Optical information recording medium and method for recording and reproduction information thereon

An optical information recording medium comprising

• a recording layer that changes reversibly between a crystalline state and an amorphous state, irradiation of the recording layer with laser beams at a predetermined wavelength changing the recording layer from one selected from the group consisting of the crystalline state and the amorphous state to the other state, and
• a light beam absorption correction layer,
• wherein
• crystalline accelerating layers for accelerating the change of the recording layer from the amorphous state to the crystalline state are formed in contact with both surfaces of the recording layer,
• an absorptance Ac of the laser beams in the recording layer when the recording layer is in the crystalline state is larger than an absorptance Aa of the laser beams in the recording layer when the recording layer is in the amorphous state,
• a reflectance Rc of laser beams at the predetermined wavelength in the optical information recording medium when the recording layer is in the crystalline state is smaller than a reflectance Ra of the laser beams at the predetermined wavelength in the optical information recording medium when the recording layer is in the amorphous state,
• a refractive index of the light beam absorption correction layer at the predetermined wavelength of the laser beams is larger than 2, and
• an absorption coefficient of the light beam absorption correction layer at the predetermined wavelength of the laser beams is smaller than 2.

An optical information recording medium comprising

• a recording layer that changes reversibly between a crystalline state and an amorphous state, irradiation of the recording layer with laser beams at a predetermined wavelength changing the recording layer from one selected from the group consisting of the crystalline state and the amorphous state to the other state, and
• a light beam absorption correction layer,
• wherein
• an absorptance Ac of the laser beams in the recording layer when the recording layer is in the crystalline state is larger than an absorptance Aa of the laser beams in the recording layer when the recording layer is in the amorphous state,
• crystalline accelerating layers for accelerating the change of the recording layer from the amorphous state to the crystalline state are formed in contact with both surfaces of the recording layer,
• a refractive index of the light beam absorption correction layer at the predetermined wavelength of the laser beams is smaller than 3, and
• an absorption coefficient of the light beam absorption correction layer at the predetermined wavelength of the laser beams is smaller than 6.

An optical information recording medium comprising

• a recording layer that changes reversibly between a crystalline state and an amorphous state, irradiation of the recording layer with laser beams at a predetermined wavelength changing the recording layer from one selected from the group consisting of the crystalline state and the amorphous state to the other state,
• wherein
• an absorptance Ac of the laser beams in the recording layer when the recording layer is in the crystalline state is larger than an absorptance Aa of the laser beams in the recording layer when the recording layer is in the amorphous state,
• crystalline accelerating layers for accelerating the change of the recording layer from the amorphous state to the crystalline state are formed in contact with both surfaces of the recording layer, and
• an absorptance A′c of laser beams at the predetermined wavelength in layers in the optical information recording medium other than the recording layer when the recording layer is in the crystalline state is smaller than an absorptance A′a of the laser beams at the predetermined wavelength in the layers in the optical information medium other than the recording layer when the recording layer is in the amorphous state.

A method for recording and reproducing optical information with an optical information recording medium,

• the optical information recording medium comprising a recording layer that changes reversibly between a crystalline state and an amorphous sate, irradiation of the recording layer with laser beams at a predetermined wavelength changing the recording layer from one selected from the group consisting of the crystalline state and the amorphous state to the other state,
• wherein an absorptance Ac of the laser beams in the recording layer when the recording layer is in the crystalline state is larger than an absorptance Aa of the laser beams in the recording layer when the recording layer is in the amorphous state,
• crystalline accelerating layers are formed in contact with both surfaces of the recording layer, and
• wherein an absorptance A′c of laser beams at the predetermined wavelength in layers in the optical information medium other than the recording layer when the recording layer is in the crystalline state is smaller than an absorptance A′a of the laser beams at the predetermined wavelength in the layers in the optical information medium other than the recording layer when the recording layer is in the amorphous state,
• the method comprising the steps of focusing laser beams on a microspot on the optical information recording medium by an optical system, and irradiating the recording layer with the laser beams,
• wherein a power level of the laser beams is fluctuated between a first power level P1 and a second power level P2 to change optical information in the recording layer, and the change of the optical information is selected from the group consisting of recording, erasure and overwriting, and
• the optical information is reproduced with the laser beams of a third power level P3,
• where the first power level P1 is an amorphous state-formation level that allows a local portion in the recording film to change reversibly from the crystalline state to the amorphous state by irradiation of the laser beams,
• the second power level P2 is a crystalline stat-formation level that allows a local portion in the recording film to change reversibly from the amorphous state to the crystalline state by irradiation of the laser beams, and
• the third power level P3 is a reproduction level that is lower than the power levels P1 and P2, the irradiation level of the laser beams at P3 does not affect an optical state of the recording layer, and the irradiation of the laser beams at P3 provides a sufficient reflectance to reproduce optical information.