JPH05266521A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To enhance a recording sensitivity and carrier level and to improve stability with lapse of time by providing an interference layer, an optical recording layer and a reflection layer on a substrate and constituting the reflection layer of an Al alloy contg. Mn. CONSTITUTION:The interference layer, the optical recording layer and the reflection layer are provided on the substrate. The reflection layer is constituted of the Al contg. the Mn. The content of this Mn is >=1 atomic %, more preferably about 2 to 20 atomic %. Resins of an acrylic system, carbonate system and olefin system, aluminum, glass, etc., are used as the substrate. Amorphous magnetic alloys of rare earths and transition metals, such as PbTe, PbFeCO, TbCo and DyFeCo, perpendicularly magnetized films of polycrytals, such as MnBi and MnCuBi, etc. are used as the recording layer. The interference layer is constituted of metal oxides, metal nitrides, inorg. carbides, etc. Al2O3, Ta2O3, SiO2, etc., are used as the metal oxides constituting the interference layer, nitrides of Si, At, Ge, etc., are used as the metal nitrides, B4C, SiC, etc., are used as the inorg. carbides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium.

[0002]

BACKGROUND OF THE INVENTION Magneto-optical recording media have been actively researched and developed as high density rewritable recording media. As the recording layer of this magneto-optical recording medium, at present, a rare earth-transition metal thin film is known as the most popular one. Further, it has been proposed to provide a reflective layer in order to increase the efficiency in recording / reproducing by irradiation with laser light. It is said that this system can obtain a high C / N ratio by using the Kerr effect and the Faraday effect together.

By the way, it has been proposed to use Al or Te for the reflective layer (Japanese Patent Laid-Open No. 62-52744). However, the reflective layer made of Al has a problem that recording sensitivity is significantly lowered due to its high thermal conductivity,
Further, although the Te-made reflective layer has improved recording sensitivity, it has a problem that a sufficiently high C / N cannot be obtained because of its low reflectance.

[0004]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide an optical information recording medium having high recording sensitivity, high carrier level and excellent stability over time. An object of the present invention is an optical information recording medium in which an interference layer, an optical recording layer and a reflection layer are provided on a substrate, wherein the reflection layer is composed of an Al alloy containing Mn. And an optical information recording medium.

The Mn content of the Al alloy forming the reflective layer is preferably 0.1 atom% or more, more preferably about 2 to 20 atom%. Hereinafter, the present invention will be described in detail. The substrate used in the optical information recording medium of the present invention is made of various materials such as plastic such as acrylic resin, carbonate resin, and olefin resin, metal such as aluminum, or glass. Of course, other materials can be used, and the materials are not limited to these. The thickness of the substrate is generally about 1 to 2 mm.

Optical recording layers used in the optical information recording medium of the present invention include TbFe, TbFeCo, TbCo and D.
Amorphous magnetic alloys of rare earths and transition metals such as yFeCo and polycrystalline perpendicular magnetization films such as MnBi and MnCuBi are used. Of course, it is not limited to these,
It is preferably a rare earth-transition metal based magneto-optical recording layer. The thickness of such an optical recording layer is 150 to 1
000Å, more preferably about 200 to 500Å.

In the present invention, an interference layer is provided between the substrate and the optical recording layer. This interference layer is for reducing the noise by lowering the reflectance by utilizing the light interference effect of the transparent film having a high refractive index and improving the C / N. Although the optimum film thickness of the interference layer varies depending on the refractive index, it is preferably 400 to 1500Å, and more preferably about 500 to 1000Å. The interference layer may be a single layer film or a multilayer film. The interference layer is made of metal oxide, metal nitride, inorganic carbide, or the like.

Examples of the metal oxide forming the interference layer include Al ₂ O ₃ , Ta ₂ O ₃ , SiO, and SiO ₂ .
Alternatively, a mixture thereof, a complex oxide such as Al-Ta-O, or the like can be given. Furthermore, other elements such as Ti, Zr, W, Mo and Yb can be added to these metal oxides.
These oxides may be used alone or in combination with Al or Ta to form an oxide. That is, these metal oxides have a dense structure, prevent moisture and oxygen from entering from the outside, have high corrosion resistance, have low reactivity with the magneto-optical recording layer, and are made of resin as a substrate. When one of these is used, it has excellent adhesion to the substrate.

Examples of metal nitrides include Si, Al,
A metal nitride such as Ge, a composite nitride of two or more kinds of these, or a composite nitride of these and Nb, Ta (for example, SiNbN, SiTaN, etc.) can be used.
Of these, a nitride containing Si is preferable.
These metal nitrides have a dense structure, prevent moisture and oxygen from entering from the outside, have high corrosion resistance, and have low reactivity with the magneto-optical recording layer.

Examples of the inorganic carbide include B ₄ C and SiC. In the present invention, a reflective layer made of an Al alloy containing Mn is provided on a recording layer such as a magneto-optical recording layer. The Mn content in this Al alloy is preferably 0.1 atom% or more. More preferably about 2
It is 20 atomic%. Other elements in this Al alloy,
For example, Cu, Mg, and other unavoidable impurities may be contained. The thickness of this reflective layer is 100 to 1000.
Å, preferably about 200 to 600Å. That is, if it is too thick, the sensitivity is lowered, and if it is too thin, the reflectance is lowered.

As the means for forming the interference layer, the optical recording layer and the reflection layer which are sequentially provided on the substrate, PVD such as sputtering and ion plating, and C such as plasma CVD are used.
A thin film forming means such as VD can be used. PV
To form the interference layer, the optical recording layer, and the reflective layer in D, a target having a predetermined composition may be used and deposited on the substrate by electron beam evaporation or sputtering. The deposition rate of the film is preferably controlled to be within the range of 0.1 to 100Å / sec.

A specific example will be described below.

[0013]

【Example】

[Example 1] A polycarbonate substrate was placed in a sputtering apparatus and evacuated to 5 × 10 ^-7 torr or less,
After that, a mixed gas of Ar and N ₂ was introduced, and reactive sputtering was performed with Si as a target to form a 1000 Å thick Si ₃ N ₄ interference layer on the polycarbonate substrate.

Then, a TbFeCo photomagnetization film having a thickness of 200 Å was formed by binary co-sputtering using a Tb target and a FeCo target in an Ar gas atmosphere. After that, sputtering was performed in an Ar gas atmosphere using an Al target on which a Mn chip was arranged, and a 400 Å thick Mn-containing Al alloy reflection film was provided on the photomagnetization film. The Mn content in the reflective film was adjusted by changing the number of Mn chips.

Then, the film was taken out from the sputtering apparatus, and an ultraviolet curable resin was applied to the surface by a spin coating method so as to have a thickness of 4 μm. [Comparative Example 1] A magneto-optical disk was obtained in the same manner as in Example 1, except that the Mn chip was not used in forming the reflective film.

[Characteristics] The magneto-optical disk of each of the above-mentioned examples is PI
Recording sensitivity and C / N were measured by a dynamic characteristic detector having an N photodiode differential detector. The results are shown in FIG. The recording sensitivity was the recording power (optimum recording power) at which the secondary distortion was minimum. Recording conditions are: C
AV (constant angular velocity) 1800 rpm, radius 30 mm position,
On-groove recording, recording frequency 3.7 MHz, duty 33%. The reproduction conditions are; CAV 1800 rpm and reproduction power 1.0 mV. The composition of the reflective layer was analyzed by the plasma emission method.

From this, it can be seen that the recording medium of the present invention has a high recording sensitivity (small optimum recording power), a high C / N, and excellent reproduction characteristics. In particular, M
The n content is 0.1 at% or more, more preferably about 2
Excellent properties are exhibited when the Al alloy is in the range of 20 at%, more preferably in the range of about 3 to 18 at%.

Further, the magneto-optical disks of the above-mentioned respective examples are adhered together by an adhesive agent, and the temperature is kept at 80 ° C. and the humidity is 85%.
The acceleration test was performed for 000 hours, and the byte error rates before and after the acceleration test were measured. The results are shown in Table 1. Table 1 Mn content Initial bite error rate Bite error rate after test (atomic%) Example 0.1 3.18 × 10 ⁻⁵ 4.07 × 10 ⁻⁵ 0.9 3.21 × 10 ⁻⁵ 3. 28 × 10 ^-5 1.8 1.39 × 10 ^-5 1.37 × 10 ^-5 2.4 1.72 × 10 ^-5 1.71 × 10 ^-5 3.6 6.56 × 10 ^-6 8 .12 × 10 ^-6 7.0 8.06 × 10 ^-6 7.98 × 10 ^-6 15.6 1.62 × 10 ^-5 1.41 × 10 ^-5 18.3 1.01 × 10 ^-5 1.01 × 10 ⁻⁵ 21.2 3.18 × 10 ⁻⁵ 3.21 × 10 ⁻⁵ Comparative example 0 2.75 × 10 ⁻⁵ 5.45 × 10 ⁻⁵ According to this, the reflective layer is made of Al. It can be seen that the increase in error can be suppressed by using the —Mn-based alloy.

The recording / erasing power was made the same as the optimum recording power, the recording / erasing was repeated 1,000,000 times, and the optimum recording power and the C / N were measured again. There wasn't.

[0020]

[Effect] High recording sensitivity, high carrier level, and excellent stability over time.

[Brief description of drawings]

FIG. 1 Mn content in a reflective film and optimum recording power and C
Graph showing the relationship with / N

Claims (2)

[Claims] 1. An optical information recording medium having an interference layer, an optical recording layer and a reflective layer provided on a substrate, wherein the reflective layer is made of an Al alloy containing Mn. Optical information recording medium. 2. The optical information recording medium according to claim 1, wherein the Al alloy contains 0.1 atomic% or more of Mn.