JPH05159369A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve mechanical characteristics and to lessen the mechanical change, such as warpage, of the optical recording medium so as to decrease the burden on a system for executing recording and reproducing by forming a dielectric layer of a composite contg. at least a chalcogen compd., oxide and carbon. CONSTITUTION:Since the dielectric layer is the composite contg. at least the chalcogen compd., the oxide and the carbon, the internal stresses of the dielectric layer are decreased. The mechanical deformation, such as warpage, of the optical recording medium is, therefore, lessened. Further, the adhesive strength to the recording layer is excellent and the generation of the peeling and cracking of the film is suppressed. Since the dielectric layer is decreased in internal stresses, the dielectric layer obviates the generation of the mechanical destruction of the dielectric layer and the peeling of the recording layer and the dielectric layer by the heat cycles of heating and cooling at the time of repetition of recording and erasing. The excellent characteristics to repeat recording and erasing are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium capable of recording and reproducing information by irradiation with light.

[0002]

2. Description of the Related Art In a conventional optical recording medium, a recording layer for recording, reproducing or erasing information by utilizing an optical change undergoes oxidative corrosion due to moisture or oxygen in the air, or heat. Not only the characteristics of the recording layer are deteriorated during storage and transportation, but also an optical recording medium capable of repeated recording and erasing has a drawback that it cannot be used because the recording and erasing characteristics are deteriorated by repeated recording and erasing. .. Therefore, as disclosed in JP-A-59-110052 and JP-A-60-131659, aluminum nitride, silicon nitride, Mg
Non-oxides such as F ₂ , ZnS, AlF ₃ , etc.
-215744, SiO ₂ , SiO, Al
Known thin film formation of a dielectric layer in which an oxide such as ₂ O ₃ , ZrO ₂ or TiO ₂ or a chalcogenide such as ZnS and an oxide such as SiO ₂ are mixed as in JP-A-63-103453. The film was formed by the method as a protective layer for the recording layer.

[0003]

The dielectric layer provided in the optical recording medium is exposed to thermal and mechanical loads during recording or erasing, so it is necessary that it has excellent mechanical properties and heat resistance. In addition, it is necessary to additionally have a function of protecting the recording layer during storage of the optical recording medium.

In the case of an oxide or nitride dielectric layer, the dielectric layer itself may peel or crack during storage in a high temperature and high humidity environment, and the optical constant of the dielectric layer is not appropriate. In addition, the recording or erasing characteristics may deteriorate.

A chalcogen compound such as ZnS alone or a dielectric layer in which a chalcogen compound such as ZnS is mixed with an oxide such as SiO ₂ is generated in a film by a thin film forming method such as vapor deposition or sputtering. Since the internal stress becomes a large compressive stress, peeling is likely to occur and mechanical deformation such as warpage of the optical recording medium is large.

The present invention was devised in view of the above-mentioned drawbacks of the prior art. The purpose of the present invention is to provide a dielectric layer in which internal stress generated in the film is sufficiently reduced and to prevent mechanical deformation such as warpage. An object is to provide a high-quality optical recording medium.
Since the mechanical properties are good, the load on the system for recording and reproducing can be significantly reduced.

Another object of the present invention is to provide an optical recording medium which is excellent in the adhesive force between the dielectric layer and the recording layer, and is free from film peeling and cracking. Therefore, oxygen,
It has an excellent property of blocking moisture and the like, suppressing changes in film quality of the recording layer and performance deterioration, and ensuring long-term reliability.

Still another object of the present invention is to reduce the internal stress generated in the film of the dielectric layer itself in the case of an optical recording medium which can be repeatedly recorded and erased. It is an object of the present invention to provide an optical recording medium which is free from minute peeling of a dielectric layer, cracks, deterioration of a recording layer, etc.

[0009]

The object of the present invention is as follows.
An optical recording medium having a recording layer and a dielectric layer on a substrate, wherein the dielectric layer is composed of a composite containing at least a chalcogen compound, an oxide and carbon.

In the present invention, examples of chalcogen compounds include sulfides, selenides and tellurides. For example, ZnS, ZnSe, ZnTe, PbS,
Examples thereof may include, but are not limited to, sulfides such as PbSe and PbTe, selenides, and tellurides.

As the oxide, I in the periodic table of the elements is used.
Examples thereof include Group II, Group IV, Group V metal or metalloid oxides. For example, Si, Al, T
Examples thereof include oxides such as i, Ta, and Zr, but are not limited to these.

Further, the complex containing the chalcogen compound, the oxide and the carbon referred to here is a substance in which three or more kinds of these substances are dispersed and mixed in the order of several nanometers or less, or even in the atomic level, or several nanometers. The following is an aggregate of grains, and part or all of the grains is preferably a substance having a regular layered structure in units of several nanometers or less, or a substance mainly consisting of the substance. Not limited.

According to a study conducted by the present inventors regarding a dielectric layer used for an optical recording medium, a chalcogen compound such as ZnS formed by a known thin film forming method, for example, vapor deposition or sputtering generally causes a large compression in the film. Stress is generated. A large compressive stress also occurs in the case of a composite containing a chalcogen compound, for example, a composite of ZnS and SiO ₂ .

Since the dielectric layer in the present invention is a composite containing at least a chalcogen compound, an oxide and carbon, the internal stress of the dielectric layer is reduced. Therefore, mechanical deformation such as warpage of the optical recording medium is small. Furthermore, the adhesive strength to the recording layer is excellent, and it is possible to prevent the film from peeling or cracking. Therefore, it has an excellent barrier property against oxygen and moisture, and can suppress the film quality change and performance deterioration of the recording layer. In addition, since the internal stress of the dielectric layer is reduced, mechanical breakdown of the dielectric layer due to thermal cycles of heating and cooling during repeated recording and erasing,
The recording layer and the dielectric layer are not peeled off, and the repetitive characteristics of recording and erasing are excellent.

In particular, the heat resistance is high, and even if the recording / erasing operation is repeatedly heated, it has sufficient mechanical properties and does not break. Therefore, the recording repeatability is excellent. Since the shielding property is excellent, the recording layer has excellent protection properties, and the long-term reliability of the optical recording medium can be obtained.
S, ZnSe, and ZnTe are preferable, and S is used as the oxide.
iO ₂ , SiO, Al 2 O ₃ , TiO ₂ , Ta ₂ O ₅ , Z
rO _{2 and the} like are preferable.

The composition ratio of the chalcogen compound, the oxide and the carbon is not particularly limited, but the following composition is preferable from the viewpoint of a large effect of reducing the internal stress of the dielectric layer.

Compositional formula (A1-X BX) 1-Y CY Here, A is a chalcogen compound, B is an oxide, C is carbon, and X, Y and the numbers are the molar ratio of each element or molecule. Further, 0.02 ≦ X ≦ 0.50 0.05 ≦ Y ≦ 0.80 Furthermore, in the above composition formula, the following composition is preferable.

0.05 ≦ X ≦ 0.35 0.10 ≦ Y ≦ 0.50 The thickness of the dielectric layer is preferably in the range of 3 nm to 500 nm, more preferably 10 nm to 300 nm. 3n
If it is less than m, oxygen, moisture, etc. cannot be sufficiently blocked, and it is difficult to obtain the recording layer protection characteristics. 500n
If it is larger than m, the internal stress becomes large, peeling or cracking is likely to occur, and mechanical deformation such as warpage of the optical recording medium becomes large.

Further, in order to relieve the internal stress and adjust the refractive index of the dielectric layer, metal, semimetal, and their nitrides, carbides, fluorides, etc. are contained within a range that does not significantly deteriorate the recording characteristics and the like. It does not matter if it is included.

The optical recording medium of the present invention comprises at least a substrate, a recording layer formed on the substrate, and a dielectric layer, and the dielectric layer is adjacent to one side or both sides of the recording layer. Can be provided.

A known optical recording layer can be used as the recording layer in the present invention. For example, the crystal structure of the recording layer is changed by irradiating the laser beam focused on the recording layer (for example, from crystalline to amorphous). It is possible to use a material capable of recording information by the phase change, that is, the quality or the reverse thereof, or the hexagonal crystal to the cubic crystal or the reverse thereof). For example, T
eGe system, SnTeSe system, SbTeGe system or I
Examples include nSe-based systems, or systems obtained by modifying these systems with a small amount of additives such as metals. Also, as a material for recording information by irradiating the magnetic recording layer with focused laser light to cause magnetization reversal, TbFeC is used.
o, etc.

The substrate used in the present invention may be the same as a conventional recording medium such as plastic, glass and aluminum. In order to avoid the influence of dust adhering to the recording medium by recording, reproducing or erasing from the substrate side by the convergent light, it is preferable to use a transparent material as the substrate. Examples of the above materials include polyester resin, acrylic resin, polycarbonate resin, epoxy resin, polyolefin resin, styrene resin, glass and the like. Of these, polymethylmethacrylate, polycarbonate, and epoxy resin are preferable because they have a small birefringence and are easy to form. The thickness of the substrate is not particularly limited, but is 10 μm to 5 m
A range of m is practical. If it is less than 10 μm, it is easily affected by dust when recording, reproducing or erasing from the substrate side by convergent light, and if it is more than 5 mm, the numerical aperture of the objective lens is increased when recording, reproducing or erasing by convergent light. It becomes impossible to increase the pit size and it becomes difficult to increase the recording density.

The substrate may be flexible or rigid. The flexible substrate can be used in a tape shape or a card shape or a sheet shape such as a circle. The rigid substrate can be used in a card shape or a circular disk shape.

The light used for recording, reproducing or erasing the optical recording medium of the present invention is light such as laser light or strobe light, and in particular, the use of a semiconductor laser
It is preferable because the light source is small, consumes less power, and can be easily modulated.

The optical recording medium of the present invention has a structure in which a recording layer is formed on a substrate and the dielectric layer of the present invention is formed on the recording layer, or a dielectric layer, a recording layer and a dielectric layer are formed on the substrate. It is used as a structure laminated in this order.

Further, when a signal is read by changing the reflectance of the recording layer, a reflecting layer made of metal (for example, Al, Au, NiCr, etc.) is formed on one surface of the recording layer opposite to the light incident surface.
May be provided, and an intermediate layer may be provided between the recording layer and the reflective layer, and the dielectric layer of the present invention may be used as the intermediate layer.

An optical recording medium having a substrate on which a recording layer, a dielectric layer, and a reflection layer, if necessary, is formed is further provided with a resin layer, for example, an ultraviolet curable resin layer, on the surface on which the layer is formed. It can be provided and used as a single plate, or can be used as an air sandwich structure, an air incident structure, a contact bonding structure, or the like by laminating two members with another member or a substrate of the same kind.

In the present invention, known thin film forming techniques such as vapor deposition, sputtering, ion plating, and CVD can be used for forming the recording layer, the dielectric layer, and the reflective layer provided as necessary.

For the formation of the dielectric layer composed of a composite containing at least a chalcogen compound, an oxide and carbon, for example, in the case of vapor deposition, the chalcogen compound, the oxide and the carbon are simultaneously vaporized from different vapor sources, or It is obtained by previously mixing a material containing a chalcogen compound, an oxide and carbon in a predetermined ratio and evaporating it from one evaporation source. Further, in the case of sputtering, a target made of a chalcogen compound, a target made of an oxide and a target made of carbon are simultaneously sputtered, or a material containing a chalcogen compound and an oxide is mixed at a predetermined ratio in advance. It is obtained by sputtering the target.

A method for forming the optical recording medium of the present invention, which comprises a substrate, a dielectric layer, a recording layer and a dielectric layer, will be described below as an example.

Using a polycarbonate disk as a substrate, first, for example, a ZnS target, a SiO ₂ target and a carbon target are simultaneously sputtered to form a dielectric layer. Then, a target of a recording layer forming material is sputtered on the dielectric layer to form a recording layer, and a dielectric layer is formed on the recording layer by the same method as described above. it can.

The sputtering method is not particularly limited, and for example, a conventional means such as RF magnetron sputtering in an Ar atmosphere can be used, and the substrate is rotated to make the composition and film thickness on the substrate uniform. Is valid.

In the above manufacturing method, the composition ratio of the dielectric layer is
It is controlled by the amount of evaporation from each target. Specifically, the relationship between the power supplied to each target and the evaporation amount may be studied in advance, and the power corresponding to the desired evaporation amount may be supplied, or the evaporation amount may be adjusted by, for example, a crystal film thickness monitor. The supply power may be controlled while being monitored by.

The degree of vacuum during sputtering is not particularly limited, but is, for example, 5 × 10 ^-2 Pa to 3 Pa.
It is a degree.

[0035]

EXAMPLES The present invention will now be described based on examples, but the present invention is not limited to these.

Example 1 A ZnS target and Si were set in a sputtering apparatus capable of setting three targets and capable of simultaneous sputtering.
An O ₂ target and a C (graphite) target were set, and a disk substrate (130 mm rewritable type I
SO standard format, polycarbonate, thickness 1.
2 mm) was set. The inside of the sputtering chamber was evacuated to 2 × 10 ⁻⁴ Pa, and then Ar gas was added to 2
It was introduced so that the pressure would be × 10 ^-1 Pa. Next, while revolving the substrate to make the film thickness and composition uniform, ZnS is 56 mol%, SiO ₂ is 14 mol%, C is 30 mol%,
The power supplied to each target is controlled so that the amount of evaporation becomes equal to 3 and the three targets are simultaneously sputtered by the RF magnetron sputtering method, and sputtering is performed until the sum of the film thickness monitor values becomes 220 nm. Formed. Next, Pd1Ge17Sb26Te56 (atomic%) which is a phase change type rewritable optical recording material
Set the target and Ar gas pressure 3 × 10 ^-1 Pa
Then, in the same manner as described above, the recording layer was formed on the dielectric layer by performing sputtering until the film thickness monitor value reached 25 nm. Further, on the recording layer, a dielectric layer of ZnS 56 mol%, SiO ₂ 14 mol%, and C 30 mol% was formed in a thickness of 25 nm in the same manner as described above. After that, an Al target was further set, and a reflective layer having a thickness of 80 nm was formed under the Ar gas pressure of 3 × 10 ⁻¹ Pa in the same manner as described above. In this way, the substrate / dielectric layer (((ZnS) 0.80 (SiO2)
0.20) 0.70C 0.30) / recording layer / dielectric layer (((ZnS)
A four-layer structure of 0.80 (SiO2) 0.20) 0.70C0.30) / reflection layer was formed. An ultraviolet curable resin layer was provided on the reflective layer of this four-layer structure to a thickness of 10 μm to form an optical recording medium of the present invention.

As a result of measuring the mechanical characteristics of this optical recording medium, the maximum tilt amount was 3.4 mrad. 130m
The ISO standard value of the m-rewritable optical disc is 5 mrad or less. Since the optical recording medium of the present invention sufficiently satisfies this standard even in the single-plate construction, it is expected that even better mechanical properties will be obtained after laminating.

The entire recording area of this optical recording medium (radius 2
8 to 62 mm) was initialized (crystallized), and then recording was performed using an optical head with a numerical aperture of 0.53 for an objective lens and a wavelength of 830 nm for a semiconductor laser. Rotation speed 180
0 rpm, peak power 19 mW, recording pulse width 60 n
s and bottom power of 8.5 mW, the track No.
Among the 900 to 1000, one track with zero BER (bit error rate) was used for the initial measurement, and 1.5T
The signal (3.7 MHz) and the 4T signal (1.4 MHz) are alternately overwritten and then the B of the 1.5T signal is repeated.
ER was measured. The number of recording repetitions when the BER exceeded 1 × 10 ⁻⁴ was 220,000.

Furthermore, under the same recording conditions as above, 1.5T
The signal (3.7 MHz) is transmitted to the track No. 1001-30
It was recorded on 2000 tracks of No. 00 and the BER was measured, and the result was 1.4 × 10 ⁻⁶ . This optical recording medium is
After storing for 3000 hours in an environment of ℃ and 80% RH,
Track No. When 100 to 3000 were regenerated and the BER was measured, it was 1.6 × 10 ⁻⁶ , and the deterioration was extremely slight. It can be seen that the optical recording medium of the present invention has excellent long-term reliability.

Comparative Example 1 In Example 1, only the ZnS target and the SiO ₂ target were set without setting the C (graphite) target. The substrate and sputtering pressure conditions were the same as in Example 1, first, the two targets were simultaneously controlled by controlling the power supply to each target so that the evaporation amount of ZnS was 80 mol% and that of SiO ₂ was 20 mol%. Sputtering was performed until the sum of the film thickness monitor values reached 220 nm to form a dielectric layer. Then
The recording layer was formed to a thickness of 25 nm in the same manner as in Example 1, and ZnS 80 mol% and SiO ₂ 20 mol% were formed in the same manner as described above.
25 nm thick dielectric layer was formed. Thereafter, as in Example 1, a reflective layer made of Al was formed to a thickness of 80 nm. In this way, the substrate / dielectric layer ((ZnS) 0.80
(SiO ₂ ) 0.20) / recording layer / dielectric layer ((ZnS) 0.
A four-layer construction of 80 (SiO ₂ ) 0.20) / reflection layer was formed. An ultraviolet curable resin layer is formed on the reflective layer of this four-layer structure.
An optical recording medium was formed with a thickness of 0 μm.

As a result of measuring the mechanical characteristics of this optical recording medium, the maximum tilt amount was 5.6 mrad.

When the number of recording repetitions was measured in the same manner as in Example 1, it was 80,000.

Further, as in Example 1, at 80 ° C.,
BE after storage for 3000 hours in an environment of 80% RH
When R was measured, the initial BER 3.1 × 10 ⁻⁶ was 6.
It doubled to 4 × 10 ^-6 .

Example 2 In the same sputtering apparatus as in Example 1, (((ZnS
e) 0.90 (TiO2) 0.10) 0.80C0.20) target,
Te50Ge41 which is a phase change type write-once type optical recording material
A Ga2Bi7 (atomic%) target was set, and the same disk substrate as in Example 1 was set. The inside of the sputtering chamber was evacuated to 2 × 10 ⁻⁴ Pa, and then Ar gas was introduced so as to be 3 × 10 ⁻¹ Pa. Next, while rotating the substrate in order to make the film thickness and composition uniform, (((ZnSe) 0.90 (TiO2) 0.10)
A 0.80C0.20) target was sputtered by an RF magnetron sputtering method to form a dielectric layer by sputtering until the film thickness monitor value became 100 nm. Next, a Te50Ge41Ga2Bi7 (atomic%) target was sputtered until the film thickness monitor value reached 100 nm to form a recording layer on the dielectric layer. Further, on the recording layer, (((ZnSe) 0.90 (TiO 2)
₂ ) A dielectric layer consisting of 0.10) 0.80C0.20) 120nm
Formed. Thus, the substrate / dielectric layer (((Zn
Se) 0.90 (TiO ₂ ) 0.10) 0.80C 0.20) / recording layer /
Dielectric layer (((ZnSe) 0.90 (TiO ₂ ) 0.10) 0.80
A three-layer construction of C0.20) was formed. An ultraviolet curable resin layer was provided on the dielectric layer of this three-layer structure to a thickness of 10 μm to form an optical recording medium of the present invention.

As a result of measuring the mechanical characteristics of this optical recording medium, the maximum tilt amount was 4.2 mrad. 130m
The ISO standard value of the m-write-once type optical disc is 5 mrad or less. Since the optical recording medium of the present invention sufficiently satisfies this standard even in the single-plate construction, it is expected that even better mechanical properties will be obtained after laminating.

Further, using an optical head having a numerical aperture of 0.53 for the objective lens and a wavelength of 830 nm for the semiconductor laser,
1.5T signal (3.7 MH) under the conditions of rotation speed 1800 rpm, peak power 9.0 mW, and recording pulse width 90 ns.
z) is the track number. Recorded on 2000 tracks of 1001 to 3000 and measured BER 2.1 × 1
It was 0 ^-6. After this optical recording medium was stored for 3000 hours in an environment of 80 ° C. and 80% RH, track No. 1
When 001 to 3000 was regenerated and the BER was measured, it was 3.2 × 10 ⁻⁶ , and the BER was only slightly increased. It can be seen that the optical recording medium of the present invention has excellent long-term reliability.

Comparative Example 2 In Example 2, (((ZnSe) 0.90 (TiO ₂ ))
0.10) 0.80C 0.20) instead of the target ((ZnSe)
0.90 (TiO ₂ ) 0.10) Except that the target was set, the substrate, sputtering pressure conditions, film thickness of each layer, etc.
Substrate / dielectric layer ((ZnSe) 0.90 (T
iO ₂ ) 0.10) / recording layer / dielectric layer ((ZnSe) 0.90
A three-layer structure of (TiO ₂ ) 0.10) was formed. An ultraviolet curable resin layer was provided on the dielectric layer of this three-layer structure to a thickness of 10 μm to form an optical recording medium.

As a result of measuring the mechanical characteristics of this optical recording medium, the maximum tilt amount was 6.3 mrad.

Further, as in Example 2, at 80 ° C.,
BE after storage for 3000 hours in an environment of 80% RH
When R was measured, the initial BER was 1.9 × 10 ⁻⁶ .
It increased to 6 × 10 ⁻⁵ , about 10 times.

[0050]

The optical recording medium of the present invention has the following excellent effects because the dielectric layer is a composite containing at least a chalcogen compound, an oxide and carbon (C) as described above.

(1) Good mechanical properties. There is little mechanical deformation such as warpage of the optical recording medium, and the load on the system for recording and reproducing is significantly reduced.

(2) Recording characteristics are not deteriorated and long-term reliability is ensured during storage in a high temperature and high humidity environment.

(3) In the case of an optical recording medium capable of repeatedly recording and erasing, recording and erasing can be performed many times.

Claims (2)

[Claims] 1. An optical recording medium having a recording layer and a dielectric layer on a substrate, wherein the dielectric layer comprises a composite containing at least a chalcogen compound, an oxide and carbon (C). Medium. 2. The chalcogen compound is at least one selected from the group consisting of ZnS, ZnSe and ZnTe,
The optical recording medium according to claim 1, wherein the oxide is at least one selected from the group of oxides consisting of Si, Al, Ti, Ta and Zr.