JP2003091871A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium which has a capacity equal to or higher than that of a DVD-ROM and is suitable for recording at 7 to 17 m/s which is the 2 to 5-times reproducing line speed of the DVD-ROM. SOLUTION: 1) The optical information recording medium which is an optical information recording medium having at least a first thin-film layer (protective layer), phase transition optical recording material layer, second thin-film layer (protective layer) and reflection layer on a substrate and capable of performing recording and reproducing by irradiation with a laser beam utilizing a reversible phase transition between the amorphous phase and crystalline phase of the recording material layer and in which the second thin-film layer is composed of a material essentially consisting of a Zr oxide. 2) The optical information recording medium, in which the second thin-film layer is composed of the material essentially consisting of the Zr oxide so as to have the property that the recording layer remains in the crystalline state at a rotating line speed below 16 m/s and the amorphous phase begins to appear within a range from 16 to 20 m/s when the recording medium is rotated at a specified line speed and is irradiated with the laser beam of intensity 8 to 15 times the intensity of reproduction power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical information recording medium.

[0002]

2. Description of the Related Art Optical recording media capable of recording / reproducing and erasing information by irradiating a semiconductor laser beam include a magneto-optical recording system in which magnetization is reversed by utilizing heat and a crystalline and amorphous system. There is a phase change type optical recording method that erases recording by utilizing reversible phase change. The latter is capable of overwriting with a single beam and is characterized by a simpler optical system on the drive side, and is applied as a recording medium for computers and audiovisual. As a recording material,
Various compounds centered on chalcogen and alloys having a composition near the eutectic are used because they tend to form amorphous and composition segregation hardly occurs even after repeated recording. GeTe and Sb are practically used.
Mixture of ₂ Te _3, and there is a system in which the addition of Ag or In the _Sb-Sb 2 Te ₃ pseudo binary eutectic composition. In particular, the latter is a material that has high sensitivity and a clear outline of the amorphous portion and is suitable for high density recording. In Japanese Patent Laid-Open No. 11-070738 (prior application of the company), the number of overwrites is high,
The optimum composition ratio and optimum layer structure of the AgInSbTe quaternary material excellent in storage reliability are shown. Further, the storage characteristics are further improved by adding Cr or Zr.

Since the phase-change type optical information recording medium is expected to be used for high-density image recording in the future, it is necessary to realize high-speed overwriting. For that purpose, the crystallization rate near the melting point is high. A recording material is used. The Sb-Sb ₂ Te ₃ pseudo binary eutectic composition in order to improve the crystallization speed of the recording material based, a method of increasing the blending ratio of Sb, the element that can increase the crystallization rate There is a method of adding. For example, Japanese Patent Application Laid-Open No. 2
Japanese Patent Laid-Open No. 000-79761 (Mitsubishi Chemical) describes that a recording layer having a composition represented by the following formula is used. XαGaβMχSbδTeε (wherein X is at least one of Ag, Au, Pd, Pt, and Zn, M is at least one of Sn, Ge, Si, and Pb, 0.0 ≦ α ≦ 0.1, 0 .001 ≦ β ≦ 0.1, 0.0
1 ≦ χ ≦ 0.15, 0.5 ≦ δ ≦ 0.7, 0.15 ≦ ε
≦ 0.4, 0.03 ≦ β + χ ≦ 0.25 α + β + χ + δ + ε = 1.0)

Further, Japanese Patent Laid-Open No. 2000-313170 (Mitsubishi Chemical) discloses an optical information recording medium having at least a phase change optical recording layer on a substrate, and the phase change optical recording layer is represented by the following general formula. It is described that the composition represented by (1) is used. _{[(Sb X Te 1-X)} Y Ge 1-Y ] _{Z M 1-Z (1)} ( wherein, x is a number in the range of 0.7 ≦ x ≦ 0.9, y
Is a number in the range of 0.8 ≦ y <1, and z is 0.88 ≦ z
It is a number in the range of <1. M is In and / or Ga. )

However, the above-mentioned Japanese Patent Laid-Open No. 2000-797.
According to Japanese Patent Laid-Open No. 61, the speed is about 6 times as fast as a CD-ROM (7.
It discloses a recording layer suitable for recording / reproducing / erasing at a linear velocity of 2 to 8.4 m / s), and it is difficult to realize recording / reproducing / erasing at a higher speed based on this. On the other hand, in JP-A-2000-313170, it is possible that the desired crystallization rate can be increased by selecting a specific composition from the described wide composition range, but the crystallization rate is increased. As a result, the amorphous forming ability is lowered, and it becomes difficult to form the recording mark. Therefore, it is not possible to achieve both the erasing property (crystallization rate) and the recording property (amorphous forming ability), and as a result, it is difficult to obtain a medium having good recording properties. As described above, in order to obtain an optical information recording medium suitable for recording / reproducing / erasing at a higher linear velocity of 7 to 17 m / s, normally, the crystallization speed of the recording layer at the time of erasing is sufficiently increased to erase characteristics. It is necessary to secure good recording mark forming ability at the same time. That is, it is necessary to balance the two contradictory properties of crystallization and amorphization.

[0006]

DISCLOSURE OF THE INVENTION The present invention achieves both of the above-mentioned conflicting properties, has a capacity equal to or more than that of a DVD-ROM, and is 2 to 5 times the linear reproducing speed of a DVD-ROM. An object is to provide an optical information recording medium suitable for recording at 17 m / s.

[0007]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 17). 1) At least a first thin film layer (protective layer) on a transparent substrate,
It has a phase-change optical recording material layer, a second thin film layer (protective layer), and a reflective layer, and utilizes a reversible phase change between an amorphous phase and a crystalline phase of the recording material layer to produce a laser beam. In the optical information recording medium capable of recording and reproducing by irradiation of
An optical information recording medium, wherein the thin film layer is made of a material containing Zr oxide as a main component. 2) Since the second thin film layer is made of a material containing Zr oxide as a main component, the recording medium is rotated at a constant linear velocity to generate a laser beam having an intensity 8 to 15 times the reproducing power. When irradiated, when the rotational linear velocity is less than 16 m / s, the recording layer remains in a crystalline state and has a physical property that an amorphous phase begins to appear within a range of 16 to 20 m / s. Item 1. The optical information recording medium according to item 1. 3) The optical information recording medium according to 1) or 2), wherein the Zr oxide is ZrO ₂ . 4) The optical information recording medium according to any one of 1) to 3), wherein the second thin film layer contains TiO ₂ . 5) The ratio of TiO _{2 in} the second thin film layer is 5 to 30 m.
The optical information recording medium according to 4), which is ol%. 6) The second thin film layer contains ZnS 1)
(3) The optical information recording medium according to any one of (3). 7) The proportion of ZnS in the second thin film layer is 5 to 30 mo.
The optical information recording medium according to 6), which is 1%. 8) The second thin film layer is A (A is Y ₂ O ₃ , MgO, Ca)
O, at least 1 sort (s) of rare earth oxides), The optical information recording medium in any one of 1) -3) characterized by the above-mentioned. 9) The ratio of A in the second thin film layer is 2 to 20 mo.
The optical information recording medium according to 8), which is 1%. 10) The second thin film layer is TiO ₂ , ZnS, A (A is Y ₂
At least one of O ₃ , MgO, CaO, and rare earth oxides
1) to at least 2 kinds of
The optical information recording medium according to any one of 3). 11) TiO ₂ , ZnS, A in the second thin film layer material
(A is at least one of Y ₂ O ₃ , MgO, CaO, and a rare earth oxide), and the total ratio is 5 to 30 mol%.
The optical information recording medium described in 0). 12) The thickness of the second thin film layer is 4 to 20 nm 1) to
11. The optical information recording medium according to any one of 11). 13) The optical information recording medium according to any one of 1) to 12), wherein the second thin film layer is provided by a sputtering method using a target made of a predetermined thin film layer material. 14) The optical information as described in any one of 1) to 13), wherein 90% or more of the atomic ratio has an atomic composition represented by the following formula, where 1 is the total number of constituent atoms of the phase-change optical recording material layer. recoding media. XαSbβTeγ (wherein X represents In and / or Ga, α, β, γ represents an atomic ratio (%), and is in the following range: 1 ≦ α ≦ 10, 60 ≦ β ≦ 90, γ = 100− α-
β) 15) The optical information recording medium according to 14), wherein the optical recording material layer further contains Ag and / or Ge. 16) The optical information recording medium according to any one of 1) to 15), wherein the reflective layer is made of Ag or Ag alloy. 17) The optical information recording medium according to any one of 1) to 16), wherein the reflective layer has a thickness of 100 to 300 nm.

The present invention will be described in detail below. The present inventors have a capacity equal to or higher than that of a DVD-ROM and are 2 to 5 times the linear velocity of reproduction of a DVD-ROM.
In developing an optical information recording medium suitable for recording up to 17 m / s, the materials and film thicknesses of the first thin film layer (protective layer), the recording layer, the second thin film layer (protective layer), and the reflective layer were determined. As a result of making and evaluating variously changed discs, when the linear velocity of the initially crystallized disc was changed and a continuous laser beam of about 8 to 9 mW was irradiated, the linear velocity was in the range of 16 to 20 m / s. The present invention has been completed based on the finding that the medium in which the reflectance decreases with the appearance of the amorphous phase exhibits relatively good characteristics. That is, when the linear velocity of the initially crystallized disk is changed and a continuous laser beam of about 8 to 9 mW is irradiated, the recording layer melts, but in the subsequent cooling process, the cooling rate changes with the linear velocity change. The amorphous phase is formed when the cooling rate changes and the cooling rate when the recording layer becomes lower than the melting point becomes higher than the critical cooling rate. The formation of this amorphous phase can be judged by monitoring the reflectance.
FIG. 1 shows an example of the reflectance change when the linear velocity is changed. Figure 1
At 17 m / s, a sharp decrease in reflectance is observed, which indicates that at this linear velocity the cooling rate becomes higher than the critical cooling rate and an amorphous phase is formed. When the linear velocity is slow, there is a tendency that the reflectance is slightly higher than that before irradiation, but this is because recrystallization occurs after melting. In the case of this example, the reflectance of the disc after the initial crystallization was 20%.

The linear velocity at which the amorphous phase begins to form is
It depends on the power of the laser to irradiate. According to the conditions found by the present inventors, a power in the range of 8 to 15 times, preferably 9 to 15 times, and more preferably 10 to 13 times the reproducing power is applied, and the irradiation power is 16 to 20 times.
A disk in which the reflectance decreases at m / s due to the formation of an amorphous phase is desirable for recording at 7 to 17 m / s. A disc in which a similar decrease in reflectance appears at a power of 16 to 20 m / s at a power lower than this has a poor stability of reproducing light and is 100%.
The jitter abruptly rises after playing around 00 times.
Further, a disc having a similar decrease in reflectance at a power of 16 to 20 m / s at a power higher than this has a poor sensitivity and recording with sufficient modulation cannot be performed even at a recording power of 15 mW. It is considered that good recording can be achieved by further increasing the recording power, but the current LD with a wavelength of 660 nm
Since it is desirable that the pickup head using the above can record at 15 mW or less, it is not suitable for practical use. In addition, when the appropriate power is applied, a sharp drop in reflectance is 16
When it is slower than m / s, recording at 17 m / s is possible, but good recording cannot be performed. This is because the unerased portion due to overwriting occurs, and the recording strategy does not generate a pattern in which even interference between marks is taken into consideration. Further, if no decrease in reflectance is observed even when irradiation with appropriate power is performed and the speed is higher than 20 m / s, the sensitivity becomes poor and good recording cannot be performed.

The above relationship between the irradiation power and the linear velocity at which the reflectance decreases due to the appearance of the amorphous phase is established even when the pickup head and the layer structure are changed. For example, using a pickup head having a wavelength of 405 nm and an NA (aperture ratio) of 0.80, a reflective layer, a first thin film layer (protective layer), a recording layer, and a second thin film layer (protective layer) are formed in this order on a substrate. Is
This also applies when recording / reproducing is performed by irradiating a laser beam from the film formation surface. On the other hand, when the crystallization speed of the recording material is increased, the characteristic (recording characteristic) of whether or not good amorphous formation of the recording material can be secured becomes a problem. It is necessary to devise the layer structure of the medium so that it becomes easy. One guideline for considering an ideal medium layer structure that facilitates amorphous formation is that the maximum temperature reached by the laser beam irradiated during recording is high (higher sensitivity), and The layer structure is to increase the cooling rate thereafter (improve the critical cooling rate).

In the present invention, since the second thin film layer is formed of a material containing Zr oxide as a main component, the situation in line with the above guidelines can be realized. The second thin film layer has a role of condensing the heat applied to the recording layer due to laser light irradiation at the time of recording to store the heat, and at the same time, transfers the heat to the reflecting layer to dissipate the heat. Since the material has a low rate, the temperature of the recording layer is greatly increased by the irradiation of the laser beam during recording, and the maximum attainable temperature becomes high. That is, high sensitivity can be achieved. However, making the second thin film layer to have a low thermal conductivity is expected to bring about a decrease in the critical cooling rate to some extent from the above-mentioned viewpoint, but the inventors of the present invention evaluated the actual medium characteristics and the like. According to the knowledge obtained, the effect of increasing the sensitivity is more remarkable, and the decrease in the critical cooling rate has not been confirmed in practice. Here, ZrO ₂ is preferable as the Zr oxide from the viewpoint of stability. The second thin film layer preferably contains at least TiO ₂ . That is, the second thin film layer is preferably a mixture or solid solution of ZrO ₂ and TiO ₂ . This allows the second
The thermal conductivity of the thin film layer can be further reduced, and as a result, higher sensitivity can be achieved. Further, due to the effect of mixing, it is possible to prevent cracking due to thermal shock due to repeated recording, transformation such as film crystallization, and to realize good repeated recording characteristics.

Further, since TiO ₂ alone has a high refractive index, it is possible to increase the refractive index of the second thin film layer by mixing them. Considering the optical role of the second thin film layer, this corresponds to an increase in the optical film thickness (the product of the refractive index and the film thickness), so that the thickness of the second thin film layer can be reduced. In general, a second compound containing the Zr oxide of the present invention as a main component
When sputtering is performed using the target for the thin film layer, the deposition rate is low, and thus the production tact may increase if the film formation time of the second thin film layer is rate-determining, but for the above reason. Since the thickness of the second thin film layer can be reduced, it is possible to minimize the increase in production tact. The TiO ₂ content is preferably 5 to 30 mol%. If it is less than 5 mol%, the desired effect cannot be obtained, and if it exceeds 30 mol%, the stability of the film is lowered, or TiO ₂ becomes a mother phase to increase the thermal conductivity, so that high sensitivity cannot be achieved. Not preferable.

The second thin film layer preferably contains ZnS. That is, it is preferable to use a mixture or solid solution of the second thin film layer ZrO ₂ and ZnS. Generally, since sulfide has a high deposition rate by sputtering,
By mixing S, the deposition rate of the second thin film layer can be increased. Generally, when sputtering is performed using the target for the second thin film layer containing Zr oxide as a main component of the present invention, the deposition rate is low, and therefore, when the film formation time of the second thin film layer is rate-determining. Although there is a risk of increasing the production tact, it is possible to avoid such problems by increasing the deposition rate by mixing ZnS. In addition, Z
The nS content is preferably 5 to 30 mol%. If it is less than 5 mol%, the desired effect cannot be obtained,
If it exceeds ol%, the stability of the film is lowered, or ZnS becomes a mother phase to increase the thermal conductivity, which makes it impossible to achieve high sensitivity, which is not preferable.

The second thin film layer is made of Y ₂ O ₃ , CaO,
It preferably contains at least one of MgO and a rare earth oxide. Generally, the addition of these substances is
It is known to stabilize and toughen the r oxide, but in the present invention, it is repeated by adding at least one of them to the Zr oxide thin film as the upper protective layer of the optical information recording medium. Generation of cracks due to thermal shock due to recording and transformation such as film crystallization can be prevented, and good repetitive recording characteristics can be realized.
The total content of these substances is 2 to 20 mol%
Is desirable. If it is less than 2 mol%, the desired effect cannot be obtained, and if it exceeds 20 mol%, the stability of the film is deteriorated, which is not preferable.

Further, it is preferable to simultaneously add many kinds of the various additive materials to ZrO ₂ to the second thin film layer because the respective effects can be obtained at the same time.
For example, a thin film layer made of ZrO ₂ , TiO ₂ , and Y ₂ O ₃ , a thin film layer made of ZrO ₂ , ZnS, and Y ₂ O ₃ and the like. In these cases, the total addition amount of various additive materials is the second
The proportion of the thin film layer is preferably 5 to 30 mol%. If it is less than 5 mol%, the desired effect cannot be obtained, and if it exceeds 30 mol%, the stability of the film is deteriorated, which is not preferable. The thickness of the second thin film layer is usually 4 to
The thickness is 20 nm, preferably 4 to 15 nm. 4 nm
If it is less than 20 nm, the heat applied to the recording layer due to laser light irradiation during recording cannot be stored and the sensitivity is lowered. If it exceeds 20 nm, the cooling rate cannot be secured, which is not preferable. The second thin film layer of the present invention can be formed by reactive sputtering or the like, but since the recording material may be exposed to the reaction gas during the formation of the second thin film layer, the characteristics of the recording material may change. Not preferable. From such a viewpoint, it is preferable to form the target by a sputtering method using a target made of a predetermined thin film material.

Next, the recording layer will be described. The phase change optical recording material layer in the present invention has an atomic ratio of 90%.
The above is represented by the following equation. XαSbβTeγ (In the formula, X represents In and / or Ga, α, β, γ represents an atomic ratio (%), and is in the following range. 1 ≦ α ≦ 10,
60 ≦ β ≦ 90, γ = 100−α−β) With the above composition range, when the linear velocity of the initially crystallized disk is changed to irradiate continuous laser light of about 8 to 9 mW, It is possible to obtain a medium in which the reflectance decreases with the appearance of an amorphous phase in the speed range of 16 to 20 m / s, and it is possible to secure a necessary and sufficient crystallization speed.

Here, In and / or Ga has the effect of improving the crystallization speed of the recording layer and enabling high-speed overwriting, and the effect of increasing the crystallization temperature and improving the storage stability. . At this time, if the amount of In and / or Ga added to Sb-Te is less than 1 atomic%, the effect does not appear, and if it exceeds 10 atomic%, the overwrite characteristic is deteriorated and the reflectance after initial crystallization is deteriorated. There is an adverse effect such as unevenness. Further, in order to prepare a disk whose reflectance sharply decreases at 16 to 20 m / s, it is necessary to properly adjust the composition ratio of In and / or Ga to Sb and Te. Or Ga is 1 to 1
When the Sb content is 0 atomic%, a disk having good characteristics can be obtained by adjusting Sb to 60 to 90 atomic%. Further, with respect to (In and / or Ga) -Sb-Te, addition of Ge further improves storage stability, and addition of Ag facilitates initialization. However, the total amount of Ag and Ge added must be less than 10 atomic%. If it is more than this, the recording sensitivity and the overwrite characteristic are deteriorated.

Next, the reflective layer will be described. In the present invention, the reflecting layer plays a role as a light reflecting layer, and also plays a role as a heat radiating layer for radiating heat applied to the recording layer by laser light irradiation during recording. The formation of the amorphous mark is greatly influenced by the cooling rate due to heat dissipation, and therefore the selection of the reflective layer is particularly important in the medium corresponding to the high linear velocity. In the present invention, the reflective layer has a very high thermal conductivity A
By using an alloy containing g or Ag as a main component, the cooling rate is increased, and good amorphous formation can be realized. The thickness of the reflective layer is preferably 100 to 300 nm.
Since the heat dissipation capacity of the reflective layer is basically proportional to the thickness of the layer, if the thickness is less than 100 nm, the cooling rate will decrease, which is not preferable. On the other hand, if the thickness exceeds 300 nm, the material cost increases, which is not preferable. In the case where the reflective layer is made of Ag or an alloy containing Ag as a main component and is provided in contact with the second thin film layer, and the second thin film layer contains ZnS, pin holes are not generated due to sulfurization of Ag. In order to avoid it, it is preferable to provide a layer containing no sulfur such as SiC, SiN, GeN, and ZrO ₂ as a barrier layer between both layers.

Finally, the first thin film layer will be described. Starting
As the material for forming the first thin film layer, SiOx, ZnO, S
nO_Two, Al_Two O_Three, TiO_Two, In_TwoO_Three, MgO,
ZrO_Two, Ta_TwoO₅Metal oxides such as Si;_ThreeN_Four, A
Nitride such as 1N, TiN, BN, ZrN; ZnS, Ta
S_FourSulfides such as SiC, TaC, B_FourC, WC, Ti
Carbides such as C and ZrC are listed. These materials are
It can be used alone as a protective layer, or as a mixture.
It can also be used. As the mixture, for example, Z
nS, SiOx, Ta_TwoO₅And SiOx.
The physical properties of these materials include thermal conductivity, specific heat, and thermal expansion.
Coefficient, refractive index and adhesion to substrate material and recording layer material
Need to be considered, high melting point, small coefficient of thermal expansion
In addition, good adhesion is required. Especially,
The second dielectric layer affects repeated overwrite characteristics.
It The thickness of the first thin film layer is in the range of 50 to 250 nm.
However, 75-200 nm is preferable. Thinner than 50nm
Then, the environmental protection function is reduced, the heat resistance is reduced, and the heat storage effect is reduced.
It is not preferable because it causes deterioration. Also, thicker than 250 nm
In that case, the film temperature during the film formation process such as sputtering
Film peeling and cracks due to the rise of the
It is not preferable because it causes a decrease in degree. Second dielectric layer
The film thickness of 5 is in the range of 10 to 100 nm, and is 15 to 50
nm is preferred. Basically heat resistance when thinner than 10 nm
Is not preferable. When it exceeds 100 nm, the recording feeling
Deterioration, film peeling due to temperature rise, deformation, heat dissipation deterioration
As a result, the repetitive overwrite characteristic deteriorates.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The basic structure of an optical information recording medium (optical disc) having a structure compatible with DVD-ROM is as follows: a polycarbonate substrate with a guide groove having a diameter of 12 cm, a thickness of 0.6 mm, and a track pitch of 0.74 μm. A thin film layer (protective layer), a recording layer, a second thin film layer (protective layer), and a reflective heat dissipation layer are provided, and a diameter of 12 cm and a thickness of 0.6 mm are provided through an organic protective film formed on the reflective heat dissipation layer. It is a polycarbonate disc bonded. Recording and reproduction were performed by irradiating a laser beam from the substrate side. Recording / reproduction was evaluated using a pickup head having a wavelength of 660 nm and an NA of 0.65, a recording density of 0.267 μm / bit, and E
The FM + modulation method was used. Recorded linear velocity 7, 12, 17
The recording strategy was optimized according to each disk and linear velocity with m / s, recording power 13 to 15 mW, bias power 0.2 mW, and erasing power 6 to 8 mW. All reproduction was performed at a linear velocity of 3.5 m / s and a power of 0.7 mW.

Example 1 (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 60 nm was used as the first thin film layer, and Ge _2.5 Ga _6.5 Sb was used as the recording layer.
₇₂ Te ₁₉ with a thickness of 18 nm and ZrO 2 as the second thin film layer
₂ has a thickness of 14 nm, and Ag has a thickness of 140 n as a reflective layer.
m, each of which was formed into a disk by sputtering. This disk was initially crystallized using a laser having a diameter of 1 μm × 100 μm, an output of 680 mW, a feed of 36 μm, and a linear velocity of 3 m / s. When this initialized disk was irradiated with continuous light of 9 mW, the reflectance drastically decreased at a linear velocity of 17 m / s or more. When the recording characteristics were evaluated, it was possible to perform good recording with jitter of the order of 8% and modulation of 60% or more at each linear velocity. Overwrite 5
Up to 000 times, the increase in jitter was within 2%, and there was no change in modulation. The reproduction light stability is 0.
At 100,000 times at 8 mW, the increase in jitter was 2%.

Example 2 (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 60 nm was used as the first thin film layer, and Ge _2.5 Ga _6.5 Sb was used as the recording layer.
₇₂ Te ₁₉ having a thickness of 18 nm as the second thin film layer (Zr
O ₂ ) ₈₀ (TiO ₂ ) ₂₀ having a thickness of 12 nm and Ag as a reflective layer having a thickness of 140 nm were formed by sputtering to form a disk. Use this disc with a diameter of 1 μm x 10
Output 680mW, feed 36 with 0μm laser
Initial crystallization was performed at a linear velocity of 3 m / s at a thickness of μm. Irradiating this initialized disk with 9 mW of continuous light gives 17 m /
The reflectance decreased sharply at linear velocities of s and above. When the recording characteristics were evaluated, the jitter was in the order of 7% and the modulation was 65% or more at each linear velocity, and further excellent recording could be performed as compared with Example 1. This is the second thin film layer Z
It is considered that the addition of TiO ₂ to rO ₂ reduced the thermal conductivity of the second thin film layer and increased the recording sensitivity. Further, in this example, the thickness of the second thin film layer was made thinner than that in Example 1, but the reflectance after initialization was almost the same as that in Example 1. This is because the addition of TiO ₂ increased the refractive index of the second thin film layer, so that an optical film thickness (product of refractive index and film thickness) equivalent to that in Example 1 could be secured even with a thin film.

Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 60 nm was used as the first thin film layer, and Ge _2.5 Ga _6.5 Sb was used as the recording layer.
₇₂ Te ₁₉ having a thickness of 18 nm as the second thin film layer (Zr
O ₂ ) ₇₇ (TiO ₂ ) ₂₀ (Y ₂ O ₃ ) ₃ with a thickness of 12
nm, Ag as a reflective layer having a thickness of 140 nm, and each film was formed by sputtering into a disk. This disc is output 680 by using a laser having a diameter of 1 μm × 100 μm.
Initial crystallization was performed at mW, feed of 36 μm and linear velocity of 3 m / s.
When this initialized disk was irradiated with continuous light of 9 mW, the reflectance drastically decreased at a linear velocity of 17 m / s or more. When the recording characteristics were evaluated, jitter was 7 at each linear velocity.
Good recording could be performed with the% range and the modulation being 70% or more. In addition, the increase in jitter was within 2% and the modulation did not change until 20000 times of overwriting. Reproduction light stability is 0.8mW, 1
After 00000 times, the increase in jitter was 2%. Compared with Example 2, the number of overwrites was remarkably improved, which is considered to be because the addition of Y ₂ O ₃ increased the toughness of ZrO ₂ and suppressed the deterioration of the film due to thermal shock.

Example 4 (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 60 nm as the first thin film layer, and Ge _2.5 Ga _6.5 Sb as the recording layer.
₇₂ Te ₁₉ having a thickness of 18 nm as the second thin film layer (Zr
O ₂ ) ₈₀ (ZnS) ₂₀ having a thickness of 14 nm and Ag as a reflective layer having a thickness of 140 nm were formed by sputtering to form a disk. Use this disc with a diameter of 1 μm x 100
Output of 680 mW and feed of 36 μm using μm laser
Initial crystallization was performed at m and a linear velocity of 3 m / s. When this initialized disk is irradiated with continuous light of 9 mW, 17 m / s
The reflectance decreased sharply at the above linear velocities. When the recording characteristics were evaluated, it was possible to perform good recording with a jitter of the order of 8% and a modulation of 60% or more at each linear velocity, and recording characteristics similar to those of Example 1 were obtained. On the other hand, the deposition rate of the second thin film layer was higher than that in Example 1, and it was possible to manufacture the medium in a shorter time. In addition, the ratio of ZrO ₂ and ZnS was changed from no ZnS to 5
30mo when shaken in 3mol% steps up to 0mol%
From around 1%, the overwrite characteristic gradually deteriorated. Further, if it is less than 5 mol%, the deposition rate is not improved, and there is almost no effect of adding ZnS.

Example 5 A disk was prepared in exactly the same manner as in Example 3 except that the Ag film thickness was changed in steps of 50 nm to 30 nm, and the recording characteristics were evaluated by performing the same operation as in Example 3. , The degree of modulation increased in the range of 100 to 300 nm, the jitter at each linear velocity was in the 7% range, and the modulation was 70% or more.

Examples 6 to 9 Discs were prepared in the same manner as in Example 3 except that the composition of the recording layer was changed as follows, and the same operation as in Example 3 was carried out to evaluate the recording characteristics. And Example 3
The result is almost equal to. Example _{6 ... Ge 3 Ga 3 Sb 75} Te 19, Example _{7 ... Ge 3 Ga 7 Sb 71} Te 19, Example _{8 ... Ag 1 Ge 2 Ga 6} Sb 72 Te 19, Example 9 _... Ge 2 _In 3 Ga ₃ Sb ₇₂ Te ₂₀

Examples 10 to 12 Y ₂ O ₃ in the second thin film layer material of Example ₃ was replaced with MgO.
An optical disk was prepared and evaluated in the same manner as in Example 3 except that the elements were changed to (Example 10), CaO (Example 11), and CeO ₂ (Example 12). Results were obtained.

Comparative Example 1 An optical disk was produced in the same manner as in Example 1 except that (ZnS) ₈₀ (SiO ₂ ) ₂₀ was formed as the second thin film layer to a thickness of 20 nm. When continuous light of 9 mW was applied to this disk, the reflectance drastically decreased at a linear velocity of 17 m / s or more. However, when the recording characteristics were evaluated, the jitter exceeded 10% at each linear velocity, and the modulation was 50% or less, so that proper recording could not be performed. This is probably (ZnS) ₈₀ (SiO
₂ ) The thermal conductivity of ₂₀ is larger than that of the second thin film layer containing ZrO ₂ as a main component, and the maximum temperature reached by the laser beam irradiated during recording is lowered, and the crystal of the recording layer is reduced. It is considered that it was not possible to prevent the decrease in the amorphous forming ability with the increase in the conversion rate.

[0029]

According to the present invention, the crystallization speed of the recording layer is sufficiently increased to secure the erasing property, and at the same time, the good amorphous recording mark forming ability can be secured. It is possible to achieve both conflicting properties. As a result, it has a capacity equal to or greater than that of a DVD-ROM,
7 to 17 m / which is 2 to 5 times the linear velocity of the D-ROM.
It is possible to provide an optical information recording medium suitable for recording with S.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a change in reflectance when the linear velocity is changed.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 G11B 7/24 538F B41M 5/26 7/26 531 G11B 7/26 531 B41M 5/26 X (72) Inventor Hiroko Tashiro 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Mirai Mizutani 1-3-3 Nakamagome, Ota-ku, Tokyo Inside Ricoh (72) Invention Person Masato Hariya 1-3-6 Nakamagome, Ota-ku, Tokyo, Japan Ricoh Co., Ltd. (72) Inventor Hajime Jyohara 1-3-3 Nakamagome, Nakatagome, Ota-ku, Tokyo (72) Inventor Shinaki Onagi Tokyo Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. F-term (reference) 2H111 EA04 EA23 FA11 FA12 FA14 FA16 FA25 FA27 FB05 FB09 FB17 FB21 FB30 GA03 5D029 JA01 LA14 LA15 LA17 LB07 MA13 MA14 5D121 AA04 EE03

Claims (17)

[Claims] 1. A transparent substrate, at least a first thin film layer (protective layer), a phase change optical recording material layer, a second thin film layer (protective layer),
An optical information recording medium having a reflective layer, which can record and reproduce by irradiation of laser light by utilizing reversible phase change between an amorphous phase and a crystalline phase of the recording material layer, An optical information recording medium, wherein the second thin film layer is made of a material containing Zr oxide as a main component. 2. The second thin film layer is made of a material containing Zr oxide as a main component, so that the recording medium is rotated at a constant linear velocity and has a strength of 8 to 15 times the reproducing power. When the linear velocity of rotation is less than 16 m / s when irradiated with laser light, the recording layer remains in a crystalline state,
The optical information recording medium according to claim 1, wherein the optical information recording medium has a physical property that an amorphous phase starts to appear within the range. 3. The optical information recording medium according to claim 1, wherein the Zr oxide is ZrO ₂ . 4. The optical information recording medium according to claim 1, wherein the second thin film layer contains TiO ₂ . 5. The ratio of TiO _{2 in} the second thin film layer is 5
The optical information recording medium according to claim 4, which is -30 mol%. 6. The optical information recording medium according to claim 1, wherein the second thin film layer contains ZnS. 7. The proportion of ZnS in the second thin film layer is 5 to 5.
The optical information recording medium according to claim 6, which is 30 mol%. 8. The second thin film layer is A (A is Y ₂ O ₃ , Mg
The optical information recording medium according to claim 1, further comprising O, CaO, or at least one of rare earth oxides. 9. The ratio of A in the second thin film layer is 2 to
The optical information recording medium according to claim 8, which is 20 mol%. 10. The second thin film layer comprises TiO ₂ , ZnS, A
4. The optical information recording medium according to claim 1, wherein the optical information recording medium contains at least two kinds (A is at least one kind of Y ₂ O ₃ , MgO, CaO, and a rare earth oxide). 11. TiO ₂ , Z in the second thin film layer material
The ratio of the total amount of nS and A (A is at least one of Y ₂ O ₃ , MgO, CaO, and rare earth oxides) is 5 to 30 mol%.
The optical information recording medium according to claim 10, which is 12. The optical information recording medium according to claim 1, wherein the second thin film layer has a thickness of 4 to 20 nm. 13. The optical information recording medium according to claim 1, wherein the second thin film layer is provided by a sputtering method using a target made of a predetermined thin film layer material. 14. The phase-change optical recording material layer, wherein all the constituent atoms of the layer are 1, and an atomic ratio of 90% or more has an atomic composition represented by the following formula. Optical information recording medium. XαSbβTeγ (In the formula, X represents In and / or Ga, α, β, γ represents an atomic ratio (%), and is in the following range: 1 ≦ α ≦ 10, 60 ≦ β ≦ 90, γ = 100− α-
β) 15. The optical recording material layer further comprises Ag and / or G.
The optical information recording medium according to claim 14, wherein the optical information recording medium comprises e. 16. The optical information recording medium according to claim 1, wherein the reflective layer is made of Ag or an Ag alloy. 17. The optical information recording medium according to claim 1, wherein the reflective layer has a thickness of 100 to 300 nm.