JPS6085450A - Optical recording disc - Google Patents

Abstract

PURPOSE:To make tracking by guide grooves possible and prevent degradation of S/N ratio by forming a signal recording layer and the guide groove for tracking apart from each other in the recording/reading direction. CONSTITUTION:A signal recording layer 2 and guide grooves 3 for tracking are formed apart from each other in the recording/reading direction. With respect to this optical recording disc, the signal recording layer 2 is formed on a substrate 1, and a layer 4 where guide grooves 3 for tracking are formed is laminated on this layer 2. For example, a resin hardened by ultraviolet rays is coated on the layer, and a groove die is pressed onto this resin, and the groove die is removed after the resin is hardened by irradiation of ultraviolet rays, thus forming this layer 4 easily. In case of signal recording, a laser beam light condensed by a condenser lens 10 is irradiated to the signal recording layer 2 through guide grooves 3 for tracking to record signals. At this time, tracking control is performed by detecting reflection and diffraction of the beam light due to guide grooves 3 for tracking. It is undesirable that the length between the signal recording layer 2 and guide grooves 3 for tracking is too long, and it is desirable that a thickness (d) of the layer 4 is about 10mum.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an optical recording disk on which signals can be recorded and reproduced using laser light.

1. Prior Art FIG. 1 shows a conventional optical recording disk on which data can be recorded on the user's side. For example, a signal recording layer (2) made of a low melting point metal film such as tellurium is formed on the surface of a transparent resin substrate (1) such as acrylic, and information to be recorded is recorded on this recording film (2). Signals are recorded by irradiating a modulated laser beam through a condensing lens to form bit holes in the recording film (2). Signals are reproduced by irradiating pits on the disk with a low-energy laser beam and detecting the strength of the reflected beam.

Another method is to use a thin film such as TbFe, which exhibits a magneto-optical effect, as a signal recording layer (2) instead of a low-melting metal film, and use a laser beam focused under a magnetic field in a certain direction. Signals can also be recorded by irradiating light and reversing the magnetization direction using the heat of the laser beam.

Then, the signal is reproduced by irradiating the disc with a polarized low-energy laser beam and detecting a change in the polarization rotation angle of the reflected light or transmitted light as the strength or weakness of the light.

In such an optical recording disk, in order to increase the recording density, a tracking guide groove (3) is formed on the disk in advance, and a beam of light is irradiated along this groove (3) to remove light from the groove. It has been proposed to record signals on the signal recording film (2) within this groove (3) while performing tracking control by detecting reflected diffraction light.

Now, it is necessary to record signals under conditions with an excellent 8/N ratio as much as possible. However, the formation of the tracking guide groove causes deterioration of the 8/N ratio. Generally, when a low melting point metal film is used as a signal recording film, an S/N ratio of 55 dB or more is obtained without guide grooves, whereas an 8/N ratio of 5Q dB or more is obtained with guide grooves. It is difficult to do so. This is because when the guide groove is formed, variations and distortions occur in its shape, and this causes noise.

OBJECT OF THE INVENTION It is an object of the present invention to propose an optical recording disk that utilizes a tracking guide groove and prevents deterioration of the 8/N ratio.

The signal recording layer and the tracking guide groove of the twenty-eighth invention are formed at separate positions in the recording/reading direction.

E. Example In the example shown in FIG. 2, a signal recording film (2) is formed on the substrate (1), and a tracking guide groove (
The layer (4) formed in step 3) is laminated. Such a layer can be easily created, for example, by coating an ultraviolet curing resin, pressing a combined mold onto it, and removing the combined mold after the resin is cured by UV irradiation.

When recording a signal, the signal recording film (2) is irradiated with a laser beam focused by the condenser lens 0α through the tracking guide groove (3), thereby recording the signal. Tracking control at this time is based on the tracking guide groove (3
) can be achieved by detecting the reflected diffraction of the beam light. It is not preferable for the signal recording layer (2) and the tracking guide groove (3) to be far apart. In the experimental results, the thickness d) of layer (4) is 10μ
It is desirable that it be about m.

FIG. 6 shows another embodiment. In this case, the substrate (1
A tracking guide groove (3) is formed on the lower surface of the groove, and a reflective film (5) made of a vapor-deposited film of aluminum or the like is formed on the surface of this groove.
) is formed. Furthermore, a transparent layer (6) is laminated, and a signal recording layer (2) is formed on the surface thereof. Even in this case, the thickness d) is preferably about 10 μm.

Note that since the signal recording layer (2) has a transmittance of 40 to 50%, the beam light irradiates the tracking guide groove (3) through the recording layer even in areas where there are no pits. Therefore, tracking control is possible even in areas where there are no bits.

Effects of the Invention To provide a disk that allows tracking by the guide grooves and does not cause deterioration of the 8/N ratio with a simple structure in which the signal recording layer and the tracking guide grooves are formed at appropriately spaced positions. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional disc, FIG. 2 is a diagram showing a disc according to the present invention, and FIG. 3 is a diagram showing another embodiment of the disc according to the present invention. (1) is a substrate, (2) is a signal recording film, and (3) is a tracking guide groove.

Claims (2)

[Claims] (1) An optical recording disk characterized in that a signal recording layer and a tracking guide groove are formed at separate positions in the recording/reading direction. (2) The optical recording disk according to claim 1, wherein the distance between the signal recording layer and the tracking guide groove is approximately several tens of micrometers.