JPH0778329A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having stabilized running performance and high reliability of action and excellent in recording and reproducing characteristics. CONSTITUTION:This magnetic recording medium 1 is a magnetic recording medium obtd. by forming a magnetic layer on a nonmagnetic substrate. When the surface of the magnetic layer is brought into contact with glass 2 under 200gf/cm<2> pressure, the center line average roughness Ra of the surface of the magnetic layer brought into contact with the glass is <=8nm and the contact area ratio is <=20%, the root mean square roughness rms of the surface of the magnetic layer brought into contact with the glass is <=10nm and the average contact area of protrusions is <=60mum<2>, or the root mean square roughness rms of the surface of the magnetic layer brought into contact with the glass is <=10nm and the number of the contact points of protrusions is >=4,100 (1/mm<2>).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk.

[0002]

2. Description of the Related Art In a magnetic recording medium, the center line average roughness Ra or the root mean square roughness rms on the surface of the magnetic layer is reduced to reduce the spacing from the magnetic head, in order to increase the capacity and the density. Tends to reduce.

[0003]

The magnetic medium (the magnetic layer of the magnetic recording medium) and the surface of the magnetic head each have microscale roughness. When the magnetic medium and the magnetic head come into contact with each other, the contact occurs at the apex of the protrusions on both surfaces. The protrusions on the surface of the magnetic medium are crushed by the head load, causing an increase in the contact area. This increase in the contact area increases as the center line average roughness Ra or the root mean square roughness rms of the surface of the magnetic medium decreases, which causes an increase in the friction coefficient and reduces the running property. On the other hand, the center line average roughness Ra or the root mean square roughness rms
Becomes larger, the spacing between the magnetic head and the magnetic head becomes larger and the recording / reproducing characteristics deteriorate.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic recording medium having stable running properties, high operation reliability and excellent recording / reproducing characteristics.

[0005]

As a result of various studies on the surface state of the magnetic medium, the present inventors have found that the above object can be achieved by the magnetic medium having specific surface characteristics.

That is, the present invention has been made based on the above findings, and provides the following magnetic recording media.

A magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, the magnetic layer being in contact with glass when the surface of the magnetic layer of the magnetic recording medium is brought into contact with glass at a pressure of 200 gf / cm ^2. Center line average roughness Ra of the layer surface is 8 nm
A magnetic recording medium having the following ratio and a contact area ratio of 20% or less (hereinafter referred to as the first invention).

A magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, the magnetic layer being in contact with the glass when the surface of the magnetic layer of the magnetic recording medium is brought into contact with the glass at a pressure of 200 gf / cm ^2. The root mean square roughness rms of the layer surface is 10 n
A magnetic recording medium (hereinafter referred to as the second invention), characterized in that the average contact area of the protrusions is 60 μm ² or less.

A magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, the magnetic recording medium being in contact with the glass when the surface of the magnetic layer of the magnetic recording medium is brought into contact with the glass at a pressure of 200 gf / cm ^2. The root mean square roughness rms of the layer surface is 10 n
m or less and the number of contact points of the protrusion is 4100 (1 / mm ² )
The magnetic recording medium (hereinafter referred to as the third
Invention).

First, the first invention will be described in detail below. The magnetic recording medium of the first invention has a center line average roughness Ra of the magnetic layer surface of 8 nm or less, preferably 7 nm or less, more preferably 6.5 to 0.5 nm. When Ra is large, the relative output tends to decrease.

In the magnetic recording medium of the first invention, the contact area ratio of the magnetic layer surface is 20% or less, preferably 15% or less, more preferably 14.5 to 1%. The larger the contact area ratio, the larger the dynamic friction coefficient. As shown in FIG. 1, this contact area ratio means that when a protrusion is higher than the horizontal plane B when it is cut horizontally from the highest protrusion A on the surface of the magnetic layer at a height of 20 nm in the depth direction. It is the area ratio to the whole.

The above centerline average roughness Ra and contact area ratio are the centerline average roughness Ra and contact area ratio when the surface shape of the magnetic layer of the magnetic recording medium is measured by the following measuring method.

[Method of Measuring Ra and Contact Area Ratio] Measurement is performed using the apparatus shown in FIG. The apparatus shown in FIG. 2 has a glass slide 2 (Ra1.5n) on the magnetic layer of the magnetic recording medium 1.
m, Rms 1.9 nm, Young's modulus 50.6 GPa), and air pressure can be applied from the lower part of the magnetic recording medium 1 through the line 3. The pressure can be changed by a regulator (not shown). A pressure gauge (not shown) for measuring pressure is provided in the line 3. The magnetic recording medium 1 to be measured has an inner diameter of 6.5 mm and 2 provided to minimize pressure leakage.
Placed on two 3.1 mm O-rings 4, 5. An exhaust pipe 6 having a diameter of 1 mm is provided between the two O-rings 4 and 5, and the pressure is designed to always be applied only to the inner side of the inner O-ring 4. Then, after arranging the magnetic recording medium 1 as shown in FIG. 2, an air pressure of 200 gf / cm ² is applied from below the magnetic recording medium 1 through the line 3. Then, the surface shape of the magnetic layer of the magnetic recording medium 1 in contact with the glass slide 2 is measured through the glass slide 2 using an optical non-contact three-dimensional surface roughness meter (not shown). Then, Ra and the contact area ratio are obtained. The optical non-contact 3D surface roughness meter used has a wavelength of 63
A He-Ne laser of 2.8 nm is used as a light source, and the resolution is 0.2 Å in the vertical direction and 0.7 μm in the horizontal direction.
The measurement field of view is 0.18 mm × 0.18 mm.

The magnetic layer of the magnetic recording medium of the first invention preferably contains barium ferrite (BaFe) powder. The barium ferrite powder preferably has a hexagonal plate shape, and the particle size (diagonal length) is not particularly limited, but is 0.02 to 1.0 μm.
The thickness is generally about 0.001 to 0.1 μm. The coercive force of the barium ferrite powder is not particularly limited and may be appropriately determined depending on the desired performance of the magnetic recording medium, but is generally about 500 to 2000 Oe.

The content of the barium ferrite powder is
In the magnetic layer, 50 to 95% by weight, particularly 65 to 90% by weight is preferable. If the barium ferrite powder is not contained in the magnetic layer, the relative output tends to decrease.

The magnetic recording medium of the first invention is prepared according to a conventional method, that is, for example, by kneading magnetic powder with an organic solvent, a binder and the like to prepare a magnetic paint, and the paint is applied onto a non-magnetic support. It is manufactured by applying, drying, calendering and polishing.

As the magnetic powder, in addition to the barium ferrite powder, those conventionally used as magnetic powders for magnetic recording media (for example, γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, and Co-containing powder). γ-Fe ₂ O ₃ powder, etc.)
However, in that case, it is preferable that the content of the barium ferrite powder is 70% by weight or more in the magnetic powder.

As the above organic solvent and binder, those conventionally used (for example, as the organic solvent, methyl ethyl ketone, toluene, cyclohexanone, ethyl acetate, benzene, xylene, etc .; as the binder, vinyl chloride resin) , Polyurethane resin, nitrocellulose, epoxy resin, etc.) can be used. Also,
Additives that have been conventionally used such as fatty acids, fatty acid esters, and inorganic powders can be added to the magnetic paint.

As the non-magnetic support, synthetic resin such as polyester, non-magnetic metal and paper such as film, tape and sheet, which are conventionally used, can be used.

The above surface characteristics (center line average roughness Ra = 8)
The magnetic layer having a thickness of nm or less and a contact area ratio of 20% or less) can be obtained by appropriately adjusting the amount and particle size of the abrasive contained in the magnetic layer, calendering treatment conditions, polishing treatment conditions and the like. These preferable conditions cannot be generally stated depending on the compounding components of the magnetic layer, but are usually as follows. -Amount of abrasive and particle size contained in magnetic layer Amount of abrasive: 4 to 13 parts by weight per 100 parts by weight of magnetic powder Abrasive particle size: 0.1 to 0.3 m-Calendar processing conditions Number of stages: 3 to 9 Roll temperature: 60 to 100 ° C. Roll pressure: Linear pressure 100 to 300 kgf / cm-Polishing condition Abrasive grain size: # 6000 to 10000 Polishing pressure: 50 to 5000 g / cm ² Polishing time: 2 10 seconds

Next, the second invention will be described in detail. The magnetic recording medium of the second invention has a root mean square roughness rms of the magnetic layer surface.
Is 10 nm or less, preferably 9 nm or less, and more preferably 8.8 to 1.5 nm. When rms is large, the relative output tends to decrease.

In the magnetic recording medium of the second invention, the average contact area of the protrusions on the surface of the magnetic layer is 60 μm ² or less, preferably 30 μm ² or less, more preferably 29 to ² μm ² . The larger the average contact area of the protrusions, the larger the dynamic friction coefficient. As shown in FIG. 1, the average contact area of the protrusions is higher than that on the horizontal plane B when the protrusions on the surface of the magnetic layer are horizontally cut at a height of 20 nm from the apex A of the protrusions. It is the average area of the protrusions.

The root mean square roughness rms and the average contact area of the protrusions are measured when the surface shape of the magnetic layer of the magnetic recording medium is measured by the same method as the method of measuring Ra and the contact area ratio in the first invention. Are the root mean square roughness rms and the average contact area of the protrusions.

It is preferable that the magnetic layer of the magnetic recording medium of the second invention also contains barium ferrite powder. The barium ferrite powder is the same as the barium ferrite powder used in the first invention. The same amount is used.

The magnetic recording medium of the second invention is manufactured by the same method as the magnetic recording medium of the first invention.

The above surface characteristics (root mean square roughness rms = 1)
A magnetic layer having an average contact area of protrusions of 0 nm or less = 60 μm ² or less) can be obtained by appropriately adjusting the amount and particle size of the abrasive contained in the magnetic layer, calendering treatment conditions, polishing treatment conditions and the like. To be These preferable conditions cannot be generally stated depending on the compounding components of the magnetic layer, etc.,
It is usually as follows. -Amount of abrasive and particle size contained in magnetic layer Amount of abrasive: 4-12 parts by weight per 100 parts by weight of magnetic powder Abrasive particle size: 0.1-0.3 μm-Calendar processing conditions Number of stages: 3 to 9 Roll temperature: 60 to 100 ° C. Roll pressure: Linear pressure 100 to 400 kgf / cm-Polishing condition Grain size of abrasive: # 6000 to 10000 Polishing pressure: 100 to 5000 g / cm ² Polishing time: 2 10 seconds

Next, the third invention will be described in detail. The magnetic recording medium according to the third aspect of the invention has a root mean square roughness rms of the magnetic layer surface.
Is 10 nm or less, preferably 9 nm or less, and more preferably 8.8 to 1.5 nm. When rms is large, the relative output tends to decrease.

In the magnetic recording medium of the third invention, the number of contact points of the protrusions on the surface of the magnetic layer is 4100 (1 / mm ² ) or more,
It is preferably 4600 (1 / mm ² ) or more, and more preferably 4700 to 10000 (1 / mm ² ).
If the number of contact points of the protrusions is low, the coefficient of dynamic friction becomes large. As shown in FIG. 1, the number of contact points of the protrusions is higher than that on the horizontal plane B when cut horizontally from the highest protrusion A on the surface of the magnetic layer at a height of 20 nm in the depth direction. Is the number of.

The root mean square roughness rms and the number of contact points of the protrusions are the same as the method of measuring Ra and the contact area ratio in the above-mentioned first invention when the surface shape of the magnetic layer of the magnetic recording medium is measured. The root mean square roughness rms and the number of contact points of the protrusions.

Further, it is preferable that the magnetic layer of the magnetic recording medium of the third invention also contains barium ferrite powder, and the barium ferrite powder is the same as the barium ferrite powder used in the first invention. Are used in similar amounts.

The magnetic recording medium of the third invention is also manufactured by the same method as the magnetic recording medium of the first invention.

The above surface characteristics (root mean square roughness rms = 1)
For the magnetic layer having a thickness of 0 nm or less and the number of contact points of protrusions = 4100 (1 / mm ² ) or more), the amount and particle size of the abrasive contained in the magnetic layer, calendering treatment conditions, polishing treatment conditions, etc. are adjusted appropriately. It is obtained by doing. These preferable conditions cannot be generally stated depending on the compounding components of the magnetic layer, but are usually as follows. -Amount of abrasive and particle size contained in magnetic layer Amount of abrasive: 2 to 14 parts by weight per 100 parts by weight of magnetic powder Abrasive particle size: 0.1 to 0.3 m-Calendar processing conditions Number of stages: 3 to 9 Roll temperature: 60 to 100 ° C. Roll pressure: Linear pressure 100 to 500 kgf / cm ・ Polishing condition Grain size of abrasive: # 6000 to 10000 Polishing pressure: 100 to 4000 g / cm ² Polishing time: 2 10 seconds

[0033]

By stabilizing the surface state of the magnetic layer of the magnetic recording medium to a specific state, the running property of the magnetic recording medium is stabilized,
Improves operational reliability and improves recording / reproducing characteristics.

[0034]

The present invention will be described in more detail below with reference to examples of the present invention together with comparative examples, but the present invention is not limited to these examples.

Example 1 (Example of the first invention) 100 parts by weight of BaFe ferromagnetic powder (plate ratio 3: Hc750Oe) 6 parts by weight of vinyl chloride resin (MR110, manufactured by Nippon Zeon Co., Ltd.) Polyurethane resin (Toyobo Co., Ltd., UR8300) 6 parts by weight Myristic acid 3 parts by weight Butyl stearate 3 parts by weight α-Al ₂ O ₃ (particle size 0.1 μm to 0.3 μm) (Sumitomo Chemical Co., Ltd.) Manufactured by AKP-50) 8 parts by weight carbon black 5 parts by weight methyl ethyl ketone 75 parts by weight toluene 75 parts by weight cyclohexanone 100 parts by weight After thoroughly kneading the above composition, polyisocyanate (Coronate L, Nippon Polyurethane Industry Co., Ltd.) (3) Hardening agent manufactured by K.K.) was added to prepare a magnetic paint, and the magnetic paint was used as a non-magnetic support composed of a polyester film. It is applied on the body and dried and calendered. After that, the outer diameter is 8
A magnetic disk was obtained by punching out with 6 mm and polishing with a # 8000 polishing tape under a load of 1000 g / cm ² for 4 seconds.

Example 2 (Example of the First Invention) A magnetic disk was obtained in the same manner as in Example 1 except that the weight part of α-Al ₂ O ₃ in Example 1 was changed to 12 parts.

Example 3 (Example of the First Invention) Example 1 was the same as Example 1 except that the polishing step in Example 1 was carried out using a # 8000 polishing tape under a load of 1000 g / cm ² for 10 seconds. A magnetic disk was obtained in the same manner.

Comparative Example 1 A magnetic disk was obtained in the same manner as in Example 1 except that the weight part of α-Al ₂ O ₃ in Example 1 was changed to 14 parts.

Comparative Example 2 α-A having a particle size of 0.1 μm to 0.3 μm in Example 1
l ₂ O ₃ with α-Al ₂ O having a particle size of 0.6 μm to 0.8 μm
_{3 A} magnetic disk was obtained in the same manner as in Example 1 except that AKP-15 manufactured by Sumitomo Chemical Co., Ltd. was used.

With respect to the magnetic disks obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the center line average roughness and contact area ratio of the magnetic layer surface, the dynamic friction coefficient and the relative output are shown in the following [Table 1]. Show.

[0041]

[Table 1]

The dynamic friction coefficient is calculated by the FD drive (TOS
HIBA PD-211) was used for measurement and converted into current value. The relative output is the value of Tr. 79.2F for the standard flexible disk. [Table 2] below
The dynamic friction coefficient and the relative output in [Table 3] are also measured by the same method as described above.

Example 4 (Example of the second invention) 100 parts by weight of BaFe ferromagnetic powder (plate ratio 3: Hc750Oe) 6 parts by weight of vinyl chloride resin (MR110, manufactured by Nippon Zeon Co., Ltd.) Polyurethane resin (Toyobo Co., Ltd., UR8300) 6 parts by weight Palmitic acid 3 parts by weight Butyl stearate 3 parts by weight α-Al ₂ O ₃ (particle size 0.1 μm to 0.3 μm) (Sumitomo Chemical Co., Ltd.) Manufactured by AKP-50) 8 parts by weight carbon black 5 parts by weight methyl ethyl ketone 75 parts by weight toluene 75 parts by weight cyclohexanone 100 parts by weight After thoroughly kneading the above composition, polyisocyanate (Coronate L, Nippon Polyurethane Industry Co., Ltd.) (3) Hardening agent manufactured by K.K.) was added to prepare a magnetic paint, and the magnetic paint was used as a non-magnetic support composed of a polyester film. It is applied on the body and dried and calendered. After that, the outer diameter is 8
A magnetic disk was obtained by punching out with 6 mm and polishing with a # 8000 polishing tape under a load of 1000 g / cm ² for 2 seconds.

Example 5 (Example of the Second Invention) A magnetic disk was obtained in the same manner as in Example 4 except that the weight part of α-Al ₂ O ₃ in Example 4 was changed to 12 parts.

Example 6 (Example of the Second Invention) # 10000 polishing tape in the polishing process of Example 4
500 g / cm ²Loaded for 10 seconds
Except that the magnetic disk was polished in the same manner as in Example 4.
Got it.

Comparative Example 3 A magnetic disk was obtained in the same manner as in Example 4 except that the weight part of α-Al ₂ O ₃ in Example 4 was changed to 14 parts.

Comparative Example 4 α-A having a particle size of 0.1 μm to 0.3 μm in Example 4
l ₂ O ₃ with α-Al ₂ O having a particle size of 0.6 μm to 0.8 μm
_{3 A} magnetic disk was obtained in the same manner as in Example 4 except that AKP-15 manufactured by Sumitomo Chemical Co., Ltd. was used.

Comparative Example 5 α-A having a particle size of 0.1 μm to 0.3 μm in Comparative Example 3
l ₂ O ₃ with α-Al ₂ O having a particle size of 0.6 μm to 0.8 μm
_{3 A} magnetic disk was obtained in the same manner as in Comparative Example 3 except that AKP-15 manufactured by Sumitomo Chemical Co., Ltd. was used.

With respect to the magnetic disks obtained in Examples 4 to 6 and Comparative Examples 3 to 5, the root mean square roughness of the magnetic layer and the average contact area of the protrusions, the dynamic friction coefficient and the relative output are shown in the following [Table 2]. Shown in.

[0050]

[Table 2]

Example 7 (Example of the third invention) 100 parts by weight of BaFe ferromagnetic powder (plate ratio 3: Hc750Oe) 6 parts by weight of vinyl chloride resin (MR110, manufactured by Nippon Zeon Co., Ltd.) Polyurethane resin (Toyobo Co., Ltd., UR8300) 6 parts by weight Palmitic acid 3 parts by weight Butyl stearate 3 parts by weight α-Al ₂ O ₃ (particle size 0.1 μm to 0.3 μm) (Sumitomo Chemical Co., Ltd.) Manufactured by AKP-50) 8 parts by weight carbon black 5 parts by weight methyl ethyl ketone 75 parts by weight toluene 75 parts by weight cyclohexanone 100 parts by weight After thoroughly kneading the above composition, polyisocyanate (Coronate L, Nippon Polyurethane Industry Co., Ltd.) (3) Hardening agent manufactured by K.K.) was added to prepare a magnetic paint, and the magnetic paint was used as a non-magnetic support composed of a polyester film. It is applied on the body and dried and calendered. After that, the outer diameter is 8
A magnetic disk was obtained by punching out with 6 mm and polishing with a # 8000 polishing tape under a load of 500 g / cm ² for 2 seconds.

Example 8 (Example of the third invention) A magnetic disk was obtained in the same manner as in Example 7 except that the weight part of α-Al ₂ O ₃ in Example 7 was changed to 14 parts.

Example 9 (Example of the third invention) # 10000 polishing tape in the polishing process of Example 7
100 g / cm using ²Loaded for 10 seconds
Except that the magnetic disk was polished in the same manner as in Example 7.
Got it.

Comparative Example 6 A magnetic disk was obtained in the same manner as in Example 7 except that the weight part of α-Al ₂ O ₃ in Example 7 was changed to 20 parts.

Comparative Example 7 α-A having a particle size of 0.1 μm to 0.3 μm in Example 7
l ₂ O ₃ with α-Al ₂ O having a particle size of 0.6 μm to 0.8 μm
_{3 A} magnetic disk was obtained in the same manner as in Example 7 except that AKP-15 manufactured by Sumitomo Chemical Co., Ltd. was used. Comparative Example 8 α-A having a particle size of 0.1 μm to 0.3 μm in Comparative Example 6
l ₂ O ₃ with α-Al ₂ O having a particle size of 0.6 μm to 0.8 μm
_{3 A} magnetic disk was obtained in the same manner as in Comparative Example 6 except that AKP-15 manufactured by Sumitomo Chemical Co., Ltd. was used.

Regarding the magnetic disks obtained in Examples 7 to 9 and Comparative Examples 6 to 8, the root mean square roughness of the magnetic layer, the number of contact points of the protrusions, the dynamic friction coefficient and the relative output are shown in the following [Table 3]. Show.

[0057]

[Table 3]

[0058]

The magnetic recording medium of the present invention has stable running properties, high operational reliability, and excellent recording / reproducing characteristics.

[Brief description of drawings]

FIG. 1 is an enlarged view showing an outline of a state of protrusions on a surface of a magnetic layer.

FIG. 2 is a side view showing the outline of an apparatus for measuring the surface shape of a magnetic layer.

[Explanation of symbols]

 A Peak of highest protrusion B Horizontal plane 1 Magnetic recording medium 2 Glass slide 3 Line 4, 5 O-ring 6 Exhaust pipe

Claims (6)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided thereon, the magnetic recording medium being in contact with glass when the magnetic layer surface of the magnetic recording medium is brought into contact with the glass at a pressure of 200 gf / cm ^2. Center line average roughness Ra of the magnetic layer surface is 8 nm
A magnetic recording medium having the following ratio and a contact area ratio of 20% or less. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer contains barium ferrite powder. 3. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided thereon, the magnetic recording medium being in contact with glass when the magnetic layer surface of the magnetic recording medium is brought into contact with the glass at a pressure of 200 gf / cm ^2. The root mean square roughness rms of the magnetic layer
A magnetic recording medium, characterized in that the average contact area of the protrusions is 60 μm ² or less. 4. The magnetic recording medium according to claim 3, wherein the magnetic layer contains barium ferrite powder. 5. A magnetic recording medium comprising a non-magnetic support and a magnetic layer provided thereon, the magnetic recording medium being in contact with glass when the magnetic layer surface of the magnetic recording medium is brought into contact with the glass at a pressure of 200 gf / cm ^2. The root mean square roughness rms of the magnetic layer
m or less and the number of contact points of the protrusion is 4100 (1 / mm ² )
A magnetic recording medium having the above. 6. The magnetic recording medium according to claim 5, wherein the magnetic layer contains barium ferrite powder.