JPH04219623A - Initialization method for information recording medium - Google Patents

Abstract

PURPOSE:To offer initialization method of information recording medium by increasing the sensibility, increasing performance after repeated cylcle and prolonging life in the case of recording and erasing and beeing similiary applicable within low cost. CONSTITUTION:In the initialization method of information recording medium recording information by means of transition between two state of recording materials applying energy of electromagnetic wave, using electromagnetic wave as a energy source of initialization against optical information recording medium and also having a relation of the wave length lambdae and -0.1<=(lambda/lambdae)-1<=0.1 is claimed as a new initialization method of information recording medium.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for initializing an information recording medium, particularly a phase change type information recording medium, in which a phase change is caused in a recording layer material by irradiating a light beam, and information recording, The present invention relates to a method for initializing a readable and rewritable information recording medium, and is applied to optical memory-related equipment.

0002

[Prior Art] An optical memory medium capable of recording, reproducing, and erasing information by irradiation with electromagnetic waves, especially laser beams, uses so-called phase change that utilizes transition between crystal and amorphous phases or between crystal and crystal phases. type recording media are well known. In particular, it is possible to overwrite with a single beam, which is difficult to do with magneto-optical memory, and the optical system on the drive side is also simpler, so research and development on this topic has been active recently. As a typical material example, USP 3
, 530, 441.
, Ge-Te-S, Ge-Se-S, Ge-Se-Sb
, Ge-As-Se, In-Te, Se-Te, Se-
Examples include so-called chalcogen alloy materials such as As. In addition, Ge-Te is used for the purpose of improving stability and high-speed crystallization.
The system contains Au (Japanese Unexamined Patent Publication No. 61-219692), Sn and Au.
(JP 61-270190), Pd (JP 62-1
9490), and a material with a specified composition ratio of Ge-Te-Se-Sb (Japanese Patent Application Laid-open No. 73438/1983), with the aim of improving repeat recording/erasing performance. . However, none of them can satisfy all of the characteristics required of a phase change type rewritable optical memory medium. Especially recording sensitivity,
The most important issues to be solved are improving erasing sensitivity, preventing a reduction in erasing ratio due to eraser residue during overwriting, and extending the lifespan of recorded and unrecorded areas.

[0003] Furthermore, JP-A No. 63-251290 proposes an optical recording medium having a recording layer made of a single phase of a multicomponent compound whose crystalline state is substantially ternary or higher. Here, the term "substantially ternary or higher multicomponent single phase" is defined as a recording layer containing 90 atomic % or more of a compound having a ternary or higher stoichiometric composition (for example, In3SbTe2). The use of such a recording layer enables high-speed recording and high-speed erasing. However, the laser power required for recording and erasing has not yet been sufficiently reduced. Furthermore, it has drawbacks such as a low erasure ratio, insufficient repeatability, and insufficient long-term reliability.

It goes without saying that these characteristics are greatly influenced by the characteristics of the recording material itself, but they are also greatly influenced by the quality of the initialization state. Immediately after fabrication, the recording film is relatively unstable and amorphous, and energy is applied from the outside to raise the temperature of the recording film to the crystallization transition point or near the melting point to transition to a stable state. The closer the initialization state is to the state of the non-recorded area when the transition between the recorded area and the non-recorded area of the recording material is performed, the higher the erasure ratio and the longer the life span. At this time, the entire recording film must be uniformly and sufficiently initialized. If there is non-uniformity in the degree of initialization, the recording and erasing characteristics of the non-uniform portion will be different from those around it, causing reproduction, recording and erasing failures. The use of thermal energy seems to be the most effective way to solve this problem. When heat treatment is performed, the temperature of the entire recording medium can be raised uniformly and slowly cooled, so that very uniform and sufficient crystallization can be performed. but,
Since the substrate constituting the recording medium is generally a resin substrate with low heat resistance such as polycarbonate, which is inexpensive and easy to operate, rather than a glass substrate, an initialization method that involves applying heat to the recording medium is not appropriate. Further, even if a glass substrate is used, initialization takes a long time and is not suitable for mass production. Furthermore, when initializing the recording material by converting electromagnetic wave energy into thermal energy within the recording material, a problem arises as to whether sufficient energy for crystallization can be supplied. Current cheap and compact semiconductor lasers have weak oscillation output and cannot provide enough energy for crystallization. For this reason, laser light with a short wavelength and high oscillation output is sometimes used with its focus shifted on the medium surface. However, in this case as well, a special device for initialization is required, leading to increased costs.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for initializing an information recording medium that is improved in the following points compared to the above-mentioned prior art. (1) Improving recording and erasing sensitivity (2) Improving recording and erasing repeatability (3) Longer life (4) Low cost The purpose of the present invention is to solve the above-mentioned circumstances, and to improve recording and erasing performance. The present invention attempts to provide a method for initializing an information recording medium exhibiting erasing characteristics.

[0006]

[Means for Solving the Problems] The inventors of the present invention have conducted intensive research to improve the above-mentioned problems, and as a result, have discovered an initialization method that meets the purpose. That is, the present invention provides a method for initializing an information recording medium in which information is recorded by transitioning between two states of a recording material using the energy of electromagnetic waves, using electromagnetic waves as an energy source for initializing an optical information recording medium, Moreover, the wavelength λ is characterized by a relationship of −0.1≦(λ/λe)−1≦0.1 with the wavelength λe at which information is erased. In addition, when performing crystallization two or more times, the power PeX of the electromagnetic wave for the X-th initialization (2≦X≦n) and the power PeX for the X-th initialization and the power PeX- for the first initialization
1 is in the relationship of PeX≧PeX−1. As a result, the initialized state becomes close to the state of the non-recorded area when the transition between the recorded area and the non-recorded area of the recording material is performed, and recording and erasing sensitivity and repeatability are improved. Furthermore, since no special equipment is required for initialization, costs can be reduced.

The lattices, molecules, or electrons surrounding them forming the recording material form various energy levels, and incident electromagnetic waves are absorbed at one of the transitions between these energy levels. Therefore, if the wavelength λ used for initialization is significantly different from the wavelength λe used for erasing information, the state excited during initialization and the state excited during erasure will be different, and the irreversible portion will be recorded. It remains within the mark. Further, by gradually increasing the initialization power, transition can be promoted from a portion where a transition between energy levels is relatively likely to occur, and a stable phase can be gradually formed in the recording film. After that, when performing transitions in areas where transitions between energy levels are relatively difficult to occur, the surrounding stable phase serves to prevent chemical and physical changes in the recording film, so uniform and sufficient crystallization must be performed. I can do it. The present invention will be explained below based on the accompanying drawings. FIG. 1 shows an example of the configuration of a recording medium used in the present invention. A heat-resistant protective layer (2) and a recording layer (3) are provided on the substrate (1).
), a heat-resistant protective layer (4), and a reflective layer (5). The heat-resistant protective layer does not necessarily need to be provided on both sides of the recording layer, and a structure including only the heat-resistant protective layer (2) or only the heat-resistant protective layer (4) may be used. When the substrate is made of a material with low heat resistance, such as polycarbonate resin, it is desirable to provide a heat-resistant protective layer (2).

The substrate of the recording medium used in the present invention is usually made of glass, ceramics, or resin, and resin substrates are preferred in terms of moldability, cost, etc. Typical examples of resins include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. Polycarbonate resins and acrylic resins are preferred in terms of processability, optical properties, and the like. Further, the shape of the substrate may be a disk, a card, or a sheet.

[0009] Materials for the heat-resistant protective layer include SiO, S
iO2, ZnO, SnO2, Al2O3, TiO2, I
Metal oxides such as n2O3, MgO, ZrO2, Si3N
4. Nitride such as AlN, TiN, BN, ZrN, Zn
S, In2S3, sulfides such as TaS4, SiC, TaC
, B4C, WC, TiC, ZrC, diamond-like carbon, or a mixture thereof. These materials can be used alone as a protective layer, but
They may also be a mixture of each other. Further, it may contain impurities as necessary. However, the melting point of the heat-resistant protective layer must be higher than that of the recording layer. Such a heat-resistant protective layer can be formed by various vapor phase growth methods, such as vacuum evaporation, sputtering, plasma CVD, photoCVD, ion plating, and electron beam evaporation. The thickness of the heat-resistant protective layer is preferably 200 to 5000 Å, preferably 500 to 3000 Å. If it becomes thinner than 200 Å, it will not function as a heat-resistant protective layer, and if it becomes thicker than 5000 Å, sensitivity will decrease or interfacial peeling will easily occur. Moreover, the protective layer can be multi-layered if necessary.

The recording materials used in the recording medium include ternary or higher compounds and In, Sn, Sb, Bi, S, Se,
Examples include a mixed phase system with one or more elements selected from Te. AgInTe2, AgI as ternary or higher compounds
nS2, AgInSe2, AgGaSe2, CuInT
e2, CuInSe2 or ZnSnSb2, ZnS
nAs2, ZnSnP2, ZnGeAs2, CdSnP
2. Ib-IIIb-VIb of the periodic table of CdSnAs2
2 or IIb-IVb-Vb2, and/or Ib-Vb-VIb2
AgSbT represented by (wolfsbergite type)
Compounds with cubic crystals such as e2 are suitable. Such a recording layer can be formed by various vapor phase growth methods, such as vacuum evaporation, sputtering, plasma CVD, photoCVD, ion plating, and electron beam evaporation. In addition to the vapor phase growth method, wet processes such as the sol-gel method can also be applied. The thickness of the recording layer is 200 to 1000
The thickness is preferably 0 Å, preferably 500 to 3000 Å. Although a metal material such as Al or Au can be used as the reflective layer, it is not necessary. Such a reflective layer can be formed by various vapor phase growth methods, such as vacuum evaporation, sputtering, plasma CVD, photoCVD, ion plating, and electron beam evaporation.

[0011]

[Examples] The present invention will be specifically explained below with reference to Examples. However, these Examples do not limit the present invention in any way. Example 1 pitch 1.6 μm, depth 70
A heat-resistant protective layer, a recording layer, a heat-resistant protective layer, and a reflective layer were sequentially laminated by an RF sputtering method on a polycarbonate substrate having a groove of 0 Å, a thickness of 1.2 mm, and a diameter of 86 mm to prepare an optical disc for evaluation. Ag14In14Te29Sb43 was used as the recording material provided on the substrate, and the film thickness was 1000 Å. The reflective layer is made of Al and has a thickness of 500 Å.
And so. The heat-resistant protective layer is made of Si3N4, and the film thickness is 2 on the substrate side.
000 Å and 1000 Å on the reflective layer side. Optical disc evaluation uses semiconductor laser light with a wavelength of 830 nm and NA=0.5.
This was done by reducing the spot diameter to 1 μmφ on the medium surface through a lens and irradiating it from the substrate side. The linear velocity of the disk was 7 m/sec. The writing conditions for recording were a linear velocity of 7 m/sec and a frequency of 3.8 MHz, and the recording laser power (Pw) was varied from 4 mW to 19 mW. The erasing laser power (Pe) was 9 mW. The reading power (Pr) was 1 mW.

The recording film after film formation was amorphous, but during measurement, a semiconductor laser beam with a wavelength of 830 nm was used, and the entire surface of the disk was sufficiently crystallized with DC light of 7 mW, 8 mW, and 9 mW on the medium surface. , and set it as an initial (unrecorded) state. Initialization at 9 mW was performed until the reflectance from the medium surface was saturated. Figure 2 shows the C/N (C/N) of marks recorded on the disk after initialization.
The relationship between the carrier-to-noise ratio) value, the erasing ratio after erasing with DC light, and the recording laser power (Pw) is shown. In the figure, ● indicates the C/N value during recording, and the length of the arrow indicates the C/N value erased by DC light erasing. As can be seen from this figure, highly sensitive recording and erasing has been achieved. At a recording power of 8 to 11 mW, the C/N value is 40 dB or more, and the erasure rate is 100%.

Comparative Example 1 An optical disk for evaluation similar to that of the example was prepared, and a wavelength of 600
Initialization was performed in the same manner as in the example using a nm Ar ion laser. The recording, erasing, and reproducing methods are also the same as in the embodiment. FIG. 3 shows the relationship between the C/N (carrier-to-noise ratio) value of marks recorded on the disk after initialization, the erasure ratio after erasing with DC light, and the recording laser power (Pw). The meanings of symbols etc. in the figure are the same as in FIG. 2. The highest C/N value during recording was 47 dB, but the recording power at that time was 12 mW, which was 3 mW larger than that of the example. The erasure ratio at this time remains at 16 dB.

Comparative Example 2 An optical disk for evaluation was produced on a grooved glass substrate under the same conditions as in the example, also under the same conditions as in the example. Heat treatment was performed at 230° C. for 1 hour in the atmosphere, and the state where the material was sufficiently crystallized was defined as an initialized state. The recording, erasing, and reproducing methods were the same as in the examples. FIG. 4 shows the relationship between the C/N (carrier-to-noise ratio) value of marks recorded on the disk after initialization, the erasure ratio after erasing with DC light, and the recording laser power (Pw). The meanings of symbols etc. in the figure are the same as in FIG. 2. The highest C/N value during recording was 44 dB. It can be seen that the C/N value is saturated at approximately 10 mW, which again requires higher power than in Example 1. Further, the erasure ratio is 9 dB, and complete erasure as in the embodiment cannot be achieved.

[0015]

As explained above, in the recording medium initialization method of the present invention, since the wavelength used for initialization and the wavelength used for erasing are almost the same, the repeatability can be improved,
It is possible to record and erase with low power and extend the life of the recording medium. In addition, since no special equipment is required for initialization,
Low cost can be achieved. Further, since the power used for initialization is gradually increased, the recording film is uniformly and stably initialized, so that the same effect can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a recording medium on which the initialization method of the present invention is performed.

[Figure 2]

[Figure 3]

FIG. 4 shows the C/N (carrier-to-noise ratio) value of marks recorded on the disk after initialization and the erasing ratio after erasing with DC light in Example 1, Comparative Example 1, and Comparative Example 2, respectively; It is a graph showing the relationship with laser power (Pw).

[Explanation of symbols]

1 Board 2 and 4 Heat-resistant protective layer 3 Recording layer 5 Reflective layer

Claims (5)

[Claims] Claim 1. A method for initializing an information recording medium in which information is recorded by transitioning between two states of a recording material using the energy of electromagnetic waves, using electromagnetic waves as an energy source for initializing an optical information recording medium. , and the wavelength λ has a relationship of −0.1≦(λ/λe)−1≦0.1 with the wavelength λe at which information is erased. [Claim 2] The initialization is finally performed n times (n≧2), and the power Pe of the electromagnetic wave for the X-th initialization (2≦X≦n) is
2. The information recording medium initialization method according to claim 1, wherein X and the X-1th power PeX-1 have a relationship of PeX≧PeX-1. 3. The recording material after initialization contains a ternary or higher compound and one or more elements selected from In, Sn, Sb, Bi, S, Se, and Te, or an alloy consisting of these elements. 3. The initialization method according to claim 1, wherein an information recording medium mainly having a mixed phase is used. 4. The information recording medium according to claim 3, wherein the ternary or higher compound includes Ib-III of the periodic table.
The initialization method according to claim 1, characterized in that an information recording medium containing a chalcopyrite type compound represented by b-VIb2 or IIb-IVb-Vb2 and/or a compound having a cubic crystal is used. 5. The information recording medium according to claim 3 and claim 4, wherein an information recording medium is used which is brought into an initialized state mainly by crystallization of AgSbTe2 and/or Sb. and the initialization method according to claim 2.