JPS63200317A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance an electromagnetic conversion characteristic and to improve durability, traveling stability and static image durability by incorporating magnetic powder having specific characteristic into a magnetic layer and adding nonmagnetic polishing material particles to said magnetic powder at a specific ratio thereto. CONSTITUTION:The magnetic powder having >=35m<2>/g BET value in specific area is incorporated into the magnetic layer and the nonmagnetic polishing material particles having <=0.6mum average grain size are added to the magnetic powder in the 3-15pts.wt. range per 100pts.wt. magnetic powder. The nonmagnetic polishing agent particles having the average grain size ranging 0.1-0.4mum is particularly preferable. The higher density and higher S/N of magnetic recording are obtd. by using the magnetic power having such average grain size and the electromagnetic conversion characteristic of the high level is obtd. The combination use of the nonmagnetic polishing agent particles having <=0.6mum average grain size contributes to the enhancement in the running durability and static image durability of the magnetic recording medium and to the prevention of the wear of the magnetic layer in iterative use without impairing the electromagnetic conversion characteristic of the high level. The good electromagnetic conversion characteristic by the finer grains of the magnetic powder is thereby obtd. and the excellent surface characteristic and durability are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

BACKGROUND OF THE INVENTION In recent years, magnetic powders with smaller particle diameters have been used as magnetic materials, especially recording media for video and combination cameras, have become more dense and have a higher signal-to-noise ratio.

Generally, it is said that the S/N ratio of a magnetic recording medium is proportional to the square root of the number of particles of magnetic powder in the recording material involved in recording and reproduction. Therefore, when applying the same weight of magnetic powder,
The use of magnetic powder with a smaller particle size is more advantageous in improving the S/N.

However, when the magnetic powder is made into fine particles and its BET value is increased, the surface of the magnetic layer becomes smoother, which actually deteriorates the running durability of the tape. That is, since the above-mentioned recording medium comes into violent sliding contact with the magnetic head during recording and reproduction, smoothing of the surface increases the sliding contact area and increases the coefficient of friction, which actually deteriorates the running performance. This causes undesirable results such as wear of the magnetic coating film during repeated use, shedding of magnetic powder contained in the coating, and clogging of the magnetic head due to the fallen magnetic powder.

One possible way to improve the running durability of such magnetic recording media is to include a large amount of non-magnetic abrasive particles in the magnetic layer, but this will lead to deterioration of the electromagnetic conversion characteristics and increase the performance of the magnetic recording media. The objectives of increasing density and increasing S/N cannot be achieved.

For example, Japanese Patent Publication No. 49-39402 discloses the use of abrasive particles with a particle size of 0.7 μm or more, but this makes the particles too large and deteriorates the electromagnetic conversion characteristics.

An object of the present invention is to provide a magnetic recording medium that has high-level electromagnetic conversion characteristics, has good durability and running stability, and has excellent still image durability. It is in.

20 Structure of the invention and its effects The present invention provides a magnetic recording medium having a magnetic layer containing magnetic powder, in which the specific surface area of the magnetic powder is 35 m
''/gr or more and an average particle size of 0.6 μm or less are contained in the magnetic layer in a proportion of 3 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of magnetic powder. The invention relates to a magnetic recording medium that has unique characteristics.

According to the present invention, the specific surface area of the magnetic powder is 35 m in BET value.
”/gr or more (preferably 38 m'/gr or more), it is possible to increase the density of magnetic recording and increase the S/N,
High-level electromagnetic conversion characteristics can be obtained.

Further, according to the present invention, since non-magnetic abrasive particles with an average particle size of 0.6 μm or less are contained in the magnetic layer, magnetic recording media can be used without impairing the electromagnetic conversion characteristics at the above-mentioned high level. Improves running durability and still image durability,
It is possible to prevent the magnetic layer from being worn out or falling off during repeated use.

The reason why the average particle size of the non-magnetic abrasive particles is set to 0.6 μm or less is that if the average particle size is increased beyond 0.6 μm, the proportion of acicular non-magnetic particles will increase, and their dispersion will cause magnetic This is because the layer surface becomes rough and a space is likely to be created between the head and the magnetic recording medium, which adversely affects electromagnetic conversion characteristics (particularly output). In this regard, in the present invention, by limiting the average particle size of the non-magnetic particles as described above, it is possible to improve the running durability and the surface of the magnetic layer without impairing the good electromagnetic conversion characteristics due to the fineness of the magnetic powder. This can bring about effects such as improving the way the hair comes out due to improved sexual performance.

% [, in the above sense, those having a particle size of 0.1 to 0.4 μm are particularly preferred. Furthermore, non-magnetic abrasive particles were added to magnetic powder 10
The non-magnetic particles are contained in the magnetic layer at a ratio of 3 parts by weight or more and 15 parts by weight or less relative to 0 parts by weight. is important.

Non-magnetic particles that can be used in the present invention include alumina (preferably α-A12os), silicon carbide, chromium oxide,
Examples include silicon nitride, titanium oxide, α-iron oxide, corundum, and artificial corundum, but of course other materials may be used.

Further, as the magnetic powder used in the present invention, r-F a
Iron oxide magnetic powder such as 205, Co-containing r-Fe205, Fe3O4, Co-containing Fe 304: Fe, Ni, Co
, Fe-Ni-Co alloy, Fe-Mn-Zn alloy, Fe
-Mi-Zn alloy, Fe-Co-Ni-Cr alloy, Fe
-Co-N1-P alloy, Co-Ni alloy, etc., Fe, Ni
Metal magnetic powder mainly composed of 5Co etc.: Cr 02
Various ferromagnetic powders are mentioned.

Further, in the present invention, as the lubricant, one or more selected from the group consisting of fatty acids, fatty acid metal salts, fatty acid amides, fatty acid esters, fatty acid-modified silicones, fatty acid ester-modified silicones, and linear paraffins are magnetic powders. It may be used in a proportion of about 7 N parts or less per 100 parts by weight.

Fatty acids that can be used in the present invention may be monobasic or dibasic. Number of carbon atoms: 6 to 3 o, even 10 to
22 fatty acids are preferred. Examples of fatty acids are as follows.

(1) Caproic acid (2) Caprylic acid (3) Capric acid (4) Lafric acid (5) Myristic acid (6) Valmitic acid (7) Stearic acid (8) Isostearic acid (9) Rilunic acid (10) Linoleic acid (11) Oleic acid (12) Elaidic acid (13) Behenic acid (14) Malonic acid (15) Succinic acid (16) Maleic acid (17) Glutaric acid (18) Adipic acid (19) Pimelic acid (20) Azelaic acid (21) Sepacic Acid Examples of fatty acid esters that can be used in the present invention are as follows.

(1) Oleic oleate (2) Incetyl stearate (3) Dioleyl maleate (4) Butyl stearate (5) Butyl palmitate (6) Butyl myristate (7) Octyl palmitate (8) Octyl myristate ( 9) Amyl stearate (10) Alpalmitate (11) Isobutyl oleate (12) Stearyl stearate (13) Lacryl oleate (14) Octyl oleate (15) Isobutyl oleate (16) Methyl oleate (17) Isotridecyl oleate ( 18) 2-ethylhexyl stearate (19)
Methyl stearate (20) 2-ethylhexyl palmitate (21)
4 Soprovir palmitate (22) Isopropyl myristate (23) Methyl laurate (24) Cetyl-2-ethyl hexalate (25)
Dioleyl adipate (26) Diethyl adipate (27) Diisobutyl adipate (28) Diisodecyl adipate Examples of fatty acid metal salts that can be used in the present invention include the aforementioned fatty acids and alkali metals (Ll, Na).

K, etc.) or alkaline earth metals (Mg, Ca, Ba). Further, as the fatty acid amide, those derived from the above-mentioned fatty acids can be used.

The fatty acid-modified silicone and fatty acid ester-modified silicone used in the present invention include C00R (R=H or 01-0
2G alkyl group) modified dialkoxypolysiloxane J dialkoxypolysiloxane (alkyl has 1 to 4 carbon atoms), monoalkyl monoal: 2# Siborisiloxane (alkyl has 1 to 5 carbon atoms, alkoxy (1 to 4 carbon atoms), phenyl polysiloxane, and fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms).

The linear paraffin used in the present invention has 20 to 4 carbon atoms.
0 is preferred.

At least polycrethane can be used as the binder resin of the magnetic layer in the magnetic recording medium of the present invention, and this can be synthesized by reaction of polyol and polyisocyanate. Polyols that can be used include phthalic acid,
Organic dibasic acids such as adipic acid, azelaic acid, dimerized sulfuric acid, and maleic acid, and glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or trimethylolpropane, hexanetriol, and glycerin. A polyester polyol synthesized by reaction with any 211 or more polyol selected from polyhydric alpools such as , tolmethylolethane, and pentaerythritol; or S-caprolactam, α-methyl-1-caprolactam, 3 Examples include lactone polyester polyols synthesized from lactams such as -methyl-3-caprolactam and r-butyrolactam; and polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, and the like.

These polyols are reacted with isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., resulting in urethanized polyester polyurethanes and polyether polyurethanes, or carbonated with phosgene or diphenyl carbonate. Polycarbonate polyurethane is synthesized. These polyurethanes are usually produced primarily by the reaction of polyisocyanates with polyols, and also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or containing reactive end groups of these. (for example, in the form of a urethane elastomer).

Since the methods for producing polyurethane, urethane prepolymers, urethane distomers, curing and crosslinking methods, etc. are well known, detailed explanation thereof will be omitted.

In addition, in the present invention, if a phenoxy resin and/or a vinyl chloride copolymer is contained in addition to the above-mentioned polyurethane as a binder resin, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical properties will be improved. Strength increases. However, if only the phenoxy resin and/or the vinyl chloride copolymer is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved.

The phenoxy resin that can be used is a polymer obtained by polymerizing bisphenol A and epichlorohydrin, and is represented by the following general formula.

(However, n; 82-13) Example Eva, PKHC manufactured by Union Carbide.

There are PKHH, PKHT, etc.

Moreover, as the above-mentioned vinyl chloride copolymers that can be used, there are those represented by the following. In this case, the molar ratio derived from l and m in is 95-50 mol% for the former unit and 5-50 mol% for the latter unit. Further, X represents at least one monomer residue copolymerizable with vinyl chloride selected from the group consisting of vinyl acetate, vinyl alcohol, maleic anhydride, and the like. The degree of polymerization expressed as (l+m) is preferably 100 to 600, and if the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and
If it exceeds 0, the dispersibility will deteriorate. The vinyl chloride copolymer described above may be partially hydrolyzed. The vinyl chloride copolymer is preferably a copolymer containing vinyl chloride-vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymer"). Vinyl chloride
Examples of vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-
Various copolymers of maleic anhydride are mentioned, and vinyl chloride-
Among vinyl acetate copolymers, partially hydrolyzed copolymers are preferred. As a specific example of the above-mentioned vinyl chloride-vinyl acetate copolymer, R manufactured by Union Carbide Co., Ltd.
VAGHJ,rVYHHJ,rVMCHJ,
r S-LEC C", "S-LEC M", Denki Kagaku Kogyo ■
[Denkabinir 100OCJ "Denkabinir 100"
OWJ etc. can be used.

In addition to the above, cellulose resins can also be used as binder resins, including cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. Cellulose ether, methyl cellulose, ethyl cellulose, etc. can be used. Cellulose inorganic acid esters, nitrocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Further, as the cell a-x organic acid ester, acetyl cellulose, phlopionyl cellulose, phthyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose is the most durable.

In addition, regarding the entire binder composition, the ratio of the above-mentioned urethane resin to other resins (total amount of phenoxy resin, vinyl chloride copolymer, etc.) is 90/1 by weight.
Desirably 0 to 40/60, 85/15 to 45
155 has been found to be even more desirable. If the amount of urethane resin is outside this range, dispersion tends to be poor.
Also, if there is a large amount of other resins, surface properties tend to be poor.
In particular, if it exceeds 60% by weight, the physical properties of the coating film become less favorable overall. In the case of vinyl chloride-vinyl acetate,
It can be mixed with the urethane resin with a considerable degree of freedom, and preferably the content of the urethane resin is 15 to 75% by weight.

In addition to the binder resins mentioned above, thermoplastic resins, thermosetting resins, reactive resins, and electron beam curable resins may be used as binder resins for the layers constituting the magnetic recording medium of the present invention.

Further, according to the present invention, it is desirable that the thickness of the magnetic layer be 4.5 μm or less (more preferably 3.5 to 4.5 μm).

In the present invention, since fine magnetic powder and non-magnetic abrasive particles are used as described above, such a thin film can be achieved. Therefore, long-term recording and playback will be possible, and it is likely that the overall cost of the table type will be reduced.

However, it is thought that the thinner the recording medium is, the more likely the strength of the medium will be reduced and edge damage will occur. Therefore, in the present invention, it is desirable to have a BC layer.

The BC layer may be a normal BC layer, in which non-magnetic abrasive particles are dispersed in a binder. Examples of the non-magnetic abrasive particles include carbon black,
Inorganic powders such as titanium oxide and zinc oxide and other organic powders are used.

E, Example Hereinafter, the present invention will be explained with reference to specific examples.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

In addition, in the following examples, all "parts" are "parts by weight".
represents.

First, each magnetic layer was formed on a support as described below, and a back coat layer was further formed to prepare each magnetic tape shown in FIG.

That is, after dispersing each component shown in Figure 2, this magnetic paint was filtered with a 1 μm filter, and 5 parts of polyfunctional isocyanate was added! The mixture was then coated onto a support to a thickness of 5 μm and supercalendered to form a magnetic layer.

Next, after dispersing each component shown in FIG. 2, 20 parts of polyfunctional incyanate was added to prepare a BC layer coating solution, and this coating solution was coated as a dry film on the support opposite to the magnetic layer. Thickness 0.
A BC layer was formed by coating to a thickness of 8 μm, and slit into 1/2 inch width to obtain each videotape shown in Fig. 2 (each example,
Corresponds to the number of the comparative example. ). However, 2m in Figure 2
The following numbers represent parts by weight, and "fruit" from the second column onwards.
indicates an example, and "ratio" indicates a comparative example.

The following measurements were made on videotapes from each side described above.

Chroma S/N: Color video noise meter (-5hibaaoku9
Measured by 25D/IJ. The values are shown as relative values with the value of Example 1 set as 0.

RF output at 4MHz using a VTR deck for measuring RF output.
The output was measured and showed a value that was lower than the initial output after 10014 plays.

(Unit: dB) Still image lifespan: Indicates the time in minutes until the still image deteriorates by 2 dB. The larger the value, the higher the durability and wear resistance of the magnetic recording medium.

The performance of each videotape is shown in Figure 2.

These results show that the tape performance is significantly improved by configuring the magnetic layer according to the present invention. In addition, the specific surface area of the magnetic powder is 35 m"/gr as a BET value.
The particle size of non-magnetic abrasive particles shall be 0.6 μm or more.
It can be seen that setting the content to 3 parts by weight or more and 15 parts by weight or less brings about a remarkable improvement in tape performance.

[Brief explanation of the drawing]

The drawings show examples of the present invention, in which Fig. 1 is a partially enlarged sectional view of an example of a magnetic recording medium, and Fig. 2 shows the magnetic paint components, back layer components, and characteristics of each tape. It is a diagram. In addition, in the symbols shown in the drawings, 1... helmet/non-magnetic support 3... magnetic layer 2...
...Undercoating layer 4... Back coat layer. Agent Patent Attorney Hiroshi Aisaka Figure 1

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer containing magnetic powder, the specific surface area of the magnetic powder is 35 m^2/
The magnetic layer contains non-magnetic abrasive particles having a particle size of gr or more and an average particle size of 0.6 μm or less in a proportion of 3 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of magnetic powder. A magnetic recording medium characterized by: 2. The average particle size of the non-magnetic abrasive particles is 0.1 μm or more, 0
．． The magnetic recording medium according to claim 1, which has a diameter of 4 μm or less.