JPH07105569A - Optical information recording member - Google Patents

Abstract

PURPOSE:To make the widths of the lead part and the groove part in a recording thin film layer to be equal by forming the recording layer in such a structure that both of planes in the recessed part and projecting part of the recording layer formed according to guide groove are used as an information recording area and that the width of the guide groove in the recessed part is made larger than the width of the groove in the projecting part. CONSTITUTION:The laminated recording thin film layer 1 for information recording consists of an optically transparent first dielectric layer 3, recording layer 4, second dielectric layer 5, and reflecting layer 6 formed on a substrate 2 having tracking guide grooves. If necessary, a protective plate 7 is provided. Width Gws of the guide groove in the recessed groove part 8 is made larger than width Lws of the guide groove in the projecting land part 9. By this method, equal signal amplitudes can be obtd. from signals recorded in both of the land part and the groove part. Further, it is preferable to satisfy p>2> Gws>p/2+2Xt1, wherein P is the pitch of guide grooves and t1 is thickness of the dielectric layer.

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 member capable of recording and reproducing information by using a light beam, and more particularly to a recording member for recording a signal in a concave portion and a convex portion of a guide groove. The present invention relates to a recording / reproducing device.

[0002]

2. Description of the Related Art Currently, optical recording members that have been put into practical use include optical disks and optical cards, which record information on a thin film by finely narrowing a light beam or a recorded signal. Can be played. The recordable optical disc is a recording thin film formed on a circular substrate having spirally or concentrically formed guide grooves having irregularities on the surface, and a laser beam is made to travel along the grooves to produce information. Recording or playback of.

A recording thin film capable of optically storing information includes
Various recording methods have been proposed. A typical recording thin film is a deformation recording in which the thin film is deformed by absorbing light, a phase change recording in which the state of the thin film changes, or a recording layer having a structure in which two thin films are laminated and mutually diffused by light irradiation. There is also a phase change record. Further, as a recording medium capable of rewriting a signal once recorded, magneto-optical recording which reproduces a signal by utilizing the Kerr effect of the difference in the magnetization direction of the recording thin film, or the state change of the above-mentioned substance is reversible. There are phase change records and so on.

These optical recording media are characterized in that they have a larger information recording capacity than information recording media such as semiconductor memories, floppy disks and magnetic disks. From now on,
Efforts are being made to use the recording medium in more applications by further increasing the recording density. One of them
As a method of increasing the recording density, it has been proposed to record on both the land and the groove of a conventional optical disc that records on either of the concave and convex portions of the guide groove used for tracking. For example, Japanese Patent Publication Sho 63-5785
In Japanese Patent Publication No. 9, it is proposed that the width of the guide groove and the width of the guide groove are made substantially equal to record a signal in both.

Further, as a method of reducing crosstalk when recording signals on both the land and the groove, for example, "" High track density magn is used.
eto-optical recording usi
ng a crosscanceller "S
PIE Vol. 1316 Optical Data
Storage (1990) P.I. 35 "proposes a method of providing a special optical system and a crosstalk cancel circuit in an optical disk reproducing device. According to these methods, it is possible to realize a track density about twice as high as that of the conventional recording method.

[0006]

In the method of recording a signal on both the land and the groove, the fact that the signal quality when recording on the land and the groove is the same does not complicate the reproducing apparatus or the like. Is also desirable. For this reason, the surface of the substrate has a shape in which the widths of the groove and the land are equal so that the diffraction effect of the light by the guide groove is equal for both, and signal recording is performed by forming a thin film on the substrate. Was there.

However, when a signal is recorded on an optical disc having a recording thin film formed on a substrate having the same groove width, the land and groove may have different amplitudes. For example, in signal reproduction, the error in the reproduced signal from the groove was very small, but the error in the land portion was large. The tendency also changed greatly depending on the recording thin film structure.

In view of the above problems, an object of the present invention is to provide an optical recording member capable of reproducing a signal having the same quality from both recording sections to a medium for recording a signal on both the land and the groove. is there.

[0009]

In order to solve the above-mentioned problems, the optical information recording member of the present invention is an optical information recording member which is optically provided by irradiating light on a substrate having a spiral or linear guide groove on its surface. A recording member having a recording thin-film layer that produces a detectable change, wherein the laminated recording thin-film layer is composed of at least two thin-film layers, and the thin-film layer in contact with the substrate is an optically transparent dielectric. A recording layer which is a layer and which is in contact with the dielectric layer and whose optical properties change, and both the concave plane and the convex plane of the recording layer formed according to the guide groove are information recording areas. The groove width of the concave portion of the guide groove is larger than the groove width of the convex portion.

[0010]

According to the present invention, the width of the land portion and the groove portion of the recording thin film layer, which is a layer for forming the recording mark, can be made equal by the above constitution, and the size of the obtained recording mark becomes the same. Therefore, it becomes possible to equalize the reproduction signal quality.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical information recording / reproducing method and apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the sectional shape of the optical information recording member of the present invention. The laminated recording thin-film layer 1 for recording information includes an optically transparent first dielectric layer 3, a recording layer 4, a second dielectric layer 5, on a substrate 2 having a guide groove for tracking.
The reflective layer 6 is composed of four layers. In addition, the protective plate 7 may be provided if necessary. The surface of the guide groove is referred to as a grooved surface 8 when the recessed plane is referred to as a land portion 9. Further, the groove width Gws in the vertical direction of the track of the guide groove is set to be larger than the land width Lws. As will be described later in detail, as a result, it is possible to obtain the same signal amplitude from the signals recorded in any of the land portion and the groove portion.

As a material for forming the substrate, resin materials such as polycarbonate and polymethylmethacrylate (PMMA), and optically transparent materials such as glass can be applied. Here, an example in which polycarbonate is used for the substrate 2 will be described. As a substrate, a master is prepared by a mastering process using an exposure device using an Ar laser light source, and the substrate having the above-described structure is formed by injection molding. The surface of the substrate is a recording method in which the optical characteristics of the thin film are changed by the irradiation of light shown in the conventional example, such as deformation recording, phase change recording, magneto-optical recording,
A thin film layer corresponding to photon mode recording is provided. Here, an information signal is recorded by utilizing the state change of the thin film, and a phase change thin film that reproduces a signal by detecting the change in the optical constants accompanying the state change as a change in the reflectance of the irradiated light is provided as a recording layer. An example will be mainly described.

The depth d of the guide groove is generally set to a depth of the optical path length of λ / 8 so that the tracking signal becomes maximum when the wavelength of the light beam 10 used for reproduction is λ. is there. When recording signals on both lands and grooves, a value that minimizes the effect (also called crosstalk) of changes in the recording marks formed on adjacent tracks from the recording marks recorded on both lands and reproduction signals. It is desirable to set to. However, when there is a large difference in the amount of light reflected from the unrecorded portion and the recorded portion, as in a phase change optical disc, the amount of this crosstalk changes depending on the groove depth, and the amount of λ between λ / 8 and λ / 4 is changed. In the vicinity of / 5, there was a tendency that the recording signal was large and the crosstalk amount was small. However, as the groove depth approaches from λ / 8 to λ / 4, the servo signal used in the optical disk device becomes smaller. Therefore, an appropriate groove depth is determined in consideration of the range allowed by the device design. .

Here, the result of observing the surface shape of the substrate according to the present invention and the cross-sectional shape of the laminated recording thin film layer provided on the substrate will be described. First, a description will be given of the results of measuring the reproduction signal and the groove shape when using a substrate in which the width of the groove portion and the width of the land portion that have been conventionally proposed are set to the same value. A concrete shape including the laminated recording thin film layer is shown in FIG. Track pitch p on the surface of substrate 2
Was 1.6 μm, a groove width Gws2 = 0.8 μm, a land width Lws2 = 0.8 μm, and a guide groove having a depth d = 80 nm. Both the groove width and the land width are the distances between the centers of the slopes of the guide grooves as shown in the figure. Each layer constituting the laminated recording thin film layer 1 was formed by a sputtering method. The first dielectric layer 3 is ZnS-Si
A thin film of O ₂ is 110 nm, and the recording layer 4 is Ge-
The recording material of Sb-Te system is 25 nm, the second dielectric layer 5
Of ZnS-SiO ₂ as 18 nm and A as the reflection layer 6
Each layer of an optical disc having an alloy of 150 nm was formed by using a sputtering apparatus equipped with a material target corresponding to each composition. The thickness of the first dielectric layer is t1.

While rotating this disk at a linear velocity of 2.6 m / s, a recording / reproducing experiment was conducted by an optical head using a semiconductor laser having a wavelength of 780 nm and an objective lens having a numerical aperture of 0.55, and a groove portion and a land were obtained. The reproduced signals from the parts were compared. The signal is recorded using the ternary power modulation method used in the phase-change optical disc, the peak power of the light emitted from the objective lens is 10 mW, the bias power is 4 mW, and the recording marks formed on the disc are recorded. Irradiation was performed with light modulated at a frequency such that the pitch was 1.8 μm. The power during reproduction was set to 1 mW. The values of the peak power and the bias power shown here are measured in advance so that sufficient signal recording can be performed on the recording medium, and the amplitude difference is within 5% for a power fluctuation of 10%. You have selected a value. As a result of measuring the reproduced signal from the signal recorded on both the land and the groove, the amplitude of the land portion was 20% larger than the amplitude of the groove portion. The result is that the amplitude difference occurs even though the shape of the substrate is symmetrical between the land and the groove.

Next, in order to know the details of the shape of the recording medium, the cross section of the recording member including the guide groove was observed with a transmission electron microscope. As a result, as shown in FIG. 2, it was found that, as compared with the shape of the surface of the substrate, the width of the unevenness on the surface of the substrate was changed in the laminated recording thin film layer 1 as the layers were formed. That is, the layer formed by a thin film forming method in a vacuum such as sputtering is not deposited only in the vertical direction toward the substrate, but is also formed on the slope portion of the guide groove at the same ratio. . Therefore, compared with the edge position of the guide groove on the surface of the substrate 2, the position of the slope gradually changes as the thin films are laminated, and the groove portion width Gwr2 of the recording layer 4 becomes larger than the substrate width Gws2, for example. ing.

Therefore, in the present invention, in order to make the amplitude of the reproduction signal obtained from the entire laminated recording thin film layer 1 having the above-mentioned structure the same for the land and the groove, the land width Lwr and the groove width Gwr in the recording layer 4 are set. Tried to be equal. That is, as shown in FIG. 1, the substrate is designed including the reduction of the groove width due to the formation of the thin film. That is, assuming that the difference between the groove width and the land width of the recording layer shown in FIG. 2 is ΔWr2, the groove width of the groove portion is set wide by the width corresponding to ΔWr2 = Lwr2-Gwr2.
It is possible to make both groove widths of the recording layer the same.

Specifically, in the substrate shown in FIG.
Initially, the land width Lws and the groove width Gws of the substrate are 0.
The recording layer had a land width Lwr of 0.92 μm and a groove width of 0.68 μm, while the recording layer had a width of 8 μm. As a result, the ΔWr2 is 0.24 μm, and the slope of one side of the land portion is 0.1 while the dielectric layer 3 is formed to 110 nm.
The 2 μm land width has become narrower. in this case,
As shown in FIG. 1, the land width Lws of the substrate is set to 0.6 in advance.
By setting the groove width Gws to 8 μm and the groove width Gws to 0.92 μm, both groove widths of the recording layer can be set to the same value of 0.8 μm. In order to verify this, a substrate having the above value was formed and a signal recording experiment was conducted. Although the groove width of the obtained substrate was 0.9 μm, signal recording was performed under the same assumptions as described above, and as a result, the signal amplitude difference between the land portion and the groove portion was 5%.
Within the range and the signal reproduction, the value was not a problem.
From the above results, the width of the guide groove of the substrate according to the present invention is changed to make the widths of the land portion and the groove portion of the recording layer equal, so that the signal amplitudes obtained from both regions of the recording member become equal. It has become possible.

The above recording medium has a track pitch of 1.
In the case of 6 μm, the amplitude difference was about 20% due to the groove width of 0.12 μm, but the amplitude difference further increases at a smaller track pitch, for example 1.4 μm, and the groove width correction according to the present invention is performed. The effect of adjusting the signal amplitude is increased. At the same time, it becomes necessary to improve the correction accuracy of the groove width.

Up to now, one disk structure has been described as an example, but the effect of correcting the amplitude of the land and the groove due to the change of the groove width of the substrate of the present invention is compared with the thickness t1 of the first dielectric layer of the substrate. FIG. 3 shows the relationship between the groove width Gws and the groove width Gwr of the recording thin film layer 4.
When formed by the film forming method shown here, it can be seen that the change ΔWr in the width of the second dielectric layer and the width of the recording thin film layer is in a substantially proportional relationship. In this case, a predetermined groove condition can be obtained by estimating ΔWr according to the thickness of the first dielectric layer.

Further, the relationships shown here are established in the same film forming method, and if the sputtering conditions such as vacuum degree and power during sputtering, or the film forming method is a vacuum vapor deposition method or an ion beam method, The slope of the curve changes. By these film forming methods, the similar curve inclination, that is, ΔWr / when the thickness of the dielectric layer is t1
t1 is at least 0.4 times the thickness of the first dielectric layer
The range was 1.8 times. In general, the higher the energy level of the thin film that reaches the substrate during film formation, the smaller the slope of this curve.

In the case where the film forming method is not specified, or in the case of a thin film whose cross-sectional structure is difficult to observe, the groove width of the substrate is changed in advance according to the thickness of the dielectric layer designed as described above. Should be provided. Here, when the pitch of the guide grooves is p and the film thickness of the dielectric layer is t1, the value of the width of the recesses of the guide grooves and the groove width Gws is p / 2>Gws> p / 2 + 2 × t1 (Equation 1 It is advisable to prepare a substrate within the range. Applying the relationship of 30% to 90% of the thickness of the dielectric layer obtained from the above result, Gws is p / 2 + 0.4 × d>Gws> p / 2 + 1.8 × t1 (Equation 2 ). An optimum groove width can be obtained by forming a laminated recording thin film on this substrate and performing the following steps.
1) Using an optical recording device, a signal is recorded on both a land and a groove with a power for obtaining a sufficient recording state on a recording medium. 2) Compare the amplitudes of the signals recorded on both sides. From the above results, it is possible to specify the groove width with which the signal amplitude is equal.

As the structure of the optical recording medium, there is a case where the light beam 10 is incident from the opposite side of the substrate 12 as shown in FIG. In this case, the laminated recording thin film layer 1 is formed from the opposite layers as shown in the figure, and the reflective layer 6 and the second layer are formed on the substrate 12.
The dielectric layer 5, the recording layer 4, and the first dielectric layer 3 are sequentially formed. The shape of the substrate 12 applied to this is such that by substituting the thickness t3 of the layer formed on the substrate side of the recording layer in place of the thickness t1 of the second dielectric material described so far, By setting the groove width, the signal amplitudes from the land portion and the groove can be made equal.

In this embodiment, the laminated recording thin film layer is shown as four layers, but the effect of the present invention is that at least the structure in which the optically transparent dielectric layer is provided on the substrate. Can be applied. For example, a two-layer structure in which a dielectric layer and a recording layer are provided on a substrate and a three-layer structure in which a dielectric layer, a recording layer and a dielectric layer are provided on a substrate can be applied. Further, it may have a structure in which a plurality of first dielectric layers and a plurality of first recording layers and second dielectric layers are alternately formed on the substrate.

Up to now, the phase change medium has been mainly described as the recording medium, but like the magneto-optical recording medium or the photon mode recording medium, the recording layer is laminated after the dielectric layer or the reflecting layer is provided on the substrate. The present invention can be similarly applied to any recording medium having a structure.

[0027]

As described above, according to the present invention, by adjusting the width of the guide groove in accordance with the thickness of the dielectric layer in contact with the guide groove, the signal amplitude at the land portion and the groove becomes uniform. It is possible to obtain a recording medium showing As a result, it becomes possible to obtain a recording medium having a high track density by applying the land / groove recording.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an optical information recording member according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of an optical information recording member used for comparison with examples of the present invention.

FIG. 3 is a characteristic diagram showing the film thickness dependence of the first dielectric layer in the example of the present invention.

FIG. 4 is a partial sectional view of an optical information recording member according to an embodiment of the present invention.

[Explanation of symbols]

 1 Laminated Recording Thin Film Layer 2 Substrate 3 First Dielectric Layer 4 Recording Layer 5 Second Dielectric Layer 6 Reflective Layer 8 Groove Part 9 Land Part 10 Light Beam p Track Pitch d Groove Depth

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Akabira 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A recording member comprising a laminated recording thin film layer on a substrate having a spiral or linear guide groove on its surface, which produces a change which can be optically detected by irradiation of light. The thin film layer is composed of at least two thin film layers, the thin film layer in contact with the substrate is an optically transparent dielectric layer, and the thin film layer is in contact with the dielectric layer to change the optical property. Both the concave plane and the convex plane of the recording layer formed according to the guide groove are information recording areas, and the groove width of the concave portion of the guide groove is larger than the groove width of the convex portion. A characteristic optical information recording member. 2. When the pitch of the guide grooves is p and the film thickness of the dielectric layer is t, the width W of the recesses of the guide grooves is p / 2>W> p / 2 + 2 × t. The optical information recording member according to claim 1, which is in a relationship. 3. A recording member comprising a laminated recording thin film layer which produces a change which can be optically detected by irradiation of light on a substrate having a spiral or linear guide groove on the surface thereof. The thin film layer is composed of at least two thin film layers, and the thin film layer in contact with the substrate is an optically transparent dielectric layer, and the recording layer whose optical properties change in contact with the dielectric layer. Both of the concave plane and the convex plane of the recording layer formed according to the guide groove are information recording areas, and the groove widths of the concave section and the convex section are substantially equal to each other. And an optical information recording member. 4. A substrate having a spiral or linear guide groove on the surface thereof for forming a laminated recording thin film layer which causes a change which can be optically detected by irradiation of light, said laminated recording thin film layer. Is composed of at least two thin film layers, the thin film layer in contact with the substrate is an optically transparent dielectric layer, and is composed of a recording layer in contact with the dielectric layer and having optical properties changed Both the concave plane and the convex plane of the recording layer formed according to the guide groove are information recording areas, and the groove width of the concave portion of the guide groove is larger than the groove width of the convex portion. A substrate for an optical information recording member. 5. When the thickness of the dielectric layer is t and the pitch of the guide grooves is P, the value of the width W of the recesses of the guide grooves is P / 2>W> P / 2 + 2 × t. The substrate for an optical information recording member according to claim 4, wherein: 6. A recording member comprising a laminated recording thin film layer which produces a change which can be optically detected by irradiation of light on a substrate having a spiral or linear guide groove on the surface thereof. Information can be recorded on both the concave portion and the convex portion of the guide groove in which the thin film layer is formed, the laminated recording thin film layer is composed of at least two thin film layers, and the thin film layer in contact with the substrate is an optical layer. Is a transparent dielectric layer, and is composed of a recording layer whose optical properties change in contact with the dielectric layer, wherein the groove width of the concave portion of the guide groove is larger than the groove width of the convex portion, and the pre-recording is performed. A groove width is provided so that a change in the amount of light obtained by irradiating the member with a light beam focused on the concave portion and a change in the amount of light obtained when the recording member is irradiated with light on the convex portion are equal. Optical information recording member characterized by 7. The laminated recording thin-film layer comprises at least three layers having an optically transparent dielectric layer in contact with a substrate, a recording layer and a second dielectric layer. Alternatively, the optical information recording member described in 6 above. 8. A recording layer constituting a laminated recording thin film layer undergoes a state change depending on a light irradiation condition, and the complex reflectance of the recording thin film layer changes according to the state change. 3. The optical information recording member described in 3 or 6.