JP2604273B2 - Optical information recording method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical information recording method for recording information on an information recording medium by using a laser beam.

[Technical Background of the Invention] In recent years, information recording media using a beam of high energy density such as laser light have been developed and put into practical use. This information recording medium is called an optical disk,
It can be used as a disk audio disk, as well as a large capacity still image file and a large capacity computer disk memory. Among these information recording media, compact discs (CDs) are widely used for audio reproduction of music and the like, but CDs are for reproduction only and cannot record information. Information recording media (DRAW (Direct Read After Writ
e)) is a disc-shaped transparent substrate made of plastic, glass, etc. as a basic structure, and Bi, Sn,
And a recording layer made of a metal or semimetal such as In or Te, or a dye such as a cyanine dye. In addition, a DRAW-type CD that allows recorded information to be reproduced by a compact disk (CD) player (commercially available CD player) has been developed and has been put into practical use.

Recording of information on such an information recording medium is generally performed by irradiating a laser beam on a pre-groove for guiding a laser beam provided on a substrate to a predetermined position, and As a result of the irradiating portion absorbing the light and locally increasing the temperature, physical or chemical changes such as pit formation occur, and information is recorded by changing its optical characteristics. The laser beam irradiated at that time generally consists of pulses having a pulse width corresponding to the pit length to be recorded.

For example, when the recording layer provided on the substrate is a metal layer,
In general, a laser beam having a pulse whose pulse width is shorter than a pit length to be recorded by a certain width is used as the laser beam irradiated at the time of recording. In other words, metals generally have higher thermal conductivity and faster thermal conductivity than organic substances such as dyes, so that heat generated by irradiating the metal recording layer with laser light accumulates in the laser light irradiated portion of the metal layer. It tends to spread without. For this reason, the pit formation region tends to be larger than the laser light irradiation region.
The pits of the metal recording layer melt the metal by the heat of the laser light, and the molten metal is pushed out of the substrate surface out of the laser light irradiation area by energy generated from a difference in surface tension between the molten metal and the substrate surface. Formed. For this reason, the pit shape obtained easily changes depending on the melting point and surface tension of the metal material used for the recording layer, and the area is larger than the laser light irradiation area and tends to be non-uniform. From such a point, information recording by laser light irradiation on the metal recording layer is generally performed by irradiating laser light having a pulse whose pulse width is reduced by a certain width from the pit length to be recorded as described above. I have.

On the other hand, the recording layer made of a dye has a C /
Although the N is low and its practical use has been delayed, an optical disk having a reflective layer of Au on the dye recording layer has recently been proposed (Nikkei Electronics, page 107, published on January 23, 1989), and has been studied. I have. As described above, an optical disk having a dye recording layer with a reflective layer has an improved reflectance and a generally improved C / N ratio.

The dye has a low thermal conductivity unlike the above-mentioned metals, and has a property of decomposing or sublimating without being melted by heat unlike metals. For this reason, when the dye recording layer is irradiated with laser light, the irradiated area is decomposed or sublimated without heat conduction and disappears, so that it is considered that pits having almost the same size as the irradiated area are formed. Therefore, when the pulse width of the laser beam applied to the dye recording layer is the same as the pit length to be recorded, it is considered that a pit having substantially the same length as the pit length to be recorded is formed. .

However, it has not been clarified what pulse width of a laser beam can be applied to an optical disc comprising a substrate and a dye recording layer and an optical disc having a reflection layer provided on the dye recording layer to perform good recording. .

[Object of the Invention] The inventors of the present invention have intensively studied a method of recording a signal having excellent recording / reproducing characteristics, particularly jitter, on an optical disk having a dye recording layer and a reflective layer formed on a substrate in this order. Was. As a result, it has become clear that the dye recording layer can be used if the type, thickness, and pulse width of the laser beam at the time of recording satisfy a specific relationship, and the present invention has been achieved.

Accordingly, an object of the present invention is to provide an optical information recording method capable of recording a signal having excellent recording and reproducing characteristics on a dye recording layer type optical disk having a reflective layer.

Another object of the present invention is to provide an optical information recording method capable of recording a signal having particularly excellent jitter on a dye recording layer type optical disk having a reflective layer.

Further, the present invention provides a preferable combination of the layer thickness of the recording layer of a high-reflectance optical disc and the pulse width of a laser beam of an optical drive used for recording a CD-format EFM signal on the optical disc. Accordingly, it is an object of the present invention to provide an optical information recording method capable of performing recording with excellent reproduction characteristics.

[Summary of the Invention] The present invention provides a disk-shaped substrate having a pregroove,
An optical information recording method for recording information by irradiating a laser beam from the substrate side to an information recording medium provided with a recording layer made of a dye capable of recording information by a laser beam and a reflective layer made of a metal in this order. The pulse width of the laser beam corresponding to the pit length to be recorded has the following formula (I): [However, d (μm) represents the thickness of the bottom of the groove of the recording layer, d _ma (μm) represents the minimum thickness of the bottom of the groove of the recording layer at which the reflectance from the groove is maximum, and α is the recording thickness. P _dif (ns) represents the ratio between the layer thickness at the bottom of the groove of the layer and the layer thickness at the land portion of the recording layer. P _mdm (ns) represents the smallest pulse width of the same pulse width as the pit length to be recorded]. Optical information recording method.

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

1) The optical information recording method, wherein d (μm) is in a range of 0.05 to 0.25 μm.

2) The optical information recording method, wherein d _ma (μm) is in a range of 0.04 to 0.30 μm.

3) The optical information recording method, wherein α is in the range of 0.9 to 3.0.

4) The optical information recording method, wherein the P _dif (ns) is in a range of 0 to 400 ns.

5) The optical information recording method, wherein P _mdm (ns) is in a range of 40 to 900 ns.

6) The P _dif / P _mdm is, the optical information recording method characterized by satisfying _{0 ≦ P dif / P mdm <} 1/2.

7) The optical information recording method, wherein a protective layer is formed on the reflective layer.

8) The optical information recording method as described above, wherein the information is a CD format EFM signal.

9) The dye is a cyanine dye, an oxonol dye,
The above optical information recording method, wherein the optical information recording method is at least one selected from the group consisting of a merocyanine dye, a pyrylium dye, a thiopyrylium dye, a naphthalocyanine dye, and a phthalocyanine dye.

[Effects of the Invention] In the present invention, when information recording is performed by irradiating a laser beam having a pulse with a reduced pulse width from the substrate side to an information recording medium having the dye recording layer and the reflective layer, the dye recording is performed. Information is recorded under the condition that the thickness of the layer and the shortening width of the pulse of the laser beam at the time of recording satisfy the above formula (I).

In this way, the shortened width of the pulse of the optical drive used for recording information (shortened width may be 0) and the thickness of the recording layer and the maximum reflectance layer of the optical disc (generally known from the type of the dye) can be obtained. By adjusting, information can be recorded well. That is, the recording layer is formed by determining the maximum reflectance layer thickness of an arbitrary dye, and then determining the layer thickness of the recording layer satisfying the above formula (I) according to the pulse width at the time of recording. It is. In particular, the signal recorded in this way has excellent jitter during reproduction.

Furthermore, it is also possible to manufacture an optical disk applicable to many kinds of optical drives.

[Detailed Description of the Invention] The information recording medium used in the optical information recording method of the present invention has a basic structure in which a recording layer made of a dye and a reflective layer are laminated on a substrate in this order.

The optical information recording method of the present invention will be described with reference to the accompanying drawings.

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

FIG. 1 shows a disc-shaped substrate 1 having a pregroove, a recording layer 2 made of a dye provided on the substrate, a reflective layer 3 made of a metal provided on the recording layer, and provided on the reflective layer. A state is shown in which the laser beam 6 is irradiated from the substrate side while the information recording medium 10 composed of the protective layer 4 is being rotated, and the laser beam 6 is focused on the recording layer on the pre-groove bottom 5 of the substrate. .

More specifically, as shown in FIG. 1, information is recorded at a constant linear speed (1.2 to 1.2 in the case of a CD format).
While rotating at a constant angular velocity of 1.4 m / sec), a semiconductor laser beam or the like is irradiated from the substrate side onto the recording layer with laser light modulated to the pulse width of a recording signal to form pits. The pits are formed, for example, by changing the refractive index by forming a cavity between the recording layer or the recording layer and the reflective layer, or by causing the recording layer to change color or change the association state. As the recording light, a semiconductor laser beam having an oscillation wavelength in the range of 500 nm to 900 nm (preferably 650 nm to 850 nm) is generally used. In the present invention, a laser beam having a pulse width equal to the pit length to be recorded on the information recording medium having the dye recording layer and the reflection layer and having a pulse width reduced by a certain width (P _dif ) is applied to the substrate. This is a recording method in which information is recorded by irradiating from the side, and the information is recorded under the condition that the layer thickness of the dye recording layer and the shortening width of the laser beam pulse during recording satisfy the above-mentioned formula (I). Done.

Reproduction of the information recorded as described above can be performed by irradiating the semiconductor laser light from the substrate side while rotating the information recording medium at the same constant linear speed as above, and detecting the reflected light. .

FIG. 2 shows an information recording medium 10 for indicating the thickness of the recording layer.
It is the elements on larger scale sectional view.

d represents the layer thickness at the bottom of the groove of the recording layer 2, and d ₁ represents the layer thickness at the land (between the grooves) of the recording layer 2. Therefore, the following α is (layer thickness at the bottom of the groove of the recording layer) /
(Layer thickness of the land portion of the recording layer), i.e., it can be expressed by d / d _1. d _ma is the minimum value of the recording layer thickness at which the reflectance is maximized. This value is generally a value specific to the dye, but there are some types of dyes having the same value and different values depending on the forming method and the same dye. Therefore, in the present invention, it is defined as the characteristics of the recording layer as described above.

FIG. 3 shows a) a pit to be recorded, b) a pulse having the same pulse width as the pit to be recorded (ns: nanosecond), and c) a pulse when actually recording. 3 shows a modulated pulse.

a) shows two types of pits with different pit lengths to be recorded.
pt (ns) and pt '(ns) are shown.

b) a pulse having a pulse width of P _md (ns), in which a laser emitted from a light source is modulated by a recording signal;
A pulse having a pulse width of P _md '(ns) is shown. These are the two types of pits pt (ns) and p, respectively.
Corresponding to t ′ (ns), the pit length and pulse width are the same.

c) shows the actually recorded modulated pulse in which the pulse shown in b) is further modulated. P
_dif (ns) is the shortened width (time) when modulating the original pulse width of the recording signal to the pulse width at the time of recording, and P _Ld (ns) is
The above P _md (ns) is a pulse width modulated by shortening the time by P _dif (ns), and P _Ld ′ (ns) is also a pulse width obtained by similarly modulating the P _md ′ (ns). It is. Then, pits are formed on the recording layer corresponding to the pulse width.

P _md ^- the value of P _Ld also, P _md ^- the values of _{'P Ld', P dif (} n
s) and the shortened width is P for all pulse widths.
_dif (ns) and preferably the same. However,
In the present invention, P _dif may be zero. Further, as long as the following expression (I) is satisfied, the shortened width P _dif may be different for each pulse width. P _mdm (n
s) is the minimum pulse width of the original recording signal, b) in FIG.
Per the P _md in, EFM signals (3 CD format
T ~ 11T) is equivalent to 3T.

In the optical information recording method of the present invention, the thickness of the recording layer of the recording medium shown in FIG. 2 and the pulse width corresponding to the pit length of the laser beam to be recorded at the time of recording shown in FIG. Formula (I) of: [However, d (μm) represents the thickness of the bottom of the groove of the recording layer, d _ma (μm) represents the minimum thickness of the bottom of the groove of the recording layer at which the reflectance from the groove is maximum, and α is the recording thickness. P _dif (ns) represents the ratio between the layer thickness at the bottom of the groove of the layer and the layer thickness at the land portion of the recording layer. _Represents a shortened constant width, and P _mdm (ns) represents the smallest pulse width of the same pulse width as the pit to be recorded].

As is apparent from the above formula (I), the specific thickness d (μm) of the recording layer at the bottom of the groove and the minimum thickness d _ma (μm) of the bottom of the groove of the recording layer at which the reflectance from the groove is maximized are specified. Is defined to be close to 0 (that is, within ± 15% of d).

Therefore, in the present invention, the layer thickness d of the recording layer to be formed at the bottom of the groove is It can be considered in a simplified manner that it should be formed so as to satisfy the following.

In the above equation, the right side: Is abbreviated as X below; Is abbreviated as Y below.

When the value of Y is 1, ie, P _dif / P _mdm (the shortened width when the pulse width corresponding to the pit length to be recorded is modulated,
When the ratio of the pulse width corresponding to the pit length to be recorded to the minimum pulse width) is 0.3, X is (1−α) + α = 1.
Becomes That is, making the layer thickness d of the recording layer at the bottom of the groove substantially equal to the minimum layer thickness d _ma of the bottom of the groove having the maximum reflectance leads to an improvement in recording characteristics (jitter).

Since the dye recording layer is usually formed by coating, the coating liquid easily accumulates at the bottom of the groove. Therefore, the thickness of the recording layer at the bottom of the groove is larger than that of the land, and α is about 2 (depending on the coating method). Different, for example the solvent used,
Depending on the application amount).

For example, assuming that α is 2 (that is, the thickness of the recording layer at the bottom of the groove is twice the thickness of the land), when P _dif / P _mdm exceeds 0.3, Y becomes larger than 1 and X − Y + 2] is smaller than 1.

On the other hand, when P _dif / P _mdm is less than 0.3, Y becomes smaller than 1 and the value of [−Y + 2] of X becomes larger than 1.

As apparent from the above, the layer thickness of the recording layer at the bottom of the groove to be formed is d when P _dif / P _mdm exceeds 0.3.
The reflectivity is set to have a value smaller than the minimum layer thickness d _{ma at the} bottom of the maximum groove (for example, P _dif / P _mdm = 0.6
In the case of X = 2-α), when P _dif / P _mdm is less than 0.3, the reflectance is set to have a value larger than the minimum layer thickness d _{ma at the} bottom of the maximum groove (for example, , P _dif / P
X = α when _mdm = 0). In these cases, the value of α obviously affects the increase and decrease of the value of X.

Therefore, the thickness d of the recording layer at the bottom of the groove to be formed according to the present invention is determined by the value of P _dif / P _mdm (that is, corresponding to the irradiation time of the laser beam). The reflectivity is set so as to increase or decrease from the minimum layer thickness d _{ma at} the maximum groove bottom, and at the same time, α, ie, the film thickness of the recording layer at the groove bottom and the film thickness of the land portion (Ie, due to the method of applying the dye layer). That is, α
The greater the value, the greater the effect.

The above-mentioned α influences the thickness of the layer to be formed as follows. When the film thickness at the groove bottom is too large compared to the layer thickness at the land, it is expected to be advantageous in sensitivity. However, since the capacity of the recording layer at the groove bottom becomes large, it is necessary to obtain better jitter than the above formula X. It is considered necessary to reduce P _dif / P _mdm (increase the laser light irradiation time).

In the above formula (I), d (μm) is 0.05 to 0.25 μm.
m is preferable, and the above d _ma (μm) is 0.04 to 0.30.
The range of μm is preferred. Α is preferably in the range of 0.9 to 3.0.

The above P _dif (ns) is preferably in the range of 0 to 400 ns.
_mdm (ns) is preferably in the range of 40 to 900 ns. The present invention can be applied to the case where the pulse width at the time of laser recording is not shortened as long as the above-mentioned formula (I) is satisfied. In that case, P _dif becomes 0.

Preferably, the information to be recorded is an EFM signal in a CD format. Furthermore, if the optical drive for CD-DRAW, by P _dif / P _mdm sets the optical disk or optical drive to satisfy _{0 ≦ P dif / P mdm <} 1/2, 3 beams servo gain Is large, which is preferable.

In the present invention, information recording is performed by irradiating the information recording medium having the layer thickness of the dye recording layer with a laser beam having the above-mentioned modulated (shortened) pulse width from the substrate side. Therefore, if the modulation (shortened) pulse width of the laser beam at the time of recording by the optical drive to be used is known, the maximum reflectance layer thickness of the dye to be used can be obtained by an experiment. Is substituted into the above formula (I) to determine the layer thickness of the dye recording layer of the information recording medium for better recording. Thus, when an information recording medium having the above recording layer is manufactured, good recording (especially, excellent jitter) can be performed by an optical drive having the known modulation pulse width.

Also, if the maximum reflectance layer thickness and layer thickness of the dye recording layer of the optical disk are known, the modulation pulse width for performing good recording on the information recording medium can be obtained from the above formula (I). The optical drive can be determined by adjustment, improvement, etc.

In the present invention, the thickness of the dye recording layer, the thickness of the maximum reflectance layer, and the shortened pulse width may satisfy the above formula (I).
Therefore, the kind of the dye used in the recording layer and the method of forming the dye may be any. As described above, even if the maximum reflectance layer thickness and the type of the dye are different, there are the same ones, and the thickness differs depending on the forming method such as coating. ).

Therefore, by using the recording method of the present invention, an optical disk for an arbitrary optical drive can be manufactured. The reason can be considered as follows.

That is, generally, the formation of pits according to information on the metal recording layer is performed by irradiating a laser beam having a pulse width shorter in time than the pulse width corresponding to the pit length of the recording signal as described above. This is done because it is necessary to balance the pit shape so that good reproduction can be performed because the pit shape is easily spread by heat conduction. However, in an optical disc having a basic structure in which a dye recording layer and a reflective layer are formed in this order on a substrate, the degree of absorption of laser light energy tends to fluctuate particularly due to a difference in the layer thickness of the dye recording layer. It is considered that pits having the same shape cannot be obtained on recording layers having different layer thicknesses even when laser irradiation with the same pulse width is performed, and good reproduction cannot be performed.

Therefore, by adjusting the pulse width and the recording layer thickness using the above formula (I), it is possible to produce an optical disk corresponding to the optical drive and an optical disk having a wide applicability.

The information recording medium used in the recording method of the present invention can be manufactured, for example, by the method described below.

The disc-shaped substrate of the present invention can be arbitrarily selected from various materials used as a substrate of a conventional information recording medium. Examples of the substrate material of the present invention include glass; polycarbonate; acrylic resins such as polymethyl methacrylate; polyvinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer; epoxy resins; amorphous polyolefin and polyester; You may use together 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 undercoat layer may be provided on the surface of the substrate on which 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 undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, and chlorosulfonated polyethylene. , Nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, high molecular substances such as polyethylene, polypropylene, polycarbonate, etc., and silane coupling agent Organic substances.

The undercoat 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 0.005 to 20 μm
And preferably in the range of 0.01 to 10 μm.

On the disc-shaped substrate (or undercoat layer) of the present invention, pits and tracking grooves (pre-grooves) representing information such as address signals or music information are formed. When a resin material such as the above polycarbonate is used, it is preferable that pits and grooves are provided directly on the substrate by injection molding or extrusion molding of the resin material.

Also, the formation of a 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 mixture of the above-mentioned acrylate and a polymerization initiator on a precisely prepared master (stamper),
Further, after the substrate is placed on the coating liquid 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 prepreg layer is generally in the range from 0.05 to 100 μm, preferably in the range from 0.1 to 50 μm.

The shape of the pregroove preferably has a depth in the range of 500 to 2500 °, particularly preferably in the range of 500 to 2500 °. Also, the half width is preferably in the range of 0.2 to 0.9 μm, preferably 0.2 to 0.9 μm
Is particularly preferred.

A recording layer made of a dye is provided on the disk-shaped substrate.

Dyes used in the present invention include, for example, indolenine dyes, imidazoquinoxaline dyes, cyanine dyes such as indolizine dyes, phthalocyanine dyes, naphthalocyanine dyes, pyrylium and thiopyrylium dyes, and azulenium dyes , Squarylium dye, N
i, Cr and other metal complex dyes, naphthoquinone and anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, merocyanine dyes, oxonol dyes, aminium dyes Diimmonium dyes and nitroso compounds can be mentioned.

The dye layer is formed by dissolving the above dye and, if desired, a binder, a metal complex dye or an aminium / diimmonium dye (quencher) in a solvent to prepare a coating solution, and then applying the coating solution to the substrate surface. It can be carried out by drying after coating to form a coating film.

Ethyl acetate, as a solvent for the dye coating solution preparation,
Esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; ethers such as tetrahydrofuran, ethyl ether and dioxane; ethanol; Examples thereof include alcohols such as propanol, isopropanol and n-butanol, amides such as dimethylformamide, and fluorine-based solvents such as 2,2,3,3-tetrafluoropropanol. These non-hydrocarbon organic solvents account for 50% by volume.
As long as it is within, it may contain a hydrocarbon-based solvent such as an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, or an aromatic hydrocarbon solvent.

Antioxidants, UV absorbers, plasticizers,
Various additives such as a lubricant may be added according to the purpose.

When a binder is used, examples of the binder include cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymers such as dextran, rosin, and rubber; and polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrocarbon resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride
Thermal curing of vinyl resins such as polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins, etc. And synthetic organic polymer substances such as a precondensate of a hydrophilic resin.

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

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

The dye layer may be a single layer or a multilayer, but the layer thickness is generally in the range of 0.01 to 0.55 μm, preferably 0.05 to 0.
It is in the range of 25 μm.

Between the recording layer and the substrate, chlorinated polyolefin,
An intermediate layer made of nitrocellulose or fluorine resin may be provided.

 A reflective layer is provided on the recording layer.

The light-reflective substance that is the material of the reflective layer is a substance having a high reflectance to laser light, and examples thereof include Mg, Se,
Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, F
e, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, C
Metals and metalloids such as d, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn and Bi can be mentioned. Among these, Al, Au, Cr and Ni are preferred. These substances may be used alone or in combination of two or more kinds or as an alloy.

The reflection layer can be formed on the substrate by, for example, vapor deposition, sputtering, or ion plating of the light-reflective substance. The thickness of the reflective layer is generally in the range from 100 to 3000 °.

Further, 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 materials used for the protective layer include SiO, SiO ₂ , M
gF _2, inorganic substances such as SnO _2, Si ₃ N _4; thermoplastic resins, thermosetting resins, and organic materials such as UV curable resin.

The protective layer can be formed by, for example, laminating a film obtained by extrusion of a plastic on a recording layer (reflection layer) and / or a substrate via an adhesive layer. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating. 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 recording layer, the recording layer may be protected by providing a plastic film on the recording layer by fusing 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 configuration, or two substrates having the above-described configuration are arranged such that the recording layer faces inside,
By bonding using an adhesive or the like, a bonding type recording medium can also be manufactured. 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.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, these examples do not limit the present invention.

[Preparation of Information Recording Medium A] The following indolenine dyes: 1.7 g of the following dye (IRG-023, manufactured by Nippon Kayaku Co., Ltd.): 0.17 was dissolved in 100 ml of 2,2,3,3-tetrafluoropropanol while applying ultrasonic waves for 1 hour to prepare a dye coating solution.

Polycarbonate substrate (diameter: 120mm, inner diameter: 15mm, thickness:
1.2 mm, refractive index: 1.58, track pitch: 1.6 μm, groove width: 0.45 μm, group depth: 900 mm), while applying the above-mentioned dye coating solution by spinning the nozzle of a spinner at a speed of 200 rpm. Coating for 16 seconds, gradually increasing the number of revolutions by 50 rpm per second to 16 rpm after the final rotation speed of 1000 rpm, holding for 30 seconds and drying in this state, the layer thickness in the groove 14
A dye recording layer having a thickness of 00 ° and a thickness between the grooves of 1000 ° was formed.

On the dye recording layer, Au was sputtered with a DC sputtering apparatus under the conditions of an Ar pressure of 2 Pa and a power of 200 W to obtain a layer thickness of 1
A 000 mm reflective layer was formed to an outer diameter of the substrate of 118 mm.

The coating liquid for forming the protective layer (trade name: UV-curable resin: 3070, manufactured by Three Bond Co.) is further applied on the reflective layer by spin coating at a rotation speed of 200 rpm and maintained for 5 seconds. Was completed, the rotation speed was increased, and the substrate was dried by rotating at a final rotation speed of 1500 rpm for 30 seconds. Then, the coating layer was irradiated with ultraviolet rays ( ²⁰⁰ w / cm ² mercury lamp for 10 seconds) to form a protective layer having a thickness of 2 μm. The layer thickness at the outer peripheral edge of the protective layer was 2 to 10 μm.

Thus, an information recording medium A in which the dye recording layer, the reflective layer, and the protective layer were provided on the substrate was manufactured.

[Preparation of Information Recording Medium B] In [Preparation of Information Recording Medium A], the dye A of the dye coating solution was changed from 2.3 g to 2.3 g and the dye B from 0.17 g to 0.23 g, and the layer thickness of the obtained dye recording layer was changed. That is, an information recording medium was manufactured in the same manner as in [Preparation of Information Recording Medium A] except that the inner layer thickness of the groove was changed from 1400 ° to 1900 ° and the layer thickness between the grooves was changed from 1000 ° to 1350 °.

[Preparation of Information Recording Medium C] In [Preparation of Information Recording Medium A], the dye A of the dye coating solution was changed from 1.7 g to 2.0 g and the dye B from 0.17 g to 0.20 g, and the layer thickness of the obtained dye recording layer was changed. That is, an information recording medium was manufactured in the same manner as in [Preparation of Information Recording Medium A] except that the inner layer thickness of the groove was changed from 1400 ° to 1750 ° and the layer thickness between the grooves was changed from 1000 ° to 1250 °.

[Preparation of Information Recording Medium D] In [Preparation of Information Recording Medium A], in place of a substrate having a groove depth of 900 mm, a polycarbonate substrate having a groove depth of 1650 mm and other dimensions being the same as the polycarbonate substrate was used. Dye A1.7g of the following dye C2.6g
The information recording medium A was changed except that 0.17 g of dye B was changed to 0.26 g and the layer thickness of the obtained dye recording layer, that is, the inner layer thickness was changed from 1400 ° to 2000 ° and the inter-layer layer thickness was changed from 1000 ° to 1180 °. Preparation of Information Recording Medium].

[Preparation of Information Recording Medium E] In [Preparation of Information Recording Medium D], the dye C2.6 g of the dye coating solution was changed to 2.2 g, and the dye B 0.26 g was changed to 0.22 g. That is, an information recording medium was manufactured in the same manner as in [Preparation of Information Recording Medium D] except that the inner layer thickness of the groove was changed from 2000 ° to 1700 ° and the layer thickness between the grooves was changed from 1180 ° to 1000 °.

[Recording of information recording medium] Using an optical disk evaluation machine (DDU1000, manufactured by Pulstec Industrial Co., Ltd.) equipped with an optical head for an optical disk having a wavelength of 780 nm and NA of 0.5, the information recording mediums (A to E) were CD-formatted. The EFM signal was recorded at a constant linear velocity of 1.2 m / min at a recording power at which the jitter was minimized.

1) Pulse 1: pulse width of the EFM signal (3T: 694.2 ns) as it is (recording of 50% duty) 2) Pulse 2: 0.5 clock pulse width from the EFM signal (11
5.7 ns) 3) Pulse 3: One pulse (23
1.4ns) 4) Pulse 4: Pulse width 1.5 clocks (34
Pulse width shortened by 7.1 ns) [Comparative example 1] Information was recorded on the information recording medium A by the recording method using the pulse 1 to prepare a recorded information recording medium A.

Example 1 Information was recorded on the information recording medium A by the recording method using the pulse 2 to prepare a recorded information recording medium A.

Comparative Example 2 Information was recorded on the information recording medium A by the recording method using the pulse 3 to prepare a recorded information recording medium A.

Comparative Example 3 Information was recorded on the information recording medium A by the recording method using the pulse 4 to prepare a recorded information recording medium A.

Each of the recorded information recording media A on which recording was performed with the above four types of pulses was evaluated.

[Evaluation of Recorded Information Recording Medium A] 1) Jitter at the time of reproduction The recording signal of the information recording medium was converted into a signal using the above-described optical disk evaluation machine (DDU1000, manufactured by Pulstec Industrial Co., Ltd.).
Reproduction was performed at a constant linear speed of 1.2 m / sec and a reproduction power of 0.5 mW. The obtained FR playback signal is converted to a pulse jitter counter (TR5835,
Advantest Corp.), playback signal output AC coupling (window width: lower 575 ns, upper 575 ns, polarity:
+, Slide level: 0 V).

 Table 1 shows the measurement results.

X in the above Table 1 represents Represents

Next, recording was performed on the information recording medium B with the above four types of pulses in the same manner as the information recording medium A.

Comparative Example 4 Information was recorded on the information recording medium B by the recording method using the pulse 1 to prepare a recorded information recording medium B.

Comparative Example 5 Information was recorded on the information recording medium B by the recording method using the pulse 2 to prepare a recorded information recording medium B.

Example 2 Information was recorded on the information recording medium B by the recording method using the pulse 3 to prepare a recorded information recording medium B.

Example 3 Information was recorded on the information recording medium B by a recording method using the pulse 4 to prepare a recorded information recording medium B.

The recorded information recording medium B on which recording was performed with the above four types of pulses was evaluated in the same manner as the recorded information recording medium A.

 Table 2 shows the measurement results.

Next, recording was performed on the information recording medium C with the above four types of pulses in the same manner as the information recording medium A.

Comparative Example 6 Information was recorded on the information recording medium C by the recording method using the pulse 1 to prepare a recorded information recording medium C.

Comparative Example 7 Information was recorded on the information recording medium C by the recording method using the pulse 2 to prepare a recorded information recording medium C.

Example 4 Information was recorded on the information recording medium C by the recording method using the pulse 3 to prepare a recorded information recording medium C.

Example 5 Information was recorded on the information recording medium C by the recording method using the pulse 4 to prepare a recorded information recording medium C.

The recorded information recording medium C on which recording was performed with the above four types of pulses was evaluated in the same manner as the recorded information recording medium A.

 Table 3 shows the measurement results.

Next, recording was performed on the information recording medium D with the above four types of pulses in the same manner as the information recording medium A.

Comparative Example 8 Information was recorded on the information recording medium D by the recording method using the pulse 1 to prepare a recorded information recording medium D.

Example 6 Information was recorded on the information recording medium D by the recording method using the pulse 2 to prepare a recorded information recording medium D.

Comparative Example 9 Information was recorded on the information recording medium D by the recording method using the pulse 3 to prepare a recorded information recording medium D.

Comparative Example 10 Information was recorded on the information recording medium D by the recording method using the pulse 4 to prepare a recorded information recording medium D.

The recorded information recording medium D on which recording was performed with the above four types of pulses was evaluated in the same manner as the recorded information recording medium A.

 Table 4 shows the measurement results.

Next, recording was performed on the information recording medium E with the above four types of pulses in the same manner as the information recording medium A.

Comparative Example 11 Information was recorded on the information recording medium E by the recording method using the pulse 1 to prepare a recorded information recording medium E.

Example 7 Information was recorded on the information recording medium E by the recording method using the pulse 2 to prepare a recorded information recording medium E.

Comparative Example 12 Information was recorded on the information recording medium E by the recording method using the pulse 3 to prepare a recorded information recording medium E.

Comparative Example 13 Information was recorded on the information recording medium E by the recording method using the pulse 4 to prepare a recorded information recording medium E.

The recorded information recording medium E on which recording was performed with the above four types of pulses was evaluated in the same manner as the recorded information recording medium A.

 Table 5 shows the measurement results.

As is clear from Tables 1 to 5, the signals obtained by the recording method of the present invention are excellent in jitter at the time of reproduction and have good reproduction characteristics. When information is recorded using a combination of the recording layer thickness and the pulse width that do not satisfy the formula (I) of the present invention (Comparative Example), the jitter is large and the reproduction characteristics cannot be said to be good.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining an example of the optical information recording method of the present invention. FIG. 2 is a partially enlarged sectional view of the information recording medium 10. FIG. 3 shows a) a pit to be formed, b) a pulse having the same pulse width as the pit length,
FIG. 3C is a diagram showing a pulse when actually recording. Disc-shaped substrate: 1 Dye recording layer: 2 Reflecting layer: 3 Protective layer: 4 d: Layer thickness of groove bottom of recording layer 2 d ₁ : Layer thickness of land (between grooves) of recording layer 2 d (μm) : Is the layer thickness at the bottom of the groove of the recording layer P _md (ns), P _md ′ (ns): The pulse width P _dif (ns) of the signal at the time of recording is recorded from the pulse width having the same length as the pit width to be recorded Pulse width P _Ld (ns): P _md (ns) is reduced by P _dif (ns), and the pulse width P _Ld ′ (ns): P _md ′ (ns ) Is the pulse width shortened by P _dif (ns)

Claims (1)

(57) [Claims] 1. A disk-shaped substrate having a pre-groove,
An optical information recording method for recording information by irradiating a laser beam from the substrate side to an information recording medium provided with a recording layer made of a dye capable of recording information by a laser beam and a reflective layer made of a metal in this order. The pulse width of the laser beam corresponding to the pit length to be recorded has the following general formula (I): [However, d (μm) represents the layer thickness at the bottom of the groove of the recording layer, d _ma (μm) represents the minimum layer thickness at the bottom of the groove of the recording layer at which the reflectance from the groove is maximum, and α is the recording thickness. P _dif (ns) represents the ratio between the layer thickness at the bottom of the groove of the layer and the layer thickness at the land portion of the recording layer. P _mdm (ns) represents the smallest pulse width of the same pulse width as the pit length to be recorded]. Optical information recording method.