JP3501011B2 - Optical recording material - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical disk,
The present invention relates to an optical recording member that records information by changing the optical characteristics of a recording film by irradiating a recording laser beam.

[0002]

2. Description of the Related Art Conventionally, as an optical recording member of this type, for example, a mixed film (single layer film) of a low melting point metal (In, Zn) and a sulfide (GeSx) is used as a recording film (Japanese Patent Laid-Open Publication No. Sho. 62-
No. 226442) or a laminated film of a metal layer (first layer) made of Al, Cu, Ag or the like and a layer (second layer) made of S or Se or a mixture thereof (special feature). Kaihei 2-152029).

These recording films are formed by vapor deposition, sputtering or the like. Since the recording film has reactivity,
By irradiating a recording laser beam (applying external energy), the recording film is physically and / or chemically deteriorated, and optical characteristics such as reflectance are changed, so that information can be recorded.

[0004]

However, in the former publication, the formation of a mixed film of a low-melting point metal (In or the like) and a sulfide GeS is described in the examples in the above-mentioned publications. According to the study by the present inventors, the reaction between the metal and the sulfide considerably progresses during the formation of the film, and as a result, the overall reflectance may be considerably low. It is considered that there is a problem as a member.

Further, in the latter publication, in the embodiments,
A laminated structure of a highly reactive metal (Ag or the like) and S is shown, but according to the study of the present inventors, in such a system, the layers react with each other even during non-recording. Etc.
It is easily judged that the deterioration with time is severe, and it is considered that there is a problem as a practical recording material for practical use. In addition, the C / N (carrier ton) mentioned in the examples is used.
Oise ratio, ratio of carrier and noise output level) does not show good characteristics.

As described above, in the conventional optical recording member, since the reactive recording film is used, unnecessary reactions such as reaction in the film forming process and deterioration with time progress, and during film forming and normal use. There is a problem in that the recording characteristics such as reflectance are sometimes deteriorated. Therefore, in view of the above point, the present invention, in an optical recording member that records information by changing the optical characteristics of the recording film by irradiating the recording laser beam, the reaction of the recording film that deteriorates the recording characteristics. The purpose is to suppress.

[0007]

Means for Solving the Problems In the recording film on which recording is performed by a recording laser beam, the inventors of the present invention record information by causing the laminated layers to react with each other by laser beam irradiation to cause optical characteristics. Based on the idea that the laminated film structure may be easier to control the reaction than the single-layer film, the inventors have made earnest studies. Then, it is considered that a threshold value may be given to the occurrence of the reaction between the layers during the irradiation of the recording laser light and during the non-irradiation (including the film formation). It has come to adopt means.

That is, according to the first aspect of the invention, the first layer (4) having a metal as one of the constituent elements, and Ge
And the first layer upon irradiation of one and then the recording laser beam components sulfur (4) and the second layer reacts with (2), between the first layer (4) and the second layer (2) A single element of Si, which is provided to enable the reaction between the first layer (4) and the second layer (2) when the recording laser beam is irradiated and suppresses the reaction when the recording laser beam is not irradiated . Sulfide, nitride, boride
At least one of the following:
The recording film (10) is composed of barrier layers (3, 30) as constituent elements .

In the present invention, the first layer (4) and the second layer (2) cross the barrier layer (3, 30) at the laser light irradiation site during irradiation of the recording laser light, that is, during recording. Te, or destroy the barrier layer (3, 30) to form a chemical reaction with the reaction (e.g., sulfides, etc.). Therefore, optical characteristics (reflectance, etc.) change at this portion, and information can be recorded. When the recording laser beam is not irradiated (during film formation or normal use), the intervening barrier layer (3, 3) is used.
Since 0) suppresses the reaction between the first layer (4) and the second layer (2), the reaction of the recording film itself is suppressed, and the deterioration of recording characteristics can be prevented.

According to the study by the present inventors, the following are preferable as the first layer (4), the second layer (2) and the barrier layer (3, 30). . That is, as the first layer (4), Sn, In, Sb, Bi,
It is preferable that at least one of Pb, Cr, Mn, Fe, Ni, Cu, Zn and Ag is a constituent element, and specifically, In simple substance, Cr simple substance, In-Sn alloy, Au-.
A Cu alloy or the like can be used. Examples of the second layer (2), specifically GeSx (0 <x ≦ 2) , Ge-Z
An n-S compound, a Ge-S-O compound, etc. can be used.

Further, as the barrier layer (3, 30) ,
Specifically, C (carbon) simple substance, ZnS, Si simple substance, etc. can be used. Also, depending on the material etc.,
The thickness of the barrier layers (3, 30) is preferably 2 nm or more.

Further, the barrier layer (3, 30) may be one in which at least one of the constituents is a substance having a melting point or a decomposition temperature (hereinafter referred to as a melting point) of 300 ° C. or lower. That is, at the time of recording, a portion of the above-mentioned substance in the barrier layer (3, 30) is decomposed, sublimated, melted, etc. by being heated to a melting point or higher by laser light, so that the first layer (4) and the second layer (2) ) Can be reacted with, and information can be recorded.
Before recording, since the barrier layers (3, 30) block between the layers (2, 4), the reaction of the layers (2, 4) below the melting point of the above substances is suppressed. .

The melting point and the like of the above substances are set to 300 ° C. or less because it is not practical when the temperature is higher than 300 ° C., because the laser beam applied during recording must be extremely large. Specific examples of the above substances include alkyl compounds and various organic substances. The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments to be described later.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention shown in the drawings will be described. The optical recording member according to the present embodiment records information by irradiating a recording laser beam to physically and / or chemically change a recording film. For example, as information, music or data is recorded. It can be used for optical discs on which is recorded. FIG. 1 shows a partial cross-sectional structure of an optical disc (optical recording member) 100 according to this embodiment.

The optical disc 100 has a disc shape as a whole, and is formed by laminating a plurality of layers as shown in FIG. Reference numeral 1 is a transparent substrate made of, for example, polycarbonate formed in a disk shape (for example, a thickness of 1.2 mm),
Laser light for recording and reproducing optical information enters from one surface 1a of the substrate 1 as shown by an arrow A. One surface 1a of the substrate 1 on the laser light incident side is a flat surface, and the other surface 1b is provided with a spiral or concentric circular guide groove (track) 1c for guiding the laser light.

A GeSx (1 <x ≦ 2) film 2 as a second layer is formed on the other surface 1b of the substrate 1, and a ZnS film 3 as a barrier layer is formed on the GeSx film 2. , Z
An In film 4 as a first layer is formed on the nS film 3. Here, the ZnS film 3 is composed of the GeSx film 2 and the In film 4.
The film is formed with a film thickness (for example, 2 nm or more) suitable for suppressing a physical and / or chemical reaction with.
Here, the optical disc 100 is formed by the films 2, 3, and 4 described above.
The recording film 10 in FIG. Further, on the In film 4, a resin film (protective film) 5 made of an ultraviolet curable resin for covering and protecting the recording film 10 is formed.

Next, a method for manufacturing the optical disc 100 will be described with reference to a specific example. A substrate 1 which is a 1.2 mm-thick polycarbonate disk having a flat surface on one surface 1a and a guide groove 1c on the other surface 1b is prepared, and the other surface 1b of the substrate 1 is prepared.
First, by RF magnetron sputtering method, Ge
Sputter gas species: Ar, sputter gas pressure:
A 182 nm film was formed using a GeS ₂ target under the film forming conditions of 3 × 10 ⁻³ Torr and input power: 50 to 200 W.

Subsequently, without breaking the vacuum, the ZnS film 3 is sputtered with the RF magnetron sputtering method.
A film of 3 nm was formed using a ZnS target under the film forming conditions of Ar, sputtering gas pressure: 3 × 10 ⁻³ Torr, and input power: 50 to 200 W. Then, the In film 4 is formed by the RF magnetron sputtering method without breaking the vacuum.
Sputter gas type: Ar, sputter gas pressure: 3 × 10
A film having a thickness of 65 nm was formed using an In target under the film forming conditions of ⁻³ Torr and input power: 50 to 200 W. Finally, an ultraviolet curable resin was applied by a spin coating method, the ultraviolet curable resin was cured using a high pressure mercury lamp to form a resin film 5, and the optical disc 100 was manufactured.

The recording operation of the optical disc 100 according to this embodiment is as follows. In the portion of the guide groove 1c, the recording laser light incident (irradiated) from the arrow A is condensed on the surface of the In film 4, and the GeSx film 2 and the In film 4 cross the ZnS film 3 and undergo a chemical reaction. Therefore, the optical characteristics (reflectance, etc.) of the reaction portion change, and information can be recorded. It is considered that sulfide (In ₂ S ₃ ) or the like is formed in the reaction between the GeSx film 2 and the In film 4.

When the recording laser beam is not irradiated (for example, during film formation or during normal use), the GeSx film 2 and the In film 4 are separated by the ZnS film 3.
Since the reaction between the film 2 and the In film 4 is suppressed, the recording film 10
The reaction of itself is suppressed, and as a result, the deterioration of recording characteristics can be prevented. Optical disc 100 manufactured by the above manufacturing method (sample No. 3 in FIG. 2 described later)
The operation and effect of these embodiments will be described more specifically by using the verification result obtained for the above.

Optical disk 1 manufactured by the above manufacturing method
00, from the plane (one side 1a) side, wavelength: 780 nm
NA (numerical aperture) of the laser light (laser light for recording):
Focusing on the In film 4 surface through the 0.5 objective lens,
Recorded. At this time, the rotation speed of the optical disk is constant, the linear velocity is 2.8 m / sec, and the laser light conditions are:
The recording frequency was 400 kHz, and the recording laser waveform was a rectangular wave with a duty ratio of 50%.

The characteristics (recording characteristics) of the optical disc 100 at this time were: unrecorded portion reflectance: 65%, recording laser power: 7 mW, C / N: 50 dB, and modulation: 83%. The modulation degree is a value obtained by subtracting the reflectance after recording from the reflectance before recording and multiplying by 100, and then dividing the value by the reflectance before recording. Further, FIG. 2 shows the results obtained by measuring the same optical disk characteristics as above by changing the film thickness of the ZnS film 3 which plays the role of the barrier layer (Sample Nos. 1, 2, 4, 5). It is shown together with the number 3). The GeSx film 2 and Z
The total film thickness of the nS film 3 and the nS film 3 was a constant so-called λ / 2 optical long film thickness for the laser light wavelength λ. In FIG. 2, sample No. 6 is a comparative example of the present invention and is not provided with a barrier layer.

As shown in FIG. 2, the optical disc 100 of the present embodiment shown in sample numbers 1 to 5 has a remarkably higher reflectance than the optical disc of the comparative example (sample number 6), and the reflectance and recording power. It can be seen that the balance of the characteristics of C, C / N and modulation is excellent. This is because the reaction between the GeSx film 2 and the In film 4 is suppressed especially during film formation. From the comparison of the reflectances of Sample No. 1 and Sample Nos. 2 to 5, the thickness of the ZnS film 3 as the barrier layer is preferably 2 nm or more in terms of the characteristics of the optical disc.

Further, each of the optical discs of the sample numbers 1 to 6 was subjected to an environment resistance test at 55 ° C. for 96 hours, and the optical disc of the present embodiment (sample numbers 1 to 5).
Shows no characteristic deterioration within the measurement error range, whereas the optical disc of the comparative example cannot reproduce the stored data. In the optical disc of the comparative example,
The deterioration of reflectance (change from 35% to 28%) was particularly remarkable. This is due to the presence of the ZnS film 3 and the GeSx film 2
This is because the reaction between the In and the In film 4 is suppressed.

As described above, the optical disc of the present embodiment has a higher reflectance than the conventional optical disc having no barrier layer.
It has an excellent balance of recording characteristics such as recording power, C / N and modulation. Further, according to the present embodiment, G
By interposing the ZnS film 3 between the eSx film 2 and the In film 4, the reaction in the normal environment under the high temperature and high humidity environment such as the above environment resistance test is suppressed at the time of film formation, and the optical disc is not recorded. The reflectance (initial reflectance) can be remarkably increased, the recording characteristics (reflectance, recording power, C / N, modulation degree) can be prevented from being deteriorated, and the data retention characteristic can be remarkably improved.

(Second Embodiment) This embodiment differs from the first embodiment in that in the optical disc 100 shown in FIG. 1, the barrier layer is a carbon (C) film 30 instead of the ZnS film. In the present embodiment as well, the same operational effects as those of the above-described first embodiment are achieved, but hereinafter, the portions different from the above-described first embodiment will be mainly described. One manufacturing method of this embodiment will be described with a specific example.

First, a GeSx film 2 having a thickness of 182 nm was formed on the other surface 1b of the substrate 1 by the RF magnetron sputtering method as described above. Continue to RF without breaking the vacuum
The C film 30 was formed by a magnetron sputtering method, the sputtering gas species: Ar, the sputtering gas pressure: 3 × 10 ⁻³ Torr,
Input power: 3 nm was formed using a C target under the film forming conditions of 200 to 400 W. Further subsequently, an In film 4 having a thickness of 65 nm was formed in the same manner as above, a resin film 5 was formed, and an optical disc 100 was manufactured.

On this optical disk, a flat surface side (one surface 1a)
From the above, laser light (wavelength: 780 nm) was condensed on the surface of the In film 4 under the same laser light conditions as above, and recording was performed. The characteristics of the optical disc 100 at this time are as follows: reflectance of unrecorded portion: 65%, recording laser power: 8 mW, C / N: 4
The degree of modulation was 8 dB and the degree of modulation was 85%. Further, in FIG.
The results of measuring the same optical disk characteristics as those described above while changing the film thickness of the layer 3 (Sample Nos. 7 and 8) are shown together with the above results (Sample No. 9). The total film thickness of the GeSx film 2 and the C film 3 was similarly set to a λ / 2 optical long film thickness and was constant.
Optical disc 100 of the present embodiment shown in sample numbers 7 to 9
Also, compared with the optical disk of the comparative example (sample number 6),
The reflectance is extremely high, and the reflectance, recording power, C /
It can be seen that the balance of N and modulation characteristics is excellent. Also, due to the characteristics of the optical disc, the thickness of the C film 3 is 2 nm.
It can be seen that the above is preferable.

As described above, also in this embodiment, the presence of the C film 3 suppresses the reaction between the GeSx film 2 and the In film 4 at the time of film formation. The reaction can be suppressed. (Other Embodiments) In addition, Ge-Zn is used as the second layer.
-S compound, Ge-S-O compound, C as the first layer
Examples of u, Fe, and the barrier layer include Si and SiO _2. However, in the configuration of the optical disc 100, the same effect as each of the above-described embodiments can be obtained even if the configuration is appropriately selected and combined from these.

The barrier layers 3 and 30 may have at least one of the constituents of a substance having a melting point or decomposition temperature (hereinafter referred to as melting point) of 300 ° C. or lower. As a result, at the time of recording, by heating with laser light to a temperature equal to or higher than the melting point, parts of the above-mentioned substances in the barrier layers 3 and 30 are decomposed, sublimated, melted, and the like, and the first layer and the second layer can react with each other. Information can be recorded. On the other hand, before recording, the barrier layers 3 and 30 are in the form of blocking between the two layers 2 and 4, so that the reaction of both layers 2 and 4 below the melting point of the above substance is suppressed. Therefore, the stability of the recording film 10 against heat can be further improved.

The melting point and the like of the above substances are set to 300 ° C. or less because the recording laser beam given at the time of recording must be extremely large when the temperature is higher than 300 ° C., which is not practical. Specific examples of the substance having a melting point of 300 ° C. or lower include alkyl compounds and various organic substances. In the optical disc 100 shown in FIG. 1, the layers 2 to 4 of the recording film 10 may be laminated in the reverse order. That is, a first layer such as an In film, a first layer such as a ZnS film, a barrier layer such as a C film on the other surface 1b of the substrate 1, and a second layer such as a GeSx film on the barrier layer in this order. Alternatively, the recording film 10 may be formed by stacking. In this case, the film thickness of each layer is generally different from that in the above-described embodiment, but in particular, even if the required thickness of the barrier layer is thinner than that in the above-described embodiment, the same effect can be obtained.

Further, except for the details of the guide groove shape of the substrate, the first
An optical disc was produced in the same manner as in the second embodiment.
An optical disk 200 was manufactured using the substrate 1 on which the guide groove 1c having a groove width of 520 nm and a groove depth of 35 nm was formed on the surface 1b. This optical disc has a wavelength of 780 nm, an objective lens NA of 0.50, and after recording data, a data reproducing device having a wavelength of 780 nm and an objective lens of NA0.45 and a wavelength of 650 n.
It has a feature that data can be reproduced by any of the reproducing apparatus having the objective lens NA of 0.35. This is after recording data with a CD-R writer,
This corresponds to an unprecedented feature that data can be reproduced by any of the CD-ROM and DVD-ROM devices.

The shape of the guide groove of the substrate for exhibiting this characteristic is not limited to the above value, and the wavelength of 6
Groove width w (unit: nm) and groove depth d, where NA of the objective lens of the 50 nm reproducing device is α
(Unit: nm) may be within the range of the values shown below.
The groove width w is 400 or more, (1749.5-399
6.4 × α + 2416.9 × α ² ) or less.

The groove depth d is {48.6-11.2.
1 × (w / 100) + 1.41 × (w / 100) ² } or more, {280.9-839.8 × α + 761.1 × α ²
-18.96 x (w / 100) + 18.32 x α x (w
/100)+0.86×(w/100) ² } or less.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a partial cross-sectional structure of an optical disc according to an embodiment of the present invention.

FIG. 2 is a chart showing a relationship between a thickness of a barrier layer and recording characteristics in the first embodiment of the invention.

FIG. 3 is a chart showing the relationship between the thickness of a barrier layer and recording characteristics according to the second embodiment of the present invention.

[Explanation of symbols]

2 ... GeSx film, 3 ... ZnS film, 4 ... In film, 10 ... Recording film, 30 ... C film.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Takeda, Nagakute-cho, Aichi-gun, Aichi Prefecture 1-41 Yokomichi, Yokosuka Central Research Institute Co., Ltd. (72) Inventor Tomomi Motohiro Nagakute-cho, Aichi-gun, Aichi-gun 1 41, Yorokomichi Toyota Central Research Institute Co., Ltd. (56) Reference JP-A-7-93808 (JP, A) JP-A-4-228128 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/24

Claims (2)

(57) [Claims] 1. A recording film (10) which records information by changing its optical characteristics when irradiated with a recording laser beam, said recording film (10) comprising a metal as one of its constituent elements. one layer (4), said first layer upon irradiation of the recording laser beam as one of the components of the Ge and sulfur (4) and the second layer reacts (2)
And the first layer (4) provided between the first layer (4) and the second layer (2) during the irradiation of the recording laser beam.
Said second layer (2) to allow the reaction with the at the time of non-irradiation of the recording laser beam be those of suppressing the reaction between
Si simple substance, sulfide, nitride, boride, carbon or carbonized
An optical recording member comprising: a barrier layer (3, 30) including at least one of a phosphor and a phosphide as a constituent element . 2. The barrier layer (3, 30) is a simple substance of C, Z
Constituting at least one of nS and Si alone
The optical recording part according to claim 1, characterized in that
Material.