JPS5975432A - Magnetic recording body - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording body having excellent electromagnetic conversion characteristics and durability and an improved color S/N ratio, etc. by incorporating carbon black having an average primary particle size and pH respectively of specific values, a polishing agent having hardness of a specific value or above and a hardner in a magnetic layer. CONSTITUTION:A magnetic layer contg. carbon black having <30mmu average primary particle size and <6pH (for example, ''Ma-8'' produced by Mitsubishi Chemical Industries Ltd.), a thermosetting resin, etc. such as polyisocyanate, epoxy resin or the like as a hardener, and a polishing agent having >6 Morse hardness and 0.1-1.5mu particle size is provided on a substrate of polyethylene terephthalate or the like. A magnetic tape having excellent color S/N, running durability for 100hr, a good antistatic property, and excellent surface smoothness and durability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and its main purpose is to improve electromagnetic conversion characteristics and durability.

Conventionally, the magnetic properties of magnetic recording bodies are mainly contained in carbon black for the purpose of preventing static electricity.

However, the addition of carbon black deteriorates the smoothness of the coating film surface of the magnetic layer, so in video tapes that require high-density recording, the addition of carbon black significantly deteriorates the electrical-to-solar conversion characteristics. Revised S is a long-awaited trap. However, if the surface smoothness increases, the durability will deteriorate, so it is essential to satisfy both characteristics 1. , Gyoko J CO 1RS6I, %Ko 5J-33, ZAY) T:n unsatisfactory condition and fco
Please be specific Color F3 / , N , / 00
The aim is to provide an improved magnetic recording medium with reduced time and durability.

The above-mentioned object of the present invention is to provide a magnetic recording material comprising an S layer on a non-magnetic support, in which the magnetic layer is made of carbon black having an average particle diameter of JOmμ or more and a pH of less than %. It has been found that this can be achieved by a magnetic recording material containing a) an abrasive having a Mohs hardness of 1 or higher, and 3) a hardening agent.

The carbon black F used in the present invention may be any carbon black having an average particle size of Jamμ or less and a pH of less than 6. Particle ``ν is sweetly ko!mμ
The following is preferably less than 0mμ, more preferably i
smμ or less. The pH is preferably less than ijj, more preferably less than μ, more preferably less than 3. The amount added to ioo parts by weight of the magnetic material is preferably /-, 20 parts by weight, and more preferably 3 to 10 parts by weight. If the amount added is small, the antistatic effect will be reduced, and if the amount added is too large, the degree of filling of the magnetic material in the magnetic layer will be reduced and the surface properties of the coating film will be deteriorated.

Specific examples of the carbon black used in the present invention include ("Blackpear I/J" manufactured by Abot).
00″Columbian Carbon F!”li, aven
There are "MA-J" manufactured by Mitsubishi Chemical Industries, Ltd.

Curing agents used in the present invention include polyisocyanates, polyamides, epoxy resins, polyamines, melamine resins, phenolic resins, silicone resins, and other thermosetting resins and moisture-curing resins.1. A commonly used magnetic tape is used. The amount of hardening firmness added is preferably 1.20 to 30 parts, and preferably 1.20 to 30 parts, based on 100 parts of the total weight of the inder.

It is necessary for the curing agent to have a fine three-dimensional network structure in order to obtain the effects of the present invention, and for this purpose, the molecular weight is preferably less than 2,000, and more preferably less than 1,000. The curing agent used is a polyfunctional one, and the number of functional groups in one molecule is preferably three or more, in which case the effects of the present invention can be effectively obtained. Among them, low molecular weight polyfunctional polyisocyanates are particularly recommended.

It is essential that the abrasive used in the present invention has a Moh's hardness of 6 or more, preferably 6 or more. Further, the particle size is preferably O07~/, jμ, Oo, 2~l
μ is more preferred. The amount added is preferably 01S-10 parts by weight, more preferably i and io parts by weight, and even more preferably 1-13 to j parts by weight. Examples of abrasives include magnesium oxide (hardness: 6), Cr2O3 (
Mohs hardness r~ri), α-A120a (Mohs hardness u
trn, 5iC (Mohs hardness, s), etc., these may be used in combination 〇Magnetic material r-Fe203. FeOx (t, J J<
X < i, s), Cr 02, CO inlaid 1-Fe2O3,
CO-added FeOx (i, 3 j(x(/ , s
), tabular Ba ferrite, Fe-Co-Ni alloy powder, Fe-20 alloy powder, and other ferromagnetic powders that can be used for normal magnetic recording materials can be used in the present invention without any difference.

The shape of iron oxide magnetic material is granular, needle-like, spindle-like,
They may be in any shape, such as a flat plate, and may be used in combination if necessary.

Examples of binders other than hardening agents include polyvinyl acetate, cellulose derivatives, polyurethane, nitrile-butadiene rubber, styrene-butadiene rubber, polyester,
Acrylic resins, vinylidene chloride resins, etc. can be used, but they are not limited to these, and those commonly used for magnetic recording media can be used in the present invention.

Examples of lubricants that can be saturated in the magnetic layer include fatty acid esters, ester% fatty acids such as sorbitan fatty acid esters, various silicone oils, various fluorine-based oils, liquid paraffin, squalane, and other materials that can be normally used in magnetic recording media. is used.

There is no problem in adding stabilizers, inorganic fillers, plasticizers, etc. to the magnetic layer depending on the core material.

As for the support, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, vinyl chloride film, etc. are used, and if these are coated with a coating, they can be used without any problem even in a single film. The surface quality of the support is Color 87N for high-density small video tapes.
'c It is preferable to have something clean to make it look better. Especially when the center line average roughness (a) is 0.03 jlt or more f” (Cu”
Off 0.01 mm) is preferable, and 0.02
It is preferable to use a support having a thickness of less than 0. If necessary, supports having different smoothness on both sides may be used. The magnetic layer may be coated on one side (diamagnetic side) of the support using a FJ lubricant or surfactant coated. After coating the magnetic layer or after surface forming treatment such as calendering, an anti-polyming agent or a surfactant may be applied to the diamagnetic surface (Nil) of the support.

The composition and manufacturing method used in the present invention are as follows:
It is described in No. 0.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

In the examples, "parts" indicate "parts by weight."

Example / Co-added γ-pe2o3 / 00 parts carbon black (size/f”mμ, pHJ)
1 part α-A 120 g (Mohs hardness Y) 1 part Curing agent Polyisocyanate, Bayer Tai 1 Desmodur L-7, t" 6 parts Salt vinyl acetate resin IS part Vinylidene chloride/acrylonitrile P polymer 4', J part Meleyl oleate o, s part Solvent (cyclohexanone/methyl ethyl ketone = i7i) Appropriate amount After preparing a magnetic liquid tube with the above composition by ball mill dispersion, a back coat layer consisting of carbon black and binder with a thickness of 7 μm was applied, and a layer with a thickness of 7 μm was applied. Polyethylene terephthalate film (
RR=θ, θj lt ) by a doctor method.

Thereafter, it was calendered and cut into 1/2 inch wide pieces to obtain a small VH8 videotape (sample A/). In addition, by replacing 120 g of α-A with MgO (Mohs hardness 6), a videotape (sample A, 2) was prepared by the same operation.
I got it.

Comparative Example l Sample A of Example 1 except that the average particle size of carbon black in Example 1 was replaced with 'l<j Omμ.
Sample A J f: obtained 1 piece in the same manner as I.

Comparative Example λ A -℃ sample was obtained in the same manner as in Example 1 except that rlH70 carbon black was used instead of carbon black.

Comparison flI3 Sample Ajf was obtained in the same manner as in Sample A/ of Example 1 except that granular α-Fe203 (Mohs hardness! #) kumquat was used instead of α-Al2O5.

Comparative Example Sample 6 was obtained in the same manner as Sample A/ of Example 1 except that the curing agent was omitted from Sample A/ of Example 1.

Example In Sample A/ of Example 1, the surface properties of the support were na=0
．． A sample plate 7 was obtained which was changed to a 0 μμ sample plate.

The evaluation results for sample A/=A, 7 obtained in this way are all shown in Table 1. The method for measuring the data shown in Table 1 is as follows. The VTR used for color S/N% 700 hour running durability and dropout determination was VH8 system V.
The test was carried out at TR and Toon. Color S/N is expressed as a relative value.

In addition, the running durability of the tape is 2ioo on the VTR.
Number of scratches on the tape magnetic surface after running for a time 'i/
/, 2 inch tape width was visually measured.

Note that the color S/N is thought to correspond mainly to the surface smoothness of the magnetic layer in a relatively long wavelength region, and the IOO time running durability corresponds to the durability of the magnetic layer coating. The less the better. On the other hand, dropout is mainly related to chargeability, and the effect on W electric protection due to carbon black is less loss, and the smaller the dropout, the better.

, and the magnetic layer Jl? Even if the strength is low, there will be more dropouts.

As shown in Table 1, sample A/(invention) has better color S/N and dropout than comparative samples AJ (using carbon black of size jomμ) and A4' (using carbon black of pH 7). Excellent in that respect. , Comparative sample A that does not use a hardening agent in terms of ioo hour running durability, color S/N, and dropout.
6 shows significantly better characteristics. Sample Aj
, A, 2 is the Mohs hardness abrasive α-A7203 υ
granular α-Fe203 (Mohs hardness r, r), Mg0 (
This is a sample using 6) sound for Mohs hardness. Comparative example sample A compared to A/! The running durability between /00Ff# has deteriorated extremely, and the "i7c color S/N, Drop
It is essential that the Mohs hardness of the abrasive is 6 or higher to avoid deterioration of the abrasive. Example Sample A7 is a case where a support with poor surface properties was used, and it can be seen that Sample A/ has better color 8/N.

To summarize the above, +l+ average -order particle size is 30
Carbon black having a pH of less than mμ and less than 6, (2)
Only when combined with an abrasive having a Mohs hardness of 6 or more and (3) a phosphorizing agent can a magnetic recording medium with good lightning and ftX conversion characteristics and durability be obtained.

Claims (1)

[Claims] A magnetic recording body comprising a magnetic layer provided on a non-magnetic support, wherein the magnetic layer is l) carbon black with an average particle size of 30 mμ or less and a pH of less than 6; -) Mohs hardness 1. A magnetic recording material comprising: 6 or more abrasives; and 3) a hardening agent.