JPH09293229A - Magnetic tape for recording computer data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape for recording computer data capable of attaining high recording capacity and having excellent traveling durability and high reliability to the recording and reading of data. SOLUTION: The magnetic tape is provided with a non-magnetic layer composed mainly of a non-magnetic powder and a binder, substantially non-magnetic and 1.0-2.0μm in thickness and a magnetic layer composed mainly of a ferromagnetic powder having 1900-2600 oersteds coercive force and the square ratio of >=0.78 and a binder, 0.05-0.5μm in thickness and 2-5nm in surface roughness in this order on one side of a long-sized supporting body composed of an aromatic polyamide or an aromatic polyimide. And a back coating layer is formed on another side of the long-sized supporting body and the total thickness is controlled to <=7.0μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape used as an external recording medium for recording computer data.

[0002]

2. Description of the Related Art In recent years, with the spread of office computers such as minicomputers and personal computers, magnetic tapes (so-called backup tapes) for recording computer data as external storage media have been actively studied. . In practical application of magnetic tapes for such purposes, there is a strong demand for improvement in recording capacity in order to achieve larger recording capacities and smaller recording capacities, especially in conjunction with smaller computers and increased information processing capabilities. In addition, the use environment of magnetic tapes is widespread, so it can be used under a wide range of environmental conditions (especially in the circumstance where temperature and humidity fluctuates rapidly). Reliability for performance such as recording and reading is required more than before.

Generally, a magnetic tape has a structure in which a magnetic layer is provided on a non-magnetic support made of a flexible material such as synthetic resin. In order to achieve the large recording capacity (volume recording capacity) as described above, it is necessary to reduce the particle size of the magnetic powder, improve its dispersibility, or make the magnetic layer thinner. It is said that an effective method is to increase the recording density of the magnetic tape itself and reduce the total thickness of the magnetic tape. Further, in order to maintain good sensitivity (especially output in a high frequency region), it is preferable that the magnetic layer is smooth, but in order to prevent winding disorder and deterioration of running property due to the smoothing, the above-mentioned support is usually used. A back coat layer is often provided on the surface opposite to the magnetic layer. Further, especially when the total thickness is reduced, the self-supporting property and strength of the magnetic tape are deteriorated, so that the backcoat layer is required to be attached also for maintaining good running durability against repeated use. However, as described above, the thickness of the back coat layer needs to be relatively thin as the magnetic tape becomes thinner.

A magnetic tape in which the total thickness of the magnetic tape and the thickness of the back coat layer are relatively thin is disclosed in, for example, JP-A-6-215350. As a specific example of the magnetic tape described in this publication, an embodiment in which the total thickness of the magnetic tape is 10 μm and the layer thickness of the back coat layer is 0.5 μm, or the total thickness is 9.5 μm And a mode in which the layer thickness of the back coat layer is set to 0.5 μm. In the back coat layer in these embodiments, relatively fine carbon black is used alone in the former embodiment, and in the latter embodiment, in order to provide antistatic and stable running properties, and in the latter embodiment, a relatively fine carbon black is used. Two types of carbon black, fine particle carbon black and relatively coarse particle carbon black, are used. As a material of the nonmagnetic support used for the magnetic tape, polyester, particularly polyethylene naphthalate (PEN) is considered to be preferable.

[0005]

The present inventors have studied the use of a magnetic tape in which the total thickness of the tape and the thickness of the back coat layer are also extremely small as an external recording medium for recording computer data. As a result, as described in
It has been found that even with the thin magnetic tape described in JP-A-215350, a sufficient recording capacity cannot be achieved for computer data recording. That is, with the thickness (total thickness) of the magnetic tape described in the above publication, the required amount of tape cannot be stored in a predetermined cartridge, and therefore, in order to obtain a large volume recording capacity suitable for computer data recording, Further, it has been found that it is necessary to reduce the thickness of the tape. Also, in general, to obtain a high recording density,
It is preferable that the magnetic layer is thin, but the magnetic layer of the above magnetic tape has a thickness of about 2.0 μm, and it has been found that there is room for further improvement. On the other hand, if the total thickness of the magnetic tape is simply further reduced, the strength of the tape itself becomes insufficient as described above, and the running property deteriorates during repeated running (maintaining sufficient running durability. I can't),
Further, it has become clear that it is necessary to improve the support itself, since the adverse effects on the output and the like are likely to occur.

An object of the present invention is to provide a magnetic tape for computer data recording which can achieve a high recording capacity, has excellent running durability, and has high reliability in data recording and reading.

[0007]

As a result of the research conducted by the present inventor,
Using a relatively strong support material, a very thin magnetic layer containing a magnetic material with specific performance on one side and having a high surface property, and a non-magnetic layer that assists the performance of this magnetic layer. It was found that a magnetic tape for computer data recording having a high recording capacity, excellent running durability, and high reliability for data recording can be obtained by employing the configuration provided, and the present invention was reached. It was done.

According to the present invention, a substantially non-magnetic thickness of 1.0 to 2 mainly composed of a non-magnetic powder and a binder is provided on one side of an elongated support made of aromatic polyamide or aromatic polyimide. 0.0 μm non-magnetic layer and coercive force of 1900-
A thickness of 0.05 to 0.5 mainly composed of a ferromagnetic powder having a squareness ratio of 0.78 or more and a binder of 2600 oersteds
a magnetic layer having a surface roughness (surface roughness according to the 3D-MIRAU method) of 2 to 5 nm, in this order, and a back coat layer on the other side of the long support. A magnetic tape for recording computer data having a thickness of 7.0 μm or less.

The present invention preferably has the following aspects. (1) The magnetic layer is provided while the non-magnetic layer is in a wet state. (2) The aromatic polyamide is aramid (wholly aromatic polyamide). (3) The surface roughness of the magnetic layer (the surface roughness measured by the 3D-MIRAU method) is in the range of 2.0 to 4.0 nm. (4) The thickness of the back coat layer is in the range of 0.2 to 0.8 μm. (5) The back coat layer contains carbon black. (6) The carbon black is composed of two kinds of carbon black having different average particle sizes, that is, fine particle carbon black of 10 to 20 mμ and coarse carbon black of 230 to 300 mμ. (7) The back coat layer contains carbon black, and further contains calcium carbonate and an inorganic powder having a Mohs hardness of 5-9. (8) The average particle size of the calcium carbonate is 30 to 5
It is in the range of 0 mμ. (9) The average particle size of the inorganic powder having a Mohs hardness of 5 to 9 is in the range of 80 to 250 mμ. (10) The inorganic powder having a Mohs hardness of 5 to 9 is α-iron oxide or α-alumina. (11) The surface roughness Ra (cutoff value: 0.08 mm) of the backcoat layer is in the range of 0.003 to 0.06 μm.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic tape for recording computer data according to the present invention will be described below. The magnetic tape of the present invention has a thickness of 1.0 to 2. 1 on one side of a long support made of aromatic polyamide or aromatic polyimide.
It has a nonmagnetic layer of 0 μm and a magnetic layer having a surface roughness of 2 to 5 nm and a thickness of 0.05 to 0.5 μm on the nonmagnetic layer. A back coat layer is provided on the other side of the support, and the total thickness of the magnetic tape is 7.0 μm or less (preferably 3.0 to 7.0 μm, more preferably 4.0 to 4.0 μm). 7.0 μm). The magnetic layer of the magnetic tape of the present invention is preferably provided on the non-magnetic layer while it is in a wet state. That is, the magnetic layer is formed by applying a coating solution for a non-magnetic layer on a support and then applying the coating solution for a magnetic layer on the formed coating layer (non-magnetic layer) while the coating layer (non-magnetic layer) is in a wet state. It is preferably formed using a wet-on-wet coating method.

The wet-on-wet coating method includes, for example, the following method. (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 lubrication coating apparatus
9, JP-B 1-46-186, JP-A-2-26567
No. 2). (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, JP-A-2-2656
No. 72, each publication). (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 non-magnetic layer and the magnetic layer are preferably formed by using the simultaneous multilayer coating method. The thickness of the non-magnetic layer is preferably in the range of 1.5 to 1.8 μm. The thickness of the magnetic layer is 0.1 to 0.4 μm.
Is preferably within the range.

The support, the non-magnetic layer, the magnetic layer and the back coat layer will be described in detail below. [Support] The support of the magnetic tape of the present invention is made of aromatic polyamide or aromatic polyimide. These supports are excellent in physical properties such as tensile strength, and have sufficient strength to withstand even a very thin tape as in the present invention. The aromatic polyamide 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 each represent an aromatic ring ( The aromatic ring may be condensed) or a group containing at least one aromatic ring. The following can be mentioned as examples of Ar ¹ , Ar ² and Ar ³ .

[0014]

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 the hydrogen atom of the aromatic ring include a halogen atom (especially chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (especially a methyl group), and an alkyl group having 1 to 3 carbon atoms. An alkoxy group can be mentioned. The hydrogen atom of the amide bond, which is a constituent of the polymer, may be substituted.

The aromatic polyamide used in the present invention is preferably a polymer in which an aromatic ring is bonded at the para position and accounts for 50% or more (more preferably 70% or more) of the total aromatic ring. Further, from the viewpoint of reducing hygroscopicity, it is preferable that the aromatic ring in which hydrogen atoms on the aromatic ring are replaced by halogen atoms (particularly chlorine atom) accounts for 30% or more of the whole polymer.

The aromatic polyamide used in the present invention contains 50 mol% of the repeating unit represented by the above (I) or (II).
As described above, it is preferable that the content of the repeating unit is 70 mol% or more, but the repeating unit represented by the above formula (I) or (II) may be used as long as it satisfies the physical properties of the support. It is possible to use a polymer obtained by copolymerizing or blending the repeating unit of. In the present invention, it is preferable to use aramid (wholly aromatic polyamide). Representative examples of aramid products include Miktron (manufactured by Toray Industries, Inc.) and Aramica (manufactured by Asahi Kasei Kogyo Co., Ltd.)
Can be mentioned. The aromatic polyamide is described in JP-A-8-55327 or JP-A-8-55327.
-55328.

The aromatic polyimide used for the magnetic tape of the present invention preferably contains, for example, a repeating unit represented by the following formula (III), (IV) or (V).

[0019]

Embedded image

R ¹ , R ² and R ³ each represent an aromatic ring, a heterocyclic ring or a group containing at least one aromatic ring. The hydrogen atom of the above aromatic ring or heterocyclic ring may be substituted. Examples of the group or atom capable of substituting a hydrogen atom of an aromatic ring or a heterocyclic ring include, for example, a halogen atom (in particular, chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (in particular, a methyl group), 1-3 alkoxy groups can be mentioned. The above R ¹ , R ² and R ³
The following may be mentioned as examples of

[0021]

Embedded image

The aromatic polyimide used in the present invention comprises a repeating unit represented by the above formula (III), (IV) or (V) in an amount of 50 mol% or more, preferably 70 mol% or more. However, it is preferable that the repeating unit represented by the formula (III), (IV) or (V) is copolymerized or blended with another repeating unit as long as it satisfies the physical properties of the support. Polymers made of can be used. In the present invention, it is preferable to use wholly aromatic polyimide.

[Non-Magnetic Layer] The non-magnetic layer provided on the support of the magnetic tape of the present invention is a substantially non-magnetic layer mainly containing non-magnetic powder and a binder. This non-magnetic layer is required to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer thereabove, but a small amount so as not to affect the electromagnetic conversion characteristics of the magnetic layer. It does not matter in particular even if the magnetic powder of No. 1 is contained. In addition, the nonmagnetic layer usually contains a lubricant in addition to these components. Examples of the non-magnetic powder used in the non-magnetic layer include non-magnetic inorganic powder and carbon black. The nonmagnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of these non-magnetic inorganic powders include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, and titanium dioxide. Mention may be made of silicon, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, and barium sulfate. These can be used alone or in combination. Among these, titanium oxide, α-alumina, α
Iron oxide or chromium oxide is preferred. The average particle size of the nonmagnetic inorganic powder that can be used in the present invention is 0.01 to 1.0.
(Preferably 0.01 to 0.5, particularly 0.02 to
0.1) It is preferable to be in the range of μm. In addition, 3 to 25% by weight (preferably 3 to 20% by weight) of the nonmagnetic powder has a Mohs hardness of 5 or more (preferably 6 or more).
It is preferable to use one that can function as a so-called abrasive.

Carbon black is added in addition to the non-magnetic inorganic powder for the purpose of imparting conductivity to prevent charging and ensuring a smooth surface property of the magnetic layer formed on the non-magnetic layer. . Carbon black used in the non-magnetic layer is
The average particle size is 35 mμ or less (more preferably, 10
３５35 mμ). Its specific surface area is 5 to 500 m ² / g (more preferably 50 to 30 m ² / g).
0 m ² / g). DBP oil absorption is
10 to 1000 ml / 100 g (more preferably 50
˜300 ml / 100 g) is preferable. The pH is 2 to 10 and the water content is 0.1 to 10
%, And the tap density is preferably 0.1 to 1 g / cc. The DBP oil absorption is determined by adding the butyl phthalate to the carbon black little by little, observing the state of the carbon black while kneading the mixture, and finding the point at which a point forming one mass from the dispersed state is found. ml), which is a value generally used for evaluating the surface characteristics of carbon black.

In the present invention, 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 can be mentioned. As a specific product example of the carbon black used in the present invention, BLACKPEARLS
2000, 1300, 1000, 900, 800, 70
0, VULCAN XC-72 (all manufactured by Cabot), # 35, # 50, # 55, # 60 and # 80 (all manufactured by Asahi Carbon Co., Ltd.), # 3950B, # 3750.
B, # 3250B, # 2400B, # 2300B, # 1
000, # 900, # 40, # 30, and # 10B (all manufactured by Mitsubishi Kasei Co., Ltd.), CONDUCTEXS
C, RAVEN, 150, 50, 40, 15 (above, manufactured by Konron Beer Carbon Co., Ltd.), Ketjen Black EC,
Examples include Ketjen Black ECDJ-500 and Ketjen Black ECDJ-600 (all manufactured by Lion Agzo Co., Ltd.).

The usual amount of carbon black added is 3 to 2 per 100 parts by weight of the total non-magnetic inorganic powder in the non-magnetic layer.
The amount is 0 parts by weight, preferably 4 to 18 parts by weight, and more preferably 5 to 15 parts by weight.

The lubricant is added in order to absorb the friction between the surface of the magnetic layer and the magnetic head by exuding to the surface of the magnetic layer and to maintain a smooth sliding contact. Examples of the lubricant include a fatty acid and a fatty acid ester. Examples of the fatty acid include acetic acid, propionic acid, octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid,
Aliphatic carboxylic acids such as behenic acid, arachiic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid and palmitoleic acid or mixtures thereof can be mentioned.

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,
Butyl palmitate, 2-ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxy ethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether is acylated with stearic acid. Examples thereof include diethylene glycol dipalmitate, hexamethylene diol acylated with myristic acid to give a diol, and various ester compounds such as glycerin oleate. These can be used alone or in combination.

The lubricant is usually added in an amount of 0.2 to 20 parts by weight based on 100 parts by weight of the total nonmagnetic powder in the nonmagnetic layer.

[Magnetic Layer] The magnetic layer of the magnetic tape of the present invention is basically composed of a ferromagnetic powder and a binder. Further, the magnetic layer usually further contains a lubricant, carbon black as a conductive powder, and an abrasive.
Examples of the ferromagnetic powder that can be used in the magnetic layer include γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and FeOx.
(X = 1.33 to 1.5), CrO ₂ , Co-containing γ-F
e ₂ O _3, Co-containing FeOx (x = 1.33~1.
5), ferromagnetic metal powder, and plate-like hexagonal ferrite powder. In the present invention, it is preferable to use a ferromagnetic metal powder or a plate-like hexagonal ferrite powder as the ferromagnetic powder. Particularly preferred is a ferromagnetic metal powder.

The ferromagnetic metal powder preferably has a particle specific surface area of 30 to 70 m ² / g and a crystallite size of 50 to 300 A as determined by X-ray diffractometry. 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 impossible to cope with high-density recording. The ferromagnetic metal powder used in the present invention must contain at least Fe,
Specifically, Fe, Fe-Co, Fe-Ni, Fe-Z
It is a simple metal or alloy mainly composed of n-Ni or Fe-Ni-Co. Regarding the magnetic characteristics of these ferromagnetic metal powders, in order to achieve high recording density, the saturation magnetization amount (saturation magnetic flux density) (σs) is 110 emu /
g or more, preferably 120 emu / g or more, 170 em
u / g or less. The coercive force (Hc) is 1900-2
600 Oersted (Oe) (preferably 2000-
The range is 2400 Oe). Further, the squareness ratio (σr / σs) of the ferromagnetic metal powder used in the present invention is 0.78 or more (preferably 0.78 to 0.95, more preferably,
0.80 to 0.95). Here, σs represents the saturation magnetic flux density, and σr represents the residual magnetic flux density. When the squareness ratio is less than the above value, it becomes difficult to obtain a sufficient reproduction output. The major axis length (that is, average particle diameter) of the powder obtained by a transmission electron microscope is 0.5 μm.
m or less, preferably 0.01 to 0.3 μm, and the axial ratio (major axis length / minor axis length, acicular ratio) is 5 or more and 20 or less, 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 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 also preferable to optimize the water content depending on the type of binder. The pH of the ferromagnetic powder is preferably optimized depending on the combination with the binder used, and the pH is usually in the range of 4 to 12, 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 applying the surface treatment, adsorption of a lubricant such as 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 may be included.
If it is 000 ppm or less, it does not affect the characteristics.

As the lubricant, the lubricant which can be contained in the above-mentioned non-magnetic layer can be used. The usual amount of the lubricant is 0.2 to 20 parts by weight based on 100 parts by weight of the ferromagnetic powder in the magnetic layer.

As the carbon black, the carbon black which can be contained in the above-mentioned non-magnetic layer can be used. However, the average particle diameter of the carbon black used in the magnetic layer is preferably in the range of 5 mμ to 350 mμ (more preferably 10 mμ to 300 mμ). As the carbon black, two or more kinds having different average particle diameters can be used. The amount of carbon black added is usually 0.
It is in the range of 1 to 30 parts by weight (preferably 0.2 to 15 parts by weight).

[0035] As the polishing agent, for example, fused alumina, silicon carbide, chromium oxide (Cr ₂ 0 _3), corundum, artificial corundum, diamond, artificial diamond, garnet, emery: include (main component corundum and magnetite) be able to. These abrasives preferably have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle size of 0.05 to 1 μm (more preferably 0.2 to 0.8 μm). . The amount of the abrasive added is usually 3 to 2 with respect to 100 parts by weight of the ferromagnetic powder.
It is in the range of 5 parts by weight (preferably 3 to 20 parts by weight).

[Backcoat Layer] A backcoat layer is provided on the other side of the non-magnetic support of the magnetic tape of the present invention. In the present invention, the backcoat layer preferably contains carbon black. Furthermore, as inorganic powder, calcium carbonate and Mohs hardness of 5
It is preferable that 9 inorganic powders are contained.

In the back coat layer, it is preferable to use two kinds of carbon black having different average particle sizes. In this case, the average particle size is 10
It is preferable to use fine particle-like carbon black having a particle size of ˜20 mμ and coarse particle-like carbon black having an average particle size of 230-300 mμ. 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. Depending on the magnetic recording apparatus, many of them use the light transmittance of the tape for the operation signal, and in such a case, the addition of particulate carbon black is particularly effective. In addition, fine particulate carbon black is generally excellent in retaining force of the lubricant, and contributes to reduction of the friction coefficient when used in combination with the lubricant. On the other hand, the particle size is 230-3
The coarse particle carbon black having a particle size of 00 mμ has a function as a solid lubricant, and also forms minute protrusions on the surface of the back layer to reduce the contact area and contribute to the reduction of the friction coefficient. However, the coarse-grained carbon black has a drawback that in a harsh traveling system, the tape easily slides to fall off from the back coat layer, leading to an increase in error ratio.

The following are specific products of the particulate carbon black that can be used in the present invention. RAVEN2000B (18m
μ), RAVEN1500B (17 mμ) (above, Columbia Carbon Co., Ltd.), BP800 (17 mμ) (Cabot Co.), PRINTEX90 (14 mμ), P
RINTEX95 (15mμ), PRINTEX85
(16 mμ), PRINTEX 75 (17 mμ) (above, manufactured by Degussa), # 3950 (16 mμ) (manufactured by Mitsubishi Kasei Co., Ltd.). Further, as an example of a specific product of coarse particle carbon black, thermal black (270 mμ)
(Manufactured by Khan Kalb Co.), RAVEN MTP (275m
μ) (manufactured by Columbia Carbon Co., Ltd.).

When two kinds of back coat layers having different average particle sizes are used, they are 10 to 20 mμ.
The content ratio (weight ratio) of the fine particle carbon black of No. 2 and the coarse particle carbon black of 230 to 300 mμ is preferably in the range of former: latter = 98: 2 to 75:25, and more preferably 95: 5 to 85: It is 15. In addition, the content of carbon black (in the case of adding fine particles and coarse particles, the total amount thereof) in the back coat layer is usually 30 to 100 parts by weight of the binder described later.
It is in the range of 80 parts by weight, and preferably in the range of 45 to 65 parts by weight.

Generally, the magnetic tape for recording computer data as in the present invention is strongly required to have repetitive running property as compared with the video tape and the audio tape. In the magnetic tape for recording computer data, the addition of calcium carbonate contributes to the stabilization of the friction coefficient during repeated running, and also does not scrape the sliding guide pole.
The calcium carbonate that can be contained in the back coat layer preferably has an average particle size of 30 to 50 μm. If the average particle size exceeds 50 mμ, the particles repeatedly fall off the surface of the back coat layer due to repeated sliding of the tape, which causes dropout. In addition, the surface of the back coat layer becomes rough, and in the rolled state, it is reflected on the surface of the magnetic layer of the tape, which easily leads to a reduction in output. Further, when the tape is wound and stored in a high temperature and high humidity environment, a reaction with the lubricant contained in the magnetic layer may occur in a state where the back coat layer and the magnetic layer are in contact with each other. On the other hand, when the average particle size is less than 30 mμ, the amount of calcium carbonate present on the surface of the back coat layer is small, and a sufficient effect cannot be achieved. The content of calcium carbonate in the back coat layer is preferably in the range of 10 to 140 parts by weight, and more preferably 35 parts by weight with respect to 100 parts by weight of carbon black.
１００100 parts by weight.

The inorganic powder having a Mohs hardness of 5 to 9 is 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 and calcium carbonate,
Due to the filler effect, the back coat layer is less deteriorated even after repeated sliding and becomes a strong back coat layer. Further, if the inorganic powder used in the back coat layer has a relatively high Mohs hardness of 5 to 9, a proper polishing force is generated and adhesion to the tape guide pole or the like is reduced.
In particular, when used in combination with calcium carbonate, the sliding characteristics with respect to a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer can be stabilized. The inorganic powder having a Mohs hardness of 5 to 9 used in the present invention preferably has an average particle size of 80 to 250 mμ,
More preferably, it is in the range of 100 to 210 mμ.

The inorganic powder having a Mohs hardness of 5 to 9 which can be introduced into the back coat layer is, for example, α-
Iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ )
Can be mentioned. These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the inorganic powder having a Mohs hardness of 5 to 9 is usually 3 to 30 parts by weight with respect to 100 parts by weight of carbon black,
It is preferably 3 to 20 parts by weight. In particular, the back coat layer of the present invention preferably contains the two types of carbon black having different average particle sizes, the calcium carbonate having the above particle size, and the inorganic powder having the specific Mohs hardness.

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

[Binder] The binder constituting the non-magnetic layer, the magnetic layer and the back coat layer of the magnetic tape of the present invention will be described. Examples of the binder that can be used in these layers include thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. Examples of the thermoplastic resin 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, and vinyl. Examples include a polymer or a copolymer containing acetal and vinyl ether as constituent units. 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, butadiene -Acrylonitrile copolymer, styrene-butadiene copolymer, chlorovinyl ether-acrylate copolymer. In addition to the above, polyamide resins, fibrin-based resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, and various rubber-based resins are also used. can do.

Examples of the thermosetting resin or 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.

In the present invention, the binder for the magnetic layer and the non-magnetic layer is a vinyl chloride resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl acetate. -It is preferable that at least one resin selected from a maleic anhydride copolymer and nitrocellulose is combined with a polyurethane resin, or these are further combined with a polyisocyanate. As the polyurethane resin, known resins having a structure such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used.

The above-described binder is used in order to obtain more excellent dispersibility and durability of the obtained layer, if necessary, --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 salt,.), - OH, -NR 2, -N
⁺ R ₃ (R represents a hydrocarbon group), an epoxy group,-
It is preferable to use at least one polar group selected from SH, —CN and the like introduced by copolymerization or an addition reaction. Such a polar group is preferably introduced in an amount of 10 ⁻¹ to 10 ⁻⁸ mol / g (more preferably 10 ⁻² to 10 ⁻⁶ mol / g).

Examples of the above polyisocyanate include tolylene diisocyanate, 4-4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Examples include isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates. .

The above binder is usually used in an amount of 5 parts by weight per 100 parts by weight of the ferromagnetic powder in the magnetic layer or the nonmagnetic powder in the nonmagnetic layer.
It is used in the range of 50 to 50 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, Is preferably used in an amount ranging from 2 to 50% by weight and the polyisocyanate in an amount ranging from 2 to 50% by weight. Further, in the back coat layer, the above binder is usually used in the range of 5 to 100 parts by weight (preferably 10 to 80 parts by weight) based on 100 parts by weight of the non-magnetic powder of the back coat layer.

[Arbitrary Ingredients] In the coating liquid for producing the magnetic layer, the non-magnetic layer and the back coat layer of the magnetic tape of the present invention, magnetic powder, non-magnetic powder or the like is well dispersed in the binder. For this purpose, a dispersant can be added. If necessary, a plasticizer, conductive particles (antistatic agent) other than carbon black, an antifungal agent, etc. may 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 an alkyl or alkenyl group having 11 to 17 carbon atoms),
Metal soaps of the 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 phosphates, lecithin, trialkylpolyolefinoxy quaternary ammonium salts (Alkyl has 1 to 5 carbon atoms, olefins include ethylene and propylene, etc.), sulfate, copper phthalocyanine, and the like. 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 resin.

The magnetic tape of the present invention comprises a non-magnetic layer and a magnetic layer formed on one surface of the support as described above.
Formed using an on-wet coating method,
After drying, a back coat layer is then formed on the other surface of the support according to a usual coating method, and the back coating layer can be dried. Further, in the production of the magnetic tape, a treatment process that is usually performed (for example, random orientation treatment, calender treatment, tape cutting treatment, etc.) is included. The squareness ratio of the magnetic material and the surface properties of the magnetic layer and the back coat layer are adjusted in the manufacturing process. That is, the squareness ratio of the magnetic material is adjusted in the random orientation treatment step after applying the coating liquid for the magnetic layer, and the surface smoothness of the magnetic layer and the back coat layer is adjusted in the calendar treatment step.

The magnetic layer of the magnetic tape of the present invention obtained by the above calendering treatment has a very good surface property, and its surface roughness is measured by the 3D-MIRAU method (three-dimensional method). 2-5 nm (preferably 2-4 n
It is adjusted to the range of m). The surface roughness of the magnetic layer is 2
When the thickness is less than nm, the adhesion becomes too high and the output is improved, but on the contrary, the running property tends to be lowered. On the other hand, when the surface roughness of the magnetic layer exceeds 5 nm, the surface property is not sufficient and the reproduction output is likely to decrease. 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 Ra (center line average roughness with a cutoff of 0.08 mm) Ra of 0.00
It is preferably adjusted to be in the range of 30 to 0.060 μm.

[0053]

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.

[Example 1] [Preparation of coating liquid for forming non-magnetic layer and coating liquid for forming magnetic layer] (Component for forming non-magnetic layer) Non-magnetic powder Titanium oxide TiO ₂ (rutile type) 90 parts TiO _{2 included} Amount: 90% or more Average primary particle diameter: 0.035 μm Specific surface area by BET method: 40 m ² / g pH: 7.0 DBP oil absorption: 27 to 38 g / 100 g Mohs hardness: 6.0 Surface treatment agent (A1 _{20) 3} ) Carbon black (manufactured by Mitsubishi Carbon Co., Ltd.) 10 parts Average primary particle size: 16 mμ DBP oil absorption: 80 ml / 100 g pH: 8.0 Specific surface area by BET method: 250 m ² / g Volatile matter: 1.5% Polarity 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) -SO ₃ Na group 1 × 10 ^-4 mol / g containing polyisocyanates 3 parts (Coronate L, Nippon Polyurethane Industry (Co. )) Butyl stearate 1 part Stearic acid 2 parts Oleic acid 1 part Methyl ethyl ketone 150 parts Cyclohexanone 50 parts

(Component for forming magnetic layer) 100 parts of ferromagnetic metal powder (composition / Fe: Ni = 70: 80 (atomic ratio)) Coercive force (Hc): 2300 Oersted (Oe) Specific surface area by BET method: 57 m ² / G Crystallite size: 180A Saturation magnetization (σs): 141 emu / g Particle size (average major axis diameter): 0.08 μm Needle ratio: 7.5 pH: 9.6 Water-soluble Na: 5 ppm Water-soluble Ca: 10ppm soluble Fe: 10ppm magnetic surface treatment agent (phenylphosphonic acid) 3 parts polar group (-SO ₃ Na group) containing vinyl chloride copolymer 10 parts -SO ₃ Na group content: 5 × 10 ^-6 mol / g, degree of polymerization 350 epoxy group content: in monomer units 3.5 wt% (MR-110, manufactured by Nippon Zeon Co.) polar group (-SO ₃ Na group) containing polyester polyurethane resin 2.5 Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 (weight ratio) -SO ₃ Na group content: 1 × 10 ^-4 mol / g polyisocyanate 2.5 parts (Coronate L, Nippon Polyurethane Industrial Co., Ltd.) α-alumina (particle size: 0.3 μm) 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

The respective components forming the above non-magnetic layer or magnetic layer were kneaded with a continuous kneader and then dispersed using a sand mill. To each of the obtained dispersions, 2.5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to the dispersion of the nonmagnetic layer, and 3 parts to the dispersion of the magnetic layer. Butyl acetate 40 each
Parts were added and filtered using a filter having an average pore size of 1 μm to prepare a non-magnetic layer forming coating liquid and a magnetic layer forming coating liquid, respectively.

[Preparation of coating liquid for forming backcoat layer] (Component for forming backcoat layer) Particulate carbon black powder 100 parts (manufactured by Cabot Corp., BP-800, average particle size: 17 mμ) Coarse particle carbon black powder 10 parts (manufactured by Khan Kalb Co., thermal black, average particle size: 270 mμ) Calcium carbonate 80 parts (manufactured by Shiraishi Industry Co., Ltd., Shiroishi O, average particle size: 40 mμ) α-alumina 5 parts (manufactured by Sumitomo Chemical Co., Ltd.) , HIT55, average particle size: 200 mμ, Mohs hardness: 8.5) Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate resin 40 parts Polyester resin 5 parts Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 Part Toluene 600 parts

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

[Preparation of Magnetic Tape] The obtained non-magnetic layer forming coating solution and magnetic layer forming coating solution were formed on and above the dried non-magnetic layer to a thickness of 1.7 μm. A long aramid support (trade name: Miktron, thickness: 4.4 μm, so that the thickness of the magnetic layer after drying is 0.2 μm).
(Toray Co., Ltd.). 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. Then, it was dried to provide a non-magnetic layer and a magnetic layer. Then, on the other side of the aromatic polyamide support (the side opposite to the magnetic layer),
The thickness after drying the coating solution for forming the back coat layer,
A magnetic film having a non-magnetic layer and a magnetic layer provided on one surface of a support and a back coating layer provided on the other surface of the support. A recording laminate roll was obtained. The obtained magnetic recording laminate roll is a 7-stage calendering machine (temperature: 85 ° C., linear pressure: 300 kg / cm ² ) composed of only metal rolls.
And then calendered, then slit to a 3.8 mm width. The obtained tape (the magnetic tape according to the present invention (Sample 1)) was applied to a DDS cartridge in an amount of 125 m.
A roll-in and data storage device was manufactured. The surface roughness of the obtained back coat layer (cutoff value: 0.
08 mm) was 0.045 μm. In addition, DDS
For samples that could not be rolled into the cartridge for 125 m, they were rolled in as much as possible.

[Example 2] A magnetic tape (Sample 2) according to the present invention was prepared in the same manner as in Example 1 except that the orientation treatment by the solenoid was performed with a magnetic force of 2000 gauss.

[Embodiment 3] The present invention was carried out in the same manner as in Embodiment 1 except that the thickness of the non-magnetic layer was changed to 1.6 μm and the thickness of the magnetic layer was changed to 0.3 μm. A magnetic tape (Sample 3) according to the above was prepared.

[Example 4] A magnetic tape (Sample 4) according to the present invention was prepared in the same manner as in Example 1 except that the calendering temperature was 80 ° C in the calendering machine. Created.

Example 5 A magnetic tape (Sample 5) according to the present invention was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was changed to 0.1 μm.

Comparative Example 1 A magnetic tape for comparison (Sample 6) was prepared in the same manner as in Example 1 except that the thickness of the non-magnetic layer was changed as shown in Table 1 below.
It was created.

Comparative Example 2 A magnetic tape for comparison (Sample 7) was prepared in the same manner as in Example 1 except that polyethylene naphthalate (PEN) was used as the support.

[Comparative Example 3] A magnetic tape for comparison (Sample 8) was prepared in the same manner as in Example 1 except that the orientation treatment by the solenoid was performed with a magnetic force of 500 gauss.

[Comparative Example 4] to [Comparative Example 5] In the same manner as in Example 1, except that the calendering temperature in the calendering machine was 95 ° C. or 75 ° C. in Example 1. Magnetic tapes for comparison (Samples 9 to 10) were prepared.

[Comparative Example 6] to [Comparative Example 7] In the same manner as in Example 1 except that the layer thickness and the total thickness of the non-magnetic layer were changed as shown in Table 1 below. Magnetic tape for comparison (Samples 11-12)
It was created.

[Comparative Example 8] A magnetic tape for comparison (Sample 13) was prepared in the same manner as in Example 1 except that the magnetic material used in the magnetic layer in Example 1 was changed to the following.
It was created. Ferromagnetic metal powder (composition / Fe: Co = 95: 5) Coercive force (Hc): 1800 Oersted (Oe) Specific surface area by BET method: 57 m ² / g Crystallite size: 175 A, Saturation magnetization amount (σs): 130 emu / G Particle size (average major axis diameter): 0.11 μm Needle ratio: 7.5 pH: 9.4 Water-soluble Na: 5 ppm Water-soluble Ca: 10 ppm Water-soluble Fe: 10 ppm

[Comparative Example 9] A magnetic tape for comparison (Sample 14) was prepared in the same manner as in Example 1 except that the magnetic material used in the magnetic layer in Example 1 was changed to the following.
It was created. Ferromagnetic metal powder (composition / Fe: Co = 70: 30) Coercive force (Hc): 2600 Oersted (Oe) Specific surface area by BET method: 57 m ² / g Crystallite size: 150 A Saturation magnetization (σs): 150 emu / g Particle size (average major axis diameter): 0.5 μm Needle ratio: 7.5 pH: 9.4 Water-soluble Na: 5 ppm Water-soluble Ca: 10 ppm Water-soluble Fe: 10 ppm

The squareness ratio of the magnetic material and the surface roughness of the magnetic layer used for preparing the above magnetic tape were measured by the following methods. (Squareness ratio) The saturation magnetic flux density σs was obtained with an oscillating magnetometer in an external magnetic field of 10K Oersted. Further, the magnetic field was removed and the residual magnetic flux density σr was obtained. And squareness ratio (σr / σs)
I asked. (Surface roughness) MIR using WYKO TOPO3D
The center line average surface roughness of an area of about 250 × 250 μm of the magnetic layer was measured by the AU method and used as the surface roughness of the magnetic layer. The characteristics of the various magnetic tapes obtained are summarized in Table 1 below.

[0072]

[Table 1] Table 1 ──────────────────────────────────── Supporting material Characteristics of magnetic material Magnetic layer Thickness Non-magnetic layer Total thickness Magnetic layer surface Material Coercive force (Hc) Squareness ratio (μm) (μm) (μm) Roughness (nm) ────────────────── ────────────────── (Example) 1 PA 2300 0.82 0.2 1.7 6.8 2.5 2 PA 2300 0.85 0.2 1 .7 6.8 2.7 3 7 PA 2300 0.81 0.3 1.6 1.6 6.8 2.6 4 PA 2300 0.82 0.2 1.7 1.7 6.8 3.5 5 PA 2300 0.82 0.1 1.7 6.7 2.8 ──────────────────────────────────── (Comparison Example) 1 PA 2300 0.82 0.7 1.2 6.8 2 5 2 PEN 2300 0.82 0.2 1.7 6.8 2.5 3 3 PA 2300 0.70 0.2 1.7 6.8 2.5 4 PA 2300 0.82 0.2 1.7 6 .8 1.8 5 PA 2300 0.82 0.2 1.7 6.8 5.5 6 PA 2300 0.82 0.2 0.8 0.8 5.7 4.5 7 PA 2300 0.82 0.2 2.8 7.7 2.5 2.5 PA 1800 0.82 0.2 1.7 6.8 2.5 9 PA 2700 0.82 0.2 1.7 6.8 6.8 2.5 ───── ─────────────────────────────── In Table 1, the abbreviations mean the following. PA: Aramid (trade name: Miktron, manufactured by Toray Industries, Inc.) PEN: Polyethylene naphthalate

[Evaluation as Magnetic Tape] The characteristics of each obtained magnetic tape (sample) were evaluated by the following evaluation methods. (1) Measurement of reproduction output 13.5 MHz output Evaluated using a DDS evaluation machine ML4500B manufactured by Media Logic. In addition, the evaluation result is the result of Example 1 as 1
The relative evaluation was set to 00.

(2) Overwriting (overwrite) characteristics Evaluation was performed using a DDS evaluation machine ML4500B manufactured by MediaLogic. 13. After recording at a frequency of 4.5 MHz,
After re-recording at a frequency of 5 MHz, it was defined with an output of 4.5 MHz. In addition, the evaluation result is 0d
B is indicated by relative evaluation.

(3) Running Durability An evaluation of 5000 P (pass) was performed using TM1 defined by the ECMA standard using a DDS2 drive. The evaluation was made based on the number of passes in which a running stop occurred due to an increase in the error rate.

(4) Appropriateness of Cartridge A DDS cartridge with a magnetic tape of 125 m is represented by {circle around (1)}, and a magnetic tape with a length of 125 m is not represented by X. Table 2 shows the evaluation results.

[0077]

[Table 2] Table 2 ──────────────────────────────────── Playback output Over cartridge (dB) light (DB) Proper running durability ───────────────────────────────────────────────────────────────────────────────────────── ■ Example 2 114 0 5000P complete run ■ Example 3 96 0 5000P complete run ■ Example 4 93 0 5000P complete run ■ Example 5 99 0 5000P complete run ■ ───────────────── ─────────────────── Comparative Example 1 77 1 5000P Complete Run ■ Comparative Example 2 76 0 2000P ■ Comparative Example 3 80 0 5000P Complete Run ■ Comparative Example 4 107 0 1000P ■ Comparison Example 5 57 0 5000P complete run ■ Comparative Example 6 76 0 5000P complete run ■ Ratio Comparative Example 7 100 0 5000P Complete Run X Comparative Example 8 71 0 5000P Complete Run ■ Comparative Example 9 100 1 5000P Complete Run ■ ─────────────────────────── ──────────

From the results of Table 2 above, magnetic tapes satisfying the constitution of the present invention (Examples 1 to 5, that is, Samples 1 to 5)
Is particularly excellent in reproduction output, electromagnetic conversion characteristics related to overwrite characteristics, and running durability. Further, by using the magnetic tape according to the present invention, a predetermined amount of tape can be wound in the DDS cartridge, so that a data storage device having a large recording capacity can be manufactured. Also, when an aromatic polyimide was used as the support, excellent performances in reproduction output, overwrite characteristics, and running durability were obtained in the same manner as above.

On the other hand, as seen in Comparative Example 1 (Sample 6), when the thickness of the magnetic layer is made thicker than the range specified in the present invention, the output characteristics are lowered and the overwrite characteristics are likely to be lowered. When polyethylene naphthalate is used as the support, as in Comparative Example 2 (Sample 7), the running durability tends to decrease with the decrease in output, probably because sufficient strength cannot be obtained. When the alignment treatment is not properly performed as in Comparative Example 3 (Sample 8),
The squareness ratio of the magnetic material does not exceed a certain value and sufficient output cannot be achieved. Further, as seen in Comparative Example 4 (Sample 9) and Comparative Example 5 (Sample 10), when the magnetic layer does not have an appropriate surface property, it is easy to lead to a decrease in output and a decrease in running durability. . Further, when the thickness of the non-magnetic layer is extremely thin (Comparative Example 6, Sample 11), sufficient output cannot be obtained. Further, in the case of a magnetic tape having a large total thickness of 7.7 μm (Comparative Example 7, Sample 12),
A predetermined amount of tape cannot be wound in the cartridge, and a sufficient recording capacity cannot be obtained. Furthermore, as in Comparative Example 8 (Sample 13) and Comparative Example 9 (Sample 14),
When a magnetic material having a coercive force outside the fixed range is used, the output tends to decrease and the overwrite characteristic tends to deteriorate.

[0080]

In the magnetic tape for computer data recording of the present invention, the magnetic layer is formed extremely thin (in particular, the magnetic layer and the non-magnetic layer are formed by the so-called wet-on-wet method). ), High density recording is possible, and since the total thickness is thin, a product with high recording capacity can be provided. In addition, by using a support with a relatively high rigidity regardless of such a very thin tape, the magnetic material in the magnetic layer is composed of a material with a specific coercive force, and the surface of the magnetic layer is kept constant. By adjusting so as to have smoothness, it is possible to provide an extremely high-performance magnetic tape for recording computer data, which has never existed before.

Claims (7)

[Claims] 1. A substantially non-magnetic thickness of 1.0 to 10 consisting mainly of a non-magnetic powder and a binder is provided on one side of a long support made of aromatic polyamide or aromatic polyimide.
2.0 μm non-magnetic layer and coercive force of 1900 to 2600
Oersteds with a squareness ratio of 0.78 or more, mainly composed of ferromagnetic powder and binder, thickness of 0.05 to 0.5 μm
And a magnetic layer having a surface roughness of 2 to 5 nm in this order, and a back coat layer on the other side of the elongated support, for recording computer data having a total thickness of 7.0 μm or less. Magnetic tape. 2. The magnetic tape according to claim 1, wherein the magnetic layer is provided while the non-magnetic layer is in a wet state. 3. The magnetic tape according to claim 1, wherein the aromatic polyamide is aramid. 4. The surface roughness of the magnetic layer is 2.0 to 4.0 n.
2. The magnetic tape according to claim 1, wherein m is in the range of m. 5. The backcoat layer has a thickness of 0.2 to 0.
2. The magnetic tape according to claim 1, which is in the range of 8 [mu] m. 6. The magnetic tape according to claim 1, wherein the back coat layer contains carbon black. 7. The magnetic tape according to claim 1, wherein the back coat layer contains carbon black, and further contains calcium carbonate and an inorganic powder having a Mohs hardness of 5-9.