JPH04221421A - Magnetic tape and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape which is superb in surface roughness, envelope flattening rate, running property, and output stability by maintaining flex strength in a magnetic tape which is used for a video equipment requiring a high-density long-time recording and by solving a problem where it is difficult to obtain running stability and output stability. CONSTITUTION:A hexagonal system ferrite powder and a carbon black powder where a back coat layer 2 which is formed on other surface of a non-magnetic substrate having a magnetic layer on one surface owns a shape of plate shape ratio of 10-60 are contained, a coercive force of the backcoat layer is 1-300 oersteds, and a superb magnetic tape can be obtained by applying a magnetic field in vertical and horizontal directions for the substrate or in vertical direction for the substrate.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a magnetic tape used in video equipment requiring high-density, long-term recording, and more particularly to a thin magnetic tape with a total thickness of 14.0 μm or less and its manufacture. Regarding the method.

0002

2. Description of the Related Art In recent years, there has been remarkable progress in the miniaturization and performance improvement of audio/video equipment, and there will continue to be a demand for high-density recording and miniaturization of magnetic recording and reproducing devices.

In order to record a large amount of information in a given volume, it is necessary not only to increase the areal recording density by narrowing the gap and track of the magnetic head, but also to reduce the total thickness of the medium. extremely important.

In order to increase the recording density, it is first necessary to reduce the surface roughness of the magnetic layer of the recording medium and reduce the spacing loss between the magnetic head and the medium. For this reason, the surface roughness of nonmagnetic substrates used for high-density recording is kept small in order to produce a smooth magnetic layer surface.

[0005] Generally, the friction coefficient of a mirror-finished magnetic layer and a non-magnetic substrate with a smooth surface increases, so that the running performance of a magnetic tape in a video deck is significantly reduced.

The back coat layer is provided for the purpose of lowering the high coefficient of friction of the base film to ensure tape runnability, as well as for the purpose of reducing electrical resistivity and light-shielding properties. Prior art disclosures regarding the back coat layer include, for example, U.S. Pat. No. 2,804,401, U.S. Pat.
772, JP-A-60-1622, JP-A-60-7612, etc.

As the magnetic tape used in audio/video equipment becomes thinner, the stiffness of the magnetic tape (
(bending strength) is insufficient, resulting in increased damage such as bending of the magnetic tape and unstable reproduction output due to a decrease in head touch. The inventors have found that these problems are particularly likely to occur when the magnetic tape lacks stiffness in the width direction.

Tape damage and output instability are most dependent on the running design of the magnetic tape in the device, but the first characteristic required for any thin magnetic tape is to ensure mechanical strength in the tape width direction. There is a need to.

[0009] In order to improve the mechanical strength of the magnetic tape, it is conceivable to increase the mechanical strength of the nonmagnetic substrate. As prior disclosed technology, for example, Japanese Patent Application Laid-Open No. 63-3
No. 9133, No. 62-117137, and Japanese Patent Publication No. 1-43364 disclose thinning of the non-magnetic substrate, improvement of the mechanical strength of the non-magnetic substrate to compensate for this, and improvement of the length and width of the magnetic tape. The balance of directional strength is disclosed. According to these disclosed technologies, polyethylene-2,6-naphthalate film or aromatic polyamide film can be used instead of stretched polyethylene terephthalate (hereinafter abbreviated as PET) film, which has been conventionally used as a non-magnetic substrate. Disclosed.

0010

[Problems to be Solved by the Invention] However, even with the prior art disclosed above, there is a limit to the improvement in the mechanical strength of a non-magnetic substrate made of a polymer material, and it is difficult to improve the stiffness in the width direction of a magnetic tape. More preferably, it is extremely difficult to obtain a magnetic tape that has improved stiffness not only in the width direction but also in the longitudinal direction and that also has excellent running stability and output stability. Ta.

[0011] The present invention solves the above problems, and
The object of the present invention is to provide a thin magnetic tape that has excellent running durability and a method for manufacturing the same.

0012

[Means for Solving the Problems] The magnetic tape of the present invention includes:
In order to achieve the above objective, the back coat layer has a plate-like ratio of 1.
0 to 60 hexagonal ferrite powder and carbon black powder, and the coercive force of the back coat layer is 1.
It is configured to be set at ~300 oersteds.

The method for manufacturing a magnetic tape of the present invention is to apply a magnetic field perpendicular to the substrate in an undried state after coating the backcoat layer on a non-magnetic substrate, and immediately apply a magnetic field parallel to the running direction of the substrate. The structure is such that a magnetic field is applied.

Furthermore, the method for manufacturing a magnetic tape of the present invention includes:
In order to achieve the above object, a magnetic field is applied perpendicularly to the substrate in an undried state after coating a backcoat layer on a nonmagnetic substrate.

[0015]

Therefore, according to the structure of the present invention, the stiffness in the tape width direction can be increased due to the shape effect of the plate-shaped hexagonal ferrite powder contained in the back coat layer. In addition, because the particle size is small, it does not impair the surface properties of the back coat layer and improves running stability and
A magnetic tape with excellent output stability can be obtained.

According to the magnetic tape manufacturing method of the present invention,
With the above configuration, the plate surface of the plate-shaped hexagonal ferrite powder is oriented perpendicular to the running direction of the non-magnetic substrate, and the stiffness in the width direction of the magnetic tape is efficiently improved. Sufficient output stability and running durability can also be imparted to tape.

Furthermore, according to the method for producing a magnetic tape of the present invention, the plate surface of the plate-shaped hexagonal ferrite powder is oriented parallel to the non-magnetic substrate,
The stiffness of the magnetic tape not only in the width direction but also in the longitudinal direction can be improved, and even a thin magnetic tape can be provided with more sufficient output stability and running durability.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an outline of the method for producing a magnetic tape according to the present invention. In the figure, 1 is a magnetic tape having a magnetic layer provided on a non-magnetic substrate, and 2 is a hexagonal ferrite powder and carbon black. 3 is a paint coating part, 4 is a vertical alignment part by permanent magnets (maximum alignment magnetic field: 4000 Gauss), 5 is a longitudinal alignment part by permanent magnets (maximum alignment magnetic field: 4000 Gauss), 6 is the dry zone,
7 is a guide pole, 8 is an unwinding roll, and 9 is a winding roll.

The magnetic layer used in this example is γ
-Fe2O3, Co-containing γ-Fe2O3, Fe3O4C
o-containing Fe3O4, CrO2, Co-Ni-P alloy, C
Magnetic powder such as o-Ni-Fe alloy and barium ferrite, alumina, Cr2O3, etc. added to ensure a certain hardness of the coating film and polishing of the magnetic head, as well as reduction of electrical resistance and runnability. It can be obtained by blending appropriate amounts of materials such as carbon black for improving runnability and lubricant for improving runnability and durability into an organic binder, uniformly dispersing them, and then coating.

[0021] Regarding the material of the above-mentioned magnetic layer, specifically, Japanese Patent Publications No. 44-14090 and No. 47-2251
It is described in Publication No. 3, etc.

As the organic binder used in this embodiment, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

Examples of thermoplastic resins include vinyl chloride vinyl acetate copolymers, vinyl chloride vinylidene chloride copolymers, vinyl chloride acrylonitrile copolymers, urethane elastomers, cellulose derivatives, polyester resins, amino resins, and various synthetic rubbers. thermoplastic resins and mixtures thereof, etc. are used.

[0024] As the thermosetting resin or reactive resin,
These include phenol resins, epoxy resins, polyurethane curable resins, melamine resins, silicone resins, acrylic reaction resins, and mixtures of high molecular weight polyester resins and isocyanate prepolymers.

It is also possible to use a dispersant to improve the dispersibility of the magnetic powder. As a prior art disclosed regarding dispersants, there is, for example, Japanese Patent Publication No. 60-47650.

As the magnetic layer used in this example, in addition to the above-mentioned coated layer of fine particle magnetic powder, a thin continuous alloy layer such as Co-Ni, which exhibits excellent electromagnetic conversion characteristics, and a perpendicular magnetic recording method are used. Co-Cr capable of ultra-high density recording
An alloy thin film may also be used. Perpendicular magnetic recording technology is explained, for example, in the August 7, 1978 issue of Nikkei Electronics.

Known methods for forming a coating layer on a nonmagnetic substrate include blade coating, air knife coating, impregnation coating, reverse roll coating, gravure coating, and die coating. For example, JP-A-59-259941
JP-A No. 60-263670, etc. Using these coating techniques, the back coat layer,
A magnetic layer can be formed.

The plate ratio of the hexagonal ferrite powder used in this example is preferably 10 to 60. The plate ratio as used in the present invention is expressed as the ratio of the average particle diameter (the average value of 50 grain lengths) and the average thickness (the average value of the 50 maximum thicknesses) observed using an electron microscope. When the plate ratio is less than 10,
The strength of the coating film is low and the stiffness of the magnetic tape cannot be sufficiently increased. When the plate ratio exceeds 60, the average particle size becomes large and the surface roughness of the back coat layer becomes large. Therefore, the surface roughness of the back coat layer is transferred to the magnetic layer while the magnetic tape is stored in a wound state. It is not desirable because

Further, the coercive force of the coating film is preferably 1 to 300 Oe. This is because if the coercive force of the coating film exceeds 300 oersteds, the recorded signal of the magnetic layer will be greatly affected by the magnetism of the back coat layer. (Example 1, 2, 3) Adjustment of paint for back coat layer M-type barium ferrite
100 parts by weight Produced by hydrothermal synthesis method (Co-Ti substitution)
Plate ratio 10, average grain size 0.05μm coercive force
100 Oersted Carbon Black 1
00 parts by weight average particle size 0.
025 μm hydroxyl group-containing vinyl chloride/vinyl acetate copolymer resin
80 parts by weight polyurethane resin
80 parts by weight stearic acid
2
Part by weight Isocyanate curing agent
10 parts by weight methyl ethyl ketone
600 parts by weight toluene

600 parts by weight A back coat paint was prepared using a ball mill and a vertical sand mill with the above paint composition. Adjustment of magnetic layer paint; 100 parts by weight polyurethane resin
10 parts by weight vinyl chloride copolymer resin
10 parts by weight alumina

7 parts by weight myristic acid
2 parts by weight butyl stearate
1 part by weight methyl ethyl ketone
120 parts by weight toluene
120 parts by weight cyclohexanone
60 parts by weight isocyanate curing agent
A magnetic layer paint having the above composition was prepared using a 5 parts by weight pressure kneader/horizontal sand mill.

Next, as shown in FIG. 1, a 2.5 μm thick magnetic layer made of the above magnetic paint was formed on a PET film having a base thickness of 10 μm, dried, rolled up, and calendered on the opposite side of the magnetic tape 1. Apply the back coat paint adjusted to 0 using the paint coating section 3, and
．． After forming a film having a thickness of 5 μm, the film was longitudinally oriented by the longitudinal direction section 5, cut into a width of 1/2 inch, and wound into a VHS cassette to obtain Example 1.

Example 2 was produced in the same manner as Example 1, except that the longitudinal orientation section 5 shown in FIG. 1 was removed and vertical orientation was performed using the vertical orientation section 4.

Example 3 was produced using the same paint as in Examples 1 and 2, but without magnetic field orientation treatment. (Examples 4, 5, 6) M-type barium ferrite was used in the preparation of back coat paint.
100 parts by weight produced by hydrothermal synthesis method (Co-Ti-Zn
Replacement) Plate ratio 60, average particle size 0.2μm Coercive force 150 Oersted carbon black
Except that 100 parts by weight was used, the paint was prepared in the same manner as in Example 1, and the material was longitudinally oriented under the same conditions as Example 1, and the material was oriented vertically under the same conditions as Example 4 and Example 2. Example 6 was prepared under the same conditions as Example 5 and Example 3 but without magnetic field orientation treatment. (Comparative Example 1) Carbon black
200 parts by weight average particle size
0.025 μm hydroxyl group-containing vinyl chloride/vinyl acetate copolymer resin 80 parts by weight polyurethane resin
80 parts by weight stearic acid
2 parts by weight isocyanate curing agent
10 parts by weight methyl ethyl ketone
600 parts by weight toluene
600 parts by weight A back coat paint was prepared with the above paint composition, that is, in comparison with the example, it contained only carbon black without hexagonal ferrite as an inorganic powder, and by the same method as in the example.

Comparative Example 1 was produced using this back coat paint in the same manner as in Example 3. (Comparative Examples 2, 3, 4) M-type barium ferrite was used in the preparation of back coat paint.
100 parts by weight Produced by hydrothermal synthesis method (Co-Ti substitution)
Plate ratio: 5, average grain size: 0.05 μm Coercive force: 8
0 Oersted Carbon Black
A back coat paint was prepared using the same composition and method as in Example 1, except that 100 parts by weight was used, and it was longitudinally oriented under the same conditions as Example 1. Comparative Example 3 was the one in which the vertical alignment was performed, and Comparative Example 4 was the one in which the magnetic field orientation treatment was not performed under the same conditions as in Example 3. (Comparative Examples 5, 6, 7) M-type barium ferrite was used in the preparation of back coat paint.
100 parts by weight Produced by hydrothermal synthesis method (Co-Ti substitution)
Plate ratio 10, average grain size 0.05μm coercive force
400 Oersted Carbon Black
A back coat paint was prepared using the same composition and method as in Example 1, except that 100 parts by weight was used, and it was longitudinally oriented under the same conditions as in Example 1. Comparative Example 6 was the one in which the vertical alignment was performed, and Comparative Example 7 was the one in which the magnetic field orientation treatment was not performed under the same conditions as in Example 3.

The produced sample tape was evaluated for the following characteristics. (1) Stiffness (mg) Using a loop stiffness tester manufactured by Toyo Seiki Co., Ltd., the stiffness (flexural strength) of the tape in the longitudinal (MD) and width (TD) directions was determined. (2) Surface roughness of back coat layer (nm) Using a non-contact three-dimensional roughness meter (objective lens 20x) manufactured by WYKO,
The root mean square value (Rrms) of the surface roughness was measured five times, and the average value is shown. (3) Magnetic properties of back coat layer (Oe) After wiping off the magnetic layer of the obtained sample tape with a solvent, we measured the magnetic properties of the back coat layer in the longitudinal direction of the tape and in the direction perpendicular to the tape surface (Oe). Using VSM manufactured by Co., Ltd., the maximum magnetic field is 5.
KOe was measured at a magnetic field sweep rate of 200 Oe/min. (4) Playback envelope flatness rate (%) Using an S-VHS deck (Matsushita Electric Industrial FS-1),
Commercially available S-VHS tape (NV-ST12 manufactured by Matsushita Electric Industrial)
After reproducing 0) for 6 hours, the ratio of the minimum value and the maximum value of the 7 MHz reproduction output measured at the end of the sample tape was evaluated as the flatness rate of the envelope. (5) Output (dB) Using the above S-BHS deck, commercially available S-BHS with a total thickness of 19 μm
VHS tape (NV-ST120 manufactured by Matsushita Electric Industrial) 7
Based on the MHz output, the sample tape was run for 2 hours, and then the 7 MHz output was measured. (6) Running durability of tape Using the above S-VHS deck, 10 rolls of each sample tape were
After each sample tape was run 100 times in an environment of 0° C. and 80% RH, changes in shape of each sample tape were visually observed, and the number of turns where tape damage was clearly observed was indicated. (7) Environmental change in output (dB) Using the above S-VHS deck, 7MH
The z signal was recorded, and after being left in an environment of 50° C. and 80% RH for one week, changes in the level of the reproduced signal were examined. Comparisons were made in terms of relative values to those of the reference tape.

[0035] Table 1 shows a comparison of the above characteristics and structure between the example and the comparative example.

[0036]

[Table 1]

As is clear from Table 1, according to the above examples, it is possible to produce a magnetic tape with excellent stiffness, surface roughness, envelope flatness, and excellent running stability and output stability.

[0038]

Effects of the Invention As is clear from the above examples, the present invention includes a back coat layer containing hexagonal ferrite powder having a plate-like ratio of 10 to 60 and carbon black,
By setting the coercive force of the back coat layer to 1 to 300 Oe and by controlling the orientation direction of the plate-like particles, even if the magnetic tape is made thinner, stiffness, reproduction envelope flatness, and running durability can be improved. is good, and tape damage can be suppressed.

[0039] This makes it possible to make the magnetic tape thinner and further improve the recording time on a VTR.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of an apparatus used to carry out a magnetic tape manufacturing method in an embodiment of the present invention.

[Explanation of symbols]

1 Magnetic tape with a magnetic layer provided on a non-magnetic substrate 2
back coat layer

Claims (5)

[Claims] 1. A magnetic tape having a magnetic layer on one side of a non-magnetic substrate and a back coat layer on the other side, wherein the back coat layer is a hexagonal crystal having a shape with a plate ratio of 10 to 60. ferrite powder and carbon black powder, and the coercive force of the back coat layer is 1 to 1.
A magnetic tape characterized by a strength of 300 oersteds. [Claim 2] The hexagonal ferrite powder contains Ge, C
At least 2 of o, Ti, V, Zn, Nb, Ni
2. The magnetic tape according to claim 1, wherein the coercive force of the powder is controlled by containing different types of elements. 3. The magnetic tape according to claim 1, wherein the hexagonal ferrite powder has an average particle size of 0.05 to 0.2 μm. 4. The magnetic tape according to claim 1, 2 or 3, wherein a magnetic field is applied perpendicularly to the non-magnetic substrate in an undried state after coating the back coat layer on the non-magnetic substrate. manufacturing method. 5. After applying a back coat layer on a non-magnetic substrate, applying a magnetic field in a perpendicular direction to the non-magnetic substrate in an undried state, and then immediately applying a magnetic field in a direction parallel to the running direction of the non-magnetic substrate. Claims 1 and 2 are characterized in that they are allowed to pass through.
Or the method for manufacturing a magnetic tape according to 3.