JPS58150130A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve magnetic and electromagnetic conversion characteristics and to obtain a magnetic recording medium having high durability and good surface characteristics, by using specific compds. for a magnetic layer. CONSTITUTION:The compds. expressed by the formula are used as a binder for forming the magnetic layer. The alkyl group in the formula is preferably residual groups of straight chain or branched satd. aliphat. hydrocarbon, for which there are tricosyl groups or the like. Flexibility is improved if the compds. of the formula are blended with polyurethane resins, polyester resins, ABS resins, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with particularly improved magnetic properties and electromagnetic conversion properties, high durability, and good surface properties. It is related to.

In recent years, magnetic recording media, especially magnetic recording media for video, are required to have high reproduction output for short wavelength recording, and there is a strong tendency to use magnetic powder with finer particles and higher magnetic force than ever before. . However, as Kerr magnetic powder becomes finer and/or more magnetic, its cohesive force becomes stronger, and as a result, the dispersibility and surface properties necessary for high reproduction output of short wavelength recording are not satisfied ( Methods for improving these properties include, for example, using surfactants as dispersants, or adding hydrophilic groups in the binder, such as -
A method of increasing the content of OH groups, -C00H groups, etc. has been proposed. However, in the former method, since the surfactant used has a low molecular weight, its presence in the coating film causes disadvantages such as deterioration of physical properties, powder falling off, and blooming due to changes over time. However, with the latter method, a slight improvement in such properties was observed, or a satisfactory dispersibility was not obtained, especially for fine-grained magnetic powder.

Conventionally used binders for magnetic recording media include vinyl chloride yarn binders such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl propionate copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer. can be mentioned.

The special feature of the vinyl dichloride-vinyl acetate-vinyl alcohol co-combination is that the OH of the vinyl alcohol contributes to the dispersion of the magnetic powder, and the active hydrogen of the OH reacts with the incyanate compound to form a crosslinked structure in the coating film. It is especially widely used. However, even magnetic recording media using such binders do not have sufficient magnetic properties, electromagnetic conversion properties, and durability, and there are 4 binders that can further improve these properties. ##It had been.

Therefore, the present invention provides a medium that has improved magnetic and electromagnetic conversion characteristics, is durable, and is rated 8-9.

The binder used in this invention has the general formula: [wherein R Cf44 or CH2CH3 Te1] x80. M, -COOM, -080,
M or -P-(OM')2 1 (wherein M is a hydrogen atom, lithium, sodium or potassium; M' is a hydrogen atom, lithium, sodium,
i is from about 200 to 800; j is from 0 to about 200; l is from 1 to about 200; and m is from 1 to about 200; 1
00, and +7 is 200 or less]. In the above general formula, the alkyl group is preferably a linear or branched saturated aliphatic hydrocarbon residue having 26 or less carbon atoms, such as tridecyl group, tocosyl group, coicosyl group, nonadecyl group,
Examples include octadecyl group, hexadecyl group, tridecyl group, undecyl group, decyl group, nonyl group, octyl group, hexyl group, pentyl group, butyl group, t-butyl group, propyl group, isopropyl group, ethyl group, methyl group, etc. . In addition, in the above general formula, each component of the compound is described for convenience as being arranged regularly in sequence,
In reality, it goes without saying that each component may be regularly and repeatedly arranged in a fixed proportion, or may be arranged randomly, other than as shown in the general formula.

Further, in the general formula, for example, the groups may be the same or different in one molecule.

Even when H carries different groups, ie, a methyl group and an ethyl group, the total number of acid vinyl ester components may be within the range #I expressed by the above general formula.

Furthermore, X may be a combination of hydrophilic groups represented by the above general formula.

In the compound represented by the above general formula, in order for the compound to be used as a binder for a magnetic recording medium and to exhibit the desired effect, the vinyl chloride component contributes to the strength of the medium; If the amount is too low, the desired strength of the medium will not be obtained, and if it is too high, the solubility in dissection will be poor. In addition, the vinyl alcohol component contributes to the dispersibility of magnetic powder due to its hydrophilicity, but in order to further improve this dispersibility, a part of the OH group is transferred between the hydrophilic groups represented by X. It is extremely effective to convert

If there are too many water-breaking groups, the vibration resistance will deteriorate, which is undesirable. In addition, the functional group X I il! The molecular weight per unit is preferably about 200 to 50,000.

If this equivalent is too small.

If the hydrophilicity becomes too strong, there will be problems in terms of compatibility with other binders mixed with it and moisture resistance, and if there is too much, the effect will be insufficient. In addition, the maleic acid component is thought to contribute to dispersibility, and if the amount is too small, the effect of adding the maleic acid component will be small; will no longer contribute to Furthermore, vinyl acetate and/or vinyl propionate components are effective in increasing the solubility of the vinyl chloride component and improving flexibility, but too much of these components may actually reduce strength. It doesn't look good. Furthermore, these vinyl acetate components and vinyl propionate components may be present in combination in one molecule.

The compound represented by the substructured general formula used as a binder in this invention usually has the following general formula:
A comonomer in which there is no vinyl component having hydrophilic groups,
For example, vinyl chloride-maleic acid-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-maleic acid-vinyl alcohol copolymer, vinyl chloride-vinyl acetate copolymer It can be manufactured from a lupropionic acid vinyl maleic acid-vinyl alcohol coelectrolyte. In this case, the proportion of vinyl alcohol component is approximately 0.5]
It is preferable that the amount of electricity is between 20 and 20. These starting copolymers can be produced by conventional methods.

A compound represented by the above general formula using the above-mentioned starting material can be prepared by adding, for example, the general formula: Y-44, -X, [wherein,
Y means a halogen atom, river means an alkylene group or a phenylene group, for example with 1 to 18 carbon atoms, and Xl means -80,M, -COOM, -
010,M or -P-(OM')2 1 (wherein M and M' have the same meanings as above). Incidentally, the phenylene group represented by ``Pui Cgawa'' in the above general formula may have an appropriate substituent. Among these compounds, C! →eH2) Taking the case of using 2-805Nm as an example, the reaction is shown as follows.

(-C)l, -C ÷ +HC1'' 0(-OR,) , -80,Na Even when other compounds are used, by a uniform reaction,
Desired compounds can be produced. This reaction is carried out in an organic solvent such as dimethyl sulfoxide or dimethyl formamide in the presence of a dehydrochlorination agent such as an amine such as pyridine, triethylamine or picoline, or an epoxy compound such as ethylene oxide or propylene oxide.

In this invention, when the compound represented by the above general formula is used as a binder, it is preferable to use it in a blend with polyurethane resin, polyester resin, AB resin, etc., which are said to impart flexibility. In this case %
As a crosslinking agent, for example, an isocyanate compound, that is, a difunctional aromatic incyanate compound such as 4,4'-diphenylmethane diisocyanate or tolylene diisocyanate, a difunctional aliphatic incyanate compound such as hexamethylene diisocyanate, By using the above, a magnetic recording medium having a magnetic layer having the desired effect can be obtained.

In this invention, the magnetic layer that can be used as the a-type layer is r
-Fe20s% r -F'e20B and Fe 604
Co-doped mixed crystal of r -Fe20m or r
e@04, CrO2, barium ferrite, other ferromagnetic alloy powders (e.g. Fe-Co, Co-Ni, F
e-Co-Ni%Fe-Co-B, Fe-Co-Cr
-B%Mn-B1. Mn-An, Fe-Co-V)
, iron nitride, etc. The magnetic layer may also contain aluminum oxide, chromium oxide, silicon oxide as a reinforcing agent, squalane as a solvent, carbon black as an antistatic agent, and lecithin as a dispersant. The constituent material of the magnetic layer is prepared by dissolving it in an organic solvent to prepare magnetic 1j11fP# and coating it on the base.The solvent for the magnetic coating is ketones (e.g. acetone, methyl oleketone, methyl isobutyl ketone, cyclohexanone). ), alcohols (e.g. methanol, ethanol, propatool, butanol), esters (e.g. methyl acetate, ethyl acetate, bunal acetate, ethyl lactate, glycol acetate, monoethyl ether), glycol ethers (
Examples include ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, aromatic reverted hydrogen containing dioxane (benzene, toluene, xylene, if you ask), aliphatic proportion hydrogen (iHJ, j4f hexane, heptane), nitropropane, and the like. The base on which this magnetic paint is applied is non-magnetic and can be made of polyester (e.g. polyenalene terephthalate), polyolefin (e.g. polypropylene), cellulose derivatives (e.g. cellulose triacetate, cellulose diacetate), polycarbonate, polyvinyl chloride, polyimide, It may be made of polyamide, polyhydrazide, metal (eg aluminum, copper), paper, etc.

This invention will be explained below with reference to Examples.

EXAMPLE A compound represented by the above structural formula was synthesized from vinyl chloride-acetic acid and nyl-maleic acid-vinyl alcohol copolymer according to a conventional method.

Next, a magnetic paint having the following composition was prepared.

Composition Amount (1 part) r-it"e2u, 100 The above compound 15 Carbon black
5 lubricant
2 Abrasives 5 Methyl ethyl ketone 100 Methyl isobutyl ketone 60 Toluene
60 After mixing the magnetic paint having the above composition in a whole mill for 48 hours, 5 parts by weight of incyanate compound (Bayer IR: Desmodur L) was mixed, and 1
A polyester film having a thickness of 5 μm was coated to a dry thickness of 6 μm, the surface was treated with a super calender treatment, and the magnetic recording tape was cut into h-inch widths.

Comparative Examples In the Examples, the following were used, except that a vinyl chloride-vinyl acetate-maleic acid copolymer (manufactured by Union Carbide Co., Ltd.: VMCH) was used instead of the inder according to the present invention.
A magnetic recording tape was prepared in the same manner as in the example.

Next to the magnetic recording tape obtained above, II! The results of measuring the characteristics are shown in the table below.

]L Example Comparative example Bm (Gauss) 1350 1150Br
/Bm O,850,79 powder%l)
Q, 5 -1.5Y-1/in (aBf"
+1.5 0 Note 1) Powder falling l! The degree is expressed by subtracting points (-5 (bad) to 0 (good)) for powdery M on the running system (Kytrol etc.) after running the tape.

Note 2) Y-87N indicates the 8/N ratio of a sample recorded with a black-and-white conceit and played back.

From the above results, it was found that the magnetically-aligned tape according to the present invention was superior in all properties compared to the magnetic recording tape using a binder used as a comparative example.

Similarly, magnetic recording tapes prepared by synthesizing various compounds as described above and using them as binders all exhibited the same characteristics as the magnetic recording tapes obtained in Examples.

In this invention, since the polymer used as the binder has a hydrophilic group containing the above-mentioned group in its vinyl alcohol component, the dispersibility of the magnetic powder is significantly improved, and the resulting magnetic recording medium In addition to improving the magneto-electromagnetic conversion characteristics of % magnetic powder is also bonded through the binder and hydrophilic groups, there is less detachment of the magnetic powder, resulting in level fluctuations, output attenuation, and powder drop-off such as chloragging. The durability and surface properties of the media are significantly improved.

Claims (1)

[Claims] General formula: [In the formula, %R is -Ci15 or -, -CH2C]1. ; X is -80,M, -C(JOM, -0803M
or -P-(OM')2 1 (in the formula, 1M is a hydrogen atom, lithium, sodium or potassium; M' is a hydrogen atom, lithium, sodium,
is a hydrophilic group containing potassium or an alkyl group; i is h200 to 800; j is 0 to 200; j is 1 to 200; and m is 1 to 1
00, provided that +l is 200 or less] is used in the magnetic layer.
magnetic recording media.