JPH0573884A - Magnetic recording tape - Google Patents

Abstract

PURPOSE:To provide the magnetic recording tape which is excellent in preventing deformation of the tape, D.O. increase, lowering of envelope flatness, etc. CONSTITUTION:The surface root-mean-square roughness of a magnetic layer is 8 to 12nm and the projections having the height within a 20 to 40nm range are formed at 20 to 50 pieces per 1mm length on the surface of the magnetic layer. Further, the surface root-mean-square roughness of at least either surfaces of a nonmagnetic base is in a 0.01 to 0.025mum range and the thickness thereof is <=10mum. In addition, the Young's modulus in the longitudinal direction and transverse direction is <=5880MPa and the ratio of the ferromagnetic powder to be incorporated into the magnetic layer is specified to a 73.0 to 78.0wt.% range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording tape for use in video equipment, audio equipment, computers and the like, and more particularly to a thin magnetic recording tape suitable for a long time and its support. Is.

[0002]

2. Description of the Related Art In recent years, these various magnetic recording media have been suitable for high-density recording. Therefore, recording wavelengths are short, recording track widths are narrow, and recording media are thin. As a result, the S / N ratio, sensitivity, and frequency characteristics generally become disadvantageous, but as a countermeasure against this, methods such as making the magnetic powder fine and making the magnetic layer highly smooth are adopted. However, if only the above measures are taken, the surface property of the magnetic layer is increased and the friction coefficient is increased, which is disadvantageous in terms of runnability and durability. It is known to provide a back coat layer on the surface opposite to the surface of the magnetic layer.

[0003]

However, the conventional method as described above has a problem that durability, particularly deformation of the magnetic recording tape and dropout (DO) increase.

In view of the above problems, the present invention provides a still life, running durability, especially tape deformation, without compromising electromagnetic conversion characteristics. O. The present invention provides a magnetic recording tape having high durability, which is excellent in increase in the magnetic field, decrease in flatness of envelope, and the like.

[0005]

In order to solve the above-mentioned problems, the present invention is a magnetic recording tape having a magnetic layer provided on a non-magnetic support, the surface of the magnetic layer having a root mean square roughness of 8 20 to 50 protrusions (per length of 1 mm) having a height of ˜12 nm and a height of 20 to 40 nm,
It is formed on the surface of the magnetic layer. The non-magnetic support used in the present invention preferably has a surface root mean square roughness in the range of 0.01 to 0.025 μm on at least one of the surfaces, and a thin film having a thickness of 10 μm or less. In this case, the tensile Young's modulus in the length direction and the width direction is preferably 5880 MPa or more.

[0006]

The present invention has the above-mentioned structure, and still life, running durability, especially tape deformation, without compromising electromagnetic conversion characteristics. O. It is possible to obtain a magnetic recording tape which is excellent in increase, decrease in envelope flatness and the like. In other words, in actual use,
It is preferable to design the surface root mean square roughness of the magnetic layer to be 13 nm or more in order to obtain a running durability at a level that does not cause a problem, but in this case, the air gap loss between the magnetic layer and the magnetic head becomes large, which is sufficient. The C / N ratio cannot be obtained. On the other hand, if the surface root mean square roughness is reduced in order to obtain the C / N ratio, running durability will be a problem. Both are in a conflicting relationship. Therefore, it is possible to reduce the air gap loss between the magnetic layer and the magnetic head, and to reduce the actual contact area between the magnetic layer surface and the magnetic head, the rotating cylinder, the guide post in the traveling mechanism, etc. As a result, the surface root mean square roughness of the magnetic layer was 8 to 12 nm and the height was 20.
The number of protrusions within the range of -40 nm is 20 per 1 mm in length.
By forming 50 magnetic layers on the surface, it is possible to obtain a magnetic recording tape excellent in still life and running durability without impairing electromagnetic conversion characteristics. Such an effect is due to the improvement of the running property based on the reduction of the true contact area due to the protrusion, the reduction of sliding marks, and the appropriate stress applied to each protrusion, so that the protrusion is appropriately elastically deformed and the gap It is thought that the loss will be small.

Further, the surface property of the non-magnetic support on the side opposite to the magnetic layer side of the magnetic recording tape is transferred to the surface of the magnetic layer to prevent adverse effects due to the deterioration of the surface property.
It is possible to obtain a magnetic recording tape having excellent electromagnetic conversion characteristics, particularly C / N ratio. Further, particularly in the case of a thin tape having a thickness of 10 μm or less, the tensile Young's modulus in the longitudinal direction and the width direction of the non-magnetic support is limited in order to impart a well-balanced mechanical strength above a certain level to the magnetic recording tape. To obtain a magnetic recording tape having excellent properties, particularly tape damage, envelope flatness, and audio level fluctuation.

Further, by forming the protrusions according to the present invention on the surface of the magnetic layer, the amount of powder falling from the background portion other than the protrusions during tape running is reduced. Therefore, compared to the case where no protrusion is formed, the amount of ferromagnetic powder in the magnetic layer can be relatively increased when the protrusion is formed, and the packing density is increased. An excellent magnetic recording tape can be obtained.

More specifically, a magnetic recording tape, for example, a magnetic recording tape for a video tape recorder, runs while being wound around various posts at a certain angle, but the positions of the various posts in the height direction are restricted. Therefore, lower regulation posts and upper regulation posts are provided.
In order for the tape to run stably against the regulation post without detaching, appropriate traveling characteristics are required, and when attempting to detach and run, it is basically not detached due to the rigidity of the tape itself. Have to drive like. However, when the running property is reduced due to the improvement of the surface property for obtaining a high C / N ratio, and the rigidity of the tape is reduced as the thickness of the entire tape is reduced, the tape may be broken or the tape end portion may be uneasy. Or in the worst case, the tape breaks and loses important information. In the magnetic recording tape in which the magnetic layer is provided on the non-magnetic support as in the present invention, the surface root mean square roughness of the magnetic layer is 8
20 to 50 nm and a height within the range of 20 to 40 nm are formed on the surface of the magnetic layer at 20 to 50 protrusions per 1 mm in length, and the tensile Young in the length direction and the width direction of the nonmagnetic support is used. By designing the modulus to be 5880 MPa or more, good runnability can be obtained, and when the tape is locally bent, the elastic modulus is well balanced and reaction force acts, resulting in bending rigidity and twisting of the tape. The rigidity is increased, and the two are combined to greatly improve durability, especially tape damage.

[0010]

The present invention will be described below. Here, as the binder, the cross-linking agent, the abrasive, the dispersant optionally added, the plasticizer, the antistatic agent, the back coat layer and the like used in the present invention, conventionally known materials can be used.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. All "parts" in the component ratios shown in the examples are "parts by weight".
Is shown.

Example 1 A magnetic coating material was prepared as follows.

Fe-based alloy magnetic powder 100 parts [Coercive force H _C = 123.3 × 10 ³ A / m, BET specific surface area = 56 × 10 ³ m ² / kg, Saturation magnetization amount = 1.6 × 10 ^-4 Wb · m / kg, acicular ratio = 9/1] Vinyl chloride resin Tg = 60 ° C. 10 parts Polyurethane resin Tg = 5 ° C. 10 parts Abrasive (Al ₂ O ₃ ) [average particle size = 0.2 μm] 7 parts Carbon black [average particle size = 20 nm] 3 parts Stearic acid 1.5 parts Myristic acid 1 part Butyl stearate 1.5 parts Methyl ethyl ketone 100 parts Toluene 100 parts Cyclohexanone 60 parts The above composition is kneaded using a pressure kneader and a sand mill. A magnetic paint was prepared by dispersion. 3 parts of a polyisocyanate compound [manufactured by Bayer Co., Desmodur L] was added to the obtained magnetic paint, thoroughly mixed and stirred with a high-speed stirrer, and then filtered with a filter having an average pore diameter of 1 μm to prepare the magnetic paint. It was

Next, the above magnetic paint was applied in a thickness of 7.5 μm and a tensile Young's modulus in the length direction of 6670 MPa, a tensile Young's modulus in the width direction of 6080 MPa and a surface root mean square roughness of 0.
After coating, magnetic field orientation and drying treatment on a 023 μm polyethylene terephthalate film support, mirror finishing treatment with a super calender roll was performed to give 2.6 μm.
An original roll having a magnetic layer of m thickness was obtained. This raw roll is cured at 60 ° C. for 24 hours, and then a back coat layer having a thickness of 0.5 μm is provided on the surface opposite to the magnetic layer.
Video tape sample (250 m
Long) was prepared.

Example 2 A video tape sample was prepared in the same manner as in Example 1 except that 10 parts of the vinyl chloride resin and 10 parts of the polyurethane resin of Example 1 were replaced with 12 parts and 8 parts, respectively. did.

Comparative Example 1 A video tape sample was prepared in the same manner as in Example 1 except that the polyurethane resin Tg = 5 ° C. in Example 1 was changed to a polyurethane resin Tg = −20 ° C. .. (Comparative Example 2) A video tape sample was prepared in the same manner as in (Example 1) except that the polyurethane resin Tg = 5 ° C in Example 1 was changed to the polyurethane resin Tg = 30 ° C.

(Example 3) A magnetic paint was prepared by adding 0.5 part of triazinedithiol, which is a curing accelerator for vinyl chloride resin, to the magnetic paint to which the polyisocyanate compound of Example 1 was added. A video tape sample was prepared in the same manner as in Example 1).

(Comparative Example 3) A video tape was prepared in the same manner as in Example 1 except that the contact pressure between the calendar rolls was increased by 20% during the mirror finishing treatment with the super calendar roll of Example 1. 4) A video tape sample was prepared in the same manner as in (Example 1) except that the time required for kneading and dispersing with the pressure kneader and the sand mill in (Example 1) was reduced by 30%.

(Example 4) An abrasive (Al _{2 having} an average particle size of 0.2 μm of Example 1) (Al ₂
A video tape sample was prepared in the same manner as in (Example 1) except that O ₃ ) was replaced with an abrasive having an average particle size of 0.5 μm.

(Example 5) A video tape sample was prepared in the same manner as in Example 1 except that the polyethylene terephthalate film support of Example 1 was replaced by one having a surface root mean square roughness of 0.013 µm. Was produced.

Comparative Example 5 A video tape sample was prepared in the same manner as in (Example 1) except that the polyethylene terephthalate film support of (Example 1) had a surface root mean square roughness of 0.008 μm. Was produced.

Comparative Example 6 A video tape sample was prepared in the same manner as in (Example 1) except that the polyethylene terephthalate film support of (Example 1) had a surface root mean square roughness of 0.027 μm. Was produced.

(Example 6) The polyethylene terephthalate film support of Example 1 has a tensile Young's modulus in the length direction of 7850 MPa, a tensile Young's modulus in the width direction of 7350 MPa, and a surface root mean square roughness of 0.018 μm. A video tape sample was prepared in the same manner as in (Example 1) except that the polyethylene naphthalate film support having a thickness of 7.3 μm was replaced with the above.

(Comparative Example 7) The polyethylene terephthalate film support of (Example 1) had a tensile Young's modulus of 5590 MPa in the longitudinal direction.
A video tape sample was prepared in the same manner as in (Example 1) except that the tensile Young's modulus in the width direction was changed to 5590 MPa.

(Example 7) The proportion of the ferromagnetic powder contained in the magnetic layer of (Example 1),
A video tape sample was prepared in the same manner as in (Example 1) except that the amount of the ferromagnetic powder was increased from 73.0% by weight to 77.0% by weight.

(Comparative Example 8) The ratio of the ferromagnetic powder contained in the magnetic layer of (Example 1),
A video tape sample was prepared in the same manner as in (Example 1) except that the amount of the ferromagnetic powder was increased from 73.0% by weight to 78.0% by weight.

(Comparative Example 9) The ratio of the ferromagnetic powder contained in the magnetic layer of (Example 1),
A video tape sample was prepared in the same manner as in (Example 1) except that the amount of the ferromagnetic powder was increased from 73.0% by weight to 72.0% by weight.

The following evaluation tests were carried out on the video tape samples obtained in the above Examples and Comparative Examples. (1) Surface roughness Using a Talystep stylus type surface roughness meter manufactured by Taylor Hobson Co., a longitudinal magnification of 20 × 10 ³ times, a lateral magnification of 50 times, a stylus of 2.5 μm × 0.1 μm, and a needle pressure of 2 mg. The surface roughness was measured under the conditions, and the root mean square roughness of a height of 3 nm or more was calculated and obtained in the roughness chart. Further, the protrusion height was obtained by calculating an average value of heights of 12 nm or more in the roughness chart. (2) C / N ratio VHS system VTR (NV-FS900, Matsushita Electric Industrial Co., Ltd.) which uses an amorphous alloy head for the recording / reproducing head.
C./N ratio at a recording frequency of 7 MHz was measured. As the standard tape, a cassette tape for MII format VTR (AU-M90L manufactured by Matsushita Electric Co., Ltd.) was used, and its C / N ratio was set to 0 dB. (3) Still life VHS system VTR (NV-FS900, Matsushita Electric Industrial Co., Ltd.) that uses an amorphous alloy head for the recording / reproducing head.
Manufactured) was used to measure the still life under the environment of -10 ° C. (4) Deformation of tape VHS system VTR (NV-FS900, Matsushita Electric Industrial Co., Ltd.) which uses an amorphous alloy head as a recording / reproducing head.
Each of the video tape samples was run for 200 passes in an environment of 40 ° C. and 80% RH, and the deformation of each tape sample was visually observed to make a 5-step evaluation. The evaluation was rated as 5 when there was practically no problem, and as 1 when there was practically a problem. (5) Dropout A dropout counter (manufactured by Shibasoku Co., Ltd., VH01
BZ). For the dropout, the rate of change after the test with respect to that before the test was shown as a magnification. (6) Envelope flatness ratio After the test according to (4) above, the envelope flatness ratio of the reproduction output at a recording frequency of 7 MHz was measured. (7) Audio level fluctuation The audio head output was rectified, and the level fluctuation of the output was measured after the test according to the above (4). (8) Head powder adhesion amount After the test according to the above (4), the powder adhesion amount on the magnetic head tape sliding surface was visually observed to make a five-level evaluation. The evaluation was rated as 5 when there was practically no problem, and as 1 when there was practically a problem.

The obtained results are shown in (Table 1) and (Table 2).

[0030]

[Table 1]

[0031]

[Table 2]

As is clear from (Table 1) and (Table 2),
According to the present invention, there is provided a magnetic recording tape having a magnetic layer provided on a non-magnetic support, wherein the magnetic layer has a surface root mean square roughness of 8 to 12 nm and a height of 20 to 40 nm. The protrusion inside is 20-50 (per 1 mm length)
And the surface root mean square roughness of the non-magnetic support is in the range of 0.01 to 0.025 μm, and at least one surface of the non-magnetic support is in the range of 0.01 to 0.025 μm. The thickness is 10 μm or less, the tensile Young's modulus in the length direction and the width direction is 5880 MPa or more, and the ratio of the ferromagnetic powder contained in the magnetic layer is 73.0 to 7
By adjusting the amount to be in the range of 8.0% by weight, the still life, running durability, especially the deformation of the tape, D. O. It is intended to obtain a highly durable magnetic recording tape which is excellent in increase, decrease in envelope flatness and the like.

[0033]

As described above in detail, according to the present invention, there is provided a magnetic recording tape having a magnetic layer provided on a non-magnetic support having a surface layer root mean square roughness of 8 to 12 n.
m, and 20 to 50 protrusions (per length 1 mm) having a height within the range of 20 to 40 nm are formed on the surface of the magnetic layer, and further, the surface root mean square roughness of the non-magnetic support. However, at least one of the surfaces is 0.01 to 0.
In the range of 025 μm, the thickness is 10 μm or less, and the tensile Young's modulus in the length direction and the width direction is 5880.
Still more than MPa, and the ratio of the ferromagnetic powder contained in the magnetic layer is in the range of 73.0 to 78.0% by weight, the still life and running durability can be maintained without impairing the electromagnetic conversion characteristics. , Especially tape deformation, D.I. O. increase,
It is possible to obtain a highly durable magnetic recording tape that is excellent in envelope flatness reduction, audio level fluctuation, etc., and its practical value is great.

Claims (4)

[Claims] 1. A magnetic recording tape having a magnetic layer provided on a non-magnetic support, wherein the surface of the magnetic layer has a root mean square roughness of 8 to 12 nm and a height of 20 to 40 nm. The magnetic recording tape is characterized in that 20 to 50 protrusions per 1 mm are formed on the surface of the magnetic layer. 2. The surface root mean square roughness of the non-magnetic support is 0.01 to 0.02 on at least one of the surfaces.
The magnetic recording tape according to claim 1, which is in a range of 5 μm. 3. The non-magnetic support has a thickness of 10 μm or less and a tensile Young's modulus of 5 in the length direction and the width direction.
The magnetic recording tape according to claim 1, wherein the magnetic recording tape has a pressure of 880 MPa or more. 4. The magnetic recording tape according to claim 1, wherein the ratio of the ferromagnetic powder contained in the magnetic layer is in the range of 72.5 to 78.0% by weight.