JP2592344B2 - Stamper backside polishing method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a processing method and apparatus relating to a manufacturing process of an optical recording medium that transmits an information signal by optical change, and in particular,
The present invention relates to a method and an apparatus for polishing a back surface of an electroformed layer after an electroforming process.

[Prior art] In recent years, optical disk recording media such as an audio compact disk (CD) and a video disk (VD), which can record / reproduce information with a laser beam, such as laser vision, have become widespread. Not only dedicated but also write-once and rewritable types have been used.

Although this optical disk recording medium still has some issues such as the complicated control system of the disk drive unit and the high price, it records and reproduces signals using a light spot as small as the wavelength of light. This makes it possible to perform very high-density recording, which is about one to two orders of magnitude higher than magnetic recording, and furthermore, since information is exchanged using a non-contact method using a light beam, the signal surface is worn down. There are many advantages over conventional recording media, such as excellent recording non-volatility (retention of recorded data), and great expectation.

Such an optical disk recording medium converts an information signal, which is an analog signal, into a digital signal and records the signal, thereby increasing the dynamic range and performing recording that is resistant to noise. Generally, conversion from analog signal to digital signal is performed by pulse code modulation (PCM), and the information signal modulated to PCM signal has uneven spots on the recording film on the disk due to the light spot, and the presence or absence of a reflective film. , Deformation, change in refractive index, and magnetization reversal.

In the manufacturing process of the optical disc, there are a plurality of electroforming processes for creating a replica, and the electroforming process imparts conductivity to the photoresist surface, and the photoresist master is nickel electroformed with a nickel sulfamate bath. When the nickel layer (electroformed layer) on which the shape of the photoresist surface has been transferred from the photoresist surface is peeled off to obtain a nickel master disk, or when obtaining a mother disk from this master disk,
Further, it is used for obtaining a stamper board from a mother board. After each of these electroforming steps, there is a step of polishing the back surface of the surface of the electroformed layer, that is, the stamper board, mother board, and master board.

After forming a large number of the stamper disks, pits on the product are formed in a resin by a pressing process using the stamper disks, a reflective film of, for example, aluminum is formed thereon, and a protective film coat is formed. Thus, the above-described optical disk is manufactured.

In the present specification, the polishing of the back surfaces of the above-described stamper, mother, and master disks will be collectively referred to simply as “reverse polishing of the stamper” for convenience.

[Problems to be solved by the invention]

After the above-described electroforming step, the electroforming liquid during the electroforming step is usually kept at about 50 ° C., so that the glass master and the electroformed master are cooled by heat shrinkage after the electroforming step. In addition to the fact that the material (photoresist film, master board or mother board) is easily peeled off, and in the polishing step immediately after electroforming, a holding jig 30 as shown in FIG. There was a problem with being used.

The holding jig 30 has a ring shape (partly shown in the drawing) and has a structure for holding the outer peripheral portion of the glass master 16 (on which the electroformed layer 17 is formed) placed on the turntable 2. That is, with the leg portion 31 being in contact with the turntable 2 and the holding portion 32 being in contact with the outer periphery of the glass plate 16, the plurality of tightening bolts 11 penetrating the upper portion of the holding jig are used to turn the turntable 2. And fix it. Then, while turning the turntable 2 and supplying water, a polishing tape is appropriately pressed to polish the back surface of the stamper, which is the front surface of the electroformed layer 17. The polishing waste liquid A generated in this polishing step flows to the outside of the radius of the electroformed layer 17 due to centrifugal force, and most of the jig passes through a discharge groove 34 opened at regular intervals on an end face 33 of the pressing portion 32. The water flows into the inner space 20 and is drained from the jig inner space 20 through, for example, a hole formed in the leg 31 or a hole formed in the turntable 2.

In this way, the outer periphery of the back surface of the stamper is pressed by the pressing portion 32 so that the polishing waste liquid A is discharged from the discharge groove.
Although the waste liquid can be drained from the outer periphery of the electroformed layer 17 to the glass disk side, for example, the glass master 16 and the electroformed master material (when a master disk is prepared, the photoresist is transferred to the electroformed master). Material).

This means that by pressing the outer periphery of the stamper back surface at intervals, as described above, imbalance in the pressing force occurs between a portion pressing the stamper back surface and a portion not pressing the stamper back surface,
Thereby, the primer applied portion between the glass master 16 and the electroformed layer 17 including the electroformed master material is particularly easily peeled.
Therefore, when this peeling occurs, there is a problem that the polishing waste liquid containing the polishing debris invades the peeled portion, thereby causing scratches or defects on the electroformed original plate material and the electroformed layer 17.

An object of the present invention is to solve the above-mentioned problems, and it is possible to effectively avoid a phenomenon of separation between a glass master and a processed material such as an electroformed original plate material or an electroformed layer on the master, and even if separation occurs. Another object of the present invention is to provide a stamper back surface polishing method and apparatus that can prevent polishing waste liquid during polishing from entering between the glass master and the electroformed master.

[Means for solving the problem]

The object of the present invention is to 1) use a holding jig when polishing the back surface of a stamper on a glass master mounted on a rotating turntable after an electroforming process for forming a recording surface of an optical recording medium. Along with the glass master, the entire outer periphery of the back surface of the stamper is pressed without any gap in the circumferential direction, and the inner region of the holding jig is polished while being supplied with water, and polishing waste liquid containing polishing waste passes over the holding jig. A method for polishing the stamper back surface, characterized in that the stamper back surface is automatically radiated while supplying water to the stamper back surface on the glass master mounted on the rotating turntable. In a stamper backside polishing apparatus for polishing, an annular holding jig for pressing the stamper backside toward the turntable is provided on the turntable. The holding jig is formed in an annular shape surrounding the entire circumference of the glass master, and has a leg portion that engages with the turntable and an upper end that projects toward the center of the glass master and presses the outer peripheral edge of the back surface of the stamper over the entire circumference. An elastic member that can be in close contact with the stamper back surface is provided on the entire lower surface of the upper end portion, and the upper surface of the upper end portion is located at the center of the glass master. The present invention can be achieved by a stamper back surface polishing apparatus characterized in that the upper surface has an inclined surface whose height is gradually reduced.

(Embodiment)

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited only to this embodiment.

FIG. 1 is a schematic partial cross-sectional view of a stamper back surface polishing apparatus of the present invention in a manufacturing process of an optical disk recording medium, and FIG. 2 is an enlarged cross-sectional perspective view of a holding jig shown in FIG.

First, the manufacturing process of the optical disk recording medium will be briefly described. As a first step, a disk-shaped glass master disk whose surface is polished or ultrasonically cleaned is prepared. In order to enhance the adhesion of the photoresist formed on the surface of the glass master to the glass master, primer coating is performed, and a photoresist sensitive to only a short wavelength is applied thereon by, for example, spin coating, and then appropriately heated. After drying, a glass master 16 (also referred to as a photoresist disc) having a photoresist layer formed thereon is prepared. Next, the glass master 16 is set in a recording device (cutting device), and a desired signal is written by a laser beam.

Thereafter, the photoresist layer of the glass master 16 is developed and washed with water, and then the developed surface of the photoresist layer is formed with a metal film by a dry method or a wet method to impart conductivity, and thereafter, the photoresist layer is formed. An electroformed layer 17, for example, a nickel plating film is formed on the developed surface of the substrate by an electroforming process. The relatively thick electroformed layer 17 is peeled from the photoresist layer to obtain a master disk. Further, a plurality of mother disks are formed by repeating the peeling of the electroformed layer formed by electroforming the master disk as an electroformed original material (base) from the master disk several times, and forming the mother disks. A large number of stamper discs can be made by peeling off the electroformed layer similarly formed as the electroformed base.

A stamper backside polishing apparatus for performing each of the above polishing processes will be described with reference to FIG.

The stamper backside polishing apparatus 1 includes a turntable 2 on which the glass master 16 is placed at the center thereof. The turntable 2 is configured to be able to rotate at a desired rotation speed by a motor 4 which is directly connected to a rotation shaft 3 or connected via an appropriate speed reducer or the like. The turntable 2 is provided with a ring-shaped holding jig 5 at a position surrounding the entire circumference of the glass master 16. Further, on the side opposite to the mounted glass master 16, a polishing tape 13 wrapped around a roller 12 and a water supply pipe 14 for supplying an appropriate amount of pure water during polishing are provided.
Note that the polishing tape 13 and the water supply pipe 14 may be opposed to the glass master 16 during polishing, and are obstructed when the glass master 16 is mounted, so that the polishing tape 13 and the water supply pipe 14 can be moved between a standby position and an operation position. Have been.

The holding jig 5 has a substantially inverted L-shaped cross section including an upper end portion 7 protruding toward the center of the glass master and a leg portion 6 abutting, for example, on a groove of the turntable 2. The holding jig 5 is provided with an O-ring, which is an elastic member which can be in close contact with the surface of the electroformed layer 17 which is the back surface of the stamper, on the entire lower surface 19 of the upper end portion 7. The upper surface 8 of the portion 7 is formed as an inclined surface such that the height of the upper surface 8 decreases toward the center of the glass master 16.

The holding jig 5 is fixed to the turntable 2 through tightening bolts 11 in a plurality of bolt insertion holes 15 formed in the upper end portion 7.

The stamper backside polishing apparatus 1 configured as described above is installed in, for example, a class 10,000 clean room. Then, the glass master 16 after the electroforming step for forming the recording surface of the optical recording medium described above is mounted on the stamper backside polishing apparatus 1, and the stamper rear surface on the glass master 16 (the front surface of the electroformed layer 17) is mounted. ), The polishing is carried out by appropriately feeding out the polishing tape 13 containing alumina or the like in the vicinity of the water supply portion. In this polishing step, usually, after rough finishing, finishing is performed to enhance the smoothness of the back surface of the stamper. At this time, the entire outer periphery of the electroformed layer 17 is completely pressed down by the lower side surface 19 of the holding jig 5. However, since this pressing is made elastic by the O-ring 10, the pressing The variation in pressure can be suppressed, the damage of the pressed surface and the inner part under the pressed surface can be effectively prevented, and the sealing property of the jig inner space 20 can be improved. When the airtightness of the jig inner space 20 is enhanced, the polishing waste liquid during polishing is separated from the joining end face of the glass master 16 and the processing object formed thereon, so that it is separated at the joining end face portion. It is possible to prevent the polishing waste liquid from entering the peeled portion even when the generation occurs.

Further, since the upper side surface 8 of the upper end portion 7 is formed as an inclined surface in which the height of the upper side surface 8 decreases toward the center of the glass master 16, the polishing waste liquid is deposited on the front end portion of the upper end portion 7. The water flows along the upper side surface 8 without accumulating, and is effectively drained radially outward from the turntable through the holding jig 5.

Therefore, tightening in polishing the back surface of the stamper can be reliably performed, and troubles such as waste polishing liquid entering between the front surface side of the stamper and the glass master can be prevented.

In the above-described embodiment, the upper side surface 8 is formed as a linear inclined surface, but the inclination angle α is set to, for example, about 45 °, and the thickness t of the distal end surface 8a of the upper end portion 7 is set to 0.
The thickness t can be set to about 2 mm. However, it is desirable that the dimension of the thickness t be as close to zero as possible. In the present invention, these dimensions are naturally determined by the tightening force, material, thickness, and the like of the holding jig 5. Not only can be appropriately set according to the various conditions described above, but also the tip end surface 8a has a thread chamfering configuration, or the upper side surface 8 has an appropriately curved (either concave or convex) inclined surface. Can also.

Furthermore, in the above-described embodiment, the configuration is such that one O-ring 10 is provided. However, the present invention is not limited to this. For example, a configuration in which a plurality of O-rings are provided concentrically can be adopted.

〔The invention's effect〕

As described above, according to the present invention, when polishing the back surface of the stamper, the entire outer periphery of the back surface of the stamper is pressed by the elastic member provided on the lower surface of the holding jig, so that the pressing pressure is stabilized and the pressing is performed. In addition to the above, it is possible to effectively prevent damage to the surface and the inside below the surface, and to ensure the secure fixation of the polished object. In addition, the elastic member separates the polishing region and the outer peripheral edge of the stamper other than the polishing region from the outside. Since the peripheral portion is isolated so as not to come into contact with the polishing waste liquid, the polishing waste liquid at the time of polishing, for example, even if peeling occurs at the joint end face portion between the glass master and the processing object formed thereon, the peeling portion It is possible to extremely effectively prevent the polishing waste liquid from entering the surface.

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention, and is a partial cross-sectional schematic view of a stamper back surface polishing apparatus in a manufacturing process of an optical disk recording medium, and FIG. 2 is a cross-sectional view of a part of a holding jig shown in FIG. FIG. 3 is an enlarged perspective view, and FIG. 3 is a partial perspective view showing a partial cross section of a conventional stamper back surface polishing apparatus. Reference numerals in the drawing: 1 ... a stamper backside polishing device, 2 ... a turntable, 3 ... a rotating shaft, 4 ... a motor, 5,30 ... a holding jig, 6,31 ... a leg, 7 ... an upper end Part, 8 …… Upper side, 9 …… Bottom side, 10 …… O-ring, 11 …… Tightening bolt, 12 …… Roller, 13… Polishing tape, 14 …… Water pipe, 15… Bolt insertion hole, 16 ... Glass master, 17 ... Electroformed layer, 18 ... Conductive ring for electroforming, 19 ... Bottom surface, 20 ... Jig inner space.

Claims (2)

(57) [Claims] An electroforming process for forming a recording surface of an optical recording medium, wherein when a back surface of a stamper on a glass master mounted on a rotating turntable is polished, the stamper is fixed together with the glass master by a holding jig. The entire outer periphery of the back surface is pressed without any gap in the circumferential direction, and the inner region of the holding jig is polished while being supplied with water, and a polishing waste liquid containing polishing waste is passed over the holding jig to drain radially. Polishing method for the back surface of a stamper. 2. A stamper backside polishing apparatus for automatically polishing the backside of a stamper while supplying water to the backside of a stamper on a glass master mounted on a rotating turntable, wherein the backside of the stamper is placed on the turntable side on the turntable. An annular holding jig for pressing is provided, the holding jig is formed in an annular shape surrounding the entire circumference of the glass master, and a leg portion engaging with the turntable and a rear surface of the stamper protruding toward the center of the glass master. An upper end portion for pressing the outer peripheral edge over the entire periphery is formed in a substantially inverted L-shaped cross section. Further, an elastic member which can be in close contact with the back surface of the stamper is provided on the lower side surface of the upper end portion, and the upper end is The upper surface of the portion is formed as an inclined surface such that the height of the upper surface decreases toward the center of the glass master. Location.