JPH0489614A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve tape bending rigidity (stiffness) and to improve durability without deteriorating electromagnetic conversion characteristics by providing an intermediate layer consisting of acicular titanium dioxide layer having 30 to 120 major axis/minor axis ratio and a binder on a nonmagnetic base. CONSTITUTION:The intermediate layer consisting of the acicular titanium dioxide layer having 30 to 120 major axis/minor axis ratio and the binder is provided between the nonmagnetic base and a magnetic layer and/or the nonmagnetic base and back coat layer. The strength of the layer contg. the titanium dioxide layer having the high acicular ratio is extremely high in this way and, therefore, the degradation in the tape bending rigidity by the formation of the nonmagnetic base as a thinner film is made up and the magnetic recording medium having the improved durability is obtd. without deteriorating the electromagnetic conversion characteristics.

Description

[Detailed description of the invention] Industrial applications The present invention relates to audio tapes and video tapes.

The present invention relates to magnetic recording media used in magnetic disks and the like.

Conventional technology In recent years, high-density recording technology has developed, especially in video tapes. The thinning of each film is progressing. However, as magnetic tapes become thinner, tape bending rigidity (stiffness) decreases, resulting in a decrease in durability. As a proposal to improve the durability of magnetic tape, which decreases as the film becomes thinner,
A method of increasing the strength of a nonmagnetic support has already been adopted.

Problems to be Solved by the Invention However, with only the method described above, as the magnetic tape becomes thinner, the bending rigidity of the non-magnetic support decreases, resulting in a decrease in the staining characteristics with the magnetic head. As a result, it is unavoidable that the electromagnetic conversion characteristics are adversely affected, and it cannot be said that the state is still satisfactory.

SUMMARY OF THE INVENTION The present invention aims to solve this problem by providing a magnetic recording medium with improved durability without deteriorating electromagnetic conversion characteristics.

Means for Solving the Problems The present invention provides a method in which the ratio of major axis/minor axis is 30 to 120↑1 between the nonmagnetic support and the magnetic layer and/or between the nonmagnetic support and the pack coat layer. This is a magnetic recording medium with an intermediate layer made of titanium dioxide and a binder.

Effect The present invention has the above-described structure, which makes the strength of the titanium dioxide-containing layer with the high acicular ratio extremely high, which compensates for the decrease in tape bending rigidity due to thinning of the non-magnetic support, and reduces the deterioration of electromagnetic conversion characteristics. This makes it possible to provide a magnetic recording medium with improved durability without causing damage. If the long axis/short axis ratio of the acicular titanium dioxide is less than 30, the tape bending rigidity cannot be improved due to the low strength of the titanium dioxide-containing layer. If the long axis/short axis ratio exceeds 120, the surface roughness of the acicular titanium dioxide-containing layer deteriorates and the surface smoothness of the magnetic layer is lost, resulting in deterioration of electromagnetic conversion characteristics. When the long axis/short axis ratio of the acicular titanium dioxide is 30-120, a magnetic recording medium with improved tape bending rigidity and improved durability without deteriorating the smoothness of the magnetic layer surface can be obtained.

Example The layered titanium dioxide used in the present invention is in the rutile form.

It may be in an anacuse shape or with or without surface treatment. In addition, the binder used for the intermediate layer includes polyurethane resin with hydrophilic groups introduced, nitrocellulose resin with hydrophilic groups introduced, polyester resin with hydrophilic groups introduced,
Vinyl chloride copolymer resins into which hydrophilic groups have been introduced can be used. Examples of the ferromagnetic powder used in the magnetic layer include metal magnetic powder, cobalt-coated iron oxide powder, and barium ferrite magnetic powder.

As the binder used in the magnetic layer, polyurethane resins with hydrophilic groups introduced, nitrocellulose resins with hydrophilic groups introduced, polyester resins with hydrophilic groups introduced, and hinyl chloride copolymer resins with hydrophilic groups introduced can be used. Examples of abrasives include alumina, chromium dioxide, silicon oxide, and hengara. As the antistatic agent, conductive carbon can be used. As the lubricant, higher fatty acids, higher fatty acid esters, or various surfactants can be used alone or in combination. In addition, fillers used in the pack coat layer include carbon black, chromium dioxide, hengara, aluminum-no-graphite,
There are non-magnetic powders such as talc and calcium carbonate. Examples of the nonmagnetic support include polyethylene terephthalate film, polyethylene naphthalate film, and polyamide resin film.

Specific examples of the present invention will be described below.

[Example 1] Creation of intermediate layer Acicular titanium dioxide (major axis/minor axis ratio -40, long sleeve -5 μm
) 100 parts polyurethane resin
20 parts methyl ethyl ketone
150 parts Toluene 150 parts 10 parts of polyisocyanate was added to a coating material prepared by dispersing the above composition using a sand mill, and the mixture was coated on a 7 μm thick polyethylene terephthalate support and dried to form a 2 μm thick intermediate layer.

Creating the magnetic layer Magnetic powder 100 parts Alumina
5 parts conductive car phone
1 part vinyl chloride resin
10 parts polyurethane resin 10 parts methyl ethyl ketone 150 parts toluene
Add 150 parts of myristic acid to a magnetic paint containing the above composition dispersed with Santomil.
1 part n-butyl stearate 1 part polyisocyanate 5 parts were added, dispersed with a disper, coated on the intermediate layer, oriented,
Dried and mirror-finished by calendering to 2 μm.
A thick magnetic layer was obtained.

Preparation of Bank Coat Layer Carbon Blank Aluminide 1 Cellulose Resin Polyurethane Resin Nodyl Ethyl Ketone Toluene 100 parts 7 parts 20 parts 20 parts 200 parts 200 parts The above composition was dispersed in a pack coat paint using Santomil, and myristic acid 1 part Polyisocyanate 10 parts of the solution was added, stirred with a disperser, and coated on the support on the opposite side from the magnetic layer to form a pack coat layer with a thickness of 1 μm.

[Example 2] The acicular titanium dioxide of Example 1 was prepared with a long axis/short axis ratio of 70.
An intermediate layer having a thickness of 2 .mu.m was prepared in the same manner as in Example 1 except that the length was changed to (long axis -5 .mu.m), and then a magnetic layer and a bank coat layer were formed in the same manner as in Example 1.

[Example 3] The sword-shaped titanium dioxide of Example 1 was prepared with a long axis/short axis ratio of 10.
An intermediate layer having a thickness of 211 m was prepared in the same manner as in Example 1 except that the thickness was changed to 0 (major axis -5 .mu.m), and then a magnetic layer and a bank coat layer were formed in the same manner as in Example 1.

[Comparative Example 1] A 2 μm thick intermediate layer was prepared in the same manner as in Example 1, except that the acicular titanium dioxide in Example 1 was changed to spherical titanium dioxide with an average particle size of 0.4 μm, and then Example 1 was prepared. A magnetic layer and a bank coat layer were prepared in the same manner as in Example 1.

(Comparative Example 2) The ratio of the long axis/short axis of the acicular titanium dioxide of Example 1 was set to 20 (
An intermediate layer having a thickness of 2 .mu.m was prepared in the same manner as in Example I except that the long axis was changed to -5 .mu.m), and then a magnetic layer, a Hanokuko-1 layer, was formed in the same manner as in Example 1.

[Comparative Example 3] The long axis/short axis ratio of the acicular titanium dioxide of Example 1 was 150.
An intermediate layer having a thickness of 2 .mu.m was prepared in the same manner as in Example 1 except that the length was changed to (long axis - 5 .mu.m), and then a magnetic layer and a hack coat layer were formed in the same manner as in Example 1.

Each sample obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was obtained. For each sample obtained, the tape stiffness using a stiffness meter, the surface roughness of the magnetic layer using a stylus surface roughness meter, the visual condition of the tape after 100 passes of playback/rewind on a VTR deck, S/VH
The electromagnetic conversion characteristics of each were measured using an S deck. The results are shown in the following characteristic table.

(Margin below) Effects of the Invention As described above, according to the present invention, the long axis/
By providing an intermediate layer consisting of acicular titanium dioxide with a short axis ratio of 30 to 120 and a binder, tape bending stiffness can be improved, and durability can be improved without deteriorating electromagnetic characteristics. An improved magnetic recording medium can be obtained.

Name of agent: Patent attorney Shigetaka Kurino (1 person)

Claims (1)

[Claims] Between the non-magnetic support and the magnetic layer, or between the non-magnetic support and the pack coat layer, or both, an intermediate comprising acicular titanium dioxide having a major axis/minor axis ratio of 30 to 120 and a binder. A magnetic recording medium characterized by having a layer.