JPS6144692A - Laser beam recording member - Google Patents

Abstract

PURPOSE:To provide a laser beam recording member which makes repeated recording and erasion possible, prepared by forming on a base sheet a plurality of Te layers each sandwitched between dielectric layers and arranged alternately. CONSTITUTION:A recording member is prepared by laminating at least two layers 2, 4, 6 of dielectric substance (e.g. SiO2) and at least two layers 3, 5 alternately to form a sandwitch structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to laser beam recording members. More specifically, the present invention relates to a laser beam recording member suitable for recording information by irradiating a laser beam to cause an optical change in the irradiated portion.

Background of the Invention In recent years, with the remarkable progress in laser technology, the possibility of various applications using coherent light has been pursued. It is expected to be a useful technology in a wide variety of fields, including processing, medical, and chemical reaction applications, and has been rapidly developed and researched, with some already putting it into practical use.

Among these, recently, optical recording media that utilize the good focusing properties of laser light, such as laser discs, have been attracting attention as media for high-density information recording.

Such optical recording materials can be broadly divided into rewritable materials that allow different information to be written on the same material as many times as possible, and fixed recording materials that can only be written once. Magneto-optic materials, photochromic materials, amorphous materials, thermoplastic materials, electro-optic crystals, etc. are known, and among the latter, ablative materials, photopolymer materials, silver salt materials, photoresist materials, etc. are known.

Conventionally known methods of recording information on these materials include forming holes locally in metal films, pigment films, etc., or causing deformation. However, in this embodiment, once recorded information cannot be erased, it is used as a so-called write-once optical recording medium.

On the other hand, rewritable optical recording media include those that use Te-based chalcogenide glass that utilizes a phase change between amorphous and crystalline materials, and those that utilize a metal-semiconductor phase transition.
2, SmS, etc. are known. Among these optical recording media using Te-based chalcogenide glass, one is known in which a dielectric layer with a thickness of 40 nm or more for preventing curling is provided on a substrate.

However, it is known that when this optical recording medium is repeatedly recorded and erased many times, that is, when the crystal-amorphous transition is repeated, phase separation occurs in the chalcogenide glass, impairing the rewritability. .

This phase separation can be avoided by reducing the amount of doping and increasing the amount of Te in the chalcogenide glass, but if the amount of doping is reduced, the amorphous lifetime will be shortened and A problem arises in that the amorphous state transitions to crystalline state over time.

In addition, in optical recording media using ■0□, SmS, the volume change due to transition is large (the film is easily deformed and cracked, and recording and
Since erasing is repeated, a disadvantage is that a thermal bias must be applied, such as cooling the optical recording medium below room temperature.

Problems to be Solved by the Invention As mentioned above, along with the recent remarkable technological developments regarding lasers, optical recording materials are also facing a new phase. However, with conventional optical recording materials, it is impossible to erase information once recorded (fixed recording type materials), and even with rewritable materials, phase separation occurs when information is repeatedly recorded and erased. Various problems remain that need to be improved, such as storage problems and the need for extra operations (for example, cooling treatment).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical recording medium that does not have the dead center of conventional optical recording materials as described above and can be repeatedly recorded and erased.

Means for Solving the Problems In view of the above-mentioned current state of laser beam recording members, the present inventors aimed to obtain an optical recording medium that does not exhibit the various drawbacks of conventional products and is capable of repeated recording and erasing. As a result of various studies and studies, we found that in order to achieve the above purpose, a relatively thin T
The present invention was completed based on the discovery that it is extremely advantageous to provide two or more e-layers.

That is, the laser beam recording member of the present invention has a substrate, at least two dielectric layers and at least two Te layers provided on the substrate, and each of the Te layers has a It is characterized by having a structure in which the dielectric layers are sandwiched between the dielectric layers and the dielectric layers are alternately arranged on the substrate.

Here, as the substrate, plastics such as polycarbonate and acrylic resin, metals such as AI, glass, etc. can be used. However, the material is not limited to these, and all known materials can be used.

In addition, as a dielectric layer (insulator layer), SiO□, 5iO
181203, Y2O3, WO3, TazOs, Cr
2Q3, CeO2, TeO2, MoO2, In, O,,
Inorganic oxide materials such as GeCL, TiO2, MgF
2. Metal fluorides such as PbFz and CeFs, Al
Inorganic nitrides such as N5SisN4, metal sulfides such as ZnS, or (A) polymer materials such as polyethylene, polyvinylidene fluoride, polyphenylene sulfide, low molecular materials such as Cu phthalocyanine and fluorescein, (B) polytetrafluoroethylene. , polyvinyritine fluoride, polyimide, polyphenylene sulfide, etc., can be used, and these can be applied on the substrate or on the Te layer by vapor deposition, sputtering, etc. Note that the organic substances of group (A) are applied by a vapor deposition method, and the organic substances of group CB) are applied by a sputtering method.

Furthermore, a plasma polymerized film may be used as the dielectric layer, and may be made of olefinic compounds such as ethylene, aromatic compounds such as styrene, ice-containing compounds such as propylene hexafluoride, nitrogen-containing compounds such as acrylonitrile, Polymerized films obtained from various organic compounds such as Si-containing compounds such as hexamethyldisiloxane and organometallic compounds such as tetramethyltin can be used.

In addition to Te, chalcogenide glass containing 90 atomic % or more of Te can be used for the Te layer, and these can be formed by vapor deposition, sputtering, or the like.

was found to be advantageous. That is, the crystallization temperature is Te
The thinner the film thickness is, the higher it becomes. Therefore, the thinner the Te film thickness is, the longer the lifetime of Te in the amorphous state at room temperature becomes. On the other hand, the recording/erasing sensitivity due to crystallization decreases as the Te film becomes thinner. After all, in order to make the amorphous life at room temperature sufficiently long and to maintain the writing/erasing sensitivity at a sufficient value, it is preferable that the Te layer has a thickness within the above range.

In addition, when chalcogenide glass is used instead of Te, the crystallization temperature is originally higher than that of Te alone, so
By setting the film thickness to 30 nm or less, a sufficiently long amorphous life can be obtained, and further, considering the sensitivity of recording and erasing, the film thickness is preferably within the range of 5 to 30 nm.

It is preferable that the chalcogenide glass used instead of pure Te has a composition that does not cause phase separation, that is, 90 atomic % or more of Te, and components other than Te include S b SAs SSe N Ge % B r SS
Elements such as ISS are used and are doped into the Te in amounts up to 10 atomic percent, either alone or in combination of two or more.

Hereinafter, the laser beam recording member of the present invention will be explained in more detail with reference to the accompanying drawings.

FIGS. 1 and 2 schematically show in cross-section two different embodiments of the laser beam recording member of the present invention. The embodiment shown in FIG. 1 shows a laser beam recording medium composed of a substrate 1 and dielectric layers 2.4.6 and Te layers or Te-based chalcogenide glass layers 3.4, which are sequentially and alternately provided on the substrate 1. Ta.

According to the present invention, two or more Te layers or chalcogenide glass layers are laminated on a substrate to form a multilayer structure,
By reducing the thickness of the Te or Te-based chalcogenide glass layer, it is possible to prolong the lifetime of the amorphous state and to prevent a decrease in contrast caused by reducing the thickness. That is, in the case of a 20 nm single-layer Te film, the amorphous lifetime at room temperature is several seconds, whereas in the case of a 5-layer Te film, the amorphous state remains for more than a month at 40°C. Can be maintained stably. In addition, in the case of a single Te film of 5 layers, the reflectance decreases from 15% to 10% due to the crystal-amorphous transition.
%, but by providing two Te layers of 5 m, the reflectance shows a large change from 25% to 15%. Therefore, by forming multiple Te layers, the amorphous state is stabilized and the contrast is enhanced.

The Te layer is alternately sandwiched with dielectric layers, and the dielectric layer in contact with the substrate prevents heat from flowing to the substrate and functions as a heat insulating layer (in this case, the film thickness is approximately 50 nm). above). Further, it is advantageous that the uppermost dielectric layer has a thickness of approximately 50 nm or more in order to suppress changes in the medium. The dielectric layers other than these need only be able to separate each Te layer or Te-based chalcogenide layer, and therefore need only have a thickness of about 5 nm or more.

In addition to the function of achieving separation of the Te layer, etc., the dielectric layer also has the function of preventing deformation of the Te layer, etc., which may occur during many repetitions of recording/erasing cycles. This prevents agglomeration, fusion, etc. between recording medium particles, and maintains the particle size of the particles in a fine state.

Further, looking at FIG. 2, there is shown an embodiment in which a light reflecting layer is provided on the dielectric layer. Components other than the light-reflecting layer 7 are the same as the example shown in FIG. 1, so the reference numbers are also the same.

According to this embodiment, the light reflecting layer 7 is provided on the uppermost dielectric layer 6.
By providing a dielectric layer and controlling the thickness of the dielectric layer so as to minimize the intensity of reflected light at the recording wavelength, it is possible to increase the absorption efficiency of the recording laser beam and improve the sensitivity. In this case, in addition to a metal film such as AI or AnSAg, a Te film itself can be used as the light reflection layer. Furthermore, in the example described above, recording is generally performed by laser irradiation from the substrate side, but it is also possible to provide a light reflective layer between the substrate 1 and the dielectric layer 2 and irradiate the laser beam from the medium side. You can also.

Hereinafter, a method of laser recording and erasing on such a medium will be explained in detail. First, the Te layer is generally in a crystalline state after deposition. By irradiating this with a strong laser beam having a short pulse width, it is heated above the melting point of Te, and then rapidly cooled to cause a phase transition of Te from crystalline to amorphous. This amorphization causes a decrease in optical reflectance and an increase in transmittance, so that information can be recorded by such amorphization.

On the other hand, the information recorded by amorphizing crystalline Te through irradiation with a powerful laser can be recorded by irradiating a weak laser beam that does not cause amorphization, and using the intensity of the reflected light or the transmitted light. It can be extracted and regenerated by detecting its intensity.

In addition, to erase the information once recorded, the amorphous portion is irradiated with a laser beam of a power weaker than the laser beam used to record the information but more powerful than the reproduction beam for a relatively long period of time. This is done by causing a phase transition from amorphous to crystalline.

On the other hand, when a Te-based chalcogenide glass layer is used as the recording medium layer, the layer is in an amorphous state after being attached.
Therefore, it is possible to record information by crystallization and erase it by making it amorphous, or to crystallize it in advance by heat treatment, record information by making it amorphous, and erase it by crystallization. .

EXAMPLES Hereinafter, the laser beam recording member of the present invention will be explained in more detail according to examples. However, the scope of the present invention is not limited by the following examples.

Example 1 Polymethyl methacrylate was used as the substrate, on which a dielectric layer of S102 was deposited to a thickness of 20 nm by electron beam evaporation, and a recording medium layer of Te was deposited to a thickness of 5 nm by resistance heating evaporation. These operations were further repeated to produce a medium containing four Te layers. Here, the top layer of Si
The film thickness of O□ was 1100n.

For the medium produced in this way, the wavelength was 850 nm.
Recording and erasing experiments were conducted using a semiconductor laser. That is, when laser irradiation is performed through a substrate with a laser beam diameter of 1.6 μm, amorphization occurs at a laser power of 3 mW and a pulse width of 100 ns on the medium;
Crystallization occurred at W and a pulse width of 5 QOns. The information recorded in this way is processed using a laser power of 1 mW and a pulse width of 50 mW.
When the data was reproduced at 0 ns, no change was observed in the recording state. It has been found that the recording medium obtained according to the present invention described above maintains the same signal output as the initial value even after repeating the recording/reproducing experiment 104 times or more. Further, it was found that the amorphous Te does not crystallize even when stored at 40° C. for one month or more, and the amorphous state is stably maintained.

Example 2 The procedure of Example 1 was repeated. However, instead of the electron beam evaporated film of SiO□, Y2O3, Ta, 05, 8120
When recording media were prepared using electron beam evaporated films of 0.5iO1CeF and Cr2O5, both exhibited recording/erasing characteristics similar to those of Example 1.

Also, instead of 5in2, Pb F 2 and GaO2
, MOO3, MgF2, and TeO7 were similarly produced with respect to recording media produced using resistance-heated vapor-deposited films.

Example 3 A recording medium was produced in the same manner as in Example 1 except that a plasma polymerized film of tetramethyltin was used instead of the electron beam evaporated film of SiO□. Moreover, the polymer film thickness of the top layer in this case was 200 nm. In this medium, amorphization occurs at a laser power of 8 mW and a pulse width of 60 ns, and
- Crystallization occurred at power of 3 mW and pulse width of 500 ns. The medium on which information was thus recorded was reproduced with a laser power of 1 mW and a pulse width of 500 n's, but no change was observed in the recorded state. It was also found that the same signal output as the initial value was maintained even after 104 or more recording/reproducing experiments.

Example 4 Instead of the tetramethyltin plasma polymerized membrane of Example 3, an acetylene plasma polymerized membrane, a styrene plasma polymerized membrane, a hexamethyldisiloxane plasma polymerized membrane, and a hexafluoropropylene plasma polymerized membrane were used, respectively. ,
A medium was prepared in the same manner as in Example 3. The recording/erasing characteristics of these media were similar to those of Example 3. However, when an acetylene plasma-polymerized film and a propylene hexafluoride plasma-polymerized film were used, irreversible changes occurred in the medium after 103 recording/reproducing experiments.

Example 5 In place of the tetramethyltin plasma-polymerized film of Example 3, a polyimide sputtered film and a CU-phthalocyanine vapor-deposited film were used, respectively, and media were prepared in the same manner. The recording/erasing characteristics of the medium thus produced were similar to those of Example 3, but irreversible changes occurred in the medium after 103 recording/erasing experiments.

Example 6 Instead of the Te film of Example 1, 10 nm of Te5sSe
A medium having three layers of this Te5sSes vapor-deposited film was prepared in the same manner as in Example 1 using the Te5sSes vapor-deposited film.

The recording/erasing characteristics of the obtained product were similar to those of Example 1. Note that this medium maintained the same signal output as the initial value even after more than 105 recording/erasing experiments.

Example 7 Instead of the deposited film of Te5sSes in Example 6, T
e5oASsGes, Te5s'Ass, Te5sSt
A medium exhibiting the same characteristics as in Example 6 was also obtained when the ls vapor-deposited film was used.

Example 8 A medium containing two Te layers was prepared according to Example 1, and the thickness of the top layer 5i02 film was 150 nm, and a 50 nm AI vapor deposited film (light reflective layer) was provided thereon. In this medium, amorphization occurs at a laser power of 8 mW and a pulse width of 70 ns, and a laser power of 4 + y + I8 and a pulse width of 500 nm.
Crystallization occurred at s. This medium also had similar recording and erasing characteristics.

Effects of the Invention As described in detail above, the laser beam recording member of the present invention has a laminated structure having at least two Te layers or Te-based chalcogenide glass layers, which are alternately arranged with dielectric layers. , and by controlling the thickness of the Te layer or the Te-based chalcogenide glass layer, various characteristics of the recording medium can be greatly improved. That is, the recording medium of the present invention does not undergo phase separation even after repeated recording and erasing, and has a long life in the amorphous state. In addition, the dielectric layer prevents deformation of the recording medium, and furthermore, the dielectric layer prevents deformation of the recording medium.
Since the particle size of the e-type chalcogenide glass particles remains fine, it is extremely excellent as a laser beam recording member that can perform repeated recording and erasing.

Further, since the recording medium of the present invention uses Te or Te-based chalcogenide glass containing 90% by weight or more of Te, it has high sensitivity and excellent contrast.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a recording medium of the present invention, and FIG. 2 is a schematic cross-sectional view showing the structure of another recording medium of the present invention. (Main reference numbers) 1 Substrate, 2.4.6...Dielectric layer, 3゛, 5"・T
Te-based chalcogenide layer containing e or Te at 90 atomic % or more, 7° light reflection layer. Patent Applicant: Nippon Telegraph and Telephone Public Corporation Agent: Patent Attorney: Masahiko Arai 1: Grave Sale

Claims (3)

[Claims] (1) It has a substrate, at least two dielectric layers provided on the substrate, and a Te layer as a recording medium, and the T
A laser beam recording member characterized in that each of the e-layers is sandwiched between the dielectric layers and alternately provided with the dielectric layers on the substrate. (2) The laser beam recording member according to claim 1, characterized in that a Te-based chalcogenide glass layer containing 90 atomic % or more of Te is used in place of the Te layer. (3) The laser beam recording member according to claim 1 or 2, further comprising a light reflecting layer provided on the recording medium or at the interface between the substrate and the recording medium.