JPS62281133A - Optical disk - Google Patents

Abstract

PURPOSE:To easily make the erasure of a bit of information impossible by providing a substrate layer formed with a material forming a bubble at a heating part by heating due to at least the radiation of a light beam, and a recording layer which is laminated on the substrate, and on which the recording and the erasure of the bit of information can be performed repeatedly. CONSTITUTION:A substrate layer 2 consisting of the material which is laminated on a substrate 1, and forms the bubble at the heating part by the heating due to at least the radiation of the light beam, and a recording layer 3 which is laminated on the substrate layer 2, and on which the recording and the erasure of the bit of information can be performed repeatedly, are provided. In case of making impossible the erasure of the bit of recorded information recorded on the recording layer 3, by projecting the light beam on the recording layer 3, by projecting the light beam on the substrate layer 2 part corresponding to the recording part of the recording layer 3, and heating the part, a bubble 7 is formed at the substrate layer of the heated part, and the bubble remains as it is after being cooled. The reproduction of the bit of information can be easily performed according to a difference between the formed part, and unformed part of the bubble 7. In this way, it is possible to make the erasure of the bit of information impossible.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to an optical disc on which information is optically recorded.

(Prior Art) Optical disks have attracted attention as high-density, large-capacity recording media, and are widely used as image information files, external memories for electronic computers, and the like.

This optical disc has a read-only type and a write-once type (DRAW: Direct Read A).
There are two types: one type called ``retrieval'' and the other type, which can be used to record information by manipulating information.
Erasable types are becoming more popular due to their convenience.

As erasable type optical discs, magneto-optical types, phase change types, etc. are known depending on the recording/erasing method. For example, the magneto-optical type records information by changing the perpendicular magnetization direction of an amorphous rare earth-transition metal alloy thin film between recorded and unrecorded areas, and calculates the difference in the Kerr rotation angle of reflected light from these areas. Detecting and reproducing information.

In addition, the phase change type is described in 9. Recording is performed by changing the phase of the layer from crystal to amorphous, and the difference in reflectance between the recorded amorphous part and the unrecorded crystal part is read and reproduced. are doing.

By the way, when using an erasable optical disc such as the one mentioned above, the optical disc is There is also information that would be problematic if erased, such as the registration of a code unique to the user and address information inside the disc.

Conventionally, as an attempt to make information recorded on an erasable optical disk non-erasable, there has been a method of irradiating a powerful laser beam to form a hole in the recording portion of the recording layer. However, in general, optical discs are provided with protective layers made of SiC or the like on both upper and lower surfaces in order to prevent oxidation, deterioration, etc. of the recording layer, making it difficult to form holes. Further, there is a problem in that increasing the output of the Radhe beam to form the hole exceeds the output of a general semiconductor laser, which is 30 to 501 RW.

(Problems to be Solved by the Invention) As described above, it is difficult for conventional erasable type optical discs to have a function that makes it impossible to erase recorded information.

The present invention is based on the above-mentioned circumstances, and its object is to provide an optical disc of this type in which information can be easily erased.

[Structure 1 of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention provides a material that is laminated on a substrate and forms a bulb in the heated portion by heating by at least irradiation with a light beam. It has a formed base layer and a recording layer that is laminated on the base layer and allows information to be recorded and erased repeatedly.

(Function) When the recording layer is of a magneto-optical type, information is recorded and erased by reversibly making the perpendicular filtration direction of the recorded portion to the opposite direction to the unrecorded portion and to the same direction.

Further, when the recording layer is of a phase change type, information is recorded and erased by reversibly changing the phase of the recording portion between amorphous and crystalline states.

On the other hand, in order to make it impossible to erase the recorded information recorded on the recording layer, if a light beam is irradiated and heated on the underlayer part corresponding to the recorded part of the recording layer, bubbles will be formed in the underlayer at this heated part. Ru. This bubble remains in its shape even after cooling.

Information can be easily reproduced due to the difference in reflectance between the bubble-formed portion and the non-bubble-formed portion.

(Example) An embodiment of the optical disc according to the present invention will be described below.

FIG. 1 shows a cross-sectional configuration of a first embodiment (Example-1) of an optical disc according to the present invention, and this optical disc has the following features:
The substrate 1, the underlayer 2, the first F4 retaining layer 4a, the recording layer 3, the second protective layer 4b, and the anti! 31-5 are laminated in order to form a disk shape.

The substrate 1 is made of acrylic, epoxy, polycarbonate (P
C) A transparent substrate made of an organic resin material such as polyimide or polyamide, glass, AQ203, ZrO2, or the like.

The base Fi2 is a plasma polymerized film, and includes CI-14 (methane), C21 (a (ethane), C3H8 (propane))
, C2H4 (Ejiren), S! 02.1-14 (monosilane) or the like alone or in a mixture, or in these gases alone or in a mixture thereof.
It is formed by mixing gases that form hydrophilic functional groups such as 03, NH3, CO2, and 802 (CN)2.

The reason for mixing the gas that forms these hydrophilic functional groups is to increase the affinity with the protective layer 4a and the recording layer 3 formed of inorganic materials and to prevent peeling.

The protective layer 4a and the second M retention layer 4b of Vyl are 3i0
An inorganic dielectric material such as 5i02 or 5i02 is formed by sputtering or vapor deposition to a thickness of 19 x 50 to 5000 amps.

these! ! 1i4a and 4b prevent the formation of holes due to oxidation of the recording layer 3 and evaporation of the layer 3 during light beam irradiation.

The recording layer 3 of this example is a thin film having magnetic anisotropy perpendicular to the substrate 1, and includes Tbj"cCo, Gd Tb
It is selected from various materials such as amorphous rare earth-transition metals such as Fe, GdFeCo, etc. The film thickness is several tens of amps
~ several thousand A.

The reflective layer 5 is made of metal such as Cu, Δhair, Au, etc. and has a thickness of 1000 mm.
Laminated at about A. This reflective layer 3 allows all of the light that passes through the recording layer 3 without being reflected from the laser beam irradiated from the substrate 3 side to be reflected onto the substrate 1ff1l, so that the reflected light from the recording layer 3 and the reflected light from the reflective layer 5, and the multiple interference effect greatly improves the recording sensitivity.

In the optical disc having the above configuration, information is recorded by first focusing a laser beam modulated according to a recording information signal on the recording layer 3, which has been magnetized in a certain direction in advance, as shown in FIG. The temperature of the irradiation bit section 6 is raised, and then an external magnetic field 1-1 opposite to the magnetization direction of the optical disk is applied.

When the temperature of the irradiated bit portion 6 reaches the Curie point or above, the magnetization direction of the irradiated bit portion 6 of the recording layer 3 is reversed, and this reversed state is maintained even at room temperature, thereby recording is performed.

To reproduce recorded information, a reproduction laser beam is irradiated from the substrate 1 side, and the difference in the Kerr rotation angle between the recorded bit part and the unrecorded part of the light reflected from the recording layer 3 is detected to determine the light intensity. This is done by measuring the

In order to erase the recorded information, a magnetic field is applied to the initial magnetization direction of the recording layer 3 (the magnetization direction of the unrecorded part), and the recorded bit part to be erased is heated to more than one Curie point to change the magnetization direction. Just go back.

On the other hand, in order to make it impossible to erase the recorded information, as shown in FIG.
Bubbles 7 are formed in the base layer 2. Once this bubble 7 is formed, it becomes possible to read the information efficiently using a reading device similar to that used for conventional read-only type optical discs.

FIG. 6 shows a cross-sectional configuration of another embodiment (Example 2) of the optical disc according to the present invention, and this optical disc consists of a substrate 1, an underlayer 2, a recording layer 3, and a protective layer 4 laminated in this order. It is formed on a disk.

The substrate 1, base layer 2, and protective layer 4 have the same structure as in the first embodiment.

The recording layer 3 is made of a metal or semiconductor material that undergoes a reversible phase transition between crystal and amorphous when heated, for example, by laser beam irradiation.

Its material is selected from various materials such as Te1TeGe and InSb.

In the above configuration, information is recorded by, for example, irradiating the recording layer with a laser beam modulated by the recorded information and quickly heating and cooling the recording layer, so that the 8th layer in the laser beam irradiated area changes from crystal to amorphous, for example. This is done by undergoing a phase transition to .

Further, erasing of a record is performed by irradiating the recorded amorphous portion with an erasing laser beam to heat it, and then slowly cooling it to transform it back into a crystal. Furthermore, information is reproduced by irradiating a reproduction laser beam and reading the difference in reflectance between the amorphous portion where information is recorded and the crystalline portion where information is not recorded.

On the other hand, in order to make it impossible to erase the recorded information, as in the previous embodiment, the output and pulse width of the sea beam 11 are increased to illuminate the recorded bit area) and the bubble 7 is applied to the underlayer 2. All you have to do is form. This makes it impossible to erase the recording, and the recorded state can be stably maintained for a long period of time. Furthermore, information can be easily reproduced.

Hereinafter, specific examples will be explained.

(Example-1) A JJ board 1 made of PC64 resin was used, and a rotating table (not shown) was used.
The reaction vessel was evacuated, 3iH4 gas containing 196% CO2 was introduced, and a predetermined high frequency power was applied to the substrate 1 to form a plasma polymerized film (base layer 2) using the 3iH4 gas. Laminated.The film thickness is 1000
It was formed at 0Δ.

Next, a first protective layer 4 made of Sio is formed by sputtering.
A was laminated with a film thickness of 500 layers.

Also, the first protection midfielder! A 4 Tb Fe C on a
A photomagnetic film consisting of
was formed.

Next, on this recording layer 3, a second protective layer 4b made of SiO is laminated with a film thickness of 1 g and 500 Å, and on this protective layer 4b, a reflective layer 5 made of ΔF is laminated with a thickness of 1000 Å. The optical disc shown in the figure was created.

Top) Output (I
llW) and a laser beam with different pulse widths were irradiated to investigate its characteristics. In this case, the externally applied magnetic field was constant at 2000e.

As a result, as shown in FIG.
No change occurred, and no information could be recorded.

Furthermore, in the C region, the magnetization of the recording layer 3 was reversed and information could be recorded, and the recording could be erased by irradiation with an erasing laser beam with varying laser output and pulse width.

In this region C, no bubbles were generated in the base layer 2.

Furthermore, in the C region, the magnetization of the recording layer 3 is reversed and information can be recorded, and bubbles are formed in the underlayer 2, and these bubbles remain as they are even after cooling.

And territory 11i! The reproduction characteristics of B are: reflectance 30%, Kerr rotation angle 0.6 dec+, C/N ratio 50 d.
B (1,25MHz),! = nimeT kind u, l
Lf! I was able to do 7 things.

On the other hand, the base layer (Sit-I4+C○2 plasma polymerized film)
Both the sample on which No. 2 was formed and the sample on which no base layer 2 was formed were heated at a humidity of 65'C and a relative humidity of 90%.
An environmental test was conducted under RH to examine the change in reflectance (R/Ro).

As a result, as shown in FIG. 5, no change in the appearance of the recording layer 3 was observed even after 15 days had elapsed in the recording layer 2 having the underlayer 2 as shown by the solid line in the figure. On the other hand, the base G
With the number without J2, peeling occurs between the PC resin substrate 1 and the base layer 2, and the reflectance decreases, and after -15 days, the reflectance has decreased to about 40% of the initial reflectance RO. found.

(Example 2) A base layer 2 was formed by laminating a plasma polymerized film using CH4 gas to a thickness of 3000Δ on a substrate 1 made of PC resin.

Next, a 1n layer was deposited on the base layer 2 by dual simultaneous sputtering
The recording layer 3 made of In5oSb5o was formed with a thickness of 500Δ by adjusting the high frequency power applied to the target and the sb target.

Next, a protective layer 4 made of SiO was laminated to a thickness of 500 Å on the recording layer 3 by sputtering to obtain the optical disc shown in FIG. 4.

The optical disc thus formed was irradiated with a laser beam, and its characteristics were investigated by varying the output of the optical disc 11 and the pulse width.

As shown in FIG. 7, it was found that the cold W velocity after irradiation was relatively slow in the region, and InSb was crystallized, resulting in a decrease in the reflectance.

In addition, in the C region, the cooling rate of the recording layer is relatively fast, and the I
It was found that nSb was amorphous and the reflectance was upper bound.

Furthermore, in the CI region, CH4 plasma polymerized film (base layer)
It was found that bubble 7 was formed by gasification.

Therefore, in the optical disc of this example, it is clear that erasable information can be recorded in the C area and erased using AvA, and in order to make erasure impossible, it is sufficient to irradiate the C area with a laser beam. did. Note that no change occurred in the recording layer 3 in area C.

Next, the characteristics of this optical disk after repeated recording and erasing are determined by measuring the outputs and pulse widths of the radar beams for recording and erasing at 10 mW, 50 nscc, and 3111'v, respectively.
V, examined by 1μSQC.

As a result, as shown in Figure 8, an increase in reflectance was observed for the first 5 to 10 times, but after that it remained constant and 104
It was found that the reflectance remained stable even after repeated use.

[Effects of the Invention] As explained above, according to the optical disc of the present invention, since the base layer is laminated on the substrate to form bubbles by irradiation and heating with a light beam, information cannot be easily erased. be able to. Therefore, the range of applications of the optical disc is expanded and its convenience is improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the optical disc according to the present invention, FIG. 2 is a diagram explaining the information recording principle of the optical disc of FIG. 1, and FIG. 3 is a bubble formation of the optical disc of FIG. 1. 4 is a diagram showing the irradiation pulse width-output characteristics of the optical disk of the embodiment in FIG. 1, FIG. 5 is a diagram showing the results of the environmental test of the embodiment in FIG. 1, and FIG. 7 is a cross-sectional view showing the structure of an embodiment of the optical disc according to the present invention, FIG. 7 is a diagram showing the irradiation pulse width-output characteristics of the optical disc of the embodiment of FIG. 6, and FIG. 8 is a record of the embodiment of FIG. 6. , is a diagram showing erase repetition characteristics. 1... Substrate 2... Base layer 3... Recording layer 4.4a, 41)... Protective layer 5... Anti-0-J layer 7... Bubble

Claims (3)

[Claims] (1) A base layer made of a material that is laminated on the substrate and forms bubbles in the heated area when heated by at least light beam irradiation; and a base layer that is laminated on this base layer and allows information to be repeatedly recorded and erased. An optical disc characterized by having a recording layer. (2) The base layer is CH_4, C_2H_6, C_3
The optical disc according to claim 1, wherein the optical disc is a plasma polymerized film using a single gas of H_8, C_2H_8, C_2H_4, SiH_4 or a mixture thereof. (3) The base layer is CH_4, C_2H_6, C_3H
_8, C_2H_8, C_2H_4, SiH_4 alone or a mixture thereof with O_2, O_3, NH_
3. The optical disc according to claim 1, which is a plasma polymerized film made of a gas mixed with a gas forming a hydrophilic functional group such as CO_2, SO_2(CN)_2, etc.