JPH01153263A - Device for polishing back of optical disk molding stamper - Google Patents

Abstract

PURPOSE:To enable the back of a stamper to be polished always under the true plane condition as the stamper is left in intimate contact with a glass substrate, by forming a groove for receiving a center holding washer in the optical disk molding stamper on the surface of a pad. CONSTITUTION:A polishing pad 21 is formed in the approximately intermediate position between the outer peripheral edge OD and inner peripheral edge ID on the surface of said pad with a groove 22. The polishing pad 21 is rotated with low speed in the direction of arrow as a shaft 26 is rotated with a central washer 24 of a stamper 23 with a glass substrate being fitted in the groove 22. By the rotation of said pad 21 is rotated the stamper 23 about its own axis in the direction of arrow B while revolved in the direction of arrow A to polish the back of stamper. Then, the outer peripheral portion of stamper 23 is protruded by a predetermined dimensions d1, d2 from the inner and outer side end edges ID, OD of polishing pad 21, so that the whole stamper 23 can be polished to the uniform thickness by the polishing pad 21 even if the stamper 23 has a warp.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a manufacturing apparatus for a stamper for molding an optical disk substrate, and particularly for a write-once type (DRAW or l!l) stamper manufacturing apparatus.
OR! , () Optical disc, rewritable type (B-ORAI
The present invention relates to a back polishing apparatus for a stamper for molding a plastic disk substrate used as a substrate for an optical disk such as an optical disk (or erasable). The present invention is mainly used for polishing the back surface of a stamper for optical disk substrates with high precision as described above, but of course, the present invention is used only for read-only (read-only) stampers with relatively low precision.
It can also be used for polishing the back surface of a stamper for a ROM (ROM) type optical disk substrate.

2. Description of the Related Art The manufacturing process of a stamper for molding an optical disk, which has been commonly used in the past, will be explained with reference to FIGS. 3(a) to 3(d). First, as shown in FIG. 3(a), a photoresist 12 is coated on the surface of a glass substrate 11, and this resist 1
2, information or signals are formed as a fine relief pattern 12' using a laser cutting machine or the like (Fig. 3(b)). (However, only the final relief pattern is shown in the figure). After forming a conductive film 13 on the surface of the glass master 10 obtained in this way (FIG. 3(C)), a film 14 of metal such as nickel is formed by electroforming, vapor deposition, etc. (FIG. 3(d)). )) L
Then, the conductive film 13 and the metal film 14 are peeled off from the glass master 10 as one body. The back surface of the stamper manufactured in this manner is then polished in order to precisely fine-tune the thickness of the stamper.

In reality, when forming the metal film 14, for example, a nickel film, by electroforming, vapor deposition, etc., the glass master disk 1O must be supported on a support, so generally, as shown in FIG. As shown in FIG. 2, the glass master 10 is supported by a washer 32 and a nut 31 that is engaged with a screw protruding from the tip of the support 30.

In the case of electroforming, the washer 32 generally serves as an electrode. However, if the washer 32 is integrated in the center of the stamper, precise polishing cannot be performed.
Before polishing, the washer portion 32 is removed before polishing.

Problems to be Solved by the Invention Generally, the above-mentioned polishing is performed manually or by an automatic polishing device. However, because the stamper is thin (less than 1 mm thick), manual polishing of the back side of the stamper with sandpaper or the like may result in poor surface accuracy, the stamper may be deformed due to stress, or the thickness of the stamper may vary due to individual differences in the number of people working on the stamper. In addition to the disadvantage of fluctuations in production, the disadvantage is that productivity is low.

Therefore, it has been proposed to polish the back surface of the stamper without peeling it off from the glass master disk 10, but in this case, the stamper cannot be applied to an automatic polishing device unless the washer portion is removed. Therefore, conventionally, the stamper was peeled off from the glass original plate, the washer portion was once removed, and then the stamper was bonded to the glass original plate again and subjected to an automatic polishing machine. However, with this method, air enters between the stamper and the original glass plate during bonding, resulting in poor surface accuracy.
There were problems such as the adhesive means becoming complicated and productivity not increasing.

In order to improve these drawbacks of the conventional method, the present applicant has proposed a patent application dated November 10, 1986 entitled "Reverse Polishing Apparatus for a Stamper for Molding Optical Disk" on a glass substrate on which a stamper is formed. In a back polishing device for a stamper for forming an optical disk, the back side of the stamper is polished by a polishing pad while the stamper is attached to a support by a tool, and the center attachment corresponds to the part that comes into contact with the tool. The central attachment proposed forming a groove on the surface of the polishing pad for accommodating the tool.

However, subsequent research revealed that depending on the lot, the glass substrate on which the stamper was formed warped due to internal stress generated during electroforming.

That is, when forming the metal film 14 that is stamped during electroforming, the operating conditions are set so that the internal stress of the deposited metal is minimized, but the temperature of the electroforming bath is generally about 50°C.
It is set around ℃. Therefore, when the glass substrate 11 on which the stamper is formed after electroforming is taken out of the electroforming bath into a room temperature of approximately 25°C, the entire body warps due to the so-called bimetal effect due to the difference in thermal expansion coefficient between the glass substrate 11 and the metal film 14. It ends up. Therefore, when the glass substrate 11 on which the stamper 14 is formed in this state is placed in an automatic polishing machine, it is attached to the clamp of the automatic polishing machine in the state shown in FIG. The thickness of the stamper 14 changes between the outer peripheral portion and the outer peripheral portion.

Therefore, an object of the present invention is to solve the above-mentioned problems when polishing the back surface of a stamper using an automatic polishing device without peeling the stamp/j from the glass master disk 10.

Means for Solving the Problems In order to solve the above problems, the back polishing apparatus for a stamper for optical disk molding of the present invention is provided with a glass substrate on which a stamper is formed, which is attached to the support body by a central attachment tool. In an apparatus for polishing the back surface of a stamper for forming an optical disc for polishing the back surface of the stamper with a polishing pad, the central portion is mounted on the surface of the polishing pad corresponding to the portion that comes into contact with the tool, and the center portion is mounted on the surface of the polishing pad to accommodate the tool. A groove is formed therein, and at least a portion of the polishing pad that contacts the outer peripheral portion of the stamper is removed.

Generally, the central attachment device consists of screws and washers. Further, the stamper is manufactured by applying a photoresist to the surface of a glass substrate and forming a metal film on a glass master disk on which a fine relief pattern is formed on the photoresist. The above-mentioned fine relief pattern is generally created by laser cutting.

The present invention can be suitably used when the metal film is formed by electroforming, but it can also be applied to metal films made by any other metal film forming method such as vapor deposition.

Preferably, a conductive film is previously formed on the glass master disk on which the fine relief pattern is formed, and then the metal film is formed by the electroforming method.

As the automatic polishing device itself, any well-known device can be used, but generally, a stamper formed on a glass original plate is brought into contact with a rotating polishing pad, and the latter is rotated by the rotational movement of the polishing pad. In other words, it revolves around itself. The rotation speed of the polishing pad at this time is generally 1
It is about 100 rpm. As the polishing pad, a urethane pad or the like that is generally used for glass polishing can be used.

The groove according to the present invention may have a width and depth sufficient to accommodate the centrally attached tool.

For example, for center installation, the diameter of the washer on the tool is 20mm.
In this case, the width of the groove may also be approximately 20 mm.

A back polishing apparatus according to a preferred embodiment of the present invention includes a polishing pad that rotates on its own axis, and a clamp that rotatably supports a glass substrate on which the stamper is formed so as to rotate around the polishing pad, During at least a part of the relative movement of the glass substrate in rotation and revolution on the polishing pad while in contact with the polishing pad, an outer peripheral portion of the stamper formed on the glass substrate is separated from contact with the polishing pad. There is.

The groove may be a circular groove concentric with the rotation axis of the polishing pad.

In a further preferred embodiment of the present invention, the plane of the polishing pad has a flat annular cross section, and the central attachment is performed on the polishing pad formed on the glass substrate while the tool is housed in the groove. At least a part of the outer peripheral portion of the stamper is located outside the inner peripheral edge and/or the outer peripheral edge of the flat annular polishing pad.

The flat annular polishing pad described above can be a flat annular plane such as a perfect circle or an ellipse.

Function The present invention polishes the stamper while it is in close contact with the glass substrate using the polishing device having the above configuration, so that internal stress generated during electroforming or the glass substrate 11 and the metal film 1 are removed.
Even if there is warpage due to the difference in coefficient of thermal expansion between the stamper 14 and the stamper 14, the thickness of the stamper 14 will not change between the inner and outer circumferential portions of the stamper 14 obtained by applying the automatic polishing device. The stamper can always be finished with a uniform thickness.

In other words, it is possible to always finish a stamper with a uniform thickness by simply processing the polishing pad of a general-purpose automatic polishing device without using an expensive dedicated polishing device.

Embodiment Hereinafter, an embodiment of a back polishing apparatus for a stamper for molding an optical disk according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic longitudinal cross-sectional view of a back polishing apparatus for a stamper for molding an optical disk according to the present invention, and FIG. 2 is a conceptual plan view of the back polishing apparatus of FIG. 1.

As shown in FIG. 1, the pad section 2 of the automatic glass polishing machine
1 rotates around the center point 0 in the direction of the arrow by a motor (not shown). This polishing pad section 21 is made of urethane, is supported on a table 28, and is rotated at an autorotation speed of, for example, 90 rpm. A glass master disk 23 having a stamper formed by electroforming by a known method is fixed with a clamp 25 as shown in FIG. 2, and with a load applied in the direction of arrow C, a motor (not shown) The shaft 26 is rotated. The contact point 27' between the clamp 25 and the shaft 26 is free, and this mechanism allows uniform polishing of the entire surface of the contact surface between the pad 21 and the stamper 23 with glass substrate at all times.

During actual polishing, liquid abrasive is dripped from the upper center of the pad from a supply means (not shown), and the pad portion 21 is rotated at low speed in the direction indicated by the arrow. As a result, the stamper-attached glass substrate 23 is rotated at a medium speed in the direction of arrow B and revolved in the direction of arrow A.

In the present invention, the polishing pad portion 21 is constituted by a flat annular member having an inner edge ID and an outer edge 1i0D. A groove 2 is formed on the surface of the polishing pad portion 21 at a position approximately midway between the outer circumferential edge 00 and the inner circumferential edge ID.
2 is formed. The groove 22 may be formed by cutting a commercially available polishing pad, or a flat annular polishing pad having the groove 22 may be manufactured in advance. Groove 2 above
The width of the stamper 2 is about 15 mm, and it is sufficient that the width is such that the center washer 24 of the stamper-equipped glass substrate 23 just fits therein.

The inner end mlD and the outer end O of the polishing pad portion 21
Each radius of the stamper-equipped glass substrate 23 is measured when the center washer 24 of the stamper-equipped glass substrate 23 is fitted into the groove 22, that is, in the state shown in the plan view of FIG.
Both ends in the radial direction are the inner edge In and the outer edge OD.
The value is such that it protrudes radially inward and outward from and. The protrusion amounts d and d2 differ depending on the degree of warpage of the stamper-attached glass substrate 230. - For example, in the case of a stamper with a diameter of 200 mm, the protrusion amounts d1 and d2 are set to 20 to 30 mm.

FIG. 6 is a second embodiment showing another embodiment of the polishing pad section of the present invention.
It is a figure similar to the figure. In FIG. 6, an elliptical flat annular polishing pad is used instead of a perfect circular flat annular polishing pad. In this embodiment, the protrusion amounts d1 and d2 are substantially zero in the polishing pad areas corresponding to the upper and lower portions of the figure.

Effects of the Invention As described above, in the present invention, a groove for accommodating a part of the washer for holding the center of the stamper is formed on the pad surface of the back polishing device of the stamper for optical disc molding, so that the stamper can be kept in close contact with the glass substrate. The back side of the stamper can be polished while keeping the back side of the stamper in a flat state, and since at least a part of the polishing pad that contacts the outer periphery of the stamper is removed, it is possible to polish the back side of the stamper with a uniform thickness. It has the effect of being able to be polished.

[Brief explanation of the drawing]

FIG. 1 is a conceptual cross-sectional view of a back polishing device for a stamper for molding an optical disk according to the present invention, FIG. 2 is a conceptual plan view of the back polishing device shown in FIG. 1, and FIG. 3 shows the manufacturing process of a stamper for molding an optical disk. 4 is a conceptual sectional view for explaining the glass substrate holding means used in the manufacturing process of a stamper for molding an optical disk; FIG. 5 is a conceptual sectional view for explaining the drawbacks of the conventional method. FIG. 6 is a conceptual sectional view similar to FIG. 2, showing a polishing pad according to another embodiment of the present invention. (Symbols in the figure) 11... Glass substrate 12... Photoresistor 12'... Fine pattern 10... Glass master disk 13... Conductive film 14... Metal film 21... Pad portion 22 ... Groove 23 ... Stamper with glass substrate 24 ... Washer part 25 ... Clamp 26 ... Shaft 27 ... Contact (free) 28 ... Table In, 00 ... Inside and outside edge

Claims (5)

[Claims] (1) In an apparatus for polishing the back surface of a stamper for forming an optical disk, the back surface of the stamper is polished by a polishing pad while the glass substrate on which the stamper is formed is attached to a support body by a center mount. A groove for accommodating the center fixture is formed on the surface of the polishing pad corresponding to the portion that contacts the tool, and at least a portion of the polishing pad that contacts the outer peripheral portion of the stamper is removed. A backside polishing device for a stamper for forming an optical disk, characterized in that: (2) The back polishing device includes a polishing pad that rotates, and a clamp that rotatably supports the glass substrate on which the stamper is formed so as to rotate around the polishing pad, and the glass substrate is attached to the polishing pad. In at least a part of the relative motion of rotating and revolving above it while in contact with
2. The apparatus according to claim 1, wherein an outer peripheral portion of the stamper formed on the glass substrate is separated from contact with a polishing pad. (3) The apparatus according to claim 1 or 2, wherein the groove is a circular groove concentric with the rotation axis of the polishing pad. (4) in a state in which the polishing pad has a flat annular plane and the center mount is housed in the groove;
At least a part of the outer peripheral portion of the stamper formed on the glass substrate is located outside the inner peripheral edge and/or the outer peripheral edge of the flat annular polishing pad. An apparatus according to any one of claims 1 to 3. (5) The apparatus according to claim 4, wherein the flat annular polishing pad has a flat annular plane.