JPH05174355A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics and to obtain high reproduced outputs. CONSTITUTION:The inclination of the column structures of respective magnetic thin films is so controlled that the inclination alphan ((n) is >=2 natural number) of the axis of easy magnetization of the magnetic thin film on the upper side of the magnetic recording medium constituted by providing a magnetic layer 3 consisting of the plural magnetic thin films 2a, (b) by a vacuum vapor deposition method on a nonmagnetic base 1 is larger than the inclination alphan-1 of the axis of easy magnetization of the magnetic thin film on the lower layer side. Plural crucibles are used at the time of forming the magnetic layer in order to control the inclination of the column structures of the respective magnetic thin films in such a manner. These crucibles are disposed by shifting the crucibles in the traveling direction of the nonmagnetic base. As a result, the incident angles of the magnetic materials evaporated from the respective crusibles to the surface of the magnetic base vary according to the positions of the crucibles. The direction of the crystal growth of the resulted magnetic thin films is thus controlled.

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 forming the magnetic layer of the magnetic recording medium by such an oblique vapor deposition method, in order to regulate the incident angle of the magnetic material with respect to the non-magnetic support, in the vicinity of the cooling can, the outer circumference of the cooling can is provided. A mask is arranged along the surface, and oxygen gas is introduced to the surface of the nonmagnetic support from near the position where the mask is arranged. As a result, an oxide layer is formed on the obtained magnetic film, and the oxide layer functions as a protective film to impart durability, and at the same time, oxygen is taken into the above-mentioned magnetic film to form crystal grains. Are miniaturized, and the magnetic characteristics are improved.

In the meantime, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, in order to improve electromagnetic conversion characteristics,
A method has been proposed in which a plurality of magnetic thin films are laminated on a nonmagnetic support to form a multilayer magnetic layer. According to this method, the crystal grains forming the magnetic thin film become small, noise is reduced, and good residual magnetic flux density B _r and coercive force H _C are obtained, and electromagnetic conversion characteristics can be improved. it can.

[0005]

However, conventionally, in a magnetic layer having a multilayer structure as described above, when the magnetic thin films are formed so that the inclination directions of the easy axes of magnetization are the same (forward direction). Are formed, for example, by repeating the same vapor deposition process. For this reason, it is necessary to rewind the wound tape after vapor deposition is performed once and before vapor deposition is performed again, which causes a problem of poor productivity.

Further, in this case, since oxygen gas is introduced into the surface of the non-magnetic support during vapor deposition as described above, an oxide layer is formed on the surface of the obtained magnetic thin film, and this oxide layer is formed. When a magnetic thin film is further laminated on the magnetic thin film,
An intermediate oxide layer is interposed between these magnetic thin films. As a result, the magnetic coupling between the magnetic thin films is weakened and the noise characteristic is improved, but on the contrary, the output characteristic is deteriorated due to the reduction of the energy product.

Further, in order to obtain a high output, it is originally desirable that the upper magnetic thin film on which the recording signal in the short wavelength region is recorded has many vertical components, and the recording signal in the long wavelength region is desired. It is desirable that the lower layer side on which is recorded has many longitudinal components. However, as shown in FIG. 13, when the magnetic layer 23 is formed on the non-magnetic support 21 by repeated oblique vapor deposition as described above, the inclination directions of the easy axes of magnetization of the respective magnetic thin films 22 are the same. In addition, it is difficult to secure excellent output characteristics in both the short wavelength region and the long wavelength region.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and has a good electromagnetic conversion characteristic,
It is an object of the present invention to provide a magnetic recording medium capable of achieving high output and a manufacturing method thereof.

[0009]

Means for Solving the Problems As a result of earnest studies that the above-mentioned objects cannot be achieved, the present inventors have arranged a plurality of crucibles staggered in the running direction of the non-magnetic support and vaporized from each crucible. By making the incident angle of the magnetic material to the surface of the non-magnetic support different, it is possible to form a magnetic layer composed of a plurality of magnetic thin films by one vapor deposition,
Moreover, they have found that the inclination of the easy axis of magnetization of these magnetic thin films can be well controlled, and have completed the present invention.

That is, the first invention of the present application is a magnetic recording medium in which a plurality of magnetic thin films are laminated and formed on a non-magnetic support by a vacuum deposition method.
Between the gradient α _{n of the} easy axis of magnetization of the magnetic thin film of the first layer and the gradient α _n-1 of the axis of easy magnetization of the magnetic thin film of the (n-1) th layer, α _n-1 <α _n (n is 2 or more) Is a natural number).

A second invention of the present application is to provide a plurality of crucibles when laminating a plurality of magnetic thin films on a non-magnetic support by a vacuum vapor deposition method, and to evaporate the magnetic material from these crucibles. The angle of incidence with respect to the surface of the non-magnetic support is different depending on the position of the crucible.

In the magnetic recording medium of the first invention of the present application, the magnetic layer is composed of a plurality of magnetic thin films. The magnetic thin films are formed so that the inclination directions of the respective easy axes of magnetization are the same, and the inclination of the easy axes of magnetization of the upper magnetic thin film is larger than that of the lower magnetic thin film. It As a result, the magnetic thin film on the upper layer side where the recording signal in the short wavelength region is recorded has many vertical components,
Since the magnetic thin film on the lower layer side where the recording signal in the long wavelength region is recorded has many components in the longitudinal direction, the signal can be recorded according to the recording depth, and the high output in both the short wavelength region and the long wavelength region. Can be obtained.

As a constituent material of the magnetic thin film constituting the magnetic layer, any magnetic material which is generally used may be used, but a metal magnetic material is particularly preferable. In this case, as the metallic magnetic material, any of those usually used in this kind of magnetic recording medium can be used. Specifically, magnetic metals such as Fe, Co and Ni, and Fe-C can be used.
o, Co-Ni, Fe-Co-Ni, Fe-Co-C
r, Co-Ni-Cr, Fe-Co-Ni-Cr, etc. are mentioned.

As a method of forming the magnetic thin film made of these magnetic materials, a vacuum vapor deposition method is used, and an oblique vapor deposition method is typically adopted. The oblique vapor deposition method is a method in which a vapor flow of the magnetic material vaporized from the evaporation source is moved in a predetermined direction along the outer peripheral surface of the cooling can with respect to the normal direction of the surface of the non-magnetic support. In this method, the light is made incident from a direction forming a predetermined angle of incidence and vapor-deposited on the non-magnetic support. At this time, oxygen gas is introduced to the surface of the non-magnetic support in order to improve the magnetic properties and corrosion resistance by incorporating oxygen into the obtained magnetic thin film.

A second invention of the present application is that a plurality of crucibles are arranged so as to be displaced in the traveling direction of the non-magnetic support during such vapor deposition. According to this method, the magnetic material evaporated from the crucible arranged on the high angle side is first deposited on the non-magnetic support which is traveling, and then it is arranged on the lower angle side than the crucible. Since the magnetic material evaporated from the crucible is adhered, a plurality of magnetic thin films can be formed on the non-magnetic support by a single vapor deposition. At this time, since the crucible arranged on the high angle side and the crucible arranged on the low angle side have different incident angles of the magnetic material evaporated from each crucible with respect to the surface of the non-magnetic support, the lower layer The tilts of the column structures of the side magnetic thin film and the upper magnetic thin film are individually controlled. Therefore, the inclination of the easy axis of magnetization of each magnetic thin film can be controlled as in the first invention of the present application, and the magnetic layer corresponding to the recording depth of the recording signal can be obtained, so that high output can be achieved. Is possible.

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.

[0018]

When a plurality of crucibles are used when the magnetic layer is formed and the positions of these crucibles are displaced in the running direction of the non-magnetic support, a plurality of magnetic thin films are formed in one vapor deposition process. The magnetic layer can be formed, and the inclination of the easy axis of magnetization between the upper magnetic thin film and the lower magnetic thin film can be well controlled. This is for the following reason.

That is, the (n-1) th crucible (n is a natural number of 2 or more) arranged at a position closer to the delivery side with respect to the running direction of the non-magnetic support, and the running direction of the non-magnetic support. Compared with the incident angle of the evaporated magnetic material from the surface of the non-magnetic support from the n-th crucible arranged closer to the winding side, the former has a higher angle, The latter has a lower angle.

Therefore, when vapor deposition is performed while moving the non-magnetic support from the delivery side toward the winding side, the magnetic material evaporated from the (n-1) th crucible on the non-magnetic support. To form the (n-1) th magnetic thin film, and then the magnetic material evaporated from the nth crucible is deposited on the (n-1) th magnetic thin film. The magnetic thin film of the nth layer is formed, and a magnetic layer having a multilayer structure is obtained.

In such a magnetic layer, the gradient of the column structure of the magnetic thin film of the nth layer is the (n-1) th.
Since it is larger than that of the magnetic thin film of the layer,
The inclination α _n of the easy axis of magnetization of the magnetic thin film of the layer is the nth above.
It is larger than the inclination α _{n-1 of the} easy axis of the -1st magnetic thin film. Therefore, in this magnetic layer, a large amount of vertical component exists in the magnetic thin film of the n-th layer on the upper side, and a large amount of longitudinal component exists in the magnetic thin film of the (n-1) -th layer of the lower layer. Since it has, the information signal is written according to the recording depth of the recording signal.

[0022]

EXAMPLES Examples of magnetic recording media to which the present invention is applied will be specifically described below. In the magnetic tape of this example, as shown in FIG. 1, a magnetic layer 3 having a two-layer structure is formed on a non-magnetic support 1 made of polyethylene terephthalate.

The magnetic layer 3 is the magnetic thin film 2a of the first layer.
And the magnetic thin film 2b of the second layer, and these magnetic thin films 2a and 2b are sequentially laminated and formed.

The magnetic thin film 2a of the first layer has a gradient α _{1 of the} easy axis of 0 <α ₁ <40 °, has many longitudinal components, and is suitable for recording a recording signal in the long wavelength region. It is advantageous. In addition, the magnetic thin film 2b of the second layer has an inclination α _{2 of} easy magnetization axis of 40 ° <α ₂ <90 °, has many vertical components, and is used for recording a recording signal in a short wavelength region. It is advantageous.

Thus, the magnetic thin film 2a of the first layer is formed.
Is magnetized in a state close to the longitudinal direction, and the magnetic thin film 2b of the second layer is magnetized in a state close to the vertical direction, when recording is performed on this recording medium, the recording signal has a recording depth. Since it is recorded on the magnetic layer corresponding to the above, it is possible to obtain a high output.

The magnetic tape having such a structure can be manufactured as follows. First, the configuration of the manufacturing apparatus used in this embodiment will be described. In this manufacturing apparatus, as shown in FIG. 2, the cooling can 11 is arranged in a vacuum chamber that is in a vacuum state. The cooling can 11 is configured to rotate at a constant speed in the direction of the arrow X in the drawing, and the non-magnetic support 12 wound along the outer peripheral surface of the cooling can 11 is used as the cooling can 1.
The vehicle travels at a predetermined speed according to one rotation.

A cooling device (not shown) is provided inside the cooling can 11 so that deformation of the non-magnetic support 12 due to temperature rise can be suppressed.

A shutter 13 is arranged near the cooling can 11 along the outer peripheral surface of the cooling can 11. As a result, a part of the surface of the non-magnetic support 12 is covered, and the non-magnetic support is provided in a region up to the time point when the shutter 13 is covered by one end of the shutter 13 (end on the delivery side of the non-magnetic support 12). Deposition is performed on the support 12. Then, the minimum incident angle θ _{1 of} the evaporated metal magnetic material 17 described later with respect to the non-magnetic support 12 is regulated by one end of the shutter 13.

An oxygen gas inlet 18 is provided at one end of the shutter 13, and oxygen gas is supplied to the surface of the nonmagnetic support 12 from the oxygen gas inlet 18 during vapor deposition. As a result, oxygen is taken into the obtained magnetic thin film to improve the magnetic characteristics.

A partition plate 19 is provided on the side of the cooling can 11 on the delivery side of the non-magnetic support 12. As a result, vapor deposition is performed on the non-magnetic support 12 from the time when the non-magnetic support 12 delivered from the feed roll (not shown) passes through the partition plate 19. The partition plate 19 regulates the maximum incident angle θ _{2 of} the evaporated metal magnetic material 16 described later with respect to the non-magnetic support 12. Further, by providing such a partition plate 19, the metallic magnetic materials 16 and 17 which are evaporated above the partition plate 19 are evaporated.
Is not diffused, so that the vapor deposition efficiency is improved.

On the other hand, a first crucible 14 and a second crucible 15 are arranged below the cooling can 11, respectively, and metallic magnetic materials 16 and 17 are provided in the first and second crucibles 14 and 15, respectively. Are respectively filled. The first and second crucibles 14 and 15 are connected to the cooling can 11 described above.
It has a width substantially the same as the width. Metal magnetic materials 16 and 17 filled in the first and second crucibles 14 and 15
Is heated and evaporated by a heating means (not shown) such as an electron gun attached to the side wall of the vacuum chamber.
The heating means is arranged at a position such that the electron beam emitted from the heating means irradiates the metallic magnetic materials 16 and 17 in the first and second crucibles 14 and 15, respectively.

The evaporated metallic magnetic materials 16 and 17 are formed as magnetic layers on the non-magnetic support 12 which runs at a constant speed on the outer peripheral surface of the cooling can 11. ..

The above-mentioned first crucible 14 and second crucible 1
5 are arranged so as to be displaced in the running direction of the non-magnetic support 12, and are arranged at a position close to the delivery side of the non-magnetic support 12 on the winding side of the first crucible 14 and the non-magnetic support 12. The second crucible 15 is arranged so as to come close to it. Therefore, when vapor deposition is performed while moving the non-magnetic support 12 from the sending side toward the winding side, first, the magnetic material 16 evaporated on the non-magnetic support 12 from the first crucible 14 is firstly formed. Is deposited to form a first-layer magnetic thin film, and then the magnetic material 17 evaporated from the second crucible 15 is deposited to form a second-layer magnetic thin film. In this way, the two-layer magnetic thin film can be formed by one vapor deposition process, so that the productivity is remarkably improved. Further, since no intermediate oxide layer is interposed between these magnetic thin films, the energy product is high and high output characteristics can be obtained.

At this time, the first crucible 14 has the metal magnetic material 1 evaporated from the first crucible 14.
The second crucible 15 is arranged at a position such that the incident angle of 6 with respect to the surface of the non-magnetic support 12 becomes large.
The metallic magnetic material 17 evaporated from the second crucible 15 is arranged at a position where the incident angle becomes small. Thereby, since the inclination of the column structure of the magnetic thin film of the second layer becomes larger than that of the magnetic thin film of the first layer,
The inclination of the easy axis of magnetization of the magnetic thin film of the second layer is larger than the inclination of the easy axis of magnetization of the magnetic thin film of the first layer. Therefore, since there are many vertical components in the upper magnetic thin film of the second layer and many longitudinal components of the lower magnetic thin film of the first layer, the recording depth of the recording signal is A corresponding magnetic layer can be obtained, and high output can be realized.

In order to properly control the inclination of the easy axis of magnetization of these magnetic thin films, the incident angle of the metal magnetic material 16 evaporated from the first crucible 14 is set to 60 to 90 °, and the second crucible is set. The incident angle of the metallic magnetic material 17 evaporated from 15 is preferably 40 ° or more. By setting the incident angles of these metallic magnetic materials 16 and 17 within the above range, the inclination of the easy axis of magnetization of the obtained magnetic thin film can be well controlled, and a medium with high output can be manufactured. it can.

The first crucible 14 has the second crucible.
It is necessary to dispose the metal magnetic material 17 evaporated from the crucible 15 at a position that prevents the metal magnetic material 17 from scattering. As a result, among the metallic magnetic materials 17 evaporated from the second crucible 15, those having a high angle at the time of being incident on the surface of the non-magnetic support 12 are scattered in the middle of the first crucible. Since it is hindered by 14, the maximum value of the incident angle of the evaporated metal magnetic material 17 can be regulated by itself.

Further, a gas introducing pipe 20 is disposed on the side wall portion of the first crucible 14 on the low incident angle side, and a predetermined amount of oxygen gas is supplied from the gas introducing pipe 20 at the time of vapor deposition.
If it is introduced on the surface of No. 2, an intermediate oxide layer can be formed between the magnetic thin film of the first layer and the magnetic thin film of the second layer, and noise due to magnetic interaction between the magnetic thin films can be eliminated. Can be lowered. However, in this case, if the film thickness of the intermediate oxide layer is too thick, the output decreases due to the reduction of the energy product. Therefore, it is required to appropriately suppress the film thickness by appropriately setting the introduction amount of oxygen gas. To be done.

Therefore, a magnetic tape was manufactured as follows using such a manufacturing apparatus, and each experiment was conducted on the obtained magnetic tape. Experiment 1 In this experiment, the effect of using the two crucibles as described above at the time of vapor deposition of the magnetic layer was examined.

That is, pure Co is used as the metal magnetic material,
While running a base film made of polyethylene terephthalate at a tape speed of 28 m / min, a metal magnetic material evaporated from the first and second crucibles is applied to the base film, and the base film is formed on the base film. A magnetic thin film having a two-layer structure (forward two-layer structure) in which the directions of inclination of the easy axis of magnetization were the same was formed.

At this time, oxygen gas was introduced into the surface of the base film at a rate of 200 cc / min. Further, the incident angle of the metal magnetic material evaporated from the first crucible with respect to the surface of the base film is changed within a range of 60 to 90 °, and the incident angle of the metal magnetic material evaporated from the second crucible is changed. Was 40 ° or more. The maximum value of the incident angle of the metallic magnetic material evaporated from the second crucible is regulated by the first crucible.

The magnetic tape thus obtained and only one crucible for vapor deposition of the magnetic layer are provided, and other than that, oblique vapor deposition is performed in the same manner as in this embodiment, and the same vapor deposition is repeated. The reproduction output and C / N of the magnetic tape (comparative example) in which the first-layer magnetic thin film and the second-layer magnetic thin film were separately formed were examined. The results are shown in Table 1.

The vapor deposition conditions for forming the above-mentioned conventional magnetic tape were the same as those in this embodiment.

[0043]

[Table 1]

As shown in Table 1, as in this embodiment, 2
It has been found that when two crucibles are used and two layers of magnetic thin films are formed in one step, a high output is obtained and the C / N characteristics are remarkably improved.

Experiment 2 Next, by changing the incident angle of the metal magnetic material evaporated from the first and second crucibles, the magnetization of the magnetic thin film of the first layer and the magnetic thin film of the second layer can be easily performed. The effect of controlling the tilt of the axis was examined. That is, oblique vapor deposition was performed in the same manner as in Experiment 1 above to form a first layer magnetic thin film and a second layer magnetic thin film on the base film so as to have a thickness of 100 nm. The magnetic tape A was used.

For comparison, only the first crucible was used, and otherwise the same as in the present embodiment, and after the magnetic thin film of the first layer was formed to a thickness of 100 nm by oblique vapor deposition. , This oblique vapor deposition is repeated to obtain a film thickness of 100.
A second-layer magnetic thin film having a thickness of nm was formed and used as a magnetic tape a. In these magnetic tape A and magnetic tape a, the inclination α ₁ of the easy axis of magnetization of the first magnetic thin film (lower layer) and the inclination of the easy axis of magnetization of the second magnetic thin film (upper layer) obtained The relationship between α ₂ and the output characteristics at 1 MHz and 7 MHz was examined. The results are shown in Table 2. In Table 2, when a single-layer magnetic layer having a thickness of 200 nm was formed by a single vapor deposition using only the first crucible (magnetic tape b), only the second crucible was used. The results of the case where a single magnetic layer having a film thickness of 200 nm was formed by one-time vapor deposition (magnetic tape c) are also shown.

[0047]

[Table 2]

As shown in Table 2, when the inclination of the easy axis of magnetization of the magnetic layer is small like the magnetic tape a and the magnetic tape b, sufficient output characteristics cannot be expected, and the inclination of the easy axis of magnetization of the magnetic layer is not expected. Even with a large value, in the magnetic tape c having no magnetic thin film having a small inclination of the easy axis of magnetization, the reproduction output was deteriorated especially in the low frequency region side. On the other hand, it has been found that by stacking the upper layer having a large inclination of the easy axis and the lower layer having a small inclination of the easy axis, a high reproduction output can be obtained in both the short wavelength region and the long wavelength region.

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 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, 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 general domestic VTR.

Therefore, here, for example, a signal having a shortest wavelength of 0.5 μm is recorded for a track width of 5 μm, and the recording density is 4 × 10 ⁵ bit / mm ² or more, or 8 × 10 ⁵ bit / mm ² In addition to realizing the above, by using 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. 3 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 to.

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 order of the luminance data supplied to the blocking circuit 35 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. 5 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. Note that, in FIG. 5, solid lines indicate odd field lines, and broken lines indicate even field lines.

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,
It is combined with the channel data. Therefore, a line-sequential digital color difference signal is obtained from the sub-sampling and sub-line circuit 34. FIG. 6 shows the pixel configuration of the signal subsampled and sublined by the subsampling and subline circuit 34. In FIG. 6, ◯ 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. The blocking circuit 36, like the blocking circuit 35 on the one hand, stores the color difference data (4 lines × 4 pixels × 2 frames).
Convert to the block structure of. Then, the output signals of the blocking circuit 35 and the blocking circuit 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 this synthesizing circuit 37 is supplied to the block coding circuit 38. As the block encoding circuit 38, an encoding circuit (referred to as ADRC) adapted to the dynamic range of each block and a DCT as described later.
(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 clock and the recording 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 recorded 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 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-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 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 be compressed to about 25 Mbps, and additional information such as parity and audio signal after that 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. 4, the reproduction data from the magnetic heads 43A and 43B is first supplied to the channel decoder 45 via the rotary transformer and the reproduction amplifiers 44A and 44B. Channel decoder 45
At, 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 decomposition circuit 48 separates the respective components 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. The 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 by the bit number smaller than the bit number of the original pixel data. As another example of the block encoding circuit 38, the pixel data of each block is converted into a DCT (Discrete Cosine Tr).
After the transformation, the coefficient data obtained by the DCT may be quantized, and the quantized data may be run-length Huffman-encoded and compression-encoded.

Here, an example of an encoder that uses an ADRC encoder and in which image quality does not deteriorate even when multi-dubbing is performed will be described with reference to FIG. In FIG. 7, 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 by 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 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 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 (MIN to MIN).
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
Calculates the average value for each block, and the reset signal of the block period from the terminal 70 is averaged by the averaging circuits 68, 69.
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 that is any one of 1 bit, 2 bits, 3 bits, and 4 bits, and is subjected to edge matching quantization. The allocated bit number n is determined for each block in the bit number determination circuit 75, and the data of the bit number 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, 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 76 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 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 threshold set. 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 allocated bit number n of the block is determined. In the quantizing circuit 74, the data PDI after the minimum value removal via the delay circuit 79 is converted into the code signal DT by the edge matching quantization using the dynamic range DR ′ and the allocated 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 via the delay circuits 78 and 80, respectively, and the parameter code Pi indicating the combination 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 41 and the channel decoder 45 of FIG. 3 will be described. In the channel encoder 41, as shown in FIG. 8, an adaptive scramble circuit to which the output of the parity generation circuit 40 is supplied is provided with a plurality of M-sequence scramble circuits 81, of which the highest frequency for the input signal is obtained. The M-sequence is selected so that an output with a small number of components and DC components can be obtained. 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). The output of the precoder 82 is passed through the recording amplifiers 42A and 42B to the magnetic head 4
Recording and reproduction are performed by 3A and 43B, and reproduction output is amplified by reproduction amplifiers 44A and 44B.

On the other hand, in the channel decoder 45, as shown in FIG. 9, the arithmetic processing circuit 83 on the reproducing side of the partial response class 4 performs 1 + D arithmetic on the outputs of the reproducing amplifiers 44A and 44B. Also,
In the so-called Viterbi decoding circuit 84, decoding of data resistant to noise is performed by an operation using the correlation and accuracy of the data with respect to the output of the operation 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.

11 and 12 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, one field of data is divided into five tracks and recorded on the magnetic tape 108. 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.

[0086]

As is apparent from the above description, according to the present invention, when vapor deposition for forming a magnetic layer is performed, the positions of a plurality of crucibles to be used are shifted once in the running direction of the non-magnetic support. Since the magnetic layer having a multi-layer structure can be formed in the vapor deposition step, the productivity is remarkably improved.

Further, since the incident angle of the magnetic material evaporated from each crucible with respect to the surface of the non-magnetic support is different depending on the position of the crucible, in the obtained magnetic layer, the inclination of the easy axis of magnetization on the upper layer side is the lower layer. It can be formed to be larger than that on the side. As a result, the magnetic layer corresponding to the recording depth of the recording signal can be formed, and the high output medium can be obtained.

Further, according to the present invention, since it is possible to prevent the intermediate oxide layer from intervening between the obtained magnetic thin films, it is possible to secure a sufficient energy product and to achieve high output. It is advantageous.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an example 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 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. 4 is a block diagram showing a configuration on a reproduction side of a signal processing unit.

FIG. 5 is a schematic diagram showing an example of a block for block coding.

FIG. 6 is a schematic diagram for explaining subsampling and sublines.

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

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

FIG. 9 is a block diagram showing an outline of an example of a channel decoder.

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

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

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

FIG. 13 is a cross-sectional view showing the structure of a conventional magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support 2a ... 1st layer magnetic thin film 2b ... 2nd layer magnetic thin film 3 ... Magnetic layer

Claims (2)

[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, wherein the easy axis of magnetization of an n-th magnetic thin film on the non-magnetic support is tilted. features and alpha _n, that _{α n-1 <α n (} n is two or more natural number) the relationship between the inclination alpha _n-1 of the axis of easy magnetization of the magnetic thin film of the n-1 th layer is established And a magnetic recording medium. 2. A surface of the non-magnetic support made of a magnetic material, which is provided with a plurality of crucibles when a plurality of magnetic thin films are laminated and formed on the non-magnetic support by a vacuum deposition method. The method of manufacturing a magnetic recording medium is characterized in that the incident angle with respect to each is different depending on the position of the crucible.