JPH02278537A - Production of optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain such a medium that enables control of tracking without pregrooves, can be read out easily and can be manufactured with conventional facilities by forming bits in a fine lattice pattern concentrically or spirally disposed instead of recording in pregrooves and mesh patterns. CONSTITUTION:A glass substrate 11 coated with photoresist 12 is mounted on a turn table 13, and then rotated and irradiated with laser beam L having a slit-shape cross section through a recording lens 19. At the same time, the beam is moved in the radius direction by use of a feed screw 15 to record the bit 21 of spiral or concentrical lattice pattern on the resist 12. Then an electric conductive film is formed thereon by vapor deposition etc., which is then used as an electrode for electroforming to mold a die for the medium. A plastic substrate 25 is then molded with this die by injection molding, on which a metal thin film 27 and protective film 28 of photopolymer are formed to obtain the medium. The bit 21 is flat enough for a laser spot and gives larger difference in reflectance, which can be easily read out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an optical recording information medium, and particularly to a method of manufacturing an optical recording information medium used in a write-once disc.

(Prior art) Conventionally, the optical recording method used for write-once optical discs involves irradiating a transparent substrate with a transparent organic film and a metal film sequentially formed thereon with a laser beam from the substrate side. Some reflectance is changed by making holes and deforming the metal film. Other optical recording methods include changing the reflectance by changing the fine structure of the surface of the recording medium by irradiating it with a laser beam, or a similar method is to create a surface with unevenness that is sufficiently smaller than the recording spot on the surface of a plastic substrate. The microstructure and metal film are formed, and the microstructure is destroyed by irradiating it with laser light.
The so-called moth eyes (
The moth Eye ME) disk method is known.

FIG. 8 is a perspective view for explaining a conventional ME disk manufacturing method, which will be explained below with reference to the drawings. First, a photoresist 12 on which a pre-group pattern for track control has been exposed and developed in advance on a glass substrate 11 is irradiated with two beams of parallel laser light 20, and then the glass substrate 11 is exposed and developed.
is rotated by 90 degrees and irradiated with parallel laser light again to expose a mesh pattern of vertical stripes and horizontal stripes (to be described later) using the holographic method. Further, the above pattern can also be formed by irradiating four beams of parallel laser light from predetermined positions at once to form a mesh pattern.

FIG. 9 is a perspective view after forming a mesh pattern and a pre-group on a glass cutting board, in which 24 is a mesh-like pattern and 25 is a pre-group. FIG. 10 is a partially enlarged sectional view taken along the line II in FIG. 9. A mold (not shown) is made by electroforming from the photoresist 12 on which the mesh pattern 24 and pregroups 25 are formed, and the mesh pattern 24 and pregroups 25 are formed on one side using this mold. A plastic substrate 26 is then formed.

Next, as shown in the cross-sectional view of FIG. 11, a metal thin film 2 of platinum, nickel, chromium, etc.
7 is formed as a thin film by vapor deposition or sputtering, and a protective film 28 is further laminated on that surface to form an ME disk.

FIG. 12 is a cross-sectional view for explaining recording and reproduction of the ME disk shown in FIG. 11, and the operation will be explained using this figure. When writing is performed using the laser light focused by the recording lens 22, the mesh pattern 24 on which the metal thin film 27 is laminated becomes a light absorption layer, absorbing the laser light transmitted through the plastic substrate 26 and absorbing the laser light. The mesh pattern 24 on the surface is melted by the laser heat,
It becomes flat and information recording pits 23 can be recorded.

(Problems to be Solved by the Invention) In the conventional manufacturing method of an optical recording information medium, two steps are required: pregroup recording and mesh-like pattern recording using the holography method, and the mesh-like pattern using the holography method requires a large number of steps. There is a problem in that it is difficult to record minute uneven pits in the area, and it is not suitable for manufacturing large-sized information media.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and is a method of manufacturing an optical recording information medium in which writing is performed by irradiating a laser beam. I
・Process of recording fine lattice-like pits in concentric circles or spirals by irradiating the laser beam, and producing a mold by electroforming from the photoresist on which the lattice-like pits are recorded, and molding the above-mentioned with plastic. The process consists of the steps of creating a replicated plastic substrate having lattice-shaped pits on one side, forming a metal thin film on the surface of the replicated plastic substrate having the lattice-shaped pits, and forming a protective film on the metal thin film. It is an object of the present invention to provide a method for manufacturing an optical recording information medium characterized by the following.

(Example) FIG. 1 is a cross-sectional view for explaining the method of manufacturing an optical recording information medium according to the present invention. In the figure, 11 is a glass substrate coated with a photoresist 12, 13 is a turntable, and 14 is a motor for rotating the turntable; 15 is a feed screw for moving the turntable in the radial direction; L is a laser beam; after passing through a magnifying lens 15, it passes through a slit 17 with a width of 1.8 mm
The structure is such that a laser spot is irradiated onto the turntable by a recording lens 19 via a mirror 18.

Next, the manufacturing method will be explained. First, a glass substrate 11 coated with photoresist is placed on the turntable 3, and the turntable 13 is rotated by the motor 14. Next, the glass substrate 11 is intermittently irradiated with the slit-shaped laser light transmitted through the recording lens 19, and the rotating turntable 13 is moved in the radial direction by operating the feed screw, and the photoresist]
2, lattice-like pits 21 are recorded in a spiral or concentric solid pattern. 2 is a plan view of a lattice-like pit formed by the apparatus shown in FIG. 1, and FIG. 3 is a partial cross-sectional view taken along the line II in FIG. 2. A lattice-shaped pit 21 with an inter-track pitch of 1.6 μm is shown recorded and imaged on the top.

Next, a conductive film (not shown) is formed by vapor deposition or sputtering on the photoresist 12 on which the lattice pitch 2 is recorded. Next, a mold is created by electroforming using this conductive film as an electrode, and this mold is used to manufacture the plastic substrate 26 that will become the base of the optical recording information medium by injection molding. FIG. 4 is a sectional view of an optical recording information medium manufactured by the manufacturing method of the present invention, and the method for manufacturing this medium will be described below. First, by injection molding, there are lattice-shaped pits 21 on one side.
A thin metal film 27 of platinum, nickel, chromium, or the like is deposited on the plastic substrate 26 onto which is transferred, to a thickness of, for example, 500 mm. Next, a protective film made of photopolymer is formed on this metal thin film 27 to obtain an optical recording information medium.

Hereinafter, how to use the optical recording information medium obtained by the manufacturing method of the present invention will be explained using FIGS. 5 and 6. When recording is performed using the recording/reproducing lens 22 and a laser spot is irradiated onto the metal film 27 from the plastic substrate 26 side, the lattice-shaped pits 21- are thermally deformed by the heat and a flat portion 23 is formed. This flat part 23 is a lattice-shaped pit 21
Since the reflectance is larger than that of , it is possible to record an information signal as a difference in reflectance. As shown in FIG. 7(a), the reflectance of the flat portion 23 is high, so several 10% of the incident laser beam is reflected, but the light incident on the lattice-shaped pits 21 is 21, and the reflectance decreases, so the difference in reflectance can be reproduced as an information signal.

(Effects) As described above, when the optical recording information medium obtained by the manufacturing method of the present invention is used, there is a large difference in reflectance between the information recording pits where information is recorded and the lattice-shaped pits where information is not recorded, and it is easy to read as a signal. Moreover, the lattice-shaped pits can also serve as track control signals without the need for pre-groups required for optical discs. Furthermore, since holography technology is not used, it is possible to manufacture write-once optical recording information media using conventional manufacturing equipment for optical recording information media.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining the method of manufacturing an optical recording information medium according to the present invention, FIG. 2 is a plan view of lattice-shaped pits formed by the apparatus shown in FIG. 1, and FIG. FIG. 4 is a partial cross-sectional view taken along the I-I cutting line, and FIG. 4 is a partial cross-sectional view of an optical recording information medium manufactured by the manufacturing method of the present invention, and FIGS.
FIG. 7 is an explanatory diagram for explaining the principle of recording and reproducing the optical recording medium shown in FIG. 4, FIG. 8 is a perspective view for explaining the conventional ME disk manufacturing method, and FIG. 9 is a glass A perspective view after forming a mesh pattern and a pre-group on a substrate, FIG. 10 is a partially enlarged view taken along the cutting line I-I in FIG. 9, and FIG. 11 is a part of a conventional optical recording information medium. 12 is an explanatory diagram of the principle of recording and reproduction of the conventional ME disk shown in FIG. 10; FIG. 11...Glass substrate, 12...Photoresist, 1
9... Recording lens, 21... Grid pit, 22.
・Recording/reproducing lens, 23... Information recording pit, 25
...Pri group, 26...Plastic substrate, 2
7... Metal thin film, 28... Protective film.

Claims (1)

[Claims] A method for manufacturing an optical recording information medium in which writing is performed by irradiating a laser beam, which includes the steps of irradiating a photoresist coated on a glass disk with a laser beam to record fine lattice-like pits in concentric circles or in a spiral shape; A step of producing a mold by electroforming from a photoresist on which lattice-shaped pits are recorded, and creating a replica plastic substrate having the lattice-shaped pits on one side using plastic; 1. A method of manufacturing an optical recording information medium, comprising the steps of: forming a metal thin film on a surface having a surface having the same properties as the metal thin film; and forming a protective film on the metal thin film.