JP2866022B2 - Optical information recording medium and reproducing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium having at least a light absorbing layer and a reflecting layer on a transparent substrate, wherein pits are formed by laser light incident on the light absorbing layer from the substrate side; The present invention relates to a method for reproducing an optical information recording medium for reading a signal recorded by an optical phase difference between reflected light of the pit portion of a reading laser beam incident from a substrate side and reflected light of other portions.

[0002]

2. Description of the Related Art A so-called writable optical information recording medium on which data can be recorded by irradiating a laser beam is a metal layer of Te, Bi, Mn, etc., or a dye layer of cyanine, merocyanine, phthalocyanine, etc. The recording layer is formed by forming a through-hole pit and recording data by means such as deformation, sublimation, evaporation or denaturation of the recording layer by laser light irradiation. In an optical information recording medium having this recording layer, a gap is generally provided behind the recording layer to facilitate deformation, sublimation, evaporation or denaturation of the recording layer when forming pits. . Specifically, for example, a laminated structure called an air sandwich structure in which two substrates are laminated with a space portion interposed therebetween is employed.

[0003] An optical information recording medium of the type in which such perforated pits are formed utilizes the light absorbing property of a light absorbing material, and the light transmittance of the perforated pit portion and other portions is reduced. The reproduction contrast is determined by the difference in the amount of reflected light caused by the difference. In other words, the optical information recording medium which reads reflected light is basically the same as a transmission type optical information recording medium, and the mechanism for obtaining reproduction contrast is an optical information recording medium which can be called an absorption type.

[0004] On the other hand, a so-called ROM type optical information recording medium in which data is recorded in advance and subsequent data cannot be written or erased has already been widely put into practical use in the information processing and acoustic departments. This type of optical information recording medium has no recording layer as described above, and pits for reproducing recorded data are previously formed on a polycarbonate substrate by means such as pressing, and Au, Ag is formed thereon. , A reflective layer made of a metal film such as Cu, Al or the like is formed, and the reflective layer is further covered with a protective layer.

[0005] The most typical of the ROM type optical information recording medium is a compact disk, so-called CD, which is widely put into practical use in the audio department and the information processing department.
The specification of the recording and reproduction signals of D is standardized as the international standard IEC908, and a reproduction apparatus conforming to the standard is very widely used as a compact disk player (CD player). Each of the optical information recording media takes a disc-like form having a hole at the center for clamping to a rotation axis, that is, an optical disc form.

[0006]

Since the optical information recording medium also uses the same reproducing means as that of a CD, it is strongly desired that the optical information recording medium conforms to a CD which has already been widely used for reproduction. However, in the optical information recording medium of the type in which the perforated pits are formed as described above, the intensity of the reflected light at the portion where the absorbing layer is not removed, that is, at the portion other than the pit, is low, and the absorbing layer is removed. The intensity of the reflected light at the portion, that is, at the pit portion, becomes a high level. Therefore, when the reflected light is captured, there are bright pits due to the apertures in the background darkened by the light absorbing layer on one side, contrary to the so-called phase type CD. Therefore, if the reflectance is increased, the reproduction contrast is lowered, and if the reproduction contrast is increased, the reflectance is lowered. Therefore, under the CD standard that requires a high reflectance, both the reflectance and the modulation degree cannot be satisfied with the standard.

On the other hand, CDs that have already become widespread have to be formed by pressing a polycarbonate substrate having pits for reproducing recorded data by means such as pressing. It is not suitable for small publications. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. An output signal having a high reflectance of 70% or more and having a modulation factor conforming to the CD format can be obtained upon data reproduction. An object of the present invention is to provide an optical information recording medium suitable for small-scale publishing and a method for reproducing the information, by which information can be recorded and manufactured by simple means without using means such as a press and a press.

[0008]

That is, in the optical information recording medium according to the present invention, at least a light absorbing layer 2 and a reflecting layer 3 are sequentially formed on a light transmitting substrate 1, and the light absorbing layer 2 is formed of a dye. Ρ = nabs · given by the real part nabs of the complex refractive index, the film thickness dabs, and the wavelength λ of the reproduction light.
dabs / λ is 0.05 ≦ ρ ≦ 0.6, and the imaginary part kabs of the complex refractive index of the light absorbing layer 2 is 0.01 ≦ kabs ≦
0.3, and a pit 5 is formed which absorbs the recording laser light to generate an optical phase difference between the reading laser light incident from the substrate 1 side. Further, in the reproducing method of the optical information recording medium according to the present invention, a laser beam for reading is made incident on the optical information recording medium from the substrate 1 side, and the portion of the pit 5 of the laser beam and the other portions are read. A signal is read based on an optical phase difference of reflected light.

In the optical information recording medium, the light absorbing layer 2 is formed in a partial area on the light transmitting substrate 1, and pits for signal reproduction are previously formed in the area where the light absorbing layer 2 is not provided. It may have a pre-recording area 10. Pit 5
Although it can be formed on the substrate 1 itself, when another layer is formed between the substrate 1 and the light absorbing layer 2, pits 5 may be formed on these layers or the substrate.

The pits 5 are closer to the substrate 1 than the light absorbing layer 2 is.
The pit 5
When reading laser light is applied during playback,
The optics of the reflected light of the pit 5 part and the other part of the light
Causes a phase difference. For example, pit 5 is the light of substrate 1
Formed on the surface facing the absorption layer 2 so as to protrude toward the light absorption layer 2
Is done. The reflection layer 3 is preferably made of a film of gold or an alloy containing gold having a high reflectance.

[0011]

The present inventors have a light-absorbing layer 2 made of an organic dye and a reflective layer 3 made of a metal on a light-transmitting substrate 1. From the optical information recording medium in which pits 5 on which a CD signal is recorded by a laser beam are formed, a reflectance of 70% or more conforming to the CD format and I11 / I indicated as a modulation factor
In order to obtain a reproduced signal in which top is 0.6 or more and I3 / Itop is 0.3 to 0.7, the real part nabs of the complex refractive index of the light absorption layer 2 of the optical information recording medium and its film thickness dabs are obtained. And ρ = nabs · dabs / λ, which is given by the wavelength λ of the reproduction light, is a very important parameter. As a result of conducting experiments and simulations on this point, a relationship as shown in FIG. 7 was obtained.

FIG. 7 shows a reproduction light having a wavelength λ = 780n.
m, using Au as the reflective layer 3,
When the light absorbing layer 2 having a certain value of k is used, the real part nabs of the complex refractive index of the light absorbing layer 2 of the optical information recording medium, its film thickness dabs, and the wavelength λ of the reproduction light are given. ρ = n
5 is a graph showing the relationship between abs · dabs / λ and the reflectance of light incident from the substrate 1 side.

From this graph, it can be seen that when ρ is smaller than 0.6, a reflectance of 70% or more can be secured almost certainly. If ρ is less than 0.05,
Even in a region exceeding 0.6, a reflectance of 70% or more may be obtained. However, in the region where ρ is less than 0.05, the thickness dabs of the light absorbing layer 2 must be considerably reduced to 0.05 μm or less, so that pits for recording data are not formed. This makes it difficult to obtain a reproduction signal as described above. On the other hand, in the case of a region exceeding 0.6, it is difficult to control the film thickness to be uniform, the recording characteristics vary, and I3 / Itop is less than 0.3, and the jitter error increases. Manufacturing problems, such as That is, by setting ρ to 0.05 to 0.6, the reflectivity conforms to the CD format.
It can be seen that it can be set to 0% or more.

Further, the present inventors have further examined these results. As a result, it is not always necessary to set ρ in the range of 0.05 to 0.6 to stabilize the output signal as defined in the CD standard. It was found that kabs is an important parameter. FIG. 8 shows the reflective layer 3
In an optical information recording medium using an Au film as the light absorbing layer 2
Of the imaginary part kabs while changing the translucency of
7 is a graph showing a change in reflectance when is changed from a value close to 0 to 2.0.

From this graph, it can be seen that the reflectance increases as kabs approaches 0. According to the results of experiments and simulations, the present inventors have found that the light absorbing layer 2 has sufficiently high translucency in order to stably maintain a high reflectance in the range of 0.05 to 0.6. It has been found that the imaginary part kabs of the complex refractive index of the same layer needs to be 0.3 or less. ρ is 0.05-0.
6, if kabs is greater than 0.3, the reflectivity is 7
It is difficult to secure 0% or more.

From these results, a result as shown in FIG. 9 can be obtained. FIG. 9 shows that at values of ρ and kabs, C
It is a graph which shows the critical value of the combination based on D standard. As can be seen from this graph, in order to provide an optical information recording medium capable of obtaining a recording signal conforming to the CD standard, ρ = nabs · dabs / λ is in the range of 0.05 to 0.6, Further, it is understood that kabs needs to be 0.3 or less. Furthermore, ρ = nabs · dabs
/ Λ is desirably in the range of 0.1 or more in order to obtain a sufficient degree of modulation, and most preferably in the range of 0.45 ± 0.1 in order to obtain stable recording characteristics with a large degree of modulation. It is.

Furthermore, kabs of the optical information recording medium of the present invention
Is 0.3 or less, the reflectance increases as the distance approaches 0 as it approaches 0. Therefore, this range is most desirable. However, the closer to 0, the worse the recording sensitivity becomes.
It is necessary to be 0.01 or more, specifically,
Around 0.05 is desirable. These numerical values can be similarly applied to the case where another layer exists between the substrate 1, the light absorbing layer 2, and the reflecting layer 3. For example, when a transparent layer (for example, an enhanced layer such as SiO 2, an undercoat layer, etc.) is provided between the substrate 1 and the light absorbing layer 2, this layer is treated as a part of the substrate 1. When layers (for example, an adhesive layer and a hard layer) are provided between the light absorption layer 2 and the reflection layer 3, these layers are considered as a second light absorption layer, and ρ =
Treated as (n1 · d1 + n2 · d2) / λ. Further, when these layers are multi-layered, ρ = Σ (ni · di) / λ
(Where i is an integer).

When k is not 0, the average value of k can be determined as k = Σdiki / Σdi by the ratio of the film thickness, and the same can be handled as in the case of a single layer. When a groove is formed in the substrate 1, dabs is represented by an average value of the thickness of the light absorbing layer 2 in the groove and the thickness of the light absorbing layer 2 in the land.

The light-absorbing layer 2 is formed in a partial area on the light-transmitting substrate 1, and a pre-recording area 10 in which pits for signal reproduction are formed in advance in an area where the light-absorbing layer 2 is not provided. In the optical information recording medium, a large amount of uniform data can be recorded in the pre-recording area 10 in advance by a press or the like. Since there is no light absorbing layer 2 here, there is no risk of erroneous erasure or erroneous recording of other data. In the post-recording area 11 having the light absorbing layer 2, user-specific data is arbitrarily recorded. Then, since the data recorded in the recording area 11 can be reproduced with a signal conforming to the CD standard, the data can be reproduced by a commercially available CD player in the same manner as the information in the pre-recording area 10. These are not limited to disk-shaped recording media, but can be similarly considered for card-shaped or tape-shaped optical information recording media.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; Examples of the schematic structure of the optical information recording medium according to the present invention are shown in FIGS.
6 to FIG. In these drawings, 1 is a light-transmitting substrate, and 2 is a light-absorbing layer 2 formed thereon. Reference numeral 3 denotes a reflective layer 3 formed thereon, and reference numeral 4 denotes a protective layer 4 provided outside thereof. Further, 5 is that the laser beam emitted from the substrate 1 side is absorbed by the light absorption layer 2 to generate heat, and is melted, evaporated, sublimated, deformed or denatured, so that the laser light is emitted from the substrate 1 to the light absorption layer 2 side. These are pits formed to protrude.

Such an optical information recording medium is provided on the substrate 1
A reading laser beam is incident from the side, and a signal can be read based on an optical phase difference between reflected light of the pit 5 and the other portion of the laser beam. 1 to 3 show that the light absorbing layer 2 is formed on almost the entire surface of the light transmitting substrate 1.
4 to 6, the light absorbing layer 2 is formed only on a part of the translucent substrate 1 near the outer periphery, and this is the post-recording area 11, and This is the case where the pre-recording area 10 is formed in the peripheral portion.

Hereinafter, preferred specific embodiments will be described. The material of the light-transmitting substrate 1 is a material having a high transparency with a refractive index to laser light in a range of 1.4 to 1.6, and is preferably a resin excellent in impact resistance. Specifically, polycarbonate, acrylic and the like can be exemplified, but not limited to these. The substrate 1 is formed by using a material such as that described above, for example, by injection molding. In the case of an optical information recording medium having a prerecorded area 10 as shown in FIGS. 4 to 6, pits for recording information signals are formed only in the prerecorded area 10 on the substrate 1 at the stage of forming the substrate 1. Is done.

A pre-groove may be formed on the substrate 1 in a spiral shape. The pre-groove may be under any condition as long as it can be generally considered, but preferably has a depth of 50 to 250 nm. The pre-groove is usually formed by pressing a stamper at the time of injection molding of the substrate 1. A solvent-resistant layer such as SiO ₂ or an enhancement layer may be coated between the substrate 1 and the light absorption layer 2.

The material of the light absorbing layer 2 is preferably a light absorbing organic dye, such as cyanine dye, polymethine dye, triarylmethane dye, pyrylium dye, phenanthrene dye, tetradehydrocholine dye, triarylamine dye, squarylium dye, Croconic methine dyes, phthalocyanine dyes, azurenium dyes and the like can be exemplified, but are not limited thereto, such as low melting point metals,
Even if a known recording layer material is used, the effects of the present invention can be obtained. The light absorbing layer 2 may contain other pigments, resins (for example, thermoplastic resins such as nitrocellulose, thermoplastic elastomers), liquid rubber, and the like.

The light-absorbing layer 2 has a translucent property in which a pre-groove is formed by dissolving and solvating the above-mentioned dye and any additive with a known organic solvent (eg, alcohol, acetylacetone, toluene, etc.). It is formed on the surface of the substrate 1 or a substrate 1 on which another layer is further coated. In this case, as a forming means, a vapor deposition method,
An LB method, a spin coating method, or the like may be used.
The spin coating method is desirable because the layer thickness can be controlled by adjusting the concentration, viscosity and drying speed of the solvent.

The pre-recording area 10 shown in FIGS.
In the optical information recording medium having a pit, a pit 9 for signal reproduction (see FIG. 5) is formed in advance in a portion to be a pre-recording area 10 on the surface of the translucent substrate 1 by a stamper or the like, and post-recording outside the pit 9 is performed. It is obtained by forming the light absorbing layer 2 by coating the material only on the region 11. The reflective layer 3 is desirably a metal film, and is formed, for example, of gold, silver, aluminum or an alloy containing these by means of a vapor deposition method, a sputtering method, or the like. Since the optical information recording medium needs to have a reflectance of 70% or more, it is preferable that the optical information recording medium is formed of a metal mainly composed of gold or an alloy containing gold. Further, another layer such as an oxidation-resistant layer for preventing the reflection layer 3 from being oxidized may be interposed.

The layer on the reflection layer 3 side of the light absorbing layer 2, for example, the protective layer 4 described below may have a higher heat deformation temperature and a higher hardness than the layer on the substrate 1 side. desirable. By adopting such a configuration, an effect of reducing the block error rate of the recording signal is recognized. The protective layer 4 is desirably formed of a resin having excellent impact resistance. For example, it is formed by applying an ultraviolet curable resin by a spin coating method and irradiating ultraviolet rays to cure the resin. Further, it may be formed of an elastic material such as urethane.

Further, in the post-recording area 11, a pit 5 for recording information signals is formed in a layer adjacent to the light absorbing layer 2 by irradiating the light absorbing layer 2 with a laser beam. For example, when a layer closer to the reflective layer 3 than the light absorbing layer 2 is formed of a layer that is less likely to be thermally deformed than a layer closer to the substrate 1, the energy of the light absorbing layer 2 caused by the laser light is
Side, and as a result, a projecting pit 5 is formed in the layer on the substrate 1 side.

For example, in the case of an embodiment to be described later, as schematically shown in FIGS. 3 and 5, a pit protruding toward the light absorbing layer 2 is provided on the surface of the optical disk in contact with the light absorbing layer 2 of the substrate 1. 5 can be confirmed, and it is known that the reproduced waveform of the pit 5 thus formed is similar to that of the CD. Reproduction of a recording signal is performed by irradiating a reading laser from the substrate 1 side to read an optical phase difference between reflected light of the pit 5 and reflected light of a portion other than the pit.

A specific embodiment of this configuration will be described below. (Example 1) A polycarbonate substrate 1 having a thickness of 1.2 mm, an outer diameter of 120 mmφ, and an inner diameter of 15 mmφ formed with a spiral pre-group having a width of 0.8 μm, a depth of 0.08 μm, and a pitch of 1.6 μm is injection-molded. Molded by
0.65 as an organic dye for forming the light absorbing layer 2
g of 1,1 ′ dibutyl 3,3,3 ′, 3 ′ tetramethyl 4,5,4 ′, 5 ′ dibenzoindodicarbocyanine perchlorate (product number N
K3219) was dissolved in a diacetone alcohol solvent (10 cc), and the solution was applied on the substrate 1 by spin coating to form a light absorbing layer 2 made of a dye film having a thickness of 0.13 μm. The complex refractive index of the light absorbing layer 2 is nabs
= 2.7, kabs = 0.05. As will be described later, the wavelength λ of the semiconductor laser of the reproduction light is 780 nm, and ρ = nabs · dabs / λ = 0.45.

An Au film having a thickness of 600 Å was formed on the entire surface of the disk by sputtering.
The reflection layer 3 was formed. The complex refractive index of the reflection layer 3 is nre
f = 0.16 and kref = 4.67. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm.

The optical disk thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec at a recording power of 6.0 mW to record an EFM signal. Then, this optical disc is loaded into a commercially available CD player (Aure
x XR-V73, reproduction light wavelength λ = 780 nm). The reflectivity of this optical disk is 72%, I11 / Ito
p was 0.65 and I3 / Itop was 0.35. CD
According to the standard, the reflectance is 70% or more and I11 / Itop is 0.6.
As described above, I3 / Itop is determined to be 0.3 to 0.7, and the optical disk according to this embodiment satisfies this standard.

Example 2 0.5 g of 1,1 ′ diethyl 3,3,3 was used as an organic dye for forming the light absorbing layer 2 on the polycarbonate substrate 1 molded in the same manner as in Example 1 above. ', 3'tetramethyl 5,5'diethoxyindodicarbocyanine iodide dissolved in 10 cc of an isopropyl alcohol solvent is applied by a spin coating method, and the light absorbing layer 2 composed of a 0.10 µm-thick dye film is applied. Was formed. The complex refractive index of the light absorbing layer 2 is n
abs = 2.65, kabs = 0.05, and ρ = nab
s · dabs / λ = 0.34.

A Cu film having a thickness of 500 Å was formed on the entire surface of the disk by sputtering.
The reflection layer 3 was formed. The complex refractive index of the reflection layer 3 is nre
f = 0.12 and kref = 4.89. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm.

The optical disk thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec at a recording power of 6.0 mW to record an EFM signal. Then, this optical disk was reproduced by the same CD player as used in the first embodiment. As a result, the reflectance of the optical disk was 71%, I11 / Itop was 0.63, and I3 / Itop was 0.33. Therefore, the optical disk according to this embodiment also satisfies the CD standard, similarly to the above embodiment.

(Example 3) A GaAs film having a thickness of 900 angstroms was formed on a polycarbonate substrate 1 formed in the same manner as in Example 1 by a sputtering method.
Light absorbing layer 2 was formed. The complex refractive index of the light absorbing layer 2 is nabs = 3.6, kabs = 0.07, and ρ = n
abs · dabs / λ = 0.42. An Ag film having a thickness of 550 angstroms was formed on the entire surface of the disk by a sputtering method, and a reflective layer 3 was formed. The complex refractive index of the reflection layer 3 is nref = 0.086, kref = 5.2.
9 Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm.

The optical disk thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec at a recording power of 6.0 mW to record an EFM signal. Then, this optical disk was reproduced by the same CD player as used in the first embodiment. As a result, the reflectivity of the optical disk was 73%, I11 / Itop was 0.63, and I3 / Itop was 0.35. Therefore, the optical disk according to this embodiment also satisfies the CD standard, similarly to the above embodiment.

Example 4 0.5 μm width and 0.15 depth
A polycarbonate substrate 1 having a thickness of 1.2 mm, an outer diameter of 120 mmφ, and an inner diameter of 15 mmφ on which a spiral pre-group having a pitch of 1.6 μm was formed was formed by an injection molding method. As an organic dye for forming the light absorbing layer 2, 0.050 g of the same dye as in Example 1 and 0.005 g of nitrocellulose were added to an isopropyl alcohol solvent 10c.
c, and this was applied onto the above-mentioned substrate 1 by spin coating to form a light absorbing layer 2 made of a dye film having an average thickness of 0.025 μm. The complex refractive index of the light absorbing layer 2 is nabs = 2.0 and kabs = 0.04. The wavelength λ of the semiconductor laser of the reproduction light is 780 nm, and ρ = nab
s · dabs / λ = 0.064.

An Au film having a thickness of 500 Å was formed on the entire surface of the disk by a vapor deposition method, and a reflective layer 3 was formed. The complex refractive index of the reflective layer 3 is nref = 0.1
6, kref = 4.67. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm. An EFM signal was recorded on the thus obtained optical disc by a semiconductor laser having a wavelength of 780 nm in the same manner as in Example 1, and reproduced by a commercially available CD player. The reflectivity of this optical disk is 82%, I11 / Itop is 0.60, I3 / Itop
Itop is 0.31, and the optical disk according to this embodiment satisfies the CD standard.

Example 5 1,1′-dibutyl 3,3,3 ′, 3 ′ was used as an organic dye for forming the light absorbing layer 2 on the polycarbonate substrate 1 molded in the same manner as in Example 1.
0.050 g of tetramethyl 5,6,5 ′, 6 ′ tetramethoxyindodicarbocyanine perchlorate and 0.005 g of nitrocellulose are dissolved in 10 cc of diacetone alcohol solvent, and this is spin-coated on the substrate 1. The light absorption layer 2 formed of a dye film having a thickness of 0.020 μm was formed by coating by a method. The complex refractive index of the light absorbing layer 2 is nabs = 2.0 and kabs = 0.29. The wavelength λ of the semiconductor laser of the reproduction light is 780 nm, and ρ = n
abs · dabs / λ = 0.051.

An Au film having a thickness of 500 angstroms was formed on the entire surface of the disk by a vapor deposition method, a reflective layer 3 was formed, and an ultraviolet curable resin was spin-coated on the reflective layer 3 to form a film. Is irradiated with ultraviolet light and cured,
A protective layer 4 having a thickness of 10 μm was formed. An EFM signal was recorded on the thus obtained optical disc by a semiconductor laser having a wavelength of 780 nm in the same manner as in Example 1, and reproduced by a commercially available CD player. The reflectivity of this optical disk is 70%,
I11 / Itop is 0.61 and I3 / Itop is 0.30, and the optical disk according to this embodiment satisfies the CD standard.

(Embodiment 6) In the range of 46 to 100 mm in diameter (pre-recording area 10), the width is 0.6 μm and the depth is 0.10.
A pre-pit 8 capable of reproducing a spiral CD format signal having a pitch of 1.6 μm and a pitch of 1.6 μm is formed.
In 1), a width of 0.7 μm, a depth of 0.07 μm, and a pitch of 1.
A polycarbonate substrate 1 having a thickness of 1.2 mm, an outer diameter of 120 mmφ, and an inner diameter of 15 mmφ on which a 6 μm spiral pre-group was formed was formed by injection molding.

As an organic dye for forming the light absorbing layer 2, 0.8 g of the same dye as in Example 1 was dissolved in 10 cc of an acetylacetone solvent, and this was dissolved in
It is applied by spin coating only to the portion on the outer peripheral side from 0 mmφ, that is, on the post-recording area 11, and the film thickness is 0.17 μm
The light-absorbing layer 2 composed of the dye film was formed. The complex refractive index of the light absorbing layer 2 is nabs = 2.7 and kabs = 0.05.
It is. The wavelength λ of the semiconductor laser of the reproduction light is 780 nm, and ρ = nabs · dabs / λ = 0.59.

An Au film having a thickness of 500 angstroms was formed on the entire surface of the disk by a vapor deposition method, a reflective layer 3 was formed, and an ultraviolet curable resin was spin-coated on the reflective layer 3 to form a film. Is irradiated with ultraviolet light and cured,
A protective layer 4 having a thickness of 10 μm was formed. An EFM signal was recorded on the post-recording area 11 of the optical disc thus obtained by using a semiconductor laser having a wavelength of 780 nm, as in Example 1, and the pre-recording area 10 and the post-recording area 11 were reproduced by a commercially available CD player. The reflectivity of the rear recording area 11 of this optical disk is 70%, I11 / Itop is 0.62,
I3 / Itop was 0.32, the reflectance of the prerecorded area 10 was 90%, I11 / Itop was 0.80, and I3 / Itop was 0.50. Therefore, in the optical disc according to this embodiment, both the pre-recording area 10 and the post-recording area 11 satisfy the CD standard.

(Embodiment 7) In a range of 46 to 100 mm in diameter (pre-recording area 10), a width of 0.6 μm and a depth of 0.10.
A pre-pit 8 capable of reproducing a spiral CD format signal having a pitch of 1.6 μm and a pitch of 1.6 μm is formed.
In 1), width 0.5 μm, depth 0.18 μm, pitch 1.
A polycarbonate substrate 1 having a thickness of 1.2 mm, an outer diameter of 120 mmφ, and an inner diameter of 15 mmφ on which a 6 μm spiral pre-group was formed was formed by injection molding.

As an organic dye for forming the light absorbing layer 2, 1,1'-diethyl 3,3,3 ', 3'tetramethyl 5,7,5', 7'tetramethoxyindodicarbocyanine perchlorate 0 .55 g was dissolved in 10 cc of a diacetone alcohol solvent.
Spin coating method is applied only on the outer peripheral side from 00 mmφ, that is, on the post-recording area 11, and the average film thickness is 120
The light absorbing layer 2 made of a dye film having a thickness of 10 nm was formed. The complex refractive index of the light absorbing layer 2 is nabs = 2.9, kabs = 0.
20. Reproduction light wavelength of semiconductor laser λ = 780n
m, and ρ = nabs · dabs / λ = 0.45.

An Au film having a thickness of 500 angstroms was formed on the entire surface of the disk by a vapor deposition method, a reflective layer 3 was formed, and an ultraviolet curable resin was spin-coated on the reflective layer 3 to form a reflective layer. Is irradiated with ultraviolet light and cured,
A protective layer 4 having a thickness of 10 μm was formed. An EFM signal was recorded on the post-recording area 11 of the optical disc thus obtained by using a semiconductor laser having a wavelength of 780 nm as in Example 1, and the pre-recording area 10 and the post-recording area 11 were reproduced by a commercially available CD player. The reflectance of the rear recording area 11 of this optical disk is 70%, I11 / Itop is 0.70,
I3 / Itop was 0.40, and the reflectance, I11 / Itop, and I3 / Itop of the prerecorded area 10 were the same as those in the sixth embodiment. Therefore, in the optical disc according to this embodiment, both the pre-recording area 10 and the post-recording area 11 satisfy the CD standard.

(Comparative Example 1) On a polycarbonate substrate 1 molded in the same manner as in Example 1, 0.065 g of the same organic dye as in Example 1 was added with an isopropyl alcohol solvent 10c.
The solution dissolved in c was applied by spin coating to form a light absorbing layer 2 composed of a dye film having a thickness of 0.01 μm.
Ρ in this optical disk is nabs · dabs / λ = 0.
035.

An Al film having a thickness of 600 Å was formed on the entire surface of the disk by sputtering.
The reflection layer 3 was formed. The complex refractive index of the reflection layer 3 is nre
f = 1.87 and kref = 7.0. Further, an ultraviolet curable resin is spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, and a 10 μm thick protective layer 4 is formed.
Was formed.

The optical disk thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec to record an EFM signal.
Did not record enough. Then, this optical disk was reproduced by the same CD player as used in the first embodiment. As a result, the reflectivity of the optical disk becomes 7
0%, but I11 / Itop is 0.20, I3 / Itop
Was 0.08. That is, even if kabs is 0.3 or less, if ρ is smaller than 0.05,
In some cases, the reflectivity can be assured to be 70%, but the degree of modulation cannot be obtained and the CD standard cannot be satisfied.

Comparative Example 2 A polycarbonate substrate 1 molded in the same manner as in Example 1 was coated with 1.3 g of the same organic dye dissolved in 10 cc of an isopropyl alcohol solvent by spin coating. , Film thickness 0.
The light absorbing layer 2 composed of a 26 μm dye film was formed. In this optical disk, ρ = nabs · dabs / λ = 0.90. An Au film having a thickness of 600 Å was formed on the entire surface of the disk by sputtering, and the reflective layer 3 was formed.
Was formed. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm.

The optical disk thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec at a recording power of 6.0 mW to record an EFM signal. Then, this optical disk was reproduced by the same CD player used in the first embodiment. As a result, the reflectivity of the optical disk was 62%, I11 / Itop was 0.60, and I3 / Itop
Was 0.3, the eye pattern of the reproduced signal was not clear, and many errors were observed. From this result, kabs
Is smaller than 0.3, it is understood that if ρ is larger than 0.6, the reflectivity becomes low and the CD standard cannot be satisfied.

Comparative Example 3 0.58 g of 1,1 ′ diethyl 3,3,3 was used as an organic dye for forming the light absorbing layer 2 on the polycarbonate substrate 1 molded in the same manner as in Example 1. ', 3' tetramethylindotricarbocyanine perchlorate (manufactured by Japan Photographic Dye Laboratories, Inc.
NK2885) with isopropyl alcohol solvent 1
The solution dissolved in 0 cc is applied by spin coating,
The light absorbing layer 2 composed of a dye film having a thickness of 0.12 μm was formed. The complex refractive index of the light absorbing layer 2 is nabs = 2.7,
kabs = 1.6, ρ = nabs · dabs / λ = 0.4
2.

An Ag film having a thickness of 600 Å was formed on the entire surface of the disk by sputtering.
The reflection layer 3 was formed. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and irradiated with ultraviolet light to be cured, thereby forming a protective layer 4 having a thickness of 10 μm. The thus obtained optical disk was irradiated with a semiconductor laser having a wavelength of 780 nm at a linear velocity of 1.2 m / sec at a recording power of 6.0 mW, and an EFM signal was recorded. Then, when this optical disc was reproduced by the same CD player as used in the first embodiment, the reflectivity was only 10%, and the optical disc could not be reproduced. Thus, when ρ is 0.05 or more and 0.
Even if it is within the range of 6 or less, if kabs is larger than 0.3, the reflectivity becomes very low, and CD
It turns out that the standard cannot be satisfied.

[0055]

As described above, according to the optical information recording medium of the present invention, the reflectance is 70 in conformity with the CD standard.
%, And an output signal of I11 / Itop expressed as a modulation factor of 0.6 or more and I3 / Itop of 0.3 to 0.7 can be obtained. This makes it possible to obtain an optical information recording medium that can be reproduced using a commercially available CD player by forming pits with a laser beam without depending on publishing by a press or the like. C
D will be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic half sectional perspective view showing the structure of an optical information recording medium according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the optical information recording medium.

FIG. 3 is a sectional view of a main part of the optical information recording medium after recording.

FIG. 4 is a schematic half-sectional perspective view showing the structure of an optical information recording medium according to another embodiment of the present invention.

FIG. 5 is a sectional view of a portion A of the optical information recording medium.

FIG. 6 is a sectional view of a portion B of the optical information recording medium after recording.

FIG. 7 shows ρ = nabs · in the light absorption layer of the optical information recording medium.
It is a graph which shows the example of the relationship between dabs / (lambda) and a reflectance.

FIG. 8 is a graph showing the relationship between the imaginary part kabs of the complex refractive index and the reflectance.

FIG. 9 is a graph showing a region satisfying the CD standard when ρ = nabs · dabs / λ and kabs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Light absorption layer 3 Reflection layer 5 Pit 4 Protective layer 10 Pre-recording area 11 Post-recording area

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Arai 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Yuden Co., Ltd. (56) References JP 3-75942 (JP, B2) (58) Survey Field (Int.Cl. ⁶ , DB name) G11B 7/24

Claims (12)

(57) [Claims] 1. An optical information recording medium in which at least a light absorbing layer (2) and a reflecting layer (3) are sequentially formed on a light transmitting substrate (1), the light absorbing layer (2) is a dye film. Ρ = nabs · dabs / λ, which is given by the real part nabs of the complex refractive index, the film thickness dabs, and the wavelength λ of the reproduction light,
0.05 ≦ ρ ≦ 0.6, the imaginary part kabs of the complex refractive index of the light absorbing layer (2) is 0.01 ≦ kabs ≦ 0.3, and the recording laser beam is absorbed. A pit (5) for producing an optical phase difference of the reading laser beam incident from the substrate (1) side. 2. A light-absorbing layer (2) is formed in a partial area on a light-transmitting substrate (1), and pits for signal reproduction are formed in advance in an area without the light-absorbing layer (2). Pre-recording area (1
The optical information recording medium according to claim 1 , wherein 0) is satisfied. 3. The pit (5) is provided on the substrate from the light absorbing layer (2).
3. The optical information recording medium according to claim 1 , wherein the optical information recording medium is a protrusion formed on the (1) side . 4. An optical information recording medium according to any one of claims 1 to 3 layers pits (5) are formed, characterized in that a substrate (1). 5. The pit (5) is a light absorbing layer of the substrate (1).
The surface facing the (2) side protrudes toward the light absorbing layer (2) side.
5. The optical information recording medium according to claim 4 , wherein the optical information recording medium is formed. 6. The optical information recording medium according to any one of claims 1 to 5, wherein the reflective layer (3) is a film of an alloy comprising gold or gold. 7. At least a light absorbing layer (2) and a reflecting layer (3) are sequentially formed on a light transmitting substrate (1), and the light absorbing layer (2) is made of a dye film, and has a complex refraction. Ρ = nabs · dabs / λ given by the real part nabs of the ratio, the film thickness dabs, and the wavelength λ of the reproduction light is 0.05 ≦ ρ ≦ 0.6, and the complex refraction of the light absorbing layer (2) is The optical information recording medium in which the imaginary part kabs of the ratio is 0.01 ≦ kabs ≦ 0.3 and the pits (5) are formed by absorbing the recording laser light is read from the substrate 1 side. A method for reproducing an optical information recording medium, comprising: injecting a laser beam for use, and reading a signal based on an optical phase difference between reflected light of the pit (5) portion and the other portion of the laser beam. 8. A light-absorbing layer (2) is formed in a partial region on a light-transmitting substrate (1), and pits for signal reproduction are previously formed in a region where the light-absorbing layer (2) does not exist. Pre-recording area (1
The method for reproducing an optical information recording medium according to claim 7 , wherein 0) is satisfied. 9. The pit (5) is formed on the substrate by the light absorbing layer (2).
9. The method for reproducing an optical information recording medium according to claim 7 , wherein the optical information recording medium is a protrusion formed on the (1) side . 10. The optical information recording medium according to claim 7 , wherein the layer on which the pits (5) are formed is a substrate (1). 11. The pit (5) is a light absorbing layer of the substrate (1).
The surface facing the (2) side protrudes toward the light absorbing layer (2) side.
11. The optical information recording medium according to claim 10 , wherein the optical information recording medium is formed. 12. The optical information recording medium according to claim 7 , wherein the reflection layer is a film of gold or an alloy containing gold.