JPH0589450A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic transducing characteristics while ensuring satisfactory durability. CONSTITUTION:When a magnetic layer consisting of plural magnetic thin films 2, 3 is formed on a nonmagnetic substrate 1 by vacuum deposition, the surface of the resulting magnetic thin film 2 or 3 is subjected to bombardment with inert gas contg. reducing gas to extremely reduce the thickness of an oxidized layer formed on the surface of the thin film 2 or 3 or to remove the oxidized layer. The inert gas used for bombardment is not especially limited but gaseous Ar is generally used as the inert gas. Gaseous H2 or acetylene may be used as the reducing gas introduced into the inert gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferromagnetic metal thin film type magnetic recording medium having a magnetic layer having a multilayer structure on a non-magnetic support.

[0002]

2. Description of the Related Art A so-called ferromagnetic metal thin film type magnetic recording medium having a magnetic layer of a continuous film of a metal or an alloy such as Co--Ni is excellent in coercive force, squareness ratio, etc. and has electromagnetic conversion characteristics in a short wavelength region. It is not only excellent in magnetic properties, but also the magnetic layer can be thinned so that the thickness loss during recording demagnetization and reproduction is extremely small, and it is not necessary to mix a binder that is a non-magnetic material into the magnetic layer. Therefore, it has a number of advantages such as high packing density of the magnetic material.

This ferromagnetic metal thin film type magnetic recording medium is
It is generally manufactured by a vacuum vapor deposition method, and for example, a so-called so-called vapor-deposited magnetic material is obliquely applied to a non-magnetic support that moves and runs in a predetermined direction along the outer peripheral surface of a cooling can. The oblique deposition method has been put to practical use.

When the magnetic layer of the magnetic recording medium is formed by such an oblique vapor deposition method, oxygen gas is introduced into the surface of the non-magnetic support during vapor deposition to improve the magnetic characteristics of the obtained magnetic film. Planning is taking place.

By the way, the electromagnetic conversion characteristics of this ferromagnetic metal thin film type magnetic recording medium generally have a residual magnetic flux density B.
It is known to be proportional to _r , saturation magnetization σ _s , and coercive force H _C. Therefore, for example, in a vapor deposition tape using a magnetic thin film having a composition of Co ₈₀ Ni ₂₀ (numerical value represents weight%) as a magnetic layer, the amount of Ni added can be reduced or the non-magnetic support as described above. It is possible to increase the residual magnetic flux density B _r and improve the electromagnetic conversion characteristics by decreasing the amount of oxygen gas introduced to the surface of the magnetic film and decreasing the amount of oxide on the surface of the obtained magnetic film. It is thought to be possible.

However, as shown in FIG. 3, when the flow rate of oxygen gas introduced to the surface of the non-magnetic support during vapor deposition is reduced, the still time tends to be shortened and durability deteriorates. Further, at this time, as shown in FIG. 4, although the output characteristics of the obtained magnetic film are improved with the decrease of the oxygen gas flow rate, the C / N characteristics are significantly deteriorated.

As a solution to this problem, generally, a method of forming a plurality of magnetic thin films on a non-magnetic support to form a multilayer magnetic layer is adopted. According to this method
It is possible to improve the residual magnetic flux density B _r and the coercive force H _C while ensuring good durability and C / N characteristics.

[0008]

A magnetic recording medium having a magnetic layer composed of a multilayer film as described above can be manufactured, for example, by repeatedly performing the oblique vapor deposition as described above. If oxygen gas is introduced into the surface of the non-magnetic support from the low incident angle side, an oxide layer (a film thickness of about 10% of the magnetic thin film) may be formed on the surface of each magnetic thin film. .. Therefore, when the magnetic thin films are laminated as described above, the intermediate oxide layer is interposed between the magnetic thin films.

However, when the intermediate oxide layer is interposed between the magnetic thin films as described above, the magnetic coupling between the magnetic thin films can be weakened. In addition, the energy product may decrease, and the electromagnetic conversion characteristics may deteriorate.

Further, the surface of the magnetic layer composed of the plurality of magnetic thin films, that is, the oxide layer formed on the surface of the magnetic thin film which is the uppermost layer of the magnetic thin films, improves the durability. Although it works effectively, if the film thickness becomes thick, it causes a spacing loss. Therefore, in a magnetic recording medium having such a multilayer structure, it is an important issue to maintain the balance between durability and electromagnetic conversion characteristics.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and an object thereof is to provide a magnetic recording medium excellent in durability and electromagnetic conversion characteristics.

[0012]

Means for Solving the Problems The inventors of the present invention have earnestly studied to achieve the above-mentioned object, and as a result, bombarded the surface of a magnetic thin film formed by a vacuum deposition method to obtain a surface of the magnetic thin film. It was found that good durability and electromagnetic conversion characteristics can be obtained by making the thickness of the oxide layer formed on the layer extremely thin or by removing this oxide layer,
The present invention has been completed.

That is, according to the present invention, in a magnetic recording medium in which a plurality of magnetic thin films are laminated on a non-magnetic support by a vacuum deposition method, the surface of the magnetic thin film is bombarded with an inert gas containing a reducing gas. It is characterized by being processed.

In the magnetic recording medium of the present invention, the magnetic layer has a multilayer structure composed of a plurality of magnetic thin films. The constituent material of the magnetic thin film forming the magnetic layer may be any magnetic material that is generally used, but a metal magnetic material is particularly preferable. In this case, as the metal magnetic material, any of those usually used in this kind of magnetic recording medium can be used.
Magnetic metals such as o and Ni, Fe-Co, Co-Ni, F
e-Co-Ni, Fe-Co-Cr, Co-Ni-C
r, Fe-Co-Ni-Cr, and the like.

In the present invention, a vacuum vapor deposition method is used as a method for forming the magnetic thin film made of these magnetic materials, and oblique vapor deposition is typically performed. Oblique vapor deposition means that the vapor flow of the magnetic material evaporated from the evaporation source is moved in a predetermined direction along the outer peripheral surface of the cooling can in a predetermined direction with respect to the normal direction of the surface of the non-magnetic support. This is a method in which the magnetic layer is made to enter from a direction forming the angle of incidence and is vapor-deposited on the non-magnetic support. By repeating this oblique vapor deposition, the magnetic layer having the above-mentioned multilayer structure can be obtained.

At the time of such vapor deposition, oxygen gas is introduced into the surface of the non-magnetic support during vapor deposition in order to improve the magnetic characteristics by incorporating oxygen into the magnetic thin film. Therefore, an oxide layer is formed on the surface of the obtained magnetic thin film, and when a magnetic thin film is further laminated on this magnetic thin film, an intermediate oxide layer is interposed between the magnetic thin films. Thus, when the intermediate oxide layer is interposed between the magnetic thin films, the residual magnetic flux density B _r of the magnetic layer is lowered.

On the other hand, in the present invention, the surface of the magnetic thin film is bombarded with an inert gas containing a reducing gas during vapor deposition. As a result, the oxide layer is thinned or removed.

Actually, the thickness of the oxide layer may be as small as several tens of liters. For example, the thickness of the oxide layer formed by vapor deposition is about 20 liters by a bombarding process. If the thickness of the magnetic layer is reduced, the residual magnetic flux density B _r of the magnetic layer can be improved, and the magnetic flux generated from the magnetic thin film below the laminated magnetic thin film can be prevented from decreasing. It can be improved significantly.

The inert gas used in this bombarding treatment is not particularly limited, but Ar gas or the like is generally used. In addition, examples of the reducing gas introduced into the inert gas include H ₂ gas and acetylene.

The conditions for such bombarding treatment can be expressed using a constant K given by the following equation (1).

[0021]

[Equation 1]

In the above formula (1), E represents the voltage applied to the electrode in the processing apparatus, and I represents the current value of the electrode.
Further, v represents the tape speed when passing through the processing device, and w represents the processing width of the magnetic tape on which the bombarding processing is performed.

Therefore, it is considered that K represents the processing capacity per unit area, and in the present invention, the voltage E and the current value I of the electrodes are appropriately selected so that the values are about 10 or more. Is desirable. By controlling the value of K within the above range, it is possible to improve electromagnetic conversion characteristics while ensuring durability.

In the magnetic recording medium of the present invention, the magnetic layer may have a two-layer structure or a multi-layer structure of three or more layers. In each case, the growth directions of the magnetic thin films forming the magnetic layer are the same (forward direction).
It may be formed so that it may be formed in the opposite direction (reverse direction).

As the non-magnetic support, any of those usually used in this kind of magnetic recording medium can be used. For example, a polyester resin such as polyethylene terephthalate, polyethylene-2,6-naphthalate or an aroma. Examples thereof include group polyamide films and polyimide resin films.

Further, in the present invention, if necessary,
A step of forming an undercoat film, a step of forming a back coat layer, a top coat layer, or the like on the substrate may be added. In this case, the film forming conditions for the undercoat film, the back coat layer, the top coat layer and the like are not particularly limited as long as they are the methods usually applied to the manufacturing method of this type of magnetic recording medium.

[0027]

In order to improve the magnetic characteristics of the magnetic thin film by incorporating oxygen into the obtained magnetic thin film, when the magnetic material is vapor-deposited while introducing oxygen gas on the surface of the non-magnetic support, An oxide layer is formed on the surface of the thin film. When a magnetic thin film is further laminated on the magnetic thin film via this oxide layer, an intermediate oxide layer is interposed between these magnetic thin films, and magnetic coupling between the magnetic thin films can be weakened.

However, in reality, the film thickness of the intermediate oxide layer is
Is a few tens of liters at most, and if it is too thick, on the contrary
Energy product decreases, causing electromagnetic conversion characteristics to deteriorate.
become. Therefore, as in the present invention, the magnetic thin film is deposited during vapor deposition.
By subjecting the surface of the film to bombardment, the above-mentioned oxide layer
Is thinned or removed, the residual magnetic flux density B of the magnetic layer is
_rOf the magnetic thin film under the magnetic thin film
The decrease in magnetic flux coming out of the film is prevented, and the electromagnetic conversion characteristics are
The property is improved.

[0029]

EXAMPLES Examples of magnetic recording media to which the present invention is applied will be specifically described below. As shown in FIG. 1, the magnetic tape of this example has a first magnetic thin film 2 and a second magnetic thin film 2 formed on one main surface of a non-magnetic support 1 made of polyethylene terephthalate.
The magnetic layer having a two-layer structure composed of the magnetic thin film 3 is formed.

On one main surface of the non-magnetic support 1,
A coating film of acrylic acid ester-based polymer latex is formed as an undercoat film of the first magnetic thin film 2,
The first magnetic thin film 2 is formed on the non-magnetic support 1 via the undercoat film. This undercoat film has an average particle size of 4
It contains fine particles of 00Å.
It is formed so as to exist at a rate of 10,000 pieces / mm ² .

A first magnetic thin film 2 is formed on the undercoat film, and a second magnetic thin film 3 is formed on the first magnetic thin film 2.
Are stacked. The first magnetic thin film 2 and the second magnetic thin film 3 are obtained by the oblique vapor deposition method and are formed so that their growth directions are the same direction (forward direction). These first magnetic thin film 2 and second magnetic thin film 3
The film thickness of each is 1000 Å.

Here, the surface of the first magnetic thin film 2 is
This first magnetic thin film 2 is in a partially oxidized state.
And a second magnetic thin film 3 laminated on the first magnetic thin film 2.
And are magnetically divided. Such an oxidized state of the surface of the first magnetic thin film 2 can be realized by introducing oxygen gas into the atmosphere during oblique vapor deposition.

The surface of the first magnetic thin film 2 as described above is subjected to a bombarding treatment during vapor deposition as described later. As a result, the film thickness of the oxide layer formed on the first magnetic thin film 2 during oblique deposition is reduced or removed, and deterioration of the electromagnetic conversion characteristics of the magnetic layer due to the oxide layer is prevented.

Further, a top coat film 4 made of perfluoropolyether is formed on the second magnetic thin film 3. On the other hand, a back coat layer 5 made of carbon or urethane is formed on the other main surface of the non-magnetic support 1.

The magnetic tape having such a structure can be manufactured by using a manufacturing apparatus having the following structure.

In this manufacturing apparatus, as shown in FIG. 2, a counterclockwise in the figure is placed in a vacuum chamber 11 which is evacuated from the exhaust ports 23 provided in the head and the bottom to make the inside a vacuum state. A feed roll 13 that rotates at a constant speed in the rotating direction
A winding roll 14 that rotates at a constant speed in the clockwise direction in the drawing is provided.
The tape-shaped non-magnetic support 12 is sequentially run on the magnetic recording medium 4.

From the feed roll 13 to the take-up roll 1
A cooling can 15 having a diameter larger than the diameter of each of the rolls 13 and 14 is provided in the middle of the nonmagnetic support 12 on the fourth side. The cooling can 15 is provided so as to pull out the non-magnetic support 12 downward in the figure, and is configured to rotate at a constant speed in the clockwise direction in the figure.
The feed roll 13, the take-up roll 14 and the cooling can 15 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support 12, and inside the cooling can 15, A cooling device (not shown) is provided,
The nonmagnetic support 12 can be prevented from being deformed due to a temperature rise.

Therefore, the non-magnetic support 12 is sequentially fed from the feed roll 13, and the cooling can 1 is further fed.
It passes through the peripheral surface of No. 5, and is wound up by the winding roll 14. A guide roll 16 is provided between the feed roll 13 and the cooling can 15, and a guide roll 16 is provided between the cooling can 15 and the take-up roll 14.
17 is provided, and the cooling can 1 is fed from the feed roll 13
5 and a predetermined tension is applied to the non-magnetic support 12 running from the cooling can 15 to the winding roll 14,
The non-magnetic support 12 is designed to run smoothly.

A crucible 18 is provided in the vacuum chamber 11 below the cooling can 15.
8 is filled with a metal magnetic material (Co ₈₀ Ni ₂₀ ) 19. The crucible 18 has a width substantially the same as the width of the cooling can 15.

An electron gun 20 for heating and evaporating the metallic magnetic material 19 filled in the crucible 18 is attached to the side wall of the vacuum chamber 11. This electron gun 2
0 is arranged at a position where the electron beam X emitted from the electron gun 20 irradiates the metallic magnetic material 19 in the crucible 18. The metal magnetic material 19 evaporated by the electron gun 20 is deposited and formed as a magnetic layer on the non-magnetic support 12 that runs at a constant speed on the peripheral surface of the cooling can 15.

In the vicinity of the cooling can 15,
A shutter 22 is arranged along the peripheral surface of the cooling can 15. As a result, a part of the surface of the non-magnetic support 12 is covered, so that the incident angle of the evaporated metal magnetic material 19 on the surface of the non-magnetic support 12 can be regulated.

Therefore, in such a manufacturing apparatus,
The metallic magnetic material 19 filled in the crucible 18 is
It is heated and evaporated by the electron gun 20, and the cooling can 15
It is attached to the non-magnetic support 12 traveling on the peripheral surface.
The non-magnetic support 12 is attached to one end of the shutter 22
The end of the magnetic support 12 on the delivery side) 13a is covered.
In the region up to the point of time when the non-magnetic support 12 is vaporized.
Metal magnetic material that has been deposited and evaporated at this point
Incident angle θ of 19 with respect to the non-magnetic support 12 ₁Is the lowest
It is designed to be a value.

A partition plate 21 is provided in the vacuum chamber 11 so as to separate the lower side and the upper side of the cooling can 15. Thereby, the feed roll 1
The non-magnetic support 12 delivered from the partition 3 is the partition plate 2
The vapor deposition is carried out from the point of time when the non-magnetic support 1 of the vaporized metal magnetic material 19 is passed.
The incident angle θ ₂ with respect to ₂ has a maximum value. Further, by providing such a partition plate 21, the evaporated metal magnetic material 19 is prevented from diffusing above the partition plate 21, so that the vapor deposition efficiency is improved.

Further, an oxygen gas inlet 28 is provided in the side wall of the vacuum chamber 11 so as to penetrate the side wall of the vacuum chamber 11, and non-magnetic support is provided through the oxygen gas inlet 28 during vapor deposition. Oxygen gas is supplied to the surface of the body 12. As a result, oxygen is taken into the obtained magnetic thin film to improve the magnetic characteristics.

In this manufacturing apparatus, the guide rolls 1 on the feeding side and the winding side of the non-magnetic support 12 are also provided.
Processing devices 24 and 25 are provided in the middle of the cooling can 15 and 6, 17 respectively.

These processing devices 24 and 25 are provided to perform the bombarding treatment on the surface of the non-magnetic support 12 and the surface of the magnetic thin film formed by the oblique deposition as described above, respectively. Before and after the formation of the magnetic tape, the magnetic tape on which the non-magnetic support 12 and the magnetic thin film are formed passes through the processing devices 24 and 25, and on the surfaces of the non-magnetic support 12 and the magnetic thin film. It is configured to be bombarded.

Therefore, the non-magnetic support 12 sent out from the feed roll 13 passes through the inside of the processing device 24, runs on the peripheral surface of the cooling can 15, and further passes through the inside of the processing device 25. And is wound around the winding roll 14.

The processing devices 24 and 25 have inlets 24a and 25a and outlets 24b and 25 through which the magnetic tape on which the non-magnetic support 12 and the magnetic thin film are formed pass.
b are provided respectively, and these entrances 24a, 25
The surface of the magnetic tape on which the non-magnetic support 12 and the magnetic thin film have been formed is subjected to a bombarding treatment between the time of intervention from a into the processing device 24, 25 to the outlet 24b, 25b. To be done. By performing such a bombarding treatment, the oxide layer formed on the non-magnetic support 12 or on the magnetic thin film obtained by vapor deposition is thinned or removed, so that the oxide layer is removed. The deterioration of the electromagnetic conversion characteristics due to the presence of is prevented.

In the processing device 24 (or the processing device 25), a pair of rod-shaped electrodes 26, 26 (or electrodes 27, 2) are provided via the non-magnetic support 12 (or the magnetic tape).
7) is provided and discharge is generated between these electrodes 26, 26 (or electrodes 27, 27).
As the electrodes 26, 26 (or the electrodes 27, 27), either a DC type or an AC type can be used.

Further, in these processing devices 24 and 25,
An inert gas containing an inert gas or a reducing gas is introduced,
The electrodes 26, 26 (or the electrodes 27, 27) are water-cooled.

According to this processing apparatus, in addition to the surface of the magnetic thin film obtained by oblique vapor deposition as described above, the surface of the non-magnetic support 12 is also subjected to the bombarding treatment. It suffices that the surface of the magnetic thin film be bombarded, and the bombarding of the surface of the nonmagnetic support 12 may be omitted.

Therefore, various magnetic tapes were manufactured by using the above manufacturing apparatus according to the following procedure. Example 1 An acrylic ester polymer latex (average particle size 400Å) was applied to one main surface of a 10 μm thick polyethylene terephthalate film so that the amount was 10 million pieces / mm ² to form an undercoat film.

Next, using a Co ₈₀ Ni ₂₀ alloy (numerical values represent composition ratios) as the metallic magnetic material, a polyethylene terephthalate film having the above-mentioned undercoat film was formed to 30 m.
At the same time as running at a tape speed of / min, oblique vapor deposition was performed in vacuum while introducing oxygen gas to form a first magnetic thin film on the polyethylene terephthalate film so that the film thickness was 1000Å.

At this time, the amount of oxygen gas introduced was 200 cc /
The incident angle of the evaporated metal magnetic material with respect to the surface of the polyethylene terephthalate film was changed in the range of 45 to 90 °.

Further, during such vapor deposition, the surface of the polyethylene terephthalate film and the surface of the obtained first magnetic thin film were bombarded. The conditions of this bombarding treatment are as follows: on the surface of the polyethylene terephthalate film, the voltage of the electrode is 500 V and the current is 0.2 A in an Ar gas atmosphere, and on the surface of the first magnetic thin film, 5% H 2 Ar containing ₂ gases
In a gas atmosphere, the voltage of the electrode is 500 V and the current is 0.
3A.

Then, after rewinding the polyethylene terephthalate film wound on the winding roll, the film thickness is 1000Å in the same manner as the first magnetic thin film.
Then, the second magnetic thin film was formed so that the surface of the obtained second magnetic thin film was bombarded. The conditions of this bombarding treatment were the same as those applied to the surface of the polyethylene terephthalate film.

After such vapor deposition, a back coat layer made of carbon or urethane and a top coat layer using perfluoropolyether were formed on the obtained magnetic tape, and the magnetic tape was cut into a width of 8 mm. ..

Example 2 When the surface of the first magnetic thin film in Example 1 was bombarded, the treatment was carried out in an Ar gas atmosphere containing 5% H ₂ gas containing 4% acetylene. Ar to
A magnetic tape was produced in the same manner as in Example 1 except that the gas atmosphere was changed.

Example 3 When the surface of the first magnetic thin film in Example 1 was bombarded, the voltage of the electrode was set to 500 V and the current was set to 0.3 A. 05
A magnetic tape was produced in the same manner as in Example 1 except for A.

Example 4 When the surface of the first magnetic thin film in Example 1 was bombarded, the voltage of the electrode was set to 500 V and the current was set to 0.3 A. 9A
A magnetic tape was manufactured in the same manner as in Example 1 except for the above.

Comparative Example When the surface of the first magnetic thin film in Example 1 was bombarded, it was carried out in an Ar gas atmosphere containing 5% H ₂ gas by using Ar containing no reducing gas. A magnetic tape was produced in the same manner as in Example 1 except that the gas atmosphere was changed.

For each magnetic tape thus obtained, 0.5 according to the product name EVS-900 manufactured by Sony Corporation
The reproduction output, C / N, and error rate at a wavelength of 4 μm were measured. The results are shown in Table 1. In addition,
In Table 1, the value of the constant K (see the above formula (1)) indicating the processing capacity when the surface of the first magnetic thin film in each magnetic tape is subjected to the bombarding treatment is also shown.

[0063]

[Table 1]

As shown in Table 1, in Examples 1 to 4, it was found that the reproduction output and C / N were higher and the error rate was reduced as compared with the comparative example. Therefore, it was found that by performing the above-mentioned bombarding treatment during vapor deposition, good durability can be obtained and electromagnetic conversion characteristics can be improved.

However, if the value of the constant K in the bombarding process is small as in Example 3, the reproduction output, C / N, or error rate could not be sufficiently improved.
From this, it can be said that the value of the constant K in the bombarding process is desirably set to about 10 or more.

When the magnetic recording medium of the present invention as described above is applied to the following system, the energy product becomes small, the error rate is suppressed, and good results can be expected.

A. From the structure of the recording / reproducing apparatus, a digital VTR for digitizing a video signal and recording it on a recording medium such as a magnetic tape is a D1 format component type digital VT for a broadcasting station.
R and D2 format composite type digital V
TR has been put to 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 record it on a magnetic tape.

In any case, these digital VTs are
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 into, for example, 8 bits is substantially compressed. It is designed to record without doing anything. Therefore, for example, a D1 format digital VTR can obtain a reproduction time of at most about 1.5 hours even if a large cassette tape is used, which is unsuitable for use as a VTR for general household use.

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 the method of compressing the recorded information in such a way that there is little reproduction distortion, recording / reproducing for a long time even when using a narrow magnetic tape with a tape width of 8 mm or less Shall be applied to a digital VTR capable of

The structure of this digital VTR will be described below.

A. Signal Processing Unit First, the signal processing unit of the digital VTR used in this embodiment will be described. FIG. 5 shows the entire configuration on the recording side. The input terminals indicated by 1Y, 1U, and 1V are provided with three primary color signals R from a color video camera,
A digital luminance signal Y formed from G and B and 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 of the D1 format. That is, the respective sampling frequencies are 13.5 MHz and 6.75 MHz, and the number of bits per sample is 8 bits. Therefore, the input terminals 31Y, 31
The data amount of the signal supplied to U and 31V is about 2
It will be 16 Mbps. The amount of data is about 167 Mbps by the effective information extraction circuit 32 which removes the blanking time data from this signal and extracts only the information of the effective area.
Is compressed into.

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 so that aliasing distortion does not occur. The output signal of this 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 blocks. The block forming circuit 35 is provided for the block encoding circuit 38 provided in the subsequent stage.

FIG. 7 shows the structure of a block as a unit of coding. This example is a three-dimensional block, and for example, by dividing a screen across two frames, a large number of unit blocks of (4 lines × 4 pixels × 2 frames) are formed as shown in FIG. In addition, in FIG. 7, 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 32, two color difference signals U and V are supplied to the sub-sampling and sub-line circuit 34, and the sampling frequency is converted from 6.75 MHz to half thereof, and then 2 Two digital color difference signals are selected for each line,
Combined with channel data. Therefore, the line sampling digital color difference signal is obtained from the subsampling and subline circuit 34. FIG. 8 shows a pixel configuration of a signal subsampled and sublined by the subsampling and subline circuit 34. In FIG. 8, ∘ 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 34 is supplied to the blocking circuit 36. Similar to the one blocking circuit 35, the blocking circuit 36 converts color difference data in the scanning order of the television signal into data in the block order. This blocking circuit 36, like one blocking circuit 35, outputs color difference data (4 lines × 4 pixels × 2 frames).
Convert to the block structure. The output signals of the blocking circuits 35 and 36 are combined circuits 3
7 is supplied.

In the synthesizing circuit 37, the luminance signal and chrominance signal converted in the order of blocks are converted into 1-channel data, and the output signal of the synthesizing circuit 37 is supplied to the block coding circuit 38. As the block coding circuit 38, as will be described later, a coding circuit (referred to as ADRC) adapted to the dynamic range of each block, DCT.
(Discrete Cosine Transform)
m) A circuit or the like can be applied. The block coding circuit 38
The output signal from is further supplied to the framing circuit 39 and converted into data having a frame structure. In the framing circuit 39, the pixel system clock and the recording system clock are changed.

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

By the above-described 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 reduced to 84 Mbps by the frequency conversion, the sub-sample and the sub-line. This data is compressed and coded by the block coding circuit 38 to about 25 Mbps, and thereafter, 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. 6, first, reproduction data from the magnetic heads 43A and 43B is 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 the TBC circuit (time axis correction circuit) 46. In this 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 using the error correction code and error correction are performed. The output signal of the ECC circuit 47 is supplied to the frame decomposition circuit 48.

The frame decomposing circuit 48 separates each component of the block coded data from each other, and
The clock of the recording system is changed to the clock of the pixel system. The respective data separated by the frame decomposing circuit 48 are supplied to the block decoding circuit 49, the restored data corresponding to the original data is decoded in each block unit, and the decoding data is supplied to the distribution circuit 50. The 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 decoding data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 35 and 36 on the transmitting 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 3 fs to 4 fs.
(4fs = 13.5 MHz). The digital luminance signal Y from the interpolation filter 53 is taken out to the output terminal 56Y.

On the other hand, the digital color difference signal from the block decomposition circuit 52 is supplied to the distribution circuit 54, 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 54 are supplied to the interpolation circuit 55 and are interpolated. The interpolation circuit 55 interpolates the data of the thinned lines and pixels using the restored pixel data, and the sampling rate from the interpolation circuit 55 is 2f.
s digital color difference signals U and V are obtained, and output terminal 5
6U and 56V are taken out respectively.

B. Block Coding As the block coding circuit 38 in FIG.
C (Adaptive Dynamic Range C
oding) encoder is used. This ADRC encoder detects the maximum value MAX and the minimum value MIN of a plurality of pixel data included in each block, and the maximum value M
The dynamic range DR of the block is detected from the AX 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 38, pixel data of each block may be converted into DCT (Discrete Cosine Tr).
After the transformation, 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. 9, for example, a digital video signal (or digital color difference signal) in which one sample is quantized into 8 bits is input to the input terminal 57 from the synthesizing circuit 37 of FIG. The 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 determines the minimum value MIN and the maximum value MA for each block.
Detect X. From the delay circuit 60, 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 60 is supplied to the comparison circuit 61 and the comparison circuit 62.

The maximum value MAX from the maximum / minimum value detection circuit 59 is supplied to the subtraction circuit 63, and the minimum value MIN is supplied to the addition circuit 64. The subtraction circuit 63 and the addition circuit 64 are supplied from the bit shift circuit 65 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 65 is configured to shift the dynamic range DR by 4 bits so as to perform division by (1/16). The subtraction circuit 63 obtains a threshold value of (MAX-Δ), and the addition circuit 64 obtains a threshold value of (MIN + Δ). The threshold values from the subtraction circuit 63 and the addition circuit 64 are supplied to the comparison circuits 61 and 62, respectively. The value Δ that defines this threshold is not limited to the quantization step width, and may be a fixed value that corresponds to the noise level.

The output signal of the comparison circuit 61 is the AND gate 6
6 and the output signal of the comparison circuit 62 is supplied to the AND gate 67. The 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 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 62 becomes high level when the input data is smaller than the threshold value. Therefore, the output terminal of the AND gate 67 has
The pixel data of the input data included in the minimum level range of + Δ) is extracted.

The output signal of the AND gate 66 is supplied to the averaging circuit 68, and the output signal of the AND gate 67 is supplied to the averaging circuit 69. These averaging circuits 68, 69
Is for calculating an average value for each block.
Is being supplied to. From the averaging circuit 68, (MAX ~
The average value MAX ′ of the pixel data belonging to the maximum level range of (MAX−Δ) is obtained, and the averaging circuit 69 outputs (MIN).
The average value MIN ′ of the pixel data belonging to the minimum level range of ˜MIN + Δ) is obtained. The subtraction circuit 71 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 72, and the average value MIN' is subtracted from the input data passed through the delay circuit 73 in the subtraction circuit 72 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 74.
Is supplied to. In this embodiment, the number of bits n assigned to quantization is 0 bit (code signal is not transferred),
It is a variable length ADRC of 1 bit, 2 bits, 3 bits, or 4 bits, and is subjected to edge matching quantization. The number of allocated bits n is determined by the number-of-bits determination circuit 75 for each block, and the data of the number of bits n is supplied to the quantization circuit 74.

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 (n = 2), the block of (T3 ≦ DR ′ <T4) is (n = 3), and the block of (DR ′ ≧ T4) is The block 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 set to a predetermined value.

In the buffering circuit 76 for determining the threshold values T1 to T4 for making the generated information amount a predetermined value, a plurality of threshold value sets (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 76
1 to T4 are supplied to the comparison circuit 77, and the dynamic range DR ′ through 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 threshold values. In the comparison circuit 77, the dynamic range DR ′ of the block is compared with each threshold value, the comparison output is supplied to the bit number determination circuit 75, and the number of allocated bits n of the block is determined. In the quantization circuit 74, the data PDI after removal of the minimum value via the delay circuit 79 is converted into the code signal DT by the edge matching quantization using the dynamic range DR ′ and the assigned bit number n. The quantization circuit 74 is composed of, for example, a ROM.

The modified dynamic range DR 'and average value MIN' are output through the delay circuits 78 and 80, respectively, and the parameter code Pi indicating the set of the code signal DT and the threshold value is output. In this example, a signal that has been non-edge-match quantized is newly edge-match quantized based on the dynamic range information, so that image degradation when dubbing is small.

C. Channel Encoder and Channel Decoder Next, the channel encoder 41 and the channel decoder 45 of FIG. 5 will be described. In the channel encoder 41, as shown in FIG. 10, an adaptive scramble circuit to which the output of the parity generation circuit 40 is supplied,
A plurality of M-sequence scramble circuits 81 are prepared, and among them, the M-sequence is selected so that an output with the least high frequency component and DC component can be obtained for the input signal. The precoder 82 for the partial response class 4 detection method performs arithmetic processing of 1 / 1-D ² (D is a unit delay circuit). This precoder 82
Is output and recorded and reproduced by the magnetic heads 43A and 43B via the recording amplifiers 42A and 42B, and the reproduction output is amplified by the reproduction amplifiers 44A and 44B.

On the other hand, in the channel decoder 45, as shown in FIG. 11, the arithmetic processing circuit 83 on the reproducing side of the partial response class 4 performs 1 + D arithmetic on the outputs of the reproducing amplifiers 44A and 44B. Further, in the so-called Viterbi decoding circuit 84, the noise-resistant data is decoded by the calculation using the correlation and the accuracy of the data with respect to the output of the calculation processing circuit 83. The output of the Viterbi decoding circuit 84 is supplied to the descrambling circuit 85, the data rearranged by the scrambling process on the recording side is returned to the original series, and the original data is restored. With the Viterbi decoding circuit 84 used in this embodiment, the reproduction C / N conversion is improved by 3 dB as compared with the case of performing decoding for each bit.

D. The traveling magnetic heads 43A and 43B are attached to the drum 106 in an integrated structure as shown in FIG. A magnetic tape (not shown) is obliquely wound around the peripheral surface of the drum 106 at a winding angle slightly larger than 180 ° or slightly smaller than 180 °, and the magnetic heads 43A and 43B simultaneously scan the magnetic tape. To be configured.

Further, the directions of the gaps of the magnetic head 43A and the magnetic head 43B are inclined in opposite directions (for example, the magnetic head 43A is inclined + 20 ° with respect to the track width direction, and the magnetic head 43B is inclined -20 °. Are set so that the amount of crosstalk between adjacent tracks is reduced by so-called azimuth loss during reproduction.

13 and 14 show magnetic heads 43A,
This shows a more specific structure when 43B is an integral structure (so-called double azimuth head). For example, the magnetic head 4 is integral with the upper drum 106 rotated at a high speed.
3A and 43B are attached, and the lower drum 107 is fixed. Here, the winding angle θ of the magnetic tape 108
Is 166 ° and the drum diameter φ is 16.5 mm.

Therefore, on the magnetic tape 108, 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 by 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.

[0103]

As is clear from the above description, in the present invention, since the surface of the magnetic thin film obtained is subjected to the bombarding treatment during the vapor deposition for forming the magnetic layer, it is formed on the surface of the magnetic thin film. The thickness of the oxide layer is reduced,
Or removed. Therefore, even if the magnetic thin film is laminated repeatedly by further vapor deposition on the magnetic thin film, the adverse effect of the oxide layer can be prevented, good durability can be ensured, and electromagnetic conversion characteristics can be improved. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic view showing an example of a manufacturing apparatus used when manufacturing the magnetic recording medium of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the oxygen gas flow rate during vapor deposition and the still time of the magnetic layer obtained by this vapor deposition.

FIG. 4 is a characteristic diagram showing an oxygen gas flow rate during vapor deposition, output characteristics and C / N characteristics of a magnetic layer obtained by this vapor deposition.

FIG. 5 is a block diagram showing a configuration on a recording side of a signal processing unit of a digital VTR which compresses and records a digital image signal in a form such that reproduction distortion is small.

FIG. 6 is a block diagram showing a configuration on a reproduction side of a signal processing unit.

FIG. 7 is a schematic diagram showing an example of a block for block coding.

FIG. 8 is a schematic diagram for explaining subsampling and sublines.

FIG. 9 is a block diagram showing an example of a block encoding circuit.

FIG. 10 is a block diagram showing an outline of an example of a channel encoder.

FIG. 11 is a block diagram showing an outline of an example of a channel decoder.

FIG. 12 is a plan view schematically showing an example of the arrangement of magnetic heads.

FIG. 13 is a plan view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

FIG. 14 is a front view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

[Explanation of symbols]

 1, 12 ... Non-magnetic support 2 ... First magnetic thin film 3 ... Second magnetic thin film 4 ... Top coat film 5 ... Back coat layer 15 ... Cooling can 18. ..Crucible 19 ... Metal magnetic material 20 ... Electron gun 22 ... Shutter 24,25 ... Processing device

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yukari Yamada 6-5-6 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Magne Products Co., Ltd.

Claims (1)

[Claims] 1. A magnetic recording medium in which a plurality of magnetic thin films are laminated on a non-magnetic support by a vacuum deposition method, at least the surface of the lower magnetic thin film is bombarded with an inert gas containing a reducing gas. A magnetic recording medium characterized by the following.