Multilayer information recording medium

Abstract

A multilayer information recording medium comprising a substrate, three or more information recording layers arranged on the substrate, a plurality of transparent layers arranged between adjoining information recording layers, and a transparent cover layer. At least two transparent layers out of the plurality of transparent layers have thicknesses different from each other. When laser light having a wavelength of 400-410 nm enters vertically from the transparent cover layer side, at least one of the return light intensity and degree of modulation of two information recording layers sandwiching a thinnest transparent layer is higher than at least one of the return light intensity and degree of modulation of other information recording layers.

Description

technical field [0001] The present invention relates to a multilayer information recording medium having a plurality of recording layers for recording and / or reproducing information. Background technique [0002] In recent years, with the expansion of the amount of information handled by information equipment or audio equipment, information recording media such as optical disks that are easy to access data, can store large amounts of data, and can cope with miniaturization of equipment have attracted attention. In addition, in terms of information recording media, high-density recording of information has been studied, and as an information recording medium capable of high-density recording, an information recording medium for recording and reproducing information using a recording and reproducing device equipped with an optical head has been proposed. The optical head includes a laser light source with a wavelength of about 400nm to 410nm and a condenser lens with a numeric...

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Problems solved by technology

However, if the thickness of the transparent layer is only reduced, interlayer crosstalk in which signals generated in other layers leak into the reproduced signal of the layer is likely to occur between the two information recording layers sandwiching the thinnest transparent layer.

[0008] Based on the above reasons, in the case of forming a single-layer information recording medium, if only the information recording layers that can obtain the same level of signal quality (here defined as signal jitter) are laminated to produce multi-layer information In the case of recording media, due to the influence difference of interlayer crosstalk, the information recording layer with increased fluctuation occurs, and the deterioration of the signal fluctuation of the information recording layer most easily affected by interlayer crosstalk becomes remarkable.

In this way, there is a problem that the recording or reproduction of information cannot be performed well on the multi-layer information recording medium.

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