JPH07282465A - Optical information recording medium and its reproducing method - Google Patents

Abstract

PURPOSE:To make it possible to have a high reflectivity, to obtain an output signal of a high modulation degree complying with a CD format at the time of reproducing of data, to record information and to make production with simple means without using means, such as pressing. CONSTITUTION:At least a light absorption layer 2 ana reflection layer 3 are successively formed on a substrate 1 having translucency. The rho=nabs.dabs/lambda given by the real number part nabs of the complex refractive index of the light absorption layer 2, film thickness dabs and the wavelength lambda of the reproducing light is 0.05<=rho<=0. 6 and the imaginary part kabs of the complex refractive index of the light absorption layer 2 is 0.01<=kabs<=0.3. Pits 5 recording CD signals by an incident laser beam for recording on the light absorption layer 2 through the substrate 1 are formed on the layer on the substrate 1 side from the light absorption layer 2. The recorded signals are read by the optical phase differences of the reflected light beams of the parts of these pits 5 and the parts exclusive thereof of the laser beams for reading which are made incident from the substrate 1 side.

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 and having pits formed by laser light incident on the light absorbing layer from the substrate side, The present invention relates to a reproducing method of an optical information recording medium for reading a signal recorded by an optical phase difference between the reflected light of the pit portion of the reading laser light incident from the substrate side and the reflected light of the other portion.

[0002]

2. Description of the Related Art A so-called writable optical information recording medium capable of recording data by irradiating a laser beam is a metal layer of Te, Bi, Mn, etc., a dye layer of cyanine, merocyanine, phthalocyanine, etc. And recording data by forming a pit having a through hole by means of deforming, sublimating, evaporating or modifying the recording layer by irradiating a laser beam. In an optical information recording medium having this recording layer, a void is generally provided behind the recording layer in order to facilitate deformation, sublimation, evaporation or modification of the recording layer when forming pits. . Specifically, for example, a so-called air sandwich structure, in which two substrates are stacked with a space therebetween, is used.

The optical information recording medium of the type which forms the perforated pits utilizes the light absorbing property of the light-absorbing material, so that the light transmittance of the perforated pits and the other parts can be improved. The reproduction contrast is obtained by the difference in the amount of reflected light caused by the difference. That is, the reflected light is read, but basically the same mechanism as that of a transmission type optical information recording medium, and the mechanism for obtaining reproduction contrast is an optical information recording medium which should be called a light absorbing type.

On the other hand, a so-called ROM type optical information recording medium in which data is recorded in advance and data cannot be written or erased thereafter has been widely put to practical use in the information processing and acoustic departments. This type of optical information recording medium does not have the recording layer as described above, but pits for reproducing recorded data are formed in advance on a polycarbonate substrate by means of a press or the like, and Au, Ag are formed on the pit. A reflective layer made of a metal film of Cu, Al, or the like is formed and further covered with a protective layer.

The most typical one of the ROM type optical information recording media is a so-called CD, which is a compact disc which has been widely put into practical use in the audio department, the information processing department and the like.
The specifications of recording and reproducing signals of D are standardized as the international standard IEC908, and reproducing apparatuses conforming to the standard are very widely used as compact disc players (CD players). Each of the optical information recording media is in the form of a disk having a hole for clamping the rotary shaft in the center, that is, an optical disc.

[0006]

Since the above-mentioned optical information recording medium also uses the same reproducing means as the CD, it is strongly desired that the optical information recording medium conforms to the already widespread CD when reproducing. 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 absorption layer is not removed, that is, the portion where the absorption layer is not pit becomes low level, and the absorption layer is removed. The intensity of the reflected light at the portion, that is, the pit portion becomes a high level. Therefore, when the reflected light is captured, bright pits due to openings are present in the background darkened by the light absorption layer on the one surface, in contrast 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 decreased. Therefore, under the CD standard, which requires a high reflectance, it was not possible to satisfy the same standard in terms of reflectance and modulation degree.

On the other hand, the already widely used CD requires a polycarbonate substrate having pits for reproducing recorded data to be formed by means of a press or the like, and therefore is suitable for mass publication and is costly. From the aspect, it is not suitable for small-volume publication. The present invention has been made to solve the above-mentioned conventional problems, and has a high reflectance of 70% or more, and when reproducing data, an output signal having a modulation degree conforming to the CD format can be obtained, and It is an object of the present invention to provide an optical information recording medium and a reproducing method thereof, which can record and manufacture information by a simple means without using a means such as a press, and is therefore suitable for small-volume publication.

[0008]

That is, in an optical information recording medium according to the present invention, at least a light absorbing layer 2 and a reflective layer 3 are sequentially formed on a substrate 1 having a light transmitting property, and the light absorbing layer 2 is a dye. It is composed of a film and is given by the real part nabs of the complex index of refraction, the film thickness dabs, and the wavelength λ of the reproduction light, ρ = nabs.
dabs / λ is 0.05 ≦ ρ ≦ 0.6, and the imaginary part kabs of the complex refractive index of the light absorption layer 2 is 0.01 ≦ kabs ≦
In addition to 0.3, pits 5 are formed to absorb the recording laser light and to cause an optical phase difference of 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, in the above optical information recording medium, the reading laser beam is made incident from the side of the substrate 1 and the portion of the pit 5 and the other portion of the laser beam are read. It is characterized in that the signal is read by the optical phase difference of the reflected light.

In the above optical information recording medium, the light absorption layer 2 is formed in a partial area on the transparent substrate 1, and a pit for signal reproduction is formed in advance in the area where the light absorption layer 2 is not present. The prerecorded area 10 may be provided. Pit 5 is
Although it can be formed on the substrate 1 itself, if other layers are formed between the substrate 1 and the light absorption layer 2, the pits 5 may be formed on these layers or the substrate.

The reflective layer 3 is preferably made of a film of gold or an alloy containing gold having a high reflectance. Further, a layer that is less likely to be thermally deformed than the layer in which the pits 5 are formed on the reflective layer 3 side of the light absorption layer 2, for example, a layer having a higher thermal deformation temperature and hardness than the layer in which the pits 5 are formed, The reflective layer 3
A protective layer 4 that is less likely to be thermally deformed than the substrate 1 or the like on which the pits 5 are formed is formed thereon.

[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 substrate 1 having a light-transmitting property, and are incident on the light-absorbing layer 2 through the substrate 1 for recording. From the optical information recording medium in which the pits 5 for recording the CD signal by the laser light are formed, the reflectance according to the CD format is 70% or more, and I11 / I shown as the modulation degree.
In order to obtain a reproduced signal with top of 0.6 or more and I3 / Itop of 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 calculated. , Ρ = nabs · dabs / λ given by the wavelength λ of the reproduction light is a very important parameter. As a result of experiments and simulations on this point, the relationship as shown in FIG. 7 was obtained.

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

It can be seen from this graph that when ρ is smaller than 0.6, the reflectance can be almost certainly ensured to be 70% or more. a region where ρ is less than 0.05,
Even in a region over 0.6, a reflectance of 70% or more may be obtained. However, in the case where ρ is less than 0.05, the film thickness dabs of the light absorption layer 2 must be considerably thin, 0.05 μm or less, so that it is necessary to form pits for recording data. It becomes difficult to obtain the above-mentioned reproduced signal. On the other hand, if the area exceeds 0.6, it becomes difficult to control the film thickness to be uniform, and the recording characteristics vary, I3 / Itop is less than 0.3, and the jitter error increases. There is a problem in manufacturing, such as that That is, by setting ρ to be 0.05 to 0.6, the reflectance can conform to the CD format.
It can be seen that it can be set to 0% or more.

Further, as a result of further studying these results, the present inventors have found that just setting ρ within the range of 0.05 to 0.6 does not necessarily stabilize the output signal as specified in the CD standard. We found that kabs is an important parameter. FIG. 8 shows the reflective layer 3
In the optical information recording medium using the Au film for the light absorption layer 2
Of the imaginary part kabs while changing the translucency of
It is a graph which shows the change of the reflectance when changing from the value close to 0 to 2.0.

From this graph, it can be seen that the reflectance increases as kabs approaches 0. From the results of experiments and simulations, the present inventors show that the light absorption layer 2 has a sufficiently high light-transmitting property in order to stably maintain a high reflectance in the range of ρ of 0.05 to 0.6. It has been found that the imaginary part kabs of the complex refractive index of the same layer must be 0.3 or less. ρ is 0.05 to 0.
Within the range of 6, the reflectance is 7 when kabs is larger than 0.3.
It is difficult to secure 0% or more.

From these results, the results shown in FIG. 9 can be obtained. FIG. 9 shows C at the values of ρ and kabs.
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, Also, it is understood that kabs needs to be 0.3 or less. Furthermore, ρ = nabs.dabs
The range of / λ is preferably 0.1 or more in order to obtain a sufficient modulation degree, and is most preferably 0.45 ± 0.1 in order to obtain stable recording characteristics with a large modulation degree. Is.

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

Further, when k is not 0, if k as an average value is obtained as k = Σdiki / Σdi according to the film thickness ratio, it can be treated in the same manner as in the case of a single layer. When the groove is formed on the substrate 1, dabs is represented by the average value of the film thickness of the light absorption layer 2 in the groove and the film thickness of the light absorption layer 2 in the land portion.

The light absorbing layer 2 is formed in a partial area on the transparent substrate 1, and a prerecorded area 10 in which a pit for signal reproduction is formed in advance is provided in an area where the light absorbing layer 2 is not present. In the optical information recording medium, a large amount of uniform data can be recorded in advance in the pre-recording area 10 by a press or the like. Since there is no light absorption layer 2 here, there is no risk of erroneous erasing 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 after this can be reproduced with a signal conforming to the CD standard, it can be reproduced by a commercially available CD player as with the information in the prerecording area 10. These are not limited to the disk-shaped recording medium, and can be similarly considered in a card-shaped or tape-shaped optical information recording medium.

[0020]

Embodiments of the present invention will now be described specifically and in detail with reference to the drawings. Examples of the schematic structure of the optical information recording medium according to the present invention are shown in FIGS.
~ Shown in FIG. In these drawings, 1 is a transparent substrate, and 2 is a light absorption layer 2 formed thereon. Reference numeral 3 denotes a reflective layer 3 formed thereon, and 4 denotes a protective layer 4 provided on the outside thereof. Further, 5 is that the laser light emitted from the substrate 1 side is absorbed by the light absorption layer 2 to generate heat, and is melted, evaporated, sublimated, deformed or modified, so that the substrate 1 is transferred to the light absorption layer 2 side. It is a pit formed so as to project.

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

A preferred specific embodiment will be described below. The material of the transparent substrate 1 is a highly transparent material having a refractive index in the range of 1.4 to 1.6 with respect to laser light, and a resin having excellent impact resistance is desirable. Specific examples thereof include polycarbonate and acryl, but the invention is not limited thereto. The substrate 1 is molded by means of injection molding or the like using the above materials. In the case of the optical information recording medium having the 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 molding the substrate 1. To be done.

A pre-groove may be spirally formed on such a substrate 1. The pregroove may be under any condition that is usually considered, but a depth of 50 to 250 nm is preferable. The pre-groove is usually formed by pressing a stamper during 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, Examples include croconic methine dyes, phthalocyanine dyes, and azurenium dyes, but are not limited to these, and low melting point metals and the like,
The effects of the present invention can be obtained even if a known recording layer material is used. The light absorption layer 2 may contain other dyes, resins (for example, thermoplastic resins such as nitrocellulose, thermoplastic elastomers), liquid rubber, and the like.

The light-absorbing layer 2 has a light-transmitting property in which a pregroove is formed by dissolving and solvating the above-mentioned dye and optional additives in a known organic solvent (eg alcohol, acetylacetone, toluene). It is formed on the surface of the substrate 1 or the substrate 1 obtained by coating the substrate 1 with another layer. In this case, as a forming means, a vapor deposition method,
The LB method, the spin coating method and the like can be mentioned, but the light absorption layer 2
The spin coating method is preferable because the layer thickness can be controlled by adjusting the concentration, viscosity, and drying rate of the solvent.

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

The layer of the light absorption layer 2 on the reflection layer 3 side, for example, the protective layer 4 described below, has a higher heat distortion temperature and a higher hardness than the layer on the substrate 1 side. desirable. With this configuration, it is possible to recognize the effect of reducing the block error rate of the recording signal. The protective layer 4 is preferably 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 it with ultraviolet rays to cure it. Alternatively, it may be formed of an elastic material such as urethane.

Further, in the post-recording area 11, by irradiating the light absorption layer 2 with a laser beam, pits 5 for recording an information signal are formed in a layer adjacent to the light absorption layer 2. For example, when the layer on the reflection layer 3 side of the light absorption layer 2 is formed of a layer that is less likely to be thermally deformed than the layer on the substrate 1 side, the energy of the light absorption layer 2 caused by the laser light is the substrate 1
Side pits 5, resulting in the formation of protruding pits 5 in the layer on the substrate 1 side.

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

A concrete example of this structure will be described below. Example 1 A polycarbonate substrate 1 having a width of 0.8 μm, a depth of 0.08 μm, a spiral pregroup having a pitch of 1.6 μm, a thickness of 1.2 mm, an outer diameter of 120 mmφ, and an inner diameter of 15 mmφ is injection-molded. Was molded by.
As an organic dye for forming the light absorption layer 2, 0.65
g of 1,1 'dibutyl 3,3,3', 3 'tetramethyl 4,5,4', 5 'dibenzoindodicarbocyanine perchlorate (manufactured by Japan Photosensitive Dye Research Institute, product number N
K3219) was dissolved in 10 cc of diacetone alcohol solvent, and this was coated on the above-mentioned substrate 1 by a spin coating method to form a light absorption layer 2 made of a dye film having a film thickness of 0.13 μm. The complex refractive index of this light absorption layer 2 is nabs
= 2.7 and kabs = 0.05. As will be described later, the wavelength of the semiconductor laser for reproducing light is λ = 780 nm, and ρ = nabs · dabs / λ = 0.45.

An Au film having a film thickness of 600 Å was formed on the entire surface of this disk by a sputtering method.
The reflective layer 3 was formed. The complex refractive index of this reflective 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 was irradiated with ultraviolet rays to be cured to form a protective layer 4 having a thickness of 10 μm.

The optical disc thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec and a recording power of 6.0 mW to record an EFM signal. Then, 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 defined to be 0.3 to 0.7, and the optical disc according to this embodiment satisfies this standard.

(Example 2) 0.5 g of 1,1'diethyl 3,3,3 was added as an organic dye for forming the light absorption layer 2 on the polycarbonate substrate 1 molded in the same manner as in Example 1 above. A light-absorbing layer 2 made of a dye film having a thickness of 0.10 μm, which was prepared by dissolving a solution of ', 3' tetramethyl 5,5'diethoxyindodicarbocyanine iodide dissolved in 10 cc of isopropyl alcohol solvent by spin coating. Was formed. The complex refractive index of the light absorption layer 2 is n
abs = 2.65, kabs = 0.05, and ρ = nab
s · dabs / λ = 0.34.

A Cu film having a film thickness of 500 Å was formed on the entire surface of this disk by a sputtering method.
The reflective layer 3 was formed. The complex refractive index of this reflective 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 was irradiated with ultraviolet rays to be cured to form a protective layer 4 having a thickness of 10 μm.

The optical disc thus obtained has a wavelength of 78
A 0 nm semiconductor laser was irradiated at a linear velocity of 1.2 m / sec and a recording power of 6.0 mW to record an EFM signal. Then, this optical disk was reproduced by the same CD player as that 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 disc according to this embodiment also satisfies the CD standard as in the above-mentioned embodiment.

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

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

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

An Au film having a film thickness of 500 Å was formed on the entire surface of this disk by a vapor deposition method to form a reflective layer 3. 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 was irradiated with ultraviolet rays to be cured to form 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 as in Example 1, and was reproduced by a commercially available CD player. The reflectivity of this optical disk is 82%, I11 / Itop is 0.60, I3 /
Itop is 0.31, and the optical disk according to this example satisfies the CD standard.

(Example 5) 1,1'dibutyl 3,3,3 ', 3' was used as an organic dye for forming the light absorption layer 2 on the polycarbonate substrate 1 molded in the same manner as in Example 1.
Tetramethyl 5,6,5 ', 6' tetramethoxy indodicarbocyanine perchlorate 0.050 g and nitrocellulose 0.005 g are dissolved in diacetone alcohol solvent 10 cc, and this is spin-coated on the substrate 1. To form a light absorption layer 2 made of a dye film having a thickness of 0.020 μm. The complex refractive index of the light absorption layer 2 is nabs = 2.0 and kabs = 0.29. The wavelength of the semiconductor laser for reproducing light is λ = 780 nm, and ρ = n
It is abs * dabs / λ = 0.051.

An Au film having a film thickness of 500 Å was formed on the entire surface of this disk by a vapor deposition method to form a reflection layer 3, and then an ultraviolet curable resin was spin-coated on the reflection layer 3 to form an Au film. Irradiate it with ultraviolet light to cure it,
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 as in Example 1, and was reproduced by a commercially available CD player. The reflectance of this optical disk is 70%,
Since I11 / Itop is 0.61 and I3 / Itop is 0.30, the optical disc according to this embodiment satisfies the CD standard.

Example 6 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, and the outside thereof has a diameter of 100 to 117 mmφ (after recording area 1
1), width 0.7 μm, depth 0.07 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, in which a 6 μm spiral pregroup was formed, was molded by an injection molding method.

As an organic dye for forming the light absorption 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 the substrate 1 having a diameter of 10
The outer peripheral portion of 0 mmφ, that is, the post-recording area 11 only, is applied by spin coating to a film thickness of 0.17 μm.
The light absorption layer 2 made of the dye film of No. 3 was formed. The complex index of refraction of this light absorption layer 2 is nabs = 2.7, kabs = 0.05.
Is. The wavelength of the semiconductor laser for reproducing light is λ = 780 nm, and ρ = nabs · dabs / λ = 0.59.

An Au film having a film thickness of 500 angstrom is formed on the entire surface of this disk by a vapor deposition method to form a reflective layer 3, and further, an ultraviolet curable resin is spin-coated on the reflective layer 3, and Irradiate it with ultraviolet light to cure it,
A protective layer 4 having a thickness of 10 μm was formed. An EFM signal was recorded in the post-recording area 11 of the thus obtained optical disc by 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 post-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) A width of 0.6 μm and a depth of 0.10 are set in a range of diameter 46 to 100 mmφ (pre-recording area 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, and the outside thereof has a diameter of 100 to 117 mmφ (after recording area 1
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, in which a 6 μm spiral pregroup was formed, was molded by an injection molding method.

As the organic dye for forming the light absorption layer 2, 1,1'diethyl 3,3,3 ', 3' tetramethyl 5,7,5 ', 7' tetramethoxyindodicarbocyanine perchlorate 0 0.55 g was dissolved in 10 cc of diacetone alcohol solvent, and this was added to the substrate 1 having a diameter of 1 cc.
An average film thickness of 120 mm is applied by spin coating only on the outer peripheral side of 00 mmφ, that is, on the rear recording area 11.
The light absorption layer 2 made of a dye film having a thickness of nm was formed. The complex refractive index of this light absorption layer 2 is nabs = 2.9, kabs = 0.
Twenty. Reproducing light semiconductor laser wavelength λ = 780 n
m, and ρ = nabs · dabs / λ = 0.45.

An Au film having a film thickness of 500 angstrom was formed on the entire surface of this disk by a vapor deposition method to form a reflective layer 3, and further, an ultraviolet curable resin was spin-coated on the reflective layer 3, and Irradiate it with ultraviolet light to cure it,
A protective layer 4 having a thickness of 10 μm was formed. An EFM signal was recorded in the post-recording area 11 of the thus obtained optical disc by 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 post-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 pre-recorded area 10 were the same as those in Example 6. 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 mixed with isopropyl alcohol solvent 10c.
What was dissolved in c was applied by a spin coating method to form a light absorbing layer 2 made of a dye film having a film thickness of 0.01 μm.
Ρ on this optical disk is nabs · dabs / λ = 0.
It is 035.

An Al film having a film thickness of 600 Å was formed on the entire surface of this disk by a sputtering method.
The reflective layer 3 was formed. The complex refractive index of this reflective 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 is irradiated with ultraviolet rays to be cured to form a protective layer 4 having a thickness of 10 μm.
Was formed.

The optical disc thus obtained has a wavelength of 78
Recording of an EFM signal was attempted by irradiating a 0 nm semiconductor laser at a linear velocity of 1.2 m / sec, but the recording power was 10 mW.
I couldn't record enough. Then, this optical disk was reproduced by the same CD player as that used in the first embodiment. As a result, the reflectance of the optical disk is 7
0%, 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,
Although it is possible to secure the reflectance of 70% in some cases, it is understood that the 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 as in Example 1 dissolved in 10 cc of isopropyl alcohol solvent by spin coating. , Film thickness 0.
The light absorption layer 2 made of a 26 μm dye film was formed. In this optical disc, ρ = nabs · dabs / λ = 0.90. An Au film having a thickness of 600 Å is formed on the entire surface of this disk by a sputtering method to form a reflective layer 3
Was formed. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and was irradiated with ultraviolet rays to be cured to form a protective layer 4 having a thickness of 10 μm.

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

(Comparative Example 3) 0.58 g of 1,1'diethyl 3,3,3 as an organic dye for forming the light absorption layer 2 was formed on the polycarbonate substrate 1 molded in the same manner as in Example 1. ', 3' Tetramethyl indotricarbocyanine perchlorate (manufactured by Japan Photosensitive Dye Research Institute,
Part No. NK2885) with isopropyl alcohol solvent 1
What was dissolved in 0 cc was applied by spin coating,
The light absorption layer 2 made of a dye film having a thickness of 0.12 μm was formed. The complex index of refraction of this light absorption layer 2 is nabs = 2.7,
kabs = 1.6, ρ = nabsdabs / λ = 0.4
It is 2.

An Ag film having a film thickness of 600 angstrom was formed on the entire surface of this disk by a sputtering method.
The reflective layer 3 was formed. Further, an ultraviolet curable resin was spin-coated on the reflective layer 3 and was irradiated with ultraviolet rays to be cured to form 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 and a recording power of 6.0 mW to record an EFM signal. When this optical disk was reproduced by the same CD player as used in Example 1, the reflectance was only 10% and it was not possible to reproduce. Thus, 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 reflectance 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 according to the CD standard is 70.
It is possible to obtain an output signal in which I11 / Itop is 0.6 or more and I3 / Itop is 0.3 to 0.7, which is shown as a modulation factor. As a result, an optical information recording medium that can be reproduced by using a commercially available CD player can be obtained by forming pits with a laser beam regardless of publication by a press or the like. As a result, it is suitable for small-volume publication easily. C
D will be obtained.

[Brief description of drawings]

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

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

FIG. 3 is a sectional view of an essential part of the same 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 semi-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 B portion after recording on the optical information recording medium.

FIG. 7 shows ρ = nabs · in the light absorption layer of the optical information recording medium.
6 is a graph showing an example of the relationship between dabs / λ and 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 at ρ = nabs · dabs / λ and kabs.

[Explanation of symbols]

 1 Substrate 2 Light Absorbing Layer 3 Reflective Layer 5 Pit 4 Protective Layer 10 Pre-Recording Area 11 Post-Recording Area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G11B 7/00 R 9464-5D (72) Inventor Yuji Arai 6-16-20 Ueno, Taito-ku, Tokyo No. Taiyo Electric Co., Ltd.

Claims (14)

[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 transparent substrate (1), and the light absorbing layer (2) is a dye film. And ρ = nabsdabs / λ 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 laser light for recording is absorbed. The optical information recording medium is characterized in that pits (5) that cause an optical phase difference of the reading laser light incident from the substrate (1) side are formed. 2. The light according to claim 1, further comprising a layer on the reflective layer (3) side of the light absorption layer (2) that is less likely to be thermally deformed than a layer on which the pits (5) are formed. Information recording medium. 3. The protective layer (4) formed on the reflective layer (3), wherein the layer less susceptible to thermal deformation than the layer in which the pits (5) are formed is a protective layer (4). Optical information recording medium. 4. The layer which is less likely to be thermally deformed than the layer in which the pits (5) are formed is a layer having a higher thermal deformation temperature and hardness than the layer in which the pits (5) are formed. 3. The optical information recording medium described in 3. 5. A light absorbing layer (2) is formed in a partial area on a transparent substrate (1), and a pit for signal reproduction is previously formed in an area where the light absorbing layer (2) is not present. Pre-recorded area (1
0) The optical information recording medium according to any one of claims 1 to 4, wherein the optical information recording medium comprises: 6. The optical information recording medium according to claim 1, wherein the layer in which the pits (5) are formed is the substrate (1). 7. The optical information recording medium according to claim 1, wherein the reflective layer (3) is a film of gold or an alloy containing gold. 8. A light absorption layer (2) and a reflection layer (3) are sequentially formed on a transparent substrate (1), and the light absorption layer (2) is composed of a dye film, and its complex refraction. Ρ = nabs · dabs / λ given by the real part nabs of the index, 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 absorption layer (2) is Reading from the substrate 1 side of the optical information recording medium in which the imaginary part kabs of the ratio is 0.01 ≦ kabs ≦ 0.3 and the pit (5) is formed by absorbing the recording laser beam A reproducing method of an optical information recording medium, characterized in that a laser beam for use is incident, and a signal is read by an optical phase difference between reflected light of the pit (5) portion of the laser beam and the other portion. 9. The light according to claim 8, further comprising a layer which is less likely to be thermally deformed than a layer in which the pits (5) are formed, which layer is closer to the reflection layer (3) than the light absorption layer (2). Reproduction method of information recording medium. 10. The protective layer (4) formed on the reflective layer (3), wherein the layer less susceptible to thermal deformation than the layer in which the pits (5) are formed is a protective layer (4). Reproduction method of optical information recording medium. 11. The layer which is less likely to be thermally deformed than the layer in which the pits (5) are formed is a layer having a higher thermal deformation temperature and hardness than the layer in which the pits (5) are formed.
Or the method for reproducing the optical information recording medium according to the item 10. 12. A substrate (1) having a light absorbing layer (2) having a light transmitting property.
The pre-recording area (10), which is formed in a part of the upper area and has a pit for signal reproduction formed in advance in an area without the light absorption layer (2), according to any one of claims 8 to 11. A method for reproducing the optical information recording medium according to any one of the above. 13. The method for reproducing an optical information recording medium according to claim 8, wherein the layer in which the pits (5) are formed is the substrate (1). 14. The method for reproducing an optical information recording medium according to claim 8, wherein the reflective layer (3) is a film of gold or an alloy containing gold.