JPH05159368A - 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. and carbon. CONSTITUTION:Since the dielectric layer is the composite contg. at least the chalcogen compd. 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. Then, the property to shield oxygen, moisture, etc., is excellent and the change in the film quality of the recording layer and the deterioration in the performance are suppressed. Further, the composite prevents the diffusion of the oxygen in the dielectric substance by repetition of recording and erasing and the consequent deterioration of the characteristics of the recording layer in the case of an optical recording medium which executes the repetion of recording and erasing. The dielectric layer is particularly high in heat resistance and has the sufficient mechanical characteristics to prevent its destruction even when the layer is heated at the time of a recording operation.

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 and MgF are disclosed.
₂ , non-oxides such as ZnS and AlF ₃ , JP-A-58-215
As disclosed in Japanese Patent No. 744, SiO ₂ , SiO, Al ₂ O ₃ , Z
Oxides such as rO ₂ and TiO ₂ , and further disclosed in JP-A-63-103
As described in Japanese Patent No. 453, a chalcogenide such as ZnS and Si
A dielectric layer mixed with an oxide such as O ₂ was formed by a known thin film forming method to form 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 further, mechanical deformation such as warpage of the optical recording medium is large.

The present invention was conceived in view of the above-mentioned drawbacks of the prior art. The purpose of the present invention is to provide a dielectric layer capable of sufficiently reducing the internal stress generated in the film and to prevent mechanical deformation such as warpage. An object is to provide a few high-quality optical recording media. 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,
It excels in blocking oxygen and moisture, suppressing changes in film quality and performance deterioration of the recording layer, and ensuring long-term reliability.

[0008]

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 made of a composite containing at least a chalcogen compound and carbon (C).

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

Further, the complex containing the chalcogen compound and carbon as referred to here is a substance in which two or more kinds of these substances are dispersed and mixed in the order of several nanometers or less, or in the order of atomic level, or a grain of several nanometers or less. However, the present invention is not limited to these, and it is preferable that a part or all of the grains thereof have a regular layered structure in units of a few nanometers or less, or mainly consist of the substance.

According to a study conducted by the present inventors on the dielectric layer used for the 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 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 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.

Further, in the case of an optical recording medium which can be repeatedly recorded and erased, in the composite containing the chalcogen compound and carbon of the present invention, oxygen in the dielectric diffuses into the recording layer due to repeated recording and erasing, and the characteristics of the recording layer. Does not deteriorate.
Furthermore, since the internal stress of the dielectric layer is reduced, mechanical breakdown of the dielectric layer due to heat cycle of heating / cooling during repeated recording / erasing and peeling of the recording layer and the dielectric layer may occur. Therefore, good repeatability of recording and erasing can be expected. Since it has particularly high heat resistance and has sufficient mechanical properties and does not break even when heated during a recording operation, the chalcogen compounds are ZnS, ZnSe and ZnT.
e and the like are preferable.

The composition ratio of the chalcogen compound and 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 Here, A represents a chalcogen compound, B represents carbon, and X and the numbers represent the molar ratio of each element or molecule. Further, 0.02 ≦ X ≦ 0.80 Furthermore, in the above composition formula, the following composition is preferable.

0.10≤X≤0.60 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 in the dielectric layer and adjust the refractive index, metals, semimetals, and oxides, nitrides, carbides thereof, etc. within a range that does not significantly deteriorate the recording characteristics, etc. For example, SiO ₂ , TiO ₂ , Si ₃
It may contain N ₄ , AlN, ZrC, TiC, or the like.

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 a 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, reproduction or erasing of the optical recording medium of the present invention is light such as laser light or strobe light, and especially 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 provided 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, which is provided as necessary, is formed, and a resin layer, for example, an ultraviolet curable resin layer is further formed 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.

In the formation of the dielectric layer made of a composite containing at least a chalcogen compound and carbon, for example, in the case of vapor deposition, the chalcogen compound and carbon are simultaneously evaporated from different evaporation sources, or the chalcogen compound and carbon are contained. It is obtained by mixing materials in a predetermined ratio in advance and evaporating them from one evaporation source. Further, in the case of sputtering, it can be obtained by simultaneously sputtering a target composed of a chalcogen compound and a target composed of carbon, or by sputtering a target prepared by mixing a material containing a chalcogen compound and carbon in a predetermined ratio in advance. ..

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, a dielectric layer is formed by performing simultaneous sputtering using, for example, a ZnS target and a carbon target. Then, it can be obtained by forming a recording layer on the dielectric layer by performing sputtering using a target of the recording layer forming material, and further forming a dielectric layer on the recording layer in the same manner as described above. ..

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 for example, 5 × 10 ^-2 Pa to 3 Pa.
It is a degree.

[0033]

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 a C target were placed in a sputtering apparatus capable of setting three targets and capable of simultaneous sputtering.
A (graphite) target and a Te50Ge41Ga2Bi7 target, which is a phase-change write-once optical recording material, are set, and a disk substrate (130 mm write-once 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 3
It was introduced so that the pressure would be × 10 ^-1 Pa. Next, while rotating the substrate so as to make the film thickness and composition uniform, the electric power supplied to each target was controlled so that the evaporation amount of ZnS was 70 mol% and that of C was 30 mol%. The targets were simultaneously sputtered by the RF magnetron sputtering method, and the dielectric layers were formed by performing the sputtering until the sum of the film thickness monitor values became 80 nm. next,
A Te50Ge41Ga2Bi7 target was sputtered until the film thickness monitor value reached 100 nm, and a recording layer was formed on the dielectric layer. Further, on the recording layer, a dielectric layer of ZnS 70 mol% and C 30 mol% was formed in a thickness of 90 nm in the same manner as described above. Thus, a three-layer structure of substrate / dielectric layer ((ZnS) 0.70C0.30) / recording layer / dielectric layer ((ZnS) 0.70C0.30) was formed. An ultraviolet curing resin layer of 8 μm is formed on the dielectric layer of this three-layer structure.
Then, the optical recording medium of the present invention was formed.

As a result of measuring the mechanical characteristics of this optical recording medium, the maximum tilt amount was 4.3 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.

Using an optical head with a numerical aperture of 0.53 for the objective lens and a wavelength of 830 nm for the semiconductor laser, the number of revolutions is 1
800 rpm, peak power 10 mW, recording pulse width 8
Under the condition of 0 ns, the 1.5T signal (3.7 MHz) is transmitted to the track No. It was 3.5 × 10 ⁻⁶ as a result of recording on 2000 tracks of 1001 to 3000 and measuring the BER. After this optical recording medium was stored in an environment of 90 ° C. and 80% RH for 1500 hours, the track No. 1001-3
000 was reproduced and the BER was measured to be 4.2 × 10.
Almost no deterioration was observed at ^-6 . It can be seen that the optical recording medium of the present invention has excellent long-term reliability.

Example 2 The substrate / dielectric layer ((ZnSe) was formed in the same manner as in Example 1 except that the ZnSe target was set in place of the ZnS target in Example 1, and the conditions of the substrate, the sputtering pressure, the film thickness of each layer and the like were the same. ) 0.60C0.40) / recording layer / dielectric layer ((ZnSe) 0.60C0.40) / reflection layer. An ultraviolet curable resin layer was provided on the reflective layer of this three-layer structure to a thickness of 8 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 4.7 mrad. The optical recording medium of the present invention is sufficiently compliant with the ISO standard even in the single-plate structure, and therefore, further excellent mechanical properties can be expected after laminating.

In the same manner as in Example 1, the peak power is 8 m.
W, a recording pulse width of 100 ns, and a 1.5T signal (3.7 MHz) with a track number. 1001-3000
Was recorded on 2000 tracks and the BER was measured, and the result was 2.6 × 10 ⁻⁶ . This optical recording medium is
After storage for 1,500 hours in an environment of 80% RH, truck No. When 100 to 3000 were regenerated and the BER was measured, almost no deterioration was observed at 3.8 × 10 ⁻⁶ . It can be seen that the optical recording medium of the present invention has excellent long-term reliability.

Comparative Example 1 Substrate / dielectric layer (ZnS) / recording was carried out in the same manner as in Example 1 except that the C target was not set in Example 1, and the substrate, sputtering pressure conditions, film thickness of each layer and the like were the same. A three-layer structure of layer / dielectric layer (ZnS) / reflection layer was formed. An ultraviolet curable resin layer was provided on the dielectric layer of this three-layer structure to a thickness of 8 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 9.2 mrad.

The BER measured in the same manner as in Example 1 was 5.0 × 10 ^-6 . This optical recording medium is
Stored in an environment of 80% RH for 1500 hours, then BE
R became as large as 4.1 × 10 ⁻⁴ , which made it practically unusable.

[0043]

The optical recording medium of the present invention has the following excellent effects because the dielectric layer is formed of a composite containing at least a chalcogen compound 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) In storage under a high temperature and high humidity environment, recording characteristics are not deteriorated and long-term reliability is secured.

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 and carbon (C). 2. The optical recording medium according to claim 1, wherein the chalcogen compound is at least one selected from the group consisting of ZnS, ZnSe and ZnTe.