JPH0654549B2 - Optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium capable of recording and reproducing information by laser light, and more specifically, it forms a bit on a thin film by the thermal action of focused laser light. And an optical recording medium for recording.

(Prior Art) A write-once optical disc memory that records and reproduces information on a medium with a laser beam has an excellent feature as a large-capacity recording device because of its high recording density. As a recording medium for such a write-once type optical disk memory, low melting point metals such as Te and Bi or alloys containing them are used (for example, Japanese Patent Publication No. 54-15483).

(Problems to be Solved by the Invention) However, Sn, which is a metal having a low melting point and high sensitivity, has poor quality of a recording / reproducing signal and cannot be put to practical use.

FIG. 4 is a sectional view showing the structure of a conventional optical recording medium. Reference numeral 1 represents a substrate, and 2 represents a recording layer.

Generally, in an optical recording / reproducing apparatus, the reflectance of an optical recording medium must be large and set to a predetermined value in order to ensure the stability of focus servo and tracking servo. In the conventional medium structure as shown in FIG. 4, in order to adjust the reflectance to a predetermined value, it is necessary to adjust the thickness of the recording layer or the composition, so that a constant recording / reproducing characteristic is maintained. It was difficult.

An object of the present invention is to provide an optical recording medium having high recording sensitivity and good signal quality.

(Means for Solving the Problems) The optical recording medium of the present invention is an optical recording medium in which a recording layer is provided on one side of a transparent substrate, and information is recorded and read by irradiation of laser light. A first spacer layer that is substantially transparent and has a higher refractive index at the wavelength of the laser light than the refractive index of the substrate; and refraction that is substantially transparent to the laser light and at the wavelength of the laser light. A second spacer layer having a ratio smaller than that of the first spacer layer, and a recording layer formed of a film containing tin in a volume ratio of 30% or more and nickel oxide in a volume ratio of 20% or more. In addition, an organic layer is formed between the second spacer layer and the recording layer.

(Operation) The present invention solves this problem by the medium structure shown in FIG. That is, by providing the first spacer layer 30 and the second spacer layer 40 between the substrate 10 and the recording layer 20, the reflectance of the medium can be increased, and the refractive index of the first spacer layer 30 can be increased. By adjusting the thickness and the refractive index and the thickness of the second spacer layer 40, it is possible to adjust the reflectance to an arbitrary value in the same recording layer.

The materials and film thicknesses of the first spacer layer 30 and the second spacer layer 40 are selected so as to satisfy the following conditions. First, consider the configuration shown in FIG. 2 in which only the first spacer layer 30 is formed on the substrate 10. A part of the light 100 incident through the substrate 10 is reflected at the interface between the substrate 10 and the first spacer 30 and the interface between the first spacer 30 and the air to become reflected light 200. The magnitude of the reflected light 200 (reflected light) depends on the refractive index and the thickness of the first spacer layer 30. First spacer layer 30 used in the present invention
The material and thickness of is selected to enhance this reflected light 200. That is, the refractive index of the first spacer layer 30 needs to be higher than the refractive index of the substrate 10. next,
Consider the configuration shown in FIG. 3 in which the first spacer layer 30 is provided on the substrate 10 as described above, and the second spacer layer 40 is formed thereon. The light 100 incident through the substrate 10 receives the interface between the substrate 10 and the first spacer layer 30, the interface between the first spacer layer 30 and the second spacer layer 40, and the interface between the second spacer layer 40 and the air. A part of the light is reflected at the interface to become reflected light 300. Reflected light 300
(Reflectance) depends on the refractive index and the thickness of the second spacer layer 40. The material and thickness of the second spacer layer 40 used in the present invention are selected to minimize this reflected light 300. That is, the refractive index of the second spacer layer 40 needs to be smaller than that of the first spacer layer 30.

Although various substrates can be used, synthetic resin, glass, and porcelain are generally preferred. Examples of the synthetic resin include acrylic resin such as polymethylmethacrylate, polycarbonate, polyetherimide, polysulfone, epoxy resin and vinyl chloride resin. A heat insulating layer or a smoothing layer may be provided on the substrate. The substrate may have a disk shape, a sheet shape, or a tape shape.

Information is recorded on the recording layer by forming pits in the recording layer. In a disk medium using a disk-shaped substrate, pits are recorded so as to be formed in a large number of tracks of the same circular shape or spiral shape. In order to accurately record a large number of tracks at regular intervals, light guide grooves are usually provided on the substrate. When the light is incident on a groove having a beam diameter, the light is diffracted. The spatial distribution of the diffracted light intensity varies as the beam center deviates from the groove, and the servo system can be configured to detect this and make the beam incident on the groove center. Usually, the width of the groove is 0.3 to 1.2 μm, and the depth thereof is set to the road circumference of 1/12 to 1/4 of the recording / reproducing laser wavelength used.

The first and second spacer layers used in the present invention are preferably those that are substantially transparent at the read laser wavelength. The first spacer layer may have a refractive index higher than that of the substrate.

For example, Al ₂ O ₂ , CeO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , GeO ₂ , In
₂ O ₂ , MgO, MnO ₂ , MoO ₃ , Nb ₂ O ₅ , NiO, SiO, Sm ₂ O ₂ , Sn
O ₂ , Ta ₂ O ₅ , TeO ₂ , TiO ₂ , V ₂ O ₅ , WO ₂ , Y ₂ O ₃ , ZnO, ZrO ₂
Various oxides such as Si ₃ N ₄ , ZrN such as various nitrides, various carbides such as ZrC, various sulfides such as GeS and ZnS, various cobalt phthalocyanines, copper phthalocyanines, magnesium phthalocyanines, nickel phthalocyanines, zinc phthalocyanines, etc. Various organic substances such as organic dyes, dianhydride 3,4,9,10-perylenetetracarboxylic acid and guanine, various magnetic garnets and Si, Se, Ge, B or compounds thereof can be used. The second spacer layer may have a refractive index smaller than that of the first spacer layer.

For example, AlF ₃ , BaF ₂ , CaF ₂ , CeF ₃ , DyF ₃ , ErF ₃ , EuF ₃ ,
GdF ₃ , HfF ₄ , HoF ₃ , LaF ₃ , LiF, MgF ₂ , NaF, NdF ₃ , Pr
Various fluorides such as F ₃ , SmF ₃ , SrF ₂ , YF ₃ and YbF ₃ , Al ₂ O ₃ ,
CeO ₂ , Cr ₂ O ₃ , Dy ₂ O ₃ , Er ₂ O ₃ , Eu ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , Gd
₂ O ₃ , GeO ₂ , HfO ₂ , Ho ₂ O ₃ , In ₂ O ₃ , Lu ₂ O ₃ , MgO, MnO ₂ ,
MoO ₃ , Nb ₂ O ₅ , NiO, SiO, SiO ₂ , Sm ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ , T
Various oxides such as iO ₂ , V ₂ O ₅ , WO ₃ , Y ₂ O ₃ , ZnO and ZrO ₂ , ZrN
Various nitrides such as ZrC, various carbides such as ZrC, various sulfides such as GeS and ZnS, cobalt phthalocyanine, copper phthalocyanine, molybdenum phthalocyanine, magnesium phthalocyanine, nickel phthalocyanine, zinc phthalocyanine, various organic pigments such as Sudan Black B, various photo Various organic substances such as resists, various electron beam resists, polystyrene and guanine can be used.

The recording layer of the present invention contains 20% or more by volume of nickel oxide as an indispensable constituent element in addition to 30% or more by volume of tin. Since tin is a semi-metal having a low melting point, it has high recording sensitivity. However, since the surface property is poor due to the crystallinity of the material, unrecorded noise is a serious problem and cannot be put to practical use. We have a volume ratio of 20
The present invention has been found out that the surface property is remarkably improved by including tin in an amount of nickel oxide of not less than 100%.

The film thickness of the recording layer is preferably about 100 to 1000Å in terms of recording sensitivity and signal quality, and particularly preferably 150 to 500Å.

The recording layer has a sufficiently excellent optical recording medium property even with a mixture of only tin and nickel oxide, but contains a third substance or the like in order to further improve weather resistance and adjust the reflectance to a predetermined value. You may let me. The third substance is carbon, aluminum, titanium, chromium, iron, cobalt, nickel,
One or more of copper, zinc, germanium, zirconium, niobium, molybdenum, rhodium, palladium, silver, tantalum, tungsten, platinum and gold are desirable. Most of these are effective at a volume ratio of about 10 to 15% or less, but some substances may contain more than these.

When the second spacer layer is an inorganic material, a layer of an organic material is inserted between the recording layer and the second spacer layer to obtain a more sensitive optical recording medium. As this organic matter,
Dianhydride 3,4,9,10-perylenetetracarboxylic acid (PTCD
A), guanine, crystal violet lactone, etc., phthalocyanine dyes such as cobalt phthalocyanine, copper phthalocyanine, magnesium phthalocyanine, nickel phthalocyanine, etc., these alkyl-substituted phthalocyanine dyes, and various organic dyes such as anthraquinone dyes can be used, Organic dyes having absorption in the near infrared such as 5-amino-8- (p-ethoxyanilino) -2,3-dicyano-1,4-naphthoquinone dye can also be used. Thickness of 30 when using absorbing dye
It is desirable to insert a thin film of 0 Å or less. Even when using non-absorptive organic matter, its refractive index is
When the refractive index of the spacer layer is larger than that of the spacer layer, the effect of increasing the reflectance can be increased by reducing the thickness.

Example 1 An example of the present invention will be described below.

Insert an acrylic resin disk substrate with an inner diameter of 15 mm, outer diameter of 120 mm, and thickness of 1.2 mm with a guide groove into the vacuum evaporation system, and 2 x
Evacuation below 10 ^-5 Torr. As an evaporation source, Sn was put in a resistance heating boat made of molybdenum, and NiO and SiO ₂ were put in an electron beam heating crucible.

First, NiO was vapor-deposited at 1100Å, and SiO ₂ was vapor-deposited at 1300Å on it. Next, using a crystal oscillator type film thickness monitor,
The recording layer was formed by co-evaporating while controlling the deposition rate of NiO.

Table 1 shows the substrate incident reflectance and the signal-to-noise ratio (C / N) at a wavelength of 8300Å of the manufactured optical recording medium. When the volume ratio of NiO is less than 20%, the noise is large and the C / N is poor. When the volume ratio of Sn is less than 30%, the sensitivity is insufficient. Therefore, the volume fraction of NiO is 2
A range of 0% or more and a volume ratio of Sn of 30% or more is a practical composition range. For comparison, Sample 2
Table 2 shows the reflectance of the sample 5 without the first spacer layer (NiO) and the second spacer layer (SiO ₂ ). It can be seen that the reflectance is increased by adopting the configuration of the present invention (Table 1).

Example 2 SnO ₂ was used as the first spacer layer, guanine was used as the second spacer layer, and Sn and NiO were co-evaporated as the recording layer to prepare an optical recording medium. The characteristics are shown in Table 3.
Good medium characteristics are obtained. Since the optical recording medium of this embodiment uses an organic material as the second spacer layer, it has higher sensitivity than the optical recording medium of the first embodiment.

Example 3 1000 Å thick copper phthalocyanine as the first spacer layer,
As the second spacer layer, 1400Å thick SiO ₂ was used, and as the recording layer, Sn and NiO and a NiCr alloy with a weight ratio of 80:20 were mixed together on an acrylic substrate so that the volume ratio was 55: 40: 5. An optical recording medium was produced by vapor deposition. The reflectance was -21%, and the C / N was 48 dB or more, which was a good characteristic.

(Example 4) SnO ₂ of 900Å thickness as the first spacer layer, using the 1100 Å CEC ₂ thick as the second spacer layer, Sn and N as a recording layer
iO on the acrylic substrate in a volume ratio of 58:42
An optical recording medium was prepared by co-evaporation with a thickness of 400 Å. Reflectance is ~
It was 26%, and the C / N was 48 dB or more, which was a good characteristic.

Example 5 900 Å-thick SnO ₂ was used as the first spacer layer, 1000 Å-thick CeO ₂ was used as the second spacer layer, and 100 Å of crystal violet lactone was vapor-deposited thereon, and then Sn and NiO were deposited as the recording layers. An optical recording medium was produced by co-evaporating 400 Å thick on an acrylic substrate so that the ratio was 58:42. The reflectance was ˜26% and the C / N was 48 dB or more, which was a good characteristic. In particular, the medium of this example has a higher sensitivity than the medium of Example 4 because the organic substance is inserted between the second spacer layer of the inorganic substance and the recording layer, and the medium has a sensitivity of 10 m / m.
A C / N of 48 dB or more was obtained even at a high linear velocity of s or more.

Example 6 NiO is used as the first spacer layer and SiO _{2 is used} as the second spacer layer.
Was used and PTCDA was vapor-deposited thereon, and then Sn and NiO were co-evaporated as a recording layer to prepare an optical recording medium. The characteristics are shown in Table 4. Good medium characteristics are obtained.

(Effects of the Invention) As is clear from the above examples, according to the present invention, an optical recording medium having high recording sensitivity and good signal quality can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical recording medium which is an embodiment of the present invention,
2 and 3 are schematic diagrams for explaining the principle of the optical recording medium of the present invention, and FIG. 4 is a schematic diagram of a conventional optical recording medium. In the figure, 1 and 10 are substrates, 2 and 20 are recording layers, and 30
Is a first spacer layer, 40 is a second spacer layer, 100
Indicates incident light, and 200 and 300 indicate reflected light.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 61-267949 (JP, A) JP 60-177447 (JP, A) JP 55-126480 (JP, A)

Claims (2)

[Claims] 1. An optical recording medium in which a recording layer is provided on one side of a transparent substrate and information is recorded and read by irradiation of laser light, the optical recording medium being substantially transparent to the laser light and having a wavelength of the laser light. A first spacer layer having a refractive index higher than that of the substrate, and a first spacer layer that is substantially transparent to the laser light and has a refractive index at the wavelength of the laser light.
And a recording layer made of a material containing tin in an amount of 30% or more by volume and nickel oxide in an amount of 20% or more by volume. Medium. 2. An optical recording medium in which a recording layer is provided on one side of a transparent substrate and information is recorded and read by irradiation with laser light, the optical recording medium being substantially transparent to the laser light and having a wavelength of the laser light. A first spacer layer having a refractive index higher than that of the substrate, and a first spacer layer that is substantially transparent to the laser light and has a refractive index at the wavelength of the laser light.
A second spacer layer smaller than the spacer layer, an organic layer, and a recording layer made of a material containing tin in a volume ratio of 30% or more and nickel oxide in a volume ratio of 20% or more. An optical recording medium characterized by: