JPH0557655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of manufacturing a read-only optical recording medium.

(Prior Art) Optical recording has advantages over magnetic recording in that there is no contact between the recording medium and the reproducing head, and high-density recording is possible. As this optical recording medium, there are known read-only ones, additionally writable ones, and erasable/rewritable ones, and the read-only optical recording medium according to the present invention has already been put into practical use. Examples include compact discs (CDs) and optical video discs. The method used in these optical recording media is that information is recorded on the uneven structure formed in the medium, and in order to increase the recording density of information, the recording pits (the smallest unit of recesses or protrusions) are approximately 1 μm in size. and using a light source such as a laser to make the reproduction light about the same size as the pit, and using a light source such as a laser to narrow the reproduction light to a size about the same as the pit to read information. is being carried out, but
The fact that the readout light beam is minute causes problems in that autofocusing, autotracking techniques, and more expensive laser beams must be used for reproduction.

On the other hand, there are other types of optical recording media in which a portion with high optical reflectance and a portion with low optical reflectance are made of different materials, and this shading pattern is formed to record digital information. Are known. A method for forming a light and shade pattern using this method is, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-66346, in which an optical low reflection layer and an optical high reflection layer are laminated in this order on a substrate, and a photoresist is coated on the surface. The photoresist is coated and exposed through a mask with a fine density pattern, and then the photoresist is developed to form a resist pattern.The resist pattern is then etched in a pattern to create an optical height. This is done by removing the reflective layer and exposing the optically low reflective layer. Although this method does not require the use of expensive laser beams, it requires a large number of manufacturing steps as described above, and each step is not easy to perform.

Another method that does not use laser beams is an optical recording medium in which the recording pit, which is the smallest unit of information, is composed of a diffraction grating. It is not easy to form a diffraction grating.

(Object of the Invention) The present invention has been made in view of the problems of the prior art described above, and is a read-only optical system that allows mass duplication to be performed by a simple method without using an expensive laser beam for reading. An object of the present invention is to provide a method for manufacturing a digital recording medium.

(Summary of the Invention) The present invention involves applying a photoresist onto a substrate, forming a diffraction grating on the formed photoresist layer using a stamper having several hundred to several thousand lines per millimeter, and then forming a fine grating. Exposure is performed using a mask on which information is recorded in a pattern, and then the photoresist is developed, a stamper of the obtained recording pattern is created, and the stamper creates an optical recording in which a diffraction grating is provided in a fine pattern. A method of manufacturing an optical recording medium for duplicating the medium.

(Details of discovery) The present invention will be explained in detail below based on the drawings.

1 to 5 show the steps of manufacturing a recording pattern stamper matrix in order, and FIG. 1 explains the structure of an optical recording material 1, in which a photoresist layer 3 is laminated on a base material 2. has been done. Photoresists can be used in both positive and negative types, but
Select and use a material that can be applied evenly and easily, and has a high resolution that can sufficiently resolve fine information recording patterns during exposure. Examples of photoresists include AZ-1350 manufactured by Shipley, OFPR-2 and OFPR-5000 manufactured by Tokyo Ohka Co., Ltd., and many others. The base material 2 is selected to have characteristics suitable for the intended use, such as surface smoothness and durability, and is not affected by deterioration or deformation during post-processes such as photoresist development and stamper molding steps.

A diffraction grating can be formed by using a stamper 4 having a number of lines from several hundred to several thousand lines per millimeter and applying pressure to the photoresist layer 3 to form a diffraction grating. These stampers on which a diffraction grating is formed can be reused even if the information pattern is different once the grating constant etc. of the diffraction grating are determined, which is advantageous in terms of production efficiency. Thereafter, the photoresist layer 3 on which the diffraction grating is formed is exposed to light through a mask 5 in which information is recorded in a fine pattern (Figure 3), and then the photoresist is developed to form the diffraction grating. A resist pattern is formed (FIG. 4), and then a metal layer 6 is formed on the surfaces of the photoresist layer 3 and the base material 2 (FIG. 5). The metal layer 6 is formed by selecting a metal that is not inconvenient when applying a technical method (for example, electroforming) to form a stamper in the form (matrix) shown in FIG. be done. If the material is a metal that has a higher optical reflectance, irradiating read light to this state makes it possible to reproduce and confirm the recorded state. Examples of the metal layer 6 include Au, Ag, Cr, and Cu. A stamper is formed from a master mold obtained by a technique such as electroforming, and the obtained recording transfer stamper 7 is used to perform mass duplication of optical recording media (FIG. 6). Replication methods include injection molding, compression molding, and methods using ultraviolet curable resin, but a method that can produce high-quality and efficient replicas should be selected before proceeding. A metal having high optical reflectance is selected for the surface of the replicated base material 8, and a metal layer 9 is formed by vacuum deposition or sputtering (FIG. 7), and an optically transparent material 10 is formed on the surface of the metal layer 9 (FIG. 7). to form a protective layer (8th step)
figure). In this case, the reading light is irradiated from the side of the material 10, but it is also possible to irradiate the reading light from the side of the substrate 8 using a material that also has optically transparent properties. It is also possible to perform compression molding using a stamper 7 on a thermoplastic resin having a metal thin film having a high optical reflectance on its surface to transfer optically recorded information. In the optical recording medium obtained in this way, when the shape of the diffraction grating is a sinusoidal waveform and its depth is 0.16 μm,
When irradiated with a He-Ne laser (632.8 nm) at an incident angle of 0°, the diffraction efficiency is 33%, and the reflectance is the diffraction grating portion 34 compared to the smooth portion 100, and a contrast of approximately 60% is confirmed. The reading light is not limited to the above-mentioned laser light, and for example, a light emitting diode or the like which enables reading without selecting a special light source is provided.

This method of manufacturing an optical recording medium allows selective formation of grating portions and smooth portions, and also enables efficient mass duplication.

(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to the Examples.

Photoresist (AZ-1350) was applied with a spinner onto a glass plate with a smooth surface measuring 6 to 7 cm in length and 5 to 6 cm in width. After drying (90℃), the number of lines per millimeter was 700 on the photoresist layer. The metal plates are pressed together and then exposed to light through a mask with a fine pattern.The photoresist is then developed to form a resist pattern, and then gold is deposited on the resist pattern to form a conductive thin film. After forming this, a nickel stamper was created by nickel electroforming using a nickel sulfamic acid bath, and the shape of the nickel stamper was transferred onto a 0.5 mm thick polyvinyl chloride sheet by compression molding. When the surface was vapor-deposited with aluminum and the part with the diffraction grating and the part without it (in other words, the smooth part) were observed under a microscope, the two could be clearly distinguished. When read with a CCD line sensor, a S/N ratio sufficient for practical use was obtained.

(Effects of the present invention) According to the present invention, it is possible to selectively form the diffraction grating portion and the smooth portion, and by selecting the groove condition of the stamper, it is possible to form various diffraction gratings, and moreover, it is possible to efficiently reproduce large quantities of optical recording media. can also be done.

[Brief explanation of the drawing]

FIGS. 1 to 7 are enlarged cross-sectional views at each step of the present invention. 1: Optical recording material, 2: Base material, 3: Photoresist layer, 4: Stamper, 5: Mask, 6: Metal layer, 7: Recording transfer stamper, 8: Replicated base material, 9: Metal layer, 10: Optically transparent material.

Claims (1)

[Claims] 1. In a method for manufacturing an optical recording medium in which a concavo-convex pattern is formed of a material having an optically high reflectance and a diffraction grating is formed in at least one of the concave portions or convex portions of the concave-convex pattern, After applying a photoresist and forming a diffraction grating on the formed photoresist layer using a stamper with a number of lines from several hundred to several thousand lines per millimeter, a mask on which information is recorded in a fine shading pattern is used. exposure, then apply photoresist,
Manufacture of an optical recording medium characterized by developing the formed photoresist, using a stamper of the obtained recording pattern, and using the stamper to reproduce an optical recording medium provided with a diffraction grating in a fine pattern. Method.