JP2647982B2 - Optical memory - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical memory used for audio equipment or information equipment.

[Prior Art] Conventionally, aluminum or gold has been used as a material of a reflection film of a compact disk (hereinafter abbreviated as CD), which is one of optical storage media. However, in recent years, CD-ROMs in which computer data is recorded on CDs have become widespread, and there has been a demand for a CD-ROM having high storage stability under high temperature and high humidity.

[Problems to be Solved by the Invention] Conventionally, an optical memory using a reflective film of gold or aluminum, under such a severe environment, causes corrosion when the deposited reflective film is aluminum, and an underlayer when the deposited reflective film is gold. There has been a problem that it has been separated from the body and the error rate, which is an index of signal reading, has increased, and it has been impossible to meet the above-mentioned needs. Reflective film materials other than aluminum and gold were in a state where they could not be used due to insufficient reflectance.

The present invention has been made in order to solve the conventional problems as described above, and has an optical memory having a weather resistance, particularly excellent corrosion resistance and adhesion, and having a reflective film having a high reflectance. To provide.

[Means for Solving the Problems] The present invention provides a transparent substrate, a high refractive index layer made of any of silicon and germanium coated on a recording bit forming surface of the transparent substrate, silicon oxide, calcium fluoride, Alternatively, there is provided an optical memory element comprising a low refractive index layer made of any one of magnesium fluoride and a reflection layer made of any one of chromium, tantalum, and titanium nitride in this order.

Silicon and germanium can be used for the high refractive index layer used in the present invention.

The low refractive layer used in the present invention can use silicon oxide, calcium fluoride, or magnesium fluoride.

The reflection layer used in the present invention is chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium,
Metals such as zirconium, hafnium, manganese, rhenium, ruthenium, iron, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, zinc, cadmium, tin, lead, thallium, antimony, bismuth, indium, gallium and alloys thereof Alternatively, a metal nitride such as titanium nitride, zirconium nitride, or hafnium nitride can be used. The use of a single layer of gold or silver as the reflective layer is not desirable in terms of adhesion, and the use of copper or aluminum is undesirable in terms of corrosiveness. It is desirable to use it as an alloy with the metal to be used.

As the transparent substrate used in the present invention, acrylic resin, polycarbonate resin, polyolefin resin, epoxy resin, fluororesin, glass, sol-gel glass, or the like can be used.

The optical storage medium of the present invention is formed by alternately forming a high refractive index layer and a low refractive index layer on a transparent substrate on which recording pits are formed by injection molding or close transfer from a stamper, an ion plating method, a cluster method, or the like. It is formed by coating with an ion beam method, a plasma CVD method, a vapor deposition method, or the like, and further, if necessary, coating a reflective layer on the combination layer in the same manner as described above.

As the transparent substrate, for example, a silicate polymer is spin-coated on a glass substrate, and a pit is transferred by bringing a stamper into close contact with the glass substrate to form a pitted transparent substrate. Alternatively, a resin may be injected into the mold of the stamper and taken out of the mold to form a pitted transparent substrate.

The optical memory of the present invention thus produced has both high reflectance and high weather resistance (high adhesion and high corrosion resistance), and is far superior to the conventional one in which a gold or aluminum reflective film is directly coated on a transparent substrate. Reliable for long-term data storage.

[Operation] In the optical storage medium of the present invention, a combination layer including a high refractive index layer and a low refractive index layer is formed on a transparent substrate. Due to this combination layer, reflected light from each layer causes multiple interference,
At this time, if the thickness of each layer is selected to an appropriate value, the phases match, and the reflectance can be increased to nearly 100%. Therefore, it is not necessary to form a reflective film made of Al, Au, or the like directly on the transparent substrate as in the related art, and a highly reliable optical memory is provided.

The reflectance can be made close to 100% by using only the combination of the high refractive index layer and the low refractive index layer, but a combination of multiple layers is required. Thus, by providing a reflective layer on a combination layer of a low refractive index layer and a high refractive index layer, a high reflectance can be obtained with a small number of combined layers. In addition, as the difference between the refractive indices of the high refractive index layer and the low refractive index layer increases, the thickness of the two layers can be reduced, and the shape (depth, width, length) of the pits is hardly impaired.

Example An example of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a comparative example of an optical storage medium, wherein FIG. 1 (a) is a partial sectional view thereof, and FIG. 1 (b) is an enlarged sectional view of a portion A in FIG. 1 (a). Here, the transparent substrate 1, the high refractive index layer 2, and the low refractive index layer 3 correspond to I and II in Table 1, respectively.
Two samples coated with the materials, configurations, and film thicknesses shown in Table 1 were produced.

2A and 2B show a comparative example of the optical storage body, wherein FIG. 2A is a partial cross-sectional view thereof, and FIG. 2B is an enlarged cross-sectional view of a portion B in FIG. Here, the transparent substrate 1, the low-refractive-index layer 3, and the high-refractive-index layer 2 correspond to III and I in Table 1, respectively.
Two samples covered with the material, configuration and film thickness shown in V were prepared.

FIG. 3 is a partial cross-sectional view showing one embodiment of the optical storage body of the present invention. Here, three samples in which the transparent substrate 1, the high-refractive-index layer 2, the low-refractive-index layer 3, and the reflective layer 4 were coated with the materials, configurations, and film thicknesses shown in Tables V, VI, and VII, respectively, were used. Produced.

FIG. 4 is a partial sectional view of an embodiment in which the present invention is applied to a read-only optical storage medium. Here, 1 is a tempered glass substrate provided with recording pits by a sol-gel method, a high refractive index layer 2, a low refractive index layer 3, and a reflective layer 4, each of which is coated with the material, configuration, and film thickness shown in VIII of Table 1. Samples were made.
A silicon-based resin film 5 is formed on the reflective layer 4 in order to prevent the reflective layer and the like from being damaged when the sample is operated.
μm coated. The substrate side of the tempered glass was coated with 100 nm of silicon oxide containing 10% zirconium oxide as a protective film 6 for preventing corrosion of the glass.

 Table 1 shows the reflectances of the obtained samples.

Next, these samples and a comparative sample in which aluminum and gold were formed as reflective films on a transparent substrate made of a polycarbonate resin were subjected to a weather resistance test at a temperature of 70 ° C. and a relative humidity of 95% for 6 months. The number of errors as an index of was measured. After the weather resistance test for 6 months, the number of errors of the sample of the present invention did not deteriorate at all, but the comparative sample using the aluminum reflective film was erroneous due to corrosion, and the comparative sample using the gold reflective film was erroneous due to peeling. Deteriorated to the point that measurement of the sample became impossible.

[Effects of the Invention] As described above in detail, the optical storage medium of the present invention has excellent adhesion to a transparent substrate, has corrosion resistance and high reflectance, and uses a reflection film of aluminum or gold. The reliability can be greatly improved as compared with the optical storage medium that is used.

[Brief description of the drawings]

1 and 2 are partial cross-sectional views of a comparative example of the optical storage body. 3 and 4 are partial cross-sectional views of an embodiment of the optical storage medium of the present invention. 1 ... transparent substrate 2 ... high refractive index layer, 3 ... low refractive index layer, 4 ... reflective layer,
5: Resin film, 6: Protective film

Claims (1)

(57) [Claims] 1. A transparent substrate, a high refractive index layer made of any one of silicon and germanium coated on a recording bit forming surface of the transparent substrate, and one of silicon oxide, calcium fluoride, and magnesium fluoride. An optical memory comprising: a low-refractive-index layer; and a reflective layer made of any one of chromium, tantalum, and titanium nitride in this order.