JPH08190733A - Optical recording medium - Google Patents

Abstract

PURPOSE: To provide a phase change type optical recording medium capable of rewriting and having a high rate of erasure at the time of over-writing. CONSTITUTION: This optical recording medium has at least a 1st dielectric layer, a recording layer, a 2nd dielectric layer and an absorption correcting layer made of a material contg. one or more kinds of metallic materials as essential components and contg. at least one kind of compd. selected from among high m.p. carbides, oxides, borides and nitrides. The thickness of the 2nd dielectric layer is 1-50nm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is
The present invention relates to an optical information recording medium capable of recording, erasing and reproducing information.

In particular, the present invention relates to a rewritable phase-change type optical recording medium such as an optical disk, an optical card, an optical tape having a recording information erasing / rewriting function and capable of recording an information signal at high speed and high density. It is a thing.

[0003]

2. Description of the Related Art The conventional techniques for rewritable phase change type optical recording media are as follows. These optical recording media have a recording layer containing tellurium as a main component, and at the time of recording, a focused laser light pulse is irradiated to the recording layer in a crystalline state for a short time to partially melt the recording layer. The melted portion is rapidly cooled by thermal diffusion and solidified to form a recording mark in an amorphous state. The light reflectance of this recording mark is lower than that of the crystalline state, and it can be optically reproduced as a recording signal.

Further, at the time of erasing, the recording mark portion is irradiated with a laser beam and heated to a temperature below the melting point of the recording layer and above the crystallization temperature to crystallize the recording mark in the amorphous state, and the original unrecorded state. Return to the state.

As a material for the recording layer of these rewritable phase change type optical recording media, alloys such as Ge ₂ Sb ₂ Te ₅ (N. Yamada et al. Proc. Int. Symp.on Optical Memory 1
987 p61-66) is known.

Optical recording media using these Te alloys as a recording layer have a high crystallization rate, and high-speed overwriting with a circular single beam is possible only by modulating the irradiation power. In an optical recording medium using these recording layers, a dielectric layer having heat resistance and translucency is usually provided on both surfaces of the recording layer to prevent deformation and opening of the recording layer during recording. Further, a light reflecting metal reflection layer such as Al is provided on the dielectric layer on the side opposite to the light beam incident direction to improve the signal contrast at the time of reproduction by an optical interference effect, and There is known a technique of facilitating the formation of an amorphous recording mark by the cooling effect and improving the erasing property and the repetitive property. Particularly, in the "quick cooling structure" in which the dielectric layer between the recording layer and the reflection layer is made thinner than about 50 nm, compared to the "slow cooling structure" in which the dielectric layer is thickened to about 200 nm, rewriting of recording is repeated. It has relatively little deterioration and has a wide erase power margin (T.Ohta et al, Japanese Jounal
of Applied Physics, Vol 28 (1989) Suppl. 28-3 pp12
3-128).

The problems in the above-mentioned conventional rewritable phase change type optical recording medium are as follows. That is,
The conventional disk structure has a problem that the shape and position of a newly overwritten recording mark are modulated by the signal before overwriting, and the erasing rate and the jitter characteristic are limited. In particular, when applying high-density technology such as miniaturizing the light spot using a short-wavelength laser to achieve high density with pit position recording, or using mark length recording instead of conventional pit position recording, Further, when the high density technology is applied as in the pit position recording, or when the recording is performed at a high linear velocity, the above problems become more serious.

One of the causes of this problem is that the light absorption amount in the amorphous state of the recording layer is higher than the light absorption amount in the crystalline state because the difference in reflectance between the recorded amorphous recording mark and the crystalline state is large. It is conceivable that the recording mark portion is heated faster during recording. In other words, there is a difference in the temperature rise state during recording depending on whether the portion before overwriting is a crystal or an amorphous mark, and as a result, the shape and formation position of the newly overwritten recording mark are overwritten. It is considered that the cause is that the previous signal undergoes modulation and limits the erasure rate and jitter characteristics. Particularly, in the conventional normal quenching structure, as described above, a layer having a high thermal conductivity and a high reflectance such as an Al alloy is provided adjacent to the dielectric layer on the side opposite to the light beam incident direction. Durability and good recording characteristics were obtained, but when a layer with high reflectance was provided in this way, the amount of light absorption in the amorphous state of the recording layer was considerably larger than the amount of light absorption in the crystalline state, It is difficult to solve the above problems.

Further, in order to increase the recording density, the amplitude of the reproduction signal is reduced due to the restriction of the optical resolution in the region where the space between the recording marks is made smaller than the size (λ / NA) of the illuminating light beam. This is also considered to be one of the causes of this issue. Especially, when newly overwriting the recording with the light beam size (λ / NA) or less irradiating the space between the recording marks, the shape and position of the newly overwritten recording marks are modulated and erased. It is considered that the rate and jitter characteristics are limited.

In order to solve such a problem, the following techniques are known as means for solving the problem that the light absorption amount in the amorphous state is higher than the light absorption amount in the crystalline state. That is, as in Japanese Patent Laid-Open No. 5-159360, a second dielectric layer having a thickness of 220 nm and a thickness of 50 nm serving as an absorption correction layer are formed after the second dielectric layer.
There is known a technique in which a relatively thick Al alloy having a thickness of about 50 nm is formed as a heat dissipation layer in order to form Ti of about a certain degree and further reduce a thermal load on the light absorption layer due to a temperature rise due to light absorption. There is.

[0011]

However, the above-mentioned conventional structure is still not sufficient, and the recording characteristics are largely deteriorated due to repeated rewriting, and the characteristics such as jitter are deteriorated due to the thermal interference between the marks. Not suitable for density recording. Further, there is a problem that a sufficient carrier-to-noise ratio (C / N) cannot be obtained in the low linear velocity region.

The object of the present invention is to exhibit excellent characteristics such as the repetitive characteristics of the above rewriting. The present invention relates to improvement of erasing characteristics of a conventional optical recording medium, and an object thereof is to provide a rewritable phase change type optical recording medium having good erasing characteristics at the time of overwriting.

[0013]

According to the present invention, information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light.
It is performed by a phase change between an amorphous phase and a crystalline phase, and contains at least a first dielectric layer, a recording layer, a second dielectric layer, and one or more kinds of metal materials as essential components, and has a high melting point of carbides and oxides. An absorption amount correction layer made of a material containing at least one selected from the group consisting of an oxide, a boride and a nitride, and the thickness of the second dielectric layer is 1 nm or more and 50 nm or less. The present invention relates to an optical recording medium characterized by: This is the first invention.

The present invention also relates to the optical recording medium of the first invention, wherein the recording layer has a thickness of 10 nm or more and 45 nm or less. This is a second invention.

In the present invention, the metallic material is Nb, Mo,
The present invention relates to the optical recording medium of the first invention or the second invention, which is at least one selected from the group consisting of W, Ti, and Te. This is a third invention.

Further, according to the present invention, the absorption correction layer has a thickness of 1 n.
The present invention relates to the optical recording medium of the first invention, the second invention or the third invention, characterized in that it is not less than m and not more than 200 nm. This is a fourth invention.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A typical layer structure of a constituent member of an optical recording medium of the present invention is, for example, a transparent substrate / first dielectric layer /
A structure comprising a laminated body of recording layer / second dielectric layer / absorption amount correction layer as a member, or transparent substrate / first dielectric layer / recording layer / second dielectric layer / absorption amount correction layer / reflection layer The laminated body of is constituted as a member. However, it is not limited to this.

In the optical recording medium of the present invention, by selecting an appropriate material for the absorption correction layer, the absorption amount of light in the amorphous recording layer is reduced and the difference in absorption amount from the crystalline state is reduced. Further, the light absorption amount in the crystalline state may be larger than the light absorption amount in the amorphous state. Due to the effect of the absorption amount correction, the difference in temperature rise during recording can be reduced, and the disorder of the shape of the recording mark, the deviation of the formation position, etc. can be reduced, and therefore the erasing characteristic and the jitter characteristic at the time of overwriting can be improved.

The absorption correction layer of the present invention contains at least one metal material as an essential component and contains at least one selected from the group consisting of high melting point carbides, oxides, borides, and nitrides. Consists of.

This absorption amount correction effect is determined by the thickness of each constituent layer and the optical constants, but particularly greatly depends on the optical constants (real part and imaginary part of the refractive index) of the absorption amount correction layer. The real part and the imaginary part of the absorption correction layer are appropriately large, that is, the real part of the refractive index is preferably 1.0 or more and 8.0 or less, more preferably 2.0 or more and 5.0 or less, and Imaginary part is 1.5
The above is 6.5 or less, more preferably 2.0 or more and 5.5 or less. In the present invention, in particular, Nb, Mo, W, Ti, which has a reasonably large real part of refractive index and imaginary part of refractive index, An absorption correction layer made of a material containing at least one selected from the group consisting of Te as an essential component and containing at least one selected from the group consisting of high melting point carbides, oxides, borides, and nitrides. By providing it on the second dielectric layer, the light absorption amount of the crystal part and the recording mark part of the recording layer is optically adjusted,
The main purpose is to suppress the shape distortion of the recording mark and to reduce the deterioration of the erasing characteristics at the time of overwriting.
Further, by forming the absorption correction layer from a material containing at least one kind of metal material and at least one kind selected from the group consisting of high melting point carbides, oxides, borides, and nitrides, It is also effective in improving reliability by reducing residual stress and improving corrosion resistance.

The optical constants are measured, for example, as follows. That is, first, a thin film made of the material used for the absorption correction layer is formed on quartz glass and measured at the same wavelength as the wavelength of light for recording, erasing, and reproducing by the standard spectroscopic ellipso method using the following device. To do. When the optical recording medium is a rewritable phase change type optical disc, the layer formed by using an adhesive tape is peeled off for measurement.

Measuring device: Nikon Corporation Phase difference measuring device NPDM-1000 Spectrometer: M-70 Light source: Halogen lamp Detector surface: Si-Ge polarizer, analyzer: Gram-Thomson Analyzer rotation speed: 2 times Angle: 45-80 degree, 2 degree pitch

The material of the absorption correction layer of the present invention is N
At least one selected from the group consisting of b, Mo, W, Ti, and Te as an essential component, and contains at least one selected from the group consisting of high melting point carbides, oxides, borides, and nitrides. The material described above is preferable because it has an appropriately large optical constant. Here, the high melting point refers to a compound having a melting point of 800 ° C. or higher.

Nb and M in the material of the absorption correction layer
The amount of at least one selected from the group consisting of o, W, Ti, and Te is preferably 5 to 95 mol%, and 3
It is more preferably 0 to 95 mol%.

For example, as a high melting point carbide, Hf
C, TaC, Ta ₂ C, NbC, ZrC, TiC, V
C, W ₂ C, WC, Mo ₂ C, MoC, SiC, B
₄ C, Cr ₃ C ₂ , oxides such as ThO ₂ and HfO
₂ , MgO, ZrO ₂ , BeO, Cr ₂ O ₃ , α-Al
₂ O ₃ , TiO ₂ , and boride include HfB ₂ and Ta.
_{B 2, ZrB 2, NbB 2} , TiB 2, W 2 B 5, Cr
B ₂ , VB ₂ , FeB, Fe ₂ B, Mo ₂ B ₅ , and as the nitride, BN, TaN, TiN, ZrN, AlN, N
bN, VN, CrN, β-Si ₃ N ₄ and the like.

When the absorption correction layer of the present invention is formed, these refractory compounds and metal are formed by simultaneous vapor deposition, or
It may be vapor-deposited as one target.

The film thickness of the absorption amount correction layer is preferably 1 nm or more because the effect of correcting the light absorption amount is high, and is 200 in order to form a recording mark with a practical laser power.
nm or less is preferable.

The first and second dielectric layers of the present invention have the effect of preventing the substrate, the recording layer, etc. from being deformed by heat at the time of recording and deteriorating the recording characteristics, and the optical interference effect. There is an effect of improving the signal contrast at the time.

The material of this dielectric layer is substantially transparent at the recording light wavelength, and its refractive index is larger than that of the transparent substrate and smaller than that of the recording layer.
ZnS, SiO ₂ , aluminum oxide, silicon nitride,
Metal compounds such as metal sulfides such as ZrC and ZnSe, metal oxides, metal nitrides, metal carbides, metal selenides, and mixtures thereof.

In particular, ZnS thin film, Si, Ge, Al, T
Thin film of oxide of metal such as i, Zr, Ta, Si, Al
Thin films of nitrides such as, thin films of carbides such as Ti, Zr, and Hf, and films of a mixture of these compounds are preferable because of high heat resistance. Further, a mixture of carbon, a carbide such as SiC and a fluoride such as MgF ₂ is also preferable because the residual stress of the film is small. Especially ZnS and S
A mixed film of iO ₂ or a mixture of ZnS, SiO ₂ and carbon is preferable because deterioration of recording sensitivity, carrier-to-noise ratio (C / N), erasing rate, etc. does not easily occur even when recording and erasing are repeated.

The thickness of the first dielectric layer is determined by optical conditions, but is usually about 10 nm to 500 nm. The thickness is preferably 50 to 400 nm because it is difficult to peel from the substrate or the recording layer and defects such as cracks are hard to occur.
Particularly, from the viewpoint of the difference in the amount of light absorption between the amorphous state and the crystalline state of the recording layer, it is preferable that the thickness of the first dielectric layer be set so as to satisfy the following equation. Nλ / 4−0.2λ ≦ nd1 ≦ Nλ / 4 + 0.2λ where N is an integer selected from 1, 3 and 5, λ is a wavelength used for recording, and n is a refractive index of the first dielectric layer. (Real part), d1 is the thickness of the first dielectric layer.

The material of the second dielectric layer of the present invention may be the same as the material listed as the material of the first dielectric layer,
Different materials may be used. The thickness of the second dielectric layer is 1
It is necessary to be in the range of nm to 50 nm. If the thickness of the second dielectric layer is smaller than the above value, defects such as cracks are generated, and the durability against repetition is reduced, which is not preferable. Further, if the thickness of the second dielectric layer is thicker than the above, the degree of cooling of the recording layer becomes low, which is not preferable. Considering that the degree of cooling of the recording layer at the time of recording / erasing and a large effect of absorbing amount correction are taken into consideration, it is preferably less than 20 nm, more preferably 10 nm.
Is less than. In particular, the thickness of the second dielectric layer relates to cooling,
In order to obtain a more direct effect and to obtain better erasing characteristics and repeat durability, as described above, recording with a recording mark size interval of about the beam size (λ / NA) or less is newly overwritten. A thickness of less than 5 nm is more effective in order to obtain good erasing characteristics in write recording, and to obtain good recording / erasing characteristics in edge recording.

The recording layer of the present invention is not particularly limited, but it is an In-Se alloy, Ge-Sb-Te alloy, In-Sb-Te alloy, Pd-Ge-Sb-Te alloy, Pt-Ge. -Sb-Te alloy, Nb-Ge-Sb-
Te alloy, Ni-Ge-Sb-Te alloy, Co-Ge-
Sb-Te alloy, Ag-In-Sb-Te alloy, Pd-
There are Nb-Ge-Sb-Te alloys and the like.

Particularly, Ge-Sb-Te alloy, Pd-Ge-
Sb-Te alloy, Pt-Ge-Sb-Te alloy, Nb-
Ge-Sb-Te alloy, Pd-Nb-Ge-Sb-Te
The alloy is preferable because it has a short erasing time, can be repeatedly recorded and erased many times, and has excellent recording characteristics such as C / N and erasing rate.

The thickness of the recording layer of the present invention is 10 nm.
It is preferably not less than 45 nm and not more than 45 nm. When the thickness of the recording layer is thinner than the above, deterioration of the recording characteristics due to repetitive overwriting is significant, and when the thickness of the recording layer is thicker than the above, the recording layer is likely to move due to repetitive overwriting. Jitter gets worse.

Conventionally, when recording on an optical recording medium such as a rewritable phase change optical disk, recording is performed by irradiating a laser light pulse having a recording power level with a fixed time width according to the position of a mark to be recorded. ing. Therefore, for example, when recording is performed by the pit position recording method, recording marks of substantially constant size and area are recorded on the recording track in correspondence with the modulation code.

When the recording is rewritten by overwriting, the difference in the light absorption amount between the amorphous portion and the crystalline portion described above is set so that the amplitude of the reproduction signal of the recording mark previously recorded is made smaller. The unevenness of the temperature rise due to the difference in the thermal conductivity and the difference in the thermal conductivity are reduced, and the distortion of the reproduced waveform can be reduced as the erasing characteristic of the previously recorded mark is improved.

Further, in the recording area where the distance between the recording marks is equal to or smaller than the size (λ / NA) of the irradiated light beam, the amplitude of the reproduced waveform becomes small due to the restriction of the optical resolution. The signal amplitude becomes extremely small, making it difficult to detect normal data.

In view of this point, in the case of pit position recording, it is conceivable to utilize the thermal interference between marks within the range where the jitter characteristic is not deteriorated, and the thicker the recording layer is within the above range. On the other hand, from the viewpoint of the amount of light absorption, the thinner the thickness of the recording layer, the smaller the amount of light absorption of the recording layer in the amorphous state, and the smaller the difference from the amount of light absorption in the crystalline state. Since the light absorption in the crystalline state can be made higher than the light absorption in the recording layer in the amorphous state, the thickness of the recording layer is preferably 18 nm to 45 nm in consideration of the both. More preferably, it is 26 nm to 45 nm.

On the other hand, when the mark length recording is adopted, the recording layer is apt to move due to recording and erasing as compared with the case of the pit position recording. To prevent this, cooling of the recording layer at the time of recording is further increased. It is necessary that the thickness of the recording layer is thinner within the above range, preferably 10 nm.
˜35 nm, more preferably 15 nm to 24 nm.

Material of the reflective layer when the layer structure of the constituent members of the optical recording medium is a laminate of transparent substrate / first dielectric layer / recording layer / second dielectric layer / absorption amount correction layer / reflection layer Examples thereof include light-reflecting metals, alloys, and mixtures of metals and metal compounds. As the metal, Al,
Metals and alloys having a high reflectance such as Au, Ag, and Cu contain 80 atomic% or more of these as main components, and Ti, T
Alloys containing additional elements such as e, Cr and Hf, and metal compounds include metal nitrides such as Al and Si, metal oxides,
Metal compounds such as metal chalcogenides are preferred.

Metals such as Al and Au, and alloys containing these as the main components are preferable because they have high light reflectivity and high thermal conductivity. As an example of the above alloy, Al
Si, Mg, Cu, Pd, Ti, Cr, Hf, Ta,
At least one element such as Nb or Mn added in a total amount of 5 atomic% or less, 0.5 atomic% or more, or Au.
In addition, at least one element such as Cr, Ag, Cu, Pd, Pt, and Ni is added in a total amount of 20 atom% or less and 1 atom% or more. In particular, an alloy containing Al as a main component is preferable because the cost of the material can be reduced.

In particular, Al alloys have good corrosion resistance, so Al, Ti, Cr, Ta, Hf, Z
An alloy in which at least one metal selected from r, Mn, and Pd is added in a total amount of 5 atom% or less and 0.5 atom% or more, or an alloy in which Si and Mn are added to Al in a total amount of 5 atom% or less is preferable. .

Particularly, since the corrosion resistance and the thermal stability are high and the generation of hillocks is hard to occur, the reflective layer contains less than 3 atomic% and 0.5 atomic% or more of the additive elements in total.
f-Pd alloy, Al-Hf alloy, Al-Ti alloy, Al
-Ti-Hf alloy, Al-Cr alloy, Al-Ta alloy,
It is preferable to use an alloy containing Al as a main component, which is either an Al-Ti-Cr alloy or an Al-Si-Mn alloy.

The thickness of the reflective layer is usually about 1
It is 0 nm or more and 300 nm or less. High recording sensitivity and high reproduction signal intensity, therefore 20 nm or more 200
nm or less is preferable.

High recording sensitivity, high speed single beam
Since overwriting is possible, the erasing rate is large, and the erasing characteristics are good, it is preferable to configure the main part of the optical recording medium as follows.

[0047] That is, the dielectric layer is a mixed film of a mixed film or ZnS and SiO ₂ and carbon of the mixing ratio of SiO ₂ 15 to 35 mol% of ZnS and SiO _2, and Ge as a recording layer, Sb, Te Of an alloy containing at least the element of, and as an absorption correction layer, one or more kinds of metal materials as essential components, high melting point carbides, oxides, borides,
A film containing at least one selected from the group consisting of nitrides, more preferably a film characterized by being at least one selected from the group consisting of Nb, Mo, W, Ti, Te , The thickness (d1) of the first dielectric layer is Nλ /
4-0.2λ ≦ nd1 ≦ Nλ / 4 + 0.2λ (however, N
= 1, 3, 5), the second dielectric layer has a thickness of 1 nm or more and 50 nm or less, and the recording layer has a thickness of 10 nm or more and 45 nm or less. It is preferable that the layer has a thickness of 1 nm or more and 200 nm or less, and the composition of the recording layer is in the range represented by the following formula. _{(M x Sb y Te 1-} xy) 1-z (Te 0.5 Ge 0.5) z 0 ≦ x ≦ 0.05 0.35 ≦ y ≦ 0.65 0.2 ≦ z ≦ 0.5 where, M is At least one metal selected from palladium, niobium, platinum, silver, gold, and cobalt, x, y, z, and the numbers represent the atomic ratio of each element (molar ratio of each element).

On the absorption correction layer having the above structure, an Al alloy having a thickness of 20 nm to 200 nm may be formed as a reflective layer.

As the material of the substrate of the present invention, various transparent synthetic resins, transparent glass and the like can be used. For the purpose of avoiding the influence of dust and scratches on the substrate, it is preferable to use a transparent substrate and perform recording from the substrate side with a focused light beam.As such a transparent substrate material, glass, polycarbonate, polymethylmethacrylate, Examples thereof include polyolefin resin, epoxy resin and polyimide resin.

Particularly, a polycarbonate resin and an amorphous polyolefin resin are preferable because they have small optical birefringence, small hygroscopicity, and easy molding. When heat resistance is required, epoxy resin is preferable.

The thickness of the substrate is not particularly limited, but 0.01 mm to 5 mm is practical. 0.01 m
If it is less than m, even when recording with a light beam focused from the substrate side, it is easily affected by dust, and if it is 5 mm or more,
It becomes difficult to increase the numerical aperture of the objective lens, and the irradiation light beam spot size becomes large, which makes it difficult to increase the recording density. The substrate may be flexible or rigid. The flexible substrate is used in the form of tape, sheet or card. The rigid board is used in the form of a card or disk. In addition, these substrates may have an air sandwich structure, an air incident structure, or a close-bonded structure by using two substrates after forming a recording layer and the like.

The light source used for recording on the optical recording medium of the present invention is a high intensity light source such as laser light or strobe light. Particularly, the semiconductor laser light can be downsized, consumes less power, and can be modulated. Is preferable because it is easy.

Recording is performed by irradiating a crystalline recording layer with a laser light pulse or the like to form an amorphous recording mark. On the contrary, a crystalline recording mark may be formed on the amorphous recording layer. Erasure can be performed by irradiating a laser beam to crystallize an amorphous recording mark or to amorphize a crystalline recording mark.

A method of forming an amorphous recording mark at the time of recording and crystallizing at the time of erasing is preferable because the recording speed can be increased and the deformation of the recording layer is less likely to occur.
Further, the one-beam overwrite in which the light intensity is high when the recording mark is formed and slightly weakened when the recording mark is erased and rewriting is performed by irradiating the light beam once is preferable because the rewriting time is shortened.

Next, a method for manufacturing the optical recording medium of the present invention will be described. Examples of the method for forming the dielectric layer, the absorption correction layer, the recording layer, the reflective layer, etc. on the substrate include a known thin film forming method in vacuum, such as a vacuum vapor deposition method, an ion plating method, and a sputtering method. To be Especially composition,
The sputtering method is preferable because it is easy to control the film thickness. The thickness of the recording layer or the like to be formed can be easily controlled by monitoring the deposition state with a well-known technique such as a crystal oscillator film thickness meter.

The recording layer or the like may be formed with the substrate fixed, or moved or rotated. Since the in-plane uniformity of the film thickness is excellent, it is preferable to rotate the substrate, and it is more preferable to combine the revolution.

Further, within a range that does not significantly impair the effects of the present invention, after forming an absorption correction layer or a reflection layer, ZnS, SiO ₂ ,
A dielectric layer such as ZnS-SiO ₂ or a protective layer such as an ultraviolet curable resin may be provided if necessary. Further, a hub or the like may be provided on the substrate as needed. Furthermore, after forming the absorption correction layer or the reflection layer, or after forming the above-mentioned resin protective layer, 2
The substrates may be opposed to each other and bonded together with an adhesive.

Before the actual recording, the recording layer is preferably crystallized by irradiation with laser light, light from a xenon flash lamp or the like in advance.

[0059]

EXAMPLES The present invention will be described below based on examples.

(Analysis and measurement method) The compositions of the absorption correction layer, the recording layer and the reflection layer were confirmed by ICP emission analysis (manufactured by Seiko Denshi Kogyo KK). The C / N and erasing rate (difference in reproduced carrier signal intensity after recording and after erasing) were measured by a spectrum analyzer. The film thickness of each layer such as the recording layer was monitored by a crystal oscillator film thickness meter.

(Example 1) Thickness 0.6 mm, diameter 8.6
The recording layer, the dielectric layer, and the absorption correction layer were formed by a high frequency sputtering method while rotating a polycarbonate substrate with a spiral groove having a pitch of 1 cm and a pitch of 1 μm at 30 rpm.

First, the inside of the vacuum vessel was evacuated to 1 × 10 ^-5 Pa, and then SiO 2 in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
ZnS containing 20 mol% of ₂ was sputtered to form a first dielectric layer having a thickness of 240 nm and a refractive index of about 2.2 on the substrate. Subsequently, an alloy target made of Ge, Sb, and Te was sputtered to form a recording layer having a composition of Ge ₂₄ Sb ₂₃ Te ₅₃ (atomic%) and a film thickness of 20 nm. First
A second dielectric layer of the same material as the dielectric layer is formed to a thickness of 10 nm,
An absorption correction layer having a film thickness of 60 nm of a Te ₇₆ (TaN) ₂₄ (mol%) mixture was formed on this.

Further, after the optical recording medium was taken out of the vacuum container, an acrylic ultraviolet curable resin was spin-coated on the absorption correction layer and cured by ultraviolet irradiation to form a resin layer. The recording medium and the hot-melt adhesive were stuck together to obtain an optical recording medium of the present invention.

This optical recording medium was rotated at 2400 rpm, and a wavelength of 820 was collected from the substrate side in the radial direction into an ellipse.
The recording layer was crystallized and initialized by irradiation with a semiconductor laser beam of nm.

At a wavelength of 680 nm, the optical constants of the Te ₇₆ (TaN) ₂₄ mixture used as the absorption correction layer have a real part of the refractive index of 5.2 and an imaginary part of the refractive index of 3.2.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and thickness of each layer, and as a result, at a light wavelength of 680 nm, 60% and 64%, respectively.
The light absorption amount in the crystalline state was larger than that in the amorphous state. The reflectance of the crystal state calculated from the calculation is 26.
%, Which is almost the same as the value actually measured for the optical recording medium, confirming that this calculation result is valid.

Thereafter, this optical recording medium was rotated at a rotation speed of 3600.
Rotate at rpm, track the radius of 39mm, the numerical aperture of the objective lens 0.6, the wavelength of the semiconductor laser 680n
Using an optical head of m, a frequency of 15.3 MHz (pulse width 20 nsec), a peak power of 7 to 15 mW,
After overwriting 100 times with a semiconductor laser light modulated to each condition of a bottom power of 3 to 8 mW, a semiconductor laser light of a reproduction power of 1.2 mW is irradiated to obtain a bandwidth of 3
C / N was measured under the condition of 0 kHz.

Further, in this portion, the peak power is 7 to 1 at 5.73 MHz (pulse width 20 nsec) as in the above.
A semiconductor laser beam modulated to each condition of 5 mW and a bottom power of 3 to 8 mW was irradiated, one-beam overwriting was performed, and the erasing rate of the pre-recorded signal of 15.3 MHz at this time was measured. Hereinafter, this erase rate is referred to as a first erase rate.

Further, this portion is irradiated with a semiconductor laser beam modulated in the same manner as above at 15.3 MHz (pulse width 20 nsec) to perform one-beam overwriting, and the erasing rate of the pre-recorded signal of 5.73 MHz at this time is set. It was measured. Hereinafter, this erase rate is referred to as a second erase rate.

C / N of 50 dB or more was obtained at a peak power of 8 to 14 mW. Also, the bottom power is 3.5 to 5.
At 5 mW, an erasing rate of 20 dB or more was obtained, with a maximum erasing rate of 21 dB and a second erasing rate of 20.5 dB.

Further, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 10 mW, a bottom power of 4 mW, and a frequency of 15.3 MHz, the same measurement was performed, but the C / N and the erasing rate changed. Is 2 dB
Within, little change was observed.

(Example 2) The composition of the recording layer was Ge ₁₉ Sb _28.
An optical recording medium of the present invention was prepared in the same manner as in Example 1 except that it was Te ₅₃ . When the C / N, the erasing rate and the repeating characteristics of this optical recording medium were measured by the same method as in Example 1, almost the same characteristics as in Example 1 were obtained.

Example 3 The composition of the recording layer is Nb _0.5 Ge.
An optical recording medium of the present invention was prepared in the same manner as in Example 1 except that it was _17.5 Sb ₂₆ Te ₅₆ . When the C / N, the erasing rate and the repeating characteristics of this optical recording medium were measured by the same method as in Example 1, almost the same characteristics as in Example 1 were obtained.

Example 4 The composition of the recording layer is Pd _0.2 Nb.
An optical recording medium of the present invention was prepared in the same manner as in Example 1 except that it was _0.3 Ge _18.5 Sb ₂₇ Te ₅₄ . C of this optical recording medium
/ N, erasure rate and repetitive characteristics were measured by the same method as in Example 1, and the characteristics substantially equivalent to those in Example 1 were obtained.

(Example 5) First dielectric layer, recording layer, second layer
The thickness of each of the dielectric layer and the absorption correction layer is 23.
An optical recording medium of the present invention was prepared in the same manner as in Example 1 except that the W49 (TiC) 51 mixture was 0 nm, 30 nm, 5 nm, and 40 nm, and was used as the material of the absorption correction layer.

At a wavelength of 680 nm, the optical constants of the W ₄₉ (TiC) ₅₁ mixture used as the absorption correction layer are 3.8 for the real part of the refractive index and 3.8 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, at a light wavelength of 680 nm, 63% and 65%, respectively.
The light absorption amount in the crystalline state was slightly larger than that in the amorphous state. The calculated reflectance of the crystalline state is 26%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it was confirmed that this calculation result is appropriate.

The C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, and the peak power was 8 to
A C / N of 50 dB or more was obtained at 13 mW. Further, an erasing rate of 20 dB or more was obtained at a bottom power of 3.5 to 5 mW, and a first erasing rate of 20.5 dB at maximum and a second erasing rate of 23 dB at maximum were obtained.

Further, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 10 mW, a bottom power of 4 mW, and a frequency of 15.3 MHz, the same measurement was carried out. Is 2 dB
Within, little change was observed.

(Embodiment 6) The thicknesses of the first dielectric layer, the recording layer, and the absorption correction layer are 230 nm and 40 n, respectively.
m, 40 nm, and W as a material for the absorption correction layer
An optical recording medium of the present invention was prepared in the same manner as in Example 1 except that the ₄₈ (SiC) ₅₂ mixture was used.

At a wavelength of 680 nm, the optical constants of the W ₄₈ (SiC) ₅₂ mixture used as the absorption correction layer are 5.2 for the real part of the refractive index and 2.6 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, at a light wavelength of 680 nm, 63% and 63%, respectively.
And the light absorption amounts in the crystalline state and the amorphous state were the same. The calculated reflectance of the crystalline state is 24%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it was confirmed that this calculation result is appropriate.

The C / N and erasing rate of this optical recording medium were measured in the same manner as in Example 1, and the peak power was 7 to
A C / N of 50 dB or more was obtained at 13 mW. In addition, an erasing rate of 20 dB or more was obtained with a bottom power of 3 to 4 mW, the maximum first erasing rate was 20.5 dB, and the maximum second erasing rate was 23 dB.

Further, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 8 mW, a bottom power of 3.5 mW, and a frequency of 15.3 MHz, the same measurement was carried out. Change of 2d
Within B, almost no change was observed.

(Embodiment 7) The absorption correction layer has a thickness of 40 n.
m, and Nb ₄₃ (AlN) is used as the material of the absorption correction layer.
_{The same} as Example 4 except that a ₅₇ (mol%) mixture was used and a reflection layer of Hf-Pd-Al alloy with a thickness of 50 nm was formed on the surface of the absorption correction layer opposite to the second dielectric layer. An optical recording medium of the present invention was produced.

At a wavelength of 680 nm, the optical constants of the Nb ₄₃ (AlN) ₅₇ mixture used as the absorption correction layer are 4.0 for the real part of the refractive index and 3.5 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, they were 58% and 63% at a light wavelength of 680 nm, respectively.
The light absorption amount in the crystalline state was larger than that in the amorphous state. The reflectance of the crystalline state obtained from the calculation is 23
%, Which is almost the same as the value actually measured for the optical recording medium, confirming that this calculation result is valid.

The C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, and the peak power was 9 to
A C / N of 50 dB or more was obtained at 15 mW. Further, an erasing rate of 20 dB or more was obtained at a bottom power of 4 to 5.5 mW, a maximum first erasing rate of 22 dB and a maximum erasing rate of 20.5 dB were obtained.

Further, after repeating one-beam overwriting 10,000 times under the conditions of a peak power of 10 mW, a bottom power of 4.5 mW, and a frequency of 15.3 MHz, the same measurement was carried out. Change of 2
Almost no change was observed within dB.

(Example 8) First dielectric layer, recording layer, second layer
The thicknesses of the dielectric layer, the absorption correction layer, and the reflection layer are 220 nm, 25 nm, 15 nm, 30 nm, and 70 nm, respectively.
nm and Nb ₈₀ (Mo
C) An optical recording medium of the present invention was prepared in the same manner as in Example 7 except that the ₂₀ mixture was used.

At a wavelength of 680 nm, the optical constants of the Nb ₈₀ (MoC) ₂₀ mixture used as the absorption correction layer are 3.8 for the real part of the refractive index and 4.0 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, at a light wavelength of 680 nm, 66% and 66%, respectively.
And the light absorption amounts in the crystalline state and the amorphous state were the same. The calculated reflectance of the crystalline state is 27%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it was confirmed that this calculation result is appropriate.

The C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, and the peak power was 7 to
A C / N of 50 dB or more was obtained at 13 mW. Further, an erasing rate of 20 dB or more was obtained at a bottom power of 3 to 4.5 mW, and the maximum first erasing rate was 22 dB and the maximum erasing rate was 22 dB.

Further, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 8 mW, a bottom power of 3.5 mW, and a frequency of 15.3 MHz, the same measurement was performed. Change of 2d
Within B, almost no change was observed.

(Example 9) First dielectric layer, recording layer, second layer
The thickness of each of the dielectric layer and the reflective layer is 230 n.
m, 30 nm, 5 nm, 30 nm, and an optical recording medium of the present invention was prepared in the same manner as in Example 7 except that a Mo ₃₈ (ZrN) ₆₂ mixture was used as the material for the absorption correction layer.

At a wavelength of 680 nm, the optical constants of the Mo ₃₈ (ZrN) ₆₂ mixture used as the absorption correction layer are 3.7 for the real part of the refractive index and 3.6 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and thickness of each layer, and as a result, at a light wavelength of 680 nm, 60% and 62%, respectively.
And the light absorption amounts in the crystalline state and the amorphous state were the same. The calculated reflectance of the crystalline state is 22%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it was confirmed that this calculation result is appropriate.

The C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, and the peak power was 9 to
A C / N of 50 dB or more was obtained at 15 mW. Further, an erasing rate of 20 dB or more was obtained at a bottom power of 4.5 to 6 mW, the maximum first erasing rate was 20.5 dB, and the maximum second erasing rate was 23 dB.

Further, after repeating the one-beam overwrite operation 10,000 times under the conditions of a peak power of 10 mW, a bottom power of 5 mW, and a frequency of 15.3 MHz, the same measurement was carried out. Is 2 dB
Within, little change was observed.

(Embodiment 10) The thickness of each of the first dielectric layer, the recording layer, the second dielectric layer, and the reflective layer is 230 n.
m, 30 nm, 5 nm, 30 nm, and the same optical recording medium of the present invention as in Example 7 was prepared except that the W ₄₇ (ZrC) ₅₃ mixture was used as the material of the absorption correction layer.

At a wavelength of 680 nm, the optical constants of the W ₄₇ (ZrC) ₅₃ mixture used as the absorption correction layer are 3.7 for the real part of the refractive index and 3.4 for the imaginary part of the refractive index.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, at a light wavelength of 680 nm, 63% and 64%, respectively.
And the light absorption amounts in the crystalline state and the amorphous state were the same. The calculated reflectance of the crystalline state is 23%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it can be confirmed that the calculation result is appropriate.

The C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, and the peak power was 8 to
A C / N of 50 dB or more was obtained at 15 mW. Further, an erasing rate of 20 dB or more was obtained at a bottom power of 4 to 5.5 mW, a maximum first erasing rate of 21 dB and a maximum erasing rate of 24.5 dB were obtained.

Furthermore, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 9 mW, a bottom power of 4.5 mW, and a frequency of 15.3 MHz, the same measurement was performed. Change of 2d
Within B, almost no change was observed.

(Embodiment 11) The thicknesses of the first dielectric layer, the recording layer, the second dielectric layer, the absorption correction layer and the reflection layer are 210 nm, 30 nm, 4 nm, 50 nm and 30 respectively.
nm, and the Ti ₅₂ (Ti
C) An optical recording medium of the present invention was prepared in the same manner as in Example 7 except that ₄₈ compounds were used.

The amounts of light absorption in the amorphous state and the crystalline state of this optical recording medium were calculated from the refractive index and the thickness of each layer, and as a result, at the light wavelength of 680 nm, 59% and 60%, respectively.
And the light absorption amounts in the crystalline state and the amorphous state were the same. The calculated reflectance of the crystalline state is 23%, which is almost the same as the actually measured value of the optical recording medium. Therefore, it can be confirmed that the calculation result is appropriate.

When the C / N and erasing rate of this optical recording medium were measured by the same method as in Example 1, the peak power was 10
A C / N of 50 dB or more was obtained at -15 mW. Also,
With a bottom power of 4.5 to 6.5 mW, an erasing rate of 20 dB or more was obtained, and the maximum first erasing rate was 20.5 dB and the maximum second erasing rate was 23 dB.

Further, after repeating one-beam overwrite 10,000 times under the conditions of a peak power of 11 mW, a bottom power of 5 mW, and a frequency of 15.3 MHz, the same measurement was carried out. Is 2 dB
Within, little change was observed.

[0109]

Since the present invention comprises an optical recording medium,
The following effects were obtained. (1) Since the distortion of the recording mark at the time of overwriting can be reduced, the erasing rate can be improved. (2) It can be easily manufactured by the sputtering method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kusato Hirota 1-1-1 Sonoyama, Otsu City, Shiga Toray Co., Ltd. Shiga Plant

Claims (4)

[Claims] 1. Information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light, and the recording and erasing of information is performed in a phase between an amorphous phase and a crystalline phase. The change is performed by using at least the first dielectric layer, the recording layer, the second dielectric layer, and one or more kinds of metal materials as essential components,
It has an absorption correction layer made of a material containing at least one selected from the group consisting of high melting point carbides, oxides, borides, and nitrides, and the film thickness of the second dielectric layer is 1
An optical recording medium having a thickness of not less than 50 nm and not more than 50 nm. 2. The optical recording medium according to claim 1, wherein the recording layer has a thickness of 10 nm or more and 45 nm or less. 3. The metal material is Nb, Mo, W, Ti, Te
The optical recording medium according to claim 1 or 2, wherein the optical recording medium is at least one selected from the group consisting of: 4. The absorption correction layer has a thickness of 1 nm or more and 200 n or more.
It is m or less, Claim 1 or Claim 2 characterized by the above-mentioned.
Alternatively, the optical recording medium according to claim 3.