JPS59172154A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent blocking by relieving curling and obtaining an adequate rough surface and lubricating effect and to improve running stability by providing a resin film layer contg. fluorophosphate and non-magnetic powder on the rear of a base body on which a thin ferromagnetic metallic film layer is formed. CONSTITUTION:A resin film layer contg. fluorophosphate and non-magnetic powder is provided on the rear of a base body on the surface of which a thin ferromagnetic metallic film is formed. The fluorophosphate is used in a range of 0.05-3wt% by the total weight with the resin to be used in combination. The non-magnetic powder having <=5Mohs hardness and 0.05-5mu particle size is used in a range of 30-60wt% by the total weight with the resin to be used. The back coating layer is formed by forming the thin ferromagnetic metallic film layer by vapor deposition on the surface of the base body then mixing and dispersing fluorophosphate and non-magnetic powder with and in a soln. prepd. by dissolving one or two kinds or more of suitable resins in a suitable solvent and applying the mixture thereof on the rear of the substrate and drying the coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, such as a magnetic tape, whose recording layer is a ferromagnetic metal thin film layer made of metal or an alloy thereof.

In recent years, in response to the increasing density of magnetic recording, magnetic recording media have been developed in which a ferromagnetic metal thin film layer made of metals such as iron, cobalt, nickel, or alloys thereof is deposited on a substrate such as a plastic film by vapor deposition or other methods. is being developed.

However, magnetic recording media such as this type of magnetic tape,
Although it has characteristics suitable for high-density recording, it has the disadvantage that it tends to curl because the thermal expansion coefficient and elastic modulus of the substrate and the ferromagnetic metal thin film layer are too different.

In addition, in this type of magnetic recording medium, the smoothness of the substrate directly affects the smoothness of the ferromagnetic metal thin film layer and has a large effect on the electromagnetic conversion characteristics, so it is necessary to use a substrate with very good smoothness. Because of this, the coefficient of friction of the base is large, and the magnetic tape tends to stick to the guide rollers, etc. during running, and as a result, the magnetic tape sticks to the guide rollers, etc., causing the tape to stretch and deform, increasing output fluctuations. There are some drawbacks such as:

The inventors conducted various studies to overcome this problem, and as a result, they added fluorophosphate ester and nonmagnetic powder to the back surface of a substrate on which a ferromagnetic metal thin film layer was formed by vapor deposition as described above. When a resin film layer containing
This back coat layer corrects curls well, and the inclusion of non-magnetic powder in the back coat layer gives this layer a moderately rough surface.Furthermore, the fluorophosphate ester contained in this layer Excellent lubrication effect is exhibited, and by using both of these properties, there is no blocking phenomenon caused by sticking to the magnetic metal thin film layer at the same time as tape winding, and there is no output due to elongation and deformation caused by sticking to guide rollers etc. It has been discovered that a magnetic tape with reduced fluctuations and good running stability can be obtained, leading to the present invention.

As the fluorophosphate ester used in this invention, those having a perfluoroalkyl group and a phosphoric acid group in the molecule can be widely used, and typical examples thereof include the following structural formulas (1) and (2+). Things can be mentioned.

1 cF3+cF穐-o-P-oH...(1) Blind oH (In the formula, R1 is an alkyl group, R2 is an alkylene group, and n is an integer preferably in the range of 4 to 30.) Above If the amount of fluorophosphate used is 0.01 weight less than the total amount of the resin used together, the desired effect will not be obtained, and if it is more than 5 weight, e-rolling will occur on the surface of the back coat layer. During rotation, it transfers to the adjacent ferromagnetic metal thin film layer and adversely affects magnetic properties, so it is preferably within the range of 0.01 to 5 weight ratio, and more preferably within the range of 0.05 to 3 weight ratio. .

In addition, the non-magnetic powder used together with the above-mentioned resin preferably has a Mohs hardness of 5 or less, since if the Mohs hardness exceeds 5, it will damage the ferromagnetic gold thin film layer during winding.
For example, CaC0a powder with a Mohs hardness of 5 or less, MgO
Powder, BaC0a powder, ZnO powder, Gu20 powder, C
UO powder, MO82 powder, WS2 powder, etc. are preferably used. The particle size of these non-magnetic powders is 0.0
If a diameter smaller than 5μ is used, blocking cannot be prevented, and if a diameter larger than 5μ is used, irregularities will be transferred to the ferromagnetic metal thin film layer during winding, so 0.05 to 5μ.
It is preferable to use a non-magnetic powder within the range of 1 to 3. When such a non-magnetic powder is contained in the back coat layer together with the fluorophosphate ester, curling can be sufficiently prevented, and the surface of the back coat layer can be more properly formed. The roughened surface further reduces the coefficient of friction and completely eliminates sticking to guide rollers, etc., further improving running stability.

If the amount of such non-magnetic powder used is 20 weight less than the total amount of the resin used together, there is a risk of causing a blocking phenomenon when used in combination with a resin having polar groups such as hydroxyl groups. If the weight increases, the non-magnetic powder may fall off and adversely affect the magnetic properties, so it is preferably within the range of 20 to 80% by weight, and 30% by weight.
More preferably, the content is within the range of 60% by weight.

The resins used in this invention include vinyl chloride-vinylacetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic ester-vinylidene chloride copolymers, and acrylic esters. -Styrene copolymer, methacrylic acid-acrylonitrile copolymer, methacrylic acid ester-1 vinylidene copolymer, methacrylic acid ester-styrene copolymer, urethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer , butadiene-acrylonitrile copolymer, holamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose propionate, nitrocellulose, etc.), styrene-phtadiene copolymer, polyester resin, chlorovinyl ether-acrylic acid ester copolymer Examples include one type or a mixture of several types of polymers, amino resins, phenolic resins, epoxy resins, alkyd resins and trifunctional isocyanates.

Furthermore, if the layer thickness of the back coat layer containing such fluorophosphate ester, nonmagnetic powder, and resin is made thinner than 0.1 μm, the desired effect cannot be obtained, and if it is thicker than 2 μm, curling occurs with the back coat layer inside. 0.
It is preferably within the range of 1 to 2μ.

Any magnetic material that forms a ferromagnetic metal thin film layer on the surface of the substrate can be applied. Examples include cellulose resin, polyurethane resin, polyester resin, polyisocyanate, and vinyl chloride-vinyl acetate copolymer resin.

The back coat layer in the present invention is a paint in which a filler consisting of carbon black and zinc oxide powder is mixed and dispersed in the binder described above, and is coated on the back side of a base on which a magnetic layer has been previously formed on the main surface. Although it is formed by coating to a thickness of 3.0 μm, this layer may contain an appropriate additive such as a lubricant, if necessary.

The lubricant reduces the coefficient of friction of the backcoat layer to further improve durability, and also provides good results in preventing filler powder from falling off. Any material that is solid (semi-solid) or liquid at room temperature can be used as long as it is soluble in an organic solvent. Specific examples include fatty acids, fatty acid esters, liquid paraffin, and the like. The amount added is preferably 5 parts by weight or less (usually 0.1 to 5 parts by weight) based on 100 parts by weight of the total filler.

As described above, according to the present invention, it is possible to form a Basokuko-1 layer with low light transmittance and good durability, and to provide a magnetic recording medium that satisfies video characteristics and ground running stability. I can do it.

Next, embodiments of this invention will be described. In the following, parts shall mean parts by weight.

Example Co-containing acicular magnetic iron oxide powder 250 parts Carbon black 12" granular α-iron oxide
1o Nitrified cotton
22〃Polyurethane resin
19 Trifunctional low molecular weight isocyanate 7
〃To compound cyclohexanone 34o〃Toluene 34o〃Stearic acid-
n-butyl 3 myristic acid
3.0 A magnetic paint having the above composition was applied onto a 14 μm thick polyester base film with good surface smoothness to a dry thickness of 5 μm, dried, and then surface treated.

A backcoat layer paint having the following composition was applied to the back of the obtained magnetic tape so that the dry thickness was 1 μm, and after drying, the tape was cut into a predetermined width to produce a videotape.

Carbon blank (black pearl manufactured by Capot Co., Ltd. 30 parts, volatile component 5% by weight) Zinc oxide powder 270〃Nitrified cotton
100 ll Polyurethane resin 70 Trifunctional low molecular weight isocyanate 30 Compound n-butyl stearate 3 Myristic acid 2 Cyclohexanone
750〃Toluene
750〃Light transmittance of the magnetic part of the above videotape, durability of the back coat layer (decrease rate of video S/N ratio)
, surface roughness, color S/N ratio as a video characteristic, and running stability (wow and flutter) were investigated using the particle size of the zinc oxide powder as a parameter, and the results were as shown in the following table.

In the table, Comparative Example 1 is the result of a videotape produced in the same manner as in the Example except that the particle size of the zinc oxide powder was outside the range of the present invention, and Comparative Example 2 is the result of a videotape produced in the same manner as in the Example except that the particle size of the zinc oxide powder was changed to a value outside the range of the present invention. The results of the videotape produced in the same manner as in Example except that calcium carbonate with a particle size of 0.07 μm were used. , 1.
These are the results of a videotape produced in the same manner as in Example except that the concentration was changed to 8% by weight). Moreover, each characteristic test was conducted by the following method.

<Light transmittance>

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a resin film layer containing a fluorophosphate ester and a nonmagnetic powder is provided on the back surface of a substrate having a ferromagnetic metal thin film layer made of metal or an alloy thereof formed on the surface.