JPH0722892B2 - Backside polishing device for stamper for optical disk molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for manufacturing a stamper for molding an optical disk substrate, and in particular, an optical disk such as a write-once (DRAW or WORM) optical disk and a rewritable (E-DRAW or erasable) optical disk. The present invention relates to a back surface polishing apparatus for a stamper for molding a plastic disc substrate used as a substrate (substrate). The present invention is mainly used for polishing the back surface of a stamper for a high precision optical disc substrate as described above, but of course, for polishing the back surface of a stamper for a read-only (ROM) type optical disc substrate having a relatively low precision. It can also be used.

2. Description of the Related Art A manufacturing process of a conventionally used optical disk molding stamper will be described with reference to FIGS. 3 (a) to 3 (d). First, as shown in FIG. 3 (a), a photoresist 12 is applied on the surface of a glass substrate 11, and information or signals are formed on the resist 12 as a fine relief pattern 12 'by using a laser cutting machine or the like. Yes (Fig. 3 (b))
(In practice, there are steps of exposure-developing-fixing-washing and removing unexposed portions, but only the final relief pattern is shown in the figure). After forming the conductive film 13 on the surface of the glass master 10 thus obtained (FIG. 3 (c)), a film 14 of metal such as nickel is formed by an electroforming method, a vapor deposition method or the like (see FIG. 3 (d). )), And the conductive coating 13 and the metal coating 14 are separated from the glass master 10 as a unit. The stamper thus manufactured is then polished on the back surface of the stamper in order to finely adjust the thickness of the stamper.

In practice, the glass master 10 must be supported on a support when the metal film 14, for example, the nickel film is formed by the electroforming method, the vapor deposition method or the like. As shown in, the glass master 10 is supported by the nut 31 screwed with the screw protruding from the tip of the support column 30 and the washer 32. 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, so the washer portion 32 is removed before polishing.

Problems to be Solved by the Invention Generally, the above polishing is performed manually or by an automatic polishing apparatus. However, since the stamper is as thin as 1 mm or less,
In addition to the disadvantages that the back surface accuracy of the stamper cannot be obtained manually by sandpaper etc., the stamper may be deformed due to stress, and the thickness of the stamper may change due to individual differences in the processing. It has the disadvantage of being poor in nature. Therefore, it has been proposed to polish the back surface of the stamper without peeling it off from the glass master 10, but in this case, the automatic polishing apparatus cannot be applied 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 again adhered to the glass original plate and subjected to an automatic polishing apparatus. However, this method has a problem that air enters between the stamper and the glass original plate during the above-mentioned bonding, the surface accuracy is not obtained, the bonding means is complicated, and the productivity is not improved.

In order to remedy the drawbacks of the conventional method, the applicant of the present invention filed a patent document entitled “Back surface polishing device for stamper for optical disc molding” dated November 10, 1987 with a glass substrate on which a stamper was formed. In a back surface polishing apparatus for an optical disk molding stamper for polishing the back surface of the stamper with a polishing pad in a state where the back surface of the stamper is attached to a support body by a center mounting tool, a polishing pad corresponding to a portion that contacts the center mounting tool. It has been proposed to form a groove on the surface of the to accommodate the central fixture.

However, as a result of subsequent research, it was found that the glass substrate on which the stamper was formed warped in some lots due to internal stress generated during electroforming.

That is, when forming the metal film 14 to be the stamper 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 set at around 50 ° C. To be done. Therefore, if the glass substrate 11 on which the stamper is formed after electroforming is taken out from the electroforming bath to room temperature of about 25 ° C., the glass substrate 11 and the metal film 14 are warped as a whole due to a difference in thermal expansion coefficient. Will end up. Therefore, the glass substrate 11 on which the stamper 14 in this state is formed
When it is applied to the automatic polishing device, it is attached to the clamp of the automatic polishing device in the state as shown in FIG. I will end up.

Therefore, an object of the present invention is to solve the above-mentioned problems when the back surface of a stamper is polished by an automatic polishing apparatus in a state where the stamper is not peeled from the glass master 10.

Means for Solving the Problems In order to solve the above problems, the back surface polishing apparatus for an optical disk molding stamper according to the present invention has the glass substrate on which the stamper is formed attached to a support body by a central fixture. In a back surface polishing apparatus for an optical disk forming stamper for polishing the back surface of a center pad with a polishing pad, a groove for accommodating the center fixture is provided on the surface of the polishing pad corresponding to a portion in contact with the center fixture. At least a part of the polishing pad that is formed and is in contact with the outer peripheral portion of the stamper is removed.

Generally, the center fixture is comprised of a screw-washer. The stamper is formed by applying a photoresist on the surface of a glass substrate and forming a metal film on a glass master having a fine relief pattern formed on the photoresist. The fine relief pattern described above is generally performed by laser cutting.

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

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

As the automatic polishing apparatus itself, any known one can be used, but in general, a polishing pad that rotates is brought into contact with a stamper formed on a glass original plate, and the latter is orbited by the rotation of the polishing pad. That is, it revolves around its own axis. The rotation speed of the polishing pad at this time is generally 10
It is about 0 rpm. As the polishing pad, a urethane pad or the like generally used for glass polishing can be used.

The groove according to the present invention may have a width and a depth that can accommodate the central fixture. For example, when the washer diameter of the central fixture is 20 mm, the width of the groove may be about 20 mm.

A back surface polishing apparatus according to a preferred embodiment of the present invention includes a polishing pad that rotates, and a clamp that rotatably supports a glass substrate on which the stamper is formed so as to rotate around the polishing pad. The outer peripheral portion of the stamper formed on the glass substrate is separated from the contact with the polishing pad during at least a part of the relative motion of the glass substrate rotating around the polishing pad while rotating. There is.

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

In a further preferred embodiment of the present invention, the flat surface of the polishing pad has a flat annular cross section, and the stamper formed on the glass substrate in a state in which the central fixture is accommodated in the groove. At least a part of the outer peripheral portion of the flat annular polishing pad is located outside the inner peripheral edge and / or the outer peripheral edge of the flat annular polishing pad.

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

Action The present invention polishes the stamper that is still in close contact with the glass substrate by using the polishing apparatus having the above-described configuration, and therefore the internal stress generated during electroforming or the difference in thermal expansion coefficient between the glass substrate 11 and the metal coating 14 is caused. Even if there is a warp caused by it, the thickness of the stamper 14 does not change between the inner peripheral portion and the outer peripheral portion of the stamper 14 obtained by applying the automatic polishing device, and the stamper is always finished with a uniform thickness. You can

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

Embodiment An embodiment of the back surface polishing apparatus for an optical disk molding stamper of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic vertical sectional view showing a back surface polishing apparatus for an optical disk molding stamper of the present invention, and FIG. 2 is a conceptual plan view of the back surface polishing apparatus of FIG.

As shown in FIG. 1, the pad portion 21 of the automatic glass polishing device
Is rotated in the direction of the arrow around the center point O by a motor (not shown). The polishing pad portion 21 is made of urethane and is supported on a table 28 and rotated at a rotation speed of 900 rpm, for example. A glass master 23 having a stamper formed by electroforming by a known method is fixed by a clamp 25 as shown in FIG. 2, and a load is applied in the direction of arrow C, and a motor not shown is shown. The shaft 26 is thereby rotated. The contact point 27 between the clamp 25 and the shaft 26 is free, and this mechanism allows the contact surface between the pad 21 and the stamper 23 with a glass substrate to be always uniformly polished.

At the time of actual polishing, a liquid abrasive is dropped from a supply means (not shown) from above the center of the pad, and the pad portion 21 is rotated at a low speed in the direction of arrow A. As a result, the glass substrate 23 with the stamper is rotated at the medium speed in the direction of the arrow B and the arrow A
Revolved in the direction.

In the present invention, the polishing pad portion 21 is formed of a flat annular member having an inner edge ID and an outer edge OD. On the surface of this polishing pad portion 21, its outer peripheral edge OD
A groove 22 is formed at a position approximately in the middle of the inner peripheral edge OD. 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. The width of the groove 22 is about 15 mm,
This width may be such that the central washer 24 of the glass substrate with stamper 23 just fits.

The radii of the inner edge ID and the outer edge OD of the polishing pad portion 21 are such that the central washer 24 of the glass substrate 23 with stamper fits in the groove 22, that is, the state of the plan view of FIG. Then, the both ends in the radial direction of the glass substrate with a stamper 23 have such values as to project inward and outward in the radial direction from the inner edge ID and the outer edge OD. This protrusion amount
d ₁ and d ₂ differ depending on the degree of warpage of the stamper-equipped glass substrate 23. As an example, in the case of a stamper having a diameter of 200 mm, the protrusion amounts d ₁ and d ₂ are set to ₂₀ to 30 mm.

FIG. 6 shows a second embodiment of the polishing pad portion of the present invention.
It is a figure similar to a figure. In FIG. 6, an elliptical flat annular polishing pad is used instead of the perfect circular flat annular polishing pad. In the case of this embodiment, the above-mentioned protrusion amount d ₁ and
d ₂ is practically zero.

As described above, in the present invention, since the groove for accommodating the washer portion for holding the center of the stamper is formed on the pad surface of the back surface polishing device of the optical disk molding stamper, the stamper is kept in close contact with the glass substrate. In this state, the back surface of the stamper can be polished with the back surface always flat, and at least a part of the polishing pad that comes into contact with the outer peripheral portion of the stamper has been removed. The effect is that it can be polished.

[Brief description of drawings]

FIG. 1 is a conceptual sectional view of a back surface polishing apparatus for an optical disk molding stamper according to the present invention, FIG. 2 is a conceptual plan view of the back surface polishing apparatus of FIG. 1, and FIG. 3 is a manufacturing process of an optical disk molding stamper. FIG. 4 is a conceptual sectional view for explaining the glass substrate holding means used in the manufacturing process of the stamper for molding an optical disk, and FIG. 5 is a conceptual sectional view for explaining the drawbacks of the conventional method. A conceptual sectional view similar to FIG. 1, and FIG. 6 is a conceptual sectional view similar to FIG. 2 showing a polishing pad according to another embodiment of the present invention. (Reference numeral in the figure) 11 ... Glass substrate 12 ... Photoresistor 12 '... Micro pattern 10 ... Glass master 13 ... Conductive film 14 ... Metal film 21 ... Pad part 22 ... Groove 23 ... Glass substrate stamper 24 ... Washer part 25 ... Clamp 26… Shaft 27… Contact (free) 28… Table ID, OD… Inner and outer edges

Claims (5)

[Claims] 1. A back surface polishing apparatus for an optical disk forming stamper for polishing a back surface of the stamper with a polishing pad in a state where a glass substrate on which a stamper is formed is attached to a support member by a center portion mounting tool. A groove for accommodating the central fixture is formed on the surface of the polishing pad corresponding to the portion in contact with the partial fixture, and at least a part of the polishing pad contacting the outer peripheral portion of the stamper is removed. And a back surface polishing apparatus for an optical disk forming stamper. 2. A back surface polishing apparatus includes a polishing pad that rotates, and a clamp that rotatably supports a glass substrate on which the stamper is formed so as to rotate around the polishing pad. The outer peripheral portion of the stamper formed on the glass substrate separates from the contact with the polishing pad in at least a part of the relative motion of revolving on the polishing pad while rotating. The device according to claim 1. 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. The at least one outer peripheral portion of the stamper formed on the glass substrate in a state where the polishing pad has a flat annular flat surface and the center fixture is accommodated in the groove. 4. The portion is located outside the inner peripheral edge and / or the outer peripheral edge of the flat annular polishing pad described above. The device according to paragraph. 5. The apparatus according to claim 4, wherein the flat annular polishing pad has a flat annular flat surface.