JP2001184647A - Optical recording medium and optical recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform multi-level recording of five stages or more onto a recording layer by changing irradiating power of laser beams. SOLUTION: Virtual recording cells 40 in a groove 16 are assumed in the recording layer 12 of an optical recording medium 10, irradiating power of the laser beams is modulated to five stages or more in accordance with information to be recorded every virtual recording cell 40. Whereby, recording marks 48A-48G of different sizes and/or light transmittance of five stages or more are formed, total optical reflectivity in respective virtual recording cells 40 is modulated to a multi-stage, and total reflecting levels in the virtual recording cells 40 including the outside of the recording marks of the laser beams read out in reproducing are changed into five stages or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of irradiating an optical recording medium by switching the irradiation power of a laser beam in multiple stages in accordance with data to be recorded, forming a recording mark corresponding to the irradiation power, and forming the recording mark. Recording medium, optical recording method, and optical recording / reproducing method for multi-level recording.

[0002]

2. Description of the Related Art In contrast to a conventional optical recording medium, in which data is recorded by changing the length of a recording mark (the length of a reflection signal modulation section) in multiple steps, the depth of the recording mark (the depth of the recording mark) is reduced. Many studies have been made on a method of recording a plurality of data in an area of the same length by switching the reflection signal modulation degree in multiple steps.

According to this optical recording method, a plurality of data can be recorded in a depth direction as compared with a case where binary data is simply recorded based on the presence or absence of a pit. The amount can be increased. Therefore,
Since the linear recording density can be improved, a method using holography and an optical recording method using a multilayer recording layer have been proposed.

[0004] Here, the case where data is recorded in multiple stages by using the depth variation of the reflectance is called multi-level recording.

[0005]

In such multi-level recording, it is necessary to shorten the recording mark in order to improve the recording density.

However, if the recording mark is to be made smaller than the beam diameter when the laser used for recording and reading is focused, multilevel recording becomes difficult.

For example, Japanese Patent Laid-Open Publication No. Hei 10-134353 discloses that the amount of laser light is adjusted to perform multi-level recording. Here, when the recording medium is a dye film or a phase change film, a reproduction signal is formed by a difference in reflection between a recorded portion and an unrecorded portion. Therefore, Japanese Patent Application Laid-Open
According to the method disclosed in Japanese Patent No. 34353, the unrecorded stage and the recorded stage have a relationship with or without recording, and are not suitable for multistage recording. More specifically, there is no recorded or unrecorded intermediate state in the phase change film or the dye film.

Further, as disclosed in, for example, JP-A-1-182846, when the amount of light incident on the recording layer is given as a digital amount, the optical recording in which the absorbance of a reactant in the recording layer changes as a digital amount. There is a medium.

However, this optical recording medium is presumed to have a very small absolute value of a change in absorbance with respect to the laser irradiation amount (the number of times), and has not yet been put to practical use.

Further, as disclosed in JP-A-61-211835, the intensity of irradiation light or the number of times of irradiation of the photochromic material is changed to record at different arbitrary color density states. There is an optical recording method.

However, this optical recording method has a problem that the color density state cannot be read in five or more steps when reading by irradiating a laser beam.

The present inventor has discovered a method capable of performing multi-level recording in five or more steps by changing the laser irradiation power even under conditions where the recording mark length is shorter than the focused beam diameter. Further, they have found that a dye material having a gradual change is more suitable as a material for the recording film than a phase change material having a sharp change from unrecorded to recorded due to a temperature rise by laser irradiation.

In view of the above, the present invention utilizes an optical recording medium, such as a CD-R, which has been widely put into practical use, and performs multi-level multi-level recording to obtain good signal quality. It is an object of the present invention to provide an optical recording medium and an optical recording method that enable the above.

[0014]

Means for Solving the Problems The present inventors have conducted intensive studies on an optical recording medium and have found a recording method for performing multi-step recording on an organic dye recording layer. It has been confirmed that multi-level recording of five or more levels can be performed on a medium. In addition, the present inventors have found a recording method for modulating the light reflectance of the entire virtual recording area of a fixed area including the high light reflectance area around the recording mark in multiple steps. It was confirmed that the above high-density multi-level recording could be performed. That is, the above object can be achieved by the following present invention.

(1) An optical recording medium having an organic dye recording layer, which is irradiated with a laser beam while changing its power in five or more steps, to perform multi-level recording of data to be recorded. .

(2) An optical recording medium having an organic dye recording layer, wherein multi-level recording is performed in a depth direction of the organic dye recording layer.

(3) The optical recording medium according to (2), wherein the optical recording medium has a plurality of pits having different depths in advance.

(4) The optical recording medium according to (2) or (3), wherein the optical recording medium has a plurality of pits having a depth corresponding to the number of laser beam irradiation powers.

(5) Information is recorded by irradiating a laser beam to form a recording mark on the recording layer, and
An optical recording medium capable of reading information recorded by irradiating the recording mark with a reading laser beam, wherein the recording layer has an arbitrary unit length in a relative movement direction between the laser beam and the recording layer, and It has virtual recording cells defined in a unit width in a direction perpendicular to the moving direction and continuously set in the moving direction, and the recording layer in the virtual recording cells modulates the irradiation power of the laser beam in five or more steps. It is possible to form a recording mark in which at least one of the size and the light transmittance is different corresponding to the, based on at least one of the area ratio of the recording mark to the virtual recording cell and the light transmittance of the recording mark, An optical recording medium characterized in that light reflectance in the entire virtual recording cell is modulated to enable multi-level recording of information in five or more steps.

(6) The optical recording medium according to (5), wherein a unit length of the virtual recording cell is set substantially equal to a length of a recording mark formed by irradiating a laser beam having a maximum irradiation power.

(7) A groove for laser beam guide is provided along the recording layer, the virtual recording cell is mainly set in the groove, and the unit width is sandwiched between the grooves. The optical recording medium according to (5) or (6), wherein the distance between the center formed in the width direction and the land adjacent to the land is matched.

(8) The unit length in the virtual recording cell is equal to or smaller than the diameter of the beam waist of the reading laser beam (5) to (7).
An optical recording medium according to any of the above.

(9) The optical recording medium according to any one of (1) to (8), wherein information is multi-level recorded in advance on a part of the recording layer.

(10) A plurality of pits and / or a multi-level recorded portion has specific information, and the specific information is information indicating that the medium is an optical recording medium for multi-level recording. (3) The optical recording medium according to (4) or (9).

(11) Specific information indicating that the medium is a multi-level recording medium is recorded on at least one of the virtual recording cell and the multi-level recorded part. Any optical recording medium.

(12) A laser beam guide groove is provided along the recording layer.
(1) to (1) characterized by being partially interrupted
Any of the optical recording media according to 1).

(13) The optical recording medium according to any one of (1) to (12), wherein the recording layer is formed of an organic dye.

(14) Optical recording for recording information by irradiating a laser beam to a recording layer while moving one of the recording layer and the laser beam in a fixed direction with respect to the other, and forming a recording mark on the recording layer. A method, wherein virtual recording cells are continuously assumed in the moving direction in the recording layer, and the irradiation power of the laser beam is set to 5 for each virtual recording cell.
Modulating in stages or more, changing the size of the recording mark formed in the virtual recording cell, by at least one of the area ratio to the virtual recording cell and the light transmittance of the recording mark,
An optical recording method, comprising modulating the light reflectance of the entire virtual recording cell in accordance with the laser beam irradiation power to record information at multi-levels in five or more steps.

(15) The recording layer is made of a material in which at least one of the recording mark size and light transmittance is modulated only in accordance with the irradiation power when the laser beam diameter is constant. And irradiating with a constant laser beam diameter (14).
Optical recording method.

(16) A plurality of pits and / or a multi-level recorded portion of the optical recording medium according to (3), (4) or (9) have specific information, and the specific information is An optical recording medium reproducing method, wherein the method is read at the time of reproducing and / or recording on the optical recording medium.

(17) The recording medium is individually identified or the optical recording medium for multi-level recording is identified by the specific information (16).
Optical recording medium reproducing method.

(18) A plurality of pits having different depths and / or multi-level recording have been recorded in advance on the optical recording medium having the organic dye recording layer, and the laser power of the reading laser is adjusted according to the number of steps. An optical recording medium reproducing method, wherein the number of stages is adjusted.

In the present invention, a laser beam is applied to an optical recording medium having an organic dye recording layer by applying a power of 5 to the optical recording medium.
It is possible to perform multi-level recording of data to be recorded by irradiating in multiple stages or more, and to identify the part by forming several types of bit strings with different depths in advance or performing multi-level recording in advance. information,
That is, it is possible to recognize that the recording medium is the recording medium and read information on the light amount of the laser beam for recording and reproducing the recording medium when reproducing the optical recording medium.

In the present invention, a virtual recording cell is assumed for the recording layer, and the light reflectance of the entire virtual recording cell is read. Therefore, even when the recording mark becomes smaller than the recording beam diameter, the power of the recording laser is reduced. Is adjusted in multiple steps, so that the reflectance can be controlled in multiple steps. In other words, by modulating the laser irradiation power in a state where the cell to be read is fixed, at least one of the size and the light transmittance of the recording mark is modulated, and a fixed area including the recording mark (virtual cell) Multi-level recording was made possible by changing the overall level of light reflectance in multiple steps.

This effect was remarkable in multi-level recording of five or more steps.

In other words, multi-level recording was possible even with the usual method of modulating the length of a recording mark up to about four steps. However, when performing high-density multi-level recording of five or more steps, it is important to control the light reflectance of the entire virtual cell.

This recording method was particularly useful for an optical recording medium having a recording film using an organic dye.

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings.

The optical recording medium 10 according to the embodiment of the present invention is a CD-R using a dye for the recording layer 12, and includes a substrate 14 made of a transparent base material and one surface of the substrate 14 ( The recording layer 12 made of a dye applied to cover the laser beam guide groove 16 formed on the upper surface in FIG. 1), and reflection of gold or silver or the like formed on the upper side of the recording layer 12 by sputtering or the like. Membrane 18
And a protective layer 20 that covers the outside of the reflective film 18.

The light transmissive substrate applicable to the present invention can be arbitrarily selected from various materials used in conventional optical recording media. For example, a polycarbonate resin, a polymethyl methacrylate resin, an epoxy resin, an amorphous polyolefin resin, a polyester resin, and the like can be applied. However, a polycarbonate resin is preferable in terms of moisture resistance, dimensional stability, cost, and the like. It is preferable that irregularities (pre-grooves and pits) representing information such as tracking grooves or address signals are formed on the light transmitting substrate. The irregularities are formed by injection molding a resin material such as a polycarbonate resin. Alternatively, it can be obtained by transferring the unevenness of the matrix (stamper) by extrusion molding.

The unevenness information includes various information for more appropriately performing recording and reproduction on the optical recording medium. Such information is recorded in advance by transferring the information from the stamper and forming a plurality of pits having different depths when the light-transmitting substrate is formed, or when the optical recording medium is manufactured. By performing multi-level recording after the recording, the information can be recorded. Examples of the various information include ID information for individually recognizing the optical recording medium and an optical recording medium type for identifying the optical recording medium as an optical recording medium for multi-level recording. Identification information, information necessary for recording / reproducing such as information for determining the power of a laser beam for recording / reproducing the recording medium, furthermore, time information of the multi-level recorded contents and the information are used as the optical information. There are address information, table of contents information and the like indicating where and what kind of contents are recorded on the recording medium, and these information can be used when recording and / or reproducing the optical recording medium. In the case of a disk-shaped medium, a plurality of pieces of such information may be provided in the vicinity of the innermost circumference, the outermost circumference, or on the disk according to a certain rule.

The dyes used for the recording layer 12 are organic dyes such as cyanine, merocyanine, methine dyes and derivatives thereof, benzenethiol metal complexes, phthalocyanine dyes, naphthalocyanine dyes and azo dyes.

Solvents for the organic dye coating solution include esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform. Amides such as dimethylformamide; hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran, ethyl ether and dioxane; alcohols such as ethanol, n-propanol, isopropanol, n-butanol and diacetone alcohol; Fluorinated solvents such as 3,3-tetrafluoropropanol; glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether Such as over ethers is available,
These solvents can be used alone or as a mixture in consideration of the solubility of the organic dye used. Various additives such as a singlet oxygen quencher, an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution according to the purpose.

The concentration of the organic dye coating solution thus prepared is generally 0.01 to 10% by weight, preferably 0.1 to 10% by weight.
1 to 5% by weight. Spray method,
Spin coating, dipping, roll coating, blade coating, doctor roll, screen printing and the like can be mentioned, among which spin coating is preferable, and generally the thickness of the organic dye recording layer after drying. Is 20
It is formed to have a thickness of about 500 nm.

A light reflection layer is provided on the organic dye recording layer. The light reflection material as the material of the light reflection layer is preferably a material having a high reflectance with respect to laser beam light. Cu, Al, Ni, Pd, Pb, P
Elements such as t, Cr, Ni, and Pt are given, and these are used alone or as an alloy and formed by a sputtering method or a vacuum evaporation method. The thickness of the light reflection layer is generally 10
８００800 nm, preferably 50-300 nm.

On the light reflecting layer, a protective layer is provided for the purpose of physically and chemically protecting the organic dye recording layer, the light reflecting layer and the like. This protective layer may be provided on the side of the light-transmitting substrate on which the organic dye recording layer is not provided, for the purpose of enhancing the scratch resistance and the moisture resistance. In general, an ultraviolet-curable resin is widely used for the protective layer, and a coating solution is prepared as it is or dissolved in an appropriate solvent, and then the coating solution is applied, and the coating solution is irradiated with ultraviolet rays and cured. Form. Various additives such as an antistatic agent, an antioxidant, and an ultraviolet absorber may be added to these coating solutions according to the purpose. The thickness of the protective layer is about 0.1 to 100 μm.

The optical recording medium used in the present invention may be a single-plate type optical recording medium having the above-described configuration, or two optical recording media having the above-mentioned configuration may be provided such that the protective layer is on the inside. By facing each other and bonding with an adhesive or the like, it is also possible to obtain an optical recording medium of a bonding type, using an optical recording medium having the above-described configuration in at least one of the two optical recording media. Thus, a bonding type optical recording medium obtained by bonding can be obtained.

The method of recording on the optical recording medium obtained in this manner is, for example, using a semiconductor laser beam having a wavelength in the range of 770 to 790 nm or a wavelength in the range of 630 to 660 nm as the recording light. The method is performed by irradiating the organic dye recording layer with a laser beam suitable for it while rotating at a constant linear speed or a constant angular speed, so that the organic dye deteriorates. This is done by reading the difference in the amount of light reflected from the part.

According to the present invention, further, an input signal which changes according to data to be recorded is converted into a modulation signal of five or more stages by a modulation signal generator, and this modulation signal is sent to the modulator to increase the power of the laser beam by five stages. Recording is performed by irradiating the optical recording medium with the above-mentioned change. By doing so, information of five or more steps in the depth direction is multi-level recorded in a recording portion of a fixed length, and the amount of reflected light obtained by a laser beam irradiated at the time of reproduction can be changed to five or more steps. Become. That is, while rotating an optical recording medium on which multilevel recording is performed at a constant linear velocity or a constant angular velocity, a laser beam having a power smaller than the power of the laser beam at the time of recording, preferably 1 mW or less, is irradiated, and the reflected light is detected. By doing so, the amount of information per unit length and further the amount of information per unit area increase dramatically.

Further, in the optical recording medium,
By having a plurality of pits having a depth corresponding to the number of laser beam power levels, or by performing multi-level recording in advance on a part of the optical recording medium, these pits and / or multi-level recorded Specific information such as information for individually identifying the recording medium, information for identifying the optical recording medium for multilevel recording, information for determining the power of a laser beam for recording and reproducing the recording medium in a portion By reading the specific information at the time of reproduction and / or recording of the optical recording medium, it is possible to reliably identify the optical recording medium for multi-level recording, further identify them individually, Since the number of laser beam power steps can be determined according to the number of recorded pit steps, more reliable It is possible to perform level recording.

The multi-level recording on the optical recording medium 10 is executed by the optical recording device 30 shown in FIG.

The optical recording apparatus 30 is a CD-R recorder, and rotates the optical recording medium (disk) 10 at a constant linear velocity by a spindle motor 32 via a spindle servo 31. Thus, information is recorded on the optical recording medium (disk) 10 on the recording layer 12 formed as described above.

The laser 36 includes a laser driver 38
And outputs a laser beam. The laser beam irradiation power per one virtual recording cell (details will be described later) 40 shown in FIGS. 1 and 3 is electrically controlled (modulated) by a laser driver 38 according to information to be recorded.
It is supposed to be. In addition to electrical control such as voltage modulation by the laser driver 38, a modulator 41 for changing the amount of transmitted light may be used. As the modulator 41,
An acousto-optic modulator and an electro-optic modulator are used. Further, a modulator that changes the amount of transmitted light according to the overlapping ratio of two polarization elements having different polarization directions may be used.

Reference numeral 42 in FIG. 2 is a recording optical system including an objective lens 42A and a half mirror 42B. Focus tracking of the objective lens 42A is controlled by the focus tracking servo 44 so that the laser beam is focused on the recording layer 12. The movement of the objective lens 42A and the half mirror 42B is controlled by the feed servo 46 from the inner peripheral side to the outer peripheral side at a predetermined speed in synchronization with the rotation of the disk 10.

The spindle servo 31, the laser driver 38, the focus tracking servo 44, and the feed servo 46 are controlled by a controller 50. Recording layer 12
Is input to the control device 50.

Next, the virtual recording cell 40 and the recording marks recorded in the virtual recording cell 40 will be described.

The virtual recording cell 40 is defined to have a unit width in the radial direction and a unit length in the rotating direction of the recording medium. The unit width is equal to or smaller than the beam waist diameter of the laser beam, and is a width that can be arbitrarily selected such as a track pitch or a groove width of the disk 10. Here, the groove width corresponds to the distance between the center in the width direction of the land portion between the grooves and the center in the width direction of the adjacent land portion.

The virtual recording cell 40 of this embodiment is an example.
As shown in FIG. 1, a length (circumferential length) shorter than a beam diameter (diameter of a beam waist) D in the groove 16 in the rotational direction of the disk 10, that is, in the circumferential direction.
And the width is assumed to be equal to the group 16 and is assumed continuously in the circumferential direction.
By irradiating a laser beam every time, the recording marks 48A to 48G schematically illustrated in FIG. 3 are formed according to information to be recorded.

Here, the beam diameter D of the laser beam emitted from the laser 36 at the position of the recording layer 12 is larger than that of the virtual recording cell 40, but the material of the recording layer 12 must be selected. Accordingly, light transmittance modulation regions having different diameters, that is, recording marks 48A to 48G can be formed in the center of the laser beam according to the laser irradiation power. Here, the laser beam is substantially circular. However, since the laser beam is irradiated while rotating the optical recording medium 10, the laser beam relatively moves within the virtual recording cell 40 to become an elliptical shape. It increases according to the laser power.

The reason is that the focused laser beam generally has a Gaussian distribution in the light intensity, but the recording is performed on the recording layer 12 only in a portion where the irradiation energy of the laser beam exceeds a certain threshold value. By changing the irradiation power of the laser beam, the spot size of the laser beam that can be recorded on the recording layer 12 is changed, and thus, for example, seven-stage recording marks 48A to 48G as shown in FIG. 3 can be formed. . However, the light transmittance in each of the recording marks 48A to 48G is not uniform, and generally becomes lower toward the center.

In this case, the size of the range exceeding the threshold value of the irradiation energy of the laser beam, that is, the size of each of the recording marks 48A to 48G and the light transmittance thereof, are virtual when the reading laser beam is irradiated to the virtual recording cell 40. The light reflectance of the entire reflected light including the recording mark in the recording cell 40 and the unrecorded portion around the recording mark is set to seven levels. The light reflectance increases as the size of the recording mark decreases, and reaches a maximum reflectance in a virtual recording cell where no recording mark is formed, and a minimum reflectance in a virtual recording cell where the maximum recording mark 48G is formed.

More specifically, the light reflectance is set in consideration of the area ratio of each of the recording marks 48A to 48G to the virtual recording cell 40 and the light transmittance of the recording marks themselves.

The light transmittance of the recording marks 48A to 48G itself may be changed when the material constituting the recording layer 12 is decomposed and deteriorated by the irradiation of the laser beam and the refractive index changes, or when the thickness of the recording layer 12 changes in the thickness direction. Depends on quantity. If the light transmittance of the formed recording mark portion is zero, this need not be considered.

In the above embodiment, the optical recording medium 10 is
Although the disk is an R disk, the present invention is not limited to this, and is widely applied to other optical recording media.

In the above embodiment, the recording layer 12 uses an organic dye such as cyanine. However, the present invention is not limited to this, and the recording layer 12 may be adapted to the irradiation power of the laser beam. Organic dyes other than those described above may be used as long as they can form recording marks of different sizes in five or more steps.

However, when the above organic dye is used, it is necessary to reliably change the size of the recording mark and the light transmittance in accordance with the irradiation power of the laser beam in five or more steps. did it.

Furthermore, the above embodiment is directed to the optical recording medium 10 on which information such as data is not recorded. However, the present invention is not limited to this, and the information may be divided into five or more steps. Is applied to an optical recording medium on which multi-level recording is performed.

Further, the size of the virtual recording cell 40 set on the recording layer 12 when forming a recording mark by the optical recording device 30 is not limited to the example of the embodiment, but may be a laser beam. Can be any length equal to or less than the beam waist diameter. Further, in an optical recording medium having no groove 16, the size of the virtual recording cell 40 can be set arbitrarily, but the irradiation energy at the maximum irradiation power of the laser beam is
It is preferable to set the virtual recording cell 40 to a length substantially equal to the recording mark formed when the threshold value that causes a change in the recording mark is exceeded.

The laser beam has a substantially circular shape at the position of the recording layer 12.
In addition to A, as shown in FIG. 4, for example, by using a cylindrical lens 42C, the beam shape is
An oval or linear shape that is short in the feed direction of 0 and long in the direction perpendicular to this direction may be used. In this case, since the recording mark 49 is shortened, the virtual recording cell can be further shortened. That is, the recording density can be improved.

Further, as shown by reference numeral 52 in FIG. 1, the optical recording medium 10 has a plurality of pits having different reflectances in advance corresponding to the number of signal modulation stages, or Of a plurality of pits 52 and / or the recording marks 54 of the multi-level recorded portion, the information for individually identifying the recording medium, the multi-level recording light It has specific information such as information for identifying a recording medium, information for determining the power of a laser beam for recording and reproducing the recording medium, and the specific information is used for reproducing the optical recording medium and / or By reading at the time of recording, it is possible to reliably identify the optical recording medium for multi-level recording, to further identify them individually, It is possible or to determine the number of stages of the laser beam power in response to beforehand that is recorded in the number of stages of the pits, it is possible to perform more reliable multi-level recording. Alternatively, as shown by reference numeral 56 in FIG. 1, the same effect can be obtained by providing a groove interruption portion for partially interrupting the groove for laser beam guide. These methods can be used alone or in combination.

[0071]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is described below by showing embodiments of the present invention.

The conditions of Examples 1 to 3 and Comparative Example 1 described below are as follows.

An experiment of multi-level recording was performed using a CD-R using a dye for the recording layer 12 as the recording medium 10.

As a recording method, DDU manufactured by Pulstec (used laser wavelength =
784 nm) by connecting a high-frequency signal generator and an acousto-optic modulator (AOM).

The reproduction evaluation was also performed by connecting a digital oscilloscope to the DDU.

For multi-level recording, the disc is 4.8 m long.
/ Sec while rotating at a constant linear velocity of 4 MHz, ie, the feed time of one virtual recording cell 40 is 0.25 μsec and the laser beam irradiation time is 0.2.
In μsec, recording is performed by changing the irradiation power of the laser beam in six steps by the AOM, and for reproduction, the laser beam of 1 mW is irradiated while rotating at a constant linear speed, and the difference in the amount of reflected light for each virtual recording cell is calculated. Performed by detection.

In this case, the diameter of the recording laser beam on the recording film is 1.6 μm. The size of the virtual recording cell 40 was set to 4.8 m / 4M = 1.2 μm assuming 4 million virtual recording cells in a groove having a width of 0.35 μm equal to the groove and a total length of 4.8 m.

[0078]

Example 1 A 2% organic dye recording layer forming coating solution was prepared by dissolving a cyanine dye in a fluorinated alcohol, and this coating solution was coated on a spiral pregroove (track pitch: 1.6 μm, Groove width: 0.35 μm,
The depth of the pregroove: 0.18 μm) is made of a polycarbonate resin (manufactured by Teijin Chemicals Ltd .: Panlite AD5503) having a diameter of 120 mm.
The pre-groove side surface of the light-transmitting substrate having a thickness of 2 mm was applied by a spin coating method while changing the rotation speed from 200 rpm to 5000 rpm to form an organic dye recording layer having a thickness of about 200 nm from the bottom in the pre-groove. .

The light transmitting substrate used here includes:
A discrimination signal indicating that the optical recording medium is used for multi-level recording and an information signal relating to the power of the laser beam are recorded in advance.

Next, an Ag light reflecting layer was formed on the organic dye recording layer by a sputtering method so as to have a thickness of about 100 nm. Further, an ultraviolet curable resin (SD318, Dainippon Ink and Chemicals, Inc.) was applied onto the light reflecting layer by a spin coating method while changing the rotation speed from 300 rpm to 4000 rpm. After the application, ultraviolet rays were irradiated from above the coating film by a high-pressure mercury lamp to form a protective layer having a thickness of 10 μm.

Using the optical recording medium thus obtained, multilevel recording of the present invention was attempted.

The irradiation power of the laser beam during recording was (1) 3.5 mW, (2) 5.6 mW, and (3)
7.7 mW, (4) 9.8 mW, (5) 11.9 mW,
(6) Recording was performed in 6 steps of 14 mW. At the time of recording, a single signal was recorded over one round of the disk for each irradiation power.

When recording was performed in this manner, six-level multi-level recording could be performed. Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, the jitter value of the recorded signal at this time is compared with a digital oscilloscope LC-534 manufactured by Le Croy.
When taken into EL and measured, good results could be obtained.

The jitter value depends on the shape of a recording mark formed by irradiating the organic dye recording film with a laser beam. The smaller the jitter value, the more reliably the recording mark is formed. This means that the information has been reliably recorded, and thus the reproduction can be performed reliably.

In the jitter value measuring apparatus used this time, considering the case of recording by the conventional binary recording / reproducing method, it can be determined that good recording was performed if the jitter value was 10% or less.

[0087]

Example 2 An optical recording medium was prepared in the same manner as in Example 1 except that a phthalocyanine dye was used. Multilevel recording was attempted in the same manner as in Example 1 using the optical recording medium thus obtained. As a result, multi-level recording could be performed. Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, when the jitter value of the recorded signal at this time was measured in the same manner, good results could be obtained.

[0089]

Example 3 An optical recording medium was prepared in the same manner as in Example 1 except that an azo dye was used. Multilevel recording was attempted in the same manner as in Example 1 using the optical recording medium thus obtained. As a result, multi-level recording could be performed.
Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, when the jitter value of the recorded signal at this time was measured in the same manner, good results could be obtained.

[0091]

Comparative Example 1 CD-R which is a phase change medium as a recording medium
Using W, multilevel recording was attempted in the same manner as in Example 1. The recording power was a maximum of 14 mW.

Further, when the jitter value of the recorded signal at this time was measured in the same manner, it was found that each signal had poor jitter.

Table 1 shows the results of Examples 1 to 3 and Comparative Example 1.

[0094]

[Table 1]

[0095]

Embodiment 4 Using the optical recording medium obtained in the same manner as in Embodiment 1, multi-level recording and reproduction were attempted on Embodiment 1 by changing only the power of the laser beam during recording.
The power of the laser beam at the time of recording is (1)
4.0 mW, (2) 4.5 mW, (3) 5.0 mW,
(4) 5.4 mW, (5) 5.8 mW, (6) 6.2 m
W was recorded in 6 stages. At this time, the recording linear velocity was 1.2 m / s, the recording signal was 700 kHz, and the duty ratio during recording was 70%. The duty ratio referred to here is the ratio of the irradiation time of a laser beam to be irradiated to a unit recording time of a pit formed by recording, for example, for forming a pit having a depth of 10 in the depth direction. , 7 are output, the duty ratio is 70%. At this time, the duty ratio is 10
If it is recorded at 0%, the pit length will be deeper than 10.

When recording was performed in this manner, multi-level recording could be performed. Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, when the jitter value of the recorded signal at this time was measured using an evaluation device (TA320) manufactured by Yokogawa Electric Corporation, good results could be obtained.

This embodiment 4 and the following embodiments 5 and 6
Considering the case of recording by the conventional binary recording / reproducing method, the apparatus for evaluating the jitter value used in the above can judge that good recording could be performed if the jitter value is 35% or less.

[0099]

Example 5 An optical recording medium was prepared in the same manner as in Example 4 except that a phthalocyanine dye was used, and multilevel recording was attempted in the same manner as in Example 4 using the optical recording medium thus obtained. As a result, multi-level recording could be performed. Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, when the jitter value of the recorded signal at this time was measured using an evaluation device (TA320) manufactured by Yokogawa Electric Corporation, good results could be obtained.

[0101]

Example 6 An optical recording medium was produced in the same manner as in Example 4 except that an azo dye was used. Multilevel recording was attempted in the same manner as in Example 4 using the optical recording medium thus obtained. As a result, multi-level recording could be performed.
Also, a discrimination signal indicating that this optical recording medium is used for multi-level recording and a signal of information relating to the power of the laser beam were detected and confirmed.

Further, when the jitter value of the recorded signal at this time was measured using an evaluation device (TA320) manufactured by Yokogawa Electric Corporation, good results could be obtained.

Table 2 shows the results of Examples 4 to 6.

[0104]

[Table 2]

[0105]

According to the present invention, there is provided an optical recording medium having an organic dye recording layer,
The laser beam is irradiated with the power changed in five or more steps, and the recording / reproducing method of multi-level recording of the data to be used for recording enables the multi-level recording in the depth direction of the organic dye recording layer. By forming several types of pit strings having different depths in advance or by performing multi-level recording in advance, the specific information of the portion, that is, for recognizing that the recording medium is used or for recording / reproducing the recording medium. Information on the light amount of the laser beam can be read at the time of reproducing the optical recording medium.

Further, a laser beam is irradiated onto an optical recording medium having a recording layer while changing its irradiation power in five or more steps, and a recording method for multi-level recording of data to be recorded is performed. It has become possible to perform multi-level recording in five or more steps in the depth direction.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view showing a main part of an optical recording medium according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an optical recording apparatus for recording information on the optical recording medium using a laser beam.

FIG. 3 is a schematic diagram showing a relationship between the recording mark, a virtual recording cell, and its light reflectance when a recording mark is formed on a recording layer by the optical recording apparatus.

FIG. 4 is a schematic perspective view showing a case where a laser beam for irradiating a virtual recording cell has another shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical recording medium 12 ... Recording layer 14 ... Substrate 16 ... Groove 18 ... Reflective film 20 ... Protective layer 30 ... Optical recording device 32 ... Spindle 34 ... Disk 36 ... Laser 38 ... Laser driver 40 ... Virtual recording cell 41 ... Modulator 42: Recording optical system 42A: Objective lens 42B: Half mirror 42C: Cylindrical lens 44: Focus servo circuit 46: Feed servo circuit 48A to 48G, 49, 54: Recording mark 52: Pit 56: Groove interruption D: Beam diameter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/24 516 G11B 7/24 522L 522 B41M 5/26 V

Claims (18)

[Claims] 1. An optical recording medium characterized in that a laser beam is applied to an optical recording medium having an organic dye recording layer while changing its power in five or more steps, and data to be recorded is multi-level recorded. 2. An optical recording medium having an organic dye recording layer, wherein multi-level recording is performed in a depth direction of the organic dye recording layer. 3. The optical recording medium according to claim 2, wherein said optical recording medium has a plurality of pits having different depths in advance. 4. An optical recording medium according to claim 2, wherein said optical recording medium has a plurality of pits having a depth corresponding to the number of laser beam irradiation power steps. 5. An optical recording medium capable of recording information by irradiating a laser beam to form a recording mark on a recording layer and irradiating the recording mark with a reading laser beam to read the recorded information. The virtual recording, which is defined on the recording layer by an arbitrary unit length in a direction of relative movement between the laser beam and the recording layer and a unit width in a direction perpendicular to the direction, and is continuously set in the direction of movement. A cell, and the recording layer in the virtual recording cell is:
It is possible to form recording marks having at least one of different sizes and light transmittances in accordance with the modulation of the irradiation power of the laser beam in five or more steps, whereby the area ratio of the recording mark to the virtual recording cell and the recording mark An optical recording medium characterized in that the light reflectance of the entire virtual recording cell is modulated based on at least one of the light transmittances to enable multi-level recording of information in five or more steps. 6. An optical recording medium according to claim 5, wherein a unit length of said virtual recording cell is set substantially equal to a length of a recording mark formed by irradiating a laser beam having a maximum irradiation power. 7. A laser beam guide according to claim 5, wherein a groove for guiding a laser beam is provided along said recording layer.
The virtual recording cell is mainly set in the groove, and the unit width is equal to the distance between the center of the land formed between the grooves and the land adjacent thereto in the width direction. An optical recording medium characterized by being performed. 8. The optical recording medium according to claim 5, wherein the unit length of the virtual recording cell is equal to or less than a diameter of a beam waist of the reading laser beam. 9. An optical recording medium according to claim 1, wherein information is multi-level recorded in advance in a part of said recording layer. 10. A multi-level recording optical recording medium according to claim 3, wherein the plurality of pits and / or the multi-level recorded portion has specific information. An optical recording medium characterized by being information. 11. The multi-level recording medium according to claim 5, wherein at least one of the virtual recording cell and the multi-level recorded portion has specific information indicating that it is a multi-level recording medium. Optical recording medium. 12. The method according to claim 1, wherein
An optical recording medium, wherein a groove for laser beam guide is provided along the recording layer, and the groove is partially interrupted. 13. The method according to claim 1, wherein
An optical recording medium, wherein the recording layer is formed from an organic dye. 14. An optical recording method for recording information by irradiating a laser beam onto a recording layer while moving one of the recording layer and the laser beam in a certain direction with respect to the other, thereby forming a recording mark on the recording layer. In the recording layer, virtual recording cells are continuously assumed in the moving direction, and the irradiation power of the laser beam is modulated in five or more stages for each virtual recording cell, and formed in the virtual recording cell. The size of the recording mark to be changed is changed, and the light reflectance of the entire virtual recording cell is modulated according to the laser beam irradiation power by at least one of the area ratio to the virtual recording cell and the light transmittance of the recording mark. And a multi-level recording of information in five or more stages. 15. The recording layer according to claim 14, wherein at least one of the recording mark size and the light transmittance is modulated only in accordance with the irradiation power when the beam diameter of the laser beam is constant. An optical recording method comprising irradiating a laser beam with a constant beam diameter. 16. The optical recording medium according to claim 3, wherein a plurality of pits and / or multi-level recorded portions have specific information, and the specific information is used for reproducing the optical recording medium. And / or an optical recording medium reproducing method, which is read at the time of recording. 17. An optical recording medium reproducing method according to claim 16, wherein said specific information is used to individually identify said recording medium or to identify an optical recording medium for multi-level recording. 18. An optical recording medium having an organic dye recording layer,
An optical recording medium reproducing method, characterized in that a plurality of pits having different depths and / or multi-level recording have been recorded in advance, and the number of laser power steps in the reading laser is adjusted according to the number of steps.