JP2858013B2 - Optical recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium, and more particularly to an optical recording method using a write-once optical recording disk compatible with a compact disk.

<Prior Art> An optical recording disk that can be additionally recorded or recorded in accordance with the compact disk (hereinafter abbreviated as CD) standard has been proposed (Nikkei Electronics, January 1989).
23rd issue, No. 465, P107, Kinki Chemical Association Functional Dye Subcommittee, March 3, 1989, Osaka Science and Technology Center, PROCEED
INGSSPIE-THE INTERNATIONAL SOCIETY FOR OPTICAL EN
GINEERING VOL.1078 PP80 ~ 87, “OPTICAL DATA STORAGE
TOPICAL MEETING "17〜19, JANUARY 1989 LOS ANGELES
etc).

This is formed by providing a dye layer, an Au reflection layer, and a protective film in this order on a transparent substrate. That is, the reflection layer is provided in close contact with the dye layer.

When a recording laser beam is applied to the dye layer of such an optical recording disc, the dye layer absorbs and melts the light, and the substrate is softened. It is said to be formed at the interface with the layer.

In the past, an air layer was provided on the dye layer to form pits in the dye layer.However, in this proposal, since the reflection layer is in close contact with the dye layer, the total thickness of the CD standard disc is 1.2mm configuration is possible.

<Problems to be Solved by the Invention> The present inventors conducted various additional tests on such an optical recording disk.

As a result, only a dye layer having a constant refractive index n (real part of complex refractive index) and a constant extinction coefficient k (imaginary part of complex refractive index) and having a predetermined thickness is a close contact type. It has been found that effective recording can be performed even in the case of.

When a resin substrate is used, the pit portion generated by the irradiation of the recording light is composed of a mixed portion of the substrate and the decomposed product and a low refractive index portion on the mixed portion, whereby a predetermined portion is formed. It has been found that a decrease in the reflectivity is obtained and good recording and reproduction are performed.

An object of the present invention is to provide an optical recording method using a contact-type optical recording medium capable of performing good recording and reproduction.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1) to (6).

(1) A dye layer is provided on a resin substrate, and a reflective layer and a protective film are laminated on the dye layer. The refractive index n of the dye layer at a wavelength of 700 to 850 nm is 1.8.
3.23.2 and the extinction coefficient k is 0.04 to 0.12, the thickness of the recording light irradiating part of the dye layer is 1000 to 1500Å, and when the reproducing light is irradiated from the substrate side, the reflectance of the unrecorded part is 60. % Of an optical recording medium having a thickness of 0.1 to 0.4 times the thickness of the dye layer, and a mixture of the substrate and the dye decomposed product is generated. A low-refractive-index portion, wherein the low-refractive-index portion has a cavity and a portion containing a dye decomposition product, and the reflectance of the recorded portion is set to be 40% or less of the reflectance of the unrecorded portion. Optical recording method.

(2) The optical recording method according to the above (1), wherein the dye layer contains two or more kinds of indolenine cyanine dyes.

(3) The optical recording method according to the above (1) or (2), wherein the substrate has a groove, and the recording light is applied to the dye layer in the groove.

(4) The optical recording method according to the above (3), wherein the sum of the thickness of the dye layer and the groove depth in the land portion is larger than the thickness of the dye layer in the groove portion.

(5) The optical recording method according to (3) or (4), wherein the groove depth is 250 to 550 ° and the land width is 0.8 to 1.3 times the groove width.

(6) The optical recording method according to any one of the above (1) to (5), wherein the reflective layer is made of one of Au, an AlMg alloy, an AlNi alloy, Ag, Pt, and Cu.

<Operation> In the optical recording medium of the present invention, since the k of the dye layer is within a predetermined range, the dye layer has high light absorption and light reflectance.

Further, since the n and the thickness of the dye layer are within the predetermined ranges, a high reflectance can be obtained.

Further, by the irradiation of the recording light, a mixed portion of the thermoplastic resin substrate and the dye decomposition product and a low refractive index on the mixed portion are formed. For this reason, in the recording light irradiating section, the decrease in reflectance can be increased.

With such a configuration, the optical recording medium of the present invention exhibits a high reflectance in an unrecorded area and a large decrease in the reflectance in a recorded area, so that good optical recording that can be reproduced by a CD player is possible. Become.

<Specific Configuration> Hereinafter, a specific configuration of the present invention will be described in detail.

FIG. 1 shows an example of the optical recording medium 1 of the present invention. This optical recording medium 1 has a dye layer 3 on a substrate 2,
It is a close contact type in which a reflective layer 4 and a protective film 5 are formed in close contact with the dye layer 3.

The substrate 2 is formed of a resin which is substantially transparent (preferably, transmittance of 89% or more) with respect to recording light and reproducing light (semiconductor laser light of about 700 to 850 nm, especially 780 nm in the case of CD). This enables recording and reproduction from the back side of the substrate.

The substrate is a disk of a normal size, and when used as a CD, the thickness is about 1.2 mm and the diameter is 80 to 120 mm.
And

In the present invention, a resin material, particularly a thermoplastic resin, is used as the substrate material. There is no particular limitation on the thermoplastic resin that can be used, and any of a polycarbonate resin, an acrylic resin, an amorphous polyolefin, and TPX may be used.

It is preferable that a tracking groove is formed on the surface of the substrate 2 on which the dye layer 3 is formed.

The groove is preferably a spiral continuous groove, having a depth of 250 to 550 °, a width of 0.5 to 1.1 μm,
In particular, the width is preferably 0.5 to 0.8 μm, and the width of the land (portion between adjacent grooves) is 0.5 to 1.1 μm, particularly 0.8 to 1.1 μm.

Further, the land width is preferably 0.8 to 1.3 times, more preferably 1.0 to 1.3 times, particularly about 1.2 times the groove width.

With such a configuration of the groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion.

The grooves may be provided with irregularities for address signals.

Further, a signal for rotation control or time axis control can be provided by meandering the groove.

In the present invention, when the substrate has a groove, it is preferable that the recording light be applied to the dye layer in the groove. That is, the optical recording medium of the present invention is preferably used as an optical recording medium for groove recording.

By using groove recording, the effective thickness of the dye layer can be increased.

The extinction coefficient k (imaginary part of the complex refractive index) of the dye layer 3 at the wavelength of the recording light and the reproduction light is 0.04 to 0.12. In this case, when k is 0.04 to 0.08, a very favorable result is obtained.

In the contact type optical recording medium, the extinction coefficient k of the dye layer is 0.04.
If it is less than 1, the light absorptivity of the dye layer decreases, and recording cannot be performed with normal recording power. On the other hand, if k exceeds 0.12, the reflectivity falls below 60%, so that reproduction by a CD player cannot be performed.

The refractive index n (the real part of the complex refractive index) of the dye layer 3 is 1.8 to
3.2, preferably 2.0 to 3.0.

When n <1.8, the reflectivity decreases, the degree of decrease in the refractive index of the pit portion after recording is small, the degree of phase change of the reflected light is small, and a signal of sufficient magnitude cannot be obtained. Reproduction by the player tends to be difficult. Also, in order to satisfy n> 3.2, it is difficult to obtain a raw material dye.

There is no particular limitation on the dye used, cyanine-based, phthalocyanine-based, naphthalocyanine-based, anthraquinone-based,
Azo-based, triphenylmethane-based, pyrylium or thiapyrylium salt-based, metal complex dyes and the like are preferable.

The cyanine dye is preferably a cyanine dye having an indolenine ring.

Alternatively, the dye may be mixed with the quencher and used as a mixture, in which case the quencher functions as the dye. Further, an ion binder of a dye cation and a quencher anion may be used as the dye.

In the above case, the dye is preferably a cyanine dye having an indolenine ring, and the quencher is preferably a metal complex dye such as a bisphenyldithiol metal complex.

Details of preferred dyes, quencher and conjugates are described in JP-A-59-24692, JP-A-59-55794, and JP-A-59-55795.
Nos. 59-81194, 59-83695, 60-18387,
No. 60-19586, No. 60-19587, No. 60-35054, No. 60
-36190, 60-36191, 60-44554, 60-445
No. 55, No. 60-44389, No. 60-44390, No. 60-47069
No. 60-20991, No. 60-71294, No. 60-54892,
No. 60-71295, No. 60-71296, No. 60-73891, No. 60
No. 73892, No. 60-73893, No. 60-83892, No. 60-854
No. 49, No. 60-92893, No. 60-159087, No. 60-162611
No. 60-203488, No. 60-201988, No. 60-234886
No. 60-234892, No. 61-16894, No. 61-11292,
No. 61-11294, No. 61-16891, No. 61-8384, No. 61-
No. 14988, No. 61-163243, No. 61-210539, Japanese Patent Application No. 60
-54013 and the like.

In the present invention, a compound having n and k in the above ranges can be selected from the above-mentioned dyes, dye-quencher mixtures, and dye-quencher conjugates, or can be synthesized by newly designing a molecule.

Incidentally, k for the recording light and the reproduction light of the dye is variously changed from about 0 to about 2 depending on the skeleton and the substituent thereof. There is a limit. For this reason, the coating solvent may be limited, or the coating may not be possible depending on the material of the substrate. Alternatively, gas phase film formation may not be possible. In addition, when a new molecular design is performed, great effort is required for design and synthesis.

On the other hand, according to the experiments of the present inventors, k of the mixed dye layer containing two or more dyes is a value substantially corresponding to the mixing ratio according to k of the dye layer composed of each dye used alone. It turned out to be. Therefore, in the present invention, the dye layer 3
May be formed by dissolving two or more dyes.

At this time, k is almost proportional to the mixing ratio in the mixed system of most of the dyes. That is, assuming that the mixture fraction of i kinds of dyes and k are Ci and ki, respectively, k
Becomes almost ΣCiki. Therefore, by mixing the dyes having different k with each other while controlling the mixing ratio, k = 0.04 to 0.12.
Can be obtained. Therefore, a dye to be used can be selected from a very wide range of dye groups.

As a result, there is no restriction on the film forming method such as restrictions on the coating solvent and the like. In addition, it is possible to use an inexpensive dye that is easy to synthesize, use a dye having good characteristics, and use a hardly soluble dye. Can be.

When the dye layer 3 is a mixed dye layer, the dye used is n
= 1.9 to 3.2 and k = 0 to 2.

When measuring n and k, a dye layer is formed on a predetermined transparent substrate to a thickness of, for example, about 400 to 800 ° under actual conditions to prepare a measurement sample. Next, the reflectance through the substrate or from the dye layer side is measured. The reflectance is measured by specular reflection (about 5 °) using the recording / reproducing light wavelength. Also, the transmittance of the sample is measured. From these measured values, for example, n and k may be calculated according to Kyoritsu Zensho “Optics” Kozo Ishiguro, pages 168 to 178.

The thickness of the dye layer 3 at the portion irradiated with the recording light is:
Preferably it is 1000-1500 °. Outside this range, the reflectivity decreases, making it difficult to perform reproduction with a CD player.

In the case where a groove is formed on the substrate 2, the recording light is applied to the groove, so that the above-mentioned dye layer thickness is at the groove. When the substrate 2 has no groove, the upper surface of the dye layer 3 is flat,
If has a groove, obtain a sufficient tracking signal in the push-pull track error control described later,
In addition, when reproducing with a reproducing head, the sum of the dye layer thickness and the groove depth in the land portion is larger than the dye layer thickness in the groove portion in order to secure a sufficiently large reflection level of the groove portion and the land portion. It is preferable to be configured so that In this case, the thickness of the dye layer at the land is preferably 0.7 to 0.9 times, particularly 0.78 to 0.88 times the thickness of the dye layer at the groove. Below this range, a sufficient tracking signal cannot be obtained. When the dye layer 3 is formed by coating, it is difficult to obtain a value exceeding this range.

The thickness of the dye layer in the groove and land is
It can be measured by a cross-section measuring device using a scanning electron microscope.

When the dye layer 3 is configured as described above, the reflectance of an unrecorded portion through the substrate 2 is 60% or more, particularly 70%, when reproducing light is irradiated from the substrate 2 side after the reflective layer 4 described later is provided.
In addition, the reflectance of the recorded portion can be set to 40% or less of the reflectance of the unrecorded portion. For this reason, the optical recording medium of the present invention can favorably perform recording and reproduction by a CD player.

The method of forming the dye layer 3 is not particularly limited. However, in the present invention, it is preferable to form the dye layer 3 by coating from the viewpoint that the degree of freedom and easiness in the selection of the dye, the medium design, and the production are further increased. .

Various solvents such as ketones, esters, ethers, aromatics, alkyl halides and alcohols can be used for coating the dye layer. Spin coating or the like may be used for application.

On such a dye layer 3, a reflective layer 4 is provided in close contact with the dye layer.

Au, AlMg alloy, AlNi alloy, Ag, Pt
And high reflectivity metals such as Cu may be used.Among these, Au, AlMg alloy and
It is preferable to use any of the AlNi alloys. But,
Since Au has insufficient adhesion to the dye layer, it is preferable to use either an AlMg alloy or an AlNi alloy in order to increase the adhesion between the reflective layer and the dye layer. The Mg content in the AlMg alloy is preferably about 3 to 7% by weight. The Ni content in the AlNi alloy is preferably about 3 to 4 wt%.

The thickness of the reflective layer 4 is preferably 500 mm or more,
The layers may be formed by vapor deposition, sputtering, or the like. The upper limit of the thickness is not particularly limited, but is preferably about 1000 mm or less in consideration of cost, production work, and the like. As a result, the reflectance of the unrecorded portion of the recording layer through the substrate is 60% or more, particularly 70% or more.

 On the reflective layer 4, a protective film 5 is provided.

The protective film 5 may be generally formed of various resin materials such as an ultraviolet curable resin to a thickness of about 10 to 100 μm.

To perform recording or additional recording on the optical recording medium 1 having such a configuration, recording light of, for example, 780 nm is irradiated through the substrate 2 in a pulse shape.

The power of the recording light is preferably about 5 to 10 mW, and the linear velocity during recording is about 1.2 to 1.4 m / s.

Thereby, the dye layer 3 absorbs and generates heat, and at the same time, the substrate 2 is also heated. As a result, the dye is melted or decomposed near the interface between the substrate 2 and the dye layer 3, and pressure is applied to the interface between the dye layer 3 and the substrate 2.

Further, since the substrate 2 is formed of a thermoplastic resin,
Mixing of the substrate material and the dye decomposition product occurs.

As a result, deformation occurs in the vicinity of the interface, and as shown in FIG.
Are formed in a convex shape such as a hemisphere.

In the mixing section 7, the resin constituent material or its decomposition product and the dye or its decomposition product are present in a dispersed or compatible state with each other or partially react with each other to form a mixed state. is there.

The formation of the mixed portion can be confirmed by SEM or STM (tunnel microscope) on the substrate surface after recording and after removing the dye layer.

Further, a low refractive index portion 8 is formed on the mixing portion 7.

The low refractive index portion 8 contains a cavity and a dye decomposition product.

In the illustrated example, a cavity 81 is formed at the center of the mixing section 7, and a dye decomposition product-containing section 85 is formed around the cavity 81.

Such a state can be confirmed by the fact that the dye peak is not observed in the ESCA, FT-IR spectrum and the like, and can also be confirmed by an electron microscope.

In the present invention, the mixing section 7 and the low refractive index section 8 preferably have the following refractive indexes and dimensions.

The refractive index of the mixing portion 7 does not fall out of the range of 1.4 to 1.6 even when mixing with the dye decomposition product occurs because the refractive index of the substrate is 1.57 to 1.59.

The thickness of the mixing section 7 is preferably 0.1% of the thickness of the dye layer 3.
To 0.4 times, more preferably 0.2 to 0.4 times. Mixing unit 7
Is hardly outside this range.

The low-refractive-index portion 8 exists almost entirely between the mixing portion 7 and the reflective layer 4 in the pit portion.

After forming a recording pit composed of such a mixed portion 7 and a low-refractive-index portion 8, when a reproducing light of, for example, 780 nm is irradiated through the substrate 2, a land portion and a recorded portion or an unrecorded portion and a recorded portion are irradiated by the pit. And a phase difference of the reflected light is generated, and the reflectance is reduced by 60% or more. The power of the reproduction light is about 0.1 to 1.0 mW.

On the other hand, since the unrecorded portion has a high reflectance of 60% or more, particularly 70% or more, it can be reproduced by a CD player.

The reproduction of the optical recording medium of the present invention can be performed by a normal CD player. At this time, the tracking control is performed by a so-called push-pull track error control utilizing interference between the groove reflected light and the land reflected light. Alternatively, the tracking control may be performed by irradiating the recording pit with a laser beam for tracking control separately from the reproduction light, so-called a three-beam method.

On the other hand, since no pits are formed in an unrecorded state, it is difficult to perform three-beam tracking control during recording. For this reason, in the optical recording medium of the present invention, it is preferable to perform tracking control during recording by push-pull track error control.

<Examples> Various dye layers were provided on a polycarbonate resin substrate having a continuous groove and a thickness of 120 mm and a thickness of 1.2 mm. Groove is 300mm deep and 0.65μm wide, land width is 0.95μ
m.

On this dye layer, Au is deposited to a thickness of 1000 mm by vapor deposition to form a reflective layer, and further, an ultraviolet-curable resin containing oligoester acrylate is applied, and then ultraviolet-cured to form a reflective layer.
An optical recording disk sample was obtained using a protective film having a thickness of μm.

The dyes contained in the dye layers of Sample Nos. 1 to 3 are shown below.

The dye layer was formed by spin coating while rotating the substrate at 500 rpm.

Sample Nos. 1 and 3 used a 3.0 wt% solution of cellosolve, and Sample No. 2 used a 3.0 wt% methanol solution.
% Solution was used.

The thickness of the dried dye layer inside the groove was 1300 °, and the thickness outside the groove was 1050 °. In addition, the measurement of the thickness of the dye layer was performed by a cross section measuring device (PMS-1 manufactured by Elionix Inc.) using a scanning electron microscope.

The dyes and quenchers contained in the dye layer of each sample and their contents, and the refractive index (n) and extinction coefficient (k) of the dye layer at 780 nm are shown in Table 1 below.

n and k are obtained by forming a solution containing the above-mentioned dye and quencher into a test dye layer by forming a film having a dry film thickness of 600 ° on a measurement substrate, and measuring n and k of the test dye layer. I asked. This measurement was carried out according to the description of “Optics” (written by Kozo Ishiguro, Kyoritsu Zensho), pp. 168-178, by a method of calculating backward from the measured values of the reflectance and the transmittance.
Dichlorotan was used as a coating solvent, and a glass substrate was used as a measurement substrate.

A CD signal (9 types of pulses of 190 to 720 kHz, duty 50%) was recorded on each of the obtained samples by a laser having a wavelength of 780 nm.

The recording power was 7.0 mW, and the linear velocity during recording was 1.3 m / s.
The recording was performed in the groove portion.

Tracking during recording was performed by push-pull track error control.

Then, reproduction was performed with a commercially available compact disk player. The reproduction power was 0.2 mW.

As a result, good recording and reproduction could be performed in sample No. 1. In these samples, 70%
The above reflectance was obtained, and the reflectance of the recorded portion of the 11T pulse of the CD signal was 40% or less of the reflectance of the unrecorded portion.

After recording these samples, the reflective layer was removed, and the pits were observed by STM. As a result, voids were observed in the pits, and the decomposed matter of the dye was adhered around the pits. When the dye layer was also removed and the recording portion of the substrate was observed in the same manner, a swelling of the mixed portion having a height of 200 to 300 ° was observed.

On the other hand, in sample No. 2, the absorption of the dye layer was small, and recording was insufficient. When the recording light irradiation part of this sample was observed in the same manner as above, the cavity of the dye layer was small,
Undegraded dye remained. Further, the height of the swelling of the mixed portion of the recording portion of the substrate was 100 ° or less.

In sample No. 3, the reflection was small and reproduction was difficult. Observation of the recording light irradiated portion of this sample in the same manner as described above revealed that the dye layer had sufficient cavities and adhesion of the dye decomposed product, and the height of the swelling of the mixed portion was about 350 °.

Next, in each of the samples of the present invention, a sample in which the thickness of the dye layer in the groove portion was less than 1000 mm and a sample in which the thickness exceeded 1500 mm were produced, and the same recording and reproduction test as described above was performed. As a result, in the samples of less than 1000 ° and more than 1500 °, the reflectance of the groove portion was less than 60%, and a sufficient reflectance required for reproduction could not be obtained.

Further, in each of the samples of the present invention having a groove depth of 300 °, when the thicknesses of the dye layers in the groove portion and the land portion were 1400 ° and 900 °, respectively, sufficient tracking signals could not be obtained.

Furthermore, in each of the above-described samples of the present invention, the reflection layer was changed to any of AlMg alloy, AlNi alloy, Ag, Pt and Cu, and the same recording and reproduction were performed as described above. Was obtained.

Furthermore, for each sample having a different reflective layer constituent material, an experiment was performed in which the adhesive tape was applied on the protective film and then peeled off. In the sample having the Au reflective layer, peeling occurred between the recording layer and the reflective layer. However, no peeling was observed in the sample having the AlMg alloy reflective layer or the AlNi alloy reflective layer.

 From these results, the effect of the present invention is clear.

<Effect of the Invention> In the optical recording medium of the present invention, since the k, n and the thickness of the dye layer are within the predetermined ranges, the dye layer has a high light absorption and a high reflectance.

Then, a mixed portion of the substrate and the dye and a low refractive index portion are formed by the irradiation of the recording light, so that the reflectance of the irradiated portion of the recording light is greatly reduced. Therefore, good optical recording that can be reproduced according to the CD standard can be performed.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an optical recording medium of the present invention. DESCRIPTION OF SYMBOLS 1 ... optical recording medium 2 ... substrate 3 ... dye layer 4 ... reflective layer 5 ... protective film 7 ... mixing part 8 ... low refractive index part 81 ... cavity part 85 ... dye decomposition Material containing part

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyoshi Nanba 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Masaru Takayama 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK (56) References JP-A-1-151027 (JP, A) JP-A-2-168446 (JP, A) JP-A-2-132656 (JP, A) JP-A-2-87339 (JP, A) A) JP-A-3-52142 (JP, A) JP-A-2-23232 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7/24

Claims (6)

(57) [Claims] A dye layer is provided on a resin substrate, a reflective layer and a protective film are laminated on the dye layer, and the refractive index n of the dye layer at a wavelength of 700 to 850 nm is 1.8 to 1.8.
3.2, the extinction coefficient k is 0.04 to 0.12, the thickness of the recording light irradiation part of the dye layer is 1000 to 1500 °, and when the reproduction light is irradiated from the substrate side, the reflectance of the unrecorded part is 60%. Using the optical recording medium described above, irradiating the recording light to form a mixed portion of the substrate and the dye decomposed product having a thickness of 0.1 to 0.4 times the thickness of the dye layer, and forming a mixed portion on the mixed portion. A low-refractive-index portion, the low-refractive-index portion having a cavity and a portion containing a dye decomposition product, and the reflectance of a recorded portion being 40% or less of the reflectance of an unrecorded portion. Characteristic optical recording method. 2. The optical recording method according to claim 1, wherein said dye layer contains two or more indolenine cyanine dyes. 3. The optical recording method according to claim 1, wherein the substrate has a groove, and the recording light is applied to a dye layer in the groove. 4. The optical recording method according to claim 3, wherein the sum of the thickness of the dye layer in the land portion and the groove depth is larger than the thickness of the dye layer in the groove portion. 5. The groove has a depth of 250 to 550 °,
5. The optical recording method according to claim 3, wherein the land width is 0.8 to 1.3 times the groove width. 6. The reflection layer is made of Au, an AlMg alloy, an AlNi alloy,
The optical recording method according to any one of claims 1 to 5, wherein the optical recording method comprises any one of g, Pt, and Cu.