JPH0481952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light.

(Prior Art) Optical disk memories, which record and reproduce information on a medium using laser light, have excellent characteristics as large-capacity recording devices because of their high recording density. As materials for this optical recording medium, chalcogen elements such as Te or compounds thereof are used (Japanese Patent Publication No. 47-26897). In particular, tellurium selenium alloys are often used (Japanese Patent Publication No. 54-41902, Japanese Patent Publication No. 57-7919, Japanese Patent Publication No. 57-56058). In recent years, in order to downsize recording devices, semiconductor lasers have been used as laser light sources. Semiconductor lasers have an oscillation wavelength of around 8000 Å, and tellurium selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption (phys.stat. sol.71891964)).

(Problems to be Solved by the Invention) However, these media do not have sufficient recording sensitivity in order to use inexpensive semiconductor lasers.

An object of the present invention is to provide an optical recording medium that has good weather resistance, high sensitivity, and good signal quality.

(Means for solving the problem) The optical recording medium of the present invention is an optical recording medium in which information is recorded and read by laser light, and includes a layer of an alkyl-substituted phthalocyanine dye and a layer mainly composed of a tellurium selenium alloy. It is characterized by having at least two layers.

(Function) Optical recording media have conventionally had a structure as shown in FIG. That is, the recording layer 21 is provided on the substrate 1. The recording laser beam is focused and irradiated onto the recording layer 21 through the substrate 1, and pits 22 are formed.
As the substrate 1, synthetic resins such as polycarbonate, polyolefin, polymethylpentene, acrylic, and epoxy resins, and glass are used. Guide grooves are provided on the substrate so that pits are recorded concentrically or spirally at regular intervals with high precision. When light enters a groove with a width similar to the diameter of the laser beam, the light is diffracted, and as the beam center shifts from the groove, the spatial distribution of the intensity of the diffracted light changes.This is detected and the laser beam is directed to the center of the groove. The servo system is configured as follows. The width of the groove is usually 0.3 to 1.3 μm, and the depth of the groove is set in the range of 1/12 to 1/4 of the laser wavelength used.
A servo system is similarly configured for focusing light. Information is read by irradiating a laser beam with a power weaker than that used during recording so as to pass over the pits, and detecting changes in reflectance caused by the presence or absence of pits. Various materials can be used for the recording layer 21, but in consideration of weather resistance, a film containing tellurium selenium alloy as a main component is desirable.
However, if only the tellurium selenium alloy layer is used, an inexpensive semiconductor laser with low output power cannot be used as a recording light source. Therefore, it has been proposed that high sensitivity can be achieved by inserting an organic guanine layer between the substrate and the recording layer (Japanese Patent Application Laid-Open No. 59-232895), but the present inventors have evaluated this structure. However, it was not possible to obtain sufficient weather resistance. As a result of examining various organic materials, the present inventors found that by providing an alkyl-substituted phthalocyanine dye layer as shown in Figure 1, an optical recording medium with high sensitivity and sufficient weather resistance could be obtained. It has arrived.

(Example) Examples of the present invention will be described below.

A polycarbonate resin disk substrate with an inner diameter of 15 mm, an outer diameter of 130 mm, and a thickness of 1.2 mm, which has been annealed at 100℃ for 2 hours, is placed in a vacuum evaporation apparatus and 6×
Exhaust to below 10 ^-6 Torr. As an evaporation source, the first
A t-butyl-substituted vanadyl phthalocyanine dye was placed in a resistance heating boat, Te was placed in a second resistance heating boat, and Se was placed in a third resistance heating boat. First, a phthalocyanine dye is deposited to a thickness of 100 Å, and then co-deposited by controlling the deposition rate ratio from each deposition source using a quartz crystal detector, selenium is deposited to a thickness of about 250 Å at 23 atomic percent.
A thick tellurium selenium alloy layer was formed. After annealing this optical disk in a nitrogen atmosphere at 95° C. for 1 hour, the reflectance of the substrate at a wavelength of 8300 Å was measured and found to be 32%. Semiconductor laser light with a wavelength of 8300 Å is incident through the substrate and focused to a medium diameter of 1.6 μm on the recording layer, with a medium linear velocity of 5.6 m/sec and a recording frequency.
3.77MHz, recording pulse width 70msec, recording power
Recorded under 5.5mw conditions and played back at 0.7mw. Carrier to noise ratio (C/
N) was good at 48 dB. This optical disk
After storage for 60 hours in a high temperature and high humidity environment of 70°C and 80%, there were no changes in the above characteristics, confirming that the optical recording medium has excellent weather resistance.

For comparison, a disc using a vanadyl phthalocyanine dye without alkyl substitution had a problem in that its optical properties changed when stored for a long time under the above-mentioned high temperature and high humidity conditions. This is because unsubstituted vanadyl phthalocyanine crystallizes and its extinction coefficient at a wavelength of 8300 Å becomes large. For example, if you prepare t-butyl-substituted vanadyl phthalocyanine and unsubstituted vanadyl phthalocyanine on a glass substrate, and annealing them at 300°C for 1 hour, the unsubstituted sample will undergo crystallization. However, alkyl-substituted samples do not cause surface roughness. That is, alkyl-substituted phthalocyanine is difficult to crystallize due to its steric hindrance and has excellent weather resistance.

The t-butyl-substituted vanadyl phthalocyanine film has absorption at a wavelength of 8300 Å, and the recording pits are formed by holes in the tellurium selenium alloy layer and recesses in the phthalocyanine layer.

The thickness of the alkyl-substituted phthalocyanine dye layer is 5
The thickness of the tellurium selenium alloy layer is preferably in the range of 100 Å to 1000 Å from the viewpoint of recording characteristics. The content of selenium is desirably in the range of 2 to 50 atomic percent from the viewpoint of weather resistance.

The tellurium selenium alloy layer contains a material selected from the group of lead, arsenic, tin, germanium, cadmium, thallium, antimony, sulfur, phosphorus, indium, gallium, zinc, bismuth, aluminum, copper, silver, magnesium, tantalum, gold, and palladium. Addition of at least one element may improve the shape of the pit. However, the amount added is preferably 25% or less in terms of atomic percent.

The alkyl-substituted phthalocyanine layer and the tellurium selenium alloy layer may be formed by sputtering, ion plating, or ion beam deposition in addition to this embodiment.

(Effects of the Invention) As is clear from the above examples, the present invention provides an optical recording medium with good weather resistance, high sensitivity, and good signal quality.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the optical recording medium of the present invention, and FIG. 2 is a schematic cross-sectional view of a conventional optical recording medium. In the figure, 1 is a substrate, 2 is an alkyl-substituted phthalocyanine layer, 3 is a tellurium selenium alloy layer, 21 is a recording layer, and 22 is a pit.

Claims (1)

[Claims] 1. An optical recording medium in which information is recorded and read by laser light, characterized by having at least two layers: a layer of an alkyl-substituted phthalocyanine dye and a layer mainly composed of a tellurium selenium alloy. Medium.