and 3 (b) show another embodiment of the present invention, and FIG. 3 (a) is a sectional view showing a state where the center hole of the stamper is punched by the punching device of the present invention, b) is a view showing the shape of a recess formed in the stamper. A characteristic of this embodiment is that the center hole 14 of the knockout plate 14 for pressing the peripheral edge of the center hole 3a of the stamper 3 is pressed.
An annular projection 14b having a wedge-shaped cross section is provided so as to be concentric with the hole 14a along the peripheral edge of a, and punching is performed by the punch 12 while pressing the annular projection 14b against the peripheral edge of the center hole 3a of the stamper. Thus, the concentric indentations 3b are formed on the peripheral edge of the center hole 3a of the stamper 3. In this way, knockout plate 14 and stamper 3
By reducing the contact area between and, not only the probability of foreign matter entrapment is reduced, but also an acute-angled wedge-shaped indentation 3b is positively formed as will be described later, and this indentation 3b is used during injection molding. In order to prevent misalignment of the stamper in the mold.

4 (a) and 4 (b) are an explanatory view showing a state of injection molding using the stamper having the above-mentioned indentation and an explanatory view of a conventional injection molding state. As shown in (b), conventionally, the stamper 3 is sandwiched between the molds 20 and 21, and at the same time, the pressing ring 22 is inserted into the center hole 3a of the stamper 3 and the tip of the pressing ring is screwed into one mold 20. Although the conventional presser ring is only a member having a T-shaped cross section with a threaded portion at the tip, it is a means for fixing the positional relationship between the collar-shaped presser part 22a and the central hole 3a. Didn't exist. In other words, since the surface of the pressing portion 22a in contact with the stamper is flat, if there is a large dimensional error between the size of the central hole 3a and the diameter of the rod-shaped portion 22b of the pressing ring, play will occur there. The stamper may move in the rotation direction due to the flowing pressure of the molten resin introduced from the flow path 21a. Further, this movement causes rubbing on the back surface of the stamper. This rubbing is a major cause of shortening the life of the stamper.

On the other hand, in the embodiment of the present invention, as shown in (a), the wedge-shaped indentation 3b formed on the stamper is formed on the lower surface (contact surface with the stamper) of the pressing portion 22a of the pressing ring 22.
Since the locking annular ridge 22c that closely fits inside is provided so as to project, the wedge-shaped impression 3b can be pressed by the locking annular ridge 22c to prevent the stamper 3 from being displaced. As a result, it was possible to prevent the deviation of the stamper in the mold in the rotational direction (small rotation) and the back surface rubbing caused thereby, and to improve the life of the stamper.

The condition of the shape and size of the annular protrusion 14b of the knockout plate 14 is that the width is 0.5 mm or less,
By setting the tip R to be 0.05 mm or less and the height to be 1/4 or less of the wall thickness of the stamper 3, a disk with an eccentricity of 20 μm or less could be obtained. As a result, it becomes possible to support a disk drive device of high speed rotation specification. The punching device of the present invention is designed to finish the stamper to have predetermined inner and outer diameters in the manufacturing process of a high-precision, high-cleaning nickel stamper used for manufacturing a disc-shaped recording medium such as an optical disc, a compact disc, and a magneto-optical disc. It can be applied to the press punching device.

[0019]

As described above, in the present invention, the surface roughness R of each cutting edge 1 and 2 is maintained while the radial clearance of the upper and lower cutting edges for punching is 8% or less of the work thickness.
max is 0.1 s or less, and the surface hardness of each cutting edge is H
v500 or more and the tip R of each cutting edge is 0.05 mm
The following settings were made and each cutting edge was surface treated with titanium nitride (TiN) or ion nitriding to reduce the friction coefficient, so finishing work for deburring after punching is unnecessary and yield is improved. Can be planned.

Further, when punching the center of the stamper with a punch, an annular ridge 14b having a wedge-shaped cross section is formed around the center hole 14a of the knockout plate that holds the center of the stamper between the die and the die. By doing so, an annular indentation 3b concentric with the center hole 3a to be formed in the center of the stamper is formed, and the locking annular projection 22c provided on the holding ring 22 during injection molding is fitted into the indentation 3b. Since the eccentricity of the medium (disk) is not determined by the respective tolerances of the stamper and the pressing ring, the eccentricity can be suppressed to a minimum because the eccentricity is fixed in the pressed state. Further, it is possible to prevent the stamper from being displaced in the rotational direction during the injection molding, so that the life of the stamper can be increased.

Further, the cutting start timing of the outer peripheral cutting edge of the stamper is set slightly earlier than the cutting start timing of the central cutting edge, specifically, the upper blade for cutting the outer peripheral portion. The position of the tip of the punch is higher than the position of the tip of the punch for cutting the center by a height h (1
By locating the lower part by / 2t <h <t), the cutting of the central portion is started during the cutting of the outer peripheral portion or immediately before the end of the cutting, and the cutting of the central portion during the cutting of the outer peripheral portion by the cutting blade or immediately before the end is completed. The cutting energy by the punch can be amplified by using the amplified cutting energy. Therefore, high-speed punching is possible without increasing the output of the pressurizing means of the cutting device. As a result, it is possible to prevent plastic deformation during punching of the central hole and obtain highly accurate roundness.

[Brief description of drawings]

1A and 1B are views showing a punching state by a punching device according to a preferred embodiment of the present invention.

FIG. 2 is a diagram showing a punching state according to another embodiment of the present invention.

3 (a) and 3 (b) are views showing a punching state of a central portion and a shape of a stamper after punching according to another embodiment of the present invention.

4A and 4B are an explanatory view showing a state of injection molding using a stamper having an indentation and an explanatory view of a conventional injection molding state.

FIG. 5 is an explanatory diagram of a conventional electroforming method of a stamper used when molding a disk-shaped recording medium, in steps (1) to (5).

FIG. 6 is an explanatory view showing a punching state according to a conventional example.

FIG. 7 is a diagram showing a punching state when the radial clearance between the upper and lower cutting edges is 8% of the work thickness.

FIG. 8 is a schematic configuration explanatory view of a conventional device for punching out the center part of a stamper.

[Explanation of symbols]

1 Upper blade, 2 Lower blade, 3 Workpiece, 3a Center hole, 3b
Indentation, 10, 11 cutting edge, 12, 13 cutting edge, 14
Knockout plate, 14a center hole, 14b20,
21 mold, 22 pressing ring, 22a collar-shaped pressing portion, 22b rod-shaped portion, 22c locking annular ridge,

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[Procedure amendment]

[Submission date] July 7, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

[0019]

As described above, in the present invention, the surface roughness R of each cutting edge 1 and 2 is maintained while the radial clearance of the upper and lower cutting edges for punching is 8% or less of the work thickness.
max is 0.1 s or less, and the surface hardness of each cutting edge is H
v500 or more and the tip R of each cutting edge is 0.05 mm
Since the following settings were made and each cutting edge was surface-treated with titanium nitride (TiN) or ion nitriding treatment to reduce the friction coefficient, the quality of the stamper processed part can be stabilized, and especially burrs after punching It is possible to improve the yield without requiring finishing work for picking. Further, the life of the punching blade can be improved, and the re-polishing cost can be reduced.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0020

[Correction method] Change

[Correction content]

Further, when punching the center of the stamper with a punch, an annular ridge 14b having a wedge-shaped cross section is formed around the center hole 14a of the knockout plate that holds the center of the stamper between the die and the die. By doing so, an annular indentation 3b concentric with the center hole 3a to be formed in the center of the stamper is formed, and the locking annular projection 22c provided on the holding ring 22 during injection molding is fitted into the indentation 3b. Since the eccentricity of the medium (disk) is not determined by the respective tolerances of the stamper and the pressing ring, the eccentricity can be suppressed to a minimum because the eccentricity is fixed in the pressed state. Further, it is possible to prevent the stamper from being displaced in the rotational direction during the injection molding, so that the life of the stamper can be increased. In other words, it is possible to prevent the stamper rotation due to the imbalance of the resin spray output during molding.
The minute scratches that have occurred on the back surface of the die and stamper are eliminated, and the life of the stamper can be greatly improved. Further, by utilizing the annular mark of the knockout plate, it is possible to prevent eccentricity during molding, and it is possible to stably obtain a disk having a small surface wobbling acceleration in the radial direction.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

Further, the cutting start timing of the outer peripheral cutting edge of the stamper is set slightly earlier than the cutting start timing of the central cutting edge, specifically, the upper blade for cutting the outer peripheral portion. The position of the tip of the punch is higher than the position of the tip of the punch for cutting the center by a height h (1
By locating the lower part by / 2t <h <t), the cutting of the central portion is started during the cutting of the outer peripheral portion or immediately before the end of the cutting, and the cutting of the central portion during the cutting of the outer peripheral portion by the cutting blade or immediately before the end is completed. The cutting energy by the punch can be amplified by using the amplified cutting energy. Therefore, high-speed punching is possible without increasing the output of the pressurizing means of the cutting device. As a result, it is possible to prevent plastic deformation during punching of the central hole and obtain highly accurate roundness. In other words, even with a low-power device, high-speed punching is possible and burrs-free center processing with good roundness is possible.

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Claims (4)

[Claims] 1. A punching device including a cutting blade for punching out a central portion and an outer peripheral portion of a stamper for molding a disk-shaped recording medium, wherein a clearance between an upper blade and a lower blade constituting the cutting blade is provided. Is set to 8% or less of the wall thickness of the stamper, at the same time the surface roughness Rmax of the upper and lower blades is set to 0.1 s or less, and the surface hardness of each blade is set to Hv500 or more. A punching device for a stamper or the like, wherein the blade is surface-treated by titanium nitride (TiN) or ion nitriding. 2. An annular ridge having a wedge-shaped cross section is formed on the peripheral edge of the center hole of a knockout plate that holds the stamper center with the die when punching the stamper center, and the annular ridge is pressed against the die. An annular indentation is formed in the center of the stamper, and the locking annular projection provided on the pressing ring for pressing the stamper at the time of injection molding is fixed in the state of being fitted into the indentation of the stamper. An injection molding method using a stamper. 3. The width of the annular projection of the knockout plate is 0.5 mm or less, and the tip R is 0.05 mm or less,
The injection molding method according to claim 2, wherein the height is set to ¼ or less of the stamper thickness. 4. The position of the tip of the upper blade for cutting the outer peripheral portion of the stamper having a wall thickness t is higher than the position of the tip of the punch for cutting the center of the stamper. By arranging it by h (1 / 2t <h <t) above, cutting of the central portion is started during cutting of the outer peripheral portion, and the amplified cutting energy during cutting of the outer peripheral portion by the cutting blade is utilized. A punching device for a stamper or the like according to claim 1, wherein the cutting force by the punch is amplified.