JP2000119062A - Light transmitting film and sputtering target for forming light transmitting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film for an optical disk which reduces generation of particles during sputtering, reduces the number of times of interrupting or stopping sputtering, increases production efficiency, and has a large transmittance and a low reflectance. . SOLUTION: Nb ₂ O ₅ , V ₂ O ₅ , B ₂ O ₃ , Si
0.01 The glass-forming oxides consisting of _{O 2, P 2} O ₅
20 wt%, Al ₂ O ₃ , Ga ₂ O ₃ in 0.01 to 20%
% By weight, and optionally, a hard material oxide, Z
rO ₂ and TiO _{2 in an amount} of 0.01 to 5% by weight, and the balance I
A light transmitting film, which is at least one oxide selected from n ₂ O ₃ , SnO ₂ , and ZnO, and a sputtering target for forming the light transmitting film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-transmitting film used particularly for a protective film for an optical disk (including a material expressed as a "layer". The same applies hereinafter), and is generated when a film is formed by sputtering. The present invention relates to a light-transmitting film suitable for an optical disc, particularly a phase-change optical disc, having a high transmittance in the visible light range and a low reflectance, and a sputtering target for forming the film. .

[0002]

2. Description of the Related Art In recent years, high-density recording optical disks have been rapidly gaining interest because they can be recorded and reproduced without requiring a magnetic head. This optical disk is classified into three types: a read-only type, a write-once type, and a rewritable type. In particular, a phase change method used in a write-once type or a rewritable type has attracted attention. The principle of recording / reproducing using this phase change optical disk will be briefly described below.

In a phase change optical disk, a recording thin film on a substrate is heated and heated by irradiating a laser beam to cause a crystallographic phase change (amorphous ⇔ crystal) in the structure of the recording thin film, thereby recording and reproducing information. More specifically, information is reproduced by detecting a change in reflectance caused by a change in optical constant between the phases. The above-mentioned phase change is performed by irradiating a laser beam having a diameter of about 1 to several μm. In this case, for example, when a laser beam of 1 μm passes at a linear velocity of 10 m / s, a time at which a point on the optical disk is irradiated with light is 100 ns,
The phase change and the reflectance need to be detected within this time. In order to realize the above-mentioned crystallographic phase change, that is, the phase change between amorphous and crystalline, melting and quenching occur not only in the phase change recording layer of the optical disc but also in the heat of reflection of the surrounding protective film and aluminum alloy. It will be repeatedly applied to the film.

For this reason, as shown in FIG. 1, a phase-change optical disk has a recording thin film layer 4 of Ge—Sb—Te system or the like.
Has a four-layer structure in which ZnS.SiO ₂ -based high melting point dielectric protective films 3 and 5 are sandwiched on both sides, and an aluminum alloy reflective film 6 is further provided. Among these, the reflective film 6 and the protective films 3 and 5 are required to have an optical function of increasing the absorption between the amorphous portion and the crystalline portion and having a large difference in reflectance, and also to have the moisture resistance and the deformation of the recording thin film layer 4 due to heat. Is required, and a function of controlling thermal conditions during recording is required (see "Optics", Vol. 26, No. 1, pp. 9-15).

As described above, the protective films 3 and 5 having a high melting point have resistance to the repetitive heat stress caused by the temperature rise and the cooling.
Further, it is necessary that these heat influences do not affect the reflective film and other parts, and that they are also thin, have low reflectivity, and have toughness that does not deteriorate. In this sense, the protective films 3 and 5 have an important role. In FIG. 1, reference numeral 1 denotes a laser incident direction, reference numeral 2 denotes a substrate made of polycarbonate or the like, reference numeral 7 denotes an overcoat, and reference numeral 8 denotes an adhesive layer.

The protective films 3, 5 are usually formed by a sputtering method. In this sputtering method, a target composed of a positive electrode and a negative electrode is opposed to each other,
A high voltage is applied between the substrate and the target in an inert gas atmosphere to generate an electric field. At this time, the ionized electrons collide with the inert gas to form plasma, and the plasma is formed. This is based on the principle that positive ions collide with the surface of a target (negative electrode) and strike out constituent atoms of the target, and the ejected atoms adhere to the opposing substrate surface to form a film.

[0007] As a target for forming the protective film, ZnS-SiO ₂ sputtering target a mixture powder prepared by sintering the conventional SiO ₂ powder and ZnS powder were used. At a stage where a thin film is formed by sputtering using a ZnS-SiO ₂ target, if a certain amount or more is coated, cluster-like coarse particles called particles come to adhere to the thin film. These particles are spattered particles deposited by sputtering on the walls and various devices in the sputtering chamber, and when they exceed a certain amount, they come off and float in the sputtering chamber and re-apply to the substrate or thin film. The main cause is adhered matter.

[0008] Since such particles significantly deteriorate the properties of the thin film, when a large amount of the particles are deposited on the substrate or the thin film, the sputtering is stopped once, the sputter chamber is released, and the walls and various parts of the chamber are removed. It was necessary to clean the deposits of the film that caused particles from the equipment. This significantly reduces productivity. Although the cause of this film deposit adhering to the chamber walls and various devices is not always clearly understood, the manufacturing process of the ZnS—SiO ₂ target, that is, the mixed firing of SiO ₂ powder and ZnS powder, Even at the conclusion stage, it was expected that there was a causal relationship, but no solution could be found in the past.

Further, the protective film formed by sputtering has been required to have as low a reflectivity as possible. However, it is sufficiently examined whether the improvement can be made at the stage of the manufacturing process of the ZnS—SiO ₂ target. Had not been. Especially big problems of the conventional ZnS-SiO ₂ target is that this material can not direct-current sputtering to an insulator. Therefore, inefficient methods such as high-frequency sputtering must be adopted.For this reason, long-time sputtering is required to obtain a required film thickness, and the number of particles that must be reduced increases. That is a very undesirable problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. Basically, the sputtering target material is reviewed, the generation of particles is reduced as much as possible, and the number of times of interrupting or stopping sputtering is reduced. It is an object to obtain a protective film for an optical disk that can increase the efficiency.

[0011]

[Means for Solving the Problems] That is, the present invention provides 1)
Nb₂O₅, V₂O₅, B₂O₃, SiO₂, P₂O ₅
One or more glass-forming oxides selected from
~ 20% by weight and Al ₂O₃Or Ga₂O₃Is 0.01
-20% by weight, with the balance being In₂O₃, SnO ₂, Zn
O is at least one oxide selected from O
2) ZrO₂And / or TiO₂Hard material
Characterized by containing 0.01 to 5% by weight of a metal oxide.
3) Nb₂O₅, V
₂O₅, B₂O ₃, SiO₂, P₂O₅Selected from
0.01-20% by weight of one or more glass-forming oxides
And Al₂O₃Or Ga₂O₃0.01 to 20% by weight
Containing the balance In₂O₃, SnO₂, Selected from ZnO
Light-transmitting film, characterized in that it is at least one oxide selected from the group consisting of:
4) ZrO₂And also
Is TiO₂0.01-5% by weight of hard material oxide
3. The light-transmitting film forming switch according to the above item 3),
Providing a putting target.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An optical transmission film according to the present invention is provided on an optical disk.
When used as a protective film, sputter
Good target is In₂O₃, SnO₂Select from ZnO
One or more oxides as main components, and Nb₂O
₅, V₂O₅, B₂O₃, SiO₂, P ₂O₅Choose from
0.01 to 20 weight of one or more glass-forming oxides
%, Al ₂O₃And / or Ga₂O₃0.1-20 weight
% And, if necessary, ZrO₂And / or TiO₂Hard
Containing 0.01 to 5% by weight of a material oxide;
Mix each powder and hot press or HIP etc.
It is manufactured by sintering.

Nb ₂ O ₅ , V ₂ O ₅ , SiO ₂ , B ₂ O
₃ and P ₂ O ₅ , at least one component selected from the group consisting of 0.1 to 20 wt% is added.
This is because crystallization can be effectively suppressed by adding 0 wt%, and a stable optical disk protective layer can be formed. If it is less than 0.1% by weight, the effect of the addition is ineffective, and if it exceeds 20% by weight, the crystal phase of the added component is undesirably precipitated. From the above, the range of the addition of the oxide is preferably 0.1 to 20 wt%.

Further, Al₂O₃And / or Ga₂O₃To
0.1 to 20% by weight ₂O₃And or G
a₂O₃Content of 0.1-20 wt% or reason
Reduces the target bulk electrical resistance.
You. If it is less than 0.1 wt%, the effect of the addition is not obtained, and 20 wt%
%, The electrical resistance of the bulk increases and the electrical insulation
And the transmittance of the thin film for the protective layer in the visible light range.
Is undesirably reduced. Also, if necessary, Zr
O₂And / or TiO₂0.01 to 5 hard material oxides
Weight percent can be added to the film to make it stronger.

The above sputtering target for an optical disk protective film mainly composed of at least one oxide selected from the group consisting of In ₂ O ₃ , SnO ₂ , and ZnO provides a visible light (360-830 nm) of the protective film after film formation. 80) transmittance in the region
%, Which is a sufficient value for an optical disk protective film. The In ₂ O ₃ , SnO _2, and ZnO-based sputtering targets for forming an optical disk protective film of the present invention were able to significantly reduce the generation of particles as compared with the conventional ZnS—SiO ₂ target.
It is considered that the reason is that ZnO or the like itself has a larger adhesive force to the inner wall of the chamber or the device than ZnS.

By reducing the generation of particles in this manner, the number of times of interrupting or stopping the sputtering is reduced, and the frequency of complicated cleaning of the sputtering chamber is reduced. It has the effect that it can be raised. In addition, the sputtering target for forming an In ₂ O ₃ , SnO ₂ , or ZnO-based optical disk protective film of the present invention not only provides a film having a lower reflectance than that described above, but also increases the absorption between the amorphous part and the crystalline part. Satisfactory and stable In ₂ O _{3 for the} optical function having a large difference in reflectivity, the function of preventing the recording thin film from being deformed by heat and moisture, and the function of controlling the thermal conditions during recording. It has been found that a protective film (layer) of an optical disk, a SnO ₂ optical disk and a ZnO optical disk can be obtained with good reproducibility.

[0017]

Examples and comparative examples are described below based on examples and comparative examples. This embodiment is merely an example, and the present invention is not limited to this example. That is, the present invention is limited only by the claims, and includes various modifications other than the examples included in the present invention. The following examples are preferred and representative examples of the present invention.

(Example 1) An example relating to a protective film for an optical disk will be described. ₂ wt% of Al ₂ O ₃ powder and 10 wt% of Nb ₂ O ₅ powder were weighed, mixed with the rest of ZnO powder, and then sintered at 1400 ° C. in air to prepare a target. The density of the obtained target was 5.3 g / cm ³ . The ZnO—Al ₂ O ₃ —Nb ₂ thus obtained
A film was formed on the substrate by sputtering using an O ₅ target. The sputtering conditions are as follows. Sputter gas Ar gas pressure 0.5 Pa Substrate temperature Room temperature Film thickness 1500 Å

Examination of the coating on the substrate up to the time when the particles were generated and the inner wall of the sputtering chamber and the equipment had to be cleaned, that is, the number of sheets produced, was 3,000 to 3,500. This was 20% to 40% of the production improvement compared to the comparative examples described below (ZnS-SiO ₂ target number of products).

Further, the ZnO-Al ₂ O _{3 of} Example 1 was used.
A protective film formed by a target of -Nb ₂ O ₅
X-ray diffraction data were examined to see the crystallization when heated (atmosphere) to ° C and 400 ° C. As a comparison, the same test was conducted without heating. The results are shown in FIGS. 2 (a), (b) and (c). FIG. 2 (a) shows a case where heating is performed at 400 ° C., and FIG.
FIG. 2C shows a case where heating is not performed. As is evident from the results, even when heated to 300 ° C. and 400 ° C. (in the air), it is equivalent to the case without heating, and no crystallization is observed at all. That is, the target of the present invention was able to obtain a stable ZnO-based optical disk protective layer without crystallization.

(Example 2) 2% by weight of Al ₂ O ₃ powder and S
iO ₂ were weighed and powdered 5 wt%, was mixed with the rest ZnO powder, a target was prepared and sintered at 1400 ° C in air. The density of the obtained target was 5.2 g / cm ³ . ZnO—Al ₂ O ₃ —Si thus obtained
When a film was formed on a substrate by sputtering using an O ₂ target, and the number of particles was generated, the coating on the substrate until the inner wall of the sputtering chamber and the equipment had to be cleaned, that is, the number of sheets produced was examined. ,
The number was 3000 to 3500 sheets. This was 20% to 40% of the production improvement compared to the comparative examples described below (ZnS-SiO ₂ target number of products).

The ZnO-Al ₂ O _{3 of} Example 2 was used.
-300 ° protection film formed by SiO ₂ target
To see the crystallization when heated to C (in air), X
The data from line diffraction was examined. As in Example 1, no crystallization was observed. That is, the target of the present invention was able to obtain a stable ZnO-based optical disk protective layer without crystallization.

Example 3 2% by weight of Ga ₂ O ₃ powder and N
10 wt% of b ₂ O ₅ powder was weighed and mixed with the rest of ZnO powder, and then sintered in an atmosphere of 1400 ° C. to produce a target. The density of the obtained target is 5.2 g / cm.
It was ³ . The ZnO—Ga ₂ O ₃ − thus obtained
When a film was formed on the substrate by sputtering using an Nb ₂ O ₅ target, and the number of particles produced, the coating on the substrate until the inner wall of the sputtering chamber and the equipment had to be cleaned, that is, the number of products produced was examined. 3000 to 3500 sheets. This was a comparative example (ZnS-SiO ₂ target production number) 20% to 40% or more production improvement compared to that described below.

The ZnO-Ga ₂ O _{3 of} Example _{3 was used.}
A protective film formed by a target of -Nb ₂ O ₅
To see the crystallization when heated (atmosphere) to ° C,
Data from X-ray diffraction was examined. As in Examples 1 and 2, no crystallization was observed. That is, the target of the present invention was able to obtain a stable ZnO-based optical disk protective layer without crystallization.

In the above embodiment, Al ₂ O was added to ZnO.
₃ and Nb ₂ O ₅ added, ZnO Al ₂ O ₃ and S
Example of adding iO ₂ and Ga ₂ O ₃ and Nb ₂ O to ZnO
_Although three examples of adding ₅ are shown, when other oxides, that is, V ₂ O ₅ , B ₂ O ₃ and P ₂ O ₅ are added,
Furthermore, even when these were added in combination, the same results were obtained. Also, when one or _two of ZrO ₂ and TiO ₂ were added, the same results as in the above example were obtained. The above embodiment is a representative embodiment. Inspection results of the coating on the substrate until the time when the particles were generated and the inner wall and the equipment of the sputtering chamber had to be cleaned in the above Examples 1 to 3, that is, the results of the investigation of the number of products produced were compared with the following comparative examples, and summarized The results are shown in Table 1.

[0026]

[Table 1]

(Comparative Example) Next, 20 mol of SiO ₂ powder
% And 80 mol% of ZnS powder, and hot-pressed at 1000 ° C. and 150 kgf / cm ² in an Ar atmosphere. The density of the obtained target is 3.4
g / cm ³ . ZnS-Si thus obtained
Sputtering was performed using an O ₂ sintered body target, and when particles were generated and the inner walls of the sputter chamber and equipment had to be cleaned, the number of coatings on the substrate, that is, the number of sheets produced, was 2,500. Was. This reduced the production rate by about 30% as compared with the example. (Refer to Table 1) Further, the reflectance of the protective film formed by sputtering was high, and the transmittance was lower than expected. Note that the difference between the composition of the sputtering target and the film forming composition in the above Examples and Comparative Examples was within ± 10% of the target composition for all the added components.

[0028]

When the light transmitting film of the present invention is used as an optical disk protective film, an In ₂ O ₃ system, a SnO ₂ system, or a ZN—SiO ₂ system is used instead of a conventional ZnS—SiO ₂ sputtering target.
By using a sputtering target for an nO-based optical disk protective film, the generation of particles is significantly reduced, the uniformity of the film is improved, and a protective film having high transparency in the visible light range is reproducible under stable manufacturing conditions. It has an excellent feature that it can be obtained well. As described above, the protective film of the optical disk formed by using the target of the present invention, particularly the protective film of the phase-change optical disk, is repeatedly affected by heat when heating and cooling the phase-change recording layer by the laser beam. It has an excellent effect that a stable film can be formed without deteriorating the properties of the protective film even under the influence of severe heat. Furthermore, as described above, the In ₂ O ₃ , SnO ₂ , and ZnO-based targets of the present invention not only provide a film with a lower reflectance, but also increase the absorption between the amorphous portion and the crystalline portion to reflect light. It is possible to obtain a good and stable film with good reproducibility that satisfies the optical function with a large difference in the ratio, the function of preventing the recording thin film from moisture deformation and thermal deformation, and the function of controlling the thermal conditions during recording. It has significant features that can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a recording thin film layer structure.

FIG. 2 shows a protective film formed using a ZnO—Al ₂ O ₃ —Nb ₂ O ₅ target according to an example at 300 ° C. and 400 ° C.
It is a figure which shows the X-ray diffraction result at the time of heating to C.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser incident direction 2 Substrate such as polycarbonate 3 Dielectric protective film such as ZnS / SiO ₂ 4 Phase change recording thin film layer such as Ge / Sb / Te 5 Dielectric protective film such as ZnS / SiO ₂ 6 Al alloy reflective film 7 Overcoat 8 Adhesive layer

Claims (4)

[Claims] 1. Nb ₂ O ₅ , V ₂ O ₅ , B ₂ O ₃ , Si
0.01 to 20% by weight of at least one glass-forming oxide selected from O ₂ and P ₂ O ₅ , and Al ₂ O ₃ or Ga ₂
0.01 to 20% by weight of O ₃ , the balance being In ₂ O ₃ ,
A light-transmitting film, which is at least one oxide selected from SnO ₂ and ZnO. 2. The light transmitting film according to claim 1, wherein the light transmitting film contains 0.01 to 5% by weight of a hard material oxide of ZrO ₂ and / or TiO ₂ . 3. Nb ₂ O ₅ , V ₂ O ₅ , B ₂ O ₃ , Si
0.01 to 20% by weight of at least one glass-forming oxide selected from O ₂ and P ₂ O ₅ , and Al ₂ O ₃ or Ga ₂
0.01 to 20% by weight of O ₃ , the balance being In ₂ O ₃ ,
A sputtering target for forming a light-transmitting film, wherein the sputtering target is at least one oxide selected from SnO ₂ and ZnO. 4. The sputtering target for forming a light transmitting film according to claim 3, wherein a hard material oxide of ZrO ₂ and / or TiO ₂ is contained in an amount of 0.01 to 5% by weight.