JPH0444628A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of the medium against deformation and reduction in electromagnetic conversion characteristics by specifying the thickness of a nonmagnetic supporting body to a certain value or below, and specifying the Young's modulus and the thermal shrinkage factor of the supporting body in a longitudinal direction and a transverse direction. CONSTITUTION:The nonmagnetic supporting is specified to have <=10mum thickness, >=600kg/mm<2> Young's modulus respectively in the longitudinal direction and the transverse direction, <=2.5% thermal shrinkage factor in the longitudinal direction after heated at 150 deg.C for 30min, and the thermal shrinkage factor in the transverse direction is the same as that in the longitudinal direction or above. Thereby, the mechanical strength of the supporting body in the transverse direction is increased and the thermal shrinkage factor in the transverse direction is relatively large compared with that in the longitudinal direction. The proper curling state is obtained in the transverse direction of the tape and good tape traveling state and contact state between the tape and a head are obtained. Thus the deformation of the tape, reduction in C/N, decrease in the flatness of envelope output, and increase in dropout can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium used in video tape recorders, audio equipment, computers, etc., and particularly relates to a thin magnetic tape suitable for long-term use and its magnetic tape. It is related to the support.

BACKGROUND OF THE INVENTION In recent years, each of these magnetic recording media has become suitable for high-density recording, and for this purpose, the trend has been to shorten the recording wavelength, narrow the recording track width, and reduce the thickness of the recording medium.

As a result, the S/N, sensitivity, and frequency characteristics generally become disadvantageous.As a countermeasure, the surface properties of the magnetic layer can be further improved by making the magnetic powder finer or by using a highly smooth non-magnetic support. One method is to increase it. However, if the above measures are taken alone, the surface properties of both the front and back sides of the recording medium will increase, resulting in an increase in the coefficient of friction on both sides, which will be disadvantageous in terms of running performance and durability. It is known to provide a back coat layer on the opposite side of the support from the magnetic layer side.

However, the above-mentioned conventional methods have problems with durability, especially deformation of the magnetic tape, and deterioration of electromagnetic conversion characteristics.

The present invention solves the above-mentioned problems, and aims to provide a magnetic recording medium made of highly durable magnetic tape that is resistant to deformation and deterioration of electromagnetic conversion characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention provides a Benyo nonmagnetic support having a thickness of 10 μm or less and a tensile Young's modulus of 600 kg/mm2 or more in the length direction and width direction. and
And, after heating at 105°C for 30 minutes, the heat shrinkage rate in the length direction is 2.5% or less, and the heat shrinkage rate in the width direction is 1.0 times or more than the heat shrinkage rate in the length direction. In this way, a magnetic recording medium with excellent durability is obtained.

Since the mechanical strength in the width direction is improved and the heat shrinkage rate in the width direction of the non-magnetic support is relatively large compared to the heat shrinkage rate in the length direction, an appropriate curl state can be obtained in the tape width direction. Due to the synergistic effect of both, a good tape running condition and a good tape/head contact condition are obtained, and as a result,
A magnetic tape with excellent durability, particularly in terms of tape deformation, reduction in C/H, reduction in envelope output flatness, increase in audio level fluctuation, increase in dropout, etc. can be obtained.

Example The present invention will be specifically described below with reference to Examples.

Here, conventionally known binders, crosslinking agents, abrasives, dispersants, plasticizers, antistatic agents, etc. to be added as necessary can be used in the present invention.

There isn't. The "parts" in the component ratios shown in the examples are "8". Parts by weight are shown.

(Example 1) A magnetic paint and a back coat layer paint were prepared as follows.

Fe-based alloy magnetic powder 100 parts [Coercive force H
c = 1550 (Oe >, BET specific surface area・56
(m, /g), saturation magnetization per unit duram jL a s
= 127 (em a, 'g), acicular ratio 8/l] Vinyl chloride vinyl acetate copolymer resin 10 parts Polyurethane resin 10 parts Abrasive (A120
3) (Average particle size = 0.2 (μm)) 6 parts carphone black [average particle size - 20 (μm)] 22 parts myristic acid 1 part butyl stearate 1 part methyl ethyl ketone
100 parts toluene
100 parts cyclohexanone
Mix and disperse 60 parts of the above composition using a pressure kneader and sand mill to prepare a magnetic paint! did. To the obtained magnetic paint was added 1734 parts of a polyisocyanate compound (manufactured by Bayer AG, Desmodur), thoroughly mixed and stirred with a high-speed stirrer, and then filtered through a filter with an average pore size of 1 μm to prepare a magnetic paint.

Next, the above magnetic paint was coated with a thickness of 9.6 μm, a tensile Young's modulus in the longitudinal direction of 680 kg/mm2, a tensile Young's modulus in the width direction of 620 kg/mm2, and heat shrinkage in the longitudinal direction after heating at 105°C for 30 minutes. It was coated on a polyethylene terephthalate film with a heat shrinkage rate of 2.0% and a heat shrinkage rate in the width direction of 2.9%, subjected to magnetic field orientation and drying treatment, and then mirror-finished with a super calendar roll to a 2.7μ
A raw roll having a magnetic layer of m thickness was obtained.

This raw roll was subjected to a hardening treatment, and then a 0.5 μm thick bank coat layer was formed, and the film was cut into 1/2 inch width to produce videotape samples (250 lengths).

(Example 2) The polyethylene terephthalate film of Example 1 was
．． Tensile Young's modulus in the longitudinal direction is 620 kg/m with a thickness of 6 μm
m2, tensile Young's modulus in the width direction 690 kg, 'mm
The video tape was made in the same manner as in Example 1, except that the heat shrinkage rate in the length direction after heating at +05°C for 130 minutes was changed to one with a heat shrinkage rate of 9% and a heat shrinkage rate in the width direction of 3.1.96. A sample was prepared.

(Comparative Example 1) The polyethylene terephthalate film of Example 1 was
．． Tensile Young's modulus in the longitudinal direction at 6 μm thick: 830 kg/m
m2, tensile Young's modulus in the width direction is 450 kg/mm
2. A videotape sample was prepared in the same manner as in Example 1, except that the heat shrinkage rate in the length direction after heating at 105°C for 130 minutes was changed to one with a heat shrinkage rate of 1.2% and a heat shrinkage rate in the width direction of 0.6%. It was created.

(Comparative Example 2) The polyethylene terephthalate film r' of Example 1 was 9.6 μm thick and had a tensile Young's modulus in the longitudinal direction of 690Δ kg/nun2 and a tensile Young's modulus in the width direction of 610 kg.
/ n+m2. After heating at 105°C for 130 minutes, the heat shrinkage rate in the length direction is 2.4% and the heat shrinkage rate in the width direction is 1.6%.
A videotape sample was prepared in the same manner as in Example 1, except that the sample was replaced with a different one.

(Comparative Example 3) kg/"mm2, tensile Young's modulus in the width direction is 740 kg
/ n+m2. After heating at 105°C for 130 minutes, the heat shrinkage rate in the length direction is 1.3% and the heat shrinkage rate in the width direction is 2.5%.
A videotape sample was prepared in the same manner as in Example 1, except that the sample was replaced with a different one.

(Example 3) Polyethylene terephthalate fill of Example 1/''m
m', tensile Young's modulus in the width direction is 710 kg/m
m2! A videotape sample was prepared in the same manner as in Example 1, except that the heat shrinkage rate in the length direction after heating at 05°C for 130 minutes was changed to one with a heat shrinkage rate of 0.3% and a heat shrinkage rate in the width direction of 0.7%. Created.

(Example 4) Polyethylene terephthalate film of Example 1/'mm
2. Tensile Young's modulus in the width direction is 760 kg/mm2
Thermal shrinkage rate in the length direction after heating at 105°C for 130 minutes is 0.
．． A videotape sample was prepared in the same manner as in Example I except that the heat shrinkage rate in the width direction was changed to one having a heat shrinkage rate of 6% and 1.1% in the width direction.

(Comparative Example 4) Polyethylene terephthalate fill of Example 1, /'m
m2, tensile Young's modulus in the width direction is 610 kg/mm
A videotape sample was prepared in the same manner as in Example 1 except that the heat shrinkage rate in the length direction after heating at 1.05°C for 130 minutes was changed to one with a heat shrinkage rate of 0.4% and a heat shrinkage rate of 001% in the width direction. Created.

The following evaluation tests were conducted on the videotape samples obtained in each of the following Examples and Comparative Examples.

(1) VH3 type video tape recorder (NVF S 900) that uses an amorphous alloy head for the tape deformation recording/playback head.
, manufactured by Matsushita Electric), and rotate each videotape sample at 40°.
The state of the tape sample was visually observed for deformation after running 200 buses under the environment of C, 8096R-H.

+2) C/'N The C/N at a recording frequency of 5 MHz was measured before and after the test according to (1) above. C/N is OdB measured value before test.
The deviation value when

(3) Envelope output flatness rate The envelope output flatness rate at a recording frequency of 5 MHz was measured using an oscilloscope before and after the test in (1) above.

(4) Audio level fluctuation The audio head output was rectified, and the level fluctuation of the output was measured after the test.

(5) Dropout Momentary dropouts in the video signal were measured with a dropout counter before and after the test in (1) above. Dropout was expressed as the rate of change after the test compared to before the test.

Note that the deformation of the tape in (1) above was evaluated in five stages. The evaluation was rated 5 if there was no practical problem at all, and 1 if there was a problem in practical use. The obtained results are the first
Shown in the table.

As is clear from Table 1, it is a magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, wherein the non-magnetic support has a thickness of 10 μm or less and a tensile Young's modulus of 600 in the length direction and width direction. kg/mm2 or more and 105°C
The longitudinal heat shrinkage rate after heating for 930 minutes is 2.5% or less,
By making the heat shrinkage rate in the width direction at least 1.0 times the heat shrinkage rate in the length direction, durability, especially magnetic tape deformation, C
It is possible to obtain a magnetic tape which is excellent in that /N is reduced, envelope output surface force flatness is reduced, audio level fluctuation is increased, and dropout is increased.

Effects of the Invention As described above, according to the present invention, the thickness of the non-magnetic support is 10 μm or less, and by limiting the tensile Young's modulus and thermal shrinkage in the length direction and width direction, respectively,
It is possible to obtain a magnetic tape with high durability, particularly in preventing deformation of the magnetic tape, reduction in C/N, reduction in envelope output flatness, increase in audio level fluctuation, and increase in dropout. is of great value.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, wherein the non-magnetic support has a thickness of 10 μm or less and a tensile Young's modulus of 600 kg/mm in the length direction and width direction.
^2 or more, and the heat shrinkage rate in the length direction after heating at 105℃ for 30 minutes is 2.5% or less, and the heat shrinkage rate in the width direction is 1.0 times or more than the heat shrinkage rate in the length direction. A magnetic recording medium characterized by: