JPH0991697A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reaggregation of a magnetic coating material and to improve orientation property of a fine particle magnetic material in the production method of a magnetic recording medium having a magnetic layer containing a ferromagnetic metal powder, by performing ultrasonic treatment in an ultrasonic treating device under specified conditions. SOLUTION: This magnetic recording medium is produced by forming a coating layer on a nonmagnetic base body. The coating layer consists of a magnetic layer containing a ferromagnetic metal powder and a binder, and a lower layer of at least one nonmagnetic layer containing a nonmagnetic powder and a binder. In the production method of this magnetic recording medium, the ferromagnetic metal powder in the magnetic layer has >=120 emu/g saturation magnetization sS and <0.08μm average major axial length, and the magnetic coating material for the upper layer is treated in a ultrasonic treating device under operational conditions of 10 to 200kHz oscillation frequency and 10 to 100μm amplitude of ultrasonic waves. The ultrasonic treatment is performed under condition of 40>t>0.00015T<2> +2 and 10<=T<=1200, wherein t [sec] is the irradiation time of ultrasonic waves and T [sec] is the waiting time from the end point of irradiation of ultrasonic waves to the time when the coating material is applied on the base body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium which prevents re-aggregation of a magnetic coating material and improves the orientation of fine magnetic particles.

[0002]

2. Description of the Related Art As the density of magnetic recording media has been increased, the ferromagnetic metal powder magnetic materials used have higher σs and finer particles, and the reaggregation of the magnetic materials in the magnetic paint and the deterioration of the orientation are major problems. Has become. To solve this problem, various methods have conventionally been proposed to improve the reaggregation of the magnetic material by irradiating the magnetic paint with ultrasonic waves.

[0003]

However, in recent years, the ferromagnetic metal powder magnetic materials used have rapidly become higher in σs and finer, and the magnetic particles have a major axis length of 0.1 μm.
The sizes are getting smaller. Because of this,
Not only is it difficult to disperse the paint, but the tendency for re-aggregation to occur over time from the end of dispersion, and the difficulty in orientation have become remarkable. Can no longer get.

The present invention was devised under these circumstances, and it is an object of the present invention to provide optimum ultrasonic treatment conditions for a magnetic particle having a high σs.

[0005]

In order to solve such a problem, the inventors of the present invention diligently studied the ultrasonic treatment time of a magnetic paint using a fine particle magnetic material and the time from ultrasonic treatment to coating. Then, the ultrasonic treatment condition of the magnetic coating material having excellent orientation was found, and the magnetic recording medium of the present invention and the manufacturing method thereof were obtained.

The above problems of the present invention are as follows. A magnetic layer containing a ferromagnetic metal powder and a binder is provided on a non-magnetic support, or a magnetic layer containing a ferromagnetic metal powder and a binder on the upper layer side and a non-magnetic powder and a binder on the lower layer side. A magnetic recording medium provided with a coating layer consisting of at least one lower layer which is a non-magnetic layer, wherein the ferromagnetic metal powder contained in the magnetic layer has a saturation magnetization σs of 120 emu / g or more and an average length. Shaft length is 0.0
Oscillation frequency of less than 8 μm
A magnetic recording medium which is treated with an ultrasonic treatment device under operating conditions of 0-200 kHz and an ultrasonic amplitude of 10-100 μm, and the magnetic coating after ultrasonic treatment is applied on a support in a multilayered state in which the lower layer is undried. 40. In the method for producing a magnetic recording medium, ultrasonic treatment of the ultrasonic treatment apparatus is performed under the conditions of the following formulas (1) and (2): 40 ≧ t ≧ 0.000015T ² +2 (1) 10 ≦ T ≦ 1200 (2) t: Ultrasonic irradiation time [sec] T: Standby time [sec] from the end of ultrasonic irradiation until coating on the support

[0007] 2. A magnetic layer containing a ferromagnetic metal powder and a binder is provided on a non-magnetic support, or a magnetic layer containing a ferromagnetic metal powder and a binder on the upper layer side and a non-magnetic powder and a binder on the lower layer side. A magnetic recording medium provided with a coating layer consisting of at least one lower layer which is a non-magnetic layer, wherein the ferromagnetic metal powder contained in the magnetic layer has a saturation magnetization σs of 120 emu / g or more and an average length. The axial length is less than 0.08 μm, and the upper magnetic coating material is oscillated at an oscillation frequency of 10 to 200 kHz and an ultrasonic amplitude of 10 to 10 kHz.
In the method for producing a magnetic recording medium, the ultrasonic treatment is carried out by an ultrasonic treatment apparatus under an operating condition of 0 μm, and the magnetic coating after the ultrasonic treatment is applied on the support in a multi-layered manner with the lower layer being undried. The ultrasonic treatment of the apparatus is performed by the following formulas (1) and (2) 40 ≧ t ≧ 0.000015T ² +2 (1) 10 ≦ T ≦ 1200 (2) t: ultrasonic irradiation time [sec] T: The orientation degree is controlled under the condition of a waiting time [sec] from the end of ultrasonic irradiation to coating on the support, and the squareness ratio of the magnetic layer in the coating direction is SQx, the coating direction. And SQy is a squareness ratio in the direction perpendicular to the coated surface, SQy is 0.35 or less, and SQx and SQy satisfy the following formula (3). Method.

(SQx ² + SQy ² ) ^0.5 ≦ 0.926 (3)

[0009]

According to the present invention, since the optimum use form of the ultrasonic treatment device, the ultrasonic irradiation conditions, etc. are set, it is possible to produce a magnetic coating having excellent dispersibility of magnetic powder and less likely to cause reaggregation. As a result, a magnetic recording medium having excellent electromagnetic conversion characteristics can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The constitution of the present invention will be specifically described. The present inventors have made various studies on the ultrasonic treatment conditions of magnetic paints. Among them, the ferromagnetic metal powder (hereinafter referred to as magnetic powder) is made into fine particles and has a high σ value.
It has been found that the dispersion level of the magnetic coating thus changed changes momentarily even after a short waiting time (about 1200 seconds) from ultrasonic treatment to application, and reaggregates. Furthermore, it was found that the reaggregation rate can be controlled by the sonication time. As a result of these studies, the magnetic recording medium prepared by applying the coating using the magnetic powder within the range of the present invention under the ultrasonic treatment conditions of the present invention and applying the coating shows very good electromagnetic conversion characteristics. found.

The magnetic recording media according to the methods of the present invention also have a good degree of orientation of magnetic properties, and all samples have SQy (squareness ratio between the direction of application of the magnetic layer and the direction perpendicular to the application surface). Was 0.35 or less. Further, it was found that the balance between SQx (squareness ratio in the coating direction of the magnetic layer) and SQy is also characteristic and all fall within the range of the following formula (3).

(SQx ² + SQy ² ) ^0.5 ≦ 0.926 (3) The same ultrasonic treatment is outside the scope of the present invention and the major axis length is 0.080 μ.
When applied to a paint using magnetic powder of m or more,
The electromagnetic conversion characteristics are not at a satisfactory level as compared with those of the present invention, and the orientation degree of the magnetic characteristics is good, but SQy
It has been found that SQx tends to increase more than the rate at which becomes smaller and does not satisfy the formula (3). A coating using a magnetic powder having a major axis length of 0.080 μm or more, and ultrasonic treatment conditions outside the scope of the present invention (short treatment time and / or
Alternatively, if the coating standby time is long), the degree of orientation decreases, and SQy may be 0.35 or less and may satisfy the formula (3), but the electrical conversion characteristics at that time were poor.

The method of manufacturing the magnetic recording medium of the present invention will be described in detail below. First, the ultrasonic treatment apparatus used in the method for manufacturing a magnetic recording medium of the present invention will be described. The ultrasonic treatment apparatus includes an ultrasonic treatment tank for performing ultrasonic treatment while allowing a magnetic coating material to be treated to pass through, and an ultrasonic horn that is inserted into the ultrasonic treatment tank to apply ultrasonic vibration to the magnetic coating material. And an ultrasonic transducer connected to the base side of the ultrasonic horn. An ultrasonic wave generator is connected to the ultrasonic vibrator.

FIG. 1 shows the details of the essential parts of such an ultrasonic processing apparatus, particularly in setting the ultrasonic irradiation conditions. As shown in the figure, the ultrasonic treatment tank 20 has a cylindrical inner casing 21 for forming a space E1 in which the magnetic paint flows, and a space provided outside this, in which a coolant such as cooling water flows. An external housing 27 for forming E2 is provided. The magnetic paint 3 to be processed is on the bottom of the inner casing 21.
Is provided with a magnetic paint inlet 22 for introducing
A magnetic paint outlet 23 is provided above the inner casing 21 so that the magnetic paint 3 can continuously flow inside the inner casing 21 (from arrow (a) to arrow (b)). )). The size of the cylindrical inner casing 21 is not particularly limited, but is usually about 25 to 60 mm in diameter. On the other hand, the outer casing 27 is provided with a coolant inlet 28 and a coolant outlet 29 so that a coolant such as cooling water can circulate (arrow (c) to arrow (d)). The external housing 27 can be omitted if necessary.

The ultrasonic horn 30 which is inserted into the ultrasonic treatment tank 20 (in particular, the internal casing 21) has an operating end face 31 (horn tip) for applying ultrasonic vibration to the magnetic paint. The ultrasonic treatment tank 20 facing the operating end surface 31 from the operating end surface 31 of the ultrasonic horn 30.
The working depth H defined by the distance to the wall surface (wall surface of the inner housing 21) 23 of 2 to 40 mm, more preferably 2 to 40 mm.
It is set to 30 mm. Further, the ultrasonic horn 30
The effective dispersion chamber volume V ₀ defined by the area S of the working end face 31 and the working depth H is slightly different depending on the scale of the ultrasonic treatment tank 20, but is preferably 0.6 to 80 cm ³ , and further preferably Is set to 0.9 to 60 cm ³ . The working depth H
However, when it becomes extremely small and becomes less than 2 mm, the working end surface 31 of the ultrasonic horn 30 or the wall surface of the ultrasonic treatment tank facing the working end surface 31 due to ultrasonic vibration (the inner housing 2
The wall surface 23 of No. 1 causes extreme wear (erosion) and a sharp rise in liquid temperature, causes an extreme rise in pressure in the effective dispersion chamber volume V ₀ , and causes inconveniences such as overdispersion. On the other hand, when the operating depth H exceeds 40 mm, there arises a disadvantage that a relatively long ultrasonic wave irradiation time is required and the dispersion is not uniform.
If the effective dispersion chamber volume V ₀ becomes too small, the same inconvenience as when the operating depth H becomes extremely small occurs, and if the effective dispersion chamber volume V ₀ becomes too large, the operating depth H becomes too large. Has the same inconvenience as when the value becomes extremely large.

An ultrasonic transducer 40 is connected to the base side of the ultrasonic horn 30 having such an operation end face 31, and ultrasonic waves emitted from the ultrasonic transducer 40 are transmitted through the ultrasonic horn 30. It is transmitted to the magnetic paint from the working end surface 31. The size of the ultrasonic horn 30 used is not particularly limited, but usually the diameter is 20 to 50 m.
The size is about m.

The ultrasonic processing conditions of the present invention using such an ultrasonic processing apparatus 10 are as follows: Oscillation frequency 10 kHz to 2
00 kHz, ultrasonic amplitude of the operating end face 31 is 10 to 100 μ
m, and the ultrasonic wave irradiation time (the definition of the ultrasonic wave irradiation time will be described later) t and the waiting time T are set within the ranges of the formulas (1) and (2).

When the oscillation frequency and the amplitude deviate from these predetermined ranges, the dispersibility of magnetic powder and the like is good and reaggregation hardly occurs during the irradiation within the ultrasonic wave irradiation time satisfying the above formula (1). No magnetic paint can be obtained. Further, even if the oscillation frequency and the amplitude are within these predetermined ranges, if the ultrasonic wave irradiation time t is less than the lower limit value of the above formula (1), the dispersibility of the magnetic powder and the like is good and reaggregation does not easily occur. No magnetic paint can be obtained. Further, if the ultrasonic wave irradiation time t exceeds the upper limit of the above formula (1), the treatment becomes excessive, and bubbles may be generated during coating to cause coating defects. Further, in the above-mentioned device form, a large number of devices must be connected and processed, resulting in enormous device cost and lacking in economic effect. Further, effects such as dispersibility of the magnetic powder do not match the input cost.

Further, the ultrasonic treatment condition of the present invention is preferably a pressure of 0.01 to 8 kgf / cm ² (gauge pressure), more preferably 0.1 to 4 kgf / cm.
² (gauge pressure). The pressure is present during ultrasonic irradiation because the joint between the ultrasonic horn 30 and the inner casing 21 is in close contact with each other without a gap, and the inner casing 21 forms a sealed system except for the inlet and outlet of the magnetic paint. Because there is.

The definition of the ultrasonic wave irradiation time of the present invention will be described. FIG. 2 shows the ultrasonic processing device 10 shown in FIG.
An example of a series of path processing devices in which three units are connected in series (10a, 10b, 10c) is illustrated. In this figure,
The magnetic paint 3 sent out from the tank 2 at a flow rate Q (l / sec) passes through the pump 4a and the filter 5a,
Second and third ultrasonic processing devices 10a, 10b, 10
It goes through c, and finally pump 4b and filter 5b
It is sent to the coater 6 of the coating section via. in this case,
First, second and third ultrasonic processing devices 10a, 10
The effective dispersion chamber volumes of b and 10c are V _0a and V ₀ , respectively.
_0b and V _0c (the unit is all 1), the total ultrasonic wave irradiation time t is t = V _0a / Q + V _0b /
It is represented by Q + V _0c / Q. Of course, if only the first ultrasonic processing apparatus 10a is used, it is represented by t = V _0a / Q. Therefore, once the ultrasonic wave irradiation time t, the number of ultrasonic processing devices to be used and the effective dispersion chamber volume are determined, the flow rate Q of the magnetic paint 3 is adjusted so that the ultrasonic wave irradiation time t can be obtained.
Just adjust. In addition, in the case of this pass processing, ultrasonic irradiation from the ultrasonic processing apparatus is continuously performed without interruption. Further, excessive coating material may be withdrawn immediately before the coater so that the coating amount becomes appropriate for the flow rate Q.

Although not shown, the tank 2a shown in FIG.
The magnetic coating material that has not been subjected to ultrasonic treatment is appropriately replenished from the upper part of the.

The magnetic coating material which has been subjected to the ultrasonic treatment as described above is supplied to the coating portion, where it is coated on the support. In this case, assuming that the waiting time T (sec) is the time from ultrasonic treatment to coating on the support, the ultrasonic-treated magnetic coating is within the waiting time that satisfies the above formula (2). It is necessary to coat it on the support. When the waiting time T is more than the above range, the magnetic coating material re-aggregates, and the predetermined effect of the ultrasonic treatment cannot be obtained. Further, in order to keep T within the above range, it is necessary to install the ultrasonic treatment device and the coater very close to each other to reduce the piping capacity as much as possible. If it is too close to, the vibration of the ultrasonic treatment device will appear in the coating accuracy and uniform coating cannot be performed.

Next, the magnetic paint used in the method of manufacturing the magnetic recording medium of the present invention will be described. For magnetic paint,
Magnetic powder, a binder (binder), and a solvent are contained as main components. Examples of the magnetic powder used include ferromagnetic metal powder.

As the ferromagnetic metal powder, Fe, Ni, C
o and these alloys are illustrated, α-Fe, Fe-C
o, Fe-Ni, Fe-Co-Ni, Co, Co-Ni
When using a ferromagnetic metal element as the main component, such as
The metal (Fe, Co, Ni, etc.) or alloy is preferably contained in an amount of 70 wt% or more, and more preferably 75 wt% or more. In a ferromagnetic metal powder containing Fe as a main component and at least Co, the F
The amount of Co atoms with respect to e atoms is 5 to 40 wt%, preferably 6 to 35 wt%. Further, it is preferable that the ferromagnetic metal powder containing Fe and / or Co as a main component further contains a rare earth element containing Y. Further, the ferromagnetic metal powder may be an oxide film on the surface of the particle, a partially carbonized or nitrided ferromagnetic metal powder, or a ferromagnetic metal powder having a carbonaceous film on the surface. The ferromagnetic metal powder may contain a small amount of hydroxide or oxide. As these ferromagnetic metal powders, those obtained by a known manufacturing method can be used, and the following methods can be mentioned. Examples of the production method include a method in which an organic acid salt of ferromagnetic metal (mainly oxalate) is reduced with a reducing gas such as hydrogen, iron oxide hydroxide or iron oxide obtained by heating iron oxide hydroxide is converted into hydrogen oxide or the like. , A method of thermally decomposing a metal carbonyl compound, a method of reducing an aqueous solution of a ferromagnetic alloy with a reducing agent such as sodium borohydride, hypophosphite or hydrazine, and a low pressure metal. And a method of obtaining a fine powder by evaporating in an inert gas. The ferromagnetic metal powder thus obtained is subjected to a known slow oxidation treatment, that is, a method of immersing in an organic solvent and then drying, and immersing in an organic solvent and then sending an oxygen-containing gas to form an oxide film on the surface and drying. Any of the methods of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent can be used.

All of the above magnetic powders include Al, Si, Cr, Mn, Co, Ni, Zn and C.
u, Zr, Ti, Bi, Ag, Pt, B, C, P, N,
S, Sc, V, Mo, Rh, Pd, Sn, Sb, Te,
Ba, Ca, Ta, W, Re, Au, Hg, Pb, L
A small amount of an element such as a, Sr or a rare earth may be added, and among these elements, Al, Si,
Addition of P and rare earth elements has effects such as improving the particle size distribution and preventing sintering. Further, these magnetic powders may be covered with Al, Si, P or an oxide film thereof, or may be surface-treated with a coupling agent such as Si, Al, Ti or various surface active agents. Ferromagnetic metal powder is soluble in water Na, K, Ca, Fe, Ni
Although it may contain inorganic ions such as, the amount thereof is preferably 500 ppm or less.

These magnetic powders may be previously treated with a dispersant, a lubricant, a surfactant, an antistatic agent, etc., which will be described later, before the dispersion. The water content of the magnetic powder may be 0.1 to 2%, but it is preferably optimized depending on the type of binder. The pH of the magnetic powder is preferably optimized depending on the combination with the binder used, and the range is 4 to 12, preferably 8 to 12. The specific surface area of these magnetic powders measured by the BET method is 55 to 80 m ² / g, preferably 60 to 70 m.
² / g, noise becomes high when it is less than 55 m ² / g, and dispersion is difficult when it exceeds 80 m ² / g,
Not preferred.

Such magnetic powder is usually used in the binder 1.
The content of the magnetic powder in the magnetic layer is 75-95% of the total.
If the content of the magnetic powder is too large, the amount of additives such as resin in the magnetic layer is relatively reduced, so that the durability of the magnetic layer is reduced. However, if the number is too small, high playback output cannot be obtained. These magnetic powders may be used alone or in combination of two or more.

Among these magnetic powders, a ferromagnetic metal magnetic powder containing 5 to 40 wt% of Co with respect to Fe and having a saturation magnetization σs of 120 emu / g or more (in particular, 125 emu / g to 170 emu / g) is used. g) and the average major axis length is 0.08 μm or less (in particular, 0.06 μm to 0.
(7 μm) ferromagnetic metal magnetic powder is used, the effect of the ultrasonic treatment of the present invention becomes remarkable particularly from the viewpoint of medium characteristics. As the binder used in the magnetic paint, a thermoplastic resin, a thermosetting or reactive resin, an electron beam functional modified resin, etc. are used, and the combination thereof is appropriately selected and used according to the characteristics of the medium and process conditions. It

The thermoplastic resin has a softening temperature of 150.
C. or less, an average molecular weight of 5,000 to 200,000, and a degree of polymerization of about 50 to 2,000. Thermosetting resins, reactive resins or electron beam functional modified resins have the same average molecular weight and polymerization as thermoplastic resins. Degree of application, coating, drying,
By heating and / or irradiating with an electron beam after calendering, the molecular weight becomes infinite due to reactions such as condensation and addition.

Of these, a combination of a vinyl chloride-based copolymer and a polyurethane resin as shown below is preferably used. The vinyl chloride copolymer preferably has a vinyl chloride content of 60 to 95 wt%, particularly preferably 60 to 90 wt%, and its average degree of polymerization is preferably about 100 to 500.

Examples of such vinyl chloride resins include vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-hydroxyalkyl (meth) acrylate copolymers, vinyl chloride-vinyl acetate-maleic acid, vinyl chloride- Vinyl acetate-vinyl alcohol-maleic acid, vinyl chloride-vinyl acetate-hydroxyalkyl (meth) acrylate, vinyl chloride-vinyl acetate-hydroxyalkyl (meth) acrylate-maleic acid, vinyl chloride-
Vinyl acetate-vinyl alcohol-glycidyl (meth) acrylate, vinyl chloride-hydroxyalkyl (meth)
Acrylate-glycidyl (meth) acrylate, vinyl chloride-vinyl acetate-vinyl alcohol-glycidyl (meth) acrylate copolymer, vinyl chloride-hydroxyalkyl (meth) acrylate-allyl glycidyl ether, vinyl chloride-vinyl acetate-vinyl alcohol-
Although there are copolymers such as allyl glycidyl ether, a copolymer of vinyl chloride and an epoxy (glycidyl) group-containing monomer is particularly preferable. Such vinyl chloride copolymer, preferably those containing as a polar group a sulfate group and / or a sulfo group (hereinafter referred to as S-containing polar group), S-containing polar group (-SO 4 _Y, -SO ₃ In Y), Y may be either H or an alkali metal, but it is particularly preferable that Y = K and —SO ₄ K or —SO ₃ K, and one of these S-containing polar groups is Or both may be contained, and when both are contained, the ratio is arbitrary. In addition, these S-containing polar groups are present in the molecule as S atoms in an amount of 0.01 to 10 wt.
%, Particularly preferably 0.1 to 5 wt%.

As the polar group, if necessary, in addition to the S-containing polar group, -OPO ₂ Y group, -PO ₃ Y group, -COO.
Y group (Y is H, alkali metal), amino group (-N
R ₂ ), —NR ₃ Cl (R is H, methyl, ethyl) and the like can be contained. In this, the amino group is the above S
It does not need to be used in combination with, and may be various ones, but especially dialkylamino group (preferably having 1 carbon atom).
Alkyl of -10) is preferred.

Such an amino group is usually obtained by amine modification, and a copolymer of vinyl chloride / alkylcarboxylic acid vinyl ester is dispersed or dissolved in an organic solvent such as alcohol, and an amine compound (aliphatic amine) is contained therein. , A cycloaliphatic amine, alkanolamine, alkoxyalkylamine, etc.) and an epoxy group-containing compound for facilitating the saponification reaction. The vinyl unit having an amino group is obtained by
At t%, ammonium base may still be included as a result.

The resin skeleton to which these S-containing polar groups are bonded is a vinyl chloride resin, and vinyl chloride, a monomer having an epoxy group, and optionally other monomers copolymerizable therewith. Can be obtained by polymerizing in the presence of a radical generator having a strong acid radical containing S such as potassium persulfate and ammonium persulfate, and the amount of these radical generators is usually 0.3-9.0 wt
%, Preferably 1.0 to 5.0 wt%, and since many of them are water-soluble in polymerization, emulsion polymerization or suspension polymerization using alcohol such as methanol as a polymerization medium,
Solution polymerization using a ketone as a solvent is preferable.

At this time, in addition to the radical generator having a strong acid radical containing S, it is also possible to use a radical generator usually used for polymerization of vinyl chloride. It is also possible to combine a radical generator having a strong acid radical containing S with a reducing agent such as sodium formaldehyde sulfoxylate, sodium sulfite and sodium thiosulfate.

Further, examples of the monomer having an epoxy group include glycidyl ethers of unsaturated alcohols such as (meth) allyl glycidyl ether, glycidyl esters of (meth) acrylic acid such as glycidyl (meth) acrylate, Glycidyl-p-vinyl benzoate, methyl glycidyl itaconate, glycidyl ethyl malate, glycidyl vinyl sulfonate, glycidyl esters of unsaturated acids such as glycidyl (meth) allyl sulfonate, butadiene monooxide, vinyl cyclohexene monooxide, 2-methyl- Examples thereof include epoxide olefins such as 5,6-epoxyhexene and the like, and are generally used within a range where the amount of epoxy groups in the copolymer is 0.5 wt% or more.

In addition to vinyl chloride and a monomer having an epoxy group, examples of a monomer that can be used as required include vinyl acetate, vinyl propionate and other carboxylic acid vinyl esters, methyl vinyl ether, isobutyl. Vinyl ether, vinyl ether such as cetyl vinyl ether, vinylidene chloride, vinylidene fluoride, diethyl maleate, butylbenzyl maleate,
Unsaturated carboxylic acids such as di-2-hydroxymethyl maleate, dimethyl itaconate, methyl (meth) acrylate, ethyl (meth) acrylate, lauryl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples thereof include esters, olefins such as ethylene and propylene, and unsaturated nitriles such as (meth) acrylonitrile.

The polyurethane resin used in combination with such a vinyl chloride resin is particularly effective in that it has good abrasion resistance and adhesiveness to a support.
It may have a hydroxyl group and the like, and particularly preferably has a polar group containing sulfur or phosphorus.

These polyurethane resins are a generic term for resins obtained by reacting a hydroxy group-containing resin such as polyester polyol and / or polyether polyol with a polyisocyanate-containing compound. 500 to 20,000 in average molecular weight
Polymerized to about 0, its Q value (weight average molecular weight /
The number average molecular weight) is about 1.5 to 4.

These urethane resins have a glass transition temperature Tg of −20 ° C. ≦ Tg ≦ in the binder used.
At least two or more kinds different in the range of 80 ° C., and the total amount thereof is 10 to 90 wt% of the total binder;
Containing a plurality of these polyurethane resins is preferable in that the running stability in a high temperature environment, the calendering workability, and the electromagnetic conversion characteristics can be balanced. Further, the vinyl chloride-based copolymer and the S and / or P-containing polar group-containing urethane resin have a weight mixing ratio of 10:90.
It is preferable to use them by mixing so as to be about 90:10. In addition, in addition to these resins, various known resins may be contained in a range of 20 wt% or less of the whole.

Among these urethane resin materials, hydroxy group-containing resins include polyethylene glycol, polybutylene glycol, polypropylene glycol and other polyalkylene glycols, bisphenol A and other alkylene oxide adducts, various glycols and hydroxyl groups. Examples thereof include polyester polyols having chain ends.

As the carboxylic acid component of the polyester polyol, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalic acid, p-
Aromatic oxycarboxylic acids such as oxybenzoic acid and p- (hydroxyethoxy) benzoic acid, succinic acid, adipic acid,
Aliphatic dicarboxylic acids such as azelaic acid, sebacic acid, and dodecanedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, tetrahydrophthalic acid, unsaturated fatty acids such as tetrahydrophthalic acid and alicyclic dicarboxylic acids, trimellitic acid, trimesicin Examples thereof include tricarboxylic acids such as acids and pyromellitic acid, and tetracarboxylic acids.

As the glycol component of the polyester polyol, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, Ethylene oxide adducts such as diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, bisphenol A and propylene oxide adduct, ethylene oxide of hydrogenated bisphenol A And propylene oxide adducts, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. Further, tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol may be used in combination. Other examples of the polyester polyol include lactone-based polyester polyol chains obtained by ring-opening polymerization of lactones such as caprolactone.

The polyisocyanate used is
Tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diisocyanate methylcyclohexane, diisocyanate cyclohexylmethane, dimethoxybiphenylene diisocyanate, diisocyanate compounds such as diisocyanate diphenyl ether, or all isocyanates 7 out of the groups
A triisocyanate compound such as a trimer of tolylene diisocyanate and a trimer of hexamethylene diisocyanate in an amount of not more than mol% is exemplified.

As polar groups contained in these resins,
The S-containing group _-SO 3 M (sulfonic acid groups), - SO
₄ M (sulfate group) and a phosphoric acid-containing polar group include phosphonic acid group = PO ₃ M, phosphinic acid group = PO ₃ M, phosphinic acid group = POM, -P = O (OM1) (OM2),-
OP = O (OM1) (OM2 ), - COOM, -NR 4
X (where M, M1 and M2 are H, Li, Na, K,
-NR _4, shows a -NHR _3, R represents an alkyl group or H, X is a halogen atom) -OH, -N
R ₂ , -N ⁺ R ₃ , (R is a hydrocarbon group), an epoxy group,
It is preferable to use at least one polar group selected from —SH, —CN and the like introduced by copolymerization or an addition reaction. Among them, M is particularly preferably Na, and these polar groups are molecules as atoms. 0.01 to 1 in
It is preferably contained in an amount of 0 wt%, particularly 0.02 to 3 wt%, and these polar groups may be present in the main chain of the skeletal resin or in a branch. Such a urethane resin can be prepared by a known method using a specific polar group-containing compound and / or
Alternatively, it can be obtained by reacting a raw material containing a raw material resin or the like reacted with a specific polar group-containing compound in a solvent or in the absence of a solvent.

Examples of thermoplastic resins other than these include (meth) acrylic resins, polyester resins, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral, nitrocellulose, styrene-butadiene copolymers, polyvinyl alcohol resins. , Polyfunctional polyethers such as acetal resin, epoxy resin, phenoxy resin, polyether resin, polycaprolactone, polyamide resin, polyimide resin, phenol resin, polybutadiene elastomer, chlorinated rubber, acrylic rubber, isoprene rubber, epoxy modified Examples thereof include rubber.

Further, as the thermosetting resin, polycondensation phenol resin, epoxy resin, polyurethane curable resin, urea resin, butyral resin, polmar resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, polyamide resin , Epoxy-polyamide resin, saturated polyether resin, urea formaldehyde resin and the like.

Among the above-mentioned copolymers, those having a hydroxyl group at the terminal and / or side chain are preferable as the reactive resin because crosslinking using an isocyanate and electron beam crosslinking modification can be easily utilized. -COOH to or side chain as a polar _{group, -SO 3 M, -OSO 3 M} , -OPO
_{3 X, -PO 3 X, -PO} 2 X, -N + R 3 Cl -, -
It may contain an acidic polar group such as NR _{2 and the} like, a basic polar group and the like, and the inclusion of these is suitable for improving dispersibility. These may be used alone or in combination of two or more.

As the cross-linking agent for curing the binder resin, various polyisocyanates can be used. One or more kinds of tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate and the like, such as trimethylol propane, can be used. It is preferable to use a cross-linking agent modified to have a plurality of hydroxyl groups, or an isocyanurate-type cross-linking agent in which 3 molecules of a diisocyanate compound are bonded, and the content of the cross-linking agent is 1 to 5 with respect to 100 wt% of the resin.
It is preferably 0 wt%, and the cross-linking agent can three-dimensionally bond with a hydroxyl group or the like contained in the binder resin to improve the durability of the coating layer. Specifically, Coronate L, HL, 3041 manufactured by Nippon Polyurethane Industry Co., Ltd., 24a-100, TPI-100, BFGood manufactured by Asahi Kasei Corporation.
The death modules L and N manufactured by Rich Co. may be mentioned.
Generally, to cure such reactive or thermosetting resins, 6-100 at 50-80 ° C in a heating oven.
Heat for 80 hours or at low speed, 80-120 ℃
Or run in the oven.

Further, according to the method known to the above copolymer,
It is also possible to use those modified by electron beam functional modification by introducing a (meth) acrylic double bond. To carry out this electron beam functional modification, tolylene diisocyanate (TD
I) and 2-hydroxyethyl (meth) acrylate (2
-HEMA) has a urethane modification for reacting with a reaction product (adduct), has one or more ethylenically unsaturated double bonds and one isocyanate group in one molecule, and has no urethane bond in the molecule. Ester by reacting a compound having an improved urethane modification using a monomer (2-isocyanatoethyl (meth) acrylate) and a hydroxyl group or a carboxylic acid group with a (meth) acrylic group and a carboxylic acid anhydride or a dicarboxylic acid The method of modification is well known, but among these, the modified urethane modification is not brittle even if the content ratio of the vinyl chloride resin is increased, and it is possible to obtain a coating film excellent in dispersibility and surface property. It is preferable because it is possible.

The content of the electron beam functional group is 1 to 40 mol%, preferably 10 to 30 mol% in the hydroxyl group component in view of stability during production, electron beam curability and the like. In the case of combination, an electron beam curable resin excellent in both dispersibility and curability can be obtained by reacting a monomer so as to have 1 to 20, preferably 2 to 10 functional groups per molecule. The acrylic double bond referred to herein means a (meth) acryloyl group which is a residue of (meth) acrylic acid, (meth) acrylic ester, or (meth) acrylamide. When these electron beam functional resins are used, conventionally known polyfunctional acrylates may be mixed and used in an amount of 1 to 50 wt% in order to improve the crosslinking rate.

When the electron beam functional modified resin is used as a binder, an electron beam is used as a radiation source at the time of curing, from the viewpoint of controlling absorbed dose, introducing it into a manufacturing process line, and shielding ionizing radiation. The method and / or the method using ultraviolet rays are advantageous, in the case of electron beams an accelerating voltage of 100 KV to 750 KV, preferably 150 to 30.
Absorbed dose is 20 ~ 200 using 0KV electron beam accelerator
It is convenient to irradiate so that it is a kilogray. When electron beam cross-linking is performed, N ₂ having an oxygen concentration of 1% or less,
It is important to irradiate with an electron beam in an atmosphere of an inert gas such as He or CO ₂ , and this is to prevent O ₃ or the like generated by the irradiation of radiation from trapping radicals.

On the other hand, when ultraviolet rays are used, a conventionally known photopolymerization sensitizer is added to the binder containing the electron beam curable resin, and the irradiation thereof is performed with a xenon discharge tube or a hydrogen discharge tube. An ultraviolet light bulb or the like may be used.

The solvent contained in the magnetic paint is not particularly limited, but is appropriately selected in consideration of the solubility, compatibility and drying efficiency of the binder, and examples thereof include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. Diluents of aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, alcohols such as isopropanol and butanol, dioxane, tethydrofuran, dimethylformamide, hexane and chlorine-substituted hydrocarbons The agent or solvent is used as a single solvent or a mixed solvent of these in arbitrary ratios.

These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted products, by-products, decomposition products, oxides and water in addition to the main components. 5% by weight or less is preferable, and more preferably 3% by weight or less, and if there are many impurities, the dispersibility of the magnetic powder, the storage stability of the paint, the curing characteristics of the magnetic layer, the storage characteristics in the medium, etc. Adversely affect.

The proportion of the solvent used in the entire coating composition is solid (nonvolatile) concentration of 5 to 40 wt%, preferably 10 to
It may be used in an amount of about 35 wt%, but to determine the solvent type, mixing ratio, and usage amount, the type of pigment used in the paint, the specific surface area, the particle size, and the magnetization amount for magnetic powder, It may be used in consideration of the volume or weight filling degree of the pigment, and further the dilution stability of the coating material.

The solvent addition operation is preferably carried out stepwise in each step of the paint production, such that the solvent is sequentially added to the tank while the flow rate is regulated while stirring, or the paint is gradually mixed with a pipe. It is preferable to carry out the operation, and it is more preferable to perform filtration and / or dispersion treatment at the time of solvent addition or dilution, if possible. By carrying out these operations, the stability of the paint and the generation of aggregates and foreign substances can be prevented. It is possible to suppress.

A lubricant is usually contained in the magnetic paint. As the lubricant to be used, it is preferable to use a fatty acid and / or a fatty acid ester, among various known lubricants, which has 12 to 24 carbon atoms (may contain an unsaturated bond or may be branched). No) monobasic fatty acid, C10 to C24 (whether it contains an unsaturated bond or may be branched) monobasic fatty acid and C2 to C2
Cyclic or polysaccharide reducing alcohols such as monohydric, dihydric, trihydric, tetrahydric, pentahydric, hexahydric alcohol, sorbitan, sorbitol, etc. (including unsaturated bonds or branched) You may use together the mono fatty acid ester which consists of any one of these, a di fatty acid ester, a tri fatty acid ester, these mixtures, or 2 or more types.

Specific examples of the monobasic fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid and elaidic acid. For fatty acid ester, butyl myristate, butyl palmitate, butyl stearate, neopentyl glycol dioleate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, isocetyl stearate, isotrityl Decyl stearate, octyl stearate, isooctyl stearate, amyl stearate,
Butoxyethyl stearate and the like can be mentioned.

The effect of these fatty acids and / or fatty acid esters as lubricants and dispersants appears when the total amount of the ferromagnetic fine powder is 0.1 wt% or more, and the content rate is increased. By letting
The effect becomes remarkable, but if the total content exceeds 20 wt% with respect to the ferromagnetic fine powder, it will not be retained in the magnetic layer and will be discharged onto the surface of the coating film to stain the magnetic head. , And adversely affect the output. Therefore, the content of the fatty acid and / or the fatty acid ester in the magnetic layer is preferably 0.1 to 20 wt%, preferably 1 to 15 wt%, and more preferably 1 to 12 wt% with respect to the ferromagnetic fine powder. More preferable.

In addition to the magnetic layer, the lubricant is preferably contained in the back coat layer, the underlayer, etc. In particular, when the magnetic layer is thin, the lubricant can be contained in the underlayer to improve the still durability. Therefore, it is effective. Further, when there is a back coat layer, a large amount of lubricant can be contained on the back coat layer side to improve the surface lubricity by transfer to the surface of the magnetic layer.

These fatty acids and / or fatty acid esters are not necessarily 100% pure, and may contain impurities such as isomers, unreacted products, by-products, decomposed products and oxides in addition to the main component. . These impurities are preferably 40% or less, more preferably 20% or less.

Further, all or a part of the fatty acids, fatty acid esters, additives and the like used may be added at any step in the production of the coating material for forming the magnetic recording medium.
For example, when mixed with the pigment powder before the kneading step, when added in the kneading step with the pigment powder, the binder and the solvent, when added in the dispersion step, when added after the dispersion, when added immediately before coating, in the solvent There is a method such as applying a diluted or dispersed solution onto a previously applied layer.

The magnetic paint usually contains additives for exerting a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like. For example, silicone oils, fluorine oils, alcohols containing fluorine-substituted hydrocarbon groups, fatty acids, esters, ethers, paraffins, and metals of the above-mentioned monobasic fatty acids (Li, Na, K, Ca, Ba, C).
u, Pb, etc.) salts, alcohols for producing the fatty acid esters, alkoxy alcohols, fatty acid esters of polyethylene oxide-added monoalkyl ethers, aliphatic or cyclic amines, fatty acid amides, quaternary ammonium salts, polyolefins, Nonionic surfactants such as polyglycols, polyphenyl ethers, fluorine-containing alkyl sulfates and their alkali metal salts, alkylene oxides, glycerins, glycidols, adducts of alkylphenol ethylene oxide, and cationic surfactants such as phosphonium or sulfonium. And alkali metal salts thereof, anionic surfactants containing an acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group and phosphoric acid ester group, and alkali metal salts thereof, amino acids, aminosulfones Acids, sulfuric or phosphoric esters of amino alcohols, also amphoteric surfactants and alkyl betaines used.

These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). The total amount of these added is 10 with respect to the magnetic powder.
wt% or less, particularly 0.01 to 5 wt%, and when no magnetic powder is present, 0.005 to 50% relative to the binder.
It may be used in the range of wt%.

Further, the magnetic paint may contain an inorganic compound. Examples of the inorganic powder that can be used include inorganic powders such as metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. Specifically, α-alumina, β-alumina, γ
-Alumina, θ-alumina, δ-alumina, dichromium trioxide, α-iron oxide, γ-iron oxide, goethite, Si
O ₂ , ZnO, TiO ₂ , ZrO ₂ , SnO ₂ , silicon nitride, boron nitride, silicon carbide, titanium carbide, molybdenum carbide, boron carbide, tungsten carbide, calcium carbonate,
Barium carbonate, strontium carbonate, magnesium carbonate, barium sulfate, zinc sulfide, molybdenum disulfide, tungsten disulfide, artificial diamond and the like are used alone or in combination. These inorganic compounds are used in a weight ratio of 0.1 to 20 wt% with respect to the magnetic powder. These inorganic compounds may be appropriately combined and used according to the required characteristics of the magnetic layer.

The shape, size, etc. of the particles of these inorganic powders may be set arbitrarily, but the particle shape is preferably spherical, granular or polyhedral, and the particle size is preferably 0.01.
.About.0.7 μm, and these may be appropriately selected from the balance of durability required for the medium, head wear, and output at the shortest recording wavelength, if necessary, and may be a single system or a mixed system, and may be used alone. It is also possible to select the particle size distribution and the like. The above-mentioned inorganic compound does not necessarily have to be 100% pure, and the effect does not decrease if the main component is 70% or more.

Further, it is necessary that these inorganic compounds contain a small amount of water-soluble alkali metal, alkaline earth metal, chlorine, sulfuric acid, nitric acid, and the like, and a large amount thereof will lead to storage characteristics when used as a medium. Adversely affect. Further, these inorganic compounds may be added at the same time as kneading or dispersing with the magnetic powder, or may be added in advance with a binder and added at the time of dispersing the magnetic coating material.

Further, carbon black may be contained in the magnetic paint. Furnace carbon black, thermal carbon black,
Acetylene black or the like can be used. The particle size of these carbon blacks can be set arbitrarily, but from the balance of the electrical resistance and frictional characteristics required for the medium and the output at the shortest recording wavelength (surface roughness of the medium when carbon black is added) It may be appropriately selected, and a single system or a mixed system may be used, and the particle size distribution and the like may be independently selected. The average particle size of these carbon blacks is 10 nm to 400 nm, preferably 20 to 350 n.
m, more specifically, 20 to 40 nm is preferable when the electromagnetic conversion characteristics are prioritized, and the particle size is as large as possible in the electromagnetic conversion characteristics in the range of 40 to 350 nm when the friction characteristics are emphasized. Is preferably used. Further, in selecting carbon black, it is necessary to consider not only the particle size but also the BET value and the DBP value, but since the particle size, the BET value and the DBP value of carbon black are closely related, they are separated from each other. Since it is impossible to realize numerical values, it is necessary to experimentally select these three elements depending on the required characteristics of the medium and the dispersion characteristics and flow characteristics of the paint.

These carbon blacks are used in a range of 10 to 500 wt% with respect to the binder, or 0.1 to 20 wt% with respect to the magnetic powder. It is necessary to select experimentally according to the dispersion characteristics and flow characteristics. These carbon blacks may be appropriately combined and used according to the required characteristics of the magnetic layer, the back coat layer, the underlayer and the like.
Further, these carbon blacks may be added simultaneously at the time of kneading or dispersing with the magnetic powder, or may be previously dispersed with a binder and added at the time of dispersing the magnetic coating material. Further, these carbon blacks may be surface-treated with a lubricant, a dispersant, or the like, or a part of the surface thereof may be graphitized. 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.

Further, the magnetic paint may contain a non-ferromagnetic organic powder. As the non-ferromagnetic organic powder used, acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, phthalocyanine pigment, azo pigment, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide system Resin powder, fluorohydrocarbon resin powder, divinylbenzene resin powder and the like can be mentioned. The non-ferromagnetic organic powder has a weight ratio of 0.1 to 20 w with respect to the binder.
Used in the range of t%.

As the support coated with such a magnetic coating, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN),
Known films such as polyolefins, polyamides, polyimides, polyamideimides, polysulfone cellulose triacetate, and polycarbonates can be used, preferably PET, PEN, and aromatic polyamide, and more preferably PET or PEN. Or a composite film obtained by multi-layer coextrusion according to three or three types, or an aromatic polyamide. When these films are used, electromagnetic conversion characteristics, durability, friction characteristics, film strength,
Easy balance of productivity.

Further, it is preferable to add inorganic compounds such as oxides and carbonates of Al, Ca, Si, Ti and the like, organic compounds such as fine particles of acrylic resin and the like to these supports, It becomes possible to freely control the surface property by these amounts and sizes, and it is possible to control the electromagnetic conversion characteristics, durability, friction characteristics and the like. Further, these supports may be previously subjected to corona discharge treatment, plasma discharge and / or polymerization treatment,
You may perform an easy adhesive application process, a dust removal process, a relaxation process by heat and / or humidity control, etc.

The center line surface roughness of these supports is 0.03.
It is necessary to use those having a diameter of not more than μm, preferably not more than 0.02 μm, more preferably not more than 0.01 μm. These supports have not only a small center line average surface roughness but also a roughness of 0.5 μm or more. It is preferable that there is no protrusion.
The so-called F-5 value in the tape running direction and the tape width direction of the support is preferably 5 to 50 kg / mm ^2.
And F−5 in the tape longitudinal direction is F− in the tape width direction.
It is generally higher than 5 values, but in some cases, especially in consumer DVT tapes, it is necessary to increase the strength in the width direction. In addition, 1 in the tape running direction and the width direction of the support
The heat shrinkage rate at 00 ° 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 1% or less, more preferably 0.5% or less. Is. The breaking strength of the support is 5 to 5 in both directions.
100 kg / mm ² , elastic modulus is 100 to 2000 kg /
mm ² is preferred.

As a method for applying a magnetic coating material to such a support, an extrusion nozzle coating method is particularly preferable because it is capable of simultaneous multi-layer coating and is easy to control the coating standby time after ultrasonic treatment.

Magnetic paint applied on the support by such a method (this forms a so-called magnetic layer)
Is subjected to a magnetic field orientation treatment, a drying treatment, a smoothing treatment, and the like, if necessary. Thereafter, the magnetic recording medium is formed by, for example, cutting into a desired form. When forming the magnetic layer, a so-called two-layer laminate structure of an upper layer and a lower non-magnetic layer is generally used. In this case, the ultrasonic wave used in the present invention is applied only to the magnetic paint forming the upper layer. Treatment can be performed, or both the magnetic coating material forming the upper layer and the non-magnetic coating material forming the lower layer can be subjected to the ultrasonic treatment used in the present invention.

In particular, carbon black under the magnetic layer,
Inorganic or organic non-ferromagnetic powders with a particle size as small as carbon black and poor paint stability (hereinafter,
Even when forming a lower layer containing a non-magnetic powder), the ultrasonic treatment used in the present invention for the lower layer coating is an effective means for improving the stability of the coating. Is. As the carbon black contained in the underlayer, the above-mentioned furnace, thermal, acetylene black or the like can be used. As the inorganic non-ferromagnetic powder contained in the underlayer, the above-mentioned inorganic powders are used alone or in combination.

The particle size of such an inorganic non-ferromagnetic powder is generally 0.
01 to 0.3 μm is preferable. When the shape of the product is needle-like, the major axis length is 0.03 to 0.3 μm, preferably 0.05 to 0.15 μm, and the needle-like ratio is 5 to 2
It is set to 0, preferably 5 to 15. When the shape of this product is a plate, the plate diameter is 0.05 to 1.0 μm, preferably 0.05 to 0.5 μm, and the plate ratio (ratio between plate diameter and thickness) is It is set to 5 to 20, preferably 10 to 20. Such an inorganic non-ferromagnetic powder is not necessarily 1
It does not need to be 100% pure, and the surface may be made of other compounds such as Al, Si, Ti, Zr, Sn, S depending on the purpose.
The oxide may be formed on the surface by treatment with each compound such as b and Zn. Further, in some cases, the surface treatment may be performed with an organic substance such as polyethylene glycol. The organic non-ferromagnetic powder may be appropriately selected from the above-mentioned organic compounds. The binder used for the underlayer may be appropriately selected from the above-mentioned binders.

[0079]

EXAMPLES The constitution and effects of the present invention will be specifically described with reference to the following examples, but the components, ratios, and operation sequences shown below can be variously changed without departing from the scope of the present invention. It is not limited to the examples. still,
In the following examples, all "parts" are parts by weight.

The respective components of the upper layer magnetic coating material and the lower layer coating material having the following compositions were kneaded using a pressure kneader and then dispersed using a sand mill to prepare the upper layer magnetic coating material and the lower layer coating material.

<Magnetic Coating for Upper Layer> Ferromagnetic metal powder (long axis diameter, coercive force, saturation magnetization amount are those shown in each table) 100 parts Vinyl chloride resin containing potassium sulfonate group (Nippon Zeon Co., Ltd.) MR-110) 10 parts Sodium sulfonate group-containing polyurethane resin (UR-8700 manufactured by Toyobo Co., Ltd.) 8 parts α-alumina (average particle size: 0.15 μm) 8 parts Stearic acid 1 part Butyl stearate 1 part Cyclohexanone / Methyl ethyl ketone / toluene = 3
Adjust the solid content concentration shown in each table at a ratio of 0/35/35

<Nonmagnetic Coating for Lower Layer> Needle-like α-Fe ₂ O ₃ (major axis diameter: 0.15 μm) 100 parts Potassium sulfonate group-containing vinyl chloride resin (MR-110 manufactured by Zeon Corporation) 12 parts Sulfone Sodium acid group-containing polyurethane resin (UR-8700 manufactured by Toyobo Co., Ltd.) 8 parts α-alumina (average particle size: 0.20 μm) 5 parts Stearic acid 2 parts Butyl stearate 2 parts Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 100 parts 5 parts of a polyisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to each of the obtained upper layer magnetic coating material and lower layer non-magnetic coating material.

Examples and Comparative Examples The above-mentioned magnetic coating material for the upper layer was subjected to ultrasonic treatment under the conditions shown in each table, and then, similarly under the condition that it was applied with the waiting time shown in each table, Wet-on-using magnetic paint alone or magnetic paint for upper layer and paint for lower layer
Multi-layered support by wet method (PEN: 5.0μ
m). However, the coating was performed within 2 hours after the polyisocyanate compound was added to the paint. After coating, while the coating film is undried, use a solenoid magnet in a drying furnace to perform orientation treatment with the magnetic field strength shown in each table, then dry it, and then perform surface smoothing treatment with a calendar. Then, a single layer having the thickness shown in each table or a magnetic layer consisting of an upper layer and a lower layer was formed.

Further, a 0.5 μm back coat layer was formed on the surface (rear surface) of the support opposite to the magnetic layer to obtain a wide magnetic tape stock.

The magnetic tape stock thus obtained is 8 mm
A magnetic recording medium was prepared by slitting the sample into an 8 mm video cassette and loading it into an 8 mm video cassette.

Measuring Method <Magnetic Properties: Squareness Ratio SQx, SQy> Using VSM manufactured by Toei Industry Co., Ltd., measurement was performed with an applied magnetic field of 10 kOe.
The squareness ratios SQx and SQy in the application direction and the application orthogonal direction were measured.

<Surface roughness: Ra> A stylus of 0.1 × 25 μm was used with a surface roughness measuring device “Taristep” manufactured by Rank Taylor Hobson Co., and a magnification of 50,000 times,
Measurement length 0.5 mm, measurement speed 0.0025 mm / se
c, measured under the condition of filter cutoff 0.33 Hz,
Ra was determined according to JIS B 0601.

<Electromagnetic conversion characteristics: RF-OUT, C / N>
A Hi8 deck manufactured by Sony Corporation: EV-BS3000 was used to measure the reproduction output and C / N at a recording wavelength of 7.6 MHz. The measurement results are shown as relative values with the standard shown in each table as 0 db.

Ultrasonic Treatment Device / Conditions An ultrasonic treatment device used for ultrasonic treatment of magnetic paint and a schematic view of coating are shown in FIG. The volume of the portion sandwiched between the working end surface of the ultrasonic horn and the wall surface of the ultrasonic processing tank facing the working end surface shown in the figure is the processing capacity of this ultrasonic processing apparatus. The ultrasonic wave has an oscillation frequency of 20 kHz and an amplitude of 25 μm.
It was irradiated under the conditions of. The pressure in the ultrasonic treatment tank at this time varied depending on the flow rate of the liquid to be sent and the inner diameter of the pipe.
It was within the range of 1.5 kgf / cm ² . The ultrasonic treatment time t and the coating standby time were adjusted by changing the number of connected ultrasonic treatment devices, the flow rate of the magnetic coating solution sent, and the pipe volume from the ultrasonic treatment to the coating. The flow rate of the magnetic coating solution is composed of the required flow rate of the magnetic coating material for forming the target magnetic layer thickness on the support and the excess flow rate of the magnetic coating material, and the excess coating material is drawn out from the coater and returned to the delivery tank. However, the piping capacity for withdrawal and the capacity of the liquid transfer tank are set to be sufficiently large so that the influence of mixing of the coating material that has been ultrasonically treated once can be ignored. The volume of the pipe from the ultrasonic treatment to the coating was adjusted by changing the volume of the filter installed in the middle or changing the inner diameter of the pipe itself.

The ultrasonic processing time t is the ultrasonic processing time t = (processing capacity of one device × number of devices) /
(Required paint flow rate + excess paint flow rate) The coating standby time T is represented by the coating standby time T = (pipe volume from the ultrasonic treatment to the coater outlet) / (required paint flow rate + excessive paint flow rate). Strictly speaking, when a plurality of ultrasonic processing devices are connected and used, the ultrasonic processing time is not performed between the processing devices, but the ultrasonic processing time is the total processing time received by each processing device. The coating standby time was defined as the time from the last ultrasonic treatment (after passing through the ultrasonic operation portion in the ultrasonic treatment tank) until the coating on the support.

Results Tables 1 and 2 show examples / comparative examples in a single layer. As shown in the table, by using the magnetic powder in the range of the present invention and performing the treatment in the ultrasonic treatment condition range of the present invention, RF-OUT, C / N
In both cases, a good magnetic tape can be obtained. Under the processing conditions outside the scope of the present invention (the processing time is short or the coating standby time is long), the squareness ratios SQx and SQy are both poor, and the surface smoothness is insufficient, and RF-OUT, C / N
Both are low. When the average major axis length of the magnetic powder is 0.08 μm or more, the C / N is low, and the saturation magnetization σs is 120 emu / g.
If it is less than this, RF-OUT becomes low and a good magnetic tape cannot be obtained. In addition, in order to reduce the coating standby time to less than 10 seconds due to the structure of the coating device, the piping capacity should be minimized by, for example, connecting the ultrasonic treatment device directly to the coater or performing ultrasonic treatment in the coater. It is possible with.
However, if the coater and the ultrasonic treatment device are brought too close to each other, the effect of vibration of the ultrasonic treatment device will appear in the coating accuracy, and uniform coating cannot be performed. Especially the upper layer is 0.20
In the case of a multi-layered thin film having a thickness of μm or less, the influence becomes remarkable, and the multi-layer coating becomes impossible.

Next, Tables 3 to 6 show examples / comparative examples of a multi-layer magnetic layer using a non-magnetic layer as a lower layer. A magnetic tape having good RF-OUT and C / N can be obtained by using the magnetic powder in the range of the present invention even in the multi-layer and performing the treatment in the ultrasonic treatment condition range of the present invention. Under the processing conditions outside the scope of the present invention (the processing time is short or the coating standby time is long), the squareness ratios SQx and SQy are both poor, and the surface smoothness is insufficient, and both RF-OUT and C / N are poor. Low. When the average major axis length of magnetic powder is 0.08 μm or more, C /
When N is low and the saturation magnetization amount σs is less than 120 emu / g, RF-OUT becomes low and a good magnetic tape cannot be obtained.

Further, when the magnetic field strength of the oriented magnet is increased, the orientation degree is further improved and SQy is reduced when the ultrasonic treatment conditions of the present invention are applied, and RF-OUT, C
/ N is improved, on the other hand, the orientation degree hardly changes in the treatment under the treatment conditions (short treatment time / long coating standby time) outside the range of the present invention, and RF-OUT, C / N
There was almost no improvement in.

When the ultrasonic treatment time is set longer than 40 seconds, the treatment becomes excessive and there is a demerit that bubbles are generated in the paint. Further, a large number of ultrasonic processing devices are required, which causes a cost problem, but the effect of improving the performance due to the processing time is saturated.

In addition, by setting the thickness of the magnetic layer in the multi-layer of the lower non-magnetic layer to 0.20 μm or less, the effect of self-demagnetization is reduced, the effect of calendering is enhanced, and smoothing is achieved. As a result, the required amount of coating is reduced / the flow rate of coating is reduced, which makes it possible to increase the ultrasonic treatment time even with the same number of ultrasonic treatment devices.
Both UT and C / N are greatly improved. However, in this case, it is necessary to adjust the pipe capacity so that the coating standby time is 1200 seconds or less.

As described above, according to the present invention, the RF-OU is used.
It is possible to provide a magnetic tape excellent in T and C / N.

[0097]

[Table 1]

[0098]

[Table 2]

[0099]

[Table 3]

[0100]

[Table 4]

[0101]

[Table 5]

[0102]

[Table 6]

[0103]

EFFECTS OF THE INVENTION According to the present invention, the optimum sonication condition is provided for the fine σs fine particle magnetic substance, and the high electromagnetic conversion characteristics can be obtained by having the specific orientation balance that can be produced under the condition. The magnetic recording medium shown and the manufacturing method thereof can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of an ultrasonic processing apparatus used in the present invention.

FIG. 2 is a schematic process diagram when ultrasonic processing is performed by pass processing.

[Explanation of symbols]

 3 Magnetic Paint 10 Ultrasonic Processing Device 20 Ultrasonic Processing Tank 23 Opposing Wall Surface 30 Ultrasonic Horn 31 Operating End Face of Ultrasonic Horn 40 Ultrasonic Transducer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryosuke Isobe 1 Sakura-cho, Hino-shi, Tokyo Konica stock company (72) Inventor Yasunobu Kobayashi 1 Sakura-cho, Hino-shi, Tokyo Konica stock company (72) Inventor Kaoru Kawasaki 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Akira Saito 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDC Corporation

Claims (2)

[Claims] 1. A magnetic layer containing a ferromagnetic metal powder and a binder provided on a non-magnetic support, or a magnetic layer containing a ferromagnetic metal powder and a binder on the upper layer side and a non-magnetic layer on the lower layer side. A magnetic recording medium provided with a coating layer comprising a powder and at least one lower layer which is a non-magnetic layer having a binder, wherein the ferromagnetic metal powder contained in the magnetic layer has a saturation magnetization σs of 120 emu / g or more, the average major axis length is less than 0.08 μm, and the upper magnetic coating material has an oscillation frequency of 10 to 200 kHz and an ultrasonic amplitude of 10 to 100 μ.
In the method for producing a magnetic recording medium, the ultrasonic treatment is carried out by an ultrasonic treatment apparatus under the operating condition of m, and the magnetic coating after the ultrasonic treatment is applied on the support in a multi-layered manner with the lower layer being undried. A method of manufacturing a magnetic recording medium, characterized in that ultrasonic treatment of the apparatus is performed under the conditions of the following formulas (1) and (2). 40 ≧ t ≧ 0.000015T ² +2 (1) 10 ≦ T ≦ 1200 (2) t: Ultrasonic irradiation time [sec] T: Coated on the support from the end of ultrasonic irradiation Waiting time [sec] 2. A magnetic layer containing a ferromagnetic metal powder and a binder is provided on a non-magnetic support, or a magnetic layer containing a ferromagnetic metal powder and a binder is provided on the upper layer side and a non-magnetic layer is provided on the lower layer side. A magnetic recording medium provided with a coating layer comprising a powder and at least one lower layer which is a non-magnetic layer having a binder, wherein the ferromagnetic metal powder contained in the magnetic layer has a saturation magnetization σs of 120 emu / g or more, the average major axis length is less than 0.08 μm, and the upper magnetic coating material has an oscillation frequency of 10 to 200 kHz and an ultrasonic amplitude of 10 to 100 μ.
In the method for producing a magnetic recording medium, the ultrasonic treatment is carried out by an ultrasonic treatment apparatus under the operating condition of m, and the magnetic coating after the ultrasonic treatment is applied on the support in a multi-layered manner with the lower layer being undried. The ultrasonic treatment of the apparatus is performed by the following formulas (1) and (2) 40 ≧ t ≧ 0.000015T ² +2 (1) 10 ≦ T ≦ 1200 (2) t: ultrasonic irradiation time [sec] T: The orientation degree is controlled under the condition of a waiting time [sec] from the end of ultrasonic irradiation to coating on the support, and the squareness ratio of the magnetic layer in the coating direction is SQx, the coating direction. And SQy is a squareness ratio in the direction perpendicular to the coated surface, SQy is 0.35 or less, and SQx and SQy satisfy the following formula (3). Method. (SQx ² + SQy ² ) ^0.5 ≦ 0.926 (3)