JP4100686B2 - Protective film, method for producing protective film, and magnetic recording medium - Google Patents

Description

  The present invention relates to a protective film, a method for manufacturing a protective film, and a magnetic recording medium, and in particular, a hard film used for coating a sliding-resistant member or an abrasion-resistant member, a method for manufacturing the hard film, and the hard film. The present invention relates to a magnetic recording medium having a protective film.

  Among the hard coatings used for coating the sliding-resistant member or the wear-resistant member, there is a DLC (diamond-like carbon) film that uses carbon. The DLC film is suitable as a surface coating because it has excellent surface smoothness and high hardness.

  As a method for forming the DLC film, a sputtering method, a plasma CVD method, or the like has been used.

  In the magnetic recording medium, a protective film made of a DLC film is formed on the magnetic recording layer in order to protect the magnetic recording layer from damage caused by contact, sliding, and corrosion of the magnetic head.

  When a DLC film formed by sputtering or CVD is compared, the DLC film formed by CVD is denser and harder. This is presumably because the DLC film formed by the CVD method is formed from hydrocarbon radicals, so that it is easy to take a three-dimensional rigid tetrahedral structure through hydrogen. Therefore, in recent years, a DLC film formed by a CVD method has been used as a protective film for magnetic recording media.

The protective film of the magnetic recording medium is required to protect the magnetic recording layer from contact with the magnetic head, damage due to sliding, and corrosion, and at the same time, to reduce the adsorption of contamination gas. Since the DLC film formed by the CVD method is dense and hard, it is suitable as a protective layer, but it easily adsorbs a contamination gas such as SO ₂ as it is. The reason is considered that in the case of a DLC film formed by the CVD method, hydrogen is also present on the film surface, which is a contamination gas adsorption site.

JP 2002-32907 A JP-A-9-128732

  In order to prevent the above problem, a method of adding nitrogen to the DLC film (Patent Document 1) or laminating a protective film (Patent Document 2) has been taken.

  However, when nitrogen is added to the DLC film, the film hardness decreases, and it is not advantageous from the viewpoint of magnetic spacing to form a protective film.

  Accordingly, an object of the present invention is to provide a protective film, a protective film manufacturing method, and the protective film, which are hard films and hardly adsorb contamination gases without decreasing film hardness and increasing magnetic spacing. An object of the present invention is to provide a magnetic recording medium.

The present invention relates to a protective film covering the surface of the predetermined member, the provided on the surface of the predetermined member, it consists tetrahedral amorphous carbon film mainly containing sp ³ bonded carbon, the tetrahedral The amorphous carbon film has different composition ratios on the surface of the predetermined member by allocating the ratio of sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen at a constant composition ratio. Layers are stacked one above the other, and the ratio of the sp ³ bond carbon is 50% or more, the lower layer among the layers stacked above and below is set higher, and the concentration of hydrogen is In the protective film, 10 at. % Is set in the following, the concentration of the nitrogen, 5at in the upper layer. % At 5% in the lower layer . It is characterized by being set to less than%.

The present invention relates to a method for manufacturing a protective film covering the surface of a predetermined member, and the ratio of sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen are distributed on the predetermined member at a constant composition ratio. Thereby forming a protective film composed of a tetrahedral amorphous carbon film mainly composed of sp ³ -bonded carbon. In the amorphous carbon film, the ratio of the sp ³ bond carbon is 50% or more, and the lower layer is set higher among the upper and lower layers, and the concentration of hydrogen is determined by the protection 10 at. %, And the nitrogen concentration is 5 at. % At 5% in the lower layer. It is characterized by being set to less than% .

The present invention is a magnetic recording medium comprising a substrate, a magnetic recording layer formed on the substrate, and a protective film formed on the magnetic recording layer, the protective film comprising sp ³ bonded carbon. The tetrahedral amorphous carbon film distributes the sp ³ bonded carbon ratio, the hydrogen concentration, and the nitrogen concentration at a constant composition ratio. Thus, layers having different composition ratios are stacked on the surface of the magnetic recording layer, and the sp ³ bond carbon ratio is 50% or more, and the layers stacked above and below Of the lower layer is set higher, and the hydrogen concentration is 10 at. %, And the nitrogen concentration is 5 at. % At 5% in the lower layer. It is characterized by being set to less than% .

According to the present invention, in the protective film comprising the film surface layer 5 and the inner film layer 6 and comprising the tetrahedral amorphous carbon film, the film surface layer 5 does not contain hydrogen but contains nitrogen by nitriding, and the inner film layer 6 contains hydrogen. Since it is composed of a film that does not contain nitrogen and is richer in sp ³ -bonded carbon than the film surface layer 5, it is possible to produce a protective film that is hard and hardly adsorbs contamination gas. It is possible to produce a magnetic recording medium having excellent properties and wear resistance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First example]
A first embodiment of the present invention will be described with reference to FIGS.

(Protective film)
FIG. 1 shows a configuration example of the protective film.
In this example, a description will be given of an example in which a protective film for a sliding-resistant member or an abrasion-resistant member is formed on a magnetic recording medium.

  As shown in FIG. 1A, the magnetic recording medium 1 includes a base 2, a magnetic recording layer 3 formed on the base 2, and a protective film 4 formed on the magnetic recording layer 3. .

The protective film 4 is composed of a tetrahedral amorphous carbon film mainly composed of sp ³ -bonded carbon, and is composed of a film surface layer 5 and an inner film layer 6 as shown in FIG.

In the film surface layer 5 and the inner film layer 6, in addition to sp ³ bonded carbon as a main component, hydrogen and nitrogen as non-main components are distributed at a constant concentration ratio. The ratio of sp ³ bonded carbon is higher in the in-film layer 6 than in the film surface layer 5.

FIG. 2 shows a phase diagram of the carbon film. The ratio of sp ³ bonded carbon, is defined as (sp ³ bonded carbon) / (sp ³ bonded carbon + sp ² bonded carbon). In this example, the ratio of sp ³ bonded carbon is 50% or more.

  The concentration of hydrogen was 10 at. % Or less is desirable.

  The concentration of nitrogen is 5 at. %, And the inner layer 6 has a concentration of 5 at. The concentration is less than%, desirably a value close to zero.

Thus, the film surface layer 5 and the inner film layer 6 are characterized in that the ratio of sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen are distributed at a constant composition ratio.

(Production method)
Next, a method for manufacturing the protective film 4 will be described.
FIG. 3 shows an example of the manufacturing process of the protective film 4.
In the step of FIG. 3A, the magnetic recording layer 3 is formed on the base 2.
In the step of FIG. 3B, a protective film 4 (hereinafter referred to as a ta-C film) made of a tetrahedral amorphous carbon film containing sp ³ bonded carbon as a main component is formed on the magnetic recording layer 3.
In the step of FIG. 3C, the surface of the ta-C film 4 is nitrided to form a film surface layer 5 containing nitrogen and an inner film layer 6 having almost no nitrogen.

  FIG. 4 shows a configuration example of a filtered cathodic arc (hereinafter referred to as FCA) apparatus 20 for forming the ta-C film 4.

  The FCA apparatus 20 is roughly divided into an arc source 21, a magnetic filter 22, and a film forming chamber 23.

  As the arc source 21, a stainless steel pipe having an outer diameter of 76 mm and an inner diameter of 70 mm was used as the main body of the arc source vacuum chamber 24. The arc source vacuum chamber 24 is electrically grounded.

  The cathode 25 of the arc source 21 is made of cylindrical graphite (carbon) having a purity of 99.999%, a diameter of 30 mm, and a thickness of 30 mm, and is installed in the arc source vacuum chamber 24 without being electrically grounded. At the same time, it is connected to a DC arc power source 26. The cathode 25, anode 27, and arc source vacuum chamber 24 are water-cooled to prevent overheating during arc discharge. In addition, a striker 28 is provided for starting arc discharge in contact with the surface of the cathode 25.

  The magnetic filter 22 is composed of an electromagnetic coil 31 in which a 1/4 arc stainless steel pipe having an outer diameter of 76 mm, an inner diameter of 70 mm, and a curvature radius of 300 mm is used as a core, and a polyester-coated copper wire having a wire diameter of 2 mm is wound around the core. The number of turns per unit length of the electromagnet coil 31 is 1000 turns / m.

  In the film forming chamber 23 evacuated to vacuum, the magnetic recording medium 1 having a diameter of 65 mm formed up to the magnetic recording layer 3 is installed as a film forming substrate. Reference numeral 29 denotes a shutter, and reference numeral 30 denotes an X direction raster coil.

  Using such an FCA apparatus 20, arc discharge (formation of cathode material plasma) is started by the striker 28 of the arc source 21. As a result, as shown in FIG. 3B, the ta-C film 4 having a thickness of 4 nm can be formed on the magnetic recording layer 3 of the magnetic recording medium 1 (FCA method). However, the arc voltage was 30 V and the arc current was 120 A.

  Further, the magnetic recording medium 1 formed up to the ta-C film 4 is conveyed to a plasma processing chamber (not shown) while maintaining a vacuum, and is subjected to glow discharge under a predetermined nitrogen pressure to cause the ta-C film 4. Is nitrided (surface nitrogen plasma treatment). Thereby, as shown in FIG.1 (b), the film | membrane surface layer 5 and the film inner layer 6 can be formed.

(Composition ratio of sp ³ bonded carbon / hydrogen / nitrogen)
Next, in the magnetic recording medium 1 thus manufactured, the ratio of sp ³ bond carbon, the concentration of hydrogen, and the concentration of nitrogen contained in the film surface layer 5 and the inner film layer 6 were measured.

  The amount of hydrogen in the film surface layer 5 up to a depth of 1 nm determined by the hydrogen forward scattering method (HFS) is 1.1 at. %Met.

The ratio of sp ³ -bonded carbon obtained by peak separation of the Cls peak of X-ray photoelectron spectroscopy (XPS) was 83%.

  The amount of nitrogen in the inner layer 6 exceeding 1 nm in depth obtained by measurement in the depth direction of Auger electron spectroscopy (AES) is 0.7 at. %, And the amount of nitrogen in the film surface layer 5 up to a depth of 1 nm is 10.4 at. %Met.

FIG. 5 summarizes the ratio of sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen contained in the film surface layer 5 and the inner film layer 6 for each step.

FIG. 6 shows the depth profile characteristics of sp ³ bonded carbon ratio, hydrogen concentration, and nitrogen concentration.

The magnetic recording medium 1 is allowed to stand in a SO ₂ gas environment having a predetermined concentration at a predetermined temperature and humidity for 10 hours, and then a gas adsorption amount is measured using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). (SO ₃ ^- ions) was measured per 3 minutes, was about 920 counts.

The depth of the film surface layer 5 is in the range of about 0.0 to 1.0 nm. The depth of the inner layer 6 is in the range of about 1.0 nm to 4.0 nm. The ratio of sp ³ bonded carbon is an average value of the ratio of sp ³ -bonded carbon in the film inner layer 6.

FIG. 7 shows a comparative example of the depth profile characteristics of FIG.
Time-of-flight secondary ion mass spectrometer (TOF-SIMS) gas adsorption amount using the (SO ₃ ^- ions) was measured per 3 minutes, was about 4450 counts.

From the above measurement results, the sp ³ bonded carbon ratio, the hydrogen concentration, and the nitrogen concentration will be compared.

The ratio of the sp ³ bond carbon is lower in the film surface layer 5 than in the inner film layer 83 compared to 83% when compared after the step of forming the ta-C film 4. This is considered to be because it is lower than the inner film layer 6 due to the termination structure. Further, when compared after the nitriding treatment step, the film surface layer 5 has a considerably lower value than 83% of the inner film layer 6. This is presumably because the film was further lowered than the inner layer 6 due to the influence of the nitriding treatment in addition to the termination structure.

  As for the concentration of hydrogen, there is no difference in concentration after the formation process of the ta-C film 4 and the nitriding treatment process, and the amounts of the film surface layer 5 and the inner layer 6 are both very small and almost zero. .

  Regarding the concentration of nitrogen, there is no difference in concentration between the film surface layer 5 and the inner film layer 6 after the step of forming the ta-C film 4. After the nitriding process, the concentration change in the inner layer 6 is not observed, but the film surface layer 5 has a higher value of 10.4 at. %.

(Layer structure of membrane surface layer / inner membrane layer)
Next, the layer structure of the film surface layer 5 and the inner film layer 6 constituting the ta-C film 4 will be considered. 5, as described in FIG. 6, sp ³ ratio of bonded carbon (83%) in the film inner layer 6, the ratio of sp ³ bonded carbon of the membrane surface layer 5 that are affected by termination structures and nitride («83 %) Is considerably higher. Thus, since the ta-C film 4 has a structure having the inner film layer 6 in which the ratio of sp ³ bond carbon is set higher than that of the film surface layer 5, the film surface layer 5 is worn. However, since the hard inner film layer 6 exists below, the film hardness can be maintained over a long period of time.

6 and 7, the gas adsorption amount (SO ₃ ⁻ ions) is 920 counts compared to 4450 counts in the comparative example, so that a structure in which the contamination gas is extremely difficult to adsorb can be obtained.

[Second example]
A second embodiment of the present invention will be described with reference to FIGS. In addition, about the same part as the 1st example mentioned above, the description is abbreviate | omitted and the same code | symbol is attached | subjected.

  In this example, when the FCA apparatus 20 forms up to the ta-C film 4 in FIG. 3B, a predetermined amount of hydrogen is added at an appropriate timing, so that the film surface layer 5 up to a depth of 1 nm is obtained. Samples with various amounts of hydrogen were prepared.

  In addition, when these samples were subjected to the surface nitrogen plasma treatment of FIG. 3C, samples in which the nitrogen pressure was changed and the amount of nitrogen in the film surface layer 5 up to a depth of 1 nm were variously changed were produced. However, the amount of nitrogen in the inner layer 6 exceeding 1 nm in depth is 0.7 at. %.

Figure 8 is a gas adsorption amount ^- shows the results of measurement of (SO ₃ ion count per 3 minutes).
In FIG. 8, the amount of hydrogen and the amount of nitrogen are values at a depth of 0.0 nm of the film surface layer 5.

FIG. 9 shows the depth profile characteristics of sp ³ bonded carbon ratio, hydrogen concentration, and nitrogen concentration.
In this example, the amount of hydrogen in the film surface layer 5 in FIG. % And the amount of nitrogen is 5.7 at. It represents the measured value when%. Gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 1950 counts.

FIG. 10 shows a depth profile characteristic as a comparative example of FIG.
In this example, the amount of hydrogen in the film surface layer 5 in FIG. % And the amount of nitrogen is 10.4 at. It represents the measured value when%. Gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 2750 counts.

  As described above, in the film surface layer 5, the amount of hydrogen is 10 at. % And the amount of nitrogen is 5 at. When the percentage was greater than or equal to%, the count number was less than 2000. As a result, it was possible to produce a protective film that is hard and difficult to adsorb the contamination gas without decreasing the film hardness or increasing the magnetic spacing.

  On the other hand, the amount of hydrogen in the film surface layer 5 is 10 at. % Or the amount of nitrogen in the film surface layer 5 is 5 at. When it was less than%, the count number was 2000 or more, and a good protective film could not be obtained.

[Third example]
A third embodiment of the present invention will be described with reference to FIGS. In addition, about the same part as the 1st example mentioned above, the description is abbreviate | omitted and the same code | symbol is attached | subjected.

Samples with various sp ³ bonded carbon ratios were prepared using the FCA apparatus 20 and the sputtering apparatus. The ratio of sp ³ bonded carbon was changed by changing the substrate bias voltage in the FCA apparatus or the sputtering power in the sputtering apparatus.
Further, the surface nitrogen plasma treatment was performed as in the first example.

FIG. 11 shows the ratio of sp ³ -bonded carbon obtained by peak separation of the Cls peak of X-ray photoelectron spectroscopy (XPS), and the results of specific wear by a ball-on-disk test.

  Among samples 1 to 4, samples 1 and 2 were formed by changing the sputtering power in the sputtering apparatus, and samples 3 and 4 were formed by changing the substrate bias voltage in the FCA method of the present invention. Sample 5 is the magnetic recording medium 1 prepared in the first example described above.

FIG. 12 shows the depth profile characteristics of sp ³ bonded carbon ratio, hydrogen concentration, and nitrogen concentration.
This example represents sample 3 in FIG. 11 and shows the measured value when the ratio of sp ³ -bonded carbon is 55%. Specific wear ^{amount, 0.7 × 10 -7 mm 3 /} N · m , and the gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 920 counts.

FIG. 13 shows a depth profile characteristic as a comparative example of FIG.
This example represents sample 2 in FIG. 11 and shows the measured value when the ratio of sp ³ -bonded carbon is 28%. Specific wear ^{amount, 2.4 × 10 -7 mm 3 /} N · m , and the gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 920 counts.

From the above, the samples 1 to 5 are compared.
First, in Samples 3 to 5, the sp ³ bonded carbon ratio is 50% or more, the specific wear amount is less than 1.0 × 10 ⁻⁷ mm ³ / N · m, and a good protective film is obtained. It was.

  At this time, the amount of hydrogen in the film surface layer 5 up to a depth of 1 nm obtained by the hydrogen forward scattering method (HFS) is 1.0 at. %. Further, the amount of nitrogen in the inner layer 6 exceeding 1 nm in depth obtained by measurement in the depth direction by Auger electron spectroscopy (AES) is 1.0 at. % And the amount of nitrogen in the film surface layer 5 up to a depth of 1 nm is 10.0 at. %.

On the other hand, in samples 1 and 2, the sp ³ bond carbon ratio is less than 50%, and the specific wear amount is 1.0 × 10 ⁻⁷ mm ³ / N · m or more, which is a good protective film. Was not obtained.

  At this time, the amount of hydrogen in the film surface layer 5 up to a depth of 1 nm determined by the hydrogen forward scattering method (HFS) is 1.0 at. %. The amount of nitrogen in the inner layer 6 determined by the Auger electron spectroscopy (AES) depth measurement is 1.0 at. %, And the amount of nitrogen in the film surface layer 5 up to a depth of 1 nm is 10.0 at. %.

[Fourth example]
A fourth embodiment of the present invention will be described with reference to FIGS. In addition, about the same part as the 1st example mentioned above, the description is abbreviate | omitted and the same code | symbol is attached | subjected.

  When the ta-C film 4 was formed with the FCA apparatus 20, samples with various amounts of nitrogen in the inner layer 6 exceeding 1 nm in depth were prepared by adding a predetermined amount of nitrogen.

  FIG. 14 shows the result of the amount of nitrogen in the inner layer 6 exceeding 1 nm in depth and the specific wear amount by the ball-on-disk test. Sample 1 is the magnetic recording medium 1 prepared in the first example described above.

FIG. 15 shows the depth profile characteristics of sp ³ bonded carbon ratio, hydrogen concentration, and nitrogen concentration.
This example represents the sample 6 of FIG. 14, and the amount of nitrogen in the inner layer 6 is 2.3 at. The measured value at% is shown. Specific wear ^{amount, 0.5 × 10 -7 mm 3 /} N · m , and the gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 920 counts.

FIG. 16 shows a depth profile characteristic as a comparative example of FIG.
This example represents the sample 7 of FIG. 14, and the amount of nitrogen in the inner layer 6 is 6.5 at. The measured value at% is shown. Specific wear ^{amount, 1.2 × 10 -7 mm 3 /} N · m , and the gas adsorption amount (SO ₃ ^- ions, the number of counts per 3 minutes), the count number becomes 920 counts.

From the above, the samples 1 and 6 to 9 are compared.
First, in samples 1 and 6, the amount of nitrogen in the inner layer 6 is 5 at. %, The specific wear amount was less than 1.0 × 10 ⁻⁷ mm ³ / N · m, and a good protective film was obtained.

On the other hand, in samples 7 to 9, the amount of nitrogen in the inner layer 6 is 5 at. %, The specific wear amount was 1.0 × 10 ⁻⁷ mm ³ / N · m or more, and a good protective film could not be obtained.

It is sectional drawing which shows the structure of the protective film which is the 1st Embodiment of this invention. It is a phase diagram of a carbon film. It is process drawing which shows the manufacturing method of a protective film. It is a block diagram of a filtered cathodic arc device. The amount of hydrogen and nitrogen contained in the layer in each step is an explanatory diagram showing the ratio of sp ³ -bonded carbon. It is explanatory drawing which shows the depth profile characteristic which concerns on this invention. It is explanatory drawing which shows the depth profile characteristic as a comparative example of FIG. It is explanatory drawing which shows the gas adsorption amount with respect to the quantity of hydrogen of the film | membrane surface layer and the quantity of nitrogen which is the 2nd Embodiment of this invention. It is explanatory drawing which shows the depth profile characteristic which concerns on this invention. It is explanatory drawing which shows the depth profile characteristic as a comparative example of FIG. Is a third embodiment of the present invention, it is an explanatory diagram showing a specific and specific wear amount of sp ³ -bonded carbon. It is explanatory drawing which shows the depth profile characteristic which concerns on this invention. It is explanatory drawing which shows the depth profile characteristic as a comparative example of FIG. It is explanatory drawing which shows the quantity of nitrogen and the specific abrasion loss in the film | membrane inner layer which is the 4th Embodiment of this invention. It is explanatory drawing which shows the depth profile characteristic which concerns on this invention. It is explanatory drawing which shows the depth profile characteristic as a comparative example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Base | substrate 3 Magnetic recording layer 4 Protective film 5 Film surface layer 6 Film inner layer 20 FCA apparatus 21 Arc source 22 Magnetic filter 23 Film forming chamber 24 Arc source vacuum chamber 25 Cathode 26 DC arc power supply 27 Anode 28 Striker 29 Shutter 30 X direction raster coil 31 Electromagnetic coil

Claims (3)

A protective film covering the surface of a predetermined member,
A tetrahedral amorphous carbon film mainly composed of sp ³ bonded carbon provided on the surface of the predetermined member;
The tetrahedral amorphous carbon film is
By distributing the ratio of sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen at a constant composition ratio,
On the surface of the predetermined member, layers having different composition ratios are stacked one above the other ,
The ratio of the sp ³ bond carbon is 50% or more, and the lower layer of the layers stacked above and below is set higher.
The hydrogen concentration is 10 at. % Or less ,
The concentration of the nitrogen, 5at in the upper layer. % At 5% in the lower layer . A protective film characterized by being set to less than%. A method for producing a protective film covering the surface of a predetermined member,
A step of stacking layers having different composition ratios on top and bottom by allocating sp ³ -bonded carbon ratio, hydrogen concentration and nitrogen concentration at a constant composition ratio on the predetermined member; ,
Thereby, a protective film composed of a tetrahedral amorphous carbon film mainly composed of sp ³ bonded carbon is constituted,
The tetrahedral amorphous carbon film is
The ratio of the sp ³ bond carbon is 50% or more, and the lower layer of the layers stacked above and below is set higher.
The hydrogen concentration is 10 at. % Or less,
The nitrogen concentration is 5 at. % At 5% in the lower layer. A method for producing a protective film, characterized in that each is set to less than% . A magnetic recording medium,
A substrate;
A magnetic recording layer formed on the substrate;
A protective film formed on the magnetic recording layer,
The protective film is composed of a tetrahedral amorphous carbon film mainly composed of sp ³ bonded carbon,
The tetrahedral amorphous carbon film is
By distributing the ratio of the sp ³ bonded carbon, the concentration of hydrogen, and the concentration of nitrogen at a constant composition ratio,
On the surface of the magnetic recording layer, layers having different composition ratios are stacked one above the other,
The ratio of the sp ³ bond carbon is 50% or more, and the lower layer of the layers stacked above and below is set higher.
The hydrogen concentration is 10 at. % Or less,
The nitrogen concentration is 5 at. % At 5% in the lower layer. A magnetic recording medium characterized by being set to less than% .

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