JPH1186261A - Magnetic recording medium and magnetic recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which enables advantageous use thereof as highly reliable magnetic tape for recording computer data by achieving a larger recording memory and excellent performance in running endurance, electromagnetic conversion characteristic and the like. SOLUTION: This recording medium has a substantially non-magnetic layer containing a non-magnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder sequentially on one side of a support body made of aromatic polyamide and a back coat layer on the other. It is so arranged that the total thickness of the medium is 3.0-4.6 μm, the thickness of the magnetic layer 0.05-0.2 μm and the thickness of the non-magnetic layer 0.3-1.8 μm. The thickness of the magnetic and non-magnetic layers is 0.4-2.0 μm in total. The ratio of 'the thickness of the magnetic layer/' the total thickness of the magnetic and non-magnetic layers' is within a range of 0.05-0.15. The method of magnetically recording employs a helical scan system using a rotary magnetic head and recording is made on the magnetic recording medium with a data track 9 μm or less wide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium. The present invention relates to a magnetic recording medium which can be advantageously used as a magnetic tape for computer data recording, which is particularly suitable for a helical scan type magnetic recording / reproducing system having a narrower data recording track width.

[0002]

2. Description of the Related Art In recent years, with the spread of office computers such as minicomputers, personal computers, and workstations, magnetic tapes for recording computer data (so-called,
Backup tape) is being used. The backup tape has a large recording capacity due to the improvement of the information processing capacity of the computer and the increase in the processing speed.
Also, it is required to have high running durability. In addition, due to the widespread use environment of the computer, the backup tape has high reliability without error when recording and reproducing data under a wide range of environmental conditions (especially, temperature and humidity conditions that fluctuate greatly). Is desired.

In general, a magnetic tape has a configuration in which a magnetic layer is provided on a nonmagnetic support made of a flexible material such as a synthetic resin. In order to achieve higher recording density, a magnetic tape having a structure in which a nonmagnetic layer is provided on a nonmagnetic support and a thin magnetic layer is further provided thereon has been proposed. For example, JP-A-5-182178 discloses a non-magnetic layer,
A two-layer magnetic tape in which a magnetic layer having a thickness of 0 μm or less is provided on a nonmagnetic support in this order has been proposed. Here, there is a description that a magnetic tape having a two-layer structure having a thin magnetic layer as described above can also be used for computer data recording, and as a thickness structure of the magnetic tape, a non-magnetic support is used. The thickness of 4-80 μm, the lower non-magnetic layer has a thickness of 1-5 μm, and the upper magnetic layer has a thickness of 0.
05 to 0.6 μm (more preferably 0.05 to 0.3 μm)
μm).
Specifically, as an example, a magnetic tape in which a non-magnetic layer having a thickness of 2 μm and a magnetic layer having a thickness of 0.2 μm are sequentially provided on a support made of polyethylene terephthalate having a thickness of 7 μm is described. Have been. This publication also states that aromatic polyamide and aramid can be used as the support material.

[0004]

SUMMARY OF THE INVENTION The present inventor has proposed a magnetic tape for computer data recording which can achieve a larger recording capacity and has a high running durability and stable performance against changes in temperature and humidity. The study was conducted in search of an advantageous magnetic recording medium. According to the study, the two-layered magnetic tape having a thin magnetic layer disclosed in the above publication has a relatively small overall thickness and is advantageous for high-density recording. It has been found that it is not possible to achieve a sufficient recording capacity to use the recording medium. For this reason, it is necessary to further reduce the thickness of the entire magnetic tape. However, if the overall thickness is reduced, the strength of the magnetic tape itself becomes insufficient. It would be advantageous to use an aromatic polyamide. On the other hand, the thickness configuration of the magnetic layer and the non-magnetic layer also directly affects running durability and contact (contact state) with the magnetic head. As a result, the electromagnetic conversion characteristics such as reproduction output are likely to be affected. Therefore,
It is desired to develop a magnetic tape suitable for computer data recording that suppresses the overall thickness and satisfies these performances. As a magnetic recording / reproducing system, a helical scan method using a rotating magnetic head has been adopted, but in order to achieve higher recording density, the track width for data recording is much narrower than before. A magnetic recording system capable of recording and reproducing data has also been developed. However, when the entire thickness of the magnetic tape becomes extremely thin, problems such as easy offtrack occur. Therefore, there is a demand for a magnetic tape adapted to such a system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium which can achieve a large recording capacity, is excellent in performance such as running durability and electromagnetic conversion characteristics, and is advantageously used as a highly reliable magnetic tape for computer data recording. Is to provide a medium. Another object of the present invention is to provide a magnetic recording medium which is advantageously used as a magnetic tape for computer data recording suitable for a magnetic recording / reproducing system capable of high-density recording.

[0006]

According to the research of the present inventors,
In the thickness configuration of the magnetic layer and the non-magnetic layer, the thickness of the non-magnetic layer is made thinner than that of the conventional one, so that the running durability is improved despite the fact that the overall thickness of the medium is extremely thin. It has been found that a magnetic recording medium that can be used advantageously as a highly reliable magnetic tape for computer data recording can be obtained with little deterioration in performance and electromagnetic conversion characteristics after storage.

According to the present invention, a substantially non-magnetic non-magnetic layer containing a non-magnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder are provided on one surface of an aromatic polyamide support. A magnetic recording medium having a back coat layer on the other surface of the support, the medium having a total thickness of 3.0 to 4.6 μm and a magnetic layer having a thickness of 0.05
０．２0.2 μm, the thickness of the nonmagnetic layer is 0.3-1.8 μm,
And the sum of the thickness of the magnetic layer and the thickness of the non-magnetic layer is 0.4 to
The magnetic recording medium is characterized in that the ratio of [magnetic layer thickness] / [total thickness of magnetic layer and non-magnetic layer] is in the range of 0.05 to 0.15 at 2.0 μm.

The present invention also relates to a magnetic recording method for recording data on a tape-shaped magnetic recording medium with a data track width of 9 μm or less by a helical scan method using a rotary magnetic head.
The magnetic recording medium includes, on one surface of an aromatic polyamide support, a substantially nonmagnetic nonmagnetic layer containing a nonmagnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder in this order. And a back coat layer on the other surface of the support, wherein the total thickness of the medium is 3.0 to 4.6 μm, the thickness of the magnetic layer is 0.05 to 0.2 μm, When the thickness of the magnetic layer is 0.3 to 1.8 μm, and the total of the thickness of the magnetic layer and the thickness of the nonmagnetic layer is 0.4 to 2.0 μm, [thickness of magnetic layer] / [magnetic layer and nonmagnetic layer] Thickness).
There is also a magnetic recording method characterized by being in the range of from 0.05 to 0.15.

The present invention preferably has the following aspects. (1) The thickness of the support made of an aromatic polyamide is 2.3 to 4.
0 μm (more preferably, 2.3 to 3.8 μm). (2) The aromatic polyamide is a wholly aromatic polyamide (aramid). (3) The track width (track pitch) is less than 9 μm (more preferably in the range of 5 to 8 μm, more preferably 5 μm).
範 囲 7 μm) for a magnetic recording and reproducing system. (4) A magnetic tape for recording computer data.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention is advantageously used as a magnetic tape for computer data recording. In the following, an example of a magnetic tape for computer data recording (hereinafter simply referred to as a magnetic tape) will be described. Will be described. In the magnetic tape of the present invention, the thickness of the entire tape is 3.0 to 4.6 μm, and the thickness of the magnetic layer is 0.3 μm.
0.5 to 0.2 μm, and the thickness of the nonmagnetic layer is 0.3 to 1.8 μm
m, and the sum of the thickness of the magnetic layer and the thickness of the non-magnetic layer is 0.
The thickness is adjusted to 4 to 2.0 μm, and the ratio of the thickness of the magnetic layer / the total thickness of the magnetic layer and the nonmagnetic layer is in the range of 0.05 to 0.15. The magnetic tape of the present invention has a non-magnetic layer and a magnetic layer provided on one surface of an aromatic polyamide support with the above-described thickness relationship, and a back surface is provided on the other surface of the support. A coat layer is provided. Hereinafter, the aromatic polyamide support, the nonmagnetic layer, the magnetic layer, and the back coat layer will be described in detail in this order.

[Aromatic Polyamide Support] The aromatic polyamide used in the present invention preferably contains, for example, a repeating unit represented by the following formula (I) or (II). — (NH—Ar ¹ —NHCO—Ar ² —CO) — (I) — (NH—Ar ³ —CO) — (II) The above Ar ¹ , Ar ² and Ar ³ are each independently an aromatic ring ( The aromatic ring may be condensed) or a group containing at least one aromatic ring. Examples of Ar ¹ , Ar ² and Ar ³ include the following.

[0012]

Embedded image

Here, X and Y are -O- and -C, respectively.
H ₂ —, —CO—, —SO ₂ —, —S—, and —C (C
H ₃ ) ₂ — represents a group selected from The hydrogen atom of the aromatic ring may be substituted. Examples of the group or atom capable of substituting a hydrogen atom of an aromatic ring include a halogen atom (particularly, chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (particularly, a methyl group), An alkoxy group can be mentioned. The hydrogen atom of the amide bond which is a constituent component of the polymer may be substituted.

The aromatic polyamide is preferably a polymer in which an aromatic ring is bonded at the para position occupying 50% or more (more preferably 70% or more) of the whole aromatic ring. In addition, from the viewpoint of reducing the hygroscopicity, it is preferable that the aromatic ring in which hydrogen atoms on the aromatic ring are substituted with halogen atoms (particularly chlorine atoms) accounts for 30% or more of the entire aromatic ring.

The aromatic polyamide is the above (I) or (I)
It is preferable that the repeating unit represented by I) is composed of 50 mol% or more, preferably 70 mol% or more, provided that it satisfies the physical properties as a support.
A polymer obtained by copolymerizing or blending the repeating unit represented by the above formula (I) or (II) with another repeating unit can be used. In the present invention, it is preferable to use aramid (a wholly aromatic polyamide). Typical commercial examples of aramid include Miktron (manufactured by Toray Industries, Inc.) and Aramica (manufactured by Asahi Kasei Corporation). The aromatic polyamide is described in JP-A-8-55327 or 8-55327.
No. 328.

The thickness of the support made of the aromatic polyamide used in the present invention is preferably in the range of 2.3 to 4.0 μm, more preferably 2.3 to 3.8 μm.

[Non-magnetic layer] The non-magnetic layer is a layer comprising a non-magnetic powder and a binder. In the magnetic tape according to the present invention, even if magnetic powder is added to the non-magnetic layer,
In a magnetic recording / reproducing system using the magnetic tape, a non-magnetic layer to which the magnetic powder is added is also included in the “non-magnetic layer” in the present invention, as long as recording / reproducing can be performed without any trouble. The non-magnetic layer usually contains a lubricant in addition to these components. Examples of the non-magnetic powder used in the non-magnetic layer include a non-magnetic inorganic powder and carbon black.

The non-magnetic inorganic powder that can be used in the present invention preferably has a Mohs hardness of 3 or more (preferably 5 or more, more preferably 6 or more). Examples of these nonmagnetic inorganic powders include metals, metal oxides, metal carbonates,
Metal sulfates, metal nitrides, metal carbides, and metal sulfides can be mentioned. Specific examples of these nonmagnetic inorganic powders include titanium dioxide (rutile type, anatase type), TiO _x (x = 1.3 to 1.95), cerium oxide, tin oxide, tungsten oxide, ZnO, ZrO ₂ ,
SiO ₂ , chromium oxide (Cr ₂ O ₃ ), α-alumina, β-alumina, γ-alumina, α-alumina with α conversion of 90% or more
Iron oxide, goethite, corundum, silicon nitride, titanium carbide, magnesium oxide, boron nitride, molybdenum disulfide, copper oxide, MgCO ₃ , CaCO ₃ , BaCO
₃ , SrCO ₃ , BaSO ₄ , silicon carbide and titanium carbide. These can be used alone or in combination. Among these, titanium dioxide (titanium oxide), α-alumina, α-iron oxide or chromium oxide is preferred, and titanium dioxide or α-iron oxide is more preferred. The shape and size of these nonmagnetic inorganic powders are arbitrary. Non-magnetic inorganic powders having different sizes and the like can be combined, or a single type can be used by selecting a particle size distribution.

The non-magnetic inorganic powder used in the present invention preferably has the following characteristics. The tap density of the nonmagnetic inorganic powder is 0.05 to 2 g / cc (more preferably,
0.2 to 1.5 g / cc). The water content of the nonmagnetic inorganic powder is preferably 0.1 to 5% by weight (more preferably 0.2 to 3% by weight). The pH of the nonmagnetic inorganic powder is usually from 2 to 11, especially from 4 to 1.
It is preferably in the range of 0. The specific surface area of the nonmagnetic inorganic powder is usually 1 to 100 m ² / g (preferably 5 to 70 m ² / g).
m ² / g, more preferably from 7~50m ² / g).
The crystallite size of the nonmagnetic inorganic powder is 0.01 μm to 2 μm.
m is preferably in the range. Regarding the particle size of the nonmagnetic inorganic powder, the granular one has an average particle diameter of 0.1.
μm or less (preferably 0.08 or less), and those having a needle shape have a major axis length of 0.05 to 1.0 μm (preferably,
0.05 to 0.5 μm) and a needle ratio in the range of 5 to 20 (preferably 5 to 15). DBP
The oil absorption using (dibutyl phthalate) is usually 5 to 1
00 ml / 100 g (preferably 10 to 80 ml / 10
0 g, more preferably 20 to 60 ml / 100 g). SA (stearic acid) lubrication amount is 1 to 20 μmol /
m ² (more preferably, ^{2 to} 15 μmol / m ² ). The roughness factor of the powder surface is
It is preferably 0.8 to 1.5. The heat of wetting in water at 25 ° C. is 200 erg / cm ^{2 to} 600 erg.
/ Cm ² . In addition, a solvent having a range of the heat of wetting can be used. 100-400 ° C
The amount of water molecules on the surface of is preferably 1 to 10/100 °. The pH of the isoelectric point in water is preferably in the range of 3-9. The specific gravity is preferably 1 to 12 (more preferably, 3 to 6). The non-magnetic inorganic powder does not necessarily have to be 100% pure, but may have other compounds (eg, Al, Si, Ti, Zr) depending on the purpose.
(A substance such as Sn, Sb, and Zn) to form oxides thereof on the surface. An effect can be obtained if the purity of the nonmagnetic inorganic powder is 70% or more. The ignition loss is preferably 20% or less.

Specific examples of the nonmagnetic inorganic powder include [UA5600, UA5605] manufactured by Showa Denko KK and [AKP-20, AKP-30, AKP- manufactured by Sumitomo Chemical Co., Ltd.]
50HIT-55, HIT-100, ZA-G1]; Nippon Kogyo Co., Ltd. [G5, G7, S-1]; Toda Kogyo Co., Ltd. [TF-100, TF-120, TF-14]
0, R516]; manufactured by Ishihara Sangyo Co., Ltd. [TTO-51B,
TTO-55A, TTO-55B, TTO-55C, T
TO-55S, TTO-55D, FT-1000, FT
-2000, FTL-100, FTK-200, M-
1, S-1, SN-100, R-820, R-830,
R-930, R-550, CR-50, CR-80, R
-680, TY-50]; manufactured by Titanium Industry Co., Ltd. [ECT]
-52, STT-4D, STT-30D, STT-3
0, STT-65C]; manufactured by Mitsubishi Materials Corporation [T-
1]; manufactured by Nippon Shokubai Co., Ltd. [NS-O, NS-3Y, NS
-8Y]; manufactured by Teika Co., Ltd. [MT-100S, MT-1
00T, MT-150W, MT-500B, MT-60
0B, MT-100E]; Sakai Chemical Co., Ltd. [FINEX
-25, BF-1, BF-10, BF-20, BF-1
L, BF-10P]; manufactured by Dowa Mining Co., Ltd. [DEFIC-
Y, DEFIC-R]; manufactured by Titanium Industry Co., Ltd. [Y-LO
P] and those obtained by burning it. In addition, 3-25% by weight (preferably 3-20% by weight) of the nonmagnetic inorganic powder is a so-called abrasive having a Mohs hardness of 3 or more (preferably 5 or more, more preferably 6 or more). It is preferable to use one that can function.

Carbon black is added for the purpose of imparting conductivity to the magnetic layer to prevent electrification and ensuring the smooth surface properties of the magnetic layer formed on the non-magnetic layer. The carbon black preferably has an average particle diameter of 35 mμ or less (more preferably, 10 to 35 mμ). The specific surface area thereof, 5~500m ² / g (more preferably, 50~300m ² / g) is preferably from. DBP oil absorption is 10-1000ml / 100g
(More preferably, 50 to 300 ml / 100 g). The pH is 2 to 10, the water content is 0.1 to 10%, and the tap density is 0.1 to
It is preferably 1 g / cc.

Carbon black obtained by various production methods can be used. Examples of these include furnace black, thermal black, acetylene black, channel black and lamp black.
Specific examples of carbon black products include BLAC
KPEARLS 2000, 1300, 1000, 90
0, 800, 700, VULCAN XC-72 (all manufactured by Cabot Corporation), # 35, # 50, # 55, # 6
0 and # 80 (all manufactured by Asahi Carbon Co., Ltd.), # 395
0B, # 3750B, # 3250B, # 2400B, #
2300B, # 1000, # 900, # 40, # 30,
And # 10B (above, manufactured by Mitsubishi Chemical Corporation), CONDU
CTEX SC, RAVEN, 150, 50, 40, 1
5 (all manufactured by Columbia Carbon Co., Ltd.), Ketjen Black EC, Ketjen Black ECDJ-500 and Ketjen Black ECDJ-600 (all manufactured by Lion Aguso Co., Ltd.).

The usual addition amount of carbon black is 3 to 20 parts by weight, preferably 4 to 18 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the nonmagnetic inorganic powder.
１５15 parts by weight.

The lubricant is added to alleviate the friction between the surface of the magnetic layer and the magnetic head, the guide pole of the drive and the cylinder by oozing onto the surface of the magnetic layer, and to maintain a smooth sliding contact state. . Examples of the lubricant include a fatty acid and a fatty acid ester.
As fatty acids, for example, acetic acid, propionic acid, octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachinic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, And aliphatic carboxylic acids such as palmitoleic acid or mixtures thereof.

Examples of the fatty acid ester include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, and 2-hexyldecyl. Stearate,
Acylation of butyl palmitate, 2-ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether with stearic acid Examples thereof include diethylene glycol dipalmitate, hexamethylenediol acylated with myristic acid to form a diol, and various ester compounds such as glycerin oleate. These can be used alone or in combination. A particularly preferred combination is a combination of a fatty acid and a fatty acid ester.

The usual addition amount of the lubricant is in the range of 0.2 to 20 parts by weight (preferably 0.2 to 15 parts by weight) based on 100 parts by weight of the whole nonmagnetic powder in the nonmagnetic layer. .

[Magnetic Layer] The magnetic layer is a layer containing a ferromagnetic powder and a binder. The magnetic layer usually contains a lubricant,
A conductive powder (eg, carbon black) and an abrasive are included. Examples of the ferromagnetic powder include magnetic iron oxide F
eO _x (x = 1.33 to 1.5), Co-modified FeO _x
(X = 1.33-1.5), known strengths such as ferromagnetic alloy powder (ferromagnetic metal powder) containing Fe, Ni or Co as a main component (75% or more) and plate-like hexagonal ferrite powder. Magnetic powder can be used. In particular, the use of ferromagnetic alloy powder is preferred.

The ferromagnetic powder contains not only predetermined atoms but also Al,
Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, R
h, Pd, Ag, Sn, Sb, Te, Ba, Ta, W,
Re, Au, Hg, Pb, Bi, La, Ce, Pr, N
At least one of d, P, Co, Mn, Zn, Ni, Sr and B may be included.

The ferromagnetic powder may be previously treated with a dispersant, a lubricant, a surfactant, an antistatic agent, etc. before dispersion. Specifically, JP-B-44-14090, JP-B-45-18372, JP-B-47-22062, JP-B-47-22513, JP-B-46-28466,
JP-B-46-38755, JP-B-47-4286,
JP-B-47-12422, JP-B-47-17284
No., JP-B-47-18509, JP-B-47-1857
No. 3, JP-B-39-10307 and JP-B-48-3
No. 9639, and US Pat. No. 3,026,215.
No. 3031341, No. 3100194, No. 32
The processing methods described in the respective specifications of US Pat. Nos. 4,005,005 and 3,389,014 can be used. In addition,
The ferromagnetic alloy powder may contain a small amount of hydroxide or oxide.

As the ferromagnetic alloy powder, a powder obtained by a known production method can be used. For example, the following method can be mentioned. A method of reducing complex oxalate with a reducing gas such as hydrogen, a method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe-Co particles, a method of thermally decomposing a metal carbonyl compound, a method of ferromagnetic A method of adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of a metal to reduce the same, or a method of evaporating the metal in a low-pressure inert gas to obtain a fine powder. The ferromagnetic alloy 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 feeding an oxygen-containing gas to form an oxide film on the surface. The treatment may be performed by a method of drying, or a method of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent.

The ferromagnetic alloy powder preferably has a particle specific surface area of 30 to 70 m ² / g and a crystallite size determined by X-ray diffraction of 50 to 300 °. If the specific surface area is too small, it will not be possible to sufficiently cope with high density recording, and if it is too large, dispersion will not be sufficient,
Therefore, it is impossible to form a magnetic layer having a smooth surface, so that it is also impossible to cope with high-density recording. The ferromagnetic alloy powder contains at least Fe. Specifically, Fe-C
o, Fe-Ni, Fe-Zn-Ni or Fe-Ni-C
It is a metal alloy mainly composed of o. Note that Fe alone may be used. Regarding the magnetic properties of these ferromagnetic alloy powders, in order to achieve a high recording density, the saturation magnetization (saturation magnetic flux density) (σs) is 110 emu / g or more, preferably 120 emu / g or more, and 170 emu / g. It is as follows. The coercive force (Hc) is 1900-2600 Oersted (Oe) (preferably 2000-2500 O
e) range. The major axis length of the powder (that is, the average particle diameter) determined by a transmission electron microscope is 0.5
The axis ratio (major axis length / minor axis length, acicular ratio) is 5 μm or less, preferably 0.01 to 0.3 μm, and is 5 to 20, preferably 5 to 15. In order to further improve the properties, non-metals such as B, C, Al, Si, and P, or salts or oxides thereof may be added to the composition. Usually, an oxide layer is formed on the particle surface of the metal powder for chemical stability.

The plate-like hexagonal ferrite is a ferromagnetic material having a flat plate shape and having an easy axis of magnetization in a direction perpendicular to the flat plate surface, and specifically, barium ferrite (a magnetobranbite type or a part thereof). Magnet blambite containing spinel phase), strontium ferrite (magnet blambite or partly containing spinel phase), lead ferrite, calcium ferrite, and their cobalt-substituted products. it can. Of these, cobalt-substituted barium ferrite and cobalt-substituted strontium ferrite are particularly preferred. The plate-shaped hexagonal ferrite used in the present invention may contain Co-T
i, Co-Ti-Zr, Co-Ti-Zn, Ni-Ti
A material to which an element such as -Zn or Ir-Zn is added can be used.

In the plate-like hexagonal ferrite powder, the plate diameter means the width of the plate of hexagonal plate-like particles and can be measured by an electron microscope. The plate-like hexagonal ferrite powder used in the present invention has a particle size (plate diameter) of 0.001 to 1.0 μm.
It is preferable that the plate ratio (plate diameter / plate thickness) is 2 to 20 and the specific surface area is 1 to 60 m ² / g. For the same reason as the ferromagnetic metal powder, high-density recording becomes difficult even if the particle size of the plate-like hexagonal ferrite powder is too large or too small. Regarding the magnetic properties of these plate-like hexagonal ferrite powders, in order to achieve a high recording density, the above-described particle size is necessary, and at the same time, the saturation magnetization (σs) is at least 50 emu / g or more, preferably It is 53 emu / g or more. The coercive force (Hc) is in the range of 700 to 2000 Oe (Oe), and preferably in the range of 900 to 1600 Oe.

The water content of the ferromagnetic powder described above is 0.0
It is preferable that the content be 1 to 2% by weight. It is preferable to optimize the water content depending on the type of the binder. The pH of the ferromagnetic powder is preferably optimized by a combination with the binder used, and the pH is usually in the range of 4 to 12, and preferably in the range of 5 to 10. Ferromagnetic powder,
If necessary, a surface treatment may be performed with Al, Si, P, or an oxide thereof. The amount used for performing the surface treatment is usually 0.1 to 10% by weight based on the ferromagnetic powder.
It is. By performing the surface treatment, adsorption of a lubricant such as a fatty acid can be suppressed to 100 mg / m ² or less. Ferromagnetic powder contains soluble Na, Ca, Fe, Ni,
And inorganic ions such as Sr.
If it is less than 000 ppm, there is no effect on the characteristics.

As the lubricant, the above-mentioned lubricant which can be contained in the nonmagnetic layer can be used. The usual amount of the lubricant is based on 100 parts by weight of the ferromagnetic powder.
It is in the range of 0.2 to 20 parts by weight (preferably 0.2 to 15 parts by weight).

As the carbon black, the carbon black which can be contained in the above-mentioned nonmagnetic layer can be used. However, the carbon black used in the magnetic layer preferably has an average particle diameter in the range of 5 to 350 mμ (more preferably, 10 to 300 mμ). As the carbon black, two or more kinds having different average particle diameters can be used. The amount of carbon black is usually 0.1 to 100 parts by weight of the ferromagnetic powder.
It is in the range of 1 to 30 parts by weight (preferably 0.2 to 15 parts by weight).

Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). be able to. These abrasives have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle diameter of 0.05 to 1 μm (more preferably 0.2 to 0.8 μm). . The amount of the abrasive added is usually in the range of 3 to 25 parts by weight (preferably 3 to 20 parts by weight) based on 100 parts by weight of the ferromagnetic powder.

[Backcoat layer] The backcoat layer includes:
Preferably, carbon black is contained. Further, as the inorganic powder, a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a hard inorganic powder having a Mohs hardness of 5 to 9 are preferably contained.

In the back coat layer, it is preferable to use two types of carbon black having different average particle sizes. In this case, the average particle size is 10
It is preferable to use 20 mμ of fine particle carbon black and coarse particle carbon black having an average particle size of 230 to 300 μm. In general, the surface electric resistance of the back coat layer can be set low and the light transmittance can be set low by the addition of the fine carbon black as described above. Some magnetic recording devices use the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective. In addition, fine carbon black is generally excellent in holding power of a liquid lubricant, and contributes to reduction of a friction coefficient when used in combination with a lubricant. On the other hand, when the particle size is 230
Coarse-particle carbon black having a particle size of about 300 μm has a function as a solid lubricant, and forms fine protrusions on the surface of the back layer, thereby reducing the contact area and contributing to a reduction in the friction coefficient. However, coarse carbon black is
Severe running systems have the drawback that the tape slips easily from the backcoat layer, leading to an increase in the error ratio. 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).

In the case of using two types having different average particle sizes in the back coat layer, 10 to 20 μm
Is preferably in the range of 98: 2 to 75:25, and more preferably 95: 5. ~ 85: 15.

The content of carbon black in the back coat layer (the total amount when two types are used) is usually 30 to 80 parts by weight with respect to 100 parts by weight of the binder.
It is in the range of parts by weight, preferably in the range of 45 to 65 parts by weight.

Generally, a magnetic tape for recording computer data as in the present invention is required to have a higher repetitive running property than a video tape and an audio tape. In a magnetic tape for such use, it is preferable to add a soft inorganic powder having a Mohs' hardness of 3 to 4.5 to the back coat layer, whereby the friction coefficient can be stabilized by repeated running. . Moreover, when the Mohs hardness is 3 to 4.5, the sliding guide pole is not cut. The soft inorganic powder having a Mohs hardness of 3 to 4.5 preferably has an average particle size in the range of 30 to 50 μm. Examples of the soft inorganic powder having a Mohs hardness of 3 to 4.5 include calcium sulfate, calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate, and zinc oxide. These can be used alone or in combination of two or more. Among these, calcium carbonate is particularly preferred.

The content of the soft inorganic powder in the back coat layer is 10 to 14 with respect to 100 parts by weight of carbon black.
It is preferably in the range of 0 parts by weight, more preferably 35 to 100 parts by weight.

Hard inorganic powders having a Mohs hardness of 5 to 9 are used for the purpose of imparting repeated running durability to the tape and strengthening the back coat layer. When these inorganic powders are used together with the above-mentioned carbon black or soft inorganic powder, a strong backcoat layer is obtained with little deterioration even in repeated sliding. When an inorganic powder having a Mohs hardness of 5 to 9 is used, an appropriate polishing force is generated, and the adhesion of shavings and the like to the tape guide pole and the like is reduced. In particular, when used in combination with calcium carbonate, the sliding characteristics of a guide pole having a rough surface can be improved, and the friction coefficient of the back coat layer can be stabilized. The hard inorganic powder having a Mohs hardness of 5 to 9 has an average particle size of 80 to 250 mμ (more preferably, 100 to 250 mμ).
２１０210 mμ).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the hard inorganic powder having a Mohs hardness of 5 to 9 is usually 3 to 100 parts by weight of carbon black.
It is 30 parts by weight, preferably 3 to 20 parts by weight.

It is preferable that the back coat layer contains the above-mentioned two types of inorganic powders each having a specific average particle size and different Mohs hardness, and the above-mentioned two types of carbon blacks having different average particle sizes. Especially,
In this combination, it is preferable that calcium carbonate is contained as the soft inorganic powder. When the soft inorganic powder and the hard inorganic powder are used in combination in the back coat layer, the difference in hardness between the soft inorganic powder and the hard inorganic powder,
2 or more (more preferably 2.5 or more, especially 3 or more)
It is preferable to select and use a soft inorganic powder and a hard inorganic powder as follows. The content ratio (weight ratio) of the two types of inorganic powders having different specific Mohs hardnesses having the specific average particle size in the back coat layer and the two types of carbon blacks having different specific particle sizes is as follows: 7
It is preferably in the range of 0:30 to 30:70, and more preferably in the range of 65: 35 = 35: 65.

The back coat layer may contain a lubricant. The lubricant can be appropriately selected from the above-mentioned lubricants that can be used for the nonmagnetic layer or the magnetic layer. In the back coat layer, the lubricant is usually added in a range of 1 to 5 parts by weight based on 100 parts by weight of the binder.

[Binder] Examples of the binder used for forming the nonmagnetic layer, the magnetic layer and the back coat layer include a thermoplastic resin, a thermosetting resin, a reactive resin and a mixture thereof. it can. Examples of thermoplastic resins include:
Vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and vinyl ether as constituent units Including polymers or copolymers. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride Copolymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, vinylidene chloride-acrylonitrile copolymer Polymer,
Examples thereof include a butadiene-acrylonitrile copolymer, a styrene-butadiene copolymer, and a chlorovinyl ether-acrylate copolymer. In addition to the above,
Polyamide resins, cellulose resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, and various rubber resins can also be used.

Examples of the thermosetting resin or the reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, and epoxy resin. Examples thereof include a polyamide resin, a mixture of a polyester resin and a polyisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate.

Known polyurethane resins having a structure such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used as the polyurethane resin.

As the polyisocyanate as a curing agent, for example, tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, Isocyanates such as triphenylmethane triisocyanate,
The products of these isocyanates and polyhydric alcohols, and polyisocyanates formed by condensation of isocyanates can be mentioned.

In the present invention, the binder for the magnetic layer, the non-magnetic layer and the back coat layer is vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, chloride A combination of at least one resin selected from a vinyl-vinyl acetate-maleic anhydride copolymer and nitrocellulose with a polyurethane resin, or a combination of these with a polyisocyanate as a curing agent. preferable.

In order to obtain better dispersibility and durability of the obtained layer, the binder may be -C
_{OOM, -SO 3 M, -OSO 3} M, -P = O (OM)
_{2, -O-P = O (} OM) 2 (M represents a hydrogen atom or an alkali metal,.), - OH, -NR 2, -N + R
₃ (R represents a hydrocarbon group), epoxy group, -S
A polymer obtained by introducing at least one polar group selected from H, -CN and the like by copolymerization or addition reaction is used. Such a polar group is preferably introduced into the binder in an amount of 10 ^-1 to 10 ^-8 mol / g (more preferably, 10 ^-2 to 10 ^-6 mol / g).

The binder is usually 5 to 5 parts by weight per 100 parts by weight of the ferromagnetic powder of the magnetic layer or the nonmagnetic powder of the nonmagnetic layer.
It is used in the range of 0 parts by weight (preferably 10 to 30 parts by weight). When a combination of a vinyl chloride resin, a polyurethane resin, and a polyisocyanate is used as a binder in the magnetic layer or the non-magnetic layer, the total binder contains 5 to 70% by weight of the vinyl chloride resin, 2 to 50% by weight, and 2% by weight of polyisocyanate
It is preferred to use it in an amount in the range of ５０50% by weight. In the back coat layer, the binder is usually used in an amount of 5 to 250 parts by weight (preferably 10 to 20 parts by weight) based on 100 parts by weight of the carbon black of the back coat layer.
0 parts by weight).

[Optional Components] In a coating solution for forming a magnetic layer, a non-magnetic layer, and a back coat layer of a magnetic tape, a magnetic powder, a non-magnetic powder, and the like are preferably dispersed in a binder. , A dispersant can be added.
If necessary, a plasticizer, conductive particles (antistatic agent) other than carbon black, an antifungal agent and the like can be added to each layer. Examples of the dispersant include 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid. Fatty acids (RCOOH, R is 1 carbon atom)
1 to 17 alkyl groups or alkenyl groups), metal soaps of the above fatty acids comprising alkali metals or alkaline earth metals, compounds of the above fatty acid esters containing fluorine, amides of the above fatty acids, polyalkylene oxide alkyl phosphoric acids Esters, lecithin, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefins such as ethylene and propylene), sulfates, copper phthalocyanine and the like can be used. These may be used alone or in combination. In particular, it is preferable to use copper oleate, copper phthalocyanine, and barium sulfate in combination for the back coat layer. The dispersant is added in any layer in the range of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

[Manufacturing Method] The magnetic tape of the present invention has a specific structure in which the overall thickness, the thickness of the magnetic layer, and the thickness of the nonmagnetic layer are in specific ranges, and the thickness of the magnetic layer and the thickness of the nonmagnetic layer. Can be manufactured using conventional methods, except that is adjusted to have a particular relationship. That is, the production of the magnetic tape of the present invention comprises (1) a step of preparing a coating solution for each layer, (2) a step of applying and drying the obtained coating solution on a support, (3) a calendering step, 4)
This is performed by a cutting step and (5) a step of involving the cartridge. The following is the coating solution for the magnetic layer (magnetic paint)
And the steps of applying the obtained coating liquids (coating liquids for magnetic layers and coating liquids for non-magnetic layers) on a support and drying them are described briefly. The step of preparing the magnetic paint comprises at least a kneading step, a dispersing step, and a mixing step provided before and after these steps as necessary. Each process may be divided into two or more stages. Ferromagnetic powder,
Raw materials used in the present invention such as a binder, carbon black, an abrasive, an antistatic agent, a lubricant, and a solvent may be added at any step, or may be added at the beginning or during the step. I do not care. Further, individual raw materials may be added in two or more steps. For example, the polyurethane resin may be introduced separately in the kneading step, the dispersing step, and the kneading step for adjusting the viscosity after dispersion. The coating solution for the non-magnetic layer and the back coat layer can be prepared using the same method as described above.

The application of the prepared coating solution for the magnetic layer and the non-magnetic layer onto the support is carried out by using a conventional method. It is preferable to use a so-called wet-on-wet coating method in which a coating solution for a magnetic layer is coated on the applied coating layer (nonmagnetic layer) while the coating layer (nonmagnetic layer) is in a wet state.

Examples of the above-mentioned wet-on-wet coating method include the following methods. (1) A non-magnetic layer is first formed on a support using a gravure coating, a roll coating, a blade coating, or an extrusion coating device. Method for forming a magnetic layer by a lug coating device (Japanese Patent Application Laid-Open No. 60-23817)
9, JP-B 1-46-186, and JP-A-2-265
672). (2) A method in which a magnetic layer and a non-magnetic layer are formed almost simultaneously on a support using a coating apparatus comprising a single coating head having two coating liquid slits (Japanese Patent Laid-Open No. 63-880)
No. 80, JP-A-2-17921 and JP-A-2-26
5672). (3) A method in which a magnetic layer and a non-magnetic layer are formed almost simultaneously on a support using an extrusion coating apparatus with a backup roller (see Japanese Patent Application Laid-Open No. 2-174965). In the present invention, the application of the coating solution for the non-magnetic layer and the magnetic layer onto the support is preferably performed by using a simultaneous multilayer coating method. After application, it is dried at a predetermined temperature.

The magnetic layer of the magnetic tape of the present invention has a surface roughness of 2.0 to 4.0 nm (more preferably 2.5 to 3.5) as measured by the 3D-MIRAU method (three-dimensional method).
nm, in particular, from 2.6 to 3.3 nm). The surface property of the back coat layer tends to be transferred to the surface of the magnetic layer in a state where the tape is wound. For this reason, it is preferable that the back coat layer also has relatively high smoothness. The back coat layer of the magnetic tape of the present invention has a surface roughness (center line average roughness with a cutoff of 0.08 mm) Ra.
It is preferable that the distance is adjusted to be in the range of 0.0030 to 0.060 μm. In addition, the surface roughness can be adjusted by the material of the calender roll to be used, its surface properties, the pressure, and the like, usually in the surface treatment step using a calender after the formation of the coating film.

The magnetic tape of the present invention can be advantageously used for a magnetic recording / reproducing system capable of recording / reproducing at a narrower track pitch than the conventional one. For example, 9μ
m (preferably 5 to 8 μm, more preferably 5 μm
７7 μm) can be advantageously used in a magnetic recording / reproducing system capable of recording / reproducing at a track pitch.

[0061]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. In addition, "part" shown below represents "part by weight" unless otherwise specified.

[0062] [Example 1] [nonmagnetic layer coating solution and preparation of the magnetic layer coating solution (the non-magnetic layer forming ingredient) non-magnetic powder of titanium dioxide (rutile type) 90 parts [TiO ₂ content : 90% average primary particle size: specific surface area by 0.035 .mu.m BET ^{method: 40m 2 / g pH: 7.0} DBP oil absorption: 27~38g / 100g Mohs hardness: 6.0 surface treatment agent (A1 ₂ 0 ₃ )] Carbon black (produced by Mitsubishi Carbon Co., Ltd.) 10 parts [Average primary particle diameter: 16 μm DBP oil absorption: 80 ml / 100 g pH: 8.0 Specific surface area by BET method: 250 m ² / g Volatile content: 1.5% ] polar group (-SO ₃ Na group, an epoxy group-containing) containing 12 parts of vinyl chloride resin [(MR-110, manufactured by Nippon Zeon Co.) polar group (-SO ₃ Na group) containing polyester polyurethane Resin 5 parts [neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 (weight ratio) -containing 1 × 10 ^-4 mol / g of SO ₃ Na group] Polyisocyanate 3 parts [(Coronate L, Nippon Polyurethane Industry Co., Ltd.)] Butyl stearate 1 part Stearic acid 2 parts Oleic acid 1 part Methyl ethyl ketone 150 parts Cyclohexanone 50 parts

(Components for Forming Magnetic Layer) 100 parts of ferromagnetic metal powder [Co: 30 atomic%, Al: 11.2 atomic%, and Y: 6.3 atomic% with respect to Fe (100)] . Coercive force (Hc): 2350 Oersted (Oe) Specific surface area by BET method: 47 m ² / g Crystallite size: 175 ° Saturated magnetization (σs): 147 emu / g Particle size (average major axis diameter): 0.08 μm Needle Ratio: 7.5 pH: 9.4 Water-soluble Na: 5 ppm Water-soluble Ca: 10 ppm Water-soluble Fe: 10 ppm] Magnetic substance surface treatment agent [(phenylphosphonic acid)] 3 parts Polar group (-SO ₃ Na group) contained Vinyl chloride copolymer 10 parts [-SO ₃ Na group content: 5 × 10 ⁻⁶ mol / g, degree of polymerization 350 Epoxy group content: 3.5% by weight in monomer units (MR-110, Nippon Zeon ( Ltd.)) polar group (-SO ₃ Na group) containing polyester polyurethane resin 2.5 parts [neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 ( weight ) -SO ₃ Na group content: 1 × 10 ^-4 mol / g] Polyisocyanate 2.5 parts [manufactured (Coronate L, Nippon Polyurethane Industry (Ltd.))] alpha-Alumina [(particle size: 0.3 [mu] m) 10 parts dichromium trioxide 1 part carbon black [(particle size: 0.10 μm)] 3 parts butyl stearate 1 part stearic acid 2 parts oleic acid 1 part methyl ethyl ketone 150 parts cyclohexanone 50 parts

Each of the components forming the nonmagnetic layer or the magnetic layer was kneaded with a continuous kneader, and then dispersed using a sand mill. To each of the obtained dispersions, 2.5 parts of the above-mentioned polyisocyanate was added to the dispersion of the non-magnetic layer, 3 parts of the dispersion of the magnetic layer was added, and 40 parts of butyl acetate was added to each, and the average of 1 μm was added. The solution was filtered using a filter having a pore size to prepare a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer.

[Preparation of Coating Solution for Forming Back Coat Layer] (Component for Forming Back Coat Layer) 100 parts of fine particulate carbon black powder [(Cabot, BP-800, average particle size: 17 mμ)] Coarse particulate carbon Black powder 10 parts [(Karncarb, thermal black, average particle size: 230 mμ)] Calcium carbonate 80 parts [(Shiraishi Industry Co., Ltd., white luster O, average particle size: 40 mμ, Mohs hardness: 3.0)] α-alumina 5 parts [(Sumitomo Chemical Co., Ltd., HIT55, average particle size: 200 μm, Mohs hardness: 8.5)] Nitrocellulose resin 140 parts Polyurethane resin 15 parts [N2301, Nippon Polyurethane Industry Co., Ltd.] 40 parts of polyisocyanate [(Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.)] Ester resin 5 parts Ethylene glycol, diethylene glycol, resin made of terephthalic acid and isophthalic acid, molecular weight: 50,000] Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 parts 600 parts Toluene Barium sulfate

The components forming the back coat layer were kneaded with a continuous kneader, and then dispersed using a sand mill. The obtained dispersion was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for forming a backcoat layer.

[Preparation of Magnetic Tape] The obtained coating solution for forming a non-magnetic layer and the coating solution for forming a magnetic layer are coated on the non-magnetic layer so that the dried non-magnetic layer has a thickness of 0.435 μm. An elongated aramid support (trade name: MICRON, thickness: 2.65) such that the thickness of the dried magnetic layer is 0.065 μm.
5 μm, manufactured by Toray Industries, Inc.). Next, while both layers were still in a wet state, orientation treatment was performed using a cobalt magnet having a magnetic flux density of 3000 Gauss and a solenoid having a magnetic flux density of 1500 Gauss. Thereafter, by drying, a non-magnetic layer and a magnetic layer were formed.

Thereafter, the above-mentioned coating solution for forming a back coat layer is applied on the other side of the aramid support (the side opposite to the magnetic layer) so that the thickness after drying is 0.4 μm, and the coating is dried. Then, a back coat layer was provided to obtain a magnetic recording laminate roll in which a non-magnetic layer and a magnetic layer were provided on one side of the support, and a back coat layer was provided on the other side.

The obtained magnetic recording laminate roll was converted to a seven-stage calendering machine (temperature: 9) composed of only metal rolls.
The film was calendered at 0 ° C. under a linear pressure of 300 kg / cm ² ) and wound up at a tension of 5 kg. Next, the roll of the magnetic recording laminate after storage was slit to a width of 3.8 mm to obtain a magnetic recording medium according to the present invention (a magnetic tape for computer data recording, hereinafter simply referred to as a magnetic tape). The obtained magnetic tape is used as a cartridge for DDS.
0m involved. The surface roughness (cut-off value: center line average roughness at 0.08 mm) of the back coat layer of the magnetic tape thus obtained was 4.5 nm. The surface roughness (cut-off value: center line average roughness of 0.08 mm) of the back coat layer of the magnetic tapes obtained in the following Examples and Comparative Examples was all the same as in Example 1. .

[Example 2] to [Example 8] Except that in Example 1, the coating thickness was changed so that the thickness of the nonmagnetic layer and the thickness of the magnetic layer were as shown in Table 1 below. Produced a magnetic tape according to the present invention in the same manner.

[Examples 9] to [Example 12] In Example 1, an aramid support having a thickness of 2.9 µm was used, and the thickness of the nonmagnetic layer and the thickness of the magnetic layer were as shown in Table 1 below. A magnetic tape according to the present invention was produced in the same manner except that the coating thickness was changed so as to obtain a thickness.

[Examples 13 to 14] In Example 1, an aramid support having a thickness of 3.3 μm was used, and the thickness of the nonmagnetic layer and the thickness of the magnetic layer were as shown in Table 1 below. A magnetic tape according to the present invention was produced in the same manner except that the coating thickness was changed so as to obtain a thickness.

[Comparative Example 1] In Example 1, polyethylene terephthalate (PET) having a thickness of 4.4 μm was used as the support, and the thickness of the nonmagnetic layer and the thickness of the magnetic layer were as shown in Table 1 below. A magnetic tape for comparison was produced in the same manner except that the coating thickness was changed so as to be as follows.

Comparative Example 2 In Example 1, an aramid support having a thickness of 4.4 μm was used, and the thickness of the nonmagnetic layer and the thickness of the magnetic layer were adjusted so as to be as shown in Table 1 below. A magnetic tape for comparison was produced in the same manner except that the coating thickness was changed.

Comparative Example 3 A comparative magnetic tape was produced in the same manner as in Example 2, except that polyethylene terephthalate (PET) having a thickness of 2.5 μm was used as the support.

[Evaluation as Magnetic Tape] The characteristics of each of the obtained magnetic tapes were measured and evaluated by the following methods. (1) Appropriate Cartridge A 180 m magnetic tape was wound around the DDS cartridge, the amount of winding was inspected, and the cartridge was adjusted. Those that were involved in 180 m were regarded as acceptable products. As a result, in the magnetic tapes of Comparative Example 1 and Comparative Example 2,
180 m could not be involved.

(2) Measurement of reproduction output 13.5 MHz output Evaluation was made using a DDS evaluator (track width: 6.8 μm). In addition, the value used as a reference | standard showed the value of the reference tape for DDS as 0 dB, and was shown by relative evaluation.

(3) Output Measurement after Storage The output before storage (initial output) and the output after storage for one week in an environment of 60 ° C. and 90% RH (after storage) are the same as those in the method (1). And each was measured. Then, the obtained initial output value-output value after storage was calculated, and output reduction (dB) after storage was calculated.

(4) Coefficient of friction of the surface of the magnetic layer The lower cylinder used in the DDS drive is brought into contact with the surface of the magnetic layer of the magnetic tape by applying a load of 10 g (T1) to the lower cylinder, which is 4 mm. The tension (T2) was applied at a speed of / sec and the film was pulled, and the friction coefficient of the magnetic layer surface with respect to the lower cylinder was determined by T2 / T1. As the friction coefficient, the friction coefficient (100
Pass μ value).

(5) Measurement of output drop due to quality of contact with magnetic head Output waveform (envelope) when measuring 13.8 MHz output using a DDS evaluator is measured with a synchroscope (IW).
ATSU, SS-7635, manufactured by Iwasaki Communication Equipment Co., Ltd.). The drop (dB) of the reproduced output was measured from the waveform distorted with respect to the waveform of the initial output. Those having good head contact (contact state with the magnetic head) and having an initial output waveform show 0.0 dB as an output, and those having poor head contact and a drop in output have
The output was represented by minus (dB) with respect to 0.0 dB. Table 1 shows the evaluation results.

[0081]

[Table 1]

From the results shown in Table 1, the total thickness of the tape, the thickness of the magnetic layer, and the thickness of the magnetic layer are within specific ranges, respectively, and the thickness of the magnetic layer and the thickness of the nonmagnetic layer have a specific relationship. Magnetic tape according to the present invention (Examples 1 to 14)
In the case of (1), since the reproduction output hardly decreases and the contact state with the magnetic head is well maintained, the reproduction output hardly drops or is slight at all. Further, even in the reproduction output after storage under high temperature and high humidity, the output decrease is relatively small, indicating that the storage stability is high.
In addition, despite the thinness of the entire tape, the value of the coefficient of friction after running 100 passes is within the allowable range, and thus it can be seen that the tape has good running durability.

On the other hand, as seen in Comparative Examples 1 and 2, polyethylene naphthalate (P) having a thickness of 4.4 μm was used.
Since ET) and aramid (PA) are used, the entire thickness of the tape becomes thick, and therefore, a predetermined amount (180 m) of tape cannot be wound into a predetermined cartridge (ie, achieving a sufficient recording capacity). Can not).
In these examples, since the thickness of the nonmagnetic layer is relatively large,
The decrease in the reproduction output after storage is large, and it can be seen that the reproduction output cannot be sufficiently obtained particularly in Comparative Example 1. As seen in Comparative Example 3, the overall thickness of the tape, the thickness of the magnetic layer, and the thickness of the nonmagnetic layer are within the scope of the present invention, and the thickness of the magnetic layer and the thickness of the nonmagnetic layer are also defined by the present invention. Even if the above relationship is satisfied, since polyethylene naphthalate (PET) is used as the support material, a sufficient head contact cannot be realized, and the drop in reproduction output due to the head contact is large. I understand.

[0084]

According to the magnetic recording medium of the present invention, a large recording capacity can be achieved because the thickness of the entire medium is extremely thin. In addition, in spite of the fact that the thickness of the entire medium is extremely thin as described above, it has high running durability together with good electromagnetic conversion characteristics. Further, the upper magnetic layer is thin, which is advantageous for high-density recording. Therefore, the magnetic recording medium of the present invention can be advantageously used as a magnetic tape for recording computer data. Also,
Since the magnetic recording medium of the present invention has the above-described performance, even when used as a magnetic tape for a magnetic recording / reproducing system capable of recording / reproducing to a narrow track pitch, off-track and the like rarely occur. Therefore, highly reliable data recording / reproduction is possible.

Claims (3)

[Claims] 1. A substantially non-magnetic non-magnetic layer containing a non-magnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder are provided on one surface of an aromatic polyamide support in this order. In a magnetic recording medium having a back coat layer on the other surface of the support, the total thickness of the medium is 3.0.
To 4.6 μm, and the thickness of the magnetic layer is 0.05 to 0.4 μm.
2 μm, the thickness of the nonmagnetic layer is 0.3 to 1.8 μm, and the total of the thickness of the magnetic layer and the thickness of the nonmagnetic layer is 0.4 to 2.0
A magnetic recording medium, wherein the ratio of [thickness of magnetic layer] / [total thickness of magnetic layer and nonmagnetic layer] is in the range of 0.05 to 0.15 in μm. 2. The aromatic polyamide support having a thickness of 2.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is in a range of 3 to 4.0 µm. 3. A data recording apparatus having a data track width of 9 μm on a tape-shaped magnetic recording medium by a helical scan method using a rotating magnetic head.
m or less, wherein the magnetic recording medium has a substantially non-magnetic non-magnetic layer containing a non-magnetic powder and a binder, a ferromagnetic powder and a non-magnetic powder on one surface of an aromatic polyamide support. A magnetic layer containing a binder in this order, and a back coat layer on the other surface of the support, wherein the total thickness of the medium is 3.0 to 4.6 μm, and the thickness of the magnetic layer is Is 0.05 to 0.2 μm, and the thickness of the nonmagnetic layer is 0.3 to
1.8 μm, the total of the thickness of the magnetic layer and the thickness of the nonmagnetic layer is 0.4 to 2.0 μm, and the ratio of [thickness of magnetic layer] / [total thickness of magnetic layer and nonmagnetic layer] is 0. 0.05-0.15
A magnetic recording method characterized by being in the range described above.