JP2834420B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent substrate having at least a light-absorbing layer and a reflective layer, and a laser beam incident on the light-absorbing layer from the substrate side. Optical information recording for forming a pit protruding on the light absorbing layer side and reading a signal recorded by an optical phase difference between the pit portion of the reading laser beam incident from the substrate side and reflected light of the other portion. Regarding the medium.

[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 a so-called CD format, and a reproduction apparatus conforming to this 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 a CD, it is strongly desired that the medium conforms to a CD which has already been widely used. 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, bright pits due to apertures exist 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, CDs requiring high reflectivity
Under the standard, it was not possible to meet both standards in terms of reflectance and degree of modulation.

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. In reproducing data, an output signal having a block error rate within a range specified by a CD standard can be obtained, and without using means such as a press. It is an object of the present invention to provide an optical information recording medium that can form pits by simple means and is suitable for small-volume publishing.

[0008]

That is, an optical information recording medium according to the present invention is an optical information recording medium in which at least a light absorption layer 2 and a reflection layer 3 are sequentially formed on a light-transmitting substrate 1. The light absorbing layer 2 is made of a dye film, and the substrate 1
The absorbent layer pits 5 that protrudes to the 2 side is formed, behind side of the reflective layer 3 with respect to the light absorbing layer 2 has a high hard layer hardness than the layer in which pits 5 are formed, the substrate 1 A signal recorded is read by an optical phase difference between reflected light of the pit 5 of the reading laser light incident from the side and reflected light of the other portion.

Further, the Rockwell hardness of the hard layer is M75 or more in ASTM D785, and its heat deformation temperature is ASTM D648 (4.6 kg / cm).
In 2), the temperature is 80 ° C. or higher. Such a hard layer can also serve as the protective layer 4 formed on the reflective layer 3 by a spin coat film of an ultraviolet curable resin. The pits 5 are usually formed in a layer which is easily deformed and is adjacent to the substrate 1 and the light absorbing layer 2.

[0010]

The optical information recording medium according to the present invention, although the pits 5 which projects into the absorptive layer 2 side of the substrate 1 is formed, such pits 5, the laser spot from the substrate 1 side to the light absorbing layer 2 By applying the light, the light absorbing layer 2 as a dye film absorbs the laser light and is formed by causing the surface of the substrate 1 to deform. In this case, since a hard layer having a higher hardness than the layer in which the pits 5 are formed is provided on the back side of the reflection layer 3 with respect to the light absorption layer 2, the deformation effect on the substrate 1 side is reduced in the layer on the reflection layer 3 side. In this case, clear pits 5 protruding toward the light absorbing layer 2 are formed only on the substrate 1 side .

The pits 5 formed in this manner are recording pits that cause an optical phase difference in the reflected light of the reading laser light incident from the substrate 1 side.
It is very close to the pre-pit of a general CD formed by molding. Since deformation is unlikely to occur behind the reflective layer 3 and secondary reflected light does not occur due to the deformation, there is no distortion in the reproduced waveform, and the block error rate can be kept low. Therefore, this optical information recording medium can be reproduced by a commercially available CD player.

Also, in the optical information recording medium according to the present invention,
As will be described later, the reproduction contrast of the recording signal is the difference in the amount of reflected light generated by the optical phase difference between the pit 5 and the other portions when the reading laser beam is irradiated from the transparent substrate 1 side. Be taken. In this type of optical information recording medium, the intensity of reflected light at the pit 5 is low, and the intensity of reflected light at other portions is high. Therefore, the higher the reflectance, the easier it is to increase the reproduction contrast, and the easier it is to simultaneously clear the CD standard in terms of the reflectance and the degree of modulation.

In order to form the pits 5, the light absorbing layer 2
When a laser spot is applied to the layer, the energy generated in the same layer accompanies thermal energy. Therefore, even when the hard layer 6 is a layer having a high heat deformation temperature, it is effective to suppress the block error rate to a low level as described above. As a result of the experiment, the present inventors found that the hard layer was formed by the Rockwell hardness AS in order to obtain a reproduced signal conforming to the CD standard using the pits 5.
M75 or more in TMD785 or thermal deformation temperature A
80 in STM D648 (4.6 kg / cm ² )
It has been found that it is necessary to be higher than or equal to ° C. For example, in the case of an optical information recording medium in which a cyanine dye-based light absorbing layer 2, a reflective layer 3 made of an Au vapor-deposited film, and a hard layer obtained by UV-curing a UV-curable resin spin coat film are formed on a polycarbonate substrate. The relationship between the hardness of the hard layer and the block error rate is specifically shown in FIG.

Further, heat deformation temperature ASTM D648
(4.6 kg / cm ² ) at 80 ° C. or higher,
It was found that the preservability of the recorded shape of the pit 5 when the heat resistance test was performed was very high. The graph in FIG.
The temperature of the optical information recording medium is set to 70
This shows a change with time of reproduction of the block error rate at a temperature of 25 ° C. and a humidity of 25% RH. As can be seen from this graph, the higher the heat deformation temperature, the less the block error rate deteriorates.

As the hard layer provided behind the reflective layer 3, the above-mentioned spin-cured film of an ultraviolet curable resin can be used, so that the light absorbing layer 2 and the reflective layer 3 are not subjected to chemical changes such as external force and oxidation. Protective layer 4 formed on reflective layer 3 for protection
May be a hard layer. That is, as in the present invention, if the protective layer 4 made of a spin-coated film of an ultraviolet curable resin satisfying the above conditions is formed on the reflective layer 3,
It can be a hard layer. As a result, an optical information recording medium similar in form to a general CD can be obtained.

[0016]

[0017]

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 FIG. 1, reference numeral 1 denotes a light-transmitting substrate, and reference numeral 2 denotes a light-absorbing layer formed thereon. 3
Denotes a reflective layer formed thereon, and 4 denotes a protective layer 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.

The embodiment shown in FIGS. 1 to 3 is a case where the protective layer 4 also serves as a hard layer. On the other hand, the embodiment shown in FIGS. 4 to 6 is a case where the hard layer 6 is arranged behind the reflective layer 3. Also, in the embodiment shown in FIGS. 1 to 3, the light absorbing layer 2 is formed on almost the entire surface of the substrate 1, but in the embodiment shown in FIGS. The light absorbing layer 2 is formed only on a part of the side, which is a post-recording area 11, and a pre-recording area 10 is formed on an inner peripheral side of the light absorbing layer 2. As in the latter, the translucent group
The light absorbing layer 2 is formed in a partial area on the plate 1,
A pit for signal reproduction is previously formed in an area where the absorption layer 2 is not provided.
In an optical information recording medium having a prerecorded area,
Data can be recorded in advance in the area by pressing etc.
However, since there is no light absorption layer 2 here, erroneous erasure or other data
There is no risk of incorrect recording of data. It also has a light absorbing layer 2
In the area, user-specific data can be arbitrarily recorded.
it can. Then, the recorded data conforms to the CD standard.
Since the signal can be reproduced with the same signal,
Information, all recorded content is played back on a commercially available CD player.
Can be

FIG. 2 shows a state before the pit 5 is formed.
FIGS. 3 and 6 show the state after the pit 5 is formed, that is, by irradiating a recording laser beam from the optical pickup 8, the irradiated portion is deformed into a convex shape, and the pit 5 is formed. The state is schematically shown. FIG. 7 shows the light-transmitting substrate 1
In order to form the pit 5 along the pre-groove 12 which is the tracking display means formed on the surface of
After irradiating the light absorbing layer 2 with a laser spot modulated into an EFM signal along the pre-groove 12, the protective layer 4 and the reflective layer 3 are peeled off from the light transmitting substrate 1, and further, light is emitted from the surface of the substrate 1. The state where the absorption layer 2 is removed is schematically shown.

Further, after forming the pit 5, the STM
(Scanning Tunneling Micro
FIG. 8 shows an example of observing the state of the surface of the light-transmitting substrate 1 along the pre-groove 12 using Scope).
In the figure, the direction along the pregroove 12 of the tip (probe) a, that is, the moving distance in the tracking direction is shown on the horizontal axis, and the altitude of the surface of the translucent substrate 1 is shown on the vertical axis. FIG. 9A shows a case where the length of the pit is relatively short (10000 Å).
It can be seen that a 0 angstrom convex clear deformation is formed. FIG. 3B shows a case where the pit length is relatively long, that is, 40000 angstroms. In this case, a convex deformation having a height of about 200 angstroms is recognized, but the intermediate portion of this deformation is slightly lower. It can be seen that the peak of deformation is divided into two.

A specific example of the optical information recording medium will be described below. The material of the translucent 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 having excellent impact resistance. Specifically, polycarbonate, acrylic and the like can be exemplified, but not limited to these. Using such a material, the substrate is formed by means such as injection molding.

The pre-groove 12 may be formed in the light transmitting substrate 1 in a spiral shape. Pregroove is
Any condition may be used as long as it is normally considered, but a depth of 50 to 250 nm is preferable.
The pregroove 12 is usually formed by pressing a stamper at the time of injection molding of a substrate, but may be formed by cutting with a laser or by a 2P method. A solvent-resistant layer such as SiO ₂ or an enhancement layer may be coated between the light-transmitting substrate 1 and the light absorbing 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 is a light-transmitting substrate on which a pre-groove is formed by dissolving the above-mentioned dye and optional additives in a known organic solvent (for example, alcohol, acetylacetone, methyl cellosolve, toluene, etc.). Alternatively, it is formed on the surface of a substrate in which another layer is coated on the substrate. In this case, as a forming means, a vapor deposition method, LB
A spin coating method is preferred because the layer thickness can be controlled by adjusting the concentration, viscosity and drying speed of the solvent of the light absorbing layer. In addition,
An optical information recording medium having a pre-recording area 10 as shown in FIGS. 4 to 6 has a pre-pit 9 for signal reproduction (see FIG. 5) in a portion to be the pre-recording area 10 on the surface of the translucent substrate 1 such as a stamper. The light absorbing layer 2 is formed by coating the above-mentioned material only on the rear recording area 11 outside thereof.

The reflection layer 3 is desirably a metal film.
Gold, silver, aluminum or an alloy containing these is formed by means such as a vapor deposition method and a sputtering method. Since it is necessary for the reflectance to have 70% or more, it is desirable to form the metal mainly composed of gold or an alloy containing gold. Further, another layer such as an oxidation-resistant layer for preventing the reflection layer from being oxidized may be interposed.

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, or may have a function of a hard layer described below. The hard layer 6 can be dissolved in a solvent such as methyl ethyl ketone or alcohol and applied by a spin coating method, and a material that is cured by a physical change (heat, light, or the like) is preferable in manufacturing. The light transmission of the hard layer 3 does not matter, since it does not affect the transmission of laser light during recording and reproduction.

The hardness of the hard layer 6 is preferably 75 or more in ASTM D785, and more preferably M110 to 200. The heat deformation temperature of the hard layer is preferably 80 ° C. or higher, more preferably 100 ° C. or higher,
C or higher is best. The thickness of the hard layer 6 can be set arbitrarily, but is preferably in the range of 5 μm to 10 μm. Further, a spot of a recording laser beam is applied to the light absorbing layer 2 from the porous substrate 1 side, and pits 5 protruding toward the light absorbing layer 2 are formed in the layer on the light transmitting substrate 1 side. Here, since the layer on the reflection layer side is formed of a layer that is less likely to be thermally deformed than the layer on the substrate 1 side with respect to the light absorption layer, the laser on the light absorption layer 2 By irradiating the light, the energy of the light absorbing layer 2 caused by the laser beam is mainly given to the layer on the light transmitting substrate 1 side. As a result, clear pits 5 are formed on the layer on the light transmitting substrate 1 side. It is formed.

As will be described later, such a pit 5
It is very similar to pre-pits formed by molding in a general CD. For example, as schematically shown in FIG. 3 and FIG. 6, pits 5 protruding toward the absorption layer can be confirmed on the surface of the optical disk after recording in contact with the light absorption layer 2 of the substrate 1. The reproduced waveform of the formed pits 5 is also similar to that of a general CD.
Reproduction of a recording signal is performed by irradiating a laser beam for reading from the transparent substrate 1 side to read an optical phase difference between reflected light in a pit portion and reflected light in a portion other than the pit.

For more specific examples of the present invention,
This will be described below. (Example 1) In the range of 46 to 117 mm in diameter, the width of 0.
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 pregroove having a thickness of 8 μm, a depth of 0.08 μm, and a pitch of 1.6 μm was formed, was formed by an injection molding method. The Rockwell hardness ASTM D785 of the test piece molded using the same material as the polycarbonate substrate 1 was M75, and the heat deformation temperature ASTMD648 was 132 ° C.

As an organic dye for forming a light absorbing layer, 0.65 g of 1,1 ′ dibutyl 3,3,3 ′, 3 ′ was used.
Tetramethyl 4,5,4 ', 5' dibenzoindodicarbocyanine perchlorate (manufactured by Japan Photographic Dye Laboratories Co., Ltd., product number NK3219) is dissolved in 10 cc of diacetone alcohol solvent, and this is dissolved on the surface of the substrate 1. Was applied by spin coating to form a light absorbing layer 2 having a thickness of 130 nm.

Next, the diameter of this disk is 45 to 118 m.
A film thickness of 50 m
An Au film having a thickness of 3 nm was formed, and the reflective 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. Rockwell hardness ASTM D7 of a test piece molded using the same material as the protective layer 4
85 is M90, and the heat deformation temperature ASTM D648 is
150 ° C.

A semiconductor laser having a wavelength of 780 nm was applied to the post-recording area 11 of the optical disk thus obtained at a linear velocity of 1.
Irradiation at 2 m / sec, recording power 6.0 mW, EFM
The signal was recorded. Then, this optical disk is stored in a commercially available C
When reproduction was performed with a D player (Aurex XR-V73, reproduction light wavelength λ = 780 nm), the reflectivity of the semiconductor laser was 72%, I11 / Itop was 0.65, and I3 / Itop.
Is 0.35 and the block error rate BLER is 3.4 ×
It was 10 ^-3 .

According to the CD standard, the reflectance is 70% or more, and I11
/ Itop is 0.6 or more, and I3 / Itop is 0.3-0.
7. The block error rate BLER is determined to be 3 × 10 ⁻² or less, and the optical disk according to this embodiment satisfies this standard. Further, the protective layer 4 and the reflective layer 4 of the optical disk after recording are peeled off, the light absorbing layer 2 is washed with a solvent, and the peeled surface of the light transmitting substrate 1 is STM (Scannin).
g Tunneling Microscope), a convex deformation was observed at the pit portion.
This embodiment is an embodiment in which the protective layer 4 is used as a hard layer.

Example 2 A light absorbing layer 2 was formed on a polycarbonate (Panlite, Teijin Chemicals) substrate having the same shape and pregroove as in Example 1 in the same manner as described above. An Ag film having a thickness of 50 nm is formed thereon as a reflective layer 3 by a vacuum evaporation method, and a silicon acrylic layer having a thickness of 50 nm is formed thereon as a hard layer 6. Was formed. The Rockwell hardness ASTM D785 of the test piece molded using the same material as the substrate is M7.
5, and the heat distortion temperature ASTM D648 was 135 ° C. On the other hand, a Rockwell hardness ASTM D7 of a test piece molded using the same material as the hard layer 6 was used.
85 is M100, heat deformation temperature ASTM D648
Was 200 ° C. Data was recorded on this optical disc in the same manner as in the first embodiment, and the data was reproduced. As a result, the reflectance of the semiconductor laser was 71%, and I11 / Itop
Was 0.64, I3 / Itop was 0.34, and the block error rate BLER was 3.7.times.10.sup.- ³ .

(Example 3) A light-absorbing layer 2 was formed on a polycarbonate (Mitsubishi Gas Chemical, Iupilon) substrate having the same shape and pregroove as in Example 1 above, and then formed. An Au film having a thickness of 50 nm was formed thereon as a reflective layer 3 by a vacuum evaporation method, and an epoxy resin layer having a thickness of 7 μm was formed thereon as a hard layer 6 also serving as a protective layer. The Rockwell hardness ASTM of a test piece molded using the same material as the substrate was used.
D785 is M75, heat distortion temperature ASTM D648
Was 135 ° C. On the other hand, the test piece molded from the same material as the hard layer 6 has a Rockwell hardness ASTM D785 of M90 and a heat distortion temperature AST of ASTMD785.
MDD648 was 140 ° C. With respect to this optical disk, data was recorded and reproduced in the same manner as in the first embodiment, and the reflectance of the semiconductor laser was 72%.
I11 / Itop was 0.63, I3 / Itop was 0.33, and the block error rate BLER was 2.7.times.10.sup.- ³ .

(Example 4) A light absorbing layer 2 is formed on a polystyrene substrate having the same shape and pregroove as in Example 1 in the same manner as described above, and a reflective layer 3 is formed thereon as a vacuum. An Au film having a thickness of 50 nm is formed by an evaporation method, and a hard layer 6 serving as a protective layer is formed on the Au film to a thickness of 1 nm.
An acrylic resin layer of 0 μm was formed. The test piece molded from the same material as the substrate has a Rockwell hardness ASTM D785 of M80 and a heat deformation temperature AS
TMD648 was 89 ° C. On the other hand, the test piece molded using the same material as the hard layer 6 had a Rockwell hardness ASTM D785 of M100 and a heat deformation temperature ASTM D648 of 100 ° C. When data was recorded on this optical disk in the same manner as in the first embodiment, and the data was reproduced, the reflectance of the semiconductor laser was 72%, I11 / Itop was 0.63, I3 / Itop was 0.32, and the block error was 0.3%. Rate BLER is 7.1 × 1
It was 0 ^-3 .

Example 5 A light absorbing layer 2 was formed on a polymethyl methacrylate substrate having the same shape and pregroove as in Example 1 in the same manner as described above, and a reflective layer 3 was formed thereon. Film thickness of 50 nm by vacuum evaporation
An Au film was formed thereon, and an epoxy resin was spin-coated thereon to enhance the binding property, and then a 10 μm-thick polyester resin layer was formed as the hard layer 6 also serving as a protective layer. The test piece molded using the same material as the substrate has a Rockwell hardness ASTM D785 of M100 and a heat deformation temperature ASTM D648 of 11.
It was 0 ° C. On the other hand, a test piece molded using the same material as the test material molded using the same material as the hard layer 6 has a Rockwell hardness ASTM D785 of M110 and a heat deformation temperature ASTM D648 of 11%.
5 ° C. This optical disc is described in the first embodiment.
When data was recorded and played back in the same way as
Semiconductor laser reflectance 72%, I11 / Itop 0.6
5, I3 / Itop is 0.34, block error rate B
LER was 8.3 × 10 ⁻³ .

(Embodiment 6) 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), a width of 0.7 μm, a depth of 0.07 μm, and a pitch of 1.
A polyolefin 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.

Only on the portion on the outer peripheral side of the diameter of the substrate of 100 mmφ, that is, on the post-recording area 11, 1,1 ′ dibutyl 3, 3, 3 ′, 3 ′ tetramethyl 5, 5 ′ diethoxyindodicarbocyanine. After applying perchlorate by a spin coating method to form a light absorbing layer 2, a reflective layer 3 is formed over the entire surface of the substrate 1 to a film thickness of 5 by a vacuum evaporation method.
An Au film having a thickness of 0 nm was formed, and an epoxy resin was further spin-coated on the Au film to enhance the binding property, and then a 7 μm-thick silicon acrylic resin layer was formed as a hard layer 6 also serving as a protective layer. The Rockwell hardness ASTM D of the test piece molded using the same material as the substrate
785 is M75, heat deformation temperature ASTM D648
Was 140 ° C. On the other hand, the test piece molded using the same material as the hard layer 6 has a Rockwell hardness ASTM D785 of M100 and a heat deformation temperature AS.
TMD648 was 200 ° C.

With respect to this optical disk, data was recorded in the post-recording area 11 in the same manner as in the first embodiment, and the pre-recording area and the post-recording area were reproduced. %, I11 / Itop
Is 0.62, I3 / Itop is 0.34, the block error rate BLER is 2.4.times.10.sup.- ³ , the reflectivity of the semiconductor laser in the prerecorded area is 90%, and I11 / Itop is 0.1.
80, I3 / Itop was 0.50, and block error rate BLER was 1.0.times.10.sup.- ³ .

(Embodiment 7) 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.
An epoxy resin 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.

Only on the portion on the outer peripheral side of the substrate with a diameter of 100 mmφ, that is, on the post-recording area 11, 1,1 ′ dibutyl 3, 3, 3 ′, 3 ′ tetramethyl 5, 5 ′ diethoxyindodicarbocyanine. After applying perchlorate by a spin coating method to form a light absorbing layer 2, a reflective layer 3 is formed over the entire surface of the substrate 1 to a film thickness of 5 by a vacuum evaporation method.
An Al film having a thickness of 0 nm was formed, and a silicon resin layer having a thickness of 7 μm was formed thereon as a hard layer 6 also serving as a protective layer.
The Rockwell hardness ASTM D785 of the test piece molded using the same material as the translucent substrate 1 is M9.
0, and the heat distortion temperature ASTM D648 was 135 ° C. On the other hand, a Rockwell hardness ASTM D7 of a test piece molded using the same material as the hard layer 6 was used.
85 is M100, heat deformation temperature ASTM D648
Was 180 ° C.

With this optical disc, data was recorded in the post-recording area 11 in the same manner as in the first embodiment, and the pre-recording area and the post-recording area were reproduced. %, I11 / Itop
Is 0.62, I3 / Itop is 0.32, the block error rate BLER is 2.1.times.10.sup.- ³ , and the reflectance of the semiconductor laser in the prerecorded area is I11 / Itop, I3 / Itop,
The block error rate was the same as in the twelfth embodiment.

(Comparative Example) A Rockwell hardness ASTM D of a test piece molded using the same material as the protective layer 4 formed of an ultraviolet curable resin in Example 1 described above.
785, M60, heat distortion temperature ASTM D648 (4.
An optical disc was manufactured in the same manner as in Example 1 except that 6 kg / cm ² ) was set to 75 ° C. The optical disk was irradiated with a semiconductor laser having a wavelength of 780 nm at a linear velocity of 1.2 m / sec in the same manner as in the first embodiment, and an EFM signal was recorded. I could not confirm. And this optical disk
When the data was reproduced with the same CD player used in the first embodiment, the reflectance of the optical disk was 71%, I11 / Itop was 0.7, and I3 / Itop was 0.37, but the block error rate BLER was higher. 1.5 × 10 ^−1, and could not satisfy the above-mentioned CD standard.

[0045]

As described above, in the optical information recording medium of the present invention, a hard layer having a high hardness is provided behind the light absorbing layer 2 behind the reflective layer 3, and the light absorbing layer 2 made of a dye film is provided. A pit 5 projecting toward the light absorbing layer 2 was formed on the layer closer to the substrate 1 than the light absorbing layer 2 by applying a spot of a recording laser beam. Approximate and clear pits 5 can be formed.
Then, by reading a signal recorded by the optical phase difference between the reflected light of the pit 5 part and the other part of the pit 5 of the reading laser light made incident from the substrate 1 side, a high reflectance is obtained, A reproduction signal similar to that of a general CD can be obtained, and the block error rate of the reproduction signal can be kept within a range specified by the CD standard. Therefore, pits can be formed by simple means of irradiating a recording laser beam, so that an optical information recording medium suitable for small-volume publishing due to cost and reproducible by a general CD player can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an enlarged cross-sectional view of the optical information recording medium before forming pits, in a tracking direction.

FIG. 3 is an enlarged cross-sectional view of the optical information recording medium after forming pits, in a tracking direction.

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

FIG. 5 is an enlarged sectional view of a portion A in FIG. 4;

FIG. 6 is an enlarged sectional view of a portion B in FIG. 4;

FIG. 7 is an enlarged perspective view of a main part showing a surface of a light transmitting substrate of the optical information recording medium according to the embodiment of the present invention.

FIG. 8 shows the surface of the translucent substrate as STM (Scanni).
9 is an example of a graph showing a relationship between a moving distance of a chip along a tracking direction and an altitude when observed by g Tunneling Microscope.

FIG. 9 is a graph showing an example of the relationship between the hardness of the hard layer and the block error rate.

FIG. 10 is a graph showing a temporal change of a block error rate during reproduction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Light absorption layer 3 Reflection layer 4 Protective layer 5 Pit 6 Hard layer 10 Prerecorded area 11 Postrecorded area 12 Pregroove

Continuation of the front page (72) Inventor Yuji Arai 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Yuden Co., Ltd. (56) References JP-A 1-125741 (JP, A) JP-A 2-244433 ( JP, A) JP-A-2-306430 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/24 522 G11B 7/24 535

Claims (4)

(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. And a pit (5) protruding toward the absorption layer (2) is formed on the substrate (1), and the pit (5) is provided behind the light absorption layer (2) behind the reflection layer (3). It has a hard layer higher in hardness than the formed layer, and is formed by the optical phase difference between the reflected light of the pit (5) portion of the reading laser beam incident from the substrate (1) side and the other portion. An optical information recording medium for reading recorded signals. 2. The hard layer has a Rockwell hardness of ASTM D
The optical information recording medium according to claim 1, wherein the optical information recording medium has an M75 or more at 785. 3. The method according to claim 1, wherein the hard layer has a heat distortion temperature of ASTM D64.
3. The optical information recording medium according to claim 1, wherein the temperature is 80 ° C. or higher at 8 (4.6 kg / cm 2). 4. The method according to claim 1, wherein the protective layer (4) formed by spin-coating a UV-curable resin on the reflective layer also serves as a hard layer. Optical information recording medium.