JP2008037904A - Ether compound, lubricant and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant excellent in practical durability, also an ether compound suitably usable as the lubricant and further a magnetic recording medium excellent in durability and preservation stability by using the lubricant. <P>SOLUTION: This ether compound is expressed by formula (1) [wherein, R<SP>1</SP>is a 12-24C linear alkyl; R<SP>2</SP>is methyl or ethyl; and (n) is 1 to 6 integer]. The magnetic recording medium is provided by having at least 1 layer of a magnetic layer obtained by dispersing ferromagnetic fine powder in a binder, on a non-magnetic supporting material, and the magnetic layer contains the ether compound expressed by the formula (1). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ether compound, and also relates to a lubricant containing the ether compound. Furthermore, the present invention relates to a magnetic recording medium containing the ether compound.

Magnetic recording technology enables other recordings such as the ability to repeatedly use media, the ease of digitizing signals, the construction of systems in combination with peripheral devices, and the simple modification of signals. Since it has excellent features not found in the system, it has been widely used in various fields including video, audio, and computer applications.
Magnetic recording media that meet the recent demands for larger recording capacities and higher recording densities have extremely smooth surfaces in order to achieve their advanced electromagnetic conversion characteristics. When the recording head slides on this smooth surface at a high speed, it is extremely difficult to ensure durability with the conventional technology.
In order to improve the sliding durability of the magnetic recording medium, for example, a magnetic recording medium using a fluorine-containing compound having an oxyethylene moiety in the molecule as a surface modifier has been proposed (Patent Document 1). reference).
Further, a magnetic recording medium having a specific abrasive protrusion density on the surface and defining an acid hydrolysis rate has been proposed (see Patent Document 2).

Japanese Patent Laid-Open No. 11-12212 JP 2003-323711 A

An object of this invention is to provide the lubricant excellent in practical durability. Another object of the present invention is to provide an ether compound that can be suitably used for the lubricant.
Furthermore, another problem to be solved by the present invention is to provide a magnetic recording medium excellent in durability and storage stability using the ether compound or the lubricant.

The above-described problems of the present invention have been solved by means described in the following <1> to <3>.
<1> An ether compound represented by the formula (1).

式（１）中、Ｒ¹は炭素数１２〜２４の直鎖アルキル基を表し、Ｒ²はメチル基又はエチル基を表す。ｎは１〜６の整数を表す。

In the formula (1), R ¹ represents a linear alkyl group having 12 to 24 carbon atoms, and R ² represents a methyl group or an ethyl group. n represents an integer of 1 to 6.

<2> A lubricant comprising the ether compound described in <1>,
<3> A magnetic recording medium having at least one magnetic layer in which ferromagnetic fine powder is dispersed in a binder on a nonmagnetic support, wherein the magnetic layer contains the ether compound according to <1>. A magnetic recording medium characterized by:

According to the present invention, a lubricant excellent in practical durability can be provided. Moreover, the ether compound which can be used conveniently for the said lubricant can be provided.
Furthermore, according to the present invention, a magnetic recording medium excellent in durability and storage stability can be provided using the ether compound or the lubricant.

  The ether compound of the present invention is represented by the formula (1).

式（１）中、Ｒ¹は炭素数１２〜２４の直鎖アルキル基を表し、Ｒ²はメチル基又はエチル基を表す。ｎは１〜６の整数を表す。

In the formula (1), R ¹ represents a linear alkyl group having 12 to 24 carbon atoms, and R ² represents a methyl group or an ethyl group. n represents an integer of 1 to 6.

The ether compound of the present invention can be suitably used for a lubricant. It is preferable that the lubricant contains the ether compound of the present invention, and at least one compound is mixed as the other component.
Since the ether compound of the present invention does not absorb ultraviolet rays due to the C═O double bond as compared with a lubricant having an ester structure or a carbonate structure having the same molecular weight and viscosity, the weather resistance High nature.
In addition, in these ester compounds and carbonate compounds, phenomena due to photochemical reactivity, such as generation of fatty acids and corrosion of metals due to the generated fatty acids or generation of carbon dioxide gas derived from carbonate compounds, have become problems in practice. Yes. Therefore, the handling method of the lubricant having an ester structure or a carbonate structure is limited. The ether compounds of the present invention essentially free from these problems and remove many of the limitations of handling.
Furthermore, the ether compound of the present invention exhibits a viscosity equal to or lower than that of a fatty acid ester or carbonate ester having the same molecular weight, and therefore exhibits excellent performance as a lubricant.
In particular, when the ether compound of the present invention or a lubricant containing the ether compound is used for a magnetic recording medium, extremely high durability and storage stability can be achieved.

In formula (1), R ¹ is a linear alkyl group having 12 to 24 carbon atoms. When the carbon number of R ¹ is smaller than 12, the molecular weight is low and the volatility is high. On the other hand, when the carbon number of R ¹ exceeds 24, the viscosity becomes high and sufficient durability cannot be satisfied.
Preferably, the carbon number is an even number, and more preferably, the carbon number is any of 16, 18 or 20. An even number of carbon atoms is preferable because the corresponding raw material can be easily obtained and is inexpensive. In addition, since each value of the viscosity related to durability, the melting point related to ease of handling, and the boiling point related to volatilization in use is a preferred region, the carbon number is any of 16, 18 or 20 Is preferable.
R ¹ is preferably unsubstituted, and is preferably a linear alkyl group consisting of carbon and hydrogen.

R ² is a methyl group or an ethyl group. Preferably a methyl group is selected. When R ² is a methyl group, significant separation (phase separation) is derived from the hydrophilicity derived from the ether group in the ether compound of the present invention and the fact that it exhibits hydrophobicity with respect to the components constituting the magnetic recording medium. It is preferable because it is difficult to cause.
On the other hand, when R ² is hydrogen, the ether compound is crystallized, so that it takes a long time for dissolution before use, and further, it crystallizes on the magnetic recording medium and does not exhibit the desired lubricating action. On the other hand, when R ² is a group having more carbon atoms than the ethyl group (for example, propyl group, butyl group, etc.), the hydrophobicity becomes high and good lubricity cannot be obtained.

Moreover, n represents the integer of 1-6 in Formula (1). n is preferably 1 to 4, more preferably 1 to 3, and particularly preferably 1 to 2.
When n is 0, that is, when it does not have an oxyethylene group, the hydrophobicity is increased, phase separation from a mixed substance occurs, and long-term lubrication performance cannot be exhibited. On the other hand, when n is 7 or more, the viscosity is high and the lubricating performance is poor.

  Although the compound represented by Formula (1) of this invention is illustrated below, this invention is not limited to this.

  The ether compound of the present invention may be prepared by any method. Specifically, a method of synthesizing an ether by reacting a compound having a leaving group such as a halogen atom, a trifluoromethanesulfoxy group or a tosyloxy group on a hydrocarbon skeleton with an alkoxy anion such as an alkali metal salt of an alcohol. Preferred examples include a method of dehydrating and condensing one or two alcohols to synthesize an ether, a method of synthesizing an ether by an alcohol addition reaction to an alkene, and the like. Among these, a method of synthesizing an ether by reacting an alkoxy anion with a compound having a leaving group on the hydrocarbon skeleton is particularly preferable from the viewpoint of easy reaction and the like and ease of reaction. .

Uses of the ether compound of the present invention include additives for pharmaceuticals, additives for cosmetics, and lubricants. Preferred applications include use as additives or lubricants for cosmetics, and more preferable uses. For example, it may be used as a lubricant in a place where high-speed sliding is involved, such as a magnetic recording medium.
In addition, when using the ether compound of this invention for these uses, it can also be used individually by 1 type and can also use multiple types together.

(lubricant)
The lubricant of the present invention contains an ether compound represented by the formula (1). As the lubricant of the present invention, the ether compound represented by the formula (1) can be used alone, but it is preferable that at least one other compound is further mixed. Examples of the compound mixed with the ether compound represented by the formula (1) include various additives including a lubricating oil (lubricant base oil).
In the present invention, the lubricant contains the ether compound represented by the formula (1), but one type of the ether compound represented by the formula (1) can be used alone, or a plurality of types can be used. It can also be used together.

In the lubricant of the present invention, the following lubricating oils can be used as other components that can be used in combination with the ether compound represented by the formula (1). Examples thereof include olefin polymer oil, diester oil, polyalkylene glycol oil, and halogenated hydrocarbon oil.
Furthermore, the following compounds can also be used. That is, fatty acids having 12 to 18 carbon atoms (R, such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid ₁ COOH, R ₁ is an alkyl or alkenyl group having 11 to 17 carbon atoms), the fatty acid ester or the amide of the fatty acid, silicon oil, graphite, molybdenum disulfide, boron nitride, fluorinated graphite, fluorine alcohol, polyolefin , Polyglycol, alkyl phosphate ester, tungsten disulfide and the like.

In addition to the above, examples of additives that can be used in combination include antioxidants, oiliness improvers, extreme pressure additives, viscosity index improvers, pour point depressants, and other additives.
The antioxidant is blended in order to delay the deterioration of the acid value of the lubricant and prevent an increase in viscosity and corrosion due to the oxidation product. As the antioxidant, a chain reaction terminator, a peroxide decomposer, an ultraviolet absorber, a metal deactivator, and the like are added.
The oiliness improver is blended mainly for the purpose of reducing friction and reducing wear. Examples include long chain compounds having a polar group, such as higher fatty acids, higher alcohols, esters, amines, metal soaps, and the like.
The extreme pressure additive, when local metal contact occurs on the friction surface under severe conditions, reacts with the metal surface due to the frictional heat accompanying this to form a reaction film with low shear strength, seizing and abrasion Formulated to prevent Oil-soluble compounds such as phosphorus, sulfur and halogen, and organometallic compounds such as zinc and molybdenum are used.
The viscosity index improver is used to reduce the viscosity change due to the temperature of the lubricant, and examples thereof include polymethacrylate.
A pour point depressant is added when wax (network saturated hydrocarbon) dissolved in oil grows into a network structure and loses fluidity as the lubricant is cooled. Polymethacrylate is used as the pour point depressant.
Examples of other additives include cleaning dispersants, rust inhibitors, antifoaming agents, and emulsifiers.
Cleaning dispersants are mainly added when lubricants are used in engine oils, and are caused by deterioration products from long-term use, dirt in the engine caused by soot and incomplete combustion of fuel. And formulated to prevent troubles.
Detergents are detergents (mainly metal type and disperse sludge generated in high temperature operation) and dispersants (mainly ashless type and disperse sludge generated in low temperature operation) according to their function and function. are categorized.

When the ether compound of the present invention is used in a lubricant, the content is preferably 30% by weight or more of the entire lubricant. It is preferable for the content of the ether compound of the present invention to be in the above range since a lubricant having excellent durability can be obtained.
Moreover, as a compound used together, a C12-C18 fatty acid and its amide are preferable. The total amount of the compounds used in combination is preferably less than 70% by weight of the entire lubricant.

(Magnetic recording medium)
The magnetic recording medium of the present invention has at least one magnetic layer formed by dispersing ferromagnetic powder and a binder on a nonmagnetic support, and the magnetic layer contains the ether compound of the present invention. The ether compound of the present invention is added to the magnetic layer as a lubricant.
The magnetic layer preferably contains 0.1 to 10 parts by weight, more preferably 0.2 to 5% by weight, of the ether compound of the present invention based on 100 parts by weight of the ferromagnetic powder of the magnetic layer. In addition, when the ether compound of the present invention is used in the magnetic layer of a magnetic recording medium, it is also preferable to add it as a lubricant containing at least one compound in addition to the ether compound of the present invention. In this case, it is preferable to contain 0.2-20 weight part of lubricants with respect to 100 weight part of ferromagnetic powder, and it is more preferable to contain 0.4-10 weight part. It is preferable for the content to be in the above range since good durability and storage stability can be obtained.
The magnetic recording medium of the present invention has at least one magnetic layer formed by dispersing ferromagnetic powder and a binder on a nonmagnetic support, and the magnetic layer contains a lubricant. It is also preferable to contain the ether compound of this invention.

Conventionally, as a function of the lubricant present on the surface of the magnetic layer, it has been found that the amount of lubricant on the surface is closely related to the sliding characteristics of the head and the tape. Since the lubricant is stably present on the surface of the magnetic layer, the sliding resistance between the head and the tape can be reduced, and the running durability can be improved. With the recent demand for higher capacity of magnetic recording media, it is necessary to reduce the thickness of the magnetic layer. However, the amount of lubricant that can be impregnated in the magnetic layer decreases as the thickness is reduced. For this reason, if the lubricant is gradually removed by sliding with the recording / reproducing head and the lubricant is insufficient, the magnetic layer may be scraped and may be stopped. Further, the surface of the magnetic layer needs to be smoothed more and more in order to improve the magnetic properties. For this reason, conventional lubricants are no longer able to exhibit sufficient running performance, repeated running performance, and durability. Conventionally, if the amount of lubricant is increased in order to increase the lubrication effect, the mechanical strength of the magnetic coating film becomes weaker, the magnetic layer is scraped, the shaving powder contaminates the travel path, or sufficient repeated travel durability is achieved. I couldn't get it. A preferable thickness of the magnetic layer will be described later.
Conventionally, it is known to use a fatty acid ester such as butyl stearate and a fatty acid such as myristic acid as a lubricant for the magnetic layer. However, when the fatty acid ester and the fatty acid are mixed and used, there is a problem in that the friction increases when running in a high humidity state, and the running tension of the magnetic tape increases.
Moreover, when a fatty acid was used alone, it was necessary to use a large amount in order to obtain lubricity. In this case, the magnetic layer becomes soft, the mechanical strength decreases, and the high-speed sliding durability corresponding to the relative speed between the tape and the head deteriorates.
The combined use of a fatty acid and a fatty acid ester compound provides good high-speed sliding durability and relatively low tension, but has the disadvantage of increased running tension under high humidity conditions such as 85% RH (relative humidity). Was.

  The present inventors have found that good running durability can be secured by using the ether compound of the present invention. The ether compound of the present invention has high fluid lubricity because of its low viscosity relative to the molecular weight, and since the bond is not an ester bond such as a fatty acid ester but an ether bond, hydrolysis is unlikely to occur and storage stability is high.

I. Magnetic layer The magnetic layer in the magnetic recording medium of the present invention is a layer containing the ether compound of the present invention and in which a ferromagnetic powder is dispersed in a binder, and is a layer that contributes to magnetic recording and reproduction thereof.

<Ferromagnetic powder>
Ferromagnetic powder used in the magnetic recording medium of the present invention, S _BET specific surface area in the cobalt-containing ferromagnetic iron oxide or ferromagnetic alloy powder is preferably 40 to 80 m ² / g, more preferably 50 to 70 m ² / g. The crystallite size is preferably 12 to 25 nm, more preferably 13 to 22 nm, and particularly preferably 14 to 20 nm. The major axis length is preferably 0.05 to 0.25 μm, more preferably 0.07 to 0.2 μm, and particularly preferably 0.08 to 0.15 μm.

Examples of the ferromagnetic powder include Fe, Fe—Co, Fe—Ni, and Co—Ni—Fe containing yttrium. The yttrium content in the ferromagnetic powder is the ratio of yttrium atoms to iron atoms, Fe is preferably 0.5 atomic% to 20 atomic%, more preferably 5 to 10 atomic%. Within the above range, the ferromagnetic powder can have a high σ _S , and since the iron content is appropriate, the magnetic properties are good and the electromagnetic conversion properties are excellent, which is preferable. Furthermore, within a range of 20 atomic% or less with respect to 100 atomic% of iron, aluminum, silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, copper, zinc, molybdenum, rhodium, palladium, tin, antimony, boron, Barium, tantalum, tungsten, rhenium, gold, lead, phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium, bismuth, and the like can be included. Further, the ferromagnetic metal powder may contain a small amount of water, hydroxide or oxide.

An example of a method for producing a ferromagnetic powder incorporating cobalt and yttrium in the magnetic recording medium of the present invention will be described. An example in which iron oxyhydroxide obtained by blowing an oxidizing gas into an aqueous suspension in which a ferrous salt and an alkali are mixed is used as a starting material. As the type of this iron oxyhydroxide, α-FeOOH is preferred, and as its production method, a ferrous salt is neutralized with an alkali hydroxide to form an aqueous suspension of Fe (OH) _2. There is a first manufacturing method in which an oxidizing gas is blown into needle-like α-FeOOH. On the other hand, there is a second production method in which ferrous salt is neutralized with alkali carbonate to form an aqueous suspension of FeCO ₃ , and oxidizing gas is blown into this suspension to form spindle-shaped α-FeOOH. Such iron oxyhydroxide is obtained by reacting a ferrous salt aqueous solution with an alkaline aqueous solution to obtain an aqueous solution containing ferrous hydroxide and oxidizing it by air oxidation or the like. Is preferred. At this time, Ni salt, alkaline earth element salt such as Ca salt, Ba salt and Sr salt, Cr salt and Zn salt may coexist in the ferrous salt aqueous solution. The particle shape (axial ratio) etc. can be adjusted by selecting and using.

  As the ferrous salt, ferrous chloride, ferrous sulfate and the like are preferable. As the alkali, sodium hydroxide, aqueous ammonia, ammonium carbonate, sodium carbonate and the like are preferable. Moreover, as a salt which can coexist, chlorides, such as nickel chloride, calcium chloride, barium chloride, strontium chloride, chromium chloride, zinc chloride, are preferable. Next, when introducing cobalt into iron, before introducing yttrium, an aqueous solution of a cobalt compound such as cobalt sulfate or cobalt chloride is stirred and mixed into the iron oxyhydroxide slurry. After preparing a slurry of iron oxyhydroxide containing cobalt, an aqueous solution containing a compound of yttrium can be added to the slurry and mixed by stirring.

  In addition to yttrium, neodymium, samarium, praseodymium, lanthanum, gadolinium, and the like can be introduced into the ferromagnetic powder of the present invention. These can be introduced using chlorides such as yttrium chloride, neodymium chloride, samarium chloride, praseodymium chloride, lanthanum chloride, and nitrates such as neodymium nitrate and gadolinium nitrate. Also good. There are no particular restrictions on the shape of the ferromagnetic powder, but needle-shaped, granular, dice-shaped, rice-grained and plate-shaped ones are usually used. It is particularly preferable to use acicular ferromagnetic powder.

Hexagonal ferrite powder can also be used as the ferromagnetic powder used in the magnetic layer of the present invention.
Examples of hexagonal ferrite include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitution, and Co substitution. Specific examples include magnetoplumbite type barium ferrite and strontium ferrite, magnetoplumbite type ferrite whose particle surface is coated with spinel, and magnetoplumbite type barium ferrite and strontium ferrite partially containing a spinel phase. In addition to predetermined atoms, Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Atoms such as Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, B, Ge, Nb, and Zr may be included. For example, a material to which elements such as Co-Ti, Co-Ti-Zr, Co-Ti-Zn, Ni-Ti-Zn, Nb-Zn-Co, Sb-Zn-Co, and Nb-Zn are added is preferably used. be able to. Some raw materials and manufacturing methods contain specific impurities.

The particle size is preferably a hexagonal plate diameter of 10 to 200 nm, more preferably 20 to 100 nm. Further, when reproducing with a magnetoresistive head, it is necessary to reduce the noise, and the plate diameter is preferably 40 nm or less. Within the above range, thermal fluctuations are less likely to occur, stable magnetization can be obtained, and noise can be suppressed low, which is preferable.
The plate ratio (plate diameter / plate thickness) is preferably 1-15, more preferably 2-7. A plate ratio in the above range is preferable because sufficient orientation can be obtained, and there is little stacking between particles and noise can be kept low. The specific surface area (S _BET ) according to the BET method in this particle size range is 10 to ²⁰⁰ m ² / g. The specific surface area generally agrees with the arithmetic calculation value from the particle plate diameter and plate thickness.
The crystallite size is preferably 50 to 450 mm (5 to 45 nm), more preferably 100 to 350 mm (10 to 35 nm). The distribution of the particle plate diameter and plate thickness is generally preferably as narrow as possible. Although numerical conversion is difficult, it can be compared by randomly measuring 500 particles from a particle TEM photograph. In many cases, the distribution is not a normal distribution, but when calculated and expressed as a standard deviation with respect to the average size, it is preferable that σ / average size = 0.1 to 2.0. In order to sharpen the particle size distribution, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improvement process. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known.

The coercive force Hc measured with a magnetic material can be made up to about 500 Oe to 5,000 Oe (39.8 kA / m to 398 kA / m). A higher Hc is advantageous for high-density recording, but is limited by the capacity of the recording head. The coercive force Hc is preferably 800 Oe to 4,000 Oe (63.7 kA / m to 318.4 kA / m), more preferably 1,500 Oe (119.4 kA / m) to 3,500 Oe. (278.6 kA / m) or less. When the saturation magnetization of the head exceeds 1.4 Tesler, it is preferable to set it to 2,000 Oe or more. Hc can be controlled by the particle size (plate diameter / plate thickness), the type and amount of the contained element, the substitution site of the element, the particle generation reaction conditions, and the like.
Saturation magnetization σs is preferably 40emu / g~80emu / g (40A · m 2 / kg~80A · m 2 / kg). Higher σs is preferred, but tends to be smaller as the particles become finer. In order to improve σs, it is well known to combine spinel ferrite with magnetoplumbite ferrite and to select the type and amount of elements contained. It is also possible to use W-type hexagonal ferrite.

When the magnetic material is dispersed, the surface of the magnetic material particles is also treated with a material suitable for the dispersion medium and the polymer. As the surface treatment agent, an inorganic compound or an organic compound is used. Typical examples of the main compound include oxides or hydroxides such as Si, Al, and P, various silane coupling agents, and various titanium coupling agents. The amount is preferably 0.1 to 10% with respect to the magnetic substance.
The pH of the magnetic material is also important for dispersion. Usually, it is about 4 to 12, and there is an optimum value depending on the dispersion medium and the polymer, but about 6 to 10 is preferably selected from the chemical stability and storage stability of the medium. Water contained in the magnetic material also affects the dispersion. Although there is an optimum value depending on the dispersion medium and the polymer, it is preferably 0.01 to 2.0%.

  The hexagonal ferrite can be manufactured by (1) mixing a metal oxide replacing barium oxide, iron oxide, iron and boron oxide as a glass forming substance so as to have a desired ferrite composition, and then melting and quenching. Glass crystallization method to obtain barium ferrite crystal powder by making it amorphous and then reheating treatment, (2) neutralizing barium ferrite composition metal salt solution with alkali, Hydrothermal reaction method to obtain barium ferrite crystal powder by liquid phase heating at 100 ° C or higher after removal, washing, drying and grinding, (3) neutralizing barium ferrite composition metal salt solution with alkali, by-product There is a coprecipitation method in which the product is removed and then dried, treated at 1,100 ° C. or less, and pulverized to obtain a barium ferrite crystal powder, but the present invention does not select a production method.

Further, iron nitride particles can also be used as the ferromagnetic powder that can be used in the magnetic layer in the magnetic recording medium of the present invention.
The iron nitride particles that can be used in the present invention are spherical or spheroidal iron nitride-based magnetic materials containing at least Fe and N as constituent elements. Here, “spherical” means a particle having a ratio of the maximum length / minimum length of the particle diameter of 1 or more and less than 2, and “spheroid” means a ratio of the maximum length / minimum length of the particle diameter of 2 or more. It means particles that are less than 4.

The iron nitride based magnetic body and the method for manufacturing the same will be described below.
The iron nitride particles desirably include at least an Fe ₁₆ N ₂ phase, and preferably do not include other iron nitride phases. This is because the magnetocrystalline anisotropy of iron nitride (Fe ₄ N or Fe ₃ N phase) is about 1 × 10 ⁻¹ J / cm ³ (1 × 10 ⁵ erg / cc), whereas Fe ₁₆ N _{This is because the two} phases have a high magnetocrystalline anisotropy of 2 to 7 × 10 ⁻¹ J / cm ³ (2 to 7 × 10 ⁶ erg / cc). Thereby, a high coercive force can be maintained even when the particles are made fine.
This high magnetocrystalline anisotropy results from the crystal structure of the Fe ₁₆ N ₂ phase. The crystal structure is a body-centered tetragonal system in which N atoms regularly enter the Fe interstitial positions of Fe, and the strain when N atoms enter the lattice is considered to be the cause of high crystal magnetic anisotropy. . The easy axis of magnetization of the Fe ₁₆ N ₂ phase is the C axis extended by nitriding.

The shape of the particles containing the Fe ₁₆ N ₂ phase is preferably spherical or spheroidal. More preferably, it is spherical. This is because one of three equivalent directions of cubic α-Fe is selected by nitriding and becomes the c-axis (easy axis of magnetization). This is because particles in the direction and the major axis direction are mixed, which is not preferable. The average value of the major axis length / minor axis length ratio is preferably 1 to 2, more preferably 1 to 1.5, with the maximum diameter of one particle being the major axis length and the smallest diameter being the minor axis length. What is described as particle size represents the major axis length.

The particle size of the Fe ₁₆ N ₂ phase, which is a magnetic material, is preferably 5 to 50 nm, and more preferably 10 to 30 nm. This is because if the particle size is 5 nm or more, the influence of thermal fluctuation is small and superparamagnetization is not achieved, so that it can be suitably used for a magnetic recording medium. Also, it is preferable because the coercive force at the time of high-speed recording with a head increases due to the magnetic viscosity, and it does not become difficult to record. On the other hand, when the particle size is 50 nm or less, the saturation magnetization can be reduced, the coercive force at the time of recording is appropriate, and it can be suitably used for recording, which is preferable. Further, it is preferable that the particle size is 50 nm or less, since the particle noise when the magnetic recording medium is used is low.

The particle size distribution is preferably monodisperse. This is because, in general, monodispersion reduces the medium noise. The coefficient of variation of the particle size is preferably 20% or less (1 to 20%), more preferably 15% or less (2 to 15%), and further preferably 10% or less (2 to 10%). .
In the present specification, the “coefficient of variation in particle size” means a value obtained by calculating a standard deviation of the particle size distribution with an equivalent circle diameter and dividing this by the average particle size. The “composition variation coefficient” means a value obtained by calculating a standard deviation of the composition distribution of the alloy nanoparticles and dividing this by the average composition in the same manner as the particle diameter variation coefficient. In the present invention, these values are multiplied by 100 to display%.

  The particle diameter and the coefficient of variation of the particle diameter are obtained by placing diluted alloy nanoparticles on Cu200 mesh with a carbon film and drying it, and photographing at a magnification of 100,000 using TEM (1200EX manufactured by JEOL Ltd.). It can calculate from the arithmetic average particle diameter measured by the particle size measuring device (KS-300 by Carl Zeiss) using the obtained negative.

In the particles containing the Fe ₁₆ N ₂ phase, the content of nitrogen with respect to iron is preferably 1.0 to 20.0 atm%, more preferably 5.0 to 18.0 atm%, more preferably 8.0 to 15. 0 atm%. This is because the formation amount of Fe ₁₆ N ₂ phase is good when the nitrogen content is 1.0 atm% or more. Further, the increase in coercive force is caused by strain due to nitriding, and a good coercive force can be obtained when the nitrogen content is 1.0 atm% or more. In addition, when the nitrogen content is 20.0 atm% or less, the Fe ₁₆ N ₂ phase is a metastable phase, and thus may decompose to other nitrides that are stable phases. This is preferable because the saturation magnetization does not decrease due to this.

The fine Fe ₁₆ N ₂ phase has poor oxidation stability, and there is a concern that it will ignite if there is no surface compound phase. Therefore, a core / shell structure having a surface compound layer made of an oxide, nitride, or carbide is preferable. From the viewpoint of oxidation stability, the surface compound layer is preferably an oxide.
The surface compound layer can be formed by gradually oxidizing the Fe ₁₆ N ₂ phase, but a surface compound layer containing a rare earth element or at least one element selected from boron, silicon, aluminum, and phosphorus is used. It is preferable.
The thickness of the surface compound layer is preferably 1 to 5 nm. It is preferable that the thickness of the surface compound layer is 1 nm or more because sufficient oxidation stability can be obtained. Further, if it is 5 nm or less, the ratio of the surface compound layer in the magnetic powder is small, and even if the particle size is reduced, an appropriate amount of saturation magnetization can be maintained, which is preferable.
As for the composition of the surface compound layer, the total content of rare earth elements or boron, silicon, aluminum and phosphorus relative to iron is preferably 0.1 to 40.0 atm%, more preferably 1.0 to 30.0 atm%. More preferably, it is 3.0-25.0 atm%. When the content of these elements is 0.1 atm% or more, the surface compound layer can be formed, the magnetic powder has good magnetic anisotropy, and good oxidation stability is obtained, which is preferable. . Moreover, it is preferable that the content of these elements is 40.0 atm% or less because good saturation magnetization can be obtained.

Saturation magnetization of the Fe ₁₆ N ₂ phase ([sigma] s) is preferably ^{50~150emu / g (50~150A · m 2} / kg), in ^{70~130emu / g (70~130A · m 2} / kg) More preferably. It is preferable that the saturation magnetization is 150 emu / g (150 A · m ² / kg) or less because the holding force at the time of recording is appropriate and it can be suitably used for recording with a recording head. Also in reproduction, the MR head is not saturated and an improvement in output can be expected, which is preferable. On the other hand, it is preferable that it is 50 emu / g (50 A · m ² / kg) or more because a good reproduction output can be obtained.
The magnetic powder preferably has a BET specific surface area (S _BET ) of 40 to 100 m ² / g. When the BET specific surface area is 40 m ² / g or more, the particle size is appropriate, and when applied to a magnetic recording medium, the particle noise is low, the surface smoothness of the magnetic layer is good, and the reproduction is good. This is preferable because an output can be obtained.
Moreover, it is preferable for the BET specific surface area to be 100 m ² / g or less because the particles containing the Fe ₁₆ N ₂ phase hardly aggregate, a uniform dispersion can be obtained, and a smooth surface can be obtained.

[Synthesis of α-Fe]
A method for producing particles containing the Fe ₁₆ N ₂ phase will be described. The Fe ₁₆ N ₂ phase is obtained by nitriding α-Fe. There are two methods for obtaining α-Fe: a method in which iron-based oxides or hydroxides (eg, hematite, magnetite, goethite, etc.) are reduced in the gas phase, and a method in which they are synthesized in the liquid phase.
First, a method for reducing in the gas phase will be described. The average particle size of the iron-based oxide or hydroxide is not particularly limited, but is usually preferably about 5 to 100 nm. When the particle size is 5 nm or more, it is preferable that inter-particle sintering is unlikely to occur during the reduction treatment, and when the particle size is 100 nm or less, the reduction treatment becomes uniform and the control of the particle diameter and magnetic properties is good.

In addition, a rare earth element or a compound containing at least one element selected from boron, silicon, aluminum, phosphorus, etc. is deposited on iron-based oxide or hydroxide to prevent sintering. Is preferred. Rare earth element deposition involves dispersing a starting material in an aqueous solution of alkali or acid, dissolving a salt of the rare earth element in this, and adding a hydroxide or hydrate containing the rare earth element to the raw material powder by a neutralization reaction or the like. It can be performed by precipitation. When depositing a compound containing at least one element selected from boron, silicon, aluminum, phosphorus, etc., these compounds are dissolved in a solution in which the raw material powder is immersed and deposited by adsorption, It is deposited by precipitation.
A rare earth element and at least one element selected from boron, silicon, aluminum, phosphorus and the like may be simultaneously or alternately deposited on the hydroxide or hydrate. Moreover, in order to perform these deposition processes efficiently, it is also preferable to mix additives, such as a reducing agent, a pH buffer agent, and a particle size control agent.

Next, the hydroxide or hydrate to which the compound is applied is heated in a reducing gas stream. As the reducing gas, hydrogen gas or carbon monoxide gas can be used. Hydrogen which becomes H ₂ O after the treatment is preferably used from the viewpoint of environmental suitability.
The reduction temperature is preferably 250 to 600 ° C, more preferably 300 to 500 ° C. This temperature range is preferable because the reduction temperature sufficiently proceeds and particle sintering can be prevented.

  A method of synthesizing α-Fe in the liquid phase is preferably used as a method for avoiding the sintering of the particles in the gas phase reduction. As a method for producing iron nanoparticles (iron particles having a size of nano order), classification by precipitation method, alcohol reduction method using primary alcohol, secondary alcohol, tertiary alcohol, divalent or trivalent polyvalent A polyol reduction method using alcohol, a thermal decomposition method, an ultrasonic decomposition method, and a strong reducing agent reduction method are known. Further, the production method is classified into a reaction system, and a polymer existence method, a high boiling point solvent method, a normal micelle method, a reverse micelle method, and the like are known.

  First, the reverse micelle method which is easy to control the particle size and easily obtain a monodispersed dispersion and is preferably used in the present invention will be described.

[Reverse micelle synthesis method of iron nanoparticles]
Next, a method for producing alloy nanoparticles will be described.
The alloy nanoparticles include a reduction step in which a reverse micelle solution (I) containing one or more metal compounds and a reverse micelle solution (II) containing a reducing agent are mixed to perform a reduction treatment, and the reduction treatment as necessary. It can be manufactured by an aging process in which an aging treatment is performed later. By this production method, iron nanoparticles are produced. Hereinafter, each step will be described.

[Reduction process]
First, a reverse micelle solution (I) is prepared by mixing a water-insoluble organic solvent containing a surfactant and an aqueous solution containing one or more metal compounds. The reverse micelle solution (I) contains an iron salt used to form iron nanoparticles.

  An oil-soluble surfactant is used as the surfactant. Specifically, sulfonate type (for example, aerosol OT (manufactured by Wako Pure Chemical Industries), quaternary ammonium salt type (for example, cetyltrimethylammonium bromide), ether type (for example, pentaethylene glycol dodecyl ether) and the like can be mentioned. It is done.

Preferred as the water-insoluble organic solvent for dissolving the surfactant are alkanes and ethers. The alkane is preferably an alkane having 7 to 12 carbon atoms. Specific examples include heptane, octane, nonane, decane, undecane, and dodecane. On the other hand, the ether is preferably diethyl ether, dipropyl ether, or dibutyl ether.
The addition amount of the surfactant in the water-insoluble organic solvent is preferably 20 to 200 g / l.

  Metal compounds contained in an aqueous solution of a metal compound include nitrates, sulfates, hydrochlorides, acetates, metal complex hydrogen acids with chloride ions as ligands, and metal complex potassiums with chloride ions as ligands. Examples include salts, sodium salts of metal complexes having chloride ions as ligands, and ammonium salts of metal complexes having oxalate ions as ligands, and these can be arbitrarily selected and used in the production method of the present invention. can do.

The concentration of each metal compound aqueous solution as the metal compound is preferably 0.1 to 2,000 μmol / ml, and more preferably 1 to 500 μmol / ml.
It is preferable to add a chelating agent to the aqueous metal compound solution so that the resulting particles have a uniform composition. Specifically, DHEG (dihydroxyethylglycine), IDA (iminodiacetic acid), NTP (nitrilotripropionic acid), HIDA (dihydroxyethyliminodiacetic acid), EDDP (ethylenediamine dipropionic acid dihydrochloride), BAPTA It is preferable to use (diaminophenylethylene glycol tetraacetic acid tetrapotassium salt hydrate) or the like as a chelating agent. The chelate stability constant (log K) is preferably 10 or less.
The addition amount of the chelating agent is preferably 0.1 to 10 mol, more preferably 0.3 to 3 mol, per 1 mol of the metal compound.

  Next, a reverse micelle solution (II) containing a reducing agent is prepared. The reverse micelle solution (II) can be prepared by mixing a water-insoluble organic solvent containing a surfactant and an aqueous reducing agent solution. When two or more reducing agents are used, they may be mixed together to form a reverse micelle solution (II), but in consideration of the stability and workability of the solution, each is separately mixed in a water-insoluble organic solvent. Thus, it is preferable to prepare them as separate reverse micelle solutions ((II ′), (II ″), etc.) and to use them by appropriately mixing them.

Examples of the reducing agent aqueous solution include alcohols; polyalcohols; H ₂ ; HCHO, S ₂ O ₆ ²⁻ , H ₂ PO ₂ ⁻ , BH ₄ ⁻ , N ₂ H ₅ ⁺ , H ₂ PO ₃ ^{− and the} like and water. These reducing agents are preferably used alone or in combination of two or more.
The amount of the reducing agent in the aqueous solution is preferably 3 to 50 mol with respect to 1 mol of the metal salt.

  Examples of the surfactant and non-aqueous organic solvent used in the reverse micelle solution (II) include those used in the reverse micelle solution (I).

  The weight ratio of water and surfactant (water / surfactant) contained in each of the reverse micelle solutions (I) and (II) is preferably 20 or less. A weight ratio of 20 or less is preferable because precipitation hardly occurs and uniform particles can be obtained. The weight ratio is more preferably 15 or less, and further preferably 0.5 to 10.

  The weight ratio of the water and the surfactant in the reverse micelle solutions (I) and (II) may be the same or different, but the weight ratio is preferably the same in order to make the system uniform.

The reverse micelle solutions (I) and (II) prepared as described above are mixed. The mixing method is not particularly limited, but it is preferable to add and mix the reverse micelle solution (II) while stirring the reverse micelle solution (I) in consideration of the reduction uniformity. The reduction reaction is allowed to proceed after completion of the mixing, and the temperature at that time is preferably a constant temperature in the range of -5 to 30 ° C. If the reduction temperature is −5 ° C. or higher, the reduction reaction can be made uniform without condensation of the aqueous phase, and if it is 30 ° C. or lower, aggregation or precipitation is unlikely to occur and the system is stabilized. Is preferable. A more preferable reduction temperature is 0 to 25 ° C, and further preferably 5 to 25 ° C.
Here, the “constant temperature” means that the temperature is in a range of T ± 3 ° C. when the set temperature is T (° C.). Even in such a case, the upper limit and the lower limit of the T are in the range of the reduction temperature (−5 to 30 ° C.).

The time for the reduction reaction needs to be appropriately set depending on the amounts of the reverse micelle solutions (I) and (II), but is preferably 1 to 30 minutes, and more preferably 5 to 20 minutes.
Since the reduction reaction greatly affects the monodispersity of the particle size distribution of the alloy, it is preferable to carry out the reduction reaction while stirring as fast as possible (for example, about 3,000 rpm or more).
A preferred stirring device is a stirring device having a high shearing force. Specifically, the stirring blade basically has a turbine-type or paddle-type structure, and further, a sharp blade is attached to the end of the blade or a position in contact with the blade. It is a stirring device that has a structure and rotates blades with a motor. Specifically, devices such as a dissolver (manufactured by Special Machine Industries Co., Ltd.), an omni mixer (manufactured by Yamato Scientific Co., Ltd.), and a homogenizer (manufactured by SMT Co., Ltd.) are useful. By using these apparatuses, monodispersed nanoparticles can be synthesized as a stable dispersion, which is preferable.

  After the reaction of the reverse micelle solutions (I) and (II), at least one dispersant having 1 to 3 amino groups or carboxy groups is added in an amount of 0.001 to 10 per mole of alloy nanoparticles to be prepared. It is preferable to add a molar amount. If the addition amount of a dispersing agent is 0.001-10 mol, since the monodispersibility of an alloy nanoparticle can be improved more and aggregation does not occur, it is preferable.

As the dispersant, an organic compound having a group that adsorbs to the surface of the alloy nanoparticles is preferable. Specifically, it has 1 to 3 amino groups, carboxy groups, sulfonic acid groups or sulfinic acid groups, and these can be used alone or in combination.
As structural formulas, R—NH ₂ , H ₂ N—R—NH ₂ , H ₂ N—R (NH ₂ ) —NH ₂ , R—COOH, HOCO—R—COOH, HOCO—R (COOH) —COOH _{, R-SO 3 H, HOSO} 2 -R-SO 3 H, HOSO 2 -R (SO 3 H) -SO 3 H, R-SO 2 H, HOSO-R-SO 2 H, HOSO-R (SO 2 H) a compound represented by —SO ₂ H, wherein R is a linear, branched or cyclic saturated or unsaturated hydrocarbon residue.

A particularly preferred compound as a dispersant is oleic acid. Oleic acid is a well-known surfactant in colloidal stabilization and is used to protect iron nanoparticles. The relatively long chain of oleic acid gives an important steric hindrance that counteracts the strong magnetic interaction between particles (oleic acid has 18 carbon chains, about 2 nm in length (about 20 angstroms), double bond 1). Oleic acid is preferred because it is an inexpensive natural resource that can be easily obtained from, for example, olive oil. In addition, oleylamine derived from oleic acid is a useful dispersant like oleic acid.
In addition, similar long-chain carboxylic acids such as erucic acid and linoleic acid can be used similarly to oleic acid (for example, long-chain organic acids having 8 to 22 carbon atoms can be used alone or in combination). .

  The addition timing of the dispersant is not particularly limited, but is preferably between immediately after the reduction reaction and the start of the following aging step. By adding such a dispersant, iron nanoparticles that are more monodispersed and have no aggregation can be obtained.

[Aging process]
The production method of the present invention further includes an aging step of raising the temperature of the solution after the reaction to the aging temperature after the reduction reaction is completed.
The aging temperature is preferably a constant temperature between 30 and 90 ° C., and the temperature is suitably higher than the temperature of the reduction reaction. The aging time is preferably 5 to 180 minutes. If the aging temperature and aging time are within the above ranges, aggregation and precipitation are unlikely to occur, and the reaction can be completed and the composition can be made constant. More preferable aging temperature and aging time are 40 to 80 ° C. and 10 to 150 minutes, and further preferable aging temperature and aging time are 40 to 70 ° C. and 20 to 120 minutes.

  Here, the “constant temperature” has the same meaning as the temperature of the reduction reaction (however, in this case, the “reduction temperature” is the “aging temperature”). 30 to 90 ° C.), preferably 5 ° C. or more, more preferably 10 ° C. or more higher than the temperature of the reduction reaction. It is preferable to increase the temperature by 5 ° C. or more because a composition as prescribed can be obtained.

In the aging step as described above, iron nanoparticles having a desired particle size can be produced by appropriately adjusting the stirring speed at the temperature during aging.
After the aging, the solution after aging is washed with a mixed solution of water and a primary alcohol, and then subjected to a precipitation treatment with a primary alcohol to generate a precipitate. It is preferable to provide a washing / dispersing step for dispersing with a solvent. By providing such a cleaning / dispersing step, impurities can be removed, and the coating property when forming the magnetic layer of the magnetic recording medium can be further improved.
The washing and dispersion are each performed at least once, preferably twice or more.

  The primary alcohol used for washing is not particularly limited, but methanol, ethanol, and the like are preferable. The volume mixing ratio of water and primary alcohol (water / primary alcohol) is preferably in the range of 10/1 to 2/1, and more preferably in the range of 5/1 to 3/1. When the ratio of water is high, the surfactant may be difficult to remove, and conversely, when the ratio of primary alcohol is high, aggregation may occur.

  Nanoparticles can be stably prepared by the presence of a protective colloid when reducing or thermally depositing iron. For thermal precipitation, a method is known in which iron carbonyl is thermally decomposed to obtain iron. It is preferable to use a polymer or a surfactant as the protective colloid. Examples of the polymer include polyvinyl alcohol (PVA), poly N-vinyl-2-pyrrolidone (PVP), gelatin and the like. Of these, PVP is particularly preferable. The molecular weight is preferably 20,000 to 60,000, more preferably 30,000 to 50,000. The amount of the polymer is preferably 0.1 to 10 times the weight of the hard magnetic nanoparticles to be produced, and more preferably 0.1 to 5 times.

The surfactant preferably used as the protective colloid preferably includes an “organic stabilizer” which is a long-chain organic compound represented by the formula: R—X. R in the above formula is a “tail group” which is a linear or branched hydrocarbon or fluorocarbon chain and usually contains 8 to 22 carbon atoms. X in the above formula is a “head group” which is a moiety (X) that provides a specific chemical bond to the nanoparticle surface, and is a sulfinate (—SOOH), sulfonate (—SO ₂ OH), phosphinate (— POOH), phosphonate (—OPO (OH) ₂ ), carboxylate, and thiol are preferred.

Examples of the organic stabilizer include sulfonic acids (R—SO ₂ OH), sulfinic acids (R—SOOH), phosphinic acids (R ₂ POOH), phosphonic acids (R—OPO (OH) ₂ ), carboxylic acids (R— COOH) and thiols (R-SH) are preferred. Among these, oleic acid is particularly preferable.

  Oleic acid is a well-known surfactant in colloid stabilization and is suitable for protecting iron-based nanoparticles. Oleic acid has 18 carbon chains, and its length is ˜20 angstroms (˜2 nm). In addition, oleic acid is not aliphatic and has one double bond. And the relatively long chain of oleic acid provides an important steric hindrance that counteracts the strong magnetic interactions between the particles. Similar long chain carboxylic acids such as erucic acid and linoleic acid have been used as well as oleic acid (for example, long chain organic acids having between 8 and 22 carbon atoms can be used alone or in combination) Oleic acid is particularly preferred because it is an inexpensive natural resource (such as olive oil) that is readily available.

  The combination of the phosphine and the organic stabilizer (such as triorganophosphine / acid) can provide excellent control over particle growth and stabilization. Didecyl ether and didodecyl ether can also be used, but phenyl ether or n-octyl ether is preferably used as a solvent because of its low cost and high boiling point.

  The reaction is preferably performed at a temperature in the range of 80 ° C. to 360 ° C., more preferably 80 ° C. to 240 ° C., depending on the required nanoparticles and the boiling point of the solvent. When the temperature is in the above range, the particles are sufficiently grown, the control over the particle growth is excellent, and the production of by-products can be suppressed.

In order to increase the particle size, it is preferable to use a seed crystal method. At this time, since there is a concern about oxidation of the seed crystal iron particles, it is preferable to previously hydrotreat the particles.
It is preferable to remove the salts from the solution after the synthesis of the iron nanoparticles from the viewpoint of improving the dispersion stability of the nanoparticles. For desalting, there is a method in which alcohol is added excessively to cause light agglomeration, and natural sedimentation or centrifugal sedimentation is performed to remove salts together with the supernatant. However, in such a method, aggregation is likely to occur, so an ultrafiltration method is adopted. It is preferable.

〔Nitriding treatment〕
Prior to the nitriding treatment, when there is a concern about the oxidation of the iron nanoparticles, reduction treatment in a mixed gas stream of hydrogen or hydrogen and an inert gas (H ₂ , Ar, He, etc.) can be performed. As temperature, 200 to 300 degreeC is preferable, More preferably, it is 250 to 300 degreeC. The above range is preferable because the particles are not fused and can be sufficiently reduced.

The Fe ₁₆ N ₂ phase can be obtained by heating the iron nanoparticles in a nitrogen-containing gas stream.
As the nitriding gas, nitrogen gas, nitrogen + hydrogen mixed gas, ammonia gas, or the like can be used, but ammonia gas is convenient for use.
The nitriding treatment in the NH ₃ atmosphere is performed in an ammonia (NH ₃ ) stream or a mixed gas stream containing ammonia gas (for example, any one or more gases of argon, hydrogen, nitrogen, and ammonia gas). (Mixed gas) is preferable, and it is more preferable to perform in a relatively low temperature range of 100 to 250 ° C. When nitriding treatment temperature is within the above range, Fe ₁₆ N ₂ phase is sufficiently obtained, and the progress of Fe ₁₆ N ₂ Naru Aioi is sufficiently fast. These gases are preferably of high purity (5N or more) or oxygen content of several ppm or less.
A temperature range of 100 to 250 ° C. and a range of 0.5 to 48 hours are industrially preferable, and the treatment time depends on the particle size, but the treatment is more preferably 0.5 to 24 hours.

In such nitriding treatment, it is preferable to select the nitriding treatment conditions so that the content of nitrogen with respect to iron in the obtained magnetic powder is 1.0 to 20 atomic%. If the amount of nitrogen is 1.0 atomic% or more, the amount of Fe ₁₆ N ₂ produced is good, and the effect of improving the coercive force is obtained, which is preferable. Further, it is preferable that the amount of nitrogen is 20 atomic% or less because an Fe ₄ N or Fe ₃ N phase is hardly formed, a good coercive force is obtained, and a saturation magnetization is hardly lowered.

[Oxide film]
In order to form an oxide film, the above-mentioned thickness is obtained by treating at an temperature of 0 to 100 ° C. for 1 to 10 hours in an atmosphere of an inert gas (N ₂ , Ar, He, Ne, etc.) having an oxygen concentration of 1 to 5%. The oxide film can be formed.

In order to deposit a rare earth element, particles containing mainly Fe ₁₆ N ₂ are usually obtained by dispersing a starting material in an alkali or acid aqueous solution, dissolving a salt of the rare earth element therein, and performing a neutralization reaction or the like. In this case, hydroxides and hydrates containing rare earth elements may be precipitated.

Further, to dissolve the silicon and aluminum further compound composed of elements such as boron or phosphorus necessary, this was immersed particles comprising Fe ₁₆ N ₂ mainly the Fe ₁₆ N ₂ to mainly containing particles Thus, silicon or aluminum may be deposited. In order to perform these deposition processes efficiently, additives such as a reducing agent, a pH buffering agent, and a particle size controlling agent may be mixed.
As these deposition treatments, a rare earth element and silicon, aluminum or the like may be deposited simultaneously or alternately.

<Binder (Binder)>
In the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used as binders that can be used in the magnetic layer.
As the thermoplastic resin, the glass transition temperature is preferably −100 to 150 ° C., the number average molecular weight is preferably 1,000 to 200,000, more preferably 10,000 to 100,000, and the degree of polymerization is preferably 50 to. 1,000.
Examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, Examples thereof include polymers or copolymers containing vinyl ether as a structural unit, polyurethane resins, and various rubber resins.

  Thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, acrylic reactive resins, formaldehyde resins, silicon resins, epoxy-polyamide resins, polyesters. Examples thereof include a mixture of resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, a mixture of polyurethane and polyisocyanate, and the like.

  These resins are described in detail in “Plastic Handbook” published by Asakura Shoten. Moreover, it is also possible to use a well-known electron beam curable resin for a nonmagnetic layer (lower layer) or a magnetic layer (upper layer). These examples and their production methods are described in detail in JP-A No. 62-256219. The above resins can be used alone or in combination, but preferred are vinyl chloride resin, vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate-vinyl alcohol resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer, and , A combination of at least one selected from the group consisting of nitrocellulose and a polyurethane resin, or a combination of these with a polyisocyanate.

  Specific examples of the binder include VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, PKFE, Nissin Chemical Industries, Ltd. MPR-TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, Denki Kagaku 1000W, DX80, DX81, DX82, DX83, Nippon Zeon MR110, MR100, 400X110A, Nippon Polyurethane Nipporan N2301, N2302, N2304, Dainippon Ink Pandex T-5105, T-R3080, T-5201, Barnock D-400, D-210-80, Crisbon 6109, 7209, Toyobo U Iron R8200, UR8300, RV530, RV280, Daifer Seika's Daiferamin 4020, 5020, 5100, 5300, 9020, 9022, 7020, Mitsubishi Kasei MX5004, Sanyo Kasei Samprene SP-150, Asahi Kasei Saran F310, F210 etc. are mentioned.

Among the above, the binder that can be used in the magnetic layer is preferably a vinyl chloride binder or a polyurethane binder, and particularly preferably contains a polar group and has an aromatic ring in a skeleton of 3.5 mmol / g to 7 mmol / g-containing polyurethane.
As the polyurethane binder, polyester urethane, polyether urethane, polycarbonate urethane, polyether ester urethane, acrylic polyurethane, and the like can be suitably used. The polyurethane binder is preferable because it has high affinity with the lubricant and can control the amount of surface lubricant within an optimum range.
As the polar group that the binder may have, sulfonate, sulfamate, sulfobetaine, phosphate, phosphonate and the like are preferable. The amount of the polar group is preferably 1 × 10 ⁻⁵ eq / g to 2 × 10 ⁻⁴ eq / g.

The binder amount of the magnetic layer is preferably 10 to 25 parts by weight with respect to 100 parts by weight of the ferromagnetic powder including the curing agent, and the binder amount of the nonmagnetic layer (nonmagnetic lower layer) is 100 parts by weight of the nonmagnetic powder. The amount of binder in the magnetic layer and nonmagnetic layer is preferably 25-40 parts by weight relative to the lower layer.
In particular, the binder for a nonmagnetic layer preferably has a strong polar group such as SO ₃ Na and a skeleton containing many aromatic rings in the skeleton. As a result, the affinity between the lubricant and the nonmagnetic layer binder is further increased, and the lubricant can be present in the nonmagnetic layer in a stable and stable manner.
It is preferable that the affinity between the lubricant and the binder is moderate because the binder and the lubricant are not completely compatible with each other at the molecular level and the lubricant can be transferred to the upper layer.

<Abrasive>
The magnetic layer in the magnetic recording medium of the present invention preferably contains an abrasive.
An inorganic nonmagnetic powder can be used as the abrasive. The inorganic nonmagnetic powder can be selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. Examples of the inorganic compound include α-alumina, β-alumina, γ-alumina, α-alumina of 90 to 100%, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, oxidation Titanium, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, barium sulfate, molybdenum disulfide and the like can be used alone or in combination. Particularly preferred are α-alumina, bengara and chromium oxide. Calcium carbonate is not preferable because it becomes a source of water-soluble metal ions. The abrasive used in the present invention is preferably used by changing the type, amount, particle size, combination, shape, etc. so that the characteristics of the magnetic layer surface are in a desired range.
When only one type of abrasive is used, the average particle size of the abrasive used in the present invention is preferably 0.05 to 0.4 μm, more preferably 0.1 to 0.3 μm. More preferred. It is preferable that 1 to 40% of particles having a particle size larger by 0.1 μm or more than the average particle size are present, more preferably 5 to 30%, and most preferably 10 to 20%. The particle size of the abrasive alone affects the particle size of the abrasive particles existing on the actual magnetic layer surface, but is not equal. The particle size of the abrasive particles present on the surface of the magnetic layer varies depending on the dispersion conditions of the abrasive and the like, and there are particles that are likely to come out on the surface of the magnetic layer even in the coating and drying step, and particles that are hard to come out.

Two or more kinds of abrasives having different average particle diameters can be used in combination. In this case, in the weighted average value corresponding to the actual usage ratio of two or more kinds of abrasives to be used, the average particle size and particles having a particle size larger by 0.1 μm or more than the average particle size are in the above range. be able to. In addition, the particle size can be controlled by changing the dispersion conditions of the two types of abrasives. For example, the abrasive A is dispersed together with a binder and a solvent in advance, and the powdered abrasive B is added to a kneading treatment liquid of ferromagnetic metal powder separately kneaded with a binder and a solvent. If the dispersion treatment is performed, the dispersion treatment conditions can be different between the abrasive A and the abrasive B. That is, A is more strongly dispersed than B. The tap density of the abrasive powder is preferably 0.05 to 2 g / ml, more preferably 0.2 to 1.5 g / ml. The moisture content of the abrasive powder is preferably 0.05 to 5% by weight, more preferably 0.2 to 3% by weight. The specific surface area of the abrasive is preferably 1 to 100 m ² / g, more preferably 5 to 50 m ² / g. The amount of oil absorption using DBP is preferably 5 to 100 ml / 100 g, more preferably 10 to 80 ml / 100 g. The specific gravity is preferably 1 to 12, more preferably 3 to 6. The shape may be any of a needle shape, a spherical shape, a polyhedral shape, and a plate shape. The surface of these abrasives may be coated with at least a part of a compound different from the main component of the abrasive. Examples thereof include Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ and ZnO. In particular, when Al ₂ O ₃ , SiO ₂ , TiO ₂ , or ZrO ₂ is used, the dispersibility is improved. These may be used in combination or may be used alone.

  Specific examples of the powder of the abrasive used for the magnetic layer of the present invention include Nanotite manufactured by Showa Denko KK; Hit100, Hit82, Hit80, Hit70, Hit60A, Hit55, AKP20, AKP30, manufactured by Sumitomo Chemical Co., Ltd. AKP50, ZA-G1; ERC-DBM, HP-DBM, HPF-DBM, HPFX-DBM, HPS-DBM, HPSX-DBM manufactured by Reynolds; WA8000, WA10000 manufactured by Fujimi Abrasives; manufactured by Uemura Kogyo Co., Ltd. UB20, UB40B, Mechanox U4; Showa Light Metal Co., Ltd. UA2055, UA5155, UA5305; Nippon Chemical Industry Co., Ltd. G-5, Chromex M, Chromex S1, Chromex U2, Chromex U1, Chromex Mex X10, Chromex KX10; made by Nippon Denko Co., Ltd. D803, ND802, ND801; Tosoh Corporation F-1, F-2, UF-500; Toda Kogyo DPN-250, DPN-250BX, DPN-245, DPN-270BXTF-100, TF -120, TF-140, DPN-550BX, TF-180; Showa Mining Co., Ltd. A-3, B-3; Central Glass Co., Ltd. beta SiC, UF; Ibiden Co., Ltd. beta random Standard, Beta Random Ultra Fine; Teikoku Kogyo JR401, MT500B; Ishihara Sangyo TY-50, TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, E270, E271; STT-4D, STT-30D, STT-30, S manufactured by Titanium Industry Co., Ltd. T-65C; MT-100S, MT-100T, MT-150W, MT-500B, MT-600B, MT-100F, MT-500HD manufactured by Teika Co., Ltd. FINEX-25 manufactured by Sakai Chemical Industry Co., Ltd. BF-1, BF-10, BF-20, ST-M; HZn and HZr3M manufactured by Kitakai Chemical, DEFIC-Y and DEFIC-R manufactured by Dowa Mining Co., Ltd., AS2BM and TiO2P25 manufactured by Nippon Aerosil Co., Ltd. ; 100A, 500A manufactured by Ube Industries, Ltd .; Y-LOP manufactured by Titanium Industry Co., Ltd. and those obtained by firing it.

<Additives>
If necessary, an additive can be added to the magnetic layer in the magnetic recording medium of the present invention. Examples of the additive include a dispersant / dispersion aid, an antifungal agent, an antistatic agent, an antioxidant, a solvent, and carbon black. Moreover, you may use together the lubricant which does not contain the ether compound of this invention as an additive.
Examples of these additives include tungsten disulfide, graphite, fluorinated graphite, silicone oil, silicone having a polar group, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, and polyphenyl. Ether, phenylphosphonic acid, benzylphosphonic acid group, phenethylphosphonic acid, α-methylbenzylphosphonic acid, 1-methyl-1-phenethylphosphonic acid, diphenylmethylphosphonic acid, biphenylphosphonic acid, benzylphenylphosphonic acid, α-cumylphosphonic acid, Toluylphosphonic acid, xylylphosphonic acid, ethylphenylphosphonic acid, cumenylphosphonic acid, propylphenylphosphonic acid, butylphenylphosphonic acid, heptylphenylphosphonic acid, octylph Aromatic ring-containing organic phosphonic acids such as enylphosphonic acid and nonylphenylphosphonic acid and alkali metal salts thereof, octylphosphonic acid, 2-ethylhexylphosphonic acid, isooctylphosphonic acid, isononylphosphonic acid, isodecylphosphonic acid, isoundecyl Alkylphosphonic acids such as phosphonic acid, isododecylphosphonic acid, isohexadecylphosphonic acid, isooctadecylphosphonic acid, isoeicosylphosphonic acid and alkali metal salts thereof, phenyl phosphate, benzyl phosphate, phenethyl phosphate, α-phosphate -Methylbenzyl, 1-methyl-1-phenethyl phosphate, diphenylmethyl phosphate, biphenyl phosphate, benzylphenyl phosphate, α-cumyl phosphate, toluyl phosphate, xylyl phosphate, ethylphenyl phosphate, cumenyl phosphate , Propyl phosphate Aromatic phosphates such as phenyl, butylphenyl phosphate, heptylphenyl phosphate, octylphenyl phosphate, nonylphenyl phosphate and alkali metal salts thereof, octyl phosphate, 2-ethylhexyl phosphate, isooctyl phosphate, phosphoric acid Isononyl, isodecyl phosphate, isoundecyl phosphate, isododecyl phosphate, isohexadecyl phosphate, isooctadecyl phosphate, isoeicosyl phosphate, etc., phosphoric acid alkyl esters and alkali metal salts thereof, alkyl sulfonic acid esters and alkali metal salts thereof, Fluorine-containing alkyl sulfates and alkali metal salts thereof, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, butyl stearate, oleic acid, linoleic acid, linolenic acid, elaidic acid, erucic acid, etc. Monobasic fatty acids which may contain or branch 24 unsaturated bonds and their metal salts, or butyl stearate, octyl stearate, amyl stearate, isooctyl stearate, octyl myristate, butyl laurate, Monobasic fatty acids that may contain or be branched, such as butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, etc. Of 1-6 hexahydric alcohol which may contain or be branched with C2-C22 unsaturated bond, alkoxy alcohol which may contain C12-22 unsaturated bond or alkylene oxide or alkylene oxide polymer Mono fatty acid ester consisting of any one of monoalkyl ethers Ether, di-fatty acid esters or polyvalent fatty acid esters, fatty acid amides having 2 to 22 carbon atoms, and aliphatic amines having 8 to 22 carbon atoms can be used. In addition to the above hydrocarbon groups, alkyl groups, aryl groups, and aralkyl groups substituted with nitro groups and groups other than hydrocarbon groups such as halogen-containing hydrocarbons such as F, Cl, Br, CF ₃ , CCl ₃ , and CBr ₃ You may have.

  In addition, nonionic surfactants such as alkylene oxide, glycerin, glycidol, and alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocyclics, phosphonium or sulfoniums, etc. Amphoteric interfaces such as cationic surfactants, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, and sulfate ester groups, amino acids, aminosulfonic acids, sulfuric or phosphate esters of aminoalcohols, and alkylbetaines An activator or the like can also be used. These surfactants are described in detail in “Surfactant Handbook” (published by Sangyo Tosho Co., Ltd.).

The additives such as the dispersant and the lubricant that may be used in combination are not necessarily pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposition products, and oxides in addition to the main components. Absent. These impurities are preferably 30% by weight or less, and more preferably 10% by weight or less.
Specific examples of these additives include, for example, NAF-102, castor oil hardened fatty acid, NAA-42, cation SA, Naimine L-201, Nonion E-208, Anon BF, Anon LG, Takemoto, manufactured by NOF Corporation. Oils and fats: FAL-205, FAL-123, Shin Nippon Chemical Co., Ltd .: NJELBU OL, Shin-Etsu Chemical: TA-3, Lion Armor: Armide P, Lion: Duomin TDO, Nisshin Oil : BA-41G, Sanyo Kasei Co., Ltd .: Profan 2012E, New Pole PE61, Ionette MS-400, and the like.

  Known organic solvents can be used for the magnetic layer in the magnetic recording medium of the present invention. Organic solvents can be used in any ratio, such as ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, alcohols such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol, acetic acid Esters such as methyl, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate and glycol acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, and aromatic hydrocarbons such as benzene, toluene, xylene and cresol , Methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, chlorobenzene, dichlorobenzene, etc. Fluorinated hydrocarbons, N, N- dimethylformamide, may be used hexane, tetrahydrofuran, and the like.

  These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposition products, oxides, and moisture in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less. The organic solvent used in the present invention is preferably the same in the magnetic layer and the nonmagnetic layer. The amount added may be changed. Use a solvent with high surface tension (such as cyclohexanone or dioxane) for the non-magnetic layer to increase the coating stability. Specifically, the arithmetic average value of the magnetic layer (upper layer) solvent composition is the arithmetic average value of the non-magnetic layer solvent composition. It is important not to fall below. In order to improve dispersibility, it is preferable that the polarity is somewhat strong, and it is preferable that 50% or more of a solvent having a dielectric constant of 15 or more is included in the solvent composition. Moreover, it is preferable that a solubility parameter is 8-11.

  These dispersants and surfactants used in the magnetic layer in the magnetic recording medium of the present invention can be used properly in the magnetic layer and in the nonmagnetic layer described later as needed. For example, of course, the dispersant is not limited to the example shown here, but the dispersant has a property of adsorbing or binding with a polar group, and in the magnetic layer, mainly on the surface of the ferromagnetic powder, as will be described later. In the nonmagnetic layer, it is presumed that the organophosphorus compound adsorbed or bonded to the surface of the nonmagnetic powder mainly by the polar group and once adsorbed is difficult to desorb from the surface of metal or metal compound. Accordingly, the surface of the ferromagnetic powder of the present invention or the nonmagnetic powder surface described later is in a state of being coated with an alkyl group, an aromatic group, etc., so the affinity of the ferromagnetic powder or nonmagnetic powder for the binder resin component And the dispersion stability of the ferromagnetic powder or non-magnetic powder is also improved. Further, it is conceivable to improve the coating stability by adjusting the amount of the surfactant. All or a part of the additives used in the present invention may be added in any step during the production of the coating solution for the magnetic layer or nonmagnetic layer. For example, when mixing with a ferromagnetic powder before the kneading step, when adding at a kneading step with a ferromagnetic powder, a binder and a solvent, when adding at a dispersing step, when adding after dispersing, when adding just before coating, etc. There is.

Moreover, carbon black can be added to the magnetic layer in the magnetic recording medium of the present invention as required.
As the kind of carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. The carbon black of the radiation-cured layer should be optimized for the following characteristics depending on the desired effect, and the effect may be obtained more when used in combination.

The specific surface area of the carbon black, preferably 100 to 500 m ² / g, more preferably 150 to 400 m ² / g, DBP oil absorption amount is preferably 20 to 400 ml / 100 g, more preferably 30 to 200 ml / 100 g. The particle size of carbon black is preferably 5 to 80 nm, more preferably 10 to 50 nm, and still more preferably 10 to 40 nm. Carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / ml.

  Specific examples of carbon black that can be used in the present invention include BLACKPEARLS 2000, 1300, 1000, 900, 800, 880, 700, VULCAN XC-72, Mitsubishi Chemical Industries, Ltd. # 3050B, # 3150B, manufactured by Cabot Corporation. , # 3250B, # 3750B, # 3950B, # 950, # 650B, # 970B, # 850B, MA-600, MA-230, # 4000, # 4010, CONDUCTEX SC manufactured by Columbia Carbon Co., RAVEN 8800, 8000, 7000, 5750, 5250, 3500, 2100, 2000, 1800, 1500, 1255, 1250, Ketjen Black EC from Akzo, Ketjen Black EC from Ketjen Black International, etc. That.

  Carbon black may be surface-treated with a dispersant or the like, or may be used after being grafted with a resin, or may be obtained by graphitizing a part of the surface. Moreover, before adding carbon black to a coating material, you may disperse | distribute with a binder beforehand. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

  These carbon blacks can be used alone or in combination. When carbon black is used, it is preferably used in an amount of 0.1 to 30% by weight based on the weight of the magnetic material. Carbon black functions to prevent the magnetic layer from being charged, reduce the coefficient of friction, impart light-shielding properties, and improve the film strength. These differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention change the type, amount, and combination in the magnetic layer, and depending on the purpose based on the above-mentioned various characteristics such as particle size, oil absorption, conductivity, pH, etc. Of course, it is possible to use them properly, but they should be optimized in each layer.

II. Nonmagnetic Layer Next, the detailed contents of the nonmagnetic layer (also referred to as a nonmagnetic lower layer and a lower coating layer in the present invention) will be described.
The magnetic recording medium of the present invention may have at least one nonmagnetic layer in which a nonmagnetic powder is dispersed in a binder between the nonmagnetic support and the magnetic layer.
In the present invention, the nonmagnetic layer preferably contains a lubricant containing the ether compound of the present invention, more preferably contains the same ether compound as the ether compound used in the magnetic layer, The lubricant in the magnetic layer is preferably the same.
When the nonmagnetic layer contains the same lubricant as the magnetic layer, the lubricant consumed in the magnetic layer is supplied by oozing from the nonmagnetic layer, resulting in a magnetic recording medium having excellent storage stability and durability. Therefore, it is preferable.

<Non-magnetic powder>
The nonmagnetic powder used for the nonmagnetic layer may be an inorganic substance or an organic substance. Moreover, you may mix carbon black with a nonmagnetic powder as needed with a nonmagnetic layer.
The inorganic powder used for the lower coating layer in the present invention is a nonmagnetic powder, and is selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. be able to.

  Examples of the inorganic compound include α-alumina, β-alumina, γ-alumina, θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, goethite, corundum, silicon nitride, titanium carbide having an α conversion ratio of 90% or more. -Bite, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide and the like are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide and barium sulfate because of their small particle size distribution and many means for imparting functions, and more preferred are titanium dioxide and α-iron oxide.

The particle size of these nonmagnetic powders is preferably 0.005 to 2 μm, but if necessary, nonmagnetic powders having different particle sizes can be combined, or even a single nonmagnetic powder can have the same effect by widening the particle size distribution. You can also The particle size of the nonmagnetic powder is particularly preferably 0.01 μm to 0.2 μm. In particular, when the nonmagnetic powder is a granular metal oxide, the average particle diameter is preferably 0.08 μm or less, and when the nonmagnetic powder is an acicular metal oxide, the major axis length is preferably 0.3 μm or less. The tap density is preferably 0.05 to 2 g / ml, more preferably 0.2 to 1.5 g / ml. The water content of the nonmagnetic powder is preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, and still more preferably 0.3 to 1.5% by weight. The pH of the nonmagnetic powder is preferably 2 to 11, but the pH is particularly preferably between 5.5 and 10. The specific surface area of the non-magnetic powder is preferably 1 to 100 m ² / g, more preferably 5 to 80 m ² / g, and still more preferably 10 to 70 m ² / g. The crystallite size of the nonmagnetic powder is preferably 0.004 μm to 1 μm, and more preferably 0.04 μm to 0.1 μm. The oil absorption amount using DBP (dibutyl phthalate) is preferably 5 to 100 ml / 100 g, more preferably 10 to 80 ml / 100 g, and still more preferably 20 to 60 ml / 100 g. The specific gravity is preferably 1 to 12, more preferably 3 to 6. The shape may be any of a needle shape, a spherical shape, a polyhedron shape, and a plate shape.

The ignition loss is preferably 20% by weight or less, and it is considered most preferable that the ignition loss is not originally present. The Mohs hardness of the nonmagnetic powder used in the present invention is preferably 4 or more and 10 or less. The roughness factor of the powder surface is preferably 0.8 to 1.5, and more preferably 0.9 to 1.2. The SA (stearic acid) adsorption amount of the nonmagnetic powder is preferably 1 to 20 μmol / m ² , more preferably ^{2 to} 15 μmol / m ² , and further preferably 3 to 8 μmol / m ² . The heat of wetting of the nonmagnetic powder into water at 25 ° C. is preferably in the range of 200 erg / cm ^{2 to} 600 erg / cm ² (20 μJ / cm ^{2 to} 60 μJ / cm ² ). Moreover, the solvent which exists in the range of this heat of wetting can be used. The pH is preferably between 3-6. The non-magnetic powder preferably has 0 to 150 ppm of water-soluble Na and 0 to 50 ppm of water-soluble Ca.

The surface of these nonmagnetic powders is preferably surface-treated with Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , ZnO, Y ₂ O ₃ . Particularly preferred for dispersibility are Al ₂ O ₃ , SiO ₂ , TiO ₂ and ZrO ₂ , but more preferred are Al ₂ O ₃ , SiO ₂ and ZrO ₂ . These may be used in combination or may be used alone. In addition, a surface-treated layer co-precipitated according to the purpose may be used, or a method of treating the surface layer with silica after first treating with alumina or vice versa may be employed. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that the surface treatment layer is homogeneous and dense.

Specific examples of the non-magnetic powder used for the lower coating layer (non-magnetic layer) in the magnetic recording medium of the present invention include Showa Denko Nano Tight, Sumitomo Chemical HIT-100, ZA-G1, Toda Kogyo α Hematite DPN-250, DPN-250BX, DPN-245, DPN-270BX, DBN-SA1, DBN-SA3, Ishihara Sangyo Titanium oxide TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, α-hematite E270, E271, E300, E303, Titanium Industry Titanium Oxide STT-4D, STT-30D, STT-30, STT-65C, α-hematite α-40, Teica MT-100S , MT-100T, MT-150W, MT-500B, MT-600B, MT-100 , MT-500HD, Sakai Chemical Co. FINEX-25, BF-1, BF-10, BF-20, ST-M, Dowa Mining Ltd. DEFIC-Y, DEFIC-R, manufactured by Japan Aerosil AS2BM, TiO ₂ P25, Ube 100A, 500A manufactured, and those obtained by firing the same.

Particularly preferred nonmagnetic powders are titanium dioxide and α-iron oxide.
α-iron oxide (hematite) is carried out under the following conditions. That is, the α-Fe ₂ O ₃ particle powder that can be used in the present invention is a suspension containing a ferrous hydroxide colloid obtained by adding an equivalent amount or more of an alkali hydroxide aqueous solution to a normal (1) ferrous aqueous solution. A method of generating acicular goethite particles by conducting an oxidation reaction by passing an oxygen-containing gas at a temperature of pH 11 or higher and a temperature of 80 ° C. or lower, and (2) reacting an aqueous ferrous salt solution and an aqueous alkali carbonate solution. A method of generating goethite particles having a spindle shape by aeration of oxygen-containing gas through a suspension containing FeCO ₃ obtained by performing an oxidation reaction, and (3) less than an equivalent amount in an aqueous ferrous salt solution Acicular goethite core particles are produced by conducting an oxidation reaction by passing an oxygen-containing gas through a ferrous salt aqueous solution containing a ferrous hydroxide colloid obtained by adding an aqueous alkali hydroxide solution or an aqueous alkali carbonate solution, Ide, the ferrous salt aqueous solution containing the acicular goethite nucleus particles, after addition of more aqueous alkali hydroxide solution equivalent amount with respect to Fe ²⁺ in said aqueous ferrous salt solution, by passing an oxygen-containing gas A method of growing the acicular goethite core particles, and (4) a ferrous salt aqueous solution containing a ferrous hydroxide colloid obtained by adding less than an equivalent amount of an alkali hydroxide or alkali carbonate aqueous solution to a ferrous aqueous solution A needle-like goethite particle obtained by, for example, a method of generating needle-like goethite core particles by conducting an oxidation reaction by aeration of an oxygen-containing gas and then growing the needle-like goethite core particles in an acidic to neutral region Is a precursor particle.

It should be noted that there is no problem even if different elements such as Ni, Zn, P, and Si, which are usually added to improve the properties of the particle powder, are added during the formation reaction of the goethite particles. The acicular goethite particles, which are precursor particles, are dehydrated in a temperature range of 200 to 500 ° C. or, if necessary, annealed by heat treatment in a temperature range of 350 to 800 ° C. to obtain acicular α-Fe ₂ O. _{Get 3} particles. It should be noted that there is no problem even if a sintering inhibitor such as P, Si, B, Zr, or Sb adheres to the surface of the acicular goethite particles to be dehydrated or annealed. Annealing by heat treatment in a temperature range of 350 to 800 ° C. is performed by annealing pores generated on the particle surface of acicular α-Fe ₂ O ₃ particles obtained by dehydration, thereby causing the extreme surface of the particles to be annealed. This is because it is preferable to melt and block the pores to obtain a smooth surface form.

The α-Fe ₂ O ₃ particle powder used in the present invention is a suspension in which acicular α-Fe ₂ O ₃ particles obtained by the dehydration or annealing are dispersed in an aqueous solution, and an Al compound is added. After the pH is adjusted and the additive compound is coated on the surface of the α-Fe ₂ O ₃ particles, it is obtained by filtration, washing with water, drying, pulverization, and if necessary, deaeration and consolidation.
As the Al compound used, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride, and aluminum nitrate, and alkali aluminates such as sodium aluminate can be used.
In this case, the addition amount of the Al compound is 0.01 to 50% by weight in terms of Al with respect to the α-Fe ₂ O ₃ particle powder. The above range is preferable because the dispersion in the binder resin is sufficient, the Al compounds floating on the particle surface are few, and the Al compounds hardly interact with each other.

In the nonmagnetic powder of the nonmagnetic layer (lower layer) in the present invention, one or two compounds selected from P, Ti, Mn, Ni, Zn, Zr, Sn, and Sb, as well as an Si compound, as well as an Al compound. It can also coat | cover using the above. The amount of these compounds used together with the Al compound is preferably in the range of 0.01 to 50% by weight based on the α-Fe ₂ O ₃ particle powder. Within the above range, the effect of improving dispersibility by addition is sufficiently obtained, and there are few compounds floating on the surface other than the particle surface, and the above compounds are unlikely to interact with each other.

The production method of titanium dioxide is as follows. The production methods of these titanium oxides mainly include a sulfuric acid method and a chlorine method. In the sulfuric acid method, the source ore of illuminite is digested with sulfuric acid, and Ti, Fe, etc. are extracted as sulfates. Iron sulfate is crystallized and removed, and the remaining titanyl sulfate solution is filtered and purified, followed by thermal hydrolysis to precipitate hydrous titanium oxide. After filtering and washing this, impurities are removed by washing, and after adding a particle size adjusting agent or the like, if it is baked at 80 to 1,000 ° C., it becomes crude titanium oxide. The rutile type and the anatase type are classified according to the kind of nucleating agent added at the time of hydrolysis. This crude titanium oxide is produced by pulverizing, sizing, surface treatment and the like. Natural or synthetic rutile is used as the raw ore of the chlorine method. The ore is chlorinated in a high temperature reduced state, Ti becomes TiCl ₄ , Fe becomes FeCl ₂ , and the iron oxide that has become solid upon cooling is separated from liquid TiCl ₄ . The obtained crude TiCl ₄ is purified by rectification and then added with a nucleating agent, and is reacted instantaneously with oxygen at a temperature of 1,000 ° C. or higher to obtain crude titanium oxide. The finishing method for imparting pigment-like properties to the crude titanium oxide produced in this oxidative decomposition process is the same as the sulfuric acid method.

In the surface treatment, after the above titanium oxide material is dry-pulverized, water and a dispersant are added, and coarse particle classification is performed by wet pulverization and centrifugal separation. Thereafter, the fine slurry is transferred to a surface treatment tank, where surface coating of metal hydroxide is performed. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, Zn, etc. is added, and an acid or alkali that neutralizes this is added, and the surface of the titanium oxide particles is coated with the resulting hydrous oxide. To do. Water-soluble salts produced as a by-product are removed by decantation, filtration, and washing. Finally, the slurry pH is adjusted, filtered, and washed with pure water. The washed cake is dried with a spray dryer or a band dryer. Finally, the dried product is pulverized by a jet mill to become a product.
It is also possible to perform surface treatment of Al and Si by passing AlCl ₃ and SiCl ₄ vapor into titanium oxide powder as well as water and then flowing water vapor. GD Parfitt and KSW Sing “Characterization of Powder Surfaces” Academic Press, 1976 can be referred to for other pigment production methods.

  It is possible to reduce the surface electrical resistance Rs, which is a known effect, by mixing carbon black with the nonmagnetic layer (lower coating layer), to reduce the light transmittance, and to obtain a desired micro Vickers hardness. it can. Moreover, it is possible to bring about the effect of storing the lubricant by including carbon black in the nonmagnetic layer (lower layer). As the type of carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. The lower layer carbon black should have the following characteristics optimized depending on the desired effect, and the effect may be obtained by using it together.

The specific surface area of the carbon black in the nonmagnetic layer (lower layer) is preferably from 100 to 500 m ² / g, more preferably 150 to 400 m ² / g, DBP oil absorption, preferably 20 to 400 ml / 100 g, more preferably 30 ~ 200ml / 100g. The particle size of carbon black is preferably 5 to 80 nm, more preferably 10 to 50 nm, and still more preferably 10 to 40 nm. Carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / ml.

  Specific examples of carbon black used in the present invention include BLACKPEARLS 2000, 1300, 1000, 900, 800, 880, 700, VULCAN XC-72 manufactured by Cabot Corporation, # 3050B, # 3150B, # 3 manufactured by Mitsubishi Kasei Corporation. 3250B, # 3750B, # 3950B, # 950, # 650B, # 970B, # 850B, MA-600, MA-230, # 4000, # 4010, CONDUCTEX SC, Raven 8800, 8000, 7000, 5750, manufactured by Conlonbia Carbon Co., Ltd. , 5250, 3500, 2100, 2000, 1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo, Ketjen Black EC manufactured by Ketjen Black International, and the like.

  Carbon black may be surface-treated with a dispersant or the like, or may be used after being grafted with a resin, or may be obtained by graphitizing a part of the surface. Moreover, before adding carbon black to a coating material, you may disperse | distribute with a binder beforehand. These carbon blacks are preferably used in a range not exceeding 50% by weight with respect to the inorganic powder and not exceeding 40% of the total weight of the nonmagnetic layer. These carbon blacks can be used alone or in combination. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

An organic powder can be added to the nonmagnetic layer (lower coating layer) depending on the purpose. Examples include acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment, but polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, and polyfluorinated ethylene resin Can be used. As the production method, those described in JP-A Nos. 62-18564 and 60-255827 can be used.
As the binder, lubricant, dispersant, additive, solvent, dispersion method, etc. of the lower coating layer, those of the magnetic layer can be applied. In particular, known techniques relating to the magnetic layer can be applied to the amount of binder, type, additive, and amount of dispersant added, and type.

III. Non-magnetic support Examples of the non-magnetic support used in the present invention include known films such as polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyamideimide, aromatic polyamide, and polybenzoxidazole. In particular, a nonmagnetic support using polyethylene terephthalate, polyethylene naphthalate or aramid resin is preferred. These nonmagnetic supports may be subjected in advance to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like. In order to achieve the object of the present invention, the surface roughness of the nonmagnetic support is preferably 2 to 30 nm, more preferably 5 to 25 nm, and still more preferably 10 to 20 nm. These non-magnetic supports preferably have not only a small center line average surface roughness but also no coarse protrusions of 1 μm or more. The surface roughness shape can be freely controlled by the size and amount of filler added to the nonmagnetic support as required. These fillers include oxides and carbonates such as Al, Ca, Si, and Ti, which may be crystalline or amorphous, and organic fine powders such as acrylic and melamine. Further, in order to achieve compatibility with running durability, the surface on which the backcoat layer is applied is preferably rougher than the surface on which the magnetic layer is applied. The magnetic layer coated surface and the back coat layer coated surface of the nonmagnetic support may have the same or different surface roughness. When changing the roughness, a dual-structured support may be used, or may be changed by providing a coating layer.

The F-5 value of the non-magnetic support used in the present invention is preferably 70 to 300 MPa (7 to 30 kg / mm ² ) in both the tape running direction and the width direction, and the F-5 value in the longitudinal direction of the tape is the tape. It is generally higher than the F-5 value in the width direction, but this is not the case when it is necessary to increase the strength in the width direction. The heat shrinkage rate of the nonmagnetic support in the tape running direction and the width direction at 100 ° C. for 30 minutes is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage rate at 80 ° C. for 30 minutes is Preferably it is 1% or less, More preferably, it is 0.5% or less. The breaking strength is preferably 50 to 1,000 MPa (5 to 100 kg / mm ² ) in both directions, and the elastic modulus is preferably 1,000 to 20,000 MPa (100 to 2,000 kg / mm ² ). In the present invention, the light transmittance at 900 nm is preferably 30% or less, and more preferably 3% or less.

IV. Manufacturing Method In order to achieve the object of the present invention, a conventionally known manufacturing technique, that is, a magnetic coating material is manufactured, applied onto a nonmagnetic support, oriented, dried, subjected to a surface smoothing treatment, Obtained by cutting to the width of. The magnetic coating is prepared by kneading and dispersing components such as ferromagnetic powder, binder, carbon black, abrasive, antistatic agent, and lubricant, usually with a solvent. As the solvent used for kneading and dispersing, solvents such as methyl ethyl ketone, toluene, butyl acetate, and cyclohexanone that are usually used for the preparation of magnetic paints can be used. The method of kneading and dispersing is not particularly limited as long as it is a method that is usually used for the preparation of magnetic paints, and the order of addition of each component can be set as appropriate. Further, a part of the components can be added after being predispersed in advance, or can be dispersed separately and finally mixed. For the preparation of magnetic paints, ordinary kneaders such as 2-roll mill, 3-roll mill, ball mill, sand grinder, attritor, high-speed impeller disperser, high-speed stone mill, high-speed impact mill, disper, kneader, high-speed mixer , Homogenizers, ultrasonic dispersers, and the like can be used. Details of the technology relating to kneading and dispersion are described in TC Patton “Paint Flow and Pigment Dispersion”, John Wiley & Sons (1964), Shinichi Tanaka “Industrial Materials”, Vol. 25, p. 37 (1977). Also described in US Pat. Nos. 2,581,414 and 2,855,515. Also in the present invention, the magnetic coating material can be prepared by kneading and dispersing according to the method described in the above cited reference.

  The prepared magnetic coating is applied on the above-mentioned nonmagnetic support. At this time, the magnetic layer is applied so that the layer thickness after drying is preferably in the range of 4 nm to 1.0 μm, more preferably 4 nm to 100 nm. In the case of a multilayer configuration, a plurality of magnetic paints may be applied successively or simultaneously. Applicators for applying the above magnetic paint include air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure cord, kiss coat, cast coat, spray A coat, a spin coat, etc. can be used. For example, “Latest Coating Technology” (May 31, 1983) issued by “General Technology Center”, Inc. can be referred to. The coated layer of the applied magnetic paint is dried after subjecting the ferromagnetic powder contained in the coated layer of the magnetic paint to a magnetic field orientation treatment.

  In the magnetic field orientation treatment, it is preferable to use a solenoid of 1.25 T (1,000 gauss) or more and a cobalt magnet of 2.51 T (2,000 gauss) or more in the same pole facing each other, and the orientation after drying is further improved. It is preferable to provide an appropriate drying step in advance before orientation so as to be the highest. A backcoat layer may be provided on the surface of the nonmagnetic support on which the magnetic coating is not applied. Usually, the back coat layer is formed by applying a back coat layer forming paint in which particulate components such as abrasives and antistatic agents and a binder are dispersed in an organic solvent on the surface of the nonmagnetic support on which the magnetic paint is not applied. This is a layer provided. In addition, the adhesive layer may be provided in the application surface of the magnetic coating material of a nonmagnetic support body, and a backcoat layer formation coating material.

  The backcoat layer is preferably applied after the magnetic layer is applied and dried, but it may be applied before the magnetic layer is applied or after the surface smoothing treatment described below. After the coating layer is formed and dried, the surface is smoothed. For the surface smoothing process, for example, a super calendar roll or the like is used. By performing the surface smoothing treatment, voids generated by removing the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer is improved, so that a magnetic recording medium having high electromagnetic conversion characteristics can be obtained. it can. As the calendering roll, heat-resistant plastic rolls such as various metal rolls, epoxy, polyimide, polyamide, and polyimideamide are used. The temperature of the calender roll during calendering is preferably in the range of 60 to 150 ° C, more preferably in the range of 70 to 130 ° C, and particularly preferably in the range of 80 to 110 ° C. The pressure is preferably in the range of 1,000 to 5,000 N / cm (100 to 500 kg / cm), more preferably in the range of 2,000 to 4,500 N / cm (200 to 450 kg / cm), particularly preferably 2, It is performed by operating in the range of 500 to 4,000 N / cm (250 to 400 kg / cm). A thermo process can also be performed after a calendar process. The thermo treatment is preferably performed at 40 to 80 ° C. for 6 to 120 hours. Thereafter, it is cut into a desired width by a cutting machine such as a slitter. Furthermore, after cutting or before cutting, the surface of the magnetic layer can be blade-treated with a sapphire blade or the like.

V. Physical characteristics The magnetic characteristics of the magnetic recording medium of the present invention were measured using a VSM (vibrating sample magnetometer) at a magnetic field of 7.96 × 10 ² kA / m (10 kOe), and the squareness ratio in the tape running direction was 0. It is preferable that it is 70 or more, More preferably, it is 0.75 or more, More preferably, it is 0.80 or more. The squareness ratio in the two directions perpendicular to the tape running direction is preferably 80% or less of the squareness ratio in the running direction. The SFD of the magnetic layer is preferably 0.7 or less, more preferably 0.6 or less.
The surface roughness Ra of the magnetic layer is preferably 1 to 10 nm, but the value should be appropriately set according to the purpose. In order to improve electromagnetic conversion characteristics, (Ra) is preferably as small as possible. On the contrary, in order to improve running durability, it is preferable that it is large. The RMS surface roughness (RRMS) determined by evaluation by AFM is preferably in the range of 2 nm to 15 nm. The friction coefficient with respect to SUS420J of the magnetic layer surface and the opposite surface of the magnetic recording medium of the present invention is preferably 0.1 to 0.5, more preferably 0.2 to 0.3. The surface resistivity is preferably 104 to 1012 ohm / sq, and the elastic modulus at 0.5% elongation of the magnetic layer is preferably 1,000 to 20,000 MPa (100 to 2,000 kg / mm ^{2 in} both the running direction and the width direction). ), The breaking strength is preferably 10 to 300 MPa (1 to 30 kg / cm ² ), and the elastic modulus of the magnetic recording medium is preferably 1,000 to 15,000 MPa (100 to 1,500 kg / mm ^{2 in} both the running direction and the width direction). ), The residual elongation is preferably 0.5% or less, and the thermal shrinkage at any temperature of 100 ° C. or less is preferably 1% or less, more preferably 0.5% or less, most preferably 0.1% or less, 0% is ideal. The glass transition temperature of the magnetic layer (the maximum point of loss elastic modulus in dynamic viscoelasticity measurement measured at 110 HZ) is preferably 50 ° C. or higher and 120 ° C. or lower. The loss elastic modulus is preferably in the range of 1 × 10 ⁷ to 8 × 10 ⁸ Pa (1 × 10 ⁸ to 8 × 10 ⁹ dyne / cm ² ), and the loss tangent is preferably 0.2 or less. . It is preferable that the loss tangent is 0.2 or less because an adhesive failure hardly occurs.

The residual solvent contained in the magnetic layer is preferably 100 mg / m ² or less, more preferably 10 mg / m ² or less. The porosity of the magnetic layer is preferably 40% by volume or less, more preferably 30% by volume or less. The porosity is preferably small in order to achieve high output, but it may be better to ensure a certain value depending on the purpose. For example, in a data recording magnetic recording medium in which repetitive use is important, a larger porosity is often preferable for running durability. Although the magnetic recording medium of the present invention has at least one magnetic layer, it may have a multilayer structure depending on the purpose. Further, a nonmagnetic layer comprising at least a nonmagnetic powder and a binder may be provided between the magnetic layer and the nonmagnetic support. And it is easily estimated that various physical characteristics can be changed in each layer. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the nonmagnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

VI. Layer Structure In the structure of the magnetic recording medium used in the present invention, the preferred thickness of the nonmagnetic support is 1 to 100 μm. Further, when a smoothing layer is provided between the nonmagnetic support and the nonmagnetic layer or magnetic layer, the thickness of the smoothing layer is preferably 0.01 to 2.0 μm, and preferably 0.02 to 0.02. More preferably, it is 8 μm. The thickness of the backcoat layer provided on the surface opposite to the surface provided with the nonmagnetic layer and the magnetic layer of the nonmagnetic support is preferably 0.1 to 2.0 μm, and 0 More preferably, the thickness is 1 to 2.0 μm.

  The thickness of the magnetic layer is optimized depending on the saturation magnetization amount, head gap length, and recording signal band of the magnetic head to be used, but is preferably 4 nm to 1 μm or less, and preferably 4 nm to 100 nm. More preferred. The thickness variation rate of the magnetic layer is preferably within ± 50%, more preferably within ± 40%. There may be at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic characteristics, and a configuration related to a known multilayer magnetic layer can be applied.

  The thickness of the nonmagnetic layer is preferably 0.2 to 3.0 μm, more preferably 0.2 to 2.5 μm, and further preferably 0.2 to 2.0 μm. Note that the nonmagnetic layer in the magnetic recording medium of the present invention exhibits its effect as long as it is substantially nonmagnetic. For example, even if it contains a small amount of magnetic material as an impurity or intentionally, This shows the effect of the invention and can be regarded as substantially the same configuration as the magnetic recording medium of the invention. “Substantially the same” means that the residual magnetic flux density of the nonmagnetic layer is 10 mT (100 G) or less or the coercive force is 7.96 kA / m (100 Oe) or less, preferably the residual magnetic flux density and the coercive force. It means not having.

  The magnetic recording medium of the present invention is not particularly limited with respect to a head for reproducing a signal magnetically recorded on the magnetic recording medium, but is preferably used for an MR head. When the MR head is used for reproducing the magnetic recording medium of the present invention, the MR head is not particularly limited, and for example, a GMR head or a TMR head can be used. The head used for magnetic recording is not particularly limited, but the saturation magnetization is preferably 1.0 T or more, and more preferably 1.5 T or more.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to an Example. In the examples, “parts” means “parts by weight” unless otherwise specified.

[Synthesis Example 1]
To a 1 L flask, 54 g of stearyl alcohol, 300 ml of n-hexane, and 9 g of sodium hydride containing 60% mineral oil were gradually added with stirring, and then the internal temperature was cooled to 30 ° C. or lower. . To this, 28 g of 2-methoxyethyl chloride was dropped while maintaining the internal temperature at 40 ° C. or lower. The mixture was gradually warmed to reach 90 ° C. in 4 hours to complete the reaction.
The reaction solution is cooled to 40 ° C., washed with water and extracted with hexane. The hexane solution is further washed with water, concentrated under reduced pressure, dissolved again in hexane, passed through a 20 g silica gel column, and washed with hexane. The liquid used in the above was also concentrated under reduced pressure to obtain 58 g of ethylene glycol methyl stearyl ether (Compound A).
H ¹ -NMR (CDCl ₃ ): 3.56 ppm (m, 4H), 3.45 ppm (t, 2H), 3.39 ppm (s, 3H), 1.55-1.63 ppm (m, 2H), 1 .26 ppm (s, 30 H), 0.88 ppm (t, 3 H)
IR νmax (liquid film) 1110, 1467 cm ⁻¹
E-type viscometer measurement: 5.9 mPa · s (50 ° C.)

[Synthesis Example 2]
To a 1 L flask, 409 g of diethylene glycol monomethyl ether and then 9 g of sodium hydride containing 60% mineral oil were gradually added with stirring, and then cooled so that the internal temperature became 30 ° C. or lower. To this, 67 g of 1-stearyl bromide was added while maintaining the internal temperature at 40 ° C. or lower. The mixture was gradually warmed to reach 90 ° C. in 4 hours to complete the reaction.
The reaction solution is cooled to 40 ° C., washed with water and extracted with hexane. The hexane solution is further washed with water, concentrated under reduced pressure, dissolved again in hexane, passed through a 20 g silica gel column, and washed with hexane. The liquid used in the above was also concentrated under reduced pressure to obtain 63 g of diethylene glycol methyl stearyl ether (Compound B).
H ¹ -NMR (CDCl ₃ ): 3.63-3.67 ppm (m, 4H), 3.54-3.61 ppm (m, 4H), 3.45 ppm (t, 2H), 3.38 ppm (s, 3H), 1.53-1.62 (m, 2H), 1.25 ppm (s, 30H), 0.88 ppm (t, 3H)
IR νmax (liquid film) 1112 and 1465 cm ⁻¹
E-type viscometer measurement: 4.5 mPa · s (50 ° C)

[Preparation of magnetic liquid for upper layer (magnetic paint)]
Ferromagnetic metal powder (Co / Fe = 30 atomic%, Hc: 2350 oersted (187 kA / m), S _BET : 55 m ² / g, surface treatment layer: Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , average length Axle length: 50 nm, average needle ratio: 7, σs: 120 A · m ² / kg) 100 parts were ground with an open kneader for 10 minutes, then carbon black (average particle size 80 nm) 2 parts Vinyl chloride resin (Nippon Zeon ( MR-110) 10 parts Polyester polyurethane (Toyobo Co., Ltd .: UR8300) 6 parts (solid content)
60 parts of methyl ethyl ketone / cyclohexanone = 1/1 were added and kneaded for 60 minutes. While operating an open kneader on this kneaded product,
200 parts of methyl ethyl ketone / cyclohexanone = 1/1 were added over 6 hours. Then
20 parts of α-Al ₂ O ₃ dispersion (particle size: 0.3 μm) was added and dispersed for 120 minutes with a sand grinder. 4 parts of polyisocyanate (solid content)
(Nippon Polyurethane Industry Co., Ltd. Coronate 3041)
Lubricant Stearic acid 1 part Compound in table 2 parts Stearic acid amide 0.2 part Toluene 50 parts were added and stirred for 20 minutes.
Then, it filtered using the filter which has an average hole diameter of 1 micrometer, and prepared the magnetic liquid (magnetic coating material) for upper layers.

[Preparation of nonmagnetic liquid (nonmagnetic paint) for lower layer]
85 parts of titanium oxide (average particle size 0.035 μm, crystalline rutile, TiO ₂ content 90% or more, surface treatment layer; alumina, S _BET 35-42 m ² / g, true specific gravity 4.1, pH 6.5-8 .0),
15 parts of carbon black (Ketjen Black EC, manufactured by Ketjen Black International)
The above components were pulverized with an open kneader for 10 minutes, and then vinyl chloride copolymer MR110 (manufactured by ZEON Corporation) 17 parts sulfonic acid-containing polyurethane resin (manufactured by Toyobo, UR8200) 10 parts (solid content)
60 parts of cyclohexanone was added and kneaded for 60 minutes, and then 200 parts of methyl ethyl ketone / cyclohexanone = 6/4 were added and dispersed in a sand mill for 120 minutes. 5 parts of polyisocyanate (Nihon Polyurethane Coronate 3041) (solid content)
Lubricant Stearic acid 1 part Compound in the table 2 parts Oleic acid 1 part Methyl ethyl ketone 50 parts, and further stirred and mixed for 20 minutes, filtered using a filter having an average pore size of 1 μm Magnetic paint) was prepared.

  A polyethylene terephthalate having a thickness of 62 μm so that the thickness after drying of the obtained nonmagnetic paint becomes 1.5 μm, and immediately after that, the thickness after drying of the magnetic paint becomes 0.2 μm. A simultaneous multilayer coating was applied to the surface of the support. With magnetic coating in an undried state, magnetic field orientation is performed with a 5,000 gauss Co magnet and a 4,000 gauss solenoid magnet, and the solvent is dried to form a metal roll-metal roll-metal roll-metal roll-metal roll- After performing a calendar process by a combination of a metal roll and a metal roll (speed 100 m / min, linear pressure 300 kg / cm, temperature 90 ° C.), it was slit to a 1/2 inch width.

[Measuring method]
(1) Durability and storage stability The sliding durability of the tape was brought into contact with the AlTiC cylindrical rod under a 10 ° C. environment at 40 ° C. and a load of 100 g (T1) was applied, and the sliding speed was 2 m / sec. Tape damage after sliding up to 10,000 passes was evaluated according to the following rank.
Further, it was stored at 60 ° C. and 90% for 6 months with a tape wound on a reel for an LTO-G3 cartridge by 600 m. The tape after storage was similarly evaluated.
Excellent: Slight scratches are seen, but there are more parts without scratches.
Good: There are more flawed parts than flawless parts.
Bad: The magnetic layer is completely peeled off.

Claims (3)

An ether compound represented by the formula (1).

In the formula (1), R ¹ represents a linear alkyl group having 12 to 24 carbon atoms, and R ² represents a methyl group or an ethyl group. n represents an integer of 1 to 6.   A lubricant comprising the ether compound according to claim 1. A magnetic recording medium having at least one magnetic layer in which a ferromagnetic fine powder is dispersed in a binder on a nonmagnetic support,
A magnetic recording medium, wherein the magnetic layer contains the ether compound according to claim 1.