JPH08138267A - Optical recording medium and production of optical recording medium - Google Patents

Abstract

PURPOSE: To make it possible to execute reproducing only when a reproducing machine to be exclusively used is used and to prevent execution of 1 to 1 copying on the optical recording medium of the same size by providing the optical recording medium with a mask layer of a material having desired optical characteristics on the side outer than a recording layer. CONSTITUTION: This optical recording layer is provided with the mask layer 3 on the other side of the recording layer by using the material having the optical characteristics to generate a reversible charge in the optical characteristics when the material is irradiated with a light beam of the intensity higher than the intensity of the light beam used at the time of reproducing information from general magnetic recording medium having no mask layers. The density of the information recorded on the recording layer 3 is set higher than the max. recording density which can be read out even if there is no mask layer 3. As a result, the irradiation of the recording layer with the light spot of a desired bore is prevented by the mask layer as the power of the light beam is low when the reproducing is executed with a general reproducing machine. In addition, the recording density is high when reproduction is attempted to be executed by using the light beam of a high power, therefor, the execution of 1 to 1 copying on the recording medium of the same size is not possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copy protection of a recording medium, and more particularly to a copy preventable optical recording medium and a method of manufacturing a copyable optical recording medium.

[0002]

2. Description of the Related Art Optical recording media have been widely used in recent years as media capable of storing various kinds of information and reproducing appropriately. musics,
When images or characters are represented as digital information signals, compared to the case where they are represented as analog information signals,
Due to the characteristics of information transmission, when the information is copied, the information is less likely to deteriorate. Therefore, it is possible to copy the source information while maintaining its quality, which is currently a big problem in relation to copyright. Therefore, it is required to prohibit or limit the copying (hereinafter, referred to as digital copying) of the digital information signal as it is in the form of the digital information signal. There is a serial copy management system (hereinafter referred to as SCMS) adopted in MD (mini disk) as one of means for realizing that.

In the SCMS, a protect code regarding whether copying is possible is recorded in a part of the digital signal recorded in the MD, and when the MD device makes a copy, it refers to the protect code and makes two or more digital copies. It is a system to prevent. That is, the TO of MD
If the protect code is written in the data of the C (table of contents) area and the protect code is not protected, the MD can be copied. When copied, the TOC area of the copied MD is protected. The protect code of is written. If the protect code is protected, it cannot be copied. In this way, it is possible to prevent digital copying more than once.

[0004]

SUMMARY OF THE INVENTION However, SMCS
In such a method, a protect code is written in the information recorded on the disc, and the device determines whether copying is possible by referring to this protect code, but it is recorded on the disc. When the information is directly read as a recording signal and recorded on another disc, the protect code is copied regardless of the content of the protect code.
It was possible to copy any number of times, and it was impossible to prevent unauthorized digital copying. Therefore, according to the present invention, the information recorded on the optical recording medium cannot be reproduced by the reproducing apparatus other than the exclusive reproducing apparatus as usual, and the information recorded on the optical recording medium using the exclusive reproducing apparatus cannot be reproduced. Manufacture of an optical recording medium and a copy-preventable optical recording medium that cannot be copied onto a disc of the same area even if the data is directly read out as a recording signal but the recording density is insufficient even if it is recorded on another disc. The purpose is to provide a method.

[0005]

In order to achieve the above object, in the present invention, a mask layer whose optical characteristics reversibly change under predetermined conditions is provided outside the recording layer of an optical recording medium, and a mask layer having a predetermined strength is provided. The material of the mask layer is selected so that the effective spot diameter of the beam becomes smaller when the light beam is irradiated, and the density of the information recorded on the recording layer is set high enough. ing.

According to the present invention, an optical recording medium is provided with a layered optical characteristic changing substance whose optical characteristic is reversibly changed according to temperature change or light intensity of irradiated light, and the optical characteristic changing substance is provided in a layered form. The method utilizes a method of recording and reproducing high-density optical information by reducing the effective irradiation spot diameter of the irradiation laser light. The light intensity of the laser light for recording and reproducing of the optical recording medium usually shows a Gaussian distribution, and when such a laser beam is irradiated onto the optical property variable substance layer, the optical property variable substance layer emits the laser light. The optical characteristics change only in the central part where the temperature or the light intensity is high in the spot of
A mask effect is produced in which the spot diameter (effective spot diameter) applied to the information recording portion on which information is recorded is reduced by masking the other portion in the spot. Therefore, the fact that an identification mark (pit) smaller than the actual spot diameter of the irradiation laser light can be detected is utilized.

That is, according to the present invention, a mask layer whose optical characteristics are reversibly changed by irradiation with light having an intensity equal to or higher than a predetermined value in a predetermined wavelength band is provided outside the recording layer. In an optical recording medium capable of reading information recorded on a recording layer, the predetermined intensity higher than that of a light beam used when reproducing information from a general optical recording medium having no mask layer is used. And the density of the information recorded on the recording layer is selected such that the material of the mask layer is reversibly changed when the light beam of such high intensity is irradiated. There is provided an optical recording medium characterized by being set higher than the maximum recording density that can be read even without the mask layer.

Further, according to the present invention, the step of recording the optically readable information on the recording layer of the optical recording medium at a high density, and the step of recording the information outside the recording layer with an intensity of a predetermined value or more in a predetermined wavelength band. The step of providing a mask layer whose optical characteristics change reversibly by light irradiation, the step of setting the high density higher than the maximum recording density to be read even without the mask layer, and the predetermined value The intensity of a light beam used for reproducing information from a general optical recording medium having no mask layer is higher than that of the light beam, and the reversible change of the optical characteristic when the light beam having such a high intensity is irradiated. And a step of selecting a material for the mask layer so that the above-mentioned problem occurs.

[0009]

The method of manufacturing the optical recording medium and the optical recording medium capable of preventing duplication according to the present invention has the above-mentioned structure. Therefore, when the general reproducing apparatus other than the exclusive reproducing apparatus is used, the power of the light beam is low. The desired change in optical properties does not occur in the mask layer. That is, due to the presence of the mask layer having high transmittance due to high light intensity, the recording layer cannot be irradiated with a light spot having a desired aperture. Further, if it is attempted to reproduce by using a light beam of high power, a desired light spot size can be obtained, but a density higher than that of a normal optical recording medium, that is, an optical recording medium having no mask layer. Therefore, the amount of read data is much larger than the amount of data that can be recorded on an optical recording medium of the same size at a normal density, and one disc is copied to one disc. I can't make a copy of 1.

It is also assumed that data is read from the optical recording medium of the present invention by using a dedicated reproducing device or the like, and a normal optical recording medium, that is, a disc having no mask layer is manufactured by using the data. Also in this case, all the data in the original optical recording medium cannot be recorded unless the recording density is increased. Therefore, it is assumed that high density recording is performed so that all data is recorded. However, since there is no mask layer, it is not possible to obtain a desired light spot with a small aperture even if a dedicated reproducing device is used, and reproduction cannot be performed. Even if the desired light spot diameter is obtained by some method, proper reproduction cannot be performed because the light beam intensity is higher than that at the time of writing data. Further, in the case of an ordinary reproducing device, it is also impossible to perform proper reproduction due to the relationship between the intensity of the light beam and the recording density.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an operation when a light beam is irradiated on the optical recording medium of the present invention. FIG. 2 is a schematic diagram showing the relationship between the light spot and the pit row in FIG. 3 is a sectional view of one preferred embodiment of the optical recording medium of the present invention, and FIG. 4 is a sectional view of another embodiment.
That is, FIG. 3 shows a cross-sectional view of the read-only optical disc 10 in the track direction, and FIG. 4 shows a recordable optical disc 2.
0 shows a radial cross section of 0. An optical disc 10 shown in FIG. 3 has a light-transmissive resin substrate (hereinafter simply referred to as a substrate) 1 on which minute pits 2A corresponding to information are formed. A mask layer 3, a reflective layer 4, and a protective layer 5 are sequentially laminated on the substrate 1. Further, in the optical disc 20 shown in FIG. 4, a guide groove or groove 12A is formed in the light transmissive resin substrate 12. An information recording layer 2 (simply referred to as a recording layer), a mask layer 3, a reflective layer 4, and a protective layer 5 are sequentially stacked on the substrate 12. In the optical recording medium of FIG. 3, there is no layer corresponding to the recording layer 2 of FIG. 4, but the uppermost portion of the substrate 1 in which the pits 2A are formed is a portion for substantially recording information. The upper part of 1 is called a recording layer.

As the light transmissive resin used as the substrates 1 and 12, those which are used as substrates for ordinary optical disks such as polycarbonate, polymethacrylic acid ester resin and epoxy resin substrates can be used. Also, pit 2A
There is no particular limitation on the method of forming the guide groove 12A,
It can be formed by a known method.

The mask layer 3 provided outside (above in the figure) the recording layers on the substrates 1 and 12 has a threshold value with respect to the wavelength of a light beam supplied from a light source (not shown) used for optical recording and reproduction. It has a property that the optical properties are reversibly different between the case of higher (higher) intensity and the case of lower (lower) intensity. As a result, when the mask layer 3 is irradiated with laser light having an intensity higher than this threshold value, the effect of substantially reducing the diameter of the irradiated light spot can be exhibited. When the laser light is irradiated onto the optical disks 10 and 20, the spot diameter of the laser light transmitted through the mask layer 3 is substantially reduced, and the signal characteristics, particularly the frequency characteristics and the jitter characteristics are improved. However, it is possible to record and reproduce high density information. The reversibly changing optical characteristics include, for example, a change in transmittance and a change in refractive index, and the mask effect can be exhibited in any case. The term "reversible" as used herein means a property of returning to the original optical characteristics when the intensity of light decreases from the level at which a desired spot diameter is obtained.

When the function of the mask layer is further examined,
The effect of the mask layer 3 whose optical characteristics change depending on the intensity of the irradiated light can be explained as shown in FIG. The light intensity of the laser light for recording and reproducing of the optical recording medium usually shows a Gaussian distribution, and when such a laser light is irradiated on the optical property variable substance layer, the optical property variable substance layer is
The spot diameter (effective spot diameter) with which the optical characteristics of only the central portion of the laser light spot where the temperature or light intensity is high changes, and the other portion of the spot is masked to irradiate the information recording portion where information is recorded. Smaller) allows smaller marks to be optically identified.

For example, when a material having a high transmittance in a portion having a high light intensity is used as the mask layer, the effective spot is reduced by utilizing the fact that the transmittance is high only in the central portion of the spot. be able to. Due to such an effect, even a small size (high-density recording information) that cannot be reproduced without the mask layer 3 can be reproduced without changing the wavelength or the lens numerical aperture of the optical head of a reproducing apparatus for an ordinary optical recording medium. become able to.

As the material of the mask layer 3, various materials having the above-mentioned properties can be used, and a thermochromic substance, a saturable absorptive substance, a phase change substance, a photochromic substance, a photorefractive substance and the like can be mentioned. You can Examples of the thermochromic substance include an electron-donating color developing compound and an electron-accepting color developing agent, a mixed system of a polar compound or a mixture of an electron donating color developing compound and a phenol type color developing material. Examples of the electron-donating color-forming compound include fluoran compounds, spiropyran compounds, phthalide compounds, and lactam compounds.

For the saturable absorbent substance, various dye materials can be applied, and as the phase change substance, a metal or non-metal compound such as germanium, antimony, tellurium alloy or the like can be used. Various photochromic dye materials can be used as the photochromic substance.

The reflective layer 5 is similar to the metal reflective layer generally used in optical disks, and is formed of a thin film of metal or alloy such as gold or aluminum. The protective layer 6 provided on the reflective layer 5 is provided as necessary for the purpose of protecting the medium. The protective layer 6 can be easily formed by providing an ultraviolet curable resin by spin coating. The recording layer 2 provided on the recordable optical disk 11 is formed of a conventionally known optical recording material by spin coating or vapor deposition.
Various materials such as phase change materials and magneto-optical materials can be used.

Next, an optical disc based on the above embodiment,
An optical disc for comparison was prepared, an experiment was conducted, and the evaluation was performed. The present invention is not limited to these examples, and it goes without saying that the same effect can be obtained as the material of the mask layer 3 as long as it is a substance capable of producing a desired mask effect.

The optical discs of the above-mentioned two embodiments are provided on the polycarbonate resin injection-molded substrate 1 in which signals are provided as pits with various pit sizes and track pitches and the recording density is about 5 times that of the compact disc. Then, the mask layer 3 was formed. The mask layer 3 was formed by a vacuum deposition method using GN-169 (manufactured by Yamamoto Kasei Co., Ltd.) as an electron-donating coloring compound and a thermochromic dye of bisphenol A as a developer. Reflective layer 4 on it
As the protective layer 5, and an ultraviolet curable resin SD-17 (manufactured by Dainippon Ink) as the protective layer 5.

The optical disk manufactured by the above method is used for the wavelength 6
Playback is performed by a player equipped with a laser diode of 70 nm and an objective lens with a numerical aperture of 0.6 (reproduction conditions are linear velocity CL
V3 m / s, rotation speed 1000 rpm, reproduction power about 1.
5 mw) A good reproduction signal could be obtained. When the reproduction light intensity was 1 mw or less, good reproduction could not be performed. This means that mask hardening cannot be exhibited below the threshold strength,
This indicates that reproduction is impossible. In general, the reproduction light intensity is almost 0.5 mw or less, and reproduction cannot be performed with this light intensity.

When the mask layer 3 made of GeSbTe phase change material was provided on the same substrate by sputtering, the reproducing light intensity was 8 mw. When a phthalocyanine dye exhibiting saturable absorption characteristics is provided as the mask layer 3 by vacuum vapor deposition, the reproducing light intensity is 1.4.
It was mw.

In an ordinary optical recording medium which does not use the mask effect, the information density that can be reproduced by the player used for reproduction is about 3.5 times the density of the compact disc. Since reproduction cannot be performed unless the mask effect is used, if an attempt is made to duplicate the optical recording medium used in the example, the signal reproduced by a dedicated reproducing device must be copied to a plurality of existing recordable media. One-to-one whole-round copying of media is not possible.

The above will be explained generally with reference to FIGS. 5 and 6 for the prevention of duplication by the optical recording medium of the present invention. Originally, the high-density optical recording medium using the mask layer 3 should be reproduced by a dedicated reproducing device having a power higher than that of the normal reproducing light.
m and the optimum reproduction intensity Im. First, consider the case where a regular disc is played back by a dedicated player. As a matter of course, the dedicated reproducing device can output the intensity higher than the threshold intensity of the change in the optical characteristics of the mask layer and the reproducing intensity Ip1> Im of the dedicated reproducing device. Is possible. Further, since it is possible to support the densities up to the readable recording density Dp1 exceeding the density of the recording density Dm of the regular disc, all data can be read. For example, if the recording data is moving image data for a predetermined time, its complete reproduction is possible. It is possible (see (a) of FIG. 5).

Next, let us consider a case where the regular disc is reproduced by a device other than the dedicated reproducing device. In this case, if the reproduction intensity Ip2 of the non-dedicated reproduction device is lower than the optimum reproduction intensity Im,
The mask effect does not occur and reproduction is impossible (see FIG. 5B). If the read limit density Dp2 is lower than the recording density Dm of the regular disk, the device cannot reproduce even if it is capable of producing a reproduction intensity of Im or more (see (c) of FIG. 5), and even if it is higher than Dm. Generally, since the data processing system in the reproducing apparatus does not conform to the format of the data read, the reproduction is possible but the data reproduction is not possible (see (d) of FIG. 5). Further, if it has a function of processing in the same format, it will be substantially the same as a dedicated player and complete playback of data is possible, but playback data will be recorded on another optical recording medium. Even if an attempt is made to make a copy, all the data cannot be recorded, and a one-to-one whole copy cannot be made. This point is the same in the case (A) when the reproduction is performed by the dedicated reproduction device.

Next, consider the case where the copy disc is reproduced, assuming that the copy has been performed. The recording density of copy discs is lower than that of regular discs,
It is not possible to record all the data on the original disc, and complete reproduction of the data is impossible (see (e) in FIG. 6).

It is unthinkable that a copy disc has a higher recording density than a regular disc densified by using a mask layer, and in order to execute it, it costs a lot of equipment. It will have to be done. However, considering such a case as a virtual state, when an attempt is made to reproduce a copy disc by a dedicated playback device, the playback strength of the dedicated playback device is as described above.
Since the intensity is higher than that in the case of reproducing a disc without a mask layer, the reproduction intensity is too high and a good reproduction signal cannot be obtained (see (f) in FIG. 6).

In the case of reproduction by a non-dedicated reproduction device, if the reproduction intensity is not proper, similarly good reproduction cannot be performed (FIG. 6).
(G)). If the read limit density Dp2 is lower than the recording density D0 of the disc even if the reproduction intensity is proper, reproduction is impossible (see (h) in FIG. 6). Also, when the limit density is high, reproduction is possible, but reproduction of data is impossible as in the case of d (see (i) of FIG. 6).

As described above, complete reproduction of data by a combination other than a regular disk and a dedicated reproduction device is usually impossible, and even if reproduction is possible, one-to-one copying cannot be performed due to the amount of data. Unauthorized copying can be prevented, and the copyright of the recorded information on the optical recording medium can be protected.

[0030]

As described above, according to the optical recording medium and the method of manufacturing the same of the present invention, high-density information that cannot be read unless the mask effect is used is recorded. It cannot be played normally except on the device. Further, even if a signal from a dedicated reproducing device is to be copied, since the recording density of the source signal is higher, it is impossible to copy to the same area, and there is a substantial copy protection effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an operation when a light beam is applied to an optical recording medium of the present invention.

FIG. 2 is a schematic diagram showing the relationship between the light spot and the pit row in FIG.

FIG. 3 is a sectional view of an embodiment of the optical recording medium of the present invention.

FIG. 4 is a cross-sectional view of another embodiment of the optical recording medium of the present invention.

FIG. 5 is a flowchart in the case of trying to reproduce using a regular disc.

FIG. 6 is a flowchart in the case of attempting to reproduce using an illegally copied disc.

[Explanation of symbols]

 1, 12 Substrate 2 Recording layer 2A Pit 3 Mask layer 4 Reflective layer 5 Protective layer 10 and 20 Optical recording medium 12A Guide groove

Claims (3)

[Claims] 1. A mask layer whose optical characteristics are reversibly changed by irradiation with light having an intensity equal to or higher than a predetermined value in a predetermined wavelength band is provided outside the recording layer, and the recording layer is already recorded by irradiation with a light beam. In the optical recording medium capable of reading the stored information, the predetermined intensity is higher than the intensity of the light beam used when reproducing information from the general optical recording medium having no mask layer, The material of the mask layer is selected so that a reversible change in the optical characteristics occurs when irradiated with such a high-intensity light beam, and the density of information recorded in the recording layer is set to the mask layer. An optical recording medium characterized by being set higher than the maximum recording density that can be read even when there is no recording medium. 2. The optical recording medium according to claim 1, wherein the amount of the information recorded on the recording layer is 60% or more of the maximum allowable recording capacity of the optical recording medium. 3. Optically readable information is recorded on a recording layer of an optical recording medium at a high density, and the outside of the recording layer is irradiated with light having an intensity equal to or higher than a predetermined value in a predetermined wavelength band. Providing a mask layer whose characteristics change reversibly, setting the high density higher than the maximum recording density to be read even when the mask layer is not present, and the predetermined value includes the mask layer. The intensity of a light beam used when reproducing information from a general optical recording medium is not so high that the reversible change of the optical characteristics occurs when the light beam having such a high intensity is irradiated. A method of manufacturing an anti-duplication optical recording medium, comprising: selecting a material for a mask layer.