JPH08147772A - Roll for producing optical recording medium - Google Patents

Abstract

PURPOSE: To provide a roll capable of omitting a process for polishing a stamper and capable of considerably reducing the time and cost required to produce the stamper. CONSTITUTION: This roll is a roll for molding with a stamper through which a thermoplastic resin sheet as a substrate material for an optical recording medium is extruded by extrusion molding and a rugged preformat pattern is transferred to the sheet. The roll for molding has such a shape as to correct the thickness distribution of the stamper produced by electroforming due to the electroforming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding roll for producing a preformatted substrate for an optical recording medium.

[0002]

2. Description of the Related Art In recent years, with the progress of informationization in society, an information recording medium such as an optical disk, an optical card, an optical tape for optically recording or reproducing information and an information recording as a means for efficiently handling a wide variety of information. Many playback devices have been proposed. A feature of the optical information recording medium is that it has a high recording density and can record and reproduce in a non-contact manner.

Recently, a card type optical information recording medium (hereinafter referred to as an optical card), which is excellent in portability and has a large capacity as compared with its size, has been actively researched and developed and proposed. There is.

A substrate for an optical recording medium has a track for tracking (hereinafter referred to as a track), which has a concave or convex shape, and a pit string of preformat information such as a sector or a track number, which is previously formed on an information recording surface. There is.

As a method for continuously producing a large amount of such substrates, Japanese Patent Laid-Open No. 3-113750 discloses a method shown in FIG.
In the extrusion molding apparatus shown in FIG. 2, when the molten resin 13 heated and melted from the T die 12 through the extruder 11 is molded into a sheet, the molten resin is formed by the mirror surface roll 14 and the preformat roll 15 having an uneven preformat pattern. A method of manufacturing the substrate 16 for an optical recording medium by sandwiching and forming an uneven preformat on the surface of the resin sheet is disclosed.

In the above publication, the preformat roll is directly engraved with the preformat pattern, but it is very difficult to form the preformat pattern with submicron accuracy on the curved surface of the preformat roll.

Therefore, Japanese Patent Publication No. 50-11518, Japanese Unexamined Patent Publication No. 2-1291, and Japanese Unexamined Patent Publication No. 2-1556.
As disclosed in Japanese Unexamined Patent Publication No. 2 etc., a pre-format roll is constructed by a method in which a thin plate-shaped flat stamper having a pre-format pattern is produced and the stamper is fixed to a smooth roll with an adhesive. There is. According to this method, the stamper can be manufactured by using the photolithography method for manufacturing a conventionally known semiconductor mask. Therefore, the preformat roll can be manufactured accurately. You can

Further, in Japanese Patent Laid-Open No. 3-6993, the fixing member 10 is attached to both ends of the stamper 3 shown in FIG. 6, and the groove 17 capable of fixing the fixing member 10 shown in FIG.
There is disclosed a method of winding and fixing the pre-format roll 15 formed with the above with tension. According to this method, the stamper can be easily attached to and detached from the roll, so that even if a defect such as a scratch occurs in the preformat pattern, it can be dealt with only by exchanging the stamper.

6 (a) is a schematic plan view showing a stamper with a fixing member, and FIG. 6 (b) is a sectional view taken along the line BB '.

As a method for manufacturing the stamper, a preformat pattern is formed on a photoresist on a glass substrate as a master by using a photolithography technique, a conductive film and an electroformed film are formed on the photoresist, and the stamper is peeled off. Or a mother stamper made of 2P resin on a glass substrate from a master manufactured using a technique for manufacturing a mask for semiconductors, as disclosed in Japanese Patent Application Laid-Open No. 2-31002. A method is known in which a conductive film is formed by sputtering, a metal film is formed thereon by electroforming, and the metal film is peeled off from a glass substrate to manufacture a stamper.

[0011]

However, when a stamper is manufactured from an electroformed film, the thickness of a normal electroformed film has a distribution and its size is 30 to 60 μm. Therefore, the stamper is used as it is for extrusion. When the substrate is formed by molding, the variation in the thickness of the substrate becomes large and the birefringence becomes large.

Therefore, as a stamper manufacturing step, the surface opposite to the preformat transfer surface of the stamper is usually polished before or after the peeling step to finish it to a specified film thickness accuracy. However, it takes 3 to 5 days to polish one stamper to a specified accuracy. Also, 3 to 4 stampers are attached to the forming roll in order to improve production efficiency. Therefore, the time for polishing one roll of stamper with one polishing machine is 12 to 16
There was a problem that it took a day and a long time.

The present invention has been made in order to improve the above-mentioned drawbacks of the prior art, and it is a method of manufacturing a stamper used for forming an uneven preformat pattern on an optical recording medium substrate by extrusion molding. In the above, it is an object of the present invention to provide a roll for manufacturing an optical recording medium, which can omit the step of polishing the stamper and can significantly reduce the time and cost required for manufacturing the stamper.

[0014]

That is, according to the present invention, a thermoplastic resin sheet as a substrate material for an optical recording medium is extruded by extrusion molding, and a stamper for transferring an uneven preformat pattern is provided on the sheet. In another aspect of the present invention, there is provided a forming roll, wherein the forming roll has a shape capable of correcting the thickness distribution of a stamper produced by electroforming by electroforming.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory view showing an embodiment of a roll for producing an optical recording medium of the present invention. In FIG. 1, 1 is a preformat roll according to the present invention. Reference numeral 2 is a groove for correcting the plate thickness distribution of the electroformed film.

FIG. 2 is a schematic view showing an unpolished stamper 3 attached to the optical recording medium manufacturing roll of the present invention shown in FIG. 4 is an electroformed film. Reference numeral 5 is a conductive film.
6 is a preformat pattern of the optical recording medium.

FIG. 3 is a sectional view of the stamper 3 shown in FIG. Since the stamper 3 has not been subjected to the polishing process, the surface of the stamper opposite to the preformat pattern is not a flat surface, and as shown in the figure, there is a thickness distribution of the electroformed film. The stamper 3 is manufactured by an ordinary stamper manufacturing method, and the plate thickness distribution of the electroformed film is thinnest in the central part and becomes quadraticly thicker toward the outer peripheral part.

FIG. 4 shows the plate thickness distribution of the cross section of the stamper 3 of FIG. 2 taken along the line AA '. As an example, the size of the stamper and the minimum value of the plate thickness in the case of vertical 200 mm × horizontal 200 mm are shown. The increase rate of the plate thickness around the stamper is shown. By appropriately controlling the electroforming process, the deviation of the electroformed film distribution from the plate thickness distribution shown in FIG. 4 can be kept within ± 10 μm even when a large number of stampers are manufactured. Therefore, by forming the groove 2 for correcting the plate thickness distribution of the electroformed film in FIG. 1 in a shape obtained by rotating the curve of FIG. 4 by 180 degrees, the plate thickness distribution of the electroformed film is corrected and the preformat pattern of the stamper is formed. The surface can have a cylindrical shape with good dimensional accuracy on the roller. The processing accuracy of the correction groove is ±
Since it can be machined at 10 μm, an accuracy of ± 20 μm is obtained as the roundness of the roll.

As a method of providing the plate thickness distribution correcting groove portion 2 (see FIG. 1) on such a preformat roll,
There are methods of grinding with a wheel traverse type roll grinder or cutting with a precision lathe. A conventional stamper material can be used for the stamper 3, and typically nickel is used, and its thickness is 0.
It is set at 1 to 0.5 mm.

The step of manufacturing the stamper 3 on which the preformat pattern 6 is formed can be carried out through the same steps as those of the conventional stamper, and the method of attaching the stamper to the preformat roll is also as follows.
Known methods such as a method by adhesion and a method in which the fixing member 10 is joined to the end of the stamper and fixed to the roll can be used. Usually, a fixing method using a fixing member is used because it is easy to remove.

The joining of the end of the stamper and the fixing member is desirable because welding by electron beam or laser is superior in terms of joining strength and joining position accuracy as compared with other joining methods. The fixing member 10 is made of a material that has a strength enough to withstand the tension when fixed to the roll and has a sufficient joining strength with the stamper 3, such as carbon steel, stainless steel, or aluminum.

As the preformat roll, a roll having a form used in ordinary extrusion molding can be used.
It is made of cemented carbide and die steel (eg maraging steel, carbon steel).

As the material of the stamper, a metal that can be electroformed and has good durability due to temperature and pressure during molding is used. Nickel is a commonly used material,
Copper is used. The conductive film can also be used if it has good durability due to temperature and pressure during molding, but the same material as the electroformed material is usually used.

[0025]

EXAMPLES The present invention will be described more specifically below with reference to examples.

Example 1 The stamper 3 shown in FIG. 2 was manufactured as follows. Vertical 340 × Horizontal 340 × Thickness 10m
m photoresist on the glass substrate (trade name: AZ-1
370: manufactured by Hoechst Japan Co., Ltd.) was applied to a thickness of 3000Å by a spinner, and prebaked at 90 ° C. for 30 minutes.

Next, using a laser exposure device (trade name: Mirror Projection Aligner MPA-1500: manufactured by Canon Inc.), a preformat pattern of an optical card having a length of 54.0 × width 85.6 mm is exposed and developed. Liquid (Product name: Az312MIF: Hoechst Japan)
By developing with, a glass master having a preformat pattern for an optical card was produced.

A 2000 Å-thick nickel film 5 was formed on this master by a sputtering apparatus to provide a conductive film for electroforming.

Next, a thickness of 20 is formed on the conductive film by electroforming.
A nickel film (electroformed film) 4 having a thickness of 0 μm was formed. The electroforming liquid used here had the following composition.

[0030] sulfamyl, nickel tetrahydrate _{[Ni (NH 2 SO 3)} 2 · 4H 2 O] 500g / l boric acid [H ₃ BO _3] 35~38g bit inhibitor 2.5 ml / l Next, conductive The film and the metal film are integrated and peeled off from the glass master at the same time, the photoresist adhering to the surface is removed, and the pre-format pattern 6 is provided.
× A stamper having a size of 300 mm was obtained.

This stamper was laser-cut to a size of vertical 200 × horizontal 200 mm with a predetermined dimensional accuracy to obtain a stamper 3.

As a result of measuring the plate thickness of this stamper,
The minimum thickness of the center part of the stamper was 205 μm, and the maximum thickness of the end part was 253 μm. The plate thickness distribution is the curve of FIG.

Similarly, five stampers were prepared,
As a result of measuring the plate thickness distribution, a plate thickness distribution curve similar to that shown in FIG. 4 is drawn, and the central part has the minimum film thickness of 193 μm to 206 μm.
m, and the maximum film thickness at the edges was 248 μm to 259 μm.

Based on this result, a preformat roll having a diameter of 300 mm is used, and the plate thickness distribution correction groove portion of the preformat roll has a shape obtained by rotating the curve of FIG. 4 by 180 degrees so that the minimum value is 200 μm and the maximum value is 254 μm. And the preformat roll was ground. In the grinding, after centering the roll, the roll was placed on a grinding table, and while the roll was rotated, it was ground using a precision lathe to obtain a preformat roll as shown in FIG.

As a result of measuring the grinding accuracy with a contact type three-dimensional measuring device, it was found that the grinding could be performed with an accuracy of a set value ± 8 μm. Further, the groove for attaching the fixing member 10 of the stamper to the roll was ground by the same precision lathe to obtain a preformat roll.

The stamper 3 uses the YAG
Welded with a laser (JK701: manufactured by Lumonix).
This stamper was fixed to the preformat roll 15 by screwing.

As a result of measuring the accuracy of the preformat roll with a stamper configured as described above, the roundness is 1
The result was 5 μm, and a numerical value that can be used in extrusion molding of a substrate for an optical recording medium was obtained.

[0038]

As described above, in the optical recording medium manufacturing roll of the present invention, the stamper polishing step can be omitted in the stamper manufacturing method, and the time and cost required for manufacturing the stamper can be greatly reduced. It became possible to do.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a roll for producing an optical recording medium of the present invention.

FIG. 2 is a schematic view showing a stamper fixed to a roll for producing an optical recording medium of the present invention.

3 is a cross-sectional view of the stamper of FIG. 2 taken along the line AA ′.

FIG. 4 is a view showing a plate thickness distribution of a cross section of a stamper.

FIG. 5 is a schematic cross-sectional view of an extrusion molding device.

FIG. 6 is a schematic view showing a conventional stamper with a fixing member.

FIG. 7 is a diagram showing an example of a preformat roll.

[Explanation of symbols]

 1 Preformat Roll 2 Groove for Correcting Plate Thickness Distribution of Electroformed Film 3 Unpolished Stamper 4 Electroformed Film 5 Conductive Film 6 Preformat Pattern 10 Fixing Member 11 Extruder 12 T Die 13 Molten Resin 14 Mirror Surface Roll 15 Preformat Roll 16 Substrate for optical recording medium 17 Groove for attaching fixing member

Claims (1)

[Claims] 1. A molding roll provided with a stamper for extruding a thermoplastic resin sheet, which is a substrate material for an optical recording medium, by extrusion molding, and transferring a concavo-convex preformat pattern to the sheet. A roll for manufacturing an optical recording medium, characterized in that the stamper produced by electroforming has a shape capable of correcting the thickness distribution by electroforming.