JPH0520660A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To suppress the error rate at the time of recording digital image signals by obtaining the magnetic recording medium which is highly durable and is less deteriorated in electromagnetic conversion characteristics. CONSTITUTION:Projecting parts constituted by sticking inorg. fine particles by a high-polymer material are formed on a nonmagnetic base and a magnetic metallic thin film which is a magnetic layer is formed thereon. Particles having a small grain size distribution, such as colloidal silica, are used as the inorg. fine particles and an emulsion liquid, such as acrylate emulsion, is used as the high-polymer material. The projecting parts are formed by having some spacing and the ratio a/b between the flat part a and the projecting parts b is specified to >=0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used for magnetically recording a digital image signal in a digital VTR or the like, and in particular, compressing a digital image signal in such a form that reproduction distortion is small. The present invention relates to a magnetic recording medium for recording.

[0002]

2. Description of the Related Art In video tape recorders, image quality is being improved by high-density recording, and in order to cope with this, for example, a metal magnetic thin film is used as a magnetic layer as a magnetic recording medium for 8 mm VTR. So-called vapor deposition tapes have been put to practical use. Vapor-deposited tapes have superior magnetic characteristics to the coating type magnetic tapes that have been widely used until now, and the magnetic layer is also thin, so they exhibit higher performance than coating type magnetic tapes in terms of electromagnetic conversion characteristics. Is expected to do.

On the other hand, as a signal form in a video tape recorder, it has been considered to use a digital signal instead of an analog signal which has been used so far, and it is necessary to design a medium adapted to this. For example, 8 mm VT
In the vapor deposition tape used for R, minute protrusions (so-called wrinkle-shaped protrusions, mountain-shaped protrusions, protrusions by internal filler, or a combination thereof) are provided as a base on the base film before forming the metal magnetic thin film. Durability is ensured by reflecting on the surface property of the metal magnetic thin film. However, in a digital VTR for recording / reproducing a digital image signal, the relative speed between the magnetic head and the magnetic tape is higher than that of the 8 mm VTR. Since it is much faster than twice, it is necessary to set the height of the minute protrusions to a certain level to secure the running property and durability.

[0004]

However, although the above-mentioned method has a great effect on practical characteristics such as running property and durability, the electromagnetic conversion characteristic is deteriorated conversely and the characteristics of the metal magnetic thin film medium cannot be fully utilized. The reality is not. The deterioration of the electromagnetic conversion characteristics becomes a fatal defect particularly when recording a digital image signal, and the error rate remarkably increases.

As a method of improving the running property and durability without adopting the above-mentioned method, an inorganic substance or the like is formed on the surface of the metal magnetic thin film.
A method of forming a protective film by forming a film with a film thickness of 0 to 200Å is being studied, but such a protective film causes spacing loss as in the case of providing minute protrusions, and also deteriorates electromagnetic conversion characteristics. Is a problem.

As described above, the digital VTR for recording the digital image signal, particularly the digital VTR for compressing and recording the digital image signal in a form with less reproduction distortion.
In TR, it is indispensable to design a magnetic recording medium that can sufficiently satisfy not only running property and durability but also electromagnetic conversion characteristics. Therefore, the present invention has been proposed in view of such circumstances, and it is excellent not only in running performance and durability but also in electromagnetic conversion characteristics and recording / reproducing a digital image signal at a low error rate. It is an object of the present invention to provide a magnetic recording medium capable of achieving the above, and further to provide a manufacturing method thereof.

[0007]

In order to achieve the above object, the magnetic recording medium of the present invention has an average particle size of 100 on the surface.
The metallic magnetic thin film is magnetic on a non-magnetic support on which projections made of inorganic fine particles of Å or less and a polymer material are formed, and the ratio a / b of the projections b to the flat portion a is 0.5 or more. Formed as a layer, the input digital image signal is converted into block data composed of a plurality of pixel data and divided into blocks, the block data is compression-encoded in block units, and the compression-encoded data is formed. Is recorded by a magnetic head mounted on a rotary drum.

As shown in FIG. 1, the magnetic recording medium of the present invention has a protrusion 1 having a wrinkle shape, a circular shape or the like on a non-magnetic support 101.
No. 02 is formed, and a metal magnetic thin film which is a magnetic layer is formed thereon. Here, the metal magnetic thin film that is the magnetic layer is a single metal of Fe, Co, or Ni, or Co-
Alloys such as Ni and Co—Fe, and alloys obtained by adding additive elements to these alloys, which have been conventionally used as magnetic materials for vapor deposition tapes, can be used.

On the other hand, the projections 102 formed on the non-magnetic support 101 are substantially hemispherical projections or so-called "wrinkle" projections, and the inorganic fine particles 103 are non-magnetically supported by the binder component 104. It is formed by being attached onto the body 101. Here, the inorganic fine particles 1
As 03, fine particles of SiO ₂ or the like are used, and particularly colloidal silica having a very small particle size and a small particle size distribution is suitable.

The inorganic fine particles 103 are attached to the non-magnetic support 10
As the binder component 104 to be attached to 1,
The material is not particularly limited as long as it is a polymeric material, but it is preferable to mix and apply with an emulsion such as an acrylic ester emulsion or a synthetic rubber emulsion. Among the emulsions, the acrylic ester type emulsion is most suitable, and especially the glass transition point of -20 ° C to
A good protrusion 102 is formed by using an acrylic ester at 20 ° C. as a polymer material and using an emulsion having a gel content of 20% or more. A crosslinkable monomer such as divinylbenzene, N-methylolacrylamide, ethylene methacrylate, or glycidyl methacrylate may be added to the acrylic ester emulsion, if necessary.

When forming the protrusion 102 as described above, it is important how much the protrusion is formed.
When observing the surface shape (so-called mat shape) of the non-magnetic support 101 on which the protrusion 102 is formed, it is necessary to select the ratio of the flat portion to the protrusion within an appropriate range. That is, as shown in FIG. 1, when the dimension of the flat portion of the non-magnetic support 101 where the ground is exposed is a and the dimension of the protrusion is b, a / b ≧ 0.5. preferable. In other words, it is better that the protrusions are spaced apart from each other to some extent. This is the same for the case of the wrinkle-shaped protrusion 102 as shown in FIG. 2 and the case of the circular protrusion 102 as shown in FIG. a
If /b<0.5, it becomes difficult to secure electromagnetic conversion characteristics suitable for recording a digital image signal.

[0012]

[Function] Contains inorganic fine particles having an average particle size of 100Å or less,
The protrusion formed by attaching this to a non-magnetic support with a binder resin (polymer material) has a large effect of improving durability,
Even if they are formed with a certain distance, they exhibit a sufficient durability improving effect. On the other hand, increase the distance between the protrusions,
When the surface property is improved, deterioration of electromagnetic conversion characteristics is suppressed,
Sufficient output and C / N for recording the digital image signal are secured. In the present invention, since the digital image signal is recorded on the magnetic recording medium having such a protrusion formed as a base, the error rate is significantly improved.

[0013]

Embodiments to which the present invention is applied will be described below in detail with reference to the drawings and experimental results.

A. Structure of recording / reproducing apparatus As a digital VTR for digitizing a color video signal and recording it on a recording medium such as a magnetic tape, a component type digital VT of a D1 format for a broadcasting station is used.
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, a composite color video signal is sampled with a signal having a frequency four times as high as the frequency of a color subcarrier signal, A / D-converted, and subjected to predetermined signal processing, and then a magnetic tape. I am trying to record it.

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, in this embodiment, for example, 5 μm
A signal having a shortest wavelength of 0.5 μm with respect to the track width is recorded, a recording density of 8 × 10 ⁵ bits / mm ² or more is realized, and the recorded information is compressed in a form with little reproduction distortion. When used together, the present invention is applied to a digital VTR capable of recording / reproducing for a long time even if a magnetic tape having a tape width of 8 mm or less is used. The configuration 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. 4 shows the entire structure 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 1Y, 1U, 1
The data amount of the signal supplied to V is about 216 Mb
ps. The blanking time data of this signal is removed, and the data amount is compressed to about 167 Mbps by the valid information extraction circuit 2 which extracts only the information of the valid region.

Then, the luminance signal Y of the output of the effective information extraction circuit 2 is supplied to the frequency conversion circuit 3 and the sampling frequency is converted from 13.5 MHz to 3/4 thereof. As the frequency conversion circuit 3, for example, a thinning filter is used so that aliasing distortion does not occur. The output signal of the frequency conversion circuit 3 is supplied to the blocking circuit 5, and the order of the luminance data is converted into the order of blocks. The block forming circuit 5 is provided for the block encoding circuit 8 provided in the subsequent stage.

FIG. 6 shows the structure of a block as an encoding unit. 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. 6, a solid line indicates an odd field line, and a broken line indicates an even field line.

Of the outputs of the valid information extraction circuit 2,
The two color difference signals U and V are supplied to the sub-sampling and sub-line circuit 4, and after the sampling frequency is converted from 6.75 MHz to half thereof, the two digital color difference signals are selected line by line from each other, Combined with the data. Therefore, from this sub-sampling and sub-line circuit 4, a line-sequential digital color difference signal is obtained. FIG. 7 shows a pixel configuration of a signal subsampled and sublined by the subsampling and subline circuit 4. 7 in FIG.
Indicates a sub-sampling pixel of the first color difference signal U, and Δ
Indicates the sampling pixel of the second dye signal V, and x indicates the position of the pixel thinned out by the sub-sample.

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

In the synthesizing circuit 7, the luminance signal and the color difference signal converted in the order of blocks are converted into 1-channel data, and the output signal of the synthesizing circuit 7 is supplied to the block coding circuit 8. As the block coding circuit 8, as will be described later, a coding circuit (referred to as ADRC) adapted to the dynamic range of each block and a DCT (Dis) are used.
A create cosine transform circuit or the like can be applied. The output signal from the block encoding circuit 8 is further supplied to the framing circuit 9 and converted into frame structure data. In the framing circuit 9, the pixel system clock and the recording system clock are changed.

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

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

Next, the structure on the reproducing side will be described with reference to FIG. At the time of reproduction, as shown in FIG. 5, reproduction data from the magnetic heads 13A and 13B is first supplied to the channel decoder 15 via the rotary transformer and the reproduction amplifiers 14A and 14B. Channel decoder 15
At, the channel coding is demodulated and the output signal of the channel decoder 15 is supplied to the TBC circuit (time axis correction circuit) 16. In this TBC circuit 16, the time-axis fluctuation component of the reproduction signal is removed. The reproduction data from the TBC circuit 16 is supplied to the ECC circuit 17,
Error correction using the error correction code and error correction are performed. The output signal of the ECC circuit 17 is supplied to the frame decomposing circuit 18.

The frame decomposing circuit 18 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 18 are supplied to the block decoding circuit 19, the restored data corresponding to the original data is decoded in each block unit, and the decoding data is supplied to the distribution circuit 20. The distribution circuit 20 separates the decoded data into a luminance signal and a color difference signal. The luminance signal and the color difference signal are supplied to the block decomposition circuits 21 and 22, respectively. The block decomposing circuits 21 and 22 convert the decoding data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 5 and 6 on the transmission side.

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

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

B. Block Coding As the block coding circuit 8 in FIG.
(Adaptive Dynamic Range Co
ding) encoder is used. This ADRC encoder detects the maximum value MAX and the minimum value MIN of a plurality of pixel data included in each block, and detects the maximum value MA.
The dynamic range DR of the block is detected from X and the minimum value MIN, the coding adapted to this dynamic range DR is performed, and the requantization is performed with the number of bits smaller than the number of bits of the original pixel data. As another example of the block encoding circuit 8, pixel data of each block is converted into DCT (Discrete Cosine Tran).
After sform), the coefficient data obtained by this DCT may be quantized, and the quantized data may be run-length Huffman encoded and compression-encoded.

Here, an example of an encoder that uses an ADRC encoder and in which image quality does not deteriorate even when multi-dubbing is performed will be described with reference to FIG. In FIG. 8, 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 27 from the synthesizing circuit 7 in FIG. Input terminal 2
Blocked data from 7 is maximum value / minimum value detection circuit 2
9 and the delay circuit 30. The maximum value / minimum value detection circuit 29 determines the minimum value MIN and the maximum value MAX for each block.
To detect. The delay circuit 30 delays the input data for the time required for detecting the maximum value and the minimum value.
The pixel data from the delay circuit 30 is supplied to the comparison circuit 31 and the comparison circuit 32.

The maximum value MAX from the maximum / minimum value detection circuit 29 is supplied to the subtraction circuit 33, and the minimum value MIN is supplied to the addition circuit 34. The subtractor circuit 33 and the adder circuit 34 are supplied from the bit shift circuit 35 with a value of one quantization step width (Δ = 1 / 16DR) when performing non-edge matching quantization with a fixed length of 4 bits. The bit shift circuit 35 is configured to shift the dynamic range DR by 4 bits so as to perform division by (1/16). The subtraction circuit 33 obtains a threshold value of (MAX-Δ), and the addition circuit 34 obtains a threshold value of (MIN + Δ). The threshold values from the subtraction circuit 33 and the addition circuit 34 are supplied to the comparison circuits 31 and 32, respectively. The value Δ 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 31 is the AND gate 3
6 and the output signal of the comparison circuit 32 is supplied to the AND gate 37. The input data from the delay circuit 30 is supplied to the AND gate 36 and the AND gate 37. The output signal of the comparison circuit 31 becomes high level when the input data is larger than the threshold value, and therefore the output terminal of the AND gate 36 has the pixel data of the input data included in the maximum level range of (MAX to MAX-Δ). Is extracted. On the other hand, the output signal of the comparison circuit 32 becomes high level when the input data is smaller than the threshold value. Therefore, the output terminal of the AND gate 37 is (MIN to MIN).
The pixel data of the input data included in the minimum level range of + Δ) is extracted.

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

Further, the average value MIN 'is supplied to the subtraction circuit 42, and the average value MIN' is subtracted from the input data passed through the delay circuit 43 in the subtraction circuit 42 to form the data PDI after removal of the minimum value. . The data PDI and the modified dynamic range DR ′ are used by the quantization circuit 44.
Is supplied to. In this embodiment, the number 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 45, and the data of the bit number n is supplied to the quantization circuit 44.

The variable length ADRC has a dynamic range D
Efficient encoding can be performed by reducing the number of allocated bits n in a block having a small R ′ and increasing the number of allocated bits n in a block having a large dynamic range DR ′. That is, the threshold values for determining the number of bits n are set to T1 to T4 (T1 <T2 <T3 <
T4), the code signal is not transferred to the block of (DR ′ <T1), only the information of the dynamic range DR ′ is transferred, and the block of (T1 ≦ DR ′ <T2) is (n = 1). The block of (T2 ≦ DR ′ <T3) is (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 46 for determining the threshold values T1 to T4 for making the generated information amount a predetermined value, a plurality of threshold value groups (T1, T2, T3, T4), for example, 3 are set.
Two sets are prepared, and these sets of thresholds are distinguished by the parameter code Pi (i = 0, 1, 2, ... 31). The generated information amount is set to monotonically decrease as the number i of the parameter code Pi increases. However, the quality of the restored image deteriorates as the amount of generated information decreases.

Threshold value T from buffering circuit 46
1 to T4 are supplied to the comparison circuit 47, and the dynamic range DR ′ through the delay circuit 48 is supplied to the comparison circuit 47. The delay circuit 48 delays DR ′ by the time required for the buffering circuit 46 to determine the threshold set. In the comparison circuit 47, the dynamic range DR ′ of the block is compared with each threshold value, the comparison output is supplied to the bit number determination circuit 45, and the allocated bit number n of the block is determined. In the quantizing circuit 44, the data PDI after removal of the minimum value via the delay circuit 49 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 44 is composed of, for example, a ROM.

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

C. Channel Encoder and Channel Decoder Next, the channel encoder 11 and the channel decoder 15 of FIG. 4 will be described. As shown in FIG. 9, the channel encoder 11 is an adaptive scramble circuit to which the output of the parity generation circuit 10 is supplied, and a plurality of M-sequence scramble circuits 51 are prepared. The M-sequence is selected so that an output with a small number of components and DC components can be obtained. The precoder 52 for the partial response class 4 detection method performs arithmetic processing of 1 / 1-D ² (D is a unit delay circuit). The output of the precoder 52 is passed through the recording amplifiers 12A and 13A to the magnetic head 1
Recording and reproduction are performed by 3A and 13B, and reproduction output is amplified by reproduction amplifiers 14A and 14B.

On the other hand, in the channel decoder 15, as shown in FIG. 10, the arithmetic processing circuit 53 on the reproducing side of the partial response class 4 performs 1 + D arithmetic on the outputs of the reproducing amplifiers 14A and 14B. Further, in the so-called Viterbi decoding circuit 54, noise-resistant data decoding is performed on the output of the calculation processing circuit 53 by calculation using the correlation and the accuracy of the data. The output of the Viterbi decoding circuit 54 is supplied to the descramble circuit 55, and the data rearranged by the scrambling process on the recording side is returned to the original series to restore the original data. With the Viterbi decoding circuit 54 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 13A and 13B are attached to the drum 76 in an integrated structure as shown in FIG. A magnetic tape (not shown) is obliquely wound around the peripheral surface of the drum 76 at a winding angle slightly larger than 180 ° or slightly smaller than 180 °.
A and the magnetic head 13B are configured to scan the magnetic tape at the same time.

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

12 and 13 show magnetic heads 13A,
This shows a more specific structure when 13B has an integrated structure (so-called double azimuth head). For example, the magnetic head 13 integrated with the upper drum 76 rotated at a high speed.
A and 13B are attached, and the lower drum 77 is fixed. Here, the winding angle θ of the magnetic tape 78 is 16
The drum diameter is 6 ° and the drum diameter φ is 16.5 mm. Therefore, on the magnetic tape 78, one field of data is divided into five tracks and recorded. With this segment system, the length of the track can be shortened and the error due to the linearity of the track can be reduced.

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

B. Production of Magnetic Recording Medium Using the digital VTR having the above-mentioned configuration, magnetic recording is performed on the magnetic recording medium having the metal magnetic thin film as the magnetic layer. Therefore, in the following, a metal magnetic thin film type magnetic recording medium was actually manufactured, and durability and electromagnetic conversion characteristics were examined using the above-mentioned digital VTR.

A. Example 1 A polyethylene terephthalate (PET) film having a thickness of 10 μm was used as a base film, and an undercoat layer was previously formed on the film using an acrylic ester emulsion and colloidal silica to form protrusions. The acrylic ester emulsion used is one in which 3 parts by weight of a crosslinkable monomer is added to 100 parts by weight of an acrylic ester, and has a glass transition point Tg of 10 ° C and an average particle size (in water dispersion) of 700Å. Is. The composition of acrylic acid ester, which is the solid content, is as follows. Solid emulsion component Butyl acrylate 50% by weight Methyl methacrylate 48% by weight Acrylic acid 2% by weight

As the colloidal silica, colloidal silica in water dispersion was used, and the average particle size was set to 80Å. These acrylic acid ester emulsions and colloidal silica were added and mixed in an amount of 1% by weight to a water-ethyl alcohol mixed liquid (10:90 by weight ratio), and this was coated and dried on a polyethylene terephthalate film.

Next, a metal magnetic thin film was formed on the above base film by oblique vapor deposition in an oxygen atmosphere using a vacuum vapor deposition apparatus as shown in FIG. FIG. 14 shows an example of a vacuum vapor deposition apparatus for depositing a metal magnetic thin film as a magnetic layer. This vacuum vapor deposition apparatus has a cylindrical cooling can 87 and a partition plate 8 arranged in the central portion.
It has vacuum tanks 81c and 81d divided by 2, and vacuum exhaust systems 83a and 83b are connected to the respective vacuum tanks 81c and 81d.

Further, one of the vacuum tanks 81c is provided with a supply roll 84 and a take-up roll 85 for the base film B, and a guide for causing the base film B to run along the cooling can 87. Rolls 86a and 86b are installed. The vacuum tank 81d
The evaporation source 88 faces the cooling can 87.
Is installed in the vicinity of the cooling can 87, and a shielding plate 90 for regulating the incident angle of the evaporated metal and an oxygen gas introduction pipe 91 are provided. Evaporation source 88
As the element, it is possible to use elemental metals such as iron, cobalt, and nickel, alloys such as CoNi-based alloys, and mixtures with other elements.

Therefore, by running the base film B along the cooling can 87 and heating and evaporating the evaporation source 88 by the electron beam 89 from the electron gun 92, the metal magnetic thin film is obliquely deposited on the base film. It In this embodiment, C is used as the evaporation source.
The degree of vacuum in the vacuum chambers 81c and 81d is set to 1 by using o ₈₀ Ni _20.
A metal magnetic thin film (film thickness 2000Å) was formed under the conditions of × 10 ^-4 Torr, oxygen gas introduction rate of 300 cc / min, and running speed of base film B of 20 m / min. The angle of incidence of the evaporated metal on the base film B was 45 ° to 90 °.

After forming the metal magnetic thin film, a back coat layer was formed, and a fluorocarbon lubricant, perfluoropolyether, was applied to form a top coat layer. The top coat layer was cut into 8 mm width to form a tape. This is Example 1.

B. Example 2 The glass transition point Tg of the acrylic ester emulsion used for the undercoat layer was 0 ° C., and the average particle size (in water dispersion) was 90.
A magnetic tape was manufactured in the same manner as in Example 1 above, except for 0Å.

C. Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that an undercoat layer was formed only with an acrylic ester emulsion without mixing colloidal silica.
And

D. Comparative Example 2 A wrinkle-shaped protrusion having a height of 100Å was provided on a base film, and a water-soluble emulsion having an average particle diameter of 300Å (including an acrylate ester and a crosslinkable monomer. Glass transition point 3
(0 ° C.) was applied and dried to form an undercoat layer. Hereinafter, a magnetic magnetic thin film was formed in the same manner as in the previous example to produce a magnetic tape, which was set as Comparative Example 2.

With respect to the magnetic tapes of these Examples and Comparative Examples, the still durability, electromagnetic conversion characteristics and error rate were measured. Still durability is a measured value at 25 ° C. and 50% relative humidity. Electromagnetic conversion characteristics have a recording wavelength of 0.5 μm
The reproduction output at that time was measured by a spectrum analyzer and shown as a relative value based on Comparative Example 2. The results are shown in Table 1. Table 1 also shows the mat shape of each magnetic tape (the ratio a / b between the flat portion a and the protruding portion b).

[0058]

[Table 1]

As is clear from Table 2, in Comparative Example 1 in which colloidal silica which is an inorganic fine particle is not mixed, the still durability is deteriorated and the reproduction output is slightly improved. Comparative Example 2 in which a / b is less than 0.5
In, the still durability can be secured, but the electromagnetic conversion characteristics are deteriorated and the error rate is large. On the other hand, each of the examples to which the present invention is applied has excellent still durability and electromagnetic conversion characteristics, and has a small error rate.

[0060]

As is clear from the above description, in the present invention, a metal magnetic thin film is formed on a non-magnetic support having protrusions containing inorganic fine particles formed at appropriate intervals on the surface. Since the digital image signal is compressed and recorded in such a form that the reproduction distortion is small, the durability and electromagnetic conversion characteristics can be improved at the same time, and therefore the error rate can be greatly improved. It is possible.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part schematically showing a non-magnetic support having a surface on which projections containing inorganic fine particles are formed.

FIG. 2 is a schematic view showing a mat shape of a non-magnetic support having wrinkle-shaped protrusions formed thereon.

FIG. 3 is a schematic view showing a mat shape of a non-magnetic support having circular protrusions formed thereon.

FIG. 4 is a block diagram showing a configuration of 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. 5 is a block diagram showing a configuration on a reproduction side of a signal processing unit.

FIG. 6 is a schematic diagram showing an example of a block for block coding.

FIG. 7 is a schematic diagram for explaining subsampling and sublines.

FIG. 8 is a block diagram showing an example of a block encoding circuit.

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

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

FIG. 11 is a plan view schematically showing an example of the arrangement of magnetic heads.

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

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

FIG. 14 is a schematic view showing an example of a vacuum vapor deposition device.

[Explanation of symbols]

 1Y, 1U, 1V ... Component signal input terminals 5, 6 ... Blocking circuit 8 ... Block coding circuit 11 ... Channel encoders 13A, 13B ... Magnetic head 22・ ・ ・ Channel decoder 26 ・ ・ ・ Block decoding circuit 28, 29 ・ ・ ・ ・ Block decomposition circuit 101 ・ ・ ・ Non-magnetic support 102 ・ ・ ・ Protrusions 103 ・ ・ ・ Inorganic fine particles

Claims (1)

Claim: What is claimed is: 1. A projection formed of a polymer material and inorganic fine particles having an average particle size of 100Å or less is formed on the surface, and the projection b
And a flat portion a have a ratio a / b of 0.5 or more, a metal magnetic thin film is formed as a magnetic layer on a non-magnetic support, and an input digital image signal is divided into a plurality of pixel data in block units. Data obtained by converting the data into blocks, compression-encoding the block-encoded data in block units, and channel-encoding the compression-encoded data is recorded by a magnetic head mounted on a rotary drum. A magnetic recording medium characterized by: