JPS6286537A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve durability, output, oxidation resistance and anti electrification effect and to permit high-recording density by incorporating magnetic particle of which at least the surface is iron carbide and in which the content of the iron carbide is specific onto a recording layer on a flexible substrate. CONSTITUTION:The magnetic particle of which at least the surface is the iron carbide and the content of the iron carbide in the particle is 5-90wt% is used as the magnetic particle of the recording layer into which the magnetic particle and binder are incorporated and which is provided on the flexible substrate. The compsn. of the iron carbide of the particle of which at least the surface is iron carbide is FenC (n>2) and magnetic metallic particle, gamma-iron oxide parti cle, Co-deposited iron oxide particle or magnetic particle contg. Ba or Sr ferrite particle is preferable as the magnetic particle. The durability, wear resistance and the hardness of the coated film are upgraded by using such magnetic parti cle having the iron carbide on the surface. The chemical and magnetical stability against temp. and humidity environment is improved. Since the iron carbide is electrically conductive, the satd. magnetization is high and the magnetic disk having high recording density is obtd.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic recording media, and particularly to improvements in the composition of magnetic particles used in magnetic disks such as floppy disks and magnetic sheets for still video floppies. Prior art and its problems In recent years, home VTRs have become popular, and high-performance audio cassette tapes, video tapes, computer tapes, multi-coated tapes, magnetic disks, floppy disks, still video floppy disks, magnetic cards, etc. have been put into practical use. ,
Along with this, various magnetic particle materials for use in magnetic recording media have been developed. Among them, the representative one is acicular iron oxide. However, this alone cannot cope with the high density of magnetic recording, and metal magnetic particles using cobalt-coated iron oxide particles and magnetic metals have been studied, and are used for high-performance audio cassette tapes, video tapes, various magnetic disks, etc. It has been partially put into practical use. By the way, the range of applications of floppy disks has been expanding to include external storage media for office computers, personal computers, word processors, etc., input personal files for system programs of personal computers, word processors, etc., and data exchange. Various cobalt-based iron oxides, metals, etc. are used as magnetic particle materials, but these are insufficient in terms of output, S/N ratio, oxidation resistance, recording density characteristics, durability, etc. be. Furthermore, a non-magnetic antistatic agent such as carbon black must be added to these magnetic particles. This reduces residual magnetization, which is disadvantageous in terms of output level and resolution when attempting to increase the density of floppy disks. Therefore, improvements in the above points are desired. Furthermore, magnetic sheets for still video floppy disks are required to have high durability because the sheet rotates at high speed and is subjected to pressure that causes deformation of the sheet for recording and reproduction. In addition, in such a magnetic sheet, the reproduction output changes depending on the head position and the amount of sheet deformation, and output fluctuations occur depending on the contact state between the head and the sheet.
Therefore, the magnetic sheet must have appropriate rigidity. In magnetic sheets, the Fii layer undergoes deformation due to high-speed sliding and bending at the same time. suffer from physical fatigue. Furthermore, conventional magnetic sheets are still insufficient in terms of durability. ■ Purpose of the invention The purpose of the present invention is durability, output, and oxidation resistance. The object of the present invention is to provide a magnetic disk that has a high antistatic effect, does not cause a decrease in output due to the addition of an antistatic agent, and is advantageous in achieving high recording density. ■Disclosure of the Invention These objects are achieved by the present invention as described below. That is, the present invention provides a magnetic disk having a recording layer containing magnetic particles and a binder on a flexible substrate,
The present invention is a magnetic disk characterized in that the magnetic particles include particles whose surfaces are made of iron carbide, and the iron carbide content in the magnetic particles is 5 to 90% by weight. ■Specific structure of the invention The specific structure of the present invention will be explained in detail below. The recording layer of the magnetic recording medium of the present invention includes magnetic particles containing at least magnetic particles whose surfaces are iron carbide. Such magnetic particles are prepared by mixing iron cyanide with sulfate, sulfite, or sulfide and placing the mixture in a steel reactor to absorb CO2.
It is obtained by heating reduction and cooling while introducing. Also, JP-A-58-171765 and JP-A-60-12
As described in No. 4023 etc., a-F 6
00 H (Goethite), β-F e OO
H (Akaganite), y-F e OO
Iron oxyhydroxide such as H (Lepidacrocite), a-Fe203, y-Fe203. Iron oxides such as Fe304 and y-Fe203-Fe304 (solid solution) can be obtained by reduction using -carbon oxide or a mixed gas of hydrogen and carbon monoxide. Alternatively, a slurry mixture of these iron oxides and an aqueous colloidal carbon black particle suspension may be prepared by hydrogen reduction, -carbon oxide reduction, or mixed gas reduction of hydrogen and carbon monoxide. In addition, iron cyanide compounds such as hexacyano iron salts such as Turn Blue Blue and Berlin White, ferro or ferricyanide compounds such as screen potash, anemia soda, blush potash, and nosebleed soda are used, and as additives, potassium sulfate and sulfuric acid are used. Sulfates such as soda, ammonium sulfate, iron sulfate, sodium hydrogen sulfate, potassium hydrogen sulfate, sulfites such as potassium sulfite, sodium sulfite, ammonium sulfite, potassium hydrogen sulfite, or sodium sulfate, potassium thiosulfate, sodium sulfide, sulfide Sulfides such as potash, iron sulfide, rhodan soda, rhodan potash, sodium isothiocyanate, and potassium isothiocyanate can be used. The gas used in these heating reduction atmospheres is not limited to CO, but also C
Carbon-containing reducing gases such as H4, water gas, and propane may also be used. Furthermore, after forming pure iron particles, the various heat reduction treatments described above may be performed. In addition, what is necessary is just to make heating temperature 300-700 degreeC and heating time about 30 minutes - 10 hours in the case of reduction|restoration. As the iron carbide particles generated, in FenC, n
≧2, especially 2 to 3. In this case, n is an integer and does not necessarily have a stoichiometric composition, but Fe2 C, Fe5 C2. Fe5C is mainly produced. There may be a moisture gradient in the particles, and C does not necessarily need to be present throughout the particle as long as it is present on the surface, but iron carbide should account for 10 to 100% by weight of the particle. is preferred. The above-mentioned magnetic particles having at least the surface of iron carbide are acicular or granular, and are selected depending on the intended use as a magnetic recording medium. When used for floppy disks and magnetic sheets, those having a major axis of 0.2 to 2 l and an axial ratio of 1 to 20 are preferable. In addition, such magnetic particles account for 5 to 90% of the total magnetic particles.
Weight%. This is because if the amount is less than 5% by weight or more than 90% by weight, the effects of the present invention will not be achieved. In addition to the aforementioned magnetic particles having at least the surface of iron carbide, the magnetic particles may include metal magnetic particles, cobalt-coated iron oxide particles, γ-Fe203 particles, and barium or strontium ferrite particles. The metal magnetic particles used in the present invention are as follows. 1) a-FeOOH (goethite). β-F e OOH (Akaganite), y −
Iron oxyhydroxide such as Fe0OH (Lepidocrocite); iron oxide such as a-Fe203, y-Fe203, Fe304, y-Fe203-Fe304 (solid solution); Co, Mn, Ni, Ti, Bi, Bo, Doped with one or more metals such as Ag. A method of producing iron or a magnetic particle flux mainly composed of iron by heating and reducing the surface of which an aluminum compound or a silicon compound is adsorbed and adhered in a reducing gas stream; 2) From a metal salt aqueous solution. It can be obtained by a method of producing by liquid phase reduction with NaBH4, or by a method of producing by evaporating the metal in a low-pressure inert gas atmosphere. The composition of the metal magnetic particles is Fe, Co. Cr, Mn, and Co are added to the simple substance of Ni, alloys thereof, or simple substances and alloys of these. Ni, as well as Zn, Cu, Zr, AI, and Ti. Metals added with Bi, Ag, Pt, etc. can be used. Furthermore, the effects of the present invention are not lost even when small amounts of nonmetallic elements such as B, C, Si, P, and N are added to these metals. Alternatively, partially chambered metal magnetic particles such as Fe4N may be used. Furthermore, the metal magnetic particles may have an oxide film on the particle surface. A magnetic recording medium using metal magnetic particles having such an oxide film is advantageous in terms of characteristics deterioration due to a decrease in magnetic flux density due to external environments such as temperature and humidity, and rusting of the magnetic layer.
The electrical resistance of the magnetic layer increases, which tends to cause problems due to charging during use. The metal magnetic particles used are acicular or granular, and are selected depending on the intended use as a magnetic recording medium. When used in floppy disks and magnetic sheets, needle-like or granular forms may be selected depending on the purpose. In addition, as the γ-Fe203 particles, α-Fe OO
H (goethite) is dehydrated at 400℃ or higher to obtain α-
Fe203 is reduced at 350°C or higher in H2 gas to give Fe3O4, and then oxidized at 250°C or lower.
pidocrocite) can be dehydrated, reduced, and oxidized. As the cobalt-coated iron oxide particles, those in which Co2+ is diffused in a very thin layer within several tens of λ from the surface of γ-Fe203 particles or Fe3O4 particles may be used. As barium or strontium ferrite, B
Part of the Ba and Fe of hexagonal barium or strontium ferrite such as aFe120ts and barium or strontium ferrite are replaced with Ca, Sr, Pb, Co, and N.
i, Ti, Cr, Zn, In, Mn, Cu, Ge, N
b, those substituted with Zr or other metals, etc. are fried. Methods for producing barium or strontium ferrite include ceramic, coprecipitation-firing, hydrothermal synthesis, fusics, and glass crystallization. There are an alkoxide method, a plasma jet method, etc., and any method may be used in the present invention. For details on these methods, see Yoshiyasu Koike and Osamu Kubo “
Ceramics 18 (1983) No. 10'', etc. The thickness of the magnetic layer containing such magnetic particles may be a normal thickness, and is preferably about 0.1 to 10 mm. The binder used for this purpose is a radiation-curable resin, a thermoplastic resin, a thermosetting or reactive resin, or a mixture thereof. It is preferable to use thermoplastic resins having a softening temperature of 150° C. or less, an average molecular weight of to, ooo to 200.000, and a degree of polymerization of about 200 to 2.000. This thermoplastic resin can also be used as a thermosetting resin or a reactive resin. It has a degree of polymerization, etc., and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. It is preferable to use materials that do not soften or melt before being decomposed.Specifically, examples include phenol resin, epoxy resin, polyurethane curable resin, urea resin, butyral resin, formal resin, melamine resin, alkyd resin, silicone resin, and acrylic resin. Condensation polymerization resins such as polyamide resins, epoxy-polyamide resins, saturated polyester resins, and urea-formaldehyde resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, and mixtures of methacrylate copolymers and diisocyanate prepolymers. , mixtures of polyester polyols and polyisocyanates, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate, mixtures of the above condensation resins and crosslinking agents such as isocyanate compounds, vinyl chloride-vinyl acetate (carboxylate), etc. (including acid-containing), vinyl chloride-vinyl alcohol-vinyl acetate (including carboxylic acid-containing), vinyl chloride-
Mixtures of vinyl copolymer resins such as vinylidene chloride, chlorinated vinyl chloride, vinyl chloride-7-crylonitrile, vinyl butyral, vinyl formal, etc., and crosslinking agents, cellulose resins such as nitrocellulose, cellulose acetobutyrate, and crosslinking agents. Mixtures of synthetic rubber systems such as butadiene-acrylonitrile and crosslinking agents, and mixtures thereof are suitable. To cure such a thermosetting resin, it is generally necessary to heat it in a heating oven at 50-80°C for 6-100 hours, or alternatively, to cure it at a low speed in an oven at 80-120°C. You may run it. As the binder, it is particularly preferable to use a hardened radiation-curable compound, that is, a radiation-curable resin. Specific examples of radiation-curable compounds include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds, which exhibit radically polymerizable unsaturated double bonds, and allylic double bonds such as diallylphthalate. It is a thermoplastic resin containing or introducing into its molecules a group that can be crosslinked or polymerized and dried by radiation irradiation, such as a double bond or an unsaturated bond such as maleic acid or a maleic acid derivative.
Any compound having an unsaturated double bond that undergoes cross-linking polymerization upon irradiation with radiation can be used. The following unsaturated polyester resins are examples of resins containing groups in the molecule of thermoplastic resins that can be crosslinked or polymerized and dried by radiation irradiation. A polyester compound containing a radiation-curable unsaturated double bond in its molecular chain, for example, a saturated polyester resin consisting of an ester bond of a polybasic acid and a polyhydric alcohol as shown in (2) below, in which part of the polybasic acid is replaced by maleic acid. Examples include unsaturated polyester resins containing radiation-curable unsaturated double bonds. The radiation-curable unsaturated polyester resin is prepared by adding Malaykari L fumaric acid, etc. to one or more polybasic acid components and one or more polyhydric alcohol components, and preparing it in a conventional manner, that is, in the presence of a catalyst, at 180 to 200°C under a nitrogen atmosphere. After dehydration or dealcoholization reaction, the temperature can be raised to 240 to 280°C, and a condensation reaction can be performed under reduced pressure of 0.5 to 1 mmHH. The content of maleic acid, fumaric acid, etc. in the acid component is 1 to 40 mol%, preferably 10 to 30 mol%, in view of crosslinking and radiation curability during production. Examples of thermoplastic resins that can be modified into radiation-curable resins include the following. (1) Vinyl chloride copolymer Vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol-vinyl propionate copolymer, vinyl chloride-vinyl acetate-malein Acid copolymers, vinyl chloride-vinyl acetate-vinyl alcohol-maleic acid copolymers, hinyl chloride-vinyl acetate-terminated OH side chain alkyl group copolymers, such as VROH and VYNC manufactured by UCC. VYEGX, VERR, VYES, YMCA. VAGH, UCARMAG520. UCARMAG
52a, etc., and radiation sensitivity modification is performed by introducing an acrylic double bond, a maleic acid double bond, or an allylic double bond into this product. These may contain carboxylic acids. (2) Saturated polyester resin phthalic acid, isophthalic acid, terephthalic acid, succinic acid, 7
Saturated polybasic acids such as divic acid and sebacic acid, ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, 1.2 propylene glycol,
Esters with polyhydric alcohols such as 1.3 butanediol, dipropylene glycol, 1°4 butanediol, 1.6 hexanediol, pentaerythrift, sorbitol, glycerin, neopentyl glycol, 1,4 cyclohexane dimetatool. Saturated polyester resins obtained by bonding or these polyester resins are
Examples include resins modified with O3Na etc. (for example Vylon 53S), which also undergo radiation sensitivity modification. (3) Polyvinyl alcohol-based resin Polyvinyl alcohol, butyral resin, acetal resin, formal resin and copolymers of these components,
Radiation sensitivity modification is performed on the hydroxyl groups contained in these resins. (4) Epoxy resin, phenoxy resin Epoxy resin produced by the reaction of bisphenol A, epichlorohydrin, and methyl epichlorohydrin, such as Shell Chemical Co., Ltd. (Nipico) 152° 154, 828, foot, 1
004.10G? ), manufactured by Dow Chemical (DE N4
31, DE R732, DE R511, DE
R331), Dainippon Ink (Epicron 400, 8
00), and furthermore, UC which is a high polymerization degree resin of the above epoxy
Phenoxy resin manufactured by Company C (PKHA, PKHC, PKHH
), a copolymer of brominated bisphenol A and epichlorohydrin. Dainippon Ink Chemical Industry Co., Ltd. (Ebikuron 145.152
, 153, 1120), and these also include those containing a carboxylic acid group. Radiation sensitivity modification is performed using the epoxy groups contained in these resins. (5) Various cellulose derivatives are used, but particularly effective ones include nitrified cotton, cellulose acetobutyrate, ethyl cellulose, butyl cellulose, and acetyl cellulose. Perform sensory degeneration. Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins, and derivatives (pvp
Also effective are acrylic resins containing at least one of olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiroacetal resins, hydroxyl group-containing acrylic esters, and methacrylic esters as polymerization components. Examples of elastomers, prepolymers and oligomers are listed below. (1) The use of polyurethane elastomers, prepolymers or oligomeric polyurethanes provides abrasion resistance, and the base film,
For example, it is particularly effective in terms of good adhesion to PET film. Examples of urethane compounds include 2,4-toluene diisocyanate, 2,6-
) Luene diisocyanate, 1.3-xylene diisocyanate, 1.4-xylene diisocyanate, 1.5
- Naphthalene diisocyanate. m-phenylene diisocyanate), p-y ene diisocyanate, 3.3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4.4'-diphenylmethane diisocyanate, 3.3'-dimethylbiphenylene diisocyanate, 4.4 '-Biphenylene diisocyanenite, hexamethylene diisocyanate, infron diisocyanate, dicyclohexylmethane diisocyanate, Desmodur L, Desmodur N, etc., and linear saturated polyesters (ethylene gelicol, diethylene glycol, glycerin, trimethylol) Propane, l,4-butanediol,
Polyhydric alcohols such as l,6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, l,4-cyclohexane dimetatool, and phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, and sebacic acid. (by condensation polymerization with saturated polybasic acids such as), linear saturated polyethers (polyethylene glycol,
Polyurethane elastomers and prepolymers made of polycondensates of various polyesters such as polypropylene glycol, polytetramethylene glycol), caprolactam, hydroxyl-containing acrylic esters, and hydroxyl-containing methacrylic esters are effective. By reacting the terminal incyanate group or hydroxyl group of these urethane elastomers with a monomer having an acrylic double bond or an allylic double bond,
Modification to radiosensitivity is very effective.
It also includes those containing OH, COOH, etc. as a polar group at the end. Furthermore, monomers having an unsaturated double bond that have an active hydrogen that reacts with an incyanate group and have radiation curability, such as mono- or diglycerides of long-chain fatty acids that have an unsaturated double bond, are also included. (2) Acrylonitrile-butadiene copolymer elastomer An elastomer such as an acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group commercially available as PolyBD Retired Resin manufactured by Sinclair Chemical Co., Ltd. or Hiker +432J manufactured by Nippon Zeon Co., Ltd. is particularly suitable for use in butadiene. It is suitable as an elastomer component whose double bonds are crosslinked and polymerized by generating radicals by radiation. (3) Polybutadiene Elastomer A prepolymer having a low molecular weight terminal hydroxyl group, such as PolyBD Retired Resin R-15 manufactured by Sinclair Petrochemical Co., is particularly suitable in terms of compatibility with thermoplastic resins.
Since the R-15 prepolymer has a hydroxyl group at the molecular end, it is possible to increase the radiation sensitivity by adding an acrylic unsaturated double bond to the molecular end, making it more advantageous as a binder. In addition, polybutadiene cyclized product 1 CBR- manufactured by Nippon Synthetic Rubber Co., Ltd.
M901 also has excellent properties when combined with thermoplastic resin. Other suitable thermoplastic elastomer and prepolymer systems include styrene-butadiene rubber, chlorinated rubber, acrylic rubber, imprene rubber, and its cyclized product (ClR701 manufactured by Nippon Synthetic Rubber Co., Ltd.), epoxy-modified rubber, internal plastic Elastomers such as saturated linear polyester (Toyobo Vylon #300) can also be effectively used by subjecting them to radiation-sensitive modification treatment. Compounds having a radiation-curable unsaturated double bond used as oligomers and hexamers in the present invention include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, 1. 6-hexane glycol diacrylate, l, 6-hexane glycol dimethacrylate, N-vinylpyrrolidone. Pentaerythritol tetraacrylate (methacrylate), pentaerythritol triacrylate (methacrylate), trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyfunctional oligoester acrylate (Aronix M-71
00, M-5400, 5500, 5700, etc., Toagosei), acrylic modified products of urethane elastomers (Twinlan 4040), or those into which functional groups such as COOH are introduced, trimethylolpropane diacrylate (methacrylate) Acrylate (methacrylate) of phenol ethyleneoxide adduct, an acrylic group (
methacrylic group) or ε-caprolactone-a compound with an acrylic group. In the formula, m=l, a=2, b=4 (7) compound (hereinafter referred to as special pentaerythritol condensate A), m-1, a=3. b=3c7) compound (hereinafter referred to as special pentaerythritol condensate B), m-1, a=6.
A compound where b=0 (hereinafter referred to as special pentaerythritol condensate C), a compound where m-2, a=6, b=o (hereinafter referred to as special pentaerythritol condensate C), and a compound represented by the following general formula Examples include special acrylates. 1) (CH2=CHC00CH2)3-CCH2
0H (special acrylate A) 2) (CH2=CHC00CH2)3-CCH2
0H3 (special acrylate B) 3) (CH2=CHC0(OC3Ha)n -0
CH2) 3-CCH2CH3 (Special acrylate C) (Special acrylate D) (Special acrylate E) (Special acrylate F) (16 out of n) (Special acrylate G) 8)
CH2=CHCOO-(CH2CH20)4
C0CH=CH2 (Special acrylate H) (Special acrylate) I) (Special acrylate J) A-(X-Y÷-X-A A Niacrylic m, X: Polyhydric alcohol Y: Polybasic acid (Special acrylate) K)12)
A(-M-N+-M-AA Niacrylic acid, M:2
Valid alcohol N: dibasic acid (special acrylate L) Next, an example of synthesis of the radiation-sensitive binder will be described. a) Synthesis of acrylic modified vinyl chloride vinyl acetate copolymer resin (radiation sensitive modified resin) Partially saponified vinyl chloride vinyl acetate copolymer having OH groups (average degree of polymerization n=500
) 750 parts, toluene 1250 parts, cyclohexanone 5
Pour 00 parts into a 51 quart flask, heat and dissolve,
After raising the temperature to 80°C, 61.4 parts of 2-tolylene diisocyanate and droxyethyl methacrylate adduct* were added.
Furthermore, tin octylate 0.012 parts, hydroquinone 0
．． 012 parts of the mixture were added and allowed to react at 80°C in a N2 stream until the NGO reaction rate reached 90%. After the reaction is completed, the mixture is cooled and diluted with 1250 minutes of methyl ethyl ketone.

[*Production of 2-hydroxyethyl methacrylate (ZHEMa) adduct of tolylene diisocyanate (TDI) After heating 348 parts of TDI to 80°C in a 4-hole flask in a N2 atmosphere, 260 parts of 2-ethylene methacrylate and tin octylate. 0.07 part, hydroquinone 0.05
After the dropwise addition was completed, the mixture was stirred at 80°C for 3 hours while controlling the cooling so that the temperature inside the reaction vessel was 80 to 85°C.
Complete the reaction. After the reaction is completed, take it out and cool it to obtain a white paste-like TD.
2HEMA of I was obtained. b) Synthesis of butyral resin acrylic modified product (radiation-sensitive modified resin) Butyral resin BM-3 manufactured by Sekisui Chemical Co., Ltd. 100 parts, 191.2 parts of toluene, 51 parts of Schiff with 71.4 parts of hexanone
4 parts of 2HEMA adduct* of TDI were added after heating to 80°C, followed by 0.015 parts of tin octylate and 0.01 part of hydroquinone.
5 parts was added, and the NCO reaction rate was 90 at 80°C in a N2 stream.
% or more. After the reaction is completed, the mixture is cooled and diluted with methyl ethyl ketone. C) Synthesis of acrylic modified saturated polyester resin (radiation-sensitive modified resin) Saturated polyester resin (Toyobo Vylon RV-200)
, 100 parts to 116 parts of toluene, 1 part of methyl ethyl ketone
After heating and dissolving 16 parts of TDI at 80°C, 2HEM of TDI
Add 3°55 parts of A adduct*, further add 0.007 part of tin octylate and 0.007 part of hydroquinone,
The reaction is allowed to proceed at 0° C. in a N2 stream until the NCO reaction rate reaches 90% or more. d) Synthesis of acrylic modified epoxy resin (radiation-sensitive modified resin) Epoxy resin (Epicoat 1007 manufactured by Shell Chemical Co., Ltd.) 40
After heating and dissolving 0 parts in 50 parts of toluene and 50 parts of methyl ethyl ketone, 0.006 parts of N,N-dimethylbenzylamine was dissolved.
1 part, 0.003 part of hydroquinone was added and the temperature was adjusted to 80°C,
69 parts of acrylic acid was added dropwise and reacted at 80° C. until the acid value reached 5 or less. ■Synthesis of acrylic modified phenoxy resin (radiation-sensitive modified resin) 600 parts of phenoxy resin with OH group (PKHH: manufactured by UCC, molecular weight 30,000), 1 part of methyl ethyl ketone
Pour 800 parts into a 4-piece No. 31 flask, heat and dissolve, and after raising the temperature to 80°C, add 6.0 parts of 2-hydroxyethyl methacrylate adduct of tolylene diisocyanate, and further add 0.012 parts of tin octylate and 0/1 hydroquinone.
．． 012 parts of the mixture were added and allowed to react at 80°C in a N2 stream until the NGO reaction rate reached 90%. The molecular weight of this phenoxy modified product is 35,000. There is one double bond per molecule. e) Synthesis of acrylic modified urethane elastomer (radiation-curable elastomer) 250 parts of a diphenylmethane diisocyanate (MDI)-based urethane prepolymer having terminal incyanate (Nipporan 3119 manufactured by Nippon Polyurethane Co., Ltd.), 2HEMA32.
5 parts, hydroquinone 0.07 parts, tin octylate 0.
Pour 009 parts into a reaction vessel, heat to 80°C and dissolve, then TDI
43.5 parts were added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C. After the dropwise addition, the reaction rate was 9 at 80°C.
The reaction is allowed to occur until the concentration reaches 5% or more. f) Synthesis of acrylic modified polyether-terminated urethane-modified elastomer (radiation-curable elastomer) Polyether PTG-500, 2 manufactured by Nippon Polyurethane Co., Ltd.
50 parts, 2) IEMA 32.5 parts, hydroquinone 0.
07 parts and 0.009 parts of tin octylate were placed in a reaction vessel.
After heating and dissolving at 80°C, 43.5 parts of TDI is added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after the dropwise addition is completed, the reaction is allowed to occur at 80°C until the reaction rate reaches 95% or more. g) Synthesis of acrylic modified polybutadiene elastomer (radiation curable elastomer) Low molecular weight terminal hydroxyl group polybutadiene polyBD liquid resin R-15250 parts manufactured by Sinclair Petrochemical, 32.5 parts of 2HHMA, 0.07 part of hydroquinone, Tin octylate 0.00
Pour 9 parts into a reaction vessel, heat to 80°C and dissolve, then TDI43
．． 5 parts were added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after completion of dropping, the reaction rate was 95% at 80°C.
Let it react until it reaches the above level. It is known that some polymers disintegrate when irradiated with radiation, while others cause crosslinking between molecules.゛Those that cause crosslinking between molecules include polyethylene, polypropylene, polystyrene, polyacrylic ester, polyacrylamide, polyvinyl chloride, polyester, polyvinylpyrrolidone rubber, polyvinyl alcohol,
There is polyacrylene. Such a crosslinked polymer does not need to be particularly modified as described above. Since a crosslinking reaction occurs, these resins can be used as they are in addition to the above-mentioned modified products. To cure such radiation-curable resins, various known methods may be used. Note that when ultraviolet rays are used for curing, a photopolymerization sensitizer is added to the radiation-curable compound as described above. The photopolymerization sensitizer may be a conventionally known one, such as benzoin-based sensitizers such as benzoin methyl ether, benzoinethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, bisdialkylaminobenzophenone, etc. Ketones, quinones such as acedraquinone, phenanthraquinone,
Examples include sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.
The photopolymerization sensitizer is 0.1 to 10% by weight based on the resin solid content.
range is desirable. For ultraviolet irradiation, for example, an ultraviolet light bulb such as a xenon discharge tube or a hydrogen discharge tube may be used. On the other hand, when using an electron beam, the radiation characteristics are as follows:
Accelerating voltage 100-750KV, preferably 150-30KV
Using a 0KV radiation accelerator, the absorbed dose is 0.5-20
It is convenient to irradiate in a megadose manner. In particular, as an irradiation source, the method of using an electron beam using a radiation heater and the method of using ultraviolet rays described above are advantageous from the viewpoint of controlling the absorbed dose, introducing into the manufacturing process line, shielding ionizing radiation, etc. . Furthermore, according to this method, even a solvent-free resin that does not use a solvent can be cured in a short time, so such a resin can be used. By using such a radiation-curable resin, large diameter so-called jumbo rolls are free from tight winding, and the difference in electromagnetic conversion characteristics between the inside and outside of the jumbo rolls is eliminated and the characteristics are improved. Further, the disk-shaped magnetic sheet is advantageous in preventing curling of the magnetic sheet due to curling. Additionally, it can be done online, which improves productivity. The magnetic particles/binder have a weight ratio of l/l-9/1. In particular, it is preferable to have a ratio of 1.571 to 6/1.If the ratio is less than 1/l, the saturation magnetic flux density will be low, and if it exceeds 9/l, the surface roughness will deteriorate due to poor dispersion. Moreover, the coating film becomes brittle and becomes undesirable. In the present invention, a non-reactive solvent is used as necessary.
There are no particular restrictions on the solvent, but it is appropriately selected in consideration of the solubility and compatibility of the binder. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, esters such as ethyl formate, ethyl acetate, butyl acetate, alcohols such as methanol, ethanol, impropatol, butanol, )/L/ene, xylene, Aromatic hydrocarbons such as ethylbenzene, ethers such as isopropyl ether, ethyl ether, and dioxane, and furans such as tetrahydrofuran and furfural are used as a single solvent or a mixed solvent thereof. These solvents are used in a proportion of lO to 10,000% by weight, particularly 100 to 5,000% by weight, based on the binder. The magnetic layer may contain an inorganic pigment. Inorganic pigments include S i02 , Ti 02 , A12 as inorganic fillers.
03, Cr203, SiC, Cab, Ca
CO3, zinc oxide, goethite, γ-Fe203. Examples include talc, kaolin, CaSO4, boron nitride, graphite fluoride, molybdenum disulfide, and ZnS. In addition, the following fine particle pigments (aerosil type, colloidal type): 5i02゜AJL203, T
iO2, ZrO2, Cr203, Y203, CeO
2, Fe304, Fe203, ZrSiO4, S
b205, S n02, etc. are also used. For example, in the case of 5i02, these fine particle pigments include: ■ Ultrafine particle colloidal solution of silicic anhydride (Snowtex, water-based, methanol silica sol, etc., Nissan Chemical), ■ Ultrafine anhydrous silica produced by combustion of purified silicon tetrachloride ( Standard product 100
(Aerosil, Nippon Aerosil Co., Ltd.). Furthermore, ultrafine aluminum oxide, titanium oxide, and the above-mentioned fine particle pigments may be used, which are produced by an electrolytic method, the ultrafine particle colloidal solution described in (1) above, and a vapor phase method similar to (2). The appropriate amount of such inorganic pigments to be used is 1 to 30 parts by weight per 100 parts by weight of the magnetic particles; if the amount is too large, the coating film will become brittle and dropouts will increase. . In addition, the diameter of the inorganic pigment is 0,7 p, m or less,
Furthermore, 0.5 mm or less is preferable. In the present invention, there is no need to use a conductive agent or antistatic agent such as carbon black, graphite, graphitized carbon, etc., or only a small amount may be used. The magnetic layer may contain a dispersant. Organic titanium coupling agents, silane coupling agents, and surfactants are used as dispersants; natural surfactants such as soybean oil refined lecithin and saponin are used as antistatic agents; nonionic surfactants such as alkylene oxide types, glycerin types, and glycidol types are used as antistatic agents. Agents: higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphonium or sulfonium; acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, phosphoric ester groups, etc. Anionic surfactants containing diamino acids, aminosulfonic acids, amphoteric surfactants such as sulfuric acid or phosphoric acid esters of amino alcohols, and the like are used. The magnetic layer may contain a lubricant. As the lubricant, silicone oil, fluorine oil, fatty acid, fatty acid ester, paraffin, liquid paraffin, surfactant, etc. can be used as the lubricant conventionally used in this type of magnetic recording medium, but fatty acid and/or Preferably, fatty acid esters are used. Examples of fatty acids include fatty acids with 12 or more carbon atoms (RCO
Oh. R is an alkyl group having 11 or more carbon atoms), and fatty acid esters include fatty acid esters consisting of a monobasic fatty acid having 12 to 16 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms, and 17 carbon atoms. The total number of carbon atoms of at least one normal or iso-basic fatty acid and the fatty acid is 21 or more
A fatty acid ester consisting of a monohydric alcohol consisting of 23 atoms, etc. are used, and a metal soap, lecithin, etc. consisting of an alkali metal or alkaline earth metal of the above-mentioned fatty acid are also used. As the silicone, those made of fatty acid-modified silicones and those partially fluorine-modified are used. The alcohol used is one made of higher alcohol, and the fluorine used is one obtained by electrolytic substitution, telomerization, oligomerization, etc. Among the lubricants, it is also advantageous to use radiation-curable types. These products suppress the transfer of the back die to the back surface, preventing dropouts, reducing output differences depending on the inner and outer diameters when wound into a roll, and have other advantages such as being able to be manufactured online. have Radiation-curable lubricants include compounds that have a molecular chain exhibiting lubricity and an acrylic double bond in their molecules, such as acrylic esters, methacrylic esters, vinyl acetate esters, acrylic amide compounds, and vinyl alcohol esters. , methyl vinyl alcohol ester, allyl alcohol ester, glyceride, etc. The structural formula of these lubricants is CH2=CH-CH2C00R1 CH2= CHCON HCH2G OOR. RCOOCH=CH2. RCOOCH2-CH=CH2 etc. 1. :Co7'R is a linear or branched saturated or unsaturated hydrocarbon group,
The number of carbon atoms is 7 or more, preferably 12 or more and 23 or less,
These can also be fluorine substituted. As a fluorine substituted product, Cn F n CH2CH2NHCH2CH2+. CnF2. -10r 2 '52- etc. Preferred specific examples of these radiation-curing lubricants include:
Examples include stearic acid methacrylate (acrylate), stearyl alcohol methacrylate (acrylate), glycerin methacrylate (acrylate), glycol methacrylate (acrylate), and silicone methacrylate (acrylate). The dispersant and lubricant are preferably included in an amount of 11 to 20 parts by weight based on the magnetic particles.The lubricant may be added to the coating liquid at the time of dispersion.
Alternatively, the coating surface may be overcoated, or these may be used in combination. In addition, it is effective to use various antistatic agents, lubricants, dispersants, etc. according to the purpose, as necessary. Examples of flexible substrates used include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, polyimide, polycarbonate, polysulfone, polyethylene 2,6-naphthalate, aromatic aramid, aromatic polyester, etc. are used, but are not limited to these. Among these, it is particularly preferable to use polyester, polyamide, polyimide, and the like. In the magnetic recording medium of the present invention, it is preferable that magnetic layers are provided on both sides of such a substrate. Further, an undercoat, a backcoat, and an overcoat may be provided as necessary. In addition, when providing a back coat, it is preferable to use a composition consisting of a binder, a pigment, and a lubricant. The magnetic recording medium according to the invention may be manufactured by a conventional method. That is, a magnetic paint is prepared by mixing and dispersing magnetic particles with a binder, an organic solvent, etc., and this magnetic paint is coated with a base layer as necessary, or on a substrate such as a polyester film that has been subjected to a base treatment, such as gravure coating or reverse coating. It is applied using methods such as roll coating, air knife coating, air doctor coating, blade coating, kiss coating, and spray coating, and if necessary, it is dried after performing a random orientation treatment using a magnetic field to cancel the natural orientation that occurs during application. Preferably, a curing treatment using radiation or the like may be performed according to a conventional method, and a back coat and an overcoat may be provided as necessary. Note that in the recording medium of the present invention, 1. An undercoat layer may be provided between the substrate and the magnetic layer, but the undercoat layer of the coating film may contain a thermosetting resin or a radiation-curable compound as described above, and if necessary, a conductive pigment,
Includes inorganic fillers, lubricants, surfactants, etc. Further, an undercoat layer may be formed by a plasma polymerization method. The thickness of the undercoat layer is preferably about 10 to 57A, 1I. Note that the undercoat layer may have a thickness of 2M or more. Furthermore, especially when the magnetic layer thickness is 1 layer or less, the undercoat is effective in improving durability. Furthermore, the surface of the substrate may be subjected to corona discharge treatment or plasma treatment, and a magnetic layer may be provided on the treated surface. (2) Specific effects of the invention According to the invention, the magnetic particles contain 5 to 90% by weight of particles whose surfaces are at least iron carbide. Therefore, it has high durability, abrasion resistance, and coating hardness.
It also has high chemical and magnetic stability against temperature and humidity environments. In addition, since iron carbide particles have conductivity, there is no need to add non-magnetic antistatic agents such as carbon black to the magnetic layer, or even if they are added, only a small amount is required, resulting in high saturation magnetization and recording density. This makes it possible to create high-quality discs. Furthermore, there is little demagnetization and the corrosion resistance is extremely good. Therefore, overall, a magnetic recording medium with extremely high performance is realized. More specifically, compared to when using acicular iron oxide, 1
Magnetic properties, particularly residual magnetic flux density, are significantly improved without reducing surface smoothness, and extremely high recording density can be obtained. In addition, the magnetic properties and the output S/N ratio during analog recording are similarly improved, especially when compared with the use of Co-based iron oxide. Also, in the case of digital recording, the output during saturation recording is large, so the magnetic layer needs to be thinner to obtain the same output.
High recording density and resolution can be obtained. And compared to using metal magnetic powder, it has better moisture resistance,
Significantly improved corrosion resistance, increased magnetic and electrical reliability,
The coating strength is also significantly improved, the friction characteristics are also improved, and the durability of the disk drive is greatly improved. In addition, when using the sensing holes of 8-inch and 5.25-inch floppy disks, the blackness is high and JI
A magnetic disk can be obtained that provides a light transmittance that easily satisfies the S standard. Therefore, a magnetic disk extremely useful as a floppy disk, a still video floppy disk, etc. is realized. (2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail. [Example 1] Various samples were prepared by forming magnetic layers made of magnetic paint as shown below on both the front and back surfaces of a 757 zm thick polyester (PET) film. That is, first, a powder having at least a surface of FenC (hereinafter referred to as FenC powder) and an acicular Fe powder were prepared. Here, the acicular FenC powder is obtained by heating acicular α-FeOOH in an electric furnace at 350° C. for 5 hours in a mixed gas atmosphere of co and H 2 (mixing ratio 3 near). The axial ratio in this case was 5. The obtained product was confirmed by X-ray diffraction to be a mixed crystal of Fe5C and Fe. This one has coercive force Hc=9
The powder has a saturation magnetization σ5 of 82eμ/g. The acicular Fe powder was obtained by hydrogen reduction of acicular α-FeOOH, with an average particle length of 0.2 gm, an axial ratio of 8,
Coercive force Hc = 9000e, saturation magnetization σs = 155
It is a powder of e+su/g. Using the magnetic powder described above, a magnetic paint was prepared in the following manner at the mixing ratio (parts by weight) shown in Table 1 below. Magnetic powder 120 parts by weight α-A pattern 2
03 2 parts by weight (0.5 parts by weight) Solvent (MEK/) Luene: 100 parts by weight The above composition was mixed in a ball mill for 3 hours to thoroughly wet the magnetic powder. Note that only in Table 1 Sample No. 6 (comparison) was added 10 parts by weight of carbon black (20+sgm) to the above composition. Next, a binder I shown below was placed in a ball mill containing a magnetic liquid mixture, and mixed and dispersed again for 42 hours. Hiru El: "Hinyl chloride-vinyl acetate-vinyl alcohol copolymer (
Maleic acid content: 1% MW40.000) 8 parts by weight (solid fractionation 3I), acrylic double bond-introduced vinyl chloride-vinyl acetate copolymer (maleic acid content: 1% MW20,000) 10 parts by weight (in terms of solid content), 9 parts by weight of acrylic double bond-introduced polyether urethane elastomer (MW40,000) (in terms of solid content), 3 parts by weight of pentaerythritol triacrylate Solvent (MEK/T) Ltzn; 50150) 200
4 parts by weight of stearic acid and 10 parts by weight of isocetyl stearate were mixed and dissolved. The thus obtained magnetic paint was gravure coated on a polyester film, the orientation method was non-oriented, and the surface was smoothed by drying the solvent with a far-infrared lamp or hot air. After that, using an electron curtain type electron beam accelerator manufactured by ESI, the acceleration voltage was 150 KeV and the electrode current was 2.
The coating film was cured by irradiation with an electron beam in an N2 atmosphere under the conditions of 0 mA and a total irradiation dose of 5 Mrad. The thickness of the coating film (magnetic layer) after curing was 1.0JLll. Note that this film thickness was measured using an electronic micrometer. These coating films were formed on both sides of the film to form a double-sided coating. A 3.5-inch floppy disk was prepared using the sample thus prepared (Table 1), and its characteristics were investigated. Table 1 No. Powder
Powder l (comparison) 100 -2 (
Comparison) 95 5 6 (Comparison) 100 Characteristics were evaluated as follows. (1) Magnetic properties Hc and Br were measured using a vibrating sample magnetometer. (2) Linear recording density D5o (KFRPI) rotation speed 30
Or, p, wear 0, head: ferrite head, gap 0, linear recording density D5o (KFR
PI) was measured. (3) 40KFRPI output Measure the output at 40KFRPI in the same way as (2),
Relative values for sample N006 were determined. (4) Resolution In the measurement of the above linear recording density D5o, 64KFRPI
The resolution of /16KFRPI was calculated. Sample No. 1 O (comparison) of Example 2, which will be described later, was used as a reference, and this value was taken as 100%, and other values were converted into percentage units. (5) Electrical resistance (Ω/C) Cut the sample into a size of 100mm in width and 100cm in length. Temperature 20 on the measuring part
Measurement was carried out in the atmosphere at ±2°C and relative humidity of 65±5% by applying a DC voltage of 500V. (6) Durability The number of times the IF signal output decreased by 3 dB was measured in an environment of 20° C. and 60% RH. (7) #Brewing properties After holding the sample in an environment of 60° C. and 90% RH for 7 days, magnetic measurements were performed to determine the rate of decrease Δφm (%) in the saturation magnetic flux density φm from the initial state. The results are shown in Table 2. [Example 2] A sample (sample N
017-12) were produced. However, sample No., 1 O (comparison), No. 12 (
Comparative) only contains 10 parts by weight of carbon black (20ml) in the magnetic layer based on 120 parts by weight of magnetic powder. In this case, Co-yFe203 powder is γ-Fe203
Co2+ is diffused into a very thin layer within several dozen layers from the surface of the particles. This thing has coercive force Hc =
750 Oe powder. Furthermore, B a - F e 1! 019 powder is Ba-
F e 1201g is synthesized by a hydrothermal synthesis method with partially substituted B a and F e. Table 3 Sample Acicular FenCCo-γFe203 Ha-Fe
1201gNo. Powder Powder
Powder Powder 10 (comparison) -100- 12 (comparison) -100 3. Regarding sample Nos. 7 to 12 prepared in this way.
A 5-inch floppy disk was produced and its characteristics were investigated in the same manner as in Example 1. The results are shown in Table 4. [Example 3] Undercoat layers as shown below were formed on both the front and back surfaces of a polyester (PET) film having a thickness of 754 m. An-ko Weight part carbon black 20ml 50(A) Acrylic modified chloride, vinegar, vinyl alcohol copolymer Molecular weight 4
5.000 45(B) Acrylic modified polyurethane elastomer molecular weight 5,000
45(C) Pentaerythritol triacrylate O Stearic acid 2 Butyl stearate 2 Mixed solvent (MI
BK/ ) Luene = l/1) 300 The above mixture was dispersed in a ball mill for 5 hours, and the above polyester (P
E T) Coating onto the film to a dry thickness of 0.7 JL, surface smoothing treatment, and an acceleration voltage of 150 KeV using an electron curtain type electron beam accelerator.
Electrode current 10mA, absorbed dose 5M? ad, the undercoat layer was irradiated with an electron beam in N2 gas. The thickness of such an undercoat layer was 3JL11. Two layers are coated on both sides of the substrate provided with such an undercoat layer.
A magnetic paint was prepared in the same manner as in Example 1 using magnetic powders having the mixing ratios (% by weight) shown in Table 5 and Binder 2 below as a binder. ΔEL2 Nitrified cotton (without alcohol) (Cell line manufactured by Daicel Industries) 18 parts by weight (calculated as solid content), Urethane (Niraporan 3022 manufactured by Nippon Polyurethane Co., Ltd.)
12 parts by weight (in terms of solid content), 200 parts by weight of a solvent (MEK/cyclohexanone; 70/30), 3 parts by weight of stearic acid, and 3 parts by weight of butyl myristate were mixed and dissolved. However, after dispersion, the isocyanate compound (
5 parts by weight (in terms of solid content) of Coronate L manufactured by Nippon Polyurethane Co., Ltd. were added. The thus obtained magnetic paint was gravure coated on a 75% porcelain polyester film, with no orientation, and then the solvent was dried using a far infrared lamp or hot air, and the surface was smoothed. Thereafter, heat curing was performed at 80° C. for 48 hours. The thickness of the coating film (magnetic layer) after curing was 2 mm. Table 5 No. Powder Powder Regarding sample No. 13 prepared in this way, 3
．． A 5-inch floppy disk was produced and its characteristics were investigated in the same manner as in Example 1. The results are shown in Table 2. From the results shown in Tables 2 and 4, the effects of the present invention are clear. lJ'T-Satoni Ne Ichimasa-F (Spontaneous) November 11, 1985 Patent Application No. 226087, filed in 1985 2, Title of invention: Magnetic disk 3, Person making amendment °11 Relationship with patent application Person Poster Address 13-1 Shimome, Nihonbashi, Chuo-ku, Tokyo Name (306) TDC Co., Ltd. Representative Hiroshi Otoshi 4, Agent 101 Address 3-2-2 Iwamoto-cho, Chiyoda-ku, Tokyo [ Daita Iwamoto Building 4th floor ff1864-4498 Fax, 864-6280
,,+,)). 1 't to 12=' Specification-7 "Detailed Description of the Invention" Column 401 11. 1i 6, Contents of amendment (1) rm-14 on page 27, lines 4 and 6 of the specification
is corrected to rm=14. (2) Correct rm-2J on page 27, line 8 to rm=2. (3) After “cell line” on page 65, line 8, rF
Insert M-200J.

Claims (3)

[Claims] (1) In a magnetic disk having a recording layer containing magnetic particles and a binder on a flexible substrate, the magnetic particles include particles whose surfaces are at least iron carbide, and the iron carbide content in the magnetic particles is 5 to 5. A magnetic disk characterized in that it is 90% by weight. (2) Iron carbide of particles whose surface is iron carbide is F
Claim 1 having a composition of enC (n is 2 or more)
Magnetic disks described in section. (3) Claim 1 which includes metal magnetic particles, γ-iron oxide particles, cobalt-coated iron oxide particles, or barium or strontium ferrite particles as magnetic particles.
The magnetic disk according to item 1 or 2.