DE19655251B4 - Phase change type optical recording medium esp. CD - Google Patents

Abstract

A phase change-type optical recording medium consists of a substrate bearing a recording layer and an overlying protective layer which is a 10-30 nm thick dielectric layer. The recording layer is a 15-30 nm thick layer of at least one of the antimonide cpds. ((GeTe)y(Sb2Te3)1-y)1-xSbx (I) (x = 0 to less than 0.1, y = 0.2 to 0.9 exclusive) and (MyTe1-xSbx)1-y (II) (y = 0 to less than 0.3 x = 0.5 to 0.9 exclusive, M = one or more of In, Ga, Zn, Ge, Sn, Pb, Si, Co, Cr, Cu, Ag, Au, Pd, Pt, S, Se and O). The protective layer consists of (A) one or more sulphides or selenides of gp. IIa elements, one or more sulphides or selenides of rare earth metals or Y or one or more of TaS2, TaSe2, ZrS2 and WS2 and (B) one or more refractive cpds. which have a melting or decomposition temp. of at least 1000 deg C and which are free of sulphides and selenides. Also claimed are (i) a phase change-type optical recording medium consisting of a disk with recorded divided pulses information; (ii) a turntable unit for overwriting and reading information from a phase change-type recording medium; and (iii) an optical recording process for laser recording of data on or erasure of data from an optical information carrier medium.

Description

BACKGROUND THE INVENTION

The invention relates to a optical recording medium and an optical recording method and in particular to a recording method that allows in a phase change type optical recording method, where information by irradiation of laser beams or the like recorded, deleted or can be reproduced, to use a wide range of linear speeds.

DESCRIPTION THE PRIOR ART

Recently have been considerable Made efforts to develop optical disks that can be written with laser beams and their stored ones Information can be retrieved using laser beams to provide such a recording medium which meets the requirements in Towards greater information processing and higher Information density as well as a higher recording and retrieval speed enough. Writable optical storage disks can be storage disks which can only be written once and can be storage disks, which allow repeated recordings and deletions and are therefore arbitrary described and deleted can be. Include optical disks that can be written to multiple times magneto-optical recording media containing a magneto-optical Take advantage of effect and phase change media that have a reversible phase change between crystalline and amorphous phase.

A phase change type recording medium needed no outside magnetic Field, and allows simultaneous recording / deletion only by modulating the power of laser radiation. It also has the advantage that it a single-line overwrite process allows a single beam to be used to erasable and overwrite run simultaneously.

With a single-line overwritable Phase change type disk generally becomes a recording mark each by amorphization and recrystallization of a μm-sized section of the recording film is formed and deleted. As a recording film for the Use in a phase change type storage disc is in the generally used a film rich in ore-forming alloys is. Examples of the alloys are Ge-Te, Ge-Te-Sb, In-Sb-Te and Ge-Sn-Te-rich alloys.

With a recording medium of Phase change types are generally two levels of laser power used to characterize the two characteristic states, the crystalline and the amorphous state. As an example, a conventional one Method described in which a mark is formed by an original Crystallization state is amorphized, and then a deletion by subsequent Amorphization takes place. The crystallization is done by heat treatment of the recording layer is carried out at a temperature which is higher than the crystallization temperature and less than the melting point the recording layer. In this case, the cooling rate of the Controlled recording layer so that it is sufficiently deep So that the Crystallization from the structure of the recording layer between Insulating layers is arranged, can be achieved, or by a method can be achieved using an elliptical laser beam used that has a major axis that extends along the direction of rotation the disk, i.e., along the scanning direction of the Laser beam.

On the other hand there is amorphization through heat treatment of the recording layer is carried out at a temperature which is higher than the melting point of the recording layer, whereupon super cooling (super cooling) follows the molten recording layer. At a The phase change type recording medium becomes a single-beam overwrite performed by that a Record mark deleted is and a simultaneous recording takes place, the recording Laser pulse between the level of a recording laser power Pw and an extinguishing Laser power Pe is modulated. In this process, the above insulating layers the function of heat radiating Layers to provide adequate cooling or quenching speed to achieve. The insulating layers also function as the recording layer to protect against deformation, caused by the melting process or the change in volume during the heating or cooling step can be caused. The insulating layers also have the function thermal damage of the substrate and a degradation of the recording layer prevent. The material for the insulating layer is in view of its transparency for laser light, high melting point, high softening and decomposition points, simplicity selected in the manufacture, and adequate thermal conductivity.

Since the thermal process during reading and writing is significantly influenced by the scanning speed of the laser beam, ie the linear speed on a storage disk, the composition of the recording layer and its multilayer structure for the linear speed on the storage disk should be used in the phase-change type recording medium described above be optimized to increase the recording and erasing characteristics. An amorphous mark is generally formed by melting a µm-sized portion of the recording layer by irradiation with a recording energy, followed by cooling at a cooling rate higher than a critical cooling rate. A high cooling rate is generated by a high linear speed, while a low cooling rate is caused by a low linear speed.

A thermal distribution simulation was performed using an ordinary differential method on a disk made of a 100 nm thick ZnS-SiO ₂ mixed film, a 25 nm thick GeSbTe recording layer and a 20 nm thick ZnS-SiO ₂ -mixed film and made of a 100 nm-thick aluminum alloy film which are sequentially formed on a polycarbonate substrate, which is also used in an embodiment of the present invention. The simulation used irradiation of the disk with a recording power Pw and a basic power Pb, which have theoretical values. It was found that at a point 0.1 µm from the point from which the irradiation pulse comes and near its melting point (600 ° C) during the temperature drop after the recording layer once reached the maximum temperature of 1350 ° C, the cooling rate is a few K / ns or more for a linear velocity of 10 m / s or more, 2.2 K / ns for 4 m / s, and 0.9 K / ns for 1.4 m / s.

To delete an amorphous mark is it is necessary that the Recording layer for a given time interval at a given temperature above the crystallization temperature and below the melting point is held. This time interval at which the recording layer should be kept at a given temperature depends on the linear velocity, being higher linear velocity gets smaller and gets bigger at low linear velocity. Accordingly, if a recording system that has a relatively high linear velocity is irradiated with a focused laser beam, it follows that that a thermal distribution of the recording layer in the so irradiated Section temporally and spatially will be relatively steep, causing the intended deletion can be faulty. To such a recording system that has a relatively high linear velocity an alloy for uses the recording layer which has a composition which has a relatively high crystallization rate, and / or it a multi-layer structure is used that suppresses heat dissipation, so that a Crystallization or quenching occurs within a relatively short time interval.

Conversely, when a relatively low linear velocity recording system is used, the cooling rate is suppressed, which entails the risk of recrystallization occurring during recording. In order to provide such a recording system with a relatively low linear speed, an alloy is used for the recording layer, which has a composition which has a relatively low crystallization speed, and / or a multilayer structure is provided which increases the heat dissipation in order to form an amorphous one Prevent marking recrystallization so that an intended marking length can be achieved. In particular, for a recording medium with a high linear velocity, a multilayer structure is used in which the thickness of a thermal insulation layer disposed between the recording layer and a reflection layer increases to suppress heat dissipation. A corresponding choice can be made in the material used. For example, when a GeSbTe alloy is used, a compound such as a GeTe-Sb ₂ Te ₃ alloy or the above that promotes recrystallization is used. On the other hand, for use in a recording medium using a low linear velocity, the thickness of the thermal insulation layer is reduced to promote heat dissipation. A corresponding choice can be made by using a larger amount of Sb than the amount of Sb used when used in a recording medium which has a high linear velocity so as to suppress recrystallization during solidification.

It is possible, as mentioned above, one acceptable sensitivity in recording, erasing and the To obtain information with an intended system by the composition of the recording layer and / or the Multilayer structure is optimized. For a recording medium that for the Use in a relatively high recording system Linear speed is optimized, however, it is necessary that the crystallization speed elevated will, however, what its use in the low linear speed range prohibits because the resulting recrystallization of the formation of a stands in the way of amorphous bits. On the other hand, if a medium for a low Linear speed is optimized, causing the resulting Composition of the recording layer and / or the multilayer structure for the Formation of an amorphous bit increases the difficulty of deleting high linear speeds. Because of this, optimization can the recording medium alone does not tolerate the linear velocity tolerances for the recording medium increase.

It has recently been known that the linear velocity for the medium used has been increased during recording or erasing in order to reduce the time required for recording or erasing. On the other hand, there is a need to record information in accordance with real time when, for example, recording video, music or the like. In addition, there is an application in which a recording is made in real time and later changed at a higher rate. If it is possible to provide a common medium that can be used in a relatively low linear velocity range (in a range from 1.2 m / s to 1.4 m / s and up to four to six times this range) that can be achieved by recordable CDs and which can also be used in a high linear speed range which occurs with current magneto-optical storage disks (in the order of magnitude of 10 m / s or more), such a recording medium would preferably be used in multimedia applications.

If an attempt is made to meet these needs to be enough by simply doing a write operation at a linear velocity accomplished which is far below the linear velocity for which the Multi-layer structure and / or the composition of the recording layer of the recording medium is optimized, it results from the occurrence from recrystallization an erroneous record of the intended Mark length, which prevents the recording of information. at a phase change type recording medium becomes a recording layer irradiated by a focused laser beam to localize the layer to melt, whereupon the melt is quenched, and thereby a amorphous mark is formed. However, if the disk has a relatively low linear velocity, occurs after Melt that for the purpose of recording as described above was generated on recrystallization, which is a difficulty for formation a satisfactory amorphous label represents what that explain the failure described above can.

Retrieving a recorded mark at which crystallization occurred after melting during recording creates a waveform, as graphically in FIG 1 shown. The reflectivity in the front half of the recorded mark is not satisfactorily low. This means that recrystallization occurs mainly in the front half of the recorded mark, while an amorphous mark is mainly formed in the rear portion of the mark, which is shown in 2 is shown. This can be explained as a result of continued exposure to the laser beam at a level that corresponds to the recording power that the heat generated by the laser on an area corresponding to the rear half of the mark transfers by heat conduction to an area that the front half of the mark that had melted. The consequence of this is that the front half of the marking cannot be quenched and recrystallization is possible.

The back end of the mark is immediately after the end of the irradiation of the back No longer end irradiated with the irradiation of the laser beam on the stage that corresponds to the recording performance, and therefore there is none undesirable Warmth, whereby this melted section can become amorphous. Under consideration of these effects, it was found that the power level after Beginning of irradiation is reduced with the recording power, or if the recording pulse is divided, the recording layer will experience a temperature change over time that is used for deterrence is more appropriate, causing a degradation in the mark that through recrystallization during of the writing process is prevented.

Examples of recording methods based on this observation are in the Japanese Patent Application Laid-Open Nos. 165,420 / 1990, 212,735 / 1992, 62,193 / 1993, 325,258 / 1993, 116,927 / 1989 and in JJAP. Ed. 30, No. 4 (1991), pp. 677-681. A recording process using an off-pulse is in Extended Abstracts (40th spring meeting), the Japan Society of Applied Physics and Related Societies, 29a - B - 4 and in Japanese Patent Laid-Open Nos. 37.25111995, 4 86711994, 253.828 / 1989, 150.23011989, 315.030 / 1989, 313.816 / 1992, 199.628 / 1990 and 113.93811988 disclosed. However, these methods use a fixed technique shared impulse, and while they are effective in recording at a linear speed are in a given range, therefore becomes a desirable one Record frequently prevented under the condition in which the linear velocity deviates far from the given range. As long as a fixed shared Pulse technology is used, there is a limit to the range of linear velocities on a single solid medium with a fixed composition of a recording film and a solid filling layer structure can be applied.

The following are also known from the prior art:
Out US 5,175,722 a voltage source circuit for stabilizing the power supply of a laser diode used for writing and reading data on an optical recording medium; out EP 0 578 015 A1 a medium for the optical recording of information with recording materials of the composition MxTeySbz; and from US 5,314,734 another medium for recording information.

It is therefore an object of the present invention to provide an optical recording method for recording provide data on a phase change type recording medium in which data marks can be effectively overwritten over a wide range of linear speeds.

It is another object of the present Invention, an optical recording or recording method for recording a single fixed disk through a plurality of disk drives to provide different linear speeds in a wide range Area. It is another object of the present invention an optical recording method for recording on a ZCAV disk (Zoned Constant Angular Velocity Disk) provide in which the linear velocity with the in one specific radius range of fixed zones varies.

It is another object of the present Invention, an optical disc and a recording medium drive to provide that for the method described above are suitable.

To the tasks discussed above to solve, we propose a variable pulse sub-technology that is suitable for numerous Linear velocities during of overwriting varies systematically. With a single solid plate of the present We have successfully passed the tolerance limit of the appropriate invention Linear speeds, expanded. Especially in the event that the Linear speed is reduced, the invention provides a rapid heat dissipation that promotes amorphization, and thus allows a pulse dividing technique according to the linear speed to be specified. The invention therefore does not relate on the technique of sharing the recording pulse itself, but on the technology, the divided pulse according to the linear velocity to change.

The invention therefore provides an optical recording method for recording data, or erasing data from an optical information carrier medium, which involves the formation or deletion of optically distinguishable amorphous marks by irradiation with a focused laser beam having laser power is modulated on at least three stages according to a clock interval T, this method comprising the following steps:
Providing a linear speed V in the range between V _L and V _h on an optical recording device, the clock interval T being varied accordingly with the linear speed V;
Irradiating a focused laser beam to record a mark having a mark length nT on the optical recording medium with a mark length modulation record; and
Modulation of the laser radiation in order to have m individual pulses available, all of which have a recording power level Pw and a pulse length α _i T with an interval β _i T, which is provided between two relevant pulse lengths, in order to obtain a bias power level Pb _to provide _i , where i stands for an integer from 1 to m, and thereby a time interval of α ₁ T, β ₁ T, α ₂ T, β ₂ T, ..., α _m T and β _m T for the laser power is obtained; the improvement in which the recording method includes the step of changing at least one of the combinations of the α _i T and Pb _i according to the linear velocity V, whereby conditions of the following inequality and equations are met: n min - k ≥ 1; m = n - k; and α 1 + β 1 + ... + α m + β m = n - j; where k represents an integer of 0 ≤ k ≤ 2, and j represents a real number of 0 ≤ j ≤ 2, and nmin represents the minimum value of n.

The invention further provides a phase change type optical recording medium consisting of a substrate and a dielectric protective layer and a recording layer which is essentially composed of [(GeTe) _y (Sb ₂ Te ₃ ) _1-y ] _1-x Sb _x , where x is 0 ≤ x <0.1 and y is 0.2 <y <0.9, or [M _y (Te _1-x Sb _x ) _1-y ], where y is 0 ≤ y <0.3 and x is 0 , 5 <x <0.9, and M represents at least one element selected from the group consisting of In, Ga, Zn, Ge, Sn, Si, Pb, Co, Cr, Cu, Ag, Au, Pd, Pt, S , Se and O is selected from a dielectric protective layer and a metallic reflective layer sequentially formed on the substrate, the recording layer having a film thickness of 15 to 30 nm and the dielectric protective layer having a film thickness of 10 to 30 nm.

Furthermore, the present invention provides a recording apparatus for using phase-change type optical recording media as described above, which reads the pulse division information previously input to a disk and a recording in the recording medium to execute according to a specific modulation scheme of the marker length.

By using the recording process according to the present Invention can exceed the tolerance limit of the linear velocities Using the solid recording medium without the recording medium to be changed in particular in the direction of low linear speeds can be expanded without changing the recording medium, whereby the overwrite record of a extended range of the linear speeds is made possible. Alternatively, a common medium with a variety of drives be used, the different linear speeds during the recording process have compatibility the format of the recorded data is maintained, whereby the problem of compatibility loosened between plates that specializes in specific linear speeds are.

The invention is based on exemplary embodiments described in detail below, schematically in the drawings are shown. This shows:

1 the reflectivity of a portion of the recording layer which is partially recrystallized after being melted to form an amorphous mark in a conventional method;

2 is a schematic plan view of the portion of the recording layer of 1 ;

3 a temporal representation of the mark length-modulated pulses for recording an nT mark according to a principle of a general method, which is also used in the invention;

4 the principle of pulse division of laser radiation power for recording a mark as used in the invention;

5A and 5B Examples of timing representations of mark length modulated pulses for recording a 4T mark in a method according to an embodiment of the present invention;

6A and 6B further examples of the temporal representation of mark length modulated pulses for the recording of a 4T mark in a method according to an embodiment of the present invention, wherein Pb (<Pe) is used during part of the off-pulse (off-pulse) period βiT, wherein the divided pulse period of the header text α ₁ T = 1.5 T is longer than the following divided pulse periods α _i T (2 ≤ i ≤ m) in 6A and an off-pulse (often-pulse) period before the partial pulse period α _i T of the header text in 6A exists;

7 another example of a temporal representation of a mark length modulated pulse for the recording of a 7T mark in a method according to an embodiment of the present invention, wherein n - j <m;

8th a multilayer structure of a recording medium according to an embodiment of the present invention;

9A another example of a temporal representation of mark length modulated pulses for the recording of a sequence of successive 3T, 7T and 11T marks which contain 9T spaces according to a conventional method;

10A an oscillograph showing the signal reproduced in Example 1 while 1B another oscillograph from the comparison sample 1 reproduced signal shows;

11A and 11B the dependence of mark length or jitter on the recording laser power in Example 2 of the invention;

12A and 12B the dependence of mark length or jitter on the recording laser power in Example 3 of the invention;

13A and 13B the dependence of the mark length or jitter on the recording laser power in Example 4 of the invention;

14A and 14B another dependency of mark length or jitter on the recording laser power in Example 4 of the invention;

15A . 15B and 15C Oscillographs of the signals reproduced in Example 6 of the invention;

16 a timing chart of divided pulses for recording a marker in Example 7 of the invention;

17 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 8;

18 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 9;

19 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 10;

20 the dependence of the C / N ratio and the erasability on the repetition of the over spelling in Example 11;

21 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 12;

22 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 13;

23 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 14;

24 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Example 15;

25 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in Examples 17 and 18;

26 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in comparative samples 4 ;

27 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in comparative samples 5 ; and

28 the dependence of the C / N ratio and the erasability on the repetition of the overwriting in comparative samples 6 ,

A recording process that a used essentially constant linear velocity the popular CLV (constant linear velocity), the ZCLV (zoned CLV), where the linear velocity is constant for each zone remains or similar Procedure (see "Optical Disc Technology "at Supervised by Morio Onouye and published by Radio Engineering Co.). With the ZCLV technology, the linear velocity is within a Zone slightly changed, while it is kept essentially constant overall. It currently belongs to the State of the art to provide a variable linear speed for CD's within a single multiple range (1.2 m / s to 1.4 m / s) remains.

For a given linear velocity V _h , the length of a bit into which the bit is written is determined by the marker length nT _h . If it is desired to write a mark of the same length at a lower linear velocity V (V <V _h ), a mark of the same length should be achieved using a reference clock interval T which results from T = (V _h / V) × T _h . Adjusting the clock interval "T" in accordance with the linear velocity mentioned is generally known practice. In practice, however, a desired mark length cannot always be achieved, which is caused by an increase in the mark length by thermal diffusion or a reduction in the mark length by recrystallization. Such an effect usually occurs when the minimum linear velocity V _L remains in a lower range below about 4 to 6 m / s.

Accordingly, there is a need to regulate the temperature distribution in the recording layer by dividing the recording pulses into individual phases in order to obtain a narrow width of individual pulses. A recording method that uses such mark length modulation is shown in 3 shown. Techniques using such mark length modulation are 1-7 modulation, EFM modulation or the like. When recording such marking lengths, the positions of the leading edge and the falling edge of a recorded marking are important because they correspond to the recorded data. The edges are detected with reference to a window of every clock interval T.

In the present invention, at least one of the parameters of idle power level Pb and a combination of the parameters α _i 's that determine the divided pulse technique in the invention is changed according to the linear velocity on the disk, the combination of the α _i ' s from a pulse division is determined, which has m divided individual pulses with a recording power Pw and pulse duration α _i T (1 i i m m) with the intervals β _i T between each of the two individual pulses, where m = n - k, n min - k ≥ 1, and n - j = (α 1 + β 1 +. , , + α m + β m ) 0 ≤ j ≤ 2 hold, and n is an integer, and nmin is the smallest possible value for n. This variable pulse division technique means that a wide range of linear speeds can be applied to a single solid medium.

In particular, in accordance with the invention, when the linear velocity is reduced and it reduces the cooling rate during the reconsolidation process, the pulse width α _i T while the Pw is switched on is reduced, while the time interval β _i T during which the Pw is switched off is increased. Alternatively, the laser power Pb _{i is} reduced since the linear velocity is reduced, where Pb _{i is} the quiescent power level that is applied during the time interval β _i T during which the recording power Pw is switched off. In this way, the cooling rate is increased by suppressing the accumulation of heat in a single mark to prevent recrystallization. As a further alternative, in order to suppress the effect that an area formed by one of the divided pulses used to record a single mark is reheated by a subsequent divided pulse, the power of the radiation that is used is controlled to irradiate the recording medium during an interval between successive divided pulses so as to control the cooling rate of an area that has melted to form an amorphous mark.

To put this more generally, linear speeds V ₁ and V ₂ are first defined which are to be used in a range (V _L , V _h ) to make a recording in a phase change type optical recording medium. V ₁ and V ₂ therefore satisfy the relationship: V _L <V ₁ <V ₂ <V _h .

The parameters α _iL , α _i1 , α _i2 and α _ih represent the widths of the individual pulses, which correspond to the respective speeds V _L , V ₁ , V ₂ and V _h . In the present invention, therefore, the pulse division is controlled such that the following relationship holds: α iL ≤ α i1 ≤ α i2 ≤ α ih (1)

This applies to all "i", which satisfy the relationship 1 ≤ i ≤ m.

Alternatively, a parameter Θ _{i is} defined as the ratio of the idle power Pb _i during the interval β _i T to the extinguishing power Pe (namely, Θ _i = Pb _i / Pe). Θ _i is checked according to the invention in such a way that the following equation applies: Θ iL ≤ Θ i1 ≤ Θ i2 ≤ Θ ih (2)

In both cases, additional conditions are described by the following inequalities: α iL <α ih (3) or Θ iL ≤ Θ ih (4)

The two equations (3) and (4) apply if at least one of the "i's" is at V _L.

The magnitude of the recording power Pw and the erasing power Pe naturally vary depending on the individual linear speed. In particular, the power Pe is chosen to be at a power level capable of erasing an amorphous mark when irradiated only once as a DC power. To be more precise, the power level Pe must be chosen such that when a mark is recorded with a single frequency of either f _max = 1 / (2n _max T) or F _min = 1 / (2n _min T) , with the erase power Pe being irradiated as a direct current power, the attenuation of the carrier stage of the erased signal must generally be equal to or greater than 20 dB, where nmin and n _{max are} respectively the smallest possible and largest possible values for n.

Alternatively, the selected erase power level Pe should be selected such that when a mark recorded with a single frequency of f _max = 1 / (2n _max T) with a duty cycle of 50%, with a single signal f _min - 1 / (2n _min T) is overwritten with a duty cycle of 50% (although the recording pulse does not have to be divided, the modulation should take place between two levels of Pw and Pe), there is a difference between the carrier level of f _min and the carrier level of the deleted f _max , which is generally equal to or greater than 20 dB. It should be noted that the power level Pw is selected so that the carrier to noise ratio (C / N ratio) of signals recorded at f _max and f _min is generally 45 dB or greater. It is well recognized that the power levels Pw and Pe, like the clock interval T, are modified according to the linear velocity used during the recording process. In the present invention, however, a change in the pulse division technique is presented for the first time in accordance with a linear velocity and under a given rule. The parameters that describe a variable pulse division technique can be changed according to the linear speed, or can be changed step by step for different ranges of uniform linear speeds. The latter case is useful when the present invention is applied to the ZCAV (Zoned Constant Velocity) format.

In the optical recording method, when the idle power level Pw _i used during the time interval β _i T when the recording power is turned off is selected to take an arbitrary value which is smaller than the power level Pe which is for erasure is required if the admission operation is between three stages (see 4 ) takes place and if the magnitude of the power stage Pw can change between different values during the time interval β _i T, this enables a more precise control of the thermal distribution and thus allows the amorphous marking to be formed in one shape while jitter in a recorded signal is improved. In addition, since this process is closer to deterrence, it is possible to reduce the size of the recrystallized area, thereby increasing the sensitivity of the image.

However, it should be mentioned that Pb _i should be avoided from reaching 0 since no follow signal is available, thus preventing a follow track. When the idle power Pb _i exceeds the erase power level Pe, the recording layer tends to melt, thereby preventing erasure. Accordingly, the quiescent power level Pb _i is required to be greater than 0 and less than or equal to the extinguishing power level Pe. For a high linear velocity such as V equal to 10 m / s or greater, a medium is desirable which permits an overwrite process under a constant level of Pb _i = Pe (1 ≤ i ≤ m), since the clock interval is shortened at a high linear velocity, which requires a quick response to the shadow of the Pb _i level.

However, the clock frequency required for use at lower linear speeds is longer, which alleviates the need for a pulse control circuit response, and therefore it is sometimes advantageous to use a combination of several Pb stages as opposed to a fixed stage. to deform the amorphous mark, although the arrangement of the stream is more complex. As an example of a 4T mark shows 5A that during the β _i T interval the original stage Pw is chosen such that 0 <Pb _i <Pe, followed by the change from Pb _i to Pb _i = Pe. In 5B is preceded by the choice of Pb _i = Pe, followed by a time interval in which Pb _i <Pe.

In the case where the power Pb _{i takes} a plurality of values Pb _ij during the time interval β _i T, where β _i = Σ _j β _ij and Pb _{ij represent} a quiescent power level that is assumed during a segment β _ij T that divided by the time interval β _ij T; in this case the Θ _i mentioned above is replaced by the following Θ _i : Θ i = Σ j (Pb ij β ij T) / (Pe × β i T), so that equations (2) and (4) as mentioned above are satisfied.

When performing an optical recording process as described above, it will be noted that a front portion of a mark is usually less exposed to a temperature rise because an immediately following laser power assumes an erase power level. This can be set up by using a header sub-pulse that has a pulse width that is larger than the following sub-pulses (see 6A ).

It is not always necessary that the rising edge of each divided pulse be synchronized with the rising edge of the intended nT recorded signal. Such synchronization is desirable from the standpoint to simplify a pulse control circuit. However, if a synchronized arrangement is chosen, it should be noted that only the offset of the rising edge of the header pulse or the end pulse of a single marker length (mostly at T) is effective in order to correct for thermal interference between discrete markers. In order to additionally suppress thermal interference with a preceding marking, an off-pulse interval is directly in front of the header sub-pulse, which is used with a subsequent marking (see 6B ), or with a distance of at most 2T, although this entails a complex circuit arrangement.

It is desirable that the power input level Pw be constant at a given linear velocity regardless of the label length nT, and also constant for each divided pulse within a single label to simplify the pulse control circuit. However, in order to achieve a gradual change between the recording power of the header text pulse and the subsequent pulse in a single marker, it was found that, under certain circumstances, it is effective, in particular, to select a lower recording power for the subsequent pulse. Sometimes it happens that a longer mark than is desired is recorded when a pulse length nT is used to record an nT mark length. The use of n satisfying the following equation: (α 1 + β 1 + ... + α m + β m ) = n can result in an extended heating interval. In such a case, a real number j is chosen, which is defined by: (α 1 + β 1 + ... + α m + β m ) = n - j (0 <j ≤ 2), and the number of divided pulses m = n - k can be changed accordingly. 7 shows an example in which β _i (1 ≤ i ≤ m - 1) remains constant while only β _{m is} changed. In this case, the value (n - j) can be changed by adjusting β _m to form a desired mark length nT.

As described above, there are at least three parameters that are used to change the divided pulse technique in accordance with the linear velocity. In view of the desired simplification of the pulse control circuit, it is desirable that the number of divided pulses is m = n - k, the pulse length (n - j) as well as (α _i + β _i ) are chosen to be constant regardless of the linear speed , while an arrangement is provided that equations (1) to (4) are satisfied at the linear velocities V ₁ and V _{2 which} satisfy the relationship V _L <V ₁ <V ₂ <V _h .

A selection should be made even more advantageously, so that the equations at a maximum linear velocity V _h used α 1h = 0.5, 1.0 or 1.5 and β 1h = α 1h = 0.5 (2 ≤ i ≤ m) apply and that α i + β i = 1.0 (2 ≤ i ≤ m) applies to every linear velocity. The rising edge of each individual pulse is then synchronized with a reference clock, with the exception of a given delay, which simplifies the design of the pulse control circuit. Ultimately, in an optical recording method as described above, for a linear speed satisfying the relationship V _L <V <V _h , the pulse width can be reduced to prevent recrystallization because the linear speed is reduced. However, if the pulse width is narrowed too much, the resulting sensitivity is impaired, which is undesirable. As a consequence, there is a lower limit on the temporal resolving power, so that 0.05 <α _i .

While the invention is directed to modulating the recording of a mark length is there is no restriction in the used marking edge verification. A simple cut through a DC level or two differentiations, as in Japan. J. Appln. Phys. Vol. 31 (1992), pp. 584 to 589 is can for the detection of the peaks can be used. It is also a certain marking edge detection of the rising and falling flanks of the markings are effective, as in the same literature is disclosed.

An optical recording medium to which the invention is applicable is the so-called phase change type recording medium in which a crystallized phase represents an unrecorded state and an amorphous mark is formed to represent a recorded state. An example of such a medium is in 8th shown, but the invention is not limited to such a multilayer structure. In 8th is a substrate 1 from a soil protection layer 2 coated on which a recording layer 3 of the phase change type is formed. A top protective layer 4 protects the recording layer 3 and is in turn covered by a reflective layer 5 covered, which is formed either from metal or from a semiconductor. A final protective layer 6 is made of synthetic resin which is hardened by heat or ultraviolet radiation. The thin films 2 to 5 are usually formed using a sputtering process.

In general, a focused beam is used for the purpose of recording or retrieval, and irradiates the recording layer 3 through the transparent substrate 1 , The recording layer 3 is locally heated to be melted by the irradiation with the recording power Pw. When the exposure from the focused beam is turned off, the recording layer is rapidly cooled to harden, which is believed to assume an amorphous phase. An amorphous label is heated to a temperature below the melting point but above the crystallization temperature from the irradiation with the erasing power Pe, and so recrystallization occurs, whereby the data are erased. Materials for a recording layer that can be overwritten according to this principle include a GeSbTe alloy as mentioned above (especially a pseudo-binary alloy of GeTe and Sb ₂ Te ₃ ), and Sb ₇₀ Te ₃₀ , a compound whose composition is eutectic Compound approximates and to which at least one element of Ag, Cu, Au, Ge, Pd, Pt etc. is added. For these alloys the crystallization rate, the ability to form an amorphous phase or the crystallization temperature preferably controlled by the amount of Sb, and the alloy is optimized in accordance with the linear velocity used. The medium should have a sufficient erasability of over 20 dB at a maximum linear speed used.

For example, if the amount of the excess of Sb to the pseudo-binary alloy consisting of GeTe-Sb ₂ Te ₃ is increased, the ability to form an amorphous phase is increased while the crystallization rate is reduced; and therefore the resulting alloy is suitable for use at low linear speeds. It is also possible to control the optimal linear velocity by controlling the thickness of the recording layer 3 and the protective layers 2 and 4 and also the thermal conductivity of the protective layers 2 and 4 and the reflective layer 5 which in turn controls the supercooling rate of a molten region formed during the recording process. For example, if the thermal conductivity of the protective layers is increased or a thickness of the order of 15 to 30 nm is chosen for the recording layer and the top protective layer in order to promote the thermal diffusion from the recording layer into the reflection layer, the formation of an amorphous phase is promoted thereby , and therefore the resulting medium is suitable for use at low linear speeds.

A special application of the invention lies in writable compact discs (CD-E), where V _L = 1.2 to 1.4 m / s. It is desirable for a CD to perform single, double, quadruple, or six times the speed of V _L recording and reading operations. However, such CD-E's have not yet been released. It is known that the possibility of recording over a wide range of linear speeds from single to six times the speed is desirable for a CD that can be written once (CD-R, CD-Recordable) and is already available on the market.

In this case it is effective to use EFM modulations where m = n, n - 1 or n - 2 is a modulation scheme of the marker length to allow the speed V to be one of the finite values V _{L available} , To accept 2V _L , 4V _L and 6V _L , and to change the recording pulse sub-technology,
so that at a linear velocity V that is equal to or greater than 2V _L , the following applies: α 1h = 1.5 or 1.0 and β 1h = α ih = 0.5 (2 ≤ i ≤ m); and that at any linear velocity: α i + β i-1 = 1.0 (2 ≤ i ≤ m); and that at a linear velocity that is equal to 2V _L , the following applies:
Pb _i = Pr ± 0.5 mW (constant, independent of i)
(1 ≤ i ≤ m, and Pr stands for reproductive performance);
and that at a linear velocity equal to V _L : 0.05 <α i <0.5 (2 ≤ i ≤ m) and α iL ≤ α ih ; and that at a linear velocity that is equal to V _h = 4V _L or 6V _L , the following applies: pb i = Pe (1 ≤ i ≤ m).

In any case, β _m ≠ 0.5 can be used, which allows the possibility that β takes the value 0. In other words, a pulse duration (often pulse) β _m T on the falling edge of each nT mark can have a time interval which is different from the pulse duration in the marking (β _i T, for 1 ≤ i ≤ m) , In this manner, a single medium may be suitable for a variety of drives that perform a recording operation at different linear speeds.

In an example of the eight-to-fourteen modulation, in which a maximum linear velocity V _h ranges from 2 to 6 times the minimum linear velocity V _L , where V _L varies in the range from 1.2 V V _L m 1.4 m / s, the following pulse division technology can be used:
m = n, n - 1, or n - 2;
a linear velocity V, which takes one of the finite values V _L , 2V _L , 4V _L or 6V _L , and for each linear velocity V applies α _i + β _i = 1.0
for every i out of 2 ≤ i ≤ m;
and for every linear velocity V, Pbi = Pr ± 0.5 mW
usable for every i out of 1 ≤ i ≤ m, where Pr represents a reproductive power level; and
α _i is monotonically reduced for every i from 1 ≤ i ≤ m if the linear velocity is reduced. In the above case, β _m should not be zero.

In the above case, the clock interval T for a linear velocity V is preferably selected such that T = T _h (V _h / V), where T _{h represents} a clock interval selected for a maximum possible linear velocity V _h .

A more specific example of a CD-E recording medium suitable for use in optical recording methods consists of a dielectric protective layer of a recording layer made of [(GeTe) _y (Sb ₂ Te ₃ ) _1-y ] _1-x Sb _x , where 0 ≤ x <0.1 and 0.2 <y <0.9, a dielectric protective top layer and a reflection layer made of metal, which are arranged in succession on the substrate. The recording layer has a film thickness of 15 to 30 nm and the dielectric protective top layer has a film thickness of 10 to 30 nm.

Another example consists at least of a dielectric basic protective layer, a recording layer, which consists of (M _y Te _1-x Sb _x ) _1-y (0 ≤ y <0.3, 0.5 <x <0.9, M is at least one element made of In, Ga , Zn, Ge, Sn, Si, Co, Cr, Cu, Ag, Au, Pd, Pt, S, Se and 0), a dielectric protective layer and a metallic reflection layer, which are arranged in succession on the substrate. The recording layer has a film thickness of 15 to 30 nm and the dielectric protective top layer has a film thickness of 10 to 30 nm.

Japanese Patent Laid-Open Nos. 212,735 / 1992 and No. 62,193 / 1993 are earlier applications relating to the present application relating to a phase change type recording medium comprising a GeSbT recording layer which is rewritable at a linear speed of a CD and disclose Recording method in which a long pulse recording pulse is divided. However, these earlier applications, for example, do not have illustrations of the split pulse technique at double rate 2V _L and do not comment on the linear velocity dependency problem that occurs when recording at double, quadruple or six times the speed. Accordingly, in these earlier applications nothing is said about changing a pulse division technique for recording under a given rule to address the dependency on the linear velocity.

The Japanese patent application No. 37, 251/1995 and a publication "International Symposium on Optical Memory, 1995, Kanazawa, Japan, No. P-33 "show an example of a CD-E medium containing an AgInSbTe recording layer and use an associated recording method. However, there is again no disclosure of the problem of the dependence on the linear velocity and no suggestion to deal with it.

Another effective use The present invention is dependency to eliminate from the linear velocity that from the difference in the linear velocity between the inner and outer periphery a phase change type disk that is caused rotates at constant angular velocity (CAV). In particular for a medium with an enlarged radius in which The relationship the radii of the outer and the inner peripheries of a recording region equal to or larger than 2, it becomes a linear velocity ratio equal to or greater than 2 between the inner and outer periphery give.

The composition of a recording layer or a multi-layer structure between the inner and outer periphery to change, about dependence Eliminating from the linear velocity requires a special one Refinement during the manufacturing process that is difficult to set up. But when the variable pulse division technique according to the present invention is applied to the type of division in accordance with the linear speeds around the inner and outer periphery to change, a medium can be used which is uniform in the radial direction, for information about the entire plate surface to record what recording means without difficulty. The Change of pulse division during recording in accordance with the radial one Position can be in a locked relationship with a switching of the Reference clock interval at a relevant radial position for a Medium of the normal ZCAV (zoned CAV) type.

For a more suitable and effective use of the optical recording method according to the invention, a storage disk can initially be supplied with information which is related, for example, to the division of pulses in thermal baths of etching information. Preferably, a description of the pulse division information can be carried out such that a part of the above-mentioned parameters (Pw, Pe, Pb, m, j, k, α _i , β _i .), Which is to be kept variable, in accordance with the linear velocity can be changed, which is used or changed in accordance with the zone in ZCAV. Such a description can be made that instead of describing a pulse division technique for a linear velocity V satisfying the relationship V _L ≤ V V V _h , there is a single pulse division method for V _L and V _h alone, while a pulse division method for an intermediate one Linear velocity V by an In terpolation between V _L and V _h can be obtained. For example, α _i and Θ _i between α _iL and α _ih and between Θ _iL and Θ _iL can be reduced in proportion to the linear velocity.

For a CD-E medium mentioned above, the information relating to the pulse division technique can be introduced beforehand into the substrate by frequency modulation of a wobbled notch, ie a so-called "A TiP signal (Absolute Time in Pre-Groove)", which in leading in the area. In this process, a disc drive reads information related to a pulse division method previously written or recorded on the disc, and automatically performs a special pulse division technique and recording at the linear speed in question. In this way compatibility is achieved between a variety of phase change type media which have different dependencies on linear speeds but which use a common recording format for stored information. In this way it is achieved that a special phase change type medium, even if data is stored thereon using a disk drive using a particularly special pulse division technique, does not suffer from the problem that a normal signal due to recrystallization is not correct is recorded. With the variable pulse division technique depending on the linear speed according to the present invention, it is possible to ensure that an ideal temperature distribution is produced on the disc when recording under different conditions of the linear speed, for example in a range below V _h ≥ 2V _L , In this way, the possibility of recrystallization at low linear speed or erroneous erasure at high linear speed can be suppressed, whereby a single disk can be used over a wide range of linear speeds that could not be set up for a conventional phase change type medium.

EXAMPLES

The following are advantageous versions of the present invention. The present invention is but not to the specific examples described below limited.

In the examples and comparative samples, described below, a record (single beam overwrite) made by a drive tester manufactured by Pulsetech Co, which has a 680 nm laser diode and NA = 0.60 optical lenses, was used. The reading power Pr is 1.0 mW, and is independent of the linear velocity. The clock interval T is chosen so that it is inversely proportional to the linear velocity, and is on T = 143 nsec (7 Mhz) set to record at 1.4 m / s, and is set to T = 20.0 nsec to record at 10 m / s.

Example 1 and comparative samples 1 and 2

A magnetron method is used to create a 100 nm thick (ZnS) ₈₀ (Sio ₂ ) ₂₀ [mol%] layer, a 25 nm thick germanium .Ge ₂₂ . ₂ Sb _{22. 2} Te _56.6 [atom%] .- layer, a 20 nm thick (ZnS) ₈₀ (Sio ₂ ) ₂₀ [mol%] layer and a 100 nm thick aluminum alloy layer successively on a polycarbonate substrate. In addition, 4 μm thick synthetic resin cured with ultraviolet radiation is provided to form a storage disk. At the beginning, an evaluation is carried out using repeated patterns, all of which use a 3T / 9T / 7T / 9T / 11T / 9T pattern in which the underlined intervals represent markings and the non-underlined correspond to the space between the markings. After being overwritten several times under conditions that permit an overwrite operation, a reproduced signal is cut off from the disk in the center from peak to peak of the 11T / 9T portion to determine a mark length. A time interval analyzer (TIA, model E1725A manufactured by Hewlett Packard Co.) is used for this detection. (This method refers to the "primary peak detecting method" as described in Jpn. J. Appn. Phys., Vol 31 (1992), pages 584 to 589.)

An overwrite operation was carried out according to Example 1 by applying a pulse pattern in which the divided pulse division technique with m = n-1, j = 0 (since Pe = Pb, the same if j = 0.2), α ₁ = 1.5 , β ₁ = 0.5, α _i = β _i = 0.5 (i ≥ 2), is used, which is known for itself and for example in Proc. Int. Symp. On Optical Memory, 1991, pages 291-296. The above pulse pattern is in 9 shown. It turns out that when Pw = 12.0 mW and Pe = 4.0 mW a satisfactorily reproduced waveform was obtained, which is shown in 10A is shown. In a similar manner, another overwrite operation was carried out up to a range of 20 m / s while appropriate values of Pw and Pe were selected in accordance with the linear velocity and the clock interval was set. Satisfactory recorded waveforms were obtained in all cases.

Mark lengths of 3T, 7T and 11T with satisfactorily low jitter in the mark length of less than 10% of T were achieved. In Comparative Example 1, a similar pulse pattern was used while the clock interval alone was being set, and an overwrite operation was attempted at 1.4 m / s. However, any combination of Pw and Pe was flawed when recording 7T and 11T mark lengths. 10B shows an example of the resulting waveform, which is a relatively good sample compared to the rest. As the mark length was increased, the front half of the mark recrystallized from the recording of the rear half of the mark under the influence of the after-heat, resulting in erroneous recording of an amorphous mark. In the accompanying example 2 The composition of the recording layer, which was optimized in Example 1 for use at 1.4 m / sec, was replaced by an Sb-rich composition of Ge ₂₃ Sb ₂₈ Te ₄₉ . While an amorphous mark was satisfactorily formed, suppressed recrystallization resulted in an insufficient erase ratio of the amorphous mark at 10 m / s, and therefore the sample is not suitable for use of an overwrite operation.

An optimization of the shared pulse technology in accordance the invention is attempted by choosing a very difficult case which is a recording medium for use at high linear speeds from 10 to 20 m / s is used, excellent Make recording at 1.4 m / s, which is detailed below will describe.

Example 2

Using a disk optimized for a linear velocity of 10 to 20 m / s in Example 1, an overwrite operation of repeated patterns of marker lengths as mentioned above was used at a linear velocity of 1.4 m / s. The parameters were chosen such that m = n, j = 0.2, Pe = 4 mW, Pb = Pb; = 0.2 mW was. The width of n-divided pulses for an nT pulse was namely Tp = α _i T fixed, while Pw varies (see 9B ). At Tp ≥ 50 ns, the amorphization was essentially unsuccessful and even the detection of the marking edges with TIA was not possible. 11A and 11B show the dependence of the label length of each nT label (3T, 7T and 11T) or jitter for the label length (3T) on Pw when a shorter Tp was applied. If Tp was less than 30 ns (or less than 0.21T), an appropriate mark length at Pw = 14 to 17 mW was obtained, which corresponds to a record mark nT with a satisfactory jitter less than 0.1T. At Tp = 12 nsec (or 0.084 T), however, a recording power Pw greater than 16 mW was required, and insufficient sensitivity was found by the test device used. In this example, all β _i 's were chosen such that they are identical to each other except for β _m , which was set to j = 0.2.

Example 3

The power Pb and Pw was varied under the conditions that Tp = 20 ns (α _i = 0.14), m = n, j = 0.2 and Pe = 4 mW. 12A and 12 B show similar to 11A and 11B the dependence of the marking length and jitter on Pw and Pb. When Pb was below about 1 mW, satisfactory jitter was obtained at Pw = 14 to 17 mW, which was substantially less than 0.1 T. It turned out that the choice of 0 <Pb <Pr had no influence on the servo track setting (tracking servo). There was no exit from the servo track setting when Pb = 0.2 mW was selected and was therefore less than Pr for the time interval used.

It can be seen from Examples 2 and 3 that that if a use over an area is intended ranging from 1.4 m / s to 20 m / s stretches, it is particularly necessary is that α in combination with a reduced value of Pb (or Θ = Pb / Pe) at low speeds is reduced.

Example 4

Under the conditions that Tp = 20 nsec (α _i = 0.14) Pb = 0.2 mW and Pe = 4 mW, is similar to that in the 11A and 11B in the 13A and 13B for m = n, and in the 14A and 14B for m = n - 1 the dependence of the marking length and jitter on Pw and j "is shown. It is found that the marking length was strongly dependent on n - j = Σ (α _i + β _i ). It can be seen that an optimal point in a range of j from 0.2 to 0.7 with any choice of m that is equal to n or (n - 1). If the choice is made m = n - 1, it is only necessary that in a range of 1.4 m / s to 20 m / s only (n - j) and α _i can be varied in accordance with the linear velocity while m remains constant, which is advantageous from the point of view of the pulse control circuit over a change of m in accordance with the linear velocity.

Repeated patterns with label lengths of n = 3, 7 and 11 were used. This means that an overwrite operation over an extended range of linear speeds is possible for a pattern containing any mark length corresponding to n from 3 to 11, as in an EFM modulation scheme used with a compact disc (CD). A shortest marking length of 3T at T = 143 ns corresponds to 0.6 μm, which is a higher density than that of a currently available CD. However, if the shortest mark is allowed to extend to 0.8 to 0.9 µm as in the currently available CD, some optimization of the pulse width or the like will allow an overwrite operation over an extended range of linear speeds in a similar manner. The same applies if the shortest mark length is further reduced, as in a mark length modulation recording used in a so-called digital video disc. The problem of the dependency on the linear speed is considerably alleviated for reduced marking lengths, since recrystallization occurs less frequently. Even in such an area of a high density storage region, the present variable pulse division technique is useful.

Example 5

As an overwrite example of the above mentioned repeated pattern on the medium of the phase change type at a linear speed in the middle between 10 m / s and 1.4 m / s, a test recording was made at 2.8 m / s. It it turned out that at a divided pulse pattern with Tp = 15 to 20 ns, j = 0.2, m = n, Pe = 4 mW and Pb = 0.2 mW, with Pw greater than or equal to approximately 15 mW a usable marking length achieved with a satisfactory jitter of less than 0.1 T. has been. Therefore, for the medium of the present example has at least a similar pattern for the Single to double speed of the CD linear speed applicable. On the other hand, at 5.6 m / s, which was the order of magnitude corresponds to 4 times the CD linear speed on the condition that m = n - 1, j = 0.0, Pb = Pe, and TP = 20 ns, with Pw = 16 mW and Pe 4 mW a cheaper one Achieved jitter response that is less than 0.1T.

Example 6

The present invention is applicable when different pulse length modulation schemes are used at high and low linear speeds. To demonstrate this, an overwrite operation was attempted using (1, 7) RLL (run-length-limited code) coding (consisting of marker lengths of n = 2 to 8) (this coding is generally found in the peripheral unit of a computer and used with an optical recording medium) at a linear speed of 10 to 20 m / s with EFM modulation at 1.4 m / s. The use of a fixed clock interval T facilitates a mark edge detector circuit, although strict coincidence is not required. Since the physically shortest marking length represents a lower limit for the linear speeds, which depends on the physical properties of the special medium, it should preferably be kept constant. At this end, for example, it is effective to keep the shortest mark 2T in (1, 7) modulation and the 3T mark in EFM modulation mentioned above by changing the clock interval to 0.6 μm. 15A . 15B and 15C show eye patterns of the linear speeds of 1.4 m / s (EFM modulation), 5.6 m / s (EFM modulation) and 10 m / s (1-7 modulation). Excellent waveforms were obtained at linear speeds in question, and the jitter in the marker lengths was less than 0.1 T even with the shortest marker.

Example 7

A recording medium was produced which had a multilayer structure similar to the structure of Example 1, except for the recording layer which contains a thin alloy film having the composition of Ag _4.2 In _5.2 Sb _62.6 Te _28.0 . a semiconductor laser diode with a wavelength of 780 nm and Na = 0.55 was used in the recording for the recording medium. A recording was made at a linear speed of 4.8 m / s, which is twice the CD speed, and using an EFM modulation scheme, with a pulse division technique (see 16 ) and with Pw = 12 mW, Pe = 6 mW and Pb = Pr = 0.8 mW to create a good eye pattern. The jitter of each mark was less than 10% of the clock interval T. If a recording was made on the same medium with a similar split pulse technique, except for doubling the clock interval at a single speed of the CD linear speed, considerable recrystallization was found, which is why not a good one Pattern could be achieved. However, if the parameters were chosen such that α _i = 0.33 (2 ≤ i ≤ m), while α ₁ remained unchanged at 1.0, where Pw = 11 mW, Pe = 5 mW and Pb = Pr = 0.8 mW, an excellent eye pattern was achieved.

The following is the optical recording medium the phase change type according to the present Invention for use with the recording method described above described the invention in detail. The medium essentially exists from a substrate, from a recording layer and from one Protective layer. The substrate is made of a transparent material such as polycarbonate, acrylic resin or glass.

For a phase change type optical recording layer of the present invention, a known phase change type optical recording layer can be used. For example, compounds such as GeSbTe, InSbTe, AgSbTe, or AgInSbTe can be used, which are known as materials that allow an overwrite operation. In particular, a thin film consisting essentially of an [(Sb ₂ Te ₃ ) _1-X (GeTe) _x ] _1-y Sb _y alloy, where 0.2 <x <0.9 and 0 ≤ y <0.1, or one M _w (Sb ₂ Te _1-z ) _1-w alloy, where 0 ≤ w <0.3 and 0.5 <z <0.9, and M represents at least one element selected from the group consisting of In, Ga , Zn, Ge, Sn, Si, Cu, Au, Ag, Pd, Pt, Pb, Cr, Co, O, S, and Se, has a stable state in either crystalline or amorphous form, and allows rapid phase change between both states.

These connections have the additional Advantage that they less tend to segregate after repeated overwrites are and are therefore very practical materials. The recording layer is generally obtained by using an alloy target in a inert gas is sputtered, especially in Ar gas. Such a sprayed-on film contains usually Ar that during the spraying process is included in the film. After repetitions of overwrite operations beats that Gas sometimes lowers and forms a bubble of the order of magnitude of 0.1 μm. It is therefore desirable that this Gas contained in the recording layer is kept below 1.5 atomic% becomes. By placing a relatively high pressure on the Ar gas during the Sputtering process exercised the amount of the argon recoil can be reduced, thereby the amount of argon in the film is reduced. The use of a higher However, argon gas pressure reduces the energy of the argon that is in the film is embedded and the energy of the atoms by that Fly target, which prevents a tightly packed film, and therefore represents a compromise.

A recording film with less Density is degraded after repeated recording operations, by sinking. To prevent these sinks from occurring, is it desirable that the density the recording layer larger or is equal to 86% of a theoretical bulk density. The theoretical bulk density is determined with the atomic weight and the ratio of the atomic numbers of the recording layer forming elements, as mentioned for the protective layer as above the case is. It is particularly desirable that the Ar Share equal to or greater than Is 0.1 atomic% and less than 1.5 atomic%, and the film density is the same or greater than 86% of the theoretical density.

A recording layer made in is used in the medium of the present invention is a layer of phase change type, and preferably has a thickness in the range from 10 nm to 100 nm. A small thickness of the recording layer, which is less than 10 nm tends to be satisfactory optical contrast and a satisfactory recrystallization rate to prevent, which is a difficulty, an amorphous label to delete within an acceptable time. If on the other Side exceeded a thickness of 100 nm becomes difficult to achieve optical contrast, and it's probably breaks to cause both of which are undesirable.

At least there is a protective layer provided on the side of the recording layer which is the substrate opposite, but it is advantageous to have the recording layer on both of them opposite sides to be provided with a protective layer so that the recording layer is enclosed by protective layers. Of course you can a dielectric layer with a different composition between the substrate and the recording layer or on another Place be arranged.

A protective layer is composed of the following mixture: at least one material selected from the group consisting of (1a) sulfides or selenides of an element of the IIa group, (1b) sulfides or selenides or a rare earth metal, or (1c) at least one of the compounds TaS ₂ , TaSe ₂ , ZrS ₂ and WS ₂ ; and at least one compound selected from the group (2) or refracting compounds other than sulfides or selenides, which have a melting temperature or decomposition temperature that is equal to or greater than 1000 ° C.

Examples of the sulfides or selenides of the IIa group elements mentioned in paragraph (1a) include MgS, CaS, SrS, MgSe or the like. Examples of the sulfides or selenides or the rare earth metals mentioned in paragraph (1b) include Sc ₂ S ₃ , Y ₂ S ₃ , La ₂ S ₃ , CeS ₃ , PrS ₃ , NdS ₃ , Pm ₂ S ₃ Sm ₂ S ₃ , Eu ₂ S ₃ , Gd ₂ S ₃ , Tb ₂ S ₃ , Dy ₂ S ₃ , Ho ₂ S ₃ , Er ₂ S ₃ , Tm ₂ S ₃ , Yb ₂ S ₃ , Lu ₂ S ₃ or at least one from a group consisting of these compounds in which S is completely or partially replaced by Se. Among others, La ₂ S ₃ , Ce ₂ S ₃ , Pr ₂ S ₃ , Nd ₂ S ₃ , Sm ₂ S ₃ , Eu ₂ S ₃ , Gd ₂ S ₃ , Tb ₂ S ₃ , Dy ₂ S _{3 are} preferred. La ₂ S ₃ and Ce ₂ S ₃ are particularly advantageous in reducing costs because they are orders of magnitude cheaper than the sulfides and selenides. As mentioned, the compounds listed in paragraph (1c) include TaS ₂ , TaSe ₂ , ZrS ₂ , and WS ₂ . Among them, TaS ₂ and TaSe _{2 are} particularly advantageous because they have excellent thermal stability. The use of zirconium disulfide and tungsten disulfide is desirable to increase the recording sensitivity of a rewritable medium.

Sulfides or selenides in group (1) contain, as a generic term, the compounds in paragraphs (1a), (1b) and (1c) and contain an ore former (chalcogen), and thus have a high level of adhesion to ore formers or their peripheral elements, mainly in a Pha Type of change are included. In addition, the formation of a multilayer structure is facilitated by the interposition of S or Se, which have a high degree of hardness against an upward pressure, while being sensitive to shear stress in a two-dimensional plane, and relatively easily produce sliding between the layers , which effectively reduces the voltage. It is believed that the occurrence of small breaks can be suppressed by minimizing microscopic plastic deformation by including a material with such properties in the mixture. A compound in group (1) should preferably have a decomposition or melting temperature which is greater than or equal to 1000 ° C. Other sulfides or selenides such as MoS ₂ and NbS ₂ which have low decomposition temperatures below 500 ° C are not suitable for the protective layer of the present invention.

Essentially, every ceramic is excluding sulfides or selenides, which have a heat resistance from above 1000 ° C has suitable as a refractive compound of group (2). A heat resistance from above 1000 ° C means that the Melting temperature is equal to or greater than 1000 ° C, and that means that in essentially no decomposition takes place when heated to 1000 ° C. It goes without saying that the layer also opposite Laser radiation should be optically transparent. It is desirable that the layer the imaginary Part of a complex refractive index that is not greater than 0.05 for a wavelength range of bigger or is equal to 600 nm if its thickness is of the order of 50 nm. If the material itself is not perfectly transparent, it is possible transparency to achieve what is essentially by forming a mixed film for the Making the film is not a problem as long as the amount the addition is small.

Refraction compounds of group (2) are in particular oxides of Al, Si, Ge, Y, Zr, Ba, Ta, Nb, V, W, Hf, Sr, Zn or lanthanides; Nitrides of Al, Si, Ge, Ta and B; Fluorides of Mg, Ca, Nd, Tb, La and Nd; and carbides of Si and B. If a fluoride is used, it is advantageous to use an oxide in combination with it, in which case there is a tendency toward increased brittleness. From a cost standpoint and the simplicity of the manufacturing process, compounds such as silicon dioxide, yttrium oxide, barium oxide, tantalum oxide, LaF ₃ , NdF ₃ , TbF ₃ , SiC, Si ₃ N ₄ and AlN are advantageous.

In the entire protective layer should the content of a compound of paragraphs (1a) or (1b) is preferred be between 10 and 25 mol%. With an amount of more than 10 mol% can be a desired characteristic cannot be achieved because the optical absorption coefficient is greater than 95 mol% will be too high, which is not desirable is. Preferably the content ranges from 15 to 90 mole%. The content of a refractive compound from group (2), to the connection from the group under paragraph (1a) or (1b) admixed should preferably be in the range of 5 to 90 Mol%, and preferably less than 10 mol%. Outside this range can affect the achievement of a desired characteristic. Finally should for the entire protective layer the content of the compound from the group under paragraph (1c) preferably in the range of 10 to 80 mole% lie. A desired characteristic cannot be below 10 mol% be achieved while above 90 mol% the optical absorption coefficient will be too large which is not desirable is. The content is advantageously not greater than 60 mol%. In this Case it is advantageous that the Content of the refractive compound of group (2) is greater as the content of the compound of the group under paragraph (1c).

With a composite protective layer, which contains the connections which are selected from groups (1) and (2) should have a total content the compounds of groups (1) and (2) advantageously larger or be equal to 50 mol% and more advantageously it should be greater than Be 80 mole%. If the content is less than 50 mol%, the tendency will be observed that the Protective effect against the deformation of the substrate or the recording film is insufficient, and the protective layer cannot serve its purpose fulfill.

For the composite protective layer mentioned above is advantageous to provide a composite sputtering target that consists of a mixture of a variety of compounds used are going to make a movie. This is done in an even distribution to achieve.

It is advantageous that the film density of the protective layer according to the present invention is equal to or greater than 80% of the theoretical density, which is calculated from the sum of the bulk density of each individual compounding component multiplied by the molar content of the component, as follows Formula is described:
Theroetic density = Σ [(bulk density of each connecting component) X (molar content of the connecting component)];
the film density is easily determined from the volume, which in turn is determined from the area of the substrate and the film thickness, which is determined by a needle measuring device, and from a change in the weight of the substrate when the film is formed.

Due to a high density of the protective layer can once the consistency across from repeated recordings and on the other hand aging effects significantly be improved.

In carrying out the present invention, it is possible that a metal or a semiconductor element used in the sulfides or selenides selected from group (1) is identical with a metal or semiconductor element (M) used in the refraction compound, in particular in an oxide form selected from the group (2). This is the case when TaS _{2 is selected} from group (1) and Ta ₂ O _{5 is selected} from group (2). These materials can be used in a mixed target sputtering process, as mentioned above. Or in another way, either sulfides or selenides of M or M themselves can be reactively co-sputtered in a gas mixture of oxygen and an inert gas. (Reactive-ion co-sputtering)

As a further alternative you can either Sulfides or selenides from M or M itself can be used to make a to form a mixed target, which is then a sputtering process exposed to reactive gases. In this case, the resulting Target can be viewed as a mixture of compounds made up of the groups (1) and (2) selected are, but it can also be used as a substitution of oxygen the oxide that is selected from group (2) of S or Se selected is a homologous element like oxygen. It turned out out that the the latter method is more effective, the mechanical strength of the Increase film than the use of heterogeneous compounds that are widely scattered are.

It should also be mentioned that sulfides or selenides are often semiconductors are alone or in a mixture with M the conductivity increase, which enables DC sputtering. From the standpoint of simplicity of manufacture, is one DC sputtering process easy to control and produce advantageous a high atomization rate. Examples of M for may serve the above purpose include Ta, Zr, metals of rare earths, magnesium, calcium and Sr.

To increase the film density, it is useful to use a lower gas pressure during the sputtering process, and usually a vacuum pressure of 1 Pa or less is used; it is even more advantageous if between 0.3 and 0.8 Pa are used. It is desirable that the residual stress of the protective layer be kept below 5.9 × 10 ⁹ dynes / cm ² in order to prevent peeling or deformation of the substrate.

It is desirable that the protective layer of the invention has a complex refractive index that includes a Has a value of 0.05 or less in its imaginary part at the wavelength the for optical recording and reading is used the absorption efficiency of the energy of the recording radiation increase in the recording layer. So optical transparency It is advantageous to provide during the sputtering process a gas mixture of argon with oxygen and / or to form the film To use nitrogen. In particular, sulfur or selenium, contained in the sulfides and selenides have a high vapor pressure on, and therefore tend to while of the sputtering process to be partially decomposed or evaporated. If partial absence or lack of sulfur or selenium occurs in the protective layer, the optical absorption of the Protective layer reduced or the layer becomes opaque and shows thus also a chemical instability on what is not desirable is.

It is also desirable that the protective layer a knoop hardness which is equal to or greater than 300 according to JISZ 2251 is. The protective layer of the present invention thus obtained has a higher one mechanical strength, compared to the known layer compositions, which contain ZnS or ZnSe as their main component. Also points the protective layer has a high level of JIS (Japan Industrial Standard) Knoop hardness of more than 300, similar like that of the oxides, and has the function of preventing breaks by using them microscopic slide generated. It also has the protective layer a lower compressive stress compared to that of the oxides, making it unlikely is that a peel occurs.

The protective layer is usually formed in a thickness of 10 to 500 nm. If the thickness of the dielectric Protective layer is less than 10 nm, it becomes the substrate or can insufficiently protect the recording layer from deformations, and the protective layer cannot fulfill its purpose. Above a thickness of 500 nm there will be internal voltages within the dielectric Protective layer itself, as well as elasticity differences between the Protective layer and the substrate make it noticeable, increasing the probability of breaks occurring given is. From a productivity standpoint, it is not desirable that the Thickness of the film about Is 200 nm.

If there is a reason, a thick film from over 200 nm can form a section that is directly above the Recording layer is arranged, and about 5 to 10 nm of the total Film thickness constitutes a protective film according to the present invention be formed while the rest Film thickness may contain other dielectric materials. If the adhesion between them is low, peeling may occur, and therefore the combination of the two materials should be carefully selected. A combination that minimizes this problem is to choose one Materials of the same type as that of the refractive link of the group (2) contained in the composite protective film, and at the interface between the protective film and the recording layer is arranged.

The recording medium of the invention may also contain a reflective layer. For the material of the reflection layer, it is desirable to use a metal with high reflectivity and high thermal conductivity. Examples of such a metal are in particular gold, silver, aluminum and the like. However, to increase the width in the optical design, a semiconductor such as silicon or germanium can also be used. From the economic aspect and from the standpoint of corrosion resistance, an aluminum alloy is desirable in which Al from 0.5 to 5.0 atom% of Ta, Ti, Cr, Mo, Mg, Zr, V or Nb is added. The addition of Ta in particular increases the corrosion resistance.

Example 8

MgS selected from group (1) and SiO ₂ selected from the refractive compound of group (2) were mixed in powder form and in a molar ratio of 40:60 to provide a material for a dielectric layer which was then subjected to a hot printing process to form a composite sintered target.

A recording medium composed of a four-layer structure having a dielectric layer, a recording layer, another dielectric layer and a reflection layer each having a thickness of 200 nm, 30 nm, 30 nm and 100 nm was formed on a polycarbonate resin substrate. The composition of the recording layer was Ge ₂ Sb ₂ Te ₅ and an aluminum alloy was used for the reflection layer.

With an argon gas flow at a flow rate of 50 sccm, a dielectric film was formed by a sputtering method at a high frequency of 13.56 MHz and under a pressure of 0.7 Pa. The film had a density of 2.4 g / cc, which is equivalent to 98% of the theoretical bulk density. The film had a JIS Knoop hardness of 480 and an elongation stress of 1.1 × 10 ⁸ dynes / cm ² . The recording layer and the reflection layer were both formed by a DC sputtering method under Ar gas pressure of 0.7 Pa. In addition, approximately 5 μm thick synthetic resin hardened with ultraviolet light was applied.

The disk was initialized using an argon ion laser, or in other words crystallization was thus generated in the recording layer. Thereupon became the dynamic characteristic of the disk among those mentioned below Conditions evaluated.

In particular, during the Disk rotation at a linear velocity of 10 m / s an overwrite operation with a pulse radiation with a frequency of 4 MHz and a duty cycle of 50% with an input power Pw of 19.5 mW and an extinguishing power Pe of 9.5 mW repeated. After a given number of repetitions was completed, the C / N ratio and an extinction ratio were determined each time.

Out 17 it is clear that after 100,000 repetitions, the C / N ratio decreased by approximately 7 dB compared to the original C / N ratio. The erasability much after 100,000 repetitions compared to the initial erasability by about 12 dB. It should be noted that the melting temperature of SiO _{2 was} about 1,600 ° C and the compression stress was 3 × 10 ⁹ dynes / cm ² .

Example 9

A storage disc was manufactured in a similar manner to that described in Example 8, except that in this example, a material for the protective layer consisting of CaS from group (1) and SiO ₂ from group (2) in one molar Ratio of 40 to 60 was mixed together in powder form and the base protective layer had a film thickness of 160 nm. The result of the evaluation of the similar dynamic characteristic is in 18 shown. After 40,000 repetitions, the C / N ratio dropped approximately 10 dB compared to the original C / N ratio. The erasability decreased by about 1 dB after 40,000 revolutions compared to the original erasability. This dielectric thin film had a Knoop hardness of 480 and a compression stress of 4 × 10 ⁹ dynes / cm ² .

Example 10

As a material for a protective layer, La ₂ S ₃ from group (1) and SiO ₂ as a refractive compound from group (2) were mixed in powder form in a molar ratio of 80:20, and the mixture was subjected to a high pressure process to obtain a to provide composite sintered target.

A recording medium having a four-layer structure, comprising a dielectric layer, a recording layer, another dielectric layer and a reflection layer each having a thickness of 170 nm, 30 nm, 30 nm and 100 nm was formed on a polycarbonate resin substrate. The composition of the recording layer again consisted of Ge ₂ Sb ₂ Te ₅ and the reflection layer consisted of an aluminum alloy.

At a flow rate of argon of 50 sccm and oxygen of 1.0 ccm, the dielectric layer was formed using a sputtering process at a high frequency of 13.56 MHz and under a pressure of 0.7 Pa. The film has a density of 4.3 g / cc, which is equivalent to a theoretical density of 88%. The film had a JIS Knoop hardness of 415 and an elongation stress of 1.3 × 10 ⁹ dynes / cm ² . The recording layer and the reflection layer were both made by a DC sputtering method ren formed under an argon gas pressure of 0.7 Pa. In addition, resin hardened by ultraviolet rays was applied approximately 5 μm thick.

While the disk rotated at a linear speed of 10 m / s, became an overwrite operation with pulse radiation with a frequency of 4 MHz and a duty cycle of 50% with a recording power Pw of 13.5 mW and one erasing power Pe of 7.0 mW repeated. When a given number of The C / N ratio and the extinguishing performance were repeated each time certainly.

How out 19 Clearly, after 100,000 repetitions, the C / N ratio dropped about 2 dB compared to the original C / N ratio, while the erasing performance after 100,000 repetitions decreased about 10 dB compared to the original erasing performance. It should be noted that the melting temperature of SiO _{2 was} approximately 1600 ° C. and a compression stress of 3 × 10 ⁹ dynes / cm ^{2 was} present.

Example 11

A disk was prepared in a similar manner to the disk described in Example 10, except that the molar ratio of La ₂ S ₃ and SiO _{2 was} replaced with 60:40, and a similar evaluation of the dynamic characteristics was carried out , The results are in 20 shown. After 40,000 repetitions, the C / N ratio dropped approximately 4 dB compared to the original C / N ratio, while the erasability remained essentially unchanged from the original erasability after 100,000 repetitions. The thin film of this dielectric material had a Knoop hardness of 470 and an elongation stress of 1 × 10 ⁹ dynes / cm ² . Examination of the mixing ratio of the protective layer revealed that degradation caused by 10,000 repetitions of the overwrite operation could be largely suppressed by choosing an amount of SiO ₂ that was in a range of 10 to 90 mol%.

Example 12

A memory plate was produced in a similar manner to the memory plate described in Example 8, except that the material for the dielectric layer was replaced by a combination of Ce ₂ S ₃ and SiO ₂ in a molar ratio of 20:80. and that the thickness of the base protective layer was changed to 190 nm. A similar evaluation of the dynamic characteristics was then carried out, the result of which in 21 is shown. In 21 it can clearly be seen that after 100,000 repetitions the C / N ratio fell by approximately 6 dB compared to the original C / N ratio, while the erasability after 100,000 repetitions fell by approximately 6 dB compared to the original erasability. The dielectric film had a Knoop hardness of 410 and a compression stress of 3 × 10 ⁸ dynes / cm ² . Examination of the mixing ratio of the protective layer showed that degradation caused by 10,000 repetitions of the overwrite operation could be suppressed mainly by choosing an amount of SiO ₂ in the range of 15 to 90 mol%.

Example 13

To provide a material for the dielectric layer, TaS ₂ from group (1c) and Y ₂ O ₃ as oxide from group (2) were mixed in powder form at a molar ratio of 20:80, and the mixture was subjected to a hot printing process to provide a composite sintered target.

A recording medium having a four-layer structure including a dielectric layer, a recording layer, another dielectric layer and a reflection layer each having a thickness of 150 nm, 30 nm, 30 nm and 100 nm was formed on a polycarbonate resin. The composition of the recording layer was again Ge ₂ Sb ₂ Te ₅ and the reflective layer was made of an aluminum alloy.

At an argon flow rate of 50 sccm, the dielectric layer was formed in a film by a sputtering method at a high frequency of 13.56 MHz and under a pressure of 0.7 Pa. The film density was 5.2 g / cc, which is equivalent to 96% of the theoretical density. The film had a JIS Knoop hardness of 640 and an elongation stress of -1.0 × 10 ⁸ dynes / cm ² . The recording layer and the reflection layer were formed by a DC sputtering method under an argon gas pressure of 0.7 Pa.

In addition, with ultraviolet Blasted hardened Resin applied, which is about Was 5 μm thick.

A spoke became while the disk was rotating at a linear speed of 10 m / s Operation repeated using a pulse radiation with a frequency of 4 MHz and a duty cycle of 50% at a recording power Pw of 18.5 mW and an erasing power Pe of 8.5 mW. After a given number of repetitions, the C / N ratio and the erasability were determined.

As in 22 It can be clearly seen that the C / N ratio dropped by approximately 10 dB after 100,000 repetitions. However, the erasability remained essentially at the original level after 200,000 repetitions. It should be noted that the melting temperature of Y ₂ O _{3 was} approximately 2400 ° C and the protective layer had a Knoop hardness of 800 and a compression stress of 2 × 10 ⁹ dynes / cm ² . Examination of the mixing ratio of the protective layer revealed that degradation caused by 10,000 repetitions of the overwrite operation could be largely suppressed by an amount of Y ₂ O ₃ which was in the range of 30 to 90 mol%.

Example 14

A memory plate was prepared in a similar manner to the memory plate produced in Example 13, except that the material for the dielectric layer in Example 14 was made of TaS ₂ and Ta ₂ O ₅ in a molar ratio of 20:80 , and that the base protective layer in Example 14 had a thickness of 160 nm. A similar evaluation of the dynamic characteristics was carried out and the result is in 23 shown. The C / N ratio dropped approximately 5 dB after 100,000 repetitions compared to the original C / N ratio, while erasability increased by approximately 5 dB after 100,000 repetitions compared to the original erasability. It should be noted that the protective layer had a Knoop hardness of 440 and a compression stress of 1 × 10 ⁹ dynes / cm ² . The melting temperature of Ta ₂ O ₅ was approximately 1900 ° C and it had a Knoop hardness of 420 and a compression stress of 5 × 10 ⁹ dynes / cm ² . Examination of the mixing ratio of the protective layer showed that degradation caused by 10,000 repetitions of the overwrite operation could be largely suppressed by choosing an amount of Ta ₂ O ₅ ranging from 30 to 90 mol%.

Example 15

A memory plate was prepared in a manner similar to that of Example 14, except that the material for the dielectric layer was TaSe ₂ and Ta ₂ O ₅ in a molar ratio of 20:80. A similar evaluation of the dynamic characteristics was carried out, the results of which in 24 are shown. The C / N ratio dropped approximately 13 dB after 150,000 revolutions compared to the original C / N ratio, while the erasability was substantially unchanged from the original erasability even after 100,000 revolutions. This dielectric film had a Knoop hardness of 480 and a compression stress of 3.7 × 10 ⁹ dynes / cm ² . Examination of the mixing ratio of the protective layer showed that degradation caused by 10,000 repetitions of the overwrite operation could be largely suppressed by selecting the amount of Ta ₂ O ₅ which was in the range of 30 to 90 mol%.

Example 16

A memory plate was produced in a similar manner to the memory plate in Example 8, except that the material for the dielectric layer in Example 16 consisted of ZrS ₂ and Ta ₂ O ₅ in a molar ratio of 80:20. that the thickness of the dielectric base layer was changed to 140 nm, the thickness of the recording layer was changed to 20 nm, the thickness of the dielectric top layer was changed to 20 nm, and the thickness of the reflection layer was changed to 200 nm, and that the composition of the recording layer was ₁₅ Sb ₆₀ Sn was ₂₅ . The resulting disk was used as a write-once type optical disk, rotated at a linear speed of 9.5 m / s, while a signal on the disk using pulse radiation at a frequency of 4 MHz and a duty cycle of 50% at a recording power of 10 mW was written. After the writing, the storage disk was held in a high-temperature bath and high-humidity bath for 500 hours, specifically at a temperature of 80 ° C. and a humidity of 80%. When the plate was removed from the bath and the film surface was examined under an optical microscope, no physical damage such as breaks or dents were found. There was also no change in the disk's signal responses, such as the C / N ratio or jitter.

Example 17

TaS ₂ from group (1c) was selected as the material for the dielectric layer and a Ta target as a refractive compound from group (2). A four-layer structure recording medium was prepared which contained a dielectric layer, a recording layer, another dielectric layer and a reflection layer each having thicknesses of 160 nm, 30 nm, 30 nm and 100 nm and successively coated on a polycarbonate resin substrate , The recording layer had a composition consisting of Ge ₂ Sb ₂ Te ₅ , while the reflecting layer consisted of an aluminum alloy.

The dielectric layer was formed at argon and oxygen flow rates of 50 sccm and 6 sccm, respectively, by simultaneous high frequency sputtering (13.56 MHz), the TaS ₂ target, and DC sputtering for the Ta target under a pressure of 0.7 Pa. The level of performance used during the respective sputtering of the TaS ₂ and Ta targets was adjusted so that the resulting film contained TaS ₂ and Ta ₂ O ₅ in a molar ratio of 20:80. The film density was 7.4 g / cc, which is equivalent to a theoretical density of 87%. The film had a JIS Knoop hardness of 440 and a compression stress of 1 × 10 ⁹ dynes / cm ² . The recording layer and the reflection layer were both formed by direct current sputtering under an argon gas pressure of 0.7 Pa. In addition, a resin hardened with ultraviolet rays, which was approximately 5 μm thick, was applied. The disk thus prepared was initialized with an argon ion laser to form crystallization in the recording layer. The dynamic characteristics of the disk were then evaluated under the conditions described below.

At a linear velocity of 10 m / s rotating disk was overwritten using a pulse radiation of 4 MHz and a clock rate of 50% at a Repeated recording power Pw of 20 mW and an erasing power Pe of 9.5 mW. After a given number of repetitions was reached the C / N ratio each time and the erasability evaluated.

The results are in 25 shown. It is evident from this figure that the C / N ratio after 100,000 repetitions decreased approximately 20 dB compared to the original C / N ratio, while the erasability after 100,000 repetitions remained substantially the same as the initial erasability.

Example 18

A disk was prepared in a similar manner to the disk described in Example 17, except that DC sputtering of a TaS ₂ target and a Ta target was performed together, and a similar evaluation of the dynamic characteristic was performed. The results are in 25 shown. After 100,000 repetitions, the C / N ratio dropped approximately 10 dB compared to the original C / N ratio. After 100,000 revolutions, there was no significant change in erasability compared to the first overwrite operation. The dielectric film had a density of 7.4 g / cc, which is equivalent to 87% of the theoretical density. The film had a JIS Knoop hardness of 440 and a compression stress of 1 × 10 ⁹ dynes / cm ² .

Comparative sample 3

A memory plate was manufactured in a similar manner to the memory plate in Example 8, except that the material for the dielectric layer in this sample contained only SiO ₂ , and a similar evaluation of the dynamic characteristic was made. After 10,000 repetitions, the C / N ratio and the erasability decreased by approximately 11 dB and 17 dB compared to the original values. The dielectric film had a Knoop hardness of 300 and a compression stress of 1 × 10 ⁹ dynes / cm ² .

Comparative sample 4

A disk was prepared in a similar manner to the disk in Example 8, except that the material for the dielectric layer in this sample contained only Ta ₂ O ₅ , and a similar evaluation of the dynamic characteristic was made. The results are in 26 shown. After 20,000 repetitions, the C / N ratio and erasability dropped approximately 11 dB and 25 dB, respectively, compared to the original values.

Comparative rough 5

A disk was prepared in a similar manner to the disk in Example 8, except that the dielectric layer material in this sample contained ZnS and TiO ₂ in a molar ratio of 80:20 and the like The dynamic characteristics were evaluated. The results are in 27 shown. To 2000 Revolutions compared to the original values, the C / N ratio and the erasability decreased by approximately 11 dB and approximately 16 dB, respectively. The dielectric film had a Knoop hardness of 500 and a compression stress of 2 × 10 ⁹ dynes / cm ² . It is known that TiO ₂ begins to undergo thermal decomposition at about 600 ° C, releasing oxygen atoms and changing color to black.

Comparative rough 6

A disk was prepared in a similar manner to the disk described in Example 8, except that the material for the dielectric layer in this sample contained ZnS and MoS ₂ in a molar ratio of 80:20, and it became one similar evaluation of the dynamic characteristics made. The results are in 28 shown. After 1000 revolutions, the C / N ratio and the erasability decreased by approximately 9 dB and approximately 16 dB compared to the original values. The dielectric film had a Knoop hardness of 220 and a compression stress of 1 × 10 ⁹ dynes / cm ² . It is known that MoS _{2 is} thermally unstable at approximately 350 ° C and is therefore prone to form an alloy.

Example 18 '

The following example 18 'for the recording method according to the present Invention was accomplished using an optical drive tester (type DDU1000 from Pulsetech), which is a 780 mm wavelength laser diode and NA = 0.55 optical lenses, test signals with single-beam overwriting were recorded. The optical reading power Pb was independent of the different linear velocities at the constant value 0.8 mW held. The evaluation was made using an EFM random pattern at single, double and four times the speed of a CD (1.2 to 1.4 m / s). The clock frequency T was set to 116 ns, which is twice the speed and the period of the present used CDs corresponds. After some overwrite operations and under appropriate conditions, reproduced signals were at the middle level of the peak-to-peak signal amplitude from the 11T mark in the concerned reproduced signals truncated to the respective marker lengths in to determine the reproduced signals. A time interval analyzer (TIA) of E1725A and the procedure used in Example 1 were used again in this example. Each of the storage disks had a diameter of 120 mm, which is similar to the diameter of one Is CD, and each disk was on a polycarbonate resin substrate manufactured which is a spiral Had notch, with a slant (pitch) of 1.6 μm. The extinguishing performance Pe was chosen that the difference between the carrier level of a residual signal for an 11T mark and the carrier level a 3T mark is more than 20 dB after a mark, taken from a 22T single period (50% duty cycle) from another marker using a 6T one period (duty cycle of 50%) overwritten has been.

The storage disk A of the example was produced by successively a 100 nm thick (ZnS) ₈₀ (SiO ₂ ) ₂₀ [mol%] protective layer, a 25 nm thick GeSb _23.5 Te [at%] recording layer, a 20 nm thick ( ZnS) ₈₀ (SiO ₂ ) ₂₀ mol%] protective layer, and a 100 nm thick aluminum alloy layer were formed by means of magnetron sputtering, whereupon a 4 μm thick ultraviolet hardened synthetic resin layer was formed. Disk B of the example was made in a similar manner to disk A, except that the recording layer of B was made of AgInSbTe. These two alloys for the recording layers are common as materials for recording layers of phase-change type writable discs, and each has advantages and disadvantages, so that it is difficult to determine which is advantageous over the other for the given technical applications. These alloys for recording layers, however, have different characteristics depending on the linear velocities, depending on the processes involved in the phase change between the crystalline and amorphous states. Accordingly, in the prior art, these alloys are not interchangeable in CD-E disks in a wide range of linear speeds that vary between one speed and four times the speed, although the interchangeability can be performed at a specific speed.

Table 1 shows the excellent results obtained in this example in which single, double and quadruple speed recording operations on both disks A and B using different pulse division techniques depending on the linear speeds. The term "excellent results" used above should be understood to mean that a clear eye pattern is obtained in an EFM random pattern and the jitter is the narrowest marking length, ie a 3T marking, less than 10% of the period T. The pulse division patterns used in this embodiment are in 9 shown. In this example, a maximum linear speed V _{H was selected} at four times the speed, m was selected as m = n-1, and the reading power Pb was set to Pb = Pr, which was kept constant regardless of the linear speed. As can be seen from Table 1, single to four times the speed of V on disk A achieved excellent recording results when V _{h was} at four times the speed.

This example shows that excellent marks can be recorded on both disks A and B if for α _i , α ₁ (for i: 2 ≤ i ≤ m), β _i (for i: 1 ≤ i ≤ m - 1 ), β _m , Θ, Pw and Pe can be selected for each linear velocity at values as specified in Table 1. In each of these cases, a pulse division technique should be used in which at least one of α and Θ is reduced at a lower linear velocity.

TABLE 1

If the above signals are recorded as special information as ATIP signals, this special information can be retrieved from conventional drives described in Japanese Patent Laid-Open Nos. 103,454 / 1988, 87,344 / 1990, No. 198,040 / 1990, No. 88,124 / 1991 , Ni. 237.657 and post-test. Publication No. 3,168 / 1991. The circuit configuration for generating the pulse division pattern, as shown in Table 1 in a single drive, can also be done by a combination nation by conventional techniques. As mentioned above, the advantageous technical features of the present invention are in the pulse division technique, in which α _i , (β _i ) and / or Θ is varied in order to achieve interchangeability of the phase change type recording media, the pulse division technique being on the recording medium itself is recorded.

Example 19

In order to provide a material for the protective layer, Ce ₂ S ₃ from the group ( 1 ) and ZnO as a refractive compound from the group ( 2 ) in powder form in a molar ratio of 20:80, and the mixture was subjected to a high pressure process to provide a composite sintered target.

A recording medium having a four-layer structure including a dielectric layer, a recording layer, another dielectric layer, and a refraction layer each having a thickness of 200 nm, 20 nm, 20 nm and 200 nm was formed on a polycarbonate resin substrate. The compound consisted of Ag _6.8 In _7.1 Te _28.6 Sb _57.5 and the reflective layer consisted of an aluminum alloy.

At a flow rate of 50 sccm of argon, the dielectric layer was formed by a sputtering process at the high frequency of 13.56 MHz and under a pressure of 0.7 Pa. The film had a JIS Knoop hardness of 450 and an elongation stress of 4 × 10 ⁸ dynes / cm ² . The recording layer and the reflection layer were both formed by a DC sputtering process under Ar gas pressure of 0.7 Pa. In addition, an ultraviolet-hardened synthetic resin approximately 5 μm thick was applied.

While the rotation of the disk at a speed of 5.6 m / s were measured using a frequency of 2.24 MHz and a duty cycle of 50% with a recording power Pw of 14 mW and an erasing power Pe of 6.5 mW overwrite operations executed. After a given number of repetitions was reached the C / N ratio each time and the erasability certainly.

The C / N ratio was compared to that original C / N ratio and the erasability was compared to the original one deletability almost identical after 100,000 repetitions. It should be noted that the melting temperature from ZnO approximately 1,980 ° C is.

To summarize the above description, can be an optical recording medium according to the present invention be used effectively to create a write-once Medium to realize that a has excellent backup stability, and also an overwrite medium too realize that a variety of record and erase retries allowed.

The above embodiments of the invention are described by way of example only, and the present invention is by no means on these statements limited, and it will be for it will be apparent to those skilled in the art that numerous modifications or changes can be easily made based on the above can, all of which are within the scope of the present invention.

Claims (27)

Optical recording method ready for recording data on or erasing data from an optical information carrier medium which responds to the irradiation with a focused laser beam having laser power which has a laser power which is within a clock interval T, with the formation or deletion of optically distinguishable amorphous markings can be modulated in at least three stages, this method comprising the following steps: providing a linear speed V in the range between V _L and V _h by driving an optical recording device, the clock intervals T being varied in accordance with the linear speed V; Irradiating the information carrier medium with a focused laser beam in order to record there a mark having a mark length nT with a mark length modulation recording; and modulation of the laser radiation to provide m individual pulses, all of which have a recording power level Pw with a pulse length α _i T, followed by an interval β _i T between two pulses with a recording level Pw, in each of which a quiescent power level (bias power level ) Pbi is provided, where i stands for an integer from 1 to m, and thereby a total of a time period of α ₁ T, β ₁ T, α ₂ T, β ₂ T, ..., α _m T and β _m T for the radiation with alternating laser power is obtained in order to emit a marking of the marking length nT; characterized by changing at least one of the combinations of α _i and Pb _{i in} accordance with the linear velocity V, the following inequality and equations being fulfilled: n min - k ≥ 1 m = n - k; and α 1 + β 1 + ... + α m + β m = n - j; where k is an integer from 0 ≤ k ≤ 2, j is a real number from 0 ≤ j ≤ 2, and n _{min represents} the minimum value of n. An optical recording method according to claim 1, in which the ratio Pb _i / Pe = Θ _{i is changed in} accordance with the linear velocity V, where Pe represents the erasing power level during deletion of a mark. An optical recording method according to claim 1 or 2, in which α iL ≤ α i1 ≤ α i2 ≤ α ih for each i and for each V ₁ and V ₂ , which satisfy the condition V _L <V ₁ <V ₂ <V _h , in which α _iL T, α _i1 T, α _i2 T and α _ih T the widths of the represent individual pulses at linear speeds of V _L , V ₁ , V ₂ and V _h , and α _iL ≤ α _ih applies at least to V _L. Optical recording method according to Claim 1 or 2, in which Θ _iL ≤ Θ _i1 ≤Θ _i2 ≤ Θ _ih for each V ₁ and V ₂ which satisfy the condition V _L <V ₁ <V ₂ <V _h , where Θ _iL , Θ _i1 , Θ _i2 , and Θ _{ih represent} the ratio Pb _i / Pe = Θ _i at respective linear velocities of V _L , V ₁ , V ₂ , and V _h , and at least V _L holds Θ _il <Θ _ih . Optical recording method according to one of claims 1 to 4, in which β _{m is} not equal to zero. Optical recording method according to one of Claims 1 to 5, in which a clock interval T for a linear speed V is essentially set to T = T _h (V _h / V), where T _{h represents} a clock frequency for the linear speed V _h , where T for small variations of V and V _h in the range of + 10% of V can be kept constant. Optical recording method according to one of Claims 1 to 6, in which at a maximum linear velocity V _h , α _1h = 1.5 or 1.0, and β _1h = α _ih = 0.5 applies to all i from 2 ≤ i ≤ m, and to any one Linear velocity, α _i + β _i = 1.0, applies to all i from 2 ≤ i ≤ m, where α _ih T and β _ih T represent the width of each individual pulse and relevant interval at the maximum linear velocity V _h . Optical recording method according to one of Claims 1 to 7, in which, for a linear velocity V which satisfies the relationship V _L ≤ V <V _h , the inequalities, α _i <α _ih and 0.05 <α _i <0.5 for all i out of 2 ≤ i ≤ m apply. Optical recording method according to one of Claims 1 to 8, in which α ₁ > α _i applies to all i from 2 ≤ i ≤ m, and α _i remains constant for all i from 2 ≤ i ≤ m. Optical recording method according to one of claims 1 to 9, in which β _i remains constant for all i from 1 ≤ i ≤ m, while β _m assumes a value different from the constant including zero. Optical recording method according to one of claims 1 to 10, in which a range of n used in the mark length modulation recording technique, according to the linear speed that varies during the Record the mark is used. Optical recording method according to one of Claims 1 to 11, in which n _min T × V remains constant at least for the shortest marking length n _min T. Optical recording method according to one of Claims 1 to 3, in which: with an eight-to-fourteen modulation, the maximum linear velocity V _h in a range from 2 to 6 times the minimum linear velocity V _L , where V _L varies in the range from 1.2 to 1.4 m / s; and it holds that m = n, n - 1, or n - 2; the linear velocity V takes one of the values V _L , 2V _L , 4V _L or 6V _L ; at a linear velocity V which is equal to or greater than 2V _L , α _1h = 1.5 or 1.0 and β _ih = α _ih = 0.5 applies to all i from 1 ≤ i ≤ m; at any linear velocity V, α _i + β _{i – 1} = 1.0 for all i from 2 ≤ i ≤ m; at a linear velocity V = 2V _L , Pb _i = Pr + 0.5 mW applies to all i from 1 ≤ i ≤ m, where Pr represents the level of reproduction; at a linear velocity V = V _L , 0.05 <α _i <0.5 applies to all i from 2 ≤ i ≤ m, and α1 _L ≤ α _1h applies; at a linear velocity V _h , Pb _i = Pe applies to all i from 1 ≤ i ≤ m. An optical recording method according to claim 13, in which β _{m is} not zero. Optical recording method using a mark length modulation recording method ready for recording data or erasing data from an optical information medium that responds to irradiation with a focused laser beam to form or erase optically distinguishable amorphous marks with a variety of different mark lengths which has a laser power which can be modulated in at least three stages within a clock interval T, with a recording power Pw, an erasing power Pe and a bias power Pb, where Pb ≤Pe; the method comprises a step of radiation of a focused laser beam in order to record a mark with a mark length nT on the optical recording medium by means of mark length modulation recording, this step of radiation comprises: modulating the laser radiation so that m individual pulses each have a recording power level Pw and a pulse length α _i T, with an interval β _i T between every two pulse lengths to provide a quiescent power level Pb _i , where i stands for an integer from 1 to m; and from which a time sequence of α ₁ T, β ₁ T, α ₂ T, β ₂ T, .. α _m T, β _m T results for the laser power; Varying a linear velocity V during the radiation of the laser energy within a range V _L <V <V _h , where V _{h represents} a maximum linear velocity and V _{L represents} a minimum linear velocity; and variation of the clock interval T in accordance with the linear velocity V, where: α _i + β _i = 1.0 for all i out of 2 ≤ i ≤ m - 1; α _iL <α _i1 <α _i2 <α _ih and α _iL <α _ih for V _L <V ₁ <V ₂ <V _h and for all i; α _1h = 1.5, 1.0 or 0.5 and β _1h = 0.5; α _ih = 0.5 for all i from 2 ≤ i ≤ m; and 0.05 <α _i <0.5 for a linear velocity V from V _L ≤V <V _h and all i from 2 ≤ i ≤ m. Optical recording method using a mark length modulation recording method ready for recording data or erasing data from an optical information medium that responds to irradiation with a focused laser beam to form or erase optically distinguishable amorphous marks with a variety of different mark lengths , which has a laser power that can be modulated in at least three stages within a clock interval T, with a recording power Pw, an erasing power Pe and a bias power Pb, where Pb / Pe ≤ 0.25; the method comprises a step of radiation of a focused laser beam in order to record a mark with a mark length nT on the optical recording medium by means of mark length modulation recording, this step of radiation comprises: modulating the laser radiation so that m individual pulses each have a recording power level Pw and a pulse length α _i T, with an interval β _i T between every two pulse lengths to provide a quiescent power level Pb _i , where i stands for an integer from 1 to m; and from which a time sequence of α ₁ T, β ₁ T, α ₂ T, β ₂ T, .. α _m T, β _m T results for the laser power; Varying a linear velocity V during the radiation of the laser energy within a range V _L V V V V _h , where V _{h represents} a maximum linear velocity and V _{i represents} a minimum linear velocity; and variation of the clock interval T in accordance with the linear speed V, whereby assuming a linear speed V _L , V ₁ , V ₂ , .. and V _h , α _i corresponds to α _iL , α _i1 , α _i2 , α _ih , and the the following inequalities and equations apply: α iL <α i1 <α i2 <α ih and α iL <α ih for all i and V L <V 1 <V 2 <V H ; α 1h = 1.5, 1.0 or 0.5 and β 1h = 0.5; α ih = 0.5 for all i from 2 ≤ i ≤ m; α 1h = 0.5 for all i from 2 ≤ i ≤ m; and 0.05 <α _i <0.5 for a linear velocity V from V _L ≤ V <V _h and for all i from 2 ≤ i ≤ m. Optical recording method according to claim 16, in which α _i + β _i = 1.0 applies to all i out of 2 ≤ i ≤ m - 1. Optical recording method using a mark length modulation recording method ready for recording data or erasing data from an optical information medium that responds to irradiation with a focused laser beam to form or erase optically distinguishable amorphous marks with a variety of different mark lengths , which has a laser power that can be modulated in at least three stages within a clock interval T, with a recording power Pw, an erasing power Pe and a bias power Pb, where Pb / Pe ≤0.25; the method comprises a step of radiation of a focused laser beam in order to record a mark with a mark length nT on the optical recording medium by means of mark length modulation recording, this step of radiation comprises: modulating the laser radiation so that m individual pulses each have a recording power level Pw and a pulse length α _i T, with an interval β _i T between every two pulse lengths to provide a quiescent power level Pb _i , where i stands for an integer from 1 to m; and from which a time sequence of α ₁ T, β ₁ T, α ₂ T, β ₂ T, .. αT _m , β _m T results for the laser power; Variation of a linear velocity V during the radiation of the laser energy within a range V _L V V V V _h , where V _{h represents} a maximum linear velocity and V _{L represents} a minimum linear velocity; and variation of the clock interval T in accordance with the linear speed V, whereby assuming a linear speed V _L , V ₁ , V ₂ , .. and V _h , α _i corresponds to α _iL , α _i1 , α _i2 , α _ih , and at the linear velocity V _h , β _i corresponds in each case to β _ih , and the following inequalities and equations apply: α _i + β _i is a constant for each linear velocity and for all i; α iL ≤ α i1 ≤ α i2 ≤ α ih and α iL <α ih for V L <V 1 <V 2 <V H ; α _ih = β _ih ; and 0.05 (α _i + β _l ) <α _i <0.5 (α _i + β _i ) holds for every linear velocity V from V _L ≤ V <V _h and for all i from 2 ≤ i <m. Optical recording method according to Claim 18, in which the following applies to the rest power level Pb _i : Pb _i = Pr + 0.5 mW at β _i T for all i from 1 ≤ i ≤ m and a given reproductive power level Pr. An optical recording method according to any one of claims 1 to 19, in which: α _i is a constant; and α ₁ > α _i ; for all i from 2 ≤ i ≤ m. An optical recording method according to any one of claims 1 to 20, in which a maximum linear velocity V _h ranges from 2 to 6 times the minimum linear velocity V _L , V _L varying in the range from 1.2 to 1.4 m / s for mark length modulation recording; and m = n, n - 1, or n - 2 applies; the linear velocity V assumes one of the values V _L , 2V _L , 4V _L or 6V _L , and for each linear velocity V, α _i + β _{i − 1} = 1.0 applies to all i from 2 ≤ i ≤ m; and for each linear velocity V, Pbi = Pr ± 0.5 mW applies to all i from 1 ≤ i ≤ m, where Pr represents a reproductive power level; and α _i is monotonically reduced for all i from 1 ≤ i ≤ m when the linear velocity is reduced. An optical recording method according to any one of claims 1 to 21, in which: β _i is a constant for all i out of 1 <i <m, and β _m is not equal to the constant including zero. An optical recording method according to any one of claims 1 to 22, in which a maximum linear velocity V _h ranges from 2 to 6 times the minimum linear velocity V _L ; where the minimum linear velocity V _L varies in the range of 1.2 ≤ V _L ≤ 1.4 m / s with a marking length EFM modulation, and where: m = n, n - 1 or n - 2; the linear velocity V takes one of the values V _L , 2V _L , 4V _L or 6V _L ; at a linear velocity V greater than 2V _L , α _1h = 1.5 or 1.0 applies to all i 1 ≤ i ≤ m, β 1h = α ih = 0.5; at every linear velocity V we have α _i + β _{i – 1} = 1.0 for all i out of 2 ≤ i ≤ m; at a linear velocity V = 2V _L , Pb _i = Pr ± 0.5 mW applies to all i from 1 ≤ i ≤ m, where Pr represents a reproductive power level; at a linear velocity V = V _L , 0.05 <α _i <0.5 and α _1L ≤ α _1h for all i from 1 <i <m; and at the linear velocity V _h , Pb _i = Pe. An optical recording method according to claim 22, in which ß _m ≠ 0.5. An optical information medium for use in an optical recording method according to any one of claims 1 to 24, wherein a combination of variables selected from the group consisting of Pw, Pe, Pb, m, j, k, α _i and β _i as pulse division information from the optical information medium is recorded so that selection of a variety of pulse division methods is permitted in accordance with the linear velocity used. The information medium according to claim 25, wherein the pulse division information is recorded as concave / convex pit data. An information medium according to claim 26, wherein the pulse division information using frequency modulation technology as a wobbled notch on the optical information medium is recorded.