JP2003151124A - Digital video camera, magnetic tape for digital video camera, polyester film for magnetic tape and method for recording and reproducing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital video camera which is in the same size as a commercial DVC and compatible and which is capable of recording and reproducing for ultra-long time as long as 7 hours or more for a single cassette. SOLUTION: In the digital video tape recorder, an MR head is used as a reading magnetic head and a magnetic tape of 6.35 mm width is used for recording and reproducing. The magnetic tape comprises a polyester film and a ferromagnetic metal thin film layer formed on the film surface. The tape has 6.35 mm width, 20 to 60 nm thickness of the ferromagnetic metal thin film and 2.5 to 6.0 μm track width and is capable of digital magnetic recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video camera having extremely high quality and capable of recording for a long time, a magnetic tape for the digital video camera, a polyester film for the magnetic tape, and a recording and reproducing method using the same.

[0002]

2. Description of the Related Art A digital video tape for consumer use which was put into practical use in 1995 has a metal magnetic thin film of Co provided on a base film having a thickness of 6 to 7 μm by vacuum deposition, and a diamond-like carbon film coated on the surface thereof. Becomes D
In the case of a camera-integrated video using a V mini cassette, the basic specification (SD specification) has a recording time of 1 hour.

This digital video cassette (DVC)
Is the world's first digital video cassette for home use. Even though it is a small body, it can record a huge amount of information,
b. Image quality and sound quality do not deteriorate even after years because the signal does not deteriorate. C. Enjoy high image quality and high sound quality because it is not disturbed by noise. D. It has advantages such as that the image does not deteriorate even after repeated dubbing, and is highly evaluated in the market.

In addition, in 1998, one hour and 20 hours in SD specifications
DV mini-cassette tape (DVC-
LP tape) has been put to practical use, and the base film uses a polyethylene-2,6-naphthalate film having a thickness of 4 to 5 μm or an aromatic polyamide film. This tape also has a long recording time. , The market is highly evaluated.

Recently, there has been an increasing demand and need for recording one cassette tape for two hours or more.
The market is waiting for the emergence of digital video cameras that can record longer than 2 hours and can also use the current DV mini cassette.

[0006]

However, in order to enable a DVC video camera capable of recording for 2 hours or more,
It is necessary to reduce the thickness of the DV mini cassette tape,
The base film has 3-4 μm polyethylene-
A 2,6-naphthalate film or an aromatic polyamide film is required, but the film becomes too thin, and the magnetic tape produced from the film has a significantly poor head touch, and can record for 2 hours or more. DV
C video cameras have not been realized.

Therefore, an object of the present invention is to realize a digital video camera capable of recording for 2 hours or more.

[0008]

The present invention for achieving the above object is as follows. That is, 1. A digital video camera that uses an MR head as a reading magnetic head and uses a magnetic tape with a width of 6.35 mm for recording and playback. 2. The magnetic tape for a digital video camera as described in 1 above, wherein the magnetic tape comprises a polyester film and a ferromagnetic metal thin film layer formed on a surface thereof, and has a width of 6.35 m.
A magnetic tape having a thickness of 20 to 60 nm and a track width of 2.5 to 6.0 μm and capable of digital magnetic recording. 3. A magnetic tape comprising a polyester film having a number of surface protrusions having a height of 52 nm or more existing on the film surface of 100 / mm ² or less, and a ferromagnetic metal thin film layer formed on the surface having the number of surface protrusions. The magnetic tape described in. 4. The polyester film used for the magnetic tape according to the above 2 or 3, wherein the number of surface protrusions having a height of 52 nm or more present on the surface of the polyester film is 10
A polyester film for a magnetic tape having 0 pieces / mm ² or less. 5. 5. The polyester film for magnetic tape as described in 4 above, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 6. The digital video camera according to claim 1,
Alternatively, a recording / reproducing method for recording and / or reproducing an image by setting the magnetic tape described in 3 above. It is what

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An MR (magnetoresistive) head is used as the reading head of the digital video camera of the present invention.
MR head is an abbreviation for Magnetoresistive head,
A recording / reproducing output is obtained from a magnetic tape by using the effect of reducing the electric resistance value when a magnetic field is applied to metal. MR material is Ni / Fe alloy (80/20% by weight)
Any known material may be used as long as it has a magnetoresistive effect. The thickness of the MR film is preferably 10 to 30 nm, and particularly preferably around 20 nm. Track width is 2.5
˜6.0 μm. The structure may be a shield type structure conventionally used in a hard disk device, and may be a rotary drum mounting type in a digital video camera.

The width of the magnetic tape used in this digital video camera is 6.35 mm. With this width, the running mechanism, the recording / playback electric signal mechanism of the existing DVC camera device can be commonly used for the video camera of the present invention.

The magnetic tape used in this digital video camera has a ferromagnetic metal thin film layer formed on the surface of a polyester film, and the ferromagnetic metal thin film has a thickness of 20-6.
It is 0 nm, and a digital magnetic recording with a track width of 2.5 to 6.0 μm and a recording wavelength of 0.2 to 0.5 μm is possible. When the track width exceeds 6.0 μm, the recording time of 2 hours or more becomes difficult. If the track width is less than 2.5 μm, the dimensional change of the magnetic tape during recording and reproduction cannot be ignored, and the number of DOs increases significantly, which is not preferable. If the recording wavelength is less than 0.2 μm, the output is too low and the number of DOs is greatly increased, which is not preferable. If the recording wavelength exceeds 0.5 μm, the recording time of 2 hours or more becomes difficult.

As the ferromagnetic metal thin film, known ones can be used and are not particularly limited, but iron, cobalt, nickel,
Alternatively, those made of ferromagnetic materials of those alloys are preferable. The thickness of the metal thin film layer is preferably 20 to 60 nm. Two
If the thickness is less than 0 nm, the recording magnetic flux density becomes too low, and reproduction cannot be performed by the MR head, which is not preferable. If it is thicker than 60 nm, the magnetic characteristics of the MR film layer will be saturated, and it will not be possible to reproduce with a magnetoresistive MR head, which is not preferable.

In digital magnetic recording having a track width of 2.5 to 6.0 μm, the read head has a track width of 2.5 to 6.0 μm.
It becomes possible by setting it to 0 μm.

Digital magnetic recording with a recording wavelength of 0.2 to 0.5 μm can be performed by adjusting the number of recording heads, the drum diameter, the number of drum revolutions, and the tape running speed.
Using 3.5 MHz, the relative speed of the recording head on the tape is set to v (m / s), and an approximate value can be obtained from v / 13.5.

In the base film of the magnetic tape used in this digital video camera, the number of surface projections having a height of 52 nm or more existing on the surface (surface A) on which the ferromagnetic metal thin film layer is formed is 100 / mm ^2. The following polyester films are suitable. If the number of surface protrusions having a height of 52 nm or more exceeds 100 / mm ² , the spacing loss between the ferromagnetic metal thin film layer formed on the polyester film surface and the reading head becomes large, and it becomes difficult to obtain a reproduction output, which is preferable. Absent.

The polyester which constitutes this polyester film may be a polyester which becomes a high strength film by molecular orientation, but polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred.
That is, polyethylene terephthalate and polyethylene-2,6-naphthalate in which 80% or more of the constituents are ethylene terephthalate or ethylene naphthalate are preferable. Examples of the polyester copolymer component other than ethylene terephthalate and ethylene naphthalate include diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, diol components such as 1,4-cyclohexanedimethanol, adipic acid, Examples thereof include dicarboxylic acid components such as sebacic acid, phthalic acid, isophthalic acid and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid.

Further, the above-mentioned polyester contains at least one of an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester and a polyalkylene glycol which is substantially insoluble in the polyester in an amount not exceeding 5% by weight. You may mix in.

As the polyester film of the present invention,
The following films are preferable. On one surface A on one side of the film, a coating containing fine particles and an organic compound is formed, and there are fine surface protrusions due to the fine particles on the surface of the coating, the number of which is 5 to 90 million / m.
m ² , more preferably 9 to 60 million pieces / mm ² , and the height of the fine surface protrusions is 5 to 30 nm, more preferably 8 to 20 nm. By this fine surface protrusion,
Wear of the ferromagnetic metal thin film layer formed by vacuum deposition on the surface A by the magnetic head during recording / reproducing is reduced.
Further, since the height of the fine surface protrusions is suppressed to 30 nm or less, the height of the surface protrusions formed on the ferromagnetic metal thin film layer formed by vacuum vapor deposition is also 30 nm or less, and the MR head is scraped when reproducing the magnetic tape. Disappears.

If the number of fine surface protrusions is less than 5 million pieces / mm ² , the surface of the magnetic layer of the magnetic tape is too smooth and the ferromagnetic metal thin film layer is too smooth, and the running durability of the magnetic tape with the magnetic head is low. Is not suitable because it decreases. When the number of fine surface protrusions is more than 90 million pieces / mm ² , the magnetic layer surface of the magnetic tape becomes too rough and the dropout of the magnetic tape tends to increase, which is not suitable. The magnetic tape of the present invention is the polyester film of the present invention. A ferromagnetic metal thin film layer is provided on one side of the coated film (surface A), and is further formed by coating the surface B with a solution of solid fine particles and a binder to which various additives are added as necessary. It is preferable to provide a back coat layer, and known solid fine particles, binders, and additives can be used, and there is no particular limitation.

Next, an example of the manufacturing method of the present invention will be described.

In the present invention, the MR head has a track width of 2.5 to 6.0 μm and a thin film of a known material having a magnetoresistive effect, such as Ni / Fe alloy (80/20 wt%), having a film thickness of 10 to 30 nm. Created by providing this MR
Head is 21.7mm in diameter of existing DVC video camera
When mounted on a rotating drum, the tape running system and signal system are
Since it can be shared with VC, it is preferable. The track width of the recording head is more preferably 2.5 to 6.0 μm to match the reading head width, but the magnetic head of an existing DVC video camera may be used as the recording head. A circuit is separately manufactured for the recording system and the reproducing system. For digital signal compression, MPEG2 or MPEG4 recording is preferable to DV recording because the recording time is longer. The recording wavelength can be adjusted by adjusting the rotational speed of the rotating drum, the tape running speed, and the sampling frequency. It corresponds to the value of the relative speed of the magnetic head to the tape divided by the sampling frequency.

When the magnetic tape of the present invention is produced, a coating containing fine particles and an organic compound is formed on one surface A on one side as a base film, and the surface of the coating is formed by the fine particles. There are fine surface projections, the number of which is 5 to 90 million pieces / mm ² , more preferably 9 to 60 million pieces / mm ² , and the height of the fine surface projections is 5 to 30 nm, more preferably 8-20n
m, and using a polyester film is the surface number of protrusions than the height 52nm is 100 / mm ² or less, on the surface A consisting of iron, cobalt, nickel or ferromagnetic alloys thereof, ferromagnetic A metal thin film having a thickness of 20 to 60 nm is formed by a vacuum deposition method, and 10 n
A diamond-like carbon film having a thickness of about m is further coated, and a lubricant such as a fluorinated carboxylic acid is further coated thereon, and solid polyester such as carbon black and polyurethane, an epoxy resin, etc. are coated on the surface B of the other polyester film. It is possible to manufacture by providing a back coat layer by applying a solution consisting of the above binder containing various additives such as silicone, if necessary, and cutting the tape to a width of 6.35 mm. .

The above-mentioned polyester film of the present invention is produced by a usual plastic film manufacturing process comprising melting, molding, biaxially stretching and heat setting, using as the A-side raw material, polyester in which contained particles are removed as much as possible. But
In the stretching step, at 90 to 140 ° C., in the longitudinal and transverse directions,
Stretched to 2.7 to 5.5 times, 3.5 to 7.0 times, and 19
It is heat set at a temperature of 0 to 220 ° C. And it can manufacture by performing the following operations. 0.5 to 12.0% by weight of fine particles, preferably 0.6 to 10.% on the A-side of the smooth polyester film after stretching in one direction.
Applying a coating liquid consisting of an organic compound containing 0% by weight to the surface A
A coating layer is formed on the side and fine surface protrusions are formed on the surface A. The organic compound used in the coating layer is polyvinyl alcohol, tragacanth gum, casein, gelatin, cellulose derivative, water-soluble polyester, polyurethane,
Polar polymers such as isophthalic acid ester resin and methacrylic acid ester resin, and blends thereof can be used, but are not limited thereto. As fine particle species, polyacrylic acid, polystyrene, polyethylene, polyester, polyacrylic acid ester, polymethylmethacrylate, polyepoxy resin, polyvinyl acetate, acrylic-styrene copolymer, acrylic copolymer, various modified acrylics Organic compound particles such as resins, styrene-butadiene copolymers, various modified styrene-butadiene copolymers, etc., and particles coated with an organic polymer with inorganic particles such as silica, alumina and calcium carbonate as cores can be used. The fine particles preferably do not include particles having a diameter of 52 nm or more. The number of the fine surface protrusions can be adjusted by adjusting the type of fine particles, the average particle diameter, and the solid content coating concentration. By using the co-extrusion technique, the A / B laminated film may be melt-extruded into a film by using the raw material for the A layer and the raw material for the B layer positively containing larger particles. It is also possible to apply a coating liquid containing a lubricant to the surface B side opposite to the surface A side without using the B and B layers, and subject the B side to the easy slip treatment. The layer B may be used, and a coating liquid containing a lubricant may be further applied to the surface B for easy slipping treatment.

That is, in the magnetic recording tape of the present invention, a ferromagnetic metal thin film made of Co or the like is vacuum-deposited on the film provided on one surface A of the polyester film of the present invention to a film thickness of about 20 to 60 nm. Forming, coating a diamond-like carbon film having a thickness of about 10 nm on the metal thin film, and further applying a lubricant thereon, while
A back coat layer is provided by applying a solution consisting of solid fine particles and a binder to which various additives are added, if necessary, on one side surface B, and then cut to a tape width of 6.35 mm to manufacture. be able to. As the polyester, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable. Thickness is 4 μm
To 10 μm is preferable.

[0025]

EXAMPLES The measuring methods used in the examples are shown below. (1) Number of surface protrusions having a height of 52 nm or more on the film Silver is vapor-deposited (shadowed) at an angle of 5 ° to the surface of the film, and then platinum is coated by sputtering. The shadowed film surface is observed from directly above with a scanning electron microscope at a magnification of about 5,000 times for about 10 fields of view, and surface projections having shadows on the surface (formed by fine particles present in the polyester polymer) ), And let the height of the surface protrusion be h and the shadow length H be tan 5 °
= H / H relationship is used to estimate height from shadow length,
The number of surface protrusions having a height of 52 nm or more was determined. The number of surface projections having a height of 52 nm or more was calculated by converting the number of projections per 1 mm ² (pieces / mm ² ).

(2) Characteristic evaluation of recording and reproduction by digital video camera and magnetic tape A video cassette in which the created magnetic tape is fully wound around a 66 mm x 48 mm x 12.2 mm mini DV cassette in the created digital video camera. Was used to determine the recordable and reproducible time of the full length. Record in a quiet room, 1
The characteristics of the digital video camera and the magnetic tape were evaluated by counting the number of block-shaped mosaics (the number of dropouts (DO)) appearing on the screen after reproducing for a minute. The number of DOs was initially checked at room temperature (25 ° C.) for initial characteristics after tape production. Next, the tape was repeatedly run 100 times over the entire playback length of the tape, and the number of DOs after running 100 times was measured.

Next, the present invention will be explained based on examples.

[Example 1] Track width 5 of shield type structure
Ni / Fe (80/20 wt%) with a thickness of 20 nm in μm
An MR head having a thin film was created. A commercially available DVC rotary drum was modified to provide two MR heads adjacent to the existing head. The rotation speed of the rotating drum is 6000 rpm
And The tape speed was 3.34 mm / s. Sampling frequency is 13.5MHz, reproduction color band is 3.0M
Was set to Hz. The digital compression system was MPEG2, and the signal circuit was modified to create a digital video camera with a track width of 5 μm and a shortest recording wavelength of 0.3 μm. In addition,
This digital video camera can also be used as a DVC camera.

A polyester film having a thickness of 5.3 μm and having a number of surface protrusions of 52 nm or more in height present on the surface of 50 / mm ² was used, and partially oxidized Co was formed on the surface having the number of surface protrusions. A metal thin film layer consisting of 50 nm is formed by vacuum evaporation, a DLC film is formed with a thickness of 10 nm, a fluorinated lubricant is formed with a thickness of 5 nm, and a back surface made of silicone, carbon black or polyurethane is provided on the other surface. 66mm x 48 as a magnetic tape with a thickness of 5.9μm by coating with a thickness of 0.5μm and using it as a magnetic tape stock and slitting it to a width of 6.35mm to make a magnetic tape.
It was incorporated into a mini DV cassette of mm × 12.2 mm with a length of 84 m.

Table 1 shows the characteristics of the obtained digital video camera and magnetic tape, the characteristics of the polyester film used, and the characteristics during recording and reproduction.

Example 2 The tape running speed of the digital video camera of Example 1 was changed to 1.67 mm / s.
Otherwise, a digital video camera was prepared in the same manner as in Example 1, and the same magnetic tape was used for evaluation. Table 1 shows the characteristics of the obtained digital video camera, magnetic tape used, polyester film used, and recording and reproducing characteristics.

[Embodiment 3] The polyester film used in the manufacture of the magnetic tape in Embodiment 2 has a thickness of 4.0.
A polyethylene-2,6-naphthalate film reinforced with aluminum oxide on one side having a thickness of μm was used to manufacture a magnetic tape having a thickness of 4.6 μm, and a video cassette wound with a length of 108 m was prepared. It evaluated using the same digital video camera as 2. Table 1 shows the characteristics of the digital video camera, the magnetic tape used, the polyester film used, and recording and reproducing characteristics.

Comparative Example 1 (Comparative Example of Digital Video Camera) In the digital video camera of Example 1, the MR
A digital video camera was prepared in the same manner as in Example 1 except that the conventional head was used as it was without using the head. The obtained digital video camera was used and the other conditions were evaluated in the same manner as in Example 1. Table 1 shows the characteristics of the obtained digital video camera, magnetic tape used, polyester film used, and recording and reproducing characteristics.

Comparative Example 2 (Comparative Example of Digital Video Camera) Using the magnetic tape of Example 1, a commercially available DVC video camera was used as it was as a digital video camera for evaluation. Characteristics of digital video camera, magnetic tape used, polyester film used, and recording,
Table 1 shows the characteristics during reproduction.

[Comparative Example 3 (Comparative Example of Magnetic Tape)] In the production of the magnetic tape of Example 1, the slit width of the magnetic tape was changed to 3.8 mm, and 46 mm × 30.2 mm ×
It was assembled into an 8.5 mm MICRO MV cassette with a length of 18 m. A commercially available MICRO MV video camera was used as it was as a digital video camera for evaluation. Table 1 shows the characteristics of the digital video camera, the magnetic tape used, the polyester film used, and recording and reproducing characteristics.

Comparative Example 4 (Comparative Example of Magnetic Tape) In the production of the magnetic tape of Example 1, the thickness of the metal thin film layer was set to 1
A magnetic tape was prepared by changing the thickness to 0 nm. The obtained magnetic tape was used and the other conditions were evaluated in the same manner as in Example 1.
Table 1 shows the characteristics of the digital video camera, the magnetic tape used, the polyester film used, and recording and reproducing characteristics.

Comparative Example 5 (Comparative Example of Magnetic Tape) In the production of the magnetic tape of Example 1, the thickness of the metal thin film layer was set to 7
A magnetic tape was prepared by changing the thickness to 0 nm. The obtained magnetic tape was used and the other conditions were evaluated in the same manner as in Example 1.
Table 1 shows the characteristics of the digital video camera, the magnetic tape used, the polyester film used, and recording and reproducing characteristics.

Comparative Example 6 (Comparative Example of Film for Magnetic Tape) In the production of the magnetic tape of Example 1, the polyester film used had 120 / mm ² surface protrusions with a height of 52 nm or more on the surface. 5.3 μm
The thickness of the polyester film was changed to a magnetic tape. The obtained magnetic tape was used and the other conditions were evaluated in the same manner as in Example 1. Table 1 shows the characteristics of the digital video camera, the magnetic tape used, the polyester film used, and recording and reproducing characteristics.

[0039]

[Table 1]

As is clear from the characteristics shown in Table 1, when the digital video camera according to the present invention and the magnetic tape according to the present invention are used, it is possible to record and reproduce for a very long time of 420 minutes or more with good image quality. It was

[0041]

According to the present invention, it is possible to put into practical use a digital video camera which can be used in common with a commercially available DVC and has a high image quality and which can record and reproduce for a very long time of 7 hours or more.

Claims (6)

[Claims] 1. A digital video camera characterized in that an MR head is used as a reading magnetic head, and recording and reproduction are performed using a magnetic tape having a width of 6.35 mm. 2. The magnetic tape for a digital video camera according to claim 1, wherein the magnetic tape comprises a ferromagnetic metal thin film layer formed on a polyester film surface, and has a width of 6.35 mm. Thin film thickness is 20-60nm
And a magnetic tape capable of digital magnetic recording with a track width of 2.5 to 6.0 μm. 3. A magnetic film comprising a ferromagnetic metal thin film layer formed on the surface of a polyester film having a surface projection number of 52 nm or more and a surface projection number of 100 nm / mm ² or less on the surface of the film. The magnetic tape according to claim 2, which is a tape. 4. The polyester film used for the magnetic tape according to claim 2 or 3, wherein the number of surface protrusions having a height of 52 nm or more present on the surface of the polyester film is 100 / mm ² or less. Polyester film for magnetic tape, characterized by 5. The polyester film for magnetic tape according to claim 4, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 6. A recording / reproducing method for recording and / or reproducing an image by setting the magnetic tape according to claim 2 or 3 in the digital video camera according to claim 1.