JPH0760503B2 - video tape - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape, particularly a metal thin film type video tape.

2. Description of the Related Art Prior Art and Problems There are active developments of magnetic recording media for video, audio, etc., which have a metal thin film type magnetic layer because of their compactness when formed into a tape and wound.

As the magnetic layer of such a metal thin film type medium, vapor deposition at a predetermined inclination angle with respect to the normal to the substrate, a Co-based film formed by a so-called oblique vapor deposition method, a Co-Ni-based vapor deposition film, or the like, There are various types such as a perpendicular magnetization film made of a Co-Cr-based sputter or vapor deposition film.

For such a medium, when a thin film having a thickness of 10 μm or less is used for downsizing, long-time recording, etc., problems occur in terms of running property, occurrence of curl and half stretch, mechanical strength and the like.

Therefore, in order to eliminate these disadvantages, it has been proposed to provide a metal thin film reinforcing layer on the back surface of the film (JP-A-56-16939, 58-97131, 57-78627, 5).
7-37737 etc.).

According to these proposals, the thin metal film as the backing layer improves the Young's modulus of the medium and improves the running property, curl, mechanical strength and the like.

However, in the techniques described in the above publications, the optimum Young's modulus design has not yet been made, resulting in output reduction caused by head touch failure, envelope failure, etc., and also tape damage such as edge fold and single stretch. In addition, storage causes so-called skew.

Alternatively, traveling causes cracks in the magnetic layer, scratches in the magnetic layer, increased head wear, and increased dropout.

II Object of the Invention The object of the present invention is to optimize the mechanical strength of a medium, especially bending rigidity and Young's modulus by providing a predetermined backing layer in a video tape of 8 mm width using a metal thin film type thin film support. In addition, it improves head touch, eliminates output drop and envelope defect, eliminates tape damage such as edge fold and half stretch, eliminates skew due to storage, and further cracks magnetic layer due to running. It is to eliminate scratches and scratches, reduce the amount of head wear, and reduce dropouts.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the first invention is that Co or Co containing O is formed on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm.
Ni-based ferromagnetic metal thin film with a magnetic layer having a Co / Ni weight ratio of 1.5 or more and an O / (Co + Ni) atomic ratio of 0.15 to 0.6, and a backing layer on the other side. Then, when the bending stiffness value EI of the medium is calculated by the following formula, EI is
The video tape is characterized by having a weight of 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm.

Formula EI = (π / 4−2 / π) · W · a ³ / d · b (W is the radial direction for a ring-shaped test piece with a radius of acm and width of bcm created by cutting a magnetic sheet. The second invention is a Co or CoNi-based ferromagnetic metal thin film containing O on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm. The Co / Ni weight ratio is 1.5 or more,
It has a magnetic layer with an atomic ratio of O / (Co + Ni) of 0.15 to 0.6, a backing layer on the other side, and a backing layer on this backing layer. When calculated by the formula, EI is
The video tape is characterized by having a weight of 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm.

Formula EI = (π / 4−2 / π) · W · a ³ / d · b (W is the radial direction for a ring-shaped test piece with a radius of acm and width of bcm created by cutting a magnetic sheet. A load that causes a displacement d = 0.2πa.) The third invention is that a Co or CoNi-based ferromagnetic metal thin film containing O is formed on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm. It has a magnetic layer, has a surface layer on this magnetic layer, has a backing layer on the other side, has a backing layer on this backing layer, and calculates the bending rigidity value EI of the medium by the following formula. When EI
The video tape is characterized by having a weight of 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm.

Formula EI = (π / 4−2 / π) · W · a ³ / d · b (W is the radial direction for a ring-shaped test piece with a radius of acm and width of bcm created by cutting a magnetic sheet. It is a load that causes a displacement d = 0.2πa.) It should be noted that none of the above publications matches the bending rigidity value of the present invention. Slightly close to this, the composite Young's modulus of 1 was added to Sample 3 of Example 1 of JP-A-56-16939.
It is about 340 kg / mm ² , with an estimated bending rigidity value EI of about 2.9 gcm.

The above-mentioned flexural rigidity value range in the present invention is critical, and as will become apparent from the later description, the effect of the present invention cannot be realized if it is out of this range.

IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

The video tape of the present invention has a magnetic layer on a non-magnetic plastic film.

The magnetic layer is various kinds of continuous thin film type ferromagnetic metal thin film, and is directly formed on a plastic film by a method such as a vacuum deposition method, a sputtering method, an ion plating method, a plating method, or the like. It is installed through the stratum.

In the present invention, Co and O are essential components, and Co + O
Or Co + Ni + O. That is, the metal component may consist of Co alone or Co and Ni. In the case of Co + Ni, the weight ratio of Co / Ni is 1.5 or more.

Further, O is contained in addition to Co or Co + Ni. Since O is contained, more preferable results can be obtained in terms of electromagnetic conversion characteristics and running durability. In such a case, the atomic ratio of O / Co (when Ni is not included) or O / (Co + Ni) is 0.15 to 0.
6, especially 0.15 to 0.5.

On the other hand, when Cr is contained in the magnetic layer in addition to Co + O or Co + Ni + O, a more preferable result is obtained.
This is because the electromagnetic conversion characteristics are improved, the output and the S / N ratio are improved, and the film strength is further improved.

In such a case, the weight ratio of Cr / Co (when Ni is not included) or Cr / (Co + Ni) is preferably 0.001 to 0.1. In this case, a more preferable result is obtained when the weight ratio of Cr / Co or Cr / (Co + Ni) is 0.005 to 0.05.

Incidentally, in such a magnetic layer, other trace components,
Especially transition metal elements such as Fe, Mn, V, Zr, Nb, Ta, M
It may contain o, W, Ti, Cu, Zn, or the like.

Generally, such a Co—Ni-based magnetic layer is preferably an aggregate of particles having a columnar crystal structure inclined with respect to the normal to the main surface of the substrate. This improves the electromagnetic conversion characteristics.

In such a case, the particles having a columnar crystal structure are preferably tilted within a range of 20 to 60 ° with respect to the normal line of the main surface of the substrate.

Each columnar crystal grain usually has a length over the entire thickness direction of the magnetic layer, and its minor axis is generally about 50 to 500Å.

Then, Co and Ni, Cr, etc., which are added as necessary, constitute the columnar crystal particles themselves, and when O is added, O is usually mainly present on the surface of each columnar crystal particle mainly as an oxide. Exists in the form of.

Such a Co—Ni based magnetic layer is usually formed by the oblique vapor deposition method.

As the oblique vapor deposition method used, a known oblique vapor deposition method may be used, and the minimum value of the incident angle with respect to the normal to the substrate is preferably 30 ° or more.

The vapor deposition conditions and the post-treatment method may be according to known conditions and methods. In this case, effective post-treatment methods include known treatment methods for introducing O into the magnetic layer.

The thickness of such a magnetic layer is usually 0.05 to 0.5 μm, more preferably 0.1 to 0.25 μm in terms of electromagnetic conversion characteristics.

In this case, the magnetic layer may be directly provided on the plastic film, or may be provided on the plastic film via an underlayer.

The magnetic layer is usually formed as a single layer, but it may be formed by laminating a plurality of layers with an intermediate layer interposed in some cases.

Such a magnetic layer can be formed on various plastic films such as a polyester film, a polyamide film and a polyimide film by the method as described above.

The thickness of the plastic film used in the present invention is 10 μm or less, preferably 5 to 10 μm, more preferably 6 to 10 μm.
m, most preferably 6 to 8 μm.

If the thickness exceeds 10 μm, the objectives of downsizing the medium and recording for a long time cannot be achieved. If this thickness is too thin, the bending rigidity value EI of the medium described below will be too small to fall outside the setting range of the present invention, and problems such as runnability and output reduction will not be solved, and even if a backing layer described below is required. Even if the EI value is made thicker than the above, and the EI value is within the setting range of the present invention, in this case, there arises a problem that the magnetic surface is dislocated, the head is abraded, and the output is not stable.

A backing layer is provided on the other surface of the plastic film on which the magnetic layer is not provided.

The backing layer is preferably a thin film of Al, Cu, W, Mo, Cr, Ti, etc. which are single metals or alloys containing them, or oxides thereof.

Among the above metals, it is particularly preferable to use non-magnetic ones. The reason is, for example, when the backing layer is made of magnetic metal, when the magnetic surface is wound in a magnetized state,
If the backing layer is magnetized by the magnetic flux leaking from the magnetic layer, or if the backing layer is magnetized and re-recorded on the magnetic surface and then rewound, the magnetized state of the backing layer disturbs the magnetized state of the magnetic surface, causing noise. This is because problems such as increase in

The method of forming the lining layer is, for example, a vacuum thin film forming method such as vapor deposition, sputtering, ion plating, and various CVD.
A vapor phase growth method such as the above, a plating method or the like may be used.

The thickness of the backing layer thus formed is 0.05-1.5μ.
m, more preferably 0.07 to 0.9 μm, and even more preferably 0.07 to 0.7 μm. If this film thickness exceeds 1.5 μm, it exceeds the bending rigidity value range described below, and if it is less than 0.05 μm, it falls below the bending rigidity value range described below, causing the disadvantages described below.

Such a medium of the present invention has a content of 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · c.
It has a bending stiffness value EI of m.

EI is measured as follows.

The measurement is based on y-direction load and diameter change due to loop indentation.

That is, a ribbon-shaped test piece is cut out from the medium of the present invention, and a ring having a radius a and a width b is formed with the magnetic surface inside.
In this case, a is about 2 to 5 mm and b is about 3 to 8 mm.

As shown in FIG. 1, this ring-shaped test piece 10 is sandwiched between flat plate-shaped plates 71 and 75 and compressed at a constant speed, especially 5 mm / min, and a load bending rigidity when a displacement d = 0.2πa occurs. E
Calculate I.

EI = (π / 4-2 / π ) · W · a 3 / d · b = 0.149W · a 3 · a ·
b Note that the EI is generally different in the longitudinal direction and the width direction of the plastic film wound on the roll before coating the magnetic layer, and is usually the maximum in the longitudinal direction. And this
EI is a value in the tape longitudinal direction.

When such EI is less than 5.3 × 10 ⁻³ g · cm, running stability is deteriorated, a head touch failure occurs, output is reduced, and an envelope failure occurs. In addition, tape damage such as edge breakage and half stretch occurs. Then, run-up and jitter increase, and skew due to storage increases.

On the other hand, if the EI exceeds 8.0 × 10 ^-3 g · cm,
Cracks on the magnetic layer and scratches on the magnetic surface occur. Further, the amount of head wear increases. And dropouts increase.

The medium of the present invention having such bending rigidity may have only a backing layer on the multi-face side of the magnetic layer formation surface.

Alternatively, the backing layer may be further provided on the backing layer.

As the back surface layer, any known material can be used, and various polymer material coatings may be used, and various lubricants may be contained therein. Alternatively, a pigment, an activator or the like may be further contained.

Further, it may be a coating film of various lubricants such as fatty acids, fatty acid esters and silicones, a vapor deposition film or the like.

The back surface layer has a thickness of 2.5 μm or less, particularly about 0.3 to 1.5 μm. At this time, the bending rigidity is almost the same as when the back surface layer is not provided.

By providing such a back surface layer, the runnability is further improved.

Further, the tape of the present invention may have a surface layer formed on the magnetic layer to further improve the running property.

As the surface layer, various known ones can be applied, for example, various polymer material coatings, or those containing a lubricant, an antioxidant, a surfactant, inorganic fine particles or the like, or various lubricants. There is a coating film or a vapor deposition film.

The thickness of the surface layer is about 5 to 300 liters.

The plastic film may be subjected to various undercoating treatments, or an undercoat layer may be further formed between the plastic film and the magnetic layer or the backing layer.

V Specific Actions and Effects of the Invention The 8 mm video tape of the present invention has extremely high running stability, good head touch, and extremely low output and poor envelope due to the bending rigidity EI being regulated within a predetermined range. Also, the occurrence of tape damage such as edge breakage and half stretch is extremely small. Moreover, the occurrence of skew due to running pits, jitter, and storage is extremely small.

In addition, the occurrence of cracks in the magnetic layer and scratches on the magnetic surface due to running is extremely small, and the amount of head wear is also extremely small. And dropouts are extremely rare.

Such an effect is realized critically only in the above EI range.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples of the invention.

Example 1 A polyester (PET) film having a thickness shown in Table 1 below was moved along the circumferential surface of a cylindrical cooling can to remove O ₂ + Ar.
(Volume ratio 1: 1) flows at a speed of 800cc per minute and the degree of vacuum is 1.0 x 1
Co80, Ni20 (weight ratio) in a chamber set to 0 ^-4 Torr
Was melted and obliquely vapor-deposited only at the incident angle of 90 ° to 30 ° to form a Co-Ni-O thin film having a film thickness of 0.15 µm.

A large amount of oxygen was unevenly distributed on the interface with the base and on the surface opposite to the base. Also, the surface opposite to the base was almost entirely covered with oxide.

Hc = 1000 Oe. The average oxygen content in the film is the atomic ratio to Co and Ni. Was 40%.

An Al backing layer having a thickness shown in Table 1 below was formed on the back surface of this film by vacuum vapor deposition.

If necessary, add 100% palmitic acid on the Al backing layer.
Å It was applied to a thickness to form a back surface layer.

Furthermore, if necessary, add 25 Å myristic acid onto the magnetic layer.
It was applied thickly to form a surface layer. After that, it was cut to a width of 8 mm.

The following measurements were performed on each of the samples shown in Table 1 below formed in this way.

1) EI (g · cm) The EI in the longitudinal direction of the tape was measured by the indentation method described above.

2) Output (dB) The output at the center frequency of 5MHz was measured and the value when sample No. 1 was set to 0dB was calculated.

3) Output fluctuation (%) The maximum value of the output of 2) is set to 100% and the minimum value is displayed in%.

4) Envelope fluctuation (%) The minimum value when the maximum value of the envelope width in each sample is 100% is shown in%.

5) Dropout (pieces / minute) 6) Head wear (μm) The amount of head wear after 100 hours of continuous running was measured five times with Sony Video8 and averaged.

7) Running Naki When the head wear was measured, the presence or absence of running naki was confirmed.

8) Jitter (μsec) It was measured by connecting a jitter meter to the deck used when measuring the head wear.

9) Storage skew (μsec) After stored at 60 ° C. and 80% relative humidity for 7 days, the skew was measured using the deck.

10) Tape damage The tape running surface after 100 hours of continuous running was observed with an optical microscope (× 5
It was observed at 0, × 400).

The results are shown in Table 1.

From the results shown in Table 1, the effect of the present invention is clear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for explaining a method of measuring a bending rigidity value.

Claims (5)

[Claims] 1. A Co or CoNi-based ferromagnetic metal thin film containing O on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm.
/ Ni weight ratio is 1.5 or more, O / (Co + Ni) atomic ratio is 0.15 ~
When the bending rigidity value EI of a medium having a magnetic layer of 0.6 and a backing layer on the other surface is calculated by the following formula, EI is
Video tape characterized in that it is 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm. Formula EI = (π / 4−2 / π) · W · a ³ / d · b (W is the radial direction for a ring-shaped test piece with a radius of acm and width of bcm created by cutting a magnetic sheet. (This is the load that causes the displacement d = 0.2πa.) 2. The video tape according to claim 1, wherein the backing layer is a film of metal or its oxide. 3. The magnetic recording medium according to claim 1, wherein the backing layer has a thickness of 0.05 μm to 1.5 μm. 4. A Co or CoNi-based ferromagnetic metal thin film containing O on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm.
/ Ni weight ratio is 1.5 or more, O / (Co + Ni) atomic ratio is 0.15 ~
It has a magnetic layer of 0.6, a backing layer on the other side, and a backing layer on this backing layer, and when the bending stiffness value EI of the medium is calculated by the following formula, EI is
Video tape characterized in that it is 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm. Formula EI = (π / 4−2 / π) · W · a ³ / d · b (where W is the radial direction for a ring-shaped test piece with radius acm and width bcm created by cutting a magnetic sheet) (This is the load that causes the displacement d = 0.2πa.) 5. A magnetic layer of a Co or CoNi-based ferromagnetic metal thin film containing O is provided on one surface of a plastic film having a thickness of 10 μm or less and a width of 8 mm, and a surface layer is provided on the magnetic layer. However, it has a backing layer on the other side and a backing layer on this backing layer, and when the bending stiffness value EI of the medium is calculated by the following formula, EI is
Video tape characterized in that it is 5.3 × 10 ^{−3 to} 8.0 × 10 ⁻³ g · cm. Formula EI = (π / 4−2 / π) · W · a ³ / d · b (where W is the radial direction for a ring-shaped test piece with radius acm and width bcm created by cutting a magnetic sheet) (This is the load that causes the displacement d = 0.2πa.)