JPH0249237B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an information recording member that can directly record information such as images, audio signals, or computer information in real time using an energy beam such as a laser beam or an electron beam. In recent years, methods of writing and reading various information using energy beams such as laser beams have been attracting attention. This allows information to be stored at a high recording density, and information can be written and read without contact, that is, without destroying the information recording member during the writing and reading process, and at a high density. This is because it has the following advantages. Regarding this type of information recording method, for example,
Although it is described in detail in ``Optical disk systems emerge'' presented in IEEE Spectrum AUGUST 1978, the principle will be briefly explained based on Fig. 1. In FIG. 1, 11 is a rotating board. An information recording film 12 is formed on the substrate 11 . After the optical lens 2 is brought close to this information recording member to a predetermined distance, a pulsed laser beam corresponding to the information to be recorded is irradiated from the laser beam generator 3.
When such an operation is performed, the portion of the information recording film irradiated with the laser beam is heated by the laser beam and melts or evaporates, forming a hole or a recess. In other words, information has been recorded. Next, when a low-power laser beam is irradiated from the laser beam generator 3 through the lens 2 and the reflected light is received by the photodetector 5 through the half mirror 4, a hole or a recess is formed. The part where
Since the light reflectance has changed compared to the part that was not irradiated with laser light, it is possible to detect the presence or absence and position of holes or depressions as a change in the intensity of the reflected light, and information can be read from this. It turns out. Incidentally, there are various characteristics required for the above-mentioned information recording film, but the following two points are listed as highly important. The first is that it has high corrosion resistance, and the second is that it can be written with a low-power laser beam, that is, it has high recording sensitivity. Information recording materials are used for long periods of time, from several years to several decades.
It is required to withstand reading of recorded information, correction of error information, and writing of new information. Therefore,
The recording film used in the member must be stable against moisture and oxygen in the atmosphere over a long period of time. Therefore, noble metals such as Au, Ag, Ph, and Pt are suitable for this purpose. Known examples include US patents
No. 3474457, in which Ph is used as a recording film. However, a drawback of these information recording members using noble metal recording films is that they require a high-output laser for writing. The above US patent also uses an argon laser with an output of 1W for writing. This is due to the thermal properties of these precious metals, such as their high melting and boiling points, as well as their high light reflectivity and low absorption rate, which means that only a small portion of the energy of the irradiated light can be used for heating. This is due to the nature of The need for a high-output laser means that the information processing device using the present information recording member will be large and expensive, which will be an obstacle to the widespread use of the present information processing device. On the other hand, semimetals such as Te and Bi are known as recording films with high recording sensitivity. For example, the recording sensitivity value is
When Te is used as a recording film, writing is possible by irradiating it for several hundred milliseconds with a laser output of several milliwatts. An output level of about several mW is a level that can be obtained from semiconductor lasers that are currently being put into practical use. The advantage of using a semiconductor laser, unlike the gas laser mentioned above, is that it is extremely small and highly efficient, and can be directly modulated.As a result, information processing equipment using this information recording member can be significantly smaller and lighter. The result is a significant increase in practical benefits. The characteristics of these metalloids, contrary to those of precious metals, are that they have low melting points and low boiling points, that is, low recording temperatures, and light absorption rates of 30 to 40%.
This is due to the optical property that the previous energy is efficiently converted into thermal energy.
However, unlike the above-mentioned noble metals, these metalloids have the disadvantage that they react with moisture and oxygen in the atmosphere and deteriorate relatively easily. Furthermore, this deterioration is accelerated because the thickness of the recording film is usually made extremely thin, on the order of several hundred angstroms, in order to maintain high recording sensitivity. Therefore, information recording members using these semimetals as recording films have not yet been put into practical use. As a means for improving the corrosion resistance of an information recording member using a semimetal recording film such as Te or Bi, it is known to provide, for example, a protective layer made of an organic material on the recording film. However, organic materials have higher water permeability and air permeability than inorganic materials, and although they are recognized to have the effect of improving corrosion resistance, they are incomplete as a means of protection. An object of the present invention is to eliminate the drawbacks of such conventional information recording members, to withstand use for a long period of time for practical purposes, and to write information with a laser beam as low as that which can be provided by a semiconductor laser. The object of the present invention is to provide a recording member. The information recording film of the information recording member of the present invention is composed of two types of thin films. The first thin film is a thin film that releases volatile components at a temperature of 400°C or less when irradiated with an energy beam, the second thin film is a thin film made of a corrosion-resistant metal, and the first and second thin films are They are sequentially layered on the substrate. According to the present invention, stability against moisture and oxygen in the atmosphere is ensured by the second thin film. Furthermore, when irradiated with an energy beam, the first thin film liberates volatile components at a relatively low temperature, and these components form holes in the second thin film and are released, resulting in a reduction in the output of the energy beam required for writing. is planned. FIG. 2 shows the basic structure of the information recording member of the present invention. In FIG. 2, 21 is a substrate, 22 is a first thin film that releases volatile components at a temperature of 400°C or less, and 23
is a second thin film made of a corrosion-resistant metal. As the first thin film, metal nitrides or oxynitrides that have a weak bond with nitrogen are suitable;
Te-N, Te-O-N, Ag-N, Ag-O-N,
Obtained from Au-N and Au-O-N systems. All compounds obtained from these systems liberate _N2 gas at temperatures between 100 and 400 °C, but especially Te-
Thin films obtained from N-based and Te-O-N-based materials are preferred. All of these compounds can be produced by sputtering the metal using nitrogen plasma. The second thin film is made of metals with a boiling point of 2000℃ or higher, such as noble metals such as Au, Ag, Pt, Pd, Ph, Ir, transition metals such as Cu, Nb, Ta, Ti, Os, Zr, Hf, Al is suitable, and particularly suitable is
Au and Ag. In such an information recording member, when a laser beam is irradiated from the second thin film 23 side, a part of the irradiated light is reflected and a part is absorbed and converted into heat, thereby heating the recording film. As a result, the first thin film 2
_N2 gas is liberated from the second thin film 23, and this _N2 gas is released by forming holes in the second thin film 23 even at a low temperature such that the second thin film 23 does not evaporate and melt. In other words, although it has the advantage of good corrosion resistance, it is difficult to put it into practical use because it requires too much energy to write.It records with an output of several milliwatts, which can be extracted from a semiconductor laser. You can. FIG. 3 shows another example of the structure of the information recording member of the present invention. In Fig. 3, 31 ₁ and 31 ₂ are transparent substrates, 32
₁ and 32 ₂ are the first thin films that release volatile components at temperatures below 400°C, and 33 ₁ and 33 ₂ are the boiling points.
This is a second thin film made of a metal with a temperature of 2000°C or higher. 3
Reference numeral 4 denotes a spacer for adhering and integrating two substrates on which recording films are formed at a predetermined distance. The first and second thin films can be the same as the information recording member shown in FIG. 2. When this information recording member is irradiated with _a laser beam from the substrate side, like the information recording _member shown in _FIG .
Even at such low temperatures that ₁ or 33 ₂ does not evaporate or melt, holes are formed in the second thin film 33 ₁ or 33 2 and the second thin film 33 1 or 33 ₂ is released. The advantages of this information recording member are that the recording film is protected from dust in the atmosphere and scratches that may occur during operation, and that double-sided recording is possible. In the case of the information recording members shown in Figures 2 and 3, it is the first method that can record information on precious metals and transition metals, which have an extremely high boiling point of 2000°C or higher and have good corrosion resistance, with a laser output of several mW. This is due to the presence of a thin film, and the thickness of these corrosion-resistant metal films alone cannot be increased.
Even if the thickness is reduced to less than 100 Å, recording with a laser output of several mW is not possible. This is because when the film thickness is made thin, most of the irradiated laser beam is transmitted, and the proportion absorbed is extremely small, resulting in the recording film being hardly heated. In addition, if a semimetal such as Te or Bi, which has a low melting point and boiling point and high recording sensitivity, is used for the first thin film, and a second recording film with good corrosion resistance made of a noble metal or a transition metal is further laminated, Te, A semimetal film such as Bi has no components that are liberated upon heating, and recording is not possible unless the semimetal film itself is heated to its boiling or melting point. Therefore, it is essential to use a film that releases volatile components at relatively low temperatures as the first thin film. The temperature at which free components are released from the first thin film is 400°C.
The reason for limiting the temperature to below 400°C is that if the free temperature is higher than 400°C, the secondary temperature with a boiling point of 2000°C or higher
The problem is that it is not possible to record on a thin film with a laser output of several mW. Next, the thickness of the first and second thin films will be explained. The thickness of the second thin film is preferably 300 Å or less. This is because when the thickness is greater than 300 Å, most of the irradiated laser beam is reflected on the surface of the second thin film or absorbed by the second thin film itself, and does not pass through to the first thin film. This is because the thin film is not heated and recording cannot be performed with a laser beam as low as that provided by a semiconductor laser. However, if it is too thin, it cannot be expected to improve the corrosion resistance, which is the purpose of forming the second thin film. From the above, the second
The optimal range for the thickness of the thin film was between 50 and 200 Å. The thickness of the first thin film is preferably 300 Å or more. This is because the first thin film is different from the second thin film.
This is because it is formed for the sole purpose of absorbing the irradiated laser beam. That is, the first
If the thin film is thinner than 300 Å, the laser beam irradiated through the second thin film will not be sufficiently absorbed by the first thin film, and will also pass through the first thin film, causing Efficient release of free components, which is the purpose of formation, cannot be expected. Specific examples will be described below. Example 1 After exhausting the pressure of the vacuum container to 10 ^-7 Torr, H ₂ O gas was introduced to bring the pressure to 10 ^-5 Torr. Then _N2
A gas is introduced to a pressure of 5×10 ^-3 Torr, and a high-frequency electric field is applied between the electrodes to generate plasma.
Sputter the target onto the acrylic substrate.
A first thin film having a composition of Te ₄₀ O ₅₆ N ₄ was formed. The thickness of the first thin film is 4000 Å. Next, after evacuating the vacuum container to 10 ^-7 Torr again, Ar gas was introduced to a pressure of 10 ^-4 Torr, and a high frequency electric field was applied between the electrodes.
Generate plasma and spatter the Au target,
A second thin film was formed on the first thin film. The film thickness is
It is 100Å. Next, as a comparative example, an information recording member was manufactured using a Te film sputtered with argon plasma as a recording film. These information recording members were evaluated by the following method. First, these information recording members are irradiated with a pulse-modulated laser beam corresponding to the same recorded information,
I made a record. The laser is a semiconductor laser (wavelength
830 nm), and the beam diameter is approximately 1 μmφ. The output of the recording laser beam was varied from 1 to 10 mW. Readout is performed with a 0.5mW laser beam,
This was done as a change in the intensity of reflected light. Recording sensitivity was determined from the recording readout process described above using the following method. The intensity of the reflected light is Imax, and the intensity of the reflected light from the hole is Imin.
The modulation degree M was defined by the following formula. M=Imax-Imin/Imax+Imin The relationship between the recording laser beam output and the modulation degree M was as shown in Table 1.

[Table] As can be seen from the first table, the information recording member of this example has a recording sensitivity equal to or higher than that of the information recording member using a recording film made of Te. Next, these information recording members were heated to 80℃ and 80%RH.
The corrosion resistance was evaluated by placing it in a constant temperature and humidity chamber.
In contrast to the recording member in which the recording film was made of Te, the recording film was oxidized and partially became transparent after 200 hours, no change was observed in the recording member of this example. Also, the recording and reading characteristics at this point are 8mW.
A modulation depth of 0.8 is obtained for a laser beam output of
No deterioration in recording sensitivity was observed. Example ₂ Ag, _Cu , _pt , Ir,
A second thin film consisting of Nb, Ta, Ti, Pd, Os, Zr, Hf, and Al was formed to a thickness of 100 Å by vapor deposition or sputtering. When the recording sensitivity of these information recording members was measured in the same manner as in Example 1, it was found that for a recording laser beam output of 8 mW, M = 0.7 when the second thin film was made of Ag, and M = 0.7 when the second thin film was made of Ag, and when Pt or
A modulation degree of M=0.6 for Ph, M=0.5 for Cu, Ir, Ti, Pd, and Al, and M=0.4 for Nb, Ta, Os, and Zr was obtained. Example 3 After evacuating the pressure of the vacuum container to 10 ^-6 Torr, N ₂ gas was introduced to a pressure of 10 ^-4 Torr or higher, and then a high frequency electric field was applied between the electrodes to generate plasma and target Te. A first thin film having a composition of Te ₈₀ O ₂ N ₁₈ was formed on the acrylic substrate by sputtering. Next, after evacuating the vacuum container to 10 ^-6 Torr again, Ar
By introducing gas and applying a high frequency electric field between the electrodes,
Plasma was generated and the Au target was sputtered to form a second thin film. When the recording sensitivity of this information recording member was measured in the same manner as in Example 1, it was found that for the output of an 8 mW recording laser beam,
A modulation depth of 0.6 was obtained. Example 4 After the pressure of the vacuum container was evacuated to 10 ^-7 Torr, N ₂ gas was introduced so that the pressure became 10 ^-2 Torr. Then,
A high-frequency electric field was applied in a vacuum container to generate plasma, and an Ag target was sputtered to form a first thin film having a composition of Ag ₉₅ N ₅ on the acrylic substrate.
Next, the vacuum chamber was evacuated to 10 ^-5 Torr again, and Ag was sputtered onto the first thin film using argon gas plasma to form a second thin film. When the recording sensitivity of this information recording member was measured by the method of Example 1, it was found that 10
A modulation depth of 0.3 was obtained for a laser beam output of mW. Example 5 After the pressure of the vacuum container was evacuated to 10 ^-7 Torr, N ₂ gas was introduced so that the pressure became 10 ^-2 Torr. Then,
Plasma was generated by applying a high frequency electric field in a vacuum chamber, and an Au target was sputtered to form a first thin film having a composition of Au ₉₀ N ₁₀ on an acrylic substrate. Then, after evacuating the vacuum container to 10 ^-5 Torr again,
A second thin film was formed by sputtering Au onto the first thin film using argon gas plasma. When the recording sensitivity of this information recording member was measured by the method of Example 1, a modulation degree of 0.3 was obtained for a laser beam output of 10 mW. As described above, the information recording member of the present invention has better corrosion resistance than conventional materials and has properties suitable as a recording film of an information recording member. By using a noble metal or transition metal film as a recording film, which could not be recorded without using a laser, it is possible to record with a laser beam as low as that provided by a semiconductor laser. This is because, in the present invention, these corrosion-resistant metals are used as the second thin film, and the first thin film is a thin film that liberates the constituent components at a relatively low temperature of 400° C. or less. Furthermore, in the information recording member of the present invention, since a material with a relatively high light reflectance is selected for the second thin film,
Even when the reflected light from the first thin film is low during readout, a sufficiently good degree of modulation can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an optical information recording and reproducing method.
FIG. 2 and FIG. 3 are diagrams showing an example of the structure of the information recording member of the present invention. 21,31 ₁ ,31 ₂ ...Substrate, 22,32 ₁ ,
32 ₂ ... first thin film, 23, 33 ₁ , 33 ₂ ...
Second thin film, 34...spacer.

Claims (1)

[Scope of Claims] 1. An information recording member in which an information recording film is formed on a substrate and information is written by changing the optical characteristics of the information recording film by irradiation with an energy beam, wherein the information recording film is , consisting of a first thin film made of a metal and a volatile component, which releases the volatile component at a temperature of 400°C or less, and a second thin film made of a corrosion-resistant metal formed thereon. An information recording member characterized by: 2 The first thin film is made of Te-N, Te-O-N, Ag-N, Ag-O, which releases _N2 gas at temperatures below 400℃.
-N, Au-N, Au-O-N system, and the second thin film is Au, Ag, Cu, Pt,
The information recording member according to claim 1, characterized in that it is one selected from Ph, Ir, Nb, Ta, Ti, Pd, Os, Zr, Al, and Hf.