JP2001176123A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk which can exhibit a sufficient mask effect even in recording and in reproducing. SOLUTION: This optical disk is formed by laminating layers 6 for recording and reproducing information and mask layers 12 having a mask effect to increase light transmittance when the intensity of irradiation light increases. The diameter of the light spot transmitted through the mask layers is made substantially smaller than the diameter of the light spot incident on the mask layers 12 and the layers for recording and reproducing the information are irradiated with the light. The mask layers consist of a low-sensitivity mask film 12B having low sensitivity, a high-sensitivity mask film 12A having high sensitivity and an isolation film 14 interposed between these two mask films for preventing the mixing of the materials of these two mask films. As a result, the sufficient mask effect may be exhibited in recording and reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk capable of optically recording and reproducing information at high density, and more particularly to an optical disk having a mask layer capable of recording and reproducing information at high density. In this specification, the term “recording / reproducing” means recording, reproducing, and reproducing while recording.

[0002]

2. Description of the Related Art In general, an optical disk is known as a recording medium capable of recording a large amount of information and having a short access time. However, with the development of an information society, higher density recording is desired. I have. As a method for optically recording and reproducing information at high density, for example, the following methods have been proposed. That is, this method includes shortening the wavelength of the recording / reproducing laser beam, increasing the NA (numerical aperture) of the lens focused on the optical disk, increasing the number of recording layers for recording information, and recording. There are methods such as multiplex recording by changing the wavelength of laser light, and forming a mask layer to substantially reduce the light spot diameter. Among them, a method of forming a mask layer to substantially reduce the spot diameter is described in, for example, Japanese Patent Application Laid-Open No. 5-12673.
JP-A-5-12715, JP-A-5-28498, JP-A-5-28535, JP-A-5-739
No. 61 and JP-A-5-234136.

A conventional optical disk having a mask layer is formed, for example, as shown in FIG. FIG. 7 shows a sectional view of an optical disk capable of recording and reproduction. As shown, the optical disk is formed by sequentially laminating a mask layer 4, a recording layer 6, and a protective layer 8 on a transparent substrate 2. Guide grooves, address information, and the like (not shown) are formed on the surface of the transparent substrate 2 on the mask layer 4 side. Then, recording or reproducing laser light L is irradiated from the transparent substrate 2 side.
Generally, a phase change material, a photochromic material, a thermochromic material, or the like is used as a material of the mask layer 4. When the mask layer 4 is not irradiated with the laser beam L or when the laser beam L is weak, the transmittance is small, and when the light intensity is increased, the mask layer 4 may optically or absorb light to increase the temperature. As a result, the light transmittance increases, and the diameter of the spot transmitted through the mask layer substantially decreases as shown in FIG. That is, FIG. 8 is a diagram schematically illustrating an example of the intensity distribution of light incident on the mask layer and the intensity distribution of light transmitted through the mask layer. The intensity distribution of light transmitted through the mask layer is narrowed. Thus, it is possible to record and reproduce small pits using this effect.
Actually, the peak of the transmitted light intensity is slightly shifted in the disk rotation direction. FIG. 9 shows a state of a light spot appearing on the optical disk surface when this function is used.

FIG. 9 is a diagram showing the relationship between a light spot incident on a mask layer and a light spot transmitted through the mask layer, which absorbs light and raises the transmittance as the temperature rises.
When light of a constant intensity is continuously irradiated while rotating the optical disc, for example, point B on the optical disc becomes light spot 1
Light having an intensity obtained by integrating the light intensity from point A to point B of 0 is applied. The temperature rises by the heat obtained by subtracting the heat lost by heat conduction and radiation from the heat converted by absorbing the light, thereby increasing the transmittance of the mask layer. Therefore, the part where the transmittance increases is
In the direction of rotation of the optical disk, the spot diameter is behind (the downstream side) the spot diameter, and the spot diameter is substantially reduced. In the figure, the hatched area C indicates a light spot transmitted through the mask layer, and the circular area D excluding this area C indicates a light spot not transmitted through the mask layer. Thus, by forming the mask layer,
The spot diameter is substantially reduced, and recording and reproduction of a high-density optical disk can be performed.

[0005]

By forming the mask layer 4 as described above, the spot diameter can be substantially reduced and high-density optical disk recording and reproduction can be performed. There was a problem. That is, in the reproduction of the optical disk having the mask layer 4, it is necessary to reproduce the information recorded on the optical disk without destroying the information recorded on the optical disk at the reproduction light intensity at which the mask effect becomes the best at the time of reproduction. When a rewritable phase-change material is used as the material, when the irradiation light intensity at the time of reproduction is increased, information recorded in an amorphous state gradually crystallizes, and as a result, the information is destroyed. there were.

In general, the irradiation light intensity at the time of recording is higher than the irradiation light intensity at the time of reproduction. Therefore, if a large mask effect is obtained at the time of reproduction, the mask effect is almost eliminated at the time of recording. In addition, if the mask effect is made large during recording, the mask transmittance will be small at the time of reproduction and the reproduction output will be hardly obtained, so that the mask effect can be increased at the time of reproduction and the mask effect should be at the time of recording. Is very difficult. The present invention has been made in view of the above problems, and has been conceived in order to effectively solve the problems. The purpose of the present invention is to provide an optical disc capable of exhibiting a sufficient mask effect both during recording and during reproduction. To provide.

[0007]

According to a first aspect of the present invention, a layer for recording / reproducing information and a mask layer having a mask effect of increasing light transmittance when the intensity of irradiation light is increased are formed by laminating. An optical disc in which a light spot diameter transmitted through the mask layer is substantially smaller than a light spot diameter incident on the mask layer to irradiate a layer for recording and reproducing the information, wherein the mask layer has a sensitivity A low-sensitivity mask film having a low sensitivity, a high-sensitivity mask film having a high sensitivity, and an isolation film interposed between these two mask films to prevent mixing of the materials of the two mask films. It is an optical disk. As a result, a mask effect is provided both during recording and reproduction, and two layers of mask films having different sensitivities are provided in order to prevent destruction of recorded information during reproduction. Further, an isolation film is formed between the mask films having different sensitivities. Therefore, the materials of the two-layered mask film are not mixed even when used repeatedly, and the number of times of repeated use can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical disk according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an enlarged schematic cross-sectional view showing an example of the optical disk of the present invention, FIG. 2 is a graph showing a change in light transmittance with respect to irradiation light intensity of a high-sensitivity mask film and a low-sensitivity mask film, and FIG. FIG. 4 is a graph showing a change in light transmittance with respect to intensity, and FIG. The same parts as those of the above-described conventional optical disk are denoted by the same reference numerals and described.
As shown in FIG.
Indicates a single-plate disk, and is formed by sequentially laminating a mask layer 12, a recording layer 6 as a recording / reproducing layer, and a protective layer 8 on a transparent substrate 2 on a transparent substrate 2. A guide groove, address information, and the like (not shown) are formed on the surface of the transparent substrate 2 on the mask layer 12 side. And
The recording and reproducing laser light L is incident from the transparent substrate 2 side. Here, in the present invention, the mask layer 12
Are a high sensitivity mask film 12A and a low sensitivity mask film 12B
And an isolation film 14 interposed between the two mask films 12A and 12B to prevent the materials of the two mask films 12A and 12B from being mixed. That is, a high-sensitivity mask film 12A, an isolation film 14, and a low-sensitivity mask film 12B were laminated on the transparent substrate 2 in this order.

As the transparent substrate 2, for example, a polycarbonate resin can be used. As the recording layer 6, a phase change material, a magneto-optical material, an organic material, or the like can be used. When a phase change material is used as the recording layer 6, the recording layer 6 is composed of a plurality of laminated films. To describe this laminated film specifically, from the side closer to the mask layer 12,
ZnS—SiO ₂ dielectric film 6A, AgInSbTe or G
Phase change material film 6B such as eSbTe, ZnS—SiO ₂
The dielectric film 6C is a heat transfer film 6D such as an Al film. As a material of the protective layer 8, a photopolymer or the like is used.

[0010] As a material of the mask layer 12, a thermochromic material or a phase change material can be mainly used. FIG. 2 shows the high-sensitivity mask film 12A and the low-sensitivity mask film 1
The change of the light transmittance of 2B is shown. Specifically, here, thermochromic is used as a material of the high-sensitivity mask film 12A, and when the intensity of light incident on the mask film 12A increases, the intensity of light to be absorbed increases, and the temperature of the mask film 12A increases. Is increased. The high-sensitivity mask film 12A uses, for example, GN2 (trade name, manufactured by Yamamoto Kasei Co., Ltd.) as a color former and BHPE as a color developer. These color formers and developers were simultaneously vapor deposited using a binary vapor deposition machine. In the high-sensitivity mask film 12A, the mask effect preferably appears when the irradiation light intensity during reproduction is about 1 to 2.5 mW, but according to the graph, the mask effect is sufficiently large at about 1.5 mW. I have. The intensity distribution of the light irradiating the mask film 12A has a Gaussian distribution as shown in FIG. 8, so that most of the light is transmitted through the central portion of the Gaussian distribution, but almost no light is transmitted through the peripheral portion. Does not transmit.
The material of the low-sensitivity mask film 12B is also thermochromic. For example, GN2 (trade name, manufactured by Yamamoto Kasei Co., Ltd.) is used as a colorant, and BHPE is used as a developer material. This low-sensitivity mask film 12B was formed using a binary vapor deposition machine. At this time, the low-sensitivity mask film 12B is used to lower the sensitivity.
When the material MgF ₂ used for the isolation film 14 is simultaneously deposited,
The binding between the color former and the developer is inhibited, and the sensitivity is reduced.

As shown in FIG. 2, the high sensitivity mask film 12A
The characteristics of the low-sensitivity mask film 12B are that when the irradiation light intensity is low, the change in the light transmittance is large, the rise is sharp, and the light transmittance sharply increases. The change in transmittance is small, and the light transmittance increases as the irradiation light intensity increases. Further, the isolation film 14
Materials include MgF ₂ , SiO ₂ , hydrazone, Zn
S or the like can be used, and these are formed by a vapor deposition method or a sputtering method, for example, so that the film thickness is about 20 to 100 nm. Then, the high-sensitivity mask film 12A and the low-sensitivity mask film 12B having the characteristics shown in FIG.
FIG. 3 shows the light transmittance characteristics of the mask layer 12 formed by laminating them with the isolating film 14 interposed therebetween. The characteristic of the light transmittance rises to some extent, if not sharply, as much as the characteristic of the high-sensitivity mask film 12A shown in FIG. 2, and then becomes substantially linear in substantially proportion to the irradiation light intensity. It has characteristics that are increasing.

The recorded information on the optical disk D formed as described above was repeatedly reproduced using a recording / reproducing apparatus as shown in FIG. The recording / reproducing apparatus 20 includes a laser element 22 that generates a laser beam L for reproduction, a collimator lens 24 that converts the laser beam L into a parallel light beam, and a polarizing prism 2.
6, the quarter-wave plate 28, and the laser light L
Lens 30 for condensing the reflected light from the optical disc D branched from the polarizing prism 26, and a cylindrical lens 34 for obtaining focus information and tracking information from the reflected light.
And a photodetector 36 for detecting the condensed light. The optical detector 36
The information recorded on the optical disc D is reproduced by detecting the reflected light from the optical disc D. The recording / reproducing conditions here are, for example, that the wavelength of the laser beam L is 650 nm and the NA of the objective lens 30 is 0.6.

When information was recorded / reproduced on the optical disk D of the present invention using the recording / reproducing apparatus 20 as described above, the recorded information could be reproduced many times without destroying the recorded information even with a large reproducing power. Could be reproduced. In the present embodiment, as shown in FIG. 2, a low-sensitivity mask film 12B having a light transmittance of about 44% at a place where the irradiation light intensity is low is laminated on the high-sensitivity mask film 12A. As the irradiation light intensity is increased, first, the light transmittance of the high-sensitivity mask film 12A sharply increases, and a mask effect is generated by the reproduction power. Thereafter, the light transmittance of the low-sensitivity mask film 12B increases, and the recording power increases. A mask effect occurs. However,
Since the light transmittance at low power where the mask effect of the low sensitivity mask film 12B does not occur is as high as about 44%, the mask effect is small as compared with the case where the light transmittance at low power is small.

When a AgInSbTe phase change material is used as the material of the recording layer 6 in a general optical disk without a mask layer, the reproducing power is reduced when the recording / reproducing conditions are set and the linear velocity is 3.5 m / s. Otherwise, the recorded information will be destroyed. Further, as shown in FIG. 7, in an optical disc having a single mask layer 4, when the AgInSbTe phase change material is used as the material of the recording layer 6, if the reproducing power is 1 mW or more, the same place is continuously If recorded for a long time, the recorded information will be destroyed. In this case, the light transmittance of the entire irradiation light intensity is small at around 60%, but the intensity at the center of the Gaussian distribution is large, and heat due to light absorbed by the mask layer is transmitted to the recording layer, thereby destroying recorded information. Will be done.

On the other hand, in the optical disk structure of the present invention as shown in FIG. 1, light is absorbed by the low-sensitivity mask film 12B, and light transmitted through the high-sensitivity mask film 12A is attenuated. Further, the low-sensitivity mask film 12B becomes a layer for blocking the heat generated by the high-sensitivity mask film 12A, and the recorded information is not destroyed. When the mask layer 12 having the light transmittance characteristic as shown in FIG. 3 is provided, the reproducing power is 1.8.
No breakdown occurred at mW. Thus, by forming the isolation film 14 between the two mask films 12A and 12B, the mask layer 12 maintains the relationship between the irradiation light intensity and the transmittance shown in FIG. As a result, the recorded information was not destroyed and good reproduction was possible.

For comparison, an optical disc for comparison was prepared by removing only the isolation film 14 from the optical disc having the structure shown in FIG. 1, and its reproduction characteristics were measured. As a result, when the irradiation was repeated several thousand times, the materials of the two mask films 12A and 12B were mixed, and the relationship between the irradiation light intensity and the transmittance as shown in FIG. 5 was exhibited, and the characteristics were deteriorated. In FIG. 5, the dashed line indicates the light transmittance characteristic shown in FIG. 3, and the light transmittance is reduced by the amount indicated by the downward arrow A, and the characteristic is deteriorated. Then, when the irradiation light intensity of the laser beam was increased so that the mask effect was sufficiently exhibited during reproduction, the recorded information was destroyed. Further, if the reproducing power is set so as not to cause the destruction of the recorded information, the output of the reproduced signal is small and the jitter value of the reproduced signal is increased, which is not preferable.

The low-sensitivity mask film 12B is provided on the transparent substrate 2 side by changing the lamination order of the high-sensitivity mask film 12A and the low-sensitivity mask film 12B, and the high-sensitivity mask film When the film 12A is provided, the light attenuated by the low-sensitivity mask film 12B is incident on the high-sensitivity mask film 12A. Good results could not be obtained because the mask effect was small. In the above embodiment, a single-plate optical disk has been described as an example. However, the present invention is not limited to this. For example, as shown in FIG. 6, two optical disks each having the protective layer 8 removed from the optical disk structure shown in FIG. , Back to back, with an adhesive layer 4 in the middle
Needless to say, the present invention can be applied to a bonded double-sided optical disk or the like formed by bonding with an intervening zero.

[0018]

As described above, according to the optical disk of the present invention, the following excellent operational effects can be exhibited. It has a mask effect at the time of recording and reproduction, and has different sensitivities to prevent destruction of recorded information during reproduction.
Since a mask film of two layers is provided and an isolation film is formed between the mask films having different sensitivities, the materials of the two mask films are not mixed even when used repeatedly, thereby improving the number of times of repeated use. be able to.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic sectional view showing an example of an optical disk of the present invention.

FIG. 2 is a graph showing a change in light transmittance of a high-sensitivity mask film and a low-sensitivity mask film with respect to irradiation light intensity.

FIG. 3 is a graph showing a change in light transmittance with respect to an irradiation light intensity of a mask layer.

FIG. 4 is a diagram illustrating an example of a recording / reproducing device.

FIG. 5 is a graph showing a light transmittance characteristic of an optical disk having no masking layer provided with an isolation film.

FIG. 6 is a partial sectional view showing a modified example of the optical disk of the present invention.

FIG. 7 is a sectional view showing an optical disc capable of recording and reproduction.

FIG. 8 is a diagram schematically illustrating an example of an intensity distribution of light incident on a mask layer and an intensity distribution of light transmitted through the mask layer.

FIG. 9 is a diagram illustrating a relationship between a light spot incident on the mask layer and a light spot transmitted through the mask layer, which absorbs light and raises the transmittance when the temperature rises.

[Explanation of symbols]

2: transparent substrate, 6: recording layer (layer for recording and reproducing information),
8: protective layer, 12: mask layer, 12A: high sensitivity mask film, 12B: low sensitivity mask film, 14: isolation film, D: optical disk.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Dai Hatakeyama 3-12-12 Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa Japan F-term (reference) 5D029 MA39 NA08 NA09

Claims (2)

[Claims] An information recording / reproducing layer is formed by laminating a mask layer having a mask effect of increasing light transmittance when the intensity of irradiation light is increased, and a diameter of a light spot passing through the mask layer is determined by the mask. An optical disk for irradiating a layer for recording and reproducing information with a size substantially smaller than a diameter of a light spot incident on the layer, wherein the mask layer comprises a low-sensitivity low-sensitivity mask film and a high-sensitivity high-sensitivity mask film. An optical disc comprising: a mask film; and an isolation film interposed between the two mask films to prevent mixing of materials of the two mask films. 2. The optical disk according to claim 1, wherein the high-sensitivity mask film, the isolation film, and the low-sensitivity mask film are formed in this order from the light spot incident side.