JPH03260909A - Magnetic tape - Google Patents

Abstract

PURPOSE:To improve traveling stability and to eliminate output variation and dropout by providing a magnetic layer incorporating magnetic powder and a binder so that the magnetic layer has specified center-line average surface roughness on one side of a nonmagnetic body having the specified number of projections of specified maximum height and average particle size and specified center-line average surface roughness. CONSTITUTION:The nonmagnetic supporting body has the projections of <=1.0 mum maximum height and <=30 mum average size with 2-5 projections/50 cm<2> distributions and 0.020-0.035 mum center-line average surface roughness. The magnetic layer incorporating magnetic powder and the binder is formed on the supporting body so that the layer has <=0.020 mum center-line average surface roughness to constitute the magnetic tape. As for the nonmagnetic body, polyesters such as polyethylene terephthalate, or polyolefins such as polypropylene are used, and the magnetic powder used is, as usual, powders or metal-type magnetic powders such as gamma-Fe2O3, Co-contg.gamma-Fe2O3. As for the binder, polyurethane resin, polyvinylbutylal resin, etc., are used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a magnetic tape useful for audio tapes and the like.

[Conventional technology]

Generally, this type of magnetic tape is manufactured by using a flexible resin film such as polyethylene terephthalate film as a non-magnetic support, and coating one side of this support with a magnetic paint containing magnetic powder and a binder and drying it. It is manufactured by forming a thick magnetic layer.

In order to ensure running stability when such magnetic tape is loaded into a cassette or the like and recorded and played back by a recorder, the surface roughness of the back side of the magnetic tape that comes into contact with guide pins, guide rollers, etc. must be reduced. For example, by increasing the height or number of the surface protrusions of the support film, the coefficient of friction on the back side is made appropriate.

[Problem to be solved by the invention]

However, when the surface roughness of the back surface of the tape is increased as described above, the surface roughness is transferred to the surface of the magnetic layer at the same time as the tape is wound, resulting in a problem that output fluctuations during reproduction become large. In addition, during the calendering process after forming the magnetic layer in the magnetic tape manufacturing process, the surface protrusions on the back of the tape are scratched, and the fine particles are transferred to the surface of the magnetic layer, resulting in frequent dropouts during playback. There were also problems.

The object of the present invention is to overcome the above-mentioned conventional problems, that is, to provide a magnetic tape that can both ensure running stability and reduce output fluctuations and tropouds.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventor identified the surface roughness of a non-magnetic support such as a polyester film in terms of the maximum height, size, number, etc. of surface protrusions, and By specifying the surface roughness of the magnetic layer provided on one side of the support, we learned that it was possible to both ensure running stability and reduce output fluctuations and dropouts, which led us to complete this invention. It's arrived.

That is, this invention provides 2 to 5/50 surface protrusions with a maximum height of 1.0 μm or less and an average size of 30 μm or less.
cnl, and the centerline average surface roughness is 0.020 to 0.
The present invention relates to a magnetic tape in which a magnetic layer containing magnetic powder and a binder and having a center line average surface roughness of 0.020 μm or less is provided on one side of a non-magnetic support having a diameter of 0.035 μm.

[Structure and operation of the invention]

As the non-magnetic support in this invention, a flexible resin film having a thickness of usually about 5 to 15 μm, such as polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, boria carbonate, polyimide resin, etc., is used. Preferably used.

Conventionally, this resin film has a high surface roughness, with the height of the surface protrusions being increased or the number of the protrusions being increased as much as possible, as described above, but in this invention, the maximum height of the surface protrusions is is 1.0 μm or less, and the average size is 30 μm or less, and the number of surface protrusions is limited to 2 to 5 a per 50 cJ, and the center line average surface roughness is 0.020. ~0.03
A material with a thickness in the range of 5 μm is used.

Using a resin film with such a specific surface roughness provides good running stability, reduces output fluctuations during playback, and eliminates surface protrusions during calendering after magnetic layer formation. There will be no deviation and dropouts during playback will also be reduced. On the other hand, if any one or more of the maximum height, thickness, and number of surface protrusions and the center line average surface roughness deviate from the specified range of the present invention, output fluctuations and dropouts may occur. It will increase or the driving stability will become worse.

In this specification, the maximum height, size, and number of surface protrusions are all based on multiple interference micrographs (magnification: 200
The center line average surface roughness was measured using a stylus surface roughness meter (stylus speed Q, 1 mt/sec, cutoff 0.081 m).
(1.1 mm traveling under the conditions of 1.1 mm).

In order to set the surface roughness of the resin film as a non-magnetic support within the above-mentioned specific range, for example, the type of inorganic filler added to the resin composition when extruding the resin composition into a film shape, This may be done by selecting the amount, or by appropriately selecting the conditions of stretching treatment, mirror polishing treatment, etc. that are usually performed after extrusion molding, and the means for setting these is not particularly limited.

In addition, when the above-mentioned stretching process is uniaxial stretching in the longitudinal direction of the tape, the surface protrusions of the formed film have an elliptical shape, and in this case, there is a major axis diameter in the tape longitudinal direction and a minor axis diameter in the width direction. become.

In this invention, the average size of the surface protrusions is 3 as described above.
Although it is set to 0 μm or less, in the case of the above-mentioned elliptical shape, the average value of the major axis diameter may be set to the above-mentioned value.

In this invention, a magnetic paint containing magnetic powder, a binder, and various additives blended as necessary is coated on one side of such a non-magnetic support, and dried to a thickness of approximately 3 to 10 mm.
After forming a μm magnetic layer, calendering is performed,
Further, a magnetic tape is produced through necessary processes such as a cutting process.

Here, it is necessary that the center line average surface roughness of the magnetic layer after calendering is 0.020 μm or less,
If it is larger than this, it becomes difficult to obtain good results in terms of output fluctuations, etc. The above-mentioned surface roughness can be easily set by selecting the calendering conditions. In addition, during this calendering process, since the surface roughness of the back surface of the tape is set within the specified range, the conventional problem of shearing no longer occurs.

As the magnetic powder used in the magnetic paint, a wide variety of conventionally known magnetic powders can be used, such as γFe2O3, CO
Containing γ-Fe203, oxide magnetic powder such as Ba ferrite, F6. Examples include metal-based magnetic powders such as Co and N1. The same applies to the binder, including polyurethane resin, polyvinyl butyral resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride acrylic copolymer, polyester resin, and polyester as a crosslinking agent. Any conventionally known compounds such as isocyanate compounds and radiation-curable resins can be used. Further, additives that may be added as necessary include a dispersant 1, a lubricant, an abrasive, a colorant, an antistatic agent, a filler, and the like.

In the magnetic tape of the present invention, a known back coat layer may be provided on the back side of the tape, and in this case, the surface roughness of the back side of the tape after providing the back coat layer may be set within the above range. , whereby the same effects as those described above can be achieved.

〔Effect of the invention〕

As described above, in the present invention, the surface roughness of a non-magnetic support is specified by the maximum height, size, number, etc. of surface protrusions, and one side of this support has a specific surface roughness. By providing a magnetic layer, it is possible to obtain a magnetic tape that satisfies running stability and has less output fluctuation and dropout.

〔Example〕

Next, examples of the present invention will be described in more detail. In addition, the following parts shall mean parts by weight.

Example 1 A non-magnetic support had 2/50 cta of surface protrusions with a maximum height of 0.5 μm, an average major axis diameter of 25 μm, and an average minor axis diameter of 15 μm, and a center line average surface. A polyethylene terephthalate film (hereinafter referred to as PET film) with a thickness of 7 μm and a roughness of 0.025 μm was used.

On the other hand, γ-Fe203 magnetic powder (average major axis diameter 0°3 μm
, average axial ratio 10, coercive cuff 00 oersted, saturation magnetization 76 parts mu/g) 80 parts, hydroxyl group-containing vinyl chloride-vinyl acetate copolymer (U, C, C).

10 parts of polyurethane resin (trade name: VANDEX-T5250, manufactured by Dainippon Ink Co., Ltd.), 8 parts
1 part, 2 parts of polyisocyanate compound (trade name Coronate L manufactured by Nippon Polyurethane Co., Ltd.), carbon black (trade name Asahi H3500 manufactured by Asahi Carbon Co., Ltd., average particle size 43 mμ
), 50 parts of cyclohexanone, 50 parts of methyl ethyl ketone, and 2 parts of palmitic acid were mixed and dispersed in a bowl for 70 hours to prepare a magnetic paint.

Next, this magnetic paint was applied to one side of the non-magnetic support so that the thickness after drying was 5 μm, and then dried.
Calendered and center line average surface roughness is 0.01
A magnetic layer of 0 μm was formed.

Thereafter, it was cut to a width of 3.8 mm to produce a magnetic tape.

Example 2 A non-magnetic support had 4/50 ca surface protrusions with a maximum height of 0.7 μm, an average major axis diameter of 30 μm, and an average minor axis diameter of 25 μm, and a center line average surface. A 7 μm thick PET film with a roughness of 0.030 μm was used.

A magnetic coating similar to that in Example 1 was applied to one side of this support so that the thickness after drying was 5 μm, and after drying, calendering was performed to obtain a center line average surface roughness of 0.012.
A magnetic layer with a thickness of μm was formed.

Thereafter, it was cut into a 3.8w width to produce a magnetic tape.

Comparative Example 1 A nonmagnetic support having 10/50 ctA of surface protrusions with a maximum height of 1.2 μm, an average major axis diameter of 50 μm, and an average minor axis diameter of 30 μm, and a center line average surface A 7 μm thick PET film with a roughness of 0.038 μm was used.

A magnetic paint similar to that in Example 1 was applied to one side of this support so that the dry thickness was 5 μm, and after drying, calendering was performed to obtain a center line average surface roughness of 0.018.
A magnetic layer with a thickness of μm was formed.

Thereafter, it was cut to a width of 3.8 mm to produce a magnetic tape.

Comparative Example 2 A non-magnetic support had one surface protrusion of 150 CII+ with a maximum height of 0.2 μm, an average major axis diameter of 15 μm, and an average minor axis diameter of 10 μm, and a center line average surface roughness. A PET film with a thickness of 7 μm and a diameter of 0.010 μm was used.

On one side of this support, a magnetic coating similar to that in Example 1 was applied to a dry thickness of 5 μm, dried, and then calendered to give a center line average surface roughness of o, o.
A magnetic layer of 0 s μm was formed.

Thereafter, it was cut to a width of 3.8 to produce a magnetic tape.

Regarding each of the magnetic tapes of the above Examples and Comparative Examples, running stability, output fluctuation, and dropout were measured by the following methods. These measurement results were as shown in Table 1 below.

<Running Stability> Wow when running at a tape speed of 4.76 cm/sec.
Flutter (%) was measured.

Output fluctuation> The specified bias current is applied to the sample tape, and the specified input level is 2.
An 8 KHz signal was recorded with an input level 0 dB lower, and this was played back to measure changes in the output level.

<Dropout> According to the standards of the Magnetic Tape Industry Association, tape speed 4.
The number of dropouts (depth of 2 dB or more) was measured using a dropout counter when running at 76c+n/sec for 3 minutes.

Table 1 2 As is clear from the results in Table 1 above, the magnetic tape of the present invention not only has good running stability, but also has little output fluctuation and dropout.

Claims (1)

[Claims] (1) Maximum height is 1.0μm or less, average size is 30μm
A center line containing magnetic powder and a binder is placed on one surface of a non-magnetic support having 2 to 5 surface protrusions of m or less/50 cm^2 and a center line average surface roughness of 0.020 to 0.035 μm. A magnetic tape provided with a magnetic layer having an average surface roughness of 0.020 μm or less.