JPH05266512A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide the optical recording medium which can record and reproduce information by light, such as semiconductor laser. CONSTITUTION:A recording layer is constituted by contg. at least >=1 kinds of a metal phthalocyanine deriv. and metal naphthalocyanine deriv. and an azo benzene deriv. Rerecording is prevented by decreasing the light absorbance of the recording layer after optical recording. The erasure of information by rerecording is prevented by subjecting the optical recording medium to a heating treatment after the recording at this time.

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 capable of recording and reproducing information with light from a semiconductor laser or the like.

[0002]

2. Description of the Related Art Optical discs capable of high-density recording are expected to become the mainstream of recording media in the future.
Play-only optical discs have already formed a large market in the audio field. The write-once optical disc in the optical disc is a disc in which only information can be recorded, and development has been advanced mainly on inorganic materials. On the other hand, in addition to inorganic materials,
Many organic materials, which are considered to be excellent in terms of multifunctionality, low toxicity, economical efficiency, etc., have also been proposed.

When an organic material is used as a recording material for a write-once optical disc, the low thermal conductivity of the organic material is utilized to
The mainstream method is to record small holes called pits with high density. In this case, the organic recording material is required to have various properties in terms of optical characteristics, thermal characteristics, environment resistance and the like. For example, tracking servo characteristics and C /
In order to improve N, a recording material having high reflectance and excellent environmental resistance is preferable. In order to solve this requirement, for example, JP-A-2-116592 and JP-A-2-1383.
82, JP 61-177287, and JP 63.
JP-A-274591, JP-A-2-147664 and the like disclose phthalocyanine dyes and naphthalocyanine dyes having high reflectance and durability. Also,
These phthalocyanine dyes and naphthalocyanine dyes are compatible with lasers having absorption wavelengths of 830 nm and 780 nm, which are currently the mainstream of semiconductor lasers, and short wavelength lasers of 630 nm to 670 nm, which are expected to spread in the future.

Since the phthalocyanine dye and the nafrocyanine dye are recording materials having good recording characteristics, they are write-once type optical disks suitable for recording information. However, depending on the type of information to be recorded, it may be desirable to permanently save the recorded content.
In the case of such information, it is not preferable that the information is erroneously added after the recording or the information is intentionally destroyed. Therefore, an optical recording medium having a function of preventing disappearance of recorded information is desired.

In order to solve this problem, Japanese Patent Laid-Open No. 2-24
Japanese Patent No. 9685 discloses that a specific naphthalocyanine formed by vacuum vapor deposition is subjected to aging treatment after recording to reduce the absorbance of the recording film. However, in this case, there is a problem that the cost becomes high because the vacuum process is used.

[0006]

The present inventor provides an optical recording medium capable of forming a film by coating, which is an advantage of organic substances, and having a function of preventing the disappearance of information.

[0007]

The optical recording medium in the present invention has a recording layer containing at least one or more of a metal phthalocyanine derivative and a metal naphthalocyanine derivative and an azobenzene derivative, and pits are formed in the recording layer. Then, after the optical recording is performed, the re-recording can be prevented by reducing the absorbance of the recording layer.

The above-mentioned metal phthalocyanine derivative and metal naphthalocyanine derivative have a substituent such as an alkyl group, an alkoxyalkyl group, an alkoxycarbonyl group, an alkylsulfoninyl group, an alkylthio group or an alkylsilyl group on the benzene ring or naphthalene ring in the molecule. It is preferable that the compound has the property of improving solubility in an organic solvent. The central metal in the molecular structure is Fe or Zn.
The phthalocyanine derivative and the naphthalocyanine derivative are preferably tetra tert-butyl phthalocyanine zinc, tetra tert-butyl phthalocyanine iron,
Tetrahexyl thiophthalocyanine zinc, tetrahexyl thiophthalocyanine iron, tetradecyl sulfonyl phthalocyanine zinc, tetradecyl sulfonyl phthalocyanine iron, tetraoctyl carbonyl phthalocyanine zinc,
Tetraoctylcarbonyl phthalocyanine iron, tetra-t
ert-butylnaphthalocyanine zinc, tetra-tert-butylnaphthalocyanine iron, tetrahexylthionaphthalocyanine zinc, tetrahexylthionaphthalocyanine iron, tetradecylsulfonylnaphthalocyanine zinc,
There are tetradecylsulfonylnaphthalocyanine iron, tetraoctylcarbonylnaphthalocyanine zinc, tetraoctylcarbonylnaphthalocyanine iron, and the like.

The above-mentioned azobenzene derivative has one or more substituents having an amino group or a hydroxyl group in its molecular structure, and is represented by, for example, Chemical formula 1 [General formula (I)]

[Chemical 1] [However, in the general formula (I), R ¹ , R ² , R ³ and R
⁴ are each independently hydrogen, amino group, hydroxyl group,-(C
H) _n -NH ₂ or -O- (CH) _n -NH ₂ (where n is an integer of 1 to 5), and 2 to 3 of these are hydrogen] It is a derivative.

Examples of the azobenzene compound represented by the general formula (I) include p-hydroxyazobenzene, m-hydroxyazobenzene, p, p'-dihydroxyazobenzene, p-aminoazobenzene, m-aminoazobenzene and p, p'-diamino. Azobenzene, m, p'-diaminoazobenzene, p- (1-aminomethyl) azobenzene, p- (2-aminoethyl) azobenzene, p-
(3-aminopropyl) azobenzene, p- (4-aminobutyl) azobenzene, p- (5-aminoamyl) azobenzene, m- (1-aminomethyl) azobenzene,
m- (2-aminoethyl) azobenzene, m- (3-aminopropyl) azobenzene, m- (4-aminobutyl) azobenzene, m- (5-aminoamyl) azobenzene, p- (1-aminomethoxy) azobenzene, p −
(2-Aminoethoxy) azobenzene, p- (3-aminopropyloxy) azobenzene, p- (4-aminobutyloxy) azobenzene, p- (5-aminoamioxy) azobenzene, m- (1-aminomethoxy) azobenzene , M- (2-aminoethoxy) azobenzene, m
-(3-aminopropyloxy) azobenzene, m-
(4-aminobutyloxy) azobenzene, m- (5-
Aminoamioxy) azobenzene and the like. Among the azobenzene compounds represented by the general formula (I), those having a hydroxyl group are particularly preferable.

The optical recording medium of the present invention can be produced by forming a recording layer on a suitable substrate. The recording layer can be prepared by dissolving the phthalocyanine derivative or the naphthalocyanine derivative and the azobenzene derivative in an organic solvent to prepare a uniform solution, and then coating and drying the solution on a substrate by a spin coating method or a solvent cast method. The substrate is preferably a synthetic resin such as an acrylic resin, a polycarbonate resin, an epoxy resin or a polyolefin resin, glass or the like, and the shape thereof is not particularly limited, but a plate surface having a smooth surface is preferable. On the surface of the substrate,
A thin film of Si, Ni, Si ₃ N ₄ , TiO ₂ , ZnO or the like may be formed. Further, a reflective layer made of gold, aluminum or the like may be laminated on the recording layer.

The optical recording medium of the present invention is heated at 40 ° C. to 80 ° C. during or after the film formation as described above or by irradiating the recording film with ultraviolet rays to obtain wavelengths of 630 to 85.
The absorption newly appears in the 0 nm region, or the absorbance increases. The optical recording medium of the present invention preferably records information in this state. Information is recorded by irradiating a laser beam so that the recording layer absorbs the light, and thereby the laser beam irradiated portion of the recording layer is decomposed or melted to form a pit in that portion. The laser used is preferably a semiconductor laser having a wavelength in the range of 630 nm to 850 nm. After recording, heat energy is externally applied to reduce the absorbance of the unrecorded layer. As a result, it is preferable to heat the recording layer to 100 ° C. or higher, but the upper limit is the temperature at which the substrate and the recording film do not melt. Due to this heating, the absorbance of the unrecorded portion is remarkably reduced, and even if the unrecorded portion is irradiated with the recording laser light, the light is not sufficiently absorbed and therefore no pit is formed.

[0013]

EXAMPLES Examples of the present invention are shown below, but the present invention is not limited to these.

Example 1 1 mole of tetra-tert-butylphthalocyanine zinc and 5 moles of p-hydroxyazobenzene were dissolved in 5 ml of carbon tetrachloride and filtered through a filter having a separation diameter of 0.2 μm to obtain a uniform solution. .. This solution is 120m in diameter
An optical disk was obtained by forming a recording film by spin-coating and drying on a disk substrate of m polycarbonate groove (made by Idemitsu Petrochemical Co., Ltd.). The disc was heated at 60 ° C. for 10 minutes, and the absorption spectrum was measured. The result is shown as graph 1 in FIG. It can be seen that the absorption wavelength region appears in the region of 780 to 830 nm in the above-mentioned heat-treated optical disc (recording layer).

Next, the optical disc was heat-treated at 120 ° C., and then the absorption spectrum of the recording layer was measured. The result is shown as graph 2 in FIG. It can be seen that the heat treatment causes the optical disc (recording layer) to significantly reduce the absorbance in the absorption wavelength range of 780 to 830 nm.

An optical disc manufactured in the same manner as above
After heating at 0 ° C. for 10 minutes, an optical recording characteristic evaluation device (OMS200) equipped with a semiconductor laser having a wavelength of 830 nm is mounted.
0, trade name of Nakamichi Co., Ltd.) was used to evaluate the recording and reproduction of the optical disc. The recording conditions were such that the rotation speed was 3 m / s, the frequency was 1 MHz, and the laser power was changed at a duty of 50%. As a result, it is possible to record with a laser power of 7 mW or higher, and at 12 mW, the C / N is the highest of 40 dB.
showed that. Next, after heat-treating this optical disc for 10 minutes at 120 ° C., a frequency of 2 MHz was applied to a track on which a 1 MHz signal had already been input under the conditions of a rotation speed of 3 m / s, a duty of 50%, and a laser power of 12 mW. I tried to input the signal. After this operation, if you play the same track, 1M
Only the Hz signal could be reproduced, and the 2 MHz signal could not be reproduced. That is, the above 12
It was shown that no new recording was possible after the heat treatment at 0 ° C. Even if a 1 MHz signal was input to another unrecorded track under the condition of a signal input of 2 MHz, this signal could not be reproduced in the same manner.

[0017]

In the optical recording medium according to the first aspect of the present invention, it is possible to prevent the erasing of information by re-recording by lowering the absorbance of the recording film by the heat treatment after recording the information.

[Brief description of drawings]

FIG. 1 is an absorption spectrum of the optical disc obtained in Example 1.

[Explanation of symbols] 1 ... Absorption spectrum after heating to 60 ° C, 2 ... Absorption spectrum after heating to 120 ° C.

Claims (1)

[Claims] 1. A recording layer comprising at least one or more of a metal phthalocyanine derivative and a metal naphthalocyanine derivative and an azobenzene derivative, wherein pits are formed in the recording layer to perform optical recording and then the absorbance of the recording layer. An optical recording medium that can prevent re-recording by reducing