JPH038007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium, and particularly to a high-density magnetic recording medium having excellent lubricity and durability. BACKGROUND ART Magnetic recording media, particularly video tapes, require a low coefficient of friction and smooth and stable running over long periods of time because the tape runs while contacting magnetic heads, drums, guide poles, etc. In particular, tapes for rotating head type video tape recorders are required to have excellent durability because they are subjected to severe friction by the rotating magnetic head. For this reason, higher fatty acids, higher fatty acid esters, paraffinic hydrocarbons, silicone oil, etc. have traditionally been added to magnetic paints containing ferromagnetic powder and binders. However, these additives are not sufficient in imparting sufficient lubricity and durability to the videotape. It is also necessary to use a mixture of materials with good lubricity and materials with good durability. In addition, a so-called blooming phenomenon in which the magnetic layer oozes out onto the surface of the magnetic layer tends to occur, which causes sticking of the tape during storage. The main objects of the present invention are, firstly, to provide a new magnetic recording medium that improves the above-mentioned drawbacks, and secondly, to provide a magnetic recording medium that has excellent slipperiness and stable running properties. The third object is to provide a durable magnetic recording medium with excellent wear resistance, and the fourth object is to provide a magnetic recording medium free from the blooming phenomenon. As a result of intensive research, the present inventors found that remarkable results were obtained when a polyethylene glycol derivative represented by the following general formula was used as an additive.
This led to the present invention. That is, the above-mentioned object of the present invention is achieved by incorporating a polyethylene glycol ester represented by the following general formula into the magnetic layer. RCOO (-CH ₂ CH ₂ O) - _o H or RCOO (-CH ₂ CH ₂ O) - _o COR' [wherein, n is an integer from 5 to 500, and R and R' have a carbon number of 1 to 20 is a saturated or unsaturated aliphatic group. ] In the above formula, the saturated aliphatic or unsaturated aliphatic group having 1 to 20 carbon atoms in R is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, tridecyl, pentadecyl, It includes straight chain or branched saturated or unsaturated aliphatic groups such as heptadecyl and nonadecyl. Further, as _a specific example of the compound represented by the general formula, KESSCO PEG6000 distearate [6000 (MW)/ ₄₄ (M.
W.)≒136, n=136] PEG6000 monostearate, PEG1540 distearate [1540 (MW)/
44 (MW of CH ₂ CH ₂ O) = 35, n = 35], PEG1540
Monostearate, PEG200 distearate [200 (MW)/44 (MW of CH ₂ CH ₂ O) ≒ 5, n
=5], PEG200 monostearate, etc. Furthermore, esters of polyethylene glycol synthesized by dehydration condensation of polyethylene glycol and saturated or unsaturated aliphatic carboxylic acids are also specific examples of the above general formula. The polyethylene glycol mono- or diester represented by the above general formula is used in an amount of 0.1 to 5 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the ferromagnetic powder.
It can be contained in an amount of 3 parts by weight. If the amount of these compounds added is less than 0.1 part by weight, no reduction in the coefficient of dynamic friction will be observed, and if it is more than 5 parts by weight, the blooming phenomenon will easily occur, resulting in a decrease in the strength of the magnetic layer and poor wear resistance. The matter was confirmed. The magnetic recording material of the present invention is prepared by coating a non-magnetic support with a magnetic coating solution prepared by kneading and dispersing ferromagnetic fine powder, a binder, and a polyethylene glycol mono- or diester represented by the general formula using an organic solvent, and then drying. The magnetic layer is formed by doing this. In addition, it may contain several types of additives having functions such as dispersants, lubricants, abrasives, and antistatic agents. Ferromagnetic powders include γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and
Iron oxide ferromagnetic materials such as solid solutions of other metals such as Co and Zn, CrO ₂ or Li,
Metal atoms such as Na, Sn, Pb, Fe, Co, Ni, Zn,
These are chromium dioxide-based ferromagnetic materials such as those containing halogen atoms, etc., and metal ferromagnetic materials such as metals and alloys made of Fe, Co, Ni, etc. Among these, metal ferromagnetic materials have large saturation magnetization σs and coercive force Hc,
This has the advantage that a magnetic recording medium with high S/N and high recording density can be obtained. As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. As a thermoplastic resin, the softening temperature is 150℃ or less,
Average molecular weight is 10000~200000, degree of polymerization is about 200~
2000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer,
Vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic Acid ester styrene copolymer, urethane elastomer polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose protein) pionate, nitrocellulose, etc.), styrene-butadiene copolymer,
Polyester resins, amino resins, various synthetic rubber-based thermoplastic resins (polybutadiene, polychloroprene, polyisoprene, styrene-butadiene copolymers, etc.), and mixtures thereof are used. As a thermosetting resin or a reactive resin, it has a molecular weight of 200,000 or less in the state of a coating solution, and can be heated or otherwise processed after coating and drying to cause condensation,
The molecular weight becomes infinite due to reactions such as addition, such as phenol/formalin-novolac resin, phenol/formalin-resol resin, phenol/furfural resin, xylene/
Formaldehyde resin, urea resin, melamine resin, drying oil-modified alkyd resin, carbonic acid resin-modified alkyd resin, maleic acid resin-modified alkyd resin, unsaturated polyester resin, epoxy resin and curing agent (polyamine, acid anhydride, polyamide resin, etc.) , terminal isocyanate polyester moisture-curable resin, terminal isocyanate polyether moisture-curable resin, polyisocyanate prepolymer (compound having three or more isocyanate groups in one molecule obtained by reacting a diisocyanate and a low molecular weight triol, diisocyanate) trimers and tetramers), polyisocyanate prepolymers and resins containing active hydrogen (polyester polyols, polyether polyols, acrylic acid copolymers, maleic acid copolymers, 2-hydroxyethyl methacrylate copolymers, para-hydroxystyrene copolymers) polymers, etc.), oligomers and polymers with addition-polymerizable double bonds at their terminals or side chains, and mixtures thereof. These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic powder and the binder is 8 to 400 parts by weight of the binder to 100 parts by weight of the ferromagnetic powder, preferably 8 to 400 parts by weight.
It is used in an amount of 10 to 200 parts by weight, more preferably 10 to 100 parts by weight. In addition to the above-mentioned binder and fine ferromagnetic powder, additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be added to the magnetic recording layer. Dispersants include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Fatty acids with 12 to 18 carbon atoms such as linolenic acid and stearolic acid (R ₁ COOH, R ₁ is an alkyl or alkenyl group with 11 to 17 carbon atoms); Alkali metals of the above fatty acids (Li, Na, K, etc.) ) or alkaline earth metals (Mg, Ca, Ba); fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids; polyalkylene oxide alkyl phosphates; lecithin; Tetraammonium salts (alkyl having 1 to 5 carbon atoms, olefin being ethylene, propylene, etc.) are used. In addition, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder. As lubricants, conductive fine powder such as graphite; inorganic fine powder such as molybdenum disulfide and tungsten disulfide; polyethylene, polypropylene,
Fine plastic powder such as polyethylene vinyl chloride copolymer and polytetrafluoroethylene; α-
Olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olefin double bond is bonded to the terminal carbon, approximately 20 carbon atoms); a monobasic fatty acid with 12 to 20 carbon atoms and a carbon number Fatty acid esters consisting of 3 to 12 monohydric alcohols can be used. These lubricants are based on 100 parts by weight of binder.
It is added in a range of 0.2 to 20 parts by weight. Commonly used abrasive materials include fused alumina, silicon carbide, chromium oxide, corundum,
Artificial corundum, diamond, artificial diamond, garnet, emery (main ingredients: corundum and magnetite), etc. are used. These abrasives have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm.
A size of 0.1 is particularly preferable.
~2 μm. These abrasives are added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder. Antistatic agents include conductive fine powder such as carbon black and carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines, and quaternary surfactants. Cationic surfactants such as ammonium salts, pyridine and other heterocycles, phosphonium or sulfoniums; Anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups; Amino acids ,
Ampholytic activators such as aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, etc. are used. The above conductive fine powder is added in an amount of 0.2 to 20 parts by weight, and the surfactant is added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder. These additives may be added alone or in combination. These are used as dispersants, lubricants, abrasives, and antistatic agents, respectively, but are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids. In some cases. The magnetic recording layer of the present invention is formed by dissolving the above-mentioned composition in an organic solvent, kneading and dispersing, and coating each coating solution on a non-magnetic support and drying. After the magnetic layer is coated and before it is dried, a treatment for orienting the magnetic powder in each magnetic layer can be carried out, or a surface smoothing treatment can be carried out for each magnetic layer after drying. Materials for this non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose triacetate,
Cellulose derivatives such as cellulose diacetate, plastics such as polycarbonate, polyimide, and polyamide, non-magnetic metals such as Cu, Al, and Zn, and ceramics such as glass, porcelain, and earthenware are used. These nonmagnetic supports preferably have as good a surface roughness as possible, with a surface roughness of about 0.4 μm or less, preferably 0.3 μm or less, as measured by a stylus method. In addition, the form of the non-magnetic support is film, tape,
It may be a sheet, a disk, a card, a drum, etc., and various materials are selected as necessary depending on the form. The thickness of these non-magnetic supports is about 2 to 50 μm, preferably 3 to 25 μm when they are in the form of films, tapes, or sheets. Further, in the case of a disk or card shape, it is about 0.5 to 10 mm, and in the case of a drum shape, it is cylindrical, and the shape is determined depending on the recorder used. In the case of flexible supports such as films, tapes, sheets, thin flexible plates, etc., the non-magnetic support mentioned above is used on the opposite side of the magnetic layer for the purpose of preventing static electricity, preventing transfer, preventing wow and flutter, etc. The surface may be provided with a so-called backcoat. The magnetic powder, the above-mentioned binder, the organic silicone compound of the present invention, a dispersant, a lubricant, an abrasive, an antistatic agent, a solvent, etc. are kneaded to form a magnetic paint. During kneading, the magnetic powder and each of the above-mentioned components are fed into a kneader either simultaneously or individually one after another. For example, there is a method in which magnetic powder is first added to a solvent containing a dispersant and kneaded for a predetermined period of time to obtain a magnetic paint. Various kneaders are used for kneading and dispersing the magnetic coating liquid. For example, two-roll mill, three-roll mill, ball mill, pebble mill, tron mill, sand glider, Szegvari attritor,
These include high-speed impeller dispersion machines, high-speed stone mills, high-speed impact mills, dispers, kneaders, high-speed mixers, homogenizers, and ultrasonic dispersion machines. Methods for coating the magnetic recording layer on the support include air doctor coating, blade cord coating,
Air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, etc. can be used, and other methods are also possible. In the magnetic recording material of the present invention, a magnetic layer is coated on a nonmagnetic support by the above coating method and dried. Alternatively, two or more magnetic layers may be provided by repeating this step and performing a continuous coating operation. Furthermore, two or more magnetic layers may be provided simultaneously by a multilayer simultaneous coating method. Organic solvents used during coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid. Ester systems such as glycol monoethyl ether; glycol ether systems such as ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; tar systems (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, and tetrachloride Carbon, chloroform, ethylene chlorohydrin, chlorinated hydrocarbons such as dichlorobenzene, etc. can be used. By such a method, the magnetic layer coated on the support is optionally treated to orient the magnetic powder in the layer as described above, and then the formed magnetic layer is dried. Further, the magnetic recording body of the present invention is manufactured by subjecting it to surface smoothing processing or cutting it into a desired shape, if necessary. In particular, in the present invention, it has been found that by subjecting the magnetic recording layer to surface smoothing treatment, a magnetic recording body with a smooth surface and excellent wear resistance can be obtained. In this case, the orienting magnetic field is approximately 500
~2000 Gauss. The drying temperature of the magnetic layer is approximately
The temperature is about 50 to 120°C, preferably 70 to 100°C, particularly preferably 80 to 90°C, and the air flow rate is 1 to 5 K/m ² .
Preferably 2-3K/ ^m2 and drying time about 30 seconds.
It is about 10 minutes, preferably 1 to 5 minutes. The orientation direction of the magnetic material is determined by its use. i.e. sound tape, small video tape,
In the case of a memory tape, etc., the orientation is parallel to the length direction of the tape, and in the case of a broadcast video tape, etc., it is oriented at an angle of 30° to 90° with respect to the length direction. To smoothen the coating film of each of the magnetic layers before drying, a method such as a magnetic smoother, smoothing coil, smoothing blade, smoothing blanket, etc. may be used as necessary. The surface smoothing treatment after drying each of the magnetic layers described above is performed by calendering or the like. In the case of calendering, it is preferable to carry out the supercalendering method in which the material is passed between two rolls such as a metal roll and a cotton roll or a synthetic resin (for example, nylon) roll. The conditions of supercalender are about 25-100Kg/cm ² , preferably 30-80Kg/cm ² inter-roll pressure, about 35-100℃,
Preferably at a temperature of 40-80℃, 5-120m/min
It is preferable to carry out the processing at a processing speed of . Temperature and pressure above these upper limits have an adverse effect on the magnetic layer and non-magnetic support. Also, the processing speed is 5m/
If it is less than min, the effect of surface smoothing cannot be obtained, and about
If the speed is more than 120m/min, processing operation becomes difficult. It goes without saying that by adding the polyethylene glycol ester compound according to the present invention to the magnetic layer, the running properties and durability of the magnetic recording medium using metal oxide powder as the ferromagnetic material have been improved. It has been found that the running properties and durability of magnetic recording bodies using fine alloy powder, which have been difficult to satisfy these characteristics, are significantly improved. The present invention will be explained in more detail below using Examples and Comparative Examples. It will be readily understood by those skilled in the art that the ingredients, proportions, operations, order, etc. herein may be modified without departing from the spirit of the invention. Therefore, the present invention is not limited to the following examples. In addition, in the following Examples and Comparative Examples, all "parts" indicate "parts by weight." Example 1 Co-containing bertolite iron oxide 300 parts FeO _1.4 (Contains Co1.5 atom) Hc: 610 Oe Particle length: 0.6 μm Acicular ratio: 10/1 Maleic acid-containing vinyl chloride vinyl acetate copolymer
50 parts Copolymerization ratio (mole ratio): Vc/VAC/MA=86/
13/1 Polymerization degree: approx. 400 Polyester polyurethane 25 parts Reaction product of polyethylene adipate and 4,4'-diphenylmethane diisocyanate Average molecular weight (styrene equivalent molecular weight): approx. 130000 Polyethylene glycol disalate 6 parts (product name "PEG200") Distearate (manufactured by Armor) Butyl acetate 500 parts Methyl ethyl ketone 200 parts The above composition was placed in a ball mill and kneaded and dispersed for 24 hours to form 25 parts of a polyisocyanate compound (1 mol of trimethylolpropane and 3 mol of tolylene diacetate). 75wt of isocyanate adduct
% ethyl acetate solution) was added, followed by high-speed shear dispersion for 2 hours. After the above treatment, it was passed through a filter having an average pore size of 3 μm to obtain a magnetic coating solution. The magnetic coating solution described above was applied to a polyethylene terephthalate film (surface roughness, 0.3 μm) with a thickness of 14 μm to a dry thickness of 5 μm, oriented in the length direction of the film using a DC magnetic field, and after drying, super calendered. After processing, a wide magnetic field film was obtained.
This was slit into 1/2 inch width to obtain a 1/2 inch width videotape. Example 2 In Example 1, “PEG200 distearate”
A videotape was obtained in the same manner as in Example 1 using "PEG200 monostearate" instead of "PEG200 monostearate". Example 3 “PEG200 distearate” in Example 1
A videotape was obtained in the same manner as in Example 1 using "PEG6000 distearate" instead of "PEG6000 distearate". Comparative example 1 “PEG200 distearate” in Example 1
Example 1 using amyl stearate instead of
A videotape was obtained in the same manner. Comparative example 2 “PEG200 distearate” in Example 1
A videotape was obtained in the same manner as in Example 1 except that stearic acid was used instead of stearic acid. Example 4 Fe:Co:Ni (90:5:5wt%) alloy fine powder
300 parts Hc: 1400Oe Particle size: 0.5μm Maleic acid-containing vinyl chloride vinyl acetate copolymer
50 parts Copolymerization ratio (mol): Vc/VAc/MA=86/
13/1 Degree of polymerization: Approx. 400 Polyester polyurethane 25 parts Average molecular weight of reaction product of polyethylene adipate and 4,4'-diphenylmethane diisocyanate (styrene equivalent molecular weight): Approx.
130000 Polyethylene glycol distearate (trade name: "PEG200 distearate" manufactured by Armor) 6 parts Butyl acetate 500 parts Methyl ethyl ketone 400 parts Place the above composition in a ball mill and disperse for 24 hours.
25 parts of a polyisocyanate compound was added and the same operation as in Example 1 was carried out to obtain a videotape. Example 5 “PEG200 distearate” in Example 4
A videotape was obtained in the same manner as in Example 4 using "PEG200 monostearate" instead of "PEG200 monostearate". Example 6 “PEG200 distearate” in Example 4
Using "PEG6000 distearate" instead of
A videotape was obtained in the same manner as in Example 4. Comparative example 3 “PEG200 distearate” in Example 4
A videotape was obtained in the same manner as in Example 4, using amyl stearate instead. Comparative example 4 “PEG200 distearate” in Example 4
A videotape was obtained in the same manner as in Example 4 using stearic acid instead. Comparative example 5 “PEG200 distearate” in Example 4
A videotape was obtained in the same manner as in Example without adding. Table 1 shows the characteristics of the video tapes obtained in the above Examples and Comparative Examples, such as the coefficient of dynamic friction, steel durability, and running stability. Comparative example 6 “PEG200 distearate” in Example 1
A videotape was obtained in the same manner as in Example 1 except that polyethylene glycol (n=5) was used instead.

[Table] Example 7 “PEG200 distearate” in Example 1
A videotape was obtained in the same manner as in Example 1 using polyethylene glycol monostearate or polyethylene glycol distearate shown in Table 2 instead. Table 2 shows the properties of the videotape obtained in the above example, such as the coefficient of dynamic friction, steel durability, and running stability.

【table】

[Table] (1) Stainless steel pole (surface roughness 0.1s, 5mmφ)
In contact with, load pressure 50g, speed 3.3cm/sec
The coefficient of friction when running the tape (25℃,
(65%RH) (2) Electronic Industries Association of Japan (EIAJ) standard VHS standard
Still image installed in VTR cassette
mode, tape running is stopped, only the rotary head is rotated, and the same location on the tape is moved by the video head. At this time, the tape is
The time until the playback output obtained from the video head of the signal that has been scraped by the head and previously recorded on tape becomes almost zero. (3) In an EIAJ/VAS standard VTR, a certain tape length (for example, 10 m) is installed in a VHS standard cassette half, a certain signal is recorded on the 10 m tape length, and this is repeatedly played back. Measure the tape damage at this time. As shown in Table 1, the polyethylene glycol ester derivative represented by the general formula [] of the present invention is effective in reducing the coefficient of dynamic friction, provides extremely excellent durability, and has excellent running stability. It was confirmed that it imparts sex. Conventional lubricants include ester compounds with good still durability,
Although combination systems with long-chain fatty acids that have good running stability are well known, it has been confirmed that the polyethylene glycol ester derivative of the present invention has an even more excellent lubricating effect when used alone.

Claims (1)

[Scope of Claims] 1. A magnetic recording material comprising a binder and a magnetic layer made of fine ferromagnetic powder dispersed therein on a non-magnetic support, wherein the magnetic layer is made of polyethylene glycol represented by the following general formula: A magnetic recording medium characterized by containing an ester. RCOO(-CH ₂ CH ₂ O)- _o H or RCOO(-CH ₂ CH ₂ O)- _o COR' [wherein, n is an integer from 5 to 500, and R and R' have a carbon number of 1 to 20 represents a saturated or unsaturated aliphatic group. ]