JPH0477974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an optical memory device that records, reproduces, erases, etc. information using light such as a laser.

<Prior Art> In recent years, optical memory devices are high-density, large-capacity memories, and are therefore expected to have a promising future, and various research and development efforts are being carried out in a variety of fields. The reason why this optical memory element has a high density and a large capacity is that the bit, which is the unit of recording information, is determined only by the beam diameter of the light, so its shape can be reduced to a size of about 1 μm. However, this imposes many restrictions on devices that write and read information to and from optical memory elements. That is, in order to record information at a fixed location or to reproduce information recorded at a fixed location, the light beam must be positioned extremely accurately. Generally, in a playback-only optical memory, address information can be stored in advance in the recorded bits, making it possible to position the light beam while playing back the recorded information, but in an additional recording memory or a rewritable memory, Since it is difficult to record address information at the time of response recording, in this case a method is adopted in which some kind of guide signal and guide address are stored in advance on the memory board. For example, Fig. 1 shows a partial perspective view of a memory board of a conventional additional recording memory or rewritable memory.As shown in the figure, uneven grooves are formed on the board, and information is stored along the grooves. It is recorded or played back. Further, the uneven groove has a shape that is interrupted in the circumferential direction, and this provides bit information indicating the address of the groove. Although several methods for forming the uneven grooves have already been proposed, the following two methods are common in terms of productivity. One is a stamper with uneven grooves (for example, as shown in Figure 2).
There is a method in which uneven grooves are directly transferred to a resin substrate 2 such as acrylic or polycarbonate by injection molding using Ni (made of Ni) 1, and the other method is to transfer uneven grooves directly to a substrate 4 made of glass or acrylic etc. as shown in Fig. 3. This is a method (referred to as 2P method) in which an ultraviolet curing resin 3 is inserted between a stamper 1 having grooves and uneven grooves are transferred to the ultraviolet curing resin 3. A recording medium is subsequently formed on the uneven grooved substrate thus produced. This recording medium is an additional recording type.
There are materials such as TeOx, TeSe, and TeC, and rewritable materials such as GdTbFe, GdTbDyFe, and TbFe are known. However, most of these recording media lack corrosion resistance, which is often a disadvantage as optical memory devices. For example, in Te-based materials, which are representative of the additional recording type, progress of oxidative corrosion caused changes in reflectance and transmittance, resulting in deterioration of playback characteristics. In addition, rare earth metals in rare earth/transition metal alloys that are used in rewritable media are particularly susceptible to oxidation, which causes changes in coercive force as oxidation corrosion progresses, resulting in the undesirable problem of fluctuations in recording sensitivity. was. The cause of such corrosion is oxygen and moisture adsorbed on the substrate before the recording medium is formed, or oxygen generated by separation of substrate components during film formation on the substrate in the case of film formation methods such as sputtering. etc., and separated oxygen mixed in during formation of the oxide protective film after medium formation. Furthermore, in optical memory devices equipped with a resin substrate with grooves and grooves, oxygen, moisture, and the like entering through the resin substrate has been a major problem.

<Objective> The present invention is an improvement on the above-described conventional technology, and an object of the present invention is to provide an optical memory element that has high reliability against corrosion of a recording medium due to moisture, oxygen, etc.

<Example> Hereinafter, an example of the optical memory device according to the present invention will be described in detail with reference to the drawings. FIG. 4 is a partial side sectional view showing the structure of an embodiment of the optical memory device according to the present invention. Reference numeral 5 denotes a glass or acrylic substrate, on which is provided an ultraviolet curable resin layer 3 having uneven grooves formed by the 2P method described above, and on top of which is formed AlN (aluminum nitride) with a film thickness of 900 to 1000 Å. Film 6 (transparent dielectric film) is formed by reactive sputtering of aluminum in a nitrogen atmosphere, and a film thickness of 300-500 Å is deposited thereon.
A GdTbFe amorphous alloy thin film 7 (recording medium made of rare earth/transition metals) is formed by sputtering, an AlN film 8 with a thickness of 400 to 500 Å is formed on top of it, and Cu, Al, stainless steel, etc. A reflective film 9 made of metal such as Ni is formed. The nitride film 6 prevents oxygen and moisture from entering the alloy thin film 7 from the grooved ultraviolet resin layer 3 side. Since both this nitride film 6 and the nitride film 8 that protects against oxygen and moisture entering from the outside are nitrides, there is no possibility that separated oxygen will be generated during film formation. Further, in this example, the nitride films 6, 8 and the reflective film 9 also promote improvement in the characteristics of the magneto-optic effect.

Note that the nitride film is AlN used in the example.
(aluminum nitride) and TiN (titanium nitride)
etc. can be used.

<Effects> According to the present invention, in an optical memory element equipped with a resin material in which guide grooves are formed by injection molding or the 2P method, recording is possible by having a structure in which a recording medium is sandwiched between oxygen-free nitride films. This makes it possible to prevent deterioration of the medium due to oxidation and to obtain a highly reliable optical memory element.

[Brief explanation of the drawing]

Figure 1 is a partial perspective view of a conventional memory board, Figure 2 is a partial perspective view of a conventional memory board.
3 and 3 are explanatory diagrams showing the manufacturing process of the grooved memory substrate, and FIG. 4 is a partial side sectional view showing the structure of an embodiment of the optical memory element according to the present invention. In the figure, 1: stamper, 2: resin substrate, 3: ultraviolet curing resin, 4: substrate, 5: glass or acrylic substrate, 6: AlN film, 7: alloy thin film, 8:
AlN film, 9: reflective film.

Claims (1)

[Claims] 1. A substrate made of glass or acrylic, an ultraviolet curable resin layer having uneven grooves formed on the substrate, and a third layer made of aluminum nitride or titanium nitride formed on the ultraviolet curable resin layer. a transparent dielectric film of No. 1; an optical memory recording medium thin film made of a rare earth/transition metal alloy formed in contact with the first transparent dielectric film; and an optical memory recording medium thin film made of a rare earth/transition metal alloy formed in contact with the first transparent dielectric film; An optical memory element comprising: a second transparent dielectric film made of titanium nitride; and a metal reflective film.