JPS60193131A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent wear resistance and low transmittance by incorporating black titanium oxide as nonmagnetic powder into the magnetic layer of the magnetic recording medium. CONSTITUTION:Black titanium oxide powder having 0.03-3.0mum grain size, antistatic agent, thermosetting binder, higher fatty acid ester, higher fatty acid and lecithin, etc. are added to magnetic powder and are thoroughly mixed and dispersed together with a solvent by a mixer to manufacture a magnetic coating liquid having a desired component ratio. Said liquid is coated on a base such as a polyester film. The base is thereafter passed through a magnetic field having suitable intensity by using a magnetic field orienting device for orienting the magnetic powder in the coated film in one direction just prior to drying. The coated film is dried to remove the solvent after such orienting treatment and is subjected to surface finishing treatment by super calender rolls in order to smooth further the magnetic layer surface of the coated and dried broad magnetic film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes and magnetic sheets used in audio/video equipment, computers, and the like.

Conventional Structures and Their Problems In recent years, there has been a growing trend towards higher density recording in these magnetic recording media. As a result, recording and
It became necessary to reduce reproduction loss, and measures were taken to make the gap between the magnetic head and the magnetic recording medium even smaller, leading to a situation where the surface of the magnetic recording medium became highly smooth and the magnetic powder became finer. There is.

However, such measures give rise to the following problems. First, as the surface of the magnetic recording medium is made highly smooth, the coefficient of friction of the magnetic recording medium increases, which is disadvantageous in running performance and durability. Second, as the magnetic powder becomes finer, long wavelength light becomes less likely to be scattered by the magnetic powder. In other words, because the light transmittance increases, it is necessary to lower the light transmittance more than before in magnetic recording media that perform end detection using the difference in light transmittance between the nonmagnetic support and the magnetic recording layer. . In response to the above problems, low light transmittance,
That is, it is necessary to include colored nonmagnetic powder in the magnetic layer, but conventional products do not have sufficient abrasiveness for magnetic heads, and the amount added is limited.

OBJECTS OF THE INVENTION An object of the present invention is to obtain a magnetic recording medium with excellent wear resistance and low transmittance by incorporating black titanium oxide as non-magnetic powder into the magnetic layer of the magnetic recording medium.

Structure of the Invention The present invention provides a magnetic recording medium having a magnetic layer on one or both sides, which has excellent abrasion resistance and low light transmittance by containing black titanium oxide fine particles in the magnetic layer. This was based on the discovery that a medium could be obtained.

The particle size of this black titanium oxide powder is not particularly limited, but a particle size of 0.03 to 3.0 μm is used. The black titanium oxide mentioned here is different from T102, and T
It is a compound with a composition near iO, and is generally black in color.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described using a magnetic tape as an example.

First, the magnetic layer is formed as follows.

Magnetic powders include magnetic iron oxide and chromium dioxide.

Any metal magnetic powder may be used. Antistatic agents include carbon blanks or graphite particles.

These inorganic pigments, thermosetting binders, higher fatty acid esters, higher fatty acids, lecithin, etc. are sufficiently mixed and dispersed with a solvent in a mixer to prepare a magnetic coating liquid having a desired component ratio.

The organic solvent used here mainly includes methyl ethyl ketone, toluene, methyl isobutyl ketone, synchlohexane, ethyl acetate, and the like. A ball mill is used as a mixing machine.

You can use a sand mill, desilver, attritor, high speed mixer, kneader, etc.

A magnetic coating solution is applied onto a support such as a polyester film. The coating method may be a doctor blade method, a grapier method, or a reverse roll method. Immediately after coating, a smoother is brought into contact to further improve the smoothness of the coating film, and any one of a bar smoother, wire smoother, film smoother, etc. may be used for this purpose.

Thereafter, just before drying, a magnetic field orientation device is used to align the magnetic powder in the coating film in one direction, and the film is passed through an appropriate magnetic field strength. This magnetic field strength varies depending on the coercive force of the magnetic powder, but is preferably about 2 to 4 times the coercive force. Magnets include permanent magnets and electromagnets. After such orientation treatment, the film is dried to remove the solvent.

In order to further smoothen the surface of the magnetic layer of the coated and dried wide magnetic film, surface treatment is performed using a super calender roll. The surface properties of the calender roll at this time greatly affect the electromagnetic conversion characteristics of the magnetic tape. Calendar conditions include temperature 60~1oO℃, pressure eso
~4oon/cm, speed 20-200 m 7 minutes is preferred.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be specifically described. It should be noted that all parts in the component ratios described in the examples are parts by weight.

(Example 1) The magnetic paint was prepared as follows.

Co-containing -Fe2O3 magnetic oxide powder 100 parts Polyurethane resin 16 parts Vinyl chloride-vinyl acetate copolymer 6 parts Nitrocellulose resin 6s Black titanium oxide powder 3 parts Average particle size = 0.1/Im Lecithin 2 parts Methyl ethyl ketone 100 parts Methyl isobutyl ketone 100 parts Toluene 100 parts After mixing and dispersing the above composition in a ball mill for 48 hours, adding part e of hardener (Coronet), the resulting kneaded product was filtered through a filter having an average pore size of 3 μm. A magnetic coating solution was prepared.

Next, the above magnetic coating solution was applied onto a 12 μm thick polyester film, oriented and dried, and then the magnetic layer was surface-treated using a super calendar roll to give a magnetic film thickness of 5 μm.
A wide jumbo roll was obtained, and this was cut into % inch width to produce video chives.

(Example 2) In the magnetic paint of Example 1, black titanium oxide powder with an average particle size of 0.5 μm was used instead of the black titanium oxide powder with an average particle size of 0.1 μm, but the rest was exactly the same as in Example 1. A magnetic tape was produced using the following method.

(Comparative Example 1) In the magnetic paint of Example 1, 3 parts of T 102 powder (average particle size 0.5 μm) was used in place of the black titanium oxide powder, and a magnetic tape was prepared in the same manner as in Example 1, except that Created.

(Comparative Example 2) In the magnetic paint of Example 1, 3 α-A1203 powder (average particle size 0.4 μm) was used instead of black titanium oxide powder.
A magnetic tape was prepared in the same manner as in Example 1, except that the following parts were used.

Scratch resistance of each sample above2. -Warmth.

The light transmittance is shown in the table below.

In the above table, (1) Scratch resistance was determined by observing the streaks when a 4.7φ steel ball was rubbed on the same track 30 times on the tape surface at a speed of 20 f/sec with a load of 407 applied. Depending on the degree of damage, there may be none, very slight presence, or slight presence.

It is divided into four stages: Yes.

(2) Surface roughness is measured using the stylus type surface roughness rule,
The ten-point average roughness R2 was calculated from "Japanese Industrial Standard (JIS) B 6001 (7) r Surface Roughness."

(3) Light transmittance is VH8 videotape recorder p
- (VTR) NV-82001 (manufactured by Matsushita Electric Industrial Co., Ltd.) terminal detection device was used, and the state of transmitting light was tested 1o○.
The measurement was made with a state in which no light passes through as 0%.

As is clear from the above table, the magnetic tape obtained as described above has superior durability and abrasion resistance, and has a lower light transmittance than conventional products. Although the above embodiments have been described with respect to magnetic tapes, it is not to be said that the present invention can be applied not only to magnetic tapes but also to other magnetic recording media such as magnetic sheets.

Effects of the Invention As detailed above, according to the present invention, a magnetic recording medium with excellent wear resistance and low light transmittance can be obtained, and therefore has great practical value.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on one or both sides, the magnetic layer containing fine particles of black titanium oxide.