JP2001351218A - Magnetic recording medium, and its hardness measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability performance, without deteriorating the tape polishing force or the electromagnetic conversion characteristics of a magnetic recording medium, such as video tapes, audio tapes, or computer tapes. SOLUTION: This magnetic recording medium 3 is provided with a magnetic layer containing magnetic powder and binder, and the magnetic layer exhibits hardness of 1,000 or larger, represented by defining equation 1. Defining equation 1: Hardness = load (mg)/pushing-in depth (μm). A loading section 19 is moved by a bimorph 6, while the magnetic recording medium 3, in provided with the magnetic layer containing the magnetic powder and the binder, is supported and loaded on the loading section 19 in a side opposite the magnetic layer, the magnetic layer is abutted on a load-detecting section 2, and the hardness of the magnetic layer is calculated by the definition equation 1 below, based on a correlation between the pushing-in depth of the load detecting section 2 with respect to the magnetic layer and the applied load. In this way, the magnetic medium 3 and a hardness measuring device 9 are constructed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a method and apparatus for measuring the hardness of a magnetic recording medium suitable for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, high-definition VTR (Video tape)
As the performance of VTRs typified by recorders and digital VTRs increases, there is a demand for improved characteristics of magnetic recording media. For this reason, the development of a vapor deposition type magnetic recording medium capable of obtaining higher output electromagnetic conversion characteristics than the coating type has been actively conducted.

[0003] However, a vapor deposition type magnetic recording medium is
Since magnetic metals such as iron, cobalt, and nickel are formed by vapor deposition on a non-magnetic support in a vacuum, the magnetic surface has a high surface energy, and there is a problem of deterioration of durability due to friction.

Further, in the vapor deposition process, a vacuum device and a device such as a laser for converting metal into vapor are complicated and expensive, and the productivity is higher than that of other coating type magnetic recording media. bad.

For this reason, the development of a high-performance coating type magnetic recording medium has been actively studied. In recent years, the recording wavelength has been further shortened in order to achieve high density and large capacity, and the size of magnetic powder used has also been reduced to fine particles.

[0006] Generally, in a magnetic recording medium, a VTR is used.
When the vehicle is run on a magnetic recording medium,
It is required to ensure durability so that abnormalities in recording and reproduction of a signal called “head clog” that accumulates on a magnetic head such as R and the like do not occur.

For this reason, it is urgently necessary to ensure the durability of the magnetic recording medium using high-performance fine magnetic powder.

In general, the durability of a magnetic recording medium is evaluated based on the time from when the magnetic recording medium is run on a VTR or the like until "head clog" occurs.

[0009] Further, after traveling, the surface of the magnetic head of the VTR is observed with a microscope, and the measurement of the “powder amount” for measuring the amount of the falling-off material from the magnetic recording medium is used in an auxiliary manner.

Here, as a method of evaluating the durability of a magnetic recording medium, a method called "PH" (print house mode) is used. In this method, a video tape is copied only once and a large number of cassettes are used without overwriting. There are two methods: a method of repeating one pass per cassette and a method of repeating a cassette a number of times called a "shuttle". However, since falling objects from the magnetic recording medium tend to decrease as the number of runs increases, it is generally considered that “PH” is more severe as a durable running mode than “shuttle”. .

Heretofore, as a means for improving the durability of a magnetic recording medium, attention has been paid to the abrasives and binders contained in the magnetic layer, and studies have been made by changing them.

[0012]

Generally, when the amount of the abrasive is increased or the particle size is increased, the durability of the magnetic recording medium is improved. On the other hand, however, since the surface properties of the magnetic layer become rough, spacing loss increases, and electromagnetic conversion characteristics deteriorate. Furthermore, the polishing power of the tape is improved,
Since the amount of wear of the magnetic head during VTR running increases, there is a disadvantage that the life of the magnetic head is shortened.

Regarding the above-mentioned problem, the durability was changed by changing the kind and the mixing ratio of the binder, but the index affecting the durability was unclear, and the same binder was used in the same amount. Even when used, the durability was significantly different under subsequent manufacturing conditions. Therefore, the durability of the magnetic recording medium has been ensured by sacrificing the wear amount of the magnetic head and the electromagnetic conversion characteristics to some extent. For this reason, a management method that can accurately grasp the durability of the magnetic recording medium has been required.

It has been conventionally known that, in a magnetic recording medium, increasing the hardness of the magnetic layer deteriorates the contact property with the magnetic head, thereby deteriorating the electromagnetic conversion characteristics. The hardness specified by the formula 1 is in the range of about 600 to 800. However, in each case, the PH durability was not sufficiently satisfied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional circumstances, and has as its object to reduce the tape polishing force and electromagnetic force of a magnetic recording medium such as a video tape, an audio tape, and a computer tape. An object is to improve the durability performance without deteriorating the conversion characteristics.

[0016]

Means for Solving the Problems The present inventor conducted a sincere study in view of such a situation and found that the "hardness" of the magnetic layer of the magnetic recording medium affects the durability of the magnetic recording medium. The present invention was completed by maintaining this at a certain value or more.

That is, the present invention relates to a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder, wherein the magnetic layer has a hardness of 1000 or more represented by the following definition formula 1. is there. Definition formula 1: Hardness = load (mg) / indentation depth (μm)

Further, according to the present invention, there is provided a driving means in which a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder is supported and mounted on a mounting portion on a surface opposite to the magnetic layer. By moving the mounting portion according to the above, the magnetic layer is brought into contact with the load detection unit, and the hardness of the magnetic layer is defined by the following definition formula 1 by the correlation between the load and the load of the load detection unit against the magnetic layer. The present invention relates to a method for measuring the hardness of a magnetic recording medium, which is determined based on the following formula. Definition formula 1: Hardness = load (mg) / indentation depth (μm)

Further, according to the present invention, a load measuring means provided with a load detecting section and a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder are supported on a surface opposite to the magnetic layer. A mounting portion on which the magnetic recording medium is mounted on the mounting portion, wherein the mounting portion has a moving portion configured to move the mounting portion toward the load measuring device. By moving the mounting portion, the magnetic layer is brought into contact with the load detector, and the hardness of the magnetic layer is defined by the following definition formula 1 by the correlation between the depth of the load detector and the load on the magnetic layer and the load. The present invention relates to an apparatus for measuring the hardness of a magnetic recording medium, which is configured to be determined based on the above. Definition formula 1: Hardness = load (mg) / indentation depth (μm)

According to the present invention, the hardness of the magnetic layer of the magnetic recording medium is determined by the above-mentioned definition formula 1, and the hardness according to the definition formula 1 is kept as high as 1000 or more, so that the electromagnetic conversion characteristics of the magnetic recording medium and the magnetic head The durability of the magnetic recording medium can be improved without significantly deteriorating the amount of wear, thereby providing a magnetic recording medium that can support high-density digital recording.

On the other hand, the definition formula 1 is used for measuring the hardness of the magnetic layer.
It has been found that the use of a commercially available hardness tester that is not dependent on the above is susceptible to external vibration and the measurement environment, and that reproducibility of the measured hardness value cannot be obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the magnetic recording medium of the present invention, the hardness of the magnetic layer is 1300 or less, and the center line average roughness Ra of the surface of the magnetic layer is 1.6 μm.
The value measured by a non-contact type roughness meter is preferably 13 to 21 nm.

In the method and apparatus for measuring the hardness of a magnetic recording medium according to the present invention, the mounting section comprises a head section for mounting the magnetic recording medium and a driving section for driving the head section. Preferably, both ends of the magnetic recording medium are pulled in opposite directions.

Further, the load detecting section has a needle-like tip pushed into the magnetic layer, the head section is driven by a bimorph as a driving means, the bimorph is operated by a DC power supply, and the head section moves. It is desirable to do.

Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.

In the present invention, a schematic diagram of the hardness measuring device 9 used for measuring the hardness of the magnetic recording medium is shown in FIG. 2, and the measuring method will be described in detail. In addition, the following hardness tester 9
The head is used to correspond to the actual use situation.

First, the magnetic recording medium 3 is mounted on the mounting section 19 on the head 4 having the core 16 with the magnetic layer facing upward. Next, the magnetic recording medium 3 supported by the guide 5
Attach weights 7 to both ends of. The mounting portion 19 of the head 4 has a mirror surface and a moderately curved surface so that no gap is formed between the mounting portion 19 and the magnetic recording medium 3.

Further, a bimorph 6 which expands and contracts linearly with the applied voltage is attached to the lower portion of the head 4.
By changing the applied voltage from the DC power supply 8, the head 4 moves vertically (shown) in the vertical direction.

The load meter 1 is fixed above the head 4 in the vertical direction, and the load detector 2 attached to the load meter 1 is a stylus having a tip having a radius of curvature of 1 μm.

Next, as shown in FIG. 3A, the voltage applied to the bimorph 6 is changed by the DC power supply 8 (not shown), and the mounting portion of the head 4 on which the magnetic recording medium 3 is mounted is set. 19 is moved upward in the vertical direction. Note that the measurement display of the load meter 1 indicates 0 until the magnetic recording medium 3 placed on the mounting portion 19 on the head 4 contacts the tip of the load detection portion 2 of the load meter 1, and the load is measured simultaneously with the contact. You. Then, as the upward moving distance of the head 4 increases, the force of the magnetic recording medium 3 mounted on the mounting portion 19 on the head 4 to push up the load detecting unit 2 increases, and the load increases.

Next, as shown in FIG. 3B, after the magnetic recording medium 3 mounted on the mounting portion 19 on the head 4 comes into contact with the tip of the load detecting portion 2 of the load meter 1, a load of 300 mg is applied. The vertical movement distance α (unit μ)
m) is defined as “indentation depth” in the following definition formula 1.

The “hardness” of the following definition formula 1 is defined as “load” of 300 mg with a stylus having a radius of curvature of 1 μm from the top of the magnetic layer of the magnetic recording medium 3 in the vertical direction.
"Push depth" of magnetic recording media when adding
(D). That is, the “load” in the definition formula 1 is 300
mg. For example, assuming that “load” is 300 mg and hardness is 1000 or more, “indentation depth” (d)
Is 0.3 μm or less.

Definition 1: Hardness = Load (mg) / Deeping depth d (μm)

In the hardness meter 9 described above, the shape, diameter, length, material and the like of the load detector 2 can be freely selected as long as there is no inconvenience in the measurement. Further, the shape, material, angle of the top curved surface and the like of the head 4 can be freely changed.

Further, the position at which the guide 5 is mounted, the diameter,
The width, number, etc. can be freely changed. The weight 7 may be not only a simple weight but also a traction device, and the weight may be freely changed according to the strength of the magnetic recording medium.

The constitutional requirement of the present invention is that the magnetic layer of the magnetic recording medium has a “hardness” represented by the above-mentioned definition formula 1.
However, in the conventional hardness measurement method, the variation in the numerical value was too large, which was not suitable for measurement of a soft material such as a tape. It is also known that, in a magnetic recording medium, increasing the hardness of the magnetic layer deteriorates the contact property with the magnetic head, thereby deteriorating the electromagnetic conversion characteristics. It is manufactured in a hardness range of about 600 to 800. However, in each case PH
The durability was not sufficiently satisfied. However, according to the hardness measuring method and the hardness measuring apparatus of the present invention, a magnetic recording medium having a higher hardness than a conventionally used range can be controlled with a new measurement index.

Next, a comparison between the hardness meter of the present invention and a conventional hardness meter is shown below.

In the present invention, the surface hardness of the magnetic recording medium, which cannot be detected by a conventional hardness meter, was successfully detected. The hardness meter used in the present invention facilitates measurement of surface hardness that affects the durability of a magnetic recording medium. This becomes more effective by using a magnetic head as a support for the magnetic recording medium when measuring the hardness. In the method of a conventionally known measuring method (reference patent) described later, the influence of the surface roughness that cannot be separated from the surface hardness and the influence of the elasticity of the base film that is the base material are large. By minimizing the influence, the hardness of the pole surface which affects the durability of the magnetic recording medium can be accurately grasped.

In the present invention, in order to achieve a hardness of 1000 or more, the ratio (P / B ratio) of the ferromagnetic powder to the binder (binder), the conditions of calendering,
It is adjusted by a combination such as Tg (glass transition temperature) of the binder. However, when hardness is used as an index with a conventional hardness meter, durability can be ensured by increasing the hardness, but this is not practical because it adversely affects running properties and electromagnetic conversion characteristics. For this reason, among the conventional magnetic recording media, those having a hardness of 1000 or more according to the hardness measurement method of the present invention have not been put to practical use.

As described above, the hardness meter used in the present invention makes it possible to clarify the factors affecting the durability, so that the running performance, the durability, and the electromagnetic conversion characteristics can be satisfied in a well-balanced manner. By controlling conditions that are considered to be harder and more impractical than in the past, characteristics that are better than those of known magnetic recording media can be obtained.

For reference, the apparatus for measuring the hardness and the like according to known patents of other companies are shown below.

TDK Company (See Japanese Patent Publication No. 7-24083)
Has a hardness value of 65 to 70, a hardness tester manufactured by Vickers, and a load of 300 g as a condition. Kao Corporation (refer to Japanese Patent Application Laid-Open No. 11-296838) has a 0.5 to 0.
The hardness value was 9 GPa. Mitsubishi Chemical Corporation (JP-A 9-1
No. 61269) has a hardness value of 30 to 35 g / μm ² using a DUH-50 hardness tester manufactured by Shimadzu Corporation with a load of 0.1 gf. Fuji Film Co., Ltd.
190714) uses an HMA-400 hardness tester manufactured by NEC. Konica Corporation (JP-A-5-3077)
No. 39) uses a thin film hardness meter manufactured by NEC Corporation as a hardness meter.

As a method for controlling the "hardness", the ratio of the magnetic powder to the binder (P / B
Ratio): powder / binder ratio, type of binder, and blending ratio (for example, polyurethane PU / other binder = 8)
0/20 to 30/70), and further, by changing the calendar conditions, line speed, and the like at the time of production.

On the other hand, if only the "hardness" is improved, a problem may occur in running properties or electromagnetic conversion characteristics.
Therefore, as will be described later, preferably, the center line average roughness Ra of the magnetic layer surface is 13 to 21 nm as measured by a non-contact type roughness meter having a laser spot diameter of 1.6 μm (spot radius 0.8 μm). Ideally,

Next, the composition of the magnetic recording medium of the present invention will be described.

The ferromagnetic powder used in the present invention includes:
γ-FeOx (x = 1.33 to 1.5), Co-modified γ-
Known ferromagnetic materials such as FeOx (x = 1.33 to 1.5), a ferromagnetic alloy containing Fe, Ni, or Co as a main component (75% or more), barium ferrite, and strontium ferrite can be used. In addition, these ferromagnetic powders include Al, Si, S, Sc, Ti, V,
Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, S
b, Te, Ba, Ni, Ta, W, Re, Au, Hg,
Pb, Bi, La, Ce, P, Mn, Zn, Co, S
It may contain atoms such as r and B.

More useful magnetic powders in the present invention are ferromagnetic fine metal powders, σs = 100 Am ² / kg to 200 Am ² / kg, specific surface area by BET method of 45 to 60 m ² / g, coercive force 90 kA / g. , From 200kA /
A remarkable effect is seen with g.

In addition, in the magnetic recording medium according to the present invention, a binder, an abrasive, an antistatic agent, a rust preventive, or a magnetic paint other than the nonmagnetic support and the ferromagnetic powder mixed in the magnetic layer are prepared. Any known solvent can be used for this purpose without any limitation.

For example, as the material of the nonmagnetic support, those generally used for magnetic recording media can be used. For example, polyesters such as polyethylene terephthalate and polyethylene naphthalate, and polyolefins such as polyethylene and polypropylene , Cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyimide, polyamide imide, other plastics, metals such as aluminum and copper, aluminum Alloys, light alloys such as titanium alloys, ceramics, single crystal silicon, and the like.

In the present invention, the amount of the polyurethane resin to be added is preferably 1 to 20 parts by weight, more preferably 15 to 5 parts by weight in terms of a magnetic substance fine powder weight ratio. When the amount of the polyurethane resin is small, the adhesiveness to the nonmagnetic support is poor, and the durability is poor. In addition, when the amount of polyurethane resin is large, adverse effects due to adhesion when stored for a long period of time in a magnetic recording medium such as a tape are likely to occur. Therefore, a resin having good compatibility with the polyurethane resin is used in combination in an appropriate amount.

Other known binders can be used for the magnetic layer. That is, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer Copolymer, acrylate-vinylidene chloride copolymer, acrylate-acrylonitrile copolymer, methacrylic acid-vinylidene chloride copolymer, methacrylate-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyfluorinated Vinyl, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer,
Acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde Resin, polyvinyl acetal resin, and a mixture thereof are exemplified.

Of these, polyurethane resins and polyester resins which are supposed to provide flexibility, acrylonitrile-butadiene copolymer and cellulose derivatives which are supposed to provide stiffness, phenol resins and epoxy resins are preferred. The aforementioned binder improves the durability by crosslinking the isocyanate compound, or
It may have a suitable polar group introduced.

Here, in some cases, a layer (undercoat layer) containing the above-mentioned well-known binder as a main component may be provided between the nonmagnetic support and the lower layer for the purpose of increasing the adhesive strength or the like. Absent.

Next, any carbon may be used as the carbon black used in the magnetic layer. Carbon black includes acetylene black, furnace black and the like depending on the production method.

Here, the DBP oil absorption is 30 to 150 m
1 / 100g, preferably 50-150ml / 100g
And the average particle size is 5 to 150 nm, preferably 1
When the specific surface area by the BET method is 5 to 50 nm, it is 40 to 3
00m ² / g, preferably effective ones is 100 to 250 m ² / g. The water content is 0.1 to 10
%, Tap density: 0.1-1 g / cc, pH: 2.0
To 10 are preferred. In addition, carbon black having a larger DBP oil absorption amount has a high viscosity, and the dispersibility is significantly deteriorated. On the other hand, when the amount is small, the dispersibility is poor, so that the dispersing step takes a long time. The smaller the average particle diameter, the longer the dispersion time is required, but the better the surface properties. The larger the average particle diameter, the worse the surface properties. Therefore, the above-mentioned range is preferable.

The carbon black satisfying the above conditions is, for example, RAVEN 1250 (particle size: 23 nm, BET value: 13) manufactured by Columbian Carbon Co., Ltd.
5.0 m ² / g, DBP oil absorption 58.0 ml / 100
g), 1255 (particle size: 23 nm, BET value: 125.0 m)
² / g, DBP oil absorption 58.0 ml / 100 g), 10
20 (particle diameter 27 nm, BET value 95.0 m ² / g, DB
P oil absorption 60.0 ml / 100 g), 1080 (particle size 2
8 nm, BET value 78.0 m ² / g, DBP oil absorption 6
5.0ml / 100g), raben 35, raben 10
40, Raven 1060, Raven 3300, Raven 450, Raven 780, etc., or CONDUCTEX SC (particle diameter 20 nm, BET value 220.
0 m ² / g, DBP oil absorption 115.0 ml / 100 g)
May be. Asahi Carbon Co., Ltd. # 80 (particle size 23n
m, BET value 117.0 m ² / g, DBP oil absorption 11
3.0 ml / 100 g), Mitsubishi Chemical # 22B (particle size 4
0 nm, BET value 5.0 m ² / g, DBP oil absorption 13
1.0 ml / 100 g), # 20B (particle size 40 nm, B
ET value 56.0 m ² / g, DBP oil absorption 115.0 ml
/ 100g), Cabot Black Pearls (BLAC
K PEARLS) L (particle size 24 nm, BET value 250.0 m ²
/ G, DPB oil absorption 60.0 ml / 100 g), Black Pearls 800 (particle size 17.0 nm, BET value 24)
0.0 m ² / g, DBP oil absorption 75.0 ml / 100
g), Black Pearls 1000, Black Pearls 1
100, Black Pearls 700, Black Pearls 9
05 or the like may be used.

In the magnetic recording medium of the present invention, a non-magnetic back coat layer may be provided on the surface of the non-magnetic support opposite to the magnetic layer side. The thickness of the back coat layer is 0.1 to
2.0 μm, preferably 0.3-1.0 μm,
Known ones can be used.

Known lubricants can be used in the present invention. For example, higher fatty acid esters, silicone oils, fatty acid-modified silicones, fluorine-containing silicones, or other fluorine-based lubricants, polyolefins, polyglycols, alkyl phosphates and metal salts, polyphenyl ethers, fluorinated alkyl ethers, alkyl carboxylate amines Amine-based lubricants such as salts and amine salts of fluorinated alkylcarboxylic acids, and C12 to C24
(Which may be unsaturated or branched, respectively), higher fatty acids having 12 to 24 carbon atoms, and the like.

The higher fatty acid ester component used in the present invention is a higher fatty acid ester having 12 to 32 carbon atoms (each of which may be unsaturated or branched). Myristic acid,
Palmitic acid, stearic acid, isostearic acid, arachiic acid, oleic acid, eicoic acid, elaidic acid, hebenic acid, linoleic acid, linoleic acid, etc., methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, pentyl ester, hexyl Esters, heptyl esters, octyl esters and the like.
Specific compound names include butyl stearate, pentyl stearate, heptyl stearate, octyl stearate, isooctyl stearate, butoxyethyl stearate, octyl myristate, isooctyl myristate, butyl palmitate, and the like. Further, the lubricant may be mixed with a plurality of lubricants.

Examples of the abrasive used in the present invention include α-alumina, β-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, diamond, quartzite, garnet, Known materials having a Mohs' hardness of 6 or more, containing silicon nitride, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium oxide, or the like as a main component, are used alone or in combination.

The average particle size of these abrasives is from 0.01 to
Although 2 μm is preferred, abrasives having different particle sizes may be combined as needed, or a single abrasive may be used with a broad particle size distribution.

Similarly, as the antistatic agent, known antistatic agents such as natural surfactants, nonionic surfactants and cationic surfactants can be used in addition to the above-mentioned carbon black.

In the present invention, a known coupling agent may be used. Examples of the coupling agent include a silane coupling agent, a titanate-based coupling agent, and an aluminum-based coupling agent. Here, the addition amount of the coupling agent to 100 parts by weight of the magnetic substance is preferably 0.05 to 10.00 parts, more preferably 0.1 to 5.00 parts.

The silane coupling agent includes γ
-Vinyl silane compounds such as methacryloxy propyl trimethoxy silane, vinyl triethoxy silane and β-
Epoxysilane compounds such as (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimex Aminosilane compounds such as silane and mercaptosilane compounds such as γ-mercaptopropyltrimethoxysilane can be suitably used.

As the titanate coupling agent, tetra-n-butoxytitanium, tetraisopropoxytitanium, bis [2-[(2-aminoethyl) amino]
Ethanolate] [2-[(2-aminoethyl) amino]
Ethanolate-0] (2-propanolate) titanium, tris (isooctadecanoate-0) (2-propanolate) titanium, bis (ditridecylphosphite-0 ″) tetrakis (2-propanolate) dihydrozentitanate, bis (Dioctyl phosphite-
0 ") tetrakis (2-propanolate) dihydrozentitanate, tris (dioctylphosphite-
0 ") (2-propanolate) titanium, bis (dioctylphosphite-0") [1,2-ethanediolate (2-)-0,0 '] titanium, tris (dodecylbenzenesulfonate-0) ( 2-propanolate)
Titanium, tetrakis [2,2-bis [(2-propenyloxy) methyl] -1-butanolate titanate, and the like can be mentioned. Commercially available products are Ajinomoto Co., Inc., Prenact KRTTS, KR 46B, KR 55, and KR 41.
B, KR 38S, 338X, KR 138S, KR
238S, KR 12, KR 44, KR 9SA, KR
34S or the like can be suitably used.

Examples of the aluminum-based coupling agent include acetoalkoxyaluminum diisopropylate and the like, and commercial products such as Ajinomoto's Plenact AL-M can be suitably used.

Next, as a method of adjusting the magnetic paint,
In each case, a known method can be used. For example, roll mill, ball mill, sand mill, tron mill, high-speed stone mill, basket mill, disper, homomixer,
Kneaders, continuous kneaders, extruders, homogenizers, ultrasonic dispersers and the like can be used.

In the application of the magnetic paint, a pretreatment such as a corona discharge treatment or an electron beam irradiation is applied to the undercoat layer such as an adhesive layer or the nonmagnetic support before the coating is directly performed on the nonmagnetic support. You can do it.

Next, the method of coating on the non-magnetic support includes air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, gravure coat, transfer roll Coating, cast coating, and other methods can be used, and methods other than these can also be used. Further, simultaneous multilayer coating by extrusion coating may be used.

The magnetic recording medium of the present invention may contain an isocyanate-based curing agent having an average number of functional groups of 2 or more in order to impart more solvent resistance. That is, any of a polymer of polyisocyanate and a polyol adduct of polyisocyanate can be suitably used in the present invention.

In the present invention, when an isocyanurate group is introduced, performance excellent in heat resistance and durability can be exhibited. Here, when a certain ratio of isocyanurate groups and / or other isocyanate polymers are contained in the polyisocyanate compound molecule, it is possible to introduce a branch point in the produced polyurethane-based component to such an extent that gelation is not reached.

Next, examples of the curing agent include aromatic polyisocyanates and aliphatic polyisocyanates, and adducts of these with active hydrogen compounds are preferred.

As the aromatic polyisocyanate, toluene diisocyanate (TDI), 1,3-xylene diisocyanate, 1,4-xylene diisocyanate,
4,4-diphenylmethane diisocyanate (MD
I), p-phenyl diisocyanate, m-phenyl diisocyanate, 1,5-naphthyl diisocyanate and the like. As the aliphatic polyisocyanate, hexamethylene diisocyanate (HD
I), dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate (IPDI) and the like.

The active hydrogen compounds forming adducts with these include ethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, diethylene glycol, trimethylolpropane,
Glycerin and the like, and the average molecular weight is 100 to 5,000.
Those in the range of 0 are preferred.

Next, the addition amount of the curing agent is generally 0 to 20 parts by weight of the binder resin, and preferably 0 to 10 parts. Here, theoretically, the amount of the curing agent that is equivalent to the active hydrogen in the polyurethane resin composition (or the binder resin composition) is a sufficient amount to be added. However, in actual production, the isocyanate of the curing agent component reacts due to moisture and the like, and therefore, the amount of isocyanate equivalent to active hydrogen is often insufficient.
It is effective to add 0% to 50% excess of the curing agent.

Further, when a hardening agent composed of polyisocyanate is used, the magnetic paint is coated and then heated to 40 ° C.
By accelerating the curing reaction for several hours at a temperature of ８０80 ° C., stronger adhesion can be obtained.

For this reason, the present invention keeps the magnetic surface hardness of the magnetic recording medium high at 1000 or more (according to the above defined formula 1), thereby deteriorating the electromagnetic conversion characteristics and the wear of the magnetic head of the magnetic recording medium. Without this, the durability performance of the magnetic recording medium can be improved, thereby providing a magnetic recording medium that can support high-density digital recording.

The constitutional requirement of the present invention is that the magnetic layer of the magnetic recording medium has a “hardness” of 1 as defined by the above-mentioned definition formula 1.
000 or more, conventionally, it is known that by increasing the hardness of the magnetic layer in a magnetic recording medium, the contact property with respect to the magnetic head is deteriorated, which leads to deterioration of electromagnetic conversion characteristics. Generally 600
It is manufactured in a hardness range of about 800. However, in each case, the PH durability was not sufficiently satisfied. However, according to the hardness measuring method and the measuring device of the present invention, a magnetic recording medium having a higher hardness than the conventionally used range can be controlled with a new measurement index.

[0079]

Embodiments of the present invention will be described below in detail.
The present invention is not limited to the following experimental examples (examples and comparative examples). Unless otherwise specified, “parts” and “%” in Examples 1 to 16 and Comparative Examples 1 to 16 mean “parts by weight” and “% by weight”, respectively.

Examples 1 to 17 and Comparative Examples 1 to 16 First, magnetic coatings for forming magnetic layers according to Examples 1 to 17 and Comparative Examples 1 to 16 are described below. Prepared with composition.

The following magnetic coating composition was kneaded with a continuous kneader, dispersed using a sand mill, added with 4 parts by weight of polyisocyanate and 1 part by weight of myristic acid, and filtered through a filter having an average diameter of 1 μm. It was a magnetic paint.

Fe-based metal magnetic powder (σs = 150 Am ² / kg, BET value = 56 m ² / g, Hc = 127 kA / m) 100 parts by weight Binder (see Tables 1 and 2) Abrasive (Tables 1 and 2) (See Table 2) Carbon black (BP-L manufactured by Cabot Corporation) 2 parts by weight 1 part by weight of butyl stearate 80 parts by weight of methyl ethyl ketone 80 parts by weight of methyl isobutyl ketone 80 parts by weight of toluene

The magnetic coating liquid obtained as described above was
After applying to a polyethylene terephthalate film having a thickness of 10 μm with a groove having a thickness of 3.0 μm by die coating, a wide magnetic film obtained by calendering under the conditions shown in Tables 1 and 2 below was cured. After doing
A video tape was prepared by cutting to a 1/2 inch width.

For each of the video tapes of the examples and comparative examples prepared as described above, the durability was evaluated by “output fluctuation” due to PH running, “clog time”, “amount of powder drop”, and “electromagnetic conversion characteristics”. (DB) "," running performance "," amount of magnetic head abrasion "as evaluation of tape polishing force, and" hardness of magnetic layer "and" surface roughness "were evaluated.

[Durability Evaluation] Digital Betacam VTR
(Sony, product name DVW-500, video head cleaner is in OFF state) using 20 ° C, 60% R
After recording the full length of a 124-minute tape (L cassette 732 m) under the condition of H (relative temperature), the full-length reproduction was continuously performed three times, and the results were expressed according to the following evaluation items.

[Output Fluctuation] The envelope of the output signal is recorded on the pen recorder, and the output when the maximum output attenuation is shown by the end of the running of the third volume with reference to the output X immediately after the running of the first videotape. Using Y, calculation was performed according to the following definition formula 2 (shown below), and the calculated value was represented by the following symbols (、, 、, ×). Definition formula 2: Output fluctuation = 20 × LOG (Y / X) [unit dB]

In Tables 3 and 4, ○ indicates that the output fluctuation is less than 1 dB, ▲ indicates that the output fluctuation is 1 to 6 dB, and X indicates that the output fluctuation is 6 dB or more. Indicates something.

[Clog time] Immediately after the running of the first video tape, the above output fluctuation (1 dB or more, ie, ▲)
And the range of x) were defined as clog time. Then, when there was no output fluctuation by the end of the running of the third winding, a circle was displayed.

[Dust Falling Amount] Next, after running three turns of the video tape, the sliding surface of the video tape on the head of the drum was observed during the rotation of the VTR, and the adhered area of the dropped material from the magnetic recording medium was determined. It was expressed as a percentage of the area ratio of the tape sliding surface on the head.

[Electromagnetic Conversion Characteristics] Next, the electromagnetic conversion characteristics were measured using a digital beta cam VTR (manufactured by Sony Corporation, trade name DVW-500) at a measurement frequency of 32 MHz and an output of Comparative Example 2 at 0 dB. The output difference from Comparative Example 2 was measured.

[Drivability] Next, the digital beta cam VT
Using R (manufactured by Sony Corporation, product name DVW-500), the following running mode is repeated, and the number of repetitions (number of passes) until the stop of tape running or occurrence of an abnormality such as head clog is calculated as follows. Judge based on the evaluation criteria. The running mode is as follows: tape insertion → PLAY running for 10 seconds → rewinding of the running section → pausing for 10 seconds → PLAY for 10 seconds
Running → rewinding of running section → tape removal → tape insertion (second pass).

In the symbols shown in Tables 3 and 4, ２０００ indicates 2000 passes or more, and ○ indicates 1000 passes or more.
Less than 000 passes, ▲ represents more than 500 passes, less than 1000 passes, and x represents less than 500 passes.

[Magnetic Head Wear] Next, a digital beta cam-VTR (DVW-500, manufactured by Sony Corporation)
After recording the full length of a 124-minute tape (L cassette 732 m) under the conditions of 20 ° C. and 60% RH (relative humidity), full-length reproduction and rewinding were repeated six times. Then, before and after traveling, the protrusion of the magnetic head, that is, the height of the magnetic head from the outer peripheral surface of the rotating drum on which the magnetic head is attached is measured, and the difference between before and after traveling is measured by the amount of magnetic head wear. And The results were determined according to the following evaluation criteria.

That is, in the symbols shown in Tables 3 and 4, ○ indicates that the wear amount was less than 0.1 μm, ▲ indicates that the wear amount was 0.1 μm or more and less than 0.2 μm, and X indicates that the wear amount was 0. 2 μm or more.

[Hardness] The method of measuring the hardness is as described above.

[Surface Roughness] Next, a non-contact type surface roughness meter 1
The center line average roughness Ra according to 7 is measured in principle by a critical angle method with a non-contact type surface roughness meter 17 shown in FIG. 4 using a laser beam. That is, in FIG. 4, an optical measurement system including a laser oscillation source 1, a critical angle prism 11, an objective lens 2, photodiodes 13a and 13b, and a differential amplifier 14 is used. Then, each surface of the measured surface (A, B, C) corresponding to the unevenness of the measured surface, that is,
It is assumed that the objective lens 2 has an A-plane at the focal point, a B-plane at the focal point, and a C-plane outside the focal point.

First, the laser light reflected on the focal plane B and passing through the objective lens 2 becomes a parallel light flux as shown by a thin line, enters the critical prism 11, is reflected, and is reflected by the two photodiodes 13a. , 13b obtain the same amount of reflected light, and the output of the differential amplifier 14 becomes zero.

On the other hand, the laser light reflected on the in-focus A surface and passing through the objective lens 2 becomes a divergent light beam, and the laser light reflected on the out-of-focus C surface and passing through the objective lens 2 becomes a convergent light beam. And enters the critical angle prism 11. The convergence light beam reflected on the out-of-focus C-plane passes through the critical angle prism 11 as indicated by a broken line, and the divergent light beam reflected on the A-plane within the focus as indicated by a dashed line. However, the laser light incident at an angle larger than the critical angle is totally reflected, and the state of reflection is different above and below the incident optical axis. Therefore, the two photodiodes 13a and 13b receive different reflected light amounts. Then, ± analog displacement output is obtained in the differential amplifier 14 between the A plane and the C plane. As described above, the unevenness of the surface to be measured is obtained from the displacement output within ± with the focus position set to 0.

In the actual measurement, the wavelength 780
Laser light from a laser diode of nm was focused on a spot having a diameter of 1.6 μm on the surface to be measured, and measurement was performed with a cutoff of 80 μm. The measurement length was 0.25 mm, the same surface was measured three times, and the average value was used as data.

Next, Tables 3 and 4 show the evaluation results of Examples 1 to 17 and Comparative Examples 1 to 16 for each of the above evaluation items.

The abbreviations shown in Tables 1 to 4 are described below.

First, the abbreviation of the composition of the binder shown in Composition 1 of Table 1 and Table 2 is explained. PVC is (MR-1
10 manufactured by Zeon Corporation), and NC is (NC-1
/ 1H, manufactured by Asahi Kasei Co., Ltd., and PU1 is (isophthalic acid / adipic acid / NPG / EG-HDI based polyurethane molecular weight Mn = 30000, SO ₃ Na = 0.2 mmol)
1 / g contained), PU2 is (isophthalic acid / terephthalic acid / NPG / EG-MDI type polyurethane molecular weight Mn = 30000, SO ₃ Na = 0.2 mmol / g)
Content).

Next, as shown in composition 1 in Tables 1 and 2, P /
B represents the ratio of the weight of the metal magnetic powder to the weight of the binder in the magnetic paint.

Next, in the measurement of the hardness of the magnetic layer shown in Tables 3 and 4, * 1 represents a value measured by the hardness meter of the present invention, and * 2 represents a conventional hardness measurement method. , Shimadzu DUH-50 represents the measured values,
As a condition, the load is 0.1 gf.

Next, the calendering condition 2 shown in Tables 1 and 2 will be described. In the strong case, the temperature is 90 ° C. and the pressure is 20 [kN / cm]. ° C
And the pressure indicates 25 [kN / cm].
At 10 ° C., the pressure indicates 30 [kN / cm].

Next, description will be given of the type of abrasive 3) shown in Tables 1 and 2. HIT-50 means (α-alumina particle diameter = 0.5 micron manufactured by Sumitomo Chemical Co., Ltd.)
AKP-30 indicates (α-alumina particle diameter = 0.8 micron manufactured by Sumitomo Chemical Co., Ltd.).

[0107]

[Table 1] Table 1 Preparation conditions in the example

[0108]

[Table 2] Table 2 Preparation conditions in comparative example

[0109]

[Table 3]

[0110]

[Table 4]

In the evaluation results in Tables 2 and 4, the composition ratio of the binder and the P / B ratio in Comparative Examples 1 to 9 were made the same, and 7 parts by weight of the abrasive (HIT-50) was used. Comparative Examples 4 to 6, in which 7 parts by weight of the abrasive (AKP-30) were mixed, and the abrasive (HIT-5), based on Comparative Examples 1 to 3 that were mixed.
Comparative Examples 7 to 9 containing 12 parts by weight of (0) increased the particle size of the abrasives of Comparative Examples 1 to 3 shown in Table 4 (Comparative Examples 4 to 6) and increased the amount of the abrasive. Results (Comparative Examples 7 and 8). Note that the calendar processing conditions are set to medium and high for each group of each comparative example. Although the durability is improved, the electromagnetic conversion characteristics are deteriorated due to the increase of the negative value, and the wear of the magnetic head is slightly deteriorated due to the increase of x.

Next, Comparative Examples 10 to 10 shown in Tables 2 and 4 were used.
12 is an evaluation result of a video tape in which the abrasive was changed in the same manner as in Comparative Examples 1 to 3 and the composition was changed by changing the composition ratio of the binder and the P / B ratio. 1-9
Is less than 1000 and the value of 900 units.
According to Table 4, the values of "output fluctuation" and "clog time" are not very good except for "amount of powder falling off", and it is considered that there is no improvement in durability.

In Examples 1 to 9 shown in Tables 1 and 3, the conditions of the calendering treatment and the composition of the polishing agent were the same, and the composition and ratio of the binder and P / B were changed. hardness"
Is an evaluation result when is set to 1000 or more. Comparative Example 1 above
When compared with １２12 (the value of the hardness of the magnetic layer is 900 units), it can be said that the durability such as the output fluctuation, the clog time and the amount of powder falling is all good. In addition, it can be said that the running performance, the electromagnetic conversion characteristics, the wear amount of the magnetic head, and the like are generally good.

Next, as shown in Tables 1 to 4, the same conditions were applied to the binder, the abrasive, and the calendering conditions,
Evaluation results in Comparative Examples 13 to 16 and Examples 10 to 17 in which only the composition of the / B ratio was changed are shown below.

First, the magnetic layer hardness * shown in Tables 3 and 4
Comparative Examples 13 to 16 show the relationship between the value of 1 and the amount of powder falling.
When the hardness is in the range of 800 to 900 units, the amount of powder falling is in the order of 2 digits, which is relatively large. However, as in Examples 10 to 17, when the hardness gradually increases from the hardness of 1000, The falling amount is considerably small and the amount is stable. Next, the relationship between “magnetic layer hardness” and “electromagnetic conversion characteristics” shown in Tables 3 and 4 is shown. When the hardness of the magnetic layer exceeds 1200 as shown in Examples 14 to 17, Electromagnetic conversion characteristics are likely to deteriorate.

The relationship between "magnetic layer hardness", "running performance", and the wear of the magnetic head shown in Tables 3 and 4 is shown in Examples 14 to 17, when the hardness becomes 1200 or more. Although it starts to deteriorate, especially when the hardness of the magnetic layer exceeds 1300, the values of the traveling property and the wear amount of the magnetic head are likely to deteriorate.

FIG. 1 is a graph showing the correlation between the amount of powder falling off, the hardness of the magnetic layer and the electromagnetic conversion characteristics in each of Comparative Examples 13 to 16 and Examples 10 to 17 described above.

First, the amount of powder falling decreases as the hardness of the magnetic layer (shown at the bottom of the graph) near the value of 900 increases as the hardness increases. Then, when the hardness becomes a value higher than around 1000, the amount of powder falling becomes extremely small.

Therefore, the hardness of the magnetic layer should be 1000 or more even in view of the tendency to reduce the amount of powder falling.

Next, regarding the electromagnetic conversion characteristic value, the hardness is 80
It is gently descending from 0 to 1200,
If the hardness exceeds about 1250, the electromagnetic conversion characteristic value tends to deteriorate.

Therefore, the hardness is preferably 1300 or less, and preferably 1250 or less, and the value of the electromagnetic conversion characteristic is +0.
It can be said that 1200 or less, which is 0 or more, is more preferable.

Next, through Examples and Comparative Examples shown in Tables 1 to 4, the values of the durability, running properties, electromagnetic conversion characteristics, and wear of the magnetic head are the best. Examples 3 to
Looking at No. 7, the magnetic layer surface roughness Ra is 13 to 21 nm, and the electromagnetic conversion characteristics and running properties are also improved. Therefore, it can be said that the surface roughness Ra of the magnetic layer is preferably 13 to 21 nm in addition to the hardness of the magnetic layer of 1000 or more.

Next, Tables 3 and 4 show a conventional method for measuring the hardness of the magnetic layer (for example, using DUH-50 manufactured by Shimadzu Corporation) and a comparison between the hardness at that time and the hardness measured by the hardness tester of the present invention. This is performed using

The values of the hardness measurement value according to the present invention and the commercially available device measurement value (Shimadzu DUH-50) are each * of the magnetic layer hardness.
The hardness indicated by the hardness meter device according to the embodiment of the present invention, which is represented by * 1, * 2 but represented by * 1, changes according to a slight change in the P / B ratio, but is a commercially available device represented by * 2. The value measured by the above does not tend to increase in hardness, even if the composition of the P / B ratio is changed, but the value slightly increases or decreases.

Therefore, it is suggested that the conventional hardness measurement method is not accurately reflected on the surface hardness of the magnetic recording medium because it is affected by the surface roughness and the substrate.

From the evaluation results of each of the above Examples and Comparative Examples, as a control method of “hardness” at the time of forming the magnetic layer, the ratio of the magnetic powder to the binder in the magnetic layer, the ratio of the binder, It is thought that it is possible by changing the kind, the mixing ratio, the calendar conditions at the time of production, and the like.

However, on the other hand, if only the “hardness” of the magnetic layer is improved, a problem may occur in the running property or the electromagnetic conversion characteristics. For this purpose, preferably, the center line average roughness Ra of the magnetic layer surface is such that the laser spot diameter is 1.
The value measured by a non-contact type roughness meter having a diameter of 6 μm (spot radius: 0.8 μm) seems to be ideally 13 to 21 nm.

The constitutional requirement of the present invention is that the magnetic layer of the magnetic recording medium has a “hardness” represented by the following definition formula 1.
To have more than 1,000. Conventionally, in a magnetic recording medium, by increasing the hardness of the magnetic layer,
Since the contact property with the magnetic head deteriorates,
It is known that electromagnetic conversion characteristics are deteriorated, and generally, it is manufactured in a hardness range of about 600 to 800. However, in each case, the PH durability was not sufficiently satisfied. According to the hardness measuring method and the hardness measuring device of the present invention, a magnetic recording medium having a higher hardness than a conventionally used range can be controlled with a new measurement index. Definition formula 1: Hardness = load (mg) / indentation depth (μm)

The present invention maintains the magnetic surface hardness of the magnetic recording medium at a high level so that the electromagnetic conversion characteristics of the magnetic recording medium and the wear of the magnetic head are not significantly deteriorated, and the durability of the magnetic recording medium is improved. , Thereby providing a magnetic recording medium that can support high-density digital recording.

While the embodiments and examples of the present invention have been described above, the above-described embodiments and examples can be further modified based on the technical idea of the present invention.

[0131]

According to the present invention, there is provided a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder, wherein the magnetic layer has a hardness of 1000 or more represented by the following definition formula 1. The hardness is measured by the following method or device. That is,
The mounting unit is moved by the driving unit in a state where the magnetic recording medium having the magnetic layer containing the magnetic powder and the binder is supported and mounted on the mounting unit on the surface opposite to the magnetic layer, The magnetic layer is brought into contact with a load detection unit, and by a correlation between a load and a load of the load detection unit with respect to the magnetic layer,
A method for measuring the hardness of a magnetic recording medium, a load measuring unit provided with a load detecting unit, and a magnetic layer containing a magnetic powder and a binder, wherein the hardness of the magnetic layer is determined based on the following definition formula 1. A mounting portion for supporting and mounting the magnetic recording medium having the surface on the side opposite to the magnetic layer, and moving means for moving the mounting portion to the load measuring means side; In the state where the magnetic recording medium is mounted on the mounting portion, the mounting portion is moved by the driving means, the magnetic layer is brought into contact with the load detecting portion, and the depth of the load detecting portion into the magnetic layer is reduced. A hardness measuring device for a magnetic recording medium, which is configured to determine the hardness of the magnetic layer based on the correlation between the magnetic layer and the load, based on the following defining equation 1. Definition formula 1: Hardness = load (mg) / indentation depth (μm)

Therefore, according to the present invention, by keeping the magnetic surface hardness of the magnetic recording medium higher than the hardness 1000 represented by the above-mentioned definition formula 1, the electromagnetic conversion characteristics and the wear amount of the magnetic head of the magnetic recording medium can be considerably reduced. The durability of the magnetic recording medium can be improved without deteriorating the magnetic recording medium, thereby providing a magnetic recording medium that can support high-density digital recording.

The constitutional requirement of the present invention is that the magnetic layer of the magnetic recording medium has a hardness of 10
Conventionally, it is known that, in a magnetic recording medium, increasing the hardness of the magnetic layer deteriorates the contact property with respect to the magnetic head, thereby deteriorating the electromagnetic conversion characteristics. , Generally 60
It is manufactured in a hardness range of about 0 to 800. However, in each case, the PH durability was not sufficiently satisfied. However, according to the hardness measuring method and the measuring device of the present invention, a magnetic recording medium having a higher hardness than the conventionally used range can be controlled with a new measurement index.

[Brief description of the drawings]

FIG. 1 is a correlation diagram showing characteristics of an amount of powder falling, a measured value of a magnetic surface hardness, and electromagnetic conversion characteristics in an example of the present invention.

FIG. 2 is a schematic diagram of a hardness meter device according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of the vicinity of the head end of the same.

FIG. 4 is a schematic diagram of a non-contact type surface roughness meter according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Load meter, 2 ... Load detection unit, 3 ... Magnetic recording medium, 4 ...
Magnetic head, 5 ... guide, 6 ... bimorph, 7 ... weight,
8 DC power supply 9 Hardness device 10 Laser oscillation source 11 Critical angle prism 12 Objective lens 13
a, 13b: photodiode, 14: differential amplifier, 1
5A, B, C: surface to be measured, 16: core, 17: non-contact surface element meter, 19: mounting part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Reiko Watanabe 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Makoto Takeda 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5D006 BA19 5D112 AA05 JJ06

Claims (11)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a magnetic powder and a binder, wherein the magnetic layer has a hardness of 1000 or more represented by the following definition formula 1. Definition formula 1: Hardness = load (mg) / indentation depth (μm) 2. The magnetic recording medium according to claim 1, wherein the hardness of the magnetic layer is 1300 or less. 3. The center line average roughness Ra of the surface of the magnetic layer.
The magnetic recording medium according to claim 1, wherein a value measured by a non-contact type roughness meter having a spot diameter of 1.6 μm is 13 to 21 nm. 4. A driving means in a state where a magnetic recording medium having a magnetic layer containing magnetic powder and a binder is placed and supported on a mounting portion on a surface opposite to the magnetic layer. The magnetic layer is brought into contact with the load detecting section by moving the mounting section, and the hardness of the magnetic layer is determined based on the following definition formula 1 by the correlation between the load and the load of the load detecting section with respect to the magnetic layer. A method for measuring the hardness of a magnetic recording medium as required. Definition formula 1: Hardness = load (mg) / indentation depth (μm) 5. A head unit on which the magnetic recording medium is mounted and a driving unit for driving the head unit constitute a mounting unit, and both ends of the magnetic recording medium are pulled in opposite directions. Item 6. A method for measuring hardness of a magnetic recording medium according to Item 4. 6. The hardness measurement of a magnetic recording medium according to claim 4, wherein the load detector has a needle-like tip pushed into the magnetic layer, and the head is driven by a bimorph as a driving unit. Method. 7. The method for measuring the hardness of a magnetic recording medium according to claim 6, wherein the bimorph is operated by a DC power supply to move the head unit. 8. A mounting method in which a load measuring means provided with a load detecting section and a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder are supported and mounted on a surface opposite to the magnetic layer. Mounting part, and a driving means for moving the mounting part to the side of the load measuring means, wherein the mounting part is moved by the driving means in a state where the magnetic recording medium is mounted on the mounting part. The magnetic layer is brought into contact with the load detection unit by moving the magnetic layer, and the hardness of the magnetic layer is determined based on the following definition formula 1 based on the correlation between the load and the load of the load detection unit with respect to the magnetic layer. A hardness measuring device for a magnetic recording medium. Definition formula 1: Hardness = load (mg) / indentation depth (μm) 9. The magnetic recording medium according to claim 9, wherein the mounting section comprises a head section for mounting the magnetic recording medium and a driving section for driving the head section, and both ends of the magnetic recording medium are pulled in opposite directions. Item 10. A hardness measuring device for a magnetic recording medium according to item 8. 10. The hardness of the magnetic recording medium according to claim 8, wherein the load detector has a needle-like tip pushed into the magnetic layer, and the head is driven by a bimorph as a driving unit. measuring device. 11. The magnetic recording medium hardness measuring apparatus according to claim 10, wherein the bimorph is operated by a DC power supply, and the head section moves.