JPH06162576A - Production of optical master disk - Google Patents

Abstract

PURPOSE:To produce the optical master disk which varies in signal pit depth alternately between adjacent tracks and has less defects in order to attain high-density recording. CONSTITUTION:A photoresist 25 is formed on a disk (or a base material transferred from this disk) having V-grooves 23 directly worked and the signals are recorded by irradiating the inside of these grooves and the parts between the grooves respectively with a laser beam 27. The photoresist of the parts irradiated with the laser beam is removed. Then, a wet process, such as lithography, is used just once and the signal pits 28, 29 varying in the depth within and between the grooves are stably formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical disc master capable of storing information at a high density.

[0002]

2. Description of the Related Art In order to increase the density of optical discs, it has been considered to shorten the wavelength of a reproducing laser and increase the NA of an objective lens, but at present, the wavelength is 670 nm and the NA is 0.6.
Is the limit, and some methods have been proposed that do not rely on shortening the wavelength or increasing the NA.

As one of them, there is a method described in Japanese Patent Laid-Open No. 54-136303 which alternately changes the depth of signal pits in adjacent tracks. The reflected light is received by a detector that is divided into two photo detectors, and the sum signal of the two photo detectors is used to reproduce the signal pit train at one depth, and the other signal pit train is reproduced. If the difference signal of these two photodetectors is used, the crosstalk from the adjacent tracks is small, and the pitch can be narrowed to increase the density.

A method of manufacturing an optical disk master of this system will be described with reference to FIG. Once it is necessary to manufacture a substrate having concave and convex grooves, a glass plate 41 is coated with a photoresist 42 (FIG. 6A), and a laser beam 43 is continuously irradiated (see FIG. 6B). )), Developing is performed to remove the photoresist in the laser irradiation portion (FIG. 6C), the groove 44 is formed in the glass plate by etching (FIG. 6D), and then the photoresist is removed (FIG. 6C). (E)).

Next, the substrate 45 having the groove of the uneven shape is formed.
The photoresist 42 is applied again on the top (FIG. 6 (F)),
By irradiating the laser beam 43 in and between the grooves to record a signal (FIG. 6 (G)) and developing it to remove the photoresist in the recording portion (FIG. 6 (H)), An optical disc master in which signal pits having different depths are formed is possible.

[0006]

However, this manufacturing method has the following problems.

Defects on the optical disk master are mainly generated by lithography, which is a wet process such as photoresist coating, laser recording, and development. It is not possible to use a single-time lithographic process to manufacture a master in which the depth of signal pits is changed by the conventional method. When the photoresist is applied again on the defect generated in the first lithography, the defect becomes a nucleus and the number of defects increases several times or more. Especially, in the high density optical disc master, since the interval between the signal pits is narrow,
The number of signal pits affected by one defect is so large that it cannot be used as an optical disc master. That is, it is extremely difficult to reduce defects in a method that requires lithography twice as a wet process.

[0008]

[Means for Solving the Problems] In order to overcome the above problems and achieve high density of an optical disk, a disk in which a groove is directly processed or a substrate in which a groove is transferred from the disk is used as a base. A photoresist thin film is formed on the substrate, a laser beam is radiated in each of the grooves and between the grooves to record a signal, and the photoresist in the laser-irradiated portion is removed to manufacture an optical disc master.

[0009]

The operation of the above means is as follows. If a photoresist thin film is formed on the substrate on which the groove is formed by a method such as coating, the surface of the photoresist becomes closer to a flat surface rather than being formed along the shape of the groove. It is possible to form signal pits having different photoresist film thicknesses and different depths in and between the grooves.

Further, a disk directly processed with a groove, or
Since the substrate on which the groove is transferred is used as a base, the wet process such as lithography is used only once, and defects can be reduced.

[0011]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for forming concave and convex grooves.
Is a disk and 12 is a diamond tool. This tool 12
Has a flat tip with a width of about 0.4 μm.
The diamond tool 12 is slightly cut while rotating the disk 11, and the tool 12 is moved in the radial direction of the substrate to form the concave and convex grooves 13.

As a disk for processing the groove, a material which can be easily processed by the diamond tool 12 is preferable, and a copper-plated disk having a Vickers hardness of 200 HV or more, or an acrylic resin is suitable. To keep the groove depth constant, it is necessary to precisely control the cutting depth of the diamond tool.

Alternatively, a metal thin film such as copper is formed on the hard glass disk to have the same thickness as the groove depth, and the groove and groove are formed on the disk with a diamond tool. The hard glass surface limits the amount of cutting of the tool, and it becomes possible to process concave and convex grooves of a constant depth relatively easily. The metal thin film is formed on the glass disk by using the ion assisted sputtering method or the like.

FIG. 2 shows a method of manufacturing an optical disk master, which is based on a disk in which the concave and convex grooves are directly processed as described above. A photoresist 15 is applied on the substrate 14 on which the uneven grooves 13 are formed (FIG. 2A). The photoresist coated surface 16 will be closer to a flat surface rather than along a relief groove. The laser beam 17 is squeezed and radiated in the groove and between the grooves to record a signal (FIG. 2 (B)).

Next, after development, the photoresist portion irradiated with the laser is removed to form signal pits 18 and 19 (FIG. 2C). It is possible to manufacture a high-density optical disc master in which the depth of the signal pits is different between the grooves of the concave-convex groove and between the grooves, and the depth of the signal pits changes in adjacent tracks. This method is the same as in FIGS. 6 (F) to 6 (H) of the conventional example, but since a disk in which uneven grooves are directly processed is used as a substrate on which grooves are formed, lithography which is a wet process is used for forming the grooves. Since it does not exist, the increase of defects can be prevented.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

In FIG. 3, reference numeral 21 is a disk, and 22 is a diamond tool having a V-shaped tip. The V-shaped groove 23 is directly formed in the disk as in the first embodiment. In the processing of the concave-convex groove of the first embodiment, it is necessary to precisely control the cutting amount of the diamond tool. However, in the processing of the V-shaped groove of the second embodiment, the diamond tool 22 is rotated by several μm while rotating the disk 21. Since the cutting is performed and the tool 22 is moved in the radial direction of the disk at a constant pitch to cut the V-shaped groove in an overlapping manner, it is not necessary to precisely control the cutting amount of the tool.

As in the first embodiment, the material used for forming the groove is a material that can be easily processed by the diamond tool 22,
A copper plating machine having a Vickers hardness of 200 HV or more or an acrylic resin is suitable.

FIG. 4 shows a method of manufacturing an optical disk master based on a disk in which V-shaped grooves are directly processed. V-shaped groove 23
Photoresist 25 is applied on the substrate 24 on which is formed (FIG. 4A). The photoresist coated surface 26 will be near a plane rather than along a V-shaped groove. A laser beam 27 is focused on each of the valleys and peaks of the V-shaped groove to irradiate the signal to record a signal (FIG. 4 (B)). Next, the photoresist portion irradiated with the laser beam is developed and the signal pits 28 and 29 are formed (FIG. 4C). It is possible to manufacture a master for a high-density optical disc in which the depths of signal pits differ depending on the valleys and peaks of the V-shaped groove, and the depths of signal pits change in adjacent tracks.

Since the disk in which the V-shaped groove is directly processed is used as the substrate in which the groove is formed in the second embodiment, the increase of defects can be prevented because the wet process lithography is not used for forming the groove. In the method using the V-shaped groove, the bottom of the signal pit is not a perfect plane, but the influence on the signal reproduction is not great.

(Embodiment 3) In Embodiments 1 and 2, a disk in which a direct groove is processed is used as a base, but a stamper is manufactured from the disk in which the direct groove is processed, and the stamper is used as a base for manufacturing a master. You can also do things. Also, the optical disk master of the present invention can be manufactured by transferring the groove from the stamper to the resin and using the resin base material as a base. In that case, the bases 14 and 24 in FIGS. 2 and 4 are stampers having grooves formed therein, or resins having the grooves transferred from the stampers.

A stamper can be manufactured by forming a thin metal film of nickel or the like on a disk in which a groove is directly processed by a sputtering method or the like, plating a metal thin film of nickel or the like on the thin film, and peeling the metal from the substrate.

There are two methods for transferring the groove from the stamper to the resin. One is a method using an ultraviolet curable resin. An ultraviolet curable resin is sandwiched between a stamper and a resin base material such as acrylic, and the ultraviolet curable resin is irradiated from the resin base material side to harden the ultraviolet curable resin, and the groove shape of the stamper is transferred to the resin base material.

The other is a method of transferring the groove to the resin by injection molding. A resin such as acrylic or polycarbonate is raised in temperature and softened, poured into a mold, and cooled while pressing a stamper to manufacture a resin base material having grooves transferred.

(Embodiment 4) When a photoresist is applied to a metal substrate such as a metal stamper manufactured from a direct grooved copper-plated substrate or a direct grooved disk, a gap between the metal and the photoresist is used. Since the reflectance is high,
The tracking signal generated from the groove shape is large, and the laser beam can be accurately and easily tracking-controlled along the groove.

However, when the photoresist is applied to the resin disk in which the groove is directly processed or the resin substrate in which the groove is transferred from the stamper, the refractive index of the resin such as acrylic or polycarbonate is about 1.5, Since the refractive index of the AZ type photoresist is about 1.7, the reflectance between the resin base material and the photoresist is about 0.4%.
On the other hand, the reflectance of the photoresist surface is 6% or more. Since the surface of the photoresist is almost flat, no tracking error signal generated from the groove shape is generated from the surface, so that tracking control is not impossible just because the reflectance between the resin base material and the photoresist is small. However, the higher the reflectance, the easier the tracking control.

Therefore, as shown in FIG. 5, a thin film 33 having a refractive index different from that of the photoresist 32 is formed on the resin base material 31 in which the groove is formed, and the photoresist 32 is formed on the thin film 33.
By coating, the tracking error signal for generating the groove shape becomes large and tracking control becomes easy. As the thin film 33, a metal or a dielectric material having a large refractive index is suitable. For example, a thin film of gold, nickel, ZnS or the like may be used as the resin base material 31.
It is formed on the top by a sputtering method or the like.

[0029]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a disk in which a direct groove is processed or a base material in which a groove is transferred from a disk in which a direct groove is processed is used as a base, and a photoresist thin film is formed on the base. , A signal is recorded by irradiating a laser beam in the groove and between the grooves, and the photoresist on the portion irradiated with the laser is removed to manufacture an optical disk master, so that a wet process such as lithography is used only once to make a defect. It is possible to manufacture an optical disk master having less signal pits and forming signal pits having different depths in and between the grooves.

[Brief description of drawings]

FIG. 1 is an explanatory view of a groove processing step in a first embodiment of a method for manufacturing an optical disk master according to the present invention.

FIG. 2 is a manufacturing process diagram of an optical disc master according to the embodiment.

FIG. 3 is a process chart of processing a V-shaped groove in the second embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of an optical disc master according to the embodiment.

FIG. 5 is a manufacturing process diagram of an optical disk master according to a fourth embodiment of the present invention.

FIG. 6 is a manufacturing process diagram of a conventional optical disc master.

[Explanation of symbols]

 12, 22 Tool 13, 23 Groove 14, 24, 31 Substrate 15, 25, 32 Photoresist 17, 27 Laser beam 18, 19 Signal pit 28, 29 Signal pit 33 Thin film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kishi Shunho 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshiki Miyamoto, 1006 Kadoma, Kadoma City Osaka Prefecture (72) Inventor Shinya Abe, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A method for manufacturing an optical disk master in which a photoresist thin film is formed on a substrate, a signal is recorded by irradiating a laser beam, and the photoresist in a portion irradiated with the laser beam is removed to directly manufacture the optical disk master. By using a disc processed with grooves or a base material with grooves transferred from the disc as a base and irradiating a laser beam inside and between the grooves on the base to record signals, A method for manufacturing an optical disc master, which comprises forming signal pits or signal grooves having different depths. 2. A groove having an uneven cross section in a radial direction is formed on a substrate, a photoresist thin film is formed on the substrate, and a laser beam is irradiated inside and between the grooves. The signal pits or the signal grooves having different depths are formed in and between the concave and convex grooves.
A method for manufacturing the described optical disc master. 3. A groove having a V-shaped cross section in a radial direction is formed on a base, and a photoresist thin film is formed on the base, along a valley (inside the groove) and a peak (between grooves) of the V-shaped groove. 2. The method for manufacturing an optical disk master according to claim 1, wherein signal pits or signal grooves having different depths are formed at the peaks and valleys of the V-shaped groove by irradiating each with a laser beam. 4. The groove according to claim 1, wherein the groove is directly processed on the metal disk by using a tool having the same shape as the cross-sectional shape of the groove at a tip portion thereof. Optical disc master manufacturing method. 5. The groove according to claim 1, wherein the groove is directly processed on the resin disk by using a tool having the same cross-sectional shape as that of the groove at a tip portion thereof. Optical disc master manufacturing method. 6. The method of manufacturing an optical disk master according to claim 5, wherein the resin disk is an acrylic resin. 7. A stamper is manufactured by directly processing a groove on a metal or resin base using a tool having a tip having the same shape as the cross-sectional shape of the groove, and the stamper is used as the base. The method for manufacturing an optical disc master according to any one of claims 1 to 3, wherein 8. A stamper is manufactured by directly processing a groove on a metal or resin base using a tool having a tip having the same shape as the cross-sectional shape of the groove, and using the ultraviolet curable resin from the stamper. 4. The method for manufacturing an optical disk master according to claim 1, wherein a base material having the groove transferred is used as a base. 9. A stamper is manufactured by directly processing a groove on a metal or resin substrate by using a tool having a tip end having the same shape as the cross-sectional shape of the groove, and the groove is formed by injection molding from the stamper. 4. The method for producing an optical disk master according to claim 1, wherein a substrate on which the image is transferred is used as a base. 10. Between the substrate and the photoresist film,
The method of manufacturing an optical disk master according to claim 1, wherein a thin film having a refractive index different from that of the photoresist is formed.