JPS59168945A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To improve the transferability and to reduce the influence upon a reproducing picture signal and to obtain a stable tracking signal by forming a guide groove so that its sectional shape is U-shaped and has no polygonal parts and is smooth. CONSTITUTION:When a Te-C layer 402 and an Au layer 403 are formed on a glass substrate 401 and laser light 404 is irradiated from the side of the film surface, swellings 405 are formed in laser light irradiated parts by the discharge of gas from the Te-C layer due to the laser light irradiation, and an original disc 406 with guide grooves is produced by continuous irradiation. The shape of formed guide grooves 503 has no polygonal parts and are smooth. Desirablly, a groove width 2A is set to >=40% of the beam diameter of the laser light (diameter in the position where the intensity is 1/e<2> of the intensity in the center) on the guide groove 503, and a maximum depth H of the groove is set to 5-20% of a used laser light eavelength in terms of optical length. Thus, the transferability of the groove shape in each process is improved without the influence upon the reproducing picture signal neither the degradation of a tracking signal output characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical information recording medium that records and reproduces information signals using, for example, laser light.

[Technical Background of the Invention and its Problems] In recent years, so-called optical disks have been attracting attention as recording and reproducing devices that perform high-density, large-capacity signal recording. For example, a laser beam is narrowed down to a diameter of about 1 .mu.m to form a recording track at a pitch of 1.5 to 2 .mu.m to record a signal, and this is similarly reproduced using the laser beam. 0.1-0.2 μm for this type of device
Since a high degree of tracking accuracy is required, a method is used in which tracking guide grooves are provided in advance on the recording medium and tracking is performed optically, instead of relying on conventional mechanical tracking.

Fig. 1 shows the main part of an example of an optical disc having a conventional rectangular (Fig. 1a) or 7-shaped (Fig. 1b) shaped guide groove.
A continuous guide groove 12 is formed on the recording surface 1, and a recording layer 13 is formed on the recording surface by vapor deposition.

Information recording is performed by irradiating a laser beam 16 from the substrate 11 side through an objective lens 15 to record information on the recording layer 1 along the guide groove 12.
This is done by changing the reflectance or transmittance of 3. Further, signal reproduction is performed by irradiating a laser beam from the side of the burnt substrate 11 and detecting changes in the intensity of reflected or transmitted signals due to pits corresponding to recording signals formed in the guide grooves 12. Tracking control is
This is done by detecting changes in the intensity of reflected or transmitted signals depending on the positional relationship of the beam spotter guide groove 12 when the laser beam 16 is irradiated.

FIG. 2 is a schematic diagram of a recording/reproducing apparatus using an optical disk having such a continuous guide groove. 201 is a laser light source whose output laser beam is passed through a modulator 202, a lens 203, a polarizing beam splitter 204, a lens 205, a quarter wavelength plate 206, a rotating mirror 207,
Optical disc 2 through condensing lens (objective lens) 208
It is designed to irradiate at 09. 210a.

210b is a two-split detector, 211 is an adder, 212 is a difference device, and 213 is a rotating mirror driver. Here, the tracking signal can be extracted from a two-part detector 210a, 210b placed substantially parallel to the tracking direction (tangential direction of the track) and in a far field plane with respect to the recording surface. That is, when the center of the laser beam coincides with the center of the guide groove of the optical disc 209, the two-split detector 210a.

The outputs from the two left and right detectors of 210b will be equal, but if the centers are shifted, the output of one will be larger than the other depending on the direction of the shift, so the difference in the outputs from these detectors will be By detecting this with the subtractor 212 and adding it to the rotating mirror driver 213, tracking can be performed.

Further, as described above, the recording signal can detect the change in reflected light intensity depending on the presence or absence of the bit formed in the guide groove by adding the outputs of the two-split detectors 210a and 210b using the adder 211. .

Here, the shape of the guide groove in a recordable and reproducible optical disc is such that the two-divided detector 21
It is desirable to have a shape that has a small influence on the addition output of 0a and 210b and has a large degree of modulation of the differential output due to the deviation between the center of the laser beam and the center of the guide groove. V-shaped groove with
-55448, JP-A-55-55449) and a rectangular groove (IPEB8PECTRUM AUGU) in which the phase difference between the inside and outside of the guide groove is m/s (m: odd number) of the wavelength used
8T 1979 p, 26-p, 33) have been proposed in the past.However, the conventional rectangular or V-shaped groove shapes have the following problems. Substrates with guide grooves are generally manufactured in a process similar to that used for manufacturing video discs. That is, first, a photoresist is applied onto a glass substrate using a spinner or the like, and a laser beam is irradiated onto the resist using a master disk manufacturing device having the same structure as the optical disk device shown in 1 in FIG. 2 to form guide grooves. By exposing the pattern and etching it, a master disk having guide grooves of a predetermined shape is produced.

Next, master disks, mother disks, etc. are sequentially produced from this master disk by silver plating, nickel plating, etc., and a large number of substrates with guide grooves are produced using a stamper plate casting method or an injection molding method. Copy to. At this time, with the conventional groove shape,
Guide groove pitch 1.6~2.0μm, groove width 0.6~1.0
Because of the extremely high precision of μm, the transferability of the rectangular or V-shaped groove-shaped edge portion 14 is poor, and each time a board is copied from a master disc, a mother disc, a stamper disc, and a stamper disc, the initial The shape of the guide groove deteriorates.

Particularly in the process of duplicating a substrate from a stamper disk, the flow of plastic resin, which is the substrate material, into the grooves of the stamper disk is restricted, which is a major cause of poor transferability. In addition, with acrylic resins that have good optical properties, lowering the viscosity of the resin to improve transferability will deteriorate the heat resistance and reduce the life and reliability of the board. There is a reciprocal effect in that increasing the temperature will result in poor transferability.

As described above, with conventional groove shapes, the transferability of the guide groove is poor, and it is necessary to design the groove shape in advance to take into account deterioration of the groove shape. There was a difficult problem that required control and management.

[Object of the Invention] An object of the present invention is to provide an optical recording medium having a guide groove shape that has good transferability of the guide groove shape, has less influence on reproduced image signals as described above, and can obtain stable tracking signals. It is on offer.

[Summary of the Invention] The fourth feature of the present invention is that the shape of the guide groove is a shape without broken lines, such as a part of a curved line represented by an ellipse or a perfect circle. More preferably, the groove width is the beam diameter of the laser beam on the guide groove (1/e2 of the center intensity).
The maximum depth of the groove is converted into an optical length of 14.5±9.5 inches of the wavelength of the laser beam used.

[Effects of the Invention] According to the present invention, since the shape of the guide groove is smooth without any broken lines, it is possible to transfer from an original to a duplicate substrate without affecting the reproduced image signal or deteriorating the tracking signal output characteristics. The transferability of the groove shape in each of the steps described above can be greatly improved.

[Embodiment of the invention] As shown in FIG. 4, on a glass substrate 401, 3000
Te-0 with energy absorption and gas release properties of ^^
When a layer 402 and an Au layer 403 are formed and a laser beam 404 is irradiated from the film surface side, a bulge 405 is formed in the laser beam irradiated area due to the release of gas from the Te-C layer due to the laser beam irradiation. A master disk 406 with guide grooves can be produced by continuous irradiation.

The shape of the guide groove formed in this way is different from the conventional rectangular or V-shaped guide groove due to its manufacturing principle. A recording body can be provided.

Now, the far-field distribution of the reflected and diffracted light from the guide groove formed on the optical recording medium can be approximated by Fourier transformation. That is, as shown in FIG. 5, the amplitude distribution of the laser spot 502 focused on the optical disk 501 is υ(X), the amount of center deviation between the laser beam spot 502 and the guide groove 503 is ΔX, and the guide groove 503 is If the groove width is 2A, the maximum depth is H, and the guide groove shape is approximated by an ellipse, then the two-split detector 50 placed on the far field surface
The complex amplitude distribution R(ξ) of the reflected and diffracted light on 4 is expressed by the following equation.

R(ξ)= f u(x) ・exp[-jk・2T(
x-△X)]・eXp[-j2rξx]dx-~
...(I)
however.

k=2'r/λ: λ laser wavelength used...(
2) ffx) = H-J 1- (X/A)2・(2
)' is. Here, the reason for using the complex amplitude distribution R(ξ) instead of simply using the amplitude distribution of the reflected diffraction light is that 1. it is affected by the multiphase effect depending on the reflected diffraction light power and the depth of the guide groove 503. . This effect is expressed as exp[-jk・2T(X-ΔX)
]. Further, T(X) represents the shape of the guide groove 503.

Next, the respective outputs I a #I b of the two-split detectors 504a and 504b are expressed as follows using equation (1).

However, ξ1 is the highest spatial frequency determined by the condenser lens 505.

That being said, the sum signal output IADD from the guide groove 503.

The tracking error signal output InEr can be calculated using the following formula 0 IADD ” Ia + Ib ... (
6) IDEF "Ia Ib...
・(7) Groove width A at tracking position (△x=0) in Figure 6
IADD sum signal output characteristics when using as a parameter, Figure 7
shows the IDEF) racking error signal output characteristics when the groove width 2 A = 0.8 μm and the maximum depth H of the groove is used as a parameter. However, the laser wavelength λ = 0.83 μm, the N and A- of the condensing lens 505 = 0.6, the diameter of the condensing laser spot 502 = 1.4 μm (1/e2 where the intensity is at the center)
The direction of incidence of the laser beam is from the guide groove 503 side.

As mentioned above, the shape of the guide groove 503 is required to have a small influence on the reproduced image signal and to obtain a stable tracking signal. (approx.
It can be seen that the above conditions are satisfied in the range 40 (=0.04 to 0.16 μm).

[Other Embodiments of the Invention] In the above embodiments, the laser beam is incident from the guide groove forming side, but as shown in FIG. Even when a protective layer is further formed on the recording layer 504 formed on the guide groove, the groove depth H shown in the above embodiment is adjusted by adjusting the refraction of the substrate or the protective layer so that the optical lengths are equal. The value divided by the rate n,
That is, it is clear that similar results can be obtained by setting '/n.

Further, even in a pigeon coop where signal detection is performed using transmitted light, the same effect can be obtained by approximately doubling the depth of the guide groove.

Furthermore, even if the signal detection position is at the imaging position of the recording surface or in the Fresnel region, the effects of the present invention will not be impaired in any way.

In addition, in the examples so far, the groove shape is concave with respect to the direction of incidence of the laser beam, but this can be conversely convex with respect to the direction of incidence of the laser beam, that is, the depth of the groove is replaced with the height of the groove. It is clear that exactly the same results are obtained.

Further, in the embodiment, one method for producing the master disc was shown, but the method for producing the master disc is not limited at all, only the shape of the guide groove is limited.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional guide groove shape, Fig. 2 is a schematic configuration diagram of a recording/reproducing device using this type of optical information storage medium, and Fig. 3 is a guide groove shape according to the present invention. A cross-sectional view showing
Fig. 4 is a diagram showing the principle of producing a master disc of an optical information recording medium having a guide structure according to the present invention, Fig. 5 is a diagram showing the principle of signal detection from the guide groove in the embodiment, and Fig. 6 is a diagram showing the tracking position. IAD when the groove width is changed by (△x=0)
FIG. 7 is a diagram showing the D sum signal output characteristic, and FIG. 7 is a diagram showing the racking error signal output characteristic when the groove width is constant and the maximum depth of the groove is changed. 405...Bulge.

Claims (3)

[Claims] (1) An optical information recording medium in which a guide groove for tracking is formed, wherein the cross-sectional shape of the guide groove is U-shaped and smooth without a broken line portion. (2) When the groove width of the guide groove is approximated by a Gaussian distribution of the incident light flux onto this guide groove, the center intensity of the incident light flux is 1
The optical % formula % according to claim 1, characterized in that the position is 40% or more of the position where % is /2. (3) Optical information according to claim 1, characterized in that the maximum depth of the guide groove corresponds to an optical length of 5 to 20 − of the wavelength of the incident light flux irradiated to the guide groove. recoding media.