JP2633835B2 - Optical information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information recording medium such as an optical disk, an optical tape, and an optical card for recording and reproducing optical information.

(Prior Art) As an optical disk device for recording and reproducing information by condensing a laser beam with an objective lens and irradiating the same onto an optical disk as an optical information recording medium, the one shown in FIG. 5 is known. .

The laser beam emitted from the semiconductor laser 1 is converted into a parallel beam by the coupling lens 2, passes through the polarizing beam splitter 3 and the quarter-wave plate 4, is condensed by the objective lens 5, and has a diameter on the recording surface of the optical disc 6. A minute light spot of about 1 μm is formed. The reflected light from the optical disk 6 passes through the objective lens 5, has its polarization plane changed by a quarter-wave plate, is separated from the incident light by the polarization beam splitter 3, passes through the detection lens 7, and is guided to the photodetector 8. . The photodetector 8 is composed of a two-division light receiving element composed of PIN photodiodes 8a and 8b, and adds the sum of the light intensity received by the PIN photodiode 8a and the light intensity received by the PIN photodiode 8b. The information signal calculated by the device 50 is
The difference is calculated by the subtractor 51 to obtain a tracking error signal indicating which position the spot is shifted from the groove. When the spot is successfully irradiated on the guide groove 10 of the optical disc 6 as shown by the solid line in FIG. 5, the light intensity received by the photodiodes 8a and 8b is equal to each other, so that the difference is 0. If the spot deviates from the guide groove 10 as indicated by a virtual line, the mirror surface portion 10 'increases on one side, so that a difference occurs in the light intensity received by the photodiodes 8a and 8b. If a difference occurs, a servo system (not shown) is operated by the difference, that is, the tracking error signal referred to here, and the objective lens 5 is moved in the direction of the mark A so that the spot is focused on the guide groove 10. Move to, record,
Perform playback.

The optical disk 6 of the optical disk device is provided with a preformat section W in which an address signal and a synchronization signal are recorded. As shown in FIG. 6, the optical disk 6 includes a guide groove 10 and a non-guide groove 11. As shown in the figure, the guide groove 10 and the non-guide groove
11 are provided alternately, and the duty ratio, that is, the ratio of the length X of the guide groove 10 to the sum Y of the lengths of the guide groove 10 and the non-guide groove 11 is approximately 50%. Here, when the spot is focused on the guide groove 10, since most of the light is diffracted, the intensity of the received light is weakened, and the level of the information signal detected as a sum signal is low as shown in FIG. However, when the spot is focused on the non-guide groove 11, most of the light is reflected due to the mirror surface, so that the intensity of the received light is high and the level of the information signal is high. This continuous high / low level signal becomes the preformat signal F, and the greater the difference in height, the better.

Here, as shown in FIG. 8, when the spot is applied to the guide groove 10 of the preformat portion W, and the spot is in focus (the spot P indicated by the solid line in the drawing), the difference in light intensity as described above is obtained. Is 0, no tracking error signal is generated, but when out of focus (the spot Q of the imaginary line in the figure), a tracking error signal is generated because the difference in light intensity is not 0. Moves the objective lens 5 in the direction of arrow C to focus the spot on the guide groove 10.

However, when the spot is irradiated on the non-guide groove 11 of the preformat portion W, if the irradiation light and the disk are perpendicular, there is no difference in the light intensity received by the photodiodes 8a and 8b, so that the tracking error signal is generated. Although it should not occur, if the optical disk 6 is tilted due to warping, the direction of the reflected light changes, and even if there is no track deviation, a difference occurs in the light intensity received by the photodiodes 8a and 8b. The result is a tracking error signal.

Then, even if the spot is at a regular position, it can be moved by the servo system. In addition, in the preformat portion W, the duty ratio is approximately 50%, that is, since the length of the non-guide groove 11 and the length of the guide groove 10 are substantially equal, an error in the tracking error signal is likely to occur.

Here, an invention for reducing the error of the tracking error signal by setting the duty ratio of the preformat portion W to 75% or more, that is, X / Y × 100 ≧ 75 (%),
It has been published as No. 5453, In this way, in order to become a limited modulation scheme of the preformat signal, FM modulation, MFM modulation, 2-7 modulation, M ² modulation, 8-10 conversion ,, 4
There is a problem that it is difficult to apply to -5 conversion and the like.

Further, when the optical recording layer 21 made of a light absorbing and reflecting metal, alloy, or dye is formed by solvent coating, as shown in FIG. 6, the thickness becomes D in the groove portion, and becomes d in the non-groove portion,
Since the thickness of the non-groove portion is smaller than that of the groove portion, there is also a problem that the non-groove portion is liable to be deteriorated in characteristics by irradiation with laser light.

(Purpose) An object of the present invention is to provide an optical information recording medium that performs stable tracking while keeping the information signal level in a preformat section constant and prevents deterioration of an optical recording layer.

(Configuration) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, on a transparent substrate 20 made of PMMA resin having a thickness of 1.15 mm to which guide grooves have been transferred by a photopolymer method, a Shinian dye having an average thickness of 500 mm (having the following structural formula) A recording film 21 as a light reflection / absorbing optical recording layer made of is formed, and the preformat portion W has a V-shaped cross section, a half-width of 0.4 μm, and a maximum depth of 0.175λ. The duty ratio is about 50%. Here, the conventional non-guide groove 11 is provided with a second guide groove 12 connected to the first guide groove 10 and having a smaller depth and a same or smaller width than the first guide groove 10. ing.

An experiment was performed on the optical disk 6 'as the optical information recording medium using the semiconductor laser 1 having a wavelength of 790 nm using the optical disk device shown in FIG. 5, and the results shown in FIG. 2 were obtained.

FIG. 2 shows the intensity of the signal level received by the photodetector 8 which varies depending on the depth ratio between the first guide groove 10 and the second guide groove 12. A represents the intensity of the signal level received by the photodiode 8a (see FIG. 5), and B represents the intensity of the signal level received by the photodiode 8b (see FIG. 5). (AB) is a subtractor 51 (see FIG. 5).
Represents the output of the difference between A and B, where (A + B) is the adder 50
(Refer to FIG. 5) represents the sum of A and B. (A-
B) PP / 2 represents 1/2 of the PP amplitude when the spot crosses the preformat portion, that is, the level of the tracking error signal, and (AB) offset is when the optical disk is inclined by 1 °. , That is, the error level of the tracking error signal.
B) If the offset> (AB) P-P / 2, it means that tracking control is not possible. Therefore the second
As shown in the figure, the ratio of the groove depth when the signal level of (AB) p-p / 2 is equal to the signal level of (AB) offset (second
Depth of guide groove / first guide groove depth) is represented by E, Must.

The (A + B) signal is an information signal (A + B).
B) Since H of the signal represents the level of the reflected light from the second guide groove and L represents the level of the reflected light from the first guide groove, the larger the difference between H and L is, the better the preformat signal is. ing. Therefore, it can be seen from FIG. 2 that while maintaining the difference between H and L to some extent, (AB) P-P / 2> (A-
B) The ratio of the depth of the first groove to the second groove, which is an offset, is preferably about 0.2 to 0.7. Further, it was found from other experiments that the width of the second guide groove was 1/3 to 1 times as good as the width of the first guide groove.

If the polarity of the tracking error signal due to the light reflected from the first guide groove 10 and the polarity of the tracking error signal due to the light reflected from the second guide groove 12 are not the same, the duty ratio is about 50% in the preformat unit. Because there is
That is, since the first guide groove and the second guide groove are alternately continuous in half and half, the polarities of the tracking error signals are alternately reversed, and the tracking error signals cancel each other. It will be smaller. Then, the tracking becomes unstable despite the presence of the second guide groove, so that the polarities of the tracking error signals from the first guide groove 10 and the second guide groove 12 must be the same.

According to the experiment of the present invention, the polarity of the tracking error signal changes as follows depending on the depth of the groove and the shape of the sag.

Let λ be the wavelength of the laser beam in the transparent substrate 20, and if the groove has a rectangular cross section as shown in FIG.
The polarity is inverted every 41/4 times of.

However, as shown in FIG. 4, when the dye recording film 21 is applied, there is a tendency that the dye recording film 21 is thickly attached and sagged in the concave portion.
5) Must be twice as deep.

Repeated playback of the same track at a linear velocity of 1.2 m / sec and a playback power of 0.2 mW resulted in the following table.
It has been proved that the deterioration of the characteristics, which tends to occur in the conventional non-guide groove, can be prevented by forming the second guide groove so that the coating film thickness 21 can be increased.

(Effects of the Invention) As described above, according to the present invention, the first guide grooves are placed on the flat portions between the first guide grooves of the preformat portion formed by the intermittent operation of the first guide grooves. A second guide groove having a continuous execution depth of 0.2 to 0.7 times that of the first guide groove and a tracking error signal having the same polarity as the tracking error signal from the first guide groove; Is provided, and the optical recording layer having light absorption and reflection is formed in the first guide groove and the second guide groove by applying a solvent. Therefore, the number of times of reproduction can be greatly increased by preventing deterioration of the optical recording layer. In addition, stable tracking is performed while maintaining the information signal level constant.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical disc showing one embodiment of the present invention,
FIG. 2 is a diagram showing the intensity of the signal level which varies depending on the ratio of the depth of the first and second guide grooves, FIG. 3 is a schematic sectional view of a regular rectangular groove, and FIG. FIG. 5 is a schematic configuration diagram of a conventional optical disk device, FIG. 6 is a schematic diagram showing a preformat unit, FIG. 7 is a diagram showing an information signal level from the preformat unit, FIG. The figure is a schematic diagram showing a deviation of a spot irradiated on the preformat portion. 6, 6 '... optical information recording medium, 10 ... first guide groove, 1
1... Non-guide groove, 12... Second guide groove, W.

Claims (1)

(57) [Claims] 1. An optical information recording medium for recording and reproducing optical information, wherein a preformat portion formed by intermittent first guide grooves has a flat portion between the first guide grooves.
The first guide grooves are connected to each other, the effective depth is 0.2 to 0.7 part of the first guide grooves, and the polarity of the tracking error signal is the same as the polarity of the tracking error signal from the first guide grooves. An optical information recording medium comprising: a second guide groove which is the same as the first guide groove; and a light absorbing and reflecting optical recording layer formed by applying a solvent to the first guide groove and the second guide groove. .