WO1999033052A1

WO1999033052A1 - Optical recording medium and method of producing the same, and recording signal reproducing device for the medium

Info

Publication number: WO1999033052A1
Application number: PCT/JP1998/005712
Authority: WO
Inventors: Ichiro Yokota
Original assignee: Ichiro Yokota
Priority date: 1997-12-19
Filing date: 1998-12-17
Publication date: 1999-07-01
Also published as: JPH11185300A

Abstract

An optical recording medium comprises a substrate (1) on a transparent disk where projections and recesses representing information signals are formed, a reflecting thin film (2) formed on the substrate (1), and a protective film (3) formed on the reflecting thin film (2) over the whole surface of the disk by coating. The inner and outer edges of the medium are smoothed, and light absorbing layers (5, 6) are formed by coating on the smoothed surfaces. Hence laser light or extraneous light incident on the light absorbing layers is absorbed, and further light irregularly reflected inside the optical disk is effectively absorbed, resulting in enhancing the S/N ratio of the reproduced signal.

Description

TECHNICAL FIELD The present invention relates to an optical recording medium, a method for manufacturing the same, and a recording signal reproducing apparatus for the medium.

The present invention relates to an optical recording medium with improved reading accuracy of CD, LD, etc. for reproducing a signal using a laser beam, a method for manufacturing the same, and a recording signal reproducing apparatus for the medium.

Background art

Optical discs such as CDs and LDs have an aluminum layer that records digitized information on the surface of a resin disk in the form of pits with irregularities. A transparent plastic layer for protection is provided on the surface of this aluminum layer. Have. To reproduce recorded information, laser light of a small spot is focused and irradiated on the recording surface, and the reflection of laser light from a pit portion having an uneven shape formed according to the information is detected by an optical pickup. . The detected digital signal is DZA-converted by a D / A converter to obtain an analog audio signal or a video signal.

As described above, the optical pickup detects the reflection of the laser light corresponding to the irregular shape of the recording surface, so that the light irregularly reflected from the optical disk surface other than the pit portion or the optical pickup optical system structure is used for signal reproduction. It will have an adverse effect. The diffusely reflected interfering light causes a signal error and a signal phase shift (jitter) in the detected digital signal. Since the information is recorded digitally, certain signal errors and phase shifts can be corrected electronically. However, correction using an electric circuit is not perfect and increases costs.

For this purpose, a technique for preventing irregular reflection of laser light has been conventionally known. Japanese Utility Model Application Laid-Open No. 5-36661 discloses a technique in which a sound quality improving agent that absorbs laser light is applied to an outer peripheral edge or an inner peripheral edge of an optical disc. Japanese Patent Laying-Open No. 3-191551 also discloses a technique for forming an anti-reflection portion on the outer peripheral edge or inner peripheral edge of an optical disc. In addition, Japanese Utility Model Publication No. There is disclosed a technology for applying a green coating film for the purpose of preventing irregular reflection of laser light inside a pickup optical system structure.

The above-described prior art prevents irregular reflection of laser light, and is therefore effective in improving the sound quality of a reproduced analog signal. By providing a light absorbing layer on the outer peripheral edge or inner peripheral edge of the optical disc other than the information recording section, laser light or external light incident on the light absorbing layer from the outside of the optical disc is absorbed and used for signal reproduction. There is no adverse effect.

Conventional optical disks cannot effectively absorb light that has been irregularly reflected inside the optical disk. Light arriving from the inside of the optical disk to the outer or inner peripheral surface of the optical disk is irregularly reflected at an interface between the side surface and the light absorbing layer applied thereto, and the irregularly reflected light may interfere with a reproduced signal. all right.

Moreover, the absorption of diffuse reflection in the conventional configuration is only partially performed. If partial reflection can be partially absorbed, even if a certain effect is produced, it cannot be completely suppressed.

The present invention provides a light absorbing layer at an outer peripheral edge or an inner peripheral edge of an optical disc other than the information recording section, thereby absorbing laser light or external light incident on the light absorbing layer from outside the optical disc, The purpose is to effectively absorb the light irregularly reflected inside the optical disk, thereby increasing the SN ratio of the reproduced signal.

Another object of the present invention is to completely suppress diffuse reflection including diffuse reflection occurring inside the optical pickup optical system structure. Disclosure of the invention

The optical recording medium of the present invention comprises a substrate 1 on a transparent disk on which irregularities indicating information signals are formed, a reflective film 2 formed on the substrate 1 as a thin film, and a coating on the entire surface of the disk on the reflective film 2 Protective film 3 provided. Then, the optical recording medium is characterized in that the inner peripheral side surface and the outer peripheral side surface are smoothed, and the light absorbing layers 5 and 6 are applied after the smoothing process.

The method for manufacturing an optical recording medium according to the present invention comprises forming irregularities indicating information signals on one main surface of a substrate 1 on a transparent disk, forming a thin reflective film 2 on the surface of the substrate 1 on which the irregularities are formed, Then, a step of applying a protective film 3 on the entire surface of the disk on the reflective film 2 is provided. Thereafter, the inner peripheral side surface and the outer peripheral side surface of the optical recording medium are subjected to a smoothing process, and at least the outer peripheral edge and the inner peripheral edge portion including the smoothed inner peripheral side surface and the outer peripheral side surface are subjected to light absorbing layers 5 and 6. Is applied.

A recording signal reproducing apparatus of the present invention is an apparatus used with the above optical recording medium, comprising: means for controlling the rotational drive of the optical recording medium for reproducing the recording signal; and an inner surface coated with a light absorbing layer, and A casing 11 containing an optical recording medium to be rotationally controlled, an inner surface coated with a light-absorbing layer, and a laser beam focused and irradiated on an information track of the optical recording medium. An optical pick-up optical system that reproduces an information signal by detecting reflection that changes in accordance with the unevenness of the reflection film indicating a signal is provided.

The optical recording medium of the present invention is characterized in that the inner peripheral side surface and the outer peripheral side surface of the optical recording medium are smoothed, and a light absorbing layer is applied thereon. Alternatively, while absorbing external light, it also effectively absorbs light that has been irregularly reflected inside the optical disk, thereby increasing the SN ratio of the reproduced signal.

In addition, the self-recording signal reproducing device of the present invention has a light absorbing layer applied to the inner surface of the casing and the inner surface of the optical pickup. Can be suppressed. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plan view of an optical disk to which the present invention is applied.

FIG. 2 is a cross-sectional view taken through the center of the optical disc illustrated in FIG. 1. FIG. 3 is a view for explaining the effect of light absorption on the outer peripheral edge of the optical disc whose side surfaces have not been smoothed. is there.

FIG. 4 is a diagram for explaining the effect of light absorption of a configuration to which the present invention is applied in which the outer peripheral side surface is smoothed.

FIG. 5 shows an example of an optical disk reproducing apparatus to which the present invention is applied. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a plan view of an optical disk to which the present invention is applied, and FIG. 2 is a cross-sectional view taken through the center of the optical disk of FIG. In these figures, 1 is a substrate made of a light-transmitting material such as polycarbonate, for example, and 2 is a reflective film made of aluminum or the like formed on one main surface of a substrate having irregularities indicating information signals. And 3, a protective film further formed thereon. Reference numeral 4 denotes a hole formed at the center of the optical disk, through which a spindle of a playback device (not shown) is inserted. Reference numeral 5 denotes a light absorbing layer applied to at least the inner peripheral side surface of the optical disk on which the optical disk has been smoothed, and 6 denotes a light absorbing layer similarly applied to the outer peripheral edge portion. 7 indicates an information recording unit.

The optical pickup optical system is arranged below in FIG. 2, from which laser light is focused and irradiated. This laser light passes through the substrate 1 of the optical disk, and changes in the laser light reflected from the reflection film in response to the presence or absence of pits are detected by an optical pickup to reproduce the recorded information signal. be able to. Since the information is digitally recorded, the reproduced signal is a logical 1 or 0 signal. This digital signal is DZA-converted by a DZA converter to obtain analog audio (or a video signal).

In detecting the reflected laser light, it is necessary to detect the reflected light directly from the pit portion. For example, light other than directly reflected light, such as light that is scattered and reflected from the pit in directions other than the pickup, then scattered and reflected again, and enters the pickup, must be removed as unnecessary light. The light absorbing layer 5 applied to the inner peripheral edge and the light absorbing layer 6 applied to the outer peripheral edge absorb such unnecessary light.

FIG. 3 is a diagram for explaining the effect of light absorption on the outer peripheral edge of the configuration of the present invention except that the side surface is not smoothed. The inner peripheral edge is also basically the same in configuration and operation as the outer peripheral edge, so that the illustration of the inner peripheral edge is omitted. In the present specification, the outer peripheral edge portion or the inner peripheral edge portion includes at least an outer peripheral side surface, and as shown, means a portion including a substrate side edge surface and a protective film side edge surface as necessary. . The light absorbing layers 5 and 6 are at least on the inner peripheral side of the optical disc or It is necessary to apply to the peripheral side. Then, on the substrate side surface on which the laser beam is incident, the light absorbing layer applied to the inner peripheral side surface and the outer peripheral side surface is provided on the inner peripheral surface and the outer peripheral surface except for the information recording section 7 where information is recorded. It can be applied continuously. Further, on the protective film side, even if applied on the entire surface, the action of the irradiation laser beam is not disturbed, but the inner peripheral surface and the information recording portion 7, that is, the pit portion with the reflective film, and It is sufficient to apply to the outer peripheral surface, which is also applied continuously to the inner and outer peripheral surfaces.

Light incident on such a light absorbing layer from outside the optical disk is almost completely absorbed, and light from the inside can be absorbed to a considerable extent. It cannot absorb light from inside completely. For example, as a result of diffuse reflection, if a laser beam as illustrated in FIG. 3 is incident on the outer peripheral side surface from the inside of the optical disk, it will be scattered from the outer peripheral side surface as shown in the figure. This is because the outer peripheral side surface (inner peripheral side surface) is not smooth and has an uneven surface. Part of the light incident here is scattered and reflected, and finally enters the optical pickup as a disturbing signal.

FIG. 4 is a diagram for explaining the light absorption effect of the configuration to which the present invention is applied in which the outer peripheral side surface (內 peripheral side surface) is smoothed. Due to the smoothing process on the outer side surface (inner side surface) as shown in the figure, the light incident here no longer scatters or reflects, but all goes to the light absorption layer and is absorbed here. .

Next, an example of a method for manufacturing an optical disk to which the present invention is applied will be described. The optical disk substrate is made of a transparent disc-shaped synthetic resin material such as acrylic, polycarbonate, or polymethyl methacrylate, or a glass material by a molding method such as injection molding. The irregularities shown are formed. A reflective film made of aluminum or the like is formed on the concave / convex pattern of the substrate by a vacuum thin film forming method such as sputtering or vacuum evaporation. Then, a polymer material such as an ultraviolet curable resin is uniformly applied on the entire surface of the reflective film by a spin coat method or a roll coat method, and then cured to form a protective film. Usually, since the optical disk is manufactured in such a process, the inner peripheral side surface and the outer peripheral side surface of the optical disk are not smooth but have fine irregularities. One of the features of the present invention is that the inner peripheral side surface and the outer peripheral side surface of such an optical disk are smoothed. Such a smoothing process can be performed by polishing with an abrasive. For example, when polishing with a polishing agent for paint with a particle size of 0.5 micron, the sound quality of the finished optical disk was greatly improved. Alternatively, a coating treatment can be performed with a polymer material used as a protective film, whereby the inner peripheral side surface and the outer peripheral side surface can be smoothed. It is applied to the inner side surface and the outer side surface of the optical disk which has been subjected to the smoothing process. More preferably, it can be applied to the inner peripheral surface and the outer peripheral surface on the substrate side and the protective film side, respectively, continuously with the light absorbing layers on the inner peripheral side surface and the outer peripheral side surface. As such a light absorbing layer, an ivory black paint can be used. Also, a paint such as carbon black can be used.

As a result, an optical disk having a high SN ratio in which light scattering is suppressed is completed. However, as another feature of the present invention, light scattering is suppressed in all parts of the laser light path. This will be described with reference to FIG. 5, which shows an example of an optical disk reproducing apparatus to which the present invention is applied.

The optical disk reproducing device conceptually illustrated in FIG. 5 reproduces a signal from an information pit formed in an irregular shape on a circular information track provided on the optical disk. In the figure, i 0 is the optical disk described above with reference to FIGS. 1 and 2, 11 is a casing for an optical disk, 12 is a spindle motor, 13 is a rotating shaft of the motor, Reference numeral 14 denotes an optical disk mounting unit mounted on the rotation shaft. And 15 is the optical pickup.

The optical disc 10 is rotatably driven by the spindle motor 12 while being housed in the casing 11. The optical pickup 15 is configured to be movable by well-known moving means (not shown), for example, a linear motor and a guide rail, and is configured to track and control an information track.

As an operation of the optical pickup 15, the laser light emitted from the laser light source 20 is collimated by the collimator lens 21 and passes through the beam splitter 22. The laser beam passing through the beam splitter 22 is condensed by the objective lens 23. Focus a light spot on the optical disc 10. The light spot is controlled by well-known tracking control means so as to pass through the center of the information track.

The laser light reflected by the reflection film of the optical disk 10 passes through the objective lens 23, is reflected by the beam splitter 22, and enters the condenser lens 24. The collected laser light is incident on the photodetector 25 and detected as an information signal.

In the optical disk reproducing apparatus to which the present invention is applied, a light absorbing layer is applied to the inner surface of the optical disk casing 11 and the inner surface of the optical pickup 15. As the light absorbing layer, the above-mentioned paint such as ivory black and carbon black can be used. As a result, unnecessary light and disturbing light are not only absorbed by the light absorption layer applied to the optical disk itself as described above, but also absorbed all around the laser light path, and the unnecessary light and disturbing light are eliminated. The removal can be complete. Industrial applicability

As described above, according to the present invention, the inner side surface and the outer side surface of the optical recording medium are smoothed, and the light absorbing layer is applied thereon. In addition to absorbing laser light or external light, it also effectively absorbs light that has been irregularly reflected inside the optical disc, thereby increasing the SN ratio of the reproduced signal. By applying the light absorbing layer to the inner surface of the casing and the inner surface of the optical pickup, it is possible to completely suppress any irregular reflection generated from inside the recording signal reproducing device structure.

Claims

The scope of the claims

1. Light composed of a substrate on a transparent disk on which irregularities indicating information signals are formed, a reflective film formed on the substrate as a thin film, and a protective film coated on the entire surface of the disk on the reflective film In the recording medium,

An optical recording medium comprising a light absorbing layer applied on inner and outer peripheral side surfaces subjected to smoothing treatment.

2. On one main surface of the substrate on the transparent disk, irregularities indicating information signals are formed, a thin reflective film is formed on the substrate surface on which the irregularities are formed, and the entire surface of the disk is protected on the reflective film. In a method for manufacturing an optical recording medium comprising applying a film,

Smoothing the inner and outer peripheral sides of the optical recording medium,

Applying a light absorbing layer to at least the outer peripheral edge and the inner peripheral edge including the inner peripheral side surface and the outer peripheral side surface subjected to the smoothing treatment;

A method for producing an optical recording medium, comprising:

3. An apparatus for reproducing a signal recorded on an optical recording medium according to claim 1, wherein: a means for rotationally controlling the optical recording medium for reproducing a recording signal;

A casing having an inner surface coated with a light absorbing layer and containing an optical recording medium to be rotationally controlled;

It has an inner surface coated with a light absorbing layer, and focuses and irradiates a laser beam onto an information track of an optical recording medium, and detects reflection that changes in accordance with unevenness of a reflection film showing an information signal, thereby obtaining information. An optical pickup optical system for reproducing a signal,

A recording signal reproducing device comprising: