JPS6120237A - Optical information recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information recording medium used for optical video discs, digital audio discs, electronic files, and the like.

[Prior art]

A laser beam is irradiated onto the thin film layer formed on the substrate,
Various optical information recording media have been proposed for recording and reproducing information.

For example, a light-absorbing recording thin film layer is formed using a low-melting point metal such as bismuth or tellurium, and this is locally irradiated with laser light to melt and evaporate the irradiated area to form recording pits, thereby recording information. There are known people who do this. However, such a record form! The drawback is that a high-power laser beam is required to form recording pits.

Furthermore, in Japanese Patent Laid-Open No. 58-127937, a recording medium of a different type from the above is disclosed. An example of this is shown in FIG. Here, 7 is a substrate, 8 is an intermediate layer, and 9 is a metal layer. When this recording medium is irradiated with a writing beam, the intermediate layer 8 is locally heated, and this portion expands or releases gas, thereby creating a protrusion lO on the metal layer 9. Information is recorded using the raised portions 10 as recording pits. During reproduction, a reading beam is irradiated onto this recording medium, this reflected light is detected, and the change in reflectance due to the raised portions 10 is utilized. Read information.

However, in the conventional example shown in Fig. 4, there was a drawback that the reproduction C/N ratio was low because there was little change in reflectance due to the raised portion lO and the contrast between the recorded and non-recorded areas was weak. .

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and allows recording with relatively small energy, and
An object of the present invention is to provide an optical information recording medium with a high reproduction C/N ratio.

[Structure of the invention]

The above objects can be achieved by the following optical information recording medium of the present invention. In other words, the optical information recording medium of the present invention includes a light-transmitting substrate, a light absorption layer formed on the substrate, whose temperature rises by irradiation with a predetermined light energy, and which is stable against this temperature rise; A light-transmitting layer formed on the light-absorbing layer and deforming or releasing gas as the temperature of the light-absorbing layer increases; and a light-transmitting layer formed on the light-transmitting layer, containing a metal, and reflecting a predetermined light. It has at least a reflective layer that can be used.

The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a basic embodiment of the optical information recording medium of the present invention. This recording medium has a substrate l
, light absorption layer 2, light transmission W! ! 3 and a reflective layer 4.

The substrate 1 is made of a light-transmitting material such as glass or acrylic resin.

The light absorption layer 2 is formed on the substrate 1, exhibits a high absorption rate for light of a specific wavelength, and functions to convert the optical energy of this light into thermal energy. When the light absorption layer 2 is locally irradiated with light of a specific wavelength, this energy conversion effect occurs substantially only in the irradiated portion. It is desirable that the light absorption layer 2 undergoes no physical or chemical changes within the temperature range raised by light irradiation. As a material for forming such a light absorption layer 2, T
i, Fe, Ni, Cr, Rh, V, Pt, Si
, Bi253°GeS, Sb2S3, CdSe,
Examples include CdTe.

The light-transmitting layer 3 is coated on the light-absorbing layer 2, and the light-absorbing layer 2 is locally heated by a local temperature rise, and only the heated portion undergoes deformation such as expansion or contraction, or gas It consists of a material that emits . Materials that can be used on the light transmitting layer 3 include organic compounds such as polystyrene, polycarbonate, polymethyl methacrylate, cellulose derivative silicone resin, and ABS resin, or, for example, PbF2,
Examples include fluorides, nitrides, and oxides with relatively low boiling points such as GaN, 5b03, TaO5, Na2O, and pbo. Among these materials, some organic compounds undergo deformation such as expansion and contraction when heated, while others release gas, and fluorides, nitrides, oxides, etc. mainly release gas when heated. .

The reflective layer 4 is formed by deformation or gas release of the light transmitting layer 3.
A raised portion is formed, and this raised portion functions as a recording bit to record information. This reflective layer 4 is formed on the light-transmitting layer 3 and has a hardness that can cause ridges due to the deformation of the light-transmitting layer 3 or the pressure of gas release, and the ridges may cause cracks or holes. It is necessary to have high ductility so as not to cause Furthermore, it is desirable that the material exhibits a reflectance of at least 50% for reproduction light for reproduction. Examples of materials for such a reflective layer include metals such as Au, Pt, Cu, and Ag, or mixtures of these metals and dielectrics such as SiO, 5iO2, TiO2゜Ta, 09, and MgF2. can.

The method for manufacturing this optical information recording medium will be briefly described below.

First, the material of the light absorption layer 2 is used at a predetermined position on a substrate l having an arbitrary size and shape by a film forming method such as various vacuum evaporation methods such as an ion blasting method or an electron beam method. The film is usually formed to a thickness of about 10 to 5000 Å.

Next, a film is formed on the light absorption layer 2 using the material for the light transmission layer 3 described above. If the material is organic, the light transmitting layer 3 is formed by a dipping method, a spin code method, a bar code method, a vapor deposition method, or the like. If the material is inorganic, the same film-forming method as the light-absorbing layer 2, such as vapor deposition, can be used. Although the thickness of the light-transmitting layer 3 varies depending on the material constituting the layer, the thickness of the reflective layer 4 may vary depending on the layer's deformation or gas release.
The minimum thickness required is such that it is possible to create ridges on the surface. If the material is organic, usually 100~
About 100OOA, usually 100-500 for inorganic materials
The thickness is about 0A.

Next, the reflective layer 4 is formed on the light transmitting layer 3 using the material for the reflective layer 4 as described above. This film formation can be performed by a vapor deposition method similar to that described above. The thickness of the reflective layer 4 needs to be such that local deformation can occur due to deformation of the light absorption layer 3 or gas release.

If the light transmitting layer has a thickness as described above, it is usually 10
The configuration for recording and reproducing information on this optical information recording medium, which is preferably for about 0 to 1000 people, will be described below.

Laser light, which is recording light, is irradiated from the side of the recording medium having the substrate l. In the portion irradiated with the laser light of light absorption e2, light energy is converted into natural energy, and the temperature locally rises. Due to this temperature rise, the light transmitting layer 3 is also locally heated from the side in contact with the light absorbing layer 2, causing deformation or gas release in that part, and causing the second
As shown in the figure, the reflective layer 4 is raised to form recording bits.

The recorded information is reproduced by irradiating the recorded bit with reproduction light and detecting the difference between the reflectance of the reflected light and the reflectance of the reflected light on which no recorded bit is formed. At this time, the power of the laser used for readout can be sufficiently lower than that for recording, so the recording light and the playback light that are not recorded by the laser light used for readout are usually Uses laser light.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the optical information recording medium of the present invention. This recording medium has an air sandwich structure in which a protective substrate 6 is bonded with a spacer layer 5 in between to protect the recorded bits recorded on the reflective layer 4 of the recording medium shown in FIG. be. This protective substrate 6 can be made of glass, metal, plastic, or the like.

〔Effect of the invention〕

The optical information recording medium of the present invention enables highly sensitive recording with less energy than conventional optical information recording media. Furthermore, it has become possible to improve playback characteristics.

Next, specific examples of the optical information recording medium according to the present invention will be shown, and the present invention will be further explained in detail.

[Example 1] G was deposited on a disk-shaped glass substrate l by vacuum evaporation.
A film of eS was formed to a thickness of 500 Å to form a light absorbing layer N2. Thereon, a nitrocellulose film was formed as a light-transmitting layer 3 to a thickness of 500 Å by a dipping method. Reflection J on top of that! 54, Au film thickness 40O
A film was formed by vacuum evaporation. Record this R
A layer of reflection W! A protective substrate 6 made of glass was bonded with a spacer layer 5 in between to protect I4, and an optical information recording medium having an air sand inch structure as shown in FIG. 3 was prepared to protect the recording layer. This recording medium is 18QO
Recording was performed by irradiating a semiconductor laser with a wavelength of 820n+i while rotating at cpm. The laser power at that time was 5 mW on the surface of the recording medium, the spot was focused to a diameter of 1.2 μm, the recording frequency was 4 MHz, and the duty ratio was 50%. This is the recording medium surface.
When I played back with the setting set to W, a good signal was obtained.
The IN was 53 dB. When the recorded recording medium was left in an atmosphere of 45° C. and 95% RH for 500 hours and reproduced in the same manner, there was no decrease in CIN.

[Example 2] C was deposited on a disk-shaped glass substrate l by vacuum evaporation.
The light absorbing layer 2 was formed by forming a film of 150 Å in thickness. Thereon, a PbO film was formed as a light transmitting layer 3 to a thickness of 400 nm by vacuum evaporation. Thereon, a reflective layer 4 of Au was formed by vacuum evaporation to a film thickness of 1'740 OA.

In order to protect the reflective layer 4, which is a recording layer, a protective substrate 6 made of glass is bonded with a spacer layer 5 in between, and to protect the recording layer, an air sand inch structure is used for optical information as shown in FIG. Created a recording medium. When this recording medium was used for recording and reproduction in the same manner as in Example 1, a good signal was obtained and the C/N was 54 dB.

[Example 3] An optical information recording medium was produced in the same manner as in Example 1, except that the absorption layer 2 was formed to have a film thickness of 200A. Recording was performed using this recording medium in the same manner as in Example 1.
When played back, the C/N was 51 dB.

In this embodiment, when the reproduction light is irradiated, the reflectance R1 of the non-recorded area (that is, before recording), the reflective area R2 of the peripheral area of the recorded bit,
The reflectance R3 at the center of each recording bit was measured. The results are shown in Table 1.

[Comparative example]

Four types of conventional optical information recording media without a light absorption layer were formed in the following manner by varying the thickness of the intermediate layer. That is, first, 50% of nitrocellulose was used as the intermediate layer.
Films were formed on glass substrates by a dipping method so as to have four types of film thickness: 0OA, 100OA, +50OA, and 2000A.

Next, a film was formed on each intermediate layer by vacuum evaporation to an Auft film thickness of 400 layers, thereby forming four types of optical information recording media. R1, R2, and R3 of each of these recording media were measured in the same manner as in the example. The results are shown in Table 1.

A small R1 leads to an improvement in recording sensitivity, and
The larger 2/R1 or R3/R1 is, the larger the reproduction S/N ratio becomes. Comparing Examples and Comparative Examples, it can be seen that the optical information recording medium of the present invention has improved recording feel, direction, and reproduction characteristics compared to conventional media.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the optical information recording medium of the present invention, FIG. 2 is a schematic cross-sectional view showing the state of the recording medium shown in FIG. 1 after recording, and FIG. , is a diagram showing another implementation of the optical information recording medium of the present invention. FIG. 4 is a schematic cross-sectional view showing an example of a conventional optical information recording medium, and FIG. 5 is a diagram showing a reproduction light irradiation method for measuring reflectance in Example 3 and Comparative Example. . 1.7 Two substrates 2: Light absorption layer 3: Light transmission layer 4: Reflection layer 5 One layer of varnish spacer 6: Protective substrate 8 - Intermediate layer
9: Metal layer 10: Protuberance! +: Irradiation light for R' measurement 12: Irradiation light for R2 measurement +3: Irradiation light for R3 measurement Figure 1 Figure 2 Figure 3 Kazuko] Figure 4 Figure 5

Claims (1)

[Claims] a light-transmitting substrate, a light-absorbing layer formed on the substrate, whose temperature rises by irradiation with a predetermined light energy, and which is stable against this temperature rise; a light-transmitting layer that deforms or releases gas as the temperature of the absorption layer increases;
An optical information recording medium comprising at least a reflective layer formed on the light transmitting layer, containing metal, and capable of reflecting predetermined light.