JPH01196394A - Optical storage medium - Google Patents

Abstract

PURPOSE:To contrive higher sensitivity, environmental stability and contrast, by using carbon and nickel as main constituents. CONSTITUTION:An optical storage medium comprises a thin film of a storage material comprising carbon and nickel as main constituents, on a substrate. The film is provided by reactive sputtering, reactive vapor deposition, plasma CVD, photo CVD or the like. The storage medium is free of rising of peripheral parts of bits due simply to heat, and is free of lowering in C/N at the time of reproduction. The medium has a high contrast because of a large difference between the reflectance before recording and the reflectance after recording. Further, oxidation is prevented, ensuring stableness, and high absorption and reflection are obtained over the wavelength range of 370-800nm, so that a variety of lasers can be used for writing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical memory medium that can be used as a memory device, an optical disk, a document/image file, and the like.

[Prior Art] Conventionally, as a heat mode (melting, evaporation type) optical memory medium, metal thin films such as Al5Cr, Cu5Au, and Ni5Ti (Kogyo Shimbun, Kogyo Shimbun, April 1, 1987) have been used.
411 edition), or Te.

A chalcogenide vapor-deposited film such as a Te compound [M.

Tcrao, ct al: J, Appl, Phys.
50.6881 (1979) Ko, etc. are known. However, since the metal vapor deposited film has poor laser light absorption efficiency, it is necessary to use strong laser light and time (loo +
++W x l tt 5ee), the sensitivity is insufficient for recording at high speed rotation, and noise during reproduction tends to increase due to the swelling around the pits that occurs when bits are formed. Further, the chalcogenide vapor-deposited film has the disadvantage that it deteriorates due to heat, humidity, and the like.

As a phase change type optical memory, chalcogen evaporated HM [S, R.

0vshinsky;Appl, Phy's, Lett
, 18.254 (1971)], but it has the drawback that the change in reflectance during recording is about 10% and the contrast is small.

[Information] The object of the present invention is to provide a novel optical memory medium free from such drawbacks.

[Structure] In order to solve the above-mentioned problems, we have conducted repeated research and found that it is effective to use a material whose main components are carbon and nickel, which led to the present invention. .

That is, the present invention is an optical memory medium characterized by containing carbon and nickel as main components.

Further, the optical properties of the optical memory medium of the present invention are 370~
In the wavelength region of 800 nm, 0<R≦60 0<A≦65 0≦T<100 where R+A+T −100 R: reflectance, A: absorptance, T: transmittance.

The optical memory medium of the present invention has a thin film made of the above memory material formed on a substrate.

Film formation is by reactive sputtering, reactive vapor deposition, plasma CV
D. This can be done by photo-CVD or the like. Although the film thickness is not particularly limited, it is preferably in the range of 100 to 5,000 people, preferably 200 to 5,000 people. The composition of the film is preferably 5 to 95% carbon, preferably 20 to 80%, and 5 to 9596 nickel, preferably 20 to 8096 nickel.

By applying sufficient energy (approximately 400° C.) to oxidize nickel to the film as it is formed (before recording), the reflectance of the film is significantly reduced. By applying this principle, it becomes possible to form and reproduce bits using laser light.

There are no particular restrictions on the material of the substrate on which the memory material of the present invention is formed, and various plastics (for example, polymethyl methacrylate, polycarbonate, etc.), glass,
It may be made of ceramic, metal, etc. Furthermore, a preformat for address signals and a pregroove for guide grooves may be formed on the surface of the substrate. The shape of the substrate may be arbitrary, such as a tape, a disk, a drum, or a belt, depending on the intended use.

The optical memory medium of the present invention basically consists of a base material and the above-mentioned memory material, but depending on the purpose, other layers (for example, an accent protection layer) may be present. Air Φ Santoy Sochi) Tomazou (can also be used to prevent dust and scratches from forming).

Next, a method for manufacturing the optical memory medium of the present invention will be specifically explained. .

The optimal method according to the present invention is to deposit an organometallic compound or a metal complex containing at least nickel as one of the starting materials onto a substrate set in a vacuum reaction layer using plasma plasma.
This is a method of forming a film using the VD method. Among these, the plasma CVD method using glow discharge is more preferable. Typical manufacturing conditions include starting materials such as nickel acetylacetonate, nickel kojate, nickel acetate, nickel citrate, and nickel benzoate, as well as fluorinated materials for each, and as a carrier gas. For example, He5NeSAr, N2, etc. are used, and reaction gases such as 02, Co, CO2, CH
4, C2H4, etc. are used. The glow discharge device may be a direct current glow discharge device or a capacitively or inductively coupled alternating current glow discharge device. Reaction gas pressure is 0
．． 01 to several Torr, preferably 0.05 to 2 Torr
It is. 7u power is 1~300W, preferably 5~100W
W, and the discharge time is 1 to 120 minutes, preferably 2 to 6 minutes.
It is 0 minutes. The substrate temperature is 0-350℃, preferably 20-350℃
The temperature is 200°C.

Furthermore, examples for producing the optical memory medium of the present invention will be given below. Table 1 shows the manufacturing conditions for each example. However, the manufacturing apparatus used was a plasma CVD apparatus shown in FIG.

In Figure 1, 1 is an RF main power source 2 is a thermocouple, 3 is an electrode, 4 is a substrate, 5 is a starting material, 6 is a heater, 7 is a counter electrode, 8 is a vacuum 1, 9 is an oil diffusion pump, 10 1 is an oil rotary pump, and 11 is a heater control unit.

The pressure during the reaction was 1. It was fixed at OX 10' Torr.

Table 1 Conditions for Preparing Memory Thin Films As shown in Table 2, the reflectance, absorption, and transmittance of the obtained thin films varied greatly depending on the film forming conditions. Further, the reflection, absorption, and transmittance of each film were within ±5% in the wavelength range of 370 to 800 nm. The differences in reflectance, absorption, and transmittance in Examples 1 to 11 are due to the film thickness, and there is no essential difference in film structure.

Table 2 Optical memory - Reflectance, absorption, and transmission $
(at 800 nm) Figures 2 to 4 show the relationship between film thickness, reflectance, absorption rate, and transmittance. The reflectance of the film increased linearly with the age of about 300 people (Figure 2). The absorption rate of the film is 5
There was a tendency for saturation between 0 and 100 people, which was about 40% (Figure 3). The transmittance of the membrane is 50% up to a thickness of about 100 L.
%, and then gradually decreased thereafter.

From the XPS spectra, these films are mainly composed of carbon and nickel, with C-0, C-Hl-0H,
No notable peaks indicating NiO or the like were observed.

Table 3 shows Ni/C when a film surface with a reflectance of 46%, an absorption rate of 40%, and a transmittance of 14% was sputtered with Ar plasma for 5 minutes and 15 minutes. Sputtering for 5 minutes Ni/C=
1.1% sputtering for 15 minutes Ni/C-9,I
It was found that the plasma CVD thin film of N1AA was composed of carbon and nickel in an almost equal elemental ratio. In addition, the differences in reflectance, absorption, and transmittance in Examples 1 to 11 are due to the film jv as described above, and the XPS spectra indicate that each film has carbon and nickel as its main components. It became clearer.

Table 3 When these films were heat-treated at 400°C in the air, they turned brown and transparent, with a reflectance of 10% or less, an absorption rate of 20% or less, and a transmittance of 70% over the wavelength range of 370 to 800 nm.
That's all. FIG. 5 shows an example of reflectance changes before and after heat treatment. Analysis by XPS spectroscopy after the heat treatment confirmed the formation of NiO and the desorption of carbon in the film.

Next, the optical writing performance of the film produced as described above was evaluated under the following conditions.

The sample was fixed on a rotating disk of 5On+iφ and was heated to 21t.
While rotating at 3 rpm, a NEC Ar laser (GL G 3000, GLS3) was used as a writing laser.
000) onto the sample using a condensing lens.
When writing was performed with an output of 10 mW by condensing the light to φ, recording pits with a line width of about 1 μm could be formed in an irradiation time of several n5 cc. Further, when the shape of the peripheral part of the bit was observed, it was found to be extremely smooth without any noticeable ridges. Furthermore, writing could be done in the same way using a semiconductor laser that emits an oscillation wavelength of 780 to 800 nm instead of the A laser.

[Effects] When the N, i-C film according to the present invention is used as a memory material, the following effects can be obtained.

Unlike metals, chalcogen, organic compounds, and other simple thermally melted/sublimated memory materials, there is no low C/N ratio during playback due to swelling around the bit.

The contrast is large because the change in reflectance before and after recording is large.

The recording part is made of stable nickel oxide, and the recording bits have a long life. In addition, the non-recording part is carbon-containing H nickel,
It is stable and prevents oxidation.

Due to the high absorption and reflection over the wavelength range of 370-800 nm, various lasers can be used for writing.

The starting materials, such as nickel acetylacetonate, nickel acetate, nickel kojate, nickel citrate, and nickel benzoate, are non-polluting and inexpensive, so the production cost is low.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a plasma CVD apparatus, and Figure 2 is an N
Figure 3 is a diagram showing the relationship between the thickness and reflectance of a 1AA plasma CVD thin film, Figure 3 is a diagram showing the relationship between thickness and absorption rate of a N1AA plasma CVD film, and Figure 4 is a diagram showing the relationship between thickness and transmittance of a N1AA plasma CVD thin film. FIG. 5 is a diagram showing changes in reflectance of N1AA plasma CVD thin film due to heat treatment.

Claims (1)

[Claims] An optical memory medium characterized by containing carbon and nickel as main components.