JPH0287339A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain the output signal complying with the format of a compact disk CD at the time of data reproduction by respectively specifying the values of the real number part and imaginary number part of the complex index of refraction of a light absorption layer. CONSTITUTION:The surface of a light transparent substrate 1 is subjected to a solvent resistance treatment by spin coating of, for example, a silicone coating agent; thereafter, soluble phthalocyanine as an org. dye for forming the light absorption layer 2 is dissolved in a dimethylformamide solvent and the soln. is applied on the substrate 1 by spin coating to form the light absorption layer 2 consisting of the dye film. The real number part nabs of the complex index of refraction of the absorption layer 2 is required to be >=1.8 and the imaginary number part kabs thereof to be 0.001 to 0.3. The reproduction signal complying with the CD format is obtd. in this way in case of recording the data on the absorption layer 2 and reproducing the data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a writable optical information recording medium having at least a light absorption layer and a reflection layer on a transparent substrate.

[Prior Art] Optical information recording media on which data can be recorded by irradiation with laser light have a recording layer consisting of a metal layer such as T ex Bi, Mn, etc., or a pigment layer such as cyanine, merocyanine, phthalocyanine, etc. By irradiating with laser light,
Data is recorded by forming pits by deforming, sublimating, evaporating, or denaturing the recording layer. In optical information recording media having such a recording layer, a void is generally provided behind the recording layer in order to facilitate deformation, sublimation, evaporation, denaturation, etc. of the recording layer when forming pits. It is being done. Specifically, for example, a so-called air sandwich, in which two substrates are stacked with a space in between, also has a stacked structure called η structure.

In this optical information recording medium, pits are formed by irradiating laser light from the side of the transparent substrate 1. When reproducing recorded data, a laser beam with a lower power than during recording is irradiated from the substrate l side, and a signal is read based on the difference in reflected light between the pit and other parts.

On the other hand, so-called ROM type optical information recording media, on which data is recorded in advance and cannot be subsequently written or erased, have already been widely put into practical use in the information processing and audio sectors. This type of optical information recording medium does not have the above-mentioned recording layer, but bits for reproducing recorded data are formed in advance on a polycarbonate substrate by means such as pressing, and Au1 Ags Cu is deposited on this substrate. A reflective layer made of a gold H film such as At is formed, and this is further covered with a protective layer.

The most typical type of ROM-type optical information recording medium is the compact disc, or so-called CD, which is widely used in the audio and information processing sectors.The specifications of the recording and playback signals of this CD are in the so-called CD format. It has been standardized as a compact disc player (CD player), and playback devices that comply with this standard have become extremely popular as compact disc players (CD players).

[Problems to be Solved by the Invention] Since the above-mentioned optical information recording medium is a recording and reproducing means that uses the same laser beam as a CD, it is strongly desired that the reproduction conforms to the already widely used CD.

However, the writable optical information recording medium is CD
It has a recording layer that is not present in the recording layer, and has a gap behind it to make it easier to form bits in this recording layer, so the laser light that passes through the recording layer is not reflected. This greatly attenuates the amount of light reflected to the incident side of the laser beam, so the reflectance of the laser beam is lower than that of a CD.
It is difficult to satisfy the above-mentioned CD format, which defines standards for so-called CDs. Therefore, in the past, it has not been possible to provide a write-once optical information recording medium or a writable optical information recording medium that is compatible with CDs.

The present invention has been made to solve the above-mentioned conventional problems, and has a high reflectance and a C
An object of the present invention is to provide a writable optical information recording medium that can obtain an output signal conforming to the D format.

[Means for Solving the Problems] In other words, the gist of the means adopted in the present invention to achieve the above object is that a light absorption layer is formed directly or through another process on a transparent substrate. In an optical information recording medium in which a light reflection layer is formed directly on the light absorption layer or via another layer, the real part nabs of the complex refractive index of the light absorption layer is nmb*≧1. 8, and its imaginary part k abs satisfies 0.001≦k abs≦0.3.

[Function] Real part n of the complex refractive index of the light absorption layer of the optical information recording medium
. , the film thickness d mbs and the wavelength of the laser light ρ
=nabs' The relationship between dabs/λ and reflectance is expressed by a periodic function, as an example of which is shown in FIG.

In order to flatten the reflectance, it is desirable to select the vicinity of the first peak (ρ = 0) or the second or third peak. Third
After the peak, it is desirable to select areas near the second and third peaks. After the third peak, the reflectance is lower than the eleventh second peak.

Furthermore, the sensitivity and thermal energy stored in the absorption layer at the first peak are lower than those at the second and subsequent peaks. Therefore, for the second peak reflectance, which is more suitable for use, nsl
FIG. 5 shows an example of the relationship with +s. This is an example in which the reflective layer 3 is formed of Au and provided directly on the light absorption layer 2, and Kabs = Q, 06, λ = 780
It was calculated using nm.

Based on the relationship shown in this graph, the inventors of the present invention set the real parts n, b of the complex refractive index of the light absorption layer to 1.
It has been noticed that by setting the reflectance to 8 or more, the reflectance can be made 70% or more in accordance with the CD format. Furthermore, this optical information recording medium may include, for example,
Semiconductor laser with a wavelength of 780nm at a linear velocity of 1.2m/5ec
1. When irradiating with a recording power of 6.0 mW and recording an EFM signal, if this is played back on a commercially available CD player,
A clear eye pattern conforming to the CD format is obtained, and Iz/lt, I,
is 066 or higher, Summer 3/I,. , is 0.3 to 0.6. The present invention has been made based on this consideration.

Furthermore, in order for the optical information recording medium to have the above-mentioned reflectance, the light absorption layer must have sufficient light transmittance. For example, FIG. 6 shows that in an optical information recording medium using an Au film for the reflective layer, the real part of the complex refractive index is changed by changing the light transmittance of the light absorption layer made of cyanine dye.
The reflectance is shown when the imaginary part k abs is changed from a value close to 0 to 2.0 while keeping s=2.4 and 364 constant. In order to maintain a high reflectance under the above conditions, the light absorption layer must have sufficient transparency, and the imaginary part of the complex refractive index of the layer must be 5. is 0. Must be 3 or less.

[Embodiments] Next, embodiments of the present invention will be described 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. 1 to 3. In the same figure, ■ is a substrate that develops translucency, and 2 is a light absorption layer formed on it, which absorbs the irradiated laser light and generates heat, melting, evaporating, sublimating, etc.
This layer has the function of deforming or denaturing and forming pits on the surface of the light-transmitting substrate 1.

As already mentioned, in the present invention, the real part nabs of the complex refractive index of the light absorption layer 2 is 1. 8 or more, and its imaginary part k. , , is required to be 0.001 to 0.3.

Reference numeral 3 indicates a light reflection layer formed thereon to reflect laser light, and reference numeral 4 indicates a protective layer provided outside of the light reflection layer. In addition,
Figure 2 shows the state before recording with laser light, and Figure 3 shows the state before recording with laser light.
A state after recording, that is, a state in which the surface of the substrate l is partially deformed due to local thermal deformation of the light absorption layer 2 during laser beam irradiation, and bits 5 are formed is schematically shown.

A specific example of this optical information recording medium will be described below.

(Example 1) Too, 8u, ms Depth o, 08μrrh Thickness 1.2mmt with spiral pre-grooves formed with a pitch of 1°6μm Outer diameter 120mmφ, inner diameter 15m
A polycarbonate substrate 1 having a diameter of mφ was molded by injection molding.

Approximately 20% silicone coating agent is applied to the surface of this transparent substrate l.
After spin-coding to a thickness of nm and solvent-resistant treatment, 8.5 g of soluble phthalocyanine represented by the following chemical formula was dissolved in 10 cc of dimethylformamide solvent as a dye for forming the light absorption layer 2. This was applied onto the above substrate 1 using a spin code method, and a film thickness of 160 nm was obtained.
A light absorption layer 2 consisting of a dye film was formed. The complex refractive index of this light absorption layer 2 is n*bs=L9, k-b-=0.
It is 05.

Further, an Au film with a thickness of 50 nm was formed on the entire surface of the disk by sputtering to form a reflective layer 3. Further, an ultraviolet curable resin is spin-coded on top of this reflective layer 3, and is cured by irradiating ultraviolet rays to a thickness of 10 μm.
A protective layer 4 of m was formed.

R: -C(CH*)3, M: C.

A semiconductor laser with a wavelength of 780 nm was applied to the optical disc thus obtained at a linear velocity of 1.2 m/5ees and a recording power of 6.0 m.
It was irradiated with W and the EFM signal was recorded. This optical disc is then inserted into a commercially available CD player (Aurex
When the disc was reproduced using V73 (wavelength of reproduction light λ = 780 nm), the reflectance of the optical disc was 73%, I++/It determined from the eye pattern. , is 0.63, Ia/1. ,
was 0.35.

According to the CD standard, the reflectance is 70% or more, ■, /I top
is set as 0.6 or more, and Is/It- is set as 0.3 to 0°6, and the optical disc according to this embodiment satisfies these standards.

(Example 2) In the above Example 1, as the transparent substrate 1, two
p method (photo poly-mariztion m
Using an epoxy resin disc with pre-grooves formed using the method (method), the disc was directly coated with tlcr-bis-1(2-hydroxyphenyl)azo-2-hydroxynaphthalate (manufactured by Orient Kagaku 1) without coating the disc with a silicone coating agent. , Oil Black HBB) was dissolved in 10 cc of dichloroethane solvent and spin-coded to form a light-absorbing layer 2 with a thickness of 150% m.As a light-reflecting layer 3, a 9:1 mixture of IAu and Ir was used. An optical disc was manufactured in the same manner as in Example 1 above, except that a light reflective layer made of a thin alloy film was provided. Note that the real part of the complex refractive index of the light absorption layer 2 in this optical disc is nab, 2
．． 05, and its imaginary part k sbs is 0.02.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 80%.
, Iz/I obtained from the eye pattern of the reproduced signal
top is 0.62, I3/It. , is 0.33.

(Example 3) In the above Example 1, instead of the silicon-based coating agent, a SiN layer with a thickness of 30% m was formed on the transparent substrate 1 by a reactive sputtering method using nitrogen gas,
On top of this, 6.5 g of 3.3'-(2-acetoxyethyl)lO-diphenylamino 9,1l ethylenethiashica-podianin perchlorate was added in acetylacetone solvent 1
An optical disc was produced in the same manner as in Example 1, except that the material was dissolved in 0 cc and spin-coded to form a light absorption layer with a thickness of 130% m, and the thickness of the protective layer 4 was set to 5 μm.

The real part n5bs of the complex refractive index of the light absorption layer 2 in this optical disc is 2.4, and the imaginary part k abs
is 0.06.

This is how it was obtained. When an EFM signal was recorded on an optical disc in the same manner as in Example 1, and the optical disc was then played back on a commercially available CD player, the reflectance was 78.
%, Iz/It obtained from the eye pattern of the reproduced signal.

, is 0°81°13/L. , is 0.32.

(Example 4) In the above-mentioned Example 1, instead of using a silicone coating agent on the transparent substrate 1, a thickness of 60% m was coated by a spin cord method.
A polystyrene resin layer of 7.0 g of 3.3'-di(3-
acetoxypropyl) 5.6.5'6' -tetramethoxythiadicarbocyanine toluenesulfonate was dissolved in 10 cC of hydroxyacetone solvent to form a light absorption layer 2 with spin coating) L, i = 140% m;
Example 1 above except that the light reflection layer 3 was provided directly on the light absorption layer 2 by vacuum evaporation, and the protective layer 4 was made of bisphenol curing epoxy resin with a thickness of 5 μm.
An optical disc was produced in the same manner.

Note that the real part nabs of the complex refractive index of the light absorption layer 2 in this optical disc is 2. 35, its imaginary part km
bg is 0. It is 1.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 70%.
, 1st eye/It obtained from the eye pattern of the reproduced signal. ,
is 0.62, I3/It. , is 0.33.

(Example 5) In the above Example 1, instead of using a silicon-based coating agent on the transparent substrate l, a thickness of 60% was coated by a spin code method.
6.7 m of polyvinyl acetate layer was formed on this layer.
g of 1.1" dibutyl 3.3.3'3'tetramethyl5.5'diethoxyindodicarbocyanine verchlorate was dissolved in 10 cc of diacetone alcohol solvent and spin coded to obtain a 135 nm thick light absorption An optical disc was manufactured in the same manner as in Example 1 above, except that a layer was formed and a light reflective layer 3 made of Aug was provided thereon by vacuum evaporation. The real part n mbs of the complex refractive index of 2 is 2.
6, its imaginary part k abs is 0.07.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 78%.
, Iz/L0. obtained from the eye pattern of the reproduced signal. is 0.64, +a/It. , is 0.36.

(Example 6) In Example 1 above, a glass substrate was used as the light-transmitting substrate 1, and the substrate 1 was not coated with a silicone coating agent, and was represented by the following chemical formula of i) L 4°5g. A light absorption layer 2 with a thickness of 180 nm was formed by dissolving an organic dye in 10 cc of tetrahydrofuran solvent and spin coating, and after spin-coating polybutadiene to a thickness of 10 nm on the light absorption layer 2, An optical disc was manufactured in the same manner as in Example 1 above, except that the light reflection layer 3 made of an Au film was provided by vacuum evaporation. Note that the real part nabs of the complex refractive index of the light absorption layer 2 in this optical disk is 1. 82, its imaginary part k eb
s is 0°04.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 75%.
, I++/It obtained from the eye pattern of the reproduced signal.

, is 0.62, I3/It. , is 0.32.

(Example 7) In Example 1 above, 8.0 g of an organic dye represented by the following chemical formula was dissolved in 10 cc of butanol solvent directly on the transparent substrate 1 without coating it with a silicone coating agent, and the spin coat 1 was applied. -1. , a light absorption layer 2 with a thickness of 65 nm was formed, and a thickness of 1
60 nm of 5iOa, E was interposed, and the light reflection layer 3 made of A u Ill' was provided by vacuum evaporation method.
An optical disc was manufactured in the same manner as in Example 1, except that the light reflective layer 3 was coated with polybutadiene to a thickness of 20 nm and the protective layer 4 was provided. Note that the real part n of the complex refractive index of the light absorption layer 2 in this optical disc
1b0 is 2.0, and its imaginary part k abs is 0.2.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 70%.
, I++/It obtained from the eye pattern of the reproduced signal.

. is 0.62, [3/L. , is 0.32.

R: -C(CH3)3, M: T1Cl□ (Example 8) In Example 1 above, instead of the silicon-based coating agent, SiN with a thickness of 30 nm was reactively sputtered on the transparent substrate 1. A silicone resin coating with a thickness of 40 nm was formed on the light absorption layer 2, a light reflection layer 3 was formed by a vacuum evaporation method, and a bisphenol film with a thickness of 20 nm was formed on the light reflection layer 3. Coated with curable epoxy resin, and a protective layer 4 is applied on top of this.
An optical disc was manufactured in the same manner as in Example 1 above, except for providing the following. Note that the peak value of the thermal decomposition temperature of the light absorption layer 2 in this optical disc is 400°C.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 77%.
, t, , /it obtained from the eye pattern of the reproduced signal.

, is 0.62.13/It. , is 0.32.

(Example 9) In the above Example 1, as the transparent substrate l, 2
p method (photo po!y-mariztion m
Using an epoxy resin disk with pregrooves formed using a method of
-Bis1 (2hydroxyphenyl)azo 2hydroxynaphthalate (manufactured by Orient Chemical ■, Oil Black
k ROB) 5, Og in dichloroethane solvent 10c
Example 1 described above except that the light absorption layer 2 with a thickness of 150 nm was formed by dissolving in c and spin-coding, and the light reflection layer 3 made of an Ag film was directly provided by the vacuum evaporation method. An optical disc was produced in the same manner. In addition,
The real part n abs of the complex refractive index of the light absorption layer 2 in this optical disc is 2.05, and its imaginary part k.

3 is 0.02.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 80%.
, I++/It obtained from the eye pattern of the reproduced signal.

. is 0.64.13/It0- is 0.33.

(Example 10) In Example 1, a silicone resin was formed on the transparent substrate 1 with a thickness of 20 nm using a spin cord instead of the silicone coating agent, and 6.5 g of 3. 3'
-(2-acetoxyethyl)10-diphenylamino 9
．． A light absorption layer 2 having a thickness of 130 nm was formed by dissolving 11 ethylenethiashica-podianine perchlorate in 10 cc of acetylacetone solvent, and forming a light absorption layer 2 with a thickness of 130 nm on the light absorption layer 2. alloy j of l
An optical disc was manufactured in the same manner as in Example 1 above, except that the light reflective layer 3 consisting of a opaque layer was provided. Note that the real part nab of the complex refractive index of the light absorption layer 2 in this optical disc
, is 2.4, and its imaginary part k abs is 0.06.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 78%.
, I++/L, obtained from the eye pattern of the reproduced signal.

is 0.62.13/It0- is 0.31.

(Example 11) In Example 1 above, 7.0g of silicone-based coating agent was not coated on the transparent substrate l directly.
3.3″-di(3-acetoxypropyl)5.6.5
'6'-tetramethoxythiadicarbocyanine) luenesulfonate in 10 cc of hydroxyacetone solvent.
A light absorption layer 2 with a thickness of 140 nm was formed by dissolving and spin-coding the light absorption layer 2. A polysulfide-added epoxy resin was applied to a thickness of 20 nm on the light reflection layer 3, and a protective layer 4 was formed thereon. Except for the above, an optical disc was manufactured in the same manner as in Example 1 above. Note that the real part n1s of the complex refractive index of the light absorption layer 2 in this optical disc is 2°3
5, its imaginary part k abs is 0.1.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 70%.
, I++/It obtained from the eye pattern of the reproduced signal.

, is 0.63.13/It. , is 0,32.

(Example 12) In Example 1, 6.7 g of 1.1' dibutyl was directly applied onto the transparent substrate 1 without coating the silicon-based coating agent on the transparent substrate 1. 3.3.37
3′ Tetramethyl 5.5″ Diethoxyindodicarbocyanine perchlorate in diacetone alcohol solvent 1
0CC and spin-coding to form a 135 nm thick light absorption layer, and on top of this a 60 nm thick Z
n5M was formed by vacuum evaporation method, and the luminous intensity q=
An optical disc was manufactured in the same manner as in Example 1 above, except that layer 3 was provided. Note that the real part n of the complex refractive index of the light absorption layer 2 in this optical disc. 5 is 2. 6,
The imaginary part of 8□ is 0.07.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 82%.
, Iz/L obtained from the eye pattern of the reproduced signal. , is 0662, I3/1. . , is 0.33.

(Example 13) In the above Example 1, a glass substrate was used as the transparent substrate 1, and 4.5 g of the chemical formula shown below was directly applied onto the same substrate 1 without coating with a silicone coating agent. A light absorption layer 2 with a thickness of 180 nm was formed by dissolving the organic dye in 10 cc of tetrahydrofuran solvent and spin-coding, and a SiO2 film with a thickness of 80 nm was formed on this by sputtering method, and a light reflection layer was formed on this by sputtering. An optical disc was manufactured in the same manner as in Example 1 above, except that layer 3 was provided. Note that the real part n abs of the complex refractive index of the light absorption layer 2 in this optical disc is 1. 82,
Its imaginary part 1<aba is 0.04.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was 78%.
, Iz/It obtained from the eye pattern of the reproduced signal. ,
is 0.62, and Ix/It0- is 0.32.

did. Note that the real part n of the complex refractive index of the light absorption layer 2 in this optical disc. , , is ■, 4, its imaginary part k B
bs is 0.12.

(Specific Example 1) In Example 1, 8.0 g of an organic dye represented by the following chemical formula was dissolved in 10 cC of ethanol solvent and spin-coded to form a light absorption B2 with a thickness of 120 nm; and 10n of polybutadiene on the light absorption layer 2.
An optical disc was produced in the same manner as in Example 11, except that after spin-coding to a thickness of m, a light-reflecting layer 3 made of an AU film was provided thereon by vacuum evaporation. When an EFM signal was recorded in the same manner as in Example 1, and this optical disc was then played back on a commercially available CD player, the reflectance was 58%, and r++/I to obtained from the eye pattern of the playback signal. - is 0
．． 64, Ia/Ic. . was 0.30.

This optical disc cannot satisfy the above-mentioned CD format in terms of light reflectance.

(Comparative Example 2) In the above Example 11, 6.7 g of 1. 1 diethyl 3.3.3"3'tetramethylinodotricarbocyanine perchloride-1. diacetone alcohol solvent 1.
Au was dissolved in 0cc and spin-coded to form a 120 nm thick light absorption layer 2.
An optical disc was manufactured in the same manner as in Example 11 above, except that the light reflection layer 3 made of a film was provided. Note that the real part na of the complex refractive index of the light absorption layer 2 in this optical disc is
ba is 2.6, and its imaginary part k abs is 1.6
It is.

EFM signals were recorded on the thus obtained optical disc in the same manner as in Example 1, and then this optical disc was
When played on a commercially available CD player, the reflectance was only 1.
At 9%, the eye pattern of the reproduced signal is not clear and the I++/It obtained from it. , and Ia/It. , could not be measured.

[Effects of the Invention] As explained above, according to the present invention, the reflectance is as high as 70% or more, and when data is recorded on the light absorption layer and reproduced, it can be reproduced in accordance with the CD format. A write-once type or write-once type optical information recording medium from which a signal can be obtained is obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic half-sectional perspective view showing an example of the structure of an optical information recording medium, FIG. 2 is an enlarged view of section A in FIG. 1, and FIG.
A cross-sectional view showing an example of the state of the above part A after recording, FIG. 4 is a graph showing an example of the relationship between ρ=n abs ” d abs/λ and reflectance, and FIG. 5 is an optical information recording medium. Figure 6 is a graph showing an example of the relationship between n35. and reflectance in the light absorption layer of 6. Figure 6 is a graph showing the relationship between 6. in the imaginary part of the complex refractive index and reflectance. Substrate 2...Light absorption layer 3...Reflection layer 4
...protective layer

Claims (1)

[Claims] (1) Optical information in which a light absorption layer is formed directly or through another layer on a transparent substrate, and a light reflection layer is formed on this light absorption layer directly or through another layer. In the recording medium, the real part n_a_b_s of the complex refractive index of the light absorption layer
is n_a_b_s≧1.8, and its imaginary part k
An optical information recording medium characterized in that _a_b_s satisfies 0.001≦k_a_b_s≦0.3.