JPH0896416A - Optical information recording medium - Google Patents

Abstract

PURPOSE: To make the carrier level from lands and grooves nearly equal to each other by providing a land width WL, groove width WG and the distance groove pitch PG between the adjacent groups with a relation 0.01<=|WL-WG|/ PG<=0.3. CONSTITUTION: The disk formed by laminating a dielectric layer, recording layer, etc., in such a manner that the reflectivity attains, for example, 20%, on a substrate is reproduced by matching only the focus by using an optical pickup having a wavelength of, for example, 780nmLD and numerical aperture of 0.55 of an objective lens, by which the result shown in Fig. is obtd. In order to assure >=0.05 signals, 0.02<=|WL-WG|/PG is necessary if the land width is defined as WL, the groove width as WG and the groove pitch as PG, the levels of the respective signal amplitudes are required to be equal even when the land width and the groove width are not equal and, therefore, |WL-WG|/PG<=0.3 is necessary in order to attain >=0.5 to <=0.2 amplitude ratio of both. As a result, the carrier levels from the lands and the grooves are made nearly equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium for recording and reproducing information by irradiation of laser light.

[0002]

2. Description of the Related Art In recent years, an optical disk using a laser beam has been developed as a recording medium that meets the demands for increasing the amount of information and increasing the recording and reproducing density and speed. In the optical disc, land portions and groove portions are alternately formed in a concentric circle or spiral shape in the radial direction, and reflected light from the land portions is used to guide the converged light. The method is a push-pull method that uses the difference in the intensity of the reflected light from the optical disc in the radial direction, that is, the reflected light from the land or groove and the reflected light (I1-I2 signals) from the inclined portions on both sides of the land, or the groove. Convergent light is guided by calculating the intensity of reflected light from the disc of each of the three beams of the land and the groove on both sides of the land, or the groove and the land on both sides of the land, using three focused beams arranged in the direction 3 There is a beam method. Further, in such an optical disc, when the radius movement is performed, the number of passing tracks is counted by the cross track signal (I1 + I2) to approach the target track. In an ordinary optical disk, recording / reproducing is performed only on the land portion or the groove portion, and thus the width of the land (or groove) on which recording is performed is usually about twice as wide as that of the groove (or land) on which recording is not performed. Has been done. In order to further increase the capacity, a method of recording and reproducing on both the land portion and the groove portion is also considered. If data is recorded on both the land and the groove, the capacity of the optical disk is doubled. The present invention is directed to an optical disc for recording on both the land and the groove.

[0003]

DISCLOSURE OF THE INVENTION In an optical disc in which recording is performed in both the land portion and the groove portion and the information is reproduced, unless the land width and the groove width are made substantially equal, the carrier level of the reproduction signal from the land and the groove Their career levels are too different. However, if the land and the groove have the same width, the amount of reflected light at the land and the amount of the groove become equal.
The difference in the amount of reflected light between the land portion (groove portion) and the groove portion (land portion) by the beam method becomes almost zero. Therefore, it is impossible to guide the convergent light in the three-beam method. Further, in a reproducing apparatus that counts the number of passing tracks using a cross track signal, the number of passing tracks cannot be counted, and rapid radius movement is impossible. Further, it becomes impossible to detect the center of the track in the reproducing apparatus which detects the center of the track based on the maximum value or the minimum value of the reflected light amount.

[0004]

As a result of various studies to solve the above-mentioned problems, the present invention provides a peculiar width for a spiral or concentric land and groove provided on an optical disk. The present invention has been completed by finding that the land and groove can have a structure in which the reproduced signals from the land and the groove have almost the same carrier level and a cross track signal can be obtained.

That is, the gist of the present invention is to irradiate a laser beam onto a recording layer on a substrate using an objective lens to record and reproduce information on both the land portion and the groove portion. An optical information recording medium, wherein the groove width and the distance between adjacent grooves (groove pitch) have a relationship represented by the following formula.

## EQU2 ## 0.02 ≦ | WL-WG | /PG≦0.3 where WL: land width (μm) WG: groove width (μm) PG: groove pitch (μm)

By providing the groove width wider or narrower than the land width within such a range, the carrier levels of the reproduced signals of the land and the groove are substantially equal to each other, and 3
When the beam method is applied, the difference in the amount of reflected light from the groove portion and the land portion can be clearly obtained. Therefore, when the above medium is used, the cross track signal becomes a signal reflecting the land portion and the groove portion. Therefore, when reproducing the information recording medium, as a tracking method, a push-pull method, a divided push-pull method, and a 3-beam method can be used, and the number of passing tracks is counted at the time of radius movement. It is possible to use cross track signals.

Considering the tracking servo characteristics, the groove depth is preferably in the range of λ / 10n to λ / 5n, where λ is the recording / reproducing light source wavelength and n is the substrate refractive index. λ / 6.5n to λ / 5.
A range of 5n is particularly preferred. Further, the information recording medium of the present invention is commonly applicable to magneto-optical media, phase change media, WORM and the like. The land width and groove width are defined by observing the cross section of the disk with an SEM (scanning electron microscope) or the like, the half width of the groove height is defined as the groove width, and the value obtained by subtracting the groove width from the groove pitch is defined as the land width. To be done.

[0008]

EXAMPLES Examples will be shown below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 A polycarbonate resin substrate having a guide groove having a groove interval of 1.4 μm, in which the widths of the land and the groove have a ratio as shown in FIGS. 1 and 2, was prepared. A disc in which a dielectric layer, a recording layer, a dielectric layer, and a reflective layer are sequentially laminated on the substrate so that the reflectance is 20% is used to focus only using an optical pickup having a wavelength of 780 nm LD and an objective lens numerical aperture of 0.55. Was reproduced and the cross track signal was measured when crossing the groove.

The results are shown in FIG. As shown in FIG. 1, in order to secure a cross-track signal of 0.05 or more, (however, cross-track signal = | RL−RG | / RM RL: reflection when the land portion is irradiated with the focused beam Light level RG: Reflected light level when the focused beam is applied to the groove part RM: Reflected light level when the focused beam is applied to the mirror part)

0.02 ≦ | WL-WG | / PG where WL: land width (μm) WG: groove width (μm) PG: groove pitch (μm) is understood to be necessary.

Even when the land width and the groove width are not equal, the signal amplitude levels are required to be equal. From FIG. 2, in order for the ratio of the signal amplitudes of the land portion and the groove portion to be 0.5 or more and 2.0 or less (the difference in carrier level is 6 dB or less),

It is understood that | WL-WG | /PG≦0.3 where WL: land width (μm) WG: groove width (μm) PG: groove pitch (μm) is required.

More preferably, in order for the ratio of the signal amplitude between the land width and the groove width to be 0.7 or more and 1.4 or less (the difference in carrier level is 3 dB or less), | WL-WG | / PG≤0. It turns out that 2 is desirable.

[Brief description of drawings]

FIG. 1 is a cross track signal of the optical disc of the present invention in Embodiment 1.

2 is a carrier level of the optical disc of the present invention in Embodiment 1. FIG.

[Explanation of symbols]

 1 Land Career Level 2 Groove Career Level

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hironobu Mizuno 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd.

Claims (1)

[Claims] 1. An information recording medium in which laser light is applied to a recording layer on a substrate using an objective lens to record and reproduce information on both a land portion and a groove portion, and a groove adjacent to the land width and the groove width. An optical information recording medium characterized in that a distance (groove pitch) between them has a relationship represented by the following formula. ## EQU1 ## 0.02 ≦ | WL-WG | /PG≦0.3 where WL: land width (μm) WG: groove width (μm) PG: groove pitch (μm)