JPH01287838A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase a reproduction signal and to execute initialization and recording and erasing at a high speed by incorporating an alloy having a specific compsn. into a recording layer. CONSTITUTION:The alloy of the compsn. expressed by the formula (Mg100-x-yZnxAy)100-zDz (x, y, z are, by atomic%, 0<x<100, 0<y<100, 0<z<25; A is one kind of the element from the group consisting of Te, Se, Ge, Si, and Sb; D is one kind of the element from the group consisting of Tl, Pb, Bi, Pt, and Au) is incorporated into the recording layer which causes a phase transition between two different phases in the irradiated part when subjected to irradiation of a light beam. The stabilization of the amorphous phase and the crystallization rate are enhanced if the element expressed by D is incorporated at <25atomic% into this alloy. The reproduction signal level is thereby increased and the execution of the initialization and the recording and erasing at the higher speed is enabled.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) This invention provides information by irradiating a recording layer with a light beam such as a laser beam and inducing a phase change in the irradiated area depending on the irradiation conditions. The present invention relates to an information recording medium that reproduces information by recording and erasing information and detecting changes in optical properties such as reflectance and transmittance accompanying this phase change. Examples of such information recording media include optical discs and optical cards.

(Prior Art and Section 8) Phase change type media have been widely known as information recording media from which information can be erased, such as so-called erasable optical discs. This phase change type information recording medium includes, for example, a substrate made of glass or plastic (polycarbonate resin, polymethyl methacrylate resin, etc.) and a recording layer formed on the substrate. Chalcogenide alloys such as GeTe are known as materials for forming this recording layer, and these alloys can be used for light beams under different conditions (
By irradiating it with a laser beam (for example, a laser beam), the phase changes reversibly between crystal and amorphous, so this phase change is used to record and erase information, and the reflectance associated with these phase changes is Alternatively, information can be read using changes in optical characteristics such as transmittance.

As such a recording layer, a material having a eutectic composition or a material forming an intermetallic compound that easily undergoes a phase change depending on the irradiation conditions of the light beam is suitable.

However, although alloys such as GeTe that have been conventionally used as the recording layer of phase change information recording media satisfy the above conditions, it cannot be said that they still have sufficient properties as information recording media. . In particular, it is desired to further improve the amount of change in optical properties due to phase change, that is, the magnitude of the reproduced signal, and to speed up initialization, recording, and erasing. In addition, when recording or erasing information by a phase change between crystal and amorphous, the recorded portion usually becomes amorphous, but since amorphous is generally relatively unstable, it remains in the amorphous state. It is also required to make it more stable.

This invention was made in view of such circumstances, and
It is an object of the present invention to provide an information recording medium that has a large reproduction signal, can perform initialization, recording, and erasing at high speed, and has stable recorded information.

[Structure of the Invention (Means for Solving the Problems) An information recording medium according to the present invention includes a substrate and a recording layer whose irradiated portion changes phase between two different phases when irradiated with a light beam. In the medium, the recording layer has the general formula (M groo-x-y Z n w A
y) +oo-8D, (x, y, z are expressed in atomic percent, respectively 0 × X × 100, o<y<loo,
It is in the range of 0<z<25, and A is Te, Se, Ge,
D is at least one element selected from the group consisting of Si and sb, and D is at least one element selected from the group consisting of TI, Pb, Bi, Pt, and Au.

) is characterized by containing an alloy with a composition represented by:

(Function) The Mg-Zn alloy containing the element represented by A above is a material that satisfies the conditions as a recording layer of a phase change recording medium as described above, and also The amount of change in optical properties is large. By containing less than 25 at % of the element represented by D in this alloy, the amorphous phase can be stabilized and the crystallization rate can be increased. Therefore, with the recording layer having the composition as described above, it is possible to increase the reproduction signal level and to speed up initialization, recording, and erasing, and the recorded information is stable.

(Example) Hereinafter, the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the invention. The substrate 1 is made of a material commonly used in this technical field, such as a plastic such as polyolefin, epoxy, polycarbonate (PC), polymethyl methacrylate (PMMA), or glass. On this substrate 1, a protective layer 3, a recording layer 2, a protective layer 4, and a protective layer 5 are formed in this order.

The protective layer 3 and the protective layer 4 are disposed to sandwich the recording layer 2 and are made of an organic polymer material, such as a thermoplastic resin such as PMMA or polystyrene, or an ultraviolet curing resin (so-called 2
P resin), or 5i02, Al103, AIN, ZnS
, or a dielectric material such as ZrO2. These protective layers 3.4 serve to prevent the recording layer 2 from being affected by moisture in the air, and to prevent the irradiated portion of the recording layer 2 from being scattered by a light beam such as a laser beam during recording or erasing. It has the effect of preventing the formation of holes. These protective layers 3゜4 can be formed by spin coding method, vapor deposition method,
It can be suitably formed by a sputtering method or the like. Note that the thickness of these protective layers 3 and 4 is preferably 10 to several tens of μm.

The protective layer 5 is provided to prevent scratches, dust, etc. on the surface when handling the information recording medium, and is coated with an ultraviolet curing resin using a spin code method or the like, and then cured by irradiating it with ultraviolet light. It is formed by such things as This protective layer 5
The layer thickness is preferably 100 μm to several tens of μm.

Although it is preferable to provide the protective layer 3°4.5, it is not necessary to provide it.

The recording layer 2 is (Mg+oo-m-y ZnxAy)+o
o-gDg (however, X+Y*Z is expressed in atomic %,
They are in the range of 0<x<100, O<y<100.0, respectively, and A is Te, Se, and Ge.

At least one element selected from the group consisting of St and sb, and D is TI, Pb, and Bi.

It is at least one element selected from the group consisting of pt and Au. ), and can be suitably formed by a vapor deposition method, a sputtering method, or the like. Note that when performing vapor deposition or sputtering using an alloy target, it is necessary to take into account that there is a difference between the target composition and the composition of the film actually formed. Further, the film can also be formed by multi-source simultaneous vapor deposition, multi-source simultaneous sputtering, or the like. The thickness of recording layer 2 is 10
Preferably, the number is 0 to 3000 people.

M g +00-m-y Z n forming the main body of recording layer 2
, A.

is a material whose phase can change between crystal and amorphous by changing the conditions of the irradiated light beam, and the presence of the element represented by A changes the optical properties between crystal and amorphous. (such as reflectance or transmittance) can be increased.

In addition, 25% of the element represented by D is added to the alloy with such a composition.
By containing less than atomic %, the amorphous state can be stabilized and the crystallization rate can be increased. Therefore, by making the recording layer 2 have the above-mentioned composition, it is possible to increase the reproduction signal, stably retain recorded information, and further speed up initialization, recording, and erasing. can.

Note that if the content of D element in the recording layer 2 is 25 atomic % or more, the stability of the amorphous state will decrease.
The content of the element is less than 25 at.%.

Next, an example of a method for forming the recording layer of the information recording medium according to this embodiment will be explained with reference to FIGS. 2 and 3. FIG. 2 is a longitudinal cross-sectional view showing a schematic configuration of a sputtering apparatus used to form the recording layer of this embodiment, and FIG. 3 is a cross-sectional view thereof. In the figure, 10 indicates a vacuum vessel, and this vacuum vessel 10 has a gas introduction boat 1 on its bottom surface.
1 and a gas discharge boat 12. The gas exhaust boat 12 is connected to an exhaust device 13, and the inside of the vacuum container 10 is evacuated by the exhaust device 13 via the exhaust boat 12. Further, the gas introduction boat 11 is connected to an argon gas cylinder 14, and argon gas as a sputtering gas is introduced from the cylinder 14 into the vacuum vessel lo via the gas introduction boat 11. vacuum container lo
A disk-shaped rotating base 15 for supporting a substrate is placed in the upper part thereof with its surface horizontally, and the substrate 1 is supported on the lower surface thereof and is rotated by a motor (not shown). ing. Furthermore, near the bottom of the vacuum chamber 1o, sputtering sources 21, 22, and 23 each made of a predetermined element constituting the recording layer are arranged so as to face the base 15. A high frequency power source (not shown) is connected to. These sputtering sources 21
The information of ゜22.23, respectively, includes the monitor devices 24゜25.
26, these monitoring devices monitor the amount of sputtering from each sputtering source, and adjust the amount of power input to each sputtering source so that the recording layer has a predetermined composition.

In such a sputtering apparatus, first, the inside of the vacuum chamber 1o is heated to a temperature of, for example, 10"6T or
Exhaust to r. Next, while introducing argon gas into the container 10 via the gas introduction boat 11, the exhaust device 13 is
The inside of the vacuum container 10 is maintained at a predetermined pressure in an argon gas atmosphere by adjusting the exhaust amount. In this state, while rotating the substrate 1, a predetermined power is applied to the sputtering sources 21, 22, and 23 for a predetermined time. As a result, a recording layer having a predetermined composition is formed on the substrate 1. Note that when forming the protective layer, prior to forming the recording layer 2, the protective layer 3 is formed on the substrate 1 by sputtering as described above using a sputtering source adjusted to the composition of the protective layer. Then, the protective layer 4 can be formed on the recording layer 2 under the same conditions as in the case of forming the recording layer 2 and further forming the protective layer 3.

Next, initialization, recording, erasing, and reproduction of information in the information recording medium of the present invention will be explained.

The initialization recording layer 2 is normally amorphous immediately after film formation, but it needs to be crystalline in order to record information, so the recording layer 2 is heated and slowed by irradiating the entire surface of the recording layer 2 with a light beam such as a laser beam. Cool and crystallize the recording layer 2.

A light beam with high recording power and short pulse width is irradiated onto the recording layer 2,
The irradiated area is heated and rapidly cooled to change its phase to an amorphous state, thereby forming a recording mark.

A light beam having a lower output and a longer pulse width than that used during recording is irradiated onto the recording mark portion formed on the erasing recording layer 2 to change the phase of the recording mark portion into a crystal, thereby erasing information.

A relatively weak light beam is irradiated onto the recording layer 2 on which reproduced information has been recorded, and the information is read by detecting the difference in optical characteristics, such as reflectance, between the recorded mark portion and the non-recorded portion.

Next, test examples of the present invention will be explained.

Test Example 1 Thirteen samples were prepared by forming a thin film within the composition range of the recording layer of the present invention on a heat-resistant glass substrate using the sputtering apparatus shown in FIGS. 2 and 3. The thin film composition, structure immediately after film formation, and crystallization temperature of these samples were determined first.
Shown in the table.

Table 1 At this time, the structure of the recording layer was analyzed by X-ray diffraction, and the crystallization temperature was measured by a high-sensitivity differential scanning calorimeter. As is clear from Table 1, all of the films were amorphous immediately after deposition, and their crystallization temperatures were 150° C. or higher. That is, it was confirmed that the stability of the amorphous state of these samples was high.

Test Example 2 Six samples having the layer structure shown in FIG. 1 were produced. The composition of the recording layer at that time is shown in Table 2.

Table 2 Among these samples, sample A has a recording layer of Mg-Zn.
Samples B-F are comparative examples formed of a -Te ternary alloy, and are within the scope of the present invention. For these samples, the recording layer was irradiated with a single pulse laser beam of various pulse widths from the substrate side, and the relationship between the pulse width and the reflectance of the irradiated area was determined. The results are shown in FIG.

FIG. 4 is a graph showing the relationship between these, with the horizontal axis representing the pulse width of the irradiated laser beam and the vertical axis representing the amount of change in reflectance. In this graph, the point where the amount of change in reflectance increases rapidly corresponds to a phase change from amorphous to crystalline. As is clear from this graph, TI and Pb are used as the fourth element, respectively.

It can be seen that samples B-F to which Bi, Pt, and Au are added have a shorter pulse width of the laser beam for crystallization than sample A to which no fourth element is added. That is, by adding these fourth elements, the crystallization rate could be increased.

Among them, sample B using TI as the fourth element had the highest crystallization rate.

Mg-Zn-3eSMg-Zn-Ge, Mg-Zn-T
TI and Pb as the fourth element in e.

A similar effect could be obtained when the recording layer was formed by adding Bi, Pt, and Au.

Test example 3 T as the fourth element for Mg60 Zn30 Te10
A plurality of samples were prepared in which alloy thin films each containing I, Pb, Bi, Pt, and Au in varying amounts were formed on glass substrates in the same manner as in Test Example 1. As a result of measuring the crystallization temperature of these samples using the same method as in Test Example 1, the crystallization temperature of all the samples in which the amount of the fourth element added was 25 atomic % or more was low, and the stability of the amorphous state was poor. Ta.

[Effect of the invention] According to the invention, as a recording layer (Mg +0O-x-y Z n x Ay ) to
ox D t (However, x, y, z are expressed in atomic %, respectively 0 x x 100.0 x y x 100, O < z
<25, A is at least one element selected from the group consisting of Te, Se, Ge, Si and sb, and D is selected from the group consisting of TI, Pb, Bi, Pt and Au. It is at least an IFJ element. ), the difference in optical properties between crystal and amorphous in the recording layer is large, the stability of the amorphous is high, and the crystallization rate is high. Therefore, the reproduction signal level is high and the stability of amorphous recording marks is excellent.
Moreover, it is possible to obtain an information recording medium with extremely excellent characteristics in which initialization, recording, and erasing can be carried out at high speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an information recording medium according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing a schematic configuration of an apparatus for forming a recording layer, and FIG. FIG. 4 is a graph showing the relationship between the pulse width of the irradiated laser beam and the amount of change in reflectance. 1; Substrate, 2; Recording layer, 3.4, 5. protective layer. Applicant's representative Patent attorney Takehiko Suzue G1 Ku Laser Beam 9 No. 1 Shigemasa (Hsec) No. 4

Claims (1)

[Claims] An information recording medium having a substrate and a recording layer whose irradiated portion changes phase between two different phases by irradiation with a light beam, the recording layer having a general formula (Mg_1_0_0_
-_x_-_yZn_xA_y)_1_0_0_-_z
D_z (where x, y, and z are expressed in atomic % and are within the ranges of 0<x<100, 0<y<100, and 0<z<25, respectively, and A is Te, Se, Ge, Si and at least one element selected from the group consisting of Sb, and D is at least one element selected from the group consisting of Tl, Pb, Bi, Pt and Au. An information recording medium characterized by containing an alloy.