Optical information-recording medium, novel oxonol compound and method of recording information

Abstract

An optical information-recording medium which contains a dye having at least two chromophores bonded to each other without any conjugated bond intervening between those chromophores.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a heat-mode information recording medium and an information recording method which enable write (record) and read (playback) of information by use of high energy density laser light. More specifically, the invention relates to a heat-mode information recording medium, such as a recordable digital versatile disc (DVD-R), which is suitable for recording information by use of visible laser light. [0003] 2. Description of the Related Art [0004] Information recording media on which information is recordable only once by use of laser light (optical discs) have been long known. The information recording media of such a type are referred to as recordable CDs (the so-called CD-R) as well. These disc shave an advantage in that they can be rapidly delivered in low quantities at reasonable prices, compared with traditional CDs, and the demand for them has been growing as personal computers have ...

AI Technical Summary

Benefits of technology

[0009] The present Inventors used various cyanine dye compounds and oxonol dye compounds as disclosed in the documents cited above in optical information-recording media of DVD-R type and studied performance capabilities of the resulting recording media. As a result, it has been found that while the DVD-R type of optical information-recording media containing those dye compounds in their respective recording layers showed very excellent recording characteristics in the low-speed recording at equivalent or double speed, they fell short of delivering practically sufficient performances in respects of modulation factor and reflectivity although they can show comparatively excellent recording characteristics at the time of high-speed recording at quadruple or higher speed. The use of a dye having an optical characteristic that the complex refractive index (n+ik) of the dye is greater in the real part n than those of dyes for low-speed recording use and its imaginary part k is almost the same as or smaller than those of dyes for low-speed recording use can serve the purpose of obtaining an optical information-recording medium which can maintain satisfactory recording characteristics in the recording at a low speed such as an equivalent or double speed and, at the same time, can satisfy recording performances, including sufficient reflectivity and modulation factor in particular, even in the recording at a high speed such as a quadruple or higher speed. However, it was very difficult to obtain dyes showing complex refractive indexes great in real part n and almost equal or small in imaginary part k, compared with those of dyes for low-speed recording use, while maintaining satisfactory low-speed recording characteristics. Therefore, an object of the invention is to provide a dye having a complex refractive index great in real part n and almost equal or small in imaginary part k, compared with those of dyes for low-speed recording use, and thereby ensuring a high reflectivity and a high modulation factor even in high-speed recording at quadruple or higher speed as it maintains satisfactory recording characteristics in low-speed recording at equivalent to double speed. Another object of the invention is to provide a dye attaining sufficiently low jitter at a wide range of recording speeds covering from equivalent- to octuple-speed recording.

Problems solved by technology

As a result, it has been found that while the DVD-R type of optical information-recording media containing those dye compounds in their respective recording layers showed very excellent recording characteristics in the low-speed recording at equivalent or double speed, they fell short of delivering practically sufficient performances in respects of modulation factor and reflectivity although they can show comparatively excellent recording characteristics at the time of high-speed recording at quadruple or higher speed.

However, it was very difficult to obtain dyes showing complex refractive indexes great in real part n and almost equal or small in imaginary part k, compared with those of dyes for low-speed recording use, while maintaining satisfactory low-speed recording characteristics.

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