JPH03212816A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having an excellent coefft. of friction at high temp./ high humidity and at low temp. by using such a fatty acid-modified org. silicone compd. as a lubricant that branched and satd. hydrocarbon groups having specified carbon number are used for the fatty acid parts thereof. CONSTITUTION:A magnetic layer comprising ferromagnetic powder and a binder contains an org. silicone compd. expressed by formula I. In the formula I, R is a branched and satd. hydrocarbon group having 7 - 24 carbon number, (m) is an integer from 1 to 100, (n) is an integer from 0 to 250, satisfying m>=n/5. Namely, by replacing hydrocarbon groups in the fatty acid parts of well-known fatty acid modified org. silicone by the branched and satd. hydrocarbon groups, fluidity is given to the lubricant and solubility with the binder is also improved. Thereby, the medium has excellent coefft. of friction under conditions from low temp. to high temp./high humidity.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium having a magnetic layer formed by dispersing ferromagnetic powder in a total binder on a non-magnetic support, and which can be used under a wide range of temperature and humidity conditions, especially at low temperatures. The following relates to a high-density magnetic recording medium that has excellent running properties and durability.

[Conventional technology]

In magnetic recording media, the demand for higher density recording is increasing.
9. It is known that one way to deal with this is to make the surface of the magnetic layer smooth.

However, if the six times of the magnetic layer are made smooth, the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic recording medium is running, and as a result, the magnetic layer of the magnetic recording medium is susceptible to damage after short-term use. , or the magnetic layer tends to peel off.

To address these problems, lubricants such as fatty acids, fatty acid ethers, hydrocarbons, and silicone compounds have been used.

Recently, VTRs and personal computers have been used for word processors, and as flexible disk drives for consumer use have become more widespread, the usage conditions for magnetic recording media have also changed, such as use at low temperatures or under high temperature and high humidity. Its use has become widespread. Therefore, magnetic recording media must be stable so that their running durability does not change under various expected conditions, but conventionally known lubricants are not sufficient. .

Silicone compounds have been used to solve the above problems due to their unique surface modification ability and excellent fluidity (see JP Koko Akihirota/Hiroλ≠, JP Kokai Sho!0-J1RIO≠, etc.) ). Furthermore, various fatty acid-modified silicone compounds have been investigated in order to improve the retention of lubricants in the magnetic layer of magnetic recording media (Japanese Patent Publication No. 63-22333, %KaishotO-1623.1%Kaishoj7-/ 6 octopus λ3, see Japanese Patent Application Laid-Open No. 7-37736, etc.).

However, when these fatty acid-modified silicones are modified with saturated fatty acids, they have a high melting point (softening point) and the lubricating effect at low temperatures decreases, and when they are modified with unsaturated fatty acids, they have excellent fluidity but are not suitable for high-density recording. When applied to an extremely smooth magnetic recording medium with excellent properties, the coefficient of static friction increased unsatisfactorily.

For example, an organic silicone compound having the following general formula is known from Japanese Patent Publication No. 63-22333.

(However, in the formula, R' is a saturated or unsaturated hydrocarbon group having 7 to 21 carbon atoms, m and n are integers, and 76m/jO,
0≦n, m+n≦1000. m/n=///
000~///. )However, saturated 19, in which R' has 7 to 1 carbon atoms, is an unsaturated hydrocarbon group and is known to be a straight chain. By using such a lubricant, the lubricity and wear resistance of the magnetic layer are completely improved, and the running stability and durability are completely improved. However, in the case of saturated fatty acid modification, the melting point (softening point) The lubricating effect at high and low temperatures decreased, and in the case of unsaturated fatty acid modification, although the fluidity was excellent, the coefficient of static friction increased.

Therefore, the present inventors conducted extensive studies on the structure of these lubricants and found that the fatty acid moiety of the fatty acid-modified organosilicone compound has branches with a carbon number of 7 to 2 and uses a saturated hydrocarbon group. The inventors have found that the above problems can be solved, leading to the present invention.

[Purpose of the invention]

An object of the present invention is to provide a magnetic recording medium that has improved reproduction output and exhibits an excellent coefficient of friction under high temperature, high humidity, and especially low temperature.

[Structure of the invention]

That is, the above object of the present invention is to provide a magnetic recording medium in which a magnetic layer made of ferromagnetic powder and a binder is provided on a non-magnetic support, in which the magnetic layer is made of an organic silicone compound represented by the following general formula (1). This can be achieved using a magnetic recording medium.

(1) Here, 几 is a branched/saturated hydrocarbon group having 7 to 4 carbon atoms, m is an integer of / to 100, n is an integer of ONλ to Q, and In≧n/j.

More preferably, the above-mentioned object of the present invention is such that the amount of the organic silicone compound represented by the general formula is 0.00 parts by weight per 100 parts by weight of the ferromagnetic powder. /-1 part by weight can be achieved by a magnetic recording medium having all the following characteristics.

That is, in the present invention, the hydrocarbon group in the fatty acid moiety of the conventionally known fatty acid-modified silicone is made into a branched and saturated hydrocarbon group, thereby imparting fluidity and improving liquid lubricity. Although unmodified silicone compounds have excellent fluidity, they cannot be used due to low compatibility with binders, but the present invention has improved fluidity and compatibility with binders at the same time, so it can be used under conditions ranging from low temperatures to high temperatures and high humidity. It shows an excellent coefficient of friction (μ value).

The compound of the present invention can be selected from a wide range of molecular weights, regardless of its branched structure, as long as it is an acylated silicone compound modified with a branched/saturated higher fatty acid having a specific range of carbon atoms.

Generally preferred is a saturated hydrocarbon group having a branched structure with carbon number of 3 or more and 27 or less.

Specifically, 1d) L is -C1-1(C,I(13)
C8H17°-CH(C7H15)C9H□9. -CH
(C8H17)C1oH21-CH(C1oH2□)C
2-position branched fatty acids such as 1□H25, those with a multi-fiber branched structure by the oxo method (e.g. Nissan Chemical's isonuteary/acid type), and those with a methyl group on the side of the straight chain aliphatic group. Examples include those having a mixture of isomeric structures (methyl branched fatty acids (eg, manufactured by Emery Co., USA)) with branched chains.

These branched fatty acids are ■Guerbet method, ■Oxo method-! ! Friend is derived from branched fatty acids derived from the production of by-products during dimer acid synthesis.

Specific examples of the silicone compound of the present invention are shown below.
and J compound.

When added internally to the magnetic layer of a normal coated magnetic recording medium, the amount used is O/~! relative to the ferromagnetic powder. Weight whisper is appropriate, preferably O6j arrogance to 3 attacks. When applying a top coat to the surface of the magnetic layer of a coated magnetic recording medium, λ~j01+9/? rl is appropriate.

If the amount used exceeds this range, the organosilicone compound in the blood sample will be excessive, which may cause problems such as sticking, and in the case of an internally added type, it will have the effect of plasticizing the binder in the magnetic layer. However, there are problems such as a decrease in durability.

If the amount used is below this range, the amount per person will naturally be insufficient and no effect will be obtained.

In the present invention, other lubricants may be mixed.

Lubricants that can be used in combination include saturated and unsaturated fatty acids (myristic acid, stearic acid, oleic acid, etc.)
Fatty acid amides, fatty acid esters (including various monoesters, sorbitan, fatty acid esters of polyvalent ethers such as glycerifum, ester compounds of polybasic acids, etc.), higher aliphatic alcohols, monoalkyl phosphates, dialkyl phono-7ates, trialkyl phosphates or metal salts/ammonium salts of these phosphates, alkali/
Honuho/acids or their salts, alkyl sulfates' or their salts, alkanuronic acids or their salts, paraffins, other silicone oils, animal and vegetable oils, mineral oils, higher aliphatic amines; graphite, silica, molybdenum disulfide, Inorganic fine powder such as tungsten disulfide; fine resin powder such as polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride monomer, polytetrafluoroethylene; α-olefin polymer; several unsaturated fats at room temperature Examples include group hydrocarbons, fluorocarbons, fluorine-substituted ester compounds, perfluoroalkyl polyethers, and the like.

The preferred amount of these mixed lubricants to be used varies depending on the mode of use, but is generally 10 times as much as the organic silicone compound of the present invention.

In the present invention, methods for using organic silicone compounds include incorporating them into the magnetic layer, topcoating the surface (dissolving the material in an all-organic solvent, coating or spraying it on the substrate, and then drying it, and melting the material). There are methods such as coating the material on the substrate, dissolving the material in an organic solvent and then immersing the substrate in the solution to adsorb the material to the substrate, and using the Gmuer-Projet method.

In the case of ferromagnetic powder-coated magnetic recording media, there are no particular restrictions on the composition of the ferromagnetic powder (iron oxide, cobalt-containing iron oxide, iron-based alloy, barium ferrite, etc.), size, or surface treatment. .

There is no particular restriction on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. The crystallite size of this ferromagnetic powder (measured by X-ray diffraction) is preferably μjnm or less in terms of electromagnetic conversion characteristics.

The binder forming the magnetic layer can be selected from conventional binders. Examples of binders include vinyl chloride/vinylacetate copolymer, vinyl chloride, vinyl acetate and vinyl alcohol, maleic acid/'E or acrylic acid copolymer, vinyl chloride/vinylidene chloride copolymer. Combined, vinyl chloride
Cellulose derivatives such as acrylonitrile copolymers, ethylene/vinyl acetate copolymers, nitrocellulose resins,
Examples include acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, polyurethane resin, polycarbonate polyurethane resin, and the like. In order to further improve dispersibility and durability, polar groups (epoxy groups, C
H3I, (JH.

NH, S(J3M, (J8(J3M, P(J3M2゜(
JP (J3M2. However, M is hydrogen, an alkali metal, or ammonium, and when there is more than one M in one group, they may be different from each other)'f! : I like things that are expanded. A preferable range for the content of polar groups is 70 to Q equivalents per gram of polymer.

The polymeric binders listed above are used alone or in combination, and are often hardened by adding known crosslinking agents of incyanate type.

The organic silicone compound of the present invention is also applicable to a binder system that uses an acrylic acid ester oligomer and a monomer as a binder and is cured by radiation irradiation.

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene 2,6 naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacerate; resins such as polycarbonate, polyimide, and polyamideimide. If necessary, it may be metalized with a metal such as aluminum.

The thickness of the support is 3 to iooμ, preferably 3 to θμ for magnetic tape, and 20 to 100μ for magnetic tape.
μ is the commonly used range.

The total binder content in the magnetic layer of the magnetic recording medium of the present invention is usually 10 to 60 parts by weight, preferably 20 to ≠0 parts, based on 100 M parts of ferromagnetic powder.

The magnetic layer of the magnetic recording medium of the present invention further has Mohne hardness! It is preferable to contain all of the above inorganic particles.

The inorganic particles used are not particularly limited as long as they have a Mohs hardness of 5 or more. Inorganic particles having a Mohs hardness of 5 or more include A1203 (Mohs hardness) Ti(J)
, T iU 2 (same A, j), S i
(J 2 (same 7), SnU (same A, !),
Cr 2 (J a (same), and α-F e 2
(J s (same!, j)), and all of these can be used alone or in combination.

Which Mohs hardness is particularly preferable? These are the above inorganic particles. Mohs hardness! If inorganic particles with a lower concentration than 1 are used, the inorganic particles tend to fall off from the magnetic layer and have almost no abrasive action on the head, resulting in head clogging and poor running durability.

The content of inorganic particles is usually 10O! of ferromagnetic powder! 0. The amount is in the range of 1 to 1 parts by weight, preferably 7 to 10 parts by weight.

In addition to the above-mentioned inorganic particles, the magnetic layer preferably contains carbon black (particularly one having an average particle size of 10 to 300 nm (nanometers; 10 -9 m)).

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

First, a ferromagnetic powder, a binder, the organic silicone compound of the present invention, and, if necessary, other fillers, additives, etc. are kneaded with a solvent to prepare a magnetic paint.

As the solvent used during kneading, solvents commonly used for preparing magnetic paints can be used.

There is no particular restriction on the method of mixing, and the order of addition of each component can be set as appropriate.

That is, there are cases in which a binder, a solvent, and a ferromagnetic powder are cross-dispersed in advance and then a curing agent solution is added, or a lubricant is added in a solution state at the end of the entire lubricant process.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, and other lubricants may also be used.

Examples of dispersants include fatty acids having 2 to 2 carbon atoms, their salts tri (tri), esterified products and compounds in which part or all of the hydrogen atoms of these compounds have been replaced with fluorine atoms, amides of the above fatty acids, aliphatic Amine, Aft Flucol, Polyalkyle/Oxide Alkyl Phosphate Entel, Alkyl Phosphate x p f k , 7k Kylborate,
Mention may be made of known dispersants such as sarcosinates, alkyl ether esters, trialkyl polyolefins, oxy-Z-a/monicum salts and lecithin.

When using a dispersant, the ferromagnetic powder 1 usually used is
0.00 parts by weight. /-10 parts by weight.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymers; natural surfactants such as saponins; niobium/based surfactants (such as alkylene oxides, glycerin and glycidol); Alkylamines, chlorinated ammonium salts, salts of pyridine/other heterocyclic compounds, cationic/sexual surfactants such as phosphonium and sulfonitum; force w + - + 4: ・Nochi Sacred - Yuchi Ili products - neck moat ψ
Examples include anionic surfactants containing acidic groups such as di-A groups; amphoteric surfactants such as amino acids, aminosulfo/acids, and sulfuric acid or phosphoric acid esters of amino alcohols. When using the above conductive fine powder as an antistatic agent, for example, it is used in the range of o, i to io parts by weight per 100 parts by weight of ferromagnetic powder, and the same applies when using all the surfactants. It is used in a range of 0.7.2 to IO parts by weight.

Note that the additives mentioned above, such as dispersants, antistatic agents, and lubricants, are not strictly described above and have only the following effects; for example, if the dispersant is It may also act as a lubricant or antistatic agent. Therefore, it goes without saying that the effects and effects of the cultural compounds exemplified in the above classification are not limited to those listed in the above classification, and when using all of the substances that have multiple effects and metallic odor, The amount to be added is preferably determined by taking into account all of its effects.

The magnetic coating composition prepared in this way can be applied directly onto the aforementioned non-support material, but it can also be applied onto a non-magnetic support material via an intermediate layer such as an adhesive layer. can. The intermediate layer herein refers to a layer containing an adhesive alone or a composite film layer formed by completely dispersing non-magnetic fine particles such as carbon black in a binder.

The intermediate layer containing carbon can be arbitrarily selected as a binder from among the various binders used in magnetic materials.The particle size of carbon is 10~!O+n (nanometers; ) is preferred, and the binder and carbon black have a weight ratio of 100210 to 100',
/! 0 is preferable. The thickness of the intermediate layer is 07 to 2 μm in the case of a primary adhesive layer, and 0.3 in the case of a composite layer containing non-magnetic powder.
-≠μmn is a good size.

In addition to the intermediate 1-, there is a lubricant used in the magnetic layer and '!
It is also possible to add different amounts of lubricants.

Details of the method of dispersing the above-mentioned ferromagnetic powder and binder and the method of applying it to the support are described in various publications such as JP-A-4A-≠60// and J≠-λ/♂oj. There is.

The thickness of the magnetic layer coated in this way is generally about O0! after drying. ~ioμm range, typically 0,7
The coating can be completed in the range of ~t, oμm.

When the magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic support is usually subjected to a treatment for completely orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. Conversely, in the case of a disk-shaped medium, non-orientation treatment is performed using a magnetic field in order to eliminate anisotropy in magnetic properties. Thereafter, blood collection is smoothed if necessary.

〔Effect of the invention〕

In the present invention, the hydrocarbon group in the fatty acid moiety of the conventionally known fatty acid-modified cricorn is made into a branched and saturated hydrocarbon group, so that the so-called pour point at which fluidity begins when the temperature is changed from low to high temperature is changed to a straight chain. It is lower than that of fatty acid-modified silicone, and exhibits remarkable fluid lubrication properties even at low temperatures (-to oc). Unmodified silicone oil has good fluidity, but if it is made of straight chain fatty acid-modified silicone to improve compatibility with the binder, the pour point will rise as described above, but branched and saturated fatty acid-modified silicone like the present invention By using a compound, it is possible to obtain a material with a low pour point, similar to that of unmodified silicone, and to improve compatibility with a binder.

As described above, by using the branched and saturated fatty acid ester of the present invention, a good friction coefficient can be exhibited, especially at low temperatures (-100C), and the regeneration output is also good.

The reason why it shows a good coefficient of friction even under high temperature and high humidity is considered to be as follows. That is, a branched alkyl group has a large effective formula area per group and has a large hydrophobizing effect. For this reason, it is less susceptible to the effects of water and is considered to be excellent in corner-mixed high-humidity conditions with extremely high absolute humidity.

〔Example〕

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

In addition, the expression "1 part" in the examples indicates "part by weight J."

[Example 1] The following composition was subjected to time-open cross-dispersion for 4L using a sonic ball mill, and after 7 hours, 1 part of polyisocyanate was added thereto, and after cross-dispersion for another 7 hours, it was mixed using a filter having an average pore diameter of 7 μm. It was filtered and a magnetic paint was prepared. The obtained magnetic coating material was coated six times on a polyethylene terephthalate support having a thickness of io .mu.m using Lino(-Nurol) so that the thickness after drying was ≠0 .mu.m.

Magnetic paint composition Ferromagnetic alloy powder (composition: 2Fe, Zn4→.

Ni2chi; anti-magnetic crab /! 00CJe; specific surface area ~/m) 100 parts polyester polyurethane (weight average molecular weight μ, 10,000, number average molecular weight 0,000, average 1 molecule per molecule 5t) 3N
a fund) 5 parts vinyl chloride/vinyl acetate/male anhydride/acid copolymer (E
E-honzeo y@g4tooXi10k, degree of polymerization ≠ 00) 72 parts abrasive (α-alumina, average particle size 0.3 μm) lubricant (listed in Table 1) oleic acid 1 part carbon black (
Average particle size≠Oam) 2 parts methyl ethyl keto/300 parts The non-magnetic support coated with the magnetic paint was oriented in a magnetic field with a 3000 Gauss magnet while the magnetic paint #+ was not dry, and after drying, After calendering, the tape was slit to lrmm width to produce a tmm videotape.

The videotape obtained as described above was recorded using VT standard (Fuji Photo Film ■: FUJIX-fl) at 7 MHz.
Record all the signals and play them with your friends. Next, the relative playback output of the videotape was measured using the playback output fOdB of 7 MHz recorded on the reference tape (ratio soft example/).

The obtained videotape and a stainless steel pole were brought into contact (wrapping angle/10') with a tension (T/) of 109,
Under these conditions, the videotape f! , the tension (Tλ) required to run at a speed of 3 cWL/S was measured. Based on this measured value, the friction coefficient μ of the videotape was determined using the following calculation formula.

(Table 1) μ=//π・/n(Tλ/Tl) Lake, friction coefficient test is a, -io 'C.

The test was carried out under the following conditions: b, io 0C, ro%RH.

As is clear from the results shown in Table 1, the organic silicone compound of the present invention was used. /Pull flat l~t, 10, /3. ／≠
Both have high playback output, and a.

It can be seen that the friction coefficient is low under both conditions.

On the other hand, when the compound of the present invention is not used and only conventional silicones, fatty acids, and esters are used, the regeneration output is also low, especially low! It can be seen that there is a problem in that the coefficient of friction under (a condition) is large.

Claims (2)

[Claims] (1) A magnetic recording medium comprising a magnetic layer made of ferromagnetic powder and a binder on a non-magnetic support, wherein the magnetic layer contains an organic silicone compound represented by the following general formula [I]. recoding media. [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R is a branched/saturated hydrocarbon group with 7 to 24 carbon atoms,
m is an integer of 1 to 100, n is an integer of 0 to 250,
m≧n/5. (2) Claim (1) characterized in that the amount of the organic silicone compound represented by the general formula added is 0.1 to 5 parts by weight per 100 parts by weight of the ferromagnetic powder. magnetic recording media.