JP3126025B2 - Magnetic tape - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape used in a recording / reproducing apparatus of a recording / reproducing system using a head mounted on a rotating drum, that is, a rotating head recording system.

[Conventional technology]

When recording an image on a magnetic tape, the recording capacity of the tape must be greatly increased compared to that of audio recording. Therefore, the recording density of the tape has been improved, and the recording / reproducing device has also changed from a fixed head recording system to a rotating head. By changing to a recording method, a dramatic improvement in recording density has been achieved. Similarly, in order to increase the recording capacity, a data recording tape has been developed from a fixed head recording method to a rotary head recording method.

In the rotating head recording method, in order to make the tape wound obliquely around the drum run stably, the lead that regulates the edge below the tape at the drum part has an inclined edge that regulates the edge above the tape at the entrance and exit of the winding part. A guide is provided. In addition to this complicated running system, in order to increase the recording capacity per tape, there is a tendency for magnetic tapes to be thinner and to have a lower tape speed during recording. On the device side, from the viewpoint of improvement in operability, a function of fast-forwarding and rewinding while a tape is wound around a drum is provided, and the speed of fast-forwarding and rewinding tends to increase.

[Problems to be solved by the invention]

However, in order to obtain a high recording capacity, the total thickness is 18.5 μm.
When using a very thin magnetic tape as shown below, or when performing a running operation in which the tape speed at the time of fast-forward or rewind / the tape speed at the time of recording becomes 10 times or more, damage to the tape during running may be caused. When the tape is severely damaged during repeated use, a soft pack (deformation loosening phenomenon) occurs on the take-up reel, and there has been a problem that stable running cannot be secured.

As shown in FIG. 1, the above-mentioned soft pack refers to a state in which the tape is wound so that the winding shape of the measurement surface of the take-up reel is wavy in the circumferential direction of the winding surface, and is perpendicular to the winding surface. This is different from the phenomenon of turbulence in which the tape is displaced in the direction.

To date, almost no countermeasures have been taken on the magnetic tape side, and only the adjustment of the running system on the recording / reproducing apparatus has been performed, and the results have not been satisfactory.

In view of such circumstances, the present invention provides a very thin magnetic tape having a total thickness of 18.5 μm or less in order to obtain a high recording capacity, and even when the above-described severe running operation is performed by a rotating head recording method. It is another object of the present invention to provide a magnetic tape which does not cause soft packing as in the prior art and has excellent running stability when used repeatedly.

[Means for solving the problem]

In order to achieve the above object, the present inventors first studied the cause of the conventional soft pack, and found that the downward restriction force by the upper flanges of the inclined guides provided at the entrance and exit of the tape winding portion of the drum. As a result, it has become clear that the cause is that the edge on the tape is deformed (turned up) and the winding reel cannot maintain the winding property.

Therefore, as a result of further study to eliminate the deformation of the edge on the tape, while strengthening the strength of the magnetic tape in the width direction, the coefficient of friction on the back of the tape was moderate,
Furthermore, when the thickness unevenness and tape curl in the tape width direction are reduced, the deformation phenomenon as described above is suppressed, and the winding property on the take-up reel is well maintained, and thereby the soft pack is remarkably suppressed. That led to the completion of the present invention.

That is, according to the present invention, a magnetic layer is provided on one side of a non-magnetic substrate, and a back coat layer is provided on the other side, and recording and reproduction are performed by a rotary head recording method, that is, by a head attached to a rotary drum. At the same time, in a magnetic tape having a total thickness of 6.6 to 18.5 μm used in a recording / reproducing apparatus in which the tape speed at the time of fast-forward and rewind while being wound on the drum is 10 times or more the tape speed at the time of recording, The elastic modulus in the width direction is 700 to 1,000 kg / mm ² , the surface roughness of the back coat layer is 0.009 to 0.010 μm, the thickness unevenness in the width direction (width: around 2.54 cm) is 20 μm or less / 1,000 sheets, and the tape curl (width: (Per 2.54 cm) is within ± 1 mm.

[Structure and operation of the invention]

The magnetic tape of the present invention has a basic structure in which a magnetic layer is provided on one surface of a non-magnetic substrate and a back coat layer is provided on the other surface, respectively. Alternatively, an appropriate modification such as interposition of a base layer between the back coat layer and a top coat layer on the magnetic layer may be adopted.

Such a magnetic tape is formed, for example, by applying a magnetic paint containing a magnetic powder, a binder and various additives optionally added to one surface of a non-magnetic substrate, drying the magnetic paint, and drying the magnetic layer comprising a magnetic coating film. Is formed, and a backcoat containing a carbon black, a binder, and various additives to be blended as required is applied to the other surface and dried to form a backcoat layer. Also, in some cases, instead of the above magnetic coating, by a vacuum evaporation method or the like
It can also be manufactured by forming a magnetic layer made of a thin film of a magnetic metal or alloy such as Fe, Co, and Ni.

As the non-magnetic substrate, various flexible materials including a plastic film such as a polyester film, a polyamide film, and a polyvinyl chloride film are used. The magnetic powder used for forming the magnetic coating film includes γ-Fe ₂ O
₃ , Co-containing γ-Fe ₂ O ₃ , oxide magnetic powder such as Ba ferrite, Fe, Co, metal magnetic powder such as Ni and the like, as a binder, polyurethane-based resin, polyvinyl butyral-based resin, Cellulosic resins, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acrylic copolymers, polyester resins, polyisocyanate compounds as crosslinking agents, radiation-curable resins, and the like. Additives to be blended include dispersants, lubricants, abrasives, coloring agents, antistatic agents, fillers and the like. further,
As the binder used for forming the back coat layer and the additives to be blended if necessary, the same ones as in the case of the magnetic coating film are used.

In the present invention, the recording capacity per roll in the rotary head recording system is increased by setting the total thickness of the magnetic tape thus manufactured to 6.6 to 18.5 μm. The thicknesses of the substrate, the magnetic layer and the back coat layer are 6 to 15 μm for the non-magnetic substrate and 0.1 to 4 μm for the magnetic layer (however, 0.1 to 0.
4μm, 1-4μm for magnetic coating), for back coat layer
It is desirable that the thickness be in the range of 0.5 to 1.5 μm.

Such a thin magnetic tape is loaded into a recording / reproducing apparatus of a rotary head recording type, and fast-forwarding and rewinding in a state of being mounted on a drum in view of high recording capacity and operability. The tape speed when recording is 10 times the tape speed when recording
When operating under severe conditions that are more than doubled,
Conventionally, soft packs were relatively easily generated, but according to the present invention, the strength in the width direction of the tape was increased to a certain value or more, and the coefficient of friction on the back surface of the tape was made appropriate. By making the thickness unevenness and the tape curl in the tape width direction extremely small below a specific value, the problem of the soft pack is greatly suppressed.

In the magnetic tape of the present invention, the elastic modulus in the width direction is 70.
It is 0 to 1,000 kg / mm ² , preferably 750 to 1,000 kg / mm ² . When the strength in the width direction is increased in this manner, it is possible to sufficiently resist the downward regulating force by the upper flange of the inclined guide in the tape winding portion. In addition, the thickness unevenness in the tape width direction (width: about 2.54 cm) is 20 μm or less / 1,000 sheets, preferably 10 μm or less / 1,000 sheets, and the tape curl (width: about 2.54 cm) is within ± 1 mm, preferably Is within ± 0.5 mm. By restricting in this manner, deformation of the edge on the tape when receiving the downward restricting force, that is, turning up, becomes less likely to occur. Furthermore, when the surface roughness of the back coat layer is adjusted to the range of 0.009 to 0.010 μm, the friction coefficient on the back of the tape becomes very moderate, about 0.20 to 0.26, and the frictional resistance in the running system is greatly reduced. Can be.

As described above, in the present invention, the elastic modulus in the width direction, the thickness unevenness in the width direction, the surface roughness of the tape curl and the back coat layer are specified, and the resistance to mechanical deformation and the running property are appropriately combined and improved. In this way, even when the severe running operation is performed, the edge on the tape is prevented from being deformed, and the winding property of the take-up reel is maintained, so that the conventional soft packing does not occur, and the tape is repeatedly used. A magnetic tape having extremely excellent running stability at the time was obtained.

Here, the elastic modulus in the tape width direction is determined by selecting the material of the non-magnetic substrate, or by selecting the type of binder and the content of spherical particles such as carbon black in the magnetic layer composed of the magnetic coating film. And the surface roughness of the back coat layer can be easily set by selecting the particle size and amount of the carbon black to be used. On the other hand, uneven thickness and tape curl in the width direction of the tape, when forming a magnetic coating or back coat layer,
It can be set by appropriately selecting the coating or subsequent drying conditions.For example, after sufficiently lowering the viscosity of the coating material to improve the fluidity, a coating machine such as a conventionally known roll coater, gravure coater, extrude-jion coater or the like can be used. By applying and using the following drying at a temperature as high as possible so that the solvent does not remain in the coating film, to obtain a magnetic tape satisfying the above conditions, which has a small thickness unevenness and a small tape curl. Can be.

In the present invention, the formation of the magnetic layer and the back coat layer is usually performed using a wide non-magnetic substrate, and after the formation of these layers, it is cut into a predetermined width according to the purpose of use. At that time, the waving of the tape edge
40 μm or less, preferably 30 μm or less, the edge of the tape edge is 2 μm or less / 1,000 sheets, preferably 1 μm
By appropriately selecting the cutting machine, the cutting tool conditions at the time of cutting, the tape running conditions, and the like, the resistance to the mechanical deformation is further increased, and a favorable result is obtained by preventing soft packing.

The waving of the tape edge is measured by a method of continuously reading both ends of the tape edge using a dynamic width measuring device. The rising edge of the cut edge of the tape edge and the thickness unevenness in the tape width direction are defined as a state in which a magnetic tape is wound 1,000 times around a reel, that is, in a state where 1,000 tapes are stacked, a non-contact displacement meter using a laser beam is used. The entire thickness change is read to measure how much the outer periphery of the tape edge has risen, or whether the tape edge is partially raised in the width direction. Also, the tape curl is
Place the magnetic tape on the glass plate and measure the curl in the width direction by measuring the height from the glass surface. If both edges are curled toward the magnetic layer, add +, curl toward the back coat layer. If there is, it is represented as-.

〔The invention's effect〕

As described above, according to the present invention, in order to obtain a high recording capacity, in a very thin tape having a total thickness of 6.6 to 18.5 μm, the elastic modulus in the tape width direction, the thickness unevenness in the width direction, the tape curl, and the back coat layer. By specifying the surface roughness, and more preferably also specifying the waving of the tape edge and the rising edge of the cut edge of the tape edge, by improving the resistance to mechanical deformation on the rotating drum and running performance, etc. It is possible to provide a high-recording-capacity magnetic tape that is hard to cause soft packing as in the past and has excellent running stability when used repeatedly, even under severe running operation by the rotary head recording method. .

〔Example〕

Next, the present invention will be specifically described based on examples. The following parts mean parts by weight.

Example 1 One side of a polyethylene terephthalate film (hereinafter, referred to as a PET film) having a thickness of 14.0 μm and a film width of 508 cm was coated with Fe magnetic powder (average major axis diameter 0.2 μm, average axis ratio 10;
Coercive force 1,600 ersted, saturation magnetization 125emu / g) 100 parts,
15 parts of vinyl chloride-acrylic copolymer (trade name: MR-110, manufactured by Zeon Corporation), 9 parts of polyurethane resin (trade name: N-2301, manufactured by Nippon Polyurethane), polyisocyanate compound (trade name, manufactured by Nippon Polyurethane) Name Coronate L)
8 parts, carbon black (Vulcan XC manufactured by Cabot Corporation)
−72, 3 parts of average particle diameter 0.03 μm), 8 parts of alumina powder (average particle diameter of 0.3 μm), 1 part of myristic acid (lubricant),
After adjusting the solid content of a magnetic paint composed of 150 parts of cyclohexanone and 150 parts of toluene so that the viscosity becomes 800 centipoise (cps), the thickness after drying becomes 3.2 μm using a gravure coater. Apply at 105 ℃
After drying, a mirror surface treatment was performed to form a magnetic layer.

Next, on the other side of this PET film, Mogar L (average particle diameter) manufactured by Cabo
65 parts, Conductex 975 (average particle diameter 0.046 μm) 5 parts by Columbian Carbon Co., 30 parts calcium carbonate powder, 30 parts nitrocellulose (trade name HIG1 / 2 by Asahi Kasei Corporation), polyurethane resin (0.024 μm) 35 parts of N-2309 (trade name, manufactured by Nippon Polyurethane), 16 parts of polyisocyanate compound (Coronate L, trade name of Nippon Polyurethane)
Part, cyclohexanone 410 parts, and toluene 410 parts was coated with a gravure coating machine similar to the above so that the thickness after drying was 1 μm, and 105 ° C.
To form a back coat layer.

After the magnetic layer and the back coat layer are formed in this manner, the rubber hardness of the nip roll (made of rubber) for imparting a constant tension to the tape being cut is appropriately adjusted so that the fluctuation of the tension is ± 0.1% or less, and the operating distance is reduced. Is equipped with a cutting tool with less wear at the tip of 50 km or less,
It was cut to a width of 2.54 cm to produce a magnetic tape having a total thickness of 18.0 μm.

This magnetic tape has an elastic modulus in the tape width direction of 810 kg / mm
^2. The surface roughness of the back coat layer was 0.010 μm, the thickness unevenness in the width direction was 4 μm / 1,000 sheets, the tape curl was +0.5 mm, the tape edge waving was 32 μm, and the edge of the tape edge was 0 μm / 1,000 sheets. .

The elastic modulus in the tape width direction was measured by the following vibration lead method, and the surface roughness of the back coat layer was measured by the following stylus roughness meter. Other properties were measured according to the methods described above.

<Measurement method of elastic modulus> About 5 mm from the measuring tape in the width direction of the tape and about
Cut out a 1 mm strip-shaped measurement sample, fix one end in the longitudinal direction to the vibrating part of the shaker, slowly change the frequency from low to high, and simultaneously vibrate the other end of the sample. Is measured with a non-contact displacement meter, and the excitation frequency (resonance frequency) when the amplitude becomes maximum is read,
Calculate the elastic modulus in the width direction of the sample tape according to the following formula,
The average value of 10 samples is shown.

E _TD : elastic modulus in the width direction (kg / mm ² ) a: constant (a = 3.83) ρ: tape density (g / cm ³ ) l: sample length of vibrating part (mm) t: tape thickness (mm) F ₀ : Resonance frequency (Hz) <Measurement of surface roughness> The center line average roughness Ra (μm) was measured by a stylus type roughness meter. With a stylus speed of 0.015mm / sec and a cut-off of 0.08mm
After running 0.25 mm, the above Ra was determined, and the average value of 10 times was shown.

Examples 2 and 3 The cutting conditions of the cutting machine were changed such that the rubber hardness of the nip roll was softened, the variation in tension was increased to ± 0.5%, and the waving of the tape edge was 48 μm (Example 2). Was changed so that the cutting edge of the tape edge became 2 μm / 1,000 sheets (Example 3) in place of the one with a 500 km driving distance and the tip was worn, and the other two types were completely the same as Example 1 Was produced.

Comparative Example 1 Among the binders of the magnetic paint, instead of 9 parts of a polyurethane resin (trade name N-2301 manufactured by Nippon Polyurethane Co.), a polyurethane resin (trade name N-230 manufactured by Nippon Polyurethane Co.) was used.
4) A magnetic tape was produced in the same manner as in Example 1 except that 9 parts were used. This magnetic tape has an elastic modulus in the tape width direction of 620 kg / mm ² , a surface roughness of the back coat layer of 0.010 μm, a thickness unevenness in the width direction of 6 μm / 1,000 sheets, a tape curl of 0 mm, and a tape edge webbing of 28 μm.
m, the rise of the edge of the tape edge was 0 μm / 1,000 pieces.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that 70 parts of Mogal L (average particle size 0.024 μm) manufactured by Cabo Co. was used as the carbon black of the back coat paint. This magnetic tape has an elastic modulus in the tape width direction of 780 kg / mm ² and a surface roughness of the back coat layer of 0.008 μm.
m, the thickness unevenness in the width direction was 8 μm / 1,000 sheets, the tape curl was −0.5 mm, the tape edge waving was 30 μm, and the rise of the cut edge of the tape edge was 0 μm / 1,000 sheets.

Comparative Example 3 60 parts of Mogal L (average particle diameter 0.024 μm) manufactured by Cabo Corporation and Conductex 975 manufactured by Columbia Carbon Co., Ltd.
(Average particle diameter 0.046 μm) A magnetic tape was produced in the same manner as in Example 1, except that 10 parts was used. This magnetic tape has an elastic modulus in the tape width direction of 780 kg / mm ² ,
The surface roughness of the back coat layer was 0.011 μm, the thickness unevenness in the width direction was 12 μm / 1,000 sheets, the tape curl was +0.5 mm, the tape edge waving was 28 μm, and the edge of the tape edge was 0 μm / 1,000 sheets.

Comparative Example 4 Example 1 except that the solid content concentration was adjusted so that the viscosity of the magnetic paint became 950 cps, and the thickness unevenness in the width direction of the magnetic tape as a final product was 25 μm / 1,000 sheets. A magnetic tape was produced in the same manner as described above. The elasticity of the magnetic tape in the tape width direction was 820 kg / mm ² , the surface roughness of the back coat layer was 0.009 μm, and the tape curl was +0.5.
mm, the tape edge waving was 30 μm, and the cut edge of the tape edge was 0 μm / 1,000 sheets.

Comparative Example 5 A magnetic tape was prepared in the same manner as in Example 1 except that the drying temperature after applying the magnetic paint and the back coat paint was changed to 95 ° C. so that the curl of the magnetic tape as the final product was +2 mm. Was prepared. The elastic modulus in the tape width direction of this magnetic tape was 760 kg / mm ² , the surface roughness of the back coat layer was 0.009 μm, the thickness unevenness in the width direction was 8 μm / 1,000 sheets, and the tape edge webbing was 30 μm.
m, the rise of the cut edge of the tape edge was 0 μm / 1,000 sheets.

About each magnetic tape of the above Examples and Comparative Examples,
Using a rotary head recording type recording / reproducing device, a digital VTR HV-1200 for high vision manufactured by Hitachi, Ltd., the tape speed when fast-forwarding and rewinding with a magnetic tape wound around a rotating drum is recorded. 1 reciprocation of fast-forward and rewind by 1
It was repeatedly used 5 times, and the soft pack resistance on the take-up reel was visually inspected and evaluated as follows.

◎: Extremely excellent in soft-packing resistance…: Slight edge deformation on tape, but not up to soft-packing △: Soft-packing slightly observed ×: Soft-packing remarkably observed The test results are shown in Table 1 below together with the coefficient of friction of the back coat layer examined in the following manner.

<Coefficient of friction of the back coat layer> A SUS304 cylinder (surface roughness 0.2S) with a diameter of 4mm is supported horizontally, and a magnetic tape is applied to this at an angle of 90 ° with the back coat layer in contact with the cylinder surface, and 200g is applied to one end. The stress T (g) when the other end was pulled horizontally at a speed of 3.3 cm / sec while applying the load was determined, and this was applied to the following equation to calculate the friction coefficient μ.

From the results in Table 1 above, the magnetic tapes of Examples 1 to 3 in which the elastic modulus in the tape width direction, the thickness unevenness in the width direction, the tape curl and the surface roughness of the back coat layer were defined within the scope of the present invention, Examples in which the magnetic tapes of Comparative Examples 1 to 5 each of which has one of the above-mentioned characteristics were out of the scope of the present invention were superior in soft pack resistance, and in particular, an example in which the waving of the tape edge and the rise of the cut edge of the tape edge were reduced. It can be seen that the magnetic tape No. 1 is most excellent in the soft pack resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a state where a soft pack has occurred on a magnetic tape.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masayoshi Kawarai 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-63-39132 (JP, A)

Claims (2)

(57) [Claims] 1. A magnetic layer is provided on one side of a non-magnetic substrate, and a back coat layer is provided on the other side. Recording and reproduction are carried out by a head mounted on a rotating drum, and the drum is wound around the drum. In a magnetic tape with a total thickness of 6.6 to 18.5 μm used in a recording / reproducing device in which the tape speed at the time of fast-forward and rewind in a folded state is 10 times or more the tape speed at the time of recording, the elastic modulus in the width direction is 700 to 1,000 kg / mm ² , surface roughness of back coat layer is 0.009 to 0.010 μm, thickness unevenness in the width direction (width: about 2.54 cm) is 20 μm or less / 1,000 sheets, tape curl (width: about 2.54 cm) is within ± 1 mm A magnetic tape, characterized in that: 2. The tape edge has a waving of 40 μm or less, and the tape edge has a rise of 2 μm or less / 1,0.
The magnetic tape according to claim 1, wherein the number is 00.