JP2668604B2 - Optical information recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording information on an information recording medium by light.

[0002]

2. Description of the Related Art A general DRAW (Direct Read After Wr.)
An information recording medium of the (ite, writable) type has a disc-shaped transparent substrate made of plastic, glass or the like as a basic structure, and a metal or semi-metal such as Bi, Sn, In, Te, etc. A recording layer made of dyes such as dyes. Writing of information on the recording medium is performed, for example, by irradiating the recording medium with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally rises in temperature, resulting in physical changes such as pit formation. Alternatively, information is recorded by causing a chemical change to change its optical characteristics. Reading of information from the optical disk is also performed by irradiating the optical disk with a laser beam, and information is reproduced by detecting reflected light or transmitted light corresponding to a change in the optical characteristics of the recording layer.

The above laser beam irradiation is performed by moving (guided) a laser along a pre-groove formed of an annular groove (including a spiral shape in the present invention) formed on a substrate. . Such a pre-groove is generally formed from the inner peripheral side of the substrate (generally, a mirror portion is about 5 mm radially outward from the inner peripheral edge) to the outer peripheral side (from the outer peripheral end or from the outer peripheral end to 1 to 3 mm inner peripheral side). ing. In addition, as a substrate for an optical disc, generally, the diameter is 5 inches (120 mm) and 5.25 inches (130 m).
m), 3.0 inches (80 mm) and 3.5 inches (90 mm) are used.

Among the recording layer materials, a recording layer using a dye can be easily formed by applying a dye coating solution in which a dye is dissolved in a solvent to a substrate and drying it. Therefore, it is clearly advantageous in manufacturing as compared with the metal recording layer that needs to be formed by vacuum vapor deposition or the like. Therefore, recently, many examples of using dyes as recording layer materials have been found.
Since the recording layer made of a dye generally has a low reflectance of about 30%, a DRAW type CD (a CD format signal used for an audio CD is used as a recording signal)
When information can be reproduced by a commercially available CD player, that is, when high reflectance is required, a reflective layer is generally provided. As an example of such a DRAW type CD, an optical disc having a structure in which a dye recording layer, a reflective layer of Au and a protective layer are laminated in this order on a polycarbonate substrate is Nikkei Electronics (page 107, issued January 23, 1989). It is described in.

On the other hand, a general audio CD that can be played on a commercially available CD player, which is a read-only optical disc.
The (compact disc) is manufactured by forming and molding a stamper from a cutting original plate. For this reason, it can be applied to software that is expensive to manufacture and can be sold in large quantities. However, when creating a small number of CD software or the like (an optical disk on which the same information is recorded) such as several or tens of pieces, For example, the CD-D
It was carried out by recording on a RAW (a dye recording layer, a reflective layer and a protective layer were laminated on a substrate).
That is, while the CD-DRAW is rotated at a CD reproduction linear velocity of 1.2 to 1.4 m / sec, the oscillation wavelength 780
Information was recorded by irradiating the pregroove with a laser having a wavelength of nm, and a small amount of CD software or the like was generally created. In such a creation method, since the linear velocity at the time of recording is equal to the reproduction linear velocity, it takes the same time as the reproduction time of one CD software to produce one CD software. Therefore, it is desired to reduce the time required for recording.

[0006]

As a method therefor, a method of increasing the laser power and recording at a high linear velocity can be considered. That is, information is recorded by setting a high linear velocity and increasing the oscillation frequency of the laser as the velocity increases. However, according to the study of the present inventors, it has been found that simply increasing the oscillation frequency with an increase in speed does not provide a practically sufficient reproduced signal.

An object of the present invention is to provide an optical information recording method capable of easily producing an optical disk (CD software or the like) on which a relatively small amount of the same information is recorded, such as several or several tens of sheets. I do. Further, the present invention provides an optical disk (CD software or the like) on which a relatively small amount of the same information is recorded, and which can record an EFM signal having excellent reproduction characteristics, particularly, jitter. An object of the present invention is to provide an information recording method.

[0008]

An object of the present invention is to provide an information recording medium having a recording layer provided on a disk-shaped substrate provided with a pregroove on its surface, and a linear velocity at the time of reproducing a predetermined recorded information. When recording an EFM signal by irradiating a laser from the substrate side while rotating at a higher linear velocity, the pulse width T _LD (n) of the laser for recording a pit having a pit length nT to be recorded is set as follows. (1) to (3): T _LD (n) = (nm) T (1) m = 2 x V ₁ / Va (2) T = T ₁ x V ₁ / V (3) [however, , T _LD (n) (ns) represents the laser pulse width during pit recording with a pit length of nT, n represents an integer of 4 to 11, and T (ns) represents a clock cycle during recording, and T
₁ (ns) represents the clock cycle during reproduction, and V ₁ (m /
S) represents the linear velocity during reproduction, V (m / sec) represents the linear velocity during recording, and a represents a constant in the range of 0.5 to 1.5]. The pulse width T _LD (3) of the laser for modulating and recording a pit having a pit length of 3T is set to the above (2) and (3) and the following (4): T _LD (3) = (nm−f) ) T (4) [where T _LD (3) (ns) represents the pulse width of the laser at the time of pit recording with a pit length of 3T, T (ns) represents the clock period during recording, and f is 0. It represents a constant in the range of 03 to 0.6, and m has the same meaning as above], and the recording is performed by modulating the information to record.

The preferred embodiments of the optical information recording method of the present invention are as follows.

1) The above optical information recording method, wherein a is in the range of 0.8 to 1.2.

2) The above-mentioned optical information recording method, wherein f is in the range of 0.1 to 0.4.

[0012] 3) V ₁ is, the optical information recording method comprising in the range of 1.2 to 1.4 m / sec.

4) The above optical information recording method, wherein V ₁ / V is 1/15 or more and less than 1.

5) V ₁ / V is 1/12 or more and 1/2
The optical information recording method described above, wherein

6) The optical information recording method, wherein the laser irradiation is performed while tracking the pregroove by a three-beam method.

7) The optical information recording method as described above, wherein mT represents a light emission time shortened from the end of the light emission time of a laser having a pit length of nT or 3T.

8) The optical information recording method as described above, wherein fT represents the emission time of the laser applied immediately after the emission time of the laser having a pit length of 3T.

9) The optical information recording method described above, wherein the recording layer is a layer made of a dye.

10) The above optical information recording method, wherein a reflective layer made of metal is provided on the recording layer.

(11) The optical information recording method, wherein a reflective layer and a protective layer made of metal are provided in this order on the recording layer.

[0021]

As described above, when recording an EFM signal by irradiating a laser while rotating the medium at a linear velocity higher than the linear velocity at the time of reproduction in order to record information on the information recording medium, By increasing the frequency in proportion to the linear velocity and modifying the pulse width so as to satisfy the above conditions, it is possible to obtain a reproduced signal with excellent reproduction characteristics such as jitter even at high speed recording. it can. As a result, the recording time can be shortened, that is, the linear velocity during recording can be increased. Therefore, a relatively small amount of CD software or the like of several or several tens of sheets can be easily created in a short time. By optically recording the EFM signal in this way, it is considered that the pit interval formed in the recording layer becomes appropriate and that the pit shape is made uniform, thereby significantly improving the jitter of the obtained reproduced signal. Can be further,
Since the optical recording of the present invention can be implemented by a simple circuit, an inexpensive recording device can be used.

[Detailed Description of the Invention] An information recording medium used in the optical information recording method of the present invention has a basic structure in which a recording layer is laminated on a substrate. Further, the recording layer is a dye recording layer,
It is preferable that a reflective layer is formed thereon.

The optical information recording method of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a disc-shaped substrate 11 having a pregroove, a recording layer 12 made of a dye provided on the substrate, a reflective layer 13 made of a metal provided on the recording layer, and a protection layer provided on the reflective layer. A state in which information is recorded by irradiating a laser 16 from the substrate side and condensing the laser on the recording layer on the pregroove bottom 15 of the substrate while rotating the information recording medium 10 composed of the layer 14 is shown. I have. The reproduction of the recorded information is basically the same except that the laser power is reduced and the rotation speed is reduced.

In the present invention, when the laser 16 is irradiated from the substrate 11 side to record the EFM signal while rotating the information recording medium 10 at a linear velocity higher than the linear velocity at the time of reproducing the information, Laser pulse width T for recording pits with a pit length nT to be recorded with respect to increase
_LD (n) is set to the following conditions (1) to (3): T _LD (n) = (nm) T (1) m = 2 × V ₁ / Va (2) T = T ₁ × V ₁ / V (3) [where T _LD (n) (ns) represents the pulse width of the laser at the time of pit recording with a pit length of nT, n represents an integer of 4 to 11, and T (ns) represents during recording. Represents the clock cycle (generally the same as the unit pit length), T ₁ (ns) represents the clock cycle during reproduction (unit pit length), V ₁ (m / sec) represents the constant linear velocity during reproduction, V (m / sec) represents a constant linear velocity at the time of recording, and a represents a constant in the range of 0.5 to 1.5], and a pit having a pit length of 3T is recorded. Pulse width T _LD for laser
(3) is replaced by the above (2) and (3) and the following (4): T _LD (3) = (nm + f) T (4) [where T _LD (3) (ns) is a pit length of 3T. T (ns) represents a clock cycle (unit pit length) at the time of recording, and f represents 0.03.
Representing a constant in the range of .about.0.6, and m having the same meaning as above], the recording is performed by modulating.

In the optical information recording method of the present invention, an EFM signal is used as a recording signal, and the EFM signal generally comprises pits having a pit length of 3T to 11T. T is EFM
In the case of a signal, it is generally 231.4 ns during reproduction. The optical information recording method of the present invention for recording the EFM signal at a high speed will be specifically described with reference to FIGS.

FIG. 2A shows an arbitrary pit to be recorded among the pits having a pit length of 4T to 11T.
(B) Pit and length to be recorded (ns: nanosecond)
Shows the pulse width (ns) of the same laser, and (c) and (d) show the pulse width (light emission time) at the time of actual recording.

In (a), two types of pits having different pit lengths of 4T and 6T are shown as pits to be recorded. (B) shows laser pulse widths (ns) corresponding to two different pit lengths of 4T and 6T. These correspond to pit lengths 4T and 6T of two types of pits, respectively, and have the same pit length and pulse width. (C) shows the pulse width (ns) of the laser of the present invention for forming the pits shown in (a). That is, the pulse width of the laser for forming a pit having a pit length of 4T is (4-m) T [that is, 4T-mT], and the pulse width for forming a pit having a pit length of 6T is (6-m). T [that is, 6T-mT]. mT
Is the emission time shortened from the end of the emission time of the laser having the pit length nT. mT often takes a positive value when the ratio (V ₁ / V) of the linear velocity at the time of reproduction to the linear velocity at the time of recording is large, about _１ ／, but when V ₁ / V is small (particularly 1/3). In the following, the pulse width becomes almost negative, and in this case, the pulse width becomes longer as shown in (d). The mT is preferably a light emission time shortened from the end of the light emission time of the laser having the pit length nT,
It may be before the light emission time or may be distributed before and after.

Next, a method of recording 3T pits will be described with reference to FIG. 3A shows a pit to be recorded, FIG. 3B shows a laser pulse width (ns) having the same length (ns: nanosecond) as the pit to be recorded, and FIG.
And (d) show the pulse width (light emission time) when actually recording.

FIG. 3A shows a pit having a pit length of 3T as a pit to be recorded. (B) shows the laser pulse width (ns) corresponding to the pit length of 3T. This corresponds to a pit length of 3T, and the pit length and the pulse width are the same. (C) shows the pulse width (ns) of the laser of the present invention for forming the pits shown in (a). That is, the pulse width of the laser for forming a pit having a pit length of 3T is (3-m + f) T [that is, 3T-mT].
+ FT = 3T- (mT-fT)]. (MT-f
T) is the light emission time shortened from the end of the light emission time of the laser having a pit length of 3T. m often takes a positive value when the ratio of the linear velocity at the time of reproduction to the linear velocity at the time of recording (V ₁ / V) is about 1/2, but when V ₁ / V is small (particularly 1 / V). 3 or less, it is almost negative.
-FT) also has a positive value when V ₁ / V is large, and V ₁
When / V is small, it becomes almost negative. Therefore, V ₁ / V
When V ₁ / V is large, the pulse width becomes narrower as shown in (c), and when V ₁ / V is small, the pulse width becomes long as shown in (d). The above (mT-f
T) is preferably a light emission time that is shortened (or lengthened) from the end of the light emission time of the laser having the pit length nT, but may be before the light emission time or may be sorted back and forth.

As described above, according to the present invention, the information recording medium 10 is rotated at a linear velocity higher than the linear velocity when reproducing recorded information. Therefore, the laser power of the laser 16 for recording the above information is slightly higher than that of the laser 16 for recording at the same speed as during reproduction. It is preferable to increase the power by about 2 to 50% of the percentage (%) of the increase in the speed. In particular, the range of 5 to 30% is preferable. Further, among the above constants, a is preferably in the range of 0.8 to 1.2, and f is preferably in the range of 0.1 to 0.4. V ₁ is a line speed at the time of reproduction,
Although not particularly limited, it is preferably in the range of 1.2 to 1.4 m / sec. The ratio of the linear velocity during reproduction to the linear velocity during recording (V ₁ / V) is generally 1/15 or more and less than 1, and preferably 1/12 or more and less than 1/2, The range is more preferably from 1/12 to 2/5, most preferably from 1/12 to 1/3. As described above, since information can be recorded much faster than reproduction by recording, an optical disk (CD software) on which a relatively small amount of the same information is recorded, such as several or several tens of sheets, is recorded for a short time. And can be easily created.

As described above, the information recording according to the present invention is performed, for example, on the information recording medium at the above-mentioned constant linear velocity (in the case of the CD format, it is higher than the reproducing speed of 1.2 to 1.4 m / sec). Recording light such as semiconductor laser light is emitted from the substrate side while rotating. The oscillation wavelength of the laser is
500-900 nm (preferably 650-850 nm)
Is common. The recording power is generally 5 to 10 mW. Information is recorded by forming a cavity in the recording layer by irradiation with light, or by changing the refractive index of the recording layer due to discoloration, change in association state, or the like.

The information recording medium used in the recording method of the present invention can be manufactured, for example, as follows. The disc-shaped substrate can be arbitrarily selected from various materials used as a substrate of a conventional information recording medium. As a substrate material, for example, glass; polycarbonate; acrylic resin such as polymethylmethacrylate; polyvinyl chloride,
Examples thereof include vinyl chloride resins such as vinyl chloride copolymers; epoxy resins; amorphous polyolefins and polyesters, and may be used in combination if desired. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoint of moisture resistance, dimensional stability, cost, and the like.

An intermediate layer is provided on the substrate surface of the information recording medium on the side where the recording layer is provided, for the purpose of improving flatness, improving adhesive strength, improving sensitivity and preventing deterioration of the recording layer. Examples of the material of the intermediate layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol,
N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin,
High molecular substances such as polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, comb type graft polymer; and pigments, silver acetylide compounds, silane coupling agents, etc. Organic substances.

The intermediate layer is prepared, for example, by dissolving or dispersing the above substance in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. The thickness of the undercoat layer is generally 0.1.
005 to 20 μm, preferably 0.01 to
It is in the range of 10 μm.

On the disc-shaped substrate, a tracking pre-groove representing information such as address signals or music information is formed. Further, pre-pits may be formed as desired. When a resin material such as the above polycarbonate is used, pits and grooves are preferably provided directly on the substrate by injection molding or extrusion molding of the resin material.

The formation of the groove or the like may be performed by providing a pre-groove layer. As a material for the pregroove layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used. The pre-groove layer is formed by first applying a mixed solution composed of the above-mentioned acrylate and a polymerization initiator on a precisely formed master (stamper), and then placing a substrate on the coating solution layer. The liquid layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the liquid phase. Next, the substrate provided with the pre-groove layer is obtained by peeling the substrate from the matrix. The thickness of the pre-groove layer is generally 0.
In the range of from 0.5 to 100 μm, preferably from 0.1 to 5 μm.
The range is 0 μm. The shape of the pregroove has a depth of 2
0 nm to 200 nm is preferable, and especially 30 to 170 nm
Is preferred. The half width is preferably from 0.2 to 1.2 μm, particularly preferably from 0.6 to 1.0 μm.

A recording layer is provided on the disk-shaped substrate. As a material for the recording layer, a conventional material such as a metal, a metal compound, a dye or a polymer compound can be used. Among them, dyes are preferred.

Examples of the dye include cyanine dyes such as indolenine dyes, imidazoquinoxaline dyes and indolizine dyes, phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, pyrylium / thiopyrylium dyes, and azurenium dyes. Dyes, squalilium dyes, metal complex dyes such as Ni and Cr, naphthoquinone and anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, merocyanine dyes,
Examples thereof include oxonol type dyes, aminium type / diimmonium type dyes, and nitroso compounds.

The dye layer is formed by dissolving the above dye, and optionally a binder, a metal complex salt dye or an aminium-diimmonium dye (quencher) in a solvent to prepare a coating liquid, and then applying this coating liquid. It can be carried out by coating the surface of the substrate to form a coating film and then drying.

Examples of the solvent for preparing the dye coating solution include esters such as ethyl acetate, butyl acetate and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, dichloromethane, tetrachloroethane, 1,2-dichloroethane and chloroform. Halogenated hydrocarbons, tetrahydrofuran,
Ethers such as ethyl ether and dioxane, alcohols such as ethanol, n-propanol, isopropanol and n-butanol, amides such as dimethylformamide, cellosolves such as propylene glycol monomethyl ether and propylene glycol monoethyl ether, 2, 2, 3, 3 -Fluorinated solvents such as tetrafluoropropanol. These non-hydrocarbon organic solvents may include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents as long as the content is within 50% by volume. .

Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution according to the purpose.

When a binder is used, the binder may be
For example, natural organic polymer substances such as gelatin, dextran, rosin and rubber; and cellulose derivatives such as nitrocellulose and cellulose acetate; hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene, polyvinyl chloride, polyvinylidene chloride, Vinyl resins such as polyvinyl chloride / polyvinyl acetate copolymers,
Synthetic organic polymers such as acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol and formaldehyde resins Substances can be mentioned.

Examples of the coating method include a spray method, a spin coating method, a dipping method, a roll coating method, a blade coating method, a doctor roll method and a screen printing method.

As a coating method for reducing the layer thickness of the dye recording layer on the outer peripheral side of the substrate of the present invention, for example, a dye coating solution is applied by a spin coating method at a rotation speed of 100 to 200 rpm for 5 seconds and then 1 30 to 80 rpm per second 18
Increase the speed to 00 ~ 2500rpm, 1800 ~
The dye recording layer is formed by drying by holding at 2500 rpm for 10 to 60 seconds. That is, it is mainly necessary to increase the final rotation speed to a somewhat large value.

When a binder is also used as a material for the dye layer, the ratio of the dye to the binder is generally 0.01 to 99.
% (Weight ratio), preferably 1.0 to 95%
(Weight ratio).

The recording layer may be a single layer or a multilayer, but the layer thickness is generally in the range of 10 to 550 nm, preferably 20 to 300 nm.

A reflective layer is preferably provided on the recording layer. The light-reflecting substance, which is the material of the reflecting layer, is a substance having a high reflectance for the laser light.
g, Se, Y, Ti, Zr, Hf, V, Nb, Ta, C
r, Mo, W, Mn, Re, Fe, Co, Ni, Ru,
Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, C
d, Al, Ga, In, Si, Ge, Te, Pb, P
Metals and metalloids such as o, Sn and Bi can be mentioned. Of these, preferred are Al, Au, C
r and Ni. These substances may be used alone or in combination of two or more kinds or as an alloy.

The reflective layer can be formed on the substrate by vapor deposition, sputtering or ion plating of the above-mentioned light-reflecting substance. The thickness of the reflective layer is generally in the range from 10 to 300 nm.

An enhancement layer may be provided between the dye recording layer and the reflection layer. Examples of the material include a comb-type graft polymer (eg, macromer (manufactured by Toa Gosei Chemical Industry Co., Ltd.)), silver acetylide, and the like. Of course, such an enhancement layer may be provided on the metal recording layer.

A protective layer is preferably provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the like. This protective layer may be provided on the side of the substrate on which the recording layer is not provided for the purpose of improving the scratch resistance and the moisture resistance.

Examples of the material used for the protective layer include Si
Inorganic substances such as O, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ ; and organic substances such as thermoplastic resins, thermosetting resins, and UV curable resins.

The protective layer can be formed, for example, by laminating a film obtained by extrusion processing of plastics on the recording layer (reflection layer) and / or the substrate via the adhesive layer. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating. Also,
In the case of a thermoplastic resin or a thermosetting resin, they can also be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. In the case of a UV-curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure. Various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added to these coating solutions according to the purpose. When the protective layer forming material is applied directly on the recording layer, a polybutadiene or the like is applied on the recording layer to protect the recording layer from the dissolving effect of the coating liquid for the protective layer (in this case, a solvent which does not dissolve the recording layer) Is preferable to provide an intermediate layer. The intermediate layer may be provided by depositing a thin film of metal or the like. The thickness of the protective layer is generally in the range from 0.1 to 100 μm.

Further, instead of forming the protective layer on the dye recording layer, the recording layer may be protected by providing a plastic film on the recording layer by fusion bonding on the inner and outer circumferences of the substrate. .

In the present invention, the information recording medium may be a single plate having the above-described structure, or two substrates having the above-described structure may be faced so that the recording layer is on the inside, and an adhesive or the like may be used. It is also possible to manufacture a pasting type recording medium by bonding using. Alternatively, an air sandwich type recording medium is manufactured by joining a substrate having the above configuration to at least one of the two disk-shaped substrates via a ring-shaped inner spacer and a ring-shaped outer spacer. You can also.

The information recording medium used in the present invention can be manufactured by the above method.

The information recording method is as described above, but the reproduction is performed, for example, as follows.

The information recorded as described above is reproduced by a semiconductor laser while rotating the information recording medium at a constant linear velocity (1.2-1.4 m / sec which is the reproducing velocity in the case of the CD format). It can be performed by irradiating light from the substrate side and detecting the reflected light. The oscillation wavelength of the laser is 500 to 900 nm (preferably 650 to 900 nm).
850 nm), and the power during reproduction is generally 0.05 to 1 mW.

[0058]

EXAMPLES Examples and comparative examples of the present invention will be described below. However, these examples do not limit the present invention.

[Sample 1] Disc-shaped polycarbonate substrate (outer diameter: 120 mm, inner diameter: 15 mm, thickness: 1.
2 mm, refractive index: 1.58, pre-groove: track pitch: 1.6 μm, half-width of pre-groove: 0.45 μ
m, a depth of 40 nm, and a diameter of 44 to 117 mm) were prepared as substrates for optical disks.

Dye A below: Dye A

[0061]

Embedded image

3.25 g and the following dye B: dye B

[0063]

Embedded image

0.325 g was dissolved in a mixed solvent consisting of 75 ml of 2,2,3,3-tetrafluoro-1-propanol, 20 ml of propylene glycol monoethyl ether and 5 ml of tetrachloroethane by applying ultrasonic waves for 1 hour to obtain a dye. A recording layer coating solution was prepared.

From the inner peripheral side of the disk-shaped polycarbonate substrate, the coating solution was spin-coated at a rotation speed of 20.
After applying for 5 seconds at a speed of 0 rpm, 50 rpm for 1 second
The dye having a layer thickness of 120 nm at the bottom of the pre-groove and a layer thickness of 120 nm between the pre-grooves (lands) was obtained by keeping the speed at 1000 rpm for 5 seconds to dry it, and further holding at 1700 rpm for 15 seconds. A recording layer was formed.

On the dye recording layer, Au was subjected to DC sputtering (Ar pressure: 2 Pa, power: 200 W) to form a reflective layer having a thickness of 100 nm up to a substrate diameter of 118 mm.

Further, an ultraviolet curable resin (trade name: 3070, manufactured by ThreeBond Co., Ltd.) was applied on the reflective layer by a spin coating method at a rotation speed of 200 rpm for 5 seconds, and then at a rotation speed of 1500 rpm for 30 seconds. The layer was leveled and then cured by irradiating it with ultraviolet rays (high-pressure mercury lamp 200 W / cm) for 10 seconds to form a protective layer having a layer thickness of 2 μm (a layer thickness of the outer peripheral end surface of 2 to 10 μm).

Thus, an information recording medium comprising the substrate, the dye recording layer, the reflection layer and the protective layer was manufactured. The half width and depth of the pregroove of the substrate and the thickness of the dye recording layer were obtained by measuring the cross section of the substrate with an ultra-high resolution SEM (scanning electron microscope).

[Example 1] Information was recorded on the information recording medium obtained in Sample 1 under the following conditions. Recording was performed using an optical disk evaluation device DDU1000 (manufactured by Pulstec Corporation) as a recording / reproduction evaluation device. That is,
Using an optical head having an oscillation wavelength of 780 nm and an NA of 0.5, an EFM signal in CD format at a power of 5 to 10 mW (changed every 0.5) and a linear velocity (V) of 2.8 m / sec. The clock period (T) is 115.7 ns, a in the above condition (2) is 1.0, and f in the above condition (4) is 0.
22 (that is, T _LD (n) = nT, T _LD (3) = 2.78)
Then, the information was recorded on the information recording medium at a position of 72 mm in diameter.

[Example 2] Information was recorded in the same manner as in Example 1 except that the following conditions were applied to the information recording medium obtained in Sample 1. Linear velocity (V): 4.2 m / sec, clock period (T): 7
7.13 ns and a under the condition (2): 1.17 (that is, T _LD (n) = (n + 0.5) T, T _LD (3) = 3.2).
8T).

[Example 3] Information was recorded in the same manner as in Example 1 except that the following conditions were applied to the information recording medium obtained in Sample 1. Linear velocity (V): 5.6 m / sec, clock cycle (T): 5
7.85 ns, f: 0.06 in the condition (4) and a: 1.0 in the condition (2) (that is, T _LD (n) = (n +
0.5) T, T _LD (3) = 3.39T).

Reference Example 1 Information was recorded on the information recording medium obtained in Sample 1 in the same manner as in Example 1 except that the following conditions were used. Linear velocity (V): 1.4 m / sec, clock cycle (T): 2
31.4 ns, a: 1 in the condition (2) (that is, T _LD
(n) = (n-1) T, T _LD (3) = 2.28T). This condition is based on Japanese Patent Application No. 3-81460 filed by the present inventor.
This is a good recording condition in which a low jitter can be obtained when recording is performed at the same linear velocity as in the reproduction described in the above item.

Comparative Example 1 Information was recorded on the information recording medium obtained in Sample 1 in the same manner as in Example 1, except that the following conditions were used. Linear velocity (V): 4.2 m / sec, clock period (T): 7
7.13 ns and a of the above condition (2): -0.3 (that is, T _LD (n) = (n-1) T, T _LD (3) = 2.28
T).

Comparative Example 2 Information was recorded on the information recording medium obtained in Sample 1 in the same manner as in Example 1 except that the following conditions were used. Linear velocity (V): 4.2 m / sec, clock period (T): 7
7.13 ns and a of the above condition (2): 1.67 (that is, T _LD (n) = (n + 1) T, T _LD (3) = 3.28
T).

[Comparative Example 3] In Example 1, the information recording medium obtained in Sample 1 was used except that the following conditions were satisfied.
Information was recorded in the same manner as described above. Linear velocity (V): 4.2 m / sec, clock period (T): 7
7.13 ns, a: 0.67 in the condition (2) and f in the condition (4) are set to 0 (that is, T _LD (n) = nT, T
_LD (3) = 3T).

[Evaluation of Recorded Information Recording Medium] 1) Recording Sensitivity The recorded optical disk obtained in each of the above examples has an oscillation wavelength of 7
Using an optical head of 80 nm and an NA of 0.5, a power of 0.5 mW, a linear velocity (V ₁ ) of 1.4 m / sec, and an EFM signal of CD format with a clock period (T) 231.
The signal recorded at 4 ns was reproduced. Since the recording power was changed at intervals of 0.5 between 5 and 10 mW, the value at which the asymmetry of the reproduced signal showed 0 ± 5% was defined as the recording sensitivity. In general, when an EFM signal is recorded, the center of the amplitude of the 11T reproduced signal, which is the longest signal, and the amplitude of the shortest 3T reproduced signal are shifted. The degree is called asymmetry and can be calculated by the following formula. Asymmetry = {(CB) / A} × 100 (%) where A represents an amplitude voltage of 11T, B represents a center voltage having an amplitude of 11T, and C represents a center voltage having an amplitude of 3T. Generally, when the recording power is increased, the asymmetry shifts to the negative side.

2) Jitter The recorded signal in the area having the above recording sensitivity of each medium is reproduced,
The binarized signal output by the EFM encoder of the obtained reproduced signal is input to a pulse jitter counter (TR5835, manufactured by Advantest), and the lower 5
Σ was measured under the conditions of 75 ns, 800 ns on the upper side, and polarity +. Generally, the jitter is preferably 30 ns or less.

3) Recording Time The time required for recording a CD with a reproduction time of 60 minutes on each medium was measured at the above recording sensitivity.

Table 1 shows the measurement results.

Table 1 ────────────────────────────── Recording sensitivity (mW) Jitter (ns) Recording time (min) ─ ───────────────────────────── Example 1 7.0 23 30 Example 2 8.0 24 20 Example 3 9. 0 25 15 ────────────────────────────── Reference Example 1 6.5 22 60 Comparative Example 1 9.5 35 20 20 Comparison Example 2 7.5 35 20 Comparative Example 3 8.5 32 20

As is clear from the above results, recording was performed at a high linear velocity under the above conditions of the present invention (Examples 1 and 2).
And 3) The recorded information had low jitter and could be reproduced at a normal linear velocity. That is, there was almost no difference in the jitter from the reproduced signal in Reference Example 1 in which recording was performed at the same linear velocity as during recording. The recording signal of Comparative Example 1 in which the pulse width was simply reduced in inverse proportion to the linear velocity under the conditions of Reference Example 1 had a high jitter, and had a problem in practicality. In the recording method of Comparative Example 2 in which the pulse width is out of the range of the present invention and Comparative Example 3 in which the pulse width is simply reduced in inverse proportion to the linear velocity using the same pulse width as the pit to be recorded, Again, the jitter during reproduction was high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an optical information recording method of the present invention.

FIG. 2 is a schematic diagram for explaining a pulse width during pit (nT) recording according to the present invention.

FIG. 3 is a schematic diagram for explaining a pulse width during pit (3T) recording according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Information recording medium 11 Disc-shaped substrate 12 Dye recording layer 13 Reflective layer 14 Protective layer 15 Pregroove 16 Laser

Claims (1)

(57) [Claims] An information recording medium provided with a recording layer on a disc-shaped substrate provided with a pre-groove on its surface while rotating at a linear velocity higher than a predetermined linear velocity for reproducing recorded information. When an EFM signal is recorded by irradiating a laser from the substrate side, the pulse width T _LD (n) of the laser for recording a pit having a pit length nT to be recorded is set as follows.
(1) to (3): T _LD (n) = (nm) T (1) m = 2 × V ₁ / Va (2) T = T ₁ × V ₁ / V (3) , T _LD (n) (ns) represents the laser pulse width during pit recording with a pit length of nT, n represents an integer in the range of 4 to 11, and T (ns) represents the clock period during recording. T ₁ (ns) represents a clock cycle during reproduction, and V ₁
(M / sec) represents the constant linear velocity during playback, and V (m / sec)
Represents a constant linear velocity at the time of recording, and a is 0.5 to 1.
And the pulse width T _LD (3) of the laser for recording a pit having a pit length of 3T is set to satisfy the above (2) and (3) and the following ( 4): T _LD (3) = (n−m + f) T (4) [However, T _LD (3) (ns) represents the pulse width of the laser at the time of pit recording with a pit length of 3 T, and T (ns) is Represents the clock cycle at the time of recording, f represents a number in the range of 0.03 to 0.6, and m represents the same meaning as described above. Recording method.