JPH0242629A - Method of rewriting recording information of recording medium - Google Patents

Abstract

PURPOSE:To allow recording of information simultaneously with erasing and to improve the number of rewriting times by irradiating the surface of the recording medium intermittently in such a manner that the high heat energy regions of the spots formed to adjacent positions overlap on each other, thereby erasing the recorded information. CONSTITUTION:The laser beam capable of imparting the high heat energy which can convert the recording medium material from a stable phase to a metastable phase in at least the central region of the laser beam spot formed on the surface of the recording medium to the assembly of the very small regions of the metastable phase is so formed as to have the spots of the respective laser beams, by which the surface of the recording medium is successively irradiated. The recorded information is erased by irradiating the surface of the recording medium intermittently with the laser beams in such a manner that the high heat energy regions 1 of the spots formed in the adjacent positions overlap on each other. Another information is recorded in the erased regions 2 again. Namely, the laser beam used for recording of another information is radiated from a laser beam source used for erasing of the recorded information. The erasing characteristic and the recording characteristics after the erasing are improved in this way and the number of repetition of erasing and recording is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for rewriting recorded information on an information recording medium using a high energy density laser beam.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is, for example, an optical disc such as a video disc or an audio disc, a large-capacity still image file, a large-capacity computer disk memory, an optical cart, a micro image recording medium, an ultra-micro image recording medium, or a micro image recording medium. It is applied to facsimiles, original plates for phototypesetting, etc.

An information recording medium basically consists of a transparent substrate made of plastic, glass, etc., and a recording layer provided thereon. Materials for the recording layer include Bi, Sn, In, and T.
Metals or semimetals such as e, and dyes such as cyanine, metal complex, and quinone are known.

Information is written into the information recording medium by, for example, irradiating the recording medium with a laser beam,
Information is recorded by the irradiated portion of the recording layer absorbing the light and locally increasing its temperature, causing a physical or chemical change and changing its optical properties. Typical changes in the recording layer include deformation due to hole (bit) formation, four-part formation, and interlayer bubble formation.
Among these, recording by hole formation is the most popular method. Other known recording methods include a method using a reaction between two recording layers, a method using phase change, and a method using magnetization reversal. Reading information from an information recording medium is also performed by irradiating the recording medium with a laser beam, and the information is reproduced by detecting reflected or transmitted light according to changes in the optical characteristics of the recording layer. be done.

Information recorded on an information recording medium cannot be erased unless the recording is performed by reversible changes in the recording material.
If the external shape changes due to hole formation, etc., the recording medium cannot be erased and becomes a non-rewritable type. Rewritable (or erasable) types include crystalline and amorphous phases, uniform transparent phases and phase-separated opaque phases, and regularly oriented crystalline phases and irregularly oriented (unoriented) crystalline phases. Recording and erasing are generally performed using phase change, which is a reversible change in information.

The method for rewriting an erasable information recording medium is performed in two steps or in one step. The former two steps consist of two other steps: erasing recorded information from a recording medium and recording new information on the erased medium. The latter step is performed by simultaneously performing an erasing operation and an appropriate recording operation during the erasing operation.

In the m-beam override method described in L.2, the entire surface of the recording layer is first initialized by sufficiently crystallizing it with heat, etc., and recording is performed by intermittent irradiation with high-power laser light.
This is done by forming a set of a plurality of amorphous regions in response to a digital signal of information. Information is recorded in this way. Erasing of the recorded vI information is carried out by irradiating a region including the amorphous region with a laser beam having lower thermal energy than during recording to crystallize the region. In this way, the recording layer from which information has been erased is now
The entire area is a crystalline region). Other information can be recorded in this erased area in the same manner as the first recording described above.

The above two rewriting methods have the disadvantage that a satisfactory erased state cannot be obtained by the above-mentioned erasing. This will be explained in detail with reference to the attached FIGS. 1 and 2. FIG. 1 is a schematic diagram of a recording layer irradiated with a laser beam during a recording operation.

When the recording layer is irradiated with a high-power laser beam during a recording operation, the irradiation area (irradiation spot) 1 absorbs the high energy of the laser beam and melts immediately. The laser beam then stops and then irradiates the irradiation area 1° again. The irradiation area 1° is located at an arbitrary interval from the melting area l.

During the procedure L, the molten region 1 rapidly cools down after the irradiation is stopped and changes from the original stable crystalline phase region to a metastable amorphous phase region. The formation of a series of metastable amorphous phase regions records the desired information as a digital signal. Above amorphous area (recording area)! Area 2 around recording area 1 is also heated below the melting temperature of the recording material but above the recrystallization temperature (or phase transition temperature), so at the same time as recording, recrystallization area 2 is formed around recording area 1 It is formed. The crystalline state of the recrystallized region 2 is different from that of other surrounding crystalline regions 3. Therefore, when recording is completed, the recording layer covers another surrounding crystalline region 3, an amorphous region 1 in which information has been recorded, and a crystalline region 2 surrounding the amorphous region 1.

FIG. 2 is a schematic diagram showing the erased recording layer of FIG.

In an erasing operation, the recording layer is irradiated with a relatively low power laser beam that is continuously scanned along a predetermined route to connect to the amorphous regions on which information has been recorded. The continuous strip area 4 in FIG. 2 shows the back of the scanned laser beam spot. When erasing is completed with the low power laser beam, the band-like region 4 changes to its original crystalline phase, but the regions 2a and 2b remain in different crystalline states. Therefore, the recording layer erased in this way has two types of crystalline regions with slightly different optical properties. These different phase regions present in the erased recording layer lead to errors and malfunctions in subsequent recording and ILT operation.

In order to solve the above problem, a process override method using a single beam has been proposed.

According to this method, erasure is performed using a continuous laser beam,
This is done by irradiating the recording layer on which information is recorded while keeping the power at a high level. By this operation, the amorphous phase as well as the two types of crystal phases are melted in the same way and transformed into a uniform crystal phase region. When the laser beam reaches the location where new information is to be recorded, the power of the laser beam is reduced significantly and the recording material is rendered amorphous at that location. In this method, the -F conversion of the process (combination of erasure of recorded information and subsequent recording of other information) can be carried out with -a single laser beam. According to this method, the formation of different crystal phase regions does not occur. However, since the recording layer is continuously irradiated with a high-power laser beam, irreversible changes in the recording layer are likely to occur due to deterioration of the recording material, and there is a problem that reading errors increase when rewriting is performed repeatedly.

In addition, in the above two methods, erasing, recording, and reproduction are performed using different laser powers, so
When rewriting, it is necessary to control two powers.

Yet another method is called pseudo override. This method uses two beams, erasing with an elliptical beam and recording with a circular beam at the same time.

However, this method has problems in that a conventional write-once type head cannot be used because -0 beams are required, and that it is difficult to adjust the position A of the two beams.

[Object of the invention] The present invention aims to provide a novel method for recording other information on a recording layer in which information is recorded on an erasable recording material.
] target.

Another object of the present invention is to provide a novel rewriting method that does not leave stable phases in a plurality of different states in the recording area after erasing, and does not cause deterioration of the erasable recording material.

Furthermore, the present invention provides Li
, T-degree.

Furthermore, the present invention can erase and record information at the same time! It is an object of the present invention to provide a new rewriting method which does not cause deterioration of an IL-erasable recording material and can increase the number of rewrites.

Furthermore, it is an object of the present invention to provide a simple rewriting method that allows information to be rewritten using only pulse number modulation without controlling laser power.

[Summary of the Invention] The present invention provides: [1] Recording of information based on changes in light reflectance or light transmittance between a stable phase and a metastable phase that can be reversibly converted according to oil heating conditions; A laser beam is irradiated onto the surface of the non-recording area of a flat recording medium made of an erasable material and formed from a stable phase, and recording is performed using high thermal energy given by the laser beam. A method of rewriting recorded information on a recording medium in which information is recorded as an aggregate of a plurality of discontinuous micro-areas of metastable phases in the recording medium by converting the medium material into a metastable phase. A laser beam capable of imparting high thermal energy capable of converting the recording medium material from a stable phase to a metastable phase at least in the central region of the laser beam spot formed on the surface of the recording medium to an aggregate of phase microregions, The recorded information is erased by intermittently irradiating the recording medium surface so that the high thermal energy regions of the spots formed in at least adjacent positions among the spots sequentially irradiated onto the surface of the recording medium are aligned with each other, and then, + A method for rewriting recorded information, which comprises recording another information by the same method as in the if statement; A laser beam is irradiated onto the surface of the non-recording area of a flat recording medium, which is made of a material capable of recording and erasing information based on changes in light reflectance or light transmittance, and has a non-recording area formed from a stable phase. , a record in which information is recorded in the recording medium as an aggregate of 1M discontinuous micro-regions of metastable phase by converting the recording medium material into a metastable phase using the high thermal energy given by the laser beam. A method for rewriting recorded information on a medium, the method comprising changing the recording medium material from a stable phase to a metastable phase at least in the central region of a laser beam spot formed on the surface of the recording medium in the aggregate of the metastable phase minute regions. A laser beam capable of imparting convertible high thermal energy is intermittently irradiated onto the surface of the recording medium so that the high thermal energy regions of the spots formed in at least adjacent positions overlap each other among the spots of each laser beam sequentially irradiated onto the surface of the recording medium. While erasing the recorded information, when desired, another information is recorded by irradiating the recording medium with a laser beam by extending the irradiation interval so that the high thermal energy regions of the laser beams do not overlap. This is in the method of rewriting recorded information.

Preferred embodiments of the method for rewriting recorded information on a recording medium according to Section J2 [1] of the present invention are as follows.

1) The laser beam used to record the other information is
The recorded information u according to [1] above, characterized in that it is emitted from a laser beam source used for erasing recorded information.
F conversion method.

2) The laser beam used to record the other information is
The method for rewriting recorded information according to [1] above, characterized in that the laser beam has the same thermal energy as the laser beam used to erase the recorded information.

3) The method for rewriting recorded information according to [1] above, wherein the recording medium is disk-shaped and rotates in a plane when irradiated with a laser beam in each step.

4) The method for rewriting recorded information according to [1] above, wherein the stable phase is a crystalline phase, and the metastable phase is an amorphous phase.

5) The above [1], wherein the stable phase is a regularly arranged crystal phase (oriented phase), and the metastable phase is an irregularly arranged crystal phase (orientated phase). How to rewrite recorded information.

6) The method for exchanging recorded information according to [1] above, wherein the stable phase is a transparent phase of a polymer blend, and moreover, the metastable phase or an opaque phase of a polymer blend.

Preferred embodiments of the method for rewriting recorded information on a recording medium according to the above [21] of the present invention are as follows.

1) The method for rewriting recorded information according to item [2] above, wherein the recording medium is disk-shaped and rotates in a plane when irradiated with a laser beam in each step.

2) The method for rewriting recorded information according to [2] above, wherein the stable phase is a crystalline phase, and the metastable phase is an amorphous phase.

3) The above [2], wherein the stable phase is a regularly arranged crystal phase (oriented phase), and the metastable phase is an irregularly arranged crystal phase (orientated phase). How to rewrite recorded information.

4) The method for rewriting recorded information according to [2] above, wherein the stable phase is an opaque phase of a polymer blend, and the metastable phase is a transparent phase of a polymer blend.

[Effects of the Invention] The present invention uses the above-mentioned novel 8-conversion method [1] to erase information recorded on an information recording medium by irradiating it with laser light, thereby leaving very little unerased information. Erasing characteristics are obtained, recording characteristics are also good when recording is performed after erasing, and the number of edge reversals during such erasing and recording (8 conversions) is also improved.

The present invention uses the above-mentioned novel rewriting method [2] to simultaneously erase and record information on an information recording medium by pulse number modulation that changes the pulse period.
The amount of unerased data is extremely small, the recording characteristics are good, and the number of repetitions of such 8 conversion is also increased.

That is, erasing in the +'F conversion method of the present invention involves applying a laser pulse of high thermal energy to the recording layer material (1
This is done by applying energy that creates a metastable phase and then changing it to a stable phase. At this time, the metastable phase changes to the stable phase without rapid cooling, or it changes to the stable phase through the metastable phase with rapid cooling. Therefore, since the erased state is achieved in a homogeneous stable phase, good recording characteristics can be obtained even when recording is performed.

In the case of a rewriting method in which recording is performed after erasing, recording can be performed on the recording layer in the erased state made of the above-mentioned homogeneous stable phase with the same power as during erasing or with a desired power.

Recording in a rewriting method that performs recording at the same time as erasing is performed by stopping the above-mentioned erasing state (that is, pulse number modulation) and rapidly cooling the metastable phase to maintain the metastable phase. No information is left behind. Further, immediately after this metastable phase, the next stable phase part is formed, but this part does not become a metastable phase because it is not rapidly cooled.

Further, in the present invention, the laser power level used for erasing, recording and reproduction may be one of the following:
Recording is at the same level as normal playback. In the case of a rewriting method in which recording is performed after erasing, it may be better to change the power during erasing and during recording, but power modulation is not performed. Therefore,
Since only one laser power level is used during rewriting, there is no change in the pit width that causes uncleaned areas during erasing, so the erasing characteristics are good. Further, since the present invention does not require power control as described above, it can be performed using an l-beam recording device (drive). Furthermore, since power modulation is not performed, the drive described above can be simplified.

[Detailed Description of the Invention] Erasing in the two-step rewriting method of the present invention is carried out, for example, by using a laser beam with energy capable of melting the recording material at a period shorter than the length of the high thermal energy spot in the running direction of the recording medium. This can be done by shortening the time and irradiating intermittently. The high-energy spot is formed on the recording medium by the laser beam or the central part of the laser beam.

- The process rewriting method can be implemented, for example, by a combination of the following steps.

That is, erasing is performed by intermittently irradiating a laser beam having energy capable of melting the recording material with a period fixed to be shorter than the length of the high thermal energy spot in the running direction of the recording medium.

However, the high thermal energy spot is formed on the recording medium by the laser beam or the central portion of the laser beam.

Then, rewriting on the recording material is performed by stopping or reducing the output of the laser beam and irradiating it intermittently at a period longer than the length of the high thermal energy spot in the running direction of the recording medium.

It is preferable that the overlapping of the spots satisfies the following formula (1) at 1E to obtain continuity of the erased portion. That is, the laser beam diameter (r (m
) ) is the following general formula (1): % formula % (1) [where ■ (seconds) is the period, and v (m7 seconds) is the linear velocity] The high thermal energy spot is at least A spot formed on a recording material by irradiation with a laser beam having such high thermal energy that the central part of the beam can impart sufficient thermal energy to the recording material to melt it.

The information recording medium used in the information conversion method of the present invention can be manufactured, for example, by the method described above.

The substrate can be arbitrarily selected from various materials conventionally used as substrates for information recording media; examples include glass such as soda lime glass, acrylic resin such as cell cast polymethyl methacrylate, and vinyl chloride. Examples include polycarbonate resins and polycarbonate resins. An undercoat layer may be provided on the surface of the substrate for purposes such as improving surface properties and increasing adhesive strength, or forming grooves for tracking or irregularities representing information such as address signals. A pregroove layer may be provided for this purpose.

Note that a substrate is not necessarily required when the recording layer is self-supporting.

Next, a recording layer is formed on the J and Q plates (or coating layers). A light-absorbing substance may be dispersed and contained as necessary.

The recording layer of the present invention is made of a material that can record and erase information based on a change in light reflectance or light transmittance between a stable phase and a metastable phase that can be reversibly converted depending on heating conditions. It is necessary to become.

In the present invention, a stable phase is a phase state that is reached when a material is heated to a phase transition temperature or higher and then slowly cooled, and a metastable phase is a phase state that is reached when a material is heated to a phase transition temperature or higher and then rapidly cooled. This is the phase state that occurs. Examples of stable phase to metastable phase include crystalline phase to amorphous phase, transparent phase of polymer blend (
(compatible state) - opaque phase (phase separated state), regularly arranged crystalline phase of dye (oriented phase) - irregularly arranged crystalline phase (
(no dividends, same phase), etc. Note that the stable phase of the polymer blend may be an opaque phase (phase-separated state) opposite to the above.

The temperature at which a reversible change occurs (called the r-glass transition point J in the case of a crystalline phase, and the "equinode point" in the case of a polymer blend phase) varies depending on the type of substance, or ranges from 60 to 400°C.
It is preferably in the range of 80 to 30, particularly preferably 80 to 30.
It is in the range of 0°C.

Examples of substances that undergo a state change between a crystalline phase and an amorphous phase include 5e-Te system, 5b2Se, and Te01 (0<
x<2), As-Te-Ge system, Sn-Te-
Mention may be made of metal and metalloid compounds such as the S e series. For example, sbr, -Te43 is in an amorphous state when it is formed, but becomes a crystalline state when heated to -degrees crystallization temperature or higher. In addition, when the material is rapidly cooled to a temperature above the melting point, it returns to the amorphous state. In addition, known metals, semimetals, and compounds thereof that undergo a state change between a crystalline state and an amorphous state can be used.

Furthermore, a typical example of a substance that undergoes a phase change between a transparent phase and an opaque phase (a compatible state and a phase separated state) is a polymer blend consisting of a mixture of two or more types of polymers. However, a combination of a polymer and a monomer may exhibit similar behavior, and such a composition is also included in the polymer blend in the present invention.

Polymer blends can be roughly divided into lower critical cosolution temperature (LC3T) types, which are transparent and compatible at room temperature, but phase separate and become cloudy (become opaque) at high temperatures above the equinox, and vice versa. The upper critical cosolution temperature (UCST)
) type.

Examples of LC3T type polymer blends include combinations of amorphous polymers: polystyrene and polyvinyl methyl ether;
Acrylonitrile copolymer and poly-ε-caprolactone, styrene-acrylonitrile copolymer and polymethyl methacrylate, polyvinyl nitrate and polymethyl acrylate, ethylene-vinyl acetate copolymer and chlorinated rubber, poly-6-caprolactone and polycarbonate ( Bisphenol A type), p-chlorostyrene/0-chlorostyrene copolymer and poly(2,6-dimethyl-1,4-phenylene oxide), polycarbonate (bisphenol A
type) and ethylene oxide block copolymer, butylene terephthalate/tetrahydrofuran block copolymer and polyvinyl chloride, thermoplastic polyurethane [poly-ε-
caprolactone soft block] and polyvinyl chloride; 2
) Combinations of crystalline and amorphous polymers: polyvinylidene fluoride and polymethyl acrylate, polyvinylidene fluoride and polyethyl acrylate, polyvinylidene fluoride and polymethyl methacrylate, polyvinylidene fluoride and polyethyl methacrylate, polyfluoride Vinylidene and polyvinyl methyl ketone: and 3) Combinations of crystalline polymers and crystalline polymers: polyethylene oxide and trioxane, poly-ε-caprolactone and trioxane;

Examples of U CST B2 polymer blends include:
Examples include combinations of amorphous polymers such as polystyrene and polyisoprene, polystyrene and polyisobutyne, polypropylene oxide and polybutadiene, and polyisobutyne and polydimethylsiloxane.

In addition, these polymers can be made into copolymers with other monomers as appropriate within the range showing LC3T and UCST.

Examples of pigments that cause a state change between the regularly arranged crystal phase (orientated phase) and the irregularly arranged crystal phase (disorientated phase) of the above pigments include cyanine pigments, azulenium pigments, and squarylium pigments. Examples include dyes.

In the method of the present invention, cyanine-based, metal complex-based, quinone-based dyes, etc. may be used as the light-absorbing substance, or metals or semimetals may be used.

These may be used alone or in combination as a composition. Also, metals or metalloids and their oxides,
A halide or a sulfide may be used in combination.

For the recording layer, if the substance that causes a phase change is an organic compound such as the above polymer blend or a dye such as cyanine, a coating solution is prepared by dissolving the substance and, if necessary, a light-absorbing substance in an appropriate solvent. However, it can be formed on the substrate by applying this coating 111 liquid to the substrate surface by a coating method such as a spin code method or a roll coating method and then drying it.

For example, in the case of a polymer blend, it is used in combination with the above-mentioned light-absorbing substance, but the mixing ratio of the polymer blend and the light-absorbing substance in the coating liquid is generally 10
0:0.1~100:100 (Il'jijlt>
(7) in the range, preferably 100:1 to 100:5
It is in the range of 0.

The recording layer may be m-layer or m-layer, but its layer thickness is generally 0.01 to 10 m from the viewpoint of optical density used for optical information recording.
It is in the range of μm, preferably in the range of 0.02 to 1 μm.

Note that the light-absorbing substance does not necessarily have to be contained in the recording layer, but may be contained in the layer adjacent to the recording layer (light-absorbing layer).
- may be done.

In addition, in the case where the material that causes a phase change in the recording layer is an inorganic material such as a metal, the material and, if necessary, a light-absorbing material may be deposited, sputtered, or ion-blated on the surface of the substrate. It can be formed on the substrate by. The recording layer may be a single layer or a multilayer, but its layer thickness is generally in the range of 100 to 1500, preferably 150 to 1500, in view of the optical density required for optical information recording.
It is in the range of 1000λ.

Furthermore, A2, C and C are provided on the recording layer (or light absorption layer) or between the substrate and the recording layer for the purpose of improving the S7<N ratio during information reproduction and improving the sensitivity during recording.
A light reflecting layer made of metal such as r and Ni may be provided. In addition, 5i02, M
A protective layer made of an inorganic material such as gF2.5n02 or an organic material such as a UV curable resin may be provided.

Next, regarding the method for erasing information recorded on the information recording medium of the present invention and the method for converting information into δ, information recording media provided with a recording layer that can undergo a state change between a crystalline state and an amorphous state will be described. An example of using a medium will be explained.

Na1? Initialization, recording, +lF generation and deletion of information are performed using Ga.
- Using a semiconductor laser that emits near-infrared light, such as an As laser, the surface of the information recording medium provided with the recording layer is irradiated with a laser beam that is focused according to a known method. .

It is preferable to initialize the information recording medium before recording on the information recording medium. The initialization conditions in the present invention are preferably the same as those for erasure described below. Note that in the present invention, the initialization step can also be omitted.

Subsequent optical information recording is performed by changing the recording layer from a crystalline state to an amorphous state by irradiating the recording layer with laser light, which is the rewriting method of the present invention described below. However, there is no problem with recording using other recording methods. Information is read by utilizing the difference in optical properties between the amorphous portion and the crystallized portion at this time.

Conventional erasing of information is performed by crystallizing the information using, for example, a laser beam with a lower power density than during recording.

As mentioned above, when high power laser light is irradiated during recording, as shown in Figure 1 (representing recorded bits),
A recrystallized region 2 is formed around the amorphous region 1, which is the recorded portion, because the melting temperature does not reach 8, but it is higher than the crystallization temperature. This (re)crystallized region 2 differs from the crystalline region 3 that has just been erased by the low power density laser beam in terms of crystalline state f14 (eg, crystal grain size, etc.). Furthermore, since the laser power during recording is greater than the power during erasing, the width of the crystal region is wider than the original crystal region during erasing, and outside the original crystal region 3 due to erasing. The crystal region 2 tends to remain as a signal. Therefore,
This causes information to remain even if it is erased.

The present invention has made it possible to unify the erased states by converting the crystal regions 2 and 3 in FIG. 1 into one crystal phase. That is, in the case of the erasing or rewriting method of the present invention, as shown in FIG. 1. The laser pulse spot is irradiated so that the next spot is aligned with the next spot. , ; T finely, the previous laser pulse creates a pit that has almost the same shape as the spot of the laser pulse and consists of a central melted part (a part that becomes an amorphous region during recording) and a crystalline region 2 around it. The next laser pulse is applied so that the spot formed by the laser pulse covers at least the entire melted area in the center (the part that becomes amorphous area 1 during recording) of the previous bit. A recrystallized region (erased region) 2 is formed by crystallizing the melted region by +1. When these are formed continuously, an erase area of /1 shown in FIG. 4 is formed. The melted part in the center of the pit formed by the previous laser pulse is
Depending on the irradiation interval of the next laser pulse, the state may change from a molten state to a crystallized state, or from a molten state to an amorphous state and then to a crystalline state.
In general, since the interval is constant, the erased state can be said to be always uniform.

As shown in FIG. 3, the information rewriting method is to appropriately interrupt the erasing area (one or a continuous area of 2) formed by recrystallizing the melted part according to the recording signal. It is done.

In other words, the melted part at the center of the pit (the part that becomes amorphous region 1 during recording) is formed by the irradiation of the last laser pulse in the series of pits stacked so as to cover the melted part of the pit as described above. ) The spot of the next laser pulse is formed so as to cover part or all of the recrystallized region 2 that adjoins the melted portion while avoiding the melted portion. Recording is performed by irradiating the next laser pulse in this manner. This allows the melted portion to change into an amorphous region, making it possible to record information. By forming a spot of the next laser pulse so as to avoid the central melted part of the previous pit and cover the crystal region 2 that is in contact with the melted part, the true record can be completely erased. It is preferable for the next spot to completely cover the crystal region 2 in order to perform good erasing and recording.

Note that even when no light pulse is irradiated, the +4 raw beam for performing tracking servo, focus servo, etc. is generally emitted as a continuous beam. Therefore, in the present invention, the laser power level used for erasing, recording, and reproduction may be two, and the level for recording is the same as that for normal reproduction. During erasing and recording, the reproduction beam that performs tracking servo, focus servo, etc. is generally emitted as a continuous beam, and during erasing, a light pulse is added to this, and during recording, this light pulse is stopped!
Then, the information is rewritten using only continuous reproduction light. In this case both the continuous beam and the light pulses are carried out in the same single beam. Also.

By increasing the pulse length of the last pulse of the erasing light pulse, which is just before the light pulse during recording stops,
Or by lowering the power of the pulsed light,
It may be possible to record more accurately. For this reason, although the control of the laser becomes complicated, it is also possible to perform the switching in this way.

That is, in the erasing method and rewriting method of the present invention, erasing is performed by once melting the recording layer material by a laser pulse with high thermal energy and then returning it to a crystalline state. Therefore, since the erased state is obtained in a homogeneous crystal phase (state), good recording characteristics can be obtained even when recording is performed.

Recording in the rewriting method also stops the above erased state,
Since this is done by rapidly cooling the molten state to form an amorphous phase, the information recorded just before will not remain.

In addition, the next pit overlaps immediately after this amorphous phase, but immediately after the amorphous part is an overlap of a crystallized part that has only reached the crystallization temperature, so it can be said that it has not reached the molten state. However, this portion is well reproduced as a recorded signal together with the amorphous portion.

Further, in the present invention, the laser power level used for erasing, recording, and reproduction may be two, as described above, for erasing and reproduction, and recording is at the same level as normal reproduction. Therefore,
During -2 conversion, since only one laser power level is used, there is no change in bit width that causes unerased data during erasing, so the erasing characteristics are good. Furthermore, by using one laser beam, the method of the present invention erases recorded information and replaces the information three times by modulating the number of pulses without controlling the laser power.
It also has the advantage of being able to use a conventional DRAW type head because it uses a laser beam of 70 mm. Furthermore, since rewriting can be performed simply by controlling the number of pulses, the laser drive circuit can be simplified.

Furthermore, when erasing information recorded using the erasing method of the present invention, stable recording can be performed using conventional recording methods as long as the irradiation pulse length is taken into consideration to some extent, so it can be used in combination with the erasing method of the present invention. What you do is 6-cho Noh.

In the erasing and replacement method of the present invention, a laser pulse that is capable of recording information (that is, has a temperature similar to the melting temperature of the recording layer material) is placed next to the spot of the laser pulse on the information recording medium. Erasing is performed by irradiating the two spots so that they are aligned with each other as shown in item 1. Therefore, it is preferable that the overlapping spots provided in the present invention satisfy the following formula (1) in order to obtain continuity of the erased portion. That is, the laser beam diameter (r (m)) that forms the above spot is expressed by the following general formula: % formula % (1) [where T (seconds) is the period, and v (m7 seconds) is the linear velocity. ] This makes it possible to improve the erasing recording and rewriting recording characteristics.

The above method of erasing information can be similarly applied to information recording media that utilize phase changes such as polymer blends.

EXAMPLES Examples and comparative examples of the present invention will be described below in the margins below, but these are not intended to limit the present invention.

[Actual hM example! ] A disc-shaped cell-cast polymethyl methacrylate resin substrate (outer diameter: 130 mm) equipped with a tracking guide.
, inner diameter: 15 mm, thickness = 1.2 mm, track pitch: 1.6 μm), ZnS was evaporated to a layer thickness of 80 μm.
A recording layer made of Sb 52T e 411 with a layer thickness of 800^ is obtained by forming a light-absorbing layer consisting of 0 or more and then co-depositing sb and Te in an atomic ratio of 52:48. was formed, and ZnS was further vapor-deposited on the recording layer to form a light-absorbing layer having a layer thickness of 800^. An information recording medium was thus obtained.

This information recording medium was irradiated with high frequency modulated semiconductor laser light (wavelength: 830 nm, irradiation power = 12 mW, frequency: 10 MHz, pulse length = 50 ns) at a linear velocity of 5 m/s, resulting in the first JIJI recording medium. I did it.

A normal semiconductor laser beam (wavelength:
830nm, irradiation power near mW, frequency: 2.5MH
z, pulse length: 200 ns) from the substrate side at a linear velocity of 5 m/sec to write information. Next, the recorded information was erased under the same conditions as the initialization.

[Example 2] The information recording medium on which the information obtained in Example 1 was recorded was not erased, but was exposed to high frequency modulated semiconductor laser light (wavelength: 830 nm, irradiation power: 12 mW, frequency: 10 MHz, pulse length: 50ns) at a linear velocity of 5m/
The information was rewritten by repeating irradiation for 200 ns and then irradiating the next 200 ns with a laser beam having an irradiation power of 0.8 mW (the power of the reproduction laser beam).

[Comparative Example 1] A semiconductor laser beam (wavelength: 830 nm, irradiation power: 5 mW) was applied to an information recording medium manufactured in the same manner as in Example 1.
) was irradiated from the substrate side with DC (No. 3) on the entire surface at a linear velocity of 5 m/sec to perform initial JtJf conversion.

Semiconductor laser light (wavelength: 830
nm, irradiation power: 10mW, frequency = 2.5MHz,
Information was written by irradiating a pulse (pulse length: 200 ns) from the substrate side at a linear velocity of 5 m/sec. Next, the recorded information was erased under the same conditions as the initialization.

[Comparative Example 2] In an information recording medium manufactured in the same manner as in Example 1,
Semiconductor laser light (wavelength: 830 nm, irradiation power t
omW) from the substrate side at a linear velocity of 5 m and 7 seconds.
(Initialization was performed by irradiating the entire surface with No. i).

Semiconductor laser light (wavelength: 830
Information was written by irradiating the substrate with irradiation power (irradiation power: 5 mW, frequency: 2.5 MHz, pulse length: 200 ns) from the substrate side at a linear velocity of 5 m/sec. Next, the recorded information was erased under the same conditions as the initialization.

The C/N during recording and erasing on each side and the number of rewrites (or repetitions of recording and erasing) were evaluated by the following method.

1) Recording C/N The recorded signal was reproduced and its C/N was measured using a disc evaluation machine (OMS-1000, manufactured by Nakamichi ■).

2) Erased C/N The erased signal remaining after erasing was reproduced, and its C/N was measured using a disc evaluation machine (OMS-1000, manufactured by Nakamichi ■).

3) l! : Number of times of rewriting (or number of repetitions of recording and erasing) Evaluation was made based on the number of times a constant jitter could be maintained by repeatedly performing rewriting (or recording and erasing). The evaluation was carried out using a disc evaluation machine (OMS-1000, manufactured by Nakamiji@).

The results are shown in Table 1.

Table 1 Recording C/N Erasing C/N Number of repetitions (dB)
(dB) (times) Example 1 Example 2 100 or more 100 or more Comparative example 1 45 31 5 Comparative example 2
43 23 2 As is clear from Table 1 above, the information recording medium obtained by the method of the present invention has superior erasing performance and durability against repeated use compared to Example 1. In addition, from Example 2, the rewriting (override) that allows recording at the same time as erasing of the present invention
It can be seen that this method has excellent durability for repeated use, and that it is possible to use a conventional DRAW type optical head as is and rewrite data only by modulating the number of pulses of the ejected beam.

On the other hand, it can be seen that in Comparative Examples 1 and 2, which are conventional methods, both the erasing characteristics and the repeated durability are insufficient for practical use.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a recording state on the surface of a recording layer of a recording medium on which information is recorded by a conventional method. FIG. 2 is a schematic diagram showing the erased state of the surface of the recording layer of a recording medium in which information recorded by a conventional method has been erased. FIG. 3 is a schematic diagram showing the recording state on the surface of the recording layer of an information recording medium on which information is recorded by the method of the present invention. FIG. 4 is a schematic diagram showing the erased state of the surface of the recording layer of the information recording medium from which information recorded by the method of the present invention has been erased. 4: Belt-shaped region patent applicant Fuji Photo Film Co., Ltd. Representative Patent attorney Hata Yanagawa 1.1': Amorphous region 2.2a, 2b: (Re)crystalline region 3: Another crystalline region of the laser beam Direction of travelDirection of travel of the laser beamDirection of travel of the laser beamDirection of travel of the laser beam

Claims (1)

[Claims] 1. It is made of a material that can record and erase information based on changes in light reflectance or light transmittance between a stable phase and a metastable phase that can be reversibly converted depending on heating conditions, and is formed from a stable phase. By irradiating the surface of the non-recording area of a flat recording medium having a non-recording area with a laser beam and converting the recording medium material into a metastable phase using the high thermal energy given by the laser beam, the recording medium A method for rewriting recorded information on a recording medium in which information is recorded as an aggregate of a plurality of discontinuous metastable phase microregions, the information being formed on the surface of the recording medium in the aggregate of the metastable phase microregions. A laser beam capable of imparting high thermal energy capable of converting the recording medium material from a stable phase to a metastable phase in at least the central region of the laser beam spot is applied to at least adjacent spots of each laser beam sequentially irradiated onto the surface of the recording medium. Rewriting the recorded information, which consists of erasing the recorded information by intermittently irradiating it so that the high thermal energy areas of spots formed at matching positions overlap each other, and then recording other information using the same method as above. Method. 2. It is made of a material that can record and erase information based on changes in light reflectance or light transmittance between a stable phase and a metastable phase that can be reversibly converted depending on heating conditions, and is formed from a stable phase. By irradiating the surface of the non-recording area of a flat recording medium having a non-recording area with a laser beam and converting the recording medium material into a metastable phase using the high thermal energy given by the laser beam, the recording medium A method for rewriting recorded information on a recording medium in which information is recorded as an aggregate of a plurality of discontinuous metastable phase microregions, the information being formed on the surface of the recording medium in the aggregate of the metastable phase microregions. A laser beam capable of imparting high thermal energy capable of converting the recording medium material from a stable phase to a metastable phase in at least the central region of the laser beam spot is applied to at least adjacent spots of each laser beam sequentially irradiated onto the surface of the recording medium. While erasing the recorded information by intermittent irradiation so that the high thermal energy areas of the spots formed at matching positions overlap each other, the irradiation interval is adjusted so that the high thermal energy areas of the laser beams do not overlap when desired. A method of rewriting recorded information, which consists of recording different information by irradiating a recording medium with an elongated laser beam.