JPS5982631A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability, traveling stability and surface properties of a magnetic tape by bonding directly or indirectly thio-ester groups represented by specified structural formulae to Si at terminals and/or intermediate positions of the molecular chain of an organopolysiloxane compound and by bonding the resulting compound to the magnetic layer of the magnetic tape by irradiation. CONSTITUTION:Thio-ester groups represented by a general formula -SCOR<1> (where R<1> is 7-21C univalent hydrocarbon group) and thio-ester groups represented by a general formula -SCOR<2> (where R<2> is -CH=CH2 or other group) are bonded directly or indirectly to Si at terminals and/or intermediate positions of the molecular chain of an organopolysiloxane compound, and the resulting compound is bonded to a magnetic layer by irradiation to obtain the desired magnetic recording medium. The preferred structure of the resulting organopolysiloxane compound is represented by the general formula (where A<1> is a thio-ester group represented by -R<3>SCOR<1> or -SCOR<1>, and A<2> is a thio-ester group represented by -R<3>SCOR<2> or -SCOR<2>).

Description

[Detailed description of the invention] The present invention relates to magnetic recording media.

A magnetic tape, which is one type of magnetic recording medium, is required to have low frictional resistance under low speed conditions.

For example, when the friction of a magnetic tape against a fixed head or guide roller for audio is large, the magnetic tape vibrates, causing a tape squeal phenomenon called so-called Q sound, which can become a source of nozzle generation, or in severe cases. ,
The magnetic tape may stick to the magnetic head or guide roller, making it impossible to run. Therefore, it is necessary to suppress the coefficient of friction under low speed conditions to a certain value or less.

Furthermore, when considering the friction of the magnetic tape against the video head rotating at high speed, it is required that the video head and the magnetic tape do not burn in, inducing the so-called head clog phenomenon.

In order to satisfy such characteristics, various lubricants have been added to magnetic paints containing magnetic powders such as γ-Fe2O3 and binders such as vinyl chloride9, and lubricants have been added to magnetic paints coated on the magnetic layer. There is. These lubricants include molybdenum disulfide, graphite, higher fatty acids, higher fatty acid esters, paraffinic hydrocarbons, glycerides, fatty acid metal soaps, fatty acid amides, and silicone oils (e.g. dimethyl silicone oil, diphenyl silicone oil, etc.). has been done. Although the effect of applying a lubricant is immediate, the concentration of the lubricant on the surface of the magnetic layer decreases due to penetration of the lubricant, and the magnetic tape no longer maintains its initial performance after a long period of time.

In addition, in the method of adding lubricant, in order to maintain an amount of lubricant on the surface of the magnetic tape, a much larger amount of lubricant must be added than in the coating method, which causes plasticity of the magnetic layer. It has the disadvantage that it undergoes corrosion and therefore its durability is extremely reduced.

As described above, conventional lubricants have the disadvantage that the durability, running stability, and surface properties of magnetic tapes are not very good, and that the coefficient of friction, still characteristics, and life characteristics in particular become unstable due to changes over time.

The present invention was achieved as a result of intensive research to eliminate the above-mentioned drawbacks. An organopolysiloxane in which a thioester group represented by (representing a hydrogen group) and a thioester group represented by (bJ general formula % formula % ( ) ) are bonded directly or indirectly to Si at the terminal and/or intermediate position of the molecular chain. The present invention relates to a magnetic recording medium in which a type compound is bonded to a magnetic layer by radiation irradiation.

The organopolysiloxane compound that can be used in the present invention preferably has a structural formula represented by the following general formula.

[In the formula, a thioester group of A'R'800R1 or Bar5OOR' (where R'I'' has the same meaning as above and R3 represents a divalent hydrogen group having 1 to 5 carbon atoms) ,
A2 is -R3SCOR2 or -8ooR2 (where R
2, R5 has the same meaning as above), and A is a methyl group, F (OF2)p OH20H2 (cocote).

p is an integer of 1 to 11), represents the group A1 or A2, k%1%m, n are each an integer of 21] or less, k + l + m 10n≦300. And to +/
+m+n+2≧0.1 and Ao is a methyl group or -0
H20H2(0F2)I) When F is a group, m≧1
and n≧1 (preferably n≧2), m≧1 when Ni is the same as A2, and n≧1 (preferably n≧2) when Ni is the same as A1. . ].

Although the general formula is described so that each component has a regular arrangement, the arrangement of these components is not limited to the arrangement shown in the general formula (1). It should be understood that random sequences are also included.

The hydrocarbon group R1 in the thioester group A1 includes n-heptyl, n-nonyl, 2-ethylhexyl, tridecyl, heptadecyl, heneicosyl, oleyl,
linole, etc., and the thioester groups A1 and X
Examples of the divalent hydrocarbon group R3 include methylene, ethylene, propylene, butylene, 2-methylpropylene, and the like.

mata, the group N(D uchi, -R5SOOR', -R3
Specific examples of the groups represented by "80OR" and -0H20H2(OF2)pF include the following.

-R'5OOR'nie OH280007Hls, -cH2scoc21
H43, -OH20H2S 000,5 R2,, -0
H20H20H25OOO11H25, -OH20H2
0H2800017H, 5, -0H20H20H250
00,7H35, OH3 -OH20H20H2S 0O016H51, -0H2
0H20H20H20H25OOO9H, 9°-, R3
5OOR2: 0H5 -OH20H2S000=OH2, -0H2(iH20
H25OOOH=OH2, -0H20H20H20H
20H25OOOH= OH2゜-OH20H2(OF
2) I) F Knee〇H20H20F,, -0
H20H2(OF2)2F.

-CH2CH2(CF2)4F, -0H20H2(
OF2)8F, -0H20H2(OF2), IF0 %l, m for the organopolysiloxane of the invention.

When n exceeds the above range, the viscosity increases and the properties as a lubricant deteriorate.

The organopolysiloxane compound represented by the general formula (1) has a thioester group having the above-mentioned structure directly or indirectly at a desired position of Si, so it is basically a compound that exhibits a lubricating effect. However, due to the presence of a double bond in W of the thioester group represented by the general formula (1), free radicals are generated by radiation irradiation, and these free radicals act as a reaction initiation species, resulting in The organopolysiloxane compound itself is polymerized and reacts with the binder molecules of the magnetic layer to form a graft copolymer to form a complex crosslinked structure. Therefore, the organopolysiloxane compound does not penetrate into the magnetic layer, and the amount thereof on the surface of the magnetic layer does not decrease even after running many times. In addition, it is possible to control the degree of progress of the crosslinking reaction by adjusting the radiation dose, and by sufficiently crosslinking, it is possible to prevent the organopolysiloxane compound (lubricant) from migrating to the non-magnetic base side. It can be prevented.

Further, due to the presence of the thioester groups represented by the general formulas (I) and (1), the organopolysiloxane compound has extremely excellent hydrolysis resistance after radiation irradiation, and therefore the magnetic tape according to the present invention can be used at high temperatures and high humidity. It can maintain its initial properties even after being exposed to water for a long time.

The organopolysiloxane lubricant used in the present invention is preferably applied to the magnetic layer in an amount of 50 to 800 cm per square meter. The solvent for preparing this lubricant coating solution includes:
A material that does not dissolve the magnetic layer should be used, an example of which is Freon (trade name of a fluorohydrocarbon manufactured by Du Font). The lubricant may be applied either before or after the magnetic layer is irradiated with radiation. Although it is preferable to irradiate the radiation immediately after applying the lubricant, the expected effect can be obtained even if the irradiation is performed several hours later. When a lubricant is applied after irradiating the magnetic layer with radiation, free radicals generated from binder molecules in the magnetic layer are generated in R2 of the thioester group represented by the general formula (1) of the lubricant compound. It suffices if it is sufficient to react with double bonds.

The radiation may be an electron beam, a neutron beam, etc., and the irradiation dose is preferably 1 to 10 Mrad.

Specific examples of the organopolysiloxane compounds used in the present invention include those shown below.

^ ^
ζ−ψ −I of ＾−e4?
These compounds can be made by the following general synthetic methods.

General formula [In the formula, 几3 has the same meaning as above, A4 is a methyl group, -0H20H2(0FF)pF (?:, kote, p h same as above) or 几'SH (here, W represents the group (same as above); % kl Z% m and n have the same meanings as above;
H20H2(OF2)pF 17) When it is a group, m
10n≧2, preferably m, +n≧6. ] Two types of carboxylic acid halogen compounds each represented by mercapto group-containing organoborisiloxane (where X represents a chlorine atom or a bromine atom) shown below are reacted in the presence of a hydrogen halide scavenger. This reaction is usually
It is carried out in the presence of a solvent in the temperature range from 0° to 120°C.

Examples of solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; Examples include chlorethylene. Examples of hydrogen halide scavengers include 6th class amines such as pyridine, picoline, and triethylamine.

Magnetic recording media to which the lubricant of the present invention is applied include so-called coated media having a magnetic layer mainly composed of magnetic powder and a binder, and so-called coated media having a ferromagnetic metal thin film formed by vapor deposition, sputtering, ion blating, etc. It may be a metal thin film type magnetic recording medium.

Examples of ferromagnetic powders (ferromagnetic powders) that can be used for the magnetic layer in so-called coating media include r -Fe2O3, Fe3O4
, mixed crystal of γ-Fe2O3 and Fe3O4, cobalt-doped γ-Fe2O3, cobalt-doped Fe2O
4. Chromium dioxide, barium ferrite, various alloy powder magnetic substances (e.g. F'e-Oe, 0o-Ni, Fe
-0o-Ni1Fe-Co-B, Fe-Co-0r
-B, Mn-B1, Mn-A/.

(Fe--Co--V, etc.), iron nitride, etc., and two or more of these may be used in combination. In addition, the binder that can be used for the magnetic layer is vinyl chloride-
Vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester - Vinylidene chloride copolymer, methacrylic acid ester - Vinylidene chloride copolymer, methacrylic acid ester - styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylitine chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer Polymer, acrylonitrile-butadiene-acrylic acid copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinylbutyl, polyvinyl acecool, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenolic resin, epoxy Examples include resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formterdehyde resins, and the like. Further, reinforcing agents that can be used in the magnetic layer include aluminum oxide, chromium oxide, silicon oxide, and the like alone or in mixtures. Furthermore, conventionally known fine particulate carbon black can be used as an antistatic agent, and lecithin can be used as a dispersant.

When preparing magnetic paint, organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, methanol, ethanol,
Alcohols such as globanol and butanol; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate, and monoethyl ether; glycol ethers such as ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, and dioxane;
Aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexanoate and heptane, nitropropane and the like can be used alone or as a mixture. Non-magnetic pastes for applying magnetic paint prepared with this organic solvent include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate, polyvinyl chloride, polyimide, Examples include metal materials such as aluminum and copper, and paper.

In addition, metal thin film type magnetic recording media may be those in which a layer of ferromagnetic metal such as Co, Fe, Ni, or an alloy thereof is formed on a nonmagnetic support by so-called physical or paper deposition technology such as vacuum deposition.・.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A magnetic paint was prepared using the following materials.

r-Fe203 400 li 'I
k part 0r20B (reinforcing agent) 4 parts by weight methyl ethyl ketone (solvent) 500
tt Methyl isobutyl ketone (solvent) 50
After mixing these materials in a ball mill for 24 hours, they were taken out through a filter. The obtained magnetic paint was applied onto a 12 μm thick polyethylene terephthalate hair so that the dry thickness would be 5 μm, followed by orientation and drying. On the obtained magnetic layer, a 1% Creon solution of compound (1) of the organopolysiloxane compounds listed as the specific example above was applied to a coating amount of 200 m9/m'. Magnetic tapes 1 and 2 were obtained by cutting the tapes irradiated with 5 Mrad of electron beam and those not irradiated into % inch widths, respectively.

For comparison, on the same magnetic layer, in the same procedure as above,
Solutions containing squalane and octyl myristate, respectively, were applied, dried, and cut into % inch widths to obtain magnetic tapes 6 and 4, respectively.

These four types of magnetic tapes were stored at 45° C. and under two different atmospheres: 80% RH and 25'C 150% RH, and changes over time in the coefficient of dynamic friction, still characteristics, and life characteristics were investigated. The results are shown in Figures 1 to 6. Here, the coefficient of kinetic friction is the force F when a magnetic tape is wound around a quarter circumference of a brass drum and a weight is attached to one end of the drum and the other end is pulled.
I calculated it properly. The still characteristics are expressed by the time it takes until the image quality deteriorates when a still operation is performed, and the longer this is, the better the characteristics are. Further, the life characteristic is a change in reproduction output expressed in dB, and the characteristic is good when the decrease from the initial reproduction output is small (the negative value is small).

As is clear from the results shown in Figures 1 to 6, among the four types of tapes mentioned above, tape 1 of this example was excellent in all of the coefficient of dynamic friction, methyl properties, and life properties, and the change over time of each property was the best. In particular, the change over time in a high-temperature, high-humidity atmosphere is significantly smaller than that of the other six types. This is because, on the one hand, the organopolysiloxane compound used in Example 1 is an excellent lubricant itself, and also because it was fixed on the surface of the magnetic layer by electron beam irradiation.
On the other hand, this is thought to be because the thioester group present in the lubricant molecule is difficult to undergo hydrolysis and is retained within the molecule for a long period of time.

Examples 2 to 7 Each of the magnetic tapes 5 to 1 was prepared in the same manner as the magnetic tape 1 of Example 1 using the organopolysiloxane compounds 2) to (7) mentioned as specific examples.
0 was created. The coefficients of dynamic friction of these magnetic tapes were as shown in the table below.

Example 8 100 ferromagnetic metal thin film layers of V) Oo were deposited on a 12μ thick polyethylene terephthalate base by oblique vapor deposition.
It was formed to the thickness of OA. A 1% 7 Leon solution of the compound (1) of the organopolysiloxane compounds listed in the specific examples above was applied onto this magnetic layer at a coating density of 150 μm/m, and an electron beam was irradiated at 5 Mrad to create a magnetic layer. Obtained a recording medium. The coefficient of dynamic friction of this magnetic recording medium is 0.212 (
initial value), 0.208 (after storage for 15 days in an atmosphere of 45'C1801R'H).

[Brief explanation of the drawing]

Figures 1 and 2 are graphs showing changes in the coefficient of dynamic friction over time.
Figures 6 and 4 are graphs showing changes in still characteristics over time.
FIGS. 5 and 6 are graphs showing changes in life characteristics over time. Agent Masaru Ueya Yoshio Tsuneko Toshiki Sugiura

Claims (1)

[Scope of Claims] (a) a thioester group represented by the general formula % (in the formula, R1 represents a monovalent hydrocarbon group having 7 to 21 carbon atoms); and (b) a thioester group represented by the general formula A magnetic recording medium in which an organopolysiloxane compound in which a thioester group is directly or indirectly bonded to Si at the terminal and/or intermediate position of a molecular chain is bonded to a magnetic layer by radiation irradiation.