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Information recording medium and method for manufacturing the same

a technology of information recording medium and manufacturing method, which is applied in the field of information recording medium, can solve the problems of reducing the crystallization speed remarkably, affecting the stability of the amorphous state at room temperature, and affecting the stability of the amorphous state, so as to achieve the effect of less influence, high speed and increased rewriting number

Inactive Publication Date: 2005-03-17
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The solution increases the number of rewriting repetitions, improves recording speed, and maintains signal quality by preventing phase separation and ensuring uniform composition changes between crystalline and amorphous phases, thus enhancing the overall performance and stability of the recording medium.

Problems solved by technology

However, these materials would cause a problem.
That is, when the crystallization temperature is raised, the crystallization speed is lowered remarkably, and this would make rewriting difficult.
Alternatively, when the crystallization speed is increased, the crystallization temperature is lowered sharply, and thus, the amorphous state will be unstable at a room temperature.
Though this material is reported to be excellent in the erasing performance, it has been found that the characteristics deteriorate due to the phase separation as a result of repeated overwriting.
Similarly, characteristic deterioration caused by repetition may be observed even if a stoichiometric composition is used.
As a result, the film thickness will be uneven at some parts after a big repetition.
Namely, during a repeated recording, even a slight variation that may have not caused a trouble in a conventional process will lead to errors in reading, and thus, the number of available repetitions of rewriting is decreased substantially.
This problem can be noticeable in the a case of so-called land-groove recording, in which a concave-convex-shaped groove track is formed on a substrate and information is recorded on both the groove (a region closer to the light-incident side) and the land portion (spacing between the grooves) in order to guide a laser beam for recording and reproducing.
Specifically, since the thermal and optical conditions are different between the land and groove, the repeatability will deteriorate easily, especially in the land region.

Method used

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  • Information recording medium and method for manufacturing the same
  • Information recording medium and method for manufacturing the same
  • Information recording medium and method for manufacturing the same

Examples

Experimental program
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Effect test

example 1

Example 1 is directed to a method for manufacturing an optical information recording medium according to the present invention. A substrate used in this example was a disc-shape polycarbonate resin substrate that was 0.6 mm in thickness, 120 mm in diameter and 15 mm in inner diameter. A spiral groove was formed substantially on the whole surface of the substrate. The track was a concave-convex groove having a depth of 70 nm. Both the groove portion and the land portion of the track had a width of 0.74 μm. A multilayer film would be formed on the surface later. A laser beam for recording / reproducing an information signal can move to an arbitrary position on the disk by a servo signal provided from the concave-convex shape. On the substrate, the following layers were formed in this order: a ZnS:20 mol % SiO2 protective layer 150 nm in thickness; a Ge2Sb2Te5Al0.5 thin film 20 nm in thickness; a GeN interface layer 5 nm in thickness; a ZnS:20 mol % SiO2 protective layer 40 nm in thickn...

example 2

On a quartz substrate, eight kinds of thin film material were formed by DC sputtering. The materials were represented by Ge2Sb2Te5Alx, in which Al:x=0.0, A2:x=0.2, A3:x=0.5, A4:x=1.0, A5:x=1.5, A6:x=2.0, A7:x=2.5, and A8:x=3.0. The base vacuum degree was 1.33×10−4 Pa, and Ar was introduced to make the vacuum degree to be 1.33×10−1 Pa. Under this condition, 100 W power was applied between a cathode and an alloy target of 100 mmΦ in diameter so as to form a thin film having a thickness of 20 nm. These samples were monitored by using a He—Ne laser beam in the varying strength of the transmitted light while being heated at a programming rate of 50° C. / minute in order to measure a temperature at which transmittance was decreased remarkably as a result of crystallization. The results are shown in Table 3.

TABLE 3Relationship between Al concentration in a Ge2Sb2Te5 thin filmand crystallization temperature · crystallization speedSampleA1A2A3A4A5A6A7A8Al con.1)0%2.2%5.3%10%14.3%18.2%21.7%2...

example 3

Eight optical disks from a1 to a8 were prepared by using the compositions of Example 2 in the method of Example 1. These disk media were rotated at a linear velocity of 9 m / s, and light beams having a wavelength of 660 nm emitted from a laser diode were focused on the disks by using an optical system comprising an object lens having NA of 0.6. At this time, as shown in FIGS. 6A-6C, overwriting recording was carried out in a 8-16 modulation (bit length: 0.3 μm) by applying a multi-pulse waveform corresponding to waveforms of signals ranging from a 3T signal to a 11T signal. The peak power and bias power were determined as follows. First, a power to provide an amplitude of −3 dB to a saturation value of the amplitude was obtained and the power was multiplied by 1.3 to provide a peak power. Next, the peak power was fixed while the bias power was determined to be variable for conducting 3T recording. 11T recording was conducted with the same power for measuring a damping ratio of the 3...

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Abstract

An information recording medium having such a recording material layer on a substrate where reversible phase change between electrically or optically detectable states can be caused by electric energy or electromagnetic energy. The recording material forming the recording layer is either a material having a crystal structure including lattice defects in one phase of the reversible phase change or a material having a complex phase composed of a crystal portion including a lattice defect in one phase of the reversible phase change and an amorphous portion. Both portions contain a common element. A part of the lattice defects are filled with an element other than the element constituting the crystal structure. The recording medium having a recording thin film exhibits little variation of the recording and reproduction characteristics even after repetition of recording and reproduction, excellent weatherability, strong resistance against composition variation, and easily controllable characteristics.

Description

TECHNICAL FIELD The present invention relates to an information recording medium that can record, reproduce, erase and rewrite high-density information by means of irradiation of laser beams and application of a high electric field. The present invention relates to also a method for manufacturing the information recording medium. BACKGROUND ART It is well known to apply as a memory a change in optical characteristics caused by reversible phase change of a substance, and a technique using this has come into practice as phase change optical disks such as DVD-RAM. Specifically, recording, reproducing and rewriting of signals will be available by rotating a disk medium comprising a substrate on which a recording thin film for generating reversible phase change is provided, and by irradiating the disk medium with a laser beam drawn to a sub-micron size. In the case of a phase change optical disk, overwriting by means of a single laser beam is carried out. That is, irradiation is perfor...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G03G5/02G11B7/2433G11B7/26G11B9/00G11B9/04G11B9/08G11B11/00G11B11/08G11B11/12G11B13/00G11C16/02H01L45/00
CPCG03G5/02Y10T428/21G11B7/2433G11B7/2585G11B7/26G11B7/266G11B9/00G11B9/04G11B9/08G11B11/00G11B11/08G11B11/12G11B13/00G11B2007/24306G11B2007/24308G11B2007/2431G11B2007/24312G11B2007/24314G11B2007/24316G11B2007/24322G11B2007/2571G11B2007/25713G11C13/0004G11C13/04G11C2029/0403H01L45/06H01L45/1233H01L45/144H01L45/1625H01L45/1683G11B7/243H10N70/231H10N70/026H10N70/826H10N70/8828H10N70/066
Inventor YAMADA, NOBORUKOJIMA, RIEMATSUNAGA, TOSHIYUKIKAWAHARA, KATSUMI
Owner PANASONIC CORP
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