JPH0341619A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics, durability and traveling property by using ferromagnetic alloy powder having <=500Angstrom grain size and containing >=2atomic% Al or Si to the amt. of Fe, and incorporat ing a specific fluorosilane compd. into the magnetic layer. CONSTITUTION:The ferromagnetic alloy power has <=500Angstrom grain size, containing >=2 atomic% Al or Si to Fe which is determined by X-ray diffraction analysis. A specific fluorosilane compd. expressed by formula I is incorporated into the magnetic layer. In formula I, R<1> represents a univalent hydrocarbon group with 1-6 carbon number, R<2> is a satd. or unsatd. univalent hydrocarbon group with 7-21 carbon number, m is 1-12, l is 2-20, and n is 0-2. By this constitution, low coefft. of friction of the fluorosilane compd. can be realized in the medium to give good still life. Moreover, the pot life of the magnetic coating material, which is indispensable for improvement of electromagnetic conversion characteristics, can be improved, and thus the electromagnetic conversion characteristics of the medium can be improved by using fine ferromagnetic alloy powder of small grain size.

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 fine powder in a binder on a non-magnetic support.
The present invention relates to a magnetic recording medium that has excellent durability and good electromagnetic conversion characteristics.

(Prior art) In magnetic recording media, the demand for high-density recording is increasing,
Therefore, methods for reducing the particle size of ferromagnetic fine powder,
Improved dispersibility of ferromagnetic fine powder, improved surface properties of magnetic layer,
It is necessary to improve the degree of filling of ferromagnetic fine powder.

Ferromagnetic @Equity V to improve the dispersibility of powder! 15
B-41565, JP-A-57-44227, JP-A-59
-30235, JP-A-60-238306, JP-A-60
-238309, JP-A-60=238371 and other publications include -3OJ, 05OJ, POsL, 0POJz
The use of a binder containing a polar group such as , COO group, or a binder having both these polar groups and an epoxy ring has been disclosed.

These binders have a high adsorption power to the ferromagnetic fine powder and provide better dispersibility than conventional binders. The magnetic surfaces of magnetic recording media obtained by dispersing ferromagnetic fine powder using these resins are smooth, making them suitable for video tape recorders, audio tape recorders, etc.
(Hereinafter abbreviated as "deck"), the running performance and durability of the magnetic tape become difficult, causing stain-slip phenomenon or the phenomenon that running stops.・In other words, for high-density recording 2, high S/N recording, the finer the ferromagnetic powder and/or the smoother the surface of the magnetic layer, the worse the runnability and durability of the magnetic recording medium will be. This phenomenon has led to the emergence of a magnetic recording medium capable of high-density recording with good running performance and durability.

In order to impart runnability and durability, the use of fatty acids, fatty acid esters, hydrocarbons, silicone compounds, fatty acid amides, mineral oil, etc., added to magnetic coating liquids is disclosed in Japanese Patent Application Laid-Open No. 1973-1999.
3505, Special Publication No. 47-15624, Special Publication No. 43-23
889, Japanese Patent Publication No. 51-39081, etc., but when the crystallite size of ferromagnetic fine powder is reduced to 500 Å or less for high-density recording, the addition of the lubricant disclosed above no longer improves runnability and durability. However, these technologies cannot produce magnetic recording media with high electromagnetic characteristics that improve the dispersibility of ferromagnetic fine powder with a crystallite size of 500 angstroms or less, and it is difficult to obtain magnetic recording media with high electromagnetic characteristics for high-density recording. Making the magnetic fine powder finer did not work effectively.

Furthermore, the methods described in the above-mentioned publications are unsatisfactory in terms of durability and runnability, and this worsens even further when the surface properties of the magnetic layer are smoothed in order to improve the electromagnetic conversion characteristics.

As a result of repeated experiments to add an appropriate lubricant to a magnetic recording medium, the present inventors found that a surfactant added to a magnetic recording medium lowers the surface energy and has appropriate water permeability and oil solubility. In addition, I realized that the stain with the material of the magnetic recording medium must be moderately good.

We have discovered that there is a fluorine-based surfactant with a specific chemical structure as a material that meets these conditions.

As a technology prior to the present invention, a surfactant containing a fluorine-based surfactant having a CF3 group at the end (Japanese Patent Application Laid-Open No. 5357004)
However, this application is a low boiling point fluorosurfactant,
Because no efforts were made to actively keep it in the magnetic layer,
It was distilled off during the drying process, etc., and the effect could not be fully demonstrated.

In order to solve these problems, Japanese Patent Application Laid-Open No. 61-292
proposed perfluorosulfonamide compounds in 222. This material had poor solubility in aqueous solvents and was difficult to use. This method lowered the friction coefficient and improved the reproduction RF output sensitivity.

Further, JP-A-57-92424 and JP-A-59-22228 propose that fluorine-containing organosilicon compounds exhibit good effects in repeated running tests for reducing the .mu. value.

However, ferromagnetic fine powder has a crystallite size of 500 Å.
When using a ferromagnetic alloy powder that was finely divided and contained 2 atomic% or more of A1 or Si relative to Fe according to X-ray diffraction, still life and pot life could not be sufficiently improved. .

(Objective of the Invention) The object of the present invention is to use ferromagnetic fine powder with extremely small particle size to disperse the ferromagnetic fine powder to a high degree, to achieve extremely good electromagnetic conversion characteristics, and to achieve both durability and runnability. An object of the present invention is to provide a magnetic recording medium.

(Structure of the Invention) That is, the above object of the present invention is ('11) in a magnetic recording medium having a magnetic layer on a non-magnetic support in which ferromagnetic fine powder is dispersed in a binder, the ferromagnetic fine powder has a crystallite size. is 500 Å or less, and the content of Al or Si relative to Fe determined by analysis by X-ray diffraction method is 2 ato
This can be achieved by a magnetic recording medium characterized in that it is a ferromagnetic alloy powder of mic% or more and contains a fluorine silane compound represented by the following formula in the magnetic layer.

1llll CFz(CFt)-(CL)t 51(OCOR”)
3, B+: Monovalent hydrocarbon group having 1 to 6 carbon atoms R1 = Saturated or unsaturated monovalent hydrocarbon group having 7 to 21 carbon atoms m: 1 to 12 1: 2 to 20 n: 0M2 More preferably ( 2] This can be achieved by a magnetic recording medium characterized in that the surface roughness (R,) of the magnetic layer is 0.010 μm or less (cutoff value 0.25 m+m).

As the ferromagnetic fine powder used in the present invention, ferromagnetic alloy powder, ferromagnetic iron oxide fine powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, barium ferrite, etc. can be used. The acicular ratio of the ferromagnetic alloy powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic iron oxide, and chromium dioxide is about 271 to 20/1, preferably 5/1 or more, and the average length is 0.2 to 2. A range of approximately 0 μm is effective. The present invention is particularly effective when the crystallite size is 500 angstroms or less, and even more effective when the crystallite size is 400 angstroms or less. The most effective is 250 angstroms or less (crystallite size is based on 1 diffraction). However, according to the gist of the present invention, effects such as electromagnetic conversion characteristics, runnability, and durability can be achieved by using the technology of the present invention even when the crystallite size is above this size, and it is effective when the crystallite size is below the above-mentioned crystallite size. 0 ferromagnetic alloy powder has a metal content of 75% by weight or more, and 80% by weight or more of the metal content is a ferromagnetic metal (i.e., Fe, Co5N15Fe-Ni,
Co-Ni5 FeCo-N1) particles.

The above-mentioned ferromagnetic fine powder exhibits a remarkable effect when it contains 2 atomic % or more of All or Si relative to Fe, and particularly preferably 3 atomic % or more of Si.
A ferromagnetic alloy powder having an aic% or more is preferable.

When A2 or Si is less than 2 atomic%, runnability becomes poor, or the surface of the ferromagnetic fine powder is covered with additives such as lubricants, and the additive forms a layer around the ferromagnetic fine powder. However, this is not preferable because the durability is poor, and the stability of the magnetic coating liquid over time is also poor, and the ferromagnetic fine powder aggregates, resulting in poor electromagnetic conversion characteristics. The maximum value of Ae or Si is 10ato■ic
%. If it exceeds this value, the coercive force of the ferromagnetic fine powder itself decreases, making it unsuitable as a material for high-density recording.

Specific examples of the fluorosilane compound used in the present invention include the following.

Hiroshi CH3 CFsCFz ((Jlz) tsi (OCOC+ +
1Izs) 2hl12 (CI
+3) 2CFsCPz (CHz)+. 5iOCOCt
vlhs3 C12 CFs (Ch) s (CL) tsi (OCOC
tH+ s) z 4 CI+3 CFs(Ch)s(CTo)gsi(OCOC+Jz7
)z1kL5 C old Ch(CFt)s(CHx)tsi(OCOC+5H1
) i calm 6 (CHs)z CFs(CL)s(Cflz)xsiOcOc+tll
xi floor 7 C1(3 CF3(CFt)s(CL)zsi(OCOC2ll(
41) za8 CL CFs(CFt)i(CHx)zsi(OCOCJtq
)t19 (CH3) z CF3(CPt)s(CHx)zsi-OCOC++1
lzi Touch 10 CI.

CPx (CFt)s (CIlg) gsi (OC
OC+ 5HtJ zseed11 C11゜Ch(Ch)t(CIlg)zsi(OCOCtJst
) x Hiro12 CHi CF3(CFt)v(CHt)thsi(OCOCtJ
st)tnu13 CH3 Ch(CFt)t(CL)gsi(OCOCollts
) Aim for 14 (old C) 2 CF, (CF□)t(CHt)*5iOCOC+sl.

Nu15 C11゜Ch (CF gate) * (CHz) gsi (OCOC, tll
□)□Blood 16 CI+ 3C
h (CFt) * (CHz)
) to magnetic18 (CH,)t CF3(CFg)*(CFlz)6SiOCOC+J*
wa19 C! ! .

CFs (CF2) r t (C1lz) isi
(OCOC?lIIt) zmagic20 (CHi)z Ch (CFt) + + (CFIt) asiOc
Ocl tlhs These compounds may be used alone or in combination.

A method for synthesizing these compounds is to use a chlorosilane containing a chloroalkyl group represented by R1°F(CFri-(CHi) to 5iCj!3-) and R"
It is obtained by dehydrochlorinating a fatty acid represented by 0OH in the presence of a hydrochloric acid scavenger. Preferred hydrochloric acid scavengers include triethylamine, pyridine, picoline,
Examples include N,N dimethylaniline.

The preferable range of these compounds is that R+ is a hydrocarbon group having 1 to 6 carbon atoms, examples of which include methyl group, ethyl group, propyl group, butyl group, pentyl group, and hexyl group, but it is easy to synthesize. For this reason, the methyl group is the most preferred.

R2 is a saturated or unsaturated monovalent hydrocarbon group having 7 to 21 carbon atoms, and among these, those having a linear structure are preferred; if the number of carbon atoms is less than 7, the lubricity will be insufficient;
On the other hand, if it exceeds 21, the melting point of the compound becomes too high, which tends to cause blooming and also makes the solubility in the binder resin poor. Such monovalent hydrocarbon groups include heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tridecyl group, pentadecyl group,
Examples include a heptadecyl group, an octadecyl group, a behenyl group, an oleyl group, a linole group, and a rinne group.

m needs to be in the range of 1 to 12; if it is less than 1, the lubricity and bleed-out properties to the tape surface will be poor; on the other hand, if it exceeds 12, the solubility in solvents and binders will be extremely poor. degenerates into

The fluorosilane compound of the present invention is 0.05 to 2.5 parts by weight, preferably 0.1 to 1 part by weight, based on 100% by weight of the nf fine powder.
．． If the amount is less than this, the lubricating effect cannot be achieved, and if it is more than this, the magnetic recording medium tends to stick, causing the stick-5-lip phenomenon, and the pot life of the magnetic coating liquid. This is not desirable as it may become defective.

The fluorosilane compound of the present invention can be used by being added to a magnetic coating liquid, but it may also be applied after forming a magnetic recording medium by dissolving it in an aqueous solvent or by spraying it.

In the present invention, other lubricants may be mixed. Lubricants that can be used in combination include fatty acids, fatty acid esters (including various monoesters, sorbitan, fatty acid esters of polyvalent esters such as glycerin, esters of polybasic acids, etc.), metal soaps, higher aliphatic alcohols, fatty acid amides, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, paraffins,
Examples include silicone oil, fatty modified silicon compounds, animal and vegetable oils, mineral oils, higher aliphatic amines; and inorganic fine powders such as graphite, silica, molybdenum disulfide, and tungsten disulfide.

Among these mixed lubricants, those with a carbon number of 22 to
36 fatty acid ester.

Examples of the binder used in the present invention include a vinyl chloride/vinyl acetate copolymer, a copolymer of vinyl chloride and vinyl alcohol, maleic acid and/or acrylic acid,
Vinyl chloride/vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/vinyl acetate copolymer, cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acecool resin, polyvinyl butyral resin, epoxy resin, amide resin , phenoxy resin, polyurethane resin, etc. Among these, the most preferable ones in order to further improve dispersibility and durability include polar groups (epoxy groups, COx
H,0HSNHHz,SOsM,03OsM,PO
s Mz , 0POs M-rich (where M is hydrogen, alkali metal or ammonium) is introduced into vinyl chloride resin and/or polyurethane resin. For these resins, the preferred content of polar groups is 10-S to 10-coequivalents per gram of polymer.

The urethane skeleton may be any of polyester, polyether, polyester ether, and polycarbonate. The polymeric binders listed above are used alone or in combination, and are often known as isocyanate-based crosslinking agents (
For example, tolylene diisocyanate triadduct of trimethylolpropane, etc.) is added for curing treatment.

Furthermore, a binder system that uses an acrylic acid ester oligomer and a monomer as a binder and is cured by radiation irradiation can also be used.

Details of the method of dispersing the ferromagnetic fine powder and the binder and the method of coating it on a support are described in Japanese Patent Laid-Open Publications No. 54-46011 and No. 54-21805.

The total binder content in the magnetic layer of the magnetic recording medium of the present invention is usually 10 to 10 parts by weight per 100 parts by weight of the ferromagnetic fine powder.
0 parts by weight, preferably 20 to 40 parts by weight.

Organic solvents used for kneading, dispersing, and applying the magnetic coating liquid include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid glycol monoethyl ether. Ether systems such as ethyl ether, glycol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, Chlorinated hydrocarbons such as dichlorobenzene can be selected and used.

Furthermore, additives such as an abrasive, a dispersant, an antistatic agent, and a rust preventive may be added to the magnetic coating liquid of the present invention. The abrasive used is not particularly limited as long as it has a Mohs hardness of 5 or more, preferably 8 or more.

An example of an abrasive with a Mohs hardness of 5 or more is A 130.
3 (Mohs hardness 9), Ti0 (6), Ti1t (
6.5), Siot (7), Snow (6.5), Crz Off (9), and α-
Fear's (5.5) can be mentioned, and these can be used alone or in combination. Particularly preferred is an abrasive having a Mohs hardness of 8 or more. If an abrasive with a Mohs hardness lower than 5 is used, the abrasive easily falls off from the magnetic layer and has almost no abrasive action on the head, resulting in head clogging and poor running durability. Become. The content of the abrasive is usually in the range of 0.1 to 20 parts by weight, preferably in the range of 1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic fine powder. As an antistatic agent, carbon black (especially carbon black with an average particle size of 1
0 to 300 nm (nanometers: 10-''m)).

Materials for the non-magnetic support to which the magnetic coating liquid is applied include polyesters such as polyethylene terephthalate and polyethylene 2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose jlI bodies such as cellulose triacetate; polycarbonate, polyimide, and polyamide. Plastics such as copper, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, and plastics on which metals such as aluminum are vapor-deposited can also be used. The thickness of the non-magnetic support is 3 to 100μ, preferably 3 to 20μ for magnetic tape, and 20 to 10μ for magnetic disk.
0μ is the commonly used range.

In addition, the forms of non-magnetic supports include films, tapes, sheets,
It may be a disk, card, drum, etc., and various materials are selected depending on the form as necessary.

In addition, the nonmagnetic support of the present invention is used to prevent static electricity, to prevent transfer, to prevent wow and flutter, to improve the strength of magnetic recording media, and to make the back surface matte. A so-called back coat may also be provided.

(Effect of the invention) When trying to use a fine ferromagnetic alloy powder with a small crystallite size to improve electromagnetic conversion characteristics, the fine ferromagnetic alloy powder exhibits high performance even if the crystallite size is made small. It is not possible to achieve playback output, and the friction coefficient (μ value) is high.
Moreover, the durability (still life) was insufficient, and the storage stability (pot life) of the magnetic coating liquid was poor, so it could not be put to practical use.

In addition, in order to improve the electromagnetic conversion characteristics, it is necessary to smooth the surface of the magnetic layer, and for this purpose it is essential that the magnetic coating liquid has good dispersibility. Among the magnetic alloy fine powders, especially AI or Si is 2at
By using a compound containing o+mic% in combination with the specific fluorosilane compound of the present invention, it is possible to achieve the low friction coefficient of the fluorosilane compound, surprisingly, the still life is good, and the electromagnetic conversion characteristics are improved. The bore life of the magnetic coating liquid, which is essential for the magnetic coating, has been improved, and the electromagnetic conversion characteristics have been significantly improved by using fine particles of ferromagnetic alloy powder.

The reason for this is thought to be as follows: The fluorosilane compound having the specific structure disclosed in the present invention is moderately adsorbed to the ferromagnetic alloy fine powder containing Ae or St, and the R1 or R2 of the fluorosilane compound is Due to the effects of the alkyl groups, etc. shown in , fluorosilane is adsorbed to fine ferromagnetic alloy powder due to the balance between water repellency and oil repellency possessed by the fluorosilane and lipophilicity due to the alkyl group, or by adsorbing it to the binder appropriately, it is possible to form a magnetic coating liquid. This not only improves the dispersibility of magnetic coatings, but also improves the pot life of magnetic coating liquids.

These effects are surprising and could not have been expected with compounds such as the perfluorosulfonamide carboxylate salt disclosed in JP-A No. 61-292222.

〔Example〕

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

Note that "parts" in the examples indicate "parts by weight."

(Example) Fa powder (listed in Table 1*) 100 parts by weight Vinyl chloride/vinyl acetate/glycidyl methacrylate = 86
/915 copolymer with hydroxyethyl sulfonate sodium salt added (So, Na-6*
10-'eq/g, epoxy-10-'eq/g, M
w30. 000) 10 parts by weight 5OsNa-containing urethane resin (Toyobo UR8200) 10 parts (solid content) Abrasive (A 1203 particle size 0.3 parts m) 2 parts carbon black (particle size 40 μm) 2 parts Methyl ethyl ketone/toluene - 1/1200 1 part and dispersed with a sandpaper for 120 minutes. Polyisocyanate (Korofuichi 13 manufactured by Nippon Polyurethane) was added to this.
041) 5 parts (solid content) lubricant
Types and amounts of butyl stearate listed in Table 1
1 part 50 parts of methyl ethyl ketone were added, and the mixture was further stirred and mixed for 20 minutes, followed by filtration using a filter having an average pore size of 1 μm to prepare a magnetic paint. The thickness of the obtained magnetic paint after drying is 3.0μ.
It was coated on the surface of a polyethylene terephthalate support with a thickness of 1011 m using a reverse roll so that the film thickness was 1,011 m.

A non-magnetic support coated with magnetic paint is magnetically aligned with a 3000 Gauss magnet while the magnetic paint is not dry.
After further drying and super calendering, 8
A videotape was produced by slitting the film into wide widths. The evaluation results of the obtained tapes are summarized in Table 1.

"Evaluation method" 1) Electromagnetic conversion characteristics (playback output): The videotape obtained as described above was
A 7MH signal was recorded and played back using X8. The playback output of 7MH recorded on the reference tape (Comparative Example 1) was
The relative playback power of the videotape in dB was measured.

2) Runability (μ value): The obtained videotape and a stainless steel pole were brought into contact (wrapping angle 180'') with a tension (T1) of 50g, and under these conditions, the videotape was
．． Tension (T2) required to run at a speed of 3 cm/s
) was measured. Based on this measured value, the friction coefficient μ value of the videotape was determined using the following calculation formula.

u= l/z ・1 n (T* /T+) Furthermore,! 2
The friction coefficient test was conducted at 25° C. and 170% RH.

3) Durability (still life): Tested in a still state using the above FUJ IX8, and the playback output was 5 times the recording signal.
The time until it reached 0% was measured.

At this time, the unloading function was canceled.

4) Pot life: After dispersing the coating solution, the magnetic tape was left to work for 20 hours, and the relative output was measured using the playback output of the tape when not left as OdB.

A magnetic recording medium that combines a ferromagnetic fine powder with a crystallite size of 500 Å or less and containing 2 atomic% or more of AI or Si as shown in Table 1 and a specific fluorosilane compound shown in the present invention. has high regeneration output, low coefficient of friction (μ value), good durability (still life), and long shelf life (pot life) of magnetic coating fluid.
It can be seen that the results are good. (Sample M4~8.11
~13.17.18) However, when the fluorosilane compound of the present invention is not used or the ferromagnetic fine powder of the present invention is not used, the reproduction output is low, the μ value is high, and the still life and pot life are poor. It turns out that it is enough.

Claims (2)

[Claims] (1) In a magnetic recording medium having a magnetic layer in which ferromagnetic fine powder is dispersed in a binder on a non-magnetic support, the ferromagnetic fine powder has a crystallite size of 500 Å or less and can be analyzed by X-ray diffraction. A magnetic recording medium comprising a ferromagnetic alloy powder having a predetermined content of Al or Si relative to Fe of 2 atomic % or more, and containing a fluorine silane compound represented by the following formula in the magnetic layer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ R^1: Monovalent hydrocarbon group with 1 to 6 carbon atoms R^2: Saturated or unsaturated monovalent hydrocarbon group with 7 to 21 carbon atoms m: 1 to 12 l: 2~20 n: 0~2 (2) The surface roughness (R_a) of the magnetic layer is 0.010μ
A magnetic recording medium characterized in that it is less than m (cutoff value 0.25 mm).