JPH0249488B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a ferromagnetic metal thin film type magnetic recording medium with a coating film mainly made of a resin material on the opposite side of the magnetic layer of the base film, thereby improving running performance of the magnetic recording medium, preventing static electricity, and improving environmental conditions under high temperature and humidity. The purpose is to improve corrosion resistance and blocking resistance under the surface. A metal thin film type film obtained by forming a ferromagnetic thin film mainly composed of iron, cobalt, nickel, or an alloy thereof on a polymer film support such as polyester or polyimide by vacuum evaporation, sputtering, ion plating, etc. Magnetic recording media are ideal for high-density recording, such as recording video signals. However, metal thin films generally have a problem of poor corrosion resistance in high-temperature, high-humidity environments, especially when exposed to rapid temperature changes in high humidity while being rolled up in tape form on reels, hubs, etc. , dew condensation easily occurs between the opposing magnetic surfaces and the back surface in the rolled-up state, and once condensation occurs, the gap between the magnetic surface and the back surface is narrow, making it difficult for water droplets to evaporate and leave the magnetic surface wet for a long time. It has become clear that corrosion tends to occur in that area, and when the corroded area dries, the magnetic surface and back surface tend to adhere (blocking) through the corrosion products. If the surface properties of the magnetic surface are improved in order to increase the recording density, the gap between the magnetic surface and the back surface in the rolled-up state will become smaller, and the above phenomenon will become even more pronounced. On the back side of a metal thin film type magnetic recording medium,
In addition to satisfying general characteristics of magnetic recording media such as slipperiness, prevention of scratching, and prevention of static electricity, it is necessary to deal with rust and the blocking phenomenon caused by rust, as described above. From this point of view, as a result of examining various materials, a material with excellent blocking resistance and rust prevention effect was discovered. The basic constituent materials of the present invention include antistatic agents,
Consists of water repellent, lubricant, and binding resin. As the antistatic agent in the present invention, a solid antistatic agent such as carbon black or particulate graphite is used. Conventionally, organic surfactants such as anionic surfactants, cationic surfactants, and nonionic surfactants that have been used in coated magnetic tapes have good affinity with water, so they prevent the formation of rust. This was unsuitable from the standpoint of rust prevention. In the present invention, carbon black and graphite control the roughness of the coating film surface, and together with the phenoxy resin and the water repellent, prevent the infiltration of moisture and prevent the blocking phenomenon. carbon black,
The appropriate amount of graphite to be mixed is 29 to 36 parts by weight per 100 parts by weight of the phenoxy resin. If it is less than 29 parts by weight, not only will antistatic properties become insufficient, but the roughness of the coating film surface will become smaller.
Blocking phenomenon also becomes more likely to occur. If the amount is more than 36 parts by weight, the strength of the coating film will be insufficient, causing powder to fall off during running, and in severe cases, peeling of the film. In addition, water repellent agents include higher fatty acids such as stearic acid, palmitic acid, myristic acid, lauric acid, and oleic acid, their alcohol esters, higher fatty acid esters such as polyhydric alcohol esters, and their sodium salts, potassium salts, and lithium salts. , calcium salts, barium salts, zinc salts,
Higher fatty acid metal salts such as magnesium salts, aluminum salts, lead salts, chromium salts, cobalt salts, nickel salts, copper salts, iron salts, tin salts, and mercury salts, and higher fatty acid metal salts such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, etc. Fatty alcohols and higher fatty acid amides such as lauric acid amide, myristic acid amide, and palmitic acid amide are used. In the present invention, the water repellent not only improves the water repellency of the coating surface, but also transfers to the surface of the magnetic layer when it is wound on a reel, and acts on the surface of the ferromagnetic metal thin film that constitutes the magnetic layer. It also improves the water repellency of the magnetic layer, prevents moisture from entering under high temperature and high humidity conditions, and improves corrosion resistance. The amount of water repellent to be mixed is based on 100 parts by weight of phenoxy resin.
A suitable amount is from 0.7 parts by weight to 1.4 parts by weight, and if it is less than 0.7 parts by weight, a sufficient water repellent effect cannot be obtained.
If the amount is more than 1.4 parts by weight, a sufficient water repellent effect can be obtained, but the excess water repellent may fall off or be transferred to the surface of the magnetic layer in a large amount, causing damage to posts and cylinders during running. A phenomenon of sticking to the surface may occur. graphite, higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, higher fatty alcohols,
Higher fatty acid amides have excellent lubricity, but the lubricity can be further improved by adding a solid lubricant such as molybdenum disulfide or carbon fluoride. A phenoxy resin is used as the binder resin because it has excellent compatibility with antistatic agents, lubricants, and water repellent agents, and excellent dispersibility of solid particles. Furthermore, by crosslinking with butylated melamine resin, butylated urea resin, benzoguanamine resin, blocked isocyanate, etc., adhesion, heat resistance, chemical resistance, and abrasion resistance are improved. Stearic acid and graphite were added to the phenoxy resin, a solvent was added, and a dispersion treatment was performed using a ball mill to create a coating solution. The coating solution was applied to the back surface of a metal thin film type magnetic recording medium in which a cobalt alloy was deposited on a polyethylene terephthalate film. This magnetic recording medium showed no occurrence of rust or blocking even under high temperature and high humidity environmental conditions. When I ran it using a video tape recorder, it ran stably and there was no noise caused by charging. Examples of the present invention will be specifically described below. Example 1 The following composition was prepared in a ball mill, stirred for 40 hours, and subjected to dispersion treatment. YP-50EK-40 (Phenoxy resin manufactured by Toho Kasei Co., Ltd.)
100 parts by weight Graphite ASSP (manufactured by Nippon Graphite Industries Co., Ltd.)
36 parts by weight Stearic acid 0.7 parts by weight Methyl ethyl ketone 14 parts by weight Toluene 64 parts by weight Cellosolve acetate 64 parts by weight Cobalt (80
%) and Nickel (20%) ferromagnetic alloy thin film. After drying, it was suitably cut to produce a magnetic recording medium. The coating film thickness was 3.0μ. This is designated as sample A. Example 2 The following composition was charged into a ball mill, stirred for 40 hours, and subjected to dispersion treatment to produce a paint. YP-50EK-40 (Phenoxy resin manufactured by Toto Kasei Co., Ltd.)
100 parts by weight Carbon black 29 parts by weight Molybdenum disulfide 6 parts by weight Pentaerythritol tetrastearate
1.4 parts by weight Methyl isobutyl ketone 14 parts by weight Cyclohexane 100 parts by weight Toluene 143 parts by weight The resulting paint was coated on a polyester film by vacuum evaporation using a ferromagnetic coating of cobalt (80%) and nickel (20%). It was applied to the back side of the alloy thin film. After drying, it was cut into an appropriate width to produce a magnetic recording medium. The coating film thickness was 3.8μ. This is designated as sample B. Example 3 The following composition was charged into a ball mill, stirred for 40 hours, and subjected to dispersion treatment to produce a paint. YP-50EK-40 (Phenoxy resin manufactured by Toto Kasei Co., Ltd.)
100 parts by weight Melan 11 (butylated urea resin manufactured by Hitachi Chemical Co., Ltd.)
4 parts by weight Carbon black 29 parts by weight Carbon fluoride 3 parts by weight Calcium stearate 1.1 parts by weight Methyl ethyl ketone 57 parts by weight Toluene 143 parts by weight )・Coated on the back side of a nickel (20%) ferromagnetic alloy thin film. After drying, it was cut into an appropriate width to produce a magnetic recording medium. The coating film thickness was 4.3μ. This is designated as sample C. Example 4 The following composition was charged into a ball mill, stirred for 40 hours, and subjected to dispersion treatment to produce a paint. YP-50EK-40 (Phenoxy resin manufactured by Toto Kasei Co., Ltd.)
100 parts by weight Yuban 20SE-60 (butylated melamine resin manufactured by Mitsui Toatsu Co., Ltd.) 3 parts by weight Carbon black 30 parts by weight Palmityl alcohol 0.7 parts by weight Methyl ethyl ketone 71 parts by weight Cyclohexanone 29 parts by weight Toluene 143 parts by weight Obtained paint was applied using a bar coater method to the back side of a ferromagnetic alloy thin film of cobalt (80%) and nickel (20%) created by vacuum evaporation on a polyester film. After drying, it was cut into an appropriate width to produce a magnetic recording medium. The coating film thickness was 3.5μ. This is designated as sample D. Example 5 The following composition was charged into a ball mill, stirred for 40 hours, and subjected to dispersion treatment to produce a paint. YP-50EK-40 (Phenoxy resin manufactured by Toto Kasei Co., Ltd.)
100 parts by weight Graphite ASSP (manufactured by Nippon Graphite Industries Co., Ltd.)
29 parts by weight Stearic acid amide 0.9 parts by weight Methyl isobutyl ketone 71 parts by weight Toluene 114 parts by weight Cellosolve acetate 43 parts by weight Cobalt (80%)/nickel was created by using a bar coater method to vacuum deposit the resulting paint onto a polyester film. (20%) was applied to the back side of a ferromagnetic alloy thin film. After drying, it was cut into a suitable width to produce a magnetic recording medium. The coating film thickness was 3.3μ. This is designated as sample E. As a comparative example, a magnetic recording medium in which graphite was not mixed was created in Example 1, and this was designated as Sample F. Furthermore, as a comparative example, a magnetic recording medium in which stearic acid was not mixed was prepared in Example 1, and this was designated as Sample G. When the samples A, B, C, D, and E prepared in Examples 1, 2, 3, 4, and 5, the comparative samples F and G, and the uncoated sample were wound on a reel, the temperature
An environmental test was conducted by leaving the product under conditions of 60°C and 90% humidity. In addition, the contact angle with water on the surface of the magnetic layer and the surface of the back coating film was measured to examine water repellency. The results are shown in the table below.

[Table] Antenna As is clear from the table, the material according to the present invention contains a water repellent, so when it is wound up on a reel, it is transferred to the surface of the magnetic layer, making it difficult to resist water on both sides of the magnetic recording medium. The contact angle is increased, preventing moisture from entering and improving the corrosion resistance of the magnetic thin film. Furthermore, a running test was conducted using a test machine with the same functions as a commercially available video tape recorder. In the sample whose back side was not coated, running was unstable, and noise, which was thought to be caused by triboelectric charging, was occasionally observed. In addition, in the comparative sample F, the running was stable at the beginning, but
Driving gradually became unstable. On the other hand, in Examples A, B, C, D, and E, running was stable, and no noise thought to be caused by triboelectric charging was observed. Furthermore, frictional resistance was measured with a 10g load on a mirror-finished stainless steel block. The table shows the frictional resistance of each sample, assuming that the frictional resistance of the uncoated sample on the back side is 1.00.

[Table] As is clear from the table, the product according to the present invention has low frictional resistance and excellent lubricity. As described above, according to the present invention, corrosion resistance and blocking resistance can be easily improved.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic substrate, 29 to 36 parts by weight of at least one of graphite and carbon black and 0.7 parts by weight of at least one of graphite and carbon black are added to the surface of the substrate opposite to the ferromagnetic metal thin film.
~1.4 parts by weight of higher fatty acids, higher fatty acid esters,
1. A magnetic recording medium comprising a coating film made of 100 parts by weight of a phenoxy resin containing at least one selected from the group consisting of a higher fatty acid metal salt, a higher fatty acid amide, and a higher aliphatic alcohol.