JP2000082243A - Apparatus for production of information recording medium, production of information recording medium and information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to produce a superflat disk having decreased noises, such as focus errors, by utilizing a sheet stamper obtd. by using a mastering process generally used for optical disks as it is. SOLUTION: This apparatus 10 for production produces the disk-like information recording medium 2 having information recording parts by injection molding in metal molds. The apparatus has the stamper 22 of the thin type metal formed with rugged signals by the mastering process and a reinforcing disk 1 for reinforcing the stamper 22 joined by a low melting alloy to the stamper 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a manufacturing apparatus and a manufacturing method for manufacturing an information recording medium for recording audio, video, and other various kinds of recording information.

[0002]

2. Description of the Related Art Optical recording media and magnetic recording media are known as recording media for audio, video and other various information. These recording media include a phase change type optical disk in which an information signal is written by embossed pits and grooves, a magneto-optical disk utilizing the magneto-optical effect of a recording film, and a magnetic disk in which a signal is magnetically written.

In the information recording layer, information having fine irregularities such as phase pits and pregrooves for recording data information, tracking servo signals and the like are recorded. The information recording layer is formed by using a stamper. It is common practice today to make plastic substrates by injection molding.

FIGS. 10 and 11 show a conventional thin plate stamper S. FIG.
P indicates a mold for injection molding used for manufacturing an optical disk. This mold is mounted on an injection molding machine, and a duplicate plastic substrate PD is obtained through a molding cycle shown in FIG. 12 using a stamper SP in which a mounting signal is formed in advance.

[0005] The thickness of 0.3 mm used in FIG.
The stampers SP of the front and rear thin plates are created through a mastering process and an electroforming process. The stamper SP exposes and develops a glass master with a resist by a laser exposure device, develops it by electroless plating or sputtering, and then performs an electroforming plating process (in general, plating to a thickness of about 0.3 mm). After that, the inner diameter portion and the outer diameter portion are formed by forming.

The drawback of the substrate obtained by such molding is that when the molten resin is injected into the mold cavity as shown in FIG. The stamper SP expands and contracts due to expansion and contraction, and abrasion due to friction with the mold gradually increases with the progress of molding, and many minute irregularities are generated and grown. These minute irregularities are transferred to the disk and cause a focus error and a tracking error. Due to pressure and temperature changes during injection into the substrate PD, rotational stress acts on the stamper SP in addition to elongation in the radial direction, causing scratches with the mold. On the substrate PD, molecular orientation distortion and thermal distortion of another resin remain. In the stage from cooling to solidification, the stamper shrinks due to stress relaxation within a certain period of time and progress of cooling, but due to stress unevenness during molding and minute irregularities on the contacting mold surface, it is not a linear motion but a wavy motion. Is repeated, and the fact that the conventional stamper SP is thin is also added, and the polishing trace during the surface polishing performed for adjusting the plating bump and the thickness of the stamper is transferred and remains on the substrate PD.

[0007] These problems were not recognized as problems when the optical system had a low NA (aperture ratio) when using a CD (compact disc: trade name) or VD (video disc: trade name). In a high-density disk corresponding to a large number of high NAs, the allowable value is strict because the depth of focus is shallow, and minute irregularities on the signal surface or surface contact are likely to cause a focus error or a tracking error.

On the other hand, in the case of a magnetic disk such as a discrete hard disk, there is a medium in which a fine uneven signal similar to that of an optical disk is transferred to a plastic substrate.
Unlike an optical disk, the distance between the disk and the head is extremely narrow, within 50 nm, due to the flight head, and stricter specifications than warranted for the optical disk, such as warpage, deformation, and roundness, are required.

For this reason, in a hard disk, problems such as roundness, surface accuracy, and warpage cannot be cleared due to the effects of expansion, contraction, and deformation of the stamper by molding a substrate by a stamper method. There is a direct mold method in which a resist coating laser exposure, which is a mastering process, development, etching, and a necessary uneven signal are formed on the mold surface to form a substrate. This method is shown in FIG. However, the method of forming a signal pattern directly on the mold surface requires a large process, time and cost.

[0010] As shown in FIG.
After processing the roughened mold material in (A) into a mold, it is finished to a predetermined surface roughness by surface grinding. FIG.
As shown in (B), the diamond abrasive grains are made finer in stages, and mirror lap is finally performed. In the case of polishing at the mirror surface mold level, which has been used on the reading surface of a disk, fine polishing flaws due to lapping remain, and there is a problem that the laser spot diameter is too large to use this surface as the reading surface of the disk. Although it was not, it was insufficient for use as a signal surface, and the minute scratches generated during polishing directly affected the error rate on the signal surface. Depending on the situation, finer polishing or lapping of abrasive grains of 1 μm or less may be repeated or lapping of a thin metal film such as indium on the lapping surface may be repeated several times to remove pinholes and minute scratches. Finish a flat surface similar to the surface. A mastering process as shown in FIGS. 13 (C) to 13 (F) is performed on the mirror-finished plate thus completed, and patterning is performed by exposure and development followed by etching to obtain a mold with a signal.

For a high-density disk corresponding to a high NA, 0.3
In the substrate PD of FIG. 12 obtained by a conventional thin plate stamper of about mm, the resin injection, the stress caused by cooling and solidification, the heat, the thermal expansion, the contraction of the stamper caused by thermal expansion and contraction, the deformation, the stamper and the mold surface Due to the influence of the scratches on the substrate and the trace of polishing of the back surface of the stamper on the signal side, there is noise on the signal side of the disk substrate as illustrated in FIG. Since this noise is hardly present on the reading surface of the disk as shown in FIG. 15C and is not found in the measurement result of the thin stamper alone as shown in FIG. It is clear that On the other hand, a disk obtained from the direct mold with a signal by etching shown in FIG. 13 shows almost no substrate noise on the signal surface, but it can be produced regardless of the complexity, processability, cost, and time of the direct mold making process. It is clear that the sex is bad.

[0012]

DISCLOSURE OF THE INVENTION In a disk obtained from a thin-plate stamper, a CD or a high-density information recording medium (DVD: digital versatile disk or digital video disk) having a small surface runout mold temperature caused by minute unevenness appearing on the signal surface. However, even in a high-density disk exceeding 10 giga due to the increase in NA, minute irregularities and minute surface runout on the surface of the substrate have a small focus error margin as a system. For this reason, it is necessary to produce such a substrate (disk) with little substrate noise at a low cost and as quickly as a conventional thin plate stamper.
As a means for this purpose, there is the above-mentioned direct mold method for directly creating a signal on the mold surface. However, it is desired to be able to produce and provide a disk substrate inexpensively in a short time in view of the complexity of the process, time and cost. ing.

In order to achieve the above object, the present invention utilizes a thin stamper obtained directly through a mastering process generally used in a conventional optical disc, and reduces noise such as focus error. Provided are an information recording medium manufacturing apparatus, an information recording medium manufacturing method, and an information recording medium capable of manufacturing an ultra flat disk.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is to provide a manufacturing apparatus for manufacturing a disk-shaped information recording medium having an information recording portion in a mold by injection molding. A thin metal stamper
This is achieved by an information recording medium manufacturing apparatus, comprising: a reinforcing disk joined to the stamper with a low melting point alloy to reinforce the stamper.

In the present invention, when a disk-shaped information recording medium having an information recording portion is manufactured by injection molding in a mold, a thin metal stamper is formed with a concavo-convex signal through a mastering process. The reinforcing disk is joined to the stamper with a low melting point metal to reinforce the stamper.

By doing so, the strength of the stamper is reinforced by the reinforcing disk, as compared with the case where a disk-shaped information recording medium is injection-molded in a mold using only a thin metal stamper. The heat and stress at the time of execution, the shrinkage and deformation during cooling and solidification are reduced, and the information recording medium with little noise which is less likely to cause a focus error by eliminating minute unevenness, surface runout and warpage of the surface of the disc-shaped information recording medium is obtained. be able to.

In the present invention, the low melting point alloy is preferably an alloy mainly containing lead. In the present invention, the reinforcing disk is preferably subjected to a surface treatment on a nonmetallic material. In the present invention, preferably, the nonmetallic material is ceramics, and the surface treatment is metal plating.

In the present invention, preferably, the inner diameter of the stamper is set smaller than the inner diameter of the reinforcing disk, and the outer diameter of the stamper is set larger than the outer diameter of the reinforcing disk. As a result, the low melting point metal on the joint surface between the stamper and the reinforcing disk
The stamper can be prevented from protruding from the end surfaces of the inner peripheral portion and the outer peripheral portion, and the low melting point metal can be prevented from being formed in a convex shape on the surface of the stamper.

In the present invention, preferably, a trap groove for preventing the low melting point alloy from protruding from the inner peripheral portion and the outer peripheral portion of the stamper at the time of joining is preferably formed in the outer peripheral portion and the inner peripheral portion of the joining surface of the stamper and the reinforcing disk. Are formed. This allows
The trap groove traps excess low melting point metal between the stamper and the reinforcing disk, and can prevent excess low melting point metal from protruding from the inner peripheral portion and the outer peripheral portion of the stamper.

In the present invention, preferably, the mold has a communication hole, the communication hole communicates with a trap groove on the joint surface side of the reinforcing disk, and the vacuum suction means sucks an excessive low melting point alloy through the communication hole. . Thereby, the vacuum suction means removes excess low-melting metal, gas and air between the stamper and the reinforcing disk through the communication hole, and prevents nests (voids) from being generated between the stamper and the reinforcing disk. The stamper and the reinforcing disk can be securely joined by the low melting point metal.

In the present invention, the stamper and the reinforcing disk are preferably subjected to a surface treatment with a low melting point alloy and a metal having good wettability or a metal having the same composition as the low melting point alloy. This ensures that the stamper and the reinforcing disk are joined to each other by the low melting point metal by ensuring the wettability of the low melting point metal between the stamper and the reinforcing disk.

The object of the present invention is to provide a disk-shaped information recording medium having an information recording portion, which is manufactured by injection molding in a mold, by using a thin metal sheet having a concavo-convex signal formed through a mastering process. A stamper and a reinforcing disk for reinforcing a metal stamper are joined with a low-melting alloy, and a disk-shaped information recording medium having an information recording portion is injection-molded in a mold using the stamper reinforced by the reinforcing disk. This is achieved by a method for manufacturing an information recording medium, characterized in that: By doing so, compared to a case where a disk-shaped information recording medium is injection-molded in a mold using only a thin metal stamper,
Since the strength of the stamper is reinforced by the reinforcing disk, heat and stress during injection molding, shrinkage and deformation during cooling and solidification are reduced, and fine irregularities, surface runout and warpage of the disk-shaped information recording medium are eliminated. Thus, it is possible to obtain an information recording medium with less noise that is less likely to cause a focus error.

In the present invention, preferably, the inner diameter of the stamper is set smaller than the inner diameter of the reinforcing disk, and the outer diameter of the stamper is set larger than the outer diameter of the reinforcing disk. As a result, the low melting point metal on the joint surface between the stamper and the reinforcing disk
The stamper can be prevented from protruding from the end surfaces of the inner peripheral portion and the outer peripheral portion, and the low melting point metal can be prevented from being formed in a convex shape on the surface of the stamper.

In the present invention, preferably, a trap groove for preventing the low melting point alloy from protruding from the inner and outer peripheral portions of the stamper at the time of joining is preferably formed in the outer and inner peripheral portions of the joint surface between the stamper and the reinforcing disk. Are formed. This allows
The trap groove traps excess low melting point metal between the stamper and the reinforcing disk, and can prevent excess low melting point metal from protruding from the inner peripheral portion and the outer peripheral portion of the stamper.

In the present invention, preferably, the mold has a communication hole, the communication hole communicates with a trap groove on the joint surface side of the reinforcing disk, and the vacuum suction means sucks an excessive low melting point alloy through the communication hole. . Thereby, the vacuum suction means removes excess low-melting metal, gas and air between the stamper and the reinforcing disk through the communication hole, and prevents nests (voids) from being generated between the stamper and the reinforcing disk. The stamper and the reinforcing disk can be securely joined by the low melting point metal.

The object of the present invention is to provide a disk-shaped information recording medium having an information recording section manufactured by injection molding in a metal mold, wherein a thin metal sheet having an uneven signal formed through a mastering process. A stamper and a reinforcing disk for reinforcing the metal stamper are joined by a low-melting alloy, and the information recording medium is injection-molded in a mold using the stamper reinforced by the reinforcing disk. Is achieved. By doing so, the strength of the stamper is reinforced by the reinforcing disk, as compared with the case where a disk-shaped information recording medium is injection-molded in a mold using only a thin metal stamper. By reducing heat and stress and shrinkage deformation during cooling and solidification, the disc-shaped information recording medium is free from fine irregularities, surface runout, and warpage on its surface, and is less likely to cause a focus error.

[0027]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows a preferred embodiment of the information recording medium manufacturing apparatus of the present invention. The apparatus 10 for manufacturing a disc-shaped information recording medium shown in FIG.
1, a movable mounting plate 12, a fixed plate 13, a movable mirror 14, an outer peripheral ring 15, a reinforced stamper (also referred to as a thick stamper) 20, and the like. The fixed side mounting plate 11 holds the fixed side plate 13 and the movable side mounting plate 12
Holds the movable mirror 14. The outer ring 15 is disposed on the fixed plate 13 side. Sprue 11A
Are formed on the fixed side mounting plate 11 and the fixed side plate 13 side. The information recording medium manufacturing apparatus 10 is arranged in a commonly used injection molding machine, and injects a molten resin through a sprue 11A to thereby form a disc-shaped information recording medium (hereinafter, referred to as a disc) D shown in FIG. Substrate 2
Can be injection-molded using the reinforced stamper 20.

Here, an example of the structure of the disk D using the substrate 2 manufactured by the information recording medium manufacturing apparatus 10 will be described with reference to FIG. The disk D is, for example, an optical disk, for example, a compact disk (C
D) or a high-density information recording medium (DVD) in which uneven signals 2 a and 2 b are formed on a transparent substrate 2. The uneven signals 2a and 2b of the substrate 2a constitute an information recording unit 2c. The concave portion 2a or the convex portion 2b of the information recording portion 2c has, for example, a groove type or a pit shape. The information recording section 2c has a light reflecting layer 3, a recording layer 4, and a light transmitting layer 5 as a protective film.

Next, an example of the structure of the reinforcing stamper 20 of FIG. 1 will be described with reference to FIGS. A reinforced stamper 20 is set in the mold of FIG. 1, that is, the information recording medium manufacturing apparatus 10. This reinforced stamper 20 is shown in FIG.
For example, as shown in FIG. 3, the reinforcing disk 21 includes a reinforcing disk 21 made of a thick metal plate, a stamper 22 made of a thin metal, and solder (low-melting metal) 23. The solder 23 joins the stamper 22 and the reinforcing disk 21. The reinforcing disk 21 is a stamper 2
2 is a disk that reinforces the mechanical strength. As shown in FIG. 4A, a flux F is applied to one surface of the stamper 22 and is reinforced as shown in FIGS. 4B and 4C. The flux F is also applied to one surface of the disk 21.

As shown in FIG. 5, the stamper 22 and the reinforcing disk 21 are heated and melted and pressurized by soldering the solder 25 on the reinforcing disk 21 so that excess solder 25 is formed on the inner and outer peripheral trap grooves 24 and the communication holes 33a. , 33b to the outside to be integrated. In this case, the reinforced stamper 20 as shown in FIG. 7 can be integrally joined while applying pressure by the joining mold 30. FIG. 6 shows the joined state, and the reinforced stamper 20 includes a stamper 22.
And the reinforcing disk 21 are joined in close contact with the solder 25. In order to apply pressure in this case, the joining mold 3 shown in FIG.
The upper die 31 and the lower die 32 integrally press the stamper 22 and the reinforcing disk 21 together.

The outer peripheral portion of the reinforcing disk 21 is formed with trap grooves 24 at the outer peripheral portion and the inner peripheral portion shown in FIGS. In the lower mold 32 of FIG. 7, the outer peripheral and inner peripheral trap grooves 24 shown in FIGS. 4C and 5 are formed. Further, a plurality of communication holes 33a are formed in the trap groove 24 as shown in FIG. The lower die 32 of FIG.
3b are formed, and the communication holes 33a and 33b are connected to the lower mold by the guide pins 26. Thus, when the vacuum suction means 34 is operated, excess solder, air and gas between the stamper 22 and the reinforcing disk 21 can be positively removed from between the stamper 22 and the reinforcing disk 21 to the outside. Nests (voids) can be prevented from being generated between the reinforcing disk 22 and the reinforcing disk 21.

The stamper 22 has a center hole 22A as shown in FIG. 7, and similarly, the reinforcing disk 21 also has a center hole 21A. In order to center these center holes 22A, 21A, a center positioning guide 35 is used. The center positioning guide 35 contacts the member 36 of the upper mold 31 to selectively press the vicinity of the center hole 22 of the stamper 22 earlier than other portions, thereby preventing solder leakage to the inner diameter side. We are joining. The center positioning guide 35 is preferably made of a material such as ceramic to which a T-shaped solder does not adhere when viewed in cross section.

The lower mold 32 has a hole 36 through which cooling water passes for cooling. Similarly, the upper mold 31 also has a hole 37 for cooling. The lower mold 32 has a heater hole 38 through which a heater for heating passes, and the upper mold 31 has a hole 39 through which the heater passes. The guide pin 26 includes the lower mold 32 and the reinforcing disc 2.
The plurality of communication holes 33a and 33b serve to match each other, and serve to release gas, air, and excess solder during heating and pressurization to the vacuum suction means 34. The reinforced stamper 20 obtained by heating and bonding is then cooled and solidified while keeping the stamper 22 and the reinforcing disk 21 in close contact with each other, whereby a reinforced stamper (also referred to as a thick stamper) 20 can be obtained.

In the embodiment of the present invention, as shown in FIG. 6, a stamper 22 made of a thin sheet metal having a concavo-convex signal and a reinforcing disc made of a thick sheet metal are joined and reinforced with a low-melting alloy through a mastering process, thereby strengthening the stamper. 20 (also referred to as a thick stamper) is created. The low melting point alloy is preferably an alloy composition having a liquidus within a range from the melting temperature of the resin at the time of injection molding to minus 50 ° C and a solidus temperature of 200 ° C or more. That is, it is preferable that the melting temperature is higher than the melting temperature at the time of injection molding, but it is not always necessary to be higher. For example, in the case of a polycarbonate resin used for disk molding, the melting temperature of the resin is set at a nozzle temperature of the molding machine of 300 to 3.
Although 40 ° C is generally used, heat is taken away by the mold temperature control during the process in which the resin passes from the nozzle through the sprue and gate of the mold into the cavity, and the surface temperature of the stamper becomes 250 ° C or less. In addition, this temperature is instantaneous, the mold temperature is usually 130 ° C. or less, and even DVDROMs are rapidly cooled at generally 120 ° C. or less (CD,
The disc is released at a temperature below the Tg point in addition to about 4 seconds for a DVD.
there in m ² or more pressure stamper with a low melting point alloy having a solidus above minus 50 ° C. than the nozzle temperature of the resin so even solidified in the cooling process as a solder Yoshinba so pressed against the reinforcement disc is melted I just need. The low melting point alloy used for this joining is an alloy mainly containing lead, for example, a solder 23 as shown in FIG. When solder 23 is used, the advantage of solder as a low melting point alloy is 200 ° C.
The only metal that joins the stamper and the reinforcing disk at a temperature of 350 ° C. or less is lead-based solder, and alloys such as silver that are higher than this will increase the temperature at the time of joining, and discolor the stamper surface due to workability and heat at the time of joining. In the case of electroless plating, the surface of the stamper undergoes a phase transition when the temperature exceeds 400 ° C., and becomes brittle, so that a lead-based solder alloy is preferable.

The plate thickness of the reinforcing disk 21 used for the reinforcing stamper (thick plate stamper) 20 preferably has a thickness of 2.0 mm or more. If the thickness of the reinforcing disk 21 is 2.0
If the thickness is less than 300 mm, when the soldering disc and the reinforcing disc are joined at a temperature of 300 ° C or more and the thickness of the reinforcing disc is thin, if a sudden temperature is applied, thermal expansion occurs not only in the radial direction but also in the circumferential direction. Propeller-like deformation occurs. The plate thickness for preventing this deformation is 2 mm. The minimum value of the reinforcing disk thickness is, for example, that the stamper has a thickness of 0.5 to 1.5 mm, and that the strength of the disk exceeds 2 mm in thickness because it is proportional to the cube of the thickness. That is also a numerical basis.

Regarding the inner diameter of the reinforcing stamper 20 to be joined, the inner diameter of the stamper 22 is equal to or smaller than the inner diameter of the thick reinforcing disk 21 by, for example, 0.5 mm or less. Diameter is reinforced disk 21
Is larger than, for example, 1 mm or less, so that the low-melting-point alloy on the joining surface does not protrude from the surface of the stamper 22. This prevents the low melting point metal on the joining surface between the stamper and the reinforcing disk from protruding from the end surfaces of the inner peripheral portion and the outer peripheral portion of the stamper, and prevents the low melting point metal from being formed in a convex shape on the stamper surface. Can be. In order to prevent the low melting point alloy 23 from protruding from the end faces of the inner and outer peripheries at the time of joining, a trap groove 24 is provided on the inner and outer peripheries of the joining surface between the reinforcing disk 21 and the stamper 22 so as to trap excess low melting point alloy. It has become. Thus, the trap groove traps the extra low melting point metal between the stamper and the reinforcing disk, and can prevent the extra low melting point metal from protruding from the inner peripheral portion and the outer peripheral portion of the stamper.

The inner and outer trap grooves 24 are provided with
As shown in FIG. 7B and FIG. 7, a plurality of communication holes 33a communicating with the side opposite to the bonding surface are provided, and the communication holes 33a communicate with the communication holes 33b of the lower mold 32a.
6 and joined with the vacuum suction means 34 to form the stamper 22.
Excess solder, gas and air between the plate and the thick disk 21 are removed to prevent nests (voids). Thereby, the vacuum suction means removes excess low-melting metal, gas and air between the stamper and the reinforcing disk through the communication hole, and prevents nests (voids) from being generated between the stamper and the reinforcing disk. The stamper and the reinforcing disk can be securely joined by the low melting point metal.

As a method of removing excess solder and gas or air between the stamper 22 and the reinforcing disk 21 and eliminating cavities (voids), the upper die 31 shown in FIG.
Is provided with a guide 36 made of a mountain-shaped elastic body or a guide by a spring, and is pressed from the center at the time of pressing for joining.

In order to improve the wettability of the solder alloy at the time of joining, the stamper 22 and the reinforcing disk 21 are subjected to surface treatment of a dissimilar metal on the reinforcing disk 21 side or the stamper 22 by means such as plating, silver mirror reaction, substitution reaction or sputtering. Alternatively, nests (voids) can be prevented by applying to both. In soldering metal, soldering alone does not bond the surface of the metal with dirt or an oxide film and does not join it.The flux is used to wash and reoxidize the metal surface and helps reduce the interfacial tension. There are metals that are easily soldered, such as oxide films that are difficult to remove or reoxidize immediately, and metals that are difficult to adhere. Examples of metals that can be easily soldered include brass, copper, bronze, gold, silver, nickel, and tin.
Examples of metals that are not easily soldered include aluminum, iron castings, magnesium, chromium, copper, stainless steel, and zinc. For this reason, a soft metal cannot be used as the material used for the mold, and copper or stainless steel is often used. SUS420J or the like is used for the disk mold, and since this material is not easily soldered, plating such as copper is applied to the surface. Regarding the reinforcing disk 21 and the stamper 22, as a method other than plating, a metal simple substance such as copper or an alloy having good heat conductivity is used to improve solder wettability and heat conduction of the thick plate stamper after joining. You can also.

As the reinforcing disk 21, a thick plate material such as a ceramic material other than metal, whose surface is plated or the like may be used. In a substrate obtained by injection molding using the reinforced stamper 20 as shown in FIG. 2, substrate noise due to micro-surface irregularities of the stamper at the time of molding can be reduced.
In other words, the thin stamper 22 having a fine uneven signal and a groove obtained by a mastering process and relating to a disc-shaped recording medium for recording audio, video and other various recording information is replaced with a reinforcing disc which is a thick metal plate of the same or different material. A reinforced stamper 20, which is a thick plate stamper closely contacted or bonded with a low melting point alloy (solder alloy), is formed on the stamper 21, and the reinforced stamper 20 is incorporated into a manufacturing apparatus 10 as a mold as shown in FIG. Thus, by producing the disk D, it is possible to manufacture an information recording medium (disk) without an ultra flat substrate noise. More specifically, a reinforced stamper obtained by joining a thin plate stamper 22 having a thickness of about 0.3 mm obtained by a commonly used mastering process to a reinforcing disk 21 which is a thick plate made of copper, stainless steel, nickel, or the like with a solder alloy 23 and having a thickness of 2 mm or more. 20, the strength of the thin plate stamper 22 is improved, the heat and stress of the resin during injection molding, the shrinkage deformation during cooling and solidification are reduced, and the micro unevenness, surface runout and warpage of the disk surface are reduced, and the focus error is reduced. As a result, a disk-shaped recording master and a disk D, which is an information recording medium, having less substrate noise which is less likely to occur are obtained.

FIG. 15 shows the results of noise measurement by forming an aluminum reflective film on the signal side (stamper side) and the reading surface side (corresponding to a thick plate stamper) in disk molding using a normal thin plate stamper. As is clear from the data shown in FIG. 14, the mirror surface on the conventional thin plate stamper side has a large noise. Also, since the measurement noise of the stamper alone shown in FIG. 16 is small, it is clear that the signal surface noise of the disk is caused by the expansion and contraction deformation of the stamper during molding. FIG. 14 shows the noise of the disk formed by the thick plate stamper of the present invention.
By comparing the data of the stamper side in FIG. 15, it can be understood that the noise is small.

Next, an example of a manufacturing process of the stamper 22 will be described. The stamper 22 is formed through a mastering step shown in FIG. 8 and an electroforming step shown in FIG. 9, similarly to a commonly used stamper. In the mastering step of FIG. 8, as shown in FIG.
Is manufactured and polished and cleaned. In FIG. 8B, a photoresist 22B is applied to the glass master 22A and dried. In FIG. 8C, a laser beam 22C is applied to the photoresist film 22B via a lens 22D to form a latent image 22E of a groove or pit row. In FIG. 8D, a developing process is performed to form a groove 22F or a pit 22G according to the specification.

In the plating step (conduction process) of the electroforming step of FIG. 9E, for example, a Ni plating layer 22H is formed on the pit 22G, and then the stamper 22 is formed using the Ni plating layer 22H. I do. Thus, a thin metal stamper 22 is obtained by the mastering and the electroforming process.

Next, an embodiment of the present invention will be described.

Embodiment 1 A stamper 22 made of Ni with a Pb-Sn solder and a SUS-
Reinforced stamper 2 by joining 420J-based reinforcing disk 21
If you get 0. 0.3m obtained through mastering process and electroforming
m-thick Ni-stamper with an inner diameter of 22 mm and an outer diameter of 138
and homing with a press machine or lathe. Polished SU having the same shape as the stamper 22 with a thickness of 5 mm
An S-420J-based reinforcing disk 21 is prepared. For example, trade name: STAVAXCD (Woodholm) can be used. According to the process shown in FIG. 4, a ZnC12-based flux is applied to the stamper 22 and the reinforcing disk 21 and dried. The lower mold 32 in FIG. 7 is heated by a heater, and the reinforcing disk 21 on which the flux has been applied is placed thereon and heated. Sn-Pb specified in JIS Z 3282 is placed on a solder thin plate having a composition ratio of 5:95 wt%, and the solder 23 is melted at a temperature of 315 ° C. or more. (Soldering area = liquidus temperature 314 ° C, solidus temperature 3
A guide 35 serving as a center holding jig of the center of the stamper 22 and the reinforcing disk 21 is placed on the molten solder 23.
To prevent misalignment, and set and fix to the bonding mold 30.

Next, the heated upper mold 31 shown in FIG. 7 is covered and pressurized by a hydraulic press (not shown) (gauge pressure 30 k).
g / cm ² ), the power of the heater was turned off, and the solder was taken out after the temperature reached a completely cooled and solidified temperature below the solidus line, to obtain a welded and reinforced stamper 20 as shown in FIG. When the upper mold 31 is set, a trap groove 24 and a communication hole 33 for allowing excess solder and air or gas to escape are provided at least on the outer periphery of the reinforcing disk 21 outside the disk diameter. ) Is eliminated, and the overflow of the solder from the bonding end face is prevented, which is more effective. The connection to the vacuum suction source 34 using this communication hole is more effective for voids. Thereafter, if necessary, the flux F protruding from the end face is washed. The reinforced stamper 20 thus obtained is attached to the manufacturing apparatus 10 which is the mold shown in FIG. Using the same polycarbonate resin as the conventional optical disk, a disk substrate 2 was obtained by injection molding. The molding conditions at this time are as follows. Polycarbonate (Teijin KK) Grade: AD-9000TG Glass transition point = 145 ° C Flexural modulus = 2,200 MPa Water absorption = 0.3% Molding conditions Mold temperature: 130 ° C Resin temperature: 330 ° C Injection speed: Average 160 mm / sec Cooling time: 12 seconds In the disk D as shown in FIG. 2 obtained by using the substrate of the disk obtained in this way, the remaining amount of the focus error is much smaller than that of the conventional stamper. Obtained.

Example 2 A stamper 22 with a Cu plating on the back surface and a SUS with a copper plating are used as means for obtaining good solder wettability and high bonding strength.
-Reinforcing stamper 2 by joining reinforcing disk 21 of -402J system
Make 0. * In addition to the copper plating, plating of silver, gold, or the like may be used. As a plating method, a method such as electroless plating, silver mirror reaction, or sputtering may be used instead of electroplating. In the same manner as in Example 1, the Ni plating was further plated with Cu plating by 5 to 10 while the glass master was plated to a thickness of 0.3 mm through a mastering process and electroforming plating.
μm and peeled off from the glass master.
m and homing to a size of 138 mm with a press machine or lathe. A roughly polished SU with the same shape as the stamper with a thickness of 5 mm
S-420J reinforced disc 21 (trade name: STAVAXC)
D = Woodholm Co.), and after removing the oxide film through a process such as electrolytic polishing, a copper plating is coated with 5 to 10 μm plating. A thick plate stamper was prepared in the same process as in Example 1, and the result obtained by assembling the mold into a mold and forming a disk showed characteristics similar to those of Example 1 with less substrate noise.

Example 3 A joint made of a metal material having a linear expansion coefficient relatively close to that of solder was used.
About the combination. The Ni-stamper 22 and the reinforcing disk 21 of the copper alloy used for the mold are joined. Considering the heat of the resin at the time of molding the disc and the cooling in the mold, a ternary alloy of Cu-Ni-Si used as a mold material as a combination of materials having close linear expansion coefficients and a Ni stamper. HR750 (trade name, manufactured by Kobe Steel) has a high thermal conductivity and a high cooling efficiency, so that the melting temperature of the joining solder can be lowered.

[Table 1] The solder used is Pb containing 5% Sn and 5% Ag and having a melting temperature of 309 ° C. As the flux to be used, a resin-based flux different from a ZnC12-based corrosive flux is used. The process is exactly the same as in the first embodiment. The obtained reinforced stamper 20 was inserted into the manufacturing apparatus 10 which is the mold shown in FIG. 1, and a disk was formed in the same manner as in Example 1. As a result, a disk with little substrate noise was obtained.

Example 4 A reinforcing disk 21 obtained by electroless plating of copper or nickel with a thickness of 5 to 10 μm on a ceramic 1.2 m plate other than a metal material and a thin plate Ni stamper 22 are joined by solder 23. The disk obtained from the reinforced stamper 20 subjected to the same solder bonding as in the first embodiment also has a low noise result as in the first embodiment. (1) In a high-density disk with a high NA, focus errors due to micro-deformation of a plastic substrate formed by thermal expansion or shrinkage during the disk forming process, which was not a problem in the conventional low-NA optical system, are caused by residual noise. Has been improved to almost negligible level by the reinforcing stamper (thick plate stamper) 20 of FIG. (2) In the conventional disk molding using a thin plate stamper of about 0.3 mm, the back surface of the pressurized back surface by the polishing cloth after electroforming plating appeared as macro unevenness on the signal surface due to the pressure at the time of molding. In the present invention, no polishing marks are observed at all from the reinforced stamper subjected to the solder bonding process, and the leveling action by the solder makes the unevenness with the thick stamper flat. (3) In the conventional disk molding using a thin stamper of about 0.3 mm, a disk obtained by damaging the stamper by inserting a foreign substance between the die and the die when attaching the stamper has a defect that becomes a defect. This is a problem in the work, and therefore, it is necessary to pay attention to the cleaning of the surface of the stamper and the mold and the working environment so as not to catch foreign matter. This work also required careful attention and time, but the thick plate stamper eliminated all of these problems. (4) Compared to the method of pattern lapping by mirror lapping the mold surface with the same concept as a thick stamper, there is no need for a process such as mirror lapping, so the process is simplified, the production time is simpler, and the production cost is lower than that of a conventional thin plate. Although the material involved in solder bonding and the manufacturing time are somewhat longer than those of the stamper, it has been found that the total is comparable when considering the time and labor required for attaching the thin plate stamper and the disk defect caused by foreign matter being pinched.

[0050]

As described above, according to the present invention,
An ultra flat disk with less noise such as a focus error can be manufactured by using a thin plate stamper obtained through a mastering process generally used in a conventional optical disk.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of an information recording medium manufacturing apparatus according to the present invention.

FIG. 2 is a diagram showing a structural example of a disk (information recording medium) obtained by a reinforced stamper used in the manufacturing apparatus of FIG.

FIG. 3 is a sectional view showing a structural example of the reinforced stamper of FIG. 1;

FIG. 4 is a view showing a reinforcing stamper and a reinforcing disk of FIG. 3;

FIG. 5 is a diagram showing a state in which a stamper and a reinforcing disk are joined.

FIG. 6 is a diagram showing a state where a stamper and a reinforcing disk are joined and cooled and solidified.

FIG. 7 is a view showing an example of a joining die for joining a stamper and a reinforcing disk with a low melting point alloy.

FIG. 8 is a diagram showing an example of mastering for manufacturing a sheet metal stamper of a reinforced stamper.

FIG. 9 is a diagram showing an example of an electroforming process for manufacturing a sheet metal stamper of a reinforced stamper.

FIG. 10 is a diagram showing a mold structure for manufacturing a conventional information recording medium.

FIG. 11 is an enlarged view of a portion A in FIG. 10;

FIG. 12 is a diagram showing a state in which a disk (information recording medium) is injection-molded by the mold shown in FIG. 10;

FIG. 13 is a view showing another example of a conventional mold.

FIG. 14 is a view showing a disk runout caused by the manufacturing apparatus (thick plate stamper: reinforced stamper) of the present invention.

FIG. 15 is a diagram showing a result of noise measurement performed by applying aluminum reflection to a signal side and a reading surface side of a disk formed by using a conventional ordinary thin plate stamper.

FIG. 16 is a view showing surface runout of a conventional thin plate stamper alone.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Information recording medium manufacturing apparatus, 11 ... Fixed side mounting plate, 12 ... Movable side mounting plate, 20 ... Reinforced stamper, 21 ... Reinforced disk, 22 ... Sheet metal Stamper, 24: outer peripheral trap groove, 25: solder,
33 ... communication hole, 34 ... vacuum suction means, D ...
Disc (information recording medium)

Continued on the front page (72) Inventor Shin Masuhara 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Motohiro Furuki 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Stock In-house F term (reference) 5D121 CA02 DD05 DD07 DD13 DD17

Claims (14)

[Claims] 1. A manufacturing apparatus for manufacturing a disk-shaped information recording medium having an information recording portion by injection molding in a mold, comprising: a thin metal stamper on which a concavo-convex signal is formed; An apparatus for manufacturing an information recording medium, comprising: a reinforcing disk joined to reinforce a stamper. 2. The information recording medium manufacturing apparatus according to claim 1, wherein the low melting point alloy is an alloy mainly containing lead. 3. The apparatus for manufacturing an information recording medium according to claim 1, wherein the reinforcing disk has been subjected to a surface treatment on a nonmetallic material. 4. The apparatus for manufacturing an information recording medium according to claim 3, wherein the non-metallic material is ceramics, and the surface treatment is metal plating. 5. The apparatus according to claim 1, wherein the inner diameter of the stamper is smaller than the inner diameter of the reinforcing disk, and the outer diameter of the stamper is set larger than the outer diameter of the reinforcing disk. 6. A trap groove for preventing a low melting point alloy from protruding from an inner peripheral portion and an outer peripheral portion of a stamper at the time of joining is formed in an outer peripheral portion and an inner peripheral portion of a joining surface of a stamper and a reinforcing disk. An apparatus for manufacturing an information recording medium according to claim 1. 7. The mold has a communication hole, the communication hole communicates with a trap groove on the joint surface side of the reinforcing disk, and the vacuum suction means sucks extra low melting point alloy to the outside through the communication hole. 7. The apparatus for manufacturing an information recording medium according to item 6. 8. The information recording medium manufacturing apparatus according to claim 1, wherein the stamper and the reinforcing disk are surface-treated with a metal having a good wettability with the low melting point alloy or a metal having the same composition as the low melting point alloy. 9. The apparatus for manufacturing an information recording medium according to claim 1, wherein the reinforcing disk is made of a metal having good heat conductivity. 10. When manufacturing a disk-shaped information recording medium having an information recording portion in a mold by injection molding, a thin metal stamper on which a concavo-convex signal is formed through a mastering process, and a metal stamper are reinforced. Recording medium having an information recording portion using a stamper reinforced by a reinforcing disk and injection molding in a mold using a stamper reinforced by the reinforcing disk. Manufacturing method. 11. The method according to claim 10, wherein the inner diameter of the stamper is smaller than the inner diameter of the reinforcing disk, and the outer diameter of the stamper is set larger than the outer diameter of the reinforcing disk. 12. A trap groove for preventing a low melting point alloy from protruding from an inner peripheral portion and an outer peripheral portion of a stamper at the time of joining is formed in an outer peripheral portion and an inner peripheral portion of a joining surface of a stamper and a reinforcing disk. The method for manufacturing an information recording medium according to claim 10. 13. The mold has a communication hole, the communication hole communicates with a trap groove on the joint surface side of the reinforcing disk, and the vacuum suction means sucks extra low melting point alloy to the outside through the communication hole. 13. The method for manufacturing an information recording medium according to item 12. 14. A disk-shaped information recording medium having an information recording portion manufactured by injection molding in a mold, wherein a thin metal stamper on which a concavo-convex signal is formed through a mastering process and a metal stamper are reinforced. An information recording medium characterized by being joined to a reinforcing disk by a low melting point alloy, and being injection molded in a mold using a stamper reinforced by the reinforcing disk.