JP2887322B2 - Optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for recording, reproducing, or erasing information using light such as laser light.

[Prior Art] In a conventional optical recording medium, a recording layer for recording, reproducing, or erasing information by utilizing optical change is subjected to oxidative corrosion by moisture, oxygen, or heat in the air.
During storage, transportation or use, not only the optical characteristics of the recording layer are deteriorated, but also a large number of pinholes are generated so that the recording layer cannot be used. Therefore, JP 59
No. -110052, Japanese Patent Application Laid-Open No. 60-131659, as a protective film, aluminum nitride, silicon nitride, Mg
F _2, ZnS, non-oxides such as CoF _2, AlF ₃ · 3NaF, JP-A-58
SiO _2, SiO as -215744 _{discloses, AlO 3, ZiO 2, TiO} 2
Oxides and the like, JP-A-62-254855, JP-A-62-2
No. 22454, mixed or laminated metal nitrides and metal oxides; Japanese Patent Application Laid-Open No. Sho 62-114134, a mixed layer of silicon carbide and metal oxide; Inorganic films such as CuI film and ITO film
As described in Japanese Patent No. 6942, a protective layer such as a conductive ceramic such as SnO ₂ or In ₂ O ₃ is formed by using a vacuum film forming method such as sputtering, vapor deposition, or ion plating.

[Problems to be solved by the invention] However, in the case of the above-mentioned conventional technology, there are the following problems.

That is, in the case of oxides and fluorides, the protective properties are poor, and oxygen and moisture in the air are adsorbed and penetrated, not only causing a change in the optical properties of the recording layer, but also having a drawback that pinholes are frequently generated. In addition, metal nitride has a disadvantage that cracks are easily generated when plastic is used for the substrate, and metal nitride and metal oxide are mixed or laminated, and silicon carbide and metal oxide are mixed. Insufficient protective properties also caused changes in the optical properties of the recording layer, making them impractical, such as inorganic substances such as CuI and ITO, and Sn.
Those provided with a conductive ceramic film such as O ₂ and In ₂ O ₃
Not only has the disadvantage that pinholes are easily generated, but also large traces of the previous recording remain when erasing is performed in the same manner as oxides such as SiO ₂ (that is, large erasure remains = low erasure rate). There is also a problem that the reliability is poor and the erasing speed cannot be increased.

Further, those provided with a sulfide layer of ZnS or the like have a problem that the recording layer is slow to be initialized in a certain state for recording and erasing, for example, a crystal state. In addition, the repetitive life of recording and erasing is inferior and not practical.
Further, when forming a protective layer by a sputtering method,
Since many of nitrides and oxides are insulators, there is also a problem that the DC sputtering method capable of forming a film at a high speed at a low temperature cannot be adopted and productivity is poor.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has an object of providing a good recording layer protection performance, that is, suppressing a change in film quality and performance deterioration of the recording layer, excellent storage stability, and an erasing rate. It is an object of the present invention to provide an optical recording medium having an inorganic layer which is high in erasability at high speed, has a long repetitive life of recording and erasure, is capable of high-speed initialization, and is capable of high-speed film formation.

[Means for Solving the Problems] An object of the present invention is to provide an optical recording medium having a recording layer and an inorganic layer on a substrate, wherein the inorganic layer is formed of In (indium).
And Sn (tin), and a mixture of inorganic components including O (oxygen) and Si (silicon).

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

The inorganic layer is formed from components containing In, Sn, O, and Si, and the composition of each component is not particularly limited, but the preferred content of each component in the inorganic layer is In.
Is preferably in the range of 4 to 39 atomic%, Sn in the range of 0.5 to 30 atomic%, Si in the range of 1 to 15 atomic%, and O in the range of 45 to 68 atomic%.

When In is less than 4 atomic%, there is a problem that a pinhole is easily generated in the recording layer in a moist heat environment.
When In is more than 39 atomic%, the erasing rate tends to decrease. When Sn is less than 0.5 at%, the erasing rate tends to decrease, while when Sn is more than 30 at%, the effect of protecting the recording layer in a wet heat environment tends to decrease. Further, when the content of Si is less than 1 at%, the erasing rate tends to decrease. On the other hand, when the content of Si is more than 15 at%, the change in the reflectance of the recording layer in a wet heat environment tends to increase. Also O is 45
When the content is less than atomic%, there is a disadvantage that the transparency tends to decrease. On the other hand, when the content of O is more than 68 atomic%, the optical properties of the recording layer are liable to change in a wet heat environment, which is not practical.

In particular, since the erasing rate is high, the erasing speed is high, and the optical change of the recording layer can be extremely small, the In content is 7 to 35 atomic%, the Sn content is 1 to 25 atomic%,
More preferably, the content of Si is in the range of 2 to 12 atomic%, and the content of O is in the range of 50 to 65%.

The thickness of the inorganic layer is preferably in the range of 3 nm to 400 nm, more preferably 10 nm to 300 nm.

As the recording layer in the present invention, a known optical recording layer can be used. For example, the crystal structure of the recording layer is changed by irradiating the recording layer with a focused laser beam (for example, from a crystal to an amorphous or Inverse, or from hexagonal to cubic or vice versa) that is, a material that can record information by phase transformation, or the shape of the recording part, such as making holes or forming bubbles by irradiating the recording layer with laser light. Composed of materials that record information by changing
Alternatively, a material made of a material for recording information by causing magnetization reversal by irradiating a focused laser beam to the magnetic recording layer may be used.

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 by recording from the substrate side with convergent light, it is preferable to use a transparent material for the substrate. Examples of the above materials include polyester resin, acrylic resin, polycarbonate resin, epoxy resin, polyolefin resin, styrene resin, and glass. Preferably, polymethyl methacrylate, polycarbonate, or epoxy resin is used because birefringence is small and formation is easy. Although the thickness of the substrate is not particularly limited, a range of 10 μm to 5 mm is practical. If it is less than 10 μm, it is easily affected by dust even when recording with convergent light from the substrate side.
When recording with convergent light, the numerical aperture of the objective lens cannot be increased, and the pit size increases, making it difficult to increase the recording density.

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

The light used for recording, reproducing and erasing the optical recording medium of the present invention is light such as laser light or strobe light,
In particular, it is preferable to use a semiconductor laser because the light source is small, power consumption is small, and modulation is easy.

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

When a signal is read by changing the reflectance of the recording layer, a reflective layer of metal or the like may be provided on one side of the recording layer opposite to the light incident surface, and an intermediate layer is provided between the recording layer and the reflective layer. A layer can be provided, and the inorganic layer of the present invention can be used as the intermediate layer.

An optical recording medium in which a recording layer, an inorganic layer, and a reflective layer provided as necessary are formed on a substrate, is further provided with a resin layer, for example, a layer of a radiation-curable resin, on the surface on which the layer is formed. It can be used as a plate, and can be used as an air sandwich structure, air incident structure, close bonding structure, etc. with other members or the same type of substrate.
They can also be used together.

As a method of forming the inorganic layer in the present invention, for example,
In ₂ O ₃ , SnO _2, and Si (or SiO or SiO ₂ ), three-source simultaneous evaporation, three-source simultaneous sputtering, vacuum evaporation or sputtering of a mixture of the above materials, or In
, Sn, and Si are simultaneously subjected to ion plating and sputtering in three atmospheres in an oxygen-containing atmosphere, but the method is not limited thereto.

The recording layer is formed by sputtering, vacuum deposition,
A known thin film forming technique such as an ion plating method can be used.

[Examples] Hereinafter, the present invention will be described based on examples.

The characteristics in the examples were evaluated by the following methods.

(1) Composition of inorganic layer The relative composition of In, Sn and Si in the inorganic layer was measured by ICP emission spectrometry (using FTS-1100 type manufactured by Seiko Instruments Inc.), and the relative composition of Si and O was X-ray. Photoelectron method (VG Sci
entific, ESCALAB 5).

(2) Change in reflectivity The optical recording medium is placed in 60 ° C. and 90% RH, and the reflectivity from the substrate side at each elapsed time is measured by a spectrometer (measuring wavelength: 830 nm), and reflected by the following equation. Find the rate.

(3) Evaluation of Appearance The optical recording medium is visually observed and evaluated for cracks, changes in color tone, and the like by visual observation and optical microscopy.

(4) Recording / erasing characteristics Conditions in which an optical recording medium is rotated at a linear velocity of 1.5 m / sec, and a semiconductor laser beam having a wavelength of 830 nm collected from an objective lens having a numerical aperture of 0.5 from the substrate side has an intensity of 3.4 mW on the film surface. The recording layer is crystallized by scanning between tracks while continuously irradiating the recording layer. After this, using the same optical system as above with a linear velocity of 8 m / sec, the film surface intensity 15 mW modulated at a frequency of 3 MHz and a duty ratio of 50%
After recording the amorphous recording mark with the semiconductor laser light, the recording surface is scanned and reproduced by setting the film surface intensity of the semiconductor laser light to 0.7 mW, and the carrier level, noise level and CNR of the recording signal are set to 30 kHz bandwidth. Measure with

Thereafter, the recording portion is scanned and erased while continuously irradiating a semiconductor laser beam with a film surface of 11 mW and a linear velocity of 8 m / sec, and the data is reproduced and measured under the same conditions as above.

The erasure rate is calculated by (carrier level after erasure (C _W ) −carrier level after recording (C _E )).

As for the erasing speed, crystallization, recording, and reproduction are performed in the same manner as described above, erasing is performed by changing the linear velocity and the laser light intensity, and the erasing rate at the laser light intensity suitable for each linear velocity is measured.

Example 1 While rotating a polycarbonate substrate with a group having a heat of 1.2 mm, a diameter of 13 cm and a pitch of 1.6 μm at 30 rpm,
An inorganic layer, a recording layer, and an inorganic layer were sequentially formed and laminated by DC magnetron sputtering.

First, a 12% Si chip was placed on a sintered target of In ₂ O ₃ : 95 wt% and SnO ₂ : 5 wt%, and 6 × 10 ^-1 Pa of Ar = O ₂
= 90: 10 by supplying DC power 200W in a mixed gas atmosphere (volume ratio), while monitoring a quartz vibrating-type film thickness meter was formed an inorganic layer of 1000 Å, further Sb ₅₆ Te ₃₈ Ge ₆ (figures atom%
In a 6 × 10 ^-1 Pa Ar gas atmosphere
A DC power of 100 W was applied to form a recording layer of 850 mm, and an inorganic layer was further formed on the recording layer in the same manner as described above.
Formed. Table 1 shows the results of evaluation of the optical recording medium thus produced by the above-described evaluation method.

The formation time of the inorganic layer in the preparation of this optical recording medium was 24 minutes and 50 seconds in total for the two layers. This indicates that the formation time is significantly reduced as compared with the case where the inorganic layer is formed of SiO ₂ of Comparative Example 1 described later, and that the productivity is excellent.
In addition, SiO ₂ requires RF sputtering, which is an expensive device,
The DC sputtering method of the present invention further reduces the manufacturing cost.

Examples 2 and 3 Optical recording media were formed in the same manner as in Example 1 except that the amount of Si chips was 7% and 17% in area ratio.

Table 1 shows the results of evaluating this optical recording medium by the above-described method.

Example 4 In Example 1, the inorganic layer was formed by using In ₂ O ₃ : 95 wt%
SnO ₂ : 5 wt% sintered chip on an area ratio of 12
% And the second target of Sn are simultaneously sputtered while controlling the supply power so that the first target is 40 wt% and the second target is 60 wt% by a quartz vibrating film thickness meter corresponding to each target. As a method of forming with
In Example 1, the thickness of the inorganic layer was determined as the sum of two monitored values.
An optical recording medium was prepared in the same manner as described above.

Table 1 shows the results of evaluating this optical recording medium by the above-described method.

As is apparent from Table 1, the inorganic layer containing In, Sn, Si, and O of the present invention has a small change in reflectance in a moist heat environment, so that the penetration of moisture, oxygen, and the like into the recording layer is suppressed. It is cut off to prevent corrosion of the recording layer. Further, no crack was generated, and the inorganic layer of Comparative Example 2 described later was formed of In ₂ O ₃ and SnO _2.
It is excellent in the protection of the recording layer, in which the occurrence of pinholes is remarkably reduced as compared with the case where only the recording layer is formed.

In addition, the CNR is 45 dB or more required for digital recording, and the erasure rate is 30 dB or more, which is rewritable, indicating that the optical recording medium is highly reliable.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1, except that the inorganic layer was formed by RF magnetron sputtering at 13.56 MHz in an Ar atmosphere using an SiO ₂ target at an RF power of 500 W.

 Table 1 shows the evaluation results of the optical recording medium.

The formation time of the inorganic layer in the preparation of the optical recording medium was 47 minutes and 20 seconds in total for the two layers.

Comparative Example 2 An optical recording medium was formed in the same manner as in Example 1 except that no Si chip was mounted. Table 1 shows the evaluation results.

As is clear from the comparative example, the one using only SiO _{2 for} the inorganic layer has a large reflectance change in a wet heat environment,
Both R and erasure rate are low and impractical. Further, those using only In ₂ O ₃ and SnO ₂ have many pinholes in a moist heat environment, have a low erasing rate, and are not practical.

Example 5 In the example, the substrate-side inorganic layer was 1100 mm, and the target of the recording layer was Pd ₃ Ge ₁₇ Sb ₃₀ Te ₅₀ (the number indicates atomic%), the upper inorganic layer was 2200 mm, and Au was further DC-coated thereon.
An optical recording medium was prepared in the same manner as in Example 1 with a configuration of forming 220 ° by magnetron sputtering. When the recording / erasing characteristics of this optical recording medium were evaluated, a CNR of 50 dB was obtained, and an erasing rate of 33 dB was obtained even at a linear velocity of 11.5 m / sec, enabling high-speed erasing. Furthermore, initialization was successfully performed with a semiconductor laser beam having a linear velocity of 6 m / sec and a film surface intensity of 9 mW. This indicates that the erasing rate is high and the reliability is high as compared with the case where ZnS is also used for the inorganic layer of Comparative Example 3 to be described later. In addition, high-speed erasing is possible, and the initialization speed is further improved. Is dramatically faster and more productive.

When the optical recording medium was stationary and the recording and erasing characteristics were evaluated using the same optical system described above, the pulse width was
A semiconductor laser beam with a film surface intensity of 7 mW is irradiated at 200 nsec and regenerated at 0.5 mW after crystallization, and a film surface intensity of 13 mW with a pulse width of 200 nsec
After performing recording by irradiating the semiconductor laser light of the above, it is reproduced at 0.5 mW and the contrast ((reflectance at crystallization−reflectance at recording) / (reflectance at crystallization)) is evaluated at 100 per second.
As a result, the contrast was reduced by 8% compared to the initial state even after 1,000,000 times, indicating that the repetitive life of recording and erasing was extremely long.

Comparative Example 3 In Example 5, the substrate-side film thickness was set to 10 by RF magnetron sputtering at 13.56 MHz using a ZnS target as the inorganic layer.
An optical recording medium was produced in the same manner as in Example 5, except that the thickness of the Au-side film was set to 2000 °. As a result of evaluating this optical recording medium in the same manner as in Example 5, the initialization could be performed only at a linear velocity of 0.5 m / sec or less. Although the CNR was 50 dB, the erasing rate was 28 dB at a linear velocity of 8 m / sec, and only 23 dB at a linear velocity of 11.5 m / sec. In addition, the contrast was reduced by 50% from the initial value at 200,000 cycles.

[Effects of the Invention] The optical recording medium of the present invention has the following excellent effects because the inorganic layer is formed of a component containing a specific element as described above.

(1) Permeation of moisture and oxygen in the atmosphere into the recording layer can be effectively blocked by the inorganic layer, so that a change in the film quality of the recording layer can be suppressed, and the moisture and heat resistance can be dramatically improved to extend the life. .

(2) The reliability in re-recording is dramatically improved by increasing the erasing rate.

(3) Since sputtering can be performed by DC power, the manufacturing apparatus is inexpensive, and the manufacturing cost for high-speed film formation is low.

(4) High-speed erasing is possible, and information rewriting time can be greatly reduced.

(5) The number of repetitions of recording and erasing is dramatically increased, and the life is long.

(6) Initialization is possible at high speed and the productivity is excellent.

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Claims (1)

(57) [Claims] 1. An optical recording medium comprising a recording layer and an inorganic layer on a substrate, wherein the inorganic layer is composed of In (indium) and Sn.
An optical recording medium comprising a mixture of inorganic components containing (tin), O (oxygen), and Si (silicon).