JPH02121133A - Optical recording medium and optical recording and reproducing method - Google Patents

Abstract

PURPOSE:To necessitate the smaller recording power by utilizing the phenomenon in which a reflection spectrum is changed by a change in film thickness and this change leads to a change in light reflectivity. CONSTITUTION:A recording layer contg. a dye is installed on a substrate and this recording layer is irradiated with recording light. The film thickness at the recording point is changed by the irradiation of the recording light and the recording is thereby executed. The change in the film thickness leads to a change in the reflection spectrum in this case. There are, therefore, no particular limitations for the recording light and any light which changes the film thickness at the recording spots and bits may be selected according to the dyes to be used. The use of a semiconductor laser is preferred in that the device can be miniaturized. Since the recording is executed in this way, the smaller recording power is necessitated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical recording medium, particularly a heat mode optical recording medium, and an optical recording and reproducing method using the same.

<Prior Art> Optical recording media have the characteristic that the recording medium does not deteriorate due to wear and tear because the medium and the writing or reading head are not in contact with each other, and for this reason, research and development of various optical recording media are being carried out.

Among such optical recording media, heat mode optical recording media are being actively developed because they do not require development in a dark room.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat. For example, a part of the medium is melted or removed with recording light such as a laser, and it is called a bit. There is a bit forming type in which writing is performed by forming a small hole, information is recorded using this bit, and reading is performed by detecting this bit with a readout light.

Most of these bit-forming type media, especially those using a semiconductor laser as a light source that can miniaturize the device, have a recording layer made of a material mainly composed of Te.

In addition, in recent years, organic materials mainly containing dyes have been used instead of Te-based materials due to the toxicity of Te-based materials and the need for higher sensitivity and lower manufacturing costs. There are an increasing number of proposals and reports on media using recording layers of the above-mentioned type (Japanese Patent Laid-Open No. 60-203488, etc.)
.

In such a bit-forming type optical recording medium having a recording layer such as a dye, a so-called air sandwich structure is used in which voids are provided on the recording layer in order to prevent a decrease in sensitivity.

Furthermore, when a recording layer containing these dyes is formed on a substrate and recording/reproduction is performed, recording/reproduction is usually performed by irradiating writing light and reading light from the back side of the substrate.

<Problems to be Solved by the Invention> In such a bit-forming type recording system, considerably high recording power is required to melt and remove the dye film using a laser or the like.

Furthermore, as described above, since it has a so-called air sandwich structure, it becomes thick when used as a medium, and furthermore, its robustness decreases.

The present invention can reduce recording power and provide good reproduction C.
An object of the present invention is to provide an optical recording medium with a new recording method and an optical recording/reproducing method that can obtain a high /N ratio and also make the medium thinner and more robust.

Means for Solving the Problems> In order to achieve the above objects, the present invention provides the following (1) to (4).
).

(1) In an optical recording medium in which a recording layer containing a dye is formed on a substrate, the recording layer is irradiated with recording light to change the film thickness at the recording point, and the reflection spectrum changes due to this change in film thickness. An optical recording medium characterized in that the optical recording medium is configured so that the light reflectance changes.

(2) The above (1) in which a metal reflective film is laminated on the recording layer.
The optical recording medium described in .

(3) The optical recording medium according to (1) or (2) above, wherein a protective member is closely attached and integrated on the recording layer or the metal reflective film.

(4) Irradiating the optical recording medium according to any one of (1) to 3) above with recording light to form a recording point with a film thickness and reflection spectrum different from the surroundings, and changing the reflectance of the reproduction light An optical recording and reproducing method characterized in that, when performing reproduction, reproduction is performed at a reproduction light wavelength that increases the change in reflectance between a recording point and its surroundings.

Effects> According to the present invention, when a recording layer containing a dye is irradiated with recording light, the thickness of a recording point in the recording layer changes. This change in film thickness changes the reflection spectrum, and this change in reflection spectrum changes the light reflectance.

Since recording is performed in this manner, the recording power can be small.

Furthermore, even if a metal reflective film is laminated on the recording layer, recording can be performed with low power.

Furthermore, unlike the bit forming type, there is no need to provide a gap, so a protective layer etc. can be formed in close contact with each other.

Then, reading light is irradiated onto the recording layer, light reflectance is detected, and reproduction is performed.

At this time, the reflectance changes widely due to changes in the reflection spectrum, and also changes due to changes in film thickness, and a recording point or bit shows a large change in reflectance with respect to its surroundings, so good reproduction C. /N ratio can be obtained.

During such recording and reproduction, no gaps are provided on the recording layer (and good recording sensitivity can be obtained).

In addition, Japanese Patent Application Laid-open Nos. 58-53490 and 58-68252
discloses a recording method in which bits are formed so that a dye film remains at the bottom of the bits.

However, in these cases, although a change in reflectance occurs due to a change in the film thickness of the bit, a change in reflection spectrum does not occur due to a change in film thickness.

Therefore, in the present invention, the reproduction C/N
You can get the ratio.

In addition, in the method disclosed in the above publication, when forming a bit,
Requires air sandwich construction.

Specific composition> Hereinafter, a specific configuration of the present invention will be explained in detail.

The optical recording medium of the present invention has a recording layer containing a dye formed on a substrate.

Then, this recording layer is irradiated with recording light, and the film thickness at the recording point changes due to the irradiation of this recording light, whereby recording is performed.

In the present invention, this change in film thickness at the recording point changes the reflection spectrum.

Therefore, the recording light in this case is not particularly limited as long as the film thickness changes at the recording point or bit, and can be selected depending on the dye used. Preferably, a laser is used.

The output is about 1~10mW (recording speed 1°3
m/S).

In the present invention, the film thickness of the recording point by the recording light is the recording layer (
It is preferable to change the thickness by about -5 to -50% of the film thickness (0.5 to 5).

This change in film thickness changes the reflection spectrum.

Changes in the reflection spectrum appear, for example, in the range of 650 to 850 nm, as changes in peak wavelength, generation of shoulder peaks or subpeaks, splitting of peaks, and the like.

In this case, the shift width or split width of the peak wavelength, and the wavelength difference between the peak wavelength and the generated shoulder or subpeak are, for example, about 5 to 1100 nm, particularly about 10 to 40 nm.

It is thought that the change in the reflection spectrum is caused by changes in the physical properties of the film, such as the orientation and association state of dye molecules in the film, due to changes in the thickness of the recording point of the recording layer.

In the present invention, reproduction can be carried out by reading changes in the light reflectance of the recording layer.

In this case, the reproducing light may have a wavelength that allows effective detection of the optical reflectance (specifically, as with the recording light, it is preferable to use a semiconductor laser as the light source.
For the wavelength of the reproduction light, select a wavelength with a large change in reflectance,
The wavelength of the recording light may be different.

In this case, the reflectance of the recording layer for reproduction light in the present invention is preferably 15 to 90%. This is 1
This is because if it is less than 5%, changes in reflectance based on changes in reflection spectra cannot be effectively detected.

On the other hand, the wavelength of the reproduction light is selected so that the change in the reflectance of a recording point or bit and the reflectance of its surroundings is as large as possible.

In this case, this change in reflectance is such that the reflectance of the recording point becomes small to about 5 to 95% of the surrounding reflectance, and 5 to 70% of the surrounding reflectance.
It is preferable to adjust the amount to a certain extent.

In this way, the conditions can be easily and practically determined by appropriately changing the dye used, the reproduction light wavelength, and the recording power.

Note that, depending on the case, the reproduction light wavelength may be selected so that the reflectance of the recording point is about 5 to 50% larger than the reflectance of the surrounding area.

In addition, in the present invention, it is also possible to use an erasable type in which recorded data is erased by light or heat.

In the present invention, the dye to be contained in the recording layer may be one that changes its film thickness, causes a change in reflection spectrum, and changes light reflectance when irradiated with recording light.

Specifically, naphthalocyanine dyes or phthalocyanine dyes, particularly those represented by the following formula (I) and those represented by the following formula (II), can be mentioned.

Formula (1) Formula (n) In the above formulas (I) and (II), R1-R4 is 1
Preferred substituents are halogen, sulfo group, carboxy group, hydroxy group, nitro group,
Cyano groups, substituted or unsubstituted acyl groups, acyloxy groups, alkyl groups, aryl groups, alkoxy groups,
aryloxy group, alkylthio group, arylthio group, amino group, sulfonyl group, alkoxycarbonyl group, aryloxycarbonyl group, amide group, sulfonamido group,
Examples include carbamoyl groups, sulfamoyl groups, etc., or those in which one or more of these is substituted with one or more other types.

R1-R4 may be the same or different.

M represents a metal atom or an oxide, hydrate or halide thereof. Although there is no particular restriction on the metal atom, preferred metal atoms include SL, Pb, and the like.

A ligand may be coordinated to the metal atom, or a substituent may be bonded to the metal atom. In this case, S is preferable.
Two OR' or 03iR'R'R' (
Here, R11 represents a group containing a hydrocarbon residue having 1 or more carbon atoms.

R', R' and R8 each represent a monovalent atom or group, and at least one of R6RT and R8 contains a hydrocarbon residue having 1 or more carbon atoms. ) and ■0.

Preferred examples of OR' to O5i R'R'R' include hydroxyhebutapropyleneoxydimethylsiloxy group, : [03i(CH) O(CH
CH, CH, O) H]hydroxytetrapropyleneoxydimethylsiloxy group: [O3i (CH,
) 0(CHCHs CH20) H] n-butyltriethyleneoxydimethylsiloxy group, :[O3
i (CH,) O(CH,CH20)C4H9]
)'lyhexylsiloxy group, :[OS i (Co
H+a) s ], octyloxydimethylsiloxy group: [O3i (CH-)o Ca Hl-]
, octyloxyphenylsiloxy group: [OS
i (Cs Hs ) s QCs HI71 hexyloxy group, : cocs H, ] octyloxy group, : [OCs H+t], and the like.

In the present invention, those preferably used are shown below.

■ Naphthalocyanine (I-1) M=Si-(0-SL(CHs)zO(
C,H40)s-C4Hs]aR'-R' without substitution I-2) M=SL-(0-Si(CHl)to
(Ca!(40)m-C4s]aR'~R' = C flood (r -3) M=Si-[0-5L(C)13)zO
Phthalocyanine (II-1) M=Si-[0-3i(CH-)io
(CaH,0)a-C4H,]□R1-R4 without substitution II-2) M=Pb R1-R4=-8-c> (II-3) M=VO R1-R4=-8-c > (If -4) M=V0 The recording layer may be composed only of a dye, which is preferable, but the dye accounts for 10 wt% or more of the entire recording layer, especially 20 wt%.
% or more is preferable.

The content of the dye is set to such a value because the film thickness at the recording point changes by irradiation with the recording light, and the reflection spectrum changes sufficiently, which can be sufficiently reflected in the light reflectance.

Further, the film thickness of the recording layer is 0.5 to 5-1 as described above.
In particular, it is preferably 0.8 to 3JJJfi.

With such a film thickness, changes in film thickness can be sufficiently reflected in changes in light reflectance due to changes in reflection spectrum.

In the present invention, since the recording method uses a film thickness change, the recording power can be reduced to 30 to 90% compared to a type of recording method in which bits are formed as through holes that reach the substrate.

In the present invention, the recording layer may further contain a self-oxidizing resin such as nitrocellulose, a thermoplastic resin such as polystyrene or nylon, and may also contain other additives.

In the present invention, the recording layer can be formed on the substrate by preparing a dye coating solution and coating it.

In this case, the concentration of the dye in the coating solution is preferably 0.5 to 5 wt%, more preferably 0.5 to 3 wt%. With such a concentration, a desired film thickness can be obtained.

Application may be performed using a spin cord or the like.

In addition, during coating, the viscosity of the coating solution is 0.5 to 10 cp, and the number of spinner rotations is 500 to 1.00.
It should be about Orpm.

The solvent for the dye coating solution in the present invention is not particularly limited as long as it dissolves the dye.

Specifically, keto alcohols (aliphatic keto alcohols, especially diacetone alcohol, acetol, acetoin, acetoethyl alcohol, etc.) R, O-R, -OH
[Here, R is a lower alkyl group (particularly a carbon atom number 1 to
5) R2 is a lower alkylene group (especially one having 2 to 2 carbon atoms)
5). ]; ketone systems such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester systems such as butyl acetate, ethyl acetate, carpitol acetate, and butyl carpitol acetate; ether systems such as methyl cellosolve and ethyl cellosolve; toluene; Examples include aromatic systems such as xylene, halogenated alkyl systems such as dichloroethane, water, and alcohols.

Further, the recording layer may be formed by vapor deposition.

In the present invention, a metal reflective film may be laminated on the recording layer containing the dye.

By providing such a metal reflective film, it is possible to perform a type of recording in which the reflectance at the recording point is lower than the high reflectance in the surrounding area.

The metal used is Au%Ai! ,,Ag.

Examples include Cu.

The film thickness in this case is approximately 0.03 to 1-. Then, it may be formed by steaming or sputtering.

The substrate in the present invention is preferably transparent, since it is preferable to irradiate recording light and reproduction light from the back side of the substrate.

Therefore, the material of the substrate is not particularly limited as long as it is substantially transparent to recording light and reproducing light, and may be any of various resins, glass, etc., but resin is preferred.

Such resins include polymethyl methacrylate,
Acrylic resin, epoxy resin, polycarbonate resin,
Examples include polysulfone resin, polyethersulfone, methylpentene polymer, and the like.

It is preferable that tracking groups or various formats are formed on the recording layer forming surface of such a substrate.

The depth of the groove is about E/8n, especially λ/7n to λ/12n.
(Here, n is the refractive index of the substrate.)

Further, the group formation on the substrate may be performed by a so-called 2P method or the like.

It is preferable that recording light and reproduction light are irradiated from the back side of the substrate, using the recording layer located on the flat portion, concave portion, or convex portion of the substrate as a recording track portion.

With this configuration, the writing sensitivity during recording and the C/N ratio during reading during reproduction are improved, and the tracking control signal is also increased.

Further, the track portion can also be provided with concavities and convexities for address signals.

In the present invention, a protective layer or a protective plate may be provided on the recording layer, or on the metal reflective film when laminating the metal reflective film on the recording layer. Alternatively, a recording layer or a metal reflective film laminated thereon may be formed on a pair of substrates, and these may be integrated so that the recording layer or metal reflective film is on the inside.

In these cases, voids may be provided on the recording layer or the metal reflective film to form a so-called air sandwich type.

However, in the present invention, even if the recording layer is brought into close contact with a protective plate etc.
Since bits or recording points can be formed in the recording layer, it may be of a so-called contact type.

That is, it is possible to tightly integrate a protective layer or a protective plate on a recording layer or a metal reflective film, or to tightly integrate a pair of substrates having recording layers via an intermediate layer.

Therefore, the thickness of the medium such as a disk can be reduced, and since there are no voids, the durability is improved.

<Example> Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A recording layer was formed on a polycarbonate resin substrate having a diameter of 13c+n.

Record M uses a naphthalocyanine dye [compound (I-1) described in the text] as a dye, dissolves it in methanol to make a 2 wt % solution, and uses a spin code to obtain 1300
The layer thickness was 800 or more. Sample No. 2 has a film thickness of 1,300 people, and Sample No. 2 has a film thickness of 1,800 people.

Note that the film thickness was measured using an ellipsometer.

Furthermore, a protective film made of silicone rubber is placed on the recording layer.
The layer was placed in close contact with the thickness of μ.

Reflection spectra were measured for these samples by specular reflection through the substrate.

The reflection spectrum is shown in FIG.

From the results shown in FIG. 1, it can be seen that the reflection spectrum changes as the film thickness changes.

Using the above sample No. 1, recording was performed from the back side of the substrate using a semiconductor laser 830 r+m while rotating at 1800 rpm.

In this case, the condenser output (recording power) is 3 mW and the frequency is 2.8 MHz.

Next, a semiconductor laser (780 m, condensing part output 0.2
mW) as reproduction light, the reflected light through the substrate was detected, and the C/N ratio was measured using a spectrum analyzer manufactured by Hewlett-Baracard with a band width of 30 kHz. The C/N ratio was 48 dB, which was a satisfactory level.

Furthermore, the C/N ratio was measured while changing the recording power in the range of 0.5 to 10 mW. The results are shown in Table 1.

Table (dB) In this case, when the recording points of each sample were observed by SEM, it was confirmed that the bits were clearly formed in the shape of a hole when the recording power was 4 mW or higher. However, a good bit shape has not been obtained, and therefore C/
The N ratio is low.

On the other hand, when the recording power was 3 mW or less, there was no evidence of bit formation, but the trace was slightly observed as a change in film thickness. As mentioned above, the C/N ratio was at a satisfactory level.

Moreover, such an effect was also achieved when each of the above-mentioned dyes was used.

Example 2 On the recording layer with a film thickness of 1500 layers in Example 1, A was added.
A sample was prepared in the same manner except that the u-reflection film was laminated and a UV-curable oligoester acrylate protective film was provided thereon.

This is designated as sample N003.

Using this, recording and reproduction were performed in the same manner as in Example 1, except that the recording power was set to 7 mW.

After this recording, the bit portion was observed by SEM, and no formation of bits was observed. Furthermore, it was confirmed that the reflectance at 780 nm decreased after recording. Furthermore, the C/N ratio during playback is 50dB.
was at a satisfactory level.

You can get a line type one.

Therefore, less recording power is required. Also, playback C
/N ratio also has a good value.

Such an effect can also be achieved even when the so-called air sandwich structure is not used.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the reflection spectrum of the optical recording medium of the present invention. Patent applicant TDC Co., Ltd. <Effects of the invention> According to the present invention, in a heat mode optical recording medium,
A novel FIG that takes advantage of the fact that the reflection spectrum changes as the film thickness changes, and this change in the reflection spectrum changes the light reflectance. Director Yang (nm) Procedure Ne… Author (voluntary)

Claims (4)

[Claims] (1) In an optical recording medium in which a recording layer containing a dye is formed on a substrate, the recording layer is irradiated with recording light to change the film thickness at the recording point, and the reflection spectrum changes due to this change in film thickness. An optical recording medium characterized in that the optical recording medium is configured so that the light reflectance changes. (2) The optical recording medium according to claim 1, further comprising a metal reflective film laminated on the recording layer. (3) The optical recording medium according to claim 1 or 2, wherein a protective member is closely attached and integrated onto the recording layer or the metal reflective film. (4) The optical recording medium according to any one of claims 1 to 3 is irradiated with recording light to form a recording point having a different film thickness and reflection spectrum from the surroundings, and reproduction is performed by changing the reflectance of the reproduction light. 1. An optical recording and reproducing method characterized in that reproduction is performed at a reproduction light wavelength that causes a large change in reflectance between a recording point and its surroundings.