Mitsubishi Kagaku Media Co., Ltd.

Yoshihiro Noda

Shigeyuki Furomoto

Takashi Ohno

Hideyuki Kubo

A multilayer-type optical recording medium having a translucent recording/reproducing functional layer containing a first protective layer, a second protective layer, a recording layer, a third protective layer, a reflective layer and a fourth protective layer in this order relative to incident laser light. The second protective layer and the fourth protective layer are made of the same kind of material. The refractive index of the second protective layer is higher by at least 0.3 than the refractive index of the first protective layer. When the film thickness of the second protective layer is set as D2, the film thickness of the fourth protective layer is set as D4, and the reflectivity before recording when the laser light is focused on the recording layer is set as R, the derivatives d(R)/d(D2) and d(R)/d(D4) have opposite signs from each other.

Optical recording medium

In a single-sided incident type optical recording medium having a plurality of dye containing recording layers, sufficient reflectance and excellent recording characteristics necessary to record or read information in or from a dye containing recording layer positioning farther from a side from which a light beam comes in can be obtained. The optical recording medium has a first substrate () having a guide groove, a first dye containing recording layer (), a semitransparent reflective layer (), an intermediate layer (), a second dye containing recording layer (), a reflective layer () and a second substrate () having a guide groove. Information is recorded or read in or from the first dye containing recording layer () and the second dye containing recording layer () by irradiating the light beam from the first substrate's side. The depth of the guide groove on the second substrate is within a range from 1/100&#xd7;&#x3bb; to &#x2159;&#xd7;&#x3bb; where &#x3bb; represents the recording/reading wavelength.

Optical recording medium and recording/reading method therefor

In an optical recording medium of a single-sided incident type having a plurality of recording layers, recording/reading conditions (for example, tracking polarity, recording pulse strategy, recording recommended power, etc.) can be instantaneously switched according to each of the recording layer, and recording or reading of information can be accurately and surely performed under recording/reading conditions adapted to each recording layer. A control unit reads out layer information from one recording layer of the optical recording medium in which the layer information is recorded in each of the plural layers, on which recording or reading of information can be performed by irradiating a laser beam from one side thereof (layer information reading step), and controls so that recording or reading is performed under recording/reading conditions adapted to a recording layer specified on the basis of the layer information (recording controlling step).

Recording/reading method for an optical recording medium using an irradiating a laser beam

In a single-sided incident type optical recording medium having a plurality of dye containing recording layers, sufficient reflectance and excellent recording characteristics necessary to record or read information in or from a dye containing recording layer positioning farther from a side from which a light beam comes in can be obtained. The optical recording medium has a first substrate () having a guide groove, a first dye containing recording layer (), a semitransparent reflective layer (), an intermediate layer (), a second dye containing recording layer (), a reflective layer () and a second substrate () having a guide groove. Information is recorded or read in or from the first dye containing recording layer () and the second dye containing recording layer () by irradiating the light beam from the first substrate's side. The depth of the guide groove on the second substrate is within a range from 1/100 &#xd7;&#x3bb; to 1/6 &#xd7;&#x3bb; where &#x3bb; represents the recording/reading wavelength.

In an optical recording medium having two recording layers of a first recording layer and a second recording layer, the second recording layer contains metallized azo dyes represented by the following general formula (I) or (II), and recording characteristics of the second recording layer are improved by having optical density of 1.3 times as large as, or 1.3 times greater than, that of a dye contained in the first recording layer. (In this regard, rings A1 and A2 are nitrogen-containing heteroaromatic rings, rings B1 and B2 are aromatic rings, and X is alkyl group substituted by at least two fluorine atoms).

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Tokyo, Japan

Yoshihiro Noda