JPH0557656B2 - - 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 poses a problem in that autofocusing, autotracking techniques, and more expensive laser beams must be used for reproduction.

On the other hand, as an optical recording medium of another type, an optical recording medium in which a portion having a high optical reflectance and a portion having a low optical reflectance are made of different materials, forming a shading pattern and recording digital information. It has been 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. Forming a diffraction grating is not easy.

(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 system that allows mass duplication to be carried out 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 an optical recording medium.

(Summary of the Invention) The present invention involves coating a photoresist on a substrate, exposing the formed photoresist layer to light using a mask in which information is recorded in a fine pattern of shading, and then using a laser beam to The photoresist is then developed. This is a method for manufacturing an optical recording medium, in which a stamper is raised from the obtained recording pattern, and an optical recording medium having a fine pattern of diffraction gratings is reproduced using the stamper.

(Detailed description of the invention) Hereinafter, the present invention will be explained in detail 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. A positive type photoresist can be used, and a photoresist is selected and used that can be applied evenly and easily, and has a high resolution that can sufficiently resolve fine information recording patterns during exposure. Examples of such photoresists include AZ-1350 manufactured by Shpley, 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 processes.

The photoresist layer 3 is exposed to light through a mask 4 on which information is recorded in a fine pattern of shading (Fig. 2), and then the photoresist layer 3 is holographically exposed using a laser exposure device to form a diffraction grating. A latent image is formed (Fig. 3). The laser light source used is an argon laser (458n
m), helium-cadmium laser (442nm),
Examples include. The number of grooves of the diffraction grating per unit length can be arbitrarily controlled by determining the wavelength of the laser and the setting conditions of the laser exposure device.
Furthermore, a diffraction grating in which the grooves are serrated (a blazed diffraction grating) can also be formed depending on the setting conditions of the laser exposure apparatus. Furthermore, since the diffraction grating is directly formed using laser light, a highly accurate diffraction grating can be obtained.

After that, first, the photoresist is developed to form a resist pattern in which a diffraction grating is formed (FIG. 4), and then a metal layer 5 is formed on the surfaces of the photoresist layer 3 and the base material 2 (FIG. 5). . metal layer 5
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 mold) shown in FIG. 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 5 include Au, Ag, Cr, Cu, and the like. A stamper is formed from a master mold obtained by a technique such as electroforming, and the obtained stamper 6 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 on the surface of the replicated base material 7, a metal layer 8 is formed by vacuum deposition or sputtering, and a protective layer is formed on top of the metal layer 8 using an optically transparent material 9. (Figure 7). In this case, the reading light is irradiated from the side of the material 9, but it is also possible to irradiate the reading light from the side of the substrate 7 using a material that also has optically transparent properties. It is also possible to perform compression molding using a stamper 6 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, a He-Ne laser (632.8n
m) is irradiated at an incident angle of 0°, the diffraction efficiency is 33%, and the reflectance is 33% for the diffraction grating section with respect to the smooth section 100.
4, and approximately 60% contrast is confirmed. The reading light is not limited to the above-mentioned laser light, but it is possible to use a light emitting diode or the like which enables reading without selecting a special light source.

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) is coated with a spinner on a glass plate with a smooth surface measuring 6 to 7 cm in length and 5 to 6 cm in width, and after drying (90°C), it is exposed to light through a mask with a fine pattern. Next, a latent image of a diffraction grating is formed by holographic exposure using an Ar laser (458 nm), the photoresist is developed to form a resist pattern, and then gold is deposited on the resulting resist pattern to form a conductive pattern. After forming a thin film, a nickel stamper was created using 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 aluminum was vapor-deposited on the transfer surface 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 were clearly distinguishable, and the light emitting diode was used as the reading light.
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 it is also possible to form various highly accurate diffraction gratings by recombining the laser optical device. Mass duplication of media can also be performed.

[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: Substrate, 3: Photoresist layer, 4: Mask, 5: Metal layer, 6: Stamper, 7: Replicated substrate, 8: Metal layer, 9: 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, A photoresist is applied, and the formed photoresist layer is exposed to light using a mask in which information is recorded in a fine pattern of shading, and then holographic exposure is performed using a laser beam to form a latent image of the diffraction grating. An optical recording medium characterized in that an optical recording medium in which a diffraction grating is provided in a fine pattern is reproduced by forming a stamper of the obtained recording pattern by developing the photoresist, and using the stamper. manufacturing method.