JPH0640161A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium capable of allowing large CNR and a modulation degree, in the optical recording medium constituted by forming a recording layer on a substrate having light perviousness and forming a reflecting layer on the recording layer, by using a mixture of a specific cyanine type org. dye and polymethyl methacrylate in the recording layer. CONSTITUTION:In an optical recording medium wherein a recording layer 2, a reflecting layer 3 and a resin protective layer 4 are provided on a substrate 1 having light perviousness, a mixture of a cyanine type org. dye represented by formula I (wherein R is CH3, C2H5, C3H7 or C4H9 and X<-> is Cl<-> or ClO<->4) (e.g., 1,1',3,3,3',3'-hexamethyl-2,2'-indocyanine perchlorate) and polymethyl methacrylate is used in the recording layer 2. By this constitution, the optical recording medium enabling data recording of high density using short wavelength laser and capable of allowing large CNR and a modulation degree can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording information with a laser beam, and more particularly to a recording medium which can be reproduced in conformity with the compact disc standard.

[0002]

2. Description of the Related Art A recordable optical information recording medium is a very widespread compact disc (hereinafter referred to as a CD).
It is desirable to be able to reproduce in conformity with. Therefore, many studies have been made, and one of them has been disclosed in Japanese Patent Application Laid-Open No. 2-87339. These use an organic dye-based recording film and a reflective film to obtain a high reflectivity in which the amount of light reflected on the incident side of laser light satisfies the CD standard, and when reproducing data, conform to the CD format. It is a recordable optical information recording medium which can obtain an output signal.

Further, in recent years, the development of an optical disc having a higher recording density has been advanced, and there has been a problem that the spot diameter of the light beam must be made smaller in order to increase the recording density. Therefore, conventional 780nm
From a semiconductor laser centered on the SHG element to a green laser or a blue laser in which the wavelength of light is shortened by using an SHG element or the like, and these lasers are narrowed down to the diffraction limit to reduce the beam spot diameter to reduce the recording density. Ways to raise it are under way.

[0004]

Depending on the type of dye used for recording, the reflectance can be sufficiently high, but the CNR or modulation of recorded signals may not be high enough.
The present invention provides an optical recording medium capable of recording with a laser having a short wavelength, which achieves a higher density by using a smaller recording spot, and an optical recording medium having a large CNR and a large degree of modulation while maintaining the reflectance. is there.

[0005]

Therefore, in the present invention, in an optical recording medium in which a recording layer is formed on a transparent substrate and a reflective layer is formed on the recording layer, the recording layer is formed. It is characterized by using a mixture of the cyanine-based organic dye shown in Chemical formula 1 or Chemical formula 2 and polymethylmethacrylate.

[0006]

【Example】

(Embodiment 1) An embodiment according to the present invention will be described with reference to the sectional configuration diagram of FIG. In the figure, a cyanine dye NK-3 shown in Chemical Formula 1 is formed on a substrate made of polycarbonate.
212 (1,1 ′, 3,3,3 ′, 3′-hexamethyl-2,2′-indocyanine perchlorate) [manufactured by Japan Photosensitive Dye Research Institute] 0.1 g and polymethyl methacrylate 0.1 g A recording layer 2 is formed by coating a solution dissolved in 3 ml of a mixed solution of fluoroethanol and diacetone alcohol at 6000 rpm using a spin coating method.

On the surface of the recording layer 2, a reflection layer 3 made of aluminum is formed at 500 A ° by a sputtering method. Further, a UV resin is coated by a spin coating method and irradiated with ultraviolet rays to be cured to form a protective layer 4. When an optical beam spot is radiated onto the optical recording medium having the above structure,
As shown in, the irradiated part is heated, part of the dye is decomposed, the dye in the recording layer and polymethylmethacrylate are dissolved, and the polycarbonate, which is the substrate material which is softened by heating, interacts with it. A deformed portion is formed at the interface between the recording layer and the substrate, and this becomes a recording pit.

The substrate side incident reflectance of the recording layer of this recording medium is shown in FIG. In the present embodiment, the maximum absorption wavelength is in the first half of the 400 nm range which can be recorded by a short wavelength laser, and when an 488 nm argon laser is used as the recording laser, the substrate side incident reflectance is the CD-WO, CD standard substrate side incident mirror surface. A value sufficiently satisfying the partial reflectance Ro of 70% was shown. Also,
A CNR of 48 dB was recorded on this disk at a linear velocity of 0.7 m / s and a recording power of 6 mW at 720 kHz by an argon laser of 488 nm, and an EFM signal was recorded at a recording power of 8 mW to obtain a modulation of 67.8%.

Example 2 A cyanine dye SNC-2 represented by the chemical formula (Formula 2) is formed on a substrate made of polycarbonate.
(1,1'-diethyl-3,3,3 ', 3'-tetramethyl-2,2'-indocarbocyanine iodide)
A recording layer 2 was prepared by coating a solution prepared by dissolving 0.1 g of Nihon Sensitive Dye Research Institute and 0.1 g of polymethylmethacrylate in 3 ml of a mixed solution of trifluoroethanol and diacetone alcohol at 6000 rpm using a spin coating method.
And processed in the same manner as in Example 1. The substrate-side incident reflectance of the recording layer of this recording medium is shown in FIG. In this embodiment, the maximum absorption wavelength is 500 n which can be recorded by a short wavelength laser.
In the first half of the m range, 633 nm He-Ne for recording laser
When a laser is used, the substrate side incident reflectance is CD-WO,
A value sufficiently satisfying the CD-side substrate-side incident mirror surface partial reflectance Ro of 70% was shown.

[0010]

According to the present invention, it is possible to provide an optical recording medium using a laser having a short wavelength and having a higher CNR and a higher degree of modulation.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a recording mechanism in an embodiment according to the present invention.

FIG. 3 is a diagram showing characteristics of Example 1 according to the present invention.

FIG. 4 is a graph showing characteristics of Example 2 according to the present invention.

[Explanation of symbols]

 1 substrate 2 recording layer 3 reflective layer 4 protective layer

Claims (2)

[Claims] 1. An optical recording medium in which a recording layer is formed on a transparent substrate and a reflective layer is formed on the recording layer, wherein the recording layer is a cyanine-based organic dye represented by Chemical Formula 1. An optical recording medium comprising a mixture of polymethylmethacrylate. [Chemical 1] 2. An optical recording medium characterized by using a mixture of a cyanine organic dye shown in Chemical formula 2 and polymethylmethacrylate in the recording layer. [Chemical 2]