JPH0523197B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an optical recording medium on which information can be recorded and reproduced using a laser beam, and more specifically to an optical recording medium that forms bits on a thin film by the thermal action of a focused laser beam. It is related to recording media. (Prior Art) A write-once optical disk memory that records and reproduces information on a medium using a laser beam has an excellent feature as a large-capacity recording device because of its high recording density. As a recording medium for such a write-once optical disk memory, low melting point metals such as Te and Bi or alloys containing them are used (for example, Japanese Patent Publication No. 15483/1983). (Problem to be solved by the invention) However, low melting point metals (especially Sn, which has high sensitivity)
could not be put to practical use due to the poor quality of recording and reproduction signals. An object of the present invention is to provide an optical recording material for use in an optical recording medium that has high recording sensitivity and good signal quality. (Means for Solving the Problems) The optical recording material of the present invention is an optical recording material used for the recording layer of an optical recording medium, which contains tin in a volume percentage of 30% or more, and in addition, nickel oxide is contained in a volume ratio of 30% or more. rate of 20%
It is characterized by containing the above. (Function) The recording film according to the present invention contains tin with a volume fraction of 30% or more and nickel oxide with a volume fraction of 20% or more as an essential component. Tin has high recording sensitivity because it is a semimetal with a low melting point. However, the surface properties are poor due to the crystallinity of the material, so
Unrecorded noise is a big problem, and it cannot be put to practical use. The present inventors have found that the surface properties of the recording layer are significantly improved by incorporating 20% or more of nickel oxide in volume percentage in tin,
This has led to the present invention. The film layer of the recording layer has a recording sensitivity of about 100 to 1000 Å.
It is desirable from the point of view of signal quality, particularly 150 to 500 Å. The recording layer has sufficiently excellent optical recording medium characteristics even if it is a mixture of tin and nickel oxide, but in order to further improve the weather resistance or adjust the reflectance to a predetermined value, it is necessary to contain a third substance, etc. You may let them. Third substances include carbon, aluminum, titanium,
One or more of chromium, iron, cobalt, nickel, copper, zinc, germanium, zirconium, niobium, molybdenum, rhodium, palladium, silver, tantalum, tungsten, platinum, and gold is desirable. Most of these substances are effective at a volume ratio of about 10 to 15% or less, but depending on the substance, they may be contained in a larger amount. The figure is a sectional view showing an example of an optical recording medium. 1
2 represents the substrate, and 2 represents the recording layer. Although various substrates can be used, synthetic resin, glass, and porcelain are generally preferred. Examples of synthetic resins include acrylic resins such as polymethyl methacrylate, polycarbonate, posaetherimide, polysulfone, epoxy resins, and vinyl chloride resins. The substrate may be provided with a heat insulating layer or a smoothing layer thereon. The shape of the substrate can be a disk, a sheet, or a tape. Information is recorded on the recording layer by forming bits on the recording layer. In a disk medium using a disk-shaped substrate, bits are recorded so as to form a large number of concentric or spiral tracks. In order to accurately record a large number of tracks at regular intervals, light guide grooves are usually provided on the substrate. When light enters a groove about the diameter of the beam, it is diffracted. As the beam center shifts from the groove, the spatial distribution of the diffracted light intensity changes, and a servo system can be configured to detect this and direct the beam to the center of the groove. Usually, the width of the groove is set to 0.3 to 1.2 μm, and the depth is set to a range of 1/12 to 1/4 of the wavelength of the recording/reproducing laser used. Example 1 Examples of the present invention will be described below. An acrylic resin disk substrate with a guide groove having an inner diameter of 15 mm, an outer diameter of 120 mm, and a thickness of 1.2 mm was placed in a vacuum deposition apparatus, and the atmosphere was evacuated to 2×10 ^-5 Torr or less. As evaporation sources, Sn was placed in a resistance heating boat and NiO was placed in an electron beam heating crucible. A recording layer was formed on the disk substrate by co-evaporation while controlling the deposition rate of each deposition substance using a crystal resonator type film thickness monitor. Table 1 shows the substrate incident reflectance (wavelength
8300 Å), shows how the unrecorded noise level and signal-to-noise ratio (C/N) change. Here, the wavelength of the semiconductor laser used for recording and reproduction is 8300
Å, the signal frequency is 1.2MHz, and the bandwidth is
The linear velocity of the medium is 30KHz and 5m/sec. The reflectance tends to decrease as the NiO content increases, and if the tin content is less than 30%, the reflectance does not reach 10%, which adversely affects the focus servo and poses a practical problem. The unrecorded noise level decreased sharply by adding NiO, and
% or more of NiO reaches the practical level. C/N is poor when the NiO content is less than 20% due to large noise, and Sn
If the content is less than 30%, the C/N is poor due to insufficient recording sensitivity. Therefore, if the volume content of NiO is 20% or more and the volume content of Sn is 30%,
% or more is a practical composition range. Examples in which the film thickness is other than 350 Å are shown in Table 2. It can be seen that in this case as well, the above composition range is favorable.

【table】

【table】

[Table] Example 2 Sn was put in a resistance heating boat, NiO was put in an electron beam heating crucible, Cr was put in another electron beam heating crucible, and the volume percentage was 60%, 35%,
A recording layer was formed on the acrylic disk substrate by codeposition at 5%. Recording and reproduction were performed in the same manner as in Example 1, and good recording was achieved with a C/N of about 50 dB. Example 3 Sn was put in a resistance heating boat, NiO was put in a crucible for electron beam heating, and Ni/Cr alloy with a ratio of 80:20 by weight was put in another crucible for electron beam heating, and the volume ratio was 55%. A recording layer was formed on the acrylic disk substrate by co-evaporation with , 40% and 5%. When recording and reproducing in the same manner as in Example 1, the C/N was approximately
Good recording was achieved at 50dB. Example 4 Sn was put into a boat for resistance heating, NiO was put into a crucible for electron beam heating, and Fe/Cr/Cr was put into another crucible for electron beam heating in a ratio of 70:25:5 by weight.
A recording layer was formed on a polycarbonate substrate by co-depositing an Al alloy at a volume ratio of 55%, 40%, and 5%. Recording and reproduction were performed in the same manner as in Example 1, and good recording was achieved with a C/N of approximately 49 dB. (Effects of the Invention) As is clear from the above examples, the present invention provides an optical recording material with high recording sensitivity and good signal quality.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an optical recording medium. In the figure, 1 indicates a substrate and 2 indicates a recording layer.

Claims (1)

[Claims] 1. Optical recording material used in the recording layer of an optical recording medium, characterized by containing tin in a volume percentage of 30% or more, and additionally containing nickel oxide in a volume percentage of 20% or more. material.