JPH09228029A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a magnetic recording medium having excellent electromagnetic conversion characteristics and magnetic characteristics and a small error rate by using Co as the vapor deposition source. SOLUTION: In the production method of a magnetic recording medium by forming a ferromagnetic metal thin film as a magnetic layer by vacuum vapor deposition on a nonmagnetic base body, Co is used as the vapor deposition source material. The ferromagnetic metal thin film is formed on a nonmagnetic base body by specifying the total amt. of C, Si, Mn, Al and Ti in the vapor deposition source material to <=0.2wt.%.

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 so-called metal magnetic thin film type magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by vacuum evaporation.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder non-magnetic material such as an oxide magnetic powder or an alloy magnetic powder on a non-magnetic support is used as a vinyl chloride-vinyl acetate copolymer, polyester resin, urethane resin. A coating type magnetic recording medium prepared by coating and drying a magnetic coating material dispersed in an organic binder such as polyurethane resin is widely used.

On the other hand, with the increasing demand for high density magnetic recording, Co--Ni type alloys, Co--Cr type alloys,
A magnetic metal material such as Co—O was directly deposited on a non-magnetic support such as a polyester film, polyamide, or polyimide film by plating or vacuum thin film forming means (vacuum deposition method, sputtering method, ion plating method, etc.), A so-called metal magnetic thin film type magnetic recording medium has been proposed and attracted attention.

This metal magnetic thin film type magnetic recording medium is excellent not only in coercive force and squareness ratio but also in electromagnetic conversion characteristics at a short wavelength, and because the magnetic layer can be extremely thin,
There are a number of things such as remarkably small thickness loss during recording demagnetization and reproduction, and increasing the packing density of magnetic materials because there is no need to mix a binder (binder) that is a non-magnetic material in the magnetic layer. Have advantages.

When forming a ferromagnetic metal thin film of such a magnetic recording medium, the electromagnetic conversion characteristics are improved,
In order to get a larger output,
Oblique evaporation, which obliquely evaporates magnetic materials, has been proposed and put to practical use. In the magnetic tape manufactured by this oblique deposition, the magnetic particles are oriented obliquely with respect to the surface of the non-magnetic support, and the magnetic particles have a higher density than the conventional magnetic tape in which the magnetic particles are oriented in the longitudinal direction. Various recordings are possible.

[0006]

By the way, as a vapor deposition source material used in the oblique vapor deposition, a Co--Ni system is representative, and it is disclosed in JP-A-63-195234 and JP-A-7-195234.
As disclosed in Japanese Patent Laid-Open No. 54069, there has been proposed one in which the amount of impurities such as carbon, Al, Mn and oxygen contained therein is strictly regulated.

On the other hand, as seen in the development of a DV (Digital Video) type vapor tape (DV cassette) for digital video, an information signal recorded on a magnetic recording medium is
In recent years, there is a tendency toward digitalization.

In such a vapor-deposited tape, from the viewpoint of improving electromagnetic conversion characteristics, the magnetic energy product (Br × H)
It is necessary to increase c), and for that purpose, N
It is desired to increase the composition ratio of Co having a higher magnetization than that of i.

However, when the composition ratio of Co is increased, the improvement of the electromagnetic conversion characteristics and the improvement of the error rate are important points. As a method for improving this error rate, it is effective to improve the dropout of the vapor deposition tape, but this dropout is mostly caused by the splash generated from the vapor deposition source material during vacuum vapor deposition.

Therefore, when Co is used as the vapor deposition source material, it is essential to suppress the splash, but the technology is not established for that reason.

Therefore, the present invention has been proposed in view of such conventional circumstances, and uses Co as a vapor deposition source material and is excellent in electromagnetic conversion characteristics and magnetic characteristics, and has a small error rate. The challenge is to provide.

[0012]

In order to solve the above-mentioned problems, a method of manufacturing a magnetic recording medium according to the present invention is a magnetic recording in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by vacuum evaporation. In the method for producing a medium, Co is used as a vapor deposition source material, and the total content of C, Si, Mn, Al, and Ti contained in the vapor deposition source material is 0.
It is characterized in that a ferromagnetic metal thin film is formed on a non-magnetic support with a content of 2% by weight or less. Further, the evaporation source material once used for vacuum evaporation is recovered, dissolved again, and a ferromagnetic metal thin film is formed as a magnetic layer by vacuum evaporation.

In the present invention, Co is used as the vapor deposition source material, and C, Si, Mn,
The total content of Al and Ti is restricted to 0.2% by weight or less. Thereby, when a ferromagnetic metal thin film is formed as a magnetic layer on the non-magnetic support by vacuum deposition, splash can be suppressed.

Therefore, according to the present invention, it is possible to provide a magnetic recording medium excellent in electromagnetic conversion characteristics and magnetic characteristics and having a small error rate, even though Co is used as a vapor deposition source material.

Here, a metal magnetic thin film is formed as a magnetic layer on the non-magnetic support by directly depositing the above-mentioned ferromagnetic metal material. The magnetic layer is a single layer film. Or may be a multilayer film. Furthermore, an underlayer or an intermediate layer may be provided between the non-magnetic support and the metal magnetic thin film, or in the case of a multilayer film, for improving the adhesive force between the layers and controlling the coercive force. Also,
For example, the vicinity of the surface of the magnetic layer may be an oxide to improve the corrosion resistance.

As a means for forming the metal magnetic thin film, a vacuum vapor deposition method in which a ferromagnetic material is heated and evaporated under vacuum to deposit it on a non-magnetic support.

A protective film layer may be formed on the ferromagnetic metal material formed on the non-magnetic support.
As this material, any material may be used as long as it is generally used as a protective film for an ordinary metal magnetic thin film. For example, carbon CrO ₂ , AI ₂ O ₃ , B
N, Co oxide, MgO, SiO ₂ , Si ₃ O ₄ , Si
_{N x, SiC, SiN x -SiO} 2, ZrO 2, TiO 2,
TiC and the like. These may be a single layer film or a multilayer film.

Of course, the structure of the magnetic tape according to the present invention is not limited to this, and may be changed without departing from the scope of the present invention, for example, a back coat layer may be formed or a non-magnetic layer may be formed if necessary. There is no problem in forming an undercoat layer on the support or forming a layer of a lubricant, a rust preventive, or the like. In this case, as the non-magnetic pigment contained in the back coat paint, or the material contained in the lubricant or the rust preventive, any conventionally known material can be used.

In such a magnetic recording medium, for example, an input digital image signal is converted into block data composed of a plurality of pixel data, and the data is divided into blocks. The block data is compression-encoded in block units. It is suitable for digital image signal recording, in which compressed data is channel-encoded, and the channel-encoded data is mounted on a rotary drum and recorded on a magnetic recording medium by a deaeration head. is there.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

1. Vapor Deposition Manufacturing Apparatus First, the structure of the vapor deposition manufacturing apparatus used in the embodiment of the present invention will be described.

As shown in FIG. 1, in this manufacturing apparatus, the inside of the vacuum chamber 82 is evacuated from the exhaust ports 81 provided at the head and the lower portion, and the inside of the vacuum chamber 82 is in a vacuum state. A feed roll 83 that rotates at a constant speed in a clockwise direction,
A winding roll 84 that rotates at a constant speed in the clockwise direction in the drawing is provided.
4, a tape-shaped non-magnetic support 85 is sequentially run.

From the feed roll 83 to the take-up roll 8
A cooling can 86 having a diameter larger than the diameter of each of the rolls 83 and 84 is provided in the middle of the non-magnetic support 85 running on the fourth side. The cooling can 86 is provided so as to draw the non-magnetic support member 85 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 83, the take-up roll 84, and the cooling can 86 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support 85, and the cooling can 86 also has the same shape.
Is provided with a cooling device (not shown) inside so that deformation of the non-magnetic support 85 due to temperature rise can be suppressed.

Therefore, the non-magnetic support member 85 is sequentially fed from the feed roll 83, and the cooling can 8 is further fed.
It passes through the peripheral surface of No. 6 and is wound up by the winding roll 84. Guide rolls 87 and 88 are provided between the feed roll 83 and the cooling can 86 and between the cooling can 86 and the take-up roll 84, respectively. A predetermined tension is applied to the non-magnetic support member 85 running from the cooling can 86 to the ticket collecting rolls 84 so that the non-magnetic support member 85 runs smoothly.

In the vacuum chamber 82, a crucible 89 is provided below the cooling can 86, and the crucible 8 is provided.
A magnetic metal material 90 is filled in the inside 9. The crucible 89 has substantially the same width as the longitudinal width of the cooling can 86.

On the other hand, an electron gun 91 for heating and evaporating the metallic magnetic material 90 filled in the crucible 89 is attached to the side wall of the vacuum chamber 82. The electron gun 91 is arranged at a position such that the electron beam X emitted from the electron gun 91 irradiates the metallic magnetic material 90 in the crucible 89. Then, the metallic magnetic material 90 evaporated by the electron gun 91 is deposited and formed as a magnetic layer on the non-magnetic support 85 that runs at a constant speed on the peripheral surface of the cooling can 86.

A shutter 9 is provided between the cooling can 86 and the crucible 89 and near the cooling can 86.
2 are provided. The shutter 92 is formed so as to cover a predetermined region of the non-magnetic support member 85 that runs at a constant speed on the peripheral surface of the cooling can 86, and the metal magnetic material 90 evaporated by the shutter 92 is supported by the non-magnetic support member. The vapor deposition is performed obliquely with respect to the body 85 within a predetermined angle range. Further, in the case of such vapor deposition, the oxygen gas introduction port 9 is provided which penetrates the side wall of the vacuum chamber 82.
Oxygen gas is supplied to the surface of the non-magnetic support member 85 via 4 to improve the magnetic properties, durability and weather resistance.

[0028] 2. Configuration of Magnetic Recording Medium Next, the magnetic recording medium of the present invention will be described.

The method of manufacturing a magnetic recording medium of the present embodiment is the same as the method of manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by vacuum deposition. 2% by weight or less of C, Si, M
It is characterized in that a ferromagnetic metal thin film is formed on a non-magnetic support as a vapor deposition source material consisting of n, Al and Ti.

The main manufacturing conditions of the tape used in this embodiment are shown below.

First, the base film, which is a non-magnetic support, is made of polyethylene terephthalate with a thickness of 10 μm.
The one having a width of 150 mm was used. The undercoat layer was formed by coating a water-soluble latex containing acrylic acid ester as a main component at a density of 10 million pieces / mm ² .

Deposition conditions of magnetic layer by the above-mentioned vapor deposition apparatus Ingot: Co99 wt% (details are shown in Table 1) Incident angle: 45 to 90 ° Feed rate of non-magnetic support: 25 m / min Magnetic layer thickness: 200 nm Introduced oxygen amount: 250 cc / min Deposition degree of vacuum: 7 × 10 ⁻² Pa Next, the backcoat layer was applied by mixing carbon and a urethane binder to a thickness of 0.6 μm.

As the top coat, perfluoropolyether was applied to the magnetic surface. The cutting width is 8 mm.

A sample tape like this was prepared. Table 1 shows the impurity contents of the alloys used in each of the comparative examples and the embodiments of this time.

Here, the alloy composition was measured by using an IPC emission spectrophotometer manufactured by Shimadzu Corporation, a combustion infrared absorption method and the like. That is, the metal was analyzed by an IPC emission spectrophotometer, and the carbon was measured by a combustion infrared absorption method.

Dropout is measured by Sony EV-S
Using a 900 modified machine, the playback output level is -16 dB,
Output drop of 10 μsec or more is used as dropout,
The measurement was performed for 10 minutes, and the number of dropouts per minute was calculated. Further, the deterioration of magnetic properties was measured by using a gas corrosion tester with SO ₂ gas of 0.6 ppm. Including 35 ° C 90%
The deterioration amount (Δφs) of the magnetic property (φs) after storage in an RH atmosphere for 24 hours was measured and determined by the following equation (1).

Δφs = (φs−φs ′) / φs × 100 (%) (1) φs: measured value before storage test φs ′: measured value before storage test 3. Experimental Results As described above, Tables 1 and 2 show the results of measurement using the IPC emission spectrophotometer manufactured by Shimadzu Corporation and the combustion infrared absorption method.

In this experiment, the evaporation source material was dissolved in the air the first time and in the second vacuum, but a deoxidizing agent such as Al was gradually added to the MgO container to gradually dissolve it. The oxide existing as if a film was formed on the surface of MgO was MgO.
When tilting the container and flowing the alloy out to obtain the vapor deposition source material,
It was attached to the wall of the crucible and removed.

The vapor deposition source material used here was one that was once used as a vapor deposition source material, recovered, melted again, and reprocessed into a shape to be supplied at the time of vapor deposition. By adopting such a method, a vapor deposition tape having excellent electromagnetic conversion characteristics and an excellent error rate can be realized.

On the other hand, as Co, Co containing impurities such as Ni and Fe which have been subjected to simple refining after production may be used. However, in order to enhance the purity of Co, it is preferable to carry out dissolution several times to remove impurities. In addition,
If Co containing impurities such as Ni and Fe that have been subjected to simple refining after production is used, the manufacturing cost will be low, but if melting is performed several times to remove impurities, the manufacturing cost will be high. .

[0041]

[Table 1]

The Co component has a value obtained by subtracting other trace impurities. In Table 1, "BAL" means "balance (Balan)" after subtracting other trace impurities.
ce) ”.

[0043]

[Table 2]

As is clear from Tables 1 and 2, Co is used as the vapor deposition source material, and the total content of C, Si, Mn, Al, and Ti contained in the vapor deposition source material is 0.
Comparative Examples 1 to 3 in which the amount is 2% by weight or more has a large amount of splash during vapor deposition and has a poor error rate. In particular, Comparative Example 1
Had an oxide film on the surface of the crucible during vapor deposition as if it had a film on it, and the vapor deposition rate could not be obtained unless the beam power of the electron gun was higher than usual.

On the other hand, Co is used as the vapor deposition source material, and C, Si and M contained in the vapor deposition source material are used.
In each of Examples 1 to 6 in which the total content of n, Al, and Ti is 0.2% by weight or less, the magnetic deterioration characteristics are small, and the electromagnetic conversion characteristics are improved and the error rate is improved.

In particular, as seen in the order of Example 4, Example 6, and Example 1, the error rate tends to be better as the total amount of impurities is smaller. It is considered that this is because the amount of impurities was small and the splash generated during vacuum deposition was suppressed. In addition, in Example 1, Co
In order to improve the purity of the above, dissolution was carried out several times to remove impurities.

From the above results, C was selected as the vapor deposition source material.
is used, and C and S contained in this vapor deposition source material are used.
By forming the ferromagnetic metal thin film on the non-magnetic support with the total content of i, Mn, Al, and Ti being 0.2% by weight or less, the magnetic deterioration characteristic is small, and the electromagnetic conversion characteristic is small. And the error rate is improved.

[0048] 4. Configuration of Recording / Reproducing Apparatus Next, since the present invention is suitable as a recording medium for digital recording, a recording / reproducing system of a digital VTR whose error rate is measured will be described.

As a digital VTR for digitizing a color video signal and recording it on a recording medium such as a magnetic tape, a component type digital VTR of a format for broadcasting stations and a composite type digital VTR of a D2 format have been put into practical use.

The former D1 format digital VTR
Is 1 for the luminance signal and the first and second color difference signals.
After A / D conversion at a sampling frequency of 3.5 MHz and 6.75 MHz, a predetermined signal processing is performed and recording is performed on a magnetic tape. Since the sampling frequency of these component components is 4: 2: 2. 4: 2:
It is also called two methods.

On the other hand, in the latter D2 format digital VTR, the composite color video signal is sampled with a signal having a frequency four times the frequency of the color subcarrier signal, A / D-converted, and subjected to predetermined signal processing. , I try to record on a magnetic tape.

In any case, these digital VTs are
Since R is designed on the premise 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 into, for example, 8 bits is substantially compressed. It is designed to record without doing anything.

Therefore, for example, in the D1 format digital VTR, even if a large cassette tape is used, a reproduction time of at most about 1.5 hours can be obtained, which is unsuitable for use as a general household VTR. .

Therefore, in the present embodiment, for example, 5
A signal with a shortest wavelength of 0.5 μm is recorded for a track width of μm, a recording density of 1.25 μm ² / bit is realized, and a method of compressing recorded information in a form with little reproduction distortion is also used. Depending on the tape width is 8m
The present invention is applied to a digital VTR capable of recording / reproducing for a long time even if a magnetic tape having a width of m or less is used. Therefore, the configuration of this digital VTR will be described below.

A. Signal Processing Unit First, the digital VTR signal processing unit used in this embodiment will be described. FIG. 2 shows the entire structure on the recording side. Digital luminance signals Y and digital color difference signals formed from, for example, three primary color signals R, G, B from a color video camera are provided at input terminals indicated by 1Y, 1U, and 1V, respectively. The signals U and V are supplied.

In this case, the clock rate of each signal is D1.
It is the same as the frequency of each component signal of the format. That is, each sampling frequency is 1
3.5MHz and 6.75MHz, and these 1
The number of bits per sample is 8 bits.

Therefore, the data amount of the signals supplied to the input terminals 1Y, 1U, 1V is about 216 Mbps.
Becomes Effective information extraction circuit 2 for removing the blanking time data from this signal and extracting only the information of the effective area
The data amount is compressed to about 167 Mbps.

Then, the luminance signal Y of the output of the effective information extraction circuit 2 is supplied to the frequency conversion circuit 3, and the sampling frequency is converted from 13.5 MHz to 3/4 thereof. As the frequency conversion circuit 3, for example, a thinning filter is used so that aliasing distortion does not occur. The output signal of the frequency conversion circuit 3 is supplied to the blocking circuit 5, and the order of luminance data is converted into the order of blocks. The block forming circuit 5 is provided for the block encoding circuit 8 provided in the subsequent stage. FIG.
Shows the structure of a block as a unit of coding. This example
By dividing a screen that is a three-dimensional block and extends over two frames, as shown in FIG.
A large number of unit blocks of 4 pixels × 2 frames) are formed. In addition, in FIG. 4, a solid line indicates an odd field line, and a broken line indicates an even field line.

Of the outputs of the effective information extraction circuit 2,
The two color difference signals U and V are supplied to the sub-sampling and supply line 4, and the sampling frequencies are 6.
After being converted from 75 MHz to a half thereof, two digital color difference signals are selected line by line with each other and subjected to line-sequential digitization synthesis from the data sub-sampling and supply circuit 4 of one channel. Therefore, this color difference signal is obtained. FIG. 5 shows the pixel configuration of the signal that has been subsumed and sublined by the subsampling and subline circuit 4. In FIG. 5, ◯ indicates a sub-sampling pixel of the first color difference signal U, Δ indicates a sampling pixel of the second dye signal V, and x indicates a pixel position thinned by the sub-sample.

The line-sequential output signal from the sub-sampling and sub-line circuit 4 is supplied to the blocking circuit 6. In the blocking circuit 6, one blocking circuit 5
Similarly, the color difference data in the scanning order of the television signal is converted into the data in the block order. Like the one blocking circuit 5, the blocking circuit 6 converts the color difference data into a block structure of (4 lines × 4 pixels × 2 frames). The output signals of the blocking circuit 5 and the blocking circuit 6 are supplied to the synthesizing circuit 7.

In the synthesizing circuit 7, the luminance signal and chrominance signal converted in the order of blocks are converted into one-channel signals, and the output signal of this synthesizing circuit 7 is supplied to the block coding circuit 8. As the block coding circuit 8, as will be described later, a coding circuit (referred to as ADRC) adapted to the dynamic range of each block, a DCT (Disc).
A rete cosine transform circuit or the like can be applied. The output signal from the block encoding circuit 8 is further supplied to the framing circuit 9 and converted into frame structure data. In the framing circuit 9, switching between the pixel clock and the recording clock is performed.

Then, the output signal of the framing circuit 9 is supplied to the error correction code parity generation circuit 10 to generate the error correction code parity. The output signal of the parity generation circuit 10 is supplied to the channel encoder 11, and channel coding is performed so as to reduce the low frequency part of the recording data. Channel encoder 11
Output signal of the pair of magnetic heads 13 via recording amplifiers 12A and 12B and a rotary transformer (not shown).
It is supplied to A and 13B and recorded on the magnetic tape. The audio signal and the video signal are separately compression-coded and supplied to the channel encoder 11.

By the above-mentioned signal processing, the input data amount of 216 Mbps is reduced to about 167 Mbps by extracting only the effective scanning period, and further it is 84 Mbps by the frequency conversion, the sub-sample and the sub-line.
s. This data is the block coding circuit 8
The data is compressed and encoded to about 25 Mbps. Then, additional information such as parity and audio signal is added, and the recording data amount is 31.56 Mbps.
Becomes

Next, the structure on the reproducing side will be described with reference to FIG. At the time of reproduction, as shown in FIG. 3, reproduction data from the magnetic heads 13A and 13B is first supplied to the channel decoder 15 via the rotary transformer and the reproduction amplifiers 14A and 14B. Channel decoder 15
At, the channel coding is demodulated, and the output signal of the channel decoder 15 is supplied to the TBC circuit (time base correction circuit) 16. In this TBC circuit 16, the time-axis fluctuation component of the reproduction signal is removed. The reproduction data from the TBC circuit 16 is supplied to the ECC circuit 17,
Error correction and error correction using the error correction code are performed. The output signal of the ECC circuit 17 is the frame decomposition circuit 1
8 is supplied.

The frame decomposing circuit 18 separates each component of the block code or the data, and
The transfer from the block of the recording system to the clock of the pixel is performed. The respective data separated by the frame decomposing circuit 18 are supplied to the block decoding circuit 19, the restored data corresponding to the original data is decoded for each block, and the decoding data is supplied to the distribution circuit 20. The distribution circuit 20 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 21 and 22, respectively.

The block decomposing circuits 21 and 22 convert the decoding data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 5 and 6 on the transmitting side.

The decoded luminance signal from the block decomposition circuit 21 is supplied to the interpolation filter 23. In the interpolation filter 23, the sampling rate of the luminance signal is 3 fs to 4 fs.
(4 fs: 13.5 MHz). The digital luminance signal Y from the interpolation filter 23 is taken out to the output terminal 26Y.

On the other hand, the digital color difference signal from the block decomposition circuit 22 is supplied to the distribution circuit 24, and the line-sequential digital color difference signals U and V are separated into the digital color difference signals U and V, respectively. The digital color difference signals U and V from the distribution circuit 24 are supplied to the interpolation circuit 25 and are interpolated. The interpolation circuit 25 interpolates the data of the thinned lines and pixels by using the restored pixel data, and the sampling rate from the interpolation circuit 25 is 2f.
s digital color difference signals U and V are obtained and output terminal 2
6U and 26V are taken out respectively.

B. Block Coding As the block coding circuit 8 in FIG.
(Adaptive Dynamic Range Co
ding) encoder is used. The ADRC encoder detects the maximum value MAX and the minimum value MIN of a plurality of pixel data included in each block, and detects the maximum value MA.
The dynamic range DR of the block is detected from X and the minimum value MIN, the coding adapted to this dynamic range DR is performed, and the requantization is performed with the number of bits smaller than the number of bits of the original pixel data. As another example of the block encoding circuit 8, pixel data of each block is converted into DCT (Discrete Cosine Tran).
After sform), the coefficient data obtained by this 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 in which image quality deterioration does not occur even when multi-dubbing is performed will be described with reference to FIG.

In FIG. 6, a digital video signal (or digital color difference signal) in which one sample is quantized into 8 bits is input from the synthesizing circuit 7 to the input terminal 27. The blocked data from the input terminal 27 is the maximum value,
It is supplied to the minimum value detection circuit 29 and the delay circuit 30. The maximum value / minimum value detection circuit 29 determines the minimum value MI for each block.
N, maximum value MAX is detected. From the delay circuit 30, the input data is delayed for the time required to detect the maximum value and the minimum value. The pixel data from the delay circuit 30 is supplied to the comparison circuit 31 and the comparison circuit 32.

The maximum value MAX from the maximum / minimum value detection circuit 29 is supplied to the subtraction circuit 33, and the minimum value MIN is supplied to the addition circuit 34. The subtractor circuit 33 and the adder circuit 34 are supplied from the bit shift circuit 35 with a value of one quantization step width (Δ = 1 / 16DR) when non-edge matching quantization is performed with a fixed length of 4 bits. The bit shift circuit 35 is configured to shift the dynamic range DR by 4 bits so as to perform division by (1/16). The subtraction circuit 33 obtains a threshold value of (MAX-Δ), and the addition circuit 34 obtains a threshold value of (MIN + Δ). The threshold values from the subtraction circuit 33 and the addition circuit 34 are supplied to the comparison circuits 31 and 32, respectively. The value Δ defining this threshold is not limited to the quantization step width and may be a fixed value corresponding to the noise level.

The output signal of the comparison circuit 31 is the AND gate 3
6 and the output signal of the comparison circuit 32 is supplied to the AND gate 37. The input data from the delay circuit 30 is supplied to the AND gate 36 and the AND gate 37. The output signal of the comparison circuit 31 becomes high level when the input data is larger than the threshold value. Therefore, the output terminal of the AND gate 36 has the pixel data of the input data included in the maximum level range of (MAX to MAX-Δ). Is extracted. On the other hand, the output signal of the comparison circuit 32 becomes high level when the input data is smaller than the threshold value. Therefore, the output terminal of the AND gate 37 is (MIN to MIN).
Pixel data of the input data included in the minimum level range of + Δ) is extracted.

The output signal of the AND gate 36 is supplied to the averaging circuit 38, and the output signal of the AND gate 37 is supplied to the averaging circuit 39. These averaging circuits 38, 39
Is for calculating an average value for each block, and the reset signal of the block cycle is inputted from the terminal 40 to the averaging circuits 38, 39.
Is supplied to From the averaging circuit 38, (MAX ~
The average value MAX ′ of the pixel data belonging to the maximum level range of (MAX−Δ) is obtained, and the averaging circuit 39 outputs (MIN).
The average value MIN ′ of the pixel data belonging to the minimum level range of ˜MIN + Δ) is obtained. The subtraction circuit 41 subtracts the average value MIN ′ from the average value MAX ′.
From the dynamic range DR '.

Further, the average value MIN 'is supplied to the subtraction circuit 42, and the average value MIN' is subtracted from the input data passed through the delay circuit 43 in the subtraction circuit 42 to form the data PDI after removal of the minimum value. . The data PDI and the modified dynamic range DR ′ are used by the quantization circuit 44.
Is supplied to. In this embodiment, the number n of bits assigned to quantization is 0 bit (no code signal is transferred), 1 bit, 2 bits, 3 bits, or 4 bits, which is a variable-length ADRC. Matching quantization is performed. The allocated bit number n is determined for each block in the bit number determination circuit 45, and the data of the bit number n is supplied to the quantization circuit 44.

The variable length ADRC has a dynamic range D
Efficient encoding can be performed by reducing the number of allocated bits n in a block having a small R ′ and increasing the number of allocated bits n in a block having a large dynamic range DR ′. That is, the threshold values for determining the number of bits n are set to 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 Is (n = 4).

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

In the buffering circuit 46 which determines the threshold values T1 to T4 for making the generated information amount a predetermined value, a plurality of threshold value groups (T1, T2, T3, T4), for example, 3 are set.
Two sets are prepared, and these sets of thresholds are distinguished by the parameter code Pi (i = 0, 1, 2, ... 31). The generated information amount is set to monotonically decrease as the number i of the parameter code Pi increases. However, the quality of the restored image deteriorates as the amount of generated information decreases.

Threshold value T from buffering circuit 46
1 to T4 are supplied to the comparison circuit 47, and the dynamic range DR ′ through the delay circuit 48 is supplied to the comparison circuit 47. The delay circuit 48 delays DR ′ by the time required for the buffering circuit 46 to determine the set of threshold values. In the comparison circuit 47, the dynamic range DR ′ of the block is compared with the threshold value, the comparison output is supplied to the bit number determination circuit 45, and the allocated bit number n of the block is determined.

In the quantizing circuit 44, the data PDI after removal of the minimum value, which has passed through the delay circuit 49, is converted into the code signal DT by the edge matching quantization using the dynamic range DR ′ and the number of allocated bits n. It The quantization circuit 44 is composed of, for example, a ROM.

The modified dynamic range DR 'and average value MIN' are output via the delay circuits 48 and 50, respectively, and the parameter code Pi indicating the set of the code signal DT and the threshold value is output. In this example, the signal that has been non-edge-match quantized is edge-match quantized newly based on the dynamic range information, so that image deterioration when dubbing is small.

C. Channel Encoder and Channel Decoder Next, the channel encoder 11 and the channel decoder 15 of FIG. 3 will be described.

As shown in FIG. 7, the channel coder 11 is an adaptive scramble circuit to which the output of the parity generation circuit 10 is supplied, and a plurality of M-sequence scramble circuits 51 are prepared. On the other hand, the M series is selected so that an output with the least high frequency component and DC component can be obtained.

The precoder 52 for the partial response class 4 detection method performs arithmetic processing of 1 / 1-D ² (D is a unit delay circuit). This precoder 52
Is recorded and reproduced by the magnetic heads 13A and 13B via the recording amplifiers 12A and 13A, and the reproduced output is amplified by the reproducing amplifiers 14A and 14B.

On the other hand, in the channel decoder 15, as shown in FIG. 8, in the arithmetic processing circuit 53 on the reproducing side of the virtual response class 4, 1 + D arithmetic is applied to the reproducing amplifier 14A. 14B output. Also,
In the so-called Viterbi decoding circuit 54, the noise-resistant data is decoded by the deduction using the correlation and the certainty of the data with respect to the output of the arithmetic processing circuit 53. The output of the Viterbi decoding circuit 54 is supplied to the descrambling circuit 55, the data rearranged by the scrambling process on the recording side is returned to the original series, and the original data is restored. Compared to the case where the data rearranged by this process is subjected to bit-wise decoding by the Viterbi decoding circuit 54 used in the embodiment in the original series.
Improvement is performed with a reproduction C / N conversion of 3 dB.

D. As shown in FIG. 9, the traveling magnetic heads 13A and 13B are attached to the drum 76 in an integrated structure. A magnetic tape (not shown) is obliquely wound around the peripheral surface of the drum 76 at a winding angle slightly larger than 18 ° or slightly smaller than 18 °.
A and the magnetic head 13B are configured to scan the magnetic tape at the same time.

The directions of the gaps of the magnetic head 13A and the magnetic head 13B are inclined to the opposite sides (for example, the magnetic head 13A is inclined + 20 ° with respect to the track width direction, and the magnetic head 13B is inclined -20 °. Anyway)
It is set so that the amount of crosstalk between adjacent tracks is reduced by so-called azimuth loss during reproduction.

10 and 11 show magnetic heads 13A,
This shows a more specific structure when 13B is an integral structure (so-called double azimuth head). For example, the magnetic head 13 integral with the upper drum 76 rotated at a high speed.
A and 13B are attached, and the lower drum 77 is fixed. Here, the winding angle of the magnetic tape 78 is 166.
The drum diameter φ is 16.5 mm. Therefore, on the magnetic tape 78, one field of data is divided into five tracks and recorded. With this segment system, the length of the track can be shortened, and the error due to the linearity of the track can be reduced.

As described above, by performing the simultaneous recording with the double azimuth head, the error amount due to the linearity can be reduced as compared with the case where the pair of magnetic heads are arranged at the facing angle of 180 °. In addition, since the head-to-head distance is small, the pairing adjustment can be performed more accurately. Therefore, with such a traveling system, recording / reproducing can be performed on a narrow track.

[0090]

According to the method of manufacturing a magnetic recording medium of the present invention, Co is used as the vapor deposition source material, and the total content of C, Si, Mn, Al, and Ti contained in the vapor deposition source material is 0. By forming a ferromagnetic metal thin film on a non-magnetic support at a content of 2% by weight or less, the splash generated during vacuum deposition is suppressed, so that it is excellent in electromagnetic conversion characteristics and magnetic characteristics, and has a small error rate. A recording medium can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing one configuration of a vacuum vapor deposition device.

FIG. 2 is a block diagram showing a configuration on a recording side of a signal processing unit of a digital VTR that compresses and records a digital image signal in a form such that reproduction distortion is small.

FIG. 3 is a block diagram showing a configuration on a reproduction side of a signal processing unit.

FIG. 4 is a schematic diagram showing an example of a block for a block encoding circuit.

FIG. 5 is a schematic diagram for explaining subsampling and sublines.

FIG. 6 is a block diagram showing an example of a block encoding circuit.

FIG. 7 is a block diagram showing an outline of an example of a channel encoder.

FIG. 8 is a block diagram showing an outline of an example of a channel decoder.

FIG. 9 is a plan view schematically showing an example of the arrangement of magnetic heads.

FIG. 10 is a plan view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

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

[Explanation of symbols]

 1Y, 1U, 1V Component signal input terminals 5, 6 Blocking circuit 8 Block coding circuit 9 Metal magnetic material 11 Channel encoder 13A, 13B Magnetic head 22 Channel decoder 26 Block decoding circuit 28 Block decomposition circuit

Claims (2)

[Claims] 1. In a method for manufacturing a magnetic recording medium, wherein a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by vacuum evaporation, Co is used as an evaporation source material, and C contained in this evaporation source material is used. A method of manufacturing a magnetic recording medium, comprising: forming a ferromagnetic metal thin film on a non-magnetic support with the total content of Si, Mn, Al, and Ti being 0.2 wt% or less. 2. The method for producing a magnetic recording medium according to claim 1, wherein the vapor deposition source material is a material that has been once used for vacuum vapor deposition and recovered and redissolved.