JPH0252330B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical memory disk used in an optical information processing device.

As shown in Fig. 1, this optical memory disk is made by focusing and irradiating laser light with a lens from the disk-shaped transparent substrate 1 side, locally melting and sublimating the recording layer 2, and forming a diameter of about 1 μm. In this method, small holes, so-called recording pits, are formed, and information is reproduced by changing the reflectance depending on the presence or absence of the recording pits.
In this example, two disc-shaped transparent substrates 1 each having a recording layer 2 attached thereto are prepared, the recording layers 2 are made to face each other, and spacers 3 are provided at the inner and outer peripheral ends of the transparent substrates 1. , 4 are inserted to provide a hollow region 5, and an adhesive 6 is applied between the transparent substrate top 1 and the spacers 3 and 4 to form a bonded structure.

With this structure, the recording layer 2 is sealed and sealed from the outside air, preventing deterioration due to the influence of moisture, etc.
In addition, in contrast to a recording medium with a recording layer 2 exposed to the outside air, this example in which recording and reproduction is performed from the side of the transparent substrate 1 is designed to reduce the effects of dirt, dust, scratches, etc. that adhere to the surface of the recording layer 2 by 1,000,000 minutes. As a result, the stability of the recording layer 2 and the reduction of the error rate during recording and reproduction are reasonably satisfied.

However, such optical memory disks have the following drawbacks regarding recording sensitivity, stability, and signal contrast. That is, regarding recording sensitivity, during recording, 20 to 30% of the amount of laser light passes through the recording layer 2 and is not effectively used for forming recording pits. Since it is directly adhered to the substrate, it has the disadvantage that it is easily affected by scratches and irregularities of several micrometers on the substrate surface.In addition, the relationship between recording sensitivity and stability and signal contrast is When the film thickness of recording layer 2 is made thinner to improve sensitivity, (R ₀ - R ₁ )/(R ₀ + R ₁ ) (where R ₀ and R ₁ are obtained from the unrecorded area and the recorded area, respectively). The signal contrast expressed by If the thickness of the layer 2 is increased, the recording sensitivity decreases, which are contradictory properties, so it has been impossible to achieve good conditions for both. Furthermore, during reproduction, noise is generated due to disturbance in the contour shape of the recording pit, which has the disadvantage of lowering the S/N ratio.

The purpose of the present invention was to eliminate the above-mentioned drawbacks, and in order to achieve that purpose, the present invention provides a method for disposing metal phthalocyanine, chalcogen elements, Bi, In, Pb, Cd, etc. on a transparent substrate. Sn, As
Contains 2 to 20 atomic% of at least one selected from the following in a dispersed state, and has a particle size of 1500 to 3000 Å
a first layer consisting of an organic polymer film having a film thickness of
Contains 10 to 80 atomic% of at least one selected from Ag, Al, Au, Pt, Cu, Cr, Ni, Rh, and chalcogen elements in a dispersed state, and 500 to 80 atomic%
The second layer consists of an organic polymer film with a thickness of 2000 Å.
The optical memory disk is characterized in that a convex portion is formed on the second layer by sequentially depositing the second layer and irradiating the second layer with laser light from the transparent substrate side.

Fig. 2 shows the main parts of the optical memory disk according to the present invention, and a and b in the figure show the state before and after irradiation with laser light, respectively, and the overall structure is in the shape of a disk as shown in the figure. Two transparent substrates 1 are prepared, and as shown in FIG. 1, each layer is made to face each other and joined through a spacer to form a shielding and sealing structure.

On the disc-shaped transparent substrate 1, a first layer 7 made of an organic polymer film containing metal phthalocyanine, etc.;
Second layer 8 consisting of an organic polymer film containing Ag, etc.
and are applied sequentially. The thickness of the first layer 7 is selected to be 1500 to 3000 Å, and the content of dispersed metal phthalocyanine etc. is set to 2 to 3000 Å.
By selecting 20 atomic %, the first layer 7 has light absorption properties for the wavelength of the laser beam used.
In addition, the second layer 8 is designed to have a film thickness of 500 to 2000 Å and a content of dispersed Ag or the like to be 10 to 80 atomic%, so that the second layer 8 mainly reflects the laser beam. properties and secondarily absorbability.

The laser beam is irradiated from the disk-shaped transparent substrate 1 side, and since the first layer 7 has a light-absorbing substance dispersed therein, about 10% of the light is absorbed in the first layer 7 and converted into heat. converted. This heat generates gas from the organic polymer film of the first layer 7 and releases it to the next second layer 8 side. Then, the released gas is transferred to the second layer 8
is lifted to form a convex portion 9 as shown in FIG. 2b. When forming this convex portion 9, the second layer 8
contains substances such as Ag that are dispersed inside it and secondarily absorbs the laser light that passes through the first layer and generates heat, which softens the organic polymer film. This reduces the force applied to lift the second layer 8 and promotes the formation of convex portions.
In addition, the inclusions such as Ag, which are mainly light-reflective, contained in the second layer reflect much of the laser light that has passed through the first layer and send it back to the inclusions, such as metal phthalocyanine, in the first layer. Therefore, the laser beam can be effectively absorbed by the contents of the first layer. Furthermore, since the first layer 7 is composed of an organic polymer film as a base material, it is possible to prevent thermal diffusion when substances such as metal phthalocyanine contained in each layer absorb laser light and generate heat. . By forming convex portions corresponding to conventional recording pits in this manner, the recording sensitivity of the optical memory disk can be improved. Such convex portions 9 of the second layer 8 are similar to conventional recording pits,
It is used as an information record.

In order to increase the signal contrast when reproducing information, in the present invention, the film thickness of the first layer 7 is selected so that the reflectance due to the light interference effect is maximized in the unrecorded state, and the thickness of the second layer 8 is The light is reflected mainly by dispersing a substance such as Ag that is reflective to laser light. After recording, the distance between the second layer 8 and the transparent substrate 1 increases by the amount of deformation of the convex portion 9 shown in FIG. The reflectance shifts from its maximum value and decreases. Furthermore, by forming the convex portions 9 on the second layer 8, the incident laser beam is scattered at the convex portions 9 as shown in FIG. 3, and the amount of returning light is reduced, so that the reflectance after recording is is considerably lower than the reflectance at the time of unrecording, and the signal contrast can be increased as a whole, and as a result, the S/N ratio during reproduction can also be improved. As mentioned above, the optical memory disk of the present invention can record,
It has an excellent effect during regeneration, but another effect is that since the base materials of the first layer 7 and the second layer 8 are both composed of organic polymer films, their mutual adhesion is good and the formation of convex portions is prevented. At this time, it is possible to prevent cracks from forming at the interface, and since the contained substances are isolated from the outside air, deterioration due to oxidation etc. can be prevented. In this way, deterioration of the recording layer can also be prevented. Note that the maximum reflectance may be as large as possible.

Hereinafter, specific examples of the present invention will be described.

As the disc-shaped transparent substrate 1, soda lime glass with a thickness of 1.2 mm was used, which had undergone ultra-precision processing, polishing, and cleaning steps.

The first layer 7 is made by glow-discharging ethylene gas at a gas pressure of 1×10 ^-3 Torr using a high frequency power of 100 W at 13.54 MHz, and at the same time depositing copper phthalocyanine as a material that absorbs a semiconductor laser with a wavelength of 830 nm. , was deposited on a soda lime glass substrate 1.

Since high frequency power and gas pressure are related to the adhesion rate of the polymer film on the glass substrate, it is desirable to increase the high frequency power and gas pressure from the viewpoint of shortening the film formation time, that is, increasing work efficiency. As the high-frequency power is increased, the hydrogen content in the ethylene polymer film decreases, forming a film containing a large amount of carbon, resulting in a decrease in recording sensitivity. On the other hand, if the high frequency power is reduced, the discharge becomes unstable, which is not suitable for film formation. The high frequency power should be 50 to 200W from the viewpoint of polymer film coverage, recording sensitivity, discharge instability, etc.
It is desirable that the range is 80~
It is preferable to set it as 150W. Gas pressure is also related to the instability of the discharge, and if the gas pressure is too high or too low, the discharge will become unstable, so it is recommended to form a film at an appropriate gas pressure in the range of 1 to 10 ^-3 Torr. is desirable.

The content of copper phthalocyanine in the ethylene polymer film (first layer 7) is about 5 atomic%. This increase in content leads to an increase in the light absorption rate of the first layer 7 and improves recording sensitivity. but,
If this content is increased excessively, small holes will be formed in the first layer 7 due to laser beam irradiation, making it impossible to perform recording using the convex portions 9, or increasing the reflectance of the first layer 7. , leading to deterioration of signal contrast. Conversely, if this content is too small, the sensitivity will be insufficient. Therefore, the content of copper phthalocyanine is preferably within the range of 2 to 20 atomic%.
An ethylene polymer film containing 5 atomic% copper phthalocyanine (first film) was placed on a soda lime glass substrate.
At the stage when layer 7) was applied, the reflectance determined from the soda lime glass substrate side was about 9%.
The film thickness of the first layer 7 is determined so that the light interference effect is near the maximum in order to increase the signal contrast, and is approximately 2400 Å in this example. The preferred range of this film thickness is 1500 to 3000 Å. In this way, by selecting the content of copper phthalocyanine and the thickness of the ethylene polymer film, the first layer 7
becomes absorbent to laser light.

Next, an ethylene polymer film (second layer 8) containing Ag (silver) was deposited on the first layer 7 by the same film forming method as described above. Ag was dispersed in the ethylene polymer film by vapor deposition, and the Ag content was approximately 60 atomic%. The thickness of this second layer 8 was approximately 1000 Å.
The Ag particles promote reflection and some absorption of light, and the reflected light enters the first layer 7 again and is effectively used, contributing to improving the recording sensitivity and increasing the reflectance of the second layer 8. By increasing the signal contrast, the signal contrast can be increased. Further, some of the absorbed light is converted into heat, which promotes softening of the second layer 8 and facilitates the formation of the recording convex portions 9. Since the Ag content affects light reflection and absorption, it is closely related to recording sensitivity and signal contrast, and the preferred content is 10 to 80 atomic %. The reason for this is that when the amount is less than 10 atomic percent, the signal contrast decreases, and when it is more than 80 atomic percent, the signal contrast is improved, but the formation of the convex portion 9 is inhibited. The thickness of the second layer 8 is related to the formation of the convex portions 9; if it is too thin, the convex portions 9 will not form and small holes will be formed; on the other hand, if it is too thick, the convex portions 9 will be formed. Therefore, the preferred film thickness is 500 to 2000 Å. By selecting the Ag content and the thickness of the ethylene polymer film in this manner, the second layer 8 becomes primarily reflective and secondarily absorbent with respect to the laser beam.

A semiconductor laser beam with a wavelength of 830 nm was used for recording and reproduction, and was focused by an objective lens to form a laser spot with a diameter of 1.6 μm on the surface of the recording medium, with a power of 6 mW during recording and 0.6 mW during reproduction. In that case, the recording sensitivity for forming the convex portions 9 depends on the thickness of the first layer 7 and the content of copper phthalocyanine dispersed in the first layer, and also on the thickness of the second layer 8. , varies depending on the Ag content dispersed in the second layer, but in this example, by making the selections described above, a laser pulse width of 30 ns was obtained, compared to approximately 50 ns when copper phthalocyanine was not included. It was confirmed that it was high. Furthermore, in this example, the reflectances during unrecording and recording were approximately 48% and 19%, respectively, and the signal contrast was a good value of 0.43. Furthermore, in this example, the time required for the reflectance to decrease by 30% from the initial value in a humidity test in an environment of 60°C and 90% is as follows: It was confirmed that it has excellent long-term stability as it is about 60 times longer. In the conventional comparative example, an increase in the noise level was observed due to disturbance at the edge of the recording hole, but in this example, since the convex portion 9 is continuously curved, there is a difference between the unrecorded part and the recorded part. Each noise level hardly increases,
The noise level due to the mutual difference is not detected,
It was possible to improve the S/N ratio.

The present invention is not limited to the materials listed in the above embodiments, but materials such as quartz glass, vinyl chloride resin, vinyl acetate resin, acrylic resin, methacrylic resin, polyester resin, nitrocellulose, polystyrene resin, polypropylene resin, polyamide can be used as the transparent substrate. Resin, polycarbonate resin, epoxy resin, etc. may also be used. Next, as the first layer 7 having light absorption and light interference properties, metal phthalocyanine such as lead phthalocyanine, chalcogen elements such as tellurium (Te), selenium (Se), and sulfur (S), or bismuth (Bi), indium (In), lead (Pb),
Cadmium (Cd), arsenic (As), tin (Sn) alone, their compounds, or their oxides are incorporated into olefin compounds other than ethylene polymers, benzenes, polyesters, polystyrene, acrylic polymers, cellulose acetate, Organic polymer films such as cellulose nitrate, brominated polyhydroxystyrene, chlorinated rubber, SiO, and SiO ₂ may also be used. Next, as the second layer 8, aluminum (Al), gold (Au), platinum (Pt), copper (Cu), chromium (Cr), nickel (Ni), rhodium (Rh), chalcogen elements, and An organic polymer film similar to the first layer 7 containing a compound or an oxide thereof may be used. In addition, although vacuum evaporation and glow discharge were mentioned as film forming methods in the examples, depending on the material used, direct current sputtering, high frequency sputtering,
reactive sputtering, ion plating,
Ion cluster, plating, CVD, codeposition, vapor phase growth, casting, doctor blade, magnetron sputtering or spraying, roller coating, dipping. A coating method such as spinning may also be used.

In addition, in the example, a semiconductor laser with a wavelength of 830 nm was used as a laser light source, but the wavelength used was 830 nm.
In this case, the thickness of each layer and the blending ratio of the light-absorbing substance can be determined functionally depending on the wavelength.

As described above, according to the present invention, it is possible to prevent deterioration of the recording layer, improve the recording sensitivity, improve the signal contrast, and further improve the S/N ratio during reproduction.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional optical memory disk.
FIG. 2 is a sectional view of a main part of the optical memory disk according to the present invention, and FIG. 3 is a sectional view showing scattering of incident laser light. 1... Disc-shaped transparent substrate, 7... First layer, 8...
Second layer, 9... Convex portion.

Claims (1)

[Claims] 1. On a transparent substrate, at least one selected from metal phthalocyanine, chalcogen element, Bi, In, Pb, Cd, Sn, and As is dispersed.
A first layer consisting of an organic polymer film containing 20 atomic% and having a film thickness of 1500 to 3000 Å, Ag,
Contains 10 to 80 atomic% of at least one selected from Al, Au, Pt, Cu, Cr, Ni, Rh, and chalcogen elements in a dispersed state, and has a diameter of 500 to 2000 Å
A second layer made of an organic polymer film having a film thickness of memory disk.