JPH10241143A - Metallic thin film type magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient, high-quality metallic thin film magnetic recording medium which shows stable recording reproduction characteristics even in a high temperature range of 20-60 deg.C, small size change and superior running durability. SOLUTION: A non-magnetic substrate 1 is used which features surface characteristics of an average thermal expansion coefficient (β') is a temperature range of 20-60 deg.C of 0.5-2×10<-5> deg<-1> , and an MD/TD ratio of 0.8-1.5, with an average count of rough projections larger than ϕ5μm of 0-1/cm<-2> and an average count of rough projections smaller than ϕ5μm of 5-10/cm<2> . In producing the magnetic recording medium, a unit operation is added to treat the magnetic recording medium with heat, specifically with a total calory inserted to the magnetic recording medium of larger than 20cal/g, a tensile force of smaller than 3g/mm and a heating temperature of 100-130 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin-film magnetic recording medium used in the information industry and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in the development of magnetic recording media, coating type magnetic recording media in which γ-iron oxide or Co-coated iron oxide particles are mixed with a binder have been used.

On the other hand, as a magnetic recording medium aiming at higher recording density and higher image quality, a metal magnetic recording layer is directly plated on a non-magnetic substrate by a plating method, a sputtering method, or the like.
The development of metal thin film type magnetic recording media formed by vacuum deposition, ion plating, etc. has been carried out.
Currently, it is already commercially available as a magnetic recording medium for digital video equipment.

[0004]

However, the magnetic recording medium has a problem that the magnetic head is deviated from the track due to thermal deformation, the signal is reduced, and block noise is generated due to the temperature change in the application and environmental preservation. Was. As a result, the magnetic recording medium sometimes suffers from problems such as deterioration of running durability due to damage caused by deformation during repetitive running in an environmental test or the like due to deterioration of the image quality. Therefore, in order to overcome the above-mentioned problems, Japanese Patent Application Laid-Open Nos. 6-196612 (suppressing curl in the width direction), 6-200875 (heating a recording medium), and 6-190404 (substrate) Many improvements have been proposed with the content described in the section entitled "Improvement of thermal control of shape"), but at present, only insufficient characteristics have been realized.

An object of the present invention is to provide a metal thin-film type magnetic recording medium which solves the above-mentioned problems and a method of manufacturing the same.

[0006]

In order to achieve this object, the present invention provides: 1) a thermophysical property value of a metal thin-film magnetic recording medium, 2) a non-magnetic substrate, and 3) production of a metal thin-film magnetic recording medium. It provides a solution from three aspects of the method.

First, the structure of a metal thin-film type magnetic recording medium which is the subject of the present invention will be briefly described. First, at least one selected from the group consisting of Fe, Co and Ni is placed on a non-magnetic substrate.
Ferromagnetic metals containing more than one species, or Mn, Cr,
A ferromagnetic metal containing at least one element selected from Ti, P, Y, Sm, Bi and the like or an oxide of these oxides, particularly Co, Cr and Ni, is vacuum-deposited, sputtered or the like to a thickness of from 0 to 0. A metal thin film type magnetic recording layer having a thickness of about 2 μm or less is formed, and a volatile lower hydrocarbon compound is coated on the metal thin film type magnetic recording layer with a plasma CV.
Forming a carbon protective layer composed of a carbon thin film formed to a thickness of about 100 angstroms by D, and lubricating a low molecular lubricant developed on the carbon protective layer in consideration of the bonding property with the carbon protective layer. Forming a layer. A backcoat layer having a thickness of 0.5 μm is formed on the non-magnetic substrate on the side opposite to the lamination side of each layer with a resin of a mixture paint containing carbon or the like in a binder mainly composed of a polymer material.

The metal thin-film type magnetic recording medium having the above-described structure has a thermal property value of 0.5 to 2 × 10 ^-5 deg ^-1 at an average thermal expansion coefficient (β ') in a temperature range of 20 to 60 ° C. When the MD / TD ratio is set to 0.8 to 1.5, the thermal properties are improved and the thermal deformation with small thermal expansion and thermal shrinkage is improved. , Stable recording and reproduction can be realized.

Next, a non-magnetic substrate most relevant to the present invention will be described. Non-magnetic substrates include polymer films of polyamide, polyimide, polyethylene, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and vinyl chloride. And from the requirements applied to the present invention, preferably heat resistance, heat shrinkage, surface properties, physical properties such as mechanical strength and availability, handling,
Considering price and mass productivity, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN)
Considering the direction of thinning, PEN which is advantageous in terms of mechanical strength and heat resistance is most preferable. Further, as a preferable thermophysical property value of the non-magnetic substrate, the heat shrinkage ratio is preferably small in the longitudinal direction (MD) and the width direction (TD).
<0.5% in MD direction and <0.5% in TD direction
It is better to have 0.3%. In terms of signal quality, the surface quality is 0 to the average number of coarse projections having a diameter of> φ5 μm.
1 / cm ² , average number of coarse projections of <φ5 μm is 5
With a surface property of 〜１０10 / cm ² , it is possible to improve the quality of the image by digitization.

In the unit operation of the heat treatment in the production method of the present invention, the operation is performed using a light source such as ultraviolet, infrared, electromagnetic waves, or a heating furnace such as an electric furnace, a drying furnace or a heat exchange furnace. Above all, a drying furnace is preferable in the production method of the present invention because it requires temperature setting, is easy to control, and is industrial and mass-producible.
As for the manufacturing conditions of the magnetic recording medium, optimization of conditions suitable for the present invention is examined by factors such as tension, heating temperature, and processing speed.

For example, if the tension is too high, cracks in the width direction of the magnetic recording layer will occur if the tension is too high, whereas if the tension is too low, there will be a problem in winding the magnetic recording medium, causing a problem in the manufacturing process.

If the setting of the heating temperature is too low, the processing speed becomes slow in order to obtain the amount of heat that must be inserted into the magnetic recording medium. If the temperature is too high, the influence of other constituent layers may occur, and the phenomenon of elongation is not good. Considering mass processing, industrialization, and rapid production, realization at a low processing speed is meaningless. Therefore, by optimizing the above conditions, the heat shrinkage of the magnetic recording medium can be reduced to <0.1.
The total amount of heat inserted into the magnetic recording medium so that it becomes 5%>
The heat treatment is preferably performed at 20 cal / g, a tensile tension of <3 g / mm, and a heating temperature of 100 to 130 ° C. The temperature at which the magnetic recording medium begins to expand shifts by 5 to 10 ° C. higher than that of the non-heat-treated magnetic recording medium in terms of thermal characteristics measured by TMA (thermomechanical test), and expands and contracts. It is preferable to implement a manufacturing method in which heat treatment is performed so that the temperature at which thermal deformation changes to> 5 ° C. than that of a magnetic recording medium that is not heat-treated, in order to realize a magnetic recording medium with reduced thermal deformation.

As described above, the metal thin-film magnetic recording medium shown in the present invention and the metal thin-film magnetic recording medium realized by the method for manufacturing the same have characteristics of improved thermal deformation and excellent surface properties. In addition, it is possible to provide a metal thin-film magnetic recording medium which exhibits stable recording / reproducing characteristics even with temperature changes during use and environmental preservation, has good image quality, and has excellent running durability.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention uses polyethylene naphthalate for the non-magnetic substrate, has a total thickness of the magnetic recording medium of <8 μm, and has a temperature range of 20 to 60.
The average thermal expansion coefficient (β ′) at 0.5 ° C. is 0.5 to 2 × 10 ^−5.
deg ^-1 and the MD / TD ratio is 0.8 to
A metal thin-film magnetic recording medium having a thermophysical property value of 1.5, and having an average coefficient of thermal expansion (β ′) of 0.5 to 2 × 10 ^−5.
deg ^-1 and its MD / TD ratio is 0.8 to
Since it is 1.5, the linear characteristic is 3 to 4 μm, which is almost satisfactory.

According to a second aspect of the present invention,
C. <0.5% in MD and <0.5% in TD
2. The metal thin-film magnetic recording medium according to claim 1, wherein a non-magnetic substrate having a thermophysical property value of 0.3% is used, wherein the non-magnetic substrate has a thermal shrinkage of <0.5% in the MD direction and in the TD direction. <0.
Since it is 3%, a high-quality magnetic recording medium that satisfies the linear characteristics and has a small BER value and few defects can be obtained.

According to a third aspect of the present invention, the average number of coarse projections having a surface property of> φ5 μm is 0 to 1 / cm.
² , 5 to 10 / average number of coarse projections of <φ5 μm
^2. The metal thin-film magnetic recording medium according to claim 1, wherein a non-magnetic substrate having a surface property of cm ² is used.
The average number of coarse protrusions of φ5 μm is 0 to 1 / cm ² ,
<Average number of coarse protrusions of φ5 μm is 5 to 10 / cm
^Since it is ² , a magnetic recording medium free from surface defects, excellent in image quality, and excellent in repeated running durability can be obtained.

According to a fourth aspect of the present invention, a unit operation of performing heat treatment at a total heat quantity of> 20 cal / g, a tensile tension of <3 g / mm, and a heating temperature of 100 to 130 ° C. inserted into a magnetic recording medium is described. This is a method of manufacturing a metal thin film type magnetic recording medium to be added, in which the total heat quantity is> 20 cal / g, the tensile tension is <3 g / mm, and the heat shrinkage is obtained by adding a unit operation of heat treatment at a heating temperature of 100 to 130 ° C. Is <
0.15%, so that a metal thin-film magnetic recording medium having small thermal deformation can be obtained.

In the invention according to claim 5 of the present invention, the temperature at which the expansion of the magnetic recording medium starts is shifted by 5 to 10 ° C. higher than that of the magnetic recording medium without heat treatment, and the thermal deformation changes from expansion to contraction. 5. The method for producing a metal thin film magnetic recording medium according to claim 4, wherein the heat treatment is performed so that the temperature is higher than 5 DEG C. than the magnetic recording medium which is not heat treated. A medium is obtained.

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing a configuration of a metal thin film type magnetic recording medium according to Embodiment 1 of the present invention.
On a non-magnetic substrate 1 made of a PET film having a thickness of 6.2 μm and a width of 500 mm, a 0.16 μm-thick metal thin-film type magnetic recording layer 2 is formed by laminating one layer of Co in an oxygen glow state. On the magnetic recording layer 2, a plasma C
A carbon protective layer 3 is formed by a VD film forming method, and a lubricating layer 4 is formed on the carbon protective layer 3 by applying perfluorooctyl carboxylic acid with isopropyl alcohol in which 1000 ppm is dissolved. A resin back coat layer 5 is laminated on the side opposite to the lamination side of each of the above-mentioned layers.

The metal thin film type magnetic recording medium having the above structure is
The recording tape was slit into 4 inches and stored in a cassette with a length of 60 minutes. The samples were treated with an electric furnace at the temperature of the heating conditions shown in Table 1 and left in the furnace for a period of time, and one untreated sample was produced as a comparative example.

[0021]

[Table 1]

In the evaluation, an average coefficient of thermal expansion (β ') was obtained using TMA (Vacuum Riko TM7000) which is generally used from the viewpoint of measuring thermophysical properties. After the cassette was left for 20 hours in an environment of a temperature of 60 ° C., a value was calculated from an angle change due to a track shift after reproduction.

Then, the untreated sample of the comparative example has β ′ of M
D3.3 and TD1.9 are large, and the ratio of β ′ between the longitudinal direction and the width direction and the MD / TD ratio are 1.7 and> 1.5. The linear value greatly deviated from 7 to 8 μm, and the signal drop and the block error increased. On the other hand, Sample No. 1 in Embodiment 1 of the present invention to which the heating conditions in Table 1 were added 1
~ 3 has a small value of β 'as 0.5 to 2 in the MD direction,
In addition, when the MD / TD ratio of β ′ also shows a thermophysical property value of 0.8 to 1.5, a linear characteristic of 3 to 4 μm, which is almost satisfied, is obtained. However, the sample N obtained at the same time
o. In No. 4, because the heating time was too long, the linear characteristic was 5 to 6 μm, which was improved from the comparative example, but no remarkable effect was observed, β ′ was large, and the MD / TD ratio was out of the range. .

Thus, as shown in Table 1, a magnetic recording medium satisfying the linear characteristic has a value of β ′ of 0.5 to 2 × 10 ⁻⁵ deg ⁻¹ and the value of β ′. M
It has been found that a magnetic recording medium having a D / TD ratio of 0.8 to 1.5 having thermophysical properties can be achieved only when a magnetic recording medium is used.

(Embodiment 2) A metal thin film type magnetic recording medium according to Embodiment 2 is different from Embodiment 1 in that a PEN film having a thickness of 4.8 μm is used as the nonmagnetic substrate 1 in FIG. Is the same as in the first embodiment. As shown in Table 2, three types of sample Nos. Having different thermal shrinkage rates and surface state projections were used as the non-magnetic substrate 1 in the second embodiment. The linear value and the BER were comparatively evaluated using a substrate having a large heat shrinkage ratio and a large number of surface state protrusions as a comparative sample using 5 to 7 as comparative samples.

The number of protrusions was calculated by averaging the number of protrusions at three places by surface observation, and classified into sizes of> φ5 μm and <φ5 μm to examine the influence of defects due to the protrusions.

[0027]

[Table 2]

As shown in Table 2, a high-quality magnetic recording medium which satisfies the linear characteristic and has a small BER value and few defects has a thermal shrinkage of <0.5% in the MD direction and <0.5% in the TD direction. In addition to 0.3%, in terms of surface properties, the average number of coarse projections of> φ5 μm is 0 to 1 / cm ² , <φ5 μm
The sample No. having a surface state of 5 to 10 / cm ^{2 in} average number of coarse projections of No. It has been found that this is achieved with 5-7 films. However, the comparative sample was not in this state, so that both the linear value and the BER were not good.

Therefore, when a metal thin film type magnetic recording medium is manufactured with an improved non-magnetic substrate, linearity can be achieved without the need for additional heating and the like, and the image quality is excellent because there are no surface defects. A magnetic recording medium having good repeated running durability can be obtained.

(Embodiment 3) In the method of manufacturing a metal thin film type magnetic recording medium according to Embodiment 3, Embodiment 1
6.2 μm thick PET film (sample No.
8 to 10) and a 4.8 μm-thick PEN film (Sample Nos. 11 to 12) with different temperatures, tensions, and processing speeds as shown in Table 3, and different manufacturing conditions from the above samples. For the comparative sample, the total amount of heat added during the production was calculated from the specific heat of the magnetic recording medium, and the production method of the metal thin-film magnetic recording medium was comparatively evaluated.

[0031]

[Table 3]

The evaluation was performed by measuring the heat shrinkage after leaving at a temperature of 60 ° C. for 20 hours. The expansion and contraction behavior was measured from room temperature to 150 ° C. by TMA, and the temperature at which expansion started and the temperature at which expansion was converted to contraction were determined.

As shown in Table 3, the manufacturing method of the third embodiment, that is, a tensile tension of <3 g / mm and a heating temperature of 1
00 to 130 ° C. and the total amount of heat inserted into the heating medium is> 2
At 0 cal / g, it was found that the heat shrinkage ratio was <0.15%, and the thermal deformation was reduced to one third of that of the comparative sample. In these samples, the temperature at which the metal thin-film magnetic recording medium starts to expand is shifted by 5 to 10 ° C. higher than that of the comparative sample, and the temperature at which the thermal deformation changes from expansion to contraction is similarly increased to> 5 ° C. Such a change had occurred.

Therefore, as described in the third embodiment, the thermal deformation of the metal thin film type magnetic recording medium manufactured by optimizing and controlling the temperature, tension, processing speed and the amount of heat inserted into the medium in the manufacturing method is improved. It has been found that, for the first time, a metal thin-film magnetic recording medium capable of always achieving linear characteristics can be provided.

[0035]

According to the metal thin-film magnetic recording medium and the method of manufacturing the same described in the present invention, a metal thin-film magnetic recording medium exhibiting stable recording and reproducing characteristics even in a high temperature range of 20 to 60 ° C. can be provided. In addition, a high-performance, high-quality metal thin-film magnetic recording medium with small dimensional change and excellent running durability can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a metal thin-film magnetic recording medium according to a first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 2 Metal thin film type magnetic recording layer 3 Carbon protective layer 4 Lubricating layer 5 Back coat layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Fujita 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A non-magnetic substrate made of polyethylene naphthalate, a magnetic recording medium having a total thickness of <8 μm, a temperature range of 20 to 60 ° C. and an average thermal expansion coefficient (β ′) of 0.5 to 0.5 μm.
A metal thin-film magnetic recording medium having 2 × 10 ^-5 deg ^-1 and a thermophysical property value of which the MD / TD ratio is 0.8 to 1.5. 2. The heat shrinkage at 100 ° C. is <0.
2. The metal thin-film magnetic recording medium according to claim 1, wherein a non-magnetic substrate having a thermophysical property value of 5% and <0.3% in the TD direction is used. 3. A non-woven fabric having a surface property of 0 to 1 / cm ^{2 in} average number of coarse protrusions having a diameter of> φ5 μm, and a surface property of 5 to 10 / cm ^{2 in} average number of coarse protrusions of <φ5 μm. 2. The metal thin-film magnetic recording medium according to claim 1, wherein a magnetic substrate is used. 4. The total amount of heat inserted into the magnetic recording medium is> 2
0 cal / g, tensile strength <3 g / mm, and a method of manufacturing a metal thin film type magnetic recording medium in which a unit operation of heat treatment at a heating temperature of 100 to 130 ° C. is added. 5. The temperature at which expansion of the magnetic recording medium starts is shifted by 5 to 10 ° C. higher than that of the magnetic recording medium without heat treatment.
5. The method according to claim 4, wherein the heat treatment is performed so that the temperature at which the thermal deformation changes from expansion to contraction is> 5 [deg.] C. as compared with the magnetic recording medium without heat treatment.