JPS623430A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the S/N and RF output of the titled medium by incorporating a metallic magnetic substance and an org. pigment compd. having a carbonyl group and/or a sulfonic group into the magnetic layer. CONSTITUTION:A magnetic layer 2 contg. a metallic magnetic substance, an org. azo pigment compd. having a carbonyl group and/or a sulfonic group and polyurethane and a phenoxy resin and/or a vinyl chloride coplymer as the binder resin is formed on the surface of a carrier 1. To magnetic powder, 0.1-20wt% org. pigment compd. is used. A backcoat layer 3 is formed on the rear surface of the carrier 1. Consequently, the metallic magnetic substance is stably dispersed in the magnetic layer 2 and the S/N, RF output, etc., of a magnetic recording medium is improved.

Description

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

BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint consisting of magnetic powder and binder resin onto a support and drying it.

Conventionally, in these magnetic recording media, various dispersants and surfactants have been used to disperse fine particulate magnetic powder in an organic solvent together with a binder resin when preparing a coating solution for manufacturing the media. . Examples of dispersants include oily lecithin or powdered lecithin, saturated or unsaturated fatty acids and their salts, hydrocarbons having polyoxyethylene chains, sulfuric esters of higher alcohols, and 1Jyll.
There are zx chill etc. These dispersants are added in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the magnetic powder.

In recent years, in order to manufacture high-performance magnetic tapes, it is essential to make magnetic particles ultra-fine and increase BET, but it is difficult to obtain a magnetic recording layer with desired characteristics using conventional additives. Moreover, even if a prototype in a laboratory has excellent characteristics, it may not be put to practical use due to mass production or production technology considerations. In particular, it has been difficult to produce magnetic tape coatings with uniform, low viscosity, and excellent coating properties from ultrafine magnetic powder particles.

Furthermore, in the prior art, dispersion into a binder solution by surface modification of the magnetic powder is primarily considered, and little consideration is given to the stability and applicability of the produced paint.

C. Purpose of the Invention The first purpose of the present invention is to provide a magnetic recording medium that improves dispersion stability by using a novel additive for a magnetic layer; and second, to improve coating properties and stagnation stability. Thirdly, in conjunction with the first and second objects, the purpose is to provide a magnetic recording medium with good sensitivity; and fourthly, to provide a magnetic recording medium with good sensitivity. The object of the present invention is to provide a magnetic recording medium whose layers have good durability; and fifth, to provide a magnetic recording medium whose production cost is low.

2. Structure of the invention and its effects, that is, the present invention (desirably uses iron as 8Q atomic
The present invention relates to a magnetic recording medium in which a magnetic layer contains a metal magnetic material (containing 4 or more) and an organic dye compound having a carboxyl group and/or a sulfonic acid group.

According to the present invention, since the magnetic layer contains an organic dye compound having a carboxyl group and/or a sulfonic acid group, the metal magnetic material is stably dispersed, and the S/N ratio, R, F output, etc. The following media can be provided with significant improvements.

It is preferable that the organic dye compound having a carboxyl group and/or a sulfonic acid group used in the present invention has one of the following conditions.

a) Preferably in the form of salt.

b) It is preferably an azo compound.

C) Compounds whose general formula X is represented by the following formula are preferable.

nl, n, = Q ~ 5 m, , mt = Q ~ 2 x: ci, NO,, CH,, CtH5, OCH,,
QC! H.

Y: C4 2: Carboxyl group or sulfo acid group, tt, may be in the form of a salt, and 6-salts of alkali metals, alkaline earth metals, and organic amines are preferred.

d) Exemplary compounds of the organic dye compound having a carboxyl group and/or a sulfonic acid group represented by the general formula X, which is preferably red, are as follows, but are not limited to these. Various substitutions are possible for the tth modification, such as Compound (2) Compound (3) Compound (4) CI! .

Compound (5) Compound (7) Compound (8) Compound α1 Compound aυ Compound α compound (1e Compound αη Compound α mallet) K for incorporating the organic dye compound used in the present invention into the magnetic layer of the magnetic recording medium is: At least one organic dye compound according to the present invention is dissolved in an organic solvent such as toluene, methyl ethyl ketone, or cyclohexanone, and magnetic powder is immersed in the solution at a predetermined ratio, stirred and mixed, and then filtered. The treated magnetic powder obtained by drying and drying is kneaded with a binder.Alternatively, at least one organic dye compound according to the present invention is added directly or dissolved in an appropriate solvent during dispersion of the magnetic powder. Furthermore, it is also possible to add the magnetic coating material before applying it to the support.

The organic dye compound of the present invention is usually 0.00% relative to the magnetic powder.
It is desirable to use it in a range of 1% to 1% by weight, preferably 0.1% to 10% by weight.

The magnetic paint obtained by cross-dispersing the magnetic powder and binder using the organic dye compound of the present invention using an organic solvent etc. has excellent dispersion stability and low viscosity, and furthermore, the varnish does not fade over time. It also has a low amount of water, is easy to redisperse, and has excellent coating workability.

In the present invention, it is also desirable to add another surfactant (for example, a nonionic surfactant, Compound B or B, which will be described later) in combination with this organic dye compound.

Further, the magnetic powder used in the present invention is a metal magnetic material, and includes Fe, Ni, Co, Fe-Mn-Zn.
.

Fe-AjL, Fe-Ni, Fe-Ni
-Zn, Fe-Co -Ni -Cr1Fe -C
o-Ni-P%Co-Ni etc., Fe, Ni.

Examples include metal magnetic powder containing Co or the like as a main component. Nine, the BET value of magnetic powder is 38d/g or more, is 12500
E or higher is better.

At least polyurethane can be used as the binder resin for 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, dimerized sulfuric acid, and maleic acid; glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; or trimethylolpropane, hexanetriol, glycerin, trimethylolethane, and Polyester polyol synthesized by reaction with polyhydric alcohols such as erythritol or two or more polyols selected from these glycols and polyhydric alcohols; Lactone polyester polyols synthesized from lactams such as methyl-1-caprolactam, S-methyl-3-caprolactam, and r-butyrolactam;
Examples include polyether polyols synthesized from butylene oxide and the like.

These polyols are reacted with isocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc., thereby converting them into urethanes, such as polyester polyurethanes, polyether polyurethanes, and polycarbonates carbonated with phosgene or diphenyl carbonate. 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, urethane elastomer type ○) may be used.

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

In the present invention, if a phenolic resin and/or a vinyl chloride copolymer is also contained in addition to the polyurethane described above as a binder resin, the dispersibility of the magnetic powder will be improved when applied to the magnetic layer, and its mechanical strength will be increased. increase 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 preferably a polymer obtained by polymerizing bisphenol A and epichlorohydrin, and has a basic structure represented by the following general formula. Various substituents may be further introduced into this structure.

(However, n = 82 to 13) For example, PKHC1PKHH manufactured by Union Carbide
%PKHT etc.

In addition to the above, other vinyl chloride copolymers that can be used as binder components include: The molar ratio derived from and m is 9 for the former unit.
5 to 50 molti, and for the latter unit 5 to 50 molti.
It is 50 molti. Further, X represents a monomer residue copolymerizable with vinyl chloride, and represents at least one member selected from the group consisting of vinyl acetate, vinyl alcohol, maleic anhydride, and the like. The degree of polymerization expressed as B+m) is preferably from 100 to 600; when the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and when it exceeds 600, the dispersibility deteriorates. The vinyl chloride copolymer described above may be partially hydrolyzed.

As the vinyl chloride copolymer, preferably vinyl chloride-
Examples include copolymers containing vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymers"). Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-maleic anhydride copolymers, and vinyl chloride-vinyl acetate copolymers. Among these, partially hydrolyzed nine copolymers are preferred. Specific examples of the above-mentioned vinyl chloride-vinyl acetate copolymers include "vAGH" manufactured by Union Carbide, jVYHHJ, 1-VMCHJ,
“S-LEC A” and “S-LEC Jin-5” manufactured by Okisui Kagaku@
”, “S-LEC C”, “S-LEC Ml”, “Denkabinir 100OGJ”, “Denkabinir 1000Wj” specially manufactured by Denki Kagaku Kogyo, etc. can be used.

In addition to the above, fibrous resins can also be used as binder resins, including cellulose ether,
Cellulose inorganic acid esters, cellulose organic acid esters, etc. can be used. As the cellulose ether, methyl cellulose, ethyl cellulose, etc. can be used. Inorganic cellulose [-r-stertosite, di-trocellulose, cellulose sulfate, cellulose phosphate, etc. can be used. Further, as the c-, vo-, and z-organic full esters, acetyl cellulose, propionyl cellulose, phthyryl cellulose, etc. can be used. Among these cellulose resins, nitrocellulose is preferred.

Regarding the overall 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 0-30/70, 85/15-40
It has been confirmed that /60 is even more desirable. If the amount of urethane resin is outside this range, dispersion tends to be poor.
If the amount of other resins increases, surface properties tend to be poor.

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 urethane resin has a
It is 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.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 2,000, such as acrylic ester-acrylonitrile copolymer, acrylic acid Ester-vinylidene chloride copolymers, acrylic ester-styrene copolymers, etc. are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Among these resins, those which do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, urea resin,
These include melamine resin, alkyd resin, etc.

As the electron beam irradiation hardening resin, unsaturated prepolymer,
Examples include maleic anhydride type, urethane acrylic type, and polyester acrylic type.

In the magnetic recording medium of the present invention, carbon black may be further added to the magnetic layer. It is desirable that this carbon black has electrical conductivity, but carbon black with light-shielding properties may also be added. As the highly conductive carbon black, for example, Conductex 975 (specific surface area: 250 m) manufactured by Columbia Carbon Co., Ltd.
/ g, particle size 24 mμ), Conductex 900 (
Specific surface area 1257FL/gs particle size nmp), Cabot Vulcal
XC-72 (specific surface area 254 tri/g, particle size 3
omμ), Raven 1040.420, Mitsubishi Kasei ■, etc. As the light-shielding carbon black, for example, Raven 2000 (specific surface area 1907 FL''/g, particle size 18 mμ), 2100.
1170.1000, Mitsubishi Kasei Nosu 100, Na 75
, na40, naa, naka, etc. can be used. Carbon black has an oil absorption of 90 MI (DBP) / Z
When it is oo g or more, it is easy to form a struttle structure,
It is desirable because it exhibits higher conductivity.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
A magnetic layer 2 is provided on a support 1. A BC layer 3 is provided on the opposite side of the magnetic layer 2. Although this BC layer may be provided, it is not necessary to provide it.

In addition to the above-mentioned friend metal magnetic material and organic dye compound, the magnetic layer 2 contains lubricants (e.g. silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 2 carbon atoms (e.g. Stearic acid) and a fatty acid ester consisting of a monohydric alcohol having 13 to 26 carbon atoms, etc.), an antistatic agent (for example, graphite), etc. may be added.

Incidentally, in the magnetic recording medium shown in FIG. 1, an undercoat layer (not shown) may be provided between the magnetic layer 2 and the support 1.

FIG. 2 shows other magnetic recording media.
A 00 layer 4 is provided on the magnetic layer 2 of the illustrated medium. This 00 layer 4 is provided to protect the magnetic layer 2 from damage, etc., and therefore needs to have sufficient slipperiness.

Therefore, as the binder resin for the 00 layer 4, the urethane resin used for the above magnetic layer 2 may be used (preferably in combination with a phenoxy resin and/or a vinyl chloride copolymer). The surface roughness of the 00 layer 4 is Ra≦0.01 fim, Rmax≦0.1, especially in relation to color S/N.
It is better to set it to 3 ttm. In this case, the surface roughness of the support 10 is Ra≦001 μm, Rrmax O, 13i
tm, and it is desirable to use a smooth support 1.

FIG. 3 shows a magnetic recording medium configured as a magnetic disk, with magnetic layers 2.00 on both sides of the support 1 similar to those described above.
Layers 4 are provided, and the 00 layer 4 may contain a binder resin containing the above-mentioned urethane resin as a main component.

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, "parts" represent parts by weight.

(Example 1) Abrasive (α-AJ, O,) 4 parts cyclohexanone 200 parts Toluene Part methyl ethyl ketone Recess The above composition was sufficiently stirred and mixed in a ball mill, and a polyfunctional isocyanate (Coronet manufactured by Nippon Polyurethane Co., Ltd.) was used as a curing agent. After adding 3 parts of L), the mixture was filtered through a filter. The obtained magnetic paint was applied to the surface of a 13 μm thick polyethylene tere-7 tallate base to a dry film thickness of 3 μm. Thereafter, the surface of the magnetic layer was treated using a super calendar roll to obtain a wide magnetic film having a magnetic layer of a predetermined thickness. This film was cut into 1/2 inch width to prepare a video magnetic tape and a sample was obtained.

[Examples 2 to 18, Comparative Examples 1 to 4] In place of the organic dye compound (1) according to the present invention used in Example 1, the organic dye compound (2) shown above was used.
Used at ~a. Other compositions, methods, etc. are the same as in Example 1.

Next, as comparative examples, the organic dye compound (1) according to the present invention in Example 1 was replaced as shown in Table 1 to give Comparative Examples 1 to 4, respectively, of nonionic surfactants as shown in Table 1.

**Compound B: Cs5Hss O+CHtCH2
0-) A nonionic surfactant consisting of rH.

The performance of each example videotape is shown in Table 2 and Figure 4 (unit: pB). However, the measurement method for each characteristic was as follows.

Chroma S/N: Color video noise meter "5hib"
Measured by asoku 925 D/I J, 1
The output level after 00 times is shown as a relative value.

Lumi S/N: Same as above 4MH using VTR deck for RF output measurement
The R and F outputs at z were measured, and after 100 playbacks, the values showed a decrease compared to the initial output (unit: 2 dB). (The following is a blank space, go to the next page) Table 2 From Table 2 and Figure 4, it can be seen that the system using an organic dye compound is clearly effective in terms of electromagnetic conversion characteristics and dispersibility.

(Examples 19 to 26, Comparative Examples 5 to 7) In place of the organic dye compounds (1) and (2) according to the present invention used in Example 1.2, conventionally known dispersants as shown in Table 3 were used. and the organic dye compound according to the present invention were added together. Other compositions, operating methods, etc. are the same as in Example 1. Numbers are parts by weight added.

Table 3 The performance of each example videotape is shown in Table 4 and Figure 4 (unit: dB).

Table 4 As shown in Table 4 and Figure 4, when the organic dye compound according to the present invention is used in combination with a conventional dispersant having a viscosity adjusting effect (resimen tin, phosphate ester, nonionic surfactant, etc.) The viscosity does not become too high and does not interfere with dispersion, and the electromagnetic conversion properties are also improved compared to when this organic dye compound is used alone.Next, we will discuss the stagnation stability of the magnetic paint.

Regarding Example 3.4.5 and Comparative Example 1.3, the hardening agent was added immediately after cross-fertilization in a ball mill, and the hardening agent was added for one day after storage at room temperature, day and night, in a sealed state. Table 5 shows the viscosity, gloss, and R and F outputs of the magnetic finisher paints with K and K colors, and the R and F outputs when recorded on video tape. Here, the cross is measured as follows.

Gloss: Measured at the human exit angle ω using a variable angle photometer manufactured by Murakami Color Research Institute, and the standard plate is expressed as 100 cm.

Table-5 From this table-5, the stagnation stability of magnetic paint is compound (1).
, (2) is better.

Further, changes in paint cloth and squareness ratio during kneading in Example 3 and Comparative Example 1 are shown in FIGS. 5 and 6. From these figures,
It can be seen that the dispersion time reaches the end point faster in the primary system using compounds (1) and (2).

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIGS. 1, 2, and 3 are enlarged cross-sectional views of a portion of a magnetic recording medium from each side, and FIG. FIG. 5 is a graph showing a comparison of magnetic tape crosses. FIG. 6 is a graph showing a comparison of magnetic tape squareness ratios. In addition, in the symbols used in the drawings, 2...
...... Magnetic layer 3...-- Back=I-) layer (BC layer) 4... Overcoat layer ( 00
layer).

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer contains a metal magnetic material and an organic dye compound having a carboxyl group and/or a sulfonic acid group.