JPH10302244A - Magnetic disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disc which satisfies the requirements of a high capacity and high density magnetic disc system and can realize a high density recording of 0.2-2 Gbit/inch<2> when, particularly, it is applied to a contact recording system which is expected to have high density electromagnetic conversion characteristics while the problem of running durability is avoided. SOLUTION: A magnetic disc consists of a supporter and a magnetic layer which is mainly composed of ferromagnetic powder and binder resin and formed on the supporter. The magnetic disc enables the recording with a surface recording density of 0.2-2 Gbit/inch<2> and the recording/reproduction with a revolution of higher than 1800 rpm. The magnetic layer has an average surface roughness Ra of less than 4 nm in a central surface measured by a 3D-MIRAU and 100-1000 pieces/900 μm<2> of protrusions of higher than 20 nm and 1-50 pieces/900 μm<2> of protrusions higher than 40 nm which are measured by an atomic force microscope. Further, the magnetic layer contains at least one of fatty acid and fatty acid ester and the peak intensity ratio of carbon/iron measured on the magnetic layer surface by an Auger electron spectroscopy is 10-100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic disk having a high recording density. In particular, the present invention relates to a magnetic disk for high-density recording having a magnetic layer and a substantially non-magnetic lower layer, and including a ferromagnetic metal fine powder in the uppermost layer.

[0002]

2. Description of the Related Art In the field of magnetic disks, 2 MB MF-2HD floppy disks using Co-modified iron oxide have been standardly mounted on personal computers. However, in today's rapidly increasing data capacity, the capacity cannot be said to be sufficient, and it is desired to increase the capacity of a floppy disk.
High-capacity and high-density recording such as 100M to 120M such as IP is realized, and the surface recording density is 0.2 Gbit / inch.
There is a demand for more than ^two high density recordings. Further, the demand for shortening the access time tends to increase the rotation speed of the disk.

[0003] In such a high-density, high-speed rotating magnetic disk system, higher running properties and durability than conventional media are required in order to maintain stable recording and reproduction. Hereinafter, prior arts proposed to mainly improve the recording density and running durability of a coating type magnetic recording medium will be described.

For example, Japanese Patent Application Laid-Open No. 6-52541 discloses a magnetic tape in which the average protrusion height of the abrasive on the surface of the magnetic layer is set to 15 nm or less. There is a statement that both durability and compatibility are achieved. Japanese Patent Application Laid-Open No. Hei 6-12651 discloses Ra of a magnetic layer.
Are 15 nm or less and 30 nm or more protrusions are 125,000.
A magnetic disk having a magnetic layer distributed from 0 to 250,000 pcs / mm ² and showing the amount of lubricant in the magnetic layer is disclosed.

Japanese Patent Application Laid-Open No. 6-309650 discloses that a lubricant is contained in an amount of 8 to 30 parts by weight based on 100 parts by weight of magnetic powder, and the number of protrusions higher than the highest protrusion of the magnetic layer by 20 nm is higher.
400 to 2,500 Ke / mm ² and the magnetic recording medium, i.e., by identifying the density of the protrusions of a certain height of the amount of lubricant and the magnetic layer surface of the magnetic layer, magnetism order to ensure running stability A recording medium, in particular, a magnetic disk is disclosed.

Incidentally, a dynamic loading method has been adopted in the ZIP method in order to reduce the impact on the magnetic layer surface even when the magnetic head hits the magnetic layer surface.
Although this method is basically a non-contact method, contact between the magnetic head and the magnetic layer cannot be avoided, and it has become difficult to ensure running durability at higher speeds. occured.

On the other hand, in order to obtain higher electromagnetic conversion characteristics, a so-called contact recording system in which a magnetic head contacts the surface of a magnetic layer is desirable. On the other hand, in order to realize high-density recording, the magnetic layer surface is required to have even higher smoothness, and the center line average surface roughness Ra by 3D-MIRAU method is required to be 5 nm or less.

If a contact type magnetic head system is to be adopted for such a smooth magnetic layer surface, the starting torque at the time of so-called contact start, especially when starting from a stationary state in contact with the magnetic layer surface, becomes excessive. There is a problem that defects easily occur. That is, the conventional magnetic disk medium design technology has a limit in dealing with the above problem.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to meet the demand for a high-capacity, high-density magnetic disk system in the future digital recording era.
In particular, an object of the present invention is to provide a magnetic disk capable of realizing high-density recording as high as 0.2 to ² Gbit / inch ² without a problem of running durability when applied to a contact recording system expected to have high electromagnetic conversion characteristics. I have to.

[0010]

The present invention has the following arrangement. (1) In a magnetic disk having a magnetic layer mainly composed of a ferromagnetic powder and a binder resin on a support, the magnetic disk has a surface recording density of 0.2 to ² Gbit / inch ² and is recorded at 1800 rpm or more. The magnetic layer has a center plane average surface roughness Ra of 3 nm or less according to the 3D-MIRAU method, and the magnetic layer has a protrusion of 20 nm or more measured by an AFM (atomic force microscope). 100 to 1000 heights / 900 μm ² , 40 nm
Those having the above height are 1 to 50 pieces / 900 μm ² ,
The magnetic layer contains at least one of a fatty acid and a fatty acid ester, and has a carbon / iron peak intensity ratio (C / Fe) of 10 to 100 when the surface of the magnetic layer is measured by Auger electron spectroscopy. A magnetic disk, characterized in that: (2) The magnetic disk according to (1), wherein the magnetic disk is used for a recording / reproducing system that uses a contact recording method with respect to a contact of a magnetic head. (3) The magnetic disk according to (1) or (2), wherein the thickness of the magnetic layer is 0.01 to 0.25 μm and the coercive force is 1800 to 4000 Oe. (4) The magnetic disk according to any one of (1) to (3), further including a substantially non-magnetic underlayer between the support and the magnetic layer.

The present inventor has been developing a high-capacity floppy disk exceeding the ZIP currently being implemented. Turned out to need a big difference. In the present invention, in particular, the height of the protrusions on the surface of the magnetic layer is reduced, and the density of the protrusions is significantly smaller than that of the conventional magnetic disk. By doing so, the above object can be achieved by preventing the sticking or the like from occurring not only in the dynamic loading method but also in the contact type magnetic head.

In particular, when the support is a flexible support,
The contact between the magnetic layer and the magnetic head tends to become unstable, and a considerable margin is required for the running durability of the magnetic layer. In the present invention, both the running durability and the electromagnetic conversion characteristics of the magnetic disk can be achieved irrespective of the magnetic head, the recording / reproducing method, and the head material used for recording / reproducing the magnetic disk.

In the present invention, in order to control the protrusions on the surface of the magnetic layer, a granular component contained in the magnetic layer, ie,
It is important to reduce the particle size of ferromagnetic powders, abrasives, carbon black, etc. from the conventional ones, and to maintain a high degree of dispersion on top of that, and to reduce the surface roughness of the support It is important to make it smaller.

In particular, the ferromagnetic powder, which is the main composition of the magnetic layer, usually has a major axis length of less than 0.2 μm, preferably 0.15 μm or less, more preferably 0.10 μm or less, and a crystallite size of Usually, it is in the range of 80-380 °, preferably 100-250 °. Further, even in the case of an abrasive which has been selected to have a relatively large particle size from the viewpoint of polishing performance, the lower limit is set to 0.25 μm or less, preferably 0.20 μm or less, more preferably 0.15 μm or less, and
It is effective to select the average particle diameter of 5 μm or more and increase the hardness of the ferromagnetic powder by an amount corresponding to the decrease in the polishing ability by the abrasive. The abrasive is used in an amount of usually 1 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the ferromagnetic powder. The average particle size of carbon black is usually 1
The range is from 0 to 300 nm, preferably from 30 to 200 nm.

The amount of the binder resin (including the curing agent) contained in the magnetic layer is preferably 5 to 50 parts by weight, more preferably 10 to 30 parts by weight based on 100 parts by weight of the ferromagnetic powder. It is. In order to obtain a high-capacity, high-density magnetic disk, it is particularly important to reduce the thickness of the magnetic layer to 0.30 μm or less, preferably 0.01 to 0.25 μm, from the viewpoint of demagnetization loss. In this case, the surface shape of the magnetic layer of the present invention is easily affected by the surface protrusions of the support, so it is particularly necessary to pay attention to the surface shape. Specifically, it is effective that the support has a center surface average surface roughness Ra of usually 8 nm or less, preferably 4 nm or less, as determined by the 3D-MIRAU method. Further, the lower limit of Ra of the support is preferably about 1 nm from the viewpoint of handling, running durability and the like.

In the present invention, the means for adjusting the protrusions of the magnetic layer should not be limited to those described above. Can be used, but there is also an advantage that the above-mentioned projection distribution can be obtained without intentionally performing these processes. According to the present invention, 100 to 1000 protrusions having a height of 20 nm or more are formed on a surface of a magnetic layer in a 30 μm square (900 μm ² ) by AFM.
Preferably 100 to 500, more preferably 150 to
400 protrusions are measured (hereinafter, the number of protrusions having a height of 20 nm or more is also referred to as “N _{20 nm} ”), and the number of protrusions having a height of 40 nm or more (hereinafter, “N
_{40 nm} ) is 1 to 50, preferably 1 to 30
And more preferably 5 to 20.

If the number of N _{20 nm} is less than 100, the running durability and the starting torque are not improved, and if it exceeds 1,000, the error rate is not improved. If the number of N _{40 nm} is less than 1, the running durability and the starting torque are not improved, and if it exceeds 50, the error rate is not improved. In the present invention,
The magnetic layer contains at least one of a fatty acid and a fatty acid ester (hereinafter, also referred to as “lubricant according to the present invention”). When the magnetic layer surface is measured by Auger electron spectroscopy, C / Fe is 10 to 100. It is necessary to become. In a conventional magnetic disk, C / Fe is much larger than 100, but in a high-capacity magnetic disk such as the present invention, since the C / Fe falls within the above range, the lubricant according to the present invention inside the magnetic layer gradually decreases. It can leach onto the surface and contribute to improving running durability.

The carbon peak when the surface of the magnetic layer is measured by Auger electron spectroscopy is derived from an organic compound in the magnetic layer. The organic compound in the composition of the magnetic layer is mainly a binder resin and a lubricant, but the carbon peak intensity is
Actually, it was experimentally confirmed that it was derived from a lubricant. Usually, the binder resin is cured with a curing agent to form a molecular network. However, since the lubricant has a much lower molecular weight than such a binder resin, it easily moves within the magnetic layer and is particularly magnetic. It is thought that it easily leaches out on the layer surface and can be measured by Auger electron spectroscopy.

In the present invention, the means for keeping C / Fe in the above-mentioned range includes not only selecting the amount of the lubricant according to the present invention but also appropriately selecting the composition of the magnetic layer. Especially,
It is considered that the reason why the C / Fe of the present invention can be controlled even if the compounding amount is not reduced as compared with the conventional case is due to the interaction between the magnetic layer composition and the lubricant according to the present invention.

In the present invention, it is preferable to provide a substantially non-magnetic underlayer between the magnetic layer and the support. The substantially non-magnetic underlayer means that it may have a magnetic property to the extent that it does not participate in recording, and is hereinafter simply referred to as a lower layer or a nonmagnetic layer. The magnetic layer provided with the lower layer is also referred to as an upper layer. Therefore, the lubricant according to the present invention is more preferably contained not only in the magnetic layer but also in the lower layer.

The amount of the fatty acid used is 0.1 part by weight or more, preferably 0.5 part by weight or more, for 100 parts by weight of the upper layer ferromagnetic powder in the upper layer (including the case of a single magnetic layer).
More preferably, it is at least 1 part by weight, and in the lower layer, it is at least 0.1 part by weight, preferably at least 0.5 part by weight, more preferably at least 1 part by weight, based on 100 parts by weight of the powder. It is preferable to add both. The upper limit of each layer is 10%. If the amount is too large, the surface of the magnetic layer becomes rough and the magnetic properties deteriorate, and if it is too small, the durability becomes poor.

The amount of the fatty acid ester used in the upper layer is 3 parts by weight or more based on 100 parts by weight of the upper layer ferromagnetic powder.
It is preferably at least 5 parts by weight, more preferably at least 10 parts by weight, and in the lower layer, at least 3 parts by weight, preferably at least 5 parts by weight, more preferably at least 10 parts by weight, per 100 parts by weight of the powder. It is preferable to add both the upper layer and the lower layer. The upper limit of each layer is 20%. If the amount is too large, the surface of the magnetic layer becomes rough and the magnetic properties deteriorate, and if it is too small, the durability becomes poor.

The structure of the lubricant according to the present invention is not particularly limited and may be appropriately selected and used. Examples of preferred fatty acids include those having 1 carbon atom.
0 to 24 may include monobasic fatty acids which may contain an unsaturated bond or may be branched. Examples include capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, isostearic acid, and fatty acid components of the following fatty acid esters.

The fatty acid ester used in the present invention
Although it is not particularly limited,
Or monoester is preferable, and as the diester,
A compound represented by the following general formula (1) is preferred.
No. R₁-COO-R_Two-OCO-R_Three ... (1) (where R_TwoIs-(CH_Two) N -or this-(CH
_Two) Unsaturation derived from n- (n is an integer of 1 to 12)
Represents a divalent group which may contain a bond, or
[CH_TwoCH (CH_Three)]-, R₁, R_ThreeIs carbon
A chain saturated or unsaturated hydrocarbon group of numbers 12 to 30
May be the same or different. ) The chain of the chain hydrocarbon group
The shape may be linear or branched.₁And R _Three
Are preferably linearly unsaturated, in which case R₁
And R_ThreeThose having the same structure are particularly preferable. Change
The unsaturated bond may be any of a double bond and a triple bond.
Although it does not matter, a double bond is preferable, provided that it is at least one each.
Good, two or three. The double bond is cis or
You can use either transformer.

Each of R ₁ and R ₃ has 12 to 3 carbon atoms.
0, preferably 14 to 26, more preferably 14 to 2
0. If the number of carbon atoms is less than 12, the volatility is high, so that it is volatilized from the surface of the magnetic layer during traveling, and the traveling stops. If the number of carbon atoms is larger than 30, the mobility of the molecules will be low, so that the lubricant will not easily leach out to the surface of the magnetic layer, and the durability will be poor.

R ₂ is preferably a straight-chain dihydric alcohol residue having OH at both terminals, and n is preferably 4 to 12. n
If the value is too small, the durability against repeated running is poor. If the value is too large, the viscosity becomes high, which makes it difficult to use and the durability becomes poor. The compound represented by the general formula (1) of the present invention is HO-
It is a diester of a diol represented by R ₂ —OH and an unsaturated fatty acid represented by R ₁ —COOH and R ₃ —COOH.

The unsaturated fatty acids include 4-dodecenoic acid, 5-dodecenoic acid, 11-dodecenoic acid, cis-9-
Tridecenoic acid, myristoleic acid, 5-myristoleic acid, 6-pentadecenoic acid, 7-palmitoleic acid, ci
s-9-palmitoleic acid, 7-heptadecenoic acid, oleic acid, ellagic acid, cis-6-octadecenoic acid, t
ran-11-octadecenoic acid, cis-11-eicosenoic acid, cis-13-docosenoic acid, 15-tetracosenoic acid, 17-hexacosenic acid, cis-9, cis-
12-octadienoic acid, trans-9, trans-
12-octadienoic acid, cis-9, trans-1
1, trans-13-octadecatrienoic acid, cis
Linear unsaturated fatty acids such as -9, cis-12, cis-15-octadecatrienoic acid and stearolic acid, 5-methyl-2-tridecenoic acid, 2-methyl-9-octadecenoic acid, 2-methyl-2 -Branched unsaturated fatty acids such as eicosenoic acid and 2,2-dimethyl-11-eicosenoic acid.

Examples of the diol include ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentanediol, 1,8-octanediol, Linear saturated both-terminal diols such as 1,9-nonanediol and 1,10-decanediol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 2,4-pentanediol, 2,2- Dimethyl-
1,3-propanediol, 2,5-hexanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,6-hexanediol, 1-methyl-1,7-
Branched saturated diols such as pentanediol, 2,6-dimethyl-1,7-pentanediol, 1-methyl-1,8-nonanediol, 2-butene-1,4-diol,
2,4-hexadiene-1,6-dienediol, 3-
Linear unsaturated diols such as pentene-1,7-diol, 2-methyl-2-butene-1,4-diol,
2,3-dimethyl-2-butene-1,4-diol,
Examples include branched unsaturated diols such as 2,6-dimethyl-3-hexene-1,6-diol.

Among these, particularly preferred compounds of the present invention are esters of linear unsaturated fatty acids. Specifically, myristoleic acid, 5-myristoleic acid, 7-palmitoleic acid, cis-9-palmitoleic acid, oleic acid, elaidic acid, cis-6-octadecenoic acid (petroceric acid), trans-6-octadecenoic acid (Petrosaelaidic acid), trans-11-octadecenoic acid (basenic acid), cis-11-eicosenoic acid, ci
s-13-docosenoic acid (erucic acid), cis-9, ci
Linear unsaturated fatty acids such as s-12-octadienoic acid (linoleic acid) and ethylene glycol, diethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, Esters of 7-pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and the like are preferred, and more preferably the linear unsaturated fatty acid and ethylene glycol, 1,4-butane Diol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-
Esters with decanediol and the like. Specific examples include neopentyl glycol didecanoate, ethylene glycol dioleyl, and diesters described below. Examples of diesters are as follows.

(1) -1 C ₁₇ H ₃₅ COO (CH ₂ ) ₄ OCOC ₁₇ H ₃₅ (1) -2 C ₁₁ H ₂₁ COO (CH ₂ ) ₄ OCOC ₁₁ H ₂₁ (1) -3 C ₁₇ H _{33 COO (CH 2) 2 OCOC 17} H 33 (1) -4 C 11 H 23 COO (CH 2) 4 OCOC 11 H 23 (1) -5 C 27 H 53 COO (CH 2) 4 OCOC 27 H 53 (1 _{) -6 C 11 H 21 COO (} CH 2) 4 OCOC 17 H 33 (1) -7 C 17 H 33 COO (CH 2) 11 OCOC 17 H 33 (1) -8 C 17 H 33 COOCH 2 CH = CHCH mono used for _{2 OCOC 17 H 33 (1)} -9 C 14 H 27 COOCH 2 CH = CHCH 2 OCOC 14 H 27 (1) -10 C 17 H 33 COO (CH 2) 8 OCOC 14 H 27 the present invention Preferred examples of the ester lubricant include those represented by the following general formulas (2) and (3). And the like. R ₄ —COO— (R ₅ —O) m—R ₆ (2) R ₇ —COO—R ₈ (3) (wherein m is an integer of 1 to 10, and R ₅ is — (CH ₂ ) n −
Or-(CH ₂ ) n-(n is an integer of 1 to 10)
And a divalent group which may contain an unsaturated bond derived from R ₁ and R 2, wherein R ₄ and R ₇ are linear or unsaturated hydrocarbon groups having 12 to 26 carbon atoms, which may be the same or different from each other.
R ₆ and R ₈ are linear or branched, saturated or unsaturated hydrocarbon groups having 1 to 26 carbon atoms, which may be the same or different. ) Also, a monobasic fatty acid having 10 to 24 carbon atoms (which may contain an unsaturated bond or may be branched) and a monovalent alcohol having 2 to 24 carbon atoms (including an unsaturated bond, Which may be branched).

Specific examples thereof include butyl stearate, octyl stearate, amyl stearate, isooctyl stearate, butyl myristate, octyl myristate, butoxyethyl stearate, butoxydiethyl stearate, 2-ethylhexyl stearate, Preferred are 2-octyldodecyl palmitate, 2-hexyldodecyl palmitate, isohexadecyl stearate, oleyl oleate, dodecyl stearate, tridecyl stearate, oleyl erucate and the like.

In addition, monoesters of saturated and unsaturated fatty acids and alcohols and fatty acid monoesters having an unsaturated bond, as well known in Japanese Patent Publication No. 51-39081, and Japanese Patent Publication No. 4-4917 are known. Oleyl oleate described in Japanese Patent Application Laid-Open Publication No. H11-209, etc. can also be used. Specific examples of the monoester are as follows. _{(2) -1 C 17 H 35} COOCH 2 CH 2 OC 4 H 9 (2) -2 C 17 H 35 COO (CH 2 CH 2 O) 2 C 4
H ₉ (3) -1 C ₁₇ H ₃₅ COOC ₁₇ H ₃₅ (3) -2 C ₁₇ H ₃₅ COOC ₄ H ₉ The abundance of the lubricant according to the present invention on the magnetic layer surface can be determined by Auger electron spectroscopy. C / Fe can be used as an index. The basis is that when the magnetic disk of the present invention is subjected to hexane treatment and the surface of the magnetic layer is measured by Auger electron spectroscopy except for the lubricant according to the present invention, the Fe peak is strong, but the C peak contributed by the binder is weak, Conversely, if the hexane treatment is not performed, the C peak is strong. That is,
Auger spectroscopic analysis of the magnetic layer surface reveals a peak of iron atoms derived from a magnetic substance and a peak of carbon derived from a binder and a lubricant, but most of the carbon peaks may be regarded as being derived from the lubricant according to the present invention. Because you can.

In the present invention, the measurement of C / Fe by Auger electron spectroscopy indicates a value determined as follows. Under the above conditions, Kinetic Energy range from 130 to 730eV is 3
The intensity of the KLL peak of carbon and the LMM peak of iron are obtained in the differential form, and the ratio of C / Fe is obtained.

In the present invention, the areal recording density is obtained by multiplying the linear recording density by the track density. The linear recording density is the number of bits of a signal recorded per inch in the recording direction. Track density is the number of tracks per inch. These linear recording density, track density, and areal recording density are values determined by the system.

In the field of personal computers, which are becoming increasingly multi-media, a large-capacity recording medium replacing the conventional floppy disk has begun to attract attention, and a ZIP disk (area recording density: 96 Mbit / in) from IOMEGA (Iomega), USA
ch ² ). This is an ATOMM (Advanced Super Thin) developed by the present applicant.
Layer & High Output Meta
l Media Technology) type, and 3.
A 7-inch product with a recording capacity of 100 MB is on sale. The capacity of 100 to 120 MB is almost the same as MO (3.5 inches), and 7 to 8 for one newspaper article.
It fits in for a month. The transfer rate indicating the writing / reading time of data (information) is 2 MB or more per second, which is comparable to that of a hard disk.
It is twice as fast as MO and has a very great advantage.
Further, this recording medium having a lower layer and a thin magnetic layer can be mass-produced with the same coating type medium as the current FD.
It has the advantage of being lower in price than O and hard disks.

The present inventors have conducted intensive studies based on the knowledge of such media, and as a result, have found that the ZIP disk and MO
Thus, a magnetic disk having a recording capacity much larger than (3.5 inches) and a surface recording density of 0.2 to ² Gbit / inch ² was obtained. The present invention preferably includes a magnetic layer having an ultra-thin layer containing a high-output, high-dispersion ultra-fine ferromagnetic metal powder having excellent dispersibility, a lower layer containing an inorganic powder having a spherical or acicular shape, and the magnetic layer being thin. Thus, the magnetic force canceling in the magnetic layer is reduced, the output in the high frequency region is greatly increased, and the overwriting characteristics are also improved.

By improving the magnetic head, the effect of the ultra-thin magnetic layer can be further exhibited in combination with the narrow gap head, and the digital recording characteristics can be improved. The thickness of the magnetic layer is a thin layer that matches the magnetic recording method for high-density recording and the performance required from the magnetic head. Such ultra-thin magnetic layer, which is uniform and thin, has a high level of filling by dispersing finely divided magnetic powder and non-magnetic powder with a combination of a dispersant and a binder with high dispersibility. Was completed. The magnetic material used is a ferromagnetic metal powder that is very fine particles and can achieve high output in order to maximize the suitability of large capacity and high output. Those containing Y can be used. 180
In order to realize a high transfer rate of 0 rpm or more, preferably 2400 rpm or more (upper limit is about 7200 rpm), a three-dimensional network binder system suitable for an ultra-thin magnetic layer is used to improve running stability and durability during high-speed rotation. Can be secured. In addition, a lubricant that can maintain its effectiveness even when used under a wide range of temperature and humidity conditions or when used at high speeds is placed in the upper and lower layers, and the lower layer has a role as a lubricant tank. Thus, it is possible to always supply an appropriate amount of lubricant to the upper magnetic layer, thereby improving the durability and reliability of the upper magnetic layer. Further, the cushion effect of the lower layer can provide good head touch and stable running performance.

The merits of the ATOMM configuration are considered as follows. (1) Improvement of electromagnetic conversion characteristics by thinning the magnetic layer a) Improvement of output in a high frequency region by improvement of recording demagnetization characteristics b) Improvement of overwrite characteristics (c) Ensuring window margin (2) ) High output by smoothing the upper magnetic layer (3) Easily imparting required functions by separating the functions of the magnetic layer (4) Improving durability by stable supply of lubricant These functions are simply to make the magnetic layer multilayer Cannot be achieved. In order to form a multilayer structure, a lower layer and an upper layer are applied, and a surface treatment such as a curing treatment and a calendar treatment is usually performed. The FD differs from the magnetic tape in that the same processing is performed on both sides. After the coating process, it is completed as a final product through a slitting process, a punching process, a shell assembling process, and a certifying process. If necessary, after punching in a disk shape, a burnishing process is performed with a polishing tape to perform thermoprocessing (usually 50 to 90 ° C.) at a high temperature to accelerate the hardening of the coating layer, thereby shaving surface projections. Such post-processing may be performed.

Durability is an important factor for magnetic disks. As means for improving the durability of the medium, there are a binder formulation for increasing the film strength of the disk itself and a means for adjusting a lubricant formulation for maintaining the slipperiness with the magnetic head.
The lubricant according to the present invention uses a combination of a plurality of lubricants that exhibit excellent effects under various temperature and humidity environments used, and has a wide range of temperatures (low temperature, room temperature, high temperature),
Even in a humid (low humidity, high humidity) environment, each lubricant exerts its function and can maintain a totally stable lubrication effect.

Also, by utilizing the structure of the upper and lower two layers and providing the lower layer with a lubricant tank effect, an appropriate amount of lubricant is always supplied to the magnetic layer, and the durability of the magnetic layer can be improved. The lower layer can have a function of controlling surface electric resistance in addition to the function of holding the lubricant. Generally, for controlling the electric resistance, a solid conductive material such as carbon black is often added to the magnetic layer. These not only limit the packing density of the magnetic material but also affect the surface roughness as the magnetic layer becomes thinner. These disadvantages can be eliminated by adding a conductive material to the lower layer.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION

[Magnetic Layer] In the magnetic disk of the present invention, the lower layer and the ultrathin magnetic layer may be provided on only one side or both sides of the support. After applying the lower layer, the upper and lower layers are in a wet state (W / W),
After drying (W / D), the upper magnetic layer can be provided. From the viewpoint of production yield, simultaneous or sequential wet coating is preferable, but in the case of a disc, coating after drying can be used sufficiently. Simultaneous or sequential wet coating (W /
In (W), since the upper layer and the lower layer can be formed simultaneously, a surface treatment step such as a calendering step can be effectively used, and the surface roughness of the upper magnetic layer can be improved even with an ultrathin layer. The coercive force Hc of the magnetic layer is preferably 1800 Oe or more, and Bm is 2000 to 2000.
Preferably, it is 5000G.

[Ferromagnetic Powder] The ferromagnetic powder used in the magnetic layer of the present invention is not particularly limited, but is preferably a ferromagnetic metal powder containing α-Fe as a main component. These ferromagnetic powders include Al, S
i, S, Sc, Ca, Ti, V, Cr, Cu, Y, M
o, Rh, Pd, Ag, Sn, Sb, Te, Ba, T
a, W, Re, Au, Hg, Pb, Bi, La, Ce,
It may contain atoms such as Pr, Nd, P, Co, Mn, Zn, Ni, Sr, and B. In particular, Al, Si, C
It is preferable that at least one of a, Y, Ba, La, Nd, Co, Ni, and B be contained in addition to α-Fe.
More preferably, it contains at least one of Y and Al. The content of Co is preferably from 0 atomic% to 40 atomic% with respect to Fe, more preferably from 15 atomic% to 3 atomic%.
It is at most 5%, more preferably at least 20 at% and at most 35 at%. The content of Y is preferably from 1.5 to 12 at%, more preferably from 3 to 10 at%, and still more preferably from 4 to 9 at%. Al is preferably at least 5 at.% And at most 30 at.%, More preferably at least 11 at.% And at most 20 at.%, More preferably at least 12 at.% And at most 18 at.

These ferromagnetic powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent, and the like before dispersion 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
No., JP-B-47-4286, JP-B-47-12422
No., JP-B-47-17284, JP-B-47-1850
No. 9, JP-B-47-18573, JP-B-39-103
07, Japanese Patent Publication No. 46-39639, U.S. Pat.
No. 6215, No. 3031341, No. 3100194
Nos. 3,242,005 and 3,389,014.

The ferromagnetic metal fine powder may contain a small amount of hydroxide or oxide. A ferromagnetic metal fine powder obtained by a known production method can be used, and the following method can be used. A method of reducing a complex organic acid salt (mainly 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, Thermal decomposition method, reduction method by adding reducing agent such as sodium borohydride, hypophosphite or hydrazine to aqueous solution of ferromagnetic metal, reduction of fine powder by evaporating metal in low pressure inert gas And how to get it. The ferromagnetic metal powder thus obtained is subjected to a known slow oxidation treatment, that is, a method of immersing in an organic solvent and then drying,
A method of immersing in an organic solvent, sending an oxygen-containing gas to form an oxide film on the surface, and then drying, and 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 Any of these can be used.

The coercive force of the ferromagnetic powder is 1700 Oe or more and 35
It is preferably not more than 00 Oe, more preferably not less than 1,800 Oe and not more than 3000 Oe. The water content of the ferromagnetic powder is 0.0
It is preferable to set it to 1 to 2%. It is preferable to optimize the water content of the ferromagnetic powder depending on the type of the binder. Preferably, the pH of the ferromagnetic powder is optimized by the combination with the binder used. Its range is from 4 to 12, preferably from 6 to 10. The ferromagnetic powder can be made of Al,
Surface treatment may be performed with Si, P, or an oxide thereof. The amount is 0.1 to 10 with respect to the ferromagnetic powder.
%, And surface treatment is preferable, because the adsorption of a lubricant such as a fatty acid becomes 100 mg / m ² or less. The ferromagnetic powder may contain inorganic ions such as soluble Na, Ca, Fe, Ni, and Sr. It is preferable that these are essentially absent, but if they are 200 ppm or less, there is little influence on the characteristics. The ferromagnetic powder used in the present invention preferably has a small number of vacancies, and the value is preferably 20% by volume or less, more preferably 5% by volume or less. The shape may be any of a needle shape, a rice grain shape, and a spindle shape as long as the characteristics of the particle size described above are satisfied. The SFD of the ferromagnetic powder itself is preferably small, and is preferably 0.8 or less. It is necessary to reduce the distribution of Hc in the ferromagnetic powder. When the SFD is 0.8 or less, the electromagnetic conversion characteristics are good, the output is high, and the magnetization reversal is sharp and the peak shift is small, which is suitable for high-density digital magnetic recording. In order to reduce the distribution of Hc, there are methods of improving the particle size distribution of goethite in the ferromagnetic metal powder and preventing sintering.

Hexagonal ferrite can be mentioned as a ferromagnetic powder usable in the magnetic layer of the present invention. Hereinafter, this will be described. Examples of hexagonal ferrite include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and Co-substitutes. Specifically, magnetoplumbite-type barium ferrite and strontium ferrite, magnetoplumbite-type ferrite whose particle surface is coated with spinel,
Furthermore, magnetoplumbite-type barium ferrite and strontium ferrite containing a part of spinel phase are mentioned.
Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd,
Ag, Sn, Sb, Te, Ba, Ta, W, Re, A
u, Hg, Pb, Bi, La, Ce, Pr, Nd, P,
It may contain atoms such as Co, Mn, Zn, Ni, Sr, B, Ge, and Nb. Generally, Co-Zn, Co
-Ti, Co-Ti-Zr, Co-Ti-Zn, Ni-
Ti-Zn, Nb-Zn-Co, Sb-Zn-Co, N
A substance to which an element such as b-Zn is added can be used. Some raw materials and production methods contain specific impurities.

The particle size is 10 to 200 nm in hexagonal plate diameter,
It is preferably from 10 to 100 nm, particularly preferably from 10 to 100 nm.
８０80 nm. Especially when reproducing with a magnetoresistive head to increase the track density, it is necessary to reduce noise.
The plate diameter is preferably 40 nm or less, but if it is 10 nm or less, stable magnetization cannot be expected due to thermal fluctuation. Above 200 nm, noise is high and none of them are suitable for high-density magnetic recording. The plate ratio (plate diameter / plate thickness) is desirably 1 to 15. Preferably 1
~ 7. When the plate ratio is small, the filling property in the magnetic layer is increased, which is preferable, but sufficient orientation cannot be obtained. If it is larger than 15, noise increases due to stacking between particles. The specific surface area of this particle size range by the BET method is 1
0 to 200 m ² / g. The specific surface area generally corresponds to an arithmetic calculation value from the particle plate diameter and the plate thickness. The distribution of particle plate diameter and plate thickness is generally preferably as narrow as possible. Although it is difficult to make a numerical value, it can be compared by randomly measuring 500 particles from a particle TEM photograph. The distribution is often not a normal distribution, but when calculated and expressed as a standard deviation with respect to the average size, σ / average size = 0.1 to 2.0. In order to sharpen the particle size distribution, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improving treatment. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known. Coercive force H measured on magnetic material
c can be created up to about 500 Oe to 5000 Oe. A higher Hc is advantageous for high-density recording, but is limited by the capability of the recording head. In the present invention, Hc is from 1700 Oe to 400
It is about 0 Oe, preferably 1800 Oe or more and 350
It is 0 Oe or less. When the saturation magnetization of the head exceeds 1.4 Tesler, it is preferable that the saturation magnetization be 2000 Oe or more.
Hc can be controlled by particle size (plate diameter / plate thickness), kind and amount of contained element, substitution site of element, particle generation reaction condition and the like. The saturation magnetization as is 40 emu / g to 80 emu / g. The higher the value of σs, the better, but the smaller the fine particles, the lower the tendency. It is well known to combine spinel ferrite with magnetoplumbite ferrite to improve σs, and to select the type of element contained and the amount to be added. It is also possible to use W-type hexagonal ferrite. When dispersing the magnetic material, the surface of the magnetic material particles is also treated with a substance suitable for the dispersion medium and the polymer. As the surface treatment material, an inorganic compound or an organic compound is used. Typical examples of the main compound include oxides or hydroxides of Si, Al, P, etc., various silane coupling agents, and various titanium coupling agents. The amount is 0.1 to 10% based on the magnetic material. The pH of the magnetic material is also important for dispersion. Usually, the optimum value is about 4 to 12 depending on the dispersion medium and the polymer, but about 6 to 11 is selected from the chemical stability and storage stability of the medium. Water contained in the magnetic material also affects dispersion. There is an optimum value depending on the dispersion medium and the polymer, but usually 0.01 to 2.0% is selected. Hexagonal ferrite is produced by mixing barium oxide, iron oxide, and a metal oxide that replaces iron with boron oxide as a glass-forming substance to obtain the desired ferrite composition, then melting, quenching, and then quenching the amorphous. A glass crystallization method in which a barium ferrite crystal powder is obtained by washing, pulverizing and then barium ferrite crystal powder after reheating. A hydrothermal reaction method in which a barium ferrite composition metal salt solution is neutralized with an alkali to remove by-products, heated in a liquid phase at 100 ° C. or higher, washed, dried, and pulverized to obtain barium ferrite crystal powder. The barium ferrite composition metal salt solution is neutralized with an alkali, and after removing by-products, dried, treated at 1100 ° C. or lower, and pulverized to obtain a barium ferrite crystal powder. We do not choose manufacturing method.

[Non-Magnetic Layer] Next, the details of the lower layer when the lower non-magnetic layer is provided between the support and the magnetic layer will be described in detail. The configuration of the lower layer of the present invention should not be limited as long as it is substantially non-magnetic.
At least made of resin, preferably powder, for example,
Examples thereof include those in which an inorganic powder or an organic powder is dispersed in resin. The inorganic powder is usually preferably a non-magnetic powder, but a magnetic powder can also be used as long as the lower layer is substantially non-magnetic.

The non-magnetic powder can be selected from, for example, inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides and metal sulfides. Examples of the inorganic compound include α having an α conversion of 90% or more.
-Alumina, β-alumina, γ-alumina, θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, hematite, goethite, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, oxide Tin, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide and the like are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide, and barium sulfate because of a small particle size distribution and many means for imparting functions.
More preferred are titanium dioxide and α-iron oxide. The particle size of these non-magnetic powders is preferably from 0.005 to 2 μm, but if necessary, non-magnetic powders having different particle sizes may be combined, or even a single non-magnetic powder may have the same effect by widening the particle size distribution. You can also. Particularly preferably, the particle size of the nonmagnetic powder is 0.01 μm to 0.1 μm.
2 μm. In particular, when the nonmagnetic powder is a granular metal oxide, the average particle diameter is preferably 0.08 μm or less, and when the nonmagnetic powder is a needle-like metal oxide, the major axis length is preferably 0.3 μm or less, and 0.2 μm or less. Is more preferred. Tap density is 0.05-2g / ml, preferably 0.2-1.5g / ml
It is. The water content of the non-magnetic powder is 0.1 to 5% by weight, preferably 0.2 to 3% by weight, more preferably 0.3 to 1.
5% by weight. The pH of the non-magnetic powder is from 2 to 11, and the pH is particularly preferably from 5.5 to 10. The nonmagnetic powder has a specific surface area of 1 to 100 m ² / g, preferably 5 to 80 m ² / g.
m ² / g, more preferably from 10 to 70 m ² / g. The crystallite size of the nonmagnetic powder is preferably from 0.004 μm to 1 μm, more preferably from 0.04 μm to 0.1 μm. DB
Oil absorption using P (dibutyl phthalate) is 5 to 100
ml / 100 g, preferably 10-80 ml / 100 g, more preferably 20-60 ml / 100 g. The specific gravity is 1 to 12, preferably 3 to 6. The shape may be any of a needle shape, a spherical shape, a polyhedral shape, and a plate shape. The Mohs' hardness is preferably 4 or more and 10 or less. The nonmagnetic powder has an SA (stearic acid) adsorption amount of 1 to 20 μmol / m ² , preferably ^{2 to} 15 μmol / m ² .
m ² , more preferably 3 to 8 μmol / m ² . pH 3
It is preferably between 6 and 6. Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ ,
It is preferable to perform surface treatment with SnO ₂ , Sb ₂ O ₃ , ZnO, and Y ₂ O ₃ . Al ₂ O is particularly preferable for dispersibility.
₃ , SiO ₂ , TiO ₂ and ZrO ₂ , more preferably Al ₂ O ₃ , SiO ₂ and ZrO ₂ . These may be used in combination or may be used alone. Further, a co-precipitated surface treatment layer may be used according to the purpose, or a method of first treating with alumina and then treating the surface layer with silica, or vice versa, may be employed. Although the surface treatment layer may be a porous layer depending on the purpose, it is generally preferable that the surface treatment layer be homogeneous and dense.

Specific examples of the non-magnetic powder used in the lower layer of the present invention include Nanotite manufactured by Showa Denko, HIT-100, ZA-G1 manufactured by Sumitomo Chemical Co., Ltd., α-hematite DPN-250, DPN-250BX manufactured by Toda Kogyo , DPN-24
5, DPN-270BX, DPN-500BX, DBN
-SA1, DBN-SA3, titanium oxide TT manufactured by Ishihara Sangyo
O-51B, TTO-55A, TTO-55B, TTO
-55C, TTO-55S, TTO-55D, SN-1
00, α hematite E270, E271, E300, E
303, titanium industrial titanium oxide STT-4D, STT
-30D, STT-30, STT-65C, α hematite α-40, MT-100S, MT-100 manufactured by Teika
T, MT-150W, MT-500B, MT-600
B, MT-100F, MT-500HD, FI made by Sakai Chemical
NEX-25, BF-1, BF-10, BF-20, S
TM, Dowa Mining DEFIC-Y, DEFIC-R,
AS2BM and TiO2P25 manufactured by Nippon Aerosil, 100A and 500A manufactured by Ube Industries, and baked products thereof. Particularly preferred non-magnetic powders are titanium dioxide and α
-Iron oxide.

By mixing carbon black in the lower layer, it is possible to lower the surface electric resistance Rs, which is a known effect, to reduce the light transmittance, and to obtain a desired micro Vickers hardness. In addition, it is possible to bring about the effect of storing the lubricant by including carbon black in the lower layer. As the type of carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black, and the like can be used. The following characteristics of the carbon black in the lower layer should be optimized depending on the desired effect, and the combined effect may provide more effects.

The specific surface area of the lower carbon black is 10
0 to 500 m ² / g, preferably 150 to 400 m ² / g,
DBP oil absorption is 20-400ml / 100g, preferably 30
~ 400ml / 100g. The particle size of the carbon black is 5 μm to 80 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm. Carbon black p
H is preferably 2 to 10, the water content is preferably 0.1 to 10%, and the tap density is preferably 0.1 to 1 g / ml. Specific examples of the carbon black used in the present invention include B.C.
LACKPEARLS 2000, 1300, 100
0,900,800,880,700, VULCAN
XC-72, manufactured by Mitsubishi Kasei Kogyo Co., Ltd. # 3050B, # 31
50B, # 3250B, # 3750B, # 3950B,
# 950, # 650B, # 970B, # 850B, MA
-600, MA-230, # 4000, # 4010, CONDUCTEX SC manufactured by Columbian Carbon Co., Ltd.
Raven 8800,8000,7000,575
0,5250,3500,2100,2000,180
0, 1500, 1255, 1250, and Ketjen Black EC manufactured by Akzo Corporation. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used in which a part of the surface is graphitized. Further, the carbon black may be dispersed in a binder before adding it to the paint. These carbon blacks do not exceed 50% by weight with respect to the inorganic powder, and account for 40% of the total weight of the nonmagnetic layer.
Can be used within a range not exceeding. These carbon blacks can be used alone or in combination. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

In the lower layer, an organic powder is used according to the purpose.
It can also be added. For example, acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigments, but also polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, and polyfluoroethylene resin Can be used. The manufacturing method is disclosed in
No. 18,564, and those described in JP-A-60-255827 can be used.

For the lower layer binder resin, lubricant, dispersant, additive, solvent, dispersion method, etc., those of the magnetic layer described below can be applied. In particular, binder resin amount, type, additives,
Known techniques for the magnetic layer can be applied to the amount and type of the dispersant. [Binder] As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used.

The thermoplastic resin usually has a glass transition temperature of -100 to 150 ° C. and a number average molecular weight of 1,000.
~ 200,000, preferably 10,000-100,
000 and a degree of polymerization of about 50 to 1,000.
Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylate, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene,
There are polymers or copolymers containing ethylene, vinyl butyral, vinyl acetal, vinyl ether, and the like as constituent units, polyurethane resins, and various rubber resins. Further, as the thermosetting resin or the reactive resin, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, polyester resin And a mixture of a polyester polyol and a polyisocyanate, a mixture of a polyurethane and a polyisocyanate, and the like. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. In addition, a known electron beam-curable resin can be used for each layer. These examples and the production method thereof are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but preferred are vinyl chloride resins, vinyl chloride vinyl acetate copolymers, vinyl chloride vinyl acetate vinyl alcohol copolymers, and vinyl chloride vinyl acetate maleic anhydride copolymers. And a combination of at least one of the above and a polyurethane resin, or a combination of these with a polyisocyanate.

As the structure of the polyurethane resin, known materials such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders shown here, -COO is required to obtain better dispersibility and durability.
_{M, -SO 3 M, -OSO 3} M, -P = O (OM) 2,
-OP = O (OM) ₂ , where M is a hydrogen atom,
Or an alkali metal base), OH, NR ₂ , N ⁺ R
Preferably, at least one polar group selected from ₃ (R is a hydrocarbon group), an epoxy group, SH, CN, or the like is introduced by a copolymerization or addition reaction.
The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g,
Preferably it is 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAGH and VY manufactured by Union Carbide.
HH, VMCH, VAGF, VAGD, VROH, VY
ES, VYNC, VMCC, XYHL, XYSG, PK
HH, PKHJ, PKHC, PKFE, manufactured by Nissin Chemical Co., Ltd., MPR-TA, MPR-TA5, MPR-TAL,
MPR-TSN, MPR-TMF, MPR-TS, MP
R-TM, MPR-TAO, 1000W manufactured by Denki Kagaku,
DX80, DX81, DX82, DX83, 100F
D, ZEON Corporation MR-104, MR-105, MR
110, MR100, MR555, 400X-110
A, Nipporan N2301, N2 manufactured by Nippon Polyurethanes
302, N2304, Pandex T manufactured by Dainippon Ink and Chemicals, Inc.
-5105, T-R3080, T-5201, Burnock D-400, D-210-80, Crisbon 610
9,7209, Toyobo Byron UR8200, UR
8300, UR-8700, UR-5500, RV53
0, RV280, manufactured by Dainichi Seika, Diferamine 402
0, 5020, 5100, 5300, 9020, 902
2, 7020, Mitsubishi Kasei Co., Ltd., MX5004, Sanyo Kasei Co., Ltd. Samprene SP-150, Asahi Kasei Co., Ltd. Saran F31
0, F210 and the like.

The binder used in the nonmagnetic layer and the magnetic layer of the present invention is used in an amount of 5 to 50% by weight, preferably 10 to 30% by weight, based on the nonmagnetic powder or the ferromagnetic powder. 5 to 30% by weight when using a vinyl chloride resin, 2 to 20% by weight when using a polyurethane resin,
The polyisocyanate is preferably used in combination in the range of 2 to 20% by weight. For example, when head corrosion occurs due to a slight amount of dechlorination, it is also possible to use only polyurethane or only polyurethane and isocyanate. . In the present invention, when polyurethane is used, the glass transition temperature is -50 to 150C, preferably 0C to 100C, and more preferably 30C to 95C.
° C, breaking elongation is 100-2000%, breaking stress is 0.0
Preferably, the yield point is 5 to 10 kg / mm ² and the yield point is 0.05 to 10 kg / mm ² .

The ATOMM type magnetic disk of the present invention has two or more layers. In the present invention, even when the lower layer is not provided, the magnetic layer may be provided with a plurality of layers containing magnetic powders having different functions. Therefore, the amount of the binder, the amount of the vinyl chloride resin, the polyurethane resin, the polyisocyanate or the other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of the polar group, or the resin described above. Of course, it is possible to change the physical characteristics of the non-magnetic layer and the magnetic layer as necessary, and rather it should be optimized in each layer,
Known techniques for the multilayer magnetic layer can be applied. For example, when changing the amount of binder in each layer, it is effective to increase the amount of binder in the magnetic layer in order to reduce scratches on the surface of the magnetic layer. Can be made flexible by increasing the amount of binder.

The polyisocyanates used in the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Use of isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates can do. Commercially available trade names of these isocyanates include Nippon Polyurethane Co., Ltd., Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate M
R, Millionate MTL, Takeda Yakuhin, Takenate D
-102, Takenate D-110N, Takenate D-2
00, Takenate D-202, manufactured by Sumitomo Bayer Co., Ltd., Desmodur L, Desmodur IL, Desmodur N, Desmodur HL, etc. These are used alone or in combination of two or more using the difference in curing reactivity. Each layer can be used in combination.

[Abrasive] As the abrasive used in the present invention, α-alumina, β-alumina having an α conversion of 90% or more,
Silicon carbide, chromium oxide, cerium oxide, α-iron oxide,
Known materials having a Mohs hardness of 6 or more, such as corundum, artificial diamond, silicon nitride, silicon carbide titanium carbide, titanium oxide, silicon dioxide, and boron nitride, are used alone or in combination. In addition, a composite of these abrasives (abrasives surface-treated with other abrasives)
May be used. These abrasives may contain compounds or elements other than the main component, but the main component is 90%.
If it is above, the effect is not changed.

The particle size of these abrasives is as described above, and in particular, the particle size distribution is preferably narrow in order to enhance the electromagnetic conversion characteristics. Further, in order to improve the durability, it is possible to combine abrasives having different particle sizes as needed, or to achieve the same effect by widening the particle size distribution even with a single abrasive. Tap density is 0.3-2
g / cc, water content is preferably 0.1 to 5%, pH is 2 to 11, and specific surface area is preferably 1 to 30 m ² / g. The shape of the abrasive used in the present invention may be any of a needle shape, a spherical shape, and a dice shape, but a shape having a part of a corner is preferable because of high abrasiveness.

Specifically, AKP-12, A manufactured by Sumitomo Chemical Co., Ltd.
KP-15, AKP-20, AKP-30, AKP-5
0, HIT20, HIT-30, HIT-55, HIT
60, HIT70, HIT80, HIT100, manufactured by Reynolds, ERC-DBM, HP-DBM, HPS-D
BM, manufactured by Fujimi Abrasives, WA10000, manufactured by Uemura Kogyo Co., Ltd., UB20, manufactured by Nippon Kagaku Kogyo Co., Ltd., G-5, Chromex U2, Chromex U1, Toda Kogyo Co., Ltd., TF10
0, TF140, manufactured by Ibiden Co., Ltd., Beta Random Ultra Fine, manufactured by Showa Mining Co., Ltd., and B-3.
These abrasives can be added to the nonmagnetic layer as needed. By adding to the non-magnetic layer, the surface shape can be controlled, and the projected state of the abrasive can be controlled.
The particle size and amount of the abrasive added to the magnetic layer and the non-magnetic layer should of course be set to optimal values.

[Carbon Black] As the carbon black used in the magnetic layer of the present invention, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. The specific surface area is 5 to 500 m ² / g,
The DBP oil absorption is 10 to 400 ml / 100 g, the particle diameter is 2 to 10 and the water content is 0.1 to 10 as described above.
%, And the tap density is preferably 0.1 to 1 g / cc. Specific examples of carbon black used in the present invention include BLACKPEARLS 2000, manufactured by Cabot Corporation.
1300, 1000, 900, 905, 800, 70
0, VULCAN XC-72, manufactured by Asahi Carbon Co., # 8
0, # 60, # 55, # 50, # 35, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., # 2400B, # 2300, # 900, # 100
0, # 30, # 40, # 10B, manufactured by Columbian Carbon Co., Ltd., CONDUCTEX SC, RAVEN 15
0, 50, 40, 15, RAVEN-MT-P, Japan E
C Company, Ketjen Black EC, and the like.
Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used in which a part of the surface is graphitized. Before adding the carbon black to the magnetic paint, the carbon black may be dispersed in a binder in advance. These carbon blacks can be used alone or in combination. When carbon black is used, the amount of 0.1 to the ferromagnetic powder is used.
To 30% by weight, preferably 0.5 to 10% by weight. Carbon black has functions such as antistaticity of the magnetic layer, reduction of friction coefficient, provision of light-shielding properties, and improvement of film strength, and these differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are different in type, amount, and combination in the magnetic layer and the non-magnetic layer, and are based on the above-mentioned properties such as particle size, oil absorption, conductivity, and pH. Of course, it is possible to use them properly according to the purpose, and rather, it should be optimized in each layer. The carbon black that can be used in the magnetic layer of the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

[Additives] As additives used in the magnetic layer and the nonmagnetic layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like are used. Molybdenum disulfide, tungsten disulfide, graphite, boron nitride, graphite fluoride, silicone oil, silicone with polar groups, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester,
Polyolefin, polyglycol, alkyl phosphate and its alkali metal salt, alkyl sulfate and its alkali metal salt, polyphenyl ether, phenyl phosphonic acid, α-naphthyl phosphoric acid, phenyl phosphoric acid, diphenyl phosphoric acid, p-ethylbenzene phosphonic acid, phenyl phosphinic acid , Aminoquinones, various silane coupling agents, titanium coupling agents, fluorine-containing alkyl sulfates and alkali metal salts thereof, having 10 to 24 carbon atoms
Metal salts (Li, Na, K, Cu) of monobasic fatty acids (which may contain unsaturated bonds or may be branched)
Or monovalent, divalent, trivalent, having 12 to 22 carbon atoms,
Tetrahydric, pentahydric, hexahydric alcohol (which may contain an unsaturated bond or may be branched), having 12 to 2 carbon atoms
2, alkoxy alcohols, fatty acid amides having 8 to 22 carbon atoms, aliphatic amines having 8 to 22 carbon atoms, and the like can be used in combination with the lubricant according to the present invention.

Specific examples of the alcohol include oleyl alcohol, stearyl alcohol, lauryl alcohol and the like. Also, nonionic surfactants such as alkylene oxides, glycerin, glycidol, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium or sulfoniums, etc. A cationic surfactant,
Carboxylic acids, sulfonic acids, phosphoric acids, sulfate groups, phosphate groups, anionic surfactants containing acidic groups such as amino acids, aminosulfonic acids, sulfuric acid or phosphate esters of amino alcohols, alkylbedine type,
And the like can also be used. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents and the like are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, by-products, decomposition products, oxides, etc. in addition to the main components. These impurities are 30
% Or less, more preferably 10% or less.

Each of these lubricants and surfactants used in the present invention has a different physical action.
The type, amount, and combination ratio of the lubricant that produces a synergistic effect should be optimally determined according to the purpose.
To control bleeding to the surface by using fatty acids with different melting points in the non-magnetic layer and magnetic layer, to control bleeding to the surface by using esters with different boiling points, melting points and polarities, and to adjust the amount of surfactant It can be considered to improve the stability of coating and to improve the lubricating effect by increasing the amount of the lubricant added in the intermediate layer, and it is needless to say that the present invention is not limited to the examples shown here. Generally, the total amount of the lubricant is from 0.1% to 50%, preferably from 2% to 2%, based on the magnetic or non-magnetic powder.
It is selected in the range of 5%.

All or a part of the additives used in the present invention may be added at any step in the production of magnetic and non-magnetic paints. There are a case where it is added in a kneading step using a body, a binder and a solvent, a case where it is added in a dispersion step, a case where it is added after dispersion, and a case where it is added just before coating. In some cases, the purpose may be achieved by applying a part or all of the additive simultaneously or sequentially after applying the magnetic layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering or after the slit is completed.

As the organic solvent used in the present invention, known solvents can be used, and for example, solvents described in JP-A-6-68453 can be used. [Layer Structure] The thickness structure of the magnetic disk of the present invention is such that the support is 30 to 100 μm, preferably 45 to 80 μm. When the magnetic layer is provided alone, the thickness of the magnetic layer is preferably 0.05 to 0.25 μm, more preferably 0.05 to 0.20 μm.

An undercoat layer for improving adhesion may be provided between the support and the nonmagnetic layer or the magnetic layer. The thickness of the undercoat layer is 0.01 to 0.5 μm, preferably 0.02 to
0.5 μm. When a magnetic layer is provided only on one side, a back coat layer may be provided on the side opposite to the magnetic layer side in order to obtain effects such as antistatic and curl correction.
This thickness is 0.1 to 4 μm, preferably 0.3 to 2.0
μm. Known undercoat layers and backcoat layers can be used.

The thickness of the magnetic layer of the medium of the present invention is optimized by the saturation magnetization of the head used, the head gap length, and the band of the recording signal. The magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration relating to a multilayer magnetic layer can be applied. The thickness of the nonmagnetic layer, which is the lower layer of the medium according to the present invention, is usually 0.2 μm or more.
0 μm or less, preferably 0.3 μm or more and 3.0 μm or less,
More preferably, it is 1.0 μm or more and 2.5 μm or less.
The lower layer of the medium of the present invention exerts its effect as long as it is substantially a non-magnetic layer. Needless to say, the configuration can be regarded as substantially the same as that of the present invention. Substantially a nonmagnetic layer means that the lower layer has a residual magnetic flux density of 300 G or less or a coercive force of 300 Oe or less, and preferably has no residual magnetic flux density and coercive force.

[Support] The support used in the present invention includes:
Although not particularly limited, a substantially non-magnetic and flexible material is preferable. Examples of the flexible support used in the present invention include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, polyaramid, aromatic polyamide, and polyamid. Known films such as benzoxazole can be used.
It is preferable to use a high-strength support such as polyethylene naphthalate and polyamide in addition to polyethylene terephthalate. If necessary, a laminated type support as disclosed in JP-A-3-224127 can be used to change the surface roughness of the magnetic surface and the base surface. These supports have a corona discharge treatment, a plasma treatment,
Easy adhesion treatment, heat treatment, dust removal treatment, and the like may be performed. In addition, an aluminum or glass substrate can be used as the support of the present invention.

In order to achieve the object of the present invention, the support has a center plane average surface roughness of not more than 8.0 nm, preferably not more than 4.0 nm, more preferably not more than 2.0 nm as measured by the 3D-MIRAU method. You need to use something. It is preferable that these supports not only have a small center plane average surface roughness but also have no coarse protrusions of 0.5 μm or more.
The surface roughness shape can be freely controlled by the size and amount of the filler added to the support as needed. Examples of these fillers include C
Examples include oxides and carbonates such as a, Si, and Ti, and organic fine powders such as an acrylic resin. Maximum support height SR
max is 1 μm or less, ten-point average roughness SRz is 0.5 μm or less,
Center plane peak height SRp is 0.5 μm or less, center plane valley depth S
Rv is 0.5 μm or less, center plane area ratio SSr is 10% or more and 90% or less, average wavelength Sλa is 5 μm or more and 300 μm or less.
m or less is preferable. In order to obtain the desired electromagnetic conversion characteristics and durability, the surface projection distribution of these supports can be arbitrarily controlled by a filler. Each of the particles having a size of 0.01 μm to 1 μm is reduced from 0 particles per 0.1 mm ^2. It can be controlled in the range of 2000.

The F-5 value of the support used in the present invention is preferably 5 to 50 kg / mm ² ,
The heat shrinkage at 0 minute is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0.5% or less.
Breaking strength is 5-100 kg / mm ² , elastic modulus is 100-20
00 kg / mm ² is preferred. The coefficient of thermal expansion is 10 ^-4 to 10
⁻⁸ / ° C., preferably 10 ⁻⁵ to 10 ⁻⁶ / ° C.
The coefficient of humidity expansion is 10 ⁻⁴ / RH% or less, preferably 10
^-5 / RH% or less. These thermal characteristics, dimensional characteristics and mechanical strength characteristics are preferably substantially equal to each other in the in-plane direction of the support with a difference of 10% or less.

[Production Method] The step of producing the magnetic and non-magnetic paints of the magnetic disk of the present invention comprises at least a kneading step, a dispersing step, and a mixing step provided before and after these steps as necessary. Each step may be divided into two or more steps. All raw materials such as ferromagnetic metal fine powder, non-magnetic powder, binder, carbon black, abrasive, antistatic agent, lubricant, and solvent used in the present invention may be added at the beginning or during any step. . Further, individual raw materials may be added in two or more steps in a divided manner. For example, kneading polyurethane,
In the dispersion step and the mixing step for adjusting the viscosity after dispersion, the mixture may be added separately. In order to achieve the object of the present invention,
Conventionally known manufacturing techniques can be used as some of the steps. In the kneading step, it is preferable to use one having a strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, and an extruder. When a kneader is used, all or a part of the magnetic substance or the non-magnetic powder and the binder (however, preferably 30% or more of the total binder) and the magnetic substance 1
The kneading treatment is performed in the range of 15 to 500 parts with respect to 00 parts.
The details of these kneading processes are described in JP-A-1-1063.
38, JP-A-1-79274. Also,
Glass beads can be used to disperse the magnetic layer liquid and the non-magnetic layer liquid, but zirconia beads, titania beads, and steel beads, which are high-density dispersion media, are preferable. The particle size and the filling rate of these dispersion media are optimized and used. A well-known disperser can be used.

When applying a magnetic disk having a multilayer structure in the present invention, it is preferable to use the following method. First, a lower layer is first applied by a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used in the application of a magnetic paint. Showa 60-238
179, a method of applying an upper layer using a support-pressing-type extrusion coating apparatus disclosed in JP-A-2-265672. Second, JP-A-63-88080 and JP-A-2-
No. 17971, Japanese Patent Application Laid-Open No. 2-265672 discloses a method in which upper and lower layers are coated almost simultaneously by one coating head having two built-in coating liquid passage slits. A third method is to apply the upper and lower layers almost simultaneously using an extrusion coating apparatus with a backup roll disclosed in Japanese Patent Application Laid-Open No. 2-174965. Incidentally, in order to prevent a decrease in the electromagnetic conversion characteristics and the like of the magnetic disk due to the aggregation of the magnetic particles, JP-A-62-95174 and JP-A-1-236968 have been proposed.
It is desirable to apply shear to the coating liquid inside the coating head by a method as disclosed in US Pat. Further, the viscosity of the coating liquid must satisfy the numerical range disclosed in JP-A-3-8471. In order to realize the configuration of the present invention, after applying and drying the lower layer, it does not matter whether or not to use the sequential multilayer coating for providing the magnetic layer thereon,
The effect of the present invention is not lost. However, in order to reduce coating defects and improve quality such as dropout, it is preferable to use the above-described simultaneous multilayer coating.

In the magnetic disk of the present invention, a sufficient isotropic orientation can be obtained even without orientation, without using an orientation device. It is preferable to use a known random alignment device such as applying a voltage. Generally, in-plane two-dimensional random is preferable as the isotropic orientation, but three-dimensional random may be provided with a vertical component. In addition, isotropic magnetic characteristics can be imparted in the circumferential direction by using a known method such as a different polarity opposed magnet and making the magnets vertically oriented.
In particular, when performing high-density recording, vertical alignment is preferable. In addition, circumferential orientation may be performed using spin coating.

The orientation is preferably controlled so that the drying position of the coating film can be controlled by controlling the temperature, amount of air, and coating speed of the drying air. The temperature is preferably 60 ° C. or higher, and a suitable preliminary drying can be performed before entering the magnet zone. The calendering roll is treated with a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide or a metal roll. Particularly when a double-sided magnetic layer is formed, the treatment is preferably performed with the metal rolls.
The processing temperature is preferably at least 50 ° C, more preferably at least 100 ° C. The linear pressure is preferably 200 kg / cm
It is more preferably at least 300 kg / cm.

[Physical Properties] The distribution of the coercive force of the magnetic layer of the magnetic disk according to the present invention is preferably narrow, and the SFD and SFDr are preferably 0.6 or less. The squareness ratio is 0.55 or more and 0.67 or less in the case of two-dimensional random, preferably 0.58 or more and 0.64 or less. In the case of three-dimensional random, it is preferably 0.45 or more and 0.55 or less. The orientation is 0.6 or more, preferably 0.7 or more in the vertical direction, and 0.7 or more, preferably 0.8 or more when demagnetizing field correction is performed. The orientation ratio is preferably 0.8 or more for both two-dimensional random and three-dimensional random. In the case of two-dimensional randomness, it is preferable that the squareness ratio in the vertical direction, Br, Hc, and Hr be within 0.1 to 0.5 times the in-plane direction.

The surface resistivity of the magnetic disk of the present invention is preferably 10 ⁴ to 10 ¹² ohm / sq, and the charged potential is −
The voltage is preferably within a range from 500 V to +500 V. 0.5 of magnetic layer
The elastic modulus at% elongation is preferably 100 to 2 in each direction in the plane.
000Kg / mm ² , breaking strength is preferably 10-70Kg / mm
^2. The elastic modulus of the magnetic disk is preferably 1 in each in-plane direction.
00 to 1500 kg / mm ² , preferably 0.5
%, And the heat shrinkage at any temperature of 100 ° C. or less is preferably 1% or less, more preferably 0.5% or less, and most preferably 0.1% or less. The glass transition temperature of the magnetic layer (the maximum point of the loss elastic modulus in the dynamic viscoelasticity measurement measured at 110 Hz) is preferably 50 ° C or more and 120 ° C or less,
The temperature of the lower nonmagnetic layer is preferably from 0 ° C to 100 ° C. The loss modulus is preferably in the range of 1 × 10 ⁸ to 8 × 10 ⁹ dyne / cm ² , and the loss tangent is preferably 0.2 or less. If the loss tangent is too large, adhesion failure is likely to occur. It is preferable that these thermal characteristics and mechanical characteristics are substantially equal within 10% in each direction in the plane of the medium. The residual solvent contained in the magnetic layer is preferably at most 100 mg / m ² , more preferably at most 10 mg / m ² . The porosity of the coating layer is preferably 30% by volume or less, more preferably 20% by volume or less, for both the nonmagnetic lower layer and the magnetic layer. The porosity is preferably small in order to achieve high output, but it may be better to secure a certain value depending on the purpose. In the present invention, the higher the porosity, the better the running durability in many cases.

The magnetic layer has a center plane average surface roughness Ra measured by the 3D-MIRAU method of 4 nm or less, preferably 3.8 nm.
The thickness is more preferably 3.5 nm or less. here,
The 3D-MIRAU method is TOPO-3 manufactured by WYCO.
Approximately 250 μm × MIRAU method using the surface roughness meter of D
It refers to a method of measuring with an area of 250 μm. The maximum height SRmax of the magnetic layer is 0.5 μm or less, the ten-point average roughness SRz is 0.3 μm or less, the center plane height SRp is 0.3 μm or less,
Center plane valley depth SRv is 0.3 μm or less, center plane area ratio SS
r is preferably 20% or more and 80% or less, and the average wavelength Sλa is preferably 5 μm or more and 300 μm or less. The surface protrusions of the magnetic layer have a size of 0.01 μm to 1 μm.
It is possible to set arbitrarily in the range of zero, and it is preferable to optimize the electromagnetic conversion characteristics and the friction coefficient. These can be easily controlled by controlling the surface properties by the filler of the support, the particle size and amount of the powder added to the magnetic layer, the roll surface shape of the calendering treatment, and the like. The curl is preferably within ± 3 mm.

When the magnetic disk of the present invention has a nonmagnetic layer and a magnetic layer, it is easily presumed that the physical properties of the nonmagnetic layer and the magnetic layer can be changed according to the purpose. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the nonmagnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic disk with the head.

[0083]

Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. (Example 1) <Preparation of paint> Magnetic paint ML-1 (using needle-shaped magnetic powder) 100 parts of ferromagnetic metal fine powder Composition: 90% Fe, 10% Co (atomic ratio) Hc1920 Oe, specific surface area 55 m ² / g, σs 120 emu / g Crystallite size 17 nm, major axis length 0.1 μm Vinyl chloride copolymer 10 parts MR110 (manufactured by Zeon Corporation) Polyurethane resin 4 parts UR5500 (manufactured by Toyobo) α-alumina: HIT55 (manufactured by Sumitomo Chemical) 20 parts Particles Size 0.2 μm Carbon black: # 50 (produced by Asahi Carbon Co., Ltd.) 3 parts Average primary particle diameter 0.09 μm Specific surface area 28 m ² / g DBP oil absorption 61 ml / 100 g pH 7.5 Volatile content 1.0% Phenylphosphonic acid 3 parts Ethylene glycol dioleil 10 parts Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Non-magnetic paint U-1 (spherical inorganic powder used) the non-magnetic powder TiO ₂ crystal system rutile 100 parts Average primary particle diameter 0.035 .mu.m, specific surface area 40m _² / g pH 7 TiO ² content of 90% or more measured by BET method DBP oil absorption 27 ３８38 g / 100 g Surface treatment agent Al ₂ O ₃ (8% by weight) Carbon black Ketjen Black EC (manufactured by EC Japan) 10 parts Average primary particle diameter 0.03 μm Specific surface area 900 m ² / g DBP oil absorption 61 ml / 100 g pH 7 0.5 Volatile content 1.0% Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 16 parts Polyurethane resin UR8300 (manufactured by Toyobo Co., Ltd.) 6 parts Phenylphosphonic acid 4 parts Ethylene glycol-dioldiole 15 parts Oleic acid 1.2 parts Stearin Acid 1.2 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts For, respectively, the respective components D - were were kneaded by Da, it is dispersed using a sand mill. In the obtained dispersion, polyisocyanate was added to the coating liquid for the non-magnetic layer.
Add 3 parts, 5 parts to the coating solution for the magnetic layer, further add 40 parts of cyclohexanone, and filter using a filter having an average pore size of 1 μm, to form a coating solution for forming a non-magnetic layer and a magnetic layer. Was prepared respectively.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.25 μm thereon. In this method, two layers are simultaneously coated on a polyethylene terephthalate support having a center plane average surface roughness of 5 nm. After passing through the apparatus and performing random orientation treatment and drying, it is treated at a temperature of 90 ° C. and a linear pressure of 300 Kg / cm with a seven-stage calender. And a 3.7-inch cartridge with a liner installed inside (US Io)
The cartridge was placed in a Zip-disk cartridge (manufactured by Mega Inc.), and predetermined mechanical components were added to obtain a 3.7-inch floppy disk. Also, after punching into 3.5 inches, thermo-processing
(70 ° C for 24 hours) and 3.5 with liner installed inside
A 3.5-inch floppy disk was obtained by putting into a 2 inch 2HD cartridge and adding predetermined mechanical components.

The magnetic properties, surface roughness, error rate, durability, and starting torque of the obtained sample were measured. Example 2 In Example 1, 5 parts of carbon black # 50 was added to the magnetic paint. Example 3 In Example 1, the amount of α-alumina HIT55 added to the magnetic paint was 40 parts. Example 4 The fatty acid ester to be added to the magnetic paint and the non-magnetic paint in Example 1 was changed from ethylene glycol dioleyl to isohexadecyl stearate, and 12 parts were added to the magnetic paint and 16 parts to the non-magnetic paint. Example 5 In Example 1, the fatty acid ester to be added to the magnetic paint and the non-magnetic paint was changed from ethylene glycol dioleyl to isohexadecyl stearate, and 12 parts were added to the magnetic paint and 18 parts to the non-magnetic paint. (Example 6) In Example 1, the following ML-2 was used in place of the magnetic coating material ML-1, and a simultaneous multilayer coating was performed on a polyethylene terephthalate support having a thickness of 62 µm and a center plane average surface roughness of 3 nm. went. Magnetic paint ML-2 (using needle-shaped magnetic powder) Ferromagnetic metal fine powder 100 parts Composition: 70% Fe, 30% Co (atomic ratio) Hc2350Oe, specific surface area 55 m ² / g, σs 150 emu / g Crystallite size 14 nm, major axis length 0.090 μm vinyl chloride copolymer 10 parts MR110 (manufactured by Zeon Corporation) polyurethane resin 4 parts UR5500 (manufactured by Toyobo) α-alumina 15 parts HIT60 (manufactured by Sumitomo Chemical): particle size 0.15 μm carbon black 2 parts # 50 (manufactured by Asahi Carbon Co., Ltd.) Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 1 part Ethylene glycol-dioldiole 12 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts (Example 7) In Example 1, the magnetic paint ML-2 and non-magnetic were used. Polyethylene having a thickness of 62 μm and an average surface roughness of 3 nm using paint NU-2 Nterefutare - was carried out simultaneous multilayer coating on the door support. Non-magnetic paint NU-2 (using needle-like inorganic powder) Non-magnetic powder α-Fe ₂ O ₃ hematite 100 parts Long axis length 0.15 μm, specific surface area by BET method 50 m ² / g pH 9, Surface treatment agent Al ₂ O ₃ 8% by weight Carbon black # 950B (manufactured by Mitsubishi Kasei) 15 parts Average primary particle size 0.016 μm Specific surface area 250 m ² / g DBP oil absorption 80 ml / 100 g pH 8 Volatile content 3.0% Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 7 parts Phenylphosphonic acid 4 parts Ethylene glycol-dioldiole 16 parts Oleic acid 1.2 parts Stearic acid 1.2 parts Methyl ethyl ketone / cyclohexanone (8/2 mixture) (Solvent) 250 parts (Example 8) In Example 7, the thickness of the magnetic layer was set to 0.2 μm.
m. (Example 9) After cookie punching in Example 8, surface treatment was carried out under the following conditions using a vernier FB35 manufactured by Hitec Corporation.

Polishing tape: K8000, polishing tape feed speed: 6 mm / sec, spindle rotation speed: 2000 r
pm, air pressure: 0.5 kg / cm ² Processing time: 0.5 sec (Example 10) In Example 1, the following ML-4 was used instead of the magnetic paint ML-1. Magnetic paint ML-4 (using needle-shaped magnetic powder) Ferromagnetic metal fine powder 100 parts Composition: 80% Fe, 20% Co (atomic ratio) Hc1670 Oe, specific surface area 60 m ² / g, σs 130 emu / g Crystallite size 17 nm, major axis length 0.09 μm vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 4 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 20 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 3 parts Phenylphosphonic acid 3 parts Ethylene glycol dioleil 10 parts Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts (Example 11) In Example 1, the thickness of the magnetic layer was reduced to 0.
The thickness was 35 μm. Comparative Example 1 The following ML-3 was used in Example 4 instead of the magnetic paint ML-1. Magnetic paint ML-3 Ferromagnetic metal powder 100 parts Composition: 80% Fe, 5% Co, 15% Ni (atomic ratio) Hc 1970 Oe, specific surface area 58 m ² / g, σs 140 emu / g Crystallite size 18 nm, major axis length 0.28 μm Vinyl chloride Copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR-8300 (manufactured by Toyobo Co., Ltd.) 5 parts α-alumina: AKP15 (manufactured by Sumitomo Chemical Co., Ltd.) 2 parts Particle size 0.65 μm Chromium oxide: G5 (Nippon Chemical Industry Co., Ltd.) 15 parts Particle size 0.35 μm Carbon black (Ketjen Black EC) 2 parts Carbon black 9 parts Thermax MT (manufactured by Cancarb) Average primary particle diameter 0.27 μm Specific surface area 8.5 m ² / g DBP oil absorption 36 ml / 100 g pH 7.4 isohexadecyl stearate 12 parts Stearic acid 2 parts Cthyl ethyl ketone 300 parts (Comparative Example 2) In Comparative Example 1, 30 parts of α-alumina HIT55 was added instead of 15 parts of chromium oxide added to the magnetic paint. (Comparative Example 3) After punching out a cookie in Example 8, the surface was treated under the following conditions using a Verniser FB35 manufactured by Hitec Corporation.

Polishing tape: K8000, polishing tape feeding speed: 6 mm / sec, spindle rotation speed: 2000 r
pm, air pressure: 1.0 kg / cm ² Treatment time: 1.0 sec (Comparative Example 4) In Example 8, carbon black # 50 added to the magnetic paint was 3 parts, and α alumina HIT60
And 10 parts. After punching out a cookie, surface treatment was carried out under the conditions of Comparative Example 3 using a vernier FB35 manufactured by Hitec Corporation. Comparative Example 5 In Example 1, the fatty acid ester to be added to the magnetic paint and the non-magnetic paint was changed from ethylene glycol dioleyl to isohexadecyl stearate, and 15 parts were added to the magnetic paint and 20 parts to the non-magnetic paint. Comparative Example 6 In Example 1, the fatty acid ester ethylene glycol dioleyl added to the nonmagnetic paint was 5 parts.

The performance of each magnetic disk obtained as described above was evaluated by the following method.
It was shown to. (1) Magnetic properties (Hc): Measured using a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) with Hm10KOe. (2) Center plane average surface roughness (Ra): 3D-MIRAU
Surface roughness (Ra): Ra, Rrms, Peak-Valley values of an area of about 250 μm × 250 μm were measured by MIRAU method using TOPO3D manufactured by WYKO. Spherical correction and cylindrical correction are added at a measurement wavelength of about 650 nm.
This method is a non-contact surface roughness meter that measures by light interference. (3) Thickness of the magnetic layer The magnetic recording medium was cut out to a thickness of about 0.1 μm with a diamond cutter over the longitudinal direction, and the magnification was 10,000 to 10,000 with a transmission electron microscope.
Observation was performed at a magnification of 0, preferably 20,000 to 50,000, and the photograph was taken. Photo print size is A
4-A5. Thereafter, the interface was visually judged by paying attention to the shape difference between the ferromagnetic powder and the nonmagnetic powder of the magnetic layer and the lower nonmagnetic layer, and the surface of the magnetic layer was similarly blackened. Thereafter, the length of the cut line was measured by an image processing apparatus IBAS2 manufactured by Zeiss. Sample photo length is 2
In the case of 1 cm, the measurement was performed 85 to 300 times. The average of the measured values at that time was d, and the standard deviation σ of the measured values was d. d is σ according to the description in JP-A-5-298655.
Was calculated by Equation 2. di is each measured value, n
Is 85 to 300. (4) The number of surface protrusions was determined by using a Digital Instruments Nanoscope 3 (AFM: Atomic Force Microscope) with a ridge angle of 7
Using a 0 ° square pyramid SiN probe, the number of microprojections N _{20 nm} and N within a 30 μm square (900 μm ² )
_{40 nm} was measured. (5) The amount of surface lubricant (C / Fe) is measured by Auger electron spectroscopy. Using a PHI-660 model manufactured by Φ Corporation, the range of Kinetic Energy 130 to 730 eV is integrated three times under the following conditions, the KLL peak of carbon and the LMM peak of iron are obtained in differential form, and the C / Fe It is determined by taking the ratio.

Measurement conditions Primary electron beam acceleration voltage 3 kV,
Sample current: 130 nA, magnification: 250, tilt angle: 30 ° (6) The error rate was measured by recording a signal having a linear recording density of 144 kbpi and a track density of 5,200 tpi on a disk by the (2,7) RLL modulation method. (7) Running durability: ZIP durability: 3.7 inch floppy disk, floppy disk drive (ZIP1 manufactured by Iomega, USA)
(00: 2968 rpm), the head was fixed at a position of a radius of 38 mm, recording was performed at a recording density of 34 kfci, and the signal was reproduced to make it 100%. Then, in a thermocycle environment where the following flow is one cycle, 15
It ran for 00 hours. The output is monitored every 24 hours, and the point where the output becomes 70% or less of the initial value is NG.
And

LS120 durability: 3.5 inch floppy disk, floppy disk drive (Imation
(LS-120 drive: 720 rpm), the head was fixed at a radius of 30 mm, and the recording density was 34 k.
After recording at fci, the signal was reproduced and set to 100%. Thereafter, the vehicle was run for 1500 hours in a thermocycle environment in which the following flow was defined as one cycle. The output was monitored every 24 hours of running, and the point where the output became 70% or less of the initial value was regarded as NG. (Thermocycle flow) 25 ° C, 50% RH 1 hour → (Temperature rise 2 hours) → 60
℃, 20% RH 7 hours → (Temperature drop 2 hours) → 25 ° C,
50% RH 1 hour → (Temperature drop 2 hours) → 5 ° C, 50%
RH 7 hours → (Temperature rise 2 hours) → <Repeat this> (8) Startup torque evaluation 3.5 inch floppy disk, Tohoku Seisakusho torque gauge Model 300ATG, I-made L
The starting torque at the time of head-on in the S-120 drive was measured (unit: g · cm).

[0091]

[Table 1] As is clear from the above table, Ra, N _{20 nm} ,
It can be seen that the examples showing N _{40 nm} and C / Fe have excellent error rate, running durability and starting torque. On the other hand, it can be seen that in the comparative example that does not satisfy any one of the above requirements, the improvement of the error rate and the running durability are not compatible. In addition, there was no problem in running durability at all in the LS120 durability which is a contact recording method of 720 rpm, the starting torque was low, and sufficient running durability was observed in ZIP durability which was a high-speed dynamic loading method. In view of the above, it is considered that a contact recording method of 1800 rpm or more can be easily performed.

[0092]

According to the present invention, the Ra,
Since N _{20 nm} , N _{40 nm} and C / Fe are respectively specified in appropriate ranges, a high-speed rotation of 18000 rpm or more and a head-contact type drive can obtain electromagnetic conversion characteristics, running durability, start-up torque, and stack (sticking). )
It is possible to provide a high-capacity magnetic disk recorded with an areal recording density of 0.2 to ² Gbit / inch ² .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Saito 2-12-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd.

Claims (4)

[Claims] 1. A magnetic disk having a magnetic layer mainly composed of a ferromagnetic powder and a binder resin on a support, wherein the magnetic disk is recorded at a surface recording density of 0.2 to ² Gbit / inch ² , and Recording and reproduction are performed at a rotation speed of 1800 rpm or more, and the magnetic layer has a center plane average surface roughness Ra of 4 nm or less according to a 3D-MIRAU method. 100-1000 pieces / 900 μm ² with the above height,
1 to 50 pieces with a height of 40 nm or more / 900 μm ²
And the magnetic layer contains at least one of a fatty acid and a fatty acid ester, and has a carbon / iron peak intensity ratio (C / Fe) when the magnetic layer surface is measured by Auger electron spectroscopy. A magnetic disk characterized by being 10 to 100. 2. The magnetic disk according to claim 1, wherein the magnetic disk is used for a recording / reproducing system that uses a contact recording method with respect to contact of a magnetic head. 3. The thickness of the magnetic layer is 0.01 to 0.25.
3. The magnetic disk according to claim 1, wherein the magnetic disk has a coercivity of 1800 to 4000 Oersted. 4. The magnetic disk according to claim 1, further comprising a substantially non-magnetic underlayer between the support and the magnetic layer.