JPH0119450B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a tin-copper alloy for recording media.

(Prior Art) In recent years, research and development has been actively conducted on high-density, large-capacity information recording media disks that can be accessed at high speed and randomly. new recording media that are capable of erasing recorded information and rewriting it with new information using laser light and/or appropriate auxiliary means as necessary. Explorations are also underway.

By the way, regarding a recording medium on which information is recorded and reproduced using a laser beam, what kind of physical change is caused in the recording medium by the heating effect of the spot of the laser beam? The many recording media that have been proposed to date can be categorized based on how they perform recording: pit-forming type, bubble or unevenness-forming type, magneto-optical type, and phase-change type (which uses thermal energy to generate light). It can be broadly classified into various types of recording media, such as thermal transformation type (thermal transformation type) in which changes occur in transmittance, reflectance, absorption rate, etc.

Of the various types of recording media mentioned above, phase-change recording media have attracted attention because of the possibility of erasing previously recorded information, and to date, as this type of recording media, Chalcogenide substances (germanium, tellurium, antimony,
We used thin films of compositions consisting of various combinations of silicon, arsenic, bismuth, indium, gallium, thallium, selenium, sulfur) and thin films of lower oxides (for example, mixed compositions of Te and TeO ₂ ). A recording medium is proposed.

(Problems to be Solved by the Invention) However, thin films of compositions made of various combinations of chalcogenite-based substances or thin films of lower oxides (for example, mixed compositions of Te and _TeO2, etc.) cannot be used. In the previously proposed recording medium, the laser light intensity (laser light intensity within the intensity range that can cause a phase change in the recording medium, and the portion where the recording medium is irradiated with laser light of that intensity) Since the composition range of the material constituting the thin film of the recording medium is narrow such that the second harmonic distortion in the reproduced signal from the recording medium is minimized and the laser beam intensity is constant, The problem was that it could not be easily mass-produced.

(Means for Solving the Problems) The present invention provides a tin-copper alloy for recording media, containing 40 atomic % to 60 atomic % of tin and the balance being copper.

(Example) An alloy consisting of tin and copper has long been known as bronze (commonly known as karakin), and ordinary bronze is a copper-tin alloy containing 4 to 12% by weight of tin, i.e. , an α or α+γ solid solution in a copper-tin alloy, and has been used since ancient times to produce works of art such as bronze coins and statues, gunmetal used in machine parts, bell copper, bronze for industrial materials, and other general uses. Bronze is made with different compositions, but all of the bronzes used for the various purposes mentioned above contain 10% tin by weight.
It is a copper-tin alloy with a composition of about 90% copper by weight.

By the way, the atomic weight of tin is 118.69, and
Since the atomic weight of copper is 63.546, as mentioned above, a copper-tin alloy with a moderate composition of about 10% tin and 90% by weight can be converted into an atomic% of copper. It is expressed as a copper-tin alloy containing about 94 at.% tin and about 6 at.% tin, but if you try to make an alloy by increasing the tin content, there are drawbacks such as segregation and brittleness. Therefore, the composition of bronze, which has been widely used since ancient times, is approximately 10% by weight of tin and 90% by weight of copper.
It can be said that it is about % by weight.

The present invention is a phase change type (thermal transformation type in which light transmittance, reflectance, absorption rate, etc. change due to thermal energy)
In searching for a recording material suitable for recording media, we focused on an alloy consisting of copper and tin, and by changing the composition of copper and tin in the tin-copper alloy, we created a material with tin content of 40 atomic % to 60 atomic %. Based on the discovery that a tin-copper alloy with a composition range in which the balance is copper has characteristics suitable for a phase change type recording medium, the tin-copper alloy for recording media of the present invention has been developed. It has been completed.

Next, the tin-copper alloy for recording media of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a tin-copper alloy for recording media of the present invention obtained by applying a binary vapor deposition method, that is, a tin-copper alloy containing 40 at.
1 is a perspective view showing a schematic configuration of a film forming apparatus for depositing and forming a thin film recording medium made of a tin-copper alloy for recording media on a substrate surface in which the tin-copper alloy contains 60 atomic percent and the remainder is copper; In the figure, 1 is a substrate on which a tin-copper alloy for recording media is to be adhered and formed, and the substrate 1 may be made of, for example, a glass disk, an acrylic resin disk, or any other suitable material. A disc may be used.

Reference numeral 2 denotes a rotating shaft for rotating the substrate 1 described above at high speed, and this rotating shaft 2 is rotated at a predetermined number of rotations at high speed by a rotation drive device (for example, a motor) not shown.

Reference numerals 3 and 4 are boats that accommodate evaporation materials, and 5 and 6 are heating wires that heat the boats 3 and 4, and the boat 3 and the heating wire 5 are connected to one of the evaporation sources A. The boat 4 and the heating wire 6 constitute the other evaporation source B, and the one evaporation source A heats and evaporates the tin contained in the boat 3. let me,
The other evaporation source B described above heats and evaporates the copper contained in the boat 4 thereof.

Reference numeral 7 denotes a shutter plate that can be freely moved in and out between the substrate 1 and the two evaporation sources A and B. The entirety of each of the above-described components is housed in a container (not shown), and the following film-forming operation is performed on the substrate 1 in a vacuum atmosphere formed in the container. .

That is, the substrate 1 is fixed to the rotating shaft 2, and
Tin, which is used as an evaporation material, is stored in the boat 3 of one evaporation source A, and copper, which is used as an evaporation material, is stored in the boat 4 of the other evaporation source B, and then the exhaust inside the container is to create a vacuum atmosphere with the required degree of vacuum inside the container.

Next, a shutter plate 7 is inserted between each evaporation source A, B and the substrate 1, and the substrate 1 is rotated at a high speed at a predetermined number of rotations. A predetermined heating voltage is supplied to each of the evaporation sources 6 and 6 to melt the tin contained in the boat 3 of the evaporation source A and the copper contained in the boat 4 of the evaporation source B, respectively.

By controlling the temperature of tin housed in the boat 3 of evaporation source A, the temperature of copper housed in the boat 4 of evaporation source B, and the rotation speed of the substrate 1,
A tin-copper alloy thin film having a predetermined composition, that is, a tin-copper alloy thin film having a composition of 40 atomic % to 60 atomic % tin and the remainder copper is formed on the surface of the wafer.

Further, the time length for performing vacuum evaporation with the evaporation substance on the surface of the substrate 1 is such that tin is deposited on the surface of the substrate 1 at 40%.
A thin film of tin-copper alloy having a composition of atomic% to 60 atomic% and the balance being copper is deposited to a predetermined thickness, e.g.
The time value is set so that the film is deposited to a thickness of about 1000 angstroms, and the opening and closing of the shutter plate 7 is controlled accordingly.

By applying the above-mentioned binary vapor deposition method, a thin recording layer of a predetermined thickness of a tin-copper alloy having a composition of 40 atomic % to 60 atomic % tin and the remainder copper is formed on the surface of the substrate 1. After the recording layer has been deposited, the rotation of the substrate 1 is stopped, air is introduced into the container, and then the substrate 1 with the recording layer formed on its surface is taken out from the container.

If it is necessary to form a protective layer on the surface of the recording layer formed on the surface of the substrate 1, a protective layer made of a thin film of a suitable synthetic resin is applied to the surface of the recording layer. The application of the protective layer with a thin film of synthetic resin as described above may also be carried out by evaporating a suitable synthetic resin material from an evaporation source (not shown). 40 atomic% of tin on the surface of substrate 1
Tin with a composition of 60 atomic percent to 60 atomic percent and the balance being copper.
In addition to the above-mentioned binary vapor deposition method, sputtering method or other suitable film forming method may be used as a means for depositing the copper alloy as a thin film recording layer of a predetermined thickness. Of course, if the sputtering method is adopted as a film forming method for the substrate 1, the rotational speed of the substrate 1, the energy of the ions (for example, argon ions) bombarded with the copper target, and the tin target By appropriately setting the energy of the ions (for example, argon ions) to be bombarded with the sputtering and the length of time during which sputtering should be performed, it is possible to form a surface of the substrate 1 that contains 40 to 60 atomic percent of tin and the remainder is copper. A tin-copper alloy having such a composition can be formed as a thin film recording layer of a predetermined thickness. Further, when forming a film by applying the sputtering method, the film may be formed using one target made of a tin-copper alloy whose composition takes into consideration the sputtering rate of tin and copper.

Figure 2 shows a tin-copper alloy with a composition of 53 atomic percent tin and the balance copper on the surface of a glass substrate.
A tin-copper alloy thin film deposited as a thin film with a thickness of 500 angstroms was irradiated with a He-Ne laser beam (wavelength: 6328 angstroms) at an incident angle of 45 degrees. FIG. 2 is a diagram showing the measurement results of changes in light reflectance of a tin-copper alloy thin film having the above-mentioned composition when the temperature of the alloy thin film is changed from room temperature to 200°C. As is clear from Figure 2, the reflectance of light in a thin film of a tin-copper alloy with a composition of 53 atomic percent tin and the remainder copper is as follows: (The change in light transmittance also changes significantly when the temperature of the tin-copper alloy thin film is around 120°C or higher.) It was clearly confirmed by visual observation that the color tone of the thin alloy film also changed in response to changes in temperature.

Next, on the surface of a synthetic resin substrate (acrylic resin substrate), a tin-copper alloy with a composition of 53 atomic percent tin and the balance copper is deposited as a thin film with a thickness of 500 angstroms. When a thin film of tin-copper alloy is irradiated with a laser beam spot with a wavelength of 8300 angstroms and a diameter of about 1 micron to cause a phase change in the thin film of tin-copper alloy, tin-
The copper alloy thin film has changes in light reflectance and transmittance,
Even when visually inspected under indoor light, an obvious change in color tone occurred.

When the thin film of the tin-copper alloy, which had undergone a partial phase change as described above, was observed using a scanning electron microscope, no recorded dots were observed. Changes in light reflectance, transmittance, and color tone that occur in the tin-copper alloy thin film due to spot irradiation with laser light are as follows:
This shows that this is not caused by unevenness on the surface of the tin-copper alloy thin film caused by laser light irradiation.

However, recording dots due to phase change in the tin-copper alloy thin film were clearly recognized by a change in color tone when observed with an optical microscope.

Next, a thin film of tin-copper alloy that had undergone a phase change by irradiation with a laser beam spot as described above was deposited.
The amount of oxygen and nitrogen in each of the recorded and non-recorded portions was measured using EPMA (Electron Probe Micro Analysis).
No difference was observed between the two. As mentioned above, changes in light reflectance, transmittance, and color tone that occur in a tin-copper alloy thin film due to spot irradiation with laser light are caused by tin irradiation with laser light. - This indicates that the recorded portion formed on the copper alloy thin film was not caused by being changed into a different material from the non-recorded portion due to heating by laser beam irradiation.

Considering the above experimental results, the changes in light reflectance and transmittance that occur in the tin-copper alloy thin film due to spot irradiation with laser light, as well as the changes in color tone, - Thermal energy applied to the copper alloy thin film causes a change in the atomic arrangement of the constituent materials of the tin-copper alloy thin film, thereby changing the optical properties of the tin-copper alloy thin film into recording and non-recording areas. It is inferred that there is a change in the

Figure 3 shows the tin content (atomic %) in the tin-copper alloy.
Laser light sensitivity of a tin-copper alloy thin film to changes in laser light intensity (laser light intensity within the intensity range that can cause a phase change in the recording medium, from the part where the recording medium is irradiated with laser light of that intensity) The measurement results shown in Figure 3 were obtained under the following conditions. .

That is, on the surface of a disk-shaped substrate made of synthetic resin (a disk-shaped substrate made of acrylic resin), a tin composition having a tin content in the range of 30 atomic % to 75 atomic % and the balance being copper is applied. An information recording medium disk on which a thin film of copper alloy is deposited with a thickness of 500 angstroms is fixed at its center to a rotating shaft and rotated at a speed of 900 per minute.
A spot with a diameter of 50 mm is irradiated with a spot of laser light with a wavelength of 8300 angstroms whose diameter is approximately 1 micron and whose intensity is modulated by a signal with a frequency of 500 KHz, and a 500 KHz signal is applied to the tin-copper alloy thin film. The experiment to obtain the measurement results shown in Figure 3 was conducted when the tin content was in the range of 30 atomic % to 75 atomic %, with the balance being copper. Information recording medium disks are made by depositing a tin-copper alloy with the following composition as a thin film with a thickness of 500 angstroms. This was done using a large number of information recording medium disks.

Looking at the change characteristics of the laser light intensity of the tin-copper alloy thin film with respect to the change in tin content (atomic %) in the tin-copper alloy shown in Figure 3, the laser light sensitivity of the tin-copper alloy thin film is shows that the tin content (atomic %) in the tin-copper alloy remains approximately constant over a wide range of 40 atomic % to 60 atomic %. I understand.

In this way, even if the tin content in a tin-copper alloy varies over a wide range of 40 to 60 at.%, the laser light sensitivity of the tin-copper alloy thin film remains approximately constant ( The laser light sensitivity of the tin-copper alloy thin film remains approximately constant over a wide composition range of 40 at% to 60 at% tin), so it is clear that the composition of the constituent materials of the recording layer during the production of the recording medium is The tolerance for variations is wide, thus facilitating mass production of recording media.

In addition, since there is a wide tolerance for variations in the composition of the constituent materials of the recording layer during the production of recording media as mentioned above, continuous in-line sputtering using a tin-copper alloy target made from a molten solidified product of tin and copper is also possible. It is also possible to easily manufacture an information recording medium disk using a ring.

(Effects) As is clear from the above detailed explanation, in the tin-copper alloy for recording media of the present invention in which tin is 40 atomic % to 60 atomic % and the balance is copper, the tin content is low. The laser light sensitivity of the tin-copper alloy thin film remains almost constant even when the concentration varies over a wide range of 40 to 60 atom%.
The laser light sensitivity of the tin-copper alloy thin film remains approximately constant over a wide composition range), which is something that cannot be achieved with conventional chalcogenide-based or lower oxide-based phase change recording media. However, the recording medium using the tin-copper alloy for recording media of the present invention is easier to mass produce than conventional phase change type recording media, and the present invention allows for All previous drawbacks are successfully resolved.

[Brief explanation of drawings]

Figure 1 is a perspective view showing a schematic configuration of an example of a film forming apparatus, Figure 2 is a diagram showing the relationship between temperature and light reflectance of a tin-copper alloy thin film for recording media, and Figure 3 is a diagram showing the relationship between the temperature and light reflectance of a tin-copper alloy thin film for recording media. FIG. 3 is a diagram showing the relationship between the tin content of the alloy thin film and the laser light sensitivity. 1... Board, 2... Rotating shaft, 3, 4... Boat, 5, 6... Heating wire, 7... Shutter plate, A,
B... Evaporation source.

Claims (1)

[Claims] 1. A tin-copper alloy for recording media, containing 40 atomic % to 60 atomic % tin and the balance being copper.