JP3104097B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium in which a protective film is formed on a non-magnetic support having a magnetic layer by a sputtering method.

[0002]

2. Description of the Related Art Plating and vacuum thin film forming techniques (vacuum vapor deposition,
A magnetic recording medium of the so-called ferromagnetic metal thin film type, which is directly deposited on a non-magnetic support such as a polyester film or a polyimide film by a sputtering method or an ion plating method, has excellent coercive force, squareness ratio, etc. In addition to having excellent electromagnetic conversion characteristics in the wavelength range, the thickness of the magnetic layer can be reduced, so that recording demagnetization and thickness loss during reproduction are extremely small, or a binder that is a nonmagnetic material in the magnetic layer There are a number of advantages, such as the fact that it is not necessary to mix the magnetic material to increase the packing density of the magnetic material.

In this ferromagnetic metal thin film type magnetic recording medium, a vacuum evaporation method is employed as a means for forming a magnetic layer in order to improve electromagnetic conversion characteristics and secure a larger output. A so-called oblique evaporation method is used in which a magnetic material evaporated from the surface of a moving non-magnetic support is incident on the surface of the non-magnetic support from an oblique direction and is deposited.

[0004]

Incidentally, in such a magnetic recording medium of the ferromagnetic metal thin film type, particularly, durability and rust resistance are considered to be problems. A method of forming a lubricant layer composed of a coating film of an organic material on a magnetic layer and a method of forming an undercoat film containing fine particles on the surface of a nonmagnetic support before forming a magnetic layer are being studied. .

However, these methods of forming a lubricant layer and an undercoat film cannot provide satisfactory characteristics when used in a special environment or for business use. A study has been made on a surface protective film by forming means. However, if a protective film is simply formed using a single target, a protective film exhibiting satisfactory characteristics cannot be formed, and its improvement is desired.

Accordingly, the present invention has been proposed in view of the above-mentioned conventional circumstances, and it is an object of the present invention to provide a method for producing a magnetic recording medium having good durability and rust resistance even under special use conditions. Aim.

[0007]

SUMMARY OF THE INVENTION A film forming method and a method of manufacturing a magnetic recording medium according to the present invention have been proposed to achieve the above-mentioned objects. That is, the first invention of the present application is a method for manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a vacuum thin film forming technique, and a protective film is formed on the ferromagnetic metal thin film by a sputtering method. Wherein, when forming the protective film, a plurality of targets are arranged around a can provided in a vacuum chamber, and a mechanism for dividing plasma between adjacent targets is provided. .

In a second aspect of the present invention, a ferromagnetic metal thin film is formed on a nonmagnetic support by a vacuum thin film forming technique,
In the method for manufacturing a magnetic recording medium in which a protective film is formed on the ferromagnetic metal thin film by a sputtering method, a plurality of targets are arranged around a can provided in a vacuum chamber when forming the protective film. In addition, an independent power supply is provided for each target.

Further, the third invention of the present application is to form a ferromagnetic metal thin film on a non-magnetic support by a vacuum thin film forming technique,
In the method for manufacturing a magnetic recording medium in which a protective film is formed on the ferromagnetic metal thin film by a sputtering method, a plurality of targets are arranged around a can provided in a vacuum chamber when forming the protective film. A plurality of protective films are formed in layers, and the nonmagnetic support is heated when the lowermost protective film is formed.

In the method for manufacturing a magnetic recording medium according to the present invention, the magnetic layer comprises a ferromagnetic metal thin film formed by a vacuum thin film forming technique. As the above vacuum thin film forming technique, a vacuum evaporation method in which a ferromagnetic metal material is heated and evaporated under vacuum to be deposited on a non-magnetic support, an ion plating method in which a ferromagnetic metal material is evaporated in a discharge, Blow discharge occurs in an atmosphere containing Ar gas as a main component, and the generated Ar
Any of the so-called PVD techniques such as a sputtering method in which the target surface is hit with ions can be used, but a vacuum evaporation method is preferable, and an oblique evaporation method is typically used.

In the oblique deposition method, a cooling can rotated in a predetermined direction is disposed in a vacuum chamber in which a predetermined vacuum state is maintained, and the cooling can is arranged along an outer peripheral surface of the cooling can. While the non-magnetic support is traveling at a constant speed, the ferromagnetic metal material heated and evaporated by a predetermined heating means is incident on the surface of the non-magnetic support from a direction at an angle of incidence to be deposited. Is the way.

As the ferromagnetic metal material which is a constituent material of the ferromagnetic metal thin film, any one which is usually used as a constituent material of this type of magnetic recording medium can be used. Specifically, magnetic metals such as Fe, Co, and Ni,
Fe-Co, Co-Ni, Fe-Co-Ni, Fe-C
u, Co-Cu, Co-Au, Co-Pt, Mn-B
i, Mn-Al, Fe-Cr, Co-Cr, Ni-C
r, Fe-Co-Cr, Co-Ni-Cr, Fe-Co
Ferromagnetic alloys such as -Ni-Cr.

Incidentally, such a ferromagnetic metal thin film may have only a single layer or a multilayer structure. Further, between the ferromagnetic metal thin film and the non-magnetic support, or between the ferromagnetic metal thin films when a plurality of the ferromagnetic metal thin films are formed, the improvement of the adhesion to the lower layer and the control of the coercive force are controlled. For the purpose, an underlayer or an intermediate layer may be provided. Further, the ferromagnetic metal thin film may have oxygen introduced near the surface in order to improve corrosion resistance.

In the present invention, after forming the magnetic layer, a protective film is formed on the surface of the obtained magnetic layer by a sputtering method. During the formation of the protective film, the non-magnetic support on which the magnetic layer is formed is usually cooled (or heated) to a predetermined temperature in the course of moving and moving the non-magnetic support from the feed side to the winding side in a vacuum chamber. The can is provided, and sputtering is performed on a non-magnetic support that is moved along the outer peripheral surface of the can.

In the present invention, a plurality of targets are used,
These targets are arranged around the can. Then, a mechanism for dividing the plasma between adjacent targets is provided, an independent power supply is provided for each target, or a multi-layered protective film is used to heat the non-magnetic support when the lowermost protective film is formed. By doing so, the durability is significantly improved.

In the first invention of the present application, the mechanism for dividing the plasma is not particularly limited as long as it can shield the plasma generated around each target. A plasma shielding plate made of metal or the like can be used.

As the constituent material of the protective film, any of the commonly used protective film materials can be used.
O ₂ , Si ₃ N ₄ , SiN _x , BN, carbon, ZnO
₂ , Al ₂ O ₃ , MoS ₂ , SiO, CrO ₂ , Co oxide, MgO, SiC, SiN _x —SiO ₂ , Ti
O ₂ , TiC and the like can be mentioned.

As the nonmagnetic support, any of those usually used in this type of magnetic recording medium can be used. Specific examples include polyester resins such as polyethylene terephthalate and polyethylene-2,6-naphthalate, aromatic polyamide films, and polyimide resin films. Further, in the method for producing a magnetic recording medium of the present invention, if necessary, a step of forming an undercoat film on the non-magnetic support and a step of forming a back coat layer, a top coat layer, and the like may be added. good. In this case, the conditions for forming the undercoat film, the back coat layer, the top coat layer, and the like are not particularly limited as long as they are generally applied to the method of manufacturing this type of magnetic recording medium.

[0019]

When forming a protective film on a ferromagnetic metal thin film formed on a non-magnetic support by a sputtering method, a plurality of targets are arranged around a can and plasma is divided between adjacent targets. The durability is significantly improved by providing a mechanism for performing the operation, distributing an independent power supply to each target, or forming a multi-layered protective film and heating the nonmagnetic support when forming the lowermost protective film. .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described. First, the basic configuration of a sputtering apparatus used in forming a protective film in this embodiment will be described.

In this manufacturing apparatus, as shown in FIG. 1, exhaust ports 1 provided on an upper surface 1a and a bottom surface 1b are provided.
A feed roll 3 and a take-up roll 4, which are evacuated from 5 a and 15 b and are rotated at a constant speed clockwise in FIG. Are respectively arranged. The feed roll 3 and the take-up roll 4 are formed by opposing side surfaces 1 c of the vacuum chamber 1.
1d, the tape-shaped non-magnetic support 2 having a magnetic layer formed on the feed roll 3 and the take-up roll 4 is sequentially run from the feed roll 3 to the take-up roll 4.

In the middle of the travel of the non-magnetic support 2 from the feed roll 3 to the take-up roll 4, a can 5 having a larger diameter than the feed roll 3 and the take-up roll 4 is provided. Is established. The can 5 is provided below the feed roll 3 and the take-up roll 4 in the figure, and rotates at a constant speed in the clockwise direction in the figure.

The can 5 together with the feed roll 3 and the take-up roll 4 is formed in a cylindrical shape having a length substantially equal to the width of the non-magnetic support 2, and has a cooling device (not shown) inside. Or a heating device), which is cooled (or heated) to a predetermined temperature to prevent deformation of the nonmagnetic support 2 due to heat during sputtering.

Accordingly, the non-magnetic support 2 is sequentially sent out from the feed roll 3 and travels along the outer peripheral surface of the can 5. 4 and so on. The feed roll 3 and the can 5
, And between the can 5 and the winding roll 4, guide rolls 6 and 7 having a smaller diameter than the feed roll 3 and the winding roll 4 are provided. These guide rolls 6 and 7 apply a predetermined tension to the non-magnetic support 2 sequentially fed from the feed roll 2 so as to be able to run smoothly.

On the other hand, in the vacuum chamber 1, the can 5
Are provided around the cathode electrodes 8a, 8b, 8c, and carbon targets 9a, 9b, 9c are fixed on the cathode electrodes 8a, 8b, 8c, respectively. These targets 9a, 9b, 9c are disposed facing the peripheral surface of the can 5, and have a width substantially equal to the width of the can 5 in the longitudinal direction.

The vacuum chamber 1 is provided with a gas inlet 14 penetrating through the side surface 1d, and a predetermined sputtering gas is introduced from the outside through the gas inlet 14. ing.

Therefore, in such a manufacturing apparatus,
The non-magnetic support 2 in which carbon repelled from the targets 9a, 9b, 9c passes around the can 5
It is applied to the surface of the upper magnetic layer and is formed as a protective film. Then, various magnetic tapes were produced according to the following procedures using the manufacturing apparatus having the above configuration.

Experimental Example 1 In this experimental example, a plasma shielding plate was provided between adjacent targets when forming a protective film.

First, a polyethylene terephthalate film having a thickness of 10 μm and a width of 150 mm was used as a base film, and a water-soluble latex containing acrylic ester as a main component was formed on one main surface of the base film with a surface projection density of 10 million / mm. ² was applied. And
A ferromagnetic metal thin film was formed on the base film by oblique deposition in a vacuum chamber whose inside was maintained at a degree of vacuum of 7 × 10 ⁻² Pa.

That is, in the vacuum chamber, the base film fed from the unwinding side is moved at a speed of 0.17 m / sec along the outer peripheral surface of a cooling can provided substantially at the center of the vacuum chamber. While running,
The magnetic material (Co ₈₀ Ni ₂₀ alloy: numerical value represents% by weight) filled in the crucible is heated and melted by a predetermined heating means, and the evaporated magnetic material is adhered on the base film. A ferromagnetic metal thin film was formed so as to have a thickness of 0.2 μm.

At the time of the oblique deposition, oxygen gas is introduced into the surface of the base film at a rate of 3.3 × 10 ⁻⁶ m ³ / sec. It was set to change in the range of 45 to 90 °.

Subsequently, DC magnetron sputtering was performed using the above-described sputtering apparatus, and a protective film made of a carbon film was formed on the ferromagnetic metal thin film so as to have a thickness of 0.015 μm. At the time of this sputtering, the inside of the sputtering apparatus was evacuated in advance until the degree of vacuum reached 4 × 10 ⁻³ Pa, and then Ar gas was introduced as a sputtering gas. The degree of vacuum in the sputtering device during sputtering is 2 Pa. The feed speed of the base film was 0.1 m / sec.

At this time, in this embodiment, as shown in FIG. 2, a plasma shielding plate is provided between the target 9a and the target 9b and the target 9b and the target 9c, which are disposed around the periphery of the can 5. 16a, 16b
Was arranged. Thereby, the targets 9a, 9b,
9c is generated around the plasma shielding plate 1.
6a and 16b are separated as boundaries. The power supplied to each of the cathode electrodes 8a, 8b, 8c to which the targets 9a, 9b, 9c were attached was 5 W / cm.

Thereafter, a mixture of carbon and a urethane binder was applied to a thickness of 0.6 μm on the base film opposite to the surface on which the ferromagnetic metal thin film was formed to form a back coat layer. Perfluoropolyether was applied to the surface of the protective film to perform a top coat treatment. Then, the obtained magnetic tape was cut into an 8 mm width to obtain a sample tape.

The following experiment was conducted on each of the sample tapes thus obtained in order to examine the durability and rust resistance. That is, each sample tape was subjected to still running using a modified EV-S900 (trade name) manufactured by Sony Corporation, and the still time required until the output was attenuated by 3 dB from the initial output level was measured.

Each of the sample tapes was subjected to a gas corrosion tester at a temperature of 30 ° C. containing 0.3 ppm of SO ₂ gas.
It was stored for 24 hours under the condition of a relative humidity of 90%, and the deterioration rate Δφs of the magnetic characteristics (φs) after storage was determined from the following equation (1). Table 1 shows the results. Table 1 shows the samples without the protective film and the plasma shielding plates 16a and 16a.
The measurement results of the sample on which the protective film was formed without b were also shown.

[0037]

(Equation 1)

[0038]

[Table 1]

As shown in Table 1, in Comparative Example 1, since the protective film was not provided, the still time was as short as 2 hours, and the value of Δφs was as large as 10.2%. In Comparative Example 2, the durability was as good as 24 hours or more, but Δφs was not much different from Comparative Example 1, indicating that the carbon protective film did not contribute to the improvement of weather resistance. This is presumed to be because the carbon protective film formed without providing the plasma shielding plates 16a and 16b is porous, and water molecules and SO ₂ molecules can easily contact the magnetic film.

On the other hand, in the first embodiment, since the plasma shielding plates 16a and 16b are provided at the time of forming the protective film, it is expected that the formed protective film will have a pseudo three-layer structure. And Δφs shows a very good value. Specifically, the durability is not deteriorated by providing the plasma shielding plates 16a and 16b, though it is considered that the thickness of the protective film is thinner than that of Comparative Example 2. The value of Δφs is much smaller than in Comparative Example 2.

Similarly, in Embodiment 2 in which only one plasma shielding plate 16a is provided, there is an effect of improving weather resistance.
There is no deterioration in durability.

Here, in the apparatus shown in FIG. 1, it can be considered that the multilayer structure can be similarly formed by increasing the distance between the targets 9a, 9b and 9c.
If the distance between b and 9c is large, a large number of targets cannot be manufactured side by side around the can 5, so that the production efficiency deteriorates. Generally, a large shielding effect can be obtained by providing a shielding plate having a length capable of dividing the plasma and making the distance between the can and the target as short as possible.

Further, it is conceivable that the raw material after the deposition of the ferromagnetic metal thin film is formed into a multilayer by a plurality of times of sputtering, but this is still disadvantageous in terms of productivity.

Experimental Example 2 In this experimental example, after a ferromagnetic metal thin film was formed in the same manner as in Experimental Example 1, independent (three) DC power supplies were individually applied to the three cathode electrodes in the above-described sputtering apparatus. And a protective film was formed in the same manner as in Experimental Example 1 except that the plasma shielding plate used in Experimental Example 1 was removed, and a back coat process and a top coat process were performed under the same conditions. A sample tape was prepared.

For each sample tape, the above experimental example 1
Similarly, still time and deterioration rate of magnetic property (φs) Δφ
s was measured. Table 2 shows the results.

[0046]

[Table 2]

Comparative Example 3 is data showing durability and weather resistance in a normal state when the number of cathodes and the power supply are each one, and the tape feed speed is 0.033 m / sec. Comparative Example 4 is data showing the durability and weather resistance of the abnormal discharge location under the same conditions as Comparative Example 3, and it is assumed that the film quality and the film thickness due to the abnormal discharge are inferior to those in the normal condition. Conceivable.

In the third embodiment, three cathodes are provided, a DC power source is provided for each cathode, and the feed speed is set to 0.1 m / sec, which is three times that of the third comparative example. It is set to become. In the third embodiment,
Abnormal discharge occurred only at the cathode 8a, but the remaining cathodes 8b and 8c continued normal discharge. Then, the abnormal discharge portion was cut out and the durability and weather resistance were measured. As a result, the characteristics were almost the same as those in the normal case of Comparative Example 3, and it was found that the stability and the yield in mass production were improved. found.

The data of Example 4 is obtained when abnormal discharge occurs only in the cathode 8b. It can be seen that there is almost no deterioration in characteristics in this case.

In most cases, the cause of the abnormal discharge is dust such as dust or deposits generated from a cooling can or a surrounding deposition-preventing plate, and if these adhere to the surface of the cathode, a large abnormal discharge may occur. Often become. Therefore, when a single power source is used to discharge a plurality of cathodes, if an abnormal discharge occurs at one cathode, the other effects are exerted, and a stable film quality cannot be obtained.

EXPERIMENTAL EXAMPLE 3 In this experimental example, after a ferromagnetic metal thin film was formed in the same manner as in Experimental Example 1, sputtering was repeatedly performed by rewinding using a sputtering apparatus having a single target.
A protective film consisting of upper and lower two layers was formed, and further, a back coat treatment and a top coat treatment were performed under the same conditions as in Experimental Example 1 to produce a sample tape.

Here, when the sputtering is repeatedly performed as described above, after the lower protective film is formed, the base film once wound on the take-up roll is simultaneously re-wound toward the feed roll, and the sputtering is performed simultaneously. The rewinding operation and the formation of the upper protective film were simultaneously performed.

In order to enhance the adhesion of the lower protective film to the base film, the can temperature during the first sputtering (during the formation of the lower protective film) and the can temperature during the second sputtering (the formation of the upper protective film). The can temperature at the time of film formation) was changed as shown in Table 3. For each sample tape,
The shape of the tape was examined, and, as in Experimental Examples 1 and 2, the still time and the deterioration rate of the magnetic characteristics (φs) Δφs
Was measured. Table 3 shows the results.

[0054]

[Table 3]

In Comparative Example 5, upper and lower protective films were formed by reciprocating at a can temperature of 40 ° C. and a tape speed of 0.1 m / sec. At this time, since the can temperature was 40 ° C. in both the first and second times, the base film suffered heat loss, and the shape was poor, and it was judged that commercialization was difficult. However, the durability and weather resistance were good, and the adhesion between the carbon protective film and the magnetic layer was good because of the high can temperature.

In Comparative Example 6, the protective film was formed in the same process as in Comparative Example 5 with the can temperature set to −30 ° C., but there were no problems in the tape shape, but there were problems in durability and weather resistance. Was.

On the other hand, in Example 5, the first (lower) protective film was formed by heating the can to 40 ° C. to increase the adhesiveness between the carbon protective film and the magnetic layer, and to perform the sputtering (rewinding). In the upper layer sputtering, the can was performed while cooling to -30 ° C. The feed speed is 0.1 m / sec. Although the shape was slightly inferior to Comparative Example 6, it was judged to be a practically acceptable level.

In the sixth embodiment, a sputtering apparatus having three cathodes as shown in FIG. 1 was used, and a film was formed by heating only the first two cathodes. Since the feed speed at this time was also set to 0.1 m / sec, the thickness of the lower layer is considered to be about 33% thinner than the other layers. In order to make the thickness of the protective film the same as the other examples, the feed speed during rewinding is set to 0.0
The speed was adjusted to 75 m / sec and the thickness of the upper layer was adjusted to be large. Under these conditions, good results were obtained in all of the tape shape, durability and weather resistance.

When the magnetic recording medium of the present invention as described above is applied to the following system, excellent durability can be exhibited and good characteristics can be obtained.

A. Reproducing the structure color video signal of the apparatus as a digital VTR for recording on a recording medium such as a magnetic tape and digitized, D1 format component type digital VT for broadcasters
Composite digital V in R and D2 format
TR has been put to practical use.

The former D1 format digital VTR
Indicates that the luminance signal and the first and second color difference signals are each 1
After performing A / D conversion at the sampling frequencies of 3.5 MHz and 6.75 MHz, predetermined signal processing is performed and recorded on the magnetic tape, and the sampling frequency of these component components is 4: 2: 2. 4: 2:
Also referred to as two systems.

On the other hand, the latter D2 format digital VTR samples the composite color video signal with a signal having a frequency four times the frequency of the color subcarrier signal, performs A / D conversion, and performs predetermined signal processing. , On a magnetic tape.

In any case, these digital VTs
Since R is designed on the assumption that both are used for broadcasting stations, image quality is given the highest priority, and a digital color video signal in which one sample is A / D converted to, for example, 8 bits is substantially compressed. It is made to record without doing. Therefore, for example, a digital VTR of the D1 format can obtain a reproduction time of at most about 1.5 hours even when a large cassette tape is used, and is not suitable for use as a general home VTR.

Therefore, here, for example, a signal having a shortest wavelength of 0.5 μm is recorded for a track width of 5 μm, and the recording density is 4 × 10 ⁵ bit / mm ² or more, or 8 × 10 ⁵ bit / mm ^2. In addition to realizing the above, by using a method of compressing recorded information in a form that minimizes reproduction distortion, long-term recording and reproduction can be performed even when using a magnetic tape with a tape width of 8 mm or less. The present invention is applied to a digital VTR capable of performing the following.

Hereinafter, the configuration of the digital VTR will be described.

A. First, the signal processing unit of the digital VTR used in this embodiment will be described. FIG. 3 shows the entire configuration of the recording side. Input terminals indicated by 31Y, 31U and 31V are respectively provided with a digital luminance signal Y formed from three primary color signals R, G and B from a color video camera and a digital color difference. Signals U and V are supplied. In this case, the clock rate of each signal is the same as the frequency of each component signal in the D1 format. That is, the respective sampling frequencies are 13.5 MHz and 6.75 MH
z, and the number of bits per sample is 8 bits. Therefore, the input terminals 31Y,
As the data amount of the signal supplied to 31U and 31V,
It becomes about 216 Mbps. A data amount of about 167 Mb is obtained by an effective information extracting circuit 32 which removes blanking time data from the signal and extracts only information of an effective area.
Compressed to ps.

Then, the luminance signal Y of the output of the effective information extraction circuit 32 is supplied to the frequency conversion circuit 33,
The sampling frequency is converted from 13.5 MHz to 3/4 thereof. As the frequency conversion circuit 33, for example, a thinning filter is used to prevent aliasing distortion. The output signal of the frequency conversion circuit 33 is
The luminance data is supplied to the blocking circuit 35, and the order of the luminance data is converted into the order of the blocks. The blocking circuit 35 is provided for a block coding circuit 38 provided at a subsequent stage.

FIG. 5 shows the structure of a block as a unit of encoding. This example is a three-dimensional block, for example, by dividing a screen extending over two frames, a large number of (4 lines × 4 pixels × 2 frames) unit blocks are formed as shown in FIG. In FIG. 5, a solid line indicates an odd field line, and a broken line indicates an even field line.

The two color difference signals U and V of the output of the effective information extraction circuit 32 are supplied to the sub-sampling and sub-line circuit 34, and after the sampling frequency is converted from 6.75 MHz to half thereof, respectively. Two digital color difference signals are selected line by line
Combined with channel data. Accordingly, the sub-sampling and sub-line circuit 34 provides a line-sequential digital color difference signal. FIG. 6 shows a pixel configuration of a signal sub-sampled and sub-lined by the sub-sampling and sub-line circuit 34. In FIG. 6, ○ indicates a sub-sampling pixel of the first color difference signal U, △ indicates a sampling pixel of the second dye signal V, and × indicates a position of a pixel thinned out by the sub-sample.

The line-sequentialized output signal from the sub-sampling and sub-line circuit 34 is supplied to a blocking circuit 36. In the blocking circuit 36, similarly to the blocking circuit 35, the color difference data in the scanning order of the television signal is converted into the data in the block order. This blocking circuit 36 converts the color difference data into (4 lines × 4 pixels × 2 frames) similarly to the one blocking circuit 35.
To the block structure of The output signals of the blocking circuits 35 and 36 are
7 is supplied.

In the synthesizing circuit 37, the luminance signal and the chrominance signal converted in the order of the blocks are converted into one-channel data, and the output signal of the synthesizing circuit 37 is supplied to the block encoding circuit 38. As the block encoding circuit 38, an encoding circuit (referred to as ADRC) adapted to a dynamic range of each block as described later, a DCT
(Discrete Cosine Transformer
m) A circuit or the like can be applied. The block encoding circuit 38
Is further supplied to a framing circuit 39 and converted into data having a frame structure. In the framing circuit 39, switching between the pixel system clock and the recording system clock is performed.

Then, the output signal of the framing circuit 39 is supplied to an error correction code parity generation circuit 40, and an error correction code parity is generated. The output signal of the parity generation circuit 40 is supplied to a channel encoder 41, where channel coding is performed so as to reduce the low-frequency portion of the recording data. Channel encoder 41
Are output via recording amplifiers 42A and 42B and a rotary transformer (not shown).
A, 43B and recorded on a magnetic tape. The audio signal and the video signal are compression-encoded separately and supplied to the channel encoder 41.

By the above-described signal processing, the input data amount 216 Mbps is reduced to about 167 Mbps by extracting only the effective scanning period, and further reduced to 84 Mbps by frequency conversion, sub-sampling, and sub-line. This data is compressed to about 25 Mbps by compression coding in the block coding circuit 38, and after adding additional information such as parity and audio signals, the recording data amount is 31.56 Mbps.
Becomes

Next, the configuration on the reproducing side will be described with reference to FIG. At the time of reproduction, as shown in FIG. 4, reproduction data from the magnetic heads 43A and 43B is first supplied to the channel decoder 45 via the rotary transformer and the reproduction amplifiers 44A and 44B. Channel decoder 45
In, the channel coding is demodulated, and the output signal of the channel decoder 45 is supplied to a TBC circuit (time axis correction circuit). In the TBC circuit 46, the time axis fluctuation component of the reproduction signal is removed. The reproduction data from the TBC circuit 46 is supplied to the ECC circuit 47,
Error correction and error correction using an error correction code are performed. The output signal of the ECC circuit 47 is supplied to a frame decomposition circuit 48.

The components of the block coded data are separated by the frame decomposition circuit 48, respectively.
The switching from the recording system clock to the pixel system clock is performed. Each data separated by the frame decomposing circuit 48 is supplied to a block decoding circuit 49, and the original data and the corresponding restored data are decoded for each block unit, and the decoded data is supplied to a distribution circuit 50. This distribution circuit 50 separates the decoded data into a luminance signal and a color difference signal. The luminance signal and the color difference signal are supplied to the block decomposition circuits 51 and 52, respectively. The block decomposing circuits 51 and 52 convert the decrypted data in the block order in the order of raster scanning, contrary to the blocking circuits 35 and 36 on the transmission side.

The decoded luminance signal from the block decomposition circuit 51 is supplied to the interpolation filter 53. In the interpolation filter 53, the sampling rate of the luminance signal is changed from 3 fs to 4 fs.
(4fs = 13.5 MHz). The digital luminance signal Y from the interpolation filter 53 is taken out to an output terminal 56Y.

On the other hand, the digital color difference signals from the block separation circuit 52 are supplied to the distribution circuit 54, and the line-sequentialized digital color difference signals U and V are separated into digital color difference signals U and V, respectively. The digital color difference signals U and V from the distribution circuit 54 are supplied to the interpolation circuit 55 and are interpolated. The interpolation circuit 55 interpolates the thinned line and pixel data by using the restored pixel data. The interpolation circuit 55 outputs a sampling rate of 2f.
s digital color difference signals U and V are obtained, and the output terminal 5
It is taken out to 6U and 56V, respectively.

B. Block Coding The block coding circuit 38 in FIG.
C (Adaptive Dynamic Range C)
Oding) encoder is used. This ADRC encoder detects a maximum value MAX and a minimum value MIN of a plurality of pixel data included in each block, and detects these maximum values M
The dynamic range DR of the block is detected from the AX and the minimum value MIN, encoding is performed in accordance with the dynamic range DR, and requantization is performed with a bit number smaller than the bit number of the original pixel data. As another example of the block encoding circuit 38, pixel data of each block is converted into a DCT (Discrete Cosine Tr).
After performing an transform, the coefficient data obtained by the DCT may be quantized, and the quantized data may be run-length-Huffman-encoded and compression-encoded.

Here, an example of an encoder that uses an ADRC encoder and does not cause image quality deterioration even when multi-dubbing is performed will be described with reference to FIG. 7, a digital video signal (or a digital color difference signal) in which one sample is quantized to 8 bits, for example, is input to an input terminal 57 from the synthesizing circuit 37 in FIG. Blocked data from the input terminal 57 is supplied to the maximum value / minimum value detection circuit 59 and the delay circuit 60. The maximum value / minimum value detection circuit 59 includes a minimum value MIN and a maximum value MA for each block.
X is detected. The input data is delayed from the delay circuit 60 for the time required for detecting the maximum value and the minimum value. The pixel data from the delay circuit 60 is supplied to the comparison circuits 61 and 62.

The maximum value MAX from the maximum value / minimum value detection circuit 59 is supplied to the subtraction circuit 63, and the minimum value MIN is supplied to the addition circuit 64. To the subtraction circuit 63 and the addition circuit 64, a value of one quantization step width (△ = 1 / 16DR) when non-edge matching quantization is performed with a fixed length of 4 bits from the bit shift circuit 65. The bit shift circuit 65 is configured to shift the dynamic range DR by 4 bits so as to perform division by (1/16). A threshold value of (MAX− △) is obtained from the subtraction circuit 63, and a threshold value of (MIN + △) is obtained from the addition circuit 64. The threshold values from the subtraction circuit 63 and the addition circuit 64 are supplied to comparison circuits 61 and 62, respectively. The value す る defining the threshold value is not limited to the quantization step width, but may be a fixed value corresponding to a noise level.

The output signal of the comparison circuit 61 is
6 and the output signal of the comparison circuit 62 is supplied to an AND gate 67. Input data from the delay circuit 60 is supplied to the AND gate 66 and the AND gate 67. The output signal of the comparison circuit 61 becomes high level when the input data is larger than the threshold value. Therefore, the output terminal of the AND gate 66 supplies the pixel data of the input data included in the maximum level range of (MAX to MAX- △). Is extracted. On the other hand, the output signal of the comparison circuit 62 becomes high level when the input data is smaller than the threshold value, and therefore, the output terminal of the AND gate 67 has (MIN to MIN)
+ △) The pixel data of the input data included in the minimum level range is extracted.

The output signal of AND gate 66 is supplied to averaging circuit 68, and the output signal of AND gate 67 is supplied to averaging circuit 69. These averaging circuits 68 and 69
Calculates an average value for each block. A reset signal of a block cycle is supplied from a terminal 70 to the averaging circuits 68 and 69.
Is supplied to From the averaging circuit 68, (MAX to
An average value MAX ′ of the pixel data belonging to the maximum level range of (MAX− △) is obtained.
To MIN + △), the average value MIN ′ of the pixel data belonging to the minimum level range is obtained. The average value MIN 'is subtracted from the average value MAX' by a subtraction circuit 71, and this subtraction circuit 71
To obtain the dynamic range DR '.

The average value MIN 'is supplied to the subtraction circuit 72, and the average value MIN' is subtracted from the input data passed through the delay circuit 73 by the subtraction circuit 72, thereby forming the data PDI from which the minimum value has been removed. . The data PDI and the modified dynamic range DR 'are used as the quantization circuit 74.
Supplied to In this embodiment, the number n of bits allocated to quantization is 0 (the code signal is not transferred),
This is a variable-length ADRC having any one of 1 bit, 2 bits, 3 bits, and 4 bits, and is subjected to edge matching quantization. The number n of allocated bits is determined for each block by the bit number determination circuit 75, and data of the number n of bits is supplied to the quantization circuit 74.

The variable length ADRC has a dynamic range D
Efficient coding can be performed by reducing the number of allocated bits n in a block with a small R 'and increasing the number of allocated bits n in a block with a large dynamic range DR'. That is, the thresholds for determining the number of bits n are T1 to T4 (T1 <T2 <T3 <
T4), the code signal is not transferred to the block of (DR ′ <T1), only the information of the dynamic range DR ′ is transferred, and the block of (T1 ≦ DR ′ <T2) is (n = 1) The block of (T2 ≦ DR ′ <T3) is set to (n = 2), the block of (T3 ≦ DR ′ <T4) is set to (n = 3), and the block of (DR ′ ≧ T4) is set to (n = 3). The block is set to (n = 4).

In such a variable length ADRC, the threshold values T1 to T1
By changing T4, the amount of generated information can be controlled (so-called buffering). Therefore, the variable length ADRC can be applied to a transmission path such as the digital video tape recorder of the present invention in which the amount of generated information per field or frame is required to be a predetermined value.

In the buffering circuit 76 for determining the threshold values T1 to T4 for setting the amount of generated information to a predetermined value, a plurality of sets of threshold values (T1, T2, T3, T4), for example, 3
Two sets are provided, and these sets of thresholds are distinguished by parameter codes Pi (i = 0, 1, 2,..., 31). The amount of generated information is set to decrease monotonically as the number i of the parameter code Pi increases. However, as the amount of generated information decreases, the image quality of the restored image deteriorates.

Threshold value T from buffering circuit 76
1 to T4 are supplied to the comparison circuit 77, and the dynamic range DR ′ via the delay circuit 78 is supplied to the comparison circuit 77. The delay circuit 78 delays DR ′ by the time required for the buffering circuit 76 to determine the set of thresholds. In the comparing circuit 77, the dynamic range DR 'of the block is compared with each threshold value, the comparison output is supplied to the bit number determining circuit 75, and the allocated bit number n of the block is determined. In the quantization circuit 74, the data PDI from which the minimum value has been removed via the delay circuit 79 is converted into a code signal DT by edge matching quantization using the dynamic range DR 'and the number of allocated bits n. The quantization circuit 74 is constituted by, for example, a ROM.

The modified dynamic range DR 'and average value MIN' are output via delay circuits 78 and 80, respectively, and further a parameter code Pi indicating a set of a code signal DT and a threshold value is output. In this example, since the signal once subjected to the non-edge match quantization is newly subjected to the edge match quantization based on the dynamic range information, the image degradation when dubbing is reduced.

C. Channel Encoder and Channel Decoder Next, the channel encoder 41 and the channel decoder 45 of FIG. 3 will be described. In the channel encoder 41, as shown in FIG. 8, an adaptive scrambling circuit to which the output of the parity generation circuit 40 is supplied, a plurality of M-sequence scrambling circuits 81 are prepared. It is configured such that an M-sequence that can obtain an output with a small component and a small DC component is selected. In the precoder 82 for the partial response class 4 detection method, an arithmetic processing of 1 / 1-D ² (D is a unit delay circuit) is performed. The output of the precoder 82 is supplied to the magnetic head 4 via the recording amplifiers 42A and 42B.
Recording and reproduction are performed by 3A and 43B, and a reproduction output is amplified by reproduction amplifiers 44A and 44B.

On the other hand, in the channel decoder 45, as shown in FIG. 9, the arithmetic processing circuit 83 on the reproduction side of the partial response class 4 performs 1 + D operation on the outputs of the reproduction amplifiers 44A and 44B. Also,
The so-called Viterbi decoding circuit 84 performs data decoding that is resistant to noise by performing an arithmetic operation on the output of the arithmetic processing circuit 83 using data correlation and certainty. The output of the Viterbi decoding circuit 84 is supplied to a descrambling circuit 85, and the data rearranged by the scrambling process on the recording side is returned to the original sequence to restore the original data. With the Viterbi decoding circuit 84 used in this embodiment, the reproduction C / N conversion can be improved by 3 dB as compared with the case of performing decoding for each bit.

D. Traveling system The magnetic head 43A and the magnetic head 43B are attached to the drum 86 in an integrated structure as shown in FIG. A magnetic tape (not shown) is obliquely wound around the peripheral surface of the drum 86 at a winding angle slightly larger than 180 ° or slightly smaller than 180 °.
A and the magnetic head 43B are configured to scan the magnetic tape simultaneously.

The directions of the gaps of the magnetic head 43A and the magnetic head 43B are inclined so that they are opposite to each other (for example, the magnetic head 43A is inclined by + 20 ° with respect to the track width direction, and the magnetic head 43B is inclined by -20 ° with respect to the track width direction). As described above, the amount of crosstalk between adjacent tracks is reduced by so-called azimuth loss during reproduction.

FIGS. 11 and 12 show magnetic heads 43A,
This shows a more specific configuration in the case where 43B has an integral structure (a so-called double azimuth head).
A, 43B are attached, and the lower drum 87 is fixed. Here, the winding angle θ of the magnetic tape 88 is 16
6 ° and the drum diameter φ is 16.5 mm.

Therefore, one field of data is recorded on the magnetic tape 88 while being divided into five tracks. With this segment system, the length of the track can be reduced, and errors due to track linearity can be reduced.

As described above, by performing simultaneous recording with a double azimuth head, the amount of error due to linearity can be reduced as compared with the case where a pair of magnetic heads are arranged at an opposing angle of 180 °. The pairing adjustment can be performed more accurately because the distance between the heads is small. Therefore, with such a traveling system, recording and reproduction can be performed on a narrow track.

[0096]

As is apparent from the above description, in the first invention of the present invention, a plurality of targets are provided, and a plasma dividing mechanism is provided between the targets. The protective film can be formed with high productivity, and the durability and weather resistance can be greatly improved.

In the second aspect of the present invention, since an independent power source is provided for each target, abnormal discharge can be suppressed, and a protective film having a stable film quality can be formed with a high yield. it can.

Further, in the third aspect of the present invention, since the nonmagnetic support is heated only when the lower protective film is formed, the protective film having excellent adhesion to the magnetic layer is formed in a tape shape. A film can be formed without deterioration. Therefore, according to the present invention, it is possible to manufacture a magnetic recording medium having good durability and rust resistance even under special use conditions.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of an apparatus for manufacturing a protective film used in a method for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram showing a state where a plasma shielding plate is provided between targets disposed around a can.

FIG. 3 is a block diagram showing a recording side configuration of a signal processing unit of a digital VTR for compressing and recording a digital image signal in such a manner that reproduction distortion is small.

FIG. 4 is a block diagram illustrating a configuration of a reproduction side of a signal processing unit.

FIG. 5 is a schematic diagram illustrating an example of a block for block encoding.

FIG. 6 is a schematic diagram for explaining sub-sampling and sub-line.

FIG. 7 is a block diagram illustrating an example of a block encoding circuit.

FIG. 8 is a block diagram schematically illustrating an example of a channel encoder.

FIG. 9 is a block diagram schematically illustrating an example of a channel decoder.

FIG. 10 is a plan view schematically showing an example of an arrangement of a magnetic head.

FIG. 11 is a plan view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

FIG. 12 is a front view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Nonmagnetic support 3 ... Feeding roll 4 ... Winding roll 5 ... Can 8a-8c ... Cathode electrode 9a-9c ... Target

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/84 G11B 5/851 G11B 5/72

Claims (3)

(57) [Claims] 1. A method for manufacturing a magnetic recording medium comprising: forming a ferromagnetic metal thin film on a nonmagnetic support by a vacuum thin film forming technique; and forming a protective film on the ferromagnetic metal thin film by a sputtering method. A method for manufacturing a magnetic recording medium, comprising: disposing a plurality of targets around a can disposed in a vacuum chamber when forming a film; and providing a mechanism for dividing plasma between adjacent targets. 2. A method for manufacturing a magnetic recording medium comprising: forming a ferromagnetic metal thin film on a nonmagnetic support by a vacuum thin film forming technique; and forming a protective film on the ferromagnetic metal thin film by a sputtering method. A method for producing a magnetic recording medium, comprising: disposing a plurality of targets around a can disposed in a vacuum chamber when depositing a film; and providing an independent power supply to each target. 3. A method of manufacturing a magnetic recording medium comprising: forming a ferromagnetic metal thin film on a non-magnetic support by a vacuum thin film forming technique; and forming a protective film on the ferromagnetic metal thin film by a sputtering method. In forming a film, a plurality of targets are arranged around a can arranged in a vacuum chamber, and a plurality of protective films are laminated and formed. When the lowermost protective film is formed, the nonmagnetic support is formed. A method for producing a magnetic recording medium, comprising heating.