JPH02239437A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve repetitive characteristics of phase-transition-type optical disk for recording and erasing with laser pulse irradiation by providing a protective layer of CeO2 between a recording film and a substrate and/or on the recording film. CONSTITUTION:The recording layer 12 which changes its phase by irradiation of a light is formed on the substrate 11 comprising glass or plastic material (such as polymethyl methacrylate resin or polycarbonate resin), and an inorg. protective layer 13 comprising CeO2 is deposited on the recording layer 12. Further, an org. protective layer 14 comprising UV-curing resin is formed on the inorg. protective layer 13. Other embodiments such as having the inorg. protective layer 13 between the substrate 11 and the recording layer 12, or protective layer 13 on both surfaces of the recording layer 12 may be used. The obtd. medium has improved repetitive characteristics for recording and erasing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a recording medium such as an optical disk on which information is recorded, erased, and reproduced by irradiation with a light beam such as a laser beam.

(Prior Art) In recent years, optical disks have been attracting attention as large-capacity memories.

Optical discs are broadly classified into playback-only types represented by CDs and VDs, write-once types that can be written once, such as document files and video files, and Irasable types that can be written and erased any number of times.

The recording/erasing method for erasable optical disks is to reverse the direction of the spin of perpendicular magnetization using heat from laser beam irradiation and an external magnetic field, and then use the magnetic Kerr effect and Faraday effect during playback to generate linearly polarized light. A magneto-optical type that extracts the rotation angle of the recording film as a signal, and a reversible method that takes advantage of the difference in optical properties such as reflectance between a crystalline state and a non-quality recording film depending on the laser beam irradiation conditions. There is a phase change type that undergoes a phase change.

The former has completed the research and development stage and is already at the stage of practical application. The latter phase change type can record and erase using only a light beam,
A system that can perform overwriting using a single beam is currently being developed.

When recording information on such an information recording medium, first, the entire surface of the recording medium is irradiated with a light beam to bring the recording layer into a highly crystalline state (hereinafter referred to as a crystalline state). Next, in order to record information, the recording layer is irradiated with short, strong pulsed light, heated, and rapidly cooled to bring the recording layer into a state B in which the atomic arrangement is disordered (hereinafter referred to as a non-quality state). When erasing recorded information, the recording layer is irradiated with long, weak pulsed light to heat it and slowly cool it to a crystalline state again. Since optical properties such as reflectance and transmittance change between the crystalline state and the non-quality state due to changes in atomic arrangement, information can be reproduced by detecting changes in optical properties. There is.

In such an information recording medium, a dielectric protective film is laminated on one or both sides of the recording film. This dielectric protective film has the following three functions.

(2) During recording by laser pulse irradiation, the recording film is in a molten state, which prevents it from evaporating and forming holes.

■Use the interference effect of light reflected at the interface of each layer to increase the reproduced signal.

■By appropriately selecting the thermal conductivity of the protective film, if it is made adiabatic, it can be crystallized with a low-power laser when erasing the recording film, and if it is made heat dissipating, it is easy to rapidly cool and cause deterioration during recording. becomes.

Currently, S r O , Z n S −, Z r O are used as materials for dielectric protective films that satisfy the above conditions
2nd prize is proposed.

However, the above dielectric protective film has the following drawbacks. That is, since the density and volume of the recording layer are different between the crystalline state and the non-quality state, the protective film is deformed or destroyed during repeated recording and erasing, and the reversibility of recording and erasing is lost.

Such deformation and destruction of the protective film can be caused by repeated recording and erasing by laser pulse irradiation, which occurs 100 to 1000 times.
Although it does not occur once, it occurs when repeated 10,000 times or more, and there is a problem in that recording and erasing cannot be repeated 1,000,000 times as per the target specification.

(WJ section to be solved by the invention) As detailed above, conventional SiO, Zn? ,Zr
In phase change type information recording media having a protective layer made of O2 or the like, there is a problem in that the protective layer is destroyed by repeated recording and erasing of information, making it impossible to achieve a long life.

The present invention was made in order to improve the above-mentioned disadvantages, and its purpose is to dramatically improve the repeatability of recording and erasing by laser pulse irradiation of phase change optical disks by using a new dielectric protective film. do.

[Structure of the invention]

(Means and Effects for Solving the Problems) The information recording medium of the present invention has a recording layer that can record information by causing a change in atomic arrangement by irradiation with a light beam on a substrate, and the recording layer It is characterized in that a film made of Ce02 is provided between the substrate and the recording film and/or on the recording film.

Cross-sectional views showing the structure of the information recording medium used in the present invention are shown in FIGS. 1 to 3.

Reference numeral 11 in FIG. 1 is a substrate made of glass or plastic material (for example, polymethyl methacrylate resin, polycarbonate resin, etc.), and on this substrate 11 is formed a recording layer 12 that undergoes a layer change when irradiated with a light beam. Furthermore, an inorganic protective layer 13 made of Ce 0 2 is laminated on the recording layer 12 . Furthermore, it has a layered structure in which an organic protection layer 14 made of an ultraviolet curing resin is laminated on the inorganic protection layer 13. Further, the information recording medium of the present invention includes:
As shown in FIG. 2, the inorganic protective layer 13 is laminated between the substrate 11 and the recording layer 13, or as shown in FIG. 3, the inorganic protective layer 13 is laminated on both sides of the recording layer 12. It may have a layered structure.

Next, a method for manufacturing the information recording medium will be explained with reference to FIG. 4. FIG. 4 is a side view of a film forming apparatus used in the present invention.

The vacuum vessel 17 is connected to an exhaust device 19 via an exhaust boat 18, and is also connected to an argon gas cylinder 21 via a gas introduction boat 20. Vacuum container 17
In the middle upper part, there is a support device 22 and the board 11 supported horizontally by this support device. The substrate 11 can rotate around the support device 22. In addition, the vacuum container 17
At the middle bottom, spatter sources 23 and 24 are provided for the substrate 11.
, 25 are provided, and a high frequency power source is connected to these sputter sources. Also, Suba Tsuta Source 23.24.
Monitor devices 26, 27, and 28 are installed above 25.

When forming the recording layer 12 or the inorganic protective layer 13 on the substrate 11 using this apparatus, first exhaust the air in the vacuum container 17 using the exhaust device 19, and then introduce argon gas from the argon gas cylinder 21. to maintain the specified pressure inside the container. Then, while rotating the substrate 11, power is applied to the sputter sources 23, 24, and 25 for a predetermined period of time. The monitor devices 26, 27, and 28 each detect the amount of elemental spatter from the spatter sources, and adjust the power input to each spatter source so that the detected amount becomes a predetermined value. As a result, the recording layer 12 or Ce
An O■ protective layer 13 is formed.

Furthermore, an ultraviolet curable resin is overcoated as an organic protective layer 14 on the recording layer 12 or the C e O 2 protective layer 13 using a Subin coater, and is cured by irradiation with ultraviolet rays to obtain an information recording medium.

As mentioned above, in information recording media using C e O 2 as a protective layer, C e O 2 is physically very strong, so it cannot be destroyed even by repeated recording and erasing by irradiation with a light beam. Accordingly, it is possible to provide an information recording medium that can dramatically improve the repeatability of recording and erasing without causing problems.

(Example) An example of the present invention will be described in detail below with reference to the drawings.

In this example, a C e O 2 protective layer and a recording layer (composition = (I n
S b ) T e ), C e 0 2
An information recording medium (Sample A) having a cross-sectional structure in which a protective layer and an ultraviolet curing resin were sequentially laminated was formed.

The recording layer and the two C e O 2 films have a thickness of I
It was set as OOOA. A method of manufacturing the above information recording medium will be described below with reference to FIG.

A C e O 2 sputtering source was provided in a vacuum container, and the inside of the container was evacuated to 5×10-BTorr. Next A
``Gas was introduced and the overall pressure was adjusted to 5 x 10-3 Torr. Outer diameter 1 30 thoroughly cleaned as a substrate
As, a disk-shaped carbonate substrate with a plate thickness of 1.2 l is used, and while this substrate is rotated at 60 rpm, the amount of elemental spatter is detected by a monitor, and the power input to each spatter source is controlled, and the overall A protective layer was deposited on the substrate by depositing a C e O 2 layer on the substrate until the film thickness was IOOOA.

Next, the above CeO. A recording layer was laminated on the protective layer. The sputtering source was changed to In, Sb, Te, and the inside of the container was 5 x 1.
It was evacuated to 0-6 Torr. Next, A ``Introduce gas 5
The total pressure was adjusted to X 10-3 Torr. A disk 60 ``p'' on which a C e O Z film is laminated on the substrate.
- While rotating at
The power input to each spatter source is controlled, and the total film thickness is
A recording layer was formed by depositing InSbTe until it reached OOOA.

Next, by the same method as described above, C e
A 1000A1a layer of 0.02 protective film was applied. Furthermore, this C e
An information recording medium of Sample A was obtained by overcoating the UV curable resin on the 02 protective film using a spin coater.

In addition, as a control experiment, an information recording medium (Sample B) was formed in which the inorganic protective layer was made of SiO2 and the other layer structure, layer thickness, and composition of each layer were completely the same as Sample A.

These two samples were set in a performance evaluation device (not shown), and the number of repetitions of recording and erasing was evaluated.

(1) The performance evaluation device was set to the one-track jump mode, and one track was irradiated three times with a 121 V continuous wave laser beam to initialize the InSbTe grade #jl8I in that portion.

At this time, the rotation speed is 1800 rpm, and the position of one track is on the circumference with a radius of 50 m.

(2) 4MIIz at 20sv on one crystallized track
Recording was performed using a pulsed laser beam with a duty of 50%.

Next, play with 0.8 sw continuous wave laser light,
The C/N of the reproduced signal was measured using a spectroanalyzer.

(3) One track on which the above recording was performed was irradiated with a continuous wave laser beam of 12-V to perform erasing.

Next, play with a continuous wave laser beam of 0.8 sv,
The decrease (ceramic erasure rate) from the C/N determined by the DI was measured.

The following operations (2) and (3) were automatically repeated, and each time the C/N after recording and the erasure rate after erasing were measured.

Figure 5 shows the results. In the figure, the white marks are data related to the erasure rate, and the black marks are data related to the C/N value.

In Sample A, there is almost no change in C/N and erasure rate after 108 recording/erasing repetitions, whereas in Sample B, the results are similar to those in Sample A for up to 103 repetitions. Almost the same, but 104
After repeated repetitions, the erasure rate is close to O dB and hardly disappears, and the C/N also drops to 30 dB.

After performing the above test, the sample was examined under a reflection electron microscope at 1m (S).
Changes in the shape of the membrane were observed using EM). Observation is done using UV protection aS
A three-layer structure consisting of an inorganic protective film and a recording film was formed by peeling off the film. As a result, in sample A〉, the portion where the recording pit was formed was deformed into a convex shape of about 10 OA, while in sample B〉, the film itself was destroyed and deformed by 300 OA.

As explained above, the phase change erasable optical disk using C e 0 2 as an inorganic protective film material according to the present invention is stable against repeated recording and erasing by laser pulse irradiation without deforming or destroying the recording medium. can maintain its characteristics. Furthermore, in this example, as shown in FIG.
Exactly the same effect can be expected even if C e 0 2 is provided only on the lower or upper side.

FIG. 4 is a cross-sectional structural diagram of a sputtering apparatus used to manufacture the information recording medium of the present invention, and FIG. FIG. 3 is a characteristic diagram comparing recording and erasing repetition characteristics when S i 0 is set to 2.

11...Substrate 12...Recording layer 13...Inorganic protective layer (C e O Z layer)
14...Organic substance protection layer Figure 1 Figure 2 Agent Patent attorney Nori Chika Ken Yudo Yamashita 1 3rd illustration Hanpo gone, tcOa! (times) Figure

Claims (1)

[Claims] In an information recording medium provided with a recording film on a substrate that undergoes a selective and reversible phase change between phases with different atomic arrangements by irradiation with a light beam, the recording film may be located between the recording film and the substrate, and/or An information recording medium characterized in that a protective film made of CeO_2 is provided on the film.