JPH054725B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing magnetic recording media such as metal thin film magnetic tapes and magnetic disks that can realize high-density magnetic recording. Conventional structure and its problems Traditionally, magnetic recording media have been made of γ-Fe ₂ O ₃ doped with C ₀ on a polymer substrate or aluminum substrate.
So-called coated media are produced by dispersing powdered magnetic materials such as oxide magnetic powders such as CrO ₂ or ferromagnetic alloy powders such as Fe, Co, Ni, etc. in an organic binder such as polyurethane resin, and coating and drying the mixture. It is widely used in practical applications. However, in order to meet the demands for increased recording density in recent years, coating-type coatings have reached their limits both theoretically and technically, so a new method has been developed to use a thin ferromagnetic metal film as a magnetic recording layer, regardless of whether it is on the inner surface or perpendicularly. Metal thin film magnetic recording media have attracted attention, and efforts are being made in various fields to put them into practical use. In terms of practical application of this metal thin film magnetic recording medium,
Due to the media structure itself and the media manufacturing method, there are many points where conventional coating-type technology cannot be used as is.
The reality is that it is difficult to balance practical performance such as driving performance with many other performances such as electromagnetic conversion characteristics and corrosion resistance at a high level. In other words, when a ferromagnetic thin film is formed on one side of a polymer substrate by vacuum evaporation, sputtering, ion plating, etc., the physical properties of the object on the opposite side change greatly from those obtained in the atmosphere, and the properties of the object on the opposite side change significantly from those obtained in the atmosphere. It's becoming difficult to do. Therefore, a back layer is formed on the surface opposite to the magnetic surface (hereinafter referred to as the back surface),
Driving performance needs to be improved. The basic constituent materials are antistatic agents, water repellents, lubricants, binding resins, etc., but the anionic surfactants, cationic surfactants, nonionic surfactants, etc. that were often used in the coating type Since the organic surfactant has a good affinity with water, it cannot be used as an antistatic agent because it leads to rusting of the metal ferromagnetic thin film. As a countermeasure, the use of solid antistatic agents such as carbon black and particulate graphite has begun to be considered, but if they are mixed in an amount sufficient to exert an antistatic effect, the surface shape becomes rough and driving performance is not improved. However, the C/N of the tape or disk
There is an inconvenience that it deteriorates. OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for manufacturing thin metal film magnetic recording media with good balance between running performance and high C/N in large quantities with good reproducibility. Structure of the Invention The method for manufacturing a metal thin film magnetic recording medium of the present invention involves coating and forming a layer containing carbon powder dispersed in a binder on one side of a substrate, drying the layer, and roll-pressing the layer. After the average surface roughness is reduced to 450 Å or less by calendering, a metal thin film magnetic layer is deposited on the other surface of the substrate. In addition, the method for producing a metal thin film magnetic recording medium of the present invention includes coating and forming a layer containing carbon powder dispersed in a binder on one side of a substrate, drying the layer, and then roll-pressing the layer. The method is characterized in that a metal ferromagnetic thin film is deposited on the substrate after calendering. The above-mentioned substrates include those whose magnetic surface side has a multilayer structure of a non-magnetic film and a soft magnetic film, and those whose magnetic surface side has a multilayer structure of ferromagnetic thin films, and also have an organic or inorganic thin film protection on the magnetic surface side. Of course, it also includes those in which layers are a constituent feature. In addition, regarding the material composition of the back layer, the considerations made in the preparation process of conventional magnetic paints are minimally given except for carbon powder, and furthermore,
Because the magnetic surface rusts and the target recording wavelength is short, the threshold for deterioration of surface properties that leads to spacing loss, transfer adhesion to the magnetic surface, and adhesion phenomena is different from conventional methods, and is extremely small. The design must take into consideration the following: However, according to the manufacturing method of the present invention, it is clear from the examples described below that a high level of quality stability is ensured in the width and longitudinal position between lots and within a lot. Specifically, the substrate used in the present invention is a polymer substrate such as polyethylene terephthalate, polyamide, polyimide, polyethylene naphthalate, etc.
Alternatively, it is a substrate coated on one or both of the surfaces in advance, and a thickness in the range of 4 μm to 20 μm is often used. Surface roughness is 20 Å to 300 Å on the side that forms the magnetic surface, and 200 Å to 450 Å on the back side.
The range is often used. Specifically, those that can be used as ferromagnetic metal thin films include Co-O, Ni-O, Co-Fe-O,
Co-Cr-O, Co-Ni-Cr-O based in-plane magnetization film,
Co-Cr, Co-V, Co-Ni-Cr, Co-Ni-V,
Although it is a perpendicularly magnetized film such as Co--Mo, the material composition thereof is not directly restricted by the present invention. Specifically, carbon black and fine graphite particles are used as the carbon powder, and components other than the carbon powder in the back layer include higher fatty acids and their alcohol esters, higher fatty acid esters such as polyhydric alcohol esters, Materials that improve water repellency such as higher fatty acid metal salts, higher fatty acid group alcohols, higher fatty acid amides, molybdenum dioxide,
It is possible to improve durability and heat resistance by adding solid lubricants such as carbon fluoride, non-magnetic fine particles such as calcium carbonate and barium carbonate, and fats such as nitrocellulose. , vinyl chloride copolymers, vinylidene chloride copolymers, cellulose resins, butyral resins, polyurethane resins, and the like. Furthermore, solvents and diluents can be selected freely. The manufacturing method of the present invention includes the steps of forming a back layer, coating, drying,
The order of calendering by roll pressure bonding and magnetic layer formation is important, and even if other steps are added as necessary, the order of the steps described above will not change. Further, there are no particular restrictions on other post-processes necessary to obtain magnetic tapes and magnetic disks. Regarding the coating method, there are known methods such as reverse roll method, gravure method, blade method, etc. Calendar treatment after drying is a process performed by passing the wide substrate to be treated between multiple heated rolls that are crimped together. This works to improve the C/N of the magnetic recording medium while improving the running performance. still,
In order to maintain this effect, the surface electrical resistance on the ferromagnetic side is extremely small, so if the carbon powder on the back side is removed, the frictional electrification during running will increase further due to calendering. Addition of carbon powder is essential. Incidentally, when carbon black is used as the carbon powder, it is practically advantageous because a lower resistance can be obtained with less weight than when fine particle graphite is used. Carbon black powder varies slightly depending on the resin used, but the weight per 1 resin is
It works effectively at about 0.2 to 1.0, preferably about 0.4 to 0.8. The magnetic layer can be formed by a deposition method such as electron beam evaporation, electric field evaporation, ion plating, or sputtering using a winding evaporation machine. At this time, carbon black powder is included, and the calendered surface effectively acts to cool the substrate during vapor deposition. DESCRIPTION OF EXAMPLES The present invention will be specifically described below with reference to Examples. Although the magnetic recording medium obtained by the manufacturing method of the present invention will be described by comparing its characteristics with that of a comparative example, it is needless to say that the present invention is not limited to this example. Experimental Example 1 Eslec BL-S [polyvinyl butyral manufactured by Sekisui Chemical Co., Ltd.] 100 parts, carbon black 80 parts, stearic acid 3 parts, methyl isobutyl ketone 1500 parts,
A paint for the back layer was prepared by mixing and dispersing it with a paint component consisting of 1500 parts of toluene in a ball mill for 50 hours. This paint was applied to a thickness of about 1 μm on a 10.5 μm polyethylene terephthalate film using a bar coater and dried. This 50cm wide board was processed at a temperature of 80℃ and a roll pressure of 70℃.
Calendering was carried out by passing the material between kg/cm ² rolls three times at a speed of 15 m/min. After this, while moving it along the circumferential side of the cooling canister with a diameter of 50 cm, the
An alloy of 80% Co and 20% Ni was electron beam evaporated. During vapor deposition, the maximum partial pressure of oxygen is approximately 2×10 ^-5 Torr.
A 0.15 μm Co-Ni-O based vapor deposited film was obtained. A magnetic tape with a width of 8 mm was obtained from this original tape, and a relative speed of 4 m/
sec, the tape C/N was examined and compared using a 4.5MHz signal and a 4MHz noise. As a comparative example, a sample that was not calendered and produced under the same conditions was used. The average surface roughness of the back layer according to the present invention and that of Comparative Example 1 were 400 Å and 2100 Å, respectively. Experimental Example 2 Eslec BL-1 [polyvinyl butyral manufactured by Sekisui Chemical Co., Ltd.] 200 parts, carbon black 100 parts, molybdenum disulfide 100 parts, nitrocellulose RS1/2
A paint component for the back layer was prepared by mixing and dispersing paint components consisting of 50 parts [manufactured by Daicel Chemical Industries, Ltd.], 3 parts of pentaerythritol tetrastearate, 1300 parts of methyl ethyl ketone, and 1300 parts of toluene in a ball mill for 40 hours. did. This paint was coated onto a corona-treated polyamide substrate (8 μm thick) using a bar coater to a thickness of about 2.0 μm and dried. The substrate in this state (50 cm width) was calendered by passing it twice between rolls at a temperature of 85° C. and a roll pressure of 80 kg/cm ² at a speed of 100 m/min. After this, an incident angle of 0° is applied to the surface opposite to the back layer.
A perpendicularly magnetized film of 0.2 μm consisting of 80% Co and 20% Cr was formed by a binary evaporation method of 100% Co and 100% Cr in the range of ~10°, and was cut into 1/4 inch pieces to obtain a magnetic tape. The comparative example is a medium without calendering, similar to Example 1. The average surface roughness of the present invention and Comparative Example 2 were 350 Å and 1200 Å, respectively. Example 3 VAGH [manufactured by UCC, USA, vinyl chloride-vinyl acetate-vinyl alcohol copolymer] 12 parts, Nitzpol 1432 units [manufactured by Nippon Zeon Co., Ltd., acrylonitrile]
Butadiene copolymer] 8 parts, carbon black 10 parts
A paint component for the back layer was prepared by mixing and dispersing paint components consisting of 50 parts of cyclohexanone, 50 parts of methyl isobutyl ketone, and 50 parts of methyl isobutyl ketone in a ball mill for 80 hours. This paint was applied to about 1.2 μm on one side of an 8.5 μm biaxially reinforced stretched polyethylene terephthalate film using a bar coater and dried. This 50cm wide board was processed at a temperature of 80℃ and a roll pressure of 85kg/
Calendering was performed by passing the material between cm ² rolls four times at 20 m/min. After this ^, Co78
%, Ni22% alloy was electron beam evaporated to 0.13μ
Obtain an in-plane magnetized film of Co-Ni-O of 8 m.
It was cut to mm width and its characteristics were measured. As a comparative example, one without calendering was investigated. The average surface roughness of Comparative Example 3 was 450 Å.
It was 1300Å. Experimental example 4 100 parts of thermoplastic polyurethane resin, 70 parts of carbon black [Asahi Carbon #55], 70 parts of epoxy resin
part, lecithin 3.5 parts, ethyl acetate 200 parts, toluene
A paint component for the back layer was prepared by mixing and dispersing 200 parts of paint and 100 parts of cyclohexanone in a ball mill for 30 hours, adding 10 parts of calcium carbonate (average particle size 0.7 μm) to the base, and mixing and dispersing for a further 20 hours. . Approximately 2 μm of this paint was applied to one side of an 11.5 μm polyethylene terephthalate film using a gravure coater and dried. After this, the temperature was increased to 80℃ to make the back layer mirror-like.
Calendering was carried out by passing it twice between rolls at a roll pressure of 80 kg/cm ² at a speed of 10 m/min. After this, move it to the substrate along a 50cm diameter knife ring and apply it to the surface opposite to the back layer.
A CoMo alloy thin film of 0.1 μm was formed by high-frequency magnetron sputtering using a target consisting of 86% Co and 14% Mo. The degree of vacuum during sputtering is 1/100 Torr, and the maximum partial pressure is argon. This was made into a tape with a width of 8 mm, and its properties were compared with that of a tape that was not calendered after forming the back layer. The average surface roughness of the present invention and this comparative example 4 are
They were 220 Å and 2000 Å. 100 tapes each from Experimental Example 1 to Experimental Example 4
Comparative Examples 1 to 4 were each wound on a reel in 100 m lengths and stored at 50° C. and 85% RH for one month, and the C/N before and after was shown in Table 1. For OdB, the initial value of C/N of the tape of each comparative example was adopted.

【table】

[Table] In addition, the coefficient of dynamic friction, which is a guideline for running performance, is the value at 25°C 60% RH after 100 round trips on a test machine with a running system equivalent to a commercially available VHs deck.
It looked like a table.

[Table] Effects of the Invention According to the method of manufacturing a metal thin film magnetic recording medium of the present invention, magnetic recording media required for ultra-compact VTRs and high-density information recording systems, specifically, short wavelength recording characteristics can be achieved. This makes it possible to mass-produce magnetic recording media with good reproducibility and excellent still characteristics and running durability.

Claims (1)

[Claims] 1 After coating and forming a layer containing carbon powder dispersed in a binder on one side of the substrate, this is dried, and the average surface roughness is reduced to 450 Å or less by calendering using roll compression, and then the above-mentioned A method of manufacturing a metal thin film magnetic recording medium, in which a metal thin film magnetic layer is deposited on the other side of a substrate.