JPH056679A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve durability against an optical deterioration by using a medium containing cyanine dye, a first quencher for preventing its optical deterioration, and a second quencher of an azo compound in a recording film on a light transmitting base plate. CONSTITUTION:A recording film 12, a light reflecting layer 13 formed thereon and a protective layer 14 are provided on a light transmitting board 11 of an optical recording medium 1. The film 12 contains cyanine dye as a main ingredient, and the dye is specified by Formula I. In the formula, R1 and R2 represent 1-6C or preferably 1-4C alkyl group, X<-> is a counter ion, and n is 2 or 3 or preferably 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly to a writable optical recording medium having a recording film on a transparent substrate.

[0002]

2. Description of the Related Art Conventionally, it is generally well known that organic dyes such as cyanine and phthalocyanine dyes are used for recording films of so-called writable optical recording media.

As a writing method for such an optical recording medium, a laser beam is focused on a very small area of the recording film, converted into heat energy, and the properties of the recording film are changed (pit formation). ing. In order to smoothly change the properties of the recording film, the medium may have a so-called air sandwich structure in which two recording films are provided on a substrate and the recording films are arranged to face each other. It is common.

A writing laser beam used in such an optical recording medium is irradiated from the transparent substrate side to form an optically readable pit in the recording film. The reading laser beam for reproducing the recorded data has a weaker output than that for writing, and the contrast between the portion where the pit is formed and the portion where the pit is not formed is read as an electric signal.

On the other hand, unlike the above-mentioned medium, so-called ROM (read only memo) in which data is already recorded in advance.
ry) type medium also exists and is widely put to practical use in the fields of voice recording and information processing. And, there is no writable recording film as described above. That is, the prepits and pregrooves corresponding to the data to be reproduced are already formed on the plastic substrate by press molding, and the reflective layer made of metal such as Au, Ag, Cu, Al is formed on the plastic substrate. A protective layer is formed on top. A typical medium of this ROM type is a compact disc called a so-called CD. This C
The specifications of the recording and reading signals of D are standardized,
According to this standard, a CD reproducing device is widely used as a compact disc player (CD player).

The writable optical recording medium is similar to a CD in that a laser beam is used, and is similar to a CD in that the medium has a disk shape. Therefore, many writable media that conform to the CD specifications and can be used as they are for a CD player are being actively proposed.

Such a writable optical recording medium, in particular, a medium in which a cyanine dye is used as a recording film has insufficient light resistance of the dye, and in order to solve this problem, the light of the cyanine dye is used. A method in which a recording film contains a quencher for preventing deterioration is often used.

[0008]

When the recording film contains a quencher for preventing the photodegradation of the cyanine dye, the portion where the structure of the cyanine dye remains as it is, that is, the pit is not formed. Photodegradation of the recording film portion can be effectively prevented. However, it is not possible to completely prevent the deterioration of the compound constituting the portion of the decomposition residue in which the structure of the cyanine dye is destroyed, that is, the portion in which the pits are formed, due to light. Therefore, considering the change over time of the reproduced waveform, the reflectance of the portion where the pits are formed gradually increases while gradually approaching the value of the reflectance of the portion where no pit is formed, and the reproduced waveform collapses. Eventually, there has been a problem that the reproduction signal cannot be obtained.

The present invention was devised under such circumstances, and an object thereof is to provide an optical recording medium having a recording film excellent in durability against optical deterioration.

[0010]

In order to solve the above problems, the optical recording medium of the present invention is an optical recording medium having a recording film on a light-transmissive substrate, wherein the recording film contains a cyanine dye and First to prevent photodegradation of cyanine dyes
Of the azo compound and a second quencher of the azo compound.

[0011]

The optical recording medium of the present invention is generally irradiated with recording light in pulses while rotating. At this time, a part of the recording film 12 is melted and removed, or a decomposed product diffuses into the substrate to become a recording part. The pits thus formed are formed by detecting the difference between the reflected light of the read light and the rotation of the medium.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a writable optical recording medium of the present invention, a writable medium which conforms to the so-called CD specification standard and can be used as it is for a CD player will be described as an example. FIG. 1 is a schematic perspective view in which a part of the optical recording medium of the present invention is cut away.

The optical recording medium 1 of the present invention comprises a light transmissive substrate 1.
1 has a recording film 12, a recording film 12 has a light reflecting layer 13, and a light reflecting layer 13 has a protective layer 14.

From the viewpoint of improving productivity, it is preferable to use a so-called injection-molded resin substrate as the light-transmissive substrate 11. This substrate is, for example, a polycarbonate resin (P
C), a transparent material such as polymethylmethacrylate resin (PMMA). The thickness of such a substrate 11 is about 1.0 to 1.5 mm.

A recording film 12 is formed on the substrate 11.
Is formed, and the recording film 12 contains a cyanine dye as a main component. As the cyanine dye, for example, those represented by the following general formula [I] or [II] are suitable.

[0016]

[Chemical 2] In the formula, R ₁ and R ₂ each represent an alkyl group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, X ⁻ represents a counter ion, and n represents an integer of 2 or 3, preferably 2.
Examples of X ⁻ include ClO ₄ ⁻ , I ⁻ , Br ^{− and the} like.

[0017]

[Chemical 3] In the formula, R ₃ and R ₄ each represent an alkyl group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and R ₅ and R 4
₆ represents H or Cl, respectively, and X ⁻ and n have the same meanings as in the case of the above general formula [I].

Further, the recording film 12 of the present invention contains a first quencher for preventing the above-mentioned cyanine dye from photodegradation. A metal complex is usually effective as the first quencher, and for example, a Ni complex represented by the following general formula [III] is suitable.

[0019]

[Chemical 4] In the formula, R ₇ , R ₈ , R ₉ and R ₁₀ each represent hydrogen or a substituent in place of it.

As the substituent, CH ₃ O--, CH ₃ OCH ₂ CH ₂ O--, CH ₃ COO
_{-, (n-C 3 H} 7) 2 N -, (C 2 H 5) 2 N-, C
1- and the like.

Specific examples of such a first quencher include those of the following structural formulas [Q-1] to [Q-4].

[0022]

[Chemical 5]

[0023]

[Chemical 6]

[0024]

[Chemical 7]

[0025]

[Chemical 8] Such a first quencher is contained in an amount of 0.01 to 0.5 molecule per 1 molecule of the dye. In addition to the first quencher described above, the recording film 12 of the present invention further comprises a second quencher.
Quencher is included. The second quencher is an azo compound represented by the general formula RN = NR '. Here, R and R'represent a substituted or unsubstituted alkyl group or aryl group. Such a second quencher is contained in order to prevent the structure of the cyanine dye from being destroyed by recording, that is, forming pits, and to prevent deterioration of the compound constituting the decomposition residue portion over time with light. Among them, the particularly preferable second quencher is represented by the following general formula [IV].

[0026]

[Chemical 9] In this formula, R ₁₁ and R ₁₂ represent a substituent containing one nitrogen atom. Above all, the wavelength of the light absorption peak is 400 to 500 n.
The azo compound of m is particularly preferable, and specific examples thereof include those represented by the following structural formulas [A-1] to [A-3]. When the wavelength of the light absorption peak is out of the above range, particularly when it exceeds 500 nm, there is a possibility that absorption at the recording wavelength starts and the overall characteristics of recording and reproduction are changed. Further, if it is less than 400 nm, it is merely an ultraviolet absorber, and it matches the absorption of the dye at a short wavelength, and it is meaningless to add it.

[0027]

[Chemical 10]

[0028]

[Chemical 11]

[0029]

[Chemical 12] Such a second quencher is contained in an amount of 0.01 to 0.5 molecule per 1 molecule of the dye.

The recording film 12 containing the first and second quenchers and the cyanine dye is applied by a conventional means such as spin coating. The thickness of the recording film applied is about 20 to 300 nm. As the solvent used for coating, various known solvents are used, and examples thereof include diacetone alcohol, ethyl cellosolve, methyl cellosolve, isophorone, methanol, tetrafluoropropanol, dichloroethane and the like.

A light reflecting layer 13 is provided on the recording film 12. The light reflecting layer 13 is made of Au, Ag, Cu,
It is composed of a metal such as Al and is formed by various vacuum film forming methods such as vacuum deposition, sputtering, and ion plating. The thickness of such a light reflection layer 13 is 0.
The thickness is about 02 to 2.0 μm.

On such a light reflecting layer 13, usually,
A protective layer 14 for protecting the recording film 12 and the light reflection layer 13
Is laid. The protective layer 14 is generally formed by spin-coating an ultraviolet curable resin and applying it, and then irradiating it with ultraviolet rays to cure the coating film. In addition, epoxy resin, acrylic resin, silicone resin, urethane resin, etc. are used as the protective layer 1.
It is used as the material of No. 4. The thickness of such a protective layer 14 is usually about 0.1 to 100 μm.

An intermediate layer for protecting the substrate 11 from a solvent may be provided between the substrate 11 and the recording film 12. In addition, an intermediate layer may be provided between the recording film 12 and the light reflection layer 13 to increase the light absorption and light reflection efficiency.

The present invention will be described in more detail below with reference to specific experimental examples. Experimental Example Preparation of Sample of the Present Invention As the dye contained in the recording film, R ₁ and R ₂ in the general formula [I] are each a butyl group (C ₄ H ₉ )
Was used, X ⁻ was ClO ₄ ^−, and n was 2. The substance of the above structural formula [Q-1] was used as the first quencher, and the substance of the above structural formula [A-1] was used as the second quencher. The wavelength of the light absorption peak of the substance of the structural formula [A-1] is 440 nm. Each of these dyes and the first and second quenchers were dissolved in a solvent of ethyl cellosolve, and this was applied to a polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm to a thickness of 100 nm. The content of the first and second quenchers was 10% for the first quencher in terms of weight fraction,
The second quencher was 11%. In addition, the substrate is
A spiral groove (groove pitch 1.6 μm, groove width 0.45 μm, groove depth 1200 Å) formed by injection molding was used. Further Au on the recording film
The light-reflecting layer consisting of was formed to a thickness of 1000 A by the vacuum deposition method. Further, a photopolymer protective film was formed on the recording film to prepare an optical recording medium sample of the present invention (the number of samples is five as shown in FIG. 3).

Preparation of Comparative Sample The second quencher was removed from the recording film structure of the sample of the present invention. Other than that, comparative samples were prepared in the same manner as the samples of the present invention (the number of samples was four as shown in FIG. 4).

A light resistance test was conducted on both of the sample groups thus produced in the following manner. Light resistance test An FL tube having a spectrum extremely close to that of sunlight and a UV tube for emitting ultraviolet light were arranged in close proximity to each other, and a disk sample was placed 15 cm immediately below the FL tube for testing. Light intensity is about 200
It is 001x (lux). The evaluation was performed by Block Error Rate.

The test results are shown in FIGS. 3 and 4. 3 is a graph showing the relationship between the elapsed time and the error rate of the sample of the present invention, and FIG. 4 is a graph showing the relationship between the elapsed time of the comparative sample and the error rate. From these graphs, it was confirmed that the sample of the present invention does not increase the error rate with time and is a medium having extremely excellent light resistance. The variation in the initial error rate (time 0) is due to the difference in the film forming rate of the light reflecting layer.

Further, the second sample used in the sample of the present invention is used.
Of the substance of the quencher [A-1] of the structural formula [A-2],
Samples in which the substances of [A-3] were changed were also prepared at the same time, and the above-mentioned light resistance was confirmed. These samples are also media having extremely excellent light resistance with no increase in error rate over time. It was confirmed. The wavelengths of the light absorption peaks of the substances of structural formulas [A-2] and [A-3] are 480 nm and 485 nm, respectively.

[0039]

The effects of the present invention are clear from the above results. That is, since the optical recording medium of the present invention contains the predetermined first and second quenchers in the recording film, it has an excellent durability against photodegradation.

[Brief description of drawings]

FIG. 1 is a schematic perspective view in which a part of an optical recording medium of the present invention is cut away.

FIG. 2 is a partially enlarged sectional view of a cutout portion A in FIG.

FIG. 3 is a graph showing a relationship between an elapsed time and an error rate of a sample of the present invention.

FIG. 4 is a graph showing the relationship between the elapsed time of a comparative sample and the error rate.

[Explanation of symbols]

1 ... Optical recording medium 11 ... Light-transmissive substrate 12 ... Recording film 13 ... Light reflection layer 14 ... Protective layer

Claims (4)

[Claims] 1. An optical recording medium having a recording film on a light-transmissive substrate, wherein the recording film comprises a cyanine dye, a first quencher for preventing photodegradation of the cyanine dye, and an azo. An optical recording medium containing a second quencher of a compound. 2. The optical recording medium according to claim 1, wherein the first quencher is a metal complex. 3. The optical recording medium according to claim 1, wherein the second quencher is an azo compound having a light absorption peak wavelength of 400 to 500 nm. 4. The second quencher has the following general formula: An azo compound represented by the formula (wherein R ₁₁ and R ₁₂ are nitrogen 1
An optical recording medium according to claim 1, which is a substituent containing an atom.