JPH10172128A - Magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of dew condensation by providing a ferro- magnetic metal thin film layer on one side surface A of a polyester film and making the SRa value, SRz value and surface waviness of this ferromagnetic metal thin film respectively specified values. SOLUTION: The SRa value of the ferromagnetic metal thin film layer of this magnetic tape is 2-6nm, preferably 4-6nm, and the SRz value is 40-70nm, preferably 45-60nm, and the surface waviness is 30-50nm, preferably 30-45nm. When the SRa value is <2nm, a ferromagnetic film of a video tape is weared by a video head at a recording/reproducing time in a digital video tape recorder due to that a ferromagnetic metal thin film is too smooth to be undesirable. When the SRa value exceeds 6nm, the output characteristics of the video tape is lowered due to that the ferromagnetic thin film becomes to rough to be undesirable. What the SRz value is <40nm, the durability of the ferromagnetic film is lowered. When the surface waviness is <30nm, the output characteristic of the video tape is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferromagnetic metal thin film type magnetic tape.

[0002]

2. Description of the Related Art Digital video tapes for consumer use that have recently been put to practical use are provided with a metal magnetic thin film of Co on a base film and a diamond-like carbon film coated on the surface thereof. Despite smoothing, it has good durability. Examples of the base film include a polyester film, a polyester film comprising a discontinuous film adhered to at least one surface of the film and fine particles present in the film and on the film surface (for example, Japanese Patent Publication No. Sho 62-30105). A composite film in which a layer A made of a resin and a layer B made of a thermoplastic resin containing fine particles are laminated (for example, Japanese Patent Publication No. 1-26373, Japanese Patent Publication No. 1-26)
No. 338, Japanese Patent Publication No. 1-1218, Japanese Patent Publication No. 1
No. 2224), and the like, and a base film having a smaller surface roughness for forming a metal magnetic film than a base for a Hi8ME tape is used.

[0003]

However, in such a very smooth digital video tape for consumer use, the tape is very easily adhered to a drum due to dew condensation caused by a change in temperature. Condensation is particularly frequent in camera-integrated videos, such as when suddenly entering a warm room from a cold outdoor, and during the condensation the tape sticks to the drum, recording,
I can not play it and it is a problem.

[0004] Although the tape thus produced provides high-density magnetic recording characteristics, sticking of the tape to the drum due to dew condensation was remarkable.

In the technique (1), a ferromagnetic metal is vacuum-deposited on the outer surface of the layer A to form a video tape. However, there is large variation in the electromagnetic conversion characteristics of the tape and the sticking of the tape to the drum due to condensation.

Accordingly, an object of the present invention is to provide a consumer digital videotape having good dew condensation resistance.

[0007]

In order to solve such a problem, the present invention has the following arrangement.

That is, 1. A ferromagnetic metal thin film layer is provided on one surface A of the polyester film, and the ferromagnetic metal thin film layer has an SRa value of 2 to 2.
6 nm, SRz value 40-70 nm, surface undulation 30
1. a magnetic tape having a thickness of about 50 nm; 2. The magnetic tape according to 1, wherein the magnetic tape is used for a digital cassette type video cassette recorder tape. The SRa value of the surface A on one side on which the ferromagnetic metal thin film layer of the polyester film is provided is 2 to 6 nm, and the SRz value is 4
3. The magnetic tape according to 1, wherein the magnetic tape has a thickness of 0 to 70 nm and a surface waviness of 30 to 50 nm. The polyester constituting the polyester film is polyethylene terephthalate or polyethylene-2,6
-The magnetic tape according to 1, wherein the magnetic tape is naphthalate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention may be any polyester that can form a high-strength film by molecular orientation, but polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred. Eighty percent or more of the constituent components are ethylene terephthalate, polyethylene terephthalate which is ethylene naphthalate, and polyethylene naphthalate. Ethylene terephthalate, polyester copolymer components other than ethylene naphthalate, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, diol components such as 1,4-cyclohexane dimethanol, adipic acid, 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;
-Oxyethoxybenzoic acid and the like.

The above-mentioned polyester may further comprise at least one of an alkali metal salt derivative of sulfonic acid which is not reactive with the polyester and a polyalkylene glycol which is substantially insoluble in the polyester in an amount not exceeding 5% by weight. May be mixed.

The present magnetic tape is characterized in that a ferromagnetic metal thin film layer is provided on one surface A of a polyester film, and a known metal thin film can be used.
Although not particularly limited, a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof is preferable. The thickness of the metal thin film layer is 100 to 300 nm.

SRa of the ferromagnetic metal thin film layer of the magnetic tape
Value is 2-6 nm, preferably 4-6 nm, SRz value is 4
0 to 70 nm, preferably 45 to 60 nm, and the surface waviness is 30 to 50 nm, preferably 30 to 45 nm.

If the SRa value of the ferromagnetic metal thin film layer is less than 2 nm, the ferromagnetic thin film is too smooth, and the video head wears the ferromagnetic thin film of the video tape during recording and reproduction in the digital video tape recorder. Not preferred. If the SRa value exceeds 6 nm, the ferromagnetic thin film becomes too rough, and the output characteristics of the video tape deteriorate, which is not preferable.

When the SRz value of the ferromagnetic metal thin film layer is less than 40 nm, the ferromagnetic thin film becomes too smooth, and the recording is repeated many times in the digital video tape recorder.
The durability of the ferromagnetic thin film of the video tape is undesirably reduced during reproduction. If the SRz value exceeds 70 nm, the surface becomes too rough and the number of small DOs on the video tape increases, which is not preferable.

The surface waviness of the ferromagnetic metal thin film layer is 30 nm.
If it is less than this, the contact area between the drum and the tape magnetic layer becomes large, and the sticking of the tape to the drum due to dew condensation becomes large, which is not preferable. If the surface waviness exceeds 50 nm, the contact between the head and the magnetic layer of the video tape becomes poor, and the output characteristics of the video tape deteriorate, which is not preferable.

The SRa value of one surface A of the polyester film of the present magnetic tape on which the ferromagnetic metal thin film layer is provided is 2
~ 6nm, SRz value is 40 ~ 70nm, surface undulation is 3
It is preferably from 0 to 50 nm.

If the SRa value is less than 2 nm, the ferromagnetic thin film formed on the outside of the surface A becomes too smooth, and the recording and reproduction in the digital video tape recorder after forming the video tape are performed by the video head. The ferromagnetic thin film is undesirably worn. If the SRa value exceeds 6 nm, the ferromagnetic thin film formed outside the surface A becomes too rough, and the output characteristics of the video tape deteriorate, which is not preferable.

If the SRz value is less than 40 nm, the surface A
The durability of the ferromagnetic thin film of the video tape is undesirably reduced due to the repeated recording and playback performed many times in the digital video tape recorder after the ferromagnetic thin film formed outside the tape becomes too smooth and turns into a video tape. . If the SRz value exceeds 70 nm, the ferromagnetic thin film formed outside the surface A becomes too rough, and the number of small DOs on the video tape increases, which is not preferable.

If the surface waviness is less than 30 nm, the contact area between the drum and the surface of the tape magnetic layer formed outside the surface A becomes large, and the tape sticks to the drum due to dew condensation, which is not preferable. Surface undulation is 50nm
Exceeding the limit results in poor contact between the head and the magnetic layer of the video tape, which is undesirable because the output characteristics of the video tape deteriorate.

Organic compound containing 0.5 to 10.0% by weight, preferably 0.6 to 8.0% by weight of fine particles having an average particle size of 5 to 30 nm, preferably 8 to 30 nm on the surface A of the polyester film. It is preferable that a coating layer consisting of To further increase the durability of the magnetic layer,
The average particle diameter in the polyester lower layer forming the surface A is 3
0.01 to 1.0% by weight, preferably 0.02 to 150% by weight of fine particles of 0 to 150 nm, preferably 40 to 100 nm.
It is preferable to include 0.8% by weight to have surface projections.

The fine particles include silica, calcium carbonate, alumina, polyacrylic acid spheres, polystyrene spheres and the like.
As the organic compound, a polar polymer such as polyvinyl alcohol, tragacanth rubber, casein, gelatin, a cellulose derivative, a water-soluble polyester, and polyurethane can be used, and a blend of these can be applied, but is not limited thereto.

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

In the magnetic tape of the present invention, a ferromagnetic metal thin film of Co or the like is formed on one surface A of the polyester base film of the present invention to a thickness of 100 to 200 nm by vacuum evaporation, and a film having a thickness of about 10 nm is formed on the metal thin film. A diamond-like carbon film is formed by coating. Since the thickness of the strong metal thin film is extremely thin, 100 to 200 nm, the surface of the magnetic layer reflects the surface shape of the base film as it is.

The polyester film of the present invention can be subjected to A / B by co-extrusion in the usual plastic film production process consisting of melting, molding, biaxial stretching and heat setting.
The film on which the layers are laminated is formed, or the polyester film is coated with fine particles by coating to form a film, and the film is wound, whereby the surface roughness of the layer B can be transferred to the layer A to produce the film. However, providing fine particles by coating complicates the production process and economically preferably uses a co-extrusion technique. In the present invention, a production method using the co-extrusion technique will be described.

The raw material for the layer A from which the contained particles are removed as much as possible and the raw material for the layer B containing the fine particles positively are melt-coextruded and cooled and solidified on a casting drum to obtain an unstretched film sheet. Then, it is obtained by performing uniaxial stretching, preparing a desired coating solution for forming the above-mentioned coating layer, applying and drying, and then stretching and orienting in a direction orthogonal to the uniaxial stretching direction and heat fixing. At the time of melt extrusion, the layer B side melt is preferably passed through a high-precision filter having a performance near 3 μm cut (5% cut diameter).

The layer A may contain fine particles therein to further increase the durability of the magnetic tape.

The biaxial stretching can be performed by, for example, a sequential biaxial stretching method or a simultaneous biaxial stretching method. If desired, the film is stretched again in the vertical or horizontal direction or in the vertical and horizontal directions before heat setting, and then mechanically. It is also possible to use a so-called reinforced type with increased strength.

The method for forming the coating layer is as described above.
At the stage where the stretching in the axial direction has been completed, a desired coating liquid is applied onto the base film. The coating method may be any of a doctor blade method, a gravure method, a reverse roll method, and a metering bar method.

A desired surface shape can be formed on the surface A by causing fine particles to be present in the layer B to form surface protrusions and transferring the surface shape of the layer B to the layer A by winding. The adjustment of the SRa value, the SRz value and the surface waviness of the surface A can be adjusted by adjusting the particle diameter of the fine particles contained in the B layer, the addition concentration, and by making the hardness of the A layer softer than the B layer. . If the hardness of the polyester A layer is made softer than the layer B, such as making the difference between the softening points of the polyester of the layer A and the layer B and the layer A is lower than 3 ° C or more, the surface roughness of the layer B causes the film to roll. Transferring when rolled is preferable. By providing the above ferromagnetic metal thin film layer on the surface of layer A of the polyester film thus obtained, a magnetic tape having the surface characteristics of the present invention can be obtained.

The fine particles in the layer B include calcium carbonate,
Silica, alumina, polystyrene and the like are used, but are not limited thereto. Particle size is 50-1000n
m, preferably 100 to 900 nm. The addition amount is 0.05 to 0.9% by weight, preferably 0.08 to 0.1%.
6% by weight is desirable.

The magnetic tape of the present invention is particularly suitable for use in digital video tapes because excellent results can be obtained. It is also preferable that excellent results can be obtained even when used for data storage tape applications.

[0032]

[Measurement method]

(1) SRa value, SRz value Optical stylus type (critical angle focus error detection method) manufactured by Kosaka Laboratory
Was measured using a three-dimensional roughness meter (ET-30HK).

SRa value: The average roughness of the center line surface corresponding to JIS Ra.

SRz value: Ten-point average surface roughness corresponding to JIS Rz. Enter the distance between the average of the highest to fifth peak elevations and the average of the deepest to fifth valley bottoms, using the average surface of the part extracted by the reference area from the roughness surface as the reference surface. What was converted.

The test piece was subjected to Al evaporation on the measurement surface.

The measurement direction was the width direction, the cut-off value was 0.08 mm, the measurement length was 0.1 to 0.25 mm, the feed pitch was 0.2 μm, the measurement speed was 20 μm / s, and the number of measurement was 100. . The unit was nm.

(2) Surface waviness This is the roughness of the surface that appears to be distorted to the skin when observed on the surface of the magnetic tape and the surface of the base film with a differential interference microscope (observation magnification: about 50 times). Has a pitch on the order of several μm to several hundred μm.

The deformation is obtained by searching for a dent in the three-dimensional roughness curve obtained by the measurement of the three-dimensional roughness meter (ET-30HK) described in (1), obtaining the maximum depth of the dent,
The average value of the pieces is defined as the surface undulation.

(3) The electromagnetic conversion characteristics of the magnetic tape of the present invention in which a ferromagnetic thin film is provided on the film of the present invention are as follows.
Measurement was performed using an 8 mm video tape recorder. Video S / N ratio, dropout (D
O) was determined. For measurement of S / N ratio and dropout,
A signal was supplied from a TV test signal generator, and a video noise meter and a dropout counter were used. Video S
The / N ratio was measured using commercially available standard Hi8 ME tape as zero decibel (dB). The dropout was determined to have a reproduction signal attenuation of −8 dB or more and a length of 7 μsec or more. S / N ratio, dropout is normal temperature and normal humidity (2
(5 ° C., 60% RH). The characteristics after 100 runs of the tape were also observed.

(4) Adhesion of the tape to the drum due to condensation in a camera-integrated digital video video tape recorder (DVC) is performed using a commercially available camera-integrated DVC, leaving the tape at 5 ° C. for 30 minutes, and then 25 ° C. The room was moved to a room of No. 1, and the time required for the sticking of the drum and the tape after the dew condensation to disappear was measured and evaluated. Repeat the evaluation five times, find the average time,
Compared.

[0041]

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

Example 1 Raw material A containing polyethylene terephthalate substantially free of inert particles and 0.02% by weight of silica having an average particle size of 60 nm, polyethylene terephthalate substantially free of inert particles and average particle Raw material B containing 0.20% by weight of calcium carbonate having a diameter of 300 nm and 0.10% by weight of calcium carbonate having a diameter of 800 nm is 5: 1 in thickness ratio.
And extruded at 110 ° C. by a roll stretching method.
The film was stretched twice as long. The softening points of the polyethylene terephthalates of the raw materials A and B were adjusted to 260 and 263 ° C., respectively.

In the step after the longitudinal stretching, the following aqueous solution was applied to the outside of the layer A.

Outside layer A: methylcellulose 0.10% by weight Water-soluble polyester 0.30% by weight Aminoethylsilane coupling agent 0.01% by weight Ultrafine silica having an average particle diameter of 12 nm 0.03% by weight Solid content concentration 20 mg / m ²

Thereafter, the film is laterally heated to 110 ° C. by a stenter.
, Stretched 3.3 times, heat-treated at 200 ° C, wound on an intermediate spool, slit with a slitter to a small width, wound up in a cylindrical core in a roll shape with a tension of m width 3kg, and a thickness of 6.3μ
m of a roll-shaped composite polyester film was obtained.

The raw material B was passed through a high-precision filter capable of cutting foreign substances of 3 μm.

A cobalt-oxygen thin film having a total thickness of 110 nm and a structure in which two thin film layers each having a thickness of 55 nm were laminated on the surface A of the polyester film by vacuum evaporation. Next, a diamond-like carbon film having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by a sputtering method. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone was provided in a thickness of 400 nm, slit to a width of 8 mm and a width of 6.35 mm by a slitter, and wound on a reel to form a magnetic tape.

Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Example 2 In the production of the base film of Example 1, the polyethylene terephthalate was changed to polyethylene-2,6-naphthalate, the longitudinal stretching temperature and magnification were set to 5.0 times at 135 ° C., and the transverse stretching temperature and magnification were changed. At 135 ° C., 6.0 times, further stretched transversely at 160 ° C. to 1.2 times, and changed to heat treatment at 200 ° C., and the same procedure was followed to obtain a 4.2 μm thick composite polyester film roll. . Raw material A and raw material B
Of polyethylene-2,6-naphthalate was adjusted to 270 and 273C, respectively.

A magnetic tape having a width of 8 mm and a width of 6.35 mm was prepared in the same manner as in Example 1. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.
Shown in

Example 3 A composite polyester film roll having a thickness of 4.2 μm was obtained in the same manner as in Example 2 except that in the production of the base film of Example 2, except for the silica contained in the raw material A. 8 mm in width and 6.35 m in the same manner as in Example 2.
m of magnetic tape was prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 1 In the production of the base film of Example 1, the solid content concentration of the aqueous solution applied was 10 mg / m ² . Others are Example 1.
A composite polyester film roll having a thickness of 6.3 μm was obtained in the same manner as described above, and magnetic tapes having a width of 8 mm and 6.35 mm were prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 2 In the production of the base film of Example 1, the concentration of methylcellulose in the aqueous coating solution was set to 0.16% by weight. Otherwise, in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm was obtained, and a width of 8 mm and a width of 6.35 m
m of magnetic tape was prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 3 In the production of the base film of Example 1, the concentration of the ultrafine silica in the aqueous coating solution was set to 0.02% by weight. Otherwise, in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm was obtained, and a width of 8 mm and a width of 6.35 m
m of magnetic tape was prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 4 In the production of the base film of Example 1, the average particle diameter of silica contained in the raw material A was changed to 90 nm. Otherwise, in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm was obtained, and a width of 8 mm and a width of 6.35 m
m of magnetic tape was prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 5 In the production of the base film of Example 1, the softening point of the raw material A, polyethylene terephthalate, was set to 263 ° C. Otherwise, a composite polyester film roll having a thickness of 6.3 μm was obtained in the same manner as in Example 1, and a width of 8 mm and a width of 6.3 μm
A 5 mm magnetic tape was made. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

Comparative Example 6 In the production of the base film of Example 1, the concentration of 800 nm calcium carbonate contained in the raw material B was set to 0.15% by weight, and the other conditions were the same as in Example 1 and the thickness was 6.3 μm.
And a magnetic tape having a width of 8 mm and a diameter of 6.35 mm was prepared. Table 1 shows the properties of the obtained composite polyester film and magnetic tape.
It is shown in Table 2.

Comparative Example 7 In the production of the base film of Example 2, the softening point of the raw material A, polyethylene-2,6-naphthalate, was set to 273 ° C. Otherwise in the same manner as in Example 2, a composite polyester film roll having a thickness of 4.2 μm was obtained, and magnetic tapes having a width of 8 mm and 6.35 mm were prepared. Tables 1 and 2 show the properties of the obtained composite polyester film and magnetic tape.

[0059]

[Table 1]

[Table 2]

[0060]

As is clear from the characteristics shown in Tables 1 and 2, a ferromagnetic metal thin film layer is provided on one surface A of the present invention, and the surface of the layer has an SRa value of 2 to 6 nm and an SRz value of 40 to 40. 70
A magnetic tape having a thickness of 30 nm and a surface waviness of 30 to 50 nm is a digital video tape having excellent electromagnetic conversion characteristics and durability, and hardly causing condensation. The polyester film of the present invention produces a magnetic tape having the above excellent properties.

Claims (4)

[Claims] 1. A ferromagnetic metal thin film layer is provided on one surface A of a polyester film, and the SRa
A magnetic tape having a value of 2 to 6 nm, an SRz value of 40 to 70 nm, and a surface waviness of 30 to 50 nm. 2. The magnetic tape according to claim 1, wherein the magnetic tape is used for a video cassette recorder tape of a digital recording system. 3. An SRa value of one side surface A on which a ferromagnetic metal thin film layer of a polyester film is provided is 2 to 6 nm.
The magnetic tape according to claim 1, wherein the z value is 40 to 70 nm, and the surface waviness is 30 to 50 nm. 4. The magnetic tape according to claim 1, wherein the polyester constituting the polyester film is polyethylene terephthalate or polyethylene-2,6-naphthalate.